JP2985333B2 - Position detection sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting sensor for detecting a plurality of positions of an object.

[0002]

2. Description of the Related Art Conventionally, as shown in, for example, FIG. 7, a processing tool 102 is held on a moving table 101 and is configured to be movable for a predetermined section along an arrow direction, and moves the processing tool 102 in an arrow direction. Workpiece 1
03, a processing device for processing an engine or the like is used. In such a processing apparatus, the moving table 1
It is necessary to detect that 01 has arrived at the forward position and the reverse position. For this purpose, a so-called dog 106, which is a detection object, is provided at a position facing the detection sensor of the moving table 101, and the position detection sensors 104 and 105 detect that the table has moved to a predetermined position when the dog 106 approaches. It is composed of

[0003]

However, in such a conventional position detecting sensor, a dog is provided on a table which slides in a predetermined range, and the dog is detected by the two position detecting sensors. There is a disadvantage that a plurality of sensors are required. As a result, the number of sensors increases as compared with the case where one detection sensor is used, and each sensor is a source of trouble, resulting in a low reliability.
Further, there is a disadvantage that the price for mounting the position detection sensor also increases. In addition, when aluminum chips or the like adhere to the periphery of the head of the detection switch, there is a disadvantage that malfunction is likely to occur.

The present invention has been made in view of such a problem of the conventional position detecting sensor, and a single detecting sensor detects different positions of an object, and has an adverse effect due to aluminum chips and the like. It is a technical problem to enable normal detection without receiving it.

[0005]

According to the present invention, a plurality of dogs made of a ferromagnetic material and a non-magnetic material, which are attached to different positions on a detection object, and a frequency is periodically determined based on a basic pulse having a constant period. A sweep circuit that generates a signal that continuously changes, a resonance circuit that includes a detection coil, is provided with the output of the sweep oscillator, and has a resonance frequency between the oscillation frequencies of the sweep oscillator, and a detection circuit that detects an output voltage of the resonance circuit. Circuit, a level discriminator for discriminating the output of the detection circuit at a predetermined level, and a positive and negative direction of the resonance frequency of the resonance circuit based on the discrimination phase output by the level discriminator and the phase difference of the basic pulse of the sweep oscillator. And a phase discriminating means for detecting a change in the phase difference.

[0006]

According to the present invention having such features, the sweep oscillator changes the frequency continuously at a frequency including the resonance frequency of the resonance circuit. By applying the oscillation output to the resonance circuit, when a dog made of a magnetic material or a non-magnetic material approaches the detection coil, the resonance frequency changes in a direction of decreasing and in a direction of increasing. Therefore, the voltage of the resonance circuit is detected by the detection circuit,
The level discrimination circuit discriminates the voltage, and detects a positive or negative change in the resonance frequency based on the phase difference from the fundamental pulse of the sweep oscillator to indicate the position of a dog made of a magnetic material or a non-magnetic material. An object detection signal is output.

[0007]

FIG. 1 is a block diagram showing the structure of a position detecting sensor according to an embodiment of the present invention. As shown in this figure, this position detection sensor has a sweep oscillator 1. The sweep oscillator 1 includes a pulse generation circuit 2 that generates a basic pulse having a constant period T, a sawtooth wave generation circuit 3 to which the basic pulse is applied, and a voltage controlled oscillator (hereinafter, referred to as a “oscillation frequency”) that changes the oscillation frequency by the voltage of the sawtooth wave generation circuit 3. VC
O) 4 is provided. The output of the VCO 4 is provided to a resonance circuit 5 including a detection coil L and a capacitor C. One end of the resonance circuit 5 is connected to the detection / amplification circuit 6. The detection / amplification circuit 6 detects and amplifies the signal of the resonance circuit 5, and its output is a level discriminator 7.
Given to. The level discriminator 7 discriminates the amplified output with a fixed threshold and supplies a binary signal to the phase discriminator 8. The phase discriminator 8 is phase discriminating means for detecting a change in the phase in the positive direction or the negative direction based on the basic pulse supplied from the pulse generation circuit 2 and the discriminated output,
The detection output is output to the outside via output circuits 9 and 10. Here, a dog 24 made of a ferromagnetic material such as ferrite or a dog 25 made of a non-magnetic material such as aluminum is selectively located at different positions on the detection object. I do. And the resonance circuit 5
Are the oscillation frequencies f1 and f2 of the sweep oscillator 1.
Is set to a frequency substantially at the center of.

