JP2007203918A - Center takeoff type steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that it is difficult to mount a dust boot because of a large number of indentations and projections on a surface of a rack housing. <P>SOLUTION: A rack housing assembly 10 has a center takeoff type rack housing structure for simultaneously moving a pair of tie rods steering right and left wheels in a steering device for a vehicle. A rack housing 12 has an approximate cylindrical shape, and an opening 18 having a predetermined axial length is formed at a portion on a periphery. A rack bar 30 is loosely inserted in the rack housing 12 and slides in an axial direction in the rack housing. A pair of tie rods are connected with the slider 14, and slide in the opening 18 together with the rack bar 30. A dust boot is mounted on the outer periphery of the rack housing 12 to cover the opening 18. A plurality of linear projections 22 extending at least across the entire length of the dust boot are formed on the outer periphery of the rack housing 12. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rack housing structure in a center take-off type steering apparatus.

In general, the operation of the steering wheel by the driver is transmitted to the rack bar via the steering shaft. By moving the rack bar in the left-right direction of the vehicle, the wheels can be steered via a tie rod connected to the rack bar. Patent Document 1 discloses a center take-off type rack housing structure that simultaneously moves a pair of tie rods that steer left and right wheels in a power steering apparatus.
JP 2000-85602 A JP 2003-182595 A

  A dust boot is attached to the rack housing in order to prevent foreign matter from entering the housing. However, since the surface of the rack housing is generally provided with many irregularities, there is a problem that the inside of the boot is caught by the irregularities of the rack housing when the dust boot is loosely inserted, and it is difficult to attach.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a technique for improving the ability to attach dust boots to a rack housing in a center take-off type steering apparatus.

  In one aspect of the present invention, the inner end portions of a pair of left and right tie rods are connected to a rack bar included so as to be slidable in the axial direction with respect to the rack housing through an opening formed substantially at the center of the rack housing. The center take-off type steering device includes a dust boot attached to the outer periphery of the rack housing so as to cover the opening of the rack housing. And the some convex part extended in an axial direction over the full length of the said dust boot at least is formed in the outer periphery of the said rack housing.

According to this aspect, when the dust boot is attached to the rack housing, the inside of the dust boot is guided by the convex portion formed on the circumference of the rack housing, so that the dust boot is not caught by the irregularities on the surface of the rack housing. Assembling property is improved.
The “convex portion” corresponds to, for example, the linear protrusion in the embodiment.

A diameter of a circle enveloping a plurality of convex portions on the outer periphery of the rack housing by forming annular mounting portions to which clamp portions formed at both ends of the dust boot are respectively fitted on the outer periphery of the rack housing. May be smaller than the outer diameter of the mounting portion. By setting the diameter of the circle enclosing the plurality of convex portions on the outer periphery of the rack housing to be equal to or smaller than the outer diameter of the mounting portion, the dust boot is inserted while being guided by the convex portion after the dust boot exceeds the mounting portion. Will be. Therefore, the dust boot can be easily attached to the rack housing.
The “attachment portion” corresponds to, for example, the flange in the embodiment.

  When the dust boot is inserted into the rack housing from one direction, the outer diameter of the mounting portion formed on the insertion side of the rack housing is set to be larger than the inner diameter of the clamp portion formed on the end portion on the dust boot insertion side. You may keep it small. This makes it difficult for the clamp portion on the dust boot insertion side to be caught by the mounting portion on the rack housing insertion side when the dust boot is loosely inserted. Therefore, the dust boot can be easily attached to the rack housing.

  When the rack housing is molded by casting, the convex portions may be arranged on the outer periphery of the rack housing at a position different from the parting line generated by the parting of the molding die. By disposing the convex portion at a position different from the parting line, the inner wall of the dust boot does not come into contact with the parting line when the dust boot is loosely inserted, so that damage to the dust boot can be avoided.

  According to the present invention, the mounting property of the dust boot to the rack housing is improved.

