JP2677067B2 - 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 or the like, or an axis of a rotary shaft of an electric motor (axis to be measured)
The present invention relates to a magnetostrictive torque measuring device used for non-contact detection of torque applied to a shaft by utilizing a magnetostrictive action of the shaft.

[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, Z ₁ (...), Z
₂ (~) is the impedance vector of the coils 5 and 6 shown in FIG. 1, and ~ indicates that the impedance is a complex number. 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 .

An AC voltage of V · e ^jwt is supplied to the bridge circuit 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 for separating the temperature phase from the torque phase requires a great number of man-hours for the adjustment, which is not efficient, as can be seen from the contents of the adjustment work described above. .

[0024]

OBJECTS OF THE INVENTION The present invention seeks to find a more efficient and superior method for separating the temperature phase from the torque phase.
It was made as a result of extensive studies on the characteristics of the bridge circuit, the output characteristics of the bridge circuit, the temperature coefficient of the coil, etc.
The purpose 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 a small temperature drift, and can stably measure the torque. To do.

In the process leading to the present invention, the characteristics of the bridge circuit, the output characteristics of the bridge circuit, and the like have been earnestly examined. Application ”, Ohmsha (1978) Hiroshi Hara,“ Understandable Bridge Circuit ”, Industry Report (196)
6 years) Osamu Watanabe, "Strain gauge and its application [revised version]", 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.

The present applicant has found a more effective measure for separating the temperature phase from the torque phase and has filed a separate application.

That is, a small resistor having no temperature coefficient is inserted in one of the coil sides and a small resistor having a temperature coefficient is inserted in the other side of the coil, and an impedance vector consisting of the coil and the small resistor is inserted into Z ₁ respectively. (~), Z ₂ (~),
When the angles are expressed as θ ₁ and θ ₂ , respectively, θ ₁ <θ
_The temperature phase is separated by providing a bridge circuit in which the bridge balance is set after setting the relationship of ₂ .

The present invention has the same object as the above invention, but is based on a completely different idea and concept, as will be described in detail later.

[0030]

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, the coil sides of the two sides are made different from each other to give different impedance magnitudes, and the coil side having the larger number of coil turns has a temperature coefficient. Insert a small resistor that does not have an impedance vector of the coil side consisting of the coil and the small resistance and an impedance vector consisting of only the coil side. _{Z 1 (~), Z 2} (~), angle when expressed θ _1, θ _2, respectively

[0031]

In addition, the present invention is characterized in that it is provided with a bridge circuit in which 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 to the timing of synchronous detection, and in the same embodiment, the torque phase that is the phase of the bridge circuit output when only torque is applied is set. On the other hand, it is characterized in that the timing of synchronous detection is set to the torque phase + 90 °, and the configuration of the invention relating to the above-mentioned magnetostrictive torque measuring device serves as means for solving the above-mentioned conventional problems.

Below, 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, etc. 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.

[0036]

[Formula 1]

[0037]

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.

[0039]

[Formula 2]

[0040]

[0041]

[Equation 3]

[0042]

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

[0044]

(Equation 4)

[0045]

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

[0047]

[Formula 5]

[0048]

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

[0050]

[Formula 6]

[0051]

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

[0053]

[Formula 7]

[0054]

[0055]

[Formula 8]

[0056]

[0057]

[Formula 9]

[0058]

[0059]

[Formula 10]

[0060]

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 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.

[0063]

[Formula 11]

[0064]

[0065]

[Equation 12]

[0066]

Therefore, ΔV (∼) is ΔV (∼) ≠ 0
(~).

Equation 13 is derived from Equations 3, 11 and 12, and is further modified to obtain Equation 14.

[0069]

[Formula 13]

[0070]

[0071]

[Formula 14]

[0072]

Here, the value of the equation 5 when balanced is added by [], and is expressed by the equation 15 for identification.

[0074]

[Formula 15]

[0075]

Now, Equation 14 can be expressed as Equation 16.

[0077]

[Formula 16]

[0078]

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.

[0081]

[Formula 17]

[0082]

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 (-).

[0084]

[Formula 18]

[0085]

[0086]

[Formula 19]

[0087]

That is, the part enclosed by {} in the equation 16 is impedance Z as is apparent from FIG.
It is the sensitivity factor of the bridge circuit determined by the relationship between the magnitude of ₁ (-) 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 (∼).

