JP2009281253A - Cylinder head structure in engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cylinder head structure in an engine wherein the lower part of a head cover is brought into contact with a mating surface formed at the upper part of a cylinder head via a gasket, and a head cover fastening bolt inserted in the head cover is provided integrally with the cylinder head, wherein the head cover fastening bolt is made shorter to enhance the efficiency of assembling, and weight reduction is achieved. <P>SOLUTION: A camshaft holder 68 is provided integrally with the cylinder head 39 so as to rotatably support the camshaft 63 which constitutes a part of a valve gear 57. On the upper part of the camshaft holder, the upper end of a head cover fastening boss 96 is placed in a part above the mating surface 61. While forming a space under the head cover fastening boss, the head cover fastening boss 96 is integrally provided in such a manner as to be projected from the camshaft holder 68 sideways. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  According to the present invention, a cylinder head having an intake valve and an exhaust valve that can be opened and closed is coupled to an upper portion of a cylinder block having a cylinder bore that slidably fits a piston, and the intake valve and the exhaust valve are connected to each other. A lower portion of a head cover that forms a valve operating chamber that houses a valve operating mechanism that opens and closes between the cylinder head is brought into contact with a mating surface formed on the upper portion of the cylinder head via a gasket, The present invention relates to an engine in which a head cover fastening bolt to be inserted is screwed into a head cover fastening boss provided integrally with the cylinder head, and more particularly to improvement of the cylinder head structure.

The lower part of the head cover is brought into contact with a mating surface formed on the upper part of the cylinder head via a gasket, and a head cover fastening bolt inserted through the head cover is screwed to a head cover fastening boss provided integrally with the cylinder head. An engine is known from US Pat.
JP 2007-291979 A

  However, in the engine disclosed in Patent Document 1, the head cover fastening boss is provided integrally with the cylinder head so that the upper surface thereof is flush with the mating surface. In such a structure, The head cover fastening bolt becomes very long, which may lead to an increase in weight and a decrease in assembling ability.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a cylinder head structure in an engine in which a head cover fastening bolt is shortened to improve assembly and reduce the weight. .

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a cylinder head in which an intake valve and an exhaust valve are disposed on an upper part of a cylinder block having a cylinder bore into which a piston is slidably fitted. The lower surface of the head cover that forms a valve operating chamber for housing the valve operating mechanism for opening and closing the intake valve and the exhaust valve is formed between the cylinder head and the upper surface of the cylinder head. A part of the valve mechanism is configured in an engine in which a head cover fastening bolt inserted into the head cover is screwed into a head cover fastening boss provided integrally with the cylinder head. On the upper part of the camshaft holder provided integrally with the cylinder head so as to rotatably support the camshaft. The head cover fastening boss whose upper end is disposed above the mating surface is integrally provided so as to protrude laterally from the camshaft holder while forming a space below the head cover fastening boss. It is characterized by.

  According to a second aspect of the present invention, in addition to the configuration of the first aspect of the invention, the upper portion of the cylinder head protrudes upward from a bottom portion on which the camshaft holder projects and an outer periphery of the bottom portion. The upper end is formed in a box shape opened upward with a side wall portion on which the mating surface is formed, and the head cover fastening boss is disposed at a position spaced inward from the side wall portion.

  According to a third aspect of the invention, in addition to the configuration of the first or second aspect of the invention, the cylinder block and the cylinder head are respectively screwed into a plurality of stud bolts provided in a crankcase and the stud bolts. The head cover fastening boss is connected to the upper end of a stud bolt insertion boss that is coupled to the crankcase by a plurality of nuts and is integrally provided in the cylinder head so that the plurality of stud bolts are respectively inserted therethrough. A nut engaging surface arranged in the same plane as the upper end of the nut is formed so as to abut and engage the nut.

  According to a fourth aspect of the present invention, in addition to the configuration of the third aspect of the present invention, four stud bolt insertion bosses for inserting the four stud bolts are integrated into four corners of the camshaft holder. The two head cover fastening bosses are individually and integrally connected to two stud bolt insertion bosses disposed at diagonal positions among the stud bolt insertion bosses. And

  According to a fifth aspect of the invention, in addition to the configuration of the fourth aspect of the invention, at least one of the two stud bolt insertion bosses excluding the stud bolt insertion boss in which the head cover fastening boss is integrally connected. An annular oil passage is formed between a stud bolt inserted into the specific stud bolt insertion boss and the cylinder head, and the annular oil passage is configured to guide oil to the oil passage side provided in the head cover. A branch passage branched from the middle of the cylinder head is provided in the cylinder head.

