CN1744399A - Spark plug with increased durability - Google Patents

Spark plug with increased durability Download PDF

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Publication number
CN1744399A
CN1744399A CN 200510097819 CN200510097819A CN1744399A CN 1744399 A CN1744399 A CN 1744399A CN 200510097819 CN200510097819 CN 200510097819 CN 200510097819 A CN200510097819 A CN 200510097819A CN 1744399 A CN1744399 A CN 1744399A
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spark plug
ceramic insulator
metal shell
insulation
head
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CN 200510097819
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CN100514778C (en
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阿部信男
川岛泰
后藤常利
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Denso Corp
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Denso Corp
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Abstract

A spark plug is provided which is designed to be compact without sacrificing a mechanical strength of a porcelain insulator. The spark plug includes a metal shell having a base end and a top end. The porcelain insulator is made of a hollow cylinder which includes a body and an insulator head. The body is retained within the metal shell. The insulator head extends from the base end of the metal shell in a lengthwise direction of the porcelain insulator and has a length made up of a major body leading to the body of the porcelain insulator and an end portion lying far away from the body. The major body has an outer diameter D 1 , an inner diameter D 2 , and a section modulus Z at a smallest-outer diameter portion thereof which meet relations of 7.1 mm<=D 1 <=8.8 mm, D 2 >=2.8 mm, and Z>=33 mm<3>.

Description

The spark plug that durability improves
Technical field
Present invention relates in general to be used for internal combustion engine and spark plug that durability improves, described internal combustion engine can use in automobile, co-generation unit or air feed pump.
Background technology
The internal combustion engine of use in automobile for example utilizes spark ignitor air one fuel mixture.For this kind spark plug, required to improve in-engine burning day by day to reduce fuel consumption or its toxic emission.Need be for the improvement of described burning to the improvement of the heat efficiency and the compression ratio of engine, however this can cause the spontaneous combustion of described mixture in the combustion chamber of engine, thereby cause combustion knock.
Described combustion knock can the cooling system of water jacket be reduced by for example improving, and described cooling system is to be provided with around described piston head to strengthen the cooling of engine.
For the performance of improving engine and the complexity of engine cylinder head (engine head), modern engine is equipped with direct injection mechanism or VVT gear.
The improvement of the cooling of engine thereby need the reducing of installing space of spark plug.For example, Japan is real opens flat 5-55489 communique and discloses and be used for being formed on spark plug on the metal shell of spark plug the technology that the diameter of screw thread reduces being installed.Yet this has caused reducing the diameter of the ceramic insulator of spark plug, thereby has caused the reduction of its mechanical strength.This has improved the possibility that described ceramic insulator damages owing to engine luggine.
In order to minimize from the electrical noise of ignition distributor or to simplify the arrangement mode of high-voltage circuit, use known igniter, it has ignition coil, and described ignition coil only is installed in the spark plug top in direct-connected mode with it.Described ignition coil is assembled on the ceramic insulator of spark plug and is fixed on the end cap that is installed on the described engine cylinder head.Spark plug is directly installed on the engine cylinder head.
Yet there is following problem in said structure, and promptly engine luggine can be delivered to the connecting portion between ignition coil and the spark plug, so that the mechanical load of non-expectation or stress are applied to the head of the ceramic insulator of spark plug.Especially, when the engine luggine that is applied to the engine cylinder head that spark plug installs has nothing in common with each other on direction or phase place each other with the engine luggine that is applied to the top cover that ignition coil installs, will cause bending force or stress on described ceramic insulator.The attenuation of described ceramic insulator thereby improved the possibility that ceramic insulator damages owing to engine luggine.
When being obtained spark plug and work usually, the irdome (coil boot) of ignition coil and ceramic insulator secure fit produce the electric insulation between the high-tension ignition coil.Especially, by high voltage that ignition coil produced through the terminal of spark plug be placed in central electrode that conductor in the ceramic insulator is passed to spark plug producing sparkover in the spark-discharge gap between central electrode and grounding electrode, thereby the mixture in the ignition engine.When irdome when the head of ceramic insulator unclamps, so that bigger gap appears between them, then can cause so-called flashover (flashover), promptly electric current leaks into the head of ceramic insulator in this phenomenon, it causes the discharge deficiency in the spark-discharge gap, thereby has reduced the ignitability of mixture in the engine.
