JP2020153486A - Drive shaft for vehicle - Google Patents

Abstract

To reduce design change other than a drive shaft as much as possible, and to allow a weakest part of the drive shaft to be set to a position capable of preventing the whirling that occurs when the drive shaft is broken, while maintaining production efficiency.SOLUTION: Out of a tooth part 75 of a male spline part 71 provided at an intermediate shaft 70 to be connected by spline fitting to a fixed constant velocity universal joint 10 arranged on a drive wheel side and to a sliding constant velocity universal joint 30 arranged on a differential gear side, in a region 83A in which fitting with a tooth part 19a of a female spline part 19 to be mated in spline fitting is assumed, a cutout part 82 is provided.SELECTED DRAWING: Figure 4

Description

The present invention relates to a vehicle drive shaft.

For example, a drive shaft for a vehicle is for transmitting power from a differential gear (hereinafter, simply referred to as a differential) to a drive wheel, and is a rotation output from the differential while allowing a relative displacement between the differential and the drive wheel. It is possible to transmit the driving force to the driving wheels at a constant speed. This drive shaft is usually configured by arranging a fixed constant velocity universal joint on the drive wheel side and a sliding constant velocity universal joint on the differential side, and connecting these constant velocity universal joints with an intermediate shaft. There is.

Here, the differential and the sliding constant velocity universal joint are provided in the spline fitting hole (female spline portion) provided in the side gear of the differential and the stem portion of the outer joint member constituting the sliding constant velocity universal joint. The male spline portion provided is connected by spline fitting. Further, the sliding constant velocity universal joint and the intermediate shaft, and the fixed constant velocity universal joint and the intermediate shaft are spline fitting holes (female) provided in the inner joint member or the tranion of the sliding constant velocity universal joint. Spline portion), a male spline portion provided at one end of the intermediate shaft, a spline fitting hole (female spline portion) provided in the inner joint member of a fixed constant velocity universal joint, and the other end of the intermediate shaft. The male spline portions provided are connected to each other by spline fitting.

Here, with regard to the drive shaft, the allowable strength and dimensions are set in detail compared to other parts, and if the specifications are selected according to the required performance of the vehicle, the drive shaft will be included in the drive system including the drive shaft. May be the weakest part. If the drive shaft should be damaged during driving, the shaft may swing around, causing secondary damage such as damage to peripheral parts. Therefore, for example, in Patent Document 1, a V-shaped cross section is provided on the stem portion of the outer joint member of the sliding type constant velocity universal joint located at the differential side end of the drive shaft so that the weakest portion with respect to the load torque is inside the differential case. It has been proposed to provide a shaped annular groove.

Japanese Unexamined Patent Publication No. 2012-167793

However, when the weakest portion is provided in the stem portion of the outer joint member of the sliding type constant velocity universal joint located at the end on the differential side as described above, the differential is even after the stem portion is broken in the differential case. Since the sliding type constant velocity universal joint on the side can slide, the broken stem portion may come off from the differential case, which is not preferable. Therefore, as another method, it is conceivable to set the portion of the intermediate shaft located in the boot as the weakest portion. According to this configuration, even if the intermediate shaft breaks at its weakest part, the outer joint member of the constant velocity universal joint and the intermediate shaft are connected via the boot, so that the broken shaft can swing around. It can be prevented.

As described above, when the weakest portion is provided on the intermediate shaft, the weakest portion may be set in consideration of the fact that the optimum portion varies depending on the load mode. Hereinafter, the drive shaft 150 shown in FIG. 7 will be referred to for reference. In FIG. 7, the element indicated by reference numeral 10 is the constant velocity universal joint 110 on the drive wheel (not shown) side, and the element indicated by reference numeral 130 is the constant velocity universal joint 130 on the differential (not shown) side. is there. For example, when the strength against static or impact twist is a problem, the minimum smoothness in the boot 120 (139) having the smallest cross-sectional coefficient among the intermediate shafts 170 for connecting the above-mentioned constant velocity universal joints 110 and 130. It is conceivable that the portion 173 (174) (see FIG. 7) is the weakest portion, and when the strength against repeated twisting (torsional fatigue strength) becomes a problem, the male spline portion having a complicated cross-sectional shape and easily causing stress concentration. It is conceivable that 171 (172) (see FIG. 7) is the weakest part.

On the other hand, the intermediate shaft 170 is often used by quenching carbon steel having a C (carbon) amount of 0.35 to 0.45% for the purpose of ensuring the minimum necessary torsional fatigue strength. The outer joint member 113 (131) of the constant velocity universal joint 110 (130) has the purpose of ensuring the life of the contact portion of the track groove 111 (or roller guide surface 135) with the ball 117 (or roller unit 133). Carbon steel with a larger C content than the intermediate shaft 170 (carbon steel with a C content of 0.45 to 0.60%) is used so that the maximum hardness that the steel material has when quenching the steel material can be obtained. I often do it. However, parts having a complicated cross-sectional shape such as male spline parts 171, 172, 124, 143 are likely to have excessive stress concentration parts when a torque is applied, and as the amount of C increases, they are brittlely damaged and have strength (particularly). Twist fatigue strength) tends to decrease. Therefore, if the shape is the same, the male spline portion 124 (143) of the stem portion 123 (142) having a larger C amount than the male spline portion 171 (172) of the intermediate shaft 170 has a lower torsional fatigue strength. Therefore, in this case, the outer diameter dimension D5 of the male spline portion 124 (143) of the stem portion 123 (142) is set to the male of the intermediate shaft 170 so that the male spline portion of the stem portion does not become the weakest portion of the torsional fatigue strength. It is generally larger than the outer diameter dimension D4 of the spline portion 171.

