JPH04235071A - Platen rotating mechanism in printer - Google Patents

Abstract

PURPOSE:To improve a power transmission efficiency by reducing a space for a gear speed reducer rotating a platen and reducing the number of reducing gears. CONSTITUTION:Inside a platen, an inner contact-type planetary gear consisting of an inner gear and an outer gear is formed. The rotation of a motor shaft is inputted to a planetary gear shaft. The planetary gear is eccentrically mounted so as to rotate about an input shaft and the planetary gear shaft. When the input shaft is connected to the motor shaft to be rotated, the planetary gear rotates on its axis while revolving around a sun gear having internal teeth. This rotation of the planetary gear is reduced. The reduced rotation is transmitted in the following manner: a pin is erected in the axial direction of the planetary gear; a flange is provided on the side of an output shaft opposedly to the planetary gear; a clearance hole is provided on the flange; the pin is inserted to the hole; the rotation is transmitted to the frange through the pin; and the output shaft is rotated. By fixing the output shaft, a platen roller is rotated.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer recording device that records information on recording paper using a thermal head and an ink sheet, and particularly relates to a platen rotation mechanism.

0002

[Background Art] In recent years, there has been an increasing demand for devices that can make color hard copies of images on display screens such as CRTs, and in particular, devices that are easy to maintain include color devices in which the three colors of yellow, magenta, and cyan are sequentially applied. There is a need for an apparatus that sequentially transfers and records onto recording paper using an ink sheet.

FIG. 5 shows, for example, Japanese Patent Application Laid-Open No. 61-123356.
1 is a schematic diagram showing a conventional printer device disclosed in the publication. In the figure, numeral 1 denotes a thermal head, which is pressed against the platen 2 via an ink sheet 5 and a recording paper 4. Two auxiliary rollers 3 are pressed against the platen 2. The ink sheet 5 is supplied from a supply reel 6 and wound onto a take-up reel 7. Here, the recording paper 4 and the ink sheet 5 stop rotating on the platen 2, and when the recording paper 4 reaches the heat generating position, the platen 2 stops rotating and the conveyance of the recording paper 4 also stops. During this time, the ink sheet 5 is wound up by the take-up reel 7, and stops when the second color reaches the heat generating position of the thermal head 1. Thereafter, the thermal head 1 is again pressed against the platen 2, resulting in the state shown in FIG. 5, and recording of the second color, for example magenta, is performed. In this way, recording is performed sequentially up to the third color, cyan.
A color hard copy is obtained by subtractive color mixing of yellow, magenta, and cyan. Here, the rotation speed of the platen 2 is approximately 5 RPM. The rotation speed of motor 8 is 2000~
Since it is 3000 RPM, 1/400 to 1/600
deceleration is required. Therefore, as shown in FIG. 6, many gears are combined in multiple stages to obtain the required reduction ratio.

0004

[Problems to be Solved by the Invention] Since the conventional platen rotation mechanism is constructed as described above, in order to obtain a large reduction ratio, the gears must be provided in multiple stages, which requires a large amount of space and the equipment is complicated. There was a problem with increasing the size. Furthermore, if a gear train like the one shown in Fig. 6 is used, the maximum speed reduction ratio in one gear stage is about 1/8. For example, 1/400
In order to obtain a reduction ratio of , five stages of gears are required, and conventional systems had to have multiple stages, which resulted in problems such as poor power transmission efficiency.

The present invention was made to solve the above-mentioned problems, and it is possible to obtain a large reduction ratio without using a multi-stage gear train. An object of the present invention is to obtain a platen rotation mechanism for a printing device that can be decelerated without any intervention.

[0006]

[Means for Solving the Problems] The platen rotation mechanism of the printing device according to the present invention forms an internal planetary gear mechanism inside the platen, inputs the rotation of the motor to the input shaft side, and inputs the rotation of the motor to the output shaft side. It is fixed so that it does not rotate, and the platen roller is driven to rotate.