Especially, since the raising of the ignition gap that wearing and tearing caused of the electrode of spark plug with the raising of guiding discharge voltage.In addition, irdome uses going bad or hardening of being caused to cause the reduction of its electrical isolation capabilities because spark plug is long-term, and this can cause the discharge (being flashover) on the surface of ceramic insulator, thereby causes the flame-out of engine.
On the contrary, if irdome is assemblied on the head of ceramic insulator too tightly, then need the very big power of expense that irdome is pulled out spark plug.Especially, when irdome is assemblied on the spark plug, the air in the irdome will expand when engine running and will shrink when engine stops.Usually when engine stops and cooling off, finish removing of spark plug.Negative pressure or vacuum thereby produce in irdome are so cause the bigger power of needs expense that irdome is pulled out from spark plug.Drawn if irdome is stressed, then can be caused damaging the crack on irdome or its breakage or the ceramic insulator.Especially, the secure fit of the head of irdome and ceramic insulator helps guaranteeing the electric insulation between them, otherwise can become one of following factor, promptly damages the crack on irdome or its breakage or the ceramic insulator.
Summary of the invention
Thereby, the shortcoming of avoiding prior art of main purpose of the present invention.
Another object of the present invention is the spark plug that proposes to improve structure, and it is designed to compact dimensionally but is not cost to lose its mechanical strength or durability.
According to an aspect of the present invention, propose a kind of spark plug that is used for internal combustion engine, it comprises: (a) metal shell, its have cardinal extremity and and the top, described top is along vertically relative with described cardinal extremity (promptly on the contrary) of spark plug; (b) hollow tubular ceramic insulator, it has the length that comprises body and insulation head, described body is maintained in the described metal shell, described insulation head begins to extend along vertical cardinal extremity from described metal shell of described ceramic insulator, and described ceramic insulator has the inner room that extends in described body and described insulation head; (c) central electrode, its length along described ceramic insulator remains on the interior indoor of described ceramic insulator to normal incidence; And (d) grounding electrode, its top side from described metal shell begins to extend, and defines the spark-discharge gap between self and the described ceramic insulator.The insulation head of described ceramic insulator has the length of being made up of main body and end, and described main body leads to the body of described ceramic insulator and settle away from the body of described ceramic insulator described end.Described main body partly locates to have outer diameter D 1 in its minimum outer diameter, inside diameter D 2 and section modulus Z, and their satisfy relation: 7.1mm≤D1≤8.8mm, D2 〉=2.8mm, Z 〉=33mm 3
Minimum outer diameter in described main body is partly located more than or equal to 33mm 3Section modulus Z guaranteed the expectation strength of institute's ceramic insulator, especially directed and cause intensity aspect its crooked external force perpendicular to the length direction of ceramic insulator in opposing.
It is in the scope at 7.1mm to 8.8mm and to allow described spark plug be not that cost is reduced with the mechanical strength of losing described ceramic insulator dimensionally in outer diameter D that the minimum outer diameter of described main body is partly located 1.Especially, 8.8mm or following outer diameter D 1 allow the diameter of thread of described metal shell to be reduced, and this causes the size of described spark plug to be reduced.7.1mm or bigger outer diameter D 1 has guaranteed that described section modulus Z is in the mechanical strength to guarantee that described ceramic insulator is required in the above-mentioned scope.
It is in 2.8mm or bigger scope and the resistor of guaranteeing for example central electrode, termination electrode and remaining on described ceramic insulator inboard is connected to the mechanical strength of described ceramic insulator in inside diameter D that the minimum outer diameter of described main body is partly located 2.Especially, 2.8mm or bigger inside diameter D 2 guarantee that for example glass seal will be soldered to the area of described ceramic insulator, thereby provide described central electrode is fixed on expectation strength in the described ceramic insulator.
In the preferred pattern of the present invention, metal shell is equipped with spark plug erecting tools auxiliary section, and it has the regular hexagon cross section that extends perpendicular to the axis of described metal shell.Distance H 1 between the relative dual-side of described regular hexagon cross section is selected to and satisfies relation: 11.7mm≤H1≤14mm.This allows described spark plug to be reduced dimensionally.
