JP2001226716A - High-frequency hardening method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To assure nearly a uniform hardening depth regardless of a change in thickness by the areas of a work and to drastically reduce hardening distortion. SOLUTION: In the method for high-frequency hardening of an inner peripheral surface of a constant velocity joint outer lace 1 having ball grooves 3 and inner spherical surfaces 4 while injecting a cooling liquid to its outer peripheral surface from a cooling jacket 12, the inside of the cooling jacket 12 is partitioned to plural chambers 24A and 24B in a circumferential direction by partition plates 23 and the chambers 24A corresponding to the ball grooves 3 of the outer lace 1 and the chambers 24B corresponding to the inner spherical surfaces 4 are respectively concentrated and are piped and connected to a cooling liquid supply source 13 via flow rate control valves 27A and 27B. The injection rate of the cooling liquid to the outer peripheral surface of the work corresponding to the ball grooves 3 is made smaller than the injection rate of the cooling liquid to the outer peripheral surface of the work corresponding to the inner spherical surfaces 4, by which the temperature gradient in the thickness direction of the outer lace 1 is controlled and the hardening depth is made uniform between the ball grooves 3 and the inner spherical surfaces.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for induction hardening the inner or outer peripheral surface of a cylindrical work having an unequal thickness.

[0002]

2. Description of the Related Art As this kind of work, for example, FIG.
And an outer race 1 constituting a constant velocity joint as shown in FIG. The outer race 1 is provided in one end of a shaft 2 in a cup shape, and a plurality of ball grooves 3 which are equally arranged in a circumferential direction and extend in an axial direction are formed on an inner peripheral surface thereof. In such an outer race 1, usually, in order to extend the rolling fatigue life of the ball groove 3, the ball groove 3
The surface of the ball groove 3 is induction hardened. However, the inner spherical surface 4 disposed between the ball grooves 3 is also required to have wear resistance. Conventionally, the surface of the ball groove 3 and the inner spherical surface 4 are included. The entire inner peripheral surface of the outer race 1 is induction hardened.

In order to harden the entire inner peripheral surface of the outer race 1 by induction hardening, generally, as shown in FIG. 7 described above, quenching in which a heating coil and a cooling jacket are integrally provided in the outer race 1 is performed. After the means 5 is inserted and the surface of the ball groove 3 and the inner spherical surface 4 are heated to a predetermined temperature by the heating coil, a quenching liquid is injected from the cooling jacket to cool the heated surface.

In the outer race 1 of the above constant velocity joint, a groove (boot groove) 6 for mounting a boot is formed in advance on the outer peripheral surface on the distal end side, and such an outer race 1 is simply formed by a heating coil. When heated from the inside, in the thin portion A corresponding to the bottom of the ball groove 3, the quenched layer reaches the bottom of the boot groove 6, stress is concentrated at the corner in the boot groove 6, and quenching cracks are easily generated. Become.

Therefore, conventionally, as shown in FIG.
The outer race 1 as a work is surrounded by an annular cooling jacket (outer peripheral cooling jacket) 7, and the cooling liquid is injected from an injection port 8 formed on the inner peripheral wall of the outer peripheral cooling jacket 7 during heating and cooling by the quenching means 5. And induction hardening is performed while uniformly cooling the outer peripheral surface of the outer race 1. According to such an induction hardening method, the quenching depth becomes shallow, and the quenched layer does not reach the bottom of the boot groove 6, so that the occurrence of the above-mentioned quenching cracks is prevented beforehand. become.

[0006]

However, the work (outer race) 1 having the unequal thickness portion as described above.
According to the outer peripheral surface of a method of induction hardening while uniformly cooled, as shown in FIG. 9, the outer circumferential surface temperature T ₀ of the workpiece 1
Since but a constant, the temperature gradient in the thickness direction connecting the maximum heating temperature T ₁ of the inner peripheral surface of the outer peripheral surface temperature T ₀ and the workpiece 1, the direction of the thin portion A corresponding to the bottom of the ball groove 3 It becomes considerably sharper than the thick portion B side corresponding to the inner spherical surface 4.
That is, the depth from the inner peripheral surface of the work 1 to the quenching limit temperature T ₂ , that is, the quenching depth, is the quenching depth d _A in the thin portion A is the quenching depth in the thick portion B. considerably thinner than d _B, the depth of the quenched layer S as denoted by 8 two points becomes uneven in the circumferential direction of the workpiece 1. As a result,
There is a problem in that the work 1 is distorted, and the accuracy of the ball groove 3 is inevitably deteriorated, and the ball groove 3 must be repaired by grinding, thereby increasing the cost burden.

