Patent Application
20180166861
The present invention relates to a spark plug.
A spark plug is conventionally used in an internal combustion engine. For the purpose of suppressing radio noise caused by ignition, it has been proposed to provide a resistor in a through hole of an insulator of the spark plug. It has also been proposed to provide a magnetic substance in a through hole of an insulator of the spark plug.
However, sufficient improvements and modifications have not been made to the suppression of radio noise with the use of the magnetic substance.
The present invention discloses a technique for suppressing radio noise with the use of a magnetic member.
The present invention provides, for example, the following application examples.
In accordance with a first aspect of the present invention, there is provided a spark plug comprising: an insulator having a through hole formed therethrough in a direction of an axis of the spark plug; a center electrode at least partially inserted in a front end side of the through hole; a metal terminal at least partially inserted in a rear end side of the through hole; and a connection structure arranged in the though hole to establish electrical connection between the center electrode and the metal terminal within the through hole, wherein the connection structure comprises a composite part containing a plurality of secondary particles each formed of a plurality of primary particles of iron-containing oxide as a magnetic substance, and a conductive material coating the plurality of secondary particles, wherein the iron-containing oxide includes at least one of an oxide represented by M1+AOFe2−AO3 (where −0.5≤A≤0.5; and M is at least one kind of element selected from the group consisting of Mn, Fe, Co, Ni, Cu, Mg, Zn and Ca) and an oxide represented by Q3Fe5O12 (where Q is at least one kind of element selected from the group consisting of Y, Lu, Yb, Tm, Er, Ho, Dy, Tb, Gd and Sm), and wherein, in a cross section of the composite part taken including the axis, an average particle size of the primary particles is 0.5 μm to 100 μm, an average particle size of the secondary particles is 0.5 mm to 2.0 mm, and a porosity of the inside of the secondary particles is 5% or lower.
With this configuration, it is possible to adequately suppress radio noise.
In accordance with a second aspect of the present invention, there is provided a spark plug as described above, wherein the iron-containing oxide includes an oxide represented by NixZnyFezO4 (where 0.3≤X≤0.8; 0.2≤Y≤0.7; 1.5≤Z≤2.5; and X+Y+Z=3).
With this configuration, it is possible to more adequately suppress radio noise.
In accordance with a third aspect of the present invention, there is provided a spark as described above, wherein, assuming in the cross section that the inside of the secondary particles includes an inner zone located 100 μm or more from surfaces of the secondary particles and an outer peripheral zone located 50 μm or less from the surfaces of the secondary particles, a difference between a content of iron in terms of oxide in the inner zone and a content of iron in terms of oxide in the outer peripheral zone is 5.0 wt % or less.
With this configuration, it is possible to prevent uneven distribution of the magnetic substance within the inside of the secondary particles and thereby stably suppress radio noise.
In accordance with a fourth aspect of the present invention, there is provided a spark plug as described above, wherein the composite part includes a ceramic material containing at least one of silicon (Si), boron (B) and phosphorus (P), and an alkali metal component.
With this configuration, it is possible to improve the durability of the composite part.
In accordance with a fifth aspect of the present invention, there is provided a spark plug as described above, wherein the alkali metal component is contained in an amount of 0.5 wt % to 6.5 wt % in terms of oxide in the composite part.
With this configuration, it is possible to still more adequately suppress radio noise.
It should be noted that the present invention can be embodied in various forms such as not only a spark plug but also an internal combustion engine with a spark plug.
The spark plug 100 includes: a substantially cylindrical insulator 10 having a through hole 12 formed therethrough along the axis CL (hereinafter also referred to as “axial hole 12”); a center electrode 20 held in a front end side of the axial hole 12; a metal terminal 40 held in a rear end side of the axial hole 12; a connection structure 300 arranged in the axial hole 12 to establish electrical connection between the center electrode 20 and the metal terminal 40; a metal shell 50 fixed around an outer circumference of the insulator 10; and a ground electrode 30 having one end joined to a front end face of the metal shell 50 and the other end facing the center electrode 20 via a gap g.
The insulator 10 includes a large diameter portion 19 of the maximum outer diameter and includes a front body portion 17, a first outer-diameter decreasing portion 15 and a leg portion 13 located frontward of the large diameter portion 19 in this order toward the front. The first outer-diameter decreasing portion 15 has an outer diameter gradually decreasing toward the front. The insulator also includes a second outer-diameter decreasing portion 11 and a rear body portion 18 located rearward of the large diameter portion 19 in this order toward the rear. The second outer-diameter decreasing portion 11 has an outer diameter gradually decreasing toward the rear. The insulator further includes an inner-diameter decreasing portion 16 located in the vicinity of the first outer-diameter decreasing portion 15 (in
The center electrode 20 includes a rod-shaped electrode shaft 27 extending along the axis CL and a first tip 29 joined to a front end of the electrode shaft 27. The first tip 29 is fixed to the electrode shaft 27 by e.g. laser welding. The center electrode 20 has a flange portion 28 of large outer diameter on a rear end side thereof. A frontward direction Df-side surface of the flange portion 28 is supported on the inner-diameter decreasing portion 16 of the insulator 11. A front end portion of the center electrode 20 protrudes in the frontward direction Df from a front end of the insulator 10.
The electrode shaft 27 has an outer layer 21 and a core 22. The outer layer 21 is made of a material (such as nickel-containing alloy) having higher oxidation resistance than that of the core 22. The core 22 is made of a material (such as pure copper, copper alloy etc.) having higher thermal conductivity than that of the outer layer 21. The first tip 29 is made of a material (such as iridium (Ir), noble metal e.g. platinum (Pt), tungsten (W) or an alloy containing at least one kind selected from those metals) having higher durability against discharge than that of the electrode shaft 27.
The metal terminal 40 includes a collar portion 42, a cap attachment portion 41 located rearward of the collar portion 42 and a leg portion 43 located frontward of the collar portion 42. The leg portion 43 is inserted in the through hole 12 of the insulator 10. The cap attachment portion 41 is situated rearward of the insulator 10 and exposed outside the through hole 12. The metal terminal 40 is made of a conductive material (such as metal e.g. low carbon steel). A metal layer for corrosion protection may be applied to a surface of the metal terminal 40. For example, it is feasible to apply a Ni layer by plating.
