JP5024315B2 - Steering torque detection signal transmission device and steering torque detection signal reception device - Google Patents

Description

  The present invention relates to a torque detection device used in an electric power steering device for a vehicle for assisting a steering operation of a steering wheel by a driver.

  2. Description of the Related Art Conventionally, there is known an electric power steering device that applies a steering assist torque to a driver's steering operation. The electric power steering device detects a steering torque acting on the steering shaft by a torque sensor, calculates a target assist torque that increases as the steering torque increases, and obtains the calculated target assist torque. Feedback control of the energization amount.

  In the electric power steering apparatus, in order to improve the reliability, two sets of torque sensors are provided and the detection signals of both torque sensors are transmitted to an assist ECU (electronic control unit). Are known. The two sets of torque sensors are unitized as a torque sensor unit. The torque sensor unit is connected to the assist ECU via a wire harness, receives power from the assist ECU, and outputs detection signals of the torque sensors to the assist ECU via two signal lines.

JP-A-10-197367

  However, in the conventional apparatus, if one of the two signal lines is disconnected, the sensor information is reduced to one type. That is, since it is configured to transmit only one type of sensor information to one signal line, when one signal line is disconnected, sensor information of one torque sensor is not transmitted. For this reason, the reliability of the sensor output cannot be secured, the steering assist control is stopped, and the comfort is impaired.

  Further, in order to improve the reliability of the sensor output, when configuring a triple steering torque detection system in which the torque sensor unit is provided with three torque sensors, when trying to transmit three types of sensor information to the assist ECU, The number of wirings of the wire harness further increases. For example, as shown in FIG. 4, a total of nine power supply lines LpA, LpB, LpC, ground lines LgA, LgB, LgC, and signal lines LsA, LsB, LsC are provided for each of the torque sensors A, B, C. Wiring is required. Also in this configuration, if one of the signal lines is disconnected, the sensor information of the torque sensor in which the disconnection has occurred cannot be output to the assist ECU.

  The present invention has been made to address the above-described problem. In the case where a triple steering torque detection system is configured by providing three torque sensors, both wire saving and improved reliability against disconnection are achieved. The purpose is to let you.

In order to achieve the above object, the feature of the steering torque detection signal transmitting device of the present invention is:
A steering torque detection signal that includes three steering torque sensors that detect steering torque acting on the steering shaft, and that transmits torque detection signals of the three steering torque sensors to an assist control device that drives and controls the electric motor of the electric power steering device. In the transmission device,
A power supply circuit for receiving a sine wave power supply from the assist control device via two power supply lines and a cosine wave power supply whose phase is shifted by π / 2 with respect to the sine wave power supply and converting the received power into a DC power supply;
A modulation signal generating means for generating a sine wave signal from the sine wave power source and generating a cosine wave signal from the cosine wave power source;
A first torque modulation signal obtained by superimposing the sine wave signal on a torque detection signal output from the first steering torque sensor of the three steering torque sensors; and a second steering torque sensor of the three steering torque sensors. A second torque modulation signal in which the cosine wave signal is superimposed on the torque detection signal to be output and a third torque signal in which the sine wave signal is superimposed on the torque detection signal output from the third steering torque sensor among the three steering torque sensors. Torque signal modulation means for generating a torque modulation signal and a fourth torque modulation signal in which the cosine wave signal is superimposed on the torque detection signal output from the third steering torque sensor;
A first output signal obtained by adding the first torque modulation signal, the second torque modulation signal, and the third torque modulation signal; the first torque modulation signal; the second torque modulation signal; and the fourth torque modulation signal. Output signal generating means for generating a second output signal obtained by adding the second output signal to the assist control device, and transmitting the first output signal to the assist control device via a first signal line. It is to transmit via the second signal line.

  In the steering torque detection signal transmission device of the present invention, the sine wave power source and the cosine wave power source are supplied from the assist control device via separate power supply lines (two in total). The power supplied from the assist control device is received by the power supply circuit and converted into a DC power supply, which is used as a power supply in the steering torque detection signal transmitting device. The steering torque detection signal transmitting device is provided with a first steering torque sensor, a second steering torque sensor, and a third steering torque sensor, and detects steering torque acting on the steering shaft. The steering torque detection signal transmitting device modulates a torque detection signal, which is steering torque information detected for each steering torque sensor, and transmits the modulated torque detection signal to the assist control device. The modulation signal generating means generates a sine wave signal from the sine wave power source and a cosine wave signal from the cosine wave power source as a modulation signal for modulating the torque detection signal. The sine wave signal and cosine wave signal are supplied to the torque signal modulating means.

  The torque signal modulation means includes a first torque modulation signal in which a sine wave signal is superimposed on a torque detection signal output from the first steering torque sensor, and a cosine wave signal in which a cosine wave signal is superimposed on a torque detection signal output from the second steering torque sensor. A second torque modulation signal, a third torque modulation signal in which a sine wave signal is superimposed on a torque detection signal output from the third steering torque sensor, and a cosine wave signal superimposed on a torque detection signal output from the third steering torque sensor. 4 torque modulation signals are generated.

