JP2018128130A - Differential device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a differential device for a vehicle which improves the durability of a pair of thrust bearings for rotatably supporting a drive pinion shaft to a differential carrier.SOLUTION: According to a differential device 10 for a vehicle, a longitudinal notch 42 whose dimension in a peripheral direction is longer than a dimension in a rotation axial core C direction, and in which an opposing faces opposing each other in the rotation axial core C direction adhere to each other by the impartment of a preload in the rotation axial core C direction for making inner races 18a, 20a of a front bearing 18 and a rear bearing 20 approximate each other to the inner races 18a, 20a is formed in a cylindrical spacer 24. Therefore, since an elastic coefficient of the cylindrical spacer 24 is lower than that of a cylindrical spacer 112 in which a longitudinal notch of a differential device 110 for a vehicle in, for example, a comparison example, is not formed, the reduction of a spacer load acting on the cylindrical spacer 24 at the release of an external load F is suppressed more than that in the comparison example.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a technique for improving the durability of a pair of thrust bearings that rotatably support a drive pinion shaft on a differential carrier in a vehicle differential apparatus.

  A cylindrical spacer is interposed between a pair of thrust bearings that support the drive pinion shaft on the differential carrier, and a preload in the direction of the rotation axis is applied to the cylindrical spacer, and at the same time, the cylindrical spacer rotates between the pair of thrust bearings. 2. Description of the Related Art A vehicle differential apparatus to which an axial preload is applied is known. For example, the differential apparatus for vehicles of patent document 1 is it. In the differential apparatus for a vehicle of Patent Document 1, a drive shaft such as a propeller shaft is connected to the drive pinion shaft at the shaft end opposite to the side where the drive pinion that meshes with the ring gear of the drive pinion shaft is integrally formed. The companion flange is splined. The companion flange is pressed against the inner race of one thrust bearing on the companion flange side of the pair of thrust bearings by tightening a nut screwed to a male screw provided at the end of the drive pinion shaft. Being fixed. As a result, a preload in the direction in which they approach each other is applied between the inner races of the pair of thrust bearings, and a part of the preload is caused by the cylindrical spacer provided between the pair of thrust bearings. While being supported, another part of the preload is supported by a differential carrier to which an outer race of a pair of thrust bearings is fitted. In this state, a spacer preload in the direction of the rotational axis is applied to the cylindrical spacer, and a preload between outer races in a direction approaching each other is applied to the outer races of the pair of thrust bearings.

JP-A-10-103454

  By the way, a vehicle in which a predetermined preload is applied between the inner races of the pair of thrust bearings until the cylindrical spacer interposed between the inner races of the pair of thrust bearings is plastically deformed in the plastic region. In the differential apparatus for a vehicle, for example, an excessive external load in the direction of the rotation axis that may further compress the cylindrical spacer with respect to the drive pinion shaft during vehicle travel may be considered. When such an excessive external load in the rotational axis direction is applied, the cylindrical spacer is further plastically deformed in the compression direction in the rotational axis direction. The spacer preload acting on the cylindrical spacer after the release of the excessive external load is based on the elastic coefficient of the cylindrical spacer and the amount of plastic deformation in the compression direction of the cylindrical spacer before the excessive external load is applied. Decrease from the value of. This reduction in the spacer preload of the cylindrical spacer increases the preload between the outer races in the direction of approaching each other, which has been applied to the outer race of the pair of thrust bearings, so that the durability of the pair of thrust bearings can be reduced. There was sex.

  The present invention has been made against the background of the above circumstances, and its object is to provide an outer race for a pair of thrust bearings by the input of an excessive external load in the direction of the rotational axis that compresses the cylindrical spacer. An object of the present invention is to provide a vehicle differential apparatus that suppresses a decrease in the durability of a thrust bearing due to an increase in the preload between outer races applied between them.

  The gist of the present invention is that a differential carrier that houses a differential mechanism, a drive pinion shaft that is rotatably supported by the differential carrier via a pair of thrust bearings and transmits power to the differential mechanism, A plastically deformable cylindrical spacer interposed between the inner races of the pair of thrust bearings, and the outer races of the pair of thrust bearings are respectively fitted to the differential carriers so as to be inaccessible to each other. A preload in a direction in which the inner races of the thrust bearings approach each other is applied to the inner races of the pair of thrust bearings fitted on the drive pinion shaft, and a part of the preload is supported by the cylindrical spacer. Spacer preload is applied, and the other part of the preload excluding the part is the pair of thrust bearings. A differential device for a vehicle of a type in which a preload between outer races is applied by being supported by an outer race, wherein the cylindrical spacer has a circumferential dimension longer than a dimension in the rotational axis direction, In addition, a longitudinal notch that is in close contact with the rotation axis is formed by applying the preload.

