JP5549658B2 - Telescopic shaft manufacturing method and telescopic shaft manufactured by this manufacturing method - Google Patents

Description

  The present invention relates to a telescopic shaft, particularly a telescopic shaft capable of transmitting rotational torque and capable of sliding relative to the axial direction, for example, a telescopic shaft such as an intermediate shaft or a steering shaft, and a telescopic shaft manufactured by the manufacturing method. About.

  In the steering device, a telescopic shaft such as a spline shaft that is connected so as to be capable of transmitting rotational torque and is relatively slidable in the axial direction is incorporated in an intermediate shaft, a steering shaft, or the like. In other words, when the universal joint is fastened to the pinion shaft that meshes with the rack shaft of the steering gear, the intermediate shaft is temporarily contracted and then fitted to the pinion shaft and fastened. In order to absorb water, an expansion / contraction function is required.

  In addition, the steering shaft transmits the steering force of the steering wheel to the wheel, and the position of the steering wheel needs to be adjusted in the axial direction according to the physique and driving posture of the driver. .

  In recent years, the rigidity and running stability of the entire vehicle body have been improved, so that when the steering wheel is operated, it becomes easier for the driver to feel rattling in the rotational direction of the telescopic shaft. Therefore, there is a demand for a telescopic shaft that has low backlash and sliding resistance in the rotational direction and is excellent in lubricity and durability.

  For this purpose, there is a telescopic shaft that is fitted to the female shaft after coating a resin having a small sliding resistance on the outer periphery of the tooth surface of the male shaft and applying a lubricant for lubrication. With such a telescopic shaft, if the allowable range of sliding resistance is narrow, it is difficult to manufacture the sliding resistance within the allowable range due to the processing accuracy of the male shaft, the female shaft, and the resin coating portion.

  The telescopic shaft of Patent Document 1 applies rotational torque in a state in which a female shaft is fitted to a male shaft coated with resin, and presses the inner teeth of the female shaft against the resin-coated portion of the outer teeth of the male shaft. The covering portion is compressed and cured to form a pressing depression surface on the resin covering portion. Accordingly, the sliding gap is kept constant over a long period of time, and the lubricant is stored in the pressing recess surface, so that the supply of the lubricant is improved.

  A conventional telescopic shaft is shown in FIGS. 7 is a longitudinal sectional view showing a conventional telescopic shaft, FIG. 8A is an enlarged sectional view showing an initial state in which a female shaft is externally fitted to a male shaft covering the covering portion of FIG. 7, and FIG. 7 is an enlarged cross-sectional view taken along the line C-C in FIG. 7 showing a state in which the covering portion is plastically deformed to reduce the tightening allowance. FIG. 9A is a view in FIG. -D expanded sectional view, FIG.9 (b) is the Q section expanded sectional view of Fig.9 (a).

  As shown in FIG. 7, in the conventional telescopic shaft, the vehicle body front side (left end in FIG. 7) of the male shaft 16A of the intermediate shaft 16 is fitted into the vehicle body rear side (right end of FIG. 7) of the female shaft 16B. It is connected. As shown in FIGS. 7 and 8A, the female shaft 16B is formed in a hollow cylindrical shape, and a plurality of axial tooth grooves 41 are radially formed from the axial center of the female shaft 16B on the inner periphery thereof. Is formed at equal intervals over the entire length of the expansion / contraction stroke.

  The male shaft 16A having the same number of axial protruding teeth 51 as the number of the tooth grooves 41 is slid between the axial total length of the protruding teeth 51 and the axial tooth grooves 41 of the female shaft 16B. A covering portion 61 for reducing dynamic resistance is coated. The covering portion 61 is formed thick so that the sliding resistance before running-in of the intermediate shaft 16 is larger than the lower limit value of the predetermined allowable range.

  Next, as shown in FIGS. 7 and 8A, the tooth groove 41 of the female shaft 16 </ b> B is externally fitted to the entire axial length of the protruding teeth 51 of the male shaft 16 </ b> A. Subsequently, rotational torque is applied in a state where the female shaft 16B is fitted to the male shaft 16A coated with the covering portion 61, and the tooth groove 41 of the female shaft 16B is covered with the covering portion of the protruding teeth 51 of the male shaft 16A. The cover 61 is pressed and compressed to be plastically deformed to form a pressing recess surface 611 on the cover 61 as shown in FIG.

  Since the tooth groove 41 of the female shaft 16B cannot avoid processing errors during spline processing, the position of the tooth tip of the tooth groove 41 is directed toward the axial center of the female shaft 16B depending on the axial position of the female shaft 16B. Go in and out (fluctuate). For example, the tooth tip 411D at the DD cross-section position shown in FIGS. 9 (a) and 9 (b) is more on the axial side of the female shaft 16B than the tooth tip 411C at the CC cross-section position shown in FIG. 8 (b). It may protrude toward

  Then, when the female shaft 16B is slid with respect to the male shaft 16A, the tooth surface 412 in the vicinity of the tooth tip 411D at the DD cross-sectional position of the tooth groove 41 of the female shaft 16B bites into the covering portion 61. A problem occurs in which the resistance varies. Further, since the step surface 612 is generated in the covering portion 61, the lubricating oil filled in the vicinity of the root of the protruding tooth 51 of the male shaft 16A is blocked by the step surface 612 and hardly reaches the pressing recess surface 611. The trouble that becomes.

