JP6697804B2 - Steering shaft - Google Patents

Description

  The present invention relates to a steering shaft used as a constituent element of an electric power steering apparatus for vehicles such as automobiles.

An example of a steering shaft is shown in FIG. Note that steering shafts similar to this include those described in Patent Documents 1 and 2.
The steering shaft Se shown in FIG. 2 is a hollow pipe-shaped upper shaft 1 rotated by the operation of a steering wheel 7, a shaft end 9 fitted and fixed to a terminal end portion of the upper shaft 1, a lower shaft 2, a torsion bar 3. , And a rotation restriction unit Re.
The lower shaft 2 is a shaft whose lower end portion (on the left side in the drawing) is connected to a steering gear box via a universal joint, an intermediate shaft, and the like, and from the assist motor M for electric power steering to the worm 50 and the worm wheel 51. It is possible to receive the rotational driving force via the mechanism. One end 3a of the torsion bar 3 is fitted and fixedly connected to the shaft end 9, and the other end 3b is fixedly connected to the lower shaft 2 via a pin 39.
The rotation restricting portion Re is a portion where the lower shaft 2 and the shaft end 9 are fitted to each other and serrated. As shown in FIG. 2( b ), the rotation restricting portion Re has the outer peripheral surface of the lower shaft 2 and the inner peripheral surface of the shaft end 9 which are formed in a concavo-convex shape in which serration grooves 29 and 90 are formed to engage these. It has a different structure. However, the lower shaft 2 and the shaft end 9 are formed into serrations having an appropriate play in the circumferential direction so that the lower shaft 2 and the shaft end 9 can relatively rotate within a certain angle range.

  According to such a configuration, when the steering shaft Se is operated to rotate the upper shaft 1 and the shaft end 9, and the torsion bar 3 is twisted, the twist amount is calculated as follows. The relative rotation amount between the end 9 and the lower shaft 2 can be detected using the torque sensor 8. Drive control of the assist motor M can be performed based on this detected value.

  However, in the above-mentioned conventional technique, there is still room for improvement as described below.

  That is, in the above-mentioned prior art, the upper shaft 1 is formed into a hollow pipe shape in order to reduce the weight and cost, but such an upper shaft 1 has serrations as shown in FIG. 2B. Groove processing is difficult. For this reason, the shaft end 9 is connected to the upper shaft 1 and the serration grooves 90 and 29 are formed in the shaft end 9 and the lower shaft 2. However, if such a means is adopted, the total number of parts is increased due to the use of the shaft end 9, and the raw material cost, the processing cost, and the assembly cost are required, and the overall manufacturing cost is increased. Further, if the shaft end 9 is interposed between the upper and the lower shafts 1 and 2, the center shift amount between the upper and the lower shafts 1 and 2 is increased accordingly, and the coaxiality may be deteriorated. Get higher When the coaxiality deteriorates, the resistance at the time of rotating the steering wheel 7 increases, and the operability deteriorates.

JP, 2011-98659, A JP, 2016-88491, A

  The present invention was devised under the circumstances as described above, and it is possible to reduce the manufacturing cost by reducing the number of parts, and also to improve the steering operability. The challenge is to provide a shaft.

  In order to solve the above problems, the present invention takes the following technical means.

  A steering shaft provided by the present invention includes a hollow pipe-shaped upper shaft that is rotated by operating a steering wheel, and a lower shaft that is set so as to be able to receive rotational driving force from an assist motor for electric power steering. A torsion bar having both ends connected to the upper and the lower shaft in a non-rotatable state, and a rotation restricting unit for restricting relative rotation of the upper and the lower shaft over a predetermined angle are provided. A steering shaft, wherein the upper shaft has a first fitting portion in which a terminating end portion of the upper shaft has a non-cylindrical tubular shape, and the upper fitting portion is more than the first fitting portion. A second fitting portion, which is located near the tip of the shaft and into which one end of the torsion bar is fitted so as not to rotate relative to the shaft, is provided. A deformed portion having a shape is provided, and the rotation restricting portion is characterized in that the deformed portion is fitted into the first fitting portion with play.

With such a configuration, the following effects can be obtained.
That is, the rotation restricting portion that restricts the relative rotation of the upper shaft and the lower shaft is configured by fitting the deformed portion of the lower shaft into the non-cylindrical tubular first fitting portion of the upper shaft, and The shaft and the torsion bar are directly connected by inserting one end of the torsion bar into the second fitting portion of the upper shaft. Therefore, it is possible to eliminate the shaft end used in the conventional technique and reduce the number of parts. As a result, the overall manufacturing cost can be reduced. Further, if the shaft end is not required, the amount of center deviation between the upper and lower shafts can be correspondingly reduced, and the coaxiality thereof can be improved. Therefore, it is possible to appropriately prevent or suppress the problem that the resistance when the steering wheel is rotated is increased due to the deterioration of the coaxiality.

