Electric power steering gear

Abstract

This invention discloses an electric power steering system, comprising a housing; a steering shaft reciprocatingly disposed within the housing and extending to both ends of the housing, the shaft having a rack portion and a screw portion; a planetary roller nut assembled within the housing and screwed to the screw portion; a motor controlled by an engine control unit (ECU), disposed within the housing, having an outer rotor connected to the planetary roller nut to drive its rotation, thereby driving the steering shaft to reciprocate within the housing; a first waterproof ring is provided between the planetary roller nut and the housing, and a second waterproof ring is sandwiched between the planetary roller nut and the hollow stator of the motor, thereby providing the motor with a sealed and waterproof effect, enabling the electric power steering system to achieve the purpose of preventing motor power failure.

Description

Technical Field

[0001] This invention relates to an electric power steering system, and more particularly to an RD-type EPS (Rack-direct-drive type electric power steering) electric power steering system design that can drive the steering shaft by means of a planetary roller nut driven by an external motor providing direct driving force. Background Technology

[0002] Electric power steering (EPS) is a power steering system that uses an electric motor to provide auxiliary torque. Compared to traditional hydraulic power steering, EPS can adjust the motor speed to provide optimized steering assistance as vehicle speed changes, while maintaining convenience at low speeds and stability at high speeds. In addition, because it reduces components such as oil pumps and hydraulic lines, it is easier to integrate with different vehicle models. With the introduction of advanced driver assistance systems (ADAS) and autonomous driving technologies, steering wheels and steering columns are gradually becoming unnecessary components. Therefore, reducing the size of the electric power steering mechanism and saving costs has become a problem that needs to be solved.

[0003] Furthermore, to accommodate different vehicle models, developers have focused on reducing the number of components in the reduction and transmission mechanisms. This is to prevent errors caused by component aging or interference and gaps between components from accumulating and affecting the reliability of calculating vehicle angles or output shaft positions. The RD-type EPS electric power steering system is better able to meet the requirement of reducing the space required for mechanism components. However, the drive motor used in the RD-type EPS electric power steering system is a hollow internal rotor motor, as disclosed in TWM590555, "Electric Power Steering System." Its internal rotor design limits the number of poles in the motor's structural dimensions. Motors with fewer poles exhibit high speed and low torque characteristics, which can easily lead to control point deviations when directly driving the ball nuts that require high-precision and sensitive control of the steering shaft. Moreover, the ball nuts used to control the steering shaft have limited lead reduction due to their structure, restricting the overall handling precision of the electric power steering system. This poses a significant safety concern for vehicle maneuvering in autonomous driving mode. Furthermore, the electric power steering system is located at the bottom of the vehicle's engine. When the vehicle travels through flooded terrain, it is easily splashed or submerged by water, which greatly increases the chance of the motor being damaged or failing.

[0004] In view of this, the inventors of this invention, based on the existing RD-type EPS electric power steering system which still has room for improvement, proposed the electric power steering system of this invention, which specifically adopts an external rotating motor with planetary roller nuts to achieve efficient and precise power output. At the same time, an innovative design is proposed for the waterproof structure of the motor to achieve product safety design to prevent the motor from failing due to water immersion. Summary of the Invention

[0005] The main objective of this invention is to provide an electric power steering system that enables the motor of the electric power steering system to be waterproof and resistant to failure, thereby improving the aforementioned problems.

[0006] To achieve the above objectives, the preferred embodiment of the electric power steering system of the present invention comprises a housing, a steering shaft, a planetary roller nut, and a motor, wherein:

[0007] The housing has a first housing and a second housing. The first housing is a hollow tube. The second housing is a hollow tube with multiple diameters. An accommodating space is formed inside the larger diameter end of the second housing, and a first waterproof ring is embedded at a selected location inside the accommodating space.

[0008] The steering shaft is axially reciprocatingly disposed within the housing, and its two ends extend from the first housing and the second housing respectively. The shaft body of the steering shaft has a rack portion and a screw portion.

[0009] The planetary roller nut is assembled inside the housing and screwed to the threaded part of the steering shaft. The planetary roller nut is supported and housed in the accommodating space of the second housing through a bearing. The planetary roller nut is adapted to fit the first waterproof ring. The planetary roller nut has a drive flange on one end face, and a second waterproof ring is embedded in the center of the outer end face of the drive flange.

[0010] The motor is housed within the second housing. The motor has a hollow stator and an outer rotor. The stator consists of a hollow tube through which a set of coils pass. The steering shaft passes through the hollow tube of the stator. The hollow tube of the stator is fitted with a second waterproof ring. One end of the outer rotor is engaged with a planetary roller nut to drive the planetary roller nut to rotate, thereby driving the steering shaft to move axially back and forth within the housing.

[0011] Preferably, in the above-mentioned electric power steering, the planetary roller nut has multiple locking holes on the outer ring of the drive flange for motor linkage and locking.

[0012] Preferably, in the above-mentioned electric power steering system, the axial length of the hollow seat tube is greater than the axial length of the coil.

