Rack and pinion mechanism

Abstract

To inhibit a hole cover fitted in a housing from being fallen by external force in a rack-and-pinion mechanism.SOLUTION: A rack-and-pinion mechanism includes: a housing 10; a hole cover 13 which is fitted on the housing 10 and covers a part of a pinion shaft 107; and a seal member 20 which is an annular O ring or an irregular-shaped ring sandwiched between an outer peripheral surface of the housing 10 and an inner peripheral surface of the hole cover 13. The hole cover 13 has a cylindrical female fitting part 13a. The housing 10 has a cylindrical male fitting part 10b into which the pinion shaft 107 is inserted and which is press-fitted in the female fitting part 13a.SELECTED DRAWING: Figure 3

Description

[TECHNICAL FIELD]

[0001] The present invention relates to a rack and pinion mechanism. [BACKGROUND ART]

[0002] Patent Document 1 below describes a steering device in which a hole cover that covers a part of a pinion shaft protruding from an opening of a housing is fitted by clearance fitting to the housing that accommodates a part of the pinion shaft and a rack shaft. [PRIOR ART DOCUMENT] [PATENT DOCUMENT]

[0003] [Patent Document 1] Japanese Patent No. 6799306 Specification [SUMMARY OF THE INVENTION] [PROBLEM TO BE SOLVED BY THE INVENTION]

[0004] In the steering device described in Patent Document 1, since the hole cover is fitted to the housing by clearance fitting, there is a risk that the hole cover may fall over due to an external force applied during vehicle traveling and interfere with the pinion shaft. An object of the present invention is to suppress falling of a hole cover fitted to a housing due to external force in a rack and pinion mechanism. [MEANS FOR SOLVING THE PROBLEM]

[0005] To achieve the above objective, a rack and pinion mechanism according to one aspect of the present invention comprises a housing; a rack shaft supported by the housing so as to be reciprocally movable and having rack teeth on at least a portion of its outer circumference; a pinion shaft supported by the housing so as to be rotatable and having pinion teeth that mesh with the rack teeth; a hole cover fitted onto the housing and covering a portion of the pinion shaft; and a sealing member which is an annular O-ring or a deformed ring sandwiched between the outer circumferential surface of the housing and the inner circumferential surface of the hole cover. The hole cover has a cylindrical female fitting portion, and the housing has a cylindrical male fitting portion into which the pinion shaft is inserted and which is press-fitted into the female fitting portion. [Effects of the Invention]

[0006] According to the present invention, in a rack and pinion mechanism, it is possible to suppress the hole cover fitted to the housing from falling over due to external forces. [Brief explanation of the drawing]

[0007] [Figure 1] This is an overall perspective view of an example of a rack and pinion type power steering device according to an embodiment. [Figure 2] Figure 1 is a longitudinal cross-sectional view showing the meshing portion between the rack and pinion of the steering gear. [Figure 3] This is an enlarged longitudinal cross-sectional view of portion A in Figure 2. [Figure 4] This is an enlarged longitudinal cross-sectional view of portion A in Figure 2 in the modified example. [Figure 5] This is a radial cross-sectional view of the female fitting portion in a modified example. [Figure 6] This is a partial longitudinal cross-section of the housing in a modified example. [Modes for carrying out the invention]

[0008] Embodiments of the present invention will be described in detail with reference to the drawings. The embodiments of the present invention described below are illustrative examples of devices and methods for realizing the technical concept of the present invention, and the technical concept of the present invention is not limited to the configuration, arrangement, etc. of the components described below. The technical concept of the present invention can be modified in various ways within the technical scope defined by the claims described in the patent claims.

[0009] (composition) Figure 1 is an overall perspective view of an example of a column-type power steering system according to an embodiment. As shown in Figure 1, the column-type power steering system applies steering assist force to the steering shaft from a motor 102 mounted in the middle of the column 105 in order to reduce the operating force of the steering wheel 101. The rotation of the steering shaft is transmitted to the intermediate shaft 106, which reciprocates the rack axis of the rack and pinion type steering gear 103 via the pinion shaft 107, and steers the steering wheel via the tie rod 104.