  According to a sixth aspect of the invention, in addition to the configuration of the first aspect of the invention, a screw hole for screwing the head cover fastening bolt vertically penetrates the head cover fastening boss. It is provided in the head cover fastening boss.

  According to a seventh aspect of the invention, in addition to the configuration of the sixth aspect of the invention, a lower opening end of the screw hole is disposed above the mating surface of the cylinder head.

  Furthermore, in the invention according to claim 8, in addition to the configuration of the invention according to any one of claims 1 to 6, the lower end of the head cover fastening boss is disposed above the mating surface of the cylinder head. It is characterized by that.

  According to the first aspect of the present invention, the head cover fastening boss is integrally provided on the upper portion of the camshaft holder, and the mating surface is formed on the upper portion of the cylinder head so as to abut the lower portion of the head cover via the gasket. Since the upper end of the head cover fastening boss is disposed above the head cover, the length of the head cover fastening bolt can be shortened, the weight can be reduced, and the assemblability can be improved. In addition, since a space is formed below the head cover fastening boss, weight reduction can be achieved by undercutting the head cover fastening boss.

  According to the second aspect of the present invention, the upper portion of the cylinder head is formed in a box shape opened upward from a bottom portion on which the camshaft holder is projected and a side wall portion protruding upward from the outer periphery of the bottom portion. Since the head cover fastening boss is arranged at a position spaced inward from the side wall portion where the mating surface is formed at the upper end, the head cover fastening boss does not get in the way when processing the mating surface, and processing becomes easy. In addition, if the side wall and head cover fastening boss are connected together, sinking may occur on the outer surface of the side wall during casting of the cylinder head, but the head cover fastening boss is located at a position spaced inward from the side wall. Therefore, it is easy to maintain the appearance of the cylinder head by reliably preventing the occurrence of sink marks. Furthermore, due to the structure in which the head cover fastening boss is not directly connected to the side wall portion and the bottom portion, it becomes difficult to form a concave portion in which the lubricating oil is accumulated in the upper portion of the cylinder head, and the return of the lubricating oil from the cylinder head is good.

  According to the invention of claim 3, the cylinder block and the cylinder head are coupled to the crankcase by joint fastening with a plurality of stud bolts and a plurality of nuts, and each stud bolt is inserted therethrough. A nut engaging surface is formed at the upper end of the stud bolt insertion boss provided integrally with the cylinder head, and is arranged on the same plane as the upper end of the head cover fastening boss. Processing becomes easy.

  According to the fourth aspect of the present invention, the four stud bolt insertion bosses for inserting the four stud bolts are provided integrally at the four corners of the camshaft holder. Each stud bolt insertion boss can function, and two head cover fastening bosses are individually and integrally connected to two stud bolt insertion bosses arranged at diagonal positions. The strength rigidity of the head cover fastening boss can be increased by connecting the head stud fastening boss to the high stud bolt insertion boss, and the stud bolt insertion boss and the head cover fastening boss are arranged close to each other. Tool movement to machine the top end of the insertion boss and head cover fastening boss Kotogaki to reduce the release, it can contribute to shortening the processing time. Furthermore, by connecting the stud bolt insertion bosses arranged at the diagonal positions of the four corners of the camshaft holder, the distance between the two head cover fastening bosses can be set large, thereby stabilizing the head cover. And can be fixed to the cylinder head.

  According to the fifth aspect of the present invention, between the cylinder head and the stud bolt inserted into the specific stud bolt insertion boss different from the stud bolt insertion boss integrally provided with the head cover fastening boss. An annular oil passage is formed in the cylinder head, and a branch passage branched from the middle of the annular oil passage is provided in the cylinder head. Therefore, the head cover fastening boss and the branch passage can be spaced apart from each other, and the cylinder head can be enlarged. Can be prevented.

