Steering gear box attachment structure

Abstract

In this steering gear box attachment structure, at least four vehicle body attachment parts (7) to be fixed to a vehicle body are provided to a housing (5) of a steering gear box (1). Three of the vehicle body attachment parts (7) are first vehicle body attachment parts (7A) rigidly mounted to the vehicle body. The vehicle body attachment part (7) other than the first vehicle body attachment parts (7A) is a second vehicle body attachment part (7B) bushing-mounted to the vehicle body.

Description

Steering gear box mounting structure

[0001] The present invention relates to a steering gear box mounting structure.

[0002] Patent Document 1 discloses a structure in which both housings are attached to the vehicle body frame by fastening four boss portions formed on the pinion side housing and the anti-pinion side housing to the vehicle body frame.

[0003] Japanese Patent No. 5527275

[0004] When the steering gear box is rigidly mounted with four or more vehicle body attachment portions, the mounting rigidity is improved compared to the case of rigidly mounting with three vehicle body attachment portions. However, since high accuracy is required for the positional relationship of each vehicle body attachment portion, the product cost increases.

[0005] An object of the present invention is to provide a steering gear box mounting structure capable of improving the mounting rigidity while relaxing the required dimensional accuracy.

[0006] In the steering gear box mounting structure according to an aspect of the present invention, at least four vehicle body attachment portions fixed to the vehicle body are provided on the housing of the steering gear box. Three of the vehicle body attachment portions are first vehicle body attachment portions rigidly mounted to the vehicle body. The vehicle body attachment portions other than the first vehicle body attachment portions are second vehicle body attachment portions bush-mounted to the vehicle body.

[0007] According to the above steering gear box mounting structure, it is possible to improve the mounting rigidity while relaxing the required dimensional accuracy.

[0008] FIG. 1 is a perspective view of a steering gear box mounting structure according to an embodiment. FIG. 2 is an exploded perspective view of the mounting structure of FIG. 1. FIG. 3 is a plan view of the mounting structure of FIG. 1. FIG. 4 is a cross-sectional view of the housing of the steering gear box. FIG. 5 is a cross-sectional view showing the housing of FIG. 5 together with a shaft and a steering drive mechanism. FIG. 6 is a cross-sectional view taken along line VI-VI of FIG. 5. FIG. 7 is a cross-sectional view of part VII of FIG. 5. FIG. 8 is a cross-sectional view of part VIII of FIG. 5.

[0009] The steering gearbox mounting structure according to the embodiment will be described below with reference to the drawings. In the drawings, FR and RR indicate the front and rear of the vehicle in the longitudinal direction, respectively. Similarly, LH and RH indicate the left and right sides in the vehicle width direction, and UP and DN indicate the top and bottom of the vehicle in the vertical direction, respectively.

[0010] As shown in Figures 1 to 3, the steering gearbox 1 is fixed to the front subframe 2 (hereinafter simply referred to as subframe 2), which is part of the vehicle body. The subframe 2 is a large frame component also called a suspension member. In the illustrated example, the subframe 2 has a hollow structure in which a pair of steel panels are joined vertically. The subframe 2 is attached to the underside of the vehicle's front side members (not shown) via bush mounts 3 provided at its four corners.

[0011] The steering gearbox 1 is a rack-and-pinion type steering gearbox, and as shown in Figures 4 and 5, it comprises a shaft 4 and a housing 5. The shaft 4, also called the rack bar, transmits steering force to the front wheels (not shown), which are the steering wheels. As shown in Figures 1 to 3, tie rods 6 are attached to both ends of the shaft 4 via ball joints. The ball joints are covered with bellows-shaped dust boots. The ends of the tie rods 6 are connected to the hub carriers of the front wheels, etc.

[0012] More specifically, as shown in Figures 1 to 3, a pinion shaft 10 is mounted on the right side of the housing 5. The pinion shaft 10 is connected to the steering wheel in the passenger compartment via an intermediate shaft and a column shaft. As shown in Figure 5, the pinion shaft 10 has a pinion gear that meshes with a rack gear formed on the right side of the shaft 4. A yoke 11 is provided in the housing 5 at a position opposite the pinion gear across the shaft 4. The yoke 11 presses the rack gear against the pinion gear by the biasing force of a spring. When the steering wheel is operated, its rotation is transmitted to the pinion gear of the pinion shaft 10 via the column shaft and intermediate shaft. The rotation of the pinion gear is converted into linear motion in the direction of the central axis X of the shaft 4 via the rack and pinion.

[0013] The housing 5 is made of, for example, an aluminum alloy and has a cylindrical hollow structure. Inside the housing 5, as shown in Figure 5, the shaft 4 is housed so as to be slidable in the direction of the central axis X. The housing 5 has four vehicle body mounting parts 7, as shown in Figures 2 to 5. The steering gearbox 1 is fixed to the subframe 2 via the vehicle body mounting parts 7. The vehicle body mounting parts 7 are formed directly and integrally with the housing 5. This integration improves the mounting rigidity of the steering gearbox 1 and, consequently, improves the steering feel.

