JP2015004336A - Valve gear of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve concentration of stress on a cam and a gap in valve lift timing in a valve gear to which a roller-type tappet is applied.SOLUTION: In a valve gear of an internal combustion engine, a contact part between a roller (36) of a roller-type tappet (21) and a cam (20) is arranged in a position between valve stems and displaced closer to a side of one valve stem (16a). In a guide groove (50A) of a tappet guide (22), a cam side in a guide surface (54) facing the roller (36) on the side of one valve stem (16a) projects to a roller side further than a valve side to configure a projection (56) on the cam side, and the valve side in a guide surface (55) facing the other side of a roller side surface on a side of the other valve stem (16b) projects to the roller side further than the cam side to configure a projection (57) on the valve side.

Description

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

  A general 4-stroke engine has intake / exhaust cams for opening / closing intake / exhaust valves, and the lift amount and opening / closing timing of the valve by the cams are fixed. However, the optimum lift amount and opening / closing timing differ depending on various states (rotation, load, warm-up state) in which the engine is used. Therefore, a three-stage switching type three-dimensional cam mechanism that realizes three lift amounts and opening / closing timings of high, medium, and low has been proposed.

  In a specific configuration of such a valve operating device, for example, in Patent Document 1, the stem end of the valve stem is pressed via a roller-type tappet in which the roller rolls, and the valve is opened and closed following the profile of the three-dimensional cam. Let In an engine having two intake valves per cylinder, the tappet is arranged between the two intake valves so as to operate the two intake valves simultaneously, and is installed between the stem ends. In other words, the tip end of the tappet arm extending from the both side surfaces of the tappet roller disposed at the center of the two intake valves presses the stem end of each intake valve. The tappet is floated and held in the guide groove of the tappet guide fixed to the cylinder head. When the tappet is pushed by the cam, the tappet moves while being guided by the tappet guide, and the tappet simultaneously moves the valve stems of the two intake valves. Push.

  By the way, in the above-mentioned valve operating apparatus, since the width | variety between a valve | bulb receives the restriction | limiting of a width | variety in connection with the existing cylinder head, the tappet width is suppressed by making a roller-type tappet asymmetrical. As a result, it is not necessary to change the shape of the combustion chamber and the like, and a three-stage switching type three-dimensional cam mechanism can be mounted while the cylinder head and the existing engine remain unchanged.

JP 2012-172658 A

  However, in the above-described conventional valve operating apparatus, since the roller type tappet is asymmetrical, the contact position where the tappet and the cam come into contact with each other is biased toward one valve stem as viewed from the axial direction of the valve stem. For this reason, when the tappet is pushed from the cam, a force in the direction of tilting toward the one valve stem acts on the tappet, and the arrangement posture of the tappet is inclined. In the arrangement state where the tappet is not inclined, the flat portion of the outer surface of the tappet roller is in line contact with the cam lobe, but when the tappet is inclined, the cam and the tappet roller are in point contact. In the state where the cam and the tappet roller are in point contact, there is a possibility that stress is concentrated at the pressed portion where the point contact is made and the cam is damaged. In addition, there is a problem that the timing at which the left and right valve stems are pushed by the tappet arm is shifted due to the inclination of the tappet.

  The present invention has been made in view of the above points, and by making the arrangement posture of the tappet when force is applied to the roller-type tappet from the cam, the stress concentration is improved and the valve lift timing is improved. An object of the present invention is to provide a valve gear for an internal combustion engine that can improve the deviation.

  In the valve operating apparatus for an internal combustion engine according to the present invention, a roller-type tappet that is guided by a guide portion of a tappet guide and can reciprocate in the axial direction of the valve stem is installed between the upper portions of the valve stem. Is pushed by the cam and reciprocates. By pushing down the valve spring against the elasticity of the valve spring, one roller-type tappet is configured to open two valves. From the axial direction of the valve stem As seen, in the valve operating apparatus of the internal combustion engine in which the roller-type tappet roller and the cam abutment portion are arranged between the valve stems and are biased toward one valve stem side, the guide portion is On the one valve stem side, the cam side of the guide surface facing one side of the roller side surface protrudes more toward the roller side than the valve side, and the cam side Together constitute the projecting portion, the valve side of the guide surface facing the other side of the roller side in the other of the valve stem side constitutes a projecting portion of the valve side and protrudes to the roller side than the cam side.

