Boots for constant velocity universal joints and constant velocity universal joints equipped therewith

Abstract

The present invention provides a boot for a constant velocity universal joint that offers high assembly ease even without a bellows section, and a constant velocity universal joint equipped with the boot. [Solution] This is a boot for a constant velocity universal joint, comprising a large-diameter cylindrical portion that is attached to the outer circumferential surface of the outer joint member of the constant velocity universal joint, a small-diameter cylindrical portion that is attached to the outer circumferential surface of the shaft connected to the inner joint member of the constant velocity universal joint, and a connecting portion that connects the large-diameter cylindrical portion and the small-diameter cylindrical portion and has a curved portion that is convex in the axial direction. A convex portion is provided at the end of the small-diameter cylindrical portion opposite the connecting portion in the axial direction, protruding radially outward from the outer diameter of the small-diameter cylindrical portion.

Description

Technical Field

[0001] The present invention relates to a boot for a constant velocity universal joint and a constant velocity universal joint provided with the same.

Background Art

[0002] As constant velocity universal joints, Zeppa-type constant velocity universal joints and undercut-free type constant velocity universal joints are known. These constant velocity universal joints can achieve a maximum operating angle of 45° or more, and are mainly applied to the wheel side of front drive shafts of automobiles. When such a constant velocity universal joint is provided with a boot for preventing lubricant from flowing out and sand dust or the like from entering, a boot having a bellows portion is often applied to follow a high operating angle. As shown in FIG. 5 for example, a boot 100 having a bellows portion includes a large-diameter cylindrical portion 102 attached to the outer periphery of an outer joint member 101, a small-diameter cylindrical portion 104 attached to the outer periphery of a shaft 103, and a bellows portion 105 connecting the large-diameter cylindrical portion 102 and the small-diameter cylindrical portion 104. The bellows portion 105 has alternating crests 105a protruding radially outward and troughs 105b protruding radially inward.

[0003] When assembling the boot 100, as shown in FIG. 6, a jig 106 is used to axially press the bellows portion 105 from the small-diameter cylindrical portion side of the boot as indicated by arrow A. As a result, as shown in FIG. 5, the large-diameter cylindrical portion 102 of the boot 100 is attached to the outer periphery of the outer joint member 101, and the small-diameter cylindrical portion 104 of the boot 100 is attached to the outer periphery of the shaft 103, whereby the boot 100 can be assembled.

[0004] On the other hand, constant velocity universal joints applied to the wheel side of the rear drive shaft of an automobile, or to the propeller shaft of an automobile, do not need to have a large operating angle like the constant velocity universal joints applied to the front as described above. For example, a maximum operating angle of 30° or less (mainly 20° or less) is sufficient for a rear constant velocity universal joint, and a maximum operating angle of 10° or less is sufficient for a propeller shaft constant velocity universal joint. The boots attached to these constant velocity universal joints do not need to follow high operating angles, so boots without bellows (so-called bellows-less boots) are sometimes used (for example, Patent Document 1 below).

[0005] The bellows-less boot 110, as shown in Figure 7, for example, has a large-diameter cylindrical portion 111 attached to the outer circumference of the outer joint member 101, a small-diameter cylindrical portion 112 attached to the outer circumference of the shaft 103, an annular projection 113 connected to the large-diameter cylindrical portion 111 and convex on one axial side (right side in the figure), and an annular recess 114 connected to the annular projection 113 and the small-diameter cylindrical portion 112 and convex on the other axial side (left side in the figure). The bellows-less boot 110 can have a shorter actual length compared to the boot 100 with a bellows section shown in Figure 5, thus enabling weight reduction and cost reduction. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2018-204687 [Overview of the project] [Problems that the invention aims to solve]

[0007] When assembling a boot without bellows, as described in Patent Document 1, it is necessary to press the boot using a jig, similar to the assembly of a boot with bellows. However, when pressing a boot without bellows using a jig, there are no radially protruding parts like the ridges of the bellows, making it difficult to apply stable pressure. The end face of the small-diameter cylindrical section has a small surface area, making it difficult for the jig to make stable contact.