Next, a detailed configuration of the phase discriminator 8 will be described with reference to FIG. The phase discriminator 8 is a level discriminator 7
Input pulse generating circuit 1 comprising a monostable multivibrator (hereinafter referred to as MM) which operates for a fixed time by the output of
1 and a comparison pulse generation circuit 12 composed of an MM that operates for a predetermined time by the basic pulse. Outputs of these pulse generation circuits 11 and 12 are applied to an AND circuit 13. The AND circuit 13 supplies the logical product output to the flip-flop 14 as a reset signal. The basic pulse is supplied to the RS flip-flop 14 as a set signal, and its Q output is supplied to AND circuits 15 and 16. The output of the input pulse generation circuit 11 is applied to an AND circuit 15 via a delay circuit 17 for delaying the output by the time T _H. The AND circuit 15 supplies these logical products to the output circuit 9 as advanced phase outputs. The AND circuit 15 calculates the logical product of the output of the flip-flop 14 and the output of the comparison pulse generation circuit 12 and supplies the result to the output circuit 10.

FIG. 3 shows a position detecting sensor 20 according to this embodiment.
It is a perspective view which shows the use condition of. In this embodiment, as in the above-described conventional example, an example is shown in which the sensor is used as a sensor for detecting the position of the moving table 21 reciprocating in a certain range. In this figure, a processing tool 22 is provided on a moving table 21, and an engine 2 which is a workpiece
3 are provided. A pair of dogs 24 and 25 are provided on the side of the moving table 21 as shown. Here dog 2
4 is made of a ferromagnetic material such as a ferrite material, and the dog 25 is made of a non-magnetic aluminum material.

Next, the operation of this embodiment will be described with reference to a time chart. FIG. 4 shows these dogs 24, 2
5 is a time chart showing the operation of each unit when the detection unit 5 is not close to the detection coil L, and (a) to (j) correspond to the waveforms of each unit a to j in FIGS. FIG. 4A shows an output of the pulse generation circuit 2 for generating a basic pulse, and the output is supplied to the saw-tooth wave generation circuit 3 and the phase discriminator 8. Therefore, the frequency f1 is at the lowest level of the sawtooth wave from the VCO 4, and the frequency f2 is at the highest level.
At an intermediate level, oscillation occurs at an intermediate frequency f0 between the frequencies f1 and f2. Since at this time it is the resonance frequency also frequency f0 of the resonant circuit 5, so that the highest level of the waveform at the center of the sawtooth wave is obtained as a terminal voltage e ₀ of the resonant circuit 5. This signal is amplified by a detection / amplification circuit 6 and detected to obtain a signal shown in FIG. 4C. The signal is discriminated by a threshold value indicated by a dashed line in FIG. The signal shown in d) is obtained.
In the phase discriminator 8, as shown in FIG. 4 (e), a signal which rises at time t ₂ , 同期 in synchronization with the output of the level discriminator 7 and which becomes L level with a certain operation time is input. It is obtained from the pulse generation circuit 11. The input pulse generation circuit 11 can perform signal processing when the detection waveform shown in FIG. 4C does not end within a certain period T. Well This signal is applied to the delay circuit 17, it is supplied to the AND circuit 15 as a stand rise signal from the time t ₃ with a predetermined delay time T _H as shown in FIG. 4 (f). Here, the comparison pulse generation circuit 12 operates after a fixed time from the rising times t ₁ , t ₅ } of the basic pulse, and the intermediate time points t ₄ , の between the two signals shown in FIGS. Shall be set to rise. In this case, the flip-flop 1 at time t ₄
4 is reset, the Q output of the flip-flop 14 is as shown in FIG. Therefore AND circuit 1
Since the AND condition by 5 and 16 is not satisfied, FIG.
No output is obtained as shown in (i) and (j).

Next, when the ferromagnetic dog 24 comes close to the detection coil L, the inductance increases if attention is paid to the inductance component of the detection coil. Thus the resonant frequency of the resonant circuit 5 is reduced becomes example f0-Δf _a. Therefore, the peak position of the terminal voltage of the resonance circuit 5 is also in the first half of the sweep period T. Since the peak value as shown in FIG. 5 (c) in this case moves to the front of the saw-tooth wave, from the time t ₁₂ as shown in the output also FIG 5 (d) of the level discriminator 7 Correspondingly It becomes a rising signal. Therefore, the outputs of the input pulse generation circuit 11 and the delay circuit 17 in the phase discriminator 8 are as shown in FIGS. The output of the comparison pulse generating circuit 12 in this case because the standing climb again time t ₁₄ of FIG. 4, FIG. 5 (g), the identical the output of flip-flop 14 as shown in (h). Therefore, from time t ₁₃
logical product condition is satisfied by the AND circuit 15 between t _14,
A signal is output to the output circuit 9 as shown in FIG. Accordingly, the ferromagnetic dog 24 is detected and the output circuit 9
A detection signal of the dog 24 is output to the outside.

