JP2024041101A - steering gear - Google Patents

Abstract

[Problem] To provide a steering device that can realize weight reduction and cost reduction. [Solution] A cover member 21 has a snap fit portion 23 for engaging and holding the reduction gear housing 12, and a flange portion 22 to which a liquid gasket 25 is applied to seal the gap with the reduction gear housing 12. [Selected Figure] Figure 3

Description

The present invention relates to a steering device.

Patent Document 1 discloses a steering device including a dual pinion electric power steering device having a worm reduction gear. The opening of the housing facing the worm accommodating portion is covered with a cover member.

Japanese Patent Application Publication No. 2015-155745

However, the conventional steering device described above requires bolts for fixing the cover member to the housing and an O-ring for sealing, and there is a possibility that weight reduction and cost reduction cannot be achieved.
One of the objects of the present invention is to provide a steering device that can realize weight reduction and cost reduction.

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

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

1 is a diagram showing the overall configuration of a steering device A according to a first embodiment. 2 is a cross-sectional view of the reduction gear housing 12 of the first embodiment taken along a plane passing through the rotation axis O of the second pinion shaft 17. FIG. 3 is an enlarged view of the main part of FIG. 2. FIG. FIG. 3 is a perspective view of the cover member 21 of Embodiment 1 viewed from the positive x-axis direction side. FIG. 3 is a view of the cover member 21 of Embodiment 1 viewed from the positive x-axis direction side. FIG. 3 is a cross-sectional view in the x-axis direction of the second snap-fit piece 29 of Embodiment 1. 7 is a view of the cover member 21 of Embodiment 2 viewed from the positive x-axis direction side. FIG. 7 is a view of the cover member 21 of Embodiment 3 viewed from the x-axis positive direction side. FIG. 7 is a diagram of a cover member 21 of Embodiment 4 viewed from the positive x-axis direction side. FIG. FIG. 7 is a cross-sectional view in the X-axis direction of a cover member 21 of Embodiment 5.

[Embodiment 1]
FIG. 1 is a diagram showing the overall configuration of a steering device A according to a first embodiment.
The steering device A has a rack housing 2 that extends in the left-right direction of the vehicle, and a rack bar (steering shaft) 3 is installed in a rack bar accommodating portion 2a in the rack housing 2 in the left-right direction (vehicle width direction) of the vehicle. It is slidably housed. Ends of the rack bar 3 protrude from openings at both ends of the rack housing 2, and a tie rod 4 is connected to this end via a joint 5. The end of the rack bar 3, the joint 5, and the vicinity of the end of the tie rod 4 on the joint 5 side are covered by a boot 6. The movement of the rack bar 3 moves the tie rod 4, and a front wheel (not shown) is steered via a steering mechanism connected to the tie rod 4.

A steering gear housing 7 is provided at one end of the rack housing 2 (on the right side in FIG. 1). An input shaft 8 connected to a steering wheel (not shown) is rotatably supported in a pinion shaft accommodating portion 7a within the steering gear housing 7. The input shaft 8 is connected via a torsion bar 9 to a first pinion shaft 10 so as to be relatively rotatable.
A torque sensor 11 is provided on the outer peripheral side of the input shaft 8. The torque sensor 11 detects the steering torque that the driver inputs to the steering wheel from the amount of relative 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 side of the rack bar 3, and transmits steering torque input to the steering wheel to the rack bar 3. .

A reduction gear housing 12 is provided at the other end of the rack housing 2 (left side in FIG. 1). This reduction gear housing 12 accommodates a power steering mechanism 13 that outputs auxiliary steering torque in response to the steering torque input by the driver to the steering wheel.
A housing 1 is composed 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 wheel that rotates integrally with the worm wheel 16. It has a pinion shaft 17. 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 the worm wheel 16 are a transmission mechanism that transmits the driving force generated by the electric motor 14 to the second pinion shaft 17.

FIG. 2 is a cross-sectional view of the reduction gear housing 12 of the first embodiment taken along a plane passing through the rotation axis O of the second pinion shaft 17. In the following description, the x-axis is set along the rotation axis O, and the direction from the bottom to the top of the paper in FIG. 2 is defined as the positive x-axis direction, and the opposite direction is defined as the negative x-axis direction. Further, the radial direction with respect to the rotational axis O is referred to as a radial direction, and the direction around the rotational axis O is referred to as a circumferential direction.

