JPS59133405A - Position detector - Google Patents

Abstract

PURPOSE:To stabilize a position detection output by detecting the level of a frequency signal of specified intermittent frequency supplied to a resonance circuit through an averaging circuit, and providing a temperature compensating circuit. CONSTITUTION:A coil 21 varies in inductance as a core 17 moves, and the resonance frequency of the resonance circuit is varied and set. When the inductance of the coil 21 is maximum, the resonance frequency of the resonance circuit 23 is made coincident with a frequency signal from an oscillation circuit 25. A stabilized voltage Vcc is supplied through a resistance 27 at a point A as an output terminal and the point is grounded through the averaging circuit 30 consisting of a resistance 28 and a capacitor 29. An averaged voltage signal is supplied to the analog/digital (A/D) converting circuit 31 of processing and operation part 24 to obtain a digital measurement detection signal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a position detection device that is effectively used as a detection signal output means of a sensor mechanism such as a pressure sensor used in a control system of an automobile engine.

For example, in the control system of an automobile engine, various sensor mechanisms such as pressure sensors are used. A sensor mechanism such as a pressure sensor has an actuator mechanism that is driven according to the detected amount, and by electrically detecting the position of such an actuator, the detected amount is converted into an electrical detection signal. I'm trying to convert it. Specifically, a coil wound in an annular manner is fixedly set, and a columnar core is provided in the central hollow part of this coil to be moved in the axial direction by the actuator, and the position of the coil is determined by the position of this core. It is configured to detect inductance electrically and electrically.

As a means for detecting changes in the inductance of this coil, a capacitor is connected in parallel to this coil to form an LC resonant circuit, and an alternating current signal of a specified frequency is supplied to this resonant circuit. , an impedance change corresponding to a difference between the frequency of the alternating current signal and the resonant frequency of the resonant circuit is detected as a voltage change.

In such a means, as a means for detecting a change in impedance of a resonant circuit, the AC signal of the specified frequency is averaged and extracted, and a rectifier circuit using a diode is used for this purpose. However, the diode has a temperature characteristic in which the forward impedance changes in response to temperature changes, and errors occur in detected values as the temperature changes.

For sensor mechanisms, such as pressure sensors, in addition to the fundamental condition of obtaining highly accurate detection signals over a wide pressure range, especially when used for automobile engine control, etc., it is necessary to It is also required that highly accurate detection output can be obtained.

This invention was made in view of the above points, and it is possible to obtain a sufficiently stable position detection output even when there are temperature changes, and to enable effective use in, for example, automobile engine control systems. The present invention aims to provide a detection device.

Furthermore, in the present invention, even if a change occurs in the pressure detection mechanism in response to a temperature change, the error in the detected value due to this change can be reliably compensated for. The purpose is to obtain.

That is, the position detection device according to the present invention detects the positional fluctuation in the detector section as an inductance change, forms a parallel resonant circuit by this inductance and a capacitor, and transmits a specified intermittent frequency to this resonant circuit. In addition, a temperature compensation circuit is provided which is set to a temperature characteristic corresponding to the output fluctuation due to temperature change of the detector including the variable inductance mechanism, and the output from the averaging circuit is adjusted based on the correction signal from this temperature compensation circuit. This is to correct the signal.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment applied to a pressure sensor, in which a container 12 is divided by a diaphragm 13 into an atmospheric pressure chamber 14 and a negative pressure chamber 15. communicates with a negative pressure source (not shown) so that the diaphragm 13 is driven in response to the negative pressure.

A columnar core 1 made of high magnetic permeability, such as ferrite, is attached to the diaphragm 13 via a support member 16.
7 is attached so that the core 11 is moved in response to the movement of the diaphragm 13 due to negative pressure fluctuations.

In this case, the diaphragm 13 is balanced and supported from both sides by springs 18m and 18b, and the negative pressure detection reference is adjusted and set by the adjustment screw 19.

A coil 21 made of non-magnetic material such as synthetic resin is wound around the outer periphery of the pin 20 around the outer periphery of the core 17.

That is, the core 11 changes as the diaphragm 13 changes in response to the negative pressure value in the negative pressure chamber 15. The position of the coil 21 changes in the axial direction within the pin 20, and the inductance of the coil 21 is set to vary in accordance with the position of the core 17 within the pin 20. For example, as shown in FIG. 2, the amount of movement of the core 17 is set in accordance with the pressure difference between the atmospheric pressure chamber 14 and the negative pressure chamber 15, and the inductance of the coil 21 is set in accordance with the movement of the core 17. It begins to change as shown in FIG.

