JP2006258417A - Ceramic heater and ceramic glow plug - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic heater and a ceramic glow plug capable of quickly raising the temperature, and capable of exhibiting excellent conductive durability at a low cost. <P>SOLUTION: A length occupied in the axial direction of a ceramic heater main body 2 of a resistor heating body 6' located inside a metallic outer cylinder 4 sheathing the ceramic heater main body 2 is set to be a length or more occupied in the axial direction of the ceramic heater main body 2 located outside the metallic outer cylinder 4. Further, the length of a heating section 7 is set to be 30 to 100% of the length occupied in the axial direction of the ceramic heater main body 2 of a resistor heating body 6" located outside the metallic outer cylinder 4. According to this arrangement, the resistor heating body demonstrates its self-control function, realizes a quick temperature rise, and increases a heating value to a maximum limit of an area of the heating section of the resistor heating body, so that the starting performance of an engine is improved by the ceramic glow plug which uses the ceramic heater. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a ceramic heater used for, for example, a ceramic glow plug mounted on a diesel engine, and a ceramic glow plug using the ceramic heater.

  Conventionally, as a ceramic heater such as a ceramic glow plug to be mounted on a diesel engine, a rod-shaped insulating ceramic heater body that sheathes a metal outer cylinder, and a metal or non-metal resistance heating element embedded in the ceramic heater body And what is comprised from the lead for electrode extraction is known. As a specific structure thereof, a temperature control resistor is interposed between a central shaft that holds one end of the ceramic glow plug in the metal shell and a lead coil that is connected to an electrode lead of the ceramic heater, The main shaft and the lead coil can be broadly divided into those directly connected.

  Among the above-mentioned conventional ceramic heaters, those having a temperature control resistor interposed between the lead shaft and the central shaft that holds one end in the metal shell are embedded by the interposed temperature control resistor. Rapid heating of the resistance heating element is possible, and sufficient heat generation for engine startability is possible. However, since the temperature control resistor needs to be built in the metal shell, the manufacturing cost increases, and there is a problem that the ceramic glow plug has to be expensive.

On the other hand, in the case where the central shaft and the lead coil connected to the electrode lead lead embedded in the ceramic heater body are directly connected, the rapid heating by the resistance heating element embedded in the ceramic heater body as described above. It cannot be expected. For this reason, the structure between the central shaft and the ceramic heater is simple, but in order to ensure sufficient engine startability in the ceramic glow plug using this ceramic heater, the following points must be considered. Don't be. That is, if it is intended to provide sufficient heat generation to enable rapid heating of the ceramic heater, it is conceivable that the saturation temperature of the resistance heating element is extremely increased or the applied voltage is controlled by the controller. However, if the saturation temperature of the resistance heating element embedded in the ceramic heater body is extremely high, the durability of the ceramic heater itself will be reduced, and if the applied voltage is controlled by the controller, the cost of the product as a whole due to its structure. There is a problem that increases significantly.
JP-A-9-190874

  Problems to be solved are an increase in manufacturing cost, a rapid increase in temperature due to the resistance heating element embedded in the ceramic heater body, and a decrease in durability of the ceramic heater itself.

For this purpose, the ceramic heater of the present invention is used for a ceramic glow plug, for example, and comprises a ceramic heater body made of an insulating ceramic covering a metal outer cylinder, and a resistance heat generation embedded in the ceramic heater body. It consists of a body and a lead for taking out an electrode. The resistance heating element embedded in the ceramic heater body forms a heating part outside the metal outer cylinder, and the heating part per unit length is more than twice that of the resistance heating element except for itself. The resistance value and the length occupied in the axial direction occupies 30 to 100% of the length occupied by the resistance heating element located outside the metal outer cylinder in the axial direction . occupy a length occupied in the axial direction of the ceramic heater body of the resistance heating element located in a metal outer tube to the exterior to the ceramic heater body, the axial direction of the ceramic heater body of the resistance heating element located outside the metallic outer cylinder not less than the length, there is and peak temperature of 1200 ° C. or more, and to have a self-regulating function of saturation below the peak temperature.

