Patent Application
20060045612
1. Field of the Invention
A joint section between a shaft and a universal joint yoke according to the present invention is used for example in a steering apparatus, for connecting the ends of a variety of shafts constituting the steering apparatus to a universal joint yoke.
2. Description of the Related Art
In order to apply a steering angle to the front wheels of a motor vehicle, a steering apparatus transmits movement of a steering shaft rotating in association with operation of a steering wheel, to a steering gear input shaft via a cross-shaft type universal joint 1 as shown in
When assembling a steering apparatus employing such a universal joint 1, for example, one yoke 2 (on the right in
Therefore, of the yokes 2 and 3 of the universal joint 1 constituting the steering apparatus, it is desirable that at least the other yoke 3 is of a so-called “side-insertion-type (slap type)” which can be connected without moving the shaft 6 in the axial direction, as described for example in Patent Document 1 (U.S. Pat. No. 5,358,350). For example, with the universal joint 1 shown in
The base end portion 8 of this side-insertion-type yoke 3 comprises a pair of clamping plates 9a and 9b. Mutually parallel clamping surfaces 10 are disposed on the inside surfaces of these mutually separated clamping plates 9a and 9b. A nut 11 is inserted and fixed into the opening side end portion of one clamping plate 9a (on the left in
On the other hand, at least the tip end portion of the shaft 7 joined to the yoke 3 constructed as described above is of oval cross-section as shown in
When the end portion of the shaft 7 having the aforementioned shape is connected and fixed to the base end portion 8 of the yoke 3, at first, as shown by the solid line in
As described above, if the end portion of the shaft 7 is inserted in the base end portion 8 of the yoke 3, and the clamping surfaces 10 and the outside flat surfaces 14 (
Moreover, clearances 16 can be provided between the clamping surfaces 10 and the outside flat surfaces 14 as shown in
In such a structure, when the clamping bolt is tightened in the threaded hole 12, and the clamping surfaces 10 are brought into contact with the outside flat surfaces 14, the clamping surfaces 10 and the outside flat surfaces 14 are in contact at the opening side of the base end portion 8 (top of
That is to say, when the clamping bolt is tightened in the threaded hole 12, the clamping plates 9a and 9b approach each other from the opening side of the base end portion 8. Thus the clamping surfaces 10 and the outside flat surfaces 14 first come into contact at this opening side portion. This opening side portion comes into contact, however, since each clamping surface 10 and outside flat surface 14 do not approach each other any further at the connecting portion 17 side, a clearance develops at this part. With the clamping bolt tightened in this manner, clearances exist between clamping surfaces 10 and outside flat surfaces 14 on the connecting portion 17 side, and application of a large twisting torque to the shaft 7 may result in movement of the shaft 7 within the clearances, and play may develop. Such play in the shaft 7 presents the driver with an unnatural feeling when using the steering wheel, and is therefore not desirable.
Moreover, with the structure described in Patent Document 2, as shown in
On the other hand, in Patent Document 5 (JP Patent Application Publication No. H09-291910), a structure is described in which the angle formed between the clamping surfaces of the pair of clamping plates and the outside flat surfaces of the shaft is between 1° and 2° prior to tightening the clamping bolt. That is to say, by inclining both clamping surfaces so that the space between the clamping surfaces increases towards the opening side of the base end portion where there is the through-hole and the threaded hole through which the clamping bolt is inserted and screwed into respectively, the angle formed by each clamping surface and the outside flat surfaces is between 1° and 2°. With this configuration, each clamping surface and outside flat surface is readily brought into contact at the opening side of the base end portion and at the connecting portion, with the clamping bolt tightened. That is to say, the space between the clamping surfaces is gradually reduced as the bolt is tightened, and the clamping surfaces become parallel with each other, with the clamping surfaces and outside flat surfaces being in contact. Thus, each clamping surface and outside flat surface, not only at the opening side portion, but also at the connecting portion being the part on the opposite side to the opening side portion, are readily brought into contact.
