Adjustment drive method for operating electric adjustable steering column, control unit, steering column and motor vehicle

Abstract

The invention relates to a method for operating an adjustment drive (13) of an electrically adjustable steering column (10) for a motor vehicle, said steering column comprising an actuator unit (11) with a rotatably mounted steering shaft (12) on which a steering wheel is mounted, the actuator unit (11) being adjusted by means of at least one adjustment drive (13), the invention relates to a method for setting a longitudinal position and / or a height position of a steering wheel, comprising: a) pre-defining a setpoint (SW) of an adjustment speed of an actuator unit (11); b) driving at least one control drive (13) with a voltage signal by at least one controller on the basis of the setpoint (SW); c) detecting an actual value of the control speed of the actuator unit (11) after a predetermined time period (t1) and comparing it with the setpoint value (SW); and d) lowering the setpoint value (SW) as a function of the result of the comparison of the setpoint value (SW) with the actual value (IW) until the voltage signal for driving the regulating drive (13) falls below the maximum value of the supply voltage, in particular the maximum value of the on-board electrical system voltage of the motor vehicle.

Description

[0001] The invention relates to an adjustment drive method for operating an electrically adjustable steering column, a control unit, a steering column and a motor vehicle.

[0002] Modern motor vehicles are often equipped with an adjustable steering column that can be adjusted in the longitudinal and / or height direction by means of an electric motor. In this way, a steering wheel position that is convenient for the driver can be set. The adjustment movement of the steering wheel is realized by means of an electric motor, which moves an actuator unit, which comprises a rotatably mounted steering shaft and a steering wheel, relative to a carrier unit that carries the actuator unit. This approach is known, for example, from DE 10 2019 004 840 A1.

[0003] When adjusting the actuator unit of the steering column, the adjustment speed at which the actuator unit and thus the steering wheel are to be moved is predefined. The predefined speed may result in a voltage signal for the drive motor being in a range above the supply voltage of the onboard electrical system of the motor vehicle. Influencing parameters of such a voltage signal may include, for example, temperature, friction, inaccurate installation of the motor, etc.

[0004] The disadvantage is that the electric motor cannot move the actuator unit at the desired adjustment speed. In this state, the speed of the electric motor cannot be effectively controlled by the controller because the on-board electrical system cannot provide the required operating voltage for the electric motor. The on-board electrical system and the controller are in a saturated state. For example, when adjusting the electric motor, the actuator unit may move at a speed lower than the desired adjustment speed. The disadvantage is that noticeable speed fluctuations and motor vibration noises that are annoying to vehicle occupants are generated.

[0005] Therefore, the object of the present invention is to provide an adjustment drive method for operating an electrically adjustable steering column, which method can improve the acoustic effect and achieve a uniform adjustment movement when adjusting the steering column. The object of the present invention is also to provide a control unit for driving the adjustment drive device, a steering column and a motor vehicle.

[0006] According to the invention, this object is achieved by the method as claimed in claim 1. With regard to the control unit, the steering column and the motor vehicle, this object is achieved by the subject matter of claim 7 (control unit), claim 9 (steering column) and claim 10 (motor vehicle), respectively.

[0007] The object is achieved in particular by a method for operating an adjustment drive of an electrically adjustable steering column of a motor vehicle, the steering column comprising an actuator unit with a rotatably mounted steering shaft, to which a steering wheel is fastened, wherein the actuator unit can be adjusted by at least one adjustment drive to set the longitudinal position and / or the height position of the steering wheel, the method comprising:

[0008] a) predefining a set value for the adjustment speed of the actuator unit;

[0009] b) based on the set value, driving at least one regulating drive device with a voltage signal through at least one controller;

[0010] c) detecting an actual value of the adjustment speed of the actuator unit after a predetermined period of time and comparing it with a set value; and

[0011] d) reducing the setpoint value as a function of the comparison result of the setpoint value and the actual value until the voltage signal for driving the control drive is below the maximum value of the supply voltage, in particular the maximum value of the voltage of the onboard electrical system of the motor vehicle.

