Planetary roller screw electric power steering device

Abstract

The utility model relates to electric power steering device technical field, and disclose planetary roller screw type electric power steering device, this planetary roller screw type electric power steering device is applicable to medium -sized, heavy -duty truck, medium -sized, heavy -duty bus etc. Commercial vehicle. The device includes input shaft, torsion bar, torque angle sensor, brushless motor controller integrated machine, worm, worm wheel, planetary roller screw assembly and sector gear shaft, torsion bar connects input shaft and screw rod, torque angle sensor is fixed through laser welding, worm wheel is connected with screw rod and is engaged with worm, roller nut and sector gear shaft transmission connection. The core improvement is to adopt planetary roller screw as secondary transmission, it adopts line contact design, and contact stress is reduced by more than 80%, and the bearing capacity is 3-5 times of ball screw, and the transmission efficiency reaches 90%-98%, and the highest precision reaches C0 grade The device solves the problem of low efficiency and poor reliability of traditional circulating ball type steering device, and adapts to the large torque steering demand of commercial vehicle.

Description

Technical Field

[0001] This utility model relates to the technical field of electric steering devices, specifically a planetary roller screw type electric steering device. Background Technology

[0002] Commercial vehicles (medium-duty trucks, heavy-duty trucks, electric buses, and coaches) adopt hydraulic recirculating ball power steering and recirculating ball electric power steering systems.

[0003] The device uses an electric motor to drive a first-stage worm gear transmission, a second-stage recirculating ball screw transmission, and a third-stage gear and rack transmission. However, the recirculating ball screw has limited high-torque output, slow dynamic response, low transmission efficiency, and no self-locking function. Utility Model Content

[0004] To address the shortcomings of existing technologies, this invention provides a planetary roller screw-type electric steering device, which solves the problems of low efficiency and poor reliability of recirculating ball-type electric steering devices.

[0005] This utility model provides the following technical solution: a planetary roller screw type electric steering device, including a housing, a cylindrical pin, and a torque angle sensor. One end of the housing is provided with an input shaft, and a torsion bar is provided inside the housing. One end of the torsion bar is connected to the input shaft through the cylindrical pin, and a planetary roller screw assembly is provided inside the housing.

[0006] The planetary ball screw assembly includes a ball screw, rollers, a ball nut, and a cage. The other end of the torsion bar is interference-fitted to the ball screw. The input shaft is laser-welded to the torque angle sensor body, and the rotor of the torque angle sensor is laser-welded to the ball screw. A rack is formed on the surface of the ball nut, and a sector gear shaft is disposed inside the housing, with the rack meshing with the sector gear shaft.

[0007] The housing has an internal transmission drive with a worm gear, which is interference-fitted with the ball screw. The housing also has an internal transmission drive with a worm, which meshes with the worm gear. The housing has an external brushless motor controller unit, whose output is fixedly connected to the worm.

[0008] Preferred technical solution 1: The thread structure of the roller screw 6 adopts a triangular tooth profile with a tooth profile angle of 30°-40° and a helix angle of 10°, ensuring that the contact area between the roller 7 and the thread raceway is >85%.

[0009] Preferred technical solution 2: The cage is an integral metal cage, and the material is brass.

[0010] Preferred technical solution 3: The internal thread of the roller nut 8 is completely consistent with the parameters of the roller screw 6, and the surface roughness of the raceway is ≤0.4μm.

[0011] Preferred technical solution four: The diameter of the roller 7 satisfies R=1.1, and a multi-ring planetary arrangement is adopted, with 3-5 rings and 12-20 rollers per ring.

[0012] Compared with the prior art, the present invention provides a planetary roller screw type electric steering device, which has the following advantages:

[0013] (1) The planetary roller screw electric steering device adopts a line contact design for the planetary roller screw, with a contact area of ​​0.15-0.3 mm², reducing the contact stress by more than 80%, and significantly improving the load-bearing capacity, which is 3-5 times that of the ball screw.

[0014] (2) The planetary roller screw electric steering device has a transmission efficiency of 90%-98%, which is more than 10% higher than that of traditional ball screws. Its axial stiffness is 30%-50% higher than that of ball screws, and its volume is reduced by 33%, which is suitable for the installation space requirements of commercial vehicles.

[0015] (3) The planetary roller screw electric steering device has a rated life of 100,000 to 150,000 hours, which is 10 to 15 times that of the ball screw. The multi-roller load-sharing structure naturally has fault redundancy. Even after 20% of the rollers fail, it can still maintain 70% of the rated load. Combined with the dual motor setting, the system safety factor is increased by more than 2 times. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of this utility model;

[0017] Figure 2 This is an enlarged view of a partial structure of the present invention.