  FIG. 1 is a perspective view of a rack housing assembly 10 according to an embodiment of the present invention. The rack housing assembly 10 is a center take-off housing structure that simultaneously moves a pair of tie rods that steer left and right wheels in a vehicle steering apparatus.

  An input shaft 20 of a vehicle steering wheel (not shown) is connected to an output shaft (not shown) via a torsion bar in the gear box 48. On the left side of the gear box 48, a rack housing 12 having a substantially cylindrical shape is provided. The rack housing 12 and the gear box 48 are preferably integrally formed by casting.

  A rack bar 30 that is slidable in the axial direction is loosely inserted into the rack housing 12. At one end of the rack bar 30, a rack 32 is formed that meshes with a pinion gear formed on the output shaft (see FIG. 2). A steering assist force from a motor (not shown) is also input to the output shaft, thereby realizing a power steering device.

  The rack housing 12 is formed with an opening 18 having a predetermined axial length at a part of its circumference. An elongated plate-like guide shoe 26 is attached to a flat surface formed at the center of the rack bar 30 (see FIG. 2). The guide shoe 26 slightly protrudes from the opening 18 of the rack housing 12 and slides with respect to the side surface of the opening 18.

  FIG. 2 is a cross-sectional view of the rack housing assembly 10 shown in FIG. 1 cut along the center plane of the guide shoe 26.

  The slider 14 is attached to the guide shoe 26 by a bolt 28 fastened to the bolt hole 24. A pair of left and right tie rods (not shown) are fixed in mounting holes 16 formed in the slider 14. The slider 14 slides in the left-right direction in FIG. 2 within the opening 18 of the rack housing 12.

  In order to prevent foreign matter from entering the inside of the rack housing 12 from the opening 18, a dust boot 50 is attached to the outer periphery of the rack housing 12 to cover the opening 18. The dust boot 50 is assembled to the rack housing 12 from the direction of the arrow 60 in FIG. The dust boot 50 includes a small-diameter side bellows portion 50a, an opening covering portion 50b, and a large-diameter side bellows portion 50c. The opening covering portion 50 b located at the center of the dust boot 50 is sandwiched between the slider 14 and the guide shoe 26 by a bolt 28. The small-diameter side bellows portion 50 a and the large-diameter side bellows portion 50 c located at both ends of the dust boot 50 are fitted to annular mounting surfaces 42 and 44 formed on the outer peripheral surface of the rack housing 12, respectively. The attachment structure of the small diameter side bellows portion 50a and the large diameter side bellows portion 50c will be described later with reference to FIGS.

  In the above-described configuration, when the rack bar 30 slides in the rack housing 12 due to the rack 32 meshing with the pinion, the guide shoe 26, the slider 14 and the tie rod move integrally left and right, and the left and right via the link mechanism (not shown). Steer the wheels. As the slider 14 moves in the axial direction, the opening covering portion 50 b of the dust boot 50 moves in the opening 18. At this time, the small-diameter side bellows part 50a and the large-diameter side bellows part 50c expand and contract and continue to cover the opening 18.

  By the way, in general, the rack housing 12 is provided with a rib for ensuring the strength or being stealed for weight reduction or prevention of a cast hole. For this reason, the outer periphery of the rack housing 12 is not uniform and has a large number of irregularities. Therefore, when the dust boot 50 is loosely inserted into the rack housing 12 from the direction of the arrow 60 in FIG. 2, the inside of the bellows portions 50a and 50c is easily caught by the irregularities on the surface of the rack housing, and there is a problem that the mounting is troublesome. .

  Therefore, in the present embodiment, a plurality of linear protrusions 22 extending in the axial direction at least over the entire length of the dust boot 50 are formed on the outer periphery of the rack housing 12. The linear protrusion 22 is formed between the annular mounting surfaces 42 and 44 so as to have an outer diameter from the convex portion formed on the surface of the rack housing 12. Accordingly, when the dust boot 50 is loosely inserted into the rack housing 12, the inner walls of the bellows portions 50 a and 50 c of the dust boot 50 are inserted while touching the tips of the linear protrusions 22. The dust boot 50 can be attached to the rack housing 12 without being caught by the unevenness.

