JPH11294768A - Glow plug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glow plug having a structure in which it is excellent in strength irrespective of a sheath tube being a small diameter, and a required heat production characteristic is easily secured, and further it is difficult to shortcircuit a heating coil and the sheath tube. SOLUTION: A sheath heater 2 includes a sheath tube 11 with its tip end closed, a heating coil 21 disposed on a tip end side in the sheath tube, and a control coil 23 which is connected in series with a rear side of the heating coil 21 for receiving heat from the heating coil 21 to increase electric resistance and hence control power supply to the heating coil 21. An axial cross sectional diameter of a heating coil containment portion 11a of the seed tube 11 is set to be 3.0 to 4.4 mm with its thickness of 0.3 to 0.75 mm. A value of t/D1 when the axial cross sectional diameter is set to be D1 is assumed to be 0.08 to 0.2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a glow plug used for preheating diesel engines and the like.

[0002]

2. Description of the Related Art A glow plug as described above generally uses a sheathed heater in which a heating coil formed of a resistance heating wire is sealed together with an insulating powder inside a sheathed tube made of a heat-resistant metal. ing. A metal shell is attached to the sheathed heater, and is used by being attached to an engine block of a diesel engine such that a heat generating portion at a tip is located in a combustion chamber by a screw portion formed on an outer peripheral surface thereof.

[0003]

In recent years, as the performance and size of diesel engines have become higher and smaller, the size of the glow plug has been required to be smaller, and the projection of the sheath tube from the metal shell has been required. The outer diameter is, for example, 5
The diameter tends to be reduced to a dimension of less than mm. However, when the sheath tube is reduced in diameter, the strength is insufficient. For example, if the sheath tube is accidentally dropped during installation and a large impact is applied, the heater is likely to be damaged. Also,
Since the size of the heat generating coil is reduced, it may be difficult to obtain necessary heat generating performance or temperature rising characteristics. On the other hand, as the diameter of the sheath tube is reduced, the heating coil is more likely to come into contact with the inner surface of the sheath tube, and the problem of short circuit (short circuit) is liable to occur.

SUMMARY OF THE INVENTION An object of the present invention is to provide a glow plug having a structure that is excellent in strength despite the small diameter of the sheath tube, easily secures necessary heat generation performance, and is less likely to cause a short circuit between the heating coil and the sheath tube. Is to provide.

[0005]

In order to solve the above problems, a first configuration of a glow plug according to the present invention comprises a sheath tube having a closed distal end, and a sheath tube having a distal end inside the sheath tube. The outer diameter of a portion (heating coil housing portion) of the sheathed tube housing the heating coil is 3.0 to 4.4 mm, and the thickness t of the portion is 0.3. 0.75 mm and the value of t / D1 is 0.08 when the outer diameter is D1.
０．２0.2.

That is, in the configuration of the glow plug according to the present invention, the outer diameter of the heat generating coil accommodating portion of the sheath tube is set to a numerical value of 3.0 to 4.4 mm in order to meet the need for miniaturization. In the first configuration, the thickness t of the heating coil housing portion of the sheath tube is set to 0.3 to 0.7.
By setting the value of t / D1 to 0.08 to 0.2 when the outer diameter is 5 mm and also the outer diameter is D1, sufficient strength can be ensured despite the reduced diameter of the sheathed tube, and by extension Breakage and the like when receiving an impact due to the above. In addition, by setting the above numerical range, the outer diameter of the heat generating coil can be set relatively large even though the diameter of the sheath tube is reduced, and it becomes easy to secure necessary heat generating performance.

If the thickness t is less than 0.3 mm, the strength of the sheathed tube becomes insufficient. For example, if the sheath tube is accidentally dropped during installation and a large impact is applied, the heater is likely to be damaged. On the other hand, in the present invention, since the outer diameter of the sheathed tube is limited to 4.4 mm or less, if the wall thickness t exceeds 0.75 mm, the inner diameter of the sheathed tube becomes too small, and the diameter of the heating coil is sufficiently reduced. In some cases, it is not possible to secure the required heat generation performance. In this case, if the diameter of the heating coil is forcibly increased, it is needless to say that a short circuit easily occurs between the inner surface of the sheath tube and the heating coil and the control coil. The thickness t is desirably adjusted in the range of 0.45 to 0.6 mm.

Next, a second configuration of the glow plug of the present invention includes a sheath tube having a closed distal end, and a heating coil disposed at the distal end in the sheath tube. When the outer diameter of the housing part (heating coil housing part) is 3.0 to 4.4 mm and the inner diameter of the heating coil housing part is D2 and the outer diameter of the heating coil is d1, Radius difference CG =
(D2-d1) / 2 is adjusted in the range of 0.1 to 0.8 mm.

[0009] In the second configuration, the CG is set to 0.1 to
By adjusting the diameter within the range of 0.8 mm, short-circuiting between the heating coil and the sheathed tube can be suppressed even though the sheathed tube is reduced in diameter. C
When G is less than 0.1 mm, a short circuit easily occurs between the inner surface of the heating coil housing and the outer surface of the heating coil.
Heat generation performance may be degraded. On the other hand, CG is 0.8
If the diameter exceeds mm, for example, the heating coil and the control coil are sealed together with an insulating material (for example, magnesia powder) in a sheath tube, and further reduced in diameter by forging to produce a glow plug. , It is easy to meander, and a short circuit is also likely to occur.
Note that the value of CG is desirably adjusted in the range of 0.2 to 0.6 mm.

