JP2011084461A - Glass composition for forming resistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the reliability and the productivity of a spark plug by creating a glass composition for forming a resister sufficiently suppressing generation of high frequency noise radio waves even if the diameter of the spark plug is reduced. <P>SOLUTION: The glass composition for forming a resister contains as a glass composition, by mass, 35-60% of SiO<SB>2</SB>, 25-55% of B<SB>2</SB>O<SB>3</SB>, 0-20% of Li<SB>2</SB>O+Na<SB>2</SB>O+K<SB>2</SB>O and 0.1-25% of ZnO. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a glass composition for forming a resistor, and more particularly to a glass composition for forming a resistor suitable for forming a resistor for a spark plug and a spark plug having the resistor. Note that the resistor of the spark plug can act as an electromagnetic wave absorber that absorbs electromagnetic waves such as high-frequency noise radio waves.

  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, the resistor material is a granulated composite powder containing coarse glass powder, fine glass powder, ceramic powder, conductive powder, and the like. Resistors made using this resistor material have a coarse glass powder or ceramic powder that retains its original shape, and a bonded glass phase in which fine glass powder melts and solidifies in the gaps between these particles. It becomes. 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, especially meridian. When the spark plug is reduced in diameter, the inner diameter of the insulator is also reduced, so that the volume of the resistor is inevitably reduced, and as a result, the resistor becomes difficult to absorb high-frequency noise radio waves. 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 has been 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 suppress the leakage 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 the case of a spark plug with a reduced diameter.

  In addition, when the spark plug is reduced in diameter, 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 increases. It tends to vary. 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.

  Therefore, the present invention improves the reliability and productivity of a spark plug by creating a glass composition for forming a resistor that can sufficiently suppress the generation of high-frequency noise radio waves even when the spark plug is made more compact. This is a technical issue.

  Furthermore, an object of the present invention is to provide a spark plug having a resistor formed of a resistor forming material that can sufficiently suppress the generation of high-frequency noise radio waves.

As a result of diligent efforts, the present inventor can solve the above technical problem by reducing the dielectric constant of glass while maintaining the softening properties of glass, specifically by introducing ZnO into borosilicate glass. Are proposed as the present invention. That is, the glass composition for forming a resistor of the present invention has, as a glass composition, mass%, SiO ₂ 35-60%, B ₂ O ₃ 25-55%, Li ₂ O + Na ₂ O + K ₂ O (Li ₂ O, Total amount of Na ₂ O and K ₂ O) 0 to 20% and ZnO 0.1 to 25%.

  The glass composition for resistor formation of the present invention regulates the glass composition range as described above. In this way, since the dielectric constant of the glass can be reduced, the generation of high-frequency noise radio waves during ignition of the spark plug can be suppressed, and as a result, the spark plug can be easily reduced in diameter. In this way, the thermal expansion coefficient of the glass can be lowered while increasing the thermal stability of the glass without unduly increasing the yield point of the glass.

  Secondly, the glass composition for forming a resistor 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, since the generation of high-frequency noise radio waves can be suppressed when the ignition plug is ignited, the resistor can sufficiently absorb high-frequency noise radio waves even if the volume of the resistor is small. For this reason, it becomes easy to reduce the diameter of the spark plug. Here, “dielectric constant at 25 ° C. and 1 MHz” is a measurement of a plate glass of 50 × 50 × 3 mm (a glass powder densely sintered) or a plate glass ingot of 50 × 50 × 3 mm. It is used as a sample, and refers to a value measured by attaching electrodes of 30 mmφ on the front and back surfaces of optically polished glass and applying a voltage between the electrodes.

  The present inventor pays attention to the fact that the dielectric constant of the resistor can be reduced by reducing the dielectric constant of the glass. In order to reduce the dielectric constant of the resistor, the glass composition range is regulated as described above. I found a good thing. Thereby, since the effective dielectric constant between the center electrode and the terminal electrode is reduced, the capacity discharge current generated at the time of ignition of the spark plug can be reduced, and as a result, generation of high frequency noise radio waves can be suppressed.

