JP2008164150A - Extensible rotation transmission shaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure for smoothly attaining axial extension/contraction without causing looseness in a rotating direction and moreover hardly causing damage such as an indentation following torque transmission. <P>SOLUTION: The width, related to a rotating direction, of portions for holding respective steel balls 21, 21 out of respective circumferential clearance parts 30, 30 existing between an outer shaft 19 and an inner shaft 20 combined to transmit rotation and to be relatively displaceable in an axial direction, is gradually narrowed radially outward. Further, the respective steel balls 21, 21 are pressed radially outward by plate springs 22, 22. The inclination angles of outer side stepped face parts 25, 25 and inclined face parts 29 of inner side stepped face parts 28 abutting on the surfaces of the respective steel balls 21 are regulated to make the respective steel balls 21, 21 displaceable radially inward against the resilience of the plate springs 22, 22 when the mutual spaces of both face parts 25, 29 are narrowed. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The telescopic rotation transmission shaft according to the present invention is used, for example, as a steering shaft that constitutes a telescopic steering device for adjusting the front-rear position of the steering wheel in accordance with the physique and driving posture of the driver. When the front / rear position is adjusted, the entire length of the steering wheel is expanded / contracted. During normal operation, that is, when the steering wheel is operated, the steering wheel does not rattle (no transmission loss occurs) and the steering gear. To communicate.

  The steering device for an automobile is configured as shown in FIG. 14, for example, so that the movement of the steering wheel 1 is transmitted to the steering gear 2. The movement of the steering wheel 1 is transmitted to the input shaft 6 of the steering gear 2 through the steering shaft 3, the universal joint 4a, the intermediate shaft 5, and the universal joint 4b. Then, the steering gear 2 pushes and pulls the tie rods 7 and 7 to give a desired steering angle to the steered wheels. In the example shown in FIG. 14, an electric power steering device is incorporated in which an electric motor 8 applies an assisting force corresponding to the force applied by the driver to the steering wheel 1 to the steering shaft 3.

  When the front-rear position of the steering wheel 1 is adjusted according to the physique and driving posture of the driver with the steering device as described above, the steering shaft 3 and the steering column 9 that rotatably supports the steering shaft 3 are used. And extend and contract. For this purpose, the steering shaft 3 is a so-called telescopic steering shaft in which the outer shaft 10 and the inner shaft 11 are freely combined with expansion and contraction and transmission of rotational force by a spline engaging portion. Further, the steering column 9 is a combination of an outer column 12 and an inner column 13 that can be expanded and contracted.

  In order to improve the operational feeling of the steering wheel 1 in a normal state, it is necessary to prevent the rotational direction from rattling in the axial sliding portion such as the spline engaging portion of the steering shaft 3. There is. On the other hand, in order to be able to adjust the front-rear position of the steering wheel 1 with a light force, the axial sliding portion needs to be configured to be easily displaced in the axial direction. Conventionally, a structure described in Patent Document 1 is known as a structure that satisfies such conflicting requirements. FIG. 15 shows an example of a conventional structure described in Patent Document 1.

  In the case of this conventional structure, between the inner peripheral surface of the outer shaft 10a made of metal pipe and the outer peripheral surface of the inner shaft 11a each having a petal-shaped cross-sectional shape, a portion between rotational side surfaces facing each other in the rotational direction. The cages 14 and 14 are arranged. And the steel balls 16 and 16 hold | maintained in the pockets 15 and 15 of these each holder | retainers 14 and 14 are clamped between the said rotation direction side surfaces. The cages 14 and 14 are prevented from being displaced from the above portions by the positioning elements 17 and 17. Since the width dimension of each said part becomes narrow toward the back, each said steel ball 16 and 16 bites into these each said part in a wedge shape, and is an engagement part of the said outer shaft 10a and the said inner shaft 11a. Prevents rattling. Further, when the shafts 10a and 11a are relatively displaced in the axial direction, the steel balls 16 and 16 roll so that the relative displacement is performed with a light force.

  In the case of the conventional structure as described above, when the rotation is transmitted between the outer shaft 10a and the inner shaft 11a, the steel balls 16 and 16 do not move between the portions, and the rotational force (Torque) is transmitted. That is, in the case of the conventional structure, after the steel balls 16 and 16 are pushed into the portions between the parts, the steel balls 16 and 16 are moved at the time of relative displacement in the axial direction between the shafts 10a and 11a. Only the two shafts 10a and 11a roll in the axial direction. Accordingly, the steel balls 16 and 16 are repeatedly pressed against the same portion of the side surfaces in the rotational direction of the shafts 10a and 11a during steering. As a result, indentations may occur in a part of the side surfaces in the rotational direction of the shafts 10a and 11a. When the indentation is generated, there is a possibility that rattling occurs at the time of steering, or the relative displacement in the axial direction between the shafts 10a and 11a cannot be smoothly performed.

  Indentations that cause such inconvenience are more likely to occur as the torque to be transmitted increases. For example, the steering device shown in FIG. 14 is a so-called column-type electric power steering device in which the electric motor 8 as an auxiliary power source is provided on the steering column side. Such an electric power steering device. In this case, the torque transmitted by the intermediate shaft 5 is increased by the amount of auxiliary power compared to the torque transmitted by the steering shaft 3. Therefore, when the conventional structure as shown in FIG. 15 is applied to the intermediate shaft 5, the indentation is easily generated. Even when applied to the steering shaft 3, this indentation may occur. In particular, in the case of a structure without a power steering device, the indentation is likely to occur on the steering shaft 3.

US Pat. No. 6,200,285

  In view of the circumstances as described above, the present invention can smoothly expand and contract in the axial direction without causing backlash in the rotational direction, and even when a large torque is transmitted, The invention was invented to realize a telescopic rotation transmission shaft that is not easily damaged.

The telescopic rotation transmission shaft of the present invention includes an outer shaft, an inner shaft, and a plurality of transmission pieces, as in the case of the conventional structure shown in FIG. 15, and the outer shaft and the inner shaft. , Combining the transmission of rotation and the relative displacement in the axial direction between each other.
Of these, the outer shaft has at least a portion in the axial direction as a cylindrical portion that opens to one end surface in the axial direction and has a noncircular shape on the inner peripheral surface. However, it may be formed in a tubular shape over the entire length in the axial direction, and the whole may be a cylindrical portion.
The inner shaft has at least a part in the axial direction as an insertion portion that can be loosely inserted into the cylindrical portion and has a non-circular shape on the outer peripheral surface. However, the entire cross-sectional shape may be the same over the entire length in the axial direction, and the whole may be used as the insertion portion.
Each of the transmission pieces includes an outer peripheral surface of the insertion portion that is present between a plurality of circumferential positions on the outer peripheral surface of the insertion portion and a plurality of circumferential positions on the inner peripheral surface of the cylindrical portion. It arrange | positions in the state clamped between the peripheral surfaces of these both shafts in the circumferential clearance part which mutually opposes the internal peripheral surface of the said cylindrical part regarding the rotation direction of both said shafts. The “outer peripheral surface of the insertion portion” or “inner peripheral surface of the cylindrical portion” referred to in this specification and claims refers to a surface constituting the outer shape of the insertion portion or the inner shape of the cylindrical portion. Therefore, it is not necessarily limited to the surface facing the radial direction, but includes the surface facing the rotation direction.

