JP4902043B2 - Torque sensor abnormality detection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an abnormality detection device in a torque sensor that detects torque based on an inductance change of a pair of coils.
[0002]
[Prior art]
A differential amplifying circuit having a pair of coils whose inductances change in opposite directions according to torque, and a differential amplifying circuit for differentially amplifying the pair of detection voltages induced in both the coils; A torque sensor that detects torque based on the output of is known in the art.
[0003]
The detected voltage (first subvoltage S1, second subvoltage S2) of the pair of coils and the output voltage (main voltage V) of the differential amplifier circuit in such a torque sensor correspond to the left steering torque and the right steering torque. As shown in FIG.
[0004]
If it is normal, the first sub-voltage S1 and the second sub-voltage S2 are substantially vertical symmetrical lines whose characteristic curves are positive and negative with respect to each other as shown in FIG. V is also a curve with a certain slope.
The voltage S1 + S2 obtained by summing the first sub-voltage S1 and the second sub-voltage S2 should be a substantially horizontal straight line as shown in FIG.
[0005]
Here, as an abnormality detection method when a failure occurs in the torque sensor main body, the connection system, the amplifier circuit, etc., an upper limit voltage value Vu1 and a lower limit voltage value Vd1 are set in FIG. 9, and the first subvoltage S1 or the second subvoltage is set. There is a detection method in which an abnormality is determined when the voltage S2 exceeds the upper limit voltage value Vu1 or falls below the lower limit voltage value Vd1.
[0006]
Also in FIG. 10, the upper limit voltage value Vu2 and the lower limit voltage value Vd2 are set, and when the voltage S1 + S2 exceeds the upper limit voltage value Vu2 or falls below the lower limit voltage value Vd2, a detection method for determining an abnormality There is.
[0007]
[Problems to be solved by the invention]
Since the first and second sub-voltages S1 and S2 change due to the temperature change of the torque sensor, the upper-limit voltage value Vu1 and the lower-limit voltage value Vd1 in FIG. 9 and the upper-limit voltage value Vu2 and the lower-limit voltage value in FIG. It was necessary to set a wide range between Vd2 in consideration of the temperature change.
[0008]
Therefore, the abnormality detection accuracy was inferior.
In addition, the abnormality detection method may not detect abnormality depending on the torque state.
[0009]
The present invention has been made in view of such a point, and an object thereof is to provide an abnormality detection device for a torque sensor capable of performing abnormality detection with high accuracy regardless of a temperature change of torque.
[0013]
[Means for solving the problems and effects]
In order to achieve the above object, the invention according to claim 1 inputs a pair of coils whose inductances change in opposite directions according to torque, and both sub-voltages based on the respective inductance changes of the two coils. Differential amplifying means for amplifying the difference between the sub-voltages and outputting it as a main voltage, and in a torque sensor for detecting torque by the output main voltage of the differential amplifying means, the X-axis is changed to one sub-voltage. Map storage means for storing a coordinate map in which an upper limit curve and a lower limit curve are set based on ideal relationship characteristic curves of both sub-voltages obtained in advance in a normal state at room temperature in XY coordinates whose axis is set to the other sub-voltage; a temperature correction means for temperature compensation in the sub voltage at room temperature each said two sub voltages, enter both correction sub voltage value corrected by the temperature correction unit, a coordinate map of the map storage means for storing Takes a abnormality determining means for determining an abnormality when the two correction sub voltage value coordinate point indicated does not exist between the upper curve and the lower limit curves, the temperature correction means, which has a temperature sensor, wherein both Each sub-voltage correction amount for correcting the sub-voltage to a sub-voltage at normal temperature is prepared in advance as each temperature correction map, and each sub-voltage correction amount is obtained by comparing the temperature detected by the temperature sensor with each temperature correction map , An abnormality detection device for a torque sensor that corrects both the sub-voltages to sub-voltages at room temperature by the sub-voltage correction amounts .
[0014]
The temperature correction means obtains each sub-voltage correction amount by comparing the detected temperature against the temperature correction map, and uses the sub-voltage correction amounts to correct both sub-voltage values to sub-voltages at room temperature, The correction sub-voltage value is checked against the coordinate map at normal temperature in which the upper limit curve and lower limit curve stored by the storage means are judged to determine whether or not there is an abnormality, so the upper limit on the coordinate map previously determined at normal temperature in the normal state It is not necessary to set a large distance between the curve and the lower limit curve in consideration of the temperature change, and abnormality detection can be performed with high accuracy.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment according to the present invention will be described with reference to FIGS.
