JP4969286B2 - Moving quenching method and moving quenching apparatus - Google Patents

Description

  The present invention relates to a moving quenching method and a moving quenching apparatus for quenching while moving an axial workpiece having a rack portion in the axial direction.

  As a method of quenching a long shaft-like member such as a screw shaft used in a ball screw mechanism, for example, as described in Patent Document 1, the shaft-like member is rotated in a high-frequency non-oxidation quenching apparatus. While moving in the axial direction, the surface of the shaft-shaped member moved in the axial direction is heated by a high-frequency induction heating coil provided in the high-frequency non-oxidation quenching apparatus, and a coolant is sprayed onto the surface of the heated shaft-shaped member. In some cases, the surface of the shaft-like member is subjected to a quenching treatment in a non-oxidized state.

Since the shaft-shaped member is like a screw shaft having substantially the same cross-sectional shape over the entire length, the shaft-shaped member is heated under the same conditions over the entire length of the shaft-shaped member. Quenching with a uniform quenching depth and quenching hardness over the entire length of the member can be performed with little difficulty.
JP-A-11-21619 (paragraphs 0010 to 0012, FIG. 1)

  On the other hand, in the case where the target workpiece to be quenched has a rack portion having a cross-sectional shape different from that of the ball screw groove portion, such as a ball screw shaft used in an electric power steering device, for example, both axial ends of the rack portion When the step portion is formed in the portion, there is a problem that it is difficult to put the quenching hardness and the quenching depth of the rack portion within predetermined standards.

  That is, as shown in FIG. 8, the rack portion 13 is connected to the cylindrical shaft portion 11 via the steps 17 and 18, so that the end portion of the rack tooth 15 is heated at a high frequency. When passing through the coil, the current concentrates on the corners 17a and 18a of the steps 17 and 18, and the current does not easily flow through the rack teeth 15, so that the ends of the rack teeth 15 are sufficiently heated. There is a risk of disappearing. In addition, when the high-frequency heating coil has a ring shape that surrounds the rack portion, the gap amount between the high-frequency heating coil changes between the rack teeth 15 and the back side 16 of the rack teeth 15. If the quenching conditions are changed so that the quenching depth of the rack teeth 15 becomes shallow and the quenching depth and quenching hardness of the rack teeth 15 are within the specifications, this time, the quenching depth of the rear side 16 is changed. In addition, there is a difficult problem that the quenching hardness deviates from the standard.

  For this reason, in a shaft-shaped workpiece having a rack part, the rack teeth of the rack part and the circumferential part including the back side are separately heated using a divided high-frequency heating coil with different output power, etc. Therefore, there is a problem that the structure of the quenching apparatus becomes complicated and the equipment cost increases.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a moving quenching method and a moving quenching apparatus that can eliminate the above-described conventional problems by shifting a heating device with respect to the workpiece in the radial direction of the workpiece. .

  In order to solve the above-mentioned problem, the feature of the invention according to claim 1 is that a shaft-like workpiece having a rack portion on which rack teeth are formed is heated while moving up and down relatively in the axial direction, and then cooled, In the moving quenching method in which the surface of the workpiece is subjected to a quenching treatment, the surface of the workpiece is moved while moving the workpiece relatively in the axial direction in the center of a high-frequency heating coil having a substantially annular heating portion. The high-frequency heating coil is heated with respect to the workpiece when the workpiece is relatively moved to a position where the high-frequency heating coil corresponds to an end of the rack tooth of the workpiece. The rack teeth are moved closer to the high-frequency heating coil so that the relative movement speed in the axial direction of the workpiece and Control at least one of the output power of the high-frequency heating coil, and after the end portion has passed the position corresponding to the high-frequency heating coil, the high-frequency heating coil is shifted relative to the workpiece in the radial direction of the workpiece. With the workpiece returned to the center of the high-frequency heating coil, the workpiece is relatively moved in the axial direction so that the surface of the rack portion including the rack teeth is heated by the high-frequency heating coil. It is a moving quenching method.

  A feature of the invention according to claim 2 is the moving quenching method according to claim 1, wherein the heating portion of the high-frequency heating coil is configured in a substantially horseshoe shape complemented to a cross-sectional shape perpendicular to the axis of the workpiece.

  According to a third aspect of the present invention, in the first or second aspect, the workpiece has a ball screw groove portion, and when the ball screw groove portion is heated by the high-frequency heating coil, the workpiece is rotated. This is a moving quenching method in which relative movement in the axial direction is performed.

