Compact electric power steering column, column electric power steering and automotive

Abstract

The invention relates to a compact electric power steering column which comprises a shell, an upper steering shaft, a lower steering shaft, a torsion rod, a motor, a planetary gear train, a torque sensor and a controller. The shell is fixedly connected to an upper casing pipe and a lower casing pipe, the upper steering shaft is sleeved with the upper casing pipe, the lower steering shaft is sleeved with the lower casing pipe, the torsion rod is arranged between and connected with the upper steering shaft and the lower steering shaft, the motor is installed in the shell and comprises a motor rotor and a motor stator which are arranged in the same axial direction with the upper steering shaft, the planetary gear train is installed in the shell, the input end and the output end of the planetary gear train are connected with the output end of the motor and the lower steering shaft respectively, the planetary gear train is used for amplifying power torque output by the motor, the torque sensor is installed on the torsion rod and used for detecting torque signals at the position, and the controller is used for receiving the torque signals and controlling operating of the motor according to the torque signals, and then the power torque output by the motor is amplified by the planetary gear train and then output by the lower steering shaft. The invention further relates to a columnar electric power steering gear and an automobile.

Description

technical field [0001] The invention relates to the technical field of electric power steering systems, in particular to a compact electric power steering column, a column type electric power steering device and an automobile equipped with the compact electric power steering column. Background technique [0002] In recent years, the application of electric power steering system (EPS) with environmental protection and energy saving functions and superior performance in complete vehicles has gradually increased. The column-assisted electric power steering column is more widely used than other forms (such as rack-assisted) EPS due to its simple structure and strong portability. The output torque of the column-assisted electric power steering column can reach 60-100Nm, while the EPS is limited by the layout space, etc., its motor torque is generally 3-5Nm, which requires a large transmission ratio (at least 20 or more ) of the deceleration mechanism plays the role of lowering (...

AI Technical Summary

Problems solved by technology

[0003] At present, most of the reduction mechanisms used in EPS are worm gear mechanisms, but there are some disadvantages as follows: (1) The positive efficiency is low, and the current maximum is only 85%, which means that a worm gear with a transmission ratio of 20 loses 15% of the energy. The converted effective transmission ratio is only 17, which requires the actual increase of the worm gear ratio to more than 23, so the size of the reduction mechanism needs to be additionally increased; (2) The inverse efficiency is low, generally only about 20%, that is to say, the EPS does not work (or when the EPS function is lost), if you want to turn, turn the steering wheel, and the worm gear will drive the worm (at this time, it is reverse transmission, and the transmission efficiency is extremely low), which requires a lot of torque to turn the steering wheel and turn the wheels. Extremely inconvenient; (3) Since the worm wheel is generally made of nylon, and the worm is made of steel, the worm wheel will be worn out after the EPS has been used for a period of time, resulting in a gap between the worm gear and the worm, which affects the smoothness of the transmission. Affected, there will be greater torque fluctuations (torque fluctuations are originally large under normal conditions), and the teeth of the worm gear will also produce noise due to the knocking of the gap; (4) due to the use of the worm gear reduction mechanism, it is inevitable The axis of the power assist motor must be perpendicular to the axis of the steering column, which is equivalent to increasing the space occupied by the motor in the radial direction of the steering column, causing the volume of the EPS to become larger in the radial direction. It is impossible to arrange down-column EPS on a narrow vehicle, forcing the selection of a more expensive rack-assisted EPS, which will undoubtedly lead to cost waste or direct abandonment of EPS

Depend on figure 2 It can be seen that since the axis of the motor 118 is perpendicular to the axis of the worm gear 115 (that is, the upper steering shaft 100), and needs to be arranged beside the steering shaft (or called the steering column), it occupies a large space, causing some models to may not be arranged

In addition, since the movement form between the worm gear and the worm is sliding, the energy loss is large and the inverse efficiency is particularly low, so under the same effective transmission ratio, the size of the worm gear should be increased.

In addition, after long-term wear between the worm gear and worm, the meshing gap will increase, so that the transmission noise and torque fluctuation will increase

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