KR20200080606A - Manufacturing Method of Glow Plug of Silicon Nitride for Diesel Vehicles - Google Patents

Abstract

The present invention relates to a manufacturing method of a silicon nitride glow plug for a diesel automobile having excellent durability. More specifically, the manufacturing method of a silicon nitride glow plug for a diesel automobile comprises: a step of preparing silicon nitride powder; a step of burying and forming a coiled heating element in the silicon nitride powder, and then pressing and sintering the silicon nitride powder in which the heating element is buried to manufacture a glow plug sintering body; a step of processing the glow plug sintering body into a bar shape; and a step of forming an electrode on the glow plug sintering body processed into the bar shape. The silicon nitride powder consists of mixed powder comprising 70-90 wt% of α-Si_3N_4 and 10-30 wt% of β-Si_3N_4. A sintering aid comprising 1.0-3.0 wt% of MgO, 1.0-3.0 wt% of Al_2O_3, 1.0-6.0 wt% of Y_2O_3, and 1.0-3.0 wt% of Ti with respect to the total weight of the mixed powder is further included.

Description

Manufacturing Method of Glow Plug of Silicon Nitride for Diesel Vehicles

The present invention relates to a method for manufacturing a silicon nitride glow plug for a diesel vehicle, and more specifically, it is excellent in vibration resistance and high temperature mechanical properties (thermal shock resistance, bending strength, Vickers hardness, fracture toughness, etc.) of a diesel vehicle, thereby preheating the eco-friendly diesel vehicle. It relates to a method for manufacturing a silicon nitride glow plug for a diesel vehicle used as an ignition source, an ignition source for a DPF (Smoke Reduction Device).

In general, four silicon nitride glow plugs and igniter products are currently installed for preheating diesel engines, and conventional sheath type glow plugs have a low temperature rise rate and a low temperature rise temperature of about 800°C. Due to the low temperature, the engine efficiency is low, and a large amount of pollutants (PM) are discharged, which has emerged as a major obstacle to reducing the emission of diesel engines.

Air pollution caused by these diesel vehicles has become a major cause of fine dust in the air, and automobile manufacturers have developed and commercialized eco-friendly engines that reduce emissions.

The development of this eco-friendly diesel engine is equipped with a ceramic glow plug of 4/set, which increases the preheating temperature of the engine and increases the heating rate, thereby reducing the source of emission pollutants.

On the other hand, the conventional technologies include silicon nitride batch composition, glow blog assembly structure, internal heating element resistance pattern, composition, sintering conditions, etc. Kyo Cera Co., Ltd JP 1999-218125, JP1999-218126, NGK Co. JP 1998-369735, JP 1998-179572, NGK Spark Plug Co., Ltd US-07/357786.

The present invention was devised to solve the above-mentioned problems. First, a resistance heating element can be easily implemented, and the structure of the resistance and heating range of the heating element can be easily produced, and the resistance coil can freely adjust the tungsten diameter to DC 650V. The objective is to provide a method for manufacturing a silicon nitride glow plug for diesel vehicles capable of designing a high capacity of 4KW/ea.

In addition, it shows excellent characteristics in terms of durability, and the formation of a resistance coil is a Tunsten Wire Winding & Rewindibg M/C, which can be manufactured as a large area large capacity silicon nitride heater when designed to match various resistances and expansion coefficients according to silicon nitride volume. Another object is to provide a method for manufacturing a silicon nitride glow plug.

In addition, another object of the present invention is to provide a method for manufacturing a silicon nitride glow plug for a diesel vehicle, which can more efficiently and mass-produce a high-density heating element having a smaller diameter and a smaller thermal range, such as a glow plug.

Meanwhile, the objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned will be clearly understood by those skilled in the art from the following description.

The present invention is a step of preparing a silicon nitride powder to achieve the above-mentioned objects, after embedding and molding a heating element coiled in the silicon nitride powder, and then pressurizing and sintering the silicon nitride powder embedded with the heating element to produce a glow plug sintered body. A step, a step of processing the glow plug sintered body into a rod shape and a step of forming an electrode in the glow plug sintered body processed into a rod shape may be included.

Preferably, the silicon nitride powder is composed of a mixed powder of α-Si ₃ N ₄ 70-90 wt% and β-Si ₃ N ₄ 10-30 wt%, MgO 1.0-3.0 wt%, Al compared to the total weight of the mixed powder _{2 O 3 1.0 ~ 3.0wt%,} Y 2 O 3 sintering aid of 1.0~6.0wt% and Ti 0.1 ~ 3.0wt% is may be further included.

