JP6057139B2 - Manufacturing method of power transmission shaft - Google Patents

Description

  The present invention relates to a method for manufacturing a power transmission shaft.

  An intermediate shaft or the like of the vehicle steering apparatus is configured by an extendable power transmission shaft. This power transmission shaft has, for example, a configuration in which a male shaft and a female shaft are spline-fitted. A resin coating layer may be formed on the male spline teeth of the male shaft (see, for example, Patent Documents 1 to 4). In Patent Document 4, a groove called sink is provided on the surface of the resin coating layer, and a lubricant (grease) can be held in the groove.

  The surface of the resin coating layer may be trimmed by rubbing during production of the power transmission shaft (see, for example, Patent Documents 5 to 7).

US Pat. No. 2,844,489 Japanese Patent Publication No. 45-5081 JP-A-9-105419 Japanese Patent Laid-Open No. 64-55411 Japanese Patent No. 4045112 JP-A 63-176824 JP 2009-168194 A

  As a result of intensive studies, the present inventor has conceived that a power transmission shaft having a resin coating layer is produced by the following method. Specifically, a molten resin is applied to the surface of a metal male spline shaft and cured. Next, the male spline shaft is inserted into the female spline shaft, and both shafts are relatively moved in the axial direction. Thereby, the surface of the resin coating layer can be adjusted to a shape that fits the surface of the female shaft.

  However, when the male shaft manufacturing intermediate and the female shaft manufacturing intermediate are slid relative to each other in the axial direction, the friction between the surface of the resin coating layer of the male shaft and the surface of the female shaft is large. Then, frictional heat and shear stress between these surfaces increase. As a result, the resin softens and roller-like wear powder is generated. If the wear powder is interposed between both shafts that slide relative to each other in the axial direction, the surface of the resin coating layer is roughened by the wear powder. As a result, if the surface of the resin coating layer becomes rough, rattling occurs between the male shaft and the female shaft when the power transmission shaft is used, resulting in the generation of rattle noise and a decrease in steering feeling. .

In addition, as described above, the frictional heat generated when the intermediate shafts for both shafts are slid becomes a problem, so the intermediate shafts for manufacturing both shafts cannot be slid at high speed, and the resin coating layer It takes time to finish the surface of the surface.
The present invention has been made under such a background, and an object of the present invention is to make the surface of a resin smoother when manufacturing a power transmission shaft having a resin coating on a sliding portion.

  Another object of the present invention is to shorten the time required for finishing the surface of the resin.

In order to achieve the above object, according to the present invention, an inner shaft (35) having an outer spline (37) provided on the outer periphery and an inner spline (38) slidably engaged with the outer spline are provided on the inner periphery. In a method of manufacturing a power transmission shaft (5) including a cylindrical outer shaft (36) and a resin coating (139) provided on at least one of the outer spline and the inner spline, the inner shaft is manufactured. The intermediate axis (L2) of the intermediate body (147) and the central axis (L1) of the intermediate intermediate body for manufacturing (46) are made to coincide with each other, and each intermediate intermediate for manufacturing is relative to the axial direction (X1). A sliding process that generates frictional heat by sliding and heats the resin film with the frictional heat while adapting the surface (139a) of the resin coating. Lubricant between intermediates 48) and is interposed, the familiar process, after the temperature of each of the manufacturing intermediate member (TP) exceeds a predetermined temperature (TP1), and sliding load of each of the manufacturing intermediate member (F) Is completed when the load falls below a predetermined load (F1) .

  According to the present invention, in the conforming step, the lubricant is interposed between the production intermediates. Thereby, it can suppress that the frictional resistance which acts on the surface of a resin film becomes large more than necessary in a conforming process. Therefore, it is possible to suppress the softening of the resin film due to frictional heat and the generation of roller-like wear due to the shear stress generated in the resin film, and it is possible to suppress the abrasion powder from roughening the resin film. The surface of the resin coating can be finished very smoothly.

In addition, since the frictional heat of the resin coating can be lowered in the conforming step, the production intermediates can be relatively slid relative to each other at a higher speed while suppressing the generation of roller-like wear powder. Thereby, since the conforming process can be completed in a short time, the power transmission shaft can be manufactured more efficiently. Furthermore, it is not necessary to accurately position and hold each manufacturing intermediate prior to the conforming step. Accordingly, the time required for holding each production intermediate can be shortened. Thereby, the time required for finishing the resin coating can be shortened, and the power transmission shaft can be manufactured more efficiently.
In the familiarization process, when the relative sliding of the manufacturing intermediate is started, first, the temperature of the manufacturing intermediate rises due to the sliding friction of each manufacturing intermediate. Then, by continuing the relative sliding, the surface of the resin film becomes familiar with the surface of the counterpart member. Thereby, the sliding resistance of each intermediate for production decreases. Further, as the sliding resistance of each production intermediate decreases, the temperature of each production intermediate also decreases. In this way, after the temperature of each manufacturing intermediate exceeds the predetermined temperature and at the timing when the sliding load of each manufacturing intermediate falls below the predetermined load, the familiar process is appropriately performed. It can be completed at the right time.