  According to the present invention, the cylindrical spacer is formed with a longitudinal notch that is longer in the circumferential direction than the dimension in the direction of the rotation axis, and that adheres in the direction of the rotation axis by the application of the preload. ing. For this reason, the elastic coefficient in the direction of the rotation axis of the cylindrical spacer is lower than, for example, the cylindrical spacer in which the longitudinal notch is not formed. Therefore, an excessive external load input to the drive pinion shaft The reduction of the spacer load acting on the cylindrical spacer after the release is reduced is suppressed as compared with the cylindrical spacer in which the longitudinal notch is not formed. Thereby, since the increase in the preload between the outer races applied between the outer races of the pair of thrust bearings after the release of the external load is suppressed, a decrease in the durability of the pair of thrust bearings is suppressed.

  Here, the pair of thrust bearings means bearings having a function of receiving a thrust load. The pair of thrust bearings preferably includes a tapered roller bearing, but may be a ball bearing that can receive a thrust load in addition to a radial load, for example. The cylindrical spacer may have a cross-sectional shape that is not only circular but also polygonal or elliptical.

FIG. 3 is a diagram illustrating a partial cross-sectional view of the vehicle differential device according to the present embodiment when viewed from the horizontal direction, and the loads acting on the front bearing, the cylindrical spacer, the rear bearing, and the like in the assembled state are indicated by black arrows. Yes. FIG. 2 is a perspective view schematically showing a state before assembly of a cylindrical spacer between a front bearing and a rear bearing in the vehicle differential device of FIG. 1. FIG. 2 is a side view schematically showing a state of a cylindrical spacer in an assembled state assembled between a front bearing and a rear bearing in the vehicle differential device of FIG. 1. FIG. 3 is a deflection-load characteristic diagram of the cylindrical spacer of FIG. 2. It is a figure which shows typically the state before the assembly | attachment of the cylindrical spacer in the differential apparatus for vehicles of a comparative example. FIG. 2 is a partial cross-sectional view of the vehicle differential device of FIG. 1 viewed from the horizontal direction, and a drive pinion shaft tensile load when an external load F in the direction of the rotational axis C is applied to the front bearing and the rear bearing; The bearing load is indicated by a white arrow. FIG. 2 is a partial cross-sectional view of the vehicle differential device of FIG. 1 viewed from the horizontal direction, after the external load F is released when the external load F applied to the front bearing and the rear bearing in the direction of the rotation axis C is eliminated. , The loads acting on the front bearing, the cylindrical spacer, the rear bearing and the like are indicated by black arrows. In the differential apparatus for vehicles of FIG. 1, it is a figure which shows the relationship between KB * KS / (KB + KDP) and KB in Formula (12) established after external load F releasing. It is a side view which shows typically the state before the assembly | attachment of the cylindrical spacer in the differential apparatus for vehicles of another Example.

  Hereinafter, an embodiment of a differential device for a vehicle according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram illustrating a partial cross-sectional view of a vehicle differential apparatus 10 according to the present embodiment as viewed from the horizontal direction. The vehicle differential device 10 is a differential gear device that distributes a driving force (torque) transmitted from a propeller shaft to a pair of left and right axles and allows differential rotation of the pair of left and right axles. As shown in FIG. 1, the vehicle differential apparatus 10 includes a differential mechanism 11, a ring gear 22 attached to the differential mechanism 11, a drive pinion shaft 16 that transmits power to the differential mechanism 11, and a differential. A differential carrier 12 that is a non-rotating member that houses the mechanism 11 and the drive pinion shaft 16, and a pair of bearings that support the drive pinion shaft 16 so as to be rotatable (spinning) around the rotation axis C with respect to the differential carrier 12. That is, the front bearing (front bearing) 18 and the rear bearing (rear bearing) 20 are made of a metal that can be elastically deformed and plastically deformed, for example, and interposed between the inner races 18a and 20a of the pair of front bearing 18 and rear bearing 20. A cylindrical spacer 24. The drive pinion shaft 16 includes a drive pinion 14 that meshes with the ring gear 22. The differential mechanism 11 includes a pair of pinions disposed on the inner peripheral side of the ring gear 22, a pair of side gears meshed with the pair of pinions, and a differential case in which the ring gear 22 is attached by bolts or the like. ing. The ring gear 22 is fixed to the differential case, and the differential case is rotatably supported by the differential carrier 12 via a bearing provided between the differential gear 12 and the differential case 12.

  The drive pinion shaft 16 is connected to the propeller shaft via a companion flange 26 and a universal joint so as to be rotated integrally with a propeller shaft (not shown). The drive pinion shaft 16 serves as an input rotation member of the vehicle differential device 10. Equivalent to. The companion flange 26 includes a cylindrical portion 28 having a spline formed on the inner peripheral surface. The drive pinion shaft 16 has a spline on its outer peripheral surface at the shaft end opposite to the shaft end where the drive pinion 14 is provided, and a male screw 30 on the opposite side of the drive pinion 14 from the spline. I have. The companion flange 26 is configured such that the cylindrical portion 28 is fitted to the shaft end portion of the drive pinion shaft 16 opposite to the drive pinion 14 by spline fitting, and the nut 32 screwed into the male screw 30 is on the drive pinion 14 side. It is connected to the drive pinion shaft 16 in a state where it is pressed against the inner race 18a of the front bearing 18 via the disc-like member 19 by the tightening force.

