JP2010101230A - Piston for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piston for an engine, reducing slap noise caused by the enlargement of a clearance to a bore at low temperatures. <P>SOLUTION: The piston 1 includes a latent heat storage material 13 disposed at a skirt 4, and a mass member 14 acting to accelerate the phase change of the latent heat storage material 13 in a supercooled state at the time of engine start by acting according to piston motion. The mass member 14 acting according to piston motion acts to accelerate the phase change of the latent heat storage material 13 in the supercooled state at the time of engine start by applying impact on the latent heat storage material 13 through a soft member 12, concretely speaking. At that time, the latent heat storage material 13 releases stored latent heat. Temperature of the skirt 4 is raised thereby, and the skirt 4 is expanded through heat. Consequently, the clearance to the bore is quickly reduced. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an engine piston, and more particularly to an engine piston that reduces slap noise.

  Conventionally, in an engine, it is known that a slap sound is generated by contact with a bore by swinging a piston. In this regard, for example, Patent Documents 1 and 2 disclose techniques that are considered to be related to the present invention in terms of reducing slap sounds. Conventionally, a latent heat storage material (for example, sodium acetate trihydrate) that releases heat by nucleating in a supercooled state is known. In this regard, for example, Patent Documents 3 to 5 disclose techniques that are considered to be related to the present invention in that they include a latent heat storage material.

JP 2007-239509 A (paragraph 15) JP 2000-282951 A Japanese Patent Laid-Open No. 3-9104 JP 2007-30541 A JP 2007-85330 A

  By the way, slap noise generally tends to be generated when the piston and the bore are made of different materials. This is because the clearance between the two changes according to the temperature due to the difference in the coefficient of thermal expansion, and as a result, the clearance becomes larger than necessary depending on the temperature. In this regard, in an engine, for example, when an aluminum alloy is used as the material of the piston and iron is used as the material of the bore, the clearance becomes large at low temperatures. When the clearance becomes large at low temperatures, there is a problem in that a slap noise may occur after the engine is cold started.

  Accordingly, the present invention has been made in view of the above problems, and an object thereof is to provide an engine piston capable of reducing a slap sound generated due to a large clearance formed between a bore and a bore at a low temperature. And

  The piston of the engine of the present invention for solving the above-described problem is a phase of the latent heat storage material provided in the skirt portion and the latent heat storage material in an overcooled state when the engine is started by operating according to the piston motion. And a mass member that acts to promote change.

  According to the present invention, it is possible to reduce the slap sound generated due to the clearance formed between the bore and the bore being increased at a low temperature.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram schematically showing a cross section of a piston (hereinafter simply referred to as a piston) 1 of an engine according to this embodiment. The material of the piston 1 is an aluminum alloy, and the material of an engine (not shown) to which the piston 1 is applied is iron. That is, a material having a higher thermal expansion coefficient than that of the engine is applied to the piston 1.
The piston 1 includes a head portion 2, a pin boss portion 3, and a skirt portion 4. A cavity 2 a is formed on the top surface of the piston 1 in the head portion 2. A pin hole 3 a is formed in the pin boss portion 3. The skirt portion 4 includes a thrust side skirt portion 4a and an anti-thrust side skirt portion 4b. Inside the skirt portions 4a and 4b, grooves 4c and 4d each having a U-shaped cross section are formed.

  The piston 1 includes a nucleation device 10 in the skirt portion 4. Specifically, the nucleation device 10 is provided in each of the grooves 4c and 4d. FIG. 2 is an enlarged schematic view of the nucleation device 10 shown in FIG. The nucleation device 10 includes a case 11, a soft member 12, a latent heat storage material 13, a mass member 14, and an elastic member 15. The nucleation device 10 is configured with a case 11 as a housing. For example, a synthetic resin having a high coefficient of thermal expansion can be used as the material of the case 11. The internal space of the case 11 is divided into two by the soft member 12. The two internal spaces divided by the soft member 12 are provided in a line along the central axis direction of the piston 1. For example, synthetic resin can be applied to the material of the soft member 12.