  According to the sixth aspect of the present invention, the screw hole for screwing the head cover fastening bolt is provided in the head cover fastening boss so as to penetrate the head cover fastening boss vertically. In addition to easy threading, chip removal is also facilitated. In addition, since the height of the head cover fastening boss can be set in accordance with the required screw hole distance, the head cover fastening boss can be miniaturized and the weight reduction can be further promoted.

  According to the seventh aspect of the present invention, since the lower opening end of the screw hole is above the mating surface of the cylinder head, the lower opening end of the screw hole can be easily seen, and the tool is attached to the lower opening end of the screw hole. Since it becomes easy to put in the side, deburring work becomes easy.

  Furthermore, since the lower end of the head cover fastening boss is above the mating surface of the cylinder head, the weight reduction of the head cover fastening boss can be further promoted.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on one embodiment of the present invention shown in the accompanying drawings.

  1 to 9 show an embodiment of the present invention, FIG. 1 is a right side view of a motorcycle, FIG. 2 is a vertical side view of a power unit, and FIG. 3 is a sectional view taken along line 3-3 in FIG. 4 is a sectional view taken along line 4-4 in FIG. 2, FIG. 5 is a sectional view taken along line 5-5 in FIG. 4, FIG. 6 is a sectional view taken along line 6-6 in FIG. 8 is a cross-sectional view taken along line 8-8 in FIG. 2, and FIG. 9 is a cross-sectional view taken along line 9-9 in FIG.

  First, in FIG. 1, a body frame F of the motorcycle includes a head pipe 16 that supports a front fork 15 that pivotally supports a front wheel WF at a lower end portion, and a rear pipe that extends rearward from the head pipe 16 and bends. In the main frame 17, a main frame 17 having a hanging portion 17a extending downward at the rear, a pair of left and right down frames 18 inclined downward from the head pipe 16 and disposed below the main frame 17, A pair of left and right seat rails 19 extending rearward from the upper portion of the hanging portion 17a, and a pair of left and right connecting frames 20 connecting the lower portion of the hanging portion 17a and the middle portion of both seat rails 19 are provided.

  A steering handle 21 is connected to the upper end of the front fork 15, an occupant seat 22 is provided on the seat rail 19, and a fuel tank 23 straddling the main frame 17 in front of the occupant seat 22 is provided. Attached to the main frame 17.

  A power unit P is disposed in a portion surrounded by the main frame 17 and the down frames 18. Thus, the first bracket 24 is provided at the lower ends of the down frames 18. The second and third brackets 25, 26 are provided at two positions spaced above and below the hanging portion 17 a of the main frame 17. The power unit P is attached to the first to third brackets 24, 25, and 26.

  A pivot plate 27 is fixed between the second and second brackets 25 and 26 in the hanging portion 17a of the main frame 17, and a swing arm that pivotally supports the rear wheel WR at the rear end thereof. The front end portions of the rear seats 28 are pivotably supported via a support shaft 29, and a rear cushion unit 30 is provided between the seat rails 19 and the swing arms 28.

  Between the countershaft 53 provided in the power unit P and the axle 32 of the rear wheel WR, a driving sprocket 33 provided on the countershaft 53, a driven sprocket 34 fixed to the axle 32, a driving sprocket 33 and a driven sprocket. A chain transmission means 36 comprising an endless chain 35 wound around 34 is provided.

  In FIG. 2, the power unit P includes a single-cylinder engine E having a crankcase 37 attached to the first to third brackets 24, 25, and 26, and shifts and decelerates the power of the engine E to the rear wheel WR. It consists of a constantly meshing gear transmission M that is housed in the crankcase 37 so as to transmit.

  The engine E includes a crankcase 37, a cylinder block 38 coupled to the top of the crankcase 37, a cylinder head 39 coupled to the upper end of the cylinder block 38, and a head cover 40 coupled to the cylinder head 39. Is provided.

  The upstream ends of the intake pipes 41 connected to the rear side surface of the cylinder head 39 are connected to an air cleaner 43 via a carburetor 42, and the air cleaner 43 is fixedly disposed above the rear portion of the power unit P. An exhaust pipe 44 connected to the front side surface of the cylinder head 39 passes below the power unit P and extends rearward, and is connected to an exhaust muffler 45 disposed on the right side of the rear wheel WR.

  The crankcase 37 is formed by joining a pair of left and right case halves 46 and 47, and a crankshaft 48 having an axis along the width direction of the motorcycle is rotated by both case halves 46 and 47. It is supported freely.

