WO2018105528A1

WO2018105528A1 - Resin boot

Info

Publication number: WO2018105528A1
Application number: PCT/JP2017/043328
Authority: WO
Inventors: 憲司信末; 怜小出
Original assignee: 株式会社フコク
Priority date: 2016-12-06
Filing date: 2017-12-01
Publication date: 2018-06-14
Also published as: JPWO2018105528A1

Abstract

In order to provide a resin boot that is capable of preventing co-rotation even in toe-in adjustment during wheel attachment while maintaining sealability, a resin boot or the like that is employed penetrates and protects a shaft body of an object to be mounted, and is characterized by comprising a cylindrical body and a cylindrical seal part that is connected to an end of the body and that adheres to the outer peripheral surface of the shaft body penetrating the body, wherein the inner peripheral surface of the seal part is provided with: an annular seal projection that projects more inward than the inner diameter of the inner peripheral surface; and an annular recess.

Description

Resin boots

The present invention relates to a resin boot for a vehicle that covers a connecting portion of two members such as a steering device and a constant velocity joint.

Conventionally, a rack and pinion type steering device is well known as a vehicle steering device. In the rack-and-pinion type steering device, a pinion gear that meshes with the steering rack is connected to the tip of a steering shaft that extends from the steering wheel. A tie rod is connected to both ends of the steering rack via a ball joint, and one end of a knuckle arm is connected to a tie rod end which is an end of the tie rod via a ball joint. A tire wheel is connected to the other end of the knuckle arm via a knuckle that rotatably holds the tire wheel. Therefore, when the steering wheel is rotated, the pinion gear rotates, the steering rack meshing with the pinion gear moves in the vehicle width direction, and accordingly, the tie rod moves in the vehicle width direction. As the tie rod end moves in the vehicle width direction, the tire wheel steers the wheel in a predetermined direction via the ball joint, knuckle arm, and knuckle.

In general, the connecting part between the end of the steering rack and the tie rod prevents the entry of earth, sand, muddy water, dust, etc. into the interior and performs a stable operation. As a free protection means, it is covered with steering boots.

For example, there are protective bellows disclosed in Patent Document 1 and Patent Document 2 as conventional means for protecting the connecting portion. The protective bellows disclosed in Patent Document 1 is made of a thermoplastic elastomer material, and has a fixing collar that is clamped by clamping means on the outer periphery of the protective bellows. It is disclosed that the fixing collar is securely clamped by the clamping means by forming irregularities on the fixing collar outer peripheral surface side.

The boot disclosed in Patent Document 2 forms an annular lip on the inner surface of the boot. It is disclosed that when the boot is tightened with a fixing ring, the annular lip deformed by pressing is pressed against the outer surface of the shaft member so as to achieve a sealing property or a retaining.

JP-A-7-259996 Japanese Patent No. 4120817

Generally, the rack and pinion type steering device performs toe-in adjustment that adjusts the length of the tie rod by rotating a part of the tie rod in order to finely adjust the posture of the left and right wheels when the wheel is attached. However, a boot (protective bellows) as typified by Patent Document 1 is formed such that the inner diameter of the boot is smaller than the outer diameter of the tie rod. For this reason, when the boot is mounted on the tie rod, the two members are fitted with a constant tightening force, so that the boot rotates together with the tie rod during toe-in adjustment. When this co-rotation occurs, only one end side of the boot fixed to the tie rod rotates, and the boot is deformed in a twisted state. Such a deformation of the boot may cause a problem that the boot is bitten in the housing or a part of the boot comes into contact with a peripheral member such as a suspension to cause abnormal wear. Further, such deformation of the boot hinders normal expansion / contraction operation of the bellows-shaped main body portion, and causes local damage to the boot, which may cause damage or the like.

Therefore, the market has demanded the development of resin boots that can prevent co-rotation in the toe-in adjustment at the time of wheel mounting while maintaining the sealing performance.

As a result of earnest research, the inventors of the present invention provide a resin boot capable of reducing the frictional resistance with the outer peripheral surface of the mounting target object and preventing co-rotation in advance while maintaining the sealing performance. It came.

That is, the resin boot according to the present invention protects the shaft body of the mounting object by being inserted, and is connected to the cylindrical main body and the end of the main body, and the shaft inserted into the main body. A cylindrical seal portion that is in close contact with the outer peripheral surface of the body, and includes an annular seal protrusion that protrudes inward from the inner diameter of the inner peripheral surface and an annular recess on the inner peripheral surface of the seal portion. It is characterized by that.

It is preferable that the resin boot according to the present invention includes an annular intermediate ridge in which a tightening member abuts on the outer peripheral surface of the seal portion at a position facing the seal protrusion.

It is preferable that the resin boot according to the present invention includes a pair of edge-side ridges on the outer peripheral surface of the seal portion that have the same outer diameter as that of the intermediate ridges and that come into contact with the edge of the fastening member.

