JP3835893B2 - Overhead internal combustion engine and method for manufacturing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an overhead valve type internal combustion engine and a method of manufacturing the same, and more particularly to a mounting structure for a valve operating apparatus in an overhead valve type four-cycle internal combustion engine having an intake valve and an exhaust valve.
[0002]
[Prior art]
In an air-cooled overhead valve type 4-cycle internal combustion engine, a bathtub type and a pent roof type are used as the combustion chamber type.
The present applicant has proposed the invention of Japanese Patent Application No. 8-37557 as one of air-cooled single-cylinder internal combustion engines (hereinafter referred to as engines) having the bathtub-type combustion chamber.
In this invention, the intake / exhaust valve layout is such that the intake valve and the exhaust valve are arranged in parallel to the axis of the cylinder, and a pair of rocker arms are swingably attached to one rocker arm shaft. The intake / exhaust valve is driven through a rocker arm.
However, the engine equipped with the bathtub-type combustion chamber is relatively easy to process and assemble the valve operating device, but is inferior to the pent-roof type in terms of combustion efficiency. It is like that.
[0003]
10 to 11 show an example according to the prior art of an air-cooled overhead valve type single-cylinder four-cycle internal combustion engine having the pent roof type combustion chamber, and FIG. 10 is a sectional view including the center of the cylinder and the center of the push rod. FIG. 11 is a ZZ sectional view of FIG. 10.
10 to 11, 1 is a combustion chamber, 2 is an air-cooled cylinder, 5 is a crankshaft, 6 is a connecting rod, 7 is a piston, 8 is a cylinder head, 14a is an intake valve, 14b is an exhaust valve (hereinafter referred to as the above-mentioned). The intake valve 14a and the exhaust valve 14b are collectively referred to as the intake / exhaust valve 14).
[0004]
Reference numeral 17 denotes a camshaft that is linked to the crankshaft 5 through a gear train, 17a is a cam formed on the camshaft 17, 16 is a tappet, 15 is a push rod, and 13 is fixed to the upper surface of the cylinder head 8. A rocker arm shaft fixedly supported by the rocker arm support 22, 11 is a rocker arm fitted to the rocker arm shaft 13 in a swingable manner, 18 is a valve spring, and 19 is a valve spring holder. A head cover 9 is attached to the upper surface of the cylinder head 8, that is, the mating surface 8b, and covers the valve mechanism. During the operation of the engine, the intake / exhaust valve 14 is opened / closed at a timing determined by the rotating cam 17a that is decelerated to 1/2 through a timing gear (not shown) from the rotation of the crankshaft 5. The
That is, in FIG. 10, the push rod 15 is pushed up by the rotation of the cam shaft 17a, the rocker arm 11 swings around the rocker arm shaft 13 and pushes up the intake valve 14a or the exhaust valve 14b against the elasticity of the valve spring 18, Let the valve open.
[0005]
In such an engine, in order to accurately transmit the movement of the cam 17a to the intake / exhaust valve 14 via the push rod 15, the valve spring 18 is composed of a so-called strong spring having a relatively large spring constant, and the rocker arm shaft. 13 has a relatively large diameter.
Further, during the operation of the engine, in order to prevent an excessive force from being applied to the joint portion of the valve operating mechanism due to the temperature rise of the cylinder head 8, the adjustment portion for adjusting the clearance is provided at the joint portion between the rocker arm 11 and the push rod 15. A screw (not shown) is provided.
In the cylinder head 8, the head cover 9 is fixed in a watertight manner to the mating surface 8b which is the upper surface of the peripheral wall 8c, and the rocker arm is fixed to the upper surface 8a of the central portion which is depressed by a certain amount from the mating surface 8b. The abutment 22 is fixed with bolts.
[0006]
JP-A-5-133204 and JP-A-5-133205 have been proposed as overhead valve engines having hemispherical combustion chambers and radially arranged intake and exhaust valves. The support mechanism of the valve mechanism in the cylinder head has a three-dimensional arrangement, and it is quite difficult to obtain high machining accuracy, and the torsional force acts on the components of the valve mechanism when the valve is driven. have.
