JP2006170038A - Ohc engine and its assembling method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain a certain central distance between a gear on a cylinder block side and a gear on a cylinder head side, straddling a gasket and meshed with each other, by absorbing the difference in the thickness of the gasket disposed between the cylinder block and the cylinder head. <P>SOLUTION: Upon disposing the gasket 27 having a thickness different from a standard thickness, in order to maintain the central distance L132 to a set value between the gear 11 on the cylinder block 1 side and the gear 12 on the cylinder head 3 side which are meshed with each other, a position determining means is provided for determining the position of the cylinder head 3 in a state where it is transferred from a standard mounting position in the width direction of the cylinder block 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an OHC engine having a timing gear train that transmits rotation of a crankshaft provided in a cylinder block to a camshaft provided in a cylinder head via a plurality of gears, and an assembling method thereof.

  An OHC (overhead camshaft) engine is a cylinder head provided with a camshaft for opening and closing intake and exhaust valves. In such an OHC engine, an engine having a timing gear train connecting a crankshaft on the cylinder block side and a camshaft on the cylinder head side is known (see Patent Documents 1 and 2, etc.).

  For example, as shown in FIGS. 9A and 9B, the OHC engine includes a cylinder block (engine block) 1 and a cylinder head 3 provided on the top of the cylinder block 1 via a gasket 2. Yes. An oil pan 4 is provided below the cylinder block 1. An engine cover 5 is provided on the upper part of the cylinder head 3. A crankshaft 6 is rotatably supported at the lower end of the cylinder block 1, and a crank gear 7 is attached to the crankshaft 6. A cam shaft 8 is rotatably supported on the upper end portion of the cylinder head 3, and a cam gear 9 is attached to the cam shaft 8.

  The rotation of the crankshaft 6 is reduced to 1/2 rotation by the plurality of idle gears and the cam gear 9 and transmitted to the camshaft 8. The plurality of idle gears include a first block-side idle gear 10 meshed with the crank gear 7, a second block-side idle gear 11 meshed with the first block-side idle gear 10, and the second The head-side idle gear 12 is engaged with the block-side idle gear 11 across the gasket 2 and meshed with the cam gear 9. The first block side idle gear 10 and the second block side idle gear 11 are respectively attached to a first block side idle shaft 13 and a second block side idle shaft 14 that are rotatably supported by the cylinder block 1. . The head-side idle gear 12 is attached to a head-side idle shaft 15 that is rotatably supported by the cylinder head 3. These gears 7, 9, 10, 11 and 12 constitute a timing gear train.

  As shown in FIG. 10, the cylinder head 3 is positioned with respect to the cylinder block 1 by a plurality of cylindrical dowel pins (positioning pins) 41. The dowel pin 41 is fitted at its lower end to a dowel hole (positioning hole) 42 provided at the upper end of the cylinder block 1, and the upper end of the dowel pin 41 is provided at the lower end of the cylinder head 3. 43. In this state, the bolt 44 is inserted into the bolt insertion hole 45 and the dowel pin 41 provided in the cylinder head 3, and the bolt 44 is screwed into the screw hole 46 provided in the cylinder block 1. It is attached to the cylinder block 1 via the gasket 2.

  By the way, between the tooth surfaces of each gear (drive side gear and load side gear) constituting the timing gear train, there is a tooth thickness error of each gear, a center distance error between each gear (an axis between shafts to which each gear is mounted). A backlash (play) (see symbol J21 in FIG. 10) is provided for absorbing the distance error. For this reason, every time the load torque of the cam of the camshaft fluctuates, the load side gear moves by the amount of backlash, and the load side gear collides with the drive side gear, so-called rattling occurs. The noise generated by this gearing (gearing noise) is the main factor (about 60%) of noise during idle operation, but it is effective to reduce backlash to reduce gearing noise. I know it.

  Accordingly, in the OHC engine shown in FIG. 9, the gears 7, 9, 10, 11, 12 are set appropriately so that the backlash between the gears 7, 9, 10, 11, 12 is set to be small. Center distances L211, L221, L231, and L241 are set appropriately.