Further, in the present invention, the conforming step is completed when the temperature of each of the manufacturing intermediates reaches a peak temperature and when the sliding load of each of the manufacturing intermediates falls below a predetermined load. (Claim 2 ).
In addition, in the above, the numbers in parentheses represent reference numerals of corresponding components in the embodiments described later, but the scope of the claims is not limited by these reference numerals.

It is a mimetic diagram showing a schematic structure of a steering device for vehicles which has an intermediate shaft as a power transmission shaft manufactured by a manufacturing method of one embodiment of the present invention. It is a partially broken side view of an intermediate shaft. It is sectional drawing which follows the III-III line of FIG. (A)-(j) is the schematic which shows the manufacturing process of an intermediate shaft in order. It is a perspective view which shows the principal part of the slide apparatus as a manufacturing apparatus for performing a heat-fitting process. (A) is a side view which shows the structure of the periphery of a 1st holding mechanism, and has shown one part by the cross section, (B) is a disassembled perspective view which shows a part of 1st holding mechanism. (A) is the schematic diagram of the principal part for demonstrating the heating familiarization process of the intermediate body for manufacture by the slide apparatus of this invention, (B) is the heating familiarity of the intermediate body for manufacture by the slide apparatus of a comparative example. It is a schematic diagram of the principal part for demonstrating a process. It is a graph which shows the relationship between the sliding load and time in a heat-fitting process, and the graph which shows the relationship between the temperature of the resin film of a manufacturing intermediate, and time.

A preferred embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram of a vehicle steering apparatus having an intermediate shaft to which a power transmission shaft manufactured by a manufacturing method according to an embodiment of the present invention is applied. Referring to FIG. 1, a vehicle steering apparatus 1 includes a steering shaft 3 connected to a steering member 2 such as a steering wheel, and a power transmission shaft (spline telescopic shaft connected to the steering shaft 3 via a universal joint 4. ) As an intermediate shaft 5, a pinion shaft 7 connected to the intermediate shaft 5 via a universal joint 6, and a rack 8 a that meshes with a pinion 7 a provided near the end of the pinion shaft 7. And a rack shaft 8.

  A steering mechanism A1 is configured by a rack and pinion mechanism including the pinion shaft 7 and the rack shaft 8. The rack shaft 8 is supported by a housing 10 fixed to the vehicle body side member 9 so as to be movable in an axial direction along the left-right direction of the vehicle (a direction orthogonal to the paper surface). Each end portion of the rack shaft 8 is connected to a corresponding steered wheel via a corresponding tie rod and a corresponding knuckle arm, although not shown.

  The steering shaft 3 includes a first steering shaft 11 and a second steering shaft 12 that are connected coaxially. The first steering shaft 11 has an upper shaft 13 and a lower shaft 14 which are fitted so as to be able to rotate together and be slidable relative to each other in the axial direction using spline coupling. One of the upper shaft 13 and the lower shaft 14 constitutes an inner shaft, and the other constitutes a cylindrical outer shaft.

The second steering shaft 12 includes an input shaft 15 connected to the lower shaft 14 so as to be able to rotate together, an output shaft 16 connected to the intermediate shaft 5 through the universal joint 4, and the input shaft 15 and the output shaft 16 And a torsion bar 17 for connecting the two in a relatively rotatable manner.
The steering shaft 3 is rotatably supported by a steering column 20 fixed to the vehicle body side members 18 and 19 via a bearing (not shown).

The steering column 20 includes a cylindrical upper jacket 21 and a cylindrical lower jacket 22 that are fitted so as to be relatively movable in the axial direction, and a housing 23 connected to the lower end in the axial direction of the lower jacket 22. The housing 23 houses a speed reduction mechanism 25 that decelerates the power of the steering assisting electric motor 24 and transmits it to the output shaft 16.
The speed reduction mechanism 25 has a drive gear 26 that is connected to a rotation shaft (not shown) of the electric motor 24 so as to be able to rotate together with the drive gear 26 and a driven gear 27 that meshes with the drive gear 26 and rotates together with the output shaft 16. . The drive gear 26 is composed of, for example, a worm shaft, and the driven gear 27 is composed of, for example, a worm wheel.

  The steering column 20 is fixed to the vehicle body side members 18 and 19 via an upper bracket 28 on the vehicle rear side and a lower bracket 29 on the vehicle front side. The upper bracket 28 uses a fixing bolt (stud bolt) 30 that protrudes downward from the vehicle body side member 18, a nut 31 that is screwed to the fixing bolt 30, and a capsule 32 that is detachably held by the upper bracket 28. The vehicle body side member 18 is fixed.

The lower bracket 29 is fixed to the housing 23 of the steering column 20. Further, the lower bracket 29 is fixed to the vehicle body side member 19 using a fixing bolt (stud bolt) 33 protruding from the vehicle body side member 19 and a nut 34 screwed into the fixing bolt 33.
Referring to FIGS. 1 and 2, intermediate shaft 5 as a power transmission shaft is capable of sliding and transmitting torque between inner shaft 35 and cylindrical outer shaft 36 along axial direction X <b> 1 of intermediate shaft 5. It is made by spline fitting. One of the inner shaft 35 and the outer shaft 36 constitutes the upper shaft, and the other constitutes the lower shaft. In this embodiment, the outer shaft 36 is connected to the universal joint 4 as an upper shaft, and the inner shaft 35 is connected to the universal joint 6 as a lower shaft.

