JP2008122188A - Vehicle radar device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle radar device capable of improving design flexibility and endurance reliability by resolving performance degradation due to variations among shapes of flat reflectors. <P>SOLUTION: In the vehicle radar device, a flat reflector 1 having a plurality of parallel straight line conductors forming a slit permits electromagnetic waves to reflect/pass through it by selecting them based on the deflection direction. The electromagnetic waves reflected from the flat reflector 1 is received by a parabolic reflector 4, undergoing deflection twist reflection, and radiated through the flat reflector. The flat reflector is made of a metal plate with a plurality of straight line conductors. The straight line conductors may also be arranged in a grid form. The flat reflector is installed in the inside or outside of a cover being spaced from the cover. Accordingly, the performance, durability, and design flexibility are improved. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a vehicular radar apparatus, and more particularly to an antenna apparatus that scans a beam irradiation direction.

  A conventional vehicular radar device is used to monitor the surroundings of a host vehicle, irradiates the surroundings of the host vehicle with electromagnetic waves, and receives reflected waves from the obstacles if there are obstacles. It detects the distance, relative speed, and direction to obstacles around the vehicle.

  For example, in the radar apparatus described in Patent Document 1, a planar reflecting mirror that is configured by a large number of parallel linear conductors formed by plating or the like on the cover of the radar apparatus, and reflects or transmits electromagnetic waves according to the deflection direction. 1 is provided. The electromagnetic wave from the primary radiator 2 is radiated toward the plane reflecting mirror 1, and is reflected from there toward a paraboloid reflecting mirror having a deflection torsion reflecting means. In the parabolic reflecting mirror, the electromagnetic wave is reflected toward the planar reflecting mirror again by changing the deflection direction by the deflecting torsion reflecting means. The electromagnetic wave whose polarization direction has been changed passes through the plane reflecting mirror 1 and is radiated to the target area. In order to scan the target area, a driving device 5 is also provided which changes the radiation direction of the electromagnetic wave by driving the parabolic reflecting mirror 4.

JP 2001-217646 A

  In the conventional radar apparatus, the linear conductor constituting the plane reflecting mirror is integrally formed on the inner surface of the cover by plating or the like. In conventional vehicle radar devices, the cover is made of a resin molded product such as plastic, so it is difficult to ensure flatness. This decrease in flatness is caused by the line width and pitch when the linear conductor is plated on the cover. These factors cause variations, and these factors such as a decrease in flatness of the plane reflecting mirror and variations in the conductor line width and pitch have greatly reduced the performance of the vehicle radar device.

  In addition, when a planar reflecting mirror is configured by plating the inner surface of the cover as in a conventional vehicle radar device, the arrangement and shape of the cover are fixed due to restrictions on the reflection position, etc., and the degree of freedom in structural design is low. There was a problem.

  In addition, as a planar reflecting mirror, a resin film in which a linear conductor is formed integrally with a cover and a film in which a film is adhered to a cover by welding or using an adhesive have been proposed. In addition to the difficulty of securing the degree, the manufacturing process is complicated and it is difficult to set stable manufacturing conditions, and it is impossible to use the same material for the cover resin and film resin. Due to the difference in expansion coefficient, there is a risk that the film will crack or peel off from the cover.

  Therefore, an object of the present invention is to eliminate a reduction in radar performance due to variations in the shape of a plane reflecting mirror and the size of a straight conductor, and to improve the degree of freedom in structural design and durability reliability. Is to provide a device.

  A vehicle radar device according to the present invention includes a planar reflector that selectively reflects or transmits electromagnetic waves according to a deflection direction, a primary radiator that radiates electromagnetic waves toward the planar reflector, and electromagnetic waves from the planar reflector. A parabolic reflector that has a deflecting torsion reflecting means for receiving and changing the deflection direction and reflecting the electromagnetic wave whose deflection direction has been changed by the deflecting torsion reflecting means toward the flat reflecting mirror and transmitting the flat reflecting mirror; The parabolic reflecting mirror is driven to change the radiation direction of the electromagnetic wave, and the planar reflecting mirror is a metal plate having a plurality of linear conductors.