  A feature of the invention according to claim 4 is that a shaft-like workpiece having a rack portion in which rack teeth are formed is heated while being moved relatively up and down in the axial direction, and then cooled, and the surface of the workpiece is quenched. A high-frequency heating coil having a substantially annular heating part for heating the surface of the workpiece, and a moving means for moving the workpiece up and down relatively in the axial direction relative to the high-frequency heating coil. And a shift that causes the high-frequency heating coil to shift relative to the work in the radial direction of the work when the work is relatively moved to a position where the high-frequency heating coil corresponds to an end of the rack tooth. And relative to the workpiece in the axial direction in a state where the high-frequency heating coil is shifted relative to the workpiece in the radial direction by the shift means. A moving quenching apparatus and a control means for controlling at least one of the output power of the dynamic speed and the high-frequency heating coil.

  The invention according to claim 5 is characterized in that, in claim 4, the heating portion of the high-frequency heating coil is configured in a substantially horseshoe shape complemented to the cross-sectional shape perpendicular to the axis of the workpiece, and the high-frequency heating coil is formed by the shift means. This is a moving quenching apparatus in which the substantially linear portion of the horseshoe shape is relatively moved in a direction approaching the rack teeth of the workpiece.

  The invention according to claim 6 is characterized in that, in claim 4 or claim 5, the workpiece has a ball screw groove, and the workpiece is rotated when the ball screw groove is heated by the high-frequency heating coil. When the rack portion is heated by the high-frequency heating coil, the moving quenching apparatus includes a rotating unit that stops the rotation of the workpiece.

  According to the first aspect of the present invention, when the work is relatively moved to the position where the high-frequency heating coil corresponds to the end of the rack tooth, the high-frequency heating coil is shifted relative to the work in the radial direction of the work. Since the rack teeth are brought close to the high frequency heating coil and at least one of the relative movement speed in the axial direction of the workpiece and the output power of the high frequency heating coil is controlled, the rack teeth approach the high frequency heating coil. The heating action at the end portion of the rack tooth can be enhanced, and the conventional lack of heating at the end portion of the rack tooth can be solved. Moreover, by controlling at least one of the relative movement speed in the axial direction of the workpiece and the output power of the high-frequency heating coil, a hardened layer that satisfies the standard value can be formed on both the rack teeth and the back surface side.

  According to the invention of claim 2, since the high-frequency heating coil is configured in a substantially horseshoe shape complemented with the cross-sectional shape perpendicular to the axis of the workpiece, the rack teeth on the plane can be heated evenly, Even if the rack teeth are shifted in the direction approaching the high-frequency heating coil, both end corners in the circumferential direction of the rack teeth do not excessively approach the high-frequency heating coil, and the occurrence of spark-out can be prevented.

  According to the invention of claim 3, the workpiece has a ball screw groove portion, and when the ball screw groove portion is heated by the high frequency heating coil, the workpiece is relatively moved in the axial direction while rotating the workpiece. A hardened layer having a required quenching hardness and quenching depth can be formed on the rack teeth of the rack portion and the back surface thereof, and even if the high frequency heating coil is formed in a substantially horseshoe shape, the ball screw groove portion The outer surface of can be evenly quenched.

  According to the invention which concerns on Claim 4, when a workpiece | work is relatively moved to the position where a high frequency heating coil respond | corresponds to the edge part of a rack tooth, a high frequency heating coil is shifted relatively to the radial direction of a workpiece | work with respect to a workpiece | work. And controlling the relative movement speed in the axial direction of the work and the output power of the high-frequency heating coil in a state where the high-frequency heating coil is shifted relative to the work in the radial direction by the shift means. Control means, the rack teeth approaching the high-frequency heating coil can promote the necessary heating at the rack tooth end, and the conventional lack of rack tooth end heating can be eliminated. By controlling at least one of the relative movement speed in the axial direction of the workpiece and the output power of the high-frequency heating coil, the standard value is satisfied on both the rack teeth and the back side. Moving quenching apparatus capable of forming a quenched layer to be able to easily embody.

