JP3001881B1 - Torque sensor - Google Patents

Abstract

A torque sensor that eliminates the need for a temperature sensor, facilitates midpoint setting work, and can correct the temperature of a sensor output regardless of the ambient temperature at which the sensor is used and the applied torque. provide. A torque sensor including a pulse power supply, a bridge circuit, and a voltage detection unit including a deviation voltage detection unit, a temperature correction unit, an amplification unit, and an adjustment unit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque sensor for detecting a torque based on a change in inductance of a detection coil, and more particularly to a torque sensor capable of performing temperature compensation of a torque output that changes with a change in temperature.

[0002]

2. Description of the Related Art As disclosed in Japanese Patent Application Laid-Open No. 07-333083 by the present applicant, a conventional torque sensor has a core that is displaced in accordance with torque and is symmetrically arranged in a displacement direction from a neutral position of the core. Two detection coils are provided, and the number of turns of the two detection coils is made different to compensate for temperature.

When the temperature changes, the inductance of the detection coil changes due to the temperature coefficient of the detection coil, the coefficient of thermal expansion of the core and members around the detection coil, and the core moves from the neutral position despite no torque being applied. The displacement causes the reference value of the torque sensor to change (when the torque is 0, the sensor value is also 0).

In the torque sensor disclosed in Japanese Patent Application Laid-Open No. 07-333083, the change in the inductance of the two detection coils due to the displacement of the core from the neutral position due to the temperature change is defined by two coils having different numbers of turns. The core, the detection coil, and members around the detection coil are selected so as to cancel by a change in inductance due to the temperature coefficient of the detection coil, and temperature compensation is performed.

In the conventional torque sensor, a temperature sensor for detecting the temperature of the torque sensor is provided, and the amount of change from the reference value of the sensor with respect to the temperature is stored in advance as data, and the detected value detected by the torque sensor is stored. Is compensated by correcting the temperature from the reference value with respect to the temperature at the time of detection to perform temperature compensation.

[0006]

Problems to be Solved by the Invention
In order to perform temperature compensation, it is essential for the torque sensor disclosed in Japanese Patent Publication No. 83 to set the number of turns of the detection coil and select the core, the detection coil, and members around the detection coil. There is a problem that becomes complicated.

In addition, it is necessary to consider the arrangement of the core, the detection coil, and members around the detection coil, and there is a problem that the number of assembling steps increases.

On the other hand, a torque sensor using a temperature sensor has a problem that a temperature sensor is required in addition to the components constituting the original torque sensor, which leads to an increase in the number of components and an increase in cost.

The present invention has been made to solve such a problem, and has as its object a simple configuration that does not require selection of components for temperature compensation and does not require a temperature sensor. An object of the present invention is to provide a torque sensor that can compensate.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a voltage detecting means of a torque sensor according to the present invention corrects a temperature of a deviation voltage based on a sum of respective transient response voltages from two reference resistors. And a temperature correcting means for performing the following.

In the torque sensor according to the present invention, the voltage detecting means includes temperature correcting means for correcting the temperature of the deviation voltage based on the sum of the respective transient response voltages from the two reference resistors. Irrespective of the ambient temperature used and the applied torque, the temperature of the sensor output can be corrected.

The temperature correcting means according to the present invention comprises an adding means for adding the respective transient response voltages from the two reference resistances at an arbitrary temperature when no torque is applied, and an added value from the adding means. Subtraction means for calculating the difference between the reference response value obtained by adding the respective transient response voltages from the two reference resistances at the reference temperature when no torque is applied, and multiplying the output from the subtraction means by a constant coefficient. Multiplication means for calculating a temperature correction value, a deviation calculation means for calculating a deviation between the deviation voltage and the temperature correction value, and storage means for storing a reference added value and a constant coefficient.