The resin boot according to the present invention protects the shaft body of the mounting object by being inserted, and is connected to the cylindrical main body and the end of the main body, and the shaft body is inserted into the main body. A cylindrical seal portion that is in close contact with the outer peripheral surface, the outer peripheral surface of the seal portion is provided with a plurality of annular ridges on which the tightening member abuts, and the plurality of ridges are edges of the tightening member And a pair of edge-side ridges, and between the pair of edge-side ridges, at least one or more annular intermediate ridges that contact the fastening member.

More preferably, the resin boot according to the present invention includes an annular seal protrusion on the inner peripheral surface of the seal portion at a position facing the intermediate protrusion.

The resin boot according to the present invention more preferably includes an annular recess on the inner peripheral surface of the seal portion.

In the resin boot according to the present invention, it is preferable that a plurality of the seal protrusions are provided on the inner peripheral surface of the seal part, and the recesses are located between the seal protrusions.

The resin boot according to the present invention preferably has a flat region between the seal protrusion and the recess.

In the resin boot according to the present invention, the inner diameter of the flat region is preferably equal to the inner diameter of the inner peripheral surface of the seal portion.

In the resin boot according to the present invention, it is preferable that a base end portion of the seal protrusion has an R shape.

The resin boot according to the present invention includes, on the outer peripheral surface of the seal portion, the edge-side ridge, the intermediate ridge, and a band mounting portion on which the fastening member is mounted, and the edge-side ridge and the intermediate The total length of the ridges in the resin boot longitudinal direction is preferably 35% to 55% when the total length of the band attaching portion in the resin boot longitudinal direction is 100%.

In the resin boot according to the present invention, the seal part is more preferably a small diameter side seal part.

The resin boot according to the present invention is preferably a rack boot used in a rack and pinion type steering device.

The present invention provides a resin boot that penetrates and protects the shaft body of the mounting object, and includes an annular seal protrusion that protrudes inward from the inner diameter of the inner peripheral surface of the seal portion, and an annular recess. While maintaining the sealing performance by the seal portion, it is possible to reduce the frictional resistance with the outer peripheral surface of the mounting object and prevent co-rotation in advance.

Further, the present invention provides a resin boot that penetrates and protects a shaft body of a mounting object, and has a plurality of ridges with which a tightening member abuts on an outer peripheral surface of a seal portion that is continuously provided at an end portion of the cylindrical main body. The plurality of ridges are provided with a pair of edge-side ridges on which the edges of the tightening member abut, and a plurality of intermediate ridges abutting on the tightening member between the pair of edge-side ridges. In addition, while maintaining the sealing performance by the sealing portion, it is possible to reduce the frictional resistance with the outer peripheral surface of the mounting object and prevent co-rotation in advance.

Furthermore, even when a strong rotational force is applied to the mounting object, for example, toe-in adjustment, the problem that the resin boot itself is twisted and deformed by co-rotating the seal portion of the resin boot is solved. It is possible to prevent damage due to torsional deformation.

The schematic block diagram of the rack and pinion type steering device as an embodiment provided with the resin boot of the present invention. The elements on larger scale which show the mounting state of the rack boot which concerns on this embodiment. FIG. 3 is an overall view of the rack boot of FIG. 2. Sectional drawing which shows the state which mounts a rack boot to a tie rod. The expanded sectional view of a small diameter side seal part. The whole view of the rack boot provided with the protruding item | line on the outer peripheral surface of the small diameter side seal part. The enlarged view of the small diameter side seal part of the rack boot of FIG. Sectional drawing which shows the state which mounts a rack boot to a tie rod. The expanded sectional view of the small diameter side seal | sticker part of other embodiment provided with three intermediate protrusions. The expanded sectional view of the small diameter side seal part of other embodiments.

Hereinafter, a case where the present invention is applied to a rack boot used in a rack and pinion type steering device provided in a vehicle will be described as an embodiment of a resin boot according to the present invention.

FIG. 1 is a schematic configuration diagram of a rack and pinion type steering apparatus including a rack boot according to the present embodiment. A rack and pinion type steering device 1 according to the present embodiment includes a steering wheel 2 for steering and a rack and pinion mechanism 4 as a steering mechanism for steering steered wheels (wheels) 3. The rack and pinion mechanism 4 is connected to the steering wheel 2 via a steering shaft 5 and an intermediate shaft 6.

The rack and pinion mechanism 4 includes a cylindrical rack housing 10 that extends in the vehicle width direction of the vehicle, and a pinion gear and a steering rack (not shown) housed in the rack housing 10. The pinion gear is connected to the tip of an intermediate shaft 6 that is connected to the rack and pinion mechanism 4. Therefore, the pinion gear rotates as the steering wheel 2 rotates. The steering rack extends in the vehicle width direction of the vehicle, and rack teeth are formed to mesh with the above-described pinion gear. Therefore, when the pinion gear rotates, the steering rack moves in the vehicle width direction of the vehicle due to the engagement between the pinion gear and the rack teeth. Both end portions of the steering rack protrude from both ends of the rack housing 10, and tie rods 14 are connected to the end portions via ball joints (not shown) so as to be tiltable. A knuckle arm 16 is connected to the other end of the tie rod 14 via a ball joint 15, and the steered wheel 3 is connected to the knuckle arm 16.

