JP2013152035A - Glow plug and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glow plug capable of preventing contact of coils themselves of resistance coils in a sheath tube, and to provide a method for manufacturing the same.SOLUTION: A glow plug includes a main metal fitting and a sheath heater mounted on the metal fitting. The sheath heater includes a cylindrical sheath tube 7 whose distal end is closed, an energizing terminal shaft whose distal end side faces into the tube 7, a resistance line coil 9 whose rear end is connected to the shaft and whose distal end is connected to the distal end inner surface of the sheath tube 7, insulating powder 10 filling the inside of the sheath tube 7, and a sealing member closing the rear end opening of the sheath tube 7. The sheath tube 7 is drawn to a predetermined diameter by swaging machining, a coil pitch P2 of a coil distal end 9t connecting to the distal end inner surface of the sheath tube 7 before the swaging is set larger than a coil pitch P1 of a main part continuous to the coil distal end 9t in the state before filling the sheath tube 7 in the resistance coil 9.

Description

  The present invention relates to a glow plug mainly used for preheating a diesel engine and a method of manufacturing the glow plug.

  A conventional glow plug will be described with reference to FIGS. For convenience of explanation, the glow plug is defined as “front” on the side facing the combustion chamber of the engine and “rear” on the opposite side.

The glow plug 100 is generally composed of a cylindrical metal shell 200 having both ends opened, and a sheath heater 300 that penetrates the center of the metal shell 200.
The sheath heater 300 is a metal sheath tube 300a having a cylindrical shape with an open rear end and a closed front end, and a circle in which the front end side of the sheath heater 300a faces the inside of the sheath tube 300a from the rear end side of the sheath tube 300a. A column-shaped energizing terminal shaft 300b, a resistance wire coil 300c having its distal end connected to the energizing terminal shaft 300b and having its distal end connected to the inner surface of the distal end of the sheath tube 300a, and the sheath tube 300a are filled. An insulating powder 300d (for example, magnesia powder) for embedding the leading end side of the energizing terminal shaft 300b and the resistance wire coil 300c, and an annular shape between the energizing terminal shaft 300b and the inner peripheral surface of the rear end of the sheath tube 300a. Sealing member 300e (for example, insulative / elastic) A rubber packing) deformable, schematically composed.
And the said sheath tube 300a is formed by restrict | squeezing to a predetermined diameter by swaging with the sealing member 300e mounted | worn with the rear end opening mounted | worn (patent document 1).

JP 2004-264013 A

In recent years, the resistance wire coil 300c, which is a heat generation source of the glow plug 100, has a tendency to reduce the coil pitch. By doing so, the temperature rise time of the glow plug 100 is shortened, and the startability of the diesel engine is improved.
On the other hand, when the coil pitch of the resistance wire coil 300c is reduced, the resistance wire coil 300c may come into contact with each other as shown in the enlarged view of FIG. 6 and FIG. 7C. Contact between the coils of the resistance wire coil 300c is not preferable because there is a possibility that the resistance value decreases due to a short circuit and the designed temperature rise performance cannot be obtained.

Such contact between the resistance wire coils 300c is likely to occur particularly when the sheath heater 300 is manufactured, particularly at the closed end portion of the sheath tube 300a.
That is, in a general manufacturing method of the sheath heater 300, the sheath tube 300a loaded with the resistance wire coil 300c is vertically supported, the rear end opening is directed upward, and the sheath tube 300a is filled with the insulating powder 300d in that state. After that, the sealing member 300e is attached to the rear end opening and sealed, and then the sheath tube 300a is squeezed together with the insulating powder 300d and the resistance wire coil 300c to reduce the diameter to a predetermined diameter. It is.
In such a manufacturing method, first, as shown in FIG. 7A, the resistance wire coil 300c is also supported vertically in the sheath tube 300a standing vertically, so that the coil pitch of the resistance wire coil 300c is equal to the resistance wire. Decrease in response to the weight of the coil 300c and the weight of the energizing terminal shaft 300b. The degree of reduction of the coil pitch due to its own weight or the like is greatest at the coil tip portion 300f of the resistance wire coil 300c to which the total weight is applied, and in some cases, the coils contact each other.
On the other hand, the reduction in coil pitch due to the weight of the resistance wire coil 300c is almost eliminated by the swaging of the sheath tube 300a performed at the final stage of the manufacture of the sheath heater 300. This is because the resistance wire coil 300c extends in the axial direction together with the sheath tube 300a due to the swaging, thereby increasing the coil pitch.
However, the distal end of the sheath tube 300a has a shape that is gradually closed after being gradually reduced in diameter, such as a substantially hemispherical shape or a substantially conical shape, and is mostly a portion narrower than the tube diameter after swaging. Not easily affected by Accordingly, the coil pitch of the resistance wire coil 300c at the distal end portion of the sheath tube 300a remains narrow.
Further, when the swaging of the sheath tube 300a is performed from the rear end to the front end direction (hereinafter also referred to as “reverse swaging”), the insulating powder 300d that receives the pressure in the swaging direction is the sheath tube 300a. Since the resistance wire coil 300c at the tip portion is pushed in, the coil pitch of the coil tip portion 300f of the resistance wire coil 300c at that portion is further reduced.
Therefore, contact between the resistance wire coils 300c is likely to occur at the distal end portion of the sheath tube 300a (that is, the coil distal end portion 300f of the resistance wire coil 300c).

