Telescopic shaft, steering device

Abstract

To provide a telescopic shaft and a steering device capable of securing large telescopic stroke without extending a fitting length between a male shaft and a female shaft.SOLUTION: A telescopic shaft has: a male shaft 15; a female shaft 16; and a plurality of rolling elements 17 arranged in a rollable manner between a male shaft side rolling surface provided in a first male shaft side groove 15a formed in the male shaft 15, and a female shaft side rolling surface provided in a first female shaft side groove 16a formed in the female shaft 16, where a distance from contact points B, B of the rolling element 17 to the male shaft side rolling surface to a rolling axis P of the rolling element 17 is different from a distance from a contact point A of the rolling element 17 to the female shaft side rolling surface to the rolling axis P.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a telescopic shaft that is axially extendable and retractable and capable of transmitting torque, and to a steering device equipped with the telescopic shaft. [Background technology]

[0002] Conventionally, telescopic shafts are known that are used as intermediate shafts or steering shafts of steering devices mounted on automobiles, etc. When a large telescopic stroke is required for a telescopic shaft due to requirements such as installation in a vehicle, a large telescopic stroke is ensured by extending the rolling grooves of a cylindrical male shaft and a cylindrical female shaft that are fitted together via rolling elements to increase the length of the fitted portion (fitting length) (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-275897 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional telescopic shafts described above, the mating length between the male and female shafts is long, which can make it difficult to ensure a collapse stroke during a secondary collision. In addition, the long mating length of the male and female shafts makes them heavy, which can lead to problems with fuel efficiency and costs.

[0005] The present invention has been made in consideration of the above problems, and has an object to provide a telescopic shaft and a steering device that ensure a large telescopic stroke without extending the fitting length between the male shaft and the female shaft. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention provides: A columnar male shaft; A cylindrical female shaft fitted onto the male shaft; a plurality of rolling elements arranged freely to roll between a male shaft rolling surface provided in a first male shaft groove extending in the axial direction and formed on an outer peripheral surface of the male shaft and a female shaft rolling surface provided in a first female shaft groove extending in the axial direction and formed on an inner peripheral surface of the female shaft, When viewed from the axial direction, the shortest distance from the contact point of the rolling element with the male shaft side rolling surface to the rolling axis of the rolling element is different from the shortest distance from the contact point of the rolling element with the female shaft side rolling surface to the rolling axis. the law of nature, The rolling element is in contact with the male shaft rolling surface at two points and in contact with the female shaft rolling surface at one point. The present invention provides a telescopic shaft characterized by the above-mentioned.

[0007] The present invention also provides The present invention provides a steering device comprising the telescopic shaft. Effect of the Invention

[0008] According to the present invention, it is possible to provide a telescopic shaft and a steering device that ensure a large telescopic stroke without extending the fitting length between the male shaft and the female shaft. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view (partially sectional view) of a steering device equipped with a telescopic shaft according to an embodiment of the present application, viewed obliquely from the front. [Diagram 2] FIG. 2 is a cross-sectional view showing the configuration of a telescopic shaft according to an embodiment of the present application. [Diagram 3] FIG. 3 is an enlarged cross-sectional view of a fitting portion between a male shaft and a female shaft of a telescopic shaft according to an embodiment of the present application. [Figure 4] 4(a) is a cross-sectional view taken along line 3A-3A in FIG. 3, and FIG. 4(b) is a cross-sectional view taken along line 3B-3B in FIG. [Diagram 5] FIG. 5 is a perspective view of a flat spring of an extension shaft according to an embodiment of the present application, as viewed obliquely from the front. [Figure 6] FIG. 6 is a partially enlarged view of FIG. [Figure 7]7(a) and 7(b) are side views showing first and second modified examples of the rolling elements of the telescopic shaft according to the embodiment of the present application. [Figure 8] 8(a) and 8(b) are enlarged cross-sectional views (corresponding to FIG. 6) showing the configuration of a conventional telescopic shaft, and FIG. 8(b) is a cross-sectional view (corresponding to FIG. 3) showing the configuration of a conventional telescopic shaft different from that of FIG. 8(a). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A steering device including a telescopic shaft according to an embodiment of the present application as an intermediate shaft and a steering shaft will be described with reference to the accompanying drawings. 1, a steering device 1 according to an embodiment of the present application is a column-assist rack-and-pinion electric power steering device for a vehicle in which an electric assist mechanism is attached to a steering column. The steering device 1 includes, in order from the rear side of the vehicle body, i.e., the right side in FIG. 1, a steering wheel 2, a column 4 containing a telescopic shaft (steering shaft) 3, an electric assist mechanism 5 including a motor, a telescopic shaft (intermediate shaft) 6, and a steering gear unit 7.

