JPH0826400B2 - Stable quenching and cooling method for the root and bottom end surfaces - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a tooth root and a tooth bottom end surface in the case where all tooth shapes of an outer gear or an internal gear are rapidly cooled and quenched by one-shot heating using a high frequency induction heating coil. To a method for stable quenching and cooling of parts.

(Prior art) When all teeth of an outer gear or an internal gear (hereinafter referred to as a gear) are to be quench hardened, it is usually the fourth gear.
As shown in FIG. 3A, the high-frequency induction heating coil C (hereinafter referred to as a heating coil), which is supplied with power from a power source of a predetermined frequency, maintains the upper end surface and the lower end surface vertical to the axial direction of the gear G horizontally, Face the outer or inner circumference where the tooth profile is formed, and add the tooth top gt, tooth flank ga, root portion of each tooth profile.
Cooling injected from the cooling fluid injection hole s formed on the peripheral surface facing the gear G of the cooling jacket that is induction-heated from the gr to the tooth bottom part gb and is replaced by the heating coil C or the position of the heating coil C and displaced. The fluid is struck on the heating surface to quench and quench.

(Problems existing in the related art) Conventionally, when gear G is one-shot hardened, the tooth top
Since the gt and tooth flank ga are close to the heating coil C or the cooling jacket, the temperature rise is sufficient and the cooling is also sufficient, so that a hardened layer is easily formed. On the other hand, from the root portion gr to the bottom portion gb, there is a distance from the heating coil C and the mass is large, so the heating action is thin. Especially, the root part gr is hard to be heated due to the behavior of magnetic flux. Of course, heating is done at the root
r, the bottom of the tooth gb is raised at least above the quenching temperature as a guide, since it is performed after selecting the predetermined frequency, there is no problem with heating itself, but the root portion gr, the bottom of the tooth The heating temperature of gb is the tooth top gt and the tooth abdomen ga
In order to avoid overheating, the temperature cannot be sufficiently higher than the quenching temperature. Therefore, sufficient quenching is required to form a quench hardened layer on the tooth root portion gr and the tooth bottom portion gb. However, the tooth root portion gr and the tooth bottom portion gb have a larger distance from the cooling fluid injection hole s than the tooth top portion gt and the tooth abdomen ga, and if the injection pressure of the cooling fluid fluctuates even slightly,
Immediately, there is a possibility that the quenching finish may vary. In particular, the decrease of the injection pressure has a great influence on the end surface portions of the tooth root portion gr and the tooth bottom portion gb, and the quenching pattern is as shown by the double-hatched portion h in FIGS. 4 (a) to 4 (c). In this case, the quench-hardened layer on the lower end surface tends to have a bottom shape, and the hardened layer on that portion is extremely thin or is not quenched.
The so-called burn-through occurs, resulting in a partial lack of strength, and the gear G in use begins to break in the direction indicated by the arrow in FIG. 5 and causes an accident. It was a problem.

(Progress of Invention) The present invention relates to the behavior of the cooling fluid during quenching,
It was completed based on the results of the following analysis.

Originally, the cooling fluid after hitting the tooth profile of the gear G with the upper end surface and the lower end surface vertical to the axial direction of the gear G is horizontal, exceeds the upper end edges of the root portion and the bottom portion on the upper side. It escapes in the radial direction, and on the lower side, it flows down as it is from the lower edges of the root part and the root part according to gravity. Therefore, when the injection pressure of the cooling fluid is strong, the surface to be heated is cooled only by the direct impact cooling ability of the cooling fluid, and the tooth top portion gt and the tooth flank portion ga, as well as the tooth root portion gr, Also on the tooth bottom portion gb, a quench hardened layer having a substantially uniform depth is formed in the width direction of the gear G.

However, as described above, the root portion gr and the tooth bottom portion gb are large in distance from the cooling fluid injection hole s and the heating temperature is relatively low.
Shows a sensitive reaction to a decrease in injection pressure.

That is, when the injection pressure of the cooling fluid is slightly reduced, a large amount of the heated cooling fluid after the impingement on the surface to be heated follows the arrow from the lower end side due to the action of gravity as shown in FIG. 4 (a). The vertical output flows downward from the edge, and from the upper end side, the output of the cooling fluid that still retains cooling capacity along the upper end face weakens, causing a slight stagnation on the upper end face. The formation of a hardened layer pattern h having a ship bottom shape at the lower end and a delta shape at the upper end is observed.