The temperature correcting means according to the present invention calculates an added value of the respective transient response voltages from the two reference resistors at an arbitrary temperature when no torque is applied, and no torque is applied from the added value. A constant correction coefficient is obtained by multiplying a value obtained by subtracting a reference addition value obtained by adding the respective transient response voltages from the two reference resistances at the reference temperature at the time by a constant coefficient. The temperature of the torque signal can be corrected by the value.

Further, the constant coefficient according to the present invention is a ratio of a slope obtained by linearly approximating the deviation voltage characteristic with respect to a temperature change when no torque is applied, and a slope obtained by linearly approximating the added value characteristic. It is characterized by the following.

Since the ratio between the slope obtained by linearly approximating the deviation voltage characteristic with respect to the temperature change when no torque is applied and the slope obtained by linearly approximating the added value characteristic is a constant coefficient,
By multiplying the addition value by a constant coefficient, the temperature change amount of the addition value can be converted into the temperature change amount of the deviation voltage to be used as the temperature correction value of the deviation voltage.

Further, the voltage detecting means according to the present invention includes an amplifying means for level-shifting the deviation voltage as a sensor signal, and an adjusting means for adjusting the sensor signal to a midpoint potential. .

The voltage detection means according to the present invention can shift the deviation voltage to a sensor signal by level-shifting, and can adjust the sensor signal when no torque is applied to a midpoint potential.

[0018]

Embodiments of the present invention will be described below with reference to the accompanying drawings. It should be noted that the present invention has two changes: a change in the inductance of the detection coil caused by a change in the position of the core caused by a difference in the coefficient of thermal expansion due to a change in the ambient temperature; The change in the midpoint potential due to the factor is corrected, and the temperature of the sensor signal at an arbitrary temperature and an arbitrary torque is corrected.

FIG. 1 is a basic configuration diagram of a displacement detector of a torque sensor according to the present invention. (A) is a configuration diagram of a displacement detector including a displaceable core, and (b) is a bridge circuit (electrically equivalent circuit diagram) of the displacement detector.

In FIG. 1 (a), a displacement detector of a torque sensor is arranged symmetrically with respect to a core 2 which can be displaced in both directions from a neutral position in accordance with an applied torque, and symmetrically in the displacement directions X1, X2 of the core 2 from the neutral position. And two detection coils 3 whose inductance changes differentially according to the displacement of the core 2.
A and 3B, two reference resistors RF and RF connected in series to the two detection coils 3A and 3B, respectively, and a pulse power supply 4.

One end of each of the detection coils 3A and 3B is connected to one end of each of reference resistors RF and RF, and their connection points are connected as terminals S1 and S2 to voltage detection means described later. The other ends of the detection coils 3A and 3B are commonly connected, and are connected to one end of the pulse power supply 4. In addition, 2
The other ends of the reference resistors RF and RF and the other end of the pulse power supply 4 are grounded (GND).

In FIG. 2B, a bridge circuit 5, which is an electrical equivalent circuit of FIG. 2A, has an inductance L1 of a detection coil 3A and an inductance L1 of a detection coil 3B.
2. Equipped with reference resistances RF and RF, and inductances L1 and L
2, the + side (voltage VI) of the pulse power supply 4 is connected, and the-side (GND) of the pulse power supply 4 is connected to the connection point between the reference resistances RF and RF.

An inductance L1 and a reference resistor RF are connected in series, and this connection point is used as a terminal S1 to form a bridge circuit 5
Is one of the detection terminals. Further, the inductance L2 and the reference resistor RF are connected in series, and this connection point is used as a terminal S2 as the other detection terminal of the bridge circuit 5. Terminal S1
The terminal S2 forms an LR integration circuit of the inductance L1 and the reference resistance RF, and the inductance L2 and the reference resistance RF when driven by the pulse power supply 4 with respect to the ground (GND).