When the first configuration is combined with the second configuration, in addition to the effect of preventing the short circuit, the effect of improving the strength of the sheathed tube or easily securing the heat generation performance can be achieved. More desirable.

In any of the above first and second configurations, if the outer diameter of the heat generating coil accommodating portion of the sheath tube is less than 3.0 mm, the outer diameter of the heat generating coil becomes too small, and sufficient heat generating performance is obtained. Is not obtained, so the outer diameter is set within a range of 3.0 mm or more.

The outer diameter d1 of the heating coil is 1.5 to
It is good to be 3.0 mm. If the outer diameter d1 is less than 1.5 mm, required heat generation performance may not be obtained. On the other hand, if it exceeds 3.0 mm, the outer diameter of the heating coil accommodating portion of the sheathed tube is limited to 4.4 mm or less, so that the thickness t becomes too small, leading to a problem of insufficient strength. Also, the outer diameter d1 of the heating coil
And the ratio d1 / D2 of the inner diameter D2 to the inner diameter D2 of the heating coil housing portion is 0.5.
It is preferred that the adjustment be made in the range of -0.8. When d1 / D2 exceeds 0.8, the heat generation performance may be reduced, and a short circuit may easily occur between the inner surface of the heat coil housing and the outer surface of the heat coil. On the other hand, when d1 / D2 is less than 0.5, the coil is likely to meander in the sheath tube, and similarly, a short circuit is likely to occur.

The sheath tube can be made of, for example, any of stainless steel, iron-based heat-resistant alloy, and Ni-based heat-resistant alloy. For example, when a sheathed heater is used as a glow plug, the durability of the sheathed tube which is directly exposed to a high-temperature gas flow in the engine combustion chamber can be improved by using these materials. As the stainless steel, various austenitic stainless steels having particularly good corrosion resistance can be suitably used in the present invention.

In this case, particularly when heat resistance is required, a Ni-based heat-resistant alloy, for example, a Ni-based super heat-resistant alloy such as Inconel601 (Inconel is a trade name) can be suitably used. In addition, when used in an environment with a high swirl flow rate, such as a high-speed injection type diesel engine, a composition having a particularly high Ni content among austenitic stainless steels is used to suppress oxidative consumption due to a high-temperature gas flow. (For example, SUS310S) or an austenitic heat-resistant steel having a similar composition (for example, SUH309, SUH310, SUH330, etc.) can be preferably used.

The material of the heat generating coil is the same as that of a known glow plug, for example, an iron-chromium alloy (for example, an alloy mainly containing iron and containing 13 to 30% by weight of chromium), a nickel-chromium alloy (for example, Alloys mainly containing nickel and containing 8 to 22% by weight of chromium). On the other hand, as the material of the control coil, a material having a larger temperature coefficient of electrical resistivity than the material of the heating coil is used. For example, a cobalt-iron alloy (a material mainly containing cobalt and containing about 6 to 18% by weight of iron) is used. ) Is excellent in durability and thus can be suitably used in the present invention. In addition, nickel-plated iron wires and nickel wires can also be used.

The heating coil and the control coil are electrically connected at room temperature by setting the electric resistance of the heating coil to RH and the electric resistance of the control coil to RC by selecting appropriate materials, wire diameters and coil lengths. The value of the resistance ratio (RH / RC) RT becomes 1 or more, and the electric resistance ratio (RH / R) at 800 ° C.
C) It is preferable to adjust the value of 800 to be 0.1 to 0.4. If the value of (RH / RC) RT is less than 1, the rapid heating property of the heater may not be sufficiently secured. On the other hand,
When the value of (RH / RC) 800 is less than 0.1, the power supply control by the control coil becomes excessive, and the heat generating coil may not be able to generate heat sufficiently. On the other hand, when (RH / RC) 800 exceeds 0.4, the power supply control effect of the control coil becomes insufficient, and the heating coil tends to be excessively raised.

Next, the length of the projecting portion of the sheath tube from the metal shell is preferably set to 24 to 50 mm. If the length of the protruding portion is less than 24 mm, the space for accommodating the heating coil and the control coil in the protruding portion becomes insufficient, and the coil length necessary for obtaining the desired temperature rise characteristics (or heat generation performance) can be secured. May disappear. On the other hand, when the length exceeds 50 mm, the sheath tube diameter is small, so the strength of the protruding portion is insufficient, and breakage or the like is likely to occur when an impact or the like is applied. The length of the protrusion is desirably 28 to 40 mm.

In the glow plug, a resistance wire coil (a heating coil or a heating coil and a control coil) disposed in the sheath tube is connected to the sheath tube via an energizing terminal shaft inserted from the base end side of the sheath tube. It is common to energize the battery. In this case, the tip of the energization terminal shaft can be connected to the rear end of the resistance wire coil, and the end of the energization terminal shaft can be positioned so as to protrude from the end face of the metal shell. For example, when a lateral force acts on the projecting portion of the sheath tube, a strong bending force tends to concentrate on the contact position with the inner edge of the opening of the metal shell. Therefore, by projecting the end of the current-carrying terminal shaft from the end face of the metal shell, the contact portion of the sheath tube is reinforced, and the bending strength is improved. In this case, since the concentration position of the force on the sheath tube when the bending force is applied is rather near the front end position of the conducting terminal shaft, the length from this position to the front end of the sheath tube is 24 to 50 mm, desirably. 24-42m
m.