[0010] Figure 2 is a longitudinal cross-sectional view showing the meshing portion between the rack and pinion of the steering gear in Figure 1. Figure 3 is an enlarged longitudinal cross-sectional view of portion A in Figure 2. The steering gear 103 of this embodiment is mounted on a vehicle frame, such as a front subframe (not shown). A rack shaft 11 is fitted inside the housing 10 of the steering gear 103 so as to be slidable in the vehicle width direction perpendicular to the plane of the paper in Figure 2. Ball joint sockets (not shown) are screwed into both ends of the rack shaft 11 in the vehicle width direction, and tie rods 104, 104 connected to the ball joint sockets are connected to the wheels via knuckle arms (not shown).

[0011] The pinion shaft 107 comprises a pinion 12 having pinion teeth formed on it that mesh with rack teeth provided on at least a portion of the outer circumference of the rack shaft, and an extension shaft 14 bolted to the pinion 12 by bolts 15. In the following explanation, the direction in which the pinion shaft 107 extends (i.e., the axial direction of the pinion shaft 107) will be referred to as the "axial direction," the direction perpendicular to the axial direction will be referred to as the "radial direction," and the direction of rotation of the pinion shaft 107 (i.e., the circumferential direction around the pinion shaft 107) will be referred to as the "circumferential direction." Furthermore, the direction from the lower end to the upper end of the pinion shaft 107 when mounted on the vehicle is defined as the "upward direction," and the direction from the upper end to the lower end of the pinion shaft 107 when mounted on the vehicle is defined as the "downward direction."

[0012] The pinion 12 is inserted into the housing 10 through an opening at the upper end of the housing 10 and is pivotally supported in the housing 10 by a ball bearing 16a. In other words, the pinion 12 is rotatably supported in the housing 10. The bolt 15 that fastens the pinion 12 to the extension shaft 14 fastens the pinion 12 to the extension shaft 14 at a position above the upper end 10a of the housing 10. The outer ring of the ball bearing 16a is fitted into a circular hole formed in the housing 10 and fixed to the housing 10. The inner ring of the ball bearing 16a is fixed to the pinion 12 by being sandwiched between a crimping ring 18, which is fitted into the groove 12a of the pinion 12 and crimped, and the stepped surface 12b of the pinion 12. The crimping ring 18 is an example of the "fastener" described in the claims.

[0013] Furthermore, the lower part of the pinion 12 is supported radially only by a needle bearing 16b in the housing 10. The rotation of the pinion shaft 107 (extension shaft 14 and pinion 12) is transmitted to the rack teeth of the rack shaft 11, and the direction of the steering wheel is changed via the tie rods 104, 104 shown in Figure 1, which are connected to the rack shaft 11.

[0014] A guide hole 17a having a circular cross-section is formed in the housing 10 in the left-right direction of FIG. 2, and a columnar rack guide 17b is slidably fitted in the guide hole 17a in the left-right direction of FIG. 2. The rack guide 17b is formed with a concave arcuate surface having substantially the same curvature as the curvature of the convex arcuate outer peripheral surface of the rack shaft 11, and this concave arcuate surface is in contact with the outer peripheral surface of the rack shaft 11 to press the rack guide 17b against the outer periphery of the rack shaft 11.

[0015] The adjustment cover 17c is rotated to appropriately adjust the screwing distance, and the rack guide 17b is pressed toward the rack shaft 11 via the coil spring 17d, so that the rack guide 17b is pressed against the outer periphery of the rack shaft 11. This eliminates backlash at the meshing portion between the pinion shaft 107 and the rack shaft 11, allowing the rack shaft 11 to move smoothly. With the above configuration, the rack shaft 11 is supported by the housing 10 so as to be capable of reciprocating movement.

[0016] A hole cover 13 that covers at least a part of the pinion shaft 107 protruding from the opening at the upper end of the housing 10 is fitted onto the outside of the housing 10. A cylindrical male fitting portion 10b that fits with the hole cover 13 is formed on the upper part of the housing 10, and the pinion shaft 107 is inserted into the male fitting portion 10b. Further, the housing 10 has a flange-shaped seating portion 10c having an outer diameter larger than that of the male fitting portion 10b at a position below the male fitting portion 10b, and the axial relative position of the hole cover 13 with respect to the housing 10 is positioned by the contact between the hole cover 13 and the seating portion 10c.