[0012] A core concept of the invention is to reduce the predefined control speed setpoint value when the actual value of the control speed of the actuator unit does not correspond to the predefined control speed setpoint value after a predefined period of time. By detecting the actual value after a predefined period of time, it is first possible to wait for the activation of the control drive, in particular the activation ramp. In this way, a meaningful actual value of the control movement of the actuator unit can be detected.

[0013] If the actual value falls below the set value for the regulating speed after a predetermined period of time, this indicates that the supply voltage available from the motor vehicle is too low to operate the regulating drive and thus to enable the actuator unit to reach the set regulating speed set value. The set regulating speed can also be referred to as the target regulating speed. In this case, the entire system and its controller are in a saturated state and the controller is no longer able to control the regulating speed of the actuator unit. In the saturated state, noticeable speed fluctuations occur in the regulating movement of the actuator unit. In addition, audible oscillating regulating noises occur, which can be annoying to the vehicle occupants.

[0014] The invention counteracts this effect by reducing the set value of the regulating speed until the voltage signal driving the regulating drive is lower than the maximum supply voltage that the motor vehicle can provide. The standard supply voltage for motor vehicles is 12 volts. Other voltage values ​​can also be used as the supply voltage.

[0015] Lowering the setpoint creates a control margin for the controller, in particular a buffer, which enables the controller to compensate for speed fluctuations and thus smooth out the motor vibration noise. In other words, the method according to the invention has the advantage that the adjustment movement of the actuator unit can be carried out at a uniform speed and the adjustment noise is also more uniform, in particular, less. This has a positive effect on the acoustic effect of the adjustment process, so that the vehicle occupants convey a high-quality processing feel and a high-quality impression.

[0016] Whether the actuator unit does not reach the set adjustment speed or the system enters a saturated state may depend on many internal and external influencing factors. For example, at low ambient temperatures, the internal friction that occurs when adjusting the steering column may increase. The actuator unit is hindered in its mobility, so that the adjustment drive needs to be driven with a higher voltage signal in order to achieve the predefined adjustment speed setpoint. At excessively high ambient temperatures, the performance of the adjustment drive may decrease. Other influencing factors include too low a supply voltage, for example due to the on-board electrical system, inaccuracies in the mounting of the adjustment drive on the steering column and / or too high a tightening torque of the adjustment drive fasteners. Other influencing factors are also possible.

[0017] The controller for driving the adjusting drive is preferably a speed controller. The controller is preferably integrated in an ECU (electronic control unit). The adjusting drive is preferably an electric drive, in particular an electric motor.

[0018] The actual value of the adjustment speed of the actuator unit can be detected in various ways. The adjustment speed can be detected directly by measuring the adjustment speed. At least one sensor can be provided for this purpose. Additionally or alternatively, the adjustment speed can be detected indirectly by calculating the adjustment speed from other measured values ​​or deriving the adjustment speed based on these values. For example, the adjustment speed can be determined from the rotational speed of the adjustment drive, in particular the electric motor, based on a known transmission ratio, such as a spindle drive.

[0019] The set value and the actual value of the adjustment speed are preferably detected or set in millimeters of adjustment stroke per second (mm / s).

[0020] The actual adjustment speed is detected after a predetermined period of time, i.e. at a certain point in time. The actual value is therefore a snapshot at that point in time. This does not exclude that the actual adjustment speed may fluctuate within a certain range. In other words, during this period, the actual adjustment speed may fluctuate in the form of vibrations. In this case, the actual speed may vary between an upper and a lower limit. A completely linear speed curve (ideal curve) may also occur. The actual adjustment speed preferably follows an oscillation-like curve, depending on the rotational speed of the adjustment drive. An additional cause for such an oscillating curve may be a screw drive coupled to the adjustment drive. Other influencing factors may also exist.

[0021] Preferred embodiments of the invention are given in the dependent claims.

