JPS6052712A - Position detecting circuit - Google Patents

Abstract

PURPOSE:To obtain a position detection result as a digital signal directly by comparing repeat periods of the first and the second pulse signals with each other to obtain data according to a ratio of the inductance of a detecting coil to that of a reference coil. CONSTITUTION:A detecting coil 3 whose inductance value La is changed in accordance with the position of an object 2 to be detected and a reference coil 4 which is set to a certain inductance value Lo are provided, and the first output voltage V1 and the second output voltage V2 are inputted to a signal switching circuit 10 in response to a pulse signal P outputted from a pulse generator 5 and are outputted alternately in accordance with the level of a switching control pulse signal CS. A voltage Vout is impressed to one input terminal of a voltage comparator 14 and is taken out as an output pulse signal Pout from a pulse generating circuit 15, and an output pulse C1 from the first counter 19 and the switching control pulse signal CS are inputted to a logic circuit 21. A synthetic output pulse signal Po is inputted to a processor 22, and digital data indicating the operation result is outputted as position data indicating the operation result is outputted as position data Dp.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a position detection circuit, and more particularly, to a position detection circuit capable of extracting a digital signal according to the position of a detected object.

In general, conventional position detection circuits used to output electrical signals according to the position of a detected object are disclosed in, for example, Japanese Patent Laid-Open No. 58-48402 or Japanese Patent Laid-Open No. 58-80304.
As disclosed in the above publication, a sine wave signal from a sine wave oscillator is applied to a circuit consisting of a detection coil whose inductance changes depending on the position of the object to be detected and a reference coil connected in series to the detection coil. is applied, a sine wave signal of a level corresponding to the position of the detected object generated at both ends of the detection coil is converted into a DC voltage signal, and the DC voltage signal is output as a position detection voltage. .

However, in a control system using a microprocessor that has been widely used in recent years, when trying to use this type of position detection circuit, it is necessary to use an A/ This necessitates the provision of a D converter, which poses a problem in that the configuration of the position detection circuit becomes complex, bulky, and expensive.

Furthermore, conventional position detection circuits also have the disadvantage of low detection accuracy because the level of the output DC voltage tends to change due to changes in temperature and the like.

Therefore, an object of the present invention is to provide a position detection circuit which can directly obtain a position detection result as a digital signal, has high detection accuracy, and has a simple configuration.

The configuration of the present invention includes a pulse generator that outputs a pulse signal with a repetition period according to a synchronous input signal, a detection coil whose inductance changes depending on the position of the detected object, and a pulse generator connected in series with the detection coil. means comprising a resistor for outputting a first pulse response output signal in response to the pulse signal according to the current inductance value of the detection coil; a reference coil of predetermined constant inductance; and a reference coil in series with the reference coil. means for outputting a second pulse response output signal corresponding to an inductance value of the reference coil in response to the pulse signal, the first pulse response output signal and the second pulse; a first pulse signal having a repetition period corresponding to the inductance value of the detection coil in response to the output signal from the switch means, and a first pulse signal having a repetition period corresponding to the inductance value of the reference coil; pulse signal generating means for generating a second pulse signal having a repetition period in alternation W; means for applying an output pulse signal from the pulse signal generating means to the pulse generator as a synchronization input signal; a calculation means for calculating a ratio between the inductance value of the detection coil and the inductance value of the reference coil in response to the signal and the second pulse signal, and the digital output from the calculation means is applied to the detected object. The feature is that it is configured so that it can be used as location data.

The I and second pulse signals can be obtained by inputting the first and second pulse response output signals to a voltage comparator that compares them to a reference voltage at a predetermined level. That is, since the rise and fall characteristics of the first and second pulse response output signals change depending on the inductance value of each coil, the reference voltage at a predetermined level and the level of the first and second pulse response output signals change. By comparing these, pulse signals having a repetition period corresponding to each inductance can be obtained as the first and second pulse signals.

By comparing the repetition periods of these first and second pulse signals, it is possible to obtain data according to the ratio of the inductance of the detection coil to the inductance of the reference coil.

