JPH0671305B2 - Color thermal printer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color thermal printer. More specifically, the paper sandwiched between a platen roller and a thermal head is moved forward together with an ink ribbon, and then the paper. The present invention relates to a color thermal printer that forms a color image by performing an operation of returning only a plurality of times.

<Prior Art> Conventionally, as a color thermal printer, a timing belt is used to transmit a rotational force from a main motor pulley to a platen pulley, and a paper sandwiched between a platen roller and a thermal head is fixed together with an ink ribbon. It is generally adopted that a color image is formed on a sheet by performing a plurality of operations of moving the sheet backward by a distance and then returning only the sheet by a distance equal to the forward distance.

That is, the rotational force is transmitted from the main motor pulley to the platen pulley by using a timing belt that does not cause slip, and the rotation amount of the main motor pulley is accurately controlled to rotate the platen roller. The amount is controlled to match the transfer areas of the ink ribbons of the respective colors onto the paper.

<Problems to be Solved by the Invention> In the above-described conventional color thermal printer, the main motor pulley and the platen pulley are connected by a timing belt that does not cause a slip. The pulley frequently rotates forward and backward, and the amount of forward and reverse rotation of the platen pulley that accompanies it cannot exactly match the amount of forward and reverse rotation of the main motor pulley. However, there is a problem that the quality of the product deteriorates.

To explain this problem in detail, the timing belt (40) suspended between the main motor pulley (38) and the platen pulley (39) is
With the change in the rotation direction of 8),
As shown in the figure, the tension side and the bending side occur alternately.

When the tension direction and the flexion side are alternately generated, the rotation amount of the main motor pulley (38) is used to tension the flexion side when the rotation direction changes, and the main motor pulley (38) is used. The rotation amount of the platen pulley (39) is smaller than the rotation amount of. Therefore, even if the amount of rotation of the main motor pulley (38) is accurately controlled,
As a result, the amount of rotation of the platen pulley (39) cannot always be accurately controlled.

For example, assuming that the shaft distance between both pulleys (38) and (39) is 74.14 mm, and the number of teeth on the timing belt (40) is 106, it will occur when the flex side moves to the tension side. The displacement of the pulleys (38) (39) is about 0.1 mm. Considering the operation for forming a color image over a length of 100 mm under these set conditions, when first performing thermal transfer from a yellow (hereinafter abbreviated as Y) ink ribbon, Since the sheet conveyed in the state shown in FIG. 1 is further conveyed by 100 mm, the conveying distance is exactly 100 mm. Then, when reciprocating by 100 mm, the above-mentioned deviation acts and only 99.9 mm is actually recoiled. After that, in order to perform thermal transfer from magenta (hereinafter abbreviated as M) and cyan (hereinafter abbreviated as C) ink ribbons, a state in which the ink ribbons are conveyed and a state in which only the paper is moved back are performed. However, since the transport distance and the return distance are 99.9 mm in each case, only the Y transfer portion is 0.1 mm on the leading edge side of the color image, as shown in FIG.
It will be in a shifted state.

Although the ratio of the deviation to the entire color image obtained is very small, it cannot be neglected in terms of color image quality.

<Objects of the Invention> The present invention has been made in view of the above problems,
An object of the present invention is to provide a color thermal printer capable of completely eliminating the deviation of the thermal transfer area from the ink ribbon of each color.

<Means for Solving Problems> In order to achieve the above-mentioned object, the color thermal printer of the present invention forms a color image by the moving distance by the rotation of the main motor pulley when the first color thermal transfer is performed. This is the distance required for forming the color image because the return movement of only the paper for printing the second and subsequent colors and the movement distance due to the rotation of the main motor pulley when the paper and the ink ribbon are moved forward are formed. Is set to a predetermined distance larger than that required for printing the second color and thereafter, the main motor pulley is rotated by the difference between the predetermined distance and the distance required for image formation to move the paper and the ink ribbon forward. The printing is started from.

<Operation> In the color thermal printer having the above configuration, the timing belt is used to transmit the rotational force from the main motor pulley to the platen pulley, and the paper sandwiched between the platen roller and the thermal head is used together with the ink ribbon. First, after moving forward for a predetermined distance, only the paper is returned, and then
When a color image is formed on the paper by performing the forward movement of the paper and the ink ribbon a plurality of times, the moving distance due to the rotation of the main motor pulley when the thermal transfer of the first color is performed forms the color image. This is the distance required for forming the color image because the return movement of only the paper for printing the second and subsequent colors and the movement distance due to the rotation of the main motor pulley when the paper and the ink ribbon are moved forward are formed. Is set to a predetermined distance larger than the required distance, and when printing the second and subsequent colors, the main motor pulley is rotated by the difference between the predetermined distance and the distance required for image formation to move the paper and ink ribbon forward. Since the printing is started after that, it occurs when the bending side shifts to the tension side when changing the rotation direction of the main motor pulley. The displacement of the pulley can be absorbed by a distance greater than the distance required for color image formation, to match the thermal transfer region from the color ink ribbon.