  According to this configuration, in a state where the roller-type tappet is not pushed from the cam, the lower portion of the tappet is disposed on one valve stem side rather than the cam-side protruding portion with respect to the guide surface on one valve stem side, The upper part of the tappet is arranged on the other valve stem side with respect to the guide surface on the other valve stem side rather than the protruding part on the valve side, so that the tappet is held in a posture inclined to the other valve stem side. . When a tappet that is tilted toward the other valve stem is pushed from the cam, the tappet tilts toward one valve stem due to the stress that the tappet receives from the cam, and the upper part of the tappet protrudes toward the one valve stem. The lower part of the tappet approaches the protruding part on the valve side. As a result, the inclination of the tappet with respect to the cam is eliminated, the cam and the roller are changed from the point contact to the line contact, and the stress concentration on the cam is greatly improved. When the tappet is pushed from the cam, the tappet is tilted toward one valve stem, and as a result, the tappet is parallel to the mounting surface of the tappet guide to the cylinder head. Thereby, the height of the upper end part of a valve stem becomes the same position in the axial direction of a valve stem, and it can improve so that the timing of valve lift may become right and left simultaneously.

  Further, in the valve operating apparatus for an internal combustion engine according to the present invention, the guide portion forms the cam-side protruding portion by forming the both guide surfaces at a predetermined angle in the same direction from a perpendicular to the mounting surface of the cylinder head. In addition, the protruding portion on the valve side may be configured. Thereby, since a required protrusion part can be comprised only by processing both guide surfaces of a guide part into a planar shape, the shape of a guide surface can be simplified and a manufacturing process can be simplified.

  In the valve operating apparatus for an internal combustion engine according to the present invention, when the roller comes into contact with the cam-side protruding portion and the valve-side protruding portion, the valve pressing portion of the roller-type tappet is attached to the cylinder head. You may comprise so that it may become parallel with respect to. Thereby, when the tappet is pushed from the cam, that is, when the roller comes into contact with the protruding portion on the cam side and the protruding portion on the valve side, the inclination of the tappet is eliminated. can do.

  According to the valve operating apparatus for an internal combustion engine of the present invention, since the cam-side protrusion and the valve-side protrusion are provided on the guide surface of the tappet guide, the arrangement posture of the tappet when a force is applied to the roller-type tappet. Can be set to an appropriate posture, and the stress concentration of the cam can be improved and the deviation of the valve lift timing can be improved.

It is a top 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 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 the upper side figure and side view of the intake side structure in the valve gear which concern on embodiment of this invention. It is the figure which expanded the cam part of the intake side structure shown in FIG. FIG. 5 is a top view from the tappet to the intake valve according to the embodiment of the present invention and a cross-sectional view taken along the line BB. It is a perspective view of a tappet and a tappet guide concerning an embodiment of the present invention. It is a schematic diagram which shows the inclination of the guide groove which concerns on embodiment of this invention, and the arrangement | positioning attitude | position of a tappet. It is a schematic diagram which shows the modification of the guide groove of a tappet guide.

  Hereinafter, preferred embodiments of a valve operating apparatus for an internal combustion engine according to the present invention will be described with reference to the drawings. In the present embodiment, an example in which a three-stage switching type three-dimensional cam mechanism is applied to a multi-cylinder engine of a motorcycle as a valve operating device will be described.

  1 to 3 show a configuration example of a cylinder head in the engine according to the present embodiment. In the following description, the front of the vehicle is indicated by an arrow Fr, the rear of the vehicle is indicated by an arrow Rr, the left side of the vehicle is indicated by an arrow L, and the right side of the vehicle is indicated by an arrow R.

  The cylinder head 10 is fixed to the upper part of the cylinder body 11 and accommodates a valve operating device therein. In this embodiment, a parallel four-cylinder engine is illustrated, and each cylinder has two valves on the intake side (IN) and the exhaust side (EX). 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 four cylinders # 1 to # 4, and the cylinder head cover 12 attached to the upper part forms a sealed structure in the accommodating space of the valve gear. 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 camshaft 18 is rotatably supported by the cylinder head 10 via a plurality of bearings 19 along the cylinder arrangement direction above the valve stem 16a, which is the axial direction of the intake valve 16. A cam 20 fixed in the shaft rotation direction is mounted on the camshaft 18 so as to be slidable in the shaft axis 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 (valve stem 16a), a roller type tappet 21 guided by a tappet guide 22 and reciprocating in the axial direction of the valve stem 16a is disposed. Details of these will be described later.