By the way, in the development of a vehicle, for example, an increase in the size of a drive shaft may be considered for the purpose of meeting the required strength at a high operating angle of a constant velocity universal joint. Here, since the components of the constant velocity universal joint as a mass-produced product are standardized, for example, as shown in FIG. 8, in the high-sized constant velocity universal joint 110B, the outer joint member which is the component is The size of 113B and the inner joint member 116B also increases. As a result, the outer diameter dimension D2 of the male spline portion 171B of the intermediate shaft 170B for spline fitting with the spline fitting hole (female spline portion 119B) of the inner joint member 116B also increases. On the other hand, since the size of the peripheral parts of the drive shaft 150 is designed so as not to change as much as possible, the size of the stem portion 123B (the outer diameter dimension D1 of the male spline portion 124B) is compared with the size increase of the constant velocity universal joint 110B. ) Is almost the same as the outer diameter dimension D5 (see FIG. 7) in the case of the low size. As a result, the torsional fatigue strength of the male spline portion 171B of the intermediate shaft 170B becomes larger than that of the male spline portion 124B of the stem portion 123B, and the male spline portion 171B may not be the weakest portion.

For example, if the outer diameter dimension D3 of the minimum smoothing portion 173 is reduced until the minimum smoothing portion 173 of the intermediate shaft 170 becomes the weakest portion of the torsional fatigue strength, the weakest portion of the intermediate shaft 170 can be provided in the boot 120. However, if this is the case, the static or impact torsional strength may be significantly reduced, and it cannot be practically adopted. Therefore, it is necessary to increase the outer diameter dimension D5 of the male spline portion 124 of the stem portion 123 or decrease the outer diameter dimension D4 of the male spline portion 171 of the intermediate shaft 170, but the male spline portion 124 of the stem portion 123 If the outer diameter dimension D5 is increased, it becomes necessary to review the design of the hub bearing and the differential that are fitted to the male spline portion 124. This is not preferable because it requires a large design change including the peripheral parts of the drive shaft 150 in order to satisfy the design of the weakest part of the drive shaft 150. On the other hand, when the outer diameter dimension D4 of the male spline portion 171 of the intermediate shaft 170 is reduced, the number of types of the inner joint member 116 increases due to the difference in the spline fitting diameter, which increases the management man-hours, which results in production. There is a problem of reduced efficiency. In addition, as the number of types of parts increases, the risk of incorrect assembly (misassembly of incorrectly combined parts) increases, so careful work is required, which also reduces production efficiency. Occurs.

In view of the above circumstances, in this specification, it is possible to prevent the weakest part of the drive shaft from swinging when the drive shaft is damaged, while minimizing design changes other than the drive shaft and maintaining production efficiency. The technical issue to be solved is to be able to set the position.

The solution to the above problems is achieved by the drive shaft according to the present invention. That is, this drive shaft is at least one of a fixed constant velocity universal joint arranged on the drive wheel side and an intermediate shaft connected to a sliding constant velocity universal joint arranged on the differential gear side by spline fitting. In a vehicle drive shaft provided with a boot that covers a connecting portion between one constant velocity universal joint and an intermediate shaft, among the teeth of the male spline portion provided on the intermediate shaft, a female spline that is a partner for spline fitting. It is characterized by the fact that a notch is provided in a region where the portion is expected to fit with the tooth portion. In addition, the "region where the female spline portion that is the mating partner of the spline fitting is expected to be fitted with the tooth portion" is defined as the tooth portion of the male spline portion of the intermediate shaft that has no notch. This means a region where the female spline portion, which is the partner of the spline fitting, is expected to be fitted with the tooth portion.

As described above, in the drive shaft according to the present invention, it is assumed that among the tooth portions of the male spline portion of the intermediate shaft constituting the drive shaft, the tooth portion of the female spline portion which is the partner of the spline fitting is fitted. A notch was provided in the area. By providing the notch in the above-mentioned region, the area where the tooth portion of the male spline portion and the tooth portion of the female spline portion fit is reduced, and the area where the tooth portion of the male spline portion fits is reduced by that amount. The stress can be increased preferentially. Therefore, even when the outer diameter of the male spline portion of the intermediate shaft is about the same as the outer diameter of the male spline portion provided on the stem portion of the outer joint member, the male spline portion of the intermediate shaft is twisted on the drive shaft. It can be the weakest part of fatigue strength. As a result, it is not necessary to increase the outer diameter dimension of the male spline portion of the stem portion, so that it is not necessary to increase the inner diameter dimension of the female spline portion on the hub bearing side or the differential side that fits with the male spline portion. Conventionally designed parts can be used as peripheral parts of the drive shaft. Further, since the position of the weakest portion can be adjusted on the side of the intermediate shaft, it is possible to standardize the parts of the inner joint member or the trunnion of the constant velocity universal joint. On the other hand, since the intermediate shaft has specifications unique to the vehicle (so to speak, one item is uniform), it is easy to adjust the shape individually. Therefore, even if the shape of the male spline portion is changed as in the present invention, it is within the range of individual adjustment, and there is no possibility that the overall production efficiency and production cost will be significantly affected. Of course, by providing the weakest portion in the male spline portion of the intermediate shaft, even if the portion is damaged, the outer joint member of the constant velocity universal joint and the shaft can be maintained in a state of being connected by boots. Therefore, it is possible to prevent the drive shaft from swinging after being damaged, and thereby it is possible to prevent secondary damage such as damage to peripheral parts.

