JOINT STRUCTURE FOR AXLE HOUSING BALL-END

Abstract: In a joint structure for an axle housing ball-­ end, a seal (3) mounted on each knuckle (2) is disposed to obliquely cross the axis connecting king-pin bearings (19) for rotatably supporting upper and lower king-pins (4), and a king-pin seal is disposed around at least one of the king-pin bearings. The seal is mounted at a position corresponding to the substantial largest diameter of the axle housing ball-end. The end of an axle shaft disposed in the spherical surface at each axle housing ball-end constitutes an outer race of a constant-velocity joint. In addition, in the joint structure for an axle housing ball-end, the knuckle (2) is obliquely divided into a knuckle member (2a) including an upper king-pin hole and a knuckle member (2b) including a lower king-pin hole. The seal (3) is firmly clamped between the upper and the lower knuckle members.

Description: Background of the Invention Field of the Invention: The present invention relates generally to a joint structure for each ball-end of an axle housing, and more particularly to a joint structure at each ball-end of an axle housing for a driving axle with a steering device. Description of the Prior Art: A typical driving axle with a rigid type steer­ ing device used in an all wheel drive type vehicle or the like has heretofore included a spherical por­ tion equipped with a dust-tight seal so as to prevent foreign matter from entering the interior of each joint. This type of joint structure for an axle housing ball-end is disclosed, for example, in the specification of Japanese Patent Laid-Open No. 24226/­ 1981. A follower steering shaft of the type dis­ closed in the above-mentioned specification will hereinafter be described with reference to Fig. 7. Referring to Fig. 7, the follower steering shaft is essentially constituted by three components which can be separated from one another: a shank 71 coupled to a differential unit; a constant-velocity joint 72; and a steering shaft 74 for driving a boss or a sun gear (not shown) within a planetary unit. The constant-velocity joint 72 includes a spherical external coupling member 75 mounted on one end of the shank 71 and an internal coupling member 77 mounted on a corresponding end of the steering shaft 74. A bellows 73 hermetically seals the inner chamber of the constant-velocity joint 72, the bellows being detachably mounted on the external coupling member 75 of the constant-velocity joint 72, and a neck 76 of the bellows 73 being maintained in airtight con­ tact with the steering shaft 74 for free movement along the axis thereof. The bellows 73 has an axial residual stress, and is therefore formed strongly enough to be extended to its maximum axial length. The constant-velocity joint 72 equipped with the bellows 73 can be removed without the need to release it. In general, a conventional type arrangement has difficulties in ideally disposing the seal on the spherical portion of each of the axle housing ends since the ends of king-pins, that is, dust-tight seals are hindrances. The spherical portion at the axle housing ball-end housing the driving axle therein forms a member for supporting a load as a portion of an axle casing. For this reason, the conventional configuration of a rotary body housing an axle shaft which is worked by means of a lathe does not allow for any reduction in the diameter of the neck from the viewpoints of strength, so that a seal sliding surface necessary for satisfactory steering cannot be ensured and the maximum steering angle possible is therefore restrained up to about 30°. However, since the internal structure of each joint and as­ sociated components are actually arranged to allow to a maximum steering angle of about 40°, a demand has arisen with respect to a seal having a steering-­ angle function to be matched with such structure. For the above-described reason, the prior art discloses an elliptic-seal structure in which a sur­ face of each knuckle on which a seal is mounted is inclined with respect to the spherical portion of an associated axle housing end. This type of struc­ ture is disclosed, for example, in the specifications of Japanese Utility Model Laid-Open No. 37386/1984 and 37387/1984. First of all, a diagrammatic description will be made with respect to a front-wheel support device for a front drive vehicle described in Japanese Util­ ity Model Laid-Open No. 37386/1984. Either an oil seal member or an oil seal protection member is so formed as to have an axial length greater on the rear side than on the front side in the direction of move­ ment of the vehicle when a knuckle housing is mounted. The seal of this prior art is disposed around a king-­ pin for pivoting the knucle housing and a trunnion socket in an inclined manner at a predetermined angle, so that, when a vehicle is moved straight, a flat surface including the seal edge of either the oil seal member or the oil seal protection member is disposed closer to the shaft of the trunnion socket on the front side than on the rear side. In