JP2009168194A - Method of manufacturing for telescopic shaft, and telescopic shaft manufactured thereby - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing for a telescopic shaft having a covering portion reducing the slide resistance and making slide resistance easily fall within a predetermined narrow allowable range, and to provide a telescopic shaft manufactured by the method of manufacturing for the telescopic shaft. <P>SOLUTION: The groove 41 of a female shaft 16B is fitted around the teeth 51 of a male shaft 16A after the tooth 51 of the male shaft 16A is formed with the coating portion 61. Under this condition, the male shaft 16A is relatively axially slid with respect to the female shaft 16B, and the slide resistance before running is measured. Next, when alternating current is led to flow into a heating apparatus 71, the female shaft 16B is heated by electromagnetic induction, and the covering portion 61 is heated to a predetermined temperature according to the slide resistance before running. When the covering portion 61 is heated, the covering portion 61 expands over the whole axial length of the teeth 51 of the male shaft 16A. Therefore, the covering portion 61 evenly causes plastic deformation and creep deformation over the whole axial length of the teeth 51 to cause compressive strain. <P>COPYRIGHT: (C)2009,JPO&INPIT

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 where the female shaft is fitted to the 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. It hardens | cures and forms the press dent surface in the resin coating part. 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. However, since the telescopic shaft of Patent Document 1 has a pressing depression surface, there is a problem in that a gap is formed between the inner teeth of the female shaft and the outer teeth of the male shaft, causing backlash in the rotational direction.

  In the state where the female shaft is fitted to the male shaft coated with the resin, the telescopic shaft of Patent Document 2 is softened by heating the resin from the outside to form a gap between the internal teeth of the female shaft and the external teeth of the male shaft. The resin coating is molded. As a result, the meshing gap between the inner teeth and the outer teeth is made uniform, the play in the rotational direction is reduced, and the sliding resistance in the axial direction is improved. However, the telescopic shaft disclosed in Patent Document 2 has a problem in that rattling occurs in the rotational direction because there is a meshing gap between the inner teeth of the female shaft and the outer teeth of the male shaft.

  Moreover, since the both ends of the axial direction of the coating | coated part of a male shaft become an edge in the expansion-contraction shaft of the said patent document 1 and the patent document 2, the lubricant apply | coated to the contact part of the tooth surface of a male shaft and a female shaft is carried out. The edge of the covering part is swept out of the contact part, the supply of the lubricant is insufficient, the sliding resistance increases, and the life of the telescopic shaft may decrease.

JP 2004-66970 A JP 2002-321627 A

  The present invention relates to a telescopic shaft having a covering portion for reducing sliding resistance, and a method for manufacturing the telescopic shaft that can easily fit the sliding resistance within a predetermined narrow tolerance, and the manufacturing method. It is an object to provide a telescopic shaft.

  The above problem is solved by the following means. That is, the first invention is a male shaft having a non-circular outer peripheral shape, and a non-circular inner peripheral shape that is fitted on the outer periphery of the male shaft so as to be capable of relative sliding in the axial direction and to transmit rotational torque. A method of manufacturing a telescopic shaft formed on a non-circular outer periphery of the male shaft and having a covering portion that reduces a sliding resistance between the female shaft and the inner periphery of the female shaft. Forming a covering portion for reducing sliding resistance between the inner periphery of the female shaft on a circular outer periphery, and a non-circular inner periphery of the female shaft on a non-circular outer periphery of the male shaft on which the covering portion is formed. The step of measuring the sliding resistance before acclimation by sliding the male shaft relative to the female shaft in the axial direction, the pre-acclimation sliding resistance from the pre-tested data. Addition to achieve predetermined sliding resistance Obtaining a condition and sliding conditions, a method of manufacturing a telescopic shaft, characterized in that it comprises the step of heating the coated portion in the heating condition.

  According to a second aspect of the present invention, the method for manufacturing the telescopic shaft of the first aspect further includes a step of sliding the male shaft relative to the female shaft in the axial direction under the sliding condition. It is the manufacturing method of the characteristic telescopic shaft.

  A third aspect of the invention is a method for manufacturing an extendable shaft according to any one of the first and second aspects of the invention, wherein the covering portion is cooled using chiller cooling. .

  According to a fourth aspect of the present invention, in the method of manufacturing the telescopic shaft according to the first or second aspect, the heating condition and the sliding condition are determined for each group having a range of sliding resistance before the break-in. This is a method for manufacturing the telescopic shaft.

