JP2012167599A - Dynamic valve device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dynamic valve device for an internal combustion engine capable of making a cylinder head compact in size effectively and efficiently.SOLUTION: The dynamic valve device is equipped with a cam shaft 18 pivotally supported by the cylinder head 10, a cam 20 installed on the cam shaft 18 in such a way as integrally rotating therewith, a tappet roller 36 rolling in slide contact with the cam 20, and a tappet 21 to press the end of the valve stem so as to put a valve 16 in opening/closing motions via the tappet roller in tracing the profile of the cam 20. The tappet roller 36 is installed between two adjoining valve springs 32 in such an arrangement that part thereof overlaps the valve springs 32 in a height direction of the cylinder head.

Description

  The present invention relates to a valve operating apparatus that variably controls a lift amount and a working angle of a valve in accordance with an accelerator opening in an internal combustion engine in a motorcycle or an automobile.

  In this type of internal combustion engine, various ideas or proposals have been made in order to improve the combustion efficiency. Beginning with a variable phase system in which the valve opening and closing timing is shifted, variable control of the valve lift by switching the cam, valve suspension, and the like have been adopted. In this cam switching system, two cams for low speed and high speed are prepared, and the cam is switched from a small valve operating angle to a large one according to the engine output.

  More recently, a combination of variable phase and cam switching has started, and after that, a system using a three-dimensional cam in which the valve operating angle and the lift amount are continuously variable has been proposed. For example, there is a type in which a follow-up mechanism for a change in contact angle is provided at the top of a direct hitting cylindrical tappet, and a valve lift is steplessly varied by sliding a three-dimensional cam in the axial direction.

  In a specific configuration of a conventional valve gear, for example, disclosed in Patent Document 1, the tappet clearance for a three-dimensional cam is adjusted using an adjustment screw. In this case, the outer periphery of the roller portion of the tappet is arranged at a height position slightly overlapping the valve spring.

JP 2008-25487 A

  However, in the above-described conventional valve operating apparatus, the distance from the outer periphery of the roller portion of the tappet to the stem end (upper end side) of the valve stem is small, that is, the roller portion of the tappet and the valve stem are connected in the valve stem axial direction. Placed in. For this reason, the total length of these members in the valve stem axial direction is increased, and the height of the valve operating system is increased. Along with this, the height of the cylinder head becomes large, and it is impossible to mount a three-dimensional cam type engine as it is unless the vehicle dimensions and the like are largely changed.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a valve operating apparatus for an internal combustion engine capable of effectively and effectively downsizing a cylinder head.

  A valve operating apparatus for an internal combustion engine according to the present invention includes a camshaft rotatably supported on a cylinder head, a cam provided integrally with the camshaft, and a tappet roller that slides in contact with the cam and rolls. And a tappet that presses a valve shaft end so as to open and close the valve following the profile of the cam, wherein the tappet roller includes two adjacent valve springs. A part of which is disposed so as to overlap the valve spring in the cylinder head height direction.

  Further, in the valve operating apparatus for an internal combustion engine according to the present invention, the tappet roller is arranged at the same position as or below the center of the height of the arm portion of the tappet in the height direction of the rotation center axis. To do.

  Further, in the valve operating apparatus for an internal combustion engine according to the present invention, the tappet guide has a guide groove formed in a substantially cross shape in a top view so that the tappet roller can be operated only in a valve stem bearing direction. To do.

  In the valve operating apparatus for an internal combustion engine according to the present invention, a valve clearance adjusting shim is inserted between the tappet arm and the valve shaft end.

  In the valve operating apparatus for an internal combustion engine according to the present invention, the lower surface of the tappet guide is formed so that a range overlapping with the spring retainer in the valve operating direction is thinner than the surroundings.

  In the valve operating apparatus for an internal combustion engine according to the present invention, the cam is movable in the axial direction of the camshaft, and the cam lobe is a three-dimensional cam having an axially inclined surface.

  According to the present invention, the height of the valve operating system can be reduced by lowering the height position of the tappet roller with respect to the valve stem. As a result, the layout of the valve train can be made without substantially changing the height of the cylinder head from that of the conventional engine, and a three-dimensional cam engine can be mounted only by making a small change on the vehicle side.