  Thirdly, the glass composition for forming a resistor of the present invention is characterized in that a dielectric loss tangent at 25 ° C. and 1 MHz is 0.0008 or more. If it does in this way, since the absorption capability of the high frequency noise radio wave of glass will increase, it will become easy to make a spark plug thin. Here, “dielectric loss tangent at 25 ° C. and 1 MHz” is a measurement of a plate glass of 50 × 50 × 3 mm (a glass powder densely sintered) or a plate glass ingot of 50 × 50 × 3 mm. It is used as a sample, and refers to a value measured by attaching electrodes of 30 mmφ on the front and back surfaces of optically polished glass and applying a voltage between the electrodes.

  As a result of detailed investigation, the present inventor has found that when the dielectric loss tangent of glass is increased, the ability of glass to absorb high-frequency noise waves increases. Although the details of this mechanism are not clear and are currently under scrutiny, the present inventor has found that when the dielectric loss tangent of the glass is large, the interface of the coarse glass powder contained in the resistor when the spark plug is ignited. , It is estimated that the energy of the high frequency noise radio wave is easily converted into thermal energy, and the high frequency noise radio wave is attenuated.

  Fourth, the resistor-forming glass composition of the present invention is characterized by a glass transition point of 430 to 570 ° C. Here, the “glass transition point” refers to a value measured by a push rod type thermal expansion coefficient measurement (TMA) apparatus.

  Fifth, the glass composition for forming a resistor of the present invention is characterized in that a yield point is 500 to 680 ° C. Here, the “bend point” refers to a value measured with a TMA apparatus.

Sixth, the glass composition 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 an average value measured in a temperature range of 30 to 380 ° C.

  Seventh, the glass composition 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 does not contain PbO” refers to a case where the content of PbO in the glass composition is 1000 ppm or less.

  Eighth, the resistor-forming glass composition of the present invention is characterized by being used for a spark plug.

  Ninthly, the glass powder for forming a resistor of the present invention is characterized in that it contains a glass powder made of the above glass composition for forming a resistor.

  Tenth, the resistor forming glass powder of the present invention is characterized by having phase separation. Here, “having phase separation” 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, and is observed with, for example, TEM (Transmission Electron Microscope) or the like. If it does, it can be determined whether 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 as “having phase separation”.

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. In general, the silica-rich phase has a skeleton, and a low-viscosity glass phase exists in the gap. When the coarse-grained glass powder has phase separation, it becomes difficult to dissolve 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 coarse glass powder has phase separation, it is plastically deformed due to the softening flow of the low-viscosity glass phase in the hot pressing process, but its shape is maintained by the presence of the silica-rich phase and functions as block particles. be able to.

  Eleventh, the resistor forming glass powder of the present invention is characterized in that the particle size of the glass powder is 150 to 450 μm.

  Twelfth, the spark plug of the present invention includes an insulator having an axial hole extending in the axial direction, a center electrode provided on one end side of the axial hole, and a terminal electrode provided on the other end side of the axial hole. A spark plug including a resistor disposed between the center electrode and the terminal electrode, the glass composition range of the resistor-forming glass composition constituting the resistor is regulated as described above. . In this way, since the dielectric constant of the glass can be reduced, the generation of high-frequency noise radio waves during ignition of the spark plug can be suppressed, and as a result, the spark plug can be easily reduced in diameter. In this way, the thermal expansion coefficient of the glass can be lowered while increasing the thermal stability of the glass without unduly increasing the yield point of the glass. Further, the “resistor” means a resistor whose resistance value is usually 100Ω or more.

Thirteenth, the resistor forming a glass composition constituting the resistor spark plug has the present invention, further by _{mass%, ZnO 7.1~12.2%, Li 2} O + Na 2 O + K 2 O 2. It contains 6 to 12%. By restricting ZnO and Li ₂ O + Na ₂ O + K ₂ O to the above range, the sealing performance at the time of hot pressing at 850 ° C. is improved, that is, it is possible to suppress the occurrence of a problem that the terminal floats at the time of hot pressing. It becomes. However, when Li ₂ O + Na ₂ O + K ₂ O is 19% or more, the sealing performance is good without depending on the amount of ZnO.

