Jammed adjusting plug for a rack and pinion steering system

Abstract

Steering system (10) with a rack and pinion, comprising: a rack housing (16) defining a rack housing bore (40) extending along a rack housing axis (34); a rack bearing (18) arranged in the rack housing bore (40), the rack bearing (18) having a first bearing section (60) connected to a second bearing section (62) by a preload, the first bearing section (60) and the second bearing section (62) extending along the rack housing axis (34) between a first end (50) of the rack bearing (18) and a second end (52) of the rack bearing (18); and an adjusting plug (20) arranged in the rack housing bore (40), wherein the adjusting plug (20) comprises an adjusting plug body (88) extending along the rack housing axis (34) between a first end (90) of the adjusting plug (20) engaging with the second end (52) of the rack bearing and a second end (92) of the adjusting plug (20), and wherein the adjusting plug (20) comprises a retaining device (122) extending axially away from the first end (90) of the adjusting plug (20); wherein the part of the second end (92) of the adjusting plug (20) which is not part of a bushing (108) extending from the second end (92) of the adjusting plug (20) to the first end (90) of the adjusting plug (20) is planar; wherein the first end (90) of the adjusting plug (20) defines a radially outer engagement surface (94) of the adjusting plug (20); wherein the engagement surface (94) of the adjusting plug (20) extends completely radially outwards to a radially outer end of the adjusting plug body (88); wherein the entire engagement surface (94) of the adjusting plug (20) is arranged in a non-parallel and non-perpendicular relationship with respect to the second end (92) of the adjusting plug (20); wherein the engagement surface (94) of the adjusting plug (20) extends continuously in a non-parallel and non-perpendicular relationship from the radially outer end to a radially inner end of the engagement surface (94) of the adjusting plug (20); and wherein a radially outer side of the holding device (122) and the inner radial end of the engagement surface (94) of the adjusting plug (20) define a first recess (102) radially between them, and wherein a radially inner side of the holding device (122) defines at least partially a second recess (104) which is arranged concentrically with the first recess (102).

Description

BACKGROUND

[0001] A rack and pinion steering system operates by converting rotational motion into linear motion. The rack and pinion steering system may include an elongated steering rack (i.e., a toothed rod), tie rods, a steering shaft, and a pinion gear. The tie rods may be connected to at least one steerable wheel attached to the steering rack. The pinion gear operatively meshes with the teeth of the steering rack such that the pinion gear rotates in response to rotation of the steering shaft, moving the rack in a linear manner.

[0002] System components such as a rack yoke or rack shoe can facilitate the effective meshing of the pinion gear with the rack. Axial or radial play between the rack yoke or rack shoe and a mating component can result in unwanted noise, provide undesirable steering feel, or increase system complexity.

[0003] Consequently, it is desirable to minimize system noise, improve steering feel, reduce system complexity, and improve the reliability of pinion gear meshing with the rack.

[0004] US 5,937,703 A discloses a steering device with a rack and pinion. The steering device comprises a housing in which a rack guide is housed. The rack guide is arranged between the rack and a locking cap, with a compressed spring provided between the rack guide and the locking cap. The surface of the locking cap facing the rack guide runs perpendicular to a longitudinal axis of the rack guide. Further prior art is known from WO 2009 / 097 648 A1, KR 10 2003 0 054 495 A, KR 10 2013 0 143 275 A, JP H09-175 413 A, JP H06- 137 396 A, DE 11 2007 000 157 T5 and DE 10 2017 110 693 A1. SUMMARY

[0005] The object of the invention is to provide an improved steering system with a rack and pinion.

[0006] To achieve this objective, a steering system having the features of claim 1 is provided. Advantageous embodiments of the invention can be found in the dependent claims, the description, and the drawings.

