JPH0996678A - Obstacle detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an obstacle detector in which a detection distance of several cm or thereabouts can be sustained using a simple circuitry. SOLUTION: When the detector approaches an obstacle, parameters around the antenna of an oscillation circuit, i.e., a sensor S, are varied to cause variation in the input impedance of sensor S. Consequently, the resonance frequency is varied through an impedance Z1 forming the oscillation circuit together with two other impedances Z2, Z3. A decision circuit 2 detects lowering of oscillation level of the oscillation circuit and an oscillation control circuit 3 varies the impedance forming the oscillation circuit in response to the lowering of oscillation level. Oscillation frequency of the oscillation circuit is confined within a predetermined frequency range and an obstacle is detected base on whether a predetermined oscillation can be sustained or not.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an obstacle detection device for an automobile, and more particularly, it uses an antenna to detect an obstacle such as a person, an object, a building, or a metal that interferes with the movement of the automobile. The present invention relates to an obstacle detecting device.

[0002]

2. Description of the Related Art As conventional techniques for detecting obstacles in automobiles, there are JP-A-58-115384, JP-A-60-111983, and JP-A-3-233390.
The techniques described in Japanese Patent Publication No. 3689814 and US Pat.

The prior arts of this kind are all related to an obstacle detecting device for an automobile, and the detection principle is as shown in FIG.
Through FIG. 11.

FIG. 9 is a principle diagram of an automobile obstacle detection device disclosed in Japanese Patent Laid-Open No. 60-111983. FIG. 10 is a principle diagram of an obstacle detection device for an automobile disclosed in Japanese Patent Laid-Open No. 59-115384. FIG. 11 is a principle diagram of an obstacle detection device for an automobile disclosed in Japanese Patent Laid-Open No. 3-233390.

In FIG. 9, the output of the oscillator circuit OSC is connected to a series circuit composed of a resistor R1 and a capacitor C1. If a plate A having an area So is used as a sensor,
Depending on the presence or absence of the obstacle G and its distance Dw, the electrostatic capacitance (capacitor) C which is the stray capacitance between the electrode plate A and the obstacle G.
1 is formed. This electrostatic capacitance C1 becomes the capacitor C1 that constitutes the series circuit described above.
The terminal voltage of the capacitor C1 changes due to the change in the capacitance, and the obstacle G is detected by this voltage change. In addition,
Here, when it means stray capacitance or its capacitance, it is described as electrostatic capacity, and when it has a constant meaning as a circuit element,
Although described as a capacitor, both basically have the same meaning.

Generally, if the capacitance C1 formed is an area where the obstacle G is close to the electrode plate A of the sensor, the capacitance C1 is expressed by εo.εr.S / Dw. Here, εo is the permittivity in vacuum, and εr is the relative permittivity of the medium.

However, the relative permittivity εr of the medium changes due to environmental conditions such as weather, and the terminal voltage level of the capacitor C1 also changes.

Therefore, in the technique shown in FIG. 10, a series resistance composed of the capacitance C2 and the resistance R2 that changes under the same conditions with respect to the change of the capacitance C1 due to environmental conditions is prepared, and the series resistance of If the relative permittivity εr of the medium changes due to environmental conditions, the terminal voltage of the capacitor C2 also changes. Therefore, the output of the oscillator circuit OSC is connected to the resistor R1 and the capacitor C1.
Is connected to a bridge composed of a series circuit composed of a resistor R2 and a capacitor C2 having an intervening electrode such as air as a resistor R2, and an obstacle is detected by the potential difference between the two.

The technique shown in FIG. 11 is an example of detecting another obstacle.

In FIG. 11, a plurality of capacitors C2
, C3, C4 and the electrostatic capacitance C1 determined by the environmental conditions constitute an oscillator circuit OSC. Then, the oscillation frequency of the oscillation circuit OSC is frequency-voltage converted by the F / V conversion circuit F, and when the obstacle G approaches, the oscillation circuit OS
The oscillation condition of C changes, and as a result, the oscillation frequency changes. By detecting this change, the presence or absence of the obstacle G is detected.

Further, in the former case, the magnitude of the amount of change is detected to detect an obstacle, and if the vehicle is left with the distance Dw sufficiently small, the distance Dw is constant when the vehicle is moved again. , The capacitor C1 also does not change and the obstacle G cannot be detected. Therefore, the voltage level immediately after the automobile is left unattended is stored, and the magnitude of the change amount is determined from the level.

[0012]

In the circuits shown in FIGS. 9 and 10, when the distance Dw is "0", the capacitor C1 becomes infinite, and the terminal voltage of the capacitor C1 becomes a very small value (infinitesimal small). In the state where the obstacle G is close to the electrode plate A, the terminal voltage detects a very small level change.

In order to detect such a minute level change, it is generally necessary to use an amplifier having an amplification degree higher than a predetermined level. However, when the distance Dw between the electrode plate A of the sensor and the obstacle G is infinite, the capacitor C1 becomes infinitely small, the terminal voltage of the capacitor C1 becomes a very large value, and the output of the amplifier saturates. Degree to distance Dw
It is necessary to set a different value depending on the value of. That is, a variable amplifier is required.

Further, in the obstacle detection device for an automobile shown in FIGS. 9 to 11, since the distance Dw is targeted at the closest distance, generally, the detection of a minute level is performed and the signal processing of the minute level is performed, so that the band furnace is used. Since it becomes necessary to remove noise by the wave filter, the number of circuit components must be increased.

For example, in the above-mentioned conventional technique, the distance D
w cannot be set to more than 40 cm. In addition, the initial capacitance due to the size of the sensor increases the amount of coupling to the parallel resonant circuit and reduces the detection accuracy, that is,
It will reduce the resolution.

On the other hand, in the technique of US Pat. No. 3,698,814, a loop antenna made of metal as a sensor is connected to the other end of a coil whose one end is grounded. On the other hand, a metal foil is installed at the upper end of the frame of the window that is controlled to move up and down by the motor, and the capacitance formed between this metal foil and the loop antenna is detected. . With this type of technology, this capacitance can be detected only at a very short distance or contact. This is because the capacitance formed has an extremely small equivalent area compared to the electrode area for attachment. In addition, it is impossible to distinguish between environmental changes (temperature, humidity, etc.) and the approach of obstacles.