  According to the present invention, since the planar reflecting mirror is formed of a thin sheet metal, it is possible to improve the flatness accuracy of the planar reflecting mirror, which has been difficult with the conventional vehicle radar apparatus, and the line width of the linear conductor of the planar reflecting mirror, Since variations in pitch can also be reduced, performance variations in the vehicle radar device can be reduced. In addition to improving the durability and reliability of the flat reflector, the degree of freedom in cover arrangement and vehicle radar structure design is increased.

Embodiment 1 FIG.
1 to 8 show a vehicular radar apparatus of the present invention. 1 to 3, a vehicular radar apparatus includes a plane reflecting mirror 1 that selectively reflects electromagnetic waves according to a deflection direction, a primary radiator 2 that radiates electromagnetic waves toward the plane reflecting mirror 1, and a plane reflecting mirror. The deflecting torsion reflecting means 3 that receives the electromagnetic wave reflected from 1 and changes the deflection direction is reflected. The deflecting torsion reflecting means 3 reflects the electromagnetic wave whose polarization direction has been changed, and transmits it through the plane reflecting mirror 1 for radiation. The object reflecting mirror 4 and a driving device 5 that drives the parabolic reflecting mirror 4 and changes the radiation direction of the electromagnetic wave are provided.

  The vehicular radar apparatus also includes a housing 6 that houses and supports the above-described components. The housing 6 includes a housing body 7 and a cover 8 made of a dielectric material such as plastic.

  The planar reflecting mirror 1 is a planar conductive metal plate such as stainless steel as shown in FIGS. 2 and 4, and has a large number of parallel linear conductors 10 inside the frame 9. Slits 11 are formed and supported by the cover 8 at the four corners of the frame 9. In the illustrated example, a round hole 12 is provided in the frame 9, and the tip of a stepped projection 13 provided on the inner surface of the cover 8 is inserted into the round hole 12, and the protruding tip is rivet-shaped by heat caulking or the like. The head 14 is fixed to the cover 8. If the plane reflecting mirror 1 and the cover 8 come into contact with each other on the surface, vibration noise (sound) may be generated due to vibrations when the vehicle is mounted on the surface. It is.

  The straight conductor 10 is formed by, for example, a process combining plating and etching, and is a multi-band conductor having the same interval and width and being parallel to each other, and the slit 11 having the same interval and width is formed therebetween. Therefore, the plane reflecting mirror 1 is a reflecting mirror for realizing selective reflection according to the deflection direction of the electromagnetic wave.

  In the plane reflecting mirror 1, among the radiated electromagnetic waves from the primary radiator 2 that radiates linearly polarized waves, the polarized waves parallel to the linear conductor 10 of the plane reflecting mirror 1 are totally reflected by the plane reflecting mirror 1. On the other hand, the polarized wave perpendicular to the linear conductor 10 of the plane reflecting mirror 1 is transmitted through the slit 11 between the linear conductors 10 of the plane reflecting mirror 1 and radiated to the space. The plane reflecting mirror 1 realizes polarization selective reflection in this way.

  FIG. 4 shows an enlarged detailed view of a metal plate having a straight conductor 10 and a slit 11 for realizing the function of the plane reflecting mirror 1 and its slit pattern. The flat reflecting mirror 1 is made of a non-magnetic material such as SUS, Cu, Al, etc., and its flatness is preferably 0.1 mm or less in consideration of radar performance. Further, the sheet thickness is preferably thin so as not to affect the radar performance. However, in the illustrated example, the sheet thickness is set to 0. 0 in consideration of the conductor line width and slit width accuracy, flatness, sheet metal rigidity, and the like. It was 3 mm. Since the slit 11 of the plane reflecting mirror 1 can be formed by a metal etching process, there is an advantage that an inexpensive and highly accurate object can be stably manufactured as compared with the conventional resin plating process. In FIG. 4, p represents the pitch of the slits 11, and W represents the width of the straight conductor 10.

  The plane reflecting mirror 1 reflects the polarized wave (horizontal polarized wave) parallel to the straight conductor 10 and transmits the polarized wave selective reflection (vertical polarized wave) to maximize the efficiency of polarization selective reflection. The line width of 10 and the width of the slit 11 are selected.

Shows the reflection coefficient Rh ² conductors slit and polarization parallel (horizontally polarized wave) to the following equation. However, P: slit pitch, L: slit width, λ: spatial wavelength of electromagnetic wave.

