JP6996848B2 - Glow plug - Google Patents

Description

The present invention relates to a glow plug, and more particularly to a glow plug capable of increasing the heat generation temperature.

Glow plugs used as auxiliary heat sources for internal combustion engines such as diesel engines by the compression ignition method are required to have a high heat generation temperature while the regulations for internal combustion engines are becoming stricter. In Patent Document 1, in a glow plug in which a coil is arranged in a tube, a refractory metal containing W or Mo, which has a higher melting point than FeCrAl alloy or NiCr alloy, is used as a main component in order to meet the demand for high heat generation temperature. The technique used for the coil is disclosed.

International Publication No. 2014/20847

However, since the resistivity ratio of heat-resistant metals such as W and Mo is larger than that of FeCrAl alloys and NiCr alloys, in the above-mentioned conventional technique, a constant voltage is applied to the coil in order to raise the temperature to a predetermined temperature (for example, 1000 ° C.). When applied, the resistance of the coil increases sharply and the current value drops sharply. Here, the resistivity ratio is "the ratio of the resistance value at 1000 ° C. to the resistance value at 20 ° C. of the coil", and the larger the value of the resistance ratio, the larger the resistance value at high temperature. Since the calorific value is proportional to the square of the current value, there is a problem that it is difficult to raise the temperature to a predetermined temperature.

On the other hand, it is conceivable to join a rear end coil made of FeCrAl alloy or NiCr alloy having a resistance ratio smaller than the resistance ratio of the refractory metal to the rear end side of the coil made of refractory metal (tip coil). As a result, when a voltage is applied to the coil, the tip end side of the tip coil and the tube can be raised to a predetermined temperature without excessively increasing the resistance value of the entire coil.

By the way, the coil heated to a predetermined temperature needs to be saturated in the vicinity of a predetermined temperature (for example, 1100 ° C.). Therefore, it is necessary to reduce the applied voltage of the coil, but this transfers heat to the rear end side of the tube, which has a lower temperature than the tip side of the tube, and the temperature on the tip side of the tube temporarily drops significantly. It becomes easier to do. As a result, there are problems that the combustion of the engine becomes unstable and the exhaust gas emission increases.

On the other hand, by reducing the wall thickness of the entire tube, the heat capacity of the tube can be reduced, and the heat transfer from the front end side to the rear end side of the tube can be suppressed. However, if the wall thickness of the entire tube is reduced, the durability until the through hole is formed in the tube may be shortened or the tube may be deformed due to oxidative wear, and the durability may be lowered.

The present invention has been made to solve the above-mentioned problems, and can suppress a temperature drop when the applied voltage is lowered to further saturate the temperature while ensuring durability and a high temperature of heat generation. The purpose is to provide glow plugs.

In order to achieve this object, the glow plug of the present invention has a bottomed cylindrical tube extending in the axial direction, a front end coil and a rear end coil arranged in the tube, and a center pole connected to the rear end of the rear end coil. And. The tip coil is mainly composed of W and Mo while the tip of the tip coil is connected to the tip side of the tube. The rear end coil whose tip is connected to the rear end of the tip coil has a resistance ratio R1 which is the ratio of the resistance value at 1000 ° C to the resistance value at 20 ° C of the rear end coil at 20 ° C of the tip coil. It is smaller than the resistance ratio R2, which is the ratio of the resistance value at 1000 ° C. to the resistance value of. The tube is provided at the tip of the tube provided from the tip of the tube to a position surrounding the center in the axial direction of the tip coil, and after the tube provided at a position surrounding the rear end of the rear end coil to the tip of the rear end coil. The wall thickness A at the tip of the tube is 0.5 mm or more, the wall thickness B at the rear end of the tube is 0.3 mm or more, and the minimum wall thickness B1 at the rear end of the tube is provided with an end portion. Is smaller than the wall thickness A at the tip of the tube.

According to the glow plug according to claim 1, a tip coil containing W or Mo as a main component is connected to the tip end side of the tube, and the resistivity ratio R1 is smaller than the resistivity ratio R2 of the tip coil at the rear end of the tip coil. The rear end coil is connected. As a result, even if a constant voltage is applied, the tip end side of the tip coil and tube containing W or Mo as a main component can be raised to a predetermined temperature, and a high heat generation temperature can be ensured.

Further, the wall thickness A at the tip of the tube is 0.5 mm or more, and the wall thickness B at the rear end of the tube is 0.3 mm or more. This suppresses the shortening of the durability time until a through hole is formed in the tube due to oxidative wear on each of the rear end of the tube and the tip of the tube whose temperature rises compared to the rear end of the tube. Or, the deformation of the tube can be suppressed. Therefore, durability can be ensured.