  Here, the drive pinion 14 and the ring gear 22 meshed with each other are, for example, a hypoid gear pair whose axes do not intersect each other, and the rotational axis of the drive pinion 14 is lower than the rotational axis of the ring gear 22. The relative positional relationship is on the side (vertically below). Further, the pair of pinions of the differential mechanism 11 are provided on the inner peripheral side of the ring gear 22 so as to be capable of rotating about the axis, and the axis is rotated integrally with the rotation of the ring gear 22. It is configured. The pair of side gears of the differential mechanism 11 are meshed with the pair of pinions and are coaxially connected to the pair of axles, respectively, and are output rotation members that are rotated integrally with the axles. It corresponds to. The front bearing 18 and the rear bearing 20 are preferably formed by inner races 18a and 20a fixed to the outer peripheral surface of the drive pinion shaft 16 and outer races 18b and 20b fixed to the differential carrier 12. These are tapered roller bearings (tapered roller bearings) in which a plurality of tapered rollers 18c and 20c are disposed as rolling elements, and correspond to a pair of thrust bearings of the present invention. Since the drive pinion shaft 16 has a larger diameter on the outer peripheral surface on the drive pinion 14 side than the diameter of the outer peripheral surface of the other part, the diameter of the inner peripheral surface of the inner race 20a of the rear bearing 20 is the inner diameter of the front bearing 18. It is larger than the diameter of the inner peripheral surface of the race 18a.

  In the inner race 20a of the rear bearing 20, an annular end surface on the drive pinion 14 side is brought into contact with the drive pinion 14, and an annular end surface on the companion flange 26 side is a large-diameter portion 38 (described later in FIG. 2) of the cylindrical spacer 24. ). The outer race 20 b of the rear bearing 20 is brought into contact with an annular inner peripheral protrusion 34 whose annular end surface on the companion flange 26 side protrudes inward from the differential carrier 12 via a disk-like member 35. The outer race 18b of the front bearing 18 is brought into contact with an annular inner peripheral protrusion 36 whose inner end surface on the drive pinion 14 side protrudes inward from the differential carrier 12. The inner race 18a of the front bearing 18 has an annular end surface on the companion flange 26 side abutted against the cylindrical portion 28 of the companion flange 26 via the disk-shaped member 19, and an annular end surface on the drive pinion 14 side is a cylindrical spacer. 24 is brought into contact with an annular end surface of a small-diameter portion 40 (shown in FIG. 2) described later. The outer race 18b of the front bearing 18 and the outer race 20b of the rear bearing 20 are fitted to the differential carrier 12 so as to be inaccessible to each other by the inner peripheral protrusions 34 and 36.

  FIG. 2 is a perspective view schematically showing a state before the cylindrical spacer 24 is assembled between the front bearing 18 and the rear bearing 20 in the vehicle differential apparatus 10. FIG. 3 is a side view schematically showing the state of the cylindrical spacer 24 in the assembled state assembled between the front bearing 18 and the rear bearing 20 in the vehicle differential apparatus 10. Here, in the assembled state, the cylindrical spacer 24 is plastically deformed in the plastic region by a load in the compression direction in the direction of the rotation axis C. In FIG. 2, the cylindrical spacer 24 has a cylindrical shape, and both end surfaces thereof are annular end surfaces on the companion flange 26 side of the inner race 20 a of the rear bearing 20 or annular rings on the drive pinion 14 side of the inner race 18 a of the front bearing 18. The diameter of the inner peripheral surface on the rear bearing 20 side is made larger than the diameter of the inner peripheral surface on the front bearing 18 side so as to be brought into contact with the end surfaces. That is, the cylindrical spacer 24 includes a cylindrical large-diameter portion 38 on the rear bearing 20 side, and a cylindrical small-diameter portion 40 on the front bearing 18 side. The cylindrical spacer 24 is one notched in the circumferential direction around the rotation axis C from the rear bearing 20 side end of the large diameter portion 38 so that the dimension in the circumferential direction is longer than the dimension in the rotation axis C direction. A longitudinal notch 42 is provided. When the cylindrical spacer 24 is in an assembled state in which the cylindrical spacer 24 is deformed at least in the plastic region by the tightening force of the nut 32 screwed into the male screw 30 provided at the shaft end portion of the drive pinion shaft 16, The opposing surfaces 44 facing each other in the direction of the rotational axis C of the cylindrical notch 42 are in close contact with each other, and the longitudinal notch 42 is crushed. The close contact surface where the opposing surfaces 44 facing each other in the direction of the rotation axis C of the longitudinal notch 42 are in close contact with each other is a spiral shape in the cylindrical large diameter portion 38, and in FIG. 3, the close contact surface is indicated by a solid line and a broken line. Has been.

