JPH10196671A - Structure for fixing shaft and gear and printer using this structure - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To over-rotate a paper feed roller when a paper feed roller shaft and a gear are firmly connected and a rear end of the paper passes through a pressing portion between the paper feed roller and a pressure roller. To prevent white streaks from appearing on the printed surface. A cylindrical portion of a bush is provided between an inner peripheral surface of a hole of a gear and an outer peripheral surface of a paper feed roller shaft.
Press-fit. Gear inner peripheral surface 21 and bush outer peripheral surface 33
Are formed in the same direction, and a slit S is formed in the bush. As the bush is pressed into the opposite end portion 35 forming the slit, the shaft 1
A biting portion 36 that bites into 0 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printer and, more particularly, to a fixing structure of a paper feed roller shaft and a gear fixed thereto. Furthermore, the invention relates not only to a printer but also to a structure for fixing a shaft and a gear.

[0002]

2. Description of the Related Art FIG. 7 is a schematic side view mainly showing a paper feed mechanism of a conventional printer, and FIG. 8 is a perspective view showing a conventional structure for fixing a paper feed roller shaft and a gear.

In these figures, 5 is a paper feed roller,
Reference numerals 7 and 8 denote pressing rollers. Reference numeral 9 denotes a head as printing means.

The paper feed roller 5 has a metal shaft 5a. One end of the shaft 5a has a paper feed gear 4 made of synthetic resin.
Has been fixed. In FIG. 7, 1 is a motor,
A pinion 2 fixed to an output shaft of the motor 1 meshes with the paper feed gear 4 via an intermediate gear 3. Therefore, when the motor 1 rotates, its power is transmitted to the intermediate gear 3.
To the paper feed gear 4 to rotate the paper feed roller 5.

[0005] As shown in FIG.
a one end of a metal pin 6 in a direction orthogonal to the shaft 5a.
Grooves 4a, 4 fitted into the pins 6 are provided.
a is formed continuously with the hole 4b of the reduction gear 4.

The gear 4 made of synthetic resin is weakly press-fitted into the shaft 5a and fixed. If the press-fitting is strongly performed, the reduction gear 4 is deformed in the initial stage of being mounted on the shaft 5a.

The pressure rollers 7 and 8 are attached to a paper guide (not shown), and are pressed against the paper feed roller 5 by urging means (for example, a spring) not shown.

The head 9 is mounted on a carriage (not shown), and prints on the paper P while reciprocating in a direction orthogonal to the paper surface of FIG.

The above-described printer normally operates as follows.

The paper P is supplied from a paper feeding device (not shown) to a paper feed roller 5 as shown by an arrow a in FIG. When the paper is supplied, the paper feed roller 5 is driven to rotate. When the leading end of the supplied paper P reaches the pressing portion 7 a between the paper feed roller 5 and the pressure roller 7, the paper feed roller 5 rotates. The sheet is conveyed while being nipped by the roller 5 and the pressure roller 7.

As the paper feed roller 5 continues to rotate, the leading end of the paper P further passes through the pressing portion 8a between the pressing roller 8 and the paper feed roller 5. In this way, the paper P is conveyed while being wound around the paper feed roller 5, and then separated from the paper feed roller 5, guided by a paper guide (not shown), and sent below the head 9.

When the leading edge of the paper reaches a predetermined position below the head 9, the rotation of the paper feed roller 5 is temporarily stopped, and printing by the head 9 is started.

When printing for one line is performed by the head 9, the paper feed roller 5 is driven again to feed the paper P in the direction of the arrow Y between the lines, and the head 9 prints the next line.

After predetermined printing is performed on the paper P by repeating such an operation, that is, a printing operation by the head 9 and a paper feeding operation by the paper feeding roller 5 at every line pitch, the paper P is discharged to a discharge unit (not shown). Is discharged.

FIG. 11 is a plan view schematically showing the above printing operation.

As shown in FIG. 1, the head 9 has a nozzle row N composed of a plurality of nozzles n. The head 9 selectively ejects ink droplets from the nozzles n while moving in the direction of the arrow X11 or X22 in the figure to print characters and other images on the paper P. In the drawing, reference numeral P1 denotes a printing area formed by one printing operation by the head 9, and is equal to the length L of the nozzle row N.