In order to prevent contact between the resistance wire coils 300c as described above, conventionally, when the sheath tube 300a is filled with the insulating powder 300d, the resistance wire coil 300c is lifted so that the coil pitch is not narrowed. ing. However, since an extra mechanism and control for that purpose are required, extra costs are required for both hardware and software.
Further, conventionally, the sheath tube 300a is swung from the front end to the rear end in response to the decrease in the coil pitch of the resistance wire coil 300c during the above-described swaging (hereinafter also referred to as “forward swaging”). I am doing so. However, the forward swaging has a problem that it is easy to bend because the axial compressive force acts on the sheath tube 300a. Therefore, it is necessary to lengthen the swaging processing time or to divide the swaging in several times. ineffective.

  This invention is made | formed in view of the above, The objective is to provide the manufacturing method of the glow plug which can prevent the contact of the coils of a resistance wire coil in a sheath tube, and a glow plug.

In order to achieve the above object, the present invention
A cylindrical metal shell,
A sheath heater mounted on the inner side of the metal shell,
The sheath heater is
A metal sheath tube having a cylindrical shape with an open rear end and a closed front end;
A column-shaped energizing terminal shaft facing the front end side of the sheath tube from the rear end side of the sheath tube;
A resistance wire coil having a rear end connected to the current-carrying terminal shaft and a tip connected to the inner surface of the sheath tube;
Insulating powder filled in the sheath tube;
A sealing member disposed in an annular shape between the energizing terminal shaft and the rear end inner peripheral surface of the sheath tube, and closing the rear end opening of the sheath tube;
Furthermore, the sheath tube is a glow plug that is squeezed to a predetermined diameter by swaging,
In the state before the resistance coil is loaded into the sheath tube, the coil pitch of the coil tip connected to the inner surface of the tip of the sheath tube before swaging is set larger than the coil pitch of the main part continuous to the tip. Provide glow plugs that are

Another invention for achieving the above object (claim 2)
A cylindrical metal shell,
A sheath heater mounted on the inner side of the metal shell,
The sheath heater is
A metal sheath tube having a cylindrical shape with an open rear end and a closed front end;
A column-shaped energizing terminal shaft facing the front end side of the sheath tube from the rear end side of the sheath tube;
A resistance wire coil having a rear end connected to the current-carrying terminal shaft and a tip connected to the inner surface of the sheath tube;
Insulating powder filled in the sheath tube;
A glow plug manufacturing method comprising: a sealing member disposed annularly between the energizing terminal shaft and a rear end inner peripheral surface of the sheath tube, and closing a rear end opening of the sheath tube,
In the sheath heater, the sheath tube loaded with the resistance wire coil is vertically set up with a rear end opening facing upward, and in that state, the sheath tube is filled with the insulating powder and the rear end opening is filled with the sealing member. And thereafter, squeezing the sheath tube by swaging and reducing the diameter to a predetermined diameter,
The sheath tube has a reduced diameter boundary portion in which the outer diameter of the self tube begins to be reduced before swaging, and the tip gradually decreases from the reduced diameter boundary portion,
In the state before the resistance wire coil is loaded into the sheath tube, the coil pitch of the coil tip portion substantially corresponding to the region from the tip inner surface of the sheath tube before swaging to the reduced diameter boundary portion is set to the coil tip. Provided is a method for manufacturing a glow plug that is set to be larger than the coil pitch of a main part continuous to the part.