In particular, in the telescopic rotation transmission shaft of the present invention, the width in the rotation direction of at least the portion between which the transmission pieces are sandwiched among the circumferential gap portions, with respect to the radial direction of the shafts. It gradually becomes narrower toward either direction.
Further, an elastic member is provided for pressing each transmission piece in the radial direction toward a portion having a narrow width in the rotational direction among the circumferential gap portions.
Further, the circumferential direction gap portions are partitioned on both sides in the rotational direction, and the inclination angle between a pair of surfaces in contact with the transmission pieces is set so that the transmission pieces are made elastic when the distance between the two faces is reduced. It is restricted to a size that can be displaced in each circumferential clearance portion against the elastic force of the member (in relation to the size of the elastic force and the frictional force acting on the contact portion).

Preferably, when carrying out the present invention as described above, as described in claim 2, each of the transmission pieces has a circular cross-sectional shape with respect to a virtual plane existing in a direction perpendicular to the central axis of both shafts. For example, balls or cylindrical rollers are used. Then, the outer peripheral surfaces of the transmission pieces are brought into contact with the peripheral surfaces of the shafts.
Further, when carrying out the invention described in claim 2, preferably, as described in claim 3, at least a part of the peripheral surface of one shaft is inclined to each transmission piece. Both the outer diameter side and the inner diameter side, whose directions are different from each other, are made continuous at the radial intermediate portion. A part of the peripheral surface of the one shaft is a concave surface in which the radial intermediate portion is most recessed in the circumferential direction. Further, in a state where each of the transmission pieces is displaced against the elasticity of the elastic member, the outer peripheral surface of each of the rolling pieces can be brought into contact with both the outer diameter side and the inner diameter side at the same time.

  Further, when the present invention as described above is carried out, for example, as described in claim 4, the outer side small-diameter circular arc surface portions each having a plurality of locations in which the inner peripheral surface of the cylindrical portion is alternately arranged in the rotation direction. And a stepped shape in which the outer-side large-diameter arc surface portion is continuous at the outer-side step surface portion. On the other hand, the outer peripheral surface of the insertion portion has a stepped shape in which inner side small-diameter arc surface portions and inner-side large-diameter arc surface portions arranged alternately with respect to the rotation direction are made continuous at the inner side step surface portion. And And each said circumferential direction clearance gap part exists between each these inner side level | step difference surface parts and each said outer side level | step difference surface part.

  Alternatively, when the present invention as described above is carried out, as described in claim 5, the inner peripheral surface of the cylindrical portion is formed of a pair of outer side flat surface portions parallel to each other, and each of these cylindrical portions A pair of outer arcuate surface parts centering on the central axis of the outer part, both end edges of both outer arcuate surface parts, and both end edges in the width direction of the outer flat surface parts. It consists of two pairs of outer side continuous surface portions, one pair for each of these outer side arc surface portions, which are inclined in a direction in which the distance between the outer side arc surface portions increases from the surface portion toward the both outer side arc surface portions. It is set as the shape where the space | interval became large gradually in the part which remove | deviated from the said both outer side flat surface part. In addition, the outer peripheral surface of the insertion portion has a shape including a pair of inner side flat surface portions parallel to each other. And each said circumferential direction clearance gap part exists between these each inner side flat surface part and each said outer side continuous surface part.

Further, when implementing the present invention as described above, preferably, as described in claim 6, a plurality of transmission pieces for each of the circumferential gap portions are spaced apart from each other in the axial direction of both shafts. Place with a gap.
In carrying out the invention described in claim 6, preferably, as described in claim 7, the plurality of transmission pieces arranged in the circumferential gap portions are held in the cage. This regulates the interval between these transmission pieces.
Alternatively, as described in claim 8, a separator holding recess having a plurality of holding recesses formed on a side that is long in the axial direction of both shafts and has a narrow width in the rotational direction among the circumferential clearance portions. Further, by holding a plurality of transmission pieces arranged in the circumferential gap portions, the interval between the transmission pieces is regulated. Further, the separator is pressed by the elastic member to the side where the width in the rotational direction becomes narrower among the circumferential gap portions.
Moreover, when implementing the invention described in the seventh to eighth aspects, preferably, as described in the ninth aspect, a plurality of transmission pieces disposed in the circumferential gap portions are arranged. The pitch in the axial direction of both shafts is made shorter at the both ends in the axial direction than at the center.

Further, when the present invention as described above is carried out, preferably, as described in claim 10, the shafts are in contact with each other and are relatively displaced when the shafts are relatively displaced in the axial direction. A surface treatment layer for improving wear resistance is formed on at least one of the surface of the transmission piece, the inner peripheral surface of the cylindrical portion, and the outer peripheral surface of the insertion portion.
As such a surface treatment layer, a hardening hardening layer, a nitriding treatment tank, a carburizing hardening layer, a hardening layer by shot peening or shot blasting, a lubricating layer made of a low friction material such as DLA, MoS ₂ , PTFE, etc. Can be adopted.

According to the present invention configured as described above, it is possible to smoothly expand and contract in the axial direction without causing rattling in the rotational direction, and even when a large torque is transmitted, damage such as indentation is caused. It is possible to realize a telescopic rotation transmission shaft that is less prone to occur.
First, the occurrence of shakiness in the rotational direction can be prevented by pressing each transmission piece with an elastic member toward a portion of each circumferential clearance that has a narrow width in the rotational direction. The surface of each transmission piece is always in contact with a pair of surfaces that partition both sides in the rotational direction of each circumferential gap portion. In other words, there is no gap between the surface of each transmission piece and any surface that divides both sides in the rotational direction of each circumferential gap portion. For this reason, when torque transmission is started between the outer shaft and the inner shaft, rattling based on the gap does not occur.

  In addition, smooth expansion and contraction in the axial direction can be achieved by relatively displacing the surface of each transmission piece and a pair of surfaces partitioning both sides in the rotational direction of each circumferential gap portion. Although these surfaces are always in contact with each other due to the elastic force of the elastic member, the surface pressure of the contact surfaces is limited unlike a structure in which the surfaces are combined by, for example, an interference fit. Therefore, the force required to relatively displace the surfaces is small, and the axial expansion and contraction can be performed smoothly.

