Internal Combustion Engine

1. Field of the Invention

This invention relates to an internal combustion engine, and more particularly to a four cycle engine of the type including a crankshaft.

2. Description of Relevant Art

An outside member of an internal combustion engine is conventionally constituted either from four components including a cylinder head, a cylinder block and a crankcase consisting of a pair of symmetrical members, or from three components including an integral cast member presenting a cylinder block and a crankcase upper half, a cylinder head and a crankcase half. Accordingly, such a conventional internal combustion engine has various disadvantages to be eliminated or improved: it includes various components which are complicated in configuration, which results in an increase of fastening or binding parts such as bolts which are used in assembling these components; besides, mounting holes must be worked or drilled for individual ones of such components, which results in an increase of working and assembling operations; and hence production costs are inevitably increased; and so on.

The present invention has been thus made, on one hand, to improve such deficiencies of a conventional internal combustion engine, and with particular attention being paid to a structure of an internal combustion engine of the type including a cantilever type crankshaft.

Meanwhile, a four cycle engine including a vertically arranged crankshaft which is used as a general purpose engine and so on, commonly includes an oil lubricating mechanism and a governor mechanism. Since such an oil lubricating mechanism normally includes either an oil pump or an oil raking up blade wheel provided on a separate shaft for effecting lubrication of oil, it is disadventageous in that it requires an increased number of parts and makes the structure thereof complicated, and so on.

Accordingly, the present invention has been made, on the other hand, to improve these disadvantages of an engine which employs an oil raking up type lubricating system.

According to the present invention, there is provided a four cycle internal combustion engine of the type including a cantilever type crankshaft wherein it comprises an outside member including a cylinder block section and a crankcase half section which both are formed into a single body, the crankcase half section having at least a bearing portion for supporting the crankshaft thereon and being open in a direction of an axis of the crankshaft and also in a direction of an axis of an inner bore of a cylinder to define an opening which has an opening edge arranged in an inclined relationship to the center axis of the cylinder and also to the center axis of the crankshaft, and a crankcase half having an inclined opening edge corresponding to the opening edge of the crankcase half section for covering the opening of the crankcase half section.

According to another aspect of the invention, there is provided a four cycle internal combustion engine of the type including a vertically disposed crankshaft and a valve motion wherein it comprises a camshaft disposed perpendicularly to a shaft portion of the crankshaft and connected to the crankshaft such that it is driven by the crankshaft, and a governor slider of a speed governor mechanism provided on an end of the camshaft an including a raking up portion provided thereon for raking up oil.

It is an object of the present invention to provide a four cycle internal combustion engine of the type including a cantilever type crankshaft which includes an outside member whereby parts of complicated configuration can be decreased in number and hence reduction of the total number of components, facilitation of production and assemblage, and reduction of production costs can be easily attained.

It is another object of the invention to provide a four cycle internal combustion engine of the type including a vertically disposed crankshaft and a valve motion in which a structure for lubricating oil is simplified to improve the facility of production and assemlage of the same and hence reduction of production costs can be attained advantageously.

It is a further object of the invention to provide a four cycle internal combustion engine of the type including a cantilever type crankshaft which includes a crankshaft supporting structure which can assure an advantageous operation of the crankshaft by a simplified structure.

Further features, objects and advantages of the present invention will be apparent to those skilled in the art from the following detailed description of preferred embodiments of the invention, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a longitudinal sectional view of an outside member in an assembled position of an internal combustion engine according to a first embodiment of the present invention;

FIG. 2 is a longitudinal sectional view of the internal combustion engine of FIG. 1;

FIG. 3 is a longitudinal sectional view of an internal combustion engine according to a second embodiment of the invention;

FIG. 4 is a transverse sectional view of the internal combustion engine of FIG. 3, as seen from above;

FIG. 5 is a transverse sectional view of the internal combustion engine of FIG. 3, as seen from below;

FIG. 6 is a longitudinal sectional view of an internal combustion engine according to a third embodiment of the invention; and

FIG. 7 is a longitudinal sectional view of an internal combustion engine according to a fourth embodiment of the invention.