  In the present embodiment, the power transmission shaft is described as applied to the intermediate shaft 5, but the power transmission shaft of the present invention is applied to the first steering shaft 11, and the first steering shaft 11 has a telescopic adjustment function, You may make it fulfill | perform an impact absorption function. In the present embodiment, the vehicle steering device 1 is described as an electric power steering device. However, the power transmission shaft of the present invention may be applied to a vehicle steering device for manual steering. .

Referring to FIG. 2, universal joint 4 constitutes a first universal joint (first joint). The universal joint 4 includes a yoke 61 provided on the output shaft 16 of the steering shaft 3, a yoke 62 provided at one end of the outer shaft 36, and a cross shaft 63 that connects the yokes 61, 62. ing.
The yoke 61 is Y-shaped and has a cylindrical base 61a and a pair of limbs 61b and 61b extending from the base 61a. A fitting hole is formed in the base 61a, and the output shaft 16 is fitted and fixed to the fitting hole. The pair of rims 61b and 61b extend in parallel to each other.

The yoke 62 is formed in the same shape as the yoke 61. Specifically, the yoke 62 is U-shaped and has a base portion 62a and a pair of rims 62b and 62b extending from the base portion 62a (in FIG. 2, one rim 62b is not shown). One end of the outer shaft 36 is fixed to the base 62a. The pair of rims 62b and 62b extend in parallel to each other.
The cross shaft 63 is disposed between the pair of rims 61b and 61b and the pair of rims 62b and 62b. The four tip portions of the cross shaft 63 are connected to the rims 61b, 61b, 62b, 62b via bearings (not shown), respectively. Thereby, the yoke 61 and the yoke 62 are relatively rotatable around the center 63 a of the cross shaft 63. The center 63 a of the cross shaft 63 is disposed on the center axis L <b> 1 of the outer shaft 36.

The universal joint 6 constitutes a second universal joint (second joint). The universal joint 6 includes a yoke 61 provided at one end of the pinion shaft 7, a yoke 62 provided at one end of the inner shaft 35, and a cross shaft 63 that connects the yokes 61, 62. . The center 63 a of the cross shaft 63 of the universal joint 6 is disposed on the central axis L <b> 1 of the inner shaft 35.
The structures of the universal joints 4 and 6 are the same. Therefore, in the following, the universal joint 6 is assigned the same reference numeral as the corresponding component of the universal joint 4 and detailed description thereof is omitted.

  3 is a cross-sectional view taken along line III-III in FIG. Referring to FIGS. 2 and 3, an outer spline 37 provided on the outer periphery 35 a of the inner shaft 35 and an inner spline 38 provided on the inner periphery 36 a of the outer shaft 36 are fitted to each other. In the present embodiment, as shown in FIG. 3, at least the tooth surface 37a of the outer spline 37 is provided with a resin coating 139 having a surface 139a subjected to heat-fitting processing (see FIG. 4H) for the outer shaft 36. Is formed. Specifically, at least the tooth surface 37 a of the outer spline 37 is formed by at least a part of the resin coating 139 coated around the cored bar 350 of the inner shaft 35.

A process of manufacturing the intermediate shaft 5 will be described with reference to FIG. 4 which is a schematic view.
First, in the forging step shown in FIG. 4A, an inner shaft manufacturing intermediate 41 in which the outer spline 40 is formed is obtained by forging the material.
Next, in the pretreatment step shown in FIG. 4B, pretreatment for coating is performed on at least the tooth surface of the outer spline 40 of the intermediate shaft manufacturing intermediate 41 in FIG. 4A. Specifically, in order to smooth the tooth surface of the outer spline 40 as a pre-stage process when the resin layer 44 is formed in the covering step of FIG. 4C, for example, the shot blasting, primer application, etc. Perform ground processing. As a result, an inner shaft manufacturing intermediate 43 (corresponding to the core metal 350 of the inner shaft 35) having the outer spline 42 with the tooth surface pretreated as shown in FIG. 4B is obtained.

  Next, in the coating step (coating step) shown in FIG. 4C, a resin layer 44 is formed on at least the tooth surface of the outer spline 42 of the intermediate shaft manufacturing intermediate 43 in FIG. The intermediate shaft manufacturing intermediate body 45 having the resin layer 44 formed thereon is obtained. Specifically, after the inner shaft manufacturing intermediate 43 that has been subjected to the pretreatment is heated, the manufacturing intermediate 43 is immersed in a fluid immersion tank in which the resin powder is in a fluidized state for a predetermined time. Thereby, the resin powder adhering to the inner shaft manufacturing intermediate 43 is melted by heat, and the resin layer 44 is formed. The cross section of the outer periphery of the resin layer 44 is circular or substantially circular. As the resin forming the resin layer 44, a thermoplastic resin such as polyamide or polyacetal can be used. The resin layer 44 may be injection molded.

