Steering column for steer-by-wire steering system

Abstract

A steering column for a steer-by-wire steering system for a motor vehicle, comprising a steering wheel (1) having a fixed-position steering wheel hub (2) and a force feedback unit capable of transmitting torque to the steering wheel (1), the force feedback unit comprising a first electric motor (3) and a second electric motor (12), the first electric motor (3) acting directly on the steering wheel (1) and the second electric motor (12) acting on the steering wheel (1) via a transmission (13).

Description

[Technical field]

[0001] The present invention relates to a steering column for a steer-by-wire steering system for a motor vehicle.

[0002] Background technology In conventional steering systems, the desired steering angle is transmitted from the steering wheel via a mechanical linkage to both front wheels. The steering torque is multiplied by a servo transmission, which allows simple steering.

[0003] Steer-by-wire steering systems eliminate the need for a mechanical connection between the steering wheel and the steered wheels: the steering angle adjusted at the steering wheel is detected by a sensor and electronically transmitted to a steering actuator, which then adjusts the front wheels accordingly.

[0004] A vehicle driver requires feedback at the steering wheel about the driving conditions at the wheels, e.g. the condition of the road surface. Furthermore, the feedback creates a speed-dependent steering feel. In conventional steering systems, such feedback forces are transmitted from the wheels to the steering wheel via a mechanical connection.

[0005] In a steer-by-wire steering system, the feedback is no longer transmitted mechanically, since there is no longer a mechanical connection between the steering column and the steering transmission. Therefore, in a steer-by-wire steering system, the feedback to the driver must be simulated in the steering wheel. This is done by an electric motor that acts on the steering wheel directly or indirectly via a transmission.

[0006] An electric feedback motor must provide sufficient torque in a timely manner for the required feedback. A higher torque requires a correspondingly larger motor. A directly acting motor has a very good response behavior since there is no gearing. However, to generate the required torque, the motor must be dimensioned larger. The torque of a smaller motor can be increased through an additional gearing, but this may result in more noise.

[0007] The object of the present invention is to provide a steering column for a steering system with a feedback actuator that does not require a large motor, but which nevertheless requires that the feedback actuator has a very good response behavior.

[0008] This problem is solved by the subject matter of claim 1. Advantageous embodiments are the subject matter of the further claims and will become apparent from the following description of the invention.

[0009] According to the invention, by using two smaller motors for the feedback actuator, which are combined and variably used, a compact feedback actuator with good response behavior is obtained. A first electric motor is arranged in the steering wheel and acts directly on it. This motor can generate a relatively small torque. A second electric motor is arranged behind the first motor and acts on the steering wheel via a transmission. This motor can generate a relatively large torque, if required.

[0010] The behavior of the feedback actuator is variable and depends on the vehicle's driving conditions, such as speed or steering angle. The two motors may be used separately or simultaneously.

[0011] The steering shaft and steering wheel hub are stationary in the present invention, i.e., cannot rotate. The steering column feedback actuator consists of a primary feedback unit and a secondary feedback unit.

[0012] The primary feedback unit is located near the steering wheel and consists of a small motor that acts directly on the steering wheel or steering rim. The inner part of the motor is attached to a fixed steering shaft. The outer part of the motor is rotatable and is coupled to a housing of the primary feedback unit. The housing of the primary feedback unit further carries the steering wheel rim.

[0013] The primary feedback unit is supported within a housing of the steering column via rolling bearings, thereby allowing it to rotate within the housing.

[0014] The secondary feedback unit comprises a small motor acting on the primary feedback unit via a gearing, which allows a higher torque to be generated.

[0015] As is known from steering columns with fixed hub and steering shaft, it is possible to better use suitable airbag concepts or additional operating elements in the hub. Electric cables may also be guided through the hollow steering shaft.

[0016] An embodiment will be described below with reference to the drawings. [Brief description of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view of a steering column according to the present invention. [Diagram 2] FIG. 2 is a detailed view of a steering column according to the present invention.

[0018] In figure 1 the steering column according to the invention can be seen in cross section. The steering wheel 1 consists of a steering wheel rim 7 and a fixedly configured steering wheel hub 2. The steering wheel hub 2 is attached to the end of a steering shaft 6 which likewise cannot rotate.

[0019] The steering column feedback actuator consists of a primary feedback unit and a secondary feedback unit. The primary feedback unit comprises a motor 3 arranged inside the steering wheel 1. The motor 3 has an inner part 5, which is fixedly arranged on the steering shaft 6 and therefore also cannot rotate. The outer part 4 of the motor 3 is rotatable and is connected to a housing 8 of the primary feedback unit, which in turn carries the steering wheel rim 7. The motor 3 thus acts directly on the steering wheel 1.

[0020] The primary feedback unit is supported on the steering shaft 6 by two rolling bearings 9. Furthermore, the primary feedback unit is partially pressed into a housing 11 and supported therein via a rolling bearing 10. Thus, the primary feedback unit is arranged rotatably.

[0021] The housing 11 contains a secondary feedback unit, which comprises an electric motor 12, which acts via a transmission 13 on the rotatable primary feedback unit.

[0022] This can be seen in the detailed view of Figure 2, where the transmission 13 is shown in a bottom view of the arrangement of Figure 1. A gear wheel 15 is fixed in the housing 8 of the primary feedback unit by press fitting. An electric motor 12 supports the gear wheel 14 and thereby drives the gear wheel 15. For the gear wheels 14, 15 a corresponding tooth shape can be selected, for example a helical tooth arrangement, which allows low-noise operation.

[0023] As an alternative to gear transmissions, other types of transmissions are also possible, for example belt transmissions.

Claims

1. A steering column for a steer-by-wire steering system for a motor vehicle, comprising: A steering wheel (1) having a fixed position steering wheel hub (2), a force feedback unit capable of transmitting torque to the steering wheel (1); Equipped with The force feedback unit comprises a first electric motor (3) and a second electric motor (12). In the steering column, said first electric motor (3) acting directly on said steering wheel (1); The second electric motor (12) acts on the steering wheel (1) via a transmission (13). A steering column characterized by:

2. 2. A steering column according to claim 1, characterized in that the first electric motor (3) and a housing (8) form a primary feedback unit, the primary feedback unit being rotatably supported in a second housing (11), the housing (8) carrying a steering wheel rim (7).

3. the first electric motor (3) has an inner part (5) which is fixedly arranged on a fixed steering shaft (6); The first electric motor (3) has an outer part (4) which can rotate and is coupled to the housing (8).

3. A steering column according to claim 2.

4. the second electric motor (12) and the transmission (13) form a secondary feedback unit, the secondary feedback unit being arranged in the second housing (11); The electric motor (12) acts on the primary feedback unit via the transmission (13).

3. A steering column according to claim 2.

5. The transmission (13) is formed as a gear transmission having a plurality of gears (14, 15), The gear (15) is rigidly connected to the housing (8); The gear (14) is disposed on the shaft of the motor (12).

5. A steering column according to claim 4.

6. 6. A steering column according to claim 4 or 5, characterized in that the primary feedback unit and the secondary feedback unit can be used separately or simultaneously, respectively, depending on the driving conditions of the vehicle.

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