JP2005121542A - Proximity sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a proximity sensor easy to detect a short distance and capable of manufacturing it economically. <P>SOLUTION: The microwave oscillator part 30 having an automatically controllable oscillation function for adjusting frequencies of the microwaves radiated by conductive outside panels 11-14 as an antenna with a specific frequency of sufficiently shorter waves to the size of the outside conductive panels 11-14 can detects a person of detecting object 27 in the detection regions 11A-14A set on the outside of the panels 11-14 attached integrally or separately to the vehicle 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a proximity sensor suitable for a vehicle or the like that detects a change in a specific electromagnetic radiation space that is used to detect a short-distance state, and uses a microwave with a use frequency of 300 MHz to 300 GHz. The present invention relates to a versatile proximity sensor.

  A conventional proximity sensor includes an oscillating means, a resonant means that resonates with a harmonic of the oscillation frequency of the oscillating means, a detection electrode connected to the resonant means, and an electrostatic capacitance between the detection electrode and the object to be detected. The detection means detects a signal change based on a change in capacitance.

  The oscillating means oscillates at a predetermined frequency, and the resonance means composed of the LC series resonance circuit does not resonate with the oscillation frequency but resonates with the harmonics of the oscillation frequency.

  Therefore, when the object approaches the detection electrode, the capacitance between the object surface and the detection electrode changes, and the signal changes. The approach of the object can be detected by monitoring this signal change.

In this type of proximity sensor, the initial value of the capacitance is set to a value that is increased by a predetermined amount from the value when it matches the resonance frequency to improve the characteristics against temperature change and aging degradation. ing.
JP 2001-55852 A

  In the conventional proximity sensor described above, since the electrostatic capacitance between the object and the detection electrode is detected, the detection distance differs depending on the size of the person or the object, and there is a possibility that the accuracy is poor and malfunctions. There are also many malfunctions due to changes in rain and humidity. When the proximity sensor is disposed on the conductive panel, it is difficult to distinguish between the opening / closing operation of the door and the case where the proximity sensor is sandwiched between the door and the like. Furthermore, since the electrostatic capacitance between the detection electrode and the vehicle body ground is detected, there is a problem that it is difficult to install the detection electrode on the metal body of the vehicle.

  Therefore, an object of the present invention is to provide a proximity sensor that can be detected with high accuracy without malfunction due to environmental changes due to changes in rain or humidity.

  The proximity sensor according to claim 1 is sufficient for a conductive panel that is attached to an object to be attached integrally or separably, a detection area that is set outside the conductive panel, and a size of the conductive panel. And a microwave oscillating unit that forms a microwave resonance circuit including the detection region using the conductive panel as an antenna at a specific frequency with a short wavelength.

  Therefore, a microwave resonant circuit is formed by using the conductive panel as an antenna at a specific frequency with a sufficiently short wavelength with respect to the size of the conductive panel, and including a detection target such as a person in the detection region. When oscillated, several standing waves are generated in the conductive panel. Due to the relationship between the detection region and the conductive panel, a specific frequency is radiated from the conductive panel corresponding to several standing waves. Therefore, even if the oscillation frequency is radiated as electromagnetic waves from the conductive panel, there is no change in the electromagnetic wave radiation space if there is no detection target, so the frequency fluctuation of the oscillation frequency at that time is specified by the actual construction conditions. Is done. However, when a detection target such as a person approaches or near the conductive panel, the electric field in the electromagnetic radiation space is reflected or absorbed by the detection target, and the field of the electromagnetic radiation space in the detection region changes. For example, a wavelength component (frequency component) corresponding to a distance from a detection target such as a person becomes an antenna, and the antenna is coupled with a conductive panel that functions as an antenna. A plurality of output oscillation frequencies are affected, and the frequency for increasing the amplitude and the frequency for decreasing the amplitude change due to reflection or absorption of the detection target. Although there are two or more types of frequency changes at the same time, in reality, the frequency is the sum of both frequencies, and the frequency of the resonance phenomenon changes to one frequency. By detecting this frequency change, the detection target is detected.

