阅读说明：本技术 汽车转向装置 (Automobile steering device ) 是由 杨涛涛 王式民 刘畅 于 2021-10-11 设计创作，主要内容包括：本发明公开了一种汽车转向装置,包括电动助力机构,所述电动助力机构包括壳体,所述壳体内设置有相啮合的蜗轮与蜗杆,所述蜗杆的端部通过轴承连接于所述壳体上,还包括恒定力间隙调整组件,所述恒定力间隙调整组件包括摩擦筒、摩擦柱以及挤压弹簧,所述摩擦柱滑动连接于所述摩擦筒中,所述挤压弹簧的两端分别接收所述摩擦柱以及所述蜗杆的挤压限位；所述蜗轮与蜗杆之间的挤压力大于所述摩擦柱与所述摩擦筒之间的最大静摩擦力。本发明提供的一种汽车转向装置,利用摩擦筒、摩擦柱之间的摩擦力作为基准,构建了蜗轮、蜗杆、挤压弹簧、摩擦柱、摩擦筒的压力传导机构,如此通过挤压摩擦柱即可维持蜗轮与蜗杆间的挤压力处于基本恒定的状态。(The invention discloses an automobile steering device, which comprises an electric power-assisted mechanism, wherein the electric power-assisted mechanism comprises a shell, a worm wheel and a worm which are meshed with each other are arranged in the shell, the end part of the worm is connected to the shell through a bearing, the automobile steering device also comprises a constant force gap adjusting assembly, the constant force gap adjusting assembly comprises a friction cylinder, a friction column and an extrusion spring, the friction column is connected in the friction cylinder in a sliding manner, and two ends of the extrusion spring respectively receive the friction column and the extrusion limit of the worm; the extrusion force between the worm wheel and the worm is larger than the maximum static friction force between the friction column and the friction cylinder. The invention provides an automobile steering device, which utilizes the friction force between a friction cylinder and a friction column as a reference to construct a pressure transmission mechanism of a worm wheel, a worm, an extrusion spring, the friction column and the friction cylinder, so that the extrusion force between the worm wheel and the worm can be maintained in a basically constant state by extruding the friction column.)

1. An automobile steering device comprises an electric power-assisted mechanism, wherein the electric power-assisted mechanism comprises a shell, a worm wheel and a worm which are meshed with each other are arranged in the shell, and the end part of the worm is connected to the shell through a bearing; the extrusion force between the worm wheel and the worm is larger than the maximum static friction force between the friction column and the friction cylinder;

the reset assembly is used for intermittently driving the friction column to extrude the extrusion spring.

2. The steering device for the vehicle according to claim 1, wherein one end of the worm is a pressing end protruding from the bearing, and the pressing spring realizes the pressing limit through the pressing end.

3. The steering device for a vehicle according to claim 2, further comprising an intermediate member provided on a pressing end, the pressing spring receiving pressing of the worm through the intermediate member.

4. The steering apparatus for a vehicle according to claim 3, wherein the intermediate member includes an intermediate lever, and both ends of the intermediate lever are provided with a pressing portion, and both the pressing portions abut against both sides of the pressing portion, respectively, and the intermediate lever is rotatable at a middle portion thereof, which receives the pressing of the pressing spring.

5. The steering device for the vehicle according to claim 4, wherein one end of the pressing spring is provided with a pressing post, and a middle portion of the intermediate lever is rotatably connected to the pressing post.

6. The steering device for the vehicle according to claim 1, wherein the bearing is internally housed in a fixed cylinder, and the pressing spring performs the pressing limit by pressing the fixed cylinder.

7. The automobile steering device according to claim 6, wherein one end of the worm is provided with a self-aligning ball bearing, and the fixed cylinder is sleeved on a bearing at the other end of the worm.

8. The steering device for a vehicle according to claim 1, wherein the friction cylinder and the friction column are made of the same metal material.

9. The steering device for the automobile according to any one of claims 1 to 8, wherein an opening of an end of the friction cylinder facing away from the friction column is closed with a soft cloth.

10. The steering device for an automobile according to claim 1, further comprising a friction force adjusting mechanism for adjusting the magnitude of the maximum static friction force between the friction column and the friction cylinder.

Technical Field

The invention relates to an automobile steering technology, in particular to an automobile steering device.