[0007] A rack and pinion steering system is disclosed, comprising a rack housing, a rack bearing, and an adjustment plug. The rack housing defines a rack housing bore extending along an axis. The rack bearing is disposed within the rack housing bore. The rack bearing has a first bearing portion connected to a second bearing portion by preload. The first bearing portion and the second bearing portion extend along the axis between a first end of the rack bearing and a second end of the rack bearing. The adjustment plug is disposed within the rack housing bore. The adjustment plug includes an adjustment plug body extending along the axis between a first end of the adjustment plug, which engages the second end of the rack bearing, and a second end of the adjustment plug.The adjustment plug further includes a retaining feature extending axially away from the first end of the adjustment plug. The portion of the second end of the adjustment plug that is not part of a bushing extending from the second end of the adjustment plug to the first end of the adjustment plug is planar. The first end of the adjustment plug defines a radially outward engagement surface of the adjustment plug. The engagement surface of the adjustment plug extends completely radially outward to a radially outer end of the adjustment plug body. The complete engagement surface of the adjustment plug is arranged in a non-parallel and non-perpendicular relationship with respect to the second end of the adjustment plug. The engagement surface of the adjustment plug extends in the non-parallel and non-perpendicular relationship continuously from the radially outer end to a radially inner end of the engagement surface of the adjustment plug.A radially outer side of the retainer and the inner radial end of the engagement surface of the adjusting plug define a first recess radially therebetween, wherein a radially inner side of the retainer at least partially defines a second recess arranged concentrically with the first recess.

[0008] In addition to one or more of the features described here, the rack bearing is made of a non-metallic material.

[0009] In addition to one or more of the features described herein, the rack bearing includes a spring element extending between the first bearing portion and the second bearing portion.

[0010] In addition to one or more of the features described herein, a rack is supported by the rack housing and engages a gear.

[0011] In addition to one or more of the features described here, the rack and the gear are axially preloaded against each other by the rack bearing.

[0012] In addition to one or more of the features described herein, the first bearing portion and the second bearing portion are biased toward engagement with the rack housing bore.

[0013] In addition to one or more of the features described herein, the second end of the rack bearing defines an engagement surface of the rack bearing.

[0014] In addition to one or more of the features described herein, the engagement surface of the rack bearing is arranged in a non-parallel and non-perpendicular relationship with respect to the first end of the rack bearing.

[0015] In addition to one or more of the features described herein, the engagement between the engagement surface of the rack bearing and the engagement surface of the adjusting plug further biases the first bearing portion and the second bearing portion toward engagement with the rack housing bore.

[0016] In addition to one or more of the features described herein, a biasing element is disposed between and engaged with the rack bearing and the adjusting plug.

[0017] In addition to one or more of the features described herein, the preloading element preloads the first end of the rack bearing in the axial direction against the rack.

[0018] Also disclosed is an adjustment plug for a steering system having a rack and pinion. The adjustment plug includes an adjustment plug body extending between a first end of the adjustment plug and a second end of the adjustment plug along an axis. The first end of the adjustment plug defines an engagement surface of the adjustment plug arranged in a non-parallel and non-perpendicular relationship with respect to the second end of the adjustment plug.

[0019] In addition to one or more of the features described herein, the adjustment plug body defines a sealing recess disposed between the first end of the adjustment plug and the second end of the adjustment plug and extending toward the axis.

[0020] In addition to one or more of the features described herein, the first recess extends axially from the first end of the adjustment plug toward the second end of the adjustment plug.

[0021] In addition to one or more of the features described herein, the second recess is arranged concentrically with the first recess and extends axially from the first end of the adjustment plug toward the second end of the adjustment plug.

[0022] In addition to one or more of the features described herein, a retaining device is arranged radially between the first recess and the second recess.

[0023] In addition to one or more of the features described herein, the adjustment plug body defines a central opening extending through the second recess and extending axially toward the second end of the adjustment plug.

[0024] In addition to one or more of the features described herein, the adjustment plug body defines a bushing extending from the second end of the adjustment plug to the first end of the adjustment plug.

[0025] Further disclosed is a rack bearing for a steering system having a rack and pinion. The rack bearing includes a first bearing portion connected by preload to a second bearing portion. The first bearing portion and the second bearing portion each extend along a first axis between a first end of the rack bearing and a second end of the rack bearing. The second end of the rack bearing defines a rack bearing engagement surface arranged in a non-parallel and non-perpendicular relationship with respect to the first end of the rack bearing.

[0026] In addition to one or more of the features described herein, the engagement surface of the rack bearing is arranged to engage an adjustment plug engagement surface of an adjustment plug.