However, even with the structure described in Patent Document 5, when the clearance between each clamping surface and each outside flat surface is large prior to tightening the clamping bolt, the same problems may occur as with the structure shown in
The joint section between a shaft and a universal joint yoke of the present invention takes the foregoing into consideration, and has been invented in order to realize a structure in which the occurrence of play, even when a large twisting torque is applied to the shaft, is prevented by bringing the clamping surfaces of the pair of clamping plates and the outside flat surfaces of the shaft into contact at the opening side and the connecting portion side of the base end portion, with the clamping bolt tightened, irrespective of the size of the clearances between these surfaces, and the plate thickness of both clamping plates.
In all cases, the joint section between a shaft and a universal joint yoke of the present invention comprises, as with the conventional joint section between a shaft and a universal joint yoke; a shaft, a pair of outside flat surfaces, a yoke, a pair of clamping plates, a connecting portion, a through-hole or a threaded hole, and a clamping bolt.
The shaft rotates in use.
The outside flat surfaces are formed on an outer peripheral surface of a tip end portion of the shaft.
The yoke is made of metal, and constitutes a universal joint, and has a base end portion with an approximate U-shape in cross section, that is open on one side.
The clamping plates are arranged separated from each other and constitute the base end portion, wherein the respective inside surfaces serve as clamping surfaces opposed to the outside flat surfaces;
The connecting portion is for connecting together the clamping plates at a part on the opposite side to the opening of the base end portion.
The through-hole or threaded hole are formed in the clamping plates substantially concentric with each other.
Moreover, the clamping bolt has a male thread portion formed at the tip end portion which when inserted through the through-hole is screwed into the threaded hole or a nut.
Particularly in the joint section between a shaft and a universal joint yoke described according to a first aspect of the invention, in the case where it is assumed that prior to tightening the clamping bolt, a virtual centerline dividing in two in the width direction a gripping portion between the clamping plates, and a virtual centerline dividing in two in the width direction a part of the tip end portion of the shaft inserted in the gripping portion are aligned, and an outer surface of the shaft and an inner surface of the connecting portion are brought into contact, clearances exist between the outside flat surfaces and the clamping surfaces, which are narrow at the connecting portion side, and wide at the opening side of the base end portion in which the through-hole or threaded hole are formed. Moreover, when the minimum value for the width of both clearances is S (mm), the angle formed between the outside flat surfaces and the clamping surfaces at the portion at which these surfaces are non-parallel is θ (°), and the plate thickness of the both clamping plates is t (mm), θ/S≧−8.5t+67.2 is satisfied when the plate thickness t is within a range of between 5.5 mm and 7.5 mm.
Furthermore, in the joint section between a shaft and a universal joint yoke described according to a second aspect of the invention, in the case where it is assumed that prior to tightening the clamping bolt, a virtual centerline dividing in two in the width direction a gripping portion between the clamping plates, and a virtual centerline dividing in two in the width direction a part of the tip end portion of the shaft inserted in the gripping portion are aligned, and an outer surface of the tip end portion of the shaft and an inner surface of the connecting portion are brought into contact, clearances exist between the outside flat surfaces and the clamping surfaces. Moreover, of the outside flat surfaces, a step is provided between first flat surfaces existing towards the connecting portion side from the shaft center, and second flat surfaces existing towards the opening side of the base end portion in which the through-hole or threaded hole is formed, than the first flat surfaces, so that the spaces between the second flat surfaces and the clamping surfaces are larger than the spaces between the first flat surfaces and the clamping surfaces. In addition, when the minimum value for the width of the clearances between the outside flat surfaces and the clamping surfaces is S (mm), the angle formed between the virtual surfaces connecting the connecting portions of the step portions and the first flat surfaces, and the edge on the opening side of the second surfaces, and the clamping surfaces, is θ (°), and the plate thickness of the both clamping plates is t (mm), θ/S≧−8.5t+67.2 is satisfied when the plate thickness t is within a range of between 5.5 mm and 7.5 mm.
