JP4200045B2 - Glow plug - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a glow plug used for preheating a cylinder in a diesel engine and a heating plug for preheating water.
[0002]
[Prior art]
Conventionally, a glow plug 100 as shown in FIG. 4 is known as a glow plug used for preheating a diesel engine. The glow plug 100 includes a sheathed tube 103 having a cylindrical shape with a distal end closed, a current-carrying terminal shaft 104 for disposing the distal end side of the sheath tube 103 inside the sheath tube 103, and a rear end side of the sheath tube 103 itself. Is provided with a metal shell 102 to be inserted into the interior. (See Patent Document 1)
[0003]
[Patent Document 1]
JP 2003-74848 A (FIGS. 13 and 14)
[0004]
Inside the sheath tube 103, there is disposed a resistance coil 105 that electrically connects the tip of the sheath tube 103 to the tip of the sheath tube 103 and electrically connects the rear end to the energizing terminal shaft 104. (Refer to FIG. 5) The resistance wire coil 105 has a positive resistance temperature coefficient so as to generate heat when a current flows through it, and has an electric resistance at 1000 ° C. with respect to an electric resistance R20 at 20 ° C. The resistor R1000 is made of a material having a ratio R1000 / R20 of 3 or less.
[0005]
Such a glow plug 100 is attached to, for example, a cylinder head (not shown) of a diesel engine so that the distal end side of the sheath tube 103 protrudes into the combustion chamber, and a voltage is supplied to the energizing terminal shaft 104 using a battery (not shown) as a power source. Is applied, current flows from the energizing terminal shaft 104 to the cylinder head through the resistance wire coil 105, the sheath tube 103, and the metal shell 102. Thereby, a large current flows through the resistance wire coil 105 to generate heat, and the sheath tube 103 is heated accordingly.
[0006]
[Problems to be solved by the invention]
However, when a voltage is applied to the glow plug 100 as described above, the heat generation near the center portion of the resistance wire coil 105 increases more than the tip portion of the resistance wire coil 105, and the temperature near the center of the sheath tube 103 is increased. It becomes higher than the tip of 103. When the glow plug 100 is attached to the engine head of a diesel engine, the vicinity of the center portion of the sheath tube 103 may not be disposed in the combustion chamber of the engine, which may prevent efficient preheating.
[0007]
Therefore, the resistance wire coil is disposed only at the distal end portion of the sheath tube by extending the distal end portion of the energizing terminal shaft toward the distal end side in the sheath tube. By doing so, the vicinity of the central portion of the resistance wire coil that generates a large amount of heat can be brought closer to the distal end side of the sheath tube, and the temperature of the distal end portion of the sheath tube can be increased. Therefore, when the glow plug is attached to the engine head or the like, the preheating efficiency can be improved.
[0008]
Note that the glow plug in which the resistance wire coil is arranged at the tip of the sheath tube is a length of the sheath tube in the longitudinal direction of the resistance wire coil by reducing the pitch of the resistance wire coil while maintaining the number of turns of the resistance coil. A glow plug that shortens the length (hereinafter also simply referred to as the coil length) can be considered. However, the glow plug does not heat the whole sheath tube by the resistance wire coil, but only the tip portion of the sheath tube surrounding the resistance wire coil. Thus, the volume of the sheathed tube heated by the resistance wire coil is reduced compared to the conventional glow plug. In contrast, the heating value of the resistance wire coil is the same as the heating value of the conventional glow plug. Therefore, in the glow plug, the resistance wire coil may be abnormally heated and the resistance wire coil may be disconnected.
[0009]
In addition, as a glow plug for placing a resistance wire coil at the tip of a sheath tube, a glow plug that shortens the coil length of the resistance wire coil by reducing the number of turns of the resistance wire coil while maintaining the pitch of the resistance wire coil. Can be considered. Also in the glow plug, the volume of the sheathed tube heated by the resistance wire coil is reduced as compared with the conventional glow plug. Further, by reducing the number of turns of the resistance wire coil, the entire length of the resistance wire coil is shortened, and the heat generation amount of the resistance wire coil is increased more than the heat generation amount of the conventional glow plug. Therefore, even in the glow plug, the resistance wire coil may be abnormally heated and the resistance wire coil may be disconnected.