The reduction gear housing 12 has a worm wheel accommodating portion 18 that accommodates the worm wheel 16. A ball bearing 19 is fixed to the x-axis positive direction side of the worm wheel accommodating portion 18. The ball bearing 19 rotatably supports the second pinion shaft 17. The worm wheel 16 is fixed to the end of the second pinion shaft 17 in the negative direction of the x-axis. 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 end of the reduction gear housing 12 on the negative side of the x-axis. The central axis of the opening 20 extends in the positive x-axis direction. The opening 20 is covered with a cover member 21 made of resin.

The cover member 21 has a flange portion 22 that covers the opening 20 from the negative side of the x-axis, and a snap fit portion 23 that locks and holds the cover member 21 on the reduction gear housing 12. The flange portion 22 is formed into a substantially disk shape. As shown in FIG. 3, a surface (matching surface) 22a of the flange portion 22 on the positive side of the X-axis is in contact with a bottom surface 24a of the recess 24 provided at the end of the opening 20 in the negative direction of the X-axis. 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 recessed portion 24, and the predetermined gap is provided to seal between the flange portion 22 and the reduction gear housing 12. The liquid gasket 25 is filled. The predetermined gap is set according to the viscosity of the liquid gasket 25.

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 in the positive direction of the x-axis. A claw portion 26a that projects outward in the radial direction is provided at the tip (the end in the positive x-axis direction) of the first snap-fit piece 26. When the cover member 21 is assembled to the reduction gear housing 12, the claw portion 26a engages with the locking groove 27 formed in the inner circumferential surface 20a of the opening 20, thereby locking the cover member 21 in the x-axis negative direction. Movement to is regulated.

A tapered surface 28 continuous from the bottom surface 24a of the recess 24 is formed on the inner peripheral surface 20a of the opening 20. The tapered surface 28 is set so that the inner diameter of the opening 20 gradually increases as it progresses from the positive side to the negative side of the x-axis. This tapered surface 28 allows the snap fit portion 23 to be gradually elastically deformed when the cover member 21 is assembled to the reduction gear housing 12, thereby 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 and on the radially outer side of the snap fit portion 23. The grooves 22c are provided to prevent the uncured liquid gasket from entering the cover member 21 through the gaps between the snap-fit pieces immediately after the liquid gasket 25 is applied.

Further, on the mating surface 22a, an annular column portion 22d is provided on the radially inner side of the snap fit portion 23. The pillar portion 22d is for suppressing the uncured liquid gasket that has entered the inside of the cover member 21 through the gaps between the snap-fit pieces from adhering to the worm wheel 16 and the like. The column portion 22d also has a function of suppressing the snap fit portion 23 from falling inward in the radial direction. In the first embodiment, the height (length in the x-axis direction) of the pillar portion 22d is set shorter than the snap fit portion 23, but it may be set to have the same length as the snap fit portion 23. Thereby, the effect of suppressing the fall of the snap-fit portion 23 becomes more significant.

FIG. 4 is a perspective view of the cover member 21 of Embodiment 1 seen from the x-axis positive direction, and FIG. 5 is a diagram of the cover member 21 of Embodiment 1 seen from the x-axis positive direction.
The snap-fit portion 23 includes a second snap-fit piece 29 in addition to the first snap-fit piece 26 . In the snap fit portion 23, a plurality of first snap fit pieces 26 and a plurality of second snap fit pieces 29 are disposed intermittently over the entire circumference. The first snap-fit piece 26 and the second snap-fit piece 26 have the same height (length in the x-axis direction) and width (length in the circumferential direction). Further, the gaps between the snap fit pieces are uniform. The snap fit section 23 of the first embodiment has four first snap fit pieces 26 and twelve second snap fit pieces 29. That is, the snap-fit pieces are arranged at intervals of 22.5° in the circumferential direction. In the first embodiment, three consecutive second snap fit pieces 29 are arranged to be sandwiched between two first snap fit pieces 26 in the circumferential direction.

FIG. 6 is an x-axis cross-sectional view of the second snap-fit piece 29 of the first embodiment, showing a 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 in the positive direction of the x-axis. A ridge portion 29a having a substantially triangular cross section and projecting radially outward is provided on the tip side (the end side in the positive x-axis direction) of the second snap-fit piece 29. The second snap-fit piece 29 is located radially inward from the inner circumferential surface 20a of the opening 20, excluding the peak 29a. When the cover member 21 is assembled to the reduction gear housing 12, the mountain portion 29a comes into pressure contact with the inner circumferential surface 20a of the opening 20, thereby restricting movement of the cover member 21 in the radial direction.

