JP2014240644A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make combustion speeds in a combustion chamber of an internal combustion engine uniformly approximate each other.SOLUTION: An internal combustion engine comprises at least one exhaust valve 6 and a plurality of intake valves 5 in one cylinder, and comprises an ignition plug 3 between the intake valve 5 and the exhaust valve 6, and is controlled so that a swirl flow is generated in a combustion chamber 2 by forming phase differences at valve open times of the intake valves 5. The ignition plug 3 is arranged to a side of the intake valves 5 rather than an axial core p of the cylinder. Since the ignition plug 3 is arranged to the side of the intake valves 5 rather than the axial core p of the cylinder, combustion at an intake side which is relatively weak in disturbance can be promoted. By this constitution, a combustion speed at an exhaust side which is relatively strong in disturbance and a combustion speed at the intake side which is relatively weak in disturbance are levelled, thereby the combustion speeds in the combustion chamber 2 are made to approximate each other, and as a result, knocking can be suppressed.

Description

  The present invention relates to an internal combustion engine having a plurality of intake valves per cylinder.

  As an internal combustion engine used for an automobile or the like, one having a plurality of intake valves and exhaust valves per cylinder is known. In addition, the variable valve mechanism can be applied to change the opening and closing timings of both the intake and exhaust valves. By adjusting the opening and closing timing of each valve, the return of intake and exhaust in the combustion chamber is optimized, and the output is improved. And improved fuel economy.

  For example, in Patent Document 1, two exhaust valves and two intake valves are provided per cylinder, the opening / closing timing is shifted between two intake valves and between two exhaust valves, and one set of A technique for overlapping the opening operation of the intake valve and the exhaust valve and the other set of the intake valve and the exhaust valve is described.

  By shifting the opening and closing timings of the two intake and exhaust valves and overlapping the opening of the intake and exhaust valves, the swirl flow that forms the swirl flow around the cylinder axis of the cylinder is promoted and the combustion performance is improved. We are trying to improve.

JP 2010-150939 A

  For example, as shown in FIG. 6, when the two intake valves 5a and 5b are opened simultaneously, the intake air S10 from both intake valves 5a and 5b is along the circumferential direction of the inner peripheral surface 2a in the combustion chamber 2. The two swirl flows S11 collide on opposite sides of the intake valve 5 on the exhaust valve side. After that, it also collides with intake air S12 which is another flow from the intake valves 5a and 5b. Due to these collisions, the momentum of the swirl flow in the combustion chamber 2 is reduced.

  In this state, even if the intake air is compressed by the piston 10 immediately before ignition, the state of turbulence generated in the combustion chamber 2, that is, the degree of occurrence of small vortex aggregates is weak. This is because if the momentum of the swirl flow is weak, the generation of small vortices in the compression stroke is reduced. For this reason, there is a problem that the combustion speed of the air-fuel mixture is slow and the thermal efficiency is lowered.

At this time, the distribution of turbulence during compression is as shown in FIG. 7, for example. Here, a code A portion indicating a relatively weak disturbance (hereinafter referred to as “weak disturbance portion A”), a code C portion indicating a strong disturbance (hereinafter referred to as “strong disturbance portion C”), and the middle thereof. A portion indicated by symbol B (hereinafter referred to as “medium disturbance portion B”) exists in the combustion chamber 2.
As shown in the figure, the weakly turbulent portion A and the middle turbulent portion B have portions D and E (hereinafter referred to as the intruding portions D and B) that greatly enter the inner diameter side (to the side away from the inner peripheral surface 2a) on the intake side and the exhaust side, respectively. E)) has occurred. Since the turbulence is particularly weak at the entrances D and E, the combustion speed becomes slow. For this reason, knocking is likely to occur, which may cause output and fuel consumption deterioration. In addition, the fact that the portion C of the strong turbulence is distributed to the exhaust side with respect to the axial center of the cylinder also causes a difference in combustion speed between the exhaust side and the intake side.