Further, when the injection pressure of the cooling fluid further decreases, as shown in FIG. 4 (b), from the lower end side, a larger amount of the cooling fluid heated after the surface to be heated hits the arrow due to the action of gravity. As a result, the cooling fluid, which has a low cooling capacity, stagnates at the upper end surface and slightly escapes in the radial direction from the upper end side. The formation of a hardened layer pattern h and a thin hardened layer h along the upper end surface is observed.

Further, when the injection pressure of the cooling fluid decreases, as shown in FIG. 4 (c), from the lower end side, most of the heated cooling fluid after the impingement on the surface to be heated follows the arrow due to the action of gravity. It flows down vertically from the edge and from the upper end side, the cooling fluid without cooling capacity only slightly overflows in the radial direction along the end face, so both upper and lower end parts ..... especially the lower end part Is sometimes observed, and sometimes the bottom edge is not cured at all ..........................................,.

The behavior of the cooling fluid was analyzed as described above. From the analysis result, it is preferable that the delta hardened layer formed at the upper end portion shown in FIG. 4 (a) improves the strength of the portion. On the other hand, the bottom bottom hardened layer pattern at the lower end must be avoided as described above.Therefore, regardless of the injection pressure of the cooling fluid, the root portion gr and the bottom portion g are always
The present invention was completed based on the idea that by forming delta type hardened layers on both upper and lower ends of b, the mechanical strength of the part can be dramatically improved.

(Object of the Invention) The present invention has been made to solve the above-mentioned problems existing in the conventional quenching and cooling method when all tooth shapes of the outer gear or the internal gear are subjected to one-shot heating / quenching by using a high frequency induction heating coil. It is possible to form a quench hardened layer with a sufficient depth on the end surface of the root and bottom of the tooth.
Thus, it is an object of the present invention to provide a stable quenching and cooling method for the root and the bottom of the gear that can improve the mechanical strength of the gear.

(Structure of the Invention) The structure of the present invention is as follows: (1) The heating coil is opposed to the tooth profile of the entire circumference of the outer gear or the inner gear mounted with the upper end surface and the lower end surface perpendicular to the axial direction of the gear horizontal. In one-shot quenching in which heating is performed and then cooling fluid is jetted from the direction opposite to the tooth profile for rapid cooling, the cooling fluid after impacting the tooth profile overflows along the upper end surface and the lower end surface perpendicular to the axial direction of the gear. In addition to the setting, (3) the stable quenching and cooling method of the tooth bottom is characterized in that the cooling fluid overflow amount or cooling capacity in each of the upper and lower directions is set to be substantially equal.

(Effect of the Invention) The present invention is designed such that the cooling fluid injected into the heated gear having the upper end surface and the lower end surface vertical to the axial direction of the gear is horizontal from the lower end surface edge due to gravity after impact on the heated surface. It has the effect of preventing vertical flow-down and allowing the cooling fluid to substantially and equally cool near the upper and lower ends of the tooth root and the tooth bottom, and then to overflow along the upper end surface and the lower end surface.

(Example) The present invention will be described in detail below according to the example shown in FIG.

In the figure, G is an internal gear, C is a heating coil, s is a cooling fluid injection hole provided on the outer periphery of the heating coil C, and 1 and 2 are lower and upper cooling fluid guide plates, respectively.

The lower and upper cooling fluid guide plates 1 and 2 are heating coils C.
Which is not affected by the magnetic flux generated from the gear G and can withstand the radiant heat of the gear G that heats up. Is at least sufficiently smaller than the inner diameter of the gear G, and is slightly smaller than the outer diameter of the heating coil C in this embodiment. The lower and upper cooling fluid guide plates 1 and 2 are arranged substantially parallel to each other on the lower and upper end faces of the gear G with different gaps. More specifically, the size of the gap cannot be quantitatively set based on the flow rate relationship of the cooling fluid, but the relationship of lower gap <upper gap is always maintained. Thus, each of the gaps constitutes the outflow passages 31 and 32 that overflow toward the outer circumference of the gear G after the cooling fluid injected from the cooling fluid injection hole s after heating hits the tooth profile. The gaps that form the passage 31 and the outflow passage 32 are set so that the overflow amount or cooling capacity of the cooling fluid is substantially equal in the upper and lower directions of the end surface of the gear G, for example, by an experiment or calculation performed in advance before the heat treatment. To be done.