Next, in the glow plug, when the outer diameter of the sheath tube is reduced, the assembling property to the metal shell may be deteriorated. In this case,
The inner diameter of the hole in which the sheath tube is disposed is formed to be larger than the protrusion of the sheath tube from the metal shell, and the base end of the sheath tube has dimensions corresponding to the hole inner diameter of the metal shell. The diameter can be expanded as described above, and the expanded portion can be joined to the hole of the metal shell by any of brazing, welding, and press fitting. The above-described assemblability can be improved by increasing the diameter of the base end of the sheath tube and joining it to the metal shell at this enlarged diameter portion.

In the glow plug, a plurality of resistance wire coils are arranged in the sheath tube in the axial direction, and the resistance wire coil is formed in the sheath tube at a heating coil disposed at a tip end thereof and a heating coil of the heating coil. A control coil connected to the rear side in series with the coil and receiving heat from the heat generating coil to increase the electric resistance value and control energization of the heat generating coil can be included.

For the heater temperature rise performance of the glow plug, a so-called fast heat property that reaches the saturation temperature in as short a time as possible is often required to improve the startability of the engine. One method is to increase the temperature rise rate by passing a large current through the heating coil at the beginning of energization.However, the coil temperature tends to rise excessively, leading to troubles such as coil disconnection and sheath tube erosion. There is. In the glow plug having the above structure, since the temperature of the control coil is low and the electric resistance value is small in the initial stage of energization, a relatively large current flows through the heating coil to rapidly raise the temperature. Then, when the temperature of the heating coil rises, the control coil is heated by the heat generation, the electric resistance value increases, and the value of the current supplied to the heating coil decreases. As a result, the temperature rise characteristic of the heater is such that after the temperature rises rapidly in the early stage of energization, the energizing current is suppressed by the action of the control coil and the temperature becomes saturated. Ascent can also be suppressed.

When the glow plug of the present invention is used as a glow plug of a vehicle diesel engine,
It is desirable to have a temperature rising characteristic which has a peak temperature TP at the beginning of energization and saturates below the peak temperature TP (hereinafter, this is referred to as an excessively rising prevention type temperature rising characteristic). That is, in a vehicle or the like, a battery is used as a power supply for the glow plug. In this case, the glow plug is not always energized with a constant battery voltage (for example, 12 V), but normally a superimposed voltage from an alternator or the like is applied to the glow plug, and the glow plug has a higher voltage side (for example, about 14 V at maximum) than the battery voltage. It is more likely to be energized in a fluctuating form. In this case, since the temperature rise characteristics are as described above, it is possible to effectively prevent the heater from excessively rising.

Also, the control coil can be directly connected to the rear end of the heat generating coil with a coil gap larger than the winding pitch of the heat generating coil. In this case, the size of the gap between the coils is 0.8 to 3 mm.
It is good to adjust. 3m gap between coils
If m is exceeded, the heating of the control coil by the heating coil becomes difficult to progress, and the heating coil easily rises excessively. On the other hand,
When the size of the gap between the coils becomes less than 0.8 mm,
In some cases, the resistance value of the control coil becomes too large to secure the rapid heating property, or the saturation temperature becomes too low to obtain sufficient heat generation performance. In addition,
The size of the gap between the coils is more desirably 1 to 1.
It is better to adjust to 2 mm. In the present invention, the gap between the coils is a coil between a position moved by a half turn along the heating coil from a connection point of the heating coil and the control coil and a position moved by a half turn toward the control coil similarly. Defined as the distance in the axial direction.

Next, the glow plug of the present invention has a peak temperature TP of 800 when the temperature rise characteristic is measured at room temperature with an applied voltage of 11 V in order to satisfy the requirement of quick heat property.
C. or higher, and the energization time t800 until reaching 800 ° C. on the way to the peak temperature TP is 8
It is desirably less than seconds (preferably less than 5 seconds).

In the glow plug, when the temperature rise characteristic is measured at room temperature at an energizing voltage of 11 V, the peak temperature TP and the temperature 60 seconds after the start of energization (hereinafter referred to as the temperature after 60 seconds). It is desirable that the difference TP−TS from TS be 50 to 200 ° C. TP-TS
Is less than 50 ° C., the heater tends to be overheated when the energization voltage fluctuates in a higher direction. On the other hand, TP
If -TS exceeds 200 ° C, the saturation temperature becomes too low,
Necessary heat generation performance cannot be secured. TP−TS is desirably 80 to 150 ° C.

The peak temperature TP is 900 to 1150
The temperature should be in ° C. If the peak temperature TP is less than 900 ° C., heat generation becomes insufficient, and functions such as engine preheating may not be sufficiently performed. On the other hand, when the peak temperature TP exceeds 1150 ° C., the heat generation becomes excessively large, which may cause a reduction in the life of the heat generating coil. The peak temperature TP is desirably 80 to 150 ° C.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below with reference to the embodiments shown in the drawings. FIG. 1 is an overall view showing an example of a glow plug of the present invention and a longitudinal sectional view thereof. The glow plug 1 includes a sheath heater 2 and a metal shell 3 disposed outside the sheath heater 2. Sheath heater 2
As shown in FIG. 2, two resistance wire coils, that is, a heating coil 21 disposed on the distal end side, and a control coil connected in series to the rear end by welding or the like inside a sheath tube 11 having a closed distal end side. 23 are enclosed together with magnesia powder 27 as an insulating material.

