JPH0255232B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a guide plate for a wire dot printer made of a composite body in which the open pores of a porous silicon carbide sintered body are filled with resin, and a method for manufacturing the same. In particular, the present invention relates to filling the open pores of a porous silicon carbide sintered body with open pores, which is sintered without substantially shrinking the shape of the formed body formed into a predetermined shape by firing. A guide plate for wire dot printers made from a composite material made of
The present invention also relates to a method of manufacturing the guide plate at low cost and easily without substantially requiring finishing processing such as machining.

[Conventional technology]

Conventional guide plates for wire dot printers (hereinafter simply referred to as guide plates) are made of various plastic materials, photoetched glass materials, alumina sintered bodies, ruby or sapphire, and the like.

The print head of a wire dot printer generally has an impact wire made of a hard metal such as tungsten or tungsten carbide and having a circular cross section facing toward a guide plate at the tip.

Therefore, the guide plate made of the plastic material suffers from significant wear and has a short service life, and the guide plate made of the photoetched glass material is expensive because it is difficult to align the holes in a straight line. Not only that, but it also has drawbacks such as being easily damaged and having a short service life.

On the other hand, guide plates made of alumina sintered bodies, ruby, sapphire, etc. have relatively high hardness, so finishing them by machining is difficult and expensive, as well as being relatively brittle. It is very difficult to drill independent circular holes at small intervals.

Furthermore, for example, according to Japanese Patent Application Laid-Open No. 56-89962, ``the base of a dot printer guide plate made of carbon is reacted with silicon oxide to convert the entire base to a silicon carbide layer, or the entire base is converted into a silicon carbide layer. "A guide plate for a wire dot printer, characterized in that the entire surface or a dispersed partial surface is formed with a silicon carbide layer."

The above guide for wire dot printers is used when the impact wire is reciprocated by a solenoid and slides on the guide plate when printing, and the tip of the impact wire hits the ribbon to print characters. It is something. Since the impact wire operates very quickly and reciprocates many times, the guide plate is likely to wear out due to sliding of the impact wire. Also,
The smaller the distance between the dots that make up the letters, the easier it is to read, so the distance between the holes in the guide plate should be as small as possible.

JP-A-56-89962 discloses a compound guide plate in which the entire or surface of the substrate is converted to silicon carbide by reacting silicon oxide with a carbon substrate. The reaction for converting the carbon substrate surface into silicon carbide is as follows.

2C + SiO → SiC + CO Therefore, it is generally difficult to adjust the size of SiC particles produced by the above reaction formula,
The generated SiC particles grow large and the surface particles become rough, so the inner surface of the hole must be polished before it can be used.

[Problem that the invention seeks to solve]

The present invention aims to eliminate and improve the drawbacks of the conventional guide plates made of various materials, and to improve the high dimensional accuracy, abrasion resistance, durable strength, and prevention of powder falling off during use, which are originally required for guide plates. The present invention provides a guide plate for a wire dot printer, which is made of a composite material in which the open pores of a porous silicon carbide sintered body are filled with resin, and has all of the various properties, and a method for manufacturing the same.

That is, for the above purpose, the open pores of a silicon carbide sintered body, which is a porous body having open pores and is sintered in a predetermined shape without substantially firing shrinkage, are filled with a resin. The present invention provides a guide plate with high dimensional accuracy, excellent practical durability strength and wear resistance, and a method for manufacturing the same.

[Means for solving problems]

According to the present invention, it is necessary to use a silicon carbide sintered body as a base material, which is a porous body having open pores and is sintered into a predetermined shape without substantially shrinking.

In general, silicon carbide sintered bodies have high hardness, high thermal shock resistance, and high strength at high temperatures, and have excellent wear resistance, oxidation resistance, and corrosion resistance, and good thermal conductivity.
Because it has excellent chemical and physical properties such as a low coefficient of thermal expansion, it is widely used as a wear-resistant sliding material such as mechanical seals and bearings, and as a durable material such as pump parts that require corrosion resistance.