  Other features and advantages of the present invention will become more apparent from the following description of the embodiments of the invention with reference to the accompanying drawings.

(A) is an important section sectional view showing an example of a steering shaft concerning the present invention, and (b) is an I-I important section sectional view of (a). (A) is a principal part sectional view which shows an example of a prior art, (b) is a II-II principal part sectional view of (a).

Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings.
Note that, for ease of understanding, in the following description, the same or similar elements as those of the conventional technique shown in FIG.

  The steering shaft S shown in FIG. 1 is for an electric power steering device, and includes an upper shaft 1, a lower shaft 2, a torsion bar 3, and a rotation restricting portion R. Further, as components attached to these, a steering column 4, an upper bracket 5a for attaching the upper end side of the steering column 4 to the vehicle body, and first and second units in which the lower end of the steering column 4 is connected. Housings 6a, 6b, and lower brackets 5b for mounting the first and second housings 6a, 6b on the vehicle body.

  The upper shaft 1 is a hollow pipe having a steering wheel 7 attached to its tip (upper end) and rotated by the operation of the steering wheel 7. The upper shaft 1 is inserted into the steering column 4 and rotatably supported. There is. The upper shaft 1 is formed by pressing a cylindrical metal pipe, for example. First and second fitting portions 11 and 12 for directly fitting the lower shaft 2 and the torsion bar 3 are provided at a terminal end portion (lower end portion) of the upper shaft 1 and a region in the vicinity thereof. However, the details will be described later.

  The torsion bar 3 is inserted into a through hole in the axial direction of the lower shaft 2, and one end portion 3 a of the torsion bar 3 is fitted into the second fitting portion 12 of the upper shaft 1 so as not to rotate relative to the second fitting portion 12. ing. More specifically, the second fitting portion 12 is a portion in which a small-diameter cylindrical portion is partially formed in the upper shaft 1, and the one end portion 3a of the torsion bar 3 cannot rotate in this portion. Has been pressed into. As a means for accurately performing this press-fitting, a means may be employed in which the inner peripheral surface of the second fitting portion 12 is machined (cut) to improve the dimensional accuracy of the inner diameter. Further, as a means for connecting the torsion bar 3 and the upper shaft 1 in a relatively non-rotatable manner, unlike the present embodiment, one end portion 3a of the torsion bar 3 has a non-circular cross section and a second fitting. The portion 12 may have a shape (non-cylindrical tubular shape) corresponding thereto and a means for fitting them may be adopted. The other end 3b of the torsion bar 3 is fixed to the lower shaft 2 using a pin 39 so as not to rotate relative to the lower shaft 2. As a result, the torsion bar 3 is twisted due to the relative rotation between the upper shaft 1 and the lower shaft 2.

  In the present embodiment, as a means for supporting the upper shaft 1 in the steering column 4, a bearing 40a is provided near the upper end of the steering column 4, but at a location near the lower end of the steering column 4. , Bearings are not provided. That is, although two bearings 40a and 40b are used in FIG. 2, one bearing 40b is not used in the present embodiment.

  The lower shaft 2 is rotatably held in the first and second housings 6a and 6b via bearings 68a and 68b, and receives the driving force of the assist motor M via the worm 50 and the worm wheel 51. It is provided. An intermediate shaft (not shown) is connected to the lower end side of the lower shaft 2 via a universal joint 55, and the rotation of the lower shaft 2 is transmitted to a steering gear box (not shown) via the intermediate shaft. ..

The rotation restricting portion R is a portion where the first fitting portion 11 formed at the terminal end portion of the upper shaft 1 and the deformed portion 20 provided on the lower shaft 2 are fitted to each other. The reference numeral 2 is a part that restricts relative rotation only within a predetermined angle range and prevents further relative rotation. As shown in FIG. 1B, the first fitting portion 11 of the upper shaft 1 is a non-cylindrical tubular portion, for example, a rectangular tubular portion. On the other hand, the deformed portion 20 of the lower shaft 2 is a portion whose outer peripheral contour is non-circular in cross section, and is, for example, substantially rectangular in cross section (strictly speaking, a hole through which the torsion bar 3 is inserted is formed inside). It has a cylindrical shape). The deformed portion 20 is fitted into the first fitting portion 11 with an appropriate play (gap C). Deformed part 2
When the corner portion of 0 comes into contact with the inner surface of the first fitting portion 11, further relative rotation is prevented. This appropriately prevents the twist amount of the torsion bar 3 from exceeding a predetermined amount. Further, even if the assist motor M is not driven, it is possible to appropriately rotate the lower shaft 2 along with the rotation of the upper shaft 1.

