JP7017062B2 - Electronic key system for vehicles - Google Patents

Description

The disclosure herein relates to an electronic key system for a vehicle comprising an electronic key and an on-board unit that wirelessly communicates with the electronic key.

Conventionally, there is known an electronic key system for a vehicle that permits or executes predetermined processing for a vehicle such as locking / unlocking a vehicle or starting an engine based on wireless communication between an on-board unit and an electronic key.

In the vehicle electronic key system, processing is permitted or executed according to the position of the electronic key with respect 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 a combination of the received signal strength when the electronic key receives the vehicle signal transmitted from one vehicle-mounted antenna and the received signal strength when the electronic key receives the vehicle signal transmitted from the other vehicle-mounted antenna. To determine the position of the electronic key.

Specifically, in Patent Document 1, 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 passenger seat antenna are two-dimensionally shown. The position of the electronic key is determined by comparing the point with the determination line.

Japanese Unexamined Patent Publication No. 2011-144625

By the way, it is inevitable that the radio wave reception sensitivity of the electronic key will vary from individual to individual. For example, within the tolerance range of the reception sensitivity determined from the required specifications of the electronic key, the reception sensitivity of one electronic key becomes high sensitivity, and the reception sensitivity of another electronic key becomes low sensitivity. Such variation in reception sensitivity causes deterioration of the position determination accuracy of the electronic key based on the reception signal strength of the vehicle signal. This is because even if the electronic key detects the same value of the received signal strength, the actual distance from the in-vehicle antenna that emitted the vehicle signal to the electronic key differs depending on the level of the reception sensitivity of the electronic key. be. From a different point of view, the position of the electronic key with respect to the vehicle calculated based on the received signal strength of the vehicle signal may deviate from the actual position of the electronic key with respect to the vehicle due to the variation in the reception sensitivity for each individual electronic key.

The position determination of the electronic key in Patent Document 1 is two-dimensional, which is 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 passenger seat antenna. The upper point is compared with the judgment line. The points on the two dimensions vary depending on the reception sensitivity of the electronic key solid. That is, in Patent Document 1, the variation in reception sensitivity for each electronic key solid is not taken into consideration.

An object of the disclosure in this specification is to provide a vehicle electronic key system capable of highly accurate position estimation of an electronic key in consideration of a variation in reception sensitivity for each electronic key individual.

An example of an electronic key system for vehicles to achieve the above objectives is
An on-board unit (110) mounted on a vehicle provided with a plurality of in-vehicle transmitting antennas (181, 181R, 181L, 181B) and an in-vehicle receiving antenna (195).
The key-side receiving antenna (215), the reception strength detection unit (211) that detects the reception signal strength when the vehicle signal transmitted from each of the in-vehicle transmission antennas is received by the key-side reception antenna, and the key-side transmission antenna (211). 221), and an electronic key (200) that performs wireless communication with the in-vehicle device.
An electronic key system for vehicles equipped with
It is a reception strength distance relationship that represents the relationship between the reception signal strength of the vehicle signal from the vehicle-mounted transmission antenna detected by the reception strength detection unit and the distance from the vehicle-mounted transmission antenna to the electronic key, and is the reception strength detection. A storage unit (130) that stores a plurality of reception intensity distance relationships (133, 135) having different reception sensitivities.
The distance from one vehicle-mounted transmitting antenna constituting the two vehicle-mounted transmitting antennas included in the plurality of vehicle-mounted transmitting antennas to the electronic key and the distance from the other vehicle-mounted transmitting antenna of the two vehicle-mounted transmitting antennas to the electronic key. A distance calculation unit (122) that determines the reception signal strength of the vehicle signal from each of the two in-vehicle transmission antennas detected by the reception strength detection unit by applying the reception signal strength to a plurality of reception strength distance relationships.
The distance calculated by the distance calculation unit is used as the radius, and the candidate for the position of the electronic key is based on the intersection of the circle centered on the position of one in-vehicle transmitting antenna and the circle centered on the position of the other in-vehicle transmitting antenna. Candidate point calculation unit (123) that calculates the candidate points to be obtained for a plurality of reception sensitivities, and
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 is calculated as a candidate line (L, L1, L2, L3) at the position of the electronic key. Candidate line calculation unit (124) to execute
A position estimation unit (129) that estimates the position of the electronic key based on the candidate line calculated by the candidate line calculation unit, and
It is also an electronic key system for vehicles.

In this vehicle electronic key system, the storage unit stores a plurality of reception intensity distance relationships assuming different reception sensitivities as the reception sensitivities of the electronic keys. Then, using the plurality of reception strength relationships and the reception signal strength of the vehicle signal from each of the two vehicle-mounted transmitting antennas detected by the reception strength detection unit, the distance from the two vehicle-mounted transmitting antennas to the electronic key is determined. Further, the candidate point of the position of the electronic key is determined based on the intersection of the circles centered on the two in-vehicle transmitting antennas with this distance as the radius. The candidate line is calculated based on a plurality of candidate points calculated for a plurality of reception sensitivities.

The reception sensitivity of the electronic key that received the vehicle signal is unknown. However, when the reception sensitivity changes, the radii of the two circles indicating the candidate points of the electronic key, which can be estimated from the received signal intensities of the vehicle signals from the two in-vehicle transmitting antennas, both increase or decrease in the same tendency.

