JPS61160264A - Thermal transfer printer - Google Patents

Abstract

PURPOSE:To obtain a thermal printer reduced in noise and having high printing accuracy, by bringing the timing pulley of a platen side to three-division constitution of an inner ring and the outer ring engaged with said inner ring through a buffer cylinder comprising an elastomer. CONSTITUTION:The timing pulley 4 of a platen side is constituted of a mere disc shaped inner ring 4a directly engaged with and fixed to a platen shaft 10 and the outer ring 4b engaged with said inner ring 4a through a buffer cylinder 4c comprising an elastomer and having teeth provided to the outer peripheral surface thereof. In a vibration mode, one present in the side of external force F is the outer ring 4c of the timing pulley 4 with mass Ma and constitute a forcible vibration system with degree of freedom of 1. In a frequency region 2<1/2> times or more a resonance frequency 1/2pi (K/Ma)<1/2> (wherein K is a spring constant), a transmission ratio comes to 1 or less and the generation of noise based on the external force F of the platen shaft 10 in the radius direction thereof is reduced. Only the other ring 4c of the timing pulley 4 is displaced by the intermittent tension of a timing belt 5 and any relative displacement is not generated between a platen 3 and a thermal head 7 and, therefore, printing accuracy is not lowered.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a thermal transfer printer.

[Technical aspirations of the invention and its problems] An example of a conventional thermal transfer printer will be explained with reference to FIGS. 9 and 10. FIG. 9 is a side view thereof, and FIG. 10 is a plan view thereof. In these figures, a step motor 1 intermittently rotates the platen 3 via a timing pulley 2 attached to its output shaft and timing bells 1 to 5 attached to the lζ timing pulley 4. .

Incidentally, the timing bell 1-5 is configured such that its upper running portion is on the belt tension side. On the other hand, the ink ribbon 6 is run directly under the platen 3, and the thermal head 7 is positioned directly facing the platen, sandwiching the ink ribbon. Note that the recording paper 8 is connected to the platen 3 and the ink ribbon 6.
The vehicle passes through the gap between the two, and is made to travel approximately halfway around the platen 3. In addition, 9 in the figure is a frame that supports the platen,
Reference numeral 10 indicates a platen shaft, and reference numeral 11 indicates a bearing that supports the platen shaft. -Hiki Susei's conventional thermal transfer printer,
Main scanning is performed by the thermal head 7, and sub-scanning is performed by intermittent rotation of the platen 3. The ink ribbon 6 is brought into contact with the recording paper 8 wound around the platen 3, and the thermal head 7 performs thermal transfer to print. At this time,
Since the thermal head 7 is pressed against the platen 3 with a force of several kilograms, a large amount of torque is required for intermittent rotation of the platen. Intermittent tension acts on the timing belt due to the intermittent drive of the platen, and due to this intermittent tension and the frictional load of the thermal head, the platen shaft has a periodically varying shaft radius. A directional force was applied, which was transmitted to the frame, causing it to vibrate and generate noise.

In order to prevent the transmission of vibrations and suppress the generation of noise as described above, attempts have been made to interpose a cylindrical anti-vibration rubber between the frame 9 and the bearing 10 that supports the shaft of the platen. If this is done, a relative positional change will occur between the thermal head 7 and the platen 3, which may reduce printing accuracy.

[Object of the Invention] The present invention was developed in view of the circumstances of distribution, and an object of the present invention is to obtain a thermal printer with low noise and high printing accuracy.

[Summary of the Invention] The thermal printer of the present invention performs main scanning with a thermal head and sub-scanning by intermittently rotating a platen with a step motor via a timing bell 1. The pulley is characterized by having a three-part structure including an inner ring and an outer ring engaged with the inner ring via a buffer cylinder made of an elastic body.

[Embodiment of the Invention] Fig. 1 and Fig. 2, in which the same parts as in Fig. 19 to Fig. 10 are given the same reference numerals, are a side view and a plan view schematically showing an embodiment of the present invention. In the figure, the platen side timing pulley 4 has a simple disc-shaped inner ring 4a that is directly fitted and attached to the platen shaft 10, and a cylindrical loose cylinder/IC made of an elastic body that is fitted to this inner ring 4a. and an outer ring 4b having teeth on its outer peripheral surface.

In the thermal transfer printer of the present invention having the above configuration, when the timing pulley 4 is intermittently rotated by the timing belt 5, the radial force acting on the platen shaft 10 is
be relieved by h. Figure 3A is a vibration model of the platen axis in the radial direction of the thermal transfer printer of the present invention, B is a vibration model of the platen axis in the radial direction of a conventional thermal transfer printer that does not use a buffer, and C is a vibration model of the conventional thermal transfer printer/Z. A model of vibration in the radial direction of the platen axis is shown in which a buffer is inserted between the bearing and the frame. In these figures, Ma is the mass of the outer ring 4C of the timing pulley 4 on the platen side, and Moto is the mass of the inner ring 4a of the timing pulley 4 and the platen 3.
1 is the timing pulley 40 =
-a and mα1 indicate the mass of the platen 3, K and 1 indicate the spring constant of the elastic body, and F indicates the external force acting on the timing pulley due to the intermittent tension of the timing bell 1.