Japanese Patent Laid-Open No. 5-141207 JP-A-10-299758

  By the way, the gasket interposed between the cylinder block and the cylinder head not only functions to prevent pressure leakage in the cylinder (combustion chamber) of the cylinder block, but also functions to finely adjust the volume in the cylinder (combustion chamber). Also have. Specifically, since the volume in the cylinder is slightly different for each engine due to manufacturing variations of cylinder blocks, pistons, and the like, gaskets having different thicknesses are applied to each engine according to the volume difference in the cylinder. By doing in this way, it becomes possible to always make the volume in a cylinder constant.

  In order to finely adjust the volume in the cylinder, usually about three types of gaskets are prepared in advance. For example, if the volume in the cylinder is a specified value, use a gasket with a standard thickness. If the volume in the cylinder is smaller than the specified value, use a gasket that is thicker than the standard thickness. If the volume is larger than the specified value, a gasket formed with a thickness thinner than the standard thickness is used.

  Here, in the OHC engine shown in FIG. 9, when the thinnest gasket 2 is interposed, the second block side idle gear 11 and the head side idle gear 12 do not interfere with each other, and the standard thickness gasket is used. 2 so that the backlash J21 between the second block side idle gear 11 and the head side idle gear 12 is appropriate, that is, the second block side idle gear 11 and the head side idle gear 12 are interposed. The positions of the gears 11 and 12 are set so that the center distance L231 between the gears 11 and 12 is appropriate.

  However, as shown in FIG. 11, when the thickest gasket 2 is interposed, the center distance L232 between the second block side idle gear 11 and the head side idle gear 12 is the standard thickness gasket 2 interposed. It becomes larger than the center distance L231 (appropriate center distance). As a result, the backlash J22 between the second block side idle gear 11 and the head side idle gear 12 becomes larger than the backlash J21 (appropriate backlash) when the gasket 2 having a standard thickness is interposed. This will lead to worsening of rattling noise.

  Accordingly, an object of the present invention is to absorb the difference in the thickness of the gasket interposed between the cylinder block and the cylinder head and to engage the gear on the cylinder block side and the gear on the cylinder head side that are engaged across the gasket. Is to provide an OHC engine that can keep the center distance constant.

  In order to achieve the above object, according to the present invention, a cylinder head is provided on a cylinder block via a gasket, and a timing gear train connecting the crankshaft on the cylinder block side and the camshaft on the cylinder head side is provided. In the OHC engine, when a gasket having a thickness different from the standard thickness is interposed, the above-mentioned cylinder is used to keep the center distance between the gear on the cylinder block side and the gear on the cylinder head meshed with the gear at the set value. Positioning means for positioning the head in a state in which the head is moved in the width direction of the cylinder block from the standard mounting position is provided.

  Here, the positioning means comprises dowel holes provided in the cylinder block and the cylinder head, respectively, and dowel pins fitted to both the dowel holes, and the cylinder head is located at the standard mounting position. In addition, one of the dowel holes on the cylinder block side and the cylinder head side may be formed to be offset in the width direction of the cylinder block with respect to the other dowel hole.

  The present invention also provides a method for assembling an OHC engine in which a cylinder head is provided on a cylinder block via a gasket and a timing gear train connecting the crankshaft on the cylinder block side and the camshaft on the cylinder head side is provided. In order to maintain the center distance between the gear on the cylinder block side and the gear on the cylinder head side meshed with the gear when the gasket having a thickness different from the standard thickness is interposed, the cylinder head is standard. The cylinder block is moved from the mounting position in the width direction of the cylinder block.

  According to the present invention, the difference in the thickness of the gasket interposed between the cylinder block and the cylinder head is absorbed, and the gear on the cylinder block side and the gear on the cylinder head side meshed across the gasket. The center distance can be kept constant. Therefore, the backlash between the gear on the cylinder block side and the gear on the cylinder head side can always be set appropriately, and the rattling noise is not deteriorated.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic view of an OHC engine with a standard thickness gasket interposed according to an embodiment of the present invention. FIG. 2 is a plan view of the cylinder block. 3 is a cross-sectional view taken along line III-III in FIG. FIG. 4 is a bottom view of the cylinder head. 5 is a cross-sectional view taken along line VV in FIG.

