Internal-Combustion Engine Piston and Method for Controlling Cooling of Internal-Combustion Engine Piston

Patent metadata

Field	Value
Publication number	US-2021102511-A1
Application number	US-201816606992-A
Country	US
Kind code	A1
Filing date	Apr 12, 2018
Priority date	Apr 25, 2017
Publication date	Apr 8, 2021
Grant date	—

Abstract

It is an object of the present invention to provide a novel internal-combustion engine piston which makes it possible to achieve both an improvement in thermal efficiency and a reduction in exhaust harmful components, and to suppress the occurrence of abnormal combustion such as knocking and pre-ignition. A cooling passage is formed in a piston, and on a top face of the piston are provided a first heat shielding layer composed of a material having a lower thermal conductivity and volumetric specific heat than those of a piston base material, and a second heat shielding layer composed of a material having a lower thermal conductivity and volumetric specific heat than those of the first heat shielding layer, wherein a first distance between the first heat shielding layer and the cooling passage is set to be less than a second distance between the second heat shielding layer and the cooling passage. A cooling loss can be reduced by the second heat shielding layer, and the vaporization of fuel adhering to the piston can be promoted by the first heat shielding layer to reduce exhaust gas harmful components. Since the first distance is less than the second distance, the temperature of the first heat shielding layer does not rise excessively, whereby the occurrence of knocking and pre-ignition can be suppressed.

First claim

1 . An internal-combustion engine piston comprising: a piston body including a cooling passage formed in the piston body; and a first heat shielding layer and a second heat shielding layer formed on a top face of the piston body and forming a part of a combustion chamber, wherein
the first heat shielding layer is composed of a material having a lower thermal conductivity and volumetric specific heat equal to or lower than those of a piston base material forming the piston body, the second heat shielding layer is composed of a material having a lower thermal conductivity and volumetric specific heat than those of the first heat shielding layer, and a separation distance between the first heat shielding layer and the cooling passage is set to be less than a separation distance between the second heat shielding layer and the cooling passage.

2 . The internal-combustion engine piston according to claim 1 , wherein the first heat shielding layer is formed at a position where the first heat shielding layer overlaps at least a part of the cooling passage when viewed from a side of the combustion chamber in a sliding direction of the piston body.

3 . The internal-combustion engine piston according to claim 2 , wherein a ratio of an overlapping projected area of the first heat shielding layer and the cooling passage to a projected area of the first heat shielding layer is set to be greater than a ratio of an overlapping projected area of the second heat shielding layer and the cooling passage to a projected area of the second heat shielding layer when viewed from the side of the combustion chamber in the sliding direction of the piston body.

4 . The internal-combustion engine piston according to claim 1 , wherein at least a part of a lower surface of the first heat shielding layer is positioned lower than a lower surface of the second heat shielding layer when a direction of movement of the piston body to a bottom dead point is a lower side.

5 . The internal-combustion engine piston according to claim 1 , wherein the first heat shielding layer is disposed on a region having a greater combustion chamber radius than that of a region in which the second heat shielding layer is disposed.

6 . The internal-combustion engine piston according to claim 1 , wherein the first heat shielding layer and the cooling passage are formed in a circular shape or an arc shape, and disposed in the piston body.

7 . The internal-combustion engine piston according to claim 1 , wherein the cooling passage is formed closer to an exhaust side than a vicinity of a center of the combustion chamber.

8 . The internal-combustion engine piston according to claim 1 , wherein
a cavity is formed in the top face of the piston body, and the first heat shielding layer is provided on at least a bottom face of the cavity.

9 . The internal-combustion engine piston according to claim 8 , wherein the cavity and at least a part of the cooling passage overlap when viewed from the side of the combustion chamber in the sliding direction of the piston body, and a width of the cooling passage on a side of the cavity is greater than that of the cooling passage on a side facing the cavity.

