JP2524290Y2 - Engine combustion chamber 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 combustion chamber structure of an engine in which two intake ports and two exhaust ports are opened in one cylinder.

[0002]

2. Description of the Related Art In recent years, so-called multi-valve engines having a plurality of intake / exhaust valves for one cylinder have been used in engines for automobiles and the like in order to achieve higher output and higher efficiency. In particular, a four-valve type having two intake valves and two exhaust valves is widely used. Further, there are various combustion chamber shapes, one of which has a conical combustion chamber shape and a projection formed on the upper bottom of the piston so as to correspond to the combustion chamber shape. Have been. In addition, the valve diameter of the intake valve is
Usually, it is set larger than that of the exhaust valve.

Further, in the engine, in order to improve fuel economy, the flow of intake air in the cylinder is changed to a swirl flow circulating in a plane perpendicular to the cylinder axis, or in a plane parallel to the cylinder axis. It may be a tumble flow to return.

[0004]

In the above four-valve engine, a spark plug is usually provided facing a bore center of a cylinder surrounded by intake and exhaust valves. It could be broken. The main cause of this breakage is vibration (seating vibration) generated when the valve is closed.

In an engine in which the shape of the combustion chamber is conical and a projection is formed at the upper bottom of the piston so as to correspond to the shape of the combustion chamber, interference between the projection and the electrode of the ignition plug is caused by the projection. In order to avoid this, a recessed portion must be provided, and there is a problem that the combustion efficiency or fuel efficiency is reduced accordingly.

[0006] The present invention has been made in view of the above points, and aims at, in particular, that the main cause of breakage of the plug electrode is due to seating vibration when the valve is closed. Considering that the seating vibration is large on the intake valve side where the valve diameter is large, the layout of the ignition plug is properly arranged to prevent breakage of the plug electrode, and the recess provided on the protrusion at the top bottom of the piston. It is an object of the present invention to provide a combustion chamber structure of an engine which can be eliminated or reduced to improve combustion performance.

[0007]

According to a first aspect of the present invention, as a combustion chamber structure of an engine, two intake ports and two exhaust ports are opened in one cylinder. It is assumed that the opening of the intake port is formed larger than the opening of the exhaust port, and a protrusion is formed on the upper bottom of the piston so as to correspond to the shape of the conical combustion chamber. A spark plug is provided at a position sandwiched between the openings of the four intake and exhaust ports and offset toward the exhaust port with respect to the bore center of the cylinder, and the electrodes of the spark plug are arranged in the same direction as the arrangement direction of the same kind of ports. It is configured to face the direction.

[0008] The invention according to claims 2 and 3 is a more concrete example of the invention according to claim 1 described above. That is, the invention according to claim 1 uses the intake port as a tumble port that induces the flow of intake air in the cylinder as a tumble flow. The invention according to claim 3 is
A mark indicating the position of the electrode is provided on the main body of the spark plug, and the mark allows the electrode of the spark plug to be oriented in the same direction as the arrangement direction of the ports of the same type in all cylinders.

[0009]

With the above arrangement, the invention according to claim 1 has the following features.
The spark plug is provided at a position offset toward the exhaust port from the bore center of the cylinder interposed between the openings of the four intake and exhaust ports, and the opening and the valve itself (intake valve) for closing the opening are large, and the seating vibration is large. Because it is relatively far from the opening of the intake port, it is less susceptible to the effects of sitting vibration. Further, the electrodes of the ignition plug are oriented in the same direction as the arrangement direction of the same type of ports (that is, the intake ports and the exhaust ports), and the distance between two intake valves or exhaust valves seated simultaneously is different. Therefore, the seating vibration is not transmitted from both intake valves or exhaust valves to the electrodes of the ignition plug at the same time, but is transmitted in a state where they are out of phase with each other and cancel each other. From the above, the breakage of the plug electrode due to the sitting vibration is prevented.

In addition, since the spark plug is offset from the bore center of the cylinder and its electrodes are oriented in the same direction as the arrangement direction of the ports of the same kind, the plug electrode and the protrusion on the upper bottom of the piston are separated. Interference is reduced, and the recess for avoiding the interference can be eliminated or reduced.

Further, in the invention according to the second aspect, the tumble flow of the intake air drawn into the cylinder from the tumble port is such that the electrodes of the ignition plug are oriented in the same direction as the arrangement direction of the ports of the same type. As a result, the ignitability is improved.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

1 to 3 show the structure of a combustion chamber of an engine according to an embodiment of the present invention.
A cylinder block 3 having a piston is slidably fitted in each of the cylinders 2, and 4 is a cylinder head mounted on the cylinder block 1. Two intake ports 5, 6 and two exhaust ports 7, 8 are formed for each cylinder 2,
The intake ports 5 and 6 and the exhaust ports 7 and 8 are
It is open to.

