JP2677066B2 - Magnetostrictive torque measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive shaft of an automobile, a spindle of a machine tool, a rotary shaft of an electric motor, and the like. The present invention relates to a magnetostrictive torque measuring device used for non-contact detection using a strain effect.

[0002]

2. Description of the Related Art As a torque measuring device of this type, there is a device utilizing a magnetostrictive action of a shaft (shaft to be measured) (for example, JP-A-62-179627 and JP-A-63-117).
230, JP-A-1-170823).

FIG. 1 shows an example of a torque detecting section of a torque measuring device utilizing the magnetostrictive action of a shaft to be measured, and FIG.
3 is a diagram showing an example of a bridge circuit and a signal processing circuit which constitute a torque detection circuit of the torque measuring device.

A torque detector 1 of the torque measuring device shown in FIG. 1 includes a shaft to be measured 2 having a magnetostrictive action, and the shaft 2 to be measured for transmitting torque is provided with shape anisotropy. Partial spiral grooves 3 and 4 are provided symmetrically, and the structure is such that the coils 5 and 6 for excitation and detection facing the partial spiral grooves 3 and 4 are held in a non-contact manner by a yoke or the like not shown. ing.

In the bridge circuit of the torque detection circuit 10 of the torque measuring device shown in FIG. 2, reference numerals 5 and 6 are the coils shown in FIG. 1 whose impedance vectors are Z ₁ (-) and Z ₂ (-), respectively. Indicates that the impedance is complex. Further, in the following, the same symbol, which is used to indicate that it is an AC signal, will be used.

In the bridge circuit of the torque detector 10 shown in FIG. 2, reference numerals 7 and 8 are fixed resistors having resistance values R ₁ and R ₂ , and the resistors 7 and 8 and the coils 5 and 6 form a bridge. Forming a circuit. Reference numerals 11 and 12 are variable resistors having bridge resistances having resistance values of Rex ₁ and Rex ₂ .

The bridge circuit is supplied with an AC voltage of V · e ^jωt from the oscillator 13 of the signal processing circuit. Here, V is the amplitude, and ω = 2πf is the angular frequency (f: frequency).

The output voltage of this bridge circuit is generated by the differential amplifier 14.

[0009]

The signal is amplified to and is synchronously detected by the synchronous detector 15, and the device output ΔV (-) is output as a direct current. The reference signal (phase, θt) for synchronous detection is supplied from the oscillator 13 via the phase shifter 16.

When the torque T applied to the shaft 2 to be measured is measured by the magnetostrictive torque measuring device having the structure shown in FIGS. 1 and 2, the variable resistor 11 is not applied. , 12 resistance values Rex ₁ , Rex
Adjust ₂ to balance the bridge, {△ V
(~) = 0 (~)}.

Thereafter, when torque T is applied as shown in FIG. 1, the impedance of one coil 5 increases and the impedance of the other coil 6 decreases, so that an imbalance occurs in the bridge output voltage. △ V
(~) ≠ 0 (~)}. Since this imbalance is proportional to the magnitude of the applied torque T, the device output is

[0013]

The relationship is as follows.

By the way, since actual shafts such as automobiles and machine tools are required to have sufficient mechanical strength, heat-treated steel is used as the shaft material that also serves as a part of the torque measuring device. Often used.

In the magnetostrictive torque measuring device using steel, a relatively high circuit amplification factor is required to obtain device sensitivity to torque.

Therefore, it becomes sensitive to temperature changes,
The zero point of a torque measuring device often drifts with temperature.

Therefore, the phase of the bridge circuit output when only the temperature is uniformly changed, that is, the temperature phase is separated from the phase of the bridge circuit output when only the torque is applied, that is, the torque phase, and the temperature phase is detected. As a result, measures have been taken to eliminate the zero point drift.

[0019]

At the stage where the temperature phase is not adjusted, the temperature phase of the magnetostrictive torque measuring device differs from device to device.

Therefore, in the conventional method of separating the temperature phase from the torque phase, first, the bridge of the torque detection circuit is balanced at room temperature, the torque detection unit is uniformly raised to a predetermined temperature, and the temperature in the unadjusted stage is adjusted. It is basically necessary to examine the phase.

Next, an adjustment work is performed to separate the temperature phase from the torque phase by a predetermined angle or more.

This temperature phase is determined by the temperature coefficient of the coil, and it is known that the temperature phase can be moved by changing the magnitude relationship of the temperature coefficient. Therefore, a small resistor having a temperature coefficient is inserted on one coil side, The adjustment is repeated until the temperature phase deviates from the torque phase by a predetermined angle or more.

As described above, the conventional method of separating the temperature phase from the torque phase has a problem that it requires a great number of man-hours for adjustment and is not efficient, as can be seen from the contents of the adjustment work described above.

