JP2014043839A - Piston of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piston of an internal combustion engine, capable of suppressing the occurrence of knocking before and after the top dead center.SOLUTION: A piston 10 of an internal combustion engine slides in a cylinder 14, and includes: a recess 33 formed on a top face of a head 31; and an engaging member engaging with the recess. The engaging member can operate in a sliding direction of the piston so that an engagement state with the recess changes before and after the top dead center. The engaging member includes: a cover 34 having a shape corresponding to the recess; a through hole 36 provided on the cover; a support shaft 35 penetrating the through hole; and an enlarged diameter part 37 provided at a tip of the support shaft and having a diameter larger than an inner diameter of the through hole.

Description

  The present invention relates to a piston for an internal combustion engine.

  As a piston used in an internal combustion engine, for example, a piston body is divided into a first component member that forms a piston top portion and a second component member that forms a piston skirt portion, and the first component member and the second component member are divided. Are connected via an elastic body (for example, see Patent Document 1).

  In such a piston, when the combustion pressure becomes equal to or higher than a reference value, the first constituent member constituting the piston top portion compresses the elastic body and softens the impact on the second constituent member forming the piston skirt portion. . By being configured in this way, this piston has excellent durability that does not break even if an abnormal combustion pressure exceeding the reference value is generated.

Japanese Patent Laid-Open No. 9-21350

  However, in a piston having a flat piston top as described in Patent Document 1, self-ignition occurs when the air-fuel mixture in the vicinity of the piston becomes high temperature and high pressure before ignition. . That is, in such a piston, there is a problem that abnormal combustion called knocking may occur while the piston exists around the top dead center.

  Therefore, an object of the present invention is to solve the above-described problems of the prior art, and to provide a piston for an internal combustion engine that can suppress the occurrence of knocking around the top dead center.

  A piston of an internal combustion engine of the present invention is a piston of an internal combustion engine that slides in a cylinder, and includes a recess formed on a top surface of a head portion, and an engagement member that engages with the recess. The member is configured to be operable in the sliding direction of the piston so that the engagement state with the recess changes before and after top dead center.

  In the present invention, the engagement state between the engagement member and the recess is changed before and after the top dead center, so that a gap is formed between the engagement member and the recess or the gap disappears. Thereby, the airflow in the combustion chamber flows and accelerates the combustion earlier, thereby suppressing knocking.

  It is preferable that the engaging member is configured to engage with the recess before reaching the top dead center, and to disengage the engaging member from the recess when the top dead center is reached in this state. By forming in this way, a gap is formed between the engaging member and the recess at the top dead center, and the air-fuel mixture flows into this gap, so that the temperature of the air-fuel mixture decreases and the pressure decreases. In addition, the airflow in the combustion chamber flows and promotes combustion faster. Therefore, knocking is suppressed.

  It is preferable that the engaging member is configured to be disengaged from the recess before reaching the top dead center, and to be engaged with the recess when the top dead center is reached in this state. By forming in this way, the gap between the engaging member and the concave portion disappears at the top dead center, and the air-fuel mixture flows out from the gap, so that the airflow in the combustion chamber flows and promotes combustion faster. . Therefore, knocking is suppressed.

  In a preferred embodiment of the present invention, the engaging member includes a plate-like member having a shape corresponding to the recess, a through hole provided in the plate-like member, a support shaft that passes through the through-hole, and the support. And a diameter-enlarged portion provided at the tip of the shaft and having a diameter larger than the inner diameter of the through hole.

  It is preferable that an elastic member is provided between the plate-like member of the enlarged diameter portion and the enlarged diameter portion. The elastic member can suppress a collision sound between the plate-like member and the enlarged diameter portion.

  It is preferable that the peripheral portion has a sloped shape. Since the peripheral edge is inclined, the air-fuel mixture is more likely to flow into and out of the gap, and knocking can be effectively suppressed.

  As preferable embodiment of this invention, it is mentioned that the said elastic member is a spring.

  According to the piston of the internal combustion engine of the present invention, it is possible to achieve an excellent effect that the occurrence of knocking can be suppressed.

1 is a schematic cross-sectional view of an engine showing a configuration example of a combustion chamber according to Embodiment 1. FIG. 1 is a schematic cross-sectional view of an engine showing a configuration example of a combustion chamber according to Embodiment 1. FIG. The typical expansion perspective view of the piston which shows the example of composition of the piston of Embodiment 1. FIG. 3 is a schematic cross-sectional view of the engine for explaining the operation of the piston according to the first embodiment. FIG. 3 is a schematic cross-sectional view of the engine for explaining the operation of the piston according to the first embodiment. The typical sectional view of the engine for explaining the operation of the piston of Embodiment 2. The typical sectional view of the engine for explaining the operation of the piston of Embodiment 3. The typical sectional view of the engine for explaining the operation of the piston of another embodiment.

