JP2619352B2 - Flywheel manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing an engine flywheel.

[Prior art] A flywheel for an automobile engine has a structure in which a ring gear made of carbon steel for machine structure of about S45C is shrink-fitted to the outer periphery of a flaky graphite cast iron flywheel of about FC20. However, the following problems remain.

[Problems to be solved by the invention]

(1) Since the flaky graphite cast iron of about FC20 has insufficient damping ability, the flywheel itself generates a speaker effect, which causes an undesired state in which the engine sound is enlarged and emitted to the outside.

(2) However, when flaky graphite cast iron of about FC10 is used, the damping capacity is increased and noise can be suppressed, but the mechanical properties are deteriorated and the strength is insufficient, so that it cannot be used.

(3) Further, since the outer diameter of the flywheel and the inner diameter of the ring gear are machined and shrink-fitted, the number of machining steps is increased and the production cost is increased.

(4) Further, when the ring gear is shrink-fitted, the tooth profile is deformed, and the dimensional accuracy of the tooth profile is reduced.

An object of the present invention is to provide a flywheel manufacturing method capable of preventing noise and greatly reducing manufacturing costs.

[Means for solving the problem]

The present invention relates to a method of manufacturing a flywheel having a ring gear integrally on an outer periphery, injecting a molten metal having a spheroidal graphite cast iron composition into a portion corresponding to a ring gear in a rotating centrifugal casting mold, and then adding flake graphite cast iron. After injecting the molten metal of the composition, solidifying it, taking it out of the mold, holding it at 830 to 900 ° C for 0.5 to 3 hours, quenching it to 200 to 400 ° C and holding it for 0.5 hours or more It is characterized in that the structure is a mixed structure of bainite and austenite.

Hereinafter, a method of manufacturing a flywheel according to the present invention will be described in detail.

First, the chemical composition of the molten metal to be poured is the same as that of generally known spheroidal graphite cast iron or flaky graphite cast iron, and its component range is also well known, so description thereof will be omitted.

After maintaining the flywheel made of spheroidal graphite cast iron and flaky graphite cast iron having a normal chemical composition as described above, austenitizing conditions at 830 to 900 ° C. for 0.5 to 3 hours,
It is quickly immersed in a salt bath at 200 to 400 ° C. or a fluidized bed, rapidly cooled, maintained for 0.5 hours or more, transformed into bainite, and then cooled to room temperature.

The reason for limiting the austempering process conditions will be described.

The reason for setting the austenitizing condition to 830 to 900 ° C × 0.5 to 3 hours is that when the thickness is below 830 ° C, the time required for austenitizing increases when the product is thicker. To do that.

Although the holding time varies depending on the thickness, the minimum time required for austenitization is 0.5 hour, and it is sufficient to hold the thick portion for 3 hours.

The reason why the constant temperature transformation treatment condition is 200 to 400 ° C. × 0.5 hours or more is that when the temperature is 200 ° C. or less, the hardness increases and the machinability decreases.

Further, at a temperature of 400 ° C. or more, a great effect on wear resistance cannot be expected, and it is disadvantageous in terms of thermal energy, which unnecessarily increases the cost. Processing time must be at least 0.5 hour.

[Example 1 (direct type)] (1) Chemical composition of spheroidal graphite cast iron (FCD) composition As shown in Table 1.

(2) Injection temperature: 1,400 to 1,420 ° C (3) Chemical composition of flaky graphite cast iron (FC) composition As shown in Table 2.

(4) Injection temperature 1,380 to 1,400 ° C (5) Heat treatment When the product taken out of the mold is cooled to 870 ° C, it is kept at this temperature for 2 hours, quenched to 380 ° C and kept for another 2 hours, and then at room temperature Cooled down.

(6) Mechanical properties As shown in Table 3.

Example 2 (Reheating Type) (1) Chemical Components of Spheroidal Graphite Cast Iron (FCD) Composition As shown in Table 4.

(2) Injection temperature 1,400 to 1,420 ° C (3) Chemical composition of flaky graphite cast iron (FC) composition As shown in Table 5.

(4) Injection temperature 1,380 to 1,400 ° C (5) Heat treatment After taking out from the mold, once cooled to room temperature,
After reheating to 2 ° C. and maintaining for 2 hours, the mixture was rapidly cooled to 270 ° C. and maintained for 2 hours, and then cooled to room temperature.

(6) Mechanical properties As shown in Table 6.

[Effects of the Invention] The features of the flywheel manufactured according to the present invention are listed below.

(1) Since it is a composite casting of spheroidal graphite cast iron and flaky graphite cast iron, the number of machining steps can be significantly reduced.

(2) The ring gear portion has the most preferable characteristics as a gear material having toughness and wear resistance.

(3) The flywheel portion has a flaky graphite structure, has a large damping ability, and has an effect of suppressing noise.

(4) Since both the spheroidal graphite cast iron and the flaky graphite cast iron have a mixed structure of bainite and austenite by austempering, they have excellent mechanical properties and can significantly improve safety and reliability.

As is apparent from the above description, the flywheel manufactured according to the present invention has remarkable industrial effects such as improvement of metal structure, improvement of mechanical properties, and reduction of manufacturing cost by shortening the manufacturing process. Things.

Further, in the embodiment of the direct mold in which the mold is separated and the austempering treatment is performed immediately after the mold is separated, a further effect of preventing unnecessary loss of heat energy can be expected.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-29420 (JP, A) JP-A-60-92055 (JP, A) Real opening Sho-54-180880 (JP, U)

Claims (1)

(57) [Claims] When manufacturing a flywheel having a ring gear integrally on its outer periphery, a molten metal having a spheroidal graphite cast iron composition is poured into a portion corresponding to the ring gear in a rotating centrifugal casting mold, and then flaky graphite cast iron. Inject the molten metal of the composition,
After solidification, remove it from the mold and at 830-900 ° C 0.5 ~
A method for manufacturing a flywheel, wherein the base structure is a mixed structure of bainite and austenite by performing an austempering treatment in which the base structure is maintained for 3 hours, rapidly cooled to 200 to 400 ° C. and maintained for 0.5 hours or more.