JP2015200468A - glow plug - Google Patents

Abstract

A technique for suppressing oxidation of Al in a coil provided in a glow plug is provided. A glow plug includes a sheath tube having one end closed, a coil disposed inside the sheath tube, and an oxide disposed between the sheath tube and the coil. The coil is formed of a clad material including a core material containing aluminum and a nickel layer covering the outer periphery of the core material. [Selection] Figure 1

Description

  The present invention relates to a glow plug.

  The glow plug generally includes a coil and a sheath tube. An oxide such as MgO is filled between the coil and the sheath tube. When the glow plug is used, heat generation and cooling are repeated, so that the metal component in the coil may react with oxygen in the oxide and the coil may be oxidized. Regarding such a problem, for example, in Patent Document 1, the coil is covered with platinum to prevent oxidation of iron (Fe) in the coil.

JP 2001-153359 A JP 2004-263951 A

  As a material for the coil, an alloy containing aluminum (Al) in addition to Fe may be used. In this case, Al has a higher ionization tendency and is more easily oxidized than Fe. Therefore, a technique capable of suppressing the oxidation of Al in the coil provided in the glow plug is desired.

  The present invention has been made to solve the above-described problems, and can be realized as the following forms.

(1) According to one aspect of the present invention, a glow plug is provided. The glow plug includes: a sheath tube closed at one end; a coil disposed inside the sheath tube; and an oxide disposed between the sheath tube and the coil, wherein the coil is made of aluminum. It is formed by the clad material containing the core material containing this and the nickel layer which coat | covers the outer periphery of the said core material. In the case of such a glow plug, since the core material is covered with the nickel layer, it is possible to suppress oxidation of aluminum in the core material due to oxygen in the oxide.

(2) In the glow plug of the above aspect, the nickel layer may have a thickness of 10 μm or more. If it is such a form, it can suppress effectively that durability and temperature performance of a coil fall.

(3) In the glow plug of the above aspect, the nickel layer may have a thickness of 50 μm or less. If it is such a form, it can suppress effectively that the temperature performance of a coil will fall by coat | covering a core material with a nickel layer.

(4) In the glow plug of the above aspect, the core material may further include iron and chromium.

  The present invention is not limited to the above-described form as a glow plug, and can be realized in various forms. For example, it can be realized in the form of a glow plug manufacturing method, an internal combustion engine or a vehicle equipped with a glow plug.

It is explanatory drawing which shows the glow plug as one Embodiment of this invention. It is sectional drawing which shows the detailed structure of a sheath heater. It is sectional drawing of a heat generating coil.

A. Embodiment:
FIG. 1 is an explanatory view showing a glow plug 10 as an embodiment of the present invention. The glow plug 10 includes a sheath heater (heat generating device) 800 that generates heat, and functions as a heat source that assists ignition when starting an internal combustion engine such as a diesel engine. The glow plug 10 includes a center shaft 200 and a metal shell 500 in addition to the sheath heater 800. These members constituting the glow plug 10 are assembled along the axis O of the glow plug 10. In FIG. 1, an external configuration is illustrated on the right side of the drawing from the axis O, and a cross-sectional configuration is illustrated on the left side of the drawing from the axis O. In this specification, the sheath heater 800 side of the glow plug 10 is referred to as a “front end side”, and the engagement member 100 side is referred to as a “rear end side”.

  The metal shell 500 is a member obtained by forming carbon steel into a cylindrical shape. The metal shell 500 holds the sheath heater 800 at the end on the distal end side. The metal shell 500 holds the central shaft 200 via the insulating member 410 and the O (O) ring 460 at the end on the rear end side. The position along the axis O of the insulating member 410 is fixed by crimping the ring 300 in contact with the rear end of the insulating member 410 to the middle shaft 200. Further, the metal shell 500 includes a portion of the central shaft 200 that extends from the insulating member 410 to the sheath heater 800.

  The metal shell 500 includes a shaft hole 510, a tool engaging portion 520, and a male screw portion 540. The shaft hole 510 is a through hole formed along the axis O and has a larger diameter than the middle shaft 200. In a state where the middle shaft 200 is positioned in the shaft hole 510, a gap is formed between the shaft hole 510 and the middle shaft 200 to electrically insulate them. A sheath heater 800 is press-fitted and joined to the distal end side of the shaft hole 510. The tool engaging portion 520 of the metal shell 500 is engaged with a tool used for attaching and removing the glow plug 10. The male screw portion 540 is fitted to a female screw formed in the internal combustion engine.

  The middle shaft 200 is a member formed of a conductive material into a cylindrical shape. The middle shaft 200 is assembled along the axis O while being inserted into the shaft hole 510 of the metal shell 500. The middle shaft 200 includes a front end portion 210 formed on the front end side and a male screw portion 290 provided on the rear end side. The distal end portion 210 is inserted into the sheath heater 800. The male screw portion 290 protrudes from the metal shell 500 to the rear end side. The engaging member 100 is fitted into the male screw portion 290.

  FIG. 2 is a cross-sectional view showing a detailed configuration of the sheath heater 800. The sheath heater 800 is press-fitted into and joined to the shaft hole 510 of the metal shell 500 with the distal end portion 210 of the middle shaft 200 inserted in the sheath heater 800. The sheath heater 800 includes a sheath tube 810, a heating coil 820, a control coil 830, and insulating powder 840.

  The sheath tube 810 is a cylindrical member that extends in the direction of the axis O and has one end (tip) closed. The sheath tube 810 includes a heat generating coil 820, a control coil 830, and insulating powder 840. The sheath tube 810 includes a distal end portion 811 that is formed round toward the outside, and a rear end portion 819 that is an end portion that opens to the opposite side of the distal end portion 811. The distal end portion 210 of the central shaft 200 is inserted from the rear end portion 819 into the sheath tube 810. The sheath tube 810 is electrically insulated from the central shaft 200 by the packing 600 and the insulating powder 840. On the other hand, the sheath tube 810 is in contact with and electrically connected to the metal shell 500. The sheath tube 810 is made of, for example, an austenitic stainless material containing iron, chromium, and carbon.

  The heating coil 820 is disposed along the axis O direction inside the sheath tube 810 and generates heat when energized. The heating coil 820 includes a front end portion 821 that is a coil end portion on the front end side, and a rear end portion 829 that is a coil end portion on the rear end side. The distal end portion 821 is electrically connected to the sheath tube 810 by welding to the inner wall of the distal end portion 811 of the sheath tube 810. The rear end 829 is electrically connected to the control coil 830 by being welded to the control coil 830. Details of the heating coil 820 will be described later.

  The control coil 830 is a coil formed of a conductive material (for example, nickel or cobalt-nickel alloy) having a temperature coefficient of electrical specific resistance larger than that of the material forming the heating coil 820. The control coil 830 is provided inside the sheath tube 810 and controls the power supplied to the heating coil 820. The control coil 830 includes a front end portion 831 that is a coil end portion on the front end side, and a rear end portion 839 that is a coil end portion on the rear end side. The distal end portion 831 is electrically connected to the heating coil 820 by being welded to the rear end portion 829 of the heating coil 820. The rear end portion 839 is electrically connected to the middle shaft 200 by being joined to the front end portion 210 of the middle shaft 200.

  The insulating powder 840 is a powder of an insulating material having electrical insulating properties. As the insulating powder 840, for example, magnesium oxide (MgO) powder is used. The insulating powder 840 is filled (arranged) between the sheath tube 810, the heating coil 820 and the control coil 830, and each gap between the sheath tube 810, the heating coil 820, the control coil 830 and the middle shaft 200 is electrically connected. Insulate.

  FIG. 3 is a cross-sectional view of the heating coil 820. FIG. 3 shows a cross section of the heating coil 820 in a half cross section along the axis O of the sheath heater 800. The heating coil 820 is formed of a clad material that includes a core material 822 containing aluminum and a nickel layer 823 that is bonded to the outer periphery of the core material 822 and covers the outer periphery of the core material 822.

  In this embodiment, an iron (Fe) -chromium (Cr) -aluminum (Al) alloy is used as the core material 822. For example, Fe is 60 to 80% by mass, Cr is 15 to 30% by mass, and Al is 4 to 10% by mass. In this embodiment, Fe is 65 mass%, Cr is 26 mass%, and Al is 7.5 mass%. The nickel layer 823 is formed of nickel (Ni) having a purity of 99.0% or more. The Al content of the nickel layer 823 is 0.10% by mass or less, and preferably 0% by mass. In addition to Ni, the nickel layer 823 includes, for example, carbon (C) of 0.02 mass% or less, sulfur (S) of 0.01 mass% or less, manganese (Mn) of 0.30 mass% or less, and Fe of 0. .40% by mass or less, silicon (Si) may be contained by 0.30% by mass or less, and copper (Cu) may be contained by 0.20% by mass or less.

  The clad material used as the material of the heating coil 820 is formed by inserting a core into a pipe-shaped material made of Ni to form an intermediate body, and drawing the intermediate body to a predetermined diameter (for example, 0.4 mm). It is formed by narrowing down. The heating coil 820 is formed by subjecting the clad material thus formed to coil winding.

  As described above, in the present embodiment, the heating coil 820 is formed of a clad material containing nickel. Therefore, welding with the control coil 830 containing nickel can be performed satisfactorily. In the present embodiment, since the heating coil 820 is formed of a clad material containing nickel, the proportion of the Fe component can be reduced as compared with the case where the heating coil 820 is formed of only an Fe—Cr—Al alloy. Therefore, the corrosion resistance at the welded portion between the tip 821 of the heating coil 820 and the inner wall of the sheath tube 810 can be improved.

  In the present embodiment, the glow plug 10 includes two types of coils, that is, a heating coil 820 and a control coil 830, but the glow plug 10 may include only the heating coil 820. good.

B. Glow plug rating:
Table 1 below shows the results of an evaluation test on the glow plug. In this evaluation test, seven types of glow plug 10 samples shown in Table 1 were prepared, and the temperature performance, performance degradation, and durability of each sample were evaluated. Sample 1 is a sample in which the heating coil 820 is formed only of a core material (that is, Fe—Cr—Al alloy). Samples 2 to 4 are samples in which nickel plating is formed on the outer periphery of the core material 822. Samples 5 to 7 are samples in which the nickel layer 823 is formed on the outer periphery of the core material 822 by using the clad material according to the above embodiment.

  In sample 2 and sample 5, the thickness (thickness T in FIG. 3) of the outer layer (nickel plating or nickel layer 823 formed by the clad material) formed on the outer periphery of the core material is less than 10 μm. Specifically, samples with an outer layer thickness of 5 μm were used as Sample 2 and Sample 5. In Sample 3 and Sample 6, the outer layer has a thickness of 10 μm or more and 50 μm or less. Specifically, samples 3 and 6 having outer layer thicknesses of 10 μm, 30 μm, and 50 μm were used. Samples 4 and 7 have an outer layer thickness of more than 50 μm. Specifically, Sample 4 or Sample 7 having an outer layer thickness of 80 μm was used. The diameter of the heating coil 820 of each sample is 0.4 mm, including the thickness of the outer layer.

  Table 2 shows the evaluation methods for temperature performance, performance deterioration, and durability, and the criteria for the evaluation results (“◯”, “Δ”, “×”) in Table 1.

  As shown in Table 2, the temperature performance is measured by applying a rated voltage (for example, 11 V) to the glow plug 10 and measuring the temperature of the highest heat generating part 30 seconds after the sheath heater 800 with a radiation thermometer. The temperature was evaluated by comparing Sample 1 with the temperature measured under the same conditions. In the evaluation result of the temperature performance, “◯” indicates that the temperature was lower than the sample 1 in a range within 2%. “Δ” indicates that the temperature was lower than Sample 1 in the range of more than 2% and less than 10%. “X” indicates that the temperature was 10% or more lower than that of Sample 1. As shown in Table 1, according to the evaluation result of this temperature performance, the evaluation of samples 2, 3, 5 and 6 was “◯”, and the evaluation of samples 4 and 7 was “Δ”. That is, the thickness of the outer layer (nickel plating or nickel layer 823) covering the outer periphery of the core material 822 is preferably 50 μm or less. The reason why the temperature performance decreases as the thickness of the outer layer increases is that the diameter of the core material 822 becomes smaller and the electrical resistance decreases as the thickness of the outer layer increases.

  As shown in Table 2, with respect to performance deterioration, a rated voltage was applied to the glow plug 10 for 60 seconds, and then an energization endurance test was repeated in which the air cooling cycle was repeated for 60 seconds. % Cycle number was evaluated by comparing Sample 1 with the cycle number measured under the same conditions. In the evaluation result of this performance deterioration, “◯” indicates that the number of cycles increased by 10% or more with respect to Sample 1. “Δ” indicates that the number of cycles increased by less than 10% with respect to Sample 1. “X” indicates that the number of cycles is equal to or inferior to that of Sample 1. As shown in Table 1, according to this performance degradation evaluation test, the evaluation of samples 6 and 7 was “◯”, and the evaluation of samples 4 and 5 was “Δ”. Samples 2 and 3 were evaluated as “x”. That is, as the outer layer of the heating coil 820, the nickel layer 823 formed of the clad material is preferable to the nickel plating, and the thickness of the nickel layer 823 is preferably 10 μm or more. .