In some cases, a method has been proposed in which the inner peripheral surface is induction hardened while cooling only the outer peripheral surface corresponding to the thin portion of the outer race (see, for example, Japanese Patent Laid-Open No. 58-1).
In such a method, the difference between the temperature gradient of the thin portion and the temperature gradient of the thick portion is further increased, and the variation in the quenching depth in the circumferential direction is further increased. The strain is even greater.

The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to secure a substantially uniform quenching depth regardless of a change in wall thickness depending on a part of a work. Accordingly, it is an object of the present invention to provide an induction hardening method and apparatus which can achieve a significant reduction in quenching strain and thereby greatly contribute to a reduction in manufacturing cost.

[0009]

According to the present invention, there is provided an induction hardening method according to the present invention, which cools an outer peripheral surface or an inner peripheral surface of a cylindrical work having an unequal thickness portion with a cooling liquid. In the method of induction hardening the surface opposite to the surface being cooled, the flow rate of the cooling liquid is adjusted so that the quenching depth by the induction hardening is substantially constant on the inner circumferential surface or the outer circumferential surface of the work. It is characterized in that it is changed according to the part of the work.

In the induction hardening method performed in this manner, for example, while the flow rate of the cooling liquid for the thin part of the work is reduced, the flow rate of the cooling liquid for the thick part of the work is increased, thereby cooling the work with the cooling liquid. A temperature difference corresponding to the thickness of the work occurs on the outer peripheral surface or the inner peripheral surface of the work, and the temperature difference in the thickness direction of the work becomes substantially constant regardless of the thickness of the work due to the temperature difference. It is also almost constant. In this case, the temperature of the outer peripheral surface or the inner peripheral surface of the work to be cooled with the cooling liquid is detected, and based on the detected temperature, the flow rate of the cooling liquid is controlled so that the detected point has a preset temperature. This may control the temperature gradient in the thickness direction of the work to a more ideal state.

[0011] In order to achieve the above object, an induction hardening apparatus according to the present invention comprises a quenching means for induction hardening an inner peripheral surface or an outer peripheral surface of a cylindrical work having an unequal thickness portion, and the quenching means. In the induction hardening apparatus including an annular cooling jacket for injecting a cooling liquid onto a surface opposite to the quenching surface by the quenching and a cooling liquid supply source for pumping the cooling liquid to the cooling jacket, the inside of the cooling jacket is circulated. Along with partitioning into a plurality of chambers in the direction, the plurality of chambers are divided into groups according to the thickness of the work, and each group is connected to the cooling liquid supply source via a flow control valve, and further, the cooling jacket and Liquid guide means for guiding the cooling liquid ejected from each chamber of the cooling jacket toward the work is provided between the cylindrical work and the cylindrical work. In the induction hardening apparatus configured as described above, the liquid guide means disposed between the cooling jacket and the cylindrical work concentrates the coolant at a desired flow rate at a corresponding position on the outer peripheral surface or the inner peripheral surface of the work. The temperature gradient in the thickness direction of the work can be controlled to a more ideal state.

[0012]

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

FIG. 1 and FIG. 2 show one embodiment of an induction hardening apparatus according to the present invention. In addition,
Since the workpiece to be hardened in the present embodiment is the outer race 1 constituting the above-described constant velocity joint, the outer race 1 has the same reference numerals as those shown in FIGS. 7 and 8. I will attach it. This induction hardening apparatus is a hardening device for induction hardening the entire inner peripheral surface of the work 1 including the surface of the ball groove 3 and the inner spherical surface 4 and a work receiving table 10 for supporting the outer race (work) 1 upright. Inlet means 11, an annular outer cooling jacket 12 for spraying a cooling liquid to the outer peripheral surface of the work 1, a cooling liquid supply source 13 for pumping the cooling liquid to the outer cooling jacket 12, and an inner peripheral surface of the outer cooling jacket 12. Injection port 14
And a liquid guiding means 15 for guiding the cooling liquid jetted from the nozzle to the outer peripheral surface of the work 1.

