JP2012225278A - Camshaft support structure of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cam bearing structure of an internal combustion engine, for favorably ensuring supporting stiffness while preventing an increase in weight of a bearing portion of a camshaft as much as possible.SOLUTION: A straight line L4 passes through a center point C3 of a camshaft 38, and extends in a direction of the cylinder axis C2 of a cylinder block 5a in which a cylinder head 5b is erected. A straight line L3 passes through the center point C3 of the camshaft 38 and extends in the application direction L2 of a reaction force of a valve spring 33e. A width dimension of a second cam journal 43 on a side where the straight line L3 deviates with respect to the straight line L4 is set to be larger than a width dimension of the second cam journal 43 located on the opposite side across the straight line L4.

Description

  The present invention relates to a camshaft support structure for an internal combustion engine.

  Conventionally, a cam bearing that supports the camshaft is divided into upper and lower parts, and a counterbore is formed in the lower half of the cam bearing so that the width of the upper half is set thicker than the lower side ( Patent Document 1).

  In this structure, when the cam of the camshaft directly presses the valve, a load is applied to the camshaft by the reaction force of the valve, but since the load can be received by the cam bearing of the upper width, the support rigidity Can be kept good.

Japanese Patent Laid-Open No. 8-218836

  By the way, as described above, the camshaft support is generally divided, but a valve such as an SOHC (Single OverHead Camshaft) that drives the valve via a rocker arm with a single cam. In the mechanism, the reaction force from the valve may not always be generated in the same direction (for example, the vertical direction) as the camshaft bearing splitting direction. In such a case, the valve reaction force is received by both of the bearing halves, and it may be necessary to enlarge the entire bearing in order to ensure the support rigidity of the camshaft. If it is increased as a whole, the problem of an increase in the weight of the cylinder head occurs.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a cam bearing structure for an internal combustion engine that can ensure good support rigidity while suppressing the increase in the weight of the bearing portion of the camshaft as much as possible. .

  As a means for solving the above problems, the invention according to claim 1 is characterized in that the engine valve (33) biased in the closing direction by the valve spring (33e) and the biasing force of the valve spring (33e) are against the biasing force. A camshaft (38) that opens the engine valve (33), and the camshaft (38) is rotatably supported by a cam journal (43) provided in the cylinder head (5b). In the shaft support structure, a first straight line (L4) that passes through the center point (C3) of the camshaft (38) along the cylinder axis (C2) direction of the cylinder block (5a) that erects the cylinder head (5b). ) As a reference, a second straight line (L) passing through the center point (C3) of the camshaft (38) along the direction (L2) of the reaction force of the valve spring (33e). ) Of the cam journal (43) on the side deviating from the first straight line (L4) in the axial direction of the cam shaft (38), the width dimension on the opposite side across the first straight line (L4) A camshaft support structure for an internal combustion engine is provided, wherein the cam journal (43) is set to be larger than a width dimension of the cam journal (43).

  According to a second aspect of the present invention, in the camshaft support structure of the internal combustion engine according to the first aspect, the cam journal (43) is split in a direction perpendicular to the first straight line (L4). And the width dimension in the axial direction of the camshaft (38) of the cam journal (43) located on both sides of the split surface (PL) is divided in the first straight line (L4) direction. The cam journal (43) is set to be larger than the width dimension of the cam journal (43) located on the opposite side across the first straight line (L4).

  According to a third aspect of the present invention, in the camshaft support structure of the internal combustion engine according to the second aspect, the cam journal (43; 43a, 43b) divided across the split surface (PL) is divided. Further, the positioning is performed by positioning pins (94) provided across both the cam journals (43; 43a, 43b), and an insertion hole (95) through which the positioning pins (94) are inserted is provided on the width-thickness side. And

  According to a fourth aspect of the present invention, in the camshaft support structure of the internal combustion engine according to the third aspect, the positioning pin (94) sandwiching the camshaft (38) in the cam journal (43; 43a, 43b). A tube member (96) for positioning the cam journal (43; 43a, 43b) divided and through which the journal fastening bolt (46) is passed is provided on the opposite side.

  The invention according to claim 5 is the camshaft support structure for an internal combustion engine according to any one of claims 2 to 4, wherein the sliding surface (43d) of the camshaft (38) in the cam journal (43) is provided. ), An oil groove (97) is formed along the outer periphery of the camshaft (38), and both ends of the oil groove (97) are separated from the split surface (PL).

  The invention according to claim 6 is the camshaft support structure for an internal combustion engine according to any one of claims 2 to 5, and is located on the cylinder block (5a) side with the split surface (PL) interposed therebetween. The cam journal (43; 43a) extends along the first straight line (L4) dividing the sliding contact surface (43c) with the cam shaft (38) of the cam journal (43; 43a). A bolt insertion hole (93) is formed.

  The invention according to claim 7 is the camshaft support structure for an internal combustion engine according to any one of claims 2 to 5, and is located on the cylinder block (5a) side with the split surface (PL) interposed therebetween. The cam journal (43) is detachably attached to the journal wall (200) erected on the cylinder head (5b), and the camshaft (38) is in sliding contact with the journal wall (200). A bolt insertion hole configured to support the sliding contact portion (201), extends along the first straight line (L4) to the journal wall portion (200), and penetrates the journal wall portion (200). (204) is formed, and the sliding contact portion (201) is attached to the journal wall portion (200) so as to close the bolt insertion hole (204).

  The invention according to claim 8 is the camshaft support structure of the internal combustion engine according to claim 7, wherein the sliding contact portion (201) is arranged on the sliding contact portion (201) across the split surface (PL). The cam journal (202) located on the opposite side and the journal wall (201) are clamped and bolted.

According to the first aspect of the present invention, the width dimension of the portion of the cam journal where the reaction force of the valve spring acts greatly is larger than necessary by increasing the width dimension of the portion where the reaction force of the valve spring does not act relatively. In addition, the surface pressure against the reaction force of the valve spring can be lowered without increasing the size of the cam journal, and the support rigidity of the cam journal can be ensured satisfactorily.
According to the second aspect of the present invention, the reaction force of the valve spring is increased by increasing the width dimension of the portion where the load is largely applied by the reaction force of the valve spring in both of the cam journals divided across the split surface. It is possible to sufficiently reduce the surface pressure against.
According to the third aspect of the present invention, by providing the insertion hole for the positioning pin on the width-thickness side, it is possible to suppress a decrease in rigidity as much as possible.
According to the fourth aspect of the present invention, the space for arranging the cam journal positioning member can be reduced on the side of the thin cam journal.
According to the invention described in claim 5, by forming the oil groove so that both ends of the oil groove in the circumferential direction of the cam shaft are separated from the split surface, both lubrication of the cam shaft and ensuring of the rigidity of the cam journal can be achieved. .
According to the sixth aspect of the present invention, even when the sliding contact area of the cam journal with the camshaft is reduced by the bolt insertion hole, the width dimension of the portion of the cam journal where the reaction force of the valve spring acts largely Since the reaction force of the spring can be increased relative to a portion where the reaction force does not act relatively, the support rigidity of the cam journal can be satisfactorily ensured without enlarging the cam journal more than necessary.
According to the seventh aspect of the present invention, even when the sliding contact area of the cam journal with the camshaft is reduced by the bolt insertion hole, the sliding contact area is provided by providing a separate sliding contact portion with the camshaft. The surface pressure due to the reaction force of the valve spring can be reduced.
According to invention of Claim 8, the special member at the time of attaching a sliding contact part can be eliminated.

