JP5625838B2 - Piston and spark ignition internal combustion engine - Google Patents

Description

  The present invention relates to a piston for an internal combustion engine and a spark ignition internal combustion engine including the piston.

  In internal combustion engines, it has been proposed or practiced to improve the piston shape or configuration, for example to improve the combustion of the mixture in the combustion chamber. For example, Patent Document 1 shows a piston used for a small diesel engine or the like according to the description, and the piston has a large number of striations formed in a concave shape in a cross section in the top land portion. And when forming these many striations, soft materials, such as carbon, are embed | buried. This improves the familiarity between the cylinder inner wall and the top land of the piston, and prevents the top land portion from being seized.This also reduces the compression ratio even when the engine is not running well. In addition, Patent Document 1 describes that generation of unburned gas components can be effectively suppressed.

  On the other hand, a supercharger is mounted on an internal combustion engine, thereby increasing the supercharging pressure and increasing the engine output.

Japanese Utility Model Publication No. 61-27946

  In an internal combustion engine, increasing the in-cylinder pressure increases the possibility of knocking, for example. For example, when a high-pressure portion is generated in the combustion chamber due to knocking, a pressure wave generated due to the high-pressure portion may enter a gap between the outer peripheral side surface of the piston and the cylinder wall surface. As a result of intensive studies, the present inventors have found that when a local pressure increase occurs in the gap, the surface of the surrounding piston may become rough.

  Accordingly, the present invention has been made in view of such circumstances, and one object thereof is to suppress a local pressure increase in a gap between the outer peripheral side surface of the top land of the piston and the cylinder wall surface.

  According to one aspect of the present invention, a piston for an internal combustion engine, wherein a groove having an end opened to the top surface is formed on the outer peripheral side surface of the top land adjacent to the top surface of the piston. A piston is provided.

Preferably, the groove includes a circumferential groove portion connected to the end portion and extending in the circumferential direction on the outer peripheral side surface of the top land.
Preferably, the outer peripheral side surface of the top land includes a first region corresponding to a pressure increasing possibility portion and a second region different from the first region, and the groove is connected to the end portion and the outer peripheral side surface of the top land. A circumferential groove extending in the circumferential direction, the circumferential groove extending in the circumferential direction in the first region of the outer periphery of the top land, and the end of the groove being the second of the outer periphery of the top land. Open to the top surface in the region.

  Preferably, the piston includes two recesses formed in the top surface of the piston so as to be adjacent to the outer peripheral side surface of the top land, and when defining a plane including the center line of the piston, the piston is divided by the plane. The two recesses are present on one side of the piston and the circumferential groove of the groove is defined to extend between the two recesses on the one side of the piston. The end portion of the groove extends in the first region on the outer peripheral side surface of the top land, and the end of the groove opens to the top surface in a second region different from the first region on the outer peripheral side surface of the top land.

  Preferably, the circumferential groove portion of the groove extends continuously over the entire circumference of the piston.

  Preferably, the groove is formed in a portion of the top land outer peripheral side surface on the top surface side.

The groove may be formed such that the cross-sectional area of the groove decreases as the end of the groove is approached.
Preferably, the groove includes a circumferential groove portion, and the groove is formed such that a cross-sectional area of the groove decreases as the groove moves away from the circumferential groove portion and approaches the end portion.

  The present invention also resides in a spark ignition type internal combustion engine provided with a piston as described above.

It is a perspective view which shows the conventional piston as an example. It is a top view which shows the piston of FIG. It is a figure which shows a mode that a pressure wave collides in the piston of FIG. It is a perspective view of the piston which concerns on 1st Embodiment of this invention. FIG. 5 is a partial cross-sectional view of the piston of FIG. 4. FIG. 6 is an enlarged view of a region surrounded by a circle VI in FIG. 5. It is a perspective view of the piston which concerns on 2nd Embodiment of this invention.

  First, the configuration of a conventional piston for an internal combustion engine and the knowledge of the inventors as the basis of the present invention will be described.

  It is known that surface roughness may occur in the piston of an internal combustion engine due to the operation of the internal combustion engine. As a result of diligent research through various experiments (including actual machine tests and computer simulation tests (CFD analysis)), the present inventors have found the cause and mechanism of such piston surface roughness and made use of this. The present invention has been invented. A brief description is given below.