[Effects of the Invention]
According to the joint section between a shaft and a universal joint yoke of the present invention constructed as described above, the minimum value S for the width of the clearances between the outside flat surfaces and the clamping surfaces, and the angle θ (°) formed between the outside flat surfaces and the clamping surfaces at the part at which these surfaces are non-parallel (in the first aspect), or the angle θ (°) formed between the virtual surfaces connecting the connecting portions of the step portions and the first surfaces, and the edge on the opening side of the second surfaces, and the clamping surfaces (in the second aspect), are regulated by the relationship with the thickness t of the pair of clamping plates. Therefore the outside flat surfaces and the clamping surfaces can be brought into contact at the opening side of the base end portion and at the connecting portion side irrespective of the clearances and thickness of the clamping plates. That is to say, the present inventor found the relationship between the minimum value S for the clearance and the angle θ, in the case where the thickness t of both clamping plates is set to a fixed value, to make outside flat surfaces and the clamping surfaces bring into contact at the opening side of the base end portion and at the connecting portion side, by experiment and by analysis using the finite element method. The equation θ/S≧−8.5t+67.2 was then derived from this relationship.
If the relationship between θ/S and t satisfies the aforementioned equation, the outside flat surfaces and the clamping surfaces can be brought into contact at the opening side of the base end portion and at the connecting portion side. A proviso is that the thickness t of both clamping plates is within a range of between 5.5 mm and 7.5 mm in normal use (more desirably within a range of between 6.0 mm and 7.0 mm). Furthermore, the yoke is manufactured of a ferrous metal material (steel) such as hot rolled mild steel plate. As described above, if the outside flat surfaces and the clamping surfaces can be brought into contact at the opening side of the base end portion and at the connecting portion side, the occurrence of play can be prevented even when a large twisting torque is applied to the shaft.
In order to execute the present invention, it is desirable that θ/S>16.2 when the thickness t of both clamping plates is 6 mm.
Moreover, θ/S>12 when the thickness t of both clamping plates is 6.5 mm.
Furthermore, θ/S>7.7 when the thickness t of both clamping plates is 7 mm.
When constructed as described above, of the contacting portions of the outside flat surfaces and the clamping surfaces, the contact surface pressure at the connecting portion side of the base end portion can be made large, and the occurrence of play in the joint section between the shaft and the yoke can be suppressed to a greater extent. Of course, the relationship between each plate thickness t and each θ/S satisfies the aforementioned equation θ/S≧−8.5t+67.2.
In the present embodiment, a part between the two clamping plates 30a and 30b that grips the tip end portion of the shaft 7 is a gripping portion 31. Furthermore, a virtual centerline N dividing the gripping portion 31 in two in the width direction (left-right direction in
Therefore, in the present embodiment, with both clamping plates 30a and 30b in the unrestrained condition, the clamping surfaces 10b are inclined so that the space between the clamping surfaces 10b is narrow at the connecting portion 17 side, and wide at the opening side of the base end portion 8b. That is to say, by inclining both clamping plates 30a and 30b so that the space between the two becomes wider towards the opening side of the base end portion 8b, the respective clamping surfaces 10b are inclined as mentioned above. On the other hand, the outside flat surfaces 14 are formed so that the outside flat surfaces 14 become mutually parallel. As a result, prior to tightening the clamping bolt 18, the aforementioned wedge-shaped clearances 16a exist between the respective clamping surfaces 10b and the respective outside flat surfaces 14 in the unrestrained condition of the clamping plates 30a and 30b.
Moreover, in the present embodiment, the respective through-holes 13a and 13 formed in the opening side of the clamping plates 30a and 30b for insertion of the clamping bolt 18, are formed so that the central axes of these through-holes 13a and 13 are parallel to a virtual line perpendicular to the outside flat surfaces 14 of the shaft 7. Consequently, the central axes of these through-holes 13a and 13 are inclined with respect to a virtual line perpendicular to the clamping surfaces 10b. That is to say, the clamping plates 30a and 30b are inclined with respect to the outside flat surfaces 14 of the shaft 7 in the unrestrained condition as described above. Therefore, in the case where the through-holes 13a and 13 are formed so that their central axes are parallel to a virtual line perpendicular to the clamping surfaces 10b, the central axes of the through-holes 13a and 13 are not aligned in the unrestrained condition of both clamping plates 30a and 30b. When the central axes are not aligned in this manner, the clamping bolt 18 is not easily inserted into the through-holes 13a and 13. On the other hand, in the present embodiment, by forming the respective through-holes 13a and 13 parallel to a virtual line perpendicular to the respective outside flat surfaces 14, the central axes of these through-holes 13a and 13 are aligned.