Further, in the vehicle drive shaft according to the present invention, the intermediate shaft has a cut-up portion located on the base end side of the male spline portion and increasing as the outer diameter dimension increases from the tip end side, and the notch portion has a notch. Of the teeth of the male spline portion, the female spline portion may be provided closer to the cut-up portion than the central position in the axial direction of the region where the fitting with the tooth portion of the female spline portion is assumed. The "axial center position" of the region where the female spline portion is expected to be fitted with the tooth portion is the axial distance to one end in the axial direction of the region and the other end in the axial direction of the region. Means an axial position equal to the axial distance of.

By providing the cut-up portion on the intermediate shaft in this way, stress concentration is likely to occur on the proximal end side of the male spline portion. Therefore, by providing the notch portion at a position closer to the cut-up portion in the region where the female spline portion is expected to fit with the tooth portion described above, the stress generated on the cut-up portion side of the male spline portion is further increased. It is possible to increase it effectively.

Further, in the vehicle drive shaft according to the present invention, the tooth portion of the male spline portion may extend in a direction having a predetermined twist angle with respect to the central axis of the male spline portion.

By imparting a twist angle to the tooth portion of the male spline portion in this way, the tooth portion of the male spline portion comes into contact with the tooth portion of the female spline portion so as to be strongly pressed at both ends in the axial direction. Therefore, in this case, by providing the notch portion on the proximal end side of the region where the female spline portion is expected to fit with the tooth portion in the axial direction as described above, the proximal end side of the male spline portion is provided. The stress generated in the tooth can be increased more effectively.

Further, in the vehicle drive shaft according to the present invention, the notch portion is the base end of the tooth portion of the male spline portion rather than the axial center position of the region where pressure contact with the tooth portion of the female spline portion is assumed. It may be provided on the side. The term "pressure contact of the female spline portion with the tooth portion" as used herein means a state in which the tooth portion of the male spline portion and the tooth portion of the female spline portion are in contact with each other at an appropriate surface pressure, and are fitted together. In terms of the definition of, it means a state of substantially more than an intermediate fit. Further, the "region where pressure contact of the female spline portion with the tooth portion is assumed" referred to here is a spline fitting partner when there is no notch portion in the tooth portion of the male spline portion of the intermediate shaft. It means a region where pressure contact of the female spline portion with the tooth portion is expected.

As described above, in the actual spline fitting, at least a part of the male spline portion is fixed to each other in a state of being pressed against the female spline portion. Therefore, by providing a notch on the proximal end side of the region where pressure welding is expected among the regions where the female spline portion is expected to fit with the tooth portion, the stress generated on the proximal end side of the male spline portion can be reduced. It can be enhanced more effectively. In particular, when the tooth portion of the male spline portion has a predetermined twist angle as described above, the region where the pressure welding is assumed varies depending on the magnitude of the torque applied to the intermediate shaft. Therefore, by setting the position and range (axial dimension) of the notch portion according to the assumed torque, it is possible to appropriately adjust the torsional fatigue strength of the male spline portion.

Further, in the vehicle drive shaft according to the present invention, the notch portion is a region of the tooth portion of the male spline portion that is expected to be fitted with the tooth portion of the female spline portion, and is a region of the male spline portion. It may be provided at a position where the tooth portion is divided in the axial direction.

According to the above configuration, the notch portion can be provided so as to avoid both ends in the axial direction of the tooth portion of the male spline portion. Therefore, as described above, when the tooth portion of the male spline portion is provided with a predetermined twist angle, the notch portion is provided in the region where the female spline portion is expected to be fitted with the tooth portion. However, it is possible to reliably fit the male spline portion with the female spline portion at both ends in the axial direction of the tooth portion. Therefore, it is possible to reduce the backlash in the circumferential direction at the spline fitting portion between the intermediate shaft and the female spline portion such as the inner joint member, while providing the notch portion and providing the weakest portion in the male spline portion. Become.

Further, in the vehicle drive shaft according to the present invention, the amount of C of the male spline portion of the intermediate shaft is the stem portion provided on the outer joint member of one of the constant velocity universal joints that is the partner of the spline fitting. It may be less than the amount of C.

In the vehicle drive shaft according to the present invention, even if the outer diameter of the male spline portion of the intermediate shaft is the same as the outer diameter of the stem portion of the outer joint member, the male spline of the intermediate shaft The weakest part can be provided in the part. Therefore, even if the amount of C in the stem portion of the outer joint member is larger than the amount of C in the male spline portion of the intermediate shaft, the stem portion of the outer joint member preferentially brittle fractures with respect to torsional fatigue load. The weakest part can be maintained at the male spline part of the intermediate shaft by avoiding the situation.

