JP2003120219A - Valve system for air cooled two cylinder engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the cooling ability of a pair of cylinders equal in the valve system for air cooled two cylinder engines. SOLUTION: In the valve system of the air cooled two cylinder engine, which is provided with a timing transmitting device 60 comprising a timing drive pulley 57 driven by a crank shaft 6, a cam shaft 62 pivotally supported on a cylinder head 4, a timing driven pulley 58 belted around the cam shaft 62, and a timing belt 59 belted around the timing drive pulley 57 and the timing driven pulley 58, and wherein intake and exhaust valves 23 and 24, and 23 and 24, which correspond to a pair of cylinders 18 and 18, are connected to the cam shaft 62 continuously through intake and exhaust rocker arms 70 and 71 and 70 and 71, which are supported on a pair of rocker shafts 69 and 69 rockably, the timing transmitting device 60 is arranged between a pair of cylinders 18 and 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a timing drive pulley driven by a crank shaft commonly connected to pistons in a pair of parallel cylinders, a cam shaft pivotally supported by a cylinder head, and this cam. A timing driven device consisting of a timing driven pulley fixed to the shaft and a timing belt wound between the timing driving pulley and the timing driven pulley is provided. The camshaft has a cylinder head corresponding to a pair of cylinders. The present invention relates to an improvement in a valve operating system of an air-cooled two-cylinder engine, which is connected to intake and exhaust valves corresponding to a pair of cylinders via intake and exhaust rocker arms that are respectively swingably supported by a pair of rocker shafts supported by the.

[0002]

2. Description of the Related Art In a conventional valve operating system for a two-cylinder engine,
For example, as disclosed in Japanese Patent Application Laid-Open No. 60-19923, a timing transmission device is arranged outside a pair of cylinders.

[0003]

When such a conventional training is applied to an air-cooled two-cylinder engine, the timing transmission device becomes
Since the cooling performance of the cylinder adjacent to it is affected to some extent, a difference in cooling performance easily occurs between the two cylinders.

The present invention has been made in view of such circumstances, and makes it possible to equalize the cooling performance of a pair of cylinders.
An object is to provide a valve operating system for an air-cooled two-cylinder engine.

[0005]

To achieve the above object, the present invention provides a timing drive pulley driven by a crankshaft commonly connected to pistons in a pair of parallel cylinders, and a cylinder head. The camshaft is provided with a timing driven device that includes a camshaft that is axially supported, a timing driven pulley that is fixedly mounted on the camshaft, and a timing belt that is wound between the timing driving pulley and the timing driven pulley. , Air cooling 2 connected to the intake / exhaust valves corresponding to the pair of cylinders via the intake / exhaust rocker arms that are swingably supported by the pair of rocker shafts supported by the cylinder head corresponding to the pair of cylinders 2 The first feature of the valve operating system for a cylinder engine is that the timing transmission is arranged between a pair of cylinders.

According to the first feature, since the timing transmission is arranged between the pair of cylinders, the cooling performance of both cylinders is not impaired and the cooling performance of both cylinders is equalized. be able to.

In addition to the first feature of the present invention, in addition to the first feature, suction and exhaust cams corresponding to a pair of cylinders that actuate an exhaust valve and an exhaust cam are formed symmetrically with a driven pulley in between.
A second feature is that the rocker shaft corresponding to the pair of cylinders is arranged above the cam shaft and in parallel therewith.

According to the second feature, the valve operating device, particularly the camshaft axial direction, can be made compact, and the spark plug which is not disturbed by the valve operating device at both outer ends of the cylinder head. It is possible to secure a wide installation space and improve maintainability.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below based on the embodiments of the present invention shown in the accompanying drawings.

FIG. 1 is a vertical sectional side view of a main part of a general-purpose engine equipped with a valve operating system of the present invention, FIG. 2 is a view taken in the direction of arrow 2 in FIG. 1, FIG. 3 is a view taken in the direction of arrow 3 in FIG. 1, and FIG. 1 is a sectional view taken along line 4-4, FIG. 5 is a sectional view taken along line 5-5 of FIG. 1, and FIG. 6 is a sectional view taken along line 6-6 of FIG.
7 is a view taken along arrow 7 of FIG. 2, FIG. 8 is a cross-sectional view taken along line 8-8 of FIG.
9 is a sectional view taken along line 9-9 of FIG. 6, and FIG. 10 is a longitudinal sectional view (A) showing a cam shaft, a left side view (B) and a right side view (C).

