JPH0370769B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides an origin circuit, in particular, 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 in response to the output of an origin detector from selection signals whose generation timing is variable within intervals of grid points.

BACKGROUND TECHNOLOGY 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 using the magnetic scale device 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.

Moreover, 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 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 circuit that can electrically adjust the generation timing of a selection signal for selecting the output signal of an origin detector at the origin position.

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

Summary of the Invention In order to achieve the above object, the origin circuit of the present invention has the following features:
A position detector that periodically generates a position detection signal according to the relative movement with the object to be measured, an origin detector installed near the origin position of the relative movement, and a position detection signal for each lattice point of the scale of the position detector selection signal generation means for generating a selection signal with variable generation timing within the interval between the grid points, and origin reference signal generation means for generating an origin reference signal at a predetermined position timing within the interval between the grid points based on the position detection signal; a detection means for detecting coincidence with the origin reference signal by adjusting the timing of the selection signal; and a detection means for selecting the output signal of the origin detector based on the selection signal when the coincidence with the origin reference signal and the position detection signal is used to generate an origin position signal. and an origin position signal selection means for generating the origin position signal.

In particular, the circuit of the present invention is a position detector in which the position detector employs a phase modulation method having a magnetic scale, and the selection signal generating means generates the selection signal from a reference signal of a different frequency from the position detector. If configured in such a manner, it is suitable as an origin circuit capable of electrically adjusting the origin position with high precision.

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
8 is a phase shifter, 8 is a mixer amplifier circuit, 9 is a band pass filter, 10 is a limiter amplifier, and 11 is a known origin detector such as the above-mentioned high precision switch arranged near the origin position. The output signal of the step-down circuit 5
f _p /2, and its angular frequency is ω _p /2, f ₀ = sin ω _c t f ₀ /2 = sin _{ω c} t/2, and the output of the limiter amplifier 10 (phase modulation signal)
If the grid 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).

FIG. 2 is a circuit diagram showing the configuration of an embodiment of the origin circuit according to the present invention, in which FF ₁ and FF ₂ are flip-flop circuits, INV ₁ to INV ₃ are inverter circuits,
LGP, LZDS and LZGS are light emitting diodes,
AND ₁ to AND ₃ are AND circuits, MM is a monostable multivibrator circuit, and T is a digital selection circuit.

The digital selection circuit T has a plurality of switches S ₁ to
S _o , exclusive OR circuit EX ₁ ~ EX _o and AND circuit
AND ₃ , etc., and one input of each of the circuits EX ₁ to EX _o is connected to the frequency reduction circuit 5 of the position detection circuit.
Reference signals f ₀ to _{nf 0} with different frequencies are given,
The other input is grounded via switches S ₁ to S _o , and the output of each exclusive OR circuit is an AND circuit.
Connected to one input of the AND circuit _AND1 via _AND3 .

A phase modulation signal S is applied to the D ₁ terminal of the flip-flop circuit FF ₁ and the input of the monostable multivibrator circuit MM, and the output of the circuit MM is connected to the other input of the AND circuit AND ₁ .
The output of the AND circuit is connected to the light emitting diode LGP via the inverter circuit _INV1 .

The input of the AND circuit AND ₂ is the AND circuit AND ₃ .
The output A of AND 2, the phase modulation signal S, and _one terminal output of flip-flop circuit FF ₁ are given, and the output C of AND ₂ is the clock terminal of flip-flop circuit FF ₂ .
Connected to CK ₂ .

The output signal ZDS of the origin detector 11 is sent to the _D2 terminal of the flip-flop circuit _FF2 and to the inverter circuit.
_{The Q 2 terminal} of FF ₂ is connected to the light emitting diode LZGS and to the output terminal 0 via an inverter circuit INV ₃ .

In the digital selection circuit T, switches S ₁ to
S _o is a binary switch that can be turned on and off in a binary manner, and by appropriately selecting and turning on this switch, the output (selection signal A) of the AND circuit AND ₃ (selection signal A) will be at the lattice point of the scale, as shown in Figure 3. The timing of its occurrence can be adjusted within the interval t. In addition, the monostable multivibrator circuit MM responds to the phase modulation signal S and generates an output signal (origin reference signal B) at a predetermined position timing (for example, at the center) within the grid point interval as shown in FIG.

Now, when the object to be measured, such as a tool of a machine tool, is moved relative to the scale and comes near the origin position, the above movement is performed slowly until the light emitting diode LZDS lights up. light emitting diode
The movement is stopped the moment LZDS lights up, and at this time, the output signal ZDS of the origin detector 11 is generated to set the flip-flop circuit _FF2 .

At the above stop position, switches S ₁ to S _o are appropriately selected and turned on so that the light emitting diode LGP lights up. At this time, the selection signal A matches the origin reference signal B as shown in FIG. 4a, and therefore is set at the center of the grid point interval.

Next, when the object to be measured is moved further from the above-mentioned stop position, the relative positional relationship between the selection signal A set as described above and the phase modulation signal S becomes as shown in FIG. 4b, and at this time, the AND circuit Origin selection signal C is output from AND ₂ , and flip-flop circuit FF ₂
clock terminal _CK2 . Therefore, at this phase (true origin), the output terminal 0 from the Q ₂ terminal of FF ₂
Accurate origin position signal ZGL can be obtained.

Note that the origin position signal generation can be confirmed using a light emitting diode.
It may be done with LZGS, but this is not required.

Furthermore, the present invention is not limited to the above-mentioned embodiments, but can be applied, for example, to cases in which the selection signal is matched to the position of a gate signal having a predetermined width, such as that produced by a window comparator or the like.

Effects of the Invention As is clear from the above explanation, according to the present invention, it is possible to obtain a home position signal that accurately corresponds to the true home position, and also to generate a selection signal for selecting the home position detector output. Since the timing can be adjusted electrically and digitally, no mechanical fine-tuning of the origin detector is required. Therefore, the accuracy of the origin detector does not necessarily have to be high.
It is particularly suitable for cases where the lattice point pitch is narrow, such as in magnetic scales.

[Brief explanation of drawings]

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 Figs. 3 and 4 a and b are waveform diagrams for explaining the operation of the above embodiment. be. 1... Magnetic scale, 2, 3... Head, 11
...Origin detector.

Claims (1)

[Scope of Claims] 1. A position detector that periodically generates a position detection signal in response to relative movement with the object to be measured, an origin detector installed near the origin of the relative movement, and the position detection device selection signal generating means for generating a selection signal whose generation timing is variable within the interval of the grid point for each grid point of the scale of the device; and generating an origin reference signal at a predetermined position timing within the grid point interval from the position detection signal. origin reference signal generating means; detection means for detecting coincidence with the origin reference signal by adjusting the timing of the selection signal; and an output signal of the origin detector based on the selection signal and the position detection signal when the selection signal coincides with the origin reference signal. and an origin position signal selection means for selecting and generating an origin position signal. 2. The position detector is a position modulation type position detector having a magnetic scale, and the selection signal generating means comprises a digital selection circuit that digitally selects reference signals of different frequencies from the position detector. An origin circuit according to claim 1. 3. The digital selection circuit according to claim 2, wherein the digital selection circuit includes a plurality of switches and a plurality of exclusive OR circuits into which the switches and the reference signals having different frequencies are respectively input. Origin circuit.