JP4235505B2 - Quenching method of inner surface of outer ring of constant velocity universal joint - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to quenching of the inner surface of a cylindrical portion of a bottomed cylinder, for example, quenching of the inner surface of an outer ring of a constant velocity universal joint used in a power transmission mechanism of an automobile.
[0002]
[Prior art]
In a power transmission mechanism from a transmission of a vehicle to a wheel, a constant velocity universal joint is used to transmit power following the movement of a steering device or a suspension device of the wheel. In the constant velocity universal joint, a ball rolls between an inner ring and an outer ring, and the outer ring has an appearance as shown in FIG. The inner surface 2 of the outer ring 1 is subjected to surface hardening by high frequency in order to obtain a required surface hardness.
[0003]
In the case of a cylindrical constant velocity universal joint outer ring as shown in FIG. 1, that is, when the cross-sectional shape does not change in the axial direction, induction hardening is usually performed by moving quenching as shown in FIG. 2 shows a cross section parallel to the axial direction of the outer ring of the constant velocity universal joint, but the coil 3 having a shape along the inner surface 2 to be quenched is as indicated by an arrow upward from the lower end of the section to be quenched. Heating is performed by sequentially moving at a constant speed. The watering device 4 moves in a state adjacent to the lower side of the coil, and the heated portions are sequentially filled with water and quenched. The ball rolls not only on the entire inner surface of the outer ring of the constant velocity universal joint, but only on the race portion. However, due to the arrangement of the coil as described above, quenching is performed over the entire inner surface.
[0004]
The bottomed cylindrical body targeted by the quenching method of the present invention is a typical example of the constant velocity universal joint outer ring as described above, and the following description will be made in principle for the constant velocity universal joint outer ring. In addition, as seen in the example of the constant velocity universal joint outer ring, in the bottomed cylindrical body referred to in the present invention, the bottom portion does not necessarily need to form a closed bottom, and the bottom surface is continuous with the periphery of one end of the cylindrical portion. Is formed, a hole may be formed in the center of the bottom surface, or a small-diameter cylinder may be connected.
[0005]
In this way, when the surface of the race portion of the constant velocity universal joint outer ring is moved and quenched by a normal method, the quenching depth differs depending on the circumferential position of the side surface, but the constant depth from the surface over the entire length of the quenching section in the axial direction. Resulting in a hardened layer. At this time, quenching distortion usually occurs, but complex deformations with different deformation amounts depending on the position in the axial direction often occur. For example, FIG. 6 is a graph showing an example of deformation when the conventional moving quenching method is used, where the horizontal axis is the dimensional difference before and after quenching, that is, the amount of deformation due to quenching, and the vertical axis is the bottom surface. It shows the axial position from the opposite end, that is, the distance from the lower end in FIG. The measurement point is the distance between the opposing surfaces of the three grooves 5 in the cross-sectional view perpendicular to the axial direction of the outer ring of the constant velocity universal joint shown in FIG. 5 (the shape is slightly different from that of FIG. 1), that is, the track The diameter 6 is measured, and the measured values of the three grooves are averaged. Looking at this, the amount of deformation at the top is slightly negative, that is, contracted, but as a whole, it is deformed to become positive, that is, widen as it goes downward.
[0006]
[Problems to be solved by the invention]
The deformation of the material that occurs during the surface hardening as described above is limited because it becomes an obstacle in use, such as if the amount is large, the amount of polishing must be increased and corrected. In the method of surface hardening currently performed, the deformation amount is almost the limit of the limit, and depending on the variation of individual materials, the deformation may exceed the limit amount. Therefore, an object of the present invention is to minimize the deformation accompanying quenching in the surface quenching of the inner surface of the constant velocity universal joint outer ring.
[0007]
[Means for Solving the Problems]
The present invention has been made to solve the above problems, the hardening of the inner surface of the moving quenching by the constant velocity universal joint outer ring water cooling and heating while moving the high-frequency heating coil cooling means in the axial direction, quenching Among the sections, the moving speed in the section having a length of 10% to 50% with respect to the entire length of the section to be quenched from the end of the bottom surface of the outer ring of the constant velocity universal joint is moved in the remaining length section. The depth of the hardened and hardened layer should be kept the same in the quenching section by changing the power supplied to the high-frequency heating coil in response to the change in the speed of movement, and at least 20% larger than the speed of And quenching the inner surface of the outer ring of the constant velocity universal joint .