  The cylinder block 38 is connected to a crankcase 37 in such a manner that the cylinder block 38 is inclined forwardly forward in the traveling direction of the motorcycle, and a piston 49 is slidably fitted into the cylinder block 38. A cylinder bore 50 to be aligned is provided, and the piston 49 is connected to a crankpin 48 a provided in the crankshaft 48 via a connecting rod 51.

  The constantly meshing gear transmission M is provided with a gear train having a plurality of shift stages that can be selectively established between a main shaft 52 to which power is transmitted from the crankshaft 48 and a counter shaft 53. The main shaft 52 and the counter shaft 53 have an axis parallel to the crank shaft 48 and are rotatably supported by the crank case 37, and protrude from the case half 46 of the crank case 36. The drive sprocket 33 is fixed to the end of the shaft 53.

  By the way, the cylinder head 39 is provided with an intake valve 55 and an exhaust valve 56 that can be opened and closed while being urged by a spring in the valve closing direction, and a valve operating mechanism 57 that opens and closes the intake valve 55 and the exhaust valve 56 is provided. A valve operating chamber 58 is formed between the cylinder head 39 and the head cover 40.

  Referring also to FIG. 3, a spark plug 60 is attached to the cylinder head 39 so that the top of the piston 49 faces the combustion chamber 59 formed between the cylinder block 38 and the cylinder head 39. .

  The upper portion of the cylinder head 39 is formed in a box shape opened upward by a bottom portion 39a facing upward and a side wall portion 39b protruding upward from the outer periphery of the bottom portion 39a and continuing in an endless manner. A lower portion of the head cover 40 formed in a box shape that is open to the bottom is brought into contact with a mating surface 61 formed on the upper surface of the side wall 39b via a gasket 62.

  The valve operating chamber 58 is formed between the upper portion of the cylinder head 38 and the head cover 40, and the valve operating mechanism 57 accommodated in the valve operating chamber 58 has an axis parallel to the crankshaft 48. A cam shaft 63 disposed between the intake valve 55 and the exhaust valve 56, an intake side rocker arm 66 disposed between the intake side cam 64 and the intake valve 55 disposed on the cam shaft 63, and a cam shaft 63. And an exhaust side rocker arm 67 provided between the exhaust side cam 65 and the exhaust valve 56.

  4 to 6 together, in order to rotatably support the cam shaft 63, the cylinder head 39 has a pair of cams protruding upward from the bottom portion 39a of the upper portion of the cylinder head 39. Shaft holders 68, 69 are integrally provided with an interval in the axial direction of the camshaft 63. Between the inner periphery of the support hole 72 provided in one camshaft holder 68 and the outer periphery of one end of the camshaft 63. The ball bearing 70 is interposed between the cam shaft 63 and the inner periphery of the support hole 73 provided in the other camshaft holder 69 so as to be coaxial with the support hole 72.

  The support hole 73 provided in the other camshaft holder 69 is formed to have a larger diameter than the support hole 72 provided in one camshaft holder, and the camshaft in which ball bearings 70 and 71 are mounted on the outer periphery. 63 is assembled to the cylinder head 39 so as to be inserted into the support holes 72 and 73 of both camshafts 68 and 69 from the other camshaft holder 69 side, and the camshaft 63 is attached to the other camshaft holder 69. The engagement plate 74 is engaged by the outer ring of the ball bearing 71 interposed between the camshaft holder 69 and contacted from the outside to prevent the camshaft 63 from being separated from the camshaft holders 68 and 69 by bolts 75. It is concluded.

  By the way, the axes of the support holes 72 and 73 and the camshaft 63 lie on a plane along the mating surface 61. In order to allow the camshaft 63 to be assembled to the cylinder head 39, A semicircular cutout 76 is provided on the side wall 39b in the upper part of the cylinder head 39 at a portion facing the end so that the camshaft 63 can be inserted into the support holes 72 and 73. A lid 62 a for closing the notch 76 is formed integrally with the gasket 62.

  Rotational power from the crankshaft 48 is transmitted to the camshaft 63 at a reduction ratio of ½ by the timing transmission means 78. The timing transmission means 78 is provided on the crankshaft 48. A drive sprocket (not shown), a driven sprocket 80 fixed to the other end of the camshaft 48, and an endless timing chain 81 wound around the drive sprocket and the driven sprocket 80, The cylinder block 38 and the cylinder head 39 are formed with a chain travel passage 82 that allows the timing chain 81 to travel.