A transient response voltage VS1 is generated at a terminal S1 when the integration circuit of the inductance L1 and the reference resistance RF is driven by the pulse power supply 4, and an inductance L2 is generated at a terminal S2.
And a transient response voltage VS2 when the integrating circuit of the reference resistor RF is driven by the pulse power supply 4. By taking the difference (= VS1−VS2) between the transient response voltage VS1 and the transient response voltage VS2, an electrical differential deviation voltage VD (= VS1−VS2) corresponding to the displacement of the core 2 in the displacement detector can be obtained. .

It should be noted that the inductance L1 and the inductance L2 are equal to X when the core 2 shown in FIG.
Indicates a value in the case of displacement in the 1 or X2 direction, and is equal when the core 2 is in the neutral position (L1 = L2 = L)
Value. The pulse power supply 4 sets the reference to the potential VI,
The falling pulse waveform changes from the potential VI to the GND potential.

FIG. 2 shows a transient response voltage (VS) according to the present invention.
1, VS2). (A) is a waveform diagram when the pulse width of the pulse power supply is set to be sufficiently larger than the time constant of the LR integration circuit.
FIG. 4 shows a waveform diagram when the time constant is set near the time constant of the integration circuit.
2 shows that the core 2 is displaced from the neutral point in FIG.
The case where the inductance L1 of the bridge circuit 5 is larger than the inductance L2 (L1> L2) is shown.

In FIG. 3A, the transient response voltage VS1 decreases exponentially with a time constant (RF / L1) as the time t elapses from the peak value VI of the pulse power supply 4, and the time t = T approaches 0 as much as possible. on the other hand,
The transient response voltage VS2 also decreases exponentially with a time constant (RF / L2) from the peak value VI with the elapse of time t, and approaches zero at time t = T.

The differential deviation voltage VD is the transient response voltage VS1
And the transient response voltage VS2 (= VS1-VS2),
(A) As is clear from the figure, at time t = 0, the difference is 0 or at time t = T, the difference becomes 0, and the displacement of the core 2 cannot be detected. Therefore, when detecting the displacement, the difference (= V
The sensitivity of the torque sensor 1 can be increased by detecting the deviation voltage VD at the time t = tM when S1−VS2) becomes maximum (VD = VDMAX).

In FIG. 3B, since the pulse width T1 of the pulse power supply 4 is set near the time constant of the transient response voltage VS1 and the transient response voltage VS2, the transient response voltage VS1 and the transient response voltage at time t = T1. The difference between VS2 (= VS1-VS2) can be detected as the deviation voltage VD.

Although FIG. 2 shows the case where the core 2 is displaced and the inductance L1 of the bridge circuit 5 is larger than the inductance L2 (L1> L2), the core 2 is displaced in the opposite direction and the bridge circuit is displaced. 5 is smaller than the inductance L2 (L1
<L2), the display of the transient response voltages VS1 and VS2 in FIG. (A) or (b) is switched (VS1 → VS).
2, VS2 → VS1), the deviation voltage VD can be similarly explained.

Also, instead of the pulse power supply 4 shown in FIG. 1, one end of two reference resistors RF of the bridge circuit 5 is connected to a DC power supply (DC voltage value VI), and the detection coils 3A,
3B is grounded via a switching element such as a transistor, and this switching element is turned on with the pulse width (time T or T1) shown in FIG. From both ends of the connected detection coil coils 3A, 3B, the transient response voltages VS1,
A bridge circuit may be configured to obtain VS2.

In the state shown in FIG. 2, the steering is performed when the steering wheel is operated clockwise (right steering), for example, when the positive (+) detection direction of the torque sensor 1 is used for a steering torque sensor of a vehicle. Assuming torque, transient response voltage V
Swap the display of S1 and VS2 (VS1 → VS2, VS2 → VS
1) The state may be a negative (-) detection direction of the torque sensor 1, for example, an operation in the counterclockwise direction (left steering) of the steering wheel of the vehicle.

As described above, by setting the difference between the transient response voltage VS1 and the transient response voltage VS2 as the deviation voltage VD (= VS1-VS2), the absolute value | VD | of the deviation voltage VD and the deviation voltage VD
The magnitude and direction of the torque (for example, steering torque) applied to the torque sensor 1 can be detected with the polarity (+ or −).

