JP2016020774A - Glow plug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the movement of the highest temperature part in a glow plug to a rear end side even if the motion of heat generation by electricity-carrying is repeated.SOLUTION: A glow plug comprises a sheath tube 810 and a power generation coil 820, and has a heater element 800 to which a tip of the sheath tube 810 and a tip of the power generation coil 820 are fused. When a resistance value between the forefront of the heater element 800 and a first position that is a position at 1 mm from the forefront of the power generation coil 820 up to a rear end side in an axial line direction is set as R1, a resistance value between the forefront and a second position that is a position at 3 mm from the forefront of the power generation coil 820 up to the rear end side in the axial line direction is set as R3, and a resistance value between the forefront and a third position that is a position at 6 mm from the forefront of the power generation coil 820 up to the rear end side in the axial line direction is set as R6, R1/R3 is not larger than 0.60, and R3/R6 is not smaller than 0.45.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a glow plug.

  As a heater provided in the glow plug, a heater element is known that includes a cylindrical sheath tube whose tip is closed, and a heating coil that is disposed in the sheath tube and generates heat when energized. In the heater element, generally, the tip of the heating coil is welded to the tip of the inner surface of the sheath tube (see, for example, Patent Document 1 and Patent Document 2).

JP 2001-330249 A JP 2013-152035 A

  When the glow plug is used as a heat source for assisting ignition at the start of an internal combustion engine such as a diesel engine, for example, the glow plug is disposed so that the tip portion thereof is exposed in the combustion chamber of the internal combustion engine. The glow plug functions as an auxiliary heat source for ignition of the internal combustion engine when the tip portion of the glow plug exposed in the combustion chamber becomes sufficiently high in temperature. Therefore, in the glow plug, it is desirable that the tip portion exposed in the combustion chamber has the highest temperature portion (the place where the temperature becomes highest), and it is desirable that the heat generation performance of the tip portion in the glow plug be maintained for a long time. . Conventionally, in the glow plug, it has been known that the highest temperature portion gradually moves to the rear end side when the operation of heat generation by energization is repeated. When the maximum temperature portion moves to the rear end side, the heating in the combustion chamber by the glow plug may be insufficient, leading to a decrease in performance of the glow plug as a heat source. For this reason, it has been desired to suppress the movement of the glow plug toward the rear end side even when the operation of heat generation by energization is repeated.

  The present invention has been made to solve the above-described problems, and can be realized as the following forms.

(1) According to one aspect of the present invention, it includes a cylindrical sheath tube extending in the axial direction and closed at the tip, and a heat generating coil housed in the sheath tube, the tip of the sheath tube A glow plug having a heater element welded to the tip of the heating coil is provided. The resistance value between the leading edge of the heater element and the first position that is 1 mm from the leading edge of the heating coil to the rear end side in the axial direction is R1, the leading edge, and the heating coil. R3 is a resistance value between the leading edge and the second position, which is a position of 3 mm from the leading edge to the trailing edge in the axial direction, and the leading edge of the heating coil from the leading edge in the axial direction. Assuming that the resistance value between the third position, which is 6 mm on the side, is R6, R1 / R3 is 0.60 or less, and R3 / R6 is 0.45 or more.
According to the glow plug of this form, the maximum temperature portion in the heater element is kept on the axis line even if the heat generation by the energization is repeated in the glow plug while the heat generation amount at the tip portion of the heater element related to the heating performance of the glow plug is ensured. It is possible to suppress the movement to the rear end side in the direction, and to suppress the performance deterioration of the glow plug.

(2) In the glow plug of the above aspect, the heating coil is formed in a spiral shape, and an average value of the coil pitch of the heating coil between the forefront of the heater element and the first position is: It is good also as being larger than the average value of the coil pitch of the said exothermic coil between the said 1st position and the said 2nd position.
According to the glow plug of this aspect, the average value of the coil pitch of the heat generating coil between the forefront of the heater element and the first position is set to the coil of the heat generating coil between the first position and the second position. By making it larger than the average value of the pitch, a glow plug having R1 / R3 of 0.60 or less can be easily realized.

(3) In the glow plug of the above aspect, the heating coil includes a spirally wound winding portion, and an extending portion that linearly extends from the tip of the winding portion toward the tip of the heater element. The boundary between the winding part and the extension part may be present on the tip side in the axial direction with respect to the first position.
According to the glow plug of this form, the boundary between the winding part and the extension part is located on the tip end side in the axial direction from the first position, so that the glow plug having R1 / R3 of 0.60 or less is obtained. It can be easily realized.

(4) In the glow plug of the above aspect, the sheath tube includes a straight portion formed in a cylindrical shape in which an outer diameter of a cross section perpendicular to the axial direction is constant over the axial direction, and the straight portion is more than the straight portion. A reduced diameter portion that is formed continuously with the straight portion on the distal end side in the axial direction and has a closed distal end while reducing its outer diameter toward the distal end side in the axial direction; The boundary between the wound portion and the extending portion may be present on the tip end side in the axial direction with respect to the boundary between the straight portion and the reduced diameter portion.
According to this form of the glow plug, even when the straight portion is formed by swaging when the heater element is manufactured, the heating coil is caused by the swaging of the boundary portion between the winding portion and the extension portion in the heating coil. Damage can be suppressed.

  The present invention can be realized in various forms other than those described above. For example, the present invention can be realized in a form such as a glow plug manufacturing method, a glow plug heater element, and a heater element manufacturing method.

It is explanatory drawing which shows a glow plug. It is explanatory drawing which shows the detailed structure of a heater element. It is explanatory drawing which expands and shows the structure of the front-end | tip part of a heater element. It is process drawing which shows the manufacturing method of a glow plug. It is explanatory drawing which shows the structure of the front-end | tip part of a heater element. It is explanatory drawing which shows collectively the value and evaluation result of "R1 / R3" and "R3 / R6" in each sample.

A. First embodiment:
(A-1) Overall configuration of glow plug:
FIG. 1 is an explanatory view showing a glow plug 10 as a first embodiment of the present invention. The glow plug 10 of this embodiment functions as a heat source that assists ignition at the time of starting an internal combustion engine such as a diesel engine. As shown in FIG. 1, the glow plug 10 includes a heater element 800 that generates heat when energized, a metal shell 500, and a central shaft 200 as main components. In FIG. 1, the appearance configuration is illustrated on the right side of the drawing from the axis O of the glow plug 10, and the cross-sectional configuration is illustrated on the left side of the drawing from the axis O. In the present specification, the heater element 800 side along the axis O in the glow plug 10 is referred to as “front end side”, and the middle shaft 200 side is referred to as “rear end side”.