[0011] The steering gear unit 7 has a pinion shaft 9 connected to the intermediate shaft 6 via a universal joint 8, a rack shaft (not shown) extending in the left-right direction of the vehicle body and meshing with the pinion shaft 9, and a housing 11 that accommodates these. Wheels (not shown) are attached to both ends of the rack shaft via tie rods 12, 12, etc.

[0012] With this configuration, when the driver of the vehicle rotates the steering wheel 2, the pinion shaft 9 rotates via the steering shaft 3 and the intermediate shaft 6, and the rack shaft moves in the left-right direction of the vehicle body accordingly, changing the steering angle of the wheels. At this time, a steering assist force is applied to the steering shaft 3 by the motor of the electric assist mechanism 5, so the force required by the driver to operate the steering wheel 2 can be reduced.

[0013] Here, the column 4 and the steering shaft 3 are extendable and contractible in the axial direction, and the column 4 and the electric assist mechanism 5 are attached to the vehicle body 13 so that the tilt can be adjusted. Therefore, the height of the steering wheel 2 and its position in the fore-and-aft direction of the vehicle body can be adjusted (tilt / telescopic adjustment).

[0014] 2, the intermediate shaft 6 has a cylindrical male shaft 15, a cylindrical female shaft 16 fitted onto the male shaft 15, and a plurality of balls 17, a leaf spring 18, and rollers 19 interposed between them. Note that the axial direction, radial direction, and circumferential direction of the intermediate shaft 6 will hereinafter be simply referred to as the axial direction, radial direction, and circumferential direction.

[0015] The male shaft 15 is made of metal and consists, in order from the rear side of the vehicle body, i.e., the right side in Figure 2, of a large diameter shaft portion 21 that is large in diameter and solid, and a small diameter shaft portion 22 that is integrally formed with the large diameter shaft portion 21, has a smaller diameter than the large diameter shaft portion 21, and is hollow. As shown in Figures 3 and 4(a), on the outer peripheral surface of the vehicle body front side part of large diameter shaft portion 21, three male shaft side trapezoidal grooves 15a extending in the axial direction as first male shaft side grooves and three male shaft side circular grooves 15b extending in the axial direction as second male shaft side grooves are formed alternately at equal intervals along the circumferential direction, i.e., at 60 degree intervals.

[0016] Male shaft side trapezoidal groove 15a has a cross section in the shape of a trapezoid with a narrow bottom width, and extends parallel to the central axis of intermediate shaft 6. In detail, male shaft side trapezoidal groove 15a is configured symmetrically with bottom wall 15c and side walls 15d, 15d extending radially outward in a V-shape from both ends of bottom wall 15c, as shown in Fig. 4(a). Note that, as shown in Fig. 3, a vertical wall 15e perpendicular to the axial direction is formed at the rear end of male shaft side trapezoidal groove 15a in order to regulate the axial rolling of balls 17, which will be described later, in the axial direction. Male shaft-side circular groove 15b has a semicircular cross section and extends parallel to the central axis of the intermediate shaft 6. As shown in Fig. 3, a vertical wall 15f perpendicular to the axial direction is formed at the rear end of male shaft-side circular groove 15b toward the vehicle body in order to support rollers 19, which will be described later.

