JPH0352971Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to an intake and exhaust valve device for an engine, particularly an intake and exhaust valve device for an engine that has two exhaust ports per cylinder and a spark plug is disposed between them. This invention relates to improvements in valve guides that hold exhaust valves.

(Prior Art) In general, the intake valve and exhaust valve, which are provided in the cylinder head 1 of an engine and control the introduction of intake air into the combustion chamber and the discharge of exhaust gas from the combustion chamber, are always held in the closed direction by a valve spring. The valve springs are rotated at predetermined times by a camshaft rotating in synchronization with the crankshaft, and the opening and closing operations of these valves are In order to perform this operation smoothly, the stem portions of the valves are each slidably held by a cylindrical valve guide fixed to the cylinder head 1.

On the other hand, when considering the influence of intake valves and exhaust valves on engine performance, it is desirable to make the opening area of these valves into the combustion chamber as large as possible. Increasing the intake air filling amount is important for increasing engine output. Based on this idea, for example, JP-A-57-
There is an engine disclosed in Publication No. 102506. As shown in FIGS. 4 and 5, this engine is provided with two intake ports 3, 3 and two exhaust ports 4, 4 for one combustion chamber 2 in a cylinder head 1,
2 for opening and closing the openings 3a, 3a, 4a, 4a of these ports 3, 3, 4, 4 to the combustion chamber 2, respectively;
The intake valves 5, 5 and the two exhaust valves 6, 6 are provided, and in particular, the diameter of the intake port openings 3a, 3a or the intake valves 5, 5 is the same as that of the exhaust port opening 4.
The diameter of the exhaust valves 6 and 6 is larger than that of the exhaust valves 6 and 6. According to this, the intake and exhaust efficiency, especially the intake air filling rate, is improved, and an engine with excellent output performance is realized.

However, since this engine is a single-cylinder engine with a relatively small heat load, it rarely causes any particular thermal problems. If an attempt is made to improve output, the exhaust valve around which high-temperature exhaust gas passes tends to overheat, resulting in thermal deterioration and reduced durability of the exhaust valve. Furthermore, when arranging a spark plug between two exhaust ports as in the engine shown in Figures 4 and 5, there is not enough space for arranging the ignition plug, so the layout of the ignition plug is restricted. There is also the problem of

(Purpose of the invention) The purpose of this invention is to deal with the above-mentioned problems regarding engine intake and exhaust valve devices, and to sufficiently dissipate heat from the exhaust valve to the cylinder head, which is easily overheated by combustion heat and exhaust gas heat. By doing so, the exhaust valve is prevented from overheating, thereby preventing thermal deterioration and decrease in durability of the exhaust valve, and in addition, when a spark plug is disposed between two exhaust ports, The purpose is to improve the degree of freedom in the layout of the plug.

(Structure of the invention) That is, the intake and exhaust valve device for an engine according to the invention includes two exhaust ports for each cylinder provided in the cylinder head, and a spark plug intersecting the exhaust valve between these exhaust ports. In an engine in which a valve guide that slidably holds the stem portion of the intake and exhaust valve is fixed to the cylinder head, the valve guide of the exhaust valve is reduced in outer diameter to reduce the intake air intake. It is characterized by having a thinner wall than the valve guide of the valve, which allows for good heat radiation from the exhaust valve, which is easily overheated by combustion heat and exhaust gas heat, to the cylinder head.

By the way, as in the engine shown in Figs. 4 and 5, one combustion chamber is equipped with two intake and two exhaust valves, and these valves are driven by one overhead camshaft, so-called 4-valve one overhead camshaft. In a type engine, the spark plug is installed in an inclined manner between the two exhaust valves to avoid interference with the camshaft, but in this invention, the ignition plug is installed between the two exhaust ports in this way. When the plug is arranged, especially when the plug is arranged so as to intersect with the exhaust valve, the wall thickness of the valve guide of the exhaust valve is made thinner by reducing its outer diameter. Extra space is created on the side of the cylinder head 1 on the exhaust valve side, which facilitates the layout of the spark plug between the two exhaust valves.In addition, in the case of a water-cooled engine, water is removed around the stem of the exhaust valve. It becomes possible to increase the volume of the jacket, which also prevents overheating of the exhaust valve.

(Effects of the invention) As described above, according to the invention, in an engine in which a spark plug is arranged between two exhaust ports so as to cross the exhaust valve, the outer diameter of the valve guide of the exhaust valve can be reduced. By making the wall thickness thinner than the valve guide of the intake valve,
Heat is efficiently radiated from the exhaust valve to the cylinder head via the valve guide, which prevents problems such as overheating of the exhaust valve and associated reduction in the durability of the valve. . Also, 2
This simplifies the layout of the spark plugs, which are placed across the exhaust valve between the two exhaust ports, and also makes it possible to expand the volume of the water jacket around the stem of the exhaust valve. Overheating can be more effectively prevented.