[0007]
[Problems to be solved by the invention]
On the upper surface of the cylinder head 8 of the overhead valve type four-cycle internal combustion engine according to the prior art as shown in FIGS. 10 to 11, the mating surface 8 b for fixing the head cover 9 and the rocker arm abutment 22 are fixed. It is necessary to finish the two mounting surfaces 8a to a certain degree of smoothness by machining.
However, in such a conventional cylinder head 8, the height of the mating surface 8b for mounting the head cover 9 and the mounting surface 8a for mounting the rocker arm abutment 22 is different, so that two-stage processing is performed or the processing tool is replaced. Therefore, there are problems that the number of processing steps increases and extra processing preparation costs are required.
[0008]
In the overhead valve internal combustion engine having one intake valve and one exhaust valve, the mounting surface of the rocker arm abutment of the cylinder head and the mating surface of the head cover can be formed on the same plane. It is another object of the present invention to simplify the means for assembling the valve mechanism to the cylinder head, reduce the processing man-hours and assembly man-hours, and reduce the cost of the apparatus.
[0009]
[Means for Solving the Problems]
The present invention solves such a problem. As a first invention, a cylinder head having a combustion chamber formed in an upwardly convex curved surface, such as a hemispherical type or a pent roof type, is provided with an intake valve and an exhaust valve. A rocker arm abutment fixed to the upper surface of the cylinder head, a rocker arm shaft supported by the abutment, and a central portion swingably inserted into the rocker arm shaft. And a rocker arm to which the push rod and the intake / exhaust valves are respectively connected at both ends, and a head cover that covers the valve mechanism comprising the intake / exhaust valve, the rocker arm abutment, the rocker arm shaft, the rocker arm, etc. In the overhead valve internal combustion engine fixed to the upper surface of the cylinder head, the cylinder head forms a mating surface with the head cover on the upper surface of the peripheral wall Both the rocker arm abutment surface is formed on the upper surface of the boss portion extending from the peripheral wall of the cylinder head to the inner peripheral side and formed near the center of the head, and the attachment surface of the rocker arm abutment is connected to the mating surface. The rocker arm abutment is mounted near the center of the upper surface of the cylinder head, and the intake and exhaust valves are provided on both sides of the abutment. The rocker arm shaft is fixed to the rocker arm abutment symmetrically with respect to the center of the cylinder, and a pair of intake valve and exhaust valve is provided. Both shaft centers are attached to the rocker arm abutment. Arranged so as to be parallel to each other in a plane parallel to the surface, and the rocker arms are respectively fitted and inserted into the rocker arm shafts for the intake valve and the exhaust valve. The overhead characterized in that a first arm part connected to the push rod and a second arm part for pressing the intake / exhaust valve are provided at both ends sandwiching the insertion part to the rocker arm shaft. A valve-type internal combustion engine is proposed.
[0010]
In the first aspect of the invention, preferably, the cylinder head is formed with a mating surface with the head or the bar on the upper surface of the peripheral wall, and the mounting surface of the rocker arm abutment is arranged on the inner peripheral side from the peripheral wall. It is formed on the upper surface of the boss part extending to the top.
[0011]
According to the first aspect of the invention, the rocker arm, the accessory such as the adjusting screw attached to the rocker arm, the mounting surface of the cylinder head for attaching the rocker arm abutment for supporting the rocker arm shaft and the like and the peripheral wall of the cylinder head are formed. The mounting surface for mounting the head cover is provided on the same plane or the mounting surface formed near the center of the cylinder head so as to be positioned slightly above the mating surface. The surface can be machined simultaneously.
This eliminates the need for two-stage machining or tool change during machining, unlike the prior art, and greatly reduces the machining man-hours. As described above, since the machining is simultaneous, high flatness, that is, machining accuracy is achieved. can get.
[0012]
Further, the following three inventions are proposed as specific configurations of the valve operating mechanism in the first invention.
[0013]
(1) In the first configuration, the rocker arm abutment is attached near the center of the upper surface of the cylinder head, and the intake valve and the exhaust valve are respectively provided on both sides of the abutment. A pair of intake and exhaust valves are fixed to the rocker arm abutment symmetrically about the cylinder center, and both axes are parallel to each other in a plane parallel to the mounting surface of the rocker arm abutment. The rocker arms are respectively fitted and inserted into the rocker arm shafts for the intake valve and the exhaust valve, and are connected to push rods at both end portions of the rocker arms sandwiching the fitting portions of the rocker arms into the rocker arm shaft. And a second arm portion that presses the intake / exhaust valve.