The profile of described spark plug erecting tools auxiliary section is limited shape alternatively in the following manner, i.e. two measure-alike positive hexagonal portion mutual superposition, and circumferentially staggered with 30 ° around its axis along described metal shell.Distance H 2 between the relative dual-side of each described regular hexagon cross section is selected to and satisfies relation: 11.7mm≤H2≤14mm.
Described metal shell has and is used for described spark plug is installed in screw thread in the internal combustion engine, and described screw thread has the diameter of thread M that satisfies 8mm≤M≤12mm relation.
The insulation head of described ceramic insulator has the length L that satisfies 22mm≤L≤28mm relation.This guarantees the described insulation head opposing mechanical load directed perpendicular to the length of described ceramic insulator.
The main body of the insulation head of described ceramic insulator can have smooth unrippled surface, and it has at 400mm 2To 600mm 2Area in the scope.This has realized that described insulation head cooperates with the expectation of the irdome of for example ignition coil.
The main body of the insulation head of described ceramic insulator has the ripple that is formed on its outer surface alternatively.Described outer surface occupies the area of 0mm to 0.1mm depth bounds at 400mm from the top of each ripple 2To 600mm 2Scope in.
According to a further aspect of the invention, proposition can be used for the igniter of fire fuel in internal combustion engine, it comprises: (a) be installed in the spark plug in the cylinder head for internal combustion engines, and (b) ignition coil, the insulation head of itself and described spark plug is aligning and is being installed in the end cap that covers described engine cylinder head.Described spark plug has any aforementioned structure.
Description of drawings
Accompanying drawing by the following detailed description that provides and the preferred embodiment of the present invention, with complete understanding the present invention more, yet, they should not thought the present invention only for these certain embodiments, and should think that they only are for explaining and illustrative purposes.
In each accompanying drawing:
Fig. 1 is a longitudinal sectional view, and it shows the spark plug according to first embodiment of the invention;
Fig. 2 is a vertical view, and it is to see from the base end side of spark plug shown in Figure 1;
Fig. 3 is a longitudinal sectional view, and it shows the igniter that spark plug shown in Figure 1 is housed;
Fig. 4 is a vertical view, and it is to see from the base end side of the spark plug of second embodiment of the invention;
Fig. 5 is local longitudinal sectional view, and it shows the spark plug according to third embodiment of the invention;
Fig. 6 is the zoomed-in view of Fig. 5;
Fig. 7 is an end view, and it shows and is used for assessing the vibration detection device of spark plug to the opposing of mechanical oscillation;
Fig. 8 is a curve chart, and it shows the vibration frequency of the spark plug that is added in the vibration detection device of Fig. 7.
Embodiment
Referring now to accompanying drawing,, Fig. 1 particularly, it shows the spark plug that is used for car combustion engine according to first embodiment of the invention.
Spark plug 1 roughly comprises hollow tubular metal shell 2, ceramic insulator 3, central electrode 4 and grounding electrode 5.Described ceramic insulator 3 is maintained in the described metal shell 2, to have the insulation of extending in described metal shell 2 outsides towards the base end side of spark plug 1 (promptly seeing top in the past from accompanying drawing) 31.Central electrode 4 is maintained in the centre bore 32 that is formed in the ceramic insulator 3.Grounding electrode 5 is faced described central electrode 4 from described metal shell 2 extensions and through a spark-discharge gap 14.
Metal shell 2 has screw thread 21 and turret head 22; Described screw thread 21 is to be used for realizing being installed in the internal combustion engine, and a spanner will be fitted on the described turret head 22 spark plug 1 is put into engine or take out from engine.
Insulation 31 has the length L of extending in the outside of the end of metal shell 2.Length L is made of main body 366 and tapering point 311.Main body 366 partly locates to have outer diameter D 1 in its minimum outer diameter, inside diameter D 2 and section modulus (section modulus) Z, and their satisfy following relation:
7.1mm≤D1≤8.8mm
D2≥2.8mm
Z≥33mm 3
Tapering point 311 has the 4mm length of counting from the cardinal extremity of insulation 31 (promptly seeing upper end in the past from accompanying drawing).
Main body 366 can be directly to extending and having a constant diameter.In this case, main body 366 has outer diameter D 1 along its whole length.
Insulation 31 a minimum outer diameter part with outer diameter D 1, inside diameter D 2 and section modulus Z do not comprise tapering point 311, its reason is, the bending load or the stress that are applied in the insulation 31 are not concentrated in its end usually, and in other words, the end of insulation 31 is stress influence by bending least easily.
Minimum outer diameter in insulation 31 is partly located, and inside diameter D 2 equals the diameter of centre bore 32.
Turret head 22 as shown in Figure 2 has the regular hexagon cross section that extends perpendicular to the longitudinal centre line of metal shell 2 (being piston head 1).Distance H 1 between the opposed side edges of described hexagonal transverse cross section is selected to and satisfies relation: 11.7mm≤H1≤14mm.
Screw thread 21 has diameter of thread M, and it satisfies relation: 8mm≤M≤12mm.
As mentioning at this, to be ceramic insulator 31 as described above extend to the part of the end of tapering point 311 from the cardinal extremity (promptly seeing upper end in the past from accompanying drawing) of metal shell 2 to the length L of insulation 31.Length L is selected to and satisfies relation: 22mm≤L≤28mm.
In the centre bore 32 of ceramic insulator 3, central electrode 4, resistor 12 and termination electrode 11 are aligned layout each other.Resistor 12 is interposed between central electrode 4 and the termination electrode 11 hermetically through glass seal 13.Glass seal 13 in centre bore 32 bonded the or end that is welded to the inwall of ceramic insulator 3 and resistor 12 so that resistor 12 is held in place.
Resistor 12 is made by carbon-based material, and forms by filling centre bore 32 with certain pressure with carbon dust.Each glass seal 13 is to be formed by copper glass, and described copper glass is made up of the mixture of glass and copper (Cu) powder.
Insulation 31 has smooth, unrippled outer surface.The main body 366 of insulation 31 has 400mm 2To 600mm 2Outer circumferential area.
Fig. 3 shows the igniter 6 that spark plug 1 and ignition coil 63 are housed.Spark plug 1 is installed in the cylinder head 61 of internal combustion engine.Ignition coil 63 is installed in the end cap 62 and with spark plug 1 and is electrically connected, and described end cap 62 is placed on the cylinder head 61 attached to engine.
Ignition coil 63 is exactly so-called bar-shaped coil and has the irdome of being made by hard rubber 631.Irdome 631 is assembled in the insulation 31 of spark plug 1.As mentioned above, the outer circumferential area of the contact area of irdome 631 and insulation 31 and main body 366 is identical.In other words, irdome 631 is arranged to roughly to contact with the whole periphery of insulation 31.
Cylinder head 61 and end cap 62 have formation jack 611 and 621 within it, and spark plug 1 and ignition coil 63 will be installed in these jacks.Cylinder head 61 also has the formation plug that aligns with jack 611 dress hole 612 within it, and the head 21 of spark plug 1 is screwed togather in the plug dress hole 612.
The water jacket 613 of engine and valve 614 are settled around jack 611.
As mentioned above, spark plug 1 partly locates to have section modulus Z in the minimum outer diameter of the main body 366 of insulation 31, and it is more than or equal to 33mm 3, thereby guaranteed the expectation strength of ceramic insulator 3, especially directed and cause intensity aspect its crooked external force perpendicular to the length direction of ceramic insulator 3 in opposing.
Insulation 31 partly locates to have outer diameter D 1 in the minimum outer diameter of main body 366, and it is selected in the scope of 7.1mm to 8.8mm, thereby to allow the size of spark plug 1 needn't be that cost is reduced with the intensity of loss ceramic insulator 3.Especially, 8.8mm or following outer diameter D 1 allow the diameter of thread of metal shell 2 to be reduced, thereby reduce the size of spark plug 1.7.1mm or bigger outer diameter D 1 guarantees that described section modulus Z is in the aforesaid scope mechanical strength to guarantee that ceramic insulator 3 is required.
Insulation 31 also has inside diameter D 2 at the minimum outer diameter place of main body 366, and it is selected in 2.8mm or bigger scope, thereby guarantees that central electrode 4, termination electrode 11 and resistor 12 are connected to the mechanical strength of ceramic insulator 3.Especially, 2.8mm or bigger inside diameter D 2 guarantee that glass seals 13 will be soldered to the area on the ceramic insulator 3, thereby provide central electrode 4 is fixed on expection intensity in the ceramic insulator 3.