  The metal shell 500 is a member obtained by forming carbon steel into a cylindrical shape. The metal shell 500 holds the heater element 800 at the end on the front end side. The metal shell 500 holds the central shaft 200 via the insulating member 410 and the O-ring 460 at the end on the rear end side. The position of the insulating member 410 in the direction of the axis O is fixed by crimping the ring 300 in contact with the rear end of the insulating member 410 to the middle shaft 200. By this insulating member 410, the metal shell 500 and the middle shaft 200 are electrically insulated. The metal shell 500 includes a portion of the central shaft 200 that extends from the insulating member 410 to the heater element 800. The metal shell 500 includes a tool engaging portion 520 and a male screw portion 540, and a shaft hole 510 is formed therein.

  The tool engaging portion 520 engages with a tool (not shown) used for attaching and removing the glow plug 10. The male screw portion 540 is fitted to a female screw formed in an internal combustion engine (not shown). The shaft hole 510 is a through-hole formed along the axis O and has an inner diameter larger than the outer diameter of the middle shaft 200. In a state where the middle shaft 200 is positioned in the shaft hole 510, a gap is formed between the shaft hole 510 and the middle shaft 200 to electrically insulate them. A heater element 800 is press-fitted and joined to the distal end side of the shaft hole 510.

  The middle shaft 200 is a member obtained by forming a conductive material into a cylindrical shape. The middle shaft 200 is inserted into the shaft hole 510 of the metal shell 500 and assembled along the axis O. The middle shaft 200 includes a middle shaft front end portion 210 formed on the front end side and a connection portion 290 provided on the rear end side. The middle shaft tip 210 is inserted into the heater element 800. The connection part 290 protrudes from the metal shell 500. The engaging member 100 is fitted in the connecting portion 290.

(A-2) Configuration of heater element:
FIG. 2 is an explanatory diagram showing a detailed configuration of the heater element 800. The heater element 800 includes a sheath tube 810, a heating coil 820 as a heating element, a control coil 830, and insulating powder 840. In FIG. 2, the sheath tube 810 shows a cross section, and the heating coil 820 and the control coil 830 show the appearance.

  The sheath tube 810 is a cylindrical member that extends in the direction of the axis O and has a closed end, and is made of, for example, stainless steel. As shown in FIG. 2, the sheath tube 810 includes a straight portion 860 having a constant outer diameter in a transverse section (cross section perpendicular to the axis O) in the direction of the axis O, and a straight portion 860 closer to the distal end than the straight portion 860. And a reduced diameter portion 865 formed so as to gradually reduce the diameter continuously. The outer diameter of the sheath tube 810 can be set to 3 to 7 mm, for example. Moreover, the thickness of the sheath tube 810 can be 0.3-0.6 mm, for example.

  Inside the sheath tube 810, a heating coil 820, a control coil 830, and an insulating powder 840 are arranged. FIG. 2 shows the sheath tube tip 811 and the sheath tube rear end 819 in the sheath tube 810. The sheath tube most distal end 811 is an end portion of a portion of the sheath tube 810 that is formed in a round shape toward the outside while being gradually reduced in diameter toward the distal end side. The sheath tube rear end portion 819 is an end portion opened on the rear end side of the sheath tube 810. The distal end side of the central shaft 200 is inserted into the sheath tube 810 from the sheath tube rear end 819. The sheath tube 810 is electrically insulated from the middle shaft 200 by the packing 600 and the insulating powder 840. The packing 600 is an insulating member sandwiched between the middle shaft 200 and the sheath tube 810. The sheath tube 810 is electrically connected to the metal shell 500.

  The heating coil 820 is a spiral coil made of a conductive material. The heating coil 820 is disposed along the axis O direction inside the sheath tube 810 and generates heat when energized. The heat generating coil 820 includes a heat generating coil front end portion 821 that is an end portion on the front end side, and a heat generating coil rear end portion 829 that is an end portion on the rear end side. By welding the distal end portion of the heating coil 820 to the sheath tube 810, a melted portion formed by melting the heating coil 820 and the sheath tube 810 is formed near the distal end of the sheath tube 810. Is electrically connected to the sheath tube 810. The heating coil tip 821 corresponds to the boundary between the heating coil 820 and the melting part. The wire diameter of the heating coil 820 can be set to 0.2 to 0.5 mm, for example.

  The control coil 830 is disposed on the rear end side of the heating coil 820 and is formed of a conductive material (for example, an alloy containing cobalt or nickel as a main component) having a higher temperature coefficient of electrical resistivity than the material forming the heating coil 820. Spiral coil. The control coil 830 controls the power supplied to the heat generating coil 820. The control coil 830 includes a control coil front end portion 831 that is an end portion on the front end side, and a control coil rear end portion 839 that is an end portion on the rear end side. The front end 831 of the control coil is electrically connected to the heat generating coil 820 by being welded to the heat generating coil rear end 829. The control coil rear end portion 839 is electrically connected to the middle shaft 200 by being joined to the middle shaft tip portion 210.

  The insulating powder 840 is a powder having electrical insulating properties. As the insulating powder 840, for example, a powder of magnesium oxide (MgO) can be used. The insulating powder 840 is filled inside the sheath tube 810 and electrically insulates a gap between the sheath tube 810, the heating coil 820, the control coil 830, and the central shaft 200.

(A-3) Configuration of the tip of the heater element:
FIG. 3 is an explanatory diagram showing an enlarged structure of the tip portion of the heater element 800. In FIG. 3, the sheath tube 810 shows a cross section including the center line of the heater element 800 in the direction of the axis O, and the heating coil 820 shows its appearance. In the present embodiment, the center line of the heater element 800 coincides with the axis O of the glow plug 10.