Next, the effects of the first embodiment will be explained.
Conventionally, a steering device including a dual pinion electric power steering device having a worm reduction gear is known. The opening of the housing facing the worm accommodating portion is closed with a cover member, and the cover member is fastened to the housing with two bolts. Further, the gap between the opening and the cover member is sealed with an O-ring. For this reason, it was difficult to shorten the overall length and reduce the number of parts, making it impossible to achieve weight reduction and cost reduction.

In contrast, in the steering device A of the first embodiment, the cover member 21 is coated with a liquid gasket 25 that seals between the snap fit portion 23 for locking and holding the reduction gear housing 12 and the reduction gear housing 12. flange portion 22. The snap fit section 23 includes a first snap fit piece 26 that restricts movement of the cover member 21 in the x-axis direction, and a second snap fit piece 29 that restricts movement of the cover member 21 in the radial direction. have Since the cover member 21 is fixed to the reduction gear housing 12 by snap-fitting, bolts for fastening are not required, and weight reduction and number of parts can be reduced. Furthermore, since the structure is such that the liquid gasket 25 seals between the flange portion 22 and the reduction gear housing 12, an O-ring is not required, and further weight reduction and reduction in the number of parts can be achieved. In addition, by eliminating the O-ring groove, the length of the cover member 21 can be shortened. As a result, in the steering device A of the first embodiment, weight reduction and cost reduction can be achieved.

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 of the reduction gear housing 12, and the liquid gasket 25 is filled in the predetermined gap. Therefore, it is easy to apply the liquid gasket 25, and the state of application of the liquid gasket 25 over the entire circumference of the flange portion 22 can be easily visually confirmed after the cover member 21 is assembled, so that workability can be improved.

An annular groove 22c is provided in a mating surface 22a of the flange portion 22 with the reduction gear housing 12 at a position radially outward of the snap fit portion 23. Thereby, it is possible to suppress the uncured liquid gasket from entering the inside of the cover member 21 through the gaps between the snap-fit pieces.
Furthermore, an annular column portion 22d is provided at a position radially inside the snap fit portion 23. That is, in the circumferential direction, the length of the column portion 22d is greater than the distance between the gaps between the snap fit pieces. Therefore, it is possible to prevent the liquid gasket that has entered the interior of the cover member 21 through the gaps between the snap-fit pieces from adhering to the worm wheel 16 or the like and causing problems such as getting caught.

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 slip-off at equal angles, the inclination of the cover member 21 with respect to the central axis of the opening 20 can be suppressed, so that the positioning of the cover member 21 in the radial direction with respect to the opening 20, that is, centering. is done automatically.
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 intervals of 120°. By arranging the second snap-fit pieces 29 for eliminating backlash at equal angles, the cover member 21 is pressed toward the center axis of the opening 20, so that the centering of the cover member 21 is automatically performed.

[Embodiment 2]
Since the basic configuration of the second embodiment is the same as that of the first embodiment, only the parts that are different from the first embodiment will be described.
FIG. 7 is a diagram of the cover member 21 of Embodiment 2 viewed from the x-axis positive direction side.
The snap fit section 23 of the second embodiment has three first snap fit pieces 26 and nine second snap fit pieces 29. In the circumferential direction, each snap-fit piece is spaced at 30° intervals. In the second embodiment, three consecutive second snap fit pieces 29 are arranged to be sandwiched between two first snap fit pieces 26 in the circumferential direction.
Therefore, in the second embodiment, the same effects as in the first embodiment are achieved.

[Embodiment 3]
Since the basic configuration of the third embodiment is the same as that of the first embodiment, only the parts that are different from the first embodiment will be described.
FIG. 8 is a diagram of the cover member 21 of Embodiment 3 viewed from the x-axis positive direction side.
The snap fit section 23 of the third embodiment 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 arranged at 90° intervals. The width (length in the circumferential direction) of the second snap-fit piece 29 is a little less than twice that of the first snap-fit piece 26.
Therefore, in the third embodiment, the same effects as in the first embodiment are achieved.

