JPS6054603B2 - distance measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an object that approaches or leaves a point in a straight line, and when the moving distance is relatively large,
The present invention relates to a device that precisely measures the distance traveled by the object in a non-contact manner.

When an object moves as described above, a device that measures the amount of movement without contact is a capacitive type that measures the change in capacitance between an electrode attached to the object and a detector electrode that face each other. , the conductor plate attached to the object (not required when the object is a conductor) and the w resonance circuit of the detector are made to face each other, and magnetic flux is radiated from the detector to generate an eddy current in the conductor plate. There are eddy current types that measure changes in the inductance of the detector. When an object moves and the distance between it and the detector changes, in the capacitive type the distance between the two electrodes changes, resulting in a change in capacitance, and in the eddy electric type, the distance between the two electrodes changes. As a result, the magnitude of the generated eddy current changes depending on the distance, which changes the inductance of the detector.

Therefore, by detecting changes in capacitance or inductance using a detector, it is possible to measure changes in distance. However, these methods use a fixed detector, and the size of the detector must be increased depending on the distance between the detector and the measurement point. If the value becomes large, a large detector is required.

Therefore, it is inevitable that a larger detector will have a correspondingly lower measurement resolution, making it impossible to measure minute amounts of movement, resulting in lower accuracy. By the way, this type of detector generates an output depending on the distance between it and the object to be measured, so considering the conditions for generating a constant output for a constant distance, the distance sensor For example, in order to avoid contact between the object to be measured and the detector, it is possible to issue an alarm when the object to be measured approaches a certain distance. The smaller the distance, the higher the accuracy by using a smaller detector. The present invention uses a small highly accurate detector as a distance sensor to accurately measure a large moving distance of an object to be measured. The purpose of this method is to measure the moving distance of the measured object by making it follow the measured object over a small fixed distance, and by changing the drive current of the drive mechanism required for the tracking.

INDUSTRIAL APPLICABILITY The present invention is used to inspect the shape of a rotating body, such as an eccentric disk or a polygonal plate, in a non-contact manner while rotating the rotating body.

Examples will be described in detail below.

This is an example for inspecting the shape of a cam, and the cam to be measured (not shown) is fixed to a rotating shaft arranged horizontally, and is supported by a guide cylinder below the cam to be measured vertically. By arranging a T-shaped rod that can move freely in the direction, and interposing a compression spring between the lower surface of the horizontal part of the rod tip and the upper end surface of the guide cylinder, the tip is pressed against the cam surface and the rotation of the cam is controlled. The blade can be moved vertically in accordance with the displacement curve of the young rod by the movement of the rod.

Then, the moving distance of the lower end protruding end surface of this rod is measured. In FIG. 1, a conductive plate is fixed to the lower end surface of the rod, and the conductive plate that moves integrally with the rod is used as the object to be measured 20, and the detector 5 as a distance detector is equipped with an eddy current type. There is an example using a product.

In the figure, 1 is a bottom plate, on the upper surface of which an inner cylinder 3 and an outer cylinder 2 made of a magnetic conductive material are fixed concentrically, and the inner cylinder 3
A gap is provided between the outer cylinder 2 and the outer cylinder 2.

A lower half of a rod-shaped movable element 4 is slidably inserted into the inner cylinder 3, and an upper end of the movable element 4 is inserted into the inner cylinder 3. A detector 5 is fixed to the. This device has a pressure-resonant circuit built-in, and can accurately detect minute distances with high resolution. Also,
The lower end of the spring 6 is fixed to the lower end of the mover 4.
The lower end of is fixed to the bottom plate 1, and the mover 4 is kept in a fixed position!
held. Then, when a load is applied to the mover 4,
It can be moved up and down using the inner surface of the inner cylinder 3 as a guide.
Reference numeral 8 denotes a letter-shaped mounting rod fixed to both sides of the mover 4, and its downward hanging portion extends into the gap between the inner cylinder 3 and the outer cylinder 2, and the lower end of both hanging portions is attached to the inner cylinder 3. A coil 1 concentric with the mounting rod 8 is fixed, and the mounting rod 8 and the coil 1 are kept in a non-contact state with the outer and inner surfaces of the inner and outer cylinders 3 and 2.

