JPH10110953A - Glow plug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrict temperature rise pre-heating operation while a rapid heat generating characteristic is being held at a glow plug. SOLUTION: A first resistor member 4 and a second resistor member 5 having a higher positive resistance temperature coefficient than that of the first resistor member 4 and electrically connected in series with the first resistor member 4 are stored in a heater tube provided with a small diameter part 31 and a large diameter part 32. In addition, the first resistor member 4 and a part with a length of 3/4 of that of the second resistor member 5 are stored in the small diameter part 31. Thus, it is possible to keep low thermal capacity of the first resistor member 4 and the second resistor member 5 and to improve a temperature increasing characteristic in the second resistor member 5, and subsequently a resistance increasing characteristic in the second resistor member 5. Accordingly, a supplied voltage for the first resistor member 4 can be restricted at an early time and it is possible to restrict a continuation in increasing in temperature after a glow plug 1 reaches a set temperature (for example, 80 deg.C). In addition, since a thermal capacity of the first resistor member 4 is also low, it is possible to attain a rapid heat generating characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glow plug for improving the startability of a diesel engine or the like.

[0002]

2. Description of the Related Art Conventionally, a glow plug 1 as shown in FIG. 8 has been proposed in JP-A-3-99122. The glow plug 1 includes a first resistor 4 serving as a heating element.
And a second resistor having a larger positive temperature coefficient of resistance than the first resistor 4.
The resistor 5 is built in the heater tube 3. As a result, a large current can be supplied to the first resistor 4 immediately after energization of the glow plug 1, causing the first resistor 4 to generate heat and increasing the temperature on the second resistor 5 side after a lapse of a predetermined time. Thereby, the resistance value of the second resistor 5 is increased, the power supplied to the first resistor 4 is reduced, and disconnection or the like of the first resistor 4 due to overheating can be prevented.

[0003] The diameter of the portion of the heater tube 3 in which the first resistor 4 is incorporated is set to the second diameter of the heater tube 3.
The diameter is smaller than the diameter of the portion where the resistor 5 is built. Thereby, the heat capacity near the first resistor 4 is reduced by the second resistor 5.
It is possible to make the first resistor 4 generate heat promptly immediately after the energization by making it smaller than the heat capacity in the vicinity. In particular,
During normal engine preheating (eg, about 5 seconds), the tip of the glow plug 1 can reach a normally required set temperature (eg, 800 ° C.).

[0004]

However, in the above-mentioned prior art, even after the tip reaches the above-mentioned temperature, the temperature further rises to a high temperature, and the maximum temperature becomes, for example, about 1050 ° C. Here, the supply voltage at the time of the preheating is about 12 V, but when the preheating is completed and the engine is started, the set voltage of the regulator for controlling the generation voltage of the charging generator to a predetermined voltage is about 14 V. Become. And
When this voltage is supplied to the glow plug 1 in the high temperature state, the resistors 4, 5 of the glow plug 1 are further increased.
Rises, causing oxidation and disconnection of the resistors 4 and 5,
The durability of the glow plug 1 may be adversely affected.

The present invention has been made in view of the above problems, and has as its object to suppress a rise in temperature after preheating while maintaining rapid heat generation.

[0006]

In order to achieve the above object, according to the present invention, the large-diameter portion (32) of the elongated substantially cup-shaped heater tube (3) is provided with the housing (3). 2) is inscribed and fixed at one end (2a) side. The heater tube (3) has a first resistor (4) and a positive temperature coefficient of resistance greater than that of the first resistor (4), and is electrically connected in series to the first resistor (4). And a second resistor (5) to be used. And the first
It is characterized in that the resistor (4) and at least a part of the second resistor (5) are built in the small diameter portion (31).

According to such a configuration, the heat capacity of the second resistor (5) can be reduced in addition to the first resistor (4), and the temperature rise of the second resistor (5), and thus the second resistor (5), can be reduced. The resistance of the resistor (5) can be increased. As a result, the power supplied to the first resistor (4) can be suppressed at an early stage, and the temperature of the first resistor (4) can be suppressed at an early stage. After the temperature reaches 800 ° C.), it is possible to suppress a further increase in temperature.

Therefore, even if a voltage of about 14 V is supplied to the glow plug (1), the glow plug (1)
Can be suppressed from abnormally high temperature, and the oxidation and disconnection of the first and second resistors (4, 5) can be suppressed, so that the possibility of adversely affecting the durability of the glow plug (1) can be suppressed. Since the first resistor (4) is also built in the small-diameter portion (31), the heat capacity of the first resistor (4) is also small as in the prior art. ) Can quickly generate heat.

