JPS60117030A - Glow plug for diesel engine - Google Patents

Abstract

PURPOSE:To improve a durability, stability and fast heating characteristic by a method wherein the second and third resistors having high positive resistance coefficient of temperature are connected in series with the first resistor acting as a heating body, and the third resistor is formed to have a delay time in respect to the second resistor to increase the temperature. CONSTITUTION:The second and third resistors 7 and 10 having a high positive resistance temperature coefficient are connected in series with the first resistor acting as a heating body. When the engine is started to show a preheating condition, a high electric power is supplied to the first resistor 6 during the energization stress under a control action of the second resistor 7, a rapid heating is made. However, after desired time elapses, the heating body is saturated at the specified temperature, its overheating is prevented and a proper heating characteristic can be attained as a glow plug 1. In case of an after-glow in which an engine is started, a temperature in the third resistor 10 is also increased, the supplying of electric power for the first and second resistors 6 and 7 is controlled as the resistance is increased. This may act as to decrease the temperature at the extremity end of the sheath 2 and an overheating at the heating part is prevented.

Description

[Detailed description of the invention] [Technical field of the invention] Misfire f! A relates to a glow plug used for preheating the auxiliary combustion chamber or combustion chamber of a diesel engine, and particularly relates to a self-temperature control type glow plug that is equipped with a power supply control function.

[Prior art]

-ff, diesel engines have poor starting performance at low temperatures, so by installing a glow plug in the auxiliary combustion chamber or combustion chamber and passing an electric current through it to generate heat, it is possible to raise the intake temperature or use it as an ignition source. A method has been adopted to improve the starting performance of the engine. Various structures have been known for this type of glow plug, but all of them have problems in functioning as a fast heating type, and the supply of glow plugs is required to prevent overheating of the heating wire. It is necessary to provide temperature control means for controlling electric power on all circuits, which has the disadvantage of increasing the cost of the entire device.

Therefore, in order to solve all of the above-mentioned problems, the applicant has
By using a skillful combination of resistors made of two types of materials, we have developed a self-temperature control type glow plug that can exhibit the full effect of a fast heating type and also achieve stable FC heating characteristics. This was previously proposed in Publication No. 57-182026.

To briefly explain this using Fig. 1, there is a sheath 2 made of heat-resistant metal such as glow plug ore or stainless steel, and a tubular housing 3 that holds this sheath 2 at its tip. An electrode rod 5 is concentrically attached to the rear end of the housing 3 via an insulating bushing 4, and the tip of the electrode rod 5 is inserted into the sheath 2.

The inner space on the distal end side of the sheath 1 is filled with a conductive material (5×10
A first resistor 6, which is formed in a spiral shape and serves as a heat generating element, is disposed along the axial direction, and one end thereof is electrically connected to the sheath 2. In addition, the sheath 1
The internal space on the rear end side is made of a conductive material with a large positive temperature coefficient of resistance (5 x 1o-3/℃), such as nickel 6 or low carbon steel with a carbon content of 0.25% or less.
A second resistor I, which is formed in a spiral shape and functions as a heating element and a temperature control means as will be described later, is disposed along the axial direction between the first resistor 6 and the electrode rod 5, Each is connected in series. In addition, 8 in the figure is a heat-resistant insulating powder such as magnesia filled in the sheath 2 so as to embed the above-mentioned double-folded antibodies 6 and 1.

In the above-mentioned configuration, the first and second resistors 6 and 7 are connected such that their spiral ends face each other with a predetermined gap (GAP) t- as shown. There is. 1 during this time! i? The reason for providing this is so that the second resistor 1 can effectively control the power supplied to the first resistor 6. Keep the time interval to prevent the heat influence from coming out.

By adopting such a configuration, a time delay t is caused in the temperature rise in the second resistor 7, and a large amount of power is supplied to the Ml resistor 6 at the initial stage of energization, causing it to rapidly become red hot. This greatly improves the temperature rise characteristics of the glow plug, and the second resistor 7, whose resistance value gradually increases after a predetermined period of time, reduces the power supply and prevents overheating in the first resistor 6. It becomes possible to do so. Of course, this second resistor 1 itself functions as a heat generating element, and can greatly improve the overall heat generating characteristics of the glow plug as a whole.

Therefore, according to the glow plug 1 having the above-described structure, by skillfully combining the resistors 6 and 7'ft made of two types of materials, it is possible to heat up quickly and eliminate the need for temperature control means on the circuit side. Although the device as a whole has advantages such as cost reduction, some problems occur during preheating after starting the engine, so-called after-glowing.

That is, even after the engine has been started, the engine may be too cold, for example in cold regions, and it may take some time to warm up.