[0027] These and other advantages and features will be better understood from the following description when taken in conjunction with the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The subject matter of the present disclosure is particularly disclosed and specifically claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the present disclosure will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: Fig. Figure 1 is a partial cross-sectional view of a steering system having a rack and pinion; Fig. Figure 2 is a partial cross-sectional view of a rack bearing and an adjusting plug of the rack and pinion steering system; Fig. Figure 3 is a first perspective view of the rack bearing; Fig. Figure 4 is a second perspective view of the rack bearing; Fig. 5 is a first perspective view of the adjusting plug; and Fig. 6 is a second perspective view of the adjusting plug. DETAILED DESCRIPTION

[0029] Referring now to the figures, in which the present disclosure is described with reference to specific embodiments, without being limiting thereof, it is to be understood that the disclosed embodiments are merely illustrative of the present disclosure, which may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be highlighted or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art how to variously utilize the present disclosure.

[0030] With reference to Fig. 1 shows a rack and pinion steering system 10. The rack and pinion steering system 10 includes an elongated steering rack 12, a gear 14, a rack housing 16, a rack bearing 18, and an adjusting plug 20.

[0031] The elongated steering rack 12 is rotatably supported by the gear 14. The elongated steering rack 12 may be provided with a plurality of teeth, threads, or the like extending along a length of the elongated steering rack 12. The gear 14 may be a pinion gear that meshes with the elongated steering rack 12. The gear 14 may be attached to a steering shaft and may rotate about a rotation axis 32. Rotation of the gear 14 about the rotation axis 32 translates the elongated steering rack 12 along a translation axis 30.

[0032] The elongated steering rack 12 and the gear 14 are preloaded against each other in the axial direction relative to a rack housing axis 34 by the rack bearing 18. The axial preload between the elongated steering rack 12 and the gear 14 ensures meshing engagement between the elongated steering rack 12 and the gear 14.

[0033] The rack housing 16 defines a rack housing bore 40 extending along the rack housing axis 34. The rack housing axis 34 may be arranged transversely to both the gear 14 and the translation axis 30 of the elongated steering rack 12.

[0034] The rack bearing 18 is disposed within the rack housing bore 40. The rack bearing 18 is arranged to transmit a preload to the elongated steering rack 12 and to the gear 14 by being able to slide within the rack housing bore 40. The rack bearing 18 is arranged to expand radially relative to the rack housing axis 34 to axially preload the rack bearing 18 against the rack housing bore 40 and to relieve the rack bearing 18 of any clearance with the rack housing bore 40.

[0035] The rack bearing 18 extends along the rack housing axis 34, or an axis substantially parallel to the rack housing axis 34, between a first rack bearing end 50 and a second rack bearing end 52. The first rack bearing end 50 may be provided with a profile that generally matches the profile of the elongated steering rack 12, such that the first rack bearing end 50 extends partially around the elongated steering rack 12. The first rack bearing end 50 is arranged for engagement with the elongated steering rack 12, and the second rack bearing end 52 engages the adjustment plug 20.

[0036] The rack bearing 18 defines a first slot 54 (as in Fig. 1 and Fig. 2) and in some embodiments, a second slot 56 (as shown in Fig. 3 and Fig. 4), which extends / extends at least partially through the rack bearing 18 such that the rack bearing 18 is partially segmented into a first bearing portion 60 and a second bearing portion 62, which are interconnected by preload.

[0037] The first slot 54 and / or the second slot 56 extend generally through the center of the rack bearing 18. The first slot 54 and / or the second slot 56 is / are radially offset from the axis along which the rack bearing 18 may extend and are not disposed within a common imaginary plane. As shown in Fig. 1, the first slot 54 and / or the second slot 56 is / are radially offset from the rack housing axis 34.

[0038] The at least partial segmentation of the rack bearing 18 into the first bearing portion 60 and the second bearing portion 62 by the first slot 54 and / or the second slot 56 defines a Gothic arch or spring element 64 extending between the first bearing portion 60 and the second bearing portion 62 to eliminate play between the rack bearing 18 and the rack housing bore 40.

[0039] In the embodiments described in Fig. 1-4, the spring element 64 may be a portion of a flexible material defined by the first slot 54 and / or the second slot 56. The spring element 64 allows the rack bearing 18 to expand in a radial direction such that outer surfaces of the first bearing portion 60 and the second bearing portion 62 are biased into engagement with the rack housing bore 40. In embodiments where the first slot 54 and / or the second slot 56 extend substantially completely through the rack bearing 18, the spring element 64 may be a separately provided biasing element extending between the first bearing portion 60 and the second bearing portion 62.