[0014]
According to this configuration, since the rocker arm shaft for the intake / exhaust valve is supported by the rocker arm abutment on both ends, the bending stress acting on the rocker arm shaft during operation of the rocker arm is reduced, and the rocker arm and rocker arm with high strength are reduced. A shaft support structure is obtained.
[0015]
(2) In the second configuration, the rocker arm abutment is attached to a center portion of the upper surface of the cylinder head, and the intake valve and the exhaust valve are respectively provided on both sides of the abutment. An end portion on the center side is fixed to the abutment in a cantilevered manner, a rocker arm shaft for an intake valve extending from the fixed portion in a direction perpendicular to the axial center of the intake valve, and an axial center of the exhaust valve from the fixed portion A rocker arm shaft for an exhaust valve extending in a direction perpendicular to the rocker arm, and the rocker arm is provided with a pair of center portions fitted in the respective rocker arm shafts, and at both ends of each rocker arm sandwiching the fitting insertion portion. A first arm portion connected to the push rod and a second arm portion that presses the intake valve or the exhaust valve are provided.
[0016]
According to this configuration, since the rocker arm shaft is fixedly supported on both sides of the rocker arm abutment by a cantilever type, the rocker arm abutment can be downsized and the area of the mounting surface of the cylinder head can be reduced. Surface processing man-hours are reduced.
Further, the arm length of the rocker arm can be increased, and an excessive force can be prevented from being applied to the valve operating device.
[0017]
(3) In the third configuration, the pair of rocker arm shafts are separated from the center side toward the outside with respect to a line connecting the intake valve center and the exhaust valve center in a planar arrangement. In this way, it is inclined at a certain angle.
According to such a configuration, the connection point of the rocker arm to the push rod side and the contact point of the intake / exhaust valve side are located on a substantially straight line across the rocker arm axis, and the connection point on the axis is There is no displacement between the contact point and the contact point, and no rocker arm bending moment is generated by the displacement, and a rocker arm with high strength can be obtained.
[0018]
2. The overhead valve according to claim 1, wherein the rocker arm shaft and the rocker arm are assembled with the rocker arm shaft so that the rocker arm can be attached to the mounting surface of the cylinder head. An internal combustion engine is proposed.
[0019]
According to the present invention, as a preferred method for manufacturing such an internal combustion engine, the upper surface of a cylinder head having a combustion chamber formed in an upwardly convex curved shape is extended from the peripheral wall of the head to the inner peripheral side. A cylinder head formed so that the mounting surface of the rocker arm abutment formed on the upper surface of the boss portion provided near the center is positioned to be the same as or slightly above the mating surface of the head cover;
The rocker arm abutment is fixed to the rocker arm abutment and is provided with a pair for intake valve and exhaust valve, and both axes are parallel to each other in a plane parallel to the mounting surface of the rocker arm abutment. Prepare an assembly product that assembles the rocker arm shaft and the rocker arm for intake valve and exhaust valve,
While fixing the assembly including the rocker arm abutment on the upper surface of the cylinder head, the intake valve and the exhaust valve are arranged symmetrically with respect to the cylinder axis, and assembled.
The present invention proposes a method for manufacturing an overhead valve type internal combustion engine characterized in that a push rod and the intake / exhaust valves are respectively connected to both ends of the rocker arm.
[0020]
More preferably, as described in claim 4,
Incorporate combustion chamber air supply and exhaust valves and push rods into the cylinder head,
Next, the mounting surface of the rocker arm abutment formed on the upper surface of the boss part extending from the peripheral wall of the cylinder head to the inner peripheral side and provided near the center of the head is the same as or aligned with the mating surface of the head cover. On the mounting surface of the rocker arm abutment formed so as to be slightly above the surface, the rocker arm for the intake valve and the exhaust valve, the shaft of the pair of rocker arm shafts for the intake valve and the exhaust valve fixed by both ends A valve mechanism in which a rocker arm abutment, a valve gap adjusting screw and a lock nut, which are arranged so that their cores are parallel to each other in a plane parallel to the mounting surface of the rocker arm abutment, is assembled in a unit shape in advance. rear,
A method for manufacturing an overhead valve type internal combustion engine, characterized in that a head cover is fixed to a cylinder head.