In this non-warmed-up state, there are problems such as large noise during idling, white smoke generation due to incomplete combustion, and engine stalling.

In order to prevent this, in recent years the after-glow method described above has been adopted, in which the glow plug is kept energized for a certain period of time after the engine has started, thereby warming the inside of the engine and allowing smooth combustion. There is.

By the way, there are two types of diesel engines, direct injection type and sub-combustion chamber type.In the case of the former direct injection type, the above-mentioned afterglow time is sufficient within about 30 seconds. The glow plug 1 described above has no adverse effects on its performance, durability, etc., and there is no problem in its use.

However, in the latter type of sub-combustion chamber type diesel engine, one hour of afterglow is not enough for about 30 seconds, and may extend to about 3 degrees, and in such cases, the durability of each part of the glow plug 1 is adversely affected. There is a possibility that they will attempt to do so. In other words, in this type of glow plug, the supply voltage during normal preheating (approximately 5 degrees of sand) is approximately IIV, or when the engine is started, the regulator's set voltage is generally 14V, and this is the glow plug. 1, so if the afterglow is extended for one hour, the temperature will rise too high due to the high voltage, which may affect the durability, such as oxidation or melting, especially at the resistor 6.7 part. ing.

[Summary of the invention]

The present invention has been made in view of the above-mentioned circumstances, and in contrast to the first resistor which serves as a heat generating element, the second resistor has a large positive temperature coefficient of resistance. A third resistor is connected in series, and a third resistor is connected in series.
By forming the first resistor so that the current density is small or the amount of heat dissipated is large so that the temperature can rise with a time delay compared to the second resistor, the afterglow can last for a long time. Even if it crosses the third
The total power supplied as a whole is properly controlled by the resistor,
To provide an inexpensive glow plug for a diesel engine that can eliminate any negative effects in terms of durability and performance and provide stable and rapid heat generation characteristics.

〔Example〕

Hereinafter, the present invention will be explained in detail using the embodiments shown in the drawings.

FIG. 2 shows seven embodiments of a glow plug for a diesel engine according to the present invention, and in the figure, the same or corresponding parts as in FIG. 1 are given the same numbers and their explanations will be omitted.

According to the present invention, the first and second resistors 5 and 7 disposed in the sheath 1 as heating elements are made of nickel or low carbon steel in the same way as the second resistor γ. A spiral-shaped third resistor 10 made of a conductive material with a large positive temperature coefficient of resistance, such as It is characterized in that it is formed so that the temperature can rise with a certain delay.

Here, in order to make the temperature rise in the third resistor 10 more gradual than that in the second resistor T, the outer diameter (coil diameter) of the third resistor 10 must be This can be achieved by making the resistor 7 larger, by increasing its wire diameter 9, or by increasing its helical pitch, as described above. The current density at the body 10 is smaller than that at the second resistor T side,
Alternatively, it may be obvious that heat dissipation improves and the temperature rise becomes more gradual. Of course, the third resistor 1 mentioned above
In order to improve heat dissipation in the 0 part, the surrounding area may be filled with a heat-resistant insulating material 11 having high thermal conductivity, such as magnesia.
In order to increase the packing density in the resistor 10 portion, the resistor 10 may be embedded in a liquid ceramic material or the like in advance and then incorporated. This is because the higher the packing density of the heat-resistant insulating material 11 mentioned above, the more securely the resistor 1° is insulated and fixed, and the oxidation etc. of the resistor 1° is prevented.
This is obvious from the improvement in thermal conductivity.

In addition, in this embodiment, the third resistor 10 described above is arranged so as to be interposed in the middle of the electrode rod 5 within the housing 3 detached from the sheath 2, so that the installation space is wide and thick. It can be formed by winding a wire rod with a larger coil diameter and pinch, and as mentioned above, it reduces the current density and improves heat dissipation. The overall heat generation characteristics of the glow plug 1 can be greatly improved. Furthermore, in the above-described configuration, since the distal end of the sheath 2 serving as a heat generating section is provided at a sufficient distance via the distal end electrode rod 5ak, the thermal influence is exerted on the third resistor 10iIll.
This is effective in keeping the temperature rise in this area at a gentle level.

As described above, with respect to the first resistor 6 which becomes a heating element, the second and third resistors 1 having a large positive temperature coefficient of resistance are arranged.
, 10 are connected in series, the solder is rapidly heated to red heat by supplying a large amount of power to the first resistor 6 side by the control action of the second resistor T during preheating at the time of starting the engine. At the same time, the glow plug saturates at a certain temperature, completely preventing overheating, and providing appropriate heat generation characteristics as the glow plug 1. At this time, the temperature of the third resistor 10 is insufficiently increased for the reason described above, and the power supply cannot be completely controlled.