Therefore, regardless of the reception sensitivity of the electronic key that has received the vehicle signal, the candidate point of the electronic key that reflects the difference in the reception sensitivity of the electronic key is a 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.

The reference numbers in parentheses are merely examples of the correspondence with the specific configuration in the embodiment described later, and are intended to limit the technical scope. It's not a thing.

It is a figure which shows the schematic structure of the electronic key system 1 for a vehicle of 1st Embodiment. It is a figure explaining the detection area 301, 302 of the vehicle-mounted LF antenna 181R, 181L of 1st Embodiment. It is a figure explaining the RSSI distance relation 133, 135 of 1st Embodiment. It is a figure explaining the distances D_max, D_min calculated by the RSSI distance relations 133, 135 of 1st Embodiment. It is a figure explaining the candidate point P_max, P_min and the candidate line L of the candidate position of the electronic key 200 of 1st Embodiment. It is a figure explaining the comparative example about the candidate position of the electronic key 200 of 1st Embodiment. It is a figure explaining the estimated position area R of the electronic key 200 of 1st Embodiment. It is a flowchart explaining the on-board unit side position estimation process executed by the collation ECU 110 of 1st Embodiment. It is a flowchart explaining the key side position estimation process executed by the electronic key 200 of 1st Embodiment. It is a figure which shows the schematic structure of the electronic key system 2 and 3 for a vehicle of 2nd Embodiment and 3rd Embodiment. It is a figure explaining the detection area 301, 302, 303 of the vehicle-mounted LF antennas 181R, 181L, 181B of the 2nd embodiment and the 3rd embodiment. It is a figure explaining the candidate lines L1, L2 and the candidate line intersection P_cross of the candidate position of the electronic key 200 of the 2nd embodiment. It is a figure explaining the comparative example about the candidate position of the electronic key 200 of 2nd Embodiment. It is a figure explaining the candidate line L1, L2, L3 of the 3rd Embodiment. It is a partially enlarged view which expanded the region shown by XV of FIG. It is a figure which shows the schematic structure of the electronic key system 4 for a vehicle of 4th Embodiment.

Hereinafter, a plurality of embodiments of the vehicle electronic key system (hereinafter, electronic key system) will be described with reference to the drawings. In a plurality of embodiments, functionally and / or structurally corresponding parts and / or associated parts are designated by the same reference numeral. References can be made to the description of other embodiments for the corresponding and / or associated parts.

(First Embodiment)
FIG. 1 shows a schematic configuration of the electronic key system 1 of the first embodiment. The electronic key system 1 has a function of executing collation of the electronic key 200 by the collation ECU 110 based on wireless communication between the in-vehicle system 100 and the electronic key 200, and executing or permitting a predetermined process when the collation is established. Have. The ECU is an abbreviation for an electronic control unit.

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

Upon receiving the request signal, the electronic key 200 transmits a response signal including an ID unique to itself. When the vehicle-mounted system 100 receives the response signal as the response of the request signal by the vehicle-mounted RF antenna 195, the collating ECU 110 collates the electronic key 200 by collating the ID included in the response signal.

Examples of the predetermined processing permitted or executed when the collation is established include the following. Allows the vehicle engine to start when the legitimate electronic key 200 is located in the vehicle interior. The passenger compartment does not include the trunk room. In addition, unlocking of the vehicle door is permitted when the legitimate electronic key 200 is located in a predetermined area outside the vehicle. Further, when the regular electronic key 200 approaches the vehicle by a predetermined distance, a welcome process for turning on the hazard lamp of the vehicle or the like is executed. As described above, the electronic key system 1 permits or executes different processes depending on the position of the electronic key 200 with respect to the vehicle.

The electronic key system 1 of the present embodiment estimates the position of the electronic key 200 with respect to the vehicle in executing or permitting the predetermined processing by the above 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 vehicle-mounted system 100 includes a collation ECU 110, a vehicle-side transmitting unit 180, a first vehicle-mounted LF antenna 181R, a second vehicle-mounted LF antenna 181L, a vehicle-side receiving unit 190, and an vehicle-mounted RF antenna 195.

The collation ECU 110 is mainly composed of a microcomputer. The collation ECU 110 performs various processes including collation of the electronic key 200 described above and position estimation of the electronic key 200 described later by executing a program stored in a storage device such as a ROM by a processor such as a CPU. It has a function to execute in cooperation with. At least a part of the function of the collation ECU 110 may be provided by a dedicated IC or the like. The collation ECU 110 corresponds to an on-board unit.

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

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

The first vehicle-mounted LF antenna 181R and the second vehicle-mounted 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 in which the vehicle signal transmitted from each of the vehicle-mounted LF antennas 181R and 181L can be received by the electronic key 200 with a reception signal strength (hereinafter, RSSI) equal to or higher than a predetermined threshold value. The size of the detection area can be set to a desired size (for example, 10 m or the like) by, for example, setting the transmission output of the first vehicle-mounted LF antenna 181R and the second vehicle-mounted LF antenna 181L. Each in-vehicle LF antenna 181 corresponds to an in-vehicle transmitting antenna.