Further, the minimum wall thickness B1 at the rear end of the tube is made smaller than the wall thickness A at the tip of the tube. As a result, the heat capacity per unit length of the rear end portion of the tube (the portion forming the minimum wall thickness B1) can be made smaller than the heat capacity per unit length of the tip portion of the tube. As a result, when the applied voltage is lowered, the amount of heat transferred from the tube front end to the tube rear end can be suppressed. Therefore, even when the applied voltage of the coil is lowered in order to saturate the temperature of the coil, the temperature drop on the tip end side of the tube can be suppressed.

The term "main component of W or Mo" means that the total content of W or Mo with respect to the total content of the coil material is 50 wt% or more.

Further, the "tube tip" indicates a part of the tube that becomes hotter than other parts when the coil generates heat. Specifically, "the tip of the tube surrounds the center of the tip coil in the axial direction". "Parts provided up to the position" is shown. On the other hand, the "rear end of the tube" indicates a portion where the temperature is lower than that of the tip of the tube and heat is easily transferred from the tip of the tube. "A portion provided up to a position surrounding the tip of the end coil" is shown.

Further, "thickness A at the tip of the tube" and "thickness B at the rear end of the tube" are "thickness at all parts of the tip of the tube" and "thickness at all parts of the rear end of the tube", respectively. Indicates that there is. "Minimum wall thickness B1 at the rear end of the tube" indicates "the smallest wall thickness among all the parts of the rear end of the tube (that is, the wall thickness B at the rear end of the tube)".

The wall thickness A is 0.7 mm or less, and the ratio A / B1 of the wall thickness A to the wall thickness B1 satisfies A / B1 ≧ 1.11. When the wall thickness A is 0.7 mm or less, it is possible to prevent the heat capacity per unit length of the tube tip from becoming excessive. This makes it possible to improve the ability to raise the temperature of the tube tip to a predetermined temperature in a short time (hereinafter referred to as "rapid temperature rise").

Further, the ratio A / B1 of the wall thickness A to the wall thickness B1 satisfies A / B1 ≧ 1.11. As a result, even when the applied voltage of the coil is lowered in order to saturate the temperature of the coil, the temperature drop on the tip side of the tube can be further suppressed.

The wall thickness A is 0.56 mm or more, and the ratio A / B1 satisfies A / B1 ≧ 1.24. As a result, in addition to the effect of claim 2, the life until the through hole is formed in the tube due to the oxidative wear of the tip of the tube can be extended, and the applied voltage of the coil is lowered in order to saturate the temperature of the coil. The temperature drop on the tip side of the tube can be further suppressed.

The wall thickness A is 0.58 mm or more and 0.64 mm or less, and the ratio A / B1 satisfies A / B1 ≧ 1.29. As a result, the heat capacity per unit length of the rear end of the tube can be made smaller than the heat capacity per unit length of the tip of the tube, so that the effect of suppressing the temperature drop when the applied voltage is lowered, the durability and the rapid rise can be achieved. The warmth can be further improved.

The wall thickness A is 0.62 mm or less. As a result, the rapid temperature rise property can be further improved.

According to the glow plug according to claim 2 , the wall thickness C of the tube from the tip of the tube to the position surrounding the end of the first winding from the tip of the rear end coil is 0.5 mm or more. The heat generated in the tip coil is easily transmitted not only to the part of the tube surrounding the tip coil but also to the part of the tube surrounding the first roll of the rear end coil. Therefore, by setting the wall thickness C of the tube to 0.5 mm or more, in addition to the effect of claim 1, durability at this portion can be ensured.

It is one side sectional view of the glow plug. It is sectional drawing of the glow plug which was partially enlarged. It is a schematic diagram which shows the relationship between the voltage applied to a glow plug and the heat generation temperature.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. The glow plug 10 according to the embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a one-sided cross-sectional view of the glow plug 10, and FIG. 2 is a partially enlarged cross-sectional view of the glow plug 10. In FIGS. 1 and 2, the lower side of the paper surface is referred to as the front end side of the glow plug 10, and the upper side of the paper surface is referred to as the rear end side of the glow plug 10.

As shown in FIG. 1, the glow plug 10 includes a center pole 20, a main metal fitting 30, a tube 40, and a coil 50. These members are assembled along the axis O of the glow plug 10. The glow plug 10 is an auxiliary heat source used when starting an internal combustion engine (not shown) such as a diesel engine.