  For example, when the torque detection signal output from the first steering torque sensor is T1, the torque detection signal output from the second steering torque sensor is T2, and the torque detection signal output from the third steering torque sensor is T3, the first torque The modulation signal is represented as T1 × sin (ωt), the second torque modulation signal is represented as T2 × cos (ωt), the third torque modulation signal is represented as T3 × sin (ωt), and the fourth torque modulation signal. Is expressed as T3 × cos (ωt). The torque signal modulation means supplies these four modulation signals to the output signal generation means.

  The output signal generation means includes a first output signal obtained by adding the first torque modulation signal, the second torque modulation signal, and the third torque modulation signal, the first torque modulation signal, the second torque modulation signal, and the fourth torque modulation signal. Are added to generate a second output signal. For example, the first output signal is expressed as T1 × sin (ωt) + T2 × cos (ωt) + T3 × sin (ωt), and the second output signal is T1 × sin (ωt) + T2 × cos (ωt) + T3 ×. Expressed as cos (ωt).

  The steering torque detection signal transmission device transmits a first output signal to the assist control device via the first signal line, and transmits a second output signal via the second signal line. Therefore, each signal line includes steering torque information that is a detection result of the three steering torque sensors. Therefore, as many signal lines as the number of steering torque sensors are not required. Also, even if one of the signal lines is disconnected, three pieces of steering torque information can be transmitted. Furthermore, power is supplied to the power supply circuit from the two power supply lines, converted to DC power by the power supply circuit, and supplied to the electric load in the steering torque detection signal transmitting device, so that one of the power supply lines is disconnected. Even so, the power supply can be maintained. As a result, when three steering torque sensors are provided to configure a triple steering torque detection system, both wire saving and improved reliability against disconnection can be achieved.

Another feature of the present invention is that
A steering torque detection signal receiving device connected to the steering torque detection signal transmitting device according to claim 1 provided in the assist control device,
A power supply circuit for supplying the sine wave power supply and the cosine wave power supply to the power supply circuit of the steering torque detection signal transmitting device via the two power supply lines;
A first signal in which the first output signal and the second output signal are received via the first signal line and the second signal line, and a sine wave signal synchronized with the sine wave power source is superimposed on the first output signal; A second signal in which a cosine wave signal synchronized with the cosine wave power source is superimposed on the first output signal, a third signal in which the sine wave signal is superimposed on the second output signal, and the second output signal Torque extraction signal generating means for generating a fourth signal on which the cosine wave signal is superimposed;
For the first signal and the third signal, a signal output when the signal phase angle is π / 2 is obtained, and for the second signal and the fourth signal, the signal phase angle is 0. And a torque detection signal extracting means for acquiring a signal output at the time of

In the steering torque detection signal receiving device of the present invention, a sine wave power source and a cosine wave power source are supplied to the power circuit of the steering torque detection signal transmission device via two power supply lines. Further, the first output signal and the second output signal output from the steering torque detection signal transmission device are received via the two signal lines. The torque extraction signal generation means includes a first signal obtained by superimposing a sine wave signal on the received first output signal,
A second signal in which a cosine wave signal is superimposed on the first output signal, a third signal in which a sine wave signal is superimposed on the second output signal, and a fourth signal in which the cosine wave signal is superimposed on the second output signal are generated. . This sine wave signal is synchronized with the sine wave power source (the phase and the period are equal) and becomes a signal having the same waveform as the sine wave signal generated by the steering torque detection signal transmission device. Further, the cosine wave signal is synchronized with the cosine wave power source (the phase and the period are equal), and becomes a signal having the same waveform as the cosine wave signal generated by the steering torque detection signal transmission device.

Therefore, for example, the first signal can be expressed as T1 × sin ² (ωt) + T2 × sin (ωt) × cos (ωt) + T3 × sin ² (ωt). Similarly, the second signal can be expressed as T1 × sin (ωt) × cos (ωt) + T2 × cos ² (ωt) + T3 × sin (ωt) × cos (ωt), and the third signal is T1 × sin ² (ωt) + T2 × sin (ωt) × cos (ωt) + T3 × sin (ωt) × cos (ωt), and the fourth signal is T1 × sin (ωt) × cos (ωt) + T2. Xcos ² (ωt) + T3 × cos ² (ωt).

Further, the first signal to the fourth signal can be modified as follows.
First signal: (T1 + T3) × sin ² (ωt) + T2 × sin (2ωt) / 2
Second signal: (T1 + T3) × sin (2ωt) / 2 + T2 × cos ² (ωt)
Third signal: T1 × sin ² (ωt) + (T2 + T3) × sin (2ωt) / 2
Fourth signal: T1 × sin (2ωt) / 2 + (T2 + T3) × cos ² (ωt)

Then, the torque detection signal extracting means obtains a signal output when the signal phase angle (ωt) is π / 2 for the first signal and the third signal, and for the second signal and the fourth signal. Thus, the signal output when the signal phase angle becomes 0 is acquired. For example, in the above equation, when the signal phase angle (ωt) is π / 2, since sin ² (ωt) = 1 and sin (2ωt) = 0, the first signal is (T1 + T3), and the third signal Becomes T1. Similarly, in the above equation, when the signal phase angle (ωt) is 0, cos ² (ωt) = 1 and sin (2ωt) = 0, so that the second signal is T2 and the fourth signal is (T2 + T3). ) In obtaining the signal output, the analog signal may be obtained by converting it into a digital value using an A / D converter.