First, the overall structure of the engine will be described.

In FIGS. 1, 4 and 5, an engine body 1 of an air-cooled two-cylinder engine E with a balancer comprises a crankcase 2 and a cylinder block protruding from one side surface of the crankcase 2 with a slight upward inclination. 3 and a cylinder head 4 joined to the head of the cylinder block 3.
A large number of air cooling fins 3a and 4a (see FIG. 5) are formed on the outer surfaces of the cylinder block 3 and the cylinder head 4. The crankcase 2 is mounted on an engine bed of various types of work equipment at an installation surface 5 on the lower surface thereof.

The crankcase 2 is a cylinder block 3
A case body 1a which is cast integrally with and has one end open
And a side cover 2b connected to the open end of the crankshaft 6 and the case body 1a and the side cover 2b. Both ends of the crankshaft 6 rotate via ball bearings 7 and 7'and oil seals 8 and 8 '. Freely supported. The crankshaft 6 has one end as an output shaft portion 6o and the other end as an accessory mounting shaft portion 6a, which are projected outside the crankcase 2, respectively, and the flywheel 10 is keyed to the accessory mounting shaft portion 6a. At the same time, it is fixed with bolts 11, and a cooling fan 12 for supplying cooling air to each part of the engine body 1 and a carburetor 30 described later is fixed with bolts 13 on the outer end surface of the flywheel 10. A recoil type engine starter 14 is arranged outside the cooling fan 12.

Flywheel 10 of crankcase 2
The stator 15a of the generator 15 is attached to the outer end surface of the flywheel 10 that faces the stator 1.
It is provided with a plurality of magnets 15b arranged on the outer periphery of 5a and also serves as a roller of the generator 15. A cooling fan 12 for supplying cooling air to each part of the engine body 1 and a carburetor 30 described later is fixed to the outer end surface of the bolt 10 with bolts 13.
A recoil type engine starter 14 is arranged outside the cooling fan 12.

The crankshaft 6 is provided with a pair of left and right crankpins 6p, 6p having a phase difference of 360 ° in the crankcase 2. A pair of left and right pistons 17, 17 are connected to the crank pins 6p, 6p via connecting rods 16, 16, and a pair of left and right cylinders 18, 18 into which the pistons 17, 17 are slidably fitted are connected to the cylinder block 3.
Are formed parallel to each other.

The cylinder head 4 has cylinders 18, 1
8 corresponding to combustion chambers 20, 20, intake ports 21, 21
The exhaust ports 22, 22 are formed, and the intake ports 23, 23 and the exhaust valves 24, 24 for opening and closing the intake ports 21, 21 and the exhaust ports 22, 22 are mounted. At that time, the intake ports 21, 21 and the exhaust ports 22, 22
Are arranged above and below, and the upstream ends of the intake ports 21 and 21 open to the upper surface of the cylinder head 4, and the exhaust ports 22 and 2
The downstream end of 2 opens to the lower surface of the cylinder head 4.

The spark plugs 25, 25, which expose the electrodes to the combustion chambers 20, 20, are screwed to the cylinder head 4 from both left and right sides thereof.

As shown in FIGS. 1, 2, 6 and 7,
An intake manifold 27 is fixed to the upper surface of the cylinder head 4 with bolts 28. This intake manifold 27 is
The intake ports 21 and 21 are respectively provided with a pair of intake passages 29 and 29 which extend horizontally and individually communicate with each other.
The upstream end of 9 is the cooling fan 1 of the cylinder head 4.
2 Open to one side on the same side as 2
A continuous vaporizer 30 is connected. Thus vaporizer 30
Are arranged adjacent to the cooling fan 12 in the radial direction.

An air cleaner 32 is connected to the upstream end of the carburetor 30 via an intake duct 31 with the upstream end facing upward. This air cleaner 32 is used for the cylinder block 3
And above the cylinder head 4.

