EP2853701A1

EP2853701A1 - Variable valve gear of internal combustion engine

Info

Publication number: EP2853701A1
Application number: EP14175267.5A
Authority: EP
Inventors: Dai Kataoka; Makoto Fujikubo; Yoshiyuki Sekiya; Yohei Nakamura; Kazuyuki Kosei
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 2013-09-30
Filing date: 2014-07-01
Publication date: 2015-04-01
Anticipated expiration: 2034-07-01
Also published as: EP2853701B1; ES2564550T3; JP2015068317A; JP6069766B2

Abstract

In a variable valve gear for an internal combustion engine in which a connection pin capable of connecting first and second rocker arms to each other is slidably fitted in the two rocker arms arranged adjacent to each other, and a press rod having a pressing portion abutting on a pressed portion formed at one end of the connection pin is movably supported in a support wall provided on a cylinder head to face the first rocker arm from the opposite side from the second rocker arm, the connection pin and the press rod are caused to abut on each other, while an increase in stiffness of a support wall is enabled with a structure capable of avoiding upsizing of the cylinder head.

An accommodating hole (113) in which the pressing portion (104a) of the press rod (104) abuts on the pressed portion (97a) of the connection pin (97) is formed in the interior of the first rocker arm (71) to permit a relative movement of the press rod (104) to rocking of the first locker arm (71).

