Steering control device and vehicle

Abstract

A steering control device (7) is provided with a charge removal circuit (39) that, when an input to a buffer amplifier (37), which generates an excitation signal to be supplied to a rotation sensor (28), is switched from a first excitation pulse to a second excitation pulse, removes the charge charged in an excitation capacitor (38) before the switching.

Description

Steering control device and vehicle

[0001] The present disclosure relates to a steering control device and a vehicle.

[0002] As is well known, most vehicles, such as automobiles, are equipped with a steering control device for assisting the steering force of the vehicle driver. The steering control device is configured to generate an assist torque proportional to the steering force of the driver using an electric motor and apply it to the vehicle's steering mechanism, and obtains the rotation speed and rotation angle of the electric motor based on rotation information of the electric motor detected by a rotation sensor, and controls the electric motor using the obtained rotation speed and rotation angle to generate the assist torque from the electric motor.

[0003] In the case of the steering control device described above, even when the main power supply is turned off and the assist function for the driver's steering is cut off, it is possible that the steering shaft may rotate due to some external force. Therefore, even when the main power supply is turned off, the rotation state of the rotor of the electric motor is monitored by a backup circuit that is always connected to the battery, and the device is configured to be prepared for the case when the main power supply is turned on and the driver starts steering.

[0004] For example, a conventional steering control device disclosed in Patent Document 1 is configured such that, while the main power supply is on, a main circuit equipped with a main CPU (Main Central Processing Unit) continuously applies a normal excitation signal to an excitation coil of a resolver serving as a rotation sensor to detect the rotation state of the rotor of the electric motor, and while the main power supply is off, a backup circuit that is constantly connected to a battery applies an intermittent excitation signal to the excitation coil of the resolver to monitor the rotation state of the electric motor.

[0005] The conventional steering control device disclosed in the aforementioned Patent Document 1 is configured to switch the period of the intermittent excitation signal applied to the excitation coil of the resolver by the backup circuit in accordance with the terminal voltage of the electric motor, and is further configured to perform various monitoring by the backup circuit itself and various diagnoses of the backup circuit by the main CPU of the main circuit.

[0006] Patent No. 5140122

[0007] The conventional steering control device disclosed in Patent Document 1 needs to be equipped with a rotation control circuit having a latch circuit, a decoder, a rotation number counter, etc. for controlling steering angle information from a rotation sensor while the main power is on, and a monitoring backup circuit for monitoring the rotation state of the rotor of the electric motor while the main power is off. However, since it is necessary to provide two circuits, the rotation control circuit and the monitoring backup circuit, the number of electronic components mounted on the control board increases, the size of the control board increases, the steering control device becomes larger, and ultimately the vehicle equipped with the steering control device becomes larger.

[0008] Furthermore, according to the conventional steering control device disclosed in Patent Document 1, while the main power supply is on, a normal excitation signal is continuously applied to the rotation sensor from a main circuit having a main CPU, and while the main power supply is off, an intermittent excitation signal is applied to the rotation sensor from a backup circuit. Therefore, when the main power supply is switched on and off, the normal excitation signal and the intermittent excitation signal may interfere with each other, which may result in the rotation state of the electric motor being erroneously detected as abnormal, resulting in unstable operation.

[0009] The present disclosure discloses a technique for solving the above-mentioned problems, and aims to provide a steering control device that achieves miniaturization and stable operation.

[0010] Another object of the present disclosure is to provide a vehicle that achieves compactness and stable operation.

[0011] The steering control device disclosed herein is a steering control device that drives a steering mechanism of a vehicle with an electric motor to assist the steering force of a driver, and includes: a rotation sensor that has an excitation coil and that detects the rotation state of a rotor of the electric motor when the excitation coil is energized and outputs a rotation detection signal based on the rotation state; a main circuit that is supplied with power when the vehicle is in operation, calculates the rotation speed and rotation angle of the electric motor based on the rotation detection signal output from the rotation sensor, controls driving of the electric motor using the calculated rotation speed and rotation angle, and generates a first excitation pulse; a backup circuit that is always supplied with power, calculates the rotation speed and rotation angle of the electric motor based on the rotation detection signal output from the rotation sensor, and transmits the calculated rotation speed and rotation angle to the main circuit when the main circuit is started, and generates a second excitation pulse; and a buffer amplifier to which the first excitation pulse is input when power is supplied to the main circuit, and to which the second excitation pulse is input when power is not supplied to the main circuit. the rotation sensor comprises an excitation capacitor connected in series between the buffer amplifier and the excitation coil; and a charge removal circuit connected between both terminals of the excitation capacitor, wherein the buffer amplifier is configured to generate a first excitation signal based on the first excitation pulse when the first excitation pulse is input, and to generate a second excitation signal based on the second excitation pulse when the second excitation pulse is input; the charge removal circuit is configured to remove the charge stored in the excitation capacitor before the input to the buffer amplifier is switched from the first excitation pulse to the second excitation pulse; and the excitation coil of the rotation sensor is configured to be energized by the first excitation signal or the second excitation signal via the excitation capacitor.

[0012] The steering control device disclosed in the present application is a steering control device that drives a steering mechanism of a vehicle with an electric motor to assist the steering force of a driver, and includes: a rotation sensor that has an excitation coil and that detects the rotation state of a rotor of the electric motor when the excitation coil is energized and outputs a rotation detection signal based on the rotation state; a main circuit that is supplied with power while the vehicle is in operation, calculates the rotation speed and rotation angle of the electric motor based on the rotation detection signal output from the rotation sensor, controls driving of the electric motor using the calculated rotation speed and rotation angle, and generates a first excitation pulse; and a backup circuit that is constantly supplied with power, calculates the rotation speed and rotation angle of the electric motor based on the rotation detection signal output from the rotation sensor, and transmits the calculated rotation speed and rotation angle to the main circuit when the main circuit is started, and generates a second excitation pulse. a buffer amplifier to which the first excitation pulse is input when power is supplied to the main circuit and to which the second excitation pulse is input when power is not supplied to the main circuit; an excitation capacitor connected in series between the buffer amplifier and the excitation coil; and a pull-down resistor connected between the buffer amplifier and the excitation capacitor, wherein the buffer amplifier is configured to generate a first excitation signal based on the first excitation pulse when the first excitation pulse is input, and to generate a second excitation signal based on the second excitation pulse when the second excitation pulse is input, the pull-down resistor is configured to discharge the charge stored in the excitation capacitor when the first excitation pulse is input to the buffer amplifier, and the excitation coil of the rotation sensor is configured to be energized by the first excitation signal or the second excitation signal via the excitation capacitor.

