JP2009061894A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device with a brushless motor for continuously assisting the steering of a steering wheel without the need for complicated constitution even if a trouble occurs in a motor driving means. <P>SOLUTION: The electric power steering device 1 comprises an emergency control device 25 for driving the brushless motor 21 when a trouble occurs in a control device 3. The emergency control device 25 uses a relay 257 for changing over the phase sequence of a three-phase AC voltage supplied to the brushless motor 21. The brushless motor 21 to which the three-phase AC voltage is supplied with the phase sequence changed over generates reverse torque. Therefore corresponding torque in the steering direction can be generated by a simple constitution. Thus, the device 1 with the brushless motor 21 continuously assists the steering of the steering wheel 4 without the need for a complicated constitution even if a trouble occurs in the control device 3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electric power steering apparatus that assists steering of a steering wheel.

  Conventionally, as an electric power steering device for assisting steering of a steering wheel, for example, an electric power steering device disclosed in Japanese Patent Laid-Open No. 2003-40123 or an electric steering device disclosed in Japanese Patent Laid-Open No. 2003-200840 is available. is there.

  The electric power steering device disclosed in Japanese Patent Application Laid-Open No. 2003-40123 includes a motor drive circuit having two systems of bridge circuits and a brushless DC motor having two systems of coils. Therefore, even if the bridge circuit or coil of any system is damaged, the steering can be continuously assisted by the bridge circuit or coil of the remaining system.

Moreover, the electric steering apparatus disclosed in Japanese Patent Application Laid-Open No. 2003-200840 includes three electric motors that operate in parallel and three control apparatuses that operate in parallel. Therefore, even if one of the electric motors or the control device breaks down, the remaining electric motor or the control device can continuously assist the steering.
JP 2003-40123 A JP 2003-200840 A

  However, in the above-described electric power steering apparatus and electric steering apparatus, one set of originally sufficient bridge circuits and coils, and a plurality of sets of electric motors and control devices must be provided. In addition, a plurality of sets having exactly the same configuration must be provided. In particular, when the motor is a brushless motor, it is difficult to simplify the drive circuit. Therefore, there is a problem that the configuration becomes complicated and the cost increases.

  The present invention has been made in view of such circumstances, and in an electric power steering apparatus provided with a brushless motor, even if the motor driving means fails without complicating the configuration, the steering wheel can be continuously operated. An object is to provide an electric power steering device capable of assisting steering.

Means for Solving the Problems and Effects of the Invention

  Therefore, the present inventor has intensively studied and solved trials and errors in order to solve this problem. As a result, the present inventor has two motor driving means, but the second motor driving means used when the first motor driving means fails. By simplifying the drive system, the inventors have come up with the idea that the steering can be continuously assisted without complicating the configuration, and the present invention has been completed.

  That is, an electric power steering device according to claim 1 is a brushless motor that generates torque for assisting steering of a steering wheel, a rotation angle detection unit that detects a rotation angle of a rotor of the brushless motor, and a brushless motor. Magnetic pole position detection means for detecting the magnetic pole position of the rotor, torque detection means for detecting the steering direction and steering torque of the steering wheel, steering direction and steering torque detected by the torque detection means, and rotor detected by the rotation angle detection means The first motor driving means for driving the brushless motor based on the rotation angle and the first motor driving means, when the first motor driving means fails, instead of the first motor driving means, regardless of the steering torque detected by the torque detecting means, The steering direction detected by the torque detection means and the magnetism of the rotor detected by the magnetic pole position detection means And having a second motor drive means for driving the brushless motor based on the position.

  According to this configuration, when the first motor driving unit fails, the brushless motor can be driven by the second motor driving unit. Therefore, the steering wheel can be continuously assisted. In addition, the first motor driving unit drives the brushless motor based on the steering direction and the steering torque, whereas the second motor driving unit drives the brushless motor based on the steering direction regardless of the steering torque. Further, the first motor driving means drives based on the rotation angle of the rotor, whereas the second motor driving means drives based on the magnetic pole position of the rotor. Therefore, the configuration of the second motor driving unit can be simplified as compared with the first motor driving unit. Therefore, it is possible to continuously assist the steering wheel without complicating the configuration.

  According to a second aspect of the present invention, in the electric power steering device according to the first aspect, the second motor driving unit is configured to detect the torque detection unit based on the magnetic pole position of the rotor detected by the magnetic pole position detection unit. The brushless motor is driven so as to generate torque in the detected steering direction. According to this configuration, torque can be generated in the steering direction. Therefore, even when the first motor driving means fails, the steering feeling is lowered, but the steering wheel can be reliably assisted.

