JPH0251043B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an intake system for a three-cylinder gasoline engine, and in particular improves the arrangement of intake valves, exhaust valves, spark plugs, etc., and the direction of intake ports, thereby reducing swirl generated within each cylinder. In addition to strengthening and uniformizing the engine, the aim is to reduce the size of the entire engine and equalize the distribution of intake air to each cylinder.

Generally, in a gasoline engine, a swirl is generated in the intake air flowing into the combustion chamber to prevent knotting, but in a three-cylinder engine, the intake passage from one carburetor to each cylinder cannot be formed symmetrically. Because of this difficulty, it is difficult to distribute the air-fuel mixture evenly to each cylinder compared to other engines with an even number of cylinders, resulting in variations in the strength of the swirl. It has the disadvantage of producing vibrations due to fluctuations.

As an example of an improved intake manifold structure to eliminate such drawbacks,
Intake manifolds described in Japanese Utility Model Application No. 48-11208 are known, but both of them are equipped with a baffle plate called a separation wall or shroud in the intake passage of the intake manifold. Uniform intake air distribution is achieved by slightly restricting the flow of air-fuel mixture to the intake valve, which has a large amount of intake air, due to reasons such as low resistance.

However, it is desirable to make the passage from the carburetor to the intake valve as straight as possible to reduce the pipe resistance and strengthen the swirl.In particular, it is desirable to avoid resistors that cause complicated bends in the passage, such as baffles and bent parts. If provided, not only will the intake flow rate to each cylinder be reduced and the momentum of the swirl will be reduced, but also a swirling flow will occur in the opposite direction to the direction of the swirl at the baffle plates and bends as mentioned above, which will cause the swirl to occur earlier. It will be attenuated to

In addition, as a measure to obtain a uniform swirl within the combustion chamber, a guide wall as seen in Japanese Patent Application Laid-open No. 88219/1988 is installed inside the combustion chamber, and the degree of flow resistance due to this guide wall is adjusted for each cylinder. Intake devices that achieve uniform swirl are known, but in this case too, the pipe resistance due to the guide wall is large, and the aim is to equalize it by attenuating the momentum of the swirl, so it is necessary to strengthen the overall swirl. is not done.
In addition, in this device, the guide wall protrudes into the combustion chamber, and furthermore, the swirl that is formed is attenuated by the jet that is compressed between the guide wall and the top surface of the piston and ejected in the direction of the cylinder axis (so-called squish). The degree of this is so great that it is virtually useless for preventing knocking.

In addition, in recent years there has been a strong demand for economical compact cars in line with the demand for resource conservation, and there is a strong consumer preference for FWD cars with transversely mounted engines that offer good driving performance.
In the case of such a horizontal engine, it is essential to downsize the engine in a direction perpendicular to the axial direction of the crankshaft, and in particular, it is necessary to downsize the intake manifold and exhaust manifold, which occupy a large volume.

However, in the cylinder block of a conventional three-cylinder gasoline engine, the intake valves, exhaust valves, etc. are arranged in the same direction across all cylinders, as seen in the above-mentioned Japanese Patent Application Laid-Open No. 57-88219. This is because, as mentioned above, the swirling force of the relatively low-temperature intake air is weak, so it is not possible to bring the particularly high-temperature exhaust valves in adjacent cylinders closer together. If possible, it would be possible to shorten the distance between cylinders, making it possible to provide a more compact engine.Therefore, an object of the present invention is to improve the arrangement of intake/exhaust valves and spark plugs, and further improve the arrangement of each cylinder. By connecting the intake port that supplies the air-fuel mixture to the combustion chamber in the direction that strengthens the intake swirl, we aim to strengthen the swirl, improve the cooling effect of the swirl, and downsize the engine mainly in the axial direction of the crankshaft. The point is that it is not intended.

