JP3014185B2 - Engine cylinder head structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder head structure for an engine.

[0002]

2. Description of the Related Art Among engine cylinder head structures, there is a multipoint ignition type in which a plurality of ignition gaps are provided for one combustion chamber. Japanese Patent Application Laid-Open No. S57-148022 discloses an annular holding plate interposed between a cylinder head and a cylinder block. The holding plate holds a number of spark plugs. A configuration in which a plurality of ignition gaps are located at intervals in the circumferential direction is disclosed. In this way, rapid combustion is performed by simultaneous ignition by a large number of ignition gaps to obtain ideal equal-volume combustion in an Otto-type engine.

[0003]

Recently, in addition to a central spark plug having an ignition gap at the center of a combustion chamber, a peripheral spark plug having an ignition gap at an outer peripheral edge of the combustion chamber is arranged. Is desired. This is because, by igniting from the periphery of the combustion chamber, the combustibility at the outer peripheral portion of the combustion chamber is improved to reduce HC, and the second combustion is performed at a low load, for example, according to the engine operating state.
The ignition is performed only by the spark plug, and the combustion ratio within a predetermined period is made as uniform as possible, that is, the peak value of the combustion speed (combustion ratio) is made as small as possible to reduce NOx. .

[0004] As for the above-mentioned peripheral spark plug, it is desired to locate an ignition gap below the intake port in the outer peripheral edge portion of the combustion chamber from the viewpoint that the mixture becomes rich and the ignitability is improved. (Hereinafter, the ignition gap located at the outer peripheral edge of the combustion chamber below the intake port is
"Specific ignition gap"). On the other hand, from the viewpoint of the serviceability of the ignition plug, it is desired that the ignition plug can be easily attached to and detached from the cylinder head. For this purpose, the high pressure side of the ignition plug which is exposed to the outside is desired. It is important that the terminal side be easily accessible without being disturbed by other members.

When a specific ignition gap is located at the outer peripheral edge of the combustion chamber below the intake port, how to improve the serviceability of the ignition plug becomes a problem.
In other words, from the viewpoint of serviceability, it is conceivable that the spark plug is extended toward the upper part of the cylinder head and disposed, as is generally done. Penetrating through the port, which is virtually impossible.

In the case where there are two intake ports defined by a partition, it is possible to form a mounting hole for a spark plug in the partition and extend the spark plug above the cylinder head. Since the spark plug has a considerably large diameter, the thickness of the partition wall becomes extremely thick, which imposes a large restriction on the design of the intake port, such as an increase in intake resistance and a restriction on the bent shape of the intake port. It is not preferable because it will be given.

It is also conceivable that the mounting hole for the ignition plug for the specific ignition gap is opened along the intake port on the side of the cylinder head where the intake port is opened. However, in this case, the high pressure side terminal portion of the ignition plug exposed to the outside is covered from above by the intake pipe connected to the intake port, and the serviceability cannot be sufficiently satisfied.

Accordingly, an object of the present invention is to improve the serviceability of a spark plug in which an ignition gap is located at the outer peripheral edge of a combustion chamber below the intake port without greatly restricting the setting of the intake port. It is an object of the present invention to provide an engine cylinder head structure that can be improved.

[0009]

In order to achieve the above object, the present invention takes advantage of the fact that an intake port is often curved to form a swirl, and has the following structure. is there. That is, the intake port formed in the cylinder head is curved so that the upstream end is offset from the downstream end in the crankshaft direction. The ignition plug is mounted such that the ignition gap is located at a predetermined position below the port, and the mounting hole of the ignition plug formed in the cylinder head is located below the intake port and on the side where the intake port is open. The mounting hole is formed so as to open to the side surface of the cylinder head, and the mounting hole is formed so as to extend in a direction opposite to the offset direction as it moves away from the combustion chamber and to be inclined with respect to the crankshaft direction. is there.

[0010]

According to the offset for forming the curve, the intake port and the intake air connected thereto in the direction opposite to the offset direction, that is, when the offset direction is one direction of the crankshaft, in the other direction of the crankshaft. A dead space where the tube is not located will be formed. The spark plug mounting hole opens toward the dead space portion, and more specifically, moves away from the combustion chamber toward the side of the intake port and the intake pipe. As a result, it is possible to obtain an arrangement in which the high-pressure terminal side portion of the ignition plug is located in the dead space and the intake pipe is not located above the dead space. This improves the serviceability of the ignition plug.

