Safety device for a steer-by-wire system

Abstract

Safety device for a steer-by-wire system, comprising: a first rotating plate (215) formed at an end portion of an input shaft (221) or output shaft (201) which are separated from each other, the first rotating plate (215) having a through hole (301, 401) located at a position remote from its center and being provided with a first position detecting sensor (303); a second rotatable plate (223) formed at an end portion of the other of the input shaft (221) or output shaft (201) opposite to the first rotatable plate (215), wherein the second rotatable plate (223) has an actuating element (225) coupled thereto and is provided with a second position detecting sensor (307) that interacts with the first position detecting sensor (303), and the actuating element (225) comprises a force receiving part (305) that is inserted into or withdrawn from the through hole (301, 401); and a control unit (213) receiving a signal for a relative rotation angle between the first and second rotatable plates (215, 223) from the first and second position detecting sensors (303, 307) and controlling the actuating member (225) such that the force receiving part (305) is pulled out of the through hole (301, 401) when the steer-by-wire system is operating normally and the force receiving part (305) is engaged in the through hole (301, 401) when the steer-by-wire system is operating incorrectly.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The present invention relates to a safety device for a steer-by-wire system, and more particularly to a safety device for a steer-by-wire system that can ensure the safety of a steer-by-wire system by using a simple and compact structure and can be manufactured at a low cost. 2. Description of the state of the art

[0002] A steer-by-wire (SBW) system refers to a device that controls steering using hydraulic pressure or electrical power only through an electrical signal instead of a mechanical structure connecting the rotation of a steering wheel and the rotation of the wheels.

[0003] The steering angle sensor generally comprises a steering angle sensor on its steering input side and a steering output sensor and a steering actuator on its steering output side. The steering angle sensor detects the steering angle, the steering output sensor detects the rotation angle of a wheel, and the steering actuator generates auxiliary power to rotate the wheel.

[0004] When a driver turns a steering wheel, the steering angle sensor detects the number of revolutions of the steering wheel to transmit it to an electronic control unit (ECU), and the ECU controls the steering actuator, which can turn the wheel to produce a steering output.

[0005] However, in the SBW system, fatal errors may be caused by a non-steerable condition in which an electrical signal is not delivered due to a short circuit or a fault in the contacting of a wire on the signal path through which steering is detected and transmitted to the actuator, and thus a driver's steering intention is not correctly transmitted to the wheel, or in which the steering actuator or the electronic control unit fails and malfunctions.

[0006] A clutch-driven safety device for a steer-by-wire system is described as an example embodiment of a safety device for preventing such problems from occurring.

[0007] Fig. 1 is a clutch-driven safety device for a steer-by-wire system according to the prior art.

[0008] As in Fig. 1, the prior art clutch-driven safety device for a steer-by-wire system includes a first column shaft 102, a second column shaft 104, an electromagnetic winding 106, an armature 108, an output hub 110, an armature hub 112, and a disc spring 114.

[0009] The armature hub 112 is fixed to the first column shaft 102, which is connected to a steering wheel (not shown), and the disc spring 114 is connected to the armature hub 112.

[0010] The armature 108 is attached to the disc spring 114.

[0011] The output-side hub 110 is connected to the second column shaft 104 and is encompassed by the electromagnetic winding.

[0012] When the steer-by-wire system is operating normally, the first and second column shafts 102, 104 are mechanically separated from each other. Therefore, a driver's steering force transmitted to the first column shaft 102 is not mechanically transmitted to the second column shaft 104. However, if a fault occurs in the steer-by-wire system, a current is applied to the electromagnetic coil 106, generating a magnetic field. The magnetic field attracts the armature 108 against the restoring force of the disc spring 114, bringing the armature 108 into contact with the output-side hub 110.

[0013] When the armature 108 is brought into contact with the output-side hub 110, the first and second column shafts 102, 104 are mechanically connected to each other and the driver's steering force is transmitted to the wheels, thereby avoiding a fatal failure that could be caused by a malfunction of the steer-by-wire system.