FIG. 3 is a block diagram showing a basic part of an embodiment of the voltage detecting means of the torque sensor according to the present invention.
3, the voltage detecting means 6 includes a deviation voltage detecting means 7, a temperature correcting means 8, an amplifying means 14, and an adjusting means 15.

The deviation voltage detecting means 7 has a subtractor or a soft control subtraction function, calculates the deviation between the transient response voltage VS1 and the transient response voltage VS2, and calculates the deviation voltage VD (= VS1-VS).
2) is supplied to the temperature correction means 8.

The temperature correction means 8 includes an addition means 9, a storage means 10, a subtraction means 11, a multiplication means 12, and a correction calculation means 13.
Is provided. The adding means 9 has an adder or an addition function of software control, adds the transient response voltage VS1 and the transient response voltage VS2, and supplies an added value VP (= VS1 + VS2) to the subtracting means 11.

The storage means 10 is composed of a rewritable memory such as an EEPROM or a RAM, and has a reference addition value VPR (= VRP (= R) obtained by previously adding the transient response voltage VS10 and the transient response voltage VS20 at the reference temperature TO when the torque is 0. VS10 + VS20) and supplies the reference addition value VPR to the subtraction means 11.

The storage means 10 stores a deviation voltage VDK (= VS1K-VS2K) with respect to a temperature change when the torque is 0 in advance.
Is measured, and the slope K2 obtained by approximating the measured deviation voltage VDK characteristic with a straight line and the added value VPK (= VS1K + VS2K) with respect to the temperature change when the torque is 0 are actually measured, and the actually measured added value VPK is obtained.
A constant coefficient K (= K2 /
K1) is calculated, this constant coefficient K is stored, and the constant coefficient K is supplied to the multiplication means 12.

FIG. 4 shows a temperature T-added value (V) according to the present invention.
(S1K + VS2K) characteristic diagram. In FIG. 4, the broken line display is obtained by actually measuring and plotting the added value (VS1K + VS2K) when the temperature T is changed (for example, −30 ° C. to + 90 ° C.). A straight line approximation (shown by a solid line) is performed from the characteristic diagram of the added value (VS1K + VS2K), and the slope K1 of the approximated straight line is obtained. In the linear approximation (shown as a solid line), the amount of change in the added value (VS1K + VS2K) increases on the low temperature side.
The calculation is performed with the added value (VS1K + VS2K) characteristic of up to + 90 ° C. so that the difference between the approximate linear characteristic and the added value (VS1K + VS2K) characteristic is minimized.

The temperature TO is a reference temperature (for example, normal temperature), and the relationship between the amount of change in the added value (VS1K + VS2K) at an arbitrary temperature TK from the reference added value (VS10 + VS20) when the torque is 0 and the slope K1 is expressed by the following equation. Is represented by

[0041]

K1 = ｛(VS1K + VS2K) − (VS10 + VS2
0)｝ / (TO−TK)

The reference addition value (VS10 + VS20) is stored in the storage means 10 as VPR from the actually measured value shown in FIG.

FIG. 5 is a temperature T-deviation voltage (VS1K-VS2K) characteristic diagram according to the present invention. In FIG. 5, the dashed line changes the temperature T (for example, −30 ° C. to + 90 ° C.).
The deviation voltage (VS1K-VS2K) at this time is measured and plotted. A straight line approximation (shown as a solid line) is performed from the deviation voltage (VS1K-VS2K) characteristic diagram, and the slope K of the approximated straight line
Ask for 2. In the linear approximation (shown by a solid line), the amount of change in the deviation voltage (VS1K−VS2K) increases on the low temperature side.
For example, when used for a steering torque sensor, the temperature range is set to a deviation voltage (VS1K-VS2K) characteristic of -10 ° C. to + 90 ° C. so that the difference between the approximate linear characteristic and the deviation voltage (VS1K-VS2K) characteristic is minimized. To

The temperature TO is a reference temperature (for example, normal temperature), and the reference deviation voltage VSD (= VS10-VS) when the torque is 0 is set.
20), the deviation voltage (VS1K−VS2) at an arbitrary temperature TK
The relationship between the amount of change in K) and the slope K2 is expressed by Equation 2.

