JP2007064051A - Valve train support structure for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a valve train support structure for internal combustion engine with high support stiffness, in which structure supporting a camshaft and rocker arm shafts can be easily assembled to the inside of a valve chamber. <P>SOLUTION: A valve train 40 comprises: the camshaft 41 disposed in the valve chamber 25 rotated to be interlocked with the crankshaft 6; cams 51, 61 disposed to the camshaft 41; rocker arms 52, 62 whose one end parts 52a, 62a are brought into contact with the cams 51, 61 and other end parts 52c, 62c are brought into contact with valves 20, 25; the rocker arm shafts 53, 63 supporting the rocker arms 52, 62 to be capable of rocking. A rocker arm shaft holder 70 to which the rocker arm shafts 53, 63 are journaled is provided, a camshaft support part 45 to which the camshaft 41 is journaled is disposed integrally with a cylinder head 2, and the camshaft support part is disposed separately from the rocker arm shaft holder 70. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a valve mechanism support structure for an internal combustion engine, and more particularly to a structure for supporting a camshaft and a rocker arm shaft constituting the valve mechanism.

  An internal combustion engine in which a camshaft constituting a valve operating mechanism for driving an intake / exhaust valve is disposed in a valve operating chamber inside a cylinder head is referred to as an OHC type and has been well known. The valve mechanism of the internal combustion engine is configured to control the operation of a cam provided on a camshaft rotatably supported in a valve operating chamber via a rocker arm that is swingably supported by a rocker arm shaft that is a fixed shaft. It is comprised so that a valve | bulb may be driven by making it transmit to. The rocker arm is swingable with one end contacting the cam and the other end contacting the valve. The cam pushes up one end of the rocker arm so that the other end faces downward. It swings and the valve is pushed down. An internal combustion engine having such a valve mechanism is provided with a structure for supporting a camshaft and a rocker arm shaft in a valve chamber.

  Conventionally, the camshaft is pivotally supported by a camshaft holder created separately from the cylinder head. The camshaft holder is housed in the valve operating chamber and assembled with the cylinder head. Further, the camshaft holder is integrally formed with a support portion for supporting the rocker arm shaft, and the rocker arm shaft is pivotally supported by the support portion (for example, Patent Document 1).

JP 2004-116297 A

  However, according to the conventional support structure, the camshaft is supported while the camshaft is supported on the camshaft holder and the rocker arm shaft supporting the rocker arm is supported on the camshaft holder. There was a problem that it was difficult to assemble because it had to be assembled in the valve chamber.

  According to Patent Document 1, the conventional camshaft holder has a left side portion and a right side portion that respectively support the end portions of the rocker arm shaft, and a front side connecting portion and a rear side connecting portion that connect these left and right portions. Configured. However, since these two connecting portions are configured to connect the lower portions of the left and right portions, a load acting on the rocker arm is received when the cam pushes up one end portion of the rocker arm upward by the operation of the valve mechanism. As a result, the rocker arm arm shaft may bend. For this reason, ensuring the intensity | strength of the structure for supporting a rocker arm shaft has been a subject.

  In view of such problems, the present invention can easily assemble the structure for supporting the camshaft and the rocker arm shaft in the valve operating chamber, and can ensure the strength for supporting the rocker arm shaft. An object is to provide a valve mechanism support structure for an internal combustion engine.

  To achieve the above object, a valve mechanism support structure for an internal combustion engine according to the present invention includes a cylinder in which a piston is slidably disposed, and a combustion chamber that is coupled to the cylinder to form a combustion chamber together with the piston. A cylinder head that forms a cylinder, a crankshaft that rotates in conjunction with a piston, a valve that is disposed in the valve chamber and opens and closes with respect to the combustion chamber, and a valve that is disposed in the valve chamber and drives the valve In the valve mechanism support structure of the internal combustion engine configured by the mechanism, the valve mechanism is disposed in the valve chamber and rotates in conjunction with the crankshaft; a cam provided on the camshaft; A rocker arm having one end in contact with the cam and the other end in contact with the valve, and a rocker arm shaft that swingably supports the rocker arm. By swinging the rocker arm is configured to drive the valve receiving. A rocker arm shaft holder that pivotally supports the rocker arm shaft is provided, and a camshaft support portion that pivotally supports the camshaft is provided integrally with the cylinder head and is provided separately from the rocker arm shaft holder.

