Rear wheel steering gear

Abstract

The utility model discloses a rear wheel steering gear, relates to the technical field of rear wheel steering gears, and adopts the technical scheme that the rear wheel steering gear comprises a lead screw nut pair, the lead screw nut pair comprises a trapezoidal lead screw and a nut, the lead angle of the trapezoidal lead screw is smaller than the equivalent friction angle, and a lubricating layer is arranged on the surface of the trapezoidal lead screw. The rear wheel steering gear has the advantage of being simple in structure.

Description

Technical Field

[0001] The utility model relates to the technical field of rear wheel steering gears, and more particularly to a rear wheel steering gear. Background Art

[0002] Currently, the rear wheels of vehicles are in a follow-up state, resulting in a large turning radius. To reduce this radius, a rear-wheel steering gear is installed between the two rear wheels. Existing rear-wheel steering gears typically use planetary ball screws to achieve high transmission efficiency, but these lack a self-locking function and typically require an additional self-locking mechanism, which is complex.

[0003] Therefore, a new solution needs to be proposed to solve this problem. Utility Model Content

[0004] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a rear wheel steering gear that solves the problem of the complex self-locking structure of the existing rear wheel steering gear.

[0005] The above technical objectives of the present utility model are achieved through the following technical solutions: An embodiment of the present application provides a rear wheel steering gear, including a screw-nut pair, the screw-nut pair including a trapezoidal screw and a nut, the helix angle of the trapezoidal screw is smaller than the equivalent friction angle, and the surface of the trapezoidal screw is provided with a lubricating layer.

[0006] In one embodiment, the lubricating layer includes a nitride layer, and a hard coating is provided on the outer side of the nitride layer.

[0007] In one embodiment, an oil filling hole is provided on the nut.

[0008] In one embodiment, it also includes a shell for accommodating the screw-nut pair, the shell including an accommodating cavity, a motor is fixed on the shell, a pulley transmission assembly is provided in the accommodating cavity, the pulley transmission assembly includes a large pulley and a small pulley connected by a belt drive, the small pulley includes a wheel shaft, the output shaft of the motor is connected to the wheel shaft through a coupling, the large pulley is fixedly connected to the nut by a screw, a bearing groove is provided in the accommodating cavity, a ball bearing for limiting the nut is installed in the bearing groove, and the two ends of the trapezoidal screw are respectively fixedly connected with a first connecting rod and a second connecting rod.

[0009] In one embodiment, the inner ring of the ball bearing is tightly fitted with the nut.

[0010] In one embodiment, the inner ring of the ball bearing can cover the oil filling hole.

[0011] In one embodiment, a grease receiving cavity is provided on the nut, and oil seals are provided at both ends of the nut, and the oil seals and the nut are interference fit.

[0012] In summary, the utility model has the following beneficial effects: the utility model provides a trapezoidal lead screw, and sets the trapezoidal lead screw so that the helix angle is smaller than the equivalent friction angle, so that the trapezoidal lead screw has a self-locking ability, and there is no need to set up an additional self-locking structure, so that the structure of the rear wheel steering gear is simple, and by providing a lubricating layer on the surface of the trapezoidal lead screw, the transmission efficiency of the trapezoidal lead screw is improved, that is, the self-locking ability and high transmission efficiency of the rear wheel converter are guaranteed at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A cross-sectional view of a rear wheel steering gear according to an embodiment of the present application;

[0014] Figure 2 This is a schematic diagram of the connection relationship between the trapezoidal lead screw and the nut in the rear wheel steering gear of an embodiment of the present application.

[0015] In the figure: 1. Trapezoidal screw; 11. First connecting rod; 12. Second connecting rod; 2. Nut; 23. Oil filling hole; 24. Oil seal; 3. Housing; 31. Motor; 32. Small pulley; 33. Belt; 34. Large pulley; 341. Screw; 35. Ball bearing; 4. Coating area. DETAILED DESCRIPTION

[0016] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0017] like Figure 1 and Figure 2 As shown, an embodiment of the present application provides a rear wheel steering gear, including a screw-nut pair, wherein the screw-nut pair includes a trapezoidal screw 1 and a nut 2, the helix angle of the trapezoidal screw 1 is smaller than the equivalent friction angle, and the surface of the trapezoidal screw 1 is provided with a lubricating layer.

[0018] Specifically, a coating area 4 is provided on the trapezoidal lead screw 1 , and the lubricating layer is provided in the coating area 4 .

[0019] It should be noted that the tooth profile of the trapezoidal screw 1 is set so that the helix angle is smaller than the equivalent friction angle, so that the screw nut pair has self-locking ability, and a lubricating layer is provided on the surface of the trapezoidal screw 1, so that the surface of the trapezoidal screw is smoother and the transmission efficiency is higher. Experimental data shows that the friction coefficient of the trapezoidal screw 1 without the lubricating layer is between 0.15 and 0.78, while the friction coefficient of the trapezoidal screw 1 with the lubricating layer is between 0.09 and 0.11. It can be seen that the lubricating layer significantly improves the friction force and improves the transmission efficiency. At the same time, the mechanical self-locking ability will only be lost when the friction coefficient is less than 0.044, so the trapezoidal screw with the lubricating layer can still maintain its self-locking ability.

[0020] The above-mentioned structure is set up by setting a trapezoidal screw rod 1 and setting the trapezoidal screw rod 1 to have a spiral lead angle less than the equivalent friction angle, so that the trapezoidal screw rod 1 has a self-locking ability, and there is no need to set up an additional self-locking structure, so that the structure of the rear wheel steering gear is simple. By setting a lubricating layer on the surface of the trapezoidal screw rod 1, the transmission efficiency of the trapezoidal screw rod 1 is improved, that is, the self-locking ability and high transmission efficiency of the rear wheel converter are guaranteed at the same time.