1 is a side perspective view of an internal combustion engine (engine) including a variable valve mechanism according to an embodiment of the present invention. 1 is a schematic side view of an internal combustion engine including a variable valve mechanism according to an embodiment of the present invention. It is side surface perspective drawing inside the cylinder head of an internal combustion engine provided with the variable valve mechanism which concerns on embodiment of this invention. It is a top view inside a cylinder head of an internal-combustion engine provided with a variable valve mechanism concerning an embodiment of the present invention. It is a top view inside a cylinder head of an internal combustion engine provided with a variable valve mechanism concerning an embodiment of the present invention, and is a top view inside a cylinder head in the state where a member which constitutes a variable valve mechanism was removed. It is a top view inside a cylinder head of an internal-combustion engine provided with a variable valve mechanism concerning an embodiment of the present invention. It is the figure which showed the intake side rocker arm of the variable valve mechanism based on embodiment of this invention, (A) is a perspective view of an intake side rocker arm, (B) is a front view of an intake side rocker arm, (C) Is a side view of the intake side rocker arm, and (D) is a top view of the intake side rocker arm. It is a schematic sectional drawing of the intake side rocker arm of the variable valve mechanism which concerns on embodiment of this invention. It is the figure which showed the positional relationship of the intake side rocker arm and camshaft of the variable valve mechanism which concerns on embodiment of this invention. It is the figure which showed the cam journal erected in the cylinder head of the internal combustion engine provided with the variable valve mechanism which concerns on embodiment of this invention. It is the figure which showed the half body of the said cam journal, (A) is a longitudinal cross-sectional view of a half body, (B) is a bottom view of a half body. It is a figure which shows schematic structure of the variable valve mechanism based on embodiment of this invention. It is sectional drawing of the hydraulic actuator of the variable valve mechanism based on embodiment of this invention, (A) is a figure which shows the state which moved the rocker arm shaft to the left, (B) is a right side of a rocker arm shaft. It is a figure which shows the state moved to the direction. It is the figure which showed the hydraulic piston of the hydraulic actuator of the variable valve mechanism which concerns on embodiment of this invention. FIG. 3 is an arrow view of the internal combustion engine viewed in the direction of arrow X in FIG. 2. FIG. 3 is an arrow view of the internal combustion engine viewed in the direction of arrow Y in FIG. 2. 1 is an overhead view of an internal combustion engine for explaining an arrangement relationship between an intake valve drive mechanism in an internal combustion engine including a variable valve mechanism according to an embodiment of the present invention and a hydraulic actuator of the variable valve mechanism. It is a figure which shows the modification of the cam journal of the variable valve mechanism which concerns on the said embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. For convenience of explanation, the arrow FR indicates the front, the arrow LH indicates the left side, and the arrow UP indicates the upper side.

  An engine 1 that is an internal combustion engine according to the present embodiment shown in FIG. 1 is a V-type four-cylinder engine that causes a rotation center axis (axis) C0 of a crankshaft 2 to run along the left-right direction perpendicular to the paper surface when mounted on a vehicle. There is a front cylinder part 4 extending obliquely upward in the front and a rear cylinder part 5 extending obliquely upward in the rear on the crankcase 3. Pistons 6 and 7 are fitted in the front and rear cylinder parts 4 and 5 so as to be able to reciprocate. The reciprocating movements of the pistons 6 and 7 are converted into rotational movements of the crankshaft 2 through connecting rods 8 and 9, respectively. .

  The front and rear cylinder parts 4 and 5 are respectively provided with cylinder blocks 4a and 5a coupled to the crankcase 3, cylinder heads 4b and 5b coupled to the cylinder blocks 4a and 5a, and head covers 4c and 5c covering the cylinder heads 4b and 5b. The cylinder blocks 4a and 5a are formed with cylinders 4d and 5d into which the pistons 6 and 7 are fitted. The engine 1 is a V-type four-cylinder engine, and a pair of cylinders 4d and 5d is formed in each of the cylinder blocks 4a and 5a. In the figure, C1 indicates the center axis (axis) of the cylinder 4d, and C2 indicates the center axis (axis) of the cylinder 5d.

  A throttle body 12 connected to the intake ports 10 and 11 is disposed between the front and rear cylinder parts 4 and 5, and exhaust pipes are connected to the front of the front cylinder part 4 and the rear of the rear cylinder part 5, respectively. Exhaust ports 13 and 14 are formed. The throttle body 12 includes a front throttle body 15 connected to the intake port 10 of the front cylinder portion 4 and a rear throttle body 16 connected to the intake port 11 of the rear cylinder portion 5.

  Each throttle body 15 and 16 includes intake pipes 15a and 16a connected to the intake ports 10 and 11, and intake control valves 15b and 16b disposed in the intake pipes 15a and 16a to electronically control the intake air amount. The rear throttle body 16 is provided with an intake valve drive mechanism 17 for driving the intake control valves 15b and 16b. The intake valve drive mechanism 17 includes a motor 18 and a speed reduction mechanism 19 that decelerates the driving force of the motor 18, and a link mechanism 20 is provided between the front throttle body 15 and the rear throttle body 16. The driving force of the intake valve drive mechanism 17 is directly transmitted to the intake control valve 16b of the rear throttle body 16, and is also transmitted to the intake control valve 15b via the link mechanism 20, and the intake control valves 15b and 16b are Drive synchronously.

  In the figure, reference numeral 21 denotes a transmission housed in the rear part of the crankcase 3, reference numeral 21a denotes a main shaft which is an input shaft of the transmission 21, reference numeral 21b denotes a counter shaft which is an output shaft of the transmission 21, and reference numeral 22 denotes The change mechanism which switches the gear stage of the transmission 21 is shown. Reference numeral 23 denotes an oil pan attached below the crankcase 3, and reference numeral 24 denotes an oil pump unit that pumps engine oil in the oil pan 23 to various parts of the engine.

  An oil filter 25 that filters oil pumped from the oil pump unit 24 is provided at the front of the crankcase 3, and a starter motor 26 that is a starting device is provided adjacent to the oil filter 25. The driving force of the starter motor 26 is transmitted to the crankshaft 2 through a reduction gear.

  A variable valve mechanism 31 that opens and closes combustion chambers 29 and 30 formed in the cylinder heads 4b and 5b by intake and exhaust valves in valve chambers 27 and 28 formed by the cylinder heads 4b and 5b and the head covers 4c and 5c. , 32 are accommodated. The engine 1 according to this embodiment is a four-valve type, and the variable valve mechanisms 31 and 32 include a pair of left and right intake valves 33 and exhaust valves 34 for each cylinder. The variable valve mechanisms 31 and 32 can change the lift amount (operation characteristic) of the intake valve 33. For example, the lift amount of the intake valve 33 is set in a high speed rotation range where the engine speed is 9000 rpm (Revolutions Per Minute) or more. Enlarge.

  The variable valve mechanisms 31 and 32 change the lift amount of the intake valve 33 using hydraulic pressure as a power source. As shown in FIG. 2, the cylinder heads 4b and 5b have a configuration of the variable valve mechanisms 31 and 32, respectively. Hydraulic actuators 35 and 36 which are members are provided. The hydraulic actuators 35 and 36 are arranged near the V bank formed by the front cylinder part 4 and the rear cylinder part 5. The hydraulic actuators 35 and 36 are operated by engine oil pumped from the oil pump unit 24. The details of the hydraulic oil path connecting the oil pump unit 24 and the hydraulic actuators 35 and 36 will be described later.

