Linear gear arrangement and motor vehicle with linear gear arrangement

Abstract

The present invention relates to a linear drive assembly with a threaded spindle (01) and a spindle nut (02) arranged coaxially thereto, which is movable along the threaded spindle (01). The linear drive assembly further comprises a first motor (03) with a first belt (05) running around a first drive wheel (04), and a second motor (06) with a second belt (08) running around a second drive wheel (07). The two belts (05, 08) wrap around the spindle nut (02) and are axially adjacent to each other against the spindle nut (02). A separating element (09) is arranged in a radially extending plane located axially between the belts (05, 08). The separating element (09) extends radially at least far enough to shield the sections of the two belts (05, 08) from each other. The separating element (09) extends coaxially around the spindle nut (02).An angle sensor (12) is arranged on the separating element (09), wherein the angle sensor (12) interacts with a target (13) arranged on the spindle nut (02) to detect the angular position of the spindle nut (02).

Description

[0001] The present invention relates to a linear drive arrangement. The invention further relates to a motor vehicle with this linear drive arrangement, in particular for use in a steering device, also known as a "steer-by-wire" system.

[0002] Various steering devices for motor vehicles are known. For example, steering devices can have a drive with one or two motors and / or one or two belts that transmit a steering force to a steering linkage.

[0003] From EP 3 782 875 A1, for example, a steering device with two motors, two ball nuts on each ball screw part and with each belt is known.

[0004] To replace a mechanical steering column, steer-by-wire (SbW) systems are used. Steer-by-wire systems typically include a front axle steering module, the Road Wheel Actuator (RWA), and a steering actuator, the Hand Wheel Actuator (HWA). The steering angle is determined by the steering wheel, which is controlled by the driver. Based on this, the steering is actuated by the Road Wheel Actuator. These components require fail-safe operation.

[0005] In known steer-by-wire systems, which, for example, have two redundant linear drives (e.g., dual-pinion), a fault can cause the entire drive to either lock up or become stiff. This prevents the redundant drive from functioning correctly, as it is supposed to "take over" in the event of a failure. In alternative steer-by-wire systems, which, for example, only have one belt, the drive or the belt opens, meaning that this design also does not offer complete fail-safe operation.

[0006] In dual-winding motor configurations, where two three-phase windings are applied to a single stator, rotor, and housing, the winding systems can negatively affect each other in the event of a fault. Electronic malfunctions, such as those caused by heat or fire, can also destroy electronic components within the same housing, leading to system failure.

[0007] German patent application DE 10 2022 200 037 A1 describes a linear steering system for a motor vehicle comprising a first and a second drive unit. The first drive unit is connected to an output rod by a first ball screw drive; in particular, a first electric motor is connected to a first steering control unit. The second drive unit is connected to the output rod by a second ball screw drive; in particular, a second electric motor is connected to a second steering control unit. The first and second ball screw drives are configured to drive and support the output rod.

[0008] From US Patent 2024 / 0227921 A9, a steering device for a vehicle is known, comprising a threaded spindle with two opposing ends connected to wheels. The spindle is axially movable within a housing. The steering device further includes a ball nut that engages with the threaded spindle. A first and a second pulley are coupled to the ball nut. The steering device also includes a first motor for applying torque to the ball nut via the first pulley and a second motor for exerting torque on the ball nut via the second pulley. The centrally located ball nut drive requires two bearing elements at the ends of the wheel actuator.

[0009] From DE 10 2022 212 649 A1, a steering drive for a motor vehicle is known, which includes an electric motor. The motor is operatively connected to an actuator element via a belt drive. The belt drive comprises a drive wheel and a driven wheel around which a belt runs. Furthermore, the steering drive includes a monitoring device for recording the operating parameters of the belt drive. A plurality of belts can be arranged in parallel for the drive, with at least one guide element arranged between the belts.

[0010] In such belt drives, the drive wheel and driven wheel can be jointly referred to as belt wheels or pulleys.

[0011] One object of the present invention, starting from the prior art, is to provide an improved, compact and fail-safe linear drive arrangement that can be used primarily in steering systems, especially steer-by-wire systems. Furthermore, a motor vehicle equipped with such a linear drive arrangement is to be provided.

[0012] The aforementioned problem is solved by a linear gear arrangement according to the attached claim 1 and by a motor vehicle with a linear gear arrangement according to the attached dependent claim 10.