Distance H 1 between the relative side of turret head 22 is set in the scope of 11.7mm to 14mm as described in Figure 2, thereby to allow spark plug 1 to be made compact dimensionally as mentioned above and need not with loss section modulus Z be cost.
The diameter of thread M of metal shell 2 is in the scope of 8mm to 12mm as described in, thereby also to allow spark plug 1 to be made compact dimensionally and need not with loss section modulus Z be cost.
The length L of insulation 31 is as mentioned above in the scope of 22mm to 28mm, thereby guarantee that its renitent mechanical strength, described pressure are directed and the perpendicular direction of length of ceramic insulator 3 and the insulation resistance between metal shell 2 and central electrode 4.
The main body 366 of insulation 31 has 400mm as mentioned above 2To 600mm 2Outer circumferential area, thereby guarantee the desired amount that cooperates with the irdome 631 of ignition coil 63.Especially, between insulation 31 and irdome 631, obtain to cooperate closely and help irdome 631 31 is removed easily from insulating.This guarantees the insulation property of ceramic insulator 3 and has also minimized the mechanical damage of ceramic insulator 3 or irdome 631.
As can be as seen from Figure 3, igniter 6 be designed to have the ignition coil 63 that will be assembled in the insulation 31 of spark plug 1.Usually, the mechanical oscillation of engine are delivered to cylinder head 61 and end cap 62.In some cases, acting on vibration on the cylinder head 61 compares with the vibration on the end cap 62 and can change aspect direction and the phase place, this has caused ignition coil 63 on being installed in the spark plug 1 in the cylinder head 61 and being installed in end cap 62 with different each other directions and phase oscillation, thereby has caused acting on a mechanical stress that insulate on 31; Described insulation 31 is used as being connected between spark plug 1 and the ignition coil 63.In order to resist this stress, spark plug 1 is designed to have above-mentioned parameter.
Spark plug 1 is allowed to reduce its size as mentioned above, thereby makes and will be enhanced around quilt such as the water jacket 613 of spark plug 1 or the occupied installing space of part of valve 614, thereby improves the performance of engine.
Fig. 4 is a vertical view, and it shows the metal shell 2 according to the spark plug 1 of second embodiment of the invention.Metal shell 2 has spark plug erecting tools auxiliary section 22, and its turret head 22 with the spark plug 1 of as illustrated in fig. 1 and 2 first embodiment has identical functions.
The profile of spark plug erecting tools auxiliary section 22 is limited shape in the following manner, i.e. two measure-alike positive hexagonal portion mutual superposition, and circumferentially staggered with 30 ° around its longitudinal midline along metal shell 2.
Distance H 2 between the relative side of each in the hexagonal portion of mutual superposition is selected to the relation that satisfies 11.7mm≤H2≤14mm.
The spark plug 1 of other structure and first embodiment identical, and it is described in detail in this will omits.
Fig. 5 and 6 shows the spark plug 1 according to third embodiment of the invention, and it has the insulation 31 that has rib or ripple (corrugation).Each ripple is limited by bottom or trough 312 and top or crest 313 respectively along the circumferential extension of insulation 31 and each.
Insulation 31 has outer diameter D 1 at each trough 312 place as shown in Figure 5, its with embodiment 1 in identical.
As first embodiment, the main body 366 of insulation 31 has 400mm 2To 600mm 2Outer circumferential area, this promptly insulate an outer surface of 31 will with the irdome 631 contacted areas of the igniter 6 of Fig. 3, and in Fig. 6, illustrate with black solid line.Especially, outer circumferential area is that main body 366 is the outside area in the depth bounds of 0mm to 0.1mm at the crest 313 from each ripple.In other words, its outside area of equaling that part that ceramic insulator 3 extends in metal shell 2 outsides outside area and each trough 312 of having deducted tapered portion 311 is the outside area in 0.1mm or the above depth bounds from corresponding crest 313.
Other structures of described spark plug 1 are identical with embodiment's 1, and it is described in detail in this will omits.
In the said structure of spark plug 1, insulation 31 part that form trough 312 within it have low relatively mechanical strength.In order to ensure required mechanical strength, insulation 31 is designed to have outer diameter D 1, inside diameter D 2 and section modulus Z at trough 312 places, and they satisfy following relationship respectively.
