JP5691695B2 - Valve operating device for internal combustion engine - Google Patents

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 operating device, for example, disclosed in Patent Document 1, an accelerator shaft arranged in parallel with a camshaft in a cam moving mechanism, and a plurality of members fixed to the accelerator shaft and connected to the cam. Includes an accelerator fork. The accelerator shaft is supported by a cylinder head so as to be slidable in the axial direction, and is slid by a driving force of a driving motor connected to one end thereof. The sliding of the accelerator shaft causes the cam to slide along the camshaft through the accelerator fork.

JP 2003-3811 A

  In the above-described conventional example, the drive motor is arranged on one end side of the accelerator shaft. In yet another example, the drive motor has a drive shaft parallel to the accelerator shaft, and any one of a plurality of accelerator forks is connected to the drive shaft. However, the one that slides the entire accelerator shaft has been developed. Each cam fork is cantilevered by an accelerator shaft, and a bending moment with respect to the cam fork when the cam slides is received by bearings on both sides of the cam fork. Since a specific bearing among a plurality of bearings is subjected to a large load at the time of cam slide, there is a problem that not only the required bearing strength is increased, but also the drive motor is increased in size.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a valve operating apparatus for an internal combustion engine that reduces a resistance load during cam movement and realizes smooth operation.

A valve operating apparatus for an internal combustion engine according to the present invention includes a cam that is rotatably supported by a cylinder head and movable in the axial direction thereof, a cam fork shaft that moves the cam in the axial direction via a cam fork, And a thrust generating mechanism for converting a rotational force of a drive motor in a camshaft direction, wherein the valve driving device of the internal combustion engine connects a plurality of the cam forks and from the thrust generating mechanism to the cam fork shaft. It has a coupling mechanism that is configured to transmit the thrust, and the bearing of the thrust generating mechanism, and a fastening member between said cam fork and the coupling mechanism in a top view, in a direction perpendicular to the cam fork shaft It is arranged so that it overlaps .

  In the valve operating apparatus for an internal combustion engine according to the present invention, the plurality of cam forks connected to the coupling mechanism are arranged so as to sandwich at least one bearing supporting the cam fork shaft. .

  Further, in the valve operating apparatus for an internal combustion engine according to the present invention, the thrust generating mechanism includes a ball screw and a slide nut configured to be advanced and retracted via a screw mechanism by a driving force of the driving motor, and the slide The nut and a fastening member between the cam fork and the coupling mechanism are arranged so as to overlap with the cam fork shaft in a direction orthogonal to the top view.

  In the valve operating apparatus for an internal combustion engine according to the present invention, a tool access portion is provided at a portion of the ball screw facing the fastening member.

According to the present invention, by distributing the thrust of the thrust generating mechanism to two locations and transmitting the thrust to the cam fork shaft, it is possible to reduce the load acting on each portion where the thrust on the cam fork shaft side is transmitted. it can.
In this case, typically, two cam forks to which the coupling mechanism is connected are arranged so as to sandwich at least one bearing supporting the cam fork shaft. By distributing the thrust of the thrust generating mechanism transmitted through the coupling mechanism to the plurality of bearings, the load that each bearing bears is reduced.

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. (A) which shows the tappet which concerns on embodiment of this invention is a longitudinal cross-sectional view which follows the C'-C 'line | wire of FIG. 4, (b) is a cross-sectional view of the arrow Y direction of (a). It is each a perspective view of the tappet and 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. It is sectional drawing which follows the DD line | wire of Fig.16 (a), and sectional drawing which follows the EE line | wire. It is a fragmentary perspective view which shows the main structures of the cam slide mechanism which concerns on embodiment of this invention.

A preferred embodiment of a valve gear 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 rotate synchronously with 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 FIG. 14. 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. 15-18 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 the cam slide mechanism is operated using the accelerator motor 33 as a drive source. 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 cam head 20 is rotatably supported by the cylinder head 10 and is movable in the axial direction. And a thrust generating mechanism that converts the rotational force of an accelerator motor 33 that is a drive source for the motor 20 in the camshaft direction. Specifically, this thrust generation mechanism is configured by a ball screw 42 and a slide nut 46 configured to be able to advance and retract via a screw mechanism by the driving force of the accelerator motor 33.
In particular, a coupling mechanism configured to connect a plurality of cam forks 48 and transmit thrust from the thrust generation mechanism to the cam fork shaft 41 is provided.

  That is, in the thrust generating mechanism, when the ball screw 42 is driven to rotate by the rotation of the accelerator motor 33 via the gear 44 and the pinion gear 45, the slide nut 46 that meshes with the ball screw 42 is restricted by the nut fork 47. For this reason, along the axial direction of the ball screw 42, it reciprocates, that is, advances and retreats according to the rotation direction of the ball screw 42. A thrust for sliding the cam 20 is generated by the reciprocating motion of the ball screw 42.

  The coupling mechanism is specifically constituted by a nut fork 47 and its base plate 47a which are integrated with each other. In this embodiment, as shown in FIG. 8 as a plurality of cam forks 48, the two cam forks 48 and the base plate 47a for the # 2 and # 3 cylinders are coupled to each other. The base plate 47a is disposed so as to be bridged between two adjacent cam forks 48 in parallel with the cam fork shaft 41 and on the ball screw 42 side. In this case, the base plate 47a is fastened to the boss portions or base portions 48a of the two cam forks 48 by means of bolts 50A and 50B as fastening members. As shown in FIG. 18, the nut fork 47 has a pair of engaging pieces 51 having inner parallel surfaces parallel to each other and extending in a forked manner from the base plate 47a to the ball screw 42 side. On the other hand, an engagement groove (detailed illustration is omitted) for engaging the engagement piece 51 of the nut fork 47 is formed on the outer peripheral portion of the large diameter of the slide nut 46. It comes to fit.