[0013] Furthermore, the steering control device disclosed in the present application is a steering control device that drives a steering mechanism of a vehicle with an electric motor to assist the steering force of a driver, and includes: a rotation sensor that has an excitation coil and that detects the rotation state of a rotor of the electric motor when the excitation coil is energized and outputs a rotation detection signal based on the rotation state; a main circuit that is supplied with power while the vehicle is in operation, calculates the rotation speed and rotation angle of the electric motor based on the rotation detection signal output from the rotation sensor, controls driving of the electric motor using the calculated rotation speed and rotation angle, and generates a first excitation pulse; and a backup circuit that is constantly supplied with power, calculates the rotation speed and rotation angle of the electric motor based on the rotation detection signal output from the rotation sensor, and transmits the calculated rotation speed and rotation angle to the main circuit when the main circuit is started, and generates a second excitation pulse. the excitation coil; a buffer amplifier to which the first excitation pulse is input when power is supplied to the main circuit and to which the second excitation pulse is input when power is not supplied to the main circuit; an excitation capacitor connected in series between the buffer amplifier and the excitation coil; a charge removal circuit connected between both terminals of the excitation capacitor; and a pull-down resistor connected between the buffer amplifier and the excitation capacitor, wherein the buffer amplifier is configured to generate a first excitation signal based on the first excitation pulse when the first excitation pulse is input, and to generate a second excitation signal based on the second excitation pulse when the second excitation pulse is input; the charge removal circuit is configured to remove the charge stored in the excitation capacitor before the input to the buffer amplifier is switched from the first excitation pulse to the second excitation pulse; and the pull-down resistor is configured to discharge the charge stored in the excitation capacitor when the first excitation pulse is input to the buffer amplifier. The rotation sensor is characterized in that the excitation coil of the rotation sensor is configured to be energized by the first excitation signal or the second excitation signal via the excitation capacitor.

[0014] Furthermore, the vehicle disclosed in the present application is a vehicle equipped with a steering wheel, a steering mechanism for steering the steering wheel, and a steering control device for applying an assist torque to the steering mechanism to assist the steering force of the driver of the vehicle, and is characterized in that the steering control device is configured by any one of the steering control devices described above.

[0015] According to the steering control device of the present disclosure, a steering control device that achieves miniaturization and stable operation can be obtained.

[0016] Furthermore, the vehicle according to the present disclosure can provide a vehicle that is compact and has stable operation.

[0017] 9 is a schematic diagram showing the overall configuration of a steering control device and a vehicle according to embodiment 1 and embodiment 2. FIG. 10 is a block diagram showing the configuration of an ECU in the steering control device according to embodiment 1 and embodiment 2. FIG. 11 is a block diagram showing the circuit configuration of the steering control device according to embodiment 1. FIG. 12 is a waveform diagram showing a normal excitation signal in the steering control device according to embodiment 1. FIG. 13 is a waveform diagram showing an intermittent excitation signal in the steering control device according to embodiment 1. FIG. 14 is a waveform diagram showing the relationship between the voltage of an exciting capacitor, the normal excitation signal, and the intermittent excitation signal. FIG. 15 is a circuit diagram showing the circuit configuration of a portion of FIG. 3. FIG. 16 is a waveform diagram showing the waveforms when switching between the normal excitation signal and the intermittent excitation signal in the steering control device according to embodiment 1. FIG. 17 is a block diagram showing a portion of the circuit configuration of the steering control device according to embodiment 2. FIG. 18 is a waveform diagram showing the relationship between the voltage of an exciting capacitor and the normal excitation signal.

[0018] A steering control device and a vehicle according to the present disclosure will be described below with reference to the drawings. In each drawing, the same reference numerals indicate the same or corresponding parts.

[0019] Embodiment 1. Figure 1 is a schematic diagram showing the overall configuration of a steering control device and a vehicle according to embodiments 1 and 2. In Figure 1, a vehicle 100 includes steerable wheels 1 and 2 as a pair of front wheels, drive wheels 4 and 5 as a pair of rear wheels driven by a vehicle drive device 3 such as an internal combustion engine or an electric motor, a vehicle control device 6 that controls the vehicle drive device 3, and a steering control device 7 as an electric power steering device.

[0020] The steered wheel 1 is rotatably supported by a steering knuckle 8. The steering knuckle 8 is fixed integrally with a knuckle arm 10, and is rotatably supported together with the knuckle arm 10 on a knuckle shaft 81. The steered wheel 2 is rotatably supported by a steering knuckle 9. The steering knuckle 9 is fixed integrally with a knuckle arm 12, and is rotatably supported together with the knuckle arm 12 on a knuckle shaft 91.

[0021] An end of the knuckle arm 10 is rotatably connected to one end of a tie rod 11, and an end of the knuckle arm 12 is rotatably connected to the other end of the tie rod 11. A rack gear 16 fixed to the tie rod 11 is engaged with a pinion gear 14 fixed to one end of a steering shaft 13. When the steering shaft 13 rotates about its axis X, the rack gear 16 is driven by the pinion gear 14, causing the tie rod 11 to move to one side or the other in the axial direction.

[0022] The steered wheels 1 and 2 are steered to the left or right in the figure by movement of the tie rod 11 via the knuckle arms 10 and 12 and the steering knuckles 8 and 9. Note that the steered wheels 1 and 2 may also serve as drive wheels that drive the vehicle 100, but in this example, the vehicle 100 is driven by the drive wheels 4 and 5, which are rear wheels.

