JP2019085734A - Vehicle electronic key system - Google Patents

Abstract

To enable an estimation of a position of an electronic key in consideration of the reception sensitivity variation of each individual electronic key.SOLUTION: A vehicle electronic key system includes: an RSSI detection circuit 211 which detects the received signal strength when an electronic key 200 receives vehicle signals transmitted from two on-vehicle LF antennas 181R, 181L; a storage unit 130 which stores a received signal strength distance relationship between the received signal strength and a distance from each of the two on-vehicle LF antennas to the electronic key with respect to different received sensitivities; a distance calculation unit 122 which determines the received signal strength detected by the RSSI detection circuit by applying the received signal strength to the received signal strength distance relationship; a candidate point calculation unit 123 which calculates, for a plurality of reception sensitivities, a candidate point as a candidate for a position of an electronic key on the basis of the distance calculated by the distance calculation unit; and a position estimation unit 129 which estimates the position of the electronic key on the basis of a candidate line which is a line segment determined from a plurality of candidate points calculated for the plurality of reception sensitivities.SELECTED DRAWING: Figure 1

Description

  The disclosure in this specification relates to an electronic key system for a vehicle including an electronic key and an on-board unit wirelessly communicating with the electronic key.

  BACKGROUND Conventionally, there has been known a vehicle electronic key system which permits or executes predetermined processing for a vehicle such as locking and unlocking of a vehicle and engine start based on wireless communication between a vehicle-mounted device and an electronic key.

  The vehicle electronic key system permits or executes the process according to the position of the electronic key relative to the vehicle. Therefore, it is necessary to determine the position of the electronic key.

  Patent Document 1 discloses a technique for determining the position of an electronic key with respect to a vehicle as follows. Based on the combination of the received signal strength when the electronic key receives a vehicle signal transmitted from one onboard antenna and the received signal strength when the electronic key receives a vehicle signal transmitted from another onboard antenna Thus, the position of the electronic key is determined.

  Specifically, in Patent Document 1, the two-dimensionality indicated by the magnetic field strength when the electronic key receives the radio wave from the driver's seat antenna and the magnetic field strength when the electronic key receives the radio wave from the front passenger seat antenna The position of the electronic key is determined by comparing the point of and the determination line.

JP, 2011-144625, A

  By the way, it is inevitable that the radio wave reception sensitivity of the electronic key varies to some extent for each individual. For example, the reception sensitivity of one electronic key is high sensitivity and the reception sensitivity of another electronic key is low sensitivity within the tolerance of the reception sensitivity determined from the required specification of the electronic key. Such variation in reception sensitivity causes deterioration in the accuracy in determining the position of the electronic key based on the received signal strength of the vehicle signal. This is because, even when the electronic key detects the received signal strength of the same value, the actual distance from the on-vehicle antenna that has issued the vehicle signal to the electronic key varies according to the level of the reception sensitivity of the electronic key. is there. If the view is changed, the position of the electronic key relative to the vehicle calculated based on the received signal strength of the vehicle signal may be offset with respect to the actual position of the electronic key relative to the vehicle due to variations in reception sensitivity among the electronic key individuals.

  The position determination of the electronic key of Patent Document 1 is performed in two dimensions indicated by the magnetic field strength when the electronic key receives the radio wave from the driver's seat antenna and the magnetic field strength when the electronic key receives the radio wave from the front passenger seat antenna. The upper point is compared with the judgment line. This two-dimensional point varies due to the reception sensitivity of the electronic key solid. That is, in patent document 1, the receiving sensitivity dispersion | variation for every electronic key solid body was not considered.

  An object of the disclosure in this specification is to provide an electronic key system for a vehicle that can estimate the position of an electronic key with high accuracy in consideration of variations in reception sensitivity among individual electronic keys.

One example of a vehicle electronic key system for achieving the above object is
An on-vehicle unit (110) mounted on a vehicle provided with a plurality of on-vehicle transmission antennas (181, 181R, 181L, 181B) and an on-vehicle reception antenna (195);
A key-side receiving antenna (215), a reception-strength detecting unit (211) for detecting a received signal strength when the vehicle signal transmitted from each of the on-vehicle transmitting antennas is received by the key-side receiving antenna; And an electronic key (200) wirelessly communicating with the on-vehicle device,
A vehicle electronic key system comprising:
Reception strength distance relation representing a relation between the reception signal strength of the vehicle signal from the in-vehicle transmission antenna detected by the reception strength detection unit and the distance from the in-vehicle transmission antenna to the electronic key A storage unit (130) storing a plurality of reception intensity distance relationships (133, 135) having different reception sensitivities of the units;
The distance from one in-vehicle transmitting antenna to the electronic key that constitutes two in-vehicle transmitting antennas included in a plurality of in-vehicle transmitting antennas and the distance from the other in-vehicle transmitting antenna to the electronic key among the two in-vehicle transmitting antennas A distance calculation unit (122) which determines the received signal strengths of the vehicle signal from each of the two on-vehicle transmission antennas detected by the received strength detection unit by applying to a plurality of reception strength distance relationships;
The distance calculated by the distance calculation unit is a radius, and the candidate for the position of the electronic key is based on the intersection of a circle centered on the position of one in-vehicle transmission antenna and a circle centered on the position of another in-vehicle transmission antenna. A candidate point calculation unit (123) which calculates candidate points to be
Candidate line calculation processing of calculating a line segment determined from a plurality of candidate points (P_max, P_min) calculated by the candidate point calculation unit for a plurality of reception sensitivities as candidate lines (L, L1, L2, L3) of the position of the electronic key A candidate line calculation unit (124) for executing
A position estimation unit (129) for estimating the position of the electronic key based on the candidate line calculated by the candidate line calculation unit;
It is an electronic key system for vehicles further provided.

  In the vehicle electronic key system, the storage unit stores a plurality of reception intensity distance relationships in which different reception sensitivities are assumed as the reception sensitivity of the electronic key. Then, using the plurality of reception strength relationships and the reception signal strength of the vehicle signal from each of the two on-vehicle transmission antennas detected by the reception strength detection unit, the distances from the two on-vehicle transmission antennas to the electronic key are Further, with this distance as a radius, candidate points for the position of the electronic key are determined based on the intersection of circles respectively centered on the two on-vehicle transmission antennas. The candidate lines are calculated based on a plurality of candidate points calculated for a plurality of reception sensitivities.

  The reception sensitivity of the electronic key that has received the vehicle signal is unknown. However, if the reception sensitivity changes, the radii of the two circles indicating candidate points of the electronic key, which can be estimated from the received signal strengths of the vehicle signals from the two on-vehicle transmission antennas, both increase and decrease in the same manner.

  Therefore, no matter what the sensitivity of the electronic key receiving the vehicle signal is, the candidate point of the electronic key on which the difference in the reception sensitivity of the electronic key is reflected is the point on the candidate line. Since the position estimation unit estimates the position of the electronic key based on this candidate line, it is possible to estimate the position of the electronic key with high accuracy, which is less affected by the variation in the reception sensitivity of the electronic key.

  In addition, the reference numerals in the above-mentioned parentheses only show an example of the correspondence with specific configurations in the embodiments described later for the purpose of easy understanding, and it is intended to limit the technical scope in any way. It is not a thing.