Further, in the vehicle drive shaft according to the present invention, the male spline portion of the intermediate shaft may be finished by rolling.

In the case of the notch portion according to the present invention, for example, at the stage before rolling, a recess corresponding to the notch is formed at the same time as turning the male spline portion having the shape before rolling, and the male spline portion is formed. By rolling the recesses at the same time as the rolling process of the above, a male spline portion having a notch portion can be easily formed. When the notch portion is formed by cutting after the formation of the male spline portion, the step of cutting and removing is increased, burrs are likely to occur, and the step of deburring may be required. Therefore, it is possible to manufacture the male spline portion at a lower cost by forming a concave portion as a base of the notch portion before rolling.

As described above, according to the vehicle drive shaft according to the present invention, the weakest part of the drive shaft is damaged while the design change other than the drive shaft is minimized and the production efficiency is maintained. It is possible to set the position so that the swing that sometimes occurs can be prevented.

It is sectional drawing of the drive shaft which concerns on one Embodiment of this invention. It is sectional drawing of the fixed type constant velocity universal joint shown in FIG. It is an enlarged view of the main part of the intermediate shaft shown in FIG. It is an enlarged view of the main part which shows the spline fitting state of the intermediate shaft and the inner joint member shown in FIG. In the enlarged view of the main part of the drive shaft according to another embodiment of the present invention, spline fitting between the intermediate shaft and the inner joint member in the case where the tooth portion of the male spline portion of the intermediate shaft is provided with a twist angle. It is the figure which viewed the state in a plan view. FIG. 5 is an enlarged view of a main part showing a spline fitting state between the intermediate shaft and the inner joint member shown in FIG. It is sectional drawing of the conventional drive shaft. FIG. 5 is a cross-sectional view of a fixed constant velocity universal joint having a higher size than the fixed constant velocity universal joint shown in FIG. 7. It is an enlarged view of the main part which shows the spline fitting state (the conventional spline fitting state) of an intermediate shaft and an inner joint member when there is no notch part which concerns on this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a partial cross-sectional view of a drive shaft 50 according to an embodiment of the present invention. The drive shaft 50 is for connecting the constant velocity universal joint 10 on the drive wheel (not shown) side, the constant velocity universal joint 30 on the differential (not shown) side, and these constant velocity universal joints 10, 30. It includes an intermediate shaft 70. Here, the constant velocity universal joint 10 on the drive wheel side is a fixed constant velocity universal joint, and the constant velocity universal joint 30 on the differential side is a sliding constant velocity universal joint. Further, one end 70a of the intermediate shaft 70 is connected to the inner joint member 16 constituting the fixed constant velocity universal joint 10, and the inner joint member (here, tripod) constituting the sliding constant velocity universal joint 30 is connected. The other end 70b of the intermediate shaft 70 is connected to the boss 36) of the member 32. First, the configuration of the fixed constant velocity universal joint 10 located on the drive wheel side of the drive shaft 50 will be described.

As shown in FIG. 1, the fixed constant velocity universal joint 10 includes an outer joint member 13 in which arcuate track grooves 11 extending in the axial direction are formed at a plurality of locations in the circumferential direction of the spherical inner peripheral surface 12 and an outer side. An inner joint member 16 in which arc-shaped track grooves 14 extending in the axial direction in pairs with the track groove 11 of the joint member 13 are formed at a plurality of locations in the circumferential direction of the spherical outer peripheral surface 15, and a track of the outer joint member 13. A ball 17 that transmits torque interposed between the groove 11 and the track groove 14 of the inner joint member 16, and a spherical inner peripheral surface 12 of the outer joint member 13 and a spherical outer peripheral surface 15 of the inner joint member 16. A cage 18 is provided between the cages 18 for holding the balls 17.

Further, the inner joint member 16 of the fixed constant velocity universal joint 10 and one end 70a of the intermediate shaft 70 are connected to each other by spline fitting. In this case, a female spline portion 19 as a fitting hole is provided on the inner circumference of the inner joint member 16, and a male spline portion 71 that fits with the female spline portion 19 is provided at one end portion 70a of the intermediate shaft 70. It is provided.

A boot 20 is attached between the fixed constant velocity universal joint 10 and the intermediate shaft 70 so as to cover the connecting portion between the inner joint member 16 and one end 70a of the intermediate shaft 70. The boot 20 is provided for the purpose of preventing the leakage of a lubricant such as grease sealed inside the fixed constant velocity universal joint 10 and preventing the intrusion of foreign matter from the outside, and the large diameter side end portion thereof. 21 is fitted and fixed to the outer peripheral surface of the outer joint member 13, and the small diameter side end portion 22 is fitted and fixed to the outer peripheral surface of the intermediate shaft 70.

