JPS6014144Y2 - Glow plug for diesel engine - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a glow plug for preheating the inside of a cylinder of a diesel engine.

In general, diesel engines have poor startability at low temperatures, so a method is used to increase the temperature inside the cylinder by installing a glow plug inside the cylinder and heating it by passing an electric current through it, thereby improving the startability of the engine. It is being

Conventional glow plugs of this type use a so-called sheathed heater, in which a heat-resistant metal sheath is filled with heat-resistant insulating powder and a coiled heating wire is embedded.
Since this is indirect heating, there is a problem in that it takes too much time to raise the temperature inside the cylinder.

In other words, the heat generated by passing a current through the heating wire and heating it is transferred to the sheath side through the heat-resistant insulating powder, and the heat is radiated from the sheath into the cylinder, which poses a problem in terms of heat transfer efficiency. be.

For example, it takes several watts of seconds to bring the temperature inside the cylinder to 800°C.

If the applied current is increased in order to shorten such a long heating time, the heating wire is likely to melt or the sheath is damaged due to high heat.

Furthermore, in the above-mentioned structure, it is desirable to prevent short circuits between the heating wire and the sheath when burying it, and for this purpose, the heating wire is covered with an insulating material in advance, or an insulating layer is formed on the inner wall of the sheath. There is also the problem that it is necessary to take measures such as manufacturing, and the manufacturing work is troublesome.

Furthermore, Japanese Patent Application Laid-Open No. 54-109536 discloses a ceramic heater for glow plugs that applies multilayer substrate technology to improve the heat transfer efficiency described above, but this ceramic heater uses a printed resistor. It is made by laminating a large number of thin ceramic green sheets on a disk and integrating them into a rod shape, which is difficult to manufacture and requires extremely complicated work.

In particular, a large number of resistors are required on the narrow green sheet surface, and in order to connect the resistors on each sheet, both ends of the resistor exposed on the outer periphery of the sheet must be connected in series or in parallel. Naturally, the work for this is complicated, and it is difficult to imagine that it is possible to easily obtain the desired connection state.

In particular, it is desirable for the above-mentioned glow plug for a diesel engine to prevent the heater part, especially the heat-generating part at the tip of the heater, from rapidly becoming red hot, and to prevent the heat influence from reaching each member. In this case, it is necessary to efficiently and reliably supply power to the heater section.

This invention was made in view of these circumstances,
A plurality of metal coating layers are formed on the outer periphery of a ceramic heater rod containing a built-in resistor, and the ends of the resistor are connected to the coating layer, and the heater rod is inserted into a metal pipe supported by a holder. The present invention provides a glow plug for a diesel engine, in which one of the metal coating layers is positioned and fixed at the tip of the pipe.

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

1 and 3 show an embodiment of a glow plug for a diesel engine according to the present invention, and in these figures, the glow plug, designated as a whole by the reference numeral 10, has a conductive material on one joint surface. A ceramic heater rod 14 is formed of a pair of ceramic rods 12 and 13 made of a silicon-based ceramic material that is pressurized and fired with a resistor 11 interposed therein, and this heater rod 14 is placed at the tip end. A substantially tubular holder 15 for holding the holder 1 is provided.
At the rear end of 5 is an insulating bushing 1 made of synthetic resin or the like.
An external connection terminal 17 is fitted through the heater rod 6, and the external connection terminal 17 is connected to the rear end of the heater rod 14 through a conductive wire 18 having the required flexibility.

Here, the heater rod 14 is connected to the pair of ceramic rods 12 described above so that its cross-sectional shape is approximately circular.
, 13.

In this case, the reason why the cross-sectional shape of the heater rod 14 is approximately circular is that the density of the ceramic material is improved compared to a circular shape, and its heat resistance strength, insulation properties, and thermal conductivity are more effective. It's for a reason.

Furthermore, the material of the pair of ceramic rods 12 and 13 mentioned above may be a silicon-based non-oxide material, which is a silicon-based ceramic material known as so-called fine ceramics, which has excellent insulation properties and thermal shock resistance, for example. Silicon-based nitrides and the like are preferred.

Further, the resistor 11 in the heater rod 14 is formed on the joint surface 12a of the one ceramic rod 12 in a state as shown in FIG.

That is, the above-mentioned resistor 11 includes a heater portion 11a having a large electric resistance value that is curved and formed at a portion located on the tip side of the heater rod 14, and a heater portion 11a having a large electric resistance value and extending along the heater rod 14 from one end of the heater portion 11a. A ground side lead portion 11c having a resistance value smaller than that of the heater portion 11a extends in a substantially straight line to approximately the center thereof and has an end exposed on the outer surface of the heater rod 14; It extends from the other end in a substantially straight line in parallel with the earth side lead part lie, and its resistance value is
1c, and the ground side lead part 11c, which extends in a substantially straight line continuously to the rear end of the heater rod 14 and is exposed on the outer surface thereof, has a resistance value smaller than that of the intermediate part 11c. and a current-carrying side lead portion 11b having a rear end portion, which is connected to the bonding surface 12.
They are formed in series on a.