The work receiving table 10 has a through hole 16 at the center thereof for inserting the quenching means 11 and an annular recess 17 around which the tip of the work 1 is fitted and supported. Is provided. This work cradle 10
Further, a plurality of liquid discharge ports 18 for discharging the cooling liquid injected from the outer peripheral cooling jacket 12 to the work 1 are provided at positions around the annular concave portion 17.

Here, the quenching means 11 has a triple structure in which a magnetic shielding member 21 such as a silicon steel plate is disposed between a hollow heating coil 19 on the outer peripheral side and a cooling jacket 20 on the central side. The heating coil 19 is supplied with high-frequency current from a high-frequency power supply (not shown), and the cooling jacket 20 is supplied with quenching liquid from liquid supply means (not shown). The cooling jacket 20 is provided with a plurality of injection ports 22 which are directed to the axial direction and the direction inclined to the axis on the upper side, and through which the quenching liquid is injected to the inner peripheral surface of the work 1. become. In addition,
Cooling water is circulated in the heating coil 19.

On the other hand, the inside of the outer peripheral cooling jacket 12 is partitioned into a plurality of chambers in a circumferential direction by a partition plate 23. More specifically, the partition plate 23 places the first chamber 24 </ b> A at a position corresponding to the ball groove 3 of the work 1,
Are positioned such that the second chambers 24B are arranged at positions corresponding to the inner spherical surfaces 4, respectively, so that the inside of the outer peripheral cooling jacket 12 has a plurality of (here, six) first chambers 24A. And the same number of second chambers 24B are divided into a plurality (here, 12) in the circumferential direction. Note that the plurality of injection ports 14 provided on the inner peripheral surface of the outer peripheral cooling jacket 12 are grouped into those that communicate with the first chamber 24A and those that communicate with the second chamber 24B. Become.

The first inside the outer peripheral cooling jacket 12 described above
The branch pipes 26A and 26B branched from the main pipes 25A and 25B connected to the coolant supply source 13 are connected to the chamber 24A and the second chamber 24B, respectively. Each main pipe 26
A and 26B are provided with flow control valves 27A and 27B, respectively, whereby a plurality of first chambers 24A and a plurality of second chambers 24B are provided with flow control valves 27A and 27B, respectively.
A predetermined amount of cooling liquid set by B is supplied independently.

Further, the liquid guide means 15 has an integral structure comprising a plurality of shielding plates 28 arranged radially and a connecting ring 29 for connecting the upper ends of these shielding plates 29 to each other. The liquid guiding means 15 is disposed in an annular space between the outer peripheral surface of the workpiece 1 and the inner peripheral surface of the outer peripheral cooling jacket 12, and has its shielding plate 28 placed on the work receiving table 10. The position is fixed by engaging a projection 28 a on one side edge of the lower end of the workpiece 28 with the outside of the work receiving table 10. The shielding plate 28 is provided on the outer peripheral cooling jacket 12.
The outer peripheral cooling jacket 12 is arranged in the annular space between the outer peripheral surface of the work 1 and the inner peripheral surface of the outer peripheral cooling jacket 12.
The first guide path 30A and the second guide path 30B are formed so as to be partitioned in an arrangement that matches the first and second chambers 24A and 24B. The width of the shielding plate 28 is set so as to form a slight clearance (0.1 to 3.0 mm) between the outer peripheral surface of the work 1 and the inner peripheral surface of the outer peripheral cooling jacket 12. The plurality of drain ports 18 provided in the work receiving table 10 are positioned in the first guide path 29A and the second guide path 29B.

