JP2015004335A - Valve gear of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a gap in valve lift timing without extending a distance between a pair of valve stems in a valve gear to which a roller-type tappet is applied.SOLUTION: In a valve gear of an internal combustion engine, a roller-type tappet (21) is pushed by a cam to reciprocate, and a valve spring (32) pushed down by opposing the resilience of the valve spring (32) allows one roller-type tappet (21) to open a pair of intake valves (16). The valve spring (32) includes a different diameter spring of which a diameter on a side of the tappet (21) is smaller than a diameter on a side of the intake valve (16). Viewing from the axial direction of valve stems (16a, 16b), a contact part (36c) of the tappet (21) and the cam is arranged in the center between the pair of valve stems (16a, 16b).

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. That is, the tip ends of the tappet arms extending from the both side surfaces of the tappet roller disposed at the center of the two intake valves to the left and right are arranged so as to press the stem ends of the respective intake valves. 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 gear, since the roller-type tappet is asymmetrical, the contact position where the tappet and the cam abut 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. As a result, there is a problem in that the timing of pushing the left and right valve stems by the tappet arm is shifted due to the inclination of the arrangement posture of the tappet.

  For example, it is conceivable to arrange the contact position where the tappet and the cam contact each other at a position that is an equal distance from each valve stem. However, in this case, it is necessary to increase the distance between the pair of valve stems in order to avoid interference between the tappet and the valve spring, and the distance between the pair of valve stems is increased. There is a problem that it becomes impossible to do.

  The present invention has been made in view of such a point, and an object of the present invention is to provide a valve operating apparatus for an internal combustion engine that can improve the deviation in valve lift timing without increasing the distance between a pair of valve stems. And

  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 disposed above the pair of valve stems. Of the internal combustion engine configured such that one roller type tappet opens a pair of valves by pushing down the valve spring against the elasticity of the valve spring. In the valve device, the roller spring is configured with a different diameter coil spring having an outer diameter on the tappet side smaller than the outer diameter on the valve side, and when viewed from the axial direction of the valve stem, the roller type The contact portion between the tappet and the cam is disposed in the center between the pair of valve stems.

  According to this configuration, the contact portion between the roller-type tappet and the cam is disposed at the center between the pair of valve stems when viewed from the axial direction of the valve stem. It can be made to act equally with respect to a pair of valve stems (a pair of valves) along the axial direction, and a situation where the tappet is inclined can be suppressed. In addition, since the valve spring is composed of a different diameter spring whose roller tappet side is smaller than the valve side, the roller tappet or tappet guide guide is utilized by utilizing the space near the small diameter portion of the valve spring. The distance between the pair of valve stems can be adjusted while avoiding interference between the tappet and the valve spring. Can be prevented from expanding. As a result, it is possible to improve the deviation of the valve lift timing without increasing the distance between the pair of valve stems.

  In particular, in the valve operating apparatus for an internal combustion engine of the present invention, a part of the roller portion of the roller-type tappet is disposed at a position overlapping the large diameter portion of the valve spring as viewed from the axial direction of the valve stem. It is preferable. In this case, by utilizing the space between the pair of valve stems enlarged by the small diameter part of the valve spring, it is possible to arrange so that a part of the roller part of the roller-type tappet enters the enlarged space. it can. And, as seen from the axial direction of the valve stem, a part of the roller part is arranged so as to overlap the large diameter part of the valve spring, so the difference in diameter between the small diameter part and the large diameter part of the valve spring is utilized. Without increasing the distance between the pair of valve stems, it is possible to effectively arrange the roller type tappet in a balanced manner at the distance between the pair of valve stems of the existing engine.

  Further, in the valve operating apparatus for an internal combustion engine of the present invention, the guide portion of the tappet guide and the small diameter portion of the valve spring as viewed from the direction perpendicular to the plane including the shaft cores of the pair of valve stems, Are preferably arranged in an overlapping manner. In this case, since the formation area of the guide part can be secured by utilizing the space formed in the vicinity of the small diameter part, the size and thickness dimension of the guide part can be increased, the rigidity of the guide part can be secured, The durability is improved and the movement of the roller type tappet can be reliably guided. Thereby, since the roller type tappet at the time of the reciprocating motion can be held in an appropriate posture, the roller type tappet can be smoothly reciprocated along the axial direction of the valve stem.

