JP2008025487A - Valve gear and internal combustion engine having the valve gear - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a valve gear and an internal combustion engine having the valve gear, for effectively preventing generation of fretting corrosion and a hitting sound. <P>SOLUTION: A valve lifter has an arm part 22 capable of pressing a valve stem 31a, and a roller tappet 21 rotatable to the arm part 22. The arm part 22 has a pressure receiving part abutting on a biasing member 28 having biasing force in the direction for expanding a mutual distance between the part and the valve stem 31a, by arranging an adjusting screw 26 and the valve stem 31a on the substantially same line, by fastening the adjusting screw 26 capable of adjusting a clearance with the valve stem 31a to a distal end part. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a valve operating apparatus that variably controls a lift amount, a lift timing, 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 recent internal combustion engines, a combination of variable phase and cam switching has started, and then a valve operating system using a three-dimensional cam that continuously varies the operating angle and lift amount has been proposed. For example, there is a type in which a follow-up mechanism for contact angle change is provided at the top of a direct hitting cylindrical tappet, and a valve lift amount is varied steplessly by sliding a three-dimensional cam in the axial direction.

  This type of valve operating device has been developed that includes four intake / exhaust valves per cylinder and further has a mechanism for changing the operation timing of these valves. For example, the combustion phase is improved by variably controlling the cam phase on the intake side and changing the overlap amount with the exhaust side according to the engine speed.

  For example, Patent Document 1 discloses a valve gear using a three-dimensional cam. Japanese Patent Application Laid-Open No. H10-228707 discloses a tappet guide provided between a valve lifter and a three-dimensional cam so as to cover an arm portion. In this example, since there is a tappet guide, it is possible to prevent the valve lifter from being inclined by mistake.

JP 2003-003811 A JP 2004-251144 A

  In general, a rocker arm type (swing arm type) valve operating mechanism is employed when the direct hitting cam mechanism is not used. In the rocker arm type, the rocker arm is pivotally supported by a rocker arm that is separate from the camshaft, and the rocker arm swings according to the lift characteristics of the cam, so that the valve stem moves forward and backward. ing.

  At that time, it is particularly necessary to prevent fretting corrosion (abrasion caused by a slight rubbing operation) and sound generation between the slipper surface of the rocker arm and the cam or between the rocker arm adjusting screw and the valve stem. Therefore, the slipper surface of the rocker arm or the adjustment screw is always brought into contact with the cam or the valve stem. Specifically, a torsion spring is interposed between the rocker shaft and the rocker arm, and a part of the rocker arm is urged against the cam or the valve stem.

  However, when a so-called floating valve lifter that is not a rocker arm type is used, the above-mentioned torsion spring cannot be mounted because it does not have a shaft (corresponding to a rocker shaft) for supporting the valve lifter on the cylinder head. If the floating valve lifter is used as it is, it is difficult to effectively prevent fretting corrosion and generation of hitting sound.

  In the conventional example, particularly in the one described in Patent Document 2 or the like, the direction when removing the tappet guide is the same as the direction for removing the valve lifter. At this time, the valve lifter may be lifted by mistake, and as a result, the ball in the valve lifter may fall off.

  In view of such circumstances, the present invention has an object to provide a valve operating device that effectively prevents the occurrence of fretting corrosion and hammering between a valve lifter and a cam or valve stem, and an internal combustion engine equipped with the same. .

  The valve operating apparatus of the present invention has a three-dimensional cam slidable in the cam shaft direction and includes a valve lifter that moves a plurality of valves back and forth with one cam. The valve lifter is an arm portion that can press the valve stem. And a roller tappet that is rotatable with respect to the arm portion, and the arm portion fastens an adjustment screw capable of adjusting a clearance with the valve stem at a tip portion, and the adjustment screw and the valve stem are connected to each other. The pressure receiving portion is disposed on substantially the same line, and has a pressure receiving portion that comes into contact with an urging member having an urging force in a direction of increasing the distance from the valve stem.

  In the valve operating apparatus of the present invention, the urging member has an urging force in the axial direction of the valve stem and is disposed concentrically with the valve stem, and includes at least the valve stem and the adjustment screw. It is arranged to wrap a part.

  Further, in the valve operating apparatus according to the present invention, the biasing member has one end abutted on a valve cotter provided on the valve stem upper part, and the other end abutted on the arm part side of the valve lifter. It is characterized by making it.

