JP5018577B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering device, and more particularly to an electric power steering device that diagnoses and determines the connection state between a detection coil of a non-contact torque sensor and other circuit elements.

  As a torque sensor applied to a conventional electric power steering device, a pair of detection coils whose impedances change in opposite directions according to the torque generated on the rotating shaft and a pair of resistors are individually connected in series. A so-called non-contact torque sensor is known in which an alternating voltage is applied to a bridge circuit and a torque is detected based on a differential voltage between the alternating voltages appearing at the terminal portions of the pair of detection coils (see, for example, Patent Document 1). ).

The detection coil and printed wiring board are connected by soldering, etc., but if the connection is not made securely due to poor soldering, contact resistance is generated between the detection coil or resistor and the printed wiring board, which is inaccurate. Here, an abnormal detection coil resistance is detected based on the phase difference between the waveform of the applied AC voltage and the waveform of the difference between the AC voltages appearing on the pair of detection coil terminals. To detect.
Japanese Patent No. 3649057

However, in the torque sensor described in Patent Document 1, since a method of monitoring phase fluctuations from the AC differential output of the pair of detection coils is applied, there is no difference between the pair of detection coils and the bridge circuit. Abnormality cannot be detected in a defective mode in which the impedance fluctuates in the same manner and the differential output does not change from normal.
Further, in the torque sensor described in Patent Document 1, since the operation of the non-contact torque sensor is accompanied when detecting an abnormality, the abnormal operation should be avoided in advance if the connection has been poor. I can't.

  Then, this invention makes it the subject to provide the electric power steering apparatus which can diagnose appropriately the connection state of the detection coil of a non-contact torque sensor, and a bridge circuit.

In order to solve the above problems, an electric power steering device according to a first aspect of the present invention includes a pair of detection coils whose impedances change in opposite directions according to torque generated on the rotating shaft, and a pair of resistors, respectively. A torque sensor that detects the steering torque based on the difference between the AC voltages appearing at the terminals of the pair of detection coils, and a driver's steering burden on the steering system. An electric power steering apparatus comprising: an electric motor that applies a steering assisting force that reduces power; and a control unit that drives and controls the electric motor based on at least a steering torque detected by the torque sensor,
An abnormality detection means for diagnosing the connection state of the detection coil based on a voltage generated between terminals of the detection coil when a current is applied to the detection coil or a voltage is applied to the detection coil when the torque sensor is not operated. And the abnormality detection means applies a predetermined current to one detection coil of the pair of detection coils, and detects the detection based on an inter-terminal voltage generated in the detection coil supplied with the predetermined current. It is characterized by diagnosing the connection state of the coil .

According to another aspect of the present invention, there is provided an electric power steering apparatus in which a pair of detection coils whose impedances change in opposite directions according to torque generated on a rotating shaft and a pair of resistors are individually connected in series. A torque sensor that applies an alternating voltage to the bridge circuit and detects a steering torque based on a difference between the alternating voltages appearing at the terminals of the pair of detection coils, and a steering assist force that reduces a driver's steering burden on the steering system An electric power steering apparatus comprising: an electric motor for applying a control signal; and a control unit that controls driving of the electric motor based on at least a steering torque detected by the torque sensor,
An abnormality detection means for diagnosing the connection state of the detection coil based on a voltage generated between terminals of the detection coil when a current is applied to the detection coil or a voltage is applied to the detection coil when the torque sensor is not operated. The abnormality detection means applies a predetermined voltage to one of the pair of detection coils, and based on an excitation voltage generated between the terminals of the other detection coil, It is characterized by diagnosing the connection status.

According to a third aspect of the present invention, in the electric power steering apparatus according to the second aspect , the abnormality detecting means applies a predetermined voltage to one of the pair of detection coils, and the other of the pair of detection coils. After diagnosing the connection state of both detection coils based on the excitation voltage generated between the terminals of the detection coil, a predetermined voltage is applied to the other detection coil and generated between the terminals of the one detection coil. Based on the excitation voltage, the connection state of both detection coils is diagnosed twice.

  According to the electric power steering device according to the present invention, when the non-contact torque sensor is not operated, when the current is applied to the detection coil or the voltage is applied, the voltage is generated between the terminals of the detection coil. Diagnoses the connection status of the detection coil, so that the impedance between the pair of detection coils and the bridge circuit will fluctuate in the same way, and even if it is in a defective mode where the differential output does not change from normal, abnormalities are reliably detected In addition, since the abnormality detection is performed when the non-contact torque sensor is not operated, it is possible to avoid the abnormal operation in advance even if the connection is poor.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a main part of an electric power steering apparatus according to the present invention, and FIG. 2 is a perspective view showing a configuration of a torque detector.
In the figure, reference numerals 5a and 5b denote housings, which have a two-part structure of an input shaft side 5a and an output shaft side 5b. Inside the housings 5a and 5b, an input shaft 1, a torsion bar 3 disposed therein, and an output shaft 2 connected to the input shaft 1 via the torsion bar 3 are rotated by bearings 6a, 6b and 6c. It is supported freely.