  According to a third aspect of the present invention, in the electric power steering device according to the second aspect, the second motor driving means supplies the brushless motor to generate torque in the steering direction detected by the torque detecting means. It is characterized in that the phase sequence of the AC voltage to be switched is switched. According to this configuration, the phase sequence of the AC voltage supplied to the brushless motor can be switched. The brushless motor can switch the direction of the torque generated by switching the phase sequence of the supplied AC voltage. Therefore, it is possible to reliably generate torque according to the steering direction.

  According to a fourth aspect of the present invention, in the electric power steering device according to any one of the first to third aspects, the magnetic pole position detecting means includes a magnetic detection element that detects a magnetic flux generated by the magnetic pole of the rotor. It is characterized by. According to this configuration, the magnetic pole position of the rotor can be reliably detected.

  Next, an embodiment is given and this invention is demonstrated in detail.

  First, the configuration of the electric power steering apparatus will be described with reference to FIGS. Here, FIG. 1 is a configuration diagram of the electric power steering apparatus in the present embodiment. FIG. 2 is a block diagram of the electric power steering apparatus. FIG. 3 is a cross-sectional view of the electric power steering unit. FIG. 4 is a configuration diagram of the torque sensor. FIG. 5 is an explanatory diagram for explaining a change in magnetic flux in the air gap of the torque sensor. FIG. 6 is a graph showing the magnetic flux in the air gap of the torque sensor. FIG. 7 is a graph showing the output voltage of the magnetic sensor constituting the torque sensor. FIG. 8 is a circuit diagram of the emergency control device. FIG. 9 is a circuit diagram of the connection switching device. FIG. 10 is a block diagram of the control device. 1 and 3 to 5 are introduced for convenience in order to distinguish the directions.

  As shown in FIG. 1, the electric power steering device 1 includes an electric power steering unit 2 and a control device 3 (first motor drive means). The steering wheel 4 is fixed to one end portion of the steering shaft 5, specifically, the upper end portion of the upper steering shaft 50. A pinion gear (not shown) is formed at the other end of the steering shaft 5, specifically, at the lower end of the lower steering shaft 51. The pinion gear meshes with a rack 7 accommodated in the steering gear box 6. Wheels 11 fitted with tires 10 are rotatably fixed to both ends of the rack 7 via tie rods 8 and knuckle arms 9.

  The electric power steering unit 2 is a device that generates torque for assisting steering of the steering wheel 4. The electric power steering unit 2 is installed between the upper steering shaft 50 and the lower steering shaft 51. Further, it is connected to a battery 12 that supplies a DC voltage.

  The control device 3 is a device that controls the electric power steering unit 2. Specifically, it is a device that drives a brushless motor 21 described later based on a steering direction and a steering torque detected by a torque sensor 20 described later, and a rotation angle of a roller detected by a rotation angle sensor 210 described later. The control device 3 is connected to the battery 12. Further, it is connected to the electric power steering unit 2.

  As shown in FIG. 2, the electric power steering unit 2 includes a torque sensor 20 (torque detection means), a brushless motor 21, a rotation angle sensor 22 (rotation angle detection means), and a magnetic pole position sensor 23 (magnetic pole position detection means). ), A speed reduction device 24, an emergency control device 25 (second motor driving means), and a connection switching device 26. As shown in FIG. 3, the torque sensor 20 and the speed reduction device 24 are accommodated in a housing 27. The emergency control device 25 and the connection switching device 26 are also accommodated in the housing 27 (not shown). The brushless motor 21 is fixed to the housing 27. The rotation angle sensor 22 and the magnetic pole position sensor 23 are installed in the brushless motor 21 (not shown).

  As shown in FIGS. 3 and 4, the torque sensor 20 is a device that detects the steering direction and steering torque of the steering wheel 4. The torque sensor 20 includes a torsion bar 200, a magnet 201, magnetic yokes 202 and 203, and a magnetic sensor 204.

  The torsion bar 200 is a columnar member made of an elastic body that constitutes an intermediate portion of the steering shaft 5 and generates a twist as the steering wheel 4 is steered. An upper end portion of the torsion bar 200 is fixed to the upper steering shaft 50. A lower end portion of the torsion bar 200 is fixed to the lower steering shaft 51 via a support member 242 described later.