In order to achieve the above object, the present invention provides an intake system for a three-cylinder engine in which the cylinders are arranged substantially in a straight line, in which the intake valve of each cylinder is arranged close to the inner circumferential surface of the cylinder bore in plan view. At the same time, the distance from the intake valve of the central cylinder to the intake valves of the cylinders on both sides is different, and the intake valve, spark plug, and exhaust valve are arranged in this order in the direction of the flow of intake swirl in the combustion chamber. Furthermore, among the above-mentioned respective cylinders, a carburetor is arranged approximately on the central extension line between the cylinder bores of two adjacent cylinders, and the intake passage and this intake passage are arranged with the central extension line as an axis of symmetry. The intake ports connecting the intake valves and the intake valves are oriented substantially tangentially to the inner circumferential surface of the cylinder bore, and the exhaust valves connect the intake passages to one of the two adjacent cylinders to the throttle of the carburetor. an intake port that is provided substantially symmetrically with respect to the central extension line about a straight line that is substantially perpendicular to the rotational axis of the valve and passes through the center of the throttle valve, and that connects the intake passage to the first cylinder and the intake valve; The main configuration is that the cylinder is oriented substantially tangentially to the inner circumferential surface of the cylinder bore of the one cylinder.

In the above configuration, "the cylinders are arranged substantially in a straight line" means that each cylinder C ₁ , C ₂ , C ₃
When the centers O ₁ , O ₂ , O ₃ of are all on one straight line 2, as shown in figure b, each center O ₁ , O ₂ , O ₃
This includes all cases where the center of each cylinder is arranged approximately in a straight line, such as a case where the cylinders are not on a straight line but are slightly eccentric from the axis 3 of a crankshaft (not shown).

Next, embodiments embodying the present invention will be described with reference to the accompanying drawings starting with FIG. 2, to provide an understanding of the present invention. Here, FIG. 2 is a plan view of an intake device according to an embodiment of the present invention, and FIG. 3 is a diagram showing the operation of the same embodiment.
A schematic plan view of the intake device showing the effect. Note that the same reference numerals are used for elements common to those shown in the first figure. Furthermore, the following description is all based on the state in plan view as viewed in the axial direction of the cylinder.

In Fig. 2, IN ₁ , IN ₂ , IN ₃ are intake valves, P ₁ , P ₂ , P ₃ are spark plugs, EX ₁ ,
EX ₂ and EX ₃ indicate exhaust valves, and O ₁ , O ₂ , and O ₃ indicate cylinder centers, respectively. Here, subscripts 1, 2, and 3 indicate components of cylinders C ₁ , C ₂ , and C _3, respectively. Further, in this example, cylinder centers O ₁ to _{O 3} exist on a straight line 2 parallel to the axis of a crankshaft (not shown). The same applies to the following description.

An intake manifold 4 is connected to a cylinder head 5 on a cylinder block (not shown).
An intake passage G ₁ arranged in the intake manifold 4,
G ₂ and G ₃ are branched from the bore 8 in which the throttle valve 7 of the carburetor 6 is disposed, and are connected to each of the above-mentioned intake valves via intake ports IP ₁ , IP ₂ , and IP ₃ bored in the cylinder head 5, respectively. Connected to IN ₁ , IN ₂ , and IN ₃ .

The intake valves IN ₁ , IN ₂ , and IN ₃ provided in each cylinder are all provided close to the inner circumferential surface of each cylinder bore CB ₁ , CB ₂ , and CB ₃ , thereby aligning the position of the spark plug P to the center of the cylinder bore CB. O as close as possible, it is possible to uniformly spread combustion outward, the propagation of combustion waves spreads evenly radially from the center, and knotting is prevented.
The above intake ports IP ₁ , IP ₂ , connected to each intake valve
The swirl of intake air flowing into each combustion chamber from IP ₃ (indicated by arrows D ₁ , D ₂ , and D ₃ ) is strengthened.

Further, in order to further strengthen the swirl, the intake ports IP ₁ , IP ₂ , IP ₃ are oriented substantially tangential to the inner circumferential surfaces of the cylinder bores CB ₁ , CB ₂ , CB ₃ as shown in the figure.

The directions of such intake ports IP ₁ , IP ₂ , IP ₃ are:
As shown in the figure, the axes of the intake ports IP 1 _and IP 3 communicate in the direction of the extension line of the intake passages G _{1 ,} G ₂ , and G ₃ , that is, the cylinders C ₁ and C ₃ (in the case of the figure, J ₁ and J ₃ ) and the straight line 2 connecting the cylinder centers O ₁ and O ₃ is preferably oriented in such a way that each side of the triangle is formed. By arranging it in such a direction, the momentum of the swirl becomes even stronger.