Generally, the oscillation condition of the oscillator circuit OSC must satisfy both the amplitude condition and the frequency condition at the same time. However, when the obstacle G approaches the electrode plate A, the frequency changes and the amplitude also changes. Further, when the two conditions cannot be satisfied, the oscillation is stopped.

In particular, the technique of FIG. 11 utilizes an F / V conversion circuit F that changes a change in frequency into a voltage level.
Generally, the F / V conversion circuit F obtains a voltage output corresponding to a change in frequency when the amplitude is constant, but when the amplitude and the frequency change at the same time, the distance Dw from the obstacle G is constant. However, since the obtained signal level after F / V conversion is accompanied by fractation, it is necessary to make a determination in consideration of this uncertainty. Furthermore, changes in frequency and amplitude due to the influence of environmental conditions such as temperature and humidity, and ambient conditions, that is,
It is also necessary to remove the fractionation due to these effects from the voltage output after the F / V conversion, and the zero point correction is always required. This kind of support is possible with the current technology, but if mass productivity and cost are taken into consideration, the commercial value becomes poor except for the field of measuring instruments and the like. In addition, the detection of the obstacle G immediately after the power is turned on is performed after the zero point correction, so that a delay time is involved.

As described above, the value of the capacitance (capacitor C1) formed by the electrodes constituting the sensor and the obstacle and its change are generally extremely small, and as a result, the detection distance is several cm. If this capacitance is used as a part of the oscillation constant of the oscillation circuit OSC, both the oscillation frequency and the amplitude fluctuate as the obstacle approaches, and the determination becomes complicated.

Therefore, an object of the present invention is to provide an obstacle detecting device capable of detecting an obstacle at a distance of about 40 cm and realizing it with a simple circuit.

[0021]

An obstacle detecting apparatus according to a first aspect of the present invention includes a sensor whose input impedance changes when approaching an obstacle, and an impedance which changes a resonance frequency due to a change in the input impedance of the sensor. An oscillation circuit formed together with the other two impedances, and a decrease in the oscillation level from the oscillation circuit is detected, and the impedance forming the oscillation circuit is changed in response to the decrease in the oscillation level. And an oscillation control circuit for setting the oscillation frequency of the device within a predetermined frequency range.

An obstacle detecting device according to a second aspect of the present invention is an impedance detecting device having an impedance Z2 and an impedance Z3 connected in series.
And the impedance Z1 connected to both terminals of the impedance Z2 and the impedance Z3 determines an oscillation condition, and the obstacle detection apparatus includes an oscillation circuit having a resonance circuit of the impedance Z1 and the impedance Z3 having the same polarity. The impedance Z3 of the circuit is the resonance frequency f3 and the Q factor of the circuit Q
3 and the impedance Z1 of the resonant circuit is
If the resonance frequency is f1 and the Q factor of the circuit is Q1, then f1> f3 and Q3> Q1
The impedance Z3 is an electromechanical oscillator, and the impedance Z1 is a coil and a capacitor.

An obstacle detecting device according to a third aspect of the present invention controls the difference between the resonance frequency f3 of the impedance Z3 and the resonance frequency f1 of the impedance Z1 so that the oscillation level of the oscillation circuit becomes constant. is there.

In the obstacle detecting device according to a fourth aspect of the present invention, the impedance Z1 of the oscillation circuit is added to the impedance of the capacitor formed by the sensor and the obstacle to convert the impedance into a change in the oscillation level without changing the oscillation frequency. To do.

In the obstacle detecting device according to the fifth aspect, the change of the electrostatic capacitance applied to the impedance Z1 is performed by the variable capacitance diode coupled to the coil of the parallel resonance circuit.

An obstacle detecting device according to a sixth aspect of the present invention holds a detected state of the obstacle when the sensor and the obstacle come close to each other by a predetermined amount or more.

In the obstacle detecting device according to a seventh aspect, when the sensor and the obstacle come close to each other by a predetermined amount or more, the oscillation of the oscillation circuit is stopped to maintain the detected state of the obstacle.

[0028]

Embodiments of the present invention will be described below.

FIG. 1 is an explanatory view of a basic principle of a known oscillator circuit for explaining an obstacle detecting device according to a first embodiment of the present invention, and FIG. 1A is an oscillator circuit diagram using an FET.
(B) is an oscillation circuit diagram using a transistor, and (c) is an equivalent circuit diagram.

Here, the principle will be described with the circuit using the FET shown in (a), but the basic operation is the same for the transistor.

The oscillation circuit shown in FIG. 1A has an impedance Z2 connected between the drain D and the gate G of a field effect transistor (hereinafter simply referred to as "FET"),
The oscillation condition is determined by the impedance Z3 connected between the source S and the gate G of the FET and the impedance Z1 connected between both terminals of the impedance Z2 and the impedance Z3, that is, between the drain D and the source S of the FET.

This equivalent circuit can be represented as an equivalent circuit using the mutual conductance gm and the drain resistance rd as a combination of the amplifier circuit A and the feedback circuit F, as shown in FIG. Here, in order to clarify the principle, the source grounded type is used, the gate resistance RG is assumed to be sufficiently large and omitted from the equivalent circuit, and the impedances Z1, Z2 and Z3 are pure imaginary numbers.

The oscillation condition at this time is calculated as follows.

-Rd.gm-1-Z2 / Z3 = rd (Z1 + Z2 + Z3) / (Z1.Z3) (1) The left side of the equation (1) is a real number and the right side is an imaginary number. It becomes a frequency condition.

Rd · gm · Z1 · Z3 + Z1 · Z3 + Z1 · Z2 ≦ 0 ··· (2) Z1 + Z2 + Z3 = 0 (3) Here, the equation (2) relates to the amplitude. Equation (3) is a condition corresponding to the change in frequency. From equations (2) and (3), it can be seen that the amplitude changes as the frequency changes. In general,
Impedance Z1 and Z3 are inductive, impedance Z
The case where 2 is made capacitive is called the Hartley type, and the opposite combination of impedances where the impedances Z1 and Z3 are made capacitive and the impedance Z2 is made inductive is called the Colpitts type.

