STEERING DEVICE FOR A VEHICLE

Abstract

The invention relates to a steering device (1) for a vehicle with a steering actuator (2) with a planetary gear (3) comprising a first planetary gear element, a second planetary gear element and a third planetary gear element from the group consisting of sun gear (7), planet carrier (9) and ring gear (8), and an electric motor (4) with a rotor (5) which is connected or connectable in a rotationally fixed manner to at least one planetary gear element of the planetary gear (3) via at least one coupling device (15), wherein an output shaft (11) connected to a further planetary gear element of the planetary gear (3) is connected or connectable to at least one wheel carrier (14). In order to minimize or avoid phase shifts between the steering wheel and the steering actuator (4) in the simplest possible way, it is provided that in at least a first operating range of the steering device (1) the planetary gear (3) can be driven by the rotor (5) via the first planetary gear element - preferably formed by the sun gear (7) - while the second gear element - preferably formed by the ring gear (8) - is held stationary, and that in at least a second operating range either at least two gear elements can be rigidly connected to each other in order to operate the planetary gear (3) in block rotation, or the planetary gear (3) can be driven by the rotor (5) via the second gear element - preferably formed by the ring gear (8) - while the first gear element is held stationary.

Description

[0001] The invention relates to a steering device for a vehicle, in particular for a steer-by-wire steering system, with a steering actuator with a planetary gear unit comprising a first planetary gear unit, a second planetary gear unit and a third planetary gear unit from the group consisting of sun gear, planet carrier and ring gear, and an electric motor with a rotor which is rotationally fixed to or connectable with at least one planetary gear unit of the planetary gear unit, wherein an output shaft connected to a further planetary gear unit of the planetary gear unit is connected to or connectable with at least one wheel carrier.

[0002] With so-called steer-by-wire technology, driver commands are transmitted entirely via electronic signals to the steering system, eliminating the need for a mechanical connection between the steering wheel and the front axle's steering system or individual wheels. This enables safety and comfort features such as autonomous evasive maneuvers and automated parking in tight spaces.

[0003] Due to the variable steering ratio inherent in steer-by-wire systems and the reduction of the maximum steering wheel angle to <180°, even high-performance steering systems are unable to follow driver inputs at the steering wheel without phase shift. This leads to both a loss of comfort and, in some cases, safety-critical steering maneuvers.

[0004] To meet this requirement, conventional steer-by-wire steering systems typically use very powerful electric motors. However, this has a very negative impact on energy consumption – especially in electric vehicles – and drastically increases the cost of the steering systems.

[0005] CN 106080754 A discloses a steering system with a drive-by-wire steering device and a redundant steering system with two switchable steering actuators, each comprising a steering motor, a clutch, a planetary gear set, and a variable-speed gearbox. The two ends of the clutch are each connected to a motor shaft of the steering motor and a gear shaft of a sun gear in the planetary gearbox. A shift fork and shift sleeves allow an output shaft leading to a steering gearbox to be connected to a ring gear or a planet carrier of the planetary gearbox.

[0006] WO 2005036027 A1 describes a vehicle steering system with a gear ratio changing device and an electric auxiliary drive. The gear ratio changing device includes an auxiliary drive comprising a stator and a rotor, which superimposes the driver's steering inputs via a steering wheel and transmits them to the steering movement of the wheels. The system includes a drive unit driven by the steering wheel, an output element connected to the steered wheels, and at least two planetary gear sets. One of the planetary gear sets is driven by the rotor of an electric motor. The drive torque from the steering wheel is superimposed on the drive torque from the electric motor, and these are combined to be introduced as output torque into the output element. The ratio of the rotational speeds of the drive unit and the output element is adjustable.