[0014] Three of the four body mounting sections 7 are first body mounting sections 7A that are rigidly mounted to the subframe 2. The remaining body mounting sections 7, other than the first body mounting sections 7A, are second body mounting sections 7B that are bush-mounted to the subframe 2. In the example shown in Figures 1 to 5, one first body mounting section 7A and one second body mounting section 7B are located near the rear center of the housing 5. The remaining two first body mounting sections 7A are located at both ends of the front of the housing 5. In other words, the body mounting sections 7 are offset forward and rearward with respect to the central axis X of the shaft 4.

[0015] As shown in Figures 4 and 5, each vehicle body mounting portion 7 has a bolt insertion hole 7a. Bolts 8 are inserted through the bolt insertion holes 7a, as shown in Figures 7 and 8. The subframe 2 is provided with bolt holes 9 at positions corresponding to each vehicle body mounting portion 7, as shown in Figure 2. In the illustrated example, the axes of all bolt insertion holes 7a are parallel to each other, making it easier to ensure the height accuracy of each vehicle body mounting portion 7 when fixing the housing 5 to the subframe 2.

[0016] As shown in Figure 8, a bolt 8 is inserted through the bolt insertion hole 7a of the first vehicle body mounting portion 7A. Specifically, the bolt 8 is inserted through the washer 22, the reinforcing sleeve 9a of the bolt hole 9, and the bolt insertion hole 7a of the first vehicle body mounting portion 7A. A flange nut 21 is screwed onto the upper end of the bolt 8. The reinforcing sleeve 9a is provided inside the subframe 2, and its upper end is welded to the upper panel of the subframe 2.

[0017] As shown in Figure 7, a split-type bush 19 is attached to the bolt insertion hole 7a of the second vehicle body mounting portion 7B. The lower bush 19 is inserted into the second vehicle body mounting portion 7B from below, and the upper bush 19 is inserted into the second vehicle body mounting portion 7B from above. Each bush 19 has a flange formed for axial positioning in the bolt insertion hole 7a. The bolt 8 is inserted through the reinforcing sleeve 9a and the upper and lower bushes 19. A washer 20 is inserted through the upper end of the bolt 8, and a flange nut 21 is screwed on. The material of the bush 19 is not particularly limited and can be appropriately selected from, for example, rubber, resin, etc. Also, the shape of the bush 19 is not particularly limited and may be a one-piece bush that is not split.

[0018] The steering gearbox 1 includes a steering drive mechanism. In the illustrated example, the steering drive mechanism is a ball screw mechanism driven by a motor 12, and is the driving force source for a power steering mechanism for reducing steering force. The steering drive mechanism can also function as part of a vehicle behavior control mechanism or as part of an autonomous driving mechanism.

[0019] In the ball screw mechanism, as shown in Figure 5, a helical ball groove is formed on the left side of the shaft 4, and a nut 13 is attached so as to cover a part of the ball groove. A helical ball groove is formed on the inner surface of the nut 13, and a recirculating ball is held between the ball groove of the shaft 4 and the ball groove of the nut 13. The small diameter portion on the left side of the nut 13 is rotatably held inside the housing 5 by a ball bearing 14. A gear sleeve 15 is fixed to the large diameter portion on the right side of the nut 13. A gear (not shown) is attached to the rotating shaft 16 of the motor 12 (see Figure 6). A gear belt 17 is wound around the gear sleeve 15 and the gear of the motor 12, and the rotation of the motor 12 is transmitted to the nut 13 via the gear belt 17. The nut 13, gear belt 17, and the gear of the rotating shaft 16 of the motor 12 are housed in a storage space S formed inside the housing 5. Note that in Figure 6, the nut 13, gear belt 17, and the gears of the rotating shaft 16 of the motor 12 are not shown. When the nut 13 is rotated by the motor 12, the recirculating ball moves in a circular motion between the shaft 4 and the nut 13, causing the shaft 4 to move in the direction of the central axis X.

[0020] In this way, the steering gearbox 1 transmits the linear motion of the shaft 4, obtained by the rack and pinion and / or steering drive function, to the front wheels as steering force.

[0021] As shown in Figures 4 and 5, the housing 5 is divided in the direction of the central axis X of the shaft 4. Specifically, it is divided into a first housing 51 and a second housing 52. This allows the housing 5 to accommodate the steering drive mechanism inside. A motor 12 for driving the ball screw mechanism is mounted in the second housing 52. The motor 12 may also be mounted in the first housing 51.

[0022] As shown in Figure 6, the motor 12 is offset above the vehicle with respect to the central axis X of the shaft 4. The joint surface P (see Figures 4 and 5) where the first housing 51 and the second housing 52 are joined has a vertically elongated shape. At the joint surface P, the first housing 51 and the second housing 52 are bolted together at six fastening points 18. The joint surface P forms the low-rigidity section of the housing 5, where the bending rigidity is lowest.

