JPH07318602A - Measuring device of coil - Google Patents

Abstract

PURPOSE:To prevent misjudgment by providing a switch for applying a voltage to a coil to be measured, a counting means that counts a time period from the time when a voltage is applied to when a counter electromotive force is lowered to a prescribed value, a memory means and a comparing means. CONSTITUTION:A NAND gate 7 is controlled such that the passing or blocking of a clock CLK inputted to a clock terminal 8 is determined by inverting it in accordance with an output of an operational amplifier 4. A counter 9 counts the inverted clock CLK. A counting means consists of the amplifier 4, NAND gate 7, counter 9 and the like. A latch circuit 10 stores the counted value of the counter 9. A value comparator 11 compares a present counted value of the counter 9 with the counted value stored in the latch circuit 10. Thereby, it is possible to discriminate the increase or decrease of an inductance of a coil 1 to be measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coil measuring device for measuring a change in coil inductance.

[0002]

2. Description of the Related Art A conventional coil inductance measuring method is a method of measuring the absolute value of the inductance value by using an AC power source or a bridge circuit. Therefore, when this is applied to a device that detects the on / off driving state of a solenoid used for a solenoid valve, a plunger, etc., from the change in the position of the iron core in the solenoid, the inductance of each solenoid must be absolute. It was necessary to measure the value, and it was necessary to set a comparison reference value for the inductance. When there are a large number of solenoids, it is necessary to measure each solenoid for each state, and when the types of solenoids are different, it is necessary to individually set an inductance comparison reference value for each solenoid.

[0003]

However, in such an inductance measuring method, it is necessary to provide the measuring device with a wide range capable of measuring the absolute value of all the inductances, and the inductance comparison standard for each coil. Since it is necessary to set the value, there is a problem that the circuit becomes complicated and the circuit scale becomes large, and when the semiconductor integrated circuit is used, the chip size becomes large and the cost becomes high.

The present invention has been made in view of the above points, and an object thereof is to make it possible to detect how the value of the inductance changes relatively, and to reduce the cost with a simple circuit. It is to provide a coil measuring device that can be realized.

[0005]

According to a first aspect of the present invention, a switch for applying a voltage to a coil to be measured, and a voltage of a counter electromotive force generated in the coil to be measured by the applied voltage is a voltage application timing. To a predetermined value, a counting unit that counts the time until it decreases to a predetermined value, a storage unit that stores the count value of the counting unit, a count value previously stored in the storage unit, and a current count value by the counting unit. A comparison means for comparison is provided.

A second invention is a switch for applying a voltage to a coil to be measured and a counter electromotive force voltage generated in the coil to be measured by the applied voltage until the voltage application timing is lowered to a predetermined value. Counting means, a storage means, a comparing means for comparing a value stored in the storing means with a current count value of the counting means, and a comparison result of the comparing means is the counting means. When the count value of is larger than the value of the storage means, a specific value is subtracted from the count value of the counting means and updated and stored in the storage means, and when it is smaller, the specific value is added from the count value of the counting means and stored. And means for adding and subtracting for updating and storing the means.

[0007]

In the first aspect of the present invention, the increase or decrease of the inductance of the coil to be measured can be detected by the comparison result of the comparison means. As a result, a change in the position of the shaft in the solenoid can be detected, and the open / closed state of the solenoid valve, the driving state of the plunger, etc. can be detected. Since this measurement only identifies the magnitude relation of the inductance, it is not necessary to set the inductance comparison reference value, the circuit configuration is simple, and it can be used as it is for the measurement of many types of measured coils.

In the second invention, in addition to the operation of the first invention, the comparison of the detection of the next count value is carried out by modifying the obtained count value so as to make a difference from the count value obtained next. Since it becomes the reference value, it is possible to avoid the influence of counting error due to noise or the like.

[0009]

EXAMPLES Examples of the present invention will be described below. FIG. 1 is a block diagram of a coil measuring device according to the first embodiment.
Reference numeral 1 denotes a coil to be measured, which is connected in series with the power supply voltage Vcc together with the resistor 2 and the switch 3. Reference numeral 4 is an operational amplifier as a voltage comparator for inputting the voltage applied to the coil to be measured 1 to the non-inverting input terminal (+), and the inverting input terminal (-) thereof is connected to the power supply voltage Vcc by resistors 5 and 6.
The reference voltage Vref obtained by dividing is applied.