[0021]
According to such a configuration, the rocker arm shaft, the rocker arm and its accessories are assembled into a unit by assembling the rocker arm abutment, and this unit is assembled to the cylinder head, so that the assembly and adjustment of the valve mechanism is simplified and the assembly man-hour is reduced. The
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, and are merely illustrative examples. Only.
Figure 1 Embodiment of the present invention FIG. 2 is a plan view of the air-cooled head valve type single-cylinder four-cycle internal combustion engine including the cylinder center and the push rod center, FIG. 2 is a plan view excluding the head cover in FIG. It is.
1 to 3, 1 is a combustion chamber, 2 is an air-cooled cylinder, 5 is a crankshaft, 6 is a connecting rod, 7 is a piston, 8 is a cylinder head, 14a is an intake valve, 14b is an exhaust valve (hereinafter referred to as an intake valve). 14a and the exhaust valve 14b are collectively referred to as the intake / exhaust valve 14), 51 is a spark plug, and 52 is a crankcase.
[0023]
17 is a camshaft linked to the crankshaft 5 through a gear train, 17a is a cam formed on the camshaft 17, 16 is a tappet, 15 is a push rod, and 18 is a valve for the intake / exhaust valve 14. A spring 19 is a spring bearing that supports the valve spring 18. A head cover 9 is attached to the upper surface of the peripheral wall 8c of the cylinder head 8, that is, the mating surface 101, and covers a valve mechanism to be described later.
[0024]
The combustion chamber 1 is a so-called pent roof type combustion chamber. For this reason, the intake valve 14a and the exhaust valve 14b are arranged such that their axial centers 103 and 104 extend upward with respect to the cylinder center 102 as shown in FIG. In other words, it is inclined by an inclination angle θ so as to be radial.
The inclination angle θ is 2θ = about 22 ° to 45 °, preferably around 45 °.
[0025]
Reference numeral 21 denotes an intake valve rocker arm, and reference numeral 21 ′ denotes an exhaust valve rocker arm having a symmetrical shape with respect to the intake valve rocker arm 21 and the cylinder center 102. Reference numerals 23 and 23 denote rocker arm shafts, and reference numeral 22 denotes a rocker arm abutment.
The rocker arms 21 and 21 ', the rocker arm shaft 23, the rocker arm abutment 22, the cam 17a, the tappet 16, the push rod 15 and the like constitute a valve operating mechanism.
[0026]
As shown in FIG. 2, the rocker arm abutment is fixed by four bolts 25 to the upper surface of the boss 8d extending from the peripheral wall 8c of the cylinder head 8 to the inner peripheral side, that is, the mounting surface 100. The rocker arm shafts 23 and 23 for the intake valve and the exhaust valve are supported by the both ends by the four support portions 22a and 22b formed symmetrically with respect to the cylinder center 102, and the two rocker arm shafts 23 and 23 are supported. Are fixedly supported in parallel.
[0027]
Further, as shown in FIG. 2, the rocker arm shafts 23, 23 are mounted on the rocker arm support 22 so that the shaft centers 23a, 23a are perpendicular to a line 105 connecting the center of the intake valve 14a and the center of the exhaust valve 14b. Installed.
[0028]
As shown in FIG. 2, the intake valve rocker arm 21 and the exhaust valve rocker arm 21 'have a central cylindrical portion with a large diameter so as to have a sufficiently large bearing area. The first arm portions 21b and 21′b are formed on the push rod 15 side of the rocker arm shafts 23 and 23 in the axial direction, and are supported by the rocker arm shafts 23 and 23. Second arm portions 21c and 21′c are formed on the side of 14a and the exhaust valve 14b.
[0029]
Adjustment screws 24 and 24 for adjusting the clearance of the valve operating mechanism are screwed into the first arm portions 21b and 21'b, respectively. Each adjustment screw 24, 24 is provided with a spherical bearing at its tip, and is connected to the push rods 15, 15 for the intake valve and the exhaust valve via the spherical bearing. The second arm portions 21c and 21'c are in contact with the intake valve 14a and the exhaust valve 14b via the metal pads 21a and 21a made of wear-resistant material.