  First, names of respective parts of a conventional piston for an internal combustion engine will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective view of a conventional piston 1 as an example, and FIG. 2 is a plan view of the piston 1 of FIG. However, the piston 1 is a piston of a spark ignition type internal combustion engine such as a gasoline engine.

  In the plan view shown in FIG. 2, orthogonal coordinates are defined with the center line (axis line) O of the piston 1 as the origin, the axis extending in the horizontal direction in the figure is defined as the X axis, and the axis extending in the vertical direction in the figure is defined as the Y axis. . The X axis is parallel to the centerline of the piston pin hole (not shown in FIGS. 1 and 2) and the centerline of the crankshaft (not shown). On the other hand, the Y axis is orthogonal to the X axis. With respect to the X axis, the lower side in FIG. 2 is the intake side, and the upper side is the exhaust side. For ease of explanation, the right side of FIG. 2 is the front and the left side is the rear with the Y axis as a boundary. The X axis divides the piston 1 into an intake side and an exhaust side, or bisects it. The Y axis divides the piston 1 into a front side and a rear side, or bisects it. For ease of explanation, the front side in the thickness direction of the paper along the piston center line O is up, and the back side is down.

  As shown in FIGS. 1 and 2, the piston 1 has an outer peripheral side surface 2 and a top surface 3 (hereinafter referred to as a piston outer peripheral side surface 2 and a piston top surface 3 respectively). A plurality of ring grooves, in this case, three ring grooves 4, 5, 6 are formed on the piston outer peripheral side surface 2 to accommodate the piston rings. A top ring (not shown) is accommodated in the uppermost ring groove or top ring groove 4, and a second ring (not shown) is accommodated in the intermediate ring groove or second ring groove 5. An oil ring (not shown) is accommodated in the oil ring groove 6. A skirt 7 is formed below the oil ring groove 6.

  On the other hand, in the piston 1, a top land 8 is formed above the top ring groove 4. Here, the top land 8 refers to the entire meat portion of the piston 1 located above the top ring groove 4. A portion of the piston outer peripheral side surface 2 belonging to the top land 8 forms a top land outer peripheral side surface 9. A second land 10 is formed between the top ring groove 4 and the second ring groove 5, and a third land 11 is formed between the second ring groove 5 and the oil ring groove 6.

  A plurality of recesses are formed on the piston top surface 3. Specifically, the piston top surface 3 is provided with a plurality of intake valve recesses 12F and 12R on its intake side, and a plurality of exhaust valve recesses 13F and 13R on its exhaust side. The intake valve recesses 12F and 12R are for avoiding interference with an intake valve (not shown) that is an on-off valve that opens and closes the downstream end of the intake passage, and are recessed in the piston top surface 3. The exhaust valve recesses 13F and 13R are for avoiding interference with an exhaust valve (not shown) that is an on-off valve that opens and closes the upstream end of the exhaust passage, and are recessed in the piston top surface 3. .

  Here, the number of intake valve recesses is two. The front intake valve recess is represented by 12F, and the rear intake valve recess is represented by 12R. These intake valve recesses 12F and 12R are substantially semicircular in a plan view (FIG. 2), have the same diameter, and are arranged symmetrically with respect to the Y axis.

  Similarly, the number of exhaust valve recesses is two here. The front exhaust valve recess is represented by 13F, and the rear exhaust valve recess is represented by 13R. These exhaust valve recesses 13F and 13R are substantially semicircular in plan view (FIG. 2) and have the same diameter, but are smaller in diameter than the intake valve recesses 12F and 12R. And it arrange | positions symmetrically with respect to the Y-axis.

  As is known, the bottom surfaces of the intake valve recesses 12F and 12R and the exhaust valve recesses 13F and 13R are inclined so that their positions are lowered as they are separated from the X axis. Each of the front intake valve recess 12F and the rear intake valve recess 12R extends adjacent to the piston outer peripheral side surface 2, particularly inscribed therein. Thereby, the upper end edge part of the topland outer peripheral side surface 9 has a shape that is cut out downward at the connection position with the front intake valve recess 12F and the rear intake valve recess 12R. The front and rear cutouts are indicated by 14F and 14R in FIG. These front and rear cutout portions 14F and 14R are arranged symmetrically with respect to the Y axis, and here, the intake valve recesses 12F and 12R and the piston outer peripheral surface 2 are connected approximately smoothly.

