JPH0514766B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for induction hardening gears that combines high frequency heating and injection of quenching fluid.

<Prior Art> As is well known, a gear that has been cut is subjected to a quenching process to harden the outer peripheral portion where the teeth are formed. As a method for quenching, a method that combines high-frequency heating and injection of quenching fluid is often used.

In this type of conventional method, a gear is rotated inside a high-frequency heating coil to heat its outer circumference. Rotation of the gear is performed at least several times during the heating time for uniform heating. When the high-frequency heating is completed, the gear is immersed in a quenching liquid. In the quenching liquid, the gear 10 rotates inside the annular nozzle header 60, as shown in FIG.
The outer periphery of the gear 10 is rapidly cooled by the quenching injection liquid 31 that is injected from zero toward the center. As a result, as shown in FIG. 5, a hardened layer 14 is formed around the entire outer circumference of the gear 10.

<Problems to be Solved by the Invention> However, in the conventional method described above, since the gear is rotated at the same speed during heating and cooling, the rotational speed during cooling becomes excessive and the outer circumference of the gear is not uniform. The problem is that it is not cooled down. In other words, if the gear rotates quickly during cooling, the tooth bottom 12 and the tooth surface 1
As the quenching hardness of No. 3 decreases, the effective quenching depth D
becomes shallow. This is because before the quenching liquid injected from the nozzle header sufficiently cools a specific tooth root 12 and tooth flanks 13, 13 of the gear, the next tooth root
This is considered to be because the tooth bottom 12 and the tooth surfaces 13, 13 are insufficiently cooled as a result of rotation of the tooth bottom 12 and the tooth surfaces 13, 13. If the gear is a helical gear, the tooth surface 1 should be sufficiently exposed to the quenching injection liquid.
3 and tooth flanks 13 that do not touch, the problem of uneven cooling becomes even more pronounced.

On the other hand, when the rotation of the gear during cooling is slowed down, the quenching hardness of the tooth bottom 12 and the tooth surface 13 decreases, and the effective quenching depth D becomes shallow. If the rotation of the gear is slowed down during cooling, the quenching injection liquid will reach the tooth bottom 12.
However, the quenching injection liquid that bounced back from the tooth bottom 12 collides with the next quenching injection liquid, causing air bubbles to occur between the tooth surfaces 13, 13, and on the contrary, cooling is hindered. This is thought to be because For this reason, in some cases, the injection direction of the quenching liquid is tilted, but in this case, as in the case of a helical gear, tooth surfaces 13 are not sufficiently hit by the quenching liquid.

The present invention was made in view of the above circumstances, and its purpose is to promote cooling of the tooth bottom and tooth surface of a gear, and to form a hardened layer of sufficient hardness and depth in these parts. The purpose of the present invention is to provide a method for induction hardening gears.

<Means for Solving the Problems> The method of induction hardening a gear according to the present invention involves high-frequency heating the outer peripheral portion of the gear in which the teeth are formed, and then immersing the gear in a quenching liquid. The gear is characterized in that the gear is oscillated in both forward and reverse directions and moved up and down in the axial direction while injecting quenching fluid from the outer circumferential side to the outer circumferential portion of the gear.

<Function> By rotating the gear in both forward and reverse directions at an appropriate speed while injecting the quenching liquid onto the outer periphery of the heated gear, the quenching liquid sufficiently reaches the bottom of the gear. Moreover, the quenching liquid is evenly and sufficiently distributed over the tooth surfaces on either side. Furthermore, air bubbles generated between the tooth surfaces are discharged from between the tooth surfaces by vertical movement of the gear in the axial direction. Therefore, the tooth bottom and tooth surface are uniformly and sufficiently cooled.

<Examples> Examples of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory cross-sectional view showing the heating process of an example of the hardening method according to the present invention, and FIG. 2 is an explanatory cross-sectional view showing the cooling process.

The gear 10 to be hardened is a vertical cylinder 2
It is attached concentrically to the tip of 0.

The cylinder 20 passes through a tank 40 containing the quenching fluid 30, and rotates forward and backward and moves up and down by a drive mechanism (not shown). A high frequency heating coil 50 is disposed above the tank 40 so as to surround the gear 10 to be induction hardened.
The annular nozzle header 60 disposed inside the tank 40 has a large number of nozzle holes 61 formed at predetermined intervals in the circumferential direction of its inner circumferential surface. The liquid is sprayed all at once.

Note that the circular metal plates 70, 70 bonded to both sides of the gear 10 are called concentrating rings, and are used to suppress heating of both sides of the gear 10 and prevent the quenched and hardened layer from wrapping around both sides. be.

After the gear 10 is mounted on the cylinder 20, the gear 10 is first placed inside the high frequency heating coil 50. Next, the high-frequency heating coil 50 is energized and the cylinder 20 is rotated. As a result, the gear 10 rotates inside the high-frequency heating coil 50, and the outer peripheral portion where the teeth are formed is heated. To uniformly heat the outer periphery, gear 1
The number of rotations at 0 is usually several times or more during the heating time.

