JPH0762638B2 - Magnetostrictive stress measurement device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a magnetostrictive stress measuring device.

2. Description of the Related Art Among magnetostrictive stress measuring devices, there is, for example, JP-A-57-77326.
As shown in the publication, first and second segments for converting the stress of the shaft to be measured into magnetostriction are provided on the circumferential surface of the shaft to be measured in a substantially C-shape at a required angle in the axial direction, and the first segment The excitation coil and the detection coil are fitted on the outer periphery of the second segment without contact, and the excitation coil and the detection coil are also fitted on the outer periphery of the second segment without the contact so that the respective excitation coils are energized. By applying a twist to the shaft to be measured, the inductance of each detection coil is changed by the magnetostrictive effect of the first and second segments, and the magnitude of the circumferential stress of the shaft to be measured is determined based on the amount of change in the inductance. It is known that the direction and the direction are measured.

Problems to be Solved by the Invention Automation of manufacturing work using the above-mentioned magnetostrictive stress measuring device, for example, the output shaft of the motor to which the grindstone of the grinder unit is mounted is the shaft to be measured. It is conceivable to arrange the segment, the exciting coil, and the detection coil while inputting the output of the detection coil to the controller of the industrial robot to which the grinder unit is attached to automatically perform the grinding work. However, in this case, since the magnitude and the direction of the axial stress of the shaft to be measured cannot be measured at the same time, the pressing force of the grindstone against the work cannot be monitored accurately.

Therefore, the present invention provides a magnetostrictive stress measuring device capable of measuring the magnitude and direction of the circumferential stress and the axial stress of the shaft to be measured.

Means for Solving the Problems First and second segments that are provided in a substantially C-shape on the circumferential surface of the shaft to be measured at a required angle in the axial direction and convert the stress of the shaft to be measured into magnetostriction; First contactlessly fitted to the outer circumference of the second segment to convert the magnetostriction of the first and second segments into an amount of change in inductance
A second coil and a calculation means for calculating the circumferential stress and the axial stress of the measured shaft based on the amount of change in the inductance of the first and second coils.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

As shown in FIGS. 1 to 6, the magnetostrictive stress measuring device of this embodiment roughly includes an output shaft 6 of a motor 5 to which a grindstone 4 is attached in a grinder unit 3 attached to an arm 2 of an industrial robot 1. It is configured as a shaft to be measured, and has first and second segments 7,8 and first and second coils 9,10.
And the first and second bridge circuits 11 and 12 and the calculating means 13. The first and second segments 7 and 8 are provided on the peripheral surface of the shaft 6 to be measured in a substantially C-shape with a required angle θ, for example 45 degrees, in the axial direction. In this embodiment, since the shaft 6 to be measured is made of a material having a magnetostrictive effect, as shown in FIG.
A plurality of grooves 7a, 8a are formed in the circumferential direction on the circumferential surface of the
It is constituted by the outer peripheral surface portion of the shaft to be measured 6 which exists symmetrically between a and 8a. Here, the relationship between the stress generated in the shaft 6 to be measured and the magnetostriction of the first and second segments 7 and 8 is as shown in FIG. For example, assuming that a clockwise torque T indicated by an arrow T is applied to the measured shaft 6,
The first segment 7 resulting magnetostriction arrow sigma _T, the second segment 8 results magnetostriction arrow - [sigma] _T.
Further, if it is assumed that an axial external force indicated by arrow F is applied to the shaft 6 to be measured, the arrow σ is applied to the first and second segments 7 and 8.
_It produces a magnetostriction of _F. Therefore, when the clockwise torque T and the external force F in the axial direction are simultaneously applied to the measured shaft 6, from the above-mentioned magnetostriction σ _T , -σ _T , σ _F , the first segment 7 is combined with the arrow σ ₁ . Magnetostriction is generated, and a synthetic magnetostriction (same as −σ ₁ ) indicated by an arrow σ ₂ is generated in the second segment 8. When this is made into an equation, σ ₁ = σ _T + COS θ · σ _F = σ _T + COS 45 ° · σ _F …… (1) σ ₂ = −σ _T + COS θ · σ _F = −σ _T + COS 45 ° · σ _F ...... ( 2)

Therefore, the above equation (1) + (2) The more _{σ 1 + σ 2 = 2COSθσ F} = 2COS45 ° sigma _F ...... (3), the above equation (1) - ₁ from _{(2) σ -σ 2 = 2σ} T ... … (4).

