JP2009227571A - Glass powder for forming resistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the reliability and productivity of a small-sized spark plug by creating a glass powder for forming a resistor, having high ability to absorb high frequency noise radio waves and properly functioning as block particles, in order to form a resistor efficiently absorbing the high frequency noise radio waves. <P>SOLUTION: The glass powder for forming a resistor contains, by mol, 40-60% SiO<SB>2</SB>, 28-40% B<SB>2</SB>O<SB>3</SB>, 1-20% of Li<SB>2</SB>O+Na<SB>2</SB>O+K<SB>2</SB>O, 0.1-20% CaO, and 0-7% BaO, as a glass composition. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a resistor forming glass powder, and more particularly to a resistor forming glass powder suitable for forming a resistor of a spark plug.

  2. Description of the Related Art Resistor-containing spark plugs are widely used as spark plugs for engines such as automobiles. As shown in FIG. 1, the spark plug with a resistor is provided between a conductive glass body 2 a in contact with the terminal electrode 1 and a conductive glass body 2 b in contact with the center electrode 3 in an inner hole of an insulator (not shown). The resistor 4 is interposed. If a resistor is introduced into the spark plug, leakage of high-frequency noise radio waves generated when the spark plug is ignited can be suppressed.

  Generally, a spark plug with a resistor is manufactured as follows. After inserting the center electrode 3 into the lower end of the inner hole of the insulator and filling the inner hole of the insulator with a predetermined amount of the conductive glass body material, press pressure is applied to the conductive glass body material to Make it flat. Next, after filling a predetermined amount of resistor material on the conductive glass body material, a pressing pressure is applied to the resistor material to flatten the surface of the resistor material. Thereafter, a predetermined amount of conductive glass body material is filled on the resistor material. Here, the conductive glass body material and the resistor material are processed into granules in order to easily fill the inner holes of the insulator. Next, after inserting the terminal electrode 1 into the upper end of the inner hole of the insulator, the conductive glass body material and the resistor material are sintered by a so-called hot pressing process in which a load is applied to the terminal electrode 1 while heating at about 900 ° C. Then, the conductive glass bodies 2a, 2b and the resistor 4 are formed, the tip of the terminal electrode 1 is press-fitted into the conductive glass body 2a, and the tip of the center electrode 3 is press-fitted into the conductive glass body 2b. Finally, an insulator is fixed to a housing provided with a ground electrode to form a spark plug.

  In general, a resistor material obtained by granulating a resistor material made of coarse glass powder, fine glass powder, ceramic powder, conductive powder or the like is used. The resistor produced using this resistor material has a state in which a coarse glass powder or a ceramic powder retains its original shape, and a bonded glass phase in which the fine glass powder is melted and solidified exists in the gap between these particles. Become. In addition, conductive powder is dispersed in the binder glass phase, and the coarse glass powder functions as block particles that bend (detour) the conductive path (see, for example, Patent Documents 1 and 2). It is known that when the conductive path is bent, the resistance of the resistor to absorb high-frequency noise radio waves increases.

JP 9-306636 A JP 2005-340171 A JP 2007-122879 A

  In recent years, engines tend to be miniaturized, and spark plugs also tend to be miniaturized. However, when the spark plug is reduced in size, it is necessary to reduce the content of the resistor formed in the inner hole of the insulator. In other words, coarse glass that absorbs high-frequency noise radio waves inside the spark plug Since it is necessary to reduce the content (glass layer) of the powder or the like, the resistor is difficult to suppress leakage of high-frequency noise radio waves due to this. Note that, when the spark plug is ignited, high-frequency noise radio waves are generated. If a large amount of this high-frequency noise radio waves leaks, there is a risk that the vehicle-mounted TV, radio, radio, etc. will be disturbed.