Further, the outer joint member 13 is integrally provided with a stem portion 23 extending toward the drive wheel side, and is provided on the male spline portion 24 provided on the stem portion 23 and the fitted component on the drive wheel side. The female spline portions (not shown) are connected to each other by spline fitting. The male spline portion 24 is made of, for example, carbon steel having a C content of 0.45% to 0.60%. When the male spline portion 24 is integrally formed as a part of the outer joint member 13 as in the present embodiment, the entire outer joint member 13 including the male spline portion 24 has a C amount of 0.45% to 0.60%. It is made of carbon steel. Further, the entire or part of the outer joint member 13 (male spline portion 24) may be provided with a thermosetting layer on the surface layer by heat treatment such as induction hardening.

Next, the configuration of the sliding constant velocity universal joint 30 located on the differential side of the drive shaft 50 will be described.

As shown in FIG. 1, the sliding constant velocity universal joint 30 is a so-called double roller type tripod type constant velocity universal joint, and mainly includes an outer joint member 31, a tripod member 32, and a roller unit 33. ..

On the inner peripheral surface of the outer joint member 31, three linear track grooves 34 extending in the axial direction (only one track groove 34 is displayed in FIG. 1) are formed at equal intervals in the circumferential direction. To. Each track groove 34 has a pair of roller guide surfaces 35 (only one roller guide surface 35 is displayed in FIG. 1) facing each other on both inner walls thereof. The roller guide surface 35 has an arcuate cross section and extends linearly in the axial direction of the outer joint member 31.

Although not shown, the tripod member 32 has three leg shafts 37 extending in the radial direction of the boss 36 integrally on the outer peripheral surface of the cylindrical boss 36 at equal intervals (120 ° intervals) in the circumferential direction. It was formed. The tip of the leg shaft 37 extends radially to the vicinity of the bottom of the track groove 34. The other end 70b of the intermediate shaft 70 is connected to the shaft hole of the boss 36 by spline fitting. In this case, the shaft hole of the boss 36 is provided with a female spline portion 38 as a fitting hole, and the other end 70b of the intermediate shaft 70 is provided with a male spline portion 72 that fits with the female spline portion 38. Has been done.

In the sliding constant velocity universal joint 30 having the above configuration, the leg shaft 37 of the tripod member 32 and the roller guide surface 35 of the outer joint member 31 engage with each other in the rotational direction of the two shafts via the roller unit 33. , The rotational torque is transmitted from the drive side to the driven side at a constant speed. Further, since the roller unit 33 rolls on the roller guide surface 35 while rotating with respect to the leg shaft 37, relative axial displacement and angular displacement between the outer joint member 31 and the tripod member 32 are allowed. Will be done.

A boot 39 is attached between the sliding constant velocity universal joint 30 and the intermediate shaft 70 so as to cover the connecting portion between the tripod member 32 (boss 36) and the other end 70b of the intermediate shaft 70. .. The boots 39 are provided for the purpose of preventing leakage of a lubricant such as grease sealed inside the sliding constant velocity universal joint 30 and preventing foreign matter from entering from the outside, and the large diameter side end thereof. The portion 40 is fitted and fixed to the outer peripheral surface of the outer joint member 31, and the small diameter side end portion 41 is fitted and fixed to the outer peripheral surface of the intermediate shaft 70.

Further, the outer joint member 31 is integrally provided with a stem portion 42 extending to the differential side, and is provided on the male spline portion 43 provided on the stem portion 42 and the fitting component on the differential side. Female spline portions (not shown) are connected to each other by spline fitting. The male spline portion 43 is made of, for example, carbon steel having a C content of 0.45% to 0.60%. When the male spline portion 43 is integrally formed as a part of the outer joint member 31 as in the present embodiment, the entire outer joint member 31 including the male spline portion 43 has a C amount of 0.45% to 0.60%. It is made of carbon steel. Further, the entire or part of the outer joint member 31 (male spline portion 43) may be provided with a thermosetting layer on the surface layer by heat treatment such as induction hardening.

The intermediate shaft 70 has a shape substantially symmetrical in the axial direction, and has a male spline portion 71 at one end 70a and a male spline 72 at the other end 70b. Further, on the side closer to the axial center of the intermediate shaft 70 than the male spline portions 71 and 72, the cross-sectional shape is a perfect circular shape, and the minimum smooth portion having the smallest outer diameter dimension in the intermediate shaft 70. 73 and 74 are provided. In this embodiment, the boots 20 and 39 cover the periphery of each of the minimum smoothing portions 73 and 74.

FIG. 3 is an enlarged view of one end 70a of the intermediate shaft 70 on the side connected to the fixed constant velocity universal joint 10. As shown in FIG. 3, one end 70a of the intermediate shaft 70 is provided with a male spline portion 71 formed by arranging a plurality of axially extending tooth portions 75 at a plurality of locations in the circumferential direction. In the present embodiment, each tooth portion 75 extends in a direction parallel to the central axis X of the male spline portion 71.

The same number of groove portions 76 extending in the axial direction are provided between the tooth portions 75 adjacent to each other in the circumferential direction. In the present embodiment, the base end side of the male spline portion 71 is provided with a cut-up portion 77 whose outer diameter dimension increases as the distance from the tip end side of the intermediate shaft 70 increases. The cut-up portion 77 is composed of, for example, an enlarged diameter surface 78 that smoothly expands in diameter in an arc shape, and is smoothly connected to the end portion on the proximal end side of the groove portion 76. In this case, the end portion 75a on the proximal end side of each tooth portion 75 extends to the distal end portion on the proximal end side of the cut-up portion 77.