  As a result, three types of steering torque information can be extracted from the two output signals received via the two signal lines. Also, even if one of the two signal lines is disconnected, three types of steering torque information can be extracted. Therefore, it is possible to reduce the line while maintaining high reliability.

1 is a schematic configuration diagram of an electric power steering apparatus including a steering torque detection signal transmission device and a steering torque detection signal reception device as an embodiment. It is a block diagram of the torque sensor unit as an embodiment. It is a block diagram of the steering torque detection part in the assist calculating part as embodiment. FIG. 3 is a wiring configuration diagram of a triple steering torque detection system that is not wire-saving.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an electric power steering system including a steering torque detection signal transmission device and a steering torque detection signal reception device as an embodiment.

  The electric power steering device for a vehicle includes a steering mechanism 10 that steers left and right front wheels FW1 and FW that are steered wheels by steering a steering handle 11, and a power assist unit 20 that is provided in the steering mechanism 10 and generates steering assist torque. And an assist control device 30 (hereinafter referred to as an assist ECU 30) for driving and controlling the electric motor 21 of the power assist unit 20, a vehicle speed sensor 40, and a torque sensor unit 100.

  The steering mechanism 10 includes a steering shaft 12 that is connected to a steering handle 11 so as to integrally rotate at an upper end, and a pinion gear 13 is connected to a lower end of the steering shaft 12 so as to rotate integrally. The pinion gear 13 meshes with rack teeth formed on the rack bar 14 to constitute a rack and pinion mechanism. Left and right front wheels FW1, FW2 are connected to both ends of the rack bar 14 via a tie rod and a knuckle arm (not shown) so as to be steerable. The left and right front wheels FW1 and FW2 are steered to the left and right according to the axial displacement of the rack bar 14 as the steering shaft 12 rotates about the axis.

  A power assist unit 20 is assembled to the rack bar 14. The power assist unit 20 includes a steering assist electric motor 21 (for example, a brushless motor) and a ball screw mechanism 22. The rotating shaft of the electric motor 21 is connected to the rack bar 14 through the ball screw mechanism 22 so as to be able to transmit power, and assists the steering of the left and right front wheels FW1, FW2 by the rotation. The ball screw mechanism 22 functions as a speed reducer and a rotation-linear converter, and decelerates the rotation of the electric motor 21 and converts it into a linear motion and transmits it to the rack bar 14.

  The assist ECU 30 includes an assist calculation unit 31 including a microcomputer including a CPU, a ROM, a RAM, an A / D converter, and the like as main parts, and a motor drive circuit 32. The motor drive circuit 32 receives the PWM control signal from the assist calculation unit 31 and controls the duty ratio of the internal switching element to adjust the energization amount to the electric motor 21. The motor drive circuit 32 is provided with a current sensor 33 that detects a current flowing through the electric motor 21.

  The assist calculation unit 31 connects the current sensor 33, the vehicle speed sensor 40, and the torque sensor unit 100. The vehicle speed sensor 40 outputs a vehicle speed detection signal representing the vehicle speed. The torque sensor unit 100 detects a steering torque that acts on the steering shaft 12 by a turning operation of the steering handle 11, and will be described later.

  Next, the steering assist control performed by the assist calculation unit 31 will be briefly described. The assist calculation unit 31 acquires a vehicle speed and a steering torque based on detection signals from the vehicle speed sensor 40 and the torque sensor unit 100, and calculates a target assist torque based on the acquired vehicle speed and the steering torque. The target assist torque is set so as to increase as the steering torque increases and to decrease as the vehicle speed increases with reference to an assist map (not shown). Then, a target current necessary to generate the target assist torque is calculated, and a target command is calculated using a PI control (proportional integral control) equation based on the deviation between the actual current detected by the current sensor and the target current. The voltage is calculated and a PWM control signal corresponding to the target command voltage is output to the motor drive circuit 32. Thus, a target current that rotates in the same direction as the driver's steering direction flows through the electric motor 21 by current feedback control, and assists the driver's steering operation appropriately.

  In order to appropriately perform such steering assist control, it is necessary to detect steering torque with high reliability. Therefore, in this embodiment, the steering torque is detected with the following configuration.

  First, the torque sensor unit 100 will be described. FIG. 2 is a schematic configuration diagram of the torque sensor unit 100. The torque sensor unit 100 (hereinafter referred to as the sensor unit 100) corresponds to the steering torque detection signal transmission device of the present invention, and includes two power supply lines Lp1 and Lp2, and two signal lines Ls1 and Ls2. It is connected to the assist calculation unit 31 of the assist ECU 30 through three ground lines Lg1, Lg2, and Lg3.

  The sensor unit 100 includes a power supply circuit 110, a modulation signal generation unit 120, a torque sensor unit 130, a torque signal modulation unit 140, and an output signal generation unit 150.

