Title of Invention

"A DIRECT-DRIVE INTERNAL COMBUSTION ENGINE"

Abstract

This invention concerns to a direct-drive internal combustion engine provided with valve lifters that are between a camshaft and inlet and exhaust valves for imparting pressure to the inlet and exhaust valves in an axial direction by following a rotation of said camshaft, the engine comprising: a cylindrical head portion; a cylindrical head cover portion; a cam chamber provided in the cylinder head portion and the cylinder head cover portion; said camshaft being disposed in said cam chamber; said camshaft having cam profiles thereon; wherein a valve lifter is disposed in the cylinder head portion and provided between the cam profile and inlet and exhaust valves instrument introducing holes running from the outside of cylinder head portions towards a contact area of the cam profiles and the valve lifters.

Full Text

The present invention relates to a direct-drive internal combustion engine which is provided with cam peep holes into which a fixture for measuring the tappet clearance of a camshaft can be inserted. For example, there is disclosed in Japanese Patent Laid-Open Publication No. Sho 60-192202 a construction which has a hole for introducing a tappet clearance measuring fixture and a relief for a cam profile provided in the cylinder head separately. In addition, provision in this way of a hole for introducing a tappet clearance measuring fixture may need to have a packing surface provided for sealing on a camshaft. (Problems to Be Solved by the Invention) In the example cited above, it is necessary to separately work out a hole for introducing a tappet clearance measuring fixture and a relief for a cam profile, which results in an increased number of man-hours. Moreover, provision of a packing surface on a camshaft contributes to making a seal construction complicated . Thus, it is the object of the invention to solve those problems. A direct-drive valve engine of a first feature of the invention is, in order to solve the foregoing problems, an internal combustion engine with valve lifters between a camshaft and inlet and exhaust valves for imparting pressure to inlet and exhaust valves in an axial direction by following a rotation of the camshaft, is provided with an instrument introducing holes running from the outside toward a contact area of the camshaft and the valve lifters. A direct-drive valve engine of a second feature of the invention is the engine of the first feature provided with cap members in the instrument introducing holes. A direct-drive valve engineof a third feature of the invention is the engine of the first feature having an inner diameter of the instrument introducing holes that ;s greater than a thickness of the cam provided in the camshaft. A direct-drive valve engine of a fourth feature of the invention is the internal combustion engine described above is provided with cam peep holes running to the caiii room in the head cover in extensions of the axes of valve lifter holes for sliding the valve lifters.. [eeegT In a direct-drive valve engine of a fifth feature of the invention, the cam peep holes set forth as the fourth feature have a diameter approximately identical to that of the valve lifters, and are sealed with cap members. [Effects of the Invention] According to the first feature, the instrument introducing holes for inserting a tappet clearance measuring fixture serve as a relief for the cam profile. Thus, forming bottom holes for the instrument introducing holes serves as forming a relief for the cam profile, which results in a reduced number of man-hours. According to the second feature, provision of cap members in the instrument introducing holes contributes to making a seal composition simplified. According to the third feature, because an inner diameter of the instrument introducing holes is greater than a thickness of the cam provided in the camshaft, the relief for the cam profile 15 secured by working out bottom holes for the instrument introducing holes. According to the fourth feature, because of the cam peep holes running to the cam room are provided in the head cover on extensions of the axes of the valve lifter holes for sliding the valve lifters, it is possible for the valve lifter holes to be formed easily, in addition to their being able to function as peep holes for checking the position of cams when, for instance, the valve clearances are measured. According to the fourth feature, because of the cam peep holes having a diameter approximately identical to that of the valve lifters as well as their being closed with the cans, it is possible to make a seal construction simplified. Accordingly, the present invention relates to a direct-drive internal combustion engine provided with valve lifters that are between a camshaft and inlet and exhaust valves for imparting pressure to the inlet and exhaust valves in an axial direction by following