With such a configuration, when the steering wheel 2 is rotated, the pinion gear rotates via the steering shaft 5 and the intermediate shaft 6, and the steering rack moves in the vehicle width direction by meshing between the pinion gear and the steering rack. Accordingly, the tie rods 14 connected to both ends of the steering rack swing with respect to the steering rack and turn the steering wheel 3 in a predetermined direction via the ball joint 15 and the knuckle arm 16.

At this time, rack boots 20 are attached to the connecting portion between the both ends of the steering rack and the tie rod 14 to prevent intrusion of earth and sand, muddy water, dust and the like, and outflow of internal lubricating oil.

Hereinafter, the rack boot 20 according to the present embodiment will be described with reference to a partially enlarged view showing the mounting state of the rack boot 20 of FIG.

The rack boot 20 according to the present embodiment is a resin boot that penetrates and protects a tie rod 14 as a shaft body of a mounting object, and includes a bellows-like cylindrical main body 21 made of an elastic body. The tubular main body 21 is extendable in the X direction (shown in FIG. 2). A rack housing 10 from which an end portion of the steering rack protrudes is inserted through one end of the cylindrical main body 21 of the rack boot 20, and a tie rod 14 connected to the steering rack is inserted through the other end. A cylindrical large-diameter side seal portion 22 is connected to one end of a cylindrical main body 21 that penetrates the rack housing 10, and a cylindrical shape is also provided to the other end of the cylindrical main body 21 that penetrates the tie rod 14. A small-diameter side seal portion 23 (seal portion) is continuously provided. The cylindrical main body 21, the large-diameter side seal portion 22 and the small-diameter side seal portion 23 constituting the rack boot 20 are preferably formed by, for example, blow molding using a thermoplastic elastomer material.

A boot band 24 as a fastening member is attached to the outer periphery of the large diameter side seal portion 22 of the rack boot 20, and the large diameter side seal portion 22 is fastened to the rack housing 10 by the boot band 24. On the other hand, a boot band 25 as a fastening member is attached to the outer periphery of the small diameter side seal portion 23 of the rack boot 20, and the small diameter side seal portion 23 is fastened to the tie rod 14 by the boot band 25. In FIGS. 4 and 8 to 10 described later, the boot band 25 is indicated by a broken line, and at the same time, the mounting position of the boot band 25 is indicated.

In this way, the steering rack (not shown) in a state where the large-diameter side seal portion 22 of the rack boot 20 is fastened to the rack housing 10 by the boot band 24 and the small-diameter side seal portion 23 is fastened to the tie rod 14 by the boot band 25. ) Moves in the vehicle width direction, the cylindrical main body 21 of the rack boot 20 expands and contracts in the axial direction following the movement of the steering rack. Even when the tie rod 14 moves up and down according to the behavior of the wheel 3 bouncing due to a step, the cylindrical main body 21 of the rack boot 20 expands and contracts following the up and down movement of the tie rod 14.

Next, the small-diameter side seal portion of the resin boot according to the present invention will be described in detail for an inner peripheral surface and an outer peripheral surface. First, the inner peripheral surface of the small-diameter side seal portion will be described with reference to the rack boot 20A shown in FIGS. 3 is an overall view of the rack boot 20A, FIG. 4 is a cross-sectional view showing a state in which the rack boot 20A is mounted on the tie rod 14, and FIG. 5 is an enlarged cross-sectional view of the small-diameter side seal portion 23 of FIG.

The resin boot according to the present invention is characterized in that the inner peripheral surface of the small-diameter side seal portion includes an annular seal protrusion protruding inward from the inner diameter of the seal portion inner peripheral surface, and an annular recess. To do.

Specifically, as shown in FIGS. 4 and 5, the rack boot 20 A according to the present embodiment has

annular seal protrusions

41 and 42 on the inner peripheral surface 23 B of the small diameter side seal portion 23, and an annular shape. Concave portions 46 to 48 are formed.

Further, the

seal protrusions

41 and 42 are formed to protrude inward from the inner peripheral surface 23B of the small diameter side seal portion, that is, toward the axis of the tie rod 14. The seal protrusions 41 and 42 are formed in a substantially triangular shape that becomes thinner toward the tip end side of the protrusion. In addition, the shape of the protrusion may be an arc shape or a trapezoid. In particular, the cross-sectional area of the projections is preferably set to 0.03mm ^² ~ 0.3mm ^2. In this way, when the boot band 25 is tightened, the

seal protrusions

41 and 42 are almost completely crushed, so that the sealing performance can be secured. Further, when a strong rotational force is applied to the tie rod 14 at the time of toe-in adjustment, the

seal protrusions

41 and 42 are partially crushed, reducing the frictional resistance between the small diameter side seal portion inner peripheral surface 23B and the tie rod 14 and rotating together. Can be prevented.