  In the conventional hydraulic power steering apparatus, the torque applied to the intermediate shaft 16 is relatively small, whereas in the column assist type electric power steering apparatus, the torque applied to the intermediate shaft 16 is large. Therefore, the deformation of the covering portion 61 of the intermediate shaft 16 becomes large, and the tooth tip of the female shaft 16B may bite into the covering portion 61 of the tooth base of the male shaft 16A, causing a problem that the sliding resistance fluctuates.

JP 2004-66970 A

The present invention relates to a telescopic shaft having a covering portion for reducing sliding resistance, which reduces the variation in sliding resistance due to the sliding position of the telescopic shaft and expands and contracts for a steering device with good lubricating oil lubrication performance. and to provide a manufacturing method of the shaft and its.

The above problem is solved by the following means. That is, the first invention is a male shaft having a plurality of protruding teeth formed on the outer periphery, and a plurality of external fittings that can slide relative to each other in the axial direction and transmit rotational torque to the protruding teeth of the male shaft. The female shaft in which the tooth groove is formed on the inner periphery, the covering portion coated on the tooth surface of the protruding tooth of the male shaft, and the tooth groove of the female shaft on the protruding tooth of the male shaft forming the covering portion A telescopic shaft for a steering device that is externally fitted so as to have a tightening margin, and a tooth surface near a tooth tip of a tooth gap of the female shaft on a covering portion of a tooth surface near a tooth root of the protruding tooth of the male shaft A relief portion is formed so as not to come into contact, and the radius of curvature of the covering portion of the tooth surface in the center portion of the protruding teeth forming the relief portion of the male shaft is R1, and the female shaft formed smaller than the curvature radius R2 of the tooth surface of the central portion of the tooth depth direction of the tooth The wedge-shaped gaps that increase in the gap from the central part of the toothed direction toward the both ends are formed at both ends of the toothed part of the meshed part of the tooth surface of the protruding tooth surface and the tooth surface of the tooth gap. Formed at both ends in the direction of brushing of the covering portion of the tooth surface of the protruding tooth, the respective radii of curvature are R3, R4, and R1> R3
, R4, and a telescopic shaft for a steering device, wherein a convex R chamfer is formed outward in the radial direction.

The second invention is a steering device for a telescopic shaft of claim 1, said covering portion steering apparatus for a telescopic shaft, characterized in that it is bonded by an adhesive to the tooth surface of the ridge teeth It is.

Third invention is a steering device for a telescopic shaft of claim 2, a telescopic shaft for steering apparatus characterized by fine irregularities on the tooth surface of the ridge teeth are formed.

Fourth invention, in the third steering device for telescopic shaft of the invention, the fine unevenness are press forming the protruding teeth in the axial direction, during cutting ridges teeth, shot ridge teeth A telescopic shaft for a steering device, which is formed by any of pickling treatment of ridge teeth during peening.

Fifth invention is a steering apparatus for a telescopic shaft of any of the first to fourth, the telescopic shaft is coupled to an output shaft of the assist device for imparting an auxiliary torque to the steering shaft constituting the steering device A telescopic shaft for a steering device, wherein the telescopic shaft is an intermediate shaft.

A sixth invention is a male shaft having a plurality of protruding teeth formed on the outer periphery, and a plurality of teeth externally fitted to the protruding teeth of the male shaft so as to be capable of relative sliding in the axial direction and to transmit rotational torque. It grooves a inner formed female shaft circumferentially, and a manufacturing method of a steering device for a telescopic shaft having a coating portion coated on the tooth surface of the ridge teeth of the male shaft, the male shaft is formed with the cover portion the externally fitted so as to have a margin tighten the teeth grooves of the female shaft ridges teeth, after accordingly, to impart compressive stress to the coated portion by plastically deforming the coated portion prescribed to reduce the interference with Sliding resistance is used , and a relief portion is formed so that the tooth surface near the tooth tip of the tooth groove of the female shaft does not contact the covering portion of the tooth surface near the tooth root of the protruding tooth of the male shaft. It is a manufacturing method of a telescopic shaft for a steering device .

  In the manufacturing method of the telescopic shaft of the present invention and the telescopic shaft manufactured by this manufacturing method, the tooth near the tooth tip of the tooth gap of the female shaft is formed on the covering portion of the tooth surface near the tooth root of the protruding tooth of the male shaft. An escape portion is formed so that the surfaces do not contact.

  Therefore, even after the covering portion is plastically deformed, the state where the escape portion is recessed from the plastic deformation surface is maintained. Therefore, since the tooth surface near the tooth tip of the tooth groove of the female shaft does not bite into the covering portion, the sliding resistance does not fluctuate. Further, since there is no step at the joint between the plastic deformation surface of the covering portion and the relief portion, the lubricating oil filled in the vicinity of the root of the protruding tooth of the male shaft smoothly reaches the plastic deformation surface.