[0023] As shown in Figures 4 and 5, the second body mounting portion 7B is positioned closer to the low-rigidity portion of the housing 5 (i.e., the coupling surface P) than any of the first body mounting portions 7A. In other words, each first body mounting portion 7A is positioned further away from the low-rigidity portion than the second body mounting portion 7B.

[0024] (1) In the above mounting structure, the housing 5 of the steering gearbox 1 is provided with four body mounting parts 7 that are fixed to the vehicle body (subframe 2 in the illustrated example). Three of the body mounting parts 7 are first body mounting parts 7A that are rigidly mounted to the vehicle body, and the body mounting parts 7 other than the first body mounting parts 7A are second body mounting parts 7B that are bush-mounted to the vehicle body. Therefore, for example, the positional error of the second body mounting parts 7B with respect to the plane defined by the three first body mounting parts 7A can be absorbed by the bush mount (bush 19) at the second body mounting parts 7B. In other words, the above mounting structure makes it possible to improve mounting rigidity while relaxing the required dimensional accuracy.

[0025] (2) The second body mounting portion 7B may be positioned closer to the lowest rigidity portion of the housing 5 (in the illustrated example, the joint surface P of the first housing 51 and the second housing 52) than any of the first body mounting portions 7A. In this case, the portion farther from the low rigidity portion will be rigidly mounted by the first body mounting portion 7A. When a bending moment acts on the housing 5 and deformation occurs in the low rigidity portion, the displacement will be greater in the portion farther from the low rigidity portion. With the above arrangement, this displacement can be suppressed by rigid mounting. This effectively suppresses the deformation of the entire housing 5. In addition, stress concentration that may occur around the body mounting portion 7 closest to the low rigidity portion can be mitigated compared to the case where the first body mounting portion 7A is positioned closest to the low rigidity portion. Note that a bending moment acting on the housing 5 may occur, for example, when the steering wheel collides with a curb or the like. Specifically, a large load is applied to the shaft 4 in the direction of the central axis X from the steering wheel when it collides with a curb or the like, and this load is input to the housing 5 via the rack and pinion and the steering drive mechanism. At this time, since the vehicle body mounting portion 7 of the housing 5 is offset with respect to the central axis X of the shaft 4, a bending moment acts on the housing 5.

[0026] (3) The housing 5 may be divided into a first housing 51 and a second housing 52 in the direction of the central axis X, which is the axial direction of the shaft 4 that transmits steering force to the steering wheel. The low-rigidity portion may be a coupling surface P to which the first housing 51 and the second housing 52 are joined. This allows the position of the low-rigidity portion to be actively set and the position of the second vehicle body mounting portion 7B to be determined. Also, as in the illustrated example, if the motor 12 of the steering drive mechanism is placed near the coupling surface P, the transmission of vibrations of the motor 12 to the vehicle body can be suppressed by the bush mount of the second vehicle body mounting portion 7B.

[0027] The embodiments described above are merely illustrative examples provided to facilitate understanding of the invention. The technical scope of the invention is not limited to the specific technical matters disclosed in the embodiments above, but also includes various modifications, changes, and alternative technologies that can be easily derived therefrom.

[0028] For example, in the above embodiment, four vehicle body mounting portions 7 were provided, but five or more vehicle body mounting portions 7 may be provided. In this case, three of the vehicle body mounting portions 7 are first vehicle body mounting portions 7A, and the other two or more vehicle body mounting portions 7 are second vehicle body mounting portions 7B. This makes it possible to obtain the effect of (1) above. Furthermore, each of the two or more second vehicle body mounting portions 7B can be positioned closer to the low-rigidity portion of the housing 5 than any of the first vehicle body mounting portions 7A. In other words, each first vehicle body mounting portion 7A can be positioned further away from the low-rigidity portion than any of the second vehicle body mounting portions 7B. In this case, it makes it possible to obtain the effect of (2) above.

[0029] 1 Steering gearbox 2 Subframe (body) 4 Shaft 5 Housing 51 First housing 52 Second housing 7 Body mounting part 7A First body mounting part 7B Second body mounting part 8 Bolt 19 Bushing P Joint surface (of the first housing 51 and the second housing 52) X Central axis (of the shaft 4)

Claims

1. A steering gearbox mounting structure comprising: a steering gearbox housing provided with at least four vehicle body mounting portions fixed to the vehicle body, three of the vehicle body mounting portions being first vehicle body mounting portions rigidly mounted to the vehicle body, and the vehicle body mounting portions other than the first vehicle body mounting portions being second vehicle body mounting portions bush mounted to the vehicle body.

2. The steering gearbox mounting structure according to claim 1, wherein the second vehicle body mounting portion is located closer to the lowest rigidity portion of the housing, which has the lowest bending rigidity, than any of the first vehicle body mounting portions.

3. The steering gearbox mounting structure according to claim 2, wherein the housing is divided into a first housing and a second housing in the axial direction of the shaft that transmits steering force to the steering wheel, and the low-rigidity portion is the joint surface to which the first housing and the second housing are joined.

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