JPH0120687B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to two types of glow plugs that are incorporated in order to function as a self-temperature control type in a glow plug used for preheating the auxiliary combustion chamber or combustion chamber of a diesel engine. The present invention relates to a method of manufacturing a heating element made of a spiral wire rod.

[Conventional technology]

In general, diesel engines have poor startability 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 air temperature or use it as an ignition source to improve engine startability. A method has been adopted to improve the By the way, what is required of this type of glow plug is that it can improve its temperature rise characteristics and function as a fast heating type by supplying a large amount of power to the heating element built into it at the initial stage of energization, and that it can function as a fast heating type. In order to prevent melting, etc., the saturation temperature is set appropriately to prevent overheating, and stable heat generation characteristics can be obtained, and durability is guaranteed due to exposure to high temperature gas in the sub-combustion chamber or combustion chamber. The goal is to satisfy the performance requirements such as being able to do the same.

In the well-known conventional sheath-type glow plug, a sheath made of a heat-resistant metal is filled with heat-resistant insulating powder to embed a spiral heating element made of a material such as nickel. The power supply is limited to prevent adverse effects on the heating element and other parts, which poses a problem in terms of temperature rise characteristics.Moreover, in order to function as a fast heating type, temperature control is required to prevent the heating element from overheating. The disadvantage is that it is necessary to provide a separate means, which increases the cost of the entire device.

In addition, as shown in Japanese Patent Application Laid-Open No. 54-109538, for example, as a device that improves the temperature rise characteristics described above and has a self-temperature control means,
A glow plug has also been proposed that uses heating elements each made of two types of materials with different temperature coefficients of resistance. However, although this type of structure functions as a fast-heating type to some extent, it is difficult to manufacture and expensive, and its heat generation characteristics are not good, so it cannot be said that it can satisfy all of the above-mentioned performances. It was difficult. This is because in conventional glow plugs of this type, a heating element with a small temperature coefficient of resistance is provided at the tip side, and a heating element with a large temperature coefficient of resistance is placed on the rear end side, and resistance changes due to temperature changes in the heating element on the rear end side. By using this method, a large amount of power is supplied to the front end heating element immediately after energization, so that it quickly becomes red hot.However, because both heating elements are placed too close to each other, the rear end heating element This was because the temperature suddenly rose due to the thermal influence from the tip side, and as a result, the power supplied to the tip side was controlled.
Due to these problems, it lacked heat generating properties and was unable to exhibit its effectiveness as a rapid heating type.

For this reason, the present applicant has conducted various research and development to effectively utilize the advantages of using heating elements made of two types of materials as described above, and has developed a method of connecting two types of heating elements with a predetermined gap between them. JP-A-Sho has developed an inexpensive, self-temperature-controlled glow plug for diesel engines that prevents thermal effects during the initial stage of energization and provides stable and fast heating properties.
It was previously proposed in Publication No. 57-182026.

To explain this simply, this glow plug includes a first spiral heating element (hereinafter referred to as the first heating element) made of a conductive material with a small positive temperature coefficient of resistance, such as iron chromium or nickel chromium alloy. , a second spiral heating element (hereinafter referred to as the second heating element) formed of a conductive material with a large positive temperature coefficient of resistance, such as nickel or low carbon steel with a carbon content of 0.25% or less. The spiral parts are connected so as to face each other with a predetermined gap (GAP) between them, and these are embedded in heat-resistant insulating powder such as magnesia (MgO) within the sheath.

By providing a certain gap between the spiral portions of both heating elements in this way, the time interval can be maintained to prevent the thermal influence from the first heating element on the second heating element, which has been a problem in the past. The current control by the second heating element is delayed in time to extend the time for supplying large power to the first heating element, and the first heating element is rapidly heated to red-hot temperature, thereby greatly improving the temperature rise characteristics of the glow plug. Furthermore, the resistance value of the second heating element is gradually increased after a predetermined period of time has elapsed, thereby reducing the supplied current and preventing overheating in the first heating element.
The glow plug itself acted as a heating element and was able to significantly improve the heat generation characteristics of the glow plug as a whole.

