JP2012132399A - Structure of piston - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the structure of a piston capable of improving the reduction and the knocking of a cooling loss while controlling the lowering of piston strength.SOLUTION: The structure of the piston is applied to the piston 53 of an engine 50. The structure of the piston is made into a structure in which a cooling channel 53a for circulating oil is provided in a partial annularity by corresponding to a portion in which combustion speed is low among combustion chambers E of the engine 50. The portion in which the combustion speed is low is made into a portion in which the combustion speed is lowered relatively in comparison with other portions when the engine 50 is in a given operating condition. Concretely, it is a portion of an exhaust side in which the combustion speed is lowered relatively in comparison with a portion of an intake side when rotating speed NE of the engine 50 is high at a high tumble ratio.

Description

  The present invention relates to a piston structure applied to an engine piston.

  Engine pistons with cooling channels are known. Patent Document 1 discloses a piston for an internal combustion engine in which a passage cross section of an annular cooling channel is formed in a wide shape in which the length in the piston radial direction is larger than that in the piston axial direction. Patent Document 2 discloses a cooling structure for a piston for an internal combustion engine in which a cooling channel extending annularly in the upper part of the piston is provided.

JP 2009-185745 A JP 2002-480001 A

  FIG. 5 is a diagram showing an example of a knocking generation position according to the engine speed and the tumble ratio (the number of times the tumble flow rotates while the piston reciprocates once). FIG. 5 shows a case where the tumble ratio is a low tumble ratio and a case where the tumble ratio is high. For example, in an engine that generates a tumble flow in a combustion chamber, when the engine speed is high and the tumble ratio is high, strong turbulence tends to occur in the intake side of the combustion chamber. Then, as a result of a significant breakdown in the combustion speed balance between the intake side and the exhaust side of the combustion chamber, knocking tends to occur on the exhaust side of the combustion chamber where the combustion speed becomes extremely slow.

  On the other hand, in order to improve knocking, for example, an annular cooling channel over the entire circumference can be provided in the piston. However, in this case, the piston strength may decrease, and the piston may be easily damaged. Further, as a result of excessive cooling of the intake side portion of the piston, there is a possibility that the cooling loss increases.

  In view of the above problems, an object of the present invention is to provide a piston structure capable of reducing cooling loss and improving knocking while suppressing a decrease in piston strength.

  The present invention is a structure of a piston that is applied to a piston of an engine and in which a cooling medium passage for circulating a cooling medium is provided in a partial annular shape corresponding to a portion having a low combustion speed in the combustion chamber of the engine.

  According to the present invention, it is possible to reduce cooling loss and improve knocking while suppressing a decrease in piston strength.

It is a schematic block diagram of an engine. It is a top view of a piston. It is a schematic block diagram of ECU. It is a figure which shows operation | movement of ECU with a flowchart. It is a figure which shows an example of the generation | occurrence | production position of knocking according to an engine speed and a tumble ratio.

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

  FIG. 1 is a schematic configuration diagram of the engine 50. The engine 50 is a spark ignition internal combustion engine, and includes a cylinder block 51, a cylinder head 52, a piston 53, an intake valve 54, an exhaust valve 55, an ignition plug 56, an oil jet 57, an electric pump 58, and the like. It has.

  A cylinder 51 a is formed in the cylinder block 51. A piston 53 is accommodated in the cylinder 51a. The piston 53 is provided with a cooling channel 53a. The cooling channel 53 a is provided on the upper portion of the piston 53. A cylinder head 52 is fixed to the upper surface of the cylinder block 51. The combustion chamber E is formed as a space surrounded by the cylinder block 51, the cylinder head 52 and the piston 53.

  The cylinder head 52 is formed with an intake port 52a that guides intake air to the combustion chamber E and an exhaust port 52b that discharges gas from the combustion chamber E. The intake port 52a introduces intake air so as to generate a tumble flow T in the combustion chamber E. For this reason, the intake air introduced into the combustion chamber E forms a tumble flow T. In generating the tumble flow T, the engine 50 may include, for example, an airflow control valve for generating the tumble flow T at the intake port 52a. The cylinder head 52 is provided with an intake valve 54 that opens and closes an intake port 52a and an exhaust valve 55 that opens and closes an exhaust port 52b. In addition, the cylinder head 52 is provided with a spark plug 56.

  The oil jet 57 is an oil injection unit and is provided in the cylinder block 51. The oil jet 57 is provided so as to inject oil toward the cooling channel 53a. The electric pump 58 supplies oil to the oil jet 57. The electric pump 58 is a variable oil pump capable of changing the oil discharge amount.

  FIG. 2 is a top view of the piston 53. The cooling channel 53 a is provided along the circumferential direction of the piston 53. An oil inlet In is provided at one end of the cooling channel 53a, and an oil outlet Out is provided at the other end. Both the oil inlet In and the oil outlet Out are open on the back side of the piston 53. Specifically, the oil jet 57 injects oil toward the oil introduction port In. The injected oil is introduced into the cooling channel 53a from the oil introduction port In, and after flowing through the cooling channel 53a, is discharged from the oil discharge port Out.

  The cooling channel 53 a is provided in a ring shape inside the piston 53 so as to correspond to a portion of the combustion chamber E where the combustion speed is low. The portion where the combustion speed is slow is a portion where the combustion speed is relatively slow compared to other portions when the engine 50 is in a predetermined operating state. Specifically, the portion where the combustion speed is slow is a portion on the exhaust side of the combustion chamber E. Further, when the rotational speed NE of the engine 50 is high and the tumble ratio is high, the combustion speed is a portion that is relatively slow compared to the intake side portion.