The carburetor 30 and the intake duct 31 are connected to the intake manifold 27 by a plurality of through bolts 33. The air cleaner 32 is attached to the intake duct 31 by a single mounting bolt 34 that is planted in the intake duct 31.

An exhaust manifold 35 is fixed to the lower surface of the cylinder head 4 with bolts 39. The exhaust manifold 35 is provided with a single exhaust passage 36 that communicates with the exhaust ports 22 and 22 and extends horizontally, and opens toward the other side of the cylinder head 4 of the exhaust passage 36. An exhaust pipe 37 arranged on the other side of the cylinder head 4 opposite to the carburetor 30 is connected to the downstream end of the exhaust manifold 35, and the muffler 3 is attached to the upper end of the exhaust pipe 37.
8 are connected. Thus, the air cleaner 32 and the muffler 38 are arranged adjacent to each other above the cylinder block 3 and the cylinder head 4 along the axis of the crankshaft 6, as shown in FIGS.

A fuel tank 41, which is supported by a bracket 40 protruding from the upper surface of the crankcase 2 and is adjacent to the air cleaner 32 and the muffler 38, is arranged above the crankcase 2 (see FIGS. 1 and 3).

In FIGS. 4 and 8, an eccentric shaft portion 42 is formed at the center of the crankshaft 6, and a large end portion of a link 43 is rotatably fitted to the eccentric shaft portion 42. A balance weight 45 is connected to the end portion of the crankshaft 6 through a pivot 44 parallel to the crankshaft 6. The balance weight 45 is fixed to the inner wall of the crankcase 2 and extends parallel to the axes of the cylinders 18, 18. A guide hole 47 of the weight 45 is slidably fitted to the outer circumference of the weight 46. The balance weight 45 is formed by the pistons 17, 1 that slide in the cylinders 18, 18 while the engine E is operating.
It reciprocates in the direction opposite to 7, and at that time, it exerts an inertial force that substantially balances the inertial forces of both pistons 17, 17.

Incidentally, the crankshaft 6 is the auxiliary equipment mounting shaft portion 6
a, a crankshaft half body 6A having a drive timing pulley 57 (described later) and an eccentric shaft portion 42, and a crankshaft half body 6B having an output shaft portion 6o are divided to form an eccentric shaft portion 42.
After assembling the link 43 to the crankshaft half 6
Opposing ends 6Aa and 6Ba of A and 6B are press-fitted to each other.

Thus, the engine E is configured as a parallel two-cylinder engine of equidistant explosion by giving a phase difference of 360 ° to the pair of crank pins 6p, 6p of the crankshaft 6. Therefore, even if the displacement is increased, the vibration can be reduced by the dispersion of the explosion vibration, and the vibration of the engine E can be further reduced by the balance action of the inertial force between the balance weight 45 and the pistons 17, 17. be able to. Moreover, by arranging the intake and exhaust manifolds 27 and 35 horizontally above and below the inclined cylinder head 4, and by disposing the carburetor 30 and the exhaust pipe on opposite sides of the cylinder head 4 respectively, The area around the cylinder head 4 is made compact,
A large installation space for the air cleaner 32 and the muffler 38 can be secured above the cylinder block 3 and the cylinder head 4, which can contribute to downsizing of the engine E. Moreover, heating of the intake system by the exhaust system can be avoided without using a special heat shield plate, which can contribute to simplification of the structure.

Further, since the carburetor 30 is arranged so as to be adjacent to the cooling fan 12 connected to one end of the crankshaft 6 in the radial direction, the space around the cooling fan 12 is effectively used as a carburetor installation space. Available,
This can further contribute to downsizing of the engine E.

Further, an air cleaner 32 and a muffler 38 are provided above the cylinder block 3 and the cylinder head 4, respectively.
Since the fuel tank 41 adjacent to the air cleaner 32 and the muffler 38 along the axial direction of the crankshaft 6 is arranged above the crankcase 2, the cylinder block 3, the cylinder head 4 and the crankcase 2 are arranged above each other. The space can be effectively used as an installation space for the air cleaner 32, the muffler 38, and the fuel tank 41.
The engine E can be made more compact.

