JPH0441203Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The invention has two intake valves and two exhaust valves for one cylinder, which are connected by one overhead camshaft through a rocker arm. The present invention relates to a valve driving device for an engine, and more particularly to the shape and arrangement structure of each rocker arm.

(Prior art) As an engine for automobiles, etc., one cylinder has two
2. Description of the Related Art A four-valve engine has been put into practical use, and has four intake valves and two exhaust valves arranged in a substantially rectangular shape. According to this engine, the intake air filling efficiency and the exhaust efficiency are improved, and the combustion state is improved, thereby realizing high output of the engine. In addition, in this four-valve engine, the intake valve diameter is configured to be larger than the exhaust valve diameter in order to ensure the required intake air filling efficiency, and accordingly, the distance between the centers of the intake valves is also smaller than the center of the exhaust valves. It is customary for each valve to be arranged such that it is large compared to the distance between them.

On the other hand, a dual overhead camshaft engine in which the intake valve and the exhaust valve are driven by different camshafts has been put into practical use. According to this engine, by eliminating the rocker arm in the valve mechanism, the reciprocating inertial mass that impedes high engine speed is reduced, making it possible to increase the engine speed.
However, this double overhead camshaft engine has a disadvantage in that it has a significantly complicated structure and is therefore expensive.

Therefore, in the case of an engine that requires high output but does not require particularly high revolutions, each cylinder is equipped with two intake valves and two exhaust valves, and these valves are driven by one overhead camshaft. , it is possible to secure the required output and reduce costs. Such a four-valve single overhead camshaft engine is shown in, for example, Japanese Patent Laid-Open No. 59-96405. This has two intake valves and two exhaust valves arranged in a rectangular shape for one combustion chamber, and one valve located above the center of the combustion chamber.
A camshaft is provided, and two intake cams and two exhaust cams are alternately formed on the camshaft,
These cams drive the intake valve and exhaust valve via the intake valve rocker arm and the exhaust valve rocker arm.

(Problem that the invention aims to solve) By the way, the intake and exhaust valves and the intake and exhaust valves above the combustion chamber,
When actually manufacturing a four-valve single overhead camshaft engine as described above in which a rocker arm is interposed between each engine and the exhaust cam, the following points need to be taken into consideration.

In other words, each of the above-mentioned intake and exhaust cams is required to have as wide a cam width as possible (width of the part that actually slides in contact with the rocker arm) so that the surface pressure is small, and each rocker arm is required to have the widest cam width possible. It is desirable to use the same type of parts to avoid incorrect assembly and cost increases during manufacturing. However, in reality, each suction is arranged in a roughly rectangular shape.
Since it is necessary to have both ends of the rocker arm in contact with the exhaust valve and each of the four intake and exhaust cams (for one cylinder) formed in a line along the camshaft, a sufficient cam width was ensured. It is difficult to use the same type of rocker arms for all of the four rocker arms above. In other words, when using the same type of rocker arm, the cam width must be sacrificed. On the other hand, if four rocker arms of different types are used, a sufficient cam width can be secured for each intake and exhaust cam, but on the other hand, there will be an increase in cost as mentioned above. Problems such as incorrect assembly will occur.

Furthermore, in the case of engines with this type of locker arm, in order to prevent uneven wear of the valve face portions of each intake and exhaust valve and the corresponding valve seats, the valve stem portion of the locker arm is attached to the stem portion of each valve. You will need to offset the side edges slightly.

The present invention addresses the above-mentioned actual situation regarding the valve drive system for a four-valve single overhead camshaft engine.In this type of valve drive system, the intake and exhaust cams are For the cam width, we have made it possible to obtain the maximum value determined by the cylinder bore diameter, etc., and we have also made it possible to use two types of rocker arms, thereby improving productivity, ease of assembly, and reliability. The aim is to simultaneously achieve this goal. In addition to this purpose, the present invention also aims to ensure required valve diameters in the intake and exhaust valves and to prevent uneven wear of the valves, valve seats, etc.

(Means for Solving the Problems) In order to achieve the above object, the engine valve drive device according to the present invention has two intake valves and two exhaust valves for one cylinder in a position between the centers of the intake valves. one overhead cam shaft arranged in a substantially rectangular shape so that the distance is greater than the distance between the exhaust valve centers, and two intake cams and two exhaust cams are arranged alternately; Two intake valve rocker arms and two exhaust valve rocker arms are interposed between the stem portion and cam of the valve in correspondence with each of the valves and cams, respectively, and two rocker arms are arranged on both sides of the camshaft. The device has two rocker arm shafts that pivotally support rocker arms for intake valves and exhaust valves, respectively, and each of the valves is driven by a camshaft via each rocker arm, and is configured as follows. Features.