[0017] The female shaft 16 is made of metal, and as shown in Figures 3 and 4(a), three female shaft side circular grooves 16a extending in the axial direction as first female shaft side grooves and three female shaft side circular grooves 16b extending in the axial direction as second female shaft side grooves are formed alternately at equal intervals along the circumferential direction, i.e., at 60 degree intervals. The female shaft side circular groove 16a has a semicircular cross section and extends parallel to the central axis of the intermediate shaft 6 so as to face the male shaft side trapezoidal groove 15a. The groove radius of the female shaft side circular groove 16a is designed to be larger than the radius of the ball 17. With this configuration, the ball 17 comes into contact with the female shaft side circular groove 16a at one point (A) at the apex of the groove bottom (see FIG. 6). In this way, the groove surface of the female shaft side circular groove 16a forms the female shaft side rolling surface along which the ball 17 rolls. The female shaft side circular groove 16b has a semicircular cross section and extends parallel to the central axis of the intermediate shaft 6 so as to face the male shaft side circular groove 15b. The axial lengths of the male shaft side trapezoidal groove 15a, leaf spring 18 described below, and male shaft side circular groove 15b are designed to be shorter than the axial lengths of the female shaft side circular groove 16a and female shaft side circular groove 16b.

[0018] With this configuration, the male shaft trapezoidal groove 15a and the opposing female shaft circular groove 16a form three sets of ball rolling paths 23 along which a plurality of balls 17 roll, and the male shaft circular groove 15b and the opposing female shaft circular groove 16b form three sets of roller sliding paths 24 along which rollers 19 slide. Therefore, in the male shaft 15 and the female shaft 16, three sets of ball rolling paths 23 and three sets of roller sliding paths 24 are provided alternately at equal intervals along the circumferential direction, i.e., at 60 degree intervals.

[0019] A plurality of metallic balls 17 serving as rolling elements are freely arranged in each of the three sets of ball rolling paths 23. In each of the ball rolling paths 23, a metallic leaf spring 18 serving as a biasing member is arranged between the male shaft side trapezoidal groove 15a and the plurality of balls 17.

[0020] As shown in Figures 4(a) and 5, the leaf spring 18 is composed of a bottom plate 18a that contacts the bottom wall 15c of the male shaft side trapezoidal groove 15a, inner plates 18b, 18b that extend radially outward from both ends of the bottom plate 18a in a V-shape and are approximately parallel to the side walls 15d, 15d of the male shaft side trapezoidal groove 15a, and outer plates 18c, 18c that turn back circumferentially outward from the ends of the inner plates 18b, 18b and extend approximately parallel to and contact the side walls 15d, 15d of the male shaft side trapezoidal groove 15a, and are bilaterally symmetrical. The axial length of the leaf spring 18 is approximately the same as the axial length of the male shaft side trapezoidal groove 15a as shown in Figure 3.

[0021] The leaf spring 18 having such a configuration is disposed between the male shaft side trapezoidal groove 15a and the balls 17, and elastically deforms so that the outer plates 18c, 18c abut against the side walls 15d, 15d of the male shaft side trapezoidal groove 15a, and the inner plates 18b, 18b abut against the balls 17. In detail, the balls 17 contact the inner plates 18b, 18b of the leaf spring 18 at two points (B, B), one each (see FIG. 6). As a result, the balls 17 are urged radially outward of the male shaft 15 and are constantly pressed against the apex of the groove bottom of the female shaft side circular groove 16a with a predetermined urging force, eliminating any backlash between the balls 17 and the male shaft side trapezoidal groove 15a and the female shaft side circular groove 16a. In this way, the working surface of the leaf spring 18 constitutes the male shaft side rolling surface when the balls 17 roll. Here, the acting surface refers to the surface that applies a biasing force to the ball 17, specifically, the radially outer surface of the inner plates 18b, 18b. As shown in Figures 4(b) and 5, the three leaf springs 18 arranged in each ball rolling path 23 have the vehicle body front end of their respective bottom plates 18a integrally connected to the outer edge of a radially extending circular connecting plate 25 at equal intervals along the circumferential direction, i.e., at 120 degree intervals.

