JP3154229B2 - Method for manufacturing vehicle member - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flywheel having a gear attached to a rotating shaft of an engine and having an outer peripheral portion meshing with a starter gear, and a boss portion used as a component of a suspension system of an automobile. A member or sliding member having a tooth profile on the outer periphery of the member and a serration tooth on the inner periphery of the boss hole, such as a lower arm or upper arm having a wear-resistant sliding portion in the hole, and a ball joint socket. The present invention relates to a vehicle member such as a member having a moving surface and a method of manufacturing the same.

[0002]

2. Description of the Related Art Among the above-mentioned vehicle members, for example, a conventional flywheel is formed by forming a rod-shaped steel material (equivalent to S48C) having a square cross section into a ring shape, and flush padding both ends thereof. After being joined by welding or the like, a gear is cut on the outer periphery thereof to form an annular material a as shown in FIGS. 1 (a) and 1 (b). It is manufactured by fitting to the outer periphery of a flywheel body b formed by machining a necessary portion of a casting (equivalent to FC25) by shrink fitting or by welding after fitting. In addition, since the gear portion locally requires strength, high-frequency hardening is performed. Gears such as a crankshaft gear, an oil pump gear, and a parking gear of an automobile have been subjected to forging and then machined for teeth.

Vehicle components requiring wear resistance, such as rotating members used for suspension devices such as parking gears, lower arms, upper arms, and ball joints, are subjected to hot forging, and then to drilling and inner surfaces of the holes. Need to press-fit the bush. Further, if necessary, necessary portions are induction hardened.

[0004]

In the above-described conventional method for manufacturing a vehicle member such as a flywheel, the method includes a ring material a made of steel and a flywheel body b made of a casting, so that a large amount of machining is required and the manufacturing cost is reduced. As a result, the deformation due to shrink-fitting or welding has to be performed, so that it is necessary to correct the overall shake detection distortion.

[0005] In the case of the flywheel, inertia (inertial force) for smoothing the rotation operation of the engine is as follows.
The weight of the outer periphery is more effective than the shaft center, and ideally,
It is desirable that the weight of the outer periphery is large and the weight of the shaft center is minimized.

However, in the above-mentioned conventional flywheel, the flywheel body b is formed of flaky graphite cast iron (grey cast iron, equivalent to FC25). Failed in strength.

That is, in this kind of flywheel,
Since the stress due to centrifugal force is accumulated and concentrated near the center of rotation, when the flywheel body is made of the above-mentioned flaky graphite cast iron, its strength is low. If the thickness is reduced, a burst (destruction) may occur in this portion.

In a conventional flywheel body made of flaky graphite cast iron, the sliding surface of a clutch plate provided on the flywheel body is
During excessive use, this surface may be worn, and smooth clutch operation may not be possible.

Further, when the starter motor is rotated to start the engine, an unpleasant noise is often generated. However, in the conventional flywheel, a ring-shaped gear is fitted to a flywheel body b made of cast iron. The annular material a is provided with a ring-shaped gear, and the annular material a is made of steel (S
(Equivalent to 48C), the damping ability of this portion against the noise and vibration was low, and the generation of noise at the start could not be suppressed.

Further, conventional suspension members such as lower arms and upper arms and rotating members such as parking gears have been formed by forging mainly because of their strength. There is a problem that it takes a lot of time to be done.

The present invention has been made in view of the above, and can be manufactured at a low cost with high productivity. In the case of a flywheel, the thickness of the central portion can be made thinner than that of the outer peripheral portion so that the inertia performance can be reduced. In addition, the surface roughness due to wear of the sliding contact surface of the clutch plate can be prevented, and the generation of abnormal noise in the ring-shaped gear portion at the start of the engine can be reduced. Also in this case, it is an object of the present invention to provide a method for manufacturing a vehicle member that can be constituted by a casting.