  14thly, the glass composition for resistor formation which comprises the resistor which the spark plug of this invention has is characterized by the dielectric constant in 25 degreeC and 1 MHz being 5.5 or less. In this way, since the generation of high-frequency noise radio waves can be suppressed when the ignition plug is ignited, the resistor can sufficiently absorb high-frequency noise radio waves even if the volume of the resistor is small. For this reason, it becomes easy to reduce the diameter of the spark plug. Here, “dielectric constant at 25 ° C. and 1 MHz” is a measurement of a plate glass of 50 × 50 × 3 mm (a glass powder densely sintered) or a plate glass ingot of 50 × 50 × 3 mm. It is used as a sample, and refers to a value measured by attaching electrodes of 30 mmφ on the front and back surfaces of optically polished glass and applying a voltage between the electrodes.

  The present inventor pays attention to the fact that the dielectric constant of the resistor can be reduced by reducing the dielectric constant of the glass. In order to reduce the dielectric constant of the resistor, the glass composition range is regulated as described above. I found a good thing. Thereby, since the effective dielectric constant between the center electrode and the terminal electrode is reduced, the capacity discharge current generated at the time of ignition of the spark plug can be reduced, and as a result, generation of high frequency noise radio waves can be suppressed.

  15thly, the glass composition for resistor formation which comprises the resistor which the spark plug of this invention has is characterized by the dielectric loss tangent in 25 degreeC and 1 MHz being 0.0008 or more. If it does in this way, since the absorption capability of the high frequency noise radio wave of glass will increase, it will become easy to make a spark plug thin. Here, “dielectric loss tangent at 25 ° C. and 1 MHz” is a measurement of a plate glass of 50 × 50 × 3 mm (a glass powder densely sintered) or a plate glass ingot of 50 × 50 × 3 mm. It is used as a sample, and refers to a value measured by attaching electrodes of 30 mmφ on the front and back surfaces of optically polished glass and applying a voltage between the electrodes.

  As a result of detailed investigation, the present inventor has found that when the dielectric loss tangent of glass is increased, the ability of glass to absorb high-frequency noise waves increases. Although the details of this mechanism are not clear and are currently under scrutiny, the present inventor has found that when the dielectric loss tangent of the glass is large, the interface of the coarse glass powder contained in the resistor when the spark plug is ignited. , It is estimated that the energy of the high frequency noise radio wave is easily converted into thermal energy, and the high frequency noise radio wave is attenuated.

  16thly, the glass composition for resistor formation which comprises the resistor which the ignition plug of this invention has is characterized by a glass transition point being 430-570 degreeC. Here, the “glass transition point” refers to a value measured by a push rod type thermal expansion coefficient measurement (TMA) apparatus.

  Seventeenth, the glass composition for forming a resistor constituting the resistor included in the spark plug of the present invention is characterized in that the yield point is 500 to 680 ° C. Here, the “bend point” refers to a value measured with a TMA apparatus.

Eighteenth, the glass composition for forming a resistor constituting the resistor included in the spark plug of the present invention is characterized by having 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 an average value measured in a temperature range of 30 to 380 ° C.

  Nineteenth, the glass composition for forming a resistor constituting the resistor included in the spark plug of the present invention is characterized by containing substantially no PbO. In this way, environmental demands in recent years can be satisfied. Here, “substantially does not contain PbO” refers to a case where the content of PbO in the glass composition is 1000 ppm or less.

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

  The reason why the glass composition range is limited as described above in the resistor-forming glass composition 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 35 to 60%, preferably 40 to 58%. More preferably, it is 42 to 56%. If the content of SiO ₂ is less than 35%, the glass becomes thermally unstable and it becomes difficult to stably produce the glass. In addition, the coefficient of thermal expansion of the glass increases excessively, 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 less than 35%, the coarse glass powder easily dissolves the conductive powder in the hot pressing step. On the other hand, if the content of SiO ₂ is more than 65%, the yield point of the glass is unduly raised, and the glass is difficult to deform in the hot pressing process, and as a result, problems such as terminal floating are likely to occur.

B ₂ O ₃ is a component that forms a 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 25 to 55%, preferably 30 to 50%, more preferably 33 to 46%. If the content of B ₂ O ₃ is less than 25%, the glass becomes thermally unstable, and it becomes difficult to stably produce the glass. In addition, the yield point of the glass is unreasonably raised, Glass becomes difficult to be deformed, and as a result, problems such as terminal floating are likely to occur. On the other hand, if the content of B ₂ O ₃ is more than 55%, 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, since the phase separation property of the glass decreases, the coarse glass powder easily dissolves the conductive powder in the hot pressing step.