It should be noted that the lower cooling fluid guide plate 1 is integrated with, for example, the heating coil C via a connecting member, and the upper cooling fluid guide plate 2 from the operation such as loading / unloading of the gear G or raising / lowering of the heating coil C. Has an appropriate design such that it can be displaced upward or laterally by a displacement mechanism, and any means for displacement can be used as long as it occupies a predetermined position at least during quenching and cooling.

Further, the material of the cooling fluid guide plates 1 and 2 may be one that can withstand radiant heat in the process of carrying the gear G into the cooling station after heating it with the heating station.

(Experimental Example) The present inventor conducted the following experiment in order to confirm the effect of the present invention.

Specimen: Internal gear Material; S48C shape; Outer diameter …………………… 799mm Inner diameter ………………… 689mm Standard pitch circle diameter ………………… 721mm Module ……… 10 Number of teeth ……………………………………………………………………………………………………………… nor against regardless at [95 mm] Experiment method: Two pieces of the above-mentioned specimens are used, and upper and lower cooling fluid guide plates are arranged in the specimen A as shown in FIG. Cooling according to the method of the present invention is performed, B specimen is cooled according to the conventional method, all other conditions are the same conditions shown in the next section, while rotating each of the specimens A and B, After quenching, and then tempering at a temperature of 180 ° C., an accuracy test was performed.

☆ Quenching conditions: The conditions were as follows.

Common conditions for specimens A and B Power supply: Frequency ……………… 3KHz Output ……………… 580Kw Heating ； Time ……………… 98sec Cooling: Time ……………… 100sec Coolant ………… ………… PVA 3.2% Tank pressure ………… 3.1Kg / cm ² Water temperature ……………… 28 ℃ Applicable conditions for sample A only Coolant fluid outflow channel (gap) Lower ……………… 30mm Upper …… ……………… 40mm However, this is the result of making the amount of cooling liquid overflow from the lower and upper gaps the same prior to the experiment.

☆ Probability test: Specimens A and B that have been quenched and tempered
The tooth root cut surface of the test piece tooth profile cut out from each arbitrary position was macro-etched and subjected to a total hardened layer depth observation test and a hardness measurement test. The measurement positions in the hardness measurement test were positions at distances of 1, 3 and 10 mm from the chamfering edges of the upper and lower end faces and the gear width center position, and were measured from the surface to the depth direction.

☆ Test results: ○ Depth observation test of all hardened layers; Test results of each of the specimens A and B are shown in FIGS. 2 (a) and 2 (b). In the figure, a portion which is deeply discolored from the viewpoint of observation, that is, a portion which is recognized as an effective hardening layer is shown as H in black and a portion which is lightly discolored, that is, a portion which is recognized as a heat-affected layer is shown as he in dotted form is there.

Although the heat-affected layer he has almost the same pattern in both figures, it is confirmed that the effective hardened layer HH is formed in the delta shape on the upper and lower end surfaces of the sample A on which the method of the present invention is carried out. Then, in the sample B which was subjected to the conventional method, the formation of a substantially semicircular shape at the upper end surface portion and the ship bottom shape at the lower end surface portion were observed.

○ Hardness measurement test; the measurement results are plotted on a chart with the hardness on the vertical axis and the distance from the surface on the horizontal axis, and the upper end surface portion, the center, and the lower end surface portion of the specimen A are each shown in FIG.
In (c), and the upper end surface portion, the center, and the lower end surface portion of the specimen B are displayed as line graphs in FIGS. 3 (d) to (f), respectively, in order to compare the same positions, (a) and (d) ), (B) and (e) and (d) and (f) are posted on the same page.

From the HRc45 level, which is the effective hardness indicated by the broken line in each figure, and the distance from the surface above the level at the measurement position written and displayed, the depth indicating the effective hardness or higher is in the center of both specimens. Both A and B are exactly the same, but both specimens A and B show a marked difference in the upper and lower end face parts. That is, in the specimen A on which the method of the present invention was carried out, the deeper the effective hardness was, the closer it was to both end surfaces, whereas on the specimen B on which the conventional method was carried out, the effective hardness range was Extremely shallow,
In particular, it is clear that the tendency is remarkable at the lower end surface portion.

From the above experimental results, it was proved that the present invention uniformly and sufficiently cools the upper and lower end surfaces of the root portion gr and the bottom portion gb of which cooling action is unstable and forms a deep effective hardened layer.

