Variable-pitch screw of electric recirculating ball steering gear

Abstract

The utility model discloses a variable pitch screw of an electric recirculating ball steering gear, which comprises a screw and a nut, a spiral raceway I is arranged on the outer circumferential surface of the middle of the screw, the pitch of the middle position of the spiral raceway I is larger than that of the two ends of the spiral raceway I, and the pitch of the middle position of the spiral raceway I is gradually reduced from the pitch of the two ends of the spiral raceway I to the pitch of the two ends of the spiral raceway I; an upper bearing mounting part, a worm wheel mounting part and a stator mounting part are sequentially arranged at the upper end of the screw rod, a spiral raceway I of the screw rod is matched with the nut, a lower bearing mounting part is arranged at the lower end of the screw rod, an input shaft limiting groove is machined in the upper end of the screw rod, a torsion bar hole is machined in the groove bottom of the input shaft limiting groove, and the input shaft limiting groove, the torsion bar hole and the screw rod are concentric; the structural design is simple, and the screw and the nut are designed to be of a variable-pitch structure, so that the electric recirculating ball steering gear is small in transmission ratio and flexible in rotation at the middle position; the transmission ratio is large and the output torque is large at the two ends, so that the output torque at the two ends of the product is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of recirculating ball steering gears, in particular to a variable pitch screw rod of an electric recirculating ball steering gear. Background Art

[0002] Electric recirculating ball steering gears are mainly used in commercial vehicle steering systems, and have the advantages of reducing vehicle energy consumption and improving vehicle handling stability. However, due to the power limitation of the motor controller, the product output torque is limited, and it can currently only be used in models with a front axle weight of less than 6 tons. The transmission of torque of recirculating ball steering gears is mainly transmitted by the combination of screws and nuts. The disadvantage is that the transmission ratio and output torque are constant and limited, and cannot adapt well to the working conditions of the entire vehicle.

[0003] Chinese patent application No. 201921215785.9 discloses a variable transmission ratio automotive steering gear, including an inner rack, a sliding sleeve, a transmission ball groove on the outer surface of the cylindrical rack, the transmission ball groove is spirally distributed on the rack, a sliding groove matching the transmission ball groove distribution structure on the rack is opened on the inner wall of the sliding sleeve, a steel ball is installed in the middle of the sliding groove, the outer side of the sliding sleeve is tightened by a belt, and the other end of the belt is driven by a motor. The structure drives the sliding sleeve to rotate by driving the transmission belt through a power-assisting motor, and drives the rack to move axially according to different transmission ratios to achieve power assistance. In addition, the pitch is processed so that the pitch spacing in the middle part is small, and the pitches distributed symmetrically on both sides gradually increase. Gradually increases, such a structure cannot achieve a small intermediate transmission ratio of the steering gear and a large transmission ratio on both sides, and there is a principle error; the Chinese patent previously applied for by the applicant, application number 202221698204.3 discloses an electric circulating ball steering gear, the screw and nut are conventional structures, the transmission ratio and output torque are constant, and they cannot adapt well to the working conditions of the whole vehicle; Chinese patent application number 202221483064.8 discloses a vehicle circulating ball electric steering gear, including a housing, a screw, a rack nut and a gear fan. The pitch of the screw is constant, and the output torque of the product is limited, and the same problem exists; therefore, in response to the above-mentioned problems, a variable pitch screw for an electric circulating ball steering gear is proposed. Utility Model Content

[0004] The technical problem to be solved by the utility model is to overcome the existing defects and provide an electric circulating ball steering gear with a variable pitch screw. The structural design is simple. By designing the screw and the nut as a variable pitch structure, the electric circulating ball steering gear has a small transmission ratio and flexible rotation when it is in the middle position; when it is at the two end positions, the transmission ratio is large and the output torque is large, thereby improving the output torque at both ends of the product, better adapting to the working conditions of the whole vehicle, expanding the application scope of the product, and effectively solving the problems in the background technology.

[0005] To achieve the above-mentioned purpose, the utility model provides the following technical solutions: a variable pitch screw of an electric recirculating ball steering gear, comprising a screw and a nut, a spiral raceway I being arranged on the outer circumferential surface of the middle part of the screw, the pitch of the spiral raceway I at the middle position being greater than the pitch at the two ends, and the pitch of the spiral raceway I at the middle position gradually decreases toward the two end positions, an upper bearing mounting portion, a worm gear mounting portion and a stator mounting portion are sequentially arranged at the upper end of the screw, the spiral raceway I of the screw cooperates with the nut, and a lower bearing mounting portion is arranged at the lower end of the screw.

[0006] Furthermore, an input shaft limiting groove is processed at the upper end of the screw rod, a torsion bar hole is processed at the bottom of the input shaft limiting groove, and the input shaft limiting groove, the torsion bar hole and the screw rod are concentric.

[0007] Furthermore, a spiral raceway II is processed inside the nut. The spiral raceway II has the same structure as the spiral raceway I, and the pitch of the spiral raceway II gradually decreases toward the two end positions.

[0008] Furthermore, the nut and the screw are connected via a steel ball, a guide tube is installed on the nut, the guide tube is fixed to the nut by bolts via a pressure plate, and a tooth shape is processed on the nut.

