JP3556403B2 - Automotive radar equipment - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a radar device mounted on an automobile for transmitting radio waves and receiving reflected waves of the radio waves. INDUSTRIAL APPLICABILITY The present invention is used as a device which is mounted on an automobile, automatically measures an inter-vehicle distance with a preceding vehicle during traveling, and issues an alarm when the inter-vehicle distance becomes short. The present invention relates to a technique for removing snow attached to an antenna of a radar device.
[0002]
[Prior art]
Developed an in-vehicle radar that transmits radio waves in the tens of GHz band toward the front of the vehicle, receives reflected waves of the radio waves, and measures the distance to an object in front of the vehicle based on the time difference between the transmission timing and the reception timing. Have been. In recent years, it has been specified in Japan that a 60 GHz (wavelength 5 mm) band is used as the frequency of a vehicle-mounted radar, and an inter-vehicle distance warning device in this frequency band is being studied. The concept of this conventional example is shown in FIGS. FIG. 8 is a diagram showing a running example of a radar-equipped vehicle and a target vehicle during snowfall. FIG. 9 is a diagram illustrating an example of mounting an antenna. In the example of FIG. 9, the transmitting / receiving antenna 12 is provided with a rectangular hole having a side of about several cm in the bumper of the automobile, and the antenna surface is mounted flush with the front edge of the bumper, or protruded or recessed. At the time of snowfall as shown in FIG. 8, the holes are clogged with snow, or snow adheres to the antenna surface, which hinders transmission and reception of radio waves.
[0003]
Conventionally known techniques for removing snow from a radar antenna include a method using a blower that blows air to blow off snow, a method using a wiper whose arm reciprocates on the antenna surface, and a method of installing a radome and warming the inside. There are a method of melting snow, a method of applying an anti-snow coating to an antenna or a radome, and the like.
[0004]
[Problems to be solved by the invention]
The method using a blower requires an air pump and an air pipe for blowing air to the surface of the antenna. In addition, although the air pump has an intake port, it is necessary to take measures to prevent the intake port from being blocked by snow or ice. In the method using the wiper, the radio wave is disturbed because the metal arm reciprocates on the antenna surface, so that the snow removing operation cannot be performed during use of the radar. The method for warming the inside of the radome requires a large-scale apparatus because the radome is prepared. Further, since a large heater is used to warm the inside, power consumption is increased. The method using a paint has low durability of the paint and needs to be regularly repainted.
[0005]
The present invention has been made in such a background, and an object of the present invention is to provide an in-vehicle radar device capable of removing snow with a simple configuration. An object of the present invention is to provide an on-vehicle radar device that can automatically remove snowfall. An object of the present invention is to provide an on-vehicle radar device that can operate normally even during snowfall. An object of the present invention is to provide a heater device that does not deteriorate the characteristics of radio waves.
[0006]
[Means for Solving the Problems]
The present invention relates to an on-vehicle radar device, an oscillator having an oscillation frequency of several tens of GHz, an antenna for transmitting the output of the oscillator as a radio wave toward a traveling direction space of a vehicle and receiving a reflected wave of the radio wave, An on-vehicle radar device comprising: an arithmetic circuit that calculates a distance to an object in front of a vehicle from a time difference between a transmission timing of a radio wave and a reception timing of the reflected wave. A feature of the present invention resides in that an electric heater for heating snow accumulation on the antenna surface is provided. The electric heater is linear and is desirably disposed so as to be substantially orthogonal to the polarization direction of the transmission radio wave.
[0007]
That is, a radio wave has a property that it is difficult to pass through a slit parallel to the polarization direction which is the vibration direction of the electric field. Therefore, in order to transmit light through the slit, the direction of the slit must be a direction orthogonal to the polarization direction. Since the heater wire is made of metal, it is arranged in parallel to form a slit. Therefore, it is preferable that the heater wire be disposed so as to be substantially orthogonal to the polarization direction of the transmission radio wave so as not to affect the transmission radio wave as much as possible.