As shown in FIG. 2, the first detection area 301 and the second detection area 302 are formed inside and outside the vehicle, respectively. Further, the first detection area 301 and the second detection area 302 are formed so that these overlapping regions 310 extend inside and outside the vehicle. Such a detection area formed inside and outside 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 by an RF (Radio Frequency) wave from the electronic key 200 via the vehicle-mounted RF antenna 195. The vehicle-side receiving unit 190 amplifies the electric signal acquired from the vehicle-mounted RF antenna 195, demodulates the key signal from the electric signal, and outputs the key signal to the collation ECU 110. The in-vehicle RF antenna 195 is provided at a position appropriately designed in the vehicle. For example, the vehicle-mounted 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 reply to the request signal is the above-mentioned response signal. The key signal may further include RSSI information indicating the RSSI when the electronic key 200 receives the vehicle signal. The RSSI information includes identification information that makes it possible to identify whether the source of the RSSI and the vehicle signal is the first vehicle-mounted LF antenna 181R or the second vehicle-mounted LF antenna 181L. The in-vehicle RF antenna 195 corresponds to an in-vehicle receiving antenna.

The electronic key 200 is a portable device carried by the user, and includes a key-side receiving unit 210, a key-side LF antenna 215, a key-side transmitting unit 220, a key-side RF antenna 221 and a key-side control unit 230. To prepare for.

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

The RSSI detection circuit 211 is provided in the key side receiving 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 RSSI of the detected vehicle signal to the key side control unit 230. The RSSI detection circuit 211 corresponds to the reception intensity detection unit.

The key-side transmission unit 220 modulates and amplifies the key signal with an RF wave under the control of the key-side control unit 230, and transmits the key signal from the key-side RF antenna 221. 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 the unique ID of the electronic key 200. Since the above-mentioned response signal is also a source key signal, the response signal also includes a unique ID. The key-side RF antenna 221 corresponds to the key-side transmission antenna.

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

<About the function of the collation ECU 110>
Next, the function of the collation 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 collation ECU 110 includes a vehicle-side control unit 120 and a storage unit 130.

The vehicle-side control unit 120 includes 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 as functional blocks.

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

The distance calculation unit 122 calculates the distance from the first vehicle-mounted LF antenna 181R to the electronic key 200 and the distance from the second vehicle-mounted LF antenna 181L to the electronic key 200 based on the first RSSI and the second RSSI. The distance calculation unit 122 calculates the distance from each in-vehicle LF antenna 181R, 181L to the electronic key 200 by using the RSSI distance relationship stored in the storage unit 130. The RSSI distance relationship is the 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 by the required specifications of the electronic key 200 and the like. Therefore, two types of RSSI distance relationships are stored in the storage unit 130 so that it can be taken into consideration that the reception sensitivity varies from individual to individual.

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

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

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

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

As shown in FIG. 3, when RSSI is applied to the first RSSI distance relationship 133, the estimated maximum distance D_max is determined as the distance from the vehicle-mounted 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, the estimated minimum distance D_min, which is smaller than the estimated maximum distance D_max, is determined as the distance from the vehicle-mounted LF antenna to the electronic key 200.

Here, the 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 that actually has the highest reception sensitivity assumed in the first RSSI distance relationship and the electronic key 200 that actually has 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 with respect to the vehicle-mounted LF antenna 181 that actually has the maximum reception sensitivity is on the circle shown by the broken line in FIG. 4 having a radius of the estimated maximum distance D_max centered on the vehicle-mounted LF antenna 181. On the other hand, the position of the electronic key 200 with respect to the vehicle-mounted LF antenna 181 that actually has the minimum reception sensitivity is on the circle shown by the solid line in FIG. 4 having a radius of the estimated minimum distance D_min centered on the vehicle-mounted 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. Therefore, the distance from the in-vehicle LF antenna based on RSSI to the electronic key 200 can be narrowed down to the estimated minimum distance D_min at the lower limit and the estimated maximum distance D_max at the upper limit in consideration of the reception sensitivity variation for each electronic key individual. can. As can be seen from FIG. 3, the error in 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 slope of the RSSI distance relationship becomes smaller as the distance increases.

The explanation returns to the explanation of the distance calculation unit 122. The distance from the first vehicle-mounted LF antenna 181R to the electronic key 200 and the distance from the second vehicle-mounted LF antenna 181L to the electronic key 200, which are calculated using the same RSSI distance relationship, are 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 reception sensitivities.

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

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

The candidate point calculation unit 123 has a radius calculated by the distance calculation unit 122, and is an intersection of a circle centered on the position of the first vehicle-mounted LF antenna 181R and a circle centered on the position of the second vehicle-mounted LF antenna 181L. Based on the above, a candidate point that is a candidate for the position of the electronic key 200 is calculated. Candidate points are calculated for each of the first RSSI distance relationship 133 and the second RSSI distance relationship 135.

Specifically, the candidate point calculation unit 123 calculates the candidate point P at 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 candidate point P_min. The far side candidate point P_max and the near side candidate point P_min can be calculated by, for example, the following procedure.