[0011] Further, since the ignition plug mounting hole is formed in the cylinder head below the intake port, there is virtually no restriction on the setting of the intake port. Of course, a curved swirl port can form a desirable swirl. Preferred aspects of the invention and its advantages will be apparent from the description of the following examples.

[0012]

1, a combustion chamber 2 is defined by a cylinder head 1, a cylinder block 15, and a piston 16, as shown in FIG. The cylinder head 1 is formed with two intake ports 3A and 3B and two exhaust ports 4A and 4B that open to the combustion chamber 2, respectively. Intake and exhaust ports 3A, 3B, 4A, 4B
Is opened and closed at a known timing by an intake / exhaust valve (not shown) in synchronization with the rotation of the crankshaft as is known.

The two intake ports 3A and 3B are connected to the combustion chamber 2
Are opened in the combustion chamber 2 on one side of the cylinder head 1 with respect to a straight line L1 parallel to the crankshaft passing through the center of the cylinder head, and are formed in parallel with each other in the crankshaft direction. Also, 2
The two exhaust ports 4A, 4B open to the combustion chamber 2 on the other side of the cylinder head 1 beyond the straight line L1, and
They are formed in parallel in the crankshaft direction. The intake ports 3A and 3B open on one side of the cylinder head,
The exhaust ports 4A and 4B are open on the other side of the cylinder head 1, and the cylinder head 1 is of a so-called cross-flow type.

The downstream ends of the two intake ports 3A and 3B, that is, the portions near the combustion chamber 2 are formed as branch portions 3a and 3b defined by a partition wall 5, and the upstream portions are assembled together. The gathering part 3c is provided. Intake port 3A
From the upstream side to the downstream side, that is, the collecting portion 3c
And a straight line extending substantially perpendicularly to the crankshaft from the branch portion 3a.

The intake port 3B is curved from the branch portion 3b toward the collecting portion 3c. Describing this curve, consider a straight line L2 passing through the center of the combustion chamber 2 and orthogonal to the crankshaft (orthogonal to the straight line L1). At this time, the upstream end of the partition wall 5 is on the straight line L2, and therefore, the branch portion 3b is curved so as to be offset toward the intake port 3A. That is,
In the present invention, the offset direction is below FIG.
The direction opposite to the offset direction is in the upper part of FIG.

A swirl valve 6 is disposed in the collecting part 3c. The swirl valve 6 is swingable about a rotation shaft 7 provided at an upstream end thereof. A state shown by a solid line in FIG. 1 is a fully closed state, and a state shown by a chain line is a fully open state. is there. The rotating shaft 7 is located in the collecting portion 3c, at a position immediately adjacent to the side wall opposite to the intake port 3B, that is, offset in the offset direction, and in the fully closed state, downstream of the swirl valve 6. The end (free end) is located at a small distance from the upstream end of the partition wall 5. When the swirl valve 6 is fully open, the swirl valve 6 is in a state substantially perpendicular to the crankshaft, that is, in a state in which the swirl valve 6 extends substantially in parallel with the substantially straight intake port 3A. In the embodiment, the swirl valve 6 is fully closed at a low load, the opening degree increases as the load increases at a medium load, and fully opens at a high load. The top wall and the bottom wall of the collecting part 3c are formed as substantially flat surfaces as shown in FIG.

As shown in FIG. 2, a bulging portion 8 bulging upward is formed on the upper wall of the collecting portion 3c, and a fuel injection valve 17 is attached to the bulging portion 8. reference). The bulging portion 8 has a downstream portion branched into a branch portion 8a extending toward the intake port 3A and a branch portion 8b extending toward the intake port 3B.