Rh ² = 1 / {1 + [(2P / λ) ln [cos (πL / 2P)]}

Further, the reflection coefficient Ry ² of the polarization perpendicular to the conductor slit (vertical polarization) is expressed by the following equation.

Ry ² = [(2P / λ) ln [sin (πL / 2P)] / {1 + [(2P / λ) ln [sin (πL / 2P)]]}

  FIG. 5 is a graph showing the reflection coefficient of vertical and horizontal polarization in the 76 GHz band when the width of the slit 11 is fixed at L = 0.15, 0.2, and 0.3 mm and the slit pitch P is changed. It is. FIG. 6 is a graph showing the reflection coefficient of vertical and horizontal polarization in the 76 GHz band when the slit pitch is fixed to P = 0.3, 0.4, 0.4, and 1.0 mm and the slit width L is changed. It has become. 5 and 6, the polarization parallel to the straight conductor 10 (horizontal polarization) is totally reflected, and the reflectance of the polarization perpendicular to the slit (vertical polarization) is kept small, that is, the transmittance of the vertical polarization is reduced. In order to increase it, it was necessary to set the relationship of L / P in the vicinity of 0.5. Therefore, in the present invention, L / P was set to 0.5.

  The parabolic reflecting mirror 4 of the vehicular radar apparatus has a structure as shown in FIGS. 7 and 8, and has a deflecting torsion reflecting means 3 that changes the deflection direction in response to the electromagnetic wave reflected from the planar reflecting mirror 1. The reflecting means 3 reflects the electromagnetic wave whose polarization direction has been changed toward the plane reflecting mirror 1 and transmits it through the plane reflecting mirror 1 to radiate it in the direction to be scanned by the radar apparatus.

  The parabolic reflecting mirror 4 includes a dielectric 17 having a uniform thickness having first and second paraboloids 15 and 16 and a first parabolic surface 15 on the first paraboloid 15 as the deflection torsion reflecting means 3. A plurality of strip-shaped linear conductors 19 extending along the parabolic surface 15 and forming a plurality of slits 18 therebetween, and a linear conductor provided so as to cover the entire surface along the second parabolic surface 16. And a back conductor 20 that reflects electromagnetic waves transmitted through the dielectric 17 through a plurality of slits 18 between 19.

  Here, the linear conductor 19 of the parabolic reflecting mirror 4 is not strictly a straight line but is curved along the first parabolic surface 15. In addition, the linear conductor 10 and the slit 11 on the planar reflecting mirror 1 are projected onto the parabolic reflecting mirror 4 along the central axis of the parabolic reflecting mirror 4, and the shape is 45 around the central axis. ° Projected figure rotated. In other words, when the plane projection figure along the central axis (the traveling direction of the electromagnetic wave) of the parabolic reflector 4 of the linear conductor 19 is rotated by 45 °, it coincides with the shape of the linear conductor 10 of the plane reflector 1. I can say that.

  The linear conductor 19 and the back conductor 20 of the parabolic reflector 4 are respectively formed on the first and second paraboloids 15 and 16 of the dielectric 17 by plating or the like, and the distance between them is the dielectric 17. The phase difference of 90 ° is generated between the electromagnetic wave reflected by the straight conductor 19 and the electromagnetic wave reflected by the back conductor 20.

  When the polarization direction of the radiated electromagnetic wave of the vehicle radar apparatus is tilted 45 degrees to the left, the electromagnetic wave radiated from the primary radiator 2 with the right polarized wave of 45 ° is totally reflected by the linear conductor 10 of the plane reflecting mirror 1. The linear conductor 19 and the back conductor 20 of the paraboloidal reflector 4 arranged in a plane perpendicular to the traveling direction of the electromagnetic wave with respect to the linear conductor 10 of the plane reflecting mirror 1, that is, the deflected torsional reflecting means 3. As a result, the polarization direction is changed by 90 degrees to become a polarized wave inclined to 45 degrees to the left, and is transmitted through the plane reflecting mirror 1 and emitted into the air.

