JPH0216320A - Cylinder head cooling structure for four-cycle engine - Google Patents

Abstract

PURPOSE:To uniformalize the temperature distribution of a cylinder head at an engine equipped with three air intake valves and two exhaust valves, by constituting exhaust passages with two independent exhaust passages, and forming a head side liquid cooled jacket between both independent exhaust passages. CONSTITUTION:At an engine in which three air intake valves 23-25 and two exhaust valves 26,27 are collected at one side of a combustion chamber and the other side thereof and also, are arranged so as to be along the perimeter wall of the combustion chamber, three air intake valve openings 17-18 are led out backward by means of three branching off air intake passages 31a-31c formed in parallel mutually, and are converged at one common air intake passage 31 within a cylinder head 11, and then, are led out to the back wall of the cylinder head. Also, two exhaust valve openings 20,21 are led out to the front wall of the engine by means of two independent exhaust passages 32,32 formed separately so as to extend to an oblique outer part. And a head side water cooled jacket 15 formed so that is may possess a front portion 15a which extends to a space between independent exhaust passages 32,32.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a cooling structure for a cylinder head employed in, for example, a water-cooled four-stroke engine for motorcycles, and in particular, relates to a cooling structure for a cylinder head that has three intake valves and two exhaust valves. The present invention relates to an improvement in the arrangement structure of an intake passage, an exhaust passage, and a water jacket that can uniformly cool the entire cylinder head in the case of a 5-pulp engine.

[Conventional technology]

In general, the combustion system of a four-stroke engine has an intake valve opening in the combustion chamber guided to the outside of the cylinder head through an intake passage, a fuel supply device such as a carburetor connected to the outside opening, and an exhaust valve opening connected to an exhaust passage. The exhaust pipe is connected to the outside opening, and the low-temperature air-fuel mixture is taken in through the intake passage, and the high-temperature exhaust gas is discharged through the exhaust passage. Therefore, large deviations in temperature distribution tend to occur near the combustion chamber of the cylinder head where the intake passage and exhaust passage are formed. If this temperature deviation becomes too large, various troubles may occur due to thermal distortion and the like.

[Problem that the invention seeks to solve]

By the way, the above temperature deviation is due to the large number of intake valves and exhaust valves (
I see, it tends to increase, so in the case of a 5-valve engine with a large number of valves, for example, 3 intake valves and 2 exhaust valves, in order to equalize the 1 degree distribution of the cylinder head,
A cooling structure is required that takes into consideration the arrangement of intake passages, exhaust passage water jackets, etc. However, in the conventional five-valve engine, a cooling structure similar to that of the two-valve engine is adopted, and the reality is that a sufficiently uniform temperature distribution has not been achieved.

Therefore, the present invention has three intake valves and two exhaust valves.
The purpose of this invention is to provide a cooling structure for cylinders that can equalize the temperature distribution of the cylinder head in a valve engine.

[Means for solving problems]

The present invention provides a cylinder head cooling structure for a four-cycle engine in which three intake valves and two intake valves are arranged along the peripheral wall of a combustion chamber, and the intake passage formed in the cylinder head is connected to a fuel supply device. The exhaust passage is composed of one common intake passage that communicates with the opening, and three branch intake passages that are branched from the common intake passage and communicate with each of the intake valve openings, and the exhaust passage is connected to each of the exhaust valve openings. It is characterized in that it is composed of two independent exhaust passages that lead out separately to an exhaust pipe connection opening, and that a liquid cooling jacket is formed in a portion of the cylinder head between the two independent exhaust passages.

Here, the present invention is applicable not only to water-cooled engines but also to engines cooled with liquid such as oil.

[Effect]

According to the cylinder head cooling structure according to the present invention, since the three branch intake passages are combined into one common intake passage in the cylinder head, the area of the wall surface constituting the outer surface of the intake passage of the cylinder head is It is narrower than when the passage is led outward as it is, and therefore less heat is transferred from the cylinder head to the low temperature intake air (mixture) side, which reduces the temperature drop in the intake passage side of the cylinder head. be done. Furthermore, in this case, since the central branch intake passage is sandwiched between the branch intake 1ffi passages on both sides, the amount of heat transferred from the cylinder head to the central branch intake passage side is further reduced. The temperature drop in the intake passage side portion of the head is reduced.