  In view of such circumstances, in paragraphs [0011] to [0013] of the specification of Patent Document 3, “the spark plug of the present invention has a through hole extending in the axial direction, and the through hole is the first through hole. An insulator serving as a second through hole having a hole diameter larger than that of the first through hole on the rear end side of the hole and the first through hole; and a center electrode disposed in the first through hole of the insulator; A spark plug comprising a terminal fitting disposed in the second through hole of the insulator, and formed of a conductive ceramic sintered body in the second through hole, and the center electrode and the A ceramic sintered body resistor that is electrically connected to the terminal fitting is disposed, and an axial length of the ceramic sintered body resistor is 40% or more of an axial length of the second through hole. In the present invention, it is preliminarily sintered as such a resistor. By inserting the ceramic sintered body resistor into the second through-hole of the insulator, the length of the ceramic sintered body resistor is sufficiently long without being restricted by the length of manufacturing as in the prior art. As a result, the effective dielectric constant between the center electrode and the terminal electrode can be reduced, the capacitive discharge current generated during ignition can be reduced, and the noise prevention effect can be increased. By setting the length (LR) of the combined resistor to 40% or more of the length (LH) of the second through hole ((LR / LH) × 100 ≧ 40), the distance between the center electrode and the terminal electrode is increased. It is possible to reduce the effective dielectric constant, reduce the capacity discharge current generated at the time of ignition, and obtain a sufficient noise prevention effect.The length (LR) of the ceramic sintered body resistor is the second through hole. When the length (LH) is less than 40%, sufficient effect is obtained. Furthermore, the more preferable length (LR) of the ceramic sintered body resistor is 50% or more of the length (LH) of the second through hole ((LR / LH) × 100 ≧ 50). It is shown that by optimizing the structure of the spark plug, the effective dielectric constant between the terminal electrode and the center electrode is reduced to prevent the generation of high-frequency noise radio waves. However, even if such optimization is performed, leakage of high-frequency noise radio waves cannot be sufficiently suppressed.

  In addition, when the spark plug is downsized, the mechanical strength of the resistor decreases, or the frictional resistance at the time of press-fitting the terminal electrode increases, so that it becomes difficult to press-fit the terminal electrode, and the resistance value of the resistor varies. It becomes easy. In addition, it is considered that it is easily affected by fluctuations in the hot press temperature, and the resistance values of the resistors are likely to vary. In the spark plug manufacturing process, it is difficult to strictly regulate the hot press temperature, and the hot press temperature must be managed with a certain fluctuation range.

  In view of the above, the present invention is to create a resistor-forming glass composition that has a high high-frequency noise radio wave absorption capability and can function properly as block particles in order to form a resistor that efficiently absorbs high-frequency noise radio waves. Therefore, it is a technical subject to improve the reliability of a small spark plug.

As a result of diligent efforts, the present inventors reduced the dielectric constant of the glass while maintaining the softening properties of the glass. Specifically, the content of BaO in the glass composition while introducing CaO into the glass composition. It is found that the above-mentioned technical problem can be solved by regulating the amount to a predetermined amount or less, and is proposed as the present invention. That is, the glass powder for the resistor forming the present invention, as a glass composition, in _{mol%, SiO 2 40~60%, B} 2 O 3 28~40%, Li 2 O + Na 2 O + K 2 O 1~20%, CaO It contains 0.1 to 20% and BaO 0 to 7%.

  The glass powder for resistor formation of the present invention regulates the glass composition range, particularly the CaO and BaO content range as described above. In this way, since the dielectric constant of the glass can be lowered, the glass's ability to absorb high-frequency noise radio waves can be significantly increased, and as a result, the spark plug can be easily downsized. In this way, the thermal expansion coefficient of the glass can be lowered while improving the thermal stability of the glass without unduly increasing the yield point of the glass.

  Secondly, the resistor-forming glass powder of the present invention is characterized in that the CaO content is 3 mol% or more as a glass composition.

Thirdly, the glass powder for the resistor forming the present invention, a glass composition, the content of B ₂ O ₃ is characterized in that it is 30 to 35 mol%.

  Fourthly, the resistor forming glass powder of the present invention is characterized in that the particle size is 150 to 450 μm. If the particle size of the glass powder is regulated as described above, it can be deformed without taking in the conductive powder in the hot pressing process, and if processed into granules, it becomes easy to fill the glass powder in the inner holes of the insulator.

  Fifth, the resistor-forming glass powder of the present invention is characterized in that the dielectric constant at 25 ° C. and 1 MHz is 5.5 or less. In this way, the ability of glass to absorb high-frequency noise radio waves is significantly improved, and even if the glass content in the resistor is small, high-frequency noise radio waves can be sufficiently absorbed, making it easier to reduce the size of the spark plug. . Here, the “dielectric constant at 25 ° C. and 1 MHz” is a glass substrate of 50 × 50 × 3 mm (a glass powder densely sintered) or a glass ingot of 50 × 50 × 3 mm as a measurement sample. It refers to a value measured by attaching electrodes of 30 mmφ to the front and back surfaces of an optically polished glass substrate and applying a voltage between the electrodes.

  The inventors of the present invention focused on the fact that the dielectric constant of the resistor can be reduced by reducing the dielectric constant of the glass, and for this purpose, the inventors have found that the glass composition range should be regulated as described above. . As a result, the effective dielectric constant between the center electrode and the terminal electrode is reduced, the capacity discharge current generated when the ignition plug is ignited can be reduced, and as a result, the ability to absorb high-frequency noise radio waves can be improved.