[0040] The spring element 64 applies a radial preload of the first bearing portion 60 and the second bearing portion 62 of the rack bearing 18 to the rack housing bore 40. The radial preload of the rack bearing 18 against the rack housing bore 40 can provide an outer surface fit between outer surfaces of the first bearing portion 60 and the second bearing portion 62, between the rack bearing 18 and the rack housing bore 40. The radial preload between outer surfaces of the first bearing portion 60 and the second bearing portion 62 and the rack housing bore 40, along with the axial preload of the rack bearing 18 against the elongated steering rack 12, improves the rattle, knock, and feel of the steering behavior of the rack and pinion steering system 10.

[0041] The rack bearing 18 may be made of a non-metallic material, such as a polymer. The rack bearing 18 may be a plastic injection-molded rack bearing.

[0042] The spring element 64 connects the first bearing portion 60 to the second bearing portion 62 in a hinged or preloaded manner such that the first bearing portion 60 and the second bearing portion 62 radially expand or contract relative to each other in response to changes in rack load or temperature. As the temperature increases, the rack bearing 18 may thermally expand and expand radially within the rack housing bore 40. As the temperature decreases, the rack bearing 18 may thermally contract, and the spring element 64 may assist in radially expanding the rack bearing 18 such that the first bearing portion 60 and the second bearing portion 62 remain engaged with the rack housing bore 40.

[0043] With reference to Fig. 3 and Fig. 4, the spring member 64 may include a central portion 70. The central portion 70 may be a bulbous member or a generally circular member substantially centered within the rack bearing 18. The central portion 70 may be disposed between and spaced apart from ends of the spring member 64 that are directly connected to the first bearing portion 60 and the second bearing portion 62. A first inner surface 72 of the first bearing portion 60 may define a first recess 74 positioned to at least partially receive the central portion 70. A second inner surface 76 of the second bearing portion 62 may define a second recess 78 positioned to at least partially receive the central portion 70. The central portion 70 may be at least partially received within the first recess 74 and / or the second recess 78.

[0044] With reference to Fig. 1-4, the second end 52 of the rack bearing defines a rack bearing engagement surface 80 arranged for engagement with the adjustment plug 20. The rack bearing engagement surface 80 is arranged in a non-parallel and non-perpendicular relationship with respect to the first end 50 of the rack bearing. A portion of the rack bearing engagement surface 80 of the first bearing section 60 can progressively approach the first end 50 of the rack bearing in a direction extending radially from the outer surface of the first bearing section 60 to the first inner surface 72. A portion of the rack bearing engagement surface 80 of the second bearing section 62 can progressively approach the first end 50 of the rack bearing in a direction extending radially from the outer surface of the second bearing section 62 to the second inner surface 76.

[0045] With reference to Fig. 1, Fig. 2 and Fig. 4, the rack bearing 18 defines a cavity 82 and a plurality of reinforcement members 84. The cavity 82 extends from the rack bearing second end 52 to the rack bearing first end 50. The plurality of reinforcement members 84 extend radially toward an axis substantially parallel or coplanar with the rack housing axis 34. The plurality of reinforcement members 84 extend axially from the rack bearing second end 52 to the rack bearing first end 50.

[0046] The adjusting plug 20 can influence the radial preload of the rack bearing 18 against the rack housing bore 40 and maintain the centering of the rack bearing 18 in the rack housing bore 40. The adjusting plug 20 is arranged in the rack housing bore 40 and engages the rack bearing 18.

[0047] With reference to Fig. 1, Fig. 2, Fig. 5 and Fig. 6, the adjustment plug 20 includes an adjustment plug body 88 extending along the rack housing axis 34, or an axis substantially parallel to the rack housing axis 34, between a first end 90 of the adjustment plug and a second end 92 of the adjustment plug. The adjustment plug body 88 may be a unitary body having a one-piece construction. The first end 90 of the adjustment plug defines an adjustment plug engagement surface 94 that engages the engagement surface 80 of the rack bearing.