On the other hand, if one of the two intake valves is opened and then the other is opened with delay as in Patent Document 1, the intake air from the one intake valve that has been opened first causes the combustion chamber to enter the combustion chamber. Since a stable swirl flow is formed, even if the other intake valve is opened later, the swirl flow is not easily inhibited. For this reason, it is thought that the weakness of the disturbance at the time of compression may be solved somewhat.

  However, when a phase difference is provided in the valve opening timing of the intake valve, the intake side D on the exhaust side is eliminated in the compression stroke, but the bias of the intake part E and the turbulent part C may still exist. It has been found through experiments. That is, even in an internal combustion engine in which a phase difference is provided at the opening timings of a plurality of intake valves, the combustion speed in the combustion chamber is not completely equalized.

  Accordingly, an object of the present invention is to make the combustion speed of the entire combustion chamber as uniform as possible.

  In order to solve the above problems, the present invention provides at least one exhaust valve provided per cylinder, a plurality of intake valves provided per cylinder, and provided between the intake valve and the exhaust valve. The plurality of intake valves are controlled to generate a swirl flow in the combustion chamber by providing a phase difference between the opening timings of the intake valves, and the ignition plugs are connected to the shafts of the cylinders. The internal combustion engine is arranged such that the disturbance generated in the combustion chamber on the intake valve side or the exhaust valve side from the center is shifted to a relatively small side.

  When the disturbance generated on the intake valve side relative to the cylinder axis is relatively smaller than the disturbance generated on the exhaust valve side, the ignition plug is disposed closer to the intake valve than the cylinder axis. It can be an institution.

  Here, the spark plug provided for each cylinder includes a center electrode positioned at the axial center of the shell and a side electrode rising from the center electrode as an electrode for generating a spark. The shell includes a screw portion corresponding to the plug hole of the cylinder, and the electrode is provided on the tip side of the screw portion.

  Here, it is preferable that the side electrode is disposed so as to rise on the side where the turbulence generated in the combustion chamber is relatively larger than the axial center of the shell.

  The side electrode includes a rising portion fixed to the shell and a tip portion protruding from the rising portion toward the axial center of the shell, and the rising portion connects the exhaust side and the intake side. It is desirable that the width in the orthogonal direction is wider than the width of the tip portion in the direction orthogonal to the direction. Furthermore, it is desirable that the rising portion has an arc shape that is convex toward the side where the turbulence generated in the combustion chamber is relatively large.

According to this invention, a phase difference is provided in the valve opening timing between the intake valves to generate a swirl flow, and further, the spark plug is arranged to be shifted to the side where the turbulence is relatively smaller than the axis of the cylinder. In the compression stroke, combustion on the side with relatively little turbulence can be accelerated. Thereby, the combustion speed on the exhaust side, which is relatively strong in turbulence, and the combustion speed on the intake side, which is relatively weak in turbulence, can be leveled. That is, even if a weakly disturbed portion in the compression process is biased toward the intake side, the combustion speed in the combustion chamber can be made uniform and knocking can be suppressed.

The flow of the intake air in the combustion chamber of one Embodiment of this invention is shown, (a) is a top view which shows a combustion chamber, (b) is a front view. It is a top view which shows distribution of the intensity of the turbulence in a combustion chamber in a compression process. (A)-(d) is a graph which shows the tendency of the various performance by the difference in direction of the side electrode of a spark plug. (A) is a front view of a spark plug, (b) is a BB arrow view of (a), (c) is a modification of (b). It is a time chart which shows the example of operation | movement of an intake valve and an exhaust valve. The flow of the intake air in a combustion chamber in case two intake valves open and close simultaneously is shown, (a) is a plan view showing the combustion chamber, and (b) is a front view. It is a top view which shows distribution of the strength of the disorder in a combustion chamber in a compression process in case two intake valves open and close simultaneously.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The internal combustion engine of this embodiment is an automobile engine, and FIGS. 1A and 1B show a main part of the combustion chamber 2 in one cylinder provided in the engine.

