JP2009197911A - Telescopic shaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inhibit sudden extension and contraction in torque loss in a telescopic shaft employed to an intermediate shaft of a steering mechanism, or the like. <P>SOLUTION: This telescopic shaft is provided with a cylindrical female shaft 21 and a male shaft 22 fitted inside of the female shaft 21, and can be extended and contracted by allowing slide in only axial direction of both shafts. The telescopic shaft is provided with a pair of rolling grooves 23, 24 formed on an inner circumference surface of the female shaft 21 and an outer circumference surface of the male shaft 22 and opposing along the axial direction, balls 26 put between the pair of rolling grooves 23, 24, and a sliding contact pin 29 inserted in at least one of one end side and another end side along the axial direction of the pair of rolling grooves 23, 24 and applying prescribed sliding resistance on the pair of rolling grooves 23, 24. The prescribed sliding resistance includes a value in a range in which smooth slide of the female shaft 21 and the male shaft 22 is not deteriorated. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a telescopic shaft employed in an intermediate shaft or the like of a steering mechanism.

A linear motion guide structure in which a male shaft is fitted into a cylindrical female shaft, and a plurality of balls are interposed along the axial direction between the inner peripheral surface of the female shaft and the outer peripheral surface of the male shaft; A key structure that interposes a needle roller parallel to the direction is formed at a predetermined interval in the circumferential direction, thereby smoothing the sliding in the axial direction while preventing relative rotation between the female shaft and the male shaft. There was a thing (refer patent document 1).
JP 2004-130928 A

  In the invention described in the above-mentioned patent document 1, the linear motion of the linear movement between the female shaft and the male shaft smoothens the axial displacement and vibration that can occur in the telescopic shaft. Can be absorbed smoothly. However, when the needle roller as the key structure transmits torque between the female shaft and the male shaft, its sliding resistance increases, so that an axial load is input to the telescopic shaft. Even if it exists, the sliding of the axial direction of a female shaft and a male shaft will be suppressed. When the torque is lost and the load is removed in the state where the axial load is input, the female shaft and the male shaft released from the suppressed state suddenly slide in the axial direction. This may cause vibration transmission to the steering wheel and abnormal noise.

  An object of the present invention is to suppress sudden expansion and contraction when torque is lost.

  The telescopic shaft according to claim 1 of the present invention includes a cylindrical female shaft and a male shaft fitted inside the female shaft, and is telescopic by allowing sliding only in both axial directions. A telescopic shaft, a pair of rolling grooves formed on an inner peripheral surface of the female shaft and an outer peripheral surface of the male shaft and facing each other along the axial direction, and a rolling element interposed between the pair of rolling grooves And a sliding contact member that is inserted into at least one of the one end side and the other end side along the axial direction of the pair of rolling grooves and gives a predetermined sliding resistance to the pair of rolling grooves. It is characterized by providing. The predetermined sliding resistance is a value in a range that does not impair smooth sliding between the female shaft and the male shaft.

  The telescopic shaft according to claim 2 of the present invention is characterized in that the sliding contact member is formed with crowning having an outer diameter smaller toward the end portion at both end sides along the axial direction.

  According to the present invention, at least one of the one end side and the other end side along the axial direction of the pair of rolling grooves is provided with a sliding member that gives a predetermined sliding resistance between the pair of rolling grooves. Thus, it is possible to prevent the female shaft and the male shaft from sliding suddenly in the axial direction when the torque is lost.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 is a schematic configuration diagram of a steering mechanism, FIG. 2 is a longitudinal sectional view of an intermediate shaft, FIG. 3 is a sectional view taken along the line AA of the intermediate shaft, FIG. 4 is a single part diagram of a leaf spring, and FIG. FIG. 6 is a graph showing the relationship between transmission torque and sliding resistance.
As shown in FIG. 1, the steering wheel 1 is connected to one end of a steering shaft 2, and the steering shaft 2 is rotatably held by a steering column 3. The other end of the steering shaft 2 is connected to the upper end of the intermediate shaft 5 via the cardan shaft joint 4, and the lower end of the intermediate shaft 5 is connected to the upper end of the pinion shaft 7 via the cardan shaft joint 6. Is connected to the rack shaft 8.

  The steering column 3 is attached to a member 13 on the vehicle body side via the upper bracket 11 on the upper side and the lower bracket 12 on the lower side. A rack housing 14 that accommodates the rack shaft 8 so as to advance and retract is fixed to a frame 16 on the vehicle body side via an elastic body 15.

  The steering shaft 2 and the intermediate shaft 5 are constituted by telescopic shafts that are extendable in the axial direction. As a result, the steering shaft 2 can arbitrarily adjust the telescopic position of the steering wheel 1, and the intermediate shaft 5 can absorb axial displacement and vibration generated during travel. The axial displacement and vibration that occur during traveling are caused by the fact that the member 13 and the frame 16 are separate, the rack housing 14 being fixed to the frame 16 via the elastic body 15, and the like. is doing.

