JP4792423B2 - Air-cooled V-type engine - Google Patents

Description

  In the present invention, first and second banks each having a cylinder bore and arranged in a V shape so as to define a valley between them are connected to a crankcase that supports a crankshaft, and each bank Cooling fins are provided on the outer wall of each bank, and suction and exhaust valves are arranged in a V shape on the heads of the banks. A valve operating device for opening and closing the suction and exhaust valves is disposed above the crankshaft. The camshaft driven from the crankshaft, the first suction, the exhaust cam follower and the second suction, the exhaust cam follower, and the first suction, the exhaust cam follower and the second suction which are respectively lifted and lowered by the suction of the camshaft and the exhaust cam. The first suction, the exhaust push rod and the second suction, the exhaust push rod, and the first suction and the exhaust, which are respectively connected to the exhaust cam follower and connected to the bottom side of the first and second banks respectively. Push rod Beauty second intake, the upper end of the corresponding bank intake of the exhaust push rod, a first intake which connects respectively to the exhaust valve, the exhaust rocker arm and the second intake relates to an improvement in air-cooled engine that is constituted by the exhaust rocker arm.

Such an air-cooled V-type engine is already known as disclosed in Patent Document 1, for example.
JP-A-3-107515

  In such an air-cooled V-type engine, since the rod chambers for accommodating the intake and exhaust push rods were integrally formed at the time of casting each bank, each bank itself increased in size, and at the corner of the rod chamber. Inevitably, a lot of meat was added, making it difficult to reduce the weight. In addition, since the portion of the outer wall of the cylinder bore of each bank facing the rod chamber cannot be exposed to the outside air, the air cooling effect is somewhat reduced.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an air-cooled V-type engine capable of reducing the weight of each bank and improving the air-cooling effect.

In order to achieve the above object, the present invention provides a crankcase that has a cylinder bore and supports first and second banks arranged in a V shape so as to define a trough between the first and second banks. In addition, a cooling fin is provided on the outer wall of each bank, and suction and exhaust valves are arranged in a V shape on the heads of the banks, and the valve operating devices for opening and closing the suction and exhaust valves are provided. A camshaft disposed above the crankshaft and driven from the crankshaft, a first suction, an exhaust cam follower and a second suction, and an exhaust cam follower that are lifted and lowered by the suction and exhaust cams of the camshaft, respectively. Suction, exhaust cam follower and second suction, exhaust cam follower is connected to the lower end of the first and second banks, respectively, the first suction, exhaust push rod and second suction, exhaust push rod And these Air-cooled V-type composed of one suction, exhaust push rod and second suction, upper suction pump rod at the corresponding bank suction, first suction, exhaust rocker arm and second suction, exhaust rocker arm respectively connected to the exhaust valve In an engine, a cylinder block having a cylinder bore and a cylinder head that supports suction and exhaust valves are integrally formed to constitute each bank, and each suction and exhaust rocker arm of each bank is configured with these suction and exhaust push rods. side end portion disposed in V-shape in plan view so as to be close to each other, each intake and exhaust push rods in proximity to one another, each intake, each pair of parallel with each other to accommodate individual exhaust push rod provided in the lower end portion of the rod cover tubular to the lower support portion that projects on the valley side respectively are formed integrally with the cylinder block of each bank Each of the pair of lower mounting holes is press-fitted, and the upper ends of the pair of tubular rod covers are formed integrally with the cylinder heads of the banks and are provided on upper support portions projecting toward the valleys. The upper mounting hole is formed in a larger diameter than the lower mounting hole, and the upper end portion of the rod cover is formed into a large diameter portion larger than the portion other than the upper end portion. formed, the cooling fins of each bank, a notch that allows close proximity to each bank outer wall of the rod cover, the inner surface of the notch is of the rod cover, the small diameter of the intermediate portion outer periphery than the large diameter portion that provided so as to face the shall be the feature.

According to the onset bright, each intake, it is the majority of the exhaust push rod can be arranged outside each bank, along with eliminating the need for formation of the rod chamber to each bank, to reduce the paddings, each bank Therefore, the outer wall of the cylinder bore of each bank can be exposed to a wide range and the air cooling effect can be enhanced.

Further, the suction and exhaust push rods arranged outside each bank are individually accommodated in a pair of tubular rod covers supported by upper and lower support portions projecting from the upper and lower ends of each bank to the valley side. In addition, the rod cover is arranged on the valley side between the first and second banks, so that both banks can protect the rod cover from contact with other objects. Ru it is possible to reduce the size of the engine.

In addition, each bank is formed by integrally forming a cylinder block and a cylinder head, and the upper support portion is formed integrally with the cylinder head, and the lower support portion is formed integrally with the cylinder block. Coaxial machining of the upper and lower mounting holes for press-fitting the upper and lower ends of the rod cover into the lower support part is possible, and the coaxial accuracy of these can be improved, and as a result, the rod cover to the upper and lower mounting holes can be improved. The press-fitting is always appropriate, and the sealing property of the press-fitting part can be secured.

