JP2012081789A - Steering shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steering shaft that makes a male spline directly spline-engaged with female splines without using a different member.SOLUTION: In the steering shaft which is constituted of an inner shaft 1 and an outer shaft 2, inserts the inner shaft 1 into the outer shaft 2, and makes them spline-engaged with each other, the outer shaft 2 has, at its inner peripheral surface, the end-opening side female spline 22 continuous to the extending direction of a pipe body 21 and the pipe-body center side female spline 23 in a range not longer than the extension length of the male spline 12 which is continuous to the extending direction of a shaft body 11 and formed at the outer peripheral surface of the inner shaft 1.

Description

  The present invention relates to a steering shaft having an expansion / contraction function (telescopic function).

  A steering shaft having a telescopic function (hereinafter simply referred to as a steering shaft) includes an inner shaft in which male splines made of a plurality of protrusions extending in the extending direction of the shaft body are formed on the outer peripheral surface, and a plurality of extending in the extending direction of the tubular body. The female spline is formed of an outer shaft formed on the inner peripheral surface, and the inner shaft is inserted into the outer shaft to fit the male spline and the female spline to the spline. As a result, the steering shaft changes the insertion amount of the inner shaft relative to the outer shaft to realize an expansion / contraction function, while rotating the outer shaft and the inner shaft integrally by spline fitting to transmit the rotation operation of the steering wheel to the steering wheel. Let

  At this time, if the clearance between the male spline and the female spline is large, the inner shaft rattles with respect to the outer shaft, and the steering feeling is deteriorated or abnormal noise is generated during steering. Moreover, in order to ensure rigidity in spline fitting, the amount of fitting between the male spline and the female spline is required to be more than a certain level, but when the clearance between the male spline and the female spline is reduced, either the outer shaft or the inner shaft is A slight bend makes spline fitting impossible.

  From this, it is considered difficult to directly fit both the male spline and the female spline in the steering shaft, and while the clearance between the male spline and the female spline is reduced to a certain extent, a resin member or A resin layer is interposed (Patent Document 1) or a spring member (Patent Document 2) is interposed. In addition, unlike spline fitting, there is also a steering shaft in which a pair of recesses corresponding to the outer peripheral surface of the inner shaft and the inner peripheral surface of the outer shaft are formed, and a bearing member is interposed between both recesses ( Patent Document 3).

  In the steering shaft disclosed in Patent Document 1, a resin member is externally fitted to a male spline (outer peripheral engagement portion), the inner shaft is once inserted into the outer shaft, and the outer shaft is heated to soften the resin member. A female spline (inner peripheral engagement portion) is transferred to the outer peripheral surface of the member (Patent Literature 1, [Claim 1] and [Claim 2]). Also in the case of injecting the resin material, by heating the outer shaft, the injected resin material is kept in a molten state and diffused to form a resin layer to which the female spline is transferred. With such a resin member or resin layer, both are engaged with moderate tightness without leaving a gap between the male spline and the female spline.

  The steering shaft disclosed in Patent Document 2 is between the inner shaft (inner shaft) and the outer shaft (outer shaft) within a range where the male spline (inner spline) and female spline (outer spline) do not fit together. Outer shaft caused by clearance of male spline and female spline with spring ring pressed against inner surface (inner surface) of outer shaft and outer surface (outer surface) of inner shaft. The backlash of the inner shaft with respect to the inner surface is suppressed (Patent Documents [Claim 2] and [Claim 3]). The spring ring is a metal ring having a split extending in the axial direction of the steering shaft. The ridges (dents) along the cracks are formed on the inner peripheral surface of the outer shaft, and the ridges (dents) along the cracks are also formed on the inner shaft. The outer peripheral surface is pressed (Patent Document [0030]).

  In the steering shaft disclosed in Patent Document 3, a pair of axial grooves are formed on the outer peripheral surface of the inner shaft (male shaft) and the inner peripheral surface of the outer shaft (female shaft), and the above-described steering shaft is interposed through the elastic body for preload. A rolling element is interposed between the axial grooves, and a sliding element is interposed between the axial grooves (Patent Document [Claim 1]). The rolling element is spherical (Patent Document, [Claim 3]). Further, the sliding body is a needle roller (Patent Document, [Claim 4]). The elastic body is a leaf spring (Patent Document, [Claim 5]). Since the steering shaft disclosed in Patent Document 3 transmits excessive torque between the inner shaft and the outer shaft via the sliding body, the rolling element adheres indentations to the axial grooves, and the sliding performance of the rolling element deteriorates. (Patent Documents [0022] [0023]).