1 is a side view showing an example of the overall configuration of a motorcycle according to an embodiment of the present invention. It is a top view of the cylinder head concerning the embodiment of the present invention. It is a side view of the cylinder head concerning the embodiment of the present invention. It is sectional drawing which follows the AA line of FIG. It is sectional drawing which follows the BB line of FIG. It is sectional drawing which follows the CC line of FIG. It is the side view, top view, and front view which show the ball screw housing which concerns on embodiment of this invention. It is a perspective view of a cylinder head in the state where a cylinder head cover concerning an embodiment of the present invention was removed. It is a top view of a cylinder head in the state where a cylinder head cover concerning an embodiment of the present invention was removed. It is a front view of a cylinder head in the state where a cylinder head cover concerning an embodiment of the present invention was removed. It is the side view, top view, and front view which show the cam housing which concerns on embodiment of this invention. It is the perspective view and side view of a tappet which concern on embodiment of this invention. It is the longitudinal cross-sectional view and cross-sectional view of the tappet which concern on embodiment of this invention. It is each a perspective view of the tappet and tappet guide which concern on embodiment of this invention. It is the perspective view and sectional drawing of a tappet and a tappet guide which concern on embodiment of this invention. It is a perspective view which shows the main structures of the cam slide mechanism which concerns on embodiment of this invention. It is the top view and front view of the valve gear which concern on embodiment of this invention. FIG. 18A is a cross-sectional view taken along line DD and a cross-sectional view taken along line EE in FIG. It is a fragmentary perspective view which shows the main structures of the cam slide mechanism which concerns on embodiment of this invention. It is the top view and front view around a tappet and a tappet guide which concern on embodiment of this invention.

A preferred embodiment of a valve operating apparatus for an internal combustion engine according to the present invention will be described below with reference to the drawings.
First, FIG. 1 is a side view of a motorcycle as an application example of the present invention. The overall configuration of the motorcycle 100 will be described with reference to FIG. In the drawings used in the following description, including FIG. 1, the front of the vehicle is indicated by an arrow Fr, the rear of the vehicle is indicated by an arrow Rr, and the lateral right side of the vehicle is indicated by an arrow R as necessary. The left side is indicated by an arrow L.

  In FIG. 1, two front forks 103 are provided on the front of a main frame 101 made of steel or aluminum alloy so as to be turnable left and right by a steering head pipe 102. A handle bar 104 is fixed to the upper end of the front fork 103, and grips 105 are provided at both ends of the handle bar 104. A front wheel 106 is rotatably supported at the lower portion of the front fork 103, and a front fender 107 is fixed so as to cover the upper portion of the front wheel 106. The front wheel 106 has a brake disc 108 that rotates integrally with the front wheel 106.

  The main frame 101 is connected to the rear part of the steering head pipe 102, and further, a pair of left and right branches into a bifurcated shape toward the rear, and each of them extends while being inclined downwardly to the rear. From the vicinity of the rear part of the main frame 101, the seat rail 101A extends moderately upward and supports a seat described later. The main frame 101 and the seat rail 101A constitute a vehicle body frame. A swing arm 109 is swingably coupled to the rear portion of the main frame 101, and a rear shock absorber 110 is mounted between the swing arm 109 and the swing arm 109. A rear wheel 111 is rotatably supported at the rear end of the swing arm 109. The rear wheel 111 is rotationally driven via a driven sprocket 113 around which a chain 112 for transmitting engine power, which will be described later, is wound. An inner fender 114 that covers the vicinity of the front upper portion is provided in the immediate vicinity of the rear wheel 111, and a rear fender 115 is disposed above the inner fender 114.

  The engine unit 116 (dotted line portion) mounted on the main frame 101 is supplied with an air-fuel mixture from a fuel supply device (not shown), and exhaust gas after combustion in the engine is exhausted through the exhaust pipe 117. . In the present embodiment, the engine may be, for example, a 4-cycle multi-cylinder, typically a 4-cylinder engine. The exhaust pipes 117 of the respective cylinders are coupled to the lower side of the engine unit 116, and then are exhausted from the exhaust device 118 near the rear end of the vehicle through the exhaust chamber.

  A fuel tank 119 is mounted above the engine unit 116, and a seat 120 is continuously provided behind the fuel tank 119. The sheet 120 includes a rider sheet 120A and a tandem sheet 120B. A footrest 121 and a footrest or pillion step 122 are arranged corresponding to the rider seat 120A and the tandem seat 120B. In this example, on the left side of the vehicle, a prop stand (not shown) is provided at a substantially central lower portion in the front-rear direction.