[0014] However, the prior art clutch-driven safety device for a steer-by-wire system has a complex structure, and the electromagnetic winding used for the clutch-driven safety device for a steer-by-wire system has limitations in cases where a large driving force is required due to its low driving force, and its high production cost is a disadvantage.

[0015] From DE 603 06 463 T2, a steering control system is known that includes a plate mounted on one side of the motor output shaft and a locking member receiving portion provided with a position sensor. Opposite the plate, an input shaft is coupled to a rotatable motor housing, which is provided with another position sensor. An electromagnet actuates a locking portion of a locking member to engage or withdraw from the locking member receiving portion depending on control signals from a control unit that receives a signal for a relative angle of rotation between the rotatable plate and the rotatable motor housing from the two position sensors. SUMMARY OF THE INVENTION

[0016] The present invention has been conceived to solve such problems of the prior art, and it is an object of the present invention to provide a safety device for a steer-by-wire system which can ensure the operational safety of a steer-by-wire system, using a simple and compact structure and which can be manufactured at low cost.

[0017] The aspect of the invention is not limited thereto, and other aspects of the present invention not mentioned can be clearly appreciated by those skilled in the art from the following description.

[0018] In accordance with one aspect of the present invention, a safety device for a steer-by-wire system comprises: a first rotatable plate formed at an end portion of one of an input shaft and an output shaft that are separated from each other, the first rotatable plate having a through-hole located at a position away from its center and provided with a first position detecting sensor; a second rotatable plate formed at an end portion of the other of the input shaft and output shaft and opposite to the first rotatable plate, the second rotatable plate having an actuating member coupled thereto and being provided with a second position detecting sensor that interacts with the first position detecting sensor, the actuating member including a force receiving part that is inserted into or withdrawn from the through-hole;and a control unit that receives a signal for a relative rotation angle between the first and second rotatable plates from the first and second position detecting sensors and controls the actuator such that the force receiving part is pulled out from the through hole when the steer-by-wire system operates normally and the force receiving part is inserted into the through hole when the steer-by-wire system operates abnormally.;

[0019] As described above, according to the embodiment, it is possible to ensure the safety of a steer-by-wire system while providing a simple and compact structure and to achieve a reduction in manufacturing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings in which: Fig. 1 shows a clutch-driven safety device for a steer-by-wire system according to the prior art. Fig. 2 shows a structure of a steering device with a safety device for a steer-by-wire system according to an embodiment of the invention. Fig. 3 are a partial cross-sectional view and a perspective view of a safety device for a steer-by-wire system according to an embodiment of the invention. Fig. 4 are a partial cross-sectional view and a perspective view of a safety device for a steer-by-wire system according to another embodiment of the invention. Fig. 5 and Fig. 6 are partial cross-sectional views of a safety device for a steer-by-wire system according to embodiments of the invention. Fig. 7 is a partial cross-sectional view showing an operating state of a safety device for a steer-by-wire system according to an embodiment of the invention. DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0021] Some embodiments of the present invention will now be described in detail with reference to the exemplary figures. For the purposes of the following description, it should be noted that when a component is described as being "connected," "coupled," or "affiliated" with or to another component, a third component may be "connected," "coupled," and "affiliated" between the first and second components, although the first component may be directly connected, coupled, or affiliated with the second component.

[0022] Fig. 2 shows a structure of a steering apparatus with a safety device for a steer-by-wire system applied thereto according to an embodiment of the invention. Fig. 3 is a partial cross-sectional view and a perspective view of a safety device for a steer-by-wire system according to an embodiment of the invention, Fig. 4 is a partial cross-sectional view and a perspective view of a safety device for a steer-by-wire system according to another embodiment of the invention, Fig. 5 and Fig. 6 are partial cross-sectional views of a safety device for a steer-by-wire system according to embodiments of the invention, and Fig. 7 is a partial cross-sectional view showing an operating state of a safety device for a steer-by-wire system according to an embodiment of the invention.