  FIG. 3 shows an enlarged view of the valve operating chamber 28 formed by the cylinder head 5b and the head cover 5c. In FIG. 3, the intake / exhaust valves 33 and 34 constituting the variable valve mechanism 32 and the intake side are shown. A rocker arm 37, a single camshaft 38, an exhaust-side rocker arm 39, etc. are shown. Hereinafter, although the variable valve mechanism 32 in the rear cylinder part 5 is demonstrated, since the variable valve mechanism 31 in the front cylinder part 4 is equipped with the same structure, description is abbreviate | omitted. In the following description, the configuration of the variable valve mechanism 32 for one cylinder will be mainly described.

  In the variable valve mechanism 32, the intake and exhaust valves 33 and 34 extend rod-shaped stems 33b and 34b from the umbrella-shaped valve bodies 33a and 34a aligned with the openings formed in the combustion chamber 30, respectively, to the valve operating chamber 28 side. Thus, the stems 33b and 34b of the intake and exhaust valves 33 and 34 are held by the cylinder head 5b through valve guides 33c and 34c, respectively, so as to be able to reciprocate. Retainers 33d and 34d are respectively attached to the distal ends of the stems 33b and 34b on the valve operating chamber 28 side, and valve springs 33e and 34e are respectively contracted between the retainers 33d and 34d and the cylinder head 5b. Yes. The intake and exhaust valves 33 and 34 are biased upward by the spring force of the valve springs 33e and 34e, and the valve bodies 33a and 34a close the opening of the combustion chamber 30.

  The stems 33b and 34b of the intake and exhaust valves 33 and 34 are provided so as to be inclined with respect to the cylinder center axis C2 so as to form a V shape in a side view, and an intake-side rocker arm is disposed above the intake-side stem 33b. 37 abuts, and the exhaust side rocker arm 39 abuts on the upper part of the exhaust side stem 34b. The intake side rocker arm 37 and the exhaust side rocker arm 39 are swingably supported by the cylinder head 5b, respectively, and are swung by the camshaft 38 to push down the stems 33b and 34b.

  A camshaft 38 is disposed above the intake side rocker arm 37. The camshaft 38 is supported by the cylinder head 5b so as to be rotatable about its axis, and is linked to the crankshaft 2 when the engine 1 is in operation. Rotating drive. Reference numeral C3 in the figure indicates a central axis (cam axis) of the camshaft 38. The camshaft 38 is rotationally driven to swing the intake-side rocker arm 37 and the exhaust-side rocker arm 39 to attach valve springs 33e and 34e. Stroke the intake / exhaust valves 33, 34 against the force to release the valve bodies 33 a, 34 a of the intake / exhaust valves 33, 34 away from the opening of the combustion chamber 30.

  FIG. 4 shows a top view of the cylinder head 5b when the cylinder center axis C2 is set in the vertical direction. A cam drive sprocket 40, which is a member constituting a cam drive mechanism, is provided at the right end of the cam shaft 38. FIG. ing. The cam drive sprocket 40 is disposed in a cam chain chamber 41 formed on the right side of the cylinder head 5b, and a cam chain (not shown) is wound around the cam drive sprocket 40. The cam chain chamber 41 communicates with the crankcase 3, and the cam chain extends to the crankshaft 2 and is wound around a sprocket provided on the crankshaft 2. As a result, the camshaft 38 is driven in conjunction with the crankshaft 2.

  The camshaft 38 is rotatably supported by a first cam journal 42, a second cam journal 43, and a third cam journal 44 that are erected from the bottom of the cylinder head 5b. The first cam journal 42, the second journal The cam 43 and the third cam journal 44 support the camshaft 38 in order from the left in the direction of the axis C3 of the camshaft 38. The first cam journal 42 supports the left end of the camshaft 38, the second cam journal 43 supports the approximate center in the axial direction of the camshaft 38, and the third cam journal 44 supports the right end of the camshaft 38. I support it.

  Each of the cam journals 42 to 44 has a vertically divided structure with the cylinder center axis C2 as the vertical direction. As shown in FIG. 5, the first to third journal wall portions 42a to 44a rising from the bottom of the cylinder head 5b, 3, the upper journal halves 42b to 44b are arranged above the first to third journal wall portions 42a to 44a. Referring to FIG. 3, PL indicates a split surface of each cam journal 42 to 44, and the split surface PL of each cam journal 42 to 44 is set in a direction orthogonal to the cylinder center axis C <b> 2. In FIG. 3, only the second cam journal 43 is shown, and only the upper journal half 43b is shown. However, for convenience of explanation, the upper journal half 42b of the first and third cam journals 42, 44 are shown. Reference numeral 44b is also given a reference numeral in parentheses.

  As shown in FIG. 5, the first to third journal wall portions 42a to 44a are respectively provided with lower sliding contact portions 42c to 44c with the camshaft 38 at the upper portion. The half bodies 42 b to 44 b have arcuate upper sliding contact portions 42 d to 44 d that are continuous with the lower sliding contact portions 42 c to 44 c and extend along the circumferential direction of the camshaft 38. A pair of journal fastening bolt holes 45 (FIG. 5) are formed on both sides of the lower slidable contact portions 42c to 44c in the upper portions of the first to third journal wall portions 42a to 44a. . As shown in FIG. 3, the upper journal halves 42 b to 44 b are fastened to the bolt holes 45... By inserting journal fastening bolts 46. It is being fixed with respect to the parts 42a-44a.

  Referring to FIG. 5, intake and exhaust valves 33 and 34 for one cylinder are located between the first cam journal 42 and the second cam journal 43 in the cylinder head 5 b, and the second cam journal 43 and the third cam journal 44. As shown in FIG. 4, the camshaft 38 has a pair of left and right exhaust cams 47, 48 and a pair of left and right exhaust cams 47 and 48. Intake cams 49 and 50 are provided. The exhaust cams 47 and 48 are formed with the same profile, and the intake cams 49 and 50 have different profiles. The intake cam 49 is formed for low speed and the intake cam 50 is formed for high speed. The intake cam 50 is set to have a higher profile than the intake cam 49. The camshaft 38 has intake cams 49 and 50 arranged between the exhaust cams 47 and 48, the intake cam 49 is arranged on the left side, and the intake cam 50 is arranged on the right side.

  One intake-side rocker arm 37 is provided for each cylinder, and one exhaust-side rocker arm 39 is provided for each cylinder. The intake side rocker arm 37 swings in contact with either of the intake cams 49 and 50, and the pair of exhaust side rocker arms 39 contacts and swings in the exhaust cams 47 and 48, respectively. The single intake side rocker arm 37 is pressed against the pair of left and right intake valves 33 simultaneously, and the exhaust side rocker arm 39 is pressed against the corresponding exhaust valve 34 respectively.

  As shown in FIG. 3, the intake-side rocker arm 37 is connected to an intake-side rocker arm shaft 51 arranged in parallel with the camshaft 38 in front of the upper portion of the stem 33 b of the intake valve 33 (in the intake port 11 side in a side view). It is supported so as to be swingable about its axis and slidable in the axial direction, and moves in the axial direction on the intake side rocker arm shaft 51 so as to come into contact with either of the intake cams 49 and 50. 4 shows a state in which the intake-side rocker arm 37 is in contact with the low-speed intake cam 49, and FIG. 6 shows a state in which the intake-side rocker arm 37 is in contact with the high-speed intake cam 50. In the figure, the symbol C4 indicates the central axis (axis) of the intake side rocker arm shaft 51.

