Flexible limiting device of hydraulic recirculating ball steering gear

Abstract

The invention discloses a flexible limiting device of a hydraulic recirculating ball steering gear, which comprises a shell, an input screw is arranged in the shell, an upper end bearing is arranged at one end of the input screw, a lower end bearing is arranged at the other end of the input screw, a limiting boss is arranged outside the input screw, and the lower end bearing is arranged at the other end of the input screw. The shell is provided with a plurality of detachable flexible limiting stoppers, and the flexible limiting stoppers are matched with the limiting bosses. The hydraulic unloading device solves the problems that a hydraulic unloading device in an existing hydraulic recirculating ball steering gear is complex in structure, slow in response, large in impact and the like, boss limiting is achieved when the steering stroke reaches the limiting position through mechanical cooperation of the limiting boss and the flexible limiting stopper, a spring is used for buffering, a traditional hydraulic unloading device is replaced, and the reliability of the hydraulic recirculating ball steering gear is improved. And a flexible limiting function is realized.

Description

Technical Field

[0001] The invention belongs to the field of commercial vehicle steering systems, and in particular relates to a flexible limiting device of a hydraulic circulating ball steering gear. Background Art

[0002] Recirculating ball steering gears are widely used in commercial vehicle steering systems due to their strong load-bearing capacity and high transmission efficiency. Hydraulically assisted recirculating ball steering gears are currently the predominant form of commercial vehicle steering system. They utilize an engine-driven hydraulic pump to provide steering assistance, reducing the driver's steering burden. In hydraulically assisted recirculating ball steering gears, to prevent the oil pump from operating at continuous high pressure when the steering wheel is turned to its extreme position, thereby damaging the hydraulic pump or other hydraulic components, an unloading device is often added to prevent excessive hydraulic system pressure. The unloading device is typically a hydraulic unloading valve integrated into the steering gear, consisting of a valve core, valve seat, and elastic element. When the system pressure reaches a safety threshold or the steering nut of the steering gear moves to its extreme position, the valve core overcomes the spring force and opens the hydraulic unloading valve, bypassing the oil in the high-pressure chamber directly to the low-pressure chamber, thereby limiting the maximum system pressure and protecting the hydraulic system.

[0003] However, under the harsh working conditions and long life requirements of commercial vehicles, the unloading device will lead to performance degradation due to wear, seal failure, etc. after long-term use, affecting system stability and causing problems such as weakened steering power assistance and slow response; secondly, the maintenance cost of the unloading device is high, and regular inspection and replacement of seals are required; in addition, the unloading device has a lag in dynamic response, which may cause slow unloading action, generate pressure shock during extreme steering, and accelerate fatigue damage to key components such as gear fans and bearings; in addition, the unloading device has the risk of valve core jamming, which may completely lose the unloading function or cause power assistance failure. Summary of the Invention

[0004] In order to solve the deficiencies of the prior art, the present invention proposes a flexible limiting device for a hydraulic circulating ball steering gear.

[0005] A flexible limit device for a hydraulic circulating ball steering gear includes a housing, an input screw is arranged in the housing, an upper end bearing is arranged at one end of the input screw, a lower end bearing is arranged at the other end of the input screw, a limit boss is arranged on the outside of the input screw, and a plurality of detachable flexible limiters are provided on the housing, and the flexible limiters cooperate with the limit bosses.

[0006] As a preferred embodiment of the present invention, the flexible limiter includes a hollow limit screw barrel, the outer wall of the limit screw barrel is provided with a screw barrel thread, the flexible limiter is fixed to the shell through the screw barrel thread, the interior of the limit screw barrel is provided with a flexible limiter upper end, a compression spring and a flexible limiter contact, the upper end of the compression spring is welded to the upper end of the flexible limiter, and the lower end of the compression spring is welded to the flexible limiter contact,

[0007] The limiting boss includes a cylindrical boss body, a boss center screw hole is provided in the center of the boss body, the internal thread of the boss center screw hole and the external thread of the input screw are rollingly matched by a ball screw, and a pair of limiting grooves are provided on the outer wall of the boss body, and the limiting grooves are matched with the flexible limiter contacts of the flexible limiter.