As shown in FIG.
The main body portion 11a accommodating the heating coil 21 and the control coil 23 has a front end protruding from the metal shell 3 to form a protruding portion. The main body 11a is formed in a cylindrical shape having a substantially uniform outer diameter D1 (the tip is rounded), and the diameter D1 is 3.0 to 4.4 mm (preferably 3.5 to 4.4 mm). 4.0 mm). Here, the heat generating coil 21 is electrically connected to the sheath tube 11 at its tip, but the outer peripheral surfaces of the heat coil 21 and the control coil 23 and the inner peripheral surface of the sheath tube 11 are insulated by the interposition of magnesia powder. It has become.

In FIG. 2, the heating coil 21 has, for example, an electric resistivity ρ20 at 20 ° C. of 80 to 180 μΩ · c.
m, the electrical resistivity at 800 ° C. is ρ800, and ρ800 / ρ
20 is about 0.9 to 1.2, specifically, an iron-chromium alloy wire or a nickel-chromium alloy wire. The wire diameter k of the coil is 0.15 to 0.4 m
m, coil length CL1 is 5 to 12 mm, coil outer diameter d1 is 1.5 to 3.0 mm, and winding pitch P is 0.2 to 0.8 m
m and the number of winding turns N are 8 to 15.

The control coil 23 is, for example,
Electrical resistivity ρ20 at 5 ° C is 5 to 25 μΩcm, 800 ° C
Where ρ800 / ρ20 is 7 to 12, where
It is made of a material of a certain degree, specifically, an iron-chromium alloy wire or a nickel-chromium alloy wire. The wire diameter k of the coil is 0.17 to 0.3 mm, the coil length CL2 is 10 to 32 mm, and the coil outer diameter d1 is 1.5 to 3.0 m.
m, the winding pitch P is 0.2 to 0.8 mm, and the number of winding turns N is 25 to 40.

The heating coil 21 and the control coil 23 have an electric resistance ratio (RH / RH) at room temperature, where RH is the electric resistance of the heating coil and RC is the electric resistance of the control coil.
(RC) RT is adjusted to be 1 or more, and the electric resistance ratio (RH / RC) 800 at 800 ° C. is adjusted to be 0.1 to 0.4. Between the heating coil 21 and the control coil 23, an inter-coil gap 25 larger than the winding pitch of the heating coil 21 is formed. The size JL of the gap 25 between the coils is adjusted in the range of 0.8 to 3 mm, preferably 1 to 2 mm. In addition, when this is taken in terms of the winding pitch P of the heating coil 21, a value of 0.
2 to 0.8 pitch (preferably 0.3 to 0.6 pitch)
Is adjusted within the range.

Next, the sheath tube 11 has the above-described main body 11a and an enlarged-diameter portion 11b formed on the base end side with a larger diameter. And the main body 11
The thickness t of a is 0.3 to 0.75 mm (preferably 0.4 mm).
5 to 0.6 mm) and the value of t / D1 is 0.08
To 0.2 (preferably 0.11 to 0.17 mm). When the inner diameter of the main body 11a is D2 and the outer diameters of the heating coil 21 and the control coil 23 are d1, the value of the difference CG = (D2-d1) / 2 between 0.1 and 0.1 is 0.1 to
0.8 mm (preferably 0.2 to 0.6 mm). Further, the ratio d1 / D2 of the outer diameter d1 of the coils 21 and 23 to the inner diameter D2 of the main body 11a is 0.5 to 0.8.
(Preferably 0.6 to 0.7).

A rod-shaped current-carrying terminal shaft 13 is inserted into the sheath tube 11 from the base end side, and its distal end is connected to the control coil 2.
3 is connected to the rear end by welding or the like. On the other hand, as shown in FIG.
3a are formed.

The structure of the sheathed heater 2 can be manufactured, for example, as follows. That is, as shown in FIG. 3B, a heating coil and a control coil are sealed together with magnesia powder in a sheath tube 11 'formed to have a diameter larger than the final dimension by a processing allowance. By subjecting 11 ′ to rotational forging (swaging), the main body 11a and the enlarged diameter portion 11b are formed.
And are formed.

The swaging can be performed, for example, using a swaging machine 70 shown in FIG. In the swaging machine 70, a plurality of dies 7 arranged so as to surround the sheath tube 11 'are provided.
3 are supported by respective hammers 72, which are arranged in a rotating main shaft 74 and are integrally rotated. The rotating main shaft 74 rotates inside a cage 75 having a plurality of rollers 71 made of hardened steel or the like. When the hammer 72 comes to the position of the roller 71 while rotating with the rotating main shaft 74. , The die 73 is compressed and the hammer 72 is adjacent to the rollers 71, 7.
When the distance is between 1, the die 73 is opened by centrifugal force. Therefore, if the rotation speed of the rotating main shaft 74 is increased to a certain value or more, the compression processing by the die 73 can be repeated many times.

Next, the metal shell 3 is, as shown in FIG.
The sheathed heater 2 is formed in a cylindrical shape having an axial through-hole 4, and the sheathed heater 2 is inserted and fixed in such a manner that the distal end side of the sheathed tube 11 protrudes from an opening end by a predetermined length. A hexagonal cross-section tool engaging portion 9 for engaging a tool such as a torque wrench when attaching the glow plug 1 to a diesel engine is mounted on the outer peripheral surface of the metal shell 3.
Are formed, and a screw portion 7 for mounting is
Are formed.