As shown in FIG. 5, a circle is drawn centered on the first vehicle-mounted LF antenna 181R and having a radius of the first estimated maximum distance D1_max. Draw a circle centered on the second vehicle-mounted LF antenna 181L and having a radius of the second estimated maximum distance D2_max. The coordinates of the intersection of these two circles are calculated as the far side candidate point P_max. As shown in FIG. 5, two far-side candidate points P_max are usually calculated. 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 centered on the first vehicle-mounted LF antenna 181R and having a radius of the first estimated minimum distance D1_min. Draw a circle centered on the second vehicle-mounted LF antenna 181L and having a radius of the second estimated minimum distance D2_min. The coordinates of the intersection of these two circles are obtained and calculated as the near candidate point P_min. As shown in FIG. 5, two near candidate points P_min are usually calculated.

The candidate line calculation unit 124 calculates a linear 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 at the position of the electronic key 200. Specifically, as shown in FIG. 5, the candidate line calculation unit 124 has a remote candidate point P_max in each of the two regions divided by the straight line passing through the first vehicle-mounted LF antenna 181R and the second vehicle-mounted LF antenna 181L. The 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 vehicle-mounted LF antenna 181R and the second vehicle-mounted 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 variation in reception sensitivity for each electronic key, the distance from each in-vehicle LF antenna 181 to the electronic key 200 based on RSSI can 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. .. Based on this, the region where the annular region centered on the first vehicle-mounted LF antenna 181R and the annular region centered on the second vehicle-mounted LF antenna 181L overlap (see the shaded portion in FIG. 6) can be calculated. In the comparative example, this overlapping region is calculated as a candidate position of the electronic key 200.

On the other hand, in the present embodiment, the candidate position of the electronic key 200 is narrowed down to the candidate line L composed of the line segment narrowed down from the area of FIG. This is done by paying attention to 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 solid, the same electronic key 200, that is, the same solid receives both the vehicle signal transmitted from the first vehicle-mounted LF antenna 181R and the vehicle signal transmitted from the second vehicle-mounted LF antenna 181L. That is, the reception sensitivities when the first RSSI and the second RSSI are received are substantially the same. Although the actual reception sensitivity at this time is unknown, the radii of the two circles indicating the 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. It increases or decreases with the same tendency according to the level of sensitivity. Therefore, regardless of the reception sensitivity of the electronic key 200 that has received the vehicle signal, the candidate points P_max and P_min of the electronic key reflecting the difference in the reception sensitivity of the electronic key 200 are points L on the candidate line. become.

In the present embodiment, both end points of the candidate line L are the far side candidate point P_max corresponding to the first RSSI distance relationship 133 assuming the highest sensitivity and the near side candidate point corresponding to the second RSSI distance relationship 135 corresponding to the lowest sensitivity. It is set to 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 for calculating the candidate line L may be any candidate points corresponding to different RSSI distance relationships assuming different reception sensitivities. For example, as shown in FIG. 5, the ideal candidate point P_ideal specified from the distance set consisting of the first ideal distance D1_ideal and the second ideal distance D2_ideal corresponding to the ideal RSSI distance relationship assuming the ideal value as the reception sensitivity is calculated. A line segment having the ideal candidate point P_ideal and the distant 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 minimum sensitivity and the ideal sensitivity in the range of the reception sensitivity variation. Further, three or more candidate points P corresponding to three or more different reception sensitivities may be calculated, and the candidate line L may be calculated as an approximate curve passing through these candidate points P.

The position estimation unit 129 calculates the estimated position where the electronic key 200 is estimated to exist based on the candidate line L. For example, as shown in FIG. 7, the position estimation unit 129 calculates a rod-shaped region within a predetermined error distance from the candidate line L as an estimated position region R. The predetermined error distance is predetermined to represent the error of the estimated position of the electronic key 200 due to the transmission output error of the first vehicle-mounted LF antenna 181R and the second vehicle-mounted LF antenna 181L that were not considered in the calculation of the candidate line L. The amount. In the present embodiment, the predetermined error distance is stored in advance in the ROM or the like of the collation ECU 110.

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

Alternatively, it can be determined which of the two candidate lines L is appropriate as the candidate line indicating the position of the electronic key 200 as follows. A plurality of in-vehicle RF antennas 195, for example, three are provided in the vehicle. The position estimation unit 129 acquires the reception time when the three vehicle-mounted RF antennas 195 receive one key signal transmitted from the electronic key 200. From the difference in reception time of the three vehicle-mounted RF antennas 195, the direction in which the electronic key 200 exists is narrowed down, and the candidate line L consistent with this direction is selected from the two candidate lines L.

<About the function of the key side control unit 230>
Next, the function of the key side control unit 230 of the electronic key 200 for performing the position estimation of the electronic key 200 with respect to the vehicle in cooperation with the collation ECU 110 will be described.

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

Further, 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 vehicle-mounted LF antenna 181R and the second vehicle-mounted LF antenna 181L within a predetermined time. Have. The predetermined time can be predetermined from the transmission time interval when the first vehicle-mounted LF antenna 181R and the second vehicle-mounted LF antenna 181L sequentially transmit the vehicle signal.

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

<On-board unit side position estimation process>
Next, the on-board unit side position estimation process executed by the vehicle side control unit 120 of the collation ECU 110 in order to perform the position estimation of the electronic key 200 with respect to the vehicle in cooperation with the electronic key 200 will be described with reference to FIG. .. The on-board unit 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 push switch for starting a vehicle engine (not shown) provided in the vehicle interior is pressed.