  Further, the rocker arm shaft holder includes a plurality of shaft support portions that respectively support end portions of the rocker arm shaft, and a connection portion that connects the plurality of shaft support portions, and the connection portion is pivoted by the plurality of shaft support portions. It is preferable to provide it on the opposite side to the side where the contact part which the cam and the one end part of a rocker arm contact is located with respect to the axis line of the rocker arm shaft supported. Furthermore, it is preferable that the rocker arm shaft holder pivotally supports a plurality of rocker arm shafts, and the connecting portion is provided across the plurality of rocker arm shafts when viewed in the axial direction of the cylinder.

  According to the valve mechanism support structure of the internal combustion engine according to the present invention configured as described above, the camshaft is pivotally supported by the camshaft support portion integrated with the cylinder head, and the rocker arm shaft is connected to the camshaft support portion. Is supported by a separate rocker arm shaft holder. Accordingly, the camshaft and the rocker arm shaft can be assembled separately in order, and the valve mechanism can be easily assembled in the valve chamber.

  The rocker arm shaft holder includes a plurality of shaft support portions that respectively support end portions of the rocker arm shaft, and a connection portion that connects the plurality of shaft support portions, and the connection portion is connected to the axis of the rocker arm shaft. On the other hand, the cam and the rocker arm are provided on the side opposite to the side where the contact portion is located. Thereby, the load which acts on the rocker arm shaft when one end of the rocker arm is pushed up by the operation of the cam can be received by the connecting portion located on the opposite side of the contact portion with respect to the shaft. Thus, the support rigidity of the rocker arm shaft is improved, and the bending of the rocker arm shaft that may occur when the valve operating mechanism is activated can be suppressed.

  Further, when a plurality of rocker arm shafts are provided, the connecting portion is provided so as to straddle the plurality of rocker arm shafts. Thereby, bending with respect to each of a plurality of rocker arm shafts can be suppressed.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. 1 and 2 are sectional views of an engine E having a valve mechanism support structure for an internal combustion engine according to the present invention. In the following, the direction of the arrow F in the figure is the front, the direction of the arrow U is the upward, and the direction of the arrow R is the right. The engine E includes a head cover 1, a cylinder head 2, a cylinder block 3, and a crankcase 4, and these members 1 to 4 are connected vertically to form a housing H of the engine E. Inside the housing H, a piston 5, a crankshaft 6, an intake valve 20 and an exhaust valve 25, a chain transmission mechanism 30, and a valve mechanism 40 are disposed.

  The engine E is an OHC type internal combustion engine configured by providing the cylinder head 2 with a camshaft 41 that constitutes the valve mechanism 40, and is disposed in a vehicle such as a two-wheeled vehicle to constitute a power train. The engine E is disposed in the vehicle such that the cylinder shaft A extends in the front-rear direction.

  The cylinder block 3 has a cylindrical cylinder chamber 3a formed therein, and a piston 5 is slidably disposed in the cylinder chamber 3a. The crankcase 4 is integrated by joining right and left case halves (only the right case half 4R is shown), and a crank chamber 4a is formed inside. The crankcase 4 is coupled to the rear portion of the cylinder block 3, and the crank chamber 4a communicates with the cylinder chamber 3a. A crankshaft 6 that is rotatably supported is accommodated in the crank chamber 4a. The crankshaft 6 is integrally formed by connecting left and right shaft portions 6R, 6L by crankpins 6P. The piston 5 and the crankshaft 6 are connected via a connecting rod 7 so that the reciprocating sliding of the piston 5 and the rotation of the crankshaft 6 are interlocked.