  A portion of the piston top surface 3 between the two intake valve recesses 12F and 12R forms a squish portion 15 that is a convex portion that protrudes toward the combustion chamber. The squish portion 15 is located on the outer peripheral side of the piston top surface 3 and has a substantially fan shape in plan view (FIG. 2). Further, the cross-sectional shape of the squish portion 15 on a plane defined to include the Y axis and the center line O of the piston 1 is a substantially triangular shape, and the squish portion 15 is connected to the piston outer peripheral side surface 2 almost smoothly. The outer inclined surface 15a, the inner inclined surface 15b facing the center of the combustion chamber, and an edge (top edge) 15c extending between the outer inclined surface 15a and the inner inclined surface 15b (see FIG. 2). The squish part 15 which is a convex part is formed so as to control the flow of fluid in the combustion chamber, and is provided here particularly to promote the formation of a squish flow, and a cylinder block and a cylinder head (both not shown) during engine operation. The squish flow that flows out from the gap between the two is positively hit. The squish portion 15 is arranged symmetrically with respect to the Y axis. Thus, the squish portion 15 is a convex portion formed on the piston top surface 3 adjacent to the piston outer peripheral side surface 2 so as to be sandwiched between the intake valve recesses 12F and 12R which are two concave portions.

  The portion of the top land outer peripheral side surface 9 connected to the squish portion 15 is the radius of the portion of the top land outer peripheral side surface 9 indicated by L in the drawing, that is, the boundary between the intake valve recesses 12F and 12R and the squish portion 15. It is a part of the top land outer peripheral side surface 9 between two piston circumferential direction positions which are the outer sides in the direction. The portion of the top land outer peripheral side surface 9 connected to the squish portion 15 is distinguished by using a reference numeral 9L, and is also referred to as a squish connection top land. The squish connection top land 9L is arranged symmetrically with respect to the Y axis.

  The intermediate position 9Lm in the circumferential direction of the squish-connected top land 9L exists on the Y axis. The front end 9Lf and the rear end 9Lr of the squish connection top land 9L are present at positions farthest forward and backward along the circumferential direction from the circumferential intermediate position 9Lm. The front and rear cutout shape portions 14F and 14R are further away from the front end 9Lf and the rear end 9Lr in the front-rear direction along the circumferential direction from the circumferential intermediate position 9Lm.

  A central recess 16 that is slightly recessed is formed at the center of the piston top surface 3. A spark plug (not shown) is attached to the cylinder head just above the central recess 16.

  An experimental result using a spark ignition internal combustion engine provided with a piston having the same characteristics as the piston 1 will be briefly described. In the test, knocking was intentionally generated, or a high pressure portion was generated in the combustion chamber by simulating the occurrence of knocking. The pressure wave generated due to the generation of the high pressure portion propagates and enters between the gap between the piston outer peripheral side surface and the cylinder wall surface, in particular, between the top land outer peripheral side surface and the cylinder inner wall surface. It was found that the pressure wave that entered from the point of collision might amplify. In particular, in an internal combustion engine having a piston such as the piston 1, as shown in FIG. 3, the pressure waves P1F and P2F that reach the outer peripheral side surface of the top land via the intake valve recesses 12F and 12R and the squish portion 15 are It has been found that there is a possibility that the pressure wave P2 reaching the outer peripheral side surface of the top land may collide on the outer peripheral side surface of the top land. In this case, it has been found that these impacts create very strong pressure locally, which can cause roughness at the impact site and / or the surrounding piston surface. As a result of investigation by the present inventors, it was found that such piston surface roughness was mainly caused by erosion, which is a thinning phenomenon due to physical or mechanical action.

  Therefore, when a high-pressure part is generated in the combustion chamber, it is not preferable that a pressure wave generated due to the high pressure part enters between the top land outer peripheral side surface of the piston and the cylinder wall surface to cause a local pressure increase. Accordingly, as a result of intensive studies, the present inventors have devised the present invention so as to suppress the occurrence of such a pressure increase. The piston according to the present invention is generally characterized in that a groove (or a recess) is provided on the outer peripheral side surface of the top land. The said groove | channel is equipped with the structure which opened the edge part toward the piston top surface. This makes it possible to suppress the pressure increase as described above. Preferably, this groove effectively creates an unintentional high-pressure part in the combustion chamber (for example, by knocking), and even if a pressure wave resulting therefrom propagates and enters between the piston and the cylinder. It is formed so as to escape and suppress the pressure increase as described above.