  In particular, in the valve operating apparatus for an internal combustion engine of the present invention, it is preferable that a portion located between the pair of valve stems is removed in the guide portion of the tappet guide. In this case, it is possible to improve the durability by ensuring the rigidity of the guide portion while reliably preventing the guide portion of the tappet guide from interfering with the valve spring, and smoothly reciprocate the roller type tappet. It becomes possible.

  Further, in the valve operating apparatus for an internal combustion engine of the present invention, the roller-type tappet has a pair of arm portions that push down the upper end portions of the pair of valve stems, It is good also as a structure by which the rib is provided along the direction where the said arm part is extended. In this case, since the rib is provided on the lower surface of the base end portion of the arm portion along the direction in which the arm portion extends, the rigidity of the tappet can be secured as the rigidity of the arm portion is improved. It becomes possible to push down the valve stem appropriately against the urging force of the spring.

  According to the valve operating apparatus for an internal combustion engine of the present invention, it is possible to improve the deviation of the valve lift timing without increasing the distance between the pair of valve stems.

It is a top view of the cylinder head concerning this embodiment. It is sectional drawing which follows the AA line shown in FIG. It is a top view of a cylinder head in the state where a part of cylinder head cover concerning this embodiment was removed. It is the upper side figure and side view of an intake side structure in the valve gear which concerns on this Embodiment. It is an enlarged view of the cam part of the intake side structure shown in FIG. It is a top view from a tappet concerning this embodiment to an intake valve, and a sectional view which meets a BB line. It is a perspective view of a tappet and a tappet guide concerning this embodiment. It is the top view from the tappet of the valve operating apparatus which concerns on a reference example to an intake valve, and sectional drawing which follows CC line. It is a top view from a tappet and an intake valve concerning a modification of this embodiment, and a sectional view which meets a DD line.

  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 this embodiment, an example in which a three-stage switching type three-dimensional cam mechanism is applied to a multi-cylinder internal combustion engine of a motorcycle as a valve operating device will be described. In this embodiment, a four-valve internal combustion engine, which is a parallel four-cylinder internal combustion engine, has two valves on each of the intake side (IN) and the exhaust side (EX) for each cylinder is illustrated. 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 following description, the front of the vehicle is indicated by an arrow FR, the rear of the vehicle is indicated by an arrow RE, 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.

  With reference to FIG.1 and FIG.2, the cylinder head by which the valve gear which concerns on this Embodiment is mounted is demonstrated. FIG. 1 is a top view of a cylinder head according to the present embodiment. 2 is a cross-sectional view taken along line AA in FIG. FIG. 2 shows a state in which the internal combustion engine is in an upright position, but it is assumed that the internal combustion engine is actually mounted tilted forward.

  As shown in FIGS. 1 and 2, the cylinder head 10 accommodates a valve operating device therein, and a cylinder head cover (head cover) 12 is attached to make the housing space of the valve operating device a sealed structure. The cylinder head 10 is fixed to the upper part of the cylinder body 11. Four cylinders (not shown) are disposed in the cylinder body 11 in the vehicle width direction, and a piston (not shown) is accommodated in each cylinder so as to be able to reciprocate. The cylinder head 10 is formed with a pair of intake ports 14 for taking air into each cylinder and a pair of exhaust ports 15 for discharging exhaust gas from each cylinder. The intake port 14 opens to the vehicle rear side of the cylinder head 10, and the exhaust port 15 opens to the vehicle front side of the cylinder head 10.

  Also, the cylinder head 10 has a pair of intake valves 16 and a pair of exhaust valves 17 that open and close a pair of intake ports 14 and a pair of exhaust ports 15 corresponding to each cylinder, respectively, arranged in the arrangement direction of each cylinder. (See FIG. 4). The intake port 14 and the exhaust port 15 are communicated with a combustion chamber 13 formed by the bottom of the cylinder head 10 and the upper surface of the piston of each cylinder. The intake valve 16 and the exhaust valve 17 are driven and controlled at a predetermined timing by a valve gear provided at the upper part of the cylinder head 10 to appropriately control intake and exhaust for each cylinder.

  The valve gear includes a pair of camshafts 18 and 23 that are independent on the intake side and the exhaust side along the arrangement direction of the cylinders. The intake side camshaft 18 is rotatably supported by the cylinder head 10 and the cover member 35 via a bearing 19. A plurality of cams 20 are mounted on the camshaft 18 so as to be slidable in the rotation axis direction. The intake-side cam 20 is a three-dimensional cam and has a three-stage cam profile with different lift amounts along the rotational axis direction (see FIG. 5). Between the intake side cam 20 and the intake valve 16, the movement following the shape of the cam 20 is changed according to the contact position with the cam 20 which is in contact with the cam 20 and changes as the camshaft 18 rotates. A roller-type tappet 21 that transmits to is disposed.

  The exhaust-side camshaft 23 is rotatably supported by the cylinder head 10 and the cover member 34 via a bearing (not shown). A plurality of cams 25 are fixed to the camshaft 23, and each cam 25 on the exhaust side is constituted by a flat plate cam constituted by a curved surface parallel to the axial direction of the camshaft 23. Between the cam 25 on the exhaust side and the valve stem 17 a of the exhaust valve 17, the movement following the shape of the cam 25 is made depending on the contact position with the cam 25 which changes with the rotation of the camshaft 23. Direct hitting tappets 26 that transmit to each exhaust valve 17 are arranged. One end sides of the intake-side camshaft 18 and the exhaust-side camshaft 23 are connected to a crankshaft through a power transmission mechanism such as a sprocket 28 (see FIG. 5) and a cam chain. As the camshafts 18 and 23 rotate synchronously with the rotation of the crankshaft, the intake valve 16 and the exhaust valve 17 are driven.

  The valve stems 16a (16b) and 17a of the intake valve 16 and the exhaust valve 17 are guided by a valve guide 29 so as to be reciprocally movable. Further, a spring seat 31 is provided around each valve guide 29, and a spring retainer 30 is attached to end portions of the valve stems 16a (16b) and 17a. A valve spring 32 is mounted between the spring seat 31 and the spring retainer 30. The valve spring 32 biases the valve stems 16a (16b) and 17a toward the intake side cam 20 or the exhaust side cam 25. The intake valve 16 and the exhaust valve 17 are normally urged in the closing direction. At this time, the tappets 21 and 26 are in contact with the upper ends of the valve stems 16a (16b) and 17a. When the tappets 21 and 26 are pushed down against the elasticity of the valve spring 32 by the cams 20 and 25, the valve stems 16a (16b) and 17a are pushed down, and the intake valve 16 and the exhaust valve 17 are opened. As will be described in detail later, the valve spring 32 has a conical shape (bell shape).

  Next, the internal configuration of the valve gear will be described in detail with reference to FIGS. FIG. 3 is a top view of the cylinder head with a part of the cylinder head cover according to the present embodiment removed. FIG. 4 is a view showing an intake side configuration of the valve gear according to the present embodiment. 4A is a diagram in which a portion of the intake side configuration is extracted from FIG. 3, and FIG. 4B is a side view of FIG. 4A as viewed from the vehicle rear side (RE side). FIG. 5 is an enlarged view of the cam portion of the intake side configuration shown in FIG.

  FIG. 3 shows a state in which the cylinder head cover 12 is partially removed from the cylinder head 10. In this case, in the cam / camshaft unit which is a main component of the valve operating apparatus, the exhaust-side camshaft 23 (see FIG. 2) is completely covered by the cover member 34, and the intake-side camshaft 18 is covered by the cover. Part of the opening of the member 35 is exposed. A cam slide mechanism 4 that slides the cam shaft 18 is provided on the cover member 35, and the cam slide mechanism 4 is connected to the cam shaft 18 through an opening of the cover member 35. An accelerator motor 33 is mounted on the cover member 35 as a drive source for the cam slide mechanism 4.

  In the cam slide mechanism 4, a cam fork shaft 41 is disposed in parallel to the cam shaft 18. The cam fork shaft 41 is supported by five bearing portions 35 b provided on the cover member 35 so as to be slidable in the axial direction. Further, a ball screw 42 is arranged 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 provided near both ends thereof. A gear 44 is fixed to one end of the ball screw 42 and meshes with a pinion gear 45 of the output shaft of the accelerator motor 33. A slide nut 46 is screwed onto the ball screw 42.

  A nut fork 47 is connected to the slide nut 46. A cam fork shaft 41 is connected to the nut fork 47 via a base plate 47a. Four cam forks 48 are fixed to the cam fork shaft 41 corresponding to each cylinder. As described above, the slide nut 46 and the cam fork shaft 41 are connected, so that the cam fork 48 is driven by the power of the accelerator motor 33 and the cam 20 on the intake side is slid.