[0007] From EP 1985520 A1, another steering device with a variable gear ratio is known, comprising a steering actuation element, a rotary unit for rotating a vehicle wheel, and a unit for changing the gear ratio, which is arranged between the steering actuation element and the rotary unit. The unit for changing the gear ratio includes a differential gear, a motor for controlling the gear ratio, and a motor for assisting the steering torque. The differential gear mechanism has a first internally toothed gear coupled to the steering actuation element, a second internally toothed gear coupled to an input shaft of the rotary unit and arranged coaxially with respect to the first internally toothed gear, at least one internal gear that meshes with both the first and the second internal gear, and an internal gear carrier element that rotatably supports the internal gear.The transmission control motor is connected to the internal gear carrier. The steering torque assist motor is connected to the second internal gear.

[0008] The object of the invention is to minimize, and in particular avoid, the phase shift between the steering wheel and the steering actuator in a steering device for a steer-by-wire steering system in the simplest possible way.

[0009] The problem is solved in a steering device of the type mentioned above by the fact that, in at least a first operating range of the steering device, the planetary gear can be driven by the rotor via the first planetary gear element – ​​preferably formed by the sun gear – while the second gear element – ​​preferably formed by the ring gear – is held stationary, and that in at least a second operating range either at least two gear elements can be rigidly connected to each other in order to operate the planetary gear in block rotation, or the planetary gear can be driven by the rotor via the second gear element – ​​preferably formed by the ring gear – while the first gear element is held stationary.

[0010] Preferably, it is provided that the first transmission element and / or the second transmission element can be blocked by at least one clutch device.

[0011] In particular, it is provided that at least two planetary gear elements can be locked by the at least one coupling device.

[0012] Advantageously, the first operating range of the steering device is assigned to a first speed range of the rotor and the second operating range of the steering device to a second speed range of the rotor.

[0013] According to one embodiment of the invention, the clutch device has at least two switching positions and is designed to connect the second transmission element to a housing of the planetary gear in a rotationally fixed manner in at least one first switching position associated with the first operating range and simultaneously disconnect the rotationally fixed planetary gear elements. Furthermore, the clutch device is designed to connect at least two planetary gear elements to each other in a rotationally fixed manner in at least one second switching position associated with the second operating range of the steering device in order to operate the planetary gear in block rotation and simultaneously disconnect the rotationally fixed connection between the second transmission element and the housing of the planetary gear.

[0014] In a further embodiment of the invention, the clutch device has at least two switching positions and is designed to connect the rotor to the first gear element in a rotationally fixed manner in at least one first switching position associated with the first operating range of the steering device, and simultaneously to disconnect the rotary connection between the rotor and the second gear element and to hold the second gear element in place. Furthermore, the clutch device is designed to connect the rotor to the second gear element in a rotationally fixed manner in at least one second switching position associated with the second operating range of the steering device, and simultaneously to disconnect the rotary connection between the rotor and the first gear element and to hold the first gear element in place.

[0015] According to a simple embodiment of the invention, the output shaft is connected to the second planetary gear element – ​​preferably formed by the planet carrier – in a rotationally fixed manner.

[0016] This makes it possible to avoid a phase shift with low power from the electric motor.

[0017] Advantageously, in an embodiment according to the invention, the coupling device is provided to be switchable depending on the rotational speed.

[0018] In one embodiment of the invention, the coupling device comprises an electromagnetic clutch, preferably one that can be actuated by a control unit depending on the rotor speed. The rotor speed of the electric motor is determined, for example, by means of a speed sensor and supplied to the control unit, which compares the current speed value with a stored limit speed value and actuates the coupling device based on the result of this comparison.

[0019] According to one embodiment of the invention, the rotational speeds of the first speed range are lower than the rotational speeds of the second speed range, wherein preferably the first speed range is separated from the second speed range by a defined threshold value.

[0020] The output shaft can, for example, be connected via at least one steering gear element to exactly one wheel carrier of a steerable wheel of the vehicle. Thus, two steering actuators are used for one steerable axle.

[0021] The problem is further solved by a method for actuating the steering device in that, in at least a first operating range of the steering device, the second gear element is held in place and the planetary gear is driven by the rotor via the first gear element, and that, in at least a second operating range, either at least two gear elements are rigidly connected to each other and the planetary gear is operated in block rotation, or the first gear element is held in place and the planetary gear is driven by the rotor via the second gear element.