The connection structure 300 is arranged between the center electrode 20 and the metal terminal 40 within the axial hole 12 for electrical connection between the center electrode 20 and the metal terminal 40. The connection structure 300 includes a composite part 200 containing a magnetic substance and a conductive substance so as to suppress radio noise. The connection structure 300 further includes a first seal part 60 held in contact with the center electrode 20 and the composite part 200 and a second seal part 80 held in contact with the composite part 200 and the metal terminal 40. The seal parts 60 and 80 are made of, for example, particles of glass (such as B2O3—SiO2 glass) and particles of metal (such as Cu, Fe etc.).
The metal shell 50 has a substantially cylindrical shape with a through hole 59 formed therethrough along the axis CL. The metal shell 50 is fixed around the outer circumference of the insulator 10 as the insulator 10 is inserted in the through hole 59 of the metal shell 50. A front end portion of the insulator 10 is exposed outside the through hole 59, whereas a rear end portion of the insulator 10 is exposed outside the through hole 59. The metal shell 50 is made of a conductive material (such as metal e.g. low carbon steel).
The metal shell 50 includes a body part 55 with a thread portion 52 formed on an outer circumferential surface thereof for screw engagement in a mounting hole of an internal combustion engine (such as gasoline engine). The metal shell also includes a seat portion 54 located rearward of the body part 55. An annular gasket 5 is fitted between the seat portion 54 and the thread portion 52. The metal shell further includes a deformation portion 58, a tool engagement portion 51 and a crimp portion 53 located rearward of the seat portion 54 in this order toward the rear. The deformation portion 58 is deformed such that a middle region of the deformed portion 58 protrudes outwardly in the radial direction (i.e. in the direction apart from the center axis CL). The tool engagement portion 51 is shaped (e.g. hexagonal in shape) such that a spark plug wrench can be engaged on the tool engagement portion 51. The crimp portion 53 is situated rearward of the second outer-diameter decreasing portion 11 of the insulator 10 and is bent inwardly in the radial direction.
There is a space SP surrounded by an inner circumferential surface of the metal shell 50 and an outer circumferential surface of the insulator 10 at a location between the crimp portion 53 of the metal shell 50 and the second outer-diameter decreasing portion 11 of the insulator 10. A first rear packing 6, a talc 9 and a second rear packing 7 are arranged within the space SP in this order toward the front. In the present embodiment, C-rings of iron are used as the rear packings 6 and 7. (These packings can be made of any other material.)
The body part 55 of the metal shell 50 includes an inner-diameter decreasing portion 56 having an inner diameter gradually decreasing toward the front. A front packing 8 is disposed between the inner-diameter decreasing portion 56 of the metal shell 50 and the first outer-diameter decreasing portion 15 of the insulator 10. In the present embodiment, a C-ring of iron is used as the front packing 8. (This packing can be made of any other material (such as other metal e.g. copper)).
During manufacturing of the spark plug 100, the crimp portion 53 is bent inwardly by crimping and thereby pressed toward the frontward direction Df side. Consequently, the deformation portion 58 is deformed to push the insulator 10 toward the front side through the packings 6 and 7 and the talc 9 within the metal shell 50. The front packing 8 is then pressed between the first outer-diameter decreasing portion 15 and the inner-diameter decreasing portion 56, thereby providing a seal between the metal shell 50 and the insulator 10 to prevent leakage of gas from a combustion chamber of the internal combustion engine through between the metal shell 50 and the insulator 10. In this state, the metal shell 50 is fixed to the insulator 10.
The ground electrode 30 includes a rod-shaped electrode shaft 37 and a second tip 29 joined to a distal end portion 31 of the electrode shaft 37. The ground electrode 30 is joined at one end thereof to the front end face of the metal shell 50 (by e.g. resistance welding). The electrode shaft 37 has a shape extending from the metal shell 50 in the frontward direction Df and bent to direct the distal end portion 31 toward the center axis CL. The second tip 39 is fixed to a rear side surface of the distal end portion 31 (by e.g. laser welding). The gap g is defined between the second tip 39 of the ground electrode 30 and the first tip 29 of the center electrode 20.
The electrode shaft 37 has a base 35 defining a surface of the electrode shaft 37 and a core 36 embedded in the base 35. The base 35, the core 36 and the second tip 39 of the ground electrode 30 are made of the same materials as those of the outer layer 21, the core 22 and the first tip 29 of the center electrode 20, respectively. At least either one of the first tip 29 and the second tip 39 may be omitted.
As shown by illustration, the target section 800 (that is, the cross section 900 of the composite part 200) includes a ceramic region 810, a conductive region 820 and a magnetic region 830. The magnetic region 830 contains a plurality of particulate areas 835 (hereinafter also referred to as “magnetic particle areas 835” or simply referred to as “particle areas 835”). The magnetic region 830 corresponds to a region of iron-containing oxide as the magnetic substance. Examples of the iron-containing oxide are spinel ferrite such as (Ni, Zn)Fe2O4 and garnet ferrite such as Y3Fe5O12. The plurality of magnetic particle areas 835 are formed by using a powder of the iron-containing oxide as a material of the composite part 200. In the present embodiment, there are provided particulate clusters in each of which a plurality of particles of the iron-containing oxide included in the powder material are combined together as one magnetic particle area 835. The particulate clusters are produced by adding and mixing a solution of a binder etc. to the powder of the iron-containing oxide. The plurality of particles of the iron-containing oxide are formed into the particulate clusters of larger diameter by aggregation and by being bonded together via the binder. Herein, a plurality of particles forming a particulate cluster are referred to as “primary particles”; and a plurality of particulate clusters each formed from a plurality of primary particles are referred to as “secondary particles”. In the cross section 900, one magnetic particle area 35 corresponds to a cross-sectional area of one secondary particle.
Although omitted from illustration, the plurality of secondary particles corresponding to the magnetic particle areas 835 have their respective surfaces coated by coating layers of conductive material. Examples of the conductive material are metals (such as Ni and Cu), perovskite oxides (such as SrTiO3 and SrCrO3), carbon (C) and carbon compounds (such as Cr3C2 and TiC).