That is, in order to ensure good engine startability in a ceramic glow plug that uses this ceramic heater, the area of the heat generating portion of the resistance heating element located outside the metal outer cylinder is set to a rapid temperature rise in this heat generating portion. It is desirable to be the maximum within the range that allows Therefore, among the resistance heating elements embedded in the ceramic heater body, the length of the heating section in the axial direction of the ceramic heater body located outside the metal outer cylinder is the length of the resistance heating element in the axial direction. If it is 30% or less, partial temperature rise in the heat generating portion is possible, but the portion that becomes high temperature concentrates on a part, and the energization durability decreases. Further, the area of the heat generating portion is reduced, and the engine startability is also deteriorated. On the other hand, when the length is 100% or more, heat is generated also in the metal outer cylinder that is sheathed on the ceramic heater body. Therefore, the brazing material that joins the ceramic heater main body and the metal outer cylinder mounted on the ceramic heater main body may melt and disappear, leading to damage to the ceramic heater itself. Therefore, among the resistance heating elements embedded in the ceramic heater body, the length of the heating section in the axial direction of the ceramic heater body located outside the metal outer cylinder is the length of the resistance heating element located outside the metal outer cylinder. 30 to 100% of the length of the ceramic heater body in the axial direction. As a result, the area of the heat generating portion in the resistance heating element of the ceramic heater main body can be ensured to the maximum, and good engine startability of the ceramic glow plug using this ceramic heater can be ensured.

Furthermore, in the present invention, with respect to the resistance heating element embedded in the ceramic heater body, the length of the resistance heating element located in the metal outer cylinder in the axial direction of the ceramic heater body is outside the metal outer cylinder. If the resistance heating element is not longer than the length of the ceramic heater body in the axial direction, a sufficient self-control function cannot be exhibited. Also, the length of the resistance heating element positioned in the metal outer cylinder in the axial direction of the ceramic heater body is at least three times the length of the resistance heating element positioned outside the metal outer cylinder in the axial direction of the ceramic heater body. However, only a self-control function similar to that in the case of about twice can be exhibited. Therefore, a sufficient self-control function can be achieved by setting the length of the resistance heating element located inside the metal outer cylinder to be equal to or greater than the length of the resistance heating element located outside the metal outer cylinder in the axial direction of the ceramic heater body. Can be made. Therefore, when a voltage is applied to this ceramic heater, the resistance located in the metal outer cylinder that is externally mounted on the ceramic heater body during the latter stage of temperature rise at the heating portion of the resistance heating element located outside the metal outer cylinder. Temperature rise also occurs in the heating element. Then, the power consumption in this part increases, and the temperature control function similar to that of the temperature control resistor is achieved, so that the control by the controller and the saturation voltage can be performed without interposing the temperature control resistor. The temperature of the resistance heating element of the ceramic heater can be raised rapidly without being extremely high.

Therefore, as shown in FIG. 2, the resistance heating element positioned inside the metal outer cylinder occupies the length of the resistance heating element positioned outside the metal outer cylinder in the axial direction of the ceramic heater body. The case where the length ratio is 1 or more is referred to as “Graph 1”. Further, when the ratio is less than 1, the graph 2 shows the temperature rise of the ceramic heater, and when the ratio is less than 1, natural saturation occurs. On the other hand, when the ratio is 1 or more, the heating part of the resistance heating element from the edge of the metal outer cylinder to the tip of the ceramic heater body once raises the temperature to 1250 to 1280 ° C. Even in the resistance heating element located in the outer cylinder, the temperature rises and the power consumption increases. As a result, the amount of power supplied to the heat generating part is reduced, so that the temperature of the heat generating part is lowered to 1200 ° C. Therefore, the same result as that in which the temperature control resistor is interposed is shown, and the peak temperature is The temperature rises above the saturation temperature (for example, 1200 ° C.), and a rapid temperature increase is possible.