Moreover, since the upper mounting hole is formed to have a larger diameter than the lower mounting hole, the upper end portion of the rod cover is formed to have a larger diameter portion than the portion other than the upper end portion. Insertion into the mounting hole can be easily performed, and the upper end and lower end of each rod cover can be press-fitted almost simultaneously into the upper and lower mounting holes, thereby facilitating press-fitting work.

In particular, the suction and exhaust rocker arms of each bank are arranged in a letter C shape in plan view so that the suction and exhaust push rod side ends are close to each other, and the suction and exhaust push rods are close to each other. The cooling fins of each bank have notches that allow the rod covers that individually accommodate the suction and exhaust push rods to be placed close to the outer walls of the banks, and the inner surfaces of the notches are the rod covers. Since it is provided so as to face the outer periphery of the intermediate portion having a smaller diameter than the large diameter portion, the width of the notch can be minimized, and the deterioration of the heat radiation function of the cooling fin due to the notch can be minimized.

  The form of the Example of this invention is demonstrated below based on the suitable Example of this invention shown to an accompanying drawing.

  1 is a longitudinal front view of an air-cooled general-purpose V-type engine according to the present invention, FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1, FIG. 3 is a view taken along arrow 3 in FIG. 4 is a sectional view taken along the line 5-5 in FIG. 4, FIG. 6 is a sectional view taken along the line 6-6 in FIG. 4, FIG. 7 is an explanatory diagram for installing the vaporizer, and FIG. 8 is an explanatory diagram for installing the air cleaner. FIG. 9 is an enlarged view of the first bank portion in FIG. 1, FIG. 10 is a sectional view of the first bank along the line 10-10 in FIG. 9, FIG. 11 is a view taken in the direction of arrow 11 in FIG. FIG. 13 is a cross-sectional view taken along line 12-13 in FIG. 9, FIG. 13 is a cross-sectional view taken along line 13-13 in FIG. 12, FIG.

  First, in FIGS. 1 to 3, the air-cooled general-purpose V-type engine includes a first bank B <b> 1 and a second bank B <b> 2 that are arranged in a left and right V-shape on the upper side of the crankcase 1. An installation flange 2 is formed at the bottom. Further, the starter St is provided on one side of the crankcase 1 so as to be accommodated in the space below the one bank B1.

  Each of the first bank B1 and the second bank B2 has a cylinder block 3 having a cylinder bore 3a and bolted to the crankcase 1, and a combustion chamber 4a connected to the cylinder bore 3a, and is integrally connected to the cylinder block 3. The head cover 5 is bolted to the end surface of the cylinder head 4. The banks B1, B2 are integrally formed by casting, and a large number of air cooling fins 6, 6,.

  One crankshaft 7 is supported by both front and rear walls of the crankcase 1, and pistons 8 fitted to the cylinder bores 3a and 3a of the first and second banks B1 and B2 are mounted on the crankpin 7p of the crankshaft 7. 8 are connected via connecting rods 9 and 9. The front and rear end walls 1a of the crankcase 1 can be attached to and detached from the main body side of the crankcase 1 while being able to support one end of the crankshaft 7.

  As shown in FIG. 1, the first and second banks B1 and B2 have an opening angle α between both banks B1 and B2, that is, the cylinder center line A1 of the first bank B1 and the cylinder center line 2 of the second bank B2. The formed angle α is 90 °. On the other hand, a counterweight 7w that counterbalances the inertial force of the piston 8 of each bank B1, B2 is attached to the crankshaft 7 opposite to the crankpin 7p.

  In the first and second banks B1, B2, the cylinder center line A1 of the first bank B1 and the cylinder center line A2 of the second bank B2 are respectively opposite to the banks B1, B2 from the rotation center A3 of the crankshaft 7. It is arranged so as to pass through the biased point P. According to this arrangement, the valley 11 defined between the first and second banks B1 and B2 can be widened while maintaining the opening angle α = 90 ° between the banks B1 and B2. The valley portion 11 accommodates the entire carburetor C, which is an auxiliary machine for the V-type engine E, and a part of the air cleaner Ac that contains the cleaner element 10.

  As clearly shown in FIG. 6, the carburetor C has first and second horizontal directions (directions orthogonal to the crankshaft 7) aligned with the carburetor body 12 in the arrangement direction of the first and second banks B <b> 1 and B <b> 2. The air intake passages 131 and 132 are formed in a close-up arrangement, and a float chamber 12a and a fuel cut solenoid valve 12b are attached to the lower part of the carburetor body 12.