  According to the fifth aspect of the present invention, the high frequency heating coil is configured in a substantially horseshoe shape complemented to the cross-sectional shape perpendicular to the axis of the workpiece, and the substantially linear portion of the horseshoe shape of the high frequency heating coil is rack teeth of the workpiece by the shift means. The rack teeth on the plane can be heated evenly, and even if the rack teeth are shifted in the direction approaching the high-frequency heating coil, the rack teeth can be heated evenly. It is possible to embody a moving quenching apparatus that can prevent the occurrence of spark-out without excessively approaching the high-frequency heating coil at both end corners of the teeth in the circumferential direction.

  According to the invention of claim 6, the workpiece has a ball screw groove portion, the workpiece is rotated when the ball screw groove portion is heated by the high frequency heating coil, and the workpiece portion is heated when the rack portion is heated by the high frequency heating coil. Since the rotating means for stopping the rotation is provided, the hardened layer having the required hardened hardness and hardened depth can be easily formed on the rack teeth of the rack portion and the back surface thereof, and the high frequency heating coil Even if it is formed in a substantially horseshoe shape, it is possible to embody a moving quenching apparatus that can uniformly quench the outer surface of the ball screw groove.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings with respect to an example in which a ball screw shaft 10 used in an electric power steering apparatus is quenched. As shown in FIG. 7, the ball screw shaft 10 has a cylindrical shaft portion 11 over the entire length in the axial direction, a ball screw groove portion 12 is formed at a substantially central portion in the axial direction, and one end in the axial direction. A rack portion 13 is formed on the top. Rack teeth 15 are formed on the rack portion 13, and both ends of the rack teeth 15 and the shaft portion 11 are connected with steps 17 and 18 as shown in FIG.

  1 and 2, reference numeral 21 denotes a main body of the moving quenching apparatus. A slider 22 is guided to the main body 21 so as to be slidable in the vertical direction, and is slid in the vertical direction by a lifting motor 23 via a ball screw mechanism 24. It has come to be. An upper support frame 25 and a lower support frame 26 are respectively installed on the upper end portion and the lower end portion of the slider 22.

  The upper support frame 25 is provided with an upper support device 28 having an upper center 27 attached to the upper end of the ball screw shaft 10 so as to be engaged with the upper end of the ball screw shaft 10 and rotatably supported. A lower center 29 that is engaged with and rotatably supported is attached.

  As shown in FIG. 3, the upper support device 28 includes a rotary shaft 31 that is supported on the upper support frame 25 so as to be rotatable around a vertical axis, and a rotation provided on the slider 22 at the upper end of the rotary shaft 31. The motor 32 is connected via a gear mechanism 33. A center shaft 34 is inserted through the rotation shaft 31, and a spline shaft 35 formed integrally with the center shaft 34 is spline-engaged with a spline sleeve 36 provided on the rotation shaft 34 so as to be slidable in the vertical direction. . The spline shaft 35 is rotatably supported by a joint 38 that is moved forward and backward by a predetermined amount by a forward / backward cylinder 37 installed on the slider 22. An upper center 27 is attached to the lower end of the center shaft 34, and a key member (not shown) that engages with a key groove (not shown) formed in the ball screw shaft 10 is attached to the upper center 27.

  As a result, the center shaft 34 to which the upper center 27 is attached is moved forward and backward by a predetermined amount by the advance / retreat cylinder 37, and is rotationally driven integrally with the rotation shaft 34 by the rotation motor 32. The ball screw shaft 10 supported along the vertical axis line between the upper center 27 and the lower center 29 is transmitted to the rotation shaft 34 through the key member, and is slid in the axial direction by the slide of the slider 22. Along the vertical direction.

  The slider 22, the lifting motor 23, the ball screw mechanism 24, and the like constitute moving means for moving the ball screw shaft 10 in the vertical direction, and the upper center 27 and the lower center 29, etc. A support means for supporting the screw shaft 10 in the vertical axis direction is configured.

  A shift stand 40 is slidably guided in the movable quenching apparatus main body 21 behind the slider 22 so as to be horizontally slidable by the shift motor 43 via the ball screw mechanism 44. ing. The shift table 40 is provided with a transformer 42 of an induction hardening unit 41. A support plate 45 made of an insulator projects from the transformer 42, and the support plate 45 extends to the axial center positions of the centers 27 and 29 through an opening 22 a that is elongated in the vertical direction formed in the slider 22. Be present. A heating device 47 for heating the outer surface of the ball screw shaft 10 is disposed on the support plate 45. As shown in FIGS. 4 and 5, the heating device 47 accommodates a high-frequency heating coil 48 having a heating portion 48 a formed in an annular shape so as to surround the ball screw shaft 10, and a heating portion 48 a of the high-frequency heating coil 48. And a heating housing 49 in which a rectangular heating chamber 49a is formed.

