JP2653688B2 - Dimension measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a dimension measuring device for measuring dimensions such as an inner diameter of a hole and an outer diameter of a cylindrical object.

[Prior art]

Conventionally, as shown in FIG. 4, a detecting unit 31 composed of a pair of serially connected coils CL1 and CL2 whose impedance increases and decreases according to the displacement of the core CR, and a coil of the detecting unit 31 which generates a sine wave. Sine wave oscillation circuit 32 applied to one end of CL1
And a connection point between a phase inversion circuit 33 that inverts the phase of the sine wave generated by the sine wave generation circuit 32 and applies it to one end of the coil CL2 of the detection unit 31, and a pair of coils CL1 and CL2 of the detection unit 31 AC amplifier circuit that amplifies the output signal from the
There is a dimension measuring device including a 35, a smoothing circuit 36, and an adjustment voltage adding circuit 37. Here, the pair of coils, the impedance of one coil CL1 Z _1, the impedance of the other coil CL2 and Z _2. These impedances Z ₁ and Z
₂ increases or decreases according to the displacement x of the core CR. And the detection unit 3
When one core CR is in the middle position between a pair of coils CL1 and CL2,
The values of impedances Z ₁ and Z ₂ are equal and the value is Z ₀ .
The output E _m sinωt from the sine wave oscillation circuit 32 is one coil C
L1 is applied to, and the output E _m sin from sinusoidal oscillator circuit 32
The phase of ωt is −E _m sin
ωt and is applied to the other coil CL2. Then, the core CR of the detector 31 is moved from the intermediate position of the pair of coils CL1, CL2, the impedance Z ₁ is Z ₀ -? Z, the impedance Z ₂ is Z ₀ + [Delta] Z, the output signal E _c of the detector 31 , E _c = [(Z ₀ + ΔZ) / {(Z ₀ −ΔZ) + (Z ₀ + ΔZ)}] 2E _m sinωt−E _m sinωt = (ΔZ / Z ₀ ) E _m sinωt. Therefore, after amplifying the output signal, performing synchronous rectification, smoothing, and adding a zero-point adjustment voltage, the displacement x = 0 when the core CR of the detection unit 31 is at the intermediate position between the pair of coils CL1 and CL2.
As a result, a DC voltage proportional to the displacement x is obtained.

[Problems to be solved by the invention]

In the dimension measuring device, the third
As shown in the partial cross-sectional views of FIG. 3A and FIG. 3B, there is no interference between the tips of the feelers F ₁ and F ₂ and the workpiece W, which does not hinder the measurement. to so, after the closed state the tip of the feeler F _1, F _2, insert a feeler F _1, F ₂ in a position to be measured of the object W, the feeler F _1, F ₂ tip Is required to perform a preparatory operation before shifting to dimensional measurement, such as contacting the object to be measured W with the device opened. However, as is clear from the partial sectional views of FIGS. 3 (a) and 3 (b),
When the pair of feelers F ₁ and F _{2 of the} measuring head that are integrally operated with the CR and the pair of coils CL 1 and CL ₂ are largely closed (or opened), the core CR of the detecting unit 31 is connected to the pair of coils CL 1 and CL 2.
Will stand out from the inner, the impedance Z ₁ and Z ₂ coil CL1 and the coil CL2 is equal, the output signal of the detection unit 31 is E _c = 0 (core with respect to the pair of coils CL1, CL2 CR
2 (a) showing the displacement x of FIG. 2 and FIG. 2 (c) showing the change of the analog output with respect to the displacement x). For this reason, when the core CR of the detection unit 31 is at the intermediate position between the pair of CL1 and CL2, it cannot be distinguished from E _c = 0, which is an output signal, and the state that the feeler is largely closed (or opened) cannot be detected. There was a problem. For this reason, in the conventional dimension measuring device, the closing (or opening) of the feelers F ₁ and F ₂ is detected by an optical sensor or the like, and after receiving a confirmation signal that the operation has been reliably performed, The feelers F ₁ and F ₂ have been inserted into the measurement target W at positions to be measured. SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and an object of the present invention is to detect closing (or opening) of a feeler of a measuring head easily without changing a mechanical configuration. It is an object of the present invention to provide a dimension measuring device which can be realized only by adding a simple circuit.