Description

The present invention relates to a variable valve gear of an internal combustion engine in which: first and second rocker arms arranged adjacent to each other, at least one of which is operationally connected to an engine valve, are rockably supported by a cylinder head through a rocker shaft and also are structured to rock in mutually different rocking manners in a non-connection state of the rocker arms; a connection pin having an axis extending parallel to the rocker shaft is slidably fitted to the first and second rocker arms to be movable, in a span of the first and second rocker arms, between a connection position in which the two rocker arms are connected to each other and a disconnection position on the first rocker arm in which the first rocker arm moves away from the second rocker arm to release the connection of the two locker arms; a pressed portion is formed at one end of the connection pin on the opposite side from the second rocker arm; and a press rod having a pressing portion formed at an end facing the connection pin to abut on the pressed portion is supported movably in a direction parallel to the rocker shaft to be capable of pressing the connection pin by a support wall provided on the cylinder head to face the first rocker arm from the opposite side from the second rocker arm.
A variable valve gear of an internal combustion engine known from JP-A No. 2012-77633 is designed such that a connection pin is slidably fitted to first and second rocker arms arranged adjacent to each other to be switchable between connection and disconnection of the rocker arms, and a press rod capable of pressing the connection pin toward the connection position is supported by a support wall provided on a cylinder head to face the first rocker arm from the opposite side from the second rocker arm.
In the variable valve gear disclosed by JP-A No. 2012-77633 , however, the connection pin and the press rod permit rocking of the connection pin together with the first rocker arm in relation to the pressing rod located in a fixed position in a direction perpendicular to the axis. Because of this, the connection pin and the pressing rod abut on each other in a space between the first rocker arm and the support wall, requiring a relatively large space between the first rocker arm and the support wall. Therefore, if the thickness of the support wall is increased to increase the stiffness of the support wall, upsizing of the cylinder head results.
Accordingly, the present invention has been made in light of such circumstances and provides a variable valve gear for an internal combustion engine designed to cause a connection pin and a press rod to abut on each other while enabling an increase in stiffness of a support wall with a structure capable of avoiding upsizing of a cylinder head.
To attain this object, a first aspect of the present invention provides a variable valve gear of an internal combustion engine, in which: first and second locker arms arranged adjacent to each other, at least one of which is operationally connected to an engine valve, are rockably supported by a cylinder head through a rocker shaft and also are structured to rock in mutually different rocking manners in a non-connection state of the rocker arms; a connection pin having an axis extending parallel to the rocker shaft is slidably fitted to the first and second rocker arms to be movable, in a span of the first and second rocker arms, between a connection position in which the two rocker arms are connected to each other and a disconnection position on the first rocker arm side in which the connection pin moves away from the second rocker arm to release the connection of the two locker arms; a pressed portion is formed at one end of the connection pin on the opposite side from the second rocker arm; and a press rod having a pressing portion formed at an end close to the connection pin to abut on the pressed portion is supported movably in a direction parallel to the rocker shaft to be capable of pressing the connection pin by a support wall provided on the cylinder head to face the first rocker arm from the opposite side from the second rocker arm. In the variable valve gear of an internal combustion engine, an accommodating hole in which the pressing portion of the press rod abuts on the pressed portion of the connection pin is formed in the interior of the first rocker arm to permit a relative movement of the press rod to rocking of the first locker arm.
A second aspect of the present invention is that, in addition to the construction of the first aspect, the area of the pressing portion of the press rod is set to be smaller than the area of the pressed portion of the connection pin.
A third aspect of the present invention is that, in addition to the construction of the first or second aspect, the connection pin is formed to have an outer peripheral surface continuously extending between both ends in an axial direction.
A fourth aspect of the present invention is that, in addition to any of the construction of the first to third aspects, the press rod is formed to have an outer peripheral surface continuously extending from at least a middle portion in an axial direction to the pressing portion.
A fifth aspect of the present invention is that, in addition to any of the construction of the first to fourth aspects, the press rod is placed to have an axis offset from the axis of the connection pin toward the rocker shaft.
A sixth aspect of the present invention is that, in addition to any of the construction of the first to fifth aspects, a fit hole in which the connection pin is slidably fitted is provided in the first rocker arm in such a manner that a step facing toward the second rocker arm is formed between the accommodating hole and the fit hole.
A seventh aspect of the present invention is that, in addition to the construction of the sixth aspect, the accommodating hole and the fit hole of circular cross section are provided in the first rocker arm to be linked to each other by offsetting the axis from the axis of the fit hole toward the rocker shaft.
An eighth aspect of the present invention is that, in addition to any of the construction of the first to seventh aspects, a press-rod support hole extending through the support wall such that the press rod is slidably fitted in the press-rod support hole, and a rocker-shaft support hole supporting the rocker shaft inserted into the rocker-shaft support hole, are provided parallel to each other in the support wall, and the press rod is formed in a shape enabling insertion of the press rod into the press-rod support hole from the opposite side to the first rocker arm.
According to the first aspect of the present invention, since the connection pin and the press rod abut on each other in the accommodating hole formed in the first rocker arm, the support wall of the cylinder head is able to be placed close to the first rocker arm, making it possible to avoid upsizing of the cylinder head even if the thickness of the support wall is increased for higher stiffness.
According to the second aspect of the present invention, since the area of the pressing portion of the press rod is smaller than that of the pressed portion of the connection pin, this makes it possible to reduce the size of the press rod and also to reduce the size of the accommodating hole for miniaturization of the first rocker arm.
According to the third aspect of the present invention, since the outer peripheral surface of the connection pin extends continuously between both ends in the axis direction, this enables simplification of component geometry of the connection pin, leading to productivity gains and reductions in cost.
According to the fourth aspect of the present invention, since the press rod has an outer peripheral surface continuously extending from at least a middle portion in the axis direction to the pressing portion, this makes possible simplified shapes of components including at least the pressing portion of the press rod and a smaller size of the accommodating hole.
According to the fifth aspect of the present invention, since the axis of the press rod is offset from the axis of the connection pin toward the rocker shaft, this makes it possible to decrease the amount of relative movement of the first rocker arm and the press rod, thus reducing the size of the accommodating hole.
According to the sixth aspect of the present invention, since the fit hole provided in the first rocker arm to be slidably fitted over the connection pin has the step formed between the accommodating hole and the fit hole facing toward the second rocker arm, the movement of the connection pin toward the support wall of the cylinder head is restricted by causing the connection pin to abut on the step, thus preventing the connection pin from falling out of the first rocker arm.
According to the seventh aspect of the present invention, since the accommodating hole and the fit hole of circular cross section are linked to each other by offsetting the axis of the accommodating hole from the axis of the fit hole toward the rocker shaft, the step for restricting the movement of the connection pin toward the support wall of the cylinder head is easily formed and compact design of the first rocker arm is enabled.
According to the eighth aspect of the present invention, since the press rod is able to be inserted into the press-rod support hole provided in the support wall from the opposite side to the first rocker arm, mounting and demounting of the press rod to and from the support wall is facilitated.

Fig. 1 is a side view of a motorcycle.
Fig. 2 is a cross sectional view of the essential parts of a power unit.
Fig. 3 is a view taken in the direction of arrow 3 in Fig. 2.
Fig. 4 is a sectional view taken along line 4-4 in Fig. 3.
Fig. 5 is a sectional view taken along line 5-5 in Fig. 4.
Fig. 6 is an essential enlarged view of Fig. 4.