However, on the other hand, silicon carbide sintered bodies having high hardness have the disadvantage of being expensive and difficult to finish by machining, like the alumina sintered bodies, ruby or sapphire. Especially for guide plates for wire dot printers, for example, the vertical dimension is 6 mm, the horizontal dimension is 3 mm, and the plate thickness is 1 mm.
However, as shown in FIG. 1, a hole having 9 to 24 holes with a diameter of 200 to 3000 μm has the disadvantage of high finishing cost.

Therefore, the present invention provides a silicon carbide sintered body sintered by a method that does not substantially cause firing shrinkage, that is, a porous body having open pores, which is substantially formed of a green body. It is possible to sinter a large number of molded bodies having the above-mentioned shape and dimensions as exemplified in Figure 2 in a predetermined shape with almost no sintering shrinkage, and virtually no finishing processing such as machining is required. The base material is a porous silicon carbide sintered body.

If a silicon carbide sintered body is used as the base material of the guide plate in this way, there is no need to finish finishing materials with relatively high hardness such as conventional alumina sintered bodies, ruby, or sapphire. The amount required can be manufactured at a low cost.

In addition, the inherent properties of the silicon carbide sintered body itself, particularly its high hardness and excellent wear resistance, as well as its excellent corrosion resistance against ink and other chemicals, can be utilized as they are.

Further, according to the present invention, it is necessary to form a composite body in which the open pores of the silicon carbide sintered body sintered in the predetermined shape are filled with resin. The reason for this is that by filling the open pores of the silicon carbide sintered body with resin, it is possible to prevent the detachment of crystal grains from the silicon carbide sintered body, significantly improving wear resistance. This is because it can be done.

The resins to be filled in the silicon carbide sintered body include epoxy resin, polyimide resin, trimazine resin, polyparabanic acid resin, polyamideimide resin, silicone resin, epoxy silicone resin, acrylic acid resin, methacrylic acid resin, aniline resin,
Phenol resin, urethane resin, furan resin, fluororesin, acetal resin, nylon resin, polyethylene resin, polycarbonate resin,
It is preferable to use resins selected from polybutylene terephthalate resin, styrene acrylonitrile resin, polypropylene resin, polyurethane resin, and polyphenylene sulfide resin alone or in combination.

The filling rate of the resin is 100% of the open pores.
It is preferable that at least 10 parts by volume of the resin be filled with respect to each volume part. The reason for this is that if the filling amount of metallic silicon is less than 10 parts by volume, the effect of preventing the detachment of crystal grains from the silicon carbide sintered body will not be sufficient and it will be difficult to improve the wear resistance. be.

Further, it is preferable that the silicon carbide sintered body has an average grain size of crystals of 5 μm or less. If the average particle size exceeds 5 μm, the surface roughness of the sintered body surface will increase, making it difficult to make the guide plate surface smooth.
Moreover, the dimensional accuracy of the sintering itself deteriorates.

The density of the silicon carbide sintered body is 1.4~
Preferably, it is 2.6 g/cm ³ . The density is 1.4
This is because a sintered body smaller than 2.6 g/cm ³ has fewer bonding points between silicon carbide particles, making it difficult to produce ^a sintered body with sufficient durable strength. This is because it is extremely difficult and impractical to produce a larger sintered body with a corresponding density.

It is important that the silicon carbide sintered body has excellent dimensional accuracy, and it is advantageous that the silicon carbide sintered body has a three-dimensional network structure composed of silicon carbide crystals with an average aspect ratio of 5 or less. be.

Next, a method of manufacturing a guide plate for a wire dot printer according to the present invention will be explained.