Furthermore, by setting the inner diameter of the small-diameter side seal portion including the

seal protrusions

41 and 42 to be smaller than the outer diameter of the tie rod 14, the

seal protrusions

41 and 42 can be easily crushed, thereby realizing excellent sealing performance. it can.

Further, since

such seal protrusions

41 and 42 are present on the inner peripheral surface 23B of the seal portion, in a temporarily assembled state such as toe-in adjustment (= a state in which the rack boot 20A is not completely fastened by the boot band 25). The frictional resistance between the tie rod 14 and the rack boot 20A can be reduced, and the assembly workability can be easily performed.

Further, the recesses 46 to 48 described above are formed so as to be recessed with a predetermined curvature (for example, a curvature radius of 0.8 mm to 3.0 mm) in the circumferential direction of the inner peripheral surface 23B of the small diameter side seal portion. Here, as shown in FIG. 5, the inner diameter U of the recesses 46 to 48 is formed to be substantially the same, and is at least larger than the inner diameter S of the inner peripheral surface 23B. Further, the thickness of the small-diameter side seal portion 23 in the portion where the recesses 46 to 48 are formed is 70 as the thickness of the small-diameter side seal portion 23 in the portion where the

seal protrusions

41 and 42 and the recesses 46 to 48 are not formed. % To 92% is preferable. If it is less than 70%, the drawability from the mold is deteriorated, and if it is more than 92%, when the

seal projections

41 and 42 are crushed by the pressure when the boot band 25 is fastened, This is because sufficient absorption is not possible at 48, and a gap is generated between the tie rod 14 and the inner peripheral surface 23B of the small-diameter side seal portion, and sufficient sealing performance cannot be secured.

The recesses 46 to 48 are preferably arranged alternately with the

seal protrusions

41 and 42 described above in the X direction (FIG. 3) of the small diameter side seal portion inner peripheral surface 23B. In the present embodiment, the recesses 46 to 48 are concentrically formed between the plurality of

seal projections

41 and 42 described above or on both sides of each

seal projection

41 and 42 and in the circumferential direction.

Further, between the

seal projections

41 and 42 and the recesses 46 to 48 in the X direction, the inner diameter is larger than the inner diameter T of the

seal projections

41 and 42 and smaller than the inner diameter U of the recesses 46 to 48, that is, the seal More preferably, there are flat regions 49 to 52 having an inner diameter substantially equal to the inner diameter S of the small-diameter side seal portion 23 in which no protrusions or recesses are formed. Since the flat regions 49 to 52 exist on the inner peripheral surface 23B of the small-diameter side seal portion, the

seal protrusions

41 and 42 can be prevented from being completely crushed in the temporary assembly state such as toe-in adjustment. The frictional resistance can be reduced, and it is possible to effectively prevent co-rotation during toe-in adjustment while ensuring the freedom during assembly.

Further, as shown in FIG. 4, a concave portion 14B into which the positioning projection 40 of the rack boot 20A is fitted is formed on the outer peripheral surface 14A of the tie rod 14. The inner diameter V of the positioning protrusion 40 is preferably smaller than the inner diameter T of the

seal protrusions

41 and 42 and the outer diameter W of the tie rod 14. With this configuration, even when the small-diameter side seal portion 23 is fastened with the boot band 25 or when it is temporarily assembled such as toe-in adjustment, the positioning projection 40 is displaced in the recess 14B with a constant pressure. Since it fits completely, the position shift of the boot longitudinal direction (X direction. FIG. 3) does not occur. For this reason, since the tightening force of the boot band 25 is transmitted to the

seal protrusions

41 and 42 without being dispersed, it is possible to achieve good sealing performance or reduction in frictional resistance.

Further, as shown in FIG. 5, the

base end portions

41r and 42r of the

seal projections

41 and 42 of the small-diameter side seal portion 23 and the base end portion 40r of the positioning projection 40 have a predetermined curvature (for example, a radius of curvature of 0.1 mm). It is preferably an R shape having 1 mm to 0.5 mm). Here, the base end portion means the root portion of the protrusion. Since the base end portions of the

seal projections

41 and 42 and the positioning projection 40 have an R shape, even if the tightening force by the boot band 25 is applied to the

seal projections

41 and 42 and the positioning projection 40, the base end portions are cracked. It becomes difficult to enter, and problems such as breakage of each protrusion can be prevented in advance. Further, since all the corners on the inner peripheral side of the rack boot 20A have an R shape, the pullability from the mold during the blow molding of the rack boot 20A becomes good.

In this embodiment, as shown in FIGS. 4 and 5, the two

seal protrusions

41 and 42 are provided on the small diameter side seal portion 23, but the number of seal protrusions is not limited to this. One or more is sufficient.