7.1mm≤D1≤8.8mm
D2≥2.8mm
Z≥33mm 3
Insulation 31 is designed to have 400mm as mentioned above 2To 600mm 2Outer circumferential area, it will cooperate with the irdome 631 of ignition coil 63, thereby guarantee the desired amount that contacts with the irdome 631 of ignition coil 63.Especially, between insulation 31 and irdome 631, obtain to cooperate closely and help irdome 631 31 is removed easily from insulating.This guarantees the insulation property of ceramic insulator 3 and has also minimized the mechanical damage of ceramic insulator 3 or irdome 631.
Ripple has been used for improving the outside area of ceramic insulator 31 per unit lengths, thereby has improved its insulation property.
We have finished test with the opposing of assessment spark plug 1 for mechanical oscillation.Our preparation and use as shown in Figure 3 igniter 6 and except parameter D1, D2, Z with the spark plug sample of spark plug 1 same structure of as illustrated in Figures 5 and 6 embodiment 3.
Especially, we prepare the spark plug sample and have following different value, i.e. outer diameter D 1 in 7.0 to 7.6mm scopes, the inside diameter D 2 in 2.5 to 4.5mm scopes, and 27.9 to 42.6mm 3Section modulus Z in the scope; And as shown in Figure 7, we finish test by following steps under constant condition, being about to each spark plug sample and ignition coil 63 is installed in the jack 611 and 621 of engine cylinder head 61, engine cylinder head 61 is contained on the platform 71 of vibration generator 7, and shown in the arrow A of Fig. 7, along continuous straight runs vibrates described platform 71.
The maximum vibration acceleration that is added on the connecting portion between spark plug sample and the cylinder head 61 is selected as 50G, and it is the twice that is directly installed on typical high-performance 2000 sparks, four cylinders and operates in the peak acceleration 25G that the in-engine spark plug part under the 8400rpm stood.
As shown in Figure 8, the vibration frequency that is added on the spark plug sample is to change in the scope of 0Hz to 300Hz.Especially, vibration frequency is brought up to 300Hz from 0Hz in ten minutes very first time section, and then is reduced to 0Hz from 300Hz in next ten minutes time period.Repeated one hour like this.
After the vibration-testing, we remove each spark plug sample from vibration generator 7, check the crack in the ceramic insulator 3 and assess the mechanical strength that termination electrode 11 is connected to ceramic insulator 3.As follows, table 1 has illustrated the existence in crack of the ceramic insulator 3 of each spark plug sample.Table 2 has illustrated the bonding strength of the termination electrode 11 of each spark plug sample.In table 1, " zero " is illustrated in and does not have the crack in the ceramic insulator 3, and " * " is illustrated in the ceramic insulator 3 and has the crack.Section modulus Z is by Z=(π/32) * (D1 4-D2 4The relation of)/D1 obtains.In table 2,70% or above situation before the also surplus test of the bonding strength between " zero " expression termination electrode 11 and the ceramic insulator 3, the bonding strength between " * " expression termination electrode 11 and the ceramic insulator 3 drops to the situation less than 70% before the test.
Table 1
Figure A20051009781900171
Table 2
Figure A20051009781900172
Table 1 explanation, when section modulus Z greater than 33mm 3The time, do not have the crack to appear in the ceramic insulator 3, and when inside diameter D 2 be 4.0mm or following and outer diameter D 1 for 7.2mm or when bigger, do not have the crack to appear in the ceramic insulator 3.
Table 2 explanation, when inside diameter D 2 was 2.5mm, the bonding strength of termination electrode 11 was owing to the vibration that adds thereon descends, and when inside diameter D 2 be 3.0mm or when bigger, the bonding strength of termination electrode 11 has the degree of expection.
We have also finished the reduction of durability test with the bonding strength of the termination electrode 11 of each spark plug sample of assessment use; Used spark plug sample has inside diameter D 2 values of various insulation 31, and it is chosen in the scope of 2.5mm to 3.0mm.
Especially, our preparation has the outer diameter D 1 of identical 7.6mm but inside diameter D 2 is the spark plug sample of different value 2.6mm, 2.7mm, 2.8mm and 2.9mm.The structure of each spark plug sample is identical with above-mentioned test with test mode.
