DE102007000588A1 - Active steering system i.e. angle superposition steering system, for vehicle, has brake device with brake disk to produce braking effect on electric motor such that disk is either connected with fixed part or eddy current is induced in disk - Google Patents

Abstract

The system (ALS) has a differential drive (UEG) controlled by an electric motor (EM). The drive adds an additional steering angle to a steering angle that is adjusted by a steering wheel (L). A brake device (WSB) has a rotatable and electrical conductive brake disk for producing a braking effect on the electric motor such that the brake disk is either connected with a fixed part in a friction-engaged manner, or an eddy current is induced in the brake disk. The brake disk is axially and shiftably arranged on a shaft that is connected with the motor.

Description

The The invention relates to an active steering system according to the preamble of the claim 1 and one for it provided braking device according to the preamble of the sibling Claim.

in the Range of vehicle steering also becomes steering assistance Angle superposition steering used, usually also be referred to as active steering. In an active steering system is the driver's specific steering angle with an additional Steering angle superimposed. This is usually between steering wheel or steering column and steering gear controlled by an electric motor superposition gear used, depending on the actual steering angle from the rotor movement of the electric motor an additional Steering angle added. The sum angle thus generated then becomes the steering gear guided and transferred from there to the steering mechanism (eg rack or ball screw), with the then the vehicle wheels (eg front wheels) be deflected. The actual Steering angle at the front wheels Thus, the actual steering wheel angle results with the additional steering wheel angle Motor angle (rotor angle of rotation of the electric motor) to a sum angle is added. In the event of a malfunction of the electric motor during operation, especially during its control, the electric motor should as soon as possible to a standstill be brought to prevent further false rotational movement to become. This is to prevent a wrong and not adequate steering angle is generated. Also supposed to be prevented be that the steering movement of the driver on the steering wheel is not in the electric motor, but is properly directed to the wheels to be deflected.

Around in case of failure to prevent the electric motor from rotating further, become common used mechanical brakes and / or pawls. This pure Mechanically acting braking devices have the disadvantage that they wear out or even by overuse or fatigue can break.

Therefore The present invention is based on the object, an active steering system in which the problems are overcome and one as possible wear-free Achieved braking effect and achieved a secure blocking effect can be.

Is solved the task by an active steering system with the features of Claim 1 and by a provided braking device with the characteristics of the sibling Claim.

Therefore It is proposed that in the active steering system, a braking device is provided or integrated, which is used to generate a braking effect to generate a braking effect on the electric motor a rotatable and electrically conductive Brake disc which frictionally with a fixed Part of the active steering system is connectable and in an eddy current is inducible. Thus, preferably, the rotatable brake disc alternately either frictionally with be connected to the fixed part of the active steering system or acted upon by the eddy current induced in the brake disc become. When a malfunction of the active steering system detected is that z. B. occurs in a power failure on the electric motor, so by the mechanical blocking is still useful Steering function ensures.

On the other hand can be canceled during normal operation of the active steering system of the frictional engagement and the rotatable brake disc with the brake disc Induced eddy current can be applied to a controllable and wear-free or to maintain a gentle braking effect, possibly even completely can be switched off.

Preferably the brake disc is axially displaceable on one with the electric motor arranged connectable shaft, being at or near the rotatable Brake disc is a first permanent magnet, which is the brake disc pulls on the fixed part of the active steering system, so that the friction Connect, and further wherein an activatable magnet, in particular a current coil is arranged to the first permanent magnet counteract and that between the brake disc and the fixed Part made frictional To cancel the connection. In this case, the activatable magnet is preferably designed as a controllable current coil. For this purpose, the active steering system or the braking device a controlling device for detection a fault occurring in the active steering system, in particular an error during operation and / or in the control of the electric motor.

Either in normal operation as well as in case of error causes the braking device always effective and targeted a speed reduction or blocking of the motor.