When one printing operation is completed, the above-described motor 1 is rotated, and the paper P is moved by the paper feed roller 5 to an arrow Y.
In the direction, the sheet is fed by the length L, and the head 9 prints on the next print area P2.

[0018]

The above-mentioned conventional printer has the following problems.

At the time of driving the motor 1, FIGS.
As shown in (a), when the side walls 4a2, 4a2 on one side of the grooves 4a, 4a of the paper feed gear 4 press the pin 6, the rotational force is transmitted from the gear 4 to the shaft 5a. Therefore, conversely, the side walls 4a2, 4a2 on one side of the grooves 4a, 4a
Is pressed by the pin 6.

The paper feed gear 4 is made of synthetic resin to reduce the cost, and the gear 4 is attached to the shaft 5a with a weak press fit.
When the motor 1 is driven, the side walls 4a2 on one side of the grooves 4a, 4a
When the pin 4a2 is pushed by the pin 6, the gear 4 is deformed, and FIG.
As shown in (a), the side walls 4a on the opposite side of the grooves 4a, 4a
Gaps A1 and A1 are formed between the pins 1 and 4a1 and the pins 6.

On the other hand, as the above-described printing operation is performed, the trailing end of the paper P is held at the pressing portions 7a, 8a between the paper feed roller 5 and the first and second pressing rollers 7, 8 as shown in FIG. Pass through. FIG. 10 shows a state in which the rear end portion PE of the sheet passes through the pressing portion 7 a between the sheet feed roller 5 and the pressure roller 7. With reference to this figure, a case where the trailing end portion PE of the paper passes through the pressing portion 7a will be described as an example. The paper P is pressed against the paper feed roller 5 by the pressing force F1 of the pressing roller 7, and is conveyed. The rear edge of the paper
When the sheet passes through the pinching portion 7a, a force F2 is applied to the rear end portion PE so as to repel the rear end portion PE in the sheet feeding direction (the direction of the arrow Y).

At this time, the pressing roller 7 is connected to the rear end portion PE of the sheet.
Of the paper feed roller 5, a force F3 is applied to the paper feed roller 5 to turn the paper feed roller 5 in the paper feed direction (the direction of the arrow Y) via the rear end portion PE of the paper.

Since the gaps A1 and A1 are formed in the grooves 4a and 4a of the reduction gear 4 as described above, when the rear end portion PE of the sheet passes through the pressing portion 7a, such a gap is formed. When the force F3 is applied, as shown in FIGS. 9B and 10, the paper feed roller 5 is rotated by the gap A1 more than the rotation amount of the reduction gear 4.

That is, the paper feed roller 5 rotates more than the paper feed amount originally intended to be fed, and the pitch of the paper feed amount is shifted.

When such a pitch shift occurs, the print position by the head 9 shifts accordingly, and the print areas P1 and P2 as shown in FIG. 11 are separated from each other. Minutes appear as white streaks on the printed surface.

In particular, when a full-color image is to be obtained by an ink-jet head, for example, as shown in FIG. 12, a head array 9 is provided with nozzle rows NR, NB, NY composed of a plurality of nozzles n. A full-color image is formed by selectively discharging a red ink droplet from the NR, a blue ink droplet from the nozzle line NB, and a yellow ink droplet from the nozzle line NY. In this case, the arrangement of the nozzles n constituting the nozzle row is, for example, as shown in FIG. 13, the nozzles n of each color are arranged not linearly in the direction orthogonal to the paper feed direction Y, as shown in FIG. And print areas P1 and P2
Is intentionally partially overlapped with each other, and ink droplets of different colors are overlapped to form a high-resolution color image. The overlapping portion P12 between the printing areas P1 and P2 is formed by printing the printing area P1 and then feeding the paper P by the length L12. At this time, different overlapping colors P12 In order for ink droplets to overlap properly, high paper feed accuracy, at least the distance between the nozzles of the inkjet head that are closest in the paper feed direction (for example, Lp in FIG. 13) is defined as the minimum feed unit. Paper feed accuracy is required.

However, as described above, if the pitch of the paper feed amount is shifted, white streaks appear, and there is a problem that the white streaks become conspicuous in full-color printing.