  On the other hand, the exhaust-side rocker arm 39 is supported by an exhaust-side rocker arm shaft 52 disposed in parallel with the camshaft 38 between the intake and exhaust valves 33 and 34 in a side view so as to be swingable about its axis. The left and right end portions are supported by the first journal wall portion 42a and the third journal wall portion 44a (see FIG. 4). In addition, the code | symbol C5 in the figure has shown the center axis line (axis line) of the exhaust side rocker arm shaft 52 (FIG. 3).

  Referring to FIG. 4, the intake side rocker arm 37 has a cylindrical support boss portion 37 a that is inserted into the intake side rocker arm shaft 51, and the arm portion 37 b extends above the stem 33 b from the support boss portion 37 a. In addition, a pressing portion 37c that contacts the pair of stems 33b at the same time as the lower end of the arm portion 37b is set. As shown in FIG. 3, the intake-side rocker arm 37 is a roller-type rocker arm, and the arm portion 37 b is provided with a roller 37 d that selectively contacts either one of the intake cams 49 and 50 of the camshaft 38. ing. The roller 37d contacts the intake cams 49 and 50 of the cam shaft 38 from below when the cylinder center axis C2 is viewed along the vertical direction.

  4 and 5, in the intake side rocker arm 37, the pressing portion 37c is formed wide in the direction of the axis C3 of the cam shaft 38, and is in contact with the intake cam 49 on the low speed side and on the high speed side. In the state where it is in contact with the intake cam 50, it is in contact with the pair of left and right stems 33b simultaneously. The width dimension of the support boss part 37a in the direction of the axis C3 of the cam shaft 38 is set to be narrower than the width dimension between the exhaust cams 47 and 48, and the arm part 37b is directed from the pressing part 37c toward the support boss part 37a. Accordingly, the width dimension is gradually reduced.

  Further, as shown in FIG. 3, the exhaust side rocker arm 39 includes a cam side arm portion 39b extending from the cylindrical support boss portion 39a through which the exhaust side rocker arm shaft 52 is inserted to the camshaft 38 side, and a support boss portion. And a stem side arm portion 39c extending from the side 39a to the side of the stem 34b. A roller 39d that contacts the exhaust cam 47 or 49 is provided at the tip of the cam side arm 39b, and a pressing portion 39e that contacts the stem 34b is provided at the tip of the stem side arm 39c. The roller 39d abuts against the exhaust cam 47 or 49 of the cam shaft 38 from the rear when the cylinder center axis C2 is viewed along the vertical direction.

  In FIG. 3, L1 indicates a straight line that passes through the center point (C3) of the camshaft 38 and is orthogonal to the cylinder center axis C2. Comparing the contact positions of the roller 37d and the roller 39d with the camshaft 38 on the basis of the straight line L1, the contact position of the roller 37d with the camshaft 38 across the straight line L1 is the camshaft 38 of the roller 39d. Is set on the opposite side of the contact position.

  Referring to FIGS. 3 to 5, the intake side rocker arm shaft 51 includes a first boss portion 53, a second boss portion 54, which are formed in the cylinder head 5 b so as to be separated from each other in the direction of the axis C <b> 4 of the rocker arm shaft 51. The first boss portion 53, the second boss portion 54, and the third boss portion 55 are arranged in order from the left in the direction of the axis C4 and support the intake side rocker arm shaft 51. Yes.

  The first boss portion 53 is provided adjacent to the inner wall side of the first cam journal 42, the second boss portion 54 is provided adjacent to the left and right of the second cam journal 43, and the third boss portion 55 is the third cam. It is provided adjacent to the inner wall side of the journal 44. 3 shows only the first boss portion 53, the boss portions 53 to 54 are formed so as to protrude from the front inner wall 56 on the front side (the intake port 11 side) of the cylinder head 5b. . The front inner wall 56 in which the boss portions 53 to 54 are formed is formed to be inclined upward in a direction away from the cylinder center axis C2.

  As shown in FIG. 4, the left end of the intake side rocker arm shaft 51 passes through the first boss portion 53 and the first cam journal 42 and is connected to the hydraulic actuator 36. The hydraulic actuator 36 is configured to be movable back and forth in the direction of the axis C4. The hydraulic actuator 36 includes a cylinder body 58 having a cylinder chamber 57 to which hydraulic oil is supplied, and a hydraulic piston 59 housed in the cylinder chamber 57. The left end portion of the intake side rocker arm shaft 51 is hydraulic. Connected to the piston 59.

  The intake-side rocker arm shaft 51 is in the left limit position, and in this state, the intake-side rocker arm 37 is in contact with the low-speed intake cam 49, while in FIG. In this state, the intake side rocker arm 37 is in contact with the intake cam 50 on the high speed side. The intake-side rocker arm 37 is moved from the low-speed side to the high-speed side or from the high-speed side to the low-speed side using the biasing force of the spring stored as the intake-side rocker arm shaft 51 moves. The accumulation of the urging force of the spring is performed by the first accumulation mechanism 60 and the second accumulation mechanism 61 provided on the intake side rocker arm shaft 51.

  The first force accumulation mechanism 60 is located on the left side of the support boss portion 37a of the intake side rocker arm 37 and applies a force to the left end portion of the support boss portion 37a to the movement from the low speed side to the high speed side. A spring 62 and a first spring receiving collar 63 which is located on the left side of the first spring 62 and fixedly attached to the outer periphery of the intake side rocker arm shaft 51 so as not to move in the axial direction. . Similarly, the second energy storage mechanism 61 is positioned to the right of the support boss portion 37a of the intake side rocker arm 37 and applies a force to the right end portion of the support boss portion 37a to the movement from the high speed side to the low speed side. The second spring 64 and a second spring receiving collar 65 fixed to the outer periphery of the intake-side rocker arm shaft 51 and fixed to the outer periphery of the intake-side rocker arm shaft 51 so as not to move in the axial direction. ing.

  When the intake side rocker arm 37 is moved from the low speed side to the high speed side or from the high speed side to the low speed side, the variable valve mechanism 32 locks the intake side rocker arm 37 with a locking lever 66 to restrict movement. In this state, the intake-side rocker arm shaft 51 and the first spring receiving collar 63 and the second spring receiving collar 65 are moved together in the axial direction of the intake-side rocker arm shaft 51 to thereby move the springs 62, 64. A predetermined elastic force difference is generated in Then, the intake side rocker arm 37 is released from the low speed side by releasing the engagement state of the intake side rocker arm 37 at a predetermined timing by a trigger mechanism 67 (see FIG. 3) that releases the engagement state of the intake side rocker arm 37. From the high speed side or from the high speed side to the low speed side.

  As shown in FIG. 3, the locking lever 66 is disposed above the intake side rocker arm 37, and the trigger mechanism 67 causes the support boss portion 37a of the intake side rocker arm 37 and the intake side rocker arm shaft 51 to be orthogonal to the axis C4. It includes a trigger pin 68 that penetrates up and down in the direction of the movement.

  The locking lever 66 is swingably supported by a support shaft 69, and the support shaft 69 is supported by a support hole 71 of a support portion 70 formed so as to protrude from the front inner wall 56 of the cylinder head 5b. Yes. The site | part in which the support part 70 is formed in the front inner wall 56 is formed so that it may bend inward from the site | part in which the 1st-3rd boss | hub parts 53-55 are formed. As shown in FIG. 4, the support portion 70 is formed so as to protrude from the front inner wall 56 in a pair of left and right, and is provided for each cylinder. That is, one support portion 70 is provided between the first boss portion 53 and the second boss portion 54, and one support portion 70 is provided between the second boss portion 54 and the third boss portion 55.