Preferably, the heating element may coil the tungsten wire having a diameter of 120 µm to have a diameter of 0.29 to 1.0 mm so that the resistance value is 0.4 to 1.6 MPa.

Preferably, a tungsten terminal wire is inserted into the coiled heating element, and the heating element with the terminal wire inserted is immersed in an active metal paste solution and then taken out and heat-treated at 900°C for 10 minutes using a brazing electric furnace. .

Preferably, the manufacturing of the glow plug sintered body comprises: wet mixing the mixed powder in which the silicon nitride powder and the sintering aid powder are mixed together with the prepared ethyl alcohol, drying the wet mixed mixed powder slurry and drying the mixed powder Crushing, filling the pulverized mixed powder into a mold of a certain shape, then filling the heating element with a terminal wire inserted therein, press forming and degreasing the mixed powder in which the heating element is embedded, and preparing a molded body; and The molded body may be pressure-sintered to produce a glow plug sintered body.

Preferably, both ends of the terminal wire may be exposed to the outside of the glow plug sintered body by a predetermined length.

Preferably, the mixed powder is wet-mixed for 4 hours using a ball mill, dried at 80° C. for 2 hours, and press-formed at a pressure of 100 kg/cm ² , 1700 to 1850 in a graphite crucible in an N ₂ gas atmosphere. It can be pressure-sintered for 1 to 3 hours at a temperature of ℃.

Preferably, in the step of processing the glow plug sintered body into a rod shape, the glow plug sintered body may be first processed into a polygon using a cylindrical grinding machine, and then processed into a rod shape using a coreless machine.

Preferably, the step of forming an electrode on the sintered body of the glow plug processed into the rod shape is performed by immersing the exposed portions of both ends of the terminal wire in an active metal paste solution and taking it out and heat-treating it at 1000° C. for 10 minutes in a brazing electric furnace. Forming two electrode layers so as not to contact each other on the outer surface of the glow plug sintered body, and after winding a nickel wire on the electrode layer, heat-treating for 30 minutes at 900° C. in a brazing electric furnace using Ag-Cu as a brazing material. It can contain.

Preferably, one of the electrode layers may form the + electrode of the glow plug and the other-electrode.

Preferably, the active metal paste solution may be one or two or more selected from the group consisting of Mo, V, Ti, Mn, Zr and Si.

The present invention has the following excellent effects.

First, the present invention is easy to implement a resistance heating element and can easily fabricate the structure of the resistance and heating range of the heating element, and the resistance coil can freely adjust the tungsten diameter, thereby enabling high-capacity DC 650V 4KW/ea design.

In addition, it shows excellent characteristics in terms of durability, and the formation of a resistance coil is a Tunsten Wire Winding & Rewindibg M/C. It is also possible to manufacture a large area large capacity silicon nitride heater when designed to match various resistances and expansion coefficients according to silicon nitride volume.

In addition, a high-density heating element having a small diameter such as a glow plug and a small thermal range is more economical and has an excellent effect in mass production.

1 is an overall process diagram of a method for manufacturing a silicon nitride glow plug for a diesel vehicle according to an embodiment of the present invention.
2 is a view showing a terminal wire exposed to the glow plug sintered body.
3 is an image in which an electrode is formed on a sintered glow plug.
4 is a side view (a) and a side cross-sectional view (b) of a silicon nitride glow plug for a diesel vehicle manufactured according to an embodiment of the present invention.
5 is an etching surface SEM image of a glow plug sintered body (sintering temperature: 1,800° C., sintering time: 2 hr, pressure: 35 ton, gas atmosphere: N ₂ Pressure (3 MPa)) according to an embodiment of the present invention.
FIG. 6 is an SEM image showing the microstructure of the interface between the heating element and the sintered body in the sintered body of FIG. 5 (where (a) is 50 μm and (b) is 10 μm image).
7 to 13 is a graph showing the 12V glow plug ON-Off test results.
14 to 20 is a graph showing the 24V glow plug ON-Off test results.

The terms used in the present invention have been selected as general terms that are currently widely used, but in certain cases, there are also terms that are arbitrarily selected by the applicant. The meaning should be grasped.

Hereinafter, the technical configuration of the present invention will be described in detail with reference to preferred embodiments illustrated in the accompanying drawings.

However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. The same reference numerals throughout the specification indicate the same components.