  As described above, since the present invention is configured, ceramics can be rapidly produced without exerting a temperature control resistor by exerting a sufficient self-control function, without excessively increasing the control or saturation voltage by the controller. The temperature of the resistance heating element of the heater can be raised. In addition, since the area of the heat generating part can be maximized, a ceramic glow plug using this ceramic heater can ensure good engine startability at a low cost and sufficiently improve its durability. It has an excellent effect that can.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  The present invention will be further described with reference to the embodiments shown in the drawings. (1) is a ceramic heater which is an embodiment of the present invention. The ceramic heater (1) includes a ceramic heater body (2) made of a rod-like insulating ceramic that covers a metal outer cylinder (4), and a metal or non-metal resistance embedded in the ceramic heater body (2). It consists of a heating element (6) and an electrode lead (8).

A resistance heating element (7) having a resistance value per unit length that is more than twice that of the other part and occupying in the axial direction of the ceramic heater body in the axial direction of the ceramic heater body (4) 6 ″) is set to 30 to 100% of the length of the ceramic heater body in the axial direction.

Furthermore, with respect to the resistance heating element (6) embedded in the ceramic heater body (2), the resistance heating element (6 ′) located in the metal outer cylinder (4) occupies in the axial direction of the ceramic heater body. The length is equal to or greater than the length of the resistance heating element (6 ″) located outside the metal outer cylinder (4) in the axial direction of the ceramic heater body.

The ceramic heater (1) which is an embodiment of the present invention has the above configuration. In order for the ceramic glow plug of the embodiment of the present invention to ensure good engine startability, the area of the heat generating portion (7) of the resistance heating element (6 ″) located outside the metal outer cylinder (4) is It is desirable that the maximum value be within a range that allows rapid temperature rise in the heat generating part (7), and therefore the heat generating part (7) among the resistance heat generating elements (6) embedded in the ceramic heater body (2). The length of the ceramic heater in the axial direction of the ceramic heater is 30 to 100% of the length of the resistance heating element (6 ″) positioned outside the metal outer cylinder (4) in the axial direction of the ceramic heater body. As a result, the area of the heat generating part (7) in the resistance heating element (6) of the ceramic heater body (2) can be secured to the maximum, so that the engine startability of the ceramic glow plug using the ceramic heater (1) is good. Can be ensured.

Furthermore , with respect to the resistance heating element (6) embedded in the ceramic heater body (2), the resistance heating element (6 ′) located in the metal outer cylinder (4) that is externally mounted on the ceramic heater body (2). The length of the ceramic heater body in the axial direction is equal to or greater than the length of the resistance heating element (6 ″) located outside the metal outer tube (4) in the axial direction of the ceramic heater body. Therefore, when a voltage is applied to the ceramic heater (1) according to the embodiment of the present invention, the resistance heating element (6) located outside the metal outer cylinder (4) is provided. The temperature rise also occurs in the resistance heating element (6 ′) located in the metal outer cylinder (4) in the late stage of the temperature rise when the peak temperature is 1200 ° C. or higher in the heating part (7) of “”). As a result, the power consumption increases and performs the same temperature control function as the temperature control resistor, and saturates at 1200 ° C. or below the peak temperature without interposing the temperature control resistor (see FIG. 2, graph 1). In addition, the resistance heating element (6) of the ceramic heater (1) can be rapidly heated without excessively increasing the control by the controller or the saturation voltage.