[0024]

SUMMARY OF THE INVENTION The present invention has been made as a result of extensive studies on the characteristics of a bridge circuit and the output characteristics of a bridge circuit in order to find a more efficient and excellent method for separating the temperature phase from the torque phase. The object is to provide a magnetostrictive torque measuring device that does not require a great amount of adjustment man-hours when separating the temperature phase from the torque phase, has little temperature drift, and can stably measure the torque. To do.

By the way, in the course of reaching the present invention, the output characteristics of the bridge circuit and the like have been earnestly examined. As a document describing such a bridge circuit, there is a work by Osamu Nishino, "Bridge Circuit and Its Application". (Showa 52) Hiroshi Hara, "Easy-to-understand bridge circuit", industry report (196)
6 years) Osamu Watanabe, "Strain gauge and its application [revised edition]" Nikkan Kogyo Shimbun (sho 52), etc.

Although it is described therein that the bridge sensitivity becomes maximum when the impedances of the respective sides are equal, the details of the bridge circuit output peculiar to the magnetostrictive torque measuring device which is the content of the present invention are described. There was no description of the characteristics.

[0027]

In a magnetostrictive torque measuring device according to the present invention, two sides adjacent to each other are coil sides provided on a shaft to be measured, and the other two sides are fixed resistors to form a bridge. A bridge circuit in which two variable resistors for bridge balance adjustment are respectively provided in parallel with the two coil sides and the two fixed resistance sides is provided, and the torque applied to the shaft to be measured is magnetostrictive. In the magnetostrictive torque measuring device for detecting with the bridge circuit, by inserting a small resistor having no temperature coefficient in one of the coil sides and a small resistor having a temperature coefficient in the other of the coil sides, And the impedance vector of the coil side consisting of a small resistance is Z ₁ (~), Z
₂ (-), when the angles are expressed as θ ₁ and θ ₂ , respectively, by adjusting the value of each of the two small resistances inserted in the coil side, the bridge balance is set after the relationship of θ ₁ <θ ₂ is set. In the embodiment of the magnetostrictive torque measuring device according to the present invention, the temperature phase, which is the phase of the bridge circuit output when only the temperature changes, is set. , The synchronous detection timing is set, and in the same embodiment, the synchronous detection timing is set to the torque phase + 90 ° with respect to the torque phase which is the phase of the bridge circuit output when only the torque is applied. The present invention relates to the above-mentioned magnetostrictive torque measuring device and has a constitution of the invention as means for solving the above-mentioned conventional problems.

In the following, using mathematical expressions and numerical analysis examples,
The configuration of the present invention will be described in more detail.

[Operation Principle, Bridge Circuit Characteristic, Bridge Circuit Output Characteristic] First, the operation principle of the magnetostrictive torque measuring device, the bridge circuit characteristic, the bridge circuit output characteristic and the like will be described using mathematical expressions.

FIG. 3 shows a simplified bridge circuit, and the output ΔV (∼) of the bridge circuit is expressed by the following mathematical formula 1.

[0031]

[Formula 1]

[0032]

Therefore, the impedances Z ₁ (~), Z ₂ (~) of the coils 5, 6 and the resistance value R of the fixed resistors 7, 8 are set.
Including ₁ and R ₂ , ΔV (∼) is expressed by Equations 2 and 3.

[0034]

[Formula 2]

[0035]

[0036]

[Equation 3]

[0037]

Further, V (-) is a bridge applied voltage from the oscillator 13 and is expressed by the equation (4).

[0039]

(Equation 4)

[0040]

On the other hand, the balance condition is ΔV (∼) = 0.
Since it is (~), Equation 5 is obtained from Equation 3.

[0042]

[Formula 5]

[0043]

When the balance is good,
Equation 6 is derived from Equation 5.

[0045]

[Formula 6]

[0046]

Here, the impedance Z in Equation 6
Substituting ₁ (~) and Z ₂ (~) into Equations 7 and 8 respectively yields Equations 9 and 10 below.

[0048]

[Formula 7]

[0049]

[0050]

[Formula 8]

[0051]

[0052]

[Formula 9]

[0053]

[0054]

[Formula 10]

[0055]

That is, when the balance is established, the angles θ ₁ and θ ₂ of the impedances Z ₁ (-) and Z ₂ (-) are equal.

Now, when the torque T is applied to the shaft 2 to be measured, or when the temperature of the torque detecting portion 1 changes, the impedances Z ₁ (~) and Z ₂ (~) of the coils 5 and 6 are given by Equation 11 and Each changes as in Expression 12.

[0058]

[Formula 11]

[0059]

[0060]

[Equation 12]

[0061]

Therefore, ΔV (∼) is ΔV (∼) ≠ 0
(~).

Mathematical formula 13 is derived from Mathematical formula 3, Mathematical formula 11 and Mathematical formula 12 and is further modified to obtain Mathematical formula 14.