When the present invention is carried out, either the Hartley type or the Colpitts type can be used, but the description will be given here assuming that the Hartley type is used.

The oscillator circuit using the transistor TR shown in FIG. 1B has substantially the same operation, so its explanation is omitted.

FIG. 2 is a diagram illustrating the basic principle of the Hartley oscillator circuit for explaining the obstacle detecting device according to the first embodiment of the present invention. FIG. 3 is an equivalent circuit diagram of the impedance Z3 of FIG. 2, and FIG. 4 is a characteristic diagram showing the relationship between the frequency and the reactance of FIG.

In FIG. 2, a resistor RG is a resistor for DC bias of the gate G of the FET, a resistor Rs is a resistor for DC bias of the source S of the FET, and a capacitor C is used.
s and capacitor Cc are capacitors for bypass.
Therefore, the factors that determine the oscillation conditions are impedances Z1 and Z1.
2 and Z3. In the present embodiment, the impedance Z
2 is capacitive, that is, the capacitor Cdg, and the impedance Z3 is inductive such as a crystal oscillator. Impedance Z1 to inductive and capacitive inductance L
And a resonance circuit including a capacitor C.

As shown in the equivalent circuit of FIG. 3, the impedance Z3 is represented by a series circuit composed of a resistor R3, a capacitor C3 and a reactance L3, and a capacitor C0 connected in parallel to the circuit. The resonance frequency f3s of the series circuit composed of the resistor R3, the capacitor C3 and the reactance L3 is f3s = 1 / 2π√ (L3 · C3), and the resonance frequency f3p of the parallel circuit is f3s = 1 / 2π√ {( L3 ・ C3 ・ C0) / (C3 + C
0)}. That is, as shown by the solid line in FIG. 4, the resonance frequency f3s
And the resonance frequency f3p.

Therefore, if the reactance of the impedance Z1 shown by the broken line in FIG. 5 is inductive, the frequency f3s
It can be seen that oscillation occurs between frequencies f3p. That is, the resonance frequency f1 of the impedance Z1 = 1 / 2π√ (L ·
If C) is adjusted so that f1> f3p and f1> f3s, oscillation will occur.

Generally, the Q factor of an electromechanical oscillator is very large, and the resonance frequency is f3p≈f3s. Given this oscillation frequency f3, the oscillation frequency f1 of the oscillation circuit is f1.
If it is> f3, it oscillates at the oscillation frequency f3 within the range of the arbitrary frequency difference Δf = f1−f3 which satisfies the equation (3) and satisfies the equation (2). That is, if the oscillation frequency is fixed, a change in the oscillation level can be detected. However, since the frequency difference Δf that satisfies the expression (2) has a predetermined frequency range, the oscillation level does not have a constant value.

Therefore, the resonance frequency f1 of the impedance Z1 forming the resonance circuit is changed within a range satisfying the frequency condition expression (3), that is, f1> f3, and the oscillation level V0 is changed.
Is always kept constant, a change in the oscillation level is detected, and when the change is removed, the obstacle G is detected.

FIG. 5 is an overall circuit diagram of the obstacle detecting device according to the first embodiment of the present invention.

In FIG. 5, the impedance Z2 connected between the drain D and the gate G of the FET is the capacitor C
z2, an impedance Z3 composed of a crystal resonator XTAL connected between the source S and the gate G of the FET, and between both terminals of the impedance Z2 and the impedance Z3, that is, between the drain D and the source S of the FET. The oscillation condition is determined by the impedance Z1. These, FET and impedance Z1, impedance Z2
, Impedance Z3 constitutes an oscillation circuit. The basic circuit configuration is the same as that of the circuit shown in FIG. 2, and therefore its explanation is omitted.

The detection circuit 1 connected to the drain D side of the FET via the coupling capacitor C10 is composed of a diode D11, a diode D12, a resistor R11 and a capacitor C11, and the voltage applied to the resistor R11 is the diode D12. The capacitor C11 is charged via With this circuit, the oscillation level is converted into the DC voltage V0 by the detection circuit 1 and transmitted to the determination circuit 2 and the oscillation control circuit 3.

On the other hand, the judging circuit 2 has a resistor R21 and a resistor R22 in which the voltage supplied from the constant voltage power source Vcc is connected in series.
A predetermined threshold voltage VT1 that is applied to and is divided by the input is input to the other, and the DC voltage V0 obtained by the detection circuit 1 is input to the other, and both are compared by the comparison circuit COMP. When the DC voltage V0 obtained by the detection circuit 1 is larger than the threshold voltage VT1, the output of the comparison circuit COMP becomes "L", and when the DC voltage V0 is smaller than the threshold voltage VT1, the output of the comparison circuit COMP is "H". "It becomes. The threshold voltage VT1 in the normal state is smaller than the DC voltage V0, and the output of the comparison circuit COMP is "L".

In the oscillation control circuit 3, the constant voltage power source V
The voltage supplied from cc is applied to the resistor R31 and the resistor R32 connected in series, and the divided predetermined threshold voltage V1 is input,
On the other hand, the DC voltage V0 obtained by the detection circuit 1 is applied to the input resistor R
Input through 30 and output V2 is V2 = V1−
V0 is obtained as the output of the operational amplifier OP, which is applied to the variable capacitance diode VD via the output resistors R33 and R35. Resistance R33 and resistance R35 of the output of the operational amplifier OP
Is connected to a constant voltage power supply Vcc by a parallel circuit of a resistor R34 and a capacitor C31, and a diode D
Reference numeral 31 is connected to the ground to prevent the output of the operational amplifier OP from becoming negative and to increase its changing speed. Operational amplifier OP set to threshold voltage V1
Thus, the control voltage V2 is generated so that the DC voltage V0 obtained by the detection circuit 1 becomes equal to the threshold voltage V1. The control voltage V2 is applied to the variable capacitance diode VD connected to the impedance Z1, and the resonance frequency f1 of the impedance Z1 is controlled so as to have a constant value of V2 = V0.