[0045]

K2 = ｛(VS1K−VS2K) − (VS10−VS2)
0)｝ / (TO−TK)

The reference temperature TO is, for example, a temperature at which the reference deviation voltage (VS10-VS20) becomes zero, as shown in FIG.

FIG. 6 shows the sum (VS1K + VS) according to the present invention.
2K) -deviation voltage (VS1K-VS2K) characteristic diagram. In FIG. 6, the added value (VS1K + VS2K) and the deviation voltage (VS1K
K-VS2K) uses the approximate straight lines shown in FIGS.

The slope of the linear characteristic shown in FIG. 6 is a constant coefficient K (= K2 / K1) which is a ratio of the slope K2 of the approximate straight line shown in FIG. 5 to the slope K1 of the approximate straight line shown in FIG. Coefficient K
Is represented by Equation 3 from Equations 1 and 2.

[0049]

K = K2 / K1 = ｛(VS1K−VS2K) − (VS10
−VS20)｝ / ｛(VS1K + VS2K) − (VS10 + VS2
0)｝

From equation (3), the relationship between the deviation voltage (VS1K-VS2K) and the added value (VS1K + VS2K) is as follows: the added value (VS1K + VS2K).
K) is multiplied by a constant coefficient K to obtain a deviation voltage (VS1K-V
S2K).

The constant coefficient K calculated by the equation (3) is stored in the storage means 10, and the constant coefficient K is supplied to the multiplication means 12.

Returning to FIG. 3, the subtraction means 11 has a subtractor or a soft control subtraction function. The addition value VP (= VS1 + VS2) supplied from the addition means 9 and the reference addition value supplied from the storage means 10 The difference from VPR (= VS10 + VS20) is calculated, and the difference addition value VS (= VP-VPR) is provided to the multiplying means 12.

Since the addition value VP (= VS1 + VS2) is equal to (VS1K + VS2K) at an arbitrary temperature TK when the steering torque is 0, the difference addition value VS (= VP-VPR) is represented by the denominator ｛= (VS1K + VS2K)-(VS10 + VS20)}.

The multiplication means 12 has a multiplier or a software-controlled multiplication function, and calculates the product of the constant coefficient K provided from the storage means 10 and the difference addition value VS supplied from the subtraction means 11 (= K * VS), and supplies the calculation result to the correction calculation means 13 as a temperature correction value VH.

Expression 3 is expressed by using the temperature correction value VH.
Equation 4 is obtained.

[0056]

(VS1K−VS2K) − (VS10−VS20) = VH where VH = K * ｛(VS1K + VS2K) − (VS10 + VS2
0)｝

Further, the reference deviation voltage (V
S10-VS20) is required.

[0058]

## EQU5 ## (VS10-VS20) = (VS1K-VS2K) -VH

As is clear from FIG. 5, Equation 5 calculates the difference between the deviation voltage VDK (= VS1K−VS2K) at the arbitrary temperature TK and the temperature correction value VH at the arbitrary temperature TK. (VS10-VS20).

The correction operation means 13 has a subtractor or a soft control subtraction function. The deviation voltage VD (= VS1−VS2) supplied from the deviation voltage detection means 7 and the temperature correction value supplied from the multiplication means 12 The deviation of VH is calculated, and the temperature-compensated deviation voltage VO (= VD-VH) is supplied to the amplification means 14.

