JP2013142437A - Telescopic shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a telescopic shaft prevented from a plastic flow and wear of a coating part caused by rotational torque applied to the telescopic shaft having the coating part for reducing sliding resistance.SOLUTION: A projecting tooth 51 of a male shaft 16A made of metal is coated with a coating part 61 for reducing sliding resistance between itself and a tooth groove 41 of a female shaft 16B, and the inner periphery 612 of the coating part 61 is bonded to the tooth surface 511 of the projecting tooth 51 with a bond. The adhesive strength of the coating part 61 is increased by providing the tooth surface 511 of the projecting tooth 51 with linear machining marks left when cutting the projecting tooth 51, or micro unevenness formed by shot peening work or a pickling process. Since the coating part 61 is bonded to the tooth surface 511 of the projecting tooth 51, elastic deformation in three directions, i.e., a compressing direction (arrows α3, α4 in Fig.4), a circumferential direction (arrows β3, β4 in Fig.4) and an axial direction (a direction orthogonal to the paper face in Fig.4) is restrained.

Description

  The present invention relates to a telescopic shaft, in particular, a telescopic shaft capable of transmitting rotational torque and relatively sliding in the axial direction, for example, a telescopic shaft such as an intermediate shaft or a steering shaft.

  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. A conventional telescopic shaft is shown in FIGS. FIG. 6 is an enlarged cross-sectional view showing a conventional fitting portion between a protruding tooth and a tooth gap of a telescopic shaft, FIG. 7 is an enlarged sectional view of an R portion of FIG. 6, and FIG. It is an expanded sectional view which shows the state where the abrasion powder of the coating | coated part was pinched | interposed between them.

  As shown in FIGS. 6 to 8, in the conventional telescopic shaft, a male shaft (male intermediate shaft) 16A of the intermediate shaft 16 is internally fitted and connected to a female shaft (female intermediate shaft) 16B. On the inner circumference of the female shaft 16B, a plurality of axial tooth grooves 41 are formed at equal intervals over the entire length of the expansion / contraction stroke, radially from the axis of the female shaft 16B.

  The male shaft 16A having the same number of axial protruding teeth 51 as the number of the tooth grooves 41 is slid between the axial total length of the protruding teeth 51 and the axial tooth grooves 41 of the female shaft 16B. A resin coating 61 that reduces the dynamic resistance is coated. The conventional covering portion 61 shown in FIGS. 6 to 8 is not bonded to the tooth surface 511 of the protruding tooth 51.

  In recent years, there has been an increase in the number of electric power steering devices that are excellent in weight reduction and fuel efficiency. In particular, the column assist type electric power steering device is added to the intermediate shaft 16 as compared with the conventional hydraulic power steering device. The rotational torque is increased by about 10 to 40 times. Therefore, as shown in FIG. 6, when a large rotational torque T is applied to the intermediate shaft 16 of the column assist type electric power steering device, the covering portion 61 is compressed.

  Since the covering portion 61 is not bonded to the tooth surface 511 of the ridge tooth 51, the covering portion 61 moves relative to the tooth surface 511, compressing direction (arrows α1, α2 in FIG. 6), circumferential direction (arrow β1 in FIG. 6). , Β2) and elastically deformed in three directions in the axial direction (direction perpendicular to the paper surface of FIG. 6). As a result, the outer periphery 611 of the covering portion 61 plastically flows into the grease reservoir portion of the covering portion 61, and the backlash between the covering portion 61 and the tooth surface 411 of the tooth groove 41 of the female shaft 16 </ b> B increases, resulting in a sound. There was a risk of occurrence.

  In particular, when the male shaft 16A is formed in a hollow cylindrical shape, the protruding teeth 51 of the male shaft 16A are elastically deformed by the rotational torque T, and the relative movement between the tooth surface 511 of the protruding teeth 51 and the covering portion 61 is performed. As a result, the inner periphery 612 of the covering 61 is worn. As a result, as shown in FIGS. 7 and 8, wear powder 613 is sandwiched between the tooth surface 511 of the protruding tooth 51 and the inner periphery 612 of the covering portion 61, and the tooth groove 41 of the covering portion 61 and the female shaft 16 </ b> B. The tightening allowance between the tooth surface 411 increases, the sliding resistance between the covering portion 61 and the tooth surface 411 increases, and the vibration on the wheel side is easily transmitted to the steering wheel via the intermediate shaft 16. Therefore, the malfunction that a steering feeling falls arises.