It is a figure which shows schematic structure of the electronic key system 1 for vehicles of 1st Embodiment. It is a figure explaining detection area 301, 302 of in-vehicle LF antenna 181R and 181L of a 1st embodiment. It is a figure explaining the RSSI distance relationship 133, 135 of 1st Embodiment. It is a figure explaining distance D_max and D_min calculated by RSSI distance relation 133, 135 of a 1st embodiment. FIG. 7 is a diagram for explaining candidate points P_max and P_min of candidate positions of the electronic key 200 of the first embodiment and a candidate line L. It is a figure explaining the comparative example regarding the candidate position of the electronic key 200 of 1st Embodiment. It is a figure explaining presumed position field R of electronic key 200 of a 1st embodiment. It is a flowchart explaining the onboard equipment side position presumption processing which collation ECU110 of a 1st embodiment performs. It is a flowchart explaining the key side position estimation process which the electronic key 200 of 1st Embodiment performs. It is a figure which shows schematic structure of the electronic key systems 2 and 3 for vehicles of 2nd Embodiment and 3rd Embodiment. It is a figure explaining detection area 301, 302, 303 of in-vehicle LF antenna 181R, 181L, 181B of a 2nd embodiment and a 3rd embodiment. It is a figure explaining candidate lines L1 and L2 of a candidate position of electronic key 200 of a 2nd embodiment, and candidate line crossing P_cross. It is a figure explaining the comparative example regarding the candidate position of the electronic key 200 of 2nd Embodiment. It is a figure explaining candidate line L1, L2, L3 of a 3rd embodiment. It is the elements on larger scale which expanded the area | region shown by XV of FIG. It is a figure which shows schematic structure of the electronic key system 4 for vehicles of 4th Embodiment.

  Hereinafter, several embodiments of a vehicle electronic key system (hereinafter, electronic key system) will be described with reference to the drawings. In embodiments, functionally and / or structurally corresponding parts and / or parts that are associated are given the same reference numerals. The description of the other embodiments can be referred to for the corresponding parts and / or parts to be associated.

First Embodiment
FIG. 1 shows a schematic configuration of the electronic key system 1 according to the first embodiment. The electronic key system 1 executes the verification of the electronic key 200 by the verification ECU 110 based on the wireless communication between the in-vehicle system 100 and the electronic key 200, and executes the function to execute or permit the predetermined processing when the verification is established. Have. ECU is an abbreviation of electronic control unit.

  The collation of the electronic key 200 is to confirm whether the electronic key 200 is a legitimate electronic key previously associated with the in-vehicle system 100, and is executed as follows, for example. The verification ECU 110 of the in-vehicle system 100 transmits a request signal from the first in-vehicle LF antenna 181R and the second in-vehicle LF antenna 181L. When the first in-vehicle LF antenna 181R and the second in-vehicle LF antenna 181L are not distinguished from one another, they are referred to as an in-vehicle LF antenna 181.

  When the electronic key 200 receives the request signal, the electronic key 200 transmits a response signal including an ID unique to itself. When the in-vehicle RF antenna 195 receives a response signal as a response to the request signal, the in-vehicle system 100 collates the electronic key 200 by collating the ID included in the response signal.

  As predetermined processing permitted or executed in the case of matching being established, for example, the following may be mentioned. When the authorized electronic key 200 is located in the vehicle compartment, the vehicle engine is allowed to start. The car room does not include the trunk room. Besides, when the authorized electronic key 200 is located in a predetermined area outside the vehicle, the unlocking of the vehicle door is permitted. In addition, when the regular electronic key 200 approaches the vehicle by a predetermined distance, a welcome process is performed to light the hazard lamp of the vehicle. Thus, the electronic key system 1 permits or executes different processing depending on the position of the electronic key 200 with respect to the vehicle.

  The electronic key system 1 according to the present embodiment estimates the position of the electronic key 200 with respect to the vehicle when executing or permitting the predetermined process based on the above-mentioned collation. Hereinafter, the configuration of the electronic key system 1 for estimating the position of the electronic key 200 with respect to the vehicle will be described.

<Configuration of Electronic Key System 1>
As shown in FIG. 1, the electronic key system 1 includes an in-vehicle system 100 provided in a vehicle, and an electronic key 200 carried by a user.

  The in-vehicle system 100 includes a verification ECU 110, a vehicle-side transmission unit 180, a first in-vehicle LF antenna 181R, a second in-vehicle LF antenna 181L, a vehicle-side reception unit 190, and an in-vehicle RF antenna 195.

  The verification ECU 110 is mainly configured of a microcomputer. The verification ECU 110 executes various programs including the verification of the electronic key 200 and the position estimation of the electronic key 200 described later by the processor such as the CPU executing a program stored in a storage device such as a ROM. Have the function to execute in cooperation with At least a part of the functions of the verification ECU 110 may be provided by a dedicated IC or the like. The verification ECU 110 corresponds to a vehicle-mounted device.

  The vehicle side transmission unit 180 modulates and amplifies the vehicle signal with the LF wave or the VLF wave under the control of the matching ECU 110 and transmits the modulated signal from the first in-vehicle LF antenna 181R and the second in-vehicle LF antenna 181L. LF is an abbreviation for Low Frequency, and VLF is an abbreviation for Very Low Frequency. The term LF is used herein, including VLF. When the above-described request signal is transmitted as a vehicle signal, information for requesting the electronic key 200 to return a response signal including the unique ID is included. Each vehicle signal includes identification information that makes it possible to identify whether the transmission source is the first in-vehicle LF antenna 181R or the second in-vehicle LF antenna 181L.

  As shown in FIG. 2, the first on-vehicle LF antenna 181R is provided on the driver's seat side door. More specifically, the first on-vehicle LF antenna 181R is provided on the outside door knob or the inside door knob of the driver's seat side door. In addition, the second on-vehicle LF antenna 181L is provided on the passenger side door. More specifically, the second in-vehicle LF antenna 181L is provided on the outside door knob or the inside door knob of the passenger side door.

  The first in-vehicle LF antenna 181R and the second in-vehicle LF antenna 181L form a first detection area 301 and a second detection area 302, respectively. Here, the detection area can be defined as, for example, an area where the electronic key 200 can receive vehicle signals transmitted from the in-vehicle LF antennas 181R and 181L with received signal strength (hereinafter, RSSI) equal to or higher than a predetermined threshold. The size of the detection area can be set to a desired size (for example, 10 m) by, for example, setting the transmission output of the first in-vehicle LF antenna 181R and the second in-vehicle LF antenna 181L. Each in-vehicle LF antenna 181 corresponds to an in-vehicle transmission antenna.

  As shown in FIG. 2, the first detection area 301 and the second detection area 302 are respectively formed over the inside and the outside of the vehicle. Furthermore, the first detection area 301 and the second detection area 302 are formed such that the overlapping area 310 extends in and out of the vehicle. Such a detection area formed over the inside and outside of the vehicle is realized by limiting the electromagnetic shielding function of the vehicle body by, for example, forming the vehicle body with resin.

  As shown in FIG. 1, the vehicle-side receiving unit 190 receives a key signal transmitted from the electronic key 200 by an RF (Radio Frequency) wave via the on-vehicle RF antenna 195. Vehicle-side receiver 190 amplifies the electrical signal acquired from in-vehicle RF antenna 195, demodulates the key signal from the electrical signal, and outputs the key signal to verification ECU 110. The on-vehicle RF antenna 195 is provided at an appropriately designed position in the vehicle. For example, the on-vehicle RF antenna 195 is provided at a position near the center of the vehicle in the vehicle interior.

  The key signal including the unique ID transmitted from the electronic key 200 as a response to the request signal is the response signal described above. The key signal may further include RSSI information indicating the RSSI when the electronic key 200 receives the vehicle signal. The RSSI information includes the RSSI and identification information capable of identifying whether the transmission source of the vehicle signal is the first in-vehicle LF antenna 181R or the second in-vehicle LF antenna 181L. The on-vehicle RF antenna 195 corresponds to an on-vehicle reception antenna.

  The electronic key 200 is a portable device carried by the user, and includes a key side reception unit 210, a key side LF antenna 215, a key side transmission unit 220, a key side RF antenna 221, and a key side control unit 230. Equipped with

  The key side reception unit 210 acquires an electrical signal indicating a radio wave transmitted from each of the first in-vehicle LF antenna 181 R and the second in-vehicle LF antenna 181 L via the key side LF antenna 215. The key side reception unit 210 modulates and demodulates the electric signal to take out the transmission source signal, and outputs the transmission source signal to the key side control unit 230. The key side LF antenna 215 corresponds to a key side receiving antenna.