  The intake side rocker arm 66 is swingably supported by an intake side rocker shaft 83 provided between the camshaft holders 68 and 69, and an intake side cam 64 is attached to one end portion of the intake side rocker arm 66. A roller 87 that is in rolling contact is pivotally supported, and a tappet screw 88 that abuts on the upper end of the intake valve 55 is screwed to the other end of the intake side rocker arm 66 so that the forward / backward position can be adjusted. The exhaust-side rocker arm 67 is swingably supported by an exhaust-side rocker shaft 84 provided between the camshaft holders 68 and 69, and an exhaust-side cam is provided at one end of the exhaust-side rocker arm 67. A roller 89 that is in rolling contact with the roller 65 is pivotally supported, and a tappet screw 90 that is in contact with the upper end of the exhaust valve 56 is screwed to the other end of the exhaust-side rocker arm 67 so that the forward / backward position can be adjusted.

  In FIG. 7, one camshaft holder 68 is provided with a bottomed support hole 91, and the other camshaft holder 69 is provided with a support hole 92 that is a through hole coaxial with the support hole 91. The side rocker shaft 83 is fitted into the support holes 91 and 92 from the support hole 92 side, and a distal end portion is provided on the outer periphery of the intake side rocker shaft 83 in order to determine the axial position of the intake side rocker shaft 83. A screw member 85 that engages the camshaft holder 68 is screwed into the camshaft holder 68.

  The exhaust side rocker shaft 84 is fitted to the camshaft holders 68 and 69 in the same manner as the intake side rocker shaft 83, and is a screw member 86 for determining the axial position of the exhaust side rocker shaft 84 (see FIG. 4). Is fitted to the camshaft holder 69.

  Incidentally, the lower portion of the head cover 40 is brought into contact with a mating surface 61 formed at the upper end of the side wall portion 39b of the cylinder head 39 via a gasket 62. Two head cover fastening bolts 95 inserted through the head cover 40 are provided. , 95 are respectively screwed into two head cover fastening bosses 96, 97 provided integrally with the cylinder head 39, whereby the head cover 40 is coupled to the cylinder head 39.

  The head cover fastening bosses 96 and 97 are provided on upper portions of camshaft holders 68 and 69 provided integrally with the cylinder head 39 so as to rotatably support a camshaft 63 constituting a part of the valve operating mechanism 57. The head cover fastening bosses 96 and 97 are integrally provided so that the upper end is disposed above the mating surface 61, and the head cover fastening bosses 96 and 97 form a space below the head cover fastening bosses 96 and 97. The camshaft holders 68 and 69 are integrally provided on the upper portions of the camshaft holders 68 and 69 so as to protrude laterally from the camshaft holders 68 and 69. Moreover, the space below the head cover fastening bosses 96 and 97 is formed by a sand core when the cylinder head 39 is cast.

  By the way, the cylinder block 38 and the cylinder head 39 include a plurality of, for example, four stud bolts 98, 99, 100, 101 provided on the crankcase 37 and a plurality of, for example, four screwed to the stud bolts 98 to 101, respectively. Four stud bolt insertion bosses 103, 104, 105, 106 through which the stud bolts 98 to 101 are inserted are integrated with the cylinder head 39 by being fastened together by two nuts 102. Is provided.

  The four stud bolt insertion bosses 103 to 106 for allowing the four stud bolts 98 to 101 to pass therethrough are integrally provided at the four corners of the both camshaft holders 68 and 69. Two head cover fastening bosses 96 and 97 are individually and integrally connected to two stud bolt insertion bosses 103 and 105 arranged at diagonal positions among the bolt insertion bosses 103 to 106. Moreover, the head cover fastening bosses 96 and 97 are disposed at positions spaced inward from the side wall 39 b in the upper part of the cylinder head 39.

  Nuts engaging surfaces 103a, 104a, 105a, 106a are formed on the upper ends of the stud bolt insertion bosses 103-106, which are arranged in the same plane as the upper ends of the head cover fastening bosses 96, 97, and stud bolts 98-101. The nuts 102 to be screwed together are brought into contact with and engaged with the nut engaging surfaces 103a to 106a through washers 107.