Next, in the joint joining step shown in FIG. 4D, the universal joint 6 is connected to the end of the inner shaft manufacturing intermediate 45.
Next, in the broaching process shown in FIG. 4 (e), an outer shaft manufacturing intermediate 46 is prepared. The outer shaft manufacturing intermediate 46 is formed by forging a material into a cylindrical shape, and an inner spline 38 is formed on the inner periphery. Is formed. The universal joint 4 is attached to one end of the outer shaft manufacturing intermediate 46. Broaching is performed by inserting the inner shaft manufacturing intermediate 45 on which the resin layer 44 is formed into the outer shaft manufacturing intermediate 46. As a result, the inner shaft manufacturing intermediate 47 having the molded resin film 39 is obtained by the tooth surfaces of the inner splines 38 of the outer shaft manufacturing intermediate 46 as shown in FIG.

In the broaching process, when broaching, as shown in FIG. 4 (e), the surplus portion 44a of the resin layer 44 is scraped off, and like a saw dust, outside the outer shaft manufacturing intermediate 46 as a counterpart shaft. Discharged.
Next, in the groove forming step of FIG. 4F, a laser 51 (for example, YVO4 laser or CO2 laser) is irradiated from the laser irradiation unit 50 in a direction crossing the axial direction X1 onto the surface 39a of the resin coating 39. Thereby, a part of the resin is thermally decomposed and removed. Thus, an inner shaft manufacturing intermediate 147 having the resin coating 139 in which the spiral groove 52 is formed as shown in FIG. 4G is obtained.

The groove 52 is formed at a predetermined depth from the surface 139a of the resin coating 139. The groove 52 extends so as to cross the outer splines 37 of the inner shaft manufacturing intermediate 147.
Note that the grooves 52 may be formed using water grooves or fine groove processing using compressed air containing hard fine particles instead of processing using the laser 51.
Referring to FIG. 4G, grease 48 as a lubricant is applied to the inner shaft manufacturing intermediate 147 in which the groove 52 is formed. The grease 48 is the same as the grease applied when the intermediate shaft 5 is shipped. The grease 48 is applied to the tip of the inner shaft manufacturing intermediate 147, for example. Note that only the base oil having the same component as the base oil of the grease 48 may be applied to the outer peripheral surface of the inner shaft manufacturing intermediate 147 as a lubricant.

  4H, the inner shaft manufacturing intermediate body 147 is inserted into the outer shaft manufacturing intermediate body 46 as the counterpart shaft. At this time, the interference between the outer shaft manufacturing intermediate 46 and the resin coating 139 of the inner shaft manufacturing intermediate 147 is about several tens of μm, which is an interference fit. Then, the inner shaft manufacturing intermediate 147 is forcibly slid with respect to the outer shaft manufacturing intermediate 46 via the grease 48 in the axial direction X1. Thereby, the inner shaft 35 covered with the resin coating 139 having the surface 139a fitted to the tooth surface of the inner spline 38 of the intermediate body 46 for manufacturing the outer shaft, and the outer shaft 36 are completed.

  In the heat-familiarization process, frictional heat generated by forced sliding of the production intermediates 46 and 147 is used. As a result, the surface layer portion of the resin coating 139 in contact with the outer shaft manufacturing intermediate 46 is heated to a temperature equal to or higher than the melting point of the resin of the resin coating 139 and melted. The surface layer portion of the resin coating 139 is adapted to the inner spline 38 of the outer shaft manufacturing intermediate 46 while promoting the softening of the resin in this heated state. Thereafter, the resin coating 139 is cooled by air or the like sprayed from the nozzle 53. Thereby, the surface 139a of the resin coating 139 can be fitted to the tooth surface of the inner spline 38 of the outer shaft 36 at a surface roughness level (surface roughness level of about several tens of μm). Thereby, the inner shaft 35 is completed.

Next, in the grease application process shown in FIG. 4 (i), the grease 48 is applied to the surface of the resin coating 139 of the inner shaft 35. The inner shaft 35 coated with the grease 48 is incorporated into the outer shaft 36, and the intermediate shaft 5 as a spline telescopic shaft is completed as shown in FIG. 4 (j).
Of the manufacturing process of the intermediate shaft 5 described above, the heat-fitting process will be described in more detail.
FIG. 5 is a perspective view showing a main part of a slide device 90 as a manufacturing apparatus for performing the heat-fitting process.

  The slide device 90 holds the intermediate bodies 46 and 147 so that they can be aligned while aligning the central axis L1 of the outer shaft manufacturing intermediate body 46 with the central axis L2 of the inner shaft manufacturing intermediate body 147. Is configured to do. The slide device 90 is configured to heat and conform (finish) the surface of the resin coating 139 by causing the production intermediates 46 and 147 to slide relative to each other in the axial direction X1.

The slide device 90 includes a drive mechanism 93 and a first holding mechanism 91 and a second holding mechanism 92 as a pair of holding mechanisms.
The drive mechanism 93 is provided to relatively slide the manufacturing intermediate bodies 46 and 147 in the axial direction X <b> 1 via the first holding mechanism 91. The drive mechanism 93 is configured by, for example, a hydraulic cylinder as an actuator. The hydraulic cylinder includes a rod 94. The rod 94 is configured to be capable of linear reciprocation in the direction in which the first and second holding mechanisms 91 and 92 face each other (axial direction X1).