The openings 5a, 6a of the intake ports 5, 6 and the openings 7a, 8a of the exhaust ports 7, 8 are arranged around a bore center P of the cylinder 2. Specifically, the openings 5a, 6a of the intake ports 5, 6 and the openings 7a, 8a of the exhaust ports 7, 8 are arranged on opposite sides of a straight line L passing through the bore center P in the engine axial direction. , Openings 5a, 6 of intake ports 5, 6
a and the openings 7a and 8a of the exhaust ports 7 and 8
Each is arranged side by side at a predetermined distance from the straight line L. The diameters of the openings 5a, 6a of the intake ports 5, 6 are set larger than those of the openings 7a, 8a of the exhaust ports 7, 8. Opening 5 of each intake port 5, 6
a, 6a are provided by the exhaust valves 7, 12 by the intake valves 11, 12, respectively.
The openings 7a, 8a are opened and closed at predetermined timing by exhaust valves 13, 14, respectively, and the intake and exhaust valves 11 to 14 are driven by a valve operating device (not shown) including a camshaft and the like. It is configured as follows.
Further, although not shown, the intake ports 5 and 6 are provided with a mask on the intake side of the peripheral wall, and the like. It is configured as a tumble port.

A combustion chamber 15 is constituted by the upper inner peripheral surface of the cylinder 2, the lower surface of the cylinder head 4, and the upper surface of the piston 3 (also referred to as the upper bottom of the piston). The combustion chamber 1
5 is formed in a conical shape by providing a concave portion 16 on the lower surface of the cylinder head 4, and a truncated conical protruding portion protruding corresponding to the conical combustion chamber shape is formed on the upper bottom of the piston 3. 20 are formed. A spark plug 18 has an electrode 18a connected to the combustion chamber 15 on the cylinder head 4.
It is attached to face. The spark plug 18
It is interposed between the openings 5a to 8a (that is, the intake and exhaust valves 11 to 14) of the four intake and exhaust ports 5 to 8 and is provided at a position offset from the bore center P of the cylinder 2 by a predetermined distance Δ toward the exhaust port. And the spark plug 18
The electrode 18a is directed in the same direction as the arrangement direction of the same type of ports (the intake ports 5, 6 or the exhaust ports 7, 8), that is, in the axial direction of the engine. In order to orient the electrode 18a in the axial direction of the engine, as shown in FIG. 4, a mark 19 indicating the position of the electrode (specifically, the side electrode) 18a is provided on the plug body 18b of the spark plug 18. . The washer 18c of the ignition plug 18 is broken when a predetermined fastening torque is applied, and is always fastened with a constant torque.

Reference numeral 21 denotes a cooling water passage formed in the cylinder head. Cooling water flows through the passage 21 along the engine shaft from the rear side (the side connected to the transmission) to the front side (the connection to the radiator). Side). The bent portion of the electrode 18a of the ignition plug 18 is located on the upstream side in the flow direction A of the cooling water.

Next, the operation and effect of the above embodiment will be described. Of the four intake / exhaust ports 5-8 opened to one cylinder 2 among the openings 5a-8a, the openings 5a of the intake hoods 5, 6 are provided. , 6a (that is, the intake valves 11, 1 that close it)
2) is larger than the openings 7a and 8a of the exhaust ports 7 and 8 (exhaust valves 13 and 14 that close them), and
The seating vibration generated when the intake valves 11 and 12 close the openings at a and 6a is greater than the seating vibration generated when the exhaust valves 13 and 14 close the openings 7a and 8a.

On the other hand, in the above-described embodiment, when the ignition plug 18 is provided between the openings 5a and 8a of the four intake and exhaust ports 5 to 8, the cylinder 2
Opening 5a of the exhaust ports 5, 6 than the bore center P of
6a is provided at a position offset to the side of the intake valve 1 described above.
Since the large seating vibration generated at the time of closing of the seat plugs 1 and 12 is relatively difficult to be transmitted, the ignition plug 18
Of the electrode 18a (specifically, the side electrode) can be prevented. The electrode 18a of the ignition plug 18
Are openings of the same type of port (that is, openings 5a and 6a of intake ports 5 and 6 or openings 7a and 8a of exhaust ports 7 and 8).
And the distance between the two intake valves 11 and 12 or the exhaust valves 13 and 14 which are seated at the same time as the bent portion of the electrode 18a is different from each other. 11, 12 or exhaust valves 13, 14
Is not transmitted to the bent portion of the electrode 18a of the spark plug 18 at the same time, but is transmitted in a state where they are out of phase with each other and cancel each other. As a result, breakage of the plug electrode 18a due to sitting vibration can be more reliably prevented.