Background

Currently, power steering systems are already standard for automobile steering devices, and power steering systems in the prior art include mechanical hydraulic power steering systems, electronic hydraulic power steering systems, electric power steering systems, and the like, wherein electric power steering systems are increasingly used due to compact structure, good direction, high speed stability, energy saving, and the like.

Most commonly, the electric power steering system uses a worm gear as a core speed reduction transmission mechanism, so that the matching performance of the worm gear directly determines the hand feeling and the performance of the electric power steering, and after long-term use, the clearance between the worm gear and the worm gear is increased due to abrasion and the like, so that the hand feeling is poor, and the noise is increased. In order to solve the problem, some high-end vehicle models begin to release an electric power assisting system with clearance compensation, and the principle is as follows: the worm is extruded by an elastic extrusion mechanism, so that the worm is driven by the extrusion of the elastic extrusion mechanism after the clearance between the worm and the worm wheel is enlarged, and the clearance between the worm and the worm wheel is kept smaller than a preset value. For example, the invention patent with publication number CN107985394B, publication date 20210101, entitled "clearance compensation mechanism for speed reduction mechanism of electric power steering system", includes a speed reduction box body, and a worm wheel and a worm engaged with each other, where the clearance compensation mechanism includes a first bearing sleeved on the worm, a tolerance compensation ring sleeved on the first bearing, and a jackscrew assembly for providing elastic supporting force to the worm. Tolerance compensation ring includes outer support ring, sets up in the inside of outer support ring interior support ring circle, with outer support ring and interior support ring connection's connecting block, set up on outer support ring and be used for providing the first supporting shoe of supporting role to interior support ring in the first direction and set up on outer support ring and be used for playing limiting displacement's second supporting shoe to interior support ring in the second direction, the first direction with the axis of worm wheel parallels, and interior support ring has lets first bearing male centre bore. For example, the invention patent application with application publication number CN102765418B adopts the above working principle, that is, an elastic extrusion mechanism is used to abut against the worm, and when the gap between the worm and the worm wheel becomes larger, the elastic extrusion mechanism deforms to drive the worm to approach the worm wheel, thereby reducing the gap.

Obviously, the prior art better solves the problem that the gap between the worm and the gear becomes larger, but the solution method depends on the deformation of a compressed elastic extrusion mechanism such as a spring, an elastic sheet and the like for supplement, which brings the following problems that firstly, the elastic force provided by the elastic extrusion mechanism under different deformation amplitudes is different, which actually causes the extrusion force between the worm and the gear to be changed, and the different extrusion force further causes the problem of aggravation of abrasion; secondly, the elastic pressing mechanism, such as the elastic sheet, reaches the vicinity of the deformation limit capability due to the large deformation amplitude or material aging, and the gap compensation capability thereof is greatly reduced. The prior art also attempted to solve the problem, such as CN107985394B, in which the spring is pressed by the rotation of the screw rod, so as to control the deformation amplitude of the spring, but the adjustment method completely depends on blind measurement, and has no quantitative parameter control and guidance, so as to be rather boring.

Disclosure of Invention

The invention aims to provide an automobile steering device to solve the defects in the prior art.

In order to achieve the above purpose, the invention provides the following technical scheme:

an automobile steering device comprises an electric power-assisted mechanism, wherein the electric power-assisted mechanism comprises a shell, a worm wheel and a worm which are meshed with each other are arranged in the shell, the end part of the worm is connected to the shell through a bearing, the automobile steering device also comprises a constant force gap adjusting assembly, the constant force gap adjusting assembly comprises a friction cylinder, a friction column and an extrusion spring, the friction column is connected in the friction cylinder in a sliding manner, and two ends of the extrusion spring respectively receive the friction column and extrusion limit of the worm; the extrusion force between the worm wheel and the worm is larger than the maximum static friction force between the friction column and the friction cylinder;

the reset assembly is used for intermittently driving the friction column to extrude the extrusion spring.

In the automobile steering device, one end of the worm extends out of the extrusion end of the bearing, and the extrusion spring realizes extrusion limiting through the extrusion end.

The automobile steering device further comprises an intermediate piece, the intermediate piece is arranged on the extrusion end, and the extrusion spring receives extrusion of the worm through the intermediate piece.

In the automobile steering device, the intermediate piece comprises the intermediate rod, two extrusion parts are respectively arranged at two ends of the intermediate rod and respectively abutted against two sides of the extrusion ends, the intermediate rod can rotate by the middle part of the intermediate rod, and the middle part of the intermediate rod is extruded by the extrusion spring.

