JP2005313691A - Telescopic shaft for vehicle steering - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain a positive prevention of looseness of a telescopic shaft in its rotational direction and transmit torque under a high rigid state. <P>SOLUTION: The characteristic shown at (b) indicates that a predetermined twisting rigidity (K1) Nm/deg can be kept at a pre-loading region near a neutral value. This twisting rigidity (K1) is 5 Nm/deg or more. Accordingly, when a steering operation is carried out at a pre-loading region near a neutral value, the torque is positively transmitted without any looseness at all. That is, it is possible to perform a transmittance of a steering torque through rollers 7 while applying a load between a male shaft 1 and a female shaft 2 through a resilient member 9. With this arrangement, it is possible to provide a telescopic shaft having a hybrid structure showing both a rolling having no looseness at all and a sliding having no looseness and to keep a stable steering performance without feeling any delay in operation of a vehicle when the vehicle is steered. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a telescopic shaft for vehicle steering that is incorporated in a steering shaft of a vehicle and has a male shaft and a female shaft that are non-rotatable and slidably fitted to each other.

  The telescopic shaft of the steering mechanism portion of the automobile is required to absorb the axial displacement generated when the automobile travels and to transmit the displacement and vibration on the steering wheel. Further, in order to obtain an optimum position for the driver to drive the automobile, a function of moving the position of the steering wheel in the axial direction and adjusting the position is required.

  In any of these cases, the telescopic shaft is required to reduce the rattling noise, to reduce the rattling on the steering wheel, and to reduce the sliding resistance during the sliding operation in the axial direction. The

  For this reason, conventionally, the male shaft of the telescopic shaft is coated with a nylon film, and grease is applied to the sliding portion to absorb or alleviate metal noise, metal hitting sound, etc., and to reduce sliding resistance. The rotation direction play has been reduced.

  However, there is a case where wear of the nylon film progresses with the progress of use and the play in the rotational direction increases. In addition, under conditions where the engine room is exposed to high temperatures, the nylon membrane changes in volume, and the sliding resistance may increase remarkably or wear may be significantly accelerated, resulting in increased rotational play. .

  For this reason, in Patent Document 1, rolling occurs in the axial relative movement of both shafts between a plurality of pairs of axial grooves formed on the outer peripheral surface of the male shaft and the inner peripheral surface of the female shaft. A torque transmitting member (spherical body) is fitted.

  Further, in Patent Document 1, a male shaft and a female shaft are interposed between a pair of axial grooves in a radial direction inside or outside of a spherical body that is a torque transmission member and a pair of axial grooves. A leaf spring, which is an elastic body for preloading, is provided for applying preload to the plate.

  As a result, when torque is not transmitted, the spherical body, which is a torque transmitting member, is preloaded to the extent that there is no backlash by the leaf spring, so that backlash between the male shaft and the female shaft is prevented. The male shaft and the female shaft can slide in the axial direction with a stable sliding load without rattling.

  In addition, when transmitting torque, the spherical body, which is a torque transmission member, can be constrained in the circumferential direction by a leaf spring, so that the male shaft and female shaft are prevented from rattling in the rotational direction and have high rigidity. Torque can be transmitted in this state.

  Moreover, in the structure disclosed in FIG. 1 to FIG. 5 of Patent Document 1, one leaf spring for preloading a set of torque transmission members (spherical bodies) and another set of torque transmission members adjacent in the circumferential direction ( The other leaf spring that preloads the spherical body is connected in the circumferential direction by a web that is an arc-shaped connecting portion extending in the circumferential direction.

  This connecting portion (web) is for applying a tensile force or a compressive force to the two leaf springs to generate a preload on the two leaf springs.

  In the structure disclosed in FIGS. 6 and 7 of Patent Document 1, a separate elastic body is interposed between the leaf spring and the axial groove without connecting the two leaf springs by the connecting portion (web). Thus, preload is generated in the radial direction.

Furthermore, in patent document 2, it is trying to hold down the sliding resistance at the time of a slide by coating a spline part, and there is no backlash.
German Patent Invention DE 3730393C2 JP 2000-9148 A

  However, in the structure disclosed in Patent Document 1, first, in order to generate a preload between the male shaft, the spherical body, and the female shaft, the leaf spring changes its curvature and the curvature of the axial groove. It is intervening. Therefore, the leaf spring cannot take a large amount of bending. If there is variation in processing accuracy, this variation in processing accuracy cannot be allowed with this amount of bending of the leaf spring.

  Secondly, when torque is input, the male shaft, the leaf spring, the spherical body, and the female shaft narrow each other and transmit torque, so the contact point between the spherical body and the leaf spring is: Very high surface pressure. In other words, a high stress is generated in the leaf spring when torque is transmitted, which causes a “sag” due to the permanent deformation of the leaf spring, making it difficult to maintain the preload performance over a long period of time, and hindering the life of the steering shaft. There is a risk of being.

  Third, during torque transmission, the leaf spring slides in the circumferential direction from the axial groove, leading to a decrease in the transmission torque, and the magnitude of hysteresis cannot be controlled, and hysteresis is excessively generated. There is a fear.

  Fourth, when no torque is applied, the contact point is not on the same line between the male shaft, spherical body, leaf spring, and female shaft. As a result, not only the linear torsional characteristics required for the steering shaft cannot be obtained, but also there is a possibility that an appropriate hysteresis cannot be obtained.

  In Patent Document 2, since the spline structure is sliding, it is physically impossible to completely eliminate the backlash no matter how small the backlash in the circumferential direction is.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a telescopic shaft for vehicle steering that can reliably prevent rotational backlash and transmit torque in a highly rigid state. To do.

In order to achieve the above object, a telescopic shaft for vehicle steering according to claim 1 of the present invention is incorporated in a steering shaft of a vehicle, and is used for vehicle steering in which a male shaft and a female shaft are fitted non-rotatably and slidably. In the telescopic axis,
The telescopic shaft is
A preload torque transmission unit that transmits the steering torque while preloading between the two shafts when the steering torque is a predetermined value or less;
When the steering torque exceeds a predetermined value, a rigid torque transmission unit that transmits the steering torque by the rigid body contact between the two shafts,
The torsional rigidity generated by the preload torque transmitting unit is 5 Nm / deg or more.

The telescopic shaft for vehicle steering according to claim 2 of the present invention is characterized in that the preload torque transmitting portion is formed between at least one row of axial grooves formed on the outer peripheral surface of the male shaft and the inner peripheral surface of the female shaft. In addition, the first torque transmission member is interposed via the elastic body,
The rigid torque transmission part is
A second torque transmission member is interposed between at least one other groove direction formed on the outer peripheral surface of the male shaft and the inner peripheral surface of the female shaft, respectively.

The telescopic shaft for vehicle steering according to claim 3 of the present invention is a rolling element in which the first torque transmission member rolls in the axial relative movement of the two shafts,
The second torque transmission member is a sliding body that slides and slides when the both wheels move in the axial direction relative to each other.

  The telescopic shaft for vehicle steering according to claim 4 of the present invention is characterized in that the predetermined torsional rigidity is generated by a frictional force between the male shaft and the elastic body.

  The telescopic shaft for vehicle steering according to claim 5 of the present invention is characterized in that the predetermined torsional rigidity is generated by a frictional force and a biasing force of the male shaft and the elastic body.

  In the telescopic shaft for vehicle steering according to claim 6 of the present invention, the angle until the rotation of the rigid torque transmission part or the second torque transmission member from the neutral position by the contact of the rigid body is 0. It is set in the range of 01 to 0.25 °.

  As described above, according to the present invention, the torsional rigidity generated in the preload torque transmission unit is 5 Nm / deg or more. Can be suppressed and steering stability can be improved.

  Further, by preventing an excessive stress from being generated in the leaf spring, it is possible to suppress the “sag” of the leaf spring and maintain the preload performance required over a long period of time.

  Hereinafter, a telescopic shaft for vehicle steering according to an embodiment of the present invention will be described with reference to the drawings.

(Overall structure of vehicle steering shaft)
FIG. 1 is a side view of a steering mechanism portion of an automobile to which a vehicle steering telescopic shaft according to an embodiment of the present invention is applied.

  In FIG. 1, an upper steering shaft portion 120 (a steering column 103 and a swinging shaft 104 rotatably supported by the steering column 103 are attached to a member 100 on the vehicle body side via an upper bracket 101 and a lower bracket 102. A steering wheel 105 attached to the upper end of the steering shaft 104, a lower steering shaft portion 107 connected to the lower end of the steering shaft 104 via a universal joint 106, and a steering shaft joint 108 to the lower steering shaft portion 107. A pinion shaft 109 connected via a pin, a steering rack shaft 112 connected to the pinion shaft 109, and the steering rack shaft 112 is supported to be elastic to another frame 110 of the vehicle body. Steering mechanism from a fixed steering rack support member 113 via 111 is formed.

  Here, the upper steering shaft portion 120 and the lower steering shaft portion 107 use the vehicle steering telescopic shaft (hereinafter referred to as the telescopic shaft) according to the embodiment of the present invention. The lower steering shaft portion 107 is formed by fitting a male shaft and a female shaft. The lower steering shaft portion 107 absorbs axial displacement generated when the automobile travels, and the steering wheel. The performance which does not transmit the displacement and vibration on 105 is required. In such performance, the vehicle body has a sub-frame structure, and the member 100 for fixing the upper part of the steering mechanism and the frame 110 to which the steering rack supporting member 113 is fixed are separated, and the steering rack supporting member 113 is This is required in the case of a structure that is fastened and fixed to the frame 110 via an elastic body 111 such as rubber. In other cases, when the steering shaft joint 108 is fastened to the pinion shaft 109, an operator may need to have a telescopic function so that the telescopic shaft is once contracted and then fitted to the pinion shaft 109 and fastened. . Further, the upper steering shaft portion 120 at the upper part of the steering mechanism also has a male shaft and a female shaft fitted to each other. The upper steering shaft portion 120 is used for a driver to drive a car. In order to obtain an optimal position, the function of moving the position of the steering wheel 105 in the axial direction and adjusting the position is required, and thus a function of expanding and contracting in the axial direction is required. In all the cases described above, it is possible to reduce the rattling noise of the fitting portion on the telescopic shaft, to reduce the backlash feeling on the steering wheel 105, and to reduce the sliding resistance when sliding in the axial direction. Required.

(Extension shaft with no play and torsional rigidity)
FIG. 2 (a) is a characteristic diagram of the rotation angle and torque when using an expansion / contraction shaft having a conventional structure, and FIG. 2 (b) is a rotation angle and torque for an expansion / contraction shaft without any play. FIG.

  FIG. 2A shows the characteristics of a conventional telescopic shaft. In the case of a spline structure, there is always a circumferential play in the vicinity of neutral. The backlash means that there is a region where torque transmission is not performed at all due to the existence of a gap without using a preload mechanism. Therefore, theoretically, the torsional rigidity of this portion is 0 Nm / deg. However, in an actual case, even if there is a gap, “twist” or “falling” occurs between the male shaft and the female shaft. Will be shown. This variation in characteristics is a factor that deteriorates steering stability and is not preferable.

  On the other hand, in the characteristics according to the present invention shown in FIG. 2B, a predetermined torsional rigidity (K1) Nm / deg can be maintained in the preload region near the neutral. The torsional rigidity (K1) near neutral in this characteristic is 5 Nm / deg or more. Therefore, when steering is performed in the preload region near the neutral position, torque is transmitted without fail.

  That is, as will be described later, the steering torque can be transmitted by the rolling element 7 while preloading between the male shaft 1 and the female shaft 2 via the elastic body 9. As a result, it is possible to provide a telescopic shaft having a hybrid structure having the advantages of rolling and sliding without any play, and it is possible to maintain stable steering performance without feeling a delay in vehicle behavior during steering.

  The torsional rigidity (K1) of 5 Nm / deg is a minimum required torsional rigidity determined based on a steering stability test using a vehicle. When the driver actually steers, the steering speed is said to be 10 Hz or less. That is, when steering at 10 Hz or less, if the torsional rigidity (K1) is 5 Nm / deg or more, stable steering performance can be maintained without feeling a delay in vehicle behavior during steering.

  Furthermore, when the steering torque is greater than or equal to a predetermined value, the predetermined torsional rigidity (K2) Nm / deg can be maintained by the contact of the rigid body, so that the steering torque can be transmitted. That is, as will be described later, the steering torque can be transmitted by the cylindrical body 8 between the male shaft 1 and the female shaft 2.

  In this case, as will be described later, the angle until the cylindrical body 8 (that is, the stopper pin) starts rotating from the neutral position by the contact of the rigid body is set in the range of 0.01 to 0.25 °. It is. Thereby, by preventing an excessive stress from being generated in the leaf spring 9, it is possible to suppress the “sag” of the leaf spring 9 and maintain the preload performance required over a long period of time.

(Embodiment)
FIG. 3 is a longitudinal sectional view of the telescopic shaft for vehicle steering according to the embodiment of the present invention. 4 is a cross-sectional view taken along the line IX-IX in FIG. FIG. 5 is a perspective view of a leaf spring that is an elastic body.

  As shown in FIG. 3, the telescopic shaft 10 for vehicle steering includes a male shaft 1 and a female shaft 2 that are non-rotatable and slidably fitted to each other.

  As shown in FIG. 4, three axial grooves 3 that are equally arranged at intervals of 120 degrees (phase) in the circumferential direction are formed to extend on the outer peripheral surface of the male shaft 1. Correspondingly, three axial grooves 5 that are equally arranged at intervals of 120 degrees (phase) in the circumferential direction are formed to extend on the inner peripheral surface of the female shaft 2.

  Between the axial groove 3 of the male shaft 1 and the axial groove 5 of the female shaft 2, a plurality of rigid spherical bodies 7 (rolling bodies, which roll when the two shafts 1 and 2 move in the axial direction relative to each other). Ball) is installed to roll freely. The axial groove 5 of the female shaft 2 has a substantially arc-shaped cross section or a Gothic arch shape.

  The axial groove 3 of the male shaft 1 is composed of a pair of inclined planar side surfaces 3a and a bottom surface 3b formed flat between the pair of planar side surfaces 3a.

  A leaf spring 9 for contacting and preloading the spherical body 7 is interposed between the axial groove 3 of the male shaft 1 and the spherical body 7.

  As shown in FIG. 5, the leaf spring 9 has a substantially arc-shaped spherical body side contact portion 9a that contacts the spherical body 7 at two points, and a predetermined interval in the circumferential direction with respect to the spherical body side contact portion 9a. The groove surface side contact portion 9b, which is bent and spaced apart and can contact the planar side surface 3a of the axial groove 3 of the male shaft 1, the spherical body side contact portion 9a and the groove surface side contact portion 9b are separated from each other. And an urging portion 9c bent so as to be urged elastically in the direction to be moved, and a flat bottom surface 9d facing the flat bottom surface 3b of the axial groove 3.

  The urging portion 9c has a substantially U shape and is bent in a substantially arc shape, and the spherical body side contact portion 9a and the groove surface side contact portion 9b are mutually connected by the bent urging portion 9c. Can be elastically biased so as to be separated from each other.

  A minute gap (Δ1) is set between the urging portion 9 c or the groove surface side contact portion 9 b and the planar side surface 3 a of the axial groove 3.

  Further, when the leaf spring 9 is bent, the tip of the groove surface side contact portion 9b is bent in the arrow (G) direction so as not to contact the planar side surface 3a of the axial groove 3 as shown in FIG. ing.

  The largest outer shape portion of the R shape of the bent portion (the urging portion 9 c or the groove surface side contact portion 9 b) is set so as to be closest to the planar side surface 3 a of the axial groove 3.

  This is to make the thickness of the bent portion (the urging portion 9c or the groove surface side contact portion 9b) of the leaf spring 9 constant at any location. This is because the torsional rigidity of the preload portion is not stable if the tip of the bent portion (the urging portion 9c or the groove surface side contact portion 9b) falls apart at each location.

  As shown in FIGS. 4 and 5, in this embodiment, the spherical body side contact portion 9 a that contacts the spherical body 7 is formed in a substantially arc shape larger than the radius of the spherical body 7. Thereby, a contact surface pressure with the spherical body 7 can be reduced rather than a planar shape.

  As shown in FIG. 4, three axial grooves 4 that are equally arranged at intervals of 120 degrees (phase) in the circumferential direction are formed to extend on the outer circumferential surface of the male shaft 1. Correspondingly, three axial grooves 6 that are equally arranged at intervals of 120 degrees (phase) in the circumferential direction are formed to extend on the inner peripheral surface of the female shaft 2.

  A plurality of rigid cylindrical bodies 8 (sliding bodies) that slide between the axial grooves 4 of the male shaft 1 and the axial grooves 6 of the female shaft 2 when the two shafts 1 and 2 move relative to each other in the axial direction. , A needle roller) is interposed with a minute gap. The axial grooves 4 and 6 have a substantially circular arc shape or a Gothic arch shape in cross section.

  A minute gap (Δ2) is set between the cylindrical body 8 and the axial groove 6 of the female shaft 2. However, the axial groove 4 of the male shaft 1 4 -the cylindrical body 8 -the axial groove 6 of the female shaft 2 may always be in contact with each other in the axial direction.

  A small diameter portion 1 a is formed at the end of the male shaft 1. The small diameter portion 1 a is provided with a stopper plate 11 that restricts the axial movement of the needle roller 8. The stopper plate 11 includes an axial preload elastic body 12 (that is, a disc spring) and a pair of flat plates 13 and 13 (that is, plain washers) that sandwich the axial preload elastic body 12.

  That is, in the present embodiment, the stopper plate 11 is fitted to the small diameter portion 1a in the order of the flat plate 13, the axial preloading elastic body 12, and the flat plate 13, and is firmly fixed to the small diameter portion 1a by caulking. .

  Thereby, the stopper plate 11 is being fixed to the axial direction. The fixing method of the stopper plate 11 is not limited to caulking, but may be a retaining ring, a screwing means, a push nut or the like. Further, the stopper plate 11 is configured such that the flat plate 13 is brought into contact with the needle roller 8 and the needle roller 8 can be appropriately preloaded by the axial preload elastic body 12 so as not to move in the axial direction.

  Further, in the present embodiment, the six axial grooves 3 and 4 and the axial direction are formed on the outer peripheral surface of the male shaft 1 through gaps in the radial direction in the six axial grooves 5 and 6 of the female shaft 2. Six substantially arc-shaped protrusions 15 that are coaxially formed are fitted.

  Therefore, when the spherical body 7 and the cylindrical body 8 are dropped or broken from the male shaft 1 for some reason, the protruding portion 15 of the male shaft 1 is fitted in the axial grooves 5 and 6 of the female shaft 2. Thereby, the male shaft 1 and the female shaft 2 can transmit torque and can play a role of a fail-safe function.

  At this time, since a gap is provided between the axial grooves 5 and 6 and the projection 15, the driver can feel a large backlash on the steering wheel, and the steering system fails. Etc. can be detected.

  Furthermore, since the protrusion 15 of the male shaft 1 is coaxial with the spherical body 7 and the cylindrical body 8 in the axial direction, it also serves as a stopper for restricting the movement of the spherical body 7 and the cylindrical body 8 in the axial direction. It is possible to further improve the fail-safe function by reducing the possibility of the body 7 and the cylindrical body 8 coming off.

  Furthermore, since the protrusion 15 of the male shaft 1 is coaxial with the spherical body 7 and the cylindrical body 8 in the axial direction, the radial dimension of the male shaft 1 and the female shaft 2 can be reduced to achieve compactness. it can.

  Further, a lubricant may be applied between the axial groove 3 of the male shaft 1, the axial groove 5 of the female shaft 2, the leaf spring 9, and the spherical body 7. A lubricant may also be applied between the axial groove 4 of the male shaft 1, the cylindrical body 8, and the axial groove 6 of the female shaft 2.

  In the telescopic shaft configured as described above, the spherical body 7 is interposed between the male shaft 1 and the female shaft 2, and the spherical body 7 is preloaded to the extent that the female shaft 2 is not rattled by the leaf spring 9. Therefore, the play between the male shaft 1 and the female shaft 2 can be reliably prevented, and when the male shaft 1 and the female shaft 2 move relative to each other in the axial direction, there is no stable play. It is possible to slide with the sliding load.

  At the time of torque transmission, the leaf spring 9 is elastically deformed to constrain the spherical body 7 in the circumferential direction, and the three rows of cylindrical bodies 8 interposed between the male shaft 1 and the female shaft 2 play a main role in torque transmission. Fulfill.

  For example, when torque is input from the male shaft 1, since the preload of the leaf spring 9 is applied in the initial stage, there is no backlash, and the leaf spring 9 generates a reaction force against the torque and transmits the torque. . At this time, overall torque transmission is performed in a state where the transmission torque and the input torque between the male shaft 1, the leaf spring 9, the spherical body 7, and the female shaft 2 are balanced.

  As the torque further increases, the clearance in the rotational direction of the male shaft 1 and female shaft 2 via the cylindrical body 8 disappears, and the subsequent torque increase is transmitted via the male shaft 1 and female shaft 2 to the cylindrical body. 8 communicates. Therefore, it is possible to reliably prevent backlash in the rotational direction of the male shaft 1 and the female shaft 2 and to transmit torque in a highly rigid state.

  As described above, according to the present embodiment, since the cylindrical body 8 is provided in addition to the spherical body 7, most of the load can be supported by the cylindrical body 8 when a large torque is input. Therefore, the contact pressure between the axial groove 5 of the female shaft 2 and the spherical body 7 can be reduced to improve durability, and torque can be transmitted in a highly rigid state at the time of a large torque load. .

  Thus, according to the present embodiment, it is possible to realize a stable sliding load, reliably prevent backlash in the rotational direction, and transmit torque in a highly rigid state.

  The spherical body 7 is preferably a rigid ball. The rigid cylindrical body 8 is preferably a needle roller.

Since the cylindrical body (hereinafter referred to as a needle roller) 8 receives the load by line contact, it has various effects such as a lower contact pressure than a ball that receives a load by point contact. Therefore, the following items are superior to the case where the entire row has a ball rolling structure.
・ The damping effect at the sliding part is larger than that of the ball rolling structure. Therefore, vibration absorption performance is high.
・ Since the needle roller is in minute contact with the male shaft and the female shaft, the fluctuation range of the sliding load can be kept low, and the vibration due to the fluctuation is not transmitted to the steering.
-If the same torque is transmitted, the needle roller can keep the contact pressure lower, so the axial length can be shortened and the space can be used effectively.
-If the same torque is transmitted, the contact pressure of the needle roller can be kept lower, so that an additional step for curing the axial groove surface of the female shaft by heat treatment or the like is unnecessary.
・ The number of parts can be reduced.
・ Assembly can be improved.
・ Assembly costs can be reduced.

As described above, the needle roller serves as a key for transmitting torque between the male shaft 1 and the female shaft 2, and is in sliding contact with the inner peripheral surface of the female shaft 2. The use of the needle roller is superior to the conventional spline fitting as follows.
・ Needle rollers are mass-produced products and are very low cost.
-Since the needle roller is polished after heat treatment, it has high surface hardness and excellent wear resistance.
-Since the needle roller is polished, the surface roughness is fine and the coefficient of friction during sliding is low, so the sliding load can be kept low.
-Since the length and arrangement of the needle roller can be changed according to the use conditions, it can be used for various applications without changing the design concept.
・ Depending on the conditions of use, the friction coefficient during sliding may have to be further reduced. At this time, if only the needle roller is surface treated, its sliding characteristics can be changed, so the design philosophy is not changed. Can support various applications.
Since a needle roller having a different outer diameter can be manufactured at a cost of several microns, the gap between the male shaft, the needle roller, and the female shaft can be minimized by selecting the needle roller diameter. Therefore, it is easy to improve the torsional rigidity of the shaft.

  In addition, as described above, the leaf spring 9 is separated from the spherical body-side contact portion 9a that contacts the spherical body 7 at two points, and is spaced apart from the spherical body-side contact portion 9a by a predetermined interval in a substantially circumferential direction. The groove surface side contact portion 9b that contacts the planar side surface 3a of the axial groove 3 of the male shaft 1, and the spherical body side contact portion 9a and the groove surface side contact portion 9b are elastically biased in a direction away from each other. The urging portion 9c and the bottom surface 9d facing the bottom surface 3b of the axial groove 3 are paired on the left and right.

  The urging portion 9c has a substantially U shape and is bent in a substantially arc shape, and the spherical body side contact portion 9a and the groove surface side contact portion 9b are mutually connected by the bent urging portion 9c. Can be elastically biased so as to be separated from each other. Therefore, the spherical spring side contact portion 9a of the leaf spring 9 can be sufficiently bent through the biasing portion 9b, and a sufficient amount of bending can be ensured.

  Accordingly, the leaf spring 9 is provided with a space between the spherical body side contact portion 9a that contacts the spherical body 7 and the groove surface side contact portion 9b that contacts the axial groove 3, and the space is elastically connected therebetween. It is. Therefore, the stress generated at the contact portion between the spherical body 7 and the leaf spring 9 can be relieved at the time of setting, and the desired preload performance can be obtained over a long period by preventing the leaf spring 9 from sag due to permanent deformation. it can.

  Further, if the spherical body side contact portion 9a that contacts the spherical body 7 is formed in a substantially arc shape larger than the radius of the spherical body 7, the contact surface pressure with the spherical body 7 can be lowered than the planar shape, Further preferred.

  Further, the leaf spring 9 can secure a sufficient amount of bending, and the spherical body 7 and the leaf spring 9 are not subjected to an excessive load (stress). In addition, the stress generated at the contact point with the leaf spring 9 can be relieved, so that high stress is not generated, “sagging” due to permanent deformation is prevented, and preload performance is maintained over a long period of time. be able to.

  Furthermore, the contact point with the spherical body 7 is strong, and the portion exhibiting the spring property is easily bent so that the race surface and the spring property can be achieved with a single member. Further, in the present embodiment, the cylindrical body 8 mainly transmits torque, so that no excessive stress is generated between the male shaft 1, the female shaft 2, the leaf spring, and the spherical body 7.

  Accordingly, it is necessary to prevent excessive stress from being generated in the leaf spring 9 to prevent the leaf spring 9 from sag, to maintain desired preload performance over a long period of time, and to strictly control the dimensional accuracy. In addition, the leaf spring 9 and the race portion can be formed from a single material, and the manufacturing cost can be reduced by facilitating the assembly.

(First working example of embodiment)
FIG. 6 is a partial cross-sectional view of the vehicle steering telescopic shaft according to the embodiment of the present invention in a state where no torque load is applied.

  In FIG. 6, the chain line indicates the state of the spherical body 7 and the leaf spring 9 before the female shaft 2 is fitted, and the solid line indicates the spherical body 7 and the leaf spring after the female shaft 2 is fitted. 9 shows the state.

  FIG. 7 is a partial cross-sectional view of the vehicle steering telescopic shaft according to the embodiment of the present invention in a state where torque load is started.

  The first working example is characterized in that the torsional rigidity (K1) is generated by the frictional force between the male shaft 1 and the leaf spring 9 with a minimum value of 5 Nm / deg.

  In this operation example, by using the frictional force as described above, the load on the leaf spring 9 (repetitive application of high stress to the bent portion) can be reduced, and the spring property can be maintained for a long time. . In addition, since no new parts are added, the cost can be reduced. That is, the structure is sufficient to maintain the minimum required torsional rigidity (5 Nm / deg).

  As shown in FIG. 6, by fitting the female shaft 2, the spherical body 7 is pressed in the direction of the arrow (x).

  Next, since the leaf spring 9 has a wedge angle (θ), the flat bottom surface 9 d is strongly pressed against the bottom surface 3 b of the axial groove 3 while opening in both directions of the arrow (y).

  In this state, there is a minute gap (Δ1) between the urging portion 9 c or the groove surface side contact portion 9 b of the leaf spring 9 and the planar side surface 3 a of the axial groove 3.

  Further, a lubricant such as grease is applied to the flat bottom surface 9 d of the leaf spring 9 that is strongly pressed against the bottom surface 3 b of the axial groove 3. The same applies to the other sliding surfaces.

  Next, as shown in FIG. 7, when a predetermined steering torque in the direction of the arrow (z) is applied to the male shaft 1, the male shaft 1 → the leaf spring 9 → the spherical body 7 → with the contact angle indicated by the symbol (B). Torque is transmitted in the order of the female shaft 2.

  At this time, the frictional force on the surface (A) plays an important role. That is, a friction force obtained by multiplying the force (F) pressed in the (x) direction of FIG.

  When the torque in the direction of the arrow (z) becomes larger than this frictional force, the leaf spring 9 starts to slide on the surface indicated by the symbol (A).

  Next, at the same time as this phenomenon, that is, before the groove surface side contact portion 9b of the leaf spring 9 contacts the planar side surface 3a of the axial groove 3 at the point (C), the cylindrical body 8 has the code (D ) Contacts the axial grooves 4 and 6 at a point.

  That is, the contact between the male shaft 1 → the cylindrical body 8 → the female shaft 2 is more firmly brought into contact with the contact angle of the point (D). Thereafter, a steering torque having a predetermined torsional rigidity (K2) is transmitted.

  As described above, in the first working example, the leaf spring 9 is used, but the reason why the torsional rigidity is generated with the minimum value of 5 Nm / deg is on the surface of the reference (A). Frictional force.

(Second working example of embodiment)
FIG. 6 is a partial cross-sectional view of the vehicle steering telescopic shaft according to the embodiment of the present invention in a state where no torque load is applied.

  In FIG. 6, the chain line indicates the state of the spherical body 7 and the leaf spring 9 before the female shaft 2 is fitted, and the solid line indicates the spherical body 7 and the leaf spring after the female shaft 2 is fitted. 9 shows the state.

  FIG. 7 is a partial cross-sectional view of the vehicle steering telescopic shaft according to the embodiment of the present invention in a state where torque load is started.

  The second working example is characterized in that the torsional rigidity (K1) is generated by the frictional force and the biasing force of the male shaft 1 and the leaf spring 9 with a minimum value of 5 Nm / deg.

  In this example, when the torsional rigidity is tuned (higher torsional rigidity is required), both the frictional force and the urging force generated at the bent portion (the urging part 9c) of the leaf spring 9 are combined. Can be used to obtain the required torsional rigidity. In this case as well, the load on the leaf spring 9 can be reduced by combining with the frictional force, compared to the case where the torsional rigidity is generated only by the bent portion (the urging portion 9c) of the leaf spring 9. That is, by preventing an excessive stress from being generated in the leaf spring 9, the “sag” of the leaf spring 9 can be suppressed and the preload performance required over a long period can be maintained.

  As shown in FIG. 6, by fitting the female shaft 2, the spherical body 7 is pressed in the direction of the arrow (x).

  Next, since the leaf spring 9 has a wedge angle (θ), the flat bottom surface 9 d is strongly pressed against the bottom surface 3 b of the axial groove 3 while opening in both directions of the arrow (y).

  In this state, there is a minute gap (Δ1) between the urging portion 9 c or the groove surface side contact portion 9 b of the leaf spring 9 and the planar side surface 3 a of the axial groove 3.

  Further, a lubricant such as grease is applied to the flat bottom surface 9 d of the leaf spring 9 that is strongly pressed against the bottom surface 3 b of the axial groove 3. The same applies to the other sliding surfaces.

  Next, as shown in FIG. 7, when a predetermined steering torque in the direction of the arrow (z) is applied to the male shaft 1, the male shaft 1 → the leaf spring 9 → the spherical body 7 → with the contact angle indicated by the symbol (B). Torque is transmitted in the order of the female shaft 2.

  At this time, the frictional force on the surface (A) plays an important role. That is, a friction force obtained by multiplying the force (F) pressed in the (x) direction of FIG.

  When the torque in the direction of the arrow (z) becomes larger than the frictional force, the leaf spring 9 starts to slide on the surface indicated by the symbol (A).

  Next, in this example, as the leaf spring 9 moves due to frictional force, the leaf spring 9 comes into contact with the planar side surface 3a of the axial groove 3 at the point (C), and the bent portion of the leaf spring 9 (biased) The part 9c) exhibits a spring force (biasing force).

  Next, simultaneously with such a phenomenon, that is, after the groove surface side contact portion 9b of the leaf spring 9 contacts the planar side surface 3a of the axial groove 3 at the point (C), the cylindrical body 8 is denoted by the symbol (D). Contact the axial grooves 4, 6 at a point.

  After that, the cylindrical body 8 makes a more firm contact between the male shaft 1 → the cylindrical body 8 → the female shaft 2 with a contact angle of the point (D), and generates a steering torque with a predetermined torsional rigidity (K2). To communicate.

  As described above, in the second working example, the elastic contact at the point (C) occurs before the rigid contact at the point (D). That is, the reason why the torsional rigidity is generated with 5 Nm / deg as a minimum value is that the frictional force on the surface (A) and the spring force (applying portion 9 c) of the bent portion of the leaf spring 9 (attachment). Power).

  In addition, this invention is not limited to embodiment mentioned above, A various deformation | transformation is possible.

1 is a side view of a steering mechanism portion of an automobile to which a telescopic shaft for vehicle steering according to an embodiment of the present invention is applied. (A) is a characteristic diagram of the rotation angle and torque when using a telescopic shaft having a conventional structure, and (b) is a characteristic of the rotation angle and torque on an elastic shaft having no backlash. FIG. It is a longitudinal cross-sectional view of the telescopic shaft for vehicle steering which concerns on embodiment of this invention. FIG. 4 is a transverse sectional view taken along line IX-IX in FIG. 3. It is a perspective view of the leaf | plate spring which is an elastic body. It is a partial cross section in the state where torque load is not applied to the telescopic shaft for vehicle steering according to the embodiment of the present invention. It is a partial cross section in the state where torque load was started to a telescopic shaft for vehicle steering concerning an embodiment of the invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Male shaft 1a Small diameter part 2 Female shaft 3 Axial groove 3a Planar side surface 3b Bottom surface 4 Axial groove 5 Axial groove 6 Axial groove 7 Spherical body (ball, rolling element)
8 Cylindrical body (needle roller, sliding body)
9 Leaf spring (elastic body)
9a Spherical body side contact part (transmission member side contact part)
9b Groove surface side contact portion 9c Energizing portion 9d Bottom surface 10 Telescopic shaft 11 Stopper plate 12 Axial preload elastic body 13 Flat plate 15 Projection portion 16 Solid lubricating film 100 Member 101 Upper bracket 102 Lower bracket 103 Steering column 104 Steering shaft 105 Steering Wheel 106 Universal joint 107 Lower steering shaft portion 108 Steering shaft joint 109 Pinion shaft 110 Frame 111 Elastic body 112 Steering rack 120 Upper steering shaft portion

Claims (6)

In a telescopic shaft for vehicle steering that is incorporated in a steering shaft of a vehicle and has a male shaft and a female shaft that are non-rotatable and slidably fitted.
The telescopic shaft is
A preload torque transmission unit that transmits the steering torque while preloading between the two shafts when the steering torque is a predetermined value or less;
When the steering torque exceeds a predetermined value, a rigid torque transmission unit that transmits the steering torque by the rigid body contact between the two shafts,
A telescopic shaft for vehicle steering, wherein the torsional rigidity generated by the preload torque transmitting portion is 5 Nm / deg or more. The preload torque transmission unit is
Between the outer circumferential surface of the male shaft and the inner circumferential surface of the female shaft, the first torque transmission member is interposed between the at least one row of axial grooves formed through the elastic body,
The rigid torque transmission part is
The second torque transmission member is interposed between at least one other groove direction formed on the outer peripheral surface of the male shaft and the inner peripheral surface of the female shaft, respectively. Telescopic shaft for vehicle steering as described. The first torque transmission member is a rolling element that rolls in the axial relative movement of the two shafts,
The telescopic shaft for vehicle steering according to claim 2, wherein the second torque transmission member is a sliding body that slides and slides when the two wheels are axially moved relative to each other.   The telescopic shaft for vehicle steering according to claim 2 or 3, wherein the predetermined torsional rigidity is generated by a frictional force between the male shaft and the elastic body.   The telescopic shaft for vehicle steering according to claim 2 or 3, wherein the predetermined torsional rigidity is generated by a frictional force and a biasing force of the male shaft and the elastic body.   The angle from the neutral position until the rigid torque transmission part or the second torque transmission member starts to rotate due to the contact of the rigid body is set in the range of 0.01 to 0.25 °. The telescopic shaft for vehicle steering according to any one of claims 1 to 5, characterized in that:

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