  FIG. 3 is a perspective view of the rack housing assembly 10 as seen from another angle. FIG. 3 also shows a plurality of linear protrusions 22 extending in the axial direction of the rack housing 12. As can be seen from FIGS. 1 and 3, it is preferable to arrange at least three linear protrusions 22 at equal intervals around the circumference of the rack housing 12. The linear protrusions 22 also function as ribs that improve the bending strength of the rack housing 12.

  4 is a cross-sectional view taken along the line AA in FIG. 2, and FIG. 5 is a cross-sectional view taken along the line BB in FIG. As illustrated, the linear protrusion 22 is located on the outermost periphery of the rack housing 12 over the entire length inside the dust boot.

  The linear protrusions 22 are preferably arranged at positions different from the parting lines 46 when the rack housing 12 is cast. The parting line 46 is formed as a burr at the time of casting. This prevents the inside of the dust boot from being caught by the parting line generated by the parting of the molding die on the outer periphery of the rack housing, thereby preventing the inside of the dust boot from being damaged and reducing the durability of the dust boot.

  FIG. 6 is an enlarged view of a portion C in FIG. On the outer periphery of the rack housing 12 on the insertion side (that is, the left side in FIG. 2), annular small-diameter flanges 34 and 36 are formed. A small diameter clamp portion 52 is formed at the end of the small diameter side bellows portion 50 a of the dust boot 50. The small-diameter side bellows portion 50 a is fixed to the rack housing 12 by fitting the small-diameter clamp portion 52 to the annular mounting surface 42 between the small-diameter flanges 34 and 36.

  FIG. 7 is an enlarged view of a portion D in FIG. Ring-shaped large-diameter flanges 38 and 40 are formed on the outer side opposite to the insertion side of the rack housing 12, that is, on the outer periphery on the gear box 48 side. A large-diameter clamp portion 54 is formed at the end of the large-diameter side bellows portion 50 c of the dust boot 50. The large-diameter side bellows portion 50 c is fixed to the rack housing 12 by fitting the large-diameter clamp portion 54 to the annular mounting surface 44 between the large-diameter flanges 38 and 40.

  In the following, the diameter of the circle enveloping the tip of the linear protrusion 22 formed on the outer periphery of the rack housing 12 is φQ, the outer diameters of the small-diameter flanges 34 and 36 of the rack housing 12 are φP, and the bellows portion 50a of the dust boot 50, The inner diameter of 50c is represented by φS, and the inner diameter of the large-diameter clamp portion 54 of the dust boot 50 is represented by φT.

In the rack housing assembly in the present embodiment, the following relationship is established.
φQ ≦ φP <φS ≦ φT

  In order, φQ ≦ φP, that is, the diameter of the circle enclosing the plurality of linear protrusions 22 on the outer periphery of the rack housing is set to be equal to or smaller than the outer diameter of the small-diameter flanges 34 and 36, whereby the dust boot 50 is loosely inserted into the rack housing 12. In this case, after the dust boot exceeds the small-diameter flanges 34 and 36, the inner walls of the bellows portions 50a and 50c of the dust boot are inserted while being guided by the linear protrusions 22. Therefore, the dust boot can be easily attached to the rack housing.

  Since φP <φS, that is, the inner diameters of the bellows portions 50a, 50c of the dust boot 50 are larger than the outer diameters of the small-diameter flanges 34, 36, when the dust boot 50 is loosely inserted into the rack housing 12, the bellows portions 50a, The inner wall of 50c is not easily caught by the small-diameter flanges 34 and 36. Therefore, the dust boot can be easily attached to the rack housing.