  Therefore, in order to confirm the temperature rise performance and energization durability in the ceramic heater which is an embodiment of the present invention, actual machine tests were conducted under various conditions, and the effects were compared. That is, A is the total length of the resistance heating element (6) embedded in the ceramic heater body (2) constituting the ceramic heater (1) in the axial direction of the ceramic heater body, and the outer metal outer cylinder (4). Let B be the length of the resistance heating element (6 ′) located inside the ceramic heater body in the axial direction. Further, the length of the resistance heating element (6 ″) located outside the metal outer cylinder (4) in the axial direction of the ceramic heater body is C, and in addition, per unit length of the resistance heating element (6 ″). Let D be the length in the axial direction of the ceramic heater body of the heat generating part (7) whose resistance value is at least twice that of the other parts. At that time, the resistance heating element (6 ″) located outside the metal outer cylinder (4) has a length within the metal outer cylinder (4) which is externally mounted on the ceramic heater body (2) with respect to the length of the ceramic heater body in the axial direction. The ratio of the length of the resistance heating element (6 ′) in the axial direction of the ceramic heater body is defined as B / C, and the metal outer cylinder with respect to the length of the heating part (7) in the axial direction of the ceramic heater body (4) The ratio C / D of the length of the resistance heating element (6 ″) located outside in the axial direction of the ceramic heater body is obtained. Among them, the temperature after the energization time of 5 seconds elapses in a product in which the length of the heat generating part (7) whose resistance value per unit length is more than twice that of the other part is changed and 1200 ° C is saturated. Is measured as temperature rise. Furthermore, an energization durability test was conducted to determine how many cycles the disconnection of the heat generating portion (7) occurs, with one cycle being the energization after the energization and heating at 1400 ° C. for 1 minute. By these, the effect of this invention was recognized notably (refer FIG. 3). The length of the resistance heating element (6 ″) located outside the metal outer cylinder (4) in the axial direction of the ceramic heater main body is within the ceramic heater main body (2) of the ceramic heater according to the embodiment of the present invention. This is related to the value of the embedded resistance heating element (6) However, the length value varies depending on the type of engine and the resistance heating element (6) is a metal coil, printing It can be applied regardless of a non-metallic heating element such as a non-metallic heating element or an injection molding.

  The present invention can be applied not only to a ceramic heater mainly used for a ceramic glow plug or the like mounted on a diesel engine, but also to a heating element for burner ignition or an oxygen sensor.

In the ceramic heater which is an Example of this invention, it is an expanded sectional view of what uses a metal coil as a resistance heating element. The length of the resistance heating element positioned in the axial direction of the ceramic heater body of the resistance heating element positioned outside the metal outer cylinder relative to the length of the resistance heating element positioned in the metal outer cylinder according to the embodiment of the present invention. It is a graph which shows the temperature rising state of a ceramic heater when the ratio of each is 1 or more and less than 1. The temperature rise property with respect to the ceramic heater which is an Example of this invention is shown, and the test result of the electricity supply durability is shown. (A) is an enlarged cross-sectional view of a ceramic heater according to another embodiment of the present invention, which is a resistance heating element by printing, and (b) is an enlarged cross-sectional view rotated 90 °. In the ceramic heater which is the other Example of this invention, it is an expanded sectional view of what becomes a resistance heating element by injection molding.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ceramic heater 2 Ceramic heater main body 3 Tip of (ceramic heater main body) 4 Metal outer cylinder 5 End edge of (metal outer cylinder) 6 Resistance heating element 6 'Resistance (located in the metal outer cylinder exterior to the ceramic heater main body) Heating element 6 "Resistance heating element (located outside the metal outer cylinder) 7 Heating part 8 Lead for electrode removal

Claims (3)

In a ceramic heater composed of a ceramic heater body made of an insulating ceramic covering a metal outer cylinder, a resistance heating element embedded in the ceramic heater body, and a lead for electrode extraction, the ceramic heater body is embedded in the ceramic heater body. The length of the resistance heating element in the axial direction of the ceramic heater body positioned in the metal outer cylinder that is externally mounted on the ceramic heater body with respect to the resistance heating element is the ceramic heater of the resistance heating element positioned outside the metal outer cylinder. A ceramic heater that is longer than the length of the main body in the axial direction. Of the resistance heating element embedded in the ceramic heater body made of an insulating ceramic that covers the metal outer cylinder, the metal outer cylinder of the heat generating part whose resistance value per unit length is more than twice that of other parts The ceramic heater according to claim 1, wherein a length of the ceramic heater body located outside in the axial direction is 30 to 100% of a length of the resistance heating element in the axial direction of the ceramic heater body. A ceramic glow plug comprising the ceramic heater according to claim 1.

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