The central axes of these through-holes 13a and 13 need not necessarily be aligned (concentric). That is to say, when the clamping bolt 18 is inserted through the through-holes 13a and 13, and screwed and tightened into the nut 11, the outer peripheral surface of the clamping bolt 18 need only be in contact with the inner peripheral surfaces of the through-holes 13a and 13 at the periphery of the opening side of both clamping plates 30a and 30b. Therefore, as shown in
Furthermore, in the present embodiment, a chamfer 20 for guiding the clamping bolt 18, and formed on the side of the through-hole 13a from which the clamping bolt 18 is inserted (left side in
Furthermore, in the present embodiment, if the minimum value for the width of the clearances 16a is S (mm), the angle formed between the outside flat surfaces 14 and the clamping surfaces 10b is θ (°), and the plate thickness of the clamping plates 30a and 30b is t (mm), the angle θ and the minimum value S are regulated to ensure that the plate thickness t is 6.5 mm and θ/S is a value greater than 12 (θ/S>12). It is desirable that this minimum value S is 0.25 mm or less. That is to say, as the minimum value S for the clearances 16a decreases, the strength of the coupling between the shaft 7 and the yoke 3b can be increased, however when the dimensions of the clearances 16a become negative, assembly work becomes difficult. Therefore, when manufacturing errors between the outside flat surfaces 14 and the clamping surfaces 10b are considered, it is desirable that the minimum value S is 0.25 mm or less (more desirably 0.15 mm). In the case where the minimum value S is made less than 0.15 mm, and dimensional accuracy is ensured so that the dimensions of the clearances 16a do not become negative irrespective of manufacturing errors, manufacturing costs undesirably increase.
Moreover, in the case where the minimum value S is made 0.25 mm, the angle θ is greater than 3°. On the other hand, when the minimum value S is 0.15 mm, the angle θ is greater than 1.8°. In order to improve the ease of machining to form the through-holes 13a and 13 at the opening side of the clamping plates 30a and 30b, and to ensure the function of the universal joint, an angle θ of 4° or less is desirable. In other words, the through-holes 13a and 13 are formed by machining, in a condition inclined with respect to a virtual line perpendicular to the clamping surfaces 10b. Thus, when the angle of inclination of the clamping surfaces 10b is large, machining becomes difficult, resulting in increased manufacturing costs. Furthermore, when the clamping bolt 18 is inserted in the through-holes 13a and 13 and tightened by screwing into the nut 11, the clamping plates 30a and 30b deform towards each other, and the arm portion 32 (see
Also in the embodiment configured as described above, as with the aforementioned conventional structure, the tip end portion of the shaft 7 is inserted between the clamping plates 30a and 30b constituting the base end portion 8b of the yoke 3b. In this condition, as shown in
In any case, by screwing and tightening the clamping bolt 18 and the nut 11 together, the both clamping plates 30a and 30b are displaced towards each other. In the present embodiment, since the dimensions of the clearances 16a between the outside flat surfaces 14 and the clamping surfaces 10b are regulated as described above, by screwing and tightening the clamping bolt 18 and the nut 11 together, the surfaces 14 and 10b are brought into contact at the opening side of the base end portion 8b and at the connecting portion 17 side respectively. In other words, as shown in
That is to say, if the thickness t of the clamping plates 30a and 30b is 6.5 mm, and the relationship between θ and S of the clearances 16a is θ/S>12, when the clamping bolt 18 and the nut 11 are screwed and tightened together, of the opposing parts of the surfaces 14 and 10b, the part A at the connecting portion 17 side of the base end portion 8b comes into contact first in relation to the central axis G of the shaft 7. Then when the tightening torque of the nut 11 is further increased, the contact area of the surfaces 14 and 10b increases, and the mutually opposed parts of the surfaces 14 and 10b are in almost complete contact. Furthermore, when the tightening torque of the nut 11 is increased to the prescribed magnitude, of the opposing parts of the surfaces 14 and 10b, the contact surface pressure between the surfaces 14 and 10b reaches a maximum at part B on the opening side of the base end portion 8b. In this case, the contact between the surfaces 14 and 10b at part A is maintained. As a result, even when a large twisting torque is applied to the shaft 7, occurrence of play in the joint section between the shaft 7 and the yoke 3b can be prevented.