Next, the outer peripheral surface of the small-diameter side seal portion will be described with reference to the rack boot 20B shown in FIGS. 6 is an overall view of the rack boot 20B provided with protrusions on the outer peripheral surface 23A of the small diameter side seal portion, FIG. 7 is an enlarged view of the small diameter side seal portion 23 of the rack boot 20B, and FIG. It is sectional drawing which shows the state to do.

The resin boot according to the present invention includes a plurality of ridges on which the fastening member (boot band) abuts on the outer peripheral surface of the small-diameter side seal portion, and the plurality of ridges are a pair of ridges on which the edges of the fastening member abut. An intermediate ridge that contacts the fastening member is provided between the edge-side ridge and the pair of edge-side ridges.

Specifically, as shown in FIGS. 7 and 8, the rack boot 20 B according to the present embodiment has a plurality of protrusions with which the boot band 25 comes into contact with the outer peripheral surface 23 A of the small-diameter side seal portion 23 that is in close contact with the tie rod 14. The ridges 31 to 34 and the

positioning protrusions

38 and 39 for positioning the boot band 25 are formed, which are at least larger in outer diameter than the ridges 31 to 34. Between the

positioning protrusions

38 and 39, a plurality of ridges 31 to 34 are provided. Further, a band attaching portion 26 for mounting the boot band 25 is formed between the pair of positioning

protrusions

38 and 39.

In the present embodiment, among the plurality of ridges 31 to 34, the ridge 31 and the ridge 32 are the edges of the boot band 25, that is, the pair of edge side protrusions with which the

ends

25A and 25B of the boot band 25 abut. The ridges 33 and the ridges 34 are a plurality of intermediate ridges that are formed between the edge-

side ridges

31 and 32 and abut against the boot band 25.

The pair of edge-

side ridges

31 and 32 and the

intermediate ridges

33 and 34 have an annular shape extending along the circumferential direction of the outer peripheral surface 23A of the small-diameter side seal portion, and their outer diameters are substantially the same. It is formed to become. And each edge side protruding item |

line

31 and 32 and each intermediate protruding item |

line

33 and 34 are formed in the X direction (boot longitudinal direction. FIG. 3) at predetermined intervals. Further, the outer diameter of the bottom surface of the recess (not shown) between the edge-

side ridges

31 and 32 and the respective

intermediate ridges

33 and 34 is larger than the outer diameter of the edge-

side ridges

31 and 32 and the

intermediate ridges

33 and 34. And is formed in a groove shape in the circumferential direction of the outer peripheral surface 23A of the small-diameter side seal portion. Therefore, when the boot band 25 is attached to the small-diameter side seal portion 23, the inner peripheral surface 25C of the

end portions

25A and 25B of the boot band 25 abuts on the edge-

side ridges

31 and 32, and the inner peripheral surface 25C Other portions are in contact with the outer peripheral surfaces of the

intermediate ridges

33 and 34.

In this embodiment, as shown in FIG. 7 and FIG. 8, two intermediate ridges are provided on the small-diameter side seal portion 23, but the number of the intermediate ridges is not limited to this, One or more is sufficient. For example, as shown in FIG. 9, three

intermediate ridges

35, 36 and 37 may be provided between the edge-

side ridges

31 and 32.

Hereinafter, the relationship between the total length in the X direction of the edge-side ridges and the intermediate ridges, the sealing property, and the common rotation will be described with reference to FIG. Total length Z (31z + 32z + 33z + 34z) in the X direction (boot longitudinal direction, FIG. 3) of the rack boot 20B of the edge-

side ridges

31 and 32 and the intermediate ridges 33 and 34 (intermediate ridges 35 to 37) of the small-diameter side seal portion 23 Is preferably 35% to 55% when the total length Y in the X direction (the boot longitudinal direction, FIG. 3) of the band attaching portion 26 is 100%. If the total length Z is less than 35%, the contact area between the outer peripheral surface of these edge-side ridges and intermediate ridges and the inner peripheral surface 25C of the boot band 25 cannot be sufficiently secured. The tightening force cannot be transmitted to the

seal protrusions

41 and 42. For this reason, the

seal protrusions

41 and 42 are not sufficiently crushed, and it becomes difficult to ensure the sealing performance between the inner peripheral surface 23B of the small diameter side seal portion and the outer peripheral surface 14A of the tie rod 14. Further, if the total length Z is larger than 55%, the contact area between the inner peripheral surface 25C of the boot band 25 and the outer peripheral surface 23A of the small-diameter side seal portion becomes large, and in a temporarily assembled state such as toe-in adjustment. The seal protrusions 41 and 42 are excessively crushed, and the frictional resistance between the small-diameter side seal portion 23 and the outer peripheral surface 14A of the tie rod 14 cannot be reduced. Therefore, when a strong rotational force is applied to the tie rod 14, a large frictional resistance between the small-diameter side seal portion 23 and the outer peripheral surface 14A of the tie rod 14 causes co-rotation during toe-in adjustment, and the small-diameter side seal portion 23 is The rack boot 20B on the provided side is easily twisted and deformed.

