JPH0341078Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a piston device for an internal combustion engine, and particularly to a piston device with improved startability.

Conventionally, in internal combustion engines, an oil scraper ring has been used to scrape off excess lubricating oil inside the cylinder. A coil spring is placed on the back of the oil scrubbing ring, and this coil spring presses against the back of the oil scrubber ring, generating high surface pressure.

By the way, when the surface pressure of the oil scraper ring is increased as described above, although the scraping action described above is effectively performed, on the other hand, there is a drawback that the startability of the engine becomes poor. In other words, when the engine is started or warmed up, both the lubricating oil temperature and the engine temperature are low, so the viscosity of the lubricating oil is high, and this, together with the high surface pressure of the oil spool ring as described above, increases engine resistance. This is because the amount increases.

This idea was devised in view of the above, and its purpose was to reduce the surface pressure on the piston ring when starting the engine, resulting in good starting performance, and to reduce the pressure on the piston ring when the lubricating oil temperature or engine temperature rises. An object of the present invention is to provide a piston device for an internal combustion engine that can increase surface pressure and perform a predetermined function.

A piston device for an internal combustion engine according to the present invention in accordance with the above object is a piston device for an internal combustion engine comprising an expansion ring disposed at the back of a piston ring, in which the expansion ring is made of a shape memory alloy, and the ring is made of a shape memory alloy. It is characterized by being treated so that it is in a contracted state at low temperatures and in an elongated state at high temperatures.

As a result of the above, since the expansion ring is in a contracted state when the engine is started, the surface pressure on the piston ring is reduced, making it possible to improve the startability. On the other hand, when the engine temperature rises and the expansion ring is heated after a predetermined period of time has elapsed after startup, the expansion ring will be in an extended state and the surface pressure on the piston ring will increase. It becomes possible to perform the action.

Next, specific embodiments of the piston device for an internal combustion engine of this invention will be described in detail with reference to the drawings.

In the figure, 1 indicates a piston, and a top ring 2, a second ring 3, and an oil scraper ring 4 are arranged in this piston in order from top to bottom.On the back of the oil scraper ring 4, An expansion ring 5 such as a coil spring is arranged.

In this case, the expansion ring 5 is made of a two-way (reversible) shape memory alloy such as copper-based or Ti-Ni-based, and is in a contracted state at a low temperature of about room temperature (martensitic phase). At a high temperature (matrix) of about 0.degree. C., it is treated so that it remains in an elongated state. That is, at low temperatures, the expansion ring 5 is in a contracted state (martensitic phase) and does not generate tension, and the surface pressure of the oil scrubbing ring 4 is kept low, while at high temperatures, the expansion ring 5 is in an extended state.
(mother phase) to generate tension and press the oil scrubber ring 4 with a predetermined surface pressure.

In the piston device as described above, at the time of starting, although the viscosity of the lubricating oil is high, the surface pressure of the oil scrubber ring 4 is low, so the engine resistance is small, and as a result, it is possible to improve starting performance. Become. In addition, normally, problems such as scuffing are likely to occur due to insufficient lubricating oil between the cylinder liner and piston ring immediately after starting, but as mentioned above, oil scrubber ring 4 Since the tension is reduced, a sufficient amount of lubricating oil can be supplied between the cylinder liner and the piston ring, making it possible to prevent problems such as scuffing. On the other hand, as the lubricating oil and engine temperature rise, the expansion ring 5 is heated, and when the temperature reaches a high temperature, the expansion ring 5 shifts to an extended state, generating high tension, and the surface pressure of the oil scrubbing ring 4 increases. Therefore, it is possible to perform the same function as a conventional oil scrubbing ring.

Although one embodiment of the piston device for an internal combustion engine of this invention has been described above, the piston device of this invention is not limited to the above embodiment, and can be implemented with various modifications. For example, in the above example, an oil paddle ring is used as the piston ring and a coil spring is used as the expansion ring, but other types of piston rings may be used, or other types of expansion such as wave springs may be used. It is also possible to implement it using a ring.

The internal combustion engine piston device of this invention is constructed as described above, and therefore, according to this invention, when the engine is started, the surface pressure of the piston ring is low, so starting performance is good, and the lubricating oil When the temperature of the piston ring or the engine temperature rises, the surface pressure of the piston ring increases, making it possible to provide a piston device that can perform the specified action. suitable.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an embodiment of a piston device for an internal combustion engine according to the present invention, and FIG. 2 is an enlarged sectional view of its essential parts. 4... Oil scrubbing ring, 5... Expansion ring.

Claims (1)

[Scope of utility model registration request] A piston device for an internal combustion engine comprising an expansion ring arranged at the back of a piston ring, wherein the expansion ring is made of a shape memory alloy, and
A piston device for an internal combustion engine, characterized in that the ring is treated to be in a contracted state at low temperatures and in an extended state at high temperatures.