Next, when the dog 25 made of an aluminum material approaches, the inductance becomes small if attention is paid to the inductance component of the detection coil L. Therefore, the resonance frequency of the resonance circuit 5 is higher than f0 (f0 + Δf _b ), and the peak position of the terminal voltage of the resonance circuit 5 is also in the latter half of the sweep period T. In this case, the output of the detection / amplification circuit 6 is shown in FIG.
(C) is obtained. Therefore, the signal is output to the level discriminator 7.
At the time t as shown in FIG.
_A signal rising at ₂₂ is obtained. Therefore, the phase of the signal supplied to the input pulse generation circuit 11 is delayed as compared with the case of FIG. 4, and the output of the delay circuit 17 is also delayed. On the other hand, the output of the comparison pulse generating circuit 12 is constant, and the output of the flip-flop 14 is as shown in FIG. 6 (h).
The signal is output to Therefore, the detection signal of the dog 25 is output from the output circuit 10 to the outside. As described above, in the present invention, the dog of the ferromagnetic material and the dog of the non-magnetic material can be detected by one detection switch. When the aluminum chips accumulate around the detection coil L, the loss resistance of the coil increases, but the change in the susceptance component is very small. Therefore, malfunction does not occur even if aluminum chips are attached.

Here, the magnitude of the detected phase can be adjusted by the magnitude of the delay time T _H of the delay circuit 17. This makes it possible to adjust the operating distance of the dog.
Further, in the above-described embodiment, the input pulse generation circuit 11 when there is no dog at the rising time of the output of the comparison pulse generation circuit 12
And the output of the delay circuit 17, the operating distance between the two dogs can be changed by changing this forward and backward. In this embodiment, ferrite and aluminum dogs are used as ferromagnetic and non-magnetic dogs. However, the present invention is not limited thereto, and various ferromagnetic and non-magnetic dogs may be used. It goes without saying that you can do it.

[0014]

As described above in detail, according to the present invention, ferromagnetic and non-magnetic dogs are provided at a plurality of positions of an object, and these dogs are detected, whereby one position detection sensor is used. Multiple positions of the object can be detected. Therefore, the number of sensors can be reduced, and the price of the position detection device itself can be reduced. Also, when non-magnetic metal powder or the like adheres to the detection coil,
Since the susceptance component does not change merely by increasing the loss resistance of the detection coil of the resonance circuit, it is possible to identify a dog of a non-magnetic material with almost no malfunction.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a position detection sensor according to one embodiment of the present invention.

FIG. 2 is a block diagram illustrating an example of a configuration of a phase discriminator according to the embodiment.

FIG. 3 is a schematic diagram showing an arrangement state of a moving table and a position detection sensor in which the present embodiment is used.

FIG. 4 is a time chart illustrating an operation of each unit in a state where the dog does not approach the detection coil in the embodiment.

FIG. 5 is a time chart illustrating an operation when a dog of a ferromagnetic material approaches in this embodiment.

FIG. 6 is a time chart illustrating an operation when a dog of a non-magnetic material approaches in the embodiment.

FIG. 7 is a schematic diagram showing the arrangement of a conventional moving table and position detection sensors.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 sweep oscillator 2 pulse generation circuit 3 sawtooth wave generation circuit 4 voltage controlled oscillator (VCO) 5 resonance circuit 6 detection and amplification circuit 7 level discriminator 8 phase discriminator 9, 10 output circuit 11 input pulse generation circuit 12 comparison pulse generation circuit 13, 15, 16 AND circuit 14 Flip-flop 17 Delay circuit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-42202 (JP, A) JP-A-56-125602 (JP, A) JP-A-2-19713 (JP, A) JP-A 49-125 104661 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01B 7/00

Claims (1)

(57) [Claims] A plurality of dogs attached to different positions of a detection object, the dogs being made of a ferromagnetic material and a non-magnetic material;
A sweep oscillator for generating a signal whose frequency continuously changes based on a basic pulse having a constant period, and a detection coil, wherein an output of the sweep oscillator is provided and a resonance frequency is set between the oscillation frequencies of the sweep oscillator. A resonance circuit, a detection circuit for detecting an output voltage of the resonance circuit, a level discriminator for discriminating an output of the detection circuit at a predetermined level, a discrimination phase output by the level discrimination device, and a basic pulse of the sweep oscillator. And a phase discriminating means for detecting a change in the resonance frequency of the resonance circuit in the positive direction and the negative direction based on the phase difference.