JPH0422868B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a highly wear-resistant ceramic material with excellent workability, and more particularly to a ceramic sintered body suitable as a material for a pin guide for a dot printer.

[Technical background of the invention and its problems] In recent years, with the spread of office automation equipment, small printers have been widely used. Among such printers, the so-called impact type printer, in which printing is performed by pressing a pin against a ribbon impregnated with ink, is particularly widely used.

For such impact printers,
A pin guide member is provided for holding the above-mentioned printing pins at predetermined intervals, and the pins are slidably inserted through a plurality of guide holes bored in the guide member and held.

In such a pin guide member, since the pin moves frequently and slides into the guide hole, the pin is made of a material that does not wear out the guide hole due to this contact movement, that is, a material with high wear resistance. It is necessary to form a guide member.

Generally, high-speed steel, tungsten carbide, etc. are used as the material for the pin, and HIP sintered bodies of alumina (Al ₂ O ₃ ), ruby, etc. have been mainly used as the pin guide member.

However, the wear resistance of pin guide members made of these materials is limited; for example, at a printing speed of 240 prints/sec, the guide hole will wear out and the hole diameter will expand after 200 million to 400 million times. There was a problem.

In order to solve this problem, attempts have been made to form the pin guide member with a silicon nitride (Si ₃ N ₄ )-based sintered body, which has particularly excellent wear resistance, instead of the above-mentioned alumina and ruby. There is.

However, although the Si ₃ N ₄ sintered body has excellent wear resistance, it has poor workability due to its extremely high hardness, and it takes a lot of time for finishing cutting and drilling guide holes. As a result, there is a problem in that the manufacturing cost increases.

[Object of the Invention] The present invention solves the conventional problems and provides a printer pin with good machinability without impairing the inherent high wear resistance of silicon nitride sintered bodies. It is an object of the present invention to provide a highly wear-resistant ceramic material with excellent workability and suitable as a material for a guide member.

[Summary of the Invention] In the course of intensive research to achieve the above object, the present inventor discovered that the size of pores in a Si ₃ N ₄ sintered body and the content thereof are determined by the cutting of the sintered body itself. We focused on the effect on sexuality. In other words, in general, the fewer pores a Si ₃ N ₄ sintered body contains, and even if they do exist, the smaller their diameter, the denser and higher quality the sintered body will be. . However, such a Si ₃ N ₄ sintered body
Since the hardness is extremely high, it takes a lot of time for cutting, and there is a problem that, for example, the grindstone becomes clogged with cutting waste.

On the other hand, if the pores contained in the Si ₃ N ₄ sintered body have a large diameter and are contained in large quantities, the hardness will decrease and machinability will improve, but the wear resistance will decrease.

Based on the above, the present inventor has conducted various studies on the pore diameter and pore content that satisfies the abrasion resistance required for printer guide members and also has good workability, and as a result, the following will be described below. The present invention was completed by finding the optimum value range.

That is, the highly wear-resistant ceramic material with excellent workability of the present invention is made of a silicon nitride sintered body in which pores with a pore diameter of 20 to 60 μm exist at a rate of 300 to 1500/mm ² . It is characterized by

The ceramic material of the present invention is suitable for use in various parts that only require both high wear resistance and good machinability, and rather do not require high mechanical strength, such as pin guides for printers as described above. It is particularly suitable as a material for members.

Moreover, such ceramic materials, namely,
In addition to Si ₃ N ₄ , the Si ₃ N _4- based sintered body contains, for example,
_Al2O3 , _{Y2O3 ,} AlN, _{TiO2 ,} etc. may be included as a sintering aid.

This Si ₃ N ₄ based sintered body is mainly composed of pores with a diameter of 20 to 60 μm (50% or more of the total number of pores, preferably 70% or more). It is necessary that This pore diameter is 20μ
If it is less than m, the wear resistance is excellent, but
Poor machinability. Moreover, when the pore diameter exceeds 60 μm, the machinability improves, but the wear resistance significantly decreases.

In addition, the content of such pores is 300 to 1500/
^mm2 . Furthermore, it is preferable that the hardness of the obtained sintered body is set to be 1600 to 1800 in terms of Vickers hardness.

The ceramic material made of the Si ₃ N ₄ based sintered body of the present invention is manufactured as follows.

First, sintering aid powder is mixed with Si ₃ N ₄ powder at a predetermined ratio, and then granulated.

Then, the obtained granulated powder is molded. Although normal press molding or the like can be applied to the molding process, it is preferable that the molding density is about 1.5 to 2.0 g/cm ² .

After that, the obtained molded body is degreased and further
Sinter at 1700-1800°C for 0.5-6 hours. At this time, a sintered body having a theoretical sintered density ratio of 95 to 99% is obtained.

[Embodiments of the invention] For Si ₃ N ₄ powder, sintering aids Al ₂ O ₃ , Al N,
A mixed powder containing Y ₂ O ₃ and TiO ₂ is granulated,
Granules with an average particle size of 100 μm were obtained. After molding this granulated powder, it was degreased and further sintered at 1770°C for about 4 hours to produce a sintered body measuring 4 mm long, 6 mm wide and 1 mm thick. As a result of observing the cross section of this sintered body with a metallurgical microscope, about 600 pores/mm ² with an average diameter of 20 to 60 μm were observed. Further, a guide hole with a diameter of 0.25 mm was formed in this sintered body to obtain a pin guide member for a printer.

This pin guide member is attached to an actual printer, and printing speeds of 240 are achieved using pins made of cemented carbide.
As a result of a durability test conducted at characters/sec, there was no wear on the guide holes and the printing remained clear even after 1 billion cycles.

For comparison, a similar durability test was also conducted on guide members obtained in the same manner as in the above example, except that the pore diameters of the obtained sintered bodies were approximately 10 μm and approximately 70 μm. Summer. the result,
The one with a pore diameter of 10 μm showed good durability as in the above example, but it
It took twice as long. On the other hand, in the case of the one with a pore diameter of 70 μm, the guide hole was worn out after 100 million cycles, and the wall between adjacent holes was damaged, making it difficult to use.

[Effects of the Invention] As is clear from the above description, the ceramic material of the present invention is a silicon nitride sintered body that has both good machinability and excellent wear resistance, and is particularly suitable for pin guide members for dot printers. When applied to , it is possible to obtain members with excellent printing performance with high manufacturing efficiency, so its industrial value is extremely large.

Claims (1)

[Claims] 1. High durability with excellent workability, characterized by being made of a silicon nitride-based sintered body in which pores with a pore diameter of 20 to 60 μm exist inside, and the number of pores is 300 to 1500/ ^mm2 . Abradable ceramic materials.