  In FIG. 3, the position of the sheath tube tip 811 with respect to the direction of the axis O is indicated by a broken line α0. The sheath tube tip 811 is specified as an intersection of a portion representing the outer surface of the sheath tube 810 (hereinafter referred to as an outer surface line) and the center line in a cross section including the center line in the axis O direction of the heater element 800. The sheath tube leading edge 811 corresponds to “the leading edge of the heater element” in the means for solving the problem. Further, in FIG. 3, a position 1 mm away from the sheath tube leading edge 811 toward the rear end side in the axis O direction is indicated by a broken line α1, and a position 3 mm away from the sheath tube leading edge 811 toward the rear end side in the axis O direction is indicated by a broken line α3. A position 6 mm away from the sheath tube distal end 811 toward the rear end side in the axis O direction is indicated by a broken line α6.

  In FIG. 3, the resistance value between the sheath tube tip 811 and the position 1 mm from the sheath tube tip 811 in the heating coil 820 to the rear end side in the axis O direction (position overlapping the broken line α1) is R1, and the sheath tube The resistance value between the leading edge 811 and the position 3 mm on the rear end side in the axis O direction from the sheath tube leading edge 811 in the heating coil 820 (the position overlapping the broken line α3) is R3, the sheath tube leading edge 811 and the heat generation A resistance value between a position 6 mm (position overlapping the broken line α6) on the rear end side in the axis O direction from the sheath tube distal end 811 in the coil 820 is R6. At this time, in the heater element 800 of the present embodiment, R1 / R3 is 0.60 or less, and R3 / R6 is 0.45 or more.

  The conditions relating to the resistance values R1, R3, and R6 described above are conditions that are satisfied by the glow plug before use (before starting the operation of heat generation by energization). Further, the position of 1 mm from the sheath tube leading edge 811 to the rear end side in the direction of the axis O corresponds to the “first position” in the means for solving the problem of the present application. The position of 3 mm on the rear end side in the O direction corresponds to the “second position” in the means for solving the problem of the present application, and the position of 6 mm on the rear end side in the axis O direction from the sheath tube distal end 811 is This corresponds to the “third position” in the means for solving the problem of the present application.

  The resistance values R1, R3, and R6 in the heater element 800 can be obtained as follows. First, a part of the sheath tube 810 included in the heater element 800 is removed by a file along the axis O direction, and a part of the insulating powder 840 is further removed to expose the heating coil 820. Then, the resistance value between the sheath tube tip 811 and a plurality of arbitrary measurement points on the exposed heating coil 820 is measured.

  In FIG. 3, the measurement point M is shown as an example of the measurement point. In FIG. 3, the measurement point M is a point on the center line of the metal wire (element wire) constituting the heating coil 820, and is represented as a point that overlaps the axis O in the side view shown in FIG. 3. Yes. Further, in FIG. 3, the position of the measurement point M with respect to the direction of the axis O is represented by a broken line β1 perpendicular to the axis O, and the resistance value between the sheath tube tip 811 and the measurement point M is represented by Rm. .

  As described above, the resistance value between the sheath tube tip 811 is measured at least five measurement points M in the range from the sheath tube tip 811 to 6 mm on the rear end side in the axis O direction. The resistance value may be measured while measuring the position by enlarging the heater element 800 by 20 times using a projector (for example, a universal projector manufactured by Nikon Corporation). Then, the relationship between the distance from the sheath tube leading edge 811 (the distance between the broken line α0 and the broken line β1) and the resistance value (resistance value Rm) between the sheath tube leading edge 811 is 2 by the least square method. Approximate next. The resistance values R1, R3, and R6 described above are derived using the quadratic expression obtained by the quadratic approximation. In this way, in the exposed heat generating coil 820, the resistance values R1, R3, and R6 can be set even if the positions of 1 mm, 3 mm, and 6 mm are not exposed from the sheath tube distal end 811 to the rear end side in the axis O direction. Can be sought. A specific configuration of the heater element 800 that satisfies the conditions relating to the resistance values R1, R3, and R6 described above will be described in detail below.

  The heat generating coil 820 of this embodiment includes a winding portion 870 that is wound in a spiral shape, and a linear shape in the direction of the axis O without winding from the tip of the winding portion 870 toward the tip of the heater element 800. And an extending portion 875 that extends. Thus, by providing the extending portion 875 having a lower resistance value per unit length in the direction of the axis O than the winding portion 870 at the distal end portion of the heating coil 820, “R1 / R3 is 0.60 or less” It becomes easy to satisfy the conditions. The length of the extending portion 875 in the direction of the axis O to satisfy the condition of “R1 / R3 is 0.60 or less” is the material of the heating coil 820 and the sheath tube 810, the wire diameter of the heating coil 820, and the winding portion 870. What is necessary is just to set suitably according to the shape (wire diameter, coil pitch, etc.). In addition, the coil pitch of the winding part 870 is the distance between the adjacent parts in the direction of the axis O in the wire constituting the winding part 870 of the heating coil 820, and is the center of each adjacent wire part. The distance in the axis O direction between the lines. In FIG. 3, the center line of the adjacent wire portion described above is indicated by a broken line, and an example of the coil pitch of the winding portion 870 (distance between the center lines) is indicated as the coil pitch p.

  As shown in FIG. 3, in the present embodiment, the entire extending portion 875 exists in a range (between the broken line α0 and the broken line α1) from the sheath tube distal end 811 to the rear end side in the axis O direction up to 1 mm. That is, the boundary between the winding portion 870 and the extending portion 875 exists on the distal end side in the axis O direction from the position 1 mm (position of the broken line α1) on the rear end side in the axis O direction from the sheath tube distal end 811. In FIG. 3, the position of the boundary between the winding part 870 and the extending part 875 with respect to the direction of the axis O is indicated by a broken line β2. However, the boundary between the winding part 870 and the extending part 875 may be on the broken line α1, and the extending part 875 may be provided so as to extend further to the rear end side in the axis O direction than the broken line α1, It is only necessary to satisfy the condition “R1 / R3 is 0.60 or less”. As described above, the resistance value R1 is also measured at a plurality of measurement points on the winding portion 870, as described above, even when the extending portion 875 is formed extending from the broken line α1 to the rear end side in the axis O direction. What is necessary is just to obtain | require based on the result of secondary approximation using the measured resistance value.