  The cylinder S includes an intake port 1 for sending an air-fuel mixture generated by fuel injection of a fuel injection valve into the combustion chamber 2 for each cylinder containing the piston 10, an exhaust port 7 for sending exhaust gas out of the combustion chamber 2, A spark plug 3 or the like disposed downward from the cylinder head side along the axis p of the cylinder (cylinder) is provided. The intake port 1 and the exhaust port 7 are opened and closed by an intake valve 5 and an exhaust valve 6, respectively. In FIG. 1B, the exhaust port 7 and the exhaust valve 6 are not shown.

  Since the intake valve 5 and the exhaust valve 6 are connected to a camshaft provided on the cylinder head side via a valve lifter, the intake port 1 and the exhaust port 7 are opened and closed at a predetermined timing by the rotation of the camshaft. Power is transmitted to the camshaft by connecting a sprocket provided on the camshaft side and a sprocket provided on the crankshaft side by a timing chain or the like.

  As shown in FIG. 1A, two intake valves 5 are provided in one cylinder. A control device including a camshaft, a valve lifter, and the like is set so that the opening and closing timings of the first intake valve 5a that is one intake valve 5 and the second intake valve 5b that is the other intake valve 5 are different from each other. ing.

  In addition, two exhaust valves 6 are provided in one cylinder as shown in FIG. A control device including a camshaft, a valve lifter, and the like is set so that the opening timing of the first exhaust valve 6a which is one exhaust valve 6 and the second exhaust valve 6b which is the other exhaust valve 6 are the same. ing.

An example of the operation of the intake valve 5 and the exhaust valve 6 is shown in FIG. The opening timing of the first intake valve 5a is set earlier than the closing timing of the two exhaust valves 6a, 6b, and an overlap period is provided between the opening timings of both. The second intake valve 5b and the two exhaust valves 6a and 6b are set in a state where no overlap occurs during the valve opening period. It is also possible to set so that no overlap occurs during the opening period of the first intake valve 5a and the two exhaust valves 6a, 6b. It is also possible to provide a phase difference between the closing timing of the two intake valves 5a and 5b and the opening timing and the closing timing between the two exhaust valves 6a and 6b.
It is possible to set the opening / closing timing of each valve under the above conditions and operate the vehicle at a fixed valve timing, but a variable valve device is used for the opening timing and closing timing of each of these valves. Thus, it can be changed appropriately during driving according to the driving state of the vehicle.

  Further, as described above, after the first intake valve 5a of the two intake valves 5a and 5b is opened, the second intake valve 5b is opened with a delay. As described above, a stable swirl flow S1 is formed in the combustion chamber 2 by the intake air S0 from the first intake valve 5a opened first, and the swirl flow S1 is inhibited even if the second intake valve 5b is opened later. A large swirl flow S3 is formed in the combustion chamber 2 as shown in FIG.

  Based on this valve operation, the distribution of turbulence in the combustion chamber 2 in the compression process is as shown in FIG. Here, the “weak turbulence portion A” having a relatively weak turbulence, the “strong turbulence portion C” having a strong turbulence, and the “medium turbulence portion B” indicating the middle thereof are as described above.

Here, of the first intake valve 5a and the second intake valve 5b, the first intake valve 5a is opened, and then the second intake valve 5b is opened with a delay. The entry portion D is eliminated.
However, the intake portion E on the intake side is not eliminated, and the weakly disturbed portion A and the moderately disturbed portion B are distributed with a bias toward the intake side as a whole with respect to the axial center p of the cylinder. In addition, the turbulent portion C is distributed with a bias toward the exhaust side as a whole with respect to the axial center p of the cylinder.

  In order to cope with this, in the combustion chamber 2, the axis q of the shell 3a of the spark plug 3 is biased closer to the intake valve 5 by a distance w than the axis p of the cylinder, as shown in FIG. Arrange with heart.