  3. The glow plug according to claim 2, wherein the sheath tube is reduced in diameter to a predetermined diameter by reverse swaging in which the sheath tube is swaged from the rear end toward the front end. Provide a method.

  In the present invention, since the resistance wire coil of the sheath heater is set to be larger than the coil pitch of the main portion continuous to the distal end portion before the sheath tube is loaded, the resistance wire coil is supported vertically. In this case, even if the coil pitch is reduced due to its own weight or the like, there is almost no possibility of contact. Therefore, when manufacturing the sheath heater, a mechanism or control for pulling up the resistance wire coil supported vertically is unnecessary.

  Further, since the resistance wire coil of the present invention has a large coil pitch at the tip as described above, there is a low possibility of contact even if it is pressed with an insulating powder during swaging of the sheath tube. Therefore, a glow plug with stable quality can be efficiently manufactured by performing forward swaging or reverse swaging on the sheath tube or alternately with the sheath tube according to the method for manufacturing a glow plug of the present invention.

  Further, in the method for manufacturing a glow plug according to the present invention, when the swaging direction of the sheath tube is reverse swaging, the resistance wire coil is difficult to contact even if pressed by insulating powder during swaging. Due to the characteristics of the glow plug of item 1, the negative surface of reverse swaging, which is pushed by insulating powder during swaging and easily touches the resistance wire coil, is canceled, and conversely, the sheath tube is short without bending. The plus side of reverse swaging that diameter can be reduced by machining time is utilized.

It is a longitudinal cross-sectional view of the glow plug including a partially enlarged view. (A), (b) is a longitudinal cross-sectional view of the sheath heater explaining a manufacturing method. It is a longitudinal cross-sectional view of the sheath heater which shows the state before swaging. (A) is sectional drawing of the front-end | tip part of the sheath tube which shows the state before filling with an insulating powder material, (b) is sectional drawing of the front-end | tip part of the sheath tube which shows the state after filling with insulating powder, (c). FIG. 4 is a cross-sectional view of the distal end portion of the sheath tube showing a state after swaging. It shows another form, (a) is a cross-sectional view of the distal end portion of the sheath tube showing a state before filling with the insulating powder material, (b) is a distal end of the sheath tube showing the state after filling with the insulating powder. Sectional drawing of a part, (c) is sectional drawing of the front-end | tip part of a sheath tube which shows the state after swaging. It is a longitudinal cross-sectional view of the conventional glow plug including a partially enlarged view. FIG. 2 shows a conventional technique, in which (a) is a cross-sectional view of a distal end portion of a sheath tube showing a state before filling with an insulating powder material, and (b) is a distal end portion of the sheath tube showing a state after being filled with insulating powder. (C) is sectional drawing of the front-end | tip part of a sheath tube which shows the state after swaging.

Embodiments of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, the glow plug 1 is generally composed of a cylindrical metal shell 2 having both ends opened, and a sheath heater 3 penetrating the center of the metal shell 2.

  The metal shell 2 has a center hole 4 penetrating in the axial direction, and, as shown in FIG. 1, a male screw portion 5 that is screwed into a female screw portion (not shown) of a plug mounting hole on the engine side. For example, a hexagonal column-shaped tool engaging portion 6 that can be engaged with a tightening tool such as a plug wrench is provided at the rear end.

  The sheath heater 3 includes a metal sheath tube 7 having a hemispherical cylindrical shape with a rear end opened and a distal end gradually reduced in diameter, and the sheath tube 7 from the rear end side of the sheath tube 7. A cylindrical current-carrying terminal shaft 8 with its front end facing inside, and its rear end is connected to the current-carrying terminal shaft 8 by, for example, winding or welding, and the front end is connected to the inner surface of the distal end of the sheath tube 7 A resistance wire coil 9 formed by spirally winding a resistance wire connected by welding (for example, arc welding), and the sheath tube 7 filled in the sheath tube 7 and the resistance wire coil 9. And an insulating powder 10 (for example, magnesia powder), which is annularly disposed between the current-carrying terminal shaft 8 and the inner peripheral surface of the rear end of the sheath tube 7, and seals the rear end opening of the sheath tube 7. Sealing member to stop 1 (e.g., isolatable, elastically deformable rubber packing), schematically composed.