In the bulging portion 8, the upstream side of the branch portions 8a and 8b is a gathering portion 8c. The gathering portion 8c extends substantially in the direction of the straight line L2 so as to face the upstream end of the partition wall 5. Is formed. In other words, the collecting portion 8c is formed at a position offset toward the intake port 3B with respect to the center of the collecting portion 3c of the intake port. As shown in FIG. 3, such a collecting portion 8c is inserted and attached such that the tip end of the fuel injection valve 17 has its axis substantially aligned with the direction of the straight line L2. The fuel injection valve 17 is of a two-hole type that directs the injected fuel in the two directions of the branch portions 8a and 8b.
It is also possible to use a one-hole type having a spray width approximately equal to the branch spread of a and 8b.

In the fully closed state of the swirl valve 6, most of the intake air is supplied only from the intake port 3B, and a swirl of intake air in the clockwise direction in FIG. The swirl becomes weaker as the swirl valve 6 opens. Even when the swirl valve 6 is fully closed, a small amount of intake air flows to the intake port 3A, thereby preventing a large amount of fuel from adhering to the inner wall of the intake port (branch 3a). Even when the swirl valve 6 is fully opened, a swirl is formed by the curvature of the intake port 3B. At this time, the swirl valve 6
Is in a state substantially parallel to the intake port 3A, which is preferable for minimizing the intake resistance of the swirl valve 6 as much as possible and ensuring a fully open output.

The combustion chamber 2 has a total of four ignition gaps 1.
1a, 12a, 13a and 14a are located. Of these four ignition gaps, the ignition gap 11a is located at the center of the combustion chamber 2, and the other three ignition gaps 12a to 12a
Reference numerals 14a are respectively located at the outer peripheral edges of the combustion chamber 2.

As shown in FIG. 3, the ignition gap 12a is located below the intake ports 3A and 3B and between the intake ports 3A and 3B, that is, below the upstream end of the partition wall 5. Is located. The ignition gap 13a is connected to the intake port.
Port 3A and the exhaust port 4A. The ignition gap 14a is located between the intake port 3B and the exhaust port 4B. However, the ignition gaps 13a and 14a are located closer to the exhaust ports 4A and 4B than the straight line L1 in the direction of the straight line L2. In the embodiment, the position of the ignition gap 13a is slightly closer to the straight line L1 than that of 14a.

When the load is low, the ignition is performed by the peripheral ignition gaps 12a to 14a. As a result, the combustion is performed from around the combustion chamber 2, and the amount of HC that is likely to be generated around the combustion chamber is reduced. Since the flame surfaces coincide with each other in the circumferential direction of the cylinder before they coincide with each other at the center of the combustion chamber 2, the situation where the flame surface spreads rapidly in a short time is suppressed, and the combustion rate within a predetermined period is reduced. Uniform and NOx
Is also suppressed.

When the load is high, all the ignition gaps 11a
14a is performed. Thereby, rapid combustion is performed and knocking is prevented. When the load is extremely low, the ignition may be performed by all of the ignition gaps 11a to 14a to secure combustion stability.

Spark plug 1 having ignition gap 12a
The mounting hole 22 for the second port extends below the intake ports 3A and 3B so as to be inclined with respect to the straight lines L1 and L2 and away from the combustion chamber 2 so that the intake ports 3A and 3B are open. An opening is provided on one side of the cylinder head 1 on the side of the cylinder. More specifically, the mounting hole 22 extends in a direction (upward in FIG. 1) opposite to the offset direction of the intake port 3B as the distance from the combustion chamber 2 increases. Thus, the mounting hole 22 is formed so as to obliquely cross the intake port 3B at a considerably short distance.

Attachment and removal of the spark plug 12 to and from the attachment hole 22 are performed from one side of the cylinder head 1 while gripping the high-voltage terminal side thereof. Spark plug 1
When the cylinder 2 is mounted on the cylinder head 1, the high-pressure terminal side portion is located at a position where it does not vertically overlap the intake ports 3A, 3B. Therefore, the spark plug 12
Can be easily approached while avoiding interference with the intake pipes connected to the intake ports 3A and 3B. By setting the mounting mode of the spark plug 12, it is not necessary to form a mounting hole for mounting the spark plug 12 in the partition 5, and the thickness of the partition 5 can be reduced to reduce intake resistance. Is preferred.

Each of the ignition plugs 11, 13, and 14 having the ignition gaps 11a, 13a, and 14a is as shown in FIG. It is designed to be mounted and removed from above the cylinder head 1.