The impedance Z1 is the inductance L
And a resonance circuit consisting of a capacitance C,
The inductance L is composed of a mutual inductance having a winding ratio of 1: n. The capacitor C is connected to the winding ratio 1 side of the inductance L. A series circuit of a capacitor Cz1 and a variable capacitance diode VD is connected to the winding ratio n side of the inductance L. A sensor S made of a plate material or a wire material is arranged at a connection point between the winding ratio n side of the inductance L and the capacitor Cz1.

Next, the operation of the obstacle detection device of this embodiment will be described.

First, when an obstacle G such as a person, a building, or a metal is approached, the median constant around the obstacle G changes, the input impedance of the sensor S functioning as an antenna changes, and the capacitance changes. Added to impedance Z1,
The resonance frequency f of the oscillation circuit changes, the DC voltage V0 obtained by the detection circuit 1 also decreases, and the obstacle G continues to be detected. Here, the oscillation control circuit 3 uses the DC voltage V0 and the predetermined threshold voltage V0.
Compared with 1, the DC voltage V0 obtained by the original detection circuit 1
In order to change the output V2 of the operational amplifier OP,
The change in the output V2 is applied to the variable capacitance diode VD, and the resonance frequency f of the impedance Z1 is controlled to be a constant value. In this way, by making the change of the predetermined threshold voltage V1 respond only to the change of the environment and keeping the oscillation frequency f of the oscillation circuit constant, the oscillation level also becomes constant. Accordingly, it is possible to automatically correct a change in the capacitance of the sensor S that does not contribute to the obstacle G, such as a change over time. Further, the initial capacitance due to the size of the sensor S can be arbitrarily set by changing the amount of coupling to the parallel resonant circuit.

Further, when the sensor S and the obstacle G are stopped at a position close to each other, the DC voltage V obtained by the detection circuit 1
0 decreases, and the obstacle G continues to be detected. However, the decrease of the DC voltage V0 obtained by the detection circuit 1 becomes a phenomenon similar to the change of environment. Therefore, the output V2 of the operational amplifier OP is changed so that the DC voltage V0 obtained by the detection circuit 1 becomes equal to the predetermined threshold voltage V1. As a result, the DC voltage V0 obtained by the detection circuit 1 gradually becomes equal to the predetermined threshold voltage V1, and it is considered that there is no obstacle G. As a result, when the vehicle stops at a position close to the obstacle G, the obstacle G is no longer detected with the passage of time, and the state becomes the initial state as the state of the environment.

On the other hand, when the obstacle G is approached by a predetermined amount or more, the impedance of the sensor S functioning as an antenna changes, and as a result, it is added to the impedance Z1 as a change in capacitance, and the resonance of the oscillation circuit is generated. The frequency f changes, the frequency conditional expression (3) is not satisfied, and the oscillation stops. As a result, the DC voltage V obtained by the detection circuit 1
0 also decreases, the DC voltage V0 becomes smaller than the threshold voltage VT1 of the comparison circuit COMP, the output of the comparison circuit COMP becomes "H", and it is detected that the obstacle G is approached by a predetermined amount or more.

Further, when the input impedance of the sensor S changes and the change is added to the impedance Z1 and the resonance frequency f of the oscillation circuit changes faster than the change in the resonance frequency f of the oscillation circuit, when the obstacle G is rapidly approached, the detection circuit 1 DC voltage V obtained
0 decreases, the DC voltage V0 becomes smaller than the threshold voltage VT1 of the comparison circuit COMP, the output of the comparison circuit COMP becomes "H", and the obstacle G is detected.

In this embodiment, when the vehicle stops at a position close to the obstacle G, the obstacle G is no longer detected with the passage of time and the state is judged to be the environmental state. The detection of can be stored.

FIG. 6 is an overall circuit diagram of the obstacle detecting device of the second embodiment of the present invention.

In the drawings, the same reference numerals and symbols as those in the first embodiment show the same or corresponding components as those of the first embodiment, and therefore, duplicated description will be omitted here.

In FIG. 6, the impedance Z1 is a resonance circuit consisting of an inductance L and a capacitance C. As this inductance L, one coil is connected to a terminal at a winding ratio of 1: n, It is composed of a single turn coil composed of Lz10 and inductance Lz11. A series circuit of a capacitor Cz1 and a variable capacitance diode VD is connected to the terminal drawn from the inductance L. Further, a sensor S made of a plate material or a wire is provided at a connection point between the terminal of the inductance L and the capacitor Cz1, and a connection point between the capacitor Cz1 and the variable capacitance diode VD is connected to the oscillation control circuit 3. The output V2 of the operational amplifier OP is input.

Since the operation of this circuit is basically the same as that of the first embodiment, its explanation is omitted.

FIG. 7 is an overall circuit diagram of the obstacle detecting device of the third embodiment of the present invention.

In the drawings, the same reference numerals and symbols as those in the above-mentioned embodiment indicate the same or corresponding components as those of the above-mentioned embodiment, and therefore, the duplicated description will be omitted here.

In FIG. 7, the judgment circuit 2 inputs a predetermined threshold voltage VT1 to one side and the DC voltage V0 obtained by the detection circuit 1 to the other side, compares both of them with a comparison circuit COMP, and outputs a threshold value. When the DC voltage V0 obtained by the detection circuit 1 is larger than the voltage VT1, the output of the comparison circuit COMP is "L".
When the DC voltage V0 is smaller than the threshold voltage VT1, the output of the comparison circuit COMP becomes "H". The threshold voltage VT1 in the normal state is smaller than the DC voltage V0, and the output of the comparison circuit COMP is "L".

The n-bit up / down counter 1
For 0, the output of the comparison circuit COMP is preset at "L". The clock input is input through an AND gate that is opened / closed by the clock start / stop of the counter control logic 13, and the output of the oscillation circuit via a waveform shaping circuit (not shown) is used. Further, the n-bit up / down counter 10 receives a counter control signal as an addition or subtraction command from the counter control circuit 13 and an enable signal for operating the n-bit up / down counter 10. Note that the clock signal input to the AND gate uses the signal of its own oscillation circuit in the present embodiment, but in the case of implementing the present invention, even if a clock signal is input from another clock generator. Good.