  The head cover fastening bolts 95 are inserted into the head cover 40 with an annular seal member 108 interposed between the head cover 40 and the head cover fastening bosses 96 and 97. , And screw shaft portions 95b projecting coaxially from the flange portion 95a. The screw shaft portions 95b are screwed into the screw holes 109, 110 provided in the head cover fastening bosses 96, 97. Is done.

  By the way, the lower ends of the head cover fastening bosses 96 and 97 are disposed above the mating surface 61 of the cylinder head 39, and the screw holes 109 and 110 are lower openings of the screw holes 109 and 110, respectively. The end is disposed above the mating surface 61 of the cylinder head 39 so as to vertically penetrate the head cover fastening bosses 96 and 97.

  2, 3, 8 and 9, the head cover 40 is provided with an oil passage 111 extending in a direction perpendicular to the axis of the camshaft 63, and as shown in FIGS. 2 and 8, Two oil jets 112 and 113 communicating with the oil passage 111 are provided in the head cover 40 so as to eject oil to the valve operating mechanism 57 side.

  By the way, among the four stud bolt insertion bosses 103 to 106, a specific stud bolt insertion which is at least one of the two except for the stud bolt insertion bosses 103 and 105 in which the head cover fastening bosses 96 and 97 are integrally connected. As shown in FIG. 5, an annular oil passage 114 is formed between the boss, the stud bolt 99 inserted into a specific stud bolt insertion boss 104, which is one in this embodiment, and the cylinder head 39. The Thus, an annular oil passage 115 connected to the annular oil passage 114 is also formed between the stud bolt 99 and the cylinder block 38. The annular oil passage 115 is not shown through an oil passage 116 provided in the crankcase 37. Connected to oil supply.

  A branch passage 117 branched from the middle of the annular oil passage 114 so as to guide oil to the oil passage 111 side of the head cover 40 is provided in the cylinder head 39 so as to extend obliquely upward. The lower end of the communication passage 118 extending downward and the upper end of the branch passage 117 are connected via a sleeve 119 sandwiched between the cylinder head 39 and the head cover 40.

  Next, the operation of this embodiment will be described. Above the camshaft holders 68 and 69 provided integrally with the cylinder head 39 so as to rotatably support the camshaft 63 constituting a part of the valve operating mechanism 57. Since the head cover fastening bosses 96 and 97 whose upper ends are disposed above the mating surface 61 of the upper end of the cylinder head 39 are integrally provided so as to protrude sideways from the camshaft holders 68 and 69. The length of the head cover fastening bolts 95 can be shortened, and the weight can be reduced and the assembling property can be improved. In addition, since a space is formed below the head cover fastening bosses 96 and 97, weight reduction can be achieved by removing the thickness below the head cover fastening bosses 96 and 97. Further, by forming the space with a sand core at the time of casting the cylinder head 39, it is not necessary to increase the core, and a space can be formed below the head cover fastening bosses 96 and 97 while suppressing an increase in cost. it can.

  The upper portion of the cylinder head 39 is formed in a box shape opened upward by a bottom 39a on which the head cover fastening bosses 96 and 97 project and a side wall 39b protruding upward from the outer periphery of the bottom 39a. Since the head cover fastening bosses 96 and 97 are disposed at positions spaced inward from the side wall portion 39b where the mating surface 61 is formed, the head cover fastening bosses 96 and 97 become an obstacle when the mating surface 61 is processed. If the side wall 39b and the head cover fastening bosses 976 and 97 are integrally connected, there is a possibility that the outer surface of the side wall 39b may sink when the cylinder head 39 is cast. Since the head cover fastening bosses 96 and 97 are disposed at positions spaced inward from the head, it is possible to reliably prevent the occurrence of the above-mentioned sinking and Easily retain the appearance of de 39. Further, the structure in which the head cover fastening bosses 96 and 97 are not directly connected to the side wall portion 39b and the bottom portion 39a makes it difficult to form a recess in the upper portion of the cylinder head 39 to collect lubricating oil. The return of is good.