At first, reference is made to FIGS. 1 and 2 in which an internal combustion engine according to a first embodiment of the invention is shown. FIG. 1 illustrates only an outside member of the internal combustion engine which includes a main block 1 and a crankcase half 21. The main block 1 includes a cylinder head section 2, a cylinder block section 3 below the cylinder head section 2, and a crankcase half section 4. These sections 2, 3 and 4 are all casted into a single body, and the cylinder head section 2 and the cylinder block section 3 have each a plurality of cooling fins 5 provided on an outer surface thereof. In the embodiment, the crankcase half section 4 has an opening 9 formed at an end thereof and has a portion 4a opposite to the opening 9 and extending therefrom in an axial direction of the crankcase; the crankcase half section 4 is extended from part of an upper wall 4b of the portion 4a thereof to form a push rod housing 6 in an integral relationship therewith; the housing 6 has therein a passage 6a extending in an axial direction of the cylinder; the housing 6 has one end connected to the exdending portion 4a of the crankcase half section 4 and the other end extended outwardly beyond the cylinder head section 2 to form a cover mounting portion 7; and the cylinder block section 3 has integrally formed thereon supporting portions 8 which connect with the cover mounting portion 7. Portions 5a of the cooling fins 5 are connected to portions 6b of an outer wall of the housing 6 to increase the strength of the entire outside member.

The opening 9 is formed to extend from a portion 3a of a lower part of an outer periphery of the cylinder block section 3 to bottom portion 4c of the crankcase half section 4. An edge 9a of the opening 9 is in a plane which is in an inclined relationship to a cylinder center axis N--N and also to a crankshaft center axis N1--N1 and the top end 9b of the opening edge 9a is adjacent a part 3a of a lower portion of the cylinder block 3 forwardly (upwardly) of the crankshaft axis while the bottom end 9c of the opening edge 9a is located rearwardly of an extension line N2 of an inner bore 3b of the cylinder block 3. The crankcase half section 4 has a bearing portion 11 for a crankshaft formed on an end wall 4d thereof and has another bearing portion 10 formed on a portion thereof adjacent the opening 9a. The cylinder head section 2 has an igition plug mounting hole 12 formed in a side portion thereof and suction and exhaust valve ports 13 formed in a top potion 2a thereof. Outwardly of the suction and exhaust valve ports 13, the cylinder head section 2 further has a valve rod receiving hole 13a formed to extend through one of the supporting portions thereof and a supporting hole 14 formed to extend through the other supporting portion thereof.

Drilling of holes and openings in the cylinder head, working of the ceiling and machining of the inner bore of the cylinder can all be carried out from below the cylinder inner bore. Since the opening 9 is in an inclined position and is opened outside an extension line of the cylinder inner bore, such machining can be carried out easily without a trouble. Also, working of the bearing portions 10 and 11 can be easily carried out through the opening 9 without a trouble since the opening 9 is open from a lower part of the cylinder block section to the bottom of the crankcase half section.

The crankcase half 21 is in the form of a cap and has an inclined opening edge 22a which corresponds to the opening edge 9a. the crankshaft half 21 may be either a part made of a steel plate and shaped by press work or a part molded from an aluminum alloy or a synthetic resin material. The crankcase half 21 is placed on the crankcase half section 4 such that the the opening edge 22a thereof is opposed to the opening edge 9a of the crankcase half section 4 with a packing or the like interposed therebetween and is fastened thereto by means of a bolt or the like.

Preceding to such fastening of the crankcase half 21, inside components are assembled to the main block 1. In particular, as seen in FIG. 2, a journal section of a cantilever type crankshaft 34 is inserted through the crankcase half section 4 to mount the crankshaft 34 on the main block 1 and then a minor end 32a of a con'rod 32 is connected to a piston 31 by means of a pin 33. The journal section includes a first journal portion 34b which is downstream of a web 34a and a second journal portion 34c which is further downstream of the web 34a. The second journal portion 34c is supported by the bearing portion 11 through a bearing 35 while the first journal portion 34b is supported by the bearing portion 10 through another bearing 36. The opposite major end 32b of the con'rod 32 has a hole 32c which receives therein a pin portion 34d formed on and adjacent one end of the web 34a. A stopper 37 is placed on the pin portion 34d and the major end 32b of the con'rod 32 from outside and is fastened thereto by means of a bolt 38 so as to prevent the con'rod 32 from being removed from the crankshaft 34. An ignition plug 39 is screwed into the opening 12 of the cylinder head section 2 and one of suction and exhaust valves 40 is fitted in the opening 13 with a stem 40a thereof extending through the hole 13a of the opening 13. An end of the stem 40a of the valve 40 is engaged with one end of a rocker arm 42 supported on a support member 41 which is in turn supported in the supporting hole 14 of the supporting portion 8. The other end of the rocker arm 42 is engaged with one of a push rod 43 which extends in the direction of the cylinder axis through the passage 6a within the housing 6. In the meantime, a cam shaft driving gear portion 44 is provided between the first and second journal portions 34b, 34c of the crankshaft 34 and is meshed with a driven gear 46 on a cam shaft 45 which is disposed perpendicularly to the crankshaft 34. The cam shaft 45 has a cam section 45a which is engaged with a valve lifter 47 which is in turn engaged with the opposite end of the push rod 43, thereby constituting a valve motion. A cover 48 is provided which is disposed over the cylinder head section 2 to cover the valve motion from above.