Furthermore, coated paper or the like generally used for performing full-color printing is thicker than plain paper, so that the rear end of the paper is largely repelled by the pressure roller, and white stripes are formed. But it was even more noticeable.

The present invention has been made to solve the above problems, and a first object of the present invention is to provide a fixing structure capable of firmly fixing a shaft and a gear.

A second object is that when the trailing edge of the paper passes through the pressure portion between the paper feed roller and the pressing roller, the paper feed roller rotates more than the paper feed amount originally intended to be fed. It is an object of the present invention to provide a printer which can suppress the occurrence of white lines on the printing surface.

[0031]

According to a first aspect of the present invention, there is provided a structure for fixing a shaft and a gear, the shaft, a gear having a hole into which the shaft is inserted, and a gear. A bush having a cylindrical portion press-fitted between the inner peripheral surface of the hole and the outer peripheral surface of the shaft, wherein the inner peripheral surface of the gear hole and the outer peripheral surface of the cylindrical portion have the same direction. A taper is formed, and a slit is formed in the cylindrical portion in the axial direction.

[0032] The structure for fixing the shaft and the gear according to the second aspect is as follows.
2. The fixing structure of a shaft and a gear according to claim 1, wherein a biting portion that bites into the shaft as the bush is press-fitted is formed at a facing end portion of the bush where the slit is formed. And

According to a third aspect of the present invention, there is provided a structure for fixing a shaft and a gear,
3. The fixed structure of a shaft and a gear according to claim 1, wherein the bush has a flange formed integrally with the tubular portion, and a boundary portion between the flange and the tubular portion. 4. A ring-shaped groove is formed, and the slit is formed over the cylindrical portion and the flange portion.

[0034] In order to achieve the second object, a fourth aspect is provided.
The printer described above is a paper feed roller that feeds paper, a pressure roller that is pressed against the paper feed roller and presses the paper against the paper feed roller, and a printing unit that prints on the paper sent by the paper feed roller, A gear fixed to the shaft of the paper feed roller, wherein the shaft of the paper feed roller and the gear are fixed by the shaft and gear fixed structure according to claim 1, 2, or 3. Features.

According to a fifth aspect of the present invention, in the printer according to the fourth aspect, the printing means includes a plurality of nozzle rows for ejecting inks of different colors, and a color is obtained by ejecting ink from each of the nozzle rows. An ink jet head capable of performing printing, wherein the paper feed roller feeds paper at a paper feed amount with a minimum feed unit being a distance between nozzles that are closest to each other in a paper feed direction of the ink jet head. It is characterized by.

[0036]

According to the first aspect of the present invention, the shaft is inserted into the hole of the gear, and the cylindrical portion of the bush is provided between the inner peripheral surface of the gear hole and the outer peripheral surface of the shaft. The shaft and the gear are fixed by press fitting.

The inner peripheral surface of the hole of the gear and the outer peripheral surface of the cylindrical portion are tapered in the same direction, and a slit is formed in the cylindrical portion in the axial direction. Therefore, the bush will play a role as a wedge by tightening the shaft so that the slit of the tubular portion becomes narrower as the bush is pressed, so that the shaft and the gear are firmly fixed.

Moreover, since the cylindrical body is press-fitted between the inner peripheral surface of the gear hole and the outer peripheral surface of the shaft, the concentricity between the shaft and the gear can be maintained even if it is strongly pressed. There is no loss.

According to the fixed structure of the shaft and the gear according to the second aspect, in the fixed structure of the shaft and the gear according to the first aspect,
At the opposite end portion forming the slit of the bush, a biting portion that bites into the shaft as the bush is pressed is formed, so that when the bush is pressed,
With this, the opposite end portion forming the slit acts so that the biting portion bites the shaft while narrowing the slit, so that the shaft and the gear are more firmly fixed. .

According to the fixed structure of the shaft and the gear according to the third aspect, in the fixed structure of the shaft and the gear according to the first or second aspect, the bush has a flange portion integrally with the cylindrical portion. Since it is formed, it is possible to obtain an operation and effect that the press-fitting operation of the cylindrical portion can be easily performed.

Further, since the slit is formed over the cylindrical portion and the flange portion, the above-described operation of the cylindrical portion at the time of press-fitting the bush is not impaired.

