JPH041857B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a defective mark detection device for a pulse encoder that detects defects in marks formed on an optical pulse encoder or the like.

Conventionally, many measuring instruments have been used that measure by counting marks provided on an optical encoder or the like. but,
For example, if the mark is a hole, the diameter of the hole is a few millimeters at most, so the hole may become clogged with dirt, etc., and such a hole may cause damage to the measuring device. This may cause measurement errors. Particularly, in the case of measuring instruments used outdoors, this type of hole clogging occurs significantly. Furthermore, even when marks are placed on magnetic tape or represented by symbols such as barcodes, such marks may be scratched or the information may be erased due to external disturbances. Sometimes it happens.

In view of this, an object of the present invention is to provide a defective mark detection device for a pulse encoder that can detect defective states of marks formed on a pulse encoder or the like and prevent measurement errors.

As shown in FIG. 1, the configuration of the present invention is that when a mark is detected by the first detection means a, the first pulse signal generation means b generates a pulse width corresponding to the size of the mark. On the other hand, when the mark is detected by the second detection means c, the second pulse signal generation means d detects the mark in a normal state and generates a first pulse signal. A second pulse signal is output that is synchronized with the middle edge of the pulse of the first pulse signal and has a pulse width smaller than the pulse width of the first pulse signal. and,
The defective mark detection means e detects defective marks by comparing the first pulse signal with a changed pulse width generated by the first pulse signal generation means b and the second pulse signal. ing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below with reference to embodiments with reference to the drawings.

In this example, an electronic tape measure 1 is provided with a defective mark detection device according to the present invention, and an aperture 8 formed in a measuring tape 7 is used as a mark.

FIG. 2 shows an electronic tape measure 1.
A keyboard 4, a digital display 5, and a buzzer 6 are provided on the front panel 3 of the tape measure main body 2, and the tape measure tape 7 can be pulled out from one side of the tape measure main body 2 up to a certain scale value (for example, 5 m). It can also be stored freely within the main body 2.
By inputting from the keyboard 4, normal four arithmetic operations are possible, and the measuring tape 7
When the measuring tape 7 is being pulled out, the amount of the measuring tape 7 to be pulled out is displayed on the digital display 5 in priority to input from the keyboard 4.

The amount of drawout of the tape measure tape 7 is measured by counting the openings 8 provided at intervals (for example, 2 mm) in the length direction of the tape measure tape 7, and if the holes 8 are clogged. In such a case, the scale value of the location where the hole clogging occurs is displayed on the digital display 5, and a buzzer 6 is used to notify the user.

Next, FIG. 3 illustrating the hardware of the electronic tape measure 1 having various functions as described above will be described.

9 is a central processing unit (hereinafter referred to as CPU), 1
0 is an input side interface that intervenes to input various input signals to the CPU 9, and 11 is an output side interface that sends output signals from the CPU 9 to various output devices. 12 is RAM,
13 is a ROM, and the contents of the RAM 12 are retained by a backup power source (not shown) even when the power is turned off.

Three projectors 14a, 1 are installed at intervals equal to the pitch of the apertures 8 formed in the measuring tape 7.
4b, 14c are provided, and these floodlights 14a,
14b and 14c emit light to light receivers 15a, 15b and 15c provided below the measuring tape 7, respectively.

When the light emitted from the light emitters 14a, 14b passes through the aperture 8 and is received by the light receivers 15a, 15b, the phase differs from that of the light receiver by 90 degrees, and the opening degree of the aperture 8 Two types of pulse signals S1 and S2 (see FIG. 4) having directly proportional pulse widths are generated and input to the counter 16 with direction discrimination.

In the counter 16 with direction discrimination, the pulse signal S
1, in response to S2, it is determined whether the tape measure tape 7 is moving in the pull-out direction or in the storage direction, and a multiplication pulse signal S3 corresponding to the detected number of holes is output, and the multiplication pulse signal S3 is outputted. Pulse signal S
3 is input to the input side interface 10.

On the other hand, when the light emitted from the light emitter 14c passes through the aperture 8 and is received by the light receiver 15c, the light receiver 15c detects a hole 8 that is not clogged and generates a pulse signal. Synchronized with the middle edge part 17 of the pulse of S1, and in addition, the pulse signal S1
A pulse signal S4 having a pulse width smaller than the pulse width of is output. Preferably, the pulse width of the pulse signal S4 is set to approximately 90% or more of the pulse width of the pulse signal S1.

