JP2014034938A - Combustion chamber structure of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combustion chamber structure of an internal combustion engine capable of suitably suppressing the degradation of pre-ignition resistance obtained by scavenging action by intake air, against pre-ignition caused by air-fuel mixture residing in a plug pocket.SOLUTION: A combustion chamber structure 50 of an internal combustion engine includes an ignition plug 1 and two intake valves 10 provided in a combustion chamber C. When a fixed end E of a ground electrode 5 is arranged in the combustion chamber C at the exhaust side out of the intake side and the exhaust side, at an equal distance from the two intake valves 10, it is located between a center point O1 as the center point of one of the two intake valves 10 and the fixed end E in view along the extending direction of the combustion chamber C. A protruded part 40 protruded from a wall face of the combustion chamber C is also provided in the combustion chamber C.

Description

  The present invention relates to a combustion chamber structure of an internal combustion engine.

  An internal combustion engine having a spark plug may cause preignition. As an internal combustion engine provided with an ignition plug, there is generally known an internal combustion engine provided with two intake valves in the same combustion chamber together with an ignition plug. (For example, refer to Patent Document 1). In addition, as a technique considered to be related to the present invention, Patent Document 2 discloses a direct-injection spark ignition engine including a guide wall having a surface facing an air flow toward an ignition plug.

JP 2007-187166 A Japanese Patent Laid-Open No. 2004-44427

  It has been found that pre-ignition has a mode in which an air-fuel mixture staying in a plug pocket formed between a housing portion and an insulator receives heat and becomes high temperature. On the other hand, the pre-ignition resistance against the pre-ignition generated in such a manner is obtained by scavenging the air-fuel mixture staying in the plug pocket. However, in an internal combustion engine in which an ignition plug and two intake valves are provided in the same combustion chamber, intake air flows as shown below, and as a result, the pre-ignition resistance obtained in this way may be reduced. .

  FIG. 4 is an explanatory view of a general intake air flow. 4A is a view of a combustion chamber structure of a general internal combustion engine along the extending direction of the combustion chamber C. FIG. FIG. 4B is an enlarged view of a main part of the combustion chamber structure of the internal combustion engine shown in FIG. FIG. 4C is a view of a main part of a combustion chamber structure of a general internal combustion engine along a direction orthogonal to the extending direction of the combustion chamber C.

  The spark plug 1, the two intake valves 10, and the two exhaust valves 20 are provided in the combustion chamber C by being provided in the cylinder head 30. The spark plug 1 is disposed in the center of the combustion chamber C when viewed along the extending direction of the combustion chamber C. The two intake valves 10 are arranged around the spark plug 1 together with the two exhaust valves 20. The spark plug 1 includes a housing part 2, an insulator 3, a center electrode 4, and a ground electrode 5. A plug pocket P is formed between the housing part 2 and the insulator 3.

  The intake air introduced into the combustion chamber C when the two intake valves 10 are at a low lift is ejected radially into the combustion chamber C. Then, a part of the intake air introduced into the combustion chamber C tends to flow into the plug pocket P from the portion on the intake side of the insulator 3 in the intake / exhaust direction D rather than the portion protruding into the combustion chamber C. On the other hand, the position along the circumferential direction of the fixed end E of the ground electrode 5 is generally not fixed. For this reason, the ground electrode 5 may be provided such that the fixed end E thereof is located on the exhaust side of the insulator 3 in the intake / exhaust direction D with respect to the portion protruding into the combustion chamber C.

  However, in this case, the other part of the intake air introduced into the combustion chamber C merges with each other, so that it has directivity to flow into the plug pocket P through the ground electrode 5. As a result, intake air also flows into the plug pocket P from a portion of the insulator 3 on the exhaust side of the portion protruding into the combustion chamber C. For this reason, in this case, it is difficult for the air-fuel mixture to flow out of the plug pocket P, and thus there is a possibility that the air-fuel mixture will not be sufficiently scavenged. As a result, there is a risk that the pre-ignition resistance against the pre-ignition generated in the above-described manner is lowered.

  In view of the above problems, the present invention provides an internal combustion engine capable of suitably suppressing a decrease in pre-ignition resistance obtained by scavenging intake air against pre-ignition generated due to an air-fuel mixture remaining in a plug pocket. An object is to provide a combustion chamber structure.

  The present invention includes a housing part, an insulator held in the housing part, a center electrode exposed from the insulator, and a ground electrode that discharges between the center electrode, and the housing part and the insulator A spark plug having a plug pocket and two intake valves are provided in the same combustion chamber, and the fixed end of the ground electrode is located on the exhaust side of the intake side and the exhaust side in the combustion chamber. When arranged evenly with respect to the two intake valves, between the center point of one of the two intake valves and the fixed end when viewed along the extending direction of the combustion chamber The combustion chamber structure of the internal combustion engine is further provided in the combustion chamber.

  ADVANTAGE OF THE INVENTION According to this invention, with respect to the pre-ignition which originates in the air-fuel | gas mixture which retains in a plug pocket, the fall of the anti-pre-ignition property obtained when an intake air scavenges can be suppressed suitably.