[0008] Therefore, the present invention provides a constant velocity universal joint boot that offers high assembly ease even without having a bellows section, and a constant velocity universal joint equipped with the same. [Means for solving the problem]

[0009] The constant velocity universal joint boot of the present invention comprises a large-diameter cylindrical portion that is mounted on the outer circumferential surface of the outer joint member of the constant velocity universal joint, a small-diameter cylindrical portion that is mounted on the outer circumferential surface of a shaft connected to the inner joint member of the constant velocity universal joint, and a connecting portion that connects the large-diameter cylindrical portion and the small-diameter cylindrical portion and has a curved portion that is convex in the axial direction, wherein a convex portion is provided at the end of the small-diameter cylindrical portion opposite to the connecting portion in the axial direction, and the convex portion protrudes radially outward from the outer diameter of the small-diameter cylindrical portion.

[0010] The constant velocity universal joint boot of the present invention has a protrusion on the end of the small diameter cylindrical portion that is axially opposite to the connecting portion, which protrudes radially outward from the outer diameter of the small diameter cylindrical portion, thereby increasing the surface area of ​​the end face of the small diameter cylindrical portion. When assembling the boot, the jig contacts the end face of the small diameter cylindrical portion and presses the boot toward the outer joint member. By increasing the surface area of ​​the end face of the small diameter cylindrical portion and increasing the contact area of ​​the jig, the jig can contact the end face of the small diameter cylindrical portion stably, and the pressing of the boot becomes stable. As a result, the attachment of the small diameter cylindrical portion to the shaft becomes stable.

[0011] In the above configuration, it is preferable that the protrusions are made up of projections provided at multiple positions in the circumferential direction. In this case, it is preferable that the projections be provided at four or more different positions in the circumferential direction. Alternatively, the protrusions may be made up of a continuous annular shape in the circumferential direction. By configuring the protrusions in these ways, in all cases the jig will make stable contact with the small-diameter cylindrical portion, and the attachment of the small-diameter cylindrical portion to the shaft will be more stable.

[0012] In the above configuration, it is preferable that the maximum outer diameter of the protrusion is smaller than the inner diameter of the boot band before it is tightened and fixed to the outer surface of the small diameter cylindrical portion. This prevents the boot band from being impeded and prevents it from falling off.

[0013] Furthermore, it is preferable that the radial dimension from the inner diameter surface of the end of the small-diameter cylindrical portion opposite the connecting portion in the axial direction to the apex of the protrusion be 15% or more and 30% or less of the inner diameter of the small-diameter cylindrical portion. Setting it to 15% or more ensures a sufficient area for the jig to stably contact the end face of the small-diameter cylindrical portion. Setting it to 30% or less prevents excessive protrusion of the protrusion and reduces costs by using only the necessary amount of material.

[0014] The constant velocity universal joint of the present invention comprises an outer joint member, an inner joint member, and a torque transmission member interposed between the outer joint member and the inner joint member, wherein the inside of the joint is sealed with a boot, and the boot is a constant velocity universal joint boot of the present invention.

[0015] The boots of the present invention are particularly suitable for constant velocity universal joints installed on drive shafts with small maximum operating angles (e.g., 20°), but the boots of the present invention can also be applied to constant velocity universal joints installed on propeller shafts. [Effects of the Invention]

[0016] The constant velocity universal joint boot of the present invention provides stable attachment of the small-diameter cylindrical section to the shaft and offers high ease of assembly even without a bellows section. [Brief explanation of the drawing]

[0017] [Figure 1] This is a cross-sectional view of a constant velocity universal joint fitted with a constant velocity universal joint boot according to the first embodiment of the present invention. [Figure 2] This is a front view of the constant velocity universal joint boot shown in Figure 1, as seen from the small diameter cylindrical section. [Figure 3] This is a cross-sectional view showing the state before the constant velocity universal joint boot is attached in Figure 1. [Figure 4] This is a front view of a constant velocity universal joint boot according to a second embodiment of the present invention, as seen from the small diameter cylindrical portion side. [Figure 5]This is a cross-sectional view of a boot for a constant velocity universal joint having a bellows portion. [Figure 6] This is a cross-sectional view showing a state before the boot for a constant velocity universal joint having a bellows portion is attached in the aforementioned Figure 5. [Figure 7] This is a cross-sectional view of a conventional boot for a constant velocity universal joint that does not have a bellows portion. [Mode for Carrying Out the Invention]

[0018] Hereinafter, a boot for a constant velocity universal joint according to the first embodiment of the present invention will be described based on Figure 1 to Figure 3. The constant velocity universal joint shown in Figure 1 is a fixed constant velocity universal joint provided at the outboard side end portion of a drive shaft for a rear wheel of a vehicle. The maximum operating angle of this constant velocity universal joint may be smaller than that when mounted on a front wheel, and the maximum operating angle is, for example, 20° or less. In the following description, in the axial direction of the constant velocity universal joint, the side that becomes the inner side in the vehicle width direction when mounted on a vehicle (the right side in Figure 1) is referred to as the "inboard side", and the side that becomes the outer side in the vehicle width direction (the left side in Figure 1) is referred to as the "outboard side".