[0030]
The mounting surface 100 of the rocker arm support 22 on the upper surface of the cylinder head 8 is formed so as to be flush with the mating surface 101 for mounting the head cover 9.
The mounting surface 100 and the mating surface 101 are most preferably the same plane, but may be slightly up and down. In this case, the mounting surface 100 on the outside is the mounting surface 100 on the outside in processing. It is preferable to be slightly below.
[0031]
During the operation of the engine, the intake / exhaust valve 14 is opened and closed at a timing determined by a cam 17a that is decelerated to 1/2 by a timing gear (not shown) from the rotation of the crankshaft 5 and rotates. The
That is, the push rods 15 and 15 are pushed up by the rotation of the cam shaft 17a, and the rocker arm 21 or 21 'for the intake valve or the exhaust valve swings around the rocker arm shaft 23 so that the intake valve 14a or the exhaust valve 14b becomes a valve spring. Push up against the elasticity of 18, 18 to open the valve.
In such an engine, the valve spring 18 comprises a so-called strong spring having a relatively large spring constant in order to accurately transmit the movement of the cam 17a to the intake / exhaust valve 14 via the push rods 15, 15. As described above, the rocker arm shaft 23 has a relatively large diameter.
[0032]
The upper surface, that is, the mounting surface 100 of the cylinder head 8 to which the rocker arm abutment 22 for supporting the valve mechanism for performing such an operation on the cylinder head 8 side is attached to the mating surface 101 for mounting the head cover 9 as described above. They are formed on the same plane. For this reason, the two surfaces of the mounting surface 100 and the mating surface 101 can be finished by machining at the same time, and there is no need for two-step processing or replacement of processing tools as in the prior art.
[0033]
Further, in this embodiment, the rocker shafts 23 and 23 are fixed to the rocker arm abutment 22, and the intake valve rocker arm 21 and the exhaust valve rocker arm 21 ′ are screwed into the rocker shafts 23 and 23 with the adjusting screw 24. The unit can be inserted into the unit, and the unit can be assembled to the cylinder head 8. This facilitates assembly and adjustment of the valve mechanism.
[0034]
In this embodiment, the rocker arm shafts 23 and 23 for the intake valve and the exhaust valve are supported on the support portions 22a and 22b of the rocker arm abutment 22 by a both-end support type, so that the rocker arms 21 and 21 ' The bending stress acting on the rocker arm shafts 23, 23 during operation is reduced, and a rocker arm having a high strength and a support structure for the rocker arm shaft can be obtained.
[0035]
4 to 6 show the present invention. First reference example 4 is a plan view corresponding to FIG. 2, FIG. 5 is a sectional view taken along line BB in FIG. 4, and FIG. 6 is a view taken in the direction of arrow C in FIG.
this Reference example The configuration of the rocker arm abutment, rocker arm shaft and rocker arm Real Different from the embodiment.
[0036]
4 to 6, reference numeral 27 denotes a rocker arm support, which extends in a direction perpendicular to a line 105 connecting the center of the intake valve 14a and the center of the exhaust valve 14b of the cylinder center 102, and is provided with two bolts 25, 25. Accordingly, the cylinder head 8 is fixed to the mounting surface 100 on the boss 8d extending inward from the peripheral wall 8c of the cylinder head 8.
The mounting surface 100 of the rocker arm support 27 is also provided so as to be flush with or slightly above the mating surface 101 for mounting the head cover 9, as in the first embodiment.
[0037]
Reference numerals 28 and 28 denote rocker arm shafts, and as shown in FIG. 4, the rocker arm abutment is arranged so that the axial center 28a thereof is substantially parallel to the line 105 connecting the centers of the intake / exhaust valves 14a and 14b. A portion near the center is fixed to 27 and is supported in a cantilever manner.
Further, as shown in FIG. 5, the rocker arm shafts 28, 28 are arranged in the direction of the cylinder center line 102, and the axial centers 14a of the intake valves 14a and the exhaust valves 14b in which the axes 28a, 28a are radially arranged. ₁ And 14b ₁ It is inclined so as to be substantially perpendicular to the direction.
An intake valve rocker arm 26 and an exhaust valve rocker arm 26 have a symmetrical shape with respect to the cylinder center 102, and a cylindrical portion at the center of the rocker arm is swingable with respect to the rocker arm shafts 28, 28. The movement in the direction is restricted and inserted.