[0064]

[Formula 13]

[0065]

[0066]

[Formula 14]

[0067]

Here, the value of the equation 5 when balanced is added with [], and is expressed by the equation 15 so as to be identified.

[0069]

[Formula 15]

[0070]

Now, the equation 14 can be expressed as the equation 16.

[0072]

[Formula 16]

[0073]

It has been confirmed that this approximation is a sufficiently satisfactory approximation and has almost no effect on the result.

The part enclosed by {} in the equation 16 can be transformed into the equation 17 by the equation 5 or the equation 15 which is the balance condition.

[0076]

[Formula 17]

[0077]

Then, by substituting the equation 18 into the equation 17, the equation 19 can be obtained, where θ ₁ is the angle of the impedance Z ₁ (-).

[0079]

[Formula 18]

[0080]

[0081]

[Formula 19]

[0082]

That is, the portion enclosed by {} in the equation 16 is impedance Z ₁ as is apparent from FIG.
It is the sensitivity factor of the bridge circuit determined by the relationship between the magnitude of (-) and the resistance value R _1, and this sensitivity factor has the maximum value when X = 1.

That is, when the magnitude of the impedance Z ₁ (-) and the magnitude of the resistance value R ₁ are equal, the bridge sensitivity factor becomes the largest. It is a well known fact that the bridge sensitivity becomes maximum when the impedances of the bridge sides are equal.

The part enclosed by () on the right side of Expression 16 is the essential part of the bridge circuit determined by the variation of Z ₁ (-) and Z ₂ (-).

Here, the following replacement is performed.

[0087]

[Formula 20]

[0088]

[0089]

[Formula 21]

[0090]

[0091]

[Equation 22]

[0092]

[0093]

[Formula 23]

[0094]

Further, equation 15, equation 22 and equation 2
Equation 24 is obtained from 3.

[0096]

[Equation 24]

[0097]

Next, in Equation 16, Equation 4, Equation 7, and Equation 2
Equation 25 is derived by substituting 0, Equation 21 and Equation 23 and expressing the impedance Z (-) by Ze (jθ).

[0099]

[Formula 25]

[0100]

On the other hand, since Δθ _C can be expressed as Equation 26 from Equation 24, Equation 27 is derived from Equation 25.

[0102]

[Equation 26]

[0103]

[0104]

[Equation 27]

[0105]

When Equation 27 is written in the form of Equation 28, Equation 29 and Equation 30 are derived. In both equations, ΔZ
_C and θ _C are related to the essential part of the bridge circuit.

[0107]

[Formula 28]

[0108]

[0109]

[Equation 29]

[0110]

[0111]

[Formula 30]

[0112]

The part enclosed by {} in the equation 29 is expressed as the equation 31 (see the equation 19).

[0114]

[Formula 31]

[0115]

Here, the impedances Z ₁ (~) and Z ₂ (~) are expressed as in Expressions 32 and 33.

[0117]

[Equation 32]

[0118]

[0119]

[Formula 33]

[0120]

Then, torque or temperature is applied,
It is assumed that the inductance L and the resistance R are represented by the following mathematical formulas.

[0122]

[Equation 34]

[0123]

[0124]

[Formula 35]

[0125]

[0126]

[Formula 36]

[0127]

[0128]

[Formula 37]

[0129]

At this time, α is a torque dependence coefficient [1 / kg
m] or temperature coefficient [1 / ° C], and t is torque [kgm] or temperature [° C]. L _AO , R _AO
Etc. are the values of the inductance L and the resistance R at 0 ° C. when no torque is applied.

Then, ΔZ ₁ (~) and ΔZ ₂ (~)
Is the following Expression 38 and Expression 3 from Expressions 32 to 37.
It can be represented by 9.

[0132]

[Formula 38]

[0133]

[0134]

[Formula 39]

[0135]

Further, the formula 22 is the formula 38 and the formula 39.
Can be expressed as

[0137]

[Formula 40]

[0138]

Further, ΔZ _C can be expressed by the following equation 24 as follows.

[0140]

[Formula 41]

[0141]

Therefore, Expression 42 is derived from Expression 40 and Expression 41.

[0143]

[Formula 42]

[0144]

On the other hand, the equation 43 is derived from the equation 5 and the equations 32 to 37 which are the balance conditions.
Mathematical expressions 44 and 45 are derived as below by associating the real number part and the imaginary number part of

[0146]

[Formula 43]

[0147]

[0148]

[Formula 44]

[0149]

[0150]

[Formula 45]

[0151]

That is, the equation 42 is expressed as follows.

[0153]

[Equation 46]

[0154]

Further, θ _C is represented by the following equation by the equation 40 and the like.

[0156]

[Formula 47]

[0157]

Therefore, when the torque dependence coefficient α or the temperature coefficient α is constant, θ _C is a constant, and ΔZ _C is proportional to the torque t or the temperature t.
It can be seen that Vd of θ and θd of Equation 30 are determined by ΔZ _C and θ _C , respectively.