The center pole 20 is a cylindrical metal conductor, and is a member for supplying electric power to the coil 50. A coil 50 is electrically connected to the tip of the center pole 20. The center pole 20 is inserted into the main metal fitting 30 with its rear end protruding from the main metal fitting 30.

In the present embodiment, the center pole 20 has a connecting portion 21 made of a male screw formed at a rear end portion thereof. The center pole 20 has an O-ring 22 made of insulating rubber, an insulator 23 which is a tubular member made of synthetic resin, a ring 24 which is a tubular member made of metal, and a metal nut 25 in order from the tip side at the rear end portion. Is assembled. The connection portion 21 is a portion to which a connector (not shown) of a cable that supplies power from a power source such as a battery is connected. The nut 25 is a member for fixing the connected connector (not shown).

The main metal fitting 30 is a substantially cylindrical member made of carbon steel or the like. In the main metal fitting 30, the shaft hole 31 penetrates along the axis O, and the threaded portion 32 is formed on the outer peripheral surface. The main metal fitting 30 has a tool engaging portion 33 formed on the rear end side of the screw portion 32. The shaft hole 31 is a through hole into which the center pole 20 is inserted. Since the inner diameter of the shaft hole 31 is larger than the outer diameter of the center pole 20, a gap is formed between the center pole 20 and the shaft hole 31. The screw portion 32 is a male screw that fits into an internal combustion engine (not shown). The tool engaging portion 33 is a portion having a shape (for example, a hexagon) in which a tool (not shown) used for fitting or disengaging the screw portion 32 into or disengaging a screw hole (not shown) of an internal combustion engine is involved. ..

The main metal fitting 30 holds the center pole 20 on the rear end side of the shaft hole 31 via the O-ring 22 and the insulator 23. By crimping the ring 24 to the center pole 20 with the ring 24 in contact with the insulator 23, the position of the insulator 23 in the axial direction is fixed. The insulator 23 insulates the rear end side of the main metal fitting 30 from the ring 24. In the main metal fitting 30, the tube 40 is fixed to the tip end side of the shaft hole 31.

The tube 40 is a metal tubular body with a closed tip 41. The tube 40 is fixed to the main metal fitting 30 by being press-fitted into the shaft hole 31. Examples of the material of the tube 40 include heat-resistant alloys such as nickel-based alloys and stainless steel.

The tip side of the center pole 20 is inserted into the tube 40. Since the inner diameter of the tube 40 is larger than the outer diameter of the center pole 20, a gap is formed between the center pole 20 and the tube 40. The sealing material 26 is a cylindrical insulating member sandwiched between the tip end side of the center pole 20 and the rear end end of the tube 40. The sealing material 26 maintains a distance between the center pole 20 and the tube 40, and seals between the center pole 20 and the tube 40. The coil 50 is housed in the tube 40 along the axis O. The insulating powder 60 is filled in the tube 40.

As shown in FIG. 2, the coil 50 is formed in a spiral shape and generates heat when energized. The coil 50 includes a tip coil 51 joined to a portion of the tube 40 on the tip 41 side, and a rear end coil 52 joined to the tip of the center pole 20.

In the tip coil 51, the tip 54 (the boundary between the tip coil 51 and the melt) is joined to the tip 41 of the tube 40 via a melting portion (not shown) by welding. The material of the tip coil 51 is made of a refractory metal containing W and Mo as main components. A simple substance of these elements or an alloy containing any of these elements as a main component can be used as the tip coil 51. The rear end of the tip coil 51 is joined to the rear end coil 52 by welding. A fused portion 53 is formed between the front end coil 51 and the rear end coil 52, which is melted by welding and the weld metal is solidified.

The rear end coil 52 is a member connected in series with the front end coil 51 via the melting portion 53. The rear end coil 52 is made of a conductive material having a resistance ratio R2 smaller than the resistance ratio R1 of the front end coil 51. Examples of the material of the rear end coil 52 include FeCrAl alloy and NiCr alloy. The rear end coil 52 is housed in the tube 40 along the axis O (see FIG. 1), and the rear end 55 is joined to the tip of the center pole 20 by welding. The center pole 20 is electrically connected to the tube 40 via the rear end coil 52 and the tip coil 51.

The insulating powder 60 is a powder having electrical insulation and thermal conductivity at high temperatures. The insulating powder 60 is filled inside the coil 50 between the coil 50 and the tube 40, between the center pole 20 and the tube 40. The insulating powder 60 has a function of transferring heat from the coil 50 to the tube 40, a function of preventing a short circuit between the coil 50 and the tube 40, and a function of making the coil 50 difficult to vibrate and preventing disconnection. Examples of the insulating powder ₆₀ include oxide powders such as MgO and _Al2O3 . In addition to oxide powders such as MgO and Al ₂ O ₃ , powders such as CaO, ZrO ₂ and SiO ₂ and Si can be added. In the present embodiment, the insulating powder 60 contains 85% by mass or more and less than 100% by mass of MgO powder with respect to the total mass of the insulating powder 60, and also contains Si powder.