On the other hand, since the exhaust passage is composed of two independent exhaust passages, with a liquid cooling jacket formed between them, the high temperature exhaust gas is cooled by the coolant, which is lower in temperature than this, and is transmitted from the exhaust gas to the cylinder head side. The amount of heat is reduced, and therefore the temperature rise in the exhaust passage side portion of the cylinder head is reduced.

In this way, the temperature drop in the intake passage side portion of the cylinder head is reduced, and the temperature rise in the exhaust passage side portion is reduced, so that as a result, the temperature distribution of the cylinder head becomes uniform as a whole.

Furthermore, when looking at the dimension (width dimension) of the engine in the camshaft direction, the width dimension is well balanced between the intake side portion and the exhaust side portion. That is, generally speaking, the width of the intake side with three valves is larger than the exhaust side with two valves, but in the present invention, the exhaust passage is provided independently, and a liquid cooling system is installed between the two independent exhaust passages. Since the jacket is provided, the width on the exhaust side becomes larger and the difference from the intake side becomes smaller.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

1 to 4 are diagrams for explaining a valve train for a four-stroke engine according to a first embodiment of the present invention.

In the figure, reference numeral 1 denotes a motorcycle equipped with a four-stroke engine to which the device of this embodiment is applied, and a front fork 4 that pivotally supports a front wheel 3 at its lower end is supported at the front end of a body frame 2 of this vehicle. At the lower center end, a rear arm 6 that pivotally supports the rear wheel 5 at the rear end is pivoted so as to be able to swing up and down.Furthermore, at the rear is a large fuel tank 7, and above it is a seat 8.
are installed in each. Note that 62 to 64.58 are an oil tank, a radiator, an air cleaner, and a carburetor, respectively.

A water-cooled four-stroke single-cylinder engine unit 9 is mounted on the front portion of the vehicle body frame 2. This engine unit 9 includes a cylinder 10, a cylinder head 1
1. The head cover 12 is stacked on the crankcase 14. The center part of the upper surface of the head cover 12 is suspended from the tension pipe 2a of the body frame 2 via a bracket 61, and the center part of the front side of the crankcase 14 is suspended by a down tube 2C extending downward from the head pipe 2b. There is.

The cylinder 10 has a cylindrical cylinder liner 10c inside a cylinder body 10b in which a water cooling jacket 10a is formed.
cylinder liner 10c.
A piston 14 is slidably inserted therein.

Further, a combustion chamber recess 16 is formed substantially in the center of the base of the cylinder head 11 and forms a combustion chamber A with the upper surface of the piston 14. Three intake valve openings 17 to 19 and two exhaust valve openings 20 and 21 are formed approximately on the circumference along the periphery of the combustion chamber recess 16.

The above three intake valve openings 17 to 19 are the cylinder head 1]
It is led out rearward by three branch intake passages 31a to 31b that are formed parallel to each other so as to extend toward the rear of the vehicle, and after merging into one common intake passage 31 within the cylinder head 11, It is led out to the wall. Two carburetors 58 and 59 are connected to the outer opening 31d of the shared intake passage 31 via a carburetor joint 57. This cab joint 57 is a bulkhead 57a.
It is defined into two joint passages 57b and 57C.

Here, in this embodiment, 50% of the total intake air flow is set to flow through the central branch intake passage 31b, and the remaining 25% and 25% flow through the left and right branch intake passages 31a and 31c, respectively. . This is because, as will be described later, the amount of heat transferred from the cylinder head 11 is reduced as much as possible by increasing the intake flow rate at the center.

The two exhaust valve openings 20.21 are led out to the front wall of the engine by two independent exhaust passages 32.32 formed separately in the cylinder hood 11 so as to extend toward the front of the vehicle and diagonally outward. ing. An exhaust pipe 33 is connected to the outside opening 32a of each independent exhaust passage 32, and each exhaust pipe 33 passes through the outside of the down tube 2C, is bent downward, and extends from the bottom of the engine to the rear end of the vehicle. ing.

The intake valve openings 17 to 19 and the exhaust valve opening 2021 include
Intake valves 23 to 25 and exhaust valves 26 and 27 that open and close each opening
A valve plate portion is arranged. These intake and exhaust valves 23 to 2
The valve shaft portion of No. 7 penetrates the ceiling wall portion of the branch intake passages 31a to 31C1 and the independent exhaust passages 32, 32 and projects into the upper end opening of the cylinder head 11. A biasing spring 35 is disposed between a retainer 34 attached to the upper end of this protrusion and a spring seat tta attached to the cylinder head 11.
21 is biased to close.