Here, due to the effect of the explosion pressure or the like generated in the combustion chamber of the engine, the heater tube (3)
A force is applied such that the closed portion (3a) side of the heater tube (3) moves in the radial direction around a portion (34) inscribed in the inner peripheral portion on one end (2a) side of the housing (2). On the other hand, in the present invention, since the large-diameter portion (32) is internally fixed to the housing (2), the strength in the vicinity of the inscribed portion (34) can be secured, and the glow plug (1) can be used. The possibility that the vicinity of the inscribed portion (34) of the heater tube (3) bends or breaks can be suppressed.

According to the second aspect of the present invention, at least half of the length of the second resistor (5) is incorporated in the small diameter portion (31) of the heater tube (3). According to this, it is confirmed by an experiment described later that the temperature rise after preheating can be suppressed more effectively than in the related art. According to the third aspect of the present invention, the large diameter portion (3
The outer diameter of 2) is 4.5 mm to 6.0 mm. This is because when the outer diameter of the large diameter portion (32) is smaller than 4.5 mm, the inscribed portion (3) of the heater tube (3) is formed.
This is because the strength of 4) may not be secured.
Also, if the outer diameter of the large diameter portion (32) is larger than 6.0 mm, the entire glow plug (1) becomes large, and the mountability to the engine or the like may be deteriorated.

According to the present invention, the outer diameter of the small-diameter portion (31) is 0.6 times or more the outer diameter of the large-diameter portion (32).
0.9 times. This is because if the outer diameter of the small diameter portion (31) is smaller than 0.6 times the outer diameter of the large diameter portion (32), the small diameter portion (31) is too thin, so that the production of the small diameter portion (31) is difficult. This is because it becomes difficult. When the outer diameter of the small diameter portion (31) is larger than 0.9 times the outer diameter of the large diameter portion (32), the small diameter portion (31) is not sufficiently thin, and the first and second diameter portions (31) are not sufficiently thin.
This is because the heat capacity of the resistors (4, 5) may not be sufficiently reduced.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention. (First Embodiment) A glow plug 1 of the present invention shown in FIG.
Are mounted on a plurality of (for example, four cylinders) cylinders (not shown) of the diesel engine, respectively, to promote ignition and combustion of fuel at the time of engine start.

The glow plug 1 has a hollow cylindrical housing 2 made of an iron-based material. The housing 2 is provided with a screw portion 21 for detachably attaching the glow plug 1 to a cylinder. ing. An elongated cup-shaped heater tube 3 is internally fixed to one end 2a of the housing 2 by brazing or the like. This heater tube 3 is excellent in heat resistance and oxidation resistance.
The closing portion 3 is made of a conductive material (for example, a stainless steel material).
A small-diameter portion 31 is provided on the a side, and a large-diameter portion 32 having a diameter larger than the small-diameter portion 31 is integrally provided on the opening 3b side. The closed end 3a of the heater tube 3 is connected to one end 2a of the housing 2.
The large-diameter portion 32 of the heater tube 3 is exposed from the side.
Is inscribed and fixed to one end 2a side of the housing 2.

The small diameter portion 3 of the heater tube 3
1 and the large diameter portion 32, the small diameter portion 31 to the large diameter portion 32
And a taper portion 33 whose diameter gradually increases toward. The tapered portion 33 is formed on the large diameter portion 3 for manufacturing reasons.
2 is formed to have an inclination angle of, for example, about 15 °. Inside the heater tube 3, first and second coil-shaped resistors 4 and 5 are provided along the axial direction of the heater tube 3. The first resistor 4 is built in the heater tube 3 on the closed portion 3a side, and the second resistor 5 is
The first resistor 4 is provided closer to the opening 3 b of the heater tube 3 than the first resistor 4. Then, at least a part of the first resistor 4 and the second resistor 5 (3 of the length of the second resistor 5).
/ 4) are built in the small diameter portion 31.