  The slide device 90 is arranged vertically, and the displacement direction of the rod 94 coincides with the vertical direction. Thereby, it is possible to suppress the bending force caused by the weight of the manufacturing intermediate bodies 46 and 147 held by the slide device 90 from acting between the manufacturing intermediate bodies 46 and 147. In addition, it is good also considering the displacement direction of the rod 94 as a horizontal direction by arrange | positioning the slide apparatus 90 sideways.

A disc-shaped connecting plate 95 is fixed to the tip of the rod 94. The connection plate 95 has a plurality of screw holes 95a.
The first and second holding mechanisms 91 and 92 are provided to hold the manufacturing intermediate bodies 46 and 147 in a state of being fitted to each other.
The first holding mechanism 91 is coupled to the connection plate 95 and can reciprocate linearly with the rod 94. The first holding mechanism 91 is configured to hold the universal joint 4 provided in the outer shaft manufacturing intermediate 46.

FIG. 6A is a side view showing a configuration around the first holding mechanism 91, and a part thereof is shown in cross section. FIG. 6B is an exploded perspective view showing a part of the first holding mechanism 91. As shown in FIGS. 6A and 6B, the first holding mechanism 91 includes a first plate 101, a second plate 102, a third plate 103, and a fixing screw 104. .
The first plate 101 is formed in a disc shape. A screw insertion hole 101 a is formed in the first plate 101. The first plate 101 is fixed to the connecting plate 95 by a fixing screw 105 that is inserted through the screw insertion hole 101a and screwed into the screw hole 95a.

  In the first plate 101, a convex portion 101b and a screw hole 101c are formed in addition to the screw insertion hole 101a. The convex portion 101b is formed at the center of the upper surface 101d of the first plate 101 and protrudes upward. The convex portion 101 b is fitted in a fitting hole formed in the yoke 61 of the universal joint 4. Accordingly, the yoke 61 can be positioned so that the yoke 61 (the center 63a of the universal joint 4) passes through the central axis L3 of the rod 94. The upper surface 101 d of the first plate 101 is in surface contact with one end surface of the base 61 a of the yoke 61.

A plurality of screw holes 101c are provided in the outer peripheral portion of the first plate 101, and are arranged at equal intervals in the circumferential direction of the outer peripheral portion. The screw insertion holes 101 a and the screw holes 101 c are alternately arranged in the circumferential direction of the first plate 101.
The second plate 102 is formed in a U-shape and includes a pair of facing portions 102a and 102a. The facing portions 102a and 102a extend in parallel to each other. A plurality (for example, four) of screw insertion holes 102b are formed in the facing portions 102a and 102a of the second plate 102. The facing portions 102a and 102a are disposed so as to sandwich the rims 62b and 62b of the yoke 62 of the universal joint 4. Inner side surfaces 102c and 102c of the opposing portions 102a and 102a are adjacent to outer sides of the rims 62b and 62b, and can contact these rims 62b and 62b. With this configuration, it is possible to restrict the yoke 62 from excessively swinging with respect to the yoke 61 (excessive swinging of the yoke 62 around the straight line L4 passing between the pair of rims 61b and 61b).

  The third plate 103 is provided to press the base 61 a of the yoke 61. The third plate 103 is formed in a rod shape. The cross-sectional shape of the third plate 103 is a substantially rectangular shape. The intermediate portion of the third plate 103 is in contact with the base portion 61a of the yoke 61, and the yoke 61 is sandwiched between the third plate 103 and the first plate 101 in the axial direction X1. Both end portions in the longitudinal direction of the third plate 103 are pressed downward by the facing portions 102 a and 102 a of the second plate 102. Further, screw insertion holes 103 a and 103 a are formed at both ends of the third plate 103.

A plurality of fixing screws 104 are provided, are inserted into the screw insertion holes 102 b and 103 a of the second plate 102 and the third plate 103, and are screw-coupled to the screw holes 101 c of the first plate 101. Thus, the second plate 102 and the third plate 103 are detachably fixed to the first plate 101.
With reference to FIG. 5, the second holding mechanism 92 is fixed to a fixing member 106 provided in the slide device 90. The second holding mechanism 92 is configured to hold the universal joint 6 provided in the inner shaft manufacturing intermediate 147. The second holding mechanism 92 has the same configuration as the first holding mechanism 91. Therefore, each component of the second holding mechanism 92 is denoted by the same reference numeral as the corresponding component of the first holding mechanism 91, and detailed description thereof is omitted. The rim 61 b of the yoke 61 of the universal joint 6 is held between the first plate 101 and the third plate 103 of the second holding mechanism 92.

