KR100511758B1 - Overhead valve engine - Google Patents

Abstract

The present invention relates to an overhead valve engine, wherein the intake port (1) and the exhaust port (2) are drawn in opposite directions from the intake valve port (3) and the exhaust valve port (4), In the overhead valve engine in which the valve shaft 45 is inclined in the derivation direction of the intake port 1 and the valve shaft 46 of the exhaust valve 6 is inclined in the derivation direction of the exhaust port 2, the cylinder center When viewed from the direction parallel to the axis line 7, the direction of the crankshaft center axis line 8 is the front-rear direction and the direction orthogonal to the crankshaft center axis line 8 is the left-right direction, and the angle of the valve actuating camshaft 9 Any of the valve shafts 45 and 46 and the respective ports 1 and 2 of the valves 5 and 6 are oriented substantially in the front-back direction, and the valve-operated camshaft 9 and the tappet 10 and push The rod 11 is disposed on the left and right sides of the cylinder block 12, the rocker arm 40 is installed on the cylinder head 14, and the rocker arm pivoting portion 1 which is substantially oriented in the left and right directions. 3) are installed side by side in front and rear, each rocker arm output unit 15 is drawn from one end of each rocker arm pivoting unit 13 toward the opposite direction between the rocker arm pivoting unit 13, and each rocker arm input unit ( 16) is drawn between the rocker arm pivoting section 13 from the other end of each rocker arm pivoting section 13, and each rocker arm input section 16 is installed side by side between the rocker arm pivoting sections 13 side by side. It features.

Description

Overhead Valve Engine {OVERHEAD VALVE ENGINE}

The present invention relates to an overhead valve engine.

In the prior art of an overhead valve engine, an intake port and an exhaust port are drawn in opposite directions from the intake valve port and the exhaust valve port, and the valve shaft of the intake valve inclines in the derivation direction of the intake port. In some cases, the valve shaft of the exhaust valve is inclined in the discharge direction of the exhaust port.

In this type of engine, a large intake / exhaust valve can be provided, and the degree of bending of the intake / exhaust port can be reduced, so that the intake and exhaust efficiency can be improved.

In the above prior art, since the intake and exhaust valve shaft is arranged in a " V " shape, a so-called overhead cam type valve operating mechanism is adopted. The valve actuation mechanism is provided with a lapping motor in front of the cylinder block, with the crankshaft center axis in the front and rear direction, and a valve actuating camshaft or tappet provided at the cylinder head.

The prior art has the following problems.

Lapping motors are installed in front of the cylinder block, but the device consists of a driving wheel, a driven wheel, a lapping motor belt, a tension, and an electric cover that covers them integrally. For this reason, the front-back dimension of an engine becomes long.

Since the lapping motor is installed in front of the cylinder block, when a series of maintenance is performed from the lapping motor to the intake / exhaust valve, the motor cover in front of the cylinder block and the head cover of the cylinder head are removed and repaired in two directions. It is necessary to perform maintenance, and the work becomes complicated.

Moreover, since the maintenance and maintenance conditions are difficult, the payload model is greatly limited.

Since the valve-operated camshaft or tappet is provided on the cylinder head, the dimension in the direction of the cylinder center axis of the engine becomes long.

An object of the present invention is to provide an overhead valve engine that has a short front and rear dimension and easy maintenance.

The invention configuration of Claim 1 is as follows (refer FIG. 1A, FIG. 2, and FIG. 6A).