The tube 40 includes a tube tip 43 and a tube rear end 46. The tube tip 43 is a position 42 that surrounds the center 56 (the midpoint of the line segment connecting the position of the tip 54 and the position of the melting portion 53) in the axis O direction (axial direction) of the tip coil 51 from the tip 41 of the tube 40. It is a part provided up to. The tube rear end portion 46 is a portion provided from a position 44 surrounding the rear end 55 of the rear end coil 52 to a position 45 surrounding the tip 57 (position of the melting portion 53) of the rear end coil 52. FIG. 2 illustrates the range of the tube tip 43 (from the tip 41 of the tube 40 to the position 42) and the range of the tube rear end 46 (from the position 44 to the position 45 of the tube 40), respectively.

In the present embodiment, the wall thickness A of the tube tip 43 is 0.5 mm or more, the wall thickness B of the tube rear end 46 is 0.3 mm or more, and the minimum of the tube rear end 46. The wall thickness B1 is smaller than the wall thickness A of the tube tip 43.

In the present embodiment, the tube tip 43 and the tube rear end 46 have the same outer diameter, and the inner diameter of the tube tip 43 is made smaller than the inner diameter of the tube rear end 46 on the rear end side. , The minimum wall thickness B1 of the tube rear end portion 46 is made smaller than the wall thickness A of the tube tip portion 43. Further, in the tube 40, the wall thickness C of the portion 48 from the tip 41 of the tube 40 to the position 47 surrounding the winding end 58 of the first winding from the tip 57 (melting portion 53) of the rear end coil 52 is 0.5 mm or more. Is set to.

Next, with reference to FIG. 3, the relationship between the voltage V applied to the glow plug 10 and the heat generation temperature T of the glow plug 10 will be described. FIG. 3 is a schematic diagram showing the relationship between the voltage V and the heat generation temperature T of the glow plug 10. In FIG. 3, the horizontal axis represents time (seconds), the solid line indicates the heat generation temperature T, and the broken line indicates the voltage V.

When a voltage V is applied between the connection portion 21 of the glow plug 10 and the main metal fitting 30, the voltage V is divided by the sum R ₁ + R ₂ of the resistance value R ₁ of the front end coil 51 and the resistance value R ₂ of the rear end coil 52. The generated current I flows through the coil 50. The calorific value of the front end coil 51 per unit time is R ₁ · I ² , and the calorific value of the rear end coil 52 per unit time is R ₂ · I ² .

The coil 50 is set so that the resistance value R ₂ of the rear end coil 52 at 20 ° C. is larger than the resistance value R ₁ of the front end coil 51 at 20 ° C. This is to secure the current I (inrush current) flowing through the coil 50 at room temperature and to generate heat of the coil 50.

Since the rear end coil 52 has a resistance ratio R2 smaller than the resistance ratio R1 of the front end coil 51, the resistance value _R1 of the front end coil 51 becomes the resistance value _R2 of the rear end coil 52 as the temperature rises due to the heat generation of the coil 50. Will be larger than. As a result, the calorific value R1 · I ² per unit time of the front end coil 51 can be made larger than the calorific value _R2 · I ² _per unit time of the rear end coil 52. Since the tip coil 51 is made of a refractory metal containing W and Mo as main components, the heat generation temperature T can be increased. Thereby, the heat generation temperature T of the tip coil 51 and the tube tip 43 can be raised to a desired temperature (for example, 1000 ° C.).

Since the tube tip 43 heated by the tip coil 51 has a wall thickness A of 0.5 mm or more, it is possible to suppress shortening of the durability time until a through hole is formed in the tube tip 43 due to oxidative wear. Since the heat generation temperature of the tube rear end 46 located on the rear end side of the tube 40 is lower than that of the tube tip 43, the wall thickness B of the tube rear end 46 should be 0.3 mm or more. Therefore, it is possible to shorten the durability time until a through hole is formed in the rear end portion 46 of the tube due to oxidative wear and to suppress deformation of the rear end portion 46 of the tube. Since the tip coil 51 formed of a refractory metal containing W and Mo as main components is easily oxidized, there is a high possibility that the tip coil 51 will be oxidized and broken when a through hole is formed in the tube 40. By suppressing the formation of through holes in the tube tip 43 and the tube rear end 46 while suppressing the deformation of the tube rear end 46, it is possible to suppress the disconnection of the tip coil 51 due to oxidation, and the durability is improved. Can be improved.