With the above-described configuration, the universal joints 4 and 6 allow the tilt displacement of the manufacturing intermediate bodies 46 and 147 held by the slide device 90. In addition, the slide device 90 holds the manufacturing intermediate bodies 46 and 147 through the universal joints 4 and 6 so that they can be aligned, and is connected to the manufacturing intermediate bodies 46 and 147 through the universal joints 4 and 6. Thrust force for relative sliding of both is applied.
Further, the slide device 90 is provided with a load cell 107 as a load detection device for detecting a sliding load when the production intermediates 46 and 147 are slid in the axial direction X1. The load cell 107 is attached to the rod 94, for example.

Further, the slide device 90 is provided with a temperature sensor 108 for detecting the temperature of the resin coating 139 as the temperature of the production intermediates 46 and 147. The temperature sensor 108 is, for example, a non-contact type temperature sensor.
The load detection signal of the load cell 107 and the temperature detection signal of the temperature sensor 108 are input to the control device 109. The control device 109 controls the drive mechanism 93 based on the input detection signal.

Next, the operation of the slide device 90 in the heat-fitting process will be described.
In the heat-fitting process, the control device 109 drives the drive mechanism 93 to cause the production intermediates 46 and 147 to slide relative to each other in the axial direction X1 and apply frictional heat to the resin coating 139. When the inner shaft manufacturing intermediate body 147 is pushed into the outer shaft manufacturing intermediate body 46, the rod 94 of the drive mechanism 93 is displaced to one X2 (upward) in the axial direction X1. As a result, the first plate 101, the universal joint 4 and the outer shaft manufacturing intermediate body 46 of the first holding mechanism 91 are displaced together with the rod 94 to one X2 side in the axial direction X1. At this time, the first plate 101 of the first holding mechanism 91 applies an upward force to the yoke 61 of the universal joint 4, so that the universal joint 4 is displaced upward. On the other hand, the universal joint 6 is received by the first plate 101 of the second holding mechanism 92. Thereby, the displacement to the one X2 of the axial direction X1 of the intermediate body 147 for inner shaft manufacture is controlled.

  In the operation of pulling the outer shaft manufacturing intermediate 46 with respect to the inner shaft manufacturing intermediate 147, the rod 94 of the drive mechanism 93 is displaced to the other X3 (downward) in the axial direction X1. At this time, the third plate 103 of the first holding mechanism 91 presses the base portion 61a of the yoke 61 of the universal joint 4 to the other X3 in the axial direction X1. Accordingly, the intermediate shaft manufacturing intermediate body 46 is displaced together with the rod 94 to the other X3 side in the axial direction X1. At this time, since the base 61a of the universal joint 6 is received by the third plate 103 of the second holding mechanism 92, the inner shaft manufacturing intermediate 147 is restricted from being displaced in the other direction X3 in the axial direction X1. .

  By the above operation, the production intermediates 46 and 147 are repeatedly expanded and contracted. Then, as described above, frictional heat is generated by forced sliding of the outer shaft and the inner shaft manufacturing intermediates 46 and 147. As a result, the surface layer portion of the resin coating 139 in contact with the outer shaft manufacturing intermediate 46 is heated to a temperature equal to or higher than the melting point of the resin of the resin coating 139 and melted. The resin film 139 is made to conform to the inner spline 38 of the outer shaft manufacturing intermediate 46 while promoting softening of the resin in this heated state.

  During this heat-fitting process, an unintended force (for example, a radial force P1) acts on the rod 94 as a force in a direction different from the axial direction X1 of the production intermediate bodies 46 and 147 at rest. There are things to do. When such a force P <b> 1 is generated, the manufacturing intermediate bodies 46 and 147 to which the universal joints 4 and 6 are attached, before the slide by the drive mechanism 93 is started, as shown in the schematic diagram of FIG. Tilt from when it is stationary. As a result, it is possible to suppress the application of a force (unintentional force) other than the thrust force along the axial direction X1 between the manufacturing intermediates 46 and 147 at all times. Thereby, it can suppress that local force acts on the resin film 139.

  For example, as shown in FIG. 7B, a slide device 90 ′ that slides the production intermediates 46 and 147 while holding the production intermediates 46 and 147 directly without using the universal joints 4 and 6 is provided. Think. In the slide device 90 ′, an unintended radial force P1 as a force other than the thrust force along the axial direction X1 acts between the manufacturing intermediates 46 and 147 due to a reaction force during driving. There is. At this time, a bending force acts between the manufacturing intermediates 46 and 147, and a large force acts locally on a part of the resin coating 139, making it difficult to smooth the resin coating 139.

  FIG. 8 is a graph showing the relationship between the sliding load F and the time TM in the heat-fitting process, and the graph showing the relationship between the temperature TP of the resin coating 139 of the inner shaft manufacturing intermediate 147 and the time TM. As shown in FIG. 8, in the heat-fitting process using the slide device 90, the manufacturing intermediates 46 and 147 slide relative to each other with the start of the drive of the slide device 90 from time TM <b> 0. As a result, the temperature TP of the resin coating 139 increases with time until the predetermined time TM1. At this time, the surface of the resin coating 139 is leveled while being heated by sliding with the outer shaft manufacturing intermediate 46. Thereby, the sliding resistance, that is, the sliding load F gradually decreases.