The torque sensor 1 according to the present embodiment is applied to a vehicle power steering apparatus, and its schematic structure is shown in FIG.
[0018]
An input shaft 3 and an output shaft 4 that are rotatably supported on the housing 2 via bearings 5 and 6 and are coaxially connected to each other are connected to each other by a torsion bar 7.
A cylindrical core 8 is serrated to the outer peripheral surface of the large-diameter end portion 4 a of the output shaft 4, is slidable only in the axial direction with respect to the output shaft 4, and is a slider protruding from the input shaft 3 The pin 9 is engaged with the spiral groove 8a of the core 8 through a long hole extending in the circumferential direction of the large-diameter end 4a.
[0019]
Two torque detection coils 11 and 12 supported inside the housing 2 are provided on the outer periphery of a cylindrical core 8 that slides in the axial direction via a gap.
The two coils 11 and 12 are arranged on opposite sides with respect to the axial movement center of the core 8.
[0020]
When a torsional force acts on the input shaft 3, a rotational force is transmitted to the output shaft 4 through the torsion bar 7, but the torsion bar 7 is elastically deformed and rotates between the input shaft 3 and the output shaft 4. A relative displacement in direction occurs.
The relative displacement in the rotational direction causes the core 8 to slide in the axial direction through the engagement between the slider pin 9 and the spiral groove 8a.
[0021]
When the core 8 moves in the axial direction, the area surrounding the core 8 of each of the coils 11 and 12 changes, and when one area increases, the other area decreases.
When the area surrounding the core 8 increases, the magnetic loss increases and the inductance of the coil decreases. Conversely, when the area surrounding the core 8 decreases, the magnetic loss decreases and the inductance of the coil increases.
[0022]
Therefore, when the torque that moves the core 8 toward the coil 11 acts, the inductance L1 of the coil 11 decreases, the inductance L2 of the coil 12 increases, and conversely, the torque that moves the core 8 toward the coil 12 acts. When the inductance L1 of the coil 11 increases, the inductance L2 of the coil 12 decreases.
[0023]
An electrical circuit portion of the torque sensor 1 that detects torque based on changes in the inductances L1 and L2 of the coils 11 and 12 is shown in FIG. 2 as a schematic configuration diagram.
The coils 11 and 12 are suspended at a positive voltage E through a resistor 13 (R1) and a resistor circuit 14 (R2), respectively, and the other ends of the coils 11 and 12 are both oscillation outputs of the control board 20a mounted with the CPU 20. It is connected to the terminal osc.
[0024]
The resistor circuit 14 has a configuration in which a resistor 15 is connected in parallel to the resistor 16 and the thermistor 17 connected in series, and the temperature compensation function is achieved by the action of the thermistor 17.
That is, the thermistor 17 has such a temperature characteristic that the resistance value R2 always satisfies R1 / L1 = R2 / L2 regardless of the temperature change.
[0025]
The voltage signal line 21 extending from the connection portion of the coil 11 and the resistor 13 is branched and connected to the rectifying / smoothing circuits 23 and 25, respectively. The voltage signal line 22 extending from the connection portion of the coil 12 and the resistance circuit 14 is They are branched and connected to rectifying / smoothing circuits 24 and 26, respectively.
[0026]
That is, a bridge circuit is configured by the coils 11, 12, the resistor 13, and the resistor circuit 14, an oscillation voltage is input to the bridge circuit, and an output voltage thereof is input to the rectifying / smoothing circuits 23, 24, 25, and 26.
[0027]
The output voltage of the bridge circuit is rectified and smoothed by the rectifying / smoothing circuits 23, 24, 25, and 26, and the buffer circuits 27 are respectively provided as first, second, third, and fourth sub-voltages S1, S2, S3, and S4. , 28, 29 and 30 are output.
[0028]
The output terminals of the buffer circuits 27 and 28 are connected to the inverting input terminal and the non-inverting input terminal of the differential amplifier 41 via resistors 31 and 32, respectively.
Similarly, the output terminals of the buffer circuits 29 and 30 are connected to the inverting input terminal and the non-inverting input terminal of the differential amplifier 42 via resistors 33 and 34, respectively.