[0038]
The intake valve rocker arm 26 and the exhaust valve rocker arm 26 'are respectively provided with first arm portions 26b and 26'b on the push rod 15 side with the rocker arm axis 28a interposed therebetween, and the intake valve 14a side and Second arm portions 26c and 26'c are provided on the exhaust valve 14b side.
Then, adjustment screws 24 and 24 for adjusting the clearance of the valve operating device are screwed into the first arm portions 26b and 26'b, respectively, and are connected to the push rods 15 and 15 via spherical bearings at the tips thereof. Yes.
Further, the respective second arm portions 26c and 26'c are in contact with the intake valve 14a and the exhaust valve 14b through a metal pad 26a.
Other configurations are shown in FIGS. Fruit It is the same as that of embodiment, and the same member is shown with the same code | symbol.
[0039]
this Reference example In the front Real Similar to the embodiment, the mounting surface 100 of the rocker arm abutment on the upper surface of the cylinder head 8 is formed on the same plane as the mating surface 101 for mounting the head cover 9 on the peripheral wall 8c or slightly higher than the mating surface 101. Therefore, processing in one stage is possible and the number of processing steps is reduced. In addition to this, the rocker arm abutment 27 is reduced in size, and the area of the mounting surface 100 of the cylinder head 8 is smaller than that in the first embodiment. Therefore, the mounting surface 100 can be further easily processed and the number of processing steps can be reduced.
Further, the length of the rocker arms 26 and 26 'can be increased due to the structure, the design of the valve mechanism can be afforded, and excessive force can be prevented from being applied to the valve operating device.
[0040]
7 to 9 show the present invention. Second reference example 7 is a plan view corresponding to FIG. 2, FIG. 8 is a sectional view taken along the line DD of FIG. 7, and FIG. 9 is a view taken along arrow E of FIG.
this Second reference example Said First reference example The rocker arm abutment and the rocker arm shaft arrangement are First reference example And different.
[0041]
7 to 9, reference numeral 32 denotes a rocker arm support, which extends in a direction perpendicular to a line 105 connecting the center of the intake valve 14a and the center of the exhaust valve 14b of the cylinder center 102, and is provided with two bolts 25, 25. Thus, the cylinder head 8 is fixed to the mounting surface 100 on the boss 8d extending inward from the peripheral wall 8c of the cylinder head 8. As with the first and second embodiments, the mounting surface 100 of the rocker arm support 32 is also provided so as to be flush with or slightly above the mating surface 101 for mounting the head cover 9.
[0042]
Reference numerals 33 and 33 denote rocker arm shafts, and as shown in FIG. 7, when the shaft center 33a is arranged in a plane, the angle α with respect to the line 105 connecting the intake and exhaust valves 14a and 14b ₁ , Α ₂ Only the central portion is fixed to the rocker arm abutment 32 so as to be inclined outward from the central portion and supported in a cantilever manner.
As shown in FIG. 8, the rocker arm shafts 33, 33 are arranged in the direction of the cylinder center line 102. As shown in FIG. 8, the shaft centers 33a, 33a of the intake valves 14a and exhaust valves 14b are arranged radially. ₁ And 14b ₁ It is made to be in a direction substantially perpendicular to the direction.
Reference numeral 31 denotes an intake valve rocker arm, 31 ′ denotes an exhaust valve rocker arm, which has a symmetric shape with respect to the cylinder center 102, and a cylindrical portion at the center of the rocker arm is swingable with respect to the rocker arm shafts 33 and 33, The movement in the direction is restricted and inserted.
[0043]
The intake valve rocker arm 31 and the exhaust valve rocker arm 31 ′ are provided with first arm portions 31b and 31′b on the push rod 15 side with the rocker arm axis 33a interposed therebetween, and the intake valve 14a side. The second arm portions 31c and 31′c are provided on the exhaust valve 14b side.
Then, adjustment screws 24 and 24 for adjusting the clearance of the valve operating device are screwed into the first arm portions 31b and 31'b, respectively, and are connected to the push rods 15 and 15 via spherical bearings at the tips thereof. Yes.