[0008]
The electric heater may be configured to include a hollow box provided in close contact with the antenna surface and a heater element for heating air inside the hollow box. That is, a hollow box made of a material that does not affect radio waves is installed on the surface of the antenna, and a heater element is installed in a place that does not affect radio waves in the hollow box. By melting the snow by heating the air by the heater element, it is possible to remove snow accretion without affecting radio waves.
[0009]
It is preferable that the arithmetic circuit includes means for detecting the level of the reflected wave having a very small time difference, and a switch circuit for automatically energizing the electric heater when the level exceeds a predetermined value. Thus, snow accumulation can be automatically detected, and the electric heater can be automatically heated to remove snow accumulation.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
[0011]
【Example】
The configuration of the embodiment of the present invention will be described with reference to FIG. FIG. 1 is an overall configuration diagram of an embodiment of the present invention.
[0012]
The present invention relates to an on-vehicle radar device, comprising an oscillator 1 having an oscillation frequency of several tens of GHz, and an antenna for transmitting an output of the oscillator 1 as a radio wave toward a space in a traveling direction of a vehicle and receiving a reflected wave of the radio wave. 2 is a vehicle-mounted radar device including a distance measuring unit 3 as an arithmetic circuit that calculates a distance to an object in front of a vehicle based on a time difference between a transmission timing of the radio wave and a reception timing of the reflected wave.
[0013]
Here, the feature of the present invention resides in that an electric heater 4 for heating snow accumulation on the surface of the antenna 2 is provided.
[0014]
The apparatus includes a snow accretion detecting section 5 as means for detecting the level of the reflected wave whose time difference is extremely small, and a switch circuit 6 for automatically energizing the heater 4 when the level exceeds a predetermined value.
[0015]
Next, the operation of the embodiment of the present invention will be described. When snow accumulates on the antenna 2, a part of the radio wave generated by the oscillator 1 is reflected by the snow accretion and input to the distance measuring unit 3. The radio wave reflected by the snow is input to the distance measuring unit 3 via a short path of the oscillator 1 → the antenna 2 → the distance measuring unit 3. Absent. That is, in the on-vehicle radar device, as shown in FIG. 8, the distance to the target vehicle is determined by the frequency distribution of the beat signal generated by the phase difference between the radio wave reflected back to the target vehicle and the radio wave generated by the oscillator 1. Is measured, the beat signal of the radio wave reflected by snow accretion is a beat signal having a beat frequency near zero frequency, and can be easily distinguished from the beat signal of the radio wave reflected on the target vehicle. The beat signal whose beat frequency is close to zero frequency is detected by the snow accretion detecting section 5.
[0016]
According to the detection result, the snow detection unit 5 closes the switch circuit 6. Thus, the heater 4 is energized and heated. This heat can melt the snow on the antenna 2.
[0017]
(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a view showing the heater 4 according to the first embodiment of the present invention. FIG. 3 is a diagram showing a state where the heater 4 is mounted on the antenna 2. In the first embodiment of the present invention, it is assumed that the polarization of the transmission radio wave is in the horizontal direction. The arrangement direction of the heater wire 7 that has the least influence on the transmission radio wave is a direction orthogonal to the polarization. Therefore, as shown in FIG. 2, the heater wires 7 are arranged in the vertical direction. The heater 4 is mounted on the surface of the antenna 2 as shown in FIG.
[0018]
(Second embodiment)
A second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a view showing a heater 4 according to a second embodiment of the present invention. In the second embodiment of the present invention, it is assumed that the polarization of the transmission radio wave is in the vertical direction. The arrangement direction of the heater wire 7 that has the least influence on the transmission radio wave is a direction orthogonal to the polarization. Therefore, as shown in FIG. 4, the heater wires 7 are arranged in the horizontal direction. The heater 4 is mounted on the surface of the antenna 2 as shown in FIG. 3 in the first embodiment of the present invention.