The intake port 1 and the exhaust port 2 are led in opposite directions from the intake valve port 3 and the exhaust valve port 4 so that the valve shaft 45 of the intake valve 5 is connected to the intake port 1. In an overhead valve engine inclined in the discharge direction and the valve shaft 46 of the exhaust valve 6 is inclined in the discharge direction of the exhaust port 2,

From the direction parallel to the cylinder center axis line 7, the direction of the crankshaft center axis line 8 is made into the front-back direction and the direction orthogonal to the crankshaft center axis line 8 is made to the left-right direction, Any of the valve shafts 45 and 46 and the ports 1 and 2 of the respective valves 5 and 6 are oriented substantially in the front and rear directions, and the valve actuating camshaft 9 and the tappet 10 The push rod 11 is disposed on the left and right sides of the cylinder block 12, the rocker arms 40 and 40 are installed in the cylinder head 14, and the rocker arm pivoting portion 13 which is substantially oriented in the left and right directions. (13) is installed side by side in front and rear, and each rocker arm output unit 15, 15 is spaced between the rocker arm pivoting unit 13, 13 from one end of each rocker arm pivoting unit 13, 13 and Directed toward the opposite direction, each rocker arm input 16, 16 is drawn between the rocker arm pivoting portions 13, 13 from the other end of each rocker arm pivoting portion 13, 13, and each rocker arm Input section (16 ) Is installed side by side between the rocker arm pivoting portions 13 and 13.

The invention of claim 1 shows the following effects (see FIGS. 1A, 2 and 6A).

Since the valve actuating mechanism in which the valve actuating camshaft 9, the tappets 10, 10, and the push rods 11, 11 are arranged on the left and right sides of the cylinder block 12 is used, the lapping transmission is performed in front of the cylinder block. Compared with the overhead cam type valve actuation mechanism that requires the device, the dimensions of the front and rear direction of the engine can be shortened. In addition, since the valve operation mechanism can be made compact compared to the lapping motor, the dimensions in the right and left directions of the engine are not so large.

When a series of maintenance is performed from the push rod 11 to each of the valves 5 and 6, the head cover 20 of the cylinder head 14 may be removed to perform maintenance in one direction. This is simplified.

In addition, since there is a margin for maintenance, the mounting model is limited.

Although the rocker arms 40 and 40 are provided in the cylinder head 14, the dimension in the direction of the cylinder center axis line 7 of an engine can be shortened compared with the overhead cam type | mold in which a valve actuating camshaft or a tappet is provided in a cylinder head. .

Since each rocker arm input part 16, 16 is installed side by side between the rocker arm pivoting parts 13, 13, each rocker arm input part 16 is compared with the case where they are provided in the butted shape. Since the proper arm length of 16 and each rocker arm output part 15 and 15 can be ensured, the operation reliability of a valve operation apparatus can be improved.

In addition to the effect of Claim 1, invention of Claim 2 has the following effect (refer FIG. 1A, FIG. 6A).

When viewed in a direction parallel to the cylinder center axis line 7, each cam 9a of the valve actuating camshaft 9 is interposed between the rocker arm pivoting portions 13 and 13 between the center portions and disposed back and forth, and the rocker arm input portion Since the 16 and 16 are arranged side to side with the center axis line 9b of the valve actuating camshaft 9 interposed therebetween, each of the push rods 11 and 11 with respect to the tappets 10 and 10 is arranged. By setting the inclination angle equally small, the operation reliability of the valve operating device can be improved.

In addition to the effect of Claim 1 or 2, invention of Claim 3 has the following effect (refer FIG. 1A, FIG. 6A).

One intake valve 5 and one exhaust valve 6 are provided for one combustion chamber 17, and the valve shaft 45 of each valve 5, 6 is viewed in a direction parallel to the cylinder center axis line 7. ) 46 is disposed at a position displaced toward the push rods 11 and 11 with respect to the crankshaft center axis line 8, and the rocker arm output portions 15 and 15 are in contact with the end of each valve shaft. As a result, the rocker arm pivoting portions 13 and 13 are formed short, and the twisting can be reduced, so that the accuracy of the valve operation timing is further increased.

Invention of Claim 4 adds effect to any of Claims 1 to 3, and shows the following effect (refer FIG. 2).

Since the combustion chamber 17 is a pent roof type, the arrangement | positioning space of each valve 5 and 6 is large, it can be arrange | positioned without difficulty and a combustion performance can be improved.

Invention of Claim 5 adds effect to any of Claims 1-4, and shows the following effect (refer FIG. 1A, FIG. 6A).