The through hole 4 of the metal shell 3 has a large-diameter portion 4b located on the opening side from which the sheath tube 11 protrudes, and a small-diameter portion 4a following the large-diameter portion 4a. The large-diameter portion 11b formed on the side is press-fitted and fixed. On the other hand, a counterbore 3a is formed in the opening on the opposite side of the through hole 4, and the current-carrying terminal shaft 13
An O-ring 15 made of rubber and an insulating bush (for example, made of nylon) 16 are fitted. Further, on the further rear side, the energizing terminal shaft 13 includes:
A retaining ring 17 for preventing the insulating bush 16 from falling off is mounted. The pressing ring 17 is fixed to the energizing terminal shaft 13 by a caulking portion 17a formed on the outer peripheral surface, and a knurl portion 13b for increasing a caulking coupling force is provided on a corresponding surface of the energizing terminal shaft 13. Is formed. Reference numeral 19 denotes a nut for fixing the power supply cable to the power supply terminal shaft 13.

The projecting length L2 of the sheath tube 11 from the metal shell 3 is 24 to 50 mm (preferably 28 to 40 m).
m). As shown in FIG. 2, the position of the leading end of the energizing terminal shaft 13 substantially coincides with the opening end surface of the metal shell 3.

Hereinafter, the dimensions and the like of each part of the glow plug 1 of FIG. 1 will be specifically exemplified (see also FIG. 2).・ L1 = 145mm. (Heating coil 21) Material: iron-chromium alloy (composition: Al = 7.5% by weight;
Cr = 26% by weight; Fe = remainder, ρ20 = 160 μΩ · c
m, ρ800 / ρ20 = 1.0).・ Dimensions: k = 0.22mm, CL1 = 10mm, d1 =
1.7 mm, P = 1.0 mm, N = 10. The electrical resistance RH at 20 ° C. of the entire coil is 1Ω. (Control coil 23) Material: cobalt-iron alloy (composition: Fe = 8% by weight; C
o = remainder, ρ20 = 8 μΩ · cm, ρ800 / ρ20 = 9.8, and the resistance value rises convexly with increasing temperature up to 800 ° C.). Dimensions: k = 0.2 mm, CL2 = 15 mm, d1 = 1.
7 mm, P = 0.5 mm, N = 30. The electrical resistance value RC at room temperature of the entire coil is 0.33Ω.

(RH / RC) RT: 3. -(RH / RC) 800: 0.3. (Coil gap 25) JL: 2 mm.

(Seed tube 11) Material: SUS310S.・ Dimensions: D1 = 3.5 mm, t = 0.5 mm, t / D1 =
0.14 mm, CG = 0.4 mm, outer diameter D3 =
4.4 mm, L2 = 36 mm.

(Metal fitting 3) Material: Carbon steel for machine structure (S45C). -Dimensions: The part located on the tip side from the thread part 7 (hereinafter, referred to as
The length L3 of the main part 5 is 53 mm, the outer diameter D4 of the main part is 8.2 mm, the length L4 of the screw part 7 is 27 mm, and the outer diameter D5 of the screw part 7 is 10 mm.

Hereinafter, the operation of the glow plug 1 of FIG. 1 will be described. The glow plug 1 has a screw portion 7 of the metal shell 3.
In the cylinder block of a diesel engine. Thereby, the tip of the sheath tube 11 in which the heating coil 21 and the control coil 23 are accommodated is positioned in the combustion chamber (or the auxiliary combustion chamber) of the engine. In this state, when a voltage is applied to the energizing terminal shaft 13 using a vehicle-mounted battery as a power source, the energizing terminal shaft 13 → the control coil 23 → the heat generating coil 21 → the sheath tube 11 → the metal shell 5 → (ground via the engine block). It is energized by the route.

As a result, in the sheath heater 2 of the glow plug 1, since the temperature of the control coil 23 is low and the electric resistance value is small at the beginning of energization, a relatively large current flows through the heating coil 21 and the temperature is rapidly raised. Let it. Then, when the temperature of the heating coil 21 rises, the control coil 23 is heated by the heat generation, the electric resistance value increases, and the value of the current supplied to the heating coil 21 decreases. As a result, the temperature rise characteristic of the heater is such that after the temperature rises rapidly in the initial stage of energization, the energizing current is suppressed by the operation of the control coil and the temperature is saturated thereafter.

The main body 11 of the sheath tube 11
a is a cylindrical shape having a substantially uniform outer diameter D1, and D1
Is set to a value of 4.4 mm or less.
After 50 seconds, the difference from the temperature TS is 50-200 ° C, the peak temperature TP is 900-1150 ° C, and the energizing time t800 until the temperature reaches 800 ° C is 8 seconds or less. And can be realized.

Further, the thickness t of the sheath tube 11 is 0.3 to 0.75 mm, and the value of t / D1 when the outer diameter is D1 is 0.08 to 0.2. Thus, the desired heat generation performance is ensured despite the small diameter of the heater, and the strength of the sheath tube 11 is also sufficient. For example, even if the sheath tube 11 is dropped at the time of installation, the heater is hardly damaged. In addition, since the clearance CG between the heating coil 21 and the control coil 23 in the main body 11a of the sheath tube 11 is adjusted within the range of 0.1 to 0.8 mm, the inner surface of the sheath tube 11 and each coil 21 are controlled. , 23 are unlikely to occur, and the production yield can be improved.