After the heat generation temperature T reaches a desired temperature (here, 1000 ° C.), the voltage V applied to the glow plug 10 is lowered in order to bring the heat generation temperature T to a stable saturation temperature (for example, 1100 ° C.). Since the calorific value of the rear end coil 52 is smaller than the calorific value of the tip coil 51, the calorific value of the tip coil 51 and the tube tip 43 moves to the rear end coil 52 and the tube rear end 46 at the transition when the voltage V is lowered. .. As a result, the heat generation temperature T, which is highly dependent on the tip coil 51, temporarily decreases by the temperature D. When the temperature D increases and the heat generation temperature T decreases significantly, the combustion of the engine becomes unstable and the exhaust gas emission increases.

In order to prevent this, the glow plug 10 makes the minimum wall thickness B1 of the tube rear end portion 46 smaller than the wall thickness A of the tube tip portion 43. As a result, the heat capacity per unit length of the tube rear end portion 46 (the portion forming the minimum wall thickness B1) can be made smaller than the heat capacity per unit length of the tube tip portion 43. As a result, when the voltage V is lowered in order to shift the heat generation temperature T of the tube 40 to the saturated state, the amount of heat transferred from the tube tip portion 43 to the tube rear end portion 46 can be suppressed. Therefore, it is possible to suppress the temperature drop (temperature D) at the time of transition when the voltage V is lowered in order to saturate the heat generation temperature T. As a result, it is possible to suppress the temperature decrease when the voltage V is lowered in order to saturate the heat generation temperature T while ensuring the durability and the high temperature of the heat generation temperature T. Therefore, the glow plug 10 can assist the combustion of the engine, stabilize the idle operation of the engine after starting, and can reduce the emission of exhaust gas.

Further, it is preferable that the wall thickness B of at least half or more of the rear end portion 46 of the tube is smaller than the wall thickness A of the tube tip 43 (see FIG. 2). As a result, it is possible to further suppress the temperature drop when the voltage V is lowered in order to saturate the heat generation temperature T.

The glow plug 10 has a wall thickness C of 0.5 mm or more in the portion 48 from the tip 41 of the tube 40 to the position 47 surrounding the end 58 of the first winding from the tip (melting portion 53) of the rear end coil 52. Therefore, even if the heat generated in the tip coil 51 is transferred to the portion 48 of the tube 40, the durability of the tube 40 in the portion 48 can be ensured.

Since the insulating powder 60 contains Si powder, the thermal conductivity of the insulating powder 60 can be deteriorated as compared with the case where all of the insulating powder 60 is MgO powder. As a result, the heat dissipation of the tip coil 51 due to the heat conduction of the insulating powder 60 can be suppressed, so that the heat generated by the tube tip 43 ensures the rapid temperature rise at the time of plunge and suppresses the temperature drop at the transition. 60 encourages.

The glow plug 10 is manufactured, for example, as follows. First, a resistance heating wire having a predetermined composition is processed into a coil shape to manufacture a front end coil 51 and a rear end coil 52, respectively. Next, the ends of the front end coil 51 and the rear end coil 52 are joined by welding to form a coil 50. Next, the rear end 55 of the rear end coil 52 of the coils 50 is joined to the tip of the center pole 20.

On the other hand, a metal steel pipe having a predetermined composition is formed to have a diameter larger than the final size of the tube 40, and the tip thereof is reduced in diameter from other portions, so that the tip is open and the tip is a constricted tube precursor. To manufacture. A coil 50 integrated with the center pole 20 is inserted inside the tube precursor, and the tip 54 of the tip coil 51 is arranged in the narrowed opening of the tube precursor. The opening of the tube precursor and the tip 54 of the tip coil 51 are melted by welding to close the tip portion of the tube precursor to form a heater precursor in which the coil 50 is housed.

Next, after filling the tube 40 of the heater precursor with the insulating powder 60, the sealing material 26 is inserted between the opening at the rear end of the tube 40 and the center pole 20 to seal the tube 40. Next, the tube 40 is swaged until the tube 40 has a predetermined outer diameter.

Next, the swaging-processed tube 40 is press-fitted and fixed in the shaft hole 31 of the main bracket 30, and the O-ring 22 and the insulator 23 are fitted between the main bracket 30 and the center pole 20 from the rear end of the center pole 20. The center pole 20 is crimped with the ring 24 to obtain the glow plug 10.