  The power supply circuit 110 takes in power from the two power supply lines Lp1 and Lp2 and generates power for the circuit in the sensor unit 100. The power supply line Lp1 is supplied with a 12V sine wave power supply (a power supply whose voltage waveform is a sine wave) from the assist ECU 30, and the power supply line Lp2 is supplied with a 12V cosine wave power supply (a voltage waveform having a voltage waveform). The power to be a cosine wave is supplied. The sine wave power source and the cosine wave power source have the same period and are out of phase with each other by π / 2. The power supply circuit 110 includes in parallel power supply lead lines 113 and 114 for taking in power from the power supply lines Lp1 and Lp2 via the diodes 111 and 112, respectively, and smoothes the load side of the confluence of the power supply lines 113 and 114. The capacitor 115 and the regulator 116 are connected. The regulator 116 converts the input power supply to a voltage level (for example, 5 V) used in each circuit in the sensor unit 100, and supplies a stable DC power supply Vcc to each circuit. Since the power supply circuit 110 receives power supply from the two power supply lines Lp1 and Lp2, even if the power supply line Lp1 (Lp2) on one side is disconnected by adjusting the capacitance C of the capacitor 115, the sensor Power can be supplied to each circuit in the unit 100. In the present embodiment, the above configuration is adopted to simplify the circuit configuration. However, for example, a configuration in which rectification is performed using a diode bridge circuit may be used.

  The modulation signal generation unit 120 includes a sine wave generation circuit 121 that generates a 5V sine wave signal (sin (ωt)) from a 12V sine wave power supply, and a 5V cosine wave from the 12V cosine power supply. A cosine wave generation circuit 122 for generating a signal (cos (ωt)). The sine wave signal (sin (ωt)) and the cosine wave signal (cos (ωt)) are supplied to the torque signal modulator 140. The sine wave generation circuit 121 is set so that the output signal becomes high level when the power supply line Lp1 is disconnected. Similarly, the cosine wave generation circuit 122 is also set so that its output signal becomes high level when the power supply line Lp2 is disconnected.

  The torque sensor unit 130 includes a first torque sensor 131, a second torque sensor 132, and a third torque sensor 133. Each torque sensor 131, 132, 133 outputs a torque detection signal that represents the steering torque acting on the steering shaft 12. The torque detection signal output from the first torque sensor 131 is referred to as a first torque signal T1, the torque detection signal output from the second torque sensor 132 is referred to as a second torque signal T2, and is output from the third torque sensor 133. This torque detection signal is referred to as a third torque signal T3. Each torque sensor 131, 132, 133 is supplied with power from the power supply circuit 110, and the ground terminal is connected to the ground of the assist ECU 30 via the ground lines Lg 1, Lg 2, Lg 3. The first torque signal T1, the second torque signal T2, and the third torque signal T3 are supplied to the torque signal modulator 140.

  The torque signal modulation unit 140 includes a first multiplication circuit 141, a second multiplication circuit 142, a third multiplication circuit 143, and a fourth multiplication circuit 144. The first multiplication circuit 141 generates a signal obtained by superimposing the sine wave signal (sin (ωt)) output from the sine wave generation circuit 121 on the first torque signal T1 output from the first torque sensor 131, A signal representing the generated (T1 × sin (ωt)) is output. The second multiplication circuit 142 generates a signal obtained by superimposing the cosine wave signal (cos (ωt)) output from the cosine wave generation circuit 122 on the second torque signal T2 output from the second torque sensor 132, A signal representing the generated (T2 × cos (ωt)) is output. The third multiplication circuit 143 generates a signal obtained by superimposing the sine wave signal (sin (ωt)) output from the sine wave generation circuit 121 on the third torque signal T3 output from the third torque sensor 133, A signal representing the generated (T3 × sin (ωt)) is output. The fourth multiplication circuit 144 generates a signal obtained by superimposing the cosine wave signal (cos (ωt)) output from the cosine wave generation circuit 122 on the third torque signal T3 output from the third torque sensor 133, A signal representing the generated (T3 × cos (ωt)) is output. The signals generated by the multiplication circuits 141 to 144 are supplied to the output signal generation unit 150.

  The output signal generation unit 150 includes a first addition circuit 151, a second addition circuit 152, and a third addition circuit 153. The first adder circuit 151 generates a signal obtained by adding the output of the first multiplier circuit 141 (T1 × sin (ωt)) and the output of the second multiplier circuit 142 (T2 × cos (ωt)). A signal representing (T1 × sin (ωt) + T2 × cos (ωt)) is output. The second adder circuit 152 adds a signal obtained by adding the output of the first adder circuit 151 (T1 × sin (ωt) + T2 × cos (ωt)) and the output of the third multiplier circuit 143 (T3 × sin (ωt)). And a signal representing the generated (T1 × sin (ωt) + T2 × cos (ωt) + T3 × sin (ωt)) is output. A signal output from the second adder circuit 152 is referred to as a first output signal S1. The third adder circuit 153 adds a signal obtained by adding the output of the first adder circuit 151 (T1 × sin (ωt) + T2 × cos (ωt)) and the output of the fourth multiplier circuit 144 (T3 × cos (ωt)). And a signal representing the generated (T1 × sin (ωt) + T2 × cos (ωt) + T3 × cos (ωt)) is output. A signal output from the third addition circuit 153 is referred to as a second output signal S2.