In this regard, first, FIG. 1 is an overall process diagram of a method for manufacturing a silicon nitride glow plug for a diesel vehicle according to an embodiment of the present invention, FIG. 2 is a diagram showing a state in which a terminal wire is exposed to a sintered glow plug, and FIG. 3 is a glow An image in which an electrode is formed on a plug sintered body, FIG. 4 is a side view (a) and a side sectional view (b) of a silicon nitride glow plug for a diesel vehicle manufactured according to an embodiment of the present invention, and FIG. 5 is a view according to an embodiment of the present invention Etching surface SEM image of the glow plug sintered body (sintering temperature: 1,800℃, sintering time: 2hr, pressure: 35ton, gas atmosphere: N ₂ Pressure (3MPa)), μ 6 is the microstructure of the interface between the heating element and the sintered body in the sintered body of FIG. SEM images showing, 7 to 13 is a graph showing the 12V glow plug ON-Off test results, Figures 14 to 20 are graphs showing the 24V glow plug ON-Off test results.

1 to 20, a method for manufacturing a silicon nitride glow plug for a diesel vehicle according to an embodiment of the present invention includes preparing a silicon nitride powder (S100).

At this time, the silicon nitride powder according to an embodiment of the present invention is composed of a mixture of α-Si ₃ N ₄ 70-90 wt% and β-Si ₃ N ₄ 10-30 wt%, MgO relative to the total weight of the mixed powder _{1.0 ~ 3.0wt%, Al 2 O} 3 1.0 ~ sintering aid of _{3.0wt%, Y 2 O 3 1.0~6.0wt} % and 0.1 ~ 3.0wt% Ti is further contained.

At this time, the β-Si ₃ N ₄ And Al ₂ O ₃ By adding, the sinterability and mechanical strength of the glow plug sintered body are improved.

On the other hand, the method for manufacturing a silicon nitride glow plug for a diesel vehicle according to an embodiment of the present invention is embedded and molded in a heating element coiled in the silicon nitride powder, and then pressurized and sintered the silicon nitride powder in which the heating element is embedded to obtain a glow plug sintered body. It includes a step of manufacturing (S200).

In addition, the method of manufacturing a silicon nitride glow plug for a diesel vehicle according to an embodiment of the present invention further includes Ti as a sintering aid, wherein the Ti is combined with sintered Si ₃ N ₄ crystal particles of a nitride sintered body and Ti will be described later. By strengthening the bonding force between the outer surface of the heating element and the nitride ceramics, pores are not formed outside the heating element buried portion.

On the other hand, the method for manufacturing a silicon nitride glow plug for a diesel vehicle according to an embodiment of the present invention is embedded and molded in a heating element coiled in the silicon nitride powder, and then pressurized and sintered the silicon nitride powder in which the heating element is embedded to obtain a glow plug sintered body. It includes a step of manufacturing (S200).

Hereinafter, the step (S200) of manufacturing the glow plug sintered body will be described in detail.

First, the step of manufacturing the glow plug sintered body (S200) includes wet mixing the mixed powder in which the silicon nitride powder and the sintering aid powder are mixed together with the prepared ethyl alcohol, and the wet mixing step uses a ball mill. And then mixed for 4 hours.

Thereafter, drying and mixing the wet mixed powder slurry includes crushing the dried powder, and filling the pulverized mixed powder in a molding mold having a predetermined shape, and then filling the heating element with the terminal wire inserted therein.

At this time, the heating element according to an embodiment of the present invention is characterized in that the resistance value is 0.4 to 1.6 하여 by coiling a tungsten wire having a diameter of 120 μm to have a diameter of 0.29 to 1.0 mm.

Meanwhile, the reason for limiting the diameter of the heating element as described above is as follows.

In this regard, first, in the case of a tungsten coil-type resistance heating element, if the diameter is large, when the heat-generating silicon nitride sintered body and the tungsten metal expansion coefficient are mismatched, the silicon nitride sintered body has a fracture phenomenon due to expansion, so to have durability without such destruction phenomenon It is very important to control the diameter of the silicon nitride sintered body and the tungsten metal wire, and it is important to control the wire diameter and length according to the resistance value.

Accordingly, in one embodiment of the present invention, a coil of tungsten wire having a wire diameter of 120 μm was coiled to produce a coil having a constant length of 0.29 to 1.0 mm, and the resistance value of the coil was 0.4 to 1.6 MPa.

On the other hand, a tungsten terminal wire is inserted inside the coiled heating element, and the heating element having the terminal wire inserted is immersed in an active metal paste solution and then taken out and heat-treated at 900°C for 10 minutes using a brazing electric furnace. do.

At this time, the terminal wire is exposed to a predetermined length on the outer surface of the sintered glow plug as shown in FIG. 2 and can form an electrode layer to be described later by the exposed length, and improves the bonding strength with the nickel wire to improve silicon nitride for diesel vehicles. The service life and durability of the glow plug can be secured for more than 10 years.