  The sheath tube 7 in FIGS. 1 and 4 (c) is in a state of being reduced in diameter by swaging, and the sheath tube 7 before swaging is as shown in FIGS. 4 (a) and 4 (b). Naturally, the diameter is larger than that after the swaging, and the tip shape is closed by gradually reducing the diameter from the reduced diameter boundary portion 7L to the substantially conical shape from the reduced diameter boundary portion 7L.

  Similarly, the resistance wire coil 9 of FIG. 1 and FIG. 4 (c) is in a state in which the diameter of the sheath tube 7 is reduced by receiving the influence of the swaging of the sheath tube 7 through the insulating powder 10. As shown in FIGS. 4A and 4B, the coil diameter of the coil 9 is naturally larger than that after swaging. The coil pitch of the resistance wire coil 9 before swaging is such that the coil tip corresponding to the region from the inner surface of the distal end of the sheath tube 7 to the reduced diameter boundary portion 7L from the coil pitch P1 of the main portion where the coil diameter is substantially constant. The coil pitch P2 of the part 9t is set to be larger. The coil pitch P2 may be set to be larger than the coil pitch P1, but is preferably 0.03 mm or more in order to prevent a short circuit of the coil tip portion 9t after swaging.

  Alternatively, the coil pitch of the resistance wire coil 9 before the swaging is approximately reduced in diameter boundary portion 7L (specifically, from the coil pitch P1 of the main portion, as shown in FIGS. 5A and 5B). The coil pitch P2 of the coil front end portion 9t corresponding to the region from the reduced diameter boundary portion 7L to the inner surface of the front end portion of the resistance wire coil 9 by about one turn is set to be larger.

Next, a method for manufacturing the glow plug 1 will be described focusing on the sheath heater 3.
First, the rear end of the resistance wire coil 9 is connected to the front end of the energizing terminal shaft 8, and the resistance wire coil 9 is loaded into the sheath tube 7, and the front end of the resistance wire coil 9 is attached to the inner surface of the distal end of the sheath tube 7. Weld.

  Next, as shown in FIG. 2 (a), the sheath tube 7 loaded with the resistance coil 9 is erected vertically and supported with the rear end opening facing upward. At this time, the resistance wire coil 9 is not pulled up. In this state, the weight of the current-carrying terminal shaft 8 and the weight of the resistance wire coil 9 are added to the tip of the resistance wire coil 9, but the coil weight P2 of the coil tip 9t of the resistance wire coil 9 is large. Even if it receives, coils do not contact (FIG. 4A).

Next, as shown in FIG. 2 (b), the sheath tube 7 is filled with the insulating powder 10, the sealing member 11 is fitted to the energizing terminal shaft 8, and the sealing member 11 is attached as shown by the arrow in the figure. The sheath tube 7 is slid toward the distal end side to close the rear end opening of the sheath tube 7.
The sheath tube 7 of the sheath heater 3 thus assembled is passed through the die 12 and swaged as shown in FIG. This swaging is forward swaging in which the die 12 is relatively moved from the distal end side to the rear end side of the sheath tube 7 and reversely that the die 12 is relatively moved from the rear end side to the distal end side of the sheath tube 7. Either direction swaging may be used, but in the embodiment, the diameter of the sheath tube 7 is reduced to a predetermined diameter by reverse swaging. By this swaging, the outer diameter of the sheath tube 7 is reduced to a predetermined diameter including the reduced diameter boundary portion 7L.

  The sheath heater 3 manufactured as described above is passed through the center hole 4 of the metal shell 2 to press-fit (press-fit) the sheath tube 7, and to the energizing terminal shaft 8 protruding from the rear end opening of the metal shell 2. When the insulating bush 13 is passed, the insulating bush 13 is fitted into the rear end opening of the metal shell 2 and tightened with the nut 14, the glow plug 1 is completed. The structure for attaching the sheath heater 3 to the metal shell 2 is not limited to the above, and any structure may be used.