These and further advantageous embodiments of the invention will become apparent also from the dependent claims.

following is an embodiment of Invention closer with reference to the accompanying drawings, in which:

the 1 schematically shows the structure of an active steering system with a braking device according to the invention; and

the 2 shows a schematic structure of the braking device according to the invention.

The 1 shows a block diagram of the structure of an inventively designed active steering system ALS. The system ALS consists essentially of a steering gear LG, which is connected to a (not shown) steering mechanism and a superposition gear UEG is upstream. In the superposition gearing UEG, the steering angle set by the driver on the steering wheel L is subjected to an additional steering angle, which is generated by an electric motor EM.

In error-free normal operation, the optimum additional angle is thus continuously generated by the electric motor EM and added to the actual steering angle and fed as a sum angle into the steering gear LG. In order to ensure that no false additional angle is generated by the electric motor EM in normal operation as well as in the event of a fault, the in 1 illustrated arrangement provided which has a braking device WSB for the electric motor EM. This braking device WSB works occasionally either according to the eddy current principle for a wear-free braking or purely mechanically by frictional engagement for a fixed blocking of the electric motor EM and can, as in 2 represented, be constructed. Therefore in the further on the 2 Referenced.

The braking device WSB is designed as a combination of an eddy current brake function with a friction brake or blocking function. For this purpose, a shaft connected to the rotor of the electric motor EM is used 2 (designed here as a hollow shaft) an axially displaceable brake disc 1 arranged, which consists of an electrically conductive material, here z. B. steel. On an opposite surface of the housing 3 is a first magnet in the form of a permanent magnet 5 arranged, the brake disc 1 attracts and in the blocking case, a frictional connection between the rotating part, so the brake disc 1 , And the fixed part, ie the opposite surface of the housing 3 , manufactures. This will be the brake disc 1 arrested and blocked the electric motor EM. This condition is established in case of error.

Normally, during operation of the active steering system ALS, the frictional engagement should be canceled. This is done near the brake disc 1 and the first permanent magnet 5 a current coil 4 arranged, which is driven by a (not shown) electronics. This allows the frictional connection between the brake disc 1 and housing part 3 canceled and yet achieved a reduced controllable braking effect during operation. This is the current coil 4 driven, so that their magnetic field is the field of the permanent magnet 5 weakens and the brake disc 1 separates from the opposite surface, moves axially to the right and is freely rotatable. The effect of the resulting magnetic field results in an eddy current, the brake disc 1 something slows down. By appropriate control of the current coil 4 can the resulting magnetic field and thus in the brake disc 1 induced eddy current can also be reduced to zero, leaving the brake disc 1 unrestrained rotation. This can be done by controlling the current coil 4 a completely wear-free braking effect can be set optimally for normal operation. In case of error, the current coil 4 de-energized, so that the frictional braking or blocking the brake disc 1 or the rotor of the electric motor EM automatically adjusts.

In order to cancel the frictional engagement faster for normal operation, an additional second permanent magnet can 6 be provided, the magnetic field of the first permanent magnet 5 is opposite and thus weakens its effect to the detachment of the brake disc 1 from the surface of the housing 3 to facilitate. As soon as an air gap forms between them, only the non-contact and wear-free eddy current brake is effective.

One Advantage of the solution presented here is u. a. in that the rotation in normal operation wear-free and can be selectively reduced. In case of error, especially in the event of a total failure of the supply voltage, the rotor braking takes place and blocking purely mechanically. This results in an automatic Fail-safe function.

The active steering system ALS presented here is thus immediately blocked in the event of a power failure. In order to produce the frictional blocking in another error case, the system ALS or the braking device WSB has a (not shown) controlling means for detecting a malfunction occurring in the system, in particular an error during operation and / or in the control of the electric motor EM , The controlling device then determines that for the current coil 4 required electricity.

Due to the combination of the friction brake function and the eddy current brake function, there is also an advantage in comparison with conventional, purely mechanical friction brakes or blocking devices that no springs with a relatively high degree of elasticity are used here Spring forces must be used to achieve high braking performance or locking the rotating parts. As a result, the required electrical power for driving can be reduced to a very low level. The superposition gear UEG can z. B. be a planetary gear or a corrugated transmission.

The Invention has been described on the example of an active steering, in which a superposition gear adds an additional steering angle generated by an electric motor becomes. However, the invention is not limited to this type of steering, but can be on any similar Type of steering that is supported by a motor.

WHEN

Active Steering System

L

steering wheel

LEL

Superposition gear

LG

steering gear

EM

electric motor

WSB

braking device (Eddy current brake with locking device)

1

brake disc

2

hollow shaft

3

casing

4

current coil (activatable electromagnet)

5

first permanent magnet

6

second permanent magnet

Claims (12)

Active steering system (ALS) with a controlled by an electric motor (EM) superposition gear (UEG), which adds to an adjusted via the steering wheel (LR) steering angle, an additional steering angle, characterized in that a braking device (WSB) is provided which for generating a Braking effect on the electric motor (EM) a rotatable and electrically conductive brake disc ( 1 ) which frictionally engages with a stationary part ( 3 ) of the active steering system (ALS) is connectable and in which an eddy current is inducible. Active steering system (ALS) according to claim 1, characterized in that the rotatable brake disc ( 1 ) alternately either frictionally engaged with the fixed part ( 3 ) of the active steering system (ALS) is connected or with the in the brake disc ( 1 ) induced eddy current is applied. Active steering system (ALS) according to claim 1 or 2, characterized in that during normal operation of the active steering system (ALS) the rotatable disc ( 1 ) is acted upon by the eddy current induced in the brake disk. Active steering system (ALS) according to one of claims 1 to 3, characterized in that the rotatable brake disc ( 1 ) frictionally engaged with the fixed part ( 3 ) of the active steering system (ALS) is connected when a malfunction of the Active Steering System (ALS) is detected. Active steering system (ALS) according to one of the preceding claims, characterized in that the brake disc ( 1 ) axially displaceable on a shaft connectable to the electric motor (EM) ( 2 ) is arranged. Active steering system (ALS) according to one of the preceding claims, characterized in that on or in the vicinity of the rotatable brake disk ( 1 ) a first permanent magnet ( 5 ) is arranged, which the brake disc ( 1 ) to the fixed part ( 3 ) of the active steering system (ALS) pulls to make the frictional connection. Active steering system (ALS) according to claim 6, characterized in that on or in the vicinity of the rotatable brake disc ( 1 ) an activatable magnet, in particular a current coil ( 4 ) is arranged to the first permanent magnet ( 5 ) and between the brake disc ( 1 ) and the fixed part ( 3 ) released frictional connection. Active steering system (ALS) according to claim 6 or 7, characterized in that on or in the vicinity of the rotatable brake disc ( 1 ) a second permanent magnet ( 6 ) is arranged to the first permanent magnet ( 5 ) and between the brake disc ( 1 ) and the fixed part ( 3 ) at least weaken frictional connection produced. Active steering system (ALS) according to one of claims 6 to 8, characterized in that at least one of the permanent magnets ( 5 . 6 ) and / or the activatable magnet, in particular the current coil ( 4 ), the eddy current in the rotatable and electrically conductive brake disc ( 1 ). Active steering system (ALS) according to one of claims 6 to 9, characterized in that the activatable magnet is a controllable current coil ( 4 ). Active steering system (ALS) according to claim 6, characterized in that the active steering system (ALS) is a braking device (WSB) controlling means for detecting one in the active steering system (ALS) occurring misconduct, in particular an error in Operation and / or in the control of the electric motor (EM) having. Braking device for a Aktivlenkungssys tem (ALS) with a controlled by an electric motor (EM) superposition gear (UEG), which adds to an adjusted via the steering wheel (LR) steering angle, an additional steering angle, characterized in that the braking device (WSB) for generating a braking effect on the electric motor (EM) a rotatable and electrically conductive brake disc ( 1 ) which frictionally engages with a stationary part ( 3 ) of the active steering system (ALS) is connectable and in which an eddy current is inducible.