Since contact at part A and part B of the surfaces 14 and 10b is maintained even when the relationship between θ and S for the clearances 16a is θ/S≈12, play in the joint section between the shaft 7 and the yoke 3b can be prevented to a greater extent than with the structure shown in FIGS. 7 through 11. That is to say, when θ/S≈12, and the clamping bolt 18 and the nut 11 are screwed and tightened together, of the opposing parts of the surfaces 14 and 10b, the part A and part B come into contact almost simultaneously. When the tightening torque of the nut 11 is increased to the prescribed magnitude, the contact surface pressure between the surfaces 14 and 10b reaches a maximum at part B. In this case, as well, contact is maintained at the part A of these surfaces 14 and 10b. However, when θ/S≈12, and the clamping bolt 18 and the nut 11 are screwed and tightened together, since the surfaces 14 and 10b are simultaneously in contact at part A and part B, by subsequently increasing the tightening torque of the nut 11, the contact surface pressure on the part A side does not so much increase as the increase of the tightening torque of the nut 11. Thus, in comparison with θ/S>12 mentioned above, rigidity in relation to the twisting torque applied to the shaft 7 is reduced. Therefore, as in the present embodiment, it is desirable that θ/S>12. Here, θ/S≈12 and θ/S>12 satisfy θ/S≧−8.5t+67.2 described below.
The reason why play in the joint section between the shaft 7 and the yoke 3b can be prevented by making θ/S>12, is described below. Of the mutually opposed parts of the outside flat surfaces 14 and the clamping surfaces 10b, referred to in relation to the central axis G of the shaft 7 as part A towards the connecting portion 17 side and part B towards the opening side, the present inventor found the conditions under which the surfaces 14 and 10b are both in contact at these parts A and B, by experiment and by analysis with the finite element method. As a result, it was found that, with a plate thickness t of 6.5 mm, and θ/S≈12, the surfaces 14 and 10b are simultaneously in contact at the parts A and B, when the clamping bolt 18 is tightened.
The yoke 3b employed in the aforementioned experiment and analysis was manufactured of JIS-standard hot rolled mild steel plate, being hot rolled mild steel plate for automobile structural uses (JIS G 3113) formed by pressing, with through-holes 13a and 13 machined at the prescribed locations on the opening sides of the clamping plates 30a and 30b respectively. Moreover, the plate thickness t was approximately 6.5 mm over the entirety of the yoke 3b (except at the undercuts 19). Thus, the plate thickness t of the clamping plates 30a and 30b was also 6.5 mm. Variation in this plate thickness was approximately ±0.2 mm. Furthermore, the length L from the center of the cross shaft 4 connecting the yoke 3b and the yoke 2 to the end surface of the base end portion 8b of the yoke 3b (see
In the experiments and analysis conducted under the aforementioned conditions, it was found that, with a plate thickness t of 6.5 mm for the clamping plates 30a and 30b, and at θ/S≈12, the surfaces 14 and 10b are simultaneously in contact at the parts A and B at which the outside flat surfaces 14 and the clamping surfaces 10b are mutually opposed. It was then found, that when the θ/S value was increased beyond 12, the surfaces 14 and 10b were first in contact at part A, and by increasing the tightening torque of the nut 11, the contact surface pressure at the part A could be increased. Therefore, θ/S>12 was selected for the present embodiment. Even when θ/S≈12 is selected, the strength of the coupling between the shaft 7 and the yoke 3b can be increased in comparison to the conventional structure, as described above.