[Problem to be solved by the invention]

Incidentally, in the glow plug having the above-described structure, the first and second heating elements are connected in such a way that heat transfer is minimized within the certain gap, but there are manufacturing and Problems have arisen in terms of quality. That is, these first and second heating elements are arranged such that the end surfaces of the linear end portions extending in the axial direction from the ends of the respective final helical portions face each other and abut against each other, or It has generally been considered to overlap the ends of the metal parts over a predetermined length and then weld and connect them by plasma arc welding, spot welding, or the like. However, as mentioned above, when connecting both heating elements exhibiting a spiral shape with the linear ends extended from the end of the final spiral part, workability at the time of connection,
Various problems have arisen in terms of durability and operational reliability.

In other words, the wire diameter of both heating elements is 0.3φ.
The coil diameter is approximately 2.8φ, and the coil length is also quite small, 3 mm and 7 mm. When welding the parts by abutting or overlapping them, the positioning and alignment between the two linear ends is troublesome and complicated, and lacks reliability. This is because the linear end drawn out from each spirally wound heating element inevitably bends in the axial direction of the heating element. This is because it is difficult to align the heating elements in the circumferential direction and hold them parallel to each other. Furthermore, welding work on such minute and difficult to align parts is troublesome and difficult, resulting in a high defect rate, which poses a major problem in mass production.

In particular, when welding together the linear ends extending from both spiral heating elements as described above, the welded portion or burrs may protrude outside of the heating elements, or cause damage to both heating elements. They are often connected with their axes misaligned, and this has the disadvantage that when they are assembled into a sheath and buried in heat-resistant insulating powder, they come into contact with the inner wall of the sheath and cause short circuits. . Further, in the case of a connection portion where positioning is difficult as described above, it is also difficult to maintain the above-mentioned gap constant, resulting in variations. Furthermore, in the case of the above-mentioned welded parts, it is difficult to obtain the required joint strength due to misalignment or displacement between the two linear ends, and accidents such as wire breakage may occur after assembly.

Furthermore, in the above configuration, the closer the part to be welded to the spiral part of each heating element, the more difficult it is to weld, and not only are there restrictions on the welding location and connection structure, but also welding within this gap. A small diameter part is created at the connection part, which increases the current density,
This caused problems in terms of durability, as it caused a rise in temperature when energized and was susceptible to deterioration and disconnection.
That is, according to this type of glow plug, after incorporating the heating element together with the heat-resistant insulating powder into the sheath,
Generally, swaging is performed to prevent oxidation, etc., but when such swaging is performed, the sheath diameter of the helical parts of both heating elements becomes smaller, the coil diameter becomes smaller, and the coil length becomes longer. On the other hand, it has been confirmed that the stress distribution increases the wire diameter. On the other hand, the diameter at the connection part between the straight ends in the gap described above hardly changes, and as a result, the above-mentioned problem occurs due to the difference in wire diameter with the spiral part of the heating element. It is necessary to adopt a simple connection structure that takes these points into consideration.

[Means to solve the problem]

In order to meet such demands, the method for manufacturing a heating element in a diesel engine glow plug according to the present invention uses two types of wire rods forming the first and second heating elements made of materials having different positive temperature coefficients of resistance. After preparing, both of these wire rods are fed out in the axial direction in a straight line from the feeding parts disposed opposite to each other, and the tips of each are overlapped over a length corresponding to the gap, Both wire rods are welded and connected at least at two points corresponding to the tips of each wire rod, and then, with this overlapping portion held by a holder, the wire rod portions other than this overlapping portion are each spirally wound. By rotating, a heating element consisting of the first and second heating elements is formed.

Furthermore, the method for manufacturing a heating element according to the present invention involves unwinding two types of wire rods from both ends of the spirally wound guide rod, and after welding the overlapped portions of both wire rods, this portion is held by a holder. The helical portion of the first and second heating elements is formed by rotating the guide rod in a spiral manner while holding the other portions alternately or simultaneously by a guide means. It is.

[Effect]

According to the present invention, the first and second spirally shaped
When connecting and connecting the heating elements with a predetermined gap between the linear ends, the wires forming each heating element are first overlapped in a straight state and connected by welding, Next, with this overlapping portion held by a holder, the remaining portion is wound from a linear state to a spiral state to form a spiral portion.