  The heating housing 49 is installed on the support plate 45, and the upper open end of the heating housing 49 is closed by the cover plate 50. The support plate 45 and the cover plate 50 are formed with insertion holes 45a and 50a for inserting the ball screw shaft 10 supported by the centers 27 and 29. The insertion holes 45a and 50a have diameters of the ball screw shaft 10. The inner diameter is slightly larger than that.

  The heating part 48 a of the high-frequency heating coil 48 is formed in a substantially horseshoe shape that complements the cross-sectional shape perpendicular to the axis of the rack part 13 of the ball screw shaft 10, and this horseshoe shape is large enough to pass through the ball screw shaft 10. Is formed. That is, the heating part 48a has a cylindrical part 48a1 corresponding to the shaft part 11 with an interval, and a linear part 48a2 formed in one circumferential direction of the cylindrical part 48a1 and parallel to the rack teeth 15 of the rack part 13. It is formed in the shape which connected.

  The heating chamber 49a of the heating housing 49 provided with the heating unit 48a is filled with nitrogen gas or the like injected from a gas injection device (not shown), thereby keeping the inside of the heating housing 49 in an unoxidized state. The heat treatment can be performed while preventing oxidation of the heating surface of the ball screw shaft 10.

  A cooling device 51 that rapidly cools the outer surface of the ball screw shaft 10 heated by the heating device 47 is disposed on the support plate 45 below the heating housing 49. As shown in FIG. 6, the cooling device 51 includes a substantially annular coolant supply member 52 into which the ball screw shaft 10 supported by the centers 27 and 29 can be inserted. The coolant supply member 52 is composed of coolant supply chambers 53 and 54 having two C-shapes divided into two in the circumferential direction. The two coolant supply chambers 53 and 54 are joined to each other at one end and are slightly separated from each other to form a limited radial gap 55 that opens laterally toward the outside. The inner diameter of the coolant supply member 52 is outside the ball screw shaft 10 so as to form a coolant storage chamber 57 that can be filled with a sufficient volume of coolant with the outer surface of the ball screw shaft 10. It is set considerably larger than the diameter.

  The two cooling liquid supply chambers 53 and 54, when cooling the rack portion 13, have a first cooling liquid supply chamber 53 corresponding to the rack teeth 15 and a second cooling corresponding to the back side 16 of the rack teeth 15. It functions as the liquid supply chamber 54. A plurality of injection holes 59 are opened in the inner periphery of the first coolant supply chamber 53 toward the axial center of the ball screw shaft 10, and a ball screw is provided in the inner periphery of the second coolant supply chamber 54. A plurality of injection holes 60 are opened toward the axial center of the shaft 10. The number of injection holes 59 formed in the first coolant supply chamber 53 corresponding to the rack teeth 15 is larger than the number of injection holes 60 formed in the second coolant supply chamber 54 corresponding to the back side 16. Many are formed, and more coolant can be ejected than the first coolant supply chamber 53. Separate cooling liquid supply pipes 61 and 62 are connected to the first and second cooling liquid supply chambers 53 and 54, and the first and second cooling liquids are connected via the cooling liquid supply pipes 61 and 62. The coolant is supplied to the supply chambers 53 and 54 at a predetermined flow rate ratio so that more coolant is supplied to the first coolant supply chamber 53.

  A discharge control plate 63 is attached to the lower end of the coolant supply member 51 so as to close the lower end of the coolant storage chamber 57. The discharge control plate 63 is provided with an insertion hole 63 a through which the ball screw shaft 10 is inserted, and a limited annular gap 65 is formed between the insertion hole 63 a and the outer surface of the ball screw shaft 10.

  As a result, the coolant at a predetermined flow rate supplied to the first and second coolant supply chambers 53 and 54 from the coolant supply pipes 61 and 62 is supplied to the coolant storage chamber 57 from the injection holes 59 and 60. Then, the coolant is discharged from the coolant storage chamber 57 through a radial gap 55 formed between the first and second coolant supply chambers 53 and 54.