[0029]
The differential amplifiers 41 and 42 are negatively fed back by resistors 35 and 36, respectively, to function as differential amplifiers, and their outputs are input to the electronic control unit ECU 50 as the first main voltage M1 and the second main voltage M2. Is done.
[0030]
Further, neutral point adjustment voltages V1, V2 are input to the non-inverting input terminals of the differential amplifiers 41, 42 from the neutral point voltage setting circuits 43, 44 through the buffer circuits 45, 46 and the resistors 37, 38, respectively. .
[0031]
The neutral point voltage setting circuits 43 and 44 receive the respective adjustment signals from the neutral point adjustment output terminals aj1 and aj2 of the control board 20a, and set the neutral point voltages V1 and V2 according to the adjustment signals.
[0032]
Therefore, the differential amplifier 41 multiplies the difference between the first sub-voltage S1 and the second sub-voltage S2 by an amplification factor A, and outputs a voltage obtained by adding the neutral adjustment voltage V1 as a bias voltage as the first main voltage M1.
That is, the first main voltage M1 is
M1 = (S2-S1) .A + V1
It is.
[0033]
Similarly, for the differential amplifier 42, the output second main voltage M2 is
M2 = (S4-S3) .A '+ V2
It is.
Here, there is a relationship of V1≈V2 and A≈A ′.
[0034]
The neutral main voltage that is not biased to either the right steering torque (right torsion torque) or the left steering torque (left torsion torque) is referred to as a neutral point voltage, and the neutral point adjustment voltage V1. , V2 becomes a neutral point voltage.
[0035]
The ECU 50 outputs a motor control instruction signal to the motor driver 51 based on the first main voltage M1, and the motor 52 that assists steering is driven by the motor driver 51.
[0036]
The second main voltage M2 is used for detecting an abnormal state, and the ECU 50 determines whether or not the difference between the first main voltage M1 and the second main voltage M2 is within a predetermined allowable range, and sets the allowable range. If it exceeds, the torque sensor 1 is assumed to be in some abnormal state, an abnormal state signal is output, and the control of the motor 52 is stopped.
[0037]
The control board 20a receives the first, second, third and fourth sub-voltages S1, S2, S3 and S4 and the first and second main voltages M1 and M2, and the control board 20a Abnormalities of the torque sensor 1, the connection system, the amplifier circuit, and the like are determined based on the fourth sub-voltages S3 and S4. If there is an abnormality, an abnormality detection signal is output from the abnormality output terminal fs to the abnormal-time switch circuit 49.
The abnormality switch circuit 49 is directly connected to the ECU 50 and outputs an ON signal to the ECU 50 when an abnormality detection signal is inputted from the abnormality output terminal fs.
[0038]
In addition, a neutral point adjustment signal AJS for instructing neutral point adjustment is input from the neutral point adjustment switch AJS-SW47 to the neutral point adjustment terminal ajs, and the neutral point voltage setting state can be stored and rewritten in the control board 20a. E ² PROM 48 is connected to the neutral point voltage setting terminal rom.
[0039]
Further, a thermistor 55 suspended at a positive voltage is grounded via a resistor 56, a signal line extending from a connection portion between the thermistor 55 and the resistor 56 is connected to a temperature terminal tmp, and a thermistor voltage indicating temperature is Input to the control board 20a.
[0040]
The torque sensor 1 has a schematic circuit configuration as described above, and operates in accordance with the first, second, third, and fourth sub-voltages S1, S2, S3, and S4 and the first and second main voltages M1 and M2. This will be described below with reference to FIG.
In the coordinates shown in FIG. 3, the vertical axis is voltage, the horizontal axis right direction is right steering torque, and the horizontal axis left direction is left steering torque, and the origin 0 is a neutral point.
[0041]
FIG. 3 shows the torque sensor 1 operating normally. When the right steering torque increases, the core 8 moves to the coil 11 side due to the relative rotation of the input shaft 3 and the output shaft 4, and the inductance of the coil 12. L2 is increased to increase the induced electromotive force, and conversely, the inductance L1 of the coil 11 is decreased to decrease the induced electromotive force. Therefore, the second and fourth sub-voltages S2 and S4 increase, The third sub-voltages S1 and S3 are reduced (see (1) and (2) in FIG. 3).
[0042]
On the other hand, when the left steering torque is increased, the second and fourth sub-voltages S2 and S4 are decreased and the first and third sub-voltages S1 and S3 are increased (FIG. 3 (1), ▲). 2 ▼).