[0010]
The present invention has been made in view of these problems, and it is possible to improve the efficiency of preheating by increasing the temperature of the tip portion of the sheath tube, and to suppress the disconnection of the resistance wire coil. The purpose is to provide a plug.
[0011]
[Means and Actions for Solving the Problems]
In order to achieve this object, the present invention (the invention according to claim 1) includes a sheath tube having a cylindrical shape with a closed front end side, and a distal end side of the sheath tube disposed inside the rear end side of the sheath tube. energizing terminal shaft to its own tip connected to the distal end of the sheath tube, to connect the rear end to the energization terminal shaft, it has a positive resistance temperature coefficient, and 1000 to electrical resistance R20 at 20 ° C. A resistance wire coil having a ratio R1000 / R20 of electrical resistance R1000 at 3 ° C. of 3 or less, the resistance wire coil being connected in series by welding to the rear end side of the first coil and the first coil. The wire diameter of the first coil is smaller than the wire diameter of the second coil, the R1000 / R20 of the first coil and the second coil are the same, Exothermic temperature It is higher than the heat generation temperature of the serial second coil.
[0012]
In the glow plug of the present invention, the resistance wire coil includes a first coil and a second coil connected in series to the rear end side of the first coil. That is, by providing the second coil, the entire length of the resistance wire coil becomes long, and the heat generation amount of the first coil can be reduced more than the heat generation amount of the resistance wire coil of the conventional glow plug. Thereby, even if the volume of the sheath tube heated by the first coil is reduced with respect to the conventional glow plug, it is possible to suppress the first coil from being abnormally heated and the first coil from being disconnected. it can.
[0013]
Further, the heat generation temperature of the first coil is set higher than the heat generation temperature of the second coil. The heat generated by the first coil at the tip of the sheath tube increases, so the temperature at the tip of the sheath tube increases, and the efficiency of preheating can be improved when the glow plug is attached to the engine head, etc. . The heat generation temperatures of the first coil and the second coil are the temperatures at the center of the first coil and the second coil, respectively, in the longitudinal direction of the sheath tube.
[0014]
Further, wire diameter of the first coil, you smaller than the wire diameter of the second coil. Thus, by making the wire diameter of the first coil smaller than the wire diameter of the second coil, the resistance value of the first coil becomes larger than the resistance value of the second coil, and the heat generation amount of the first coil is large. Become. As a result, the heat generation of the first coil at the tip of the sheath tube increases, and the temperature at the tip of the sheath tube increases, so that the efficiency of preheating can be improved.
[0015]
Further, first and second coils are connected in series by welding. When R1000 / R20 of the first coil is different from that of the second coil, the weldability is poor, and the welded part is alloyed, so that the welded part may become unstable with respect to temperature. However, when R1000 / R20 of the 1st coil and the 2nd coil are the same, weldability is good and it can control that a welding part becomes unstable to temperature further.
[0016]
Note that the first coil, the pitch of the second coil or equal to 0.3Mm～1.2Mm. If it is less than 0.3 mm, the pitch is short, and the first coil or the second coil may be abnormally heated and disconnected. If the pitch is 1.2 mm or more, the total length of the resistance wire coil becomes long, the glow plug becomes large, and the cost increases. Therefore, by setting the pitch as described above, the glow plug of the present invention can increase the temperature on the tip side of the sheath tube, and the resistance wire coil is abnormally heated, and the resistance wire coil is disconnected. Can be suppressed.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 of the present invention will be described below with reference to the drawings.
FIG. 1 shows a structure of a glow plug 1 as an example of the present invention, and FIG. 2 is an enlarged view of a main part on the tip side of the glow plug 1. The glow plug 1 is generally composed of a cylindrical metal shell 2 extending in the direction of the axis O, a cylindrical sheath tube 3 positioned on the distal end side of the metal shell, and an energizing terminal shaft 4 serving as an electrode.
[0018]
The sheath tube 3 is made of stainless steel such as SUS310S. The front end side of the sheath tube 3 is closed, and the rear end side is fixed and joined to a metal shell 2 described later by press fitting, brazing, or the like. In addition, inside the rear end side of the sheath tube 3, the front end side of the energizing terminal shaft 4 is arranged at an interval.