  The magnet 201 is a cylindrical member that forms a magnetic field and generates a magnetic flux. On the outer peripheral surface of the magnet 201, N poles and S poles are alternately magnetized at equal intervals in the circumferential direction. Thereby, a magnetic field is formed on the outer peripheral side of the magnet 201. The magnet 201 is coaxially fixed to the upper end side of the torsion bar 200.

  The magnetic yokes 202 and 203 are substantially cylindrical members that are arranged in a magnetic field formed by the magnet 201 and are made of a magnetic material that forms a magnetic path. The magnetic yokes 202 and 203 are composed of annular portions 202a and 203a and claw portions 202b and 203b. The annular portions 202a and 203a are annular portions. The claw portion 202b is an isosceles triangular portion that extends upward in the axial direction from the inner peripheral edge of the annular portion 202a. The claw portion 203b is an isosceles triangular portion that extends downward in the axial direction from the inner peripheral edge of the annular portion 203a. The widths of the claw portions 202b and 203b are set to be equal to the width of the magnetic pole of the magnet 201. The claw portions 202b and 203b are arranged at equal intervals in the circumferential direction. The number of the claw portions 202b and 203b is set to be equal to the number of N poles or S poles of the magnet 201. The magnetic yokes 202 and 203 are arranged such that the annular portions 202a and 203a are arranged at predetermined intervals in the axial direction, and the claw portions 202b and 203b are alternately arranged in the circumferential direction, and are opposed to the outer peripheral surface of the magnet 201 with a predetermined interval. In this state, the support member 242 is fixed to the upper end surface. When the torsion bar 200 is not twisted, the fixing positions of the magnetic yokes 202 and 203 are such that the areas of the claw parts 202a and 203a facing the N pole are equal to the areas of the claw parts 202a and 203a facing the S pole. Has been adjusted. As a result, the magnetic yokes 202 and 203 are disposed in the magnetic field formed by the magnet 201.

  The magnetic sensor 204 is an element that detects the magnetic flux in the air gap 205 formed between the magnetic yokes 202 and 203. Specifically, it is a Hall IC. The magnetic sensor 204 outputs a voltage corresponding to the applied magnetic flux density. The magnetic sensor 204 is disposed in an air gap 205 formed in the axial direction between the annular portions 202a and 203a.

  In FIG. 3, when the torsion bar 200 is not twisted, as shown in FIG. 5A, the area of the claw portions 202b and 203b facing the N pole is equal to the area facing the S pole. Therefore, no magnetic flux is generated in the gap 205 formed between the annular portions 202a and 203a.

  However, when the torsion bar 200 is twisted and the magnetic yokes 202 and 203 rotate clockwise with respect to the magnet 201 when viewed from the upper end side of the torsion bar 200, as shown in FIG. The area facing the south pole of 202b increases, and the annular portion 202a becomes the south pole. Further, the area of the claw portion 203b facing the N pole increases, and the annular portion 203a becomes the N pole. Therefore, a downward magnetic flux indicated by an arrow is generated in the gap 205.

  On the other hand, when the torsion bar 200 is twisted and the magnetic yokes 202 and 203 are rotated counterclockwise with respect to the magnet 201, as shown in FIG. The annular portion 202a becomes the N pole. Moreover, the area facing the south pole of the claw portion 203b increases, and the annular portion 203a becomes the south pole. Therefore, a magnetic flux is generated in the gap 205 in the upward direction opposite to that in FIG.

  As a result, the magnetic flux in the air gap 205 changes as shown in FIG. 6 with respect to the twisting direction of the magnetic yokes 202 and 203. When the magnetic yokes 202 and 203 are not twisted with respect to the magnet 201, the magnetic flux in the gap 205 is zero. On the other hand, when the magnetic yokes 202 and 203 are twisted clockwise with respect to the magnet 201, the magnetic flux in the gap 205 becomes positive. And as the twist increases, the magnitude of the magnetic flux also increases. Further, when twisted counterclockwise, the magnetic flux in the gap 205 becomes negative. And as the twist increases, the magnitude of the magnetic flux also increases.

  Therefore, the output voltage of the magnetic sensor 204 changes as shown in FIG. 7 with respect to the magnetic flux of the air gap 205, that is, the twist direction of the magnetic yokes 202 and 203. When the magnetic yokes 202 and 203 are not twisted with respect to the magnet 201, the magnetic sensor 204 outputs a voltage V0. When the magnetic yokes 202 and 203 are twisted clockwise with respect to the magnet 201, the output voltage of the magnetic sensor 204 becomes higher than V0. As the twist increases, the output voltage further increases. On the other hand, when twisted counterclockwise, the output voltage of the magnetic sensor 204 becomes smaller than V0. As the twist increases, the output voltage further decreases. Thereby, the steering direction and steering torque of the steering wheel 4 can be detected.