In the automobile steering device, the extrusion column is arranged at one end of the extrusion spring, and the middle part of the intermediate rod is rotatably connected to the extrusion column.

In the automobile steering device, the bearing is sleeved in the fixed cylinder, and the extrusion spring is used for realizing extrusion limiting through extruding the fixed cylinder.

In the automobile steering device, one end of the worm is provided with the self-aligning ball bearing, and the bearing at the other end of the worm is sleeved with the fixed cylinder.

In the automobile steering device, the friction cylinder and the friction column are made of the same metal material.

In the automobile steering device, the opening at one end of the friction cylinder, which is far away from the friction column, is sealed with soft cloth.

The automobile steering device further comprises a friction force adjusting mechanism, and the friction force adjusting mechanism is used for adjusting the maximum static friction force between the friction column and the friction cylinder.

In the technical scheme, the pressure transmission mechanisms of the worm wheel, the worm, the extrusion spring, the friction column and the friction cylinder are constructed by using the maximum static friction force between the friction cylinder and the friction column as a reference, so that the extrusion force between the worm wheel and the worm can be maintained in a state of being basically constant, namely equal to the maximum static friction force by intermittently extruding the friction column through the reset assembly.

Drawings

In order to more clearly illustrate the embodiments of the present application or technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments described in the present invention, and other drawings can be obtained by those skilled in the art according to the drawings.

Fig. 1 is a schematic structural view of a steering apparatus for a vehicle according to an embodiment of the present invention;

fig. 2 is a schematic structural view of a steering apparatus for a vehicle according to another embodiment of the present invention;

FIG. 3 is a schematic diagram of a constant force gap adjustment assembly according to an embodiment of the present invention;

FIG. 4 is a schematic structural view of an intermediate rod and a crush end provided by an embodiment of the present invention;

fig. 5 is a schematic structural diagram of a reset assembly according to an embodiment of the present invention.

Description of reference numerals:

1. a worm gear; 2. a worm; 2.1, extruding the end; 2.11, an arc-shaped groove; 3. a friction cylinder; 4. a friction column; 5. a compression spring; 6. a reset assembly; 7. an intermediate lever; 8. a pressing section; 9. a bearing; 10. a self-aligning ball bearing; 11. a fixed cylinder; 12. soft cloth; 13. a second sphere.

Detailed Description

In order to make the technical solutions of the present invention better understood, those skilled in the art will now describe the present invention in further detail with reference to the accompanying drawings.

As shown in fig. 1 to 5, an automobile steering device provided in an embodiment of the present invention includes an electric power-assisted mechanism, the electric power-assisted mechanism includes a housing, a worm wheel 1 and a worm 2 engaged with each other are disposed in the housing, an end of the worm 2 is connected to the housing through a bearing 9, and the electric power-assisted mechanism further includes a constant force gap adjusting assembly and a reset assembly 6, the constant force gap adjusting assembly includes a friction cylinder 3, a friction column 4 and an extrusion spring 5, the friction column 4 is slidably connected to the friction cylinder 3, and two ends of the extrusion spring 5 respectively receive extrusion limit of the friction column 4 and the worm 2; the extrusion force between the worm wheel 1 and the worm 2 is larger than the maximum static friction force between the friction column 4 and the friction cylinder 3. The reset component 6 is used for intermittently driving the friction column 4 to press the pressing spring 5.