The D / A conversion circuit 11 has n bits up /
Upon receiving the counter output of the down counter 10, the analog output V01 is output.

The output control circuit 12 receives the DC voltage V0 obtained by the detection circuit 1 and the analog output V01 from the D / A conversion circuit 11, and compensates the output difference V0-V01. The resonance frequency f of the impedance Z1 is controlled to be a constant value by being added to the variable capacitance diode VD via.

On the other hand, the DC voltage V0 obtained by the detection circuit 1
And the analog output V01 from the D / A conversion circuit 11 are input to the counter control circuit 13, and the output difference V0-V01.
The increase / decrease of the counter output of the n-bit up / down counter 10 is determined by the polarity of the n-bit up / down counter 10. When the magnitude of the output difference V0-V01 exceeds a predetermined range, the n-bit up / down counter 10 is set to the operating state. Output signal and open AND gate, impedance Z1
, Z2, Z3 from an oscillator circuit through an unillustrated waveform shaping circuit to n-bit up / down counter 1
The clock signal is 0.

Here, the n-bit up / down counter 10, the D / A conversion circuit 11, the output control circuit 12, and the counter control circuit 13 constitute an oscillation control circuit 30.

Next, the operation of the obstacle detection device of this embodiment will be described.

First, when an obstacle G such as a person, a building, or a metal is approached and environmental conditions are gradually changed, the input impedance of the sensor S is changed, which is added to the impedance Z1 as a change in capacitance. The resonance frequency f of the oscillation circuit changes, the DC voltage V0 obtained by the detection circuit 1 decreases,
Obstacle G is detected. Here, the output control circuit 12 uses the DC voltage V0 and the predetermined threshold voltage V01 from the D / A conversion circuit 11.
In comparison with the above, the output V2 of the output control circuit 12 is changed in order to obtain the DC voltage V0 obtained by the original detection circuit 1,
The change in the output V2 is applied to the variable capacitance diode VD, and the resonance frequency f of the impedance Z1 is controlled to be a constant value. Naturally, the oscillation frequency f is constant,
The oscillation level also becomes constant. Even if the sensor S and the obstacle G stop at a predetermined close position, the DC voltage V0 obtained by the detection circuit 1 decreases, the obstacle G is detected, and the state corrected as an environment change is detected. maintain. Accordingly, it is possible to automatically correct a change in the capacitance of the sensor S that does not contribute to the obstacle G, such as a change over time. Further, the initial capacitance due to the size of the sensor S can be arbitrarily set by changing the amount of coupling to the parallel resonant circuit.

However, when the obstacle G is approached more than a predetermined amount,
The input impedance of the sensor S changes, and as a result, the capacitance changes and is added to the impedance Z1, the resonance frequency f of the oscillation circuit changes, the frequency condition is not satisfied, oscillation stops, and the oscillation level suddenly changes. Fall to. As a result, the DC voltage V0 obtained by the detection circuit 1 also decreases, and the DC voltage V0 becomes smaller than the threshold voltage VT1 of the comparison circuit COMP that constitutes the determination circuit 2, and the comparison circuit C
The output of OMP becomes "H", and the obstacle G is detected.

At the same time, the n-bit up / down counter 10 is preset and the DC voltage V obtained by the detection circuit 1
0 and the analog output V01 from the D / A conversion circuit 11 are input to the counter control circuit 13, and the increase or decrease of the counter output of the n-bit up / down counter 10 is determined by the polarity of the output difference V0-V01, and the output difference V0. When the magnitude of the absolute value of -V01 is more than a predetermined range, an enable signal for operating the n-bit up / down counter 10 is output, and the AND gate is opened to set the impedance Z1,
It is used as a clock signal for the n-bit up / down counter 10 from an oscillation circuit composed of Z2 and Z3 via a waveform shaping circuit (not shown). N due to the output difference V0-V01
The bit up / down counter 10 counts, the count value of the n-bit up / down counter 10 is converted into an analog value by the D / A conversion circuit 11, and the output difference V0-
The n-bit up / down counter 10 counts until V01 becomes equal to or less than a predetermined value, and the count value of the n-bit up / down counter 10 is converted into an analog value by the D / A conversion circuit 11, and a predetermined output difference is obtained. When V0-V01, for example, V0-V01 becomes substantially zero, n bits up /
The control by the down counter 10 is stopped.

In this state, for example, when V0> V01, the oscillation circuit continues to oscillate again at the oscillation frequency f, during which the n-bit up / down counter 10 is preset and the n-bit up / down counter 10 Returns to the initial value.

However, in this state, for example, V0> V01
If not, the oscillation circuit cannot oscillate at the oscillation frequency f, the n-bit up / down counter 10 is stopped, and the detection state in which the sensor S and the obstacle G approach each other is maintained. That is, the obstacle detection state in which the sensor S and the obstacle G are close to each other is maintained.

In this embodiment, the n-bit up / down counter 10 is used to increase the accuracy of the analog output V01 from the D / A conversion circuit 11. However, when implementing the present invention, it is also possible to set the minimum counter value. However, at this time, the circuit can be simplified.

FIG. 8 is an overall circuit diagram of the obstacle detecting device of the fourth embodiment of the present invention.

In the drawings, the same reference numerals and symbols as those in the above-mentioned embodiment indicate the same or corresponding components as those of the above-mentioned embodiment, and therefore, the duplicated description will be omitted here.

In FIG. 8, the decision circuit 2 inputs a predetermined threshold voltage VT1 to one side and the DC voltage V0 obtained by the detection circuit 1 to the other side, compares both of them with a comparison circuit COMP, and outputs a threshold value. When the DC voltage V0 obtained by the detection circuit 1 is larger than the voltage VT1, the output of the comparison circuit COMP is "L".
When the DC voltage V0 is smaller than the threshold voltage VT1, the output of the comparison circuit COMP becomes "H". The threshold voltage VT1 in the normal state is smaller than the DC voltage V0, and the output of the comparison circuit COMP is "L".