  In FIG. 2, a brushless motor 21 is a device that generates torque for assisting steering of the steering wheel 4 by being supplied with an AC voltage. Specifically, it is a brushless DC motor that generates torque by being supplied with a three-phase AC voltage. The brushless motor 21 generates reverse torque by switching the phase order of the supplied AC voltage.

  The rotation angle sensor 22 is a device that detects the rotation angle of the rotor of the brushless motor 21. The rotation angle sensor 22 is installed on the rotor of the brushless motor 21.

  The magnetic pole position sensor 23 is a device that detects the magnetic pole position of the rotor of the brushless motor 21. The magnetic pole position sensor 23 includes magnetic sensors 230 to 232 (magnetic detection elements). The magnetic sensors 230 to 232 are elements that detect magnetic flux generated by the magnetic poles of the rotor. Specifically, it is a Hall IC. The magnetic sensors 230 to 232 output a voltage corresponding to the applied magnetic flux density. The magnetic sensors 230 to 232 are arranged at positions corresponding to the U-phase coil, V-phase coil, and W-phase coil of the brushless motor 21 and detect the magnetic pole position of the rotor.

  The reduction device 24 is a device that transmits the torque generated by the brushless motor 21 to the torsion bar 200 by reducing the rotation speed. As shown in FIG. 3, the speed reducer 24 includes a worm wheel 240 and a worm 241.

  The worm wheel 240 is disposed so as to cover the lower end portion of the torsion bar 200 and is coaxially fixed to a bottomed cylindrical support member 242 fixed to the lower end surface. Further, it is rotatably supported by the housing 27 via a bearing 243. As a result, the torsion bar 200 is also supported rotatably with respect to the housing 27. A lower end portion of the support member 242 is fixed to the lower steering shaft 51.

  The worm 241 is fixed coaxially to the shaft 212 of the brushless motor 21. The worm 241 meshes with the worm wheel 240.

  In FIG. 2, an emergency control device 25 (second motor driving means) is a device that controls the brushless brushless motor 21 instead of the control device 3 when the control device 3 fails. Specifically, when the control device 3 fails, the detected steering direction and the magnetic pole position of the rotor detected by the magnetic pole position sensor 23 are replaced by the control device 3 regardless of the steering torque detected by the torque sensor 20. It is an apparatus which drives the brushless motor 21 based on only. More specifically, it is a device that switches the phase sequence of the three-phase AC voltage supplied to the brushless motor 21 so as to generate torque in the detected steering direction based on the detected magnetic pole position of the rotor. As shown in FIG. 8, the emergency control device 25 includes an inverter circuit 250, an inverter drive circuit 251, comparators 252 and 253, a NOT circuit 254, transistors 255 and 256, and a relay 257. .

  The inverter circuit 250 is a circuit that converts the DC voltage of the battery 12 into a three-phase AC voltage and supplies it to the brushless motor 21. The inverter circuit 250 includes transistors 250a to 250f. The transistors 250a to 250f are connected in a three-phase bridge. The collectors of the upper three transistors 250 a to 250 c are connected to the positive terminal of the battery 12. The emitters of the three transistors 250 d to 250 f on the lower side are connected to the negative terminal of the battery 12. The bases of the transistors 250a to 250f are connected to the inverter drive circuit 251, respectively. Further, a connection point between the transistors 250 a and 250 d and a connection point between the transistors 250 b and 250 e are connected to the relay 254. The connection point of the transistors 250c and 250f is connected to the connection switching device 26.

  The inverter drive circuit 251 is a circuit for driving the inverter circuit 250 based on the detection result of the magnetic pole position sensor 23. The inverter drive circuit 251 switches a predetermined transistor among the transistors 250a to 250f in accordance with the outputs of the magnetic sensors 230 to 232. Signal input terminals of the inverter drive circuit 251 are connected to the magnetic sensors 230 to 232, respectively. The signal output terminals are connected to the bases of the transistors 250a to 250f, respectively.

  The comparator 252 is an element that compares the output voltage of the magnetic sensor 204 with the voltage Vh of the reference power supply 258 and outputs a signal corresponding to the comparison result. When the output voltage of the magnetic sensor 204 exceeds the voltage Vh of the reference power supply 258, the comparator 252 outputs a high level signal. Here, the voltage Vh of the reference power supply 258 is set to a value larger than V0 as shown in FIG. The inverting input terminal of the comparator 252 is connected to the reference power source 258, the non-inverting input terminal is connected to the output terminal of the magnetic sensor 204, and the output terminal is connected to the transistor 255.