  The input shaft 1, the torsion bar 3, and the output shaft 2 are arranged coaxially. The input shaft 1 and the torsion bar 3 are spline-connected, and the torsion bar 3 and the output shaft 2 are also spline-connected. In FIG. 1, a steering wheel (not shown) is integrally attached to the left end side of the input shaft 1. Further, a pinion shaft 2a is formed integrally with the output shaft 2, and the pinion shaft 2a meshes with a rack 4 to constitute a known rack and pinion type steering mechanism.

  A worm wheel 7 that is coaxial with the output shaft 2 and rotates integrally therewith is fixed to the output shaft 2 and meshes with a worm 8 that is driven by an electric motor (not shown). In the worm wheel 7, a synthetic resin tooth portion 7b is integrally fixed to a metal hub 7a. The rotational force of the electric motor is transmitted to the output shaft 2 through the worm 8 and the worm wheel 7, and a steering assist torque in an arbitrary direction is applied to the output shaft 2 by appropriately switching the rotation direction of the electric motor.

Next, the configuration of the torque detector of the torque sensor will be described with reference to FIGS. The torque detection unit includes a sensor shaft portion 11 formed on the right end side in FIG. 1 of the input shaft 1, detection coils 13 and 14 disposed inside the housing 5a, and a cylindrical member 12 disposed therebetween. Composed.
FIG. 2 is a perspective view showing the configuration of the torque detector. A sensor shaft portion 11 made of a magnetic material is formed on the outer side of the input shaft 1 near the right end in FIG. 1, and a plurality of (in the illustrated example, axially extending) surfaces are formed on the surface of the sensor shaft portion 11. Nine) ridges 11a are formed at equal intervals along the circumferential direction, and groove portions 11b wider than the width t1 of the ridges 11a are formed between the ridges 11a.

Further, on the outside of the sensor shaft portion 11, a cylindrical member 12 made of a conductive and non-magnetic material, for example, aluminum, which is close to the sensor shaft portion 11, is arranged coaxially with the sensor shaft portion 11, The extension 12 e of the cylindrical member 12 is fixed to the outside of the end 2 e of the output shaft 2.
The cylindrical member 12 includes a plurality (9 in FIG. 2) of rectangular windows 12a arranged at equal intervals in the circumferential direction at positions facing the protrusions 11a on the surface of the sensor shaft portion 11 described above. A plurality of (9 in FIG. 2) rectangular windows having the same shape as the window 12a but having different phases in the circumferential direction at positions shifted in the axial direction from the first window row. And a second window row made of 12b.

  The outer periphery of the cylindrical member 12 is surrounded by a yoke 15 around which detection coils 13 and 14 of the same standard are wound. That is, the detection coils 13 and 14 are arranged coaxially with the cylindrical member 12, the detection coil 13 surrounds the first window row portion formed of the window 12a, and the detection coil 14 includes the second window row portion formed of the window 12b. Siege. The yoke 15 is fixed inside the housing 5a, and the output lines of the detection coils 13 and 14 are connected to a circuit board 16 arranged inside the housing 5a.

  FIGS. 3A and 3B are diagrams for explaining the protrusions on the surface of the sensor shaft portion and the window arrangement of the cylindrical member. FIG. 3A is a reference position (a state where the torsion bar 3 is not twisted). 3) shows the positional relationship between the projections 11a on the surface of the sensor shaft portion 11 and the windows 12a of the first window row in the cylindrical member 12, and FIG. 3 (b) shows the reference position (the state where the torsion bar 3 is not twisted). FIG. 6 is a diagram illustrating a positional relationship between the protrusions 11 a on the surface of the sensor shaft portion 11 and the windows 12 b of the second window row in the cylindrical member 12.

In this embodiment, since nine windows 12a and 12b are provided, the window 12a of the first window row and the window 12b of the second window row each have an angle θ = 360/9 = 40 in the circumferential direction. It will be shifted by degrees.
The angle a of the windows 12a and 12b is set smaller than the angle b of the portion without the windows 12a and 12b (a <b), and the angle c of the ridge 11a is set smaller than the angle d of the groove 11b (c <d). Is done. This is to make the change in impedance of the detection coil steep.