It is a figure which shows the combustion chamber structure of an internal combustion engine. It is explanatory drawing of the installation aspect of a protrusion part. It is explanatory drawing of the flow of the intake air in an Example. It is explanatory drawing of the flow of general intake air.

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

  FIG. 1 is a view showing a combustion chamber structure (hereinafter referred to as a combustion chamber structure) 50 of an internal combustion engine. FIG. 1 shows the combustion chamber structure 50 as viewed along the extending direction of the combustion chamber C. FIG. The combustion chamber structure 50 includes an ignition plug 1, an intake valve 10, an exhaust valve 20, and a cylinder head 30. The spark plug 1, the intake valve 10, and the exhaust valve 20 are provided in the combustion chamber C by being provided in the cylinder head 30.

  The spark plug 1 is disposed in the center of the combustion chamber C when viewed along the extending direction of the combustion chamber C. Two intake valves 10 and two exhaust valves 20 are provided. Two intake valves 10 (specifically, intake valves 10a and 10b) are arranged adjacent to each other. The same applies to the two exhaust valves 20. The cylinder head 30 forms a combustion chamber C together with a piston and a cylinder block (not shown). The two intake valves 10 are arranged around the spark plug 1 together with the two exhaust valves 20. The combustion chamber structure 50 can be applied to a spark ignition type gasoline engine in which the cam driving system is DOHC (double overhead cam).

  The spark plug 1 includes a housing part 2, an insulator 3, a center electrode 4, and a ground electrode 5. The housing part 2 has a cylindrical shape and holds the insulator 3. A plug pocket P is formed between the housing part 2 and the insulator 3. The plug pocket P is formed around the insulator 3 and opens to the combustion chamber C. The insulator 3 is provided around the center electrode 4. The center electrode 4 is exposed from the insulator 3 at the end on the side where the ground electrode 5 is provided in the axial direction of the spark plug 1. The ground electrode 5 is provided on the housing part 2. The ground electrode 5 is discharged between the center electrode 4.

  The combustion chamber structure 50 further includes a protrusion 40. The protrusion 40 is provided in the combustion chamber C by being provided in the cylinder head 30. The protrusion 40 protrudes from the wall surface of the combustion chamber C (specifically, the wall surface of the cylinder head 30 that forms the combustion chamber C). The protruding part 40 can be constituted by a part of the cylinder head 30. The protrusion 40 may be formed of a member different from the cylinder head 30. When the fixed end E of the ground electrode 5 is equally disposed with respect to the two intake valves 10 on the exhaust side of the intake side and the exhaust side in the combustion chamber C (hereinafter referred to as a predetermined arrangement case). ) Is located as follows.

  FIG. 2 is an explanatory diagram of an installation mode of the protrusion 40. FIG. 2 shows the combustion chamber structure 50 as viewed along the extending direction of the combustion chamber C. FIG. When the projecting portion 40 is in a predetermined arrangement, the center point O1 or O2 (here, the center point O1) that is the center point of one of the two intake valves 10 when viewed along the extending direction of the combustion chamber C. And the fixed end E. The center point O1 is the center point of the intake valve 10a, and the center point O2 is the center point of the intake valve 10b.

  The center point O1 can be a point where the surface including the ring-shaped end portion of the umbrella portion of the intake valve 10a and the central axis of the intake valve 10a intersect. The center point O1 can be a center point when the intake valve 10a is closed. The center point O1 may be at least one of the center points from when the intake valve 10a is closed to when the lift is low (for example, when lift is 3 mm or less). The same applies to the center point O2.

  Specifically, the protrusion 40 is provided so as to be positioned between the center point O1 and the fixed end E as follows. Here, the center point O1 and the fixed end E form a region R which is a predetermined region in a predetermined arrangement. The region R is a region connecting the center point O1 and the fixed end E when viewed along the extending direction of the combustion chamber C. The intake valve 10a having the center point O1 is the intake air introduced into the combustion chamber C, and the flow of the intake air flowing toward the ground electrode 5 in the predetermined arrangement is along the extending direction of the combustion chamber C. Region R will be distributed.

  On the other hand, the protrusion 40 is provided from one boundary B1 to the other boundary B2 of the region R when viewed along the extending direction of the combustion chamber C, so that the gap between the center point O1 and the fixed end E is provided. It is provided so that it may be located in. The boundary B1 is a boundary located on the intake side (the side where the intake valve 10a is provided) of the intake side and the exhaust side when viewed along the extending direction of the combustion chamber C, and the boundary B2 is the boundary of the combustion chamber C. This is a boundary located on the exhaust side (the side opposite to the side where the intake valve 10a is provided) of the intake side and the exhaust side when viewed along the extending direction.

  More specifically, the protrusion 40 is provided so as not to exceed the boundary B1 when viewed along the extending direction of the combustion chamber C. The protrusion 40 may be provided beyond the boundary B2 and further beyond the boundary B1 when viewed along the extending direction of the combustion chamber C. The protrusion 40 can be provided at least in part within the range from the boundary B1 to the boundary B2 of the region R when viewed along the extending direction of the combustion chamber C. The height of the protrusion 40 (projection length from the cylinder head 30) can be 3 mm or less.