  In FIG. 1, the static differential assembly 10 for the vehicle acts on the companion flange 26, the front bearing 18, the cylindrical spacer 24, the rear bearing 20, the drive pinion shaft 16 and the drive pinion 14, respectively. The load is indicated by a black arrow. Here, the static assembled state of the vehicle differential device 10 is a state in which an excessive external load F in the compression direction for compressing the cylindrical spacer 24 in the direction of the rotation axis C is not applied. When the nut 32 is tightened, a load equal to the drive pinion shaft tensile load (D / P tensile load) FDP0 acting in the opposite directions in the rotational axis C direction is applied from the companion flange 26 to the inner race 18a of the front bearing 18. In addition, the drive pinion 14 acts on the inner race 20 a of the rear bearing 20. That is, the preload FDP0 in the direction in which they approach each other is applied to the inner race 18a of the front bearing 18 and the inner race 20a of the rear bearing 20 fitted to the drive pinion shaft 16. Part of the preload FDP0 in the direction in which the inner races 18a and 20a are brought close to each other is supported by the cylindrical spacer 24, so that the cylindrical spacer 24 faces the rotation axis C of the longitudinal notch 42. In the state where the opposed surfaces are in close contact with each other, deformation occurs in the plastic region, and the cylindrical spacer 24 is given a spacer preload FS0. In addition, the other part of the preload FDP0 in the direction in which the inner races 18a and 20a are brought closer to each other, except for the part of the preload FDP0, is an inner peripheral protrusion 36 that contacts the outer race 18b of the front bearing 18 and the rear. By being supported by the inner peripheral protrusion 34 that contacts the outer race 20b of the bearing 20, the outer races 18b and 20b are given a preload FB0 between the outer races in a direction approaching each other.

  FIG. 4 is a deflection-load characteristic diagram of the cylindrical spacer 24 provided in the vehicle differential apparatus 10. 4 shows a deflection-load characteristic diagram of the cylindrical spacer 24, the horizontal axis representing the amount of displacement (the amount of deflection) xs (mm) in the compression direction of the cylindrical spacer 24 in the rotational axis C direction, and the spacer load fs ( kN) and a vertical axis representing kN). Further, in FIG. 4, the relationship between the displacement amount xs in the compression direction of the cylindrical spacer 24 and the spacer load fs (the deflection-load characteristic line) is a range where the displacement amount xs is smaller than the lower limit value Xs1 of the assembly range described later. In FIG. 1, the amount of displacement xs is indicated by a thick solid line in the range of the assembly range lower limit value Xs1 or more. Here, the assembling range is that the spacer load fs input to the cylindrical spacer 24 by the tightening force of the nut 32 becomes the plastic region load Fsy, and the cylindrical spacer 24 is compressed in the plastic region in a static assembled state. This is a set range of the displacement amount xs of the cylindrical spacer 24 suitable for guaranteeing plastic deformation in the direction. Here, the plastic region is a region where only the displacement amount xs of the cylindrical spacer 24 increases without increasing the spacer load fs, and the plastic region load Fsy is the spacer load fs in the plastic region. That is, in FIG. 4, the deflection-load characteristic line of the cylindrical spacer 24 indicates that the spacer load fs is smaller than the plastic zone load Fsy, and there is a proportional relationship between the displacement amount xs of the cylindrical spacer 24 and the spacer load fs. The elastic region is indicated by a one-dot chain line, and the plastic region where the spacer load fs does not change in the plastic region load Fsy is indicated by a thick solid line. In addition, in FIG. 4, the deflection-load characteristic diagram of the cylindrical spacer 112 of the differential device 110 for a vehicle according to the comparative example described later shows the elastic region and the plastic region with thick solid lines, so that the cylindrical shape of this embodiment is obtained. It is shown together with a deflection-load characteristic diagram of the spacer 24.

  Here, the cylindrical spacer 112 of the differential apparatus 110 for vehicles of a comparative example is demonstrated using FIG. The cylindrical spacer 112 of the vehicle differential apparatus 110 is similarly configured with the same material as the cylindrical spacer 24 of the present embodiment. However, as illustrated in FIG. 5, the cylindrical spacer 112 includes the large-diameter portion 114. Alternatively, the small-diameter portion 116 does not have a longitudinal cutout in which the circumferential dimension around the rotation axis C is longer than the dimension in the rotation axis C direction.

