JP5425558B2 - Glow plug housing and glow plug - Google Patents

Description

  The present invention relates to a glow plug housing and a glow plug for constituting a glow plug used in an internal combustion engine such as an automobile diesel engine.

  Conventionally, glow plugs have been used to promote startup of internal combustion engines such as automobile diesel engines. As such a glow plug, the front end side protrudes from the front end portion of the housing and the rear end side is accommodated in the housing in a cylindrical housing provided with a screw portion for engine attachment on the outer peripheral surface. The thing of the structure which supported the ceramic heater via the heater holding | maintenance outer cylinder is known.

  In the case of the glow plug having the above configuration, the ceramic heater and the heater holding outer cylinder are fixed by, for example, press-fitting the ceramic heater into the heater holding outer cylinder, and then the heater holding outer cylinder and the housing are welded all around by laser. It is also known that the structure is fixed by, for example, Patent Document 1).

JP 2008-8607 A

  In the above glow plug, since the heater holding outer cylinder is required to have more corrosion resistance, for example, the housing is made of stainless steel such as SUS430, while the housing is considered to be made of carbon steel because the ease of processing is important. ing. Here, when carbon steel is used as a welding material, the carbon content is generally 0.3 mass% or less. This is because the heat-affected zone becomes harder as the carbon content increases. However, in the case of a housing for a glow plug, when the carbon content is 0.3 mass% or less, the tensile strength, the yield point, the proof stress is lowered, and when the glow plug is tightened to an automobile diesel engine or the like, The housing may be deformed, and in order to satisfy the strength, the carbon content is preferably about 0.35 mass% or more.

  However, as described above, a material made of carbon steel having a carbon content of 0.35 mass% or more, for example, S40C (JIS: C = 0.37 to 0.43 mass%), STKM16C (JIS: C = 0. When the housing is configured using 35 to 0.45 mass%), there is a problem that surface cracks occur in the welded portion when the housing and the heater holding outer cylinder are welded. As described above, the heater holding outer cylinder is often made of a ferritic stainless steel (for example, SUS430) having a carbon content of 0.12% by mass or less.

  The present invention has been made to solve the above problems. The present invention can ensure sufficient mechanical strength that does not cause deformation when tightened to a diesel engine for automobiles and the like, and surface cracks of the welded portion occur during welding with the heater holding outer cylinder. An object of the present invention is to provide a glow plug housing and a glow plug that can prevent this.

The glow plug housing according to the present invention includes a heater having a rod shape along an axis, a ferritic stainless steel heater holding outer cylinder fitted to the outer periphery of the heater, and a cylinder extending along the axis. The heater holding outer cylinder is fixed to the front end side by welding, and the rear end side of the heater is connected to the heater in a state where the front end side of the heater protrudes from the front end side of the heater. A glow plug housing used as a housing for a glow plug having a housing held inside through a holding outer cylinder, wherein the Si content is 0.40 mass% or less, and the Mn content is 0. .40 to 1.00% by mass, P content is 0.040% by mass or less, C content is 0.37 to 0.44% by mass, and C content and S content are Relationship is 0.42 quality When% <C ≦ 0.44% by mass, S ≦ (−0.75C (% by mass) +0.33) (% by mass), and when 0.37% by mass ≦ C ≦ 0.42% by mass, S ≦ (−0.1C (mass%) + 0.057) (mass%), and the balance is made of Fe and inevitable impurities.

A glow plug according to the present invention includes a heater having a rod shape along an axis, a heater holding outer cylinder made of ferritic stainless steel fitted to the outer periphery of the heater, and a cylindrical shape extending along the axis. The heater holding outer cylinder is fixed to the front end side by welding, and the rear end side of the heater is placed outside the heater holding side with the front end side of the heater protruding from the front end side of the heater. A glow plug including a housing held inside through a cylinder, wherein the housing has a Si content of 0.40% by mass or less, a Mn content of 0.40 to 1.00% by mass, The P content is 0.040% by mass or less, the C content is 0.37 to 0.44% by mass, and the relationship between the C content and the S content is 0.42% by mass < When C ≦ 0.44 mass%, S ≦ (−0.75 (Mass%) + 0.33) (mass%), and when 0.37 mass% ≦ C ≦ 0.42 mass%, S ≦ (−0.1 C (mass%) + 0.057) (mass%) And the balance consists of Fe and inevitable impurities.