Test result explanation, when inside diameter D 2 be 2.6mm and 2.7mm, bonding strength be reduced to before the test below 70%, and when inside diameter D 2 be 2.8mm and 2.9mm, bonding strength is also surplus arrive test preceding 70% or more than.Thereby find that the inside diameter D 2 of insulation 31 is 2.8mm or bigger preferably.
Although to disclose preferred embodiment in order helping better understanding the present invention here, to have it should be understood that the present invention is not breaking away under its principle condition and can implement in various mode.Thereby the present invention should be understood to include the remodeling of all possible embodiment and described embodiment, and they can be implemented under the principle of the invention condition that does not break away from claims to be proposed.

Claims (8)

1. be used for the spark plug of internal combustion engine, comprise:
Metal shell, its have cardinal extremity and and the top, described top is vertically relative with described cardinal extremity along spark plug;
Hollow tubular ceramic insulator, it has the length that comprises body and insulation head, described body is maintained in the described metal shell, described insulation head begins to extend along vertical cardinal extremity from described metal shell of described ceramic insulator, and described ceramic insulator has the inner room that extends in described body and described insulation head;
Central electrode, its length along described ceramic insulator remains on the interior indoor of described ceramic insulator to normal incidence; And
Grounding electrode, its top side from described metal shell begin to extend, and define the spark-discharge gap between self and the described central electrode;
Wherein, the insulation head of described ceramic insulator has the length of being made up of main body and end, described main body leads to the body of described ceramic insulator and settle away from the body of described ceramic insulator described end, described main body partly locates to have outer diameter D 1 in its minimum outer diameter, inside diameter D 2 and section modulus Z, and they satisfy following relationship:
7.1mm≤D1≤8.8mm
D2≥2.8mm
Z≥33mm 3.
2. spark plug as claimed in claim 1, it is characterized in that, described metal shell is equipped with spark plug erecting tools auxiliary section, described spark plug erecting tools auxiliary section has the regular hexagon cross section that extends perpendicular to the axis of described metal shell, and the distance H 1 between the relative dual-side of described hexagonal transverse cross section is selected to and satisfies relation: 11.7mm≤H1≤14mm.
3. spark plug as claimed in claim 1, it is characterized in that, described metal shell is equipped with spark plug erecting tools auxiliary section, the profile of described spark plug erecting tools auxiliary section is limited shape in the following manner, i.e. two measure-alike positive hexagonal portion's mutual superposition and circumferentially staggered with 30 ° around its axis along described metal shell, the distance H 2 between the relative dual-side of each described hexagonal transverse cross section is selected to and satisfies relation: 11.7mm≤H2≤14mm.
4. spark plug as claimed in claim 1 is characterized in that, described metal shell has and is used for described spark plug is installed in screw thread in the internal combustion engine, and described screw thread has the diameter of thread M that satisfies 8mm≤M≤12mm relation.
5. spark plug as claimed in claim 1 is characterized in that, the insulation head of described ceramic insulator has the length L that satisfies 22mm≤L≤28mm relation.
6. spark plug as claimed in claim 1 is characterized in that, the main body of the insulation head of described ceramic insulator has smooth unrippled outer surface, and its area is at 400mm 2To 600mm 2Scope in.
7. spark plug as claimed in claim 1, it is characterized in that, the main body of the insulation head of described ceramic insulator has the ripple that is formed on its outer surface, and described outer surface begins area to 0mm to the 0.1mm depth bounds at 400mm from the top of each ripple 2To 600mm 2Scope in.
8. igniter comprises:
Be installed in the spark plug in the cylinder head for internal combustion engines, described spark plug has as the arbitrary structure that limits of claim 1 to 7, and
Ignition coil, the insulation head of itself and described spark plug is aligning and is being installed in the end cap that adheres to described engine cylinder head.
CNB2005100978195A 2004-08-31 2005-08-30 Spark plug Expired - Fee Related CN100514778C (en)

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CN101043124B (en) * 2006-03-21 2012-05-16 日本特殊陶业株式会社 Spark plug
CN101496239B (en) * 2006-06-19 2012-04-04 费德罗-莫格尔公司 Small diameter/long reach spark plug with improved insulator design
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