[0021] In this embodiment, the lubricating layer includes a nitride layer, and a hard coating is provided on the outer side of the nitride layer.

[0022] Specifically, the nitride layer is obtained by nitriding the surface of the trapezoidal thread using a nitriding process, and the hard coating is obtained by spraying the outer side of the nitrided layer. The hard coating can specifically be a metal nitride or a metal carbide such as TiCN.

[0023] The above structure increases the hardness and smoothness of the surface of the trapezoidal lead screw 1 and enhances its wear resistance by adding a nitride layer to the surface of the trapezoidal lead screw 1. On this basis, a hard coating is provided to further increase the surface hardness.

[0024] In this embodiment, an oil filling hole 23 is provided on the nut 2 .

[0025] The above structure is arranged so that the oil filling hole 23 is provided on the nut 2, thereby facilitating lubrication of the connection between the nut 2 and the trapezoidal lead screw 1.

[0026] In this embodiment, a shell 3 for accommodating the screw-nut pair is further included, the shell 3 including an accommodating cavity, a motor 31 is fixed on the shell 3, a pulley transmission assembly is provided in the accommodating cavity, the pulley transmission assembly includes a large pulley 34 and a small pulley 32 connected by a belt 33, the small pulley 32 includes a wheel shaft, the output shaft of the motor 31 is connected to the wheel shaft through a coupling, the large pulley 34 is fixedly connected to the nut 2 by a screw 341, a bearing groove is provided in the accommodating cavity, a ball bearing 35 for limiting the nut is installed in the bearing groove, and the two ends of the trapezoidal screw 1 are respectively fixedly connected to the first connecting rod 11 and the second connecting rod 12.

[0027] During operation, the motor 31 transmits the rotational torque to the small pulley 32, and the small pulley 32 transmits the torque to the large pulley 34 through the belt 33. The large pulley 34 drives the nut 2 to rotate, and the nut 2 drives the trapezoidal screw 1 to move. The trapezoidal screw 1 moves in the direction of the first connecting rod 11 or the second connecting rod 12. The first connecting rod 11 and the second connecting rod 12 are both connected with a yoke, and the yoke is connected to the rear wheels of the vehicle. The movement of the yoke causes the rear wheels to steer. Since the trapezoidal screw 1 has self-locking ability, the rear wheels will not swing freely when subjected to the reaction force of the ground.

[0028] In this embodiment, the inner ring of the ball bearing 35 is tightly fitted with the nut 2 .

[0029] The above-mentioned structure can reduce the friction loss between the nut 2 and the ball bearing 35 by making the inner ring of the ball bearing 35 fit tightly with the nut 2.

[0030] In this embodiment, the inner ring of the ball bearing 35 can cover the oil filling hole 23 .

[0031] The above-mentioned structure enables the oil filling hole 23 to be covered by the inner ring of the ball bearing 35 , and since the ball bearing and the nut are tightly fitted, the grease is not likely to leak out.

[0032] In this embodiment, a grease receiving cavity is provided on the nut 2 , and oil seals 24 are provided at both ends of the nut 2 . The oil seals 24 are interference fit with the nut 2 .

[0033] The above structure can provide good lubrication for the nut 2 and the trapezoidal lead screw 1 by providing a grease receiving chamber and an oil seal 24 on the nut 2, and prevent grease leakage.

[0034] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiment. All technical solutions based on the concept of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, certain improvements and modifications that do not depart from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A rear wheel steering gear, comprising a screw-nut pair, characterized in that: The screw-nut pair comprises a trapezoidal screw (1) and a nut (2); the helix angle of the trapezoidal screw (1) is smaller than the equivalent friction angle; and a lubricating layer is provided on the surface of the trapezoidal screw (1).

2. The rear wheel steering gear according to claim 1, characterized in that: The lubricating layer includes a nitride layer, and a hard coating is provided on the outer side of the nitride layer.

3. The rear wheel steering gear according to claim 1, characterized in that: An oil filling hole (23) is provided on the nut (2).

4. The rear wheel steering gear according to claim 3, characterized in that: The invention also includes a housing (3) for accommodating the screw nut pair, the housing (3) including an accommodating cavity, a motor (31) being fixedly connected to the housing (3), a pulley transmission assembly being provided in the accommodating cavity, the pulley transmission assembly including a large pulley (34) and a small pulley (32) connected by a belt (33), the small pulley (32) including a wheel shaft, the output shaft of the motor (31) being connected to the wheel shaft by a coupling, the large pulley (34) being fixedly connected to the nut (2) by a screw (341), a bearing groove being provided in the accommodating cavity, a ball bearing (35) being installed in the bearing groove for limiting the nut (2), and a first connecting rod (11) and a second connecting rod (12) being fixedly connected at both ends of the trapezoidal screw (1).

5. The rear wheel steering gear according to claim 4, characterized in that: The inner ring of the ball bearing (35) is tightly matched with the nut (2).

6. The rear wheel steering gear according to claim 4, characterized in that: The inner ring of the ball bearing (35) can cover the oil filling hole (23).

7. The rear wheel steering gear according to claim 1, characterized in that: The nut (2) is provided with a grease receiving cavity, and both ends of the nut (2) are provided with oil seals (24), and the oil seals (24) and the nut (2) are interference fit.

Images