Since each port (1) (2) is led in the opposite direction from the valve opening (3) (4) in the opposite direction to the section between the valve openings (18), the cross flow method can be adopted, and the scavenging of the combustion chamber (17) (Iii) can improve efficiency.

Invention of Claim 6 adds an effect to any of Claims 1-5, and shows the following effect (refer FIG. 5).

As seen from the direction parallel to the crankshaft center axis line 8, the cylinder 19 is inclined, and the valve actuating camshaft 9, the tappet 10, 10 and the push rod at the lower left and right sides of the cylinder block 12 Since 11) (11) is arrange | positioned, the dimension of the height direction of an engine can be shortened.

The invention of claim 7 has the following effects in addition to the effects of claim 1 (except by the addition of the rocker arm input unit) (see FIGS. 1A and 3A).

On the surface of each bearing boss portion 36 at a high position in the rocker arm chamber 20a, an oil guide groove 41a having a tapered shape is formed, whereby the crank chamber is formed through the communication hole 35. The oil mist introduced into the rocker arm chamber 20a flows down to the upper surface of each bearing boss portion 36 at a high place, and the oil gathers along the oil guide groove 41a to each rocker arm pivoting portion 13 by its own weight. Inflow.

As a result, it can be carried out cheaply by simple modification as compared with the case of supplying lubricating oil to the valve operation mechanism in the rocker arm chamber through the feed passage, and lubrication even when the rocker arm boss 13a is long High performance can be maintained.

The invention of claim 8 shows the following effects in addition to the effects of claim 7 (see FIG. 1A).

The oil collected along the oil guide groove 41a is formed by forming an oil inlet 43a opposite the lower opening of the oil guide groove 41a at the upper end of each rocker arm boss 13a. It is introduced into the rocker arm boss 13a along the oil inlet 43a facing the lower end opening of the) to lubricate the rocker arm pivoting portion 13.

For this reason, the said effect can be exhibited more reliably.

Invention of Claim 9 shows the following effect in addition to the effect of Claim 7 or 8. (refer FIG. 3C).

By narrowing the diameter of the axial middle portion of the pivot 38 to form the oil reservoir 38b in each of the rocker arm bosses 13a, the oil introduced into the rocker arm boss 13a from the oil inlet 43a, It is stored in the oil reservoir 38b formed in the rocker arm boss 13a to lubricate the rocker arm pivoting portion 13a.

For this reason, the said effect can be exhibited more reliably.

Best Mode for Carrying Out the Invention Embodiments of the present invention will be described below with reference to the drawings.

1 to 5 are diagrams illustrating the first embodiment of the present invention. In this first embodiment, a spark ignition type inclined engine of an air cooled stage cylinder is used.

The engine consists of:

As shown in FIG. 5, the cylinder block 12 is formed as the crankcase wall 42 and the cylinder 19, the cylinder head 14 is assembled on the top dead center side of the cylinder 19, and the cylinder head 14 The head cover 20 is assembled.

A crankshaft 23 and a valve actuating camshaft 9 are temporarily installed in the crankcase 42a. The piston 25 is fitted in the cylinder 19, and the crankshaft 23 and the piston 25 are connected by a con'rod 24. The valve actuating cam gear 26 is meshed with the crank gear 34, and the valve actuating camshaft 9 is driven by the crankshaft 23.

The idle gear 27 is meshed with the crank gear 34, the gabner gear 28 is meshed with the idle gear 27, and the governor 32 is driven by the crankshaft 23.

The configuration of the cylinder head 14 and the valve operating mechanism is as follows.

As shown in FIG. 2, the intake port 1 and the exhaust port 2 are led in opposite directions from the intake valve port 3 and the exhaust valve port 4, and the valve shaft of the intake valve 5 ( 45 is inclined in the derivation direction of the intake port 1, and the valve shaft 46 of the exhaust valve 6 is inclined in the derivation direction of the exhaust port 2.