It is to be noted that, while the embodiment is designed as an overhead valve engine, the present invention can be easily applied to a side valve engine. Also, while the cylinder head section of the embodiment is formed in an integral relationship with other sections of the engine, it may be formed as a separate body.

Referring now to FIGS. 3 to 5, there is illustrated an internal combustion engine according to a second embodiment of the invention. The internal combustion engine is generally designated by reference numeral 101 and includes a cylinder head section 102, a cylinder block section 103 and a crankcase section 104 which sections are all casted into a single body. The crankcase section 104 has an opening 105 formed at an end thereof adjacent a crankshaft 114. The opening 105 is inclined relative to an axis of the crankshaft 114 and also to an axis of a cylinder 103a and extends from a base end of the cylinder block section 103 to a bottom portion 104a of the crankcase section 104 which is located outwardly as viewed from an inner bore 103b of the cylinder 103a. The opening 105 is closed up with a cover 106 made of a steel plate or the like. A piston 107 is fitted for sliding motion in the horizontal cylinder inner bore 103b the cylinder block section 103. The cylinder head section 102 has an ignition plug 108 mounted in an inclined position therein and also has a pair of valves 109 (only one is shown in the drawings) disposed in a vertical direction in a central portion thereof and operable to open and close suction and exhaust passages 102a and a combustion chamber 102b. A stem 109a of each valve 109 extends outwardly through the head section 102 and has an outer end thereof engaengaged with an end of one of a pair of valve rocker arms 110. The other end of each rocker arm 110 is engaged with an end of one of a pair of push rods 111 which are disposed in a substantially parallel relationship to the axis of the cylinder 103a. The crankcase section 104 has a downwardly extending supporting portion 104b provided at a portion thereof outwardly of the cylinder block section 103. A first bearing portion 104c is provided at a portion of the crankcase section 104 above the supporting portion 104b in a position on an extension line of the cylinder inner bore 103b while a second bearing portion 104e is provided at a lower end wall 104d of the crankcase section 104 in a spaced relationship in a direction of the axis of the crankshaft 114 from the first bearing portion 104c. The crankcase section 104 further has a pair of push rod housing portions 112 provided adjacent the cylinder block section 103 between the first and second bearing portions 104c and 104e and extending in a parallel relationship to the cylinder block section 103. Each housing portion 112 has a passage 112a therein which has one end communicated with the inside of the supporting portion 104a of the crankcase section 104 and the other end opened within the cylinder head section 102. The piston 107 is connected to a minor end of a con'rod 113, which has a major end thereof connected to a pin portion 114a of the cantilever type crankshaft 114. Thus, also according to this embodiment, machining of the cylinder inner bore 103a and the first and second bearing portions 104c and 104e can be carried out easily since, while the cylinder head section 102, the cylinder block section 103 and the crankcase section 104 are all casted into a single block, the opening 105 is formed in an inclined relationship as described above. The crankshaft 114 has a web 114b adjacent the pin portion 114a thereof and a shaft portion 114c extending downwardly from the web 114b. A first journal portion 114d of the shaft portion 114c of the crankshaft 114 adjacent the web 114b is supported by the bearing portion 104c through a bearing 115 while a second journal portion 114e adjacent the lower end of the shaft portion 114c is supported by the bearing portion 104e through a bearing 116. The lower end of the shaft portion 114c extends outwardly through the end wall 104d to form an output portion 114f. An oil seal 116c is provided for the crankshaft 114 outwardly of the bearing 116.