JP 2002-321627 A JP 2003-139157 A JP 2003-336658 A

  The steering shaft disclosed in Patent Document 1 is excellent in that the male spline and the female spline can be engaged with each other with moderate tightness without leaving a gap because the female spline is transferred to the molten resin member or resin material. Yes. However, since either the resin member or the resin material expands or contracts due to a change in temperature or humidity, it cannot be denied that the tight engagement state is lost due to deterioration over time. In addition to the inner shaft and outer shaft, a separate resin member is required, and even when a resin material is injected, a heating process is necessary. There is also.

  In the steering shaft disclosed in Patent Document 2, since the spring ring is a metal ring, unlike the resin member or resin layer in the steering shaft disclosed in Patent Document 1, there is no fear of deterioration over time. However, in order to press the ridges on the inner peripheral surface of the outer shaft and the concave ridges on the outer peripheral surface of the inner shaft to an extent that suppresses rattling of the inner shaft with respect to the outer shaft, Sliding is difficult to smooth. Further, when a large torque is applied such that the spring ring itself is greatly bent, the inner shaft may rattle against the outer shaft. As described above, a separate spring ring is required, and there is a problem that an increase in material cost and processing cost (assembly cost) cannot be avoided.

  The steering shaft disclosed in Patent Document 3 suppresses rattling of the inner shaft relative to the outer shaft by pressing a rolling element against the axial groove of the outer shaft by a preloading elastic body in a pair of axial grooves. . Since the rolling element is spherical, sliding of the inner shaft relative to the outer shaft is less likely to be inhibited compared to the inner shaft disclosed in Patent Document 2. However, it is difficult to form the outer shaft and the inner shaft, and many separate members such as a rolling element, an elastic body, and a sliding body are required. In addition to the above-mentioned Patent Document 1 or Patent Document 2, material cost, processing cost (assembly cost) ) Is inevitable.

  In this way, in order to suppress the shakiness of the inner shaft relative to the outer shaft, it is only necessary to intervene some other member between them, but in addition to the problems that occur, a problem that causes a cost increase above all. There is. In this regard, cost reduction can be solved by simply spline fitting a male spline and a female spline. Therefore, the male spline and female spline are directly spline-fitted without using a separate member so that the inner shaft does not rattle against the outer shaft, and either the outer shaft or the inner shaft is slightly bent. In order to develop a steering shaft that can be spline-fitted, it was studied.

  The result of the study was the development of an inner shaft formed with a male spline consisting of a large number of ridges extending in the direction of extension of the shaft on the outer peripheral surface, and a female spline consisting of a large number of recesses extending in the direction of extension of the tube. In the steering shaft that inserts the inner shaft into the outer shaft and fits the male spline and female spline to the spline, the outer shaft is continuous in the extending direction of the shaft body. The steering shaft is characterized in that two female splines that are intermittent in the tube extending direction are provided on the inner peripheral surface within a range shorter than the extending length of the male spline formed on the outer peripheral surface of the inner shaft. .

  The steering shaft of the present invention has two locations on the inner peripheral surface of the outer shaft intermittently in the tube extending direction with respect to the male spline formed on the outer peripheral surface of the inner shaft continuously in the shaft extending direction. A female spline formed separately is directly fitted to the spline. The two female splines are "intermittent in the tube extension direction within a range shorter than the extension length of the male spline" means that each female spline has a concave line aligned in the circumferential direction of the tube, and It means that the distance between the starting end and the end of the groove on the far side is shorter than the extending length of the male spline, and the extending length of each female spline is the distance between the starting end and the end of the groove. Can be much shorter than the distance. From this, the fitting length of the female spline and the male spline of the present invention is compared with the fitting length of the conventional female spline and male spline which are continuous in the tube extending direction within the range including two female splines. Naturally, even if the clearance between the male spline and the female spline is made small, the spline cannot be fitted due to the bending of the inner shaft. Further, the spline fitting at two distant points improves the bending rigidity of the inner shaft that is the shaft body.