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The present inventor conducted various tests while changing the conditions when moving and quenching the inner surface of the cylindrical portion of the bottomed cylindrical body such as the outer ring of the constant velocity universal joint, and studied to minimize the deformation caused by the quenching. Possible mechanisms for generating strain by quenching include strain due to residual stress of the material, strain due to thermal stress during quenching, and strain due to transformation stress. Regarding the strain due to the residual stress, the constant velocity universal joint outer ring described above as an example is manufactured by forging, and therefore the residual stress when the material is stretched by forging is inherent. This is because the residual stress in the portion is released due to the temperature rise during the surface quenching, and the balance of the stress inside the material changes to generate strain.
[0009]
As for the strain due to thermal stress, for example, if the entire thickness of a thin plate is heated and cooled, it expands freely during heating and contracts freely during cooling, so that strain due to thermal stress does not occur. However, in the quenching of the inner surface of the constant velocity universal joint outer ring, the inner surface expands due to heating to the quenching temperature and the inner diameter expands, but at higher temperatures, the material softens and does not have strength, so the restraining force by parts other than the surface Therefore, the deformation corresponding to the thermal expansion does not occur. However, when it is cooled, the shrinkage including the amount that should have been thermally expanded occurs, so that the inner surface dimension is finally reduced. As for the strain due to transformation stress, when the inner surface is martensitic transformed by quenching, the volume expands, so that the inner surface dimension is expanded.
[0010]
Strain due to actual quenching occurs in a state where the above-described residual stress, thermal stress, and strain due to transformation are combined. Therefore, in the quenching of the inner surface such as the outer ring of the constant velocity universal joint which is the subject of the present invention, it becomes a problem how these strains are related, but if the influence of strain due to release of residual stress is large, Conceivable. That is, in the example shown in FIG. 6, the amount of deformation due to quenching is the same for the entire quenching condition, so the thermal stress and distortion due to transformation are the same throughout the quenched zone.筈 who is working for. However, it is considered that the influence of the strain due to the residual stress is large because there are a portion where the size is expanded and a portion where the size is shrunk depending on the position of the quenching section as shown in FIG. This is because whether the strain due to the residual stress acts in the expansion direction or the shrinkage direction may vary depending on the position of the quenching section. Furthermore, regarding the magnitude of the distortion, it is considered that the influence of the restraining force due to the form of the material is large. That is, in quenching of a cylindrical portion of a bottomed cylindrical body such as a constant velocity universal joint outer ring, a restraining force is exerted by the bottom portion. Therefore, even when the same strain stress is applied, the deformation amount is small at a location near the bottom portion.
[0011]
Therefore, the present inventor conducted various investigations on how the generation of strain changes depending on heating conditions during quenching of the inner surface of the constant velocity universal joint outer ring. As a result, it has been found that the moving speed of the coil affects the heating conditions. FIG. 7 shows the amount of deformation when the moving speed of the heating coil is made larger than that in FIG. 6, and the measurement points are the same as in FIG. In this case, since the heating power per distance is decreased by increasing the moving speed, the power supplied to the high-frequency heating coil is increased to maintain the thickness of the hardened hardening layer equal. In this case, the strain pattern, that is, the state of expansion deformation and contraction deformation depending on the axial position is basically the same as in the case of FIG. 6, but the degree is changed and the deformation amount is reduced as a whole. On the other hand, although not shown again, when the speed of movement of the heating coil is made smaller than in the case of FIG. 6, the state of expansion deformation and contraction deformation by the axial position is the same as in FIG. 6, but the deformation amount increases as a whole. .
[0012]
Here, an attempt was made to change the moving speed of the heating coil in the section to be further quenched, and the occurrence of distortion was investigated. FIG. 4 shows the amount of deformation when the moving speed is increased in a part of the section 7 reaching the bottom surface in the case of FIG. 6 in the case of FIG. Same as the case. In this case, since the heating power per distance decreases in the section 7 in which the moving speed is increased, the power supplied to the high-frequency heating coil is increased to maintain the same depth in the entire section where the depth of the hardened layer is quenched. In the example of FIG. 4, attention is paid to the fact that in the section 7 near the bottom surface where the moving speed is increased, what has been contracted before has turned into expansion, that is, positive deformation. Thus, it was found that when the coil moving speed is changed corresponding to the position in the quenching section, the deformation pattern, that is, the positional relationship between expansion and contraction changes, unlike the case of changing the entire quenching section. .
[0013]
As described above, the present invention changes the speed of movement of the heating coil in accordance with the position in the quenching section, and changes the power supplied to the high-frequency heating coil in response to the change in the speed of movement. By doing so, the thickness of the hardened and hardened layer is equally maintained within the quenching section. As a result, in the moving quenching of the inner surface of the cylinder portion to the bottomed cylinder, the amount of distortion can be reduced by effectively changing the distortion occurrence state. It is presumed that the change of the release state of the residual stress is related to the reason that the pattern of expansion and contraction at the section position changes when the moving speed of the heating coil is changed. Even if the moving speed of the coil is changed for the entire quenching section, the pattern of expansion and contraction in the section position does not change so much. For example, the contracted portion does not turn into expansion due to a change in the moving speed of the coil. As described above, the influence of the moving speed of the coil on the thermal strain and transformation strain is considered to be relatively small. That is, when the ratio of thermal strain or transformation strain changes over the entire quenching section, the tendency of either expansion or contraction should appear uniformly weighted over the entire quenching section. However, since this is not the case in reality, the effect of residual strain is considered to be large.