  The boundary between the winding part 870 and the extension part 875 can be specified as follows. That is, when the heat generating coil 820 is projected onto a plane parallel to the axis O, it is defined by a plane perpendicular to the axis O, including the inflection point of the portion where the center line of the wire constituting the heat generating coil 820 is bent. The position can be specified as the boundary between the winding part 870 and the extension part 875.

  In the present embodiment, the condition “R3 / R6 is 0.45 or more” is that the coil pitch of the winding part 870 in the range from the broken line α1 to the broken line α3 is the winding pitch 870 in the range from the broken line α3 to the broken line α6. This is realized by making it smaller than the coil pitch. That is, in the winding part 870, the resistance value per unit length in the direction of the axis O in the range from the broken line α1 to the broken line α3, and the resistance value per unit length in the direction of the axis O in the range from the broken line α3 to the broken line α6. It is realized by raising it. The coil pitch in the winding part 870 for satisfying the condition “R3 / R6 is 0.45 or more” depends on the material of the heating coil 820 and the sheath tube 810, the wire diameter of the heating coil 820, and the length of the extension part 875. Accordingly, it may be set appropriately.

  In the present specification, the coil pitch in the predetermined range refers to the average value of the coil pitch in the predetermined range. The average value of the coil pitch is a value obtained by dividing the length of the predetermined range in the direction of the axis O by the number of turns of the heating coil 820 in the predetermined range. For example, the coil pitch of the winding portion 870 in the range from the broken line α1 to the broken line α3 is 2 mm, which is the length in the direction of the axis O in the range from the broken line α1 to the broken line α3, in the range from the broken line α1 to the broken line α3. It is a value divided by the number of turns of the winding part 870.

  The number of turns of the heating coil 820 in the predetermined range can be obtained as follows. For example, in the heating coil 820, when the end portion on the tip side of the predetermined range is set as the start point, the number of portions overlapping the start point in the axial direction in the predetermined range may be counted. At this time, in the predetermined range, the most rear end portion (rear end side integer point) of the start point and the axial direction overlaps with the rear end side end point (end point) of the predetermined range. In such a case, the number of turns in the predetermined range is not an integer. In this case, based on the shape (fractional part shape) of the heating coil 820 from the rear end side integer point to the end point, from the rear end side integer point to the position of one turn, the end point to the rear end Just draw a virtual coil to the side. And what is necessary is just to let the ratio of the fraction part shape which occupies for the last one volume containing a virtual coil be the number of turns of the part of a rear end side rather than the said rear end side integer point.

(A-4) Glow plug manufacturing method:
FIG. 4 is a process diagram showing a method for manufacturing the glow plug 10 of the present embodiment. When manufacturing the glow plug 10, first, the sheath tube 810 and the heating coil 820 are prepared (step S100). Thereafter, the heating coil 820 and the like are arranged in the sheath tube 810, and the heater element 800 is assembled (step S110).

  The sheath tube 810 prepared in step S100 has an opening at the tip, and is formed into a shape that gradually decreases in diameter toward the opening. Such a sheath tube 810 is formed by, for example, rolling a plate material into a cylindrical shape and arc welding, or by deep drawing the plate material to produce a cylindrical member, and subjecting the obtained cylindrical member to a drawing end. Can be obtained. Further, the heat generating coil 820 prepared in step S100 has a portion that becomes the extending portion 875 at the tip portion and that extends in the direction of the axis O without being wound.

  When assembling the heater element 800 in step S110, first, the control coil 830 is welded to the heating coil 820 prepared in step S100, and the control coil rear end 839 and the middle shaft front end portion 210 of the middle shaft 200 are joined. (See FIG. 2). Then, the heating coil 820 integrated with the central shaft 200 and the control coil 830 is inserted into the sheath tube 810 prepared in step S100, the distal end portion of the heating coil 820 and the distal end portion of the sheath tube 810 are welded, and the sheath The tip of the tube 810 is closed. The welding can be, for example, arc welding. After welding, the sheath tube 810 is filled with insulating powder 840 to complete the assembly of the heater element 800.

  After the assembly of the heater element 800, swaging processing is performed on the heater element 800 (step S120). The swaging process is a process of applying a striking force to the heater element 800 to reduce the diameter of the heater element 800 and densify the insulating powder 840 filled in the sheath tube 810. The swaging apparatus used for the swaging process includes a plurality of swaging dies arranged radially along the outer periphery of the heater element 800, and these swaging dies are used to radially inward the heater element 800. Add the striking force to go. When a striking force is applied to the heater element along with the swaging, the striking force is transmitted to the inside of the heater element 800, whereby the insulating powder 840 is densified. Further, when the striking force is transmitted, in the heating coil 820 (and the control coil 830), a change occurs in which the outer diameter of the coil is reduced, the wire diameter is increased, and the coil pitch is increased.

  In the heater element 800, the straight portion 860 is a region where a striking force from a swaging die is applied. Further, the reduced diameter portion 865 has an outer diameter smaller than the outer diameter of the straight portion 860 after the swaging from before the swaging process, and the striking force from the swaging die is not applied. It is. Therefore, in the heating coil 820, the portion on the rear end side in the axis O direction from the boundary between the straight portion 860 and the reduced diameter portion 865 becomes smaller in coil outer diameter, larger in wire diameter, and coil pitch by swaging. Becomes wider.

  In the present embodiment, the boundary between the straight portion 860 and the reduced diameter portion 865 coincides with a position (broken line α1) that is 1 mm away from the sheath tube distal end 811 toward the rear end side in the axis O direction. However, the boundary may not be the same as the broken line α1. The boundary between the straight portion 860 and the reduced diameter portion 865 can be specified as follows. That is, in order to specify the boundary between the straight portion 860 and the reduced diameter portion 865, first, the sheath tube 810 is enlarged 50 times using a projector in the orientation shown in FIG. The outer diameter (tube diameter) of the sheath tube 810 is measured at intervals of 0.05 mm in the direction. [(Tube diameter at the position of X mm from the tip to the axis O direction) − (Tube diameter at the position of (X−0.05) mm from the tip to the axis O direction)] was initially 0.02 mm or less. A point on the outer periphery of the sheath tube 810 at the position X is defined as the boundary.

