JPH0820318B2 - Magnetostrictive stress measuring device for grinder unit - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetostrictive stress measuring device for simultaneously measuring the pressing force and torque of a grinder unit held by an arm of an industrial robot.

2. Description of the Related Art Among magnetostrictive stress measuring devices, for example, Japanese Patent Laid-Open No. 57-7732
As shown in Japanese Patent Publication No. 6, 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.
The excitation coil and the detection coil are fitted on the outer periphery of the segment without contact, and the excitation coil and the detection coil are also fitted on the outer periphery of the second segment without contact to energize the respective excitation coils. Every time, a torsional force is applied 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 stress in the circumferential direction of the shaft to be measured is changed based on the amount of change in the inductance. It is known that the magnitude and direction, that is, the magnitude and direction of torque are measured.

Problems to be Solved by the Invention When performing grinding with a grinder unit supported by an arm of an industrial robot, the above-mentioned magnetostrictive stress measuring device is used to output the output shaft of a motor to which a grindstone is attached. Is the axis to be measured, and the first and second segments, the exciting coil and the detection coil are arranged on the axis, while the output of the detection coil is input to the controller of the industrial robot to grind while monitoring the grinding state. It is possible to perform the work automatically.

However, in this case, even if it is possible to detect the twisting torque of the output shaft that depends on the magnitude and direction of the twisting torque of the output shaft, that is, the sharpness of the grindstone, etc., unless another strain gauge is used, Since it is not possible to simultaneously measure the magnitude and the direction of the axial stress of, the result is that the pressing force of the grindstone against the work cannot be accurately monitored.

Therefore, the present invention provides a grinder unit magnetostrictive stress measuring apparatus capable of simultaneously measuring not only the magnitude and direction of the circumferential stress of the output shaft but also the magnitude and direction of the axial stress.

Means for Solving the Problems The present invention is a device for simultaneously measuring the torque applied to the output shaft of the grinder unit and the pressing force when grinding is performed by the grinder unit supported by the arm of the industrial robot. And is provided on the peripheral surface of the output shaft to which the grindstone is attached at a predetermined angle in the axial direction in a substantially C-shape to convert the stress of the output shaft into magnetostriction.
・ No contact with the outer circumference of the second segment and the outer circumference of the first segment, and the first and second coils that are placed outside the outer circumference of the first segment without contact to convert the magnetostriction of the first segment into the amount of change in inductance Applied to the output shaft by inputting a voltage corresponding to the amount of change in the inductance of the first and third coils and the third and fourth coils externally arranged to convert the magnetostriction of the second segment into the amount of change in the inductance The configuration is provided with a subtracter that outputs a torque value and an adder that outputs a pressing force in the axial direction applied to the output shaft by inputting a voltage corresponding to the amount of change in the inductance of the second and fourth 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 5, the magnetostrictive stress measuring device of this embodiment roughly includes the output 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. The shaft 6 is configured as the shaft to be measured, and the first and second segments 7 and 8 and the first and second
Third and fourth coils 9,10,11,12 and first and second bridge circuits
It is provided with 13, 14 and a subtractor 25 and an adder 29.

The first and second segments 7 and 8 are provided on the peripheral surface of the output shaft 6 in a substantially C-shape with a required angle θ, for example 45 degrees, in the axial direction. In this embodiment, since the output shaft 6 is made of a material having a magnetostrictive effect, the first and second segments 7 and 8 are circumferentially arranged on the peripheral surface of the output shaft 6 as shown in FIG. A plurality of grooves 7a and 8a are formed, and the outer peripheral surface portion of the output shaft 6 that is present symmetrically between the grooves 7a and 8a is formed.