[Means for Solving the Problems]

The configuration of the invention for solving the above-mentioned problems includes a detecting unit including a pair of coils connected in series whose impedance increases and decreases according to the displacement of the core, and a sine wave to generate one end of the pair of coils of the detecting unit. A sine wave oscillating circuit applied to the sine wave oscillating circuit, a phase inverting circuit for inverting the phase of a sine wave generated by the sine wave oscillating circuit and applying the same to the other end of the pair of coils of the detecting unit, A dimension measuring device comprising: a circuit for amplifying an output signal from a connection point of a coil; a constant current circuit for generating a constant current; a sine wave generated by the sine wave oscillation circuit; and a sine wave generated by the constant current circuit. An addition circuit for adding the obtained constant current to one end of a pair of coils of the detection unit; a low-pass filter for removing an AC component from an output signal of the detection unit amplified by the amplification circuit; Characterized by comprising a comparison circuit for comparing an output value that has passed through the value and the low-pass filters.

[Action]

The addition circuit adds and applies a sine wave generated by the sine wave oscillation circuit and a constant current generated by the constant current circuit to one end of a pair of coils of the detection unit. The phase of the sine wave generated by the sine wave oscillation circuit is inverted and applied to the other end of the coil. Therefore, the application of the constant current increases the DC voltage between the terminals of the pair of coils. The DC voltage between the terminals is determined by the sum of the impedances of the pair of coils at that time, is further divided into the impedance ratio of both coils, and is added to the output signal as a DC component. By the way, one coil impedance takes the maximum value when the core is completely included in the coil, takes the minimum value when the core exists outside the coil, and takes the maximum value when the core is partially included in the coil. Take the intermediate value of the minimum value.
The series impedance of both coils takes a certain maximum value regardless of the position of the core when the core is included in the series-connected coil, and takes the minimum value when the core is outside the series coil. Therefore, comparing the DC voltage of the output signal when the core is in the displacement detectable range including the zero point and the DC voltage of the output signal when the core is outside the coil, the former is higher than the latter. From this, it is possible to detect that the feeler is out of the displacement detectable range in distinction from the zero point. In order to detect this DC voltage, an output signal from the detection unit is amplified by an amplifier circuit and input to a low-pass filter. Then, the DC voltage is compared and determined by a comparison circuit with a preset value to obtain a determination output as to whether or not the core is out of the pair of coils.
The displacement was obtained by amplifying the output signal from the detection unit with an amplifier circuit, removing the DC component thereof with a DC cut circuit, and passing through a synchronous rectification circuit, a smoothing circuit, and an adjustment voltage addition circuit. It can be obtained from an analog signal.