[0023] As shown in the figures, a safety device for a steer-by-wire system according to an embodiment of the present invention comprises: a first rotatable plate 215 formed at an end portion of an input shaft 221 or output shaft 201 which are separated from each other, the first rotatable plate 215 having a through hole 301 located at a position away from its center and provided with a first position detecting sensor 303;a second rotatable plate 223 formed at an end portion of the other of the input shaft 221 and the output shaft 201 opposite to the first rotatable plate 215, the second rotatable plate 223 having an actuator 225 coupled thereto and being provided with a second position detecting sensor 307 that interacts with the first position detecting sensor 303, and the actuator 225 including a force receiving part 305 that is inserted into or withdrawn from the through hole 301;and a control unit 213 that receives a signal for a relative rotation angle between the first rotatable plate 215 and the second rotatable plate 223 from the first and second position detecting sensors 303, 307 and controls the actuator 225 such that the force receiving part 305 is pulled out from the through hole 301 when the steer-by-wire system operates normally and the force receiving part 305 is inserted into the through hole 301 when the steer-by-wire system operates incorrectly.

[0024] Although it is explained below by way of example that the first rotatable plate 215 is formed at one end portion of the output shaft 201 and the second rotatable plate 223 is formed at one end portion of the input shaft 221, they may also be arranged in the reverse manner.

[0025] A gear 203 formed on the lower end portion of the output shaft 201 meshes with a rack gear 207 formed on a rack 205. A drive motor 209 is coupled to the rack 205, and the rack 205 is linearly moved left and right by the drive force of the drive motor 209 to steer wheels 211.

[0026] The drive motor 209 receives a control signal from the control unit 213 and generates a driving force for moving the rack 205 to the left and right.

[0027] That is, the control unit 213 receives signals from a first sensor 229 arranged on the input shaft 221, from a sensor 231 arranged on the output shaft 201 and from various other types of sensors and controls the drive motor 209 to satisfy the moving distance of the rack 205 according to the rotation angle of a steering wheel 227.

[0028] The first rotatable plate 215 is coupled to the upper end portion of the output shaft 201 and has the through hole 301 and the first position detecting sensor 303 formed therein.

[0029] Here, the through-hole may be arranged at a position away from the center of the first rotatable plate 215, and the first position detecting sensor 303 may be arranged to be symmetrical to the through-hole 301 with respect to the center of the first rotatable plate 215.

[0030] According to the embodiment of the present invention described in Fig. 3, a plurality of through holes 301 and first position detection sensors 303 are formed along a circumferential direction of the first rotatable plate 215. In this case, as shown in Fig. 4, a plurality of through holes 401 may be formed such that adjacent through holes overlap each other.

[0031] That is, as in Fig. 3, the plurality of through holes 301 may be arranged adjacently so as to be spaced apart from each other in the circumferential direction of the first rotatable plate 215. Alternatively, as shown in Fig. 4, the plurality of through holes 401 may be formed such that the adjacent through holes overlap each other, whereby wide cross sections A and narrow cross sections B may be alternately formed in the circumferential direction, and the upper and lower surfaces of the first rotatable plate may communicate with each other.

[0032] In particular, in cases where the through holes 401 are formed in such a way that the adjacent through holes overlap each other, as in Fig. 4, the gear mechanism 207 formed on the rack 205 may be configured, for example, as a variable speed gear mechanism. Thus, even if an interval exists where the rotation angles of the input and output shafts 221, 201 are different from each other, the power receiving portion 305 of the operating member 225 can be effectively inserted into or withdrawn from the through hole 401 in cases where a failure occurs in the steer-by-wire system, thereby ensuring sufficient steering stability.