  Below, piston 1A concerning a 1st embodiment of the present invention is explained. This piston 1A is a piston for a spark ignition type internal combustion engine. The same or similar components as those already described in the piston 1 are denoted by the same reference numerals in the following description of the piston 1A, and their description is omitted. However, the piston 1 </ b> A does not include the squish portion 15 in the piston 1.

  The piston 1A according to the first embodiment includes a groove 20 on the outer peripheral side surface 9 of the top land. The groove 20 includes an end 20e that opens (communicates) with the piston top surface 3, and a circumferential groove 20c that is connected to the end 20e.

  The groove 20 is generally extended in the circumferential direction to a portion of the top land outer peripheral side surface 9 adjacent to a region where pressure is likely to increase locally as described above (hereinafter, referred to as a pressure increase possibility portion). Is formed. Here, the pressure increase possibility portion is a first top land outer peripheral side surface region (hereinafter referred to as a first region) that is defined to extend between the intake valve recesses 12F and 12R in the top land outer peripheral side surface 9. 9A1. More specifically, the first region 9A1 has both ends at the top land outer peripheral side 9 side, that is, the imaginary lines that extend from the outer end portions of the intake valve recesses 12F and 12R located on the outermost radial direction to the top land outer peripheral side 9 as they are. 4 is a substantially defined region, and a region S1 in FIG. 4 represents a range of an edge portion on the piston top surface 3 side in the first region 9A1 of the topland outer peripheral side surface 9. As described above with reference to FIGS. 1 to 3, there is a high possibility that pressure waves propagate from the intake valve recesses 12 </ b> F and 12 </ b> R to the gap between the piston outer peripheral side surface and the cylinder wall surface and collide with each other. Therefore, the region where the pressure can be increased is defined in the first region 9A1 here. In addition, the pressure increasing possibility portion which is the first region 9A1 corresponds to the squish-connected top land 9L of the piston 1.

  As described above, the groove 20 extends in the first region 9A so as to extend in the circumferential direction. Further, the groove 20 is defined so as to include the center line O and the X axis of the piston 1A beyond the first region 9A1. Until the first plane is reached, it extends in the circumferential direction on the piston outer peripheral surface 2 so as to extend substantially on a second plane defined so as to be substantially orthogonal to the center line O. Thus, the portion of the groove 20 extending in the circumferential direction corresponds to the circumferential groove portion 20 c of the groove 20. And in 2nd top land outer peripheral side surface area | region (henceforth 2nd area | region) 9A2 which is a part of top land outer peripheral side surfaces 9 other than 1st area | region 9 A1, the edge part 20e of the groove | channel 20 is connected with the piston top surface 3, The groove 20 opens to the piston top surface 3. Therefore, the end 20e of the groove 20 is an open end. Note that the pressure around the second region 9A2 tends not to increase as compared with the periphery of the first region 9A1.

  Reference is now made to the cross-sectional views of FIGS. 5 and 6 of a portion of the piston 1A in a plane defined to include the centerline O and the X axis of the piston 1A. In FIG. 6, the top land thickness in the direction of the center line O of the piston 1A, that is, the distance from the piston top surface 3 to the upper end of the top ring groove 4 is denoted by reference numeral H1, and the top ring groove 4 in the direction of the center line of the piston 1A. The distance from the upper end of the groove 20 to the lower end of the circumferential groove 20c of the groove 20 is denoted by reference numeral H2. The distance H2 is set to ½ or more of the distance H1. Therefore, the groove 20 including the circumferential groove portion 20c and the end portion 20e is formed in a portion on the top surface 3 side of the top land outer peripheral side surface 9, and more specifically, the top on the piston top surface 3 side with respect to the third plane. It extends to the top surface side outer peripheral side surface 9 t of the land outer peripheral side surface 9. The third plane is a surface that bisects the top land 8 in the direction of the center line O of the piston 1A, that is, the upper end of the piston top surface 3 and the top ring groove 4 in the direction of the center line O of the piston 1A. Is defined as a plane perpendicular to the center line O passing through the midpoint between the two.