The spark plug 18 is connected to the opening 7a, 8a of the exhaust port 7, 8 from the bore center P of the cylinder 2.
Side, and since the electrode 18a is oriented in the same direction as the arrangement direction of the openings of the same type of port, the interference between the plug electrode 18a and the protrusion 20 on the upper bottom of the piston is reduced. The recess for avoiding this interference can be eliminated or reduced. still,
Even when the spark plug 18 is similarly offset from the bore center P of the cylinder 2 toward the openings 7a and 8a of the exhaust ports 7 and 8, the electrode 18a of the spark plug 18 is bored in a direction orthogonal to the arrangement direction of the openings of the same kind. Center P
From the plug electrode 18a.
To avoid interference with the protrusion 20 on the piston bottom
A recess 31 must be provided in the protrusion 20.

Further, in the case of this embodiment, the intake ports 5 and 6 are tumble ports which make the flow of intake air in the cylinder 2 a tumble flow circulating in a plane parallel to the cylinder axis. Since the electrode 18a of the plug 18 is oriented in the same direction as the arrangement direction of the openings 5a and 6a of the intake ports 5 and 6, the tumble flow is generated by the electrode 1a of the spark plug 18.
8a (center electrode and side electrode), and as a result, ignitability can be improved.

In addition, the electrode 18a of the spark plug 18
Is located on the upstream side in the flow direction A of the cooling water flowing in the cooling water passage 21 of the cylinder head 4 as a mounting member of the ignition plug 18, so that the cooling performance for the ignition plug 18 can be improved. . Therefore, the heat value of the ignition plug 18 increases, and the cooling loss is reduced, so that the fuel efficiency can be improved.

[0022]

As described above, according to the combustion chamber structure of the engine according to the first aspect of the present invention, the spark plug is offset to the exhaust port side from the bore center of the cylinder, and its electrode is arranged in the same type of port. By merely arranging in the same direction as the direction, it is possible to make it difficult for seat vibration to be transmitted to the plug electrode, and to prevent breakage thereof. In addition, the recess for avoiding interference between the plug electrode and the protrusion on the upper bottom of the piston can be eliminated or reduced, and the combustibility can be improved.

According to the second aspect of the present invention, the tumble flow of the intake air drawn into the cylinder from the tumble port passes between the electrodes of the spark plug oriented in the same direction as the arrangement direction of the ports of the same kind. Is also improved.

Further, according to the present invention, the marks of the spark plug can be easily and reliably oriented in the arrangement direction of the same type of ports in all the cylinders by the marks at the time of mounting the spark plug, thereby speeding up the operation. Further, it is possible to make the combustibility between the cylinders uniform.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a combustion chamber structure of an engine according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a state in which a spark plug is attached to a combustion chamber.

FIG. 3 is an arrangement diagram showing an arrangement relationship between an opening of an intake / exhaust port and a spark plug with respect to a cylinder;

FIG. 4 is a side view of a spark plug.

[Explanation of symbols]

 2 Cylinder 3 Histone 5, 6 Intake port 5a, 6a Intake port opening 7, 8 Exhaust port 15 Combustion chamber 18 Spark plug 18a Electrode 19 Mark 20 Projection P Cylinder bore center

Claims (3)

(57) [Scope of request for utility model registration] 1. A cylinder has two intake ports and two exhaust ports each open, and the opening of the intake port is formed larger than the opening of the exhaust port. In the combustion chamber structure of the engine, in which a protruding portion is formed corresponding to the shape of the combustion chamber, the ignition plug is sandwiched between the openings of the four intake and exhaust ports and on the exhaust port side with respect to the bore center of the cylinder. A combustion chamber structure for an engine, wherein the ignition plug is provided at an offset position and the electrodes of the spark plug are oriented in the same direction as the arrangement direction of the ports of the same kind. 2. A combustion chamber structure for an engine according to claim 1, wherein the intake port is a tumble port that induces a flow of intake air in the cylinder as a tumble flow. 3. The spark plug body is provided with a mark indicating the position of the electrode, and the mark directs the electrode of the spark plug in the arrangement direction of the same type of port in all cylinders. Engine combustion chamber structure.