  Further, even when a large torque is transmitted while preventing rotation in the rotational direction, it is difficult to cause damage such as indentation. This can be achieved by displacing in the radial direction. That is, at the time of torque transmission, of these transmission pieces, half of the transmission pieces existing on the torque transmission side have a width dimension in the rotational direction among the circumferential gap portions against the elasticity of the elastic member. It tends to displace to the wide side. On the other hand, the remaining half of the transmission pieces present on the counter-torque transmission side tend to be displaced to the side having a smaller width dimension in the rotational direction among the circumferential gap portions based on the elasticity of the elastic member. become. In this way, the transmission pieces move in opposite directions on the torque transmission side and the counter-torque transmission side, so that the surfaces of the transmission pieces and the circumferences of the transmission pieces are independent of the displacement of the transmission pieces. The pair of surfaces partitioning both sides in the rotational direction of the direction gap portion can be kept in contact with each other. For this reason, even when the direction of torque transmission changes suddenly, rattling based on the gap does not occur. Further, the amount that each of the transmission pieces is displaced in the circumferential gap portions increases as the torque to be transmitted increases. For this reason, at the time of torque transmission, among the pair of surfaces partitioning both sides in the rotational direction of each circumferential clearance portion, the portion that contacts the surface of each transmission piece changes frequently, and the pair of surfaces have indentations and the like. Damage is less likely to occur.

In particular, as described in claim 2, if each of the transmission pieces has a circular cross-sectional shape and the outer peripheral surfaces of the transmission pieces are brought into contact with the outer peripheral surfaces of the outer and inner shafts, By smoothly displacing the transmission pieces in the circumferential gap portions in the width direction, the effect of preventing damage such as the indentation can be further improved.
Further, as in the invention described in claim 3, when transmitting an excessive torque between the two shafts, the outer peripheral surface of each rolling piece is formed on the outer diameter side and the inner diameter side both surfaces having different inclination directions. If it is possible to make contact at the same time, the surface pressure of the contact portion between each of the transmission pieces and at least one of the peripheral surfaces of the shaft provided with both outer diameter side and inner diameter side can be reduced. Further, the transmission pieces can be prevented from being displaced in the radial direction of the shafts from the state in which they are simultaneously in contact with both the outer diameter side and the inner diameter side. For this reason, it can prevent that the elastic member which is pressing each said transmission piece is elastically deformed excessively, and can ensure the durability of this elastic member.

  When implementing the present invention, generally, the cross-sectional shape of the outer shaft and the inner shaft is made close to a circle as the structure described in claim 4. However, as the structure described in claim 5, the cross-sectional shapes of the outer shaft and the inner shaft can be flattened. Which structure is adopted is selected in design according to the magnitude of torque to be transmitted, the volume of the space in which the telescopic rotation transmission shaft is to be installed, and the like.

Further, when carrying out the present invention, as described in claim 6, if a plurality of transmission pieces are arranged at intervals in the axial direction of the two shafts for each circumferential gap portion, The bending rigidity of the combined portion of the outer shaft and the inner shaft can be improved.
In this case, if the distance between the transmission pieces is regulated by a cage as described in claim 7 or regulated by a separator as described in claim 8, the expansion and contraction of the telescopic rotation transmission shaft is achieved. Even if is repeated, the interval between the transmission pieces does not become irregular.
Further, as described in claim 9, if the pitch between the transmission pieces in the axial direction of both shafts is made shorter than the central part at both axial ends, the total number of the transmission pieces is suppressed. The bending rigidity can be improved.
Further, when the present invention is carried out, as described in claim 10, if a surface treatment layer for improving wear resistance is formed, the wear of each surface due to use over a long period of time is suppressed, and the expansion and contraction is suppressed. The durability of the rotary transmission shaft can be improved.

  1-3 show a first example of an embodiment of the present invention corresponding to claims 1 to 4 and 6. This example shows a structure when the telescopic rotation transmission shaft of the present invention is implemented as the steering shaft 18. The steering shaft 18 includes an outer shaft 19, an inner shaft 20, a plurality of steel balls 21 and 21 each serving as a transmission piece, and a plate that is an elastic member that elastically presses the steel balls 21 and 21. Springs 22, 22. And the said outer shaft 19 and the said inner shaft 20 are combined so that rotation transmission and axial relative displacement between each other are possible. The plate springs 22 and 22 are generally made of metal, but can be made of synthetic resin.

Outer shaft 19 is obtained by directly obtaining a finished metal tube by extrusion, or by bending a round tube made of metal by a known method and having a circular cross section. It is a formed metal tube. The outer shaft 19 has a full length corresponding to the cylindrical portion described in the claims. The inner peripheral surface of such an outer shaft 19 has a plurality of outer-side small-diameter arc surface portions 23, 23, outer-side large-diameter arc surface portions 24, 24, and an outer side that connects these arc-surface portions 23, 24 together. It is a stepped shape in which the step surface portions 25 and 25 are alternately arranged in the rotation direction. Among these outer side stepped surface portions 25, 25, the crossing angle θ25 between the paired outer side stepped surface portions 25, 25 sandwiching the outer side small-diameter arc surface portions 23, 23 from both sides in the rotational direction is determined by the outer outer stepped surface portions 25, _25. The side step surface portions 25 and 25 are larger than the case where the side step surface portions 25 and 25 are present in the diametrical direction of the outer shaft 19 (become a central angle). The outer-side small-diameter arc surface portions 23, 23 and the outer-side large-diameter arc surface portions 24, 24 are both convex outer peripheral surfaces, but are not necessarily concentric.

  On the other hand, the inner shaft 20 has a cross-section obtained by directly obtaining a metal rod having a completed shape by extrusion processing, or by machining a round bar made of metal by a known method and having a circular section. It is a metal bud formed in a petal shape. Such an inner shaft 20 corresponds in length to the insertion portion described in the claims. Such an outer peripheral surface of the inner shaft 20 has a plurality of inner-side small-diameter arc surface portions 26, 26, inner-side large-diameter arc surface portions 27, 27, and inner-side steps that connect these arc-surface portions 26, 27 together. It is the stepped shape which arrange | positioned the surface parts 28 and 28 alternately regarding the rotation direction. The outer diameter side end portions of the inner side step surface portions 28 and 28 are in a direction approaching the outer side step surface portions 25 and 25 as they go radially outward in a state where the shafts 19 and 20 are combined. The inclined surfaces 29 and 29 are inclined. On the other hand, the inner diameter side end portions or the radial intermediate portions of the inner side stepped surface portions 28 and 28 are inclined in the opposite direction to the inclined surface portions 29 and 29 with respect to the radial direction of the cross section of the inner shaft 20. ing.

In the case of this example, each of the inclined surface portions 29, 29 is the outer diameter side surface described in claim 3, and the inner diameter side end portion to the radial direction intermediate portion of each of the inner side step surface portions 28, 28 is also the inner diameter side surface. It is. Coupled with the restriction of the inclination angle (intersection angle θ ₂₅ ) of the outer stepped surface portions 25, 25 as described above, the outer stepped surface portions 25, 25 and the inner stepped surface portions 28, 28 The distance between the outer side stepped surface portions 25 and 25 and the inner side stepped surface portions 28 and 28, the outer diameter side half portions of the circumferential clearance portions 30 and 30, the both shafts. 19 and 20 become narrower toward the outside in the radial direction. On the other hand, in the inner diameter side half of each of the circumferential clearance portions 30, 30, the distance between each of the outer side step surface portions 25, 25 and each of the inner side step surface portions 28, 28 is set so that both the shafts 19. , 20 becomes narrower toward the inside in the radial direction. The inner side small-diameter arc surface portions 26, 26 and the inner side large-diameter arc surface portions 27, 27 are both convex on the outer peripheral surface, but are not necessarily concentric.