The coil 21 supplies a frequency signal of a specified frequency from an oscillation circuit 25 connected in parallel with a capacitor 22 via a capacitor 26 . The oscillation circuit 25 generates a frequency signal in a state in which a voltage signal in the positive direction is intermittently generated, for example, by turning on a switch. It is assumed that the

Here, the inductance of the coil 21 changes as described above due to the movement of the core 17, and the resonant frequency of the resonant circuit 23 is variably set in accordance with the position of the core 17. The frequency of the frequency signal from the oscillation circuit 25 is specified to match the resonant frequency of the resonant circuit 23 when the inductance of the coil 21 is at its maximum.

Further, at point A, which is the output terminal of the frequency signal from the oscillation circuit 25, a stabilizing voltage VCC is supplied via a resistor 27, and this point A is connected to a resistor 28 and a capacitor 29.
Ground through.

This resistor 28 and capacitor 29 constitute an averaging circuit 30 which is an integrating circuit, and is designed to generate an averaged voltage signal of the amplitude level of the frequency signal at point A. 24 analog-to-digital conversion (A/D) circuits 3 to obtain a digital measurement detection signal.

That is, when the alternating current component of the intermittent frequency signal from the oscillation circuit 25 is applied to the resonant circuit 23 while the core 17 is at the position where the inductance of the coil 2 is maximized, the resonant circuit 23 will resonate. Since the frequencies match those of the frequency signals, the resonant circuit 23 is in a resonant state. When the core 17 moves from this state due to a change in negative pressure, the inductance of the coil 21 also changes, and the resonant circuit 23 comes out of the resonant state.

Theoretically, the impedance of the resonant circuit 23 is infinite in the resonant state, but when the resonant circuit 23 is out of the resonant state, the impedance of the resonant circuit 23 has a finite value. When the resonance circuit 23 is completely removed from resonance, the impedance of the resonant circuit 23 becomes close to zero.

Here, assuming that the capacitance of the capacitor 26 is larger than that of the capacitor 22, the equivalent circuit shown in FIG. 4 is established. In this Fig. 4, impedance 23
0 is the impedance seen from point A of the circuit constituted by the capacitors 22 and 26, and the impedance value changes in response to the movement of the core 17. That is, this impedance 230 corresponds to a change in the position of the core 1yo,
It changes from approximately zero to infinity.

Therefore, the level of the output frequency signal from the oscillation circuit 25 at point A changes as shown by A in FIG.

Since this frequency signal is a positive vibration waveform, the resistor 28
The detection output signal from the averaging circuit 3o composed of the capacitor 29 and the capacitor 29 becomes a DC voltage signal as shown by B in FIG.

Therefore, since such position detection devices do not use circuit elements whose impedance changes in response to temperature changes, such as diodes, detection circuits that are not affected by temperature changes are not available. As configured, a detection signal without temperature characteristics can be obtained.

However, if this pressure sensor 11 is set in a place where there is a large temperature change, there is a possibility that the output of the averaging circuit 30 will have temperature characteristics. The cause is core 17
This is due to the difference in coefficient of thermal expansion due to the difference in the materials of the support member 16 and the pin 20, and the relative positional relationship between the coil 21 and the core 17 changes due to temperature changes. The characteristics of the DC output voltage of the averaging circuit 30 at this time are as shown in (4) of FIG. Here, if the room temperature is To, the output voltage of the averaging circuit 30 with respect to the movement of the core 17 changes in the form of a circuit line with respect to temperature. Moreover, the voltage levels also change approximately in parallel as shown in the figure.

In order to compensate for such temperature characteristics, a temperature compensation circuit 32 is further provided. This circuit 32 has a stabilizing voltage vcc
is supplied to the 0 point via a resistor 33, and this 0 point is grounded via a resistor 34 and a forward diode 35, and the potential at the 0 point is used as a temperature correction signal to the processing calculation unit 24.
It is supplied to the A/D conversion circuit 36 of.

The forward voltage V of the diode 35 of this temperature compensation circuit 32
D can be approximated by VD=-AT+B with respect to temperature. Here, T, A, and B are temperature and forward voltage, respectively. is the temperature change rate and offset voltage.

Now, assuming that the output voltage at point 0 is the resistance value of each of the va1 resistors 33 and 34 as R1*J, then ■A is expressed by the following equation.

'a = (Vc c-■0) ” R, + R, +
The rate of change of the Vn output voltage va with respect to temperature is the rate of change A of the forward voltage VD of the diode 35, r Rs/(Rz
+Rt) is multiplied by J. Therefore, the rate of change of the output voltage V of the temperature compensation circuit 32 with respect to temperature can be arbitrarily selected by selecting the resistance values of the resistors 33 and 34.