A toothed gear 117 is formed around an outer periphery of the shaft portion 114c of the crankshaft 114 between the bearings 115 and 116 and is meshed with another toothed gear 119 formed on a camshaft 118 which is disposed perpendicularly to the shaft portion 114c of the crankshaft 114. In the meantime, the push rods 111 are disposed to extend through the passage 112a within the housing 112 as described hereinbefore and have their ends engaged with cam portions 118a of the camshaft 118 via respective lifters 120. A governor slider 122 is mounted for integral rotation with and for axial sliding motion on an end 118b of the camshaft 118 which is nearer to a carburettor 121 disposed externally of the engine 101. The slider 122 holds thereon a centrifugally diffusing weight 123 which has a base portion thereof engaged with a stopper 124 for the slider 122 mounted at the end 118b of the camshaft 118. If the crankshaft 114 is driven to rotate the camshaft 118 at a predetermined rotational frequency, then the weight 123 is thrown open outwardly to slide the slider 122 in an axial direction on the camshaft 18. The axial motion of the slider 122 is imparted to a motion transmitting rod 125 which is bent in configuration as shown in FIG. 5. The rod 125 has one end connected to the slider 122 and has the opposite end extending outwardly of the crankcase section 104 and connected to one end of a connecting rod 126 which has its opposite end connected to a throttle valve shaft 27 of the carburettor 121 in order to effect speed governing in a known manner. The governor slider 122 has a portion 122a in the form of a disk as seen in FIG. 5. The disk-formed portion 122a has a plurality of radial blades 128 provided on one face thereof and almost a half of the portion 122a is sunk under oil 129 collected on the bottom of the crankcase section 104 in order that the oil 129 may be raked up by the blades 128 to effect intended lubrication when the camshaft 118 is rotated.

The camshaft 118 has the opposite end 118c journalled in a side cover 130 for the crankcase section 104, as seen in FIG. 4. An output power shaft 131 is mounted on the cover 130 and is arranged perpendicularly to the camshaft 118. The output power shaft 131 is connected to the camshaft 118 through a gearing including a gear 132 mounted on the output power shaft 131 and another gear 133 mounted at the end 118c of the camshaft 118 so as to obtain an output power from the camshaft 118. It is to be noted that the camshaft may otherwise have an end extended outwardly of the cover so as to provide an output power portion instead of the output power shaft of the embodiment.

It is also to be noted that, while the embodiment just described includes a cantilever type crankshaft, the present invention may also be applied to an engine which includes a center crankshaft therein.

Now, reference is made to FIG. 6 which illustrates an internal combustion engine 201 according to a third embodiment of the invention. The internal combustion engine 201 has an outside member 201b including a main block 202 which in turn includes a cylinder block section 203 constituting a circumferential wall for a cylinder chamber 201a and a crankcase section 204 for accommodating a crankshaft 221 therein which section 204 is made by casting in an integral relationship with the cylinder block section 203. The outside member 201b further includes a cylinder head 205 mounted to cover the cylinder block section 203, and a cover 207 for covering an opening 206 which is open to one side of the engine 201 and extends from a lower end of the cylinder block section 203 to the bottom of the crankcase section 204 of the main block 202. On the opposite side to the opening 206, the cylinder block section 203 has a housing 209 for accommodating therein push rods 232 formed in an integral relationship therewith and also in a mutually continued relationship with a plurality of cooling fins 208 on an outer surface of the cylinder block section 203 in such a manner as to constitute a part of the main block 202. A lower end of the housing 209 is continued to a shaft supporting portion 204a of the crankcase section 204 which extends in a direction away from the opening 206. The passage 209a is formed in the housing 209 in a substantially parallel relationship to an axis of the cylinder chamber 201a and communicates with the inside of the shaft supporting portion 204a of the crankcase section 204. On the same side with the housing 209, the cylinder head 205 has an extension 210 formed in an integral relationship therewith which is joined together to the housing 209 during assembly. Also, the cylinder head 205 has a plurality of cooling fins 211 formed around an outer periphery thereof. The cylinder head 205 having such a construction as described above is joined together to the top of the cylinder block section 203, and then the cover 207 is joined together to close up the opening 206. Interior parts are then assembled to the thus constituted outside member 201b.