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 0 to 20%, preferably 0.1 to 15%. Preferably it is 1 to 10%, more preferably 2 to 8%. If the content of Li ₂ O + Na ₂ O + K ₂ O is more than 20%, the coefficient of thermal expansion 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, the coarse glass powder easily dissolves the conductive powder in the hot pressing process.

Li ₂ O is a component for reducing the yield point of the glass and remarkably promoting the phase separation of the glass, and its content is 0 to 20%, 0.1 to 10%, 1 to 7%, 2 to 5% is particularly preferable. When the content of Li 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. In addition, from the viewpoint of promoting the phase separation of the glass, it is preferable to contain Li ₂ O as an essential component in the glass composition at 1% or more, preferably 2% or more.

Na ₂ O is a component for reducing the yield point of the glass and promoting phase separation of the glass, and its content is preferably 0 to 20%, 0 to 10%, particularly preferably 0 to 2%. When the content of Na 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.

K ₂ O is a component for reducing the yield point of the glass and promoting the phase separation of the glass, and its content is 0 to 20%, 0 to 15%, 0 to 5%, particularly 0 to 2. % Is preferred. When the content of 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.

  ZnO is a component for remarkably reducing the dielectric constant of the glass and remarkably promoting the phase separation of the glass, and is a component for reducing the thermal expansion coefficient of the glass. It is 1 to 25%, preferably 1 to 15%, more preferably 3 to 12.5%, still more preferably 5 to 11%. When the content of ZnO is less than 0.1%, it becomes difficult for the glass to prevent generation of high-frequency noise radio waves, and it is difficult to reduce the diameter of the spark plug. In addition, if the ZnO content is less than 0.1%, the phase separation of the glass decreases, and the coarse glass powder does not function as block particles, resulting in a decrease in the high frequency noise radio wave absorption capability of the resistor. It becomes easy. On the other hand, even if the ZnO content is more than 25%, the phase separation of the glass is lowered, and the coarse glass powder does not function as block particles. As a result, the high frequency noise radio wave absorption ability of the resistor tends to be lowered. Become.

  In addition to the above components, for example, the following components can be added to the glass composition.

Al ₂ O ₃ is a component that increases the water resistance of the glass and lowers the thermal expansion coefficient of the glass, and its content is preferably 0 to 10%, particularly 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, and the glass is difficult to be deformed in the hot pressing process, and as a result, problems such as terminal floating tend to occur.

  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, the easier the phase separation of the glass. Specifically, as the ionic radius decreases in the order of BaO, SrO, CaO, MgO, the phase separation tendency of the glass increases. When the phase separation tendency of the glass increases, the phase separation state fluctuates greatly even with a small change in the heat treatment temperature, and if the hot press temperature fluctuates due to the influence, the spark plug resistance value tends to vary. Become. On the other hand, when the phase separation tendency of glass becomes small, it becomes difficult for the coarse glass powder to function as block particles. Further, the smaller the molecular weight, the lower the dielectric constant of the glass. Specifically, as the molecular weight decreases in the order of BaO, SrO, CaO, and MgO, the dielectric constant of the glass decreases. Furthermore, as the molecular weight decreases in the order of BaO, SrO, CaO, and MgO, the yield point of the glass increases. As is apparent from the above, it is preferable to add an alkaline earth metal oxide as appropriate in consideration of the overall characteristics of glass such as dielectric constant, phase separation, yield point, etc., and its content is 0. -25%, especially 1-15% is preferred.

  MgO is a component that lowers the dielectric constant of the glass and is a component for promoting the phase separation of the glass, and its content is preferably 0 to 20%, 0 to 10%, particularly preferably 0 to 5%. If the content of MgO is more than 20%, the thermal stability of the glass tends to decrease.

  CaO is a component that lowers the dielectric constant of glass, and its content is preferably 0 to 20%, 0 to 10%, particularly preferably 0 to 5%. When there is more content of CaO than 20%, the thermal stability of glass will fall easily.

  SrO is a component that lowers the dielectric constant of glass and a component that lowers the yield point of glass. SrO is a component that prevents a problem that the resistance value of the spark plug varies when the hot press temperature fluctuates, and the content thereof is 0 to 25%, 0 to 20%, 0 to 15%, particularly 0 to 8%. % Is preferred. When the content of SrO is more than 25%, 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.