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

In S120, the vehicle-side control unit 120 determines whether or not a key signal including RRSI information indicating RSSI when each of the vehicle signals transmitted in S110 is received by the electronic key 200 is received via the vehicle-mounted RF antenna 195. do. If a negative determination is made in S120, the on-board unit side position estimation process is terminated. If an affirmative determination is made in S120, the process proceeds to S130.

In S130, 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 by using the function of the RSSI acquisition unit 121. The first RSSI is an RSSI when the electronic key 200 receives the vehicle signal transmitted from the first vehicle-mounted LF antenna 181R. The second RSSI is an RSSI when the electronic key 200 receives the vehicle signal transmitted from the second vehicle-mounted LF antenna 181L.

In S140, the vehicle-side control unit 120 applies the first RSSI and the second RSSI to the first RSSI distance relationship 133 by 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. First distance set is calculated. Further, in S140, the vehicle-side control unit 120 calculates a second distance set having a first estimated minimum distance D1_min and a second estimated minimum distance D2_min by applying the first RSSI and the second RSSI to the second RSSI distance relationship 135.

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 by using the function of the candidate point calculation unit 123, and is specified by the second distance set. The near 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 set a 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 at the position of the electronic key 200. Calculated as.

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

In the above-mentioned on-board unit side position estimation process, S130 to S160 configure a candidate line calculation process for calculating a candidate line L using the first RSSI and the first RSSI as inputs. S170 constitutes a position estimation process for calculating the estimated position of the electronic key 200 using the candidate line L as an input.

<Key side position estimation process>
Next, the key-side position estimation process executed by the key-side control unit 230 of the electronic key 200 in order to perform the position estimation of the electronic key 200 with respect to the vehicle in cooperation with the collation 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 or not the key-side receiving unit 210 has received vehicle signals sequentially transmitted from the first vehicle-mounted LF antenna 181R and the second vehicle-mounted LF antenna 181L at predetermined time intervals. If an affirmative determination is made in S210, the process proceeds to S220. When a negative determination is made in S210, the key side position estimation process this time is terminated.

In S220, the key side control unit 230 acquires the first RSSI and the second RSSI detected by the RSSI detection circuit 211 when the vehicle signal from the first vehicle-mounted LF antenna 181R and the second vehicle-mounted LF antenna 181L is 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 to end the key-side position estimation process. do.

In the above embodiment, in the candidate line calculation process for calculating the candidate line L, the distance set is calculated by 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 the two circles. Then, the procedure for calculating the candidate line L from those two candidate points P_max and P_min is 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 may be various calculation procedures in which the first RSSI and the second RSSI and the RSSI distance relationship are input and the candidate line L is output.

<Summary of the first embodiment>
In the above configuration, the RSSI distance representing the relationship between the RSSI of the vehicle signal transmitted from each vehicle-mounted LF antenna 181 detected by the RSSI detection circuit 211 and the distance from the vehicle-mounted LF antenna 181 to the electronic key 200. The relationship is stored in the storage unit 130. Specifically, two RSSI distance relations assuming different reception sensitivities within the range of the reception sensitivity variation of the electronic key 200 are stored in the storage unit 130. The reception intensity distance relationship may directly or indirectly indicate the RSSI distance relationship as shown in FIG.

Then, two circles having the first estimated maximum distance D1_max and the second estimated maximum distance D2_max as radii, which can be determined by using the first RSSI distance relationship 133 and the RSSI of the vehicle signal from the two in-vehicle LF antennas 181R and 181L, are formed. draw. The intersection of these two circles is defined as the far side candidate point P_max. Further, two circles having the first estimated minimum distance D1_min and the second estimated minimum distance D2_min as radii, which can be determined by using the second RSSI distance relationship 135 and the RSSI of the vehicle signal from the two in-vehicle LF antennas 181R and 181L, are formed. draw. The intersection of these two circles is defined as the near candidate point P_min. The two vehicle-mounted LF antennas 181R and 181L correspond to the two vehicle-mounted transmitting antennas. One of the two vehicle-mounted LF antennas 181R and 181L corresponds to one vehicle-mounted transmitting antenna, and the other corresponds to the other vehicle-mounted transmitting 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 RSSI of the vehicle signals from the two in-vehicle LF antennas 181R and 181L, both increase or decrease in the same tendency.

Therefore, regardless of the reception sensitivity of the electronic key 200 that has received the vehicle signal, the candidate point P of the electronic key 200 that reflects the difference in the reception sensitivity of the electronic key 200 is the far side candidate point P_max. It becomes a point on the candidate line L having the near side candidate point P_min as 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 in the reception sensitivity of the electronic key 200. can.

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

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

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

Further, in the above configuration, the collation ECU 110 causes the position estimation unit 129 to transmit a vehicle signal from each of the plurality of vehicle-mounted LF antennas 181 in response to the push switch for starting the engine in the vehicle interior being pressed. The position of the electronic key 200 is estimated. The plurality of vehicle-mounted LF antennas 181 correspond to the plurality of vehicle-mounted transmitting antennas.

