JPH0322553Y2 - - Google Patents

Description

[Detailed explanation of the idea]

(Field of Industrial Application) The present invention relates to an energization control device for a ceramic glow plug or the like used as a starting ignition device for a diesel engine, for example. (Prior art) Conventionally, for example, a ceramic glow plug for a diesel engine has been used for about 3 hours after starting, as shown in Fig. 8.
In order to rapidly raise the temperature to approximately 900℃ in seconds, a large voltage V ₁ is applied at the initial stage of energization, and the temperature reaches approximately 1050℃, which is a temperature that does not cause cracks in the sintered body of the glow plug and is capable of igniting. small voltage when
The application of V ₂ is controlled to maintain a stable temperature, and this is done as one cycle when the engine is started. [Problem to be solved by the invention] However, the power applied to the glow plug during this one cycle or during many cycles during long-term repeated use generally only controls the DC voltage from the battery and remains constant. Only the polarity of was applied. Therefore, in products that employ this type of energization control method, when voltage is repeatedly applied, mass transfer occurs inside the ceramic sintered body at a particularly high temperature (1150°C or higher), which causes the ceramic to deteriorate. Cracks tended to occur in the sintered body, making it difficult to use it at higher temperatures. [Means for Solving the Problem] In view of the above points, the present applicant has conducted intensive research and found that the polarity of the applied current can be changed during one cycle of the above-mentioned energization control process, during multiple cycles over a long period of time, or during continuous energization. It has been found that by doing so, cracks are less likely to occur in the sintered body even when the temperature reaches a relatively high temperature, and even during long-term cycles and long-term energization. Therefore, the present invention provides an energization control device for ceramic glow plugs that is resistant to cracks in the sintered body used in ceramic glow plugs and has excellent durability against repeated high-temperature use and long-term continuous energization at high temperatures. The purpose is to provide According to the present invention, at least one set of two glow plugs are provided, which are connected in parallel to the power supply at the initial stage of energization and in series at the time of temperature saturation. There is provided an energization control device for a ceramic glow plug, characterized in that an alternating current is applied to the glow plug during multiple cycles or during continuous energization. Furthermore, there is provided an energization control device for a ceramic glow plug in which neither of the two terminals of the ceramic glow plug is grounded to the body. The ceramic sintered body of the present invention includes non-oxide ceramics such as silicon nitride (Si ₃ N ₄ ) or oxide ceramics such as alumina (Al ₂ O ₃ ). The principle of the energization control device can be applied to a wide range of ceramic sintered bodies. The following two methods can be considered for alternating current polarity in the energization control device of the present invention. Direct current is always applied, and the polarity of (+) and (-) is changed and applied in the energization control process. Converts direct current to alternating current and applies it. For example, in the case of a glow plug, change the polarity of the DC voltage from the battery from (+) to (-).
A control circuit may be configured to convert from (-) to (+). In this case, for example, in a glow plug, an energization control circuit is configured to apply a DC voltage from a battery when applying an initial voltage, and apply an AC voltage from an alternator when the temperature is saturated. A glow plug employing the above method does not have a body earth electrode. When the body is grounded, the ground side is fixed as (-) polarity, making it virtually impossible to convert the polarity. The present invention will be described in detail below based on embodiments. (Example 1) Figure 1 shows a DC voltage applied single wire insulated glow plug (one buried heating wire and two terminals), which is initially energized to the DC power battery 1. Two glow plugs Ga and Gb are connected in parallel to each other and connected in series at temperature saturation.
As one set, multiple sets Ga1, Gb1, Ga2, Gb2,
It is equipped with... That is, the (+) side of battery 1, which is a DC power source, is connected to glow plugs Ga1, Gb1, Ga2, Gb2, Ga3, Gb through relay 2.
3... are respectively connected to one electrode side a... of the glow plugs Ga1, Ga2, Ga3... through the normally open contact 3a of the two-contact relay 3. ing. The (-) side of the battery 1 is the normally closed contact 4 of the 2-contact relay 4.
Glow plugs Gb1, Gb2, Gb3... through b
is connected to the other electrode side C... On the other hand, the (-) side of the battery 1 is connected to the glow plugs Ga1, Ga2,
Ga3... is connected to the other electrode side b..., and the (+) side of the battery 1 is connected to the glow plug Gb1, via the normally open contact 4a of the two-contact relay 4.