  Here, by setting the discharge area composed of the radial gap 55 and the annular gap 65 in accordance with the supply flow rate of the cooling liquid supplied to the first and second cooling liquid supply chambers 53, 54, the coolant is stored. The cooling liquid discharged from the chamber 57 through the radial gap 55 and the annular gap 65 is restricted, and the cooling liquid storage chamber 57 can be always filled with a sufficient amount of cooling liquid. In addition, the coolant is discharged not only from below but also from the lateral direction through the radial gap 55, thereby promoting the circulation of the coolant stored in the upper portion of the coolant storage chamber 57, and the ball screw shaft. The cooling liquid whose temperature has been increased by cooling 10 is prevented from being accumulated in the cooling liquid storage chamber 57, and the cooling efficiency is improved.

  The upper portion of the insertion hole 63a of the discharge control plate 63 is chamfered to deflect the flow direction of the coolant, and the coolant discharged below the annular gap 65 by this chamfer is applied to the outer surface of the ball screw shaft 10. The cooling liquid is effectively applied to the outer surface of the ball screw shaft 10 by deflecting in the direction toward which the cooling liquid is prevented from scattering in the radially outward direction of the ball screw shaft 10, thereby cooling the ball screw shaft 10. To improve.

  The up / down motor 23, the rotation motor 32, the shift motor 43, and the transformer 42 are connected to a control device 70 as shown in FIG. The raising / lowering motor 23, the rotation motor 32, and the shift motor 43 are controlled to be started and stopped by the control device 70, and are rotationally driven at a commanded rotation speed. Further, the transformer 42 is configured such that the output power for controlling the high-frequency heating coil 48 by the control device 70 is controlled according to the vertical position of the ball screw shaft 10.

  Next, the quenching process operation of the ball screw shaft 10 in the above configuration will be described. When the ball screw shaft 10 is attached or detached, the slider 22 is positioned at the rising end, and the upper center 27 is held at the rising end by the advancing / retreating cylinder 37 with respect to the slider 22. In this state, the ball screw shaft 10 is carried between the upper and lower centers 27 and 29 in a posture with the rack portion 13 upward, and the lower end of the ball screw shaft 10 is raised to a position penetrating the heating device 47 and the cooling device 51. The lower center 29 is engaged and supported.

  Subsequently, the upper center 27 is lowered by the advancing / retreating cylinder 37 and engaged with the upper end of the ball screw shaft 10, whereby both ends of the ball screw shaft 10 are supported in the vertical axis direction by the centers 27 and 29. At the same time, a key member (not shown) provided at the upper center 27 is engaged with the key groove of the ball screw shaft 10.

  In this state, the elevating motor 23 is driven, the slider 22 is lowered at a rapid feed speed via the ball screw mechanism 24, and the ball screw shaft 10 supported by both the centers 27 and 29 is lowered integrally with the slider 22. At the same time, nitrogen gas or the like is supplied into the heating housing 49 of the heating device 47 to make it non-oxidized. When the quenching start position (lower end) of the ball screw shaft 10 is moved to a position corresponding to the high frequency heating coil 48, the lowering operation of the slider 22 is temporarily stopped.

  Subsequently, the slider 22 starts to descend at a relatively low speed by the elevating motor 23, and the rotating motor 32 is driven so that the ball screw shaft 10 rotates about the vertical axis about the centers 27 and 29. Is done. Thereby, the ball screw shaft 10 is fed into the heating device 47 and the cooling device 51 while being rotated.

  At this time, the control device 70 controls the transformer 42 so that a predetermined output power is supplied to the high-frequency heating coil 48 at a predetermined frequency (for example, 100 kHz), and the shaft portion 11 at the lower end of the ball screw shaft 10 is The high-frequency heating coil 48 is intruded, and the outer surface of the shaft portion 11 is heated to a predetermined temperature (for example, 900 ° C.) in a non-oxidized state. The shaft portion 11 heated to a predetermined temperature by the heating device 47 is then transferred to the cooling device 51, immersed in the cooling liquid filled in the cooling liquid storage chamber 57, and cooled. Thereby, a hardened layer having a predetermined hardness and a predetermined depth is formed on the outer surface of the shaft portion 11 of the ball screw shaft 10.

  Since the shaft portion 11 is heated while the ball screw shaft 10 rotates, the outer surface of the shaft portion 11 is evenly heated even if the high-frequency heating coil 48 has a substantially horseshoe shape. The outer surface of the shaft portion 11 is evenly cooled even when different flow rates of coolant are supplied from the injection holes 59 and 60 of the first and second coolant supply chambers 53 and 54 in 51.