[0033] When the power receiving part 305 of the operating member 225 is pulled out of the through-hole 401 due to a failure in the steer-by-wire system, a special case may occur in which the power receiving part 305 is stopped by the narrow cross sections B of the through-holes 401. However, since a predetermined relative rotation angle interval (namely, an angular interval in which the output shaft 201 does not rotate together with the input shaft 221 even if a driver turns the steering wheel 227 by a predetermined angle to rotate the input shaft 221) exists between the input shaft 221 and the output shaft 201, the case in which the power receiving part 305 is stopped by the narrow cross sections B of the through-holes 401 does not occur, so that the safety device for the steer-by-wire system malfunctions.

[0034] That is, even if the aforementioned special situation occurs when the driver slightly turns the steering wheel 227 without realizing it, the force receiving part 305 leaves the narrow cross section B of the through holes 401 and then enters the wide cross section A thereof in the process of rotating the input shaft 221 connected to the steering wheel 227. Therefore, the aforementioned erroneous operation of the safety device for the steer-by-wire system does not occur.

[0035] Referring to the Fig. 3 and Fig. 4, a plurality of first position detecting sensors 403 may be arranged at a distance from each other in the circumferential direction in the first rotatable plate 215 in which the through holes 401 are formed.

[0036] The input shaft 221, which is connected to the steering wheel 227, is rotated together with the steering wheel 227 when the driver turns the steering wheel 227.

[0037] The second rotatable plate 223 is coupled to the lower end portion of the input shaft 221 and is provided with the actuator 225 and the second position detecting sensor 307.

[0038] The actuating element 225 includes the force-receiving part 305, which is inserted into or withdrawn from the through-holes 301 of the first rotatable plate 215. The through-holes 301 have a slightly larger diameter than the force-receiving part 305, so that in an emergency, the force-receiving part can be properly inserted into the through-holes 301. The actuating element 225 can be, for example, a solenoid valve.

[0039] The second position detection sensor 307 is arranged in the second rotatable plate 223 to interact with the first position detection sensor 303 arranged in the first rotatable plate 215. The first position detection sensor 303 and the second position detection sensor 307 may be, for example, a magnetic sensor, and they are arranged opposite each other when the safety device for the steer-by-wire system according to the embodiment of the invention is mounted in a vehicle.

[0040] As in the Fig. 3 and Fig. 4, in cases where a plurality of first position detecting sensors 403 are provided, a plurality of second position detecting sensors 407 are also provided on the second rotatable plate 223 to correspond to the first position detecting sensors.

[0041] As in Fig. 5, the force receiving part 305 may also have a diameter-reduced portion 305a at one end portion, which has a gradually decreasing outer diameter, or, as shown in Fig. As shown in Figure 6, the through-holes 301 may have a diameter-enlarged portion 301a at one end portion, which has a gradually increasing inner diameter and into which the force-absorbing part 305 is inserted. Alternatively, the force-absorbing part 305 may have the diameter-reduced portion 305a, and at the same time, the through-holes 301 may have the diameter-enlarged portion 301a.

[0042] In this way, the force-receiving part 305 has the reduced-diameter portion 305a and / or the through-holes 301 have the enlarged-diameter portion 301a. Thus, when the first and second rotatable plates 215, 223 are not in the correct positions, even if the driver slightly turns the steering wheel 227, the force-receiving part 305 of the operating element can be easily inserted into the through-holes 301.

[0043] When the safety device for the steer-by-wire system according to the embodiment of the present invention is mounted in a vehicle, the first and second position detecting sensors 303, 307 are arranged to oppose each other, and the control device 213 can determine that the first rotatable plate 215 and the second rotatable plate 223 are initially arranged at the correct positions at which the force receiving part 305 of the operating member 225 can be inserted into the through hole 301.

[0044] When the first and second rotatable plates 215, 223 leave a predetermined relative rotation angle range, the control device 213 can also identify the state.

[0045] The control device 213 receives a signal for a relative rotation angle between the first and second rotatable plates 215, 223 from the first and second position detecting sensors 303, 307 and controls the actuator 225 to pull the force receiving part 305 out of the through hole 301 when the steer-by-wire system operates normally (see Fig. 7(a)), and insert the force receiving part 305 into the through hole 301 when the steer-by-wire system malfunctions (see Fig. 7(b)).