a rotation of said camshaft, the engine comprising: a cylindrical head portion; a cylindrical head cover portion; a cam chamber provided in the cylinder head portion and the cylinder head cover portion; said camshaft being disposed in said cam chamber; said camshaft having cam profiles thereon; wherein a valve lifter is disposed in the cylinder head portion and provided between the cam profile and inlet and exhaust valves instrument introducing holes running from the outside of cylinder head portions towards a contact area of the cam profiles and the valve lifters. [Brief Description of the accompanying Drawings] Fig. 1 is a sectional view showing the construction of the instrument introducing hole 91 and the relief. Fig. 2 is an overall sectional view of the engine involved in the embodiment. Fig. 3 is a view showing the right face with the inlet cover removed. Fig. 4 is a sectional view of the body. [Description of the Preferred Embodiment] A preferred embodiment of the invention as applied to a water cooled 4-cycle small displacement engine for use in a lightweight motorcycle will now be described in detail with reference to the drawings Fig. 1 is a sectional view showing a valve lifter hole and an instrument introducing hole; Fig. 2 is an overall sectional view of an engine involved in the embodiment, showing a right face of the body with an inlet cover removed; Fig. 3 shows a left face of the body with a cam chain cover removed; and Fig. 4 is a section -1 view of the body. To begin with, an outline of the construction of the engine will be given with reference to Figs. 2 through 4. The engine is designed so that it can be assembled and mounted on a crankcasc (not shown) by fixing an inlet cover 2 and a cam chain cover 3 to two faces opposite to each other approximately in parallel being formed along the length of the body 1 approximately of the shape of a rectangular parallelepiped formed by means of a die-casting which employs such appropriate metals as aluminum alloy. The body 1 is cast integrally to have a cylinder 5 for housing a piston 4 that is interconnected with a crankshaft (not shown) via a connecting rod 4a as well as a head 8 that is provided with a cam room 7 for rotatably housing a camshaft G. In this application, a portion of the head that covers the cam room 7 is particularly called as a head cover. For the sake of convenience, faces of the body 1 are each called p.s follows : the face on which to fix the inlet cover 2 is called as a right face 10; the face on which to fix the cam cover 3 is called as a left face 11 (Fig. 6); of two faces opposite to each other approximately orthogonal, sandwiched between the two faces, the one to which to fix a radiator to be described later is called as a front face 12, and the other id called as a back face 13 (Fig. 3). Furthermore, the outer surface of the ceiling of the head cover 9 is called as a top face 14, and the face to be fixed to the crankcase is called as a bottom face 15. In the cylinder section, a cylinder 16 is formed extending from the side of the bottom face 15 up to an approximately intermediate point along the length of the body 1, and a combustion chamber 17 formed at the side of the head 8, the deepest portion of the cylinder 16, is interconnected with an inlet port 18 and exhaust port 19. The opening of each port at the side of the combustion chamber 17 is opened/closed by an inlet valve 20 and an exhaust valve 21. Each of valve axes Cl and C2 is at a specified included angle with respect to the cylinder axis C. Reference numerals 20a and 2 la denote stem holders. The inlet port 18 interconnects with a suction air passage 22 formed in the inlet cover 2, which extends obliquely outward on an extension of the inlet port 18 to connect with a carburetor ( not shown) via an inlet pipe 23. The exhaust port 21 extends bending approximately at a right angle with respect to the inlet port 18 to connect with an exhaust pipe 24 at the back face 13. Reference numerals 29 in Figs. 2 and 3 denotes a spark plug. Valves are each driven directly by cams 27 and 28 via valve lifters 25 and 26 provided at ends of the respective shafts. The camshaft provided with the cams 27 ard 28 is supported by bearings 30 and 31 at the ends of both openings in the cam room which is tapered and runs through between the right face 10 and left face 11. The sliding surfaces of the cams 27 and 28 are slanting in correspondence to the slanting sliding surfaces of the valve lifters 25 and 26 respectively. Moreover, an oil feeder 6a is formed between one end of the camshaft 6 and inlet cover 2. The other end of the camshaft 6 protrudes into a chain room 32 formed between the cam chain cover 3 and left face 11, and a cam sprocket 33 is fixed at the end of the protrusion by bolts 33. The cam sprocket 33 is connected to a drive sprocket provided on the crank shaft, not shown, via a cam chain 35. On the extensions of the valve axes Cl