  The cylinder head 2 is coupled to the front portion of the cylinder block 3 and is surrounded by the rear wall surface of the cylinder head 2 and the front surface of the piston 5 to form a combustion chamber 10. A spark plug 8 is attached to the cylinder head 2, and a tip 8 a of the spark plug 8 faces the combustion chamber 10. A head cover 1 is coupled to the front portion of the cylinder head 2, and a valve operating chamber 15 surrounded by the inner wall surface of the cylinder head 2 and the inner wall surface of the head cover 1 is formed inside the cylinder head 2. . In the valve operating chamber 15, an intake valve 20, an exhaust valve 25, and a valve operating mechanism 40 are disposed.

  As shown in FIG. 2, the cylinder head 2 is formed with an intake port 11 and an exhaust port 13 that open to the combustion chamber 10, respectively, and an intake port 12 that communicates the intake port 11 with the outside, and an exhaust port 13. And an exhaust port 14 communicating with the outside is formed inside. Two intake ports 11 and two exhaust ports 13 are formed.

  The intake valve 20 is provided inside the intake port 11. The stem 21 is lifted forward and a face 21 a is formed at the rear end thereof, the retainer 22 and spring seat 23 attached to the stem 21, and the retainer 22. And a valve spring 24 mounted between the spring seats 23, and the face 21 a is always urged by the valve spring 24 so as to close the intake port 11. Two intake valves 20 are provided to open and close the two intake ports 11.

  The exhaust valve 25 is provided at the inner end of the exhaust port 13, and has a stem 26 that is lowered forward and has a face 26 a formed at the rear end, a retainer 27 and a spring seat 28 that are attached to the stem 26, and a retainer. 27 and a valve spring 29 attached between the spring seat 28, and the face 26 a is always urged by the valve spring 29 so as to close the exhaust port 13. Two exhaust valves 25 are provided to open and close the two exhaust ports 13.

  As shown in FIG. 1, on the right side of the cylinder chamber 3a, there is a chain chamber 30a that connects the crank chamber 4a and the valve operating chamber 15 by the right case half 4R, the cylinder block 3, and the cylinder head 2. The chain transmission mechanism 30 is disposed in the chain chamber 30a. The chain transmission mechanism 30 is hung between the drive sprocket 31 attached to the right shaft portion 6R of the crankshaft 6, the driven sprocket 32 attached to the camshaft 41 constituting the valve mechanism 40, and both the sprockets 31 and 32. The cam chain 33 is provided.

  The drive sprocket 31 is fitted to the right shaft portion 6R and rotates integrally with the crankshaft 6. The driven sprocket 32 is fastened by a press-fit member 42 press-fitted into the camshaft 41 and a bolt 43 and rotates integrally with the camshaft 41. By such a chain transmission mechanism 30, the rotation of the crankshaft 6 is transmitted to the camshaft 41, and the camshaft 41 rotates in conjunction with the crankshaft 6. The chain transmission mechanism 30 is configured to rotate the camshaft 41 once when the rotation ratio of the drive sprocket 31 and the driven sprocket 32 is 2: 1 and the crankshaft 6 rotates twice.

  The valve mechanism 40 is disposed in a substantially V-shaped space formed between the intake valve 20 that is lifted forward and the exhaust valve 25 that is lifted forward. The valve mechanism 40 includes a camshaft 41 rotatably supported, an intake cam 51 provided on the camshaft 41, one end 52a in contact with the intake cam 51, and the other ends 52c and 52c at the intake valve. 20, an intake rocker arm shaft 53 that pivotally supports the intake rocker arm 52, an exhaust cam 61 provided on the camshaft 41, and one end 62 a for exhaust. The exhaust rocker arm 62 is in contact with the cam 61 and the other end portions 62c and 62c are in contact with the exhaust valve 25. The exhaust rocker arm shaft 63 pivotally supports the exhaust rocker arm 62.