In
Although omitted from illustration, there is a case where two composite particle areas 840 are located apart from each other in the target section 800 (that is, the cross section 900). These two composite particles areas 840 apart from each other in the target section 800 may correspond to cross sections of two three-dimensional particles that make contact with each other at a position in front or back of the target section 800. Namely, the plurality of composite particle areas 840, located in contact with or apart from each other in the target section 800, develop the current conduction paths from the rearward direction Dfr side to the frontward direction Df side such that electric current flows through the composite part 200 along the plurality of coating areas 825 of the plurality of composite particle areas 840 (that is, the conductive region 820) during discharge.
As mentioned above, the magnetic region 830 is covered by the conductive region 820. In other words, the current conduction paths are developed to surround the magnetic substance. The generation of radio noise by discharge is suppressed when the magnetic substance is located in the vicinity of the current flow path. For example, the radio noise can be suppressed by the action of the current conduction path as an inductance element. The radio noise can be effectively suppressed as the inductance of the current conduction path becomes high.
The magnetic particle area 835 is shown in enlargement in the lower-left side of
The ceramic region 810 is of ceramic material. As the ceramic material, there can be used e.g. a ceramic material containing at least one of silicon (Si), boron (B) and phosphorus (P). The ceramic material may be in the form of a glass. The glass may contain one or more oxides arbitrarily selected from silica (SiO2), boron oxide (B2O5) and phosphorus oxide (P2O5). Alternatively, there can be used a ceramic material free of Si, B and P (such as a material containing Al2O3, BeF2 etc.). The plurality of composite particle areas 840 (i.e. the plurality of magnetic particle areas 835 and the plurality of coating areas 825 coating the magnetic particle areas 835) are surrounded by the ceramic region 810. In other words, the plurality of composite particle areas 840 (conductive region 820 and magnetic region 830) are supported by the ceramic region 810.
In the lower-center side of
It is feasible to adopt any method as a manufacturing method of the spark plug 100 according to the first embodiment. The spark plug can be manufactured by e.g. the following method. First, powder materials for production of the insulator 10, the center electrode 20, the metal terminal 40, the conductive seal parts 60 and 80 and the composite part 20 are prepared.
For example, the powder material for production of the composite part 20 is prepared by the following procedure. The powder (of primary particles) of the iron-containing oxide is formed into secondary particles by adding and mixing therein the solution of the binder etc. As mentioned above, the secondary particles are formed by e.g. aggregation of the primary particles. The coating layers are formed on the secondary particles by plating so as to coat the surfaces of the secondary particles. Then, the powder material of the composite part 20 is prepared by mixing a powder of the ceramic material with the secondary particles coated by the coating layers. A substance containing an alkali metal (such as alkali metal oxide) may be added to the powder material of the composite part 200. The alkali metal refers to a metal element that belongs to group 1 of the periodic table. Specific examples of the alkali metal are lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs) and francium (Fr). The coating layers may be provided by applying the binder solution to the surfaces of the secondary particles and thereby adhering particles of the conductive material to the secondary particles in place of plating. Even in this case, the powder material of the composite part 20 is prepared by mixing the powder of the ceramic material with the secondary particles coated by the coating layers.
The center electrode 20 is inserted in the though hole 12 of the insulator 10 (see
The powder materials of the first seal part 60, the composite part 200 and the second seal part 80 were charged and subjected to forming one by one in order from the part 60 to the part 200 and then to the part 80. Each of the powder materials was charged into the though hole 12 from the rear opening 14 and formed by the use of a rod inserted from the rear opening 14 into substantially the same shape as that of the corresponding part.
The insulator 10 is heated to a predetermined temperature higher than softening points of glass components contained in the respective powder materials. While the insulator 10 is heated at the predetermined temperature, the metal terminal 40 is inserted into the through hole 12 from the rear opening 14 of the through hole 12. As a result, the seal parts 60 and 80 and the composite part 200 are formed by compression and sintering of the powder materials.
After that, the metal shell 50 is assembled to the outer circumference of the insulator 10; and the ground electrode 30 is fixed to the metal shell 50. The ground electrode 30 is then subjected to bending. With this, the spark plug is completed.
The following explanation will be given of evaluation tests on a plurality of kinds of samples of the spark plug 100 shown in
In the evaluation tests, 84 kinds of samples numbered A-1 to A53 and B-1 to B-31 were evaluated. A plurality of samples produced under the same conditions were used as samples of the same kind in order to identify the relationships of the after-mentioned plurality of parameters and the plurality of evaluation test results. The sample number, the configurations of the composite part 200 and the evaluation test results of the respective samples are listed in TABLES 1 to 5. The configurations of the magnetic region 830, the composition of the conductive substance (conductive region 820), the iron content difference, the kind of the element Si, B, P contained in the ceramic region 81, the kind and amount of the alkali metal element contained in the composite part 200 are presented as the configurations of the samples. The composition of the iron-containing oxide contained in the magnetic region 830, the primary particle size (i.e. the average particle size of the primary particles), the porosity (i.e. the porosity of the secondary particles (magnetic particle areas 835)) and the secondary particle size (i.e. the average particle size of the secondary particles) are presented as the configurations of the magnetic region 830. The results of noise evaluation test and vibration test are presented as the results of the evaluation tests.
The composition of the iron-containing oxide was determined by ICP (Inductively Coupled Plasma) analysis, X-ray diffraction (XRD) and EPMA (Electron Probe Micro Analyser). In the tables, only the composition of the iron-containing oxide is indicated for each sample. In fact, however, various impurities could be contained in trace amounts in the magnetic region 830 during the process of sample production.
The primary particle size (i.e. the average particle size of the primary particles) was determined as follows. In each sample, the composite part 200 was cut along a plane including the center axis CL as explained above with reference to
In the SEM image, the phase of the primary particles was distinguished from the other phase by EPMA. The apparent particle size Da(i) of the primary particles was measured by the following intercept method.
In the intercept method, the primary particles intersecting at least either one of two diagonal lines DG1 and DG2 of the SEM image were selected (see
The secondary particle size (i.e. the average particle size of the secondary particles) was determined as follows. A portion of the cross section of the composite part 200, including the target section 800 of 2 mm×3 mm as explained above with reference to
The porosity was defined as the ratio of the area of the pores 832 to the area of the secondary particle (including the area of the pores 832 (see
The conductive material contained in the powder material of the composite part 200 is indicated as the conductive substance (i.e. the composition of the conductive region 820) in the respective tables. The composition of the conductive substance may be identified by any analytical means such as micro X-ray diffraction.