〔Example〕

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

Figures 1 and 2 show an embodiment of a glow plug for a diesel engine to which the method of manufacturing a heating element according to the present invention is applied, and in these figures, the overall schematic structure will be briefly described by reference numerals. 1 is a sheath made of a heat-resistant metal material such as stainless steel; 2 is a cylindrical housing that holds the sheath 1 at its tip; an electrode rod 4 is concentrically connected to the rear end of the housing 2 via an insulating bushing 3; The tip of the electrode rod 4 is inserted into the sheath 1.

A first heating element 5 is disposed along the axial direction in the inner space on the distal end side of the sheath 1, and is made of a conductive material with a small positive temperature coefficient of resistance, such as iron chromium or nickel chromium alloy. One end is electrically connected to the tip of the sheath 1.
A second heating element 6 is also disposed along the axial direction in the inner space on the rear end side of the sheath 12, and is made of a conductive material with a large positive temperature coefficient of resistance, such as nickel or low carbon steel. One end thereof is electrically connected to the rear end of the first heating element 5, and the other end is electrically connected to the tip of the electrode rod 4.

Both of these heating elements 5 and 6 have straight end portions 5b and 6 extending in the axial direction from the respective final spiral portion ends 5a and 6a so as to face each other.
b are overlapped over a predetermined length range and welded together, thereby connecting the helical portions with a constant gap (GAP) between them.

In the figure, 7 is a heat-resistant insulating powder such as magnesia (MgO) that is filled in the sheath 1 and embeds both the heating elements 5 and 6, and 8 is a heat-resistant insulating powder that is disposed to penetrate inside the heating elements 5 and 6. An insulator made of a heat-resistant insulating material such as ceramic that holds these in a predetermined position improves the ease of assembling both heating elements 5 and 6, and maintains the gap between the above-mentioned heating elements 5 and 6 appropriately, resulting in heat generation characteristics. This is useful for stabilizing the environment.

By using a glow plug with such a configuration, the resistance of the second heating element 6 is small immediately after the start of energization, so that large electric power is transferred to the first heating element 5.
can be concentrated and quickly generate heat. Furthermore, the presence of the gap described above allows a time delay to be provided before the thermal influence from the first heating element 5 is transmitted to the second heating element 6 and increases its resistance value. This allows a longer period of time for large electric power to concentrate on the first heating element 5, resulting in better heating speed in this area.

On the other hand, the second heating element 6 also gradually generates heat due to the supplied power over time, and its resistance value increases with the temperature of the generated heat and the thermal influence from the first heating element 5. As a result, the first heating element 5
In addition to reducing the power supplied to the sheath 1 to prevent overheating, it also acts as a heating element, and the sheath 1 is sequentially heated, resulting in the temperature rising to the temperature required for engine starting with better temperature rise characteristics. becomes.

Now, according to the present invention, in the glow plug configured as described above, the first and second heating elements 5 and 6 disposed within the sheath 1 as the heating element 10 are arranged as shown in FIG. , when manufacturing the helical parts in a connected state with a desired gap between them, the two types of wire rods 11 and 12 forming both heating elements 5 and 6 are oriented in the axial direction while remaining in a straight state. After overlapping the ends of each wire over a predetermined length, the overlapping portions of each wire rod 11 and 12 are welded and connected at multiple points, and then this overlapping portion is attached to an appropriate holder. While holding the wire at the
They are each characterized by being formed by spirally winding.

According to such a configuration, when the wire rods 11 and 12 forming the two heating elements 5 and 6 are overlapped and welded, the wire rods 11 and 12 forming the two heating elements 5 and 6 can be welded while keeping each wire in a straight state. Compared to the case of positioning and overlapping the linear ends separately extending from the end of the helical part in parallel, the positioning, alignment, and welding of the overlapping parts can be easily and reliably performed, and the connection length and connection can be easily and reliably performed. It is possible to ensure strength, stabilize workability and quality, and further improve durability and operational reliability, which is highly effective in mass production. In particular, according to the present invention, the ends of the two types of wire rods 11 and 12 are fed out from opposite directions, overlapped, and welded together. This method has the advantage that the jig and the like are simpler than when welding small parts together.