According to the present invention, a ceramic raw material containing silicon carbide powder as a main component is formed into a predetermined shaped green body, and the green body is grown in a non-oxidizing atmosphere to a high dimension without substantially shrinking the shape of the green body. A wire dot printer manufactured by a method characterized in that it is made from a composite body obtained by impregnating a resin into the open pores of a porous silicon carbide sintered body having open pores obtained by sintering in a precise state. It is possible to manufacture guide plates for

The silicon carbide powder preferably has an average particle size of 5 μm or less. The reason for this is that although silicon carbide with a grain size larger than 5 μm is preferable for suppressing firing shrinkage, it reduces the number of bonding points between grains within the sintered body, making it difficult to obtain a high-strength silicon carbide sintered body. This is because it not only becomes difficult, but also deteriorates the surface roughness.

By the way, the crystal system of silicon carbide has α type and β type.
There are two types: type and amorphous, and any of them or a mixture thereof can be used. Among them, β type is easy to obtain in fine powder form with a diameter of 5 μm or less, and is relatively expensive. It can be advantageously used because a strong sintered body can be produced, and in particular, it is advantageous to use silicon carbide powder containing 50% by weight or more of β-type silicon carbide.

Advantageously, the silicon carbide powder has a total content of boron, aluminum and iron of 0.3% by weight or less in terms of elements. The reason for this is that if the total content of boron, aluminum and iron is more than 0.3% by weight in terms of elements, sintering will occur during sintering due to interaction with free carbon contained in silicon carbide powder. This is because it tends to shrink, making it difficult to manufacture a sintered body without causing substantial shrinkage.

In addition, when the content of boron, aluminum, and iron in the silicon carbide powder is within the above range, a carbonaceous substance can be added to make the starting material contain 5% by weight or less of free carbon.
The free carbon has the effect of suppressing the coarsening of crystal grains, and by making it present in the starting raw material, it is possible to make the crystal grain size of the sintered body uniform and obtain a sintered body with relatively high strength. can. The reason why the free carbon content is set to 5% by weight or less is that if it is more than 5% by weight, excessive carbon will exist between the silicon carbide powder particles, which will significantly inhibit the bonding between the particles. This is because the strength of the sintered body deteriorates.

The carbonaceous material may be any material that allows carbon to be present at the start of sintering, such as various organic materials such as phenolic resin, lignin sulfonate, polyvinyl alcohol, cornstarch, sugar, coal tar pitch, and alginate. Alternatively, pyrolytic carbon such as carbon black or acetylene black can be advantageously used.

The silicon carbide powder has a total content of boron, aluminum, and iron of 0.3 in terms of elements.
When the content exceeds 0.6% by weight, it is advantageous that the content of carbonaceous substances and free carbon is 0.6% by weight or less in terms of fixed carbon content. The reason is that when the total content of boron, aluminum and iron exceeds 0.3% by weight in terms of elements, the content of carbonaceous substances and free carbon exceeds 0.6% by weight in terms of fixed carbon content. As I explained earlier, if there are many,
This is because the interaction between boron, aluminum, or iron and carbon tends to cause sintering shrinkage during sintering, making it difficult to obtain a sintered body without substantial shrinkage.

In addition, if the content of boron, aluminum, and iron is too high, it will deteriorate the physical properties of the sintered body, so it is desirable that the content be as low as possible, and the total content should be 2% by weight or less in terms of elements. It's advantageous.

Various conventionally known forming methods can be used to form the ceramic raw material containing silicon carbide powder as a main component into a predetermined shaped product, such as embossing, casting, and isostatic pressing. Alternatively, injection molding can be used to form a product into a desired predetermined shape. Among these, the injection molding method is advantageous because it can produce a product with a complex shape and high precision.

The resulting body is fired within a temperature range of 1400-2100°C. The reason for this is that if the temperature is lower than 1400°C, the bond between grains is insufficient and the strength is extremely low, whereas if the temperature is higher than 2100°C, the nets that have grown once are smaller than a certain size. This is because the particles become constricted or, in severe cases, disappear, resulting in a decrease in strength, and some of the particles become coarse, resulting in a deterioration in surface roughness.