  As shown in FIGS. 1, 4 and 5, the cylinder heads 4 and 4 of the first and second banks B1 and B2 include an intake port 14 opened to each combustion chamber 4a in addition to each combustion chamber 4a. An exhaust port 15 is formed. Open ends of the intake port 14 and the exhaust port 15 to the combustion chamber 4a are formed in the intake valve seat 80 and the exhaust valve seat 81, respectively. At that time, the intake valve seat 80 is formed with a larger diameter than the exhaust valve seat 81. The intake valve seat 80, the exhaust valve seat 81, and the plug mounting hole 87 into which the spark plug 23 is screwed are disposed so as to surround the center of the combustion chamber 4a.

  As shown in FIGS. 9 to 11, the cylinder heads 4 of the banks B1 and B2 have intake valves that open and close the intake ports 14 and 15 in cooperation with the intake valve seats 80 and the exhaust valve seats 81, respectively. 35a, 35b and exhaust valves 36a, 36b are attached, and a spark plug 23 is screwed so that the electrode faces the combustion chamber 4a. At this time, the intake valves 35a and 35b and the exhaust valves 36a and 36b are arranged in a V shape, and the intake and exhaust valves 35 and 36 are valve springs 61 and 62 for urging them in the valve closing direction. Is installed.

  As shown in FIG. 10, the inclination angles θ1 and θ2 of the axes of the intake valves 35a and 35b and the exhaust valves 36a and 36b arranged in a V shape with respect to the center line of the cylinder bore 3a are as shown in FIG. The seat 81 is set as large as possible within a range that can be cut by the rotary blades 82 and 83 inserted into the cylinder bore 3a.

  As shown in FIGS. 1, 4, 5, and 6, the first and second intake passages 131, 132 are connected to the intake ports 14, 14 of the first and second banks B 1, B 2 through the intake manifold 16. Connected.

  That is, the intake manifold 16 is U-shaped on the outer side of the valley portion 11 on the horizontal plane so as to communicate between the intake ports 14 and 14 of the first and second banks B1 and B2 and the first and second intake passages 131 and 132, respectively. The first and second pipes 17 and 18 are curved in a shape, and individual flanges 191 and 192 are formed at the downstream ends of the first and second pipes 17 and 18, respectively. Are connected to the cylinder heads 4 and 4 of the first and second cylinder heads 4 and 4 by bolts 24 and 24, respectively. The common flange 20 includes a heat insulating plate 21, first and second attachment flanges 28 and 29 formed at the downstream end and the upstream end of the vaporizer C, and the outer periphery of the elbow-shaped air outlet pipe 22 of the air cleaner Ac. The mounting flange 30 formed in the step is fastened together by a plurality of bolts.

  Next, the joint fastening structure will be described with reference to FIGS.

  Two stud bolts 25 and 25 and two holding bolts 26 and 26 are used in the above-described tightening structure. The two stud bolts 25, 25 are planted in two places above and below one side of the common flange 20 of the intake manifold 16, and two holding bolts 26, 26 are screwed on the other side of the common flange 20. A pair of upper and lower screw holes 27, 27 to be worn are provided. The first and second mounting flanges 28 and 29 of the heat insulating plate 21 and the vaporizer C and the mounting flange 30 of the air cleaner Ac are provided with first bolt holes 31, 31, 31 ′ through which the two stud bolts 25, 25 pass. 31 'and second bolt holes 32, 32 through which the two holding bolts 26, 26 pass. In particular, the first bolt holes 31', 31 'of the first mounting flange 28 of the vaporizer C are The flange 28 is formed in a notch shape opened to the outside.

  In addition, a gasket is interposed before and after the heat insulating plate 21 as necessary.

  1-3, FIG. 9, FIG. 14 and FIG. 15, the valve operating device 37 for opening and closing the intake valves 35a and 35b and the exhaust valves 36a and 36b of the first and second banks B1 and B2 is the crankcase 1. To the cylinder heads 4 of the banks B1 and B2. The valve operating device 37 includes a camshaft 38 supported by the front and rear end walls of the crankcase 1 directly above and parallel to the crankshaft 7, and the rotation of the crankshaft 7 is reduced by half to the camshaft 38. And a timing transmission device 39 (see FIG. 2) for transmission. The timing transmission device 39 meshes with the drive timing gear 40 fixed to the crankshaft 7 at a position adjacent to the inner surface of the detachable end wall 1 a of the crankcase 1 and the camshaft 38. And a driven timing gear 41.

  As shown in FIGS. 14 and 15, an intake cam 38 i and an exhaust cam 38 e are integrally formed on the cam shaft 38. The intake cam 38 i includes first and second intake cam followers 42 a and 42 b, first and second intake cam followers 42 a and 42 b. It is connected to the intake valves 35a and 35b of the first and second banks B1 and B2 via the second intake push rods 44a and 44b, the first and second intake rocker arms 71a and 71b (see FIGS. 1 and 3), and The exhaust cam 38e is connected to the first and second banks B1 and B2 via the first and second exhaust cam followers 43a and 43b, the first and second exhaust push rods 45a and 45b, and the first and second exhaust rocker arms 72a and 72b. Are connected to the exhaust valves 36a and 36b. The intake push rods 44a and 44b and the exhaust push rods 45a and 45b are arranged along the side surfaces of the corresponding banks B1 and B2 on the valley 11 side.