  Since the spark plug 3 is disposed closer to the intake valve 5 than the cylinder axis p, combustion on the intake side, which is relatively less disturbed, can be accelerated. Further, combustion on the exhaust side, which is relatively turbulent, can be delayed. As a result, the combustion speed on the exhaust side, which is relatively strong in turbulence, and the combustion speed on the intake side, which is relatively weak in turbulence, can be leveled, so that the combustion speed in the combustion chamber can be made uniform. If the combustion speed is made nearly uniform, problems such as spontaneous combustion of the air-fuel mixture in the compression stroke are solved, so that knocking can be suppressed.

  If knocking can be suppressed, a high compression ratio can be easily achieved. In addition, knocking can be easily suppressed even when low-octane fuel is used, at low speed and high load, during supercharging, etc., so that the thermal efficiency of the internal combustion engine can be increased, and the output and fuel consumption can be improved.

  FIG. 4A shows an overall view of the spark plug 3. FIG. 4B shows the electrode 4 of the spark plug 3 in a plan view. The center electrode 4c arranged at the axis q of the shell 3a of the spark plug 3 is designed as a positive electrode that emits electrons as a cathode. The side electrode (side electrode) 4a is a ground electrode, and is fixed to the tip of a screw part (a screw part corresponding to the plug hole on the cylinder side) 3b provided on the tip side of the shell 3a by welding. The side electrode 4a includes a rising portion 4d that rises at a position eccentric from the axial center of the spark plug 3. The tip of the rising portion 4d bends approximately 90 degrees in an L shape, and the tip portion 4b becomes the center electrode 4c. It faces with a predetermined gap.

  In this embodiment, as shown in FIG. 1 (b), the side electrode 4a is disposed so as to rise on the exhaust valve 6 side with respect to the axis q of the shell 3a. A side electrode 4a is interposed between the strong exhaust side and a part of the spark is shielded. On the other hand, since there is no spark shielding member on the intake side, which is relatively less disturbed, the spark generated between the electrodes directly faces the space on the intake side. For this reason, the combustion speed on the exhaust side and the combustion speed on the intake side can be made more uniform.

  3A to 3D show trends in various operating performances of the engine E due to differences in the direction of the side electrode 4a of the spark plug 3 (direction of the rising portion 4d with respect to the axis q). The rising position of the side electrode 4a indicates values on the intake side, the exhaust side, the front side, and the rear side (transmission side) in order from the left side in FIGS. The direction of the side electrode 4a of the spark plug 3 with respect to the combustion chamber 2 and the direction with respect to the vehicle body on which the engine is mounted are shown in FIG.

  FIG. 3A shows a difference in generated torque (Nm) due to a difference in direction of the side electrode 4a. When the direction of the side electrode 4a is set to the exhaust side, the highest torque is shown. FIG. 3 (b) also shows the difference in volumetric efficiency (%). When the direction of the side electrode 4a is the exhaust side, the highest volumetric efficiency is shown. FIG. 3 (c) also shows the difference in the main combustion period (10-90% (° CA)). The case where the direction of the side electrode 4a is set to the exhaust side indicates the fastest combustion speed. FIG. 3 (d) also shows the difference in isovolume (%). When the direction of the side electrode 4a is set to the exhaust side, the thermal efficiency is most improved.

  FIG. 4C shows a modification of the spark plug 3. In this example, the side electrode 4a is a member having an arcuate shape in plan view in which a rising portion 4d fixed to the shell 3a is formed around the axis q of the shell 3a. The tip portion 4b is provided so as to protrude from the center of the rising portion 4d in the arc direction toward the axis q of the shell 3a. If the rising portion 4d is a member in the shape of a circular arc in plan view formed around the axis q of the shell 3a, the area that shields the spark from the exhaust side becomes large, so that the combustion speed can be made more uniform. Become.

  When the rising portion 4d of the side electrode 4a is a member having an arc shape in plan view, the central angle α around the axis q of the arc shape member in plan view is preferably in the range of 45 ° to 75 °. By making the rising portion 4d into an arc shape in plan view, the distance between the center electrode 4c and the side electrode 4a is constant over the width direction of the rising portion 4d, and stable ignition is possible.