  Further, in the valve gear of the present invention, the roller tappet is provided with a cylindrical portion having a flat portion in contact with the cam lobe, and makes a line contact between the cylindrical portion and the cam lobe. And

  In the valve gear of the present invention, the cylindrical portion is in line contact with a base circle surface of the cam lobe.

  In the valve operating apparatus according to the present invention, the valve lifter is characterized in that a needle bearing is interposed between the arm portion and the roller tappet.

  The internal combustion engine of the present invention is an internal combustion engine in which intake and exhaust are controlled by an intake valve and an exhaust valve, and is provided with any of the above valve operating devices on the intake side or the exhaust side. .

  According to the present invention, in this type of engine, the valve lift amount and the operating angle are variably controlled in accordance with the accelerator opening. In this case, a plurality of cylinders can be synchronized by a simple operation with a simple configuration.

  In particular, the valve stem and the adjusting screw are arranged on the same straight line, a spring is provided on the outside thereof, and both ends of the spring are brought into contact with the valve stem side and the valve lifter side in a compressed state. As a result, the valve lifter can always be urged in the valve closing direction, and the roller tappet can always be brought into contact with the cam lobe. Thereby, generation | occurrence | production of fretting corrosion and a hitting sound can be prevented effectively.

  Further, the cam lobe slidable contact surface of the roller tappet has a curved shape, and the slidable contact surface has an apex (ridge line) continuous in the circumferential direction of the roller tappet. The shape is a roller tappet that forms a cylindrical portion. As a result, fretting corrosion due to the inclination of the valve lifter can be further reduced.

Hereinafter, preferred embodiments of a valve gear according to the present invention and an internal combustion engine including the same will be described with reference to the drawings.
(First embodiment)
The valve gear according to the present invention can be effectively applied to various gasoline engines mounted on a motorcycle or a four-wheeled vehicle. In this embodiment, for example, as shown in FIG. To do.

  First, the overall configuration of the motorcycle 100 according to the present embodiment will be described. In FIG. 1, two left and right front forks 103 supported by a steering head pipe 102 so as to be pivotable to the left and right are provided at a front portion of a body frame 101 made of steel or aluminum alloy. 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.

  A swing arm 109 is swingably provided at the rear part of the body frame 101, and a rear shock absorber 110 is mounted between the body frame 101 and the swing arm 109. A rear wheel 111 is rotatably supported at the rear end of the swing arm 109, and the rear wheel 111 is rotationally driven via a driven sprocket 113 around which a chain 112 is wound.

  The engine unit 1 (solid line portion) mounted on the vehicle body frame 101 is supplied with an air-fuel mixture from an intake pipe 115 coupled to an air cleaner 114, and exhaust gas after combustion is exhausted through an exhaust pipe 116. The air cleaner 114 is installed in a large space behind the engine unit 1 and below the fuel tank 117 and the seat 118 to secure capacity. Therefore, the intake pipe 115 is coupled to the rear side of the engine unit 1, and the exhaust pipe 116 is coupled to the front side of the engine unit 1. A fuel tank 117 is mounted above the engine unit 1, and a seat 118 and a seat cowl 119 are connected to the rear of the fuel tank 117.

  Here, an accelerator motor 44, which will be described later, is mounted on predetermined portions of the cylinder head 2 to the cylinder head cover 2a in the engine unit 1. The accelerator motor 44 is provided, for example, on the side of the cylinder head cover 2a, but is disposed so as not to interfere with the fuel tank 117 and other parts or members around the engine.

  Further, in FIG. 1, 120 is a head lamp, 121 is a meter unit including a speedometer, tachometer, or various indicator lamps, and 122 is a rearview mirror supported by the handlebar 104 via a stay 123. A main stand 124 is swingably attached to the lower part of the body frame 101, and the rear wheel 111 can be grounded or floated from the ground. The vehicle body frame 101 extends obliquely downward and rearward from the head pipe 102 provided at the front portion, and is bent so as to wrap under the engine unit 1, and then forms a pivot 109 a that is a shaft support portion of the swing arm 109. The tank rail 101a and the seat rail 101b are connected.

