JPH0367236B2 - - Google Patents

Description

TECHNICAL FIELD The present invention relates to an object detection device that detects a state in which an object such as an obstacle is approaching a sensor at a relative speed.

Conventional technology Conventionally, an object detection device used for detecting obstacles while driving a car, for example, emits directional radio waves or ultrasonic waves from a transmitter, and receives reflected waves from the object using a receiver. This method is used to detect objects such as obstacles, but it requires a pair of transmitters and receivers, making the device complex, and since it has directivity, it is difficult to detect objects in close proximity. It has become something that creates a dead zone.

Conventionally, a pair of antennas is provided and a high-frequency signal of the same frequency is applied to each antenna, and when an object to be detected faces the pair of antennas, an imbalance in capacitance between each antenna and the object occurs. A device that detects objects according to the difference in oscillation frequency has been developed (Special Publication Publication No. 47-7852).
In such a device, two systems of antennas and oscillators are required, making the device complicated, and the object is evenly positioned with respect to the pair of antennas, making it difficult to connect each antenna to the object. If there is no unbalance in the capacitance between the two, the disadvantage is that even if an object is present, it will not be detected.

Purpose The present invention was made in consideration of the above points, and
An object detection device that uses a simple configuration to reliably detect approaching objects such as obstacles, and selectively detects only objects in the desired direction so that they are not affected by external disturbances. It provides:

Configuration An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 2 is a circuit diagram showing the basic principle of object detection according to the present invention. When a high frequency signal is applied to a series circuit of electrode member 1 and resistor R, electrode member 1 and object O
Focusing on the fact that the stray capacitance C between them changes depending on the distance between the electrode member 1 and the resistor R, and the output voltage at the voltage dividing point between the electrode member 1 and the resistor R changes, the electrode member 1 can be used as a sensor. By using this, the falling state of the output voltage when the object O is approaching the sensor at a relative speed is detected, thereby detecting the state that the object O is approaching.

At that time, for example, if the sensor (electrode member) 1 is plate-shaped as shown in the figure, the sensor 1
Not only the object O1 facing the front surface but also the object O2 facing the back surface of the object O1 will be detected.

Therefore, in particular, in the present invention, when the object O2 is not a detection target, the rear surface of the sensor 1 is set so that only the object O1 facing the target surface of the sensor 1 can be selectively detected. An electrostatic shielding member (ground conductor) is provided at a position opposite to the object O2 to prevent electrostatic capacitance from being formed between the object O2 and the object O2. Therefore, the object O
Even when the sensor 2 approaches the sensor 1, the capacitance does not change, and the approaching state is not detected at all.

In Figure 3, a rod-shaped sensor is used as sensor 1,
Furthermore, in order to prevent objects O1, O3 and O4 located below and to the right from being detected, the portion of the sensor 1 corresponding to the direction in which objects are not detected is covered with an electrostatic shielding member 2, This shows a case where only the object O2 in the direction can be selectively detected. Therefore, when such a rod-shaped sensor 1 is embedded, for example, in a bumper made of a non-conductive material of a car to detect obstacles ahead when the car is running, it is necessary to By embedding the electrostatic shielding member 2 in the bumper portion so as to cover the vehicle, it becomes possible to remove surrounding disturbances such as unevenness of the road surface and detect only the target obstacle ahead. . In that case, sensor 1
It goes without saying that the vehicle body may also serve as an electrostatic shielding member that covers the rear of the vehicle.

FIG. 1 shows an embodiment of an object detection device according to the present invention constructed based on the above-mentioned basic principle. A network 4 consisting of a resistor dividing circuit, a sensor 1 and an electrostatic shielding member 2 consisting of electrode members connected to dividing points of the network 4, and the network 4
A bandpass filter amplifier 5 performs noise removal and amplification processing on a high-frequency output signal from a high-frequency output signal, a detector 6 detects the amplified output signal, and detects the approach of an object by observing the falling state of the detected voltage signal. and a voltage fluctuation detection circuit 7 which detects the current state and gives an alarm command to the driver 8 of the alarm device 9.