[0008] As a preferred embodiment of the present invention, the limiting boss is integrally machined from a cylindrical aluminum block.

[0009] As a preferred embodiment of the present invention, the width of the limiting groove is adapted to the size of the flexible limiter contact, and the depth of the limiting groove is determined by a preset limiting boss curve.

[0010] As a preferred embodiment of the present invention, the spring stiffness of the compression spring is expressed as: Where, F x represents the horizontal force of the limiting boss acting on the flexible limiter, and θ represents the tangential angle;

[0011] in, η1 is the steering column transmission efficiency, η2 is the screw-limiting boss transmission efficiency, R is the steering wheel radius, P is the lead of the input screw, F h is the maximum force of the driver operating the steering wheel as specified in the national standard; when the flexible limiter reaches the limit position of the limit boss, the spring compression of the compression spring is the largest, and θ is determined in this state.

[0012] As a preferred embodiment of the present invention, the expression of the limiting boss curve is:

[0013]

[0014] Where S represents the maximum distance that the limiting boss moves left or right, y max Indicates the height of the limit boss, and a indicates the distance from the highest point of the curve to the center line of the boss.

[0015] Compared with the prior art, the present invention adopts the above technical solution and has the following effects:

[0016] The present invention proposes a flexible limit device for a hydraulic circulating ball steering gear, which adopts a flexible limit device to replace the traditional stroke unloading valve, simplifies the structure of the hydraulic circulating ball steering gear and reduces the complexity of the system; the limit boss in the flexible limit device adopts a hyperbolic sine curve, and the flexible limiter is equipped with a spring to absorb impact, reduce rigid collision and improve durability; the invention effectively limits the maximum pressure of the system, thereby improving the reliability of the hydraulic steering system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of the installation of the flexible limiting device of the present invention;

[0018] Figure 2 Schematic diagram of the cross-sectional structure of the flexible limiting device of the present invention;

[0019] Figure 3 for Figure 2 Schematic diagram of the structure of the flexible limiter;

[0020] Figure 4 for Figure 2 A schematic diagram of the structure of the limiting boss in FIG.

[0021] Figure 5 for Figure 4 A design plan view of a limiting boss curve of the limiting boss;

[0022] Figure 6 for Figure 4 Force analysis diagram of the limiting boss in FIG;

[0023] In the figure: 1. Flexible limit device; 11. Input screw; 12. Upper end bearing; 13. Flexible limiter; 14. Limit boss; 140. Boss center screw hole; 141. Boss body; 142. Limit slot; 15. Lower end bearing; 16. Housing; 17. Upper end of flexible limiter; 18. Compression spring; 19. Flexible limiter contact; 20. Limit screw barrel; 201. Screw barrel thread; 2. Hydraulic circulating ball steering gear. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0025] like Figure 1 and Figure 2As shown, the flexible limit device 1 of the hydraulic recirculating ball steering gear includes a housing 16, an input screw 11 is provided in the housing 16, an upper end bearing 12 is provided at one end of the input screw 11, a lower end bearing 15 is provided at the other end of the input screw 11, a limit boss 14 is provided on the outside of the input screw 11, and a plurality of detachable flexible limiters 13 are provided on the housing 16, and the flexible limiters 13 cooperate with the limit boss 14.

[0026] like Figure 2 As shown, during installation, the flexible limit device 1 is connected to the hydraulic recirculating ball steering gear 2, the left end of the flexible limit device 1 is connected to the steering column and the steering wheel, and the right end is connected to the input shaft of the recirculating ball steering gear 1 through a spline.

[0027] like Figure 3 As shown, the flexible limiter 13 includes a hollow limit screw barrel 20, and a screw barrel thread 201 is provided on the outer wall of the limit screw barrel 20. The flexible limiter 13 is fixed to the shell 16 through the screw barrel thread 201. The interior of the limit screw barrel 20 is provided with a flexible limiter upper end 17, a compression spring 18 and a flexible limiter contact 19. The upper end of the compression spring 18 is welded to the flexible limiter upper end 17, and the lower end of the compression spring 18 is welded to the flexible limiter contact 19.