Reference numeral 7 is a NAND gate, which is a clock CLK input to the clock terminal 8 by the output of the operational amplifier 4.
Is controlled so as to be inverted and passed or not passed. 9 is a clock CL obtained by inverting this clock CLK.
This is a counter that counts K '. The operational amplifier 4, the NAND gate 7, the counter 9, and the like described above constitute a counting means. Reference numeral 10 is a latch (storage means) for storing the count value of the counter 9, and 11 is a numerical comparator (comparing means) for comparing the current count value of the counter 9 and the count value stored in the latch 10.

When measuring the change in the inductance of the coil to be measured 1, the switch 3 is first turned on. As a result, a counter electromotive force is generated in the measured coil 1. The voltage of this counter electromotive force is, as shown in A of FIG.
The voltage reaches its maximum value at time T1 when the switch is turned on, and the voltage gradually decreases thereafter. That is, this voltage V (t) is V (t) = (Vcc / R) exp [-(, where L is the inductance of the coil to be measured 1 and R is the resistance value of the resistor 2 connected in series thereto). R / L) t]. The resistance value of the measured coil 1 was ignored.

Therefore, in the operational amplifier 4, this voltage V
The output is held at the high potential level only while (t) is V (t)> Vref. This held period is time T1 to T2. Since the NAND gate 7 opens the gate during this holding time, the clock CL
The clock CLK 'which is the inverted K is input to the counter 9 and counted only during this period. And the operational amplifier 4
After the output of is reduced to the low potential level, the count value of the counter 9 is held and stored in the latch 10. The counter 9 is cleared and the switch 3 is reset (turned off) after a lapse of a predetermined time from the time when the output of the operational amplifier 4 drops to the low voltage level.

Next, after it seems that the inductance of the coil to be measured 1 has changed, that is, for example, this coil to be measured 1 is a solenoid, and the solenoid is driven from a driving state to a non-driving state or from a non-driving state. After changing to the state, the switch 3 is turned on again.

At this time, if the inductance of the coil to be measured 1 is increased, as shown in FIG. 2B, the voltage at the non-inverting input terminal (+) of the operational amplifier 4 is reduced to the reference voltage Vref. If the time becomes longer, and conversely the inductance decreases, the time becomes shorter as shown in C of FIG. This time is detected by the counter 9.

Therefore, by comparing the count value stored in the latch 10 with the current count value of the counter 9 by the numerical comparator 11, if the count value of the counter 9 is larger, the measured coil 1 It can be identified that the inductance of the coil has increased, and that it has decreased if it is small.

When the coil to be measured 1 is a solenoid,
The inductance increases as the iron core insertion amount increases, and decreases as the iron core insertion amount decreases.Therefore, it is possible to determine the driving state of the solenoid by increasing or decreasing the inductance.
For example, an electromagnetic valve can detect the open / closed state of the valve, and a plunger can detect its axial position. Since the increase / decrease of the inductance is detected in this way, it is not necessary to set the inductance comparison reference value as in the case of detecting the absolute value of the inductance.

Further, even when the coil to be measured 1 is changed, other circuit portions can be used as they are without adjustment, and the measurement circuit can be constructed, which is extremely general compared to the conventional absolute value measurement. It is highly likely.

In the first embodiment, if the relationship between the count value obtained by the counter 9 and the inductance value is stored in a table, the absolute value of the inductance can be measured. For example, replacing the latch 10 with a normal memory,
If a lookup table having the count output of the counter 9 as an address value is stored in this memory, the inductance value can be known directly from the output of that memory.

FIG. 3 is a block diagram showing a second embodiment of the present invention. The contents up to the preceding stage of the counter 9 are the same as those shown in FIG. Reference numeral 12 is an addition / subtraction circuit for adding or subtracting a predetermined value to the count value of the counter 9, 13 is a latch for storing the contents of the addition / subtraction circuit 12, 14 is a numerical comparison for comparing the contents of the latch 12 with the count contents of the counter 10. It is a vessel.

In the second embodiment, the switch 3 is turned on and the voltage of the counter electromotive force of the measured coil 1 at that time is the voltage V.
The counter 9 measures the time until it decreases to ref, and the count value obtained at that time is compared with the value in the latch 13 stored when the switch 3 was turned on last time by the numerical comparator 14. From this, it can be seen that when the count value of the counter 9 is small, the inductance changes to a smaller one, and when it is larger, it changes to a larger one.