[0013] The linear drive assembly according to the invention comprises a threaded spindle and a spindle nut arranged coaxially thereto, which together form the linear drive. As is known, a threaded spindle is a machine element that, together with other elements, converts a rotary motion into a translational motion. The threaded spindle is also referred to as a steering rod. The spindle nut is axially movable along the threaded spindle during relative rotation around the threaded spindle. Furthermore, the linear drive assembly comprises a first motor with a first belt running around a first drive wheel and a second motor with a second belt running around a second drive wheel. As is known, such belts have sections that run between a drive wheel and an output wheel, or vice versa. The two belts also encircle the spindle nut, which serves as the output wheel.The two belts are arranged axially adjacent to each other on the spindle nut. The linear drive assembly further comprises a separating element located axially between the two belts, which advantageously serves to protect one belt against a malfunction of the other belt, such as tearing or jumping off. The separating element is arranged in a radially extending plane. The radial extent of the separating element corresponds to the extent of the belt sections, so that the belt sections are axially shielded from each other by the separating element. Furthermore, the separating element is arranged coaxially around the spindle nut, so that the spindle nut is completely or at least partially surrounded radially by the separating element. An angle sensor, particularly and advantageously for determining the angular position of the spindle nut, is also attached to the separating element, wherein the angle sensor interacts with a target arranged on the spindle nut.

[0014] The linear gear arrangement according to the invention has the advantage that, through the use of the separating element and the angle sensor arranged thereon with the target located on the spindle nut, a space-neutral measurement setup for the continuous monitoring of the gear arrangement is enabled. A further advantage of the present linear gear arrangement is that it provides a high degree of reliability (fail-functionality), i.e., a solution for correcting malfunctions or for reliably responding to malfunctions. With this linear gear arrangement, functionality can be maintained in the event of a failure of a linear gear or a component of one of the two linear gears (e.g., one of the two motors or one of the two belts), since the angular position of the spindle nut and thus the absolute position can be unambiguously determined.Furthermore, the arrangement with two linear drives and a sensor assembly allows the redundant linear drive to open the malfunctioning drive in the event of a failure, thus enabling the other linear drive to continue operating smoothly and without interruption. Suitable gear or coupling elements for this purpose are known and can be selected by those skilled in the art. The present invention allows for their precise control, as a malfunction is always reliably detected. Therefore, the present linear drive arrangement advantageously exhibits high robustness against motor, control, and electronic defects. The arrangement of the angle sensor on or attached to the separating element and the opposing target on the spindle nut advantageously ensures high measurement accuracy.

[0015] The measurement accuracy results from the design of the linear gear arrangement and the applicable measurement method, which is briefly explained below.

[0016] The diameters of the two drive wheels (also called pulleys) are preferably identical. Alternatively, the drive wheels have different diameters. The diameters of the two drive wheels preferably result in gear ratios of 2 to 4, and particularly preferably 3. In one embodiment, the diameters are selected such that different gear ratios result, enabling unambiguous multi-turn angle measurement of the spindle nut using the vernier principle (vernier effect). With different drive wheel diameters, the number of pinions applicable to the vernier principle varies. The absolute spindle nut position is determined using the vernier algorithm. The vernier principle is known to those skilled in the art and is used, among other things, in...in EP 3 733 483 A1 discussed a steering device with two motors and a signal acquisition device with two rotation angle sensors for determining an absolute position of a steered shaft.

[0017] Preferably, the spindle nut used in the linear drive is a ball screw nut. The spindle nut is preferably made of metal. Alternatively, the spindle nut can be made of plastic. In a preferred embodiment, a plastic element is arranged between the metallic spindle nut and the belts, wherein the plastic element has axially extending grooves on its radial outer surface into which the belt ribs can engage.

[0018] The linear drives can preferably be a ball screw drive, a trapezoidal screw drive or a planetary roller drive.

[0019] The spindle nut preferably has a rib on its outer surface, i.e., its circumferential surface. The rib can also be referred to as a center board or stop. The rib extends radially outwards from the outer surface of the spindle nut and forms a projection located axially between the two belts, particularly between the two bearing surfaces of the belts, on the spindle nut. The target is preferably arranged on the rib. Preferably, a radially extending shoulder is formed on the rib, to which the target is preferably axially and directly attached. Alternatively, the rib can have several projections or cams around its circumference, which serve as the target.

[0020] The target is preferably made of a metal. Preferably, the target has a ring shape; in particular, the target is a metal ring arranged coaxially to the spindle nut. In one embodiment, the target is a metal ring with wings. Alternatively, the target can be a ring with several circumferential recesses, the recesses preferably being arranged radially outwards.

[0021] The separating element is preferably located radially indirect to the web of the spindle nut. The separating element is preferably a separating disc, which can also be referred to as a separator. In one embodiment, the separating element projects radially beyond the belt sections. Preferably, the separating element has recesses in the area of ​​the drive wheels, in particular at least partially circular recesses, through which a motor shaft and / or a drive wheel can protrude.

[0022] Preferably, the separating element consists of a metal, a metal-coated plastic, or several layered materials. Particularly preferred is a sensor board that simultaneously serves as protection and as a carrier for the angle sensor element, the angle sensor element being integrally formed with the separating element. If the separating element is made of metal, the angle sensor can be arranged on the separating element in the form of a printed circuit board (PCB). Alternatively, the angle sensor, e.g., in the form of a PCB, is integrated into the separating element. Printed circuit boards are known to have conductive traces, which can preferably be configured as antenna and receiver traces for RF (radio frequency) signals. Particularly preferred is the angle sensor, and especially the PCB, having a crescent-shaped structure that extends axially onto the surface of the separating element.

[0023] Thus, the sensor arranged on the separating element preferably operates inductively, interacting with the target located on the spindle nut. Due to the crescent-shaped structure of the angle sensor attached to the separating element and the, for example, wing-shaped structure of the target, the angle sensor and the target overlap to varying degrees depending on the angle of rotation, resulting in a variable signal. The signal is generated by RF reflection at the metallic target, with the reflection intensity representing the angle.

[0024] Alternatively, the sensor arranged on the separating element operates according to the Hall principle, wherein several Hall sensors (Hall sensor chips) are arranged on the separating element, particularly in a crescent-shaped, axially oriented zone, and wherein the target consists of one or more permanent magnets. A signal is generated when the target overlaps with the sensor. The permanent magnets can have the same or different orientations, allowing for additional encoding of the angular position.

[0025] In one embodiment, several sensors are attached to the separating element. These sensors can have the same or different designs and / or operating principles. For example, an additional sensor can be used to determine the angle of one or both drives. This additional sensor then enables multi-turn evaluation (vernier principle) of the spindle nut's rotation angle. Likewise, the additional sensor can serve as a safeguard and provide redundancy for the first sensor. Similarly, the additional sensor can extend a limited angular range of the first sensor (e.g., only 180°) to a full 360° range.

[0026] Preferably, a housing is arranged around the motors. Furthermore, a sealing surface can be provided on the housing. The separating element is preferably detachably connected to the housing. Alternatively, the separating element can be permanently connected to the housing. The two motors are preferably arranged in a single mounting plane, for example, on the housing. Alternatively, the two motors are arranged in mounting planes offset from each other.

[0027] Preferably, the motor axes are parallel to the axis of the threaded spindle. In one embodiment, the distances of the motor axes to the threaded spindle axis are identical. Alternatively, the distances of the motor axes to the threaded spindle axis are different, with the offset between the two motor axes being particularly preferably less than 20%. The selection of the distances between the motor axes and the threaded spindle axis is defined according to the available installation space.

[0028] Since the motors can be arranged parallel to each other, preferably on the same side, with respect to the separating element, the arrangement is advantageously compact and space-neutral.

[0029] It is possible that at least one further linear drive, comprising a motor, a belt and a drive wheel, is located in the linear drive arrangement.

[0030] Furthermore, the linear gear arrangement preferably includes a control unit.

[0031] In a further developed embodiment, at least one anti-rotation device (ARD) can be arranged on the threaded spindle to prevent the free rotation of the spindle nut. The anti-rotation device can be a ball guide, a roller, a sliding piece, or a sliding sleeve.

[0032] Furthermore, the invention relates to a motor vehicle with a linear gear arrangement, according to the linear gear arrangement described above with all its embodiments.

[0033] Further advantages, details, and modifications of the invention will become apparent from the following description of a preferred embodiment, with reference to the drawing. The drawing shows: Fig. 1: a perspective view of a linear gear arrangement according to the invention; Fig. 2: a sectional view of the Fig. 1 linear gear arrangement shown; Fig. 3: a simplified schematic representation of a section of the linear gear arrangement; Fig. 4: Another perspective view of the linear gear arrangement; and Fig. 5: A perspective view of a road wheel actuator with the linear gear arrangement.

[0034] Fig. Figure 1 shows a perspective view of a linear gear arrangement according to the invention, comprising a threaded spindle 01 and a ball screw nut 02 arranged coaxially thereto. The ball screw nut 02 consists of several components. The linear gear arrangement further comprises a first motor 03 with a first belt 05 running around a first drive wheel 04, and a second motor 06 with a second belt 08 running around a second drive wheel 07. The ball screw nut 02 serves as the output wheel for both belts 05 and 08, around which the two belts 05 and 08 run. The first belt 05 and the second belt 08 are arranged axially adjacent to each other, with a separating element 09 positioned between the two belts 05 and 08. The separating element 09 lies axially between the two belts 05 and 08 in a radially extending plane and is arranged such that the sections of the belts 05 and 08 are shielded from each other.

[0035] The arrangement includes redundant components, namely the motors 03 and 06, the drive wheels 04 and 07, and the belts 05 and 08, which serve to ensure the reliability of the linear drive. This reliability is advantageously increased by arranging the separating element 09 between the belts 05 and 08, so that if one of the two belts 05 and 08 slips off or breaks, the failed belt does not impair the function of the still functioning belt.

[0036] Furthermore, the separating element 09 extends coaxially around the ball screw nut 02. The separating element 09 is attached to a housing (not shown) by means of fastening elements 11. On an axially oriented side surface, the separating element 09 has a crescent-shaped angle sensor 12, which is designed, for example, in the form of a printed circuit board. The angle sensor 12 serves to measure the angular position of the ball screw nut 02, and it is connected to a target (13) arranged on the ball screw nut 02. Fig. 3) works together.

[0037] The present linear gear arrangement allows the absolute angular position of the ball screw nut 02 to be determined using the vernier scale principle. For this purpose, the two drive wheels 04, 07 have slightly different diameters, resulting in a gear ratio, preferably approximately 3. This advantageously gives the linear gear arrangement high measuring accuracy and high robustness against motor, control, and electronics defects, thus ensuring reliability.

[0038] Fig. 2 shows a sectional view of the Fig. 1 linear gear arrangement shown, where the motors 03; 06 and the drive wheels 04; 07 are not shown. In Fig. Figure 2 shows that the ball screw nut 02 has a circumferential rib 14. The rib 14 serves as a stop for the two belts 05, 08, but also as a support for the target 13.

[0039] Fig. Figure 3 shows a simplified schematic representation of a section of the linear gear arrangement. First, in Fig. 3 A rotation axis 15 of the threaded spindle 01 is symbolized by a dashed line. The ball screw nut 02, with its radially extending web 14, lies coaxially to the rotation axis 15. The web 14 lies axially between the first belt 05 and the second belt 08. The target 13, which is preferably ring-shaped with wings or cams, is arranged on the web 14. The target 13 is particularly located on a shoulder formed on the web 14. In the illustrated example, the target 13 is metallic, so that, in conjunction with the angle sensor 12, it generates an RF signal upon overlap, from which the angular position of the ball screw nut 02 can be determined. Fig. 3 the angle sensor 12 is integrated in the separating element 09.

[0040] Fig. Figure 4 shows another perspective view of the linear gear arrangement, with the representation initially Fig. 1 is the same, however belts 05 and 08 are not shown. Clearly recognizable in Fig. 4 is the crescent-shaped angle sensor 12 arranged on the separating element 09. Furthermore, the target 13, arranged coaxially to the ball screw nut 02, is shown, which has cams or protrusions radially circumferential.

[0041] Fig.Figure 5 shows a perspective view of a road wheel actuator with the linear gear arrangement. The road wheel actuator shown here is a module for steering the front axle, which is regularly used in steer-by-wire systems. The linear gear arrangement described above is shown enclosed in a housing 16. The position of the steering rod, formed by the threaded spindle 01 described above, and the ball screw nut 02 attached to it, must be very precisely determinable for correct steering, which is achievable with the linear gear arrangement described above. Reference symbol list 01 Threaded spindle 02 Ball screw nut / Spindle nut 03 first engine 04 first drive wheel 05 first belt 06 second engine 07 second drive wheel 08 second belt 09 Separating element 10 - 11 Fastening element 12 Angle sensor 13 Target 14 Bridge 15 Rotation axis 16 cases 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] EP 3 782 875 A1

[0003] DE 10 2022 200 037 A1

[0007] US 2024 / 0227921 A9

[0008] DE 10 2022 212 649 A1

[0009] EP 3 733 483 A1

[0016]

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