[0023] The drive wheel 4 is fixed to an axle 17, and the drive wheel 5 is fixed to an axle 18. The axles 17 and 18 are each driven by the vehicle drive device 3 via a differential mechanism 19. The vehicle drive device 3 is controlled by the vehicle control device 6.

[0024] A handle 15 that is operated by the driver is fixed to the other end of the steering shaft 13. When the driver operates and rotates the handle 15, the steering shaft 13 rotates about the axis X.

[0025] The steering control device 7 includes an electric motor 20, an ECU (Electronic Control Unit) 21, and a torque sensor 22. The electric motor 20 is configured, for example, by an AC brushless motor, and is connected to the steering shaft 13 via a reduction gear 23. The torque sensor 22 faces a torsion bar 221 fixed to the steering shaft 13 across a gap, and detects the steering torque applied to the steering shaft 13 by the driver based on the torsion angle of the torsion bar 221.

[0026] Next, the configuration of the ECU 21 in the steering control device 7 will be described. Fig. 2 is a block diagram showing the configuration of the ECU in the steering control device according to the first and second embodiments. In Fig. 2, the ECU 21 is made up of a main circuit 25 that operates while the key switch 24 of the vehicle 100 is on, and a backup circuit 27 that operates by being constantly backed up by the battery 26 of the vehicle 100. Here, the time when the key switch 24 is on is referred to as the time when the vehicle is operating, regardless of whether the vehicle 100 is running or stopped.

[0027] The rotation sensor 28 provided inside the electric motor 20 is connected to both the main circuit 25 and the backup circuit 27. The main circuit 25 and the backup circuit 27 transmit and receive information to each other via serial communication 29. The rotation sensor 28 is configured by, for example, a resolver, and includes an excitation coil and a detection coil, which are provided on the stator side and will be described later, and a resolver rotor.

[0028] Next, a description will be given of the circuit configuration of the steering control device 7 according to embodiment 1. Fig. 3 is a block diagram showing the circuit configuration of the steering control device according to embodiment 1, and mainly shows the circuit configuration of the ECU 21 in Fig. 2 described above. In Fig. 3, the ECU 21 includes a main circuit 25 and a backup circuit 27.

[0029] In FIG. 3, for convenience of illustration, the key switch 24, the electric motor 20, and the rotation sensor 28 are shown within the solid line frame representing the ECU 21, but these are located outside the ECU 21 and are electrically connected to the ECU 21.

[0030] The rotation sensor 28 is configured, for example, by a resolver built into the electric motor 20, and includes a resolver rotor that rotates together with the rotor of the electric motor 20, and a resolver stator that faces the resolver rotor across an air gap. The resolver stator includes an excitation coil 281 that excites the resolver rotor, and a detection coil 282. The detection coil 282 is configured by a sine detection coil and a cosine detection coil (neither of which are shown) that are arranged so that their phases differ from each other by 90 degrees.

[0031] When the excitation coil 281 of the resolver is excited, a detection waveform whose amplitude is modulated according to the rotation angle of the resolver rotor is extracted from the detection coil 282. Specifically, a sine signal Sin1 corresponding to the rotation angle of the resolver rotor is output from the sine detection coil that constitutes the detection coil 282, and a cosine signal Cos1 corresponding to the rotation angle of the resolver rotor is output from the cosine detection coil.

[0032] The main circuit 25 includes a main circuit power supply 30, a main CPU 31, a power conversion circuit 32, and a FET (Field Effect Transistor) driver circuit 33. When the key switch 24 is on, the main circuit power supply 30 receives a battery voltage B from the battery 26 and generates a DC voltage to be supplied to the main CPU 31.

[0033] The power conversion circuit 32 is composed of a three-phase bridge circuit consisting of a U-phase arm 32U having a positive DC terminal connected to the positive terminal of the battery 26 via the key switch 24, a V-phase arm 32V having a positive DC terminal connected to the positive terminal of the battery 26 via the key switch 24, and a W-phase arm 32W having a positive DC terminal connected to the positive terminal of the battery 26 via the key switch 24.

[0034] The U-phase arm 32U is composed of a U-phase upper arm switching element 32UP made of an FET, a U-phase lower arm switching element 32UN made of an FET, a U-phase smoothing capacitor 32UC connected in parallel to the series circuit of the U-phase upper arm switching element 32UP and the U-phase lower arm switching element 32UN, a U-phase terminal switching element 32US made of an FET inserted into a U-phase AC terminal 32UT derived from the series connection portion of the U-phase upper arm switching element 32UP and the U-phase lower arm switching element 32UN, and a U-phase shunt resistor 32UR connected between the U-phase lower arm switching element 32UN and the ground potential portion GND.

[0035] The V-phase arm 32V is composed of a V-phase upper arm switching element made of an FET, a V-phase lower arm switching element made of an FET, a V-phase smoothing capacitor connected in parallel to the series circuit of the V-phase upper arm switching element and the V-phase lower arm switching element, a V-phase terminal switching element made of an FET inserted into the V-phase AC terminal 32VT derived from the series connection part of the V-phase upper arm switching element and the V-phase lower arm switching element, and a V-phase shunt resistor connected between the V-phase lower arm switching element and the ground potential part.

[0036] The W-phase arm 32W is composed of a W-phase upper arm switching element made of an FET, a W-phase lower arm switching element made of an FET, a W-phase smoothing capacitor connected in parallel to the series circuit of the W-phase upper arm switching element and the W-phase lower arm switching element, a W-phase terminal switching element made of an FET inserted into the W-phase AC terminal 32WT derived from the series connection part of the W-phase upper arm switching element and the W-phase lower arm switching element, and a W-phase shunt resistor connected between the W-phase lower arm switching element and the ground potential part.

[0037] The U-phase AC terminal 32UT of the power conversion circuit 32 is connected to the connection between the U-phase armature winding U and the V-phase armature winding V of the electric motor 20, the V-phase AC terminal 32VT is connected to the connection between the V-phase armature winding V and the W-phase armature winding W of the electric motor 20, and the W-phase AC terminal 32WT is connected to the connection between the W-phase armature winding W and the U-phase armature winding U of the electric motor 20.