BRIEF DESCRIPTION OF THE DRAWINGS The steering apparatus which has the expansion-contraction shaft of this invention is shown whole, it is the side view which cut | disconnected one part, Comprising: The Example applied to the electric power steering apparatus which has a steering assistance part is shown. It is a longitudinal cross-sectional view which shows the manufacturing process of the expansion-contraction shaft of Example 1 of this invention. 2 is an enlarged cross-sectional view of FIG. 2, (a) is an enlarged cross-sectional view showing an expansion / contraction shaft coated with a sleeve, and (b) is an enlarged cross-sectional view showing an expansion / contraction shaft coated with a covering portion. It is a perspective view which shows the male shaft of the expansion-contraction shaft of Example 1 of this invention. FIG. 3B is an enlarged cross-sectional view of a P part in FIG. 3B showing a manufacturing process of the telescopic shaft according to the first embodiment of the present invention, and FIG. 3A shows an initial state in which a female shaft is externally fitted to a male shaft coated with a covering part. FIG. 2B is an enlarged cross-sectional view of FIG. 2A, showing a state where the covering portion is plastically deformed to reduce the tightening margin. FIG. 3 is an enlarged cross-sectional view taken along the line B-B in FIG. It is a longitudinal cross-sectional view which shows the conventional expansion-contraction axis. FIG. 7A is an enlarged cross-sectional view showing an initial state in which a female shaft is externally fitted to the male shaft covering the covering portion of FIG. 7, and FIG. 7B is a view showing a state in which the interference is reduced by plastic deformation of the covering portion. It is CC sectional drawing of no. (A) is the DD expanded sectional view of FIG. 7 which shows the state which carried out the plastic deformation of the coating | coated part and made the interference margin small, (b) is the Q section expanded sectional view of (a). The expanded sectional view of the expansion-contraction shaft of Example 2 of this invention is shown, and FIG.3 (b) equivalent of Example 1 is shown. FIG. 11 is an enlarged cross-sectional view of a portion R in FIG. 10, corresponding to FIG. It is the S section expanded sectional view of Drawing 11. It is an expanded sectional view of the meshing part of the expansion-contraction shaft of Example 3 of this invention.

    Embodiments 1 to 3 of the present invention will be described below with reference to the drawings.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side view of the steering device having the telescopic shaft according to the present invention, partially cut away, showing an embodiment applied to an electric power steering device having a steering assisting portion. FIG. 2 is a longitudinal sectional view showing a process for manufacturing the telescopic shaft according to the first embodiment of the present invention. 3 is an enlarged cross-sectional view of FIG. 2, FIG. 3 (a) is an enlarged cross-sectional view showing the telescopic shaft covering the sleeve, and FIG. 3 (b) is an enlarged cross-sectional view showing the telescopic shaft coated with the covering portion. .

  4 is a perspective view showing the male shaft of the telescopic shaft according to the first embodiment of the present invention, and FIG. 5 is an enlarged sectional view of a portion P in FIG. 3B showing the manufacturing process of the telescopic shaft according to the first embodiment of the present invention. FIG. 5A is an enlarged sectional view showing an initial state in which the female shaft is externally fitted to the male shaft coated with the covering portion, and FIG. 5B shows a state in which the tightening margin is reduced by plastically deforming the covering portion. It is an AA expanded sectional view of FIG. FIG. 6 is an enlarged cross-sectional view taken along the line BB in FIG. 2 showing a state where the covering portion is plastically deformed to reduce the tightening allowance.

  As shown in FIG. 1, the steering device having the telescopic shaft of the embodiment of the present invention has a steering shaft 12 on which a steering wheel 11 can be mounted on the rear side of the vehicle body (right side in FIG. 1), and this steering shaft 12 is inserted. A steering column 13, an assist device (steering assisting portion) 20 for applying auxiliary torque to the steering shaft 12, and a front side of the vehicle body (left side in FIG. 1) of the steering shaft 12 via a rack / pinion mechanism (not shown) And a connected steering gear 30.

  The steering shaft 12 is formed by combining an outer shaft 12A and an inner shaft 12B so that rotational torque can be transmitted and relative displacement can be performed in the axial direction. That is, a plurality of male splines are formed on the outer periphery of the inner shaft 12B on the vehicle body rear side. A plurality of female splines are formed at the same phase position as the male splines on the inner periphery on the front side of the vehicle body of the outer shaft 12A. The female spline of the outer shaft 12A is externally fitted with a predetermined gap with the male spline of the inner shaft 12B, and is engaged so as to be able to transmit rotational torque and be relatively displaceable in the axial direction. Therefore, when the outer shaft 12A and the inner shaft 12B collide, the engaging portions can slide relative to each other to shorten the entire length.

  Further, the cylindrical steering column 13 inserted through the steering shaft 12 combines the outer column 13A and the inner column 13B so that they can be telescopically moved. It has a so-called collapsible structure in which the entire length is shortened while absorbing water.

  The vehicle body front side end portion of the inner column 13B is press-fitted and fixed to the vehicle body rear side end portion of the gear housing 21. Further, the vehicle body front side end portion of the inner shaft 12B is passed through the inside of the gear housing 21, and is coupled to the vehicle body rear side end portion of the input shaft (not shown) of the assist device 20.

  The steering column 13 is supported by a support bracket 14 at a middle portion thereof on a part of the vehicle body 18 such as a lower surface of the dashboard. Further, a locking portion (not shown) is provided between the support bracket 14 and the vehicle body 18, and when an impact in a direction toward the front side of the vehicle body is applied to the support bracket 14, the support bracket 14 is locked to the locking bracket 14. It moves away from the vehicle and moves to the front side of the vehicle.

  The upper end portion of the gear housing 21 is also supported on a part of the vehicle body 18. In the case of this embodiment, by providing a tilt mechanism and a telescopic mechanism, the position of the steering wheel 11 in the longitudinal direction of the vehicle body and the height position can be freely adjusted. Such a tilt mechanism and a telescopic mechanism are well known in the art and are not characteristic features of the present invention, and thus detailed description thereof is omitted.

  The output shaft 23 protruding from the end face on the vehicle body front side of the gear housing 21 is connected to a rear end portion of a male intermediate shaft (hereinafter referred to as a male shaft) 16A of the intermediate shaft 16 through a universal joint 15. Further, an input shaft 31 of the steering gear 30 is connected to a front end portion of a female intermediate shaft (hereinafter referred to as a female shaft) 16B of the intermediate shaft 16 via another universal joint 17.