The resulting shaped body is fired in a non-oxidizing atmosphere without substantial shrinkage. The reason for this is that shrinkage during sintering is preferable for improving the strength of the sintered body, but generally speaking, the amount of shrinkage during sintering has a large effect on the density of the formed body, so it is necessary to generate uniform shrinkage. Therefore, it is important to obtain a formed body with uniform density. However, it is extremely difficult to obtain a formed body having such uniform density, and it is therefore difficult to produce a sintered body with extremely high dimensional accuracy by causing firing shrinkage.

In addition, in order to obtain a sintered body with high dimensional accuracy as described above, the firing shrinkage rate when sintering without substantially shrinking is preferably 2% or less, particularly 1% or less. is more suitable.

In addition, the formed body has a gas partial pressure of at least one of CO or N ₂ in the atmosphere of 100 Pa for at least 10 minutes within a temperature range of 1400 to 2100°C.
It is advantageous that the firing is carried out in an atmosphere maintained above. The reason for this is that by increasing the partial pressure of at least one of CO or _N2 in the atmosphere to 100 Pa or higher for at least 10 minutes within the above temperature range, the growth of the nets can be promoted and the sintering of silicon carbide can be accelerated. This is because shrinkage during firing can be effectively suppressed.

According to the present invention, it is advantageous to charge the green body into a heat-resistant container in which the firing atmosphere can be controlled and fire it. The reason why it is advantageous to charge the material into a heat-resistant container and fire it while controlling the firing atmosphere is because it can promote bonding between adjacent silicon carbide crystals and the growth of nets. . The reason why bonding between adjacent silicon carbide crystals and the growth of nets can be promoted by charging the formed body into a heat-resistant container and firing while controlling the firing atmosphere as described above is because the carbonization This is thought to be because movement of silicon carbide between silicon particles through evaporation-recondensation and/or surface diffusion can be promoted.

As the heat-resistant container, materials such as graphite and silicon carbide, and materials having functions equivalent to these materials can be advantageously used.

Furthermore, it is advantageous to control the volatilization rate of silicon carbide to 5% by weight or less during firing by charging the formed body into a heat-resistant container in which the firing atmosphere can be controlled and firing it.

Advantageously, the product form has a density of 45 to 80% by volume. The reason for this is that if the density of the formed body is lower than 45% by volume, there will be fewer points of contact between the silicon carbide particles, which will inevitably result in fewer bonding points, making it difficult to obtain a high-strength sintered body. , on the other hand, because formed bodies with a volume content higher than 80% are difficult to manufacture.

Also, in the temperature increase process up to 1400℃ mentioned above,
By maintaining the total gas partial pressure of CO and N ₂ in the atmosphere at 100 Pa or less at 1300℃ or higher for at least 30 minutes, the nets between silicon carbide particles are uniformly generated and bonded firmly. be able to.

According to the present invention, it is necessary to fill the open pores of the silicon carbide sintered body with resin. The reason for this is that by filling the open pores of the silicon carbide sintered body with resin, it is possible to prevent the detachment of crystal grains from the silicon carbide sintered body, significantly improving wear resistance. This is because it can be done.

Methods for filling the pores of the silicon carbide sintered body include methods of heating and melting the resin and impregnating it, methods of dissolving the resin in a solvent and impregnating it, and methods of impregnating the resin in a monomer state and then forming it into a polymer. Alternatively, a finely divided resin is dispersed in a dispersion medium, and a silicon carbide sintered body is impregnated with this dispersion,
After drying, a method of baking the resin at its melting temperature can be applied.

According to the present invention, at least 10% of the resin is added to 100 parts by volume of open pores of the silicon carbide sintered body.
It is advantageous to fill the volume. The reason is,
This is because if the filling amount of the resin is less than 10 parts by volume, the effect of preventing the detachment of crystal particles from the silicon carbide sintered body will not be sufficient, and it will be difficult to improve the wear resistance.