Therefore, by setting the total length Z within the predetermined range described above, it is possible to ensure good sealing performance with the outer peripheral surface 14A of the tie rod 14 by the small diameter side seal portion 23. Thus, it is possible to reduce the frictional resistance between the small diameter side seal portion 23 and the tie rod 14 by using the current resin boot material without changing the material of the resin boot. In the embodiment shown in FIG. 8, the total length Z in the X direction of the edge-side ridges and the intermediate ridges is 52.8%, and in the embodiment shown in FIG. 9, it is 45.5%.

Further, the

base end portions

31r and 32r of the edge-

side ridges

31 and 32 of the small-diameter side seal portion 23 and the

base end portions

33r and 34r (35r to 37r) of the intermediate ridges 33 and 34 (intermediate ridges 35 to 37). Further, the

base end portions

38r and 39r of the

positioning projections

38 and 39 are preferably R-shaped having a predetermined curvature (for example, a maximum curvature radius of 0.5 mm). Here, the base end portion means the root portion of the protrusion. By making the shape of the base end cross section of the edge-

side ridges

31 and 32 and the

intermediate ridges

33 and 34 into an R shape, the tightening force by the boot band 25 is applied to the edge-

side ridges

31 and 32 and the

intermediate ridges

33 and 34. Even if added, cracks are less likely to occur at these base end portions, and problems such as breakage of each protrusion can be prevented in advance. In addition, by making all the corners on the inner peripheral side of the rack boot 20B into an R shape, the drawability from the mold at the time of blow molding of the rack boot 20B becomes good.

In the rack boot 20B, a plurality of

annular seal protrusions

41 and 42 are formed on the inner peripheral surface 23B of the small-diameter side seal portion, similarly to the rack boot 20A described above. The seal protrusions 41 and 42 are formed at positions facing the

intermediate protrusions

33 and 34 formed on the outer peripheral surface 23A of the small diameter side seal portion. Further, in the rack boot 20B, similarly to the rack boot 20A, an annular recess or a flat region may be formed on the inner peripheral surface 23B of the small diameter side seal portion. In addition, since the said recessed part and flat area have been described by description of the rack boot 20A, description here is abbreviate | omitted.

Further, the lengths 41z to 45z in the X direction (boot longitudinal direction, FIG. 3) of the seal projections 41 to 45 shown in FIGS. 8 and 9 are the X directions (boots) of the intermediate ridges 33 to 37 formed at the opposed positions. In the longitudinal direction, it is preferably formed to be equal to or shorter than the lengths 33z to 37z in FIG. Thus, when the intermediate ridges 33 to 37 are pressed by the boot band 25, the tightening force by the boot band 25 is efficiently transmitted to the seal protrusions 41 to 45, and the seal protrusions 41 to 45 are pressed and deformed. Thereby, the sealing property between the tie rods 14 can be improved.

In the embodiment shown in FIG. 8, two

intermediate protrusions

33 and 34 are formed at positions facing the

seal protrusions

41 and 42, and in the embodiment shown in FIG. 9, at positions facing the seal protrusions 43 to 45. Three intermediate ridges 35 to 37 are formed. Thus, although the same number of intermediate protrusions and seal protrusions are provided, the present invention is not limited to this. However, since the same number of intermediate protrusions and seal protrusions are formed in this way, it is possible to further improve the sealing performance and at the same time reduce the frictional resistance and prevent co-rotation.

By the way, the rack boot 20A shown in FIGS. 4 and 5 is similar to the rack boot 20B shown in FIGS. 7 to 9, and the plurality of protrusions 31 to 34 described above on the outer peripheral surface 23A of the small diameter side seal portion. Further, positioning

protrusions

38 and 39 for positioning the boot band 25 at least larger in outer diameter than those of the ridges may be provided. In addition, about each said protruding item | line and positioning protrusion, since it has described in description of the rack boot 20B, description here is abbreviate | omitted.

Hereinafter, as another embodiment, a rack boot 20C having both the features of the rack boot 20A and the features of the rack boot 20B will be described with reference to FIG. The rack boot 20C includes the rack boot 20B shown in FIG. 8 and the annular recesses 46 to 48 and flat regions 49 to 52 of the rack boot 20A described above. Further, the rack boot 20C is provided with the ridges 31 to 34 of the rack boot 20B described above. Hereinafter, in this embodiment, only characteristic portions that are not present in the rack boot 20A and the rack boot 20B will be described.

In this embodiment, flat regions 49 to 52 are formed between the

seal projections

41 and 42 and the recesses 46 to 48 in the X direction (boot longitudinal direction, FIG. 3), as in FIG. The inner diameters of the flat regions 49 to 52 are equal to the inner diameter S of the inner peripheral surface 23B of the small diameter side seal portion as shown in FIG. Due to the presence of the flat regions 49 to 52, it is possible to prevent the

seal protrusions

41 and 42 from being completely crushed in a temporarily assembled state such as toe-in adjustment, and to reduce the frictional resistance during toe-in adjustment. Can be prevented.