this front-wheel support device for a front drive vehicle, the seal is formed in a special shape so as to in­ crease the steering angle. However, even if the seal is formed in such a special shape, it is not neces­ sarily satisfactory in respect of its strength, seal­ ing characteristics and durability. In addition, this type of seal is difficult to produce and of no practical use, thus leading to various problems. In the second place, a diagrammatic description will be made with respect to an oil seal device for a front-wheel support of a front drive vehicle de­ scribed in the specification of Japanese Utility Model Laid-Open No. 37387/1984. Referring to an oil seal member in this prior art, a rubber-made seal body has an equal width along its entire cir­ cumference in a natural state, and a circumferential groove of a L-shaped in section is formed from a mounting flange of the seal body to an arm portion perpendicular to the mounting flange. A reinforced flange member of a metal-made cylindrical flange body has a cut surface on the cylindrical side, such cut surface being inclined with respect to a flange surface, and is adherently engaged with the circum­ ferential groove in a state wherein this groove is under an elastic tension. The reinforced flange member is also disposed around a king-pin for pivot­ ing the knuckle housing and the trunnion socket in an inclined manner at a predetermined angle, so that, when a vehicle is moved straight, a flat surface including the edge of the annular seal is positioned nearer the trunnion socket on the front side than on the rear side. As in the case of the above-­ described example, this oil seal device for the front-wheel support of a front drive vehicle needs a seal with a special shape, and thus there is a problem in that the seal provided may not necessarily be satisfactory from the viewpoint of strength, seal­ ing characteristics and durability, nor with respect to considerations regarding the production of the seal. Summary of the Invention It is an object of the present invention to provide a joint structure for an axle housing ball-­ end, which solves the above-described problems and improve the structure relating to knuckles, an axle housing ball-end and king-pins, increasing the in­ flective angle of each joint with respect to the spherical portion of the respective axle housing ends, that is, the steering angle, and yet of ensur­ ing the strength of the axle. It is another object of the present invention to provide a joint structure for an axle housing ball-end, in which the seal mounted on each knuckle is disposed to obliquely cross the axis connecting king-pin bearings which rotatably support the re­ spective upper and lower king-pins, the position of the dust-guard seal with respect to a steering angle is set to the middle position of the slide surface of the spherical portion, thereby ensuring response to a steering angle needed when large wheels are used. It is another object of the present invention to provide a joint structure for an axle housing ball-end capable of reducing the interference produced between the axle shaft and the axle housing ball-end during a steering operation, and yet increasing the steering angle of the wheels, thereby reducing the turning radius of a vehicle and improving the steer-­ ability of the vehicle when making sharp turns. It is another object of the present invention to provide a joint structure for an axle housing ball-end, in which a seal mounting position is set to a position corresponding to the substantial largest diameter of the spherical portion of the axle housing ball-end, and in which, during assembly, the seal can be removed from the spherical portion by virtue of its own flexibility, and thus assembly is enabled without the need to partially cut seal rubber or its retainer. It is another object of the present invention to provide a joint structure for an axle housing ball-end, in which a knuckle is obliquely divided into a knuckle member including an upper king-pin bearing and a knuckle member including a lower king-pin bear­ ing, the seal being firmly clamped between the knuckle member on the upper side and the knuckle member on the lower side, and the respective knuckle members being easily disassembled without the need to pull the king-pins out of the axle housing ball-end. It is another object of the present invention to provide a joint structure for an axle housing ball-end, in which a king-pin seal is disposed around at least one of the king-pin bearings. It is a further object of the present invention to provide a joint structure for an axle housing ball-end, in which, when the dust guard seal removes dried mud from the spherical portion, physical re­ sistance can be reduced because the seal is arranged to obliquely scrape against the mud, and in which the seal need not be formed into a special shape, and yet the seal suffers no problems from the view­ point of strength, sealing characteristics and du­ rability, nor with respect to considerations regarding the production of the