  Sixth, the resistor-forming glass powder of the present invention is characterized in that the dielectric loss tangent at 25 ° C. and 1 MHz is larger than 0.0018. Here, “dielectric loss tangent at 25 ° C., 1 MHz” is a glass substrate of 50 × 50 × 3 mm (a glass powder densely sintered) or a glass ingot of 50 × 50 × 3 mm as a measurement sample. It refers to a value measured by attaching electrodes of 30 mmφ to the front and back surfaces of an optically polished glass substrate and applying a voltage between the electrodes.

  Through detailed investigations by the present inventors, it has been found that increasing the dielectric loss tangent of glass increases the ability of glass to absorb high frequency noise. The details of this mechanism are not clear and are currently under scrutiny. It is estimated that the noise radio wave energy is easily converted into thermal energy, and the high frequency noise radio wave is attenuated.

  Seventh, the resistor-forming glass powder of the present invention is characterized by having phase separation characteristics. Here, “having phase separation characteristics” refers to a case where glass undergoes phase separation when heat treatment is performed at any temperature of 600 to 900 ° C. for 10 minutes, for example, by TEM (Transmission Electron Microscope) or the like. If observed, it can be determined whether the glass is phase-separated. In addition, when the glass powder for forming a resistor is already phase-divided before the heat treatment is performed, it is determined that it has “phase-separation characteristics”.

In general, the phase separation refers to a state in which the glass component is separated into a high-viscosity silica-rich phase mainly composed of SiO ₂ and a low-viscosity glass phase composed of other components. Usually, the silica-rich phase has a skeleton, and a low-viscosity glass phase exists in the gap. When the resistor forming glass powder has phase separation characteristics, the coarse glass powder hardly dissolves conductive powder such as carbon black, titanium carbide, titanium nitride, and silicon carbide in the glass in the hot pressing step. On the other hand, the fine glass powder dissolves the conductive powder in the glass in a hot pressing process. As a result, a conductive path made of conductive powder can be formed in the vicinity of the coarse glass powder. The reason why the coarse glass powder does not take in the conductive powder in the hot pressing process is thought to be due to the phase separation of the glass, but the detailed mechanism is unknown and is currently under intensive investigation. In addition, when the resistor forming glass powder has phase separation characteristics, the coarse glass powder undergoes plastic deformation due to the softening flow of the low-viscosity glass phase in the hot pressing process. The shape can be maintained and it can function as a block particle.

  Eighth, the resistor-forming glass powder of the present invention is characterized by having a glass transition point of 485 to 560 ° C. Here, the “glass transition point” refers to a value measured by a push rod type thermal expansion coefficient measurement (TMA) apparatus.

  Ninthly, the glass powder for resistor formation of this invention is characterized by a yield point being 530-700 degreeC. Here, the “bend point” refers to a value measured with a TMA apparatus.

Tenth, the glass powder for forming a resistor of the present invention is characterized by a thermal expansion coefficient of 40 to 60 × 10 ⁻⁷ / ° C. Here, the “thermal expansion coefficient” refers to a value measured with a TMA apparatus, and refers to a value measured within a temperature range of 30 to 380 ° C.

  Eleventh, the glass powder for forming a resistor according to the present invention is characterized by containing substantially no PbO. In this way, environmental demands in recent years can be satisfied. Here, “substantially no PbO” refers to the case where the content of PbO in the glass composition is 1000 ppm (mass) or less.

  Twelfth, the glass powder for forming a resistor of the present invention is characterized by being used for a spark plug.

It is explanatory drawing which shows the principal part of a spark plug with a resistor.

  The reason for limiting the glass composition range as described above in the resistor-forming glass powder of the present invention will be described below.

SiO ₂ is a component that forms a skeleton of the glass, is a component that thermally stabilizes the glass and lowers the thermal expansion coefficient of the glass, and its content is 40 to 60%, preferably 45 to 58%. More preferably, it is 48 to 54%. When the content of SiO ₂ is less than 40%, the glass becomes thermally unstable, and it becomes difficult to stably produce the glass. In addition, the thermal expansion coefficient of the glass increases too much, and the resistor and the conductive glass. Peeling or cracking is likely to occur at the interface of the body or insulator. On the other hand, when the content of SiO ₂ is more than 60%, the yield point of the glass is unreasonably raised, and the glass is difficult to be deformed in the hot press process, and problems such as terminal floating are likely to occur.

