JPS58941B2 - Shift arm manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a shift arm, and more particularly to a method for manufacturing a shift arm by locally chill hardening spheroidal graphite cast iron.

The shift arm of a synchronous transmission, which has sliding parts and requires great strength, has traditionally been manufactured from forged or malleable cast iron, and the sliding parts are induction hardened or induction hardened. Hard chrome plating was later applied to improve wear resistance.

However, with induction hardening, it is difficult to perform hardening to an appropriate depth, and if the hardened thickness is small, it is difficult to improve wear resistance.

Further, in hard chromium plating, the economical plating thickness is, for example, about 10 μm, but at such a plating thickness, the plating is difficult to peel off.

Furthermore, under conditions of high temperature and high load, sufficient wear resistance cannot be ensured by the above-described treatments.

Therefore, an object of the present invention is to solve the above-mentioned technical problems and provide a method for manufacturing a shift arm that has excellent wear resistance even under high temperature and high load conditions.

The present invention will be explained in detail below with reference to the drawings.

FIG. 1 shows a shift arm 1 to be manufactured according to the present invention.
FIG. 2 is a sectional view taken along line II-II in FIG. 1. FIG.

The shift arm 1 is combined with parts (not shown) such as an input shaft, an output shaft, gears, and a conical clutch to form a synchronous transmission.

The two pawls 2a and 2b of the shift arm 1 are slidably fitted into an annular sleeve groove 4 formed on the outer peripheral surface of a ring-shaped sleeve 3 spline-coupled to the output shaft.

The shift arm 1 is connected to the shift shaft 6 by the change lever 5.
along the axial direction of the sleeve 3
is nail 2a.

2b and is displaced, meshing with the gear connected to the input shaft and transmitting driving force to the output shaft.

The sleeve 3 is meshed with the gear and rotated around the output shaft, so that the side surfaces 7, 8 and end surfaces 9 of the claws 2a, 2b are in sliding contact with the sleeve groove 4.

Therefore, the side surfaces 7, 8 and end surface 9 of the claws 2ay and 2b need to have high hardness and high wear resistance.

Moreover, it is desired that the parts of the shift arm other than the pawls 2a and 2b have excellent machinability so that they can be easily machined.

Spheroidal graphite cast iron has the same strength as forged or malleable cast iron, and has the oil-retaining property (wet type) and self-lubricating property (dry type) of spheroidal graphite.
It has excellent abrasion resistance, and cementite provides excellent abrasion resistance at high temperatures.

Therefore, by casting the shift arm 1 from spheroidal graphite cast iron and chill-hardening the side surfaces 7, 8 and end surfaces 9 of the claws 2a, 2b, it is possible to further improve wear resistance at high temperatures and high loads.

However, spheroidal graphite cast iron undergoes relatively large expansion and contraction during casting.

However, in the conventional chill hardening method, which uses a flat mold for cooling, the mold fluctuates, which can lead to variations in hardness and defects such as cracks, leading to unstable product quality. .

FIG. 3 shows a shift arm 1 to be manufactured according to the present invention.
FIG. 4 is a sectional view taken along line IV-IV in FIG. 3. FIG.

A mold for the shift arm 1 is formed using foundry sand 10 and a mold 11 shown in stippling.

The mold 11 has two claws 2a that should improve the wear resistance of the shift arm 1.

2b, and claws 2a at both ends thereof.

The shift arm 1, which has a substantially U-shaped mold portion 12 that forms the side surfaces 7, 8 and end surface 9 of the shift arm 2b, has a substantially semicircular arc shape as shown.

The pawls 2a, 2b are formed on a single point radial line of the shift arm 1, and protrude radially inward.

The mold 11 extends on the -diameter heddle where these claws 2a, 2b are located.

The thickness 11c (see FIG. 4) of the portion of the mold portion 12 that sandwiches the claws 2a, 2b is selected to be approximately equal to the thickness 12 of the claws 2a, 2b.

Molten spheroidal graphite cast iron is poured into a mold through a runner 13, thereby casting the shift arm 1.

The side surface 7.8 and the end surface 9 of the claw 2 are rapidly cooled by a mold 11 and chill-hardened.