  According to a fifth aspect of the present invention, in the method of manufacturing the telescopic shaft of the first or second aspect of the invention, the cooling of the covering portion is performed by replacing the female shaft with a mold having a temperature lower than that of the heated covering portion. Or it is a manufacturing method of the expansion-contraction axis | shaft characterized by making it contact with a male shaft and carrying out by heat conduction.

  According to a sixth aspect of the present invention, in the method for manufacturing the telescopic shaft according to the first or second aspect, the heating condition is measured in the vicinity of the covering portion measured before the covering portion is heated to a predetermined temperature. It is a manufacturing method of a telescopic shaft characterized by changing according to temperature.

  According to a seventh aspect of the invention, in the method of manufacturing the telescopic shaft according to the first or second aspect of the invention, the cooling of the covering portion is performed by supplying a gas having a temperature lower than that of the heated covering portion to the female shaft or It is a manufacturing method of an expansion-contraction shaft characterized by ventilating a male shaft.

  According to an eighth aspect of the present invention, in the method for manufacturing the telescopic shaft of the first or second aspect, the heating condition is a heating time for heating the covering portion to a predetermined temperature. It is the manufacturing method of the characteristic telescopic shaft.

  A ninth aspect of the invention is a method for manufacturing an extendable shaft according to any one of the first to eighth aspects of the invention, wherein the covering portion is heated using electromagnetic induction. is there.

  According to a tenth aspect of the present invention, in the method for manufacturing the telescopic shaft according to any one of the first to eighth aspects of the invention, the heating of the covering portion is performed by replacing the object having a higher temperature than the covering portion with the female shaft or the male shaft. This is a method for producing a telescopic shaft, which is performed by heat conduction.

  An eleventh aspect of the invention is the method for manufacturing an extendable shaft according to any one of the first to eighth aspects of the invention, wherein the sliding condition is that the male shaft is slid relative to the female shaft in the axial direction. It is the manufacturing method of the expansion-contraction shaft characterized by being the frequency | count of sliding to be moved.

  According to a twelfth aspect of the invention, in the method for manufacturing the telescopic shaft according to any one of the first to eighth aspects, the pre-breaking sliding resistance is set to a predetermined sliding resistance based on previously tested data. The method for manufacturing the telescopic shaft is further characterized by further comprising the step of cooling the covered portion after the step of obtaining the cooling condition and the step of sliding in the axial direction under the cooling condition.

  In a thirteenth aspect of the invention, in the method for manufacturing a telescopic shaft according to any one of the first to twelfth aspects, the covering portion is at least one of rubber, a polymer material, and a solid lubricant. It is a manufacturing method of the expansion-contraction shaft characterized by being formed with the material.

  A fourteenth aspect of the invention is a telescopic shaft manufactured by the manufacturing method of the telescopic shaft of any one of the first to thirteenth aspects of the invention.

  In the telescopic shaft manufacturing method of the present invention and the telescopic shaft manufactured by this manufacturing method, a step of forming a covering portion on the noncircular outer periphery of the male shaft to reduce the sliding resistance between the inner periphery of the female shaft And a step of fitting the non-circular inner periphery of the female shaft to the non-circular outer periphery of the male shaft having the covering portion formed thereon, and sliding the male shaft relative to the female shaft in the axial direction. The step of measuring the previous sliding resistance, the step of obtaining the heating condition and the sliding condition for making the sliding resistance before the break-in the predetermined sliding resistance from the previously tested data, and the above heating condition A step of heating the covering portion;

  Therefore, the covering portion is strongly compressed between the non-circular outer periphery of the male shaft and the inner periphery of the female shaft to cause a predetermined compressive strain, and to ensure that the sliding resistance after the break-in is within a predetermined allowable range. Is possible.

  Hereinafter, Example 1 to Example 2 of the present invention will be described 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 AA enlarged cross-sectional view of FIG. 2, wherein (1) is an enlarged cross-sectional view showing a telescopic shaft coated with a sleeve, and (2) is an enlarged cross-sectional view showing a telescopic shaft coated with a covering portion.

  FIG. 4 is a perspective view showing the male shaft of the telescopic shaft according to the first embodiment of the present invention. FIG. 5 shows a manufacturing process of the telescopic shaft according to the first embodiment of the present invention, and is an enlarged cross-sectional view of a portion P in FIG. FIG. 6 is an enlarged cross-sectional view of a portion P in FIG. FIG. 7 is a heating / cooling curve of the coated portion showing the manufacturing process of Example 1 of the present invention.