Although the structure of the intermediate shaft 5 will be described here as the telescopic shaft, the steering shaft 2 has the same structure, and therefore detailed description thereof is omitted.
As shown in FIGS. 2 and 3, the intermediate shaft 5 includes a cylindrical female shaft 21 connected to the downstream side (pinion shaft 8 side) and an upstream side (steering shaft 2 side). And a male shaft 22 fitted inside.

  On the inner peripheral surface of the female shaft 21, rolling grooves 23 having an arc-shaped cross section are formed along the axial direction at three locations that are equally spaced in the circumferential direction. A substantially trapezoidal rolling groove 24 is formed at a position facing the moving groove 23 along the axial direction. A plate spring 25 is laid in each rolling groove 24 of the male shaft 22, and a plurality of balls 26 are interposed between the plate spring 25 and the rolling groove 23. The ball 26 contacts the leaf spring 25 and the rolling groove 23 at two points.

  A cylindrical sliding contact pin 29 parallel to the axial direction is inserted between the leaf spring 25 and the rolling groove 23 at one end side along the axial direction. Is given a predetermined sliding resistance. The predetermined sliding resistance is a value within a range that does not impair smooth sliding between the female shaft 21 and the male shaft 22. The sliding contact pin 29 is in line contact with the leaf spring 25 and the rolling groove 23 at two locations in the circumferential direction.

  As shown in FIGS. 3 and 4, the cross section of the leaf spring 25 has a substantially corrugated shape in which the side plate 25b is raised from both sides of the bottom plate 25a and the tip of the side plate 25 is folded outward and folded into a bowl shape. 24 is in surface contact with the bottom surface of the side plate 24, and the tip side of the side plate 25 b is in surface contact with the side surface of the rolling groove 24. Due to the elastic force of the pair of side plates 25 b, the ball 26 is pressed in the radial direction against the female shaft 21, so that radial preload acts on the female shaft 21 and the male shaft 22.

  As shown in FIG. 2, the leaf spring 25 is engaged at both ends by a radial step 24 a serving as a terminal end of the rolling groove 24 and an annular stopper 27 fixed to the tip of the male shaft 22. Positioning in the axial direction with respect to 22 is performed (held). An annular elastic body 28 is interposed between the stopper 27 and the leaf spring 25.

  The ball 26 rolls according to the axial sliding of the female shaft 21 and the male shaft 22. That is, when the female shaft 21 and the male shaft 22 slide in the extending direction, the ball 26 rolls in a direction approaching the elastic body 28, and when the female shaft 21 and the male shaft 22 slide in the contracting direction, The ball 26 rolls in a direction approaching the step 24a. By the rolling of the ball 26, the sliding between the female shaft 21 and the male shaft 22 becomes smooth.

  On the other hand, on the inner peripheral surface of the female shaft 21, key grooves 31 having an arc-shaped cross section are formed along the axial direction at three positions that are shifted from the rolling groove 23 by a half cycle and at equal intervals in the circumferential direction. On the outer peripheral surface of the male shaft 22, a key groove 32 having an arc-shaped cross section is formed along the axial direction at a position facing each key groove 31. The key grooves 31 and 32 have the same length as the rolling grooves 23 and 24, and an elongated cylindrical roller 33 is interposed between the key grooves 31 and 32. The roller 33 makes line contact with the key grooves 31 and 32 at two locations in the circumferential direction. Further, both ends of the roller 33 are locked by the radial step 32 a serving as the terminal end of the key groove 32 and the stopper 27 described above, and the roller 33 is positioned (held) in the axial direction with respect to the male shaft 22.

  The ball 26 is in point contact with each of the rolling groove 23 and the leaf spring 25, but the roller 33 is in line contact with each of the key grooves 31 and 32. It is mainly the roller 33 that transmits torque to and from the shaft 22.

Further, when the female shaft 21 and the male shaft 22 slide in the axial direction, slip occurs between the keyway 31 and the roller 33. On both ends of the roller 33, as shown in FIG. 5, crowning 33a having an outer diameter that decreases toward the end is formed. Therefore, the concentrated stress (contact surface pressure) generated at both ends is reduced. Further, when a slip occurs between the keyway 31 and the roller 33, even if there is an error in the parallelism between the keyway 31 and the roller 33, a certain amount of error is allowed and a sudden change in the sliding resistance is caused. Is alleviated.
From the above, the ball 26 corresponds to the “rolling element” and the sliding contact pin 29 corresponds to the “sliding contact member”.

Next, the function and effect of the first embodiment will be described.
As the ball 26 rolls, the sliding between the female shaft 21 and the male shaft 22 becomes smooth, so that axial displacement and vibration that can occur in the intermediate shaft 5 are smoothly absorbed. However, when the roller 33 is transmitting torque between the female shaft 21 and the male shaft 22, the sliding resistance increases, so that an axial load is input to the intermediate shaft 5. Even so, sliding in the axial direction between the female shaft 21 and the male shaft 22 is suppressed. When the torque is lost and the load is removed with the axial load being input, the female shaft 21 and the male shaft 22 released from the suppressed state suddenly slide in the axial direction. Therefore, there is a possibility of causing vibration transmission to the steering wheel 1 and generation of abnormal noise.