  A camshaft 23 is rotatably supported by the cylinder head 10 via a plurality of bearings 24 along the cylinder arrangement direction above the valve stem 17a, which is the axial direction of the exhaust valve 17. A cam 25 is attached and fixed to the cam shaft 23 at a predetermined position in the axial direction. A total of eight cams 25 are provided corresponding to the pair of exhaust valves 17 of each cylinder, and each cam 25 on the exhaust side is formed as a flat plate-like flat cam. 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 disposed.

  Sprockets 27 and 28 are fixed to one end of the intake-side camshaft 18 and the exhaust-side camshaft 23, and a cam chain is wound between the sprockets 27 and 28 and a drive sprocket fixed to one end of the crankshaft. Rotated. As a result, the camshaft 18 and the camshaft 23 rotate synchronously with the rotation of the crankshaft.

  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 the shim 40. When the cam 20 pushes down the tappet 21 against the elasticity of the valve spring 32, the valve stem 16a is urged downward to open the intake valve 16.

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

  An accelerator motor 33 is mounted and supported on the cylinder head cover 12 as a drive source for a cam slide mechanism that moves the cam 20 along the cam shaft 18. In this example, the accelerator motor 33 is disposed at the corner on the right rear side of the cylinder head 10 and is coupled to the ball screw housing 34 via the flange 33a. A member such as a ball screw described later is accommodated in the ball screw housing 34.

  FIG. 3 shows a state where 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. A part of the cam housing 35 is exposed.

  4A and 4B show an intake side configuration example of the valve gear, and FIG. 5 is an enlarged view of the cam portion of the intake side configuration. The intake-side cam 20 is configured as a three-stage three-dimensional cam, and one cam 20 is provided for each cylinder. The three-dimensional cam is formed so that its outer diameter (cam profile) changes not only in the cam rotation direction but also in the axial direction. The three-stage three-dimensional cam is configured by connecting three cam shapes that are three types of cam profiles for high load, medium load, and low load along the rotation axis direction of the cam. There are three lift amounts and opening / closing timings: high, medium and low. The cam 20 has cam lobes 20a, 20b, and 20c (flat portions) that are high, medium, and low along the rotational axis direction of the cam, and is gently inclined in the axial direction of the camshaft 18 so as to connect the flat portions. Cam lobes 20d and 20e having profiles to Basically, the cam lobes 20d and 20e which are inclined and abutted against the tappet 21 by the cam lobes 20a to 20c of the flat portion and continuously inclined become the switching transition section of the cam 20. 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 and switching the cam height in three stages, the lift amount, operating angle, and lift timing of the intake valve can be variably controlled in three stages.