  A torque sensor 8 is arranged in the second housing 6b, and the torque sensor 8 is configured to detect the relative rotation angle of the upper shaft and the lower shafts 1 and 2 as the twist amount of the torsion bar 3. ing. Based on this detection data, the drive control of the assist motor M is performed so as to minimize the twist amount of the torsion bar 3.

  Next, the operation of the steering shaft S having the above configuration will be described.

  First, as a means for connecting the upper shaft 1 and the torsion bar 3 together with the rotation restricting portion R that restricts the relative rotation of the upper and lower shafts 1 and 2, the shaft end of the prior art shown in FIG. 9 is not used. Therefore, it is possible to reduce the number of members constituting the steering shaft S and reduce the manufacturing cost of the steering shaft S. The first fitting portion 11 of the upper shaft 1 has, for example, a rectangular tubular shape, and such a portion can be manufactured at a low cost and size by press-working the end portion of the hollow pipe-shaped upper shaft 1. It can be formed with high precision. Further, the deformed portion 20 of the lower shaft 2 only needs to be processed so that the contour of the outer circumference is, for example, a rectangular shape in cross section. It's easy. As described above, the rotation restricting portion R in the present embodiment can be manufactured easily and inexpensively, and is excellent in productivity.

  Although the upper shaft 1 and the torsion bar 3 are directly fitted to each other, according to such a configuration, the coaxiality between the upper shaft 1 and the torsion bar 3, and hence the coaxiality between them and the lower shaft 2 are also increased. It is possible. Therefore, due to the poor coaxiality of the above-mentioned members, the resistance at the time of rotating the steering wheel 7 is not increased, and the smoothness of the steering operation or the operation feeling is not impaired. In the present embodiment, as described above, the bearing corresponding to the bearing 40b shown in FIG. 2 is omitted to further reduce the cost. However, due to the omission of the bearing 40b, for example, the upper shaft 1 It is also possible to prevent the fitting portion between the and torsion bar 3 from causing a problem such as a large swing during rotation.

  The present invention is not limited to the contents of the above-mentioned embodiment. The specific configuration of each part of the steering shaft according to the present invention can be modified in various ways within the scope intended by the present invention.

The first fitting portion 11 of the upper shaft 1 may be a non-cylindrical tubular shape, and is not limited to a rectangular tubular shape. For example, various shapes such as an elliptical or elliptic cylindrical shape or a polygonal cylindrical shape can be used. Similarly, the specific cross-sectional shape of the deformed portion 20 of the lower shaft 2 may be any shape as long as the contour of the outer circumference is non-circular in cross section. The point is that the non-cylindrical first fitting portion 11 of the upper shaft 1 is fitted with the deformed portion 20 of the lower shaft 2 with play, so that the upper and lower shafts 1, 2 exceed a predetermined angle. It suffices that the rotation restricting portion R capable of restricting relative rotation be configured.
As described above, the fitting of the one end 3a of the torsion bar 3 into the second fitting portion 12 of the upper shaft 1 is not limited to press fitting, and they are fitted in a state in which they cannot rotate relative to each other. Just do it.
The upper shaft 1 has a double-tube structure for shock absorption, that is, a structure in which two pipe materials forming the upper shaft slide to exhibit a shock absorbing effect when a thrust load of a predetermined value or more is input. You can also do it.

R Rotation restriction part S Steering shaft 1 Upper shaft 11 First fitting part 12 Second fitting part 2 Lower shaft 20 Deformed part 3 Torsion bar

Claims (1)

A hollow pipe-shaped upper shaft that is rotated by operating the steering wheel,
A lower shaft that is set so as to be able to receive rotational driving force from an assist motor for electric power steering,
A torsion bar having both ends connected to the upper and lower shafts such that they cannot rotate relative to each other;
A rotation restricting portion that restricts relative rotation of the upper and lower shafts beyond a predetermined angle,
A steering shaft comprising:
The upper shaft has a first fitting portion in which the end portion of the upper shaft has a non-cylindrical tubular shape, and is located closer to the tip end portion of the upper shaft than the first fitting portion. And a second fitting portion into which one end portion of the torsion bar is fitted so as not to rotate relatively, is provided,
The lower shaft is provided with a deformed portion whose outer peripheral contour is non-circular in cross section,
A steering shaft, wherein the rotation restricting portion is configured such that the deformed portion is fitted into the first fitting portion with play.

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