  Here, in the periphery of the region where the striking force from the swaging die is applied, specifically, a position 2 to 3 mm (dashed line α1) from the boundary between the straight portion 860 and the reduced diameter portion 865 to the rear end side in the axis O direction. To the vicinity of the broken line α3), the applied striking force is smaller than the other area on the rear end side of the straight portion 860. Therefore, in the heating coil 820, in the range from the broken line α1 to the vicinity of the broken line α3, the spread of the coil pitch is suppressed and the coil wire diameter is thicker than the portion closer to the rear end side in the axis O direction than the broken line α3. It can be suppressed.

  In the present embodiment, as described above, in the heating coil 820, the coil pitch in the range from the broken line α1 to the broken line α3 is made smaller than the coil pitch in the range from the broken line α3 to the broken line α6, thereby obtaining “R3 / R6. Is 0.45 or more ". In order to form the heat generating coil 820 in such a shape, the coil pitch of the portion corresponding to the range from the broken line α1 to the broken line α3 is previously formed smaller than the coil pitch of the portion corresponding to the range from the broken line α3 to the broken line α6. A method of preparing the generated heating coil 820 in step S100 is conceivable.

  Alternatively, a method using the deformation of the heating coil 820 accompanying the swaging process in step S120 is also conceivable. Specifically, in step S100, a heating coil 820 having a uniform coil pitch over the entire portion corresponding to the range from the broken line α1 to the broken line α6 is prepared. Then, in the swaging process in step S120, the coil pitch in the range from the broken line α1 to the broken line α3 is set in the heating coil 820 by using the relatively small impact force applied in the range from the broken line α1 to the vicinity of α3. The coil pitch may be smaller than the coil pitch in the range from the broken line α3 to the broken line α6. The heater element 800 finally obtained through the swaging process only needs to satisfy the condition of “R3 / R6 is 0.45 or more”.

  After the swaging process, a member including the heater element 800 and the metal shell 500 is assembled (step S130), and the glow plug 10 is completed. Specifically, the heater element 800 in which the middle shaft 200 is integrated is press-fitted into the shaft hole 510 of the metal shell 500 and fixed, and the O-ring 460 and the insulating member 410 are attached to the middle shaft 200 at the rear end portion of the metal shell 500. And the engaging member 100 is fastened to the connecting portion 290 of the central shaft 200 provided at the rear end of the metal shell 500. In step S130, the glow plug 10 is subjected to an aging process. Specifically, the heater element 800 is heated by energizing the assembled glow plug 10 to form an oxide film on the outer surface of the heater element 800.

  According to the glow plug 10 of the present embodiment configured as described above, by satisfying “R1 / R3 is 0.60 or less” in the heater element 800, the resistance value in the most distal portion including the sheath tube most distal portion 811 is satisfied. Is kept low. Therefore, even when the glow plug 10 repeatedly generates heat by energization, the maximum temperature portion of the heater element 800 can be prevented from moving to the rear end side in the axis O direction, and the performance degradation of the glow plug 10 can be suppressed. Further, by satisfying the condition of “R3 / R6 is 0.45 or more” in the heater element 800, the heat generation amount at the tip portion of the heater element 800 related to the heating performance of the glow plug is secured, and the performance of the glow plug is secured. can do. The position of the highest temperature portion in the heater element 800 can be specified by measuring the temperature of the heater element 800 using, for example, a radiation thermometer.

  The reason why the effect of suppressing the maximum temperature portion of the heater element 800 from moving to the rear end side in the axis O direction can be obtained by satisfying “R1 / R3 is 0.60 or less” is as follows. The inventors of the present application have examined the glow plug in which the highest temperature portion has moved to the rear end side after repeating the operation of heat generation by energization. As a result, in the heating coil, a portion in the vicinity of the heating coil tip portion 821 (the heating coil tip portion 821). To the range of one coil), metal components constituting the sheath tube were detected (data not shown). This is because when the operation of energizing the glow plug is repeated, the temperature in the vicinity of the tip of the heater element 800 rises, and the region including the heating coil tip 821 softens, melts, and expands. This is considered to indicate that a portion separated from the heating coil tip 821 and a tip portion of the sheath tube (a melted portion formed by welding the heating coil and the sheath tube) are in contact with each other. As described above, when the region including the heating coil tip 821 is softened / melted / expanded, the tip of the heating coil 820 comes into contact with the melted portion formed at the sheath tube tip (the tip of the heating coil 820 is shortened). ), The amount of heat generated at the tip of the heating coil decreases with a decrease in the resistance value at the tip of the heating coil 820, and the maximum temperature portion is considered to move toward the rear end side in the axis O direction. According to this embodiment, the resistance value in a specific range including the heating coil tip 821 is reduced to suppress heat generation, so that the tip of the heating coil 820 is separated from the heating coil tip 821 and the melting portion. It is considered that the contact of the heat generation coil 820 can be suppressed and the retreat of the maximum temperature portion in the heating coil 820 can be suppressed.

  In particular, in the present embodiment, the extension portion 875 is provided at the distal end of the heating coil 820, and a simple configuration in which a portion that is not wound around the distal end of the heating coil 820 is provided makes it easier for “R1 / R3 to be 0.00. The condition “60 or less” can be satisfied. Further, by providing an extension 875 at the tip of the heating coil 820, the winding portion 870 is physically separated from the melting portion formed in the sheath tube 810 and the winding portion 870 of the heating coil 820. The effect which suppresses that it contacts with a fusion | melting part can be heightened.

  Further, according to the present embodiment, in the heating coil 820, the boundary between the winding part 870 and the extension part 875 (position of the broken line β2) is 1 mm away from the sheath tube tip 811 toward the rear end side in the axis O direction. It is formed closer to the tip side in the direction of the axis O than (the position of the broken line α1). Therefore, the resistance value (resistance value R1) in the range from the sheath tube leading edge 811 to the rear end side in the axis O direction in the heating coil 820 is reduced to 1 mm, and the sheath tube leading end 811 is moved from the sheath tube leading edge 811 to the rear end side in the axis O direction. It becomes possible to secure a resistance value in a range (between the broken line α1 and the broken line α3) from the position of 1 mm to the position of 3 mm. Therefore, it becomes easy to ensure a sufficiently large resistance value R3.