Further, since a ring-shaped groove is formed at the boundary between the flange and the cylindrical portion, the above-described deformation of the cylindrical portion is favorably performed, and the connection between the flange and the cylindrical portion is improved. Inconveniences such as stress concentration at the boundary portion and breakage from here are prevented.

According to the printer of the fourth aspect, a paper feed roller for feeding paper, a pressure contact roller pressed against the paper feed roller and pressing the paper against the paper feed roller, and a paper fed by the paper feed roller And a gear fixed to the shaft of the paper feed roller, wherein the shaft of the paper feed roller and the gear are the gears.
Since the shaft and the gear are fixed by the fixing structure described in 2 or 3, the following operation and effect can be obtained.

That is, when the rear end portion of the paper passes through the pressure portion between the paper feed roller and the pressure roller, a force acting to push the rear end portion of the paper in the paper feed direction acts on the rear end portion of the paper. Then, a force for rotating the paper feed roller acts on the paper feed roller. However, according to this printer, since the shaft of the paper feed roller and the gear are firmly fixed, the gear The shaft of the paper feed roller does not rotate more than the amount of rotation of the paper feed roller, and the paper feed roller is prevented from rotating more than the paper feed amount originally intended to be fed.

Therefore, when the trailing edge of the sheet passes through the pinching portion, the pitch of the sheet feeding amount does not shift, and the effect that the white streaks hardly appear on the printing surface can be obtained.

According to a fourth aspect of the present invention, as described in the fifth aspect, the printing means of the printer includes a plurality of nozzle arrays for ejecting inks of different colors, and ink is ejected from each of the nozzle arrays. An ink jet head capable of performing color printing by performing the above operation, wherein the paper feed roller feeds a paper at a feed amount with a distance between nozzles in a paper feed direction of the nozzle row being a minimum feed unit. This is particularly effective, and is more effective when the paper to be printed is a relatively thick paper such as coated paper.

That is, when trying to obtain full-color printing by ejecting inks of different colors from each nozzle row,
As described above, printing is performed by overlapping the printing areas. However, according to the configuration of the fourth aspect, the desired paper feeding accuracy can be obtained, so that the printing areas can be accurately overlapped. Becomes Therefore, white streaks hardly appear on the printing surface, and a high-quality color image can be obtained.

Further, even when performing full-color printing using thick coated paper or the like, the pitch of the paper feed amount does not shift when the trailing edge of the paper passes through the above-described clamping portion. Therefore, white streaks are less likely to appear on the printed surface,
High quality color images can be obtained.

[0049]

Embodiments of the present invention will be described below with reference to the drawings.

<Embodiment of Fixed Structure of Shaft and Gear> FIG. 1 is a sectional view showing an embodiment of a fixed structure of a shaft and a gear according to the present invention. Diagram,
(B) is a diagram in which the shaft before fixing is omitted. 2A and 2B are views showing a bush, FIG. 2A is a partially cut front view, and FIG. 2B is a side view. FIGS. 3A and 3B are explanatory diagrams of the operation.

In FIG. 1, 10 is a shaft, 20 is a gear, 3
0 is a bush.

The gear 20 has a hole 21 into which the shaft 10 is inserted.
Are formed, and a taper T1 is formed on the inner peripheral surface 22 of the hole 21. This taper T1 is, for example, 1/1.
The taper is about 6.

As shown in FIG. 2, the bush 30 has a tubular portion 31 and a flange portion 32 integral with the tubular portion 31. The slit S (S) extends over the tubular portion 31 and the flange portion 32. 2 is formed in the axial direction. The outer peripheral surface 33 of the cylindrical portion 31 is formed with a taper T2 in the same direction as the taper T1 of the inner peripheral surface 22 of the hole 21. The taper T2 is, for example, 1/16 as in the case of the taper T1.
It is a taper of the degree. Flange part 32 and cylindrical part 31
A ring-shaped groove 34 is formed at the boundary between the two.
As shown in FIG. 2, the opposing end portions 35, 35 forming the slit S are provided at their inner ends with biting portions 36, which bite on the shaft 10 as the bush 30 is press-fitted, as described later. 36 are formed. This biting part 3
6 and 36 are formed by not chamfering the edge portions (36) and (36) formed when the slit S is formed. The distance C between the slits S is such that when the bush 30 is press-fitted as described later, the opposing end portions 35, 35 do not come into contact with each other, or even if they do, they do not strongly contact but lightly contact. Is set to The inner diameter of the bush 30 is formed slightly larger than the outer diameter of the shaft 10.

