Steering gear

Abstract

To provide a steering gear which can realize reduction in the weight and cost.SOLUTION: A cover member 21 comprises: a snap fit part 23 which is engaged to and held by a reduction gear housing 12; and a flange part 22 which is applied with a liquid gasket 25 that seals a gap between the reduction gear housing 12 and itself.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a steering device.

Background Art

[0002] Patent Document 1 discloses a steering device provided with a dual pinion type electric power steering device having a worm reduction gear. An opening facing the worm housing portion of the housing is closed by a cover member.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the steering device of the above prior art, bolts for fixing the cover member to the housing and O-rings for sealing are required, and there is a possibility that weight reduction and cost reduction cannot be achieved. One object of the present invention is to provide a steering device capable of achieving weight reduction and cost reduction.

Means for Solving the Problems

[0005] In the steering device according to an embodiment of the present invention, the cover member has a snap fit portion for locking and holding to the housing, and a flange portion coated with a liquid gasket for sealing between the cover member and the housing.

Effects of the Invention

[0006] Therefore, in the steering device of the present invention, weight reduction and cost reduction can be achieved.

Brief Description of the Drawings

[0008] [Embodiment 1] Figure 1 shows the overall configuration of the steering device A of Embodiment 1. The steering system A has a rack housing 2 that extends in the left-right direction of the vehicle, and a rack bar (steering shaft) 3 is housed in a rack bar housing section 2a within the rack housing 2 so as to be slidable in the left-right direction (vehicle width direction) of the vehicle. The ends of the rack bar 3 protrude from openings at both ends of the rack housing 2, and tie rods 4 are connected to these ends via joints 5. The ends of the rack bar 3, the joints 5, and the area around the end of the tie rod 4 on the joint 5 side are covered by boots 6. The movement of the rack bar 3 moves the tie rod 4, and the front wheels (steering wheels) (not shown) are steered via a steering mechanism connected to the tie rod 4.

[0009] A steering gear housing 7 is provided at one end of the rack housing 2 (right side in Figure 1). An input shaft 8, connected to a steering wheel (not shown), is rotatably supported in the pinion shaft housing portion 7a within the steering gear housing 7. The input shaft 8 is connected to the first pinion shaft 10 via a torsion bar 9 so as to be rotatable relative to it. A torque sensor 11 is provided on the outer circumference of the input shaft 8. The torque sensor 11 detects the steering torque that the driver inputs to the steering wheel from the relative amount of rotation between the input shaft 8 and the first pinion shaft 10. The first pinion shaft 10 has pinion teeth (not shown) that mesh with the first rack teeth 3a formed on one end of the rack bar 3, and transmits the steering torque input to the steering wheel to the rack bar 3.

[0010] A reduction gear housing 12 is provided at the other end of the rack housing 2 (left side in Figure 1). This reduction gear housing 12 houses a power steering mechanism 13 that outputs auxiliary steering torque in response to the steering torque input by the driver to the steering wheel. The housing 1 is comprised of a rack housing 2, a steering gear housing 7, and a reduction gear housing 12. The power steering mechanism 13 includes an electric motor (drive source) 14, a worm shaft 15 connected to the output shaft of the electric motor 14, a worm wheel 16 that meshes with the worm shaft 15, and a second pinion shaft 17 that rotates integrally with the worm wheel 16. The second pinion shaft 17 meshes with second rack teeth 3b formed on the other end of the rack shaft and transmits the motor torque input from the electric motor 14 to the rack bar 3. The worm shaft 15 and worm wheel 16 are a transmission mechanism that transmits the driving force generated by the electric motor 14 to the second pinion shaft 17.

[0011] FIG. 2 is a cross-sectional view of the reduction gear housing 12 of Embodiment 1 cut along a plane passing through the rotation axis O of the second pinion shaft 17. In the following description, an x-axis is set in the direction along the rotation axis O, the positive x-axis direction is from the lower side to the upper side of the paper surface of FIG. 2, and the opposite direction is the negative x-axis direction. Also, the radial direction with respect to the rotation axis O is referred to as the radial direction, and the direction around the rotation axis O is referred to as the circumferential direction.