  The male shaft 16A is coupled to the female shaft 16B so as to be capable of relative sliding in the axial direction and to transmit rotational torque. A pinion (not shown) is formed at the front end of the input shaft 31. A rack (not shown) meshes with the pinion, and the rotation of the steering wheel 11 moves the tie rod 32 to steer a wheel (not shown).

  A case 261 of an electric motor 26 is fixed to the gear housing 21 of the assist device 20. The direction and magnitude of torque applied from the steering wheel 11 to the steering shaft 12 is detected by a torque sensor. In response to this detection signal, the electric motor 26 is driven to cause the output shaft 23 to generate auxiliary torque with a predetermined magnitude in a predetermined direction via a speed reduction mechanism (not shown).

  As shown in FIG. 2, the telescopic shaft according to the first embodiment of the present invention is applied to the male shaft 16 </ b> A and the female shaft 16 </ b> B of the intermediate shaft 16. The vehicle body front side (left end in FIG. 2) of the male shaft 16A is fitted and connected to the vehicle body rear side (right end in FIG. 2) of the female shaft 16B.

  As shown in FIGS. 2, 3 (a) and 3 (b), the female shaft 16B formed of carbon steel or aluminum alloy is formed in a hollow cylindrical shape, and the shaft of the female shaft 16B is formed on the inner periphery thereof. A plurality of axial tooth spaces 41 are formed at equal intervals over the entire length of the expansion / contraction range (extension / contraction stroke) radially from the center.

  In the example of FIG. 3A, the sliding between the protruding tooth 51 of the male shaft (male spline shaft) 16A formed of carbon steel or aluminum alloy and the tooth groove 41 of the female shaft (female spline cylinder) 16B. An example of a telescopic shaft that covers a sleeve is shown as the covering portion 61 that reduces the dynamic resistance.

  That is, the male shaft 16A having four axial ridge teeth 51 as a non-circular outer peripheral shape for transmitting rotational torque has a total length in the axial direction of the ridge teeth 51 and the teeth of the female shaft 16B. A sleeve is covered as the covering portion 61 that reduces the sliding resistance with the groove 41.

  Further, the example of FIG. 3B shows a covering portion that reduces the sliding resistance between the protruding tooth 51 of the male shaft (male spline shaft) 16A and the tooth groove 41 of the female shaft (female spline cylinder) 16B. An example of a telescopic shaft coated with 61 is shown. That is, the male shaft 16A having 18 axial ridge teeth 51 as a non-circular outer peripheral shape for transmitting rotational torque has the axial length of the ridge teeth 51 in the axial direction of the female shaft 16B. The covering portion 61 for reducing the sliding resistance between the direction tooth spaces 41 is coated.

  3A and 3B is preferably made of at least one of rubber, for example, natural rubber, synthetic rubber, or a mixture of natural rubber and synthetic rubber. . Further, the material of the covering portion 61 may be composed of at least one solid lubricant selected from molybdenum disulfide, graphite, and fluorine compounds.

  Furthermore, the material of the covering portion 61 is at least one of natural rubber, synthetic rubber, or a mixture of natural rubber and synthetic rubber, and at least one of molybdenum disulfide, graphite, and fluorine compounds. You may comprise with the material which contained the solid lubricant.

  The covering portion 61 is made of polytetrafluoroethylene, phenol resin, acetal resin, polyimide resin, polyamideimide resin, polyethersulfone resin, polyphenylene sulfide resin, polyether / etherketone resin, polyamide resin, polyacetal (POM). ) It is preferably composed of at least one polymer material of resins.

  Furthermore, the material of the covering portion 61 is made of at least one polymer material selected from polytetrafluoroethylene, phenol resin, acetal resin, polyimide resin, polyamideimide resin, polyethersulfone resin, and polyphenylene sulfide resin. You may comprise with the material which contained the solid lubricant at least any one of molybdenum sulfide, a graphite, and a fluorine compound.

  As shown in FIG. 5 (a), a covering portion 61 that reduces the sliding resistance with the tooth groove 41 of the female shaft 16B is formed on the entire axial length of the protruding teeth 51 of the male shaft 16A. The thickness of the covering portion 61 is formed so that the sliding resistance before the break-in of the intermediate shaft 16 is larger than the lower limit value of the predetermined allowable range of the sliding resistance. It sets so that the surface 413 and the coating | coated part 61 may have a fastening allowance.

  In the covering portion 61, a relief portion 613 is formed so that the tooth surface 412 in the vicinity of the tooth tip 411 </ b> A of the tooth groove 41 of the female shaft 16 </ b> B does not contact the covering portion 61 in the vicinity of the root of the protruding tooth 51. To do. The amount by which the intermediate shaft 16 is acclimated and the covering 61 is compressed and plastically deformed is 1 to 10 microns. Therefore, the depth α1 of the relief portion 613 before applying compressive stress to the covering portion 61 to plastically deform the covering portion 61 is preferably 10 microns or more.

  Next, as shown in FIG. 2, the tooth groove 41 of the female shaft 16 </ b> B is fitted over the entire length of the protruding teeth 51 of the male shaft 16 </ b> A in the axial direction. Since the thickness of the covering portion 61 is formed so that the sliding resistance before the break-in of the intermediate shaft 16 is larger than the lower limit value of the allowable range of the predetermined sliding resistance, the tooth gap The tooth surface 413 of 41 and the coating | coated part 61 have a fastening margin and fit. A predetermined amount of grease having a predetermined hardness (consistency) is filled between the tooth groove 41 of the female shaft 16 </ b> B and the outer periphery of the covering portion 61.