[0022] In each of the three sets of roller slideways 24, a roller (columnar body) 19 made of metal and having a substantially cylindrical shape extending in the axial direction is slidably disposed. As shown in FIG. 3, the roller 19 is formed by integrally molding a torque transmission portion 19a and tapered portions 19b, 19b provided on both ends of the torque transmission portion 19a.

[0023] Torque transmission portion 19a is a roller portion that abuts against male shaft side circular groove 15b and the opposing female shaft side circular groove 16b to transmit torque from male shaft 15 to female shaft 16 or from female shaft 16 to male shaft 15. This torque transmission portion 19a has a cylindrical shape and its outer diameter is designed to be slightly smaller than the inner diameter of roller slideway 24, i.e., the cylindrical space formed by male shaft side circular groove 15b and female shaft side circular groove 16b.

[0024] The tapered portions 19b, 19b have an outer diameter that decreases toward both axial ends, so that the rollers 19 can be smoothly inserted into the roller slideways 24 during the manufacture of the intermediate shaft 6. In this embodiment, the torque transmission portion 19a and the tapered portions 19b, 19b are cylindrical in shape, but the present invention is not limited to this. For example, the torque transmission portion 19a and the tapered portions 19b may be cylindrical in shape with an elliptical cross section.

[0025] The roller 19 having such a configuration is biased toward the rear of the vehicle body by a stopper 26 provided on the small diameter shaft portion 22 of the male shaft 15, and its axial movement is restricted. The stopper 26 is made up of a ring-shaped leaf spring 27 made of metal and having a circular ring shape as a biasing member, and a pair of metal flat plates 28a, 28b, each having a circular ring shape, which sandwich the leaf spring 27. A connecting plate 25 of the leaf spring 18 and a stopper 26 are fitted onto the small diameter shaft portion 22 in this order from the rear side of the vehicle body, i.e., from the right side in Fig. 3. The end of the small diameter shaft portion 22 on the front side of the vehicle body is crimped, so that the stopper 26 fitted onto the small diameter shaft portion 22 will not fall off towards the front side of the vehicle body. Note that the stopper 26 may be fixed by a retaining ring, a nut, a push nut, or the like, without being limited to crimping.

[0026] In the stopper 26, the ring-shaped leaf spring 27 applies a force toward the rear of the vehicle body to the flat plate 28b opposite to the flat plate 28a by contacting the flat plate 28a fixed to the vehicle body front end of the swaged small diameter shaft portion 22. The rear side of the flat plate 28b contacts the vehicle body front end face of the roller 19, and the force of the ring-shaped leaf spring 27 is applied to the roller 19, so that the vehicle body rear end face of the roller 19 contacts the vertical wall 15f of the male shaft side circular groove 15b. In this way, the roller 19 is biased toward the rear of the vehicle body by the stopper 26 and is always pressed against the vertical wall 15f, so that the roller 19 can be arranged between the flat plate 28b and the vertical wall 15f without any backlash in the axial direction. The stopper 26 also serves to restrict the rolling of the ball 17 toward the vehicle body front side, thereby preventing the ball 17 from falling off the ball rolling path 23.

[0027] It should be noted that other elastic members, such as a disk-shaped resin, may be used instead of the ring-shaped leaf spring 27 of the stopper 26. When a disk-shaped resin is sandwiched between the flat plates 28a, 28b to form an integrally molded product, the number of parts is reduced to one, which improves the ease of assembly of the intermediate shaft 6 and allows for shortening the assembly time and reducing the manufacturing cost.

[0028] Here, the length of the small diameter shaft portion 22 is designed so that there is a gap (axial gap) between the vehicle body rear side surface of the flat plate 28b of the stopper 26 and the vehicle body front side surface of the connecting plate 25 of the leaf spring 18 (see FIG. 3). In addition, the diameter of the circular opening of the connecting plate 25 is designed to be larger than the outer diameter of the small diameter shaft portion 22, and a gap (radial gap) is created between the circular opening and the small diameter shaft portion 22 (see FIG. 4(b)). Due to these axial and radial gaps, the connecting plate 25 does not restrict the movement of each of the leaf springs 18 even if the three leaf springs 18 are deformed during torque transmission, which will be described later. In addition, the number of parts is reduced to one by integrating the three leaf springs 18 via the connecting plate 25, which improves the ease of assembly of the intermediate shaft 6, shortening the assembly time and reducing the manufacturing cost.

