US-12623713-B2 - Electric power steering system for a vehicle

US12623713B2US 12623713 B2US12623713 B2US 12623713B2US-12623713-B2

Abstract

Disclosed is an electric power steering system for a vehicle, the power steering system including: an electric motor configured to provide mechanical power to a steering mechanism of the vehicle for steering the vehicle; a housing in which the electric motor is disposed, wherein the housing comprises an inner housing in which the electric motor is disposed, and an outer housing disposed around the inner housing, and wherein an air flow path is defined within the housing, the air flow path being defined at least in part by a gap between the inner housing and the outer housing; and an air flow source arranged to generate an air flow along the air flow path to cool the electric motor, wherein the air flow source is independent from the electric motor.

Inventors

George Karl SCHOLZ

Assignees

McMurtry Automotive Limited

Dates

Publication Date: 20260512
Application Date: 20210728
Priority Date: 20200731

Claims (19)

1 . An electric power steering system for a vehicle, the electric power steering system comprising: an electric motor configured to provide mechanical power to a steering mechanism of the vehicle, the steering mechanism adapted to steer the vehicle; a housing comprising an inner housing and an outer housing, the inner housing having said electric motor disposed therein, said outer housing being disposed around the inner housing, wherein a gap between the inner housing and the outer housing defines an air flow path; and an air flow source arranged to generate an air flow along the second fixed part so as to cool said electric motor, said air flow source being independent from said electric motor, wherein said electric motor has a first electric motor and a second electric motor, wherein both of the first electric motor and the second electric motor are disposed in said housing and configured to respectively apply a torque to a common shaft used to steer the vehicle, said air flow source being configured to cool the first electric motor and the second electric motor.
2 . A vehicle comprising the electric power steering system of claim 1 .
3 . The electric power steering system of claim 1 , wherein the plurality of fins are configured to accelerate the air flow or to increase turbulence of the air flow along the air flow path.
4 . The electric power steering system of claim 1 , wherein a height of at least one fin of the plurality of fins adjacent to the air inlet is smaller than a height of another fin of the plurality of fins away from the air inlet.
5 . The electric power steering system of claim 1 , wherein the plurality of fins are configured to uniformly distribute air flowing along the air flow path.
6 . The electric power steering system of claim 1 , wherein the plurality of fins are aligned along substantially parallel planes.
7 . The electric power steering system of claim 1 , wherein the air flow path has a plurality of branches configured to cool different portions of said electric motor.
8 . The electric power steering system of claim 1 , wherein the air flow path is defined at least in part by a channel formed in a wall of said housing.
9 . The electric power steering system of claim 1 , wherein the air flow path is defined at least in part by a surface of said electric motor.
10 . The electric power steering system of claim 1 , wherein the air flow path is defined at least in part by a gap between a rotor and a stator of said electric motor.
11 . The electric power steering system of claim 1 , wherein the air flow path extends around at least a portion of a circumference of said electric motor.
12 . The electric power steering system of claim 1 , wherein said housing has a plurality of fins that guide air flow along the air flow path, the plurality of fins being disposed on at least one of the inner housing and the outer housing, the plurality of fins being arranged in the gap between the inner housing and the outer housing.
13 . The electric power steering system of claim 1 , wherein said air flow source comprises a fan mounted on said housing.
14 . The electric power steering system of claim 1 , wherein said housing has an air inlet and an air outlet, the air flow path extending between the air inlet and the air outlet.
15 . The electric power steering system of claim 14 , further comprising: an air filter positioned adjacent at least one of the air inlet and the air outlet.
16 . The electric power steering system of claim 1 , wherein the air inlet and the air outlet are arranged on opposite sides of said housing.
17 . The electric power steering system of claim 1 , further comprising: a controller, said air flow source adapted to cool said controller.
18 . The electric power steering system of claim 17 , wherein said controller is positioned in said housing.
19 . The electric power steering system of claim 18 , wherein said electric motor is disposed in a first portion of said housing, said controller being disposed in a second portion of said housing, the air flow path has a first air flow path defined in the first portion of said housing and a second air flow path defined in the second portion of said housing, wherein said air flow source generates the air flow along the first air flow path and the second fixed part so as to respectively cool said electric motor and said controller.

Description

FIELD OF THE INVENTION The present invention relates to an electric power steering system for a vehicle, in which an electric motor is configured to provide mechanical power to a steering mechanism of the vehicle. BACKGROUND When no power steering is used in a vehicle, all of the steering power is provided by the driver rotating the steering wheel. The steering wheel is typically directly coupled to a steering rack of the vehicle via a steering column and pinion. When a driver turns the steering wheel, the steering column and pinion are rotated, which causes the steering rack to be translated and the wheels to turn left or right (depending on the direction in which the steering wheel is turned). Thus, when all of the steering power is provided by the driver, a large amount of effort may be required from the driver in order to turn the wheels. Power steering systems are often used in vehicles in order to facilitate steering and manoeuvring of the vehicle. Power steering systems reduce an amount of effort that is required from the driver in order to turn the wheels, by providing mechanical power for steering the vehicle. There exist various types of power steering systems. One type of power steering system is an electric power steering system, which uses an electric motor for applying a torque to the steering mechanism. In such an electric power steering system, when the driver rotates the steering wheel, a torque sensor detects a torque applied by the driver. A control unit of the electric power steering system then calculates, based on the detected torque, a torque to be applied to the steering mechanism by the electric motor. The control unit then transmits a control signal to a controller for the electric motor, to cause the electric motor to apply the calculated torque to the steering mechanism. In this manner, the torque applied by the driver may be supplemented by that from the electric motor, which may greatly facilitate turning the wheels. Electric power steering systems may also be used to perform steering in autonomous (i.e. self-driving) vehicles. In such a case, the control unit may calculate the torque to be applied by the electric motor based on an input signal from an autonomous driving system of the vehicle, in order to turn the wheels in a desired direction. An overview of electric power steering systems is provided, for example, in “New Electrical Power Steering Systems” by Mathias Würges (Encyclopedia of Automotive Engineering, 2014, DOI: 10.1002/9781118354179.auto008) SUMMARY OF THE INVENTION At its most general, a first aspect of the present invention provides an electric power steering system for a vehicle, the power steering system having an electric motor for providing mechanical power to a steering mechanism of the vehicle, where the electric motor is cooled by forced air cooling. By actively cooling the electric motor using forced air cooling, heat may be efficiently removed from the electric motor, which may enable the electric motor to achieve a higher continuous power output than an equivalent electric motor without forced air cooling. Using forced air cooling to efficiently remove heat from the electric motor may enable the electric motor to effectively deliver high levels of mechanical power for steering the vehicle. As a result, a performance of the power steering system may be improved, which may in turn improve steering performance and controllability of the vehicle. In particular, this may facilitate steering and control of the vehicle in conditions where high levels of power are required to turn the vehicle, such as when the vehicle is turning through a large angle or manoeuvring, e.g. parking. Actively cooling the electric motor may further reduce a risk of failure of the electric motor (e.g. due to overheating), thus improving overall safety of the power steering system. The inventors have found that conventional electric power steering systems which are capable of delivering high levels of mechanical power are usually large and heavy, which makes them difficult to incorporate into smaller vehicles, or into vehicles where weight is a concern (e.g. motorsport vehicles). However, the inventors have realised that by actively cooling the electric motor using forced air cooling, a size of the electric motor can be reduced compared to systems where no active cooling is used. This is because a smaller, actively cooled electric motor can be used to achieve similar levels of mechanical power to a larger, uncooled electric motor. Thus, the invention enables a size and weight of electric power steering systems to be reduced, whilst still enabling high levels of mechanical power to be provided for steering the vehicle. According to the first aspect of the invention, there is provided an electric power steering system for a vehicle, the power steering system comprising: an electric motor configured to provide mechanical power to a steering mechanism of the vehicle for steering the ve