Further, even when the flatness of the flat regions 49 to 52 is slightly broken due to the influence of the squeezed

seal protrusions

41 and 42 when the small-diameter side seal portion 23 is tightened by the boot band 25, the flat regions 49 to Since the recesses 46 to 48 exist outside the 52, it is possible to absorb the collapsed flatness and form a new flat region, thereby realizing good sealing performance with the outer peripheral surface 14A of the tie rod 14. can do. As described above, the rack boot 20C according to the present embodiment reduces the frictional resistance with the outer peripheral surface 14A of the tie rod 14 while maintaining the sealing performance in the small-diameter side seal portion 23, and prevents co-rotation in advance. It becomes possible. Therefore, it is possible to prevent the trouble that the rack boot 20 C is caught in the rack housing 10 and the abnormal wear due to contact with peripheral members such as the suspension.

In addition, in the present embodiment, the small-diameter side seal portion 23 is formed with edge-

side ridges

31 and 32 that come into contact with both

end portions

25A and 25B of the boot band 25, and the seal protrusion 41 formed on the inner peripheral surface 23B. , 42 are provided with a plurality of

intermediate ridges

33, 34 in contact with the boot band 25. At this time, the boot band 25 is held in a state of being in contact with both the outer circumferential surfaces of the edge-

side ridges

31 and 32 and the

intermediate ridges

33 and 34 of the small-diameter side seal portion 23. Therefore, the frictional resistance with the outer peripheral surface 14A of the tie rod 14 can be reduced as compared with the case where the entire inner peripheral surface 25C of the boot band 25 is attached in contact with the entire outer peripheral surface of the small-diameter side seal portion 23. Therefore, even when a strong rotational force is applied to the tie rod 14 as in toe-in adjustment, it is possible to prevent the small diameter side seal portion 23 of the rack boot 20C from rotating together with the rotation of the tie rod 14 in advance. It is possible to prevent the rack boot 20C itself from being twisted and deformed, and at the same time to prevent damage due to the torsional deformation of the rack boot 20C.

As described above, in the present embodiment, the friction resistance between the outer peripheral surface 14A of the tie rod 14 and the small diameter side seal portion 23 is reduced, and at the same time, the

edge side protrusions

31 and 32 are provided, thereby reducing the thickness of the small diameter side seal portion 23. It is possible to prevent the boot from being damaged by the accompanying fatigue. Further, the edge protrusion 31 can prevent the positioning protrusion 40 from being displaced.

Specific examples to which the present invention is applied will be shown. In this example, the rack boot was manufactured using a polyolefin-based elastomer which is a thermoplastic elastomer. In the embodiment, the thickness of the small-diameter side seal portion 23 is 1.9 mm, and the edge-

side ridges

31 and 32 with which both ends 25A and 25B of the boot band 25 abut on the outer peripheral surface 23A (FIG. 7) of the small-diameter side seal portion 23 Two

intermediate ridges

33, 34 were formed, and seal

protrusions

41, 42 were formed on the inner peripheral surface 23B at a position facing the intermediate ridges 33, 34 (FIG. 8). In FIG. 8, the thickness of the small diameter side seal part 23 is shown as t. The total length Z in the X direction (boot longitudinal direction, FIG. 3) of the edge-

side ridges

31 and 32 and the

intermediate ridges

33 and 34 in the present embodiment is 52 when the total length Y of the band attachment portion 26 is 100%. 8%.

Comparative example

Next, a rack boot as a comparative example will be described. A rack boot as a comparative example was produced using a polyolefin-based elastomer, which is a thermoplastic elastomer, as in the example. In the comparative example, the thickness of the small-diameter side seal portion 23 (see t in FIG. 8) is 1.9 mm, and the outer peripheral surface 23A (FIG. 7) of the small-diameter side seal portion 23 is shown in FIG. Without forming such edge-side ridges and intermediate ridges, only the

seal protrusions

41 and 42 were formed on the inner peripheral surface 23B of the small-diameter side seal portion.

In order to confirm the effect obtained by forming the edge-side ridges and the intermediate ridges on the outer peripheral surface of the small-diameter side seal portion, the torsion test was performed on the rack boots of the above-described examples and comparative examples. The torsion test was performed by attaching a small diameter side seal portion of the rack boot to a φ18 mm tie rod and tightening the rack boot to the tie rod with a boot band. In this state, the slip torque was measured using a torsion tester.

The results of the torsion test are shown in Table 1 below.

As shown in Table 1, the slip start angle of the example was 7.04 °, and the torque at that time was 1.65 N · m. In addition, the torque at the time of 60 ° rotation in the example is. It was 0.76 N · m. In contrast, the slip start angle of the comparative example was 9.21 °, the torque at that time was 2.01 N · m, and the torque at the time of 60 ° rotation was 1.08 N · m.