When the inductance changes to a smaller value, a specific value (for example, a value of several% to several tens% of the change width of the count value) is added from the count value of the counter 9 in the adder / subtractor circuit 12, The value obtained by this addition is updated and stored in the latch 13. When the inductance changes to a larger value, the addition / subtraction circuit 12 subtracts a specific value from the count value of the counter 9, and the value obtained by this subtraction is updated and stored in the latch 13.

As described above, by adding or subtracting the specific value to or from the count value, the count value is corrected so as to be different from the count value corresponding to the next change of the coil to be measured 1, and the latch 13 is used as the comparison reference value. Since it is updated and stored in, it is possible to absorb this even if there is a count error.

That is, the first count value is, for example, 1
000, the second count value is 2000, and the third count value is 1950, assuming that the first and second counts are normal, the inductance should not change during the third count and should be 2000. However, it has an error of -50 counts.

At this time, in the case of the first embodiment,
In the third time, it is erroneously determined that the inductance of the measured coil has decreased.

However, in the case of the second embodiment, 2
A specific value (for example, 100) is subtracted from the count value of the third time and stored as 1900, and this 1900 is compared with the count value 1950 of the third time, so it is not determined that the inductance has decreased. Since it has been determined that the inductance has increased by the second count value determination, it is determined that the inductance has increased in the third time by determining whether the inductance has not changed or has decreased. No judgment is made.
Therefore, unlike the above, the count value of the third time is 2100.
In the case of 1, the error is 100 counts, but even when compared with the reference value 1900 obtained the second time, it is not determined that the inductance has increased, but it is determined that there is no change.

In this way, when the inductance value increases, the specific value is subtracted and the comparison reference value is corrected to a low value, so that a count value lower than the original value can be obtained due to noise or the like at the next counting. However, the error determination can be prevented. This specific value may be set to a value that exceeds the count error. When the inductance value decreases, by adding a specific value and modifying the comparison reference value to a high value, it is possible to prevent error determination even if a higher count value than the original value is obtained due to noise etc. at the next counting. .

[0027]

According to the first aspect of the present invention, an increase or a decrease in the inductance of the coil to be measured is detected, that is, a magnitude relationship is discriminated to detect a position change of the iron core in the solenoid. It is not necessary to set the reference value, the circuit configuration is simple, it is possible to avoid an increase in the chip area when the semiconductor integrated circuit is formed, and it can be used as it is for the measurement of many kinds of measured coils.

According to the second aspect of the invention, the value to be compared is corrected so as to have a difference from the count value obtained in the next measurement, so that the influence of a count error due to noise or the like can be avoided.

[Brief description of drawings]

FIG. 1 is a block diagram of a coil measuring device according to a first embodiment of the present invention.

FIG. 2 is a voltage characteristic diagram of a back electromotive force generated in a coil.

FIG. 3 is a block diagram of a coil measuring device according to a second embodiment of the present invention.

[Explanation of symbols]

1: coil to be measured, 2: resistor, 3: switch, 4: operational amplifier (voltage comparator), 5: resistor, 6: resistor, 7: NAND gate, 8: clock input terminal, 9: counter, 1
0: latch, 11: numerical comparator, 12: adder / subtractor circuit, 1
3: Latch, 14: Numerical comparator.

Claims (2)

[Claims] 1. A switch for applying a voltage to a coil to be measured, and a time period until a voltage of a counter electromotive force generated in the coil to be measured by the applied voltage decreases from the voltage application timing to a predetermined value. A counting means for counting; a storage means for storing the count value of the counting means; and a comparing means for comparing the count value previously stored in the storage means with the current count value by the counting means. Characteristic coil measuring device. 2. A switch for applying a voltage to the coil to be measured, and a time period until the voltage of the counter electromotive force generated in the coil to be measured by the applied voltage decreases from the voltage application timing to a predetermined value. Counting means for counting, storage means, comparing means for comparing the value stored in the storage means with the current count value of the counting means, and the comparison result of the comparing means is the count value of the counting means. Is larger than the value of the storage means, a specific value is subtracted from the count value of the counting means and updated and stored in the storage means, and when smaller, a specific value is added from the count value of the counting means and updated to the storage means. A coil measuring device, comprising: an adder / subtractor for storing.