  The support shaft 69 is formed to be shorter than the length between the first boss portion 53 and the second boss portion 54 and is disposed so as to straddle between the pair of left and right support portions 70. The end is locked to the C clip 72 and is attached so as not to move in the axial direction. The locking lever 66 is located between the pair of left and right support portions 70. In FIG. 3, C6 indicates the axis center (and axis) of the support hole 71, and P1 indicates an intersection with a straight cylinder center axis C2 passing through the axis C6 and orthogonal to the cylinder center axis C2. P2 indicates an intersection with a straight cylinder center axis C2 passing through the axis (C3) of the camshaft 38 and orthogonal to the cylinder center axis C2, and P3 is an axis center (C4) of the intake side rocker arm shaft 51. ) And an intersection with a straight cylinder center axis C2 perpendicular to the cylinder center axis C2. As is apparent with reference to these points, the support portion 70 is configured such that the shaft center C6 of the support hole 71 is based on the cylinder center axis C2 and the shaft center (C3) of the camshaft 38 and the intake side rocker arm shaft. It is set between 51 and the axial center (C4).

  Further, as is apparent from FIG. 3, the support portion 70, when viewed in the direction of the axis C <b> 6 of the support shaft 69, supports the support hole 71 through the support holes 53 a of the first to third boss portions 53 to 55 of the intake side rocker arm shaft 51. It arrange | positions in the position which does not overlap with -55a. The support portion 70 is separated from the support boss portion 37 a and the arm portion 37 b of the intake side rocker arm 37, and is cut out in a range that does not interfere with the rocker arm when the intake side rocker arm 37 is moved.

  Referring to FIGS. 4 and 6, the locking lever 66 has left and right engaging claws 74 and 75 extending from the cylindrical base 73 through which the support shaft 69 is inserted to the intake side rocker arm 37 side, and a coil spring 76. Is biased toward the intake side rocker arm 37. When the intake side rocker arm 37 is on either the low speed side or the high speed side, the locking lever 66 has the left and right engagement claws 74 and 75 connected to the left engagement groove 77 formed in the intake side rocker arm 37 and the center engagement. The engaging groove 78 and the right engaging groove 79 are engaged to make the sliding movement of the intake side rocker arm 37 in the direction of the axis C4 impossible. Further, the locking lever 66 swings to separate the left and right engagement claws 74 and 75 from the left engagement groove 77, the center engagement groove 78, and the right engagement groove 79 of the intake side rocker arm 37. The sliding movement of the side rocker arm 37 in the direction of the axis C4 is allowed.

  FIG. 7 shows a perspective view, a front view, a side view, and a top view of the intake side rocker arm 37. As shown in these drawings, the left engagement groove 77, the center engagement groove 78, and the right engagement groove 79 are formed in the support boss portion 37a of the intake side rocker arm 37 side by side in order. When the intake-side rocker arm 37 is on the low speed side, the locking lever 66 engages the left and right engaging claws 74 and 75 with the center engaging groove 78 and the right engaging groove 79 so that the intake-side rocker arm 37 is on the high speed side. The locking lever 66 engages the left and right engaging claws 74 and 75 with the left engaging groove 77 and the center engaging groove 78.

  Here, the configuration of the intake side rocker arm 37 will be described in detail with reference to FIGS. 4 and 6. In the intake side rocker arm 37, the arm portion 37 b and the pressing portion 37 c are divided into two in the direction of the axis C <b> 3 of the camshaft 38. The left and right arm portions 80 and 81 and the left and right pressing portions 82 and 83 are configured. A gap 84 is formed between the left and right arm portions 80 and 81 and the left and right pressing portions 82 and 83, and left and right roller holding walls 85 rising to the camshaft 38 side along the swinging direction are formed on the left and right arm portions 80 and 81. Is formed. The roller 37d is disposed in the gap 84 and is held by a support shaft (not shown) straddling the roller holding wall 85.

  Left and right reinforcing ribs 86 that rise toward the camshaft 38 are connected to the swing side ends of the left and right pressing portions 82 and 83, and the left and right reinforcing ribs 86 are connected to the left and right roller holding walls 85, respectively. The left and right reinforcing ribs 86 are each formed in a triangular shape so as to be inclined and rise from the left and right pressing portions 82 and 83 to the corresponding roller holding wall 85, and as shown in FIG. It is formed so as to extend close to a straight line connecting the shaft center C4 of 51 and the center point C7 of the roller.

  Further, the width dimensions of the divided left and right pressing portions 82 and 83 in the direction of the axis C3 of the camshaft 38 are different, and the right and left pressing portions 82 and 83 corresponding to the left cylinder in the cylinder head 5b are positioned rightward. The width of the portion 83 is wider than that of the left pressing portion 82. As shown in FIG. 7B, the inclination angle of the right reinforcing rib 86 on the side of the right pressing portion 83 that becomes wider is set to be gentler than the inclination angle of the left reinforcing rib 86 on the side that the width dimension becomes narrower. . As is apparent from FIG. 4 and the like, the left and right pressing portions 82 and 83 corresponding to the right cylinder in the cylinder head 5b are set to be in contrast with the left and right pressing portions 82 and 83 corresponding to the left cylinder.

  FIG. 8A shows a state in which the intake side rocker arm 37 is on the low speed side. In this state, the locking lever 66 engages the left and right engaging claws 74 and 75 with the center engaging groove 78 and the right engaging groove 79. The movement of the intake side rocker arm 37 is restricted. FIG. 8B shows a state in which the intake side rocker arm 37 is on the high speed side. In this state, the locking lever 66 causes the left and right engaging claws 74 and 75 to become the left engaging groove 77 and the central engaging groove 78. The movement of the intake side rocker arm 37 is regulated by engaging. Next, referring to FIG. 8, the trigger mechanism 67 is provided with a notch recess 87 extending over a predetermined length in the direction of the axis C <b> 4 at a portion inserted into the support boss portion 37 a of the intake side rocker arm shaft 51. The intake-side rocker arm shaft 37 formed in the recess 87 is configured by holding the trigger pin 68 so as to hang down in a slit-like through-hole 88 extending in the direction of the axis C4 that passes vertically in the direction orthogonal to the axis C4. ing.

  The trigger pin 68 is supported so that the intake side rocker arm shaft 37 can move in the direction of the axis C <b> 4, and the top part thereof is engaged with the central engagement groove 78 of the intake side rocker arm 37. It is made to contact | abut to either the right-and-left engaging claws 74 and 75 of the latching lever 66 which joined. The notch recess 87 includes a central plane portion 89 and left and right inclined portions 90 and 91, and when the intake side rocker arm shaft 51 is moved in the axial direction, either of the left and right inclined portions 90 or 91 triggers the trigger pin 68. Float up. As a result, the trigger mechanism 67 can lift the locking lever 66 upward and release the locking state with the intake-side rocker arm 37.

  That is, in the variable valve mechanism 32, when the intake side rocker arm 37 is moved from the low speed side to the high speed side, the intake side rocker arm shaft 51 is moved rightward by the hydraulic actuator 36 from the state shown in FIG. Then, the first spring receiving collar 63 is moved to store the urging force in the first spring 62, and the trigger pin 68 is lifted along with the movement of the intake side rocker arm shaft 51, and the locking lever 66 and the intake side rocker arm are moved. 37 is released and the urging force of the first spring 62 is released to move the intake side rocker arm 37 from the low speed side to the high speed side.