As shown in FIG. 1A, in the direction parallel to the cylinder center axis line 7, the direction of the crankshaft center axis line 8 is the front-rear direction and the direction orthogonal to the crankshaft center axis line 8 is the left-right direction. The valve actuating camshaft 9, the valve shafts 45 and 46 and the ports 1 and 2 of the valves 5 and 6 are substantially oriented in the front-rear direction. The valve actuating camshaft 9 is in the direction parallel to the crankshaft center axis line 8.

When viewed in a direction parallel to the cylinder center axis line 7, each valve 5, 6 and each port 1, 2 is oriented substantially forward and backward along the crankshaft center axis line 8.

The valve actuated camshaft 9, the tappets 10, 10, and the push rods 11, 11 are arranged on the left side of the cylinder block 12, and the rocker arms 40, 40 are mounted on the cylinder head 14. And rocker arm pivoting portions 13, 13, which are oriented substantially in the left and right directions, are installed side by side in front and rear, and each rocker arm output portion 15, 15 is disposed of each rocker arm pivoting portion 13, 13; The rocker arm inputs 16 and 16 are drawn from the right end from the left end of each rocker arm pivoting part 13 and 13 and are drawn in the opposite direction between the rocker arm pivoting parts 13 and 13. It is drawn between the pivoting parts 13 and 13, and each rocker arm input part 16 and 16 is installed side by side between the rocker arm pivoting parts 13 and 13 side by side.

Viewed in a direction parallel to the cylinder center axis line 7, each cam 9a, 9a of the valve actuating camshaft 9 is interposed between the rocker arm pivoting portions 13, 13 between the centers and disposed forward and backward. The rocker arm input portions 16 and 16 are arranged left and right, sandwiching the central axis 9b of the valve actuating camshaft 9 therebetween.

The rocker arm pivoting portions 13 and 13 are configured by the rocker arm bosses 13a and 13a being fitted out to the pivots 38 and 38 that are substantially oriented in the left and right directions.

Each rocker arm input 16, 16 is in contact with the output end of each push rod 11, 11, and each rocker arm output 15, 15 is a valve shaft of each valve 5, 6. It is in contact with the end. As seen from the direction parallel to the cylinder center axis line 7, the rocker arm pivoting part 13 is substantially oriented in the front-back direction along the direction orthogonal to the crankshaft center axis line 8. Each valve 5, 6 is biased toward the valve closing position by the valve springs 31, 31.

As shown in FIG. 2, one intake valve 5 and one exhaust valve 6 are provided in one combustion chamber 17, and as shown in FIG. 1A, the direction parallel to the cylinder center axis line 7 is shown. As seen from the above, the valve shafts 45 and 46 of the respective valves 5 and 6 are disposed at positions displaced toward the push rods 11 and 11 with respect to the crankshaft center axis line 8, and each valve The rocker arm output units 15 and 15 are in contact with the shaft end.

The combustion chamber 17 is a pen loop type.

As shown in FIG. 1B, the valve openings 3 and 4 and the spark plug insertion openings 22 are opened in the piston facing surface 39 of the cylinder head 14. The spark plug 21 is inserted into the spark plug insertion port 22, and the electrode portion thereof is disposed at the center of the combustion chamber 17.

As shown in FIG. 1A, in the direction parallel to the cylinder center axis line 7, each port 1, 2 is opposite from the valve port 3, 4 from the valve port part 18. Is derived.

As shown in FIG. 5, the cylinder 19 is inclined as viewed in a direction parallel to the crankshaft center axis line 8, and the valve actuating camshaft 9 and the tappet are to the left of the left and right sides of the cylinder block 12. (10) 10 and push rods 11 and 11 are arranged.

The valve actuating camshaft 9 is arranged to the left side of the lower side in the crankcase 42a, and the cabner 32 is arranged to the right side of the upper side of the crankcase 42a. A fuel tank 29 is disposed above the crank case 42a, and an air cleaner 30 and an exhaust muffler (not shown) are disposed above the cylinder head 14.