  Further, in FIG. 1, 123 is a headlamp, 124 is a meter unit including a speedometer, tachometer or various indicator lamps, and 125 is a rearview mirror supported by the handlebar 104 via a stay 126.

  In the vehicle exterior, the front and side portions of the vehicle are mainly covered by the fairing 127 and the side cowl 128, and a side cover or a seat cowl 129 is attached to the rear of the vehicle, and these exterior members have a so-called streamline type. The appearance form of the vehicle is formed.

  Here, the engine unit 116 in this embodiment includes a cylinder or cylinder block 116A that accommodates a piston in a reciprocable manner, and a crankcase 116B disposed below the cylinder block 116A, and these are integrally coupled. To do. Further, the engine unit 116 is suspended and supported by the main frame 101 through a plurality of engine mounts so as to be integrally coupled and supported by the main frame 101, and acts as a rigid member of the main frame 101 itself.

  As shown in FIG. 1, a fuel tank 119 having a dome shape or a shell shape is mounted and supported on the main frame 101 so as to cover the entire upper side of the main frame 101 from above. Further, an air cleaner 130 for supplying clean air to the intake device is disposed above the cylinder head cover of the cylinder block 116A. The air cleaned by the air cleaner 130 is taken in by the intake device, and then fuel is mixed in the intake pipe 131 as shown in FIG. 1 and supplied to the engine unit 116 as an air-fuel mixture.

  2 to 6 show configuration examples of the cylinder block 116 </ b> A of the engine unit 116, particularly the cylinder head 10. In the cylinder block 116A, the cylinder head 10 is fixed to the upper part of the cylinder body 11, and accommodates the valve operating device therein. As shown in these drawings, this embodiment may be a parallel four-cylinder engine, and each cylinder has two valves on the intake side (IN) and the exhaust side (EX), that is, four valves. ing. In this embodiment, a three-dimensional cam is applied to the intake side, but it can also be applied to both the intake side and the exhaust side. In the cylinder body 11, the piston reciprocates substantially up and down.

  In this example, the cylinder head 10 is extended along the arrangement direction of the # 1 to # 4 cylinders, and the cylinder head cover 12 attached to the upper part forms a sealed structure in the accommodating space of the valve operating device. A combustion chamber 13 corresponding to each cylinder is formed at the bottom of the cylinder head 10, and an intake port 14 and an exhaust port 15 are formed in communication with each combustion chamber 13. The combustion chamber 13 and the intake port 14 are opened and closed by a pair of intake valves 16 arranged adjacent to each other, and the combustion chamber 13 and the exhaust port 15 are opened and closed by a pair of exhaust valves 17 arranged adjacent to each other. By driving and controlling the intake valve 16 and the exhaust valve 17 at a predetermined timing, intake and exhaust with respect to the cylinder of each cylinder can be appropriately controlled.

  A cam shaft 18 is rotatably supported by the cylinder head 10 via a plurality of bearings 19 in the axial direction of the intake valve 16, that is, above the valve stem 16a, along the cylinder arrangement direction. A cam 20, which will be described later, is mounted on the camshaft 18 so as to be slidable in the axial direction. The cam 20 is fixed to the camshaft 18 in the rotational direction. The camshaft 18 has a hollow structure, and a lubricating oil passage can be formed in the hollow to lubricate the cam 20 or the like. There are a total of four cams 20 corresponding to each cylinder, and each cam 20 is formed as a three-dimensional cam. Between the cam 20 and the intake valve 16 (the valve stem 16a), a roller-type tappet 21 that is guided by a tappet guide 22 and can reciprocate in the axial direction of the valve stem 16a is disposed. Details of these will be described later.

  A cam shaft 23 is rotatably supported by the cylinder head 10 via a plurality of bearings 24 in the axial direction of the exhaust valve 17, that is, above the valve stem 17 a along the cylinder arrangement direction. A cam 25 is attached and fixed to the cam shaft 23 at a predetermined position in the axial direction. There are a total of four cams 25 corresponding to each cylinder, and each cam 25 is formed as a flat so-called flat cam on the exhaust side. Between the cam 25 and the valve stem 17a of the exhaust valve 17, a direct hitting tappet 26 that can reciprocate in the axial direction of the valve stem 17a is arranged.