  In the telescopic shaft of Patent Document 1, an annular groove deeper than the root of the protruding tooth is formed on the outer peripheral surface of the male shaft, and the covering portion is coated on the annular groove and the tooth surface of the protruding tooth. Is integrated with the male shaft.

Japanese Patent Laid-Open No. 55-24290

  It is an object of the present invention to provide a telescopic shaft in which the covering portion does not plastically flow or the covering portion is not worn by the rotational torque acting on the extending and contracting shaft having the covering portion that reduces sliding resistance.

  The above problem is solved by the following means. That is, the first invention is a metal male shaft having a plurality of protruding teeth formed on the outer periphery, and is externally slidable in the axial direction and capable of transmitting rotational torque to the protruding teeth of the male shaft. A female shaft in which a plurality of tooth grooves to be fitted are formed on the inner periphery, a covering portion coated on the tooth surface of the protruding tooth of the male shaft, and a protruding tooth of the male shaft forming the covering portion, It is an expansion / contraction shaft that externally fits a tooth gap, wherein the covering portion is bonded to the tooth surface of the protruding tooth with an adhesive.

  According to a second aspect of the present invention, there is provided a telescopic shaft characterized in that in the telescopic shaft of the first aspect, minute irregularities are formed on the tooth surface of the protruding tooth.

  According to a third invention, in the telescopic shaft of the second invention, the minute unevenness is formed by any one of a shot peening process and a pickling process at the time of cutting the ridge teeth. It is a characteristic telescopic shaft.

  A fourth aspect of the invention is the telescopic shaft according to any one of the first to third aspects of the invention, wherein the male shaft is hollow.

  According to a fifth invention, in the telescopic shaft according to any one of the first to third inventions, the telescopic shaft is connected to an output shaft of an assist device for applying auxiliary torque to the steering shaft. The telescopic shaft is characterized by being a shaft.

  In the telescopic shaft of the telescopic shaft of the present invention, it is a telescopic shaft in which the tooth groove of the female shaft is externally fitted to the male tooth projecting tooth on which the covering portion is formed, and the covering portion is attached to the tooth surface of the projecting tooth by an adhesive. It is glued. Therefore, when a large rotational torque is applied and the covering portion is compressed, the covering portion is bonded to the tooth surface of the protruding tooth, so that elastic deformation in the three directions of the compression direction, the circumferential direction, and the axial direction is suppressed. The As a result, the backlash between the covering portion and the tooth surface of the tooth groove of the female shaft is suppressed, so that no sound is generated. Further, since the relative movement between the tooth surface of the ridge tooth and the covering portion is also suppressed, the wear on the inner periphery of the covering portion is suppressed, so that the sliding resistance between the covering portion and the tooth surface is increased. Is suppressed.

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 expansion-contraction axis | shaft of the Example of this invention. It is an AA expanded sectional view of FIG. It is the P section expanded sectional view of FIG. It is the Q section expanded sectional view of Drawing 4. It is an expanded sectional view which shows the fitting part of the protrusion tooth | gear and tooth space of the conventional expansion-contraction shaft. It is the R section expanded sectional view of FIG. FIG. 7 is an enlarged cross-sectional view showing a state in which wear powder of the covering portion is sandwiched between the covering portion and the protruding teeth of FIG. 6.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side view of the steering device having the telescopic shaft according to the present invention, partially cut away, showing an embodiment applied to an electric power steering device having a steering assisting portion. 2 is a longitudinal sectional view showing the telescopic shaft of the embodiment of the present invention, and FIG. 3 is an AA enlarged sectional view of FIG. 4 is an enlarged cross-sectional view of a portion P in FIG. 3, and FIG. 5 is an enlarged cross-sectional view of a portion Q in FIG.

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

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

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

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

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

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

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

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

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

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

  As shown in FIGS. 2 to 4, a metallic female shaft 16B formed of carbon steel or an aluminum alloy is formed in a hollow cylindrical shape, and radially extends from the axial center of the female shaft 16B on the inner periphery thereof. The plurality of tooth gaps 41 in the axial direction are formed at equal intervals over the entire length of the expansion / contraction range (extension / contraction stroke).