St represents the neutral point voltage of the third and fourth sub-voltages S3 and S4.
[0043]
The first and second main voltages M1 and M2 which are the outputs of the differential amplifiers 41 and 42 obtained by multiplying the difference between the two sub-voltages by A (A ') and adding the neutral point voltage are shown in FIGS. As shown by ▼, it becomes an upwardly inclined line passing through V1 and V2 at the neutral point.
[0044]
The ECU 50 compares the first and second main voltages M1 and M2 and determines whether the difference between the two is within an allowable range.
If it is normal, the changes in the first and second main voltages M1 and M2 are substantially the same as shown in FIG.
[0045]
If it is determined to be normal, an instruction signal for driving the motor 52 is output to the motor driver 51 based on the first main voltage M1.
In this way, the assisting force by the motor corresponding to the steering torque acts on the steering to execute power steering.
[0046]
Here, the control board 20a is further provided with means for detecting abnormalities in the torque sensor 1, the connection system, the amplifier circuit, and the like based on the third and fourth sub-voltages S3 and S4 as described above.
[0047]
A coordinate map of XY coordinates shown in FIG. 4 is stored in the memory of the control board 20a.
The coordinate map shows the ideal relationship characteristic curve L of the third and fourth sub-voltages S3 and S4 at normal temperature at the XY coordinates where the X-axis is the third sub-voltage S3 and the Y-axis is the fourth sub-voltage S4. Is obtained in advance, and the upper limit curve Lu and the lower limit curve Ld are set approximately symmetrically with respect to the ideal relationship characteristic curve L.
[0048]
Since the third and fourth sub-voltages S3 and S4 move symmetrically, the ideal relationship characteristic curve L in FIG. 4 is a curve that is close to a substantially straight line with a downward slope, and is above and below the ideal relationship characteristic curve L. The widths of the upper limit curve Lu and the lower limit curve Ld set to be set so narrow that no false detection occurs.
[0049]
Furthermore, a temperature correction map for correcting the temperature of the third and fourth sub-voltages S3 and S4 is stored in the memory of the control board 20a.
The temperature correction map is a map of correction amounts α and β of the third and fourth sub-voltages S3 and S4 with respect to the temperature by preliminarily grasping the temperature characteristics of the torque sensor 1 with output changes of the third and fourth sub-voltages S3 and S4. Remembered.
[0050]
FIG. 5 is a map showing the temperature characteristics of the third sub-voltage correction amount α.
A third sub-voltage correction amount α is derived by comparing the thermistor voltage value detected by the thermistor 55 with the map.
Similarly, FIG. 6 is a map showing the temperature characteristics of the fourth sub-voltage correction amount β, and the fourth sub-voltage correction amount β is derived by comparing the thermistor voltage value with the map.
[0051]
The CPU 20 of the control board 20a has a control program for detecting an abnormality using the above coordinate map and temperature correction map, and a flowchart showing the control procedure of the control program is shown in FIG.
[0052]
First, the third and fourth sub-voltage values S3 and S4 are read in step 1, the thermistor voltage is read in step 2, and the third and fourth from the temperature correction maps of FIGS. 5 and 6 based on the thermistor voltage in the next step 3. Sub-voltage correction amounts α and β are derived.
[0053]
In step 4, the third and fourth corrected subvoltages are temperature-corrected by adding the third and fourth subvoltage correction amounts α and β to the third and fourth subvoltage values S3 and S4 read in step 1, respectively. Values S3 and S4 are calculated.
[0054]
In step 5, the upper limit fourth subvoltage value S4u and the lower limit fourth subvoltage value S4d indicated by the upper limit curve Lu and the lower limit curve Ld corresponding to the third corrected subvoltage value S3 are determined according to the coordinate map with reference to FIG. To derive.
[0055]
In the next step 6, it is determined whether or not the fourth corrected sub voltage value S4 corrected in step 4 is between the upper limit fourth sub voltage value S4u and the lower limit fourth sub voltage value S4d. If it is not between the upper limit fourth sub-voltage value S4u and the lower limit fourth sub-voltage value S4d, the process proceeds to step 8 where it is determined that there is an abnormality. The detection signal is output to the switch circuit 49 when there is an abnormality.
[0056]
When the abnormality detection signal is output to the abnormal time switch circuit 49, an ON signal is output from the abnormal time switch circuit 49 to the ECU 50, and the ECU 50 stops the control of the motor 52.