  As shown in Table 2, regarding the durability, the glow plug 10 was subjected to the above-described energization durability test, and the number of cycles in which the heating coil 820 was disconnected was compared with the number of cycles in which the sample 1 was measured under the same conditions. It was evaluated by doing. In this durability evaluation result, “◯” indicates that the number of cycles increased by 10% or more with respect to Sample 1. “Δ” indicates that the number of cycles increased by less than 10% with respect to Sample 1. “X” indicates that the number of cycles is equal to or inferior to that of Sample 1. As shown in Table 1, according to this durability evaluation test, the evaluation of samples 6 and 7 was “◯”, and the evaluation of samples 4 and 5 was “Δ”. Samples 2 and 3 were evaluated as “x”. That is, also in this durability evaluation test, as in the performance deterioration evaluation test, the outer layer of the heating coil 820 is preferably a nickel layer 823 formed of a clad material rather than nickel plating. It was shown that the thickness of the layer 823 is preferably 10 μm or more.

  In the above-described performance degradation evaluation test and durability evaluation test, the nickel layer 823 formed of the clad material was evaluated better than the nickel plating, even though the plating process increased the thickness. This is probably because the formation of pinholes cannot be avoided, and Al in the core material 822 reacts with “O” in the insulating powder (MgO) 840 through the pinholes. When Al in the core material 822 reacts with “O” in the insulating powder 840 to oxidize the core material 822, the resistance value of the core material 822 at that portion decreases, and therefore the resistance value distribution on the core material 822 is reduced. Occurs. As a result, a part of the heating coil 820 may locally rise in temperature, leading to performance deterioration and durability reduction.

  According to the results of the evaluation test described above, it is preferable that the heating layer 820 of the glow plug 10 is formed with a nickel layer 823 by using a clad material rather than being plated with nickel. It was shown that the thickness of the nickel layer 823 is preferably 10 μm or more and 50 μm or less. With such a glow plug 10, when the glow plug 10 is used repeatedly, the oxidation of Al in the core member 822 constituting the heating coil 820 is suppressed, so that the change in resistance value is small. Therefore, since the change in the temperature distribution of the heating coil 820 is also reduced, it is possible to provide the glow plug 10 that is unlikely to cause an abnormality such as a locally high temperature and that has high durability (that is, is not easily disconnected). Become.

  Whether the outer layer of the heating coil 820 is formed of a clad material or plating is determined by forming a section of the heating coil 820 by CP (cross section polisher) processing as shown in FIG. It is possible to discriminate by observing the portion with a scanning electron microscope or the like. Specifically, if a uniform structure is observed in the outer layer portion, it can be determined that the outer layer is formed of a clad material. On the other hand, if a columnar structure extending in the thickness direction is observed in the outer layer portion, it can be determined that the outer layer is formed by plating. CP processing is a technique for processing a cross section of a sample using an ion beam and a shielding plate.

  The present invention is not limited to the above-described embodiment, and can be realized with various configurations without departing from the spirit of the present invention. For example, the technical features of the embodiments corresponding to the technical features in each embodiment described in the summary section of the invention are intended to solve part or all of the above-described problems, or part of the above-described effects. Or, in order to achieve the whole, it is possible to replace or combine as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 10 ... Glow plug 100 ... Engagement member 200 ... Middle shaft 210 ... Tip part 290 ... Male screw part 300 ... Ring 410 ... Insulation member 460 ... Ring 500 ... Metallic metal body 510 ... Shaft hole 520 ... Tool engagement part 540 ... Male screw part DESCRIPTION OF SYMBOLS 600 ... Packing 800 ... Sheath heater 810 ... Sheath pipe | tube 811 ... Tip part 819 ... Rear end part 820 ... Heat generating coil 821 ... Tip part 822 ... Core material 823 ... Nickel layer 829 ... Rear end part 830 ... Control coil 831 ... Tip part 839 ... Rear end 840 ... Insulating powder O ... Axis

Claims (4)

A sheath tube closed at one end;
A coil disposed inside the sheath tube;
An oxide disposed between the sheath tube and the coil;
A glow plug comprising
The glow plug is characterized in that the coil is formed of a clad material including a core material including aluminum and a nickel layer covering an outer periphery of the core material. A glow plug according to claim 1,
A glow plug, wherein the nickel layer has a thickness of 10 μm or more. A glow plug according to claim 1 or claim 2, wherein
A glow plug, wherein the nickel layer has a thickness of 50 μm or less. A glow plug according to any one of claims 1 to 3, wherein
The glow plug according to claim 1, wherein the core material further includes iron and chromium.

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