[0029] In the intermediate shaft 6 configured as described above, for example, when torque is applied to the male shaft 15, the torque is transmitted to the female shaft 16 via the rollers 19, balls 17, and leaf spring 18, allowing the male shaft 15 and the female shaft 16 to rotate smoothly together. Regarding the transmission of torque in detail, when the torque applied to the male shaft 15 is small, the torque is transmitted from the male shaft 15 to the female shaft 16 via the leaf spring 18 and the ball 17. As described above, the ball 17 is biased radially outward by the leaf spring 18, and the backlash between the male shaft side trapezoidal groove 15a and the female shaft side circular groove 16a is eliminated, so that it is possible to prevent the ball 17 from colliding with the female shaft side circular groove 16a and generating a hitting sound.

[0030] As the torque applied to the male shaft 15 increases, the leaf spring 18 elastically deforms, specifically, the leaf spring 18 bends inward in the circumferential direction (rotational direction) and radial direction, increasing the force applied to the ball 17. When the amount of elastic deformation of the leaf spring 18 becomes equal to the amount of circumferential clearance between the outer circumferential surface of the torque transmission portion 19a of the roller 19 and the male shaft side circular groove 15b and the female shaft side circular groove 16b, the outer circumferential surface of the torque transmission portion 19a comes into contact with the male shaft side circular groove 15b and the female shaft side circular groove 16b, and torque is transmitted from the male shaft 15 to the female shaft 16 via the torque transmission portion 19a. This transmission of torque also makes it possible to prevent the roller 19 from colliding with the male shaft side circular groove 15b and the female shaft side circular groove 16b and generating a hitting sound. Although the contact point of ball 17 with female shaft side circular groove 16a moves slightly from the apex of the groove bottom due to the elastic deformation of leaf spring 18, ball 17 can stably contact the apex of female shaft side circular groove 16a when no torque is loaded, i.e., when no torque is applied to male shaft 15 or female shaft 16.

[0031] In addition, the intermediate shaft 6 can expand and contract by the male shaft 15 and the female shaft 16 moving relative to each other in the axial direction as the balls 17 roll within the ball rolling path 23 and the rollers 19 slide axially within the roller sliding path 24.

[0032] As described above, the ball 17 in the ball rolling path 23 makes rolling contact with the female shaft side circular groove 16a at one point, and makes rolling contact with the inner plates 18b, 18b of the leaf spring 18 at two points, one each. With this configuration, the relative movement distance between the female shaft 16 and the ball 17 can be made larger than the relative movement distance between the male shaft 15 and the ball 17 when the intermediate shaft 6 extends or retracts.

[0033] Specifically, in this embodiment, as shown in Fig. 6, in a torque-unloaded state, the ball 17 contacts the apex of the female shaft side circular groove 16a at one point (A) on the female shaft 16 side as viewed from the axial direction. The ball 17 is designed so that the shortest distance (L) between the line connecting the two points (B, B) where the ball 17 contacts the inner plates 18b, 18b of the leaf spring 18 on the male shaft 15 side and the center O of the ball 17 is 1 / 2 the radius (2L) of the ball 17. With this design, the shortest distance (2L) from the rolling axis P of the ball 17 to the contact point A on the female shaft 16 side is twice the shortest distance (L) from the rolling axis P to the contact points B, B on the male shaft 15 side. That is, when the intermediate shaft 6 expands and contracts, while the ball 17 rolls in the male shaft side trapezoidal groove 15a by L, it rolls in the female shaft side circular groove 16a by 2L. Therefore, when the intermediate shaft 6 extends or retracts, the male shaft 15 can move 2Lπ per one rotation of the ball 17, and the female shaft 16 can move 4Lπ in the opposite direction to the male shaft 15. The rolling axis P is a line passing through the center O of the ball 17 and is a line (imaginary line) that is the center of rotation of the ball 17 rolling in the ball rolling path 23. This allows the axial length L15 of the rolling surface of the shaft with which the ball 17 makes two-point contact (the male shaft-side rolling surface of the male shaft 15) to be reduced to about half the axial length L16 of the rolling surface of the shaft with which the ball 17 makes one-point contact (the female shaft-side rolling surface of the female shaft 16), as shown in Fig. 3.