The device output ΔV (-) is obtained by synchronously detecting ΔV (-). When the detection timing is θt, ΔV (-) is from θt + π, and -ΔV (is from θt + π to θt + 2π. Since the integrated value of ˜) is ΔV (−), the following expression is obtained from Expression 28.

[0160]

[Formula 48]

[0161]

From this equation, when θt = θd, ΔV
(−) Is 0, and ΔV when θt−θd = 90 °
(-) Is the largest value.

The above is the bridge circuit characteristic, the bridge circuit output characteristic and the operating principle.

[Regarding Torque Phase, Temperature Phase, and Elimination Method of Temperature Dependent Component, etc.] Hereinafter, with specific numerical values,
Proceed with explanation.

Using a numerical value of a torque measuring device prototyped from steel having a shaft diameter of 19 mm, 90 turn coil, frequency 30 kHz
Use the value at.

[0166]

[Formula 49]

[0167]

The torque dependence coefficient when + torque is applied is

[0169]

[Formula 50]

[0170]

And the temperature dependence coefficient is

[0172]

[Formula 51]

[0173]

It was

By the way, when the bridge is balanced at a certain temperature and no torque is applied, ΔV (∼)
It can be set to = 0 (-). However, even if the torque is not applied, if only the temperature changes, ΔV (-) ≠ 0 (-).

The reason is that the coefficient of t in the equation 46 is not zero.

As a practical matter, it is impossible that the coefficient of t is 0, that is, the temperature coefficient is the same. (See formula 51).

Therefore, the zero point of the torque measuring device drifts with temperature.

When the bridge is balanced at a certain temperature and no torque is applied, ΔV (∼) = 0
(~). In that state, θd in Expression 30 when only the torque is applied is defined as the torque phase. This torque phase θd is almost constant, and the amplitude Vd is
It changes with the magnitude of torque.

Further, θd when only the temperature changes is defined as the temperature phase. This temperature phase θd is also almost constant, and the amplitude Vd changes depending on the degree of temperature change.

The torque phase is written as θd (torque) and the temperature phase is written as θd (temperature).

Now, θd (torque) and θd (temperature) are 9
When the distance is about 0 °, the detection timing θt is set to θd
Assuming (temperature), the temperature-dependent amount can be eliminated as is clear from the equation (48), and the device output can be effectively output only for the torque. This is the method of eliminating the temperature-dependent component by performing synchronous detection in the temperature phase.

Now, comparing θd (torque) and θd (temperature) is essentially the same as comparing θ _C (torque) and θ _C (temperature). This is because θ _A and θ _B in Equation 30 can be regarded as constants.

Note that θ _C is an unmeasurable quantity, and what can be measured is θ d.

Next, θ _C (torque) will be considered with reference to the vector diagram of FIG.

In Equation 47, the signs of α _LA and α _LB are opposite, and the signs of α _RA and α _RB are also opposite, and they result in a sum.

Generally, in the torque dependence coefficient,

[0188]

The relationship is as follows. (See Formula 50). Therefore, θ _C (torque) is expressed by the following equation.

[0190]

[Equation 52]

[0191]

For reference, when X = 1, that is, R ₁ = Z ₁
In the case of, θ ₁ = θ _A / 2. (See vector diagram in FIG. 6).

Further, when the balance is established by the equation 2, since θ _A = θ _B ,

[0194]

It becomes:

Now, in the torque dependence coefficient,

[0197]

The reason why is also mentioned.

The impedance Z (-) of the coil is expressed by the following equation, as described above.

[0200]

[Equation 53]

[0201]

On the other hand, the AC magnetic permeability μ as a characteristic of the material
(-) Is represented by Expression 54, and μ ′ and μ ″ have the following relationship with the inductance L and the resistance R.

[0203]

[Equation 54]

[0204]

[0205]

[Formula 55]

[0206]

Here, Rac is an AC resistance component and can be expressed as in Equation 56.

[0208]

[Formula 56]

[0209]

Rdc is the DC resistance of the coil, and its value is smaller than that of Rac.

That is, when torque is applied, μ ′ and μ ″
Changes to the same extent,

[0212]

That is,

Next, θ _C (temperature) will be considered with reference to the vector diagram of FIG.

In Expression 47, α _LA and α _LB have the same sign, and α _RA and α _RB have the same sign, and the difference between them is related. (Formula 51).

Generally, since the differences in temperature coefficients, Δα _L , and Δα _R have a variation of about ± 2%, θ _C (temperature)
Varies depending on the torque measuring device.

Therefore, the temperature drift is different for each torque measuring device.

The variation of the temperature coefficient is μ ′, μ ″, Rd
It is considered that this is due to the variation in the temperature coefficient of c.

In the case of steel having a shaft diameter of 19 mm, the values of θ _C (torque) and θ _C (temperature) are checked. The following values are obtained from the equations 47, 49 and 50.