The iron content difference was defined as the difference in iron content between an inner zone and an outer peripheral zone of the secondary particle. The inner and outer peripheral zones are schematically shown in the lower-right side of
More specifically, the iron content difference was given as an absolute value of the difference between the iron content of the inner zone 835i and the iron content of the outer peripheral zone 835o as measured at the cross section of the composite part 200 shown in
In the respective tables, any of Si, B and P contained in the ceramic region 810 is indicated in the column of “Si (silicon), B (boron), P (phosphorus)”. Herein, the symbol “x” is indicated in the column of “Si, B, P” in the case where none of Si, B and P was contained in the ceramic region 810. The element Si, B, P contained in the ceramic region 810 was identified from the components of the powder material of the ceramic region 810. The element contained in the ceramic region 810 may alternatively be identified by any analytical means such as EPMA.
The kind of the alkali metal element contained in the composite part 200 is indicated in the column of “Alkali” under the heading of “Element” in the respective tables. The “Element” column is left blank in the case where no alkali metal was contained in the composite part 200. The alkali metal element contained in the composite part 200 was identified from the alkali metal component of the material of the composite part 200. The alkali metal element contained in the composite part 200 may alternatively be identified by any analytical means such as ICP analysis, X-ray diffraction or EPMA.
The amount of the alkali metal element contained in the composite part 200 is indicated in the column of “Alkali” under the heading of “Content” in the respective tables. Herein, the amount of the alkali metal contained in terms of alkali metal oxide (J2O (where J is alkali metal)) is indicated as the content. The unit of this content value is percent by weight. In the case where a plurality of kinds of alkali metals were contained in the composite part 200, the sum of the amounts of the alkali metals contained is indicated as the content in the respective tables. The amount of the alkali metal element contained in the composite part 200 was identified by ICP analysis.
The noise evaluation test was carried out by measuring the intensity of noise according to “Motorcycles—Radio Noise Characteristics—Second Part, Measuring Method of Prevention Device, Current Method” of JASO D-002-2 (Japan Society of Automotive Engineers transmission standard D-002-2). More specifically, the distance of the gap g in the spark plug sample was adjusted to 0.9 mm±0.01 mm. Discharge was induced by applying a voltage of 13 kV to 16 kV to the sample. During the discharge, the amount of current flowing through the metal terminal 40 was measured by the use of a current probe. The measured current value was converted to dB for comparison purposes. Herein, noises of three frequencies: 30 MHz, 100 MHz and 300 MHz were measured as the noise. Each numerical value indicated in the respective tables is indicative of the intensity of the noise relative to a predetermined reference level as determined as the average value of five measurement results. The higher the numerical value, the stronger the noise. Further, a difference between the maximum and minimum values, among the 100-MHz noise measurement results of ten samples, is indicated as the noise variation in the respective tables. The smaller the difference (i.e. noise variation), the more stable the noise suppression effect.
The vibration test was carried out in accordance with “Impact Resistance Test”, paragraph 7.4 of JIS B 8031. In this evaluation test, each sample was mounted on an impact resistance test machine and tested by applying an impact to the sample with a stroke of 22 mm for 60 minutes at a rate of 400 times per minute. After the impact resistance test, the electrical conduction between the center electrode 20 and the metal terminal 40 was checked. The above test operation was performed on twenty samples. The rate of the samples in which the electrical conduction was not detected (i.e. in which disconnection occurred), out of the twenty samples, was determined and indicated as NG rate (in units of %) in the respective tables. The lower the NG rate, the higher the impact resistance.
In the samples No. A-1 to A-53, the composition of the iron-containing oxide was any of the following as indicated in TABLES 1 to 3.
[Type-1 Iron-containing Oxides] MnFe2O4, NiFe2O4, CuFe2O4, ZnFe2O4, CoFe2O4, FeFe2O4, MgFe2O4, Cu0.5Fe2.5O4, Mg0.8Fe2.2O4, Mn0.6Zn0.3Fe2.1O4, Co1.5Fe1.5O4, Ni0.25Zn0.75Fe2O4, Ni0.7Zn0.8Fe1.5O4, Ni0.8Zn0.2Fe2O4, Ni0.3Zn0.7Fe2O4, Ni0.8Zn0.7Fe1.5O4, Ni0.3Zn0.2Fe2.5O4, Ni0.4Zn0.4Fe2.2O4, Ni0.5Zn0.4Fe2.1O4, Ni0.6Zn0.3Fe2.1O4
[Type-2 Iron-containing Oxides] Y3Fe5O12, Dy3Fe5O12, Lu3Fe5O12, Yb3Fe5O12, Tm3Fe5O12, Er3Fe5O12, Ho3Fe5O12, Tb3Fe5O12, Gd3Fe5O12, Sm3Fe5O12
The above type-1 iron-containing oxides are also called spinel ferrite. The above type-2 iron-containing oxides are also called garnet ferrite.
In samples No. A-1 to A-53 where the composition of the type-1 iron-containing oxide was represented by M1+AOFe2−AO3, the element M was one kind or two kinds selected from Mn, Ni, Cu, Zn, Co, Fe and Mg. Further, the value A was −0.5, −0.2, −0.1, 0 or +0.5, that is, within the range of −0.5 to 0.5.
In the samples No. A-1 to A-53 where the composition of the type-2 iron-containing oxide was represented by Q3Fe5O12, the element M was either one kind selected from Y, Dy, Lu, Yb, Tm, Er, Ho, Tb, Gd and Sm.
In particular, the composition of the iron-containing oxide used in the samples No. A-18 to A-23 was of the type-1 iron-containing oxide in which the content ratio values of at least two among a plurality of elements other than oxygen (O) were not integers. The composition of the iron-containing oxide used in the samples No. A-24 to A-35 was NiFe2O4. The composition of the iron-containing oxide used in the samples No. A-36 to A-40 was of the type-1 iron-containing oxide containing Ni, Zn and Fe.