  As apparent from FIGS. 3A and 3B, when the torsion bar 3 is not twisted, that is, when the steering torque is zero (0), the sensor is located at the center of the circumferential width of the window 12a. One end portion in the circumferential direction of the ridge 11a of the shaft portion 11 is located, and the other end portion in the circumferential direction of the ridge 11a is located in the center portion of the width in the circumferential direction of the window 12b. The circumferential width of the windows 12a and 12b, the width of the ridge 11a, and the relative positional relationship of the windows 12a and 12b in the circumferential direction are set. That is, the positional relationship in the circumferential direction between the windows 12a and 12b with respect to the ridge 11a is opposite to each other.

When the steering system is in a straight traveling state and the steering torque is zero, the torsion bar 3 is not twisted and the input shaft 1 and the output shaft 2 do not rotate relative to each other. Therefore, relative rotation does not occur between the protrusion 11a on the surface of the sensor shaft portion 11 on the input shaft 1 side and the cylindrical member 12 on the output shaft 2 side.
On the other hand, when a rotational force is applied to the input shaft 1 by operating the steering wheel, the rotational force is transmitted to the output shaft 2 via the torsion bar 3. At this time, a frictional force such as a frictional force between the steered wheel and the road surface or a meshing gear of a steering mechanism coupled to the output shaft 2 acts on the output shaft 2. Torsion is generated in the torsion bar that joins between them, and relative rotation occurs between the protrusion 11a on the surface of the sensor shaft portion 11 on the input shaft 1 side and the cylindrical member 12 on the output shaft 2 side.

When the cylindrical member 12 has no window, the cylindrical member 12 is made of a conductive and nonmagnetic material. Therefore, when an alternating current is generated in the detection coils 13 and 14 to generate an alternating magnetic field, the cylindrical member 12 An eddy current in the direction opposite to the coil current is generated on the outer peripheral surface of the coil. When the magnetic field due to the eddy current and the magnetic field due to the coil current are superimposed, the magnetic field inside the cylindrical member 12 is canceled out.
When a window is formed in the cylindrical member 12, the eddy current generated on the outer peripheral surface of the cylindrical member 12 cannot circulate around the outer peripheral surface by the windows 12a and 12b. Therefore, the cylindrical member 12 is formed along the end surfaces of the windows 12a and 12b. Around the inner peripheral surface, flows in the same direction as the coil current, and returns to the outer peripheral surface along the end surfaces of the adjacent windows 12a and 12b to form a loop. That is, a state occurs in which eddy current loops are periodically arranged in the circumferential direction inside the detection coil.

The magnetic field generated by the coil current and the magnetic field generated by the eddy current are superimposed, and a magnetic field that periodically changes in strength in the circumferential direction and a magnetic field having a gradient in the radial direction that decreases toward the center are formed inside and outside the cylindrical member 12. It is formed. The strength of the periodic magnetic field in the circumferential direction is strong at the center of the windows 12a and 12b affected by the adjacent eddy currents, and becomes weaker as it deviates from the center.
A sensor shaft portion 11 made of a magnetic material is coaxially arranged inside the cylindrical member 12, and the ridges 11a are arranged at the same cycle as the windows 12a and 12b.

  A magnetic material placed in a magnetic field is magnetized to generate a magnetic flux, but the amount of magnetic flux increases according to the strength of the magnetic field until it is saturated. For this reason, the magnetic flux generated in the sensor shaft portion 11 by the cylindrical member 12 due to the strength of the periodic magnetic field in the circumferential direction and the magnetic field having a gradient in the radial direction that decreases toward the center is generated between the cylindrical member 12 and the sensor. It increases or decreases depending on the relative phase with the shaft portion 11.

The phase at which the magnetic flux is maximum is such that the centers of the windows 12a and 12b of the cylindrical member 12 and the center of the ridge 11a of the sensor shaft portion 11 coincide with each other, and the inductances of the detection coils 13 and 14 according to the increase and decrease of the magnetic flux. Increase / decrease and change to a substantially sinusoidal shape.
In the state where torque does not act, the center of the ridge 11a of the sensor shaft portion 11 is the ridge 11a with respect to the phase where the inductance is maximum (the phase where the windows 12a and 12b coincide with the center of the ridge 11a). Since the torque acts to twist the torsion bar 3 and a phase difference occurs between the sensor shaft portion 11 and the cylindrical member 12, One of the inductances of the detection coils 13 and 14 increases and the other decreases.

  FIG. 4 is a diagram for explaining the magnitude of torque and the change in inductance of the detection coils 13 and 14, where the horizontal axis indicates the torque T and the vertical axis indicates the inductance L. When the right steering torque is generated, the cylindrical member 12 rotates clockwise in FIGS. 3A and 3B. Therefore, as shown in FIG. 4, the inductance L13 of the detection coil 13 increases as the torque increases. The inductance L14 of the detection coil 14 decreases.

  Further, when the left steering torque is generated, the cylindrical member 12 rotates counterclockwise in FIGS. 3A and 3B, so that the inductance L13 of the detection coil 13 increases as the torque increases as shown in FIG. It decreases, and the inductance L14 of the detection coil 14 increases.