  Further, a plurality of the steel balls 21, 21 are arranged in the circumferential gap portions 30, 30 for each of the circumferential gap portions 30, 30. Then, the steel balls 21, 21 are elastically pressed by the leaf springs 22, 22 toward the radially outer sides of the shafts 19, 20 within the circumferential gap portions 30, 30. ing. For this purpose, a locking groove 31 formed in the center in the width direction of each of the leaf springs 22 and 22 and the center in the rotational direction of the inner side small-diameter arc surface portions 26 and 26 among the outer peripheral surfaces of the inner shaft 20. The engagement protrusions 32, 32 formed in the above are engaged to prevent the plate springs 22, 22 from shifting. In this state, both end portions in the width direction of the plate springs 22 and 22 are brought into contact with the steel balls 21 and 21 and pressed against the steel balls 21 and 21 in the above direction. In this state, the surface of each steel ball 21, 21 abuts on each of the outer stepped surface portions 25, 25 and each of the inclined surface portions 29, 29 of the inner side stepped surface portions 28, 28. .

In addition, the inclination angle of each said outer side level | step-difference surface part 25 and 25 and each said inclined surface part 29 and 29 with which the surface of each said steel ball 21 and 21 contact | abuts, ie, each said circumferential direction clearance gap part 30 and 30. the wedge angle theta ₃₀ is about narrower as the outer diameter side end portion is directed radially outward, the size of the torque transmitted between the between the two shafts 19 and 20 (the maximum value or average value), the It regulates appropriately by the relationship between the elasticity of each leaf | plate spring 22 and 22, and the friction coefficient of the contact part of the surface of each said steel ball 21 and 21 and each said surface part 25 and 29. FIG. The point that restricts the wedge angle θ ₃₀ will be described below.

  When the rotational force (torque) is transmitted between the shafts 19 and 20, the inner diameter of each of the steel balls 21 and 21 disposed in the circumferential clearance portions 30 and 30 is large. The steel balls 21, 21 existing on the front side in the rotation direction with respect to the circular arc surface portions 27, 27 are strongly sandwiched between the outer side step surface portions 25, 25 and the inclined surface portions 29, 29, thereby transmitting the torque. To be served. On the other hand, the steel balls 21, 21 existing on the rear side in the rotation direction with respect to the inner-side large-diameter arc surface portions 27, 27 are not used for the torque transmission, and the outer-side step surface portions. 25 and 25 and the inclined surface portions 29 and 29 are not strongly clamped.

And each said steel ball 21 and 21 used for the said torque transmission is pushed by each said outer side level | step-difference surface part 25 and 25 and each said inclined surface part 29 and 29, and the elasticity of each said plate spring 22 and 22 is carried out. On the contrary, it tends to be displaced inward in the radial direction among the circumferential clearance portions 30 and 30. Therefore, when transmitting a certain degree of torque between the shafts 19 and 20 (e.g., required when a large steering angle is applied during low speed traveling), the torque is transmitted to the torque. The elasticity of the leaf springs 22 and 22 and the wedge angle θ _{30 so} that the steel balls 21 and 21 are actually displaced radially inward in the circumferential gap portions 30 and ₃₀ . Is regulated. Such regulation is obtained by calculation based on the frictional force acting between the surface of each steel ball 21, 21 and each outer stepped surface portion 25, 25 and each inclined surface portion 29, 29. In this case, if the calculated value is corrected by experiment, an appropriate value with high reliability can be obtained as the wedge angle θ ₃₀ .

According to the structure of this example configured as described above, it is possible to smoothly expand and contract in the axial direction without causing backlash in the rotational direction, and in addition, even when a large torque is transmitted, an indentation, etc. Thus, the telescopic steering shaft 18 can be realized.
First, in order to prevent rattling in the rotational direction, the width of the steel balls 21 and 21 in the circumferential direction of the circumferential gap portions 30 and 30 is reduced by the leaf springs 22 and 22. It can be achieved by pressing towards the part. As described above, when a certain amount of torque is transmitted, the steel balls 21, 21 used for the torque transmission are radially inward of the circumferential clearance portions 30, 30. Displace. The outer stepped surface portions 25 and 25 and the inclined surface portions 29 and 29 sandwiching the steel balls 21 and 21 are surfaces such as the raceway surfaces of the rolling bearing, even if they move in the distance. No relative displacement in the direction. Therefore, the steel balls 21 and 21 are not in pure rolling contact with the double-sided portions 25 and 29. However, since a rolling element is added to the relative displacement state of the abutting portion and a wedge-shaped gap exists around the abutting portion, it is effective to incorporate a lubricant such as grease into the abutting portion. To be done. Therefore, the steel balls 21 and 21 are smoothly displaced in the circumferential gap portions 30 and 30 in the circumferential direction.

  Further, as described above, in the state where the steel balls 21 and 21 on the front side in the rotational direction (torque transmission side) are displaced inward in the radial direction, they exist on the front side in the rotational direction with respect to the respective inner-side large-diameter arc surface portions 27 and 27. Whereas the width dimension of each of the circumferential gap portions 30 and 30 is narrowed, the width dimension of each of the circumferential gap portions 30 and 30 existing on the rear side in the rotational direction (the anti-torque transmission side) is widened. . Thus, in the part where the width dimension of each circumferential direction clearance gap part 30 and 30 became wide, each said steel ball 21 and 21 is displaced to radial direction outward by said each leaf | plate spring 22 and 22. FIG. Accordingly, the steel balls 21 and 21, the outer stepped surface portions 25 and 25, and the inclined surface portions 29 and 29 remain in contact with each other not only on the front side in the rotational direction but also on the rear side in the rotational direction. In other words, there is no gap between the surface of each of the steel balls 21 and 21 and any surface that divides both sides of the circumferential gap portions 30 and 30 in the rotational direction.

  In this way, the steel balls 21 and 21 move in opposite directions on the torque transmission side and the counter-torque transmission side, so that the steel balls 21 and 21 are displaced regardless of the displacement of the steel balls 21 and 21. 21 and the surface of 21 and 21 and the said both-surfaces part 25 and 29 which are a pair of surfaces which divide | segment the both sides of the rotation direction of each said circumferential direction gap part 30 and 30 can be made to contact | abut. Therefore, even when the direction of torque transmission changes suddenly, rattling based on the gap does not occur. For this reason, when torque transmission is started between the outer shaft 19 and the inner shaft 20, or when the transmission direction is suddenly changed, rattling based on the gap does not occur.

  Further, when the shafts 19 and 20 are relatively displaced in the axial direction in order to expand and contract the steering shaft 18, the rolling surfaces of the steel balls 21 and 21 correspond to the outer stepped surface portions 25 and 25. 25 and the respective inclined surface portions 29, 29 while allowing the relative displacement. The movement of the steel balls 21 and 21 in this state is close to that even if it is not pure rolling, so that the force required for expansion and contraction of the steering shaft 18 can be kept small. In other words, the surface of each steel ball 21, 21, each outer stepped surface portion 25, 25 and each inclined surface portion 29, 29 are always in contact with each other by the elasticity of each leaf spring 22, 22. For example, unlike the structure combined by interference fitting, the contact pressure of the contact surface is limited. Accordingly, the force required to relatively displace the surfaces is small, and the steering shaft 18 can be expanded and contracted with a light force.

  Further, even when a large torque is transmitted, it is difficult to cause damage such as indentation, etc., because the steel balls 21 and 21 are moved in the circumferential gap portions 30 and 30 with the torque transmission. This can be achieved by reciprocating in and out of the radial direction of the shaft 18. That is, of the steel balls 21 and 21 at the time of torque transmission, half of the steel balls 21 and 21 existing on the front side in the rotation direction resist the elastic force of the plate springs 22 and 22, and each circumferential gap The portions 30 and 30 are displaced inward in the radial direction. On the other hand, the remaining half of the steel balls 21, 21 existing on the rear side in the rotational direction are radial in the circumferential gap portions 30, 30 based on the elasticity of the leaf springs 22, 22. Displace outward. In the case of the steering shaft 18 of this example, the frequency with which the steel balls 21 and 21 are displaced radially outward is the same as the frequency with which the steel balls 21 and 21 are similarly displaced radially inward.

  Further, the amount of displacement of the steel balls 21 and 21 in the radial direction of the steering shaft 18 at the circumferential gap portions 30 and 30 increases as the torque to be transmitted increases. For this reason, at the time of torque transmission, among the outer side stepped surface portions 25 and 25 and the inclined surface portions 29 and 29, which are a pair of surfaces partitioning both sides in the rotational direction of the circumferential clearance portions 30 and 30. The portions in contact with the surfaces of the steel balls 21 and 21 frequently change. As a result, unlike the structure described in Patent Document 1 described above, unlike the case of repeatedly pressing one place, the surface portions 25 and 29 are less likely to be damaged such as indentations.

  However, in a state where the torque to be transmitted is excessively large, the steel balls 21 and 21 remain in the intermediate portions of the circumferential gap portions 30 and 30 with respect to the radial direction of the steering shaft 18. That is, when the torque is zero or very small, as shown in FIG. 3A, the steel balls 21 and 21 are pushed almost uniformly by the leaf springs 22 so that the circumferential directions. It stays at the portion near the outer diameter of the gap portions 30, 30. On the other hand, when the torque increases, as described above, the steel balls 21 and 21 are displaced toward the inner diameter side against the elastic force of the plate springs 22 on the torque transmitting side, and the torque is reduced. Displaces to the outer diameter side on the non-transmitting side. In the case of this example, as described above, the distance between each outer-side step surface portion 25, 25 and each inner-side step surface portion 28, 28 is the outer-diameter-side half of each circumferential gap portion 30, 30. The shafts 19 and 20 are narrower toward the outer side in the radial direction, and the inner half is narrower toward the inner side in the radial direction. Therefore, when the torque becomes extremely large, as shown on the left side of FIG. 3B, the steel balls 21 and 21 are intermediate portions of the inner side stepped surface portions 28 and 28, respectively. It stays at the most concave position in the circumferential direction.

  In this state, the steel ball 21 used for torque transmission among the steel balls 21 and 21 and the inner side stepped surface part 28 used for torque transmission among the inner side stepped surface parts 28 and 28 are: , Each abuts at two positions. As a result, the contact area between the steel ball 21 used for torque transmission and the inner side stepped surface portion 28 can be increased, and a large indentation can be prevented from being formed on the inner side stepped surface portion 28. Furthermore, no matter how large the torque is, the steel balls 21 and 21 are not displaced to the inner diameter side than the state shown on the left side of FIG. Therefore, the plate springs 22 pressing the steel balls 21 and 21 to the outer diameter side are not excessively pressed, and the durability of the plate springs 22 can be ensured.

[Second Example of Embodiment]
FIG. 4 shows a second example of an embodiment of the present invention corresponding to claims 1 to 4, 6 and 7. In the case of the first example of the above-described embodiment, as shown in FIG. 1, the steel balls 21, 21 are arranged in the circumferential gap portions 30, 30 in a state of abutting each other. In such a structure, when the number of the steel balls 21 is the same, the range in which the steel balls 21 and 21 are arranged is narrow with respect to the axial direction of the steering shaft 18 (the axial length is short). This is disadvantageous in terms of ensuring the bending rigidity of the steering shaft 18. On the other hand, in the case of the steering shaft 18a of this example, the intervals between the steel balls 21, 21 arranged in a plurality in the circumferential gap portions 30, 30 are regulated by the cages 33, 33. Yes.

  Each of the cages 33 and 33 is formed by bending a metal plate such as a stainless steel plate or by injection molding a synthetic resin. A pair of holding plate portions 35, 35 bent inward in the radial direction of the inner shaft 20 from both edges in the width direction of the plate portion 34 are provided. These holding plate portions 35, 35 are provided with circular pockets intermittently in the axial direction of the inner shaft 20. And each said steel ball 21 and 21 is hold | maintained inside each of these pockets so that rolling is possible. In the case of this example, in order to support the connecting plate portion 34 of each of the cages 33, 33 without large rattling, the outer side large-diameter arc surface portions 24a, 24a of the inner peripheral surface of the outer shaft 19a are arranged. The middle part is biased radially inward. With this configuration, the gaps between the outer-side large-diameter arc surface portions 24 a and 24 a and the inner-side large-diameter arc surface portions 27 and 27 in the outer peripheral surface of the inner shaft 20 are narrowed. The connecting plate portion 34 of each of the cages 33 and 33 can be freely displaced in the gap portion in the axial direction (front and back direction in FIG. 4) of the steering shaft 18a without causing large backlash. ing.

  According to such a structure of this example, the range in which the steel balls 21 and 21 are arranged can be widened in the axial direction of the steering shaft 18a without increasing the number of the steel balls 21 and 21 (axis It is easy to secure the bending rigidity of the steering shaft 18a. Since the configuration and operation of other parts are the same as those of the first example of the above-described embodiment, illustration and description regarding the equivalent parts are omitted.

[Third example of embodiment]
FIG. 5 shows a third example of the embodiment of the invention corresponding to claims 1 to 4 and 6. In the case of this example, the direction in which the steel balls 21 and 21 are displaced during torque transmission is opposite to the case of the first example of the embodiment and the second example described above with respect to the radial direction of the steering shaft 18b. I have to. For this purpose, the shape of the inner peripheral surface of the outer shaft 19b and the shape of the outer peripheral surface of the inner shaft 20a are different from those of the first and second examples, and the circumferential clearance portions 30a, 30a with respect to the rotational direction. Among these, the width dimension of the portion where the surfaces of the steel balls 21 are in contact with each other is made narrower toward the radially inner side of the steering shaft 18b.

  Specifically, of the inner peripheral surface of the outer shaft 19b, the outer side step surface portions 25a and 25a are formed in a direction that coincides with the radial direction of the outer shaft 19b. On the other hand, of the outer peripheral surface of the inner shaft 20a, the inner diameter side half portions of the inner side step surface portions 28a, 28a are inclined in a direction approaching the outer side step surface portions 25a, 25a as they go radially inward. The inclined surfaces 29a and 29a are used. And each said steel ball 21 and 21 arrange | positioned in each said circumferential direction clearance gap part 30a, 30a is pressed to the radial direction inner side of the said steering shaft 18b with the front-end | tip part of leaf | plate spring 22a, 22a. In the case of this example, the base end portions of the leaf springs 22a and 22a are caulked and fixed to the inner-side large-diameter arc surface portions 27 and 27 in the outer peripheral surface of the inner shaft 20a.

In the case of this example, when a certain amount of torque is transmitted between the outer shaft 19b and the inner shaft 20a, the inner side large-diameter arc surface portions 27, 27 are more forward in the rotational direction (torque transmission). The steel balls 21, 21 existing on the side) are displaced radially outward of the steering shaft 18 b against the elasticity of the leaf springs 22 a, 22 a. At the same time, the steel balls 21 and 21 existing on the rear side in the rotational direction (on the counter-torque transmission side) are displaced inward in the radial direction of the steering shaft 18b based on the elasticity of the leaf springs 22a and 22a.
Since the structure and operation of other parts are the same as those in the first and second examples of the above-described embodiment, a duplicate description is omitted.

[Fourth Example of Embodiment]
FIG. 6 shows a fourth example of an embodiment of the present invention corresponding to claims 1 to 4 and 6. In the case of this example, the leaf springs 22b and 22b for pressing the steel balls 21 and 21 are held by the outer-side large-diameter circular arc surface portions 24 and 24 among the inner peripheral surface of the outer shaft 19b. . Further, a locking protrusion 31a formed at the center of the outer peripheral surface of each of the leaf springs 22b and 22b is engaged with the locking groove 31a at the center in the circumferential direction of the outer-side large-diameter circular arc surface portions 24 and 24. The plate springs 22b and 22b are prevented from slipping. Since the configuration and operation other than the difference in the installation structure of each of the leaf springs 22b and 22b are the same as in the case of the third example of the above-described embodiment, redundant description is omitted.

[Fifth Example of Embodiment]
FIG. 7 shows a fifth example of the embodiment of the invention corresponding to claims 1 to 4 and 6. In the case of this example, the cross-sectional shape of the outer side step surface portions 25b and 25b in the inner peripheral surface of the outer shaft 19c, and the cross-sectional shape of the inner side step surface portions 28b and 28b in the outer peripheral surface of the inner shaft 20b. These are composite concave arcs such as Gothic arches. Since the cross-sectional shape of each step surface portion 25b, 28b that contacts the surface of each steel ball 21, 21 is a concave arc, the contact portion between the surface of each steel ball 21, 21 and each step surface portion 25b, 28b The area of becomes wide. As a result, it is possible to more effectively prevent indentations from being formed on these stepped surface portions 25b and 28b.
Since the configuration and operation of the other parts are the same as in the fourth example of the above-described embodiment, a duplicate description is omitted.

[Sixth Example of Embodiment]
FIG. 8 shows a sixth example of an embodiment of the present invention corresponding to claims 1 to 4 and 6. In the case of this example, elastic sheets 36, 36 made of elastomer such as rubber are used as elastic members for pressing the steel balls 21, 21 radially inward. In the case of this example, such an elastic sheet 36, 36 is positioned at a position sandwiching the outer-side small-diameter arc surface portion 23 and the outer-side step surface portions 25a, 25a from both sides in the rotational direction on the inner peripheral surface of the outer shaft 19b. It is arranged. In the case of this example, a cage for separating the steel balls 21 from each other can also be provided.
Since the configuration and operation other than the change of the elastic member from the leaf spring to the elastic sheets 36 and 36 are the same as those in the third to fourth examples of the above-described embodiment, redundant description is omitted.

[Seventh example of embodiment]
FIG. 9 shows a seventh example of the embodiment of the invention corresponding to claims 1 to 5. In the case of this example, the cross-sectional shape of the outer shaft 19d is a drum shape in which both end surfaces swell in an arc shape. The outer shaft 19d has a tubular shape, and the outer shaft 19d has a cylindrical portion over its entire length, as in the case of the examples described above. This outer shaft 19d is made by extruding a metal material. The inner peripheral surface has a pair of outer sides parallel to each other in the middle in the longitudinal direction (vertical direction in FIG. 9) related to the cross section. Flat surface portions 37 and 37 are provided. In addition, a pair of outer arcuate surface portions 38, 38 each having a center axis of the outer shaft 19d are provided at both ends in the length direction.

The width dimension W ₃₈ of the outer arcuate surface portions ₃₈ , ₃₈ in the width direction of the cross section (the left-right direction in FIG. 9) is larger than the distance D ₃₇ between the outer outer flat surface portions _{37, 37} (W ₃₈ > D ₃₇ ). Then, both end edges in the width direction of both outer flat surfaces 37, 37 (end edges in the length direction of the cross section) and both end edges in the width direction of the outer arcuate surfaces 38, 38 are continuously connected on the outer side. The surface portions 39 and 39 are made continuous. These outer side continuous surface parts 39, 39 are inclined in a direction in which the distance between the outer side flat surface parts 37, 37 increases from the outer side flat surface parts 37, 37 toward the outer outer side arc surface parts 38, 38. Two pairs are provided in total, one pair for each of the surface portions 38 and 38.

  On the other hand, the outer peripheral surface of the inner shaft 20c combined with the outer shaft 19d as described above has a drum shape in which both end surfaces swell in an arc shape. The inner shaft 20c has a rod-like shape, and the inner shaft 20c is used as an insertion portion over its entire length as in the case of the examples described above. The inner shaft 20c is formed by extruding a metal material or by machining a metal round bar, and the outer circumferential surface has a longitudinal direction (a vertical direction in FIG. 9) on the cross section. ) A pair of inner side flat surface portions 40, 40 parallel to each other are provided in the intermediate portion. A pair of inner-side arcuate surface portions 41, 41 each having a center axis of the inner shaft 20c are provided at both ends in the length direction.

Above regarding the cross-section of the width direction (lateral direction in FIG. 9), the width W ₄₁ of both inner side arc surface portion 41 is larger than the both inner side flat surface portions 40, 40 spacing D ₄₀ between the (W ₄₁ > and D ₄₀₎ was. Then, both end edges in the width direction of the inner flat surfaces 40, 40 (end edges in the longitudinal direction of the cross section) and both end edges in the width direction of the inner arcuate surfaces 41, 41 are continuously connected on the inner side. The surface portions 42 and 42 are made continuous. These inner side continuous surface portions 42 and 42 are inclined in a direction in which the distance between the inner side continuous surface portions 42 and 42 increases toward the both inner side arcuate surface portions 41 and 41 from the both inner side flat surface portions 40 and 40. A total of two pairs are provided, one for each of the surface portions 41, 41.