  The RSSI detection circuit 211 is provided in the key side reception unit 210. The RSSI detection circuit 211 is a circuit that detects the RSSI of each vehicle signal received by the key side LF antenna 215. The RSSI detection circuit 211 outputs the detected RSSI of the vehicle signal to the key-side control unit 230. The RSSI detection circuit 211 corresponds to a reception strength detection unit.

  The key side transmission unit 220 modulates and amplifies the key signal with an RF wave and transmits the modulated key signal from the key side RF antenna 221 under the control of the key side control unit 230. The key signal is generated by the key side control unit 230. The key signal includes RSSI information indicating the RSSI of the vehicle signal and a unique ID of the electronic key 200. Since the response signal described above is also a transmission source key signal, the response signal also includes a unique ID. The key side RF antenna 221 corresponds to a key side transmitting antenna.

  The key side control unit 230 is mainly configured of a microcomputer. The key-side control unit 230 executes various processes including collation of the electronic key 200 described above and position determination of the electronic key 200 described later by the processor such as the CPU executing a program stored in a storage device such as a ROM, for example. It has a function to execute in cooperation with the in-vehicle system 100. At least a part of the functions of the key-side control unit 230 may be provided by a dedicated IC or the like.

<About the function of verification ECU 110>
Next, the function of the matching ECU 110 for estimating the position of the electronic key 200 with respect to the vehicle will be described. As shown in FIG. 1, the verification ECU 110 includes a vehicle-side control unit 120 and a storage unit 130.

  The vehicle-side control unit 120 includes, as functional blocks, an RSSI acquisition unit 121, a distance calculation unit 122, a candidate point calculation unit 123, a candidate line calculation unit 124, and a position estimation unit 129.

  When the RSSI information is included in the key signal received by the vehicle-side receiving unit 190, the RSSI acquisition unit 121 acquires the RSSI when the electronic key 200 receives the vehicle signal. Specifically, the RSSI acquisition unit 121 acquires, as a first RSSI, an RSSI when the electronic key 200 receives a vehicle signal transmitted from the first in-vehicle LF antenna 181R. The RSSI acquisition unit 121 acquires, as a second RSSI, an RSSI when the electronic key 200 receives a vehicle signal transmitted from the second in-vehicle LF antenna 181L.

  The distance calculation unit 122 calculates the distance from the first onboard LF antenna 181R to the electronic key 200 and the distance from the second onboard LF antenna 181L to the electronic key 200 based on the first RSSI and the second RSSI. The distance calculation unit 122 calculates the distances from the on-vehicle LF antennas 181R and 181L to the electronic key 200 by using the RSSI distance relationship stored in the storage unit 130. The RSSI distance relationship is a reception intensity distance relationship.

  By the way, the reception sensitivity of the electronic key 200 varies from individual to individual within the allowable error range of the reception sensitivity determined from the required specification of the electronic key 200 and the like. Therefore, two kinds of RSSI distance relationships are stored in the storage unit 130 so that it is possible to consider that the reception sensitivity varies for each individual.

  Here, the RSSI distance relationship and the method of calculating the distance using the RSSI distance relationship will be described with reference to FIGS. 3 and 4.

  FIG. 3 conceptually shows the RSSI distance relationship. As shown in FIG. 3, the horizontal axis in the RSSI distance relationship is a distance. This distance is the distance from the on-vehicle LF antenna 181 to the electronic key 200. The vertical axis is the RSSI detected when the electronic key 200 receives the vehicle signal transmitted from the in-vehicle LF antenna 181.

  The storage unit 130 stores a plurality of RSSI distance relationships that assume different reception sensitivities as the reception sensitivities of the electronic key 200. In the present embodiment, a first RSSI distance relationship 133 and a second RSSI distance relationship 135 are stored as the plurality of RSSI distance relationships.

  The first RSSI distance relation 133 is an RSSI distance relation when the reception sensitivity is assumed to be the highest sensitivity within the reception sensitivity variation range. The second RSSI distance relation 135 is an RSSI distance relation when the reception sensitivity is assumed to be the lowest sensitivity within the range of the reception sensitivity variation. These relationships are obtained by experiment in advance.

  As shown in FIG. 3, when the RSSI is applied to the first RSSI distance relationship 133, the estimated maximum distance D_max is determined as the distance from the in-vehicle LF antenna 181 to the electronic key 200. On the other hand, when the same RSSI is applied to the second RSSI distance relationship 135, an estimated minimum distance D_min smaller than the estimated maximum distance D_max is determined as the distance from the in-vehicle LF antenna to the electronic key 200.

  Here, technical meanings of the estimated maximum distance D_max and the estimated minimum distance D_min will be described with reference to FIG. It is assumed that the electronic key 200 actually having the highest reception sensitivity assumed in the first RSSI distance relationship and the electronic key 200 actually having the lowest reception sensitivity assumed in the second RSSI distance relationship detect the same RSSI. In this case, the position of the electronic key 200 actually having the highest reception sensitivity with respect to the in-vehicle LF antenna 181 is on the circle indicated by the broken line in FIG. 4 whose radius is the estimated maximum distance D_max around the in-vehicle LF antenna 181. On the other hand, the position of the electronic key 200 actually having the lowest reception sensitivity relative to the in-vehicle LF antenna 181 is on the circle indicated by the solid line in FIG. 4 whose radius is the estimated minimum distance D_min around the in-vehicle LF antenna 181.

  By the way, the actual value of the reception sensitivity of each electronic key 200 is unknown within the range of the reception sensitivity variation. For this reason, the distance from the in-vehicle LF antenna to the electronic key 200 based on RSSI may be narrowed down so that the lower limit is the estimated minimum distance D_min and the upper limit is the estimated maximum distance D_max, considering the reception sensitivity variation for each electronic key it can. As can be seen from FIG. 3, the error of the estimated distance, which is the difference between the estimated minimum distance D_min and the estimated maximum distance D_max, increases as the RSSI decreases, that is, as the actual distance between the electronic key 200 and the in-vehicle LF antenna increases. Become. The reason for this is that, as shown in FIG. 3, the inclination of the RSSI distance relationship decreases as the distance increases.

  The description returns to the distance calculation unit 122. The distance calculated from the first in-vehicle LF antenna 181R to the electronic key 200 and the distance from the second in-vehicle LF antenna 181L to the electronic key 200 and calculated using the same RSSI distance relationship is defined as a distance set. The distance calculation unit 122 calculates a plurality of distance sets corresponding to a plurality of RSSI distance relationships assuming different reception sensitivities as the reception sensitivities.

  Specifically, as shown in FIG. 5, the distance calculation unit 122 sets the distance corresponding to the first RSSI distance relationship 133, and calculates the first estimated maximum distance D1_max and the second estimated maximum distance D2_max. The first estimated maximum distance D1_max is a distance obtained by applying the first RSSI to the first RSSI distance relation 133. The second estimated maximum distance D2_max is a distance obtained by applying the second RSSI to the first RSSI distance relation 133.

  Further, the distance calculation unit 122 sets the distance corresponding to the second RSSI distance relationship 135 and calculates the first estimated minimum distance D1_min and the second estimated minimum distance D2_min. The first estimated minimum distance D1_min is a distance obtained by applying the first RSSI to the second RSSI distance relation 135. The second estimated minimum distance D2_min is a distance obtained by applying the second RSSI to the second RSSI distance relationship 135. Furthermore, as shown in FIG. 5, the first ideal distance D1_ideal and the second ideal distance D2_ideal may be calculated by setting the distance using the RSSI distance relationship assuming an ideal value as the reception sensitivity. The ideal value is, for example, an intermediate value between the highest sensitivity and the lowest sensitivity.

  The candidate point calculation unit 123 sets a distance calculated by the distance calculation unit 122 as a radius, and an intersection point of a circle centered on the position of the first on-vehicle LF antenna 181R and a circle centered on the position on the second on-vehicle LF antenna 181L. The candidate point which becomes a candidate of the position of the electronic key 200 is calculated based on. The candidate points are calculated for each of the first RSSI distance relation 133 and the second RSSI distance relation 135.