  The vehicle body frame 101 is provided with a radiator 125 in parallel with the vehicle body frame to avoid interference with the front fender 107, and a cooling water hose 126 is provided along the vehicle body frame 101 from the radiator 125, and an exhaust pipe 116. It communicates with the engine unit 1 without interfering with.

  Next, FIG. 2 is a plan view showing the valve gear in this embodiment, FIG. 3 is a sectional view taken along the line AA in FIG. 2, and FIG. 4 is a sectional view taken along the line BB in FIG. A piston reciprocates up and down in a cylinder of an engine unit 1 that is an internal combustion engine, and a valve operating device is housed in a cylinder head 2 disposed on the top of the piston. The engine unit 1 described in the present embodiment is, for example, a parallel two-cylinder (vehicle width direction) engine, and has two valves on each of the intake side (IN) and the exhaust side (EX) in each cylinder.

The valve gear of the present embodiment includes a cam / camshaft unit 10 on the intake side, a valve lifter unit (or tappet unit) 20 disposed below the cam / camshaft unit 10, and a valve unit 30 that controls intake. including. Further, the exhaust side includes a cam / camshaft unit 10 _EX , a tappet unit 20 _EX disposed below the cam / camshaft unit 10 _EX , and a valve unit 30 _{EX for} exhaust control.

Further, an accelerator shaft unit 40 for displacing the cams 13 and 13 _EX of the cam / camshaft units 10 and 10 _EX according to the accelerator opening is included. In this embodiment, the intake side cam / camshaft unit 10 and the exhaust side are included. The cam / camshaft unit 10 _EX is shared between the intake side and the exhaust side. A single accelerator shaft is used for two cylinders.

The intake-side cam / camshaft unit 10 includes a camshaft 11 rotatably supported via bearings 12 and 12 'in the cylinder head 2 as shown in FIG. It extends across the cylinder. One end of the cam shaft 11 fixed sprockets 15, one end similarly sprocket 15 _Ex camshaft 11 _Ex of the exhaust side is fixed, and these sprockets 15, 15 _Ex as shown in FIG. 5 A cam chain 4 is wound around a drive sprocket 3 fixed to one end of a crankshaft (not shown). As shown in FIG. 5, a chain guide 5, a chain tensioner 6, a tensioner adjuster 7 and the like are included so that the cam chain 4 travels properly.

  A cam 13 is slidably mounted on the cam shaft 11 in the axial direction. In this example, a key 14 is interposed between the camshaft 11 and the cam 13, the relative rotation between the cam 13 and the camshaft 11 is restricted, and the cam 13 linearly moves (linear motion) along the camshaft 11. It is like that. The camshaft 11 generally has a hollow structure, and the inside of the hollow serves as a lubricating oil passage and can lubricate the inner diameter portion of the cam 13.

  Here, the cam 13 is configured as a “three-dimensional cam”, has a cam surface 13 a that is inclined in the longitudinal direction (the axial direction of the cam shaft 11), and has 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.

Incidentally, the cam / camshaft unit 10 _EX the exhaust side, although the same basic configuration as the cam / cam shaft unit 10 of the intake side as shown in FIG. 4 or FIG. 5, the specific specifications of the cam 13 _EX Is different from the cam 13.

  As shown in FIG. 4, the intake-side valve lifter unit 20 includes a roller tappet 21 whose outer peripheral surface is a substantially spherical surface (the specific shape will be described later), and the outer peripheral surface contacts the cam 13. . An arm 22 is disposed in the roller tappet 21. The inner peripheral surface of the roller tappet 21 is a spherical surface, and a ball 24 is interposed between the inner peripheral surface and the large diameter portion at the center of the arm 22. Therefore, the roller tappet 21 is rotatably supported via the ball 24, and the arm 22 can swing. Even when the arm 22 is tilted with respect to the roller tappet 21, the centering function that allows the roller tappet 21 to rotate normally is exhibited.

  A tappet guide 23 is arranged so as to cover the arm 22. The tappet guide 23 has a reverse concave portion when viewed from the front direction (FIG. 3), and both end portions of the arm 22 protrude from both end openings as shown in FIG. The tappet guide 23 is fixed to the cylinder head 2 by mounting bolts 25.