  The first output signal S1 and the second output signal S2 generated by the output signal generation unit 150 are transmitted to the assist calculation unit 31 of the assist ECU 30 via the signal lines Ls1 and Ls2, respectively.

  As described above, in the sensor unit 100, the modulation signal of the first torque signal T1, the modulation signal of the second torque signal T2, and the modulation signal of the third torque signal are added to the assist calculation unit 31 of the assist ECU 30. First output signal S1 (= T1 × sin (ωt) + T2 × cos (ωt) + T3 × sin (ωt)), second output signal S2 (= T1 × sin (ωt) + T2 × cos (ωt) + T3 × cos ( ωt)) is output. Therefore, three types of torque information detected by the three torque sensors 131, 132, and 133 are placed on the signal lines Ls1 and Ls2, respectively.

  Next, the assist calculation unit 31 of the assist ECU 30 that receives the first output signal S1 and the second output signal S2 will be described. Here, only the configuration for receiving steering torque information and detecting steering torque will be described. FIG. 3 is a diagram illustrating a configuration of the steering torque detection unit 200 provided in the assist calculation unit 31. The steering torque detector 200 corresponds to the steering torque detection signal receiving device of the present invention.

  The steering torque detection unit 200 includes a power supply unit 210, a torque extraction signal generation unit 220, and a microcomputer 230.

  The power supply unit 210 supplies sine wave power and cosine wave power to the sensor unit 100, and includes a pulse generator 211, a sine wave generation circuit 212, a cosine wave generation circuit 213, a first multiplication circuit 214, and a second multiplication circuit. 214.

  The pulse generator 211 generates a rectangular wave signal having a preset frequency f, and supplies the rectangular wave signal to the sine wave generation circuit 212 and the cosine wave generation circuit 213. The sine wave generation circuit 212 generates a rectangular wave signal that is inverted at the rising edge of the rectangular wave signal supplied from the pulse generator 211, and performs a band-pass filter process on the rectangular wave signal to remove a DC component. Extracts a sine wave signal. The sine wave generation circuit 212 outputs a sine wave signal having a frequency of f / 2 because the rectangular wave signal supplied from the pulse generator 211 is divided. Further, the cosine wave generation circuit 213 generates a rectangular wave signal that is inverted at the falling edge of the rectangular wave signal supplied from the pulse generator 211, and performs a band-pass filter process on the rectangular wave signal to thereby generate a DC component. The cosine wave signal is extracted. The cosine wave generation circuit 213 outputs a cosine wave signal having the same frequency f / 2 that is shifted in phase by π / 2 from the sine wave signal in the sine wave generation circuit 212.

  The first multiplication circuit 214 superimposes the sine wave signal (sin (ωt)) output from the sine wave generation circuit 212 on the 12V DC power supply V supplied from an in-vehicle battery (not shown), and the voltage waveform becomes ( A sine wave power supply of V × sin (ωt)) is output. The second multiplication circuit 215 superimposes the cosine wave signal (cos (ωt)) output from the cosine wave generation circuit 213 on the 12V DC power supply V supplied from an in-vehicle battery (not shown), and the voltage waveform becomes ( A cosine wave power source of V × cos (ωt)) is output.

  The torque extraction signal generator 220 generates a sine wave signal (sin (ωt)) and a cosine wave signal (cos (ωt)) for each of the first output signal S1 and the second output signal S2 output from the sensor unit 100. The first multiplication circuit 221, the second multiplication circuit 222, the third multiplication circuit 223, and the fourth multiplication circuit 224 are provided.

The first multiplication circuit 221 is a first signal obtained by superimposing a sine wave signal (sin (ωt)) on the first output signal S1 (= T1 × sin (ωt) + T2 × cos (ωt) + T3 × sin (ωt)). X1 is generated. Therefore, the first signal X1 output from the first multiplication circuit 221 is expressed by the following equation.
X1 = S1 × sin (ωt)
= T1 × sin ² (ωt) + T2 × sin (ωt) × cos (ωt) + T3 × sin ² (ωt)
= (T1 + T3) × sin ² (ωt) + T2 × sin (2ωt) / 2 Formula (1)

The second multiplication circuit 222 is a second signal obtained by superimposing a cosine wave signal (cos (ωt)) on the first output signal S1 (= T1 × sin (ωt) + T2 × cos (ωt) + T3 × sin (ωt)). X2 is generated. Therefore, the second signal X2 output from the second multiplication circuit 222 is expressed by the following equation.
X2 = S1 × cos (ωt)
= T1 × sin (ωt) × cos (ωt) + T2 × cos ² (ωt) + T3 × sin (ωt) × cos (ωt)
= (T1 + T3) × sin (2ωt) / 2 + T2 × cos ² (ωt) Equation (2)