According to the manufacturing method of the heating element 10 according to the present invention, the manufacturing apparatus shown in FIGS. By automatically performing this in a series of operations, it becomes possible to achieve further mass productivity and cost reduction.

Here, in FIG. 4, reference numeral 20 denotes a jig that is sequentially conveyed on a conveyor 22 while holding a spirally wound guide bar 21. At a section A on this conveyor 22, the axial direction of the guide bar 21 with respect to the jig 20 is The apparatuses shown in FIG. 5 are sequentially transferred to section B arranged on both sides.

Briefly explaining the apparatus shown in FIG. 5, reference numerals 23 and 24 refer to feeding parts where the wire rods 11 and 12 forming the heating elements 5 and 6 are wound in each lot and are arranged facing each other. bobbin as, 2
5 and 26 are the wire rods 1 from each of these bobbins 23 and 24.
1 and 12 from both ends of the guide rod 21 in the axial direction so as to face each other;
Each wire rod 11, 12 fed out by 5, 26
on the guide rod 21, and 29
Reference numerals a and 29b are bits that are freely adjustable so as to cut each wire rod 11 and 12 to a desired length.

In such a configuration, the roller 2
By rotating the wire rods 5 and 26, the wire rods 11 and 12 are sequentially fed out along the axial direction from both ends to the upper part of the guide rod 21 held by the jig 20, and the tip of each rod is connected to the heating element. 5,6
The length should be overlapped according to the gap between them.

Next, a pair of welding guide jigs 31a, 31 as shown in FIG.
b is assembled from both sides of the guide rod 21 and held in the groove 31c formed between them, and the holding members 32, 32a, 32b as shown in FIG. 7 are lowered from above the groove 31c to hold it. It is pressed and held, and in this state, at least two locations at both ends of the overlapping portion 30 are connected by, for example, laser welding, resistance welding, plasma welding, or the like. Note that this welding location includes both wire rods 11,
In order to obtain the connection strength etc. at the overlapping part 30 of the 12 parts, it is necessary to weld at least two places at both ends as shown in FIG.
As shown in FIG. 7 and FIG. 7, three or more locations including the center may be welded. In addition, the welding guide jigs 31a and 31b and the holding member 3 described above are also provided.
2, 32a, 32b, etc., and the driving method thereof, various modifications are possible.In short, any structure that can hold and hold the overlapping portion 30 of both wire rods 11, 12 during welding is possible. It's good,
Furthermore, these jigs 31a and 31b are attached to the wire rod 1.
It goes without saying that the wire rod 1 and 12 may be pre-assembled to the guide rod 21 during feeding, and the groove 31c may be used for guiding the feeding of the wire.

With this configuration, workability and quality stability are greatly improved compared to the conventional method of welding the straight ends of spirally wound wire rods by overlapping them. It is easy to understand that this can be done. Furthermore, since the ends of each wire rod 11, 12 can be joined to the other end, there are great advantages in terms of strength and performance.

Further, after the above-mentioned welding is completed, by rotating the rollers 25, 26, 23, and 24 in the opposite direction, the tensile strength test of the welded portion can be performed, which is also advantageous compared to the conventional method. .

Furthermore, after the above-mentioned strength test is completed, the eighth
As shown in Figures a and b, holders 33 that hold the wire rods 11 and 12 on both ends of the guide rod 21
a, 33b, and in this state, the byte 2
Each wire rod 11, 12 is cut to a desired length using 9a, 29b. At this time, the welding guide jigs 31a, 31b and the holding member 32 are removed.

Note that the cutting lengths of the wire rods 11 and 12 described above are the same as those of the first and second heating elements 5 and 12 in FIG.
The length is set so that the lengths of the spiral parts L _R and L _B of 6 can be formed, and the wire diameter is determined for each lot to obtain the required resistance value. Ru.

After each of the above-mentioned steps is completed, a holder 34 as shown in FIGS. Remove the
It is transferred from section B to section C on the conveyor 22 shown in FIG.