(Embodiment 1)
As shown in FIG. 1, an engine (internal combustion engine) 11 including a piston 10 includes a cylinder block 12 and a cylinder head 13. The piston 10 is slidably moved in each cylinder 14 of the cylinder block 12 so as to be reciprocally movable. A connecting rod 16 is fixed to the piston 10 by a piston pin 15, and the piston 10 is connected to a crankshaft (not shown) via the connecting rod 16.

  A head recess 17 is formed on the lower surface of the cylinder head 13, and a so-called pent roof type combustion chamber 18 is formed by the head recess 17 and the top surface of the piston 10. That is, the head recess 17 is composed of two first inclined surfaces 17a and second inclined surfaces 17b that are inclined in opposite directions. The cylinder head 13 is provided with a spark plug 19 at a position corresponding to the center of the combustion chamber 18. The cylinder head 13 is formed with a pair of intake ports 20 and a pair of exhaust ports 21 on both sides of the spark plug 19. In the present embodiment, each intake port 20 is provided on the first inclined surface 17a, and each exhaust port 21 is provided on the second inclined surface 17b. Each intake port 20 is provided with an intake valve 22, and the intake valve 20 can be opened and closed by the intake valve 22. Similarly, an exhaust valve 23 is provided in each exhaust port 21, and the exhaust port 21 can be opened and closed by the exhaust valve 23.

  Hereinafter, the structure of the piston 10 forming the combustion chamber 18 will be described in detail.

  As shown in FIGS. 2 and 3, the piston 10 includes a cylindrical head portion 31 that slides in the cylinder 14 to form the combustion chamber 18, and a pair of skirt portions 32 provided on the lower side thereof. ing.

  A concave portion 33 is formed in the central portion of the top surface of the head portion 31. The concave portion 33 has a circular shape in a top view, a central portion thereof is a flat surface, and a peripheral portion thereof is an inclined surface directed downward.

  The head portion 31 is provided with a lid portion (plate member) 34 formed so as to be engaged with the concave portion 33. That is, the lid portion 34 has a circular shape when viewed from above. Further, on the head portion 31 side (back side) of the lid portion 34, the central portion thereof is a flat surface corresponding to the concave portion 33, and the peripheral portion thereof is an inclined surface facing upward. The front surface side (cylinder head side) of the lid portion 34 is configured to be flush with the top surface of the head portion 31 when the rear surface side of the lid portion 34 is engaged with the recess 33. Further, the upper surface of the lid 34 is a flat surface and constitutes the combustion chamber 18. That is, in this embodiment, the top surface of the piston 10 is formed by the top surface of the head portion 31 and the top surface of the lid portion 34, and the combustion chamber 18 is formed by the top surface of the piston 10 and the head recess 17. ing.

  A support shaft 35 is provided at the center of the recess 33. In the support shaft, a through hole 36 is provided in the lid portion 34, and a support shaft 35 passes through the through hole 36. That is, the support shaft 35 is longer than the thickness of the lid portion 34 and protrudes toward the cylinder head 13. An enlarged diameter portion 37 is provided at the tip of the support shaft 35. The enlarged diameter portion 37 has a diameter larger than the inner diameter of the through hole 36 and the shaft diameter of the support shaft 35. Accordingly, the lid portion 34 can move the support shaft 35 from the recess portion 33 by the enlarged diameter portion 37.

  Between the enlarged diameter portion 37 and the lid portion 34, there is provided a spring 38 having the enlarged diameter portion 37 as a spring seat and through which the support shaft 35 passes. The spring 38 is biased downward, that is, toward the lid 34 side. Thereby, the cover part 34 is engaging with the recessed part 33 in the state which does not apply a pressure.

  The lid 34 is provided with a plurality of openings 39. In the present embodiment, as an example, the lid portion 34 is provided with four circular openings 39 in a top view. From each opening 39, the top surface of the head portion is exposed.

  The operation of the piston in the compression stroke will be described with reference to FIGS.

  FIG. 4 shows the state in the cylinder 14 during the compression stroke. As shown in FIG. 4, the piston rises during the compression stroke. In this case, since the lid portion 34 is pressed downward by the spring 38, the lid portion 34 is in a closed state (the lid portion 34 is engaged with the concave portion 33). Immediately before the piston 10 reaches top dead center, the air-fuel mixture at the corner of the combustion chamber 18 is in a high temperature and high pressure state.