[0034] Here, in a conventional intermediate shaft in which the balls in the ball rolling path make contact with the female shaft side circular groove at two points and with the inner plate of the leaf spring at two points as shown in Figure 8(a), if the intermediate shaft is designed so that the shortest distance (L) between the center of the ball and the line connecting the two points where the ball makes contact with the inner plate of the leaf spring is the same as the shortest distance (L) between the center of the ball and the line connecting the two points where the ball makes contact with the female shaft side circular groove, then when the intermediate shaft extends or retracts, the male shaft moves 2Lπ for each rotation of the ball, and the female shaft moves 2Lπ in the opposite direction to the male shaft.

[0035] Therefore, compared to the conventional intermediate shafts as described above, the intermediate shaft 6 in this embodiment can ensure that the movement distance of the female shaft 16 during extension and contraction is twice the movement distance of the male shaft 15, without extending the length of the male shaft 15 and the male shaft side trapezoidal groove 15a, and can ensure a large range of relative movement between the male shaft 15 and the female shaft 16 in the axial direction, i.e., a large extension and contraction stroke of the intermediate shaft 6.

[0036] As described above, in this embodiment, the ratio of the shortest distance from the rolling axis P of ball 17 to contact point A on the female shaft 16 side to the shortest distance from the rolling axis P to contact points B, B on the male shaft 15 side is 1:2, but this ratio is not limited to this.

[0037] In a conventional intermediate shaft in which both the trapezoidal groove on the male shaft side of the male shaft and the circular groove on the female shaft side of the female shaft are extended and rollers and dummy rollers are arranged in the roller sliding path in order to increase the extension / contraction stroke as shown in Fig. 8(b), the fitting length of the male shaft and the female shaft, in other words the length of the portion where the trapezoidal groove on the male shaft side and the circular groove on the female shaft side face each other, is long. Furthermore, because the fitting length of such a conventional intermediate shaft is long, it is heavy and leads to deterioration in fuel efficiency and costs.

[0038] In contrast, the intermediate shaft 6 in this embodiment can ensure a large expansion and contraction stroke without extending the male shaft 15 and the male shaft side trapezoidal groove 15a as described above. Therefore, since there is no need to increase the engagement length between the male shaft and the female shaft, a large engagement length does not hinder the assurance of a collapse stroke in the event of a secondary collision. In addition, the weight of the intermediate shaft 6 does not increase, resulting in a deterioration in fuel efficiency and costs.

[0039] When the intermediate shaft 6 extends or retracts, the outer circumferential surface of the torque transmission portion 19a of the roller 19 comes into contact with the male shaft side circular groove 15b and the female shaft side circular groove 16b. As described above, the intermediate shaft 6 in this embodiment can ensure a large extension stroke of the intermediate shaft 6 without extending the male shaft side trapezoidal groove 15a, so there is no need to lengthen the roller 19. Therefore, the contact area between the torque transmission portion 19a of the roller 19 and the male shaft side circular groove 15b and the female shaft side circular groove 16b does not increase. Therefore, the sliding load during extension or retraction of the intermediate shaft 6 does not increase, and the intermediate shaft 6 can extend or retract smoothly and stably.

[0040] As described above, the roller 19 is biased toward the rear of the vehicle body by the stopper 26, and is positioned without any axial play between the flat plate 28b of the stopper 26 and the vertical wall 15f of the male shaft 15, so that it is possible to prevent the roller 19 from colliding with the flat plate 28b or the vertical wall 15f and generating a collision sound (smacking sound). In addition, the rollers 19 do not tilt with respect to the axial direction within the roller slideway 24. This prevents the rollers 19 from contacting the male shaft side circular groove 15b or the female shaft side circular groove 16b while tilting with respect to the axial direction, which would cause an increase in sliding resistance. Furthermore, the male shaft side circular groove 15b and the female shaft side circular groove 16b are not worn down by the tilted rollers 19 being pressed against them, which extends the life of the male shaft 15, the female shaft 16 and the rollers 19, and ultimately the intermediate shaft 6.

[0041] In the steering device 1 of this embodiment, the configuration of the steering shaft 3 is similar to the configuration of the intermediate shaft 6 described above.

[0042] The steering device 1 equipped with the intermediate shaft 6 and steering shaft 3 configured as described above can smoothly transmit the torque applied by the driver to the steering wheel 2 to the steering gear section 7 via the steering shaft 3 and the intermediate shaft 6, thereby realizing a good steering feeling of the steering wheel 2. In addition, the steering device 1 can smoothly extend and retract the steering shaft 3 during tilt / telescopic adjustment of the steering wheel 2 or during a secondary collision, and can smoothly extend and retract the intermediate shaft 6 during driving to effectively absorb axial displacement.

[0043] As described above, the intermediate shaft 6 in this embodiment is configured to include the male shaft trapezoidal groove 15a on the outer circumferential surface of the male shaft 15 and the female shaft circular groove 16a on the inner circumferential surface of the female shaft 16. However, the positional relationship of the grooves is not limited to this, and a circular groove similar to the female shaft circular groove 16a may be provided on the outer circumferential surface of the male shaft 15, and a trapezoidal groove similar to the male shaft trapezoidal groove 15a may be provided on the inner circumferential surface of the female shaft 16, and the leaf spring 18 may be disposed in the trapezoidal groove. In other words, the ball 17 may be configured to contact the male shaft 15 at one point and the female shaft 16 at two points. This allows the relative movement distance between the male shaft 15 and the ball 17 to be larger than the relative movement distance between the female shaft 16 and the ball 17 when the intermediate shaft 6 is extended or contracted.

[0044] Furthermore, the intermediate shaft 6 in this embodiment is configured to include the leaf spring 18 between the male shaft side trapezoidal groove 15a and the ball 17 as described above. However, the present invention is not limited to this, and the male shaft side trapezoidal groove 15a may be made smaller in size to omit the leaf spring 18, and the ball 17 may contact each of the side walls 15d, 15d of the male shaft side trapezoidal groove 15a at one point each, for a total of two points. In this case, the groove surface of the female shaft side circular groove 16a constitutes the female shaft side rolling surface of the ball 17, and the groove surfaces (side walls 15d, 15d) of the male shaft side trapezoidal groove 15a constitute the male shaft side rolling surface.

[0045] Further, in the intermediate shaft 6 in this embodiment, the spherical balls 17 are used as the rolling elements as described above, but the present invention is not limited to this. For example, a rugby ball-shaped rolling element 31 as shown in Fig. 7(a) may be used instead of ball 17. In this case, the shapes of female shaft side circular groove 16a, male shaft side trapezoidal groove 15a and leaf spring 18 may be changed so that rolling element 31 comes into contact with female shaft side circular groove 16a at contact point A and comes into contact with inner plates 18b, 18b of leaf spring 18 at contact points B, B. Also, instead of the balls 17, stepped rollers 32 shown in Fig. 7(b) may be used. The stepped rollers 32 are formed by integrally providing small-diameter cylindrical portions concentrically at both axial ends of a cylindrical member. In this case, the shapes of the female shaft-side circular groove 16a, the male shaft-side trapezoidal groove 15a, and the leaf spring 18 may be changed so that the female shaft-side circular groove 16a comes into contact at contact point (line) A, and the leaf spring 18 comes into contact with the inner plates 18b, 18b of the leaf spring 18 at contact points (lines) B, B.