  The thrust generated by the thrust generating mechanism is transmitted to the base portions 48a of the two adjacent cam forks 48 through the base plate 47a. In this way, by distributing the thrust of the thrust generating mechanism to two positions and transmitting the thrust to the cam fork shaft 41, the load acting on each part where the thrust on the cam fork shaft 41 side is transmitted can be reduced. .

  In this case, the two cam forks 48 to which the coupling mechanism is coupled are arranged so as to sandwich at least one bearing that supports the cam fork shaft 41. In this embodiment, it arrange | positions so that one bearing part 35b may be pinched | interposed between the two cam forks 48 which the base plate 47a fastens.

  With such an arrangement relationship, the force to move the cam fork shaft 41 is mainly between one bearing portion 35b and the two cam forks 48 between the two cam forks 48 as described above. Each is supported by a total of three bearing portions 35b including two outer bearing portions 35b. In this way, by distributing the thrust of the thrust generating mechanism transmitted through the coupling mechanism to the three bearing portions 35 so as to be handled, the load that the individual bearing portions 35b handle is reduced. As a result, the resistance associated with the movement of the cam 20 is reduced, and as a result, the accelerator motor 33 as a drive source can be downsized and the engine can be downsized.

  Further, the bearing 43 of the thrust generating mechanism and the fastening member between the cam fork 48 and the coupling mechanism are arranged so as to overlap with the cam fork shaft 41 in a top view. In the present embodiment, as shown in FIG. 9, the bolt heads of the bolts 50 </ b> A and 50 </ b> B and the bearing 43 overlap with the cam fork shaft 41 in a position orthogonal to each other.

  Thus, by arranging the bolt heads of the bolts 50 </ b> A and 50 </ b> B and the bearings 43 in an overlapping manner, the distance between the cam fork shaft 41 and the ball screw 42 can be reduced. Accordingly, it is possible to reduce the size around the cylinder head 10, particularly in the direction orthogonal to the camshaft 18.

  In the above case, there is no problem in the operation of the thrust generating mechanism even if the bolt head overlaps with the bearing 43. FIG. 8 or FIG. 9 shows a state at a low engine speed. At this time, the tappet 21 is in contact with a portion of the cam 20 where the cam height is low. When the accelerator is opened, the tappet 21 gradually comes into contact with a portion having a high cam height as the cam 20 is slid by the operation of the accelerator motor 33. As the slide nut 46, the left side in FIG. 8 and FIG. , 50 </ b> B moves away from the bearing 43. The state of FIG. 8 or FIG. 9 substantially shows one moving end of the bolts 50A and 50B, and does not approach the bearing 43 side any more, so that safe operation is ensured without interference.

Further, the relationship between the slide nut 46 and the bolt heads of the bolts 50 </ b> A and 50 </ b> B is also arranged so as to overlap the cam fork shaft 41 in the orthogonal direction in a top view.
In this case as well, the distance between the cam fork shaft 41 and the ball screw 42 can be reduced.

  Further, a tool access portion is provided at a portion of the ball screw 42 facing the fastening member. Specifically, as shown in FIGS. 9 and 10, in this example, a two-sided width 52 formed by cutting a part of the outer periphery of the ball screw 42 is formed facing the bolt head of the bolt 50 </ b> B. In addition, in FIG. 9 etc., it is a slide moving end of the slide nut 46, and the slide nut 46 does not approach the width across flats 52 side from the illustrated state.

  A tool such as a spanner can be applied to the width across flats 52 to tighten the nut 53 at the tip of the ball screw 42. In this case, the portion provided with the two-surface width 52 is a dead space in the ball screw 42, and convenience can be improved by effectively using such a portion.

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.
In the above embodiment, the example in which the coupling mechanism constituted by the nut fork 47 and its base plate 47a is connected to the two cam forks 48 has been described, but it is connected to three or more cam forks 48 depending on the number of cylinders. Can do.
Further, although an example in the case of a four-cylinder engine has been described, 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 gear, 46 Slide nut, 47 Nut fork, 48 Cam fork, 48a Base, 49 Bearing, 50A, 50B Bolt, 51 Engagement piece, 52 Width across flats, 53 Nut, 100 Motorcycle, 116 Engine unit, 116A Cylinder block .

Claims (4)

A cam rotatably supported on the cylinder head and movable in the axial direction;
A cam fork shaft for moving the cam in its axial direction via a cam fork;
A valve drive device for an internal combustion engine, comprising: a thrust generation mechanism that converts a rotational force of a drive motor into a camshaft direction;
Thereby connecting a plurality of the cam fork, it has a coupling mechanism that is configured to transmit a thrust to the cam fork shaft from the thrust generating mechanism,
A valve operating apparatus for an internal combustion engine , wherein a bearing of the thrust generation mechanism and a fastening member between the cam fork and the coupling mechanism are arranged so as to overlap with the cam fork shaft in a direction orthogonal to the top view. .   2. The valve operating apparatus for an internal combustion engine according to claim 1, wherein the plurality of cam forks connected to the coupling mechanism are disposed so as to sandwich at least one bearing supporting the cam fork shaft. The thrust generation mechanism includes a ball screw and a slide nut configured to be able to advance and retreat via a screw mechanism by a driving force of the drive motor, and between the slide nut, the cam fork and the coupling mechanism. The valve operating apparatus for an internal combustion engine according to claim 1 or 2 , wherein the fastening member is disposed so as to overlap with the cam fork shaft in a direction orthogonal to the fastening member. The valve operating apparatus for an internal combustion engine according to claim 3 , wherein a tool access portion is provided at a portion of the ball screw facing the fastening member.

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