  The camshaft 41 includes a main shaft portion 41a and a flange portion 41b integrally formed in a hook shape at the axial center of the main shaft portion 41a. The left end portion of the main shaft portion 41a has a smaller diameter than the whole. The cam shaft 41 is rotatably supported by a first bearing 46 and a second bearing 47 that constitute a cam shaft support portion 45 provided in the cylinder head 2.

  The intake cam 51 and the exhaust cam 61 are each formed separately from the camshaft 41. Both the cams 51 and 61 are press-fitted and attached from the left end of the main shaft portion 41 a, are positioned on the left end side of the flange portion 41 b and are fixed to the main shaft portion 41 a, so as to rotate integrally with the cam shaft 41. It has become. Note that the intake cam 51 is mounted on the left side of the exhaust cam 61.

  The camshaft 41 is formed with an oil hole 41d extending in the axial direction from the left end portion of the main shaft portion 41a. An oil hole 41e is formed extending radially between the intake cam 51 and the exhaust cam 61, and both the oil holes 41d and 41e communicate with each other.

  The intake rocker arm 52 includes an end 52a that contacts the intake cam 51, an arm 52b that extends from the one end 52a, and an intake valve 20 that is positioned at the tip of the arm 52b and contacts the intake valve 20. It consists of an end 52c. The reason why the arm portion 52b is bifurcated is that two intake valves 20 are provided.

  A circular hole is formed through one end 52a of the intake rocker arm 52, and an intake roller 55 is pivotally connected to a roller pin 54 inserted into the circular hole. The intake roller 55 contacts the intake cam 51. Further, a circular hole is formed in the one end 52a so as to be located on the other end side of the circular hole to which the roller pin 54 is attached, and the intake rocker arm shaft 53 is inserted into the circular hole. The intake rocker arm 52 is swingably supported by the intake rocker arm shaft 53.

  Screw insertion holes 52d and 52d are formed through the other ends 52c and 52c in the front-rear direction, and a tappet 52e is attached to the screw insertion holes 52d and 52d. The rear end of the tappet 52e contacts the front end of the stem 21 of the intake valve 20.

  In the intake rocker arm 52, when the intake cam 51 rotates with the rotation of the camshaft 41, one end 52a to which the intake roller 55 that contacts the intake cam 51 is attached is moved forward by the operation of the cam. Pushed up. As a result, the other end portions 52 c and 52 c of the intake rocker arm 52 swing rearward to push down the stem 21 of the intake valve 20, and the intake valve 20 resists the urging force of the valve spring 24 and pushes the intake port 11. The air-fuel mixture from the intake port 12 is supplied to the combustion chamber 10. As described above, when the intake cam 51 rotates once, that is, when the piston 5 reciprocates twice and the crankshaft 6 rotates twice, the intake valve 20 opens at a predetermined timing.

  The exhaust rocker arm 62 has the same structure as the intake rocker arm 52. The exhaust rocker arm 62 has one end portion 62a that contacts the exhaust cam 61, an arm portion 62b that extends from the one end portion 62a, and an arm portion 62b. It consists of the other end portions 632c and 62c that are located at the tip and contact the exhaust valve 25.

  An exhaust roller 65 is pivotally connected to a roller pin 64 inserted into a circular hole formed through the end portion 62 a of the exhaust rocker arm 62, and the exhaust roller 65 contacts the exhaust cam 61. . The one end portion 62a is formed with a circular hole penetrating from the circular hole to which the roller pin 64 is attached, and the exhaust rocker arm shaft 63 is inserted into the circular hole. The exhaust rocker arm 62 is swingably supported by the exhaust rocker arm shaft 63.

  Screw insertion holes 62d and 62d are formed through the other ends 62c and 62c in the front-rear direction, and a tappet 62e is attached to the screw insertion holes 62d and 62d. The rear end of the tappet 62e contacts the front end of the stem 26 of the exhaust valve 25.