FIG. 4 shows an example in which the present invention is applied to an in-line four-cylinder engine. As shown in FIG. 4, the intake port offset direction is set to the other end of the crankshaft direction in the two cylinders at one end (upper side in FIG. 4) in the crankshaft direction (the direction of the straight line L1). In the two cylinders on the end side, it is on one end side in the crankshaft direction. In this manner, the length of the intake manifold connected to each of the intake ports 3A and 3B in the crankshaft direction can be reduced.

FIG. 5 shows an example in which one intake port 3 and one exhaust port 4 are provided for one combustion chamber 2. In the present embodiment, the center ignition gap is not provided, but the center ignition gap may be arranged substantially at the center of the combustion chamber 2.

[Brief description of the drawings]

FIG. 1 is a plan view showing an arrangement relationship among an intake port, an exhaust port, and an ignition gap with respect to a combustion chamber.

FIG. 2 is a diagram when the inside of the intake port is viewed from the opening side of the intake port to the outside of the cylinder head.

FIG. 3 is a longitudinal sectional view of a cylinder head portion.

FIG. 4 is a simplified plan view when the present invention is applied to an in-line four-cylinder engine.

FIG. 5 shows a modification of the present invention, and is a view corresponding to FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder head 2 Combustion chamber 3A Intake port 3B Intake port 3a Branch part 3b Branch part 3c Assembly part 4A Exhaust port 4B Exhaust port 5 Partition wall 6 Swirl valve 8 Inflated part (fuel injection valve) Attachment hole) 12 Ignition plug 12a Ignition gap 13a Ignition gap (second ignition gap) 14a Ignition gap (third ignition gap) 22 Ignition plug attachment hole L1 Crank shaft direction line L2 Direction line orthogonal to crank shaft

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI F02P 13/00 301 F02P 13/00 301A 15/08 302 15/08 302A (72) Inventor Kazuyoshi Tamamoto 3 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture No. 1 Mazda Engineering Co., Ltd. (56) References JP-A-57-148021 (JP, A) JP-A-63-73535 (JP, U) JP-A-2-78725 (JP, U) JP-A-1 −124333 (JP, U) Actually open 60-43178 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02F 1/24 F02B 23/08 F02B 31/02 F02F 1/42 F02P 13/00 F02P 15/08

Claims (7)

(57) [Claims] An intake port formed in a cylinder head is curved so that an upstream end is offset from a downstream end in a crankshaft direction, and is formed on a cylinder head at an outer peripheral edge of a combustion chamber. An ignition plug is mounted so that an ignition gap is located at a predetermined position below the intake port, and a mounting hole for the ignition plug formed in the cylinder head is opened below the intake port and the intake port is opened. The mounting hole is formed so as to open to the side of the cylinder head on the side of the cylinder, the mounting hole extends in the direction opposite to the offset direction as it moves away from the combustion chamber, and is formed to be inclined with the crankshaft direction. A cylinder head structure for an engine. 2. The fuel cell system according to claim 1, wherein a second ignition gap is provided at an outer peripheral edge of the combustion chamber and between the intake port and the exhaust port in one circumferential direction of the combustion chamber from the intake port. Further, a third ignition gap is arranged in the other circumferential direction of the combustion chamber from the intake port. 3. The intake port according to claim 1, wherein two intake ports are formed at intervals in the crankshaft direction, and the ignition gap is located between the two intake ports. 4. The intake port according to claim 3, wherein the two intake ports are formed as an assembly part in which upstream parts are assembled together, and the downstream parts are independent of each other by a partition formed in a cylinder head. What is considered a branch. 5. The branch according to claim 4, wherein, of the two branches downstream of the gathering portion, only one of the branches is greatly curved by the offset, and the other branch is in the crankshaft direction. One that is formed almost straight across the gathering portion so as to be substantially orthogonal. 6. The swirl valve according to claim 5, wherein a swirl valve for adjusting an intake air amount to the other branch portion is disposed at a position offset in the offset direction in the collecting portion. 7. The fuel injection valve according to claim 5, wherein a mounting hole for a fuel injection valve is formed at an upper portion of the collecting portion so as to be located substantially on an extension of the partition wall.