[0012] The reduction gear housing 12 has a worm wheel housing portion 18 that houses the worm wheel 16. A ball bearing 19 is fixed to the positive x-axis side of the worm wheel housing portion 18. The ball bearing 19 rotatably supports the second pinion shaft 17. The worm wheel 16 is fixed to the negative x-axis end of the second pinion shaft 17. An opening 20 for assembling the second pinion shaft 17 and the worm wheel 16 into the reduction gear housing 12 is provided at the negative x-axis side end of the reduction gear housing 12. The central axis of the opening 20 extends toward the positive x-axis side. The opening 20 is closed by a resin cover member 21.

[0013] The cover member 21 has a flange portion 22 that covers the opening 20 from the negative x-axis side and a snap fit portion 23 for locking and holding the cover member 21 to the reduction gear housing 12. The flange portion 22 is formed in a substantially disk shape. As shown in FIG. 3, the surface (contact surface) 22a on the positive x-axis side of the flange portion 22 is in contact with the bottom surface 24a of the recess 24 provided at the negative x-axis end of the opening 20. In the radial direction, a predetermined gap is provided between the outer peripheral surface 22b of the flange portion 22 and the side surface 24b of the recess 24, and the predetermined gap is filled with a liquid gasket 25 for sealing between the flange portion 22 and the reduction gear housing 12. The predetermined gap is set according to the viscosity of the liquid gasket 25.

[0014] The snap - fit portion 23 has a first snap - fit piece 26. The first snap - fit piece 26 protrudes from the mating surface 22a of the flange portion 22 toward the positive x - axis side. At the tip (positive x - axis end) of the first snap - fit piece 26, a claw portion 26a that protrudes radially outward is provided. When the cover member 21 is assembled to the reduction gear housing 12, the claw portion 26a engages with a locking groove 27 formed on the inner peripheral surface 20a of the opening 20, thereby restricting the movement of the cover member 21 toward the negative x - axis side.

[0015] On the inner peripheral surface 20a of the opening 20, a tapered surface 28 that is continuous from the bottom surface 24a of the recess 24 is formed. The tapered surface 28 is set such that the inner diameter of the opening 20 gradually expands as it proceeds from the positive x - axis side to the negative x - axis side. With this tapered surface 28, when the cover member 21 is assembled to the reduction gear housing 12, the snap - fit portion 23 can be gradually elastically deformed, facilitating the assembly work. In the cover member 21, an annular groove 22c is provided on the mating surface 22a of the flange portion 22, radially outside the snap - fit portion 23. The groove 22c is for suppressing the liquid gasket before curing from entering the inside of the cover member 21 through the gap between the snap - fit pieces immediately after the application of the liquid gasket 25.

[0016] Also, on the mating surface 22a, an annular column portion 22d is provided radially inside the snap - fit portion 23. The column portion 22d is for suppressing the cured - before liquid gasket that has entered the inside of the cover member 21 through the gap between the snap - fit pieces from adhering to the worm wheel 16 or the like. Also, the column portion 22d has a function of suppressing the radial - inward collapse of the snap - fit portion 23. In Embodiment 1, the height (length in the x - axis direction) of the column portion 22d is set shorter than that of the snap - fit portion 23, but it may be set to the same length as the snap - fit portion 23. Thereby, the effect of suppressing the collapse of the snap - fit portion 23 becomes more prominent.