  As the sliding load F decreases, the sliding operation between the manufacturing intermediates 46 and 147 becomes smooth, and the amount of heat generation decreases. Then, the temperature TP of the resin coating 139 rises to the maximum temperature TP1 as the predetermined temperature in the predetermined time TM1, and then decreases. After the temperature TP of the resin coating 139 exceeds the maximum temperature TP1, when the sliding load F falls below the predetermined load F1 (at time TM2), the surface of the resin coating 139 is sufficiently smooth. It has become. At this time, the heat-fitting process is completed.

  As described above, according to the present embodiment, in the heat-fitting process, the manufacturing intermediates 46 and 147 are held by the slide device 90 so as to be aligned. That is, each manufacturing intermediate 46 is controlled so that the force that changes the state in which the central axes L1 and L2 of the manufacturing intermediates 46 and 147 coincide with each other is prevented from acting on each manufacturing intermediate 46 and 147. , 147 are held to be displaceable in directions other than the axial direction X1. Thereby, it can suppress that the force (for example, radial force P1) as force other than thrust force, such as bending force, acts on each intermediate body 46,147 for manufacture.

  By performing the conforming step in this state, the entire surface of the surface 139a of the resin coating 139 that is in contact with the counterpart outer shaft manufacturing intermediate 46 is evenly distributed on the outer shaft manufacturing intermediate 46. It can be brought into sliding contact with the surface. In addition, in the heat-fitting process, the grease 48 is interposed between the production intermediates 46 and 147. Thereby, it can suppress that the frictional resistance which acts on the surface of the resin film 139 becomes larger than necessary in the heat-fitting process.

  Therefore, it is possible to suppress the softening of the resin film 139 due to frictional heat and the generation of roller-like wear due to the shear stress generated in the resin film 139, and it is possible to suppress the abrasion powder from roughening the resin film 139. In combination with the effect of maintaining the alignment of the manufacturing intermediates 46 and 147 and the effect of interposing the grease 48 in the heat-fitting process, the surface 139a of the resin coating 139 can be finished extremely smoothly.

In addition, since the frictional heat of the resin coating 139 can be lowered in the heat-fitting process, the production intermediates 46 and 147 can be slid relative to each other at a higher speed while suppressing the generation of roller-like wear powder. Thereby, since the heat-fitting process can be completed in a short time, the intermediate shaft 5 can be manufactured more efficiently.
Further, since the manufacturing intermediates 46 and 147 are attached to the first and second holding mechanisms 91 and 92 having an alignment function prior to the heat-fitting process, the manufacturing intermediates 46 and 147 are accurately positioned and held. There is no need to do. Therefore, the time for attaching the manufacturing intermediates 46 and 147 to the slide device 90 can be shortened. Thereby, the time required for finishing the resin coating 139 can be shortened, and the intermediate shaft 5 can be manufactured more efficiently.

  In the heat-fitting process, the production intermediates 46 and 147 are held via the universal joints 4 and 6 so that they can be aligned. As a result, in the heat-fitting process, when the manufacturing intermediates 46 and 147 of the respective shafts are relatively slid, a force other than the thrust force in the axial direction X1 (unintentional force such as the radial force F1) is applied to each manufacturing intermediate. When trying to act on the bodies 46, 147, the manufacturing intermediates 46, 147 are inclined. Thereby, it can suppress reliably that said unintentional force acts on the intermediate bodies 46 and 147 for manufacture of each axis | shaft in a heat-familiarization process.

  Thus, with the simple configuration of using the two universal joints 4 and 6, it is possible to reliably suppress the unintended force from acting on the manufacturing intermediates 46 and 147 in the heat-fitting process. Further, like the intermediate shaft 5 of the vehicle steering apparatus 1, when manufacturing a power transmission shaft having universal joints 4 and 6 at one end of the inner shaft 35 and one end of the outer shaft 36, respectively, By using the joints 4 and 6, the intermediates 46 and 147 for manufacturing can be held so as to be aligned. As a result, the number of dedicated parts for holding the manufacturing intermediates 46 and 147 in an alignable manner can be reduced in the heat-fitting process. In addition, the equipment for holding the manufacturing intermediates 46 and 147 so that they can be aligned can be reduced in size.

Further, the heat-familiarization process is performed after the temperature TP of each production intermediate 46, 147 exceeds the maximum temperature TP1 and when the sliding load F of each production intermediate 46, 147 falls below a predetermined load F1. Complete.
In the heat-fitting process, when the relative sliding of the manufacturing intermediates 46 and 147 is started, first, the temperature of the manufacturing intermediates 46 and 147 rises due to the sliding friction of the manufacturing intermediates 46 and 147. Then, by continuing the relative sliding, the surface of the resin coating 139 becomes familiar with the inner surface of the inner shaft manufacturing intermediate 147. Thereby, the sliding resistance of each of the production intermediates 46 and 147 is lowered. Further, as the sliding resistance of each manufacturing intermediate 46, 147 decreases, the temperature TP of each manufacturing intermediate 46, 147 also decreases. Thus, after the temperature TP of each manufacturing intermediate body 46, 147 exceeds the maximum temperature TP1, and at the timing when the sliding load F of each manufacturing intermediate body 46, 147 falls below the predetermined load F1, the heat is applied. By completing the process, the heat-fitting process can be completed at an appropriate timing.