  Further, a guide hole 23a (see FIG. 3) is formed in the tappet guide 23, and the roller tappet 21 is disposed inside the guide hole 23a. The guide hole 23a is formed along the axial direction of the valve stem, so that the roller tappet 21 can move only in the axial direction of the valve stem. When the roller tappet 21 is pressed against the cam surface 13 a of the cam 13, it functions as a valve lifter that moves the valve back and forth. The both ends of the arm 22 are provided with pressing portions that come into contact with tappet shims of a valve unit, which will be described later. In addition, this press part is comprised by the front-end | tip (lower end) of the adjustment screw 26, as FIG. 4 shows.

The exhaust-side tappet unit 20 _EX has the same basic configuration as the intake-side tappet unit 20 as shown in FIG.

  As shown in FIGS. 3 and 4, the valve unit 30 on the intake side includes two intake valves 31 in which a valve stem 31 a is guided by a valve guide 32. When the intake valve 31 is lifted, the air introduced from the air cleaner 114 (FIG. 1) via the intake port 33 and the fuel sprayed from an injector (not shown) disposed on the downstream side of the intake port 33 are mixed. Qi is introduced into the combustion chamber of each cylinder.

  A valve retainer 35 is provided at the end of each valve stem 31a via a cotter 34. The valve retainer 35 is subjected to the elastic force of a valve spring 37 mounted between the valve seat 36 and the valve retainer 35. Furthermore, the upper end of the valve stem 31a is pressed by the pressing portion of the arm 22 described above.

The exhaust-side valve unit 30 _EX has the same basic configuration as the intake-side valve unit 30 as shown in FIG.

Next, in the accelerator shaft unit 40, as shown in FIG. 2 or 3, an accelerator shaft 41 arranged in parallel between the cam shafts 11 and 11 _EX , and supported by the accelerator shaft 41 and connected to the cams 13 and 13 _EX . An accelerator fork 42 is provided.

  Here, in the present embodiment, a reference-side accelerator fork 42A disposed in one of the two cylinders serving as a reference and an adjustment-side accelerator fork 42B disposed in the other cylinder to be adjusted are provided. The adjustment side accelerator fork 42B can be adjusted.

  The accelerator shaft 41 is supported so as to be slidable in the axial direction, and is engaged with a driven gear 43 (bevel gear) via a feed screw 41a at one end side. The driven gear 43 is rotatably supported by the cylinder head 2 and meshes with a drive gear 45 (bevel gear) fixed to the output shaft of the accelerator motor 44 (see FIG. 1) as shown in FIG. Therefore, the accelerator shaft 41 can be slid by a desired amount in the axial direction by the operation of the accelerator motor 44.

The two accelerator forks 42 extend in the direction orthogonal to the accelerator shaft 41 toward the camshafts 11 and 11 _EX, and have bifurcated tip portions on both sides thereof. Further, fork guides 47 and 47 _EX which are rotatable via bearings 46 and 46 _EX are provided at the ends of the cams 13 and 13 _EX . Each bifurcated tip of the accelerator fork 42 is engaged with the engaging groove of the fork guides 47 and 47 _EX . As a result, the cams 13 and 13 _EX slide along the cam shafts 11 and 11 _EX in synchronization with or in synchronization with the accelerator shaft 41 sliding in the axial direction.

  In the above case, the reference side accelerator fork 42 </ b> A is fixedly provided at a predetermined position of the accelerator shaft 41, while the adjustment side accelerator fork 42 </ b> B is provided slidably with respect to the accelerator shaft 41. In this case, an adjustment mechanism for adjusting the position of the adjustment-side accelerator fork 42B is provided. With this adjustment mechanism, the adjustment-side accelerator fork 42B can be regulated to a predetermined position along the accelerator shaft 41.

  As shown in FIG. 2, the specific configuration of the adjusting mechanism includes a pair of adjusting nuts 48 and fixing nuts 49 that are screwed onto the accelerator shaft 41 on both sides of the adjusting-side accelerator fork 42 </ b> B. The relative position between the accelerator fork 42A and the accelerator fork 42B can be adjusted by positioning the accelerator fork 42B with the adjusting nut 48 and fixing it with the fixing nut 49.

  On the intake side opposite to the side where the accelerator motor 44 is disposed, the cam slide amount detection sensor 50 is mounted using the cylinder head cover 2a as shown in FIG. In this example, a rotary encoder is used as a sensor, and a sensor lever 51 is attached to the rotating shaft 50a. Although the detailed structure is omitted, the tip of the sensor lever 51 is slidably engaged with the engaging groove of the fork guide 47. The sensor lever 51 is swung by the slide of the cam 13 on the intake side, the swing angle is detected by the rotary encoder, and the cam slide amount is grasped based on this detection data.