Therefore, if the value of ΔZ (-) / (Z) (-) does not depend on the magnitude of Z (-), then Z
It means that the magnitudes of ₁ (-) and Z ₂ (-) do not necessarily have to be the same, and for example, Z ₂ (-) can be changed to Z ₁
When it is made smaller with respect to (~), if R ₂ is also made smaller with respect to R ₁ at the same rate, ΔV (~) in Formula 16
/ V (-) does not change (see Formula 19).

If Z ₂ (~) and R ₂ are reduced,
A larger amount of current flows in Z ₂ (∼) than in Z ₁ (∼), but the torque dependence coefficient and the temperature dependence coefficient described later are not affected by the practical current value flowing in the coil of the torque measuring device. I hardly receive it.

Further, the torque dependence coefficient is hardly affected by the magnitude of Z (-).

Here, the following replacement is performed.

[0095]

[Formula 20]

[0096]

[0097]

[Formula 21]

[0098]

[0099]

[Equation 22]

[0100]

[0101]

[Formula 23]

[0102]

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

[0104]

[Equation 24]

[0105]

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).

[0107]

[Formula 25]

[0108]

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

[0110]

[Equation 26]

[0111]

[0112]

[Equation 27]

[0113]

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.

[0115]

[Formula 28]

[0116]

[0117]

[Equation 29]

[0118]

[0119]

[Formula 30]

[0120]

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

[0122]

[Formula 31]

[0123]

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

[0125]

[Equation 32]

[0126]

[0127]

[Formula 33]

[0128]

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

[0130]

[Equation 34]

[0131]

[0132]

[Formula 35]

[0133]

[0134]

[Formula 36]

[0135]

[0136]

[Formula 37]

[0137]

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.

[0140]

[Formula 38]

[0141]

[0142]

[Formula 39]

[0143]

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

[0145]

[Formula 40]

[0146]

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

[0148]

[Formula 41]

[0149]

Therefore, the expression 42 is derived from the expressions 40 and 41.

[0151]

[Formula 42]

[0152]

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

[0154]

[Formula 43]

[0155]

[0156]

[Formula 44]

[0157]

[0158]

[Formula 45]

[0159]

That is, the equation 42 is expressed as follows.

[0161]

[Equation 46]

[0162]

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

[0164]

[Formula 47]

[0165]

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 (-), and assuming that the detection timing is θt, ΔV (-) up to θt + π, and -ΔV (from θt + π to θt + 2π. Since the integrated value of ˜) is ΔV (−), the following expression is obtained from Expression 28.

[0168]

[Formula 48]

[0169]

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.

[Torque Phase, Temperature Phase, and Elimination Method of Temperature Dependent Component] Here, when the bridge is balanced at a certain temperature and no torque is applied, ΔV (∼) = 0 ( ~) However, if only the temperature changes even if no torque is applied, ΔV (∼) ≠ 0
It becomes (~).

The reason is that the coefficient of t in Expression 46 is not 0.

As a practical matter, it is impossible that the coefficient of t is 0, that is, the temperature coefficient is the same.

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.

It should be noted 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 Expression 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,

[0185]

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

[0187]

[Formula 49]

[0188]

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

Further, when the balance is established by the equation 2, since θ _A = θ _B , the equation 30

[0191]

It becomes:

Now, in the torque dependence coefficient,

[0194]

The reason why the reason is also mentioned.

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

[0197]

[Formula 50]

[0198]

On the other hand, the AC magnetic permeability μ as a characteristic of the material
(-) Is represented by Expression 51, and μ ′ and μ ″ have the following relationship with the inductance L and the resistance R.

[0200]

[Formula 51]

[0201]

[0202]

[Equation 52]

[0203]

Here, Rac is an AC resistance component and can be expressed by the following equation.

[0205]

[Equation 53]

[0206]

Rdc is a direct current resistance component 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,

[0209]

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.

In general, there is a slight difference in the temperature coefficient, and the difference Δα _L , Δα _{R in the} temperature coefficient may be + or −, so that θ _C (temperature) is different for each torque measuring device. Come on.

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

Therefore, by adjusting the magnitude relationship of the temperature coefficient,
_The basic idea is to set _C (temperature) apart from θ _C (torque).

[0216] [theta _C (temperature) set Concept] theta _C (torque) is approximately determined by theta _1, in the case of steel theta _1> 0 a is and shaft diameter 19mm is approximately 73 °.