The third multiplication circuit 223 is a third signal obtained by superimposing a sine wave signal (sin (ωt)) on the second output signal S2 (= T1 × sin (ωt) + T2 × cos (ωt) + T3 × cos (ωt)). X3 is generated. Therefore, the third signal X3 output from the third multiplication circuit 223 is expressed by the following equation.
X3 = S2 × sin (ωt)
= T1 × sin ² (ωt) + T2 × sin (ωt) × cos (ωt) + T3 × sin (ωt) × cos (ωt)
= T1 × sin ² (ωt) + (T2 + T3) × sin (2ωt) / 2 Formula (3)

The fourth multiplication circuit 224 is a fourth signal obtained by superimposing a cosine wave signal (cos (ωt)) on the second output signal S2 (= T1 × sin (ωt) + T2 × cos (ωt) + T3 × cos (ωt)). X4 is generated. Therefore, the fourth signal X4 output from the fourth multiplication circuit 224 is expressed by the following equation.
X4 = S2 × cos (ωt)
= T1 × sin (ωt) × cos (ωt) + T2 × cos ² (ωt) + T3 × cos ² (ωt)
= T1 × sin (2ωt) / 2 + (T2 + T3) × cos ² (ωt) Equation (4)

  The first signal X1, the second signal X2, the third signal X3, and the fourth signal X4 generated by the torque extraction signal generation unit 220 are supplied to the microcomputer 230. The microcomputer 230 includes A / D converters 231, 232, 233, and 234, and the first signal X1, the second signal X2, the third signal X3, and the fourth signal X4 are converted into A / D converters 231 and 231, respectively. In 232, 233, and 234, it converts into a digital value and takes in.

Here, when ωt = π / 2, sin ² (ωt) = 1 and sin (2ωt) = 0, so from the equation (1), X1 = (T1 + T3) × 1 + T2 × 0/2 = T1 + T3
Similarly, from equation (3), X3 = T1 × 1 + (T2 + T3) × 0/2 = T1
Thereby, only the first torque signal T1 can be extracted from the third signal X3. Further, only the third torque signal T3 can be extracted from the first signal X1 and the third signal X3.

Further, when ωt = 0, cos ² (ωt) = 1 and sin (2ωt) = 0, and therefore, from equation (2), X2 = (T1 + T3) × 0/2 + T2 × 1 = T2
Similarly, from equation (4), X4 = T1 × 0/2 + (T2 + T3) × 1 = T2 + T3
Thereby, only the second torque signal T2 can be extracted from the second signal X2. Further, only the third torque signal T3 can be extracted from the second signal X2 and the fourth signal X4.

  The microcomputer 230 receives the rectangular wave signal output from the pulse generator 211, grasps the phase angle (ωt) of the signals X1 to X4 from the rectangular wave signal, and determines the timing (ωt) based on the phase angle (ωt). Detected by the first torque sensor 131, the second torque sensor 132, and the third torque sensor 133 by issuing A / D conversion triggers to the A / D converters 231 to 234 at ωt = 0, π / 2). It is possible to acquire information representing the steering torque that has been performed.

  In this case, the microcomputer 230 converts the first signal X1 and the third signal X3 into digital values and reads them at a timing when ωt = π / 2, and the first torque sensor 131 detects the value from the value of the third signal X3. The obtained first torque information is acquired. Further, the third torque information detected by the third torque sensor 133 is acquired by subtracting the value of the third signal X3 from the value of the first signal X1.

  Further, the microcomputer 230 converts the second signal X2 and the fourth signal X4 into digital values and reads them at the timing when ωt = 0, and the second torque sensor 132 detects the second signal X2 from the value of the second signal X2. 2Torque information is acquired. Further, the third torque information detected by the third torque sensor 133 is acquired by subtracting the value of the second signal X2 from the value of the fourth signal X4.

  As a result, the torque information detected by the three torque sensors 131, 132, 133 is separated and extracted by the steering torque detector 200 from the first output signal S1 and the second output signal S2 transmitted from the sensor unit 100. Can do.

  When it is difficult to directly input an A / D conversion trigger to the microcomputer 230, a sample hold circuit (not shown) is provided outside, and the signal amplitude at ωt = π / 2 is set for the signals X1 and X3. For the signals X2 and X4, the signal amplitude at ωt = 0 may be temporarily held. In this case, the microcomputer 230 only needs to complete the A / D conversion by the next sample time, so that the design freedom of the microcomputer 230 and software can be increased.

  Next, fail safe will be described. As described above, the power supply circuit 110 inputs the sine wave power supply and the cosine wave power supply in parallel from the two power supply lines Lp1 and Lp2 and smoothes them by the diodes 111 and 112 and the capacitor 115. Even when the line Lp1 (Lp2) is disconnected, it is possible to supply power to each circuit in the sensor unit 100.