[0017] The hole cover 13 is formed of a material obtained by mixing reinforcing fillers such as glass and carbon into a synthetic resin with good oil resistance such as nylon or POM. The hole cover 13 covers the periphery of the upper part of the pinion shaft 107 and extends upward, and a rubber gasket (not shown) fixed to the upper end of the hole cover 13 abuts against the toe board (vehicle body) to restrict upward movement of the hole cover 13. The hole cover 13 prevents foreign matter from entering the gap between the housing 10 and the pinion shaft 107.

[0018] The hole cover 13 includes a cylindrical female fitting portion 13a that fits with a male fitting portion 10b of a housing 10, a conical throttling portion 13b, a large diameter portion 13d having a larger diameter than the female fitting portion 13a, and a skirt portion 13e. The female fitting portion 13a of the hole cover 13 is fitted to the male fitting portion 10b of the housing 10 by press-fitting. Accordingly, the female fitting portion 13a of the hole cover 13 and the male fitting portion 10b of the housing 10 are fixed. Therefore, even if the housing 10 and the hole cover 13 are relatively displaced under an external force from, for example, a road surface, it is possible to suppress the hole cover 13 from coming off the housing 10 and falling down. Furthermore, by fixing the hole cover 13 to the housing 10 by press-fitting, relative displacement between the housing 10 and the hole cover 13 caused by an external force can be suppressed, so that a decrease in the sealing performance between the hole cover 13 and the housing 10 can be suppressed. The skirt portion 13e suppresses the falling of the hole cover 13 by abutting against the housing 10 in a radial direction when receiving a lateral external force. The function of the large diameter portion 13d will be described later.

[0019] The seating portion 10c has an overlapping portion 21 where the upper surface of the upper portion of the housing 10 overlaps and abuts the lower surface of the lower portion of the hole cover 13 in a radial direction. By increasing the outer diameter of the seating portion 10c to increase the area of the overlapping portion 21, the load applied per unit area to the portion of the hole cover 13 that abuts the housing 10 at the overlapping portion 21 is reduced. Therefore, even an inexpensive material with low strength can be used for the hole cover 13.

[0020] An annular sealing member 20 for sealing a gap between the outer peripheral surface of the housing 10 and the inner peripheral surface of the hole cover 13 is sandwiched between the outer peripheral surface of the housing 10 and the inner peripheral surface of the hole cover 13. For example, the sealing member 20 may be an O-ring with a circular or elliptical cross-sectional shape. Alternatively, the sealing member 20 may be a non-standard shaped ring with a trapezoidal, rectangular, polygonal, or other cross-sectional shape. The sealing member 20 is a radial seal that generates a radial tension force (compression reaction force) when compressed radially. The material of the sealing member 20 may be an elastic body made of a soft material such as rubber or resin.

[0021] Refer to Figure 3. The sealing member 20 is press-fitted onto the outer circumference of the seal placement portion 10e between the male fitting portion 10b and the seating portion 10c of the housing 10. For example, an outer circumference groove 10g may be formed on the outer circumference surface of the seal placement portion 10e, and the sealing member 20 may be placed in the outer circumference groove 10g. The outer diameter of the housing 10 at the seal placement portion 10e may be larger than the outer diameter of the male fitting portion 10b and smaller than the outer diameter of the seating portion 10c. By making the outer diameter of the housing 10 at the male fitting portion 10b smaller than the outer diameter of the seal placement portion 10e, it is possible to suppress the seal member 20 from getting caught in the male fitting portion 10b when the seal member 20 is press-fitted into the seal placement portion 10e. To suppress the seal member 20 from getting caught in the male fitting portion 10b, a taper 10f may be formed on the outer circumferential surface of the upper end of the male fitting portion 10b.