[0220]

[Formula 57]

[0221]

On the other hand,

[0223]

Therefore,

[0225]

The following relationship is established. (See Formula 52).

Further, θ _C (temperature) is expressed by the equations 47, 49, 5
The following values are obtained from 1.

[0228]

[Formula 58]

[0229]

In this case, the temperature phase is the torque phase,
It is almost the same place.

Since θc (torque) is about + 73 °,
Consider setting θc (temperature) to −. Now, since α _L (temperature coefficient) is α _LA −α _LB > 0, α _RA −α
_It suffices if _RB <0 is satisfied, and a small resistance having a temperature coefficient is inserted in Z ₂ (to) to increase α _RB .

[0232] Therefore, when put 1Ω (0.004 / ° C) α RB = 1.4271 × 10 - becomes ³ / ° C, this time, to obtain the following values.

[0233]

[Formula 59]

[0234]

Therefore, the temperature phase is separated by about 80 °, and it is expected that the temperature dependence can be eliminated by detecting the temperature phase.

[0236] Now [.theta.c (temperature) set of ideas] and rearranging the above, theta _C (torque) is approximately determined by theta _1, a theta _1> 0 and the shaft diameter 19mm Steel The case is about 73 °.

Therefore, the magnitude relationship of the temperature coefficient may be set as in the following equation so that the value of θ _C (temperature) takes a negative value.

[0238]

[Equation 60]

[0239]

In the equation 60, the following values are obtained for steel having a shaft diameter of 19 mm.

[0241]

[Equation 61]

[0242]

FIG. 7 is an explanatory diagram for setting θ _C (temperature).

[Actual Bridge Circuit] In the actual bridge circuit, as shown in FIG. 2, resistors Rex ₁ and Rex ₂ for balance adjustment are put in parallel.

FIG. 8 is a rewrite of the actual bridge circuit for easier understanding.

FIG. 8 is exactly the same as FIG. 2, and the magnitudes of the external resistors when the balance is established are R _Z1 and Rexr.
It is represented by ₁ .

Now, the combined impedance of each side of the bridge circuit when resistors are inserted in parallel is Z ₁ ′ (˜), R ₁
If expressed as ′ etc., the equation calculated so far can be used as it is.

By the way, in the case of steel having a shaft diameter of 19 mm, θ _C (temperature) should be always a value of − according to the expectation from the numerical formula 59, but in the result of the experiment using the actual bridge circuit, , Θ _C (temperature) did not become −.

The fact that the inventors have earnestly researched for this is the reason why the present invention can be realized.

[Change of Temperature Coefficient by Bridge Balance] For example, the temperature coefficients α _LA and α of Z ₁ (∼) are
_RA (or torque dependent coefficient) is subject to slight changes after balancing the bridge.

That is, α is the temperature coefficient in the combined impedance Z ₁ ′ (˜) on the side on the Z ₁ (˜) side.
_LA ′, α _RA ′ is the temperature coefficient α of Z ₁ (˜) alone.
Differences from _LA and α _RA will be referred to as changes here (the same applies to other quantities).

Further, R _AO and L _AO are slightly modified, and Z ₂ (-) is also similarly modified.

Therefore, it is possible that θ _C (temperature) in Expression 47 does not change as expected.

When the bridge balance is established, as already described in formula 10, the combined impedances Z ₁ ′ (to) and Z ₂ ′ with the external resistors for balance adjustment.
The angles θ ₁ ′ and θ ₂ ′ of (-) are equal to each other. Moreover, the angle is slightly smaller than the smaller one of θ ₁ and θ ₂ .

For example, when θ ₁ > θ ₂ , θ ₁ becomes θ ₂
The value will change to a slightly smaller value θ ₁ ′ (= θ ₂ ′).

It is considered that when the angle is changed, the temperature coefficient is also changed, and a detailed study was made by numerical analysis.

Analysis was performed based on the data of steel having a shaft diameter of 19 mm.

Rex ₁ = Rex ₂ = 500 kΩ and Z
FIG. 9 shows the result of analysis of how the temperature coefficient changes when θ ₂ of ₂ (-) is changed from −3.0 ° to + 3.0 °.

[0259] In FIG. 9, the vertical _axis, for the first temperature coefficient _Z 1 (~) or _Z 2 (~), _Z 1 after being bridge balance '(...) and _Z 2' (-) It shows how large the temperature coefficient of is.

On the other hand, the horizontal axis of FIG. 9 shows how many times the angle changes after the bridge balance is taken, from −3 ° to
In the range of 0 °, θ ₁ decreases by that angle, and 0 ° to + 3 °
Then θ ₂ is reduced by that angle. In other words, the temperature coefficient changes as the angle changes. For example, if the angle changes by 1 degree, α _L decreases by about 5% and α _R decreases by about 4%.
You can see that it decreases by%. (Note that the various quantities in the combined impedance will be described without the suffix, and this will be the same in the following.) Next, the case of Expression 59 will be examined again.