(Other Embodiments) In the above embodiment, an example in which the cooling fluid guide plates 1 and 2 are arranged facing each other on the upper and lower end surfaces of the gear G has been described, but the injection pressure of the cooling fluid is relatively stable. If it can be maintained, the cooling fluid guide plate may be simply opposed to the lower end surface, and the cooling fluid may be allowed to naturally overflow beyond the end surface on the upper end surface side. In this case, the clearance between the cooling fluid guide plate and the gear end surface, which are arranged opposite to the lower end surface, is substantially equal to the natural overflow rate or cooling capacity of the cooling fluid overflowing through the clearance toward the upper end surface. Will be adjusted accordingly.

In the above embodiment, the cooling fluid guide plate is an annular plate material. However, when the heating station and the cooling station are separate, the upper and lower cooling fluid guide plates may be disk members, and the coil C is a cooling fluid. If the structure is provided with the injection holes s and heating / cooling is performed at the same position, it may be appropriately designed such that one of the cooling fluid guide plates is a disc material in consideration of the carry-in / out or relative movement relationship. .

Further, in the above-mentioned Examples and Experimental Examples, the case where the method of the present invention is applied to the internal gear has been described, but the method of the present invention is also applied to the outer gear. In this case, since the jetting of the cooling fluid is in the axial direction, only the point that the cooling fluid after cooling the surface to be heated overflows in the outflow passage 3 in the axial direction, and of course the same action and effect can be obtained. Is.

Although the heating coil C also serves as a cooling jacket in the embodiment, the present invention can be applied without any problems even when the gear G after heating is replaced by the position of the heating coil C and cooled by the displaced cooling jacket. To be done.

(Effects of the Invention) According to the present invention, all-tooth tooth one-shot heating / quenching of the outer gear or the internal gear performed by using the high-frequency induction heating coil does not only form a predetermined hardening layer on the tooth top and tooth flank. Not only that, the root and bottom of the gear, especially both end faces of each, are sufficiently cooled and a deep quench hardened layer is formed in those parts, which dramatically improves the mechanical strength of the gear and damage during use. It is used as a stable quenching and cooling method that can prevent unexpected accidents, and its effect is remarkable.

[Brief description of drawings]

FIG. 1 is a partial sectional front view showing an embodiment of the method of the present invention,
2 (a) and 2 (b) are front views of the root cutting surface macro-etching showing the results of the total hardened layer depth observation test performed on the sample of the present invention and the sample of the conventional method, respectively, in experimental examples. 3 (a)-(c) and (d)-
(F) is a diagram showing the hardness measurement test results of the method-implemented specimen of the present invention and the conventional-method specimen, respectively. FIG. 5 is a front view of a tooth root cut surface for explaining the problems of the conventional method, and FIG. G …… Gear gr …… Gear root gb …… Gear bottom C …… Heating coil 1 …… Lower cooling fluid guide plate 2 …… Upper cooling fluid guide plate 31,32 …… Cooling fluid outflow passage

Claims (3)

[Claims] 1. A heating coil is made to face the tooth profile of the outer gear or the internal gear which is placed with the upper end face and the lower end face perpendicular to the axial direction of the gear horizontal, and then the tooth is cooled from the tooth profile facing direction. In one-shot quenching in which fluid is sprayed and rapidly cooled, the cooling fluid after hitting the tooth profile is set to overflow along the upper end surface and the lower end surface perpendicular to the axial direction of the gear, and the upper and lower directions are respectively set. The method for stable quenching and cooling of the tooth root and the bottom surface of the tooth bottom is characterized in that the cooling fluid overflow amount or the cooling capacity is set to be substantially equal. 2. An adjusted gap is provided between the upper end surface and the lower end surface of the cooling fluid, which are perpendicular to the axial direction of the gear, and a cooling fluid guide plate which is arranged substantially parallel to the both end surfaces, respectively. Claims 1 that each overflow as an outflow passage
The method for stable quenching and cooling of the tooth root and the end face of the tooth bottom described in the item. 3. A cooling fluid guide plate in which the cooling fluid naturally overflows along the upper end surface perpendicular to the axial direction of the gear along the upper end surface and is arranged substantially parallel to the lower end surface facing the lower end surface. The method for stable quenching and cooling of a tooth root and an end surface of a tooth bottom according to claim 1, wherein an adjusted gap between the tooth gap and the tooth gap overflows as an outflow passage.