Thus, on the outer peripheral surface of the work 1, the center of the thin portion A corresponding to the bottom of the ball groove 3 of the work 1 and the center of the thick portion B corresponding to the inner spherical surface 4 of the work 1 are located. Temperature sensor (thermocouple) 31 for detecting temperature with position
A and 31B are joined. Each thermocouple 31A, 31B
Is sent to a separately installed control device (not shown), and the control device transmits each thermocouple 31A,
31B, the flow control valves 27A, 27
A signal for controlling B is output.

Hereinafter, a quenching method using the induction hardening apparatus configured as described above will be described. At the time of quenching, the liquid guiding means 15 is previously lifted up,
The work 1 is set on the work receiving table 10, and then the liquid guiding means 15 is lowered from above to move the liquid guiding means 15 to the work receiving table 10.
Place and fix on top. After that, the through hole 1 of the work receiving table 10
The quenching means 11 is inserted into the work 1 from below through 6, and the coolant is supplied from the coolant supply source 13 to the outer peripheral cooling jacket 12 simultaneously with the completion of the insertion. This coolant is
First and second chambers 24 </ b> A, 2 </ b> A in the outer peripheral cooling jacket 12.
From the injection port 14 facing 4B, it is injected to the outer peripheral surface of the work 1 through first and second guide paths 29A and 29B defined by the liquid guide means 15. At this time, one main pipe 25A
The flow control valves 27A and 27B are adjusted so that a relatively small amount of coolant is supplied to the main pipe 25B and a relatively large amount of coolant is supplied to the other main pipe 25B.
A relatively small flow rate of the cooling liquid is applied to the thin portion A (FIG. 3) corresponding to the ball groove 3 of the work 1 and to the thick portion B (FIG. 3) corresponding to the inner spherical surface 4 of the work 1. A relatively large flow of cooling liquid is injected respectively.

Next, a high-frequency current is supplied from a high-frequency power supply (not shown) to the heating coil 19 of the heating means 11, and the inner surface of the ball groove 3 and the inner spherical surface 4 of the work 1 are rapidly heated.
Then, at the same time as the above-described respective surfaces are heated to a predetermined temperature, the current supply to the heating coil 19 is cut off, and at the same time, the injection port 22 of the cooling jacket 20 in the heating means 11 is heated.
Quenching liquid is sprayed from the inside, whereby the inner peripheral surface of the work 1 is rapidly cooled. Meanwhile, during this time, the outer peripheral surface of the work 1 is cooled by the cooling liquid injected from the outer peripheral cooling jacket 12, but as compared with the thin portion A corresponding to the ball groove 3 of the work 1 as described above. Since a relatively small flow rate of the cooling liquid is sprayed onto the thick portion B corresponding to the inner spherical surface 4 of the workpiece 1, a relatively large flow rate of the cooling liquid is sprayed. The outer peripheral surface temperature of the thick portion B is maintained at a relatively high temperature.

That is, the temperature of the outer peripheral surface of the work 1 is as shown in FIG.
As shown in the figure, the portion of the thin portion A corresponding to the ball groove 3
(The part where thermocouple 30A is installed)_0A,
A portion of the thick portion B corresponding to the inner spherical surface 4 (the thermocouple 30B is provided).
Relatively low temperature T _0BAnd as a result,
Outer surface temperature T_0A, T_0BAnd the highest on the inner peripheral surface of work 1
Heating temperature T₁The temperature gradient in the thickness direction connecting
There is no significant difference between the thin portion A and the thick portion B. This
As a result, the quenching limit temperature T _Two Reached
The depth to reach, the so-called quenching depth, is
Quenching depth d_AAnd quenching depth d in thick part B_B And in
As shown in FIG. 3, the depth of the quenched layer S is almost the same.
Are substantially uniform in the circumferential direction of the work 1. Accordingly
As a result, quenching distortion hardly occurs in the work 1 and the ball groove
3 can be used as it is with hardened skin.
Even if grinding is required, only a little grinding is required.