  Sprockets 27 and 28 are fixed to one end of the intake-side camshaft 18 and the exhaust-side camshaft 23 (see FIGS. 6 and 9). Although not shown, a cam chain is wound around the sprockets 27 and 28 and a drive sprocket fixed to one end of the crankshaft. Note that the cam chain is properly driven by an attached chain guide, chain tensioner, chain adjuster, and the like. As a result, the camshaft 18 and the camshaft 23 are synchronously rotated by the rotation of the crankshaft.

  More specifically, the intake valve 16 reciprocates in the axial direction of the valve stem 16 a by the valve stem 16 a being guided by the valve guide 29. A valve spring 32 is mounted between a spring retainer 30 attached to an end of the valve stem 16a and a spring seat 31, and the valve stem 16a is always urged upward by the elasticity of the valve spring 32. At this time, the tappet 21 contacts the upper end of the valve stem 16a via a shim described later. When the cam 20 pushes down the tappet 21 against the elasticity of the valve spring 32, the valve stem 16a is biased downward, that is, the intake valve 16 is opened.

  As with the intake valve 16, the exhaust valve 17 is also provided with a valve spring 32 between a spring retainer 30 attached to the end of the valve stem 17 a and the spring seat 31. Also in this case, the tappet 21 is pushed down by the cam 25 and the exhaust valve 17 is operated. However, the lift timing and the valve lift amount are set differently from those of the intake valve 16.

  Here, the intake-side cam 20 is configured as a “three-dimensional cam” as described above, and one cam 20 is provided for each cylinder. The cam 20 has a cam lobe having a profile that gently slopes in the longitudinal direction, which is the axial direction of the camshaft 18, and is formed into a shape that continuously changes the valve lift amount. In this case, the cam operating angle and the lift timing change simultaneously with the cam height, that is, the cam operating angle increases as the valve lift amount increases, and the valve lift timing can also be changed. By moving the cam 20 along the camshaft 18, the lift amount, operating angle, and lift timing of the intake valve can be variably controlled steplessly. The moving mechanism of the cam 20 will be described later.

  A cam slide mechanism for moving the cam 20 along the cam shaft 18 is provided, and an accelerator motor 33 is mounted and supported on the cylinder head cover 12 as a drive source thereof as shown in FIGS. In this example, the accelerator motor 33 is disposed at the corner on the right rear side of the cylinder 10 and is coupled to the ball screw housing 34 (see also FIG. 7) via its flange 33a. A member such as a ball screw described later is accommodated in the ball screw housing 34.

  Next, FIGS. 8 to 10 show a state in which the cylinder head cover 12 is removed from the cylinder head 10. The cam / camshaft unit, which is a main component of the valve gear, is housed in a cam housing 35 that is fixedly attached to the cylinder head 10. In this case, the camshaft 23 and the cam 25 on the exhaust side are substantially entirely. The cam housing 35 is completely accommodated. On the other hand, the camshaft 18 and the cam 20 on the intake side are connected to or linked to a cam slide mechanism disposed substantially outside the cam housing 35. Therefore, an open structure is provided so that such a connection structure can be provided. That is, a part of the cam housing 35 is exposed. Here, FIG. 11 shows the cam housing 35 in the present embodiment. The cam housing 35 as a whole has a cover structure that covers the top of the camshaft 18 and the camshaft 23, but the intake side has an open structure except for a frame portion 35a and the like necessary for mounting the cam slide mechanism. ing.

  As described above, the tappet 21 is guided by the tappet guide 22. The tappet unit will be further described. As shown in FIGS. 12 and 13, as shown in FIGS. 12 and 13, the tappet roller 36 formed in a generally donut shape having a housing portion for housing the bearing 37 therein, and the tappet roller 36 is supported via the bearing 37. And an arm 39 extending outward from both sides of the core 38. The tappet roller 36 contacts the cam lobe of the cam 20 based on the elasticity of the valve spring 32. In this example, the bearing 37 is a plurality of needle bearings arranged along the outer periphery of the core portion 38. The arm 39 extends to the upper end of the valve stem 16a and indirectly contacts the upper end of the valve stem 16a via the shim 40. A protrusion 38A extending from both outer sides of the core portion 38 toward the tappet roller 36 is provided to prevent the bearing 37 from falling off when the tappet roller 36 is assembled.