  Then, as shown in FIG. 5, when the piston 10 rises and reaches top dead center, the piston 10 changes its moving direction and turns downward. At the moment of turning down, the lid 34 is raised by the inertial force applied to the lid 34 itself. That is, when the lid 34 is raised, the lid 34 is in an open state (the lid 34 is not engaged with the recess 33). Even if the lid portion 34 is raised, its rise is restricted by the enlarged diameter portion 37 of the support shaft 35. As the lid portion 34 rises, a gap 40 is formed between the lid portion 34 and the recess 33.

  When the gap 40 is formed, the air-fuel mixture flows into the gap 40. When the air-fuel mixture flows into the gap 40, the air-fuel mixture is not in a high pressure state, and the temperature of the air-fuel mixture is instantaneously lowered so that it is not in a high temperature state. Thereby, the knocking which arises when an air-fuel | gaseous mixture becomes a high voltage | pressure high temperature state can be suppressed.

  Furthermore, since the air-fuel mixture flows into the gap 40 in this way, the flow of the air flow in the combustion chamber 18 becomes intense, so that the speed of flame propagation at the time of ignition is increased. Even if an unburned mixture remains in the corner of the combustion chamber 18 at the time of ignition, the flame reaches the unburned mixture before knocking occurs because the speed of flame propagation increases in this way. Knocking can be suppressed.

  As described above, in the present embodiment, the piston 10 is provided with the lid portion 34 at the portion facing the combustion chamber 18 on the top surface, and the lid portion 34 is closed during the compression stroke, and at the top dead center. The lid 34 is configured to be in an open state. By changing the open / close state of the lid 34 near the top dead center, the air-fuel mixture is not in a high temperature / high pressure state in the combustion chamber, and the speed of flame propagation at the time of ignition can be increased. Can be suppressed.

  Thereafter, since the inertial force is also reduced, the lid portion 34 is also lowered around the support shaft 35 and engaged with the concave portion 33. By this engagement, the air-fuel mixture escapes from the gap 40 between the lid portion 34 and the concave portion 33 and is returned to the combustion chamber. Combustion is further promoted by the flow of the air-fuel mixture. The piston descends with the lid 34 engaged with the recess 33.

  Thus, in the present embodiment, the lid 34 is closed using the inertial force at the top dead center during the vertical movement of the piston. When the lid portion 34 is in an open state, that is, when the gap 40 is formed, the air-fuel mixture flows into the gap 40, so that knocking can be suppressed.

  Further, in the present embodiment, since the spring 38 is provided between the lid portion 34 and the enlarged diameter portion 37, the enlarged diameter portion 37 and the lid portion 34 are not in direct contact with each other. Therefore, a collision sound due to the opening / closing operation of the lid portion 34 can be suppressed.

  Further, since the peripheral edge of the concave portion 33 and the peripheral edge of the lid portion 34 are inclined surfaces, the air-fuel mixture easily flows into the gap 40 between the concave portion 33 and the lid portion 34. As a result, more air-fuel mixture can easily flow into the gap 40, so that knocking can be further suppressed.

  Furthermore, in this embodiment, since the opening is provided in the lid portion 34, only the lid portion 34 is lifted by inertia force when the piston turns from rising to lowering, and the piston body (the head portion 31 and the skirt). The part 32) can be lowered.

  Thus, according to the piston 10 shown in this embodiment, knocking can be effectively suppressed.

(Embodiment 2)
In the piston shown in the second embodiment, the position where the spring 38A is provided is different from that in the first embodiment. Specific description will be given below. In the second embodiment, a storage portion 41A is further formed in order to store the spring 38A on the bottom surface of the central portion of the recess 33A. A support shaft 35A is installed on the bottom surface of the storage portion 41A, and the bottom surface of the storage portion 41A is a spring seat. The support shaft 35A penetrates the inside of the spring 38A, and the other end side of the spring 38A is installed on the back surface side of the lid portion 34A. The spring 38A is biased upward.

  As shown in FIG. 6 (1), in the present embodiment, since the spring 38A is biased upward in the initial stage of the compression stroke, the piston 10A has a gap 40A between the lid portion 34A and the recess 33A. Arise. Thereafter, when the pressure increases on the top surface of the piston 10A in the compression stroke, the lid portion 34A moves to the concave portion 33A side. Then, as shown in FIG. 6B, in the vicinity of the top dead center, the lid portion 34A engages with the concave portion 33A and the gap 40A disappears. After that, since the spring is urged upward as the piston 10A descends, a gap 40A is generated again between the lid portion 34A and the concave portion 33A in the piston.