A camshaft 36 is disposed above the center of the combustion chamber A so as to cross it. The left and right ends and center of this camshaft 36 are supported by left and right bearings and solid bearings, respectively.

The right bearing part and the solid bearing part have a two-part structure consisting of a lower half part formed on the cylinder/door 11 side and an upper half part formed on the head cover 12 side. Further, one end of this camshaft 36 projects into the chain chamber lIb, and is connected to the crankshaft via a chain and a chain fixed to the projecting portion.

And the combustion chamber recess 16 of the cylinder head 11
The head-side water cooling jacket 15 is a space surrounded by a ceiling wall 16a constituting the head, a boundary wall 16b between the cam chamber containing the cam shaft 36, etc., and a peripheral wall. A plug hole 22 is formed at approximately the center of the boundary wall 16b and communicates with the combustion chamber at the center, and the plug hole 22 is led out to the outside of the engine by a plug insertion hole 29.

This plug insertion hole 29 is connected to the cylinder head 11. It is a cylindrical member composed of a linear cylindrical portion 29a929b formed on the head cover 12, and extends diagonally upward through the head side water cooling jacket 15, approximately parallel to the exhaust valves 25,26. In addition, the spark plug 3 is located in the plug hole 22.
0 is attached.

The front portion 15a of the head side water cooling jacket 15 extends forward to between the two single room exhaust passages 32,32. The head-side water cooling jacket 15 has a central inlet 53a formed in the front portion 15a, and both roads 3.
2. Left and right inlet ports 53b formed on the left and right outer sides of 32
, 53C, the cylinder side water cooling jacket 10a
is connected to. Further, each of the inflow ports 532 to 53C faces each of the branch intake passages 312 to 31C.

In addition, left and right outlet ports 54a and 54b are formed through the shared intake passage 31 at both left and right positions to allow the head side water cooling jacket 15 to communicate with the outside. A fastening pole 1-60 is located outside. Further, the external openings of both the above-mentioned outflow ports 54a, 54b are connected to connection joints (55a, 5) attached to the respective outlets.
5b and a joint pipe 56a.

This joint pipe 56a is connected to the above-mentioned cab joint 5.
7, that is, the cylinder head 11 and the carburetor 58.
59, and the joint pipe 56a is connected to the radiator through the left side of the cylinder head 11 by a cooling water return pipe 56b.

Next, the effects of this embodiment will be explained.

First, cooling water is supplied to the lower part of the cylinder side water cooling jacket 10a of the cylinder 10, and from the jacket 10a,
It is supplied to the front portion 15a of the head side water cooling jacket 15 between the two single room exhaust passages 32, 32 and the farmer side portion thereof through the exhaust side inflow ports 532 to 53c. The cooling water then passes through the head side water cooling jacket 15 on both sides of the plug insertion hole 29 (see Figures 1 and 3).
It passes below the solid bearing portion 39 of the camshaft 36 and flows uniformly toward the branched intake passages 31'a to 31C, and is divided into left and right sides along the wall surface of the passage, and left and right outflow holes 54a. , 54b
It flows out from the joint pipe 56a and the return pipe 56b and is led to the radiator.

Next, the outside air becomes a mixture in the carburetor 58, 59, passes through the common intake passage 31 from the carburetor joint 57, branches at branch intake passages 312 to 31e, and is sucked into the combustion chamber A, where it explodes and burns. Exhaust gas passes through each independent exhaust passage 32 and is discharged from each exhaust pipe 33 to the rear of the vehicle.

Here, in order to make the temperature distribution of the cylinder head 11 uniform, as mentioned above, on the intake side portion of the cylinder head 11,
It is necessary to suppress as much as possible the temperature drop caused by the low-temperature air-fuel mixture and the temperature rise in the exhaust side portion caused by the high-temperature exhaust gas.

In this embodiment, on the intake side, the three branch intake passages 312 to 31C are merged into one common intake passage 31 and then led out to the outside, so the outer circumferential wall of this intake passage (
The area of the boundary wall with the cylinder head 11 itself (which becomes a heat transfer surface) is narrower than when the three passages are led out as they are, and therefore the area from the cylinder head 11 to the low-temperature air-fuel mixture The amount of heat transferred to is reduced accordingly.