Embodiments of the present invention will be described in detail below with reference to the accompanying Fig. 1 to Fig. 6. In the following description, "front", "rear", "left", "right", "up" and "down" refer to the respective directions as viewed by an occupant riding on the saddle-ride type vehicle.
First, in Fig. 1, a body frame F of a scooter-type motorcycle includes at its front end a front fork 11 for journaling a front wheel WF and a head pipe 13 which is connected to the front fork 11 and steerably supports a steering handlebar 12. A power unit P exerting power to drive the rear wheel WR is vertically rockably supported in a middle portion of the body frame F in the front-rear direction.
The power unit P includes an internal combustion engine E located forward of the rear wheel WR and a transmission system M that transmits output power of the internal combustion engine E to the rear wheel WR. The transmission system M is housed in a transmission case 15 which is contiguous with an engine body 14 of the internal combustion engine E and extends leftward of the rear wheel WR. A rear cushion unit 16 is mounted between a rear portion of the transmission case 15 and a rear portion of the body frame F.
The body frame F and a part of the power unit P are covered with a body cover 17 which has a pair of left and right footrests 18 on which the occupant is to place his/her feet and a floor tunnel 19 raised upward between the left and right footrests 18. The body cover 17 is attached to the body frame F. An occupant seat 20 placed rearward of the floor tunnel 19 and a passenger seat 21 placed rearward of the occupant seat 20 are placed on the body cover 17.
Referring also to Figs. 2 and 3, the engine body 14 of the internal combustion engine E includes: a crankcase 25 which rotatably supports a crankshaft 24 having an axis extending in the vehicle-width direction; a cylinder block 26 which has a cylinder bore 30 slidably fitted over a piston 29 and is joined to the crankcase 25; a cylinder head 27 which is joined to the cylinder block 26; and a head cover 28 which is joined to the cylinder head 27. The cylinder axis C of the engine body 14, that is, the axis of the cylinder bore 30, is inclined slightly upward toward the front, and the piston 29 is connected to the crankshaft 24.
An intake device 32 is provided for supplying air into a combustion chamber 31 faced by the top face of the piston 29 to be formed between the cylinder block 26 and the cylinder head 27. The intake device 32 includes: an air cleaner 33 which is placed above the transmission case 15 on the left side of the rear wheel WR, and supported by the transmission case 15; and a throttle body 34 placed between the air cleaner 33 and the cylinder head 27. A fuel injection valve 35 is mounted on an upper side wall of the cylinder head 27.
As shown in Fig. 1, an exhaust device 36 is connected to a lower side wall of the cylinder head 27 for emitting exhaust gases from the combustion chamber 31. The exhaust device 36 includes: an exhaust pipe 37 which extends rearward from the lower side wall of the cylinder head 27 in a position below the engine body 14; and an exhaust muffler (not shown) which is placed on the right side of the rear wheel WR in such a manner as to be connected to the downstream end of the exhaust pipe 37.
The crankcase 25 is formed by joining a first case half 38 on the right side and a second case half 39 on the left side together. An outer rotor 40 is secured to a right end of the crankshaft 27 rotatably extending through the first case half 38. An inner stator 41, which is surrounded by the outer rotor 40 so as to form a generator 42 in conjunction with the outer rotor 40, is secured to a support plate 43 fastened to the first case half 38.
The first case half 38 is joined to a cylindrical-shaped generator cover 44 surrounding the generator 42, and in turn a radiator 45 is placed on the right side of the generator cover 44. A cooling fan 46 for circulation of cooling air through the radiator 45 is fixed to the crankshaft 24 such that the cooling fan 46 is located between the generator 42 and the radiator 45.
The transmission system M, which is housed in the transmission case 15 in such a manner as to transmit the rotational power of the crankshaft 24 toward the rear wheel WR, includes a V-belt continuously variable transmission 48 which steplessly changes the speed of the rotational power transmitted from the crankshaft 24, and a reduction gear mechanism (not shown) which reduce the speed of the rotational power of the V-belt continuously variable transmission 48 for transmission to an axle 50 (see Fig. 1) of the rear wheel WR.
A drive pulley 51 of the V-belt continuously variable transmission 48 is provided on the crankshaft 24 with variable winding diameter of a V belt 52. The drive pulley 51 includes a fixed sheave 53 fixed to the crankshaft 24 and a movable sheave 54 supported by the crankshaft 24 to be capable of moving toward and away from the fixed sheave 53 in the direction along the axis of the crankshaft 24. The movable sheave 54 is placed closer to the crankcase 25 than the fixed sheave 53.
The movable sheave 54 is driven toward the fixed sheave 53 in accordance with an increase in rpm of the crankshaft 24 by action of a centrifugal shift mechanism 55. The centrifugal shift mechanism 55 includes a weight 58 held between a cam surface 56 formed on the movable sheave 54 and a weight holding plate 57 fixed to the crankshaft 24.
Referring also to Figs. 4 and 5, in the cylinder head 27, a pair of intake valves 61 for control of intake from the intake device 32 to the combustion chamber 31 and a pair of exhaust valves 62 for control of exhaust from the combustion chamber 31 to the exhaust device 36 are placed to be capable of opening and closing. Each of the intake valves 61 is urged in the direction that closes the valve by a valve spring 63, and each of the exhaust valves 62 is urged in the direction that closes the valve by a valve spring 64. A spark plug 65 with a leading end facing toward the combustion chamber 31 is mounted on the left side wall of the cylinder head 27. A recess 66 is formed in the outer surface of the left side wall of the cylinder head 27 to place the spark plug 65.
A valve gear 68 driving the opening and closing of the intake valves 61 and the exhaust valves 62 is housed in a valve chamber 67 formed between the cylinder head 27 and the head cover 28.
The valve gear 68 includes: a single cam shaft 70 placed between the two intake valves 61 and the two exhaust valves 62 to be shared between the two intake valves 61 and the two exhaust valves 62; first and second intake rocker arms 71, 72 interposed between the two intake valves 61 and the cam shaft 70; and a single exhaust rocker arm 73 interposed between the two exhaust valves 62 and the cam shaft 70.
A middle portion of the exhaust rocker arm 73 is rockably supported by an exhaust rocker shaft 74 having an axis extending parallel to the cam shaft 70. A roller 76 in rolling contact with an exhaust cam 75 provided in the cam shaft 70 is journaled to one end of the exhaust rocker arm 73, while a pair of connection arms 73a, 73b individually assigned to the two exhaust valves 62 are provided integrally with the other end of the exhaust rocker arm 73. Tappet screws 77 abutting on stem ends 62a of the two exhaust valves 62 are screwed into the connection arms 73a, 73b such that their advance and retreat positions can be adjusted.
The first and second intake rocker arms 71, 72 are adjacent to each other in a side-by-side arrangement in the direction along the axis of the cam shaft 70 with at least one of them operationally connected with the intake valves 61 which are engine valves. In the embodiment, the first and second intake rocker arms 71, 72 are individually, operationally connected with a pair of intake valves 61, and rockably supported by the intake rocker shaft 78 having the axis extending parallel to the cam shaft 70. Specifically, tappet screws 79 abutting on stem ends 61a of the intake valves 61 are screwed respectively into one ends of the first and second intake rocker arms 71, 72 such that their advance and retreat positions can be adjusted.
A roller 82 in rolling contact with the first intake cam 80 provided in the cam shaft 70 is journaled to the other end of the first intake rocker arm 71. A cam slipper 83 in contact with the second intake cam 81 provided in the cam shaft 70 is provided at the other end of the second intake rocker arm 72.
The second intake cam 81 is formed to practically deactivate the intake valve 61 operationally connected to the second intake rocker arm 72 which is one of the pair of intake valves 61 while the connection between the first and second intake rocker arms 71, 72 is released. The second intake cam 81 is also formed to have an outer peripheral surface to slightly open the intake valve 61 in order to prevent occurrence of fuel accumulation when the intake valve 61 is fully closed into a deactivated state. Specifically, the first and second intake rocker arms 71, 72 are rockably supported via the intake rocker shaft 78 by the cylinder head 27, and also are structured to rock in mutually different rocking manners in a non-connection state.
The cam shaft 70 is rotatably supported by first and second support walls 85, 86 which are spaced from each other in the direction along the axis of the cam shaft 70 to be protrusively provided integrally with the cylinder head 27. The first and second support walls 85, 86 are each formed to elongate in the direction perpendicular to the axes of the cam shaft 70, the intake rocker shaft 78 and the exhaust rocker shaft 74. Stud bolts 87, 88 are placed at both ends in the longitudinal direction of the support walls 85, 86 in order to join the cylinder block 26 and the cylinder head 27 to the crankcase 25.
The rotational power of the crankshaft 24 is transmitted at a reduction ratio of 1/2 via a timing transmission mechanism 89 to one of both ends of the cam shaft 70 which is disposed on the right side to protrude from the second support wall 86. The timing transmission mechanism 89 includes a drive sprocket 90 (see Fig. 2) fixedly mounted to the crankshaft 24, a driven sprocket 91 fixed to a right end of the cam shaft 70 protruding from the second support wall 86, and a cam chain 92 wound around the drive sprocket 90 and the driven sprocket 91. A cam chain passage 93 is formed in the cylinder block 26 and the cylinder head 27 to be located on the right side of the cylinder bore 30 such that the cam chain 92 runs in the cam chain passage 93.
A water pump 94 is mounted on the right side wall of the cylinder head 27. A pump shaft 95 of the water pump 94 extends across the cam chain passage 93 to be connected coaxially to the right end of the cam shaft 70 with an inability of relative rotation.
The intake rocker shaft 78 and the exhaust rocker shaft 74 are disposed on opposite sides of the cam shaft 70, while both ends of each of the intake rocker shaft 78 and the exhaust rocker shaft 74 are fitted into and supported by the first and second support walls 85, 86.