Further, the intermediate shaft 70 is provided with a shoulder portion 79 that abuts on the proximal end side in the axial direction with the inner joint member 16 that is the partner of the spline fitting, and also abuts on the tip end side in the axial direction. A mounting groove 81 for mounting the retaining ring 80 (see FIG. 4) is provided. Therefore, as shown in FIG. 4, in a state where the male spline portion 71 of the intermediate shaft 70 is fitted to the female spline portion 19 provided on the inner circumference of the inner joint member 16 and the retaining ring 80 is attached, the male spline The portion 71 and the female spline portion 19 are fitted, and the inner joint member 16 is positioned and fixed in the axial direction with respect to the intermediate shaft 70 by the shoulder portion 79 and the retaining ring 80.

Further, the male spline portion 71 of the intermediate shaft 70 is formed with a notch portion 82 formed by notching a part of the tooth portion 75. The notch 82 is a female of the inner joint member 16 of the tooth portions 75 in a state where one end 70a of the intermediate shaft 70 and the inner joint member 16 of the fixed constant velocity universal joint 10 are connected by spline fitting. The spline portion 19 is provided in a region 83A (a region indicated by solid hatching in FIG. 9) where fitting with the tooth portion 19a is assumed. That is, as shown in FIG. 9, assuming that there is no notch 82 in the tooth portion 75, the tooth portion 75 of the male spline portion 71 is an axially predetermined region of the tooth portion 19a of the female spline portion 19 ( When fitting is expected over the entire axial direction in FIG. 9, a notch 82 is provided in the region 83A (region indicated by hatching of the alternate long and short dash line in FIG. 4) where this fitting is expected.

In the present embodiment, the notch 82 is connected to the reduced diameter portion 82a and the outer diameter portion 82a whose outer diameter dimension decreases from the tip end side to the proximal end side of the tooth portion 75, and is outside in the notched portion 82. It is composed of a bottom portion 82b having a minimum diameter dimension and an enlarged diameter portion 82c connected to the bottom portion 82b and whose outer diameter dimension increases from the tip end side to the base end side of the tooth portion 75. The tip of the reduced diameter portion 82a and the base end of the enlarged diameter portion 82c are continuous with the top surface 75b of the tooth portion 75, respectively. The outer diameter of the bottom portion 82b is set smaller than the outer diameter of the groove portion 76, but the groove portion is not fitted (interfered) with the tooth portion 19a of the female spline portion 19 which is the partner of the spline fitting. The outer diameter of the bottom 82b may be set larger than that of 76.

Further, in the present embodiment, the notch portion 82 is located at the axial center position Pc of the region 83A in which the tooth portion 75 of the male spline portion 71 is expected to be fitted with the tooth portion 19a of the female spline portion 19. It is provided on the side close to the cut-up portion 77. Specifically, the entire bottom portion 82b of the notch portion 82 is provided closer to the cut-up portion 77 than the axial center position Pc of the region 83A where fitting with the tooth portion 19a is assumed. On the other hand, the tooth portion 75 exists on the proximal end side of the male spline portion 71 with respect to the notch portion 82. That is, the notch portion 82 is provided at a position where the tooth portion 75 of the male spline portion 71 is divided in the axial direction. In this case, the tooth portion 75 is divided into a tip end side region 75c in the axial direction and a proximal end side region 75d in the axial direction by the notch portion 82. Therefore, the fitting region 83 of the female spline portion 19 with the tooth portion 19a is also divided into front and rear in the axial direction by the notch portion 82.

When the inner joint member 16 is positioned and fixed in the axial direction by the shoulder portion 79 and the retaining ring 80 as in the present embodiment, the axial dimension of the notch portion 82 (the diameter is expanded from the tip position of the reduced diameter portion 82a). The axial distance to the base end position of the portion 82c) is larger than the axial dimension of the mounting groove 81 for the retaining ring 80 (see FIG. 4). Further, as a matter of course, the mounting groove 81 is provided at a position of one end portion 70a of the intermediate shaft 70 that is out of the region 83A where fitting of the female spline portion 19 with the tooth portion 19a is assumed.

Although not shown, the other end 70b of the intermediate shaft 70 may be provided with the same configuration as the one end 70a, and at that time, the male spline portion 71 of the one end 70a may be provided. A notch portion having the same structure as the notch portion 82 provided in may be provided in the male spline portion 72 of the other end portion 70b.

The intermediate shaft 70 having the above configuration, particularly the male spline portion 71, can be manufactured by any means, and for example, one end portion 70a and the other end portion 70b of the intermediate shaft 70 can be formed by cutting, rolling, or the like. , It is possible to form male spline portions 71, 72 having a notch portion 82.