  Further, the cylinder block 38 and the cylinder head 39 are coupled to the crankcase 37 by a plurality of bolts, for example, four stud bolts 98, 99, 100, 101 and a plurality of nuts 102. Nut engagement arranged on the same plane as the upper ends of the head cover fastening bosses 96, 97 at the upper ends of stud bolt insertion bosses 103, 104, 105, 106 provided integrally with the cylinder head 39 so as to be inserted through the cylinder 101, respectively. Since the surfaces 103a, 104a, 105a, and 106a are formed, processing of the upper ends of the head cover fastening bosses 96 and 97 and the nut engaging surfaces 103a to 106a is facilitated.

  Also, since four stud bolt insertion bosses 103 to 106 for inserting the four stud bolts 98 to 101 are integrally provided at the four corners of the camshaft holders 68 and 69, the strength of the camshaft holders 68 and 69 is increased. The stud bolt insertion bosses 103 to 106 can function as rigid portions, and the two head cover fastening bosses 96 and 97 are individually provided on the two stud bolt insertion bosses 103 and 105 arranged at diagonal positions. Since the head cover fastening bosses 96 and 97 are connected to the stud bolt insertion bosses 103 and 105 having high strength and rigidity, the strength rigidity of the head cover fastening bosses 96 and 97 can be increased. , Stud bolt insertion bosses 103 and 105 and head cover fastening bosses 96 and 97 By being arranged in contact with each other, the moving distance of the tool for machining the upper end surfaces of the stud bolt insertion bosses 103 and 105 and the head cover fastening bosses 96 and 97 can be reduced, which contributes to shortening the machining time. it can.

  Further, the head cover fastening bosses 96, 97 are connected to the stud bolt insertion bosses 103, 105 arranged at the diagonal positions of the four corners of the camshaft holders 68, 69, so that two head cover fastening bosses 96, The space between the 97 can be set large, whereby the head cover 40 can be stably fixed to the cylinder head 39.

  The cylinder head 39 includes a stud bolt 99 that is inserted into a specific stud bolt insertion boss 104 that is different from the stud bolt insertion bosses 103 and 105 in which the head cover fastening bosses 96 and 97 are integrally provided. An annular oil passage 114 is formed between them, and a branch passage 117 that branches from the middle of the annular oil passage 114 and communicates with the oil passage 111 of the head cover 40 is provided in the cylinder head 39, so that the head cover fastening bosses 96 and 97, The branch passage 117 can be spaced apart, and the cylinder head 39 can be prevented from being enlarged.

  Further, since the lower ends of the head cover fastening bosses 96 and 97 are located above the mating surface 61 of the cylinder head 39, the weight reduction of the head cover fastening bosses 96 and 97 can be further promoted.

  Further, screw holes 109, 110 for screwing the head cover fastening bolts 95 ... are provided in the head cover fastening bosses 96, 97 so as to penetrate the head cover fastening bosses 96, 97 vertically. In addition to easy preparation and threading of 110, chip removal is also facilitated. Further, since the height of the head cover fastening bosses 96 and 97 can be set in accordance with a necessary screw hole distance, the head cover fastening bosses 96 and 97 can be reduced in size, and the weight reduction can be further promoted. it can.

  Moreover, since the lower opening ends of the screw holes 109 and 110 are located above the mating surface 61 of the cylinder head 39, the lower opening ends of the screw holes 109 and 110 can be easily seen, and a tool can be attached to the lower portion of the screw holes 109 and 110. Since it becomes easy to put in the opening end side, the deburring operation becomes easy.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the present invention described in the claims. It is.

1 is a right side view of a motorcycle. It is a vertical side view of a power unit. FIG. 3 is a sectional view taken along line 3-3 in FIG. 2. FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. FIG. 5 is a sectional view taken along line 5-5 of FIG. FIG. 6 is a sectional view taken along line 6-6 of FIG. FIG. 7 is a cross-sectional view taken along line 7-7 in FIG. 4. FIG. 8 is a cross-sectional view taken along line 8-8 in FIG. 2. FIG. 9 is a cross-sectional view taken along line 9-9 in FIG. 8.