A crankshaft 221 is of the cantilever type in which a shaft portion 221b is extended to one side of a web 221a thereof. The web 221a has a pin portion 221c provided at an eccentric position on an end face thereof and fitted in a direction of an axis of the crankshaft 221 in a hole 223b formed in a major end 223a of a con'rod 223 to thereby connect the crankshaft 221 to the major end 223a of the con'rod 223 by means of a stopper 224 and a bolt 225. The con'rod 223 thus connects the crankshaft 221 to a piston 222 which is fitted in an inner bore 203a of the cylinder chamber 201a. The shaft portion 221b of the crankshaft 221 has an output power end 221d extending outwardly of an outer end wall 204b of the crankcase section 204. Bearing portions 212 and 213 are provided in a concentrical and axially spaced relationship with the crankshaft 221 in a partition wall 204c on one side directly below the inner bore 203a of the cylinder chamber 201a and in the end wall 204b, respectively. Bearings 226 and 227 are fitted in the bearing portions 212 and 213, respectively, and support thereon a first journal portion 221e of the shaft portion 221b of the crankshaft 221 adjacent the web 221a and a second journal portion 221f adjacent the output portion 221d of the crankshaft shaft portion 221b.

In this way, the cantilever type crankshaft 221 is supported at two axially spaced points thereof thereby to bear two opposite forces applied thereto to assure smooth rotation of the crankshaft 221. Besides, since one of the support points is located adjacent the crank web 221a near to the cylinder chamber 201a, a load applied to the crankshaft 221 is advantageously carried at the support point thereof. An oil seal 228 is also provided for the crankshaft 221.

The cylinder head 205 has an ignition plug 229 mounted thereon and also has suction and exhaust valves 236 (only one is shown in FIG. 6) mounted thereon which communicate and discommunicate a combustion chamber 230 and suction and exhaust air passages 231 (only one is shown in FIG. 6) with each other. A stem 236a of each of the suction and exhaust valves 236 extends upwardly through the cylinder head 205 and has an end engaged with one end of a valve rocker arm 237 which has its opposite end engaged with an upper end of a push rod 232. The push rod 232 extends downwardly through a passage 210a within the housing extension 210 and the passage 209a within the housing 209 towards the shaft portion 221b of the crankshaft 221. A toothed gear 221g is formed around an outer periphery of a portion of the shaft portion 221b between the points 221e and 221f at which the crankshaft 221 is supported. The toothed gear 221g is meshed with another toothed gear 234 formed on a camshaft 233 which is disposed perpendicularly to the crankshaft 221. The opposite lower end of the push rod 232 is engaged with a lifter 235 which has an outer surface thereof engaged with a cam portion 233a of the camshaft 233, thereby constituting a valve motion 238 for actuating the suction and exhaust valves 236. Since the shaft portion 221b of the crankshaft 221 is supported at two spaced points thereof, smooth rotation of the crankshaft 221 is assured thereby and accordingly, operation of the valves 236 by the cam shaft 233 can be effected accurately. A cover 214 is provided which covers the valve motion 238 over the cylinder head 205.

While overhead valve engines have been described so far to which the present invention is applied, an embodiment of a side valve engine is described in the followings by referring to FIG. 7. The engine includes a main block 302 which includes a cylinder block section 303 and a crankcase section 304. The crankcase section 304 has an upward opening 306 formed therein which is covered with a cover 307 while the cylinder block section 303 has a valve stem guide portion 309 integrally provided thereon. The crankshaft 321 has a web 340 and is supported at a portion thereof adjacent the web 340 by means of a bearing 326 and also at another portion thereof by means of a bearing portion 304b formed directly in a lower end wall of the crankcase section 304. A toothed gear 321g is formed on a vertically intermediate portion of a shaft portion 321a of the crankshaft 321 and is meshed with another toothed gear 334 formed on a camshaft 333 which has a cam portion 333a engaged with one end of a push rod 332. The push rod 332 has the opposite end thereof engaged with an end of a stem portion 330a of a valve 330 which extends through the guide portion 309 of the cylinder block section 303. The valve 330 faces a combustion chamber 341 within the cylinder head 305.