  In this way, the shaft portion 11 on the ball screw shaft 10 is quenched, and the outer surface of the ball screw groove portion 12 is continuously heated by the heating device 47 as the ball screw shaft 10 descends, and the cooling device 51 Cooled by.

  When the ball screw shaft 10 is lowered to a predetermined position and the start end of the rack portion 13 is moved to a position approaching the high-frequency heating coil 48, the rotation motor 32 is controlled, and the ball screw shaft 10 is moved to the rack portion 13. Positioning is stopped at the angular position shown in FIG. 5 where the rack tooth 15 corresponds to the linear portion 48a2 of the heating part 48a, that is, the angular position where the rack tooth 15 complements the substantially horseshoe shape of the high-frequency heating coil 48. When the ball screw shaft 10 is lowered to a position where the high-frequency heating coil 48 corresponds to the step 17 of the rack portion 13, the shift motor 43 is driven, and the shift base 40 is moved through the ball screw mechanism 44 by a predetermined amount. Shifted. As a result, the linear portion 48 a 1 of the high-frequency heating coil 48 is shifted by a predetermined amount in a direction approaching the rack teeth 15 of the rack portion 13. At the same time, the controller 70 controls the lowering speed of the ball screw shaft 10 to a low speed and the high-frequency heating coil 48 to a preset output power.

  By such control, normally, in the step 17 portion, current intensively flows in the corner portion 17a and the start end portion of the rack tooth 15 tends to be sweetened. Due to the shifting operation in the direction approaching the teeth 15, the heating action at the ends of the rack teeth 15 is enhanced, and the rack teeth 15 are gradually heated by the decrease in the descending speed of the ball screw shaft 10. As a result, the tendency of the baking at the start end of the rack teeth 15 to be sweetened is improved, and sufficient baking is performed from the start end of the rack teeth 15. Further, since the high-frequency heating coil 48 has a substantially horseshoe shape, even if the high-frequency heating coil 48 is shifted in a direction approaching the rack teeth 15, both end corners in the circumferential direction of the rack teeth 15 are high-frequency heating coils. It is possible to prevent the occurrence of spark-out without excessively approaching 48.

  By the way, the shift operation of the high-frequency heating coil 48 in the direction approaching the rack teeth 15 increases the distance from the high-frequency heating coil 48 on the back side 16 of the rack teeth 15, which causes the back side 16 to be baked. As described above, the lowering speed of the ball screw shaft 10 is reduced and the output of the high-frequency heating coil 48 is reduced with the shift operation in the direction of approaching the rack teeth 15 of the high-frequency heating coil 48 as described above. Since the electric power is controlled, the lowering speed of the ball screw shaft 10 is reduced and the output power of the high frequency heating coil 48 is controlled so that the rear side 16 of the rack tooth 15 has a required quenching hardness and quenching depth. It is controlled so that a hardened layer can be formed.

  That is, the output of the high-frequency heating coil 48 is tuned so that the quenching hardness and quenching depth of both the rack teeth 15 and the back side 16 satisfy predetermined standard values. Will be. Specifically, the rack teeth 15 and the back side 16 have the same quenching hardness, and the depth of quenching is as shown in FIG. Quenched layers 15a and 16a having L2 are formed.

  The high-frequency heating coil 48 is shifted in a direction approaching the rack teeth 15, and the ball screw shaft 10 is moved by a slight amount in a state where the lowering speed of the ball screw shaft 10 is lowered, and the step portion of the rack teeth 15 is moved. When passing the position corresponding to the high-frequency heating coil 48, the transformer 42 of the quenching unit 41 is shifted by the shift motor 43 through the ball screw mechanism 44 so that the rack teeth 15 of the rack portion 13 are separated from the high-frequency heating coil 48. Returning is performed, and the high-frequency heating coil 48 is returned to the original position with respect to the ball screw shaft 10. At the same time, the controller 70 returns the lowering speed of the ball screw shaft 10 and the output power of the high-frequency heating coil 48 to the original values, and in this state, baking of the rack teeth 15 is continued.