  When the exhaust cam 61 rotates along with the rotation of the camshaft 41, the exhaust rocker arm 62 pushes up the one end portion 62a to which the exhaust roller 65 contacting the exhaust cam 61 is attached. As a result, the other end portions 62c and 62c of the exhaust rocker arm 62 swing back and push down the stem 26 of the exhaust valve 25. As a result, the exhaust valve 25 opens the exhaust port 13 against the urging force of the valve spring 29, and guides the burned gas in the combustion chamber 10 to the exhaust passage 14 and discharges it to the outside. As described above, when the piston 2 is reciprocated twice, the crankshaft 6 is rotated twice, and the exhaust cam 61 is rotated once, the exhaust valve 25 is opened at a predetermined timing.

  The intake and exhaust rocker arm shafts 53 and 63 have the same structure. Each of the shafts 53 and 63 is formed with notches 53c and 63c that extend in the direction perpendicular to the axis and are formed in an arc shape.

  Both rocker arm shafts 53 and 63 are pivotally supported by a rocker arm shaft holder 70 shown in FIGS. Here, FIG. 3 is a plan view of the rocker arm shaft holder 70, FIG. 4 is a bottom view, and FIGS. 5 and 6 are side sectional views. Hereinafter, the rocker arm shaft holder 70 is assembled to the engine E as in FIGS. The rocker arm shaft holder 70 will be described in accordance with the direction of the time (FIG. 3 shows a view seen from the front to the rear in the assembled state, but may be described as a plan view when describing the rocker arm shaft holder 70. ). The rocker arm shaft holder 70 includes a left shaft support portion 71 that pivotally supports left end portions 53a and 63a of both rocker arm shafts 53 and 63, and a right shaft support portion that pivotally supports right end portions 53b and 63b of both rocker arm shafts 53 and 63. 72 and a connecting portion 73 that connects the shaft support portions 71 and 72, and these portions 71 to 73 are integrally formed.

  The left shaft support portion 71 and the right shaft support portion 72 are formed with two sets of shaft insertion holes 70a and 70b having the same diameter and the same axis. These shaft insertion holes 70a and 70b are arranged in parallel in the vertical direction in the assembled state. The shaft insertion holes 70a and 70b are integrally formed by drilling from the left shaft support portion 71 side to the right shaft support portion 72 side.

  The connecting portion 73 is provided so as to connect the front sides of both the shaft support portions 71 and 72, and is provided across both shaft insertion holes 70a and 70b in a plan view as shown in FIG. As shown in FIGS. 3 and 4, the left shaft support portion 71 is formed with two bolt insertion holes 75 a and 75 b side by side extending in the front-rear direction. The bolt insertion holes 75a and 75b are respectively connected to shaft insertion holes 70a and 70b formed in the left-hand shaft support portion 71 and arranged in parallel in the vertical direction. Further, the right shaft support portion 71 also has two bolt insertion holes 75c and 75d formed at the right end edge portion, and a bolt insertion hole 74 for co-tightening located near the center. The bolt insertion holes 74, 75c, and 75d are not communicated with the shaft insertion holes 70a and 70b formed in the right shaft support portion 72. Also, as shown in FIG. 4, dowel holes 76a and 76b having a predetermined depth are formed in both shaft support portions 71 and 72, respectively.

  Hereinafter, a procedure for assembling the valve operating mechanism 40 having such components will be described. An accommodation groove is formed in the left inner wall surface of the cylinder head 2, and the first bearing 46 is accommodated and held in the accommodation groove. A mounting opening 2 a is formed in the right wall surface of the cylinder head 2, and the outside communicates with the valve operating chamber 15. The second bearing 47 is previously attached to the camshaft 41 from the right end side of the main shaft portion 41a of the camshaft 41, and the press-fitting member is attached to the camshaft 41 from the right end portion side. As a result, the second bearing 47 is sandwiched in the axial direction by the flange portion 41 b of the camshaft 41 and the press-fitting member 42.