  Specifically, the candidate point calculation unit 123 calculates a candidate point P of the position of the electronic key 200 specified by each distance set calculated by the distance calculation unit 122. Specifically, as shown in FIG. 5, the position of the electronic key 200 specified by the distance set consisting of the first estimated maximum distance D1_max and the second estimated maximum distance D2_max is calculated as the far-side candidate point P_max. Further, the position of the electronic key 200 specified by the distance set consisting of the first estimated minimum distance D1_min and the second estimated minimum distance D2_min is calculated as the near side candidate point P_min. The far-side candidate point P_max and the near-side candidate point P_min can be calculated, for example, according to the following procedure.

  As shown in FIG. 5, a circle is drawn with the radius being the first estimated maximum distance D1_max with the first vehicle-mounted LF antenna 181R as the center. A circle is drawn with a radius of the second estimated maximum distance D2_max centered on the second in-vehicle LF antenna 181L. The coordinates of the intersection of these two circles are calculated as the far-side candidate point P_max. In addition, two far side candidate points P_max are normally calculated, as shown in FIG. This is because there are usually two intersections of two circles whose centers are separated. Further, as shown in FIG. 5, a circle is drawn with the radius being the first estimated minimum distance D1_min, with the first vehicle-mounted LF antenna 181R as the center. A circle is drawn with a radius of the second estimated minimum distance D2_min centered on the second in-vehicle LF antenna 181L. The coordinates of the point of intersection of these two circles are determined and calculated as the near side candidate point P_min. As shown in FIG. 5, two near side candidate points P_min are usually calculated.

  The candidate line calculation unit 124 calculates a straight line segment having the far side candidate point P_max and the near side candidate point P_min as both end points as the candidate line L of the position of the electronic key 200. Specifically, as shown in FIG. 5, the candidate line calculation unit 124 selects the far side candidate point P_max in each of two areas divided by straight lines passing through the first in-vehicle LF antenna 181R and the second in-vehicle LF antenna 181L. A candidate line L having the near side candidate point P_min as both end points is calculated. In FIG. 5, the above two regions are an upper region and a lower region of a straight line passing through the first in-vehicle LF antenna 181R and the second in-vehicle LF antenna 181L.

  Here, the technical significance of the candidate line L calculated by the candidate line calculation unit 124 will be described in comparison with the comparative example of FIG. Considering the reception sensitivity variation for each electronic key individual, the distance from each in-vehicle LF antenna 181 to the electronic key 200 based on RSSI can be narrowed down if the lower limit is the estimated minimum distance D_min and the upper limit is the estimated maximum distance D_max . Based on this, it is possible to calculate a region where the annular region centered on the first in-vehicle LF antenna 181R and the annular region centered on the second in-vehicle LF antenna 181L overlap (see the hatched portion in FIG. 6). In the comparative example, this overlapping area is calculated as a candidate position of the electronic key 200.

  On the other hand, in the present embodiment, the candidate positions of the electronic key 200 are narrowed down to the candidate line L composed of line segments narrowed down than the area of FIG. This is done by focusing on the following points.

  The electronic key 200 has different reception sensitivities for each individual within the range of the reception sensitivity variation. Although the reception sensitivity differs for each individual, the same electronic key 200, that is, the same individual, receives the vehicle signal transmitted from the first in-vehicle LF antenna 181R and the vehicle signal transmitted from the second in-vehicle LF antenna 181L. That is, the receiving sensitivities at the time of receiving the first RSSI and the second RSSI are substantially the same receiving sensitivities. Although the actual reception sensitivity at this time is unknown, the radii of the two circles indicating candidate points P_max and P_min of the electronic key 200, which can be estimated from the RSSI of the vehicle signal from the two in-vehicle LF antennas 181, are both received The same tendency increases or decreases depending on the sensitivity level. Therefore, no matter what the sensitivity of the electronic key 200 that receives the vehicle signal is, the candidate points P_max and P_min of the electronic key on which the difference in the reception sensitivity of the electronic key 200 is reflected is the point on the candidate line L become.

  In this embodiment, both end points of the candidate line L are the far side candidate point P_max corresponding to the first RSSI distance relation 133 assuming the highest sensitivity and the near side candidate points corresponding to the second RSSI distance relation 135 corresponding to the lowest sensitivity. It is P_min.

  However, the two candidate points used to calculate the candidate line L are not limited to this example. The two candidate points used to calculate the candidate line L may be candidate points corresponding to different RSSI distance relationships assuming different reception sensitivities. For example, as shown in FIG. 5, an ideal candidate point P_ideal specified from a distance set consisting of a first ideal distance D1_ideal and a second ideal distance D2_ideal corresponding to the ideal RSSI distance relationship assuming an ideal value as the reception sensitivity is calculated. A line segment having the ideal candidate point P_ideal and the far side candidate point P_max as both end points is calculated. The candidate line L is calculated by extrapolating this line segment by a distance corresponding to the difference between the lowest sensitivity and the ideal sensitivity in the range of the reception sensitivity variation. Alternatively, three or more candidate points P corresponding to three or more different reception sensitivities may be calculated, and candidate lines L may be calculated as approximate curves passing through these.

  The position estimation unit 129 calculates, based on the candidate line L, an estimated position at which the electronic key 200 is estimated to be present. For example, as illustrated in FIG. 7, the position estimation unit 129 calculates a rod-shaped area within a predetermined error distance from the candidate line L as the estimated position area R. The predetermined error distance is a predetermined value that represents an error of the estimated position of the electronic key 200 due to a transmission output error of the first in-vehicle LF antenna 181R and the second in-vehicle LF antenna 181L that was not considered in the calculation of the candidate line L above. Amount. In the present embodiment, the predetermined error distance is stored in advance in the ROM or the like of the matching ECU 110.

  The position estimation unit 129 may further determine which candidate line L of the two candidate lines L calculated by the candidate line calculation unit 124 is valid as a candidate line indicating the position of the electronic key 200. For example, determination may be made as follows. The position estimation unit 129 calculates the distance from the in-vehicle RF antenna 195 to the electronic key 200 based on the RSSI when the in-vehicle RF antenna 195 receives the key signal transmitted from the electronic key 200. The position estimation unit 129 determines which of the two candidate lines L matches the distance from the on-vehicle RF antenna 195 to the electronic key 200.

  Alternatively, it is possible to determine which of the two candidate lines L is valid as a candidate line indicating the position of the electronic key 200 as follows. A plurality of, for example, three, in-vehicle RF antennas 195 are provided on the vehicle. The position estimation unit 129 acquires the reception time at which the three on-vehicle RF antennas 195 receive one key signal transmitted from the electronic key 200. From the difference between the reception times of the three in-vehicle RF antennas 195, the direction in which the electronic key 200 is present is narrowed down, and a candidate line L aligned with this direction is selected from the two candidate lines L.

<Function of Key Side Control Unit 230>
Next, the function of the key-side control unit 230 of the electronic key 200 for performing position estimation of the electronic key 200 with respect to the vehicle in cooperation with the matching ECU 110 will be described.

  When the key-side control unit 230 acquires a vehicle signal via the key-side receiving unit 210, the vehicle signal is transmitted to the vehicle signal as to whether the transmission source of the vehicle signal is the first on-vehicle LF antenna 181R or the second on-vehicle LF antenna 181L. It has a function to specify based on contained identification information.

  Furthermore, the key-side control unit 230 has a function of determining whether or not the key-side receiving unit 210 has received the vehicle signal transmitted from the first in-vehicle LF antenna 181R and the second in-vehicle LF antenna 181L within a predetermined time. Have. The predetermined time can be determined in advance from transmission time intervals when the first in-vehicle LF antenna 181R and the second in-vehicle LF antenna 181L sequentially transmit vehicle signals.