  As shown in FIG. 3, the cylindrical spacer 24 of the present embodiment is in a state in which the longitudinal notch 42 is crushed in the assembled state, and thus the cylindrical spacer 24 of the present embodiment and the cylindrical shape of the comparative example. The spacer 112 has the same plastic zone load Fsy. Therefore, in FIG. 4, the deflection-load characteristic line of the plastic region of the cylindrical spacer 112 of the comparative example is common to the deflection-load characteristic line of the plastic region of the cylindrical spacer 24 of this embodiment, and is represented by a thick solid line. Is done. Further, since the cylindrical spacer 112 of the comparative example does not have a longitudinal notch, the rigidity KS in the direction of the rotation axis C in the elastic region, that is, the elastic coefficient is the rotation in the elastic region of the cylindrical spacer 24 of the present embodiment. It is higher than the rigidity KS in the direction of the axis C, that is, the elastic coefficient. In FIG. 4, since the elastic modulus is expressed as an inclination in the elastic region of the deflection-load characteristic line, the inclination of the deflection-load characteristic line in the elastic region of the cylindrical spacer 112 of the comparative example indicated by a thick solid line is one point. This is larger than the inclination of the deflection-load characteristic line in the elastic region of the cylindrical spacer 24 of the present embodiment indicated by the chain line. Note that the horizontal axis of FIG. 4 indicates that the displacement amount xs in the compression direction of the cylindrical spacer 112 before assembly in the differential apparatus 110 for the vehicle of the comparative example is zero, and the deflection of the cylindrical spacer 24 of the present embodiment. The load characteristic line shows the elastic region so that the assembly range is the same as the assembly range of the cylindrical spacer 112 of the comparative example.

The inner race 18a fitted to the drive pinion shaft 16 so that the displacement amount xs in the compression direction in the direction of the rotation axis C of the cylindrical spacer 24 of the present embodiment and the cylindrical spacer 112 of the comparative example is within the assembly range. The nut 32 is tightened with a predetermined force using, for example, a torque wrench or the like so that a preload FDP0 in a direction in which the two members 20a approach each other is applied. As a result, the cylindrical spacer 24 of this embodiment and the cylindrical spacer 112 of the comparative example are plastically deformed in the plastic region, and as shown in FIG. 4, the cylindrical spacer 24 of this embodiment and the cylindrical spacer of the comparative example 112, plastic region loads Fsy that are equal to each other are respectively applied as spacer preloads FS0. FIG. 4 shows an assembly in which the spacer load fs applied to the cylindrical spacer 24 and the cylindrical spacer 112 becomes the plastic region load Fsy in the static assembled state of the vehicle differential device 10 and the vehicle differential device 110. A suitable example of the displacement amount xs within the range is shown as the I position. Further, in the vehicle differential apparatus 10 of the present embodiment and the vehicle differential apparatus 110 of the comparative example, as shown in FIG. 1, in the static assembly state, the rotational axis C obtained from the following equation (1) Direction outer race preload (bearing preload) FB0 (N) is applied to the outer race 18b of the front bearing 18 and the outer race 20b of the rear bearing 20, respectively.
FDP0 = FB0 + FS0 (1)

  Meanwhile, in the vehicle differential apparatus 10, during the traveling of the vehicle, an excessive external load F in the compression direction that compresses the cylindrical spacer 24 in the rotation axis C direction (axial direction) through the companion flange 26 and the drive pinion 14. There are cases where the inner race 18a of the front bearing 18 and the inner race 20a of the rear bearing 20 are instantaneously added. FIG. 6 is a partial cross-sectional view of the vehicle differential device 10 viewed from the horizontal direction. In a static assembly state, the companion flange 26, the front bearing 18, the cylindrical spacer 24, the rear bearing 20, and the drive pinion shaft 16 are shown. And the drive pinion when the excessive external load F in the direction of the rotational axis C is applied to the front bearing 18 and the rear bearing 20 in addition to the loads acting on the drive pinion 14 indicated by black arrows. The shaft tensile load and the bearing load are indicated by white arrows.

In the vehicle differential device 10, for example, when the external load F in the direction of the rotational axis C is applied to the inner race 18 a of the front bearing 18 or the inner race 20 a of the rear bearing 20, the cylindrical spacer 24 is plastically deformed by the external load F. Be made. At this time, as shown in FIG. 4, the displacement amount xs and the spacer load fs in the compression direction of the cylindrical spacer 24 in the direction of the rotational axis C are the plasticity indicated by the solid line from the I position in the static assembly state. The amount of displacement X (mm) in the compression direction in the plastic region due to the external load F of the cylindrical spacer 24, that is, the additional plasticity amount X (mm) of the cylindrical spacer 24, in the direction of the arrow To the J position. The spacer preload change amount ΔFS0, which is the amount of change from the spacer preload FS0 in the static assembly state when the external load F is applied, is assumed to be zero because it is a plastic region. Further, the additional plasticity amount X of the cylindrical spacer 24 is calculated from the composite spring constant K and the external load F of the drive pinion shaft, the bearing and the differential carrier based on the following equation (2).
X = F / K (2)

The combined spring constant K of the drive pinion shaft, the bearing and the differential carrier in the above equation (2) is calculated based on the following equation (3) in the direction of the rotational axis C of the combined drive spring pin KB and the drive pinion shaft 16 of the drive pinion shaft 16. Calculated from the stiffness KDP.
K = KB + KDP (3)