One end 41 of the first resistor 4 is electrically connected to the closing portion 3 a of the heater tube 3, and the other end 42 of the first resistor 4 is electrically connected to one end 51 of the second resistor 5. Connected. The other end 52 of the second resistor 5 is electrically connected to one end 61 of the center shaft 6 fixedly inserted into the housing 2. One end 61 of the center shaft 6, the first resistor 4, and the second resistor 5 are connected to the insulating powder body 3 made of a heat-resistant insulating material (such as magnesia) in the heater tube 3.
It is buried by 0. Thereby, one end 6 of the center shaft 6
On the first side, the first resistor 4 and the second resistor 5 are insulated from the heater tube 3.

The first resistor 4 is set at room temperature (20 ° C.) and at 100 ° C.
A first conductive material (for example, iron chromium) having a resistance change rate (resistance of 1000 ° C./resistance of 20 ° C.) of 0 ° C. (temperature of the first resistor 4 of the glow plug 1 at the time of preheating) is as small as about 1, for example. The second resistor 5 is made of a second conductive material (for example, nickel, low-carbon steel, or a cobalt-iron alloy) having the above-described rate of change in resistance of about 5 to 14, for example. The resistance temperature coefficient referred to in the claims is the slope of a graph obtained by plotting temperature on the horizontal axis and resistance value on the vertical axis. Therefore, the second conductive material is a material having a larger positive temperature coefficient of resistance than the first conductive material.

At the connecting portion between the first resistor 4 and the second resistor 5, a fusion portion 45 of the first resistor 4 and the second resistor 5 is formed by plasma arc welding. The fusion portion 45 is formed by applying a plasma arc to the overlapped portion in a state where the other end 42 of the first resistor 4 and the one end 51 of the second resistor 5 are overlapped.

One end 61 of the central shaft 6 is inserted into the opening 3b of the heater tube 3, and the other end 62 of the central shaft 6 is connected to the O-ring 7 made of an insulating elastic material such as fluoro rubber and a resin. The housing 9 is insulated and fixed to the other end 2b side of the housing 2 by tightening a nut 9 via a bush 8 made of stainless steel. Hereinafter, the configuration of the power supply control circuit for the glow plug 1 will be described.

As shown in FIG. 2, a plurality (for example, four)
Glow plugs 1 are arranged in parallel, and a voltage from a battery power supply (power supply source) 20 of, for example, 12 V is applied via a relay 201. As a result, each glow plug 1 generates heat and starts preheating, thereby improving the startability when the engine is started. The glow plug 1 is a body ground, in which reference numeral 202 denotes an engine key switch, 203 denotes a control device having a timer function, 204 denotes an engine coolant temperature sensor, and 205 denotes a start timing display section. When the key switch 202 is turned on, the water temperature sensor 2
04 is input to the control device 203.

In response to the signal from the control device 203, the start timing display section 205 is turned on,
When the relay 201 is activated, the glow plug 1
Is applied with a predetermined voltage (for example, 12 V), and the glow plug 1 starts preheating. And the key switch 20
After a lapse of a predetermined time (for example, 5 seconds) from the time when the switch 2 is turned on, the start timing display section 205 is turned off by a signal from the control device 203, thereby making the driver visually recognize that the preheating is completed, and the driver turns on the engine. Start.

Here, when the temperature of the engine cooling water is lower than a desired temperature (for example, about 60 ° C.) by the water temperature sensor 204, the power supply to the glow plug 1 is further continued (after glow) to heat the engine. . Then, when the temperature of the engine cooling water becomes about the desired temperature,
The power supply to the glow plug 1 is turned off in response to a signal from the control device 203. By performing the afterglow, the combustion of the air-fuel mixture in the cylinder is promoted, and the vibration of the engine and the generation of white smoke in the exhaust gas can be suppressed. After the engine is started, a voltage (for example, 14 V) higher than the predetermined voltage is supplied to the glow plug 1 by the operation of the regulator.

According to the above configuration, since the first resistor 4 and the third resistor 5 are built in the small diameter portion 31 of the heater tube 3, the first resistor 4 and the second resistor 5 are built in the small diameter portion 31. The heat capacity of the second resistor 5 in addition to the body 4 can be reduced.
The temperature-raising property of the resistor 5 and, consequently, the resistance-raising property of the second resistor 5 can be improved. As a result, the power supplied to the first resistor 4 can be suppressed at an early stage, and the temperature of the first resistor 4 can be suppressed at an early stage, so that the tip of the glow plug 1 has reached the set temperature (for example, 800 ° C.). After that, it is possible to suppress a further increase in temperature.