When the push switch provided in the vehicle interior for starting the engine of the vehicle is pressed, it is highly possible that the electronic key 200 is located in the vehicle interior. That is, there is a high possibility that the electronic key 200 is located near each in-vehicle LF antenna 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 the differences from the first embodiment.

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

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

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

The RSSI detection circuit 211 detects RSSI when the vehicle signal transmitted from the first vehicle-mounted LF antenna 181R, the second vehicle-mounted LF antenna 181L, and the third vehicle-mounted LF antenna 181B is received by the key-side LF antenna 215. The RSSI of the vehicle signal from the first vehicle-mounted LF antenna 181R is detected as the first RSSI. The RSSI of the vehicle signal from the second vehicle-mounted LF antenna 181L is detected as the second RSSI. The RSSI of the vehicle signal from the third vehicle-mounted 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 vehicle-mounted RF antenna 195.

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

The candidate point calculation unit 123 calculates the candidate point P at 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. The candidate point P specified by the first estimated maximum distance D1_max and the second estimated maximum distance D2_max is calculated. The 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. The candidate point P specified by the second estimated minimum distance D2_min and the third estimated minimum distance D3_min is calculated. As shown in FIG. 12, the candidate line calculation unit 124 calculates the first candidate line L1 and the second candidate line L2. 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 having P and both ends. The second candidate line L2 includes a candidate point P specified by the second and third estimated maximum distances D2_max and D3_max, and a candidate point P specified by the second and third estimated minimum distances D2_min and the distance D3_min. Is a line segment with both ends.

As shown in FIG. 12, the intersection calculation unit 125 calculates as a candidate line intersection P_cross, which is a point where 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. Considering the variation in reception sensitivity for each electronic key, the distance from each vehicle-mounted LF antenna 181 based on RSSI to the electronic key 200 can be narrowed down to a range between the estimated minimum distance D_min and the estimated maximum distance D_max. Based on this, the region where the annular region centered on the first vehicle-mounted LF antenna 181R, the annular region centered on the second vehicle-mounted LF antenna 181L, and the annular region centered on the third vehicle-mounted LF antenna 181B overlap. (See the shaded area in FIG. 13) can be calculated. It is also conceivable to calculate this overlapping region as a candidate position for the electronic key 200.

The reception sensitivity of the electronic key 200 varies from individual to individual within the range of variation in reception sensitivity. Therefore, the electronic key 200 receives the vehicle signals transmitted from the first vehicle-mounted LF antenna 181R, the second vehicle-mounted LF antenna 181L, and the third vehicle-mounted LF antenna 181B with substantially the same reception sensitivity within the range of the reception sensitivity variation. .. That is, the first RSSI, the second RSSI, and the third RSSI are all RSSIs when received with substantially the same reception sensitivity. Therefore, the first candidate line L1 corresponding to the first vehicle-mounted LF antenna 181R and the second vehicle-mounted LF antenna 181L, and the second candidate line L2 corresponding to the second vehicle-mounted LF antenna and the third vehicle-mounted LF antennas 181L and 181B are provided. Calculate and calculate the candidate line intersection P_cross. By doing so, the candidate positions of the electronic key 200 in consideration of the variation in reception sensitivity for each electronic key can be narrowed down to a point narrower than the region shown in FIG.

The position estimation unit 129 calculates the estimated position where the electronic key 200 is estimated to exist based on the candidate line intersection P_cross. For example, the position estimation unit 129 calculates a region within a predetermined error distance from the candidate line intersection P_cross as an estimated position region. The predetermined error distance is a predetermined amount representing an error in the estimated position of the electronic key 200 due to the transmission output error of each of the vehicle-mounted 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 vehicle signal transmitted from each of the first to third in-vehicle LF antennas 181R, 181L, and 181B is received by the key side LF antenna 215, from the first to the first. Detected as 3RSSI.

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

As described above, in the above configuration, the candidate position of the electronic key 200 in consideration of the variation in reception sensitivity for each electronic key 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. As shown in FIG. 10, the schematic configuration of the electronic key system 3 of the third embodiment is the same as that of the second embodiment, but the functions of the functional blocks are different. Hereinafter, the description of the third embodiment will be described focusing on the 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. The intersection of the circle determined by the third estimated maximum distance D3_max and the circle determined by the first estimated maximum distance D1_max is calculated as the candidate point P. The intersection of the circle determined by the third estimated minimum distance D3_min and the circle determined by the first estimated minimum distance D1_min is calculated as the candidate point P. These two candidate points P are different from the four candidate points P used for calculating the first candidate line L1 and the second candidate line L2 in the second embodiment.

As shown in FIG. 14, the candidate line calculation unit 124 calculates the third candidate line L3 in addition to the first candidate line L1 and the second candidate line L2 calculated in the second embodiment. The third candidate line L3 is a candidate line L determined based on the two candidate points P further calculated in the third embodiment described above.

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

The technical significance of the estimated position region 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, when the electronic key 200 receives the vehicle signal transmitted from the plurality of vehicle-mounted LF antennas 181, the plurality of RSSIs are both depending on the level of the reception sensitivity of the electronic key 200. Increase or decrease. The candidate line L is calculated by 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 in consideration of the error of the transmission output of each in-vehicle LF antenna 181. The error in the transmission output of each vehicle-mounted LF antenna 181 can cause the intersection of the candidate line L and thus the candidate line L calculated based on RSSI 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 depending on the height of the transmission output of the vehicle-mounted LF antenna.