Explanation of symbols

37 ... Crankcase 38 ... Cylinder block 39 ... Cylinder head 39a ... Bottom 39b ... Side wall 40 ... Head cover 49 ... Piston 50 ... Cylinder bore 55 ... Intake valve 56 ... Exhaust valve 57 ... Valve mechanism 58 ... Valve chamber 61 ... Matching surface 62 ... Gasket 63 ... Cam shaft 68, 69 ... Cam shaft holder 95 ... Head cover fastening bolts 96, 97 ... Head cover fastening bosses 96, 97 ... Head cover fastening bosses 98, 99, 100, 101 ... Stud bolts 102 ... Nuts 103, 104, 105, 106,. · Stud bolt insertion bosses 103a, 104a, 105a, 106a · · · Nut engagement surfaces 109, 110 · · · screw holes 111 · · · oil passage 114 ... the annular oil passage 117 ... branch passage E ··· engine

Claims (8)

  Cylinder head in which an intake valve (55) and an exhaust valve (56) are disposed on an upper part of a cylinder block (38) having a cylinder bore (50) into which a piston (49) is slidably fitted. 39) and a valve operating chamber (58) for accommodating a valve operating mechanism (57) for opening and closing the intake valve (55) and the exhaust valve (56) is formed between the cylinder head (39). For fastening the head cover, the lower portion of the head cover (40) is brought into contact with the mating surface (61) formed on the upper portion of the cylinder head (39) via the gasket (62) and is inserted into the head cover (40). In an engine in which a bolt (95) is screwed to a head cover fastening boss (96, 97) provided integrally with the cylinder head (39), the valve mechanism (57) Above the mating surface (61) above the camshaft holder (68, 69) provided integrally with the cylinder head (39) so as to rotatably support the camshaft (63) constituting the portion. The head cover fastening boss (96, 97) having the upper end disposed on the side protrudes laterally from the camshaft holder (68, 69) while forming a space below the head cover fastening boss (96, 97). Thus, a cylinder head structure in an engine, which is integrally provided.   The upper portion of the cylinder head (39) protrudes upward from the outer periphery of the bottom (39a) on which the camshaft holder (68, 69) is projected, and the mating surface ( 61) is formed in a box shape opened upward with the side wall portion (39b), and the head cover fastening boss (96, 97) is disposed at a position spaced inward from the side wall portion (39b). The cylinder head structure in an engine according to claim 1, wherein   The cylinder block (38) and the cylinder head (39) are respectively screwed into a plurality of stud bolts (98, 99, 100, 101) provided on the crankcase (37) and the stud bolts (98 to 101). The cylinder head (39) is integrally provided so as to be coupled to the crankcase (37) by joint tightening with a plurality of nuts (102) to be inserted into the plurality of stud bolts (98 to 101). Nut engaging surfaces (103a, 104a, 105a, 103a, 104a, 105a, 103a, 104a, 105a, 106a, 103a, 104a, 105a, 103a, 104a, 105a, 106) 106a) is formed so as to abut and engage the nut (102). Cylinder head structure in an engine according to claim 1 or 2, wherein.   Four stud bolt insertion bosses (103 to 106) for inserting the four stud bolts (98 to 101) are integrally provided at four corners of the camshaft holder (68, 69). Of the stud bolt insertion bosses (103 to 106), two stud bolt insertion bosses (103, 105) arranged at diagonal positions are individually provided with the two head cover fastening bosses (96, 97). 4. A cylinder head structure in an engine according to claim 3, wherein the cylinder head structure is integrally provided.   A specific stud that is at least one of the two stud bolt insertion bosses (104, 106) excluding the stud bolt insertion boss (103, 105) in which the head cover fastening boss (96, 97) is integrally connected. An annular oil passage (114) is formed between the stud bolt (99) inserted into the bolt insertion boss (104) and the cylinder head (49), and an oil passage (111) provided in the head cover (40). The cylinder head in an engine according to claim 4, wherein a branch passage (117) branched from the middle of the annular oil passage (114) so as to guide oil to the cylinder side is provided in the cylinder head (39). Construction.   Screw holes (109, 110) for screwing the head cover fastening bolts (95) pass through the head cover fastening bosses (96, 97) vertically so as to pass through the head cover fastening bosses (96, 97). The cylinder head structure in the engine according to claim 1, wherein the cylinder head structure is provided.   The cylinder head structure in an engine according to claim 6, wherein a lower opening end of the screw hole (109, 110) is disposed above the mating surface (61) of the cylinder head (39).   The lower end of the head cover fastening boss (96, 97) is disposed above the mating surface (61) of the cylinder head (39). Cylinder head structure in the engine.

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