Furthermore, the intake valve IN, spark plug P,
The exhaust valves EX are arranged in the order of intake valve IN → spark plug P → exhaust valve EX in accordance with the flow direction of the swirl shown by arrow D.

The positions of the intake valves IN ₁ , IN ₂ , and IN ₃ are determined by a straight line M 1 passing through each cylinder center O ₁ , O ₂ , O ₃ at right angles to the straight line 2 connecting the cylinder centers O ₁ , O ₂ , O ₃ as shown in the _figure. , M ₂ , M ₃ to the right or left, and the direction of eccentricity is changed for each cylinder. That is, in this example, the cylinder C ₁ and the center cylinder C ₂ are eccentric to the right, and the cylinder C ₃ is eccentric to the left. Therefore, the distance l ₁ between the intake valves IN ₁ and IN ₂ and the distance l ₂ between IN ₂ and IN ₃ have a relationship of l ₁ <l ₂ and are different.

Next, the axis J _{3 of the intake passage G 3 communicating} with the cylinder C ₃ ,
The axis _J2 of the intake passage _G2 communicating with the central cylinder _C2 is approximately symmetrical about a first straight line X that passes through the center 7a of the throttle valve 7 and is perpendicular to the straight line 2 connecting the cylinder centers. It is arranged so that

Here, approximately symmetrical with respect to the first straight line X,
This means that a slight deviation of each intake passage G ₃ and G ₂ from the straight line It is permissible within a range that does not cause a large difference in the pipe resistance values between G ₃ and G ₂ .

The axis J _{1 of the intake passage G 1 communicating} with the other cylinder C ₁ is centered on a second straight line Y that is approximately perpendicular to the rotation axis Z of the throttle valve 7 and passes through the throttle valve center 7a. The direction of the rotation axis Z of the throttle valve 7 and the direction of the intake passage _G1 are determined so as to be substantially symmetrical with respect to the first straight line X.

Here, the second straight line Y is made approximately perpendicular to the axis Z, and the _first straight line
J ₁ is approximately symmetrical with respect to the second straight line Y, which means that the pipe resistance in the intake passage G ₁ and the intake passage G ₂
Changing the direction of the second straight line Y or the direction of the axis J ₁ based on design requirements within a range where the difference with the pipe resistance at (or G ₃ ) does not become too large is as follows:
This means that it falls within the technical scope of the present invention.

In addition, in order to ensure uniformity in the pipe resistance of these three intake passages, the axes J ₁ , J ₂ , and J ₃ of the intake passages G ₁ , G ₂ , and G ₃ are arranged to be approximately straight lines. It is configured. Furthermore, the bore 8 of the carburetor 6 and the intake passage
The cross-sectional area A of the passage 9 that communicates G ₂ and G ₃ , and the passage 1 that also communicates the bore 8 and the intake passage G ₁ .
It is desirable that the cross-sectional areas B and B of 0 be equal to each other, or slightly different in order to reduce the difference in pipe resistance in the intake passages G ₂ , G ₃ and G ₁ communicating therewith.

The arrangement of the intake passages as described above can only be achieved by arranging the intake/exhaust valves, etc., which is the gist of the present invention.

In this case _{, as is} clear from FIG _{. 2} , _the approximately central extension line ( The positional relationship is such that the vaporizer 6 is placed on the first straight line X). Therefore, the intake manifold 4 and the intake ports IP ₂ connecting the intake manifold 4 and the intake valves IN ₂ and IN ₃ ,
IP ₃ is oriented approximately tangentially to the inner circumferential surfaces of cylinder bores CB ₂ and CB ₃ with the first straight line X as the axis of symmetry.

Next, the above embodiment will be explained in more detail with reference to FIG. 2 regarding the flow of intake air in the intake device.