  Oil corresponds to a cooling medium. The cooling channel 53a corresponds to a cooling medium passage. In the piston 53, as described above, a piston structure in which the cooling channel 53a is provided is realized.

  Next, the function and effect of the piston structure will be described. The piston has a structure in which a cooling channel 53a is provided in a partial ring shape. For this reason, it can suppress that piston intensity falls. At the same time, this piston has a structure in which a cooling channel 53a is provided corresponding to a portion of the combustion chamber E where the combustion speed is low. For this reason, the occurrence of knocking can be suppressed by the cooling effect of the oil flowing through the cooling channel 53a. Further, since the oil chamber is not cooled in the combustion chamber E other than the portion corresponding to the portion where the combustion speed is slow, an increase in cooling loss can be suppressed.

  In the structure of this piston, the exhaust side end gas region can be cooled by providing the cooling channel 53a with the exhaust side portion of the combustion chamber E being the portion where the combustion speed is slow. As a result, when the rotational speed NE is high and the tumble ratio is high, it is possible to reduce cooling loss and improve knocking while suppressing a decrease in piston strength. For this reason, the structure of the piston in which the portion on the exhaust side of the combustion chamber E has a low combustion speed is suitable when the engine is the engine 50 that generates the tumble flow T in the combustion chamber E.

  In the present embodiment, an engine control device applied to the engine 50 described in the first embodiment will be described. FIG. 3 is a schematic configuration diagram of the ECU 70. The ECU 70 is an electronic control device and corresponds to an engine control device. The ECU 70 includes a microcomputer including a CPU 71, a ROM 72, a RAM 73, and the like, and input / output circuits 74 and 75. The CPU 71, ROM 72, RAM 73, and input / output circuits 74 and 75 are connected to each other via a bus 76.

  Various sensors and switches such as a crank angle sensor 81 for detecting the crank angle of the engine 50 and an air flow meter 82 for measuring the intake air amount of the engine 50 are electrically connected to the ECU 70. Various control objects such as the electric pump 58 are electrically connected.

  The ROM 72 is configured to store a program in which various processes executed by the CPU 71 are described, map data, and the like. Various functions are functionally realized in the ECU 70 by the CPU 71 executing processing while using the temporary storage area of the RAM 73 as necessary based on the program stored in the ROM 72.

  For example, the ECU 70 functionally realizes a control unit that controls the amount of oil supplied by the electric pump 58 according to the rotational speed NE of the engine 50 and the load KL. Specifically, based on the rotational speed NE and the load KL, the control unit refers to map data in which the oil amount is set in advance according to the rotational speed NE and the load KL, and reads the corresponding oil amount. Then, by controlling the electric pump 58 so as to supply the read amount of oil, the amount of oil supplied by the electric pump 58 is controlled according to the rotational speed NE and the load KL. The map data is stored in the ROM 72 in advance.

  Next, the operation of the ECU 70 will be described using the flowchart shown in FIG. The ECU 70 detects the rotational speed NE and the load KL (step S1). The rotational speed NE can be detected by the ECU 70 based on the output of the crank angle sensor 81, for example. Further, the load KL can be detected by the ECU 70 based on the outputs of the crank angle sensor 81 and the air flow meter 82. Subsequently, the ECU 70 reads the oil amount by referring to the map data based on the detected rotational speed NE and the load KL (step S2). Thereafter, the ECU 70 controls the electric pump 58 so as to supply the read amount of oil (step S3).

  Next, the function and effect of the ECU 70 will be described. The ECU 70 controls the amount of oil supplied from the electric pump 58 according to the rotational speed NE and the load KL. For this reason, the ECU 70 does not supply oil from the electric pump 58 or supplies a smaller amount of oil than in the case of high rotation when there is a low possibility of knocking, such as when the rotational speed NE is low. By supplying, excessive cooling can be prevented. As a result, in the engine 50 including the piston 53 to which the piston structure described in the first embodiment is applied, an increase in cooling loss can be suitably suppressed according to the operating state of the engine 50.

  The ECU 70 may control the amount of oil supplied from the electric pump 58 as follows, for example. That is, the ECU 70, for example, provides combustion pressure sensors for a portion of the combustion chamber E where the combustion speed is slow (here, the exhaust side portion) and a portion where the combustion speed is fast (here, the intake side portion). Based on the output of each combustion pressure sensor, it is determined whether knocking occurs in the combustion chamber E where the combustion speed is low, and the amount of oil supplied from the electric pump 58 is controlled based on the determination result. May be.

  In this case, for example, when it is determined that knocking occurs, oil is supplied from the electric pump 58, and when it is determined that knocking does not occur, oil is not supplied from the electric pump 58 or when the engine speed is high. Even a small amount of oil can be supplied. Even in this case, an increase in cooling loss can be suitably suppressed according to the operating state of the engine 50.

  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.

Engine 50
Cylinder block 51
Cylinder head 52
Piston 53
Cooling channel 53a
Intake valve 54
Exhaust valve 55
Spark plug 56
Oil jet 57
Electric pump 58
ECU 70

Claims (1)

Applied to the piston of the engine,
A structure of a piston in which a cooling medium passage for circulating a cooling medium is provided in a partial annular shape corresponding to a portion having a low combustion speed in a combustion chamber of the engine.

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