JPH0259924B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an origin detection circuit, in particular, to a combination of a position detector and an origin detector used for controlling the tool position of a machine tool. The present invention relates to an improvement in means for adjusting the generation point of an origin position signal in an origin detection circuit which selects an origin position signal from lattice point signals corresponding to lattice points of a scale in response to the output of an origin detector.

BACKGROUND ART AND PROBLEMS Conventionally, when using a position detection device, such as a magnetic scale device, to read the tool position of a machine tool, a highly accurate origin detector is used to detect the origin, and its on-off signal is used to detect the origin. was used as the origin position signal. However, in a numerical control device, for example, a resolver, an inductosin, etc. are used as a position detection device, and the grid point signal is selected by the output of the origin detector, and it is generally used as the origin position signal. It is being done. In this case, since the pitch of the grid points of the position detection device is long (2 mm), a combination of a dog and a limit switch is used as the origin detector, and a grid point selection signal is generated from the switch.

On the other hand, even when the magnetic scale device is used as a position detection device, there is a recent demand for highly accurate position reading, and therefore, consideration is being given to adopting the origin detection method in the above-mentioned numerical control device.

However, in such a position detection device, since the grid point pitch of the magnetic scale is as short as 0.2 mm,
For example, a high-precision switch incorporating a magnetoresistive element must be used as the origin detector, and a grid point signal must be selected based on the output of the switch.

Furthermore, in order to enable highly accurate selection of grid point signals, the high precision switch must be set to be turned on at the center of the grid point pitch. This is because if the selection signal (switch output) is obtained at the center of the grid point pitch, even if the selection signal generation position shifts by half of the maximum grid point pitch due to some disturbance, the grid point signal will be highly accurate as the origin position signal. This is because it can be used.

However, it is very difficult to mechanically and accurately fine-tune the setting position of the high-precision switch so that the selection signal is obtained at the center of the grid point pitch because the grid point pitch is very short, as mentioned above. .

OBJECTS OF THE INVENTION Accordingly, an object of the present invention is to provide an origin detection circuit that does not require mechanical fine adjustment of the set position of an origin detector.

Another object of the present invention is to provide an origin detection circuit that can electrically adjust the generation timing of a selection signal for selecting a grid point signal at the origin position.

Still another object of the present invention is to provide an origin detection circuit using a phase modulation type magnetic scale device as a position detector.

Summary of the Invention In order to achieve the above object, the origin detection circuit of the present invention includes a position detector that periodically generates a position detection signal according to relative movement with the object to be measured; lattice point signal generating means for generating lattice point signals corresponding to lattice points of a scale; an origin detector installed near the origin position of the relative movement; and an output signal responsive to the output of the origin detector. timing adjustment means for varying the generation timing of the output signal within the range of the grid point spacing of the scale; The apparatus includes an origin position detection means for detecting arrival, and an origin signal selection means for selecting the lattice point signal and generating an origin position signal based on the output signal of the timing adjustment means when the origin position is reached.

In particular, the position detector is a phase modulation type position detector having a magnetic scale, and the grid point signal generating means generates the grid point signal from a phase modulation signal and a reference signal from the position detector. This configuration is suitable as an origin detection circuit that can electrically adjust the origin position with high accuracy.

Embodiment FIG. 1 is a block diagram showing the configuration of the main parts of a position detection circuit using a known phase modulation type magnetic scale device, in which 1 is a magnetic scale, 2 is a first channel head, and 3 is a second channel.・Head, 4 is an oscillator, 5 is a frequency reduction circuit, 6 is an excitation circuit, 7
is a phase shifter, 8 is a mixer amplifier circuit, 9 is a band pass filter, and 10 is a limiter amplifier. Oscillator 4
When the output signal (reference signal) of is f ₀ , the angular frequency of the oscillator output is ω _c , and the output of the step-down circuit is f ₀ /2, then f ₀ = sinω _c t f ₀ /2 = sinω _c t/2. , output of limiter amplifier 10 (phase modulation signal)
If the lattice point pitch of the scale is λ and the relative displacement between the scale and the head is x, then S=sin(ω _c t=2π/λx).

Figure 2 is a circuit diagram showing the configuration of the origin detection circuit according to the present invention.FF1 to FF3 are flip-flop circuits, AND is an AND circuit, _INV1 to _INV3 are inverter circuits, LGP, LGS, and LGC are light emitting diodes, and EX is exclusive. 11 is a timing adjustment circuit, I ₁ is a phase modulation signal input terminal, I ₂ is a reference signal input terminal, and I ₃ is a known origin detection circuit such as the above-mentioned high-precision switch installed near the origin position. An output signal input terminal from the device 12, and O is an origin position signal output terminal. It is assumed that the origin position is located at a position corresponding to the center of the predetermined grator point pitch of the scale.

The phase modulation signal S and reference signal _f0 from input terminals _I1 and _I2 are sent to flip-flop circuits FF1 and F0, respectively.
It is given to the D ₁ and D ₂ terminals of FF2, and each
Clock pulses CP ₁ and CP ₂ are applied to the CK ₁ and CK ₂ terminals. The outputs from the Q ₁ and Q ₂ terminals of FF1 and FF2 and the signals S and f ₀ are connected to an AND circuit.
It is applied to the positive and negative inputs of AND, and its output is the clock terminal of flip-flop circuit FF3.
Given to CK ₃ .