  The cam shaft 41 pivotally supports the left end portion of the main shaft portion 41 a having a small diameter from the mounting opening 2 a on a first bearing 46 provided on the left inner wall of the cylinder head 2. As a result, the contact seat surface 41c of the main shaft portion 41a contacts the first bearing 46. At the same time, the outer periphery of the second bearing 47 is accommodated in the bearing accommodation hole 2 b on the right inner wall surface of the cylinder head 2. The driven sprocket 32 is attached to the right end portion of the camshaft 41 and fastened with the press-fitting member 42.

  A cap member 48 is covered with a mounting opening 2a on the right wall surface of the cylinder head 2 via a seal member 48a. The cap member 48 has a shaft portion 48b extending in the axial direction, and is attached so as to cover the attachment opening 2a with the inner end of the shaft portion 48b being in contact with the right end portion of the camshaft 41. .

  Both rocker arms 52 and 62 are positioned behind the connecting portion 73, and the intake rocker arm shaft 51 and the exhaust rocker arm shaft 61 are directed to the shaft insertion holes 70a and 70b from the left shaft support portion 71 side to the right shaft support portion 72 side. Insert. As a result, the rocker arm shaft holder 70 is in a state of pivotally supporting the intake rocker arm shaft 53 and the exhaust rocker arm shaft 63 that support the rocker arms 52 and 62, respectively.

  A dowel hole is formed in the front end surface of the cylinder head 2, and a knock pin 82 is inserted into the dowel hole. The rocker arm shaft holder 70 is positioned with respect to the cylinder head 2 by inserting the knock pin 82 into dowel holes 76a and 76b formed on the bottom surface. Further, the intake rocker arm 52 is positioned with respect to the intake cam 51 and the intake valve 20, and the exhaust rocker arm 62 is positioned with respect to the exhaust cam 61 and the exhaust valve 25. Lubricating oil is supplied to the rocker arms 52 and 62 from a radially extending oil hole 41 e formed in the camshaft 41, lubrication of the intake cam 52 and intake roller 55, and exhaust cam 62. In addition, the exhaust roller 65 is lubricated.

  Bolts 81 are inserted into the respective bolt insertion holes 75 a to 75 d, and the rocker arm shaft holder 70 is fastened to the cylinder head 2. The bolt insertion holes 75a and 75b of the left shaft support portion 71 are communicated with shaft insertion holes 70a and 70b formed in the left shaft support portion 71, respectively. For this reason, the notches 53c and 63c formed in the rocker arm shafts 53 and 63 are positioned so that the bolt 81 inserted from the bolt insertion holes 75a and 75b reaches the cylinder head 2 side, and the rocker arm shaft 53, 63 is inserted into the shaft insertion holes 70a and 70b.

  By attaching the rocker arm shaft holder 70 in this way, the connecting portion 73 is positioned forward with respect to the rocker arm shafts 53 and 63. On the other hand, the contact portion between the intake cam 51 and the intake roller 55 and the contact portion between the exhaust cam 61 and the exhaust roller 65 are located behind the rocker arm shafts 53 and 63.

  Further, the head cover 1 is attached from the front of the cylinder head 2. At this time, the bolt insertion hole of the head cover 1 has the same axis as the bolt insertion hole 74 for joint fastening of the rocker arm shaft holder 70. A flanged bolt 83 is attached to the bolt insertion hole of the head cover 1, and an end surface 84 of the flanged bolt 83 is in contact with the front surface of the right shaft support portion 72 of the rocker arm shaft holder 70. The head cover 1 and the rocker arm shaft holder 70 are fastened by such flanged bolts 83. Accordingly, the rocker arm shaft holder 70 is disposed in the valve operating chamber 25 in a state of being fixed to the cylinder head 2 and the head cover 1 that constitute the housing H of the engine E.