  As described above, the accelerator motor 33 is mounted on the cylinder head cover 12 and operates the cam slide mechanism disposed 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 supported by a plurality of bearing portions 35b (five in this example) provided in the cam housing 35 so as to be slidable in the axial direction. 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 (see FIG. 3) is attached to the output shaft of the accelerator motor 33. The gear 44 and the pinion gear 45 are connected to each other. The ball screw 42 is rotationally driven by the operation of the accelerator 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 two cylinders # 2 and # 3 are coupled to each other. The Each cam fork 48 is rotatably engaged with the cam 20 via a bearing 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 engine is operated, the accelerator motor 33 is operated according to the operation of the accelerator grip of the motorcycle and the operating state, and the ball screw 42 is rotated to slide the cam fork shaft 41 through 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, when the engine speed is low (when the engine speed is low), the tappet 21 is in contact with the cam 20, for example, a cam lobe 20 c having a low cam height. In this state, when the acceleration, that is, the operation of opening the accelerator and the predetermined operation state, the tappet 21 comes into contact with the cam lobe 20b, which is the next highest cam height, as the cam 20 slides due to the operation of the accelerator motor 33. As a result, the valve lift increases according to the lift characteristics of the cam 20. 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 tappet unit will be described in more detail. 6 is a top view and a cross-sectional view from the tappet 21 to the intake valve 16, and FIG. 7 is a perspective view of the tappet 21 and the tappet guide 22. The tappet guide 22 is arranged and fixed at an appropriate position of the cylinder head 10 by four screws (see FIG. 4) inserted into screw holes 51 a to 51 d provided at the four corners of the tappet guide 22. The lower surface 52 of the tappet guide 22 is formed in a planar shape except for a guide groove formation region which will be described later, and serves as an attachment surface to the cylinder head 10. The tappet 21 includes a tappet roller 36 that is formed in a generally donut shape, a core portion 38 that supports the tappet roller 36 via a bearing 37, and an arm 39 that extends outward from the core portion 38. Both side surfaces 36a and 36b of the tappet roller 36 are ring-shaped planes except for the connecting portion (core portion 38) of the arm 39. Further, on the outer peripheral surface of the tappet roller 36, a contact portion 36c which is a flat portion parallel to the rotation axis of the roller (a shape portion parallel to the rotation axis in the cross section including the rotation shaft) and contacts the cam 20 is formed. Has been. The position of the contact portion 36 c on the outer peripheral surface of the tappet roller 36 is a position that is biased toward the one valve stem 16 a in the rotational axis direction of the tappet roller 36. On the outer peripheral surface of the tappet roller 36, the abutting portion 36c has a maximum diameter and is hung on the other valve stem 16b side to reduce the outer diameter. That is, the roller-type tappet 21 is asymmetrical, and the tappet roller 36 is disposed at the center of the tappet 21, but the contact position where the tappet 21 and the cam 20 abut is biased toward the one valve stem 16 a side. Yes. 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 ends of the valve stems 16a and 16b and indirectly contacts the upper ends of the valve stems 16a and 16b via the shim 40. Both end portions of the arm 39 constitute a valve pressing portion that pushes down the upper ends of the valve stems 16a and 16b. When the tappet roller 36 is pushed by the cam lobe of the cam 20, the tappet 21 causes the arm 39 to push the valve stems 16 a and 16 b against the elasticity of the valve spring 32, thereby opening the intake valve 16. Function as.

  The tappet 21 is disposed between two adjacent valve stems. 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. In this embodiment, the tappet clearance is adjusted by the shim 40. The tappet 21 can be lowered to a position where the bearing 37 in the tappet roller 36 overlaps the valve spring 32.

  The rotation axis of the tappet roller 36 is typically arranged at the same position as the center of the height of the arm 39 in the height direction as shown in FIG. 6B. Since the tappet roller 36 is in contact with the cam 20 at the upper part thereof, the rotation center axis of the tappet roller 36 is preferably arranged as low as possible in order to lower the position of the cam 20 and make the height of the cylinder head 10 compact. By arranging the rotation center axis 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 (vertical direction in an actual vehicle). Specifically, as shown in FIG. 7A and FIG. 7B, one guide groove 50 </ b> A that vertically penetrates the tappet guide 22 along the radial direction of the tappet roller 36 and the guide groove 50 </ b> A intersect with each other. And the other guide groove 50 </ b> B formed penetrating along the longitudinal direction of the arm 39, i.e., the axial direction of the camshaft 18. The tappet 21 is accommodated in these guide grooves 50A and 50B. Specifically, the cross-shaped guide groove 50 abuts against the side surface of the tappet roller 36 to maintain the posture of the tappet roller 36 and the position in the left-right direction, and the axial direction of the intake valve 16 (in this embodiment, the tappet guide 22 The guide groove 50A that guides the sliding in the thickness direction) and the side surface of the arm portion 39 are in contact with the axis position of the tappet roller 36 (the position in the direction perpendicular to the axis of the intake valve 16, the position in the front-rear direction) ) And a guide groove 50B that guides the sliding of the arm portion 39 in the axial direction of the intake valve 16 (in the present embodiment, the thickness direction of the tappet guide 22). The tappet guide 22 has an opening 51 around the end of the arm 39, and the spring retainer 30 is arranged so that the opening 51 faces from below.