Consider the case where the error of all the transmission outputs of the first vehicle-mounted LF antenna 181R, the second vehicle-mounted LF antenna 181L, and the third vehicle-mounted LF antenna 181B is zero. In this case, if there is no error requirement other than the variation in the reception sensitivity of the electronic key 200, it is considered that the first candidate line L1, the second candidate line L2, and the third candidate line L3 intersect at one point. 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 region is calculated as the estimated position region R where the electronic key 200 is estimated to be located.

In the above configuration, the candidate line calculation unit 124 uses the third RSSI and the first RSSI in addition to the first candidate line L1 and the second candidate line L2 to execute the candidate line calculation process to obtain the third candidate line L3. calculate. The position estimation unit 129 calculates the area surrounded by the first candidate line L1, the second candidate line L2, and the third candidate line L3 as the estimated position area R where 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, and L3 determined based on the RSSI of the vehicle signal from each of the three vehicle-mounted LF antennas 181 and the plurality of RSSI distance relationships. is doing. Therefore, it is possible to suppress an estimation error due to variations in reception sensitivity for each electronic key. In addition, the region surrounded by these three candidate lines L1, L2, and L3 is set as the estimated position region R where the electronic key 200 is estimated to be located, so that the transmission output error of each in-vehicle LF antenna is taken into consideration. High-precision position estimation of the electronic key 200 becomes possible.

(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 the differences from the third embodiment.

In the electronic key system 3 of the third embodiment, the in-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. Will be. Specifically, the electronic key 200 has an RSSI acquisition unit 121, a distance calculation unit 122, a candidate point calculation unit 123, a candidate line calculation unit 124, and an intersection point calculation unit 125 as functional blocks of the key side control unit 230. It has a position estimation unit 129 and. Further, the electronic key 200 has a storage unit 130.

With the provision of the position estimation function on the electronic key 200 in this way, the vehicle-side control unit 120 of the collation ECU 110 sequentially transmits vehicle signals from a plurality of vehicle-mounted LF antennas 181 for position estimation of the electronic key 200. In-vehicle antenna position information and estimated position reply request are included. The in-vehicle antenna position information and the estimated position reply request may be included in each vehicle signal or any vehicle signal.

The vehicle-mounted antenna position information is information that directly or indirectly indicates the position of each vehicle-mounted LF antenna 181. 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 RSSI, the in-vehicle antenna position information is included in the vehicle signal. It is. The position of each vehicle-mounted LF antenna is represented by, for example, the relative position of each vehicle-mounted LF antenna with respect to the coordinates (longitude, latitude) of the vehicle center. The estimated position reply request is a request to the electronic key 200 to return the estimated position calculated by the electronic key 200 to the collating ECU 110.

When the key side control unit 230 of the electronic key 200 receives the vehicle signals sequentially transmitted from the plurality of vehicle-mounted LF antennas 181, the key side control unit 230 estimates the position of the electronic key 200 using the above-mentioned functional block for estimating the position of the electronic key 200. .. When the position of the electronic key 200 is estimated, the key side control unit 230 causes the key signal including the estimated position of the electronic key 200 to be transmitted from the key side RF antenna 221.

When the collation ECU 110 of the vehicle-mounted system 100 receives the key signal including the estimated position via the vehicle-mounted RF antenna 195, the collation ECU 110 acquires 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 illustrated above, each embodiment can be variously modified. For example, the position of the vehicle-mounted LF antenna 181 is not limited to the above example. In each embodiment, the plurality of vehicle-mounted LF antennas 181 may be provided at any position as long as they are provided apart from each other in the vehicle. In the third embodiment, four or more in-vehicle LF antennas 181 may be provided, and a region surrounded by four or more candidate lines may be used as an estimated position region of the electronic key 200. Moreover, the embodiment can be variously modified and expanded. For example, the technical elements disclosed in different embodiments can be appropriately combined to form an embodiment.