Therefore, even if a voltage higher than the predetermined voltage is supplied to the glow plug 1 during after-glow, it is possible to suppress the glow plug 1 from becoming abnormally high in temperature, and the first and second resistors 4, 4. Since oxidation, disconnection, and the like of the glow plug 1 can be suppressed, the possibility of adversely affecting the durability of the glow plug 1 can be suppressed. Since the first resistor 4 is also built in the small-diameter portion 31, the heat capacity of the first resistor 4 can be reduced as in the related art, and the first resistor 4 can quickly generate heat immediately after the energization.

The following is an example of an experiment in which the glow plug 1 was evaluated for changes in overshoot temperature and rapid heat when the overlap length L1 between the second heating element 5 and the small diameter portion 31 was variously changed. Explain the objectives and results. The tapered portion 33 is not included in the small diameter portion 31. First, the first resistor 4 is made of 80 wt% Ni-20 wt.
% Cr alloy, 92 wt% Co-8 wt% of the second resistor 5
The first and second resistors 4 and 5 in an assembly state have a wire diameter of 0.35 mm, a length of the first resistor 4 of 6 mm, an outer diameter of 2.5 mm, and a coil pitch of 0 in an assembled state. .60m
m, the length L0 of the second resistor 5 is 22 mm, and the outer diameter is 2.5
mm, the coil pitch is 0.50 mm, the outer diameter of the small diameter portion 31 is 4.3 mm, and the outer diameter of the large diameter portion 32 is 5.0 mm. The dimensions and materials of the first and second resistors 4 and 5 and the dimensions and materials of the heater tube 3 are combined depending on the combination.
The saturation temperature of the glow plug 1 is set to 900 ° C.

In such a glow plug 1, by changing the length of the small-diameter portion 31, the overlap length L1 of the second resistor 5 and the small-diameter portion 31 of the heater tube 3 is changed, and the overlap ratio L1 // L0 is 0, 1/4, 1/2, 3
/ 4 and 1 were produced. Then, when a voltage of 11 V was applied to these glow plugs 1, the temperature change over time of the surface of the heater tube 3 was measured. In this measurement result, L1 / L0 is 0 (conventional product),
One half (the product of the present invention) is shown in the graph shown in FIG.

From this measurement result, the overshoot temperature T (° C.) and the time t (second) from when the voltage is applied until the tip of the glow plug 1 reaches 800 ° C. are read. 5 and a graph (shown by a white circle in the graph) shown in FIG. The overshoot temperature T
Is the difference between the maximum temperature of the glow plug 1 and the saturation temperature.

In the above experiment, the glow plug 1 in which the outer diameter of the small diameter portion 31 was 3.5 mm and the wire diameter of the first and second resistors 4 and 5 in the assembly state was 0.30 mm was also obtained. L1 / L0 is 0, 1/4, 1/2, 3 /
4 and 1 were prepared, and an experiment similar to the above experiment was performed. Based on the results, graphs shown by black circles in FIGS. 4 and 5 were obtained.

From the graph shown in FIG. 4, L1 / L
It has been found that when 0 is larger than 0, the overshoot temperature T can be reduced as compared with the case where L1 / L0 is 0. Further, when L1 / L0 is 1/2 or more, L1 / L0
It has been found that the overshoot temperature T can be greatly reduced as compared with the case where / L0 is 0 (conventional product). Therefore, L1
By making / L0 larger than 0 (that is, at least a part of the second resistor 5 is built in the small diameter portion 31),
The glow plug 1 can be prevented from being abnormally high in temperature, and oxidation and disconnection of the first and second resistors 4 and 5 can be suppressed. Therefore, the durability of the glow plug 1 can be ensured.

From the graph shown in FIG. 5, it was found that all the glow plugs 1 can reach 800 ° C. within 5 seconds, which is a normal preheating time. That is, the first resistor 4 can quickly generate heat, and the quick heat property of the glow plug 1 is ensured. (Second Embodiment) As shown in FIG. 6, a thin portion 22 is provided on one end 2a side of the housing 2 so that the inner diameter on one end 2a side of the housing 2 is larger than the inner diameter on the other end 2b side. Is provided. Thereby, a so-called pocket portion 10 is formed between the thin portion 22 and the heater tube 3, and a heat conductive material is provided between the portion of the heater tube 3 facing the pocket portion 10 and the thin portion 22. Bad air intervenes.