By adding 1Ω to Z ₂ (-), θ ₂ changes from 72.98 ° to 72.02 °. On the other hand, Z
_Since θ ₁ of ₁ (to) is 72.97 °, θ ₁ > θ ₂ . In other words, when taking bridge balance, θ ₁ is 1
° It will change slightly. At this time, α _LA is about 5%
Since it becomes smaller, the relationship of α _LA −α _LB > 0 does not hold and α _LA −α _LB <0 holds, which is the reason why θ _C (temperature) did not become − in the experiment.

Therefore, a small resistor having no temperature coefficient is also inserted in Z ₁ (-),

[0263]

Then, by slightly setting θ ₁ to be smaller, the relationship of α _LA −α _LB > 0 is established.

By the way, in general, α _LA , α _LB , α
It cannot be confirmed, including the magnitude relationship between the temperature coefficients of _RA and α _RB .

Further, it is complicated and inefficient to examine each torque measuring device.

After all, if θ ₁ is set to be smaller by about 1 °, α _LB will be reduced by about 5%, so it is certain that α _{LA is}
The relationship of −α _LB > 0 comes to hold (the temperature coefficient difference is about ± 2%).

[0268] In _{addition, 1Ω} towards the _Z 2 (~) (0.004
/ ° C), α _RB = 1.4271 × 1
It becomes 0 ⁻³ / ° C and increases by about 12%. Even if this increase is reduced by about 4%, an increase of about 8% is ensured, so that the relationship of α _RA −α _RB <0 is also established.

When a small resistance having no temperature coefficient is inserted in Z ₁ (-), α _R is reduced by that amount, so that the relationship α _RA -α _RB <0 is surely established. Become.

Based on the above consideration, let us estimate θ _C (temperature) in the case of steel having a shaft diameter of 19 mm.

[0271] towards _Z 1 of (~) is, put 2Ω a small resistance that does not have a temperature _coefficient, towards the _Z 2 (~), the temperature coefficient of 0.
If a small resistance of 1 Ω at 004 / ° C. is added, θ ₁ = 71.10
Θ, θ ₂ = 72.02 °, and θ ₂ is 0.91 °
Can be set large.

The temperature coefficient before bridge balance is the same for α _LA and α _LB, and α _RA is 1.
It becomes as small as 1465 × 10 ⁻³ / ° C, and α _RB is 1.
It increases to 4271 × 10 ⁻³ / ° C.

Then, in taking the bridge balance,
When alpha _LB is the alpha _{R B} with 5% smaller and 4% ^{_{smaller, α LB = 2.5559 × 10 -4}} / ° C, α
_{Since RB} = 1.3700 × 10 ⁻³ / ° C, the following values are obtained by substituting these values into Equation 47.

[0274]

[Equation 62]

[0275]

The value of θ _C (temperature) is almost the same as the value obtained by the experiment.

Now, the torque dependence coefficient is also slightly changed.

The results of the analysis similar to FIG. 9 show that α _L is decreased by about 1% and α _R is increased by several% after one change.

It is considered that there is almost no influence on these θ _C (torque).

Further, it is considered that there is almost no influence on the sensitivity of the torque measuring device. Means θ _C (torque)
This is because the torque dependence coefficient that determines is calculated in the form of sum as shown in Expression 47.

Further, it is the term of sin ² θ ₁ (α _LA −α _LB ) ² that determines the magnitude of ΔZ _{C in} the equation 46, and α _LA or α _LB is reduced by about 1%. Even △
This is because the size of Z _C hardly changes.

It is considered that the difference in ± sensitivity of the torque measuring device is hardly influenced, and further, it is considered that it does not cause the hysteresis with respect to the torque.

As a result of actual experiments, the above points were confirmed.

That is, although the torque dependence coefficient is also slightly changed, it has almost no effect on the output characteristic and can be ignored.

The degree of change of the temperature coefficient in FIG. 9 is θ
_This is the case when ₁ is about 73 °. When θ ₁ has a different magnitude, the degree of change in the temperature coefficient also becomes slightly different.

However, since the degree of change of the temperature coefficient does not change significantly, it is sufficient to consider based on the result of FIG.

In the above description and the embodiments described later, the description is limited to exemplifications and the like for explaining the contents of the invention, but an adjusting method in a bridge circuit utilizing the above concept is also included. Needless to say, it is included.

[0288]

Since the magnetostrictive torque measuring device according to the present invention has the above-mentioned structure, the adjustment work for setting the temperature phase apart from the torque phase can be easily performed, so that the number of man-hours required is small. In addition, since the phases can be reliably separated, the temperature drift is small and the measurement can be stably performed.

[0289]

Example 1 Chromium-molybdenum (SCM) -based steel was used as a raw material and was machined to obtain a shaft 2 to be measured for a torque measuring device having a shaft diameter of 19 mm.