  Next, the male shaft 16A is reciprocally slid relative to the female shaft 16B in the axial direction while applying a rotational torque between the female shaft 16B and the male shaft 16A. Alternatively, the male shaft 16A is reciprocated in the axial direction relative to the female shaft 16B while the male shaft 16A is bent relative to the female shaft 16B. Then, the temperature of the coating | coated part 61 rises with the frictional force at the time of sliding.

  When the temperature of the covering portion 61 rises, the covering portion 61 expands over the entire axial length of the protruding teeth 51 of the male shaft 16A. Therefore, as shown by the dashed-dotted ellipses T1 and T2 in FIG. 4, the covering portion 61 has a tightening margin between the tooth surface 413 of the tooth gap 41 and the covering portion 61 over the entire length of the protruding tooth 51 in the axial direction. Becomes larger.

  When the reciprocal sliding of the male shaft 16A with respect to the female shaft 16B is continued, the portion of the covering portion 61 that is in contact with the tooth surface 413 of the tooth groove 41 is strongly compressed, and evenly over the entire axial length of the protruding teeth 51. Causes compressive strain due to plastic deformation and creep deformation.

  By reciprocatingly sliding the male shaft 16A with respect to the female shaft 16B, the tooth groove 41 of the female shaft 16B and the protruding teeth 51 of the male shaft 16A hit equally over the entire length in the axial direction, and the sliding resistance becomes the sliding stroke. It becomes constant over the entire length. In addition, since the covering portion 61 receives a large compressive stress in a state where the temperature of the covering portion 61 is increased, the compressive strain of the covering portion 61 increases due to a creep phenomenon as time elapses.

  When the reciprocal sliding of the male shaft 16A with respect to the female shaft 16B is stopped and the covering portion 61 returns to normal temperature, the covering portion 61 contracts as shown in FIG. As a result, the covering portion 61 has a small interference between the tooth surface 413 of the tooth gap 41 and the covering portion 61, and the sliding resistance of the intermediate shaft 16 after the break-in becomes a predetermined magnitude. As shown in FIG. 5B, even after the covering portion 61 is plastically deformed, the depth of the escape portion 613 is α2, and a state where it is slightly recessed from the plastic deformation surface 614 is maintained.

  Due to the machining error during spline machining, the tooth tip 411B at the BB cross-sectional position shown in FIG. 6 is located closer to the axial center side of the female shaft 16B than the tooth tip 411A at the A-A cross-sectional position shown in FIG. It may protrude toward you.

  However, even after the covering portion 61 is plastically deformed, the escape portion 613 remains by the depth α2 as shown in FIG. Accordingly, when the female shaft 16B is slid with respect to the male shaft 16A, the tooth surface 412 in the vicinity of the tooth tip 411B of the tooth groove 41 of the female shaft 16B does not bite into the covering portion 61, so that the sliding resistance does not vary. In addition, since there is no step at the joint between the plastic deformation surface 614 and the relief portion 613 of the covering portion 61, the lubricating oil filled in the vicinity of the base of the protruding tooth 51 of the male shaft 16A is smooth to the plastic deformation surface 614. To reach.

  As another example, the female shaft 16B is fixed with a processing jig or the like (not shown), and a heating device 71 such as a high-frequency coil is fitted on the outer periphery of the female shaft 16B as shown in FIG. When an alternating current is passed through the heating device 71, the female shaft 16B is heated by electromagnetic induction, the heat is transmitted to the covering portion 61, and the covering portion 61 is heated to a predetermined temperature.

  When the covering portion 61 is heated, the covering portion 61 expands over the entire axial length of the protruding teeth 51 of the male shaft 16A. Therefore, as shown by the dashed-dotted ellipses T1 and T2 in FIG. 4, the covering portion 61 has a tightening margin between the tooth surface 413 of the tooth gap 41 and the covering portion 61 over the entire length of the protruding tooth 51 in the axial direction. Becomes larger.

  Next, as shown by an arrow R in FIG. 2, when the male shaft 16 </ b> A is reciprocated relative to the female shaft 16 </ b> B in the axial direction by a predetermined number of times, the covering portion 61 becomes the tooth surface 413 of the tooth groove 41. The portion that is in contact with is strongly compressed, and plastic deformation and creep deformation are caused uniformly over the entire axial length of the protruding teeth 51 to cause compressive strain.

  By reciprocatingly sliding the male shaft 16A with respect to the female shaft 16B, the tooth groove 41 of the female shaft 16B and the protruding teeth 51 of the male shaft 16A hit equally over the entire length in the axial direction, and the sliding resistance becomes the sliding stroke. It becomes constant over the entire length. Moreover, since the covering part 61 receives a large compressive stress in a state where the temperature of the covering part 61 is high, the compressive strain of the covering part 61 increases due to a creep phenomenon with the passage of time.

  When the covering portion 61 returns to normal temperature, the covering portion 61 contracts as shown in FIG. As a result, the covering portion 61 has a small interference between the tooth surface 413 of the tooth gap 41 and the covering portion 61, and the sliding resistance of the intermediate shaft 16 after the break-in becomes a predetermined magnitude. As shown in FIG. 5B, even after the covering portion 61 is plastically deformed, the depth of the escape portion 613 is α2, and a state where it is slightly recessed from the plastic deformation surface 614 is maintained.

  Due to the machining error during spline machining, the tooth tip 411B at the BB cross-sectional position shown in FIG. 6 is located closer to the axial center side of the female shaft 16B than the tooth tip 411A at the A-A cross-sectional position shown in FIG. It may protrude toward you.