The shaft 10, the gear 20, and the bush 30 are all made of metal.

In order to fix the shaft 10 and the gear 20 by the above structure, for example, the following is performed.

First, as shown in FIG.
The tubular portion 31 of the bush 30 is lightly fitted in the hole 21 of the bush 30.

Next, as shown in FIG.
Into the bush 30 (that is, the hole 21 of the gear 20).
To be inserted).

Thereafter, the cylindrical portion 31 of the bush 30 is placed between the inner peripheral surface 22 of the hole 21 of the gear 20 and the outer peripheral surface 11 of the shaft 10.
Press firmly.

The bush 30 and the gear 20 may be loosely mounted on the shaft 10 and then the bush may be press-fitted. Alternatively, the shaft 10 may be inserted into the gear 20 and then the bush may be press-fitted. . In any case, finally, the cylindrical portion 31 of the bush 30 is press-fitted between the inner peripheral surface 22 of the hole 21 of the gear 20 and the outer peripheral surface 10 of the shaft 10, as shown in FIG. It should just be.

When the bush 30 is press-fitted, as the press-fitting is performed, forces F1 and F1 that narrow the slit S act on the cylindrical portion 31 as shown in FIG. Forces F2 and F2 act so as to deflect the end portions 35 and 35 inward. These forces F1, F2
Is given by the inner peripheral surface (tapered surface) 22 of the gear 20 as a reaction to the press input of the bush.

Therefore, the bush 30 functions as a cylindrical wedge, so as to tighten the shaft 10 so that the slit S of the cylindrical portion 31 becomes narrower as the bush 30 is pressed. Gear 20
Is firmly fixed.

As a result of the opposing end portions 35, 35 being bent inward, the biting portions 36, 36, particularly, such that the front end portion bites on the shaft 10 as shown mainly in FIG. As a result, the shaft 10 and the gear 20 are more firmly fixed.

That is, according to the above-described fixed structure of the shaft and the gear, the following operation and effect can be obtained.

(A) The shaft 10 is inserted into the hole 21 of the gear 20, and the inner peripheral surface 22 of the hole 21 of the gear 20 and the outer peripheral surface 1 of the shaft 10
The shaft 10 and the gear 20 are fixed by press-fitting the cylindrical portion 31 of the bush 30 between them.

The inner peripheral surface 22 of the hole 21 of the gear 20 and the outer peripheral surface 33 of the cylindrical portion 31 have the same direction of taper T1,
Since T2 is formed and the slit S is formed in the cylindrical portion 31 in the axial direction thereof, the bush 30 is formed such that the slit S of the cylindrical portion 31 becomes narrower as the bush 30 is pressed. The shaft 10 serves as a cylindrical wedge to be tightened, so that the shaft 10 and the gear 20 are firmly fixed.

The cylindrical member 3 is press-fitted between the inner peripheral surface 22 of the hole 21 of the gear 20 and the outer peripheral surface 11 of the shaft 10.
1, the shaft 10 and gear 2
There is no loss of concentricity with zero.

(B) Biting portions 36, 36 which bite on the shaft 10 as the bush 30 is pressed into the opposing end portions 35, 35 forming the slits S of the bush 30.
Is formed, so that when the bush 30 is press-fitted,
The opposing end portion 3 forming the slit S with this
5, 35, while narrowing the slit S, the biting portion 3
6 and 36 act to bite on the shaft 10, so that the shaft 1
0 and the gear 20 are more firmly fixed.

(C) The bush 30 has a cylindrical portion 31
Since the flange portion 32 is formed integrally with the cylindrical member, the effect of easily performing the press-fitting operation of the cylindrical portion is obtained.

Further, since the slit S is formed over the cylindrical portion 31 and the flange portion 32, the above-described operation of the cylindrical portion 31 at the time of press-fitting the bush is not impaired.

Further, since a ring-shaped groove 34 is formed at the boundary between the flange portion 32 and the cylindrical portion 31,
The above-described deformation of the tubular portion 31 is favorably performed, and problems such as stress concentration at the boundary portion between the flange portion 32 and the tubular portion 31 and breakage therefrom are prevented.