However, in the device configured in this way, when a high frequency signal with a constant frequency Fo is applied from the oscillator 3 to the network 4, the sensor 1
A high frequency output signal that is suitably attenuated in proportion to the proximity of the object facing the is sent to the bandpass filter amplifier 5,
There, the noise induced in the sensor 1 and the like is removed, and only the high frequency component of the frequency Fo is amplified. The frequency signal with a predetermined width is detected by a wave detector 6, and a DC voltage signal corresponding to the amplitude of the input frequency signal is sent to a voltage fluctuation detection circuit 7. The voltage fluctuation detection circuit 7 detects a falling state of the applied DC voltage signal and issues an alarm command to the driver 8. As a result, alarm 9
will issue an alarm to that effect by sounding or lighting up.

FIG. 4 shows a specific configuration example of the voltage fluctuation detection circuit 7, which includes a first amplifier 71 that amplifies the output voltage Vo of the detector 6, and a first amplifier 71 that amplifies the output voltage Vo of the detector 6.
a second amplifier 72 that amplifies the voltage with a certain delay element; a comparator 73 that compares the amplified output voltages V1 and V2; and a comparator 73 that compares the amplified output voltages V1 and V2. It consists of a determination circuit 74 that determines whether the time width of the output signal S is greater than or equal to a preset time width. Note that the amplifiers 71 and 72 are set so that their respective gains are the same. Further, the offset voltage of the comparator 73 is adjusted so that it outputs a low level when V1≧V2, and outputs a high level when V1<V2.

With this configuration, as shown in FIG. 5, when the input voltage Vo falls over a period of T,
The output voltage V1 of the amplifier 71 falls in the same period T, but the output voltage V2 of the amplifier 72 falls with a certain delay.
It will descend with Td, resulting in T+
During the period Td, V1<V2, and the output S of the comparator 73 becomes high level. Therefore, the input voltage Vo
Since the falling period T varies depending on the approach of the object to the sensor 1, the comparison output S
When the time width exceeds a predetermined value, the determination circuit 74 issues an alarm command to the driver 8. Note that when the position of the object relative to sensor 1 does not change and the input voltage Vo remains constant, V1=
V2, and when the object moves away from the sensor 1, V1>V2 and the comparator 7
The output of No. 3 becomes low level, and no alarm command is issued at that time.

In this way, the object detection device according to the present invention has a simple overall configuration, so there are fewer failures, and there is no dead zone in the nearby area, so the closer the object is, the better the detection condition is. Selectively detects only objects approaching from any direction,
It is possible to issue an optimal warning according to the degree of approach, which is advantageous in, for example, detecting obstacles when driving a car.

Effects As described above, in the object detection device according to the present invention,
A means for replacing a change in stray capacitance between a sensor made of an electrode member and an object to be detected with a change in a frequency signal, a means for converting the frequency signal into a voltage signal, and a means for amplifying the voltage signal. , means for amplifying the voltage signal with a certain delay element, and means for comparing the respective amplified signals with a comparator to detect that the voltage signal is in a falling state. The sensor part corresponding to the direction in which the object is not detected, excluding the part facing the object, is covered with an electrostatic shielding member, and the simple structure ensures that the object is approaching. It has the excellent advantage of being able to detect objects in the desired direction and eliminating the influence of disturbances by detecting only objects in the desired direction.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the object detection device according to the present invention, Fig. 2 is a circuit configuration diagram showing the basic principle of object detection according to the invention, and Fig. 3 is the installation of an electrostatic shield member for the sensor. FIG. 4 is a block diagram showing a specific example of the configuration of the voltage fluctuation detection circuit in the same embodiment, and FIG. 5 is a time chart of signals of various parts in the voltage fluctuation detection circuit. DESCRIPTION OF SYMBOLS 1... Sensor (electrode member), 2... Electrostatic shielding member, 3... Oscillator, 4... Network, 5... Bandpass filter amplifier, 6... Detector, 7... Voltage fluctuation detection circuit,
8...Driver, 9...Alarm.

Claims (1)

[Claims] 1. Means for replacing a change in stray capacitance between a sensor made of an electrode member and an object to be detected with a change in a frequency signal, a means for converting the frequency signal into a voltage signal, and a means for amplifying the voltage signal. , means for amplifying the voltage signal with a certain delay element, and means for comparing the respective amplified signals with a comparator to detect that the voltage signal is in a falling state, and is the detection target. What is claimed is: 1. An object detection device characterized in that a sensor portion corresponding to a direction in which the object is not detected, excluding a portion facing the object, is covered by an electrostatic shielding member.