The combined spring constant KB of the bearing and the differential carrier in the above equation (3) is based on the following equation (4), the rigidity KBF of the front bearing 18 in the rotational axis C direction, and the rigidity of the rear bearing 20 in the rotational axis C direction. It is calculated from the KBR and the rigidity KC of the differential carrier 12 in the direction of the rotational axis C.
KB = 1 / (1 / KBF + 1 / KBR + 1 / KC) (4)

Further, in the vehicle differential apparatus 10, the outer race prediction in a static assembly state when an external load F for compressing the cylindrical spacer 24 in the direction of the rotation axis C is applied to the front bearing 18 and the rear bearing 20. Drive that is a decrease from the drive pinion shaft tensile load FDP0 in the static assembly state when the outer race preload increase ΔFB0 (N) that is an increase from the load FB0 and the external load F is applied. The pinion shaft tensile load reduction amount ΔFDP0 (N) is obtained based on the following equations (5) and (6), respectively. The relationship between the outer race preload increase amount ΔFB0 and the drive pinion shaft tensile load decrease amount ΔFDP0 is expressed by the following equation (7).
ΔFB0 = KB × X (5)
ΔFDP0 = KDP × X (6)
ΔFB0 + ΔFDP0 = F (7)

  Further, in the vehicle differential device 110 of the comparative example and the vehicle differential device 10 of the present embodiment, the combined spring constant K of the drive pinion shaft, the bearing and the differential carrier obtained from the above equations (3) and (4) is the same. Value. For this reason, when the same external load F is applied in the vehicle differential device 10 and the vehicle differential device 110, the additional plastic amount X of the cylindrical spacer due to the external load F is equal in the vehicle differential devices 10 and 110. . Accordingly, as shown in FIG. 4, similarly, when an external load F is applied in the vehicle differential device 110 of the comparative example, the displacement amount xs and the spacer load fs of the cylindrical spacer 112 in the rotation axis C direction are: It moves in the direction of the black arrow from the I position by the additional plastic amount X of the cylindrical spacer along the deflection-load characteristic line in the plastic region, and reaches the J position. Therefore, the outer race preload increase amount ΔFB0, which is an increase from the outer race preload FB0 in the static assembly state when the external load F is applied in the differential device 110 for the comparative example, is This is equal to the increase amount ΔFB0 between the outer races due to the external load F in the vehicle differential apparatus 10 of the present embodiment.

  FIG. 7 is a partial cross-sectional view of the vehicle differential apparatus 10 as viewed from the horizontal direction, and the companion after the external load F applied to the front bearing 18 and the rear bearing 20 in the direction of the rotational axis C is released. Loads acting on the flange 26, the front bearing 18, the cylindrical spacer 24, the rear bearing 20, the drive pinion shaft 16, and the drive pinion 14 are indicated by black arrows.

When the external load F is released in the vehicle differential device 10 or the vehicle differential device 110, the spacer load fS decreases due to elastic deformation (return), and the compression direction of the cylindrical spacers 24 and 112 in the direction of the rotational axis C The amount of displacement xs decreases. The spacer preload decrease amount ΔFS (N), which is a decrease amount from the spacer preload FS0 in the static assembly state, is calculated in the direction of the rotational axis C of the cylindrical spacers 24 and 112 based on the following equation (8). Rigidity KS, that is, the elastic coefficient of the cylindrical spacers 24, 112 and the additional plasticity amount X of the cylindrical spacers 24, 112. Further, the spacer preload FS after the external load F is released is obtained from the following equation (9).
ΔFS = KS × X (8)
FS = FS0−ΔFS (9)

Further, the compression is a difference between the displacement amount xs in the rotation axis C direction when the external load F of the cylindrical spacers 24 and 112 is applied and the displacement amount xs in the rotation axis C direction after the external load F is released. The position change amount Δx in the direction opposite to the direction is obtained from the spacer preload decrease amount ΔFS and the combined spring constant K of the drive pinion shaft, the bearing and the differential carrier based on the following equation (10).
Δx = ΔFS / K (10)