  The OHC engine (hereinafter referred to as an engine) of the present embodiment is a multi-cylinder (four-cylinder in the illustrated example) engine for a vehicle or the like. Examples of the engine include a SOHC (single overhead camshaft) engine and a DOHC (double overhead camshaft) engine.

  Since the main configuration of the engine is the same as that described in the background art section (see FIG. 9), the same members are denoted by the same reference numerals and description thereof is omitted.

  In the figure, 21 is a cylinder (piston bore) (see FIG. 2) provided in the cylinder block (engine block) 1, and 22 is a bore (see FIG. 4) which is provided in the cylinder head 3 and constitutes a part of the combustion chamber. ).

  Here, in this specification, the width direction of the cylinder block and the cylinder head is a direction perpendicular to the axial direction of each shaft 6, 8, 13, 14, 15, and the upper surface of the cylinder block 1 or the cylinder head 3. A direction parallel to the lower surface of the plate (vertical direction in FIGS. 2 and 4). The longitudinal direction of the cylinder block and the cylinder head is a direction parallel to the axial direction of each shaft 6, 8, 13, 14, 15 and a direction parallel to the upper surface of the cylinder block 1 or the lower surface of the cylinder head 3. (The left-right direction in FIGS. 2 and 4).

  As shown in FIGS. 1, 2, and 3, a plurality of (ten in the illustrated example) screws with which bolts 23 for attaching the cylinder head 3 to the cylinder block 1 are screwed onto the upper end portion of the cylinder block 1. A hole 24 is provided. In the present embodiment, the screw holes 24 are provided at both ends in the longitudinal direction of the cylinder block 1 and between the cylinders 21 and at both ends in the width direction of the cylinder block 1 (see FIG. 2).

  As shown in FIGS. 1, 4, and 5, the cylinder head 3 is provided with a bolt insertion hole 25 through which the bolt 23 is inserted. The bolt insertion holes 25 are provided in the same number (that is, ten) as the screw holes 24 of the cylinder block 1. Each bolt insertion hole 25 is provided in alignment with the screw hole 24 of the cylinder block 1. That is, the bolt insertion holes 25 are provided at the same interval (pitch) as the screw holes 24 of the cylinder block 1.

  As will be described later, the shape and size of the bolt insertion hole 25 does not interfere with the bolt 23 when the cylinder head 3 is attached to the cylinder block 1 while being moved in the width direction of the cylinder block 1 from the standard attachment position. Is set to various shapes and sizes.

  Here, in this embodiment, in order to finely adjust the volume (volume) in the cylinder 21 (combustion chamber) of the cylinder block 1, the gasket 26 (see FIG. 1) having a standard thickness and a thickness larger than the standard thickness are used. One of the two types of gaskets, ie, a gasket 27 (hereinafter referred to as a thick gasket) (see FIG. 7) formed with a large thickness, is applied to each engine.

  As shown in FIGS. 1 to 5, a plurality of dowel pins (positioning pins) 28 are fitted to the upper end portion of the cylinder block 1 and the lower end portion of the cylinder head 3 when a gasket 26 having a standard thickness is interposed. First dowel holes (positioning holes) 29 and 30 (see FIG. 2 and FIG. 4, two in the illustrated example) are respectively provided. A plurality of dowel pins 28 (see FIGS. 2 and 4; two in the illustrated example) are fitted into the upper end of the cylinder block 1 and the lower end of the cylinder head 3 when a thick gasket 27 is interposed. Second dowel holes (positioning holes) 31 and 32 are provided, respectively.

  In the present embodiment, the first and second dowel holes 29 and 31 on the cylinder block 1 side are circular counterbore holes provided in the upper portion of the screw hole 24, and the first and second holes on the cylinder head 3 side are provided. The dowel holes 30 and 32 are circular counterbore holes provided below the bolt insertion hole 25.

  The first dowel hole 29 on the cylinder block 1 side is formed concentrically with the screw hole 24 (see FIG. 3). The second dowel hole 31 on the cylinder block 1 side is provided eccentrically with respect to the screw hole 24 by a predetermined offset amount e according to the thickness of the thick gasket 27 (see FIG. 3). The first and second dowel holes 30 and 32 on the cylinder head 3 side are formed concentrically with the bolt insertion hole 25 (see FIG. 5). In this way, when the dowel pin 28 is fitted into the first dowel holes 29 and 30 and the cylinder head 3 is positioned at the standard mounting position, the dowel hole 31 on the cylinder block 1 side becomes the cylinder head 3 side. The second dowel hole 32 is offset in the width direction of the cylinder block 1 (see FIG. 1). Further, the dowel pin 28 of the present embodiment is formed in a cylindrical shape.