The measured shaft 2 has a width of 1 mm,
Partial spiral grooves 3, 4 with a depth of 1.5 mm (0.5R)
To form ± 45 ° (see FIG. 1). In this case, the number of grooves is 20 (divided into 20 equal parts) and the length of the groove is 1
It was set to 0 mm. Then, carburizing and quenching and tempering were performed.

With respect to the shaft 2 to be measured, coils (90 turns) 5 and 6 having a width of 5 mm were installed so as to face the partial spiral grooves 3 and 4, respectively.

The torque dependence coefficient and temperature dependence coefficient of the impedance of the coils 5 and 6 described above are measured in this state. (See Formulas 49 to 51, where θ ₁ =
72.97 °, θ ₂ = 72.98 °) And, in the bridge circuit, in order to separate the temperature phase from the torque phase, a resistance of 2Ω made of manganin wire is attached to one side and a temperature coefficient of 0. A 1Ω resistance of 004 / ° C was applied.

At that time, θ ₁ and θ ₂ at the frequency of 30 kHz measured by the impedance analyzer are θ
₁ = 71.10 °, θ ₂ = 72.02 °, and θ ₂
Was able to be set larger by 0.92 °.

Further, a variable resistance of Rex ₁ = Rex ₂ = 500 kΩ is used as a resistance for balance adjustment, and R ₁ = R ₂ =
It was set to 50Ω.

Therefore, when the bridge balance was taken at room temperature and a torque of +20 kgm was applied, the torque phase was 4.5 °.

Next, without applying torque, the temperature of the torque detector was raised uniformly to about 20 ° C. Phase at this time,
That is, the temperature phase was 94.1 °, and this phase was used as the detection timing θt.

By the way, θ _A = 38.7 °, θ _B = 38.7.
Since θ is estimated to be θ _C (torque) = 72.9 °,
θ _C (temperature) = − 16.7, and θ _C (temperature) almost agrees with the expectation of the above-mentioned formula 62.

The torque phase and the temperature phase are 89.
It is supposed to be 6 ° apart, which is a very desirable situation.

The temperature drift at the zero point when the temperature was raised to 100 ° C. was less than −0.1 kgm, and was even smaller in the temperature range below that.

In the above description, in order to confirm the contents of the invention, the description was made in order, but the actual work can be performed more easily.

That is, it is known that θ _C (torque) is approximately the angle of either one of the coils 5 and 6.

Now, when + torque is applied, the coil 5
Is set to be tensile (see Fig. 1), θ
_{Since C} (temperature) may be set to −, α _LA −α _LB > 0 and α _RA −α _RB <0 in Expression 47.

[0303] Therefore, the add small resistor having a temperature coefficient towards the coil 6, put a small resistor having no minute temperature coefficient of the coil 5, further and θ _{1 <θ 2,} in this case theta ₂ For one, make it about 1 degree larger.

In this state, bridge balance is taken at room temperature.

Next, the temperature is raised to a predetermined temperature,
At this time, the detection timing θ is set so that the device output becomes zero.
Set t.

After that, the temperature is returned to room temperature, and the calibration with respect to the torque, that is, only the gain adjustment is performed.

[0307]

Example 2 Fe: Al: 13% by weight, balance Fe
-Al alloy (high-sensitivity shaft material) was used as a raw material, and this was machined to be a measured shaft for a torque measuring device having a shaft diameter of 20 mm.

Then, a pair of partial spiral grooves having a width of 2 mm and a depth of 1 mm (1R) were formed in the ± 45 ° direction on the shaft to be measured (see FIG. 1). In this case, the number of grooves was 12 (12 equal parts), and the length of the groove was 11 mm.
Then, heat to 860 ° C in vacuum and hold for 3 hours,
A heat treatment of quenching in oil was applied.

A coil (132 turns) having a width of 10 mm was installed on the shaft to be measured so as to face the partial spiral groove.

At this time, θ ₁ and θ ₂ are θ ₁ = 72.77.
, Θ ₂ = 72.65 °, and Rex ₁ = Rex ₂ =
A variable resistance of 500 kΩ was used as a resistance for balance adjustment, and R ₁ = R ₂ = 100Ω.

Therefore, when the bridge balance is taken at room temperature and a torque of +4 kgm is applied, the torque phase is:
It was 2.2 °.

Therefore, the detection timing θt is set to 92.2 °.
However, in actual work, the detection timing θt is set so that the sensitivity is maximized.

The zero point drift was +0.11 kgm when the temperature of the torque detector was raised to 100 ° C. without applying torque.

Next, one side of the coil was provided with a resistance of 3Ω made of manganin wire, and the other side of the coil was provided with a resistance of 1.5Ω with a temperature coefficient of 0.004 / ° C.

