JPH0142830B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to an improvement of a print head in a dot-type impact printer that prints characters and the like formed in a dot matrix.

(b) Background of the Technology As a type of output device for data terminal equipment, wire dot printers are widely used because they are small, inexpensive, and easy to operate, and have shown great effects. In the print head of such a printer, the print hammer reciprocates between the magnetic attraction surface of the electromagnet and the recording medium in a short period of time at a very high speed, and high-speed printing is performed on the recording medium. It is desired to reduce the heat generated by the electromagnet in order to reduce the impact of the printing hammer on the suction surface during the suction operation and to improve the efficiency of excitation of the electromagnet.

(c) Prior Art and Problems As shown in FIG. 1, the conventional printing head in the above-mentioned wire dot printer includes a printing hammer 1 consisting of a wear-resistant wire 2 and an armature 4 with a spring steel member 3. End and the amateur 4
An electromagnet 5 and a permanent magnet 6 are respectively fixed to a support body 7 facing away from each other. Usually, the armature 4 is magnetically attracted to the iron core 5a of the electromagnet 5 by the permanent magnet 6, and is placed facing the tip of the wire 2. A platen 8 is arranged with an ink ribbon 9 and a printing paper 10 in between.

However, when printing, by energizing the electromagnet 5 based on the printing signal, the magnetism of the permanent magnet 6 is canceled and the armature 4 that was magnetically attracted to the iron core 5a of the electromagnet 5 is separated, and the spring steel material 3 is restored. The force causes the tip of the wire 2 to strike the platen 8 via the ink ribbon 9 and the printing paper 10, so that printing is performed on the printing paper 10.

By the way, in such a conventional printing head, since the printing hammer 1 is driven back and forth between the magnetic attraction surface of the iron core 5a of the electromagnet 5 and the platen 8 at a very high speed, the magnetic force of the iron core 5a is In order to eliminate damage caused by the impact of the armature 4 of the printing hammer 1 on the suction surface and magnetic stickiness due to loop-shaped residual magnetism when the armature 4 is attracted and detached, the magnetic suction surface of the iron core 5a of the electromagnet 5 is coated with polyester, for example. A non-magnetic plate made of a manufactured film or a thin rubber plate is attached to absorb kinetic energy. However, there was a drawback in that the non-magnetic plate itself constructed in this manner was easily damaged by abrasion caused by the impact of the armature 4 in a short period of time. In addition, there is a problem in that the electromagnet 5 generates a large amount of heat when it is excited, the coil resistance of the electromagnet 5 increases, and the excitation effect decreases. Therefore, an effective cooling method for the electromagnet 5 that does not use a cooling fan or the like is desired. ing.

(d) Purpose of the Invention The present invention has been made in order to eliminate the above-mentioned conventional drawbacks, and its purpose is to alleviate the impact when the printing hammer is attracted to the magnetic attraction surface of the electromagnet, and to reduce the impact of the magnetic attraction surface of the electromagnet. An object of the present invention is to provide a new print head for a dot printer, which can effectively cool the print head using high-pressure air.

(e) Structure of the Invention According to the present invention, the above-mentioned object is achieved by magnetically driving a printing hammer having a printing wire protruding from one end of an elastic arm by an electromagnet excited based on a printing signal. In a configuration in which printing is performed at the tip of the wire, an air introduction hole with an air outlet on the magnetic attraction surface side is bored inside the iron core constituting the electromagnet, and the magnetic attraction operation of the elastic arm is performed during the printing operation of the printing hammer. This is achieved by providing a printing head for a dot printer, characterized in that the relaxation control is performed by the air pressure ejected from the ejection port.

(f) Embodiments of the invention Preferred embodiments of the invention will be described in detail below with reference to the drawings.

FIG. 2 is a side cross-sectional view of main parts showing one embodiment of the printing head for a dot printer according to the present invention, and FIG.
Parts that are equivalent to those in the figures are given the same reference numerals.