  As shown in FIG. 4, a plurality of cams 20 are slidably attached to the intake-side camshaft 18 corresponding to each cylinder. Each cam 20 is provided with a connecting portion 49 to which the cam fork 48 of the camshaft 18 is connected. Each cam 20 is slid in the direction of the rotation axis when the connecting portion 49 is operated by the cam fork 48. The cam 20 is a three-stage three-dimensional cam and is formed such 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 composed of three cam profiles that are three types of cam profiles for high load, medium load, and low load. There are three medium and low lift amounts and opening / closing timing.

  As shown in FIG. 5, the cam 20 has a curved surface shape parallel to the high-load, medium-load, and low-load rotation shafts (a portion that does not change in the cam rotation axis direction, hereinafter referred to as “flat portion”). And cam lobes 20a, 20b, and 20c, and cam lobes 20d and 20e that are inclined portions that gently connect the flat portions. Basically, the internal combustion engine of the present invention is operated in a state where the tappet 21 is pushed down by the cam lobes 20a, 20b, 20c of the flat portion, and the cam lobes 20d, 20e of the inclined portion are for switching the cam lobes 20a, 20b, 20c. It is a switching transition section. In this case, the cam operating angle and the lift timing can be changed simultaneously with the cam height. That is, in the three-stage three-dimensional cam of this embodiment, the cam operating angle increases as the valve lift amount increases, and the lift timing of the intake valve 16 also changes. By moving the cam 20 along the camshaft 18 and changing the contact position with the tappet 21 described later, the cam shape (height etc.) acting on the tappet 21 is switched in three stages. The lift amount, operating angle, and lift timing of the intake valve 16 can be variably controlled in three stages.

  Below each cam 20, a roller-type tappet 21 that opens and closes a pair of intake valves 16 corresponding to each cylinder is provided. The tappet 21 is guided by the tappet guide 22 so as to be capable of reciprocating along the axial direction of the valve stems 16a and 16b. As described above, when the cam 20 pushes down the tappet 21 against the elasticity of the valve spring 32, the tip of the tappet arm 39 formed on the tappet 21 presses the intake valve 16, and the intake valve 16 opens. It has become. The detailed configuration of the roller-type tappet 21 and the tappet guide 22 will be described later.

  In the valve operating apparatus configured as described above, the accelerator motor 33 is operated in accordance with the accelerator opening degree and the operating state of the motorcycle, and the cam fork shaft 41 is slid by the movement of the slide nut 46 as the ball screw 42 rotates. Is done. When the cams 20 are simultaneously slid by the cam forks 48 of the cam fork shaft 41, the lift amount of the cams 20 is switched in three stages. For example, when traveling at a low speed, the tappet 21 is brought into contact with the cam lobe 20c having a small lift amount (low cam height). When the engine speed is increased from this state, the cam 20 is slid in the rotational axis direction, the next stage cam lobe 20b comes into contact with the tappet 21, and the intake valve 16 is driven to open and close in the shape of the cam lobe 20b. As the engine speed further increases and the engine speed rises, the cam lobe 20a having the largest lift amount (high cam height) is brought into contact with the tappet 21, and the intake valve 16 is driven to open and close in the shape of the cam lobe 20a. On the other hand, at the time of deceleration, the lift amount is reduced by an operation reverse to the above.

  Next, the tappet unit applied to the engine according to the present embodiment will be described in detail with reference to FIGS. FIG. 6 is an enlarged view around the tappet 21 according to the present embodiment. 6A is a top view around the tappet 21, and FIG. 6B is a cross-sectional view taken along the line BB in FIG. 6A. FIG. 7 is a perspective view of the tappet 21 and the tappet guide 22 according to the present embodiment. FIG. 7A is a perspective view of the tappet and the tappet guide as viewed from above, and FIG. 7B is a perspective view of the tappet and the tappet guide as viewed from below. FIG. 8 is a top view of the vicinity of the tappet of the valve gear similar to FIG. 6 according to the reference example and a cross-sectional view taken along the line CC. In FIG. 6B, a rib 39c described later is omitted for convenience of explanation. Further, in FIG. 8, for convenience of explanation, the same reference numerals are given to components common to the present embodiment.

  As shown in FIG. 6, the tappet guide 22 is disposed above the pair of adjacent valve stems 16 a and 16 b, and guides the moving direction of the roller-type tappet 21 in the guide groove 50. The tappet 21 is disposed at an upper portion between the valve stems 16 a and 16 b in a state where a part is accommodated in the guide groove 50 formed in the tappet guide 22. The tappet guide 22 is fixed at an appropriate position of the cylinder head 10 by four screws (see FIG. 4) inserted into screw holes 51a to 51d provided at the four corners. The lower surface 52 of the tappet guide 22 is formed in a planar shape excluding the formation region of the guide groove 50 and constitutes an attachment surface for the cylinder head 10. The details of the guide groove 50 in the tappet guide 22 will be described later.