It is connected to the other electrode side C... of Gb2, Gb3.... To explain the operation of this energization control circuit, when relay 2 is turned on and started, each glow plug Ga1,
The (+) power supply of battery 1 is connected in parallel to Gb1..., and the temperature rises rapidly and generates heat. Next, after a certain period of time (for example, 3 seconds), a timer (not shown) turns off the relay 2 and switches the 2-contact relay 3 to the normally open contact 3a side.
The power source is connected to the glow plug Ga from the other electrode side b...
1, Ga2, Ga3... and glow plugs Gb1, Gb
2, Gb3... are connected in series to the (-) power supply of battery 1 through the normally closed contact of 2-contact relay 4, and are kept at a constant saturation temperature (e.g. 1250℃).
maintains and generates fever. 2 after a certain period of time has passed
By switching the contact relay 3 to the normally closed contact 3b side and the 2-contact relay 4 to the normally open contact 4a side, the polarity (+) (-) of the DC voltage from the battery 1 to the glow plugs Ga1, Gb1... is changed. applied. (Example 2) Figure 2 shows a DC voltage applied double-wire insulated glow plug (having two or more buried heating wires and two terminals with these wires in parallel), which is a DC voltage source. Two glow plugs Ga and Gb are connected in parallel to the battery 21 at the initial stage of energization, and in series when the temperature is saturated.
1, Gb11, Ga12, Gb12, . . . In other words, the (+) of the battery 11 which is a DC power supply
The side is connected to the glow plug Ga11 via the relay 12,
Gb11, Ga12, Gb12, ... are respectively connected to one electrode side a..., and at the same time two-contact relay 13
Glow plug Ga11,
Ga12... are respectively connected to the other electrode side b... The (-) side of the battery 11 is connected to the glow plug via the normally closed contact 14b of the two-contact relay 14.
It is connected to the other electrode side C of Gb11 and Gb12. On the other hand, the (-) side of the battery 11 is connected to the other electrode side b of the glow plugs Ga11, Ga12 through the normally closed contact 13b of the two-contact relay 13, and the (+) side of the battery 11 is The side is the normally closed contact 14 of the two-contact relay 14.
It is connected to the other electrode side C... of the glow plugs Gb11, Gb12... through a. To explain the operation of this energization control circuit, when relay 2 is turned on and started, each glow plug Ga
11, Gb11, . . . are connected in parallel with the (+) power supply of battery 11, which rapidly rises in temperature and generates heat. Next, after a certain period of time (for example, 3 seconds), a timer (not shown) turns off the relay 12, and the 2
When the contact relay 13 is switched to the normally open contact 13a side, the (+) power source of the battery 11 is connected in series from the other electrode side b... to the glow plugs Ga11, Ga12... and the glow plugs Gb11, Gb12, It is connected to the (-) power source of the battery 11 via the normally closed contact of the two-contact relay 14, and generates heat while maintaining a constant saturation temperature (for example, 1250° C.). Then, after a certain period of time has passed, the 2-contact relay 13 switches to the normally closed contact 13b side, and the 2-contact relay 14 switches to the normally open contact 14a side.
By switching to the side, the glow plug Ga11,
The polarity (+) (-) of the DC voltage from the battery 11 is converted and applied to Gb11.... (Example 3) Figure 3 shows a DC-AC voltage applied single-wire insulated glow plug (the number of buried heating wires is one, two
A plurality of glow plugs Ga21, Gb are connected in parallel with a DC power supply battery 21 at the initial stage of energization, and connected in series with an AC power supply at temperature saturation. Gb
21, Ga22, Gb22, Ga23, Gb23...
It is equipped with the following. That is, the (+) side of the battery 21, which is a DC power source, is connected to the glow plugs Ga21, Gb21, Ga22, Gb22,
Ga23, Gb23... are connected to one electrode side a..., respectively. The (-) side of the battery 21 is connected to the other electrode side b of the glow plugs Ga21, Ga22, Ga23 through the normally closed contact 23b of the 2-contact relay 23, and is connected to the normally closed contact 24b of the 2-contact relay 24. Glow plug Gb21, Gb22,
Gb23... are connected to the other electrode side C..., respectively. On the other hand, the AC power supply (alternator) 25 is connected to the normally open contacts 23a, 2 of the 2-contact relays 23, 24a.
Glow plugs Ga21, Gb21... through 4a
are connected to the other electrode sides b and c. To explain the operation of this energization control circuit, when the relay 22 is turned on and started, the glow plug Ga
21, Gb21... are respectively DC power battery 2
1, the glow plug Ga21,
Gb21... rapidly rises in temperature and generates heat. next,
After a certain period of time (e.g. 3 seconds) a timer (not shown)
As a result, relay 22 turns off and 2-contact relay 2
3 and 24 are switched to normally open contacts 23a and 24a, and glow plugs Ga21, Gb21, . Since the (+) (-) characteristics of AC voltage are constantly converted, glow plugs Ga21, Gb21...