  Here, the microwave oscillating unit places microwaves having the conductive panel as an antenna at a frequency having a sufficiently short wavelength with respect to the entire size of the conductive panel on the conductive panel. Microwave radiation is performed, and the oscillation frequency in the resonance circuit varies depending on the state of the electromagnetic wave radiation space and the frequency of the microwave to be radiated.

  The microwave oscillator of the proximity sensor according to claim 2, wherein the microwave oscillator supplies a microwave to the microwave oscillator and generates a frequency to be radiated from the conductive panel; Mixing the frequency of the microwave obtained from the conductive panel as the antenna and the frequency obtained from the reference oscillator to detect a predetermined frequency, and only a specific frequency from the frequency mixed by the mixer A band-pass filter to be selected; and a feedback system that feeds back to the output oscillator by a standing wave having a frequency that has passed through the band-pass filter.

  In the electromagnetic wave radiation space of the resonance circuit of the microwave oscillating unit, the frequency obtained from the conductive panel and the frequency of the reference oscillator are mixed and taken out as a frequency of the fluctuation difference through a band-pass filter. Due to the presence (VSWR meter output), the frequency fed back to the output oscillator via the feedback system is generated.

  Therefore, the microwave output from the conductive panel via the mixer from the output oscillator forms a microwave resonance circuit between the detection target in the detection region, which is an electromagnetic wave radiation space, and the conductive panel, and the detection is performed. It becomes an oscillation state according to the state of the electromagnetic wave radiation space in the region. Here, even if the oscillating microwave is radiated from the conductive panel, if there is no detection target that causes reflection or absorption, the output state of a specific frequency does not change, so the frequency fluctuation of the resonance circuit does not occur. .

  However, when a detection target such as a person approaches the conductive panel or when the detection target exists, the electric field of the electromagnetic wave radiated from the conductive panel is reflected or absorbed by the detection target, and the electromagnetic radiation space in the detection region The field changes.

  Therefore, when a detection target such as a person is present in the electromagnetic wave radiation space formed by the detection region, a standing wave having a specific frequency determined with respect to the conductive panel that has been detected so far is generated. The detected standing wave changes compared to when there is no detection target such as a person in the field of the electromagnetic wave radiation space. For the changed signal, a signal corresponding to the distance, size, etc. is measured in advance as a reference signal, and if the nature is known, the reference signal and the changed signal are compared to determine the distance, size. Etc., or the distance, size, etc. can be detected by predetermined pattern recognition.

  Here, the output oscillator that outputs the microwave has a radiation frequency determined by a detection area that is a radio wave radiation space and a conductive panel that functions as an antenna. Therefore, it is a separately excited microwave oscillator that can control the oscillation frequency from others. is there. The feeding point of the conductive panel is a point roughly estimated by simulation and actual measurement, and the radiation frequency is similarly set. The reference oscillator is an oscillator that determines a mixing frequency, and may be an ordinary microwave oscillator.

  Further, the mixer mixes the frequency (f) obtained from the output oscillator and the frequency (fo) obtained from the reference oscillator, and the mixing frequency (mf + nfo; where m and n are integers from −∞ to + ∞. ). Further, the band-pass filter may be one that extracts only one of the mixing frequencies (mf + nfo), for example, the frequency (f + fo), and performs signal processing. Of course, when the present invention is implemented, any of the above mixing frequencies (mf + nfo) may be selected.

  The oscillation frequency of the microwave oscillating unit of the proximity sensor according to claim 3 is for identifying a change in the detection region by a standing wave having a frequency passed through the band-pass filter by a recognition circuit.

  That is, a standing wave having a specific frequency determined between the electromagnetic radiation space including the detection region and the conductive panel is generated in the conductive panel. The VSWR (Voltage Standing Wave Ratio) of the frequency that has passed through the detected bandpass filter changes as compared to when there is no detection target such as a person in the field of the electromagnetic wave radiation space. . For the changed signal, a signal corresponding to the distance, size, etc. is measured in advance as a reference signal, and if the nature is known, the reference signal and the changed signal are compared to determine the distance, size. Etc., or the distance, size, etc. can be detected by predetermined pattern recognition.

  The VSWR is a value obtained by dividing the absolute value of the maximum voltage of the standing wave generated from the interference between the traveling wave of the specific frequency and the reflected wave by the absolute value of the minimum voltage, and is the minimum value when there is no reflection. 1 ".

  The recognition circuit identifies a change in the detection region, which is the electromagnetic wave radiation space, by VSWR, and compares the VSWR with a reference corresponding to a known distance, size, etc., thereby determining the distance, size, etc. As long as it is constituted by an analog circuit or a digital circuit.

  The conductive panel, which is integrally or separably attached to the attachment object of the proximity sensor according to claim 4, is an open / close body that can be attached to the vehicle so as to be openable / closable, simplifying the structure, and inexpensive. Can be manufactured.

  The proximity sensor according to claim 5 has a sufficient wavelength with respect to an antenna having a planar shape that is integrally or separably attached to an attachment target, a detection region set outside the antenna, and the size of the antenna. And a microwave oscillating unit that forms a microwave resonance circuit including the detection target in the detection region using the conductive panel as an antenna at a short specific frequency.

  Therefore, when a microwave resonance circuit is formed including a detection target in the detection region at a specific frequency having a sufficiently short wavelength with respect to the size of the antenna, and the microwave is oscillated, the antenna has several standing positions. A wave is generated. Due to the relationship between the detection region and the antenna, a specific frequency is radiated from the antenna corresponding to several standing waves. Therefore, even if the oscillation frequency is radiated as an electromagnetic wave from the antenna, if there is no detection target, there is no change in the electromagnetic wave radiation space, and the frequency variation of the oscillation frequency at that time is specified by the actual construction conditions. . However, when a detection target such as a person approaches or near the antenna, the electric field in the electromagnetic radiation space is reflected or absorbed by the detection target, and the field of the electromagnetic radiation space in the detection region changes. The detection target is detected by taking out the change of each individual frequency.

  In the proximity sensor according to the first aspect, even when the frequency of the microwave oscillating unit is radiated as a microwave from the conductive panel, if there is no object to be reflected or absorbed, the frequency variation of the microwave oscillating unit is Although it does not occur, when a detection target such as a person approaches the conductive panel, the electric field of the radiated electromagnetic wave is reflected or absorbed by the detection target, the field of the electromagnetic radiation space changes, and the distance from the detection target such as a person and The wavelength component (frequency) corresponding to the magnitude changes. Based on the detected change, distance and size can be detected.

  At this time, the microwave oscillating part formed by forming a microwave resonance circuit between the detection target of the detection region which is an electromagnetic wave radiation space and the conductive panel has an oscillation state corresponding to the detection region and the detection target. Become. The microwave oscillation part in this oscillation state has a large influence between the electric field and magnetic field of the electromagnetic wave, and can be regarded as a resonance circuit of the electric field strength (magnetic field) between the detection target in the detection region and the conductive panel. It becomes difficult to be affected by the capacitance of the detection target in the radiation space.

  In particular, a microwave resonance circuit is formed between the detection area of the detection region where the microwave oscillation part is an electromagnetic wave radiation space, and the mutual influence of the electric field and magnetic field of the electromagnetic wave becomes greater, and this is applied between the antennas. Therefore, it is difficult to be influenced by the capacitance of the detection target in the detection region, so that the detection accuracy is improved. In addition, the use of microwaves with 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. in the detection area compared to the conventional capacitance detection type. Therefore, the device is inexpensive. Therefore, it is easy to detect a short distance, and it is possible to detect a state that can be manufactured at low cost. Further, unlike Doppler detection, detection is possible even if the detection target in the detection region is not moving.

  The microwave oscillating unit of the proximity sensor according to claim 2 is configured such that the microwave output from the output oscillator via the mixer has a resonance circuit between the detection target in the detection region that is an electromagnetic wave radiation space and the conductive panel. The oscillation state is formed according to the state of the electromagnetic wave radiation space in the detection region. Here, even if the oscillating microwave is radiated from the conductive panel, if there is no detection target that causes reflection or absorption, the output state of a specific frequency does not change, so the frequency fluctuation of the resonance circuit does not occur. .

  When a detection target such as a person approaches or near the conductive panel, or the detection target exists, the electric field of the electromagnetic wave radiated from the conductive panel is reflected or absorbed by the detection target, and the electromagnetic radiation space field of the detection region is Change. At this time, the wavelength component (frequency) affected by the detection target such as a person in the electromagnetic radiation space is mixed with the frequency of the reference oscillator, extracted as the frequency of the fluctuation difference through the bandpass filter, and detected by the standing wave. The presence of the object is identified.

  Therefore, when a detection target such as a person is present in the electromagnetic wave radiation space formed by the detection region, a standing wave having a specific frequency that has not been detected until then is generated. That is, the detected standing wave changes as compared with when there is no detection target such as a person in the field of the electromagnetic wave radiation space. For the changed signal, a signal corresponding to the distance, size, etc. is measured in advance as a reference signal, and if the nature is known, the reference signal and the changed signal are compared to determine the distance, size. Etc., or the distance, size, etc. can be detected by predetermined pattern recognition.

  At this time, a microwave resonance circuit is formed between the output oscillator and the detection target in the detection region that is an electromagnetic wave radiation space, and the oscillation occurs at a specific frequency according to the detection region and the detection target. The mutual influence of the electric and magnetic fields increases, making it difficult to be affected by the capacitance of the detection target in the detection region, so that the detection accuracy is improved.

  The oscillation frequency of the microwave oscillation unit of the proximity sensor according to claim 3 includes a recognition circuit that identifies a change in the detection region by a standing wave having a frequency that has passed through the band-pass filter. Therefore, in addition to the effect of claim 1 or claim 2, the VSWR of the frequency passed through the detected bandpass filter changes compared to when there is no detection target such as a person in the field of the electromagnetic radiation space. If the nature of the changed signal is known in advance using a signal corresponding to the distance, magnitude, etc. as a reference signal, the distance, magnitude, etc. are estimated by comparing the reference signal with the changed signal. Alternatively, distance, size, etc. can be detected by predetermined pattern recognition.

  The conductive panel that is integrally or separably attached to the attachment object according to claim 4 is an opening / closing body that can be freely opened and closed with respect to the vehicle. Thus, the structure can be simplified and can be manufactured at low cost.

  In the proximity sensor according to the fifth aspect, even if the frequency of the microwave oscillating unit is radiated as a microwave from the antenna, the frequency of the microwave oscillating unit does not fluctuate if there is no detection target that causes reflection or absorption. However, when a detection target such as a person approaches the antenna, the electric field of the radiated electromagnetic wave is reflected or absorbed by the detection target, and the field of the electromagnetic radiation space changes, corresponding to the distance and size from the detection target such as a person. The wavelength component (frequency component) to be changed changes. Based on the detected change, distance and size can be detected.

  At this time, the microwave oscillating unit formed by forming a microwave resonance circuit between the detection target of the detection region which is the electromagnetic wave radiation space and the antenna is in an oscillation state corresponding to the detection region and the detection target. The microwave oscillation part in this oscillation state has a large influence between the electric field and magnetic field of the electromagnetic wave, and can be regarded as a resonance circuit of the electric field strength (magnetic field) between the detection target in the detection region and the antenna. It becomes difficult to be affected by the capacitance of the detection target in the radiation space. In particular, a microwave resonance circuit is formed between the detection area of the detection region where the microwave oscillation part is an electromagnetic wave radiation space, and the mutual influence of the electric field and magnetic field of the electromagnetic wave becomes greater, and this is applied between the antennas. Therefore, it is difficult to be influenced by the capacitance of the detection target in the detection region, so that the detection accuracy is improved. In addition, the use of microwaves with 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. in the detection area compared to the conventional capacitance detection type. Therefore, the device is inexpensive. Therefore, it is easy to detect a short distance, and it is possible to detect a state that can be manufactured at low cost. Further, unlike Doppler detection, detection is possible even if the detection target in the detection region is not moving.

  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 mixer 23 are electrically connected to the outer panels 11 to 14 made of metal plates (conductive) of the doors of the vehicle 1, and the outer panels 11 to 14 of the doors serve as antennas. The outer panels 11 to 14 of each door constitute the conductive panel of the present embodiment. In the present embodiment, the case where the outer panels 11 to 14 of each door are antennas will be described, but front and rear bumpers, trunk lids, engine hoods, front doors, back doors, slide doors, swing doors, etc. The movable hood, sunroof, etc. can also be used as the conductive panel of the present embodiment in the same manner as the outer panels 11-14. Among these, the front door, back door, slide door, swing door, etc. Both can be regarded as an opening / closing body attached to the vehicle 1 so as to be freely opened and closed.

  In FIG. 2, an output oscillator 21 that oscillates microwaves having a frequency of 300 MHz to 300 GHz radiates microwaves from outer panels 11 to 14 that function as antennas, and is an electromagnetic wave radiation space around the outer panels 11 to 14. Specifically, the output oscillator 21 detects a change in the state of the areas 11A to 14A. The output oscillator 21 is a specific area determined by the detection areas 11A to 14A that are radio wave radiation spaces and the outer panels 11 to 14 (conductive panels). Since it has a radiation frequency, a separately excited microwave generator that can control the oscillation frequency from another is used. 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.

  The output oscillator 21 in the case of implementing the present invention can cope with reflection and absorption of the oscillation frequency (f) by changing the detection areas 11A to 14A which are radio wave radiation spaces. The output of the output oscillator 21 is electrically connected to the outer panels 11 to 14 via the mixer 23.

  The reference oscillator 22 detects a frequency that changes according to a change in the state of the detection regions 11A to 14A, which are radio wave radiation spaces. The reference oscillator 22 is a microwave oscillator having a specific frequency (fo), and is usually the same as the output oscillator 21. Or it is an oscillator which oscillates the microwave of 300 MHz-300 GHz which is the frequency of the vicinity. The reference oscillator 22 oscillates a stable microwave having a specific frequency, and an oscillator whose oscillation frequency (fo) is relatively stable is used.

  The mixer 23 only needs to mix the frequency (f) of the output oscillator 21 and the frequency (fo) of the reference oscillator 22 to obtain a mixing frequency (mf + nfo).

  The bandpass filter 24 is a filter that selects only one mixing frequency (f + fo), and the VSWR meter 25 detects the VSWR of the frequency that has passed through the bandpass filter 24. As a result, the frequency change is mixed by the reference oscillator (fo), the frequency of the fluctuation difference is extracted through the band pass filter 24, and the standing wave of the extracted frequency is detected by the VSWR meter 25.

  At this time, the frequency supplied to the outer panels 11 to 14 from the output oscillator 21 is normally set to a frequency at which the overall standing wave ratio is reduced when efficiently radiated from the outer panels 11 to 14. To describe just in case, the VSWR of the frequency passed through the band-pass filter when there is no detection target 27 is normally set to the minimum in the sense of improving the radiation efficiency of the microwave radiated from the conductive panel. . However, in implementing the present invention, it is not a prerequisite to minimize the VSWR.

  However, a shift occurs in the frequency matching between the outer panels 11 to 14 and the detection areas 11A to 14A due to a change in the state of the detection areas 11A to 14A, which are electromagnetic wave radiation spaces. As a detection of this matching, when the detection target 27 does not exist, the VSWR meter 25 is monitored so that the VSWR is minimized.

  That is, the microwave which forms the resonance circuit of a microwave including the detection object 27 of the detection areas 11A-14A by using the outer panels 11-14 as an antenna at a specific frequency having a sufficiently short wavelength with respect to the size of the outer panels 11-14 The oscillating unit 30 is configured.

  As described above, there are many microwave frequencies emitted from the outer panels 11 to 14. The frequency band of the output oscillator 21 includes part or all of the frequency of the emitted microwaves. 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, and measures the VSWR by the VSWR meter 25. In a state where the VSWR meter 25 is monitored and the state in which the VSWR is minimized is initially set, when a person or the like approaches the antenna, the person and the outer panels 11 to 14 are regarded as antennas. It is detected as a change in specific frequency.

  Furthermore, the recognition circuit 26 identifies a change in the state of the detection regions 11A to 14A, which are electromagnetic wave radiation spaces, based on a signal that has passed through a VSWR meter 25 that detects a VSWR having a frequency that has passed through the bandpass filter 24. This detected signal change is obtained by measuring the reference information in advance for the signal state corresponding to the distance, size, etc., and estimating the distance, size, etc. from the reference information, thereby detecting the distance, size, etc. Is to do.

  That is, at this time, information such as a person, an object, and a size as the detection target 27 is detected by comparing and referring to the characteristics mapped in the recognition circuit 26. According to this method, it is possible to distinguish between a change in automatic door opening / closing operation and an approach to a person or an object.

  The recognition circuit 26 inputs its output 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, whether the door can be opened / closed safely or whether there is no obstacle is determined. When the determination is made and a person or a structure is detected, the opening / closing of the door is stopped or an alarm sound is generated in the vehicle 1.

  At this time, the output oscillator 21, the reference oscillator 22, the mixer 23, the band pass filter 24, and the VSWR meter 25 constituting the proximity sensor 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 VSWR meter 25 is input to the recognition circuit 26 and 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.

  As described above, the proximity sensor according to the present embodiment includes the conductive panel including the outer panels 11 to 14 that are integrally or separably attached to the vehicle 1, and the detection regions 11A to 11A set on the outer side of the outer panels 11 to 14. 14A and an output oscillator 21 that oscillates a microwave having a resonance circuit as a detection target 27 of the outer panels 11 to 14 and the detection regions 11A to 14A at a frequency having a sufficiently short wavelength with respect to the size of the outer panels 11 to 14; A reference oscillator 22 that oscillates a microwave to obtain a mixing frequency, and an output frequency obtained from the microwaves obtained from the output oscillator 21 by the outer panels 11 to 14 and the detection regions 11A to 14A are obtained from the reference oscillator 22. Mixer 23 that detects a predetermined frequency by mixing the frequencies, and a band that selects only a specific frequency from the frequencies detected by mixer 23 A pass filter 24, a feedback system 28 to the output oscillator 21 that determines a specific output frequency to be radiated from the outer panels 11 to 14 by a standing wave having a frequency passed through the band pass filter 24, and a band pass filter 24 And a recognition circuit 26 that identifies changes in the detection regions 11A to 14A by a standing wave having a frequency that has been passed through.

  Here, in the proximity sensor of the present embodiment, the output oscillator 21, the reference oscillator 22, the mixer 23, the bandpass filter 24, the VSWR meter 25, and the feedback system 28 pass through the bandpass filter 24. The microwave oscillating unit 30 is configured to obtain resonance of the conductive panel including the detection regions 11A to 14A that are the electromagnetic wave radiation spaces and the outer panels 11 to 14 by the standing wave of the frequency. The microwave oscillating unit 30 is a resonance circuit that supplies a specific frequency having a sufficiently short wavelength with respect to the size of the conductive panel including the detection target 27 and the outer panels 11 to 14 in the detection regions 11A to 14A that are electromagnetic wave radiation spaces. It is composed.

  As a result, the proximity sensor of the present embodiment is provided on the outside of the conductive panel composed of the outer panels 11 to 14 and the outer panel composed of the outer panels 11 to 14 that are integrally or separably attached to the vehicle 1. Detection areas 11A to 14A using the conductive panels made of the outer panels 11 to 14 at a specific frequency having a sufficiently short wavelength as the antenna for the set detection areas 11A to 14A and the size of the conductive panel made of the outer panels 11 to 14. And a microwave oscillating unit 30 that forms a microwave resonance circuit including the detection object 27.

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

  A microwave resonance circuit is formed by using the outer panels 11 to 14 as antennas at a specific frequency having a sufficiently short wavelength with respect to the size of the outer panels 11 to 14 and including the detection target 27 in the detection regions 11A to 14A. Is oscillated, several standing waves are generated on the outer panels 11-14. Due to the relationship between the detection region and the outer panels 11 to 14, a specific frequency is radiated from the outer panels 11 to 14 corresponding to several standing waves. Therefore, even if the oscillation frequency is radiated as an electromagnetic wave from the outer panels 11 to 14, if there is no detection object 27, there is no change in the electromagnetic wave radiation space. It is determined. However, when the detection object 27 such as a person approaches or exists near the outer panels 11 to 14, the electric field of the electromagnetic wave radiation space is reflected or absorbed by the detection object 27, and the field of the electromagnetic wave radiation space of the detection regions 11A to 14A. Changes.

  In this way, the output of the output oscillator 21 at a specific frequency radiated from the outer panels 11 to 14 forming the cavity oscillation circuit in the relationship between the detection regions 11A to 14A, the outer panels 11 to 14 and the detection target 27 such as a person. Changes. As described above, when the microwave resonance circuit corresponding to the relative distance between the detection target 27 and the outer panels 11 to 14 can be formed, the mutual influence of the electric field / magnetic field of the microwave is the detection target 27. It can be regarded as the resonance circuit 31 of the electric field strength (magnetic field) between the outer panels 11 to 14 and is less affected by the capacitance of the detection target 27 in the electromagnetic wave radiation space.

  Even if microwaves are radiated from the outer panels 11 to 14 when the frequency of the output oscillator 21 is not detected in the detection regions 11A to 14A, the frequency fluctuation of the output oscillator 21 does not occur. . However, when the detection target 27 such as a person approaches or exists near the outer panels 11 to 14, the electric field of the microwave is reflected or absorbed by the detection target 27, and the field of the electromagnetic wave radiation space changes. At this time, the wavelength component (frequency) 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. Although many types of frequency components exist, in reality, the frequency of the resonance phenomenon changes to one frequency (f). The frequency obtained by introducing the output frequency (fo) of the reference oscillator 22 into the mixer 23 and down-converted by the mixer 23 by mixing is the mixing frequency (mf + nfo). The mixing frequency (mf + nfo) from the mixer 23 is extracted through the band-pass filter 24, ie, the frequency of fluctuation difference, that is, the mixing frequency (f + fo), and the standing wave of the extracted mixing frequency (f + fo) is detected by the VSWR meter 25. ing.

  The detection of the VSWR of the mixing frequency (f + fo) is identified by the change in the state of the detection regions 11A to 14A based on the magnitude of the signal passed through the VSWR meter 25 that detects the VSWR of the frequency that has passed through the bandpass filter 24 by the recognition circuit 26. To do. This detected signal change is obtained by measuring the reference information in advance for the signal state corresponding to the distance, size, etc., and estimating the distance, size, etc. from the reference information, thereby detecting the distance, size, etc. Is to do.

  Therefore, the electronic control circuit 2 that inputs the output of the recognition circuit 26 is a microcomputer that executes the obstacle detection device of the door opening and closing system in this embodiment, and when the door outer panels 11 to 14 are opened, When a person or an object approaches the outer panels 11 to 14 of the door, it is possible to stop the opening of the door or to notify the temple state. Further, even in the operation in the door closing direction, it is possible to prevent a collision with a person or an object. Therefore, the outer panels 11 to 14 are preferably members attached to an opening / closing body that is attached to the vehicle 1 so as to be freely opened and closed.

  In particular, since the output oscillator 21 is an oscillator that oscillates a microwave having a use frequency of 300 MHz to 300 GHz, the microwave can be generated at low cost, and the entire apparatus can be made inexpensive. Further, the antenna of the present embodiment is an outer panel 11 to 14 of the door of the vehicle 1. In particular, when the door of the vehicle 1 is an antenna, it can be used as a sensor for an obstacle detection device, a security system, a keyless entry system, etc. of a door opening / closing system, and the field of the electromagnetic radiation space can be used as an outer panel of the door of the vehicle 1. It can also be set within 11 to 30 cm.

  In addition, since the proximity sensor of this Embodiment is used for the vehicle, there are many components that can be used as a conductive panel such as the outer panels 11 to 14 of the door, and other components can be used. Therefore, it is preferable to use for vehicles.

  Since the present invention enables detection of a short distance of the detection target 27 without being affected by the atmosphere such as humidity, temperature, water vapor, pressure, etc. of the electromagnetic wave radiation space, an obstacle detection device for a door opening / closing system, a security system, In addition to sensors such as keyless entry systems, various short distances are not affected by changes in weather conditions such as humidity changes in the natural air compared to conventional capacitance detection type. It can be used as a sensor for detecting.

  The proximity sensor according to the embodiment of the present invention of this type can be used not only for the vehicle 1 but also for a proximity sensor for a shower toilet that detects the movement and presence of a human body, and its use is limited to the vehicle 1. It is not a thing. For example, it can be generalized like a proximity sensor of a shower toilet that detects the movement and presence of a human body. At this time, for example, the outer panels 11 to 14 may function as an antenna. Other configurations are not different from the above embodiment. In addition, the outer panels 11 to 14 that are integrally or separably attached to the object to be attached are not limited to planar panels, and can be formed into a shape obtained by processing a strip or a linear member.

  At this time, the proximity sensor according to the embodiment of the present invention has a sufficient wavelength with respect to an antenna that is integrally or separably attached to an attachment target, a detection region set outside the antenna, and the size of the antenna. And a microwave oscillating portion that forms a microwave resonance circuit including a detection target in the detection region at a short specific frequency.

  Note that a general-purpose proximity sensor can have the same configuration as that of the above-described embodiment, and has the same operational effects, and thus detailed description thereof is omitted.

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 panel)
11A to 14A Detection area 21 Output oscillator 22 Reference oscillator 23 Mixer 24 Band pass filter 25 VSWR meter 26 Recognition circuit 27 Detection target 28 Feedback system

Claims (5)

An electrically conductive panel that can be integrally or separably attached to a mounting object;
A detection region set outside the conductive panel;
A microwave oscillating unit that forms a microwave resonant circuit including the detection region using the conductive panel as an antenna at a specific frequency with a sufficiently short wavelength with respect to the size of the conductive panel. Proximity sensor. The microwave oscillation unit is
An output oscillator for supplying a microwave to the microwave oscillating unit and generating a frequency radiated from the conductive panel;
A mixer for mixing a frequency of a microwave obtained from the conductive panel as an antenna and a frequency obtained from a reference oscillator, and detecting a predetermined frequency;
A bandpass filter for selecting only a specific frequency from the frequencies mixed by the mixer;
The proximity sensor according to claim 1, further comprising a feedback system that feeds back to the output oscillator by a standing wave having a frequency that has passed through the band-pass filter.   The oscillation frequency of the said microwave oscillation part comprises the recognition circuit which identifies the change of the said detection area | region with the standing wave of the frequency which passed the said band pass filter. The proximity sensor described in 1.   The conductive panel that is integrally or separably attached to the attachment target is an opening / closing body that is attached to the vehicle so as to be openable and closable. Proximity sensor. An antenna that can be mounted integrally or separably on the mounting target;
A detection area set outside the antenna;
And a microwave oscillation unit that forms a microwave resonance circuit including the detection region using the conductive panel as an antenna at a specific frequency having a sufficiently short wavelength with respect to the size of the antenna. Proximity sensor.

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