  The rack portion 13 heated to a predetermined temperature by the heating device 47 is transferred to the cooling device 51 as the ball screw shaft 10 is lowered, immersed in the cooling liquid filled in the cooling liquid storage chamber 57, and quenched and cooled. Is done. At this time, more cooling liquid is supplied to the first cooling liquid supply chamber 53 corresponding to the rack teeth 15 than the second cooling liquid supply chamber 54 corresponding to the back side 16, and these cooling liquids are Since the spray holes 59 and 60 are sprayed into the coolant storage chamber 57, the rack teeth 15 have a higher cooling effect than the back side 16. Thereby, even if the heating conditions are different between the rack teeth 15 and the back side 16, the rack teeth 15 and the back side 16 are cooled so that the cooling rate is uniform. As a result, the bend generated in the ball screw shaft 10 is suppressed, and the bend removing operation in the post-process can be made unnecessary or can be easily performed.

  In addition, since the rack portion 13 can be cooled by the cooling liquid filled in the cooling liquid storage chamber 57, it is cooled as if it is immersed in the cooling tank while being long in the vertical direction like the ball screw shaft 10. This makes it possible to eliminate the uneven cooling of the back of the rack teeth 15 in particular, and to eliminate the uneven hardness of the rack tooth surfaces.

  Further, since the coolant injected into the coolant storage chamber 57 is also discharged from the lateral direction through the radial gap 55, the coolant whose temperature has risen by cooling the ball screw shaft 10 is cooled. The upper part of the liquid storage chamber 57 is not blocked and the cooling effect can be improved.

  When the ball screw shaft 10 is lowered to a position where the heating device 47 corresponds to the step 18 portion below the rack portion 13, the quenching unit 41 is moved by the shift motor 43 via the ball screw mechanism 44 as described above. Then, the high-frequency heating coil 48 is moved closer to the rack teeth 15 of the rack portion 13, and at the same time, the lowering speed of the ball screw shaft 10 is reduced and the output power of the high-frequency heating coil 48 is controlled. As a result, a quenching layer having a required quenching hardness and quenching depth is formed on both the rack teeth 15 and the back side 16 at the end portion of the rack teeth 15 similarly to the above-described start end portion. . Thereafter, the high-frequency heating coil 48 is shifted back, the lowering speed of the ball screw shaft 10 and the output of the high-frequency heating coil 48 are returned to the normal feed speed and output, and the remaining shaft portion 11 of the ball screw shaft 10 is moved. Quench processing.

  When the slider 22 is lowered to the lower end position and the quenching process is completed over the entire length of the ball screw shaft 10, the elevating motor 23 is driven in the opposite direction to the above, and the ball screw shaft 10 is raised together with the slider 22. The When the ball screw shaft 10 is raised, low-temperature tempering is performed in the heating device 47, and the surfaces of the rack portion 13 and the ball screw groove portion 12 on the ball screw shaft 10 are tempered sequentially. At this time, the frequency of the high frequency heating coil 48 is switched to a low frequency suitable for tempering.

  Using the ball screw shaft 10 that has been hardened as described above, as shown in FIG. 7, the rack teeth 15 and the rack teeth 15 When the quenching hardness and quenching depth on the back side 16 were measured, it was confirmed that both standards could be satisfied.

  In the above-described embodiment, the example of moving and quenching the ball screw shaft 10 used in the electric power steering apparatus has been described. However, the target workpiece to be moved and quenched is limited to such a ball screw shaft 10. Rather, it can be applied to all types of shaft-like workpieces having a rack portion.

  In the above-described embodiment, the heating device 47 side is shifted in the radial direction of the ball screw shaft 10 with respect to the ball screw shaft 10, but the ball screw shaft 10 side is shifted with respect to the heating device 47. It may be shifted. Similarly, regarding the vertical movement, the heating device 47 side may be moved up and down with respect to the ball screw shaft 10.

  In the embodiment described above, both the centers 27 and 29 are provided on the slider 22 so that one center 27 can be moved forward and backward for attaching and detaching the work (ball screw shaft 10). It is also possible to make the slider 22 have a double slide configuration so that the double slide can be operated in accordance with the axial length of the workpiece so as to be able to cope with different workpieces.

  In the above-described embodiment, the cooling device 51 is configured by the split-type coolant supply chambers 53 and 54, and the coolant supply chambers 53 and 54 have different flow rates from the separate coolant supply pipes 61 and 62. However, the configuration of the cooling device 51 is not a main part of the present invention, and is not limited to the configuration described in the embodiment.