[0038] The main CPU 31 generates a command signal Com based on the torque detection signal Ts from the torque sensor 22, the rotation detection sine signal Sin based on the sine signal Sin1 from the rotation sensor 28, the rotation detection cosine signal Cos based on the cosine signal Cos1 from the rotation sensor 28, and the feedback signal Fs from the power conversion circuit 32, and provides the generated command signal Com to the FET driver circuit 33. The main CPU 31 generates a normal excitation pulse Ep1 as a first excitation pulse at predetermined intervals.

[0039] The FET driver circuit 33 generates a drive pulse signal Ds as a drive signal for driving the semiconductor switching elements of each phase of the power conversion circuit 32 based on the command signal Com from the main CPU 31, and supplies the drive pulse signal Ds to the gates of the switching elements of each phase in the power conversion circuit 32, causing the power conversion circuit 32 to operate as an inverter. The electric motor 20 is energized by three-phase AC power supplied from the U-phase AC terminal 32UT, the V-phase AC terminal 32VT, and the W-phase AC terminal 32WT of the power conversion circuit 32, and generates an assist torque which is applied to the steering shaft 13 via the reduction gear 23 described above.

[0040] The backup circuit 27 includes a backup power supply 34 , a backup CPU 35 , an amplifier circuit 40 , a pull-up / pull-down circuit 41 , a low-pass filter 36 , a buffer amplifier 37 , an excitation capacitor 38 , and a charge removal circuit 39 .

[0041] The backup power supply 34 is always connected to the battery 26, receives the supply of battery voltage B, and generates a DC voltage to be supplied to the backup CPU 35. The backup CPU 35 is always supplied with power from the backup power supply 34, and generates an intermittent excitation pulse Ep2 as a second excitation pulse at predetermined intervals when the main CPU 31 is not operating. The intermittent excitation pulse Ep2 is generated, for example, at predetermined intervals obtained by dividing the frequency of a clock generated by an oscillator using a timing generator, with the clock period as the pulse width.

[0042] The amplifier circuit 40 processes the sine signal Sin1 and cosine signal Cos1 from the rotation sensor 28 input via the pull-up / pull-down circuit 41, and inputs the processed signals as a rotation detection sine signal Sin and a rotation detection cosine signal Cos to the main CPU 31 and the backup CPU 35, respectively.

[0043] When the key switch 24 is turned on, the normal excitation pulse Ep1 output from the main CPU 31 is waveform-shaped by the low-pass filter 36 and the buffer amplifier 37 to become the normal excitation signal Exs1 as the first excitation signal, and is supplied to the excitation coil 281 of the rotation sensor 28 via the excitation capacitor 38.

[0044] When the key switch 24 is off, the normal excitation pulse Ep1 is switched to an intermittent excitation pulse Ep2 by the backup CPU 35, and the intermittent excitation pulse Ep2 is waveform-shaped by the low-pass filter 36 and the buffer amplifier 37 to become an intermittent excitation signal Exs2 as a first political signal, which is supplied to the excitation coil 281 of the resolver, which is the rotation sensor 28, via the excitation capacitor 38.

[0045] The normal excitation signal Exs1 or the intermittent excitation signal Exs2 output from the buffer amplifier 37 passes through the excitation capacitor 38, whereby the DC component is removed, and the output current of the buffer amplifier 37 can be reduced.

[0046] As will be described later, when the input to the buffer amplifier 37 is switched from the normal excitation pulse Ep1 as the first excitation pulse to the intermittent excitation pulse Ep2 as the second excitation pulse, the charge removal circuit 39 is configured to remove the charge stored in the excitation capacitor 38 before the switching.

[0047] Next, the operation of the steering control device 7 configured as above will be described. In Figures 1, 2, and 3, when the key switch 24 is off, the backup CPU 35 is constantly supplied with power from the backup power supply 34 connected to the battery 26, and generates an intermittent excitation pulse Ep2. The intermittent excitation pulse Ep2 is input to a buffer amplifier 37 via a low-pass filter 36, and the buffer amplifier 37 generates an intermittent excitation signal Exs2 as a second excitation signal. The intermittent excitation signal Exs2 is supplied to the excitation coil 281 of the rotation sensor 28 via an excitation capacitor 38.

[0048] As a result, the rotation sensor 28 generates a sine signal Sin1 and a cosine signal Cos1 and inputs them to the pull-up / pull-down circuit 41. The sine signal Sin1 and the cosine signal Cos1 are processed by the pull-up / pull-down circuit 41 and the amplifier circuit 40, respectively, to become a rotation detection sine signal Sin and a rotation detection cosine signal Cos, which are input to the main CPU 31 and the backup CPU 35.

[0049] The backup CPU 35 counts the number of rotations of the rotor of the electric motor 20 by determining whether the difference between the amplitude of the input rotation detection sine signal Sin and the amplitude of the rotation detection cosine signal Cos is positive or negative, and waits until the key switch 24 is turned on and the vehicle 100 is in a driving state.

[0050] Next, when the key switch 24 is turned on and the main CPU 31 of the main circuit 25 is started up, the main CPU 31 calculates the steering angle based on the value of the rotor rotation speed of the electric motor 20 transmitted from the backup CPU 35 to the main CPU 31 via serial communication 29 and the amplitude of the input rotation detection sine signal Sin and rotation detection cosine signal Cos.

[0051] When the driver rotates the steering wheel 15 clockwise or counterclockwise, the steering torque applied by the driver to the steering shaft 13 is detected by the torque sensor 22, and a torque signal Ts corresponding to the detected steering torque is input to the main CPU 31.

[0052] The main CPU 31 generates a command signal Com based on the input torque signal Ts, the rotation detection sine signal Sin and the rotation detection cosine signal Cos, the calculated steering angle, and the feedback signal Fs from the power conversion circuit 32, and provides the command signal Com to the FET driver circuit 33. The FET driver circuit 33 generates a drive pulse signal Ds as a drive signal that controls the on / off of each semiconductor switching element of the power conversion circuit 32 based on the provided command signal Com, and provides the drive pulse signal Ds to the gate of each semiconductor switching element.