Furthermore, the present inventor found the relationship between θ and S at which the surfaces 14 and 10b are simultaneously in contact at the parts A and B, as with the aforementioned case, also for the case in which the plate thickness t of both clamping plates 30a and 30b was changed. As a result, the present inventor found that the surfaces 14 and 10b were simultaneously in contact at the parts A and B with θ/S≈16.2 at a plate thickness t of 6.0 mm, and with θ/S≈7.7 at a plate thickness t of 7.0 mm. The present inventor then found that with 0/S>16.2 at a plate thickness t of 6.0 mm, and with 0/S>7.7 at a plate thickness t of 7.0 mm, the strength of the coupling between the shaft 7 and the yoke 3b can be increased.
These values are plotted in
The structure of the present embodiment configured and operated as described above is suited to a column-type electrically-powered steering apparatus. This is to say, with a column-type electrically-powered steering apparatus, since a large twisting torque is readily applied to the shaft, if the strength of the coupling between the shaft and the yoke is high as in the structure of the present embodiment, play does not readily occur, eliminating the unnatural feeling for the driver (ensuring a feeling of rigidity) when steering. The structure of the present invention may be freely incorporated in sliders with spline fit and the like employed in structures for extending and contracting shafts, and in shock absorbers such as rubber couplings and the like for suppressing transmission of vibration to steering wheels. Moreover, in the present embodiment, a structure combining a cam bolt and swaged nut was adopted as a means for tightening together the clamping plates. However, the structure described in Patent Documents 2 through 4 may also be employed.
In the case of the structure of the present embodiment as described above, since control of the dimensions of the outside flat surfaces 14b formed at the tip end portion of the shaft 7b presents difficulties, manufacturing costs are increased. On the other hand, with the structure of the first embodiment, since the angle to which the clamping plates 30a and 30b are bent to incline the clamping surfaces 10b need only be adjusted, control of the dimensions is comparatively simple. Furthermore, in the structure of the present embodiment, since the shape of the tip end portion of the shaft 7b is asymmetrical in the top-bottom direction in
In the present embodiment, when the clamping bolt 18 is screwed and tightened into the nut 11 (see
With the structure of the present embodiment as described above, the outside flat surfaces 14c and the clamping surfaces 10 do not come into contact at the parallel parts 21, however, surface pressure at the contact parts increases. Moreover, these clamping surfaces 10 press the outside flat surfaces 14c towards the connecting portion 17. Thus, as with the second embodiment, the coupling strength of the shaft 7c and the yoke 3 can be ensured. In particular, since the intersection points P are on the connecting portion 17 side relative to the central axis G of the shaft 7c, the contact area is greater than in the aforementioned conventional structure shown in
Moreover, the part between clamping plates 30c and 30d, which grips the tip end portion of the shaft 7d is formed as a gripping part 31. Furthermore, a virtual centerline N dividing in two in the width direction (left-right direction in
In the present embodiment, in contrast to the aforementioned embodiments, since the outside flat surfaces 14d and the clamping surfaces 10 are formed mutually parallel, the first and second clearances 26 and 27 between the flat surfaces 14d and 10 are not wedge-shaped. Therefore, in the present embodiment, the angle formed between a virtual surface X connecting the continuous portions 28 connecting the steps 25 and the first flat surfaces 23, and the edge portions 29 on the opening side of the second flat surfaces 24, and the clamping surfaces 10, is prescribed as θ. This angle δ (°), and the minimum value S (mm) for the width of the clearances between the outside flat surfaces 14d and the clamping surfaces 10 (the width of the respective first clearances 26 in the present embodiment), are regulated with respect to the plate thickness t (mm) of the clamping plates 30c and 30d, as in the first embodiment. Therefore, the first and second flat surfaces 23 and 24 and the steps 25 are formed so that the angle θ satisfies the conditions described in the first embodiment.
In the present embodiment configured as described above, when the clamping bolt 18 and the nut 11 are screwed and tightened together (see
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-254585 | Sep 2004 | JP | national |