  The primary radiator 2 that radiates electromagnetic waves toward the plane reflecting mirror 1 is disposed at or near the mirror image position of the focal point of the parabolic reflecting mirror 4 by the plane reflecting mirror 1. In the illustrated example, the primary radiator 2 is attached to the housing main body 7 in the vicinity of the back of the central portion of the parabolic reflector 4, and the radiated electromagnetic wave is provided at the central portion of the parabolic reflector 4. It radiates | emits toward the front plane reflective mirror 1 through the formed opening 21. FIG.

  The parabolic reflecting mirror 4 can be changed in direction by a driving device 5 that changes the radiation direction of electromagnetic waves. That is, a rotation shaft 22 is provided in the vicinity of the center of gravity of the parabolic reflecting mirror 4, and the rotation shaft 22 is rotatably supported by the housing 6. The driving device 5 for changing the angle of the parabolic reflecting mirror 1 is a magnetic repulsive driving device in the illustrated example, and a pair of magnets 23 attached to the parabolic reflecting mirror 4 and the magnets 23 are used. And a pair of magnets 24 mounted on the housing 6 so as to face each other with opposite polarities, and coils 25 wound around the magnets 24, respectively. The two coils 25 are connected in series so that currents in opposite directions flow, and when energized, the respective magnetic repulsive forces between the magnets 23 and 24 are controlled in strength. The rotation direction of the parabolic reflector 4 is controlled by the direction of the current, and the rotation angle is controlled by the magnitude of the current.

  As described above, according to this embodiment, since the flat reflector is made of a thin sheet metal, the accuracy of flatness is improved, the line width and pitch variations of the straight conductor are reduced, and the performance variation of the vehicle radar device is reduced. To reduce. In addition to improving the durability and reliability of the flat reflector, the degree of freedom in cover arrangement and vehicle radar structure design is increased.

Embodiment 2. FIG.
In the plane reflecting mirror 26 shown in FIG. 9, the parallel straight conductors 27 are alternately connected to each other by the short connecting conductors 28 which are shifted in a staggered manner, and a plurality of relatively short slits 29 are arranged in a shifted manner. The overall structure is a brick pattern lattice structure (grid structure). Accordingly, the lengths of the plurality of parallelly arranged slits 29 of the plane reflecting mirror 26 which is a polarization selective reflecting mirror can be adjusted. The length G of the plurality of slits 29 is the electromagnetic wave that has passed through the plane reflecting mirror 26, and the length that shields the electromagnetic wave having the resonance frequency in the polarized wave (vertically polarized wave) perpendicular to the slit 29 is selected. To do. In FIG. 9, G represents the length of the slit 29, p represents the pitch of the slit 29, and W represents the width of the straight conductor 27. For example, in the case of an electromagnetic wave of 50 GHz, the speed of the electromagnetic wave is 3 × 10 ⁸ (m / s), so one wavelength is (3 × 10 ⁸ ) / (50 × 10 ⁹ ) = 0.006 (m). Therefore, at a half wavelength, the length is 0.006 / 2 = 0.003 (m), that is, 3 mm. By selecting the length G of the slit 29 to be 3 mm, it is possible to shield electromagnetic waves of 50 GHz or less out of polarized waves (vertically polarized waves) perpendicular to the slit 29 that are transmitted by the plane reflecting mirror 26.

  Thus, by making the plane reflecting mirror 26 have a grid structure, it is possible to realize a filter function that does not leak electromagnetic waves other than the desired frequency to the outside of the vehicle radar device or shields unnecessary electromagnetic waves from entering from the outside. In addition, since the straight conductors 27 of the flat reflecting mirror 26 are connected to each other by a large number of short connecting conductors 28, the rigidity of the flat reflecting mirror 26 formed of a thin plate such as SUS can be increased, and the slit resonance frequency can be increased.

Embodiment 3 FIG.
Various structures other than the example shown in FIG. 1 can be used as the structure for attaching the flat reflecting mirror 1 to the cover 8. For example, a push nut structure 31 as shown in FIG. 10 may be provided on a part of the frame 9 and fixed to the tip of the protrusion 13 extending from the cover 8, or the frame of the flat reflector 1 as shown in FIG. 9 may have a structure in which a long hole 32 is provided and fitted into the protrusion 13 of the cover 8 to absorb a difference in linear expansion due to the temperature of the cover 8 formed of resin and the flat reflector 1 formed of a metal plate. Further, the planar reflecting mirror 1 can be insert-molded into the cover 8 using LCP or the like as the material of the cover 8. Further, the planar reflecting mirror 1 does not need to be supported by the cover 8, and can be supported by the housing body 7, for example. Since such various mounting structures can be adopted, the degree of freedom in design is great.