  For example, STKM16C, which is a pipe material made of high carbon steel, has a Si content of 0.40% by mass or less, a Mn content of 0.40 to 1.00% by mass, and a P content of 0 according to JIS standards. 0.040% by mass or less, the C content is 0.35 to 0.45% by mass, and the S content is 0.040% by mass or less. Further, S40C, which is a rod, has a Si content of 0.15 to 0.35 mass%, a Mn content of 0.60 to 0.90 mass%, and a P content of 0.00 according to JIS standards. 030 mass% or less, C content is 0.37 to 0.43 mass%, S content is 0.035 mass% or less (as impurities, Cu is 0.30 mass%, Ni is 0.20 mass%) Ni + Cr must not exceed 0.35% by mass). However, when pipes or rods having a content of the above components in the above range are used for the glow plug housing, the necessary mechanical strength can be obtained, but the welded portion of the welded portion is welded to the heater holding outer cylinder. Surface cracks occur.

In the present invention, the content of C that can prevent the occurrence of surface cracks in the welded part during welding is specified, and the content of S that is a low melting point non-metallic inclusion and easily segregates to the grain boundary is the content of C. Therefore, the occurrence of surface cracks in the welded part during welding is prevented. That is, in the glow plug housing and the glow plug of the present invention, the Si content is 0.40 mass% or less, the Mn content is 0.40 to 1.00 mass%, and the P content is 0.040 mass%. % Or less and a C content of 0.37 to 0.44 mass% suppresses an increase in hardness due to a high temperature during welding while ensuring sufficient mechanical strength. In addition, along with this, as shown in the graph of FIG.
When 0.42% by mass <C ≦ 0.44% by mass,
S ≦ (−0.75C (mass%) + 0.33) (mass%),
In the case of 0.37 mass% ≦ C ≦ 0.42 mass%,
S ≦ (−0.1C (mass%) + 0.057) (mass%),
By prescribing the upper limit of S, which is a low-melting point non-metallic inclusion, according to the contents of and C, segregation of S to the grain boundaries is suppressed. And generation | occurrence | production of the surface crack which arises in a welding part by these effect | actions is prevented.

  In the glow plug housing and the glow plug of the present invention, the P content in the housing is preferably 0.020% by mass or less. P, like S, is a low melting point metal and is likely to segregate at the grain boundaries during welding. Therefore, if the upper limit is 0.020% by mass, the segregation of P to the grain boundaries is suppressed, and the weld zone The occurrence of surface cracks occurring in the film can be further suppressed. Further, by defining the amount of P in the above amount, it contributes to the improvement of cold brittleness.

  In the glow plug housing and the glow plug of the present invention, the Mn content in the housing is preferably 0.70 to 1.0 mass%. Mn has a property of being easily combined with S that adversely affects weldability. For this reason, the segregation of S can be suppressed and weldability can be improved by making Mn content 0.7 mass% or more. On the other hand, when the content of Mn exceeds 1.0% by mass, the hardenability is improved and the hardness is increased, and as a result, there is a high possibility of causing cold cracking during welding. For the above reasons, the amount of Mn is preferably 0.7 to 1.0% by mass.

  According to the present invention, it is possible to ensure sufficient mechanical strength that does not cause deformation or the like when tightened to an automobile diesel engine or the like, and surface cracks in the welded part during welding with the heater holding outer cylinder. It is possible to provide a glow plug housing and a glow plug that can be prevented from occurring.