Here, when the accelerator grip (or the accelerator pedal) is operated in the valve gear having the above-described configuration, the accelerator motor 44 is operated, and the accelerator shaft 41 is slid through the driven gear 43 by the rotation of the output shaft of the accelerator motor 44. In each cylinder, the cams 13 and 13 _EX slide along the cam shafts 11 and 11 _EX in conjunction with the movement of the accelerator shaft 41 via the accelerator fork 42. In this embodiment, the valve lift amount and the operating angle are variably controlled in accordance with the accelerator opening on the exhaust side as well as on the intake side.

In this way, the intake / exhaust amount is controlled from the idle rotation range to the fully open range, and intake / exhaust that is most suitable for the engine speed (or vehicle speed) can be performed. For example, when the engine low speed roller tappet 21 comes into contact with the relatively low part of the cam height relative to the cam surfaces 13a, 13a _EX cam 13, 13 _EX. When acceleration is performed in this state, that is, when the accelerator is opened, the driven gear 43 is rotated by the operation of the accelerator motor 44, and the accelerator shaft 41 slides in the direction of arrow X in FIG. The cams 13 and 13 _EX slide in the direction of the arrow X along the cam shafts 11 and 11 _EX in conjunction with the movement of the accelerator shaft 41 via the accelerator fork 42. As the cams 13 and 13 _EX slide, the roller tappets 21 and 21 _EX gradually come into contact with the relatively high cam height, and the valve lift increases. 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.

  As described above, the valve lifter unit 20 includes the arm 22 that can press the valve stem 31a and the roller tappet 21 that can rotate with respect to the arm 22, and the arm 22 includes the valve stem as shown in FIG. Adjust screws 26A and 26B that can adjust the clearance with 31a are fastened to the tip.

  In this case, one adjustment screw 26A is fixed on the upper side of the arm 22 by a nut 27A, and the other adjustment screw 26B is fixed on the lower side of the arm 22 by a nut 27B. As can be seen from FIG. 4, the nut 27 </ b> B disposed on the high speed side of the cam lobe of the cam 13 is screwed from the lower side of the arm 22 so as not to protrude toward the cam 13.

  In the present invention, particularly, the adjusting screws 26A and 26B and the valve stem 31a are arranged on substantially the same line, and the pressure receiving portion that comes into contact with the urging member having the urging force in the direction of increasing the mutual distance between the valve stem 31a. Prepare.

  In a specific configuration, each adjustment screw 26A, 26B has a spring (coil spring) 28 as an urging member as shown in FIG. Each spring 28 has a biasing force in the axial direction of the valve stem 31a and is disposed concentrically with the valve stem 31a. And it arrange | positions so that at least a part of valve stem 31a and adjustment screw 26 may be wrapped.

  The spring 28 has one end abutted against a cotter 34 provided on the valve stem 31a, and the other end abutted against the arm 22 side. In this case, the upper end of the spring 28 contacts the lower surface of the arm 22 on the adjustment screw 26A side, and the upper end of the spring 28 contacts the lower surface of the nut 27B on the adjustment screw 26B side.

  In the present invention, as shown in FIG. 8, the roller tappet 21 is provided with a cylindrical portion 21a having a flat portion that comes into contact with the cam lobe of the cam 13, and is in line contact between the cylindrical portion 21a and the cam lobe. It has become.

  For example, as shown in FIG. 8A, the center of curvature O is appropriately deviated from the center of the roller tappet 21 toward the low speed side of the cam lobe of the cam 13, and an arc (radius r) with respect to the center of curvature O and the cylindrical portion 21a. The outer peripheral surface of the roller tappet 21 is formed with the straight portion. These arcs and the cylindrical portion 21a are smoothly connected. The cylindrical portion 21 a is in line contact with the base circle surface of the cam 13.

In addition, when providing the cylindrical part 21a in the edge part (axial direction) of the roller tappet 21 like the example shown in FIG. 8, it can also provide in a center part. For example, as shown in FIG. 6, a cylindrical portion 21a _EX is provided at the center of the roller tappet 21, and arc portions are provided on both sides thereof.