The present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

<Creating a sample>
The tip coil 51 was made using a wire having a diameter of Φ0.20 mm made of an alloy containing W as a main component. Similarly, the rear end coil 52 was made using a wire rod made of NiCr alloy and having a wire diameter of Φ0.38 mm. The rear end coil 52 was joined to the tip coil 51 by welding to create a coil 50 in which the rear end coil 52 and the tip coil 51 were connected in series. The resistance value of the coil 50 measured by the four-terminal method at 20 ° C. was 0.33Ω.

Using this coil 50, a glow plug having substantially the same structure as the glow plug 10 shown in FIG. 1 was manufactured as described above, and the glow plugs in Samples 1 to 11 shown in Table 1 were obtained. Table 1 shows the maximum and minimum values of the wall thickness A of the tube tip 43, the maximum and minimum values of the wall thickness B of the tube rear end 46 (that is, the minimum wall thickness B1), and the wall thickness B1. The range of the ratio of the wall thickness A is shown.

For the glow plugs in Samples 1 to 11, the outer diameter of the tube tip 43 is set to Φ3.2 mm, the outer diameter of the tube rear end 46 is set to Φ4.0 mm, and the tube tip 43 and the tube rear end 46 are set. By adjusting the processing rate of the swaging process to be applied, the wall thickness A of the tube tip 43 and the wall thickness B of the tube rear end 46 were set to various values. For the glow plugs in Samples 1 to 11, MgO powder containing 0.2% by mass of Si powder was used as the insulating powder 60.

各サンプルのチューブ４０の先端４１から軸線Ｏ方向に２ｍｍ離れたチューブ４０の表面の位置にＰＲ熱電対を接合し、チューブ４０の先端４１付近の温度を測定した。なお、ＰＲ熱電対の代わりに放射温度計を用いても良い。

A PR thermocouple was bonded to the surface of the tube 40 2 mm away from the tip 41 of the tube 40 of each sample in the O direction of the axis, and the temperature near the tip 41 of the tube 40 was measured. A radiation thermometer may be used instead of the PR thermocouple.

For the wall thickness A of the tube tip 43 and the wall thickness B of the tube rear end 46, the cross section of the tube 40 including the axis O of each sample subjected to the swaging process at the same processing rate as the samples 1 to 11 is microscopically viewed. Observed and measured.

The wall thickness A includes a position 42 of the tube tip 43 that surrounds the center 56 of the tip 41 and the tip coil 51 in the axial direction (axial direction), and is set at equal intervals over the entire length of the tube tip 43. The wall thickness of the points (three points other than the tip 41 and the position 42) was measured, and the maximum value and the minimum value were specified.

The wall thickness B includes a position 45 surrounding the tip 57 of the rear end coil 52 and a position 44 surrounding the rear end 55 of the rear end coil 52, and is set at 10 points (equally spaced) over the entire length of the rear end portion 46 of the tube. The wall thicknesses at 8 points other than the positions 44 and 45) were measured, and the maximum and minimum values were specified.

<Temperature drop during transition>
A DC voltage is applied between the connection portion 21 of each sample and the main metal fitting 30 for 2 seconds so that the temperature near the tip 41 of the tube 40 becomes 1000 ° C. 2 seconds after the voltage is applied. I lowered the voltage. The applied voltage at this time was a rated voltage at which the temperature near the tip 41 of the tube 40 saturates at 1100 ° C. When the applied voltage was lowered, the temperature of the tube 40 temporarily dropped and increased toward a saturation temperature of 1100 ° C. over time (see FIG. 3). The temperature difference (temperature D shown in FIG. 3) between the maximum temperature of the tube 40 and the temperature of the tube 40 at the time of transition when the applied voltage was lowered was measured.

The evaluation was "A: particularly excellent" for samples with a temperature difference of less than 30 ° C, "B: excellent" for samples with a temperature difference of 30 ° C or more and less than 50 ° C, and a temperature difference of 50 ° C or more and less than 80 ° C. The sample was "C: good", and the sample with a temperature difference of 80 ° C. or more was "D: inferior". The results are shown in the column of "Temperature drop during transition" in Table 1.

<Rapid temperature rise>
A DC voltage of 11 V was applied between the connection portion 21 of each sample and the main metal fitting 30, and the temperature near the tip 41 of the tube 40 2 seconds after the voltage was applied was measured. The evaluation was "A: particularly excellent" for samples with a temperature of 950 ° C or higher, "B: excellent" for samples with a temperature of 900 ° C or higher and lower than 950 ° C, and samples with a temperature of 850 ° C or higher and lower than 900 ° C. Samples with a temperature of less than 850 ° C. were rated as "C: good" and "D: inferior". The results are shown in the "heat rising property" column of Table 1.