  The comparator 253 is an element that compares the output voltage of the magnetic sensor 204 with the voltage Vl of the reference power supply 259 and outputs a signal corresponding to the comparison result. When the output voltage of the magnetic sensor 204 exceeds the voltage Vl of the reference power supply 258, the comparator 253 outputs a high level signal. Here, the voltage Vl of the reference power supply 259 is set to a value smaller than V0 as shown in FIG. The inverting input terminal of the comparator 253 is connected to the reference power source 259, the non-inverting input terminal is connected to the output terminal of the magnetic sensor 204, and the output terminal is connected to the NOT circuit 254.

  The NOT circuit 254 is an element that inverts the output of the comparator 253. When the output of the comparator 253 is high level, a low level is output, and when the output of the comparator 253 is low level, a high level is output. The input terminal of the NOT circuit 254 is connected to the output terminal of the comparator 253, and the output terminal is connected to the transistor 256.

  The transistor 255 is an element for supplying current to the relay 257 based on the output of the comparator 252. The transistor 255 is turned on when the output of the comparator 252 is at a high level, and supplies a current to the relay 257. The base of the transistor 255 is connected to the output terminal of the comparator 252, the collector is connected to the relay 257, and the emitter is grounded.

  The transistor 256 is an element for supplying a current to the relay 257 based on the output of the NOT circuit 254. The transistor 256 is turned on when the output of the NOT circuit 254 is at a high level, that is, when the output of the comparator 253 is at a low level, and supplies a current to the relay 257. The base of the transistor 256 is connected to the output terminal of the NOT circuit 254, the collector is connected to the relay 257, and the emitter is grounded.

  The relay 257 is an element that switches the phase order of the three-phase AC voltage supplied to the brushless motor 21. The relay 257 includes contacts 257a and 257b, terminals 257c to 257g, and coils 257h and 257i. One ends of the contacts 257a and 257b are connected to terminals 257c and 257d, respectively. The terminal 257c is connected to the connection point of the transistors 250a and 250d, and the terminal 257d is connected to the connection point of the transistors 250b and 250e. The terminal 257e is connected to the terminal 257g. The terminals 257f and 257g are connected to the connection switching device 26, respectively. One end of the coil 257 h is connected to the power source, and the other end is connected to the collector of the transistor 255. One end of the coil 257 i is connected to the power source, and the other end is connected to the collector of the transistor 256. When no current flows through the coils 257h and 257i, the other ends of the contacts 257a and 257b do not contact any terminals. On the other hand, when a current flows through the coil 257h, the other ends of the contacts 257a and 257b come into contact with the terminals 257e and 257f, respectively. Further, when a current flows through the coil 257i, the other ends of the contacts 257a and 257b come into contact with the terminals 257f and 257g, respectively.

  As shown in FIG. 9, the connection switching device 26 is a device that disconnects the brushless motor 21 from the control device 3 and connects it to the emergency control device 25 when the control device 3 fails. The connection switching device 26 includes a transistor 260 and a relay 261.

  The transistor 260 is an element for supplying a current to the relay 261 based on a signal from the control device 3. The transistor 260 is turned on when the signal from the control device 3 is at a high level, and supplies a current to the relay 261. The base of the transistor 260 is connected to the signal output terminal of the control device 3, the collector is connected to the relay 261, and the emitter is grounded.

  The relay 261 is an element that disconnects the brushless motor 21 from the control device 3 and connects it to the emergency control device 25. The relay 261 includes contacts 261a to 261c, terminals 261d to 261l, and a coil 261m. One ends of the contacts 261a to 261c are connected to terminals 261d to 261f, respectively. The terminals 261d to 261f are connected to the U-phase terminal, V-phase terminal, and W-phase terminal of the brushless motor 21, respectively. The terminals 261g, 261i, and 261k are connected to the emergency control device 25, specifically, to the connection points of the terminals 257f and 257g and the transistors 250c and 250f in FIG. Terminals 261h, 261j, and 261l are connected to the control device 3, respectively. One end of the coil 261m is connected to the power source, and the other end is connected to the collector of the transistor 260. When no current flows through the coil 261m, the other ends of the contacts 261a to 261c are in contact with the terminals 261h, 261j, and 261l, respectively. As a result, the control device 3 is connected to the brushless motor 21. On the other hand, when a current flows through the coil 261m, the other ends of the contacts 261a to 261c come into contact with the terminals 261g, 261i, and 261k, respectively. Thereby, the control device 3 is disconnected, and the emergency control device 25 is connected to the brushless motor 21.