As shown in the figure, in the print head of the present invention, an air introduction hole 21 is provided which penetrates from the support 7 to the magnetic attraction surface of the iron core 5a. Reference numeral 23 denotes a non-magnetic material made of a plastic film or a thin rubber plate attached to reduce the impact of the printing hammer 1 on the magnetic attraction surface of the iron core 5a and to make it easier to instantly separate the printing hammer 1 from the magnetic attraction surface. It is a plate and has an opening that communicates with the air outlet 22 on the magnetic attraction surface.

However, the air introduction hole 21 of the iron core 5a of the electromagnet 5 of the print head configured in this way
For example, a predetermined flow rate of high-pressure air is supplied from a high-pressure air source (not shown), and the air at a predetermined pressure is constantly ejected from the jet port of the air introduction hole 21 toward the armature 4 of the printing hammer 1 facing the other side. put. In this way, printing hammer 1 during printing operation
For example, after hitting the recording medium with wire 2,
When the armature 4 is magnetically attracted to the opposite electromagnet 5 side by the repulsive force, the return speed just before attraction is attenuated by the air jet pressure, and as a result, the impact of the armature 4 on the magnetic attraction surface of the electromagnet 5 is significantly reduced. It becomes possible to relax the situation. Due to this air damping effect, the armature 4 is very gently attracted to the magnetically attracting surface, so that when the non-magnetic plate 23 attached to the magnetically attracting surface is hit and abraded, it will not get damaged. More preferably, the electromagnet 5 is controlled by controlling the magnetic attraction force on the electromagnet 5 side with respect to the armature 4, that is, the magnetic attraction force _P1 of the permanent magnet 6 acting through the electromagnet 5, and the air pressure jetted from the jet hole 22. It is also possible to stop the armature 4 which has been returned to the magnetic attraction surface with a predetermined gap therebetween, and in this case it is not necessary to attach a non-magnetic plate to the magnetic attraction surface. On the other hand, as mentioned above, since air at a predetermined pressure is constantly ejected from the air injection port 22 through the air introduction hole 21 of the iron core 5a of the electromagnet 5, the heat exchange that occurs when this high-pressure air flows inside the iron core 5a, The electromagnet 5, which generates heat, is efficiently cooled by the ejected air that hits the armature 4 and returns to the electromagnet 5 side.

(g) Effects of the Invention As explained above in detail, according to the configuration of the print head for a dot printer according to the present invention, the magnetic attraction operation of the armature during the printing operation of the printing hammer is controlled by the air perforated in the electromagnet. It is possible to perform relaxation control using the air pressure ejected from the injection port of the inlet hole, and the upper air ejection mechanism can efficiently cool the electromagnet that generates heat, thereby creating a magnetic attraction that magnetically attracts the printing hammer. Abrasion of the surface or the non-magnetic plate attached to the surface is significantly reduced or eliminated, resulting in a longer service life.
In addition, since the heat generation of the electromagnet is suppressed, the excitation efficiency is improved, so it is extremely advantageous and reliable for application not only to print heads for open type dot printers as explained in this embodiment, but also to print heads for suction type dot printers, etc. It also improves.

[Brief explanation of drawings]

FIG. 1 is a side view for explaining the structure of a conventional print head for a dot printer, and FIG. 2 is a side view showing the structure of an embodiment of the print head for a dot printer according to the present invention. In the figure, 1 is a printing hammer, 2 is a printing wire,
3 is spring steel, 4 is amateur, 5 is electromagnet, 5
Reference numeral a indicates an iron core, 6 a permanent magnet, 7 a support, 21 an air introduction hole, 22 an air outlet, and 23 a non-magnetic plate.

Claims (1)

[Claims] 1. In a configuration in which a printing hammer having a printing wire protruding from one end of an armature is magnetically driven by an electromagnet excited based on a printing signal to print at the tip of the printing wire, an iron core constituting the electromagnet. An air introduction hole with a magnetically attracting surface side as a spout is bored in the interior thereof, and the magnetic suction operation of the armature during the printing operation of the printing hammer is moderated and controlled by the air pressure spouted from the spout. A printing head for a dot printer, which is characterized by: