JP2005313693A - Telescopic shaft for vehicle steering - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a stable sliding load, positively prevent looseness of a telescopic shaft in its rotational direction and transmit torque under a high rigid state. <P>SOLUTION: The characteristic indicated at (b) shows that a predetermined twisting rigidity (K1) Nm/deg can be kept in a pre-loading region near its 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 its neutral value, a torque is transmitted without fail under no looseness at the shaft at all. That is, a steering torque can be transmitted between a male shaft 1 and a female shaft 2 through rollers 7 while applying a pre-loading through a resilient member 9. With this arrangement, it is possible to provide a telescopic shaft of hybrid structure having an advantage of rolling and sliding with no looseness at all, resulting in that a stable steering performance can be maintained without feeling any delay in an action of a vehicle at the time of steering operation. <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.

  Conventionally, the steering mechanism part of an automobile absorbs the displacement in the axial direction that occurs when the automobile travels, and the expansion and contraction is a spline fit between the male shaft and the female shaft in order not to transmit the displacement or vibration on the steering wheel. The shaft is used as part of the steering mechanism. The telescopic shaft is required to reduce the rattling noise of the spline part, to reduce the rattling on the steering wheel, and to reduce the sliding resistance when sliding in the axial direction.

  Because of this, the nylon spline part of the telescopic shaft is coated with nylon film, and grease is applied to the sliding part to absorb or reduce metal noise, metal hitting sound, etc., and sliding resistance Have been reduced and the play in the rotational direction has been reduced. In this case, as a process of forming the nylon film, cleaning of the shaft → primer application → heating → nylon powder coating → rough cutting → finish cutting → selective fitting with the female shaft is performed. The final cutting process is performed by selecting a die in accordance with the accuracy of the already processed female shaft.

  Moreover, in patent document 1, it arrange | positions a ball | bowl through the elastic body between the groove part of an inner shaft, and the ball | bowl at the groove part provided in the outer peripheral part of the inner side shaft, and the inner peripheral part of the outer side shaft, A vehicle steering telescopic shaft that reduces the sliding load of the male shaft and the female shaft by rolling the ball during the movement of the vehicle and transmits the torque by restraining the ball during the rotation is disclosed. Yes. Further, the above publication discloses that a male groove and a female groove having a combined cross section with a certain play are provided on the inner shaft and the outer shaft in order to enable transmission of torque even when the ball is broken. ing.

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.
Japanese Patent Laying-Open No. 2001-50293 (pages 7 and 13 and FIG. 12) JP 2000-9148 A

  However, in the prior art described above, it is necessary to minimize the backlash while minimizing the sliding load of the telescopic shaft. Therefore, in the final cutting, dies with different overpin diameter sizes of several microns are used. It is forced to select and process in accordance with the female shaft, resulting in an increase in processing cost. Further, wear of the nylon film progresses with the progress of use, and the rotational play is increased.

  Further, under conditions where the engine room is exposed to high temperatures, the nylon membrane changes in volume, and the sliding resistance becomes remarkably high and wear is remarkably promoted, so that the backlash in the rotational direction becomes large. Therefore, there is a demand to provide a structure that can suppress the generation of abnormal noise due to backlash in the rotational direction and the deterioration of the steering feeling over a long period of time in a telescopic shaft used for a steering shaft for an automobile.

  Further, in the telescopic shaft for vehicle steering disclosed in Patent Document 1, during normal use, a plurality of balls perform expansion and contraction operations and torque transmission by rolling. For this reason, the number of balls that can withstand the input torque must be provided structurally, and it is difficult to reduce the size of the telescopic shaft for vehicle steering, and it is difficult to take a sufficient collapse stroke at the time of a vehicle collision. There are also disadvantages.

  Further, in Patent Document 2, since the spline structure is a sliding slide, it is physically impossible to completely eliminate the evening, no matter how small the play in the circumferential direction is.

  The present invention has been made in view of the above-described circumstances, and can realize a stable sliding load, reliably prevent backlash in the rotational direction, and transmit torque in a highly rigid state. An object is to provide a telescopic shaft for steering.

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
The steering torque is provided between the outer periphery of the male shaft and the inner periphery of the female shaft so as to transmit the steering torque while preloading between the two shafts when the steering torque is a predetermined value or less. A rolling element that rolls when the shaft and the female shaft move in the axial direction, and is disposed adjacent to the rolling element in a radial direction, and is arranged between the male shaft and the female shaft via the rolling element. An elastic body for applying a preload, and a preload torque transmitting unit comprising:
When the steering torque exceeds a predetermined value, the outer periphery of the male shaft and the inner periphery of the female shaft are respectively provided to transmit the steering torque by the rigid contact between the two shafts. A rigid torque transmitting portion that transmits torque in contact with each other,
The torsional rigidity generated by the preload torque transmission unit is 5 Nm / deg or more.

  In the vehicle steering telescopic shaft according to a second aspect of the present invention, the rigid torque transmitting portion is formed on an axial ridge formed on the outer peripheral surface of the male shaft and on an inner peripheral surface of the female shaft. And an axial groove.

  The telescopic shaft for vehicle steering according to claim 3 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 4 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.

  The telescopic shaft for vehicle steering according to claim 5 of the present invention has an angle from 0.01 to 0.25 ° until the rigid torque transmitting portion starts rotating from the neutral position by the contact of the rigid body. The range is set.

  As described above, according to the present invention, the torsional rigidity generated in the preload torque transmitting 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 configuration 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 elastically move 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. 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, so that the torsional rigidity is not stable, and an unstable characteristic of 0 to several Nm / deg. 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 between the male shaft 1 and the female shaft 2 by the axial ridge 14.

  In this case, as will be described later, the angle from the neutral position until the axial protrusion 14 (that is, the rigid torque transmission portion) contacts the axial groove 6 of the female shaft 2 and starts high torque transmission is as follows: It is set in the range of 0.01 to 0.25 °. 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. FIG. 4 is a cross-sectional view taken along 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, a plurality of axial ridges 14 extend from the outer peripheral surface of the male shaft 1. These axial ridges 14 are spline-fitting male parts, but may be serration-fitting male parts or simply for convex-concave fittings.

  On the inner peripheral surface of the female shaft 2, a plurality of axial grooves 6 are formed extending at positions facing the axial ridges 14 of the male shaft 1. These axial grooves 6 are female parts for spline fitting, but may be female parts for serration fitting or simply for uneven fitting.

  A minute gap (Δ2) is set between the axial ridge 14 and the axial groove 6 of the female shaft 2.

  On the outer peripheral surface of the male shaft 1, three axial grooves 3 that are equally arranged at intervals of 120 degrees (phase) in the circumferential direction are formed to extend. 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.

  A stopper plate 11 that locks the plate spring 9 in the axial direction with a small gap so that the plate spring 9 does not fall off at the end on the side where the male shaft 1 is inserted into the female shaft 2 (that is, a flat plate). A washer 13) is crimped to the male shaft 1 by a small diameter portion 1a. The stopper plate 11 (that is, the flat washer 13) also serves to prevent the rolling element 7 from being removed from the axial groove 3 of the male shaft 1. Thus, the telescopic shaft for vehicle steering according to the present embodiment is configured.

  In the telescopic shaft as described above, when the shaft rotates (when high torque is transmitted), the axial ridge 14 and the axial groove 6 come into contact with each other to form a torque transmitting portion.

  Since the telescopic shaft of the present embodiment has such a structure, the male shaft 1 and the female shaft 2 are slidably in contact with each other at each torque transmitting portion due to the presence of the preload portion. During relative movement in the axial direction with respect to the female shaft 2, they slide with each other and the rolling element 7 can roll.

  In addition, even if the axial ridges 14 formed on the male shaft are formed on the female shaft side and the axial grooves 6 formed on the female shaft are formed on the male shaft side, the same action as in the present embodiment, An effect is obtained. Moreover, the curvature of the axial direction groove | channel 5 and the curvature of the rolling element 7 differ, and both may be formed so that a point contact may be carried out. Further, the rolling element 7 may be a spherical body. Further, the leaf spring 9 may be a leaf spring. Further, a lower sliding load can be obtained by applying grease to the sliding surface and the rolling surface.

  The telescopic shaft of the present embodiment configured as described above is superior to the prior art in the following points.

  If the sliding surface is purely sliding as in the prior art, the preload load for preventing rattling could only be kept at a certain level. That is, the sliding load is the friction coefficient multiplied by the preload, and if the preload is increased in order to prevent rattling and improve the rigidity of the telescopic shaft, the sliding load will increase. This is because it falls into a vicious circle.

  In this respect, in the present embodiment, the preload portion employs a rolling mechanism of the rolling element 7 during the relative movement in the axial direction, so that the preload is increased without causing a significant increase in sliding load. be able to. As a result, it is possible to achieve the prevention of rattling and the improvement of rigidity that could not be achieved conventionally without increasing the sliding load.

  At the time of high torque transmission, the axial ridge 14 of the torque transmission portion plays a role of torque transmission by contacting the axial groove 6, and the leaf spring 9 is elastically deformed in the preload portion so that the spherical body 7 is 1 and the female shaft 2 are restrained in the circumferential direction to prevent rattling and transmit low torque.

  For example, when torque is input from the male shaft 1, rattling is prevented because the preload of the leaf spring 9 is applied in the initial stage.

  As the torque further increases, the axial ridge 14 of the torque transmitting portion and the side surface of the axial groove 6 come into strong contact with each other, and the axial ridge 14 receives a stronger reaction force than the spherical body 7, thereby transmitting torque. The part mainly transmits torque. Therefore, in this embodiment, 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.

Further, since the axial ridge 14 and the axial groove 6 are continuously contacted in the axial direction and receive the load during torque transmission, the contact pressure is kept lower than that of the rolling element 7 that receives the load by point contact. There are various effects. Therefore, the following items are superior to the conventional example in which 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.
-If the same torque is transmitted, since the axial ridge 14 can keep the contact pressure lower, the axial length of the torque transmitting portion can be shortened and the space can be used effectively.
-If the same torque is transmitted, the contact pressure of the axial ridge 14 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.
-Since the torque transmission is mainly handled by the torque transmission part, the number of rolling elements 7 can be reduced and the collapse stroke can be increased.

Further, in terms of partially adopting the rolling elements 7, the following items are superior to the conventional example in which all rows are spline-fitted and all rows slide.
・ Since rolling is used, sliding load can be kept low.
-Preload can be increased, and long-term rattling can be prevented and high rigidity can be obtained at the same time.

  In addition to the above description, the components of the telescopic shaft according to the present embodiment are preferably configured as shown in Table 1 and Table 2 below.

また、本実施の形態では、図３、図４に示すように、雄軸１の軸方向凸条１４は、その両端部に、テーパー形状部Ｔを有している。また、軸方向凸条１４の両端部及び中間部では、その角部に、曲面形状部Ｒを有している。

Moreover, in this Embodiment, as shown to FIG. 3, FIG. 4, the axial direction protruding item | line 14 of the male shaft 1 has the taper-shaped part T in the both ends. Moreover, in the both ends and intermediate part of the axial ridge 14, it has the curved-surface-shaped part R in the corner | angular part.

  As shown in FIG. 4, the female shaft 2 is also formed at the corners of the ridge 6 a formed between the two axial grooves 6 and the standing wall 6 b on the end side of the axial groove 6. And has a curved surface portion R.

(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 the frictional force, the leaf spring 9 starts to slide on the surface indicated by the symbol (A).

  Next, simultaneously with such a 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 axial ridge 14 is (D) It contacts the axial groove 6 at a point.

  That is, with the contact angle of the point (D), the space between the male shaft 1 → the axial ridge 14 → the female shaft 2 is more firmly in contact. 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 portion 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 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 of operation, as the leaf spring 9 moves due to the 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 (biasing force) 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 axial ridge 14 is D) Contact the axial groove 6 at a point.

  Thereafter, the axial ridge 14 makes a more firm contact between the male shaft 1 → the axial ridge 14 → the female shaft 2 with a contact angle of the point (D), and has a predetermined torsional rigidity (K2). The steering torque is transmitted.

  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 minimum value of 5 Nm / deg is used to generate the torsional rigidity because the frictional force on the surface (A) and the spring force of the bent portion (biasing portion 9 c) of the leaf spring 9 ( Energizing force).

(First Modification of Embodiment)
FIG. 8 is a cross-sectional view of a telescopic shaft for vehicle steering according to a first modification of the embodiment of the present invention.

  As is apparent from the drawings, the basic structure of this modification is the same as that of the above-described embodiment, and only differences will be described.

  This modification is characterized in that the solid lubricating film 16 is formed on the outer peripheral surface of the male shaft 1. Thus, by forming the solid lubricating film 16 on the outer peripheral surface of the male shaft 1, the contact resistance between the axial ridge 14 and the axial groove 6 of the torque transmitting portion can be lowered, so that the total sliding The load (referred to as a sliding load generated during normal use in the structure of the present invention in which both rolling and sliding are applied) can be made lower than in the case of the above embodiment.

  As the solid lubricant film 16, a powder of molybdenum disulfide is dispersed and mixed in the resin, and after spraying or dipping it, a film is formed by baking, or PTFE (tetrafluoroethylene) is dispersed and mixed in the resin. A film or the like formed by spraying or dipping it after baking is used. Further, instead of the solid lubricating film 16, a resin may be coated.

  In addition, as described in the above embodiment, the leaf spring 9 slides in the circumferential direction. Therefore, when the solid lubricant film 16 is applied, the friction coefficient (μ) is stabilized, so that stable torsional rigidity is obtained. Can do. It is more preferable that grease (including molybdenum disulfide) is applied. Other configurations, operations, and effects are the same as those in the above-described embodiment.

(Second modification of the embodiment)
FIG. 9 is a cross-sectional view of a telescopic shaft for vehicle steering according to a second modification of the embodiment of the present invention.

  As is apparent from the drawings, the basic structure of this modification is the same as that of the above-described embodiment, and only differences will be described.

  In this modification, three axial ridges 14 each having a substantially arc-shaped cross-sectional shape that are equally spaced at 120 degree intervals in the circumferential direction on the outer peripheral surface of the male shaft 1 are formed to extend. Then, three axial grooves 6 having a substantially arc-shaped cross section are formed on the inner peripheral surface of the female shaft 2 so as to be opposed to the three axial ridges 14 of the male shaft 1. Yes. When sliding, the axial ridge 14 and the axial groove 6 are in principle non-contact with each other, but when high torque is transmitted, they are in contact with each other to form a torque transmission portion. The axial ridges 14 and the axial grooves 6 are substantially arc-shaped in cross section or Gothic arch shape, but may have other shapes.

  Moreover, since the outer peripheral surface of the axial ridge 14 is substantially arc-shaped, and the inner peripheral surface of the axial groove 6 is also substantially arc-shaped, and is arranged at three locations, the concavo-convex portion (axial ridge 14 The corners of the axial grooves 6) do not contact the edges of the corners and can prevent uneven wear. Furthermore, by arranging the axial ridges 14 at three equal positions, the three arcuate protrusions can receive a load evenly and transmit torque. Therefore, wear of the concavo-convex portions (axial ridges 14 and axial grooves 6) can be suppressed, and performance can be maintained over a long period of time.

  Furthermore, since the corners of the concavo-convex portions (the axial ridges 14 and the axial grooves 6) are not formed in the curved surface shape R, they have the curved surface shape (arc shape). The concavo-convex portions (the axial ridges 14 and the axial grooves 6) on the moving surface can slide smoothly without causing stick-slip. Other configurations, operations, and effects are the same as those in the above-described embodiment.

  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 diagram 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. FIG. 3 is a partial cross-sectional view in a state where a torque load is not applied to the vehicle steering telescopic shaft 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. It is a cross-sectional view of the telescopic shaft for vehicle steering which concerns on the 1st modification of embodiment of this invention. It is a cross-sectional view of the telescopic shaft for vehicle steering which concerns on the 2nd modification of embodiment of this 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 5 Axial groove 6 Axial groove 7 Spherical body (ball, rolling element)
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 14 Axial ridge 15 Protrusion 16 Solid lubricant film 100 Member 101 Upper bracket 102 Lower bracket 103 Steering column DESCRIPTION OF SYMBOLS 104 Steering shaft 105 Steering wheel 106 Universal joint 107 Lower steering shaft part 108 Steering shaft coupling 109 Pinion shaft 110 Frame 111 Elastic body 112 Steering rack 120 Upper steering shaft part

Claims (5)

In the telescopic shaft for vehicle steering, which is incorporated in the steering shaft of the vehicle and the male shaft and the female shaft are slidably fitted to each other,
The telescopic shaft is
The steering torque is provided between the outer periphery of the male shaft and the inner periphery of the female shaft so as to transmit the steering torque while preloading between the two shafts when the steering torque is a predetermined value or less. A rolling element that rolls when the shaft and the female shaft move in the axial direction, and is disposed adjacent to the rolling element in a radial direction, and is arranged between the male shaft and the female shaft via the rolling element. An elastic body for applying a preload, and a preload torque transmitting unit comprising:
When the steering torque exceeds a predetermined value, the outer periphery of the male shaft and the inner periphery of the female shaft are respectively provided to transmit the steering torque by the rigid contact between the two shafts. A rigid torque transmitting portion that transmits torque in contact with each other,
A telescopic shaft for vehicle steering, wherein the torsional rigidity generated by the preload torque transmitting portion is 5 Nm / deg or more.   2. The rigid torque transmitting portion includes an axial ridge formed on an outer peripheral surface of the male shaft and an axial groove formed on an inner peripheral surface of the female shaft. The telescopic shaft for vehicle steering described in 1.   3. The vehicle steering telescopic shaft according to claim 1, wherein the predetermined torsional rigidity is generated by a frictional force between the male shaft and the elastic body.   3. The vehicle steering telescopic shaft according to claim 1, wherein the predetermined torsional rigidity is generated by a frictional force and an urging force of the male shaft and the elastic body.   The angle from the neutral position to the start of rotation of the rigid torque transmitting portion by the contact of the rigid body is set in a range of 0.01 to 0.25 °. 5. The telescopic shaft for vehicle steering according to any one of 4.

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