  That is, in this embodiment, the force by the spring 38A and the weight of the lid portion 34A are such that the lid portion 34A is open (not engaged with the concave portion 33A) at the initial stage of the compression stroke, and the lid portion 34A is closed near the top dead center. (Engaged with the recess 33A).

  Thus, in the present embodiment, the gap 40A is formed at the initial stage of the compression stroke, and the gap 40A disappears near the top dead center, that is, the open / close state of the lid is changed before and after the top dead center. First, the air-fuel mixture that has entered the gap 40A is pushed into the combustion chamber 18A, and the flow of the airflow occurs. Since the air flow becomes intense, the speed of flame propagation at the time of ignition increases. As a result, even if an unburned mixture remains in the corner of the combustion chamber 18A at the time of ignition, the flame can reach before the knocking occurs because the flame propagation speed increases, so that the knocking occurs. Can be suppressed.

  That is, in this embodiment, the lid 34A is closed using the pressure near the top dead center during the vertical movement of the piston. Then, when the lid portion 34A is changed from the open state to the closed state at the top dead center, that is, the gap 40 disappears at the top dead center, the air-fuel mixture is pushed into the combustion chamber 18A and the air flow is caused to flow. , Knocking can be suppressed.

  Thus, according to piston 10A shown in this embodiment, knocking can be effectively suppressed.

(Embodiment 3)
The piston 10B shown in the present embodiment has the same configuration as that of the second embodiment, but the biasing force of the spring 38B is larger than that of the embodiment shown in the second embodiment, and the behavior of the lid portion 34B when the piston 10B slides. Different.

  In the present embodiment, as shown in FIG. 7A, when the piston 10B is in the initial stage of the compression stroke, the lid 34B is lifted by the biasing force of the spring 38B. And if piston 10B raises, the cover part 34B will move below by the increase in the pressure in the combustion chamber 18B. As shown in FIG. 7B, the lid 34B is completely closed before the piston 10B reaches the top dead center.

  Then, as shown in FIG. 7 (3), when the piston 10B reaches the top dead center and the sliding direction of the piston 10B is reversed, the lid portion 34B is moved upward by the inertial force, and the gap 40B is formed. The

  That is, in the piston 10B in the present embodiment, the force of the spring 38B and the weight of the lid portion 34B are such that the lid portion 34B is in an open state (not engaged with the recess 33B) at the initial stage of the compression stroke, and the lid portion in the compression stroke. 34B is gradually closed (engaged with the recess 33B), and the lid 34B is again opened (not engaged with the recess 33B) again at top dead center.

  In the piston according to the present embodiment configured as described above, as in the first embodiment, the lid portion 34B moves upward at the top dead center, so that a gap 40B is formed between the lid portion 34B and the concave portion 33B. The

  When the gap 40B is formed, the air-fuel mixture flows into the gap 40B as in the first embodiment. When the air-fuel mixture flows into the gap 40B, the air-fuel mixture is not in a high pressure state, and the temperature of the air-fuel mixture is instantaneously lowered so that it is not in a high temperature state. Thereby, the knocking which arises when an air-fuel | gaseous mixture becomes a high voltage | pressure high temperature state can be suppressed.

  Furthermore, since the air-fuel mixture flows into the gap 40B in this way, the flow of the air flow in the combustion chamber 18B becomes intense, so that the flame propagation speed at the time of ignition is increased. Thereby, even if an unburned mixture remains in the corner of the combustion chamber 18B at the time of ignition, the flame reaches the unburned mixture before knocking because the speed of flame propagation increases. Knocking can be suppressed.

  Thus, also in the present embodiment, the lid portion 34B is opened and closed using the inertial force at the top dead center in the vertical movement of the piston 10B as in the first embodiment. When the lid portion 34B is in the open state, that is, when the gap 40B is formed, the air-fuel mixture flows into the gap 40B, so that knocking can be suppressed.

  Thus, according to the piston 10B shown in the present embodiment, knocking can be effectively suppressed.

(Other embodiments)
In Embodiment 1 mentioned above, although the opening 39 was provided in the cover part 34, it is not limited to this. In the case where the inertial force is larger than the pressure applied to the piston 10 so that only the lid 34 is raised by the inertial force and the piston body can be lowered by the explosion, the opening 39 is formed. It is not necessary to provide it. Further, the size of the openings 39 and the number of the openings 39 are not limited to the above-described embodiment. For example, only one opening 39 may be provided, or five rectangular openings may be provided in a top view. Furthermore, the openings 39 may be provided in the lid portions 34A and 34B according to the second and third embodiments.