[0009] Compared with the prior art, the beneficial effects of the utility model are:

[0010] The structure is simple in design. By designing the screw and nut as a variable pitch structure, the pitch in the middle position is greater than the pitch at both ends, so that the electric recirculating ball steering gear has a small transmission ratio and flexible rotation in the middle position; at both end positions, the transmission ratio is large and the output torque is large, thereby improving the output torque of the product at both ends, better adapting to the working conditions of the whole vehicle, and expanding the application range of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a schematic diagram of the variable pitch screw structure of the utility model;

[0012] Figure 2 The utility model is a schematic diagram of the cross-sectional structure of the variable pitch screw and nut combination.

[0013] In the figure: 1 stator mounting part, 2 worm gear mounting part, 3 upper bearing mounting part, 4 spiral raceway I, 5 lower bearing mounting part, 6 input shaft limiting groove, 7 torsion bar hole, 8 nut, 9 tooth shape, 10 steel ball, 11 guide tube, 12 pressure plate, 13 bolt, 14 spiral raceway II. DETAILED DESCRIPTION

[0014] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0015] See also Figure 1-2 The utility model provides a technical solution: a variable pitch screw of an electric circulating ball steering gear, comprising a screw and a nut 8, a spiral raceway Ⅰ4 is arranged on the outer circumferential surface of the middle part of the screw, the pitch of the spiral raceway Ⅰ4 at the middle position is greater than the pitch at the two ends, and the pitch of the spiral raceway Ⅰ4 at the middle position gradually decreases toward the two end positions. According to the axial force of the screw Fa=2*π*T / t; T is the screw torque, t is the screw pitch, it can be seen that the smaller the pitch, the greater the axial force of the screw; at the same time, according to the transmission ratio i=2*π*R / t; R is the meshing radius of the output shaft gear sector, it can be seen that the larger the pitch, the smaller the transmission ratio; thereby realizing that the electric circulating ball steering gear has a small transmission ratio and flexible rotation when it is in the middle position; at the two end positions, the transmission The ratio is large, the output torque is large, and the output torque at both ends of the product is improved, which better adapts to the working conditions of the whole vehicle and expands the application range of the product. The upper end of the screw is provided with an upper bearing mounting part 3, a worm gear mounting part 2 and a stator mounting part 1 in sequence. The stator mounting part 1 rotates relative to the sensor rotor to generate a steering assist signal; the worm gear mounting part 2 is connected to the worm gear to provide assist torque, and the spiral raceway Ⅰ4 of the screw cooperates with the nut 8. A spiral raceway Ⅱ14 is machined inside the nut 8. The spiral raceway Ⅱ14 has the same structure as the spiral raceway Ⅰ4, and the pitch of the middle position gradually decreases toward the two end positions. The lower end of the screw is provided with a lower bearing mounting part 5, and the upper bearing mounting part 3 and the lower bearing mounting part 5 are connected to the bearing to support the screw.

[0016] An input shaft limit groove 6 is processed at the upper end of the screw rod, and a torsion bar hole 7 is processed at the bottom of the input shaft limit groove 6. The input shaft limit groove 6, the torsion bar hole 7 and the screw rod are concentric. The input shaft limit groove 6 and the torsion bar hole 7 are respectively matched with the input shaft and the torsion bar to transmit manual force and provide a signal change source for the sensor.

[0017] The nut 8 is connected to the screw by a steel ball 10. A guide tube 11 is installed on the nut 8. The guide tube 11 is fixed to the nut 8 by bolts 13 through a pressure plate 12. A tooth profile 9 is processed on the nut 8. As the screw rotates, the steel ball 10 circulates through the guide tube 11 in the variable pitch spiral raceway of the screw and the nut 8, so that the nut 8 moves up and down. The nut 8 transmits force through the tooth profile 9.

[0018] The basic principles, main features and advantages of the present invention are shown and described above. Without departing from the spirit and scope of the present invention, the present invention may also be subject to various changes and improvements, which are all within the scope of the present invention to be protected.

Claims

1. A variable pitch screw of an electric recirculating ball steering gear, comprising a screw and a nut (8), characterized in that: A spiral raceway I (4) is provided on the outer circumferential surface of the middle part of the screw rod. The pitch of the spiral raceway I (4) at the middle position is greater than the pitch at the two ends, and the pitch of the spiral raceway I (4) at the middle position gradually decreases toward the two ends. An upper bearing mounting portion (3), a worm gear mounting portion (2) and a stator mounting portion (1) are sequentially provided at the upper end of the screw rod. The spiral raceway I (4) of the screw rod cooperates with a nut (8), and a lower bearing mounting portion (5) is provided at the lower end of the screw rod.

2. The variable pitch screw of an electric recirculating ball steering gear according to claim 1, characterized in that: An input shaft limiting groove (6) is processed at the upper end of the screw rod, a torsion bar hole (7) is processed at the bottom of the input shaft limiting groove (6), and the input shaft limiting groove (6), the torsion bar hole (7) and the screw rod are concentric.

3. The variable pitch screw of an electric recirculating ball steering gear according to claim 1, characterized in that: A spiral raceway II (14) is machined inside the nut (8). The spiral raceway II (14) has the same structure as the spiral raceway I (4), and the pitch of the spiral raceway gradually decreases from the middle position to the two end positions.

4. The variable pitch screw of an electric recirculating ball steering gear according to claim 3, characterized in that: The nut (8) is connected to the screw rod via a steel ball (10). A guide tube (11) is installed on the nut (8). The guide tube (11) is fixed to the nut (8) via a pressure plate (12) with a bolt (13). The nut (8) is processed with a tooth shape (9).

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