[0019]
A resistance wire coil 5 is disposed in the sheath tube 3 in the axial direction. The distal end side of the resistance wire coil 5 is secured to the distal end of the sheath tube by welding such as arc welding, and the rear end side of the resistance wire coil is secured to the distal end side of the energizing terminal shaft 4 by brazing, welding, or the like. ing. The distal end side of the sheath tube 3 and the distal end side of the energizing terminal shaft 4 are electrically connected via the resistance wire coil 5. The resistance coil 5 has a first coil 51 on the front end side and a second coil 52 on the rear end side, and is joined in series by welding such as resistance welding. Thus, the resistance wire coil 5 includes the first coil 51 and the second coil 52 connected in series to the rear end side of the first coil 52, so that the amount of heat generated by the first coil 51 can be reduced by the conventional glow. The amount of heat generated by the resistance wire coil of the plug can be reduced. On the other hand, the volume of the sheath tube 3 heated by the first coil 51 on the distal end side is reduced compared to the conventional glow plug. Therefore, in the glow plug 1, it is possible to suppress the resistance wire coil 5 from being abnormally heated and the resistance wire coil 5 from being disconnected.
[0020]
Furthermore, the heat generation temperature of the first coil is set higher than the heat generation temperature of the second coil. The heat generated by the first coil at the tip of the sheath tube increases, so the temperature at the tip of the sheath tube increases, and the efficiency of preheating can be improved when the glow plug is attached to the engine head, etc. .
[0021]
Specifically, the wire diameter of the first coil 51 is 0.225 mm, and the wire diameter of the second coil 52 is 0.3 mm. Thus, by making the wire diameter of the first coil 51 smaller than the wire diameter of the second coil 52, the resistance value of the first coil 51 becomes larger than the resistance value of the second coil 52. The calorific value increases. As a result, the heat generation of the first coil 51 on the distal end side of the sheath tube 3 increases, and the temperature on the distal end side of the sheath tube 3 increases, so that the efficiency of preheating can be improved.
[0022]
The first coil 51 and the second coil 52 both have, for example, an electrical specific resistance R20 at 20 ° C. of 80 μΩ · cm to 200 μΩ · cm, an electrical specific resistance at 1000 ° C. of R1000, and R1000 / R20 The material is 0.8 to 3 or less, specifically, Fe—Cr alloy or Ni—Cr alloy. Thus, by making R1000 / R20 of the 1st coil 51 and the 2nd coil 52 into the same material, weldability is good and also controls that a welding part becomes unstable with respect to temperature. Can do.
[0023]
The electrical resistance value required for the room temperature of the entire resistance wire coil 5 is set to a minimum value that does not cause an excessive inrush current to the control device (not shown) when a voltage is applied to the glow plug 1 at room temperature. There is a need to. This is to prevent an excessive inrush current from flowing to the control device when the voltage is applied to the glow plug 1 at room temperature, which may cause an excessive inrush current and damage the semiconductor of the control device. is there.
[0024]
An insulating powder 15 made of magnesia or the like is packed around the resistance wire coil 5 (first coil 51, second coil 52) in the sheath tube so as to seal the sheath tube 3. The sheath tube 3 is sealed by the elastic packing 16 on the rear end side (between the rear end side of the sheath tube 3 and the front end side of the energizing terminal shaft 4). 3 is sealed.
[0025]
The energizing terminal shaft 4 is made of carbon steel, and protrudes from the upper end of the metal shell 2 to the upper end side (upward in the drawing) through a metal shell 2 described later. A male screw 21 is threaded on the outer periphery of the protruding portion to form the male screw 21.
[0026]
On the other hand, when the glow plug 1 is attached to a diesel engine or the like, the metal shell 2 is formed with a tool engaging portion 22 having a hexagonal cross section for engaging a tool such as a torque wrench. A mounting screw portion 23 is formed immediately on the tip side. Further, a counterbore 24 is formed in the through hole at the upper end of the metal shell 2, and a rubber O-ring 25 and a nylon insulating bush 26 are fitted on the center shaft. Further, a pressing ring 27 for preventing the insulation bush 26 from falling off is mounted. The holding ring 27 is fixed to the energizing terminal shaft 4 by a caulking portion formed on the outer peripheral surface, and the corresponding surface of the energizing terminal shaft 4 is knurled on the outer periphery in order to increase the caulking coupling force. An applied knurled portion 28 is formed. The nut 29 is for fixing a current-carrying cable to the central shaft.