  Therefore, a sliding contact pin 29 that is slidably contacted between the leaf spring 25 and the rolling groove 23 is interposed between them so that smooth sliding between the female shaft 21 and the male shaft 22 is not impaired. On the other hand, a predetermined sliding resistance was added. Thereby, it is possible to suppress sudden sliding of the female shaft 21 and the male shaft 22 in the axial direction when the torque disappears (damper effect).

The above effect will be described with reference to FIG. As the transmission torque between the female shaft 21 and the male shaft 22 increases, the sliding resistance in the axial direction increases. When the sliding resistance exceeds the threshold value Ft, sliding in the axial direction is suppressed. Here, when the sliding contact pin 29 is not inserted (dotted line), the sliding resistance when the transmission torque is T ₀ or less is F1, but when the sliding contact pin 29 is inserted ( (Solid line) Since the sliding resistance increases by that amount, the sliding resistance when the transmission torque becomes T ₀ or less becomes F2 larger than F1. Although this F2 is less than the threshold value Ft, it is closer to the threshold value Ft than F1, so that it is more difficult to slide, and sudden sliding is suppressed. T ₀ is a small value such that the transmission torque can be regarded as lost.

In the above embodiment, the male shaft 22 is connected to the upstream side of the steering system and the female shaft 21 is connected to the downstream side. However, the present invention is not limited to this, and the female shaft 21 is connected to the upstream side. You may connect and connect the male axis | shaft 22 downstream.
In the above embodiment, the leaf spring 25 is laid in the rolling groove 24 of the male shaft 22. However, the present invention is not limited to this, and the leaf spring 25 is laid in the rolling groove 23 of the female shaft 21. May be.

Moreover, in said embodiment, although the ball | bowl 26 is inserted in a pair of rolling grooves 23 and 24, it is not limited to this, You may insert a roller.
Moreover, in said embodiment, although the column-shaped sliding contact pin 29 was employ | adopted, it is not limited to this, A cylindrical body may be sufficient. In short, it is sufficient that a predetermined sliding resistance can be given to the pair of rolling grooves 23 and 24, and the shape is not limited.

In addition, when the sliding contact pin 29 is inserted as in the above embodiment, the rolling range of the ball 26 is narrowed. Therefore, as shown in FIG. A range may be secured.
In the above embodiment, the sliding contact pin 29 is inserted only at one end side along the axial direction. However, as shown in FIG. 8, the sliding contact pin 29 is inserted at both end sides along the axial direction. Alternatively, the sliding contact pin 29 may be inserted only on the other end side along the axial direction.

Next, a second embodiment of the present invention will be described.
In the second embodiment, as shown in FIG. 9, crowning 29 a having an outer diameter that decreases toward the end is formed on both ends of the sliding contact pin 29.
Thereby, when the female shaft 21 and the male shaft 22 slide in the axial direction, it is possible to avoid a situation in which the sliding contact pin 29 is caught and the sliding resistance increases unnecessarily.

  As in the application example described above, the number of balls 26 is reduced to secure the rolling range of the balls 26 as shown in FIG. 10, or both end sides along the axial direction are shown in FIG. Alternatively, the sliding contact pin 29 may be inserted.

It is a schematic block diagram of a steering mechanism. It is a longitudinal cross-sectional view of an intermediate shaft. It is AA sectional drawing of an intermediate shaft. It is a single item drawing of a leaf spring. It is a single item drawing of a roller. It is a graph which shows the relationship between transmission torque and sliding resistance. This is an application example in which the number of balls is reduced. This is an application example in which sliding contact pins are inserted at both ends. It is a single-piece figure of the sliding contact pin which shows 2nd Embodiment. This is an application example in which the number of balls is reduced. This is an application example in which sliding contact pins are inserted at both ends.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Steering wheel, 2 ... Steering shaft, 5 ... Intermediate shaft, 21 ... Female shaft, 22 ... Male shaft, 23 ... Rolling groove, 24 ... Rolling groove, 26 ... Ball, 27 ... Stopper, 29 ... Sliding contact pin

Claims (2)

A telescopic shaft comprising a cylindrical female shaft and a male shaft fitted inside the female shaft, and allowing expansion and contraction by allowing sliding only in both axial directions,
A pair of rolling grooves formed on the inner peripheral surface of the female shaft and the outer peripheral surface of the male shaft and facing each other in the axial direction, a rolling element interposed in the pair of rolling grooves, and the pair of rolling shafts A sliding contact member that is inserted into at least one of the one end side and the other end side along the axial direction of the moving groove and that gives a predetermined sliding resistance to the pair of rolling grooves. Telescopic shaft.   2. The telescopic shaft according to claim 1, wherein the sliding contact member is formed with a crowning having an outer diameter that decreases toward an end portion at both end sides along the axial direction.

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