In this case, the width of the lead portion 11a of the resistor 11 is formed to be sufficiently narrow so that the resistance thereof is increased.
On the other hand, each lead portion 11b and lie is formed to have a wider width than the lead portion 11a so as to reduce the resistance.

That is, in the illustrated example, the bonding surface 12a of the ceramic rod 12
A series of resistors 11 are formed thereon, and by appropriately selecting the width and length of the resistors 11, the resistors 11 are divided into a heater section 11a and a pair of lead sections 11b and 11c.

In this way, not only is manufacturing easy, but only the necessary portions can be heated at high speed, which is highly effective.

By changing the formation pattern of the resistor 11, it is possible to control the resistance value, and in short, the heater rod is configured to quickly heat up the tip of the heater rod, which affects the startability of the engine. There is.

Note that the heater portion flb and each lead portion 11b, 11c are connected to the heater rod 1 when the ceramic rods 12, 13 are joined.
4 completely embedded inside 1. Each t' part 11 b, 1
Only the end of 1c is exposed to the outside from the joint of the ceramic rod 12.13.

The resistor 11 may be formed by printing wiring as a thin conductive film on the bonding surface 12a of the ceramic rod 12, by pasting a wire or plate-like material of high melting point metal, or by baking, vapor deposition, or other methods. It is easily obtained, and metal materials such as tungsten can be considered as the material.

This is because the ceramic firing temperature is high, so the resistor 11
This is because it needs to be a heat-resistant material.

In addition, the outer periphery of the center portion, the outer periphery of the rear end portion, and the end surface of the heater rod 14 formed as described above include
As can be seen from FIGS. 1 and 3, a metal coating layer 19,20 is formed.

These metal coating layers 19 and 20 are for electrically connecting both ends of the resistor 11 embedded in the heater rod 14, that is, the ends of each lead portion 11b and llc, to the outside. 11b and llc are formed outside the heater rod 14 in contact with the exposed ends outside the rod body.

This is because metal members cannot be directly welded or brazed to the heater rod 14 made of ceramic material.

The metal coating layer is formed, for example, by a refractory metal method, and this method uses Mc, Mn.

A paint-like product made by adding an organic binder to a fine powder of W or a combination thereof is applied to the surface of ceramics, and after metallizing at 1300 to 17006C in humidified wood or humidified forming gas, N
This is a method of applying i-plating and brazing it to the joining metal using a brazing filler metal.

The metal coating layer is a general term for the composite layer of high melting point metal and ceramic, the composite layer with Ni, and the bonding layer such as silver solder formed in the above process.

A reinforcing metal pipe 21 is fitted into the center of the heater rod 14, and the tip of the pipe 21 is placed at the position of one of the metal coating layers 19 and 20. A terminal cap 22 for connecting the conductive wires 18 is placed on the rear end side and fixed to the heater rod 14 by silver brazing or the like.

That is, the heater rod 14 is assembled while being held at the tip of the holder 15, but in this case, since its cross-sectional shape is approximately circular, in order to securely fix it, the tip of the holder 15 is required. It is necessary to form the opening to match the heater rod 14.

However, forming such an internal opening at the tip of the holder 15 is troublesome and undesirable in terms of cost.

For this purpose, a metal pipe 21 having a through hole 21a having a substantially circular shape formed to match the shape of the heater rod 14.
By preparing the pipe 21 separately from the holder 15, fixing the pipe 21 to the heater rod 14, and then fitting and fixing the pipe 21 to the tip of the holder 15, each part can be easily formed and the cost can be reduced. Moreover, the heater rod 14 can be easily and reliably attached to the holder 15, and its strength is sufficiently guaranteed.

In particular, a diesel engine to which this type of glow plug 10 is attached generates considerable vibration during operation, and the state in which the heater rod 14 is held in the holder 15 becomes a problem.

Note that the elliptical through hole 21a of the metal pipe 21 can be formed with high precision by simple drawing or the like.

Further, one end of the resistor 11 in the heater rod 14, that is, the end of the ground side lead portion 11c is coated with a metal coating layer 19.
, are electrically connected to the holder 15 via a metal pipe 21.

Here, the metal coating layer 19 described above is inserted into the metal pipe 21 so as to be located at the tip thereof as described above, and simultaneously connects the metal pipe 21 and the heater rod 14 electrically and mechanically. , which plays the role of sealing the gas pressure within the engine cylinder, but in this case, this metal coating layer 19 has poor heat resistance, so there is a need to suppress the temperature rise in this part.