[0012]

In order to achieve the above object, a vehicle member according to the present invention is manufactured by casting a spheroidal graphite cast iron.
The molded material is turned into ferrite, and then
Plastic working or mechanical processing is applied to the outer periphery or the inner periphery of the hole.
Contact of the tooth profile or sliding surface, etc.
Form the contact area, and then aus
Tempering treatment and then induction hardening
And then apply shot peening to this part.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A flywheel according to an embodiment of the present invention will be described below with reference to FIG. In the figure, reference numeral 1 denotes a flywheel material. The flywheel material 1 includes a boss portion 2, a thin portion 3 around the boss portion, a thick portion 4 on the outer peripheral side, and a ring-shaped gear 5 provided on the outer peripheral portion of the thick portion 4. And

This flywheel material 1 has C: 3.8
wt%, Si: 1.8 wt%, Mn: 0.6 wt%,
P: 0.05 wt%, S: 0.01 wt%, Mg: 0.1%
It is formed of 04 wt% spheroidal graphite cast iron. Then, the flywheel material 1 is heat-treated after casting and formed into ferrite. This ferrite formation is obtained by heating at 850 to 920 ° C. for 0.5 to 2.0 hours and then cooling in a furnace. And the hardness at this time is Hv100
１７175.

Then, necessary portions such as the boss portion 2 and the clutch plate sliding contact portion of the flywheel material 1 are machined, and then a ring-shaped gear is formed on the ring-shaped gear portion 5 by plastic working to form a flywheel. And The plastic working of the ring gear is performed by rolling or press forming. Further, the gear may be formed by machining with a gear cutting machine or the like.

Thereafter, the entire flywheel is placed in a heat treatment furnace and subjected to austempering. As shown in FIG.
After heating for 5 to 2.0 hours,
It is performed by heating and air cooling for 〜2.5 hours.
The processing temperature and time at this time are set based on the relationship between the thickness of the flywheel 1 and the chemical components.
If the heating time at 20 ° C. is less than 0.5 hour, the austenitization may be insufficient. This is especially when chill (free cementite) is occurring. Further, even if it exceeds 2 hours, it will be unnecessarily long, and it will only waste energy and hinder productivity.

If the temperature is set at less than 850 ° C., complete austenitization may be difficult, and it may take a long time. It does not need to exceed 920 ° C.

In addition, the chemical composition of the constituent material of the flywheel material 1 basically extremely reduced the amount of Si in the matrix in order to facilitate plastic working. But,
If the content of Si is less than 0.9% by weight, deoxidation during melting is insufficient and cast iron defects occur frequently, which causes problems in casting characteristics such as molten metal flow. S
i: If it exceeds 2.4 wt%, the matrix becomes hard and brittle due to the remarkable characteristics of silicon ferrite, and plastic working becomes difficult.

On the other hand, regarding the amount of C, the carbon equivalent (C · E
= Cwt% + 1 / 3Siwt%) to eutectic (4.3 wt%
%) Or more, and at least 3.5 wt%
is necessary. In actual dissolution, a carbon equivalent of 4.2 wt% is desirable.

If the amount of Mn is less than 0.3% by weight, the effect is small, and if it exceeds 1.0% by weight, the tendency to chill increases. The amount of Mg is an optimum amount to be added to obtain spheroidal graphite. That is, 0.01 wt%
If it is less than 0.06% by weight, spheroidization is difficult.

The above content ratios of Si, C, Mn, and Mg are optimal combinations of the four major elements for spheroidal graphite cast iron.
Cu may be added in an amount of 0.4 to 1.5 wt% in order to improve heat treatment without causing embrittlement of the material.

After the austempering process, for the models that need to improve the tooth root strength of the ring gear, shot peening was applied to the ring gear. As a result of measuring the amount of retained austenite in this tooth part,
It was 38% before shot peening, but decreased to 20% after shot peening. Generally, this shot peening reduces the amount of residual austenite to 30 to
Reduced to 1%.

In another model, after the austempering, the ring gear portion is subjected to induction hardening and then shot peening to improve the hardness. The hardness at the time of the austempering was HRC30, but became HRC53 after induction hardening. Depending on the familiarity with the starter gear, higher hardness may be better. The hardness is HRC50-65 by this induction hardening.
become.

As an example of spheroidal graphite cast iron, 900 N / m
m class ² austempered spheroidal graphite cast iron (FCD90A
The mechanical properties of T) are as shown in Table 1.