  The rising portion 4d is larger than the width of the center electrode 4c with respect to a direction (t direction shown in FIG. 4C) orthogonal to a direction connecting the exhaust side and the intake side (r direction shown in FIG. 4C). It is desirable to form a member having a wide width in the orthogonal direction t, and it is desirable to form it by a member wider than the width of the tip end portion 4b in the orthogonal direction t. For this reason, the rising portion 4d is not limited to a member having an arc shape in a plan view, but may be a member that is long in a band shape in the orthogonal direction t regardless of a straight line or a curved line, for example.

In this embodiment, the weakly turbulent portion A and the middle turbulent portion B are distributed to the intake side with respect to the cylinder axis p, and the strong turbulence portion C is biased to the exhaust side with respect to the cylinder axis p. However, it is assumed that the turbulence bias state in the combustion chamber 2 is different.
For example, the weakly disturbing part A and the middle disturbing part B are distributed in the exhaust side with respect to the cylinder axis p, and the strongly disturbed part C is distributed in the intake side with respect to the cylinder axis p. In the internal combustion engine, it is desirable that the spark plug 3 is disposed so as to be shifted to the exhaust valve 6 side from the cylinder axis p. At this time, it is desirable that the side electrode 4a of the spark plug 3 is arranged to rise on the intake valve 5 side with respect to the axis q of the shell 3a.
That is, it is desirable that the spark plug 3 is disposed so as to be shifted to a side (weak side) where the turbulence generated in the combustion chamber 2 is relatively smaller than the axial center p of the cylinder. Is preferably arranged so as to rise on the side (strong side) where the turbulence generated in the combustion chamber 2 is relatively larger than the axis q of the shell 3a.

  The above description has been made on the assumption that the engine is a four-valve gasoline engine having two valves for intake and exhaust. However, if a plurality of intake valves are provided per cylinder, a valve for each cylinder is provided. The number can be set freely. For example, the number of valves can be intake side 2 and exhaust side 2, intake side 2 and exhaust side 1, intake side 3 and exhaust side 2, and the like. Further, the number of cylinders is arbitrary, and it can be applied to various reciprocating engines using gasoline as fuel, such as single cylinder, two cylinders, and four cylinders.

DESCRIPTION OF SYMBOLS 1 Intake port 2 Combustion chamber 2a Inner peripheral surface 3 Spark plug 3a Shell 3b Screw part 4 Electrode 4a Side electrode 4b Tip part 4c Center electrode 4d Rising part 5 Intake valve 5a First intake valve 5b Second intake valve 6 Exhaust Valve 6a First exhaust valve 6b Second exhaust valve 7 Exhaust port 10 Piston S Cylinder

Claims (5)

At least one exhaust valve provided per cylinder;
A plurality of intake valves provided per cylinder;
A spark plug provided between the intake valve and the exhaust valve;
The plurality of intake valves are controlled to generate a swirl flow in the combustion chamber by providing a phase difference between the opening timings of the intake valves;
The internal combustion engine, wherein the spark plug is arranged so as to be shifted to a side where the turbulence generated in the combustion chamber is relatively small on the intake valve side or the exhaust valve side from the axial center of the cylinder.   The internal combustion engine according to claim 1, wherein the spark plug is disposed closer to the intake valve than an axis of the cylinder. The spark plug includes a center electrode located at the axial center of the shell, and a side electrode that rises at a position eccentric from the center electrode,
3. The internal combustion engine according to claim 1, wherein the side electrode is disposed so as to rise on a side where the turbulence generated in the combustion chamber is relatively larger than the axial center of the shell. The side electrode includes a rising portion fixed to the shell, and a tip portion protruding from the rising portion toward the axial center of the shell,
4. The internal combustion engine according to claim 3, wherein the rising portion has a width in the orthogonal direction that is wider than a width of the tip portion in a direction orthogonal to the direction connecting the exhaust side and the intake side.
  5. The internal combustion engine according to claim 3, wherein the rising portion has a circular arc shape that protrudes toward the side where the turbulence generated in the combustion chamber is relatively large.

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