Each of the second arm portions 31c and 31'c is in contact with the intake valve 14a and the exhaust valve 14b via a stopper 26a. The other structure is the same as that of 2nd Embodiment shown in FIGS. 4-6, and the same member is shown with the same code | symbol.
[0044]
this Second reference example Even before Real Form And the first reference example Similarly, the mounting surface 100 of the rocker arm abutment on the upper surface of the cylinder head 8 is formed on the same plane as the mating surface 101 for mounting the head cover 9 on the peripheral wall 8c or slightly higher than the mating surface 101. Processing can be performed in one stage, and processing man-hours are reduced.
[0045]
Also this Second reference example As in the second embodiment, since the area of the mounting surface 100 of the rocker arm abutment 32 can be smaller than that of the first embodiment, the rocker arms 31, 31 ′ can be reduced in size and the mounting surface can be reduced. The processing of 100 is further simplified, and the arm lengths of the rocker arms 31 and 31 'can be increased structurally, so that an excessive force can be prevented from being applied to the valve operating mechanism.
[0046]
In addition, this Second reference example , The axis 33a of the rocker arm shaft 33 has the angle α ₁ , Α ₂ Therefore, the first arm portions 31b and 31'b of the intake / exhaust valves 14a and 14b are connected to the push rod 15 (the center of the adjusting screw 24) and the second arm portions 31c and 31 '. The contact point (the center of the stopper 26a) of the intake / exhaust valves 14a and 14b with c is located on the straight lines 50 and 50 'as shown in FIG. There is no deviation between the connection point and the contact point on the line 33a, and no moment is generated in the rocker arms 31, 31 'due to such deviation, and an excessive force is applied to the rocker arms 31, 31' by this moment. There is no.
[0047]
【The invention's effect】
As described above, according to the present invention, the mounting surface of the cylinder head for mounting the rocker arm support for supporting the rocker arm, the rocker arm shaft, etc., and the mating surface for mounting the head cover formed on the peripheral wall of the cylinder head are provided. By providing the mounting surface, which is formed on the same plane or near the center of the cylinder head, slightly above the mating surface, the two surfaces of the mounting surface and mating surface can be machined simultaneously. It becomes.
This eliminates the need for two-stage machining and tool change during machining as in the prior art, and can significantly reduce the number of machining steps compared to the prior art, and is simultaneous machining as described above. Degree, that is, high machining accuracy can be obtained.
[0048]
Further, according to the present invention, since the rocker arm shaft for the intake / exhaust valve is supported on the rocker arm abutment on both ends, that is, supported by both ends, the bending stress acting on the rocker arm shaft during operation of the rocker arm is reduced, High strength rocker arm and rocker arm shaft support structure can be obtained.
[0049]
[0050]
[0051]
Furthermore, according to the inventions of claims 2 to 4, since the rocker arm shaft, the rocker arm and its accessories are assembled to the rocker arm abutment to form a unit, and this unit is assembled to the cylinder head, the assembly and adjustment of the valve operating mechanism is easy. Thus, the assembly man-hour is reduced.
[Brief description of the drawings]
FIG. 1 is a sectional view including a cylinder head center and a push rod center of an air-cooled overhead valve type single cylinder four-cycle internal combustion engine according to a first embodiment of the present invention.
FIG. 2 is a plan view excluding a cylinder head cover in FIG.
FIG. 3 is a cross-sectional view taken along line AA in FIG.
FIG. 4 of the present invention First reference example FIG. 3 is a diagram corresponding to FIG.
5 is a cross-sectional view taken along line BB in FIG.
6 is a view taken in the direction of arrow C in FIG. 5 (a view seen through the valve mechanism).
[Fig. 7] of the present invention. Second reference example FIG. 3 is a diagram corresponding to FIG.
8 is a cross-sectional view taken along line DD of FIG.
FIG. 9 is a view on arrow E in FIG. 8 (a perspective view of the valve mechanism).
FIG. 10 is a view corresponding to FIG. 1 showing a conventional air-cooled overhead valve type four-cycle internal combustion engine.
11 is a sectional view taken along line ZZ in FIG.