[0046] That is, only when the steer-by-wire system malfunctions, the control device 213 controls the actuator 225 such that the force receiving part 305 of the actuator 225 engages the through hole 301 so that the input and output shafts 221, 201 are physically connected to each other, thereby enabling the driver to manually steer the wheels 211 in an emergency (e.g., in the case where a vibration of 0.13 g or more is continuously generated in the steering wheel for 20 ms or more).

[0047] The control device 213 determines whether the steer-by-wire system is operating normally based on signals sent from the first and second sensors 229, 231 for detecting the rotation angle of the input shaft 221 and the output shaft 201, respectively, and the signals sent from other various sensors.

[0048] In addition, a first gear 233 is mounted on the input shaft 221 and meshes with a second gear 237 disposed on the shaft of a motor 235, and the control device 213 controls the motor 235 to give a driver a feeling of general steering while driving a vehicle.

Claims

[1] Safety device for a steer-by-wire system, comprising: a first rotating plate (215) formed at an end portion of an input shaft (221) or output shaft (201) which are separated from each other, the first rotating plate (215) having a through hole (301, 401) located at a position remote from its center and being provided with a first position detecting sensor (303); a second rotatable plate (223) formed at an end portion of the other of the input shaft (221) or output shaft (201) opposite to the first rotatable plate (215), wherein the second rotatable plate (223) has an actuating element (225) coupled thereto and is provided with a second position detecting sensor (307) that interacts with the first position detecting sensor (303), and the actuating element (225) comprises a force receiving part (305) that is inserted into or withdrawn from the through hole (301, 401); and a control unit (213) receiving a signal for a relative rotation angle between the first and second rotatable plates (215, 223) from the first and second position detecting sensors (303, 307) and controlling the actuating member (225) such that the force receiving part (305) is pulled out of the through hole (301, 401) when the steer-by-wire system is operating normally and the force receiving part (305) is engaged in the through hole (301, 401) when the steer-by-wire system is operating incorrectly. [2] A safety device for a steer-by-wire system according to claim 1, wherein the first position detecting sensor (303) is arranged to be symmetrical with respect to the center of the first rotatable plate (215) to the through hole (301, 401). [3] A safety device for a steer-by-wire system according to claim 1 or 2, wherein a plurality of through holes (301, 401) are arranged along the circumferential direction of the first rotatable plate (215). [4] A safety device for a steer-by-wire system according to claim 3, wherein the plurality of through holes (401) are arranged such that adjacent through holes (401) overlap each other. [5] A safety device for a steer-by-wire system according to any one of claims 1 to 4, wherein the first and second position detecting sensors (303, 307) are arranged to oppose each other. [6] A safety device for a steer-by-wire system according to any one of claims 1 to 5, wherein a plurality of first position detecting sensors (303) are arranged to be spaced apart from one another in the circumferential direction of the first rotatable plate (215). [7] A safety device for a steer-by-wire system according to claim 6, wherein a plurality of second position detecting sensors (307) are arranged such that the latter are opposed to the first position detecting sensors (303). [8] A safety device for a steer-by-wire system according to any one of claims 1 to 7, wherein the force receiving part (305) has at its end portion a reduced-diameter portion (305a) having a gradually decreasing outer diameter. [9] A safety device for a steer-by-wire system according to any one of claims 1 to 8, wherein the through-hole (301) has at its end portion a diameter-increasing portion (301a) having a gradually increasing inner diameter into which the force-absorbing part (305) is inserted. [10] A safety device for a steer-by-wire system according to any one of claims 1 to 9, wherein the force receiving part (305) has on its end portion a diameter-reducing portion (305a) having a gradually decreasing outer diameter and the through hole (301) has on its end portion a diameter-increasing portion (301a) having a gradually increasing inner diameter and into which the force receiving part (305) is inserted.

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