On the other hand, during the afterglow period when the engine is started, the temperature at the third resistor 1u also rises, and the resistance value increases due to this. The power supplied to the second resistors 6 and 7 is controlled, and as shown in FIG. 3(a) or (b), it acts to lower the temperature at the tip of the sheath 2,
Even if the applied voltage increases, overheating in the heat generating part can be prevented and the durability of this part can be completely improved.As a result, even if the afterglow time is longer than 30 seconds. There is no problem.

Here, in FIG. 3(a), the supply voltage is constant (for example, 11
V) What if it is deroru? In the figure, a is the conventional type, and b is the conventional type.
is the characteristic curve of the sheath surface temperature according to the present invention. In addition, in the same figure (b), water is supplied when a supply voltage of 11 V is applied during preheating and 14 V during after-grossing. e, fij show the temperature rise characteristics at the second and third resistors 7 and 10.

Note that the present invention is not limited to the structure of the embodiment described above, and the shape, structure, etc. of each part may be modified or changed as appropriate.

For example, as described in 7 above (in the example structure, the third resistor 10
Although the case where it is arranged in the outer cylinder of the sheath 2 is shown, the fourth
Of course, as shown in the figure or FIG. be. By doing so, it is easy to manufacture and assemble the sheath 2, and by swaging the sheath 2, the packing density of the heat-resistant insulating powder 8 can be increased to improve the durability and reliability of each part. The advantages are significant. In particular, in the latter case, since the resistors 6, 7, and 10 are continuous, there is an advantage that coiling is easy.

In addition, the above-mentioned second. Even if the third resistor 7.10 is used as a conductive material with a large positive temperature coefficient of resistance,
Alternatively, the third resistor 1o11ta may be formed using a different material, and it is better to form it so that the temperature rise of the third resistor 1o11ta is delayed compared to that of the second resistor I. Therefore, as the third resistor 10, it is also possible to use a material such as lead, which has a melting point of about 330° C. and whose resistance increases significantly when melted. In this case, as shown in FIG. A cylindrical body 14 made of a heat-resistant insulating powder island made by E. et al. may be interposed between the electrode rods 5 and 58, and the above-mentioned third resistor IQk made of lead may be enclosed in the through hole thereof.

Further, in the embodiments described above, a sheath type glow plug was exemplified as a glow plug, but the present invention is not limited to this, and the heater rod embedded in each resistor 6, 7, and 10't-ceramic material. It goes without saying that the shape of each resistor is not limited to a spiral shape.

〔Effect of the invention〕

As explained above, according to the glow plug for a diesel engine according to the present invention, the first resistor is a heating element, while the second resistor is a dog having a positive temperature coefficient of resistance. The third resistor is connected in series and is formed in such a way that the temperature can rise with a delay time that is comparable to that of the third resistor Kinoshi 2, so the structure is simple and inexpensive. As a glow plug, it is possible to obtain stable and fast heating properties, and even if the after-glow period lasts for a long time of 30 seconds or more, the presence of the third resistor makes the overall It has various excellent effects such as properly controlling the power supplied to the device and completely eliminating any negative effects on durability and performance.

[Brief explanation of drawings]

FIG. 1 is a schematic longitudinal cross-sectional view of an entire example of a conventional glow plug for a diesel engine, FIG. 2 is a vertical cross-sectional view of an embodiment of a glow plug for a diesel engine according to the present invention, and FIG. 3(a) (b) is a characteristic diagram thereof, and FIGS. 4 to 6 are diagrams showing other embodiments of the present invention. 1... Glow plug, 2s @ company sheath, 3...
・Housing, 5...Electrode rod, 6...First resistor, 1...Second resistor, 8L11・φ...Heat-resistant insulating powder, 10...Third resistor resistor. Patent applicant: Jidosha Kiki Co., Ltd. Agent Masaki Yamakawa (and 1 other person)

Claims (4)

[Claims] (1) A first resistor serving as a heating element, and a second resistor connected in series to one end of the resistor and made of a material having a larger positive temperature coefficient of resistance than the first resistor. A glow plug for a diesel engine, comprising a third resistor, the third resistor being formed so that its temperature can rise with a time delay compared to the second resistor. (2) The third resistor has a smaller outer diameter than the second resistor.
The glow plug for a diesel engine according to claim 1, characterized in that it is formed in a two-person structure. (3) Claim 1, characterized in that the third resistor is formed to have a larger wire width than the second resistor.
Glow plug for diesel engines as described in section. (4) The glow plug for a diesel engine according to claim 1, wherein the third resistor has a larger helical pitch than the second resistor.