1 is a longitudinal sectional view showing an overall schematic configuration of a ceramic glow plug according to an embodiment of the present invention. The graph which shows the result of having investigated the relationship of the presence or absence of surface crack generation | occurrence | production of S amount and C amount, and the welded part.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing an overall schematic configuration of a ceramic glow plug 100 according to an embodiment of the present invention. Note that the vertical direction in the drawing is the axis AX direction, the lower part is the front end, and the upper part is the rear end.

  As shown in FIG. 1, the ceramic glow plug 100 is configured by combining a housing 10, a middle shaft 20, a ceramic heater 30, a metal ring 40, a pin terminal 50, and a heater holding outer cylinder 60.

The housing 10 is made of carbon steel and has a cylindrical shape having an inner hole 101 through which the inside of the housing 10 passes along an axis AX. The outer peripheral surface is fixed to a diesel engine (not shown). The thread portion 102 is formed by rolling or cutting. The carbon steel constituting the housing 10 has a Si content of 0.40 mass% or less, a Mn content of 0.40 to 1.0 mass%, and a P content of 0.040 mass% or less. , The C content is 0.37 to 0.44 mass%, and the relationship between the C content and the S content is
When 0.42% by mass <C ≦ 0.44% by mass,
S ≦ (−0.75C (mass%) + 0.33) (mass%)
And
In the case of 0.37 mass% ≦ C ≦ 0.42 mass%,
S ≦ (−0.1C (mass%) + 0.057) (mass%)
The balance consists of Fe and inevitable impurities.

  The rear end portion 103 of the housing 10 is formed with a tool engaging portion 104 for engaging a tool such as a hexagon wrench or a plug wrench when the housing 10 is attached to the diesel engine. In addition, a tapered portion 105 that expands the inner hole 101 toward the rear end side and a large-diameter hole 106 that is further adjacent to the rear end side of the tapered portion 105 are formed on the inner peripheral side of the rear end portion 103. ing.

  The heater holding outer cylinder 60 is made of a metal having high heat resistance and high corrosion resistance (in this embodiment, SUS430. The heater holding outer cylinder 60 has a bowl-shaped portion (large cylindrical portion 601). The inner hole 602 has a substantially cylindrical shape formed on its inner periphery, and the ceramic heater 30 is held by being press-fitted into the inner hole 602.

  The heater holding outer cylinder 60 has a relatively thin small cylindrical portion 603 on the front end side, a taper 604 that expands toward the rear end adjacent to the rear end side of the small cylindrical portion 603, and a small cylinder following the taper 604. A large cylindrical portion 601 having a larger diameter than the portion 603 and substantially the same outer diameter as the front end portion of the housing 10, and an engagement cylindrical portion 605 having a smaller diameter than the large cylindrical portion 601 on the rear end side of the large cylindrical portion 601. Is provided. When the glow plug 100 is attached to a diesel engine (not shown), the taper 604 plays a role as a seal for ensuring airtightness with the combustion chamber. The thickness of each part of the heater holding outer cylinder 60 is about several millimeters.

  The middle shaft 20 is made of a conductive metal and has a rod shape. The tip end portion of the middle shaft 20 is formed with a tip small-diameter portion 201 so as to be fitted to the metal ring 40, while the rear end portion 202 is formed with a smaller diameter than other portions because the pin terminal 50 is attached.

  The metal ring 40 has a cylindrical shape and is thinner than the heater holding outer cylinder 60 described above (thickness is about 1 mm or less). Therefore, the metal ring 40 is made of a metal having high tensile strength and high hardness, which is SUS630 in this embodiment. The inner diameter of the metal ring 40 is substantially the same as the outer diameter of each of the rear end portion 301 of the ceramic heater 30 and the tip small diameter portion 201 of the center shaft 20. On the other hand, the outer diameter of the metal ring 40 is set to be substantially the same as the outer diameter of the portion adjacent to the rear end side of the tip small diameter portion 201 of the middle shaft 20.