  As clearly shown in FIGS. 14 and 15, the first and second intake cam followers 42 a and 42 b and the first and second exhaust cam followers 43 a and 43 b are attached to the crankcase 1 immediately above and parallel to the cam shaft 38. The first cam follower shaft 46 includes a boss portion 47 that is swingably supported by the cam follower shaft 46, and a slipper portion 48 that is in sliding contact with the corresponding cams 38i and 38e. In the first and second intake cam followers 42a and 42b, The boss portions 47 and 47 are brought into contact with and adjacent to each other on the cam follower shaft 46, and the slipper portions 48 and 48 are opposed to each other across the intake cam 38i in the axial direction of the cam shaft 38. The first and second exhaust cam followers 43a and 43b also have boss portions 47 and 47 extending in a staggered manner. The cam follower shaft 46 is abutted against and adjacent to each other, and the slipper portions 48 and 48 are alternately opposed to each other along the axial direction of the cam shaft 38 so that the exhaust cam 38e is sandwiched between the slipper portions 48 and 48. It is extended to.

  One end of the cam follower shaft 46 is supported by the support hole 50 of the crankcase 1, and the other end is supported by a bracket 51 fixed to the crankcase 1 with a bolt 52. The cam follower shaft 46 includes a distance collar 53 that abuts on an outer end surface of one boss portion 47 of the first and second exhaust cam followers 43a and 43b, first and second intake cam followers 42a and 42b, and first and second. A coil spring 54 interposed between the boss portions 47, 47 of the exhaust cam followers 43a, 43b is provided, whereby the first and second suction and exhaust cam followers 42a, 43a; 42b, 43b are arranged at a predetermined intermediate position of the cam follower shaft 46. Is held adjacent to the part. And most of the suction and exhaust cams 38i and 38e and the first and second suction and exhaust cam followers 42a and 43a; 42b and 43b are extended surfaces F and F between both end surfaces of the crankpin 7p of the crankshaft 7. It is arranged to fit in.

  As shown in FIG. 15, hemispherical engagement recesses 55, 55... Are formed on the back surfaces of the first and second intake cam followers 42a, 42b and the first and second exhaust cam followers 43a, 43b. And the hemispherical lower ends of the first and second intake push locks 44a, 44b engage with the engaging recesses 55, 55 of the second intake cam followers 42a, 42b, and the first and second exhaust cam followers 43a, 43b The hemispherical lower ends of the first and second exhaust push rods 45a and 45b are engaged with the engaging recesses 55 and 55, respectively.

  As shown in FIG. 3, in the first and second banks B1 and B2, the first and second intake rocker arms 71a and 71b and the first and second exhaust rocker arms 72a and 72a are respectively connected to the corresponding cylinder heads 4 by rocker shafts. It is pivotally supported via 85 and 86. The suction and exhaust rocker arms 71a, 72a; 71b, 72b are arranged in a letter C shape in plan view so that the suction and exhaust push rods 44a, 45a; 44b, 45b side ends are close to each other. The suction and exhaust push rods 44a, 45a; 44b, 45b are arranged close to each other.

  Tubular rod covers 59 and 60 (see FIGS. 1, 9, 11 and 12) for housing the suction and exhaust push rods 44a and 45a; 44b and 45b adjacent to each other are next to the banks B1 and B2. It is attached like this.

  That is, each of the banks B1 and B2 is integrally formed with upper and lower support portions 74 and 75 projecting from the upper and lower ends thereof to the valley 11 side between the banks B1 and B2, respectively. Are provided with upper mounting holes 74h and 74h into which the upper ends of the rod covers 59 and 60 are press-fitted, and the lower support part 75 is provided with lower mounting holes 75h and 75h into which the lower ends of the rod covers 59 and 60 are press-fitted. . Each upper mounting hole 74h and lower mounting hole 75h are coaxially arranged, and the upper mounting hole 74h is formed to have a larger diameter than the lower mounting hole 75h. Correspondingly, the upper end portions 59a, 60a of the rod covers 59, 60 are formed to have a larger diameter than the other portions. Therefore, the rod covers 59 and 60 can be easily inserted into the upper mounting holes 74h and 74h from above, and can be press-fitted into the upper mounting holes 74h and 74h and the lower mounting holes 75h and 75h almost simultaneously. .

  In each of the banks B1 and B2, the valve springs 61 and 62, the intake rocker arms 71a and 71b, and the exhaust rocker arms 72a and 72b are accommodated in a valve operating chamber 63 defined between each cylinder head 4 and the head cover 5, and this valve The chamber 63 communicates with the inside of the crankcase 1 through the hollow portions of the rod covers 59 and 60.