[0017] Figure 4 is a perspective view of the cover member 21 of Embodiment 1 as seen from the positive x-axis direction, and Figure 5 is a view of the cover member 21 of Embodiment 1 as seen from the positive x-axis direction. The snap-fit ​​section 23 has a second snap-fit ​​piece 29 in addition to the first snap-fit ​​piece 26. Multiple first snap-fit ​​pieces 26 and second snap-fit ​​pieces 29 are arranged intermittently around the entire circumference of the snap-fit ​​section 23. The first snap-fit ​​pieces 26 and second snap-fit ​​pieces 26 have the same height (length in the x-axis direction) and width (length in the circumferential direction). Also, the gap between each snap-fit ​​piece is uniform. The snap-fit ​​section 23 of Embodiment 1 has four first snap-fit ​​pieces 26 and twelve second snap-fit ​​pieces 29. That is, in the circumferential direction, each snap-fit ​​piece is arranged at an interval of 22.5°. In Embodiment 1, in the circumferential direction, three consecutive second snap-fit ​​pieces 29 are arranged to be sandwiched between two first snap-fit ​​pieces 26.

[0018] Figure 6 is a cross-sectional view of the second snap-fit ​​piece 29 in the x-axis direction of Embodiment 1, showing the state before the cover member 21 is assembled to the reduction gear housing 12. The second snap-fit ​​piece 29 protrudes from the mating surface 22a of the flange portion 22 toward the positive x-axis direction. The tip side (positive x-axis end) of the second snap-fit ​​piece 29 is provided with a roughly triangular cross-section ridge 29a that protrudes radially outward. Except for the ridge 29a, the second snap-fit ​​piece 29 is located radially inward from the inner circumferential surface 20a of the opening 20. When the cover member 21 is assembled to the reduction gear housing 12, the ridge 29a presses against the inner circumferential surface 20a of the opening 20, thereby restricting the radial movement of the cover member 21.

[0019] Next, the effects of Embodiment 1 will be explained. Conventionally, steering systems equipped with a dual-pinion electric power steering system having a worm gear reducer are known. The opening facing the worm housing of the housing is closed by a cover member, which is fastened to the housing by two bolts. The gap between the opening and the cover member is sealed by an O-ring. As a result, it has been difficult to shorten the overall length and reduce the number of parts, and it has been difficult to achieve weight reduction and cost reduction.

[0020] In contrast, in the steering device A of Embodiment 1, the cover member 21 has a snap-fit ​​portion 23 for locking and holding to the reduction gear housing 12, and a flange portion 22 to which a liquid gasket 25 is applied to seal the space between the cover member 21 and the reduction gear housing 12. The snap-fit ​​portion 23 has a first snap-fit ​​piece 26 that restricts the movement of the cover member 21 in the x-axis direction, and a second snap-fit ​​piece 29 that restricts the movement of the cover member 21 in the radial direction. Because the cover member 21 is fixed to the reduction gear housing 12 by a snap-fit ​​structure, fastening bolts are not required, resulting in weight reduction and a reduction in the number of parts. Furthermore, because the space between the flange portion 22 and the reduction gear housing 12 is sealed by the liquid gasket 25, an O-ring is not required, resulting in further weight reduction and a reduction in the number of parts. In addition, by eliminating the O-ring groove, the cover member 21 can be shortened. As a result, the steering device A of Embodiment 1 can be made lighter and less expensive.

[0021] In the radial direction, a predetermined gap is provided between the outer circumferential surface 22b of the flange portion 22 and the side surface 24b of the recess 24 in the reduction gear housing 12, and the liquid gasket 25 is filled into this predetermined gap. Therefore, application of the liquid gasket 25 is easy, and after assembling the cover member 21, the application state of the liquid gasket 25 over the entire circumference of the flange portion 22 can be easily visually confirmed, thereby improving work efficiency.

[0022] An annular groove 22c is provided at the mating surface 22a of the flange portion 22 with the reduction gear housing 12, located radially outward from the snap-fit ​​portion 23. This prevents the liquid gasket before curing from entering the interior of the cover member 21 through the gaps between the snap-fit ​​pieces. Furthermore, an annular columnar portion 22d is provided at a position radially inward of the snap-fit ​​portion 23. In other words, in the circumferential direction, the length of the columnar portion 22d is greater than the distance of the gap between each snap-fit ​​piece. Therefore, it is possible to suppress the liquid gasket that has entered the interior of the cover member 21 through the gap between each snap-fit ​​piece from adhering to the worm wheel 16, etc., and causing problems such as jamming.