Next, the lubricating device for the engine E will be described.

4 and 8, the guide shaft 46, the balance weight 45, the pivot 44, the link 43, and the crank shaft 6 are provided with a series of lubricating oil passages for supplying oil to the outer peripheral surfaces of the pair of crank pins 6p, 6p. 50 is formed, and a pump oil chamber 48 is provided in the middle of this lubricating oil passage 50. This pump oil chamber 48 has a balance weight 45.
The guide hole 47 is defined by the tip of the guide shaft 46, and the volume is expanded and contracted according to the reciprocating movement of the balance weight 45.

On the other hand, an oil pump 53 driven by the crankshaft 6 via driven and driven gears 51, 52 is attached to the inner wall of the side cover 2b. The oil pump 53 has a discharge port and a guide shaft 46. An oil pipe 54 is connected to the formed inlet of the lubricating oil passage 50.

During operation of the engine E, the oil pump 53 sucks up the lubricating oil 56 stored at the bottom of the crankcase 2 through the strainer 55, and the crankpin 6p through the oil pipe 54 and the lubricating oil passage 50. , 6p to lubricate the rotary sliding surface between the connecting rods 16 and 16.

At this time, the pump oil chamber 48 in the guide hole 47
Is the volume expansion due to the reciprocating movement of the balance weight 45,
Although the contraction is repeated to exert a pumping action, when the volume contracts, the discharge pressure of the oil pump 53 becomes a resistance to prevent the reverse flow of the oil.
The oil pressure-fed from 3 can be effectively increased in pressure and supplied to the crankpins 6p, 6p side, and the above lubrication can be effectively performed. Therefore, it is possible to use the small-capacity oil pump 53, and a special one-way valve for preventing backflow of oil is not required, so that the weight and cost can be reduced.

In the middle of the lubricating oil passage 50, the oil passing therethrough can lubricate the rotating sliding surfaces of the eccentric shaft portion 42 and the pivot 44 and the sliding surface between the guide shaft 46 and the balance weight 45. .

Next, the valve operating system of the engine E will be described.

4, 5, 9 and 10, a drive timing pulley 57 adjacent to the eccentric shaft portion 42 is formed at the center of the crankshaft 6. On the other hand, a cam support shaft 61 parallel to the crank shaft 6 is attached to the cylinder head 4, and the driven timing pulley 5 at the center of the cam shaft 62 rotatably supported by the cam support shaft 61.
A timing belt 59 is stretched between the drive timing pulley 57 and the drive timing pulley 57. The driving and driven timing pulleys 57, 58 and the belt 59 constitute a timing transmission device 60 for driving the camshaft 62 from the crankshaft 6 at a speed reduction ratio of ½, and the timing transmission device 60 includes
It is arranged between a pair of left and right cylinders 18, 18.

The driven timing pulley 5 is attached to the cam shaft 62.
8, a pair of exhaust cams 66, 66 arranged side by side, and intake cams 65, 6 adjacent to the outer ends of these exhaust cams 66, 66.
5 is formed symmetrically, and the outer intake cams 65, 65 are
The inner exhaust cams 66, 66 are formed to have a diameter smaller than that of the inner exhaust cams 66, 66 so that the entire exhaust cams 66, 66 fit within the base circle. The cam shaft 62 is provided with an intake valve 23 and an exhaust valve 24.
A pair of support walls 67, which are arranged on one side of a plane P including both axes so that the axes are substantially orthogonal to the plane P, and which are formed on the cylinder head 4 to support both ends of the cam support shaft 61. , 67 restricts the movement in the axial direction. A pair of small support walls 68, 68 are integrally connected to the support walls 67, 67. The small support walls 68, 68 are parallel to the cam support shaft 61 and substantially orthogonal to the plane P. Both ends of the rocker shaft 69 that is arranged as a pair are supported. This rocker shaft 6
The intake rocker arm 70 and the exhaust rocker arm 71 are individually supported by 9 to be swingable. That is, the intake rocker arm 70 and the exhaust rocker arm 71 are supported by one common rocker shaft 69.