Specifically, the automobile steering device that this embodiment provided includes electric power assisted mechanism, and electric power assisted mechanism's reduction gear is worm wheel 1 and worm 2 of meshing mutually, and worm 2 accepts helping hand motor's drive, and worm wheel 1 realizes turning to the helping hand, and the both ends of worm 2 are all connected on electric power assisted mechanism's casing through bearing 9, and this is prior art, does not give unnecessary details. The core of this embodiment lies in providing a constant force gap adjustment assembly, the constant force gap adjustment assembly is used for providing a substantially constant resistance to adjust a gap between the worm wheel 1 and the worm 2, and preventing the gap between the worm wheel 1 and the worm 2 from being too large, and structurally, the constant force gap adjustment assembly includes a friction cylinder 3, a friction column 4 and an extrusion spring 5, wherein, a through hole is enclosed by an inner wall of the friction cylinder 3, the friction column 4 is slidably connected in the through hole, the friction column 4 and the friction cylinder 3 enclose within a predetermined range, the friction force can be effectively controlled by the control of processing precision and type selection, which is the prior art, and can also be detected and obtained by a pressure sensor, which is not repeated, two ends of the extrusion spring 5 respectively receive the extrusion limit of the friction column 4 and the worm 2, and conventionally, one end of the extrusion spring 5 is connected with the friction column 4, and the other end of the worm is connected with an end of the worm 2, the friction column 4 and the worm 2 can be directly extruded and limited obviously, preferably, the extrusion spring 5 indirectly receives the extrusion and limitation of the friction column 4 and the worm 2, for example, a protruding part is arranged on the friction column 4 or the worm 2, the protruding part is inserted into the extrusion spring 5 to realize the extrusion and limitation, or a limiting hole is arranged on the end part of the friction column 4 or the worm 2, and the end part of the extrusion spring 5 is inserted into the limiting hole to realize the extrusion and limitation; the purpose of this arrangement is to construct a pressure conduction path: the friction cylinder 3, the friction column 4, the extrusion spring 5, the worm 2 and the worm wheel 1, wherein friction force exists between the friction cylinder 3 and the friction column 4, and abutting pressure exists between other structures, obviously, based on the principle of force interaction, the friction force and the pressure in the surface are both equal and are just equal to the elastic force of the extrusion spring 5 (the maximum static friction force exists between the friction cylinder 3 and the friction column 4 in the actual operation process), in the embodiment, the extrusion force between the worm wheel 1 and the worm 2 is greater than the maximum static friction force between the friction column 4 and the friction cylinder 3, that is, in the normal motion state, the worm 2 can extrude the extrusion spring 5 to deform, if the deformation pressure of the extrusion spring 5 is less than the maximum static friction force, the extrusion spring 5 cannot further force the friction column 4 to move relative to the friction cylinder 3, but if the worm 2 can extrude the extrusion spring 5 to deform, the generated elastic force is greater than the maximum static friction force, the extrusion spring 5 extrudes the friction column 4 to enable the friction column 4 to move until the elastic force is equal to the maximum static friction force, the reset assembly 6 intermittently and actively extrudes the friction column 4 to enable the friction column 4 to move relative to the friction cylinder 3 so as to adjust the abutting pressure in the pressure conduction path, the friction column 4 is directly driven to extrude the extrusion spring 5, the elastic force generated by the deformation amplitude of the extrusion spring 5 is greater than the maximum static friction force, the feedback is inevitably generated, and the pressure of the whole pressure conduction path is equal to the maximum static friction force. That is, the object of the present invention is achieved by controlling the pressing force between the worm wheel 1 and the worm 2 to be substantially constant, which on the one hand obviously allows the control of the gap and on the other hand provides a more stable transmission relationship.

In this embodiment, since the friction is directly proportional to the pressure and the friction coefficient and is independent of the friction area, the through holes in the friction column 4 and the friction cylinder 3 may be arbitrarily set, such as a cylinder, various prisms, etc., but the processing precision relates to the friction coefficient, the matching parameter relates to the pressure, both of them need to be controlled more precisely, so the maximum static friction force between both of them can be controlled precisely, and simultaneously the extrusion force between the worm wheel 1 and the worm 2 can be detected by the pressure sensor, both of the above two pressures can be detected accurately, and it is obvious that the technical goal that the extrusion force between the worm wheel 1 and the worm 2 is greater than the maximum static friction force between the friction column 4 and the friction cylinder 3 can be conveniently realized by limited experiments. In this embodiment, it is preferable that the friction cylinder 3 and the friction column 4 are made of the same metal material, so that on one hand, the metal material has better durability and heat dissipation performance, and on the other hand, the same material is convenient for maintaining the same thermal expansion amplitude, thereby reducing the maximum static friction change caused by the difference between thermal expansion and cold contraction.

In this embodiment, the reset component 6 may be various mechanisms capable of being driven intermittently, such as a motor, a hydraulic cylinder, an electromagnetic valve, etc. which are driven intermittently, for example, once a day, and the driving manner for driving the friction column 4 is linear motion, which is the simplest driving manner, and is not described in detail, each time the extrusion is performed, the deformation amplitude of the extrusion spring 5 is smaller than the maximum deformation amplitude and larger than the deformation amplitude of the maximum static friction force between the friction column 4 and the friction cylinder 3, which can be obtained by limited experiments or calculation, and is not described in detail.