<Embodiment of Printer> FIG. 4 is a partially omitted side view showing an embodiment of a printer according to the present invention, and FIG. 5 is a partially omitted plan view showing a paper feeder.

In FIG. 4, reference numeral 100 denotes a paper feeder;
Is an ink jet printer main body, 300 is a paper feeder,
Reference numeral 410 denotes an inkjet head for full-color printing as a printing unit, and 420 denotes an inkjet head for monochrome printing.

The paper feeding device 100 includes a paper support 110
, A pair of hoppers 120 (only one side is shown), and a pair of paper feed rollers 130 (only one side is shown).

On the upper surfaces of the paper support 110 and the pair of hoppers 120, a sheet to be fed (not shown)
Is placed.

The pair of hoppers 120 can support both sides of the front part of the sheet, and are slidably inserted through the support rod 140.

The pair of paper feed rollers 130 is composed of a D-shaped roller having a rubber layer on the surface, and is fixed to a grooved paper feed roller shaft 131. Paper feed roller shaft 131
Is rotatably supported by a side frame (not shown) of the printer main body 200 via a bearing.
The sheet is rotationally driven at the time of sheet feeding by a drive mechanism (not shown).

As shown in FIG. 5, the paper feeder 300
Drive motor 310 and metal intermediate gear (reduction gear) 3
20 and a paper feed gear 321 made of a sintered metal gear
, A paper feed roller 330 made of rubber, and first and second pressing rollers 351 and 352.

As the drive motor 310, a step motor that makes one rotation with a predetermined pulse is used. The motor 310 is fixed to a side frame F of the printer main body 200, and a metal pinion 311 is fixed to an output shaft thereof.

The power of the motor 310 is
1 and the paper feed roller 3 via the gears 320 and 321.
30.

The paper feed roller 330 has a metal shaft 33.
1 is rotatably supported between the side frames F, F of the printer body 200, and one end 33 of the shaft 331.
2, the paper feed gear 321 is fixed by the fixing structure described above. In the figure, reference numeral 30 denotes a bush.

That is, the shaft 331 of the paper feed roller is
The paper feed gear 321 corresponds to the gear 20 shown in FIG.

The rotation accuracy of the paper feed roller 330, which is rotationally driven through the drive motor 310, the pinion 311, the gear 320, and the paper feed gear 321 as described above, is the closest to the ink jet head 410 described later in the paper feed direction. For example, the distance between the nozzles is (1/7
20) The paper can be fed with a paper feed amount with the inch being the minimum feed unit. In FIG. 5, 33
Reference numeral 3 denotes a cap that covers one end of the shaft 331.

As shown in FIG. 4, the first and second pressing rollers 351 and 352 are provided on a paper feed guide 350 provided along the paper feed roller 330, and the paper is pressed by urging means (not shown). Each of them is pressed against the feed roller 330.

The paper sent from the paper feeding device 100 is brought into close contact with the paper feed roller 330 by the pressing of the first and second pressing rollers 351 and 352, and is conveyed with a conveying force.

Reference numeral 340 denotes a pressing roller provided at the most downstream position in the sheet feeding direction. The pressing roller 340 presses the sheet against the sheet feeding roller 330 by an urging means (not shown), and presses the sheet wound around the sheet feeding roller 330 and conveyed. A feed angle for sending the ink jet heads 410 and 420 described below downward is defined.

In this embodiment, the pressing roller 340
After the trailing edge of the paper (not shown) has passed through the pressing portion 340a between the paper feed roller 330 and the paper feed roller 330, the printing by the inkjet heads 410 and 420 is not performed.

According to the paper feeding device 100 and the paper feeding device 300 as described above, the paper placed on the paper support 110 is fed by the pair of hoppers 120 at the time of paper feeding.
0, and is fed to the paper feeder 300 by the rotation of the paper feed roller 130. The paper fed to the paper feeder 300 is pressed and wound by the first and second pressing rollers 351 and 352, and is conveyed to the printing unit A with a feeding angle defined by the pressing rollers 340.

FIGS. 6A and 6B are plan views schematically showing the printing operation of the printer according to the present embodiment.