  The ceramic heater 30 is configured such that a heating element 32 made of a conductive ceramic and a pair of lead portions 33 and 33 are embedded in a ceramic base 31 formed in a rod shape from an insulating ceramic (silicon nitride, alumina, etc.). ing. The heating element 32 positioned inside the ceramic heater 30 is formed in a U shape with conductive ceramic. Further, the two lead portions 33 extending rearward from the respective base ends of the heating element 32 are similarly formed from a conductive ceramic.

  One of the lead portions 33 (the right lead portion 33 in FIG. 1) has a second electrode that extends in the radial direction perpendicular to the axis AX at the rear end portion 301 of the heater 30 and is exposed on the surface of the ceramic substrate 31. A portion 34 is provided. The second electrode extraction portion 34 is electrically connected to the metal ring 40. The other lead portion 33 (the left lead portion 33 in FIG. 1) extends in the radial direction perpendicular to the axis AX and is exposed on the surface of the ceramic base 31 on the tip side from the second electrode lead-out portion 34 described above. A first electrode take-out portion 35 is provided. The first electrode extraction portion 35 is electrically connected to the heater holding outer cylinder 60.

  In the ceramic glow plug 100 having the above configuration, the tip portion of the ceramic heater 30 protrudes from the tip portion of the heater holding outer cylinder 60. Then, the ceramic glow plug 100 is inserted into a plug mounting hole of a diesel engine (not shown), and the screw portion 102 is fastened to the mounting screw of the diesel engine to bring the taper 604 into contact with the diesel engine, thereby ensuring airtightness. In this state, the heater 30 is attached to the internal combustion engine so that the front end side is located in the combustion chamber, and the diesel engine is started by energizing the heater 30 through the pin terminal 50, the middle shaft 20, and the metal ring 40 to generate heat. Assist.

  In the manufacturing process of the ceramic glow plug 100 having the above configuration, first, the ceramic heater 30 is inserted (press-fitted) into the metal ring 40 to be integrated. The ceramic heater 30 integrated with the metal ring 40 is further inserted (press-fitted) into the heater holding outer cylinder 60, and the center shaft 20 is press-fitted into the metal ring 40 and laser welding is performed to produce a heater / middle shaft integral.

  Thereafter, the housing 10 is put on the assembly of the ceramic heater 30, the metal ring 40, the heater holding outer cylinder 60, and the center shaft 20, and the heater holding outer cylinder 60 and the welded portion 12 (see FIG. 1) are welded all around by laser. Then, the housing 10 and the heater holding outer cylinder 60 are fixed. Thereafter, the ceramic ring plug 100 is completed by inserting the O-ring 111 and the insulating bush 112 and caulking and fixing the pin terminal 50 to the rear end portion 202 of the middle shaft 20 protruding from the rear end portion 103 of the housing 10.

  At the time of laser welding between the housing 10 and the heater holding outer cylinder 60, for example, in the case where the housing 10 is configured from the above-described carbon steel STKM16C or S40C, there is a problem that surface cracks are likely to occur in the welded portion. . On the other hand, in this embodiment, it can prevent that a surface crack generate | occur | produces in a welding part.

As shown in Table 1, as Examples 1-9, Si content is 0.40 mass% or less, Mn content is 0.40-1.00 mass%, P content is 0.00. 040 mass% or less, the C content is 0.37 to 0.44 mass%, and the relationship between the C content and the S content is
When 0.42% by mass <C ≦ 0.44% by mass,
S ≦ (−0.75C (mass%) + 0.33) (mass%)
And
In the case of 0.37 mass% ≦ C ≦ 0.42 mass%,
S ≦ (−0.1C (mass%) + 0.057) (mass%)
The housing 10 that falls within the above range was prepared, and laser welding with the heater holding outer cylinder 60 was actually performed. The peak power of the laser during this laser welding is 1.5 to 2.0 W, the number of shots per second is 15 to 20, and the pulse waveform is increased to the peak power over several milliseconds. The shot waveform was maintained for 1 millisecond and decreased in power over several milliseconds. As a result, as indicated by a circle in the result column of Table 1, no surface cracks occurred in the weld. In addition, about said Examples 1-9 and Comparative Examples 1-9 mentioned later, the steel materials which comprise these use the cold drawn steel which cold-drawn the hot-rolled bar | burr. Cold-drawn steel can be subjected to heat treatment such as annealing, stress-relief annealing, induction hardening, and re-coalting after drawing, but steel that has not been subjected to heat treatment is used for evaluation.