FIG. 5 is a block diagram of the torque detection circuit and the EPS control circuit of the first embodiment.
The power supply voltage V and the reference voltage Vref are supplied to each circuit element of the torque detection circuit 20 via the connector 29 and the noise filter 28, and the main detection torque signal and the sub detection torque signal detected by the torque detection circuit 20 are EPS. It is output to the control circuit 40.

The bridge circuit that detects torque includes a first arm in which the detection coil 13 and the resistor R1 are connected in series, and a second arm in which the detection coil 14 and the resistor R2 are connected in series.
The oscillating unit 21 is supplied with the power supply voltage V and the reference voltage Vref and outputs an alternating voltage having a predetermined frequency. The output AC voltage is amplified by the current amplifying unit 22, and the amplified AC voltage Vosc is generated by the first arm of the bridge circuit formed by the detection coil 13 and the resistor R1, and the detection coil 14 and the resistor R2. It is supplied to the second arm of the constructed bridge circuit. Note that the values of the resistors R1 and R2 are adjusted in advance so that the voltages appearing at both ends of the detection coils 13 and 14 are equal in a state where torque is not applied.

The voltage signals appearing at both ends of the detection coil 13 and the detection coil 14 are converted and amplified and rectified by the main amplification / full-wave rectification unit 23 into a difference signal between both detection coils, and the main smoothing / neutral adjustment unit 26. After the output waveform is adjusted, the signal is output to the EPS control circuit 40 as a main detection torque signal through the noise filter 28.
Further, the voltage signals appearing at both ends of the detection coil 13 and the detection coil 14 are converted into a difference signal between the detection coils by the sub-amplification / full-wave rectification unit 24, amplified and rectified, and further sub-smooth / neutral adjustment. After the output waveform is adjusted by the unit 27, it is output to the EPS control circuit 40 as a sub detection torque signal through the noise filter 28.

  As described above, the torque detection circuit 20 individually connects each of the pair of detection coils 13 and 14 whose impedances change in opposite directions according to the torque generated on the rotating shaft, and each of the pair of resistors R1 and R2. A so-called non-contact torque sensor that detects the torque transmitted to the steering system based on the differential voltage of the AC voltage appearing at the terminal portions of the pair of detection coils 13 and 14 by applying an AC voltage to the bridge circuit connected in series It works.

  Two sets of torque detection circuits 20 including a main amplification / full wave rectification unit 23 and a main smoothing / neutral adjustment unit 26 and a sub amplification / full wave rectification unit 24 and a sub smoothing / neutral adjustment unit 27 are provided. The reason why the signal is output is that the EPS control circuit 40 compares these two sets of signals so as to detect a disconnection or short circuit of the detection coil, a failure of a circuit element, or the like. is there.

In the torque detection circuit 20, a monitoring unit 25 is provided between the sub amplification / full wave rectification unit 24 and the sub smoothing / neutral adjustment unit 27. The monitoring unit 25 detects a contact failure between the detection coil 13 or 14 and the resistor R1 or R2 by increasing the contact resistance.
The EPS control circuit 40 is disposed close to the torque detection circuit 20, and is output from the torque sensor I / F 41 to which the steering torque signal output from the torque detection circuit 20 is input and the torque sensor I / F 41. A CPU 42 to which a steering torque T is input is provided. The CPU 42 calculates a steering assist command value based on at least the steering torque T, and drives and controls an electric motor (not shown) based on the steering assist command value. The steering assist control is performed to apply a steering assist force that reduces the steering burden on the driver.

  Further, the EPS control circuit 40 includes a diagnostic current generator 43 that generates a diagnostic current for diagnosing the connection state of the detection coil 13 or 14, and a diagnostic current when the diagnostic current is passed through the detection coil 13 or 14. A connection state diagnosing unit 44 that measures the voltage between the terminals of the detection coil 13 or 14, and a connection state of the detection coil 13 or 14 is diagnosed based on the measurement result of the connection state diagnosing unit 44, and the operation determination of the torque detection circuit 20 is made. And an operation determination unit 45 to perform.

Here, the diagnostic current generator 43 sends a diagnostic current to the detection coil 14 via the path 1 or the detection coil 13 via the path 2 according to the current generation signal Si output from the operation determination unit 45. On the other hand, a diagnostic current is passed.
In FIG. 5, the torque detection circuit 20 and the torque sensor I / F 41 correspond to the torque sensor, the CPU 42 corresponds to the control means, and the diagnostic current generator 43, the connection state diagnosis device 44, and the operation determination device 45 are the abnormality detection means. It corresponds to.