  The inner shaft forms a male spline on the outer peripheral surface of the shaft body by cutting, rolling, or pressing. As with the male spline, the outer shaft forms a female spline on the inner peripheral surface of the tube body by a swaging process in addition to a cutting process or a press process. However, it is difficult to form a female spline by cutting or pressing on the inner peripheral surface of a continuous tubular body having the same diameter in the extending direction of the tubular body. Therefore, it is preferable to form a female spline on the inner peripheral surface of the concave annular portion narrowed inward in the radial direction by swaging for the outer shaft that is a tube having an inner diameter larger than the outer diameter of the inner shaft. “Radial inward” means radial inward in the cross section of the tube.

  Since the outer shaft is a tubular body having an inner diameter larger than the outer diameter of the inner shaft, the bending rigidity is improved as compared with a conventional outer shaft that is slightly larger than the inner shaft. In addition, the outer shaft is complicated in cross-section because the concave annular portion narrowed down by swaging is intermittently formed in the extending direction of the tube, and the cross-sectional shape becomes complicated. This also improves the bending rigidity. ing. Thus, the outer shaft that forms the female spline on the inner peripheral surface of the concave annular portion that is narrowed inward in the radial direction by the swaging process improves its own bending rigidity, thereby improving the bending rigidity as the steering shaft.

  When forming the female spline on the inner peripheral surface of the concave annular portion obtained by swaging the outer shaft that is a tubular body, it is conceivable to cut the inner peripheral surface, but preferably the male spline is formed on the outer peripheral surface. In a state where a spline forming jig provided with a ridge corresponding to the inner shaft formed in is inserted into the pipe body, each of two portions forming the female spline is squeezed by swaging to form a concave annular portion, A female spline is formed by pressing the inner peripheral surface of each concave annular portion against the spline forming jig. In this case, since the continuous ridges of the spline forming jig are transferred to form the female splines, the concave lines constituting the female splines are aligned in the circumferential direction of the pipe body. That is, the two female splines have a shape in which the middle of the female splines that are continuous in the extending direction of the tubular body is cut out in a range including each.

  A portion sandwiched between the two concave annular portions constitutes a hollow portion having an annular cross section surrounded by the concave annular portion, the outer peripheral surface of the inner shaft, and the inner peripheral surface of the outer shaft. In the steering shaft of the present invention, the clearance between the male spline and the female spline is only required to be directly fitted to the spline, and therefore the space portion may be left as it is. However, since the hollow portion becomes a closed space as the clearance between the male spline and the female spline is smaller, for example, grease supplied to the male spline and the female spline can be stored. In addition, a rubber pipe or a resin pipe may be externally fitted to the inner shaft so as to suppress the shakiness of the inner shaft with respect to the outer shaft due to aging deterioration.

  When forming a female spline on the inner peripheral surface of the swept concave annular part, the outer shaft is positioned at a position slightly away from the end opening by swaging the female spline near the end opening into which the inner shaft is inserted. Formed on the inner peripheral surface of the concave annular portion that is narrowed inward in the radius, and gradually expands from the female spline near the end opening toward the end opening, that is, the insertion that spreads in a “trumpet shape” It is good to provide a part. Thereby, it becomes easy to insert the inner shaft into the outer shaft.

  Since the steering shaft of the present invention has a short fitting length between the male spline and the female spline, the clearance between the male spline and the female spline is reduced to prevent the inner shaft from rattling with respect to the outer shaft and to facilitate the spline fitting. In addition, the inner shaft can be smoothly inserted into and removed from the outer shaft. Further, since the fitting length of the male spline and the female spline is short, the influence of the aging deterioration of the male spline and the female spline can be reduced, and the spline fitting without rattling can be maintained for a long time.

  The shakiness of the inner shaft with respect to the outer shaft, when using an outer shaft formed with a concave annular portion swaged to form a female spline, allows grease to be stored in a cavity sandwiched between the concave annular portions, Further suppression can be achieved by externally fitting a rubber pipe or a resin pipe to the inner shaft at the hollow portion. The rubber pipe or resin pipe does not engage the inner shaft and outer shaft in the direction of rotation, but serves as a buffering member interposed between the two, and serves to suppress rattling of the inner shaft relative to the outer shaft. To do.