That is, for a pair of rocker arms located diagonally with respect to the cylinder bore center, the valve stem side end and the cam side end thereof are offset with respect to the cam axis direction. The other pair of rocker arms shall be of the same type with a shape in which the end on the valve stem side and the end on the cam side are at approximately the same position with respect to the cam axis direction. do. On the intake side, the axes of both valve stems move away from each other along the camshaft direction, and on the exhaust side, the axes of both valve stems move toward each other along the camshaft direction. Offset with respect to the valve abutment on the corresponding rocker arm.

(Function) According to the above configuration, there are a total of 4 cylinders per cylinder.
Among the rocker arms provided separately, the rocker arms located diagonally around the cylinder bore center are the same type of rocker arm, and both ends thereof are offset so as to correspond to the valve stem and cam. The other pair of rocker arms are also the same type of rocker arms, and both ends thereof are located at approximately the same position in the cam axis direction so as to correspond to the valve stem portion and cam. Since the rocker arm is shaped as follows, the cam side end of each rocker arm can be brought into optimal contact with the intake and exhaust cams formed alternately along the camshaft. This makes it possible to use two types of rocker arms and at the same time secure the maximum cam width allowed by space, resulting in improved productivity and assembly without sacrificing reliability. It becomes possible to improve attachability.

Further, according to the above configuration, the distance between the centers of the intake valves is made larger than the distance between the centers of the exhaust valves, and the contact portion between the rocker arm and the valve is directed outward on the intake side and inward on the exhaust side. Since the valves are offset from each other, when the engine is in operation, the corresponding intake valve or exhaust valve rotates by contact with the rocker arm. This results in
It is possible to prevent uneven wear of the intake and exhaust valves and valve seats while ensuring the required valve diameter.

(Example) Examples of the present invention will be described below.

As shown in FIGS. 1 and 2, the engine 1 according to this embodiment includes a cylinder block 2 in which a plurality of cylinders are arranged in a row, and a cylinder head 3 arranged on the upper surface of the block 2 via a gasket. A combustion chamber 6 is defined by the inner peripheral surface of the cylinder 4 in the cylinder block 2, the upper surface of the piston 5 fitted in the cylinder 4, and the lower surface 3a recessed above the cylinder head 3. has been done. The cylinder head 3 also has two intake ports 7, 7 that communicate with the combustion chamber 6 from one side 3b.
and two exhaust ports 8, 8 that communicate with the combustion chamber 6 from the other side surface 3c, and the openings of these ports to the combustion chamber 6 are located on the lower surface 3a of the cylinder head.
Two intake valves 9, 9 and two exhaust valves 10, 10 are provided, which are arranged in a substantially rectangular shape and open and close each opening, respectively. Stem portions 9a, 9a, extending upwardly of each of these valves.
10a, 10a are spring retainers 11, 11, 12, 12 which protrude upward from the upper surface 3d of the cylinder head 3 and are fixed to their upper ends, respectively;
Each valve 9, 9, 10, 10 is provided between the spring seat portions 13, 13, 14, 14 formed at the protruding portion of each stem portion 9a, 9a, 10a, 10a on the upper surface 3d of the cylinder head 3. Valve springs 15, 15, 1 biased in the closing direction, respectively.
6 and 16 are installed. Here, the two exhaust ports 8, 8 in each cylinder of the cylinder head 3
An ignition plug 17 is installed between them, and its ignition part 17a is located at the center of the upper part of the combustion chamber 6.
Also, although not shown in the drawing, each intake and exhaust valve 9, 9, 10, 10 has a valve diameter and a distance between the centers of the intake valves 9, 9 that is larger than the valve diameter and center-to-center distance of the exhaust valves 10, 10. The valve diameter is also large, thereby ensuring the required valve diameter. Further, each opening in the cylinder head 3 to the combustion chamber 6 has valve seats 3',
3', 3'', and 3'' are provided, respectively.