On the other hand, as shown in FIGS. 9 and 12, the cooling fins 6 of the banks B1 and B2 have U-shaped cuts that enable the rod covers 59 and 60 to be disposed close to the outer walls of the banks B1 and B2. The notch 6a is provided so that the inner surface of the notch 6a faces the outer periphery of the intermediate portions 59b and 60b of the rod covers 59 and 60 having a smaller diameter than the large diameter portions 59a and 60a .

  In FIG. 2 again, a flat portion 64 is formed on the cam shaft 38 from the general surface of the cam shaft 38 to the base surface of the exhaust cam 38 e, and the decompression member 66 is swingable through the pivot 65 on the flat portion 64. Supported. The decompression member 66 is made of a steel plate. When the V-type engine E is stopped or started, the decompression member 66a is located on the base surface side of the exhaust cam 38e and protrudes from the base surface. And a centrifugal weight 66b for generating a centrifugal force to retreat the decompression arm 66a from the base surface during rotation more than idling. The decompression arm 66a is positioned on the base surface side of the decompression member 66. The return spring 69 that is biased in the direction to be moved is connected, and the decompression device 70 is configured as described above.

  Thus, when the V-type engine E is started, the decompression arm 66a occupies a position in which the tip of the decompression arm 66a protrudes from the base surface of the exhaust cam 38e (see the chain line in FIG. 15). By slightly opening the exhaust valves 36a and 36b of the first and second banks B1 and B2 by the minute lift of the first and second exhaust cam followers 43a and 43b, the compression pressure in the cylinder bores 3a and 3a is lowered, and the starting load is reduced. be able to. If the camshaft 38 rotates more than a predetermined number of revolutions after starting the V-type engine E, the centrifugal weight 66b swings radially outward against the set load of the return spring 69 by the centrifugal force acting on it. The decompression arm 66a is moved away from the base surface of the exhaust cam 38e.

  In the above, the suction and exhaust push rods 44a, 45a; 44b, 45b are all provided with compatibility, and the same push rod can be used. In addition, the intake and exhaust cam followers 42a, 43a; 42b, 43b are all compatible, and the same cam follower can be used. Furthermore, the rod covers 59 and 60 are provided with compatibility, and the same rod cover can be used. In this way, the mass productivity of parts can be increased.

Next, it describes the operation of this embodiment.

  As described above, the first and second banks B1 and B2 are arranged such that the opening angle α of both banks B1 and B2 is 90 °, while the crankshaft 7 has pistons of the banks B1 and B2. Since the counterweight 7w that balances the inertial force of 8 is attached opposite to the crankpin 7p, the inertial force at the top dead center and the bottom dead center of the pistons 8 of the banks B1 and B2 is, as is well known, Therefore, the primary inertial force of the V-type engine E can be balanced without providing a special primary balancer mechanism.

  Moreover, the first and second banks B1 and B2 are such that the cylinder center line A1 of the first bank B1 and the cylinder center line A2 of the second bank B2 are opposite to the banks B1 and B2 from the rotation center A3 of the crankshaft 7, respectively. Therefore, the valley portion 11 defined between the first and second banks B1 and B2 is maintained at the opening angle α = 90 ° between the banks B1 and B2. Can be widened with acupuncture and therefore. The valley portion 11 can accommodate the entire carburetor C, which is a supplement to the V-type engine E, and a part of the air cleaner Ac with a margin, and provides a compact V-type engine E with a low overall height. it can.

  Further, at that time, the carburetor C has two series of first and second intake passages 131 and 132 in a horizontal direction (a direction orthogonal to the crankshaft 7) arranged in the arrangement direction of the first and second banks B1 and B2. Since it is configured as a mold and individually connected to the intake ports 14 and 14 of the first and second banks B1 and B2 through a pair of pipes 17 and 18, intake interference between both banks B1 and B2 is avoided. In addition, the intake resistance can be minimized and the output performance of the V-type engine E can be improved.

  In addition, the pair of pipe lines 17 and 18 are formed in the intake manifold 16 by forming a common flange 20 integrally connecting them at their upstream end portions, so that the common flange 20 is double vaporized. By connecting to the downstream end of the vessel C, the intake system of the V-type engine E can be easily configured, and the assemblability of the intake system is improved.