<Example> Hereinafter, detailed description will be given with reference to the accompanying drawings illustrating an example.

FIG. 5 is a perspective view of a color thermal printer. The printer body is composed of an upper frame (1) and a lower frame (2), and at a predetermined position of the upper frame (1),
A paper feed cassette (3), a bypass bypass (4), and a discharge tray (5) are installed. The paper feed cassette (3) can be taken out in order to change the paper size.

FIG. 4 is a schematic view for explaining the internal mechanism of the color thermal printer, in which the paper transport section (6) is attached to a predetermined position of the upper frame (1) and the predetermined position of the lower frame (2). An ink ribbon cartridge (7), a thermal head (8), and a thermal head support portion (9) are attached to the.

The paper transport unit (6) includes paper feed rollers (10a) (10b), paper feed paths (11a) (11b), registration rollers (12), paper feed path (13), paper feed path switching plate (14). , Platen roller (15),
The pinch roller (16), the discharge roller (17), the reverse feed roller (18), and the reverse feed path (19).

By adopting the above configuration, the sheet feeding roller (10a) or the sheet feeding roller (10b) is selectively rotated to drive the sheet feeding cassette (3) or the bypass bypass (4). Feed the paper (P) into the paper feed path (11
The sheet (P) is conveyed through a) or the sheet feeding path (11b), and the leading end of the sheet is brought into contact with the registration roller (12) in the stopped state, thereby correcting the oblique feeding.

After that, the registration roller (12) is rotationally driven at a predetermined timing so as to pass between the platen roller (15) and the thermal head (8) through the paper feed path (13) and the paper feed path switching plate (14). Guide the paper (P), further convey the paper (P) as the platen roller (15) rotates, guide it to the pinch roller (16), and further convey the paper (P) to the discharge roller (17). You can

Further, when the paper (P) is moved back by a predetermined distance,
The platen roller (15) may be rotationally driven in the opposite direction, and the paper feed path switching plate (14) may be rotated upward.
The paper (P) returned by the platen roller (15) is guided to the reverse feed roller (18) through the paper feed path switching plate (14),
Further, it is guided to the reverse path (19).

By making the peripheral speed of the reverse feed roller (18) higher than the peripheral speed of the platen roller (15), the slack of the paper (P) at the time of reverse feed is prevented, and the resistance of a predetermined value or more is provided. The slip of the paper (P) is allowed when a force is applied.

Reference numeral (20) is a sensor for detecting the position, color and the like of the ink ribbon (25).

The above ink ribbon cartridge (7) has a lower case (2
1), an upper case (22), a feed shaft (23) rotatably housed at both ends of the lower case (21), and a winding shaft (2
4) and an ink ribbon (25) whose ends are wound around both shafts (23) and (24).
By transmitting the rotational force to the ink ribbon (2
5) so that it can be wound up. Incidentally, (26)
Is a winding assist roller, and (27), (28) and (29) are back tension rollers.

The ink ribbon (25) is formed by sequentially forming a Y area, an M area, and a C area for each predetermined length.

The thermal head (8) is entirely covered with a casing made of a material having a high light reflection coefficient such as aluminum, and the heat generating portion is pressed against the platen roller (15). An ink ribbon separating member (30) for guiding the ink ribbon (25) and the paper (P) and separating the two is attached on the downstream side in the paper transport direction.

The thermal head support portion (9) is provided on the upper surface of the fixing member (31) attached to the lower frame (2) at a predetermined position, and is an acrylide (trade name) as a thrust receiving member.
The first moving member (33), which moves in a substantially horizontal direction, is attached via the (32), and the first moving member (33) is placed in a predetermined position in a substantially vertical direction via the accuride (trade name) (34). A second moving member (35) which moves to the second moving member, a spring (not shown) which biases the second moving member (35) in a predetermined direction, and a second moving member (35). A solenoid (not shown) for releasing the urging force acting on is attached. Then, at a predetermined position of the second moving member (35) through the shaft (36) in the width direction (the platen roller (15)).
The thermal head mounting member (37) is mounted so as to be rotatable in the direction parallel to the shaft of the platen roller (15), and the grooved member (41) is provided at a predetermined position with a groove engageable with the shaft of the platen roller (15). Is installed.

By adopting the above configuration, the platen roller (1
By the movement of the first moving member (33) caused by the engagement of the shaft of 5) with the groove of the receiving member (41), the pressure contact position between the platen roller (15) and the thermal head (8) is accurately measured. It can be regulated, and by energizing the solenoid, an urging force of a spring acts to move the second moving member (35) to the platen roller side, and the thermal head (8) moves the platen roller (15). Can be pressed against.

The mechanism for transmitting the rotational force to the platen roller (15) is as shown in FIGS. 1 and 2, and is directly or indirectly connected to the output shaft of the main motor (not shown). The main motor pulley (38) and the platen pulley (39) connected to the shaft of the platen roller (15) are connected by the timing belt (40).

