Direct driven valve operating system for an internal combustion engine

Abstract: The present invention relates to a direct driven valve operating system. It comprises a valve lifter (13) composed by an outer pad (14) and disposed under pressure of a camshaft (11) in the outer face of the cover portion (13b) of the cylindrical lifter body (13) of light alloy, and a tip member (16) against which one end of a valve shaft (6a) is abuted and which rests in a mounting hole formed on the inside of said cover portion (13b), and in which valve lifter (13) said mounting hole and tip member (16) are circular-shaped and said tip member (16) is stuck to the cover portion (13b) by subjecting the peripheral edge portion of said mounting hole to plastic flow within a groove formed on the peripheral wall of said tip member (16).

Description: The present invention relates to a direct driven valve operating system for an internal combustion engine comprising a cup-shaped valve lifter having a cylindrical body and a cover portion made of a light alloy, said cover portion substantially closing one end of the cylindrical body and having an outer surface for supporting an outer pressure pad, to be actuated by a valve operating cam lobe of a camshaft and an inner surface for supporting a tip member in a mounting hole formed in said cover portion to engage an upper end of a valve stem of an associated intake or exhaust valve, said tip member having a groove fitted with said cover portion by plastic deformation thereof. A direct-acting valve system is widely used in a 4-cycle engine of nowadays for directly urging intake and exhaust valves to opening and closing positions using intake and exhaust cam shafts through a valve lifter in order to obtain increased number of revolution and increased power output. For the purpose of reduction in fuel cost, it is required for the horse power loss to be decreased by lightening the direct-acting valve system as such as possible. Conventional steel-made valve lifter has a problem that since it has a large inertia mass, such a requirement can hardly be met, and additionally, it has a small damping ratio so that its metallic noise tends to remain with subsequent increase of noises generated by the engine mechanism. Much attention is lately given to a valve lifter made of aluminium alloy which may be used in place of such a steel-made valve lifter. Because the aluminium alloy is of a relatively soft quality, a hard tip member made of carbon steel is disposed in an area against which a valve shaft is abutted by its end portion. However, with said tip member used, the cover member of the valve lifter kept in contact with the tip member is readily subjected to wear by eventual rotation or loosening of the tip member due to engine vibration or difference in the amount of thermal expansion. As a result, the clearance between the cam and outer pad may vary, thus causing foreign noises, damage of the valve lifter, or decrease in the lifting amount. In order to prevent the tip member to rotate or loosen, for example, Japan Unexamined Patent Application 63-147907 has proposed a structure of avoiding any rotation of the tip member by forming a recess defined on the cover portion of the valve lifter and a tip member received by the recess with odd shapes (not round)such as oval, star-like configurations, and subjecting the peripheral edge portion of said recess to caulk ing. As shown in figs. 17(a), (b), for example, an oval-shaped recess 41 is formed on the inside of a cover member 40a of a lifter body 40 made of aluminium alloy, a tip member 42 which is also of an oval type is disposed within said recess 41;with this arrangement, the tip member 42 may be locked by caulking the peripheral edge portion of said recess 41. In such a conventional fixing structure, however, there lie problems that a high degree of accuracy of dimension is hardly achieved due to the fact that a star-like tip member is produced by press-punching a steel plate, and the resultant tip member is liable to become distorted by reason of its odd shape, when the tip member is subjected to heat treatment such as carburizing for obtaining hardness and wear resistance which may cause dispersion in dimension. As shown in figs. 18(a) (b), in the case of said prior art valve lifter, the cover member 40a is machined by an end mill M of a small diameter being in rotary motion to form the recess 41, so that it is difficult to form a right-angled face on the peripheral side and a flat face on the bottom of said recess 41, thus resulting in a low degree of accuracy. Moreover, since the processing procedure by said end mill is carried out seprately from the cutting operation by a lathe, the machining efficiency is so much reduced. A valve operating system of the type as indicated above is known from JP-A-20 40 008. However, a rather large volume of the cover portions of the lifter body is deformed according to said document, which results in a rather weak joint and a low accuracy of the position of the tip member. Accordingly, it is an objective of the present invention to provide a valve operating system, wherein a tip member