【Example】

Hereinafter, specific examples of the present invention will be described. FIG. 1 is a block diagram showing an electrical configuration of the dimension measuring device of the present invention. The detecting unit 11 of the dimension measuring device includes a core CR and a pair of coils CL1 and CL2 whose impedances increase and decrease according to the displacement thereof. Connected to one end of the coil CL1 of the detection unit 11 is a sine wave oscillation circuit 12 for generating a sine wave, a constant current circuit 13 for generating a constant current, and an addition circuit 14 for adding the constant current and the sine wave and applying the same. Have been. Further, a phase inversion circuit 15 for inverting and applying the phase of the sine wave generated by the sine wave oscillation circuit 12 is connected to one end of the coil CL2 of the detection unit 11. An AC amplifier circuit 16 is connected to a connection point of the pair of coils CL1 and CL2 of the detection unit 11 as an amplification circuit for amplifying an output signal from the detection unit 11. Since the output signal amplified by the AC amplification circuit 16 is composed of an AC component and a DC component, a DC cut circuit 17 that removes the DC component and uses only the AC component is connected to the subsequent stage. Furthermore, DC
In the subsequent stage from the cut circuit 17, a synchronous rectifier circuit 18 for synchronously rectifying the output signal having only the AC component, a smoothing circuit 19 for smoothing the rectified output signal, and a zero point in the smoothed output signal Adjustment voltage addition circuit 20 that adds adjustment voltage
And are connected. Further, the AC amplifier circuit 16 includes a low-pass filter 21 that removes an AC component of the amplified output signal to make only the DC component, and compares the output signal from which the AC component has been removed with a predetermined value. The comparison circuit 22 is connected so as to output the result as an output signal for opening (or closing) the feeler. Next, FIG. 2 (a) showing the displacement x of the core CR with respect to the pair of coils CL1 and CL2 in the detecting unit 11 of the dimension measuring device, and FIG.
2 (b) showing the change in the impedance of FIG. 2 and FIG. 2 (c) showing the change in the analog output with respect to the displacement x. The impedance of one coil CL1 of the detection unit 11 is represented by Z ₁ ,
The impedance of the other coil CL2 and Z _2. Detector 1
One core CR is located at an intermediate position between the pair of coils CL1 and CL2 (displacement x =
0), the values of impedances Z ₁ and Z ₂ are equal and the value is Z ₀ . The current I is added to the output voltage E _m sinωt from the sine wave oscillation circuit 12 by the constant current circuit 13 by the addition circuit 14,
E _m sinωt + 2Z ₀ I is applied to one coil CL1 as the voltage E _1. Also, the output voltage E _m sinω from the sine wave oscillation circuit 12
t is -E _m sin .omega.t is applied as the voltage E ₂ to -E _m sin .omega.t next other coil CL2 by the phase inversion circuit 15. Here, the core CR of the detector 11 is moved from the intermediate position of the pair of coils CL1, CL2, the impedance Z ₁ is Z ₀ -? Z,
When the impedance Z ₂ is Z ₀ + [Delta] Z, the output voltage E _c of the detector 11, the _{E c = (ΔZ / Z 0} ) E m sinωt + (Z 0 + ΔZ) I. Therefore, when amplifying the output at the amplification factor A ₁ of the AC amplifier _{16, A 1 E c = A} 1 (ΔZ / Z 0) becomes _{E m sinωt + A 1 (Z} 0 + ΔZ) I. When this output voltage is input to the DC cut circuit 17, the DC component A ₁ (Z ₀ + ΔZ) I is removed as the output, and A
₁ (ΔZ / Z ₀ ) E _m sinωt only. When the output voltage is synchronously rectified by the synchronous rectifier circuit 18 and smoothed by the smoothing circuit 19, the output after smoothing has a value proportional to the amount of change ΔZ of the impedance, that is, the displacement x. The output voltage value is proportional to the displacement x by adding a zero-point adjustment voltage so that the analog output becomes zero when the core CR is at an intermediate position between the pair of coils CL1 and CL2 by the adjustment voltage adding circuit 20. The obtained DC voltage is obtained. On the other hand, the output amplified by the AC amplifier circuit 16 is input to the low-pass filter 21. In the low-pass filter 21, the AC component A ₁ (ΔZ / Z ₀ ) E _m sinω of the input signal
Since t is removed, the output signal is a DC component A ₁
Only (Z ₀ + ΔZ) I. Here, with reference to FIG. 2B, the impedances Z ₁ and Z ₂ of the pair of coils CL1 and CL2 with respect to the displacement x of the core CR.
Will be described in detail. Each of the impedance value of Z _1, Z ₂ of the pair of coils CL1, CL2 when located in an intermediate position of the core CR coil CL1, CL2 equals its value is Z _0, and,
For simplicity, the length of each of the coils CL1 and CL2 and the core CR is equal to 2a. Now, the impedance Z ₁ of the coil CL1 when displaced in the direction of the core CR coil CL1 is to the center position of the coil CL1 increases with increasing displacement, the maximum value at the position of x = a. Further, after the core CR the core CR is displaced impedance Z ₁ of the coil CL1 is decreased with increasing displacement went out from the coil CL1 is a constant value. Also, core CR
Is a constant value after but leaving out from the impedance Z ₁ is decreased core CR coil CL1 with increasing negative direction of displacement of the coil CL1 when displaced from the intermediate position of the coil CL1, CL2 in the opposite direction to the coil CL1 . Also changes in the same manner as the impedance Z ₁ of the coil CL1 displacement x = 0 as a symmetrical Impedance Z ₂ coil CL2. And the core CR is the coil CL
1, When going out of CL2, impedances Z ₁ and Z ₂ are equal Z
_min. , Z _min. <Z ₀ , and at that time, the DC component of the output signal is A ₁ Z _min. I. Next, this output signal is input to the comparison circuit 22, and is compared with a predetermined set value V _s [≒ A ₁ (Z _min. + Z ₀ ) I / 2]. The set value V _s corresponds to a state in which the core has left half from the coil. However, in general, the setting value V _s is A ₁ Z _min. I value greater than, less than the value of the DC component of the analog output of the detector 11 is output when exceeding the displacement detectable range Is fine. Here, the displacement detectable range of the dimension measuring device is a range in which the impedances Z ₁ and Z ₂ change by the same amount in the positive and negative directions according to the displacement x of the core CR, and the displacement x of the core CR and the analog output. , The range is strictly linear, and in terms of displacement, for example, the range is extremely near the zero point of-(a / 30) <x <(a / 30). The terminal-to-terminal voltage applied by adding the constant current I from the constant current circuit 13 to both ends of the pair of coils CL1 and CL2 in the adding circuit 14 is -a as described above.
In the range of <x <a, 2Z ₀ I. As is clear from FIG. 2 (b), when the range of −a <x <a is exceeded, both impedances Z ₁ and Z ₂ decrease. Accordingly, the inter-terminal voltage also gradually decreases. Therefore, when the value exceeds the range of -a <x <a, the DC component of the output signal also gradually decreases. When the (DC component of the output signal) <V _s, because the core CR of the detector 11 is of course the displacement detectable range of the pair of coils CL1, CL2, comparator circuit 22 outputs a signal To inform that the feeler is open (or closed). As described above, in addition to the conventional mechanical configuration, only by adding a simple circuit, the core CR of the detection unit 11 is out of the range where the pair of coils CL1 and CL2 can detect the displacement, that is,
It is possible to know that the feeler of the measuring head of the dimension measuring device is in a closed (or open) state.