Therefore, when the rotation direction of the main motor pulley (38) changes, the tension side and the bending side of the timing belt (40) are switched, and due to this switching operation, both pulleys ( 38) There will be a deviation in the rotation amount of (39).

However, in the above-described embodiment, the driving amount of the platen pulley (39) by the main motor pulley (38) is actually set when the paper of the first color or later is moved back and when the paper of the second color or later and the ink ribbon are moved forward. Since the so-called blank feed is carried out before the start of printing for the second and subsequent colors, the thermal transfer of each color due to the above-mentioned deviation of the rotation amount is performed by setting the distance more than the distance required for forming a color image. A high quality color image can be obtained by preventing the displacement of the area.

A more specific description will be given.

However, in the following explanation, the deviation caused by the replacement of the tension side and the slack side of the timing belt (40) is 0.
Assuming 1 mm, color image formation length is assumed as 100 mm.

Under this assumption, when thermal transfer is initially performed from the Y ink ribbon (25), the paper (P) is transferred between the thermal head (8) and the platen roller (15) by moving the main motor pulley (38). If it is conveyed to the nip position and moved 100 mm with the main motor pulley (38) in the normal rotation state, the platen pulley (39) also moves 100 mm, and therefore the paper (P) Is moved 100 mm from the thermal transfer part.

After the thermal transfer from the Y ink ribbon (25), the main motor pulley (38) is reversed to move the paper (P) back. At this time, if the main motor pulley (38) is rotated so that the moving distance is 100 mm + α (assuming α = 5 mm), it costs 0.1 mm to stretch the slack side during forward rotation. Laura (1
The movement distance of 5) is 104.9 mm, so the paper (P)
The actual return distance of is 104.9 mm.

After that, when the paper (P) is conveyed for thermal transfer from the M ink ribbon, if the 5 mm main motor pulley (38) is first rotated (idle feed), the forward / reverse rotation is switched. The paper (P) does not advance by only mm, and at this time, the leading end of the paper (P) is aligned with the leading end of the paper (P) when printing the first color. Printing is performed while rotating, that is, moving the paper (P) by 100 mm.

When thermal transfer is performed from the C ink ribbon, the 105 mm main motor pulley (38) is first used as in the case of M printing.
Reverse to move the paper (P) back 104.9 mm, then feed the main motor pulley (38) 5 mm in advance before printing (paper (P) moves 4.9 mm), then perform printing while rotating 100 mm. .

By controlling the rotation of the main motor pulley (38) and the energization of the thermal head (8) as described above, it is possible to make all the Y, M, and C thermal transfer areas coincide with each other, as shown in FIG. It is possible to form a high quality color image.

However, the value of α is not limited to 5 mm,
It can be arbitrarily selected.

<Effects of the Invention> As described above, according to the present invention, the distance traveled by the rotation of the main motor pulley in the case of performing the first thermal transfer is the distance required to form a color image, and the printing distance for the second and subsequent colors is reduced. The moving distance due to the rotation of the main motor pulley when returning only the paper and moving the paper and the ink ribbon forward is set to a predetermined distance that is larger than the distance required to form a color image. When printing
With the simple control of rotating the main motor pulley by the difference between the predetermined distance and the distance required for image formation to move the paper and the ink ribbon forward and then starting printing, the thermal transfer areas of the respective colors are surely matched. It has a unique effect that a high quality color image can be obtained.

[Brief description of drawings]

FIGS. 1 and 2 are views showing changes in tension belt slack and slack state based on changes in rotational direction, FIG. 3 is a schematic view showing a relationship of thermal transfer areas of respective colors, and FIG. 4 is a color thermal printer. FIG. 5 is a schematic perspective view showing the internal mechanism of FIG. 5, FIG. 5 is an external perspective view, and FIG. (38) …… Main motor pulley, (39) …… Platen pulley, (40) …… Timing belt

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuji Abe 1-2-2, Tamatsukuri, Higashi-ku, Osaka City, Osaka Prefecture Mita Industrial Co., Ltd. No. Mita Industry Co., Ltd. (72) Inventor Hiroyuki Arima 1-2-2 Tamatsukuri, Higashi-ku, Osaka City, Osaka Prefecture Mita Industry Co., Ltd.

Claims (1)

[Claims] 1. A timing belt is used to transmit a rotational force from a main motor pulley to a platen pulley, and a sheet sandwiched between a platen roller and a thermal head is first moved forward together with an ink ribbon for a predetermined distance. In a color thermal printer that forms a color image on paper by performing multiple operations of moving the paper and ink ribbon forward after moving only the paper, the main motor pulley for thermal transfer of the first color. The rotation distance of the main motor pulley is the distance required to form a color image, and the backward movement of only the paper for printing the second and subsequent colors and the forward movement of the paper and the ink ribbon. Is set to a predetermined distance that is larger than the distance required to form a color image,
When printing the second color and thereafter, the main motor pulley is rotated by the difference between the predetermined distance and the distance required for image formation to move the paper and the ink ribbon forward, and then printing is started. .