of a valve lifter may be fixedly secured to a lifter body of light alloy with increased dimensional accuracy and machining accuracy and efficiency. According to the present invention, said objective is performed in that said tip member is provided with a peripheral punch portion adjacent said groove, which is abutted against a peripheral edge portion of said cover portion defining said mounting hole for plastically deforming said peripheral edge portion to flow into said groove. According to a preferred embodiment of the present invention, the mounting hole of the lifter body and the tip member are shaped circularly for ease of machining. According to another preferred embodiment of the present invention, the tip member is made of a material which is harder than that of the lifter body and is provided with a punch portion for subjecting the peripheral edge portion of the mounting hole to plastic deformation. The advantageous effects of the present invention are such that the fixation of the tip member by plastic deformation of the surrounding portion of the lifter body enables to prevent any rotation and loosening of the tip member, due to engine vibration during the lifetime of the lifter body and prevents any wear of the valve lifter. Moreover, machining and producing the tip member from a prefabricated rod material of circular cross-section is facilitated as well as the provision of the fixing mounting hole at the side of the lifter body. The intimate contact between the tip member and the surrounding cover portion of the lifter body established by the plastic flow of material from the peripheral edge portion of the mounting hole does not only prevent any rotation and loosening of the tip member as a result of engine vibration, but also avoids any possible variation of a clearance between the cam lobe and the outer pad, so that no foreign matters can enter and damage the valve lifter or decrease the lifting stroke. Due to the arrangement and fixing of the tip member through the plastic flow of material, the mounting hole and the tip member, as already mentioned, can be made round, thereby facilitating the production of the tip member by machining a round rod through a lathe and ensuring improvement of the dimensional accuracy unlike the case in which conventional odd-shaped tip members are produced by press operation. Moreover, dimensional dispersion is reduced which conventionally is caused by torsion stress which may arise in the carburizing treatment. As, accordingly, the mounting hole of the lifter body can also be made circular, and therefore, the same procedural steps as in the turning of the lifter body itself is applicable, and improved machining accuracy and efficiency can be achieved as compared with the conventional machining process by End Mill. As the plastic deformation is performed by a punch portion of the tip member itself, the connection strength can be further increased, no mark of a pressing mould is left behind in the peripheral edge portion of the mounting hole and the lifetime of the pressing mould or dye can be enhanced. Further preferred embodiments of the present invention are laid down in other sub-claims. In the following, the present invention will be explained in greater detail by means of several embodiments thereof in conjunction with the accompanying drawings, wherein: Fig. 1 is a cross sectional view showing the cylinder head for explaining the valve lifter for engine in accordance with the first embodiment of the present invention, Fig.2 is a cross sectional view showing the state of the lifter body of the first embodiment connected with the tip member, Fig.3 is an enlarged sectional view of the connection of the first embodiment, Fig. 4 is an exploded sectional view showing the sequence in which the connection of the tip member is achieved, Fig.5 is a cross sectional view showing the process of connection by using a work punch of the tip member of the first embodiment, Fig. 6 is a view showing the steps of connection of the tip member of the first embodiment, Fig. 7 is a graph showing the effects in weight-saving by light alloy-made valve lifters of the first embodiment, Fig. 8 is a cross sectional view of a tip member connected by using a mold-punch in the first embodiment, Fig. 9 is a cross sectional view of a head cylinder shown for descriving the valve lifter for engine in accordance with the second embodiment of the present invention, Fig. 10 is a cross sectional front view of the valve lifter of the second embodiment, Fig. 11 is a cross sectional front view showing the process for exchange of the valve lifter of the second embodiment, Fig. 12 is a cross sectional front view of a variation of the valve lifter of the second embodiment, Fig. 13 is a cross sectional front view of another variation of the valve lifter of the second embodiment, Fig. 14 is a plan view of further variation of the valve lifter of the second embodiment, Fig. 15 is a cross sectional front view of further variation of the valve lifter of the second embodiment, Fig. 16 is a cross sectional front view of another variation of the valve lifter of the second embodiment, Fig. 