[0022] Alternatively, for example, the sealing member 20 may be positioned so as to abut against the end face of the seating portion 10c of the housing 10, thereby positioning the axial relative position of the sealing member 20 with respect to the housing 10. Alternatively, for example, when the sealing member 20 is positioned in the sealing portion 10e (for example, when the sealing member 20 is positioned in the outer peripheral groove 10g, or when the sealing member 20 is in contact with the end face of the seating portion 10c), a gap 22 may be formed above the sealing member 20 between the outer peripheral surface of the housing 10 and the inner peripheral surface of the hole cover 13.

[0023] By providing a gap 22 above the sealing member 20, the sealing member can expand axially even when compressed radially, thereby reducing the stress generated in the seal 20 and the hole cover 13. The large-diameter portion 13d is formed to bend moderately within the range of the gap 22, so as not to cause the seal 20 (described later) to break when it is bent by an external force.

[0024] (modified version) (1) Figure 4 is an enlarged longitudinal cross-sectional view of portion A in Figure 2 in the first modified example. An annular second sealing member 23 for sealing the space between the outer circumferential surface of the housing 10 and the inner circumferential surface of the hole cover 13 may be sandwiched between the male fitting portion 10b and the female fitting portion 13a. For example, a second outer circumferential groove 10h may be formed on the outer circumferential surface of the male fitting portion 10b of the housing 10, and the annular second sealing member 23 may be placed in the second outer circumferential groove 10h. The sealing member 20 may be a radial seal such as an O-ring with a circular or elliptical cross-sectional shape, or an irregularly shaped ring with a trapezoidal, rectangular, polygonal, etc. cross-sectional shape. The material of the second sealing member 23 may be an elastic body of a soft material such as rubber or resin.

[0025] This allows the male fitting portion 10b and the female fitting portion 13a to be fixed in place by gap fitting. Furthermore, by applying a tightening force to the housing 10 with the second sealing member 23, even if the housing 10 and the hole cover 13 are displaced relative to each other due to external forces from the road surface, the hole cover 13 is prevented from coming off the housing 10 and falling over. In addition, compared to the case where the male fitting portion 10b of the housing 10 and the female fitting portion 13a of the hole cover 13 are press-fitted, the load when inserting the housing 10 into the hole cover 13 is reduced, thus improving ease of assembly.

[0026] (2) Figure 5 is a radial cross-sectional view of the female fitting portion 13a in the second modified example. Multiple axially extending protrusions 13c may be formed on the inner circumferential surface of the female fitting portion 13a of the hole cover 13. When the male fitting portion 10b of the housing 10 is press-fitted into the female fitting portion 13a of the hole cover 13 to fit the hole cover 13 onto the housing 10, the protrusions 13c deform, causing the female fitting portion 13a and the male fitting portion 10b to be press-fitted. This allows a draft angle to be provided on the inner circumferential surface of the female fitting portion 13a of the hole cover 13, excluding the protruding ridge 13c. This improves the moldability when forming the hole cover 13 by resin injection.

[0027] (3) Figure 6 is a partial longitudinal cross-sectional view of the housing 10 in the third modified example. A circumferentially extending protrusion 10i may be formed on the outer surface of the male fitting portion 10b of the housing 10. When the male fitting portion 10b of the housing 10 is press-fitted into the female fitting portion 13a of the hole cover 13 to fit the hole cover 13 onto the housing 10, the protrusion 10i deforms, causing the female fitting portion 13a and the male fitting portion 10b to be press-fitted. This allows a draft angle to be provided on the inner circumferential surface of the female fitting portion 13a of the hole cover 13. This improves the moldability when forming the hole cover 13 by resin injection.

[0028] (Effects of the embodiment) (1) The rack and pinion mechanism comprises a housing 10, a rack shaft 11 supported by the housing 10 so as to be reciprocally movable and having rack teeth on at least a portion of its outer circumference, a pinion shaft 107 supported by the housing 10 so as to be rotatable and having pinion teeth that mesh with the rack teeth, a hole cover 13 fitted onto the housing 10 and covering a portion of the pinion shaft 107, and a sealing member 20 which is an annular O-ring or a shaped ring sandwiched between the outer surface of the housing 10 and the inner surface of the hole cover 13.