The first and second intake rocker arms 71, 72 are provided with valve operation characteristics changing means 96 for switching between a state in which, irrespective of the first intake rocker arm 71 rocking following the first intake cam 80, the cam slipper 83 of the second intake rocker arm 72 is kept in contact with the second intake cam 81 in order to practically close and deactivate one of the intake valves 61 and to effect opening/closing operation of the other intake valve 61 in an operation manner based on the cam profile of the first intake cam 80 during low speed operation of the internal combustion engine E, and a state in which the first and second intake rocker arms 71, 72 are connected in order to effect opening/closing operation of the two intake valves 61 in an operation manner based on the cam profile of the first intake cam 80 during high speed operation of the internal combustion engine E.
Referring also to Fig. 6, the valve operation characteristics changing means 96 is installed in an upper portion of the first and second intake rocker arms 71, 72 between the intake rocker shaft 78 and the cam shaft 70, and includes: a first connection pin 97 which is movable, in a span of the first and second rocker arms 71, 72, between a connection position in which the first and second intake rocker arms 71, 72 are connected to each other and a disconnection position on the first intake rocker arm 71 in which the first connection pin 74 moves away from the second intake locker arm 72 to release the connection of the first and second locker arms 71, 72, and has an axis extending parallel to the intake rocker shaft 78, and also is slidably fitted to the first and second intake rocker arms 71, 72; a second connection pin 98 which is slidably fitted to the second intake rocker arm 72 to be connected to the first connection pin 97; and a return spring 99 which is mounted between the second connection pin 98 and the second intake rocker arm 72 so as to exert a spring force urging the first connection pin 97 toward the disconnection position.
The first intake rocker arm 71 is provided with a first fit hole 100 having an axis extending parallel to the intake rocker shaft 78, while the second intake rocker arm 42 is provided with a second fit hole 101 which has an axis extending parallel to the intake rocker shaft 78 and is of a bottomed shape having an end wall 101a formed on the opposite side to the first intake rocker arm 71. Further, the first and second fit holes 100, 101 are circular in cross section with the same diameter so that the holes 100, 101 are to be coaxially contiguous with each other during a closed state of the intake valve 61.
The first connection pin 97 is able to be slidably fitted into the first and second fit holes 100, 101, and is formed in a short cylinder shape having a pressed portion 97a formed at one end on the opposite side from the second intake rocker arm 72 and an outer peripheral surface continuously extending between both ends in the axis direction. The second connection pin 98 is formed in a closed-end cylindrical shape having an open end facing toward the end wall 101a of the second fit hole 101. The return spring 99, which urges the mutually abutting first and second coupling pins 97, 98 in only one axis direction (rightward in Figs. 4 and 6), is contractedly installed between the second connection pin 98 slidably fitted into the second fit hole 101 and the end wall 101a. In addition, a communication hole 102 is formed in the second intake rocker arm 72 in such a manner as to cross the second fit hole 101 for communication between an area close to the end wall 101a which is the closed end of the second fit hole 101 and the outside.
The valve operation characteristics changing means 96 fits a part of the first connection pin 97 into the second fit hole 101 against the spring force of the return spring 99 for connection between the first and second intake locker arms 71, 72. Then, the valve operation characteristics changing means 96 moves the first and second connection pins 97, 98 in the axis direction by use of the spring force of the return spring 99 until the abutting faces of the first and second connection pins 97, 98 reach a border between the first and second intake rocker arms 71, 72 for disconnection of the first and second intake rocker arms 71, 72 from each other.
In the first support wall 85 on the opposite side of the first intake rocker arm 71 from the second intake rocker arm 72, a press rod 104, which has a pressing portion 104a formed at an end close to the first connection pin 97 to abut on the pressed portion 97a formed at the end of the first connection pin 97, is supported movably in a direction parallel to the intake rocker shaft 78 to be able to press the first connection pin 97 toward the connection position. In the embodiment, the press rod 104 is slidably fitted in a press-rod support hole 106 provided in the first support wall 85 to extend parallel to a rocker-shaft support hole 105. The rocker-shaft support hole 105 is provided in the first support wall 85 to support one end of the intake rocker shaft 78 inserted into the rocker-shaft support hole 105.
In addition, the press rod 104 is formed to have the outer peripheral surface continuously extending from at least a middle portion in the axis direction to the pressing portion 104a. In the embodiment, the press rod 104 is formed with a constant outer diameter throughout its length in the axis direction.