  Although the upper surface of the tappet guide 22 is formed substantially flat, as shown in FIG. 7B, four legs are provided on the lower surface so that a cross-shaped guide groove 50 made up of guide grooves 50A and 50B extends downward. A portion 53 is projected. The tappet 21 moves up and down according to the valve shift amount when the intake valve 16 is opened and closed, but the cross-shaped guide groove guides the tappet roller 36 and the arm 39 from both side surfaces at least when the tappet 21 moves up and down. It has a sufficient vertical length to obtain.

  Here, the inclination of the guide groove 50A in the tappet guide 22 and the arrangement posture of the tappet 21 will be described with reference to FIG. FIG. 8 is a schematic view with the same cross section as FIG. 6B, and is a cross section including the axes of the valve stems 16 a and 16 b. The guide groove 50A is formed with a pair of guide surfaces 54 and 55 that face each other with an interval corresponding to the width of the tappet roller 36 (the length in the rotation axis direction). The guide surfaces 54 and 55 are formed as a pair of parallel surfaces from the upper surface on the cam side of the tappet guide 22 to the tip of the leg portion 53. In the tappet 21 accommodated in the tappet guide 22, one side surface 36 a of the tappet roller 36 faces the guide surface 54, and the other side surface 36 b faces the guide surface 55. An appropriate gap is secured between the side surfaces 36a and 36b of the tappet roller 36 and the guide surfaces 54 and 55 so that the tappet 21 can move up and down in the guide grooves 50A and 50B.

  In the present embodiment, the guide groove 50A (guide surfaces 54 and 55) is formed to be inclined. In FIG. 8, a straight line that passes through the rotation center of the camshaft 18 and is perpendicular to the rotation axis (shaft axis) of the camshaft 18 is denoted by L1. Since the straight line L1 is orthogonal to the shaft axis direction of the camshaft 18, the cam lobes 20a to 20c formed in parallel with the shaft axis of the camshaft 18 move up and down in the straight line L1 direction. And if the contact part 36c which is a flat part in the outer peripheral surface of the tappet roller 36, and the straight line L1 cross | intersect perpendicularly, the tappet 21 will be in the state (erect state) without an inclination with respect to the camshaft 18, and contact | abutting If the part 36c and the straight line L1 do not intersect perpendicularly, it can be said that the tappet 21 is inclined (inclined with respect to the camshaft 18). The guide groove 50A is formed along the radial direction of the tappet roller 36, and is formed along a direction perpendicular to the shaft axis of the camshaft 18 when viewed from the axial direction of the valve stems 16a and 16b. As shown in FIG. 8, the guide groove 50A is inclined from the straight line L1 by an angle α. The inclination direction of the guide groove 50 </ b> A is a direction in which an upper portion on the cam side of the tappet roller 36 falls to the other valve stem 16 b side. That is, the guide groove 50 </ b> A is inclined with respect to the camshaft 18 so as to be closer to the valve stem 16 b as it approaches the camshaft 18. As shown in FIG. 8B, the inclination angle α of the guide groove 50A corresponds to the angle at which the tappet 21 is inclined when the tappet 21 is pressed due to the asymmetrical left and right of the tappet 21. That is, the tappet 21 (the tappet roller 36) is pushed by the cam 20 and falls down within a gap set between the side surfaces 36a and 36b of the tappet roller 36 and the guide surfaces 54 and 55 of the guide groove 50A. However, the guide groove 50A is arranged so that the rotation axis of the roller 36 and the shaft axis of the camshaft 18 are parallel in the limit tilted state where the side surface 36a and the guide surface 54 and the side surface 36b and the guide surface 55 are in contact with each other. The tilt angle α is set. Therefore, when the tappet 21 is pushed from the cam 20, the tappet 21 is in an upright state with no inclination when viewed from the cam 20.