From this experimental result, in comparison with the comparative example in which the boot band is in contact with the entire outer peripheral surface of the small-diameter side seal portion, in the embodiment in which the boot band is in contact with only the edge-side ridges and the intermediate ridges formed on the boot outer peripheral surface. The sliding start angle was small, and the torque at that time could be reduced. As a result, it is possible to reliably reduce the frictional resistance between the inner peripheral surface of the small diameter side seal portion and the outer peripheral surface of the tie rod when the tie rod is rotated. For example, a strong rotational force is applied to the tie rod as in toe-in adjustment. Even in this case, it was confirmed that the co-rotation of the small-diameter side seal portion can be prevented in advance. Moreover, since the torque at the time of 60 ° rotation was smaller in the example than in the comparative example, it was found that the frictional resistance could be reduced.

In the above-described embodiment, the case where the present invention is applied to the small-diameter side seal portion 23 is described. However, the present invention is not limited to this, and the present invention is applied to the large-diameter side seal portion 22. You may do it. Further, in the above-described embodiment, the rack boot used in the rack and pinion type steering device is described as an example. However, the boot of the present invention is not limited to this, for example, in a constant velocity joint. The same applies to the boots used.

The boot according to the present invention is a rack boot capable of preventing co-rotation that occurs during wheel mounting by reducing the frictional resistance between the seal portion and the mounting object while maintaining the sealability between the shaft portion and the boot. It is useful for constant velocity joint boots.

DESCRIPTION OF SYMBOLS 1 Rack and pinion type steering device 2 Steering wheel 3 Steering wheel (wheel)
4 Rack and pinion mechanism 5 Steering shaft 6 Intermediate shaft 10 Rack housing 14 Tie rod (shaft body)
14A Outer peripheral surface 14B Recess 15 Ball joint 16

Knuckle arm

20, 20A, 20B, 20C Rack boot (resin boot)
21 Cylindrical body 22 Large diameter side seal part 23 Small diameter side seal part (seal part)
23A Outer peripheral surface 23B Inner

peripheral surface

24, 25 Boot band (clamping member)
25A, 25B End portion 25C Inner peripheral surface 26

Band mounting portion

31, 32 Edge side convex strips 31r to 45r,

Base end portion

33, 34, 35, 36, 37 Intermediate

convex strips

38, 39, 40

Positioning projections

41, 42, 43 , 44, 45

Seal projection

40r, 41r, 42r Base end 46-48 Recess 49-52 Flat area

Claims

It is a resin boot that penetrates and protects the shaft of the mounting object,
A tubular body;
Consisting of an end portion of the main body, and a cylindrical seal portion that is in close contact with the outer peripheral surface of the shaft inserted through the main body.
A resin boot, comprising: an annular seal protrusion protruding inward from an inner diameter of the inner peripheral surface; and an annular concave portion on the inner peripheral surface of the seal portion.
2. The resin boot according to claim 1, wherein the seal portion includes an annular intermediate ridge with which a tightening member abuts on an outer peripheral surface of the seal portion at a position facing the seal protrusion.
3. The resin boot according to claim 2, wherein the outer peripheral surface of the seal portion is provided with a pair of edge-side protrusions having an outer diameter equivalent to that of the intermediate protrusion and the edges of the fastening member abutting against each other.
It is a resin boot that penetrates and protects the shaft of the mounting object,
A tubular body;
Consisting of an end portion of the main body, and a cylindrical seal portion that is in close contact with the outer peripheral surface of the shaft inserted through the main body.
The outer peripheral surface of the seal portion includes a plurality of annular ridges on which the tightening member comes into contact,
The plurality of ridges are a pair of edge-side ridges on which the edges of the tightening member abut, and at least one or more annular intermediate ridges that abut on the tightening member between the pair of edge-side ridges. A resin boot characterized by comprising:
The resin boot according to claim 4, wherein an annular seal protrusion is provided on the inner peripheral surface of the seal portion at a position facing the intermediate protrusion.
The resin boot according to claim 5, wherein an annular recess is provided on the inner peripheral surface of the seal portion.
The resin boot according to any one of claims 1 to 3, wherein the seal portion inner peripheral surface includes a plurality of the seal protrusions, and the concave portion is located between the seal protrusions.
The resin boot according to claim 7, which has a flat region between the seal projection and the recess.
The resin boot according to claim 8, wherein an inner diameter of the flat region is equal to an inner diameter of the inner peripheral surface of the seal portion.
2. The resin boot according to claim 1, wherein a base end portion of the seal protrusion has an R shape.
The outer peripheral surface of the seal portion includes the edge-side ridge, the intermediate ridge, and a band attaching portion for mounting the fastening member,
The total length in the resin boot longitudinal direction of the edge-side ridge and the intermediate ridge is 35% to 55% when the total length of the band attaching portion in the resin boot longitudinal direction is 100%. Or the resin boot of Claim 4.
The resin boot according to any one of claims 1 to 11, wherein the seal portion is a small-diameter side seal portion.
The resin boot according to any one of claims 1 to 12, wherein the resin boot is a rack boot used in a rack and pinion type steering device.