In addition, the central branch passage 31b has a left side, a left side, and a right side.
Since it is sandwiched between the right branch passages 31a and 31C, the amount of heat transferred from the cylinder head 11 can be reduced from this point as well. That is, in this embodiment, 50% of the total intake air flow is set to flow through the central branch passage 31b, and from the viewpoint of flow rate, the central branch passage 31b supplies the cylinder with 50% of the intake air amount.
The influence of No. 1 on temperature reduction is greater than the influence of the left and right branch passages. However, as mentioned above, the central branch passage 3
1b is sandwiched between the left and right branch passages 31a and 31c, so even though the intake air flow rate is large, the intake air 11 is not connected to the cylinder.
It is possible to suppress heat transfer from

Regarding the exhaust side, the two independent exhaust passages 32 are expanded diagonally outward and led out, and the front part 15a of the head side water cooling jacket 15 is extended between the two single room exhaust passages 32, 32. , this double cabin exhaust passage 32
．． 32 is surrounded by a water-cooling jacket, and the high-temperature exhaust gas is cooled by the cooling water in the water-cooling jacket and its temperature is lowered, thereby reducing the amount of heat transferred from the exhaust gas to the exhaust side portion of the cylinder head 11.

As described above, in this embodiment, the temperature drop due to intake air on the intake side portion of the cylinder head 11 is suppressed, and the temperature rise due to exhaust air on the exhaust side portion is suppressed, and as a result, the temperature of the cylinder head 11 is made uniform.

Further, in this embodiment, the dimensions (width dimensions) of the intake side and exhaust side portions as seen in the camshaft direction are well balanced. That is,
In a 5-valve engine with 3 intake valves and 2 exhaust valves, the width of the intake side is larger than the exhaust side depending on the number of valves.
Although there is a risk that the balance between the two may deteriorate, in this embodiment, the exhaust passages are formed into two independent exhaust passages 32.3 with a gap between them.
2, which is extended diagonally outward and guided forward, so that the width dimension is approximately equal on both the intake side and the exhaust side. Since the front portion 15a of the head-side water cooling jacket 15 is provided between the two independent exhaust passages 32, the empty space can be used effectively.
2 is led out diagonally outward, so the exhaust pipe 33 can be connected to the down tube 2C located at the center of the front side of the engine unit without interfering with it.

In addition, in the cooling structure of this embodiment, the cooling water flows in from three places on the exhaust side and flows out from two places on the left and right sides of the intake side.
Cooling water does not stagnate in any part, and the vicinity of the combustion chamber A of the cylinder head 11 and the exhaust passages 32 and 33 can be uniformly cooled.

Furthermore, the joint pipe 56a that connects the left and right outlets 54a and 54b is placed in the gap between the carburetor 58, 59 and the cylinder head 11, so dead space can be used effectively and the necessary piping space is saved. can be secured.

In the first embodiment, one plug insertion hole 29 is formed in the center of the water cooling jacket 15, but the present invention can of course be applied to a case where two plug insertion holes are provided.

5 and 6 show a second embodiment of the present invention in which two spark plugs are arranged on the left and right sides, and FIG. 5 is a sectional bottom view of the water cooling jacket portion.

In the figure, the same symbols as in FIG. 1 indicate the same or corresponding parts, 29d and 29e are the left side of the head side water cooling jacket 15
These are plug insertion holes located on both right sides. Further, the front part 15a of the head side water cooling jacket 15 is connected to the independent exhaust passage 3.
It extends between 2 and 32.

In the cooling structure of this embodiment, the cooling water flows through the independent exhaust passage 32.
cooling water inlets 53a to 5 formed between and on both sides thereof.
3c, the front part 15 is attached to the head side water cooling jacket 15.
a, and the left and right sides, and the independent exhaust passage 32
After uniformly cooling the solid bearing portion of the camshaft 36 and the left and right spark plugs 3Qa and 30b while cooling the left and right spark plugs 3Qa and 30b,
It flows outward from the right outlet ports 54a and 54b.

Also, in the second embodiment, as in the first embodiment, there is an effect that the temperature distribution of the cylinder head 11 can be made uniform, and there is also an effect that the balance of the width dimension is improved.

Also, the above 1. In the second embodiment, a 5ouc engine in which both the intake valve and exhaust valve are driven by a single camshaft has been described, but the present invention is of course also applicable to a DOHC engine in which the intake and exhaust valves are driven by separate camshafts. It can be used.

7 and 8 show a third embodiment which is applicable to a direct drive type 1) OHC engine, and in the figures, the same reference numerals as in FIGS. 1 to 6 indicate the same or corresponding parts.