[0053] In the power conversion circuit 32, each semiconductor switching element is controlled to be turned on and off by a drive pulse signal Ds from the FET driver circuit 33, and the power conversion circuit 32 operates as an inverter, converting DC power from the battery 26 into three-phase AC power, which is supplied to the U-phase armature winding U, the V-phase armature winding V, and the W-phase armature winding W of the electric motor 20. As a result, the electric motor 20 generates an assist torque proportional to the steering torque applied by the driver based on the three-phase AC power supplied from the power conversion circuit 32, and applies this assist torque to the steering shaft 13 via the reduction gear 23 to assist the steering by the driver.

[0054] When the key switch 24 is on, the steering control device 7 operates as described above to assist the driver in steering, and during this time, the main CPU 31 of the main circuit 25 generates a normal excitation pulse Ep1 as a first excitation pulse at predetermined intervals. The normal excitation pulse Ep1 is input to a buffer amplifier 37 via a low-pass filter 36 and output from the buffer amplifier 37 as a normal excitation signal Exs1 as a first excitation signal. The normal excitation signal Exs1 is supplied to the excitation coil 281 of the rotation sensor 28 via an excitation capacitor 38.

[0055] Fig. 4 is a waveform diagram showing a normal excitation signal in the steering control device according to embodiment 1. As shown in Fig. 4, the normal excitation signal Exs1 supplied to the excitation coil of the resolver constituting the rotation sensor 28 when the key switch 24 is on is composed of a continuous sine wave with a period T1 based on a predetermined constant offset voltage V1 [V].

[0056] The waveform of the normal excitation signal Exs1 output by the buffer amplifier 37 is a sine signal based on a constant offset voltage V1 [V], so when the key switch 24 is on and the main CPU 31 is operating, a constant voltage is always applied to the excitation capacitor 38 from the buffer amplifier 37. Therefore, when the main CPU 31 is operating, the excitation capacitor 38 is always charged.

[0057] On the other hand, while the key switch 24 is turned off, the main CPU 31 is stopped from operating, and therefore the intermittent excitation pulse Ep2 output from the backup CPU 35 is input to the buffer amplifier 37 via the low-pass filter 36 and output as an intermittent excitation signal Exs2, which serves as a second excitation signal, from the buffer amplifier 37. The intermittent excitation signal Exs2 is supplied to the excitation coil 281 of the rotation sensor 28 via an excitation capacitor 38.

[0058] Fig. 5 is a waveform diagram showing an intermittent excitation signal in the steering control device according to embodiment 1. As shown in Fig. 5, the intermittent excitation signal Exs2 supplied to the excitation coil 281 of the rotation sensor 28 when the key switch 24 is off is generated with 0 [V] as a reference at every predetermined period T2. The output voltage of the intermittent excitation signal Exs2 is set lower than the output voltage of the normal excitation signal Exs1 shown in Fig. 4 in order to reduce power consumption.

[0059] When the key switch 24 is switched from on to off, the output waveform of the buffer amplifier 37 is switched from the normal excitation signal Exs1 to the intermittent excitation signal Exs2. However, since the excitation capacitor 38 is charged by the normal excitation signal Exs1, if the intermittent excitation signal Exs2 is output from the buffer amplifier 37 in this state, and the voltage of the intermittent excitation signal Exs2 is equal to or lower than the voltage charged in the excitation capacitor 38, the intermittent excitation signal Exs2 cannot be applied to the rotation sensor 28. As a result, the sine signal Sin1 and the cosine signal Cos1 are not output from the rotation sensor 28, and the backup circuit 27 may detect erroneous steering angle information.

[0060] FIG. 6 is a waveform diagram showing the relationship between the voltage of the excitation capacitor, the normal excitation signal, and the intermittent excitation signal, and shows the case where the normal excitation signal Exs1 is switched to the intermittent excitation signal Exs2 while the excitation capacitor 38 is charged.

[0061] As shown in Fig. 6, even when the normal excitation signal Exs1 is switched to the intermittent excitation signal Exs2 at time t1, the excitation capacitor 38 remains charged, and the excitation capacitor 38 has a voltage E [V]. As shown in Fig. 6, the voltage E [V] of the excitation capacitor 38 gradually decreases over time, but in a region where the voltage of the intermittent excitation signal Exs2 is equal to or lower than the voltage E of the excitation capacitor 38, the intermittent excitation signal Exs2 cannot be applied to the rotation sensor 28. Therefore, in the steering control device according to embodiment 1, a charge removal circuit 39 is provided between both terminals of the excitation capacitor 38, as shown in Fig. 3.

[0062] 7 is a circuit diagram showing a portion of the circuit configuration shown in FIG. 3, illustrating the excitation capacitor 38, the charge removal circuit 39, and the peripheral circuit configuration. In FIG. 7, the charge removal circuit 39 is configured by a discharge switching element 390 made of, for example, a semiconductor switching element. The buffer amplifier 37 includes a switching element 370 connected to an excitation power supply 371, and is configured to output the normal excitation signal Exs1 or the intermittent excitation signal Exs2 by controlling the on / off of the switching element 370.

[0063] The collector terminal 391 of the discharge switching element 390 is connected to one terminal of the excitation capacitor 38 connected to the buffer amplifier 37, the emitter terminal 392 is connected to the other terminal of the excitation capacitor 38, and the base terminal 393 is connected to the output terminal of the main CPU 31 and the output terminal of the backup CPU 35, respectively.

[0064] When the main CPU 31 stops outputting the normal excitation pulse Ep1 and outputs the intermittent excitation pulse Ep2 from the backup CPU 35, that is, when switching from the normal excitation signal Exs1 to the intermittent excitation signal Exs2, the main CPU 31 simultaneously applies the charge removal signal Ed1 to the base terminal 393 of the discharge switching element 390 in the charge removal circuit 39. This makes the discharge switching element 390 conductive, and the charge stored in the excitation capacitor 38 is discharged.