In this engine, the intake port 1 is led forward and the exhaust port 2 is led backward with the cooling fan (not shown) on the front side and the valve actuating camshaft 9 on the left side. The rocker arm 40 for the intake valve 5 is disposed forward, the rocker arm 40 for the exhaust valve 6 is disposed rearward, and the rocker arm input 16 for the intake valve 5 is left. Thus, the rocker arm input portions 16 for the exhaust valve 6 are disposed to the right, respectively.

As shown in FIGS. 1A and 3A, the cylinder block 19 and the cylinder head 14 are provided with a communication hole 35 of an oil mist that communicates the crank case 42a and the rocker arm chamber 20a. This communication hole 35 is located on the inclined upper side in the vicinity of the intake valve shaft insertion hole 45a in the rocker arm chamber 20a. This is intended to allow the oil mist introduced from the crank case 42a to the rocker arm chamber 20a to flow effectively into the valve actuation mechanism.

Each rocker arm 40 includes a long rocker arm boss 13a and a rocker arm input portion 16 extending from the right end of the rocker arm boss 13a, as shown in FIGS. 1A and 4A to 4C. A rocker arm output section 15 extending in a direction opposite to the rocker arm input section 16 from the left end of the rocker arm boss 13a, and to the two pairs of left and right bearing boss sections 36 and 37 to be described later. The rocker arm bosses 13a and 13a are pivoted to the installed pivot 38, respectively.

As shown in Figs. 1A and 3A to 3C, a pair of left and right bearing bosses 36 and 36 is provided on the inclined upper portion of the rocker arm chamber 20a, and a left and right pair of bearings are provided on the inclined lower portion thereof. The boss parts 37 and 37 (two pairs of bearing boss parts 36 and 37 in total) are formed integrally with the cylinder head 14, respectively, and these bearing boss parts 36 are formed. The rocker arm bosses 13a are arranged between the 37 and are supported by the pivots 38, respectively.

On the upper surface of each of the inclined upper bearing bosses 36, as shown in Figs. 1A, 3A, and 3B, the ribs 41 and 41 that make up the pair are projected, and the lower side inclined in between is tapered. An oil guide groove 41a is formed. On the other hand, as shown in Figs. 1A, 4A, and 4B, the inclined upper end of each rocker arm boss 13a protrudes a “co” shaped rib 43, and the oil guide groove ( An oil inlet 43a is formed to face the lower end opening of 41a). Moreover, the oil outlet port 43b is formed in the inclined lower end part of each rocker arm boss 13a as shown in FIG. 4C.

According to the above constitution, the oil mist introduced into the rocker arm chamber 20a flows on the upper surface of each of the inclined upper bearing bosses 36, and the oil is inclined by simple modification. The lower side is collected along the oil guide groove 41a having a tapered shape, and is introduced into the rocker arm boss 13a from the oil inlet 43a facing the oil guide groove 41a, and the rocker arm pivoting portion 13 is formed. Lubricate. Thus, even if the rocker arm boss 13a has a long body, the lubrication performance can be maintained high.

Each pivot 38 of the rocker arm 13, as shown in Fig. 3C, has a tapered diameter in the middle portion of its axial direction, so as to form an oil reservoir 38b in each rocker arm boss 13a. It is. This is intended to store the oil introduced into the rocker arm boss 13a from the oil inlet 43a in the oil reservoir 38b to lubricate the rocker arm pivoting portion 13 more reliably.

Moreover, the provision of the oil outlet 43b at the inclined lower end of the rocker arm boss 13a is intended to replace the oil in the oil reservoir 38b with a new one over time. In addition, a retaining ring 38a is attached to an inclined upper end of the pivot 38 to prevent dropping due to its own weight.

A pair of inclined upper bearing bosses 36 are arranged in close proximity to the left and right valve spring retaining seats 33 on the left and right sides, as shown in FIG. 3B, and in a soft state to the intake and exhaust valve shafts 45 and 46. It is formed to have a "V" shape, and is integrally protruded from the inclined upper bottom portion 48 in the rocker arm chamber 20a. In this state, each bearing boss portion 36 appears to interfere with the retaining seat 33 of the valve spring 31 in plan view, but the valve shafts 45 and 46 are also arranged to form a "V" shape. As a result, each bearing boss 36 and the valve spring 31 do not interfere with each other.