  On the other hand, as Comparative Examples 1-9, the housing 10 in which the C content and the S content are outside the above ranges is prepared, and laser welding with the heater holding outer cylinder 60 is actually performed in the same manner as in Examples 1-9. Went to. As a result, as indicated by a cross in the result column of Table 1, surface cracks occurred in the weld. FIG. 2 is a graph in which the above results are plotted on a graph. In the graph of FIG. 2, the vertical axis indicates the amount of S (mass% × 1000), the horizontal axis indicates the amount of C (mass% × 100), the example is a white circle, and the comparative example is a black circle. Plotted. The straight line A represents S (mass%) ≦ −0.75C (mass%) + 0.33, and the straight line B represents S (mass%) ≦ −0.1 C (mass%) + 0.057. Yes.

  In the above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the above-described embodiment and the like, and it is needless to say that the present invention can be appropriately modified and applied without departing from the gist thereof.

  DESCRIPTION OF SYMBOLS 10 ... Housing, 20 ... Middle shaft, 30 ... Ceramic heater, 40 ... Metal ring, 50 ... Pin terminal, 60 ... Heater holding outer cylinder, 100 ... Ceramic glow plug

Claims (6)

A heater in the form of a rod along the axis;
A heater holding outer cylinder made of ferritic stainless steel fitted to the outer periphery of the heater;
A cylindrical housing extending along the axis, wherein the heater holding outer cylinder is fixed to the front end side by welding, and the front end side of the heater protrudes from its front end side, A glow plug housing used as the housing for a glow plug comprising: a housing that holds a rear end side of the heater inside via the heater holding outer cylinder;
The Si content is 0.40% by mass or less, the Mn content is 0.40 to 1.00% by mass, the P content is 0.040% by mass or less, and the C content is 0.37 to 0.00%. 44% by mass, and the relationship between the C content and the S content is
When 0.42% by mass <C ≦ 0.44% by mass,
S ≦ (−0.75C (mass%) + 0.33) (mass%)
And
In the case of 0.37 mass% ≦ C ≦ 0.42 mass%,
S ≦ (−0.1C (mass%) + 0.057) (mass%)
And
A glow plug housing, wherein the balance is made of Fe and inevitable impurities. The glow plug housing according to claim 1,
A glow plug housing, wherein the P content in the housing is 0.020 mass% or less. A glow plug housing according to claim 1 or 2,
A glow plug housing, wherein the Mn content of the housing is 0.70 to 1.00% by mass. A heater in the form of a rod along the axis;
A heater holding outer cylinder made of ferritic stainless steel fitted to the outer periphery of the heater;
A cylindrical housing extending along the axis, wherein the heater holding outer cylinder is fixed to the front end side by welding, and the front end side of the heater protrudes from its front end side, A glow plug having a housing for holding a rear end side of the heater inside via the heater holding outer cylinder,
The housing has a Si content of 0.40 mass% or less, a Mn content of 0.40 to 1.00 mass%, a P content of 0.040 mass% or less, and a C content of 0.00. 37 to 0.44 mass%, and the relationship between the C content and the S content is
When 0.42% by mass <C ≦ 0.44% by mass,
S ≦ (−0.75C (mass%) + 0.33) (mass%)
And
In the case of 0.37 mass% ≦ C ≦ 0.42 mass%,
S ≦ (−0.1C (mass%) + 0.057) (mass%)
And
A glow plug, wherein the balance is made of Fe and inevitable impurities. The glow plug according to claim 4,
A glow plug, wherein the content of P in the housing is 0.020% by mass or less. A glow plug according to claim 4 or 5, wherein
A glow plug, wherein the Mn content of the housing is 0.70 to 1.00% by mass.

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