  In attaching the heat insulating plate 21, the vaporizer C, and the air cleaner Ac to the common flange 20 of the intake manifold 16, first, as shown in FIG. The first bolt holes 31, 31 of the heat insulating plate 21 are fitted into 25, 25, and then the notched first bolt holes 31 ′, 31 ′ of the first mounting flange 28 of the vaporizer C are inserted into the stud bolts 25, 25. After engaging from the side (see FIG. 7A), the entire vaporizer C is moved to the heat insulating plate 21 side, and the first bolt holes 31, 31 of the second mounting flange 29 are inserted into the stud bolts 25, 25 (see FIG. 8). By carrying out like this, since the carburetor C whose axial direction length is comparatively long can be set to the predetermined fitting position with the implantation bolts 25 and 25 by the movement amount shorter than the axial direction length of the carburetor C, Even when there is no wide space for receiving the entire carburetor C outside the outer ends of the implanted bolts 25, 25, the setting operation can be performed quickly, and the temporary fixing of the carburetor C to the fixed position is possible. It becomes possible. In the case of this embodiment, as shown in FIG. 4, the bulging portion 1s of the crankcase 1 is present outside the outer ends of the studs 25, 25 due to the presence of the large-diameter driven timing gear 41. The bulging portion 1s prevents the float chamber 12a of the carburetor C and the fuel-cut solenoid valve 12b from receiving the implanted bolts 25, 25 outside the outer ends, so that the bulging portion 1s is not interfered with. The temporary fixing structure of the vaporizer C at a fixed position is extremely effective.

  Next, as shown in FIG. 8, the first bolt holes 31, 31 of the mounting flange 30 of the air cleaner Ac are fitted into the stud bolts 25, 25, and finally nuts 33, 33 are screwed onto the outer ends of the stud bolts 25, 25. On the other hand, the holding bolts 26 and 26 are inserted into all the second bolt holes 32 and 32 and screwed and tightened into the screw holes 27 and 27 of the common flange 20. When the presser bolt 26 is inserted into the second bolt hole 32, it is necessary to move the presser bolt 26 over the entire length of the vaporizer C. However, since the presser bolt 26 is thin, its movement space is generally easily secured. it can.

  In the above, the use of the two stud bolts 25 and 25 means that the two first bolt holes 31 and 31 of the heat insulating plate 21, the vaporizer C, and the air cleaner Ac are fitted into the stud bolts 25 and 25, respectively. Thus, a reliable temporary fixing state in which the rotation of the heat insulating plate 21, the vaporizer C and the air cleaner Ac around the implanted bolts 25 and 25 is prevented is obtained, and accordingly, the second bolt holes of the subsequent holding bolts 26 and 26 are obtained. The insertion operation to 32 and 32 and the screwing operation to the screw holes 27 and 27 become easy.

  Further, by using the holding bolts 26 and 26 together, the carburetor C can be accurately fixed in place without being affected by the presence of the notched first bolt holes 31 ′ and 31 ′. Since the first and second attachment flanges 28 and 29 formed at the downstream and upstream ends of the vaporizer C are fastened to the common flange 20 by the implantation bolts 25 and 25 and the holding bolts 26 and 26, the attachment strength of the vaporizer C Can be increased.

  When removing the vaporizer C and the air cleaner Ac from the common flange 20, the above work procedure may be reversed.

  In the valve train 37, the suction and exhaust rocker arms 71a, 72a; 71b, 75b of the banks B1, B2 are arranged so that their suction and exhaust push rods 44a, 45a; 44b, 45b side ends are close to each other. Each pair of suction and exhaust push rods 44a, 45a; 44b, 45b are arranged close to each other in plan view, and each pair of suction and exhaust push rods 44a, 45a; 44b, 45b is accommodated. The upper and lower ends of the tubular rod covers 59, 60 are supported by upper and lower support portions 74, 75 projecting from the upper and lower ends of the banks B1, B2 to the valley 11 side, respectively, and the banks B1, Since the cooling fin 6 of B2 is provided with a notch 6a that enables the rod covers 59 and 60 to be arranged close to the outer walls of the banks B1 and B2, each suction and exhaust block is provided. Most of the shrods 44a and 45a; 44b and 45b can be arranged outside the banks B1 and B2, so that the formation of the rod chambers in the banks B1 and B2 is unnecessary, and the waste is reduced. The banks B1 and B2 can be made compact, and hence lighter, and since the rod chamber is not provided, the outer walls of the cylinder bores 3a of the banks B1 and B2 can be exposed to the outside in a wide range. The air cooling effect can be enhanced.

  The suction and exhaust push rods 44a, 45a; 44b, 45b arranged outside the banks B1, B2 are upper and lower support portions that project from the upper and lower ends of the banks B1, B2 to the valley 11 side, respectively. The rod covers 59 and 60 are housed and protected by the rod covers 59 and 60 supported by 74 and 75, and the rod covers 59 and 60 are disposed on the valley 11 side between the first and second banks B1 and B2. The rod covers 59 and 60 are protected from contact with other objects by the banks B1 and B2.

  Further, each suction and exhaust rocker arm 71a, 72a; 71b, 75b of each bank B1, B2 is shaped like a letter C in plan view so that these suction and exhaust push rods 44a, 45a; 44b, 45b side ends are close to each other. The suction and exhaust push rods 44a and 45a; 44b and 45b are arranged close to each other, and the suction and exhaust push rods 44a and 45a; 44b and 45b are placed on the cooling fins 6 of the banks B1 and B2. Since the notches 6a that allow the rod covers 59 and 60 to be accommodated to be disposed close to the outer walls of the banks B1 and B2 are provided, the width of the notches 6a is minimized and the heat dissipation function of the cooling fins 6 by the notches is provided. Degradation can be minimized.

  Each cam follower 42a, 43a, 42b, 43b is mounted on a cam follower shaft 46 mounted on the crankcase 1 directly above and parallel to the cam shaft 38, and a corresponding cam 38i. In the first and second intake cam followers 42a and 42b, the boss portions 47 and 47 are brought into contact with and adjacent to each other on the cam follower shaft 46, and the slipper portion 48 and One end of the slippers 48 and 48 along the axial direction of the cam shaft 38 is alternately extended so that the 48 is opposed to the intake cam 38i, and the first and second exhaust cam followers 43a and 43b are also provided. The bosses 47 and 47 are brought into contact with and adjacent to each other on the cam follower shaft 46, and the slippers 48 and 48 are connected to the exhaust cover. Since the end portions of the slipper portions 48, 48 along the axial direction of the cam shaft 38 are alternately extended so as to face each other across the 38e, the first cam shaft 38 and the cam follower shaft 46 have a first end. The suction and exhaust cam followers 42a and 43a and the second suction and exhaust cam followers 42b and 43b can be arranged in a concentrated manner, whereby the valve operating device 37 can be made compact, in particular, the cam shaft 38 can be shortened. In addition, in each of the first and second intake cam followers 42a and 42b and the first and second exhaust cam followers 43a and 43b, the slippers 48 and 48; 48 and 48 facing each other with the cams 38i and 38e therebetween are opposed to each other. By alternately extending the end portions of the slipper along the axial direction of the cam shaft 38, it is possible to sufficiently secure a sliding contact area with the corresponding cams 38i and 38e of the slippers 48 and 48; Therefore, it is possible to sufficiently reduce the surface pressure of the sliding contact portion and contribute to the improvement of the wear resistance.

  Also, the first and second suction and exhaust cam followers 42a and 43a; 42b and 43b of both banks B1 and B2 and the majority of the suction and exhaust cams 38i and 38e are extended surfaces F of both end surfaces of the crankpin 7p of the crankshaft 7. , The valve operating device 37 can be made more compact, and the crankshaft 7 is sucked by the lubricating oil scattered around the crankpin 7p and rotated around the exhaust cams 38i and 38e while the crankshaft 7 is rotating. It can be effectively lubricated.

  Further, a flat portion 64 is formed on the cam shaft 38 from its general surface to the base surface of the exhaust cam 38e, and a decompression member 66 is pivotally supported on the flat portion 64 so that the decompression member 66 can be used as a V-type engine. When E is stopped or started, the tip of the exhaust cam 38e is at the operating position on the base surface side so that the first and second exhaust cam followers 43a and 43b are lifted during the compression stroke of the V-type engine E. A decompression arm 66a that protrudes, and a centrifugal weight 66b that generates centrifugal force to cause the decompression arm 66a to retreat from the base surface when the V-type engine E rotates more than idling, and the decompression member 66 includes Since the return spring 69 that biases the arm 66a toward the operating position is connected, the first and second exhaust cam followers 43 are connected. 43b, the bosses are abutting and adjacent to each other on the cam follower shaft, and the ends of the slippers along the axial direction of the cam shaft 38 are staggered so that the slippers face each other with the exhaust cam interposed therebetween. In combination with the extension of the decompression member 66, the distal end portion of the decompression arm 66a is slightly protruded toward the exhaust cam 38e, and the distal end portion of the decompression arm 66a is projected to the first and second exhaust cam followers 43a. , 43b can be given a minute lift while being slidably contacted substantially equally. At this time, the fact that the protruding length of the distal end portion of the decompression arm 66a toward the exhaust cam 38e is small is sufficient to reduce the size of the single decompression device 70 common to both the banks B1 and B2, and the exhaust cam. This means that it is possible to minimize the reduction of the effective area of the base surface of 38e due to the formation of the flat portion 64 and to improve the durability of the exhaust cam 38e and the exhaust cam followers 43a and 43b. To do.

  The flat portion 64 is formed from the general surface of the camshaft 38 to the base surface of the exhaust cam, and the decompression arm 66a of the decompression member 66 pivotally supported on the flat portion 64 is used when the V-type engine E is stopped or started. Since the exhaust cam 38e protrudes toward the base surface side, the slipper portions 38, 38 of the first and second exhaust cam followers 43a, 43b do not need to protrude outward from the exhaust cam 38e. Decompression at start-up can be performed while maintaining compactness.

  As mentioned above, although the Example of this invention was explained in full detail, this invention can perform a various design change in the range which does not deviate from the summary.