As shown in FIGS. 6A and 6B, the ink-jet head 410 for full-color printing and the ink-jet head 420 for monochrome printing are arranged in a direction perpendicular to the plane of FIG. The carriage 430 is moved in a direction perpendicular to the plane of FIG. 4 to move in the direction of the arrow X11 or X22 in FIGS. 6A and 6B.

The head 410 has nozzle rows NR, NB, NY composed of a plurality of nozzles n.
From the nozzle row NB, a blue ink drop from the nozzle row NB, and a yellow ink drop from the nozzle row NY. The symbol P1 in the figure indicates the nozzle arrays NR, N in one printing operation.
B and NY represent print areas to be printed.

The head 420 has a nozzle row N composed of a plurality of nozzles n, and can discharge black ink.

In the present embodiment, the distance Lp between the nozzles n, n of the head 410 that is closest in the paper feed direction Y is (1/720) inch. The paper feed roller 330 can feed the paper P by a paper feed amount with the distance Lp between the nozzles n, n being the minimum feed unit.

When monochrome printing is performed by the head 420, the motor 310 is rotated by a predetermined number of steps, whereby the paper feed roller 330 is rotated by an amount equal to the length L of the nozzle row N of the head 420. You. Then, printing is performed by the head 420 for each predetermined printing area P1.

When performing high-resolution full-color printing, the motor 310 is rotated by the required number of steps, and the distance Lp (1 / 720 inch) as the minimum feed unit, the paper feed roller 330 is rotated by an arbitrary feed amount, and three colors of ink are selectively ejected from the head 410 to perform full color printing. For example, as shown in FIG. 6B, after printing in the printing area P1, the motor 3 is moved by a predetermined number of steps (length L12).
10 is rotated to print the upper part of the next print area P2 over the lower part of the print area P1, thereby performing full-color printing. In this case, the printing area P12 is an area where printing is performed in an overlapping manner.

[0095] As shown in FIG.
The sheet P printed at 420 is transported by a pair of transport rollers 251,
52, the paper discharge tray 28 above the hopper 120 via the paper discharge roller 261
Drained above zero.

According to the printer of this embodiment, the shaft 331 of the paper feed roller 330 and the paper feed gear 321 are used.
Are fixed by the above-described fixed structure of the shaft and the gear, the following operation and effect can be obtained.

As described above, also in this printer, the trailing end of the paper has the paper feed roller 330 and the pressing roller 3
When the paper passes through the pinching portion 51 (or 352), a force is applied to the rear end of the paper in an attempt to repel the paper in the paper feeding direction. However, according to this printer, the shaft 331 of the paper feed roller and the paper feed gear 321 are firmly fixed. The shaft 331 of the paper feed roller 330 does not rotate more than the rotation amount of the gear 321 due to the force F3, and the paper feed roller 330 rotates more than the paper feed amount originally intended to be fed. Is prevented.

Therefore, when the trailing end of the sheet passes through the above-described pressure section, the pitch of the sheet feed amount does not shift, and the effect that the white streaks hardly appear on the printing surface can be obtained.

According to the printer of the present embodiment,
An ink-jet head 410 capable of performing color printing, and a paper feed for feeding the paper P by a paper feed amount having a minimum feed unit of a distance Lp between nozzles n, n of the head 410 which is closest in the paper feed direction Y. Roller 33
Since 0 is provided, the following operation and effect can be obtained.

That is, when trying to obtain full-color printing by ejecting inks of different colors from each nozzle row,
Printing is performed by overlapping the printing areas. However, according to the printer of the present embodiment, the desired paper feeding accuracy can be obtained, so that the printing areas can be accurately overlapped, and White streaks are less likely to appear on the screen. Therefore, a high quality color image can be obtained.

When a thick coated paper or the like is used to obtain full-color printing, when the trailing edge of the paper passes through the pinching portion, the trailing edge of the paper is flipped in the paper feeding direction. Although the force to be applied tends to be larger than that of plain paper, the printer of the present embodiment prevents the paper feed roller 330 from rotating more than the desired paper feed amount. Therefore, white streaks hardly appear even in full-color printing using thick coated paper, and a high-quality image can be obtained.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and can be appropriately modified and implemented within the scope of the present invention.

For example, the bush 30 does not necessarily have to have the flange 32.

The biting portions 36 need not always be formed. The portions 36, 36 may be chamfered.

The invention described in claim 4 is not limited to a printer having the above-described ink jet type head, but can be applied to other types of printers, such as a thermal transfer printer and a laser printer.

[0106]

According to any one of the first to third aspects of the present invention, the shaft and the gear are fixed firmly and the concentricity between the shaft and the gear is not impaired. The effect is obtained.

Further, according to the fixing structure of the shaft and the gear according to the second aspect, the effect that the shaft and the gear are more firmly fixed can be obtained.

According to the fixed structure of the shaft and the gear according to the third aspect, it is easy to press-fit the cylindrical portion of the bush, the deformation of the cylindrical portion is performed favorably, and the flange portion and the cylindrical shape are formed. Inconveniences such as stress concentration at the boundary with the part and breakage from here are prevented.

In any of the printers according to the fourth and fifth aspects, the effect that the shaft of the paper feed roller does not rotate more than the amount of rotation of the gear is eliminated, and that the white streaks hardly appear on the printing surface. can get.

[0110]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a fixing structure of a shaft and a gear according to the present invention, wherein (a) is a view showing a state after fixing,
(B) is a diagram in which the shaft before fixing is omitted.

FIGS. 2A and 2B are views showing a bush, wherein FIG. 2A is a partially cutaway front view, and FIG.

FIGS. 3A and 3B are explanatory diagrams of an operation.

FIG. 4 is a partially omitted side view showing an embodiment of the printer according to the present invention.

FIG. 5 is a partially omitted plan view showing the paper feeding device.

FIGS. 6A and 6B are plan views schematically showing a printing operation.

FIG. 7 is a schematic side view showing a paper feeding mechanism of a conventional printer.

FIG. 8 is a perspective view showing an end portion of a paper feed roller and a gear.

FIGS. 9A and 9B are explanatory diagrams of a conventional technique.

FIG. 10 is an explanatory diagram of a conventional technique.

FIG. 11 is a plan view schematically showing a printing operation.

FIG. 12 is a plan view schematically showing a printing operation.

FIG. 13 is an enlarged schematic plan view of a main part of a head.

[Explanation of symbols]

 Reference Signs List 10 shaft 11 outer peripheral surface 20 gear 21 hole 22 inner peripheral surface 30 bush 31 cylindrical portion 32 flange portion 33 outer peripheral surface 34 ring-shaped groove 35 facing end portion 36 biting portion S slit 321 paper feed gear 330 paper feed roller 331 shaft 351 First pressure roller 352 Second pressure roller 410 Inkjet head

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F16H 55/17 B41J 3/04 101A 57/02 521 104D

Claims (5)

[Claims] 1. A gear having a shaft, a gear having a hole into which the shaft is inserted, and a bush having a cylindrical portion press-fit between an inner peripheral surface of the hole of the gear and an outer peripheral surface of the shaft. The inner peripheral surface of the hole of the gear and the outer peripheral surface of the cylindrical portion are tapered in the same direction, and the cylindrical portion is formed with a slit in the axial direction. The fixed structure between the shaft and the gear. 2. The shaft according to claim 1, wherein a biting portion that bites into the shaft as the bush is press-fitted is formed at a facing end portion forming the slit of the bush. Fixed structure with gears. 3. The bush has a flange formed integrally with the tubular portion, and a ring-shaped groove is formed at a boundary between the flange and the tubular portion. 3. The structure according to claim 1, wherein the slit is formed over the cylindrical portion and the flange portion. 4. A paper feed roller for feeding paper, a pressure contact roller pressed against the paper feed roller and pressing the paper against the paper feed roller, a printing means for printing on the paper sent by the paper feed roller, A gear fixed to the shaft of the paper feed roller, wherein the shaft of the paper feed roller and the gear are fixed by the shaft and gear fixed structure according to claim 1, 2, or 3. Characterized printer. 5. The ink jet head according to claim 1, wherein the printing unit includes a plurality of nozzle rows that discharge inks of different colors, and performs an ink jet from each of the nozzle rows to perform color printing. 5. The printer according to claim 4, wherein the roller feeds the paper at a paper feed amount with a distance between nozzles closest to each other in the paper feed direction of the inkjet head as a minimum feed unit.