As mentioned above, various type-1 iron-containing oxides represented by M1+AOFe2−AO3 and various type-2 iron-containing oxides represented by Q3Fe5O12 were used in the samples.
The other parameters of the samples No. A-1 to A-53 were set to within the following ranges: 0.5 μm≤primary particle size≤100 μm; 0.8%≤porosity≤5.0%; 0.5 mm≤secondary particle size≤2.0 mm; and 0.5 wt %≤iron content difference≤8.1 wt %. The conductive region 820 was of either of Ni, C, Cu, LaMnO3, TiC, Inconel (trademark) or Permalloy.
In the samples No. B-1 to B-31, the composition of the iron-containing oxide was any of the following as indicated in TABLES 4 and 5.
[Iron Oxide] FeO, Fe2O3,
[Type-1 Iron-containing Oxides] MgFe2O4, Mg0.7Zn0.2Fe2.1O4, MnFe2O4, CuFe2O4, Cu0.8Zn0.3Fe1.9O4, Mg0.8Zn0.8Fe1.4O4, Mg0.8Zn0.1Fe2.1O4, CoFe2O4, Ni0.8Zn0.8Fe1.4O4, CO0.6Zn0.4Fe2O4, Ni0.8Zn0.3Fe1.9O4, Ni0.9Zn0.8Fe1.3O4
[Type-2 Iron-containing Oxides] Y3Fe5O12, Dy3Fe5O12
[Type-3 Iron-Containing Oxides] BaFe12O19, SrFe12O19, PbFe12O19
The above type-3 iron-containing oxides are also called hexagonal ferrite.
The primary particle size of the samples No. A-1 to A-35 (see TABLES 1 and 2) was in the range of 0.5 μm to 100 μm. These samples No. A-1 to A-35 had a sufficiently low noise intensity of 70 dB or lower at all frequencies. The other parameters of the samples No. A-1 to A-35 were within the following ranges: 0.8%≤porosity≤5.0%; 0.5 wt %≤iron content difference≤8.1 wt %; noise variation≤13 dB; and NG rate≤30%. The conductive region 820 was of either of Ni, Inconel, Cu, LaMnO3, C or TiC. Any of Si, B, P and alkali metal was not contained in the composite part 200.
As shown in TABLE 4, the primary particle size of the sample No. B-1 was 0.4 μm and was smaller than that of the samples No. A-1 to A-35. This sample No. B-1 had a noise intensity of 84 dB (30 MHz), 81 dB (100 MHz) or 79 dB (300 Mz), which was higher than that of any of the samples No. A-1 to A-35 at the same frequency level. The reason for such a difference in noise intensity is assumed to be the influence of the primary particle size because the other configurations of the sample No. B-1 were similar to those of the samples No. A-1 to A-35 as shown in TABLE 4. When the size of the primary particles is small, the primary particles tend to have a single-domain structure. As the single-domain magnetic substance shows no energy loss caused due to domain wall motion, the noise attenuation effect of the single-domain magnetic substance becomes weak.
As in the case of the sample No. B-1, the primary particle size of the samples No. B-10, B-12, B-14, B-23, B-24, B-26 and B-30 (each 0.4 μm or smaller) was smaller than that of the samples No. A-1 to A-35 as shown in TABLES 4 and 5. Those samples had a noise intensity higher than that of any of the samples No. A-1 to A-35 at the same frequency level. As explained above, it has been shown by the plurality of samples that the noise became strong when the primary particle size was smaller than that of the samples No. A-1 to A-35.
As shown in TABLE 4, the primary particle size of the sample No. B-2 was 110 μm and was larger than that of the samples No. A-1 to A-35. This sample No. B-2 had a noise intensity of 80 dB (30 MHz), 79 dB (100 MHz) or 79 dB (300 Mz), which was higher than that of any of the samples No. A-1 to A-35 at the same frequency level. The reason for such a difference in noise intensity is assumed to be the influence of the primary particle size because the other configurations of the sample No. B-2 were similar to those of the samples No. A-1 to A-35 as shown in TABLE 4. It is assumed that, when the size of the primary particles is large, the porosity becomes high so that partial discharge is likely to occur to cause strong noise.
As in the case of the sample No. B-2, the primary particle size of the samples No. B-11, B-13, B-15, B-22, B-24, B-27 and B-31 (each exceeding 100 μm) was larger than that of the samples No. A-1 to A-35 as shown in TABLES 4 and 5. Those samples had a noise intensity higher than that of any of the samples No. A-1 to A-35 at the same frequency level. As explained above, it has been shown by the plurality of samples that the noise became strong when the primary particle size was larger than that of the samples No. A-1 to A-35.
The samples No. A-1 to A-35, in which the primary particle diameter was set to 0.5, 10, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 45, 46, 50 or 100 (m), had a favorable noise intensity. The preferable range (upper and lower limits) of the primary particle size can be thus determined based on the above nineteen values. It is feasible to use any arbitrary one of the above nineteen values as the lower limit of the preferable range of the primary particle size. It is feasible to use, as the upper limit of the preferable range of the primary particle size, any arbitrary one of the above values larger than the lower limit value. For example, the preferable range of the primary particle size may be from 0.5 μm to 100 μm. The primary particle size can be adjusted by any method, e.g. by controlling the particle size of the powder of the iron-containing oxide.
The porosity of the samples No. A-1 to A-35 (see TABLES 1 and 2) was in the range of 0.8% to 5.0%. On the other hand, the porosity of the samples No. B-3, B-16, B-17, B-18 and B-19 was higher than that of the samples No. A-1 to A-35 and each exceeded 5.0% as shown in TABLES 4 and 5. Each of these five high-porosity samples had a noise intensity of 81 dB or higher at all frequencies, which was higher than that of any of the samples No. A-1 to A-35 at the same frequency level. The reason for such a difference in noise intensity is assumed to be the influence of the porosity because the other configurations of the samples No. B-3, B-16, B-17, B-18 and B-19 were similar to those of the samples No. A-1 to A-35 as shown in TABLES 4 and 5. It is assumed that, when the porosity is high, partial discharge is likely to occur to cause strong noise.