  A tappet guide 22 is disposed and fixed at an appropriate position of the cylinder head 10, and the tappet 21 is floated and held inside the tappet guide 22 as shown in FIGS. 14 and 15. The tappet 21 is a valve lifter that opens the intake valve 16 by the arm 39 pushing the valve stem 16a against the elasticity of the valve spring 32 when the tappet roller 36 is pushed against the cam surface of the cam 20. Function.

  FIGS. 16-19 has shown the intake-side structure example of the valve operating apparatus. As described above, the accelerator motor 33 is mounted on the cylinder head cover 12 and operates the cam slide mechanism arranged in the ball screw housing 34. First, a cam fork shaft 41 is arranged in parallel in the cylinder head cover 12 along the axial direction at a predetermined interval above the cam shaft 18. The cam fork shaft 41 is slidably supported in the axial direction by a plurality of, in this example, five bearing portions 35b (see FIG. 8 and the like) provided in the cam housing 35. Inside the ball screw housing 34, the ball screw 42 is disposed at a position substantially parallel to the cam fork shaft 41 and at the same height. The ball screw 42 is rotatably supported by a pair of bearings 43 on the mating surfaces of the cylinder head cover 12 and the ball screw housing 34 in the vicinity of both shaft ends. A gear 44 is attached to the end of the ball screw 42 on the accelerator motor 33 side, and a pinion gear 45 is attached to the output shaft of the accelerator motor 33, and the gear 44 and the pinion gear 45 are engaged, that is, the accelerator. The ball screw 42 is rotationally driven by the operation of the motor 33.

  A slide nut 46 fixed in the rotational direction meshes with the ball screw 42. The slide nut 46 is connected to the cam fork shaft 41 via a nut fork 47. The nut fork 47 has a base plate 47 a disposed in the axial direction of the ball screw 42, and the base plate 47 a is coupled to the cam fork shaft 41. More specifically, four cam forks 48 are fixed to the cam fork shaft 41 corresponding to each cylinder, and among these, the cam forks 48 and the base plate 47a for the # 2 and # 3 cylinders are coupled to each other. Each cam fork 48 is rotatably engaged with the cam 20 via a bearing 49 attached to the end of the cam 20.

  In the cam slide mechanism configured as described above, when the ball screw 42 is rotated by the accelerator motor 33, the cam fork shaft 41 slides in the axial direction via the slide nut 46 and the nut fork 47. The cams 20 slide along the axial direction of the camshaft 18 at the same time as the cam fork shaft 41 slides.

  Here, the basic operation of the valve gear configured as described above will be schematically described. When the accelerator grip of the motorcycle 100 is operated during engine operation, the accelerator motor 33 is activated, and the ball screw 42 rotates to slide the cam fork shaft 41 via the slide nut 46 and the nut fork 47. As the cam fork shaft 41 slides, the cams 20 slide simultaneously along the axial direction of the cam shaft 18. For example, the tappet 21 is in contact with the cam 20 at a low cam height at the time of engine low speed. When acceleration is performed in this state, that is, the accelerator is opened, the tappet 21 is gradually brought into contact with a portion having a high cam height as the cam 20 is slid by the operation of the accelerator motor 33, and thereby the valve lift amount according to the lift characteristics of the cam 20. Will increase. On the other hand, by returning the accelerator at the time of deceleration, the valve lift amount is reduced by the reverse operation to the above.

  Next, the characteristic configuration of the present invention and the operation and effects thereof will be described. First, in the present invention, the tappet 21 guided by the tappet guide 22 is located between two adjacent valve springs as shown in FIG. Be placed. In this case, a part of the tappet roller 36 is disposed so as to overlap the valve spring 32 in the cylinder head height direction as shown in FIG. That is, as described above, in the conventional tappet, the tappet clearance is adjusted using the adjustment screw, but in the present invention, the tappet clearance is adjusted by the shim 40 instead of the adjustment screw. 13A can be secured large, and the tappet 21 can be lowered to a position where the bearing 37 in the tappet roller 36 overlaps the valve spring 32.

  Thus, by increasing the distance (H dimension) from the tappet roller 36 to the stem end of the intake valve 16, that is, by reducing the height position of the tappet roller 36 with respect to the valve stem 16a, the height of the valve operating system is reduced. it can. Along with this, it is possible to lay out the valve train without changing the height of the cylinder head 10 from that of the conventional engine, and it is possible to mount a three-dimensional cam engine only by making a small change on the vehicle side. Conventionally, since the lower part of the tappet roller could not be arranged below the upper end of the valve spring, the valve operating apparatus could not be arranged compactly.