B ₂ O ₃ is a component that forms the skeleton of the glass, is a component that thermally stabilizes the glass and lowers the yield point of the glass, and further is a component that causes phase separation of the glass. The content is 28 to 40%, preferably 30 to 37%, more preferably 31 to 35%. If the content of B ₂ O ₃ is less than 28%, the glass becomes thermally unstable and it becomes difficult to stably produce the glass, and the yield point of the glass is unreasonably raised, Glass becomes difficult to be deformed, and problems such as terminal floating are likely to occur. On the other hand, when the content of B ₂ O ₃ is more than 40%, the thermal expansion coefficient of the glass is excessively increased, and peeling or cracking is likely to occur at the interface between the resistor and the conductive glass body or the insulator.

Li ₂ O + Na ₂ O + K ₂ O is a component for lowering the yield point of glass and promoting phase separation of glass, and its content is 1 to 20%, preferably 3 to 17%, more preferably 5 to 15%, more preferably 7 to 13%. When the content of Li ₂ O + Na ₂ O + K ₂ O is more than 20%, the thermal expansion coefficient of the glass is excessively increased, and peeling or cracking is likely to occur at the interface between the resistor and the conductive glass body or the insulator.

Li ₂ O is a component for reducing the yield point of glass and promoting phase separation of glass, and its content is 0 to 15%, preferably 0.1 to 13%, more preferably 1 to 1. 13%, more preferably 2.5 to 12%, particularly preferably 5 to 10%. When the content of Li ₂ O is more than 15%, the thermal expansion coefficient of the glass is excessively increased, and peeling or cracking is likely to occur at the interface between the resistor and the conductive glass body or the insulator. In addition, from the viewpoint of promoting the phase separation of glass, it is preferable to contain 1% or more of Li ₂ O as an essential component in the glass composition.

Na ₂ O is a component for reducing the yield point of glass and promoting phase separation of glass, and its content is 0 to 15%, preferably 0 to 12%, more preferably 0 to 0%. 3%. When the content of Na ₂ O is more than 15%, the thermal expansion coefficient of the glass is excessively increased, and peeling or cracking is likely to occur at the interface between the resistor and the conductive glass body or the insulator.

K ₂ O is a component for reducing the yield point of the glass and promoting phase separation of the glass, and its content is 0 to 15%, preferably 0 to 12%, more preferably 0 to 0%. 3%. When the content of K ₂ O is more than 15%, the thermal expansion coefficient of the glass is excessively increased, and peeling or cracking is likely to occur at the interface between the resistor and the conductive glass body or the insulator.

  CaO is a main component that significantly lowers the dielectric constant of glass and a component that lowers the yield point of glass, and its content is 0.1 to 20%, preferably 1 to 15%, more preferably. 3 to 12%, more preferably 5 to 10%. When the content of CaO is more than 20%, the thermal expansion coefficient of the glass is excessively increased, and peeling or cracking is likely to occur at the interface between the resistor and the conductive glass body or the insulator. On the other hand, if the content of CaO is less than 0.1%, the glass's ability to absorb high-frequency noise radio waves decreases, and as a result, it is difficult to reduce the size of the spark plug. On the other hand, when the CaO content is less than 0.1%, the yield point of the glass is unreasonably raised, and the glass is hardly deformed in the hot pressing process, and problems such as terminal floating are likely to occur.

  BaO is a component that lowers the yield point of the glass, and also prevents a variation in the resistance value of the spark plug when the hot press temperature fluctuates, and its content is 0 to 7%, preferably 0 to 0%. 5%, more preferably 0.1 to 3%. When the content of BaO is more than 7%, the dielectric constant of the glass increases, and the high-frequency noise radio wave absorption ability of the glass decreases. On the other hand, if the content of BaO is more than 7%, the thermal expansion coefficient of the glass is excessively increased, and peeling or cracking is likely to occur at the interface between the resistor and the conductive glass body or the insulator. In addition, it is preferable that BaO is not substantially contained as a glass composition from a viewpoint of reducing the dielectric constant of glass reliably. Here, “substantially does not contain BaO” refers to a case where the content of BaO is 3000 ppm (mass) or less in the glass composition.

  The glass powder for resistor formation of this invention can contain the following components other than the said component as a glass composition, for example.

Al ₂ O ₃ is a component that lowers the thermal expansion coefficient of glass together with a component that improves the water resistance of glass, and its content is 0 to 10%, preferably 0 to 5%. When the content of Al ₂ O ₃ is more than 10%, the yield point of the glass is unreasonably raised, the glass is hardly deformed in the hot pressing process, and problems such as terminal floating are likely to occur.