[Explanation of symbols]
1 Combustion chamber
2 cylinders
5 Crankshaft
7 Piston
8 Cylinder head
8c Surrounding wall
8d boss
9 Head cover
14a Intake valve
14b Exhaust valve
15 Push rod
16 Tappet
17 Camshaft
17a cam
18 Valve spring
21, 26, 31 Intake valve rocker arm
21 ', 26', 31 'Rocker arm for exhaust valve
22, 27, 32 Rocker arm abutment
23, 28, 33 Rocker arm shaft
24 Adjustment screw
25 volts
21b, 21′b, 26b, 26′b, 31b, 31′b First arm portion
21c, 21'c, 26c, 26'c, 31c, 31'c Second arm part
52 Crankcase
100 Mounting surface
101 mating surface

Claims (4)

A rocker arm abutment fixed to the upper surface of the cylinder head, and assembled to a cylinder head having a combustion chamber formed in an upwardly convex curved surface and assembled with an intake valve and an exhaust valve arranged symmetrically with respect to the cylinder axis. A rocker arm shaft supported by the abutment, a rocker arm having a central portion slidably fitted on the rocker arm shaft, and a push rod and the intake / exhaust valves connected to both ends, respectively. In an overhead valve type internal combustion engine in which a head cover that covers a valve mechanism composed of an exhaust valve, a rocker arm abutment, a rocker arm shaft, a rocker arm, etc. is fixed to the upper surface of the cylinder head,
The cylinder head forms a mating surface with the head cover on the upper surface of the peripheral wall, and extends to the inner peripheral side from the peripheral wall of the cylinder head and is formed on the upper surface of a boss portion formed near the center of the head. The mounting surface of the base is formed, and the mounting surface of the rocker arm abutment is formed to be the same as or slightly above the mating surface, and the rocker arm abutment is the center of the upper surface of the cylinder head The intake valve and the exhaust valve are respectively provided on both sides of the abutment, and the rocker arm shaft is fixed to the rocker arm abutment symmetrically with respect to the cylinder center. A pair of valves is provided, and both axial centers are arranged so as to be parallel to each other within a plane parallel to the mounting surface of the rocker arm abutment. A first arm portion and an intake / exhaust valve which are respectively fitted and inserted into the rocker arm shafts for the intake valve and the exhaust valve, and are connected to the push rods at both ends sandwiching the fitting insertion portions of the respective rocker arms to the rocker arm shafts An overhead valve type internal combustion engine, comprising: a second arm portion for pressing the valve.   The overhead valve type internal combustion engine according to claim 1, wherein the rocker arm shaft and the rocker arm are assembled to the rocker arm base so that the base can be attached to a mounting surface of the cylinder head. A rocker arm formed on the upper surface of a boss part extending from the peripheral wall of the cylinder head to the inner peripheral side and provided near the center of the head, with the upper surface of the cylinder chamber having a combustion chamber formed in an upwardly convex curved shape A cylinder head formed so that the mounting surface of the abutment is positioned to be the same as or slightly above the mating surface of the head cover;
The rocker arm abutment is fixed to the rocker arm abutment and is provided with a pair for intake valve and exhaust valve, and both axes are parallel to each other in a plane parallel to the mounting surface of the rocker arm abutment. Prepare an assembly product that assembles the rocker arm shaft and the rocker arm for intake valve and exhaust valve,
While fixing the assembly including the rocker arm abutment on the upper surface of the cylinder head, the intake valve and the exhaust valve are arranged symmetrically with respect to the cylinder axis, and assembled.
A method of manufacturing an overhead valve type internal combustion engine, wherein a push rod and the intake / exhaust valves are respectively connected to both ends of the rocker arm. Incorporate combustion chamber air supply and exhaust valves and push rods into the cylinder head,
Next, the mounting surface of the rocker arm abutment formed on the upper surface of the boss part extending from the peripheral wall of the cylinder head to the inner peripheral side and provided near the center of the head is the same as or aligned with the mating surface of the head cover. On the mounting surface of the rocker arm abutment formed so as to be slightly above the surface, the rocker arm for the intake valve and the exhaust valve, the shaft of the pair of rocker arm shafts for the intake valve and the exhaust valve fixed by both ends A rocker arm abutment, a valve gap adjusting screw and a lock nut, which are arranged so that their cores are parallel to each other in a plane parallel to the mounting surface of the rocker arm abutment, are assembled in advance. rear,
A method of manufacturing an overhead valve type internal combustion engine, wherein a head cover is fixed to a cylinder head.

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