  As shown in FIG. 10, the control device 3 includes a voltage conversion unit 30, a battery connection unit 31, current detection units 32 and 33, a microcomputer 34, a failure detection unit 35, and an OR circuit 36. ing.

  The voltage conversion unit 30 is a circuit block that is controlled by the microcomputer 34 to convert the DC voltage of the battery 12 into a predetermined three-phase AC voltage and supply it to the brushless motor 21. Specifically, a switching element such as a transistor is connected by a three-phase bridge connection.

  The battery connection unit 31 is a circuit block that connects the battery 12 to the voltage conversion unit 30. Specifically, it is a relay. One end of the battery connection unit 31 is connected to the positive terminal of the battery 12, and the other end is connected to the power input terminal of the voltage conversion unit 30. The signal input terminal is connected to the microcomputer 34.

  The current detection units 32 and 33 are circuit blocks that detect currents flowing in the U phase and the V phase of the brushless motor 21. The signal output terminals of the current detectors 32 and 33 are connected to the microcomputer 34, respectively.

  The microcomputer 34 is an element that controls the voltage conversion unit 30 based on detection results of the torque sensor 20, the current detection units 32 and 33, and the rotation angle sensor 22, and vehicle speed information obtained separately. Further, it is also an element that detects a failure of the voltage conversion unit 30, the battery connection unit 31, and the current detection units 32 and 33, outputs a corresponding signal, and controls the battery connection unit 31 based on the detection result. When the microcomputer 34 detects at least one of the failures of the voltage conversion unit 30, the battery connection unit 31, and the current detection units 32 and 33, the microcomputer 34 outputs a high level signal. Further, the microcomputer 34 outputs a signal having a predetermined cycle in order to detect its own failure. A signal input terminal of the microcomputer 34 is connected to the torque sensor 20, the current detection units 32 and 33, and the rotation angle sensor 22. The signal output terminals are connected to the voltage conversion unit 30, the battery connection unit 31, the failure detection unit 35, and the OR circuit 36, respectively.

  The failure detection unit 35 is a circuit block that detects an abnormality in the voltage of the battery 12 due to disconnection of the battery wiring or the like. It is also a circuit block that detects a failure of the microcomputer 34. The failure detection unit 35 detects a failure of the microcomputer 34 based on a signal of a predetermined period output from the microcomputer 34 and outputs a corresponding signal. The failure detection unit 35 outputs a high-level signal when detecting at least one of an abnormality in the voltage of the battery 12 and a failure of the microcomputer 34. The failure detection unit 35 is connected to the battery 12. The signal input terminal of the failure detection unit 35 is connected to the signal output terminal of the microcomputer 34. Further, the signal output terminal is connected to the OR circuit 36.

  The OR circuit 36 is a circuit that outputs a corresponding signal when at least one of the microcomputer 34 and the failure detection unit 35 detects a failure. The OR circuit 36 outputs a high-level signal when the voltage conversion unit 30, the battery connection unit 31, the current detection units 32 and 33, and the microcomputer 34 detect at least one of a failure and an abnormal voltage of the battery 12. . The signal input terminal of the OR circuit 36 is connected to the signal output terminals of the microcomputer 34 and the failure detector 35, respectively. The signal output terminal is connected to the connection switching device 26, specifically, the base of the transistor 260 in FIG.

  Next, the operation of the electric power steering apparatus will be described with reference to FIGS. 2 and 7 to 10. In FIG. 2, when a voltage is supplied, the electric power steering unit 2 and the control device 3 start to operate. In FIG. 10, the microcomputer 34 calculates a torque command based on the steering direction and steering torque detected by the torque sensor 20 and the vehicle speed information. Further, the voltage conversion unit 30 is controlled based on the detection results of the current detection units 32 and 33 and the circuit sensor 210. When the control device 3 has not failed, the connection switching device 26 connects the brushless motor 21 to the control device 3 as shown in FIG. In FIG. 10, the voltage conversion unit 30 converts the DC voltage of the battery 12 supplied via the battery connection unit 31 into a predetermined three-phase AC voltage, and supplies it to the brushless motor 21 via the connection switching device 26. By supplying the three-phase AC voltage, the brushless motor 21 generates torque for assisting steering of the steering wheel 4. Thereby, steering of the steering wheel 4 is appropriately assisted and the load during steering is reduced.