As described above, that is, in the drive shaft 50 according to the present invention, among the teeth 75 of the male spline portion 71 of the intermediate shaft 70 constituting the drive shaft 50, the teeth of the female spline portion 19 which is the partner of the spline fitting. A notch 82 is provided in the region 83A where fitting with the portion 19a is expected (FIG. 4). By providing the notch 82 in the above-mentioned region 83A, the area where the tooth portion 75 of the male spline portion 71 and the tooth portion of the female spline portion 19 fit is reduced, and the tooth portion of the male spline portion 71 is reduced by that amount. It is possible to preferentially increase the stress generated in the fitting portion of the 75, particularly the root portion S of the portion provided in the cut-up portion 77 in the proximal end side region 75d. Therefore, even when the outer diameter dimension D2 of the male spline portion 71 of the intermediate shaft 70 is about the same as the outer diameter dimension D1 of the male spline portion 24 of the stem portion 23 of the outer joint member 13, the male spline portion of the intermediate shaft 70 71 can be the weakest part of the torsional fatigue strength of the drive shaft 50. As a result, it is not necessary to increase the outer diameter dimension D1 of the male spline portion 24 provided on the stem portion 23 of the outer joint member 13, so that the female spline on the hub bearing side or the differential side that fits with the male spline portion 24 does not need to be increased. It is not necessary to increase the inner diameter of the portion, and conventionally designed parts can be used as peripheral parts of the drive shaft 50. Further, since the position of the weakest portion can be adjusted on the side of the intermediate shaft 70, it is possible to standardize the parts of the inner joint member 16 of the fixed constant velocity universal joint 10. On the other hand, since the intermediate shaft 70 has specifications unique to the vehicle (so to speak, one item is uniform), its shape can be easily adjusted individually. Therefore, even if the shape of the male spline portion 71 is changed as in the present invention, it is within the range of individual adjustment, and there is no possibility that the overall production efficiency and production cost will be significantly affected. Of course, by providing the weakest portion in the male spline portion 71 of the intermediate shaft 70, even if the portion is damaged, the outer joint member 13 of the fixed constant velocity universal joint and the damaged intermediate shaft 70 are connected by the boot 20. It can be kept connected. Therefore, it is possible to prevent the drive shaft 50 from swinging after being damaged, and thereby it is possible to prevent secondary damage such as damage to peripheral parts.

Further, in the present embodiment, the intermediate shaft 70 is provided with a cut-up portion 77 located on the base end side of the male spline portion 71 and increasing as the outer diameter dimension increases away from the tip side, and the notch portion 82 is provided with the male spline portion 82. Of the tooth portions 75 of the portion 71, the female spline portion 19 is provided closer to the cut-up portion 77 than the axial center position Pc of the region 83A where fitting with the tooth portion 19a is assumed (FIG. 4). ). By providing the cut-up portion 77 on the intermediate shaft 70 as described above, stress concentration is likely to occur on the proximal end side of the male spline portion 71. Therefore, by providing the cutout portion 82 at a position closer to the cut-up portion 77 in the region 83A where the fitting of the female spline portion 19 with the tooth portion 19a is expected, the cut-up portion of the male spline portion 71 is provided. It is possible to more effectively increase the stress generated on the 77 side.

The vehicle drive shaft according to the embodiment of the present invention has been described above, but the vehicle drive shaft can be appropriately modified without departing from the gist of the present invention.

FIG. 5 shows an enlarged view of a main part of the drive shaft for a vehicle according to another embodiment of the present invention, and more specifically, the tooth portion 75 of the male spline portion 71C of the intermediate shaft constituting the drive shaft is defined. A plan view of the spline fitting state of the intermediate shaft and the inner joint member 16 in the case where the twist angle of the above is given is shown. As shown in this figure, in the intermediate shaft according to the present embodiment, the tooth portion 75C of the male spline portion 71C has a predetermined twist angle. Therefore, when a predetermined torque is applied to the intermediate shaft 70, the tooth portions 75C of the male spline portion 71C mainly come into contact with the tooth portions 19a of the female spline portion 19 at both ends in the axial direction, and the reaction force Fa from each of the tooth portions 19a. , Receives Fb. In this case, the base end side of the male spline portion 71C is the side opposite to the tip end of the intermediate shaft, and the cut-up portion 77 (see FIG. 6) is provided, so that the reaction received on the base end side is received. The force Fb is larger than the reaction force Fa received on the tip side. Therefore, on the base end side of the tooth portion 75C, the tooth portion 75C of the male spline portion 71C and the tooth portion 19a of the female spline portion 19 are substantially in pressure contact with each other.

In this way, when a part of the base end side of the male spline portion 71C is fixed to each other in a state of being in pressure contact with the tooth portion 19a of the female spline portion 19, it is assumed that the female spline portion 19 is fitted with the tooth portion 19a. By providing the notch 82 in the region 84A (FIG. 6) where pressure welding is expected, among the regions 83A (see FIG. 4), the region 84A where pressure welding is expected is more preferably cut to the proximal end side of the region 84A where pressure welding is expected. By providing the notch portion 82, the stress generated on the proximal end side of the male spline portion 71C can be further effectively increased. In particular, when the tooth portion 75C of the male spline portion 71C has a predetermined twist angle as shown in FIG. 5, the position of the region 84A where the pressure welding is assumed is assumed according to the magnitude of the torque applied to the intermediate shaft. And the range fluctuates. Therefore, by setting the position and range (axial dimension) of the notch portion 82 according to the assumed torque, the torsional fatigue strength of the male spline portion 71C can be appropriately adjusted.