17 is a view of a prior art connection structure for tip member, and Fig. 18 is a view showing the process of machining a mounting hole of a conventional cover portion. Figs. 1 - 7 illustrate a valve lifter for engine in accordance with a first embodiment of the present invention. Referring to fig. 1, the numeral 1 designates a cylinder head of a 4-cycle water-cooled engine, which includes a direct-acting valve system. The cylinder head 1 has a combustion chamber 2a provided in a recessed form on the lower side thereof and including an exhaust vent 3 and an intake-vent 4. These vents have an exhaust valve 5 and an intake valve 6 respectively, the valves are supported at their shafts 5a and 6a by a valve guide 7 in such a manner that said shafts may be moved in a vertical direction. Retainers 9 are secured to the upper end of the shafts 5a, 6a of the respective valves 5, 6 via cotters 8, and a valve spring 10 is interposed between said retainer 9 and a spring washer 2b of the cylinder head 2. The exhaust and intake valves 5, 6 are biased by the valve spring 10 so as to block said vents. There are provided exhaust and intake cam shafts 11,11 above said exhasut valve 5 and intake valve 6 respectively. Each of the cam shafts 11 is rotatably supported by the upper face of said cylinder head 2 so that the former may be driven for rotation by a crank shaft not shown. Each cam shaft 11 has a cam 11a formed in the portion corresponding to each of valves 5, 6, so that said cam shaft 11a may rotate to directly drive each valves 5, 6 into opening and closing positions via a valve lifter 12. Said valve lifters 12, which are mounted in the upper ends of the shafts 5a, 6a of the valves 5, 6, each comprise lifter bodies 13, outer pads 14 placed on the lifter bodies 13, and tip members 16 on the insides of the lifter bodies 13. Each of said lifter bodies 13 is of a covered tubular type, having a cylindrical skirt 13a associated integral with a cover portion 13b, the skirt 13a being maintained slidably by a guide hole 2c formed in the cylinder head 1. Said lifter body 13 is here made from a light alloy, specifically such as aluminium alloy, magnesium alloy, or titan alloy. Said skirt 13a has a hard layer covering the outer periphery thereof, the hard layer being made by depositing a molybudenum disulfide on a hard Cr-plated or anodizing processed porous layer. Said lifter body 13 has a large-diametered recess 13d formed on the upper side of the cover portion 13b, with the outer pad 14 being releasibly mounted in the recess 13d. The outer pad 14, which is made of a very hard steel, extends with its upper portion beyond the pheripheral edge portion 13c of the recess 13d, and is in contact with said cam 11a in a slida ble manner. The outer pad 14 is selectivly set so that the clearance between the outer pad 14 and cam 11a may be equal to a predetermined value. The adjustment of clearance is achieved by forcing down the pheripheral edge portion 13c of said lifter body by means of a jig to produce a clearance between said lifter body 13 and cam shaft 11, and then an exchange takes place for another outer pad having a different thickness. Additionally, the cover portion 13b of said lifter body 13 has a small-diametered recess (mounting hole) 15 formed on the inside thereof. Said tip members 16 are positioned in the recesses 15, and abut against the upper ends of the shafts 5a, 6a of said valves 5, 6. Each of said tip members 16, in the form of a steel disk, is composed of a connection 16a positioned within said recess 15 and a punch portion 16b formed integral with the former, the punch portion 16b being intended to subject the peripheral edge portion 13e of said recess 15 to plastic deformation. Said connection 16a has an annular groove 16c formed on the outer peripheral face thereof and having a part of the peripheral edge portion 13e of said recess 15 fitted therein by an operation based on plastic deformation, whereby said tip member 16 has been fixed to the cover portion 13b. The process of fixing said tip member 16 will be described with reference to figs. 4 - 6. Firstly, the connection 16a of the tip member 16 is inserted in the recess 15 of the cover poortion 13b (see figs.4, 6(a)). Then, a lower punch A is inserted in the recess 13d for pad of the cover portion 13b, while a upper punch B is brought into contact with the upper portion of the tip member 16, which will be exerted pressure by the upper punch B. Subsequently, the punch 16b of said tip member 16 is abutted against the peripheral edge portion 13e of the recess 15 (see fig.6 (b)), and if further pressure is applied to the tip member 16, an area near the abutment between the peripheral edge portion 1 3e and the punch 16b is subjected to plastic deformation until the resultant deformed part a flows into said annular groove 1 6c (see fig.6(c)). And if the application of pressure is stopped at the time when the tip member 16 reaches the bottom face of the recess 15, the tip member 16 is found to be in a complete connection with the cover portion 13b (see figs.5 and 6 (d)). In accordance with the first embodiment, the connection between the tip