  On the other hand, in FIG. 10, when at least one of the failures of the voltage conversion unit 30, the battery connection unit 31, and the current detection units 32 and 33 is detected, the microcomputer 34 outputs a high level signal. When the failure is other than the battery connection unit 31, the battery connection unit 31 is turned off. Further, when detecting at least one of an abnormality in the voltage of the battery 12 and a failure of the microcomputer 34, the failure detection unit 35 outputs a high level signal. The OR circuit 36 outputs a high level signal when at least one of the microcomputer 34 and the failure detector 35 detects a failure. That is, when the voltage conversion unit 30, the battery connection unit 31, the current detection units 32 and 33, and the microcomputer 34 detect at least one of failure and abnormal voltage of the battery 12, a high level signal is output. When the output of the OR circuit 36 becomes a high level, in FIG. 9, the transistor 260 of the connection switching device 26 is turned on, and a current flows through the coil 261m. When a current flows through the coil 261m, the other ends of the contacts 261a to 261c come into contact with the terminals 261g, 261i, and 261k, respectively. Thereby, the control device 3 is disconnected, and the emergency control device 25 is connected to the brushless motor 21.

Regardless of the steering torque detected by the torque sensor 20, the emergency control device 25 drives the brushless motor 21 based only on the detected steering direction and the magnetic pole position of the rotor detected by the magnetic sensors 230 to 232. In FIG. 2, when the steering wheel 4 is not steered, the output voltage of the magnetic sensor 204 is V0 as shown in FIG. In FIG. 8, the comparator 252 turns off the transistor 255, and the comparator 253 and the NOT circuit 254 turn off the transistor 256, respectively. Since both the transistors 255 and 256 are off, no current flows through the coils 257h and 257i, and the contacts 257a and 257b are opened. Accordingly, the three-phase AC voltage is not supplied to the brushless motor 21 and steering is not assisted.

  On the other hand, when the steering wheel 4 is steered clockwise in FIG. 2, the output voltage of the magnetic sensor 204 becomes smaller than V0 as shown in FIG. When the output voltage becomes lower than Vl, the comparator 253 and the NOT circuit 254 turn on the transistor 256 in FIG. When the transistor 256 is turned on, a current flows through the coil 257i, and the other ends of the contacts 257a and 257b are in contact with the terminals 257f and 257g, respectively. Thereby, the three-phase AC voltage converted by the inverter circuit 250 is supplied to the brushless motor 21 via the relay 257. By supplying the three-phase AC voltage, the brushless motor 21 generates torque in the steering direction of the steering wheel 4. Specifically, a torque that rotates the steering shaft 5 clockwise is generated.

  On the other hand, when the steering wheel 4 is steered counterclockwise in FIG. 2, the output voltage of the magnetic sensor 204 becomes higher than V0 as shown in FIG. When the output voltage exceeds Vh, the comparator 252 turns on the transistor 255 in FIG. When the transistor 255 is turned on, a current flows through the coil 257h, and the other ends of the contacts 257a and 257b are in contact with the terminals 257e and 257f, respectively. As a result, an alternating voltage in which two of the three phases are switched is supplied to the brushless motor 21 via the relay 257. That is, a three-phase AC voltage whose phase order is switched is supplied. The brushless motor 21 generates torque in the steering direction of the steering wheel 4 by supplying the three-phase AC voltage whose phase order is switched. Specifically, a torque that rotates the steering shaft 5 counterclockwise is generated.

  Therefore, even if the control device 3 fails, the steering wheel 4 can be continuously assisted.

  Finally, the effect will be described. According to the present embodiment, the brushless motor 21 can be driven by the emergency control device 25 when the control device 3 fails. Therefore, the steering of the steering wheel 4 can be continuously assisted. In addition, the controller 3 drives the brushless motor 21 based on the steering direction and the steering torque, whereas the emergency control device 25 drives the brushless motor 21 based only on the steering direction regardless of the steering torque. . Further, the first motor driving means drives based on the rotation angle of the rotor, whereas the second motor driving means drives based on the magnetic pole position of the rotor. Therefore, unlike the control device 3, it is not necessary to include the microcomputer 34, and the configuration of the emergency control device 25 can be simplified. Therefore, even an electric power steering apparatus including a brushless motor can continuously assist the steering wheel 4 without complicating the configuration.

