JPH079718A - Printer - Google Patents

Abstract

PURPOSE:To make the superimposing accuracy of respective colors higher in a printer, in which colored image is obtained by superimposing a plurality of colors. CONSTITUTION:In a heat transfer color printer having the constitution, in which the printings of respective colors are performed by reciprocating recording paper P under the condition that ink film IF and the recording paper P are pinched between a platen 1 and a thermal head 2 and, at the same time, the recording paper P is delivered by being pinched between a pair of paper delivery rollers 18a and 18b when the recording paper P arrives near the final line of printing, the peripheral speeds of a pair of the paper delivery rollers 18a and 18b are set to be slightly smaller than that of the platen 1 and, at the same time, the urging forces of a pair of the paper delivery rollers 18a and 18b are controlled in relation to those of pinch rollers 3a and 3b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer type color printer used for outputting a computer graphic image and the like, and more particularly to a recording paper conveying mechanism having a high positional accuracy for superimposing a plurality of colors. It is a thing.

[0002]

2. Description of the Related Art In a conventional sublimation type full color printer,
The ink film and the recording paper were sandwiched between the thermal head and the platen, and one screen of each color was recorded. Then, when the image recording of all colors is completed, the recording paper is conveyed by the pair of paper ejection rollers and ejected out of the printer. In general,
The recording paper is held between the platen and the thermal head near the final line in image recording of each color, and the vicinity of the leading end of the recording paper is also held by the paper discharge roller pair.

[0003]

However, if the peripheral speed of the platen and the peripheral speed of the paper discharge roller do not match, the platen and the pair of paper discharge rollers cannot balance the transport speed of the recording paper, and the recording paper cannot be conveyed. There is a problem in that the accuracy of color superposition is deteriorated because the processing is not performed uniformly. Therefore, an object of the present invention is to improve the overlay accuracy when recording images on recording paper.

[0004]

In order to achieve the above object, the present invention will be described with reference to the structure shown in FIG. 1. The force F1 by which n roller members 3a and 3b press the recording paper P against each other.
In relation to the friction coefficient μ1 between the platen 1 and the recording paper P, the force F2 with which the discharge roller means 18a and 18b press the recording paper P, and the friction coefficient μ2 with the discharge roller means 18a and 18b, nμ1F1 is larger than μ2F2. Was configured to always grow.

In order to achieve the above object, the present invention is further configured so that the peripheral speed of the paper discharge roller means 18a, 18b is 1 to 3% lower than the peripheral speed of the platen 1.

[0006]

Since the present invention has the above-described structure, when the platen 1 rotates in the direction of arrow A (clockwise direction) in FIG. 1 to convey the recording paper during the printing operation, the recording paper P simultaneously ejects the recording paper P. Even if it is held by the means 18a, 18b, the pressure contact force of the paper discharge roller means 18a, 18b is properly regulated with respect to the pressure contact force of the platen 1, so that the recording paper is conveyed to the thermal head for image recording. The opposing platen 1 is predominantly controlled, and the influence of the rotation of the paper discharge roller units 18a and 18b upon image recording is reduced.

Furthermore, since the peripheral speed of the paper discharge roller means 18a, 18b is 1 to 3% lower than the peripheral speed of the platen 1, the influence of the rotation of the paper discharge roller means 18a, 18b upon image recording is further reduced. .

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing a state in which a thermal head 2, an ink film IF and an ink film mechanism are removed from the embodiment for the purpose of explanation, and FIG. 3 is an embodiment. It is a figure which shows the state which removed the rollers 20a and 20b from FIG. The configuration and operation of this embodiment will be described with reference to FIGS. 1, 2 and 3.

First, a description will be given with reference to FIG. The recording paper P is conveyed from a paper supply unit (not shown), and elliptical cams 7a and 7b driven by a motor (not shown) rotate. The arms 4a-4b, 4c-4d urged by the springs 6a, 6b in association with the rotation of the cams 7a, 7b have shafts 5a, 5b, 5c,
The arm 4a-4b, 4c-4 rotates around 5d.
The pinch rollers 3a and 3b rotatably supported by d contact the platen 1. The arms 4a-4b, 4c-4d incorporate a tension adjusting mechanism for adjusting the tension of the springs 6a, 6b so that the pressure contact force between the pinch rollers 3a, 3b and the platen 1 becomes uniform. This recording paper P is platen 1
The pinching rollers 3a and 3b hold the recording paper P in a straight line by a uniform pressure contact force without causing skew or the like.