member 16 and the cover portion 13b effected by putting and fitting the plastic-deformed peripheral edge portion 13e of the recess 15 of the light alloy-made lifter body 13 in the groove 16 of the tip member 16 may avoid any rotation or looseness caused by the vibration of engine or difference in thermal expansion, as well as any variation of the clearance between the cam 11a and outer pad 14, thereby resulting in further avoidance of any generation of foreign noises, damage of the valve lifter, or decrease of lifting amount. Furthermore, the employment of the structure wherein said tip member 16 is securedly connected with the lifter body 13 by the use of the plastic flow or metal flow allows the use of the tip member 16 which is round, and has been made from a lathe-machined round rod easily and accurately; such a tip member may have an increased accuracy in dimension as compared with a press molded tip member in odd-shape, and with a decreased dimensional dispersion resulted. Additionally, the recess 15 of said cover portion 13b may be used in a round shape, and therefore, the tip member can be formed concurrently with a lathe-machining of said lifter body, which may avoid the necessity of the conventional end milling, with so much an improvement of the processing efficiency occurred. Furthermore, the first embodiment employs the so-called work-punching process in which the peripheral edge portion 13e of said recess 15 is subjected to plastic flow by the punch 16b of the tip member 16. This permits increase of the connection strength with no trace of the upper press punch B left behind and provision of an upper punch B with a flat pressing surface, thereby ensuring a long upper punch life. Moreover, in the first embodiment, since the light alloy-made lifter body 13 is utilized, the entire acting valve system may be made light in weight, and thus, it may contribute to increase of power output on one hand, and to reduction of fuel cost on the other hand. In this connection, as shown in fig. 7, the inertia mass of the steel valve lifter was almost 30 grs in each of the components constituting the acting valve system. Contrary to this, a replacement by an aluminum alloy-made valve lifter represented more or less 40% reduction in weight for the valve lifter alone, and about 10% less in weight for the overall acting valve system. In the first embodiment, the connection of the tip member 16 with the lifter body 13 using the work punching process was described by way of example, but such a connection may be also carried out by mold punching process as shown by fig. 8 in the present invention. This particular process involves inserting a disk-like tip member 20 having a groove 20a on the outer periphery thereof in the recess 15 of the cover portion 13b for proper positioning, and applying pressure to the peripheral edge portion 13e of said recess 15 by means of a metal mold 21 having an annular ridge 21a, which may cause part of the peripheral edge portion 13e of said recess 15 to be plastic-deformed to flow into the groove 20a of said tip member 20 , thus leading to the connection of the tip member 20 with the lifter body. Figs. 9 - 11 are intended to illustrate a second embodiment of the invention. This is an example of application of the so-called non-edge typed valve lifter 12 wherein the outer pad 14 is arranged on the cover portion 13b of the light alloy-made lifter body 13 for extension of the cam-sliding plane. Said valve lifter 12 is mounted on the upper end of said valve shaft 6a, comprising lifter body 13, outer pads 14 disposed on the outside and inside of the lifter body respectively, and tip member 16. Said lifter body 13 is of a covered tubular type, having an opening formed on the upper end of the cylindrical skirt 13a and closed by the cover portion 13b, and the skirt 1 3a is slidably retained by the guide hole 2c defined in said cylinder head 1. Said lifter body 13 is made of a light alloy, such as aluminum alloy, magnesium alloy, or titan alloy. Said skirt 13a has a hard layer formed on the outer periphery thereof, the hard layer being made by depositing a molybudenum disulfied on a hard Cr-plated or anodizing processed porous layer. Said tip member 16, which is made of steel, comprises a rod-like positioning element 16a and a pressing portion 16d in the form of a disk formed integral with the lower end of the positioning element 16a, and this pressing portion 16d abuts against the upper end of the valve shaft 6a of said intake valve 6. An annular groove 16c is formed on the outer periphery of the side of the pressing portion 16d of said positioning element 16a, and the punch 16b for subjecting one part of the cover portion 13b to plastic deformation is provid ed in anannular and stepped configuration at the border area b etween said annular groove 16c and the pressing portion 16d. A plastic flowed portion a resulting from the plastic deformation by said punch 16b of one part of cover portion 13b is fitted in said annular groove 16c, whereby said tip member 16 is fixedly attached to the cover portion 13b of said lifter body 13. The positioning element 16a of said tip member 