  Since the male spline and the female spline are spline-fitted at two points separated from the female spline, the bending rigidity of the inner shaft that is supported at two points on the outer shaft via the female spline is improved. And the outer shaft which formed the female spline in the inner peripheral surface of the swallowed concave annular part has a complicated cross-sectional shape in which the inner diameter of the tube body is large and the separated concave annular part is constricted in two places. And improve the bending rigidity. Thus, the steering shaft of the present invention generally improves the bending rigidity.

  The steering shaft of the present invention provides cost reduction. Specifically, by eliminating the need for a separate member (resin material or resin layer or bearing member) that engages the inner shaft and outer shaft in the rotation direction, material costs and processing costs are reduced. In addition, the short female spline is easy to mold and correct, and the processing time is short, so that the processing cost is reduced as a whole. Furthermore, the short female spline leads to the suppression of the wear of the spline forming jig, and has the effect of extending the life of the spline forming jig. In addition, if a trumpet-shaped insertion introducing portion is provided on the outer shaft, it becomes easier to insert the inner shaft into the outer shaft, and chamfering is not required at the end of the inner shaft, which contributes to cost reduction.

It is a perspective view of an example of a steering shaft to which the present invention is applied. It is a partially broken perspective view of the steering shaft of this example. It is an extension direction sectional view of the steering shaft of this example. It is the front view of the steering shaft of this example seen from the edge part opening side of an outer shaft. FIG. 4 is a cross-sectional view in the extending direction corresponding to FIG. 3 illustrating swaging of the outer shaft of this example. FIG. 4 is a cross-sectional view in the extending direction corresponding to FIG. 3 of another example of a steering shaft to which the present invention is applied.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the present invention, as shown in FIGS. 1 to 4, the inner shaft 1 is inserted into the outer shaft 2, and the male spline 12, the female spline 22 near the end opening, and the female spline 23 near the tube center are spline-fitted. Applied to steering shaft. The steering shaft of this example has a trumpet-shaped insertion introducing portion 25 that gradually expands toward the end opening, and the tubular body 21 constituting the outer shaft 2 extends in the extending direction of the tubular body 21. The appearance is characterized by providing a pair of spaced apart concave annular portions 222,232.

  The inner shaft 1 has a configuration similar to the conventional one, and a male spline 12 including a large number of ridges 121 extending continuously in the extending direction of a metal shaft 11 extending with a constant outer diameter is provided on the outer periphery of the shaft 11. Formed on the surface. This means that the conventional structure of the steering shaft of the present invention can be used as it is with respect to the inner shaft 1. From this, the inner shaft 1 can be manufactured with a conventional manufacturing apparatus and manufacturing method (cutting, rolling, or pressing), and an increase in manufacturing cost due to the use of the present invention is suppressed. The extension length of the male spline 12 is appropriately determined according to the required expansion / contraction function.

  The outer shaft 2 is a metal tube body 21 extending with an inner diameter larger than the outer diameter of the shaft body 11 constituting the inner shaft 1 within a range shorter than the extending length of the male spline 12 formed on the outer peripheral surface of the inner shaft 1. The two ends of the female spline 22 near the end opening and the female spline 23 near the center of the tube are formed by squeezing the tube 21 radially inward by swaging. The concave annular portions 222 and 232 are provided on the inner peripheral surface. For this reason, as described above, the outer shaft 2 has an external appearance having the trumpet-shaped insertion introducing portion 25 and the pair of concave annular portions 222, 232, and the female spline 22 near the end opening and the female spline 23 near the tube center. A cavity 24 is formed therebetween.

  The steering shaft of the present invention is intermittently connected in the extending direction of the tube 21 to the male spline 12 formed on the outer peripheral surface of the inner shaft 1 continuously in the extending direction of the shaft body 11. A female spline 22 near the end opening and a female spline 23 near the center of the tubular body, which are formed separately at two locations on the peripheral surface, are directly spline-fitted. In this example, the hollow portion 24 having an annular cross section surrounded by the two concave annular portions 222 and 232, the outer peripheral surface of the inner shaft 1 and the inner peripheral surface of the outer shaft 2 is hollow. The backlash of the inner shaft 1 with respect to the outer shaft 2 may be suppressed by storing or by externally fitting a rubber pipe or a resin pipe to the inner shaft 1.