Here, in FIG. 2, the ratio CL1 / D1 of the coil length CL1 of the heating coil 21 to the outer diameter D1 of the main body of the sheath tube 11 is 1.6 to 3.5 (about 2.3.5 in this embodiment).
It is better to set to 5). That is, sheath tube 1
1 has a small diameter, heat dissipation from the tube surface proceeds more actively than a conventional large-diameter sheathed heater. Therefore, when CL1 / D1 is less than 1.6, the length of the tropical zone formed by the coil 21 is small. Insufficiently, sufficient heat generation performance cannot be obtained, and the heating state of the control coil becomes unstable, so that good overheating prevention type temperature rising characteristics may not be expected. On the other hand, if CL1 / D1 exceeds 4, a problem may occur that the tip of the sheath tube does not become the highest heat generating portion.

FIG. 4 shows a modification of the glow plug 1 of FIG. 1 (common members are denoted by the same reference numerals and description thereof is omitted). In this glow plug 100, the enlarged diameter portion 11 b on the base end side of the sheath tube 11 is formed longer than the glow plug 1 of FIG. 1, and is formed in the through hole 4 of the metal shell 3 on the projecting side of the sheath tube 11. Does not have the large diameter portion 4b as shown in FIG. 1, but has a straight form. The enlarged diameter portion 11b of the sheath tube 11 is joined to the through hole 4 by brazing.

A counterbore 3a similar to that of FIG. 1 is formed in the opening opposite to the through hole 4, but here a seal ring (for example, silicon) is used instead of the insulating bush 16 of FIG. Rubber) 10 and first washer-shaped insulating ring (for example, made of heat-resistant resin such as bakelite) 1
2 is fitted. Then, in this state, a cylindrical projection formed at the peripheral edge of the opening of the counterbore 3a is swaged to the first insulating ring 14 side to form a swaged portion 13b, and further, a current-carrying terminal is formed at the rear side. A second insulating ring 14 (same material and same shape as the first insulating ring 12) and a holding ring 17 are mounted and fixed to the shaft 13 in this order.

On the other hand, as shown in FIG.
Has a shape protruding a predetermined length from the corresponding open end of the metal shell 5, and the length L2 'from the tip of the current-carrying terminal shaft 13 to the tip of the sheath tube 11 is 24 to 24.
It is adjusted to 50 mm (preferably 24-42 mm).

In this glow plug 100, FIG.
The following effects not achieved by the glow plug 1 are achieved. That is, the distal end of the current-carrying terminal shaft 13 enters the protruding portion of the sheath tube 11 from the metal shell 3. Thereby, the sheath tube 11 has a shape in which the contact portion with the inner edge of the opening of the metal shell 3 on which a strong bending force is likely to act when a lateral force acts is reinforced by the current-carrying terminal shaft 13, Even if an impact or the like is applied, breakage or the like hardly occurs.

On the other hand, the glow plug 1 of FIG. 1 can be said to be superior to the glow plug 100 of FIG. 4 in the following points. First, since the rear end side of the current-carrying terminal shaft 13 is configured to be stopped by the caulking ring 17 via the insulating bush 16, the first insulating ring 12 and the seal ring 10 are stopped by the caulking portion 3b, Further, the number of components is smaller than that of the glow plug 100 of FIG. 4 reinforced by the second insulating ring 14 and the caulking ring 17, and the manufacture is easy. Further, in the glow plug 100 shown in FIG. 4, since the distance between the inner edge of the crimping portion 3b protruding inward and the outer surface of the energizing terminal shaft 13 is relatively small, the insulating ring 1 is used to prevent a short circuit due to water leakage or the like.
It is necessary to consider the airtightness between 2 and 14. On the other hand, in the glow plug 1 of FIG. 1, the distance from the inner edge of the opening of the metallic shell 3 to the outer surface of the energizing terminal shaft 13 is increased by the flange portion 16 a of the insulating bush 16. Water that is about to leak into the current-carrying terminal shaft 13 from the gap with the metal fitting 3 is cut off by the O-ring 15, so that a short circuit is less likely to occur. Further, in the glow plug 100 of FIG. 4, since the sheath tube 11 is joined to the metal shell 3 by brazing, it is necessary to design the strength in anticipation of the softening of the sheath tube 11a due to the heat effect at the time of brazing. On the other hand, in the glow plug 1 shown in FIG. 1, the sheath tube 11 is press-fitted to the metal shell 3, so there is no fear of softening due to heat, and there is an advantage that the strength improvement effect by processing can be more effectively utilized. .

The embodiment of the glow plug having the heating coil and the control coil has been described above. However, the present invention is not limited to this. For example, a glow plug having only the heating coil and omitting the control coil is also applicable to the present invention. Is similarly applicable.

[0054]

EXAMPLES (Example 1) Various types of glow plugs shown in FIG. 1 were manufactured with the dimensions and materials described above, except for the conditions specified below. That is, the outer diameter D1 of the main body 11a of the sheath tube 11 was changed in the range of 3.0 to 4.4 mm. The thickness t of the main body 11a is 0.25 to 0.25.
It was changed in the range of 0.75 mm. The heating coil 2
1 and the control coil 23 have an outer diameter d1 of 1.5 to 3.0 m only.
m. D1, t, of each glow plug
Specific numerical values of d1 are shown in Table 3 together with t / D1, D2 (inner diameter of sheath tube), CG (radius difference between coil and inner surface of sheath tube), and d1 / D2.