[0057]
As described above, the ideal relationship characteristic curve L of the third and fourth subvoltages S3 and S4 in the normal state (predetermined temperature) is obtained in advance, and the upper limit curve Lu and the lower limit are calculated based on the ideal relationship characteristic curve L. A coordinate map in which the curve Ld is set is stored, and a point on the coordinate map indicated by the third and fourth corrected sub-voltage values S3 and S4 actually detected and temperature-corrected is between the upper limit curve Lu and the lower limit curve Ld. Abnormality is detected based on whether or not
[0058]
Therefore, the abnormality can be detected with high accuracy regardless of the temperature change and the torque region.
[0059]
Since abnormality is detected from the coordinate map using the third and fourth corrected sub-voltage values S3 and S4 that have been temperature-corrected based on the temperature correction map, the interval between the upper limit curve Lu and the lower limit curve Ld on the coordinate map is detected. It is not necessary to set a large value in consideration of the temperature change, and abnormality detection can be performed with high accuracy.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a mechanical part of a torque sensor according to an embodiment of the present invention.
FIG. 2 is a schematic configuration diagram of an electric circuit portion of the torque sensor.
FIG. 3 is a diagram illustrating a state of first, second, third, and fourth sub-voltages and first and second main voltages in a normal state.
FIG. 4 is a diagram illustrating a coordinate map for third and fourth sub-voltages.
FIG. 5 is a diagram illustrating a temperature correction map of a third sub voltage.
FIG. 6 is a diagram showing a temperature correction map of a fourth sub voltage.
FIG. 7 is a flowchart showing a control procedure for detecting an abnormality by the control board.
FIG. 8 is a diagram showing how to use the coordinate map.
FIG. 9 is a diagram illustrating a relationship between voltage and torque for explaining a conventional abnormality detection method.
FIG. 10 is a diagram showing a relationship between voltage and torque for explaining another conventional abnormality detection method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Torque sensor, 2 ... Housing, 3 ... Input shaft, 4 ... Output shaft, 5, 6 ... Bearing, 7 ... Torsion bar, 8 ... Core, 9 ... Slider pin,
11, 12 ... coil, 13 ... resistor, 14 ... resistor circuit, 15, 16 ... resistor, 17 ... thermistor, 20 ... CPU, 20a ... control board, 21, 22 ... voltage signal line, 23, 24, 25, 26 ... Rectifier / smoothing circuit, 27, 28, 29, 30 ... buffer circuit, 31, 32, 33, 34, 35, 36, 37, 38 ... resistor,
41, 42 ... differential amplifier,
43, 44 ... neutral point voltage setting circuit, 45, 46 ... buffer circuit, 47 ... neutral point adjustment switch ^{AJS-SW, 48 ... E 2} PROM, 49 ... abnormality switch circuit,
50 ... ECU, 51 ... Motor driver, 52 ... Motor,
55 ... Thermistor, 56 ... Resistance.

Claims (1)

A pair of coils whose inductances change in opposite directions according to torque, and a differential which inputs both sub-voltages based on the respective inductance changes of both coils and amplifies the difference between both sub-voltages and outputs it as a main voltage In a torque sensor that includes an amplifying means and detects torque by the output main voltage of the differential amplifying means,
The Y axis X axis to one of the sub voltage to the XY coordinates defined in the other sub-voltage, coordinates set an upper limit curve and the lower limit curve on the basis of the ideal relationship characteristic curve of the two sub voltages obtained at room temperature in a previously normal state Map storage means for storing a map;
Temperature correction means for correcting each of the sub-voltages to a sub-voltage at normal temperature,
When both corrected sub-voltage values corrected by the temperature correcting means are input, and the point coordinates indicated by the both corrected sub-voltage values in the coordinate map stored in the map storing means do not exist between the upper limit curve and the lower limit curve An abnormality determining means for determining that the
The temperature correction means includes a temperature sensor, and each sub-voltage correction amount for correcting both the sub-voltages to sub-voltages at room temperature is provided as a temperature correction map in advance, and the temperature detected by the temperature sensor An abnormality detecting device for a torque sensor, wherein each sub-voltage correction amount is obtained in light of a temperature correction map, and both the sub-voltages are respectively corrected to sub-voltages at normal temperature based on each sub-voltage correction amount .

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