  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 25%, 0 to 20%. In particular, 0 to 15% is preferable. When the content of BaO increases, the dielectric constant of the glass increases and it becomes difficult for the glass to prevent the generation of high-frequency noise radio waves. Moreover, when the content of BaO increases, the thermal expansion coefficient of the glass increases excessively, and peeling or cracking is likely to occur at the interface between the resistor and the conductive glass body or the insulator. From the viewpoint of reliably reducing the dielectric constant of the glass, it is preferable that the content of BaO is 15% or less, desirably 10% or less, and more desirably substantially not contained as the glass composition. Here, “substantially does not contain BaO” refers to a case where the content of BaO in the glass composition is 3000 ppm or less.

Furthermore, up to 10% of various components can be added into the 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 up to 10%. In addition, although the glass composition 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 glass composition for forming a resistor of the present invention, the dielectric constant at 25 ° C. and 1 MHz is preferably 5.5 or less, 5.3 or less, 5.0 or less, particularly preferably 4.8 or less. If the dielectric constant at 25 ° C. and 1 MHz is greater than 5.5, it will be difficult for the glass to prevent the generation of high frequency noise radio waves, and if the spark plug is made thinner, the resistor will not be able to absorb the high frequency noise radio waves sufficiently. There is a risk of interference with in-vehicle TV, radio, radio, and the like.

  In the glass composition for forming a resistor of the present invention, the dielectric loss tangent at 25 ° C. and 1 MHz is preferably 0.0008 or more, 0.0010 or more, 0.0013 or more, particularly preferably 0.0018 or more. If the dielectric loss tangent at 25 ° C. and 1 MHz is less than 0.0008, it will be difficult to increase the high frequency noise radio wave absorption capacity of the glass, and if the spark plug is made thinner, it will be difficult to absorb high frequency noise radio waves. May interfere with TV, radio, radio, etc.

In the resistor forming glass compositions of the present invention, the density is less than ^{2.55g / cm 3, 2.50g / cm} 3 or less, 2.45 g / cm ³ or less, 2.40 g / cm ³ or less, particularly 2.35g / Cm ³ or less is preferable. The smaller the density, the lighter the glass and, as a result, the lighter the spark plug.

  In the glass composition for forming a resistor of the present invention, the glass transition point is preferably 430 to 570 ° C, more preferably 450 to 550 ° C, and further preferably 460 to 510 ° C. When the glass transition point is lower than 430 ° C., the coarse glass powder easily dissolves the conductive powder in the hot pressing process, so 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, if the glass transition point is higher than 570 ° C., the glass is difficult to deform in the hot pressing process, and problems such as terminal floating are likely to occur.

  In the glass composition for forming a resistor of the present invention, the yield point is preferably 500 to 680 ° C, more preferably 520 to 630 ° C, and further preferably 530 to 600 ° C. When the yield point is lower than 500 ° 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 680 ° C., the glass is not easily deformed in the hot pressing process, and problems such as terminal floating are likely to occur.

In the glass composition for forming a resistor of the present invention, the thermal expansion coefficient is preferably 40 to 60 × 10 ⁻⁷ / ° C., more preferably 40 to 55 × 10 ⁻⁷ / ° C., and 42 to 51 × 10 ⁻⁷ / ° C. Is more preferable. 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, due to an increase in the yield point of the glass, the glass is difficult to deform in the hot press process, and problems such as terminal floating are likely to 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.

  As the resistor forming glass powder of the present invention, a glass powder made of the above resistor forming glass composition is used. If it is processed into glass powder, the glass is easily deformed in the hot press process, and if it is processed into granules, it becomes easier to fill the inner hole of the insulator with the resistor material.

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

  In the glass powder for forming a resistor of the present invention, the particle size of the glass powder is preferably 150 to 450 μm, and more preferably 200 to 350 μm. If the particle size of the glass powder is 150 to 450 μm, the glass powder can easily function as block particles that bypass the conductive path. When the particle size of the glass powder is smaller than 150 μm, the glass powder easily dissolves the conductive powder in the hot pressing process, so that it becomes difficult to function as block particles, and the resistance of the resistor to absorb high-frequency noise radio waves tends to decrease. On the other hand, when the particle size of the glass powder is larger than 450 μm, in addition to being difficult to process into granules, the glass powder is difficult to be deformed in the hot pressing process, and problems such as terminal floating are likely to occur. Here, “150-450 μm particle size” means passing through a sieve having an opening of 450 μm and not passing through a sieve having an opening of 150 μm.