[0065] Fig. 8 is a waveform diagram showing the waveforms at the time of switching between the normal excitation signal and the intermittent excitation signal in the steering control device according to Embodiment 1. As shown in Fig. 8, the discharge switching element 390 becomes conductive at time t1 when the normal excitation signal Exs1 is switched to the intermittent excitation signal Exs2, whereby the charge stored in the excitation capacitor 38 is discharged, and the voltage E [V] of the excitation capacitor 38 drops to substantially 0 [V] by the time the intermittent excitation signal Exs2 is generated.

[0066] As a result, the intermittent excitation signal Exs2 is applied to the excitation coil of the rotation sensor via the excitation capacitor 38, completing the switch from the normal excitation signal Exs1 to the intermittent excitation signal Exs2. The discharge switching element 390 is turned off because the main CPU 31 stops operating when the key switch 24 is turned off.

[0067] As described above, by removing the charge of the excitation capacitor 38 before the buffer amplifier 37 outputs the intermittent excitation signal Exs2, the voltage of the excitation capacitor 38 becomes a voltage equal to or lower than the intermittent excitation signal Exs2, so that it is possible to reliably switch from the normal excitation signal Exs1 to the intermittent excitation signal Exs2.

[0068] Furthermore, the charge removal circuit 39 is configured to remove the charge stored in the excitation capacitor 38 before switching from the normal excitation pulse Ep1 as the first excitation pulse to the intermittent excitation pulse Ep2 as the second excitation pulse and inputting it to the buffer amplifier 37. Therefore, when the main circuit power supply 30 is switched on and off, there is no interference between the normal excitation signal Exs1 and the intermittent excitation signal Exs2, no abnormal detection signal is generated from the electric motor 20, and unstable operation of the steering control device 7 due to erroneous detection can be eliminated.

[0069] As described above, by discharging the charge of the excitation capacitor 38 using the charge removal circuit 39, the switching time from the normal excitation signal Exs1 to the intermittent excitation signal Exs2 is shortened, the time during which the excitation signal to the rotation sensor 28 is stopped is shortened, and erroneous calculation of steering angle information can be suppressed, allowing steering angle information to be detected more stably.

[0070] In addition, if the charge removal circuit 39 is operating when the buffer amplifier 37 outputs the normal excitation signal Exs1, this will cause an increase in current consumption, so the charge removal circuit 39 is controlled not to operate when the main CPU 31 is operating.

[0071] 7, the charge removal circuit 39 is configured to be controllable by both the main CPU 31 of the main circuit 25 and the backup CPU 35 of the backup circuit 27, and even if the main CPU 31 is unable to start the charge removal circuit 39 due to an abnormal operation of the main circuit power supply 30 or the like, the charge removal circuit 39 can be started by the backup CPU 35. Therefore, the charge in the exciting capacitor 38 can be reliably removed to energize the exciting coil of the rotation sensor 28, and steering angle information can be reliably calculated.

[0072] If the discharge current of the excitation capacitor 38 is controlled by the discharge switching element 390 , a series resistor may be provided between the excitation capacitor 38 and the discharge switching element 390 .

[0073] 1, vehicle 100 according to embodiment 1 includes steerable wheels 1 and 2, a steering mechanism that steers steerable wheels 1 and 2, and a steering control device 7 that applies an assist torque to the steering mechanism to assist the steering force of the driver of vehicle 100, and steering control device 7 is configured by the steering control device 7 according to embodiment 1 described above. Therefore, it is possible to realize a vehicle that is compact and has a stable steering function.

[0074] Embodiment 2. Next, a steering control device and a vehicle according to embodiment 2 will be described. Fig. 1 is a schematic diagram showing the overall configuration of the steering control device and vehicle according to embodiment 1 and embodiment 2, and Fig. 2 is a block diagram showing the configuration of the ECU in the steering control device according to embodiment 1 and embodiment 2, both of which are common to the above-described embodiment 1.

[0075] 9 is a block diagram showing a part of the circuit configuration of the steering control device according to embodiment 2, and shows only the backup circuit 27 of the ECU 21 and the rotation sensor 28 in the steering control device 7, omitting the main circuit 25, the battery 26, and the torque sensor 22. In FIG. 9, the configuration and operation of the charge removal circuit 39 are similar to those of the charge removal circuit 39 in the steering control device according to embodiment 1 described above.

[0076] The pull-down resistor 42 is connected between the connection point between the output side of the buffer amplifier 37 and the excitation capacitor 38 and the ground potential point GND. The other configurations are the same as those of the backup circuit 27 in FIG. 3 according to the first embodiment.

[0077] If there is no path for discharging the charge of the excitation capacitor 38 when the buffer amplifier 37 is outputting the normal excitation signal Exs1 as the first excitation signal, the excitation capacitor 38 continues to be charged by the normal excitation signal Exs1 that is the output of the buffer amplifier 37, and the voltage of the excitation capacitor 38 becomes a constant value that is greater than the maximum value of the normal excitation signal Exs1. In this state, the normal excitation signal Exs1 cannot be transmitted to the rotation sensor 28, and steering angle information cannot be calculated.

[0078] FIG. 10 is a waveform diagram showing the relationship between the voltage of the excitation capacitor 38 and the normal excitation signal Exs1 when the buffer amplifier 37 does not have a sink function.

[0079] As shown in FIG. 10 , if the buffer amplifier 37 does not have a sink function, that is, if the excitation capacitor 38 continues to be charged by the normal excitation signal Exs1 and has a constant voltage E, the maximum value of the normal excitation signal Exs1 cannot exceed the voltage E of the excitation capacitor 38, and the normal excitation signal Exs1 cannot be supplied to the excitation coil 281 of the rotation sensor 28 via the excitation capacitor 38.

[0080] Therefore, in the steering control device according to the second embodiment, a pull-down resistor 42 is provided between the output port of the buffer amplifier 37 and the ground potential part GND as a path for discharging the electric charge of the excitation capacitor 38 .