  However, even after the covering portion 61 is plastically deformed, the escape portion 613 remains by the depth α2 as shown in FIG. Accordingly, when the female shaft 16B is slid with respect to the male shaft 16A, the tooth surface 412 in the vicinity of the tooth tip 411B of the tooth groove 41 of the female shaft 16B does not bite into the covering portion 61, so that the sliding resistance does not vary. In addition, since there is no step at the joint between the plastic deformation surface 614 and the relief portion 613 of the covering portion 61, the lubricating oil filled in the vicinity of the base of the protruding tooth 51 of the male shaft 16A is smooth to the plastic deformation surface 614. To reach.

  Next, a second embodiment of the present invention will be described. 10 is an enlarged cross-sectional view of the telescopic shaft according to the second embodiment of the present invention. FIG. 11 is a view corresponding to FIG. 3B of the first embodiment, and FIG. FIG. 5B is an equivalent view, and FIG. 12 is an enlarged cross-sectional view of a portion S in FIG. In the following description, only structural parts different from the above-described embodiment will be described, and redundant description will be omitted. Further, the same parts will be described with the same numbers. Example 2 is an example in which the covering portion 61 is bonded to the tooth surface of the protruding tooth 51 with an adhesive.

  That is, as shown in FIGS. 10 to 12, the telescopic shaft of Example 2 has a female shaft 16B formed of carbon steel or aluminum alloy formed in a hollow cylindrical shape, and is formed of carbon steel or aluminum alloy. The male shaft (male spline shaft) 16A is also formed in a hollow cylindrical shape. The covered tooth 61 of the male shaft 16 </ b> A is covered with a covering portion 61 that reduces the sliding resistance with the tooth groove 41 of the female shaft (female spline cylinder) 16 </ b> B, and the tooth surface 511 of the protruding tooth 51 is covered with the covering portion. The inner circumference 615 of 61 is bonded with an adhesive. As a method of covering the protruding portion 51 of the male shaft 16A with the covering portion 61, an injection molding method or a fluid immersion method is preferable.

  As the adhesive, a primer, an epoxy resin adhesive, or a rubber adhesive is used. That is, the male shaft 16A having 18 axial ridge teeth 51 as a non-circular outer peripheral shape for transmitting rotational torque has the axial length of the ridge teeth 51 in the axial direction of the female shaft 16B. A covering portion 61 that reduces the sliding resistance with the direction tooth gap 41 is bonded and fixed.

As shown in FIG. 12, minute irregularities are formed on the tooth surface 511 of the ridge tooth 51 by leaving a machining line when the ridge tooth 51 is cut or by performing shot peening or pickling. By doing so, the adhesive strength of the coating | coated part 61 is enlarged. By pressing the protruding teeth 51 of the male shaft 16A in the axial direction, minute irregularities in the axial direction may be formed. If minute irregularities are formed on the tooth surface 511 of the ridge tooth 51 in this way, the frictional force between the tooth surface 511 of the ridge tooth 51 and the inner periphery 612 of the covering portion 61 is increased. Adhesion with an agent becomes unnecessary, which is preferable.

  In the second embodiment, similar to the first embodiment, the covering portion 61 includes a tooth surface covering portion 61 near the tooth root of the protruding tooth 51 and a tooth surface 412 near the tooth tip 411A of the tooth groove 41 of the female shaft 16B. The escape portion 613 is formed so as not to contact. Even after the male shaft 16A is reciprocally slid relative to the female shaft 16B and the covering portion 61 is plastically deformed, the depth of the escape portion 613 is α2, and the state of being slightly recessed from the plastic deformation surface 614 is maintained. I am doing so.

  As shown in FIG. 11, when a large rotational torque T is applied to the telescopic shaft of the second embodiment of the present invention configured as described above, the covering portion 61 is compressed. Particularly, in the column assist type electric power steering device, the rotational torque applied to the intermediate shaft 16 is about 10 to 40 times larger than that of the conventional hydraulic power steering device, so that a large rotational torque T is applied. However, as described above, since the inner periphery 615 of the covering portion 61 is bonded to the tooth surface 511 of the protruding tooth 51, the compression direction (arrows α3 and α4 in FIG. 11) and the circumferential direction (arrows in FIG. 11). β3, β4) and the elastic deformation in three directions in the axial direction (direction orthogonal to the paper surface of FIG. 11) are suppressed.

  If the covering portion 61 is not adhered to the tooth surface 511 when a large rotational torque T is applied, the plastic deformation surface 614 of the covering portion 61 plastically flows to the root side of the protruding tooth 51, and the escape portion 613 protrudes. It moves to the tooth base side of the tooth 51. As a result, when the female shaft 16B is slid with respect to the male shaft 16A, the tooth surface 412 in the vicinity of the tooth tip 411A of the female shaft 16B bites into the covering portion 61, and the sliding resistance fluctuates. In order to avoid this, if the length of the relief portion 613 in the tooth height direction is increased, the contact area between the tooth groove 41 and the protruding tooth 51 is reduced, resulting in a problem that durability of the contact surface is lowered.

  In the telescopic shaft according to the second embodiment of the present invention, since the inner periphery 615 of the covering portion 61 is bonded to the tooth surface 511 of the protruding tooth 51, the amount by which the escape portion 613 moves to the root side of the protruding tooth 51. Is suppressed. As a result, the tooth surface 412 in the vicinity of the tooth tip 411A of the female shaft 16B is suppressed from biting into the covering portion 61, and fluctuations in sliding resistance can be suppressed.

