JPS6034611B2 - Gear heat treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of heat treating a gear, which mainly hardens the tooth surface of the effective tooth depth of the gear.

In general, widely used heat treatment methods for gears include heating the entire gear and rapidly cooling it in the same way as heat treatment for general products, or heating mainly the teeth using high frequency and rapidly cooling them. The method is such that the entire gear, or most of the teeth, is hardened.

However, to explain the most preferable heat treatment for gears with reference to FIG. 1, the hardness of the tooth surface S' of only the so-called effective tooth that actually contacts the mating gear during the tooth height h is increased. It is said that the roots of the teeth that form the apex gap C should not be filled in. In other words, it is preferable that the surface of the contact part has high wear resistance and the root part has high impact resistance, but as mentioned above, the conventional heat treatment method that is commonly used does not It is difficult to add phosphorus, and there is a need for a heat treatment method that satisfies this requirement. On the other hand, heat treatment methods using laser beams are being developed recently.

This method uses a laser beam with high energy density for heating, so the heating time is extremely short, a shallow hardened layer can be obtained, natural cooling can be used for hardening, and therefore there is little thermal deformation. To give an example of an experiment conducted by the inventors, a sample made of FC20 was subjected to an output of 50
KCI with 0W C02 laser device and focal length f=46 fence
When using a lens consisting of the following, and competing with a defocus distance of 5 fences and a laser beam scanning speed of 21 side/sec,
A hardened layer with a depth of 30 mm was obtained. However, approximately 0.2 ribs are treated with one laser beam irradiation.

The hardness increased from Hv200 to Hv300 before quenching to Hv600 to Hv800. Further, when the treated surface has a mirror finish and Ra=8.5, a hardened layer on the 0.1 side or higher can be obtained under the above treatment conditions. When a similar sample is hardened by conventional induction hardening, the hardness obtained is about Hv360 to Hv440,
Its depth is about three sides. Therefore, in the case of laser heat treatment, the depth is very shallow, but the hardness is extremely increased, the wear resistance is significantly improved, and there is no need for final finishing because there is little deformation. In the case of the above experiment, after quenching R
It was max x approximately 1.5 mountain surface. The present invention was made in view of the above-mentioned circumstances, and is ideal by irradiating and hardening the root portion of the tooth surface where the laser beam is irradiated from a direction where the laser beam is not blocked by adjacent teeth and cannot reach the root part of the tooth surface. This is a heat treatment method for gears that can be hardened.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a diagram showing the principle of the present invention, in which the laser beam 2 is irradiated to the tooth surface S of the tooth 3 with the gear 1 stationary, and only the tooth surface S' of the effective tooth h is hardened. .

The laser beam 2 is directed from a direction such that the tip of the adjacent tooth 5 prevents the laser beam 2 from reaching the root portion 4 (hatched portion).
irradiate. If the diameter of the inside of the tooth is larger than the spot diameter of the laser beam 2, the laser beam 2 is scanned in the direction of the inside of the tooth. Next, the gear 1 is rotated by one tooth, and the above operation is repeated again to harden one side of the tooth around the entire circumference. Then, the laser beam 2a is irradiated from the opposite side in the same way, and all the teeth are hardened. The hardening of the tooth surfaces S', . . . of the effective tooth depth h is completed. - FIG. 3 is an explanatory diagram of one embodiment, in which gears la and lb, which are the same and which are to be heat treated, are each rotatably supported and are in mesh with each other.

A laser beam 2 with a power density of 1 W/ or more and a spot diameter of approximately the effective tooth depth h is irradiated onto the meshing portion lc. At this time, both gears la and lb are rotated at a predetermined speed that provides the energy density necessary for hardening. Next, the laser beam 2a is irradiated from the opposite side in the same manner to harden the tooth surface S' on the other side, completing the hardening of the entire effective tooth depth S', .

As detailed above, the present invention allows gears to mesh with each other,
Since the laser beam is applied to the meshed part to harden it, two gears can be hardened at the same time with one laser irradiation. Heat no longer affects the necessary parts.

[Brief explanation of drawings]

FIG. 1 is a front view of essential parts of a gear for explaining a conventional example, FIG. 2 is a view showing the principle of the present invention, and FIG. 3 is a front view for explaining an embodiment of the present invention. 1, la, lb...gear, 2, 2a... laser beam, 4... root, 5... adjacent tooth, S... tooth surface. Little brother 1 strategy 2 recruitment diagram

Claims (1)

[Claims] 1. In a gear heat treatment method in which the gears are hardened by irradiation with a laser beam, the gears are rotated while meshing with each other, and either the meshing start part of the meshing or the side opposite to this meshing start part is first A method for heat treating a gear, which comprises irradiating a gear with a laser beam and, after one rotation from the start of irradiation, irradiating the other gear with a laser beam to harden the other gear.