9 is a cylindrical permanent magnet, the inner periphery of which is the outer surface of the inner cylinder 3;
The outer periphery is arranged at the bottom of the gap in contact with the inner surface of the outer cylinder 2, and has magnetic poles on the inner periphery and the outer periphery. For example, if the inner periphery side is the N pole, the lines of magnetic force are the inner periphery of the permanent magnet 9. , the inner cylinder 3, the gap, the outer cylinder 2, and the outer periphery of the permanent magnet 9 form a closed magnetic path, and the magnetic field is substantially uniform throughout the space of the gap.

10 is a detection output amplifier connected to the detector 5;
The output of the amplifier 10 is applied to one input terminal of the control amplifier 11.

Note that the control amplifier 11 is made of a known type that combines a PID control circuit and a current control circuit. A predetermined voltage set by the setting device 12 is applied to the other input terminal of the control amplifier 11, and the control amplifier 11 outputs a current necessary to make the deviation between the voltages of both human inputs zero, and the current is output from the control amplifier 11 to the coil 7. added to. 13 is an ammeter inserted into the current path between the coil 7 and the control amplifier 11.

Therefore, the control amplifier 11 compares the amplified voltage obtained by multiplying the output voltage of the detector 5 by a fixed value and the set voltage of the setting device 12, and generates a control current according to the deviation. A current is applied to the coil 7 such that the amplified voltage and the set voltage finally match.

In the above system, when the bottom plate 1 of the distance measuring device is fixed to a specified surface and the detector 5 is opposed to the object to be measured 20 at an appropriate distance, the detector 5 has the object to be measured 20 and the object to be measured 20.
During this time, a voltage corresponding to the distance is generated, which is amplified by an appropriate constant value via the amplifier 10 and applied to the control amplifier 11. In this state, if the set voltage of the setter 12 is set to an appropriate constant value, the control amplifier 11 supplies the coil 7 with the current necessary to make the deviation between the amplified voltage and the set voltage O. will be done. That is, the coil 7 is in the magnetic field between the inner cylinder 3 and the outer cylinder 2, and therefore, when a current is applied to the coil 7, a force is exerted on the coil 7 according to Fleming's left hand method. In this case, the control amplifier 11 will generate a current that makes the deviation between the amplified voltage and the set voltage zero, so the force applied to the coil 7 will depend on the magnitude and polarity of the deviation. The movable element 4 that is integrated with the movable element 4 is moved upward or downward, thereby bringing the detector 5 closer to or away from the object to be measured 20,
As a result, the output voltage of the detector 5 is increased or decreased,
The detector 5 is moved to a position where the amplified voltage matches the set voltage. Next, the object to be measured 20 is
When moving a certain distance from said position, i.e. approaching or moving away from the detector 5, the amplified voltage at the output of the detector 5 increases or decreases and no longer matches the set voltage. The current necessary to move the coil 7 downward or upward is sent out depending on the magnitude and polarity of the deviation, moves the mover 4 downward or upward, and creates a gap between the detector 5 and the object to be measured 20. The distance becomes the same as above, and the amplified voltage of the output voltage of the detector 5 becomes balanced in a state where it matches the set voltage.

Therefore, the coil 7 from the control amplifier 11 at this time
The magnitude of the current supplied to the object becomes different from the above state, and the distance that the detector 5 is moved to keep the distance between it and the object to be measured 20 constant, that is, the object to be measured is This corresponds to a movement distance of 20.

As a result, the moving distance of the object to be measured 20 can be determined by reading the magnitude of this current using the ammeter 13 and comparing it with the relationship between current and distance that has been calibrated in advance.

In this case, as described above, the detector 5 is designed to accurately detect changes in minute distances, and the rate of change of the control current of the control amplifier 11 with respect to the moving distance can be adjusted by adjusting the strength of the spring 6. , is large enough. Note that the above-mentioned calibration for determining the relationship between current and travel distance is performed by directly facing the object to be measured 20 or a sample piece made of the same material as the object to be measured 20 and the distance measuring device, and setting the distance range necessary for measurement. You can do this by changing the voltage.