  In the second embodiment of the present invention, as described above, the male shaft 16A is formed in a hollow cylindrical shape. Accordingly, when the large rotational torque T is applied, if the covering portion 61 is not bonded to the tooth surface 511, the protruding teeth 51 of the male shaft 16 </ b> A are elastically deformed by the rotating torque T, and the tooth surfaces 511 of the protruding teeth 51. The inner periphery 615 of the covering portion 61 is worn by the relative movement between the cover portion 61 and the covering portion 61.

  As a result, abrasion powder is sandwiched between the tooth surface 511 of the protruding tooth 51 and the inner periphery 615 of the covering portion 61, and the tightening allowance between the covering portion 61 and the tooth surface 413 of the tooth groove 41 of the female shaft 16B is reduced. growing. Then, the sliding resistance between the covering portion 61 and the tooth surface 413 is increased, and the vibration on the wheel side is easily transmitted to the steering wheel via the intermediate shaft 16, so that the steering feeling is deteriorated. .

  In the telescopic shaft according to the second embodiment of the present invention, the inner periphery 615 of the covering portion 61 is bonded to the tooth surface 511 of the protruding tooth 51. Accordingly, since the relative movement between the tooth surface 511 of the protruding tooth 51 and the inner periphery 615 of the covering portion 61 is suppressed, the wear of the inner periphery 615 of the covering portion 61 is suppressed. An increase in sliding resistance with the surface 413 is suppressed.

  Next, a third embodiment of the present invention will be described. FIG. 13 is an enlarged cross-sectional view of the meshing portion of the telescopic shaft according to the third embodiment of the present invention. In the following description, only structural parts different from the above-described embodiment will be described, and redundant description will be omitted. Further, the same parts will be described with the same numbers. Example 3 is an example in which a wedge-shaped gap in which the gap increases toward both ends in the toothpaste direction is formed in the meshing portion between the tooth surface of the protruding tooth 51 and the tooth surface of the tooth groove 41.

  That is, as shown in FIG. 13, the telescopic shaft of Example 3 is a coating that reduces the sliding resistance between the protruding teeth 51 of the male shaft 16A and the tooth grooves 41 of the female shaft (female spline cylinder) 16B. The part 61 is covered. The plastic deformation surface 614 of the covering portion 61 of the protruding teeth 51 is formed in a convex arc shape toward the radially outer side of the male shaft 16A. The radius of curvature of the plastic deformation surface 614 is R1, which is smaller than the radius of curvature R2 of the tooth surface 413 of the tooth space 41. Further, at both ends in the brushing direction of the covering portion 61 of the ridge tooth 51, R chamfers 616 and 617 having curvature radii R3 and R4 and protruding outward in the radial direction of the male shaft 16A are formed.

  Therefore, the plastic deformation surface 614 of the covering portion 61 of the protruding tooth 51 and the tooth surface 413 of the tooth groove 41 are in contact with each other at the center portion in the tooth brushing direction and transmit rotational torque. In addition, wedge-shaped gaps 62 and 63 are formed at both ends in the toothpaste direction so that the gap increases from the center part in the toothpaste direction toward both ends.

  Further, in the third embodiment, as in the first embodiment, the covering portion 61 includes a covering portion 61 on the tooth surface near the root of the protruding tooth 51 and a tooth near the tooth tip 411A of the tooth groove 41 of the female shaft 16B. An escape portion 613 is formed so that the surface 412 does not contact. Even after the male shaft 16A is reciprocally slid relative to the female shaft 16B and the covering portion 61 is plastically deformed, the state where the escape portion 613 is slightly recessed from the plastic deformation surface 614 is maintained. A predetermined amount of grease having a predetermined hardness (consistency) is filled between the tooth groove 41 of the female shaft 16 </ b> B and the outer periphery of the covering portion 61.

  As shown in FIG. 13, when the rotational torque T is applied to the telescopic shaft of the third embodiment of the present invention configured as described above, the covering portion 61 is compressed and the wedge-shaped gaps 62 and 63 are reduced. Further, when the rotational torque T decreases, the covering portion 61 expands and the wedge-shaped gaps 62 and 63 return to their original sizes. Therefore, when the wedge-shaped gaps 62 and 63 become large, it becomes possible to suck in grease from both ends in the toothing direction toward the central portion, and grease lubrication is performed smoothly, improving the durability of the telescopic shaft. To do.

  In particular, since the escape portion 613 is formed in the covering portion 61 of the tooth surface near the root of the protruding tooth 51, the distance between the escape portion 613 serving as a grease reservoir and the wedge-shaped gap 63 is reduced. The grease can be smoothly sucked into the wedge-shaped gap 63. In addition, since the wedge-shaped gap 63 is present, the volume of the grease reservoir is increased. Therefore, the amount of change in the volume of the wedge-shaped gap 63 when the rotational torque T increases or decreases is increased, and the grease can be efficiently sucked into the wedge-shaped gap 63.

  In addition, convex R chamfers 616 and 617 are formed on both ends of the tooth surface 511 of the protruding tooth 51 in the toothing direction of the covering portion 61 toward the radially outer side of the male shaft 16A. Accordingly, since the plastic deformation surface 614 and the R chamfers 616 and 617 are smoothly connected, the grease can be efficiently sucked into the wedge-shaped gap 63.