According to the automobile steering device provided by the embodiment of the invention, the maximum static friction force between the friction cylinder 3 and the friction column 4 is used as a reference, the pressure transmission mechanisms of the worm wheel 1, the worm 2, the extrusion spring 5, the friction column 4 and the friction cylinder 3 are constructed, so that the extrusion force between the worm wheel 1 and the worm 2 can be maintained in a state of being basically constant, namely equal to the maximum static friction force by intermittently extruding the friction column 4 through the resetting component 6.

In another embodiment provided by the present invention, further, one end of the worm 2 is an extrusion end 2.1 protruding out of the bearing 9, the extrusion spring 5 realizes the extrusion limit through the extrusion end 2.1, so that the extrusion spring 5 directly extrudes the worm 2, which has two advantages, one of which extrudes the bearing 9 relatively, so as to design various extrusion structures on the extrusion end 2.1, and the other of which directly restricts the worm 2, so as to reduce the pressure brought to the bearing 9 by the radial movement of the worm 2, and prolong the service life of the bearing 9.

Furthermore, still include the middleware, the middleware sets up on extrusion end 2.1, extrusion spring 5 passes through the middleware is accepted the extrusion of worm 2, also sets up an middleware between extrusion spring 5 and worm 2, can promote spacing direction or other effects through the middleware, for setting up a cylinder on extrusion end 2.1 like aforementioned middleware, during the cylinder inserts extrusion spring 5, so realize leading spacing. In a preferred embodiment, as shown in fig. 4, the intermediate member includes an intermediate rod 7, two ends of the intermediate rod 7 are respectively provided with a pressing portion 8, two pressing portions 8 respectively abut against two sides of the pressing end 2.1, such as the upper left side and the upper right side in fig. 4, the intermediate rod 7 can rotate in the middle thereof, such as one end of the pressing spring 5 is provided with a pressing column, the middle of the intermediate rod 7 is rotatably connected to the pressing column, a torsion spring is preferably arranged on the rotating shaft of the intermediate rod 7 and the pressing column, the middle of the intermediate rod 7 is pressed by the pressing spring 5, such arrangement is that the intermediate rod 7 simultaneously presses two sides of the worm 2 through the two pressing portions 8, and the two sides are linked, when the worm 2 presses one pressing portion 8 to move, the other pressing portion 8 continues to be attached to the worm 2 due to the linkage of the intermediate rod 7, the motion stability of the worm 2 is improved.

Still further, be provided with arc wall 2.11 on the extrusion end 2.1, extrusion portion 8 extrudees in the tank bottom, so under the effect of torsional spring, extrusion portion 8 has had from the reset effect, after extrusion at every turn, because the tank bottom is located the bottom of arc wall 2.11 and the reset of torsional spring makes extrusion portion 8 have the trend of motion to the tank bottom to the realization is from restoring to the throne. Furthermore, the pressing portion 8 is a first ball body connected to the middle rod 7 in a rolling manner, so that the pressing portion 8 rolls rather than slides relative to the arc-shaped groove 2.11, which reduces the movement resistance and improves the self-resetting effect.

In yet another embodiment of the present invention, further, the bearing 9 is internally sleeved in a fixed cylinder 11, the extrusion spring 5 extrudes the fixed cylinder 11 to realize the extrusion limit, at this time, the extrusion spring 5 extrudes the fixed cylinder 11, the fixed cylinder 11 extrudes the bearing 9, and the bearing 9 extrudes the worm 2 to realize the limit, which is also a mainstream limit mode in the prior art, and can better consider the movement direction of the bearing 9, and prevent the limit of the bearing 9 and the limit of the extrusion spring 5 from interfering with each other, so as to protect the worm 2. Obviously, all the above-mentioned various limiting modes for the extrusion end 2.1 can be directly applied to the fixed cylinder 11, which is a simple application and can be understood by those skilled in the art, and thus, the detailed description is omitted.

Furthermore, one end of the worm 2 is provided with a self-aligning ball bearing 10, the bearing 9 at the other end of the worm 2 is sleeved with the fixed cylinder 11, the self-aligning ball bearing 10 allows the other end of the worm 2 to swing to a certain extent, so that the fixed cylinder 11 is limited at one end of the swing, the protection effect on the bearing 9 is improved, and the service life of the bearing 9 is prolonged.