On the other hand, a valve driving device 18 for driving the intake and exhaust valves 9, 9, 10, and 10 is provided at the upper part of the cylinder head 3. The valve drive device 18 includes a camshaft 19 that is provided at a position sandwiched between the intake valves 9, 9 and the exhaust valves 10, 10 at the upper center of the cylinder head and extends in the direction of the crankshaft of the engine 1; Two rocker arm shafts 2 are installed in parallel on both sides of the upper part of the cam shaft.
0,21. Of these, the journal portions 22...22 of the camshaft 19 are connected to a bearing wall 23 located between adjacent cylinders at the center of the upper surface of the cylinder head 3 and adjacent to both ends of the head, and two bolts 24 to each bearing wall 23...23. , 24, and the bearing cap 25...25 is fixed using the bearing 26.
It is rotatably supported on...26. Adjacent journal portions 22, 22 on the camshaft 19
In between are two intake cams 27, 27' for one cylinder.
and two exhaust cams 28, 28' are attached to the camshaft 19.
are formed alternately along the Further, the two rocker arm shafts 20 and 21 have two intake valve rocker arms 29 and 29' for each cylinder.
and two exhaust valve rocker arms 30, 3.
0' are swingably supported. Both ends of each rocker arm 29, 29', 30, 30' are connected to the circumferential surfaces of the corresponding intake cams 27, 27' and exhaust cams 28, 28', the stem portions 9a, 9a of the intake valves 9, 9, and the exhaust valves. The camshaft 19 synchronizes with the crankshaft by being in contact with the upper ends of the stem portions 10a, 10a of 10, 10, respectively.
The rotation of each rocker arm 29, 29', 3
0,30' to each valve 9,9,10,10
is the above valve spring 15, 15, 16, 16
It is becoming more and more open to the public.

Here, each of the above rocker arms 29, 29', 3
0 and 30', a contact member 29 is provided at a position facing the corresponding intake and exhaust valves 9, 9, 10, and 10.
a, 29a', 30a, 30a' are fixed respectively, and these contact members 29a, 29a', 30a,
30a' is the valve stem portion 9a, 9a, 10
a, 10a so as to come into contact with the upper ends thereof.
Further, the rocker arm shafts 20, 21 have their lower halves fitted into semicircular recesses provided on the upper surface of the bearing cap 25, and the bolts 24, which fix the bearing cap 25 to the bearing wall 23 from above, 24 through the clamping members 31, 31. Furthermore, springs 32, 32 are interposed between the two intake valve rocker arms 29, 29' and the two exhaust valve rocker arms 30, 30', so that the rocker arms 29,
29', 30, 30' in place.

However, as a feature of the present invention, the intake valve rocker arms 29, 29' and the exhaust valve rocker arms 30, 30' are constructed as follows. That is, regarding the pair of rocker arms 29' and 30' for the intake valve and the exhaust valve, which are arranged diagonally around the cylinder bore center, the ends of the rocker arms 29' and 30' on the valve stem side (the above-mentioned abutment members 29a', 30a' and the stem parts 9a, 10a of each intake and exhaust valve) and the cam side end (the part where the rocker arm 29', 30' and the intake and exhaust cam 2
The portions 29b' and 30b' in which the camshafts 7' and 28' come into sliding contact are the same type of rocker arms that are offset from the axial direction of the camshaft 19, and the other pair of rocker arms 29 and 30 are as follows. The end on the valve stem side (each of the contact members 29a, 3
0a and the stem portions 9a, 10a of the intake and exhaust valves) and the cam side ends (portions where the rocker arms 29, 30 and the intake and exhaust cams 27, 28 come into sliding contact) 29b, 30b are the above-mentioned cams. The rocker arms are of the same type and have shapes that are located at approximately the same position in the axial direction. In the rocker arms 29, 29' on the intake valve side, the contact member 2
The centers a, a' of the intake valve stem portions 9a, 29a' are offset from the centers b, b of the intake valve stem portions 9a, 9a by a predetermined amount in a direction toward each other,
In the rocker arms 30, 30' on the exhaust valve side, the centers c, c' of the valve contact members 30a, 30a' move away from each other by a predetermined amount with respect to the centers d, d of the exhaust valve stem parts 10a, 10a. offset. Here, engine 1
As mentioned above, the intake valves 9, 9 have a larger diameter than the exhaust valves 10, 10, respectively, and accordingly, the intake valve stem portion 9 has a larger diameter than the exhaust valves 10, 10, respectively.
The distance ₁ between the centers b and b of a and 9a is the distance between the centers d and d of the exhaust valve stem parts 10a and 10a.
It is configured to be larger than ₂ . Expressing these relationships as a formula, it becomes ₁ − ₂ = 4.

According to the above configuration, when the engine 1 is operated, the rotation of the camshaft 19 in synchronization with the crankshaft opens the intake valves 9, 9 during the intake stroke and the exhaust valves 10, 10 during the exhaust stroke. At that time, valve springs 15, 15 that bias these in the closing direction
And the reaction force of 16, 16 is the rock arm 29, 2
The cam 2 of the camshaft 19 via 9' and 30, 30'
7, 27' and 28, 28'.

However, in such a case, if the contact area between each corresponding cam and rocker arm is small, a large surface pressure will act between them. Each cam 27,2
7', 28, 28' are formed alternately and two types of rocker arms 29, 30 and 29', 30' are used, yet the maximum contact area can be obtained within a limited range. Since the shape of each rocker arm 29, 29', 30, 30' is set as shown, each cam 27, 27', 28, 28' and each rocker arm 2 are
The surface pressure at the contact portions with 9, 29', 30, and 30' is reduced. In other words, there are two types of rocker arms in total, four of which are provided for one cylinder, and the cam width of each cam can also be set to the maximum value determined by the cylinder bore diameter, etc.