110 ... collation 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 intensity distance) Relationship), 135 ... 2nd RSSI distance relationship (reception intensity distance relationship), 181 ... vehicle-mounted LF antenna (vehicle-mounted transmitting antenna), 181R ... 1st vehicle-mounted LF antenna (first vehicle-mounted transmitting antenna), 181L ... second vehicle-mounted LF antenna (relationship) 2nd vehicle-mounted transmitting antenna), 181B ... 3rd vehicle-mounted LF antenna (3rd vehicle-mounted transmitting antenna), 195 ... vehicle-mounted RF antenna (vehicle-mounted receiving antenna), 200 ... electronic key, 211 ... RSSI detection circuit (reception intensity detector), 215 ... Key side LF antenna (key side receiving antenna) 221 ... Key side RF antenna (key side transmitting antenna), 230 ... Key side control unit, 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-board unit (110) mounted on a vehicle provided with a plurality of in-vehicle transmitting antennas (181, 181R, 181L, 181B) and an in-vehicle receiving antenna (195).
The key side receiving antenna (215), the reception strength detecting unit (211) for detecting the received signal strength when the vehicle signal transmitted from each of the in-vehicle transmitting antennas is received by the key side receiving antenna, and the key side transmitting. An electronic key (200) provided with an antenna (221) and wirelessly communicating with the in-vehicle device.
An electronic key system for vehicles equipped with
It is a reception intensity distance relationship representing a relationship between the reception signal strength of the vehicle signal from the vehicle-mounted transmission antenna detected by the reception strength detection unit and the distance from the vehicle-mounted transmission antenna to the electronic key. A storage unit (130) that stores a plurality of reception intensity distance relationships (133, 135) having different reception sensitivities of the reception intensity detection unit, and a storage unit (130).
The distance from one vehicle-mounted transmitting antenna constituting the two vehicle-mounted transmitting antennas included in the plurality of vehicle-mounted transmitting antennas to the electronic key, and from the other vehicle-mounted transmitting antenna of the two vehicle-mounted transmitting antennas to the electronic key. Distance is determined by applying the reception signal strength of the vehicle signal from each of the two in-vehicle transmitting antennas detected by the reception intensity detection unit to the plurality of reception intensity distance relationships (the distance calculation unit ( 122) and
The electronic key is based on the intersection of a circle centered on the position of the one vehicle-mounted transmitting antenna and a circle centered on the position of the other vehicle-mounted transmitting antenna, with the distance calculated by the distance calculation unit as the radius. Candidate point calculation unit (123) that calculates candidate points that are candidates for the position of the above for the plurality of reception sensitivities, and
A line segment determined from a plurality of candidate points (P_max, P_min) calculated by the candidate point calculation unit for the plurality of reception sensitivities is calculated as a candidate line (L, L1, L2, L3) at the position of the electronic key. Candidate line calculation unit (124) that executes line calculation processing,
A vehicle electronic key system further comprising 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 vehicle-mounted transmitting antenna includes a first vehicle-mounted transmitting antenna, a second vehicle-mounted transmitting antenna, and a third vehicle-mounted transmitting antenna.
The reception strength detection unit determines the reception signal strength when the vehicle signal transmitted from each of the first vehicle-mounted transmitting antenna, the second vehicle-mounted transmitting antenna, and the third vehicle-mounted transmitting antenna is received by the key-side receiving antenna. , The first received signal strength, the second received signal strength, and the third received signal strength are detected.
The distance calculation unit applies the first received signal strength, the second received signal strength, and the third received signal strength to the plurality of received strength distance relationships from the first in-vehicle transmitting antenna to the electronic key. The distance, the distance from the second vehicle-mounted transmitting antenna to the electronic key, and the distance from the third vehicle-mounted transmitting antenna to the electronic key are calculated for each of the plurality of receiving 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 are used as radii, and a plurality of circles centered on the position of the first in-vehicle transmitting antenna and the second received signal strength are used. With a plurality of distances determined by applying the above to the plurality of reception intensity distance relationships as radii, a plurality of circles centered on the position of the second in-vehicle transmission antenna, and the third reception signal intensity as a plurality of the reception intensity. A plurality of distances determined by applying to the distance relationship are used as radii, a plurality of circles centered on the position of the third vehicle-mounted transmitting antenna are determined, and the candidate points are based on the intersections of the circles having equal reception sensitivities. Decide,
The candidate line calculation unit calculates the first candidate line (L1) based on two or more intersections having different reception sensitivities, and is two or more intersections having different reception sensitivities. , The second candidate line (L2) is calculated based on the intersection different from the one used for the calculation of the first candidate line.
The position estimation unit is a vehicle electronic key system that estimates the position of the electronic key based on a candidate line intersection (P_cross), which is a point where the first candidate line and the second candidate line intersect. In the vehicle electronic key system of claim 2,
The candidate line calculation unit is based on the intersections of two or more intersections having different reception sensitivities, which are different from those used for calculating the first candidate line and the second candidate line. Calculate the candidate line (L3) and
The position estimation unit is for a vehicle that calculates a region surrounded by the first candidate line, the second candidate line, and the third candidate line as an estimated position region (R) in which the electronic key is estimated to be located. Electronic key system. In the vehicle electronic key system 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 a reception signal strength detected by the reception intensity detection unit from the key-side transmission antenna to the vehicle-mounted device.
The on-board unit is an electronic key system for a vehicle including the storage unit, the distance calculation unit, the candidate point calculation unit, the candidate line calculation unit, and the position estimation unit. In the vehicle electronic key system 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 is an electronic key for a vehicle further comprising 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 transmission antenna to the vehicle-mounted device. system. In the vehicle electronic key system according to any one of claims 1 to 5.
The vehicle-mounted transmitting antenna includes an vehicle-mounted transmitting antenna (181R) provided on the doorknob of the driver's seat side door of the vehicle and an vehicle-mounted transmitting antenna (181L) provided on the doorknob of the passenger 's seat side door of the vehicle. Electronic key system for vehicles. In the vehicle electronic key system according to any one of claims 1 to 6.
In the vehicle-mounted device, the electronic key is transmitted to the position estimation unit by transmitting a vehicle signal from each of the plurality of vehicle-mounted transmitting antennas in response to the pressing of the engine starting push switch provided in the vehicle interior. Electronic key system for vehicles that estimates the position of the vehicle.

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