[0025]

[Table 1]

FIG. 5 shows the fatigue strength of the FCD90AT.
FIG. 6 shows a comparison of the wear resistance of the AT. FIG. 7 shows a comparison between the gear vibration damping capacity of the S48C material and the gear vibration damping capacity of the FCD90AT. From these results, it can be seen that FCD90AT is slightly inferior in wear resistance to S48C material, but is excellent in gear vibration damping ability.

The spheroidal graphite cast iron according to the embodiment of the present invention is subjected to shot peening to improve the strength of a root bending fatigue test as shown in FIG. In the figure, A shows the case where shot peening is performed, and B shows the case where shot peening is not performed.

The present invention can be applied not only to the above flywheels but also to lower arms and upper arms, which are suspension parts of automobiles conventionally manufactured by forging. In this case, the material of the lower arm and the upper arm is cast and formed from spheroidal graphite cast iron with the same chemical composition as in the embodiment of the flywheel described above, and then it is ferritized, and then has the boss and / or the tip. On the inner peripheral surface of the hole or the outer peripheral surface of the shaft portion, a smooth mirror surface portion such as a serration or a tooth portion is formed by plastic working or mechanical working. Next, this material is subjected to austempering.

As examples of vehicle members other than the above-mentioned flywheel, gears and the like generally used by being forged in vehicles such as passenger cars, parking poles, one-way clutches, injection pump pulleys, outer joints as shown in FIG. The present invention is applied to rotating members such as a lower arm, an upper arm, and a ball joint socket. If these members have teeth such as serrations or contact parts such as sliding surfaces, they are formed by plastic working or mechanical working.

[0030]

According to the present invention, a member for a vehicle, such as a flywheel, is conventionally formed by combining a steel material and flaky graphite cast iron by a cast molding alone. It can be manufactured with high productivity and at low cost. Since the strength can be made higher than that of the flaky graphite cast iron, the thickness of the central portion can be made smaller than that of the outer peripheral portion, and the inertia performance can be improved. Further, surface roughness due to wear of the sliding contact surface of the clutch plate can be prevented. Further, by providing gears on the outer peripheral portion of the integrally molded body made of the spheroidal graphite cast iron, it is possible to reduce the generation of abnormal noise in the ring-shaped gear portion when the engine is started.

In addition to vehicles other than the above-mentioned flywheels, for example, vehicle members conventionally formed of a forged material, such as gear members and outer joints, can be formed with sufficient strength by easy casting molding. The production cost of these members can be reduced, and the productivity can be improved.

[Brief description of the drawings]

FIG. 1A is a plan view showing a cross-sectional shape of a part of an annular material, which is one of the constituent members in a conventional flywheel manufacturing method, to show a cross-sectional shape, and FIG.

FIG. 2 is a cross-sectional view showing a flywheel manufactured by a conventional flywheel manufacturing method.

FIG. 3 is a sectional view showing a flywheel material as an example of a vehicle member according to the present invention.

FIG. 4 is a diagram showing austempering processing conditions.

FIG. 5 is a diagram showing the fatigue strength of FCD90AT.

FIG. 6 is a diagram showing the wear resistance of FCD90AT and S48C quenched materials.

FIG. 7 is a diagram showing a comparison of gear vibration damping abilities of FCD90AT and S48C.

FIG. 8 is a diagram showing the strength of a tooth root bending fatigue test with and without shot peening of spheroidal graphite cast iron.

FIG. 9 is a sectional view showing another example of the vehicle member according to the present invention.

[Explanation of symbols]

1: flywheel material, 2: boss, 3: thin part, 4
... Thick part, 5 ... Ring-shaped gear part.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C21D 9/00-9/40 C21D 5/00-5/16 C22C 37/00-37/10 C21D 1 / 10 C21D 1/20

Claims (1)

(57) [Claims] 1. A material cast and formed of spheroidal graphite cast iron.
Ferrite, then the outer periphery or hole of this material
Of either plastic working or machining
Form contact parts such as tooth profile or sliding surface
Then, the entire part including this contact part is austempered and
After, induction hardening is applied to the contact area,
A method for manufacturing a vehicle member, wherein shot peening is performed on a vehicle.