  FIG. 8 is a graph showing the temperature and sliding resistance drop when the coating is heated. FIG. 9 is a graph showing the number of sliding operations and the amount of decrease in sliding resistance when the telescopic shaft is slid. FIG. 10 is a graph showing the heating time and the temperature of the covering portion when the covering portion is heated. FIG. 11 is a graph showing changes in sliding resistance before and after the break-in of the telescopic shaft. FIG. 12 is a graph of another example showing the change in sliding resistance before and after the break-in of the telescopic shaft.

  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 vehicle front side (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 on the vehicle body rear side of the male shaft 12B, and a plurality of female splines are formed on the inner periphery on the vehicle body front side of the female shaft 12A at the same phase position as the male spline. The male spline of the male shaft 12B is externally fitted with a predetermined gap, and is engaged so as to be able to transmit rotational torque and be relatively displaceable in the axial direction. Therefore, the engaging portion of the female shaft 12A and the male shaft 12B can slide relative to each other at the time of collision, so that the overall length can be shortened.

  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 male 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 intermediate shaft 16A is coupled to the female intermediate 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 FIG. 2, FIG. 3 (1), (2), the female shaft 16B formed of carbon steel or aluminum alloy is formed in a hollow cylindrical shape, and the inner periphery of the female shaft 16B is an axis of the female shaft 16B. A plurality of axial grooves 41 are formed at equal intervals over the entire length of the expansion / contraction stroke, radially from the center.

  In the example of FIG. 3A, the sliding resistance between the teeth 51 of the male shaft (male spline shaft) 16A formed of carbon steel or aluminum alloy and the groove 41 of the female shaft (female spline cylinder) 16B is shown. An example of a telescopic shaft covered with a sleeve is shown as the covering portion 61 to be reduced.

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

  In the example of FIG. 3 (2), the covering portion 61 for reducing the sliding resistance between the teeth 51 of the male shaft (male spline shaft) 16A and the groove 41 of the female shaft (female spline cylinder) 16B is coated. An example of the extended telescopic axis is shown. That is, the male shaft 16A having 18 axial teeth 51 as a non-circular outer peripheral shape for transmitting rotational torque has an axial groove 41 in the axial direction of the female shaft 16B on the entire axial length of the teeth 51. A covering portion 61 that reduces the sliding resistance between them is coated.

  3 (1) and 3 (2) 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 ether ketone 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 (1), after forming a covering portion 61 that reduces the sliding resistance with the groove 41 of the female shaft 16B on the entire axial length of the teeth 51 of the male shaft 16A, FIG. As shown, the groove 41 of the female shaft 16B is fitted over the entire axial length of the teeth 51 of the male shaft 16A. 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. In this state, the male shaft 16A is slid relative to the female shaft 16B in the axial direction, and the sliding resistance before break-in is measured.

  Next, 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 around 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, and the heat is transmitted to the covering portion 61. The covering portion 61 is heated to a predetermined temperature according to the sliding resistance before the break-in. Is done. As another example, the covering portion 61 may be heated from the male shaft 16A side.

  When the covering portion 61 is heated, the covering portion 61 expands over the entire length in the axial direction of the teeth 51 of the male shaft 16A, as shown by a two-dot chain line in FIG. Therefore, as shown in the alternate long and short dashed ellipses T1 and T2 in FIG. 4 and FIG. 6A, the covering portion 61 has a side surface 411 of the groove 41 and a side surface 511 of the tooth 51 over the entire length in the axial direction of the tooth 51. The tightening margin between 511 and 511 becomes large, causing plastic deformation and compressive strain.

  Next, as shown by an arrow R in FIG. 2, when the male shaft 16 </ b> A is reciprocally slid relative to the female shaft 16 </ b> B a predetermined number of times in the axial direction, the covering portion 61 is moved to the side surfaces 511, 511 of the teeth 51. The side is strongly compressed, and plastic deformation and creep deformation are caused uniformly over the entire axial length of the tooth 51 to cause compressive strain.

  By reciprocatingly sliding the male shaft 16A with respect to the female shaft 16B, the groove 41 of the female shaft 16B and the teeth 51 of the male shaft 16A hit the entire length in the axial direction, and the sliding resistance is constant over the entire length of the sliding stroke. become. 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 tightening margin between the side surface 411 of the groove 41 and the side surfaces 511 and 511 of the teeth 51, and the sliding resistance of the intermediate shaft 16 after acclimation becomes a predetermined magnitude.