In the carburetor 6, the fuel from the fuel nozzle on the plane perpendicular to the plane of the paper passing through the second straight line Y is mixed with air to become intake air, which passes through the throttle valve 7 and flows out from the bore 8. do. _{, a} first straight line
Since the intake air branches symmetrically around the straight line Y, the same amount of intake air flows out whether it flows out toward the passage 9 as shown by the arrow 11a or flows out into the passage 10 as shown by the arrow 11b. At this time, by appropriately setting the cross-sectional areas A and B of the passages 9 and 10 as described above, the uniformity of the flow rate in both directions is further promoted.

The intake air flowing into the passage 9 is branched into two intake passages G ₃ and G ₂ that are symmetrical about the first straight line X, which is the axis of the passage 9.
It flows equally into both intake passages G ₃ or G ₂ , and then flows into the cylinder C 3 or C 2 via intake port IP ₃ , intake valve IN ₃ or intake port IP ₂ , intake valve IN ₂ , and then flows into cylinder C ₃ or C ₂ as shown by the arrow.
Generate a swirl of the same velocity, designated D ₃ or D ₂ . Intake ports IP ₃ and IP ₂ (the same applies to IP ₁ ) are connected tangentially to the cylindrical inner wall surface of each cylinder bore CB ₃ and CB ₂ , and the intake valve IN ₃
and IN ₂ (same for IN ₁ ) is the cylinder bore
Since it is provided close to the inner wall surfaces of CB ₃ and CB ₂ , the force of the swirl is maximized.

Furthermore, as shown in the figure, the intake passages G ₃ and G ₂ are arranged symmetrically about the first straight line Passageway connecting IN ₃ or IN ₂ (9→
G ₃ ) or (9→G ₂ ) becomes approximately linear, and
Since the economy from the bore 8 to the intake valve IN ₃ or IN ₂ is the shortest and the line resistance thereof is minimal and equal, the velocity of the intake air in both is equal and maximum.

Furthermore, since there are no large bends 12 and 13 like in the conventional intake passage shown by the two-dot chain line in Fig. ₃ , the pipe resistance is small and the generation of swirling flow is prevented _. This will equalize the amount of intake air, increase the flow velocity, strengthen the swirl, and make the swirl uniform.

As a result of the strengthened swirl at C ₃ and C ₂ , the low-temperature intake air collides with the highest temperature exhaust valves EX ₃ and EX ₂ and spark plugs P ₃ and P ₂ , absorbing heat. , the temperature of the cylinder head is reduced and knocking is prevented, and the temperature of the adjacent cylinder is
Distance l between exhaust valves EX ₃ and EX ₂ of C ₃ and C ₂ (Figure 3)
The degree of temperature rise caused by this is small even when the
Therefore, the overall length of the engine can be shortened, and the exhaust manifold can be made smaller.

On the other hand, for the intake air entering the intake passage _G1 , the pipe from the intake passage _G1 to the intake port _IP1 can be configured in a straight line or in a form with almost no bends, so that the resistance of the pipe is minimized and the intake and exhaust Since the arrangement of valves IN ₁ , EX ₁ and spark plug P ₁ is the same as cylinder C ₃ ,
The intake air flow in the other cylinders C ₃ and C ₂ is equivalent in quantity and speed as well.
Uniform intake air distribution, enhanced swirl, and uniformity are achieved.

Furthermore, compared to the conventional intake passage shown by the dashed-dotted line in FIG. 3, the intake passage of the intake system according to the above embodiment has an approximately triangular shape as a whole as shown by the dashed-dotted line in the same figure, and the intake manifold that incorporates this The volume of the crankshaft in the direction perpendicular to the axial direction is significantly reduced.