In the glass powder for forming a resistor of the present invention, the average particle diameter D ₅₀ of the glass powder is preferably 150 to 450 μm, and more preferably 200 to 350 μm. If the average particle diameter D ₅₀ of the glass powder 150～450Myuemu, tends to function as a block particles diverting conductive path. If the average particle diameter D ₅₀ of the glass powder is smaller than 150 μm, the glass powder dissolves the conductive powder in the hot pressing process, and it becomes difficult to function as block particles, and the high frequency noise radio wave absorption ability of the resistor tends to be lowered. On the other hand, when the average particle diameter D ₅₀ of the glass powder is larger than 450 μm, in addition to being difficult to process into granules, the glass powder is difficult to be deformed in the hot pressing process, and 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 D _max of the glass powder is preferably 450 μm or less, and more preferably 400 μm or less. When the average particle diameter D _max of the glass powder is larger than 450 μm, it becomes difficult to fill the glass powder into the inner hole of the insulator when the inner hole of the insulator is reduced in diameter. 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. When the average particle diameter D ₅₀ of the glass powder is 150 μm or more, it becomes difficult for the fine glass powder to form a bonded glass phase in the hot pressing step. 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.

  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 reduced in diameter because the generation of high-frequency noise radio waves can be suppressed even when the filling amount is small.

The resistor-forming glass composition of the present invention preferably further contains ZnO 7.1 to 12.2% and Li ₂ O + Na ₂ O + K ₂ O 2.6 to 12% by mass%. The glass composition for forming a resistor of the present invention can improve the sealing performance during hot pressing at 850 ° C.

  Hereinafter, based on an Example, this invention is demonstrated in detail. Tables 1-4 show examples of the present invention (sample Nos. 1-33) and comparative examples (sample Nos. 34-40).

  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, the molten glass was formed into a flake shape with a water-cooled roller, pulverized with a ball mill, and classified with a test sieve to obtain each glass powder.

  Sample No. For 1 to 40, the glass transition point, yield point, thermal expansion coefficient, dielectric constant, dielectric loss tangent, function as block particles, 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 50 mm x 50 mm x 3 mm thick plate glass (glass powder densely sintered) as the measurement sample, and 30 mmφ electrodes were attached to the front and back surfaces of the optically polished plate glass. The voltage was applied between the electrodes and measured. The measurement conditions were 25 ° C. and 1 MHz.

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 (particle size: 150 to 450 μm, average particle diameter D ₅₀ = 300 μm) 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 is not completely melted and the carbon black is not dissolved in the glass is marked with “○”, the glass powder is completely melted, or the carbon black is in the glass. What was melt | dissolved was evaluated as "x".

  The phase separation was evaluated by observing with a TEM a sample obtained by processing the button sample into a predetermined shape. “ボ タ ン” indicates that the entire button sample is phase-separated, “○” indicates that the button sample is partially phase-separated, and “×” indicates that no phase separation is confirmed in the button sample. .

  “Sealing performance” is an evaluation of the rate of occurrence of a problem that the terminal floats during hot pressing. “◎◎” indicates that the occurrence rate f is 0%, and “◎” indicates 0% <f ≦ 5%. “5% <f ≦ 30%” was indicated by “◯”, and 30% <f was indicated by “X”.