  Here, for example, if the male spline 12 is made unequal with respect to the female spline 22 near the end opening and the female spline 23 near the center of the tube, the ridge 121 and the female spline 22 near the end opening that constitute the male spline 12 are used. Alternatively, even if the forming accuracy of the concave strips 221 and 231 constituting the female spline 23 near the center of the pipe body varies, close spline fitting between the two can be achieved. One or both of the female spline 22 near the end opening and the female spline 23 near the center of the tube relative to the male spline 12 may be unequal. Providing unequal teeth in this way means that the clearance between the male spline 12 and the female spline 22 near the end opening and the female spline 23 near the tube center is managed by the difference in clearance between the unequal tooth and the others. Have

  The male spline 12, the end opening-side female spline 22 and the tubular body-centered female spline 23 engage the convex strip 121 and the concave strips 221 and 231 on the side surfaces so that the ceiling surface and the bottom surface do not contact each other (see FIG. 4). ). From this, the clearance between the male spline 12 and the female spline 22 near the end opening or the female spline 23 near the center of the tube is adjusted at the position of the side surface where the convex 121 and the concave 221 and 231 are engaged. For example, when making the male spline 12 unequal, increase the circumferential width of some of the ridges 121, and conversely make the female spline 22 near the end opening or the female spline 23 near the tube center unequal. In this case, the circumferential width of some of the concave strips 221 and 231 is reduced. The difference between unequal teeth and other teeth should be managed around 10μm as a guide.

  As shown in FIG. 3, the steering shaft of the present invention has a distance D between the start and end of the recesses 221 and 231 on the far side of the female spline 22 near the end opening and the female spline 23 near the center of the tube. The extension length Lf1 of the female spline 22 near the end opening and the extension length Lf2 of the female spline 23 near the center of the tube are the distance D between the starting end and the terminal end of the recesses 221 and 231. Much shorter. Thereby, even if the clearance between the male spline 12 and the female spline 22 near the end opening or the female spline 23 near the center of the tube is made small, the spline cannot be fitted due to the influence of the bending of the inner shaft 1. Further, the spline fitting at two distant points improves the bending rigidity of the inner shaft 1 that is the shaft body 11.

  The female spline 22 near the end opening and the female spline 23 near the center of the tube body, as described above, with respect to the outer shaft 2 which is the tube body 21 (see the broken line in FIG. 5) having an inner diameter larger than the outer diameter of the inner shaft 1. The tube body 21 is provided on the inner peripheral surfaces of the concave annular portions 222, 232, which are squeezed radially inward by swaging. The swaging process is also used to form a tapered overall shape found in the steering shaft of this example. Such swaging is also used to form conventional female splines. As will be understood, conventional outer shaft manufacturing equipment using swaging can be used as it is for manufacturing the outer shaft 2 of the present invention.

  The concave annular portions 222 and 232 are formed by swaging as follows. For example, the spline forming jig 3 provided with the ridges 31 corresponding to the inner shaft 1 having the male spline 12 formed on the outer peripheral surface is coaxially positioned with the tube body 21 before the swaging process in which the position is fixed and the horizontal posture is set. To insert from the horizontal direction (horizontal direction). As shown in FIG. 5, four molding dies (inward in the radial direction at equal intervals in the circumferential direction) are formed at two portions forming the female spline 22 near the end opening and the female spline 23 near the tube center. The molding die is swung around the axis of the tube body 21 while abutting a not-shown (represented by a white arrow). Thereby, each of the two portions is recessed inward in the radial direction, and the concave annular portions 222 and 232 start to be formed, and the inner peripheral surfaces of the concave annular portions 222 and 232 are pressed against the spline forming jig 3, A female spline 22 near the end opening and a female spline 23 near the center of the tube are provided on the inner peripheral surface.