  In addition, grease 48 is applied in the heat-fitting process. Thereby, the sliding resistance of the manufacturing intermediate bodies 46 and 147 can be reduced by using the grease 48 required when the intermediate shaft 5 is used. Thereby, it is not necessary to separately prepare a lubricant for reducing the sliding resistance of the intermediate bodies 46 and 147 for manufacturing each shaft in the heat-fitting process, and the manufacturing cost of the intermediate shaft 5 can be reduced.

As described above, rattling in the circumferential direction of the intermediate shaft 5 can be reduced, and the expansion and contraction operation of the intermediate shaft 5 can be performed smoothly. Thereby, the steering apparatus 1 for vehicles which is excellent in silence and excellent in steering feeling can be realized.
Further, the manufacturing intermediates 46 and 147 can be easily set on the slide device 90 by a simple operation of attaching the universal joint 4 to the first holding mechanism 91 and attaching the universal joint 6 to the second holding mechanism 92.

  Further, by providing the groove 52 on the surface 139 a of the resin coating 139, the above-mentioned wear powder can be taken into the groove 52. Therefore, abnormal wear does not occur on the surface 139a of the resin coating 139 due to the increase in wear powder. That is, since the surface 139a is not roughened, the surface 139a of the resin coating 139 can be fitted to the other party in a relatively smooth state.

Therefore, the substantial contact area between the tooth surfaces 37a, 38a of the outer spline 37 and the inner spline 38 can be increased. As a result, the intermediate shaft as a spline telescopic shaft having excellent slidability and durability. 5 can be realized. Further, when the intermediate shaft 5 is used, the groove 52 functions as a lubricant reservoir, so that a good lubrication state can be maintained for a long time.
The present invention is not limited to the contents of the above embodiments, and various modifications can be made within the scope of the claims.

  For example, in the above embodiment, the manufacturing intermediate bodies 46 and 147 are attached to the slide device 90 via the universal joints 4 and 6, but the present invention is not limited to this. The production intermediates 46 and 147 are preferably attached to the slide device 90 so as to be able to be tilted or displaced in a direction orthogonal to the axial direction X1. For example, a universal joint may be provided in the middle portion of the rod 94. In addition, instead of the universal joints 4 and 6, spherical joints or Oldham joints may be used in the heat-fitting process.

Further, instead of the first holding mechanism 91 of the slide device 90, the second holding mechanism 92 may be driven in the axial direction X1, or both the first and second holding mechanisms 91 and 92 are driven in the axial direction X1. May be.
In the said embodiment, although demonstrated according to the example which forms a resin film in the outer spline of an inner axis | shaft, it is not restricted to this. A resin film may be formed on at least the tooth surface of the inner spline of the outer shaft. In this case, when the resin layer formed on the inner spline of the outer shaft manufacturing intermediate is shaved to form a resin film, the resin layer is heat-fitted using the inner shaft manufacturing intermediate. become.

  In the above embodiment, the intermediate shaft 5 of the vehicle steering apparatus 1 has been described as an example of the power transmission shaft. However, the present invention may be applied to a power transmission shaft of another device.

  DESCRIPTION OF SYMBOLS 1 ... Vehicle steering device, 4 ... Universal joint (1st joint), 5 ... Intermediate shaft (power transmission shaft), 6 ... Universal joint (2nd joint), 35 ... Inner shaft, 36 ... Outer shaft, 37 ... Outer Spline, 38 ... inner spline, 46 ... intermediate for manufacturing outer shaft, 48 ... grease (lubricant), 139 ... resin coating, 139a ... surface of resin coating, 147 ... intermediate for manufacturing inner shaft, F ... sliding load F1 ... predetermined load, L1 ... center axis (of the outer shaft manufacturing intermediate), L2 ... center axis (of the inner shaft manufacturing intermediate), TP ... temperature of the manufacturing intermediate, TP1 ... maximum temperature ( Predetermined temperature), X1... Axial direction.

Claims (2)

Provided on at least one of the inner shaft provided with an outer spline on the outer periphery, the cylindrical outer shaft provided with the inner spline slidably engaged with the outer spline, and the outer spline and the inner spline. In a method for manufacturing a power transmission shaft including a resin film,
Friction heat is generated by causing the center axis of the intermediate intermediate for manufacturing the inner shaft and the central axis of the intermediate intermediate for manufacturing the outer shaft to coincide with each other and sliding the intermediate intermediates relative to each other in the axial direction. And generating a conforming step of conforming the surface of the resin coating while heating the resin coating with the frictional heat ,
In the conforming step, a lubricant is interposed between each of the production intermediates ,
The conforming step is completed after the temperature of each manufacturing intermediate exceeds a predetermined temperature, and when the sliding load of each manufacturing intermediate falls below a predetermined load. Shaft manufacturing method. In Claim 1 , the conforming step is completed after the temperature of each of the production intermediates reaches a peak temperature and when the sliding load of each of the production intermediates falls below a predetermined load. A power transmission shaft manufacturing method.

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