Further, the latch circuit 20 includes a comparison circuit COM.
The output of P is reset to "L". Latch circuit 2
0 is the selection circuit 21 depending on its setting or resetting.
Switch. The set signal of the latch circuit 20 inputs a predetermined threshold voltage VT2 to one side and the DC voltage V0 obtained by the detection circuit 1 to the other side, and compares both with the comparison circuit COM.
When the DC voltage V0 obtained by the detection circuit 1 is smaller than the threshold voltage VT2 compared with P2, the output of the comparison circuit COMP2 is “L”, which is a set signal, and when the DC voltage V0 is larger than the threshold voltage VT2, The output of the comparison circuit COMP2 becomes "H". The threshold voltage VT2 in the normal state is higher than the DC voltage V0, and the output of the comparison circuit COMP is "L".
It has become. Here, the relationship between the DC voltage V0 obtained by the detection circuit 1 and the threshold voltage VT1 and the threshold voltage VT2 is V0>
VT1> VT2.

When the latch circuit 20 is in the reset state, the selection circuit 21 sets its output to the output V02, and the latch circuit 2
When 0 is in the set state, its output is the output V03, which is used as the input of the output control circuit 22. Here, the detection circuit 1
DC voltage V0 and threshold voltage VT1 and threshold voltage VT2 obtained in
And the relationship between the output of the selection circuit 21 and V02> VT1
>V03> VT2.

Further, the output control circuit 22 receives the DC voltage V0 obtained by the detection circuit 1 and the output V02 or the output V03 of the selection circuit 21, and outputs the output difference V0-V02 or the output difference V0.
Compensating for -V03, which is added to the variable capacitance diode VD via the resistor R35, and the resonance frequency f of the impedance Z1 is controlled to be a constant value.

When there is no obstacle G or its influence is small, the latch circuit 20 is in the reset state, the input of the output control circuit 22 is the output of the selection circuit 21, the output is V02, and the direct current obtained by the detection circuit 1 is obtained. The relationship between the voltage V0 and the DC voltage V0 obtained by the detection circuit 1 and the threshold voltage VT1 and the threshold voltage V
The relationship between T2 and the output of the selection circuit 21 is V0.apprxeq.V
02>VT1>V03> VT2.

First, when an obstacle G such as a person, a building, or a metal is approached and environmental conditions are gradually changed, the input impedance of the sensor S is changed, which is added to the impedance Z1 as a change in capacitance. The resonance frequency f of the oscillation circuit changes, the DC voltage V0 obtained by the detection circuit 1 decreases,
Obstacle G is detected. Here, the output control circuit 22 compares the DC voltage V0 with a predetermined threshold voltage V02 from the selection circuit 21, and sets the output V2 of the output control circuit 22 to the DC voltage V0 obtained by the original detection circuit 1. The output voltage V2 is changed and applied to the variable capacitance diode VD, and the resonance frequency f of the impedance Z1 is controlled to be a constant value. Thus, the oscillation frequency f is constant,
The oscillation level also becomes constant. Even if the sensor S and the obstacle G stop at a predetermined close position, the DC voltage V0 obtained by the detection circuit 1 decreases, the obstacle G is detected, and the state corrected as an environment change is detected. maintain. Accordingly, it is possible to automatically correct a change in the capacitance of the sensor S that does not contribute to the obstacle G, such as a change over time. Further, the initial capacitance due to the size of the sensor S can be arbitrarily set by changing the amount of coupling to the parallel resonant circuit.

However, when approaching the obstacle G more than a predetermined amount,
The input impedance of the sensor S changes, and as a result, the capacitance changes and is added to the impedance Z1, the resonance frequency f of the oscillation circuit changes, the frequency condition is not satisfied, oscillation stops, and the oscillation level suddenly changes. Fall to. As a result, the DC voltage V0 obtained by the detection circuit 1 also decreases, and the DC voltage V0 becomes smaller than the threshold voltage VT1 of the comparison circuit COMP that constitutes the determination circuit 2, and the comparison circuit C
The output of OMP becomes "H", and the obstacle G is detected.

Further, the oscillation level decreases and the DC voltage V0
Becomes smaller than the threshold voltage VT2 of the comparison circuit COMP2, the output of the comparison circuit COMP2 becomes "L", the latch circuit 20 is set, and the output of the selection circuit 2
The output from 1 is switched to the output V03, and the DC voltage V0 obtained by the detection circuit 1 and the output V03 from the selection circuit 21 are
It is input to the output control circuit 22, and the output difference V0-V03
The output V2 is obtained by, and the change in the output V2 is applied to the variable capacitance diode VD to control the resonance frequency f of the impedance Z1 to a constant value. When a predetermined output difference V0-V03, for example, V0-V03, becomes substantially zero, the oscillation circuit continues to oscillate again at the oscillation frequency f, and maintains the detection state in which the sensor S and the obstacle G are close to each other. That is, the obstacle detection state in which the sensor S and the obstacle G are close to each other is maintained. However, in this state, for example, the DC voltage V0
Becomes larger than the threshold voltage VT1 of the comparison circuit COMP, the latch circuit 20 is reset and returns to the initial value.

However, in this state, for example, V0-V01
Is not substantially zero, the oscillation circuit cannot oscillate at the oscillation frequency f, the latch circuit 20 maintains the reset state, and the detection state in which the sensor S and the obstacle G approach each other is maintained. That is, the obstacle detection state in which the sensor S and the obstacle G are close to each other is maintained.

As described above, in the obstacle detecting device according to the present embodiment, when the obstacle G is approached, the intermediary constant around the sensor S as the antenna of the oscillation circuit changes, and the sensor S
Of the oscillation circuit formed by the impedance Z1 which changes the resonance frequency due to the change of the input impedance of 1 and the other two impedances Z2 and Z3, and the determination circuit 2 detects the decrease of the oscillation level from the oscillation circuit and controls the oscillation. In the circuit 3, the impedance forming the oscillation circuit is changed in response to the decrease in the oscillation level so that the oscillation frequency of the oscillation circuit 3 is within a predetermined frequency range, and a failure is caused depending on whether or not the predetermined oscillation level can be maintained. The object G is detected, and this can be an embodiment corresponding to the claims.