  Furthermore, the key-side control unit 230 has a function of acquiring the RSSI of the vehicle signal transmitted from each of the first in-vehicle LF antenna 181R and the second in-vehicle LF antenna 181L and received by the key-side receiving unit 210. Furthermore, the key-side control unit 230 has a function of transmitting, from the key-side RF antenna 221, a key signal including RSSI information indicating the RSSI of the vehicle signal and the on-vehicle LF antenna 181 that has transmitted the vehicle signal.

<On-vehicle device side position estimation processing>
Next, a vehicle-mounted-unit-side position estimation process performed by the vehicle-side control unit 120 of the matching ECU 110 to estimate the position of the electronic key 200 relative to the vehicle in cooperation with the electronic key 200 will be described with reference to FIG. . The vehicle-mounted device side position estimation process is periodically executed at a predetermined cycle. Alternatively, it is started when a predetermined condition is satisfied, such as when a vehicle engine start push switch (not shown) provided in the vehicle compartment is pressed.

  In S110, the vehicle-side control unit 120 sequentially transmits vehicle signals from the first in-vehicle LF antenna 181R and the second in-vehicle LF antenna 181L at predetermined time intervals. Each vehicle signal or any vehicle signal includes information that requests the electronic key 200 to return a key signal including RSSI information.

  In S120, the vehicle-side control unit 120 determines whether or not the key signal including the RRSI information indicating the RSSI when the electronic key 200 receives each of the vehicle signals transmitted in S110 is received through the in-vehicle RF antenna 195. Do. If a negative determination is made in S120, the present vehicle-mounted device side position estimation processing is ended. If an affirmative determination is made in S120, the process proceeds to S130.

  In S130, using the function of the RSSI acquisition unit 121, the vehicle-side control unit 120 acquires the first RSSI and the second RSSI from the RSSI information included in the key signal received in S120. The first RSSI is an RSSI when the electronic key 200 receives a vehicle signal transmitted from the first in-vehicle LF antenna 181R. The second RSSI is an RSSI when the electronic key 200 receives a vehicle signal transmitted from the second in-vehicle LF antenna 181L.

  In S140, the vehicle-side control unit 120 applies the first RSSI and the second RSSI to the first RSSI distance relation 133 using the function of the distance calculation unit 122 to obtain the first estimated maximum distance D1_max and the second estimated maximum distance D2_max Calculate a first set of distances. Furthermore, in S140, the vehicle-side control unit 120 applies the first RSSI and the second RSSI to the second RSSI distance relationship 135 to calculate a second distance set consisting of the first estimated minimum distance D1_min and the second estimated minimum distance D2_min.

  In S150, the vehicle-side control unit 120 calculates the far-side candidate point P_max of the electronic key 200 specified by the first distance set using the function of the candidate point calculation unit 123, and is specified by the second distance set The near side candidate point P_min of the electronic key 200 is calculated.

  In S160, the vehicle-side control unit 120 uses the function of the candidate line calculation unit 124 to make a candidate line L for the position of the electronic key 200 a line segment having the far side candidate point P_max and the near side candidate point P_min as both end points. Calculated as

  In S170, the vehicle-side control unit 120 uses the function of the position estimation unit 129 to calculate a rod-shaped area within a predetermined error distance from the candidate line as an estimated position area R in which the electronic key 200 is estimated to be present. The instrument-side position estimation process ends.

  In the above vehicle-mounted-device-side position estimation processing, S130 to S160 constitute candidate line calculation processing for calculating the candidate line L using the first RSSI and the first RSSI as inputs. S170 constitutes a position estimation process of calculating the estimated position of the electronic key 200 using the candidate line L as an input.

<Key-side position estimation processing>
Next, key-side position estimation processing executed by the key-side control unit 230 of the electronic key 200 in order to perform position estimation of the electronic key 200 with respect to the vehicle in cooperation with the matching ECU 110 will be described with reference to FIG. The key side position estimation process is periodically executed at a predetermined cycle.

  In S210, the key-side control unit 230 determines whether the key-side receiving unit 210 has received vehicle signals sequentially transmitted from the first in-vehicle LF antenna 181R and the second in-vehicle LF antenna 181L at predetermined time intervals. If an affirmative determination is made in S210, the process proceeds to S220. If a negative determination is made in S210, the present key side position estimation process is ended.

  In S220, the key-side control unit 230 acquires the first RSSI and the second RSSI detected by the RSSI detection circuit 211 when vehicle signals from the first in-vehicle LF antenna 181R and the second in-vehicle LF antenna 181L are received.

  In S230, the key side control unit 230 controls the key side transmission unit 220 to transmit a key signal including RSSI information indicating the first RSSI and the second RSSI from the key side RF antenna 221, and ends the key side position estimation processing. Do.

  In the above embodiment, in candidate line calculation processing for calculating the candidate line L, a distance set is calculated using the first RSSI and the second RSSI, and the RSSI distance relationship, and two circles are drawn from the distance set, Two candidate points P_max and P_min were calculated from two circles. And the procedure which calculates the candidate line L from these two candidate points P_max and P_min was shown. However, the procedure for calculating the candidate line L using the first RSSI and the second RSSI and the RSSI distance relationship is not limited to this. There can be various calculation procedures in which the candidate line L is output with the first RSSI, the second RSSI, and the RSSI distance relationship as an input.

Summary of First Embodiment
In the above configuration, the RSSI distance representing the relationship between the RSSI of the vehicle signal transmitted from each in-vehicle LF antenna 181 detected by the RSSI detection circuit 211 and the distance from the in-vehicle LF antenna 181 to the electronic key 200 The relationship is stored in the storage unit 130. Specifically, two storage units 130 store RSSI distance relationships that assume different reception sensitivities within the range of the reception sensitivity variation of the electronic key 200. Note that the reception strength distance relationship may be any one that indicates the RSSI distance relationship as shown in FIG. 3 directly or indirectly.

  Then, two circles with the first estimated maximum distance D1_max and the second estimated maximum distance D2_max as radiuses that can be determined using the first RSSI distance relationship 133 and the RSSI of the vehicle signal from the two in-vehicle LF antennas 181R and 181L Draw. The intersection of these two circles is set as the far side candidate point P_max. In addition, two circles with the first estimated minimum distance D1_min and the second estimated minimum distance D2_min as radiuses that can be determined using the second RSSI distance relationship 135 and the RSSI of the vehicle signal from the two in-vehicle LF antennas 181R and 181L. Draw. The intersection of these two circles is set as the near candidate point P_min. The two in-vehicle LF antennas 181R and 181L correspond to the two in-vehicle transmission antennas. One of the two in-vehicle LF antennas 181R and 181L corresponds to one in-vehicle transmission antenna, and the other corresponds to the other in-vehicle transmission antenna.

  The reception sensitivity of the electronic key 200 that has received the vehicle signal is unknown. However, when the reception sensitivity changes, the radii of the two circles indicating the candidate points P of the electronic key 200, which can be estimated from the RSSIs of the vehicle signals from the two in-vehicle LF antennas 181R and 181L, both increase and decrease with the same tendency.

  Therefore, no matter what the sensitivity of the electronic key 200 receiving the vehicle signal is, the candidate point P of the electronic key 200 reflecting the difference in the reception sensitivity of the electronic key 200 is the far side candidate point P_max. And the near candidate point P_min on the candidate line L at both ends. In the present embodiment, since the position of the electronic key 200 is estimated based on the candidate line L, it is possible to estimate the position of the electronic key 200 with high accuracy, which is less affected by the variation of the reception sensitivity of the electronic key 200. it can.

  Further, in the above configuration, the first in-vehicle LF antenna 181R is provided on the doorknob of the driver's seat side door of the vehicle, and the second in-vehicle LF antenna 181L is provided on the doorknob of the assistant door of the vehicle.