[0081] Fig. 11 is a circuit diagram showing a part of Fig. 9, and shows the pull-down resistor 42, the excitation capacitor 38, and the circuit configuration around them. As shown in Fig. 11, the pull-down resistor 42 is connected between the connection point between the output side of the buffer amplifier 37 and the excitation capacitor 38, and the ground potential part GND. The other configurations are the same as those in Fig. 7 of the first embodiment.

[0082] In the steering control device according to the second embodiment, a pull-down resistor 42 is provided so that when the buffer amplifier 37 outputs the normal excitation signal Exs1, the charge in the excitation capacitor 38 is discharged to the ground potential section GND via the pull-down resistor 42.

[0083] Specifically, when the switching element 370 of the buffer amplifier 37 is off, the charge stored in the excitation capacitor 38 is discharged to the ground potential GND via the pull-down resistor 42. As in the case of the first embodiment described above, the charge removing circuit 39 is not driven except when switching from the normal excitation signal Exs1 to the intermittent excitation signal Exs2.

[0084] If the resistance value of the pull-down resistor 42 is too small, the current consumption of the buffer amplifier 37 increases, and if it is too large, the charge in the excitation capacitor 38 cannot be sufficiently discharged, distorting the waveform of the normal excitation signal Exs1. If the waveform of the normal excitation signal Exs1 is distorted, the amplitude of the normal excitation signal Exs1 decreases, causing a decrease in the steering angle detection accuracy. Therefore, the resistance value of the pull-down resistor 42 is selected by calculation or experiment within a range that does not affect the steering angle detection accuracy.

[0085] Although the second embodiment includes both the pull-down resistor 42 and the charge removing circuit 39, it is also possible to include only the pull-down resistor 42.

[0086] According to the steering control device and vehicle of the second embodiment described above, when the buffer amplifier 37 outputs the normal excitation signal Exs1, the charge of the excitation capacitor 38 is discharged by the pull-down resistor 42. Therefore, the normal excitation signal Exs1 can be reliably supplied to the excitation coil 281 of the rotation sensor 28 via the excitation capacitor 38, and the operation of the steering control device 7 and the vehicle 100 can be stabilized.

[0087] 1, vehicle 100 according to embodiment 2 includes steerable wheels 1 and 2, a steering mechanism that steers steerable wheels 1 and 2, and a steering control device 7 that applies an assist torque to the steering mechanism to assist the steering force of the driver of vehicle 100, and steering control device 7 is configured by the steering control device 7 according to embodiment 2 described above. Therefore, it is possible to realize a vehicle that is compact and has a stable steering function.

[0088] Although the steering control devices and vehicles according to the first and second embodiments described above have been described as an example in which an electric power steering device is used as the steering control device, the present invention may also be applied to, for example, a steer-by-wire type steering control device, a reaction torque actuator type steering control device mounted on the steering wheel side, or a steering control device in which a brushless electric motor is used for the steering actuator mounted on steering knuckles 8, 9 connected to tie rod 11, and is not limited to steering control devices using electric power steering according to the first and second embodiments. Furthermore, the steering angle of knuckle arms 10, 12 as steered wheels may be calculated instead of the steering angle.

[0089] Although the present disclosure describes steering control devices and vehicles according to Embodiments 1 and 2, the various features, aspects, and functions described in these embodiments are not limited to application to specific embodiments, but can be applied to the embodiments alone or in various combinations. Therefore, countless modifications not exemplified are anticipated within the scope of the technology disclosed in this application. For example, this includes cases where at least one component is modified, added, or omitted, and even cases where at least one component is extracted and combined with components of other embodiments.

[0090] 100 Vehicle, 1, 2 Steering wheels, 3 Vehicle drive device, 4, 5 Drive wheels, 6 Vehicle control device, 7 Steering control device, 8, 9 Steering knuckle, 81, 91 Knuckle shaft, 10, 12 Knuckle arm, 11 Tie rod, 13 Steering shaft, 14 Pinion gear, 15 Handle, 16 Rack gear, 17, 18 Axle, 19 Differential mechanism, 20 Electric motor, 21 ECU, 22 Torque sensor, 23 Reduction gear, 24 Key switch, 221 Torsion bar, 25 Main circuit, 26 Battery, 27 Backup circuit, 28 Rotation sensor, 281 Excitation coil, 282 Detection coil, 29 Serial communication, 30 Main circuit power supply, 31 Main CPU, 32 Power conversion circuit, 32U U-phase arm, 32UP U-phase upper arm switching element, 32UN U-phase lower arm switching element, 32UC U-phase smoothing capacitor, 32US U-phase terminal switching element, 32UR U-phase shunt resistor, 32UT U-phase AC terminal, 32V V-phase arm, 32VT V-phase AC terminal. 32W W-phase arm, 32WT W-phase AC terminal, 33 FET driver circuit, 34 Backup power supply, 35 Backup CPU, 36 Low-pass filter, 37 Buffer amplifier, 370 Switching element, 371 Excitation power supply, 38 Excitation capacitor, 39 Charge removal circuit, 390 Discharge switching element, 390 Discharge switching element, 391 Collector terminal, 392 Emitter terminal, 393 Base terminal, 40 Amplification circuit, 41 Pull-up / pull-down circuit, 42 Pull-down resistor, GND Ground potential section, U U-phase armature winding, V V-phase armature winding, W W-phase armature winding, Com Command signal, Ds Drive pulse signal, Fs Feedback signal, Sin1 Sine signal, Cos1 Cosine signal, Sin Rotation detection sine signal, Cos Rotation detection cosine signal, Ep1 normal excitation pulse, Ep2 intermittent excitation pulse, Exs1 normal excitation signal, Exs2 intermittent excitation signal