In order to confirm the effect of the present invention, the resistance wire coil 9 having the coil pitch P1 = 0.40 mm of the main part, the coil pitch P2 = 0.45 mm of the coil tip 9t, and the wire diameter = φ0.38 mm is used as described above. The sheath heater 3 is manufactured (Invention 1), and the electrical resistance value of the resistance wire coil 9 (hereinafter referred to as “pre-resistance value”) before being loaded into the sheath tube 7 in the process is loaded into the sheath tube 7. Then, the electrical resistance value of the resistance wire coil 9 after filling the insulating powder 10 (hereinafter referred to as “rear resistance value”) is measured, and the maximum value of the resistance decrease (corresponding to the pre-resistance value− The post-resistance value] was determined to determine the maximum value (n = 30), and the 850 ° C. arrival time (average time of n = 50) was measured.
For comparison, the coil pitches of the main part and the coil tip are 0.40 mm (Comparative Example 1), 0.42 mm (Comparative Example 2), 0.44 mm (Comparative Example 3), and 0.45 mm (Comparative Example 4). The resistance heater coil of 0.47 mm (Comparative Example 5) was used to manufacture a sheath heater, the maximum value of the resistance decrease was obtained as described above, and the 850 ° C. arrival time was measured.
The results are shown in Table 1.

The determination of Table 1 is that the resistance reduction amount is zero, and “○” indicates that both the conditions for reaching 850 ° C. of 4.5 seconds ± 0.5 seconds are satisfied, and “△” indicates that either one is satisfied. ”, Those that did not satisfy both were designated as“ x ”.
From the results of Comparative Examples 1 to 3 in Table 1, the resistance wire coils having a coil pitch of 0.40 to 0.44 mm are in contact with each other after filling with the insulating powder because of a decrease in electrical resistance. I understand. Further, from the results of Comparative Examples 4 and 5, it is found that the resistance wire coils having a coil pitch of 0.45 mm or more are not in contact with each other even after filling with the insulating powder since the decrease in electric resistance is not confirmed. However, the sheath heaters of Comparative Examples 4 and 5 have a large coil pitch over the entire length, so that the arrival time at 850 ° C. exceeds 5.7 seconds, and is not suitable for products for rapid temperature increase.
On the other hand, the present invention 1 satisfies both the condition that the resistance reduction amount is zero and the 850 ° C. arrival time is 4.5 seconds ± 0.5 seconds. It was confirmed that both of the characteristics can be satisfied.

Next, in order to confirm the effect of the present invention corresponding to the swaging of the sheath tube, the same resistance wire coil 9, that is, the coil pitch P1 = 0.40 mm of the main part and the coil pitch P2 = 0 of the coil tip part 9t. A resistance wire coil 9 having a diameter of .45 mm and a wire diameter of φ0.38 mm is loaded into a sheath tube 7 having an outer diameter of φ5.15 mm before swaging, and the sheath tube 7 is filled with insulating powder. The sealing member 11 is fitted into the rear end opening to form an assembled state, and the sheath tube 7 of the sheath heater 3 in this assembled state is swaged to an outer diameter = φ3.5 mm (swaging rate (A / B) = 1.47). Thus, the sheath heaters 3 of the present invention 2 and 3 were manufactured. At that time, whether the sheath tube 7 is bent or not is loaded for each of the case where the machining time is shortened by reverse swaging (Invention 2) and the case where the machining time is lengthened by forward swaging (Invention 3). The maximum value (n = 30) of the amount of decrease in resistance due to the previous pre-resistance value and the post-resistance value after swaging was measured.
For comparison, sheath heaters of Comparative Examples 6 to 8 were manufactured using resistance wire coils in which the coil pitch between the main part and the coil tip part was unified to 0.42 mm. At that time, when the machining time is increased by forward swaging (Comparative Example 6), when the machining time is shortened by reverse swaging (Comparative Example 7), and when the machining time is shortened by forward swaging For each of (Comparative Example 8), the maximum value (n = 30) of the resistance reduction amount due to the presence or absence of bending of the sheath tube, the pre-load resistance value before loading, and the post-resistance value after swaging was measured.
The results are shown in Table 2.