  In the variable valve mechanism 32, when the intake side rocker arm 37 is moved from the high speed side to the low speed side, the intake side rocker arm shaft 51 is moved leftward by the hydraulic actuator 36 from the state shown in FIG. The second spring receiving collar 65 is moved to store the urging force in the second spring 64, and then the locking state between the locking lever 66 and the intake side rocker arm 37 is released by the trigger pin 68, The intake side rocker arm 37 is moved from the high speed side to the low speed side by releasing the urging force of the two springs 64.

  Here, FIG. 9 shows a view of the camshaft 38 and the intake side rocker arm 37 viewed from the cylinder axis C2 side, and FIG. 9A shows a state where the intake side rocker arm 37 is on the low speed side. 9 (B) shows a state in which the intake side rocker arm 37 is on the high speed side. The positional relationship between the pressing portion 37c of the intake side rocker arm 37 and the exhaust cams 47 and 48 will be described with reference to these drawings. As shown in FIG. 9A, the intake side rocker arm 37 is on the low speed side. In the state (when the operation characteristic switching is completed), the left end portion of the left pressing portion 82 is disposed on the radially outer side (directly below) the exhaust cam 47. 9B, when the intake-side rocker arm 37 is on the high speed side (when the operation characteristic switching is completed), the right end of the right push-down portion 83 is disposed radially outside (directly below) the exhaust cam 48. ).

  3 and 10, L2 indicates a straight line along the direction of reaction of the reaction force of the valve spring 33e acting from the stem 33b of the intake valve 33, and L3 passes through the center point (C3) of the camshaft 38. A straight line parallel to the straight line L2 is shown. L4 extends parallel to the cylinder axis C2, passes through the center point (C3) of the camshaft 38, and shows a straight line perpendicular to the split surface PL. These straight lines L2 to L4 In the variable valve mechanism 32 of the present embodiment, it can be seen that the reaction force of the valve spring 33e is biased and acts largely on the front side of the second cam journal 43 with respect to the straight line L4.

  Accordingly, in the present embodiment, as shown in FIGS. 5 and 11, a straight line passing through the center point (C3) of the camshaft 38 along the direction of action of the reaction force of the valve spring 33e with reference to the straight line L4. The width dimension in the camshaft 38 axis C3 direction of the second cam journal 43 on the side where L3 is biased with respect to the straight line L4 is set larger than the width dimension of the second cam journal 43 located on the opposite side across the straight line L4. is doing. That is, as shown by W1 and W2 shown in FIGS. 5 and 11, in the second journal wall 43a, the front side is formed wider than the rear side across the straight line L4, and in the upper journal half 43c, The front side is formed wider than the rear side across the straight line L4.

  Thus, when the cam support portion on the side on which the reaction force of the valve spring 33e is biased and acts greatly is increased, the rigidity of the second cam journal 43 with respect to the valve spring 33e is suitably ensured. Also, as shown in FIGS. 5 and 10, a bolt insertion hole for inserting a fastening bolt 92 for fixing the cylinder head 5b to the cylinder block 5a in the second journal wall 43a of the second cam journal 43. Although 93 is formed along the cylinder axis C2 and the straight line L4, sufficient rigidity is ensured by widening the predetermined portion of the second cam journal 43 as described above.

  Next, the second cam journal 43 will be described in more detail with reference to FIGS. 10 and 11. As shown in FIG. 10, the second journal wall 43a and the upper journal half 43b are separated from the journal wall 43a. Positioning is performed by positioning pins 94 provided across both upper journal halves 43b, and insertion holes 95 through which the locating pins 94 are inserted are provided on the thick side of the journal wall 43a and the upper journal half 43b.

  A tube for passing the journal fastening bolt 46 and positioning the journal wall 43a and the upper journal half 43b on the opposite side of the positioning pin 94 across the camshaft 38 between the journal wall 43a and the upper journal half 43b. A member 96 is provided. Further, as shown in FIG. 11, an oil groove 97 along the outer periphery of the camshaft 38 is formed in the upper sliding contact portion 43d of the upper journal half 43b. Both ends of the oil groove 97 are set at positions separated from the split surface PL. Referring to FIG. 2, the support portion 70 is located away from the axis of the journal fastening bolt 46.

  Referring to FIG. 12, the variable valve mechanisms 31 and 32 are operated by hydraulic oil supplied from a hydraulic control valve (OCV) 101 controlled by the ECU 100 to the hydraulic actuators 35 and 36. The ECU 100 receives the rotational speed of the engine 1 from the rotational speed sensor 102 and information from the water temperature sensor 103, the hydraulic pressure sensor 104, the oil temperature sensor 105, and the like. A hydraulic oil passage 106 extending from the downstream side of the oil filter 25 is connected to the hydraulic control valve 101 and a drain passage 107 is connected thereto. The hydraulic control valve 101 and the hydraulic actuator 35 are connected by a pair of first connection oil passages 108, and the hydraulic control valve 101 and the hydraulic actuator 36 are connected by a pair of second connection oil passages 109.

  13 is a cross-sectional view of the hydraulic actuator 36. FIG. 13A shows a state in which the hydraulic actuator 36 sets the intake side rocker arm shaft 51 to the left limit position, and FIG. The actuator 36 has shown the state which made the intake side rocker arm shaft 51 the right limit position. Hereinafter, the hydraulic actuator 36 will be described with reference to FIGS. 4, 13, and 14, but the hydraulic actuator 35 has the same configuration.

  As shown in FIG. 4, the hydraulic actuator 36 is disposed such that a part of the cylinder body 58 is accommodated inward from the left side surface of the cylinder head 5 b, and the left end portion of the intake side rocker arm shaft 51 is disposed on the cylinder body 58. Is inserted through and fixed to the hydraulic piston 59. In the hydraulic actuator 36, the intake side rocker arm shaft 51 is not allowed to penetrate the left side wall portion of the cylinder body 58, so that the pressure receiving areas on both sides of the hydraulic piston 59 are different, and the hydraulic oil is moved when moving from the low speed side to the high speed side. The pressure receiving area of the left side surface of the hydraulic piston 59 that receives the hydraulic pressure is set larger than that of the other side surface.

  The cylinder body 58 is formed with a high speed side supply hole 110 that supplies hydraulic oil to the left side of the cylinder chamber 57 partitioned by the hydraulic piston 59 and a low speed side supply hole 111 that supplies hydraulic oil to the right side of the cylinder chamber. Yes. The high speed side supply hole 110 is formed to open at a position closer to the center (C4) of the hydraulic piston 59 than the low speed side supply hole 111.

  The left side end portion of the intake side rocker arm shaft 51 is formed with a through protrusion 112 having a threaded end, and the through protrusion 112 passes through a through hole 113 formed in the hydraulic piston 59 and is fastened by a nut 114. Thus, the intake side rocker arm shaft 51 and the hydraulic piston 59 are integrated. A recess 115 is formed in the pressure receiving surface on the high speed side of the hydraulic piston 59, and the nut 114 is accommodated in the recess 115, and a gap 116 is formed between the inner wall of the recess 115 and the nut 114. Further, an elliptical key portion 117 is formed to protrude in the outer diameter direction on the outer peripheral portion on the base side of the through protrusion 112, and the key portion 117 protrudes in the outer diameter direction from the through hole 113 shown in FIG. It is engaged with an elliptical engagement portion 118 formed in the above to prevent rotation. In addition, annular recesses 119 and 120 for preventing sticking are formed on the high pressure side pressure receiving surface and the low speed side pressure receiving surface of the hydraulic piston 59, respectively.