As is apparent from Tables 1 to 4, sample No. In Nos. 1 to 33, evaluation of glass transition point, yield point, thermal expansion coefficient, dielectric constant, dielectric loss tangent, radio frequency noise radio wave, function as block particles and phase separation were good. In particular, sample no. 1 to 33, since the dielectric constant is low, the effective dielectric constant between the terminal electrode and the center electrode can be lowered. As a result, even if the spark plug is made thinner, the resistor accurately absorbs high frequency noise radio waves. It is considered possible. On the other hand, sample No. Since No. 34 does not contain ZnO in the glass composition, it is considered that the dielectric constant is high, the evaluation of phase separation is poor, and it is difficult to function as block particles. Sample No. No. 35 is considered to be difficult to function as block particles because the content of SiO ₂ is small. Sample No. No. 36 has a high ZnO content, so the evaluation of phase separation is poor, and it is considered difficult to function as block particles. Sample No. No. 37 had a very high glass transition point and yield point due to its high SiO ₂ content. Sample No. No. 38 has a large content of Li ₂ O + Na ₂ O + K ₂ O, and is therefore considered difficult to function as block particles. Sample No. No. 39 is considered to be difficult to function as block particles because of its high B ₂ O ₃ content. Sample No. No. 40 does not contain ZnO in the glass composition, so the dielectric constant is high, the evaluation of phase separation is poor, and it is considered difficult to function as block particles.

  As is clear from the above explanation, the glass composition for forming a resistor of the present invention is suitable for an electronic component equipped with an electromagnetic wave absorber, particularly an in-vehicle electronic component that is highly required to shield electromagnetic waves in a high frequency range. Specifically, it is suitable as a coarse glass powder for forming a resistor in the inner hole of the insulator of the spark plug, and can also be used as a fine glass powder.

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

Claims (19)

As a glass composition, in weight%, and characterized in that it contains _{SiO 2 35~60%, B 2 O} 3 25~55%, Li 2 O + Na 2 O + K 2 O 0~20%, a 0.1 to 25% ZnO A glass composition for forming a resistor.   2. The glass composition for forming a resistor according to claim 1, wherein the dielectric constant at 25 ° C. and 1 MHz is 5.5 or less.   3. The glass composition for forming a resistor according to claim 1, wherein a dielectric loss tangent at 25 ° C. and 1 MHz is 0.0008 or more.   A glass transition point is 430-570 degreeC, The glass composition for resistor formation in any one of Claims 1-3 characterized by the above-mentioned.   A yield point is 500-680 degreeC, The glass composition for resistor formation in any one of Claims 1-4 characterized by the above-mentioned. The glass composition for forming a resistor according to claim 1, wherein the coefficient of thermal expansion is 40 to 60 × 10 ⁻⁷ / ° C.   The glass composition for forming a resistor according to any one of claims 1 to 6, which does not substantially contain PbO.   It uses for a spark plug, The glass composition for resistor formation in any one of Claims 1-7 characterized by the above-mentioned.   A glass powder for forming a resistor, comprising the glass powder made of the glass composition for forming a resistor according to claim 1.   The glass powder for forming a resistor according to claim 9, which has phase separation.   The glass powder for resistor formation according to claim 9 or 10, wherein the particle size of the glass powder is 150 to 450 µm. An insulator having an axial hole extending in the axial direction;
A center electrode provided at one end of the shaft hole;
A terminal electrode provided on the other end side of the shaft hole;
In a spark plug comprising a resistor disposed between the center electrode and the terminal electrode,
The resistor includes a resistor-forming glass composition,
The glass composition for forming a resistor comprises, in mass%, SiO ₂ 35-60%, B ₂ O ₃ 25-55%, Li ₂ O + Na ₂ O + K ₂ O 0-20%, ZnO 0.1-25%. Spark plug characterized by containing. The resistor forming glass composition, in mass%, according to claim 12, characterized in that it contains _{7.1~12.2%, 2.6~12% Li 2 O} + Na 2 O + K 2 O ZnO Spark plug.   The spark plug according to claim 12 or 13, wherein the resistor-forming glass composition has a dielectric constant of 5.5 or less at 25 ° C and 1 MHz.   The spark plug according to any one of claims 12 to 14, wherein the resistor-forming glass composition has a dielectric loss tangent of 0.0008 or more at 25 ° C and 1 MHz.   The spark plug according to any one of claims 12 to 15, wherein the resistor-forming glass composition has a glass transition point of 430 to 570 ° C.   The spark plug according to any one of claims 12 to 16, wherein the resistor-forming glass composition has a yield point of 500 to 680 ° C. The spark plug according to any one of claims 12 to 17, wherein the resistor-forming glass composition has a coefficient of thermal expansion of 40 to 60 x ^10-7 / ° C.   The spark plug according to any one of claims 12 to 18, wherein the resistor-forming glass composition contains substantially no PbO.

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