10 . The internal-combustion engine piston according to claim 8 , wherein a cooling oil inlet of the cooling passage is formed on a side of the cavity, and a cooling oil outlet of the cooling passage is formed on an opposite side of the cavity.

11 . The internal-combustion engine piston according to claim 1 , wherein the piston body is used in an in-cylinder direct injection internal-combustion engine including a fuel injection valve for directly injecting fuel into the combustion chamber.

12 . The internal-combustion engine piston according to claim 11 , wherein the first heat shielding layer is formed at a position where the first heat shielding layer intersects with at least one of axes of spray injected from the fuel injection valve when the piston body is in a vicinity of an intermediate position between a top dead point and a bottom dead point.

13 . An internal-combustion engine piston comprising: a piston body including a cooling passage formed in the piston body; and a first heat shielding layer and a second heat shielding layer formed on a top face of the piston body and forming a part of a combustion chamber, wherein
the first heat shielding layer is composed of a material having a lower thermal conductivity and volumetric specific heat equal to or lower than those of a piston base material forming the piston body, the second heat shielding layer is composed of a material having a lower thermal conductivity and volumetric specific heat than those of the first heat shielding layer, and the first heat shielding layer is disposed closer to an intake side and an exhaust side than a vicinity of a center of the combustion chamber, and a separation distance between the first heat shielding layer and the cooling passage disposed on the exhaust side is set to be less than a separation distance between the second heat shielding layer and the cooling passage.

14 . The internal-combustion engine piston according to claim 1 , wherein the first heat shielding layer and the second heat shielding layer are formed of a porous body, and a porosity of the first heat shielding layer is set to be less than that of the second heat shielding layer.

15 . The internal-combustion engine piston according to claim 1 , wherein a thickness of the first heat shielding layer is set to be greater than that of the second heat shielding layer.

16 . The internal-combustion engine piston according to claim 1 , wherein a total area of the first heat shielding layer forming the combustion chamber is set to be less than a total area of the second heat shielding layer forming the combustion chamber.

17 . A method for controlling cooling of an internal-combustion engine piston, the internal-combustion engine including the internal-combustion engine piston according to claim 1 , cooling medium supply means for supplying a cooling medium into the cooling passage, and cooling medium variable supply means for changing a flow rate of the cooling medium,
wherein an amount of cooling medium supplied from the cooling medium supply means to the cooling passage is adjusted by the cooling medium variable supply means based on a cooling water temperature or a lubricating oil temperature of the internal-combustion engine.

18 . The method for controlling cooling of an internal-combustion engine piston according to claim 17 , wherein the amount of cooling medium supplied to the cooling passage in a case where the cooling water temperature or the lubricating oil temperature is high is increased as compared to a case where the cooling water temperature or the lubricating oil temperature is low.

19 . The method for controlling cooling of an internal-combustion engine piston according to claim 17 , wherein, when the cooling water temperature or the lubricating oil temperature is lower than a predetermined temperature, supply of the cooling medium to the cooling passage is stopped, and when the cooling water temperature or the lubricating oil temperature is higher than the predetermined temperature, the cooling medium is supplied to the cooling passage.

20 . A method for controlling cooling of an internal-combustion engine piston,
the internal-combustion engine including the internal-combustion engine piston according to claim 1 , cooling medium supply means for supplying a cooling medium into the cooling passage, and coolin

Assignees

• Hitachi Automotive Systems Ltd

Inventors

• Sukegawa Yoshihiro
• Takahashi Norikazu

Classifications

• F01M2001/086

  for lubricating gudgeon pins · CPC title

• F01M1/08

  Lubricating systems characterised by the provision therein of lubricant jetting means · CPC title

• F01P3/10

  Cooling by flow of coolant through pistons · CPC title

• F01M1/16

  Controlling lubricant pressure or quantity (rendering machines or engines inoperative or idling on lubricant pressure failure F01M1/22) · CPC title

• F02F3/14

  within combustion chambers · CPC title