The intake rocker arm 70 is supported by rocker shafts 69 on opposite side walls of the base end thereof, and its tip end abuts against the head of the intake valve 23 via an adjusting bolt 72. The arm 70a includes a second arm 70b that extends from one side wall of the first arm 70a and is in sliding contact with the outer peripheral surface of the intake cam 65.

The exhaust rocker arm 71 is supported by the rocker shaft 69 on opposite side walls of the base end while covering the base end of the first arm 70a, and the tip end thereof is attached to the head of the exhaust valve 24 by an adjusting bolt. A first arm 71a having a U-shaped cross section that abuts via the second arm 73, and a second arm 7 that extends from one side wall of the first arm 71a and is in sliding contact with the outer peripheral surface of the exhaust cam 66.
It consists of 1b.

The intake and exhaust valves 23, 24 are equipped with valve springs 74, 75 for biasing them in the valve closing direction.

Each rocker shaft 69 has an enlarged head portion 69a at an outer end portion directed to the outside of the cylinder head 4, and the head portion 69a is connected to the cylinder head 4 so as to cover the valve operating system. The head cover 76 is arranged so as to come into contact with the inner surface of the head cover 76. Therefore, when the head cover 76 is removed, the small supporting walls 68, 68 of the rocker shafts 69, 69 are removed.
However, when the head cover 76 is attached, the inner wall of the head cover 76 prevents the rocker shafts 69, 69 from being detached from the small support walls 68, 68.

A retaining pin 77 is attached to the rocker shaft 69 between the small support walls 68, 68, and the retaining pin 77 is inserted into the lateral hole 78 of the cam support shaft 61 to support the cam support shaft 61. The separation from the wall 67 is prevented.

The pair of left and right rocker shafts 69, 69 corresponding to the left and right cylinders 18, 18 are driven timing pulley 5
8 are disposed above both ends of a cam shaft 62 that is symmetrically formed with 8 in between. As a result, the valve gear, especially the camshaft 62
Axial compactification, and by extension, head cover 76, is made to be
A wide installation space for the spark plugs 25, 25 of both cylinders 18, 18 can be secured, and the maintainability is improved.

Thus, the timing transmission 6 from the crankshaft 6
When the cam shaft 62 is rotationally driven via 0, the intake and exhaust cams 65 and 66 are moved to the intake and exhaust rocker arms 70 and 7.
1 is driven individually, and in cooperation with the valve springs 73 and 74,
The intake and exhaust valves 23 and 24 can be opened and closed at their own opening and closing timings.

Moreover, the intake and exhaust rocker arms 70,
In 71, the second arms 70b, 7 which slidably contact the intake and exhaust cams 65, 66, respectively, in view of the step formed between the small-diameter intake cam 65 and the large-diameter exhaust cam 66.
The intake cam 65 and the exhaust rocker arm 7 are provided by simply projecting 1b from each of the first arms 70a and 71a in the axial direction.
1, mutual interference between the exhaust cam 66 and the intake rocker arm 70 can be avoided, so that the structure of each rocker arm 70, 71 is not complicated.

Further, the timing transmission 60 is arranged between the left and right cylinders 18, 18 so that each cylinder 18, 1
8 does not impair the cooling performance of both cylinders 18 and 18
It is possible to equalize the cooling performance of the.

Intake and exhaust rocker arms 70 and 71
By supporting one common rocker shaft 69, it is possible to reduce the number of parts, improve the assemblability, and reduce the cost.

Further, intake and exhaust rocker arms 70, 7
By supporting both side walls of the base end portions of the first arms 70a, 71a having a U-shaped cross section, on the rocker shaft 69, the support rigidity of the base end portions is increased, and the rocker arms 70, 7a.
The stable rocking of No. 1 can be assured, and moreover, the rocker arms 70 and 71 can be compactly arranged by stacking the base end portions thereof inside and outside, and the valve train can be made compact. .

The present invention is not limited to the above embodiments, and various design changes can be made without departing from the scope of the invention. For example, in the cam shaft 62, the large diameter side is the intake cam 65, the small diameter side is the exhaust cam 66, and the exhaust rocker arm 7 is inside the intake rocker arm 70.
1 can also be arranged.