[0022] According to the invention, a first operating range is assigned to a first speed range of the rotor and the second operating range of the steering device is assigned to a second speed range of the rotor, wherein preferably the speeds of the first speed range are lower than the speeds of the second speed range.

[0023] Advantageously, in the first operating range of the steering device, the planetary gear is operated with a first speed transmission ratio between the rotor and the output shaft, and in the second operating range of the steering device, the planetary gear is operated with a second speed transmission ratio between the rotor and the output shaft, wherein the first speed transmission ratio is greater than the second speed transmission ratio.

[0024] The invention will be explained in more detail below with reference to the non-restrictive embodiments shown in the figures. These schematically illustrate Fig. 1 a steering device according to the invention in a first embodiment and Fig. 2 a steering device according to the invention in a second embodiment variant.

[0025] The Fig. Figure 1 shows a steering device 1 for a steer-by-wire steering system in a first embodiment of the invention. The steering device 1 comprises a steering actuator 2 with a planetary gear 3 and an electric motor 4 with a rotor 5. The rotor 5 is connected to the planetary gear 3 via an input shaft 6. The planetary gear 3 is designed as a simple negative planetary gear and comprises a first gear element formed by a sun gear 7, a second gear element formed by a ring gear 8, and a third gear element formed by a planet carrier 9 with planet gears 10.

[0026] The output is transmitted via the planet gears 10 and the planet carrier 9 to an output shaft 11 and then directly to a wheel carrier 14 of a steerable wheel of the vehicle (not shown).

[0027] By means of at least one coupling device 15, switching between at least two gear ratios between the rotor 5 and the planet carrier 9 is possible. The coupling device 15 has at least two switching positions, with a first switching position corresponding to a first operating range of the steering device 1 and a second switching position corresponding to a second operating range of the steering device 1. The first operating range is associated with a lower first speed range Δn1 of the rotor 5, and the second operating range with a higher second speed range Δn2 of the rotor 5 of the electric motor 4. The first speed range Δn1 therefore has lower speeds than the second speed range Δn2. The first speed range Δn1 includes speeds n of the rotor 4 below a defined threshold value n. S . Rotational speeds n of rotor 4, which are at least equal to the defined threshold n SThose corresponding to the second speed range Δn2 are assigned to it.

[0028] The clutch device 15 is designed to hold the ring gear 8 of the planetary gear 3 in a first switching position associated with the first operating range of the steering gear 1, i.e., to connect it rotationally fixedly to the housing 16 of the steering device 1 and simultaneously to terminate any block rotation of the planetary gear by breaking a rotationally fixed connection between at least two gear elements. The clutch device 15 can be formed by an integral clutch unit with at least two clutch elements or by separate clutches.

[0029] The in Fig. The clutch device 15 shown in Figure 1 is further designed to firmly connect and thus lock at least two transmission elements – for example, the ring gear 8 and the planet carrier 9 – together in a second switching position associated with the second operating range of the steering gear 1. This allows the planetary gear 3 to be operated in so-called block rotation, in which the speed of the output shaft 11 corresponds to the speed of the rotor 5.

[0030] In the Fig. In the example shown in 1, the clutch device 15 is non-rotatably connected to the ring gear 8 in the first switching position and to the planet carrier 9 in the second switching position. Fig. Figure 1 shows the clutch device 15 in the first switching position in the upper half and the clutch device 15 in the second switching position in the lower half. The switching movement of the clutch device between the two switching positions is indicated by the arrow P.

[0031] The switching of the clutch device 15 occurs particularly depending on the rotational speed of the rotor 5 of the electric motor 4 or the input shaft 6 of the planetary gear set 3. The electric motor 6 thus either drives only the sun gear 7 of the planetary gear set 3 with the ring gear 8 fixed at a first speed ratio i1>1 between rotor 5 and output shaft 11, or all gear elements of the planetary gear set 3 in continuous rotation at a second speed ratio i2=1 between rotor 5 and output shaft 11. The first speed ratio i1 is therefore greater than the second speed ratio i2.

[0032] The coupling device 15 is, for example, designed to be dependent on the rotational speed and can, for example, be mechatronically actuated. For this purpose, the coupling device 15 can be electromagnetically switchable via an actuator indicated by reference numeral 18 and controlled by a control unit 19 depending on the input signal of a speed sensor 20 that detects the rotational speed n of the rotor 5.

[0033] However, it is also conceivable that the clutch device 15 is actuated by a mechanical speed-dependent actuator.

[0034] Thus, the coupling device 15 is used in the low and medium rotational speed range or rotational speed range Δn1 of the rotor 5 - i.e. below the threshold value n S - the ring gear 8 of the planetary gear 3 with the housing 16 and in the high rotational speed range or speed range Δn2 - i.e. when the threshold value n is reached Sor above the threshold n S - connected to the planet carrier 9 in a rotationally fixed manner. This results in a relatively large speed transmission ratio i1 of, for example, 2 to 20 at low rotational speed n of the rotor 5, and a small speed transmission ratio i2=1 between the rotor 5 and the planet carrier 9 or the output shaft 11 at high motor speed n. The first speed transmission ratio i1 is therefore larger than the second speed transmission ratio i2.

[0035] Via the selected gear ratios i1, i2, the ring gear 8 is connected to the housing 16 in the lower and medium rotational speed range or first speed range Δn1, and the ring gear 10 is connected to the planet carrier 9 in the high rotational speed range or second speed range Δn2. Alternatively, the sun gear 7 can also be connected in a rotationally fixed manner to the planet carrier 9, to a planet gear 10 of the planet carrier 9, or to the ring gear 8.

[0036] The selected gear ratios i1, i2 result in a higher output rotational speed range when the rotational speed range of the electric motor 4 is high. This reduces the phase shift between the steering wheel and the steering actuator 2 in steer-by-wire applications.

[0037] The Fig. Figure 2 shows a steering device 1 for a steer-by-wire steering system according to a second embodiment of the invention, with a steering actuator 2 comprising a planetary gear 3 and an electric motor 4 with a rotor 5, which is connected to the planetary gear 3 via an input shaft 6. The planetary gear 3 is again designed as a simple negative planetary gear and comprises a first gear element formed by a sun gear 7, a second gear element formed by a ring gear 8, and a third gear element formed by a planet carrier 9 with planet gears 10.

[0038] The output is transmitted via the planet gears 10 and the planet carrier 9, through an output shaft 11, directly to a wheel carrier 14 of a steerable wheel of the vehicle (not shown). Each wheel is equipped with a steering device 1 and a steering actuator. Therefore, two steering devices 1 are used for a steerable axle with two steerable wheels.

[0039] By means of at least one coupling device 15, switching between two gear ratios between the rotor 5 and the planet carrier 9 is possible. The coupling device 15 has at least two switching positions, with a first switching position corresponding to a first operating range of the steering device 1 and a second switching position corresponding to a second operating range of the steering device 1. The first operating range is associated with a lower first speed range Δn1 of the rotor 5, and the second operating range with a higher second speed range Δn2 of the rotor 5 of the electric motor 4. The first speed range Δn2 is therefore lower than the second speed range Δn2. The first speed range Δn1 includes speeds n of the rotor 4 below a defined threshold value n. S . Rotational speeds n of rotor 4, which are at least equal to the defined threshold n S Those corresponding to the second speed range Δn2 are assigned to it.

[0040] The coupling device 15 is designed to connect the rotor 5 of the electric motor 4 to the first planetary gear element – ​​i.e., the sun gear 7 – in a rotationally fixed manner in the first switching position, and simultaneously to disconnect the rotational connection between the rotor 5 and the second planetary gear element – ​​i.e., the ring gear 8. The coupling device 15 can be formed by an integral coupling unit with at least two coupling elements or by separate couplings.

[0041] The coupling device 15 is further designed to connect the rotor 5 to the second planetary gear element in a rotationally fixed manner in the second switching position and at the same time to disconnect the rotary connection between the rotor 5 and the first planetary gear element - i.e. the sun gear 7.

[0042] The planetary gear element, which is separate from the drive, is held in place by a brake element 17, i.e., connected to the housing 16 of the steering device 1. The brake elements 17 can be integrated into the clutch device 15 or designed separately from it.

[0043] The coupling device 15 thus allows the rotor 5 of the electric motor 4 to be connected to the sun gear 7 in the first switching position or to the ring gear 8 of the planetary gear 3 in a rotationally fixed manner.

[0044] The switching of the coupling device 15 takes place in particular depending on the rotational speed n of the rotor 5 of the electric motor 4 or the input shaft 6 of the planetary gear 3. The electric motor 6 thus drives either the sun gear 7 or the ring gear 10 via the coupling device 15 depending on the rotational speed n of the rotor 4 of the electric motor 4.

[0045] The coupling device 15 is, for example, designed to be dependent on the rotational speed. For this purpose, the coupling device 15 can be designed to be electromagnetically switchable and controlled by a control unit 19 depending on the input signal of a speed sensor 20 that detects the rotational speed of the rotor 5.

[0046] Thus, the coupling device 15 is used in the low and medium rotational speed range or rotational speed range Δn1 of the rotor 5 - i.e. below the threshold value n S - the rotor 5 of the electric motor 4 with the sun gear 7 and in the high rotational speed range or speed range Δn2 - i.e. when the threshold value n is reached S or above the threshold n S- connected to the ring gear 10 in a rotationally fixed manner. This results in a large gear ratio i1 at low motor speed n and a small gear ratio i2 at high motor speed n between the rotor 5 and the planet carrier 9 or the output shaft 11.

[0047] Via the selected gear ratios i1, i2, the sun gear 7 is positively connected to the electric motor 6 in the lower and medium rotational speed range or first speed range Δn1, and the ring gear 10 is positively connected to the electric motor 6 in the high rotational speed range or second speed range Δn2.

[0048] The selected gear ratios i1, i2 result in a higher output rotational speed range when the rotational speed range of the electric motor 4 is high. This reduces the phase shift between the steering wheel and the steering actuator 2 in steer-by-wire applications.

[0049] Instead of or in addition to switching the rotationally fixed connection of the drive between rotor 5 and sun gear 7 to the rotationally fixed connection of the drive between rotor 5 and ring gear 8, in the second speed range Δn2 of the rotor 5 and / or in a defined vehicle speed range Δv below a defined limit value v s At vehicle speed v, the first, second, and third planetary gear elements of the planetary gear set 3 – namely the sun gear 7, the ring gear 8, and the planet carrier 9 – are rigidly connected to one another, and the planetary gear set 3 is operated in continuous rotation – i.e., in direct drive. This results in a gear ratio of i=1 – the motor speed and torque of the electric motor 4 are thus switched through and transmitted directly. This continuous rotation operation is primarily used at low vehicle speeds v. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] CN 106080754 A

[0005] WO 2005036027 A1

[0006] EP 1985520 A1

[0007]

Claims

[1] Steering device (1) for a vehicle, in particular for a steer-by-wire steering system, with a steering actuator (2) with a planetary gear (3) with a first planetary gear element, a second planetary gear element and a third planetary gear element from the group consisting of a sun gear (7), a planet carrier (9) and a ring gear (8), and an electric motor (4) with a rotor (5) which is or can be connected in a rotationally fixed manner to at least one planetary gear element of the planetary gear (3), wherein an output shaft (11) connected to a further planetary gear element of the planetary gear (3) is or can be connected to at least one wheel carrier (14), characterized bythat in at least one first operating range of the steering device (1) the planetary gear (3) can be driven by the rotor (5) via the first planetary gear element - preferably formed by the sun gear (7) - with the second gear element - preferably formed by the ring gear (8) - held fast, and that in at least one second operating range either at least two gear elements can be firmly connected to one another in order to operate the planetary gear (3) in block circulation, or the planetary gear (3) can be driven by the rotor (5) via the second gear element - preferably formed by the ring gear (8) - with the first gear element held fast. [2] Steering device (1) according to claim 1, characterized by that the first transmission element and / or the second transmission element can be blocked by at least one coupling device (15). [3] Steering device (1) according to claim 1 or 2, characterized bythat at least two transmission elements can be blocked by the at least one coupling device (15). [4] Steering device (1) according to one of claims 1 to 3, characterized by that the first operating range of the steering device (1) is assigned to a first speed range (Δn1) of the rotor (5) and the second operating range of the steering device (1) is assigned to a second speed range (Δn2) of the rotor (5). [5] Steering device (1) according to one of claims 2 to 4, characterized by that the coupling device (15) has at least two switching positions and is designed to connect the second gear element to a housing (16) of the planetary gear (5) in a rotationally fixed manner in at least one first switching position assigned to the first operating range and at the same time to separate the planetary gear elements which are connected to one another in a rotationally fixed manner. [6] Steering device (1) according to claim 5, characterized byin that the coupling device (15) is designed to connect at least two planetary gear elements to one another in a rotationally fixed manner in at least one second switching position assigned to the second operating range of the steering device (1) in order to operate the planetary gear (3) in block circulation, and at the same time to separate the rotationally fixed connection between the second gear element and the housing (16) of the planetary gear (5). [7] Steering device (1) according to one of claims 2 to 4, characterized by that the coupling device (15) has at least two switching positions and is designed to connect the rotor (5) to the first transmission element in a rotationally fixed manner in at least one first switching position assigned to the first operating range of the steering device (1) and at the same time to separate the rotary connection between the rotor (5) and the second transmission element and to hold the second transmission element. [8] Steering device (1) according to claim 7, characterized by that the coupling device (15) is designed to connect the rotor (5) to the second transmission element in a rotationally fixed manner in at least one second switching position assigned to the second operating range of the steering device (1) and at the same time to separate the rotary connection between the rotor (5) and the first transmission element and to hold the first transmission element. [9] Steering device (1) according to one of claims 1 to 8, characterized by that the output shaft (11) is connected in a rotationally fixed manner to the second planetary gear element, preferably formed by the planet carrier. [10] Steering device (1) according to one of claims 1 to 9, characterized by that the coupling device (15) can be actuated depending on the rotational speed. [11] Steering device (1) according to one of claims 1 to 10, characterized bythat the clutch device (15) has at least one electromagnetic clutch, wherein the electromagnetic clutch can preferably be actuated by a control unit as a function of the speed of the rotor (5). [12] Steering device (1) according to one of claims 4 to 11, characterized by that the speeds of the first speed range (Δn1) are lower than the speeds of the second speed range (Δn2), wherein preferably the first speed range (Δn1) is limited by a defined threshold value (n s ) is separated from the second speed range (Δn2). [13] Steering device (1) according to one of claims 1 to 12, characterized by that the output shaft is connected to at least one wheel carrier (14) - preferably to exactly one single wheel carrier (14) of a steerable wheel - of the vehicle. [14] Method for actuating a steering device (1) according to one of claims 1 to 13, characterized bythat in at least one first operating range of the steering device (1) the second gear element is held and the planetary gear is driven by the rotor via the first gear element, and that in at least one second operating range either at least two gear elements are firmly connected to one another and the planetary gear (3) is operated in block circulation, or the first gear element is held and the planetary gear is driven by the rotor via the second gear element. [15] Method according to claim 14, characterized by that the first operating range of the steering device (1) is assigned to a first speed range (Δn1) of the rotor (5) and the second operating range of the steering device (1) is assigned to a second speed range (Δn2) of the rotor (5), wherein preferably the speeds of the first speed range (Δn1) are lower than the speeds of the second speed range (Δn2). [16] Method according to claim 14 or 15, characterized by in that in the first operating range of the steering device (1) the planetary gear (3) is operated with a first speed transmission ratio (i1) between the rotor (5) and the output shaft (11) and in the second operating range of the steering device (1) the planetary gear (3) is operated with a second speed transmission ratio (i2) between the rotor (5) and the output shaft (11), wherein the first speed transmission ratio (i1) is greater than the second speed transmission ratio (i2).

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