  Further, on the right wall surface of the head cover 1, a rear extension piece 1a extending rearward is formed. With the rearward extending piece 1a, the right wall surface of the cylinder head 2 with the cap member 48 attached to the attachment opening 2a is covered from the outside. A cap 49 made of an elastic body is attached to the outer end of the shaft portion 48b, and the cap 49 is in close contact with the inner wall surface of the rear extension piece 1a.

  As described above, in the engine 1 of this embodiment, the camshaft 41 constituting the valve mechanism 40 is pivotally supported on the camshaft support portion 45 that is provided in the cylinder head 2 and includes the first bearing 46 and the second bearing 47. The rocker arm shafts 53 and 63 are pivotally supported by a dedicated rocker arm shaft holder 70. For this reason, the camshaft 41 can be supported by the camshaft support portion 45, and then the rocker arm shafts 53 and 63 can be assembled into the valve operating chamber 25 in a state of being pivotally supported by the rocker arm shaft holder 70. In addition, the valve mechanism 40 can be easily assembled as compared with a configuration in which both the rocker arm shafts 53 and 63 must be assembled in the valve chamber 25 at the same time.

  Even if the camshaft 41 and the rocker arm shafts 53 and 63 are separately assembled, the rocker arm shaft holder 70 is accurately positioned with respect to the cylinder head 2 via the knock pin 82. The valve mechanism 40 can be easily assembled and the valve mechanism 40 can be stably operated.

  Further, according to the camshaft support portion 45 of this configuration, the second bearing 47 that rotatably supports the camshaft 41 is sandwiched between the flange portion 41 b of the camshaft 41 and the press-fitting member 42. For this reason, even if the camshaft 41 rotates, the movement in the axial direction is restricted, and the valve operating mechanism 40 can be stably operated. The press-fitting member 42 is a member that is originally used to fix the driven sprocket 32 to the camshaft 41 and rotate integrally with the camshaft 41. Such a press-fit member 42 does not increase the number of parts. It is possible to configure the valve operating mechanism 40 that is provided.

  Further, a cap 49 is attached to the outer end of the shaft portion 48b of the cap member 48 attached to cover the opening of the cylinder head 2, and the cap is attached to the inner wall surface of the rear extension piece 1a provided extending rearward from the head cover 1. 49 is closely attached. Thereby, the cap 49 can be elastically deformed to absorb the vibration accompanying the rotation of the camshaft 41, the valve mechanism 40 can be operated stably, and noise can be prevented. Moreover, the axial support force of the camshaft 41 can be enhanced by bringing the rear extension piece 1a into close contact with the rubber cap 49. Furthermore, the dimensional tolerance of the cap member 48 can be absorbed by the elastic deformation of the cap 49.

  The contact portion between the intake cam 51 and the intake roller 55 and the contact portion between the exhaust cam 61 and the exhaust roller 65 are located rearward with respect to the rocker arm shafts 53 and 63, When 61 is actuated, the cams 51, 61 swing the rocker arms 52, 62 by pushing up the rollers 55, 65 provided at the one end portions 52 a, 62 a of the rocker arms 52, 62. For this reason, by the operation of the valve operating mechanism 40, a load is applied to both the shaft support portions 71 and 72 of the rocker arm shafts 53 and 63 and the rocker arm shaft holder 70 in the forward direction. Here, the connecting portion 73 of the rocker arm shaft holder 70 of this configuration is formed so as to be positioned forward with respect to the rocker arm shafts 53 and 63 and to connect the shaft supporting portions 71 and 72. For this reason, it can receive a load by this connection part 73, and generation | occurrence | production of the bending of the rocker arm shafts 53 and 63 can be suppressed.

  The rocker arm shaft holder 70 is supported in parallel by two shafts, an intake rocker arm shaft 53 and an exhaust rocker arm shaft 63. And the connection part 73 of the rocker arm shaft holder 70 is provided so that these two shafts 53 and 63 may be straddled. Therefore, the connecting portion 73 can receive the load applied to the respective shafts 53 and 63, and in the rocker arm shaft holder configured to support the two shafts, the occurrence of bending of both shafts is suppressed.