  FIG. 6 is a flowchart showing an operation determination processing procedure executed by the operation determiner 45. In this operation determination process, first, in step S1, it is determined whether or not the torque detection circuit 20 is in an inoperative state (initial diagnosis state, rest state, test mode, etc.). It is determined that the operation determination is not performed, and the operation determination process is terminated as it is.

In step S2, the operation determination unit 45 outputs a current generation signal Si to the diagnostic current generator 43, flows a diagnostic current into the detection coil 14 through the path 1, and proceeds to step S3. Here, the diagnostic current is set to a current value that allows the operation of the detection coil to be determined based on the voltage generated when the current is applied.
In step S3, the operation determination device 45 reads the voltage between the terminals of the detection coil 14 measured in the path 3 by the connection state diagnosis device 44, and proceeds to step S4.

In step S4, the operation determination unit 45 determines the connection state of the detection coil 14 based on the voltage between the terminals of the detection coil 14 read in step S3. Here, when the measured inter-terminal voltage is equal to or higher than the predetermined voltage, it is determined that the detection coil 14 is in a connected state (a state in which no contact failure occurs between the detection coil 14 and the resistor R2).
Next, in step S5, the operation determination unit 45 determines whether or not an abnormality has occurred in the detection coil 14 from the determination result in step S4. When an abnormality has occurred in the detection coil 14, the operation determination unit 45 proceeds to step S6. Then, after the torque detection circuit 20 prohibits the output of the detected torque, the operation determination process ends. On the other hand, when it is determined in step S5 that the detection coil 14 is in the connected state, it is determined that the operation determination process is continued, and the process proceeds to step S7.

In step S7, the operation determination unit 45 outputs a current generation signal Si to the diagnostic current generator 43, flows a diagnostic current into the detection coil 13 through the path 2, and proceeds to step S8.
In step S8, the operation determination device 45 reads the voltage between the terminals of the detection coil 13 measured in the path 4 by the connection state diagnostic device 44, and proceeds to step S9.

In step S9, the operation determination device 45 determines the connection state of the detection coil 13 based on the inter-terminal voltage of the detection coil 13 read in step S8. Here, when the measured inter-terminal voltage is equal to or higher than the predetermined voltage, it is determined that the detection coil 13 is in a connected state (a state in which no contact failure occurs between the detection coil 13 and the resistor R1).
Next, in step S10, the operation determination unit 45 determines whether or not an abnormality has occurred in the detection coil 13 from the determination result in step S9. If an abnormality has occurred in the detection coil 13, the operation determination unit 45 proceeds to step S6. When it is determined that the detection coil 13 is in the connected state, the operation determination process is terminated.

Next, operations and effects in the first embodiment will be described.
Now, assuming that the electric power steering device is in an initial diagnosis state and the torque detection circuit 20 is in an inoperative state, the operation determination process of the operation determination unit 45 of the EPS control circuit 40 determines Yes in step S1, When it is determined that the operation of the torque detection circuit 20 is to be determined, the process proceeds to step S2, and the current generation signal Si is output to the diagnostic current generator 43, whereby the diagnostic current is supplied to the detection coil 14 in the path 1. Pour.

  At this time, assuming that no abnormality such as poor contact has occurred in the detection coil 14, a voltage is generated between the terminals of the detection coil 14 when a current for diagnosis is applied to the detection coil 14. Based on the measured inter-terminal voltage of the detection coil 14, it is determined in step S4 that no abnormality has occurred in the detection coil 14, so that the determination in step S5 is No and the process proceeds to step S7. Shift to pass / fail diagnosis of the connection status

  That is, in step S 7, the current generation signal Si is output to the diagnostic current generator 43, thereby causing the diagnostic current to flow into the detection coil 13 through the path 2. At this time, assuming that no abnormality has occurred in the detection coil 13, a voltage is generated between the terminals of the detection coil 13 when a current for diagnosis is applied to the detection coil 13. Therefore, the detection measured in step S <b> 8. Based on the voltage between the terminals of the coil 13, it is determined in step S9 that no abnormality has occurred in the detection coil 13, and No is determined in step S10. As described above, when both the detection coils 13 and 14 are diagnosed as being in a normal connection state, the operation determination process is ended and torque detection by the torque detection circuit 20 is started.

  When the steering assist control process is started by the CPU 42 of the EPS control circuit 40, a steering assist command value is calculated based on the steering torque signal output from the torque detection circuit 20. At this time, when the vehicle is stopped and the steering wheel is not operated, the torsion bar 3 is not twisted and the input shaft 1 and the output shaft 2 do not rotate relative to each other. Therefore, since the steering torque signal of the steering torque “0” is output from the torque detection circuit 20, the steering assist command value calculated by the EPS control circuit 40 is also “0”. As a result, the electric motor continues to be stopped.