The origin detector output ZDS from the input terminal I ₃ is applied to the timing adjustment circuit 11 . This circuit consists of, for example, a comparator A and a variable resistor R, and the output threshold value is made variable by this resistor. Therefore, as shown in Fig. 3, if the threshold value is changed from L ₁ to _{L 2} using the variable resistor R for the origin detector output ZDS, the output signal
The timing at which SL occurs changes within the range of T (range of grid point pitches). The output signal SL of the timing adjustment circuit 11 is applied to the _D3 terminal of the flip-flop circuit FF3.

The phase modulation signal S is directly applied, the reference signal f ₀ is applied to the exclusive OR circuit EX via the inverter circuit INV ₁ , and the output of EX is applied to the light emitting diode.
Added to LGP. Further, the output signal SL of the timing adjustment circuit 11 is also applied to the light emitting diode LZDS via the inverter circuit _INV2 . Furthermore, the flip-flop circuit FF3
The output from the _Q3 terminal is given to the light emitting diode LZGS via the inverter circuit _INV3 .

Now, the phase modulation signal S and the reference signal f ₀ depend on the relative movement with the object to be measured, such as a tool of a machine tool.
is applied to the flip-flop circuits FF1 and FF2 and the AND circuit AND, these signals are delayed by 1 bit by the clock pulses CP ₁ and CP ₂ , respectively, and output, and when the above-mentioned signals fall, one clock signal of the output is output. A lattice point signal corresponding to a lattice point of scale 1 is obtained by performing an AND operation on .

Furthermore, since the light emitting diode LGP is energized in response to the exclusive OR output of the phase modulation signal S and the reference signal f ₀ , the light emitting diode LGP is energized in response to the exclusive OR output of the phase modulation signal S and the reference signal f 0 . The light and dark will repeat at each pitch, but it will be the darkest (brightest) at the center of each grid point pitch.

Furthermore, since the light emitting diode LZDS is energized in response to the output of the origin detector, it lights up when it comes near the origin position due to the relative movement. In other words, by lighting the light emitting diode LZDS, it is possible to know that the position is near the origin position.

When it comes near the origin position, the light emitting diode
Slowly perform the relative movement until LZDS lights up, and then stop the relative movement at the position where the light emitting diode LGP becomes the darkest (brightest) in order to search for the origin position (the center of the grid point pitch).
This position is the center of the grid point pitch of the scale, that is, the origin position. Therefore, in order to be able to select the grid point signal at this position, the variable resistor R of the timing adjustment circuit 11 is changed to adjust the output signal generation timing so that the light emitting diode LZDS lights up when it reaches the origin position. is adjusted, and the output signal at that time is sent to the _D3 terminal of flip-flop FF3 as a grid point signal selection signal.

Thus, an accurate origin position signal is output from the _Q3 terminal of the flip-flop circuit FF3 to the output terminal O.

Note that confirmation of the generation of the origin position signal may be performed using a light emitting diode LZGS, but it is of course not limited to this.

Effects of the Invention As is clear from the above explanation, according to the present invention, it is possible to select a grid point signal in response to the output of the origin detector and obtain an origin position signal that accurately corresponds to the origin position. Since the generation timing of the selection signal for selecting the point signal can be adjusted electrically, fine mechanical adjustment of the origin detector is not required. Therefore, the accuracy of the origin detector does not necessarily have to be high, and is particularly suitable for cases where the grid point pitch is narrow, such as in a magnetic scale.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a position detection circuit, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a waveform diagram for explaining the operation of the timing adjustment circuit. 1... Magnetic scale, 2, 3... Head, 11
...Timing adjustment circuit, 12...Origin detector.

Claims (1)

[Scope of Claims] 1. A position detector that periodically generates a position detection signal in response to relative movement with an object to be measured, and a lattice that corresponds to each lattice point of the scale of the position detector based on the position detection signal. An origin detection circuit comprising a grid point signal generating means for generating a point signal and an origin detector installed near the origin position of the relative movement,
timing adjusting means for generating an output signal in response to the output of the origin detector and for varying the generation timing of the output signal within the range of the grid point spacing of the scale; an origin position detection means for detecting the arrival of the object to be measured at the origin position from the position detection signal; and an output signal of the timing adjustment means upon arrival at the origin position to select the grid point signal and determine the origin position. An origin detection circuit comprising an origin signal selection means for generating a signal. 2. The position detector is a phase modulation type position detector having a magnetic scale, and the lattice point signal generating means determines that the displacement amount of the relative movement is x, the lattice point pitch of the magnetic scale is λ, and the position detector The lattice point signal is generated from the phase modulation signal sin (ω _c t + 2π/λx) from the position detector and the reference signal sin ω _c t, with the angular frequency of the excitation signal being ω _c The origin detection circuit described in item 1. 3. The origin position detection means comprises an exclusive OR circuit that receives the phase modulation signal and the reference signal as input, a display that displays the output of the circuit, and a display that responds to the output of the origin detector. An origin detection circuit according to claim 2.