For this reason, the resistor 11 is located near the center of the heater rod 14 provided with the metal coating layer 19.
In order to avoid the heat influence on the heater part 11a, the resistor 11 located in this part (lead part 11 by 11c)
It is necessary to make the resistance value as small as possible.

Furthermore, on the rear end side of the heater rod 14, since it is more effective to reduce the temperature of that part in terms of thermal energy consumption, the current-carrying side lead part 11b formed in this part is more effective. It is desirable that the resistance value of the rear end portion of the ground side lead portion 11c (the resistance value of the potion side, which is the same at the middle portion of the current carrying side lead portion 11b) is made smaller.

On the other hand, the outer diameter of the heater rod 14 described above is subject to restrictions in terms of strength, etc., and the shape of the embedded resistor 11 within the heater rod 14 is a problem, as described above. It is important to set the resistance values between the lead portion 11a, the current-carrying side, and the ground side lead portion 11b, llc.

Then, the resistor 11 is set in consideration of such points.
As described above, the resistance value pattern is configured such that the resistance value gradually decreases toward the rear end side of the heater rod 14, and as a result, the tip portion along the longitudinal direction of the heater rod 14, The heat generation temperature characteristics can be made to have a gentle temperature gradient in three stages from the center part to the rear end part.

With such a configuration, the tip of the heater rod 14 can quickly become red hot, improve its temperature rise characteristics by rapid heating in a short time, and can fully demonstrate its performance as a fast heating type. To properly maintain the heat resistance strength of the entire heater rod 14 through such a temperature gradient, and to suppress the temperature rise at the central portion of the heater rod 14 to below the allowable heat resistance temperature of the metal coating layer 19 formed in this portion. As a result, the durability of each part of the heater rod 14 can be guaranteed, and as a result, it can be used as a heater rod for a glow plug for this type of diesel engine.

On the other hand, the other end of the resistor 11 exposed at the rear end of the heater rod 14, that is, the end of the current-carrying side lead portion 11b is connected to the holder 1.
5 is connected to an external connection terminal 17 attached to the rear end of the heater rod 14 via an insulating bushing 16. In this case, if this external connection terminal 17 is directly fixed to the rear end of the heater rod 14, the Mechanical external forces such as vibration or tightening torque may cause the connection part to come off or the heater rod 14 to
There are problems such as damage to the parts, etc., and it is necessary to connect them elastically.

In order to ensure strength against the influence of such external forces, in this embodiment, the heater rod 14 and the external connection terminal 17 are connected to a highly flexible conductor 1 such as a flexible lead wire.
8 is connected.

Further, the terminal cap 22 is used to securely fix the conducting wire 18 to the rear end of the heater rod 14.

As is clear from FIGS. 1 and 3, the terminal cap 22 has a cap shape that is fitted over the rear end of the heater rod 14, and a mounting piece 22a for fixing the conductor 18 is attached from the bottom of the terminal cap 22. It's being cut up.

One end of the conducting wire 18 is fixed to this mounting piece 22a by spot welding or the like.

Of course, the other end of the conducting wire 18 is also fixed to the tip of the external connection terminal 17 by spot welding or the like.

Note that instead of the highly flexible conducting wire 18 described above, an electrical conductor having a certain degree of flexibility such as a flexible wire is used, and this is attached to the mounting piece 2 of the terminal cap 22.
2a with elasticity, or external connection terminal 1.
It is possible to connect the metal wire elastically to the 7 side, and it is also conceivable that at least one end of the metal wire is formed with electrolyte and the connection is made using the elasticity of the metal wire.

In addition, when connecting using the above-mentioned conducting wire 18, etc., heat-resistant insulating powder,
For example, it may be filled with ceramic powder such as magnesium oxide.

In this way, the effect can be exhibited as a measure against vibration of the conducting wire 18 and the like.

The glow plug 10 configured as described above can be easily assembled as follows.

First, a heater rod 14 with excellent heat generation properties is prepared by joining a pair of ceramic rods 12 and 13 each having a resistor 11 on one joining surface.

Then, after fitting the pipe 21 and the terminal cap 22 to the central part and rear end part of the heater rod 14 and fixing them by silver brazing or the like, the terminal cap 2
One end of the conducting wire 18 is fixed to the second mounting piece 22a, and the other end is spot welded to the tip of the external connection terminal 17 into which the insulating bushing 16 is fitted.

Further, each of these members is inserted from the rear end of the holder 15, and the pipe 31 holding the heater rod 14 is fixed at the tip of the holder 15 by silver brazing, while the pipe 31 that is fitted into the rear end of the holder 15 is fixed. The assembly is fixed by caulking the insulating bushing 16 on the outer periphery of the external connection terminal 17 with the rear end of the holder 15.