  In this case, as one of the configurations for lowering the position of the cam 20 as described above, in order to arrange the lower part of the tappet roller 36 between the adjacent valve springs 32, the width of the tappet roller 36 is set to the interval between the valve springs 32. Need to be smaller than. As shown in FIG. 13, the bearing 37 disposed inside the tappet roller 36 is narrower than the tappet roller 36, and does not interfere with the valve spring 32, and the tappet roller 36 is appropriately disposed between the valve springs 32. Can do.

  Further, the rotation center shaft 36A of the tappet roller 36 is typically disposed at the same position as the center of the height of the arm 39 in the height direction as shown in FIG. Alternatively, the rotation center shaft 36 </ b> A of the tappet roller 36 may be disposed at a position below the center of the height of the arm 39.

  Since the tappet roller 36 is in contact with the cam 20 at the upper portion thereof, in order to lower the position of the cam 20 and make the height of the cylinder head 10 compact, it is better to arrange the rotation center shaft 36A of the tappet roller 36 as far as possible. By arranging the rotation center shaft 36A of the tappet roller 36 as described above, the height of the cylinder head 10 can be effectively made compact.

  Further, the tappet guide 22 is formed with a guide groove 50 in a substantially cross shape when viewed from above so that the tappet roller 36 can operate only in the valve stem axial direction and in the vertical direction in an actual vehicle. Specifically, as shown in FIG. 14A, one guide groove 50 </ b> A that vertically penetrates the tappet guide 22 along the radial direction of the tappet roller 36, that is, the direction orthogonal to the axial direction of the camshaft 18. And the other guide groove 50B penetratingly formed along the longitudinal direction of the arm 39, that is, the axial direction of the camshaft 18, so as to intersect the guide groove 50A. And the tappet 21 is accommodated in these guide grooves 50A and 50B. An opening 51 is formed around the end of the arm 39, and the spring retainer 30 is disposed so as to face the opening 51 from below.

  The upper surface of the tappet guide 22 is formed to be substantially flat. On the lower surface side, as shown in FIG. 15, a cross-shaped guide groove 50 made up of guide grooves 50A and 50B (see also the hatched portion in FIG. 20). Four leg portions 52 are provided so as to extend in the vertical direction. The tappet 21 moves up and down according to the valve shift amount when the intake valve 16 opens and closes, but the cross-shaped guide groove guides the tappet roller 36 and the arm 39 from both sides at least when the tappet 21 moves up and down. It has a sufficient vertical length to obtain.

  The tappet roller 36 of the tappet 21 is arranged so as to be sandwiched between two adjacent valve springs 32 as shown in FIG. In such a small space, even if the cam 20 rotates while moving in the axial direction of the camshaft 18, the tappet roller 36 is guided by the cross-shaped guide groove so as to operate only in the vertical direction. This ensures smooth and proper operation of the tappet roller 36 and the arm 39 itself, avoids interference with peripheral parts or members, etc., and ensures safe operation of the valve operating device.

  Further, as shown in FIG. 13A, a disc-shaped shim for adjusting the valve clearance is provided between the end of the arm 39 of the tappet 21 and the shaft end of the intake valve 16, that is, the stem end of the valve stem 16a. 40 is inserted. In this case, the shim 40 is disposed so as to overlap the spring retainer 30 in the height direction. In addition, the site | part which contact | abuts the shim 40 in the lower surface of the edge part of the arm 39 is formed as a moderate curved surface so that it may become convex toward the shim 40 side, as FIG. 13 (a) shows. Thereby, the smooth contact state of the arm 39 and the shim 40 can be ensured.

Conventionally, adjusting screws and adjusting nuts are arranged between the arm of the tappet roller and the stem end of the valve stem, and it is difficult to reduce the distance in the valve stem direction between the stem end and the rotation center axis of the tappet roller. It was.
In the present invention, the height of the cylinder head 10 is made compact by disposing such a thin shim 40 so as to overlap the spring retainer 30 in the height direction without using such an adjusting screw or an adjusting nut. be able to.

  Further, the lower surface of the tappet guide 22 is formed such that a range overlapping the spring retainer 30 in the operation direction of the intake valve 16 is thinner than the surroundings. That is, a substantially circular counterbore 53 is provided on the lower surface of the tappet guide 22 as shown in FIG.