Immediately after heating the gear 10, the cylinder 20 is lowered and the gear 10 is immersed in the quenching liquid 30 in the tank 40. Then, while positioning the gear 10 inside the nozzle header 60 and injecting the quenching liquid from the nozzle hole 61 of the nozzle header 60,
The cylinder 20 is oscillated in both forward and reverse directions at an appropriately slow speed and moved up and down in the axial direction.

Then, the quenching liquid injected from the nozzle header 60 sufficiently reaches not only the tooth tip 11 of the gear 10 but also the tooth bottom 12. Also, gear 1
By the oscillating rotation of 0, the tooth flanks 13, 1 on either side
3 is also sufficiently exposed to the quenching injection liquid. Furthermore, gear 1
0 is moved up and down in the axial direction, so even if air bubbles occur between the tooth surfaces 13 and 13 as the rotational speed of the gear 10 decreases, the air bubbles will be efficiently discharged from between the tooth surfaces 13 and 13. It will be done. Therefore, the gear 10 has not only its tooth tip 11 but also its tooth bottom 12 and tooth surface 1.
3 and 13, cooling is also promoted, and the quenched hardened layer 14 formed on the tooth bottom 12 and the tooth surfaces 13, 13.
hardness and depth increase.

The rotational speed when rotating the gear 10 in an oscillating manner should be slowed down as appropriate; however, if it is too fast, the quenching injection liquid will not reach the tooth bottom 12, and if the rotational speed is extremely reduced, uniform cooling will not be achieved. Problems arise.

Regarding the swing angle, if the angle becomes large, the gear 10 approaches a rotational motion, and even if the angle is extremely small, the purpose of the swing rotation cannot be sufficiently achieved.
Therefore, the swing angle of the gear 10 is preferably in the range of 30 to 60 degrees.

The width of the vertical movement when the gear 10 is moved up and down in the axial direction is sufficient to fulfill the purpose of vertical movement, and the quenching injection liquid does not reach the bottom 12 and the tooth surface 13 of the gear 10.
1/ of the width of the gear 10 so as to fully reach the gear 13.
It is preferable to increase the amount by 2 to 1 times.

For the same reason, the vertical movement period is preferably 2 to 10 seconds.

After the gear 10 has been hardened, the cylinder 2
0 to its original position and remove the gear 10 from the cylinder 20.

FIG. 3 is a graph showing the hardness distribution in the depth direction of the tooth bottom of a gear that has been hardened, for the conventional method and the method of the present invention. The gear is a module 5 helical gear made of S45C with a diameter of 330 mm and a width of 80 mm.

Heating is preheating + 270kw for both the conventional method and the present invention method.
It was conducted for 30 seconds at 10kHz. During cooling, in the conventional method, the gear was continuously rotated in one direction under the above conditions. In the method of the present invention, the gear is given rocking rotation and vertical movement in the axial direction, and the conditions are a rocking angle of 30 degrees, a rocking period of about 8 seconds, a vertical movement width of 40 mm, and a vertical movement period of 8 seconds. Quenching fluid is coolant UQA5%, 30℃
It was used.

The effective hardness of the quench-hardened layer is 450Hv or more in Witzkers hardness and 45HRc or more in Rockwell hardness.As shown in Figure 3, the effective quenching depth at which this hardness is ensured is The diameter is 1.2 mm, but it is increased to 1.5 mm by the method of the present invention. Furthermore, the method of the present invention achieves a significant improvement in hardness throughout the entire depth direction.

In the above embodiments, the gears were immersed in the quenching liquid during cooling, but the gears may also be cooled by only spraying the quenching liquid.

<Effects of the Invention> The method for induction hardening gears according to the present invention can supply a sufficient amount of quenching liquid not only to the tooth tips but also to the tooth bottoms and tooth surfaces, thereby reducing the quenching that is formed on the tooth bottoms and tooth surfaces. Increasing the hardness and depth of the hardened layer has a significant effect on improving the quality of gears.

[Brief explanation of drawings]

Fig. 1 is an explanatory cross-sectional view showing the heating process of an example of the hardening method according to the present invention, Fig. 2 is an explanatory cross-sectional view showing the cooling process, and Fig. 3 is a tooth of a gear after hardening. A graph showing the hardness distribution in the depth direction of the bottom for the conventional method and the method of the present invention, Figure 4 is a plan view showing the cooling process of the conventional method, and Figure 5 is a cross-sectional view of the gear after hardening. be. 10... Gear, 20... Cylinder, 30... Quenching liquid, 40... Tank, 50... High frequency heating coil, 6
0...Nozzle header.

Claims (1)

[Claims] 1. While rotating the gear to be hardened, the outer peripheral portion of the gear where the teeth are formed is heated with high frequency, and then
The gear is immersed in a quenching liquid, and the gear is oscillated in both forward and reverse directions and moved up and down in the axial direction while the quenching liquid is injected from the outer circumferential side of the gear to the outer circumference. An induction hardening method for gears.