Accordingly, the magnitude relationship of the temperature coefficients may be set as in the following expression so that the value of θ _C (temperature) takes a negative value (see Expression 47).

[0218]

[Equation 54]

[0219]

In the formula 54, the following values are obtained for steel having a shaft diameter of 19 mm.

[0221]

[Formula 55]

[0222]

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

That is, if θ _C (temperature) can be set to a negative value, the temperature phase can be separated from the torque phase by more than θ ₁ .

[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 Rz ₁ 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.

In the invention separately filed by the present applicant, for example, a small resistance having a temperature coefficient is attached to the other side of the coil side of the bridge circuit having two coil sides by α.
_RB is increased so that α _RA <α _RB . That is α _RA
-Α _RB <0.

Further, in order to surely establish the relationship of α _LA −α _LB > 0, a small resistance having no temperature coefficient is attached to one of the coil sides to establish a relationship of θ ₁ <θ ₂ and θ ₁ is better. Θ
Set about 1 ° smaller than ₂ .

When the bridge is balanced by setting the angle in this way, the angle θ ₂ ′ of the other combined impedance of the coil side at the time when the bridge is balanced becomes an angle slightly smaller than θ ₁ . At this time, the temperature coefficients α _LB ′ and α _RB ′ in the combined impedance decrease, which is called the change of the temperature coefficient by changing the angle.

Therefore, α _LA ′ −α _LB ′> 0 can be realized.

Further, since a small resistance having no temperature coefficient is attached to one of the coil sides, α _RA becomes slightly small.

With the above-mentioned structure, the content of the invention separately filed by the applicant of the present invention is such that the relationship of Expression 54 is substantially established.

In the present invention, as described below,
The relationship of Expression 54 is realized by a method based on a completely different concept.

[Coil Temperature Coefficient] Let us consider how the temperature coefficient of R is determined.

As described above, R is Rd from the mathematical expression 53.
It is represented by c + Rac. Here, when the temperature coefficient of Rdc is αdc and the temperature coefficient of Rac is αac,
Similarly, from Expression 53, R (t) at t ° C. is represented by the following expression.

[0238]

[Formula 56]

[0239]

At this time, Rdc ° and Rac ° are values at 0 ° C. and Equation 53 is transformed to obtain Equation 57.

[0241]

[Formula 57]

[0242]

Therefore, the temperature coefficient α _R of _R can be expressed by the following equation.

[0244]

[Formula 58]

[0245]

By the way, αdc is a temperature coefficient of a copper wire which is a winding, and has the following value.

[0247]

[Formula 59]

[0248]

On the other hand, αac is the temperature coefficient αμ ″ of the imaginary part μ ″ of the AC permeability, and this αμ ″ is considered to be almost the same value as the temperature coefficient αμ ′ of the AC permeability μ ′.

Since this αμ 'is the temperature coefficient of the inductance L, it is about 3 × 10 ^-4 / ° C. (value at 30 kHz) (see formula 51 and formula 52).

Therefore, the following equation is obtained.

[0252]

[Equation 60]

[0253]

That is, αac and αdc have a size of 1
It will be different.

It should be noted that Rac °> Rdc ° and α _R has a magnitude of 1 × 10 ⁻³ / ° C.

Next, considering what happens to α _R when the number of turns is changed, it can be seen that since the magnitude of Rac ° becomes larger as the number of turns increases, α _R becomes smaller than in Equation 58.

As described above, α _R becomes smaller as the number of coil turns increases.

Next, let us consider what happens to the temperature coefficient of the inductance L depending on the number of coil turns.

When an attempt was made to measure the temperature coefficient by changing the number of coil turns, the temperature coefficient of R was smaller as the number of coil turns was larger, as inferred above.

On the other hand, the temperature coefficient of the inductance L was slightly larger as the number of turns was larger.

The reason is inferred as follows.

Αμ ′ at the groove and αμ at the flat part beside it
It was estimated from the theoretical consideration and the indirect measurement data that there is a difference with ′ (see FIG. 1). In this case, it is considered that αμ ′ of the groove is slightly smaller. Therefore, it can be considered that the temperature coefficient of the inductance L becomes slightly larger because the spread of the magnetic flux becomes larger as the number of coil turns increases.

In summary, the temperature coefficient of the inductance L becomes slightly larger as the number of coil turns increases.
This means that the temperature coefficient of R becomes small.