[0029] The hole cover 13 has a cylindrical female fitting portion 13a and a conical constricted portion 13b, and the housing 10 has a cylindrical male fitting portion 10b into which the pinion shaft 107 is inserted and which is press-fitted into the female fitting portion 13a, and a gap 22 is formed above the sealing member 20 between the outer circumferential surface of the housing 10 and the inner circumferential surface of the hole cover 13. As a result, the female fitting portion 13a of the hole cover 13 and the male fitting portion 10b of the housing 10 are fixed together, so even if the housing 10 and the hole cover 13 are displaced relative to each other due to external forces from the road surface, for example, it is possible to prevent the hole cover 13 from detaching from the housing 10 and falling over.

[0030] Furthermore, by fixing the hole cover 13 to the housing 10 by press-fitting, relative displacement between the housing 10 and the hole cover 13 due to external forces can be suppressed. Even if the housing 10 and the hole cover 13 are displaced relative to each other due to external forces, the seal member 20 can be prevented from becoming misaligned due to those forces. As a result, the sealing performance (sealability, waterproofness) between the hole cover 13 and the housing 10 can be improved. Furthermore, by providing a gap 22 above the sealing member 20, the sealing member can be stretched axially even when compressed radially, thereby reducing the stress generated in the seal 20 and the hole cover 13.

[0031] (2) The housing 10 may have a seal placement portion 10e for arranging the seal member 20, which is formed below the male fitting portion 10b. The seal member 20 may be placed in an outer peripheral groove 10g formed on the outer peripheral surface of the seal placement portion 10e. This allows the axial relative position of the sealing member 20 with respect to the housing 10 to be positioned.

[0032] (3) Grease may be applied to or filled into the gap 22 between the outer circumferential surface of the housing 10 and the inner circumferential surface of the hole cover 13, which is formed on the upper surface of the sealing member 20. This reduces the assembly force between the housing 10 and the hole cover 13.

[0033] (4) Multiple axially extending protrusions 13c may be formed on the inner circumferential surface of the female fitting portion 13a of the hole cover 13. When the hole cover 13 is fitted onto the housing 10, the multiple protrusions 13c may deform, causing the female fitting portion 13a and the male fitting portion 10b to be press-fitted. This allows a draft angle to be provided on the inner circumferential surface of the female fitting portion 13a of the hole cover 13, excluding the protruding ridge 13c. This improves the moldability when forming the hole cover 13 by resin injection.

[0034] (5) A circumferentially extending protrusion 10i may be formed on the outer surface of the male fitting portion 10b of the housing 10. When the hole cover 13 is fitted onto the housing 10, the protrusion 10i may deform, causing the female fitting portion 13a and the male fitting portion 10b to be press-fitted. This allows a draft angle to be provided on the inner circumferential surface of the female fitting portion 13a of the hole cover 13. This improves the moldability when forming the hole cover 13 by resin injection.

[0035] (6) The outer diameter of the housing 10 at the male fitting portion 10b may be smaller than the outer diameter of the housing 10 at the seal arrangement portion 10e where the seal member 20 is placed in the housing 10. This makes it possible to suppress the sealing member 20 from getting caught in the male fitting portion 10b when the sealing member 20 is pressed into the sealing position portion 10e.

[0036] (7) A taper 10f may be formed on the outer surface of the upper end of the male fitting portion 10b. This makes it possible to suppress the sealing member 20 from getting caught in the male fitting portion 10b when the sealing member 20 is pressed into the sealing position portion 10e.

[0037] (8) The pinion shaft 107 comprises a pinion 12 on which pinion teeth are formed, and an extension shaft 14 bolted to the pinion 12, and the pinion 12 may be rotatably supported by a ball bearing 16a. In this way, by connecting the extension shaft 14 to the pinion 12, which has pinion teeth formed on it, to form the pinion shaft 107, the assembly of the rack and pinion mechanism becomes easier.

[0038] (9) The ball bearing 16a may have its outer ring supported by contact with the housing 10, and its inner ring may be fixed to the pinion 12 by a crimping ring 18. This allows the pinion shaft 107 to be rotatably supported in the housing 10.