and C2 in the head cover 9, cam peep holes 36 and 37 are formed which are respectively coaxial with the valve axes Cl and C2 and have a diameter approximately identical to that of the valve lifters 25 and 26. Valve lifter holes 84 and 85 are worked through the cam peep holes 36 and 37 , while valve component parts can be introduced through those holes when they are assembled, which contributes to bringing about an easier and better assembly thereof. Furthermore, since the cam peep holes 36 and 37 have caps 38 and 39 respectively for opening/closing the cam room 7 tightly enclosed by means of screws via a seal, a sealing construction can be made simpler. In the vicinity of the combustion chamber 17 of the body 1, a water pump 40 is housed in a pump mounting concave 41 formed in a side wall facing the cam chain cover 3 of the body 1 and is sealed therebetween with the outer periphery of a flange 42 formed in a portion of a resin cover constituting a profile of the water pump 40 fitted watertight via an 0-ring 44. The pump body 43 covers the water jacket 45 that is partly opened to the pump mounting concave 41. An impeller 46 which is integral with and rotatably supported by a pump shaft 41 is provided in the central portion of the pump body 43. Cooling water is fed to the center of the pump body 43 from a water passage 43a that is directly opened to the water jacket 45. One end of the pump shaft. 47 is supported rotatably by a boss 48 protruding on the outer peripheral wall of the cylinder 16. The other end of the pump shaft 47 protrudes over a cam chain 35 into a chain room 32, is provided with a magnet ring 49 thereon, and is further covered with a cylindrical portion of a resin cover which is integral with the flange 42, thereby forming a small diameter section 50. The protruding end of the small diameter section 50 is fitted into and supported by a fitting concave 51 formed in the cam chain cover 3. A water pump sprocket 53 with a magnetic ring 52 integral with the inner periphery thereof is provided on the outer periphery of the small diameter section 50. , to be driven by the cam chain 35. The outer periphery of the boss of the water pump sprocket 53 is rotatably housed via a bearing 54 into a circular water pump housing 55 formed in the cam chain cover 3. When the magnet ring 52 is rotated together with the water pump sprocket 53, it causes the magnet ring 49 inside the small diameter section 50 to be magnetically connected and rotated together, thereby rotating the impeller 46 via the pump shalt 47 which is integral with the magnet ring 49, and allowing the water pump 40 to be driven. The water pump 40 is designed so as to force cooling water to circulate via the radiator (not shown), provided in the front face 12 of the body 1, into the water jacket 45 on the side of the inlet cover 2 r r\ r\ rv m [UUioj As shown in Fig. 4, valve lifter holes 84 and 85 for housing the valve lifters 25 and 26 are formed in the head 8 of the body 1 as well as small diameter stem holder holes P6 and 87 which extend continuously from the ends of the valve lifter holes 84 and 85 to the inlet port 18 and exhaust port 19. Those holes are along the valve axis Cl or C2, the extension of the valve axis Cl or C2 intersects the axis (the central axis of the cam room) of the camshaft 6. Cam peep holes 36 and 37 are fromed on the extension thereof in the head cover 9. A relief 90 approximately in theshape of a semi-circle is formed in the upper ends of the valve lifters 27 and 28. The relief 90 is formed by working out a bottom hole 92 of an instrument introducing hole 91 drilled from the front face 12 of the body 1 toward the sliding section of the upper surfaces of the cams 27 and 28 and valve lifters 25 and 26. The instrument introducing hole 91 is for inserting a tappet clearance measuring fixture, and is provided at a location where the sliding section of the upper surfaces of the cams 27 and 28 and valve lifters 25 and 26 is within the extension of the instrument introducing hole 9] when the valves are lifted. The inner diameter of the instrument introducing hole 91 allows free entry of a tappet clearance measuring fixture when a shim 93 (Fig. 2) is adjusted, and is larger than the thickness of the cams 27 and 28 (Fig. 2). An internal thread 94 is fromed on the inner peripheral surface of the instrument introducing hole 91. a cap 95 is detachably mounted in the thread 94 via an 0-ring 96 to seal the opening. As is clear from Fig. 1, a bottom hole 92 of the instrument introducing hole 91 is formed so as to coincide with the bottom of a cam profile 97 of the cams 27 and 28. An inner peripheral surface 98 of the cam room 7 which is circular along the outer periphery of the cam profile 97 leads to the relief 9 of the instrument introducing hole 91. The cam profile 97 of the cams 27 and 28 pass into the relief 90 without any interference. A description is now given of how the embodiment operates. After the cam room 7 of the body 1 is formed by casting, the bottom hole of the instrument introducing hole 91 is drilled from the front face 12 in the direction orthogonal to the axis of the camshaft 6 so as to form the relief 90 at the intersection with the cam room 7. The relief 90 does not interfere with the cam profile 97 of the cams 27 and 28. Accordingly, the instrument introducing hole 91 also serves as a relief for the cam profile 97, .which means that just working out the bottom hole 92 for the instrument introducing hole 91 eliminates a process for working out a relief for the cam profile 97, which results in a reduced number of man-hours. 