Therefore, if the number of turns on one side of the coil is increased and the number of turns on the other side of the coil is reduced, α
_{Since LA-} α _LB > 0 and α _RA −α _RB <0, the relationship of Expression 54 can be satisfied.

It has been confirmed in an experiment that the torque dependence coefficient hardly changes depending on the number of coil turns.

The torque dependence coefficient and temperature coefficient are also
It is known that the current hardly depends on the current in the current range of several tens mA which is used in the torque measuring device.

In the above description and the embodiments described later, the description is limited to exemplifications and the like, which are very limited in order to explain the content of the invention, but also includes a method of investigating in a bridge circuit utilizing the above concept. Needless to say.

[0268]

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.

[0269]

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,
A pair of partial spiral grooves 3 and 4 having a depth of 1.5 mm (0.5 R) were formed in the directions of ± 45 ° (see FIG. 1). in this case,
The number of grooves was 20 (divided into 20 equal parts), and the groove length was 10 mm. Then, carburizing and quenching and tempering were performed.

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

In this state, various measurements were attempted by considering the number of turns of both coils 5 and 6.

The results are summarized in the contents described above.

From the result of the experiment, the number of turns of the coil 5 is 126 turns in 6 layers, and the number of turns of the coil 6 is 5.
I decided to do 105 turns as a layer.

A polyurethane-coated copper wire having a wire diameter of 0.2 mm was used for the winding.

Values of the inductance L and the resistance R at room temperature (30 kHz) when the number of turns is set as described above.
Was as in the following formula (value with axis).

[0277]

[Equation 61]

[0278]

When the temperature coefficient was also measured, the value of the following equation was obtained.

[0280]

[Equation 62]

[0281]

Here, when θ _C (temperature) is roughly estimated,
The following value is obtained from the expression 47.

[0283]

[Equation 63]

[0284]

By the way, θ ₁ = 73.80 °, θ ₂ = 7
3.26, and the relationship between θ ₁ and θ ₂ is θ ₁ > θ ₂ . If a bridge is built as it is and balanced, θ ₁ ′ (θ ₁ ′ is the angle of the combined impedance at the bridge side) when the balance is established becomes a value slightly smaller than θ ₂ , so the combined impedance at the bridge side is The temperature coefficients α _LA ′ and α _RA ′ are slightly reduced.

Therefore, α _LA ′ −α _LB ′> 0 cannot be secured.

Therefore, a small resistor having no temperature coefficient is inserted in one of the coil sides,

[0288]

It is necessary to satisfy θ ₁ <θ ₂ .

The contents of the change of the temperature coefficient by the change of the angle are included in the invention separately filed by the applicant.

Here, 1.3 created by the manganin line is used.
A resistance of Ω was attached to one side of the coil. At that time, θ ₁ was 73.16 °, which was smaller than θ ₂ by 0.1 °. In addition, by adding a resistance of 1.3Ω, α _RA of Formula 62 becomes α _RA = 1.045 × 10 ⁻³ / ° C.
Becomes

Since α _LB and α _RB can be considered to undergo almost no change in the temperature coefficient, anew, θ _C
Predicting (temperature) gives the following results.

[0293]

Equation 64

[0294]

By the way, Z ₁ = 111.9Ω, Z ₂ = 7
Since it is 9.2Ω, the fixed resistances are R ₁ = 110Ω and R ₂ = 7.
8Ω, and the balance adjustment resistance is Rex ₁ = R
ex ₂ = 500 kΩ.

Thus, the bridge was assembled and balanced at room temperature.

The temperature phase when the temperature of the torque detector was raised by 20 ° C. was 88.4 °. θ _A = 36.9 °,
Since θ _B = 36.9 ° is expected, from Equation 30, θ _C
(Temperature) is estimated to be -14.6 °. Therefore, θ _C
The value of (temperature) is almost as expected (equation 64).

The detection timing θt is set to this temperature phase (actual work is to set the detection timing so that the output of the torque measuring device becomes 0). Torque when temperature is returned to room temperature and torque is applied Phase is -0.3
°. Estimating θ _C (torque) using Equation 30 gives 74.1 °.

That is, since the original θ ₁ is 73.8 °,

[0300]

The relationship of is also established (see Formula 49).

Therefore, the temperature phase and the torque phase are 8
Since they are 8.7 ° apart, it means that they can be set in a very desirable state.