According to the configuration described above, in addition to being able to obtain a position signal directly as a digital signal, the data indicating the position is based on the ratio of the inductance value of the detection coil to a predetermined inductance value of the reference coil. The amount of change in each inductance due to the change is canceled, and more accurate position detection data can be obtained.

Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

FIG. 1 shows an embodiment of a position detection circuit according to the present invention. The position detection circuit 1 is a circuit for obtaining an electric signal indicating the position of the detected object 2 in the form of a digital signal, and includes a detection coil 3 whose inductance value La changes depending on the position of the detected object 2; The reference coil 4 is set to a predetermined constant inductance value Lo regardless of the position of the detected object 2.

One end of the detection coil 3 is connected to the output line 5a of the pulse generator 5, and the other end of the detection coil 3 is grounded via a resistor 6. A generating circuit 7 is configured. A pulse signal P (see FIG. 2(a)) output from the pulse generator 5 as described below
), the detection coil 3 is connected to both ends of the resistor 6.
A first output voltage vi whose rise characteristic changes depending on the inductance value of is generated. The first output voltage vi is a pulse-responsive voltage signal whose level repeatedly increases by 2 in response to the rising edge of the pulse signal P and decreases in response to the falling edge of the pulse signal P, and Output voltage v
The rise and fall characteristics of 1 depend on a time constant based on the inductance value La of the detection coil 3 and the resistance value of the resistor 6. Here, since the resistance value of the resistor 6 is constant, the L rising and falling characteristics of the first output voltage 1 change according to the inductance value of the detection coil 3, that is, according to the position of the detected object 2. It turns out.

On the other hand, the reference coil 4 is connected in series with the resistor 8 and the second
It constitutes a response voltage generation circuit 9, and similarly to the first response voltage generation circuit 7, outputs a second output voltage V2 having a rising characteristic according to the inductance value LO of the reference coil 4 in response to the pulse signal P. do.

The first output voltage Vl and the second output voltage v2 are input to the signal switching circuit 10, and the first output voltage vl and the second output voltage v2 are outputted alternately according to the level of the switching control pulse signal C3. The signal switching circuit IO includes an analog switch element 1 provided corresponding to the first response voltage generation circuit 7.
1, and an analog switch element 12 provided corresponding to the second response voltage generation circuit 9. Figure 2 (
The switching control pulse signal C8 shown in d) is applied directly to the analog switch element 12, and is applied to the other analog switch element 11 with its level inverted by the inverter 13. These analog switch elements 11.1
2 is configured to be closed when the applied voltage level becomes "L" level, and opened when the applied voltage level becomes "H" level. Therefore, when the switching control pulse signal C8 is at the rl (J level), only the analog switch element 12 is opened and the second output voltage V2 is output, and when the switching control pulse signal CS is at the "Lj level, the analog Only the switch element 11 is opened and the first
Output voltage vl will be output. As a result, the second
When the switching control pulse signal C5 whose level changes to copulation as shown in Figure (d) is applied to the signal switching circuit lO, the first output voltage Vl and the second output voltage V2 are outputted alternately. becomes.

Therefore, from the signal switching circuit 10, as shown in FIG. 2(b), signal blocks Ml, M
2. . . . and the second output voltage V2.
l, N2. -... and output voltage Vou are output alternately
t is obtained.

The first output voltage V1 or the second output voltage V1 included in the output voltage V out output from the signal switching circuit 10 as described above.
For the purpose of respectively outputting a first pulse signal with a repetition period according to the inductance value of the detection coil 3 and a second pulse signal with a repetition period according to the inductance value of the reference coil in response to the output voltage ■2, respectively, A pulse generating circuit 15 consisting of a voltage comparator 14 is provided.