  The tappet 21 includes a tappet roller 36 formed in a generally donut shape, a core portion 38 that supports the tappet roller 36 via a bearing 37, and a pair of arms 39 (39a, 39a, 39b) that extend outward from the core portion 38. 39b). The pair of arms 39 (39a, 39b) are arranged so that their rotational axes are connected so as to connect the centers of the valve stems 16a, 16b, as shown in FIG. 6A when viewed from the axial direction of the valve stem 16a (16b). A tappet arm 39 extends in the left-right direction (direction toward the central axis of the valve stems 16a, 16b) from both side surfaces 36a, 36b (core portion 38) of the tappet roller 36, and the valve stem 16a, It is comprised so that 16b may be pushed down. 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 that is a flat portion parallel to the rotation axis of the roller and contacts the cam 20 is formed.

  An abutting portion 36c that abuts the cam 20 on the outer peripheral surface of the tappet roller 36 is directed toward one valve stem 16a within the outer peripheral surface range of the tappet roller 36 in the rotation axis direction of the tappet roller 36 (left-right direction shown in FIG. 6). It arrange | positions in the biased position (refer FIG. 6B). On the outer peripheral surface of the tappet roller 36, the abutting portion 36c has the maximum diameter, and the outer diameter gradually decreases with respect to the other valve stem 16b. In this example, the bearing 37 is a plurality of needle bearings arranged along the outer periphery of the core portion 38.

  The arms 39a and 39b have different lengths. The arms 39a and 39b are in a state in which a contact portion 36c (more specifically, the center of the contact portion 36c) where the tappet 21 and the cam 20 contact is disposed at the center between the pair of valve stems 16a and 16b. The tip of the arm 39 has a length that reaches the central axis of the valve stem 16a, 16b so that the valve stem 16a, 16b can be pushed down by the tip of the arm 39. In other words, the arms 39a and 39b have the same length between the valve stem 16a and the contact portion 36c and the length between the valve stem 16b and the contact portion 36c (L1 shown in FIG. 6B). Has a length of In the valve operating apparatus of the present embodiment, as described above, the contact portion 36c is disposed at the center between the pair of valve stems 16a and 16b, and the outer peripheral surface of the tappet roller 36 is biased toward the valve stem 16a. Accordingly, the tappet roller 36 itself is arranged at a position biased toward the valve stem 16b, and the arm 39a is configured to be relatively long and the arm 39b is configured to be short.

  The arms 39a and 39b extend to the upper ends of the valve stems 16a and 16b, respectively, and indirectly contact the upper ends of the valve stems 16a and 16b via the shim 40. In the valve gear according to the present embodiment, both end portions (tip portions) of the arms 39a and 39b constitute valve pressing portions that push down the upper ends of the valve stems 16a and 16b. Further, the tappet 21 of the tappet 21 is pushed by the cam lobe of the cam 20, so that the arms 39 a and 39 b push the valve stems 16 a and 16 b against the elasticity of the valve spring 32, thereby the intake valve 16. It functions as a valve lifter that opens the door. The shim 40 has a function of adjusting the tappet clearance.

  As shown in FIG. 6A, the rotation axis of the tappet roller 36 is arranged so as to connect the centers of the valve stem 16a and the valve stem 16b when viewed from the axial direction of the valve stems 16a and 16b. Thus, it is typically arranged at the same position as the height center of the arm 39 in the height direction. 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 to 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.

  As shown in FIGS. 6 and 7, the tappet guide 22 is formed with an opening 51 that avoids interference between the spring retainer 30 and the shim 40 and the tappet guide 22 in accordance with the positions of the valve stems 16 a and 16 b. . In addition, the tappet guide 22 has a guide groove 50 in a substantially cross shape so that the tappet roller 36 can operate along only the axial direction of the valve stems 16a and 16b (substantially up and down in an actual vehicle) in plan view. It is formed. Specifically, as shown in FIGS. 7A and 7B, the tappet guide 22 has a thickness direction of the tappet guide 22 extending along the radial direction of the tappet roller 36 (direction perpendicular to the rotation center axis). One guide groove 50A penetratingly formed on the other side, and the other guide penetratingly formed so as to extend along the longitudinal direction of the arm 39, that is, the axial direction of the camshaft 18 so as to intersect (orthogonal) the guide groove 50A. A groove 50B is formed. The guide groove 50 </ b> B reaches the opening 51 and communicates the guide groove 50 </ b> A and the opening 51. In the tappet 21, the tappet roller 36 and the arm 39 are accommodated in the guide grooves 50A and 50B, respectively. The opening 51 of the tappet guide 22 is opened around the end of the arm 39 of the tappet 21 accommodated in the guide groove 50.