  When φS ≦ φT, that is, when the dust boot 50 is loosely inserted into the rack housing 12 by making the inner diameter of the large-diameter clamp portion 54 of the dust boot 50 equal to or larger than the inner diameter of the bellows portions 50a and 50c of the dust boot 50, The clamp portion 54 is not easily caught by the small diameter flanges 34 and 36. Therefore, the dust boot can be easily attached to the rack housing.

  As described above, according to the present invention, when the dust boot is mounted on the rack housing, the linear protrusion formed on the circumference of the rack housing is at the outermost diameter, so that the inner wall of the bellows portion of the dust boot is Assembling performance is improved without being caught by the rack housing. Further, the inside of the bellows portion is not damaged by the parting line of the rack housing. Even when the bellows portion buckles and the inner wall contacts the linear protrusion when the slider moves, the inner side of the bellows portion is not damaged because the linear protrusion is arranged at a position different from the parting line.

  Furthermore, since the rack housing can be provided with a meat stealer or a rib without considering the assembling property of the dust boot and the damage of the dust boot, the rack housing can be further reduced in weight and cost.

  The present invention has been described based on some embodiments. These embodiments are merely examples, and modifications such as arbitrary combinations of the embodiments, each component of the embodiments, and any combination of the processing processes are also within the scope of the present invention. It will be understood by those skilled in the art.

  In the embodiment, the linear protrusion is a straight line extending in the axial direction of the rack housing. However, the linear protrusion may be curved as long as it is at the outermost diameter of the rack housing over the entire length of the rack cover. For example, the linear protrusion may be formed in a spiral shape from the small diameter flange 36 to the large diameter flange 38.

It is a perspective view of the rack housing assembly concerning one embodiment of the present invention. It is sectional drawing when the rack housing assembly shown in FIG. 1 is cut | disconnected along the center plane of a slider. It is the perspective view which looked at the rack housing assembly from another angle. It is sectional drawing when cut along the AA line of FIG. It is sectional drawing when cut along the BB line of FIG. It is an enlarged view of the C section of FIG. It is an enlarged view of the D section of FIG.

Explanation of symbols

  10 rack housing assembly, 12 rack housing, 14 slider, 16 mounting hole, 18 opening, 22 linear protrusion, 26 guide shoe, 30 rack bar, 32 rack, 34, 36 small diameter flange, 38, 40 large diameter flange, 42, 44 Annular mounting surface, 46 type dividing line, 50 dust boot, 52 small diameter clamp, 54 large diameter clamp, Q envelope diameter of linear projection, P small flange outer diameter, S bellows inner diameter, T large diameter Clamp inner diameter.

Claims (4)

Center take-off type steering in which the inner ends of a pair of left and right tie rods are connected to a rack bar that is slidable in the axial direction with respect to the rack housing through an opening formed in the approximate center of the rack housing. In the device
A dust boot is provided on the outer periphery of the rack housing so as to cover the opening of the rack housing, and a plurality of protrusions extending in the axial direction at least over the entire length of the dust boot are formed on the outer periphery of the rack housing. A center take-off type steering device. On the outer periphery of the rack housing, annular mounting portions are formed to which clamp portions formed at both ends of the dust boot are respectively fitted.
The center take-off type steering apparatus according to claim 1, wherein a diameter of a circle enclosing a plurality of convex portions on an outer periphery of the rack housing is smaller than an outer diameter of the mounting portion.   When the dust boot is inserted into the rack housing from one direction, the outer diameter of the mounting portion formed on the insertion side of the rack housing is larger than the inner diameter of the clamp portion formed on the end portion on the insertion side of the dust boot. The center take-off type steering apparatus according to claim 2, wherein   4. The projection according to claim 1, wherein when the rack housing is molded by casting, the convex portion is arranged at a position different from a parting line generated by parting of a molding die on an outer periphery of the rack housing. The center take-off type steering device according to claim 1.

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