Next, the present invention will be explained with reference to Examples and Comparative Examples.

〔Example〕

Example 1 The silicon carbide powder used as a starting material consisted of 94.6% by weight of β-type crystals and the remainder substantially of 2H-type crystals, and contained 0.29% by weight of free carbon, 0.17% by weight of oxygen, 0.03% by weight of iron, It mainly contained 0.03% by weight of aluminum, had an average particle size of 0.28 μm, and no boron was detected.

5 parts by weight of polyvinyl alcohol and 300 parts by weight of water are blended with 100 parts by weight of the silicon carbide powder,
The mixture was mixed in a ball mill for 5 hours and then dried.

An appropriate amount of this dry mixture was taken, granulated, and then molded using a metal mold at a pressure of 3000 kg/cm ² . The dimensions of this generated object are 6mm x 3mm x 1mm thick.
The density was 2.0 g/cm ³ (62% by volume). Then, nine holes with a diameter of 0.2 mm were drilled in the formed body using a carbide drill, as shown in FIG. 1.

A large number of the above-mentioned green bodies were produced, charged into a graphite crucible, and fired in a Tamman-type firing furnace in an atmosphere of mainly argon gas at 1 atm. The temperature was raised to 1900℃ at a rate of 450℃/hour, and the maximum temperature
It was held at 1900°C for 10 minutes. The CO gas partial pressure during sintering was controlled by appropriately adjusting the argon gas flow rate so that it was 80 Pa or less at room temperature to 1700°C, and within the range of 300 ± 50 Pa at higher temperatures than 1700°C.

The density of the obtained sintered body was 2.05 g/cm ² , and its crystal structure, when observed with a scanning electron microscope, had a three-dimensional structure intricately intertwined in multiple directions. The linear shrinkage rate was within the range of 0.25±0.02% in any direction, and the dimensional accuracy of the sintered body was within ±0.015 mm. Furthermore, the average bending strength of this sintered body was extremely high at 18.5 Kg/mm ² .

Next, this sintered body was impregnated with a two-component type epoxy resin under vacuum, and then cured at a temperature of about 150°C to obtain a composite. The porosity of the resulting composite was about 2%.

Next, the inner surfaces of the pores of the guide plate were polished and finished.

When the wire dot printer guide plate manufactured in this way was actually attached to a printer and a durability test was conducted, it was found that the conventional plastic guide plate produced approximately 1.5 million dots, while the glass guide plate produced approximately 300 million dots. However, it was confirmed that the guide plate of the present invention has enough durability to withstand use of 500 million dots or more.

〔Effect of the invention〕

As described above, the wire dot printer guide plate of the present invention uses a porous silicon carbide sintered body sintered without substantially shrinking as a base material, and the open pores are filled with resin. Because it is a composite body, it has extremely excellent dimensional accuracy and abrasion resistance, and it is possible to supply a wire dot printer guide plate with excellent durability at a low cost without special machining.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an example of a guide plate for a wire dot printer according to the present invention.

Claims (1)

[Scope of Claims] 1. A ceramic raw material mainly composed of silicon carbide powder with an average particle size of 5 μm or less is used as a formed body in the shape of a guide plate for a wire dot printer, and the formed body is heated within a temperature range of 1400 to 2100°C. When firing, insert it into a heat-resistant container where the firing atmosphere can be controlled within a temperature range of 1400 to 2100℃,
Under a non-oxidizing atmosphere in which the partial pressure of at least one of CO or _N2 in the atmosphere is maintained at 100 Pa or more for at least 10 minutes, the volatilization rate of silicon carbide during firing is controlled to 5% by weight or less, and the Impregnating a resin into the open pores of a porous silicon carbide sintered body having open pores obtained by sintering with high dimensional accuracy without shrinking the shape of the formed body. A method for manufacturing a guide plate for wire dot printers. 2. The manufacturing method according to claim 1, wherein the shrinkage rate due to the sintering is substantially 2% or less.