  As shown in the heating / cooling curve of the covering portion 61 in FIG. 7, the covering portion 61 is heated for a predetermined time A1, and the covering portion 61 is heated from room temperature W1 to a predetermined temperature W2. Next, the male shaft 16A is reciprocally slid relative to the female shaft 16B by a predetermined number of times in the axial direction for a predetermined time A2.

  Next, the covering portion 61 is forcibly cooled, and the covering portion 61 is returned from the predetermined temperature W2 to the normal temperature W1 at a predetermined time A3. In order to control the amount of compressive strain due to the creep phenomenon to a predetermined magnitude, the covering portion 61 is forcibly cooled and the time for returning the temperature of the covering portion 61 from the predetermined temperature W2 to the normal temperature W1 is accurately controlled. It will be necessary.

  This forced cooling is performed by heat conduction by bringing a mold (not shown) cooled to a temperature lower than the ambient temperature by chiller cooling into contact with the female shaft 16A or the male shaft 16B. The forced cooling can also be performed by blowing wind at a temperature lower than the ambient temperature to the female shaft 16A or the male shaft 16B.

  As shown in FIG. 8, in order to make the sliding resistance after the acclimation of the intermediate shaft 16 a predetermined magnitude, the relationship between the temperature of the covering portion 61 and the amount of decrease in the sliding resistance is tested in advance, and data is obtained. obtain. As shown in FIG. 9, when the male shaft 16A is reciprocally slid relative to the female shaft 16B in the axial direction in order to make the sliding resistance after the acclimation of the intermediate shaft 16 a predetermined value. The relationship between the number of sliding times and the amount of decrease in sliding resistance is tested in advance to obtain data. It is desirable to test by changing the sliding speed at the time of reciprocating sliding to obtain data of appropriate sliding speed.

  The data in FIG. 9 is obtained for each temperature by heating the covering 61 to a plurality of temperatures. As shown in FIG. 9, even if the number of sliding operations is increased, the increase in the amount of decrease in sliding resistance is small, so the number of sliding operations during break-in may be constant.

  Further, as shown in FIG. 10, in order to heat the temperature of the covering portion 61 to a predetermined temperature, the relationship between the time for heating the covering portion 61 and the temperature of the covering portion is tested in advance to obtain data. In this test, data is obtained by testing in advance according to the temperature in the vicinity of the covering portion 61 measured before heating the covering portion 61 to a predetermined temperature.

  From the test data of FIGS. 8 to 10 described above, the sliding resistance after running-in falls within the allowable range S according to the sliding resistance before running-in and the temperature of the covering portion 61 before running-in as shown in FIG. In this manner, the break-in is performed by changing the heating temperature of the covering portion 61, the heating time, the number of sliding of the intermediate shaft 16, and the cooling time of the covering portion 61. The sliding resistance is measured after the break-in, and it is confirmed that the slide resistance after the break-in is within the allowable range S, and the break-in conditions C1 to C8 are determined.

  As another example, as shown in FIG. 12, with respect to a group of intermediate shafts 16 that fall within a range (V1 to V3) where the sliding resistance before running-in exists, the sliding resistance after running-in falls within an allowable range S. Conditioning is performed with the heating temperature and heating time of the covering portion 61, the number of sliding times of the intermediate shaft 16 and the cooling time of the covering portion 61 being constant. Measure the sliding resistance after running-in, confirm that the sliding resistance after running-in falls within the allowable range S, and set the running-in conditions C1-C3 for each group of the sliding resistance ranges V1-V3 before running-in. It may be confirmed.

  Therefore, according to the measured value of the sliding resistance before the break-in, the heating of the covering portion 61 and the female shaft 16B with the break-in conditions C1 to C8 or the break-in conditions C1 to C3 determined in FIG. If the reciprocating sliding of the male shaft 16A and the cooling of the covering portion 61 are performed, the sliding resistance after the break-in can be surely kept within a predetermined allowable range S.

  Next, a second embodiment of the present invention will be described. FIG. 13: is a longitudinal cross-sectional view which shows the manufacturing process of the expansion-contraction shaft of Example 2 of this invention. FIG. 14 is a perspective view showing a male shaft according to Embodiment 2 of the present invention. FIG. 15 (1) is a longitudinal sectional view showing a male shaft according to the second embodiment of the present invention, and FIG. 15 (2) is an enlarged sectional view of a portion Q in FIG. 15 (1). In the following description, only structural portions and operations different from the above embodiment will be described, and redundant description will be omitted. Further, the same parts as those in the above embodiment will be described with the same numbers.