  Furthermore, according to the present embodiment, the position of the boundary (broken line β2) between the extending portion 875 and the winding portion 870 in the heating coil 820 is more axial than the boundary (broken line α1) between the straight portion 860 and the reduced diameter portion 865. It is formed on the tip side in the O direction. Therefore, it is possible to suppress the impact force from being transmitted to the boundary between the extending portion 875 and the winding portion 870 of the heating coil 820 during the swaging process in step S120. The part including the boundary is a part having a relatively low strength. However, by suppressing the impact force during swaging, damage to the heating coil 820 caused by swaging is suppressed, and the durability of the glow plug 10 is reduced. Can be suppressed. If the striking force applied during swaging is within an allowable range, the boundary between the extending portion 875 and the winding portion 870 in the heating coil 820 is relative to the boundary between the straight portion 860 and the reduced diameter portion 865 and the axis O direction. It may exist on the rear end side in the axis O direction from the overlapping position or the boundary between the straight portion 860 and the reduced diameter portion 865.

  As described above, in the present embodiment, by satisfying the conditions of “R1 / R3 is 0.60 or less” and “R3 / R6 is 0.45 or more”, in the heater element 800, between the broken line α0 and the broken line α1. While suppressing heat generation, heat generation between the broken line α1 and the broken line α3 is secured. Thereby, in heater element 800, it becomes possible to keep a state where there is the highest temperature part with the highest temperature in heater element 800 between broken line α1 and broken line α3.

  In the heater element 800, even if the position where the highest temperature portion is located moves from the sheath tube leading edge 811 to the rear end side in the direction of the axis O toward the rear end side from the position of 3 mm (broken line α3), the highest temperature portion. If it protrudes into the combustion chamber of the internal combustion engine, the performance of the glow plug does not deteriorate immediately. However, in general, the glow plug is used in such a manner that the tip of the heater element 800 protrudes 3 mm or more into the combustion chamber. Therefore, as in the present embodiment, the state in which the highest temperature portion of the heater element 800 is between the broken line α1 and the broken line α3 can be maintained for a long time, so that the flow into the combustion chamber determined according to the usage mode of each glow plug can be maintained. Regardless of the protrusion amount of the heater element 800, the performance of the glow plug can be maintained longer.

  Further, according to the present embodiment, the glow tube is determined based on whether or not the highest temperature portion of the heater element 800 exists from the sheath tube most distal end 811 to a position of 3 mm (broken line α3) on the rear end side in the axis O direction. It becomes possible to evaluate the performance of the plug. Therefore, regardless of the amount of projection of the heater element 800 into the combustion chamber determined according to the usage mode of each glow plug, even if the type of the glow plug is different, the performance of the glow plug is determined according to the common simple standard described above. Can be evaluated.

B. Second embodiment:
FIG. 5 is an explanatory view showing the structure of the tip of the heater element 1800 provided in the glow plug according to the second embodiment of the present invention in the same manner as FIG. In the second embodiment, parts that are the same as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  The heater element 1800 of the second embodiment is common to the heater element 800 of the first embodiment in that the conditions of “R1 / R3 is 0.60 or less” and “R3 / R6 is 0.45 or more” are satisfied. doing. However, the heating coil 1820 of the heater element 1800 does not have the extending portion 875, and satisfies the above condition by changing the coil pitch for each region.

  Specifically, the coil pitch of the heating coil 1820 in the range from the broken line α0 to the broken line α1 is made larger than the coil pitch of the heating coil 1820 in the range from the broken line α1 to the broken line α3. As a result, in the heating coil 1820, the resistance value per unit length in the direction of the axis O in the range from the broken line α0 to the broken line α1 is the resistance value per unit length in the direction of the axis O in the range from the broken line α1 to the broken line α3. Smaller than that. As a result, “R1 / R3 is 0.60 or less” is realized. Further, the coil pitch of the heating coil 1820 in the range from the broken line α1 to the broken line α3 is made smaller than the coil pitch of the heating coil 1820 in the range from the broken line α3 to the broken line α6. As a result, in the heating coil 1820, the resistance value per unit length in the direction of the axis O in the range from the broken line α1 to the broken line α3, and the resistance value per unit length in the direction of the axis O in the range from the broken line α3 to the broken line α6. Is bigger than. Thereby, “R3 / R6 is 0.45 or more” is realized. The coil pitch for each region in the heating coil 1820 for satisfying the conditions of “R1 / R3 is 0.60 or less” and “R3 / R6 is 0.45 or more” is the material of the heating coil 1820 and the sheath tube 810, and the heating. What is necessary is just to set suitably according to the wire diameter of the coil 1820. FIG.

  As described above, the coil pitch in the predetermined range refers to the average value of the coil pitch in the predetermined range. Further, as described above, the resistance values R1, R3, and R6 are the resistance values between the sheath tube tip 811 and at least five measurement points in the range from the sheath tube tip 811 to 6 mm. Measurement is performed, and the relationship between the distance from the sheath tube tip 811 to the measurement point and the resistance value between the sheath tube tip 811 and the measurement point is obtained based on the result of quadratic approximation by the least square method.

  In order to manufacture a glow plug including the heating coil 1820 having a different coil pitch for each region, a heating coil having a different coil pitch for each region may be prepared in step S100 in FIG. Specifically, it is only necessary to prepare a heating coil in which the coil pitch in the portion corresponding to the range from the broken line α0 to the broken line α1 is larger than the coil pitch in the portion corresponding to the range from the broken line α1 to the broken line α3. Further, it is only necessary to prepare a heating coil in which the coil pitch in the portion corresponding to the range from the broken line α1 to the broken line α3 is smaller than the coil pitch in the portion corresponding to the range from the broken line α3 to the broken line α6.

  Further, in order to make the coil pitch in the range from the broken line α1 to the broken line α3 smaller than the coil pitch in the range from the broken line α3 to the broken line α6, the deformation of the heating coil 1820 accompanying the swaging process in step S120 can be used. . As described above, in the range from the broken line α1 to the vicinity of α3, the striking force applied during swaging is smaller than the broken line α3 compared to the rear end side in the axis O direction. For example, in step S100, a heating coil having a coil pitch of the heating coil in the range from the broken line α0 to α1 larger than that of the other part and having a uniform coil pitch in the other part is prepared in step S100. It is also possible to obtain a heater element 1800 that satisfies the conditions of “0.60 or less” and “R3 / R6 is 0.45 or more”. In the heat generating coil prepared in step S100, the coil pitch in the range from the broken line α0 to α1 is further increased in consideration of the fact that the coil pitch becomes wider due to swaging at the portion on the rear end side in the axis O direction than the broken line α1. It should be wide.