  In the configuration example shown in FIG. 8, the entire guide surfaces 54 and 55 of the guide groove 50 </ b> A are integrally inclined so that the cam side (upper portion) of the guide surface 54 on the one valve stem 16 a side is on the guide surface 54. A cam-side protruding portion 56 that protrudes toward the tappet roller 36 from the valve side (lower part) is formed. In addition, the valve side (lower part) of the guide surface 55 on the other valve stem 16b side constitutes a valve-side protruding part 57 that protrudes toward the tappet roller 36 from the cam side (upper part) of the guide surface 55. The upper side of the cam side on one side of the tappet roller 36 is in a state immediately before (or in contact with) the cam-side protrusion 56, and the lower part of the valve on the other side is the valve-side protrusion 57. In the state immediately before contact (or in the contact state), the protrusion amount of each protrusion 56, 57 to the tappet roller 36 side is set so that the inclination of the tappet 21 is eliminated. Regarding the tappet guide 22, the lower surface which is the valve side surface and is the mounting surface to the cylinder head 10 is formed on a surface parallel to the shaft axis of the camshaft 18 and perpendicular to the valve stems 16 a and 16 b. The camshaft 18 side surface (upper surface) is formed on a surface perpendicular to the guide groove 50A (guide surfaces 54 and 55) formed obliquely with respect to the lower surface. By making the upper surface a surface perpendicular to the guide groove 50A, the processing of the guide groove 50A is facilitated.

  In the tappet unit configured as described above, until the tappet 21 is pushed from the cam 20, the arrangement state of the tappet 21 may be inclined along the guide groove 50A as shown in FIG. 8A. There is. However, when the tappet 21 tilted toward the other valve stem 16b is pushed from the cam 20 (for example, when the cam lobe 20a comes into contact with the contact portion 36c of the tappet roller 36 and the tappet 21 is pushed), the tappet 21 The tappet 21 is inclined toward the one valve stem 16a by the stress received from the cam 20, and the upper portion of the tappet 21 (the tappet roller 36) approaches the cam-side protruding portion 56 on the one valve stem 16a side, and the tappet 21 (the tappet 21). The lower part of the roller 36) approaches the protruding part 57 on the valve side and is in an upright state (FIG. 8B). In a state where the tappet 21 is upright with respect to the cam 20 (FIG. 8B), the cam lobe 20a that is a flat portion and the contact portion 36c that is a flat portion on the outer peripheral surface of the tappet roller 36 are in line contact with each other in parallel. It will be. Since the cam 20 and the tappet 21 are changed from the point contact to the line contact, the force with which the cam 20 pushes the tappet 21 is evenly distributed, and the stress concentration on the cam 20 is greatly improved. When the tappet 21 is pushed from the cam 20, the tappet 21 is inclined toward the one valve stem 16 a, so that the tappet 21 is parallel to the attachment surface (52) of the tappet guide 22 to the cylinder head 11. . As a result, the heights of the upper ends of the left and right valve stems 16a, 16b when pushed by the tappet 21 are the same position in the axial direction of the valve stem, and the valve lift timing is improved at the same time on the left and right. can do.

  In addition, this invention is not limited to said each embodiment, It can change and implement variously. In the above-described embodiment, the size, shape, and the like illustrated in the accompanying drawings are not limited to this, and can be appropriately changed within a range in which the effect of the present invention is exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  For example, in the above-described embodiment, the guide groove 50A of the tappet guide 22 is inclined as a whole. However, the guide groove 50A is not inclined, and the gap between the guide surfaces is increased and the protruding portion is also configured. Similar effects can be obtained.