Here, in the present embodiment, during the above-described quenching, the temperature of the outer peripheral surface of the work 1 is reduced by the thermocouples 31A, 31A.
B, and based on these signals, the control device (not shown) determines whether the temperature of a predetermined portion on the outer peripheral surface of the work 1 has reached the set temperature, and has reached the set temperature. If not, a control signal is sent to the flow control valves 27A and 27B to adjust the supply amount of the coolant to the first and second chambers 24A and 24B in the outer peripheral cooling jacket 12. That is, the control device determines the outer peripheral surface temperature T _0A of the portion of the thin portion A (the portion where the thermocouple 30A is installed).
And the outer peripheral surface temperature T _0B of the portion of the thick portion B (the portion where the thermocouple 30B is installed) is feedback-controlled so as to be a set temperature, so that the temperature gradient in the thickness direction of the work 1 is more ideal. Can be controlled.

In the above embodiment, the liquid guiding means 15 has an integral structure comprising the shielding plate 28 and the connecting ring 29 for interconnecting the upper ends of the shielding plates 29. The structure is arbitrary. It is good also as a structure which has the board 28 separately. Further, in the above embodiment, the liquid guiding means 15 is arranged between the work 1 and the outer peripheral cooling jacket 12, but the liquid guiding means 15 increases the distance between the work 1 and the outer peripheral cooling jacket 12. If it is set appropriately, it can be omitted. Further, in the above embodiment, the work 1 having the unequal thickness portion in the circumferential direction is targeted, but the present invention is also applicable to the work having the unequal thickness portion in the axial direction. In this case, the inside of the outer peripheral cooling jacket 12 may be divided in the height direction so that different amounts of coolant are injected in the axial direction.

Furthermore, in the above-described embodiment, the case where induction hardening is performed on the inner peripheral surface of the work 1 has been described as an example. However, the present invention relates to induction hardening on the outer peripheral surface of a cylindrical work. Needless to say, in this case, the quenching means 11 is arranged outside the work, and the outer peripheral cooling jacket 12 and the liquid guiding means 15 are arranged inside the work.

[0026]

EXAMPLE For the outer race 1 of a constant velocity joint having an outer diameter of 82.5 mm, a minimum thickness of the thin portion A of 6 mm, and a thickness of the thick portion B of 12 mm, the above-described portion of the thin portion A (thermocouple) 31A
The temperature T _0A of the outer peripheral surface of the part where the
The outer peripheral surface temperature T _0B of the portion of the thick portion B (the portion where the thermocouple 31B is installed) corresponding to the temperature of 150 ° C., the maximum heating temperature T ₁ on the inner peripheral surface is 1000 ° C., and the quenching limit temperature T ₂ is 850. ° C, and the amount of cooling water supplied to the first chamber 24A of the outer peripheral cooling jacket 12 is set to about 10 l / min, and the amount of cooling water supplied to the second chamber 24B is set to about 3 l / min. Then, induction hardening was performed in the same manner as in the above embodiment. Then, after quenching, as shown in FIG. 3, the minimum thickness portion of the thin portion A of the outer race 1, the thin portion A and the thick portion B
And the depth of the quenched layer S was measured at three places, that is, a boundary part with the thick part B. FIG. 5 shows an example of a control curve of the supply amount of the coolant to the first chamber 24A and the second chamber 24B of the outer peripheral cooling jacket 12, and the set temperature T _0A of the outer peripheral surface of the outer race 1, In accordance with the deviation of the actual temperature from T _{0B, the} flow rate control valves 27A and 27B are controlled along the control curve to adjust the coolant supply amount.

For comparison, the outer peripheral surface temperature T ₀ of the outer race 1 having the same constant velocity joint as above was set to 2
At 50 ° C, the maximum heating temperature T ₁ and quenching limit temperature T
₂ is set to 1000 ° C. and 850 ° C. respectively as above, and the flow rate of the cooling liquid injected from the outer peripheral cooling jacket 7 is set to 40 l / min in the same manner as in the conventional case shown in FIG. In the same manner as described above, the depth of the quenched layer S is determined at three locations, that is, the minimum thickness portion of the thin portion A of the outer race 1, the boundary portion between the thin portion A and the thick portion B, and the portion of the thick portion B. Was measured.