[0022] In a preferred embodiment, if the actual value is below the set value after a predetermined period of time, the set value is reduced. In other words, if the comparison of the set value of the regulating speed with the actual value shows that the actual value is below the set value, the set value, i.e. the target regulating speed, is reduced in order to cancel the saturation state of the controller and to reduce fluctuations in the regulating speed as well as disturbing regulating noises. If the actual value substantially corresponds to the set value of the regulating speed, the set value is preferably only reduced if the controller is still in the saturation state. This may occur in the case of too small a control margin, i.e. the voltage signal required to drive the regulating drive is (still) too high.

[0023] Preferably, the setpoint is reduced until the voltage signal of the controller is between 60% and 95% of the maximum value of the supply voltage. As a result, the controller exits saturation and is able to compensate for speed fluctuations.

[0024] In a further preferred embodiment, the set value is reduced stepwise after a predetermined period of time at at least one predetermined time interval. It is particularly preferred that the set value for the regulating speed is reduced stepwise by a plurality of, in particular small steps. For example, the set value is reduced by an absolute value of 1 mm / s. This approach has the advantage that the set value gradually approaches the saturation limit of the controller and thus the maximum operating voltage of the regulating drive, at which it is possible for the controller to compensate for speed fluctuations.

[0025] It is advantageous if the amplitude of the actual adjustment speed fluctuations, in particular the amplitude of the oscillations, is detected and the set value is reduced as a function of this. This prevents the set value from being reduced too much unnecessarily. Preferably, a lower limit is defined for the set value, to which the set value can be reduced at most.

[0026] In a preferred embodiment, the voltage signal of the controller is measured and compared with the maximum value of the supply voltage to detect the saturation state of the controller. In this way, the saturation limit of the controller can be advantageously determined, so that the set value can be adjusted accordingly according to this limit. As a result, this allows the adjustment of the set value to be optimized.

[0027] Preferably, the controller drives the regulating drive by means of pulse width modulation. In other words, the regulating drive is preferably driven by means of a pulse width modulated signal. This utilizes the advantageous effect of pulse width modulation, i.e. in the case of pulse width modulation, the input voltage of the regulating drive, in particular the electric motor, is switched continuously at a specific, in particular high frequency. This has the advantage that the combination of the coil inductance and the drive inertia smoothes the rotational speed of the electric motor. By means of pulse width modulation, speed fluctuations during the regulating process and oscillating regulating noises are thus significantly reduced.

[0028] According to a parallel aspect, the invention relates to a control unit for operating an adjustment drive of an electrically adjustable steering column of a motor vehicle, the steering column comprising an actuator unit with a rotatably mounted steering shaft, on which a steering wheel is mounted, wherein the actuator unit can set a longitudinal position and / or a height position of the steering wheel via at least one adjustment drive, the control unit being adapted to:

[0029] a) predefining a set value for the adjustment speed of the actuator unit;

[0030] b) based on the set value, driving at least one regulating drive device with a voltage signal through at least one controller;

[0031] c) detecting an actual value of the adjustment speed of the actuator unit after a predetermined period of time and comparing it with a set value; and

[0032] d) Based on the result of the comparison between the setpoint value and the actual value, the setpoint value is reduced until the voltage signal for driving the control drive is below a maximum value of the supply voltage, in particular a maximum value of the voltage of an onboard electrical system of a motor vehicle.

[0033] The advantages associated with the method also apply to the control unit according to the invention. The steps associated with the method also apply to the control unit, in particular in a form in which the control unit is configured or adapted to perform these method steps. Therefore, generally speaking, the control unit is particularly suitable for performing the method of the invention. In particular, the control unit is designed to control the execution of the method of the invention, in particular the flow of the method of the invention.

[0034] According to a further parallel aspect, the invention relates to an electrically adjustable steering column for a motor vehicle, comprising an actuator unit with a rotatably mounted steering shaft, on which a steering wheel is mounted, and equipped with at least one control unit according to the invention, wherein the actuator unit can set the longitudinal position and / or the height position of the steering wheel by means of at least one adjustment drive device, which is driven by the control unit.

[0035] According to a further parallel aspect, the invention relates to a motor vehicle comprising at least one control unit according to the invention and / or at least one electrically adjustable steering column as described above.

[0036] With regard to the advantages of the steering column and the motor vehicle, see the advantages associated with the method. Furthermore, the steering column and the motor vehicle can have, alone or in addition, individual features or combinations of features from among the features associated with the above-described method.

[0037] The invention is explained in more detail by further detailed description in conjunction with the accompanying drawings. The illustrated embodiment constitutes an example of how the control unit and the steering column in the invention can be configured.

[0038] In the attached picture:

[0039] Figure 1 A perspective view showing a steering column according to a preferred embodiment of the present invention;

[0040] Figure 2 Shows the Figure 1 Another perspective view of the steering column;

[0041] Figure 3 The speed diagram of the adjustment drive for setting the longitudinal position and / or height position of the steering wheel is shown. Figure 1 Part of the steering column.

[0042] In the following description, the same reference signs are used to denote identical or functionally identical components.

[0043] Figure 1 An electrically adjustable steering column 10 for a motor vehicle according to a preferred embodiment of the present invention is shown. The steering column 10 comprises a carrier unit 14 which is configured as a bracket with a mounting hole 15 for fixing to a vehicle body (not shown). The carrier unit 14 supports an actuator unit 11 which is spaced apart from it by a housing unit 16 and in which the actuator unit 11 is arranged in a telescopic manner. The actuator unit 11 comprises a housing tube 17 and a steering shaft 12 which is rotatably mounted in the housing tube 17 about a longitudinal axis L. A fixing portion 19 is formed at a first end 18 (see FIG. 1 ) of the steering shaft 12. Figure 2 ), the steering wheel 100 is attached to the fixed part. At the second end 21, the steering shaft 12 is connected to the fork of the universal joint 22 by torque locking. Figure 1 It can be clearly seen in.

[0044] To better illustrate, Figure 2 The individual steering columns 10 are shown in detail. The actuator unit 11 of the steering column 10 can be adjusted longitudinally and in height relative to the carrier unit 14 by means of two adjustment drives 13. For this purpose, the adjustment drive 13 for longitudinal adjustment is coupled to a spindle nut 23 via a gear mechanism. The spindle nut 23 meshes with a threaded spindle 24, which is coupled to the housing tube 17 and pushes the housing tube 17 when the spindle nut 23 is driven in the longitudinal direction L.

[0045] The adjustment drive 13 for height adjustment drives a rotatable actuation lever 26 via a second threaded drive 25, which connects the housing unit 16 to the carrier unit 14. When the actuation lever 26 is activated, the actuator unit 11 is rotated about the carrier unit 14 relative to a horizontal pivot axis S defined by the pivot bearing 22, so that the height adjustment is achieved. The use of a lever system for force transmission means that, with a constant drive speed of the adjustment drive 13, the adjustment speed of the actuator unit 11 depends on the respective position of the actuator unit 11.

[0046] The two adjustment drive devices 13 are electric motors driven by a control unit (not shown), in particular an ECU. The control unit includes at least one controller suitable for controlling the speed of the electric motor 13. A controller can be provided for each electric motor 13, or both electric motors 13 can be driven by the same controller.

[0047] In order to produce the most uniform adjustment movement and uniform motor noise when adjusting the steering wheel position, the electric motor 13 is operated according to the following method of the invention. In this respect, Figure 3 The adjustment speed curve of the actuator unit and a voltage curve associated therewith are shown. The vertical axis corresponds to the adjustment speed of the actuator unit in millimeters of adjustment stroke per second (mm / s). The horizontal axis corresponds to time in seconds, without scale.

[0048] At this point it is pointed out that the control unit is adapted to execute the method steps described below.

[0049] In a first method step a), the control unit defines a set value SW for the adjustment speed of the actuator unit 11. The set value SW is, for example, 12 mm / s. The set value SW refers to the speed value at which the actuator unit 11 and the steering wheel 100 are expected to move in the longitudinal or height adjustment direction. The set value corresponds to the target adjustment speed of the actuator unit 11 and the steering wheel 100.

[0050] Based on this predefined setpoint value SW, in a second method step b), the control unit determines a voltage signal for driving the electric motor 13. Specifically, this is a PWM signal, ie a pulse width modulated signal.

[0051] In a third method step c), after a first predetermined time period t1, an actual value IW of the adjustment speed is detected. For example, the first time period t1 can be 200 milliseconds. The actual value IW can be detected in a variety of ways. The actual value IW can be detected directly by measuring the adjustment speed by a sensor. Additionally or alternatively, the actual value IW can be detected indirectly by calculating the actual value IW from other measured values ​​or by derivation. For example, the actual value IW of the adjustment speed can be determined from the rotational speed of the electric motor 13 based on a known transmission ratio, such as the transmission ratio of the spindle drive 23, 24, 25.

[0052] The actual value IW of the adjustment speed is detected after a predetermined period of time, i.e. at a certain point in time. The actual value IW is therefore a snapshot of this certain point in time. This does not exclude that the actual adjustment speed varies within a certain range of values ​​(see Figure 3 ). In other words, the actual regulating speed may show changes in the form of oscillations during this period. In this case, the actual speed may fluctuate between an upper limit and a lower limit.

[0053] After the actual value IW of the regulating speed has been determined, the control unit compares the predefined set value SW with the determined actual value IW. Subsequently, in a fourth step d), the set value SW is adjusted according to the comparison result. If, after a predetermined period of time t1, the actual value IW is below the predefined set value SW of the regulating speed, the set value SW is reduced by a first absolute value B1. The set value SW can be reduced by an absolute value B1 of, for example, 1 mm / s. The predefined set value SW thus becomes a reduced set value SW'.

[0054] Next, the output voltage is measured on the controller to determine whether the controller is in saturation. When the required voltage signal is not enough to drive the motor 13, or is a high percentage of the supply voltage of the onboard electrical system, the controller or the overall system of the vehicle is in saturation. In this state, the controller cannot control the speed of the motor 13. This may occur, for example, when the output voltage of the controller exceeds 95% of the maximum supply voltage. At this time, the controller is in saturation and cannot compensate for speed fluctuations through pulse width modulation (PWM).

[0055] Then, after the second predetermined time period t2, a further actual value detection of the adjustment speed is performed to determine whether the actual speed of the actuator unit 11 is substantially consistent with the set value SW' after being reduced by a first absolute value B1. If not, the set value SW' will be reduced again by a second absolute value B2. This process of gradually reducing the set values ​​SW, SW' will continue until the voltage signal of the drive motor 13 is reduced to a value lower than the maximum value of the supply voltage or the vehicle electrical system voltage or the determined voltage value UComp The voltage value U Comp Up to 95% of the maximum supply voltage can be reached. At this point, the controller is out of saturation. This reduced voltage signal creates a control margin, with which speed fluctuations can be minimized during the control movement of the actuator unit 11 via the PWM signal and a uniform, low motor noise can be generated.

[0056] It should be noted that when the target speed is not reached, the set value SW will not be reduced indefinitely. To prevent this, a lower limit of the set value SW is specified, and the set value is reduced until the lower limit. The lower limit can be, for example, 8 mm / s. All the values ​​of the set value SW, the first and second absolute values ​​B1, B2 and the lower limit mentioned above are only examples, and other values ​​are also possible. In addition, it should be noted that the above method steps can be performed in an order different from that mentioned.

[0057] List of Reference Numerals

[0058] 10 Steering column

[0059] 11Actuator unit

[0060] 12 Steering axle

[0061] 13 Adjust the drive device

[0062] 14 load-bearing units

[0063] 15 mounting holes

[0064] 16 housing units

[0065] 17 Shell tube

[0066] 18 First End

[0067] 19Fixed part

[0068] 21 Second End

[0069] 22 Universal joint

[0070] 23 Spindle nut

[0071] 24 thread spindle

[0072] 25 Thread drive device

[0073] 26 Actuating lever

[0074] 100 Steering Wheel

[0075] B1 first absolute value

[0076] B2 second absolute value

[0077] SW setting value

[0078] SW' set value after reduction

[0079] IW actual value

[0080] t1 scheduled time period

[0081] t2 scheduled time interval

[0082] L Longitudinal direction

[0083] S-Pivot

[0084] U Comp Reduced voltage signal

Claims

1. Method for operating an adjustment drive (13) of an electrically adjustable steering column (10) of a motor vehicle, the steering column comprising an actuator unit (11) with a rotatably mounted steering shaft (12) on which a steering wheel (100) is mounted, wherein the actuator unit (11) is adjusted by at least one adjustment drive (13) to set the longitudinal position and / or the height position of the steering wheel (100), wherein in the method: a) predefining a set value (SW) for regulating the speed of the actuator unit (11); b) based on the set value (SW), driving at least one regulating drive device (13) with a voltage signal via at least one controller; c) detecting an actual value of the adjustment speed of the actuator unit (11) after a predetermined period of time (t1) and comparing it with a set value (SW); and d) according to the comparison result of the set value (SW) and the actual value (IW), the set value (SW) is reduced until the voltage signal for driving the regulating drive (13) is lower than the maximum value of the supply voltage, in particular the maximum value of the on-board electrical system voltage of the motor vehicle.

2. The method according to claim 1, characterized in that If the actual value (IW) is lower than the set value (SW) after a predetermined period of time (t1), the set value (SW) is reduced.

3. The method according to claim 1 or 2, characterized in that: Reduce the setpoint (SW) until the voltage signal at the controller is between 60% and 95% of the maximum supply voltage.

4. A method according to any preceding claim, characterised in that In at least one predetermined time interval (t2), the set value (SW) is gradually reduced after the predetermined time period (t1).

5. A method according to any preceding claim, characterised in that The voltage signal of the controller is measured, and the measured voltage signal is compared with the maximum value of the supply voltage to detect the saturation state of the controller.

6. A method according to any preceding claim, characterised in that The regulating drive (13) is driven by a pulse width modulation controller.

7. A control unit for operating an adjustment drive (13) of an electrically adjustable steering column (10) of a motor vehicle, the steering column comprising an actuator unit (11) with a rotatably mounted steering shaft (12) on which a steering wheel (100) is mounted, wherein the actuator unit (11) is adjusted by at least one adjustment drive (13) to set a longitudinal position and / or a height position of the steering wheel (100), wherein the control unit is designed to predefine a setpoint value (SW) for the adjustment speed of the actuator unit (11); Based on the set value (SW), at least one controller drives at least one regulating drive device (13) with a voltage signal; detecting an actual value (IW) of the adjustment speed of the actuator unit (11) after a predetermined period of time (t1) and comparing it with the set value (SW); and According to the comparison result of the set value (SW) and the actual value (IW), the set value (SW) is reduced until the voltage signal for driving the regulating drive device (13) is lower than the maximum value of the supply voltage.

8. The control unit according to claim 7, characterized in that The control unit is configured or adapted to perform the method according to any one of claims 1 to 6.

9. An electrically adjustable steering column (10) for a motor vehicle, comprising an actuator unit (11) with a rotatably mounted steering shaft (12), on which a steering wheel (100) is mounted, and at least one control unit according to claim 7 or 8, wherein the actuator unit (11) is adjusted by at least one adjustment drive (13) to set the longitudinal position and / or the height position of the steering wheel (100), and the adjustment drive (13) is driven by the control unit.

10. Motor vehicle comprising at least one control unit according to claim 7 or 8 and / or at least one electrically adjustable steering column (10) according to claim 9.

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