【The invention's effect】

The present invention provides a constant current circuit that generates a constant current, a sine wave generated by a sine wave oscillation circuit, and a constant current generated by a constant current circuit, and adds the sine wave to one end of a pair of coils of the detection unit. An adding circuit for applying the voltage, a phase inverting circuit for inverting the phase of the sine wave generated by the sine wave oscillating circuit and applying the inverted signal to the other end of the pair of coils of the detecting unit, A low-pass filter that removes AC components from the signal,
A comparison circuit that compares a preset value with an output value that has passed through a low-pass filter is provided, so that in addition to a normal analog output, the core has a pair of coils in a relative positional relationship between the core and a pair of coils. This has the effect that even in the state of going out of the coil, it can be known by the presence or absence of the output signal from the comparison circuit.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an electrical configuration of a dimension measuring device according to a specific embodiment of the present invention. FIG. 2A is an explanatory diagram showing a displacement x of a core with respect to a pair of coils in a detection unit of the dimension measuring device. FIG. 2 (b) is an explanatory diagram showing a change in impedance of each of the pair of coils with respect to the displacement in FIG. 2 (a). FIG. 2 (c) is an explanatory diagram showing a change in analog output with respect to the displacement shown in FIG. 2 (a). FIG. 3A is a partial cross-sectional view showing a configuration of a feeler and a detection unit of the dimension measuring device. FIG. 3 (b) is FIG. 3 (a)
FIG. 4 is a partial cross-sectional view showing a state in which the feeler of the dimension measuring device shown in FIG.
FIG. 4 is a block diagram showing an electrical configuration of a conventional dimension measuring device. 11 Detector, 14 Addition circuit 21 Low-pass filter, 22 Comparison circuit CL1, CL2 Coil, CR Core

Claims (1)

(57) [Claims] 1. A detecting section comprising a pair of coils connected in series whose impedance increases and decreases according to displacement of a core, and a sine wave oscillating circuit for generating a sine wave and applying the sine wave to one end of the pair of coils of the detecting section. A phase inversion circuit that inverts the phase of a sine wave generated by the sine wave oscillation circuit and applies the sine wave to the other end of the pair of coils of the detection unit, and an output from a connection point of the pair of coils of the detection unit. In a dimension measuring device comprising an amplifier circuit for amplifying a signal, a constant current circuit for generating a constant current; and a sine wave generated by the sine wave oscillation circuit and a constant current generated by the constant current circuit. An addition circuit for adding and applying one end of a pair of coils of the detection unit; a low-pass filter for removing an AC component from an output signal of the detection unit amplified by the amplification circuit; A comparison circuit for comparing an output value passed through a pass filter with the output value.