[0049]

As described above, according to the first aspect of the present invention, a timing drive pulley driven by a crankshaft commonly connected to pistons in a pair of parallel cylinders and a shaft for a cylinder head. The cam shaft is provided with a timing driven pulley fixedly mounted on the cam shaft, and a timing transmission device including a timing drive pulley and a timing belt wound between the timing driven pulley. Two air-cooled cylinders, which are connected to a pair of rocker shafts supported by cylinder heads corresponding to a pair of cylinders, and are connected to intake and exhaust valves corresponding to a pair of cylinders through rocker arms that are swingable respectively. In the engine valve gear, since the timing transmission is arranged between the pair of cylinders, the cooling performance of both cylinders is not impaired, and It can be equalized in 却性.

According to the second feature of the present invention, in addition to the first feature, the camshaft has an intake / exhaust cam which operates the exhaust valve and an exhaust valve corresponding to a pair of cylinders, and a driven pulley sandwiches the driven cam. , And the rocker shafts corresponding to a pair of cylinders are arranged above and parallel to the cam shaft, so that the valve gear can be made compact, especially in the cam shaft axial direction, and it can be installed on both outsides of the cylinder head. It is possible to secure a wide installation space for the spark plug at the end portion, which is not disturbed by the valve operating device, and improve the maintainability.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional side view of essential parts of a general-purpose engine equipped with a valve gear of the present invention.

FIG. 2 is a view on arrow 2 of FIG.

FIG. 3 is a view on arrow 3 in FIG.

4 is a sectional view taken along line 4-4 of FIG.

5 is a sectional view taken along line 5-5 of FIG.

6 is a sectional view taken along line 6-6 of FIG.

7 is a view on arrow 7 of FIG.

8 is a sectional view taken along line 8-8 of FIG.

9 is a sectional view taken along line 9-9 of FIG.

FIG. 10 is a vertical sectional view (A), a left side view (B) and a right side view (C) showing a cam shaft.

[Explanation of symbols] E ... Air-cooled 2-cylinder engine 4 ... Cylinder head 6 ... Crankshaft 17: Piston 18: Cylinder 23 ... Intake valve 24 ... Exhaust valve 25: Spark plug 57-Drive timing pulley 58 ... driven timing pulley 59 ・ ・ ・ ・ ・ Timing belt 60: Timing transmission 62 ... Cam shaft 65 ... Intake cam 66 ... Exhaust cam 69: Rocker shaft 70 ... Intake rocker arm 71 Exhaust rocker arm

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 3G016 AA07 AA12 AA19 BA18 BA22                       BA27 BB11 BB19 BB26 CA41                       CA44 GA01                 3G024 AA18 BA29 CA19 DA01 DA06                       DA09 DA18 DA22

Claims (2)

[Claims] 1. A pair of cylinders (18, parallel to each other)
18) a timing drive pulley (57) driven by a crank shaft (6) commonly connected to pistons (17, 17), and a cam shaft (62) pivotally supported by a cylinder head (4), The timing driven pulley (58) fixed to the cam shaft (62) and the timing drive pulley (5)
7) and a timing belt (59) wound between a timing driven pulley (58) and a timing transmission device (60). The camshaft (62) has a pair of cylinders (18, 18). Correspondingly, intake and exhaust rocker arms (70, 71; 7) swingably supported by a pair of rocker shafts (69, 69) respectively supported by the cylinder head (4).
0, 71) and an intake / exhaust valve (23, 24; 23, 24) corresponding to a pair of cylinders (18, 18) connected to a valve train of an air-cooled two-cylinder engine. 60) is arranged between a pair of cylinders (18, 18). A valve operating system for an air-cooled two-cylinder engine. 2. A valve operating system for an air-cooled two-cylinder engine according to claim 1, wherein the camshaft (62) has intake and exhaust valves (23, 24; 2) corresponding to a pair of cylinders (18, 18).
Intake and exhaust cams (65, 66) for actuating 3, 24) are formed symmetrically with the driven pulley (58) in between, and rocker shafts (69, 6) corresponding to the pair of cylinders (18, 18) are formed.
9. A valve train for an air-cooled two-cylinder engine, characterized in that 9) is arranged above the cam shaft (62) in parallel therewith.