Here, the relationship between the stress generated in the output shaft 6 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 output shaft 6, a magnetostriction of an arrow σ _T is generated in the first segment 7, and a magnetostriction of an arrow −σ _T is generated in the second segment 8. . In addition, an arrow F is displayed on the output shaft 6.
Assuming that an external force in the axial direction is applied, the magnetostriction indicated by the arrow σ _F is generated in the first and second segments 7 and 8.
Therefore, when the clockwise torque T and the axial external force F are simultaneously applied to the output shaft 6, the above-mentioned magnetostriction σ _T , −σ.
_{From T} and σ _F , a synthetic magnetostriction of arrow σ ₁ is generated in the first segment 7, and a synthetic magnetostriction of arrow σ ₂ (same as −σ ₁ ) 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) Becomes

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

The first and second coils 9 and 10 are fitted on the outer periphery of the first segment 7 in a contactless manner so as to convert the magnetostriction σ ₁ of the first segment 7 into a change amount of the inductances L ₁ and L _2. Has become. The third and fourth coils 11 and 12 are adapted to convert the magnetostriction σ ₂ of the second segment 8 into the amount of change in the inductances L ₃ and L ₄ .

Specifically, the first and second coils 9 and 10 are cylindrical yokes 15.
Is mounted in two receiving recesses 16 and 17 formed in one end of the yoke, and the third and fourth coils 11 and 12 are mounted in two receiving recesses 18 and 19 formed in the other end of the yoke 15. When the first to fourth coils 9, 10, 11, 12 are energized, the first coil
9, a magnetic circuit passing through the yoke 15, the air gap g, the first segment 7, and the second coil 10, the yoke 15, the air gap g, the first
Magnetic circuit passing through the segment 7, third coil 11, yoke 1
5, magnetic circuit passing through the air gap g, the second segment 8,
The fourth coil 12, the yoke 15, the air gap g, and the magnetic circuit passing through the second segment 8 are respectively formed.

The first bridge circuit 13, as shown in FIG.
The third coil 9,11, two resistors 20,21, a variable resistor 23 for balance adjustment, and an excitation oscillator 24 as an AC power supply,
A voltage corresponding to the amount of change in the inductances L ₁ and L ₃ of the first and third coils 9 and 11 is output to the output terminals c and d. A subtractor 25 composed of an operational amplifier is connected to the output terminals c and d of the first bridge circuit 13.

As shown in FIG. 4, the second bridge circuit 14 includes second and fourth coils 10, 12 and two resistors 26, 27, a variable resistor 28 for balance adjustment, and the above-mentioned excitation oscillator 24, A voltage corresponding to the amount of change in the inductances L ₂ and L ₄ of the second and fourth coils 10 and 12 is output to the output terminals c and d. This second
An adder 29 composed of an operational amplifier is connected to the output terminals c and d of the bridge circuit 14.

According to the structure of the above embodiment, after the variable resistors 23 and 30 are operated to balance the first and second bridge circuits 13 and 14,
Grinding work is performed by the grinder unit 3.

Then, the torque T is applied to the output shaft 6 of the grinder unit 3.
And axial force (pressing force of grinder unit 3) F
Is applied, magnetostriction σ ₁ and σ ₂ are generated in the first and second segments 7 and 8, and the inductances L _{1 to} L _{4 of the first} to fourth coils 9, 10, 11 and 12 change, and these inductances L ₁ ~ L ₄
The first and second bridge circuits 13 and 14 become unbalanced according to the amount of change in the voltage, and a voltage corresponding to the amount of change in the inductances L _{1 to} L ₄ is generated at the output terminals c and d.

That is, the voltage E ₁ generated at the output terminals c of the first and second bridge circuits 13 and 14 corresponds to the magnetostriction σ ₁ of the first segment 7, and the voltage E ₁ of the first and second bridge circuits 13 and 14 is The voltage E ₂ generated at the output end d corresponds to the magnetostriction σ ₂ of the second segment 8. Then, the voltages E ₁ and E ₂ at the output terminals c and d of the first bridge circuit 13 are subtracted by the subtractor 25 and output. That is, since E ₁ −E ₂ = σ ₁ −σ ₂ = 2σ _T , the magnitude and direction of the circumferential stress of the output shaft 6, that is, the magnitude and direction of the torsion torque of the output shaft 6 can be measured.