  The second embodiment is a modification of the first embodiment, in which the axial length L2 of the heating device 71 is formed longer than the total axial length L1 of the teeth 51 forming the covering portion 61 of the male shaft 16A. In this example, a range longer than the covering portion 61 is heated.

  That is, similarly to the first embodiment, after forming the covering portion 61 that reduces the sliding resistance with the groove 41 of the female shaft 16B on the entire axial length of the teeth 51 of the male shaft 16A, The groove 41 of the female shaft 16B is fitted over the entire length of the teeth 51 in the axial direction.

  Next, 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. When an alternating current is passed through the heating device 71, the female shaft 16B is heated by electromagnetic induction, and the heat is transmitted to the covering portion 61. The covering portion 61 is heated to a predetermined temperature according to the sliding resistance before the break-in. Is done.

  When the covering portion 61 is heated, the covering portion 61 expands over the entire length of the teeth 51 of the male shaft 16A in the same manner as in the first embodiment. Therefore, as in the first embodiment, the covering portion 61 has a large fastening margin between the side surface 411 of the groove 41 and the side surfaces 511 and 511 of the tooth 51 over the entire axial length of the tooth 51.

  When the heating of the covering portion 61 is stopped, the portion of the circles U1 to U4 in FIG. 13 (the female shaft 16B is not in contact with the covering portion 61) rather than the portion where the female shaft 16B is in contact with the covering portion 61. The temperature of (part) is high. Therefore, as shown by the arrow R in FIG. 13, when the male shaft 16A is reciprocally slid relative to the female shaft 16B by a predetermined number of times in the axial direction, as indicated by the dashed line ellipses T3 to T6 in FIG. Further, the covering portion 61 in the vicinity of both ends in the axial direction of the tooth 51 is strongly heated, and the amount of expansion of the covering portion 61 in the vicinity of both ends in the axial direction of the tooth 51 increases.

  As a result, the tightening margin of the covering portion 61 in the vicinity of both ends in the axial direction of the tooth 51 is increased, so that the compressive strain in the vicinity of both ends in the axial direction of the covering portion 61 is larger than that in the central portion. The thickness in the vicinity of both ends is thinner than the central portion.

  As a result, as shown in FIGS. 15A and 15B, chamfered portions 62 and 62 are formed in the vicinity of both ends in the axial direction of the covering portion 61 of the male shaft 16A. As shown in FIG. 15 (2), the chamfered portions 62, 62 are such that the gap δ between the groove 41 of the female shaft 16 </ b> B and the covering portion 61 increases toward the axial end of the covering portion 61. Formed.

  Therefore, since there are no edges at both axial ends of the covering portion 61 of the male shaft 16A, a lubricant such as grease applied to the sliding surface between the groove 41 of the female shaft 16B and the covering portion 61 is The both ends of the covering portion 61 in the axial direction are not swept out of the sliding surface. Therefore, the lubricant is smoothly supplied to the sliding surface, the sliding resistance is kept small for a long time, and the life of the telescopic shaft is improved.

  In the above embodiment, the covering portion 61 for reducing the sliding resistance is formed on the tooth 51 side of the male shaft 16A, but the covering portion 61 for reducing the sliding resistance is formed on the groove 41 side of the female shaft 16B. Also good. Moreover, you may form the coating | coated part 61 which reduces sliding resistance in both the tooth | gear 51 of the male shaft 16A, and the groove | channel 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.

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 taken along the line AA of FIG. 2, (1) is an enlarged cross-sectional view showing a telescopic shaft covering a sleeve, and (2) is an enlarged cross-sectional view showing a telescopic 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. 4 is an enlarged cross-sectional view of a P part in FIG. 3B, showing a manufacturing process of the telescopic shaft of Example 1 of the present invention. FIG. 6 is an enlarged cross-sectional view of a P part in FIG. It is a heating-cooling curve of the coating | coated part which shows the manufacturing process of Example 1 of this invention. It is a graph which shows the fall amount of temperature and sliding resistance when a coating | coated part is heated. It is a graph which shows the frequency | count of sliding and the fall amount of sliding resistance when sliding an expansion-contraction shaft. It is a graph which shows the heating time when a coating part is heated, and the temperature of a coating part. It is a graph which shows the change of the sliding resistance before and after acclimatization of an expansion-contraction axis. It is a graph of the other example which shows the change of the sliding resistance before and after acclimatization of an expansion-contraction axis. It is a longitudinal cross-sectional view which shows the manufacturing process of the expansion-contraction shaft of Example 2 of this invention. It is a perspective view which shows the male shaft of Example 2 of this invention. (1) is a longitudinal sectional view showing a male shaft of Example 2 of the present invention, and (2) is an enlarged sectional view of a Q part of (1).