Next, in this C section, as shown in FIGS. 9a and 9b, both ends of the guide rod 21 are attached to supports 35a,
35b, and lifted from the jig 20 as shown in section D in FIG.
The wire rods 11 and 12 are preferably wound helically around the guide rod 21 by rotationally driving a pulse motor (both not shown) connected to the wire rod 5b via an electromagnetic clutch or the like.

To explain this in detail, as shown in FIG. 9a, a portion of one wire 11 slightly away from the end of the overlapping portion 30 is held by a claw tool 36 as a guide means, and this wire 11 is After bending the guide rod 21 in a direction substantially perpendicular to the axial direction, the claws 36 are successively guided to the unwinding side of the wire 11 as the motor rotates the guide rod 21 clockwise in the figure. As shown in FIGS. 10a and 10b, the first heating element 5 side can be spirally wound. Of course, this wire rod 11 has a small wire diameter, and in some cases, the wire rod 11 may be similarly wound spirally by holding it with the claw tool 36 and rotating the guide rod 21 without performing the above-mentioned bending process. It is also possible to do so. The end of the wire 11 is bent in the axial direction as shown in FIG. 10a, but this process can be easily performed.

Furthermore, after the above-described molding of the first heating element 5 is completed, as shown in FIGS. It will be easily understood that by guiding this to the unwinding side, spiral winding can be similarly performed by rotating the guide rod 21 by the motor, resulting in the state shown in FIG. 12.
It should be noted here that the bending direction of the wire rod 12 is opposite to that of the wire rod 11, and the guide rod 2
The rotation direction of No. 1 is also opposite to the counterclockwise direction in the figure. By using such a method, the heating element 10 in which both the heating elements 5 and 6 are wound in the same direction can be formed.
By removing the guide rod 21 from the state shown in FIG. 12, the heating element 10 as shown in FIG. 3 is obtained, and its manufacture is completed.

It goes without saying that after this one-cycle process is completed, the guide rod 21 is returned onto the jig 20 in FIG. 3 and is sequentially conveyed to the next process by the conveyor 22.

It should be noted that the present invention is not limited to the structure of the above-described embodiments, and the shape, structure, etc. of each part including the manufacturing equipment etc. may be modified or changed as appropriate, and various modifications may be considered.

For example, the overlapping portion 30 between both heating elements 5 and 6
13 shows the case where the bent portions leading to the ends 5a and 6a of each spiral portion are made of a single line, but as shown in FIG. 13, both end portions of the overlapping portion 30 may be bent together. It is.

In addition, in the embodiment described above, each wire rod 1
1 and 12 have been described, the case where the spiral winding is performed in stages by both forward and reverse rotation of the guide rod 21 has been described, but the present invention is not limited to this, and FIGS. 14a and 14b
Further, as shown in FIG. 15, spiral winding may be performed simultaneously by rotating the guide rods 21 in the same direction. At this time, the wire rods 11 and 12 are bent in the same direction by the respective claws 36 and 37, and the heating element 10 obtained thereby is as follows.
The first and second heating elements 5 and 6 are wound in reverse. However, in this way, when manufacturing the heating element 10, workability etc. can be improved and costs can be reduced, and there is no problem in operation. Here, both heating elements 5,
The coil lengths of No. 6 are different, but it is best to temporarily stop the motor after one end is finished, process the end, and then start the motor again, or you can keep it running. Since the length of the shorter one is fixed, there is no problem.

In addition, although the number of coil turns of each heating element 5, 6 described above needs to be changed depending on the wire diameter of the wire rods 11, 12, in reality, the variation is slight, and the position of the end of the coil winding is adjusted around the guide rod 21. It can be adjusted by changing the direction.

〔Effect of the invention〕

As explained above, according to the present invention, two types of wire rods forming the first and second spiral heating elements are prepared, these wire rods are fed out in a straight state, and welded to a predetermined length in advance. After that, the first and second heating elements are formed by winding them in a spiral shape, which is a simple, automated, and inexpensive method. It is possible to easily and reliably obtain a heating element that is connected within a gap, and it is excellent in terms of workability and stable quality, and it is also possible to improve durability and operational reliability. There are various excellent effects such as the ability to achieve mass production.