[0013] Preferably, in the above-mentioned electric power steering, the outer rotor is roughly in the shape of a cylindrical cup, and multiple perforations are provided at the bottom of the cylindrical cup shape of the outer rotor.

[0014] Preferably, in the above-mentioned electric power steering, the plurality of perforations correspond to the plurality of locking holes of the planetary roller nut drive flange. Attached Figure Description

[0015] Figure 1 This is a three-dimensional external view of the electric power steering system of the present invention.

[0016] Figure 2 This is a three-dimensional combined cross-sectional schematic diagram of the electric power steering system of the present invention.

[0017] Figure 3 This is an exploded perspective view of the electric power steering system of the present invention.

[0018] Figure 4 This is a three-dimensional perspective view of the steering shaft and the planetary roller nut in the electric power steering system of the present invention.

[0019] Figure 5 This is a partially exploded perspective view of the motor in the electric power steering system of the present invention.

[0020] Figure 6 This is a schematic cross-sectional view of the electric power steering system of the present invention.

[0021] Symbol explanation:

[0022] 1: Housing; 11: First housing; 12: Second housing; 13: First flange; 14: Second flange; 15: Accommodation space; 16: First waterproof ring; 2: Steering shaft; 21: Rack section; 22: Screw section; 3: Planetary roller nut; 31: Planetary roller; 32: Bearing; 33: Drive flange; 331: Lock hole; 34: Second waterproof ring; 4: Motor; 41: Motor stator; 411: Hollow seat tube; 412: Coil; 42: External rotor; 421: Induction magnet; 422: Perforation. Detailed Implementation

[0023] The terms “first” and “second” are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features.

[0024] The structural features and other functions and purposes of the present invention will be described in detail below with reference to the accompanying drawings and embodiments:

[0025] See Figure 1 , Figure 2 and Figure 3As shown, the electric power steering system of the present invention is an RD-type EPS (Rack-direct-drive type electric power steering) electric power steering system in which an external motor provides direct driving force to actuate a nut to drive a steering shaft. A preferred embodiment includes a housing 1, a steering shaft 2, a planetary roller nut 3, and a motor 4, wherein:

[0026] The housing 1 includes a first housing 11 and a second housing 12. The first housing 11 is a hollow tube with a first flange 13 formed on the outer edge of one end of the hollow tube for mounting the motor 4. The second housing 12 is a hollow tube with multiple diameters. A second flange 14 is formed on the outer edge of the end with the larger diameter, allowing the second flange 14 to be locked to the first flange 13. An accommodating space 15 is formed inside the end with the larger diameter, accommodating the planetary roller nut 3 and the motor 4. A first waterproof ring 16 is embedded at a selected location inside the accommodating space 15, allowing the first waterproof ring 16 to form a sleeve waterproof structure with the planetary roller nut 3.

[0027] The steering shaft 2 is axially reciprocating and is disposed within the housing 1 (e.g., Figure 2 and Figure 3 As shown), and its two ends extend from the first housing 11 and the second housing 12 respectively. The shaft of the steering shaft 2 has a rack portion 21 and a screw portion 22.

[0028] The planetary roller nut 3 is housed within the housing 1 and screws onto the screw portion 22 of the steering shaft 2. Its main function is to provide a linear actuation effect by engaging multiple planetary rollers 31 within the planetary roller nut 3 with the steering shaft 2 (please refer to [reference needed]). Figure 4 The planetary roller nut 3 of the present invention is supported and housed in the accommodating space 15 of the second housing 12 through a bearing 32. The planetary roller nut 3 and the first waterproof ring 16 are fitted together. The planetary roller nut 3 has a drive flange 33 on one end face. The outer ring of the drive flange 33 has a plurality of locking holes 331. The plurality of locking holes 331 are used for the motor 4 to lock. A second waterproof ring 34 is also embedded in the center of the outer end face of the drive flange 33.

[0029] The motor 4, located within the housing 1 and controlled by the engine control unit (ECU), drives the planetary roller nut 3 to rotate, thereby causing the steering shaft 2 to move axially back and forth within the housing 1. The motor 4 is a hollow motor, consisting of a hollow motor stator 41 and an outer rotor 42. Please refer to the attached document for further details. Figure 5As shown, the motor stator 41 is composed of a hollow base tube 411 through which a set of coils 412 are inserted. The axial length of the hollow base tube 411 is greater than the axial length of the coils 412. The hollow motor stator 41 allows the steering shaft 2 to pass through its interior, so that the motor 4 is mounted on the steering shaft 2 for driving. The outer rotor 42 adopts a multi-pole design and is slightly cylindrical. Multiple induction magnets 421 are attached to the radial inner wall of the outer rotor 42. The bottom of the cylindrical shape of the outer rotor 42 is provided with multiple through holes 422. These multiple through holes 422 correspond to multiple locking holes 331 of the planetary roller nut 3 drive flange 33, so that the outer rotor 42 can lock with the planetary roller nut 3, thereby enabling the outer rotor 42 to drive the planetary roller nut 3 to rotate.