  When the vehicle starts from this state and the driver performs a steering operation in the right direction, the torsion bar 3 connecting the input shaft 1 and the output shaft 2 is twisted, and the inductances of the detection coils 13 and 14 are generated. In L13 and L14, as shown in FIG. 4, the inductance L13 increases and the inductance L14 decreases. As a result, a difference occurs in the AC voltage generated at the terminal portions of the detection coils 13 and 14 when an AC voltage is applied to the bridge circuit, and the steering torque corresponding to the twisting force of the torsion bar 3 is detected.

In the EPS control circuit 40, a steering assist command value is calculated based on the steering torque detected by the torque detection circuit 20, and the electric motor is driven and controlled based on the steering assist command value. A steering assist force that reduces the steering burden is generated.
On the other hand, if a contact failure has occurred in the detection coil 14 in the initial diagnosis state in the operation determination process of the operation determination unit 45 of the EPS control circuit 40, it is determined Yes in step S1, and the process proceeds to step S2. By outputting the current generation signal Si to the diagnostic current generator 43, a diagnostic current is caused to flow into the detection coil 14 in the path 1, but an abnormality such as a contact failure has occurred in the detection coil 14. Based on the voltage between the terminals of the detection coil 14 measured in step S3, it is determined in step S4 that an abnormality has occurred in the detection coil 14. Therefore, it determines with Yes by step S5, transfers to step S6, and the output of the detected torque from the torque detection circuit 20 is prohibited.

  By the way, in the non-contact torque sensor applied to the electric power steering apparatus, the detection coil and the printed wiring board are connected by soldering or the like. A contact resistance is generated between the body and the printed wiring board, and an inaccurate torque signal is output. Therefore, it is known to detect an abnormality in the detection coil resistance based on the phase difference between the waveform of the AC voltage applied to the bridge circuit and the waveform of the difference between the AC voltages appearing at the pair of detection coil terminal portions. .

  However, in such a torque sensor, since the method of monitoring the phase variation from the AC differential output of the pair of detection coils is applied, the impedance between the pair of detection coils and the bridge circuit is the same. In a failure mode that fluctuates and the differential output does not change from the normal state, an abnormality cannot be detected. Further, since the operation of the non-contact torque sensor is accompanied when detecting an abnormality, the abnormal operation cannot be avoided in advance when a connection failure has occurred in advance.

  On the other hand, in the present embodiment, when the torque detection circuit is not operated, a diagnostic current is supplied to one of the pair of detection coils and is generated between the terminals of the detection coil that has supplied the current. By measuring the voltage to be measured, the quality of the connection state of the detection coil is diagnosed, so that an abnormality can be reliably detected even in the above-described failure mode. In addition, since the abnormality detection is performed when the torque detection circuit is not operated, the abnormal operation can be avoided in advance even when the connection is poor.

  Thus, in the first embodiment, since the connection state of the detection coil is diagnosed based on the voltage generated when a current is passed through the detection coil, the impedance between the pair of detection coils and the bridge circuit is In the same way, it is possible to ensure the reliability of the junction between the detection coil and the bridge circuit, such as being able to reliably detect an abnormality even in a failure mode where the differential output does not change from the normal state. it can.

In addition, since the EPS control circuit side close to the torque detection circuit diagnoses the connection state between the detection coil and the bridge circuit, abnormality detection can be performed when the non-contact torque sensor is not in operation, and the connection failure is poor in advance. Even in the case of falling into the abnormal operation can be avoided beforehand.
Furthermore, the detection coil and the bridge circuit can be connected to a connector instead of soldering, so that if any unit malfunctions, parts can be replaced and the number of soldering steps in the assembly process can be reduced. Can be reduced.

  In addition, a predetermined diagnostic current is supplied to one of the pair of detection coils, and the connection state of the detection coil is diagnosed based on the voltage between the terminals of the detection coil that has supplied the diagnostic current. Therefore, it is possible to appropriately detect an abnormality such as a contact failure occurring in each detection coil.

Next, a second embodiment of the present invention will be described.
In the second embodiment, a diagnostic voltage is applied to the detection coil 13 or 14, and the detection coils 13 and 14 are detected based on the excitation voltage generated between the terminals of the detection coil to which the voltage is not applied. The connection status is diagnosed.
That is, the torque detection circuit and the EPS control circuit of the second embodiment detect the diagnostic current generator 43 in the EPS control circuit 40 of the first embodiment shown in FIG. Since it has the same configuration as that of FIG. 5 except that it is replaced with a diagnostic voltage generator 46 that generates a diagnostic voltage to be applied to the coil 13 or 14, the description will focus on the different parts.

  The diagnostic voltage generator 46 applies a diagnostic voltage to the detection coil 14 through the path 1 or applies to the detection coil 13 through the path 2 according to the voltage generation signal Sv output from the operation determination unit 45. A diagnostic voltage is applied.