Each of these glow plugs was used for 50% for each condition.
Each of them was manufactured and the following tests were performed. Table 3 shows the results. Short-circuit (short-circuit) occurrence probability At room temperature, first, a pulse voltage (pulse length: 0.1 second) of 50 V is applied to the glow plug to measure the resistance value of the glow plug, and the measured value is set to R0. Then voltage 11V
For 30 seconds, and then apply the same pulse voltage to measure the resistance value of the glow plug.
Set to 1. If a short circuit occurs between the sheath tube and the heating coil or the control coil due to the heating, the length of the current-carrying coil is shortened, and the measured resistance value R1 decreases.
Then, the reduction rate of R1 with respect to R00 (R0−R1) / R
A glow plug having a measured value of 0% × 100 of 10% or more was judged as having a short circuit, and a glow plug having 50 measured glow plugs having a short circuit count of zero was passed (○). X). Strength evaluation (I) Each glow plug was dropped vertically while holding it vertically so that the sheath tube was down and the initial distance from the concrete test surface to the tip of the sheath tube was 1 cm. The falling is repeated while increasing step by step. After each drop, the sheath tube is visually checked to see if any breakage such as bending or breakage has occurred. And
Excellent if the maximum drop distance that does not cause breakage is 5 cm or more (A), Good from 3 cm to 4 cm (O), 2 cm
The following were judged as unacceptable (x). Strength evaluation (II) Hold the metal shell of each glow plug with a chuck so that the sheath tube is horizontal, set it on the bending tester, and extend the sheath tube protruding sideways along the axial direction from the tip of the sheath tube. The tip of the bending punch was brought into contact with the position of 1 mm to perform a cantilever bending test at a crosshead speed of 1 mm / min. The value of the maximum bending load was measured as the bending strength value. FIG. 8 is a graph in which the strength value when the outer diameter D1 of the main body 11a of the sheathed tube 11 is fixed to 3.5 mm and the thickness t is changed is plotted together with the probability of occurrence of a short circuit.

[0056]

[Table 1]

The following can be seen from the results shown in Table 1. (1) When the thickness t is 0.3 mm or more and t / D1 is 0.08 or more, the strength of the sheathed tube becomes sufficient, and breakage in a drop test hardly occurs. (2) When the CG is 0.1 mm to 0.8 mm, a short circuit is unlikely to occur.

Further, in order not to cause breakage in the drop test, t / D1 needs to be 0.08 or more. From the results of FIG. 8, the corresponding strength value is 5 kg or more. It turns out that we should do it. Note that t / D
When 1 exceeds 0.2, it can be seen that the short-circuit occurrence probability is rapidly increased.

(Example 2) The glow plug shown in Fig. 1 was manufactured in various sizes and materials as exemplified above, except for the conditions specified below. First, only the outer diameter D1 of the main body portion 11a of the sheath tube 11 is changed at various values of 2.5 to 5.0 mm. It was changed appropriately within a range of 2.5 mm. In addition, as the material of the control coil 23, a nickel-plated iron wire (having the same wire diameter and a plating thickness of about 1 μm) and a nickel wire (having the same wire diameter) were used instead of those made of the above-mentioned cobalt-iron alloy. Things were made.

The temperature rise characteristic curve (temperature-time curve) when these glow plugs were kept at room temperature and energized at an energizing voltage of 11 V was measured as follows. In the temperature measurement, the glow plug 1 is attached to a jig 2 as shown in FIG.
The test was carried out in the state of being attached to 00. The jig 200 is made of carbon steel having a vertically long cylindrical shape (outer diameter: 23 mm), and has a plug mounting hole 201 extending in the axial direction at the center thereof. In the glow plug 1 shown in FIG. 1, the distal end side is inserted into the plug mounting hole 201, and the screw portion 7 is screwed into the female screw portion 201 a formed on one end side of the plug mounting hole 201. Is attached to the jig 200. The dimensions of each part of the jig 200 are as described in the drawings (unit: mm). In addition, the tip of the sheath tube 11 of the glow plug 1
It protrudes by 10 mm from the end face of 00.

At the protruding portion of the sheath tube 11, a measurement section is set in the axial direction from the tip to 8 mm, the highest temperature position in the measurement section is checked in advance, and a thermocouple (Pt / Pt / Pt-Rh)
Is fixed, the sheath heater 2 is continuously energized, and the temperature change over time is measured to obtain a temperature rise characteristic curve (the above measurement method is
It conforms to the method specified in ISO 7578 (1986)). From the obtained temperature rise characteristic curve, the above-mentioned 800 ° C. arrival time (t800) and peak temperature (TP) were obtained.
After 60 seconds, the value of the temperature (TS) was calculated. Table 2 shows the above results.

[0062]

[Table 2]

That is, the outer diameter D1 of the main body 11a is 4.
The glow plug of No. 1 exceeding 4 mm has a large t800, lacks rapid heat resistance, and has a low temperature (which reflects the saturation temperature) TS after 60 seconds, and also has a TP-TS of 50 ° C.
It can be seen that good overheating prevention type temperature rising characteristics were not obtained. On the other hand, in the glow plugs (numbers 2 to 6, 8 to 10) using the sheath heater of the present invention in which the outer diameter D1 of the main body 11a is 3 to 4.4 mm, t80
It can be seen that the value of 0 is small and the rapid heat property is excellent, and the overheating prevention type temperature rising characteristic is also good. On the other hand, the outer diameter D1 of the main body 11a
Is less than 3 mm, the temperature TS is low after 60 seconds due to the small size of the heat generating coil, indicating that the performance of the glow plug is insufficient.