[0048] The engagement surface 94 of the adjustment plug is arranged in a non-parallel and non-perpendicular relationship with the second end 92 of the adjustment plug. A portion of the engagement surface 94 of the adjustment plug may progressively approach the second end 92 of the adjustment plug in a direction extending radially away from the rack housing axis 34 or from an axis substantially parallel to the rack housing axis 34.

[0049] The engagement between the engagement surface 80 of the rack bearing and the engagement surface 94 of the adjustment plug further biases the outer surfaces of the first bearing portion 60 and the second bearing portion 62 toward engagement with the rack housing bore 40. The amount of radial preload of the first bearing portion 60 and the second bearing portion 62 toward the rack housing bore 40 can be adjusted by changing an axial position of the adjustment plug 20 relative to the rack bearing 18.

[0050] The engagement between the engagement surface 80 of the rack bearing and the engagement surface 94 of the adjustment plug balances the separating forces from the elongated steering rack 12 on the opposite side of the rack bearing 18. The separating force from the engagement surface 94 of the adjustment plug and the spring element 64 allows the rack bearing 18 to maintain contact with the rack housing bore 40, improving the noise performance of the rack and pinion steering system 10.

[0051] The adjustment plug body 88 defines a sealing recess 100, a first recess 102, a second recess 104, a central opening 106, and a bushing 108.

[0052] With reference to Fig. 1 and Fig. 2, the sealing recess 100 is disposed between the first end 90 of the adjustment plug and the second end 92 of the adjustment plug and extends radially from an outer surface of the adjustment plug body 88 toward the axis generally parallel to the rack housing axis 34. The sealing recess 100 is arranged to receive a sealing element 120, such as an O-ring, that engages the rack housing bore 40 and can prevent water ingress.

[0053] With reference to Fig. 1, Fig. 2 and Fig. 5, the first recess 102 extends axially from the first end 90 of the adjustment plug to the second end 92 of the adjustment plug. The second recess 104 is concentric with the first recess 102 and is separated from the first recess 102 by a retainer 122 radially disposed between the first recess 102 and the second recess 104. The second recess 104 extends axially from the first end 90 of the adjustment plug to the second end 92 of the adjustment plug. The second recess 104 may extend axially toward and terminate at a spring seat 124.

[0054] The central opening 106 extends axially through the spring seat 124 of the second recess 104 and extends toward the second end 92 of the adjusting plug. The bushing 108 is arranged concentrically with the central opening 106 and is separated from the central opening 106 by a wall 130, as shown in Fig. 6. The bushing 108 extends axially from the second end 92 of the adjustment plug to the first end 90 of the adjustment plug.

[0055] A sealing plug 132 may be at least partially disposed within the sleeve 108 and may extend into the central opening 106. The sealing plug 132 may include a flange 134 that may be adjacent to a distal end of the wall 130.

[0056] With reference to Fig.1, a biasing element 140, e.g., an adjustment spring, may be disposed between and engaged with the rack bearing 18 and the adjustment plug 20. The biasing element 140 is at least partially received within the cavity 82 of the rack bearing 18 and is at least partially received within the second recess 104. The biasing element 140 is at least partially retained in the second recess 104 by the retainer 122. The biasing element 140 applies an axial preload that is transmitted from the rack bearing 18 to the elongated steering rack 12. The amount of axial preload provided by the biasing element 140 and the rack bearing 18 can be adjusted by adjusting an axial position of the adjustment plug 20 relative to the rack bearing 18.

[0057] The axial preload and radial preload applied by the rack bearing 18 compensate for added tolerances and minimize system noise, improve the feel of the steering behavior, and improve the reliability of the meshing between the pinion gear and the rack.

[0058] Although the present disclosure has been described in detail in connection with only a limited number of embodiments, it is to be readily understood that the present disclosure is not limited to the disclosed embodiments. Rather, the present disclosure may be modified to incorporate any number of variations, alterations, substitutions, or equivalent arrangements not described hereinabove, but which are consistent with the scope of the present disclosure. Furthermore, although various embodiments of the present disclosure have been described, it is to be understood that aspects of the present disclosure may include only some of the described embodiments or combinations of the various embodiments. Therefore, the present disclosure should not be construed as limited to the above description.