In still another embodiment of the present invention, as shown in fig. 3, further, a soft cloth 12 is sealed on an opening of an end of the friction cylinder 3 away from the friction column 4, and the soft cloth 12 is used for providing a sealed environment for the inside of the friction cylinder 3, so as to prevent dust from entering and affecting the friction coefficient, and thus affecting the extrusion force between the worm wheel 1 and the worm 2.

In still another embodiment of the present invention, as shown in fig. 5, the friction column 4 penetrates the friction cylinder 3, that is, both ends of the friction column 4 extend out of the friction cylinder 3, and one end of the friction column 4 is provided with a driving part which is driven by the reset component 6 to realize movement, so that the space in the friction cylinder 3 is eliminated, and self-cleaning of the relative sliding part can be realized through the reciprocating movement of the friction column 4.

Still further, the reset assembly 6 includes a transmission assembly, a power input end of the transmission assembly receives a driving of a steering column of a steering system of the vehicle, a power output end of the transmission assembly drives a driving portion, a position of the power output end of the transmission assembly is configured such that when the steering column rotates to a unidirectional limit stroke, the unidirectional direction refers to left-turning or right-turning, that is, only the steering column can drive the driving portion when hitting the limit position in the left-turning or right-turning, the power output end drives the driving portion, the driving portion drives the friction column 4, the steering column is in a rotational motion, and the friction column 4 is in a reciprocating motion, so that the transmission assembly is a transmission mechanism converting the rotational motion into the reciprocating motion, such as a link mechanism, a ball screw mechanism, and the like, and in addition, the steering column can be driven to the limit position by position arrangement, if the power input end of the transmission assembly is arranged in the limit position area of the rotation stroke of the steering column, a protrusion is arranged on the steering column, and only when the steering column rotates to the limit position, the protrusion can be abutted to the power input end to realize driving. The advantage that so set up lies in, has saved a dedicated actuating mechanism such as motor on the one hand, reduce cost, and on the other hand, the number of times that the steering column rotated extreme position is limited and can not be too frequent, the intermittent type's that satisfies friction column 4 that can be fine demand that resets.

Still further, a plurality of spherical holes are formed in the driving portion, second balls 13 are arranged in the spherical holes in a rolling mode, the second balls 13 are driven by the power output end, the arrangement is used for requiring that the friction column 4 must accept strict axial driving force due to the fact that the matching precision of the friction column 4 and the friction cylinder 3 is high, clamping stagnation and damage can be caused, component force of the power output end perpendicular to the radial direction of the friction column 4 can be removed through the second balls 13, and only the driving force of the friction column 4 in the axial direction is reserved.

In another embodiment of the present invention, the friction adjusting mechanism is further included, and is configured to adjust the maximum static friction between the friction column 4 and the friction cylinder 3, since the maximum static friction is only related to the pressure and the friction coefficient, the friction coefficient cannot be adjusted in this embodiment, such that the pressure is adjusted with skill, all mechanisms that the friction column 4 becomes large or the friction cylinder 3 becomes small can be used as the friction adjusting mechanism, for example, the friction column 4 includes two semicircular members that are oppositely arranged, a threaded column with a gradually increased radial dimension is arranged in the middle of the two semicircular members, and the thickness of the friction column 4 can be adjusted by adjusting the depth of the threaded column inserted between the two semicircular members; for the friction cylinder 3, an axial opening can be arranged on the friction cylinder 3, so that the friction cylinder 3 can deform, meanwhile, the friction cylinder 3 is hooped by one hoop member, the friction cylinder 3 is extruded by adjusting the hoop member, so that the pressure between the friction cylinder 3 and the friction column 4 is adjusted, the friction column 4 and the maximum static friction force between the friction cylinders 3 are adjusted by the friction force adjusting mechanism, the extrusion force between the worm wheel 1 and the worm 2 is actually adjusted, the hand feeling of steering is adjusted, and the extrusion force can be adjusted after the components are used for a long time.

While certain exemplary embodiments of the present invention have been described above by way of illustration only, it will be apparent to those of ordinary skill in the art that the described embodiments may be modified in various different ways without departing from the spirit and scope of the invention. Accordingly, the drawings and description are illustrative in nature and should not be construed as limiting the scope of the invention.