The first and second coils 9 and 10, respectively, are the first and second segments
It is fitted around the outer circumferences of 7, 8 without contact, and the magnetostriction σ ₁ , σ ₂ of the first and second segments 7, 8 is applied to the inductances L ₁ , L ₂
It is designed to be converted into the change amount of. Specifically, the first coil 9 is mounted in a receiving recess 15 formed in one half of the cylindrical yoke 14, and the second coil 10 is mounted in a receiving recess 16 formed in the other half of the yoke 14. When the first and second coils 9 and 10 are energized, the magnetic circuit passing through the first coil 9, the yoke 14, the air gap g, and the first segment 7, the second coil 10, the yoke 14, and the air gap g. Thus, a magnetic circuit passing through the second segment 8 is formed.

As shown in FIG. 3, the first bridge circuit 11 includes a first coil 9, a standard coil 17, two resistors 18 and 19, and a variable resistor 20 for balance adjustment. This first bridge circuit 11
An excitation oscillator 21 as an AC power source is connected to the input terminals a and b of the, and an amplifier 26 is connected to the output terminals c and d thereof.

The second bridge circuit 12 has a second coil, as shown in FIG.
It is provided with 10 and a standard coil 22, two resistors 23 and 24, and a variable resistor 25 for balance adjustment. The excitation oscillator 21 described above is connected to the input terminals a and b of the second bridge circuit 12, and the amplifier 27 is connected to the output terminals c and d thereof. Therefore, after operating the variable resistors 20 and 25 to balance the first and second bridge circuits 11 and 12, the grinder unit 3
Perform the grinding work by. And the measured shaft 6 which is the output shaft
When a torque T or an axial force F is applied to the first and second segments 7 and 8, magnetostriction σ ₁ and σ ₂ are generated, and the inductances L ₁ and L _{2 of} the first and second coils 9 and 10 are Change, the balance of the first and second bridge circuits 11 and 12 is lost according to the amount of change in these inductances L ₁ and L ₂ , and the first and second bridge circuits 11 and 12 change.
Output terminals c, d, specifically, output terminals 26a, 27a of amplifiers 26, 27
Generates a voltage corresponding to the amount of change in the inductances L ₁ and L ₂ . In order to clarify the explanation here, the above-mentioned first and second
_{First due to} magnetostriction σ ₁ and σ ₂ generated in segments 7 and 8
-It is assumed that the changes in the inductances L ₁ and L ₂ of the second coils 9 and 10 are as shown in Table 1 below.

Further, it is assumed that the output voltages of the first and second bridge circuits 11 and 12 are set to be negative when the inductances L ₁ and L ₂ increase, and conversely set to brass when the inductances L ₁ and L ₂ decrease. To do. That is, the force applied to the measured shaft 6
The relationship with T and F is as shown in Table 2 below.

As shown in FIG. 1, the output A of the first bridge circuit 11 and the output B of the second bridge circuit 12 are input to the arithmetic means 13 via separate amplifiers 26 and 27, respectively. , A judgment unit 28 for judging whether the outputs A and B are positive or negative, and the output
And a calculation unit 29 for adding and subtracting A and B.

The execution of the above embodiment will be described with reference to the flowchart shown in FIG. When the torque T and the axial force F are applied to the output shaft of the grinder unit 3, that is, the measured shaft 6, and the inductances L ₁ and L ₂ change, the outputs A and B of the first and second bridge circuits 11 and 12 are changed. It is input to the calculation unit 13. Then, the calculation unit 13 first reads the outputs A and B in the section, and then determines whether the output A is positive or negative in the section. When the output A is determined to be positive (plus), the section determines whether the output B is positive or negative. When the output B is determined to be positive, the section adds the output A and the output B to obtain a value. Calculate C and record this value C in the section. When the output B is determined to be negative (minus) in the above section, the section A is subtracted from the output A to calculate the value D, and the value D is recorded in the section. Also, if the output A is determined to be negative in the above section,
The section determines whether the output B is positive or negative. When the output B is determined to be positive, the output A and the output B are output in the section.
And the value D is calculated, and this value D is recorded in the section.