  According to this configuration, both the first in-vehicle LF antenna 181R and the second in-vehicle LF antenna 181L are provided in the vicinity of the boundary between the inside of the vehicle and the outside of the vehicle. Therefore, the detection area of the first in-vehicle LF antenna 181R and the detection area of the second in-vehicle LF antenna 181L are outside the vehicle, as compared to the case where both the first in-vehicle LF antenna 181R and the second in-vehicle LF antenna 181L are provided in the vehicle interior. It can affect a wide range.

  The above configuration is suitable for estimating the position of the electronic key 200 located near the doorknob, which is near the boundary between the inside and outside of the vehicle, for example, estimating whether the electronic key is located inside or outside the vehicle. This is because, as described in the description of FIG. 3, the error of the estimated distance from the on-board LF antenna 181 to the electronic key 200 based on the RSSI becomes smaller as the electronic key 200 is closer to the on-board LF antenna 181.

  Further, in the above configuration, the verification ECU 110 causes the position estimation unit 129 to transmit vehicle signals from each of the plurality of in-vehicle LF antennas 181 in response to pressing of the engine start push switch in the vehicle compartment. The position of the electronic key 200 is estimated. The plurality of in-vehicle LF antennas 181 correspond to the plurality of in-vehicle transmission antennas.

  When the push switch provided in the vehicle interior for starting the engine of the vehicle is pressed, the electronic key 200 is likely to be located in the vehicle interior. That is, there is a high possibility that the electronic key 200 is located near each of the on-vehicle LF antennas 181. Such a situation is suitable for position estimation of the electronic key 200 based on RSSI.

Second Embodiment
The electronic key system 2 of the second embodiment will be described. Hereinafter, the second embodiment will be described focusing on differences from the first embodiment.

  In the electronic key system 1 according to the first embodiment, as the on-vehicle LF antenna 181, a first on-vehicle LF antenna 181R and a second on-vehicle LF antenna 181L are provided in the vehicle. On the other hand, as shown in FIG. 10, in the electronic key system 2 of the second embodiment, the third in-vehicle LF antenna 181 B is added to the first in-vehicle LF antenna 181 R and the second in-vehicle LF antenna 181 L as the in-vehicle LF antenna 181. Is provided on the vehicle. The first in-vehicle LF antenna 181R corresponds to the first in-vehicle transmitting antenna, the second in-vehicle LF antenna 181L corresponds to the second in-vehicle transmitting antenna, and the third in-vehicle LF antenna 181B corresponds to the third in-vehicle transmitting antenna.

  The third on-vehicle LF antenna 181B is provided, for example, at the rear end of the vehicle. As shown in FIG. 11, the third on-vehicle LF antenna 181 B forms a third detection area 303 extending to the inside and the outside of the vehicle. The first detection area 301, the second detection area 302, and the third detection area 303 are formed such that an overlapping area 310 of these three detection areas extends in and out of the vehicle. As in the first embodiment, such a detection area formed over the inside and outside of the vehicle is realized by limiting the electromagnetic shielding function of the vehicle body by, for example, forming the vehicle body with resin.

  The verification ECU 110 controls the vehicle-side transmission unit 180 to transmit vehicle signals sequentially from the first in-vehicle LF antenna 181R, the second in-vehicle LF antenna 181L, and the third in-vehicle LF antenna 181B.

  The RSSI detection circuit 211 detects an RSSI when the key side LF antenna 215 receives a vehicle signal transmitted from the first in-vehicle LF antenna 181R, the second in-vehicle LF antenna 181L, and the third in-vehicle LF antenna 181B. The RSSI of the vehicle signal from the first in-vehicle LF antenna 181R is detected as a first RSSI. The RSSI of the vehicle signal from the second in-vehicle LF antenna 181L is detected as the second RSSI. The RSSI of the vehicle signal from the third in-vehicle LF antenna 181B is detected as the third RSSI. The first RSSI corresponds to the first received signal strength, the second RSSI corresponds to the second received signal strength, and the third RSSI corresponds to the third received signal strength.

  The key side control unit 230 controls the key side transmission unit 220 to transmit a key signal including RSSI information indicating the first RSSI, the second RSSI, and the third RSSI from the key side RF antenna 221.

  The RSSI acquisition unit 121 acquires the first RSSI, the second RSSI, and the third RSSI from the key signal received via the in-vehicle RF antenna 195.

  The distance calculation unit 122 applies the first RSSI, the second RSSI, and the third RSSI to the RSSI distance relationship to obtain the electronic key 200 from each of the first in-vehicle LF antenna 181R, the second in-vehicle LF antenna 181L, and the third in-vehicle LF antenna 181B. Calculate the distance to Specifically, as shown in FIG. 12, a first estimated maximum distance D1_max and a first estimated minimum distance D1_min are calculated as the distance from the first in-vehicle LF antenna 181R to the electronic key 200. As a distance from the second in-vehicle LF antenna 181 L to the electronic key 200, a second estimated maximum distance D2_max and a second estimated minimum distance D2_min are calculated. A third estimated maximum distance D3_max and a third estimated minimum distance D3_min are calculated as the distances from the third in-vehicle LF antenna 181B to the electronic key 200.

  The candidate point calculation unit 123 calculates a candidate point P of the position of the electronic key 200 specified by the distance calculated by the distance calculation unit 122. Specifically, the following four candidate points P are calculated. A candidate point P specified by the first estimated maximum distance D1_max and the second estimated maximum distance D2_max is calculated. A candidate point P specified by the first estimated minimum distance D1_min and the second estimated minimum distance D2_min is calculated. The candidate point P specified by the second estimated maximum distance D2_max and the third estimated maximum distance D3_max is calculated. A candidate point P specified by the second estimated minimum distance D2_min and the third estimated minimum distance D3_min is calculated. The candidate line calculation unit 124 calculates the first candidate line L1 and the second candidate line L2, as shown in FIG. The first candidate line L1 is a candidate line L specified by applying the first RSSI and the second RSSI to the RSSI distance relationship. The second candidate line L2 is a candidate line L specified by applying the second RSSI and the third RSSI to the RSSI distance relationship.

  Specifically, the first candidate line L1 is a candidate point specified by the first and second estimated maximum distances D1_max and D2_max, and the first and second estimated minimum distances D1_min and D2_min. It is a line segment whose end point is P. The second candidate line L2 is a candidate point P specified by the second and third estimated maximum distances D2_max and D3_max, a candidate point P specified by the second and third estimated minimum distances D2_min and the distance D3_min, and It is a line segment whose end point is.

  The intersection point calculation unit 125, as shown in FIG. 12, calculates as a candidate line intersection point P_cross at which the first candidate line L1 and the second candidate line L2 intersect.

  Here, the technical significance of the candidate line intersection P_cross calculated by the intersection calculation unit 125 will be described in comparison with the comparative example of FIG. 13. Considering the reception sensitivity variation for each electronic key individual, the distance from each on-board LF antenna 181 based on RSSI to the electronic key 200 can be narrowed to a range between the estimated minimum distance D_min and the estimated maximum distance D_max. Based on this, an area where the annular area centered on the first in-vehicle LF antenna 181R, the annular area centered on the second in-vehicle LF antenna 181L, and the annular area centered on the third in-vehicle LF antenna 181B overlap (Refer to the hatched portion in FIG. 13) can be calculated. It is also conceivable to calculate this overlapping area as a candidate position of the electronic key 200.

  The reception sensitivity of the electronic key 200 differs for each individual within the range of the reception sensitivity variation. Therefore, the electronic key 200 receives vehicle signals transmitted from the first in-vehicle LF antenna 181R, the second in-vehicle LF antenna 181L, and the third in-vehicle LF antenna 181B with substantially the same reception sensitivity within the range of the reception sensitivity variation. . That is, all of the first RSSI, the second RSSI, and the third RSSI are RSSIs when received with substantially the same reception sensitivity. Therefore, a first candidate line L1 corresponding to the first in-vehicle LF antenna 181R and the second in-vehicle LF antenna 181L, and a second candidate line L2 corresponding to the second in-vehicle LF antenna and the third in-vehicle LF antenna 181L, 181B The candidate line intersection P_cross is calculated. In this way, it is possible to narrow down the candidate positions of the electronic key 200 considering the variation in reception sensitivity for each electronic key individual to a point narrower than the region shown in FIG.