  The protrusion 40 can also be provided so as not to exceed the boundary B3 instead of the boundary B1 when viewed along the extending direction of the combustion chamber C. The boundary B3 passes through the center point O1 when viewed along the extending direction of the combustion chamber C, and is a portion of the insulator 3 that protrudes into the combustion chamber C and has the largest diameter at the intake side and the exhaust. It is a tangent that touches the exhaust side of the side. In this case, the projecting portion 40 can be provided so as to be installed at least partially in the range from the boundary B3 to the boundary B2 in the region R when viewed along the extending direction of the combustion chamber C.

  The protrusion 40 is intake air introduced into the combustion chamber C by one of the two intake valves 10 (here, the intake valve 10a), and flows toward the ground electrode 5 in a predetermined arrangement. It can also be said that it corresponds to an obstacle part that obstructs the flow of intake air. The protrusion 40 is provided so as not to exceed the boundary B3 when viewed along the extending direction of the combustion chamber C, so that the center of the intake valve 10a, which is one of the intake valves described above, from the center point O1 in the predetermined arrangement. As a result, it is possible to obstruct the flow of intake air from the portion on the exhaust side to the ground electrode 5 with respect to the portion of the insulator 3 protruding into the combustion chamber C.

  Next, main effects of the combustion chamber structure 50 will be described. FIG. 3 is an explanatory diagram of the flow of intake air in the combustion chamber structure 50. The combustion chamber structure 50 includes a protrusion 40. For this reason, in the combustion chamber structure 50, the intake 40 introduced by the intake valve 10 a can be prevented or suppressed from reaching the ground electrode 5 by the protruding portion 40 even in a predetermined arrangement. As a result, even if the intake air introduced by the intake valve 10 b reaches the ground electrode 5, it is possible to prevent the intake air from flowing into the plug pocket P through the ground electrode 5.

  At the same time, the protruding portion 40 causes a portion of the intake air introduced into the combustion chamber C by the intake valve 10a to flow into the plug pocket P from the portion on the intake side of the insulator 3 in the intake / exhaust direction D rather than the portion protruding into the combustion chamber C. You can also. For this reason, the combustion chamber structure 50 can suitably suppress a decrease in pre-ignition resistance obtained by scavenging the intake air with respect to pre-ignition generated due to the air-fuel mixture staying in the plug pocket P.

  When the combustion chamber structure 50 allows a portion of the intake air introduced into the combustion chamber C by the intake valve 10a to flow in as described above, specifically, when the protruding portion 40 is viewed along the extending direction of the combustion chamber C, the combustion chamber structure 50 has a boundary. It is preferable that it is the structure provided so that B1 may not be exceeded.

  Combustion chamber structure 50 is a case where it is viewed along the extending direction of combustion chamber C, and projecting portion 40 is provided so as not to exceed boundary B3 when region R includes boundary B3. You can also. In this case, the intake ground electrode 5 that is introduced by the intake valve 10a in the case of a predetermined arrangement and that may cause a decrease in pre-ignition resistance particularly by merging with the intake air introduced by the intake valve 10b. Reaching can be prevented or suppressed with a more compact protrusion 40.

  When the spark plug 1 is provided so that the protruding portion 40 does not exceed the boundary B2 when viewed along the extending direction of the combustion chamber C, intake air that may cause deterioration in pre-ignition resistance. Can be prevented or suppressed by the more compact protrusion 40.

  In the combustion chamber structure 50, when the height of the protrusion 40 is 3 mm or less, the intake air introduced by the intake valve 10a during a valve lift of about 1 mm to 3 mm where the flow of the intake air toward the spark plug 1 is particularly strong is in a predetermined arrangement. It can be suitably prevented or suppressed from reaching the ground electrode 5. The combustion chamber structure 50 can also suppress a reduction in the flow coefficient of the intake air introduced by the intake valve 10a at the same time by setting the height of the protrusion 40 to 3 mm or less. Further, as a result of the protrusion 40 becoming a point of airflow separation, it is possible to suppress the state of the airflow flowing through the combustion chamber C from becoming unstable.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

Spark plug 1
Housing part 2
Reiko 3
Center electrode 4
Ground electrode 5
Intake valve 10, 10a, 10b
Exhaust valve 20
Cylinder head 30
Protrusion 40
Combustion chamber structure 50

Claims (1)

A housing part; an insulator held by the housing part; a center electrode exposed from the insulator; and a ground electrode that discharges between the center electrode; and between the housing part and the insulator A spark plug having a plug pocket and two intake valves are provided in the same combustion chamber,
When the fixed end portion of the ground electrode is evenly arranged with respect to the two intake valves on the exhaust side of the intake side and the exhaust side in the combustion chamber, the fixed end portion of the ground electrode is viewed along the extending direction of the combustion chamber. A protrusion that protrudes from the wall surface of the combustion chamber is further provided in the combustion chamber, and is provided between the center point of one of the two intake valves and the fixed end portion. Combustion chamber structure of an internal combustion engine.

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