(Example) Hereinafter, an example of the present invention will be described. still,
In this embodiment, each cylinder has two intake and two exhaust valves.
The present invention relates to a four-valve, one-overhead camshaft type engine that has two engine parts, each of which is driven by a single overhead camshaft.

As shown in FIGS. 1 and 2, an engine 10 has a cylinder block 1 in which a plurality of cylinders are arranged in a row.
1, and a cylinder head 13 installed on the upper surface of the block 11 via a gasket 12,
A combustion chamber 16 is defined by the inner peripheral surface of the cylinder 14 in the cylinder block 11, the upper surface of the piston 15 fitted into the cylinder 14, and the lower surface 13a recessed above the cylinder head 13. Further, the cylinder head 13 is provided with two exhaust ports 17, 17 that communicate with the combustion chamber 16 from one side surface 13b, and two exhaust ports 18, 18 that communicate with the combustion chamber 16 from the other side surface 13c. Openings 17a, 17a, 18a, 18a of each of these ports to the combustion chamber 16 are arranged in a square shape on the lower surface 13a of the cylinder head, and two openings 17a, 17a, 18a, 18a are opened and closed, respectively. Intake valves 19, 19 and two exhaust valves 20, 20 are provided. Here, the diameter of the openings 18a, 18a of the exhaust ports 18, 18 is the diameter of the openings 17a, 17a of the intake ports 17, 17.
Accordingly, the exhaust valves 20, 20 have a smaller diameter and less mass than the intake valves 19, 19. Stem portions 19a, 19a, 20a, and 20a extending upwardly of each of these valves are projected upwardly from the upper surface 13d of the cylinder head 13, and spring retainers 2 are fixed to the upper ends of the stem portions 19a, 19a, 20a, and 20a, respectively.
1, 21, 22, 22, and each stem portion 19a, 19a, on the upper surface 13d of the cylinder head 13.
Between the spring seat parts 23, 23, 24, 24 formed on the protruding parts of 20a, 20a, there are valve springs 25, 25, 26 that bias each valve 19, 19, 20, 20 in the closing direction, respectively. ,26
is installed.

On the other hand, a single camshaft 27 extending in the direction of the crankshaft of the engine 10 is disposed at a position sandwiched between the intake valves 19, 19 and the exhaust valves 20, 20 at the center of the upper part of the cylinder head 13. . The journal portions 27a...27a of this camshaft 27 are
Bearing walls 28 are provided upright between adjacent cylinders at the center of the upper surface of the cylinder head 13 and at both ends of the head.
28, and a bearing cap 30 fixed to each bearing wall 28...28 using two bolts 29, 29, respectively.
... 30, and between the adjacent journal portions 27a, 27a of the camshaft 27, there are two intake cams 27b, 27b and 22 for one cylinder. Exhaust cams 27c, 27c are formed. and,
Two rocker arm shafts 31 and 32 are installed in parallel on both sides of the upper part of the camshaft 27, and
Two intake valve rocker arms 33, 33 and two exhaust valve rocker arms 34, 34 for each cylinder are swingably supported on these shafts 31, 32, and both ends of each rocker arm 33, 33, 34, 34 correspond to each other. cams 27b, 27b, 27c, 2
7c and the stem portions 19a, 19 of the intake and exhaust valves
The camshaft 27 synchronizes with the crankshaft by being in contact with the upper ends of the camshafts a, 20a, and 20a, respectively.
By the rotation of the rocker arm 33, 33, 3
Each valve 19, 19, 20, 20 is opened at a predetermined timing via valves 4 and 34. Here, the rocker arm shafts 31, 32 are attached to the upper surfaces of the bearing caps 30...30 by pressing members 35...
35 and are fixed by the bolts 29...29.

Further, a spark plug insertion hole 36 is provided in the cylinder head 13, and a spark plug 37 is inserted into the hole 36.
is installed. The insertion hole 36 is provided in an inclined manner so as to intersect the exhaust valves 20, 20 between the two exhaust ports 18, 18 in each cylinder, and its tip 36a is connected to each port on the lower surface 13a of the cylinder head 13. Openings 17a, 17
a, 18a, 18a, that is, the upper center of the combustion chamber 16, and the hole 3
The rear end portion 36b of the cylinder head 13 is located between the rear end openings of the exhaust ports 18, 18 on the one side surface 13c of the cylinder head 13 and the spring seat portions 24, 24 of the exhaust valves 20, 20 on the upper surface 13d of the head 13. It is opened so as to face the upper outer side of the head 13. A portion of the insertion hole 36 that continues from the tip 36a is a female threaded portion 36c, and a male threaded portion 37a of the ignition plug 37 is connected to the female threaded portion 36c.
When screwed together, the ignition part 37b at the tip of the plug protrudes into the upper center of the combustion chamber 16.