A housing 108 of a solenoid 107 as an actuator is mounted on a left side wall of the cylinder head 27 on the opposite side of the first support wall 85 from the first intake rocker arm 71 in such a manner as to fasten a mounting plate 109 fixedly attached to the housing 108 with a plurality of bolts, for example, three bolts 110.
The solenoid 107 has an output rod 111 protruding in the ON state caused by its energization. A guiding cylinder 112, which is fixedly mounted in the housing 108 to guide the movement of the output rod 111 in the axis direction, extends liquid-tightly through the left side wall of the cylinder head 27 to protrude into the valve chamber 67. A protruding end of the output rod 111 protrudes from the leading end of the guiding cylinder 112 to abut coaxially on one end of the press rod 104. In this regard, the output rod 111 may be formed to be integrally contiguous with the press rod 104.
Upon the solenoid 107 pressing the press rod 104, the press force acts through the pressing rod 104 on the first connection pin 97 to move the first and second connection pins 97, 98 toward the connection position. In the OFF state caused by deenergization of the solenoid 107, the first and second connection pins 97, 98 are moved to the disconnection position by act of only the spring force of the return spring 99.
In the interior of the first intake rocker arm 71 in the direction along the axis of the intake rocker shaft 78, an accommodating hole 113, which houses the abutting portion between the pressed portion 97a of the first connection pin 97 and the pressing portion 104a of the press rod 104, is formed to permit relative movement of the press rod 104 to the rocking of the first rocker arm. Specifically, the accommodating hole 113 is formed to have an adequate size to prevent interference of the press rod 140 with the inner wall face of the accommodating hole 113 in the maximum lift state and the minimum lift state of the first intake rocker arm 71.
The first fit hole 100 in which the first connection pin 97 is slidably fitted is provided in the first intake rocker arm 71 in such a manner that a step 114 facing toward the second intake rocker arm 72 is formed between the first fit hole 100 and the accommodating hole 113. The accommodating hole 113 and the first fit hole 100 of circular cross section are provided in the first intake rocker arm 71 to be linked to each other by offsetting the axis C1 of the accommodating hole 113 from the axis C2 of the first fit hole 100 toward the intake rocker shaft 78.
The area of the pressing portion 104a of the press rod 104 is set to be smaller than the area of the pressed portion 97a of the first connection pin 97. In the embodiment, the press rod 104 having a constant outer diameter throughout its length in the axis direction is formed to have a smaller diameter than the first connection pin 97 having a constant outer diameter throughout its length in the axis direction.
The axis C3 of the press rod 104 is offset from the axis of the first connection pin 97, that is, the center C2 of the first fit hole 100 toward the intake rocker shaft 78. In the embodiment the axis C3 of the press rod 104 and the center C1 of the accommodating hole 113 are offset from each other, but the axes C3, C1 may be placed on the same axis.
A plurality of lubricant injection holes 116 are placed on the inner surface of the upper side wall of the cylinder head 27 above the valve gear 68 at intervals in the axis direction of the cam shaft 70. A first oil passage 117, which extends parallel to the axis of the cam shaft 70 to be shared among the lubricant injection holes 116, is provided in the upper side wall of the cylinder head 27. A ring-shaped oil passage 119 for guiding lubricant from the oil pump disposed in the crankcase 25 is formed between the outer periphery of the upper stud bolt 88 of the stud bolts 88 placed at both ends in the longitudinal direction of the second support wall 86, and the inner periphery of a bolt insertion hole 118 provided in the cylinder block 26 and the cylinder head 27 for insertion of the stud bolt 88. A connection oil passage 120 is provided in an upper side wall of the cylinder head 27 for communication of the ring-shaped oil passage 119 with a first oil passage 117.
A second oil passage 121 for guiding lubricant from the first oil passage 117 is provided between the first support wall 85 and the left end of the cam shaft 70 in the cylinder head 27 close to the first support wall 85.
Next, operations in the embodiment will be described. The first connection pin 97, which is movable between the connection position in which the first and second intake rocker arms 71, 72 are connected to each other and the disconnection position in which the connection of the first and second intake rocker arms 71, 72 is released, is urged toward the disconnection position and slidably fitted to the first and second intake rocker arms 71, 72. The press rod 104, which has the pressing portion 104a abutting on the pressed portion 97a formed at one end of the first connection pin 97 on the opposite side from the second intake rocker arm 72, is movabley supported by the first support wall 85 provided on the cylinder head 27 to face the first intake rocker am 71 on the opposite side from the second intake rocker arm 72, with being capable of pressing the first connection pin 97 toward the connection position. In this conditions, the accommodating hole 113, which causes the pressing portion 104a of the press rod 104 to abut on the pressed portion 97a of the first connection pin 97, is formed inside the first intake rocker arm 71 in the direction along the axis of the intake rocker shaft 78 in such a manner as to permit relative movement of the press rod 104 to the rocking of the first intake rocker arm 71. This makes it possible to place the first support wall 85 in the proximity of the first intake rocker arm 71, thus averting an increase in size of the cylinder head 27 even if the thickness of the first support wall 85 is increased to improve stiffness.