[0019] The constant velocity universal joint 33 of the present embodiment includes an outer joint member 1, an inner joint member 2, balls 3 as torque transmission members, and a cage 4. On the inner peripheral surface of the outer joint member 1, a plurality of axially extending track grooves 5 are formed at equal intervals in the circumferential direction. On the outer peripheral surface of the inner joint member 2, a plurality of axially extending track grooves 6 are formed at equal intervals in the circumferential direction. The balls 3 are incorporated between the track grooves 5 of the outer joint member 1 and the track grooves 6 of the inner joint member 2 that face each other. The number of the balls 3 can be, for example, 6 or 8. A plurality of pockets 7 for retaining the balls 3 are formed in the cage 4. In this specification, the angle formed by the rotation center line of the outer joint member and the rotation center line of the inner joint member is referred to as the operating angle, the direction of the axis O of the constant velocity universal joint 33 when the operating angle is 0° (the up-down direction in Figure 1) is referred to as the "axial direction", and the circumferential direction and the radial direction of the circle centered on the axis O at this time are referred to as the "circumferential direction" and the "radial direction", respectively.

[0020] A female spline 8 is formed on the inner peripheral surface of the shaft hole of the inner joint member 2. A male spline 10 is formed at the outboard side (left side in the drawing) end of a power transmission shaft (shaft) 9. By inserting the outboard side end of the shaft 9 into the shaft hole of the inner joint member 2 and fitting the female spline 8 and the male spline 10 together, the two are coupled so as to be capable of torque transmission.

[0021] The outer joint member 1 has a cup-shaped mouth portion 11 that opens toward the inboard side (right side in the drawing), and a stem portion 12 that extends from the mouth portion 11 toward the outboard side. The opening of the mouth portion 11 of the outer joint member 1 is sealed by a boot 20.

[0022] Since the constant velocity universal joint of the present embodiment has a small maximum operating angle (for example, 20° or less), a non-bellows boot having no bellows portion can be used as the boot 20. The boot 20 of the present embodiment has a large-diameter cylindrical portion 21, a small-diameter cylindrical portion 22, and a connecting portion 23. As the material of the boot 20, an elastomer or rubber can be used. For example, thermoplastic resin elastomers, rubbers represented by CR, silicone, HNBR, ethylene chloride and the like can be used, and thermoplastic polyester elastomer is particularly desirable.

[0023] The large-diameter cylindrical portion 21 is attached to the outer peripheral surface of the mouth portion 11 of the outer joint member 1. An annular groove 26 is formed on the outer peripheral surface of the large-diameter cylindrical portion 21, and by mounting and tightening a boot band (not shown) in this annular groove 26, the large-diameter cylindrical portion 21 is fixed to the outer peripheral surface of the mouth portion 11 of the outer joint member 1.

[0024] The small-diameter cylindrical portion 22 is attached to the outer peripheral surface of the shaft 9. In the illustrated example, the small-diameter cylindrical portion 22 has a fixing portion 22a in close contact with the outer peripheral surface of the shaft 9, and a cylindrical portion 22b extending from the fixing portion 22a toward the outboard side and having a radial gap provided between itself and the outer peripheral surface of the shaft 9. An annular groove 27 is formed on the outer peripheral surface of the fixing portion 22a of the small-diameter cylindrical portion 22, and by mounting and tightening a boot band (not shown) in this annular groove 27, the fixing portion 22a of the small-diameter cylindrical portion 22 is fixed to the outer peripheral surface of the shaft 9.