  The offset amount e will be described with reference to FIG.

  In FIG. 6, the centers of the second block-side idle gear 11 and the head-side idle gear 12 when the standard-thickness gasket 26 is interposed are indicated by symbols C1 and C2, respectively.

  As shown in FIG. 6, when the gasket 26 having a standard thickness is interposed, the center distance L131 between the gears 11 and 12 becomes a predetermined value, and the backlash J11 between the gears 11 and 12 is appropriate. The positions of the gears 11 and 12 are set. In this state, if a thick gasket 27 is provided instead of the standard thickness gasket 26 in order to finely adjust (correct) the volume error in the cylinder 21 of the cylinder block 1, the center of the second block side idle gear 11 is provided. The center of C1 and the head-side idle gear 12 (see C4 in FIG. 6) is further increased in the vertical direction by a deviation (thickness change amount) t between the thickness of the standard gasket 26 and the thickness of the thick gasket 27. Spaced apart. Then, the center distance between the gears 11 and 12 (see the symbol L133 in FIG. 6) becomes larger than a predetermined value, and the backlash between the gears 11 and 12 becomes large.

  Accordingly, the center of the head-side idle gear 12 (see C3 in FIG. 6) is set to the center C1 side of the second block-side idle gear 11 by the predetermined offset amount e (that is, the figure). 6), the center distance L132 between the gears 11 and 12 when the thick gasket 27 is interposed between the gears 11 and 12 when the standard thickness gasket 26 is interposed. Can be made equal to the center distance L131.

  Here, the center distance L131 between the gears 11 and 12 when the standard thickness gasket 26 is interposed, and the center distance L132 between the gears 11 and 12 when the thick gasket 27 is interposed are expressed by the following equations. Is done.

L131 = (a ² + b ² ) ^1/2
L132 = ((ae) ² + (b + t) ² ) ^1/2
However, a is the center distance (gear reference width direction center distance) between the gears 11 and 12 with respect to the width direction of the cylinder block 1 when the gasket 26 having the standard thickness is interposed, and b is the gasket 26 having the standard thickness. This is the center distance between the gears 11 and 12 with respect to the vertical direction of the cylinder block 1 when it is interposed (reference vertical center distance).

  The center distance L131 between the gears 11 and 12 when the standard thickness gasket 26 is interposed is equal to the center distance L132 between the gears 11 and 12 when the thick gasket 27 is interposed (L131 = L132). The offset amount e obtained by the above equation is expressed by the following equation.

^{e = a- (a 2 + b} 2 - (b + t) 2) 1/2
For example, when the reference width direction center distance a is 20 mm, the reference vertical direction center distance b is 100 mm, and the thickness change amount t is 0.1 mm, the offset amount e is 0.506 mm.

  Next, a method for assembling the OHC engine of this embodiment will be described.

  First, with the cylinder head 3 and the gasket removed, the crankshaft 6 is rotated so that the piston (not shown) is positioned at the uppermost position. Next, the distance (piston protrusion amount) between the upper surface of the piston positioned at the top and the upper surface of the cylinder block 1 is measured. Next, the gasket to be used is determined according to the measured piston protrusion amount. Specifically, if the piston protrusion amount is a specified value, a standard thickness gasket 26 is used. If the piston protrusion amount is larger than the specified value (if the volume in the cylinder 21 is smaller than the specified value), a thick gasket 27 is used. use. Thus, by using the gasket according to the piston protrusion amount, the volume in the cylinder 21 of the cylinder block 1 is finely adjusted so that it always becomes a specified value.