The output of the light receiver 15a is connected to the reset terminal of the reset priority flip-flop 18, and the output of the light receiver 15c is connected to the set terminal of the reset priority flip-flop 18.

Further, the positive output Q terminal of the reset priority flip-flop 18 is connected to the set terminal of the flip-flop 19, and the flip-flop 19 receives the reset priority when the positive output Q of the reset priority flip-flop 18 reaches the "H" level even momentarily. "H"
Retains level output status. On the other hand, the reset input for clearing the holding function of the flip-flop 19 is connected to the output side interface 1.
Output from 1.

When the hole 8 is not clogged, the pulse signals S1 and S4 have the relationship shown in FIG. 4, so the output from the reset priority flip-flop 18 is always at the "L" level. However, when a clogged hole is detected and the pulse width of the pulse signal S1 changes as shown by the chain line in FIG. 4, the output of the reset priority flip-flop 18 momentarily changes from the "L" level to the "H" level. . Therefore, the output of the flip-flop 19 changes from the "L" level to the "H" level, and is held at the "H" level until the set signal is input from the output side interface 11.

In other words, the detection of hole clogging can be accomplished by monitoring the change in the output of the flip-flop 19.

The software procedure when hole clogging is detected by the hardware operations described above will be described below with reference to FIG.

In the step, it is determined whether the output of the flip-flop 19 has changed (from the "L" level to the "H" level), and when the output change is confirmed, the tape measure tape displayed on the display 5 at that time is determined in the step. Hold the withdrawal amount value of 7. Then, in the step, a buzzer 6 is sounded to inform the operator that a hole clogging has been detected. In the step, it is determined whether the stop switch 20 of the buzzer 6 (see FIG. 2A and FIG. 3) is pressed;
If it has been pressed, the buzzer 6 is stopped in step, a reset signal is output to the flip-flop 19 in step, and the process returns to step. On the other hand, if the stop switch 20 of the buzzer 6 is not pressed in step, the steps are repeated.

FIG. 6 shows another circuit used in place of the reset priority flip-flop 18 and flip-flop 19 explained in FIG. Direct AND gate 2
Connected to 1. When a hole clogging is detected, the output of the ADN gate 21 becomes "H" for a moment.
level, so it is sufficient to constantly monitor changes in the signal from the input side interface 10 side. In addition, although the above-mentioned embodiment shows the case where the aperture 8 provided in the measuring tape 7 is used as a mark, the present invention is not limited to this, and a mark can be formed on the magnetic tape according to the direction of the magnetic pole, and a Hall element can be used. The same applies to the configuration for detecting the mark as in the case of the measuring tape 7. It can also be applied to a configuration in which a colored symbol such as a bar code is used as a mark to detect the amount of light reflected.

The present invention provides a first pulse signal having a pulse width corresponding to the size of the mark formed on a pulse encoder, and a pulse middle edge of the first pulse signal generated by detecting a mark in a normal state. This defective mark detection device has an extremely simple configuration and detects a defective mark by comparing it with a second pulse signal that is synchronized with a second pulse signal and has a pulse width smaller than the pulse width of the first pulse signal. measurement errors can be prevented.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a defective mark detection device for a pulse encoder according to the present invention, FIGS. 2A and 2B show an electronic tape measure of the embodiment, and FIG. B is an enlarged view showing the base end of the measuring tape, FIG. 3 is a block diagram illustrating the hardware, and FIG. 4 is a diagram showing the pulses output by the three receivers shown in FIG. 3. FIG. 5 is a flowchart showing the operation after a defective mark is detected by the hardware shown in FIG. 3. FIG. 6 is a waveform diagram illustrating each signal. FIG. FIG. a...first detection means, b...first pulse signal generation means, c...second detection means, d...second pulse signal generation means, e...defective mark detection means, 1...
...electronic tape measure, 7...measuring tape, 8...mark, 9...central processing unit.

Claims (1)

[Claims] 1. A device for detecting defects in marks provided at intervals, comprising: first and second detection means for detecting marks; and when the first detection means detects marks. a first pulse signal generating means for generating a first pulse signal having a pulse width corresponding to the size of the mark; and a first pulse signal generating means for generating a first pulse signal having a pulse width corresponding to the size of the mark; a second pulse signal generating means for generating a second pulse signal that is synchronized with the middle edge of the pulse of the first pulse signal and has a pulse width smaller than the pulse width of the first pulse signal; A defective mark detection device for a pulse encoder, comprising defective mark detection means for detecting a defective mark by comparing a first pulse signal generated by the means with the second pulse signal.