Further, as in the present embodiment, the notch portion 82 is provided at a position where the tooth portion 75C of the male spline portion 71C is divided in the axial direction (divided into a tip end side region 75Cc and a proximal end side region 75Cd). For example, the notch 82 can be provided so as to avoid both ends in the axial direction of the tooth portion 75C of the male spline portion 71C. Therefore, as described above, when the tooth portion 75C of the male spline portion 71C is provided with a predetermined twist angle, it is assumed that the notch portion 82 is fitted with the tooth portion 19a of the female spline portion 19. Even if it is provided in the region 83A, particularly in the region 84A where pressure welding is expected, at least a part of the tooth portion 75C of the male spline portion 71C (base end side region 75Cd) can be reliably pressure-welded to the female spline portion. (In this case, a pressure contact region 84 is formed between the base end side region 75Cd of the tooth portion 75C and the tooth portion 19a). Therefore, according to this configuration, while providing the notch portion 82 and providing the weakest portion in the male spline portion 71C, the circumferential direction in the spline fitting portion between the intermediate shaft and the female spline portion 19 of the inner joint member 16. It is possible to reduce the backlash of.

In the above description, the case where the notch portion 82 is composed of the reduced diameter portion 82a, the bottom portion 82b, and the enlarged diameter portion 82c has been illustrated, but of course, the present invention is not limited to this form. As long as interference with the tooth portion 19a of the female spline portion 19 can be avoided, various forms of notch portions can be adopted. Further, the notch portion 82 does not necessarily have to be provided in all the tooth portions 75 (75C) of the male spline portion 71 (71C), and is one of a plurality of tooth portions 75 (75C) arranged in the circumferential direction, for example. A notch 82 may be provided every other time. In short, as long as one or more notches 82 are provided in the region 83A where the female spline portion 19 is expected to be fitted with the tooth portion 19a, the form, the number, and the arrangement mode are arbitrary.

10,10B Fixed constant velocity universal joint 13,13B Outer joint member 16,16B Inner joint member 17 Ball 18 Cage 19, 19B Female spline part (inner joint member)
19a Tooth part 20, 39 Boot 23, 23B, 42 Stem part 24, 24B, 43 Male spline part (stem part)
30 Sliding constant velocity universal joint 31 Outer joint member 32 Tripod member 33 Roller unit 38 Female spline part (tripod member)
50 Drive shaft 70, 70B Intermediate shaft 71, 71B, 71C, 72 Male spline part (intermediate shaft)
73,74 Minimum smoothing part 75,75C Tooth part 75d, 75Cd Base end side area 76 Groove part 77 Cut-up part 79 Shoulder part 80 Stop ring 81 Mounting groove 82 Notch part 82a Reduced diameter part 82b Bottom part 82c Enlarged part 83 Fitting Area 83A Area where the female spline part is expected to fit with the tooth part 84 Pressure contact area 84A Area where pressure contact of the female spline part with the tooth part is expected D1, D5 Outer diameter dimensions (male spline part of the stem part)
D2, D4 outer diameter dimensions (male spline part of intermediate shaft)
D3 outer diameter dimension (minimum smoothing part of intermediate shaft)
Fa, Fb Reaction force Pc Axial center position S Root X Central axis

Claims (7)

An intermediate shaft connected to a fixed constant velocity universal joint arranged on the drive wheel side and a sliding constant velocity universal joint arranged on the differential gear side by spline fitting, and at least one of the above constant velocity universal joints. In a vehicle drive shaft provided with boots covering the joint with the intermediate shaft.
Among the tooth portions of the male spline portion provided on the intermediate shaft, a notch portion is provided in a region where fitting with the tooth portion of the female spline portion to be fitted with the spline is expected. Drive shaft for vehicles. The intermediate shaft has a cut-up portion located on the proximal end side of the male spline portion and increasing in outer diameter as the distance from the distal end side of the intermediate shaft increases.
A claim in which the notch portion is provided on a side of the tooth portion of the male spline portion closer to the cut-up portion than the axial center position of the region where the female spline portion is expected to be fitted with the tooth portion. The vehicle drive shaft according to item 1. The vehicle drive shaft according to claim 1 or 2, wherein the tooth portion of the male spline portion extends in a direction having a predetermined twist angle with respect to the central axis of the male spline portion. Claims 1 to 3 in which the notch portion is provided on the proximal end side of the tooth portion of the male spline portion with respect to the axial center position of the region where pressure contact with the tooth portion of the female spline portion is assumed. The vehicle drive shaft according to any one of the items. The notch portion is a region of the tooth portion of the male spline portion that is expected to be fitted with the tooth portion of the female spline portion, and is a position at which the tooth portion of the male spline portion is divided in the axial direction. The vehicle drive shaft according to any one of claims 1 to 4 provided in the above. Claims 1 to 1 in which the C amount of the male spline portion of the intermediate shaft is smaller than the C amount of the stem portion provided on the outer joint member of any one of the constant velocity universal joints to be fitted with the spline. The vehicle drive shaft according to any one of 5. The vehicle drive shaft according to any one of claims 1 to 6, wherein the male spline portion of the intermediate shaft is finished by rolling.

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