  Further, the bolt insertion holes 75a and 75b of the left shaft support portion 71 are provided so as to communicate with the shaft insertion holes 70a and 70b, and are formed on the rocker arm shafts 53 and 63 so as to extend in the direction perpendicular to the axis. , 63c are passed through the bolts. Thereby, even if a force acts on the rocker arm shafts 53 and 63 in the rotational direction by the rocking of the rocker arms 52 and 62, the rotation of the rocker arm shafts 53 and 63 can be restricted.

  The embodiment of the valve mechanism support structure for an internal combustion engine according to the present invention has been described so far. However, the present invention is not necessarily limited to this configuration, and can be appropriately changed within the scope of the invention. For example, in the above-described embodiment, the description has been made according to the direction of the arrow in the figure, but the same applies to a vehicle in which the engine is disposed with the cylinder axis A extending upright in a substantially vertical direction. The same effect can be obtained.

It is a front sectional view of an engine provided with a rocker arm shaft holder according to the present invention. It is a sectional side view of the engine which shows a valve operating chamber. It is the top view of the rocker arm shaft holder seen in the arrow III direction shown in FIG. It is a bottom view of a rocker arm shaft holder. It is sectional drawing of the rocker arm shaft holder seen in the VV direction shown in FIG. It is sectional drawing of the rocker arm shaft holder seen in the VI-VI direction shown in FIG.

Explanation of symbols

E Engine 1 Head cover 2 Cylinder head 3 Cylinder block (cylinder)
5 Piston 6 Crankshaft 10 Combustion chamber 15 Valve chamber 20 Intake valve 25 Exhaust valve 30 Chain transmission mechanism 40 Valve mechanism 41 Camshaft 45 Camshaft support portions 51, 61 (For intake and exhaust) Cams 52, 62 (Intake) Rocker arm 53, 63 (For intake, exhaust) Rocker arm shaft 70 Rocker arm shaft holder 71 Left shaft support 72 Right shaft support 73 Connecting portion

Claims (3)

A cylinder in which a piston is slidably disposed;
A cylinder head coupled to the cylinder to form a combustion chamber together with the piston, and a valve operating chamber therein;
A crankshaft rotating in conjunction with the piston;
A valve disposed in the valve chamber and opened and closed with respect to the combustion chamber;
In a valve mechanism support structure for an internal combustion engine that is configured in the valve train chamber and configured to drive the valve,
The valve operating mechanism is disposed in the valve operating chamber and rotates in conjunction with the crankshaft; a cam provided on the camshaft; one end contacting the cam and the other end Has a rocker arm that contacts the valve and a rocker arm shaft that supports the rocker arm in a swingable manner, and the rocker arm is swung by the operation of the cam according to the rotation of the camshaft. Configured to drive the valve,
A rocker arm shaft holder that pivotally supports the rocker arm shaft;
A valve mechanism support structure for an internal combustion engine, wherein a camshaft support portion that pivotally supports the camshaft is provided integrally with the cylinder head and is provided separately from the rocker arm shaft holder. The rocker arm shaft holder includes a plurality of shaft support portions that respectively support end portions of the rocker arm shaft, and a connection portion that connects the plurality of shaft support portions,
The connecting portion is provided on the opposite side to the side where the contact portion where the cam and one end portion of the rocker arm come into contact with the axis line of the rocker arm shaft pivotally supported by the plurality of pivotal support portions. 2. A valve mechanism support structure for an internal combustion engine according to claim 1, wherein The rocker arm shaft holder pivotally supports the plurality of rocker arm shafts;
3. The valve mechanism support structure for an internal combustion engine according to claim 2, wherein the connecting portion is provided across the plurality of rocker arm shafts when viewed in the axial direction of the cylinder.

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