In addition, in the modulation signal generation unit 120, the sine wave generation circuit 121 and the cosine wave generation circuit 122 are set so that when the power supply lines Lp1 and Lp2 are disconnected, the output signal on the disconnection side becomes high level. ing. Therefore, for example, when the power supply line Lp1 is disconnected, the output of the sine wave generation circuit 121 is held at a high level (sin (ωt) = 1). For this reason, the first output signal S1 and the second output signal S2 output from the output signal generation unit 150 are expressed by the following equations.
S1 = T1 + T2 × cos (ωt) + T3
S2 = T1 + T2 × cos (ωt) + T3 × cos (ωt)

In this case, in the steering torque detector 200, the first signal X1 and the third signal X3 are expressed by the following equations.
X1 = S1 × sin (ωt)
= T1 x sin (ωt) + T2 x sin (ωt) x cos (ωt) + T3 x sin (ωt)
= (T1 + T3) × sin (ωt) + T2 × sin (2ωt) / 2 Equation (5)
X3 = S2 × sin (ωt)
= T1 x sin (ωt) + T2 x sin (ωt) x cos (ωt) + T3 x sin (ωt) x cos (ωt)
= T1 × sin (ωt) + (T2 + T3) × sin (2ωt) / 2 Equation (6)

Here, when ωt = π / 2, sin (ωt) = 1 and sin (2ωt) = 0, so from the equation (5), X1 = (T1 + T3) × 1 + T2 × 0/2 = T1 + T3
Similarly, from Equation (6), X3 = T1 × 1 + (T2 + T3) × 0/2 = T1
Thereby, the first torque information detected by the first torque sensor 131 can be acquired from the value of the third signal X3. Further, the third torque information detected by the third torque sensor 133 can be acquired by subtracting the value of the third signal X3 from the value of the first signal X1.

When the power supply line Lp2 is disconnected, the output of the cosine wave generation circuit 122 is held at a high level (cos (ωt) = 1). For this reason, the first output signal S1 and the second output signal S2 output from the output signal generation unit 150 are expressed by the following equations.
S1 = T1 × sin (ωt) + T2 + T3 × sin (ωt)
S2 = T1 × sin (ωt) + T2 + T3

In this case, in the steering torque detector 200, the second signal X2 and the fourth signal X4 are expressed by the following equations.
X2 = S1 × cos (ωt)
= T1 × sin (ωt) × cos (ωt) + T2 × cos (ωt) + T3 × sin (ωt) × cos (ωt)
= (T1 + T3) × sin (2ωt) / 2 + T2 × cos (ωt) Equation (7)
X4 = S2 × cos (ωt)
= T1 × sin (ωt) × cos (ωt) + T2 × cos (ωt) + T3 × cos (ωt)
= T1 × sin (2ωt) / 2 + (T2 + T3) × cos (ωt) Equation (8)

Here, when ωt = 0, cos (ωt) = 1 and sin (2ωt) = 0, and therefore, from equation (7), X2 = (T1 + T3) × 0/2 + T2 × 1 = T2
Similarly, from equation (8), X4 = T1 × 0/2 + (T2 + T3) × 1 = T2 + T3
Thereby, the second torque information detected by the second torque sensor 132 can be acquired from the value of the second signal X2. Further, the third torque information detected by the third torque sensor 133 can be acquired by subtracting the value of the second signal X2 from the value of the fourth signal X4.

  As a result, even if one of the power supply lines Lp1 and Lp2 is disconnected, three types of torque information can be acquired regardless of the normal time.

Next, fail safe for the disconnection of the signal lines Ls1 and Ls2 will be described. For example, when the signal line Ls1 is disconnected, the first output signal S1 is zero (S1 = 0). Therefore, in the steering torque detection unit 200, at the time of detecting the first signal X1 and the third signal X3 where the phase angle ωt = π / 2,
X1 = 0
X3 = T1
It becomes.
At the time of detecting the second signal X2 and the fourth signal X4 where the phase angle ωt = 0,
X2 = 0
X4 = T2 + T3
It becomes.

Usually, T1 = T2 = T3, so
T1 = (T2 + T3) / 2 Formula (8)
The following relational expression should hold. Therefore, the microcomputer 230 determines whether or not the equation (8) is established based on the value of the third signal X3 and the value of the fourth signal X4, and if so, the torque signals T1, T2, Assuming that T3 is normal, torque information is acquired from the third signal X3 and the fourth signal X4.

Similarly, when the signal line Ls2 is disconnected, the second output signal S2 is zero (S2 = 0). Therefore, in the steering torque detection unit 200, at the time of detecting the first signal X1 and the third signal X3 where the phase angle ωt = π / 2,
X1 = T1 + T3
X3 = 0
It becomes.
At the time of detecting the second signal X2 and the fourth signal X4 where the phase angle ωt = 0,
X2 = T2
X4 = 0
It becomes.

Usually, T1 = T2 = T3, so
T2 = (T1 + T3) / 2 Formula (9)
The following relational expression should hold. Therefore, the microcomputer 230 determines whether or not the formula (9) is established based on the values of the first signal X1 and the second signal X2, and if so, the torque signals T1, T2, Assuming that T3 is normal, torque information is acquired from the first signal X1 and the second signal X2.