The output voltage Vout from the signal switching circuit 1O is applied to the single input terminal of the voltage comparator 14, and the constant voltage VO obtained by dividing the DC power supply voltage +V by the resistor 16.17 is applied to the input terminal of the voltage comparator 14. is being applied. Note that the reference numeral 18 indicates a feedback resistor. The output voltage V out from the signal switching circuit IO is compared with a constant voltage Vo, and V
If out≧Vo, the output line 1 of the voltage comparator 14
If Vout<Vo, the level of the output line 14a becomes high and becomes a low level. The output pulses from the voltage comparator 14 are input to the pulse generator 5 as a synchronizing signal, and the pulse generator 5 outputs a pulse train signal synchronized with the output pulses from the voltage comparator 14 as the pulse signal P.

Therefore, the output pulse signal Pout from the voltage comparator 14
Both the pulse signal P and the pulse signal P have the waveform shown in FIG. 2(a).

A first counter 19 and a second counter 20 are provided on the output side of the pulse generation circuit 15 in order to generate the switching control pulse signal C5 based on the output pulse signal P out. PftJl counter 19 is a binary counter,
Every time two pulses are input, the level of the output pulse C1 is inverted (see FIG. 2(e)). The output pulse C1 is input to the second counter 20, and the output pulse C1
It outputs a switching control pulse signal CS whose output level is inverted every time 3 pulses are applied. Therefore, switching control,
The pulse signal C3 becomes a pulse signal whose level is inverted every six pulses of the output pulse signal P out (FIG. 2(d)).

Next, with reference to FIG. 2, it will be explained how the waveform shown in FIG. 2(a) is obtained as the output pulse signal P out.

First, the level of the switching control pulse signal C5 is at time 1=11.
When it changes from “L” to r) (J, the signal switching circuit 10
A second output voltage v2 is outputted from the pulse generation circuit 15, and a second pulse signal based on the second output voltage V2 is outputted from the pulse generation circuit 15 as an output pulse signal Pout. This second pulse signal is inputted to the pulse generator 5 as a synchronization signal, and thereby the inductance value LO of the reference coil 4
A second pulse signal with a repetition period corresponding to the second pulse signal is obtained. Second
The pulse signal is input to the first counter, the number of pulses thereof is counted, and the output C1 is further input to the second counter 20. At time t=t2 when six pulses constituting the second pulse signal have been output, the level of the switching control pulse signal C3 becomes "L" level. Therefore, the period ti<
At t<t 2 , the second pulse signal is output as the output pulse signal Pout.

When the switching control pulse signal C8 reaches the rLJ level, the signal switching circuit IO outputs the first output voltage Vl, and the pulse generating circuit 15 outputs a first pulse signal in accordance with the first output voltage Vl. This first pulse signal has a repetition period according to the inductance value Lo of the detection coil 3, and this first pulse signal also has a repetition period that corresponds to the inductance value Lo of the detection coil 3.
After time t2, which is input as a synchronization signal, at time t3 when six pulses constituting the first pulse signal are output, the level of the switching control pulse signal C8 becomes rHJ level again, and the second pulse voltage again becomes rHJ level. Output.

As can be seen from the above description, from the pulse generation circuit 15, a second pulse voltage of 6 pulses whose period changes according to the inductance of the reference coil 4 and a first pulse of 6 pulses whose period changes according to the inductance of the detection coil 3 are generated. The voltages are alternately output, and a pulse train signal that alternately includes the first pulse voltage and the second pulse voltage is extracted as the output pulse signal Pout.

The output pulse signal Pout, the output pulse C1 from the first counter 19, and the switching control pulse signal C5 are supplied to the logic circuit 21.
, and based on these signals, first pulses Xi, X2, . Channel identification information is added to each fist. FIG. 2(C) shows the composite output pulse signal Po to which this channel identification information is added. As can be seen from FIG. 2(C), the channel information is given by adding an "H" or rLJ level signal of a predetermined length TO to the beginning of each pulse group constituting the output pulse signal Pout. , in the illustrated example,
By adding an rHJ level signal to the first pulse group consisting of the first pulse signal, the switching control pulse signal C5
It is shown that the pulse group has an rLJ level period of
It is shown that this is a pulse group of 5 "H" level periods.