  Now, the valve lifter of the present invention has a roller tappet 21, an arm 22, and a plurality of balls interposed between these members. The roller tappet 21 advances and retreats according to the lift characteristics while rotating along the cam lobe of the cam 13, and when the valve lifter advances and retreats integrally, both ends of the arm 22 respectively push down the valve stem 31 a. At both ends of the arm 22, an adjustment screw 26 capable of adjusting the valve clearance with the valve stem 31a is provided. The adjusting screw 26 is fastened with a fixing nut 27 for fixing the adjusting screw relative to the arm 22.

  The valve lifter moves forward and backward along the guide hole (groove) 23a of the tappet guide 23 provided in the cylinder head 2, but the guide hole 23a has a shape that restricts movement in directions other than the forward / backward movement direction of the valve lifter. (Guide grooves parallel to the advancing / retreating direction are arranged on both sides of the arm 22). Unlike the conventional rocker arm swinging, the valve lifter of the present invention reciprocates linearly (back and forth). For this reason, in order to always urge a part of the valve lifter to one of the cam 13 or the valve stem 31a, it is necessary to make the urging direction coincide with the advancing / retreating direction of the valve lifter.

  For this reason, the valve stem 31a and the adjusting screw 26 of the present invention are arranged on the same straight line, and a spring 28 is provided on the outer side thereof, and both ends of the spring 28 are compressed in the valve stem 31a side and the valve lifter side. And abut. As a result, the valve lifter can always be urged in the valve closing direction, and the roller tappet 21 can always be brought into contact with the cam lobe. As a result, it is possible to solve the problem of fretting corrosion and to effectively improve the durability. This spring can be similarly employed on the exhaust side.

  In this case, the spring 28 is disposed concentrically with the valve stem 31a so as to wrap the upper part of the valve stem 31a and the lower part of the adjustment screw 26. As a result, space can be saved, and the biasing force of the spring 28 is applied to the distal end portion of the arm 22 so that a small elastic biasing force is required.

  Further, the upper end surface of the cotter 34 can be effectively used as a seating surface (pressure receiving portion) of the spring 28. In this case, the cotter 34 is always urged in the valve closing direction by a valve spring 37 having a spring constant larger than the elasticity of the spring 28, and a stable urging force can be obtained.

Furthermore, the shape of the roller tappet 21 is the cylindrical portion 21a (21a _EX ) as described above, and even in this case, the occurrence of fretting corrosion and hitting sound can be effectively reduced. That is, the valve lifter normally has a curved cam lobe contact surface of the roller tappet 21 and has a vertex (ridge line) continuous in the circumferential direction of the roller tappet 21 on the slide contact surface. A roller tappet shape is formed so as to form a substantially cylindrical portion with a surface. In particular, as shown in FIG. 8A, in this case, the cylindrical portion 21 a is in line contact with the base circle surface of the cam 13.

  In this type of valve lifter, when the valve lifter is not lifted, the roller tappet 21 is pressed against the cam 13 only by the repulsive force of the spring 28, and fretting corrosion is most likely to occur in this state. Therefore, it is effective to form the cylindrical portion 21a so as to be in line contact with the base circle surface of the cam 13 which is in a non-lift state, that is, the center line of the cylindrical portion 21a is the axis of the camshaft 11. Set to parallel. In this case, the effect can be further enhanced by using it together with the spring 28 described above.

  On the other hand, as shown in FIG. 8B, the roller tappet 21 can also form a cylindrical portion 21a not on the base circle surface but on a portion that is in sliding contact with the cam lobe sliding contact surface during valve lift. The valve lifter is a floating type, and normally the arm 22 is parallel to the camshaft 11 and the two valve stems 31a are advanced and retracted. Due to such a configuration, there is a difference in the forward / backward movement of the valve lifter, the valve lifter may tilt, and the arm 22 may not be parallel to the camshaft 11. The conventional roller tappet and the cam lobe of the three-dimensional cam are in contact at one point. However, in such point contact, the surface pressure at the contact point between the roller tappet and the cam lobe increases, thereby causing fretting corrosion. It was the cause. Therefore, this ridge line portion has a flat surface, and has a roller tappet shape that forms a substantially cylindrical portion. As a result, fretting corrosion due to the inclination of the valve lifter can be further reduced.