[0014]
Accordingly, when the moving speed of the coil is increased in a part of the quenching section, the release of the residual stress is reduced in this section, so that the occurrence of distortion in the section is reduced. Therefore, as shown in FIG. 6, when this section 8 tends to generate shrinkage strain, shrinkage due to quenching is reduced. For this reason, it is considered that it eventually drags to the location of the adjacent expansion strain and finally expands slightly as in the section 7 shown in FIG. In the present invention, a bottomed cylindrical body is used as an object to be quenched, but the bottom portion exerts a restraining force on the adjacent cylindrical portion and acts to reduce quenching strain. Although the bottomed cylinder is usually manufactured by forging, it undergoes a complicated deformation process, so that the residual stress is not uniform in the length direction of the cylindrical portion. The present invention is an effective technique for quenching such materials.
[0015]
By the way, if the moving speed of the coil is increased at a part of the quenching section as described above, the amount of power input per moving distance is reduced at that part. For this reason, the quenching depth of the part becomes shallow as it is. In order to compensate for this, the heating energy per moving distance may be kept equal by changing the power supplied to the high-frequency heating coil in response to changes in the moving speed of the coil. In this case, there is little change in the state of occurrence of distortion due to the change in power of the coil. Therefore, it is possible to avoid a change in the depth of the hardened hardened layer by changing the state of occurrence of distortion by changing the moving speed of the coil in a part of the quenching section.
[0016]
Although the depth of the hardened hardened layer is kept the same by changing the power supplied to the high frequency heating coil in response to the change in the moving speed of the heating coil as described above, the occurrence of strain is heated. The reason depends on the speed of movement of the coil, but it is considered that the time factor of the thermal cycle greatly affects the generation of distortion. In other words, the heated material is cooled by the water jet nozzle that moves with the coil, but if the moving speed of the coil is slowed down, the cooling start time is also slowed down. It will reach. On the other hand, when the power of the coil is increased, the coil is rapidly heated to the quenching temperature and the temperature range widens and the depth of the hardened hardened layer increases. Narrower than when the speed is reduced. For this reason, even if the input power per moving distance of the heating coil is increased, it is considered that the amount of distortion does not increase when the power of the coil is used. That is, since the release of the residual stress proceeds even in the portion heated to a temperature lower than the quenching temperature in the material, it is estimated that the release of the residual stress further proceeds under the condition where the heat cycle time is long.
[0017]
As described above, this is a specific method of changing the heating coil moving speed and the power supplied to the high frequency heating coil in accordance with the position in the quenching section. However, the entire length of the quenching section is divided into two or more. In each section, the speed of movement and the power supplied to the high-frequency heating coil may be different from the speed of movement and power supplied in adjacent sections. In the example shown in FIG. 4, the entire length of the quenching section is divided into two, and the moving speed in the section of 34% length from the end on the bottom surface side of the cylinder is moved in the remaining length section. It is 60% larger than the speed. For the quenching of the inner surface of the constant velocity universal joint outer ring, etc., it is divided into two at a position of 10% to 50% from the bottom side end of the cylinder relative to the total length of the quenching zone, and the moving speed of the bottom side zone is set. What is necessary is just to make it 20% or more larger than the moving speed in the remaining length section. If the division position of the section deviates from the position of 10% to 50% from the bottom side, a sufficient effect cannot be obtained, and the rate of increasing the movement speed of the section on the bottom side is the speed of movement in the remaining length section. If it is less than 20%, a sufficient effect cannot be obtained. Note that the upper limit of the rate of increasing the moving speed is sufficient up to 2.5 times. In addition, the moving speed of the heating coil and the change of the supplied power may not be changed suddenly as in the previous example, but may be changed continuously.
[0018]
【Example】
The inner surface of the constant velocity universal joint outer ring was quenched. Although the method shown in FIG. 2 was performed by moving quenching, the distance in the axial direction of the portion to be quenched was 50 mm, and the portion at the back from the position 16 mm from the end opposite to the bottom portion was quenched. The material of the member is S45C, and the frequency of the coil power supply is 60 kHz. The track diameter 6 shown in the cross section of the constant velocity universal joint outer ring in FIG. 5 was examined by the surface quenching. In the graph of FIG. 3, the horizontal axis represents the average value of the track diameter before quenching and the vertical axis. The axis | shaft has shown the axial direction position from the edge part on the opposite side to a bottom face. Although there are variations among the three track diameters of a single member, and variations among a plurality of members, the tendency is almost the same, and FIG. 3 shows an average value of these. As seen from this, the track diameter is not uniform in the axial position even before quenching, and the size is slightly larger at the position near the bottom.