[0046] In the intermediate shaft 6 of this embodiment, as described above, the balls 17 are configured to come into contact with one point on the male shaft 15 side and two points on the female shaft 16 side within the ball rolling path 23. However, the number of contact points is not limited to this, and it is only necessary that the shortest distance from the contact point of the balls 17 on the male shaft 15 side to the rolling axis P is different from the shortest distance from the contact point on the female shaft 16 side to the rolling axis P when viewed from the axial direction. For example, it is possible to design the balls 17 to come into contact with two points on the male shaft 15 side and two points on the female shaft 16 side, with the shortest distance from contact points B, B of the balls 17 on the male shaft 15 side to the rolling axis P being L and the shortest distance from contact points A, A on the female shaft 16 side to the rolling axis P being 1.5L.

[0047] In the steering device 1 of this embodiment, the intermediate shaft 6 is arranged so that the male shaft 15 of the male shaft 15 and the female shaft 16 is located on the rear side of the vehicle body, but the female shaft 16 may also be arranged so that it is located on the rear side of the vehicle body. In the steering device 1 of this embodiment, the intermediate shaft 6 is configured such that the male shaft 15 and the female shaft 16 are provided with the male shaft side circular groove 15b and the female shaft side circular groove 16b, and rollers 19 are disposed between them. However, the present invention is not limited to this, and for example, the male shaft 15 and the female shaft 16 may be configured to have projections and recesses extending in the axial direction for spline fitting, or the male shaft 15 and the female shaft 16 may be configured to mesh with each other only with rolling elements (balls 17). The different aspects of the intermediate shaft 6 in this embodiment described above are also applicable to the steering shaft 3.

[0048] In this embodiment, an example is shown in which the present invention is applied to a column assist type electric power steering device, but the present invention can also be applied to other steering devices, such as a rack assist type electric power steering device.

[0049] According to this embodiment, it is possible to realize a telescopic shaft and a steering device that ensure a large telescopic stroke without extending the fitting length between the male shaft and the female shaft. [Explanation of symbols]

[0050] 1 Steering device 3 Steering shaft 6 Intermediate shaft 15 male shaft 15a Male shaft side trapezoidal groove 15b Male shaft circular groove 16 female shaft 16a Female shaft side circular groove 16b Female shaft side circular groove 17 Ball 18 Leaf spring 19 Roller 19a Torque transmission part of roller 24 Roller slideway 23 Ball Rolling Path 26 Stopper

Claims

1. A columnar male shaft; A cylindrical female shaft fitted onto the male shaft; a plurality of rolling elements arranged freely to roll between a male shaft rolling surface provided in a first male shaft groove extending in the axial direction and formed on an outer peripheral surface of the male shaft and a female shaft rolling surface provided in a first female shaft groove extending in the axial direction and formed on an inner peripheral surface of the female shaft, When viewed from the axial direction, the shortest distance from the contact point of the rolling element with the male shaft side rolling surface to the rolling axis of the rolling element is different from the shortest distance from the contact point of the rolling element with the female shaft side rolling surface to the rolling axis, The telescopic shaft, wherein the rolling elements are in contact with the male shaft rolling surface at two points and with the female shaft rolling surface at one point.

2. a leaf spring is provided between the rolling element and the first male shaft groove for biasing the rolling element radially outward of the male shaft, The male shaft side rolling surface is formed by the acting surface of the leaf spring, 2. The telescopic shaft according to claim 1, wherein the female shaft side rolling surface is formed by a groove surface of the first female shaft side groove.

3. the male shaft side rolling surface is formed by a groove surface of the first male shaft side groove, 2. The telescopic shaft according to claim 1, wherein the female shaft side rolling surface is formed by a groove surface of the first female shaft side groove.

4. 4. The telescopic shaft according to claim 1, wherein the rolling elements are balls.

5. The first female shaft groove is a circular groove having a semicircular cross section, 5. The telescopic shaft according to claim 4, wherein the radius of the circular groove is larger than the radius of the rolling elements.

6. 6. The telescopic shaft according to claim 1, further comprising a columnar body extending in the axial direction and slidably arranged between a second male shaft side groove formed in an outer peripheral surface of the male shaft and extending in the axial direction, and a second female shaft side groove formed in an inner peripheral surface of the female shaft and extending in the axial direction.

7. A steering device comprising the telescopic shaft according to any one of claims 1 to 6.

Images