  Further, the groove 20 is formed so that the cross-sectional area (groove cross-sectional area) of the groove decreases as the open end 20e of the groove 20 is approached. Here, the groove depth of the groove 20 is indicated by a symbol D in FIG. Here, the groove cross-sectional area of the groove 20 decreases while the groove depth D decreases as the distance from the circumferential groove 20c approaches the open end 20e.

  Since it has the above-described configuration, the spark ignition type internal combustion engine including the piston 1A and the piston 1A has the following operational effects.

  The piston 1 </ b> A includes a groove 20 having an end portion 20 e that opens to the piston top surface 3 on the outer peripheral side surface 9 of the top land adjacent to the piston top surface 3. In particular, here, the groove 20 extends in the circumferential direction in the first region 9A1 corresponding to the pressure increase possibility portion, and the groove 20 opens on the piston top surface 3 in the second region 9A2 different from the first region 9A1. The periphery of the second region 9A2 is a region having a tendency that the pressure is less likely to increase compared to the periphery of the first region 9A1. Therefore, even when a pressure wave propagates to or around the surface of the first region 9A1, the pressure is released to the piston top surface 3 through the groove 20 in the second region 9A2 different from the first region. . Therefore, local increase in pressure around the first region 9A1 is suppressed. Therefore, the occurrence of roughness on the surface of the piston 1A is suppressed.

  Moreover, the groove | channel 20 is formed so that the groove | channel cross-sectional area may reduce toward the open end part 20e of this groove | channel 20 as above mentioned. Therefore, the pressure wave from the piston top surface 3 side, that is, the combustion chamber, is prevented from entering the groove 20 through the open end 20e of the groove 20. On the other hand, since the pressure released to the piston top surface 3 side through the groove 20 can be high, it can be appropriately released from such a narrow open end 20e.

  In addition, the groove | channel 20 may be formed so that a groove | channel cross-sectional area may decrease gradually toward the groove edge part 20e from the part of the circumferential direction groove part 20c in 1st area | region 9 A1.

  Next, a piston 1B according to a second embodiment of the present invention will be described. The piston 1B is also a piston for a spark ignition internal combustion engine. The same or similar components as those already described in the piston 1 are denoted by the same reference numerals in the following description of the piston 1B, and the description thereof is omitted. Further, here, only the difference, that is, the feature of the piston 1B with respect to the piston 1A will be described, and the description of the common parts or similar parts will be omitted by using the same reference numerals as described above. However, the groove of the piston 1B is indicated by the reference numeral 20B with respect to the groove 20 (20A) of the piston 1A.

  In the piston 1B according to the second embodiment, the circumferential groove portion 20c extending in the circumferential direction on the piston outer peripheral side surface 2 of the groove 20B extends continuously over the entire circumference of the piston 1B. That is, the groove 20B has a circumferential groove 20c that continuously extends in the circumferential direction in both the first region 9A1 and the second region 9A2.

  The groove 20 </ b> B has an end 20 e that opens to the piston top surface 3. The end 20e is positioned in the second region 9A2, and is connected to the circumferential groove 20c in the second region 9A2.

  As described above, the piston 1B of the second embodiment also has the circumferential groove 20c extending in the circumferential direction in the first region and the end 20e that opens to the piston top surface 3 in the second region, similarly to the piston 1A. Since it has, it can have the same effect as said piston 1A. In addition, since the groove 20B continuously extends over the entire circumference, even if a pressure wave propagates to or around the surface of the second region 9A2, it is more suitable via the groove 20. The pressure can be released.

  The groove 20B is formed so that the groove cross-sectional area gradually decreases as it moves away from the circumferential groove 20c and approaches the end 20e, as in the groove 20A, but the grooves 20B other than the circumferential groove 20c All of the portions may be formed to have the same groove cross-sectional area. However, the groove cross-sectional area of the groove 20B other than the circumferential groove 20c is preferably smaller than the groove cross-sectional area of the circumferential groove 20c. The portions of the groove 20B other than the circumferential groove portion 20c are designed to have excellent pressure release characteristics to the piston top surface 3 via the groove 20 and to suppress the pressure wave from entering the groove 20B from the top surface 3. It is good to be done.