Further, the voltages E ₁ and E ₂ at the output terminals c and d of the second bridge circuit 14 are added by the adder 29 and output. That is, E ₁ + E ₂ = σ ₁
Since + σ ₂ = 2COSθσ _F , the magnitude and direction of the axial stress of the output shaft 6, that is, the magnitude and direction of the axial pressing force applied to the output shaft 6 can be measured.

Moreover, since the first and second segments 16 and 17 are integrally formed with the output shaft 6 by the same member, the torque repeatedly applied to the shaft to be measured, for example, when a magnetostrictive film is bonded to the shaft to be measured. Also, there is no inconvenience that the adhesive is deteriorated due to temperature change and the torque applied to the shaft to be measured is deviated from the magnetostriction of the magnetostrictive film to deteriorate the detection accuracy.

The present invention is not limited to the above-mentioned embodiment, and although not shown, for example, the grooves 7a and 8a are filled with a non-magnetic good electric conductor to increase the magnetic flux density of the first and second segments 7 and 8. The detection sensitivity can be increased, or the first and second segments 7 and 8 can be formed in a convex shape on the outer peripheral surface of the output shaft 6.

EFFECTS OF THE INVENTION As described above, according to the present invention, the first bridge circuit 2
By subtracting the voltage at one output end and adding the voltage at the two output ends of the second bridge circuit, the stress in the circumferential direction and the stress in the axial direction of the output shaft can be calculated without using another strain gauge or the like. The size and direction, that is, the torque applied to the output shaft and the pressing force can be measured accurately at the same time. Therefore, noise and durability caused by slip rings, such as when using a strain gauge, etc. In addition, the reliability of measurement accuracy is improved along with the simplification of the structure.

Moreover, since the first to fourth coils are configured as self-inductances, the first and second segments and the first to second segments are compared to the conventional one configured as a mutual inductance including an exciting coil and a detection coil. The axial length of the fourth coil with respect to the output shaft can be reduced, which can also simplify the structure and reduce the size.

In particular, the torque applied to the output shaft of the grinder unit attached to the arm of the industrial robot and the pressing force can be detected at the same time, and load management in the two directions can be performed. It is possible to perform grinding work while monitoring the sharpness of the grindstone, the degree of contact, damage and grinding burn of the work, which contributes to the improvement of workability and the realization of full automation of grinding work. Has a new effect.

[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 periphery of an output shaft of the embodiment, and 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, and FIG. 5 is a perspective view showing the industrial robot of the same embodiment. 1 ... Industrial robot, 2 ... Arm, 3 ... Grinder unit, 4 ... Grindstone, 6 ... Output shaft, 7 ... First segment, 8 ... Second segment, 9 ... First coil,
10 …… Second coil, 11 …… Third coil, 12 …… Fourth coil, L _{1 to} L ₄ … Inductance, 25 …… Subtractor, 29 ……
Adder.

Claims (1)

[Claims] 1. An apparatus for simultaneously measuring a torque applied to an output shaft of a grinder unit and a pressing force when grinding is performed by a grinder unit supported by an arm of an industrial robot, and an output to which a grindstone is attached. First and second segments, which are provided in a substantially C-shape on the circumferential surface of the shaft at a required angle in the axial direction and convert the stress of the output shaft into magnetostriction, and are fitted on the outer periphery of the first segment without contact. And the first and second coils that convert the magnetostriction of the first segment into the amount of change in the inductance, and the outer circumference of the second segment are contactlessly fitted to the outside, and the magnetostriction of the second segment becomes the amount of change in the inductance. The third and fourth coils to be converted and the voltage corresponding to the amount of change in the inductance of the first and third coils are input, and the torque value applied to the output shaft is output. Of the grinder unit, and an adder that outputs a pressing force in the axial direction applied to the output shaft by inputting a voltage corresponding to the amount of change in the inductance of the second and fourth coils. Magnetostrictive stress measurement device.