[0025] The connecting portion 23 connects the large-diameter cylindrical portion 21 and the small-diameter cylindrical portion 22. The connecting portion 23 has a curved portion 24 that is convex in the axial direction. In this embodiment, two curved portions are formed: an outer diameter curved portion 24a that is continuous with the large-diameter cylindrical portion 21 and protrudes toward the small-diameter cylindrical portion, and an inner diameter curved portion 24b that is continuous with the cylindrical portion 22b of the small-diameter cylindrical portion 22 and protrudes toward the large-diameter cylindrical portion. The outer diameter side of the inner diameter curved portion 24b and the inner diameter side of the outer diameter curved portion 24a are continuous. The connection portion between the large-diameter cylindrical portion 21 and the outer diameter curved portion 24a, the connection portion between the outer diameter curved portion 24a and the inner diameter curved portion 24b, and the connection portion between the inner diameter curved portion 24b and the small-diameter cylindrical portion 22 are all smoothly continuous. Thus, the boot in the present invention does not have a bellows section in which peaks and valleys are formed alternately.

[0026] At the fixing portion 22a of the small-diameter cylindrical portion 22, a protrusion 25 is provided at the end opposite the axial direction (inboard side) from the connecting portion 23, projecting radially outward from the outer diameter of the small-diameter cylindrical portion 22. As shown in Figure 2, the protrusion 25 in this embodiment is composed of projections 26 provided at multiple positions in the circumferential direction. In the illustrated example, the projections 26 (26a, 26b, 26c, 26d) are provided at four positions at equal pitches of 90° in the circumferential direction. The outer diameter surface of the projections 26 is curved, and the shape and dimensions of the four projections 26 (26a to 26d) are all the same in this embodiment.

[0027] The maximum outer diameter dimension at the protrusion 25 is smaller than the inner diameter dimension of the boot band (not shown) before it is tightened and fixed to the outer circumferential surface of the small diameter cylindrical portion 22. Here, "maximum outer diameter dimension at the protrusion 25" refers to the dimension at which the outer diameter of the boot is maximum at the position where the protrusion 25 is provided. In this embodiment, as shown in Figure 2, the dimension L1 from the apex of projection 26a to the apex of projection 26c located on the radially opposite side of projection 26a is the maximum outer diameter dimension. Also, in this embodiment, since projections 26b and 26d have the same shape and dimensions as projections 26a and 26c, the dimension L2 from the apex of projection 26b to the apex of projection 26d located on the radially opposite side of projection 26b is the same as L1, and L2 is also the maximum outer diameter dimension. This L1 (=L2) is smaller than the inner diameter dimension of the boot band before it is tightened and fixed to the outer circumferential surface of the small diameter cylindrical portion 22.

[0028] Furthermore, as shown in Figure 1, it is preferable that the radial dimension L3 from the inner diameter surface 32 of the end of the small-diameter cylindrical portion 22 opposite to the connecting portion 23 in the axial direction to the apex of the convex portion 25 be 15% or more and 30% or less of the inner diameter dimension L of the small-diameter cylindrical portion 22.

[0029] When assembling the boot 20, as shown in Figure 3, the jig 27 contacts the end face of the small-diameter cylindrical portion 22 and presses the boot 20 toward the outer joint member as indicated by arrow A. At this time, since the small-diameter cylindrical portion 22 has a protrusion 25 that projects radially outward at the inboard end, increasing the area of ​​the end face of the small-diameter cylindrical portion 22 increases the contact area of ​​the jig 27, so that the jig 27 contacts the end face (protrusions 26b and 26d) of the small-diameter cylindrical portion 22 as shown by the dashed line in Figure 2, and the pressing of the boot 20 becomes stable. As a result, the boot 20 of this embodiment has stable attachment of the small-diameter cylindrical portion 22 to the shaft 9 and is easy to assemble even without a bellows section.

[0030] Furthermore, the maximum outer diameter dimensions of the protrusion 25 (L1 and L2 in this embodiment) are smaller than the inner diameter dimension of the boot band before it is tightened and fixed to the outer surface of the small diameter cylindrical portion 22. This prevents the boot band from being impeded and prevents it from falling off.

[0031] Furthermore, by making the radial dimension L3 from the inner diameter surface 32 of the end of the small-diameter cylindrical portion 22 opposite the connecting portion 23 in the axial direction to the apex of the protrusion 25 15% or more of the inner diameter dimension L of the small-diameter cylindrical portion 22, a sufficient area can be secured for the jig 27 to stably contact the end face of the small-diameter cylindrical portion 22. Alternatively, by making it 30% or less, excessive protrusion of the protrusion 25 can be prevented, and costs can be reduced by using only the necessary amount of material.