  MgO is a component that significantly lowers the dielectric constant of the glass and lowers the yield point of the glass, and is a component for promoting the phase separation of the glass, and its content is 0 to 20%, preferably It is 0 to 15%, more preferably 0 to 10%, more preferably 0 to 7%. When the content of MgO is more than 20%, the thermal expansion coefficient of the glass is excessively increased, and peeling or cracking is likely to occur at the interface between the resistor and the conductive glass body or the insulator.

  SrO is a component that lowers the dielectric constant of the glass and lowers the yield point of the glass, and is a component that prevents a problem that the resistance value of the spark plug varies when the hot press temperature fluctuates. The content is 0 to 20%, preferably 0 to 15%, more preferably 0 to 10%, and more preferably 0 to 7%. When the content of SrO is more than 20%, the thermal expansion coefficient of the glass is excessively increased, and peeling or cracking is likely to occur at the interface between the resistor and the conductive glass body or the insulator.

  Alkaline earth metal oxides (MgO, CaO, SrO, BaO) are components for promoting the phase separation of glass and at the same time, components that affect the dielectric constant of glass. The smaller the ionic radius of the alkaline earth metal oxide, the easier the glass is phase-separated. Specifically, the glass is more likely to phase-separate in the order of MgO, CaO, SrO, BaO. When the phase separation tendency of glass becomes high, the phase separation state easily fluctuates even with a small change in the heat treatment temperature. As a result, when the hot press temperature fluctuates, the resistance value of the spark plug varies. It becomes easy. On the other hand, the smaller the molecular weight of the alkaline earth metal oxide, the smaller the dielectric constant of the glass. Specifically, the dielectric constant of the glass decreases in the order of MgO, CaO, SrO, BaO. When characteristics such as dielectric constant, phase separation, yield point, etc. are comprehensively considered, as described in paragraphs [0034] and [0035] of the present specification, the content of CaO in the glass composition is 0.1 to 20%. The content of BaO in the glass composition is preferably 0 to 7%, preferably 0 to 5%, more preferably 1 to 15%, more preferably 3 to 12%, and still more preferably 5 to 10%. Preferably, it should be restricted to 0.1 to 3%. In this way, the ability to absorb high-frequency noise radio waves can be dramatically increased, and further, it is possible to prevent a problem that the resistance value of the spark plug varies. As a result, the reliability and productivity of the spark plug are improved. Can be improved.

Moreover, the glass powder for resistor formation of this invention can add a various component to 10% further as a glass composition. For _{example, TiO 2, ZrO 2, Bi} 2 O 3, Cs 2 O, La 2 O 3, Gd 2 O 3, V 2 O 5, WO 3, Sb 2 O 3, SnO 2, Nb 2 O 5, Y 2 O ₃ , CeO ₂ , P ₂ O _{5 and the} like can be added. In addition, although the glass powder for resistor formation of this invention does not exclude inclusion of PbO completely, it is preferable not to contain PbO substantially from an environmental viewpoint as stated above.

  In the resistor forming glass powder of the present invention, the particle size of the glass powder is 150 to 450 μm, preferably 200 to 350 μm. If the particle size of the glass powder is 150 to 450 μm, it can function properly as block particles. That is, if the particle size of the glass powder is 150 to 450 μm, the glass powder can be deformed without taking in the conductive powder in the hot pressing process, and if processed into granules, it becomes easy to fill the glass powder into the inner holes of the insulator. If the particle size of the glass powder is smaller than 150 μm, the glass powder dissolves the conductive powder in the hot pressing process, and the coarse glass powder becomes difficult to function as block particles that bypass the conductive path, and the resistor absorbs high frequency noise waves. Tends to decrease. On the other hand, when the particle size of the glass powder is larger than 450 μm, it becomes difficult to process into granules and it becomes difficult to fill the glass powder into the inner hole of the insulator, and in addition, the glass powder is difficult to deform in the hot pressing process, and the terminal floats. Etc. are likely to occur.

In the glass powder for the resistor forming the present invention, the average particle diameter _{D 50} of the glass powder is preferably 150~450μm, 200~350μm is more preferable. If the average particle diameter _{D 50} of the glass powder 150～450Myuemu, can function properly as a block particles. That is, if the average particle diameter D ₅₀ of the glass powder 150～450Myuemu, it is possible to deform without incorporating the conductive powder by hot pressing step, be processed into granules, easily the glass powder was filled in the inner hole of the insulator Become. And 150μm smaller than the average particle diameter D ₅₀ of the glass powder, the glass powder is dissolved conductive powder by hot pressing step, coarse glass powder becomes difficult to function as a block particles divert conductive path, high frequency noise of the resistor The ability to absorb radio waves tends to decrease. On the other hand, the average particle diameter D ₅₀ of the glass powder is larger than 450 [mu] m, hardly processed into granules, in addition to being difficult to fill the glass powder in the inner hole of the insulator, the glass powder is hardly deformed by hot pressing step Thus, problems such as terminal floating are likely to occur. Here, the “average particle diameter D ₅₀ ” refers to a value measured by the laser diffraction method. In the volume-based cumulative particle size distribution curve measured by the laser diffraction method, the accumulated amount is accumulated from the smaller particle. The particle diameter is 50%.