  The position estimation unit 129 calculates an estimated position at which the electronic key 200 is estimated to exist, based on the candidate line intersection P_cross. For example, the position estimation unit 129 calculates an area within a predetermined error distance from the candidate line intersection P_cross as an estimated position area. The predetermined error distance is a predetermined amount that represents an error of the estimated position of the electronic key 200 caused by the transmission output error of each of the in-vehicle LF antennas 181R, 181L, and 181B, as in the first embodiment.

  In the above configuration, the RSSI detection circuit 211 receives the RSSI when the key side LF antenna 215 receives the vehicle signal transmitted from each of the first to third in-vehicle LF antennas 181R, 181L, and 181B. 3 Detect as RSSI.

  The candidate line calculation unit 124 executes candidate line calculation processing for calculating candidate lines L1 and L2 using the RSSIs of the vehicle signals of the two sets of in-vehicle LF antennas 181. Specifically, the candidate line calculation unit 124 executes the candidate line calculation process using the first RSSI and the second RSSI to calculate the first candidate line L1, and further, the candidate line calculation process using the second RSSI and the third RSSI. To calculate the second candidate line L2. The position estimation unit 129 estimates the position of the electronic key 200 based on a candidate line intersection P_cross which is an intersection of the first candidate line L1 and the second candidate line L2.

  As described above, in the above configuration, the candidate positions of the electronic key 200 in consideration of the reception sensitivity variation for each electronic key individual can be narrowed down to the candidate line intersection P_cross as a point.

Third Embodiment
The electronic key system 3 of the third embodiment will be described. The schematic configuration of the electronic key system 3 of the third embodiment is the same as that of the second embodiment as shown in FIG. 10, but the functions of the functional blocks are different. Hereinafter, the third embodiment will be described focusing on differences from the second embodiment.

  The candidate point calculation unit 123 further calculates the next two candidate points P in addition to the four candidate points P calculated in the second embodiment. An intersection point of a circle determined by the third estimated maximum distance D3_max and a circle determined by the first estimated maximum distance D1_max is calculated as a candidate point P. An intersection point of a circle determined by the third estimated minimum distance D3_min and a circle determined by the first estimated minimum distance D1_min is calculated as a candidate point P. The two candidate points P are different from the four candidate points P used to calculate the first candidate line L1 and the second candidate line L2 in the second embodiment.

  The candidate line calculation unit 124 calculates a third candidate line L3 in addition to the first candidate line L1 and the second candidate line L2 calculated in the second embodiment, as shown in FIG. The third candidate line L3 is a candidate line L determined based on the two candidate points P further calculated in the third embodiment.

  The position estimation unit 129 calculates, based on the candidate line L calculated by the candidate line calculation unit 124, an estimated position at which the electronic key 200 is estimated to be present. As shown in FIG. 15, the position estimation unit 129 of the present embodiment is estimated that the electronic key 200 is present in the area surrounded by the first candidate line L1, the second candidate line L2, and the third candidate line L3. It is calculated as an estimated position area R.

  The technical significance of the estimated position area R surrounded by the first candidate line L1, the second candidate line L2, and the third candidate line L3 will be described. As described in the first and second embodiments, the plurality of RSSIs at the time when the electronic key 200 receives vehicle signals transmitted from the plurality of in-vehicle LF antennas 181 are both in accordance with the level of the reception sensitivity of the electronic key 200. Increase or decrease. The candidate line L is calculated paying attention to this. Therefore, the candidate line L reflects the influence of the variation in the reception sensitivity of the electronic key 200.

  However, each candidate line L is not calculated considering the error of the transmission output of each in-vehicle LF antenna 181. An error in the transmission output of each in-vehicle LF antenna 181 may cause the candidate line L calculated based on the RSSI and hence the intersection point of the candidate line L to be separated from the actual position of the electronic key 200. This is because the RSSI detected by the electronic key 200 increases or decreases according to the transmission output of the in-vehicle LF antenna.

  A case is considered in which the errors in the transmission output of all of the first in-vehicle LF antenna 181R, the second in-vehicle LF antenna 181L, and the third in-vehicle LF antenna 181B are zero. In this case, it is considered that the first candidate line L1, the second candidate line L2, and the third candidate line L3 intersect at one point unless there is an error requirement other than the reception sensitivity variation of the electronic key 200. However, when the first to third in-vehicle LF antennas 181R, 181L, and 181B have different transmission output errors, the first to third candidate lines L1, L2, and L3 do not intersect at one point as shown in FIG. There is. In this case, there is a region surrounded by these candidate lines L1, L2, and L3. This area is calculated as an estimated position area R where the electronic key 200 is estimated to be located.

  In the above configuration, in addition to the first candidate line L1 and the second candidate line L2, the candidate line calculation unit 124 executes the candidate line calculation process using the third RSSI and the first RSSI to obtain the third candidate line L3. calculate. The position estimation unit 129 calculates an area surrounded by the first candidate line L1, the second candidate line L2, and the third candidate line L3 as an estimated position area R in which the electronic key 200 is estimated to be located.

  According to this configuration, the position of the electronic key 200 is estimated based on the three candidate lines L1, L2, L3 determined based on the RSSI of the vehicle signal from each of the three in-vehicle LF antennas 181 and the plurality of RSSI distance relationships. doing. Therefore, the estimation error due to the reception sensitivity variation for each electronic key individual can be suppressed. In addition, the transmission output error of each in-vehicle LF antenna is taken into consideration by setting the area surrounded by the three candidate lines L1, L2 and L3 as the estimated position area R where the electronic key 200 is estimated to be located. It is possible to estimate the position of the electronic key 200 with high accuracy.

Fourth Embodiment
FIG. 16 shows a schematic configuration of the electronic key system 4 of the fourth embodiment. Hereinafter, the fourth embodiment will be described focusing on differences from the third embodiment.

  In the electronic key system 3 according to the third embodiment, the on-vehicle system 100 is provided with a function for estimating the position of the electronic key 200 based on the RSSI detected by the RSSI detection circuit 211. On the other hand, in the electronic key system 4 of the fourth embodiment, as shown in FIG. 16, the electronic key 200 is provided with a function for estimating the position of the electronic key 200 based on the RSSI detected by the RSSI detection circuit 211. Be Specifically, the electronic key 200 includes the RSSI acquisition unit 121, the distance calculation unit 122, the candidate point calculation unit 123, the candidate line calculation unit 124, and the intersection point calculation unit 125 as functional blocks of the key side control unit 230. And a position estimation unit 129. The electronic key 200 further includes a storage unit 130.

  As described above, with the position estimation function provided in the electronic key 200, the vehicle-side control unit 120 of the matching ECU 110 uses a vehicle signal to be sequentially transmitted from the plurality of in-vehicle LF antennas 181 for position estimation of the electronic key 200. The in-vehicle antenna position information and the estimated position return request are included. The on-vehicle antenna position information and the estimated position return request may be included in each vehicle signal or any vehicle signal.

  The on-vehicle antenna position information is information indicating the position of each on-vehicle LF antenna 181 directly or indirectly. Since the position of each in-vehicle LF antenna 181 is information necessary for the electronic key 200 to estimate the position of the electronic key 200 with respect to the vehicle based on the RSSI, the in-vehicle antenna position information is included in the vehicle signal. It is The position of each in-vehicle LF antenna is represented, for example, by the relative position of each in-vehicle LF antenna with respect to the coordinates (longitude, latitude) of the vehicle center. The estimated position return request is to request the electronic key 200 to return the estimated position calculated by the electronic key 200 to the verification ECU 110.