In addition, in the engine 1, since each intake valve 9, 9 has a larger diameter than each exhaust valve 10, 10, the centers b, b of both intake valve stem portions 9a, 9a. distance between ₁
Although the valves 9, 9, 10, and 10 are arranged so that the distance ₂ is larger than the distance 2 between the centers d and d of both exhaust valve stem portions 10a, 10a,
In that case, according to the above structure, uneven wear of the face portions of the valves 9, 9, 10, 10 and the valve seats 3', 3', 3'', 3'' is prevented in the following manner. That is, on the intake side of the engine 1, the centers a and a' of the abutment members 29a and 29a' in the rocker arms 29 and 29' for each intake valve are aligned with both members 2.
9a, 29a' inwardly by a predetermined amount with respect to the centers b, b of each intake valve stem portion 9a, 9a, respectively, and on the exhaust side, each exhaust valve rocker arm 3
Contrary to the case where the centers c and c' of the contact members 30a and 30a' at 0 and 30' are on the intake side, both members 30
The corresponding rocker arms and valves abut against each other while being offset from the centers d and d of the exhaust valve stem portions 10a and 10a by a predetermined amount in the outward direction of the exhaust valve stem portions 10a and 30a', respectively. As the valves 9, 9, 10, 10 open and close, the valves automatically rotate around their axes, and as a result, each valve 9, 9, 10, 1
0 and the valve seats 3', 3', 3'', 3'' are prevented from uneven wear.

(Effect of the invention) As described above, according to the invention, one cylinder has two intake valves, two exhaust valves, two intake cams, and two exhaust cams alternately formed. In a four-valve, one-overhead camshaft engine in which the intake valve has a larger diameter than the exhaust valve, there is a gap between the corresponding intake and exhaust valves and the intake and exhaust cams. Although there are two types of intervening four rocker arms, the contact area between these rocker arms and the above-mentioned cam, that is, the cam width, was designed so that the maximum value allowed by space was obtained. As a result, it becomes possible to reduce the surface pressure between the rocker arm and the cam while ensuring the required valve diameter. This makes it possible to use two types of rocker arms without sacrificing reliability, and improves productivity and roughness.

Further, according to the present invention, each rocker arm is positioned so that the stem portion of each of the intake and exhaust valves and the valve contact portion of the rocker arm that is in contact therewith are offset in a predetermined direction.
When the engine is operating, each of the valves rotates around its axis. This prevents uneven wear of each valve and valve seat, and improves performance from this aspect as well.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a vertical sectional view of the cylinder head and its surroundings taken at the center of the combustion chamber, and FIG. 2 is a plan view of the valve driving device. 9...Intake valve, 9a...Intake valve stem portion, 10...Exhaust valve, 10a...Exhaust valve stem portion, 18...Valve drive device, 19...Camshaft, 27, 27'...Intake cam, 28, 28'...
...exhaust cam, 29, 29'... rocker arm for intake valve, 30, 30'... rocker arm for exhaust valve, a, a', c, c'... center of valve contact part in each rocker arm (each contact axis of the member),
b...Axis of the intake valve stem, d...Axis of the exhaust valve stem.

Claims (1)

[Scope of utility model registration request] For one cylinder, two intake valves and two exhaust valves are arranged in a substantially rectangular shape so that the distance between the centers of the intake valves is greater than the distance between the centers of the exhaust valves, and One overhead camshaft on which cams and two exhaust cams are arranged alternately, and two intakes interposed between the stems and cams of the valves corresponding to the respective valves and cams. It has a valve rocker arm, two exhaust valve rocker arms, and two rocker arm shafts that are arranged on both sides of the camshaft and pivotally support the rocker arms for the intake valve and the exhaust valve, respectively. In this engine valve driving device, each of the above-mentioned valves is driven by a camshaft through a camshaft, and among the above-mentioned rocker arms, a pair of rocker arms located diagonally with respect to the cylinder bore center are located on the valve stem side. The rocker arms of the same type have shapes in which the end portion and the end portion on the cam side are offset with respect to the cam axis direction, and the other pair of rocker arms are as follows:
The rocker arm is of the same type and has a shape in which the end on the valve stem side and the end on the cam side are located at substantially the same position with respect to the cam shaft direction, and
On the intake side, the axes of both valve stem parts move away from each other along the camshaft direction, and on the exhaust side, the axes of both valve stem parts approach each other along the camshaft direction. A valve driving device for an engine, characterized in that each rocker arm is positioned so as to be offset with respect to a valve abutting portion.