[0039] (10) The bolt 15 that fastens the pinion 12 and the extension shaft 14 may fasten the pinion 12 and the extension shaft 14 at a position above the upper end 10a of the housing 10. This provides sufficient workspace when bolting the extension shaft 14 to the pinion 12. [Explanation of Symbols]

[0040] 10…Housing, 10a…Upper end, 10b…Male fitting part, 10c…Seat part, 10e…Seal placement part, 10f…Taper, 10g…Outer circumference groove, 10h…Second outer circumference groove, 10i, 13c…Protrusion, 11…Rack shaft, 12…Pinion, 12a…Groove, 12b…Stepped surface, 13…Hole cover, 13a…Female fitting part, 13b…Conical constriction part, 13d…Large diameter part, 13e…Base part, 14…Extension shaft, 15…Bolt, 16a… Ball bearing, 16b... Needle bearing, 17a... Guide hole, 17b... Rack guide, 17c... Adjusting cover, 17d... Coil spring, 18... Crimping ring, 20... Seal member, 21... Overlapped area, 22... Gap, 23... Second seal member, 101... Steering wheel, 102... Motor, 103... Steering gear, 104... Tie rod, 105... Column, 106... Intermediate shaft, 107... Pinion shaft

Claims

1. A rack and pinion mechanism comprising: a housing; a rack shaft supported by the housing so as to be reciprocally movable and having rack teeth on at least a portion of its outer circumference; a pinion shaft supported by the housing so as to be rotatable and having pinion teeth that mesh with the rack teeth; and a hole cover fitted onto the housing and covering a portion of the pinion shaft, The rack and pinion mechanism includes a sealing member which is an annular O-ring or a modified ring that is sandwiched between the outer circumferential surface of the housing and the inner circumferential surface of the hole cover. The aforementioned hole cover has a cylindrical female fitting portion, The housing has a cylindrical male fitting portion into which the pinion shaft is inserted and which is press-fitted into the female fitting portion. A rack and pinion mechanism characterized by the following features.

2. The housing has a seal placement portion for arranging the seal member, which is formed below the male fitting portion. The rack and pinion mechanism according to claim 1, characterized in that the sealing member is arranged in an outer peripheral groove formed on the outer peripheral surface of the sealing arrangement portion.

3. The rack and pinion mechanism according to claim 1, characterized in that a gap is formed above the sealing member between the outer circumferential surface of the housing and the inner circumferential surface of the hole cover.

4. The rack and pinion mechanism according to claim 3, characterized in that grease is applied to or filled into the gap between the outer circumferential surface of the housing and the inner circumferential surface of the hole cover, which is formed on the surface of the sealing member.

5. Multiple axially extending protrusions are formed on the inner circumferential surface of the female fitting portion of the hole cover. When the hole cover is fitted onto the housing, the multiple protrusions deform, causing the female fitting portion and the male fitting portion to be press-fitted together. The rack and pinion mechanism according to feature 1.

6. A circumferentially extending protrusion is formed on the outer circumferential surface of the male fitting portion of the housing. When the hole cover is fitted onto the housing, the protrusion deforms, causing the female fitting portion and the male fitting portion to be press-fitted together. The rack and pinion mechanism according to feature 1.

7. The rack and pinion mechanism according to claim 1, characterized in that the outer diameter of the housing in the male fitting portion is smaller than the outer diameter of the housing in the seal arrangement portion where the seal member is arranged in the housing.

8. The rack and pinion mechanism according to claim 1, characterized in that a taper is formed on the outer circumferential surface of the upper end of the male fitting portion.

9. The rack and pinion mechanism according to claim 1, characterized in that the hole cover has a conical constriction portion.

10. The pinion shaft comprises a pinion on which the pinion teeth are formed, and an extension shaft bolted to the pinion. The rack and pinion mechanism according to any one of claims 1 to 9, characterized in that the pinion is rotatably supported by a bearing.

11. The outer ring of the bearing is supported by contacting the housing. The inner ring of the bearing is fixed to the pinion by a fastener. The rack and pinion mechanism according to feature 10.

12. The rack and pinion mechanism according to claim 10, characterized in that the bolts fastening the pinion and the extension shaft fasten the pinion and the extension shaft at a position above the upper end of the housing.

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