  In FIG. 7, the connection state diagnosis unit 44, the operation determination unit 45, and the diagnosis voltage generator 46 correspond to the abnormality detection means.

  FIG. 8 is a flowchart showing an operation determination processing procedure executed by the operation determiner 45 of the second embodiment. First, in step S21, the operation determination unit 45 determines whether or not the torque detection circuit 20 is in an inoperative state (initial diagnosis state, rest state, test mode, etc.). It is determined that the operation determination is not performed, and the operation determination process is terminated as it is. When it is in the non-operation state, the process proceeds to step S22.

In step S22, the operation determination unit 45 outputs the voltage generation signal Sv to the diagnosis voltage generator 46, applies the diagnosis voltage to the detection coil 14 through the path 1, and proceeds to step S23. Here, the diagnostic voltage is set to a voltage value that allows the detection coil to be determined based on the excitation voltage generated when the voltage is applied.
In step S23, the operation determination unit 45 reads the excitation voltage between the terminals of the detection coil 13 measured in the path 4 by the connection state diagnosis unit 44, and proceeds to step S24.

  In step S24, the operation determination unit 45 determines the connection state of the detection coils 13 and 14 based on the excitation voltage between the terminals of the detection coil 13 read in step S23. Here, when the measured excitation voltage is equal to or higher than the predetermined voltage, it is determined that the detection coils 13 and 14 are connected.

  Next, in step S25, the operation determination unit 45 determines whether or not an abnormality has occurred in the detection coils 13 and 14 from the determination result in step S24, and when an abnormality has occurred in the detection coils 13 and 14. The process proceeds to step S26, and the operation determination process is terminated after the output of the detected torque by the torque detection circuit 20 is prohibited. On the other hand, when it is determined in step S25 that the detection coils 13 and 14 are in the connected state, the operation determination process is ended as it is.

Next, operations and effects in the second embodiment will be described.
Now, assuming that the electric power steering device is in an initial diagnosis state and the torque detection circuit 20 is in an inoperative state, the operation determination process of the operation determination unit 45 of the EPS control circuit 40 determines Yes in step S21, When it is determined that the operation of the torque detection circuit 20 is to be determined, the process proceeds to step S22, and the voltage generation signal Sv is output to the diagnosis voltage generator 46, whereby the diagnosis voltage is applied to the detection coil 14 in the path 1. Apply.

  At this time, if no abnormality such as a contact failure occurs in the detection coils 13 and 14, an excitation voltage is generated between the terminals of the detection coil 13 by applying a diagnostic voltage to the detection coil 14. Based on the excitation voltage between the terminals of the detection coil 13 measured in S23, it is determined in Step S24 that no abnormality has occurred in the detection coils 13 and 14, and No is determined in Step S25. As described above, when both the detection coils 13 and 14 are diagnosed as being in a normal connection state, the operation determination process is ended and torque detection by the torque detection circuit 20 is started.

When the steering assist control process is started by the CPU 42 of the EPS control circuit 40, a steering assist command value is calculated based on the steering torque signal from the torque detection circuit 20, and the electric assist is performed based on the steering assist command value. The motor is driven and controlled. In this way, a steering assist force that reduces the driver's steering burden is generated.
On the other hand, if a contact failure has occurred in the detection coil 14 in the initial diagnosis state in the operation determination process of the operation determination unit 45 of the EPS control circuit 40, “Yes” is determined in step S21, and the process proceeds to step S22. The diagnostic voltage is applied to the detection coil 14 in the path 1 by outputting the voltage generation signal Sv to the diagnostic voltage generator 46, but an abnormality such as a contact failure has occurred in the detection coil 14. Therefore, if no excitation voltage is generated between the terminals of the detection coil 13 and an abnormality has occurred in the detection coils 13 and 14 in step S24 based on the excitation voltage between the terminals of the detection coil 13 measured in step S23. to decide. Therefore, it determines with Yes by step S25, transfers to step S26, and the output of the detected torque from the torque detection circuit 20 is prohibited.

  As described above, in the second embodiment, a predetermined diagnostic voltage is applied to one of the pair of detection coils, and both are detected based on the excitation voltage generated between the terminals of the other detection coil. Since the connection state of the detection coil is diagnosed, it is possible to detect the abnormality of both detection coils in a short time, and to shorten the initial diagnosis time and the time until the steering assist control is started. .

  In the second embodiment, the connection state between the detection coils 13 and 14 is diagnosed based on the excitation voltage generated between the terminals of the detection coil 13 when a diagnostic voltage is applied to the detection coil 14. Although the case where it performs is demonstrated, the quality of the connection state of the detection coils 13 and 14 can also be diagnosed based on the excitation voltage which generate | occur | produces between the terminals of the detection coil 14 when the diagnostic voltage is applied to the detection coil 13.