<Durability>
A DC voltage is applied between the connection portion 21 of each sample and the main metal fitting 30 for 2 seconds so that the temperature near the tip 41 of the tube 40 becomes 1000 ° C. 2 seconds after the voltage is applied. The voltage was lowered to the rated voltage, and the rated voltage was applied for 180 seconds. The rated voltage is a voltage at which the temperature near the tip 41 of the tube 40 saturates at 1100 ° C. Then, the tube 40 was air-cooled for 120 seconds until the temperature near the tip 41 of the tube 40 became normal temperature. A test with this as one cycle was performed for 500 hours (about 6000 cycles), and the presence or absence of disconnection of the coil 50 and deformation of the tube 40 due to the formation of through holes in the tube 40 was evaluated.

A sample in which the coil 50 was not broken even after 500 hours from the start of the test was evaluated as "A: particularly excellent". A sample in which the coil 50 was broken after 300 hours (about 3600 cycles) from the start of the test and before 500 hours was evaluated as "B: excellent". A sample in which the coil 50 was broken after 100 hours (about 1200 cycles) from the start of the test and before 300 hours was evaluated as "C: good". A sample in which the coil 50 is broken before 100 hours have passed from the start of the test, or a sample in which the tube 40 is deformed before 10 hours (about 120 cycles) have passed from the start of the test is evaluated as "D: inferior". did. The results are shown in the "Durability" column of Table 1.

<Comprehensive evaluation>
Glow plugs that satisfy "durability", small "temperature drop during transition", and high "rapid temperature rise" are desirable. Therefore, among the evaluation of "durability", the evaluation of "temperature drop at the time of transition", and the evaluation of "rapid temperature rise", the lowest evaluation is described in the "Comprehensive" column of Table 1.

<Result>
As shown in Table 1, the sample 1 having a wall thickness A of the tube tip 43 of less than 0.5 mm and the sample 11 having a minimum wall thickness B (B1) of the tube rear end 46 of less than 0.3 mm are durable. The result was inferior in sex. In sample 1, since the wall thickness A of the tube tip 43 is less than 0.5 mm, a through hole was formed in the tube tip 43 at an early stage due to oxidative wear, and the coil 50 was disconnected. In the sample 11, since the minimum value (B1) of the wall thickness B of the tube rear end portion 46 is less than 0.3 mm, the tube rear end portion 46 was deformed at an early stage. On the other hand, the samples 2 to 10 having a wall thickness A of 0.5 mm or more and a wall thickness B of 0.3 mm or more satisfied the evaluation of durability with A to C. Therefore, it has been clarified that durability can be ensured by setting the wall thickness A of the tube tip 43 to 0.5 mm or more and the wall thickness B of the tube rear end 46 to 0.3 mm or more.

Further, the sample 1 (that is, A / B1 <1) in which the wall thickness A of the tube tip portion 43 is smaller than the minimum value (B1) of the wall thickness B of the tube rear end portion 46 is inferior in temperature decrease at the time of transition. Met. On the other hand, the samples 2 to 11 in which the minimum value (B1) of the wall thickness B of the rear end portion 46 of the tube is smaller than the maximum value and the minimum value of the wall thickness A of the tip portion 43 of the tube are evaluated for the temperature decrease at the time of transition. Satisfied A to C. Therefore, it has been clarified that the temperature drop at the time of transition can be reduced by making the minimum value (B1) of the wall thickness B smaller than the wall thickness A (maximum value).

Samples 1 to 7, 9 to 11 having a wall thickness A of the tube tip 43 having a wall thickness A of 0.7 mm or less were superior in rapid temperature rising property to Sample 8 having a wall thickness A larger than 0.7 mm. Therefore, as in Samples 2 to 7, 9, and 10, by setting the wall thickness A to 0.5 mm or more and 0.7 mm or less and the wall thickness B to 0.3 mm or more, the temperature rises rapidly while ensuring durability. It became clear that sex could be improved. The improvement in rapid temperature rise is due to the fact that the wall thickness A of the tube tip 43 becomes thinner, so that the heat capacity per unit length of the tube tip 43 becomes smaller, and the tube tip 43 rises due to the heat generated by the tip coil 51. It is presumed that it became easier to heat.