Normally, the above-mentioned sample piece is attached to a calibrator such as a micrometer for calibration, but of course it is also possible to calibrate using the object to be measured 20. In that case, the bottom plate 1 of the distance measuring device is fixed to the specified surface and the The detector 5 is opposed to the object to be measured 20 at a distance of . Then, the setting voltage of the setting device 12 is first set to O. In this way, an output voltage is generated in the detector 5 according to the distance between the detector 5 and the object to be measured 20,
Since the amplified voltage is larger than the set voltage, the control amplifier 1
1, a current is applied to the coil 7 in a direction to move the detector 5 away from the object to be measured 20, that is, to move the movable element 4 downward, and the output of the detector 5 is balanced in a state of 0.
The distance G at this time. is a known value in the detector 5, and the current 1. Read. Next, when the set voltage is reset to V1, the amplified voltage of the output of the detector 5 becomes smaller than the set voltage. A current that moves the movable element 4 upward is applied to the coil 7, and equilibrium occurs when the amplified voltage of the output of the detector 5 matches the set voltage. The distance G1 at this time is also known in the detector 5, and the current 11 is read. Thereafter, in the same way, a large number of different set voltages ■2, V3...■. Distance G2, G3 under
...Read the current 12, 13...h for Gn. Through the above steps, the relationship between distance and current for the measurement range of the detector 5 is determined. Next, in this state, when the set voltage is set to V1, the current becomes 11, but when the object to be measured 20 is moved upward, the detector 5 and the object to be measured 2
As a result of the distance between the detector 5 and the object to be measured 20
A current is applied to the coil 7 such that it approaches .

While monitoring this current, the object to be measured 20 is held in position until it reaches h. Measured object 2 at this time
The distance between 0 and the detector 5 is G1, and the current is h,
The detector 5 itself is at G from the above-mentioned initial position. - It has moved by Gn. In this state, set the voltage in the same manner as above.
, V3...■. , the distance between the object to be measured 20 and the detector 5 becomes G2, G3, . . .
. . . Each GO is subjected to follow-up control a, and when viewed from the above-mentioned initial position, each detector 5 is (GO-G
n) + (G1-G2) (GO-Gn) + (G1-G3)
, ・(GO+Gn)+(G1-G.) [=GO+G
. ] and G by reading the current at each set voltage. The relationship between distance and current within the +Gn distance is determined. Thereafter, by similarly performing the above calibration for the required distance range, the relationship between distance and current can be determined with high resolution. As described above, the present invention uses a highly accurate detector as a distance sensor, detects with high resolution the deviation of the distance between it and the object to be measured from a constant value, and maintains the distance at a constant value. Since current is supplied to the moving mechanism, the moving distance of the object to be measured is expanded to the magnitude of the current value, and by reading the current value, it is possible to measure a large moving distance of the object to be measured with high accuracy.

[Brief explanation of drawings]

FIG. 1 is a partially sectional front view showing an embodiment of the present invention. 1: Bottom plate, 2: Outer cylinder, 3: Inner cylinder, 4: Mover, 5:
Detector, 6: Spring, 7: Coil, 8: Mounting rod, 9: Magnet, 10: Amplifier, 11: Control amplifier, 12: Setting device, 1
3: Ammeter.

Claims (1)

[Claims] 1. A bottom plate, an inner cylinder arranged on the bottom plate, an outer cylinder arranged concentrically with the inner cylinder, a movable element slidably inserted into the inner cylinder, and a detection fixed to the tip of the movable element. a spring that connects the lower end of the mover and the bottom plate, a magnet that forms a magnetic field in the gap between the inner cylinder and the outer cylinder, a coil that is fixed to the mover and placed in the magnetic field, and the output of the detector. and a control amplifier that inputs the output of the setting device and supplies the coil with a current that provides the coil with the force necessary to match both outputs.