  In the second embodiment, a diagnostic voltage is applied to the detection coil 14, and after performing a pass / fail diagnosis of the connection state of the detection coils 13 and 14 based on the excitation voltage between the terminals of the detection coil 13, Furthermore, a diagnosis voltage can be applied to the detection coil 13 and the connection state of the detection coils 13 and 14 can be diagnosed twice based on the excitation voltage between the terminals of the detection coil 14. Thereby, the abnormality detection of both detection coils can be performed more reliably.

In each of the above embodiments, the case where the torque detection circuit 20 and the EPS control circuit 40 are arranged close to each other has been described. However, the torque detection circuit 20 and the EPS control circuit 40 are configured as an integrated substrate. The present invention can also be applied to cases where
Further, in each of the above-described embodiments, the operation determination unit 45 for determining the operation of the torque detection circuit 20 is provided in the EPS control circuit 40 separately from the CPU 43. However, the operation determination unit 45 is deleted and the CPU 43 operates. Judgment processing can also be performed.

It is sectional drawing which shows the principal part of the electric power steering apparatus of this invention. It is a perspective view which shows the structure of a torque sensor. It is a figure explaining the convex arrangement on the surface of a sensor shaft part, and window arrangement of a cylindrical member. It is a figure explaining the change of the magnitude | size of a torque sensor, and the inductance of two detection coils. It is a block diagram of the torque detection circuit and EPS control circuit of a 1st embodiment. It is a flowchart which shows the operation | movement determination processing procedure of 1st Embodiment. It is a block diagram of the torque detection circuit and EPS control circuit of 2nd Embodiment. It is a flowchart which shows the operation | movement determination processing procedure of 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Input shaft, 2 ... Output shaft, 3 ... Torsion bar, 7 ... Worm wheel, 8 ... Worm, 11 ... Sensor shaft, 12 ... Cylindrical member, 13, 14 ... Detection coil, 20 ... Torque detection circuit, 21 ... Oscillation , 22 ... current amplifying part, 23 ... main amplification / full wave rectification part, 24 ... sub amplification / full wave rectification part, 26 ... main smoothing / neutral adjustment part, 24 ... sub smoothing / neutral adjustment part, 28 ... noise filter 40 ... EPS control circuit, 41 ... torque sensor I / F, 42 ... CPU, 43 ... diagnostic current generator, 44 ... connection state diagnostic device, 45 ... operation judging device, 46 ... diagnostic voltage generator, R1, R2 ... resistance

Claims (3)

AC voltage is applied to a bridge circuit in which each of a pair of detection coils whose impedances change in opposite directions according to torque generated on the rotating shaft and each of the pair of resistors are individually connected in series, Detected by at least the torque sensor, a torque sensor that detects steering torque based on the difference in AC voltage appearing at the terminal portion of the detection coil, an electric motor that applies steering assist force to the steering system to reduce the driver's steering burden, and An electric power steering apparatus comprising a control means for driving and controlling the electric motor based on the steering torque that has been obtained,
An abnormality detection means for diagnosing the connection state of the detection coil based on a voltage generated between terminals of the detection coil when a current is applied to the detection coil or a voltage is applied to the detection coil when the torque sensor is not operated. equipped with a,
The abnormality detection means applies a predetermined current to one detection coil of the pair of detection coils, and connects the detection coils based on a voltage between terminals generated in the detection coil supplied with the predetermined current. An electric power steering apparatus characterized by diagnosing a state . AC voltage is applied to a bridge circuit in which each of a pair of detection coils whose impedances change in opposite directions according to torque generated on the rotating shaft and each of the pair of resistors are individually connected in series, Detected by at least the torque sensor, a torque sensor that detects steering torque based on the difference in AC voltage appearing at the terminal portion of the detection coil, an electric motor that applies steering assist force to the steering system to reduce the driver's steering burden, and An electric power steering apparatus comprising a control means for driving and controlling the electric motor based on the steering torque that has been obtained,
An abnormality detection means for diagnosing the connection state of the detection coil based on a voltage generated between terminals of the detection coil when a current is applied to the detection coil or a voltage is applied to the detection coil when the torque sensor is not operated. With
The abnormality detection means applies a predetermined voltage to one detection coil of the pair of detection coils, and determines a connection state of both detection coils based on an excitation voltage generated between terminals of the other detection coil. it characterized in that diagnose electric power steering apparatus. The abnormality detection means applies a predetermined voltage to one detection coil of the pair of detection coils, and determines a connection state of both detection coils based on an excitation voltage generated between terminals of the other detection coil. After diagnosing, applying a predetermined voltage to the other detection coil and diagnosing the connection state of both detection coils based on the excitation voltage generated between the terminals of the one detection coil. The electric power steering apparatus according to claim 2 , wherein the electric power steering apparatus is an electric power steering apparatus.

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