  In each of the embodiments described above, the support shafts 35, 35A, and 35B are provided so as to be located at the center of the lid portions 34, 34A, and 34B, but the present invention is not limited to this. For example, the support shafts 35, 35A, and 35B may be arranged so as to be shifted from the centers of the lid portions 34, 34A, and 34B. A plurality of support shafts 35, 35A, 35B may be provided for each of the lid portions 34, 34A, 34B.

  In the first embodiment described above, the lid portion 34 has a circular shape in a top view, but is not limited to this, but the edge portion of the lid portion 34 is arranged at a position where unburned air-fuel mixture tends to accumulate. By doing so, knocking can be further suppressed. The same applies to the second and third embodiments.

  Although the spring 38 is provided in the first embodiment described above, the present invention is not limited to this. The spring 38 may not be provided. Also in the second and third embodiments, another spring may be provided between the enlarged diameter portions 37A and 37B and the lid portions 34A and 34B. Thereby, also in the case of Embodiment 2, 3, the impact sound of the enlarged diameter parts 37A and 37B and the cover parts 34A and 34B can be reduced.

  In the above-described embodiment, the support shafts 35, 35A, and 35B penetrate the lid portions 34, 34A, and 34B, but the present invention is not limited to this. For example, as shown in FIG. 8, a support shaft 35C may be provided on the back surface of the lid portion 34C, and a spring 38C may be provided on the other end side of the support shaft 35C. The spring 38C is stored in the storage portion 41C. According to such a configuration, after the lid 34C is operated in the same manner as in the third embodiment and the lid 34C is urged upward by the spring 38C and the lid 34C is closed due to an increase in pressure in the combustion chamber 18C. When the lid portion 34C is opened at the top dead center, the air-fuel mixture flows between the lid portion 34C and the concave portion 33C, and knocking can be suppressed.

  In Embodiment 1 mentioned above, although the cover part 34 is provided corresponding to the recessed part 33, it is not limited to this. The lid part 34 should just be accommodated in the recessed part 33. FIG.

  The piston of the internal combustion engine of the present invention can suppress the occurrence of knocking. Therefore, it can be used in the vehicle manufacturing industry.

10, 10A, 10B Piston 12 Cylinder block 13 Cylinder head 14 Cylinder 15 Piston pin 16 Connecting rod 17 Head recess 18, 18A, 18B, 18C Combustion chamber 19 Spark plug 20 Intake port 21 Exhaust port 22 Intake valve 23 Exhaust valve 31 Head portion 32 Skirt portion 33, 33A, 33B, 33C Recess 34, 34A, 34A, 34C Lid portion 35, 35A, 35B, 35C Support shaft 36 Through hole 37, 37A, 37B Expanded diameter portion 38, 38A, 38B, 38C Spring 39 Opening 40 40A, 40A Gap 41, 41A, 41C Storage part

Claims (7)

A piston of an internal combustion engine that slides in a cylinder,
A concave portion formed on the top surface of the head portion, and an engaging member that engages with the concave portion,
The piston of an internal combustion engine, wherein the engagement member is configured to be operable in a sliding direction of the piston so that the engagement state with the recess changes before and after top dead center. The engaging member is
2. The internal combustion engine according to claim 1, wherein the internal combustion engine is configured to engage with the recess before reaching the top dead center, and to disengage the engagement member from the recess when the top dead center is reached in this state. Engine piston. The engaging member is
2. The internal combustion engine according to claim 1, wherein the internal combustion engine is configured so as to be disengaged from the recess before reaching the top dead center, and to engage the engagement member when the top dead center is reached in this state. Engine piston. The engaging member is
A plate-like member having a shape corresponding to the recess, a through-hole provided in the plate-like member, a support shaft that penetrates the through-hole, and a tip provided at the tip of the support shaft, which is larger than the inner diameter of the through-hole The piston of the internal combustion engine according to any one of claims 1 to 3, further comprising an enlarged-diameter portion having a diameter.   The piston of the internal combustion engine according to claim 4, wherein an elastic member is provided between the plate-like member of the enlarged diameter portion and the enlarged diameter portion.   The piston of the internal combustion engine according to any one of claims 1 to 5, wherein the concave portion has a sloped peripheral portion.   6. The piston of an internal combustion engine according to claim 5, wherein the elastic member is a spring.