  The spring retainer 30 attached to the valve stems 16a and 16b is disposed so as to face the opening 51 formed in the tappet guide 22 from below. A valve spring 32 is disposed between the spring retainer 30 and a spring seat 31 disposed at a predetermined distance. The valve spring 32 is composed of a different diameter spring whose outer diameter on the tappet 21 side (upper side shown in FIG. 6B) is smaller than the outer diameter on the intake valve 16 side (lower side shown in FIG. 6B). In the valve gear according to the present embodiment, the valve spring 32 has a small-diameter portion 32a on the tappet 21 side, a large-diameter portion 32b on the intake valve 16 side, and a generally conical shape (bell shape). Consists of a radial spring. For example, in the valve spring 32, the large diameter portion 32b can be formed at the portion where the diameter is the largest, and the small diameter portion 32a can be formed at the portion where the diameter is smaller than the large diameter portion 32b. Moreover, the small diameter part 32a can be comprised in the part where diameter becomes the smallest, and the large diameter part 32b can be comprised in the part where a diameter becomes larger than this small diameter part 32a. In the present embodiment, the former is assumed (see FIG. 6B).

  In the valve spring 32, the small diameter portion 32 a is provided on the tappet 21 side, while the large diameter portion 32 b is provided on the intake valve 16 side, so that the radial dimension of the spring retainer 30 is reduced compared to the spring seat 31. it can. Thus, the tappet guide 22 can be expanded in a region where the guide groove 50 (more specifically, the guide groove 50A) is formed, and a certain space is formed in the vicinity of the upper end portion (small diameter portion 32a) of the valve spring 32. it can. In the valve operating apparatus according to the present embodiment, the contact portion 36c of the tappet roller 36 is formed at the center between the pair of valve stems 16a and 16b by utilizing the space formed in the vicinity of the small diameter portion 32a. Adjust to be placed. Specifically, one arm 39a of the tappet 21 is lengthened while the other arm 39b is shortened, and the tappet roller 36 is biased toward the valve stem 16b, thereby being biased toward the outer peripheral surface. The contact portion 36c is disposed at the center between the pair of valve stems 16a and 16b.

  Thus, by arranging the contact portion 36c in the center between the pair of valve stems 16a and 16b, the positional relationship between the force point and the action point in the tappet 21 can be made a symmetrical arrangement structure. As a result, the arm portions 39a, 39b of the tappet 21 can equalize the force of pushing down the pair of valve stems 16a, 16b, so that the tappet 21 can be prevented from tilting and the situation where the valve lift timing is shifted can be prevented. Is possible. Further, the valve spring 32 has a conical shape in which the tappet 21 side has a smaller diameter than the intake valve 16 side, so that the space between the small diameter portion 32 a of the valve spring 32 is utilized to contact the tappet 21 and the cam 20. Since the position of the portion 36c can be adjusted, it is not necessary to increase the distance between the pair of valve stems 16a and 16b. As a result, it is possible to improve the deviation of the valve lift timing without increasing the distance between the pair of valve stems 16a and 16b with respect to the existing engine.

  If a general cylindrical shape (that is, a shape in which the diameter on the tappet 21 side and the diameter on the intake valve 16 side are the same diameter) is adopted for the valve spring 32, as shown in FIG. The dimensions in the radial direction of the spring seat 31 and the spring retainer 30 are approximately the same diameter. For this reason, when the length of the arm portions 39a and 39b is made the shortest in consideration of the width dimension of the tappet guide 22, the contact portion 36c on the tappet roller 36 is arranged biased toward the valve stem 16a. In this case, as a result of the positional relationship between the force point and the action point in the tappet 21 becoming asymmetrical, the force for pushing down the pair of valve stems 16a and 16b is not uniform, and the tappet 21 may tilt. In addition, since a space cannot be provided in the vicinity of the upper end portion of the valve spring 32, problems such as interference occur and it is difficult to adjust the position of the contact portion 36c. On the other hand, in the valve gear according to the present embodiment, the valve spring 32 is formed in a conical shape, so that the space for arranging the tappet roller 36 that enables the position adjustment of the contact portion 36c can be expanded. The position of the contact portion 36c can be adjusted without increasing the distance between the valve springs 16a and 16b.