The deviation voltage VO (= VD-
VH) is the deviation voltage VD when the deviation voltage VD (= VS1-VS2) is a value at an arbitrary temperature TK when the steering torque is 0.
K (= VS1K−VS2K), which is the same as Equation 5;
Deviation voltage VDK at arbitrary temperature TK (= VS1K-VS2K)
Is the reference deviation voltage VDO (= VS10-V) according to the temperature correction value VH.
It becomes clear that the temperature is corrected in S20).

In this embodiment, the case where the reference temperature TO is, for example, normal temperature and the reference deviation voltage VDO (= VS10−VS20) at this time becomes 0 as shown in FIG. 5 has been described. As long as the linear approximation of FIGS. 4 to 6 holds, the reference deviation voltage VDO (= VS10−VS2) corresponding to the reference temperature TO
Even if 0) is set to an arbitrary point on a straight line, the present invention is established.

However, in this case, the reference deviation voltage VDO
Since (= VS10−VS20) does not become 0, the level is shifted by the amplifying means 14 described later, and adjusted to the midpoint potential (for example, 2.5 V) by the adjusting means 15.

In this embodiment, the case where the torque is 0 has been described. However, even when the torque is a finite value other than 0, the temperature correction is performed using the added value (= VS1K + VS2K) as shown in Expression 4. can do.

FIG. 7 is a characteristic diagram of torque (steering torque signal T) -added value (VS1K + VS2K) according to the present invention. FIG.
Indicates that the added value (VS1K + VS2K) is constant irrespective of the value of the torque (steering torque signal T) in the range of the maximum value (TM +, TM-) of the actual use of the torque (steering torque signal T).

Since the addition value (VS1K + VS2K) is constant irrespective of the value of the torque (steering torque signal T), the temperature correction value VH shown in Expression 4 is calculated using the addition value (VS1K + VS2K).
Is generated, and the deviation voltage VO (= VD−VH) at an arbitrary temperature TK in a state where the torque (the steering torque signal T) is applied.
Can be corrected by the temperature correction value VH.

The amplifying means 14 is composed of, for example, an operational amplifier driven by a single power supply of 5 V with a virtual ground potential of 2.5 V.
The deviation voltage VO (= VD-
VH) is level-shifted, and if the torque is 0, a 2.5V torque signal ST, and if the torque is positive (+), 2.5V <S
A torque signal ST of T ≦ 5.0 V and a torque signal ST of 0 ≦ ST <2.5 V when the torque is negative (−) are output.

The adjusting means 15 is composed of, for example, a variable resistor RV, and varies the variable resistor RV so that the gain of the amplifying means 14 determined by the resistor RI and the variable resistor RV (RV / RI) is obtained. Adjust the torque signal ST when the torque is 0
Is adjusted to the midpoint potential (= 2.5 V).

Since the adjusting means 15 is provided, the torque signal ST can be adjusted to the midpoint potential (= 2.5 V) even when the deviation voltage VO (= VD-VH) at the time of the torque 0 is not 0. it can.

Therefore, at the reference temperature TO (normal temperature) shown in FIG. 5, the reference deviation voltage VDO (= VS10-VS20) is not based on 0, but on the basis of an arbitrary point on the approximate straight line of the slope K2. The temperature correction value VH shown in FIG. 4 becomes the same value, and the torque signal ST when the torque is 0 can be adjusted to the midpoint potential (= 2.5 V).

At the time of product shipment or maintenance or inspection at a service station or the like, the torque signal ST is adjusted by the adjusting means 15.
Is adjusted to the midpoint potential (= 2.5 V), the temperature can be corrected over the entire use environment and use condition of the torque sensor 1.

Further, the torque signal ST is set to the midpoint potential (= 2.5
The operation of adjusting to V) can be performed in an arbitrary temperature environment such as at the time of product shipment or a service station.