Embodiment 4 FIG.
In the example shown in FIG. 12, the planar reflecting mirror 1 of the vehicular radar apparatus is supported on the outside of the cover 8 by a projection 13 provided to project forward from the outer surface of the cover 8. The protrusion 13 may have the same structure as that of the protrusion 13 shown in FIGS. Various support structures can be used if necessary. When the planar reflecting mirror 1 is provided outside the housing 6 as described above, the options are widened when designing the shape and shape of the housing 6 including the cover 8. For example, the cover 8 may be configured as a known dielectric lens (not shown) instead of a flat plate as in the illustrated example.

  In addition, the planar reflecting mirror 1 formed of a thin plate such as SUS is disposed at a half position of the focal point of the parabolic reflecting mirror 4 and formed as a part of the vehicle body radome, the front grille, or the bumper cover, or inside thereof. The components on the radar apparatus main body side such as the parabolic reflector 4 can be attached in association with the planar reflector 1.

It is a schematic sectional drawing which shows the radar apparatus for vehicles of this invention. It is a schematic sectional drawing in alignment with line AA of FIG. It is a schematic sectional drawing in alignment with line BB of FIG. It is a top view which shows the plane reflective mirror of the radar apparatus for vehicles of this invention. It is a graph showing the reflection coefficient of the vertical and horizontal polarized waves in the 76 GHz band when the slit pitch p is changed with the slit width L fixed. It is a graph showing the reflection coefficient of the vertical and horizontal polarized waves in the 76 GHz band when the slit width L is changed with the slit pitch p fixed. It is a schematic plan view which shows the parabolic reflector of the radar apparatus for vehicles of this invention. FIG. 8 is a schematic side cross-sectional view of the parabolic reflector of FIG. 7. It is a top view which shows another example of the plane reflective mirror of the radar apparatus for vehicles of this invention. It is a schematic sectional drawing which shows another example of the attachment structure of the plane reflective mirror of this invention. It is a schematic sectional drawing which shows another example of the attachment structure of the plane reflective mirror of this invention. It is a schematic sectional drawing which shows another example of the attachment position of the plane reflective mirror of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Planar reflector, 2 Primary radiator, 3 Deflection torsional reflection means, 4 Parabolic reflector, 5 Drive, 8 Cover, 9 Frame, 10 Straight conductor, 11, 29 Slit, 28 Connection conductor.

Claims (5)

A plane reflecting mirror that reflects or transmits electromagnetic waves according to the direction of deflection;
A primary radiator that radiates electromagnetic waves toward the plane reflector;
It has a deflecting torsion reflecting means that receives an electromagnetic wave reflected from the plane reflecting mirror and changes the deflection direction. The deflecting torsion reflecting means reflects the electromagnetic wave whose deflection direction has been changed, and transmits the electromagnetic wave through the planar reflecting mirror to radiate. A parabolic reflector,
In the vehicle radar apparatus provided with a driving device that drives the parabolic reflecting mirror and changes the radiation direction of the electromagnetic wave,
A radar apparatus for a vehicle, wherein the planar reflecting mirror is a metal plate having a plurality of straight conductors.   2. The planar reflecting mirror includes a frame and a plurality of linear conductors extending in a continuous manner from the frame and arranged in parallel to each other so as to form a slit therebetween. Vehicle radar system.   The plane reflecting mirror is provided with a connection conductor that adjusts the length of a plurality of slits arranged in parallel in order to transmit an electromagnetic wave having a predetermined frequency and cut off a noise power source having a frequency lower than the predetermined frequency. The vehicular radar apparatus according to claim 1 or 2.   4. The vehicular radar according to claim 1, wherein the planar reflecting mirror is attached to a cover surrounding the parabolic reflecting mirror so as to be separated from the cover inside the cover. 5. apparatus.   The vehicular radar apparatus according to any one of claims 1 to 3, wherein the planar reflecting mirror is attached to the outside of a cover surrounding the parabolic reflecting mirror.

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