As described above, the present invention provides an intake system for a three-cylinder engine in which the cylinders are arranged in a substantially straight line, in which the intake valves of each cylinder are provided close to the inner circumferential surface of the cylinder bore in plan view, and The distance from the intake valve of the cylinder to the intake valves of the cylinders on both sides thereof is made different, and the intake valve, the spark plug, and the exhaust valve are arranged in this order in the direction of the flow of the intake swirl in the combustion chamber, and Among the above cylinders, the exhaust valve is disposed approximately on the central extension line between the cylinder bores of two adjacent cylinders, and with this central extension line as the axis of symmetry, the intake passage, this intake passage, and each of the above intake air The intake ports connected to the valves are oriented substantially tangentially to the inner peripheral surface of the cylinder bore, and the exhaust valves are adjacent to each other.
The intake passage for one cylinder to another cylinder,
A straight line passing through the center of the throttle valve of the carburetor is approximately perpendicular to the rotational axis of the throttle valve, and the intake passage and the intake valve to the first cylinder are provided approximately symmetrically with respect to the central extension line. Connect the intake port to the corresponding one
This is an intake system for a three-cylinder engine, characterized in that the air intake device is oriented substantially tangentially to the inner circumferential surface of the cylinder bore of the cylinder.

Therefore, in the above-mentioned intake system, the exhaust valves are arranged approximately symmetrically about the central extension line which is approximately perpendicular to the straight line connecting the cylinder centers, and the intake passages to the adjacent cylinders are arranged approximately symmetrically with respect to the central extension line which is approximately perpendicular to the straight line connecting the cylinder centers, and the intake ports are located on the inner circumferential surface of the cylinder bore. Further, the exhaust valve is oriented substantially tangentially to the inner circumferential surface of the cylinder bore, and the intake passage to the other cylinder for the adjacent cylinder is arranged substantially symmetrically to the central extension line, so that the intake port is oriented substantially tangentially to the inner circumferential surface of the cylinder bore. Because of this, the passage connecting the bore of the carburetor and each intake valve is approximately straight, and the path from the bore to the intake valve is the shortest, and the line resistance is minimized and equal, so that the passage between each cylinder is The speeds of the intake air at are approximately equal and maximum, and the swirl is strengthened.

As a result, the cooling effect of the exhaust valves is improved, and the distance between the cylinders can be shortened because each exhaust valve can be brought close to each other, thereby providing a compact cylinder head that does not cause harm due to heat.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an example of a cylinder to which the present invention can be applied, FIG. 2 is a plan view of an intake device according to an embodiment of the present invention, and FIG. 3 is a plan view of an intake device showing the effects of the embodiment. FIG. 2 is a schematic plan view of the device. Explanation of symbols, X...first straight line, Y...second straight line, _J1 to _J3 ...axis of intake passage, _G1 to _G3 ...
Intake passage, IP ₁ to IP ₃ ... Intake port, C ₁ to C ₃ ...
Cylinder, IN ₁ to IN ₃ ... Intake valve, O ₁ to O ₃ ... Cylinder center, EX ₁ to _{EX 3} ... Exhaust valve, P ₁ to P ₃ ... Spark plug, M ₁ to M ₃ ... Straight line , CB ₁ ~ CB ₃ ... cylinder bore, α ... angle, 2 ... straight line, 4 ... intake manifold, 5 ... cylinder head, 6 ... carburetor, 7 ... throttle valve, 7a ... throttle valve center , 8...bore, 9, 10... passage, 11a,
11b...Arrow.

Claims (1)

[Claims] 1. In an intake system for a three-cylinder engine in which each cylinder is arranged in a substantially straight line, the intake valve of each cylinder is provided close to the inner circumferential surface of the cylinder bore in plan view, and The distances from the intake valve of the cylinder to the intake valves of the cylinders on both sides are different, and the intake valve, spark plug, and exhaust valve are arranged in this order in the direction of the flow of the intake swirl in the fuel chamber, and further, Among the above cylinders, two have adjacent exhaust valves.
The carburetor is arranged on the approximately central extension line between the cylinder bores of the two cylinders, and this central extension line is used as the axis of symmetry.
An intake passage and an intake port connecting the intake passage and each of the intake valves are oriented substantially tangentially to the inner circumferential surface of the cylinder bore, and the exhaust valve connects two adjacent cylinders to one other cylinder. are provided approximately perpendicular to the rotational axis of the throttle valve of the carburetor and approximately symmetrical to the central extension line with respect to the straight line passing through the center of the throttle valve, and an intake passage to the first cylinder and an intake valve. An intake system for a three-cylinder engine, characterized in that an intake port connecting the two cylinders is oriented substantially tangentially to the inner circumferential surface of the cylinder bore of the one cylinder.