Claims

1. A steering control device that assists the driver's steering force by driving the vehicle's steering mechanism with an electric motor, A rotation sensor equipped with an excitation coil, which detects the rotational state of the rotor of the electric motor when the excitation coil is biased and outputs a rotation detection signal based on the rotational state, A main circuit is supplied with power when the vehicle is in operation, calculates the rotation speed and rotation angle of the electric motor based on the rotation detection signal output from the rotation sensor, controls the drive of the electric motor using the calculated rotation speed and rotation angle, and generates a first excitation pulse. A backup circuit is provided which is constantly powered, calculates the rotation speed and rotation angle of the electric motor based on the rotation detection signal output from the rotation sensor, transmits the calculated rotation speed and rotation angle to the main circuit when the main circuit is started, and generates a second excitation pulse. A buffer amplifier to which the first excitation pulse is input when power is supplied to the main circuit, and the second excitation pulse is input when power is not supplied to the main circuit, An excitation capacitor is connected in series between the buffer amplifier and the excitation coil, A charge removal circuit connected between both terminals of the excitation capacitor, Equipped with, The aforementioned buffer amplifier, The system is configured to generate a first excitation signal based on the first excitation pulse when the first excitation pulse is input, and to generate a second excitation signal based on the second excitation pulse when the second excitation pulse is input. The aforementioned charge removal circuit is When the input to the buffer amplifier is switched from the first excitation pulse to the second excitation pulse, the system is configured to remove the charge stored in the excitation capacitor before the switch. The excitation coil of the aforementioned rotation sensor is The excitation capacitor is configured to be energized by the first excitation signal or the second excitation signal. A steering control device characterized by the following features.

2. A steering control device that assists the driver's steering force by driving the vehicle's steering mechanism with an electric motor, A rotation sensor equipped with an excitation coil, which detects the rotational state of the rotor of the electric motor when the excitation coil is biased and outputs a rotation detection signal based on the rotational state, A main circuit is supplied with power when the vehicle is in operation, calculates the rotation speed and rotation angle of the electric motor based on the rotation detection signal output from the rotation sensor, controls the drive of the electric motor using the calculated rotation speed and rotation angle, and generates a first excitation pulse. A backup circuit is provided which is constantly powered, calculates the rotation speed and rotation angle of the electric motor based on the rotation detection signal output from the rotation sensor, transmits the calculated rotation speed and rotation angle to the main circuit when the main circuit is started, and generates a second excitation pulse. A buffer amplifier to which the first excitation pulse is input when power is supplied to the main circuit, and the second excitation pulse is input when power is not supplied to the main circuit, An excitation capacitor is connected in series between the buffer amplifier and the excitation coil, A pull-down resistor connected between the buffer amplifier and the excitation capacitor, Equipped with, The aforementioned buffer amplifier, The system is configured to generate a first excitation signal based on the first excitation pulse when the first excitation pulse is input, and to generate a second excitation signal based on the second excitation pulse when the second excitation pulse is input. The aforementioned pull-down resistor is When the first excitation pulse is input to the buffer amplifier, the excitation capacitor is configured to discharge the charge it has accumulated. The excitation coil of the aforementioned rotation sensor is The excitation capacitor is configured to be energized by the first excitation signal or the second excitation signal. A steering control device characterized by the following features.

3. A steering control device that assists the driver's steering force by driving the vehicle's steering mechanism with an electric motor, A rotation sensor equipped with an excitation coil, which detects the rotational state of the rotor of the electric motor when the excitation coil is biased and outputs a rotation detection signal based on the rotational state, A main circuit is supplied with power when the vehicle is in operation, calculates the rotation speed and rotation angle of the electric motor based on the rotation detection signal output from the rotation sensor, controls the drive of the electric motor using the calculated rotation speed and rotation angle, and generates a first excitation pulse. A backup circuit is provided which is constantly powered, calculates the rotation speed and rotation angle of the electric motor based on the rotation detection signal output from the rotation sensor, transmits the calculated rotation speed and rotation angle to the main circuit when the main circuit is started, and generates a second excitation pulse. A buffer amplifier to which the first excitation pulse is input when power is supplied to the main circuit, and the second excitation pulse is input when power is not supplied to the main circuit, An excitation capacitor is connected in series between the buffer amplifier and the excitation coil, A charge removal circuit connected between both terminals of the excitation capacitor, A pull-down resistor connected between the buffer amplifier and the excitation capacitor, Equipped with, The aforementioned buffer amplifier, The system is configured to generate a first excitation signal based on the first excitation pulse when the first excitation pulse is input, and to generate a second excitation signal based on the second excitation pulse when the second excitation pulse is input. The aforementioned charge removal circuit is When the input to the buffer amplifier is switched from the first excitation pulse to the second excitation pulse, the system is configured to remove the charge stored in the excitation capacitor before the switch. The aforementioned pull-down resistor is When the first excitation pulse is input to the buffer amplifier, the excitation capacitor is configured to discharge the charge it has accumulated. The excitation coil of the aforementioned rotation sensor is The excitation capacitor is configured to be energized by the first excitation signal or the second excitation signal. A steering control device characterized by the following features.

4. The charge removal circuit is composed of a discharge switching element that electrically connects or disconnects the terminals of the excitation capacitor. The steering control device according to claim 1.

5. The charge removal circuit is comprised of a discharge switching element that electrically connects or disconnects the terminals of the excitation capacitor. The steering control device according to claim 3.

6. The buffer amplifier includes a switching element connected to an excitation power supply, and is configured to generate the first excitation signal and the second excitation signal by controlling the switching element. A steering control device according to any one of claims 1 to 5, characterized by

7. The first excitation pulse and the second excitation pulse are input to the buffer amplifier via a low-pass filter. A steering control device according to any one of claims 1 to 5.

8. The rotation detection signal output from the rotation sensor is composed of a sine signal and a cosine signal corresponding to the rotational position of the rotor of the electric motor. The sine and cosine signals are configured to be input to the main circuit and the backup circuit via an amplification circuit. A steering control device according to any one of claims 1 to 5.

9. The first excitation signal is a continuously occurring normal excitation signal, and the second excitation signal is an intermittently occurring intermittent excitation signal. A steering control device according to any one of claims 1 to 5.

10. A vehicle comprising: steering wheels; a steering mechanism for steering the steering wheels; and a steering control device for applying assist torque to the steering mechanism to assist the steering force of the vehicle's driver, The steering control device is configured according to any one of claims 1 to 5. A vehicle characterized by the following features.