[0028] like Figure 4 As shown, the limiting boss 14 includes a cylindrical boss body 141, and a boss center screw hole 140 is provided at the center of the boss body 141. The internal thread of the boss center screw hole 140 and the external thread of the input screw 11 are rollingly matched by a ball screw. A pair of limiting grooves 142 are provided on the outer wall of the boss body 141, and the limiting grooves 142 are matched with the flexible limiter contacts 19 of the flexible limiter 13.

[0029] The width of the limiting slot 142 is adapted to the size of the flexible limiter contact 19 , and the depth of the limiting slot 142 is determined by a preset limiting boss curve.

[0030] It should be noted that the limiting boss 14 is integrally machined from a cylindrical aluminum block.

[0031] Furthermore, both the upper bearing 12 and the lower bearing 15 utilize angular contact ball bearings, positioned back-to-back at each end of the input screw 11. The inner rings of the upper and lower bearings 12, 15 utilize an interference fit with the input screw 11 to prevent relative rotation. The upper bearing 12, serving as the fixed end, has an interference fit on its outer ring with the housing 16, ensuring axial fixation of the input screw 11. The outer ring of the lower bearing 15 utilizes a clearance fit with the housing 16 to compensate for thermal expansion and assembly errors.

[0032] The spring stiffness of the compression spring 18 of the flexible stopper 13 is expressed as: Where, F x represents the horizontal force of the limiting boss acting on the flexible limiter, and θ represents the tangential angle;

[0033] in, η1 is the steering column transmission efficiency, η2 is the screw-limiting boss transmission efficiency, R is the steering wheel radius, P is the lead of the input screw, F h The maximum force required by the driver to operate the steering wheel as specified in the national standard. When the flexible limiter reaches the boss limit position, the spring compression inside the flexible limiter is the largest. θ is determined under this state.

[0034] like Figure 5 As shown in Figure 2, the expression of the limiting boss curve is:

[0035]

[0036] Where S represents the maximum distance that the limiting boss moves left or right, y max Indicates the height of the limit boss, and a indicates the distance from the highest point of the curve to the center line of the boss.

[0037] The following is a further explanation of the limit boss curve, as follows:

[0038] S1. Select the hyperbolic sine function y=f(x)=sinh(x+C)+D as the limit boss curve (such as Figure 5 ) expression;

[0039] S2, point (-S / 2-a,0), (-a,y max ) into the function in S1, we get:

[0040] S3, according to the hyperbolic sine difference formula Solve the equations in S2 to get:

[0041] S4. According to C and D solved in step S3, the hyperbolic sine function in the first quadrant is obtained.

[0042]

[0043] S5. According to the symmetry, the complete expression of the hyperbolic sine function is:

[0044]

[0045] S6. Determine the parameters S and a in the hyperbolic sine function;

[0046] S7. Calculate the force acting on the flexible limiter at the limit position x0

[0047] S8. Solve for the tangent angle at the extreme position, take the derivative of the hyperbolic sine function, and calculate the slope of the tangent at x = x0:

[0048] θ is the tangential angle;

[0049] S9. According to Hooke's law and the force analysis of the limiter, Figure 6 As shown, calculate the spring stiffness

[0050] Furthermore, the specific process of determining the parameters S and a in the hyperbolic sine function according to step S6 is as follows:

[0051] S61, determine S, θ csmax Indicates the maximum rotation angle of the steering gear sector, R cs It represents the pitch circle radius of the steering gear tooth sector, and S represents the maximum distance that the limit boss can move left or right. It is mainly determined by the maximum left or right displacement of the recirculating ball nut in the recirculating ball steering gear, and depends on the maximum steering angle of the vehicle steering system.