  Further, as shown in FIGS. 2 to 4, a male male shaft (male spline shaft) 16A formed of carbon steel (S48C to S50C, STKM11A to STKM19A) or aluminum alloy is formed in a hollow cylindrical shape. . The covered tooth 61 of the male shaft 16 </ b> A is covered with a covering portion 61 that reduces the sliding resistance with the tooth groove 41 of the female shaft (female spline cylinder) 16 </ b> B, and the tooth surface 511 of the protruding tooth 51 is covered with the covering portion. The inner periphery 612 of 61 is adhered with an adhesive. As a method of covering the protruding portion 51 of the male shaft 16A with the covering portion 61, an injection molding method or a fluid immersion method is preferable.

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

  The material of the covering portion 61 is at least one of polyamide 6 (PA6) resin, polyamide 66 (PA66) resin, polyether ether ketone (PEEK) resin, polyacetal (POM) resin, and polyphenylene sulfide (PPS) resin. It is preferable to comprise two polymer materials.

  The thickness of the covering portion 61 is preferably in the range of 0.1 to 1 mm, and may be in the range of 0.01 to 1.5 mm. As shown in FIG. 5, minute unevenness is formed on the tooth surface 511 of the protruding tooth 51 by leaving a processing line when the protruding tooth 51 is cut or performing shot peening or pickling. By doing so, the adhesive strength of the coating | coated part 61 is enlarged. If minute irregularities are formed on the tooth surface 511 of the ridge tooth 51 in this way, the frictional force between the tooth surface 511 of the ridge tooth 51 and the inner periphery 612 of the covering portion 61 is increased. Adhesion with an agent becomes unnecessary, which is preferable.

  As shown in FIG. 4, when a large rotational torque T is applied to the telescopic shaft of the embodiment of the present invention configured as described above, the covering portion 61 is compressed. Since the inner periphery 612 of the covering portion 61 is bonded to the tooth surface 511 of the protruding tooth 51, the compression direction (arrows α3 and α4 in FIG. 4), the circumferential direction (arrows β3 and β4 in FIG. 4), and the axial direction Elastic deformation in three directions (in a direction perpendicular to the paper surface of FIG. 4) is suppressed.

  As a result, since the play between the covering portion 61 and the tooth surface 411 of the tooth groove 41 of the female shaft 16B is suppressed, no sound is generated. Further, since the relative movement between the tooth surface 511 of the protruding tooth 51 and the inner periphery 612 of the covering portion 61 is also suppressed, the wear of the inner periphery 612 of the covering portion 61 is suppressed, so that the covering portion 61 and the tooth An increase in sliding resistance with the surface 411 is suppressed.

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

DESCRIPTION OF SYMBOLS 11 Steering wheel 12 Steering shaft 12A Outer shaft 12B Inner shaft 13 Steering column 13A Outer column 13B Inner column 14 Support bracket 15 Universal joint 16 Intermediate shaft 16A Male intermediate shaft (male shaft)
16B Female intermediate shaft (Female shaft)
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 Tooth groove 411 Tooth surface 51 Projection tooth 511 Tooth surface 61 Covering part 611 Outer periphery 612 Inner periphery 613 Wear powder

Claims (5)

A male male shaft with a plurality of protruding teeth formed on the outer periphery,
A female shaft having a plurality of tooth grooves formed on an inner periphery thereof that are externally slidable in the axial direction and capable of transmitting rotational torque to the protruding teeth of the male shaft;
A covering portion coated on the tooth surface of the protruding tooth of the male shaft;
A telescopic shaft in which a tooth groove of the female shaft is externally fitted to the protruding tooth of the male shaft that forms the covering portion,
The extendable shaft, wherein the covering portion is bonded to the tooth surface of the protruding tooth with an adhesive. The telescopic shaft according to claim 1,
A telescopic shaft characterized in that minute irregularities are formed on the tooth surface of the protruding tooth. In the telescopic shaft according to claim 2,
The minute projections and depressions are formed by any one of a shot peening process and a pickling process at the time of cutting the ridge teeth. In the telescopic shaft according to any one of claims 1 to 3,
A telescopic shaft, wherein the male shaft is hollow. In the telescopic shaft according to any one of claims 1 to 3,
The telescopic shaft is
A telescopic shaft, which is an intermediate shaft connected to an output shaft of an assist device for applying auxiliary torque to a steering shaft.

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