0034 In addition, the inner diameter of the bottom hole which forms the instrument introducing hole 91 is greater than the thickness of the cams 27 and 28, which makes it possible that a relief 90 for the cam profile 97 is secured by working out the bottom hole for the instrument introducing hole 91. By use of the instrument introducing hole 91, the tappet clearance can be measured at any time, and after the measurement, if required, it is possible to adjust the shim 3. The cap 95 is detachably mounted on the instrument introducing hole 91 via the O-ring 96 to hermetically close the opening, which contributes to eliminating the need for a seal on the camshaft 6, thereby making a sealing construction more simplified. Moreover, the fact that the cam peep holes 36 and 37 running to the cam room 7 are provided in the head cover 9 on the extension of the axis of the valve lifter holes 84 an 85 for sliding the valve lifters 25 and 26 makes it possible for the valve lifter holes 84 and 85 to he worked out easily, in addition to their being able to function as peep holes for checking the position of cams when, for instance, the valve clearances are measured. Furthermore, the cam peep holes 36 and 37 have a diameter approximately identical to that of the valve lifters 25 and 26 as well as that they are closed with the caps 38 and 39, which contributes to making a sealing construction more simple. The embodiment of the present invention has been described so far. However, the invention may be embodied with various changes applied thereto without departing from the scope and essential characteristic features of the invention. For instance, the casting method need not be a die-casting, instead any other publicly known method of casting may be adopted such as utilization of sand molds. Also, the invention is applicable to a DOHC type engine. [Description of Reference Numerals] 1 : Body, 2 : Inlet cover, 3 : Cam chain cover, 6 : Camshaft, 7 : Cam room, 8 : Head, 9 Head cover, 16 : Cylinder, 25 and 26 : Valve lifters, 27 and 28 : Cams, 90 : Relief, 9) Instrument introducing hole, 92 : Bottom hole, 95 : Cap, 97 : Cam profile WE CLAIM: 1. A direct-drive internal combustion engine provided with valve lifters that are between a camshaft and inlet and exhaust valves for imparting pressure to the inlet and exhaust valves in an axial direction by following a rotation of said camshaft, the engine comprising: a cylindrical head portion; a cylindrical head cover portion; a cam chamber provided in the cylinder head portion and the cylinder head cover portion; said camshaft being disposed in said cam chamber; said camshaft having cam profiles thereon; wherein a valve lifter is disposed in the cylinder head portion and provided between the cam profile and inlet and exhaust valves instrument introducing holes running from the outside of cylinder head portions towards a contact area of the cam profiles and the valve lifters. 2. The direct-drive valve engine as claimed in claim 1, wherein the introducing holes are provided with cap members. 3. The direct-drive valve engine as claimed in claim 1, wherein an inner diameter of the instrument introducing holes is greater than a thickness of the cam provided in the camshaft. 4. The direct-drive valve engine as claimed in any one of claims 1 to 3, wherein cam peep holes running to a cam room are provided in a head cover in extensions of the axes of valve lifter holes for sliding the valve lifters. 5. The direct-drive valve engine as claimed in claim 4, wherein the cam peep holes have a diameter identical to that of the valve lifters, and the cam peep holes are sealed with cap members. 6. A direct-drive internal combustion engine substantially as herein described with reference to and as illustrated in the accompanying drawings.

Documents:

2451-del-1998-abstract.pdf

2451-del-1998-claims.pdf

2451-del-1998-correspondence-others.pdf

2451-del-1998-correspondence-po.pdf

2451-del-1998-description (complete).pdf

2451-del-1998-drawings.pdf

2451-del-1998-form-1.pdf

2451-del-1998-form-13.pdf

2451-del-1998-form-19.pdf

2451-del-1998-form-2.pdf

2451-del-1998-form-3.pdf

2451-del-1998-form-4.pdf

2451-del-1998-form-6.pdf

2451-del-1998-gpa.pdf

2451-del-1998-petition-137.pdf

2451-del-1998-petition-138.pdf