[0027]
Hereinafter, a method for manufacturing the glow plug 1 will be described. First, the coil member 5 to which the control coil 52 and the heating coil 51 are welded is joined to the energizing terminal shaft 4 on the rear end side (control coil 52 side) by, for example, resistance welding. Then, the coil member 5 is inserted into the sheath tube 3 from the heating coil 51 side, and the distal end side of the heating coil 51 is joined to the distal end of the sheath tube 3 by welding such as arc welding. And the insulating powder 15 is filled so that the inside of the sheath tube 3 may be sealed, and the elastic packing 16 is inserted into the rear end side inside the sheath tube 3.
[0028]
Then, the rear end side of the sheath tube 3 is squeezed by swaging, and the elastic packing 16 is crimped. Further, the entire sheath tube 3 is drawn from the rear end side to the front end side so as to have a predetermined size by swaging. . After that, it is inserted into the inner hole at the front end of the metal shell 2 from the rear end side of the energizing terminal shaft 4, and is fitted into the metal shell 2 by press fitting or the like at the rear end side of the sheath tube 3. Then, the glow plug 1 is completed by sealing the O-ring 25 on the rear end side of the metal shell 2 and then inserting the insulating bush 26 and the nut 29 into the central shaft 4 in order.
[0029]
【Example】
Next, an example of a preferable specification of the resistance wire coil 5 of the glow plug 1 of the present embodiment is as follows.
Material / Fe—Cr—Al alloy (composition: Al = 7.5 wt%; Cr = 26 wt%; Fe = balance) Temperature resistance ratio R1000 / R20 = 1
Coil dimensions / length L1 of the first coil 51 = 7 mm; number of turns 10; coil winding diameter 2.5 mm; coil wire diameter 0.225 mm
-Length L1 of the second coil 52 = 12 mm; number of turns 20; coil winding diameter 2.5 mm; coil wire diameter 0.25 mm
[0030]
The temperature distribution when the resistance wire coil 5 having the above specifications is energized is shown in FIG. This temperature distribution is the temperature distribution of the glow plug 1 energized with an energization time of 30 sec and an energization voltage of 11V. As is apparent from this temperature distribution, in the glow plug 1 of the present invention, the tip portion of the sheath tube protruding into the combustion chamber becomes the maximum temperature region. In order to compare the temperature distribution, a conventional glow plug 100 was produced. And temperature distribution was produced on the same conditions. As shown in FIG. In this case, it can be seen that the maximum temperature region is near the center of the resistance wire coil.
[0032]
Moreover, although the said embodiment demonstrated the glow plug 1 used for a diesel engine, it is not restricted to this, It can utilize also as a water heater which heats water.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a glow plug 1 showing the present invention.
FIG. 2 is a sectional view of the tip side of a glow plug 1 showing the present invention.
3A is a cross-sectional view of a main part of the present invention showing a temperature distribution, and FIG. 3B is a cross-sectional view of a main part of a comparative example showing the temperature distribution.
4 is a cross-sectional view of a conventional glow plug 100. FIG.
5 is a cross-sectional view of the tip side of a conventional glow plug 100. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,100 ... Glow plug, 2,102 ... Main metal fitting, 3,103 ... Seeds tube, 4,104 ... Current-carrying terminal axis | shaft, 5,105 ... Resistance wire coil, 51 ... -1st coil, 52 ... 2nd coil, 25 ... O-ring, 26 ... Insulating bush, 27 ... Holding ring, 29 ... Nut, 15 ... Insulating powder, 16 ...・ Elastic packing

Claims (2)

A sheathed tube having a cylindrical shape with the distal end closed;
An energizing terminal shaft for disposing the front end side of the sheath tube at the rear end side thereof;
Connect its tip at the distal end of the sheath tube, to connect the rear end to the energization terminal shaft, has a positive temperature coefficient of resistance, and the electrical resistance at 1000 ° C. to electrical resistance R20 at 20 ° C. R1000 A resistance wire coil having a ratio R1000 / R20 of 3 or less,
The resistance wire coil includes a first coil and a second coil connected in series to the rear end side of the first coil by welding,
The wire diameter of the first coil is smaller than the wire diameter of the second coil;
The R1000 / R20 of the first coil and the second coil are the same,
A glow plug, wherein the heat generation temperature of the first coil is higher than the heat generation temperature of the second coil. The glow plug according to claim 1, wherein a pitch between the first coil and the second coil is 0.3 mm to 1.2 mm.

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