The samples No. A-1 to A-35, in which the porosity was set to 0.8, 1.5, 2.0, 2.1, 2.5, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.5 or 5.0(%), had a favorable noise intensity. The preferable range (upper and lower limits) of the porosity can be thus determined based on the above fifteen values. It is feasible to use any arbitrary one of the above fifteen values as the lower limit of the preferable range of the porosity. It is feasible to use, as the upper limit of the preferable range of the porosity, any arbitrary one of the above values higher than the lower limit value. For example, the preferable range of the porosity may be from 0.8% to 5.0%. It is feasible to set the porosity to zero % because the lower the porosity, the less likely it is that partial discharge will occur. Thus, the preferable range of the porosity may be from 0% to 5.0%. The porosity can be adjusted by any method, e.g. by controlling the primary particle size (due to the fact that the larger the primary particle size, the higher the porosity) or by controlling the force applied to the powder material during forming of the composite part 200 (due to the fact that the stronger the force applied, the lower the porosity).
The secondary particle size of the samples No. A-1 to A-35 (see TABLES 1 and 2) was 0.5, 1.5 or 2 (mm). On the other hand, the secondary particle size of the sample No. B-4 was 0.1 mm and was smaller than that of the samples No. A-1 to A-35. This sample No. B-4 had a noise intensity of 80 dB (30 MHz), 80 dB (100 MHz) or 76 dB (300 Mz), which was higher than that of any of the samples No. A-1 to A-35 at the same frequency level. The reason for such a difference in noise intensity is assumed to be the influence of the secondary particle size because the other configurations of the sample No. B-4 were similar to those of the samples No. A-1 to A-35 as shown in TABLE 4. The reason for increase of the noise intensity with decrease of the secondary particle size is assumed as follows. When the secondary particle size is small, a larger number of secondary particles are packed in the composite part 200 to develop a larger number of current conduction paths through the conductive region 820 around the secondary particles (magnetic particle areas 830) so that a flow of current is distributed in the composite part 200. As a consequence, the noise suppression effect of the magnetic particle areas 835 is lowered with decrease in current density.
As in the case of the sample No. B-4, the secondary particle size of the samples No. B-12, B-16, B-20, B-23, B-26, B-29 and B-30 (each smaller than or equal to 0.4 mm) was smaller than that of the samples No. A-1 to A-35 as shown in TABLES 4 and 5. Those samples had a noise intensity higher than that of any of the samples No. A-1 to A-35 at the same frequency level. As explained above, it has been shown by the plurality of samples that the noise became strong when the secondary particle size was smaller than that of the samples No. A-1 to A-35.
As shown in TABLE 5, the secondary particle size of the sample No. B-5 was 2.1 mm and was larger than that of the samples No. A-1 to A-35. This sample No. B-5 had a noise intensity of 70 dB (30 MHz), 68 dB (100 MHz) or 69 dB (300 Mz), which was equivalent to that of the samples No. A-1 to A-35. The noise intensity was at a favorable level even when the secondary particle size was larger than 2.0 mm.
When the secondary particle size is large, the filling property of the powder material of the composite part 20 into the axial hole 12 (see
The samples No. A-1 to A-35, in which the secondary particle size was set to 0.5, 1.5 or 2 (mm), had a favorable noise intensity. The preferable range (upper and lower limits) of the secondary particle size can be thus determined based on the above three values. It is feasible to use any arbitrary one of the above three values as the lower limit of the preferable range of the secondary particle size. It is feasible to use, as the upper limit of the preferable range of the secondary particle size, any arbitrary one of the above values larger than the lower limit value. For example, the preferable range of the secondary particle size may be from 0.5 mm to 2 mm. The secondary particle size can be adjusted by any method, e.g. by controlling the particle size of the power material (due to the fact that the larger the particle size of the powder material, the larger the secondary particle size) or by controlling the time for mixing the powder of the iron-containing oxide with the binder (due to the fact that the longer the mixing time, the larger the secondary particle size).
As mentioned above, the samples No. A-1 to A-35, which had a favorable noise intensity, were prepared using various iron-containing oxides represented by “M1+AOFe2−AO3” or “Q3Fe5O12” where the element M was one kind or two kinds selected from Mn, Ni, Cu, Zn, Co, Fe and Mg; the value A was in the range of −0.5 to 0.5; and the element M was either one kind selected from Y, Dy, Lu, Yb, Tm, Er, Ho, Tb, Gd and Sm.
The samples No. A-36 to A-40 shown in TABLE 3 were prepared using other various iron-containing oxides containing Ni, Zn and Fe. As shown in TABLE 3, the samples No. A-36 to A-40 had a low noise intensity of 55 dB or lower at all frequencies.
Since the other configurations of the samples No. A-36 to A-40 were similar to those of the samples No. A-1 to A-35 as shown in TABLE 3, the reason for a difference in noise intensity between these samples is assumed to be the influence of the composition of the iron-containing oxide. More specifically, the composition of the iron-containing oxide in the samples No. A-36 to A-40 was any of the following: Ni0.8Zn0.2Fe2O4, Ni0.3Zn0.7Fe2O4, Ni0.8Zn0.7Fe1.5O4, Ni0.3Zn0.8Fe2.5O4 and Ni0.4Zn0.4Fe2.2O4. When these compositions are represented by “NixZnyFezO4”, the combination of X, Y and Z is “0.8, 0.2 and 2”, “0.3, 0.7 and 2”, “0.8, 0.7 and 1.5”, “0.3, 0.2 and 2.5” and “0.4, 0.4 and 2.2”. Namely, the values X, Y and Z range as follows: 0.3≤X≤0.80, 0.2≤Y≤0.7 and 1.5≤Z≤2.5 (with the proviso that X+Y+Z=3).
It is generally assumed that a plurality of kinds of oxides represented by NixZnyFezO4 produce similar noise suppression effects when the content ratio of Ni, Zn and Fe is close to that of the above samples. It is thus possible to achieve a low noise intensity by the use of these oxides where the values X, Y and X are within the above respective ranges as in the case of the samples No. A-36 to A-40.
Hence, the iron-containing oxide preferably has a composition represented by “M1+AOFe2−AO3” or “Q3Fe5O12”, more preferably “NixZnyFezO4”.