Further, in the embodiment of FIG. 3, up to the detection of the deviation voltage VO (= VD-VH) is executed at the level of the transient response voltages VS1 and VS2 from the bridge circuit 5 shown in FIG.
Although the level is shifted by the amplifying means 14, the outputs of the transient response voltages VS1 and VS2 are changed to 2.5 as in the amplifying means 14.
The level may be shifted by using an operational amplifier driven by a single power supply of 5 V with V being a virtual ground potential.

FIG. 8 is a block diagram showing a main part of a steering torque sensor to which the torque sensor according to the present invention is applied. In FIG. 8, the steering torque sensor 40 includes a displacement detector 41 and a voltage detecting means 46.

The displacement detector 41 includes the input shaft 4
2, output shaft 43, input shaft 4
Torsion bar (not shown) that couples the output shaft 43 with the output shaft 43, a core 44, a coil 45A, and a coil 45B
And two reference resistors (not shown).

When a steering torque (T) acts on the input shaft 42 and the output shaft 43, a torsion angle (θT) is generated in the torsion bar in proportion to the steering torque (T). This twist angle (θT) is converted into a displacement (xT) of the core 44 in the shaft axial direction by the action of a pin connected to both shafts and a spiral groove and a vertical groove (both not shown) provided in the core 44. Is done.

The displacement (xT) of the core 44 is based on the change in inductance (ΔT) of the coils 45A and 45B described above.
LT), and the inductance change (ΔLT) is detected as transient response voltages VS1 and VS2 of the pulse voltage VI applied to the bridge circuit composed of the coils 45A and 45B and two reference resistors.

The voltage detecting means 46 includes a pulse generating circuit 51 for supplying the pulse voltage VI to the displacement detector 41 and a high-frequency switching noise (NS) included in the transient response voltages VS1 and VS2 detected by the displacement detector 41. Primary CR that removes and outputs pulse transient response voltage Va (VS1, VS2)
Low-pass filters 47A and 47B, bottom hold circuits 48A and 48B for holding and outputting the bottom voltages VT1 and VT2 of the pulse transient response voltages Va (VS1 and VS2), and a difference (VT2−) between the bottom voltage VT2 and the bottom voltage VT1. VT1) is calculated and amplified by the gain G1, and the reference midpoint potential is 2.5V.
And a differential amplifier 48 for level shifting the
And a variable amplifier 51 which adjusts the temperature-corrected output VO to a midpoint potential (2.5 V) and outputs a sensor signal (sensor output) ST.
And

[0079]

As described above, the torque sensor according to the present invention can correct the temperature of the sensor output regardless of the ambient temperature at which the sensor is used and the applied torque. However, an accurate sensor output can be obtained.

Since the added value of the transient response voltage is constant irrespective of the magnitude of the applied torque if the temperature is constant, the temperature of the torque signal in the arbitrary temperature and the arbitrary torque state can be corrected by temperature correction of the deviation voltage. Can be.

Since the voltage detecting means compensates for the temperature of the midpoint potential of the sensor, it is not necessary to select the core, the detecting coil and members around the detecting coil, and to set the two detecting coils to different numbers of turns.

The temperature correcting means according to the present invention calculates an added value of the respective transient response voltages from the two reference resistors at an arbitrary temperature when no torque is applied, and no torque is applied from the added value. A constant correction factor is obtained by multiplying a value obtained by subtracting the reference added value obtained by adding the respective transient response voltages from the two reference resistors at the reference temperature at that time by a constant coefficient to obtain a temperature correction value, regardless of the torque value. The temperature of the torque signal can be corrected by the value, and the temperature change of the sensor output can be accurately corrected.

Further, since the ratio between the slope obtained when the deviation voltage characteristic with respect to the temperature change when no torque is applied and the slope obtained when the added value characteristic is linearly approximated and the slope obtained when the added value characteristic is linearly approximated, the fixed coefficient is used. By multiplying the addition value, the temperature change amount of the addition value can be converted into the temperature change amount of the deviation voltage to obtain the temperature correction value of the deviation voltage, so that the sensor output is independent of the ambient temperature at which the sensor is used. Temperature correction can be performed.