[0052] S6.2. Determine y max ,y max The maximum compression of the compression spring in the flexible limiter is determined by two factors: the stroke of the compression spring must be greater than the minimum deformation required for impact buffering, and the size of the housing is limited.

[0053] S6.3. Determine a. a is mainly determined by the maximum distance that the limiting boss moves left or right.

[0054] The present invention solves the problems of complex structure, slow response, and large impact of the hydraulic unloading device in the existing hydraulic recirculating ball steering gear. Through the mechanical coordination of the limit boss and the flexible limiter, the boss is limited when the steering stroke reaches the extreme position, and a spring buffer is used to replace the traditional hydraulic unloading device to achieve a flexible limit function. In addition, the limit boss curve design adopts a hyperbolic sine function, and the spring stiffness design of the flexible limiter takes into account the maximum force limit of the driver operating the steering wheel. The present invention optimizes the steering gear structure, effectively avoids the risk of high pressure in the hydraulic system during extreme steering, and greatly improves the safety of the vehicle during extreme steering.

[0055] The above embodiments are intended only to illustrate the design concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. The scope of protection of the present invention is not limited to the above embodiments. Therefore, any equivalent changes or modifications made based on the principles and design concepts disclosed in the present invention are within the scope of protection of the present invention.

Claims

1. A flexible limit device for a hydraulic recirculating ball steering gear, comprising a housing (16), an input screw (11) provided in the housing (16), an upper bearing (12) provided at one end of the input screw (11), a lower bearing (15) provided at the other end of the input screw (11), a limit boss (14) provided on the outside of the input screw (11), a plurality of detachable flexible limiters (13) provided on the housing (16), the flexible limiters (13) cooperating with the limit bosses (14).

2. The flexible limiting device of the hydraulic circulating ball steering gear according to claim 1 is characterized in that: The flexible limiter (13) includes a hollow limit screw barrel (20), the outer wall of the limit screw barrel (20) is provided with a screw barrel thread (201), the flexible limiter (13) is fixed to the housing (16) through the screw barrel thread (201), the interior of the limit screw barrel (20) is provided with a flexible limiter upper end (17), a compression spring (18) and a flexible limiter contact (19), the upper end of the compression spring (18) is welded to the flexible limiter upper end (17), and the lower end of the compression spring (18) is welded to the flexible limiter contact (19). The limiting boss (14) includes a cylindrical boss body (141), a boss center screw hole (140) is provided at the center of the boss body (141), the internal thread of the boss center screw hole (140) and the external thread of the input screw (11) are rollingly matched by a ball screw, and a pair of limiting grooves (142) are provided on the outer wall of the boss body (141), and the limiting grooves (142) are matched with the flexible limiter contact (19) of the flexible limiter (13).

3. The flexible limiting device of the hydraulic circulating ball steering gear according to claim 2 is characterized in that: The limiting boss (14) is integrally machined from a cylindrical aluminum block.

4. The flexible limiting device of the hydraulic circulating ball steering gear according to claim 2 is characterized in that: The width of the limiting slot (142) is adapted to the size of the flexible limiter contact (19), and the depth of the limiting slot (142) is determined by a preset limiting boss curve.

5. The flexible limiting device of the hydraulic circulating ball steering gear according to claim 4 is characterized in that: The spring stiffness expression of the compression spring (18) is: Where, F x represents the horizontal force of the limiting boss acting on the flexible limiter, and θ represents the tangential angle; in, η1 is the steering column transmission efficiency, η2 is the screw-limiting boss transmission efficiency, R is the steering wheel radius, P is the lead of the input screw, F h The maximum force of the driver operating the steering wheel as specified in the national standard; when the flexible limiter (13) reaches the limit position of the limiting boss (14), the spring compression amount of the compression spring (18) is the maximum, and θ is determined in this state.

6. The flexible limiting device of the hydraulic circulating ball steering gear according to claim 4 is characterized in that: The expression of the limiting boss curve is: Where S represents the maximum distance that the limiting boss moves left or right, y max Indicates the height of the limit boss, and a indicates the distance from the highest point of the curve to the center line of the boss.

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