[0030] This invention utilizes the above-mentioned components, such as Figure 6 As shown, firstly, the outer rotor 42 of the motor 4 is locked to the drive flange 33 of the planetary roller nut 3. Then, the planetary roller nut 3 is fitted through the bearing 32 and placed together with the outer rotor 42 into the receiving space 15 of the second housing 12. The planetary roller nut 3 and the first waterproof ring 16 form a suitable fit, so that the planetary rollers 31 of the planetary roller nut 3 are screwed into the screw portion 22 of the steering shaft 2, allowing the planetary roller nut 3 to rotate in the bearing 32. The motor stator 41 is locked onto the first flange 13 of the first housing 11, so that the first housing 11 together with the first flange 13 of the first housing 12 forms a suitable fit. After the motor stator 41 is fitted onto the rack portion 21 of the steering shaft 2, the first flange 13 of the first housing 11 and the second flange 14 of the second housing 12 are engaged and locked together, and the motor stator 41 and the outer rotor 42 of the motor 4 are fitted together. At the same time, the hollow seat tube 411 of the motor stator 41 and the second waterproof ring 34 embedded in the planetary roller nut 3 are compatible with each other. In this way, the electric power steering system of the present invention is formed, which can make the overall structure more concise, and the sealing and waterproofing capability of the motor 4 can be reliably guaranteed, effectively avoiding the probability of motor damage from water immersion.

[0031] Because the planetary roller nut 3 uses planetary rollers 31 as the transmission rolling element, it has a greater load capacity and longer service life compared to the traditional ball bearing nut, which uses balls, and has a shorter lead. Furthermore, the planetary roller nut 3 does not require a return flow device, achieving a faster rotational speed than ball bearing nuts and reducing noise levels. Therefore, the use of the planetary roller nut 3 as the transmission element of the steering shaft 2 in the electric power steering system of this invention has the following advantages: the steering shaft 2 has a faster, more reliable, and precise driving stroke, and it is more shock-resistant, ensuring the sensitivity, precision, and safety stability of vehicle control.

[0032] The electric power steering system of the present invention, with the aforementioned structure, has a portion of the motor 4 that needs to be sealed and waterproof. This portion is located in the gap between the hollow seat tube 411 and the steering shaft 2, and another portion is located in the gap between the planetary roller nut 3 and the second housing 12. Waterproofing of the gap between the hollow seat tube 411 and the steering shaft 2 is achieved through a proper fit between the second waterproof ring 34 of the planetary roller nut 3 and the end diameter of the hollow seat tube 411. The waterproofing of the gap between the planetary roller nut 3 and the second housing 12 is achieved through the first waterproof ring 16 provided between the planetary roller nut 3 and the second housing 12. Through the action of the first waterproof ring 16 and the second waterproof ring 34 of the above-mentioned two waterproof structures, the motor 4 is protected from water ingress.

[0033] In summary, the electric power steering system of the present invention has indeed enabled the full utilization of the motor power of the electric power steering system, made the motor as a whole achieve a sealed and waterproof state, and its function and design purpose are indeed in line with the present invention, which can be called a reasonable advancement.

Claims

1. An electric power assisted steering gear characterised in that, Includes housing, steering shaft, planetary roller nuts, and motor, wherein: The housing has a first housing and a second housing. The first housing is a hollow tube. The second housing is a hollow tube with multiple diameters. An accommodating space is formed inside the larger diameter end of the second housing, and a first waterproof ring is embedded at a selected location inside the accommodating space. The steering shaft is axially reciprocatingly disposed within the housing, and both ends of the steering shaft extend from the first housing and the second housing, respectively. The shaft body of the steering shaft has a rack portion and a screw portion. The planetary roller nut is assembled inside the housing and screwed to the screw portion of the steering shaft. The planetary roller nut is supported and housed in the accommodating space of the second housing through a bearing. The planetary roller nut is adapted to fit the first waterproof ring. The planetary roller nut has a drive flange on one end face, and a second waterproof ring is embedded in the center of the outer end face of the drive flange. The motor is disposed within the second housing; the motor has a hollow motor stator and an outer rotor. The motor stator is composed of a set of coils passing through a hollow seat tube. The steering shaft passes through the hollow seat tube of the motor stator. The hollow seat tube of the motor stator is compatible with the second waterproof ring. One end of the outer rotor is engaged with the planetary roller nut to drive the planetary roller nut to rotate, thereby driving the steering shaft to move axially back and forth within the housing.

2. The electric power assisted steering gear of claim 1 wherein, The planetary roller nut has multiple locking holes on the outer ring of the drive flange for locking with the motor.

3. The electric power assisted steering gear of claim 1 wherein, The axial length of the hollow seat tube is greater than the axial length of the coil.

4. The electric power assisted steering gear of claim 1 wherein, The outer rotor is roughly cylindrical in shape, and multiple perforations are provided at the bottom of the cylindrical shape of the outer rotor.

5. The electric power assisted steering gear of claim 4 wherein the first and second electrical power supply units are connected in series. The plurality of perforations correspond to the plurality of locking holes of the drive flange of the planetary roller nut.

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