  As the spline forming jig 3, a configuration used for forming a conventional female spline (a female spline extending continuously in the extending direction of the tube body 21) can be used as it is. In this case, a part of the continuous ridge 31 of the spline forming jig 3 is transferred to form the ridges 221 and 231 of the female spline 22 near the end opening and the female spline 23 near the center of the tube. Are aligned in the circumferential direction of the tubular body 21. That is, the female spline 22 near the end opening and the female spline 23 near the center of the tube are cut out in the middle of the female spline continuous in the tube extending direction within the range including each, for example, the female spline near the end opening. The unequal teeth provided on the recesses 221 and 231 of the female spline 23 near the center of the tube 22 and the tube body can be formed at the same position and size.

  Since the outer shaft 2 is a tubular body 21 having an inner diameter larger than the outer diameter of the inner shaft 1, the bending rigidity is improved as compared with a conventional outer shaft that is larger than the inner shaft 1 by a thickness corresponding to the plate thickness. Further, the outer shaft 2 is formed by intermittently forming the concave annular portions 222 and 232 that are narrowed by the swaging process in the extending direction of the tube body 21, so that the cross-sectional shape becomes complicated, and this also improves the bending rigidity. ing. In this way, the outer shaft 2 that forms the female spline 22 near the end opening and the female spline 23 near the center of the tubular body on the inner peripheral surface of the concave annular portions 222 and 232 that are squeezed radially inward by swaging processing improves its bending rigidity. Therefore, the bending rigidity as a steering shaft is also improved.

  In the outer shaft 2 of this example, a female spline 22 near the end opening into which the inner shaft 1 is inserted is formed at a position slightly away from the end opening, and gradually extends from the female spline 22 near the end opening toward the end opening. A trumpet-shaped insertion introduction part 25 is provided that expands strangely. The insertion introduction part 25 makes it easy to insert the inner shaft 1 into the outer shaft 2. Further, the outer shaft 2 is provided with a trumpet-shaped insertion introducing portion 25, thereby making the cross-sectional shape more complicated, and this also improves the bending rigidity. From this, when there is no problem even if the end opening of the outer shaft 2 spreads in a trumpet shape, such as there is no interference with the assembly target and surrounding structure, the structure as in this example is preferable.

  On the other hand, when there is a problem that the end opening of the outer shaft 2 spreads in a trumpet shape, such as interfering with the assembly target or the surrounding structure, as shown in FIG. 6, in the range including the end opening. A female spline 22 near the end opening may be formed. In this case, it is not possible to improve the ease of inserting the inner shaft 1 into the outer shaft 2 or the bending rigidity by the insertion introducing portion 25 (see FIGS. 1 to 3), but the improvement of the bending rigidity by the concave annular portions 222 and 232 is exemplified above. (See FIGS. 1 to 3). Further, the distance D between the start and end of the recesses 221, 231 is shorter than the extension length Lm of the male spline, the extension length Lf1 of the female spline 22 near the end opening, and the extension length of the female spline 23 near the center of the tube If the length Lf2 is much shorter than the distance D between the start and end of the concave 221 and 231, the effect of the present invention can be enjoyed.

1 Inner shaft
11 Shaft
12 Male spline 2 Outer shaft
21 tube
22 Female spline near end opening
23 Center female spline
24 Cavity
25 Inserting section 3 Spline forming jig
31 ridges

Claims (3)

An inner shaft in which male splines consisting of a large number of ridges extending in the extending direction of the shaft body are formed on the outer peripheral surface and an outer shaft in which female splines consisting of a number of concave stripes extending in the extending direction of the tube are formed on the inner peripheral surface In a steering shaft that is composed of a shaft, inserts the inner shaft into the outer shaft, and fits the male spline and female spline to the spline,
The outer shaft has two inner female splines that are intermittently connected in the tube extension direction within the range shorter than the extension length of the male spline formed on the outer peripheral surface of the inner shaft continuously in the shaft extension direction. A steering shaft characterized by being provided on the surface. The steering shaft according to claim 1, wherein the outer shaft is a tubular body having an inner diameter larger than the outer diameter of the inner shaft, and a female spline is formed on an inner peripheral surface of a concave annular portion that is squeezed radially inward by swaging. The outer shaft is formed with a female spline near the end opening into which the inner shaft is inserted on the inner peripheral surface of the concave annular portion narrowed radially inward at a position slightly away from the end opening by swaging. The described steering shaft.

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