  In particular, in the valve gear according to the present embodiment, the tappet roller 36 has a part (part on the valve stem 16b side) having a large diameter of the valve spring 32 as viewed from the axial direction of the valve stems 16a and 16b. It overlaps with the part 32b (refer FIG. 6B). In this way, by arranging a part of the tappet roller 36 so as to overlap the large diameter portion 32b, a pair of the tappet rollers 36 can be effectively formed while utilizing the dimensional difference between the small diameter portion 32a and the large diameter portion 32b of the valve spring 32. It is possible to arrange roller type tappets in a balanced manner at a distance between the valve stems 16a and 16b.

  The upper surface of the tappet guide 22 is formed substantially flat as shown in FIG. 7A. On the other hand, on the lower surface 52 of the tappet guide 22, as shown in FIG. 7B, a cross-shaped guide groove 50 made up of guide grooves 50A and 50B is extended downward (in the axial direction of the valve stems 16a and 16b). Two leg portions 53 are provided so as to protrude. The tappet 21 moves up and down corresponding to the valve lift when the intake valve 16 is opened and closed. The cross-shaped guide groove 50 has at least a sufficient length in the vertical direction so that the tappet roller 36 and the arm portion 39 can be guided from both sides when the tappet 21 moves up and down. The guide groove 50 and the leg portion 53 constitute a guide portion of the tappet guide 22. 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).

  As shown in FIG. 7B, each leg 53 is provided from the guide groove 50B along the side edge of the guide groove 50A. Each leg portion 53 is configured such that the thickness dimension increases as the distance from the guide groove 50B increases. The thickest part of the leg 53 is a valve attached to the valve stem 16b when viewed from a direction perpendicular to the plane passing through the axis of the pair of valve stems 16a and 16b (perpendicular to the plane of FIG. 6B). The spring 32 protrudes to a position where it overlaps with the small diameter portion 32a of the spring 32 (see FIGS. 6A and 6B).

  Since the leg portion 53 of the tappet guide 22 overlaps with the small diameter portion 32a of the valve spring 32 when viewed from the direction perpendicular to the plane including the axis of both the valve stems 16a and 16b as described above, The formation area of the leg portion 53 can be secured by utilizing the space formed in the vicinity of the small diameter portion 32a. Thereby, even when the tappet roller 36 is disposed at a biased position on the one valve stem 16b side, the thickness dimension of the leg portion 53 can be increased, and its rigidity can be ensured. And the tappet 21 at the time of a reciprocating motion can be hold | maintained in an appropriate attitude | position, and it becomes possible to make the tappet 21 reciprocate smoothly along the axial direction of valve stem 16a, 16b.

  In addition, since each leg part 53 is provided so that it may extend along the side edge part of the guide groove 50A from the guide groove 50B, the leg part 53 does not exist in the position corresponding to the guide groove 50B. In other words, in the guide portion composed of the guide groove 50 and the leg portion 53 of the tappet guide 22, a portion located between the pair of valve stems 16a and 16b is removed. For this reason, a situation in which a part of the tappet 21 interferes with the guide portion of the tappet guide 22 can be reliably prevented, and the tappet 21 can be smoothly reciprocated, and interference between the guide portion and the valve spring 32 can be prevented. It has been avoided. 6A, the portion close to the guide groove 50B of the leg portion 53 is formed so that the outer surface is on the tappet roller 36 side as compared with the far portion, and the valve spring 32 is provided. And a portion far from the guide groove 50B goes around the valve spring 32 and overlaps with the small diameter portion 32a of the valve spring 32 as described above.

  Further, ribs 39c are provided on the lower surfaces of the base end portions of the arm portions 39a and 39b arranged between the leg portions 53 along the direction in which the arm portions 39a and 39b extend (FIG. 7B). reference). These ribs 39 c serve to reinforce the arm portions 39 a and 39 b and are provided on the lower surfaces of the arm portions 39 a and 39 b and the side surfaces of the core portion 38. These ribs 39c are arranged in a space formed in the vicinity of the small diameter portion 32a by making the valve spring 32 conical when the tappet 21 is accommodated in the tappet guide 22. That is, in the tappet 21 according to the present embodiment, the rib 39c for reinforcing the tappet 21 is provided by utilizing the space formed in the vicinity of the small diameter portion 32a by making the valve spring 32 conical.