  Next, when using the gasket 26 having the standard thickness, as shown in FIG. 1, after the lower end portion of the dowel pin 28 is fitted into the first dowel hole 29 on the cylinder block 1 side, The portion is fitted into the first dowel hole 30 on the cylinder head 3 side. In this way, the cylinder head 3 is positioned at the standard mounting position with respect to the cylinder block 1 so that the center distance L131 between the second block side idle gear 11 and the head side idle gear 12 becomes a set value. The Then, the bolt 23 is inserted into the bolt insertion hole 25 and the dowel pin 28 of the cylinder head 3, the bolt 23 is screwed into the screw hole 24 of the cylinder block 1, and the cylinder head 3 is inserted through the gasket 26 having a standard thickness. Install to cylinder block 1. Thereby, the backlash J11 between the second block side idle gear 11 and the head side idle gear 12 can be set appropriately.

  On the other hand, when the thick gasket 27 is used, as shown in FIG. 7, after the lower end portion of the dowel pin 28 is fitted into the second dowel hole 31 on the cylinder block 1 side, the upper end portion of the dowel pin 28 is moved to the cylinder head. It fits in the second dowel hole 32 on one side. By doing so, the cylinder head 3 is moved with respect to the cylinder block 1 in the width direction of the cylinder block 1 (see the arrow A in FIG. 7) with respect to the cylinder block 1 while being moved from the standard mounting position by the offset amount e. Is positioned. Then, the bolt 23 is inserted into the bolt insertion hole 25 and the dowel pin 28 of the cylinder head 3, the bolt 23 is screwed into the screw hole 24 of the cylinder block 1, and the cylinder head 3 is moved in the width direction of the cylinder block 1. In this state, the cylinder block 1 is attached via a thick gasket 27.

  As a result, the cylinder head 3 is attached to the cylinder block 1 while being moved in the width direction of the cylinder block 1 while keeping the center distance L132 between the second block side idle gear 11 and the head side idle gear 12 at a set value. be able to. Therefore, even if a thick gasket 27 having a thickness different from that of the standard thickness gasket 26 is provided, the center distance between the second block side idle gear 11 and the head side idle gear 12 is constant. The backlash J12 between the block-side idle gear 11 and the head-side idle gear 12 can be appropriately set.

  Here, in the present embodiment, the second dowel holes 31 and 32 and the dowel pins 28 on the cylinder block 1 side and the cylinder head 3 side constitute positioning means in the claims. In the present embodiment, the second block-side idle gear 11 and the head-side idle gear 12 form a cylinder block-side gear and a cylinder head-side gear in the claims.

  As described above, in the present embodiment, by changing the mounting position of the cylinder block 1 and the cylinder head 3 in the width direction, the standard thickness gasket 26 interposed between the cylinder block 1 and the cylinder head 3 is thick. The difference in thickness with the gasket 27 is absorbed, and the center distance between the second block-side idle gear 11 and the head-side idle gear 12 engaged across the gasket can be kept constant. Accordingly, the backlash between the second block-side idle gear 11 and the head-side idle gear 12 can always be set appropriately, and the rattling noise is not deteriorated.

  In the present embodiment, the second block-side idle gear 11 and the head-side idle gear 12 can be connected by a simple method such as changing the dowel hole in which the dowel pin 28 is fitted according to the thickness of the gasket to be used. The center distance can be kept constant. In addition, the present embodiment is highly practical because the same dowel pin 28 can be used when the standard thickness gasket 26 or the thick gasket 27 is interposed, and a jig or the like is not required.

  The present invention is not limited to the embodiment described above.

  For example, in the above embodiment, the second dowel hole 31 on the cylinder block 1 side in the standard mounting position is offset in the width direction of the cylinder block 1 with respect to the second dowel hole 32 on the cylinder head 3 side. On the contrary, the second dowel hole 32 on the cylinder head 3 side in the standard mounting position is opposite to the second dowel hole 31 on the cylinder block 1 side in the width direction of the cylinder head 3. May be offset. In this case, the second dowel hole 31 on the cylinder block 1 side is formed concentrically with the screw hole 24, and the second dowel hole 32 on the cylinder head 3 side is eccentric by a predetermined offset amount e with respect to the bolt insertion hole 25. It may be provided.

  Further, the shape of the dowel pin 28 and the dowel holes 29, 30, 31, and 32 is not limited to the above embodiment. For example, the dowel pin may be formed in a rectangular cross section or a polygonal cross section, and the dowel hole may be formed in a rectangular or polygonal shape.