[0019]
FIG. 4 shown above shows the amount of change in the track diameter when quenched by the method of the present invention, depending on the position of the member in the axial direction. The actual dimensions after quenching are as shown in FIG. 4 is added to the dimension shown in FIG. In the example of FIG. 4, the moving speed of the coil in the section 17 mm from the side where the bottom is located (34% of the length of the quenching section of 50 mm) is 14 mm / sec, and the moving speed of the coil in the remaining section is 8.75 mm / sec. Seconds (the speed of the section with the bottom increased by 60%). That is, as the quenching progressed toward the side with the bottom, the moving speed was increased from the middle. The depth of the hardened layer was set to a range of 450 HV or higher (hardness before quenching was about 300 HV), and the voltage of the heating coil was adjusted so that the hardened layer was maintained at 1.9 mm from the surface in the entire hardened zone. That is, the coil voltage in the section where the coil moving speed is increased is 180V, and the coil voltage in the remaining section is 120V.
[0020]
On the other hand, FIG. 6 shown above is a comparative example which is a conventional method, and shows the amount of change in the track diameter when quenched, by the position in the axial direction of the member. The moving speed of the coil and the coil voltage are constant throughout the entire quenching period, and are 7.5 mm / second and 100 V, respectively. Other conditions such as the type of member are the same as those in FIG. 4, and the depth of the hardened layer is also the same. FIG. 7 shown above is also a comparative example, in which the moving speed of the coil and the coil voltage are changed constant throughout the entire section. That is, the moving speed of the coil and the coil voltage are 12 mm / second and 150 V, respectively. Other conditions are the same as those in FIGS. 4 and 6, and the depth of the hardened layer is also the same.
[0021]
In the example of the present invention shown in FIG. 4, the dimensional change due to surface quenching is in the expansion direction in the entire section, but the variation in the amount is relatively small. On the other hand, in the comparative example of FIG. 6, the dimensional change due to surface quenching has a section in the expansion direction and a section in the contraction direction, and the variation due to the amount of dimensional change and the position of the section is large. In the comparative example of FIG. 7, the amount of dimensional change is small because the moving speed of the coil is increased in all the sections, but there is no difference from the example of FIG. 6 in that there are a section in the expansion direction and a section in the contraction direction. As a result, the variation in the amount of dimensional change due to the section position is considerably large.
[0022]
【The invention's effect】
As described above, the present invention moves and quenches the inner surface of the cylindrical portion of the bottomed cylinder such as the constant velocity universal joint outer ring, and the position within the section where the power supplied to the high frequency heating coil is quenched. By changing the thickness of the hardened layer in accordance with the thickness of the hardened layer, it is possible to keep the thickness of the hardened and hardened layer equal in the quenching section and to minimize the deformation caused by the quenching. As a result, in a mass-produced product, variation in dimensions between individual members can be reduced, and production efficiency can be improved by reducing the amount of polishing for dimensional correction.
[Brief description of the drawings]
FIG. 1 is an external view of a constant velocity universal joint outer ring. FIG. 2 is a cross-sectional view illustrating induction quenching by moving quenching. FIG. 3 is a graph showing an average value of track diameters before quenching. Fig. 5 is a cross-sectional view perpendicular to the axial direction of the constant velocity universal joint outer ring. Fig. 6 is a graph showing the change in track diameter when quenched by the method of the comparative example. Graph showing amount [FIG. 7] Graph showing amount of change in track diameter when quenched by the method of the comparative example [Explanation of symbols]
1 Constant velocity universal joint outer ring 2 Inner surface 3 Coil 4 Sprinkler 5 Groove 6 Track diameter 7, 8 Section

Claims (1)

In quenching of the inner surface of the outer ring of the constant velocity universal joint by moving quenching in which the high-frequency heating coil and the cooling means are moved in the axial direction while heating and water cooling , the bottom side of the outer ring of the constant velocity universal joint in the quenching section The movement speed in the section having a length of 10% to 50% with respect to the entire length of the section to be quenched from the end of the edge is made 20% or more larger than the movement speed in the remaining length section , and The inner surface of the outer ring of the constant velocity universal joint is characterized in that the power supplied to the high-frequency heating coil is changed in response to the change in the speed so that the depth of the hardened and hardened layer is kept the same in the quenching section. Quenching method.

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