Therefore, it is possible to prevent the heat of the portion facing the pocket portion 10 from escaping to the housing 2 side, and the large-diameter portion 32 is more likely to store heat. As a result, the resistance of the second resistor 5 can be further increased. Therefore, the temperature of the first resistor 4 can be suppressed earlier, and the temperature can be further prevented from continuing to rise after the tip of the glow plug 1 reaches the set temperature (for example, 800 ° C.). In addition, a part 34 of the heater tube 3 that is inscribed in the inner peripheral part on the one end 2 a side of the housing 2 is a bottom part of the pocket part 10.

(Third to Fifth Embodiments) The third to fifth embodiments correspond to the first resistor 4 in the first embodiment.
This is a modification of the connection structure at the connection portion between the first resistor 5 and the second resistor 5. First, in the third embodiment, as shown in FIG. 7A, the other end 42 of the first resistor 4 and the one end 51 of the second resistor 5 are tangentially overlapped with each other. The tip of the overlapping portion is fixed by plasma arc welding.

In the fourth embodiment, as shown in FIG. 7B, the other end 42 of the first resistor 4 and the one end 51 of the second resistor 5 extend in the axial direction. ing. The other end 42 of the first resistor 4 and the second resistor 5
Is overlapped with one end 51 side, and this overlapped portion is fixed by plasma arc welding. Here, the length of the first resistor 4 and the second resistor 5 is the length from the start to the end of winding of the coil, and the portion A extending in the axial direction is the length of the first and second resistors 4 and 5. Not included in length.

In the fifth embodiment, as shown in FIG. 7C, the other end 42 of the first resistor 4 and the one end 51 of the second resistor 5 have a shape extending in the axial direction. ing. The other end 42 of the first resistor 4 and the second resistor 5
Are overlapped and fixed at a plurality of (for example, three) laser welding positions. 7 (a) to 7 (c).
Reference numeral 5 denotes a fused portion of the first resistor 4 and the second resistor 5.

(Other Embodiments) In the above embodiment, the first
Although the resistor 4 is made of a conductive material having a small positive resistance change rate, it may be made of a conductive material having a negative temperature coefficient of resistance.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view showing an entire configuration of a glow plug according to a first embodiment of the present invention, and FIG. 1B is an enlarged view of a connection portion between first and second resistors.

FIG. 2 is a diagram showing a configuration of an energizing circuit for a glow plug.

FIG. 3 is a graph showing heat generation temperature characteristics at the tip of the glow plug of the present invention and the prior art.

FIG. 4 is a graph showing a change in overshoot temperature when an overlapping ratio L1 / L0 between a small diameter portion of a heater tube and a second resistor is changed.

FIG. 5 is a graph showing the rapid thermal properties of the tip of the glow plug when the overlapping ratio L1 / L0 between the small diameter portion of the heater tube and the second resistor is changed.

FIG. 6 is a cross-sectional view illustrating an entire configuration of a glow plug according to a second embodiment of the present invention.

FIGS. 7A to 7C are enlarged views of a connection portion between first and second resistors according to third to fifth embodiments of the present invention.

FIG. 8 is a cross-sectional view showing the entire configuration of a glow plug according to the related art.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Glow plug, 2 ... Housing, 3 ... Heater tube, 3a ... Closed part, 3b ... Opening part, 31 ... Small diameter part, 32
... Large-diameter part, 4... First resistor, 5.

Claims (4)

[Claims] 1. An elongated, generally cup-shaped housing having a substantially cylindrical housing (2), a small-diameter portion (31) on the closing portion (3a) side, and a large-diameter portion (32) on the opening (3b) side. Yes,
The large diameter portion (32) is connected to one end (2) of the housing (2).
a) a heater tube (3) internally fixed to the a) side; a first resistor (4) built in the heater tube (3) on the closing portion (3a) side; A second resistor (5) built in the opening (3b) side and electrically connected in series with the first resistor (4), wherein the second resistor (5) is The first resistor (4) and the second resistor (5) are made of a material having a larger positive temperature coefficient of resistance than the material forming the one resistor (4).
Characterized in that at least a part of the glow plug is built in the small diameter portion (31) of the heater tube (3). 2. The glow plug according to claim 1, wherein at least half of the length of the second resistor is embedded in the small diameter portion. 3. An outer diameter of the large diameter portion (32) is 4.5 m.
The glow plug according to claim 1 or 2, wherein the diameter is from m to 6.0 mm. 4. An outer diameter of said small diameter portion (31) is 0.6 to 0.9 times an outer diameter of said large diameter portion (32). The glow plug according to any one of the above.