  In the above embodiment, the first and second dowel holes 29, 30, 31, and 32 are provided in the upper part of the screw hole 24 or the lower part of the bolt insertion hole 25. The dowel holes 29, 30, 31 and 32 may be provided independently of the screw hole 24 or the bolt insertion hole 25. Alternatively, instead of the cylindrical dowel pin 28 and the first and second dowel holes 29, 30, 31, 32 provided in the upper part of the screw hole 24 or the lower part of the bolt insertion hole 25, as shown in FIG. In addition, a solid knock pin 33 may be provided, and first and second knock pin holes 34 and 35 into which the knock pin 33 is fitted may be provided independently of the screw hole 24 or the bolt insertion hole 25.

  Further, the number of gears constituting the timing gear train is not limited to the above embodiment. For example, the second block-side idle gear 11 and the cam gear 9 may be meshed, the crank gear 7 and the head-side idle gear 12 may be meshed, and further, the crank gear 7 and the cam gear 9 May be meshed directly without an idle gear.

  In the above embodiment, the gasket 27 thicker than the standard thickness is used to correct the increase in the volume in the cylinder 21 of the cylinder block 1. However, the volume in the cylinder 21 of the cylinder block 1 is corrected to be reduced. In order to achieve this, a gasket thinner than the standard thickness may be used. In that case, the cylinder head 3 may be attached by moving in the direction opposite to the above embodiment with respect to the width direction of the cylinder block 1. That is, the second dowel hole 31 on the cylinder block 1 side may be formed by being offset in the opposite direction to the above embodiment with respect to the width direction of the cylinder block 1.

  Furthermore, the OHC engine to which the present invention is applied is not limited to a multi-cylinder engine, but may be a single-cylinder engine.

1 is a schematic view of an OHC engine with a standard thickness gasket interposed according to an embodiment of the present invention. It is a top view of a cylinder block. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. It is a bottom view of a cylinder head. FIG. 5 is a cross-sectional view taken along line VV in FIG. 4. It is the schematic which shows the relationship between the thickness of a gasket, and offset amount. It is the schematic of the OHC engine which shows the state which interposed the gasket whose thickness is thicker than standard thickness. It is a principal part enlarged view of the OHC engine which shows the modification of a dowel pin and a dowel hole. (A) is a front view of an OHC engine, (b) is a side view. It is the schematic of the conventional OHC engine which shows the state which interposed the gasket of standard thickness. It is the schematic of the conventional OHC engine which shows the state which interposed the gasket whose thickness is thicker than standard thickness.

Explanation of symbols

1 Cylinder block 3 Cylinder head 11 Second block side idle gear (cylinder block side gear)
12 Head side idle gear (cylinder head side gear)
27 Gasket 28 Dowel Pin (Positioning means)
31 Second dowel hole (positioning means)
32 Second dowel hole (positioning means)
L132 Center distance

Claims (3)

In the OHC engine provided with a cylinder head on the cylinder block via a gasket and provided with a timing gear train connecting the crankshaft on the cylinder block side and the camshaft on the cylinder head side,
When a gasket with a thickness different from the standard thickness is inserted, the cylinder head is mounted as a standard so as to keep the center distance between the gear on the cylinder block side and the gear on the cylinder head side engaged with the gear at the set value. An OHC engine comprising positioning means for positioning in a state where the cylinder block is moved from the position in the width direction of the cylinder block.   The positioning means comprises a dowel hole provided in each of the cylinder block and the cylinder head, and a dowel pin fitted in both the dowel holes, and when the cylinder head is located at the standard mounting position, The OHC engine according to claim 1, wherein one of the dowel holes on the cylinder block side and the cylinder head side is formed to be offset in the width direction of the cylinder block with respect to the other dowel hole. In the method of assembling an OHC engine in which a cylinder head is provided on a cylinder block via a gasket and a timing gear train is provided to connect the cylinder block side crankshaft and the cylinder head side camshaft.
When a gasket with a thickness different from the standard thickness is inserted, the cylinder head is mounted as a standard so as to keep the center distance between the gear on the cylinder block side and the gear on the cylinder head side engaged with the gear at the set value. A method of assembling an OHC engine, wherein the OHC engine is attached to the cylinder block by moving in the width direction of the cylinder block from a position.

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