In the glass powder for forming a resistor of the present invention, the maximum particle diameter _Dmax of the glass powder is preferably 450 μm or less, and more preferably 400 μm or less. When the average particle diameter _Dmax of the glass powder is larger than 450 μm, it becomes difficult to process into granules, and when the inner hole of the insulator is reduced in diameter, it becomes difficult to fill the inner hole of the insulator with the glass powder. Here, the “maximum particle diameter D _max ” refers to a value measured by the laser diffraction method. In the volume-based cumulative particle size distribution curve measured by the laser diffraction method, the accumulated amount is accumulated from the smaller particle. The particle diameter is 99%.

The resistor-forming glass powder of the present invention can also be used as a fine-grained glass powder for forming a resistor. In that case, the average particle diameter _{D 50} of the glass powder is preferably less than 150 [mu] m, more preferably at most 100 [mu] m. If the average of the glass powder the particle diameter D ₅₀ is at 150μm or more, hardly glass powder melted in the hot pressing process, defects such as pin lifting is likely to occur. Note that if the coarse glass powder and the fine glass powder have the same glass composition, the two are firmly bonded in the hot pressing step, so that the mechanical strength of the resistor can be increased.

  In the resistor forming glass powder of the present invention, the dielectric constant at 25 ° C. and 1 MHz is preferably 5.5 or less, more preferably 5.3 or less, and even more preferably 5.2 or less. If the dielectric constant at 25 ° C. and 1 MHz is greater than 5.5, the glass's ability to absorb high-frequency noise radio waves will be low, and if the spark plug is downsized, it will be difficult to absorb high-frequency noise radio waves. May interfere with radio, radio, etc.

  In the glass powder for forming a resistor of the present invention, the dielectric loss tangent at 25 ° C. and 1 MHz is preferably larger than 0.018, more preferably 0.0020 or more, and further preferably 0.0025 or more. If the dielectric loss tangent at 25 ° C. and 1 MHz is less than 0.0018, it will be difficult to increase the high frequency noise absorption capability of the glass, and if the spark plug is downsized, it will be difficult to sufficiently absorb the high frequency noise radio waves. May interfere with TV, radio, radio, etc.

In the glass powder for the resistor forming the present invention, the density is preferably less than 2.55 g / cm ^3, more preferably 2.50 g / cm ³ or less, more preferably 2.45 g / cm ³ or less. The smaller the density, the lighter the glass and, as a result, the lighter the spark plug.

  In the glass powder for forming a resistor of the present invention, the glass transition point is preferably 485 to 590 ° C, more preferably 490 to 550 ° C, and further preferably 500 to 540 ° C. When the glass transition point is lower than 485 ° C., the coarse glass powder easily dissolves the conductive powder in the hot pressing process, so that the coarse glass powder hardly functions as a block particle that bypasses the conductive path, and the high frequency of the resistor Noise absorption capacity is likely to decrease. On the other hand, when the glass transition point is higher than 590 ° C., it is difficult for the glass to be deformed in the hot pressing process, and problems such as terminal floating are likely to occur.

  In the glass powder for forming a resistor of the present invention, the yield point is preferably 530 to 700 ° C, more preferably 540 to 650 ° C, and further preferably 550 to 600 ° C. When the yield point is lower than 530 ° C., the coarse glass powder easily dissolves the conductive powder in the hot pressing process, so that the coarse glass powder hardly functions as a block particle that bypasses the conductive path, and the high-frequency noise of the resistor The ability to absorb radio waves tends to decrease. On the other hand, if the yield point is higher than 700 ° C., the glass is not easily deformed in the hot pressing process, and problems such as floating of the terminal are likely to occur.