seal, the knuckle being capable of moving freely on the spherical portion since the seal is not hindered by the axle housing ball-end. It is a still further object of the present invention to provide a joint structure for an axle housing ball-end, which is capable of preventing the breakage and damage of large or expensive devices or components by utilizing a particular small member outside the axle shaft as a mechanical safety device with respect to torque. It is an additional object of the present invention to provide a joint structure for an axle housing ball-end, in which each end of the axle shaft disposed in the spherical portion of the axle housing ball-end constitutes an outer race of a constant-­ velocity joint. Brief Description of the Drawings Fig. 1 is a partial cross-sectional view of a joint structure for an axle housing ball-end, which is applied to a driving axle with a steering device in accordance with the present invention; Fig. 2 is a perspective view schematically showing an upper knuckle member of a knuckle shown in Fig. 1; Fig. 2B is a cross-sectional view of the upper nuckle member shown in Fig. 2A; Fig. 3A is a perspective view schematically showing a lower knuckle member of the knuckle shown in Fig. 1; Fig. 3B is a cross-sectional view of the lower knuckle member shown in Fig. 3A; Fig. 4A is a top plan view of the knuckle mounted on an axle casing of the joint structure for an axle housing ball-end, which is applied to a driving axle with a steering device in accordance with the present invention; Fig. 4B is a cross-sectional view taken along line H - H of Fig. 4A; Fig. 4C is a front elevational view taken in the direction of an arrow G of Fig. 4A; Fig. 5A is an illustration of the relationship between the spherical portion of the axle housing ball-end in the joint structure for an axle housing ball-end and the seal on the knuckle in accordance with the present invention; Fig. 5B is an illustration of the relationship between the spherical portion of the axle housing ball-end in the joint structure for an axle housing ball-end and the seal on the knuckle in accordance with the prior art; and Fig. 6 is a cross-sectional view of a joint structure for an axle housing ball-end in accordance with the prior art. Detailed Description of the Embodiment An embodiment of a driving axle with a steering device in accordance with the present invention will be described below in detail with reference to the accompanying drawings. Fig. 1 shows a preferred embodiment of a joint structure for an axle housing ball-end in accordance with the present invention. Refering to the illustrated joint structure, a spherical portion 1 is formed at an axle housing end 9, and an annular seal 3 made of rubber, felt or the like mounted on a knuckle 2 is maintained in contact with the spheri­ cal portion 1, thereby preventing foreign matter from entering the interior of the joint structure. This seal 3 is disposed to obliquely cross the vertical axis connecting king-pin bearings 19 for rotatably supporting upper and lower king-pins 4, thereby to keep the seal 3 at an ideal location. When the knuckle 2 swings about the king-pins 4, the seal 3 may perform its sealing function while it is hermet­ ically sliding over the spherical portion 1. An axle shaft 5 is supported by a bearing 7. An oil seal 8 which is radially tightened by a lip is capable of hermetically sealing a rotating or reciprocally movable portion, and prevents differen­ tial-gear lubricating oil from entering the inner chamber of the joint. Since the interference pro­ duced between the spherical portion of the axle hous­ ing end 9 and the knuckle 2 provides limitations with respect to the length of a portion extending from the respective king-pins 4 to the exterior, the por­ tion of the axle shaft 5 which interfers with the axle housing end 9 preferably has a structure as thin as possible in order to ensure a sufficient area in which the seal 3 can be moved. Since the thinnest portion of the axle shaft 5 is formed at an inter­ ference portion, it is effective from the viewpoint of the structure of the axle shaft 5 that the axle shaft 5 is disposed in a direction opposite to a normal structure, that is, the outer race 11 of the constant-velocity joint 12 is mounted on each end of the axle shaft 5. For example, if the thinnest portion of the axle shaft 5 is formed in such a manner that it is twisted off at the time of applica­ tion of an excessive power input, it is possible effectively to protect other expensive components. In addition, in order to effectively utilize the area of the slide surface of the spherical por­ tion 1 on which the seal 3 is slided, it is prefer­ able that the seal 3 is located at the middle position of the slide surface while a vehicle is moving straight forward. For this reason, in order to ide­ ally dispose the seal 3 while it has a shape easy to produce and a true circle enabling positive per­ formance of its function are maintained, it is prefer­ able that the seal 3 is disposed at an ideal position corresponding