A voltage whose polarity has been changed is always applied to the terminal. (Example 4) Figure 4 shows a DC-AC voltage applied double-wire insulated glow plug (having two or more buried heating wires and two terminals with these wires in parallel). DC power battery 2 at the initial stage of energization
Multiple sets Ga31, Gb31, Ga32, two glow plugs Ga and Gb are connected in parallel with each other and AC power source is connected in series when the temperature is saturated.
It is equipped with Gb32... That is, the (+) side of the battery 21, which is a DC power source, is connected to the relay 32.
Glow plug Ga31, Gb31, Ga3 through
2, Gb32... are connected to one electrode side a..., respectively. The (-) side of the battery 31 is connected to the other electrode side b of the glow plugs Ga31, Ga32, etc. via the normally closed contact 33b of the two-contact relay 33.
... are connected to the other electrode side c... of the glow plugs Gb31, Gb32... through the normally closed contact 34b of the two-contact relay 34, respectively. On the other hand, the AC power source (alternator) 25 is connected to the glow plug Ga via the normally open contacts 33a and 34a of the two-contact relays 33 and 34.
31, Gb31, . . . are connected to the other electrode sides b and c. To explain the operation of this energization control circuit, when the relay 22 is turned on and started, the glow plug Ga
31, Gb31, ... are connected in parallel to the DC power battery 31, respectively, and the glow plugs Ga31,
Gb31... rapidly rises in temperature and generates heat. next,
After a certain period of time (e.g. 3 seconds) a timer (not shown)
The relay 32 is turned off, and the 2-contact relay 3
3 and 34 are switched to normally open contacts 33a and 34a, and glow plugs Ga31, Gb31, . I get a fever. Since the polarity of AC voltage is always changed (+) and (-), glow plugs Ga31 and Gb3
1, . . . are always applied with a voltage whose polarity has been changed. (Example 5) In the circuit configurations of Examples 1 and 2, these energization control patterns were changed. That is, turn on relay 2 or 12 to start, and turn on the glow plug.
Ga1, Gb1... or Ga11, Gb11... are rapidly heated to generate heat. Next, after a certain period of time (for example, 3 seconds), a timer (not shown) turns off the relays 2 and 12, switches the two-contact relay 3 or 13 to the normally open contact 3a or 13a side, and glow plugs Ga1, Gb1... or Ga11, Gb11, . . . are energized to obtain a temperature saturated state, and this operation is used as one cycle. Next, 2 contact relay 3
Or return 13 to normally closed contact 3b or 13b, turn on relay 2 or 12 again to start, and glow plugs Ga1, Gb1... or Ga11,
Gb11 causes rapid temperature rise and generates heat. After a certain period of time (for example, 3 seconds), a timer (not shown)
After turning off relay 2 or 12, then
The contact relay 4 or 14 is connected to this normally open contact 4a or 1.
Switch to 4a side, glow plugs Ga1, Gb1...
Alternatively, power is applied to Ga11, Gb11, . . . to obtain a temperature saturated state. And this is the next cycle. That is, in Examples 1 and 2, two polarities were switched during one cycle, but in this embodiment, the energization was controlled so that one polarity was switched in the first cycle and the other polarity was switched in the next cycle. (Example 6) Figure 5 shows the single-wire insulated glow plug described above.
Ga1, Gb1 . . . and Ga21, Gb21 . Figure 6 shows the above-mentioned double-wire glow plug Ga.
11, Gb11... and Ga31, Gb31..., and a heating resistance wire 52,
53 is buried and terminals 55 and 56 are provided. These glow plugs Ga1, Gb1..., Ga
11, Gb11..., Ga21, Gb21...Ga3
1, Gb31... is made by filling a mold with a mixed powder of silicon nitride (Si ₃ N ₄ ) and adding a sintering aid such as a group A element or an oxide of a group A element, and then placing the above-mentioned powder on top of it. A heat generating resistance wire (high melting point metal wire such as molybdenum or tungsten) 42 or 52, 53 is set up, and the mixed powder is filled thereon and then fired at high temperature and high pressure. The surface of the sintered body thus obtained is polished and the electrode terminals 43, 44, 55, 5
6 is exposed. In reality, electrodes are drawn out on the exposed surfaces of the terminals 43, 44, 55, 56 in FIGS. 5 and 6 through means such as metallization, plating, and brazing. The currently proposed double-wire glow plug has two heating wires buried inside a sintered body, and these wires are connected in series, requiring a total of three terminals: two terminals at both ends and one terminal in the center. There is. However, if the above two heating wires are connected in parallel and used as two terminals, a set of two glow plugs according to the present invention will be generated.
It can be easily applied when switching Ga and Gb from parallel to series, and the work of polishing and metalizing the electrodes on the surface of the sintered body of the glow plug itself can be omitted for one terminal, which improves workability and economy. It is advantageous. In this example, the energization control method of Examples 1 to 5 above is applied to a ceramic glow plug in which the above-mentioned heat-generating low-drag wire is embedded in the above-mentioned silicon nitride sintered body, and the temperature increase/decrease pattern shown in FIG. 7 is achieved. 1000,