  The outer shaft 19d as described above and the inner shaft 20c as described above are inserted into the inner diameter side of the outer shaft 19d, and further, both end portions in the width direction of the both inner side flat surface portions 40, 40. And steel balls 21, 21 are combined between the outer continuous surface portions 39, 39. The steel balls 21 and 21 are cross sections of the shafts 19d and 20c by both ends of a pair of leaf springs 22c and 22c holding the respective substrate portions on the inner surfaces of the outer arcuate surface portions 38 and 38. It is elastically pressed inward in the radial direction. The width in the rotational direction of the circumferential gap portions 30b, 30b that are partitioned by the inner flat surfaces 40, 40 and the outer continuous surfaces 39, 39, in which the steel balls 21, 21 are arranged. Is narrower toward the inside in the radial direction of the cross section. Therefore, in the case of this example as well, in the same way as in the case of the third to fourth examples of the above-described embodiment, the axial direction can be smoothly expanded and contracted without causing the rattling in the rotational direction. Moreover, it is possible to realize a telescopic steering shaft 18c that is less susceptible to damage such as indentation even when a large torque is transmitted.

[Eighth Example of Embodiment]
FIGS. 10-12 has shown the 8th example of embodiment of this invention corresponding to Claims 1-4,6,8. In the structure of this example, the structure of the first example of the embodiment described above is improved, and a plurality of steel balls 21 and 21 arranged for each circumferential gap portion 30 are arranged in the axial direction of the steering shaft 18d. While being surely separated, variation in the outer diameter of each of the steel balls 21 and 21 can be absorbed. For this reason, in the case of the present example, in each of the circumferential gap portions 30, the wave plate spring 43, the separator 44, the steel balls 21, the steel balls 21, 21.

The corrugated spring 43 is formed in a portion adjacent to the inner-side stepped surface portion 28 (see FIG. 2) in the inner-side small-diameter arc portion 26 constituting the outer peripheral surface of the inner shaft 20d constituting the steering shaft 18d. The inner shaft 20d is mounted in a state where axial displacement is prevented. Therefore, in the case of this example, a holding concave hole 45 is formed in a part of the inner-side small-diameter arc portion 26, and the corrugated spring 43 is installed in the holding concave hole 45 almost without rattling. ing.
The separator 44 is made of a relatively hard rubber, an elastic material such as an elastomer such as vinyl, is long in the axial direction of the inner shaft 20d, and has a plurality of holding recesses on the outer surface side in the radial direction of the steering shaft 18d. 46 and 46 are formed intermittently in the axial direction of the steering shaft 18d.
Further, the steel balls 21, 21 are held in the holding recesses 46, 46 of the separator 44, and the outer stepped surface portion constituting the inner peripheral surface of the outer shaft 19 by the elasticity of the wave spring 43. 25 (see FIG. 2) and an inclined surface portion 29 (see FIG. 2) formed at the outer diameter side end portion of the inner side step surface portion 28.

In the case of the structure of this example configured as described above, the steering shaft 18d of the steering shaft 18d can be obtained without increasing the number of the respective steel balls 21 and 21, as in the structure of the second example of the embodiment described above. With respect to the axial direction, the range in which the steel balls 21 and 21 are arranged can be widened, and the bending rigidity of the steering shaft 18d can be easily secured.
Further, in the case of the structure of this example, the variation in the outer diameter of each of the steel balls 21 and 21 can be absorbed based on the elastic deformation of the separator 44. That is, among these steel balls 21, 21, even if the outer diameter of some of the steel balls 21 is larger than the reference, the thickness of the separator 44 is elastically reduced at the steel ball 21 portion, thereby Absorbs the difference in outer diameter. For this reason, even if the outer diameters of the steel balls 21 and 21 are not strictly regulated, harmful rattling does not occur in the portions where the steel balls 21 and 21 are installed.
The configuration and operation of the other parts are the same as in the first example of the embodiment described above. In addition, the structure provided with the corrugated leaf spring 43 and the separator 44 as in this example can also be applied to the structures shown in FIGS.

[Ninth Embodiment]
FIG. 13 shows a ninth example of an embodiment of the present invention corresponding to claims 1 to 4, 6, 8, and 9. In the case of this example, the pitch in the axial direction of the holding recesses 46, 46 provided on the outer diameter side surface of the separator 44a is wide at the intermediate portion in the axial direction and narrow at both ends. And the pitch regarding the axial direction of each steel ball 21 and 21 hold | maintained at these holding | maintenance recessed parts 46 and 46 is made shorter than the center part in the both ends of this axial direction.
In the case of such a structure of this example, the number of steel balls 21 and 21 existing at both end portions to which a bending moment applied between the outer shaft 19 and the inner shaft 20d is strongly increased increases. The bending rigidity of the steering shaft 18d constituted by the outer shaft 19 and the inner shaft 20d can be improved while the total number of 21 and 21 is suppressed. The structure and operation of the other parts are the same as in the case of the eighth example of the embodiment described above.

[Points to note when implementing the present invention]
The present invention is not limited to the structure of each embodiment described above, and can be implemented with various structures such as a combination of the structures of these embodiments as appropriate.
Further, various deflections can be implemented even with respect to the shape, structure, and material of each component. For example, the shape of the transmission piece is not limited to the sphere as in each example shown in the figure, but may be a cylinder (steel roller). When a cylindrical transmission piece is employed, the central axis of the cylinder is arranged in parallel with the central axes of both the outer and inner shafts.

In addition, about the material of each part, various materials can be used in the range which can ensure the reliability and durability which are required according to a use. For example, for both the outer and inner shafts, aluminum alloys, magnesium engagement gold, etc. can be used in addition to iron alloys. In addition, as for the transmission piece, in addition to iron-based alloys such as bearing steel, highly functional resins can be used. For the elastic member, a high-functional resin or the like can be used in addition to an iron-based alloy such as spring steel.
Further, when both the outer and inner shafts and the transmission piece are made of an iron-based alloy, a surface treatment layer for improving wear resistance as described above is formed on at least one of the surfaces. Is preferable from the viewpoint of improving durability.

  The telescopic rotation transmission shaft of the present invention can be applied to the intermediate shaft 5 among the components of the automobile steering device provided with the electric power steering device shown in FIG. However, the present invention is not limited to the intermediate shaft 5 and can be implemented as the steering shaft 3 disposed inside the steering column 9. Furthermore, the present invention is not limited to the shaft constituting the automobile steering device, but can be implemented as a rotation transmission shaft constituting various rotary machine devices such as machine tools and playground equipment.