Since the area of the pressing portion 104a of the press rod 104 is set to be smaller than the area of the pressed portion 97a of the first connection pin 97, the miniaturization of the press rod 104 is made possible, and also the size of the accommodating hole 113 can be reduced for miniaturization of the first intake rocker arm 71.
The first connection pin 97 is formed to have an outer peripheral surface continuously extending between both ends in the axis direction. This enables simplification of component geometry of the first connection pin 97, leading to productivity gains and reductions in cost.
The press rod 104 is formed to have an outer peripheral face continuously extending from at least a middle portion in the axis direction to the pressing portion 104a. In the embodiment, since the press rod 104 is formed to have a constant outer diameter throughout its length in the axis direction, this makes possible simplified shapes of components including at least the pressing portion 104a of the press rod 104 and a smaller size of the accommodating hole 113.
The axis C3 of the press rod 104 is placed to be offset from the axis C2 of the first connection pin 97 toward the intake rocker shaft 78. This make it possible to decrease the amount of relative movement between the first intake rocker arm 71 and the press rod 104, thus reducing the size of the accommodating hole 113.
The first fit hole 100 in which the first connection pin 97 is slidably fitted is provided in the first intake rocker arm 71 in such a manner that the step 114 facing toward the second intake rocker arm 72 is formed between the accommodating hole 113 and the first fit hole 100. Because of this, the movement of the first connection pin 97 toward the disconnection position is restricted by causing the first connection pin 97 urged toward the disconnection position to abut on the step 114, so that the first connection pin 97 is able to be prevented from falling out of the first intake rocker arm 71. In addition, when the first connection pin 97 is moved toward the disconnection position, the lubricant between the first intake rocker arm 71 and the first connection pin 97 easily escapes to the outside through the accommodating hole 113, thus reducing the resistance of the lubricant at low temperature.
The accommodating hole 113 and the first fit hole 100 of circular cross section are provided in the first intake rocker arm 71 to be linked to each other by offsetting the axis C1 of the accommodating hole 113 from the axis C2 of the first fit hole 100 toward the intake rocker shaft 78. Because of this, the step 114 for restricting the movement of the first connection pin 97 toward the disconnection position is easily formed and compact design of the first intake rocker arm 71 is enabled.
The press-rod support hole 106 extending through the first support wall 85 such that the press rod 104 is slidably fitted in the press-rod support hole 106, and the rocker-shaft support hole 105 supporting the intake rocker shaft 78 inserted into the rocker-shaft support hole 105, are provided parallel to each other in the first support wall 85. Then, the press rod 104 is formed in a shape enabling insertion of the press rod 104 into the press-rod support hole 106 from the opposite side to the first intake rocker arm 71. Because of this, by inserting the press rod 104 into the press rod support hole 106 of the first support wall 85 from the opposite side from the first intake rocker arm 71, mounting and demounting of the press rod 104 to and from the first support wall 85 is facilitated.
In the second intake rocker arm 72, the second fit hole 101 with a closed end permitting the second connection pin 98 abutting on the first connection pin 97 to be slidably fitted into the second fit hole 101 is formed to have an open end facing toward the first intake rocker arm 71. The communication hole 102 making communication of the interior close to the closed end of the second fit hole 101 with the outside is provided in the second intake rocker arm 72. Because of this, the lubricant between the second connection pin 98 and the second intake rocker arm 72 easily escapes to the outside through the second intake rocker arm 72 during the movement toward the connection position, leading to a reduction in resistance of the lubricant at low temperatures.
Up to this point the embodiments according to the present invention have been described, but the present invention is not limited to the aforementioned embodiments and various changes in design can be made without departing from of the invention as set forth in the claims.
For example, the aforementioned embodiment has described the case of using the intake valve 61 as an engine valve, but the present invention is applicable to the case of using the exhaust valve 62 as an intake valve.
In the aforementioned embodiment the case of using the solenoid 107 as an actuator has been described, but the use of a hydraulically-operated actuator is possible.