This assembled state is shown in Figures 3A and 3B.

Further, the glow plug 10 assembled in this manner is screwed into a screw hole formed in the cylinder head of a diesel engine, and is attached with the heater rod 14 at the tip thereof protruding into the cylinder chamber.

Then, when a voltage is applied between the external connection terminal 17 and the holder 15 and a current flows through the resistor 11 inside the heater rod 14,
The heater portion 11a is heated, and the generated heat is transmitted to the outer skin made of a ceramic material, which radiates the heat into the cylinder to increase its internal temperature, thereby improving the startability of the engine.

What should be noted here is that the heater rod 14 in which the resistor 11 is embedded is made of a ceramic material such as silicon-based non-oxide, and this ceramic material not only has good insulation properties but also has good thermal shock resistance. It is excellent and can be used in the heater part of this type of glow plug for diesel engines to demonstrate its performance.

Furthermore, the heater rod 14 made of such a ceramic material
In this case, the resistor 11 that becomes the heating element is directly buried inside the sheath, and its thermal conductivity is higher than that of the conventional case where the heating element is buried with heat-resistant insulating powder filled in the sheath. This can be significantly improved.

Therefore, such a heater rod 14 becomes red hot in a short period of time during heating, has improved temperature rise characteristics, and can fully exhibit its performance as a fast heating type.

For example, the glow plug according to the present invention can produce up to 80"C.
Experiments have confirmed that it takes less than 3 seconds to raise the temperature to .

In particular, the heater rod 14 described above has a pair of lead portions 11b, llc extending from both ends of the heater portion 11a of the resistor 11 only at the tip portion that most affects the startability of the engine.
The width of the rod is narrower than that of the rod, and its resistance value is increased.This improves the heat generation property and fully fulfills the role of a heater rod, which significantly improves engine startability. It is possible.

Also, when manufacturing the heater rod 14, a resistor 11 is attached to one joint surface 12a of the pair of ceramic rods 12 and 13.
It will be clear that this can be easily accomplished by shaping the ceramic rods 12, 13 and then joining them together.

In addition, in the embodiment described above, the pair of ceramic rods 12
, 13 has a substantially circular cross-sectional shape, and is assembled into a holder 15 using a metal pipe 21 and a terminal cap 22 shaped accordingly, and further connected to an external connection terminal 17. Although the present invention is not limited to this, it is possible to change the cross-sectional shape of the heater rod as appropriate and form each member accordingly. may be directly held at the tip of the holder, or the conducting wire may be directly fixed by soldering or the like without using a terminal cap.

As explained above, the glow plug for a diesel engine according to the present invention has a plurality of metal coating layers formed on the outer periphery of a ceramic heater rod containing a built-in resistor, and the ends of the resistor are connected to the coating layer. At the same time, the heater rod was inserted into a metal pipe supported by a holder and fixed so that one of the metal coating layers was positioned at the tip of the pipe. If you do this easily and reliably, insert the heater rod into the metal pipe so that one of the metal coating layers is located near the tip of the pipe and solder it with silver, and then insert it into the holder through the metal pipe. By supporting it, heat is effectively transferred to the holder by the metal pipe at the same time as electrical connection, and the temperature rise after the center of the heater rod can be suppressed to below the allowable heat resistance temperature of the metal coating layer.

Furthermore, the metal coating layer placed near the tip of the heater rod provides a complete seal between the metal pipe and the heater rod, and has the effect of preventing leakage of gas pressure within the engine cylinder.

[Brief explanation of drawings]

The figures show an embodiment of a diesel engine plug according to the present invention, FIG. 1 is an exploded perspective view showing the overall structure, and FIG. 2 is an enlarged view of a heater rod consisting of a pair of ceramic rods. FIG. 3A is a vertical sectional view showing the assembled state of FIG. 1, and FIG. 3B is a side view similarly seen from the tip side. 10... Glow plug, 11... Resistor, 11a... Heater part, 11b, 11c, bent/current carrying side, ground side lead part, 12.13... ...
Pair of ceramic rods, 14... Heater rod, 1
5. Song holder, 16... Insulation bushing, 17
...External connection terminal, 18...Conductor wire, 1
9, 20...metal coating layer, 21...
...Metal pipe, 22, curved, terminal cap.

Claims (1)

[Scope of utility model registration request] Forming a plurality of metal coating layers on the outer periphery of a ceramic heater rod containing a resistor, connecting the end of the resistor to the coating layer, and inserting the heater rod into a metal pipe supported by a holder. A glow plug for a diesel engine, characterized in that one of the metal coating layers is fixed at the tip of the pipe.