  In the third embodiment of the present invention, the plastic deformation surface 614 of the covering portion 61 of the protruding tooth 51 may be formed in an involute tooth profile, and the tooth surface 413 of the tooth groove 41 may be formed in a straight tooth profile. Further, the plastic deformation surface 614 of the covering portion 61 of the protruding tooth 51 may be formed in a linear tooth profile, and the tooth surface 413 of the tooth groove 41 may be formed in an involute tooth profile. Moreover, you may form both the plastic deformation surface 614 of the coating | coated part 61 of the protrusion tooth | gear 51, and the tooth surface 413 of the tooth space 41 in an involute tooth profile. In that case, the radius of curvature approximating one involute tooth profile may be formed smaller than the radius of curvature approximating the other involute tooth profile.

  In the above-described embodiment, an example in which the present invention is applied to an expansion / contraction shaft having a spline has been described. In the above embodiment, the covering portion 61 for reducing the sliding resistance is formed on the protruding tooth 51 side of the male shaft 16A, but the covering portion 61 for reducing the sliding resistance is provided on the tooth groove 41 side of the female shaft 16B. It may be formed. Moreover, you may form the coating | coated part 61 which reduces sliding resistance in both the protrusion tooth | gear 51 of the male shaft 16A, and the tooth groove 41 of the female shaft 16B. Furthermore, you may shape | mold the male shaft 16A or the whole female shaft 16B with the same material as the coating | coated part 61 which reduces sliding resistance.

  Moreover, although the said Example demonstrated the example which applied this invention to the intermediate shaft 16, it can apply to the arbitrary expansion-contraction shafts which comprise a steering apparatus, such as the steering shaft 12. FIG. Moreover, although the example applied to the steering device having the assist device (steering assist unit) 20 has been described in the above embodiment, the present invention may be applied to a steering device without the assist device.

DESCRIPTION OF SYMBOLS 11 Steering wheel 12 Steering shaft 12A Outer shaft 12B Inner shaft 13 Steering column 13A Outer column 13B Inner column 14 Support bracket 15 Universal joint 16 Intermediate shaft 16A Male intermediate shaft (male shaft)
16B Female intermediate shaft (Female shaft)
Reference Signs List 17 universal joint 18 vehicle body 20 assist device 21 gear housing 23 output shaft 26 electric motor 261 case 30 steering gear 31 input shaft 32 tie rod 41 tooth gap 411A tooth tip 411B tooth tip 411C tooth tip 411D tooth tip 412 tooth surface 413 tooth surface 51 protrusion Thread 511 Tooth surface 61 Covering portion 611 Pressing concave surface 612 Stepped surface 613 Escape portion 614 Plastic deformation surface 615 Inner circumference 616, 617 R chamfer 62, 63 Wedge-shaped gap 71 Heating device

Claims (6)

A male shaft having a plurality of protruding teeth formed on the outer periphery,
A female shaft having a plurality of tooth grooves formed on an inner periphery thereof that are externally slidable in the axial direction and capable of transmitting rotational torque to the protruding teeth of the male shaft;
A coating portion made of an elastic material coated on the tooth surface of the protruding tooth of the male shaft;
A telescopic shaft for a steering device that is externally fitted so as to have a margin for tightening the tooth groove of the female shaft on the protruding teeth of the male shaft forming the covering portion,
The relief portion is formed so that the tooth surface near the tooth tip of the tooth groove of the female shaft does not contact the covering portion of the tooth surface near the root of the protruding tooth of the male shaft,
The radius of curvature of the covering portion of the tooth surface in the center direction of the protruding teeth of the male teeth forming the relief portion of the male shaft is R1, and the tooth surface in the center portion of the tooth groove direction of the female shaft Radius of curvature R
Formed smaller than 2 ,
Wedge-shaped gaps are formed at both ends in the brushing direction of the meshing portion of the tooth surface of the protruding tooth and the tooth surface of the tooth gap, and the gap increases from the center to the both ends. And
At both ends in the brushing direction of the covering portion of the tooth surface of the protruding tooth, the respective radii of curvature are R3 and R4.
A telescopic shaft for a steering device , wherein R1> R3, R4, and a convex R chamfer is formed outward in the radial direction. The telescopic shaft for a steering device according to claim 1,
A telescopic shaft for a steering device, wherein the covering portion is bonded to a tooth surface of the protruding tooth with an adhesive. The telescopic shaft for a steering device according to claim 2,
A telescopic shaft for a steering device, wherein minute projections and depressions are formed on a tooth surface of the protruding tooth. In the telescopic shaft for a steering device according to claim 3,
The minute unevenness is formed by any one of pressing the protruding teeth in the axial direction, cutting the protruding teeth, shot peening of protruding teeth, or pickling the protruding teeth. A telescopic shaft for a steering device. The telescopic shaft for a steering device according to any one of claims 1 to 4,
The telescopic shaft for a steering device, wherein the telescopic shaft is an intermediate shaft connected to an output shaft of an assist device for applying auxiliary torque to a steering shaft constituting the steering device. A male shaft having a plurality of protruding teeth on the outer periphery, and a plurality of tooth grooves that are externally fitted to the protruding teeth of the male shaft so as to be slidable relative to each other in the axial direction and to transmit rotational torque. A method of manufacturing a telescopic shaft for a steering device having a female shaft, and a covering portion coated on a tooth surface of a protruding tooth of the male shaft,
To fit the toothed teeth of the female shaft on the protruding teeth of the male shaft forming the covering portion so as to have a margin,
After that, compressive stress is applied to the covering portion to plastically deform the covering portion to reduce the tightening margin to a predetermined sliding resistance,
A steering device characterized in that a relief portion is formed so that a tooth surface in the vicinity of the tooth tip of the tooth groove of the female shaft does not contact the covering portion of the tooth surface in the vicinity of the root of the protruding tooth of the male shaft. Of manufacturing telescopic shafts.

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