[0023] The first snap-fit ​​pieces 26 are arranged at equal intervals in the circumferential direction. By arranging the first snap-fit ​​pieces 26 for preventing detachment at equal angles, the tilt of the cover member 21 with respect to the central axis of the opening 20 can be suppressed, thereby automatically performing radial positioning, i.e., centering, of the cover member 21 with respect to the opening 20. The second snap-fit ​​pieces 29 are arranged at equal intervals in the circumferential direction. Specifically, three consecutive second snap-fit ​​pieces 29 are arranged at 120° intervals. By arranging the second snap-fit ​​pieces 29 for eliminating play at equal angles, the cover member 21 is pressed toward the central axis of the opening 20, thereby automatically centering the cover member 21.

[0024] [Embodiment 2] Since the basic configuration of Embodiment 2 is the same as that of Embodiment 1, only the differences from Embodiment 1 will be described. Figure 7 is a view of the cover member 21 of Embodiment 2 as seen from the positive x-axis direction. The snap-fit ​​portion 23 of Embodiment 2 has three first snap-fit ​​pieces 26 and nine second snap-fit ​​pieces 29. In the circumferential direction, each snap-fit ​​piece is arranged at a 30° interval. In Embodiment 2, in the circumferential direction, three consecutive second snap-fit ​​pieces 29 are sandwiched between two first snap-fit ​​pieces 26. Therefore, Embodiment 2 provides the same effects and advantages as Embodiment 1.

[0025] [Embodiment 3] Since the basic configuration of Embodiment 3 is the same as that of Embodiment 1, only the differences from Embodiment 1 will be described. Figure 8 is a view of the cover member 21 of Embodiment 3 as seen from the positive x-axis direction. The snap-fit ​​section 23 of Embodiment 3 has four first snap-fit ​​pieces 26 and four second snap-fit ​​pieces 29. In the circumferential direction, the first snap-fit ​​pieces 26 are arranged at 90° intervals, and the second snap-fit ​​pieces 29 are also arranged at 90° intervals. The width (circumferential length) of the second snap-fit ​​pieces 29 is slightly less than twice that of the first snap-fit ​​pieces 26. Therefore, Embodiment 3 provides the same effects and advantages as Embodiment 1.

[0026] [Embodiment 4] Since the basic configuration of Embodiment 4 is the same as that of Embodiment 1, only the differences from Embodiment 1 will be described. Figure 9 is a view of the cover member 21 of Embodiment 4 as seen from the positive x-axis direction. The snap-fit ​​section 23 of Embodiment 4 has three first snap-fit ​​pieces 26 and three second snap-fit ​​pieces 29. In the circumferential direction, the first snap-fit ​​pieces 26 are arranged at 120° intervals, and the second snap-fit ​​pieces 29 are also arranged at 120° intervals. The width (circumferential length) of the second snap-fit ​​pieces 29 is slightly less than twice that of the first snap-fit ​​pieces 26. Therefore, Embodiment 4 provides the same effects and advantages as Embodiment 1.

[0027] [Embodiment 5] Since the basic configuration of Embodiment 5 is the same as that of Embodiment 1, only the differences from Embodiment 1 will be described. Figure 10 is a cross-sectional view of the cover member 21 in the X-axis direction according to Embodiment 5. In Embodiment 5, the cover member 21 has the negative x-axis end of the snap-fit ​​portion 23 located on the negative x-axis side of the mating surface 22a of the flange portion 22. Therefore, the positive x-axis end of the outer peripheral surface 22b of the flange portion 22 is located on the positive x-axis side of the snap-fit ​​portion 23 on the negative x-axis side. Here, since the outer peripheral surface 22b is the application area for the liquid gasket 25, in Embodiment 5, a portion of the application area for the liquid gasket 25 overlaps with the snap-fit ​​portion 23 in the x-axis direction. In other words, in Embodiment 5, by configuring the cover member 21 to overlap a portion of the outer peripheral surface 22b with the snap-fit ​​portion 23 in the x-axis direction, it is possible to increase the seal width while suppressing the lengthening of the cover member 21.