  Here, referring to FIG. 2, the second connecting oil passage 109 for supplying the hydraulic oil pressure-fed from the oil pump unit 24 to the hydraulic actuator 36 is connected to the hydraulic actuator 36 from below, and the intake-side rocker The arm shaft 51 is disposed closer to the oil pump unit 24 than the arm shaft 51. The first connecting oil passage 108 of the hydraulic actuator 35 is also connected to the hydraulic actuator 35 from below.

  The first connecting oil passage 108 and the second connecting oil passage 109 are connected to a hydraulic control valve 101 disposed on the base side between the front cylinder portion 4 and the rear cylinder portion 5, and the hydraulic control valve 101 is connected to the crankcase 3. The formed hydraulic oil passage 106 is connected. The first connection oil passage 108 reaches the hydraulic actuator 35 through the wall portion of the cylinder block 4a and the cylinder head 4b on the V bank side, and the second connection oil passage 109 is the wall portion of the cylinder block 5a and the cylinder head 5b on the V bank side. Then, the hydraulic actuator 36 is reached.

  Hereinafter, the hydraulic oil passage 106 and the connecting hot water passages 108 and 109 will be described in detail. As shown in FIG. 2, the hydraulic oil passage 106 has a hydraulic control valve 101 of the front cylinder portion 4 as viewed in the direction of the axis C0 of the crankshaft 2. If it is arranged on one side (rear side) with respect to the cylinder axis C1, it extends in the extending direction of the front cylinder part 4 on the other side (front side) with respect to the cylinder axis C1, and then the crankshaft 2 is bypassed. The front cylinder portion 4 side of the case 3 is connected to the hydraulic control valve 101 across the cylinder axis C1.

  The oil filter 25 provided at the front portion of the crankcase 3 is fed with lubricating oil from an oil cooler 121 provided adjacent to the oil filter 25, and the hydraulic oil passage 106 is connected to the oil filter 25, the main gallery 122 at the rear, It branches from the passage 123 between and extends upward. The main gallery 122 is formed in the lower part of the crankcase 3. 15 is a view as seen in the direction of arrow X in FIG. 2, and the hydraulic oil passage 106 extends so as to bypass the starter motor 26 provided adjacent to the oil filter 25 and the oil cooler 121. To do. FIG. 16 is a view as seen in the direction of arrow Y in FIG. 2, and the hydraulic oil passage 106 passes between adjacent cylinders 4d when straddling the cylinder axis C1. Here, the interval between the cylinders 4d in the front cylinder portion 4 is set wider than the interval between the cylinders 5d in the rear cylinder portion 5, and the hydraulic oil passage 106 passes between the cylinders 4d formed to be wide.

  As shown in FIG. 15, the hydraulic control valve 101 is configured by accommodating a piston or the like in a cylindrical member, and is arranged along the axial direction C0 of the crankshaft 2. It is arranged within the width between the central axes of 4d and 5d. In the figure, reference numeral 101A denotes a solenoid for driving the hydraulic control valve 101. The first connecting oil passage 108 extending from the hydraulic control valve 101 passes between the central axes of the cylinders 4d, and then extends in the cylinder head 4b in the direction of the arrow in the drawing to reach the hydraulic actuator 35. The second connecting oil passage 109 passes between the central axes of the cylinders 5d, and then extends in the cylinder head 4b in the direction of the arrow in the drawing to reach the hydraulic actuator 36.

  By the way, the engine 1 of this embodiment employs a system in which the intake valve drive mechanism 17 is driven by a motor 18, and in FIG. 2, C8 indicates the central axis (intake axis) of the intake pipe 16a of the rear throttle body 16. The motor 18 of the intake valve drive mechanism 17 is arranged on the rear side with respect to the intake axis C8, and the speed reduction mechanism 19 extends mostly from the intake pipe 16a of the rear throttle body 16 to the rear and is connected to the motor 18. Has been.

  Here, the positional relationship between the hydraulic actuator 36 and the intake valve drive mechanism 17 will be described. In the present embodiment, the hydraulic actuator 36 is arranged on the rear side with respect to the intake axis C8 as in the intake valve drive mechanism 17. The motor 18 is disposed on the upstream side of the intake pipe 16a, and the hydraulic actuator 36 is disposed on the downstream side of the intake pipe 16a. The intake axis C8 intersects the cylinder axis C2 at an acute angle, and the motor 18 and the hydraulic actuator 36 are disposed between the cylinder axis C2 and the intake axis C8. 2 shows a state where the engine 1 is mounted on the vehicle, and the motor 18 and the hydraulic actuator 36 are arranged so that the front and rear widths of both are overlapped when viewed from the direction of the axis C0 of the crankshaft 2 when the vehicle is mounted. Is in a relationship.

  FIG. 17 shows a view of the intake valve drive mechanism 17 and the hydraulic actuator 36 from above. As shown in FIG. 17, the motor 18 and the hydraulic actuator 36 are separated in the direction of the axis C0 of the crankshaft 2. The motor 18 is arranged closer to the center of the engine 1. Further, the motor 18 and the hydraulic actuator 36 are provided on the opposite side of the side where the cam drive sprocket 40 and the like constituting the cam drive mechanism are provided across the center line of the engine 1 in the axis C0 direction of the crankshaft. In FIG. 2, in this embodiment, the hydraulic actuator 36 is relatively far from the intersection P5 between the cylinder axis C2 and the intake axis C8. However, if the hydraulic actuator 36 is brought close to the intersection P5, the hydraulic path is shortened. Can be achieved.

  As described above, the engine 1 according to this embodiment refers to the intake valve 33 biased in the closing direction by the valve spring 33e and the biasing force of the valve spring 33e with reference to FIGS. And a camshaft 38 that opens the intake valve 33 against the above, and the camshaft 38 is rotatably supported by a second cam journal 43 provided in the cylinder head 5b, and the cylinder head 5b is erected. A straight line passing through the center point C3 of the camshaft 38 along the direction L2 of the reaction force of the valve spring 33e with reference to a straight line L4 passing through the center point C3 of the camshaft 38 along the cylinder axis C2 direction of the cylinder block 5a. The second cam located on the opposite side of the straight line L4 with respect to the width dimension of the second cam journal 43 on the side where L3 deviates from the straight line L4 And a structure to set larger than the width of the journal 43. More specifically, the second cam journal 43 is divided in the direction of the straight line L4 by setting the split surface PL in a direction orthogonal to the straight line L4, and the second journal wall portion located on both sides of the split surface PL. 43a and the upper journal half 43b are set to have a width dimension on the side to be displaced larger than the width dimension of the portion located on the opposite side across the straight line L4.

  When such a support structure is used, it is necessary to increase the width dimension of the cam journal where the reaction force of the valve spring acts on the portion where the reaction force of the valve spring does not act relatively. As described above, the surface pressure against the reaction force of the valve spring can be reduced without increasing the size of the cam journal, and the support rigidity of the cam journal can be ensured satisfactorily.