Further, the samples 2 to 7, 9 and 10 having the evaluation of the temperature decrease at the time of transition of A to C satisfied A / B1 ≧ 1.1. Therefore, it is clear that by satisfying 0.5 mm ≤ A ≤ 0.7 mm, B ≥ 0.3 mm and A / B1 ≥ 1.1, durability, temperature decrease at the time of transition, and rapid temperature rise can be ensured. became.

Among the samples 2 to 7, 9 and 10, the samples 3 to 7, 9 and 10 having the wall thickness A of the tube tip 43 of 0.56 mm or more and 0.7 mm or less and satisfying A / B1 ≧ 1.24 are , The evaluation of the temperature drop at the time of transition and the evaluation of the durability both satisfied A or B. Therefore, it was clarified that by satisfying 0.56 mm ≦ A ≦ 0.7 mm and A / B1 ≧ 1.24, the durability can be improved while further suppressing the temperature decrease at the time of transition.

Among the samples 3 to 7, 9 and 10, the samples 4 to 6, 9 and 10 having the wall thickness A of the tube tip 43 of 0.58 mm or more and 0.64 mm or less and satisfying A / B1 ≧ 1.29 are , The evaluation of the temperature decrease at the time of transition and the evaluation of the durability both satisfied A, and the evaluation of the rapid temperature rise property satisfied A or B. Therefore, by satisfying 0.58 mm ≦ A ≦ 0.64 mm and A / B1 ≧ 1.29, it is possible to improve the durability while further suppressing the temperature decrease at the time of transition, and further to improve the rapid temperature rise property. It was revealed.

Among the samples 4 to 6, 9 and 10, the samples 4, 5, 9 and 10 having the wall thickness A of the tube tip 43 of 0.58 mm or more and 0.62 mm or less and satisfying A / B1 ≧ 1.29 are , Evaluation of temperature decrease at the time of transition, evaluation of durability, and evaluation of rapid temperature rise all satisfied A. Therefore, by satisfying 0.58 mm ≦ A ≦ 0.62 mm and A / B1 ≧ 1.29, it is possible to improve the durability while suppressing the temperature decrease at the time of transition, and further improve the rapid temperature rise property. It was revealed.

Although the present invention has been described above based on the embodiments and examples, the present invention is not limited to the above embodiments and examples, and various improved modifications are made without departing from the spirit of the present invention. It is easy to infer that is possible. For example, the shape of the tube 40 is not particularly limited as long as it is tubular, and the cross section orthogonal to the axis O may be circular, elliptical, polygonal, or the like.

In the above embodiment, the tube tip 43 and the tube rear end 46 have the same outer diameter, and the inner diameter of the tube tip 43 is made smaller than the inner diameter of the tube rear end 46, so that the tube tip 43 has the same outer diameter. Although the case where the wall thickness A is made larger than the wall thickness B of the rear end portion 46 of the tube has been described, the case is not necessarily limited to this. As in the embodiment, the outer diameter of the tube tip 43 may be smaller than the outer diameter of the tube rear end 46, or the outer diameter of the tube tip 43 may be larger than the outer diameter of the tube rear end 46. Is of course possible.

10 Glow plug 20 Center pole 40 Tube 41 Tip 43 Tube tip 46 Tube rear end 51 Tip coil 52 Rear end coil O axis

Claims (2)

A bottomed cylindrical tube that extends in the axial direction,
The front end coil and the rear end coil arranged in the tube,
A glow plug comprising a center pole connected to the rear end of the rear end coil.
In the tip coil, the tip of the tip coil is connected to the tip side of the tube, and W and Mo are the main components.
In the rear end coil, the tip of the rear end coil is connected to the rear end of the front end coil, and the resistance ratio R1 is the ratio of the resistance value at 1000 ° C. to the resistance value of the rear end coil at 20 ° C. Is smaller than the resistance ratio R2, which is the ratio of the resistance value at 1000 ° C. to the resistance value at 20 ° C. of the tip coil.
The tube includes a tube tip portion provided from the tip of the tube to a position surrounding the center in the axial direction of the tip coil.
A tube rear end portion provided from the rear end of the rear end coil to a position surrounding the tip of the rear end coil is provided.
The wall thickness A at the tip of the tube is 0.58 mm or more and 0.62 mm or less , the wall thickness B at the rear end of the tube is 0.3 mm or more, and the minimum wall thickness B1 at the rear end of the tube is Is smaller than the wall thickness A at the tip of the tube.
The ratio A / B1 of the wall thickness A to the wall thickness B1 is a glow plug satisfying A / B1 ≧ 1.29 . The glow plug according to claim 1 , wherein the tube has a wall thickness C of 0.5 mm or more from the tip of the tube to a position surrounding the end of the first winding from the tip of the rear end coil.

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