In the figure, the cylinder head 11 is composed of a lower head 11b and an upper head Ilc, and includes intake valves 23 to 23.
25 is configured to be driven by an intake camshaft 36a via a lifter 34a, and the exhaust valve 26.27 is driven by an exhaust camshaft 36b via a flap 34a.

The plug insertion hole 29 is formed into a cylindrical shape by insertion cylinder portions 29a to 29c integrally formed with the head cover 12°, the upper head 11C1, and the lower head Ilb, respectively, and is inclined so as to be parallel to the exhaust valve 26, 27. are doing.

Furthermore, the front portion 15a of the head side water cooling jacket 15
extends between the two chamber exhaust passages 32, 32, and communicates with the cylinder side water cooling jacket lOa through a cooling water inlet 53a.

In this embodiment as well, as in the above-mentioned embodiments, the temperature distribution of the throat 11 to the cylinder can be made uniform, the width dimensions of the intake side and the exhaust side are well balanced, and the free space between the independent exhaust passages 32 is improved. can be used effectively.

Furthermore, in this embodiment, since the plug insertion hole 29 is inclined toward the exhaust valve side, the intake valves 23 to 25 can be arranged vertically, which reduces the volume of the combustion chamber A and increases the compression ratio. It also has the effect of increasing output.

FIG. 9 is a modification of the third embodiment, and shows an example of a swing arm type DOIIC engine.

In the drawings, the same reference numerals as in FIGS. 1 to 8 indicate the same or equivalent parts. Reference numeral 34b is a swing arm, and the response is driven via this swing arm 34b by the rotation of each camshaft. The plug insertion hole 29 is inclined at about 1 so that a part thereof is located between the left and right exhaust valves 26 and 27, and the front part 15a of the head side water cooling jacket 15 is
extends between the left and right independent exhaust passages 32.32.

In this embodiment as well, the same effects as in the first to third embodiments described above can be obtained.

〔Effect of the invention〕

As described above, according to the cylinder head cooling structure for a four-stroke engine according to the present invention, the intake passage is composed of one shared intake passage and three branched intake passages, and the exhaust passage is composed of two independent exhaust passages. Since a head side liquid cooling jacket is formed between the two independent exhaust passages, the temperature drop in the intake passage side part of the cylinder head is reduced, and the temperature rise in the exhaust passage side part is reduced. This has the effect of making the temperature distribution of the cylinder head uniform as a whole, and also has the effect of making the width dimensions of the intake side and the exhaust side well balanced.

[Brief explanation of the drawing]

1 to 4 are diagrams for explaining a cylinder head cooling structure according to a first embodiment of the present invention, in which FIG. 1 is a cross-sectional plan view of the head-side water cooling jacket portion, and FIG. 2 is a cross-sectional side view. , FIG. 3 is a sectional view taken along line mm in FIG. 2, FIG. 4 is a left side view of the motorcycle to which the device of this embodiment is applied, and FIG.
6 are diagrams for explaining the second embodiment of the present invention, FIG. 5 is a sectional view taken along the line V-V in FIG. 6, FIG. 6 is a sectional side view, and FIGS. The figures are diagrams for explaining the third embodiment of the present invention, FIG. 7 is a cross-sectional side view thereof, and FIG.
FIG. 9 is a cross-sectional side view for explaining a modification of the third embodiment. In the figure, 11 is the cylinder head, 15a is the front part of the water cooling jacket on the head side (liquid cooling jacket), 17 to 19
is an intake valve opening, 20.21 is an exhaust valve opening, 23 to 25 are intake valves, 26.27 is an exhaust valve, 31 is a shared intake passage, 3
1a to 31c are branch intake passages, 31d is a connection opening, 32
is an independent exhaust passage, 58.59 is a carburetor (fuel supply device)
, A is the combustion chamber.

Claims (1)

[Claims] (1) In a cylinder head cooling structure for a four-cycle engine in which three intake valves and two exhaust valves are grouped together on one side and the other side of a combustion chamber, and are arranged along the peripheral wall of the combustion chamber, the above-mentioned cylinder The intake passage formed in the head,
An exhaust passage formed in the cylinder head, consisting of one common intake passage communicating with a fuel supply device connection opening, and three branch intake passages branching from the common intake passage and communicating with each of the above-mentioned intake valve openings. is composed of two independent exhaust passages that lead out each exhaust valve opening separately to each exhaust pipe connection opening, and a liquid cooling jacket is formed in a portion of the cylinder head between the two independent exhaust passages. Features 4
Cycle engine cylinder head cooling structure.