When the recording paper P reaches near the upstream side of the pinch roller 3a, the front end of the recording paper P is detected by a first front end detection sensor (not shown), and based on this detection signal, the thermal head 2 drives a thermal head drive mechanism (not shown). It is driven by and comes into pressure contact with the platen 1. A position detection sensor for the thermal head 2 is incorporated in the thermal head drive mechanism, and it is configured to detect whether the thermal head 2 is in a pressure contact state or a separated state. The ink film IF is, as shown in FIG.
2 and the ink film supply unit 9 are provided.

When the platen 1 rotates in the direction of arrow A, the recording paper P is held between the platen 1 and the pinch roller 3a, and the recording paper P is further wound around the platen 1 by further rotation in the direction of arrow A. On the other hand, the ink film IF resists the tension applied from the ink film supply unit 9 and is wound by the ink film winding unit 12 in synchronization with the rotation of the platen 1 in the arrow A direction. By the above operation, the recording paper P and the ink film IF are separated from each other by the platen 1 and the thermal head 2.
Be held by and.

When the recording paper P reaches a second front end detection sensor (not shown) installed on the downstream side of the pinch roller 3b,
The heating elements of the thermal head 2 are selectively heated based on image information output from a control device (not shown) to transfer the dye of the ink film IF onto the recording paper P. During printing, the ink film IF moves at a constant speed according to the peripheral speed of the platen 1 due to the internal slip of the torque limiter 11 provided in the ink film supply unit 9, and the torque limiter 11 applies a substantially constant tension to the ink film IF. . Further, in the ink film take-up unit 12, when the gear 16 is driven in the direction of the arrow M by the motor 17, the power thereof is transmitted to the ink film take-up shaft 14 via the gear 15 and the torque limiter 13, and the ink film take-up shaft 14 is moved. The ink film IF is wound up by rotating in the arrow W direction. At this time, the speed at which the gear 15 is about to be wound up by the action of the torque limiter 13 and the platen 1
And ink film IF held between the thermal head 2 and
It is possible to synchronize the difference in the moving speed between the and, and the tension at the time of winding is governed by the specified torque value of the torque limiter 13. Such an ink film winding unit 1
The ink film IF is wound up at the same peripheral speed of the platen 1, that is, the moving speed at which the recording paper P is conveyed, by the cooperation of 2 and the ink film supply unit 9, and the ink film IF is supplied to each of the ink film supply side and the take-up side. Since a substantially constant tension is applied to the ink film IF by the torque limiters 11 and 13, the ink film IF is always wound up with the tension applied, and the occurrence of wrinkles is suppressed.

The transfer operation as described above is performed over a predetermined number of lines to complete the image of the first color for one screen. When the printing is near the final line, the leading edge of the recording paper P is clamped by the paper discharge roller pair 18a, 18b. Weights 19a and 19b coaxial with the paper discharge roller 18b are provided.
A roller 20a coaxial with the platen 1 and a discharge roller pair 18
Rollers 20b coaxial with a and 18b are connected with a belt 21, and the rotational speeds of the two have a predetermined relationship described later.

When the printing of the final line is completed, the thermal head 2 is separated from the platen 1. In this separated state, the platen 1 is rotated in the direction of arrow B (counterclockwise) to rewind the recording paper P and the ink film IF, and the ink film detection sensor (not shown) sets the print start position for the second color. . After the recording paper P is detected by the second leading edge detection sensor (not shown), the platen 1 is fed for a predetermined number of lines and then the driving of the platen 1 in the direction of the arrow B is stopped. When the recording paper P is rewound, the recording paper P is held only by the platen and the pinch rollers 3a, 3b facing the platen, but the registration rollers 8a, 8b arranged at both ends of the platen 1 do not. The surface is formed with minute irregularities, and when viewed microscopically, the recording paper P and the registration rollers 8a and 8b are mechanically meshed with each other, and slippage does not easily occur. Reserved.

After the thermal head 2 is brought into pressure contact with the platen 1, the platen 1 is driven in the direction of arrow A and the recording paper P reaches a second leading edge detection sensor (not shown). The heating element of the thermal head 2 is selectively caused to generate heat on the basis of the image information output from the control device to print the second color. After the above-described printing is performed for a predetermined number of colors to form a color image on the recording paper P, the recording paper P is conveyed and discharged by the paper discharge roller pair 18a and 18b.

The force applied to the recording paper P of this printer is schematically shown in FIGS. FIG. 4 is a view during printing in which the thermal head 2 is in pressure contact, and FIG. 5 shows a state in which the thermal head 2 is separated and the recording paper P is rewound.
These operations are performed such that the pressure contact force of the thermal head 2 with respect to the platen 1 is F, the pressure contact force of the pinch rollers 3a and 3b with respect to the platen 1 is F ₁ , the pressure contact force of the discharge roller pairs 18a and 18b is F ₂ , and the tension for winding up the ink film IF. T,
The friction coefficient between the recording paper P and the platen 1 is μ ₁ , and the friction coefficient between the recording paper P and the discharge rollers 18 a and 18 b is μ ₂ .

When the thermal head 2 in the state of printing on the recording paper P is in pressure contact with the platen 1 (see FIG. 4).
Corresponding to the frictional force generated on the recording paper P at the platen 1 portion and the frictional force generated on the recording paper P at the paper discharge roller pairs 18a and 18b, the pressure contact force F of the thermal head 2 is considerably large.

[0018]

[Equation 1] μ ₁ F +2 μ ₁ F ₁ >> μ ₂ F ₂ , and the frictional force in the platen 1 part becomes considerably larger, and the conveyance in this part predominantly works. Therefore, near the final print line, the recording paper P is ejected by the paper ejection roller pair 18a,
Even if the sheet is held by 18b, the conveyance force of the platen 1 becomes dominant, so that the pair of discharge rollers 18a and 18b has little influence on the conveyance.

On the other hand, when the thermal head 2 which is in the state of rewinding the recording paper P is separated from the platen 1 (corresponding to FIG. 5), the frictional force generated on the recording paper P at the platen 1 portion and the discharge roller pair. The relationship with the frictional force generated on the recording paper P by 18a and 18b can be classified as follows.

[0020]

2 μ ₁ F ₁ <μ ₂ F _{2 In the case of the} above formula 2, the force of conveying the recording paper P by sandwiching the platen 1 and the pinch rollers 3a and 3b is the force of conveying the recording paper P to the paper discharge roller pair 18a. , 18b, which is smaller than the force for carrying the paper by holding it between the paper P and the paper discharge roller pair 18a, 1b.
Controlled by 8b transport. At the time of printing, the recording paper P was dominated by the platen 1 part, whereas when the recording paper P was rewound, the conveyance of the paper discharge roller pair 18a, 18b was dominated and the carrying state was changed. Therefore, the alignment accuracy deteriorates.

[0021]

2 μ ₁ F ₁ ≈μ ₂ F _{2 In the case of the} above expression 3, the force for transporting the recording paper P by the platen 1 and the pinch rollers 3a, 3b and the recording paper P by the pair of discharge rollers 18a, 18b. Since the force of conveyance is substantially equal to each other, the factors governing the conveyance of the paper P are likely to be uncertain. When the recording paper P is rewound, the roller that mainly conveys the recording paper P cannot be specified, so that the conveyance is not performed stably,
Skew and the like occur and the alignment accuracy deteriorates.

[0022]

2 μ ₁ F ₁ > μ ₂ F _{2 In the case of the} above formula 4, the force for transporting the recording paper P by the platen 1 and the pinch rollers 3 a and 3 b is the recording paper P.
The recording paper P is governed by the conveyance of the platen 1 because the recording paper P is larger than the force for conveying the recording paper P by the pair of paper discharge rollers 18a and 18b. Therefore, the carrying force by the pinching of the platen 1 and the pinch rollers 3a, 3b becomes more dominant than the carrying force by the nipping of the discharge rollers 18a, 18b.
Since the influence of 18b is small, the recording paper P is rewound without being influenced by the pair of discharge rollers 18a and 18b, and the alignment accuracy of each color is kept high.

From the above, the relationship between the frictional force generated on the recording paper by the platen and the frictional force generated on the recording paper P by the paper discharge roller is as follows, where n is the number of pinch rollers.