Thus, the pair of bearing bosses 36 and 36 formed to have a "V" shape is intended to make the cylinder head 14 and the head cover 20 compact.

Reference numerals 45a and 46a in FIG. 3B denote respective insertion holes of the valve shaft guide.

On the other hand, the inclined lower bearing bosses 37 and 37 also protrude integrally with the inclined lower left and right bottom portions 44 and 44 in the rocker arm chamber 20a. This is intended to suppress the increase in cost than to provide each bearing boss section separately.

In addition, between the left and right bottom portions 44 and 44, as shown in Fig. 3A, an inclined recovery groove 49 of lubricating oil is formed in a mold. This is intended to avoid lubricating oil from rectifying the bottom 44 and return the oil into the crankcase 42a.

The lower end of the inclined recovery groove 49 is connected to the lower bottom part 47 formed stepwise in the rocker arm chamber 20a, and the lower bottom part 47 has an insertion hole of the push rod 11. 11a) and 11a are opened, and the inclined bottom portion 11b of each insertion hole 11a extends to the inclined bottom circumference of the bottom bottom portion 47.

Due to this, the lubricating oil gradually dropped on the inclined bottom portion 44 is via the inclined lower portion 11b of the insertion hole 11a of the push rod 11 in the inclined recovery groove 49, It returns to the crank chamber 42a.

The first embodiment is not limited to the inclined engine but can also be applied to a horizontal engine in which the cylinder is horizontal. The engine of the second embodiment is not limited to the inclined engine but can also be applied to vertical engines and horizontal engines in which the cylinders are vertical.

As described above, the overhead valve engine of the present invention has the effect of providing an overhead valve engine having a short forward and backward dimension of the engine and easy maintenance.

1 is a view for explaining the engine according to the first embodiment of the present invention, Figure 1a is a plan view of the cylinder head, Figure 1b is a view of the piston facing surface of the cylinder head from the piston side,

2 is a longitudinal sectional side view of an essential part of the engine in which the cylinder head and cylinder block of FIG.

3 is a view illustrating the cylinder head of the engine shown in FIG. 1, FIG. 3A is a plan view of the cylinder head, FIG. 3B is a sectional view taken along the line B-B of FIG. 3A, FIG. 3C is a sectional view taken along the line C-C of FIG.

4 is a view illustrating a rocker arm of the engine shown in FIG. 1, FIG. 4A is a plan view of the rocker arm, FIG. 4B is a side view of the rocker arm, and FIG. 4C is another side view of the rocker arm,

5 is a longitudinal rear view of the engine shown in FIG. 1;

FIG. 6 is a view for explaining an engine according to a second embodiment of the present invention. FIG. 6A is a plan view of the cylinder head, and FIG. 6B is a view of the piston facing surface of the cylinder head as viewed from the piston side.

Claims (9)