Therefore, the input impedance of the sensor S functioning as an antenna changes when a medium different from the free space approaches, and this change in input impedance is
In addition to the resonance circuit consisting of the capacitor Cz1 capable of compensating the oscillation frequency and the variable capacitance diode VD, the obstacle G can be detected only by the change of the oscillation level. Therefore, the magnitude of the change amount of the voltage level per unit time is determined. However, the obstacle G can be detected. Alternatively, the obstacle G can be detected by determining a decrease in the voltage level by a predetermined amount. According to the experiments by the present inventors, since the detection is performed by the impedance change of the sensor S that functions as an antenna, the detection distance of the obstacle G of about 40 cm can be maintained, which can be realized by a simple circuit. Then, the change in the case where the capacity of the sensor S does not contribute to the obstacle, such as the change over time, can be automatically corrected. The initial capacitance due to the size of the sensor S can be arbitrarily set by changing the amount of coupling to the parallel resonant circuit.

In this embodiment, the impedance Z2 and the impedance Z3 connected in series are used.
And an oscillation circuit having a resonance circuit of impedance Z1 and impedance Z3 which have the same polarity and which have oscillation conditions determined by the impedance Z1 connected to both terminals of the impedance Z2 and impedance Z3, and the impedance Z3 of the resonance circuit The frequency is f3, the Q factor of the circuit is Q3, and the impedance Z1
Where f1> f3 and Q3> Q1 when the resonance frequency is f1 and the Q factor of the circuit is Q1,
Impedance Z3 is an electromechanical oscillator, impedance Z1 is formed by a coil and a capacitor, the oscillation frequency of the oscillation circuit is within a predetermined frequency range, and obstacle G is detected depending on whether or not a predetermined oscillation level can be maintained. The present invention is carried out, and this can be an embodiment corresponding to the claims.

That is, assuming that the impedance Z3 of the resonance circuit is f3, the resonance frequency is f3, the Q factor of the circuit is Q3, and the impedance Z1 is f1 and the Q factor of the circuit is f1, then f1> f3 The width of the frequency adjustment region is widened, the adjustment range is widened, and Q3> Q1, so that the change of Q1 is reduced even if the frequency f1 is changed. As a matter of course, Q3 >> Q1 is preferable as the Q factor of the circuit that reduces the change of Q1 even if the frequency f1 is changed.

Therefore, the input impedance of the sensor functioning as an antenna changes when a medium different from the free space approaches, and this change of the input impedance is added to the resonance circuit capable of compensating the oscillation frequency, and the change is caused only by the change of the oscillation level. Since the object G can be detected, the amount of change in the voltage level per unit time can be determined and the obstacle G can be detected. Therefore, since the detection is performed by the impedance change of the sensor S functioning as an antenna, the detection distance of the obstacle G of about 40 cm can be maintained, and it can be realized by a simple circuit. Then, the change in the case where the capacity of the sensor S does not contribute to the obstacle, such as the change over time, can be automatically corrected. The initial capacitance due to the size of the sensor S can be arbitrarily set by changing the amount of coupling to the parallel resonant circuit.

In this embodiment, the difference between the resonance frequency f3 of the impedance Z3 and the resonance frequency f1 of the impedance Z1 is controlled so that the oscillation level of the oscillation circuit becomes constant. This can be an embodiment corresponding to the claims, and the control of the oscillation frequency of the oscillation circuit and the oscillation level thereby are known, and the oscillation control of the oscillation circuit becomes easy.

Further, in this embodiment, in addition to the impedance of the coil L and the capacitor C formed by the sensor S and the obstacle G, the impedance Z1 of the oscillating circuit is changed, and the oscillation level of the oscillation level is changed without changing the oscillation frequency. Since it is converted into a change, the obstacle G can be detected by the change speed and change amount of the oscillation level without being influenced by the frequency characteristic of the oscillation circuit.

Furthermore, in this embodiment, the change in the capacitance applied to the impedance Z1 is caused by the variable capacitance diode VD connected to the coil of the parallel resonance circuit.
Since it is performed by the above, it can be set as the mutual inductance of the parallel resonant circuit, and the degree of freedom in circuit design is increased.

By the way, in this embodiment, the variable capacitance diode VD is connected to the coil L of the impedance Z1.
Are connected in parallel to obtain a change in capacitance without using mechanical displacement. However, in the case of implementing the present invention, the output of the oscillation control circuit 3 is set to the variable output of the variable capacitor or the variable reactance. Can be a variable output.

Further, in this embodiment, when the change of the input impedance due to the approach of the obstacle G is detected as the change of the oscillation level while keeping the oscillation frequency constant, the change of the input impedance of the sensor is shown in FIG. Although it is added to the secondary side of the resonance circuit coil, it can be similarly used by adding it to the intermediate tap as shown in FIG. 7.

[0096]

As described above, the obstacle detecting device according to the first aspect of the present invention changes the input impedance of the sensor when the obstacle is approached. An oscillation circuit formed together with the individual impedances, and a decrease in the oscillation level from the oscillation circuit is detected, and an oscillation control circuit changes the impedance forming the oscillation circuit in response to the decrease in the oscillation level, The oscillation frequency of the circuit is set within a predetermined frequency range, and an obstacle is detected depending on whether or not a predetermined oscillation level can be maintained.

Therefore, the input impedance of the sensor functioning as an antenna changes when a medium different from the free space approaches, and this change in input impedance is added to the resonance circuit capable of compensating the oscillation frequency. Since an object can be detected, it is possible to detect the obstacle by determining the amount of change in the voltage level per unit time. Therefore, the obstacle detection distance of about 40 cm can be maintained, which can be realized by a simple circuit.

In the obstacle detecting device according to a second aspect of the present invention, an impedance condition is determined by impedance Z2 and impedance Z3 connected in series and impedance Z1 connected to both terminals of the impedance Z2 and impedance Z3 and having the same polarity. An oscillator circuit having a resonance circuit of Z1 and impedance Z3 is provided, wherein the impedance Z3 has a resonance frequency of f3, the Q factor of the circuit is Q3, and the impedance Z1 has a resonance frequency of f1 and a Q factor of the circuit. When Q1
The impedance Z3 is an electromechanical oscillator, the impedance Z1 is formed by a coil and a capacitor, and the oscillation frequency of the oscillation circuit is within a predetermined frequency range so that f1> f3 and Q3> Q1. The obstacle is detected based on whether or not the oscillation level can be maintained.