Furthermore, when the output B is determined to be negative in the above-mentioned section, the section calculates the value C by adding the output A and the output B, and the value C is recorded in the section to perform a series of arithmetic operations. Finish the process. The value recorded in the previous section
There are cases where C and D are positive and cases where it is negative, but the relationship between the positive and negative values of these values C and D and the forces T and F is
It becomes like Table 3 below.

Now, in the above-described embodiment, the change amounts of the self-inductances L ₁ and L ₂ of the first and second coils 9 and 10 are taken into the first and second bridge circuits 11 and 12, and the first and second Since it is converted into the magnetostriction σ ₁ and σ ₂ of the segments 7 and 8, the first and second coils are composed of an exciting coil and a detection coil as in the conventional case, and the detection in the first and second coils is performed. Compared to the case where the amount of change in mutual inductance of the coils is used, the accuracy and response of measurement can be improved while having a simple and small structure. Moreover, since the first and second segments 7 and 8 are integrally formed of the same member as the shaft to be measured 6, it is repeatedly applied to the shaft to be measured as in the case where a magnetostrictive film is adhered to the shaft to be measured. There is also no inconvenience that the adhesive deteriorates due to changes in torque or temperature, and a deviation occurs between the torque applied to the shaft to be measured and the magnetostriction of the magnetostrictive film, resulting in poor detection accuracy. The present invention is not limited to the above-mentioned embodiment, and although not shown in the drawings, for example, by filling the grooves 6a, 7a with a non-magnetic electric conductor, the first
It is also possible to increase the magnetic flux degree of the second segments 7 and 8 to enhance the detection sensitivity, or to form the first and second segments 7 and 8 in a convex shape on the outer peripheral surface of the shaft 6 to be measured.

EFFECTS OF THE INVENTION As described above, according to the present invention, the magnitude and the direction of the circumferential stress and the axial stress of the shaft to be measured can be simultaneously and accurately determined according to the amount of change in the inductance of the first and second coils. It can be measured. Moreover, when automating manufacturing operations,
It is possible to manage the load on the measured shaft in two directions. In particular, since the torque and pressing force applied to the output shaft of the grinder unit attached to the industrial robot can be monitored, the sharpness, contact, damage, and grinding of the workpiece of the grindstone can be done without relying on the ecological function of the industrial robot. There is a new effect that workability can be improved by managing the above.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention, FIG. 2 is a schematic diagram showing the circumference of an axis to be measured of the embodiment, FIG. 3 is a circuit diagram showing a first bridge circuit of the embodiment, FIG. 4 is a circuit diagram showing the second bridge circuit of the same embodiment, FIG. 5 is a perspective view showing the industrial robot of the same embodiment, and FIG. 6 is a flowchart of the same embodiment. 6 ... Axis to be measured, 7 ... First segment, 8 ... Second segment, 9 ... First coil, 10 ... Second coil, 13 ...
… Calculation means, L ₁ , L ₂ …… Inductance.

Continuation of the front page (56) References JP-A-49-74992 (JP, A) JP-A-56-29133 (JP, A) JP-A-64-32135 (JP, A) Actual development 55-167138 (JP , U)

Claims (1)

[Claims] 1. A first and a second segment, which are provided on the peripheral surface of the shaft to be measured in a substantially C-shape at a required angle in the axial direction to convert the stress of the shaft to be measured into magnetostriction, and first and second segments. The first and second coils, which are externally fitted to the outer circumferences of the segments without contact and convert the magnetostriction of the first and second segments into the amount of change in the inductance, and the amount of change in the inductance of the first and second coils. A magnetostrictive stress measuring device comprising: a calculation means for calculating the circumferential stress and the axial stress of the measured shaft based on the stress.