  As described above, the pistons 1A and 1B according to the embodiment of the present invention include the pressure damping grooves 20A and 20B. However, the piston according to the present invention is not limited to these embodiments, and may include various grooves formed on the outer peripheral side surface of the top land of the piston adjacent to the top surface of the piston and having an open end on the top surface. it can.

  Moreover, although piston 1A, 1B which concerns on the said embodiment is not provided with the convex part formed so that the flow of the fluid of a combustion chamber may be controlled, for example, the squish part 15, on the top surface, the piston which concerns on this invention You may provide such a convex part. For example, the groove 20A or the groove 20B can be formed in the piston 1 described above. In this case, the first region may be the squish-connected top land 9L. When the groove 20A or the groove 20B is formed in the above-described piston 1, the pressure wave P2 shown in FIG. 3 is preferably formed before the collision with the other pressure waves P1F and P1R, preferably before reaching the top ring. Alternatively, it can be opened to the combustion chamber via the groove 20B. Therefore, the collision of the pressure waves P1F, P1R, and P2 as shown in FIG. 3 can be prevented, and as a result, the occurrence of roughness on the piston surface can be suppressed.

  In the above embodiment, the first region extends between the two intake valve recesses on one side of the piston divided by the plane when defining a plane including the center line O of the piston. However, it may be a region having another range. The first region is preferably determined based on an experiment, and the shape (depth, width, etc.) of the groove and the number of grooves may be determined based on the experiment as well. For example, the first region may be a region extending so as to be sandwiched between the exhaust valve recesses, or a region extending so as to be sandwiched between the intake valve recess and the exhaust valve recess.

  The piston according to the present invention can be applied to various internal combustion engines. Preferably, the piston according to the present invention is applied to an internal combustion engine having a configuration for increasing the in-cylinder pressure, such as an internal combustion engine having a supercharger.

  The present invention includes all modifications, applications, and equivalents included in the spirit of the present invention defined by the claims. Therefore, the present invention should not be construed as being limited, and can be applied to any other technique belonging to the scope of the idea of the present invention.

1A, 1B Piston 2 Outer peripheral side 3 Top surface 4 Top ring groove 5 Second ring groove 6 Third ring groove 8 Top land 9 Top land outer peripheral side 9L Squish connection top land 12F Front intake valve recess 12R Rear intake valve recess 14F Front notch Shape portion 14R Rear cutout shape portion 15 Squish portion 20A, 20B Groove 20c Circumferential groove portion 20e End portion O Piston center line

Claims (7)

A piston for an internal combustion engine,
A groove having an end opened to the top surface is formed on the outer peripheral side surface of the piston adjacent to the top surface of the piston ,
The outer peripheral side surface of the top land includes a first region corresponding to a pressure increase possibility portion, and a second region different from the first region,
The groove includes a circumferential groove portion connected to the end portion and extending in a circumferential direction on the outer peripheral side surface of the top land, and the circumferential groove portion extends in the circumferential direction in the first region of the outer peripheral side surface of the top land,
The end of the groove opens to the top surface in the second region of the outer peripheral side surface of the top land.
Piston characterized by that. The piston includes two recesses formed on the top surface of the piston so as to be adjacent to the outer peripheral side surface of the top land,
When defining a plane that includes the centerline of the piston, the two recesses are present on one side of the piston separated by the plane;
The circumferential groove portion of said groove extends in a circumferential direction in the first region of the top land outer peripheral surface defined as extending between the two recesses in the one side of the piston < The piston according to Claim 1 , wherein 3. The piston according to claim 1, wherein the circumferential groove portion of the groove extends continuously over the entire circumference of the piston. The groove piston according to any one of claims 1 to 3, characterized in that it is formed on the top surface of the portion of said top land outer peripheral side surface. The piston according to any one of claims 1 to 4 , wherein the groove is formed so that a cross-sectional area of the groove decreases as the end of the groove is approached.   A piston for an internal combustion engine,
  A groove having an end opened to the top surface is formed on the outer peripheral side surface of the piston adjacent to the top surface of the piston,
  The groove includes a circumferential groove,
  The groove is formed such that a cross-sectional area of the groove decreases as the groove moves away from the circumferential groove and approaches the end.
Piston characterized by that.   A spark ignition type internal combustion engine comprising the piston according to any one of claims 1 to 6.

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