In the conventional example shown in FIG. 3B, each element such as the timing pulley 4 and the platen shaft 10 are rigidly connected, so that the external force F is directly transmitted to the frame. In the conventional example shown in Fig. 3C in which a buffer cylinder is interposed between the frame and the bearing 11, the timing is 4 - the forced vibration system in which the pulley 4 and the platen 3 (mass Ma14-7rL^1) has one degree of freedom. Configure. At this time, the external force F is 0
It is well known that the value is 1 or less in a frequency range of 5 times or more. However, since the platen 3 is located on the side of the external force side compared to the vibration model C elastic body, the displacement is larger than when it is rigidly connected to the frame shown in FIG. decreases. In the vibration model of the present invention shown in FIG. 3A, on the external force F side is the outer ring 40 of the timing pulley of quality ffiMa, which constitutes a forced vibration system with one degree of freedom. Resonance frequency 14. fi】Ma-
In a frequency range of five times or more, the transmission rate is less than 1, and the generation of noise based on the external force F in the radial direction of the platen shaft 10 can be reduced. It should be noted that timing pulley 4 causes zero displacement due to intermittent tension of timing bell 1-5.
Since there is only the outer ring 4C and no relative displacement occurs between the platen 3 and the thermal transfer head 7, there is no reduction in printing accuracy.

FIG. 4 shows a comparison of the conventional thermal transfer printer shown in FIGS. 9 and 3B and the thermal transfer printer of the present invention described in section 8; From this figure, it can be seen that according to the present invention, the noise power level is 5d.
It can be seen that B is lowered.

Parts that are the same as those in Figures 1 and 2 are designated by the same symbols in Figure 5.
The figures conclude an exemplary embodiment of the invention. This embodiment is an example in which the present invention is applied to a printer that performs overlapping printing, such as a color printer, and requires precision in the paper feeding direction. In this embodiment, the buffer tube 4b is provided with a plurality of open-shape notches 12 that are equally spaced from the outer circumference toward the center, and the inner circumference of the outer ring 4C is provided with an elastic body J constituting the buffer tube/Ih. :
Made of metal, plastic, etc. with a large spring constant,
A blade 13 that engages with the notch 12 is fixed.

In general, the torsional spring constant I of a cylindrical anti-vibration rubber is expressed by the following formula (%), where G is the number of transverse elastic bodies, ■ is the axial length of the cylinder, and rl and r2 are the inner and outer diameters of the cylinder, respectively.

From formula (1) =/Ile・G・I*t;r:/ (r,” −
r2)-47C-G・1・”,' (42-1)・Seri・・・・・・・・・・・・・(2) Here, ra/IJ=
(X (> 1 >. q” with i as a parameter
/<q+"-1> is calculated and plotted in Figure 6. From this figure, it can be seen that as α approaches 1, the culm spring constant becomes large.

By the way, if the vanes 13 are provided as in the embodiment shown in FIG. It becomes equivalent.

On the other hand, the spring constant in the radial direction of the buffer tube 4b is expressed as the sum of the spring constant due to shear strain and the spring constant due to compression and tension. In general, the spring constant due to shear is smaller than that due to compression and tension, so the spring constant in the radial direction of a cylindrical anti-vibration gono is dominated by compression and tension. Therefore, in this embodiment, the blade 13 is provided with a buffer tube 4.
Even if the torsion spring constant of b is refined, the accuracy of the spring constant of r in the radial direction can be ensured.

FIG. 7, in which the same parts as those in the previous figures are given the same reference numerals, shows another embodiment of the present invention. In this example, l!
Cutting tube/11) Notch 12a similar to the above-mentioned notch 12 on the inner periphery
The inner ring /Ia of the timing pulley 4 is provided with blades 13a similar to the blades 12 described above. This embodiment also provides the same effects as the embodiment shown in FIG.

FIG. 8 shows a further embodiment of the present invention, in which the same parts as those in the previous figures are given the same reference numerals. In this embodiment, the blades 12a of the timing pulley inner ring 4a, the timing pulley, and the blades 12 of the outer ring/IC are alternately provided. This embodiment also provides the same effects as those of the embodiments described above.

[Effects of the Invention] As is clear from the above 2, the thermal transfer printer of the present invention can suppress the generation of noise due to the intermittent rotation of the platen, and also has two advantages:
(Thus, it is possible to prevent an increase in office space due to OA staff.)

[Brief explanation of drawings]

FIG. 1 is a schematic side view of an embodiment of the present invention, FIG. 2 is a schematic plan view thereof, FIG. 3 is a block diagram of the vibration system of the embodiment, and B and C in the same figure are two conventional examples, respectively. 4 is a diagram of the noise power level comparing the above embodiment and the conventional example shown in FIG. 3C, and FIG. 5 is a diagram of the second embodiment of the present invention. FIG. 6 is a diagram for explaining the theoretical basis of the embodiment, FIG. 7 is a schematic side view of the third embodiment of the present invention, and FIG. 8 is a schematic side view of the third embodiment of the present invention. FIG. 9 is a schematic side view of the fourth embodiment, FIG. 9 is a schematic side view of a conventional thermal transfer printer, and FIG. 10 is a schematic plan view thereof. 1...Step morph 2.4...Timing pulley 3...Platen 4a...Timing pulley inner ring/lh...
・・Buffer tube 4G・・・Timing pulley outer ring 5・・・・
...Timing bell 1-6...Ink ribbon 7...Thermal head 8...Old...
・Recording set 9・・・・・・Frame 10・
...Platen shaft 11 ...Bearing 12.
12a... Notch 13.13a... Hane application agent Tanukito patent attorney Kikuchi 5 part + 1 -1111, -m- to m-) De figure/θ figure

Claims (2)

[Claims] (1) In an apparatus in which main scanning is performed by a thermal head and sub-scanning is performed by intermittently rotating the platen by a step motor via a timing belt, the timing pulley on the platen side is made of an inner ring and an elastic body in the inner ring. A thermal transfer printer characterized by having a three-part structure with an outer ring engaged through a buffer tube. (2) A radial vane is fixed to either or both of the inner periphery of the outer ring or the outer periphery of the inner ring, which fits into the buffer cylinder and is made of a material with a larger spring constant than the elastic body constituting the buffer cylinder. A thermal transfer printer according to claim 1, characterized in that: