Drive unit and rear wheel steering device with the same

Abstract

Drive unit, comprising: a motor shaft, the motor shaft being arranged to rotate; a main gear, the main gear being adapted to rotate coaxially with the motor shaft; a main gear magnet attached to the main gear; a sub-gear, the sub-gear being adapted to rotate together with the main gear; a secondary gear magnet attached to the secondary gear; a main gear rotation detection sensor, wherein the main gear rotation detection sensor is configured to detect a rotation of the main gear based on a change in a magnetic field of the main gear magnet; and a sub-gear rotation detection sensor, wherein the sub-gear rotation detection sensor is configured to detect rotation of the sub-gear based on a change in a magnetic field of the sub-gear magnet.

Description

Background1. Area

[0001] The present disclosure relates to a drive unit and a rear wheel steering device having the same, and more particularly to a drive unit capable of measuring a steering angle of a wheel and a rear wheel steering device having the same. 2. Description of the state of the art

[0002] A rear wheel steering (RWS) system is a type of all wheel steering (AWS) system that can improve vehicle responsiveness and driving safety and reduce a turning circle.

[0003] Typically, the rear wheel steering device of a vehicle includes an electric motor, a screw nut that rotates under the power of the electric motor, and a lead screw that is coupled to the screw nut.

[0004] An external thread is formed on an outer surface of the lead screw, and an internal thread, which meshes with the external thread of the lead screw, is formed on an inner surface of the screw nut. When the screw nut is rotated by the electric motor, the lead screw moves accordingly in a width direction of the vehicle. This action steers the rear wheels of the vehicle.

[0005] The background technology of the present disclosure is disclosed in Korean Patent Publication No. 10-2018-0120447 (published on November 6, 2018, entitled “Rear Wheel Steering Apparatus”). Summary

[0006] Various embodiments of the present disclosure relate to a drive unit capable of measuring a steering angle via a rotation angle of a rotor shaft, and to a rear wheel steering apparatus having the same.

[0007] The drive unit according to the present disclosure may include: a motor shaft, the motor shaft configured to rotate; a main gear, the main gear configured to rotate coaxially with the motor shaft; a main gear magnet attached to the main gear; a sub-gear, the sub-gear configured to rotate together with the main gear; a sub-gear magnet attached to the sub-gear; a main gear rotation detection sensor, the main gear rotation detection sensor configured to detect rotation of the main gear based on a change in a magnetic field of the main gear magnet; and a sub-gear rotation detection sensor, the sub-gear rotation detection sensor configured to detect rotation of the sub-gear based on a change in a magnetic field of the sub-gear magnet.

[0008] A motor axis, which is defined as a first rotation axis of the motor shaft, and a sub-gear axis, which is defined as a second rotation axis of the sub-gear, may be parallel to each other.

[0009] The main gear rotation detection sensor may be arranged on the motor axis.

[0010] The auxiliary gear rotation detection sensor is arranged on the auxiliary gear axis.

[0011] The drive unit may further comprise a motor position sensor, wherein the motor position sensor is configured to detect a rotation angle of the motor shaft by the rotation of the main gear.

[0012] The accuracy of the motor position sensor can be higher than the accuracy of the main gear rotation detection sensor and the accuracy of the sub-gear rotation detection sensor.

[0013] The motor position sensor can reset the rotation angle of the motor shaft when power is supplied to the drive unit.

[0014] The motor position sensor can be arranged on a motor axis, which is the rotation axis of the motor shaft.

[0015] The drive unit may further comprise a circuit board on which the main gear rotation detection sensor, the sub-gear rotation detection sensor and the motor position sensor are mounted.

[0016] The main gear rotation detection sensor and the sub-gear rotation detection sensor may be mounted on a first side of the circuit board facing the main gear and the sub-gear, and the motor position sensor may be mounted on a second side of the circuit board facing away from the first side.

[0017] The drive unit may further comprise a controller configured to calculate a steering angle of a rear wheel when a vehicle starts moving based on a detection signal generated by the main gear rotation detection sensor and a detection signal generated by the sub-gear rotation detection sensor when a power supply to the drive unit is initiated.

[0018] The controller can calculate the steering angle of the rear wheel during operation of the vehicle based on the detection signal generated by the motor position sensor during operation of the vehicle and the steering angle of the rear wheel at the start of operation.

[0019] The power unit may further comprise a motor housing through which the motor shaft passes, and a power unit cover coupled to the motor housing, and the main gear, the main gear magnet, the sub-gear, the sub-gear magnet, the main gear rotation detection sensor, and the sub-gear rotation detection sensor may be housed in an interior space defined by the motor housing and the power unit cover.

[0020] The rear-wheel steering device according to the present disclosure may include: a steering shaft part extending in a width direction of a vehicle, the steering shaft part being configured to move in a width direction of the vehicle to change a rear-wheel steering angle of the vehicle; and a power unit comprising: a rotatable motor shaft, the rotatable motor shaft being configured to provide a force for moving the steering shaft part in the width direction of the vehicle; a main gear, the main gear being configured to rotate coaxially with the rotatable motor shaft; a main gear magnet fixed to the main gear; a sub gear, the sub gear being configured to rotate together with the main gear; a sub gear magnet fixed to the sub gear;a main gear rotation detection sensor, the main gear rotation detection sensor configured to detect rotation of the main gear based on a change in a magnetic field of the main gear magnet; and a sub-gear rotation detection sensor, the sub-gear rotation detection sensor configured to detect rotation of the sub-gear based on a change in a magnetic field of the sub-gear magnet.

[0021] The main gear may be coaxially coupled to a first side of the rotatable motor shaft, and the steering shaft part may be coupled to a second side of the rotatable motor shaft, wherein the steering shaft part may be configured to transmit power.

[0022] The steering shaft section may include a lead screw.

[0023] The rear wheel steering device may further comprise: a screw nut through which the lead screw passes and engages with the lead screw; a motor-side pulley coaxially coupled to the second side of the motor shaft; a nut-side pulley coaxially coupled to the screw nut; and a belt wrapping around the motor-side pulley and the nut-side pulley to enable power transmission.

[0024] According to the present disclosure, a device for measuring the steering angle of a rear wheel is integrated into the drive unit. Accordingly, a sensor for measuring the displacement of the lead screw and a cable connecting the sensor and the drive unit can be removed, making it easier to miniaturize the rear-wheel steering device and reduce the manufacturing cost of the rear-wheel steering device. Brief description of the drawings Fig. 1 is a perspective view showing a rear wheel steering apparatus according to an embodiment of the present disclosure. Fig. 2 is a cross-sectional view along the line AA of Fig. 1. Fig. 3 is an exploded perspective view of a drive unit of Fig. 1. Fig. 4 is an exploded and enlarged perspective view showing a motor shaft, a main gear, a sub-gear and a control board of Fig. 3 represents. Fig. 5 is an exploded perspective view showing a motor shaft, a main gear, a sub-gear and a control board of Fig. 4, with a control board arranged at the rear. Fig. 6 is a side view of a main gear, a sub-gear and a control board of Fig. 4, extracted and illustrated. Fig. 7 is an enlarged plan view showing a main gear and a sub-gear of Fig. 6 illustrates. Detailed description

[0025] A drive unit and a rear-wheel steering device equipped therewith according to an embodiment of the present disclosure will be described in detail below using various exemplary embodiments with reference to the accompanying drawings. The terms described below have been defined with their functions in the present disclosure in mind and may vary depending on the intention or approach of the user or operator. Accordingly, these terms should be interpreted based on the entire content of this description.

[0026] Fig. 1 is a perspective view illustrating a rear wheel steering apparatus according to an embodiment of the present disclosure. Fig. 2 is a cross-sectional view along the line AA of Fig. 1. Fig. 3 is an exploded perspective view showing a power unit of Fig. 1 illustrates. Fig. 4 is an enlarged exploded perspective view showing the motor shaft, the main gear, the sub-gear and the control board of Fig. 3 illustrates. Fig. 5 is an exploded perspective view showing the motor shaft, the main gear, the sub-gear and the control board of Fig. 4, with the control board located at the rear. Fig. 6 is a side view showing the main gear, the sub-gear and the control board of Fig. 4 is illustrated in an exploded view. Fig. 7 is an exploded plan view of the main gear and a sub-gear of Fig. 6.

[0027] With reference to Fig. 1 to Fig. 7, the rear-wheel steering apparatus 10 according to an embodiment of the present disclosure includes a steering shaft part 20 and a power unit 100. The steering shaft part 20 extends in the width direction of a vehicle (not shown). The steering shaft part 20 can move in the width direction of the vehicle to change a steering angle of the rear wheels (not shown) of the vehicle.

[0028] The steering shaft part 20 comprises a lead screw 21, a connecting shaft 24, a first bushing 26 and a second bushing 28. The lead screw 21 extends along an axis SX parallel to a longitudinal direction of the steering shaft part 20. The lead screw 21 may have an external thread pattern formed on its outer surface.

[0029] The connecting shaft 24 extends along the axis SX and is coupled to a first side of the lead screw 21. The first bushing 26 is coupled to a second side of the connecting shaft 24, opposite the first side coupled to the lead screw 21. The second bushing 28 is coupled to the second side of the lead screw 21, opposite the first side coupled to the connecting shaft 24. A rear wheel part, including, for example, rear wheels, a tie rod, a ball joint, etc., can be coupled to the first bushing 26 and the second bushing 28.

[0030] The rear wheel steering device 10 further includes a housing 11, a screw nut 30, a bearing 40, a motor-side pulley 50, a nut-side pulley 60, and a belt 70. The housing 11 accommodates the steering shaft part 20, the screw nut 30, the bearing 40, the motor-side pulley 50, the nut-side pulley 60, and the belt 70 therein.

[0031] The lead screw 21 extends through the screw nut 30. A through hole through which the lead screw 21 extends is arranged on the screw nut 30. An internal thread that meshes with the external thread of the lead screw 21 can be arranged on an inner surface of the through hole of the screw nut 30. The bearing 40 supports the screw nut 30 rotatably with respect to the housing 11.

[0032] The motor-side pulley 50 is rotated by the electric motor 101 of the drive unit 100. The nut-side pulley 60 is tightly fixed to an outer surface of the screw nut 30 so as to be spaced apart from the bearing 40 in a direction of the axis SX. The belt 70 is wound around the motor-side pulley 50 and the nut-side pulley 60 to connect the motor-side pulley 50 and the nut-side pulley 60 to each other to enable power transmission.

[0033] When a motor shaft 140 of the electric motor 101 rotates and the motor-side pulley 50 rotates, the belt 70 is supported by the motor-side pulley 50 and the nut-side pulley 60 to run on an endless track, and the nut-side pulley 60 and the nut 30 rotate around the axis SX. When the nut 30 rotates, the steering shaft part 20 moves in the width direction of the vehicle along the axis SX, and as a result, the rear wheels (not shown) can be steered.

[0034] The rear-wheel steering device according to another embodiment of the present disclosure may comprise a steering shaft part with, for example, a rack instead of the steering shaft part with the lead screw. In this case, the rear-wheel steering device may comprise a pinion coaxially coupled to a motor shaft of the electric motor instead of the screw nut, the motor-side pulley, the nut-side pulley, and the belt.

[0035] The drive unit 100 provides a force to move the steering shaft part 20 in the width direction of the vehicle, i.e., in the direction of the SX axis. The drive unit 100 includes the motor shaft 140, a main gear 150, a main gear magnet 156, a sub-gear 160, a sub-gear magnet 166, a main gear rotation detection sensor 173, and a sub-gear rotation detection sensor 175.

[0036] The motor shaft 140 extends along a motor axis MX parallel to the axis SX of the steering shaft part 20 and rotates about the motor axis MX.

[0037] The drive unit 100 further includes the electric motor 101 and a drive unit cover 190. The electric motor 101 includes a motor housing 102 and a motor shaft 140. The motor housing 102 includes a cylinder part 103 and a base plate part 110. A stator (not shown) may be installed in an interior of the cylinder part 103.

[0038] One side of the cylinder part 103 is open, and the stator can be inserted and installed into the interior through the open side of the cylinder part 103. The bottom plate part 110 can be coupled to the cylinder part 103 to close the open side of the cylinder part 103.

[0039] The motor shaft 140 extends through the motor housing 102. A motor shaft opening 111 is arranged in the base plate part 110 such that a first side of the motor shaft 140 protrudes from the base plate part 110. A second side of the motor shaft 140 protrudes from the cylindrical part 103. In the cylindrical part 103, the stator can surround the motor shaft 140.

[0040] The main gear 150 may be coaxially coupled to one end 143 of the motor shaft 140, which protrudes from the base plate part 110. The motor-side pulley 50 may be coaxially coupled to the other end 141 of the motor shaft 140, which protrudes from the cylinder part 103.

[0041] Accordingly, the steering shaft part 20 can be connected to the other end 141 of the motor shaft 140 to transmit power. When the motor shaft 140 rotates about the motor axis MX, the steering shaft part 20 moves in the width direction of the vehicle along the axis SX, and the rear wheels can be steered left or right by tilting.

[0042] The drive unit cover 190 is coupled to the engine housing 102. The engine housing 102 further includes a connecting flange 130 on an outer periphery of the cylinder part 103, so that the drive unit cover 190 is coupled to the engine housing 102. An interior space isolated from the outside world can be formed by the bottom plate part 110 of the engine housing 102 and the drive unit cover 190.

[0043] The main gear 150 rotates coaxially with the motor shaft 140. The main gear 150 includes a circular main gear body 151 coupled and fixed to one end 143 of the motor shaft 140, and a plurality of gear teeth 154 provided on an outer surface of the main gear body 151.

[0044] The main gear magnet 156 is mounted and secured to the main gear 150. For example, the main gear magnet 156 can be mounted and secured in a magnet mounting groove formed on the main gear body 151. The main gear magnet 156 can be arranged, for example, on the motor axis MX. The main gear magnet 156 can be a permanent magnet. The main gear magnet 156 has a halved north pole region 157 and a south pole region 158.

[0045] The sub-gear 160 rotates together with the main gear 150. The sub-gear 160 may, for example, be rotatably coupled to the base plate part 110. A sub-gear axis SG, the rotational axis of the sub-gear 160, is parallel to the motor shaft 140 and the motor axis MX, which is the rotational axis of the main gear 150.

[0046] The sub-gear 160 includes a column 163 rotatably coupled to a sub-gear coupling part 115 of the bottom plate part 110, a circular sub-gear body 161 coupled and fixed to the column 163, and a plurality of gear teeth 164 provided on an outer surface of the sub-gear body 161.

[0047] The gear teeth 164 of the sub-gear 160 mesh with the gear teeth 154 of the main gear 150, allowing the sub-gear 160 to rotate along with the rotation of the main gear 150. A diameter of the sub-gear 160 may be smaller than a diameter of the main gear 150. However, in another embodiment of the present disclosure, the diameter of the sub-gear 160 may be greater than or equal to the diameter of the main gear 150.

[0048] The number of gear teeth 154 of the main gear 150 and the number of gear teeth 164 of the sub-gear 160 may be the same or different. Accordingly, the rotational ratios of the main gear 150 and the sub-gear 160 may be different. According to the embodiment illustrated in the drawings, the number of gear teeth 154 of the main gear 150 may be greater than the number of gear teeth 164 of the sub-gear 160.

[0049] The sub-gear magnet 166 is mounted and secured to the sub-gear 150. For example, the sub-gear magnet 166 is mounted and secured in a magnet mounting groove formed on the sub-gear body 161. The sub-gear magnet 166 can be arranged, for example, on the sub-gear axis line SG. The sub-gear magnet 166 can be a permanent magnet. The sub-gear magnet 166 has a bisected north pole region 167 and a south pole region 168.

[0050] The main gear rotation detection sensor 173 detects the rotation of the main gear 150 based on a change in the magnetic field of the main gear magnet 156. The sub-gear rotation detection sensor 175 detects the rotation of the sub-gear 166 based on a change in the magnetic field of the sub-gear magnet 166. The main gear rotation detection sensor 173 may be arranged on the motor axis MX, and the sub-gear rotation detection sensor 175 may be arranged on the sub-gear axis SG.

[0051] The drive unit 100 further includes a control board 170, a power board 180, terminals 183 and 184, and a heat sink 186. The main gear 150, the main gear magnet 156, the sub-gear 160, the sub-gear magnet 166, the main gear rotation detection sensor 173, the sub-gear rotation detection sensor 175, the control board 170, the power board 180, the terminals 183 and 184, and the heat sink 186 may be accommodated in an interior space defined by the bottom plate portion 110 of the motor housing 102 and the drive unit cover 190.

[0052] The control board 170 may include a circuit that generates a control signal for controlling the operation of the electric motor 101. The power board 180 may include a circuit that supplies drive power to the electric motor 101. A connector that supplies drive power to the electric motor 101 may be mounted on the power board 180. The heat sink 186 is disposed between the power board 180 and the control board 170. The heat sink 186 may promote heat dissipation from the power board 180.

[0053] With reference to Fig. 7, an example of a method for measuring the steering angle of a rear wheel is explained below. When a reference point 155 defined on the outer surface of the main gear 150 and a reference point 165 defined on the outer surface of the sub-gear 160 are in contact, that is, when the reference point 155 of the main gear 150 is located at a position 155(0) and the reference point 165 of the sub-gear 160 is located at a position 165(0), the steering angle of the rear wheel with respect to the longitudinal direction of the vehicle can be 0°.

[0054] Since in the Fig.7, the number of gear teeth 154 of the main gear 150 and the number of gear teeth 164 of the sub-gear 160 are different, when the steering angle of the rear wheel rotates due to the rotation of the motor shaft 140, the reference point 155 of the main gear 150 may rotate counterclockwise with respect to the motor axis MX by a first angle AN1 and move to a position “155(1)”, and the reference point 165 of the sub-gear 160 may rotate clockwise with respect to the sub-gear axis SG by a second angle AN2 and move to the position “165(1)”.

[0055] The steering angle of the rear wheel can be determined by the relationship between the first angle AN1 and the second angle AN2. For example, the steering angle of the rear wheel can be increased as the value obtained by subtracting the first angle AN1 from the second angle AN2 increases.

[0056] In this way, when the rear wheel steering angle is measured, the rear wheel steering angle at the time of starting the vehicle's travel, that is, at the time of starting the vehicle's operation, can be calculated. In other words, when a vehicle power switch is pressed while the rear wheel steering angle is not set to 0° to stop the vehicle's operation, and the power switch is pressed again to resume operation, the rear wheel steering angle at the time of the vehicle's operation can be measured and displayed to the driver, thereby assisting a driver in safe driving.

[0057] The drive unit 100 further includes a controller 195. This controller calculates the steering angle of the rear wheel at the start of a vehicle's travel based on a detection signal generated by the main gear rotation detection sensor 173 and a detection signal generated by the sub-gear rotation detection sensor 175 when power is applied to the drive unit 100. The controller 195 can be integrated into the vehicle's electronic control unit (ECU). Alternatively, it can also be included in the control board 170.

[0058] The drive unit 100 further includes a motor position sensor 171 that detects the rotation angle of the motor shaft 140 through the rotation of the main gear 150. The motor position sensor 171 can be arranged on the motor axis MX.

[0059] The main gear rotation detection sensor 173, the sub-gear rotation detection sensor 175, and the motor position sensor 171 are mounted on the control board 170. The main gear rotation detection sensor 173 and the sub-gear rotation detection sensor 175 are mounted on a first side of the control board 170 facing the main gear 150 and the sub-gear 160.

[0060] The motor position sensor 171 is mounted on the first side of the control board 170, which faces away from a second side of the control board 170. More specifically, the main gear rotation detection sensor 173 and the motor position sensor 171 are arranged opposite each other on the motor axis MX, with the control board 170 located therebetween.

[0061] Each of the main gear rotation detection sensor 173, the sub-gear rotation detection sensor 175, and the motor position sensor 171 may be a Hall sensor, for example. The resolution of the motor position sensor 171 may be higher than the resolution of the main gear rotation detection sensor 173 and the resolution of the sub-gear rotation detection sensor 175. Accordingly, the detection accuracy of the motor position sensor 171 may be higher than the accuracy of the main gear rotation detection sensor 173 and the accuracy of the sub-gear rotation detection sensor 175. Furthermore, the detection speed of the motor position sensor 171 may be higher than the detection speed of the main gear rotation detection sensor 173 and the detection speed of the sub-gear rotation detection sensor 175.

[0062] The motor position sensor 171 can reset the rotation angle of the motor shaft 140 when the power supply to the drive unit 100 is initiated. In other words, the change in the steering angle of the rear wheel after the power supply is initiated can be detected in real time by the detection signal of the motor position sensor 171, but the steering angle of the rear wheel cannot be detected at the detection time.

[0063] The controller 195 calculates the steering angle of the rear wheels during vehicle operation based on the detection signal generated by the motor position sensor 171 during vehicle operation and the steering angle of the rear wheels at the time of operation start. In other words, the controller 195 calculates the steering angle of the rear wheels during vehicle operation in real time by adding the steering angle of the rear wheels at vehicle start, detected by the detection signal of the main gear rotation detection sensor 173 and the detection signal of the sub-gear rotation detection sensor 175, and the steering angle change detected by the detection signal of the motor position sensor 171 during vehicle operation.

[0064] Although exemplary embodiments of the disclosure have been presented for illustrative purposes, it will be apparent to those skilled in the art that various modifications, additions, and substitutions are possible without departing from the scope and spirit of the disclosure as defined in the appended claims. Therefore, the true technical scope of the disclosure is defined by the following claims. QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] KR 10-2018-0120447

[0005]

Claims

[1] Drive unit, comprising: a motor shaft, the motor shaft being arranged to rotate; a main gear, the main gear being adapted to rotate coaxially with the motor shaft; a main gear magnet attached to the main gear; a sub-gear, the sub-gear being adapted to rotate together with the main gear; a secondary gear magnet attached to the secondary gear; a main gear rotation detection sensor, wherein the main gear rotation detection sensor is configured to detect a rotation of the main gear based on a change in a magnetic field of the main gear magnet; and a sub-gear rotation detection sensor, wherein the sub-gear rotation detection sensor is configured to detect rotation of the sub-gear based on a change in a magnetic field of the sub-gear magnet. [2] The drive unit according to claim 1, wherein a motor axis defined as a first rotational axis of the motor shaft and a sub-gear axis defined as a second rotational axis of the sub-gear are parallel to each other. [3] A power unit according to claim 2, wherein the main gear rotation detection sensor is arranged on the motor axis. [4] A power unit according to claim 2 or 3, wherein the sub-gear rotation detecting sensor is arranged on the sub-gear axis. [5] Drive unit according to one of claims 1 to 4, further comprising: a motor position sensor, wherein the motor position sensor is configured to detect a rotation angle of the motor shaft by the rotation of the main gear. [6] The power unit according to claim 5, further comprising a circuit board on which the main gear rotation detection sensor, the sub-gear rotation detection sensor and the motor position sensor are mounted. [7] Drive unit according to claim 6, wherein the main gear rotation detection sensor and the sub-gear rotation detection sensor are mounted on a first side of the circuit board facing the main gear and the sub-gear, and wherein the motor position sensor is mounted on a second side of the circuit board facing away from the first side. [8] Drive unit according to one of claims 5 to 7, further comprising: a controller, the controller being configured to calculate a steering angle of a rear wheel when starting a vehicle based on a detection signal generated by the main gear rotation detection sensor and a detection signal generated by the sub-gear rotation detection sensor when a power supply to the drive unit is initiated. [9] Rear wheel steering device, comprising: a steering shaft part extending in a width direction of a vehicle, the steering shaft part being adapted to move in a width direction of the vehicle to change a rear wheel steering angle of the vehicle; and a drive unit comprising: a rotatable motor shaft, the rotatable motor shaft being configured to provide a force for moving the steering shaft part in the width direction of the vehicle; a main gear, the main gear being adapted to rotate coaxially with the rotatable motor shaft; a main gear magnet attached to the main gear; a sub-gear, the sub-gear being adapted to rotate together with the main gear; a secondary gear magnet attached to the secondary gear; a main gear rotation detection sensor, wherein the main gear rotation detection sensor is configured to detect a rotation of the main gear based on a change in a magnetic field of the main gear magnet; and a sub-gear rotation detection sensor, wherein the sub-gear rotation detection sensor is configured to detect rotation of the sub-gear based on a change in a magnetic field of the sub-gear magnet. [10] The rear wheel steering device according to claim 9, wherein the main gear is coaxially coupled to a first side of the rotatable motor shaft, and wherein the steering shaft part is coupled to a second side of the rotatable motor shaft, the steering shaft part being adapted to transmit power.

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