For example, when the compensation output voltage (8) rises by T from the room temperature To, the output voltage of the averaging circuit 30 changes by dV at each voltage level, as shown in FIG. 6(B). Assume. In such a case, the resistance values of the resistors 33 and 34 are selected so that the output voltage of the temperature compensation circuit 32 changes by dV when the temperature rises by T1 from the room temperature To, as shown in FIG.

Output voltage of the averaging circuit 30 and temperature compensation circuit 3
The output voltage from 2 is the A/D of the processing calculation unit 24, respectively.
They are each converted into digital values by converters 31 and 36. These digital values at room temperature To are D B
+DC. Then, let the respective digital values when the room temperature rises by 11 from the room temperature To be D□ and Dd@. In the processing calculation unit, data D at room temperature To is stored and set in advance.

Therefore, in the processing calculation section, the temperature compensation circuit 32
The difference between the output data of the A/D converter 36 corresponding to the output voltage from the A/D converter 36 and the above-mentioned stored data is calculated as a correction value, and the temperature compensation value is detected data.

FIG. 8 shows a flowchart of the above-mentioned correction operation. First, in step 101, digital data T, which corresponds to the output voltage of the temperature compensation circuit 32 when the reference room temperature TO°C. Memorize and set. Then, in step 102, the digital data P corresponding to the output of the averaging circuit 30 corresponding to the current pressure difference is
13- At the same time, in step 103, the current temperature is detected by the temperature compensation circuit 3.
The digital data TX corresponding to the correction output No. 2 is detected, and in step 104, the correction value Ddv at the current temperature is calculated by subtracting Tx from the above TTo''.

Then, in step 105, it is determined whether or not this correction value Ddv is greater than zero, and in accordance with the result of the determination, correction calculations are performed on the detected digital data P in steps 106 and 107 to obtain pressure data D. It is.

In the description of the above embodiment, the correction calculation by the temperature compensation circuit 32 is performed to compensate for the temperature characteristics based on the difference in the temperature expansion coefficient of the components of the detector, that is, the pressure sensor 11. Of course, it may also be used to compensate for the influence on the output due to the temperature characteristics of the circuit elements.

As described above, according to the present invention, an inductance change due to a position change can be effectively detected without having temperature characteristics, and can be converted into an electric signal and output, and in particular, the configuration is sufficiently simplified. can be put into a state where

In particular, complicated adjustment work such as assembly process and parts adjustment is not particularly required.

In addition, it is possible to effectively compensate for temperature characteristics caused by differences in thermal expansion coefficients of components of the detected amount due to large temperature changes. It can be used effectively even in harsh environments.

[Brief explanation of the drawing]

FIG. 1 is a block diagram illustrating an example applied to a pressure sensor mechanism according to an embodiment of the present invention, and FIGS. 2 and 3 respectively show the movement characteristics of the core of the pressure cassette/socket in the above embodiment, and FIG.
FIG. 4 is a diagram showing the circuits of the detection output section of the above device, FIG. 5 is a diagram explaining the state of the detection output signal, and FIG. 6 is a diagram showing the output fluctuation due to temperature change. FIG. 7 is a diagram explaining the compensation output for the above-mentioned output fluctuation, and FIG. 8 is a flowchart explaining the correction operation for temperature compensation. 11... Pressure sensor, 13... Diaphragm, 16
... holding member, 17 ... core, 2o ... is a bottle,
21... Coil, 22, 26.29... Capacitor, 23... Parallel resonant circuit, 24... Processing calculation unit, 2
5...Oscillation circuit, 30...Averaging circuit, 32...
Temperature compensation circuit, 35...diode.

Claims (2)

[Claims] (1) A detector that detects fluctuations in the object to be measured, a resonant circuit whose resonant frequency is set to change according to the detection position of this detector, and a frequency signal supplied as a resonant signal to this resonant circuit. and an averaging circuit that extracts the average value voltage of the frequency signal from the oscillation means as an output signal, and the frequency signal from the oscillation means is
A position detection device characterized in that the signal is intermittent at a resonant frequency of the resonant circuit corresponding to a specified detection position. (2) A detector that detects fluctuations in the object to be measured, a resonant circuit whose resonant frequency is set to change in accordance with the detection position of this detector, and a detection position specified for this resonant circuit. an oscillating means for supplying a frequency signal whose resonant frequency changes intermittently; an averaging circuit for extracting the average value voltage of the signal from the oscillating means as an output signal; A position detection device comprising: a temperature correction circuit set to a temperature characteristic; and temperature correction means for correcting an output signal from the averaging circuit using a correction signal from the temperature correction circuit.