Claims

[1] Steering system (10) with a rack and pinion, comprising: a rack housing (16) defining a rack housing bore (40) extending along a rack housing axis (34); a rack bearing (18) arranged in the rack housing bore (40), the rack bearing (18) having a first bearing portion (60) connected to a second bearing portion (62) by a preload, the first bearing portion (60) and the second bearing portion (62) extending along the rack housing axis (34) between a first end (50) of the rack bearing (18) and a second end (52) of the rack bearing (18); and an adjustment plug (20) disposed in the rack housing bore (40), the adjustment plug (20) comprising an adjustment plug body (88) extending along the rack housing axis (34) between a first end (90) of the adjustment plug (20) engaging the second end (52) of the rack bearing and a second end (92) of the adjustment plug (20), and the adjustment plug (20) comprising a retainer (122) extending axially away from the first end (90) of the adjustment plug (20); wherein the portion of the second end (92) of the adjustment plug (20) that is not part of a bushing (108) extending from the second end (92) of the adjustment plug (20) to the first end (90) of the adjustment plug (20) is planar; wherein the first end (90) of the adjustment plug (20) defines a radially outer engagement surface (94) of the adjustment plug (20); wherein the engagement surface (94) of the adjustment plug (20) extends completely radially outward to a radially outer end of the adjustment plug body (88); wherein the entire engagement surface (94) of the adjustment plug (20) is arranged in a non-parallel and non-perpendicular relationship with respect to the second end (92) of the adjustment plug (20); wherein the engagement surface (94) of the adjusting plug (20) extends in the non-parallel and non-perpendicular relationship continuously from the radially outer end to a radially inner end of the engagement surface (94) of the adjusting plug (20); and wherein a radially outer side of the retaining device (122) and the inner radial end of the engagement surface (94) of the adjusting plug (20) define a first recess (102) radially therebetween, and wherein a radially inner side of the retaining device (122) at least partially defines a second recess (104) arranged concentrically with the first recess (102). [2] A rack and pinion steering system (10) according to claim 1, wherein the rack bearing (18) includes a spring element (64) extending between the first bearing portion (60) and the second bearing portion (62). [3] A rack and pinion steering system (10) according to claim 1, further comprising a steering rack (12) supported by the rack housing (16) and meshing with a gear (14). [4] Steering system (10) with a rack and pinion according to claim 3, wherein the steering rack (12) and the gear (14) are prestressed against each other in the axial direction by the rack bearing (18). [5] A rack and pinion steering system (10) as claimed in claim 1, wherein the second end (52) of the rack bearing (18) defines an engagement surface (80) of the rack bearing (18). [6] A rack and pinion steering system (10) as claimed in claim 1, wherein the engagement surface (80) of the rack bearing (18) is arranged in a non-parallel and non-perpendicular relationship with respect to the first end (50) of the rack bearing (18). [7] A rack and pinion steering system (10) according to claim 6, wherein the engagement surface (80) of the rack bearing (18) is arranged to engage the engagement surface (94) of the adjustment plug (20) to bias the first bearing portion (60) and the second bearing portion (62) into engagement with the rack housing bore (40). [8] A rack and pinion steering system (10) according to claim 6, further comprising: a biasing member (140) disposed between and engaging the rack bearing (18) and the adjusting plug (20). [9] Steering system (10) with a rack and pinion according to claim 8, wherein the biasing element (140) biases the first end (50) of the rack bearing (18) against the steering rack (12) in the axial direction. [10] Adjustment plug (20) according to claim 1, wherein the adjustment plug (20) defines a sealing recess (100) disposed between the first end (90) of the adjustment plug (20) and the second end (92) of the adjustment plug (20) and extending toward the rack housing axis (34). [11] Adjustment plug (20) according to claim 10, wherein the first recess (102) extends from the first end (90) of the adjustment plug (20) to the second end (92) of the adjustment plug (20) in the axial direction. [12] Adjustment plug (20) according to claim 11, wherein the second recess extends in the axial direction from the first end (90) of the adjustment plug (20) towards the second end (92) of the adjustment plug (20). [13] The adjustment plug (20) of claim 12, wherein the adjustment plug (20) defines a central opening (106) extending through the second recess (104) and extending axially toward the second end (92) of the adjustment plug (20).

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