[0007]

[Operation] Since the platen rotation mechanism of the printing apparatus according to the present invention is reduced in speed by a planetary gear mechanism, a large reduction ratio can be obtained with a small number of gears. Furthermore, since the planetary gear mechanism is housed inside the platen, there is no need to interpose a gear train between the motor and the platen.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below with reference to the drawings. Figure 1
1 is a cross-sectional view showing a platen rotation mechanism of a printing device according to an embodiment of the present invention. In the figure, 2 represents the entire platen, 201 is a metal core of the platen, 202 is rubber on the outer periphery, 203 is a bearing, and 11 12 is a sun gear with cut internal teeth attached to the inner periphery of the metal core 201, and 12 is a planetary gear that meshes with the sun gear 11. The sun gear 11 and the planetary gear 12 constitute an internal planetary gear mechanism. There is. 12a is a pin installed on the planetary gear 12, 13 is an input shaft, 14 is an input bearing, 15 is an output shaft, and 16 is a substrate that supports the entire platen.

Next, the operation will be explained. In the above embodiment, the sun gear 11 attached to the metal core 201 of the platen 2 has internal teeth cut as shown in FIG. Further, the planetary gear 12 is a gear having external teeth cut as shown in FIG. 3, and has a pin 12a set up in the axial direction. The sun gear 11 and the planetary gears 12 constitute an internal planetary gear mechanism. The planetary gear 12 connects to the input shaft 1 via an input bearing 14.
However, the portion where the input shaft 13 fits into the input bearing 14 is eccentric as shown in FIG. Input shaft 13
One end is rotatably supported by a bearing 203, and the other end is rotatably supported by one end of the output shaft 15. The input shaft 13 is connected to the output shaft 8a of the motor 8, and rotation is input thereto. When the input shaft 13 rotates, the planetary gear 12 revolves around the sun gear 11 at the same rotation speed as the input shaft 13 and simultaneously rotates at a low speed. This rotational speed becomes the reduced rotational speed, and the reduction ratio becomes ω2 /ω1 = 1-S/P according to the theory of planetary gears. Here, ω1: input rotation speed, ω2: rotation speed of planetary gear,
S: number of sun gear teeth, P: number of planetary gear teeth. here,
As a structure for extracting the rotation of the planetary gear 12, a pin 12a is installed in the planetary gear 12 as shown in FIG.
As shown in the figure, the output shaft 15 is provided with a flange portion 15a, a hole 15b is provided therein, and the pin 12a is inserted into the hole 15b.
Put it in. The hole 15b is sufficiently larger than the pin 12a, and its amount is about the eccentricity of the input shaft 13. With this structure, the rotation of the planetary gear 12 is directed to the output shaft 15,
The signal is transmitted via pin 12a and hole 15b. The rotational speed of the output shaft is a reduced rotational speed. Here, output shaft 1
If the tip of the sun gear 11 is fixed by, for example, a substrate 16 to prevent it from rotating, the sun gear 11 rotates, the core metal 201 integrated therewith rotates, and the platen 2 is rotationally driven.

0010

As described above, according to the present invention, the gear train for rotationally driving the platen is built into the platen, so there is no need to interpose a speed reduction mechanism between the motor and the platen, and the device becomes compact. become. Furthermore, since a planetary gear mechanism is incorporated as a reduction mechanism, a large reduction ratio can be obtained with a small number of gears, and a high power transmission efficiency can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a platen rotation mechanism of a printing device according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a sun gear of the platen rotation mechanism of the printing apparatus according to the present invention.

FIG. 3 is a perspective view showing a planetary gear of the platen rotation mechanism of the printing device according to the present invention.

FIG. 4 is a perspective view showing an output shaft provided with a flange portion of the platen rotation mechanism of the printing device according to the present invention.

FIG. 5 is a schematic diagram showing a conventional printer device.

FIG. 6 is a perspective view showing an example of a conventional platen rotation mechanism.

[Explanation of symbols]

1 Platen 201 Core metal 202 Rubber 203 Bearing 11 Sun gear 12 Planetary gear 12a pin 13 Input shaft 14 Input bearing 15 Output shaft 16 Board

Claims (1)

[Claims] Claim 1: In a printing device that presses a thermal head against a platen roller facing the thermal head with a recording paper in between, and prints on the recording paper by a thermal transfer method, there is a A platen rotation mechanism for a printing device, which forms a pressure-type planetary gear mechanism, inputs the rotation of a motor to an input shaft side, fixes the output shaft so as not to rotate, and rotationally drives a platen roller.