In the glass powder for the resistor forming the present invention, the thermal expansion coefficient is preferably 40 to 60 × ^{10 -7} / ° C., more preferably 45~58 × ^{10 -7} / ℃, is 53~58 × ^{10 -7} / ℃ Further preferred. In order to make the thermal expansion coefficient lower than 40 × 10 ⁻⁷ / ° C., it is necessary to increase the content of SiO ₂ or the like in the glass composition. In such a case, the yield point of the glass becomes high. As a result, the glass becomes difficult to be deformed in the hot pressing process, and problems such as terminal floating easily occur. On the other hand, if the thermal expansion coefficient is higher than 60 × 10 ⁻⁷ / ° C., peeling or cracking is likely to occur at the interface between the resistor and the conductive glass body or the insulator.

  The resistor-forming glass powder of the present invention preferably has phase separation characteristics. Since the preferable reason has already been described, the description thereof is omitted here for convenience.

  The glass powder for forming a resistor of the present invention is preferably used for a spark plug. The resistor-forming glass powder of the present invention is advantageous when the spark plug is miniaturized because it can sufficiently absorb high-frequency noise radio waves even if the filling amount of the glass powder is reduced.

  Hereinafter, based on an Example, this invention is demonstrated in detail. Tables 1 to 5 show examples (sample Nos. 1 to 28) and comparative examples (sample No. 29) of the present invention. Sample No. 29 is a conventional resistor forming glass powder.

First, a glass batch in which raw materials such as various oxides and carbonates were prepared so as to have the glass composition in the table was prepared, and this was put in a platinum crucible and melted at 1300 ° C. for 2 hours. Next, a part of the molten glass was poured out into a carbon mold to obtain a plate-like glass sample. Further, the water-cooled rollers, after forming a portion of the molten glass in the flake, after grinding in a ball mill and then classified with test sieves, particle size of each glass powder 150～450Myuemu (average particle diameter _D 50 = 300 [mu] m) Obtained. During classification, glass powder that passed through a test sieve having an opening of 450 μm and not passed through a test sieve having an opening of 150 μm was collected.

  Sample No. For 1 to 29, the glass transition point, yield point, thermal expansion coefficient, dielectric constant, dielectric loss tangent, volume resistivity, function as block particles, sinterability, and phase separation were evaluated.

  The glass transition point and yield point were measured with a TMA apparatus. In addition, the measurement sample of TMA used what sintered the glass powder.

  The thermal expansion coefficient was measured in a temperature range of 30 to 380 ° C. using a TMA apparatus. In addition, the measurement sample of TMA used what sintered the glass powder.

  The dielectric constant and dielectric loss tangent were measured using a glass substrate of 50 mm × 50 mm × 3 mm thickness (glass powder densely sintered, front and back surfaces optically polished) as the measurement sample, and electrodes of 30 mmφ on the front and back surfaces of the glass substrate. The measurement was performed by applying a voltage between the electrodes. The measurement conditions were 25 ° C. and 1 MHz, and the front and back surfaces of the glass substrate were optically polished.

  The volume resistivity was measured by a method based on ASTM C657-78. A 50 mm × 50 mm × 0.7 mm thick glass substrate (glass powder densely sintered, front and back surfaces optically polished) was used as a measurement sample. A metal Al film was formed on the front and back surfaces of this glass substrate by vapor deposition to form an electrode having a thickness of about 2000 nm. The main electrode was a circle with a diameter of 29 mm, the guard electrode was a ring with an outer diameter of 44 mm and an inner diameter of 31 mm, and the bottom electrode was a circle with a diameter of 44 mm. Next, the volume resistivity at each temperature in the table was measured.

The function as a block particle was measured as follows. First, a sample in which 5% by mass of carbon black was added to each glass powder having a mass corresponding to the density of the glass was pressed into a button shape having an outer diameter of 20 mm using a mold. Subsequently, after the obtained button sample was sandwiched between alumina substrates, it was put into an electric furnace maintained at 900 ° C., heated at a press pressure of 100 kg / cm ² for 10 minutes, and then the button sample was removed from the electric furnace. The button sample was taken out and evaluated by observing the appearance of the obtained button sample. The glass powder is slightly deformed, but it is not completely melted and the carbon black is not dissolved in the glass is marked with “O”, the glass powder is completely melted, or the carbon black is not in the glass. What was melt | dissolved was evaluated as "x".

For sinterability, glass powder having a mass corresponding to the density of glass (average particle diameter D ₅₀ = 50 μm) was pressed into a button shape having an outer diameter of 20 mm using a mold, and the obtained button sample was placed on an alumina substrate. After mounting, the temperature was raised at 20 ° C./min in an electric furnace, held at 900 ° C. for 10 minutes, lowered at a rate of 20 ° C./min, and evaluated by observing the appearance of the obtained button sample. did. If the button sample is glossy and the button sample has a diameter of 17.8 mm or less, “○” is given. If the button sample is not glossy or if the button sample has a diameter greater than 17.8 mm, “×” ".