As shown in an enlarged view in FIG. 3
8, 39, and 39, respectively, and are held so as to be vertically slidable. These valve guides 38,
38, 39, 39 are the spring seat portions 23, 2 on the upper surface 13d of the cylinder head 13.
From the center of 3, 24, 24 to each port 17, 17,
Mounting holes 40, 40, 41 penetrating through 18, 18,
41, but as is clear from FIG. 3, the valve guides 39, 39 for the exhaust valves 20, 20 have a smaller outer diameter than the valve guides 38, 38 for the intake valves 19, 19. By doing so, the wall thickness is reduced. Here, in this embodiment, the stem portions 19a, 19a, 20 of the intake and exhaust valves are
The diameters of a and 20a are made equal, so that the spring retainers 21, 21, 22, 22 of the intake and exhaust valves
The retainers 42 . . . 42 for connecting the retainer to the upper end of the stem are made common. Furthermore, since the exhaust valves 20, 20 have small masses, only one valve spring 26, 26 is provided each.

According to the above configuration, one camshaft 27 disposed at the center of the upper part of the combustion chamber 16 connects two intake valves 19, 19 for each cylinder via rocker arms 33, 33, 34, 34. and exhaust valve 2
0 and 20 are valve springs 25, 25, and 2, respectively.
6, 26 at a predetermined timing, thereby allowing air to be drawn into the combustion chamber 16 from the exhaust ports 17, 17, and from the combustion chamber 16 to the exhaust ports 18, 26.
Exhaust gas is discharged to 18. In this case, since two intake valves 19 and two exhaust valves 20 are provided, the above-mentioned intake and exhaust operations are performed efficiently, and in particular, the openings 17a of the exhaust ports 17, 17,
Since the area of 17a is increased, the intake air filling amount is increased, and as a result, excellent output performance of the engine is obtained.

Therefore, the exhaust valves 20, 20 are connected to the combustion chamber 16.
In addition to the combustion heat from the exhaust valves 20, 20, the exhaust valves 20, 20 are easily overheated because they receive heat from the high-temperature exhaust gas passing through the exhaust ports 18, 18. The heat load acting on the area becomes even larger. However, since the valve guides 39, 39, which are fixed to the cylinder head 13 and slidingly guide the stem portions 20a, 20a of the exhaust valves 20, 20, are thinner than the valve guides 38, 38 for intake valves, Valve 20, 20
The heat transmitted to the valve guides 39, 39 is efficiently radiated to the cylinder head 13. This prevents the exhaust valves 20, 20 from overheating and the accompanying thermal deterioration or decrease in durability.

In particular, the valve guides 39, 39 are
Since the wall thickness is reduced by reducing the outer diameter, the boss portion 13e of the cylinder head 13 that holds the valve guides 39, 39 is reduced by the smaller outer diameter, as shown in FIG. It can be made thinner than the state shown by the dashed lines x and x. the result,
The water jacket 4 around the boss portion 13e
3 to the valve guide 39, 39 or exhaust valve 2
This makes it possible to bring the exhaust valves 20, 20 close to the stem parts 20a, 20a of the exhaust valves 20, 20.
overheating will be more effectively prevented. In addition, although the spark plug 37 is arranged between the two exhaust valves 20, 20 in an inclined manner so as to intersect with these valves 20, 20 in order to avoid interference with the camshaft 27, , Exhaust valve valve guide 3
By making the outer diameter of 9 and 39 smaller,
The space for arranging the spark plug 37 is expanded, and the degree of freedom in arranging the plug 37 is increased.

Here, the exhaust valves 20, 20 are the intake valves 19, 19.
Since the mass is smaller and the load is reduced by using only one valve spring 26, the stress acting on the valve guides 39, 39 is correspondingly smaller than that of the intake valve valve guides 38, 38.
Therefore, even if the wall thickness of the exhaust valve valve guides 39, 39 is made thinner, no strength problem will arise.

[Brief explanation of the drawing]

Figures 1 to 3 show one embodiment of the present invention.
Figure 1 is a vertical cross-sectional front view of the cylinder head and its surroundings taken at the center of the combustion chamber, and Figure 2 is the same as Figure 1.
FIG. 3 is a cross-sectional plan view of the single cylinder head cut along a line, and FIG. 3 is an enlarged vertical cross-sectional front view of the main part showing the vicinity of the intake and exhaust valves. 4 and 5 are a longitudinal sectional front view and a lateral plan view of a cylinder head and its surroundings, showing a conventional example. 13... Cylinder head, 18... Exhaust port, 19... Intake valve, 20... Exhaust valve, 19a,
20a... Stem portion, 37... Spark plug, 38
...Valve guide for intake valves, 39...Valve guide for exhaust valves.

Claims (1)

[Scope of utility model registration request] The cylinder head is provided with two exhaust ports for each cylinder, and a spark plug is placed between these exhaust ports so as to intersect with the exhaust valve. An intake and exhaust valve device for an engine in which a valve guide that is movably held is fixed, wherein the valve guide of the exhaust valve is made thinner than the valve guide of the intake valve by reducing its outer diameter. An engine intake and exhaust valve device characterized by: