JP4049081B2 - Proximity sensor - Google Patents

Description

  The present invention relates to a proximity sensor that detects a change in a specific electromagnetic wave radiation space, and relates to a proximity sensor that detects a detection object at a short distance using a microwave having a use frequency of 300 MHz to 300 GHz.

  Generally, theremin circuits that use an oscillation frequency of about 200 KHz to 1 MHz convert a change in oscillation frequency when a human hand approaches the oscillator and an antenna that is a part of the oscillator into a change in sound. It is known as an electronic musical instrument.

  If this theremin circuit is used as a proximity sensor, a change in distance can be detected as a change in frequency.

  However, in a general theremin circuit, if a human body is present or is present nearby, the amount of change in the capacitor capacity of the person in the oscillator becomes a fluctuation in frequency, and the influence of the size of the person is greater. Even if the material of the object is changed or the size of the object is increased, the accuracy of the proximity sensor cannot be improved. And detection of short distances, such as a human body, becomes impossible because the electrostatic capacitance between an antenna and a human body acts largely.

  Therefore, in Japanese Patent Laid-Open No. 2001-4741, a microwave subjected to frequency modulation over a wide band is radiated, the reflected reception signal and the transmission signal of the microwave are mixed, and the frequency according to the microwave propagation distance is obtained. The reflected wave of the microwave radiated from the antenna having the phase is detected, and a beat signal for calculating the distance to the object is output from the mixer from the time until the reflected wave is received from the radiation. Multiplying and summing the beat signal and two orthogonal reference signals having a frequency corresponding to a predetermined distance, respectively, obtaining a ratio of the two sums, obtaining a signal corresponding to the phase of the beat signal from the ratio, and The temporal or spatial change of the signal corresponding to this phase is converted into the temporal change amount or the spatial change amount of the target distance.

As a result, in order to perform measurement using radio waves such as microwaves or sound waves, the signal representing the average distance can be stabilized without the beam width being affected by the distribution of the holes and minute irregularities in the reflector. Therefore, it is not necessary to perform an averaging process separately. Further, since the received signal can be processed at high speed, the detection speed can be increased.
JP 2001-4741 A

  In such a general frequency modulation continuous wave method (FMCW method) that detects the reflection of the microwave radiated from the antenna and calculates the distance to the object from the time from the reception of the reflected wave from the radiation, For example, a high frequency has to be used in order to increase the frequency shift (sweep) width and to ensure the sharpness of the frequency. However, when a high frequency of 100 GHz or higher that satisfies the condition is used, there is a problem that the apparatus becomes expensive.

  In particular, in the frequency modulation continuous wave system described in Japanese Patent Application Laid-Open No. 2001-4741, if the sweep frequency is 1.5 GHz and the sweep frequency time is 3 ms, the distance can be estimated based on a short beat cycle. However, since the absolute distance cannot be measured, for example, a method such as laser triangulation must be used in combination. As a result, the cost, the size of the apparatus, the reflecting surface, and the like can be restricted, and it is difficult to realize low cost.

  Further, in the two-frequency continuous wave method using the known Doppler effect, distance detection is impossible in principle when the detection target object in the electromagnetic wave radiation space is stopped. Further, the pulse Doppler method requires a pulse width of about 1 ps and cannot be realized at a low price.

  Therefore, an object of the present invention is to provide a proximity sensor that can be easily detected at a short distance and can be manufactured at low cost.

According to a first aspect of the present invention, there is provided a proximity sensor comprising an opening / closing body that is openably / closably attached to a vehicle, and the conductive member serving as an antenna at a frequency having a sufficiently short wavelength with respect to the size of the conductive member. An output oscillator for supplying microwaves to be radiated, and when there is a detection target in a detection region set outside the conductive member, cavity resonance between the conductive member and the detection target in the detection region An assumed circuit regarded as a circuit is formed, the frequency of the assumed circuit is obtained from the output oscillator, and the detection target in the detection region is detected as a change in the oscillation frequency of the output oscillator. .

  A frequency having a sufficiently short wavelength with respect to the size of the conductive member is supplied from the output oscillator to the conductive member, and microwaves are radiated using the conductive member as an antenna. When a microwave is radiated by using a conductive member as an antenna, when a detection target (dielectric material) approaches a region where the microwave is radiated, a cavity resonance circuit in which the conductive member and the detection target function as an antenna with each other An assumed circuit to be regarded is formed, and the electric field of the electromagnetic wave radiated from the conductive member is reflected or absorbed by the detection target. In this assumption circuit, the electric field of the electromagnetic wave radiated from the conductive member is reflected or absorbed by the detection target, and the effect appears as a change in the output frequency of the output oscillator. Therefore, the detection target can be detected by detecting the shift of the oscillation frequency of the output oscillator and the amplitude of the specific frequency. The detection target is detected as a change in the frequency of the oscillation frequency of the output oscillator, a change in the amplitude of the frequency, the presence or absence of the detection target, the moving speed of the detection target, the size of the detection target, etc. Can be detected.

  Here, the object to be attached means an object to be attached to the proximity sensor, and the conductive member may be a conductor that can be integrated with or separated from the object to be attached, and the basic structure is a one-dimensional structure. It can be a body (mainly only in the length direction), a two-dimensional structure (mainly having only an area), or a three-dimensional structure.

  The output oscillator means a microwave oscillator that is easily drawn into the resonance condition on the output side, such as a dielectric oscillator or an LC oscillator. The reference oscillator that oscillates a stable microwave having a specific frequency is a stable microwave oscillator that does not change its own oscillation frequency due to external influences.

  The detection area is a range set outside the conductive member and is determined by the wavelength output of the conductive member and the microwave, but is usually set to an arbitrary distance within 50 cm, preferably within 30 cm. Is done.

As described above, when microwaves are radiated from a conductive member, when the detection target approaches the microwave, it is considered that the conductive member and the detection target are regarded as a cavity resonance circuit that functions as an antenna. A circuit is formed. Here, in the present invention, a two-dimensional region in which the electric field of the electromagnetic wave output from the output oscillator and radiated from the conductive member is reflected or absorbed by the detection target is the detection region, and the detection region is the tertiary. The electromagnetic radiation space is the three-dimensional space where microwaves are radiated.
Further, the conductive member that can be integrated with or separated from the attachment object is an opening / closing body that can be freely opened and closed with respect to the vehicle. Therefore, the structure can be simplified and can be manufactured at low cost.

According to a second aspect of the present invention, there is provided a proximity sensor comprising an opening / closing body that is openably / closably attached to a vehicle, and the conductive member serving as an antenna at a frequency having a sufficiently short wavelength with respect to the size of the conductive member. An output oscillator that supplies a microwave to be radiated, a mixer that obtains a frequency output from the output oscillator and mixes the frequency obtained from a reference oscillator, and a frequency that is selected and detected by the mixer. And a recognition circuit for recognizing a change in the detection target in the detection region set outside the conductive member.

  A frequency having a sufficiently short wavelength with respect to the size of the conductive member is supplied from the output oscillator to the conductive member, and microwaves are emitted using the conductive member as an antenna. When microwaves are radiated using a conductive member as an antenna, when a detection target approaches the conductive member and the detection target, the conductive member and the detection target form a circuit that is regarded as a cavity resonance circuit that functions as an antenna. The electric field of the electromagnetic wave output from the output oscillator and radiated from the conductive member is reflected or absorbed by the detection target. Due to the presence of the detection target, the electric field of the electromagnetic wave radiated from the conductive member is reflected or absorbed by the detection target, and the influence appears as a change in the output frequency of the output oscillator. The change of the output frequency of the output oscillator is mixed with the frequency obtained from the reference oscillator by the mixer, down-converted, and the deviation of the frequency passed through the mixer and the change of the amplitude of the frequency are confirmed by the recognition circuit. Thus, the presence / absence of the detection target, the moving speed of the detection target, the size of the detection target, and the like are detected.

  Here, the attachment object, the output oscillator, and the detection region are the same as those in the first aspect, and the same applies to the electromagnetic wave radiation space. The mixer mixes the obtained frequency (f) with the frequency (fo) obtained from the reference oscillator, and sets the down-converted mixing frequency (mf + nfo; where m and n are integers from −∞ to + ∞). Anything is acceptable. Further, the bandpass filter extracts only one frequency (| f + fo | or | f-fo |) of the mixing frequencies (| f + fo |, | f−fo |) mixed by the mixer, It may be either one that performs signal processing before the detector or one that performs signal processing after passing through the detector. Further, the recognition circuit normally recognizes a change in the detection region, which is the electromagnetic wave radiation space, as a change in oscillation frequency (frequency shift through the mixer, amplitude change in the frequency, etc.) The distance, size, and the like of the detection target are linearly detected by comparing with a deviation of a reference frequency corresponding to a known distance, size, etc., and a change in amplitude of the frequency. As a shift of the frequency passed through the mixer and a change in the amplitude of the frequency, the moving speed can be detected by introducing a temporal element. This recognition circuit only needs to be composed of an analog circuit or a digital circuit. Specifically, the map includes an F-V converter, an FFT, a memory, and the like, and has a map that stores a frequency shift that has passed through the mixer, an amplitude change of the frequency, and the like. It is judged by comparing with the information. Further, if the frequency that is passed through the mixer is limited, a binary output can be obtained between a predetermined threshold and the presence or absence of the passage of the frequency.

  Since the output oscillator of the proximity sensor according to the third aspect is a dielectric oscillator (DRO) or an LC oscillator, it becomes an oscillator that generates microwaves at low cost and can be expected to operate accurately.

  The proximity sensor according to claim 1 has a cavity resonance between the conductive member and the detection target in the detection region when the detection target is within the detection region set outside the conductive member attached to the mounting target. A microwave that radiates the conductive member as an antenna at a frequency sufficiently short in wavelength with respect to the size of the conductive member is formed as an assumed circuit that is regarded as a circuit. Obtained from the output oscillator to be supplied and detects the deviation, amplitude and the like of the oscillation frequency of the output oscillator.

  Therefore, the electric field of the electromagnetic wave radiated from the conductive member that forms an assumed circuit that is regarded as a cavity resonance circuit is reflected or absorbed by the detection target, and the effect thereof is a change in the output frequency of the output oscillator. Therefore, by detecting the frequency shift of the oscillation frequency of the output oscillator and the change in the amplitude of the frequency, the presence / absence of the detection target, the moving speed of the detection target, the size of the detection target, etc. are detected. be able to.

  Even if a proximity sensor is configured using a known Theremin circuit, if the distance to the detection target is short from the wavelength, the capacitance of the capacitor between the conductive member functioning as an antenna and the ground However, the present invention is regarded as a microwave cavity resonance circuit corresponding to the relative distance between the object to be detected and the conductive member functioning. Therefore, the mutual influence of the electric field / magnetic field of the electromagnetic wave becomes larger, and it becomes difficult to be affected by the capacitance of the object to be detected in the electromagnetic wave radiation space, so that the detection accuracy is improved. In addition, the use of microwaves having a frequency of 300 MHz to 300 GHz enables detection that is not affected by the atmosphere such as humidity, temperature, water vapor, pressure, etc. of the electromagnetic wave radiation space, so that the apparatus is inexpensive.

In addition, since the conductive member is an opening / closing body that can be freely opened and closed with respect to the vehicle, the structure can be simplified and can be manufactured at low cost.
Therefore, it is easy to detect a short distance, and it is possible to detect a short distance state that can be manufactured at low cost.

  The proximity sensor according to claim 2 has a cavity resonance between the conductive member and the detection target in the detection region when the detection target is in a detection region set outside the conductive member attached to the mounting target. A microwave that radiates the conductive member as an antenna at a frequency sufficiently short in wavelength with respect to the size of the conductive member is formed as an assumed circuit that is regarded as a circuit. The frequency obtained from the output oscillator to be supplied is mixed with the frequency obtained from the reference oscillator by a mixer, a specific frequency is selected and detected from the mixed frequency, and the recognition circuit uses the signal of the detected frequency to detect the conductivity. The change of the detection target in the detection region set outside the sex member is detected.

  Therefore, the electric field of the electromagnetic wave radiated from the conductive member forming the assumed circuit regarded as the cavity resonance circuit is reflected or absorbed by the detection target, and the influence appears as a change in the output frequency of the output oscillator. From the detection circuit, the frequency shift of the oscillation frequency of the output oscillator and the change in the amplitude of the frequency are detected so that the presence / absence of the detection target, the moving speed of the detection target, the size of the detection target, etc. Can be detected.

  Even if a proximity sensor is configured using a known Theremin circuit, a detection target is detected as a capacitor capacity between a conductive member functioning as an antenna and a ground, and a distance accuracy error increases. This creates a circuit that is regarded as a microwave cavity resonance circuit corresponding to the relative distance between the object to be detected and the conductive member that functions, and the influence of the electric and magnetic fields of the electromagnetic wave is greater. Thus, the detection accuracy is improved because the detection target capacitance in the electromagnetic wave radiation space is hardly affected. In addition, the use of microwaves having a frequency of 300 MHz to 300 GHz enables detection that is not affected by the atmosphere such as humidity, temperature, water vapor, pressure, etc. of the electromagnetic wave radiation space, so that the apparatus is inexpensive.

Further, since the conductive member that can be integrated with or separated from the attachment target is an opening / closing body that can be freely opened and closed with respect to the vehicle, the structure can be simplified and can be manufactured at low cost.
Therefore, it is easy to detect a short distance, and it is possible to detect a short distance state that can be manufactured at low cost.

  In the proximity sensor according to claim 3, since the output oscillator according to claim 1 or 2 is a dielectric oscillator or LC oscillator, the oscillator itself is inexpensive, and as a result, the apparatus is inexpensive. it can.

  Next, a proximity sensor according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a conceptual diagram of the overall configuration of a vehicle equipped with a proximity sensor according to an embodiment of the present invention, and FIG. 2 is a functional block diagram of the proximity sensor according to the embodiment of the present invention.

  In FIG. 1, the antenna terminals of the output oscillator 21 are electrically connected to the power supply / reception points on the outer panels 11 to 14 of the doors of the vehicle 1 so that the outer panels 11 to 14 of the doors function as antennas. It has become. The outer panels 11 to 14 constitute a conductive member that is integrally or separably attached to the vehicle 1 that is an attachment target of the present embodiment.

  In this embodiment, the case where the outer panels 11 to 14 of the doors of the vehicle 1 to be attached are antennas will be described. However, the front and rear bumpers, trunk lids, bonnets and the like to be attached are described. Can also be used in the same manner as the outer panels 11-14.

  The output of the proximity sensor 10 is input to the electronic control circuit 2. In this embodiment, the electronic control circuit 2 is composed of a microcomputer that executes obstacle detection of the door opening / closing system. When the door is opened / closed, the door can be opened / closed safely, or there is no obstacle. If a person or a structure is detected, the opening / closing of the door is stopped and an alarm sound is generated in the vehicle 1.

  The output oscillator 21 is an oscillator that oscillates a microwave having a frequency of 300 MHz to 300 GHz. The output oscillator 21 radiates microwaves from the outer panels 11 to 14 functioning as antennas, and is set in the detection regions 11A to 11A set on the outer periphery of the outer panels 11 to 14. In 14A, it is determined whether or not a detection target 27 such as a person or an object to be detected exists. The detection regions 11A to 14A are set outside the distance corresponding to the half wavelength of the frequency of the radiated microwave with respect to the outer panels 11 to 14.

  Specifically, the output oscillator 21 is a dielectric oscillator (DRO) or an LC oscillator that easily changes to an external factor that does not have a PLL circuit or the like because the oscillation frequency is likely to change due to an external factor. Is. The antenna terminal of the output oscillator 21 is electrically connected to the power supply / reception points of the outer panels 11 to 14. Therefore, the output oscillator 21 can obtain a change in wavelength, that is, a shift in the frequency of the oscillation frequency of the output oscillator 21, a change in the amplitude of the frequency, and the like according to a change in the state of the detection regions 11A to 14A.

  Here, frequency changes such as a shift in the frequency of the oscillation frequency of the output oscillator 21 and a change in the amplitude of the frequency according to the state change of the output oscillator 21 and the detection regions 11A to 14A will be described.

  The outer panels 11 to 14 receive microwaves from the output oscillator 21 and radiate microwaves outward of the outer panels 11 to 14. When the detection target 27 such as a person or an object exists in the detection regions 11A to 14A by radiating this microwave, the electric field of the electromagnetic wave radiated from the outer panels 11 to 14 is reflected or absorbed by the detection target 27, and the influence thereof. Appears as a change in the output frequency of the output oscillator 21. That is, the region where the detection target 27 is detected by the outer panels 11 to 14 functions as the resonance circuit 31. Here, depending on whether or not the detection target 27 such as a person or an object exists in the detection regions 11A to 14A, It will have countless resonance frequencies. The output oscillator 21 has a plurality of resonance frequencies of about 2 to 3 when viewed as the embodied structural device, that is, the microwave generator 32.

  Here, when the resonance circuit 31 and the microwave generator 32 are connected together, the oscillation frequency is close to the oscillation circuit 31 and the oscillation frequency of the resonance circuit 31 attracts the oscillation frequency of the output oscillator 21. Both will oscillate at one particular resonant frequency in common.

  That is, the resonance circuit 31 that radiates microwaves using the outer panels 11 to 14 as antennas and the microwave generator 32 that includes the output oscillator 21 that outputs a frequency having a sufficiently short wavelength with respect to the size of the outer panels 11 to 14 are common. As a result, an assumed circuit 33 having a specific resonance frequency is formed. The electric field of the electromagnetic wave output from the output oscillator 21 and radiated from the outer panels 11 to 14 is reflected or absorbed by the detection target 27. Due to the presence of the detection target 27 in the detection circuit 33, the electric field of the electromagnetic wave radiated from the outer panels 11 to 14 is reflected or absorbed by the detection target 27, and the influence thereof is a change in the output frequency of the output oscillator 21. appear. The state of the detection target 27 can be detected by detecting the deviation of the oscillation frequency of the output oscillator 21 and the amplitude of the specific frequency. The detection of the detection target 27 is performed by detecting the frequency change such as the frequency shift of the oscillation frequency of the output oscillator 21 and the change of the frequency amplitude, and the presence / absence of the detection target 27 and the moving speed of the detection target 27. The size of the detection object 27 can be obtained.

  As described above, when microwaves are radiated using the outer panels 11 to 14 as antennas, when the detection target 27 approaches the cavity resonant circuit, the outer panels 11 to 14 and the detection target 27 function as antennas. As a result, the circuit 33 is formed. In this detection circuit 33, the detection regions 11 </ b> A to 14 </ b> A are output from the output oscillator 21, and the electric field of the electromagnetic wave radiated from the outer panels 11 to 14 is reflected or absorbed by the detection target 27. The oscillation frequency shifts and the amplitude of the specific frequency becomes a two-dimensional region where there is a reaction. Similarly, the electromagnetic wave radiation space is a three-dimensional space where microwaves are radiated in which the detection regions 11A to 14A are three-dimensionally captured. Therefore, the detection areas 11A to 14A and the electromagnetic wave radiation space for explaining the embodiment of the present invention mean areas where the detection object 27 can be detected.

  On the other hand, the reference oscillator 22 whose output frequency is hardly changed by a PLL circuit or the like is an oscillator that oscillates a stable microwave having a specific frequency (fo) that is not affected by a change in the state of the electromagnetic wave radiation space. This is the reference frequency (fo) for down-converting the output frequency of the output oscillator 21 by the mixer 23.

  The mixer 23 mixes and down-converts the frequency (f) obtained from the output oscillator 21 and the frequency (fo) obtained from the reference oscillator 22. Specifically, the mixer 23 performs mixing frequency ( mf + nfo; provided that m and n are integers from −∞ to + ∞. The bandpass filter 24 is a filter that selects a specific mixing frequency (| f + fo |) from the mixing frequency (mf + nfo) in the present embodiment, and the detector 25 calculates the frequency that has passed through the bandpass filter 24. This circuit detects only the amplitude of a predetermined frequency. Since the band-pass filter 24 and the detector 25 need only demodulate a specific mixing frequency (f + fo), the signal processing of the band-pass filter 24 and the detector 25 is performed when the present invention is implemented. There is no question of the order. As a result, the frequency change may be mixed by the reference oscillator (fo), a specific frequency is extracted through the band pass filter 24, the extracted frequency is detected by the detector 25, and converted into an amplitude change.

  Further, the recognition circuit 26 recognizes the change in the electromagnetic wave radiation space by the frequency signal that has passed through the detector 25 that detects the frequency signal that has passed through the band-pass filter 24, and identifies the contents thereof. The detected frequency shift (shift) and the change in amplitude (voltage) of the specific frequency are determined based on the frequency shift corresponding to the distance and size of the detection target 27 such as a person or an object, and the specific frequency amplitude in advance. And detecting by estimating the distance, size, and moving speed from the frequency deviation and the reference voltage. Therefore, specifically, it has a memory map that is composed of an FV converter, FFT, etc., and a memory, and stores the frequency shift passed through the mixer 23, the amplitude change of the frequency, etc. Therefore, the change of the electromagnetic wave radiation space is determined by comparing with the information of the memory map. However, the band of the band pass filter 24 is narrowed, and the frequency (signal) that passes through the band pass filter 24 when the detection target 27 such as a person does not exist in the detection regions 11A to 14A that are the electromagnetic wave radiation spaces and when it exists. ) Can be detected by binary (ON, OFF).

  In the directional coupler 28, the output of the output oscillator 21 depends on the state change of the detection regions 11 </ b> A to 14 </ b> A that are the electromagnetic wave radiation spaces, and the output frequency changes. Therefore, only the changing frequency component is input to the mixer 23. However, the output of the reference oscillator 22 is not affected.

  The output oscillator 21, the reference oscillator 22, the mixer 23, the band pass filter 24, and the detector 25 that constitute the proximity sensor 10 of the present embodiment are the outer panels 11 to 14 and the inner panels (illustrated) of each door of the vehicle 1. Not built in between.

  The output of the proximity sensor 10 is input to the electronic control circuit 2. In this embodiment, the electronic control circuit 2 is a microcomputer that executes an obstacle detection device of a door opening / closing system.

  That is, at this time, frequency deviation and frequency amplitude information such as a person, an object, and their size are compared with reference to frequency deviation and amplitude information based on the information inside the recognition circuit 26. Thus, the distance to the detection target 27, the size of the detection target 27, and the moving speed of the detection target 27 are estimated and determined. According to this method, it is possible to distinguish a change during the automatic opening / closing operation of the door of the vehicle 1 from an approach to a person or an object. For example, when the electronic control circuit 2 opens and closes the door, the electronic control circuit 2 determines whether the door can be opened and closed safely or whether there is an obstacle, and stops the opening and closing of the door when a person or a structure is detected. An alarm sound can be generated in the inside.

  The proximity sensor of the present embodiment configured as described above operates as follows.

  The output of the output oscillator 21 radiates microwaves from the outer panels 11 to 14 to the electromagnetic wave radiation space using the outer panels 11 to 14 of the doors of the vehicle 1 as antennas. At this time, the outer panels 11 to 14 and the detection target 27 form an assumption circuit 33 that is regarded as a cavity resonance circuit that functions as an antenna. The output of the assuming circuit 33 regarded as the cavity resonance circuit appears at a frequency (f) obtained from the output of the output oscillator 21 as one frequency change. The obtained frequency (f) and the frequency (fo) obtained from the reference oscillator 22 are mixed with the frequency obtained from the reference oscillator 22 by the mixer 23, down-converted, and the frequency shift passed through the mixer 23. Then, by confirming the change in the amplitude of the frequency with the recognition circuit 26, the presence / absence of the detection target 27, the moving speed of the detection target 27, the size of the detection target 27, and the like are detected.

  In this way, since it is possible to form an assuming circuit 33 that is regarded as a microwave cavity resonance circuit corresponding to the relative distance between the detection object 27 and the outer panels 11 to 14, it is possible to form a microwave electric field / magnetic field. The mutual influence is larger than the influence of the capacitance of the detection target 27 and can be regarded as the resonance circuit 31 of the electric field strength (magnetic field) between the outer panels 11 to 14, and the electrostatic detection of the detection target 27 in the electromagnetic wave radiation space. Less susceptible to capacity.

  Even if microwaves are radiated from the outer panels 11 to 14 when the frequency of the output oscillator 21 is not detected, the frequency fluctuation of the output oscillator 21 does not occur if the detection target 27 that causes reflection or absorption is not in the electromagnetic wave radiation space.

  However, when the detection target 27 such as a person approaches the outer panels 11 to 14, the microwave electric field is reflected or absorbed by the detection target 27, and the state of the electromagnetic wave radiation space changes. At this time, the frequency component (wavelength component) corresponding to the distance from the detection target 27 of the reflected wave returned to the outer panels 11 to 14 is a frequency close to the frequency of the output oscillator 21 output from the outer panels 11 to 14. Formally, there are two types of frequencies, but in reality, they are coupled to each other, and the frequency of the resonance phenomenon changes to one frequency (f). The frequency change is introduced into the mixer 23 by the output frequency (fo) of the reference oscillator 22, and the frequency mixed by the mixer 23 becomes a mixing frequency (| f + fo |) and a mixing frequency (| f-fo |). The mixing frequency (| f + fo |, | f−fo |) from the mixer 23 is extracted through the band pass filter 24 by taking out the frequency of the fluctuation difference, that is, the mixing frequency (f + fo) or the mixing frequency (f−fo). The mixing frequency (f + fo) or the mixing frequency (f−fo) is detected by the detector (S curve characteristic device) 25, and the amplitude of the mixing frequency (f + fo) or the mixing frequency (f−fo) is detected. By confirming the deviation of the mixing frequency (f + fo) or the mixing frequency (f−fo) passed through the mixer 23 and the change in the amplitude of the frequency with the recognition circuit 26, the presence / absence of the detection target 27, the detection target The moving speed of 27, the size of the detection object 27, and the like are detected.

  Since the output oscillator 21 used in the present embodiment is a dielectric oscillator that oscillates a microwave with a use frequency of 300 MHz to 300 GHz, the microwave can be generated at low cost, and the entire apparatus is inexpensive. Can be.

  Further, the antenna of the present embodiment is an outer panel 11 to 14 of the door of the vehicle 1. In particular, if the door of the vehicle 1 is an antenna, it can be used as a sensor for a security system, a keyless entry system or the like, and the electromagnetic radiation space is set within 100 cm to 30 cm from the outer panel 11 to 14 of the door of the vehicle 1. You can also.

  Therefore, in this embodiment, the electronic control circuit 2 that inputs the output of the recognition circuit 26 is composed of a microcomputer that executes obstacle detection of the door opening / closing system, and can the door be opened and closed safely when the door is opened and closed? It is also possible to determine whether or not there is an obstacle, and when a person or structure is detected, the door can be opened and closed, and an alarm sound can be generated in the vehicle 1.

  In addition, when combined with a known smart key, the driver of the vehicle 1 can open the door by approaching the vehicle 1, but at this time, for example, a person is hidden behind the door on the driver side. If it is detected by the electronic control circuit 2, the driver can be warned, and if necessary, the driver's door should not be opened, You can also alarm. Of course, it is also possible to open only the driver's side door, speed up the driver's boarding, and lock all the doors. That is, it is possible to determine that there is a third party near the vehicle 1 by distinguishing it from the owner of the smart key, and warn the driver. In addition, by distinguishing from the smart key, the door can be opened without a key operation when a person approaches and can be closed when the person leaves.

  Since the present invention enables detection of a short distance of the detection object 27 without being affected by the atmosphere such as humidity, temperature, water vapor, pressure, etc. of the electromagnetic wave radiation space, not only a sensor such as a security system or a keyless entry system. Even if the weather conditions such as humidity change in the air in the natural world change, it is not affected by it, so it can be used as a sensor for detecting various short distances.

  In addition, even when attached to the vehicle 1, when the detection target 27 is bounced by the front bumper during traveling, it is highly likely that the detection target 27 will be placed on the hood by detecting it with the proximity sensor of the present embodiment. The bonnet can be lifted and softly landed in the form of a bonnet. Alternatively, the airbag can be actuated on the bonnet.

  And it can use also as a back sonar by attaching the proximity sensor of this Embodiment to a back bumper.

  Furthermore, the proximity sensor according to the present embodiment can be used for controlling the raising and lowering of the headrest and the like by detecting the presence / absence of the seating and the posture of the seating by being disposed on the vehicle seat.

FIG. 1 is a conceptual diagram of the overall configuration of a vehicle equipped with a proximity sensor according to an embodiment of the present invention. FIG. 2 is a functional block diagram of the proximity sensor according to the embodiment of the present invention.

Explanation of symbols

1 Vehicle 11-14 Outer panel (conductive member)
11A to 14A Detection area 21 Output oscillator 22 Reference oscillator 23 Mixer 24 Bandpass filter 25 Detector 26 Recognition circuit 27 Object to be detected 33 Look-up circuit regarded as a cavity resonance circuit

Claims (3)

A conductive member comprising an opening / closing body that is attached to the vehicle so as to be freely opened and closed;
An output oscillator that supplies a microwave that radiates the conductive member as an antenna at a frequency with a sufficiently short wavelength with respect to the size of the conductive member;
When there is a detection target in the detection region set outside the conductive member, an assumed circuit that is regarded as a cavity resonance circuit is formed between the conductive member and the detection target of the detection region, A proximity sensor, wherein the frequency of the detection circuit is obtained from the output oscillator, and the detection target in the detection region is detected as a change in the oscillation frequency of the output oscillator. A conductive member comprising an opening / closing body that is attached to the vehicle so as to be freely opened and closed;
An output oscillator for supplying a microwave that radiates the conductive member as an antenna at a frequency having a sufficiently short wavelength with respect to the size of the conductive member;
A mixer for mixing the frequency output from the output oscillator and the frequency obtained from a reference oscillator;
A proximity sensor comprising: a recognition circuit that selects a frequency mixed by the mixer and recognizes a detection target in a detection region set outside the conductive member based on a detected frequency signal. The proximity sensor according to claim 1, wherein the output oscillator is a dielectric oscillator or an LC oscillator.

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