to upper and lower substantial middle portions by taking notice of the fact that the upper and lower portions of the seal 3 is not substantially moved while the knuckle 2 is swinging. For example, as shown in Fig. 1, the seal 3 may be arranged to obliquely cross the axis connecting the upper and lower king-pins 4. The structure of the embodiment in which the seal 3 is interposed between the two-piece knuckle 2 will be described below with reference to Figs. 1, 2A, 2B, 3A and 3B. Referring to Fig. 1 showing a structure in which the seal 3 is secured at the location, the knuckle 2 is constituted by upper and lower divisions: knuckle members 2a and 2b. The seal 3 is sandwiched between the knuckle members 2a and 2b, whereby the seal 3 may be firmly mounted. Figs. 2A, 2B, 3A and 3B shows the details of the structure in wchih the knuckle 2 is divided into the knuckle members 2a and 2b. Fig. 2A is a perspective view of the knuckle member 2a, that is, the knuckle member including an upper king-pin hole 13, with Fig. 2B being a cross-­ sectional view of the member 2a shown in Fig. 2A. Fig. 3A is a perspective view of the knuckle member 2b, that is, the lower knuckle member, with Fig. 3B being a cross-sectional view of the member 2b shown in Fig. 3A. The upper king-pin hole 13 in the knuckle member 2a may be machined together with a king-pin hole 14 in the knuckle member 2b. An cutout step 15 of the knuckle member 2a is engaged with a projection 18 of the knuckle member 2b while a pro­ jection 17 of the knuckle member 2a is engaged with a cutout step 16 of the knuckle member 2b. The depth of the cutout step 15 differs from the height of the projection 18, and thus a clearance is formed there­ between for firmly clamping the seal 3. By mounting the seal 3 on the knuckle 2 in this manner, the seal 3 is disposed obliquely to cross the axis connecting king-pin bearings 19 mounted around the king-pins 4. Therefore, since either of the upper and lower king-­ pins 4 is exposed to the outside of the seal 3, a king-pin seal 6 is disposed around the exposed king-­ pin bearing 19. Another example of the inclined seal 3 mounted on the knuckle 2 will be described below with ref­ erence to Figs. 4A, 4B and 4C. Although the knuckle 2 is not divided in the accompanying drawings, it will be appreciated that the technical concept on which the knuckle 2 is inclined at a predetermined angle can be applied to the two-piece knuckle 2. Referring to Figs. 4A, 4B and 4C respectively showing a first preferred embodiment of a joint structure for an axle housing ball-end in accordance with the present invention, a knuckle 2 mounted on an axle casing 20 is schematically illustrated. Fig. 4A is a top plan view of the knuckle 2, in which a mounting surface 21 of the knuckle 2 mounted on the axle casing 20 is inclined at a predetermined angle ϑ, for example, about 4° with respect to the axis of an axle, that is, the horizontal axis of the axle casing 20. Fig. 4B shows the mounting surface 21 of the knuckle 2 which is inclined at the predeter­ mined angle ϑ, for example, about 4° with respect to the axis of the axle casing 20, and therefore has is biased a distance ℓ , for example, a distance of about 2 mm. Fig. 4C shows the mounting surface 21 of the knuckle 2 which is inclined at the predeter­ mined angle ϑ. Referring to Figs. 5A and 5B, description will be made in connection with an arrangement wherein the seal 3 is inclined with respect to the spherical portion 1, that is, a mounting structure in which the seal 3 is inclined with respect to the spherical portion 1. As shown in Figs. 5A and 5B, the spherical por­ tion 1 is integral with the axle housing end 9. Fig. 5A shows a state wherein the seal 3 is clamped between the knuckle members 2a and 2b of the knuckle 2, the seal 3 being located at positions J , K and M . Fig. 5B shows a state wherein the seal 3 is located at positions N , O and P . Fig. 5A shows an embodiment in which the mount­ ing angle of the seal 3, that is, the predetermined angle ϑ is, for example, about 4°. The position J of the seal 3 corresponds to a steering angle of 0°, the position k of the seal 3 corresponding to the maximum steering angle of the wheel on the inner side, that is, a steering angle of 38°, and the position M of the seal 3 corresponding to the maximum steering angle of the wheel on the outer side, that is, a steering angle of 30°. When the seal 3 is mounted, if the seal mounting angle is inclined at about 4°, the slide distance of the seal 3 on the side of the steered wheel on the inner side can be enlarged effectively to utilize the whole of the spherical portion 1. Fig. 5B shows an embodiment in which an angle at which the seal 3 is mounted is not inclined as in the case of the prior art, that is, the predeter­ mined angle ϑ is 0°, with the seal 3 corresponding to positions N , O and P . The position N of the seal 3 corresponds to a steering angle of 0°, the posi­ tion O of the seal 3 corresponding to the maximum steering angle of a wheel on the inner side of a curve, that is, a case wherein