The partial cutting side view which shows the 1st example of embodiment of this invention. The expanded XX sectional drawing of FIG. The expanded sectional view equivalent to the upper right part of Drawing 2 showing the state (A) at the time of torque non-transmission, and the state (B) at the time of excessive torque transmission. The figure similar to FIG. 2 which shows the 2nd example of embodiment of this invention. The figure similar to FIG. 2 which shows the 3rd example. The figure similar to FIG. 2 which shows the 4th example. The figure equivalent to the upper part of FIG. 6 which shows the 5th example. The figure similar to FIG. 7 which shows the 6th example. The figure similar to FIG. 2 which shows the said 7th example. The partial cutting side view which shows the 8th example. The separator incorporated in the eighth example is shown, (A) is a view from above of FIG. 10, (B) is a view from the same direction as FIG. 10, (C) is a view from the side of (B). Figure. The Y section enlarged view of FIG. The partial cutting side view which shows the 9th example of embodiment of this invention. The side view which shows one example of the steering device for motor vehicles. Sectional drawing similar to FIG. 2 which shows an example of the expansion-contraction type rotational transmission shaft known conventionally.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering gear 3 Steering shaft 4a, 4b Universal joint 5 Intermediate shaft 6 Input shaft 7 Tie rod 8 Electric motor 9 Steering column 10, 10a Outer shaft 11, 11a Inner shaft 12 Outer column 13 Inner column 14 Cage 15 Pocket 16 Steel ball 17 Positioning element 18, 18a, 18b, 18c, 18d Steering shaft 19, 19a, 19b, 19c, 19d Outer shaft 20, 20a, 20b, 20c, 20d Inner shaft 21 Steel ball 22, 22a, 22b, 22c Leaf spring 23 Outer side small-diameter arc surface portion 24, 24a Outer side large-diameter arc surface portion 25, 25a, 25b Outer side step surface portion 26 Inner side small-diameter arc surface portion 27 Inner side large-diameter circle Surface portion 28, 28a, 28b Inner side step surface portion 29, 29a Inclined surface portion 30, 30a, 30b Circumferential clearance portion 31, 31a Locking groove 32, 32a Locking protrusion 33 Cage 34 Connecting plate portion 35 Holding plate portion 36 Elastic sheet 37 Outer flat surface 38 Outer arc surface 39 Outer continuous surface 40 Inner flat surface 41 Inner arc surface 42 Inner continuous surface 43 Corrugated leaf spring 44, 44a Separator 45 Holding recess 46 Holding recess

Claims (10)

  An outer shaft that has at least a part in the axial direction that opens to one end face in the axial direction and has a cylindrical shape with a noncircular inner peripheral surface, and at least a part in the axial direction can be loosely inserted into the cylindrical part An inner shaft that is an insertion portion having a non-circular shape on the outer peripheral surface, and a plurality of circumferential positions on the outer peripheral surface of the insertion portion and a plurality of circumferential directions on the inner peripheral surface of the cylindrical portion. The outer peripheral surface of the insertion portion and the inner peripheral surface of the cylindrical portion, which are present respectively, are sandwiched between the peripheral surfaces of the two shafts in circumferential clearance portions facing each other in the rotational direction of the shafts. A telescopic rotation transmission shaft that combines a plurality of transmission pieces arranged in an open state, and combines the outer shaft and the inner shaft with each other so that rotation transmission between them and relative displacement in the axial direction are possible. , Above each circumferential clearance Thus, at least the width of each of the transmission pieces sandwiched in the rotational direction is gradually narrowed toward any direction with respect to the radial direction of the two shafts, and the transmission pieces are separated from the circumferential gap portions. A pair of elastic members that are pressed in a radial direction toward a portion having a narrow width in the rotational direction, and that partitions both sides in the rotational direction of each of the circumferential gap portions and contacts the transmission pieces. The inclination angle between the surfaces is restricted to such a size that each of the transmission pieces can be displaced at each circumferential gap portion against the elasticity of the elastic member when the interval between the two surfaces is narrowed. Telescopic rotation transmission shaft.   2. Each transmission piece has a circular cross-sectional shape with respect to a virtual plane that exists in a direction perpendicular to the central axis of both shafts, and the outer peripheral surface of each transmission piece is in contact with the peripheral surfaces of both shafts. The telescopic rotation transmission shaft described in 1.   At least part of the peripheral surface of the shaft facing each transmission piece, the outer diameter side and the inner diameter side are different from each other in the inclination direction, and the radial intermediate part is made circular. The concave surface is the most concave in the circumferential direction, and the outer peripheral surface of each rolling piece can be in contact with both the outer diameter side and the inner diameter side at the same time in a state where each transmission piece is displaced against the elastic force of the elastic member. The telescopic rotation transmission shaft according to claim 2.   The inner peripheral surface of the cylindrical portion has a stepped shape in which outer side small-diameter arc surface portions and outer-side large-diameter arc surface portions arranged alternately in the rotation direction are continuously provided on the outer side step surface portion, and the insertion portion The outer peripheral surface of the inner surface is a stepped shape in which a plurality of inner-side small-diameter arc surface portions and inner-side large-diameter arc surface portions arranged alternately with respect to the rotation direction are continuously connected by an inner-side step surface portion, and each circumferential clearance portion The telescopic rotation transmission shaft according to any one of claims 1 to 3, wherein each of the inner side stepped surface portion and the outer side stepped surface portion exists.   The inner peripheral surface of the cylindrical portion is a pair of outer side flat surface portions parallel to each other, a pair of outer side arc surface portions each centering on the central axis of the cylindrical portion, and the outer side arc surface portions of the two outer side arc surface portions. Both the outer edges are inclined in a direction in which the distance between the outer outer flat surfaces is increased from the outer outer flat surfaces to the outer arc surfaces. Each pair of side arcuate surface portions is composed of two pairs of outer side continuous surface portions, and the interval between the inner peripheral surfaces is gradually increased at the portion deviating from the two outer side flat surface portions. The outer peripheral surface has a shape including a pair of inner side flat surface portions parallel to each other, and each circumferential gap portion exists between each of the inner side flat surface portions and each of the outer side continuous surface portions. Item 1-3 Telescopic rotation transmitting shaft as set forth in any one of.   The telescopic rotation according to any one of claims 1 to 5, wherein a plurality of transmission pieces are arranged at intervals in the axial direction of both shafts for each circumferential gap portion. Transmission shaft.   The telescopic rotation transmission shaft according to claim 6, wherein a plurality of transmission pieces arranged in each circumferential gap portion are held by a cage to regulate the interval between the transmission pieces.   The holding recesses of the separator, which are long in the axial direction of both shafts and have a plurality of holding recesses on the side where the width in the rotational direction becomes narrower among the circumferential clearance portions, are arranged in the respective circumferential clearance portions. By holding a plurality of transmission pieces, the spacing between the transmission pieces is regulated, and the separator is pressed by the elastic member to the side where the width in the rotation direction becomes narrower in the circumferential gap portion. The telescopic rotation transmission shaft according to claim 6.   The pitch in the axial direction of both shafts of a plurality of transmission pieces arranged in each circumferential gap portion is shorter than the central portion at both ends in the axial direction. The telescopic rotation transmission shaft described in item 1.   At least one of the surface of each transmission piece, the inner peripheral surface of the cylindrical portion, and the outer peripheral surface of the insertion portion, which are in contact with each other and are relatively displaced when both shafts are relatively displaced in the axial direction. The telescopic rotation transmission shaft according to any one of claims 1 to 9, wherein a surface treatment layer for improving wear resistance is formed.

Images