  When receiving the vehicle signals sequentially transmitted from the plurality of in-vehicle LF antennas 181, the key-side control unit 230 of the electronic key 200 estimates the position of the electronic key 200 using the functional block for position estimation of the electronic key 200 described above. . When the position of the electronic key 200 is estimated, the key-side control unit 230 causes the key-side RF antenna 221 to transmit a key signal including the estimated position of the electronic key 200.

  When receiving the key signal including the estimated position via the on-vehicle RF antenna 195, the verification ECU 110 of the in-vehicle system 100 obtains the estimated position of the electronic key 200 from the key signal. In the above configuration, the electronic key 200 can be configured to estimate the position of the electronic key 200.

  Although various embodiments have been described above, each embodiment can be variously modified. For example, the position of the in-vehicle LF antenna 181 is not limited to the above example. In each embodiment, the plurality of on-vehicle LF antennas 181 may be provided at any position as long as they are provided separately in the vehicle. In the third embodiment, four or more in-vehicle LF antennas 181 may be provided, and an area surrounded by four or more candidate lines may be set as the estimated position area of the electronic key 200. Also, the embodiments can be variously modified and expanded. For example, technical components disclosed in different embodiments can be combined as appropriate to make an embodiment.

110: verification ECU (vehicle-mounted device), 122: distance calculation unit, 123: candidate point calculation unit, 124: candidate line calculation unit, 129: position estimation unit, 130: storage unit, 133: first RSSI distance relationship (reception strength distance Relation), 135 ... second RSSI distance relation (reception strength distance relation) 181 ... in-vehicle LF antenna (in-vehicle transmission antenna), 181R ... first in-vehicle LF antenna (first in-vehicle transmission antenna), 181 L ... second in-vehicle LF antenna ( Second in-vehicle transmission antenna), 181 B: third in-vehicle LF antenna (third in-vehicle transmission antenna), 195: in-vehicle RF antenna (in-vehicle reception antenna) 200, electronic key, 211: RSSI detection circuit (reception strength detection unit) 215: Key side LF antenna (key side receiving antenna) 221: key side RF antenna (key side transmitting antenna) 230: key side M, L: candidate line L, L1: first candidate line, L2: second candidate line, L3: third candidate line, P_cross: candidate line intersection, P_max: far side candidate point (candidate point), P_min: near Side candidate point (candidate point), R ... estimated position area

Claims (7)

An on-vehicle unit (110) mounted on a vehicle provided with a plurality of on-vehicle transmission antennas (181, 181R, 181L, 181B) and an on-vehicle reception antenna (195);
Key side reception antenna (215), reception strength detection unit (211) for detecting reception signal strength when vehicle signal transmitted from each of the on-vehicle transmission antennas is received by the key side reception antenna, and key side transmission An electronic key (200) having an antenna (221) and performing wireless communication with the onboard device;
A vehicle electronic key system comprising:
A reception intensity distance relationship representing a relationship between a received signal strength of a vehicle signal from the in-vehicle transmission antenna detected by the reception intensity detection unit and a distance from the in-vehicle transmission antenna to the electronic key, A storage unit (130) storing a plurality of reception intensity distance relationships (133, 135) having different reception sensitivities of the reception intensity detection unit;
The distance from one in-vehicle transmitting antenna constituting the two in-vehicle transmitting antennas included in the plurality of in-vehicle transmitting antennas to the electronic key, and the other in-vehicle transmitting antenna of the two in-vehicle transmitting antennas to the electronic key Distance calculation unit which determines the reception signal strength of the vehicle signal from each of the two on-vehicle transmission antennas detected by the reception strength detection unit to a plurality of reception strength distance relationships 122) and
The electronic key is based on the intersection of a circle centered on the position of the one on-vehicle transmission antenna and a circle centered on the position of the other on-vehicle transmission antenna, with the distance calculated by the distance calculation unit as a radius. A candidate point calculation unit (123) which calculates candidate points to be candidates for the position of a plurality of the reception sensitivities;
A candidate for calculating a line segment determined from a plurality of candidate points (P_max, P_min) calculated for a plurality of the reception sensitivities as candidate lines (L, L1, L2, L3) of the position of the electronic key A candidate line calculation unit (124) that executes line calculation processing;
A position estimation unit (129) for estimating the position of the electronic key based on the candidate line calculated by the candidate line calculation unit. In the vehicle electronic key system according to claim 1,
The in-vehicle transmission antenna includes a first in-vehicle transmission antenna, a second in-vehicle transmission antenna, and a third in-vehicle transmission antenna.
The reception strength detection unit receives received signal strength when the vehicle signal transmitted from each of the first on-vehicle transmission antenna, the second on-vehicle transmission antenna, and the third on-vehicle transmission antenna is received by the key-side receiving antenna. Detecting as the first received signal strength, the second received signal strength, and the third received signal strength,
The distance calculation unit applies the first received signal strength, the second received signal strength, and the third received signal strength to a plurality of the received strength distance relationship, so that from the first on-vehicle transmission antenna to the electronic key A distance from the second on-vehicle transmission antenna to the electronic key, and a distance from the third on-vehicle transmission antenna to the electronic key with respect to the plurality of reception sensitivities,
The candidate point calculation unit
A plurality of distances determined by applying the first received signal strength to the plurality of received strength distance relationships is a radius, and a plurality of circles centering on the position of the first on-vehicle transmission antenna and the second received signal strength A plurality of distances determined by applying the plurality of reception strength distance relationships to a radius, a plurality of circles centered on the position of the second on-vehicle transmission antenna, and a plurality of the reception strengths of the third reception signal strength A plurality of distances determined by applying to the distance relationship is defined as a radius, a plurality of circles centered on the position of the third on-vehicle transmission antenna are determined, and the candidate points are determined based on the intersections of the circles having the same reception sensitivity. To determine
The candidate line calculation unit calculates a first candidate line (L1) based on two or more of the intersections having different reception sensitivities, and is two or more of the intersections having different reception sensitivities, A second candidate line (L2) is calculated based on the intersection point different from that used in the calculation of the first candidate line,
The said position estimation part estimates the position of the said electronic key based on the candidate line intersection (P_cross) which is a point which the said 1st candidate line and the said 2nd candidate line cross | intersect. In the vehicle electronic key system according to claim 2,
The candidate line calculation unit is a third one based on two or more of the intersections having different reception sensitivities based on the intersections different from those used for the calculation of the first candidate line and the second candidate line. Calculate candidate line (L3),
The position estimation unit is for a vehicle that calculates an area surrounded by the first candidate line, the second candidate line, and the third candidate line as an estimated position area (R) in which the electronic key is estimated to be located. Electronic key system. The electronic key system for a vehicle according to any one of claims 1 to 3.
The electronic key further includes a key-side control unit (230) for transmitting a key signal including the received signal strength detected by the received strength detection unit from the key-side transmission antenna to the on-vehicle device;
The said vehicle-mounted device is an electronic key system for vehicles provided with the said memory | storage part, the said distance calculation part, the said candidate point calculation part, the said candidate line calculation part, and the said position estimation part. The electronic key system for a vehicle according to any one of claims 1 to 3.
The electronic key includes the storage unit, the distance calculation unit, the candidate point calculation unit, the candidate line calculation unit, and the position estimation unit.
The electronic key further includes a key-side control unit (230) for transmitting a key signal including the position of the electronic key estimated by the position estimation unit from the key-side transmitting antenna to the vehicle-mounted device system. The electronic key system for a vehicle according to any one of claims 1 to 5,
The on-vehicle transmission antenna includes an on-vehicle transmission antenna (181R) provided on a doorknob of a driver's seat side door of the vehicle, and an on-vehicle transmission antenna (181L) provided on a doorknob of an assistant door on the vehicle. Electronic key system for vehicles. The electronic key system according to any one of claims 1 to 6,
The vehicle-mounted device transmits the vehicle signal from each of the plurality of vehicle-mounted transmission antennas in response to pressing of an engine start push switch provided in the vehicle cabin, the electronic key is transmitted to the position estimation unit. Electronic key system for vehicles that makes it possible to estimate the position of the vehicle.

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