  Even in such a configuration, the same effect as the first embodiment can be obtained by satisfying the conditions of “R1 / R3 is 0.60 or less” and “R3 / R6 is 0.45 or more”. In addition, in the heating coil 1820, the coil pitch in the region including the heating coil tip 821 is made larger, so that the portion of the heating coil 1820 around which the wire is wound and the melted portion of the sheath tube 810 are physically present. A sufficient distance can be secured to prevent the tip portion of the heating coil 1820 from coming into contact with the melted portion. Therefore, the effect of suppressing the retreat of the maximum temperature portion in the heating coil 1820 can be enhanced.

C. Variation:
Modification 1 (deformation of heating coil):
In order to satisfy the conditions of “R1 / R3 is 0.60 or less” and “R3 / R6 is 0.45 or more” in the heater element, a configuration different from the above embodiments may be adopted. In addition to the configuration in which the extending portion 875 is provided at the tip of the heating coil and / or the coil pitch is changed for each heating coil region, or in addition to the above configuration, for example, the heating coil is configured by the portion of the heating coil The composition of the material to be used may be different. Or it is good also as changing the wire diameter of the strand which comprises a heat generating coil with the site | part of a heat generating coil.

Modification 2 (sheath tube deformation):
In each of the above embodiments, the sheath tube is formed with the reduced diameter portion 865 at the distal end portion, and the entire portion on the rear end side with respect to the reduced diameter portion 865 has a constant outer diameter in the cross section over the axis O direction. Although it is a certain straight part 860, it is good also as a different structure. For example, in the sheath tube, a plurality of portions having different outer diameters (for example, a plurality of straight portions having different outer diameters) may be formed on the rear end side of the reduced diameter portion. Even in this case, when the resistance values R1, R3, and R6 satisfy the above-described relationship at the tip portion of the heater element, the same effects as those of the embodiments can be obtained.

Modification 3 (deformation of heater element):
In each of the above embodiments, the heater element includes the heating coil 820 and the control coil 830. In contrast, the heater element may not be provided with the control coil 830 but may be provided with only a single heating coil as a coil that generates heat when energized.

  Further, the heater element may be used for, for example, a heating appliance or a cooking appliance other than the glow plug.

Modification 4 (deformation of glow plug):
The glow plug of each of the above embodiments has only a function as an auxiliary heat source, but may further have a combustion pressure sensor function. In this case, a combustion pressure sensor function can be realized by providing the heater element with a structure that can move in the direction of the axis O and providing the glow plug with a sensor that can detect the displacement of the heater element.

  The glow plug of each of the above embodiments can be used as a heat source for assisting ignition at the start of the internal combustion engine or the like, and can be used in, for example, a diesel particulate filter (DPF) reactivation burner system.

  As samples, various glow plugs having different values of “R1 / R3” and “R3 / R6” were produced, and the results of evaluating the position of the highest temperature portion in the heater element and the change thereof will be described below.

  FIG. 6 is an explanatory diagram collectively showing the values of “R1 / R3” and “R3 / R6” and the evaluation results in each sample. When manufacturing each sample, first, heater elements having different manufacturing conditions such as the presence / absence of the extending portion 875 in the heating coil, the length of the extending portion 875, and the coil pitch for each region in the heating coil were manufactured. And resistance value R1, R3, and R6 were measured by the method mentioned above about the produced heater element. Among them, a heater element having values of “R1 / R3” and “R3 / R6” shown in Table 6 is selected, and a glow plug including heater elements manufactured under the same manufacturing conditions as each heater element is shown in FIG. Each sample shown in FIG. That is, in FIG. 6, as the values of “R1 / R3” and “R3 / R6” of each sample, heater elements manufactured under the same manufacturing conditions as the heater element 800 of each sample, the resistance values R1, The measured value in the heater element used for the measurement of R3 and R6 is described.

  In FIG. 6, samples 1, 2, 7, and 8 have a value of “R1 / R3” of 0.60, samples 3 and 4 have a value of “R1 / R3” of 0.57, and sample 5 And 6, the value of “R1 / R3” is 0.62. Samples 1 to 6 have a value of “R3 / R6” of 0.45, and samples 7 and 8 have a value of “R3 / R6” of 0.44. Samples 1, 3, 5, and 7 have a heating coil (see FIG. 3) having an extension 875 at the tip, and Samples 2, 4, 6, and 8 have an extension 875 at the tip. A heating coil (see FIG. 5) is provided.

  In any sample, in the heating coil prepared in step S100, the wire diameter of the element wire was constant at 0.45 mm. Further, in any sample, the boundary between the straight portion 860 and the reduced diameter portion 865 was set to a position of 1 mm from the sheath tube distal end 811 to the rear end side in the axis O direction. In any sample, the same iron-chromium-aluminum (Fe-Cr-Al) alloy was used as the material of the wire constituting the heating coil. Further, in any sample, the heating coil is exposed from the melting portion at a position of 1 mm from the sheath tube leading edge 811 to the rear end side in the axis O direction. Further, in any of the samples 1, 3, 5, and 7, the boundary between the extending portion 875 and the winding portion 870 (the position of the broken line β2 in FIG. 3) is located after the sheath tube front end 811 in the direction of the axis O. It is the tip side from the position of 1 mm on the end side.

  For example, in the samples 1, 3, and 5, the length of the extension portion 875 is longer in the order of the value of “R1 / R3”, that is, the order of sample 3, sample 1, and sample 5. Further, in the heating coil of sample 3 having a smaller value of “R1 / R3” than that of sample 1, the coil pitch between broken line α1 and broken line α3 (see FIG. 3) is smaller than that of sample 1. Specifically, in step S100 of FIG. 4, when preparing sample 1, a heating coil having winding portion 870 having a constant coil pitch was prepared, whereas when preparing sample 3, sample 1 was prepared. A heating coil having a smaller coil pitch at the portion including the tip of the winding part 870 was prepared. In the heating coils of samples 2 and 4, sample 4 having a smaller value of “R1 / R3” has a larger coil pitch between broken line α0 and broken line α1 (see FIG. 3) than sample 2.