  As described above, since the ribs 39c are provided on the lower surfaces of the base end portions of the arm portions 39a and 39b of the tappet 21 along the extending direction of the arm portions 39a and 39b, the rigidity of the arm portions 39a and 39b is improved. Since the rigidity of the tappet 21 can be ensured, the valve stems 16a and 16b can be appropriately pushed down against the urging force of the valve spring 32. Here, a case where one rib 39c is provided on each of the lower surfaces of the arm portions 39a and 39b is shown, but two or more ribs 39c may be provided side by side.

  In the tappet unit configured as described above, the contact portion 36c between the tappet 21 and the cam 20 is disposed in the center between the pair of valve stems 16a and 16b when viewed from the axial direction of the valve stems 16a and 16b. Therefore, the pressing force from the cam 20 can be applied to the tappet 21 along the axial direction of the valve stems 16a and 16b, and the situation where the tappet 21 tilts can be suppressed. On the other hand, since the valve spring 32 is constituted by a different diameter spring having a smaller diameter on the tappet 21 side than the intake valve 16 side, the tappet 21 and the cam 20 are utilized by utilizing the space near the small diameter portion 32a of the valve spring 32. Therefore, the distance between the pair of valve stems 16a and 16b does not increase. As a result, it is possible to improve the deviation of the valve lift timing without increasing the distance between the pair of valve stems 16a and 16b.

  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, the tappet 21 according to the above-described embodiment has a left-right asymmetric shape, and the arm portions 39a and 39b are made different in length so that the contact portion 36c with the cam 20 is connected to the pair of valve stems 16a and 16b. The case where it arrange | positions in the middle of is demonstrated. However, the configuration of the tappet 21 is not limited to this, and can be changed as appropriate. For example, as shown in FIG. 9, the tappet 21 may have a symmetrical shape and the abutting portion 36 c may be disposed at the center of the tappet roller 36. Even in this case, as in the above-described embodiment, the space between the pair of valve stems enlarged by the small diameter portion of the valve spring is utilized, and the roller of the roller-type tappet is expanded in the enlarged space. It is possible to arrange a part of the part or a part of the guide part so as to improve the deviation of the valve lift timing without increasing the distance between the pair of valve stems 16a and 16b. Become.

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

16 intake valve 16a, 16b valve stem 20 cam 20a-20e cam lobe 21 roller type tappet 22 tappet guide 30 spring retainer 31 spring seat 32 valve spring 32a small diameter part 32b large diameter part 36 tappet roller 36a, 36b roller side face 36c contact part 37 Bearing 38 Core 39, 39a, 39b Arm 39c Rib 40 Shim 50, 50A, 50B Guide groove 51a-51d Screw hole 52 Lower surface of tappet guide 53 Leg

Claims (5)

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 arranged at the upper part between the pair of valve stems, and the roller-type tappet is pushed by the cam to reciprocate. In the valve operating device of the internal combustion engine configured such that one roller type tappet opens a pair of valves by pushing down the valve spring against the elasticity of the valve spring.
The valve spring is composed of a different diameter coil spring in which the outer diameter on the roller-type tappet side is smaller than the outer diameter on the valve side,
A valve operating apparatus for an internal combustion engine, wherein a contact portion between the roller-type tappet and a cam is disposed in the center between the pair of valve stems when viewed from the axial direction of the valve stem.   The operation of the internal combustion engine according to claim 1, wherein a part of a roller portion of the roller type tappet is disposed at a position overlapping with a large diameter portion of the valve spring when viewed from the axial direction of the valve stem. Valve device.   2. The guide part of the tappet guide and the small diameter part of the valve spring are arranged so as to overlap each other when viewed from a direction perpendicular to a plane including the axis of both of the pair of valve stems. Or the valve operating apparatus of the internal combustion engine of Claim 2.   4. The valve operating apparatus for an internal combustion engine according to claim 3, wherein a portion located between the pair of valve stems is removed from the guide portion of the tappet guide.   The roller-type tappet has a pair of arm portions that push down the upper end portions of the pair of valve stems, and a rib is provided on the lower surface of the base end portion of the arm portions along the direction in which the arm portions extend. The valve operating apparatus for an internal combustion engine according to any one of claims 1 to 4, wherein the valve operating apparatus is provided.

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