[0024]

For Equation 5] _{nμ 1 F 1> μ 2 F} 2 and made it is unwinding of stably recording sheet P can be performed, it can be expected to maintain a high alignment accuracy of each color. The weights 19a and 19b urge the driven-side paper discharge roller 18b against the drive-side paper discharge roller 18a so as to satisfy the above mathematical expression 5. The urging means is not limited to the weight, but may be performed by a spring, its own weight, or the like. In the case of urging by the weight, its own weight, or the like, the driven-side paper discharge roller 18b and the drive-side paper discharge roller 18a are mutually urged. It is advisable to place the center of the with a slight offset from the vertical direction.

Further, in the present embodiment, the diameters of the rollers 20a and 20b are set so that the peripheral speed of the drive side discharge roller pair 18a is lower than the peripheral speed of the platen 1 by about 1 to 3%. The rollers 20a and 2 are used to reduce the peripheral speed.
0b is connected with a toothed belt and the reduction ratio is 100: 99-
It is set to be 100: 97. The platen 1 and the discharge roller 18a on the drive side are driven by independent motors to control the respective rotation speeds and reduce the peripheral speed reduction ratio to 10.
A drive system having a control unit such as 0:99 to 100: 97 may be provided.

As described above, when the ratio of the peripheral speeds of the platen 1 and the discharge roller 18a on the driving side is set, the printing is near the final line, and the recording paper P is the discharge roller pair 18a.
When the recording paper P is clamped by 18b, the conveyance of the leading end of the recording paper P becomes slower, but the recording paper P bends in the path to absorb the difference in peripheral speed. This reduction ratio is 100: 97
When it becomes smaller, the bending of the recording paper becomes larger in the path and the paper jam easily occurs. In addition, the pair of discharge rollers 18
When the speeds of the a and 18b sides are increased, the drive side discharge roller 18a rubs the back surface of the recording paper P during printing.
Defects are more likely to occur.

In the initial stage of rewinding the recording paper P, the vicinity of the leading end of the recording paper P is clamped by the pair of discharge rollers 18a and 18b, but the bending of the recording paper P caused during the printing of the first color. Or the transport force of the pair of paper discharge rollers 18a and 18b is smaller than the transport force of the platen 1 as described above, and therefore slippage occurs on the drive side paper discharge roller 18a. And the rewinding speed of the pinch rollers 3a, 3b. Drive side ejection roller 1
Even when slippage occurs at 8a, the driven-side discharge roller 18b
Since it rolls on the surface of the recording paper P, no slippage occurs here, so that the image surface is not rubbed and the image quality is not affected.

Therefore, even if the vicinity of the leading edge of the recording paper P is pinched by the paper discharge roller pair 18a, 18b, the conveyance of the recording paper P by the platen 1 and the pinch rollers 3a, 3b at the time of rewinding is not obstructed, and recording is performed. The positional accuracy of the paper P is kept high, and the accuracy of superimposing each color can be improved.

[0029]

As described above, according to the present invention, since the platen is more dominant in the conveyance of the paper than the paper discharge roller, the accuracy of the superposition when the plural colors are superposed and printed. The effect that is improved is obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of the present invention.

FIG. 2 is a perspective view in which a thermal head, an ink film, and an ink film mechanism section are removed from the diagram showing the configuration of the present invention.

FIG. 3 is a perspective view in which a roller and a belt are removed from FIG.

FIG. 4 is a schematic diagram of a force applied when the thermal head is in pressure contact.

FIG. 5 is a schematic diagram of a force applied when the thermal head is separated.

[Explanation of symbols]

 1 Platen 2 Thermal Head 3a, 3b Pinch Roller 11, 13 Torque Limiter 18a, 18b Paper Ejection Roller P Recording Paper IF Ink Film

Claims (2)

[Claims] 1. An ink film coated in a plurality of color segments, and the ink film and recording paper are sandwiched between a thermal head and a platen, and a heating element of the thermal head is heated to form an image on the recording paper. In the printer, n roller members for pressing the recording paper against the platen, paper discharge roller means for discharging the recording paper on which an image is formed to the outside of the printer main body, and n roller members for conveying the recording paper. Is a force F ₁ for pressing the recording paper and a frictional force n μ ₁ F ₁ due to a friction coefficient μ ₁ between the platen and the recording paper, and a force F ₂ for the discharging roller means to press the recording paper and the discharging roller means for recording. Friction force due to friction coefficient with paper μ ₂ μ ₂ F ₂
A printer characterized in that it is configured to always have a larger value than that. 2. The printer according to claim 1, wherein the peripheral speed of the discharge roller means is set to be 1 to 3% lower than the peripheral speed of the platen.