  Thus, by providing the countersink 53 on the lower surface side of the tappet guide 22 to provide a guide shape for the spring retainer 30, the lower surface side of the tappet guide 22 overlaps with the spring retainer 30 in the height direction. As a result, the cam 20 can be arranged lower, and the cylinder head 10 can also be made compact in the height direction in this respect.

Further, the cam 20 in the present embodiment is movable in the axial direction of the camshaft 18, and the cam lobe is a three-dimensionally shaped cam having an axially inclined surface.
In this embodiment, the present invention was applied to a three-dimensional cam, and an excellent effect was obtained. That is, the intake valve 16 is driven and controlled so that the predetermined valve lift amount is obtained by the sliding operation of the cam 20, and a satisfactory intake / exhaust operation can be realized. At that time, the three-dimensional cam engine can be mounted without substantially changing the cylinder head height of the conventional engine.

In the above case, a shim 40 is provided between the end of the arm 39 and the stem end of the valve stem 16 a of the intake valve 16. The shim 40 is disposed so as to be fitted on the upper surface of the spring retainer 30. The valve clearance can be suitably adjusted by selecting and assembling shims 40 having different thicknesses.
Further, in order to improve the positional accuracy of the tappet roller 36, knock pins are preferably provided at about two locations between the tappet guide 22 and the cylinder head 10.
Further, in order to lower the position of the camshaft 18, the arm 39 of the tappet 21 is thinned to have a wide shape, thereby ensuring rigidity.

As mentioned above, although this invention was demonstrated with various embodiment, this invention is not limited only to these embodiment, A change etc. are possible within the scope of the present invention.
For example, in the above embodiment, an example in the case of a four-cylinder engine has been described, but the present invention can be effectively applied to a one-cylinder or three-cylinder engine, and other multi-cylinder engines.
Further, the present invention can be applied to, for example, a four-wheeled vehicle such as a passenger car or an outboard motor in addition to the case of a motorcycle, and the same effect as the above-described embodiment can be obtained.

10 Cylinder Head, 11 Cylinder Body, 12 Cylinder Head Cover, 13 Combustion Chamber, 14 Intake Port, 15 Exhaust Port, 16 Intake Valve, 16a Valve Stem, 17 Exhaust Valve, 18 Camshaft, 19 Bearing, 20 Cam, 21 Tappet, 22 Tappet guide, 23 Camshaft, 25 Cam, 26 Tappet, 27, 28 Sprocket, 29 Valve guide, 30 Spring retainer, 31 Spring seat, 32 Valve spring, 33 Accelerator motor, 34 Ball screw housing, 35 Cam housing, 36 Tappet roller , 37 Bearing, 38 Core, 39 Arm, 40 Shim, 41 Cam fork shaft, 42 Ball screw, 43 Bearing, 44 Gear, 4 Pinion gears, 46 sliding nut 47 nut fork, 48 cam fork, 50, 50A, 50B guide groove 51 opening, 52 leg, 53 spot facing, 100 motorcycles, 116 engine unit, 116A cylinder block.

Claims (6)

A camshaft rotatably supported on the cylinder head;
A cam provided integrally with the camshaft;
And a tappet that presses a valve shaft end so as to open and close the valve following a profile of the cam via a tappet roller that slides in contact with the cam. And
A valve operating apparatus for an internal combustion engine, wherein the tappet roller is disposed between two adjacent valve springs, and a part of the tappet roller overlaps the valve spring in the cylinder head height direction.   2. The valve operating device for an internal combustion engine according to claim 1, wherein the tappet roller is disposed at the same position as or below the center of the height of the arm portion of the tappet in the height direction of the rotation center axis. .   The operation of the internal combustion engine according to claim 1 or 2, wherein the tappet guide is formed with a guide groove in a substantially cross shape in a top view so that the tappet roller can operate only in a valve stem bearing direction. Valve device.   The valve operating apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein a shim for adjusting a valve clearance is inserted between an arm of the tappet and the valve shaft end.   5. The valve operating system for an internal combustion engine according to claim 3, wherein a lower surface of the tappet guide is formed so that a range overlapping with a spring retainer in a valve operating direction is thinner than a surrounding area.   The internal combustion engine according to any one of claims 1 to 5, wherein the cam is movable in the axial direction of the camshaft, and the cam lobe is a three-dimensional cam having an axially inclined surface. Engine valve gear.

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