On the other hand, the drying of the mixed powder slurry may be performed through various methods, but in one embodiment of the present invention, it is dried at 80° C. for 2 hours using various dryers.

In addition, the step (S200) of manufacturing the glow plug sintered body includes preparing a molded body by press-molding and degreasing the mixed powder in which the heating element is embedded, and manufacturing the glow plug sintered body by pressure-sintering the molded body.

At this time, the heating element is embedded in the inside of the molded body so that the tungsten heating resistance coil is located at the center, and the reason for embedding in the center is that the heating phase after sintering must be gathered at the center, and thus the durability becomes good. This is to prevent this in advance as the durability is greatly reduced due to bias.

On the other hand, the press molding and the step of pressure-sintering the molded body are press-molded at a pressure of 100 kg/cm ² , and pressure-sintered for 1 to 3 hours at a temperature of 1700 to 1850° C. in a graphite crucible in an N ₂ gas atmosphere. .

At this time, when firing in the air layer, since it may be oxidized and cannot be used as a heater, it is sintered in an N ₂ gas atmosphere so that the tungsten electrode is not oxidized and can be used as a heater. In the case of N ₂ Pressure, it can be confirmed that the densification is enhanced by controlling the particle growth of silicon nitride when the pressure rises from 3 MPa to 1 MPa.

Meanwhile, a method for manufacturing a silicon nitride glow plug for a diesel vehicle according to an embodiment of the present invention includes the step of processing the sintered glow plug into a rod (S300).

At this time, in the step (S300) of processing into the rod shape according to an embodiment of the present invention, the glow plug sintered body is first processed into a polygon using a cylindrical grinding machine, and then processed into a rod shape using a coreless machine.

In addition, the method for manufacturing a silicon nitride glow plug for a diesel vehicle according to an embodiment of the present invention includes forming an electrode on the sintered body of the glow plug processed into a rod (S400).

In this regard, referring to FIG. 3, in the forming of the electrode (S400), the exposed portions of both ends of the terminal wire are immersed in an active metal paste solution, and then taken out and heat-treated at 1000° C. for 10 minutes in a brazing electric furnace to the glow. The step of forming two electrode layers so as not to contact each other on the outer surface of the plug sintered body, and after winding the nickel wire on the electrode layer, Ag-Cu is used as a brazing material and heat-treated at 900°C for 30 minutes in a brazing electric furnace. do.

At this time, one of the electrode layers is connected to the lead wire and the + electrode of the glow plug is connected to the other lead wire to form a-electrode.

This will be described in more detail with reference to FIG. 4, wherein the electrode is a grounding portion, and a suspension or copper sleeve is bonded to the heater electrode portion at about 1000° C. in a high vacuum brazing furnace by an active metal bonding method to form an electrode.

On the other hand, the + electrode bonds the nickel wire to the top of the heater, and the silicon nitride heater wire and the metalized electrode Ni wire of the sintered body are bonded to the M4x0.7 screw portion from the top, and the bonding method is characterized by Ag brazing with Ni-Sus 304 metal bonding. do.

On the other hand, the active metal paste solution according to an embodiment of the present invention is characterized in that any one or two or more selected from the group consisting of Mo, V, Ti, Mn, Zr and Si are mixed.

Meanwhile, the characteristics of the silicon nitride glow plug manufactured according to an embodiment of the present invention are summarized in Table 1 below.

Item unit Silicon nitride glow plug Withstand voltage (5mA, 2sec) V 5,000 or more Density g/cm ³ 3.26 3-point bending strength MPa 800 Vickers hardness Kg/mm ² 1,600 Maximum operating temperature
Max. use temp. ℃ max. 1,400 Commercial use temperature
Operating temp. ℃ max. 1,300 Thermal conductivity
Thermal conductivity W/mK 31 specific heat
Specific Heat J/gK One Coefficient of linear expansion
Coef. of linear thermal expansion /℃(40-800℃) 3.7x1-6

On the other hand, referring to FIGS. 7 to 20, the silicon nitride glow plug for a diesel vehicle manufactured according to an embodiment of the present invention was found to be capable of securing durability of 5000 cycles or more.

At this time, the durability test was a test result using the On-Off Test System, and the voltage was applied by applying a voltage more severely than 14.4 V and the rated voltage of 12 V. Voltage ON-OFF test was performed as a cycle.

As a result, the method for manufacturing a silicon nitride glow plug for a diesel vehicle according to an embodiment of the present invention is first through the above-described technical configurations, the present invention is easy to implement a resistance heating element and can easily produce a structure of resistance and heating range of the heating element. , The resistance coil can freely adjust the tungsten diameter, so a high capacity DC 650V 4KW/ea design is also possible.