  Further, in the above support structure, the second cam journal 43 divided across the split surface PL is divided into the second journal wall 43a and the upper journal half 43b, and the divided second cam journal straddles both sides. The positioning hole 94 is provided, and the insertion hole 95 through which the positioning pin 94 is inserted is provided on the width-thickness side. However, with such a structure, a reduction in rigidity of the cam journal due to the positioning member can be suppressed as much as possible. Further, on the opposite side of the positioning pin 94, a tube member 96 for passing the journal fastening bolt 46 and positioning the divided second cam journal 43 is provided. The arrangement space for the journal positioning member can be reduced.

  Further, in the above support structure, the oil groove 97 along the outer periphery of the cam shaft 38 is formed in the upper journal half 43b of the second cam journal 43, and both ends of the oil groove 97 are separated from the split surface PL. However, with this structure, both the lubrication of the camshaft 38 and the securing of the rigidity of the second cam journal 43 can be achieved.

  In the above support structure, the second journal wall 43a located on the cylinder block 5a side across the split surface PL extends along a straight line L4 that divides the lower sliding contact surface 43c with the camshaft 38. Although the bolt insertion hole 93 to be formed is formed, the width and thickness of the journal are sufficiently secured as described above, so that the support rigidity of the journal is ensured satisfactorily.

  Below, the modification of the said embodiment is demonstrated using FIG. In this modification, the configuration of the second cam journal 43 that supports the camshaft 38 is different from that of the above embodiment. As shown in FIG. 18, the second cam journal 43 according to the modification is formed from the bottom of the cylinder head 5b. A second journal wall portion 200 that rises, a slidable contact portion 201 that is detachably attached to the upper portion of the second journal wall portion 200 and that supports the camshaft 38 slidably, and an upper journal that is disposed above the slidable contact portion 201 It consists of a half body 202. The slidable contact portion 201 includes a main body portion 201b on which a slidable contact surface 201a with the camshaft 38 is formed, and a pair of plate-like attachment portions 201c protruding from both sides with the slidable contact surface 201a interposed therebetween.

  The second journal wall portion 200 is formed with a concave portion 203 that is recessed downward, and the sliding contact portion 201 is disposed so as to accommodate the main body portion 201b in the concave portion 203, and the mounting portion 201c is disposed on the second journal wall portion. 200. A bolt insertion hole 204 for coupling with the cylinder block 5 a is formed in the recess 203, and the sliding contact portion 201 is attached to the second journal wall portion 200 so as to close the bolt insertion hole 204. The sliding contact portion 201 is fastened to the second journal wall portion 200 together with the upper journal half body 202 by passing a bolt penetrating the upper journal half body 202 through the attachment portion 201c.

  In the case of the configuration according to the modified example as described above, even when the sliding contact area of the second cam journal 43 with the camshaft 38 is reduced by the bolt insertion hole 204, the camshaft 38 is slidably contacted separately. By providing the sliding contact portion 201, it is possible to secure a sliding contact area and reduce the surface pressure due to the valve spring reaction force. Further, since the sliding contact portion 201 is fastened to the second journal wall portion 200 together with the upper journal half 202, a special member for the sliding contact portion 201 can be eliminated.

  Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, in the above embodiment, the intake side rocker arm 37 is moved in the axial direction, but the exhaust side rocker arm 39 may be moved in the axial direction. Moreover, although the said embodiment demonstrated the structure which provides the oil groove 97 only in the upper journal half body 43b, you may provide also in the journal wall part side. Moreover, in the said embodiment, although the structure of this invention was applied to the engine provided with a variable valve mechanism, this invention can be implemented also with an engine of another type.

5a Cylinder block 5b Cylinder head 33 Intake valve (engine valve)
33e Valve spring 38 Camshaft 43 Second cam journal (cam journal)
43a Second journal wall (cam journal)
43b Upper journal half (cam journal)
43c Lower sliding contact portion (sliding contact surface)
43d Upper sliding contact portion (sliding contact surface)
93 Bolt insertion hole 94 Positioning pin 95 Insertion hole 96 Pipe member 97 Oil groove 200 Second journal wall portion 201 Sliding contact portion 202 Upper journal half body 204 Bolt insertion hole PL Split surface

Claims (8)

An engine valve (33) biased in a closing direction by a valve spring (33e), and a camshaft (38) that opens the engine valve (33) against the biasing force of the valve spring (33e). A camshaft support structure for an internal combustion engine, wherein the camshaft (38) is rotatably supported by a cam journal (43) provided in a cylinder head (5b).
With reference to a first straight line (L4) passing through the center point (C3) of the camshaft (38) along the cylinder axis (C2) direction of the cylinder block (5a) that erects the cylinder head (5b), A second straight line (L3) passing through the center point (C3) of the camshaft (38) along the acting direction (L2) of the reaction force of the valve spring (33e) is relative to the first straight line (L4). The width dimension in the camshaft (38) axial direction of the cam journal (43) on the biased side is the width dimension of the cam journal (43) located on the opposite side across the first straight line (L4). A camshaft support structure for an internal combustion engine, characterized by being set larger than The cam journal (43) is divided in the direction of the first straight line (L4) by setting a split surface (PL) in a direction perpendicular to the first straight line (L4),
The width dimension in the camshaft (38) axial direction of the cam journal (43) located on both sides with respect to the split surface (PL) is located on the opposite side across the first straight line (L4). The camshaft support structure for an internal combustion engine according to claim 1, wherein the camshaft (43) is set to be larger than the width dimension of the cam journal (43).   The cam journals (43; 43a, 43b) divided across the split surface (PL) are positioned by positioning pins (94) provided across both of the divided cam journals (43; 43a, 43b). The camshaft support structure for an internal combustion engine according to claim 2, wherein an insertion hole (95) for positioning and inserting the positioning pin (94) is provided on the width-thickness side.   A journal fastening bolt (46) is passed through the cam journal (43; 43a, 43b) on the opposite side of the positioning pin (94) across the cam shaft (38), and the divided cam journal (43; 43a). , 43b) is provided with a pipe member (96) for positioning the camshaft support structure for an internal combustion engine according to claim 3.   An oil groove (97) along the outer periphery of the cam shaft (38) is formed on the sliding surface (43d) of the cam shaft (38) in the cam journal (43), and both end portions of the oil groove (97) are formed. The camshaft support structure for an internal combustion engine according to any one of claims 2 to 4, wherein the camshaft is separated from the split surface (PL).   The cam journal (43; 43a) positioned on the cylinder block (5a) side with the split surface (PL) interposed between the cam journal (43; 43a) and the camshaft (38) sliding contact surface ( The internal combustion engine according to any one of claims 2 to 5, wherein a bolt insertion hole (93) extending along the first straight line (L4) that divides 43c) is formed. Camshaft support structure. The cam journal (43) positioned on the cylinder block (5a) side with the split surface (PL) interposed therebetween, a journal wall portion (200) standing on the cylinder head (5b), and the journal wall portion A slidable contact portion (201) that is detachably attached to (200) and slidably supports the camshaft (38),
A bolt insertion hole (204) extending along the first straight line (L4) to penetrate the journal wall (200) is formed in the journal wall (200), and the sliding contact (201 6 is attached to the journal wall (200) so as to close the bolt insertion hole (204). 6. The camshaft support structure for an internal combustion engine according to any one of claims 2 to 5, wherein   The sliding contact portion (201) is sandwiched between the cam journal (202) located on the opposite side of the sliding contact portion (201) and the journal wall portion (200) across the split surface (PL). 8. The camshaft support structure for an internal combustion engine according to claim 7, wherein the bolt is fastened.

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