[0032] Figure 4 shows a boot for a constant velocity universal joint according to the second embodiment, in which the protrusion 30 is an annular shape that is continuous in the circumferential direction. In this case, the annular portion 31 is concentric with the fixing portion 22a of the small diameter cylindrical portion 22. In this case, the maximum outer diameter dimension of the protrusion 30 is the outer diameter dimension L4 of the annular portion 31. This maximum outer diameter dimension L4 is smaller than the inner diameter dimension of the boot band before it is tightened and fixed to the outer circumferential surface of the small diameter cylindrical portion 22.

[0033] Furthermore, in the second embodiment, as shown in Figure 4, it is preferable that the radial dimension L5 (part L3 in Figure 1) from the inner diameter surface 32 of the end of the small-diameter cylindrical portion 22 opposite to the connecting portion 23 in the axial direction to the apex of the convex portion 25 be 15% or more and 30% or less of the inner diameter dimension L of the small-diameter cylindrical portion 22.

[0034] With the above configuration, the constant velocity universal joint boot of the second embodiment also provides the same effects and advantages as the constant velocity universal joint boot of the first embodiment. In the constant velocity universal joint boot shown in Figure 4, components similar to those of the constant velocity universal joint boot of the first embodiment are denoted by the same reference numerals as in Figure 2, and their descriptions are omitted.

[0035] Although embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and can be modified in various ways. The present invention may also be applied to boots attached to other fixed constant velocity universal joints such as Zeppa type, undercut-free type, and cross-groove type, as well as to boots attached to sliding constant velocity universal joints such as double offset type and tripod type. Furthermore, the present invention is not limited to boots of constant velocity universal joints provided on drive shafts, but can also be applied to boots of constant velocity universal joints provided on propeller shafts, drive shafts of industrial machinery, etc.

[0036] In the convex portion, there only needs to be one or more protrusions, and their shape can be any shape. If multiple protrusions are provided, they do not need to all be the same shape and dimensions; they may be different shapes and dimensions. Furthermore, they may be spaced evenly or unevenly in the circumferential direction. If the convex portion is annular, it may be a perfect circle or not. [Explanation of Symbols]

[0037] 1. Outer joint member 2. Inner joint member 3 balls 20 Boots 21 Large diameter cylindrical section 22 Small diameter cylinder part 23 Connecting part 24 Curved section 25, 30 Convex part 26 Protrusion 31 Annular section 32 Inner diameter surface of the small diameter cylinder 33. Constant velocity universal joint

Claims

1. A boot for a constant velocity universal joint comprises a large-diameter cylindrical portion mounted on the outer circumferential surface of the outer joint member of the constant velocity universal joint, a small-diameter cylindrical portion mounted on the outer circumferential surface of a shaft connected to the inner joint member of the constant velocity universal joint, and a connecting portion that connects the large-diameter cylindrical portion and the small-diameter cylindrical portion and has a curved portion that is convex in the axial direction, A boot for a constant velocity universal joint, characterized in that a protrusion is provided at the end of the small-diameter cylindrical portion opposite to the connecting portion in the axial direction, the protrusion being radially outward from the outer diameter of the small-diameter cylindrical portion.

2. The constant velocity universal joint boot according to claim 1, characterized in that the aforementioned protrusion is composed of projections provided at multiple positions in the circumferential direction.

3. The constant velocity universal joint boot according to claim 2, characterized in that the protrusions are provided at four or more different positions in the circumferential direction.

4. The constant velocity universal joint boot according to claim 1, characterized in that the convex portion is an annular shape that is continuous in the circumferential direction.

5. The constant velocity universal joint boot according to claim 1, characterized in that the maximum outer diameter dimension of the protrusion is smaller than the inner diameter dimension of the boot band before it is tightened and fixed to the outer surface of the small diameter cylindrical portion.

6. The constant velocity universal joint boot according to claim 1, characterized in that the radial dimension from the inner diameter surface of the end of the small diameter cylindrical portion opposite to the connecting portion in the axial direction to the apex of the convex portion is 15% or more and 30% or less of the inner diameter dimension of the small diameter cylindrical portion.

7. A constant velocity universal joint comprising an outer joint member, an inner joint member, and a torque transmission member interposed between the outer joint member and the inner joint member, wherein the inside of the joint is sealed by a boot, A constant velocity universal joint characterized in that the boot is a constant velocity universal joint boot according to any one of claims 1 to 6.

8. The constant velocity universal joint according to claim 7, characterized in that it is provided on a drive shaft.

9. The constant velocity universal joint according to claim 7, characterized in that it is provided on a propeller shaft.

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