the maximum steering angle of the wheel on the inner side is 34°, and the position P of the seal 3 corresponding to the maximum steering angle of a wheel on the outer side of the curve, that is, a case where the maximum steering angle of the wheel on the outer side is 27°. If the seal mounting angle is 0° in this manner, when the seal 3 is mounted, the spherical portion 1 cannot be utilized from end to end, that is, it is impossible completely to utilize the entire range continuing to a position at which the seal 3 comes into contact with the axle housing end 9. Accordingly, although there is a margin equivalent to a length indicated by symbol L on the spherical portion 1, the marging cannot be covered. The embodiment of the joint structure for an axle housing ball-end in accordance with the present invention is constructed as described above. However, it will be readily understood by those skilled in the art that this invention is not confined solely to the structure described above in detail. For example, the following structure may be applied. For example, it will be appreciated that it is possible to adopt a structure in which the seal is disposed on a knuckle per se, instead of the arrangement in which the seal is clamped between a pair of knuckle members of the two-piece knuckle. As an example, the seal may be disposed in a groove formed in the inner circumference of the knuckle. Even in a conventional structure, if an axle shaft is reversed such that the front side of the seal mounting surface is inclined inwardly of a vehicle with the rear side outwardly of the same, the difference between the steering angles of the wheels on the inner and outer sides in the Ackerman steering mechanism is suitably distributed between the areas of the seal slide surfaces corresponding to the respective wheels, thereby increasing the steering angle of the wheel on the inner side, so that the turning radius of the vehicle can be reduced. Referring to a method of inclining the seal mounting surface, the inclination of the surface of a knuckle to be worked provides the advantage that if it unnecessary to prepare a seal of a special shape. The structure of this invention has the po­ tential of achieving the steering angle is 40°, 40° of wheels by disposing the seal in an obliquely crossed manner with respect to the axis connecting the king-pins. Therefore, where a difference is to be formed between the steering angles of the wheels on the inner and outer sides in the Ackerman steering mechanism, a caster angle equivalent to half the difference is formed, and in addition each terminal end of the axle housing is inclined by half of the angle difference in order to prevent the occurence of unwanted interference. By these measures, as an example, it is possible to obtain large steering angles such as 45° and 35°. As a matter of course, although the built-in constant-­ velocity joints need ability responsive to these steering angles, constant-velocity joints generally have such ability as a part of their own functions.

Claims: 1. A joint structure for an axle housing ball-end comprising: a knuckle mounted on an axle casing for support­ ing king-pin bearings which rotatably support upper and lower king-pins, respectively; a seal mounted on the inner circumference of said knuckle; and a spherical portion formed at each end of an axle housing for accommodating an axle shaft; in which said seal is disposed to obliquely cross the axis connecting said upper and lower king-­ pin bearings. 2. A joint structure for an axle housing ball-end according to Claim 1, wherein said knuckle is oblique­ ly divided into upper and lower pieces, the former being a knuckle member including said king-pin bear­ ing on the upper side and the latter being an knuckle including said king-pin bearing on the lower side. 3. A joint structure for an axle housing ball-end according to Claim 1, wherein a king-pin seal is disposed around at least one of said king-pin bearings. 4. A joint structure for an axle housing ball-end according to Claim 1, wherein said seal is mounted at a position corresponding to the substantial largest diameter of said spherical portion of said respective of axle housing ends. 5. A joint structure for an axle housing ball-end according to Claim 1, wherein each end of said axle shaft disposed in said spherical portion of said axle housing end forms an outer race of a constant-velocity joint. 6. A joint structure for an axle housing ball-end according to Claim 1, wherein said seal is firmly clamped between said knuckle members on said upper and lower sides. 7. A joint structure for an axle housing ball-end according to Claim 1, wherein said knuckle is disposed on the outer circumference of said spherical portion, said knuckle being capable of swinging on said spheri­ cal surface about the axis connecting king-pins which are rotatably supported by said king-pin bearings.

Inventors: SASA, NAOMICHI C/O ISUZU MOTORS LIMITED
Applicants: ISUZU MOTORS LIMITED
Application year: 1987
Main classification: B60K17
IPC codes: B60K17