16 protrudes upwardly with its top end from said cover portion 13 b. Said outer pad 14 is placed on a pad resting surface of said cover portion 13b, namely a flat upper face of said cover portion 13b, and the projected upper end of said positioning element 16a is received by a positioning hole 14a extending through the centeral portion of the flat upper face of the cover portion 13b, which arrangement serves to prevent a lateral movement of said outer pad 14. The top end face of said positioning element 16a is positioned somewhat below short of the upper face of the outer pad 14. The diameter d1 of the outer pad 14 is set to be a little smaller than the diameter d2 of the cover portion 13b of said lifter body 13. The difference between the both diameters is large enough to allow the contact with a stopper tool for locking the valve lifter 12 to a low position to which the valve is destined at the exchange of the outer pad. This causes the peripheral edge portion of the pad resting face of said cover portion 13b to be exposed to the cam shaft side by the amount of difference between the diameters, and the exposed portion provides a tool receiving portion b. Also, in the second embodiment, the tip member 16 is secured to the cover portion 13b by the aid of the plastic flow (or metal flow), thereby to prevent said tip member 16 from getting loose. In the instant embodiment, the exchange of the tip member 14 is performed by dropping the valve lifter 12 by the rotating cam shaft, interposing the tool T1 between said valve lifter 12 and cam shaft 11, and raising the portion of said outer pad 14 opposite to said stopper T1 by a removal tool T2 so that the outer pad 14 can be removed to substitute another outer pad with a different thickness, as shown in fig.11. In accordance with the second embodiment, the provision of the tool receiving portion b by having the outer pad 14 which is a little smaller than the cover portion 13b in diameter permits the exchange of outer pad by the use of an edgeless valve lifter and with the cam shaft 11 being maintained, thus to ensure an improvement in efficiency of the clearance adjustment. In the second embodiment, the positioning hole 14a destined to receive the positioning element 16a of the tip member 16 was referred to as its inserting into the outer pad 14, but this positioning hole may not be so deep as to extend through the outer pad 14, as seen in a positioning element 14a shown by figs.12 and 13. With regard to the process of fixing the tip member, a tip member 16' may be inserted into the fixing hole of the cover portion 13b from outwardly of the lifter body 13, as in fig. 13. In the second embodiment, the tool receiving portion b originates from the provision of the outer pad 14 being slightly smaller than the cover portion 13b in diameter, but this specific tool receiving portion can be created by other process. As illustrated in figs.14 and 15, for example, the outer pad 14 is made equal to the cover portion 13b in diameter, and the outer pad 14 is formed with a notch 14b, which provides a tool receiving portion b located outermost. The provision of such a tool receiving portion b formed by cutting part of the outer pad 14 makes it possible to realize the pad exchange even in the case of the outer pad having an identical diameter to that of the cover portion 13b, which may render the contact surface of a cam so much longer. Furthermore, the second embodiment set forth the arrangement such that all of the loads acting on the outer pad 14 is destined to be received by the lifter body 13 on the upper surface, but the tip member 13 may also share this load, as shown in fig. 16. There is provided a tip mounting hole 32 formed to extend through the axis ccnter of a cover portion 30a of a lifter body 30, and a positioning element 33a of a disk -shaped tip member 33 consisting of said positioning element 3 3a and a pressing portion 33b is received by said mounting hole 32. The base of the positioning element 32a is larger than its upper end portion in diameter. This top end portion projects from the top face of said cover 30a, and a positioning hole 31a of said outer pad 31 is fitted on this top end portion. The base of said positioning element 33a has a groove 33c formed thereon. The tip member 33 is connected to the cover portion 30a by subjecting a peripheral edge portion 30b of said mounting hole 32 to plastic flow so that the peripheral edge portion 30b flows into said groove 33c. Also, in said variation of example shown by fig. 16, a similar effect to that of said second embodiment may be obtained by the tip member 33 which has been fixedly connected by virtue of the plastic flow process. Additionally, loads acting on said outer pad 31 may be received not only by the lifter body 30, but also by the tip member 33. As described above, in accordance with the second embodiment and its variations, said tip member 33 functions as a means to position the outer pad 31, thereby to avoid the necessity of the recess intended for the outer pad 31, with the result that the outer pad 31 can have a larger diameter than the counterpart in the first embodiment.