Explanation of symbols

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)
DESCRIPTION OF SYMBOLS 17 Universal joint 18 Car 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 Groove 411 Side surface 51 Teeth 511 Side surface 61 Covering portion 62 Chamfered portion 71 Heating device

Claims (14)

A male shaft having a non-circular outer peripheral shape,
A female shaft having a non-circular inner peripheral shape that is fitted on the outer periphery of the male shaft so as to be slidable in the axial direction and capable of transmitting rotational torque;
A method for producing a telescopic shaft, which is formed on a non-circular outer periphery of the male shaft and has a covering portion that reduces sliding resistance between the inner periphery of the female shaft,
Forming a covering portion on the non-circular outer periphery of the male shaft to reduce the sliding resistance between the inner periphery of the female shaft;
A step of externally fitting the non-circular inner periphery of the female shaft to the non-circular outer periphery of the male shaft formed with the covering portion;
Measuring the sliding resistance before acclimation by sliding the male shaft relative to the female shaft in the axial direction;
From the data tested in advance, a process for obtaining heating conditions and sliding conditions for making the sliding resistance before break-in the predetermined sliding resistance,
The manufacturing method of the expansion-contraction shaft characterized by including the process of heating the said coating | coated part on the said heating conditions. The manufacturing method of the telescopic shaft described in claim 1 is:
A method for producing an extendable shaft, further comprising a step of sliding the male shaft relative to the female shaft in the axial direction under the sliding condition. In the manufacturing method of the expansion-contraction shaft as described in any one of Claim 1 or Claim 2,
The method for manufacturing an extendable shaft is characterized in that chiller cooling is used for cooling the covering portion. In the manufacturing method of the expansion-contraction shaft as described in any one of Claim 1 or Claim 2,
A method for producing a telescopic shaft, characterized in that a heating condition and a sliding condition are obtained for each group of a range having a sliding resistance before the break-in. In the manufacturing method of the expansion-contraction shaft as described in any one of Claim 1 or Claim 2,
The method of manufacturing a telescopic shaft, wherein the covering portion is cooled by bringing a die having a temperature lower than that of the heated covering portion into contact with the female shaft or the male shaft and conducting heat. In the manufacturing method of the expansion-contraction shaft as described in any one of Claim 1 or Claim 2,
A method for manufacturing an extendable shaft, wherein the heating condition is changed according to a temperature in the vicinity of the covering portion measured before heating the covering portion to a predetermined temperature. In the manufacturing method of the expansion-contraction shaft as described in any one of Claim 1 or Claim 2,
The method of manufacturing the telescopic shaft is characterized in that the cooling of the covering section blows a gas having a temperature lower than that of the heated covering section to the female shaft or the male shaft. In the manufacturing method of the expansion-contraction shaft as described in any one of Claim 1 or Claim 2,
The heating condition is a heating time for heating the covering portion to a predetermined temperature. In the manufacturing method of the expansion-contraction shaft as described in any one of Claim 1- Claim 8,
The method for manufacturing an extendable shaft, wherein the covering portion is heated using electromagnetic induction. In the manufacturing method of the expansion-contraction shaft as described in any one of Claim 1- Claim 8,
The method of manufacturing a telescopic shaft, wherein the heating of the covering part is performed by contacting an object having a temperature higher than that of the covering part with the female shaft or the male shaft and conducting heat. In the manufacturing method of the expansion-contraction shaft as described in any one of Claim 1- Claim 8,
The sliding condition is the number of times of sliding the male shaft relative to the female shaft in the axial direction. The method for manufacturing the telescopic shaft according to any one of claims 1 to 8,
A step of obtaining a cooling condition for making the sliding resistance before break-in a predetermined sliding resistance from data tested in advance;
The manufacturing method of the expansion-contraction shaft characterized by further providing the process which cools the coating | coated part which the process made to slide in the said axial direction completed on the said cooling conditions. In the manufacturing method of the expansion-contraction shaft as described in any one of Claim 1- Claim 12,
The method for manufacturing a telescopic shaft, wherein the covering portion is made of at least one of rubber, polymer material, and solid lubricant.   A telescopic shaft manufactured by the method for manufacturing the telescopic shaft according to any one of claims 1 to 13.

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