  As shown in FIG. 9, a pair of guide surfaces 58 and 59 facing the guide groove 50 </ b> A in the rotation axis direction of the roller are configured. The guide surfaces 58 and 59 are configured as parallel planes that are not inclined with respect to the straight line L1 (α = 0), and the distance between the guide surface 58 and the guide surface 59 is the rotation axis of the roller 36 when the tappet 21 is inclined. An interval corresponding to the length in the direction is set. The guide surfaces 58 and 59 only need to have a gap with the roller 36 to the extent that there is no hindrance to the assembling and sliding of the tappet 21 and is inclined with respect to the shaft axis of the camshaft 18. Also good. The cam side of the guide surface 58 protrudes toward the campet side so that the cam side (upper part) of the guide surface 58 on the one valve stem 16a side protrudes toward the tappet roller 36 side than the valve side (lower part) of the guide surface 58. A portion 61 is formed. Further, the valve side on the valve side of the guide surface 59 is such that the valve side (lower part) of the guide surface 59 on the other valve stem 16b side protrudes toward the tappet roller 36 side than the cam side (upper part) of the guide surface 59. The protrusion 62 is formed. When the tappet 21 accommodated in the tappet guide 22 is not pushed from the cam 20, the tappet 21 is inclined by the gap in the guide groove 50A. That is, the lower part of the tappet 21 is arranged on the one valve stem 16a side with respect to the guide surface 58 on the one valve stem 16a side, and the upper part of the tappet 21 is on the other valve stem 16b. The tappet 21 may be inclined to the other valve stem 16b side by being arranged on the other valve stem 16b side with respect to the guide surface 59 on the side from the protruding portion 62 on the valve side. When the tappet 21 is pushed from the cam 20 from this state, as shown in FIG. 9, the tappet 21 is tilted (raised) toward the one valve stem 16a by the force received by the tappet 21 from the cam 20, and the tappet 21 (the tappet roller) The upper portion of 36) approaches the cam-side protruding portion 61 that is the one valve stem 16a side, and the lower portion of the tappet 21 (the tappet roller 36) approaches the protruding portion 62 on the valve side (FIG. 9). The protruding tip surfaces of the cam-side protruding portion 61 and the valve-side protruding portion 62 serve as the contact surface with the tappet roller 36, and the camshaft 18 is the contact surface (tip surface) with the tappet roller 36. The distance in the shaft axis direction is the thickness dimension of the tappet roller 36. In other words, the cam-side protrusion 61 is arranged such that the rotation axis of the roller 36 and the shaft axis of the camshaft 18 are in parallel with the tappet roller 36 in contact with the cam-side protrusion 61 and the valve-side protrusion 62. The protruding position of the protruding portion 62 on the valve side is set. As a result, the cam lobe 20a and the contact portion 36c of the tappet roller 36 are in line contact with each other in a parallel state, and the cam 20 can be prevented from being damaged due to stress concentration. Further, the heights of the upper end portions of the left and right valve stems 16a, 16b are the same position in the axial direction of the valve stem, and the shift of the valve lift timing can be improved.

  As described above, the present invention is useful for improving cam stress concentration and valve lift timing deviation in a valve operating apparatus to which a roller-type tappet is applied.

  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 (one side), 16b valve stem (other side), 17 exhaust valve, 18 cam Shaft, 19 Bearing, 20 Cam, 20a-20e Cam Lob, 21 Roller Tappet, 22 Tappet Guide, 23 Camshaft, 24 Bearing, 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, 35b Bearing, 36 Tappet roller, 36a, 36b Low -Side, 36c Abutment, 37 Bearing, 38 Core, 39 Arm, 40 Shim, 41 Cam Fork Shaft, 42 Ball Screw, 43 Bearing, 44 Gear, 45 Pinion Gear, 46 Slide Nut, 47 Nut Fork, 48 Cam Fork, 50A, 50B Guide groove, 51a-51d Screw hole, 52 Tappet guide lower surface, 53 Leg part, 54, 55, 58, 59 Guide surface, 56, 61 Cam side protrusion, 57, 62 Valve side protrusion Part

Claims (3)

A roller-type tappet that is guided by the guide part of the tappet guide and can be reciprocated in the axial direction of the valve stem is installed between the upper parts of the valve stem, and the roller-type tappet is reciprocated by being pushed by the cam. By pushing down the valve spring against the elasticity of the spring, one roller type tappet is configured to open two valves, and when viewed from the axial direction of the valve stem, the roller type tappet roller and In the valve operating device for an internal combustion engine, the cam contact portion is disposed between the valve stems and is biased toward one valve stem side.
The guide portion includes a cam side protruding from the valve side toward the roller side of the guide surface facing one side of the roller side surface on the one valve stem side to form a cam side protruding portion, and on the other valve stem side. A valve operating apparatus for an internal combustion engine, characterized in that a valve side of a guide surface facing the other side of the roller side surface projects from the cam side toward the roller side to form a valve side protruding portion.   The guide portion forms the cam-side protruding portion and the valve-side protruding portion by forming both guide surfaces inclined at a predetermined angle in the same direction from the perpendicular to the mounting surface of the cylinder head. The valve operating apparatus for an internal combustion engine according to claim 1. The valve pressing portion of the roller-type tappet is parallel to the mounting surface to the cylinder head when the roller contacts the cam-side protrusion and the valve-side protrusion. The valve operating apparatus for an internal combustion engine according to claim 1 or 2.

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