FIG. 6 shows a temperature rise characteristic curve of the glow plug of No. 5. FIG. 7 shows a temperature rise characteristic curve of the glow plug of Comparative Example No. 1.

Example 3 Various types of the glow plug of FIG. 1 were manufactured with the dimensions and materials described above, except that the gap length JL between the coils was changed from 0.5 to 5 mm. Then, a temperature rise characteristic curve (temperature-time curve) was measured for these glow plugs in the same manner as in Example 2, and t800,
Each value of TP and TS was calculated. Table 2 shows the above results.

[0066]

[Table 3]

That is, it can be seen that by adjusting JL in the range of 0.8 to 3 mm, a glow plug which is particularly excellent in quick heat properties and excessive temperature rise prevention type temperature rise properties is realized.

[0068]

[Brief description of the drawings]

FIG. 1 is an overall view and a longitudinal sectional view showing an example of a glow plug of the present invention.

FIG. 2 is a cross-sectional view showing an internal structure of the sheathed heater and an enlarged schematic view of a main part thereof.

FIG. 3 is an explanatory diagram showing the concept of a swaging machine and the action of swaging.

FIG. 4 is a longitudinal sectional view showing a modification of the glow plug of FIG. 1;

FIG. 5 is a sectional view showing the internal structure of the sheathed heater.

FIG. 6 is a temperature rise characteristic curve of the glow plug of No. 5 in Example 3.

FIG. 7 is a temperature rise characteristic curve of the glow plug of No. 1 of Example 3.

FIG. 8 is a graph showing the bending strength test results of Example 1 together with the probability of occurrence of short circuits.

FIG. 9 is a schematic view of a conventional glow plug.

FIG. 10 is a longitudinal sectional view of a jig used for measuring the temperature of the glow plug.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glow plug 2 Sheath heater 3 Metal shell 7 Screw part 11 Sheath tube 11a Body part 11b Enlarged diameter part 13 Current supply terminal shaft 21 Heating coil 23 Control coil

Claims (10)

[Claims] 1. A sheath tube that includes a sheath tube having a closed distal end and a heating coil disposed on the distal end side of the sheath tube, and a portion of the sheath tube that houses the heating coil (hereinafter referred to as a heating coil housing). Part) is 3.0 to 3.0
4.4 mm, and the thickness t is 0.3 to
0.75 mm and t /
A glow plug, wherein the value of D1 is 0.08 to 0.2. 2. A portion (hereinafter referred to as a heating coil housing) of a sheath tube including a sheath tube having a closed tip end and a heating coil disposed at the tip end of the sheath tube. Part) is 3.0 to 3.0
When the inner diameter of the heating coil accommodating portion is D2 and the outer diameter of the heating coil is d1, the radial difference CG = (D2-d1) / 2 is 0.1 to 0. .8m
A glow plug characterized by being adjusted in the range of m. 3. An outer diameter of the heating coil accommodating portion of the sheath tube is 3.0 to 4.4 mm, a thickness t thereof is 0.3 to 0.75 mm, and the outer diameter is D.
The glow plug according to claim 2, wherein the value of t / D1 when set to 1 is 0.08 to 0.2. 4. A plurality of resistance wire coils are arranged in the sheath tube in the axial direction in the sheath tube, and the resistance wire coils are arranged in the sheath tube.
A heating coil disposed at the tip end thereof, connected in series with the heating coil at the rear side thereof, and receiving heat from the heating coil to increase an electric resistance value and control energization of the heating coil. 4. The glow plug according to claim 1, further comprising a control coil. 5. An outer diameter d1 of said heating coil is 1.5 to 1.5.
5. The method according to claim 1, wherein the ratio d1 / D2 of the outer diameter d1 to the inner diameter D2 of the heat generating coil housing portion is adjusted to be in the range of 0.5 to 0.8. The described glow plug. 6. The sheathed tube is made of stainless steel,
The glow plug according to any one of claims 1 to 5, wherein the glow plug is formed of one of an iron-based heat-resistant alloy and a Ni-based heat-resistant alloy. 7. A metal shell is provided to cover the sheath tube in a state where a distal end side thereof is protruded, and a length of a projection of the sheath tube from the metal shell is 2
The glow plug according to any one of claims 1 to 6, which is 4 to 50 mm. 8. A metal shell is provided for covering the sheath tube with its distal end protruding, and the distal end of a current-carrying terminal shaft inserted from the base end side of the sheath tube is located behind the resistance wire coil. 2. The end of the energization terminal shaft connected to the end, the end of the energization terminal shaft protruding from the end face of the metal shell, and the length from the end of the energization terminal shaft to the end of the sheath tube is 24 to 50 mm. 8. The glow plug according to any one of items 7 to 7. 9. An inner diameter of a hole of the metallic shell in which the sheath tube is disposed is larger than a projecting portion of the sheath tube from the metallic shell, and a base end of the sheath tube. The portion is expanded so as to have a size corresponding to the inner diameter of the hole of the metal shell, and is brazed, welded, or press-fitted into the hole of the metal shell at the expanded diameter portion. The glow plug according to any one of claims 1 to 8, which is joined. 10. The temperature rising characteristic at the front end surface of the sheath tube has a peak temperature TP at the beginning of energization and is saturated below the peak temperature TP. The glow plug according to 1.