Further, according to the present invention, two types of wire rods are fed out from both ends of the spirally wound guide rod, and after welding the overlapped portions of both wire rods, this portion is held by the holder and the other wire rods are fed out from both ends of the spirally wound guide rod. while holding the parts alternately or simultaneously by guiding means;
By rotating the guide rod in an appropriate direction, the spiral part of each heating element is formed by winding the guide rod in a spiral shape, making it easy to position, overlap, and weld the ends of the wires that make up each heating element. Not only is the work extremely easy to perform, but the spiral portion can be easily and appropriately formed by rotating the guide rod in that state and winding each wire while guiding it with a guide means such as a claw tool. , it has advantages such as being superior in terms of mass production and cost reduction.

[Brief explanation of drawings]

1 and 2 are an overall schematic sectional view and an enlarged sectional view of essential parts of a glow plug for a diesel engine according to an embodiment of the present invention, and FIG.
The figure is an enlarged view of a heating element that characterizes the present invention, Figures 4 and 5 are schematic configuration diagrams of an apparatus for carrying out the manufacturing method according to the present invention, and Figures 6 to 8 a and b are the main components thereof. Figures 9a, b to 12 are process diagrams illustrating the spiral winding state;
Figures 14a and 14b, and 15 are explanatory diagrams showing another embodiment of the present invention. 1...Sheath, 5...First spiral heating element, 6
...Second helical heating element, 5a, 6a... Spiral portion end, 5b, 6b... Straight end portion, 10... Heating element, 11, 12... Wire rod, 21... Guide rod, 3
0... Overlapping portion, 31a, 31b... Welding guide jig, 32... Holding member, 34... Holder,
35a, 35b...Supporting tools, 36, 37...Claw tools (guiding means).

Claims (1)

[Claims] 1. A first spiral heating element and a second spiral heating element formed of a material having a larger positive temperature coefficient of resistance than the first spiral heating element, respectively. A method for manufacturing a heating element in which spiral parts are connected with a gap between them, the method comprising preparing two types of wire rods forming the first and second spiral heating elements, and arranging these wire rods so as to face each other. After each wire is fed out in the axial direction from the provided feeding section in a straight line state, and the tips of each wire are overlapped over a length corresponding to the gap, both ends are tied at at least two points corresponding to the tips of each wire. A diesel engine characterized in that the wire rods are welded and connected, and then the wire rod portions other than the overlapping portion are wound in a spiral shape while the overlapping portion is held by a holder. A method for manufacturing a heating element in a glow plug for use. 2. A first helical heating element and a second helical heating element made of a material with a larger positive temperature coefficient of resistance than the first helical heating element are connected with a gap between the respective helical parts. A method for manufacturing a heating element connected at a position, wherein two types of wire rods forming the first and second spiral heating elements are prepared, and both wire rods are connected from both ends of a spirally wound guide rod in the axial direction thereof. After overlapping the ends of each wire over a length corresponding to the gap, the two wires are welded and connected at least at two points corresponding to the ends of each wire, and then this overlapped portion is is held by a holder, one of the wire rods is held by a guide means from near one end of the overlapping portion, and sequentially guided along the guide rod toward its unwinding side, and the guide rod is rotationally driven. Then, the other wire is similarly held at the overlapped part by a holder, and then held by a guide means from near the other end of this overlapped part and guided sequentially to the unwinding side. A method for manufacturing a heating element in a glow plug for a diesel engine, characterized in that the guide rod is rotated in the opposite direction and wound in a spiral manner. 3 A first helical heating element and a second helical heating element made of a material with a larger positive temperature coefficient of resistance than the first helical heating element are connected with a gap between the respective helical parts. A method for manufacturing a heating element connected at a position, wherein two types of wire rods forming the first and second spiral heating elements are prepared, and both wire rods are connected from both ends of a spirally wound guide rod in the axial direction thereof. After overlapping the ends of each wire over a length corresponding to the gap, the two wires are welded and connected at least at two points corresponding to the ends of each wire, and then this overlapped portion is is held by a holder, each of these wire rods is held by a guide means from near both ends of the overlapped portion, and sequentially guided to the unwinding side, and the guide rod is rotationally driven to form a spiral shape. A method for manufacturing a heating element in a glow plug for a diesel engine, characterized in that the heating element is wound around a glow plug for a diesel engine.