(Second Embodiment)
Next, a second embodiment of the valve gear according to the present invention will be described. The basic configuration in this embodiment is substantially the same as that of the first embodiment described above, and the same reference numerals are used for the same or corresponding members.

  In the second embodiment, in particular, the valve lifter includes an arm portion that can press the valve stem and a roller tappet that can rotate relative to the arm portion, and a needle bearing is interposed between the arm portion and the roller tappet.

  Specifically, as shown in FIG. 6, a needle bearing 29 is interposed between the roller tappet 21 and the arm 22. For convenience, FIG. 6 shows the exhaust side, but it may be on the intake side. Here, when the valve lifter is inclined, the distance between the tip of the arm 22 on the side closer to the cam lobe of the cam 13 and the valve stem increases. For this reason, when the valve lifter is pushed down by being pushed by the cam 13, a loud hitting sound is generated between the tip and the valve stem as it is. By using the needle bearing 29 as in this embodiment, the inclination of the valve lifter can be prevented, so that the hitting sound can be reduced.

  Furthermore, fretting corrosion can be further reduced by using a needle bearing 29 instead of the ball 24 between the roller tappet 21 and the arm 22 of the valve lifter. By adopting the needle bearing 29, the relative inclination of the arm 22 with respect to the roller tappet 21 does not occur, and the fretting corrosion between the ridgeline of the roller tappet 21 and the cam lobe can be reduced.

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, the specific numerical examples described in the above embodiment are not necessarily limited to this, and can be changed as necessary. In each embodiment, an example of a two-cylinder engine has been described. However, the present invention can be effectively applied to a multi-cylinder engine having three or more cylinders.

It is a figure which shows the structural example of the motorcycle containing the engine periphery which concerns on the example of application of this invention. It is a top view of the valve operating apparatus in embodiment of this invention. It is sectional drawing which follows the AA line of FIG. 2 which shows the principal part structure of the valve gear in embodiment of this invention. It is sectional drawing which follows the BB line of FIG. It is a figure which shows the crankshaft drive system which concerns on the valve gear of this invention. It is sectional drawing which follows the CC line of FIG. It is a figure which shows the structural example around the accelerator motor based on this invention. It is each sectional side view and top view which show the valve lifter circumference of this invention.

Explanation of symbols

1 Engine unit 2 Cylinder head 3 Drive sprocket 4 Cam chain 5 Chain guide 6 Chain tensioner 7 Tension adjuster 11 Cam shaft 13 Cam 15 Sprocket 21 Roller tappet 22 Arm 23 Tappet guide 29 Spring 31 Intake valve 32 Valve guide 35 Valve retainer 37 Valve spring 41 Accelerator shaft 42 Accelerator fork 44 Accelerator motor

Claims (7)

In a valve operating apparatus having a three-dimensional cam that can slide in the cam shaft direction and a valve lifter that moves a plurality of valves back and forth with one cam,
The valve lifter includes an arm portion that can press the valve stem, and a roller tappet that can rotate with respect to the arm portion.
The arm portion is fastened with an adjusting screw capable of adjusting a clearance with the valve stem at a tip portion, and the adjusting screw and the valve stem are arranged on substantially the same line, and the arm portion is mutually connected with the valve stem. A valve operating apparatus comprising a pressure receiving portion that comes into contact with an urging member having an urging force in a direction to increase the distance.   The biasing member has a biasing force in the axial direction of the valve stem and is disposed concentrically with the valve stem, and is disposed so as to wrap at least a part of the valve stem and the adjustment screw. The valve gear according to claim 1.   The biasing member has one end abutted against a valve cotter provided on the valve stem upper portion and the other end abutted against the arm portion side of the valve lifter. 2. The valve gear according to 2.   2. The valve operating system according to claim 1, wherein the roller tappet is provided with a cylindrical portion having a flat portion in contact with the cam lobe, and is in linear contact between the cylindrical portion and the cam lobe. apparatus.   The valve operating device according to claim 4, wherein the cylindrical portion is in line contact with a base circle surface of the cam lobe.   The valve operating device according to claim 1, wherein the valve lifter has a needle bearing interposed between the arm portion and the roller tappet. An internal combustion engine configured to control intake and exhaust by an intake valve and an exhaust valve,
An internal combustion engine comprising the valve gear according to any one of claims 1 to 6 on an intake side or an exhaust side.

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