  According to the present embodiment described above, the sine wave power source and the cosine wave power source are supplied to the sensor unit 100 from the steering torque detection unit 200 of the assist ECU 30 via the power supply lines Lp1 and Lp2. Output signals S1 and S2 obtained by modulating various types of torque detection signals using a sine wave signal and a cosine wave signal are transmitted to the steering torque detection unit 200 via signal lines Ls1 and Ls2. Then, the steering torque detector 200 generates signals X1 to X4 obtained by superimposing the sine wave signal and the cosine wave signal on the output signals S1 and S2, and at the timing when the signal phase angle becomes ωt = π / 2 and 0. The signals X1 and X3 and the signals X2 and X4 are read to detect the steering torque. Accordingly, three types of steering torque information can be acquired separately by the two signal lines Ls1 and Ls2. Further, even if one of the signal lines Ls1 and Ls2 is disconnected, three types of steering torque information can be acquired. In addition, since power is supplied from the assist ECU 30 to the power supply circuit 110 of the sensor unit 100 via the two power supply lines Lp1 and Lp2, and the DC power is supplied to the electric load in the sensor unit 100 by the power supply circuit 110, It also has a power backup function against disconnection. In addition, the disconnection of one of the power supply lines Lp1 and Lp2 does not affect the acquisition of steering torque information. As a result, it is possible to achieve both improvement in reliability and line saving.

  Although the present embodiment has been described above, the present invention is not limited to the above-described embodiment, and various modifications can be employed within the scope of the present invention.

  DESCRIPTION OF SYMBOLS 10 ... Steering mechanism, 11 ... Steering handle, 12 ... Steering shaft, 20 ... Power assist part, 21 ... Electric motor, 30 ... Assist control device, 31 ... Assist calculation part, 32 ... Motor drive circuit, 100 ... Torque sensor unit DESCRIPTION OF SYMBOLS 110 ... Power supply circuit 120 ... Modulation signal generation part 121 ... Sine wave generation circuit 122 ... Cosine wave generation circuit 130 ... Torque sensor part 131, 132, 133 ... 1st-3rd torque sensor 140 ... Torque signal modulator 141, 142, 143, 144 ... 1st to 4th multiplier circuit, 150 ... output signal generator, 151, 152, 153 ... 1st to 3rd adder circuit, 200 ... steering torque detector, 210 DESCRIPTION OF SYMBOLS ... Power supply part 211 ... Pulse generator 212 ... Sine wave generation circuit 213 ... Cosine wave generation circuit 214, 215 ... 1st-2nd multiplication circuit, DESCRIPTION OF SYMBOLS 20 ... Torque extraction signal generation part, 221, 222, 223, 224 ... 1st-4th multiplication circuit, 230 ... Microcomputer, Lp1, Lp2 ... Power supply line, Ls1, Ls2 ... Signal line, Lg1, Lg2, Lg3 ... Ground lines, S1, S2 ... first to second output signals, T1, T2, T3 ... first to third torque signals, X1, X2, X3, X4 ... first to fourth signals.

Claims (2)

A steering torque detection signal that includes three steering torque sensors that detect steering torque acting on the steering shaft, and that transmits torque detection signals of the three steering torque sensors to an assist control device that drives and controls the electric motor of the electric power steering device. In the transmission device,
A power supply circuit for receiving a sine wave power supply from the assist control device via two power supply lines and a cosine wave power supply whose phase is shifted by π / 2 with respect to the sine wave power supply and converting the received power into a DC power supply;
A modulation signal generating means for generating a sine wave signal from the sine wave power source and generating a cosine wave signal from the cosine wave power source;
A first torque modulation signal obtained by superimposing the sine wave signal on a torque detection signal output from the first steering torque sensor of the three steering torque sensors; and a second steering torque sensor of the three steering torque sensors. A second torque modulation signal in which the cosine wave signal is superimposed on the torque detection signal to be output and a third torque signal in which the sine wave signal is superimposed on the torque detection signal output from the third steering torque sensor among the three steering torque sensors. Torque signal modulation means for generating a torque modulation signal and a fourth torque modulation signal in which the cosine wave signal is superimposed on the torque detection signal output from the third steering torque sensor;
A first output signal obtained by adding the first torque modulation signal, the second torque modulation signal, and the third torque modulation signal; the first torque modulation signal; the second torque modulation signal; and the fourth torque modulation signal. Output signal generating means for generating a second output signal obtained by adding the second output signal to the assist control device, and transmitting the first output signal to the assist control device via a first signal line. A steering torque detection signal transmitting device that transmits the signal via a second signal line. A steering torque detection signal receiving device connected to the steering torque detection signal transmitting device according to claim 1 provided in the assist control device,
A power supply circuit for supplying the sine wave power supply and the cosine wave power supply to the power supply circuit of the steering torque detection signal transmitting device via the two power supply lines;
A first signal in which the first output signal and the second output signal are received via the first signal line and the second signal line, and a sine wave signal synchronized with the sine wave power source is superimposed on the first output signal; A second signal in which a cosine wave signal synchronized with the cosine wave power source is superimposed on the first output signal, a third signal in which the sine wave signal is superimposed on the second output signal, and the second output signal Torque extraction signal generating means for generating a fourth signal on which the cosine wave signal is superimposed;
For the first signal and the third signal, a signal output when the signal phase angle is π / 2 is obtained, and for the second signal and the fourth signal, the signal phase angle is 0. And a torque detection signal extracting means for acquiring a signal output when the steering torque detection signal is received.

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