JPS62100681A - Electrostatic capacitance type proximity detector - Google Patents

Abstract

PURPOSE:To eliminate erroneous information along with earlier return of a time constant circuit, by short-circuiting a resistance of the time constant circuit with a switch section which operates by an output of a judging section. CONSTITUTION:A detector section 8 is connected to an output of a low-frequency amplifying section 7 which it 8 is connected in parallel to a discriminator section 9 which is formed an opposite phase amplifier, for example, by reversing an input terminal of an operational amplifier. While the detector section 8 is a circuit which generates an output when an output of a detector section 6, namely, the potential at the point Vd falls, the discriminator section 9 produces an output when the potential at the point Vd rises. Therefore, the discriminator section 9 produces an output when an object to be detected leaves a sensor section 2. The output of the discriminator section 9 is applied to an analog switch SW1 of a switch section 10 to short-circuit a resistance Rt determining the time constant of the low-frequency amplifier section 7 connected in parallel to the switch SW 1. This achieves a quick return of the circuit to handle continuous access while eliminating erroneous information otherwise depending on points, remote and close, thereby upgrading practicability.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a proximity detection device that is installed in a vehicle, etc., and is used to prevent collisions, personal accidents, etc. by detecting nearby objects. In particular, high frequencies and capacitance are used for detection.

[Prior Art] Conventionally, this type of capacitance type proximity detection device has a circuit as shown in FIG. When applied to the sensor section 2, a change in current occurs due to the stray capacitance ♂C3 generated between the adjacent single-force body 3, and the resistance n
A voltage change is caused by R3. This high frequency is amplified by a high frequency amplification section 5, detected by a detection section 6, and output as a DC output. 1
1] section 7, and the detection section 8 obtains a detection output.

Problem 1 to be Solved by the Invention However, in the conventional near delusion detection device described above, for example, the approaching speed of the approaching object 3 is of a nature that cannot be predicted. The above-described low frequency amplification section is required to amplify as low a change as possible, that is, to a low frequency, and as a result, the time constant of the time constant circuit becomes large. This means that the Rt
, Ct (In) is large. Conventional proximity sensors detect the proximity of an object by the drop in potential at the point indicated by Vd in FIG. Due to the large time constant due to R1 and capacitor +l-Ct, the potential at point vi, which is the opposite pole of point Vd of capacitor C[, returns to its original potential when the nearby object disappears. Requires a long time (several seconds)
Therefore, there is a problem that objects that occur continuously may not be able to approach each other.Secondly, the potential of this point Vi is restored from the power supply via the resistor Rt, so the fish v1 The potential at point Vt decreases, and this phenomenon is the same as the approach of an object where the potential at point Vt decreases, so there is a problem in that an output is generated in the detection section even though there is no proximity of the object, resulting in a false alarm. .

Means for Solving Problem 1 The present invention provides a capacitance type proximity detection device that produces a change in high frequency output voltage due to a change in capacitance due to the proximity of an object as a specific means for solving the above problems. A discriminating section is provided to determine whether an object is near or far away by smell (), and when the object is far away, a switch section provided in parallel with the time constant circuit of the low frequency section reduces the time constant of the time constant circuit. Features and 1
By providing a capacitive proximity detection device that
This solves the conventional problems by speeding up the recovery of the time constant circuit and eliminating false alarms.

[Example] Next, the present invention will be described in detail based on an example shown in FIG. In order to facilitate understanding, parts that are the same as those in the conventional example will be described with the same reference numerals, and descriptions of overlapping parts will be omitted.

In the figure, the oscillation section indicated by reference numeral 1 to the detection section indicated by reference numeral 8 are basically the same as those shown in the conventional example, and are shown in a more specific wiring diagram. In the present invention, the detection section 8 is connected to the output of the low frequency amplification section 7, and at the same time, the detection section 8 is connected in parallel with the output of the low frequency amplification section 7, for example.
The input terminals of the null amplifier are reversed and connected to a discriminator 9 formed by an amplifier with an opposite phase. To explain this point in detail, as explained above, the detection section is a circuit that generates an output when the output of the detection section 6, that is, the potential at point Vd drops, whereas the discriminator section 9 produces an output when the potential at the point Vd rises, in other words, produces an output when the detected object moves away from the sensor section 2. The output of the determination section 9 is applied to the analog switch SWI of the switch section 10 to short-circuit the resistor Rt that determines the time constant of the low frequency amplification section 7 connected in parallel with the analog switch SW1.

[Function] According to the present invention, a determination section that generates an output when the object to be detected moves away from the sensor section, and a switch section that is turned on by the output of the determination section are provided, and the switch section generates a low frequency signal. By short-circuiting the resistance of the time constant circuit of section 1+ section, the detected object becomes Ii'! When it travels far away, the time constant becomes extremely short and it roars. Specifically, if the resistance of the time constant circuit,,'x Rt is 1MΩ, and the resistance when the switch part is conductive is 500Ω, the time constant will be 1/2.000, so at the same time The capacitor Ct of the constant circuit is also quickly charged, and the output side pole (the pole opposite to the pole connected to the point Vd) of the capacitor operates substantially the same as the input side pole. As a result, when the object to be detected moves away, the capacitor '+jC[ is completely charged at the same time and returns to a detectable state at the end of the distance, and even in the state on the way. , it is possible to prevent the phenomenon in which the potential of the output side pole decreases due to a flow of 1 m.

Effect of the Invention 1 As explained above, according to the present invention, the resistor of the time constant circuit is short-circuited by the switch section operated by the output of the determination section of the fil constant section that detects the separation of the object to be detected. When moving far away, the time constant of the low frequency section "1" was extremely shortened. Therefore, the return of the circuit was shortened to correspond to the continuous near limb, and at the same time when moving far away. This has the great effect of eliminating the occasional false alarm and increasing the practicality of the electrostatic capacitor suspended type proximity sensor.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a capacitive mother proximity detection device according to the present invention, and FIG. 2 is a schematic circuit diagram showing a conventional example. DESCRIPTION OF SYMBOLS 1... Oscillator part 2... Sen9 part 6... Detection part 7... Low frequency increase 1] part 8... Detection part 9... Judgment part 10... Switch part
Rt...Resistance Ct...Capacitor Patent Applicant Honda Motor Co., Ltd. Times Stanley Electric Co., Ltd. Figure 1 Figure 2 Procedural Amendment April 11, 1986

Claims (1)

[Claims] In a capacitive proximity detection device that causes a change in high frequency output voltage due to a change in capacitance due to the proximity of an object,
The electrostatic electrostatic device is characterized in that a discriminator is provided for determining whether an object is near or far away, and when the object is far away, a switch section provided in parallel with the time constant circuit of the low frequency section reduces the time constant of the time constant circuit. Capacitive proximity detection device.