Then, a torque application test of ± 20 kgm was conducted at room temperature, and it was found that there was almost no difference in sensitivity between + and-and that there was almost no hysteresis.

Further, the temperature drift of the zero point when the temperature of the torque detecting portion of this torque measuring device was raised to 100 ° C. was +0.1 kgm, and it was smaller in the temperature range below that.

[0305]

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 into a shaft to be measured for a torque measuring device having a shaft diameter of 19 mm.

Further, a partial spiral groove having a width of 1 mm and a depth of 1.5 mm (0.5 R) is ± 45 ° on the shaft to be measured.
A pair was formed in the direction (see FIG. 1). In this case, the number of grooves was 20 (divided into 20 equal parts) and the groove length was 10 mm. After that, a heat treatment of heating to 860 ° C. in vacuum, holding for 3 hours, and quenching in oil was performed.

It was decided to carry out the test by exchanging only the shaft to be measured having the shaft diameter of 19 mm used in the first embodiment.

By changing the number of coil turns of the two coil sides, one coil side has 126 turns and the other coil side has 105 turns. Then, a resistor made of a 1.3 Ω manganin wire was inserted into the coil side where the number of coil turns was large, and the magnitude relation of the angle of the impedance vector of the coil side was examined. As a result, θ ₁ was 0. 1
° It was getting a little smaller.

Therefore, the fixed resistors are kept R ₁ = 110Ω and R ₂ = 78Ω as in the case of the first embodiment, and the balance adjusting resistors are also Rex ₁ = Rex _2.
= 500 kΩ, a bridge was assembled and balanced at room temperature.

Since the torque phase of applying a torque of +4 kgm was -0.2 °, the detection timing θt was set to 88.8 ° (in actual work, θt should be set so that the sensitivity becomes maximum). Then, set the temperature of the torque detector without applying torque to 100.
Zero point drift is -0.01k when the temperature is raised to ° C.
It was gm.

On the other hand, the temperature phase was 88.4 ° when the temperature of the torque detector was uniformly raised to 20 ° C.

That is, the temperature phase is 8 with respect to the torque phase.
It means that they are separated by 8.6 °, and the phase relationship is almost the same as that when the shaft to be measured is steel in the first embodiment.

Since it is considered that the relationship of the temperature coefficient difference is almost the same as that of the first embodiment, the temperature coefficient measurement and the like are omitted in this embodiment.

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 for compensating for the temperature difference with four coils is taken. There is.

In the present invention, in order to explain the contents, 2
Although only the case of individual coils 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 (~)
Is a coil 6, and Z _B (~) with respect to Z _A (~)
If Z _C (-) is reduced with respect to Z _D (-) at a constant rate, the same action and effect as in the case of the two coils can be expected.

[0319]

As described above, in the magnetostrictive torque measuring device according to the present invention, the coil sides of the two sides of the bridge circuit are different in coil winding number and the coil side having the larger number of coil windings has a temperature coefficient. Insert a small resistance that does not have the angle θ ₁ and θ _{2 of} the impedance vectors Z ₁ (~) and Z ₂ (~).

[0320]

Since the configuration is such that the bridge circuit is provided in which the bridge balance is set by setting the relationship of θ ₁ <θ ₂ , the setting work for separating the temperature phase from the torque phase can be performed very easily. Therefore, it is possible to eliminate the great adjustment man-hours required up to now, 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 can be performed. It has a very excellent effect that is possible.

[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.

[Explanation of symbols]

 1 Torque detecting unit of torque measuring device 2 Axis to be measured 5, 6 Coil 10 Torque detecting 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 is provided with a bridge circuit in which two variable resistors for adjusting bridge balance are provided in parallel, and wherein the torque applied to the shaft to be measured is detected by the bridge circuit by a magnetostrictive action, The number of coil turns on each side of the coil is made different to give a difference in the magnitude of each impedance, and a small resistor without a temperature coefficient is inserted on the side of the coil with the most number of coil turns.
When the impedance vector of the coil side composed of the coil and the small resistance and the impedance vector of only the coil side are respectively expressed as Z ₁ (-) and Z ₂ (-), and the angles are expressed as θ ₁ and θ ₂ , respectively, θ ₁ ≈ θ ₂ and θ
A magnetostrictive torque measuring device comprising a bridge circuit in which a bridge balance is set after setting a relationship of ₁ <θ ₂ . 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.