Therefore, the input impedance of the sensor functioning as an antenna changes when a medium different from the free space approaches, and this change in input impedance is added to the resonance circuit capable of compensating for the oscillation frequency, and only changes in the oscillation level cause an obstacle. Since an object can be detected, the amount of change in the voltage level per unit time can be determined and an obstacle can be detected. Therefore, the obstacle detection distance of about 40 cm can be maintained, which can be realized by a simple circuit.

In the obstacle detecting device of the third aspect, the impedance Z of the oscillation circuit is set so that the oscillation level is constant.
Since the difference between the resonance frequencies of the inductive and capacitive parallel circuits of 1 is controlled, in addition to the effect of claim 2, the control of the oscillation frequency of the oscillation circuit and the oscillation level thereby become known, Will be easier.

In the obstacle detecting device of the fourth aspect, the capacitance formed by the sensor and the obstacle is added to the impedance Z1 of the oscillation circuit without changing the oscillation frequency.
Since it is converted into a change in the oscillation level, the method according to claim 2
In addition to the above effect, the obstacle can be detected without being influenced by the frequency characteristic of the oscillation circuit.

According to the obstacle detecting device of the fifth aspect, in addition to the effect of the second aspect, the change in the capacitance applied to the impedance Z1 is coupled to the coil of the parallel resonance circuit. It can be set as the mutual inductance of the parallel resonant circuit, and the degree of freedom in circuit design is increased.

In addition to the effect of claim 1, the obstacle detection device of claim 6 holds the detection state of the obstacle when the sensor and the obstacle come close to each other by a predetermined amount or more. The operation of the obstacle detection device can be confirmed, and it will not respond to an unreasonable movement that brings it closer.

The obstacle detecting device according to claim 7 stops the oscillation of the oscillating circuit to maintain the obstacle detection state when the sensor and the obstacle come close to each other by a predetermined amount or more. In addition to the effect according to any one of claims 2 to 5, the operation of the obstacle detection device can be confirmed, and the mobile device does not respond to an unreasonable movement that causes the obstacle detection device to approach further.
At the same time, the detection stops the oscillation and eliminates unnecessary power consumption.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a basic principle of a known oscillator circuit for explaining an obstacle detection device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating the basic principle of a Hartley oscillator circuit for explaining the obstacle detection device according to the first embodiment of the present invention.

FIG. 3 is an equivalent circuit diagram of the impedance Z3 of FIG.

FIG. 4 is a characteristic diagram showing the relationship between the frequency and the reactance of FIG.

FIG. 5 is an overall circuit diagram of the obstacle detection device according to the first embodiment of the present invention.

FIG. 6 is an overall circuit diagram of an obstacle detection device according to a second embodiment of the present invention.

FIG. 7 is an overall circuit diagram of an obstacle detection device according to a third embodiment of the present invention.

FIG. 8 is an overall circuit diagram of an obstacle detection device according to a fourth embodiment of the present invention.

FIG. 9 is a principle diagram of an obstacle detection device for an automobile according to a first conventional example.

FIG. 10 is a principle diagram of an obstacle detection device for an automobile according to a second conventional example.

FIG. 11 is a principle diagram of an obstacle detection device for an automobile according to a third conventional example.

[Explanation of symbols]

 FET Field effect transistor Z1 impedance Z2 impedance Z3 impedance COMP comparison circuit COMP2 comparison circuit OP operational amplifier VD variable capacitance diode L inductance C capacitor 1 detection circuit 2 judgment circuit 3,30 oscillation control circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshimitsu Oka 2-chome, Asahi-cho, Kariya city, Aichi Aisin Seiki Co., Ltd. (72) Nobuyuki Ota 2-3-chome, Showa-cho, Kariya city, Aichi prefecture Engineering Co., Ltd.

Claims (7)

[Claims] 1. A sensor, the input impedance of which changes when approaching an obstacle, an oscillation circuit formed together with an impedance that changes the resonance frequency due to a change of the input impedance of the sensor, and two other impedances; An oscillation control circuit that detects a decrease in the oscillation level from the circuit, changes the impedance forming the oscillation circuit in response to the decrease in the oscillation level, and sets the oscillation frequency of the oscillation circuit within a predetermined frequency range; An obstacle detection device comprising: 2. An oscillation condition is defined by impedance Z2 and impedance Z3 connected in series and impedance Z1 connected to both terminals of said impedance Z2 and impedance Z3, and a resonance circuit of impedance Z1 and impedance Z3 having the same polarity is formed. In the obstacle detection device including the oscillation circuit, the impedance Z3 of the resonance circuit has a resonance frequency of f
3, the Q factor of the circuit is Q3, and the impedance Z1 of the resonant circuit is f1> f3 and Q3> Q1 when the resonant frequency is f1 and the Q factor of the circuit is Q1. The impedance detection device is characterized in that the impedance Z3 is an electromechanical oscillator and the impedance Z1 is a coil and a capacitor. 3. The difference in resonance frequency between the resonance frequency f3 of the impedance Z3 and the resonance frequency f1 of the impedance Z1 is controlled so that the oscillation level of the oscillation circuit becomes constant. Obstacle detection device. 4. The impedance Z1 of the oscillator circuit,
3. The obstacle detection device according to claim 2, wherein impedance of a capacitor formed by a sensor and an obstacle is added to convert into an oscillation level change without changing an oscillation frequency. 5. The obstacle detecting device according to claim 2, wherein the capacitance applied to the impedance Z1 is changed by a variable capacitance diode coupled to a coil of a parallel resonance circuit. 6. The obstacle detection device according to claim 1, wherein the obstacle detection state is maintained when the sensor and the obstacle come close to each other by a predetermined amount or more. 7. The method according to claim 2, wherein when the sensor and the obstacle come close to each other by a predetermined amount or more, the oscillation of the oscillation circuit is stopped and the detection state of the obstacle is held. The obstacle detection device according to one.