It is a front view of the moving quenching apparatus which shows embodiment of this invention. It is a side view of the moving quenching apparatus seen from the arrow 2 direction of FIG. FIG. 3 is an enlarged cross-sectional view taken along line 3-3 in FIG. 2. FIG. 3 is an enlarged cross-sectional view of a main part of FIG. 2. It is sectional drawing cut | disconnected along 5-5 line of FIG. FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. It is a figure which shows a ball screw axis | shaft. It is a figure which shows the detail of a rack part. It is a figure which shows the quenching state of a rack part.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Ball screw shaft, 11 ... Shaft part, 12 ... Ball screw groove part, 13 ... Rack part, 15 ... Rack tooth, 16 ... Back side, 15a, 16a ... Hardened layer, rack teeth, 17, 18 ... step, 21 ... moving quenching device body, 22 ... slider, 23 ... lifting motor, 27,29 ... center, 31 ... Rotating shaft, 32... Rotating motor, 34... Center shaft, 37... Advancing and retreating cylinder, 40. ... Shift motor, 45 ... Support plate, 47 ... Heating device, 48 ... High frequency heating coil, 48a ... Heating unit, 49 ... Heating housing, 49a ... Heating chamber, 50 ... Cover plate, 51 ... Cooling device, 57 ... Coolant storage Chamber, 70 ... controller, L1, L2 ... hardened layer.

Claims (6)

In the moving quenching method in which the shaft-shaped workpiece having the rack portion on which the rack teeth are formed is heated while being moved relatively up and down in the axial direction, and then cooled, the surface of the workpiece is subjected to a quenching treatment.
The surface of the work is heated by the high-frequency heating coil while moving the work relatively in the axial direction in the center of the high-frequency heating coil having a substantially annular heating part, and the end of the rack teeth of the work When the work is relatively moved to a position corresponding to the high-frequency heating coil, the high-frequency heating coil is shifted relative to the work in the radial direction of the work, and the rack teeth are moved to the high-frequency heating coil. And at least one of the relative movement speed in the axial direction of the workpiece and the output power of the high-frequency heating coil is controlled, and the end portion passes the position corresponding to the high-frequency heating coil, and then the high-frequency heating coil is moved. The workpiece is shifted relative to the workpiece in the radial direction of the workpiece so that the workpiece is heated by the high-frequency heating coil. In a state of being returned to the heart, the moving quenching method characterized in that the surface of the rack portion including the rack teeth by relatively moving the workpiece in the axial direction so as to heat by the high-frequency heating coil.   The moving quenching method according to claim 1, wherein the heating portion of the high-frequency heating coil is configured in a substantially horseshoe shape complemented with a cross-sectional shape perpendicular to the axis of the workpiece.   3. The workpiece according to claim 1, wherein the workpiece has a ball screw groove portion, and when the ball screw groove portion is heated by the high frequency heating coil, the workpiece is relatively moved in the axial direction while rotating. A moving quenching method characterized by that. In the moving quenching apparatus in which the shaft-shaped workpiece having the rack portion on which the rack teeth are formed is heated while moving relatively up and down in the axial direction, and then cooled, and the surface of the workpiece is subjected to quenching treatment,
A high-frequency heating coil having a substantially annular heating section for heating the surface of the workpiece; a moving means for moving the workpiece relatively up and down in the axial direction relative to the high-frequency heating coil; Shift means for relatively shifting the high-frequency heating coil relative to the workpiece in the radial direction of the work when the high-frequency heating coil is relatively moved to a position corresponding to the part, and the high-frequency heating by the shift means Control means for controlling at least one of the relative movement speed in the axial direction of the workpiece and the output power of the high-frequency heating coil in a state where the coil is shifted relative to the workpiece in the radial direction. A moving quenching apparatus characterized by that.   The heating part of the high-frequency heating coil according to claim 4, wherein the heating part of the high-frequency heating coil is configured in a substantially horseshoe shape complemented with a cross-sectional shape perpendicular to the axis of the workpiece, and the horseshoe-shaped substantially linear part of the high-frequency heating coil is A moving quenching apparatus, wherein the moving quenching apparatus is relatively moved in a direction approaching a rack tooth of a workpiece.   6. The workpiece according to claim 4, wherein the workpiece has a ball screw groove portion, and when the ball screw groove portion is heated by the high frequency heating coil, the workpiece is rotated and the rack portion is heated by the high frequency heating coil. A moving quenching apparatus comprising rotating means for stopping the rotation of the workpiece when performing.

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