[0019]
(Third embodiment)
A third embodiment of the present invention will be described with reference to FIG. FIG. 5 is a view showing a heater 4 according to a third embodiment of the present invention. In the third embodiment of the present invention, it is assumed that the polarization of the transmission radio wave is in a 45-degree direction ascending left. The arrangement direction of the heater wire 7 that has the least influence on the transmission radio wave is a direction orthogonal to the polarization. Therefore, as shown in FIG. 5, the heater wires 7 are arranged in a 45 ° direction that rises to the right. The heater 4 is mounted on the surface of the antenna 2 as shown in FIG. 3 in the first embodiment of the present invention.
[0020]
(Fourth embodiment)
A fourth embodiment of the present invention will be described with reference to FIG. FIG. 6 is a view showing a heater 4 according to a fourth embodiment of the present invention. In the fourth embodiment of the present invention, it is assumed that the polarization of the transmission radio wave is a circle. The arrangement direction of the heater wire 7 that has the least influence on the transmission radio wave is a direction orthogonal to the polarization. Accordingly, as shown in FIG. 6, the heater wires 7 are arranged concentrically. The heater 4 is mounted on the surface of the antenna 2 as shown in FIG. 3 in the first embodiment of the present invention.
[0021]
(Fifth embodiment)
A fifth embodiment of the present invention will be described with reference to FIG. FIG. 7 is a view showing a heater 4 according to a fifth embodiment of the present invention. The fifth embodiment of the present invention is characterized in that a hollow box 8 is provided on the surface of the antenna 2 and the air therein is heated by a heater element 9. The material of the hollow box 8 is a material that does not affect the radio wave propagation, and the installation position of the heater element 9 is a position that does not affect the radio wave propagation. As a result, the heater 4 that hardly affects the transmission and reception of the radio wave from the antenna 2 can be realized. In the fifth embodiment of the present invention, the hollow box 8 is made of plastic. A ceramic heater was used as the heater element.
[0022]
【The invention's effect】
As described above, according to the present invention, snow accumulation can be removed with a simple configuration. In particular, it is possible to realize a heater device that does not deteriorate the characteristics of radio waves. Furthermore, snow can be automatically removed. Therefore, it is possible to realize an on-vehicle radar device that can operate normally even during snowfall.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of an embodiment of the present invention.
FIG. 2 is a diagram showing a heater according to the first embodiment of the present invention.
FIG. 3 is a diagram showing a state in which a heater is mounted on an antenna.
FIG. 4 is a view showing a heater according to a second embodiment of the present invention.
FIG. 5 is a view showing a heater according to a third embodiment of the present invention.
FIG. 6 is a view showing a heater according to a fourth embodiment of the present invention.
FIG. 7 is a view showing a heater according to a fifth embodiment of the present invention.
FIG. 8 is a diagram illustrating a running example of a radar-equipped vehicle and a target vehicle during snowfall.
FIG. 9 is a diagram showing a mounting example of an antenna.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Oscillator 2 Antenna 3 Distance measurement part 4 Heater 5 Snow detection part 6 Switch circuit 7 Heater wire 8 Hollow box 9 Heater element

Claims (1)

An oscillator having an oscillating frequency of several tens of GHz band, an antenna transmitting the output of the oscillator as a radio wave toward the traveling direction of the vehicle and receiving a reflected wave of the radio wave, a transmission timing of the radio wave and a reception timing of the reflected wave And an arithmetic circuit for calculating the distance to the object in front of the vehicle from the time difference between the radar and the in-vehicle radar device,
An electric heater for heating snow accumulation on the antenna surface is provided ,
The electric heater is provided in close contact with the antenna surface and is formed of a material that does not affect radio wave propagation, and a hollow box made of a material that does not affect radio wave propagation. And a heater element for heating the air inside the
The arithmetic circuit includes means for detecting the level of the reflected wave having the extremely small time difference, and a switch for automatically energizing the electric heater when the level exceeds a predetermined value,
The on-vehicle radar device, wherein the means for detecting the level of the reflected wave includes means for detecting that the beat frequency of the received reflected wave is a beat signal frequency near zero frequency .

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