  As shown in FIG. 4, when the external load F applied to the front bearing 18 and the rear bearing 20 in the direction of the rotational axis C is released, the cylindrical spacers 24 and 112 in the direction of the rotational axis C are released. The displacement amount xs in the compression direction and the spacer load fs are determined in the respective elastic regions from the J position where the additional load F has shifted in the black arrow direction by the external load F from the I position in the static assembly state. Along the line shown by the broken line drawn parallel to the load characteristic diagram, the spacer preload reduction amount ΔFS obtained from the above equation (8) and the position change amount Δx obtained from the above equation (10) are changed. , Respectively, R1 position and R2 position. In FIG. 4, the transition from the J position to the R2 position after deformation of the additional plasticity amount X due to the external load F from the I position in the cylindrical spacer 112 of the comparative example is indicated by a black arrow. In FIG. 4, the spacer preload decrease amount of the cylindrical spacer 24 after releasing the external load F is indicated by ΔFS1, and the spacer preload decrease amount of the cylindrical spacer 112 is indicated by ΔFS2. As described above, the rigidity KS of the cylindrical spacer 24 in the direction of the rotational axis C, that is, the elastic coefficient is lower than the rigidity KS of the cylindrical spacer 112 in the direction of the rotational axis C, that is, the elastic coefficient. The decrease amount ΔFS1 is smaller than the spacer preload decrease amount ΔFS2 of the cylindrical spacer 112. The spacer preloads FS1 and FS2 after the external load F is released at the R1 position and the R2 position of the cylindrical spacers 24 and 112 obtained from the spacer preload reduction amounts ΔFS1 and ΔFS2 are shown in FIG. 4. The spacer preload FS1 of the cylindrical spacer 24 after the external load F is released is larger than the spacer preload FS2 of the cylindrical spacer 112 after the external load F is released.

Here, in the vehicle differential device 10 and the vehicle differential device 110, the outer race in the direction of the rotation axis C acting between the outer race 18b of the front bearing 18 and the outer race 20b of the rear bearing 20 after the external load F is released. The outer race preload (bearing preload) increase amount ΔFB (N), which is the change amount (increase amount) of the preload FB, is calculated from the position change amount Δx of the cylindrical spacer, the bearing and the differential, based on the following equation (11). It is obtained from the composite spring constant KB of the carrier.
ΔFB = KB × Δx (11)

  Since the rigidity KS of the cylindrical spacer 24 in the direction of the rotational axis C is lower than the rigidity KS of the cylindrical spacer 112 in the direction of the rotational axis C, the reduction amount ΔFS1 of the spacer load fs of the cylindrical spacer 24 is less than that of the cylindrical spacer 112. It is smaller than the reduction amount ΔFS2 of the spacer load fs. For this reason, in the vehicle differential apparatus 10 of the present embodiment, the pre-load increase amount ΔFB between the outer races after the external load F is released can be reduced as compared with the vehicle differential apparatus 110 of the comparative example. . Thereby, in the vehicle differential apparatus 10 of the present embodiment, the increase in the pre-load FB between the outer races acting between the outer race 18b of the front bearing 18 and the outer race 20b of the rear bearing 20 after the external load F is released is compared. It can suppress compared with the differential apparatus 110 for vehicles of an example.

Further, the following equation (12) is derived from the above equation (3), the above equation (8), the above equation (10), and the above equation (11). From the following expression (12), it can be seen that the lower the rigidity KS of the cylindrical spacer 24 in the direction of the rotation axis C, the smaller the outer race preload increase ΔFB after the external load F is released. FIG. 8 is a diagram showing the relationship between KB × KS / (KB + KDP) and KB in the following equation (12). As shown in FIG. 8, the smaller the combined spring constant KB of the bearing and the differential carrier is, the smaller KB × KS / (KB + KDP) is. Therefore, the smaller the combined spring constant KB of the bearing and the differential carrier is, the smaller the external load is. The amount of preload increase ΔFB between outer races after F release becomes smaller.
ΔFB = KB × KS × X / (KB + KDP) (12)

The drive pinion shaft tensile load decrease amount ΔFDP (N), which is the change amount (reduction amount) of the drive pinion shaft tensile load FDP after the external load F is released, is obtained from the following equation (13). Further, the relationship between the outer race preload increase amount ΔFB, the drive pinion shaft tensile load decrease amount ΔFDP, and the spacer preload decrease amount ΔFS after release of the external load F is expressed by the following equation (14). Further, after the external load F is released, the relationship between the outer race preload FB, the drive pinion shaft tensile load FDP, and the spacer preload FS is expressed by the following equation (15).
ΔFDP = KDP × Δx (13)
ΔFB + ΔFDP = ΔFS (14)
FDP = FB + FS (15)

  As described above, according to the vehicle differential apparatus 10 of the present embodiment, the cylindrical spacer 24 has a circumferential dimension longer than the dimension in the rotational axis C direction and is fitted to the drive pinion shaft 16. Longitudinal cutouts in which opposed surfaces in the rotational axis C direction are brought into close contact with each other by applying a preload in the rotational axis C direction that brings the front bearing 18 and the inner bearings 18a of the rear bearing 20 close to each other. 42 is formed. For this reason, the rigidity KS, that is, the elastic coefficient in the direction of the rotation axis C of the cylindrical spacer 24 is lower than that of the cylindrical spacer 112 in which the longitudinal notch of the differential device 110 for a vehicle of the comparative example is not formed, for example. The amount of reduction of the spacer preload acting on the cylindrical spacer 24 after the release of the excessive external load F applied to the front bearing 18 and the rear bearing 20 and compressing the cylindrical spacer 24 in the direction of the rotation axis C ΔFS1 is smaller than the decrease amount ΔFS2 of the spacer preload after releasing the external load F of the cylindrical spacer 112 in which the longitudinal notch is not formed. Thus, from the above formula (10) and the above formula (11), in the vehicle differential apparatus 10 of the present embodiment, the pre-load increase amount ΔFB between the outer races after the external load F is released is the vehicle differential apparatus of the comparative example. The outer race preload increase amount ΔFB after the external load F is released at 110 is smaller than the outer race preload applied to the outer race 18b of the front bearing 18 and the outer race 20b of the rear bearing 20 after the external load F is released. Since the increase in the load FB is suppressed as compared with the vehicle differential device 110 of the comparative example, a decrease in durability of the front bearing 18 and the rear bearing 20 is suppressed.

