JPH03267552A - Lightweight piston - Google Patents

Abstract

PURPOSE:To prevent the deterioration of strength even after the operation for a long time by forming a piston skirt by a heat-resistive sintered body which is formed by plasma-sintering the powder particles which are made of resin and whose surfaces are covered with metal films. CONSTITUTION:The part between the first and second electrodes 2 and 3 which are fitted inside a cylindrical mold 1 is charged with composite powder material 4. The powder material 4 is formed by applying Al on the surface of the powder material made of acrylic resin through the substitution plating method. Then, the electrodes 2 and 3 are applied with pulse voltage, and a compression stress is applied on the powder body 4 from both electrodes, and the state is maintained. Then, the plasma electric discharge is generated between this powder particles of the powder material 4, and an oxidized film, etc., on the surface of Al plating the surface of the powder particle is removed. A heat-resistive sintered body 5 is heated, and arranged in a press guide 7, together with a piston head 6 of the sintered body made of the heat-resistive high strength material such as silicon nitride. A punch 8 is shifted downward, and forging is carried out, together with a base 9, and a lightweight piston 11 having a piston skirt 10 can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a lightweight piston whose piston skirt is formed of a sintered body of a heat-resistant resin.

(Prior art) In a so-called reciprocating engine, in which a piston reciprocates inside a cylinder, reducing the reciprocating inertia mass of the piston and connecting rod is necessary to increase output as the engine's maximum rotation speed increases, and to increase the speed of the crankshaft and bearings. It is known that it is very effective in reducing the so-called metal hammering noise that occurs between metal parts.

Therefore, the piston is made of an aluminum alloy to reduce the reciprocating inertial mass.

Furthermore, in order to further reduce the mass of the piston, it has also been implemented to make the piston from a magnesium alloy.

Furthermore, it has been proposed that a portion of the piston is made of resin or the like to further reduce the mass of the piston.

For example, the piston skirt is made of fiber-reinforced resin,
A composite piston in which a piston skirt made of fiber-reinforced resin is connected to a piston head made of a material with excellent heat resistance such as ceramic is described in Japanese Patent Publication No. 1-54541.

In addition, a fiber-reinforced resin piston has been developed in which a lubricating layer with excellent lubricity is applied to the outer peripheral surface of a piston skirt made of fiber-reinforced resin, improving the lubricity and wear resistance of the piston. It is described in the publication No.-79142.

(Problems to be Solved by the Invention) The fiber-reinforced resin forming the piston skirt described in each of the above-mentioned publications has a heat resistance temperature of only about 200° C. as a matrix resin.

Therefore, there is a problem in that when the engine is operated for a long time, the resin that is the matrix is denatured and its strength is reduced.

The present invention has been made in view of the above points, and aims to provide a lightweight piston in which the piston skirt is made of a resin that has better heat resistance than conventional fiber-reinforced resins.

(Means for Solving the Problems) According to the present invention, a piston skirt is made of a sintered body of powder particles made of resin and whose surface is coated with a metal film;
It is possible to provide a lightweight piston comprising a piston head made of a heat-resistant material and connected to the piston skirt.

(Function) In the lightweight piston of the present invention, the piston skirt is made of a heat-resistant sintered body made by plasma sintering powder particles made of resin and whose surface is coated with a metal film. The strength of the piston skirt does not decrease even after long-term operation.

(Example) Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing a process of creating a heat-resistant sintered body.

A first electrode 2 and a second electrode 3 fitted inside a cylindrical mold 1
Composite powder 4 is filled between the two.

Note that both the first electrode 2 and the second electrode 3 are made of graphite or a super strong alloy.

The composite powder 4 has aluminum deposited on the surface of powder particles made of acrylic resin by displacement plating.

By the way, instead of the acrylic resin, any one of polyolefin resin, vinyl chloride resin, acrylonitrile resin, phenol resin, silicone resin, and fluororesin may be used, and copper may be used instead of aluminum to be applied to the surface. You may let them.

Further, the deposition method is not limited to the displacement plating method described above, and coating may be performed by electroless plating method, magnetron sputtering method, or powder fluidized bed electroplating method.

In the state shown in this figure, the first electrode 2 and the second electrode 3 are approximately 1
A pulse voltage with a voltage of 000 KV and a pulse number of 2000 cpm is applied.

Then, along with the application of the pulse voltage, a compressive stress of about 1000 kg/crn' is applied to the mixed powder 4 by the first electrode 2 and the second electrode 3, and this state is maintained for 30 to 100 seconds.

Then, plasma discharge is generated between the powder particles of the mixed powder 4, and the oxide film on the aluminum surface adhering to the powder particle surface is removed, so that the powder particles are firmly bonded to each other. join to.

Note that during the plasma sintering, the temperature of the mixed powder 4 rises only to about 100° C., so the acrylic resin serving as the core will not be modified or volatilized.

The next step will be explained with reference to FIG.

FIG. 2 is a diagram showing the forging process.

Heat-resistant sintered body 5 created by the process shown in FIG. 1 above
is heated to about 100 to 200° C. and placed in a press guide 7 together with a piston head 6 made of a sintered body of a heat-resistant, high-strength material such as silicon nitride.

Then, the bunch 8 is moved downward in the drawing and forged with the stand 9 to manufacture the lightweight piston 11.

The next step will be explained with reference to FIG.

FIG. 3 is a diagram showing the finishing process.

11 is a lightweight piston according to the present invention as described above,
It is composed of the piston head 6 and a piston skirt 10 made of the heat-resistant sintered body 5.

2 shows a state in which a ring groove 12 and a hole 13 into which a piston pin is inserted are provided by machining on the outer circumferential surface of the piston skirt 10 after the forging process shown in FIG. 2 is completed.

As mentioned above, the surface of the resin powder particles constituting the piston skirt 10 of the lightweight piston 11 is coated with aluminum or copper, so that the heat resistance is improved compared to the case of using only resin or fiber reinforced resin.

Therefore, the lightweight piston 11 is sufficiently suitable for long-term operation of the engine.

Although the embodiments of the present invention have been described in detail above, various different embodiments can be easily constructed without departing from the spirit of the present invention. Other than limitations, the present invention is not limited to specific embodiments (effects of the invention) As explained above, according to the present invention, powder particles made of resin and whose surfaces are coated with a metal film are plasma sintered. Since the piston skirt is made from a heat-resistant sintered body created by It is possible to provide a lightweight piston that can increase the output of the engine and reduce metal hitting noise.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the process of creating a heat-resistant sintered body, FIG. 2 is a diagram showing the forging process, and FIG. 3 is a diagram showing the finishing process. 6...Piston head, 10...Piston skirt, 11...Lightweight piston.

Claims (5)

[Claims] (1) It is characterized by consisting of a piston skirt made of a sintered body of powder particles made of resin and whose surface is coated with a metal film, and a piston head made of a heat-resistant material and connected to the piston skirt. lightweight piston. (2) The resin is at least one of polyolefin resin, vinyl chloride resin, acrylic resin, acrylonitrile resin, phenol resin, silicone resin, and fluororesin.
The lightweight piston according to claim 1, characterized in that it is of the following types. (3) The lightweight piston according to claim (1), wherein the metal coating is at least one of aluminum and copper. (4) The lightweight piston according to claim (1), wherein the heat-resistant material is a ceramic sintered body. (5) The lightweight piston according to claim (1), wherein the sintered body forming the piston skirt is a sintered body created by a plasma sintering method.