At that time, θ ₁ = 71.24 °, θ ₂ = 7
It was 1.87 °, and θ ₂ could be set larger by 0.63 °.

Then, a bridge was assembled, the balance was maintained at room temperature, and the torque phase when applying a torque of +4 kgm was 1.4 °.

Therefore, the detection timing θt is set to 91.4 °.

Rex ₁ , Rex ₂ , R ₁ and R ₂ are the same, and the actual work is also the same as described above.

The drift of the zero point when the temperature of the torque detector is raised to 100 ° C. without applying torque is −
It was 0.02 kgm.

As described above, in the magnetostrictive torque measuring device using the Fe-Al alloy, which is a high-sensitivity shaft material, for the shaft to be measured, it suffices to set the temperature phase and detect the torque phase + 90 ° at room temperature. By doing so, the temperature drift can be reduced, and the drifting direction can be made constant at all times.

When a temperature difference occurs in the axial direction, an error due to the temperature difference occurs. Therefore, in a practical magnetostrictive torque measuring device, a measure is taken to compensate for the temperature difference with four coils. There is.

In the present invention, in order to explain the contents, 2
Although only the case of a single coil has been described, the present invention
Of course, it can be applied to the case of individual coils.

When four coils are used, there are four coils in the axial direction, that is, Z _C (∼), Z _A (∼), Z
_B (-) and Z _D (-) are arranged in this order, and
_A (~) and Z _B (~) are opposed to the groove portion.

Then, for example, Z _A (~) and Z _D (~)
And the pair of coils is the coil 5 and Z _B (~) and Z _C (~)
If the pair is the coil 6, the same action and effect as in the case of the previous two coils can be expected.

[0325]

As described above, in the magnetostrictive torque measuring device according to the present invention, the setting work for separating the temperature phase from the torque phase can be performed very easily, and it has been necessary until now. It is possible to eliminate a great deal of adjustment man-hours, and since the temperature phase can be reliably separated from the torque phase by 70 ° or more in one setting operation, temperature drift is reduced and stable measurement is possible. The effect is brought.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a schematic configuration of a torque detection unit of a magnetostrictive torque measuring device.

FIG. 2 is an explanatory diagram illustrating the configuration of a bridge circuit that is a torque detection circuit and a signal processing circuit of the magnetostrictive torque measuring device.

FIG. 3 is an explanatory diagram of a simplified bridge circuit used when formulating a bridge circuit output characteristic of a magnetostrictive torque measuring device.

FIG. 4 (a) is a vector diagram of impedance Z ₁ (to) when torque is applied. (B) it is a vector diagram according to a torque applied in the impedance _Z 2 (~).

FIG. 5 (a) is a vector diagram of impedance Z ₁ (˜) when temperature is applied. (B) it is a vector diagram according to the temperature applied in the impedance _Z 2 (~).

FIG. 6 is a vector diagram of impedance Z _A (˜).

FIG. 7 is an explanatory diagram showing a setting range of a phase that controls a temperature phase.

FIG. 8 is an explanatory diagram of a bridge circuit equivalent to an actual bridge circuit, which emphasizes that resistors for balance adjustment are connected in parallel.

FIG. 9 is a graph showing the rate of change of the temperature coefficient in the combined impedance of the bridge sides when the bridge is balanced when the angles of the impedance Z ₁ (-) and the impedance Z ₂ (-) are different.

[Explanation of symbols]

 1 torque detection part of torque measuring device 2 measured shaft 5, 6 coil 10 torque detection circuit of torque measuring device

Claims (3)

(57) [Claims] 1. A bridge is formed by using two sides adjacent to each other as coil sides provided on a shaft to be measured, and the other two sides as fixed resistors to form a bridge, and the two side coil sides and the two fixed resistance sides are connected. On the other hand, in the magnetostrictive torque measuring device, which comprises a bridge circuit in which two variable resistors for bridge balance adjustment are provided in parallel, and the torque applied to the shaft to be measured is detected by the bridge circuit by magnetostriction action, By inserting a small resistance having no temperature coefficient in one of the sides and a small resistance having a temperature coefficient in the other of the coil sides, impedance vectors of the coil side composed of the coil and the small resistance are respectively set to Z ₁ (~), Z
₂ (-), when the angles are expressed as θ ₁ and θ ₂ , respectively, the value of each of the two small resistances inserted in the coil side is adjusted.
A magnetostrictive torque measuring device comprising a bridge circuit in which the bridge balance is set after setting the relationship of θ ₁ <θ ₂ by doing so . To 2. A temperature phase only temperature is a bridge circuit output of the phase when the changes, the magnetostrictive torque measuring apparatus according to claim 1, characterized in that setting the timing of synchronous detection. To 3. A torque phase is a bridge circuit output of the phase at the time of applying torque only, magnetostrictive torque measurement according to claim 1, characterized in that the torque phase +90 degrees setting the timing of the synchronous detection apparatus.