  The phase separation was evaluated by observing with a TEM a sample obtained by processing the button sample into a predetermined shape. The glass was phase-separated as “◯”, and the glass not phase-separated as “x”.

  As is apparent from Tables 1 to 5, sample No. In Nos. 1 to 28, the glass transition point, yield point, thermal expansion coefficient, dielectric constant, dielectric loss tangent, function as block particles, sinterability and phase separation were good. In particular, sample no. 1 to 28 can reduce the effective dielectric constant between the terminal electrode and the center electrode because the dielectric constant is low. As a result, even if the spark plug is downsized, high-frequency noise radio waves can be absorbed accurately. it is conceivable that. On the other hand, sample No. No. 29 contains a large amount of BaO in the glass composition and does not contain CaO, and therefore has a high dielectric constant. If the spark plug is downsized, it is considered that high frequency noise radio waves leak.

  An experiment was conducted to investigate the effect of the particle size of the glass powder. The experimental results are shown in Table 6.

  First, a glass batch in which raw materials such as various oxides and carbonates were prepared so as to have the glass composition in the table was prepared, and this was put in a platinum crucible and melted at 1300 ° C. for 2 hours. Next, a part of the molten glass was formed into a flake shape with a water-cooled roller, pulverized with a ball mill under various conditions, and then classified with a test sieve to obtain each glass powder. Sample No. In the case of classification, 32-35 collected glass powder that passed through a sieve having an opening of 450 μm and not passed through a sieve having an opening of 150 μm.

The average particle diameter D ₅₀ of the glass powder was measured by a laser diffraction apparatus.

The function as a block particle was measured as follows. First, a sample in which 5% by mass of carbon black was added to each glass powder having a mass corresponding to the density of the glass was pressed into a button shape having an outer diameter of 20 mm using a mold. Subsequently, after the obtained button sample was sandwiched between alumina substrates, it was put into an electric furnace maintained at 900 ° C., heated at a press pressure of 100 kg / cm ² for 10 minutes, and then the button sample was removed from the electric furnace. The button sample was taken out and evaluated by observing the appearance of the obtained button sample. The glass powder is slightly deformed, but it is not completely melted and the carbon black is not dissolved in the glass is marked with “O”, the glass powder is completely melted, or the carbon black is not in the glass. What was melt | dissolved was evaluated as "x".

  As apparent from Table 6, the sample No. 32 to 35 are considered to function as block particles because the particle size of the glass powder is appropriate. On the other hand, sample No. Nos. 30 and 31 can be used for fine glass powder because the particle size of the glass powder is small, but it is considered difficult to function as block particles.

  As apparent from the above description, the glass powder for forming a resistor of the present invention is suitable as a coarse glass powder for forming a resistor in the inner hole of an insulator of a spark plug.

DESCRIPTION OF SYMBOLS 1 Terminal electrode 2a, 2b Conductive glass body 3 Center electrode 4 Resistor

Claims (12)

As a glass composition, in _{mol%, SiO 2 40~60%, B} 2 O 3 28~40%, Li 2 O + Na 2 O + K 2 O 1~20%, CaO 0.1~20%, the 0 to 7% BaO A glass powder for forming a resistor, comprising:   The glass powder for forming a resistor according to claim 1, wherein the glass composition has a CaO content of 3 mol% or more. The glass powder for forming a resistor according to claim 1 or 2, wherein the glass composition has a content of B ₂ O ₃ of 30 to 35 mol%.   4. The resistor forming glass powder according to claim 1, wherein the particle size is 150 to 450 [mu] m.   5. The resistor-forming glass powder according to claim 1, wherein a dielectric constant at 25 ° C. and 1 MHz is 5.5 or less.   6. The glass composition for forming a resistor according to claim 1, wherein a dielectric loss tangent at 25 ° C. and 1 MHz is larger than 0.0018.   The glass powder for forming a resistor according to any one of claims 1 to 6, which has phase separation characteristics.   A glass transition point is 485-560 degreeC, The glass powder for resistor formation in any one of Claims 1-7 characterized by the above-mentioned.   A yield point is 530-700 degreeC, The glass powder for resistor formation in any one of Claims 1-8 characterized by the above-mentioned. The thermal expansion coefficient is 40 to 60 × 10 ⁻⁷ / ° C., the resistor-forming glass powder according to claim 1.   The glass powder for forming a resistor according to any one of claims 1 to 10, which does not substantially contain PbO.   The resistor forming glass powder according to claim 1, wherein the resistor forming glass powder is used for a spark plug.