In addition, it shows excellent characteristics in terms of durability, and the formation of a resistance coil is a Tunsten Wire Winding & Rewindibg M/C. It is also possible to manufacture a large area large capacity silicon nitride heater when designed to match various resistances and expansion coefficients according to silicon nitride volume.

In addition, a high-density heating element having a small diameter such as a glow plug and a small thermal range is more economical and has an excellent effect in mass production.

As described above, the present invention has been illustrated and described with reference to preferred embodiments, but is not limited to the above-described embodiments and is within the scope of the present invention without departing from the spirit of the present invention. By this, various changes and modifications will be possible.

Claims (8)

Preparing a silicon nitride powder;
Forming a glow plug sintered body by pressing and sintering the silicon nitride powder in which the heating element is embedded, after embedding and molding the coiled heating element in the silicon nitride powder;
Processing the glow plug sintered body into a rod shape; And
Comprising the step of forming an electrode on the glow plug sintered body processed into a rod,
The silicon nitride powder is composed of a mixture of α-Si ₃ N ₄ 70-90 wt% and β-Si ₃ N ₄ 10-30 wt%, MgO 1.0-3.0 wt%, Al ₂ O ₃ relative to the total weight of the mixed powder. A method of manufacturing a silicon nitride glow plug for a diesel vehicle, further comprising 1.0 to 3.0 wt%, Y ₂ O ₃ 1.0 to 6.0 wt%, and Ti 0.1 to 3.0 wt%.
According to claim 1,
The heating element is a method of manufacturing a silicon nitride glow plug for a diesel vehicle, characterized in that a tungsten wire having a diameter of 120 µm is coiled to have a diameter of 0.29 to 1.0 mm so that a resistance value is 0.4 to 1.6 Ω.
According to claim 2,
A diesel characterized in that a tungsten terminal wire is inserted into the coiled heating element, and the heating element with the terminal wire inserted is immersed in an active metal paste solution and then taken out and heat-treated at 900°C for 10 minutes using a brazing electric furnace. Method for manufacturing silicon nitride glow plug for automobiles.
The method of claim 1 or 2,
The step of manufacturing the glow plug sintered body:
Wet mixing the mixed powder in which the silicon nitride powder and the sintering aid powder are mixed together with the prepared ethyl alcohol;
Drying the wet-mixed mixed powder slurry and crushing the dried mixed powder;
Filling the crushed mixed powder in a mold having a predetermined shape, and then filling the heating element with a terminal wire inserted therein;
Preparing a molded body by press forming and degreasing the mixed powder in which the heating element is embedded; And
It consists of a step of producing a glow plug sintered body by pressure sintering the molded body,
A method of manufacturing a silicon nitride glow plug for a diesel vehicle, wherein both ends of the terminal wire are exposed to the outside of the sintered body of the glow plug for a predetermined length.
The method of claim 4,
The mixed powder is wet-mixed using a ball mill for 4 hours, dried at 80° C. for 2 hours and press-molded at a pressure of 100 kg/cm ² , and a temperature of 1700 to 1850° C. in a graphite crucible in an N ₂ gas atmosphere Method for producing a silicon nitride glow plug for a diesel vehicle, characterized in that it is pressurized and sintered for 1 to 3 hours.
The method of claim 1 or 2,
In the step of processing the sintered body of the glow plug into a rod shape, the sintered body of the glow plug is first processed into a polygon using a cylindrical grinding machine, and then processed into a rod shape using a coreless processing machine, and then silicon nitride glow plug for diesel vehicles. Manufacturing method.
The method of claim 4,
Forming an electrode on the glow plug sintered body processed into the rod shape:
Immersing the exposed portions of both ends of the terminal wire in an active metal paste solution and then taking it out and heat-treating it at 1000°C for 10 minutes in a brazing electric furnace to form two electrode layers so as not to contact each other on the outer surfaces of the glow plug sintered body;
After winding the nickel wire to the electrode layer, Ag-Cu as a brazing material comprises a step of heat treatment for 30 minutes at 900 ℃ in a brazing electric furnace,
A method of manufacturing a silicon nitride glow plug for a diesel vehicle, characterized in that one of the electrode layers forms a + electrode of the glow plug and a-electrode of the other.
The method of claim 3 or 7,
The active metal paste solution is a method for manufacturing a silicon nitride glow plug for diesel vehicles, characterized in that any one or two or more selected from the group consisting of Mo, V, Ti, Mn, Zr and Si are mixed.

Images