1 is a longitudinal front view of an air-cooled general-purpose V-type engine according to the present invention. FIG. 2 is a sectional view taken along line 2-2 in FIG. 1. FIG. 3 is a view taken in the direction of arrow 3 in FIG. 1. FIG. 4 is a sectional view taken along line 4-4 of FIG. FIG. 5 is a sectional view taken along line 5-5 of FIG. FIG. 6 is a sectional view taken along line 6-6 in FIG. FIG. 4 is a sectional view taken along line 4-4 of FIG. Explanatory drawing of how to install the vaporizer. The enlarged view of the 1st bank part in FIG. FIG. 10 is a cross-sectional view of a first bank alone taken along line 10-10 in FIG. 9; FIG. 11 is a view taken in the direction of arrow 11 in FIG. 19. FIG. 12 is a view taken in the direction of arrow 12 in FIG. 9. FIG. 13 is a sectional view taken along line 13-13 of FIG. FIG. 14 is an enlarged view of a portion 14 in FIG. 2. FIG. 15 is a sectional view taken along line 15-15 in FIG. 14;

B1... First bank B2... Second bank E ... V-type engine 1 ... Crankcase 3 ... Cylinder block 3a ... Cylinder bore 4 ... ... Cylinder head 7 ... Crankshaft 11 ... Valleys 35a, 35b ... Intake valves 36a, 36b ... Exhaust valves 38 ... Camshafts 42a, 42b ... 1, second intake cam followers 43a, 43b ... first, second exhaust cam followers 44a, 44b ... first, second intake push rods 45a, 45b ... first, second exhaust push rods 59, 60・ ・ ・ ・ ・ Rod cover
59a, 60a ... The upper end of the rod cover (large diameter part)
59b, 60b ... Rod cover intermediate portions 71a, 71b ... Intake rocker arms 72a, 72b ... Exhaust rocker arms 74 ... Upper support 75a ... Upper mounting hole 75 ... Lower support 75a ... Lower mounting hole

Claims (1)

Each has a cylinder bore (3a) and supports the crankshaft (7) with the first and second banks (B1, B2) arranged in a V shape so as to define a trough (11) between them. In addition to the continuous connection to the crankcase (1), the cooling fins (6) protrude from the outer walls of the banks (B1, B2), and the suction and exhaust valves (35a, 36a) are placed on the heads of the banks (B1, B2). 35b, 36b) are arranged in a V shape, and a valve operating device (37) for opening and closing the intake and exhaust valves (35a, 36a; 35b, 36b) is disposed above the crankshaft (7). The camshaft (38) driven from the crankshaft (7), the suction of the camshaft (38), the first suction and exhaust cam followers (42a, 43a) which are lifted and lowered by the exhaust cams (38i, 38e), and A second suction and exhaust cam follower (42b, 43b); The first suction and exhaust cam followers (42a and 43a) and the second suction and exhaust cam followers (42b and 43b) are connected to the lower ends of the first suction and exhaust cam followers (42b and 43b). First suction, exhaust push rods (44a, 45a) and second suction, exhaust push rods (44b, 45b), these first suction, exhaust push rods (44a, 45a) and second First suction and exhaust rocker arms (71a, 72a) connected to the suction and exhaust valves (35a, 36a; 35b, 36b) of the corresponding banks (B1, B2) at the upper ends of the suction and exhaust push rods (44b, 45b) and the second intake, exhaust rocker arm (71b, 72b) in the configuration with air-cooled V-type engine out with a cylinder bore (3a) a cylinder block having a (3), Exhaust valves (35a, 36a; 35b, 36b) together constitute the integrally molded to each of the banks (B1, B2) and a cylinder head (4) which supports the, each intake of each bank (B1, B2), The exhaust rocker arms (71a, 72a; 71b, 72b) are arranged in a letter C shape in plan view so that their suction and exhaust push rod (44a, 45a; 44b, 45b) side ends are close to each other. Each suction and exhaust push rod (44a, 45a; 44b, 45b) is brought close to each other,
The lower ends of each pair of tubular rod covers (59, 60) arranged in parallel with each other to accommodate the respective suction and exhaust push rods (44a, 45a; 44b, 45b) are connected to the cylinders of the banks (B1, B2). A pair of lower mounting holes (75h) provided in the lower support part (75) formed integrally with the block (3) and projecting toward the trough part (11) are respectively press-fitted. Upper support portions (59, 60) of the rod cover (59, 60) are integrally formed with the cylinder heads (4) of the banks (B1, B2), and are extended to the trough portions (11). (74) are respectively press-fitted into the pair of upper mounting holes (74h),
The upper mounting hole (74h) has a larger diameter than the lower mounting hole (75h), and the upper end portions (59a, 60a) of the rod cover (59, 60) are other than the upper end portions (59a, 60a). Forming a larger diameter than the part of
The cooling fins (6) of each bank (B1, B2), notch that allows close proximity to each bank (B1, B2) an outer wall of the rod cover (59, 60) and (6a), notch An air-cooling type characterized in that the inner surface of (6a) is provided so as to face the outer periphery of the intermediate part (59b, 60b) having a smaller diameter than the large-diameter part (59a, 60a) of the rod cover (59, 60). V-type engine.

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