【table】

[Table] (Example 7) Furthermore, Examples 3 and 4 in which the polarity was changed
Continuous energization tests were conducted for 300 hours at 1250°C using the single-double wire glow plugs shown in Figures 5 and 6, respectively. . These results are shown in Table 3.

[Table] (Comparative example) For glow plugs similar to those shown in Figures 5 and 6, only DC was applied without any polarity conversion or conversion to DC, and 1000,
A temperature increase test was conducted repeatedly for 2000, 3000, and 5000 cycles, and the occurrence of cracks in these cases was observed. These results are shown in Table 4. However, the number of samples is 20 for each, and the applied voltage is 7V in Figure 5 and 7V in Figure 6.
900℃ in about 3 seconds during rapid heating, maximum saturation temperature is approx.
The temperature is 1250℃.

[Table] As understood from the above examples and comparative examples,
Those that adopted the energization control method of Examples 1 to 5 and 7, that is, those that changed the polarity of the applied current during the repeated heating and cooling process, did not burn out even if the temperature was repeatedly raised to a high temperature (1250°C). While no cracks occurred in the compact, cracks occurred in a considerable number of samples after 5,000 cycles in the comparative example in which direct current was applied without changing the polarity. Also, in continuous current tests, the device of this invention did not cause any cracks at a high temperature of 1250°C, whereas the device with the conventional control method was prone to cracks. In addition, although molybdenum or tungsten was shown as the heating resistance wire in the above example,
In addition, it can also be used in a type of heater in which a paste of these high melting point metals is coated on a sintered body, baked, and then laminated. (Effects of the invention) As described above, according to the invention, at least one set of two glow plugs are provided, which are connected in parallel to the power supply at the initial stage of energization and in series at the time of temperature saturation.
Since alternating current is applied to the glow plug during the repeated process of increasing and decreasing the temperature from the initial stage of energization to temperature saturation or during continuous energization, the current is applied to the glow plug in an alternating manner during the repeated process of increasing and decreasing the temperature from the initial stage of energization to temperature saturation, or during continuous energization. Cracks occurring in the ceramic sintered body can be reduced, and the reliability and durability of the ceramic heater can be improved.

[Brief explanation of the drawing]

Figure 1 shows an energization control circuit in which the present invention is applied to a DC voltage applied single wire glow plug, Figure 2 shows an energization control circuit in which the present invention is applied to a DC voltage applied double wire glow plug, and Figure 3 shows a DC - An energization control circuit for a single-wire glow plug that applies an AC voltage, Figure 4 is an energization control circuit for a double-wire glow plug that applies a DC-AC voltage, and Figure 5 is a sectional view of a sintered body of a single-wire glow plug. The figure is a cross-sectional view of the sintered body of a duplex glow plug, Figure 7 is an explanatory diagram showing a comparison of the temperature increase/decrease pattern and the relay switching control timing chart, and Figure 8 is the rapid temperature increase/temperature of a general glow plug. It is a saturation characteristic diagram. 1, 11, 21, 31...DC current, 25, 3
5...Alternating current, 42,52,53...Heating wire,
Ga1, Ga2, Gb1, Gb2, Ga11, Ga12,
Gb11, Gb12, Ga21, Ga22, Gb21,
Gb22, Ga31, Ga32, Gb31, Gb32...
...Glow plug.

Claims (1)

[Claims for Utility Model Registration] 1. At least one set of two glow plugs connected to the power supply in parallel at the initial stage of energization and in series at temperature saturation, during one cycle from the initial stage of energization to temperature saturation. Alternatively, an energization control device for a ceramic glow plug, characterized in that an alternating current is applied to each of the glow plugs during multiple cycles over a long period of time or during continuous energization. 2. The energization control device for a ceramic glow plug according to claim 1, wherein neither of the two terminals of the ceramic glow plug are body grounded. 3. A utility model according to claims 1 and 2, characterized in that the ceramic glow plug has a plurality of heat generating wires, and these heat generating wires are connected in parallel and led out with two terminals. Electricity control device for ceramic glow plugs.