According to the present invention, the side surfaces 7, 8 and end surfaces 9 of the claws 2a, 2b are three-dimensionally restrained by the mold part 12 of the mold 11 and cooled.

Therefore, even if spheroidal graphite cast iron has the characteristic of large contraction and expansion of the molten metal during pouring, the mold 11 will not fluctuate due to the contraction and expansion, resulting in variations in hardness and defects such as cracks. will not occur.

In particular, pearlite-based spheroidal graphite cast iron has good machinability and is easy to process after casting.

Next, one embodiment of the present invention will be described.

Ferrosilimagne (Fe-8i-
Mg) 120g was added, C; 3.45%, Si; 2
．． 64%, S; 0.013% and Mg; 0.042%
The shift arm 1 was produced using the mold shown in FIGS. 3 and 4.

Therefore, the mechanical properties of the portions indicated by chain lines A and B in FIGS. 5 and 6, which show cross sections of the claws 2b and 2b parallel to the shift axis 6, were examined.

As a result, the tensile strength at part A was 72.8 kg/mm.
2. Elongation of 8.2% and Brinell hardness of 380 to 410 were obtained, and Brinell hardness of 373 to 429 in part B was obtained.
was gotten.

However, it was confirmed that the original Brinell hardness (200 to 320) of untreated spheroidal graphite cast iron was significantly improved.

In the figure, C = 10mm, D = 15mm and E = 1mm.
It is.

In this example, no defects such as cracks were observed in the claws 2a, 2b.

As described above, according to the present invention, the molten spheroidal graphite cast iron is poured into a sand mold in which the mold is arranged so as to surround the part where the wear resistance should be improved, so that the expansion and contraction of the spheroidal graphite cast iron is prevented. This prevents the mold from changing due to this, and the parts where wear resistance should be improved are chill-hardened, making it possible to manufacture a shift arm that has excellent wear resistance even at high temperatures and high loads.

The claws 2a and 2b of the shift arm 1 are provided in a straight line,
A mold 11 having a mold part 12 surrounding the claws 2a and 2b is
It extends in a straight line.

Therefore, not only is the fluctuation of the mold caused by the expansion and contraction of the spheroidal graphite cast iron prevented as described above, but also the mold 11 is configured to surround the claws 2a and 2b at once, so that loss of the mold is prevented. .

Claw 2a of mold part 12. The thickness 11 of the part that sandwiches 2b is the thickness of the claw 2
The thickness is selected to be approximately equal to the thickness 12 of the claws 2a and 2b, so that both side surfaces 7, 8 and end surfaces 9 of the claws 2a and 2b are chill-hardened uniformly, eliminating uneven wear resistance.

[Brief explanation of the drawing]

FIG. 1 shows a shift arm 1 to be manufactured according to the present invention.
2 is a sectional view taken along II-II in FIG. 1,
Figure 3 is a front view of the mold for shift arm 1, and Figure 4 is a front view of the mold for shift arm 1.
5 and 6 are cross-sectional views taken along line IV--IV in the figure, and are cross-sectional views of the claws 2a and 2b whose mechanical properties were tested. 1...Shift arm, 2a, 2b...claw, 3...
Sleeve, 4... Sleeve groove, 7, 8... Claw 2a,
Side surface of 2b, 9... End surface of claws 2a, 2b, 10...
Foundry sand, 11... Mold, 12... Mold part.

Claims (1)

[Claims] 1. A generally semicircular shift arm has protruding claws 2a, 2b formed on its diameter line and protruding radially inward.
A mold for the shift arm 1 is formed by molding sand 10 and a mold 11, and the mold 11 extends on the -diameter line. Each end of the mold 11 has both sides 7 and 8 of the claws 2a and 2b.
and a substantially U-shaped mold part 12 surrounding the end surface 9;
The thickness 11 of the part sandwiching the claws 2a and 2b of 2 is the claw 2a. 2b, and a molten spheroidal graphite cast iron is poured into the mold, whereby the side surfaces 7, 8 and inner circumferential surface 9 of the claws 2a, 2b are chill-hardened by the mold 11. A method of manufacturing a shift arm.