  Further, according to the vehicle differential apparatus 10 of the present embodiment, the cylindrical spacer 24 is in a state in which the longitudinal notch 42 is crushed in the assembled state, as shown in FIG. The load Fsy is equal to the cylindrical spacer 112 of the comparative example. For this reason, in the differential apparatus 10 for vehicles of a present Example, the assembly | attachment precision can be ensured with the fastening force (set load) of the nut 32 equivalent to the differential apparatus 110 for vehicles of a comparative example.

  Further, the vehicle differential apparatus 10 according to the present embodiment includes a vehicle differential apparatus 110 including a plastic spacer in which a cylindrical notch 42 is not formed in that the cylindrical spacer 24 includes a longitudinal notch 42. Different. For this reason, in the differential apparatus 10 for vehicles of a present Example, the differential mechanism 11 and the drive pinion shaft 16 can be assembled | attached by the assembly | attachment process similar to the differential apparatus 110 for vehicles of a comparative example. Thereby, the expense for a design change from the differential apparatus 110 for vehicles of a comparative example can be suppressed.

  Next, another embodiment of the present invention will be described. In the following embodiments, parts that are substantially the same in function as those of the above embodiments are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 9 is a side view schematically showing a state before assembly of the cylindrical spacer 52 between the front bearing 18 and the rear bearing 20 in the vehicle differential device 50. The cylindrical spacer 52 of this embodiment is common except that the longitudinal notch 58 is different from the longitudinal notch 42 formed in the cylindrical spacer 24 of the above-described embodiment. Hereinafter, the cylindrical spacer 52 will be described with reference to FIG.

  In FIG. 9, the cylindrical spacer 52 is notched in the circumferential direction at an angle range of about 90 degrees around the rotation axis C, and has a longitudinal notch 58 whose circumferential dimension is longer than the dimension in the rotation axis C direction. There are several. Due to the preload in the direction of the rotational axis C that causes the inner race 18a of the front bearing 18 and the inner race 20a of the rear bearing 20 to approach each other, the opening edge of the longitudinal notch 58 is brought into close contact in the direction of the rotational axis C, thereby forming a cylindrical shape. The nut 32 is tightened so that the spacer 52 is plastically deformed in the assembly range. For example, the cylindrical spacer 52 has a lower rigidity KS in the direction of the rotational axis C than the cylindrical spacer 112 that does not have the longitudinal notch of the vehicle differential device 110 of the comparative example. For this reason, in the differential apparatus 50 for vehicles, compared with the differential apparatus 110 for vehicles of a comparative example, the spacer preload reduction | decrease amount (DELTA) FS after the external load F release can be made small. According to the vehicle differential device 50 of the present embodiment, the same effects as those of the vehicle differential device 10 of the first embodiment can be obtained.

  As mentioned above, although this invention was demonstrated in detail with reference to the table | surface and drawing, this invention can be implemented in another aspect, and can be variously changed in the range which does not deviate from the main point.

10, 50: Vehicle differential device 11: Differential mechanism 12: Differential carrier 16: Drive pinion shaft (drive pinion shaft)
18: Front bearing (thrust bearing)
20: Rear bearing (thrust bearing)
24, 52: cylindrical spacers 42, 58: longitudinal notch C: rotational axis FDP0: drive pinion shaft tensile load (preload)
FB0: Outer race preload FS0: Spacer preload

Claims (1)

A differential carrier that houses a differential mechanism, a drive pinion shaft that is rotatably supported by the differential carrier via a pair of thrust bearings and transmits power to the differential mechanism, and an inner race of the pair of thrust bearings An outer race of the pair of thrust bearings fitted on the differential carrier in an inaccessible manner, and an inner race of the pair of thrust bearings mutually A preload in the approaching direction is applied to the inner races of the pair of thrust bearings fitted on the drive pinion shaft, and a part of the preload is supported by the cylindrical spacer so that a spacer preload is applied. And the other part of the preload except the part is supported by the outer race of the pair of thrust bearings. A differential device for a vehicle of the type between outer race preload is applied by Rukoto,
The cylindrical spacer has a circumferential dimension longer than a dimension in the rotational axis direction, and is formed with a longitudinal notch that is in close contact with the rotational axis direction by applying the preload. A differential device for a vehicle.

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