The samples No. B-6 to B-9 shown in TABLE 4 were prepared using other different iron-containing oxides. The composition of the iron-containing oxide in those samples was any of the following: Mg0.8Zn0.8Fe1.4O4, FeO, Fe2O3 and BaFe12O19. Those samples had a noise intensity of 87 dB or higher at an arbitrary frequency, which was higher than that of any of the samples No. A-1 to A-35 at the same frequency level. The composition of the iron-containing oxide in those samples was different from the above preferable composition range such as “M1+AOFe2−AO3”, “Q3Fe5O12” or “NixZnyFezO4”. For example, the composition of the iron-containing oxide in the sample No. B-6 (Mg0.8Zn0.8Fe1.4O4) was represented by M1+AOFe2−AO3 where the element M was Mg; and the value A was 0.6 and was larger than 0.5, that is, the upper limit value of the above preferable range (from −0.5 to 0.5). When the value A was out of the preferable range, a different phase was formed in the magnetic region 830 in addition to the phase of the magnetic substance. It is assumed that the noise suppression effect is lowered as a result of the formation of such a different phase.
Further, the composition of the iron-containing oxide in the samples No. B-14, B-15, B-18 to B-21 and B-24 to B31 was also different from the above preferable composition range. Those samples had a noise intensity of 86 dB or higher at an arbitrary frequency, which was higher than that of any of the samples No. A-1 to A-35 at the same frequency level.
In this way, the above preferable composition contributes to a favorable noise intensity as compared to the case of any other composition. The composition of the iron-containing oxide can be adjusted by any method, e.g. by controlling the component ratio of the powder material of the iron-containing oxide.
The iron content difference of the samples No. A-41 to A-45 (see TABLE 3) was in the range of 1.6 wt % to 5.0 wt % and was smaller than that of the samples No. A-1 to A-35. These samples No. A-41 to A-45 had a noise variation of 3 dB or smaller, which was smaller than that of the samples No. A-1 to A-35.
Since the other configurations of the samples No. A-41 to A-45 were similar to those of the samples No. A-1 to A-35 as shown in TABLE 3, the reason for such a difference in noise variation is assumed to be the influence of the iron content difference. The reason for decrease of the noise variation with decrease of the iron content difference is assumed as follows. When the iron content difference is small, i.e. when a variation in the distribution of iron inside the secondary particles (magnetic particle areas 835 (see
The samples No. A-41 to A-45, in which the iron content difference was set to 1.6, 2.4, 3.5, 4.1 or 5.0 (wt %), had a favorable noise variation. The preferable range (upper and lower limits) of the iron content difference can be thus determined based on the above five values. It is feasible to use any arbitrary one of the above five values as the lower limit of the preferable range of the iron content difference. It is feasible to use, as the upper limit of the preferable range of the iron content difference, any arbitrary one of the above values higher than the lower limit value. For example, the preferable range of the iron content difference may be from 1.6 wt % to 5.0 wt %. It is assumed that the smaller the iron content difference, the smaller the variations in the noise suppression effect of the magnetic substance between the plurality of current conduction paths, the smaller the noise variation. For this reason, it is preferable that the iron content difference is small. The iron content difference may be set to zero wt %. Namely, the preferable range of the iron content difference may be from zero wt % to 5.0 wt %. Although the composition of the conductive region 820 in the samples No. A-41 to A-45 was identified as Ni or Permalloy (sample No. A-44), the conductive region is however not limited to these conductive materials. It is assumed that other various kinds of conductive materials (such as Incornel, Cu, LaMnO3, C and TiC) can also be used as in the case of the samples No. A-31 to A-35.
As shown in TABLE 3, the samples No. A-46 to A-53 also had a noise variation of 3 dB or smaller. The iron content difference of these samples was set to 0.5, 0.9, 1.5 or 1.9 (wt %). As explained above, it has been shown by the plurality of samples that the noise variation became small when the iron content difference was in the above preferable range.
The iron content difference can be adjusted by any method. For example, the iron content difference can be decreased by decreasing the size of the primary particles or by allowing the formation of the secondary particles to proceed gradually and slowly.
In the samples No. A-46 to A-53, any of Si, B and P and the alkali metal were contained in the composite part 200 as shown in TABLE 3. The combination of the elements contained in each sample was as follows: Si and Na in the sample No. A-46; Si, P, Mg and Ca in the sample No. A-47; Si, B, Ca and K in the sample No. A-48, Si, B, P and K in the sample No. A-49; Si and Na in the sample No. A-50; Si, P, Mg and Ca in the sample No. A-51; Si, B, Ca, K in the sample No. A-52; and Si, B, P and K in the sample No. A-53. These samples had a NG rate of 5% or lower, which was lower than that of the samples No. A-1 to A-35, and had a noise intensity of 67 dB or lower at all frequencies.
Since the other configurations of the samples No. A-46 to A-53 were similar to those of the samples No. A-1 to A-35 as shown in TABLE 3, the reason for a difference in NG rate between these samples is assumed to be the influence of the elements contained in the composite part 200. When any of Si, B and P and alkali metal are contained in the composite part 200, a low-melting phase is formed during sintering of the composite part 200. As a result, the composite part 200 is closely packed so as to improve the durability (more specifically, impact resistance) of the composite part 200 and to prevent fine pores from remaining in the sintered composite part 200. The noise suppression effect is enhanced with decrease in the amount of the capacity component derived from the fine pores. Furthermore, the noise is suppressed as the occurrence of partial discharge in the fine pores is prevented.
For improvement in impact resistance, the combination of any of Si, B and P and the alkali metal is not limited to the above examples. It is assumed that these elements can also be used in any other combinations. It is generally preferable to contain at least one of Si, B and P in the ceramic region 810 and contain at least one kind of alkali metal component in the composite part 200.
The alkali metal content of the samples No. A-50 to A-53 (see TABLE 3) was set to 0.5, 2.1, 4.6 or 6.5 (wt %) and was higher than that of the sample No. A-46, A-49 (0.1 wt %, 0.4 wt %) and lower than that of the sample No. A-47, A-48 (7.2 wt %, 8.6 wt %).
As seen from comparison of the samples No. A-50 and A-46, the noise intensity was increased as follows with decrease of the alkali metal content from 0.5 wt % to 0.4 wt %. The noise intensity was increased from 48 dB to 55 dB at 30 MHz, from 45 dB to 53 dB at 100 MHz and from 41 dB to 50 dB at 300 MHz. It is assumed that: when the alkali metal content is excessively low, fine pores tend to remain in the sintered composite part 200; and the noise suppression effect is lowered as a result of the occurrence of such pores.