  In this embodiment, the latent heat storage material 13 is specifically sodium acetate trihydrate. Sodium acetate trihydrate does not cause a phase change from the liquid phase to the solid phase even when cooled from a temperature state exceeding the melting point (58 ° C) to a temperature state below the melting point, and from minus 20 ° C to minus 30 ° C. It has the characteristic of being in a supercooled state while storing latent heat to the extent. The latent heat storage material 13 is sealed in the case 11. Specifically, in this embodiment, the latent heat storage material 13 is sealed in the lower internal space among the internal spaces divided into two by the soft member 12. On the other hand, the mass member 14 is provided in the upper internal space among the internal spaces divided into two by the soft member 12. In order to operate in accordance with the piston motion, the mass member 14 needs a certain amount of weight. For this reason, in this embodiment, iron is applied as the material of the mass member 14. The material of the mass member 14 is not limited to this. An elastic member 15 made of a spring is provided at a position facing the soft member 12 with the mass member 14 interposed therebetween. The elastic member 15 elastically supports the mass member 14 and urges it toward the soft member 12.

  Next, the effect of the nucleation device 10 will be described. The latent heat storage material 13 enters a liquid phase when the temperature exceeds the melting point during engine operation. Then, after that, when the engine stops and the temperature falls below the melting point, a supercooled state is established. At this time, the mass member 14 is stably stationary while being pressed against the soft member 12 by the elastic member 15. When the engine is started again in this state, the piston motion is started. When the piston motion starts, an inertial force is applied to the mass member 14. For this reason, the mass member 14 operates according to the piston motion.

  First, the mass member 14 moves upward against the urging force of the elastic member 15 when the piston 1 descends, and moves away from the soft member 12. At this time, the elastic member 15 prevents the mass member 14 from colliding with the upper wall surface. Subsequently, when the piston 1 turns from descending to ascending, the mass member 14 moves toward the soft member 12 side. At this time, the elastic member 15 biases the mass member 14 toward the soft member 12 side. As a result, the momentum at which the mass member 14 collides with the soft member 12 can be increased, so that more reliable collision due to the necessary momentum is compensated. The soft member 12 transmits the impact received from the mass member 14 to the latent heat storage material 13. Thereby, the latent heat storage material 13 in a supercooled state nucleates and changes from a liquid phase to a solid phase.

In this embodiment, the mass member 14 that operates in accordance with the piston motion applies an impact to the latent heat storage material 13 through the soft member 12 in this way, so that the phase of the latent heat storage material 13 that is in a supercooled state at the time of engine start-up. Acts to encourage change. At this time, since the latent heat storage material 13 dissipates the stored latent heat, the temperature of the skirt portion 4 rises. As a result, the skirt portion 4 is thermally expanded, and thus the clearance with the bore is quickly reduced, so that the slap noise can be reduced.
As described above, the piston 1 can reduce the slap sound generated due to the clearance formed between the piston 1 and the bore being increased at a low temperature.

The embodiment described above is a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention.
For example, in order to thermally expand the skirt 4 evenly, a plurality of the nucleation devices 10 may be provided evenly along the circumferential direction with respect to the skirt 4, and the case 11 is extended along the circumferential direction. May be.

It is a figure showing piston 1 typically in a section. It is a figure which expands and shows the nucleation apparatus 10 typically in a cross section.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piston 2 Head part 3 Pin boss part 4 Skirt part 10 Nucleation apparatus 11 Case 12 Soft member 13 Latent heat storage material 14 Mass member 15 Elastic member

Claims (1)

A latent heat storage material provided in the skirt,
An engine piston comprising: a mass member that operates in accordance with piston motion to act to promote a phase change of the latent heat storage material that is in a supercooled state when the engine is started.

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