Further, in each pulse group, the time slot in which the channel information is inserted is a pulse signal portion whose period is not stable immediately after the signal switching circuit 10 is switched, and therefore the channel information is inserted as described above. By inserting , only pulses that correctly indicate the inductance information of each coil are included in each pulse group.

The combined output pulse signal PO shown in FIG. The ratio T a /T b of the included four periods of the second pulse signal to the time length Tb is calculated, and digital data representing the calculation result is output as position data Dp.

The reference coil 4 has a semi-fixed inductance, so the value of Tb is constant regardless of changes in the position of the detected object 2, but the value of Tb is not affected by changes in temperature or changes in the peak value of the pulse signal P. It is something you receive. The effects of temperature changes and changes in the peak values of the output voltages Vl, v2 also affect the length of time Ta, so position data is created based on the calculation results of Ta/Tb. Then, temperature change and output voltage V1. Since errors in position detection data caused by V2 level changes can be removed,
Extremely accurate position detection becomes possible.

Further, according to such a configuration, adjustment of the 1-position detection circuit itself can be easily realized by using the resistor 6.8 as a variable element, and therefore, this position detection circuit can be used as a fuel injection pump for an internal combustion engine. When used for detecting the position of a fuel adjustment member, by incorporating this circuit in whole or in part in the pump, it becomes possible to trim the injection amount by adjusting the resistor 6.8.

According to the above configuration, the position signal indicating the position of the detected object can be directly output as digital data, so the position detection circuit according to the present invention can be used for detecting the position of the fuel adjustment member of an electronically controlled fuel injection pump. If the position data Dp is used as a feedback signal,
It is very convenient because it can be entered into a computer.

According to the present invention, as described above, position data can be directly output as a digital signal without using a complicated configuration, so when used in a control system using a microprocessor, an A/D converter can be used. This eliminates the need for a circuit, which allows the circuit to be configured at a low cost, and since stray capacitance in the wiring between the oscillator and the detection coil does not become a problem, there is no inconvenience in a configuration in which the detection coil and other circuits are placed apart. will not occur. Further, a reference coil is provided outside the detection coil, and the ratio of the two output data obtained by the 1III+ coil is taken to obtain the final position data, so that temperature correction is possible.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of a position detection circuit according to the present invention, and FIGS. 2(a) to 2(e) are waveform diagrams of signals at various parts of the circuit shown in FIG. 1. 1...Position detection circuit, 2...3 objects to be detected...Detection coil, 4Φ...Reference coil, 5...Pulse generator, 7...First response voltage generation circuit. 9... Second response voltage generation circuit, lO... φ signal switching circuit, 10... Signal switching circuit, 14... Voltage comparator, 15φ... Pulse generation circuit. Dp: position data, P: e pulse signal, Pouts: output pulse voltage, Pa: composite output pulse signal, vl: first output voltage, v2: second output voltage. Vout-φ・Output voltage. Patent applicant: Diesel Equipment Co., Ltd.

Claims (1)

[Claims] 1. It includes a pulse generator that outputs a pulse signal with a repetition period according to a synchronization input signal, a detection coil whose inductance changes depending on the position of the detected object, and a resistor connected in series with the detection coil. means for outputting a first pulse response output signal corresponding to the current inductance value of the detection coil in response to the pulse signal; a reference coil having a predetermined constant inductance; and a series resistor connected in series with the reference coil. a second coil according to the inductance value of the reference coil in response to the pulse signal;
means for outputting a pulse response output signal; switch means for alternately taking out the first pulse response output signal and the second pulse response output signal; A first pulse signal with a repetition period according to the inductance value of the reference coil and a second pulse signal δ with a repetition period according to the inductance value of the reference coil.
means for applying an output pulse signal from the pulse signal generating means to the pulse generator as a synchronization input signal; and means for applying the first pulse signal and the second pulse signal to the pulse generator. and calculation means for calculating a ratio between the inductance value of the detection coil and the inductance value of the reference coil in response to the above, and the digital output from the calculation means can be used as position data of the detected object. A position detection circuit characterized in that it is configured as follows.