[Embodiment 4]
Since the basic configuration of the fourth embodiment is the same as that of the first embodiment, only the parts that are different from the first embodiment will be described.
FIG. 9 is a diagram of the cover member 21 of Embodiment 4 viewed from the x-axis positive direction side.
The snap fit section 23 of the fourth embodiment 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 intervals of 120°, and the second snap fit pieces 29 are arranged at intervals of 120°. The width (length in the circumferential direction) of the second snap-fit piece 29 is a little less than twice that of the first snap-fit piece 26.
Therefore, in the fourth embodiment, the same effects as in the first embodiment are achieved.

[Embodiment 5]
Since the basic configuration of the fifth embodiment is the same as that of the first embodiment, only the parts that are different from the first embodiment will be explained.
FIG. 10 is a cross-sectional view in the X-axis direction of the cover member 21 of the fifth embodiment.
In the cover member 21 of the fifth embodiment, the end of the snap fit portion 23 in the negative x-axis direction is located on the negative side of the x-axis relative to the mating surface 22a of the flange portion 22. Therefore, the end of the outer peripheral surface 22b of the flange portion 22 in the positive x-axis direction is located on the positive side of the x-axis rather than the end of the snap-fit portion 23 in the negative x-axis direction. Here, since the outer circumferential surface 22b becomes the application area of the liquid gasket 25, in the fifth embodiment, a part of the application area of the liquid gasket 25 overlaps with the snap-fit portion 23 in the x-axis direction. That is, in the fifth embodiment, by configuring a portion of the outer circumferential surface 22b to overlap the snap-fit portion 23 in the x-axis direction, the seal width can be increased while suppressing the elongation of the cover member 21. I can figure it out.

[Other embodiments]
Although the 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 may be made within the scope of 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.

In the embodiment, the groove 22c is annular, but a structure may be adopted in which grooves 22c, which are at least as long as the gaps between the snap-fit pieces, are provided intermittently by the number of gaps.
In the embodiment, the pillar portion 22d is annular, but the pillar portion 22d may be provided intermittently in the same number of gaps as the length of the gap between the snap-fit pieces.
In the embodiment, the steering device A is configured to include a so-called double pinion type electric power steering device, but the steering device A is a so-called steer-by-wire system in which the steering wheel and the rack bar are mechanically separated. It is also applicable to other steering devices.

A... Steering device, 3... Rack bar (steered 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 section, 20...Opening section, 21...Cover member, 22...Flange section, 23...Snap fit section, 25...Liquid gasket, 26...First snap Fit piece, 29...Second snap fit piece

Claims (8)

A steering shaft that is movable in a vehicle width direction;
a pinion shaft that meshes with the steering shaft;
a transmission mechanism that transmits a driving force generated by a driving 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 has a worm wheel accommodating portion that accommodates the worm wheel, an opening that connects the worm wheel accommodating portion to the outside, and a cover member that closes the opening,
The cover member has a snap-fit portion for engaging and retaining the cover member on the housing,
the snap-fit portion has a first snap-fit piece that restricts movement of the cover member in the axial direction and a second snap-fit piece that restricts movement of the cover member in the radial direction, when a direction along a rotation axis of the pinion shaft is defined as an axial direction and a direction radial to the rotation axis is defined as a radial direction,
The cover member has a flange portion to which a liquid gasket is applied to seal between the cover member and the housing.
Steering gear. The steering device according to claim 1,
A predetermined gap is provided between the outer peripheral surface of the flange portion and the housing in the radial direction,
the liquid gasket is filled in the predetermined gap;
Steering device. The steering device according to claim 2,
At least one groove is provided on a surface of the flange portion that fits with the housing;
Steering device. The steering device according to claim 2,
In the axial direction, a part of the application area of the liquid gasket overlaps with the snap fit part;
Steering device. The steering device according to claim 1,
When the direction around the rotational axis is defined as the circumferential direction, the snap-fit portion has a plurality of the first snap-fit pieces and a plurality of the second snap-fit pieces arranged intermittently over the entire circumference,
Steering device. The steering device according to claim 5,
In the radial direction, a column portion is provided inside 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 device. The steering device according to claim 5,
The first snap-fit pieces are arranged at equal intervals in the circumferential direction,
Steering device. The steering device according to claim 5,
The second snap-fit pieces are arranged at equal intervals in the circumferential direction,
Steering device.

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