Further, the voltage detecting means according to the present invention performs the level shift of the deviation voltage to obtain a sensor signal,
Since the sensor signal when no torque is applied can be adjusted to the midpoint potential, the setting of the midpoint correction can be made extremely easy.

Accordingly, a torque sensor which eliminates the need for a temperature sensor, facilitates the operation of setting the midpoint, and can correct the temperature of the sensor output regardless of the ambient temperature at which the sensor is used and the applied torque. can do.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of a displacement detector of a torque sensor according to the present invention.

FIG. 2 is a waveform diagram of a transient response voltage (VS1, VS2) according to the present invention.

FIG. 3 is a block diagram of a basic essential part of an embodiment of a voltage detecting means of the torque sensor according to the present invention;

FIG. 4 shows a temperature T-added value (VS1K + VS2) according to the present invention.
K) Characteristic diagram

FIG. 5 shows a temperature T-deviation voltage (VS1K-VS) according to the present invention.
2K) Characteristic diagram

FIG. 6 is a characteristic diagram of an added value (VS1K + VS2K) -deviation voltage (VS1K-VS2K) according to the present invention.

FIG. 7 shows a torque (steering torque signal T) according to the present invention;
Additive value (VS1K + VS2K) characteristic diagram

FIG. 8 is a block diagram of a main part of a steering torque sensor to which the torque sensor according to the present invention is applied.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Torque sensor, 2 ... Core, 3A, 3B ... Detection coil, 4 ... Pulse power supply, 5 ... Bridge circuit, 6 ... Voltage detection means, 7 ... Deviation voltage detection means, 8 ... Temperature correction means, 9 ...
Addition means, 10 ... storage means, 11 ... subtraction means, 12 ... multiplication means, 13 ... correction operation means, 14 ... amplification means, 15 ...
Adjustment means.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-333083 (JP, A) JP-A-7-260601 (JP, A) JP-A-9-105687 (JP, A) 213257 (JP, A) JP-A-11-63911 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01L 3/10 G01D 5/20

Claims (4)

(57) [Claims] 1. A core which can be displaced in both directions from a neutral position according to an applied torque, and a core which is symmetrically arranged in the direction of displacement of the core from the neutral position, and whose inductance changes differentially corresponding to the displacement of the core. Two detection coils and this 2
Two reference resistors connected in series to each of the two detection coils, a bridge circuit composed of the two reference resistors and the two detection coils, a pulse power supply applied to the bridge circuit, Voltage detecting means for detecting a deviation voltage of each transient response voltage from the two reference resistors of the bridge circuit, and detects a displacement amount and a displacement direction of the core as a torque signal based on the deviation voltage. In the torque sensor, the voltage detecting means includes a temperature correcting means for correcting a temperature of the deviation voltage based on an added value of the respective transient response voltages from the two reference resistors. 2. The temperature compensating means includes an adding means for adding respective transient response voltages from the two reference resistances at an arbitrary temperature when no torque is applied, and an added value from the adding means and a torque. Subtracting means for calculating a difference between a reference addition value obtained by adding respective transient response voltages from the two reference resistances at a reference temperature when no voltage is applied, and multiplying an output from the subtracting means by a constant coefficient. Multiplying means for calculating a temperature correction value by using the multiplication means, deviation calculating means for calculating a deviation between the deviation voltage and the temperature correction value, and storage means for storing a reference added value and a constant coefficient. 1. The torque sensor according to 1. 3. The constant coefficient is a ratio of a slope obtained by linearly approximating a deviation voltage characteristic with respect to a temperature change when no torque is applied and a slope obtained by linearly approximating an added value characteristic. The torque sensor according to claim 2, wherein 4. The apparatus according to claim 1, wherein said voltage detecting means includes an amplifying means for level-shifting the deviation voltage to be a sensor signal, and an adjusting means for adjusting the sensor signal to a midpoint potential. The torque sensor as described.