Reference Signs List

27: Cylinder head
61: Intake valve as engine valve
71: First intake rocker arm
72: Second intake rocker arm
78: Intake rocker shaft
85: Support wall
97: First connection pin
97a: Pressed portion
100: First fit hole
105: Rocker-shaft support hole
106: Press-rod support hole
113: Accommodating hole
104: Press rod
104a: Pressing portion
114: Step
C1: Axis of accommodating hole
C2: Axis of first connection pin and first fit hole
C3: Axis of press rod

Claims

A variable valve gear of an internal combustion engine, in which:
first and second locker arms (71, 72) arranged adjacent to each other, at least one of which is operationally connected to an engine valve (61), are rockably supported by a cylinder head (27) through a rocker shaft (78) and also are structured to rock in mutually different rocking manners in a non-connection state of the rocker arms (71, 72);

a connection pin (97) having an axis (C2) extending parallel to the rocker shaft (78) is slidably fitted to the first and second rocker arms (71, 72) to be movable, in a span of the first and second rocker arms (71, 72), between a connection position in which the two rocker arms (71, 72) are connected to each other and a disconnection position in which the connection pin moves away from the second rocker arm (72) to release the connection of the two locker arms (71, 72);

a pressed portion (97a) is formed at one end of the connection pin (97) on the opposite side from the second rocker arm (72); and

a press rod (104) having a pressing portion (104a) formed at an end close to the connection pin (97) to abut on the pressed portion (97a) is supported movably in a direction parallel to the rocker shaft (78) to be capable of pressing the connection pin (97) by a support wall (85) provided on the cylinder head (27) to face the first rocker arm (71) from the opposite side from the second rocker arm (72),

wherein an accommodating hole (113) in which the pressing portion (104a) of the press rod (104) abuts on the pressed portion (97a) of the connection pin (97) is formed in the interior of the first rocker arm (71) to permit a relative movement of the press rod (104) to rocking of the first locker arm (71).
The variable valve gear of an internal combustion engine according to claim 1, wherein the area of the pressing portion (104a) of the press rod (104) is set to be smaller than the area of the pressed portion (97a) of the connection pin (97).
The variable valve gear of an internal combustion engine according to claim 1 or 2, wherein the connection pin (97) is formed to have an outer peripheral surface continuously extending between both ends in an axial direction.
The variable valve gear of an internal combustion engine according to any one of claims 1 to 3, wherein the press rod (104) is formed to have an outer peripheral surface continuously extending from at least a middle portion in an axial direction to the pressing portion (104a).
The variable valve gear of an internal combustion engine according to any one of claims 1 to 4, wherein the press rod (104) is placed to have an axis (C3) offset from the axis (C2) of the connection pin (97) toward the rocker shaft (78).
The variable valve gear of an internal combustion engine according to any one of claims 1 to 5, wherein a fit hole (100) in which the connection pin (97) is slidably fitted is provided in the first rocker arm (71) in such a manner that a step (114) facing toward the second rocker arm (72) is formed between the accommodating hole (113) and the fit hole (100).
The variable valve gear of an internal combustion engine according to claim 6, wherein the accommodating hole (113) and the fit hole (100) of circular cross section are provided in the first rocker arm (71) to be linked to each other by offsetting an axis (C1) of the accommodating hole (113) from the axis (C2) of the fit hole (100) toward the rocker shaft (78).
The variable valve gear of an internal combustion engine according to any one of claims 1 to 7, wherein a press-rod support hole (106) extending through the support wall (85) such that the press rod (104) is slidably fitted in the press-rod support hole (106), and a rocker-shaft support hole (105) supporting the rocker shaft (78) inserted into the rocker-shaft support hole (105), are provided parallel to each other in the support wall (85), and the press rod (104) is formed in a shape enabling insertion of the press rod (104) into the press-rod support hole (106) from the opposite side to the first rocker arm (71).