FIG. 6 shows the quenched layer S of the present embodiment and the comparative example.
5 shows the measurement results. From the results shown in FIG.
In the case of the present embodiment, the quenching depth is almost uniform irrespective of the part, whereas in the case of the comparative example, between the thin portion A () and the thick portion B (). A large difference is observed in the quenching depth, and it is clear that the quenching depth on the inner peripheral surface of the outer race 1 varies greatly in the circumferential direction.

[0029]

As described above, according to the induction hardening method according to the present invention, by changing the flow rate of the cooling liquid in accordance with the position of the work, almost no matter the change in the thickness of the work. An even quenching depth can be ensured, quenching strain can be significantly reduced, and grinding finish can be unnecessary or slightly suppressed. This has an effect of greatly contributing to reduction in manufacturing cost. Further, according to the induction hardening device of the present invention, a coolant having a desired flow rate can be intensively jetted to a corresponding portion on the outer peripheral surface or the inner peripheral surface of the work, and the temperature gradient in the thickness direction of the work can be increased. Can be controlled to a more ideal state.

[Brief description of the drawings]

FIG. 1 is a plan view showing a structure of an induction hardening device as one embodiment of the present invention.

FIG. 2 is a sectional view showing a structure of the induction hardening apparatus.

FIG. 3 is a plan view schematically showing the shape of an outer race of a constant velocity joint to be subjected to the induction hardening method, a state of forming a quenched layer for the outer race, and a quenching depth measurement site in the embodiment. FIG.

FIG. 4 is a schematic diagram showing a temperature distribution in a thickness direction of a work when induction hardening is performed by the induction hardening apparatus.

FIG. 5 is a graph showing a control curve of a coolant flow rate used in the present embodiment.

FIG. 6 is a graph showing a measurement result of a quenching depth in an example of the present invention in comparison with a comparative example.

FIG. 7 is a cross-sectional view showing a conventional induction hardening method for an outer race of a constant velocity joint.

FIG. 8 is a plan view schematically showing a shape of an outer race of the constant velocity joint and a state of forming a quenched layer for the outer race.

FIG. 9 is a schematic diagram showing a temperature distribution in the thickness direction of a work by conventional induction hardening.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Work (outer race of constant velocity joint) 3 Ball groove 4 Inner spherical surface 10 Work pedestal 11 Hardening means 12 Peripheral cooling jacket 13 Coolant supply source 15 Liquid guiding means 18 Drain outlet 23 Peripheral cooling jacket partitioning plates 24A, 24B Chamber in cooling jacket 27A, 27B Flow control valve 28 Shield plate of liquid guiding means 30A, 30B Guide path

Claims (3)

[Claims] 1. A method of induction hardening a surface opposite to a surface to be cooled while cooling an outer peripheral surface or an inner peripheral surface of a cylindrical work having an unequal thickness portion with a cooling liquid. An induction quenching method, wherein the flow rate of the cooling liquid is changed in accordance with a part of the work such that a quenching depth by the quenching is substantially constant on an inner peripheral surface or an outer peripheral surface of the work. 2. A temperature of an outer peripheral surface or an inner peripheral surface of a work to be cooled by the cooling liquid is detected, and a flow rate of the cooling liquid is controlled based on the detected temperature so that the temperature of the detected portion becomes a preset temperature. The induction hardening method according to claim 1, wherein: 3. A quenching means for induction hardening the inner peripheral surface or the outer peripheral surface of a cylindrical work having an unequal thickness portion, and a coolant is injected to a surface opposite to the quenching surface by the quenching means. In an induction hardening apparatus including an annular cooling jacket and a cooling liquid supply source for pumping a cooling liquid to the cooling jacket, the inside of the cooling jacket is partitioned into a plurality of chambers in a circumferential direction, and the plurality of chambers are worked. Each group is connected to the cooling liquid supply source via a flow control valve, and is further ejected from each chamber of the cooling jacket between the cooling jacket and the cylindrical work. An induction hardening device, wherein liquid induction means for guiding a cooling liquid to be directed toward a workpiece is provided.