The intake port 1 and the exhaust port 2 are led from the intake valve port 3 and the exhaust valve port 4 in opposite directions, so that the valve shaft 45 of the intake valve 5 is the intake port 1. In the overhead valve engine inclined in the derivation direction of the exhaust valve 6, the valve shaft 46 of the exhaust valve 6 is inclined in the derivation direction of the exhaust port 2, From the direction parallel to the cylinder center axis line 7, the direction of the crankshaft center axis line 8 is made into the front-back direction and the direction orthogonal to the crankshaft center axis line 8 is made to the left-right direction, Any of the valve shafts 45 and 46 and the ports 1 and 2 of the respective valves 5 and 6 are oriented substantially in the front and rear directions, and the valve actuating camshaft 9 and the tappet 10 The push rod 11 is disposed on the left and right sides of the cylinder block 12, the rocker arms 40 and 40 are installed in the cylinder head 14, and the rocker arm pivoting portion 13 which is substantially oriented in the left and right directions. 13 are installed side by side before and after, Each rocker arm output section 15, 15 is drawn from one end of each rocker arm pivoting section 13, 13 in the opposite direction between the rocker arm pivoting sections 13, and each rocker arm input section 16 (16) is drawn between the rocker arm pivoting parts (13) and (13) from the other end of each rocker arm pivoting part (13) and (13), and each rocker arm input part (16) and (16) is a rocker arm pivoting part ( 13) The overhead valve engine, characterized in that arranged side by side between (13). The method of claim 1, Viewed in a direction parallel to the cylinder center axis line 7, each cam 9a, 9a of the valve actuating camshaft 9 is interposed between the rocker arm pivoting portions 13, 13 between the centers and disposed back and forth. An overhead valve engine, characterized in that the rocker arm inputs (16) are arranged from side to side with the center axis line (9b) of the valve actuating camshaft (9) interposed therebetween. The method according to claim 1 or 2, One intake valve 5 and one exhaust valve 6 are provided for one combustion chamber 17, and the valve shaft 45 of each valve 5, 6 is viewed in a direction parallel to the cylinder center axis line 7. 46 is disposed at a position displaced toward the push rods 11 and 11 with respect to the crankshaft center axis line 8, and the rocker arm output portions 15 and 15 are in contact with each valve shaft end. There is an overhead valve engine. The method according to claim 1 or 2, An overhead valve engine, characterized in that the combustion chamber 17 is of the pent roof type. The method according to claim 1 or 2, An overhead valve engine characterized in that each port is drawn out from each valve opening (3) (4) in the direction opposite to the valve opening section (18) when viewed in a direction parallel to the cylinder center axis (7). The method according to claim 1 or 2, As seen from the direction parallel to the crankshaft center axis line 8, the cylinder 19 is inclined, and the valve actuating camshaft 9, the tappet 10, 10 and the push rod at the lower left and right sides of the cylinder block 12 11) An overhead valve engine, characterized in that (11) is arranged. The intake port 1 and the exhaust port 2 are led from the intake valve port 3 and the exhaust valve port 4 in opposite directions, so that the valve shaft 45 of the intake valve 5 is the intake port 1. In the overhead valve engine inclined in the derivation direction of the exhaust valve 6, the valve shaft 46 of the exhaust valve 6 is inclined in the derivation direction of the exhaust port 2, From the direction parallel to the cylinder center axis line 7, the direction of the crankshaft center axis line 8 is made into the front-back direction and the direction orthogonal to the crankshaft center axis line 8 is made to the left-right direction, Any of the valve shafts 45 and 46 and the ports 1 and 2 of the respective valves 5 and 6 are oriented substantially in the front and rear directions, and the valve actuating camshaft 9 and the tappet 10 The push rod 11 is disposed on the left and right sides of the cylinder block 12, the rocker arms 40 and 40 are installed in the cylinder head 14, and the rocker arm pivoting portion 13 which is substantially oriented in the left and right directions. 13 are installed side by side before and after, The crankcase 42a and the rocker arm chamber 20a communicate with the communication holes 35 of the oil mist, and the oil mist rocker arm pivoting portion 13 introduced into the rocker arm chamber 20a from the crankcase 42a is introduced. To lubricate, Two pairs of bearing bosses 36 and 37 are provided at high and low points in the rocker arm chamber 20a, and the rocker arm bosses 13a are disposed between the bearing bosses 36 and 37. FIG. Each of which is supported by a pivot (38), An overhead valve engine, characterized in that an oil guide groove (41a) is formed on the surface of each bearing boss portion (36) at a high position to form a tapered bottom. The method of claim 7, wherein An overhead valve engine, characterized in that an oil inlet (43a) is formed at an upper end of each rocker arm boss (13a) opposite the lower opening of the oil guide groove (41a). The method according to claim 7 or 8, A lubrication device for rocker arms, characterized in that an oil reservoir (38b) is formed in each of the rocker arm bosses (13a) by narrowing the diameter of the middle portion in the axial direction of each pivot (38).