  Further, according to the present embodiment, the emergency control device 25 can drive the brushless motor 21 so as to generate torque in the steering direction. Therefore, even when the control device 3 breaks down, the steering of the steering wheel 4 can be reliably assisted.

  Further, in the present embodiment, the emergency control device 25 can switch the phase sequence of the three-phase AC voltage supplied to the brushless motor 21 by the relay 257. The brushless motor 21 generates reverse torque by switching the phase order of the supplied three-phase AC voltage. Therefore, it is possible to reliably generate torque according to the steering direction.

  In addition, according to this embodiment, the magnetic pole position sensor 23 includes magnetic sensors 230 to 232 that detect magnetic flux generated by the magnetic poles of the rotor. Therefore, the magnetic pole position of the rotor can be reliably detected.

It is a lineblock diagram of the electric power steering device in this embodiment. It is a block diagram of an electric power steering device. It is sectional drawing of an electric power steering unit. It is a block diagram of a torque sensor. It is explanatory drawing for demonstrating the magnetic flux change of the space | gap of a torque sensor. It is a graph which shows the magnetic flux of the space | gap of a torque sensor. It is a graph which shows the output voltage of the magnetic sensor which comprises a torque sensor. It is a circuit diagram of an emergency control device. It is a circuit diagram of a connection switching device. It is a block diagram of a control apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electric power steering apparatus, 2 ... Electric power steering unit, 20 ... Torque sensor (torque detection means), 200 ... Torsion bar, 201 ... Magnet, 202, 203 ... Magnetic York, 202a, 203a ... annular part, 202b, 203b ... claw part, 204 ... magnetic sensor, 205 ... air gap, 21 ... brushless motor, 210 ... shaft, 22 ... Rotation angle sensor (rotation angle detection means), 23 ... Magnetic pole position sensor (magnetic pole position detection means), 230 to 232 ... Magnetic sensor (magnetic detection element), 24 ... Deceleration device, 240 ... Warm Wheel, 241 ... Worm, 242 ... Support member, 243 ... Bearing, 25 ... Emergency control device (second motor drive means), 250 ... Invar Circuit, 250a to 250f ... transistor, 251 ... inverter drive circuit, 252, 253 ... comparator, 254 ... NOT circuit, 255,256 ... transistor, 257 ... relay, 257a, 257b ... Contact, 257c to 257g ... Terminal, 257h, 257i ... Coil, 258, 259 ... Reference power supply, 26 ... Connection switching device, 260 ... Transistor, 261 ... Relay, 260a to 261c ... contact, 261d to 261l ... terminal, 261m ... coil, 27 ... housing, 3 ... control device (first motor driving means), 30 ... voltage converter, 31 ... Battery connection part, 32, 33 ... Current detection part, 34 ... Microcomputer, 35 ... Failure detection part, 36 ... OR circuit, 4 ... steering wheel, 5 ... steering shaft, 50 ... upper steering shaft, 51 ... lower steering shaft, 6 ... steering gear box, 7 ... rack, 8 ... Tie rod, 9 ... knuckle arm, 10 ... tire, 11 ... wheel, 12 ... battery

Claims (4)

  Brushless motor for generating torque for assisting steering wheel steering, rotation angle detection means for detecting the rotation angle of the rotor of the brushless motor, and magnetic pole position detection means for detecting the magnetic pole position of the rotor of the brushless motor And a torque detection means for detecting a steering direction and a steering torque of the steering wheel, a steering direction and a steering torque detected by the torque detection means, and a rotation angle of the rotor detected by the rotation angle detection means. When the first motor driving means for driving the brushless motor and the first motor driving means fail, the torque detection is performed regardless of the steering torque detected by the torque detecting means instead of the first motor driving means. Steering direction detected by the means, and magnetism of the rotor detected by the magnetic pole position detecting means. An electric power steering apparatus characterized by a second motor drive means for driving the brushless motor based on the position.   The second motor driving means drives the brushless motor so as to generate torque in the steering direction detected by the torque detecting means based on the magnetic pole position of the rotor detected by the magnetic pole position detecting means. The electric power steering apparatus according to claim 1.   3. The electric power according to claim 2, wherein the second motor driving unit switches the phase sequence of the AC voltage supplied to the brushless motor so as to generate torque in the steering direction detected by the torque detecting unit. Steering device.   The electric power steering apparatus according to any one of claims 1 to 3, wherein the magnetic pole position detection means includes a magnetic detection element that detects a magnetic flux generated by a magnetic pole of the rotor.