[0028] [Other embodiments] Although embodiments for carrying out the present invention have been described above, the specific configuration of the present invention is not limited to the configuration of the embodiments, and design changes and the like that do not depart from the gist of the invention are also included in the present invention. The number and shape of the first snap-fit ​​piece 26 and the second snap-fit ​​piece 29 can be set arbitrarily.

[0029] In this embodiment, the groove 22c is annular in shape, but it is also possible to have a configuration in which grooves 22c, each with a length at least equal to the length of the gap between each snap-fit ​​piece, are intermittently provided as there are gaps. In this embodiment, the column portion 22d is annular, but it is also possible to have a configuration in which column portions 22d, each with a length at least equal to the length of the gap between each snap-fit ​​piece, are provided intermittently for the number of gaps. In this embodiment, the steering system A is configured to include a so-called double-pinion type electric power steering system. However, the steering system A is also applicable to a so-called steer-by-wire steering system in which the steering wheel and rack bar are mechanically separated. [Explanation of Symbols]

[0030] A... Steering gear, 3... Rack bar (steering shaft), 12... Reduction gear housing (housing), 14... Electric motor (drive source), 15... Worm shaft (transmission mechanism), 16... Worm wheel (transmission mechanism), 17... Second pinion shaft (pinion shaft), 18... Worm wheel housing, 20... Opening, 21... Cover member, 22... Flange part, 23... Snap-fit ​​part, 25... Liquid gasket, 26... First snap-fit ​​piece, 29... Second snap-fit ​​piece

Claims

1. A steering axis that can move in the width direction of the vehicle, The pinion shaft that meshes with the steering shaft, A transmission mechanism that transmits the driving force generated by the drive source to the pinion shaft, A housing that accommodates the steering shaft, the pinion shaft, and the transmission mechanism, Equipped with, The transmission mechanism has a worm wheel that rotates integrally with the pinion shaft, The housing includes a worm wheel housing for housing the worm wheel, an opening connecting the worm wheel housing to the outside, and a cover member that closes the opening. The cover member has a snap-fit ​​portion for locking and holding it to the housing, The snap-fit ​​portion includes a first snap-fit ​​piece that restricts the axial movement of the cover member, and a second snap-fit ​​piece that restricts the radial movement of the cover member, when the direction along the rotation axis of the pinion shaft is defined as the axial direction and the direction radial to the rotation axis is defined as the radial direction. The cover member has a flange portion to which a liquid gasket is applied to seal the space between it and the housing. Steering gear.

2. A steering device according to claim 1, In the radial direction, a predetermined gap is provided between the outer circumferential surface of the flange portion and the housing. The liquid gasket is filled into the predetermined gap. Steering gear.

3. A steering device according to claim 2, At least one groove is provided on the mating surface of the flange portion with the housing. Steering gear.

4. A steering device according to claim 2, In the axial direction, a portion of the application area of ​​the liquid gasket overlaps with the snap-fit ​​portion. Steering gear.

5. A steering device according to claim 1, When the direction around the rotation axis is defined as the circumferential direction, the snap-fit ​​portion has multiple first snap-fit ​​pieces and multiple second snap-fit ​​pieces arranged intermittently around the entire circumference. Steering gear.

6. A steering device according to claim 5, In the radial direction, a column is provided on the inside of the gap between each snap-fit ​​piece. In the circumferential direction, the length of the column portion is greater than the distance of the gap. Steering gear.

7. A steering device according to claim 5, The first snap-fit ​​pieces are arranged at equal intervals in the circumferential direction. Steering gear.

8. A steering device according to claim 5, The second snap-fit ​​pieces are arranged at equal intervals in the circumferential direction. Steering gear.

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