As seen from comparison of the samples No. A-53 and A-48, the noise intensity was increased as follows with increase of the alkali metal content from 6.5 wt % to 8.6 wt %. The noise intensity was increased from 56 dB to 64 dB at 30 MHz, from 54 dB to 62 dB at 100 MHz and from 53 dB to 63 dB at 300 MHz. It is assumed that: when the alkali metal content is excessively high, a reaction phase is formed by the alkali metal and the iron-containing oxide during sintering of the composite part 200; and the noise suppression effect is lowered as a result of the formation of such a reaction phase.
The samples No. A-50 to A-53, in which the alkali metal content was in the range of 0.5 wt % to 6.5 wt %, had a favorable noise intensity. More specifically, the noise intensity was favorable in the samples No. A-50 to A-53 in which the alkali metal content was set to 0.5, 2.1, 4.6 or 6.5 (wt %). The preferable range (upper and lower limits) of the alkali metal content can be thus determined based on the above four values. It is feasible to use any arbitrary one of the above four values as the lower limit of the preferable range of the alkali metal content. It is feasible to use, as the upper limit of the preferable range of the alkali metal content, any arbitrary one of the above values higher than the lower limit value. For example, the preferable range of the alkali metal content may be from 0.5 wt % to 6.5 wt %. The alkali metal content can be adjusted by any method, e.g. by controlling the amount of alkali metal component added to the powder material of the composite part 200.
The “primary particle size”, the “porosity”, the “secondary particle size”, the “composition of the iron-containing oxide”, the “iron content difference”, “Si, B, P and alkali metal” and the “alkali metal content” have been explained above as the preferable configurations. These seven preferable configurations can be combined with each other. One or more of these seven preferable configurations can be selected arbitrary as the configurations of the composite part 200.
(1) In the case where the composition of the iron-containing oxide contained in the magnetic region 830 is represented by M1+AOFe2−AO3, various combinations of the element M and the value A can be used in place of those used in the above samples. The element M is not limited to those of the above samples. The element M can be at least one kind selected from Mn, Fe, Co, Ni, Cu, Mg, Zn and Ca. In the case where two or more kinds of elements are used as the element M, the total ratio of these elements is set to “1+A”. The value A can be any arbitrary value ranging from −0.5 to 0.5.
(2) In the case where the composition of the iron-containing oxide contained in the magnetic region 830 is represented by Q3Fe5O12, two or more kinds selected from Y, Lu, Yb, Tm, Er, Ho, Dy, Tb, Gd and Sm may be used as the element Q. In either case, the total ratio of all elements used as the element Q is set to “3”.
(3) It is preferable to use at least one of the above preferred oxide compounds represented by M1+AOFe2−AO3 and Q3Fe5O12 as the iron-containing oxide of the magnetic region 830. It is particularly preferable that the iron-containing oxide of the magnetic region 830 includes an iron-containing oxide represented by NixZnyFezO4 (where 0.3≤X≤0.8; 0.2≤Y≤0.7; 1.5≤Z≤2.5; and X+Y+Z=3). The magnetic region 830 may include two or more kinds of iron-containing oxides. For example, it is feasible to include both of the iron-containing oxide represented by M1+AOFe2−AO3 and the iron-containing oxide represented by Q3Fe5O12 in the magnetic region 83.
(4) As the conductive material for formation of the conductive region 820 of the composite part 200, any of the conductive materials used in the above samples No. A-1 to A-53 of favorable noise intensity (such as Ni, Inconel, Cu, LaMnO3, C, TiC and Permalloy) can be arbitrarily selected and used. It is assumed that not only these conductive materials but also other various conductive materials are usable. As the material for the conductive region 820, for example, it is feasible to use a material containing at least one of a metal, carbon, a carbon compound and a perovskite oxide. The metal can be at least one metal arbitrarily selected from Ag, Cu, Ni, Sn, Fe, Cr, Inconel, Sendust, Permalloy etc. The carbon compound can be at least one compound arbitrarily selected from Cr3C2, TiC etc. The perovskite oxide can be at least one compound arbitrarily selected from LaMnO3, SrTiO3, SrCrO3 etc. The conductive material for the conductive region 820 may contain a plurality of kinds of conductive materials. In general, it is possible by the use of the conductive material having an electrical resistance of 50 □·m to suppress deterioration caused by heat generation due to the flow of large electric current.
(5) In the composite part 200, the ceramic material is provided to support the conductive material and the magnetic substance (that is, iron-containing oxide). There can be used various kinds of ceramic materials to support the conductive material and the magnetic substance. For example, it is feasible to use an amorphous ceramic material. The amorphous ceramic material may be in the form a glass containing one or more components arbitrarily selected from SiO2, B2O5 and P2O5. It is alternatively feasible to used a crystalline ceramic material. The crystalline ceramic material may be in the form of a crystallized glass (also called glass ceramic) such as Li2O—Al2O3—SiO2 glass. As another alternative, there can be used a ceramic material free of Si, B and P.
(6) It is feasible to form the composite part 200 by any other method other rather than by placing and sintering the material of the composite part 200 in the though hole 12 of the insulator 10. For example, the composite part 200 can alternatively be formed by the following procedure. The material of the composite part 200 is formed into a cylindrical column shape by means of a forming die. The resulting formed body is sintered, thereby providing the composite part 200 in sintered cylindrical column form. Then, the powder material of the first seal part 600, the sintered composite part 200 rather than the powder material of the composite part 200, and the powder material of the second seal part 200 are put into the through hole 12 of the insulator 10 as the materials of the connection structure 300. The connection structure (e.g. the connection structure 200 of
(7) The configurations of the spark plug is not limited to those of
Although the present invention has been described with reference to the above specific embodiment and modification examples, the above embodiment and modification examples are intended to facilitate understanding of the present invention and are not intended to limit the present invention thereto. Various changes and modifications can be made without departing from the scope of the present invention. The present invention includes equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-123301 | Jun 2015 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2016/002522 | 5/25/2016 | WO | 00 |