Claims: Direct driven valve operating system for an internal combustion engine comprising a cup-shaped valve lifter (12) having a cylindrical body (13a, 30) and a cover portion (13b, 30a) made of a light alloy, said cover portion (13b, 30a) substantially closing one end of the cylindrical body (13a, 30) and having an outer surface for supporting an outer pressure pad (14), to be actuated by a valve operating cam lobe (11a) of a camshaft (11) and an inner surface for supporting a tip member (16, 33) in a mounting hole (15, 32) formed in said cover portion (13b, 30a) to engage an upper end of a valve stem (5a, 6a) of an associated intake or exhaust valve (5, 6), said tip member (16, 33) having a groove (16c, 33c) fitted with said cover portion (13b, 30a) by plastic deformation thereof, characterised in that said tip member (16,33) is provided with a peripheral punch portion (33b, 16b) adjacent said groove (16c, 33c), which is abutted against a peripheral edge portion (13e,30b) of said cover portion (13b,30a) defining said mounting hole (15) for plastically deforming said peripheral edge portion to flow into said groove (16c, 33c). Valve operating system as claimed in claim 1, characterised in that said tip member (16, 33) comprises two peripheral grooves (16c,33c) to accommodate therein the deformed material of the cover portion (13b, 30a). Valve operating system as claimed in claims 1 or 2, characterised in that said tip member (16,33) comprises a steel disc having a connection portion (16a, 33a) adjacent said flange-like punch portion (16b, 33b). Valve operating system as claimed in at least one of the preceding claims 1-3, characterised in that said connection portion comprises two peripheral grooves of triangular cross-section. Valve operating system as claimed in at least one of the preceding claims 1-4, characterised in that said tip member (16,33) is circular in cross-section. Valve operating system as claimed in at least one of the preceding claims 1-5, characterised in that said tip member (16,33) is made of a material harder than that of the surrounding cover portion of the valve lifter (12,30). Valve operating system as claimed in at least one of the preceding claims 1-6, characterised in that the inner surface of the cover portion defines an inwardly projecting boss section wherein the stepped mounting hole (15) is recessed to receive the tip member (16,31). Valve operating system as claimed in at least one of the preceding claims 1-7, characterised in that said outer surface comprises a recess for accommodating the steel outer pressure pad (14,31) therein, which projects upwardly from said outer surface. Valve operating system as claimed in at least one of the preceding claims 1-7, characterised in that said outer surface of the cover portion is flat forming an outer pad resting surface, said outer pressure pad being fixed by said tip member (33) from below. Valve operating system as claimed in claim 9, characterised in that the cover portion has a mounting through hole in alignment with a positioning hole extending through the outer pad (14,31), and that the tip member comprises an engagement portion at the front end of the connection portion engaging said positioning hole of the outer pressure pad (14,31). Valve operating system as claimed in claims 9 or 10, characterised in that said positioning hole (14a) is a through hole or a blind hole. Valve operating system as claimed in at least one of the preceding claims 9-11, characterised in that said tip member (33) has a shoulder abutting against said outer pad (31) to distribute loads acting on said outer pressure pad (31) from above to the cover portion (30a) and said tip member (33).

Inventors: MORI KAZUAKI, MORI, KAZUAKI
Applicants: YAMAHA MOTOR CO LTD, YAMAHA HATSUDOKI KABUSHIKI KAISHA
Application year: 1992
Main classification: F01L1
IPC codes: B21K25, F02B75, F01L1