In the resistance wire coil, the wire diameter is increased by swaging and the resistance value is decreased. Therefore, in the present inventions 2 and 3, the resistance is reduced as shown in Table 2. However, the resistance reduction amount of the present inventions 2 and 3 is small in comparison with the comparative examples 6 to 8, and the present invention 2 of reverse swaging and the present invention of forward swaging increase the risk of contact between coils. It can be seen that there is no contact between the coils since the amount of resistance reduction with 3 is the same.
From the results of Comparative Examples 6 and 8 and Comparative Example 7, reverse swaging is preferable for relatively shortening the processing time without bending the sheath tube. There is a downside that increases the risk of contact (see the maximum resistance reduction in Comparative Example 7). On the other hand, comparing the results of the maximum resistance reduction amounts of the present inventions 2 and 3, it can be seen that the present invention improves the negative aspect of reverse swaging.
Therefore, according to the present invention, a stable quality glow plug without instability due to contact between coils can be manufactured in a short processing time without bending the sheath tube.

  As mentioned above, although this invention was described about embodiment, of course this invention is not limited to the said embodiment. For example, in the embodiment, the distal end shape of the sheath tube 7 before swaging is substantially conical, but the distal end shape may be substantially hemispherical. Further, the resistance wire coil 9 is not limited to one configured by one material, and may have a configuration in which a plurality of resistance wire coils are connected in series.

DESCRIPTION OF SYMBOLS 1 ... Glow plug 2 ... Metal fitting 3 ... Sheath heater 7 ... Sheath tube 7L ... Reduced diameter boundary part 8 ... Current-carrying terminal shaft 9 ... Resistance wire coil 9t ... Coil tip part P1 ... Coil pitch of main part P2 ... Coil pitch of tip part 10: Insulating powder 11 ... Sealing member

Claims (3)

A cylindrical metal shell,
A sheath heater mounted on the inner side of the metal shell,
The sheath heater is
A metal sheath tube having a cylindrical shape with an open rear end and a closed front end;
A column-shaped energizing terminal shaft facing the front end side of the sheath tube from the rear end side of the sheath tube;
A resistance wire coil having a rear end connected to the current-carrying terminal shaft and a tip connected to the inner surface of the sheath tube;
Insulating powder filled in the sheath tube;
A sealing member disposed in an annular shape between the energizing terminal shaft and the rear end inner peripheral surface of the sheath tube, and closing the rear end opening of the sheath tube;
Furthermore, the sheath tube is a glow plug that is squeezed to a predetermined diameter by swaging,
In the state before the resistance wire coil is loaded into the sheath tube, the coil pitch of the coil tip connected to the inner surface of the tip of the sheath tube before swaging is larger than the coil pitch of the main part continuous to the coil tip. Glow plug characterized by being set. A cylindrical metal shell,
A sheath heater mounted on the inner side of the metal shell,
The sheath heater is
A metal sheath tube having a cylindrical shape with an open rear end and a closed front end;
A column-shaped energizing terminal shaft facing the front end side of the sheath tube from the rear end side of the sheath tube;
A resistance wire coil having a rear end connected to the current-carrying terminal shaft and a tip connected to the inner surface of the sheath tube;
Insulating powder filled in the sheath tube;
A glow plug manufacturing method comprising: a sealing member disposed annularly between the energizing terminal shaft and a rear end inner peripheral surface of the sheath tube, and closing a rear end opening of the sheath tube,
In the sheath heater, the sheath tube loaded with the resistance wire coil is vertically set up with a rear end opening facing upward, and in that state, the sheath tube is filled with the insulating powder and the rear end opening is filled with the sealing member. And thereafter, squeezing the sheath tube by swaging and reducing the diameter to a predetermined diameter,
The sheath tube has a reduced diameter boundary portion in which the outer diameter of the self tube begins to be reduced before swaging, and the tip gradually decreases from the reduced diameter boundary portion,
In the state before the resistance wire coil is loaded into the sheath tube, the coil pitch of the coil tip portion substantially corresponding to the region from the tip inner surface of the sheath tube before swaging to the reduced diameter boundary portion is set to the coil tip. A method for manufacturing a glow plug, characterized in that it is set to be larger than the coil pitch of the main part continuous to the part.   3. The method for manufacturing a glow plug according to claim 2, wherein the sheath tube is reduced in diameter to a predetermined diameter by reverse swaging in which swaging is performed from the rear end toward the front end.

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