<Test conditions>
An endurance test in which an operation of applying a voltage to each glow plug was repeatedly performed, and the tip exothermic property before the start of the durability test (initial stage) and the tip exothermic property after the durability test were evaluated. The durability test was performed for 2000 cycles, with one cycle consisting of 1000 ° C. for 2 seconds, 1100 ° C. for 180 seconds, and room temperature (25 ° C.) based on the temperature of the heater element.

  The applied voltage for heating the heater element to 1000 ° C. in 2 seconds is to raise the temperature of the highest temperature part of the heater element to 1000 ° C. in 2 seconds using a glow plug manufactured under the same conditions as each sample. The magnitude of the applied voltage required was set by examining in advance. The applied voltage for maintaining the heater element at 1100 ° C. is 1100 ° C. after the maximum temperature part of the heater element reaches 1000 ° C. using a glow plug manufactured under the same conditions as each sample. It was set by examining the magnitude of the applied voltage required to maintain the voltage in advance. The conditions for cooling the heater element from 1100 ° C. to room temperature (air cooling time) are as follows. After the temperature of the highest temperature part of the heater element is raised to 1100 ° C. using a glow plug manufactured under the same conditions as each sample, The air cooling time required for cooling the heater element to room temperature was set by examining in advance.

  The temperature measurement of the heater element and the specification of the maximum temperature part were performed using a radiation thermometer. Specifically, a 3G series of MODLINE3 manufactured by IRCON was used as a radiation thermometer, and measurement was performed at an emissivity ε = 1.0 at the time of measurement.

<Evaluation method>
Before and after the start of the durability test, the tip exotherm of the glow plug was evaluated based on the position of the highest temperature portion specified by the radiation thermometer. In FIG. 6, the evaluation results are indicated by “◯” and “×”. “◯” indicates that the highest temperature portion of the heater element exists in a range (between the broken line α0 and the broken line α3) from the sheath tube distal end 811 to 3 mm on the rear end side in the axis O direction. “X” indicates that the highest temperature portion of the heater element exists on the rear end side beyond the position of 4 mm on the rear end side in the axis O direction from the sheath tube distal end 811. As a result of the evaluation, there was no sample in which the maximum temperature portion of the heater element was present in the range from the sheath tube tip 811 beyond the 3 mm position to the 4 mm position on the rear end side in the axis O direction.

  As shown in FIG. 6, when the conditions of Samples 1 to 4, ie, “R1 / R3 is 0.60 or less” and “R3 / R6 is 0.45 or more” are satisfied, either before or after the start of the durability test In addition, the position of the highest temperature portion in the heater element was in the range of 3 mm from the sheath tube distal end 811 to the rear end side in the axis O direction. Therefore, it was confirmed that the maximum temperature portion was suppressed from moving toward the rear end side in the direction of the axis O, and the performance of the glow plug could be maintained for a longer time. When “R1 / R3 is 0.60 or less” is not satisfied, movement of the highest temperature portion toward the rear end side in the axis O direction was observed after the durability test (Samples 5 and 6). Further, when the condition “R3 / R6 is 0.45 or more” is not satisfied, the highest temperature portion of the heater element is moved from the sheath tube tip 811 to the rear end side in the axis O direction before the endurance test. It exists on the rear end side from the position of 4 mm, and the performance as a glow plug was insufficient at the initial stage.

  The present invention is not limited to the above-described embodiments, examples, and modifications, and can be realized with various configurations without departing from the spirit thereof. For example, the technical features in the embodiments, examples, and modifications corresponding to the technical features in each embodiment described in the summary section of the invention are to solve some or all of the above-described problems, or In order to achieve part or all of the above effects, replacement or combination can be performed as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 10 ... Glow plug 100 ... Engagement member 200 ... Middle shaft 210 ... Middle shaft front-end | tip part 290 ... Connection part 300 ... Ring 410 ... Insulation member 460 ... O-ring 500 ... Main metal fitting 510 ... Shaft hole 520 ... Tool engagement part 540 ... Male screw Portion 600 ... Packing 800, 1800 ... Heater element 810 ... Sheath tube 811 ... Sheath tube leading edge 819 ... Sheath tube rear end 820,1820 ... Heat coil 821 ... Heat coil tip 829 ... Heat coil rear end 830 ... Control coil 831 ... Control coil front end 839 ... Control coil rear end 840 ... Insulating powder 860 ... Straight part 865 ... Diameter reduction part 870 ... Winding part 875 ... Extension part

Claims (4)

A heater comprising: a tubular sheath tube extending in the axial direction and having a closed tip; and a heating coil housed in the sheath tube, wherein the tip of the sheath tube and the tip of the heating coil are welded A glow plug having elements,
The resistance value between the leading edge of the heater element and the first position that is 1 mm from the leading edge of the heating coil to the rear end side in the axial direction is R1, the leading edge, and the heating coil. R3 is a resistance value between the leading edge and the second position, which is a position of 3 mm from the leading edge to the trailing edge in the axial direction, and the leading edge of the heating coil from the leading edge in the axial direction. When the resistance value between the third position which is a position of 6 mm on the side is R6,
A glow plug, wherein R1 / R3 is 0.60 or less and R3 / R6 is 0.45 or more. The glow plug according to claim 1,
The heating coil is formed in a spiral shape, and an average value of coil pitches of the heating coil between the leading edge of the heater element and the first position is the first position and the second position. A glow plug characterized by being larger than the average value of the coil pitch of the heating coil between the positions. The glow plug according to claim 1,
The heating coil has a spirally wound winding part, and an extension part that linearly extends from the tip of the winding part toward the tip of the heater element,
The glow plug according to claim 1, wherein a boundary between the winding part and the extension part is present on a distal end side in the axial direction with respect to the first position. The glow plug according to claim 3,
The sheath tube has a straight portion formed in a cylindrical shape whose outer diameter in a cross section perpendicular to the axial direction is constant over the axial direction, and the straight portion is located closer to the distal end side in the axial direction than the straight portion. And a reduced diameter portion having a closed tip while its outer diameter is reduced toward the tip side in the axial direction, and formed continuously.
The glow plug according to claim 1, wherein a boundary between the winding portion and the extending portion is present on a distal end side in the axial direction with respect to a boundary between the straight portion and the reduced diameter portion.

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