[0018] In the diagram: 1. Cylindrical pin; 2. Input shaft; 3. Torque bar; 4. Torque angle sensor; 5. Worm gear; 6. Roller screw; 7. Roller; 8. Roller nut; 9. Sector gear shaft; 10. Worm; 11. Brushless motor controller integrated unit; 12. Housing. Detailed Implementation

[0019] Please see Figure 1-2 ,

[0020] Example 1: A planetary roller screw electric steering device includes a housing 12, a cylindrical pin 1, and a torque angle sensor 4. An input shaft 2 is provided at one end of the housing 12, and a torsion bar 3 is provided inside the housing 12. One end of the torsion bar 3 is connected to the input shaft 2 through the cylindrical pin 1. A planetary roller screw assembly is provided inside the housing 12.

[0021] The planetary ball screw assembly includes a roller screw 6, rollers 7, roller nuts 8, and a cage. The other end of the torsion bar 3 is interference-fitted to the roller screw 6. The input shaft 2 is laser-welded to the body of the torque angle sensor 4, and the rotor of the torque angle sensor 4 is laser-welded to the roller screw 6. A rack is mounted on the surface of the roller nut 8, and a sector gear shaft 9 is disposed inside the housing 12, with the rack meshing with the sector gear shaft 9.

[0022] The housing 12 has a worm gear 5 installed inside for transmission, and the worm gear 5 is interference-fitted with the ball screw 6. The housing 12 also has a worm 10 installed inside for transmission, and the worm gear 5 meshes with the worm 10. The housing 12 has a brushless motor controller integrated unit 11 installed outside, and the output end of the brushless motor controller integrated unit 11 is fixedly connected to the worm 10.

[0023] Example 2: The difference between this example and Example 1 is that the thread structure of the roller screw 6 adopts a triangular tooth profile with a tooth profile angle of 30°-40° and a helix angle of 10°, ensuring that the contact area between the roller 7 and the thread raceway is >85%.

[0024] Example 3: The difference between this example and Example 1 is that the cage is an integral metal cage made of brass.

[0025] Example 4: The difference between this example and Example 1 is that the internal thread of the roller nut 8 has the same parameters as the roller screw 6, and the surface roughness of the raceway is ≤0.4μm.

[0026] Example 5: The difference between this example and Example 1 is that the diameter of the roller 7 satisfies R=1.1, and a multi-ring planetary arrangement is adopted, with 3-5 rings and 12-20 rollers per ring.

[0027] In summary, this planetary roller screw electric steering device, when the driver rotates the input shaft 2, causes the torsion bar 3 to undergo torsional deformation. The torque angle sensor 4 detects this deformation and generates an electrical signal, which is then sent to the brushless motor integrated controller 11. After software processing, the controller controls the motor to rotate. The torque generated by the motor drives the worm gear 10 to rotate, which in turn drives the worm wheel 5 to rotate (forming a first-stage reduction transmission). The worm wheel 5 drives the roller screw 6 to rotate synchronously, which in turn drives the rollers 7 to perform planetary rolling, thereby driving the roller nut 8 to perform linear motion within the housing cavity (forming a second-stage reduction transmission). The roller nut 8 drives the sector gear shaft 9 to rotate (forming a third-stage gear and rack reduction transmission), ultimately achieving high-torque steering assist output.

Claims

1. A planetary roller screw type electric steering device, comprising a housing (12), a cylindrical pin (1), and a torque angle sensor (4), characterized in that: An input shaft (2) is provided at one end of the housing (12), a torsion bar (3) is provided inside the housing (12), one end of the torsion bar (3) is connected to the input shaft (2) through the cylindrical pin (1), and a planetary roller screw assembly is provided inside the housing (12). The planetary roller screw assembly includes a roller screw (6), a roller (7), a roller nut (8), and a cage. The other end of the torsion bar (3) is interference-fitted with the roller screw (6). The input shaft (2) is laser-welded to the body of the torque angle sensor (4). The rotor of the torque angle sensor (4) is laser-welded to the roller screw (6). The surface of the roller nut (8) is made of a rack. A sector gear shaft (9) is provided inside the housing (12). The rack meshes with the sector gear shaft (9). The housing (12) is internally equipped with a worm gear (5) and an interference fit between the worm gear (5) and the ball screw (6). The housing (12) is internally equipped with a worm (10) and the worm gear (5) meshes with the worm (10). The housing (12) is externally equipped with a brushless motor controller integrated machine (11) and the output end of the brushless motor controller integrated machine (11) is fixedly connected to the worm (10).

2. The planetary roller screw type electric steering device according to claim 1, characterized in that: The thread structure of the roller screw (6) adopts a triangular tooth profile with a tooth profile angle of 30°-40° and a helix angle of 10°, ensuring that the contact area between the roller (7) and the thread raceway is >85%.

3. The planetary roller screw type electric steering device according to claim 1, characterized in that: The cage is an integral metal cage made of brass.

4. The planetary roller screw type electric steering device according to claim 1, characterized in that: The internal thread of the roller nut (8) is completely consistent with the parameters of the roller screw (6), and the surface roughness of the raceway is ≤0.4μm.

5. The planetary roller screw type electric steering device according to claim 1, characterized in that: The diameter of the roller (7) satisfies R=1.1, and it adopts a multi-ring planetary arrangement with 3-5 rings and 12-20 rollers per ring.

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