JP2016139840A - Radio communication system for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio communication system for vehicle, capable of suppressing degradation in user's convenience by forming a stable detection area of a portable device.SOLUTION: The radio communication system for vehicle includes: an on-vehicle device installed on a vehicle and a portable device held by a user. The on-vehicle device and the portable device can be communicated with each other. The on-vehicle device includes: a transmission part for transmitting a radio signal to the portable device; an estimation part for estimating an ambient environment of the portable device; and an adjustment part for adjusting transmission power of the transmission part according to the estimated ambient environment.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a wireless communication system for a vehicle that controls a vehicle using wireless communication between a portable device carried by a user and an in-vehicle device mounted on the vehicle.

  As a vehicle wireless communication system, authentication is performed by wireless communication between a portable device possessed by the user and an in-vehicle device mounted on the vehicle, and based on the authentication result, without using a mechanical key, There are smart key systems that perform user-desired operations such as door unlocking and engine starting.

  In the above-described vehicle wireless communication system, there has been devised one that sets a frequency for performing wireless communication between the portable device and the vehicle-mounted device more appropriately (see Patent Document 1). In this system, communication between the portable device and the vehicle-mounted device is performed using a channel in which the received signal from the portable device in the vehicle-mounted device is maximized.

JP 2010-2322872 A

  In the prior art, the output of the transmission signal from the in-vehicle device is constant. In the portable device, the reception sensitivity of the receiving unit varies depending on the ambient temperature, and when the signal output from the in-vehicle device is constant, the distance that the portable device can receive may vary. That is, there is a problem that the detection area of the portable device of the in-vehicle device changes and a stable detection area cannot be formed. Patent Document 1 does not disclose a solution to this problem.

  For example, in FIG. 2, normally, when the detection area of the portable device is formed as 41a (including 41a1), when the reception sensitivity of the portable device is lower than normal, the inner side of the outer edge of the detection area 41a A portable device located in the vicinity (outside of 41a1) may not be able to receive a radio signal from the in-vehicle device 10 (LF transmitter 11). This can be said that the detection area 41a1 is narrower than 41a. In this state, even when the portable device is at the same position, the vehicle operation (door unlocking, etc.) may or may not be possible, and user convenience is reduced.

  Against the background of the above problems, an object of the present invention is to provide a vehicular wireless communication system that can form a stable detection area of a portable device and suppress a decrease in user convenience.

  A vehicle wireless communication system for solving the above-described problem includes an in-vehicle device mounted on a vehicle and a portable device possessed by a user, and the in-vehicle device and the portable device are capable of wireless communication with each other. Includes a transmission unit that transmits a radio signal to the portable device, an estimation unit that estimates an ambient environment of the portable device, and an adjustment unit that adjusts the transmission power of the transmission unit according to the estimated ambient environment.

  With the above configuration, by adjusting the transmission output of the radio signal from the vehicle, a constant detection area (41a in FIG. 2) can be formed regardless of the surrounding environment of the portable key. If the machine is within the normal detection area, it is possible to receive a radio signal from the in-vehicle device, so that it is possible to suppress a decrease in user convenience.

The figure which shows the structural example of the radio | wireless communications system for vehicles of this invention. The figure which shows the example of arrangement | positioning of each antenna, and the transmission range of a request signal. The flowchart explaining onboard equipment control processing. The figure which shows the relationship between external temperature and the correction value of transmission power. The figure which shows the relationship between the received signal strength and the correction value of transmission power.

  As shown in FIG. 1, the vehicular wireless communication system 1 is configured as a smart key system including an in-vehicle device 10 mounted on a vehicle and a portable device 20 carried by a user.

  The in-vehicle device 10 includes a control unit 13 (estimation unit, adjustment unit, state determination unit, verification unit of the present invention), and a signal input / output circuit (may be a LAN interface circuit) connected to the control unit 13. O14 (state acquisition unit of the present invention, outside air temperature acquisition unit, acquisition unit), LF transmission unit 11 (transmission unit of the present invention) connected to the I / O 14, RF reception unit 12 (reception unit of the present invention) .

  The LF transmitter 11 is connected to a D seat (driver seat) antenna 11a, a P seat (passenger seat) antenna 11b, an antenna 11c in the trunk, and an indoor antenna 11d. Send a request signal by radio wave. The control unit 13 instructs the LF transmission unit 11 to transmit request signals in a predetermined order. Therefore, the control unit 13 can identify whether the portable device 20 has returned the response signal in response to the request signal from which antenna.

  The LF transmission unit 11 can adjust the transmission power of the request signal based on the control command from the control unit 13. For example, the current values applied to the antennas 11a to 11d are adjusted so that the transmission power is instructed by the control unit 13. The adjustment of the current value may be a method of switching the current value by providing a current switching circuit, or a method of changing the amplification factor of the power amplifier circuit connected to the antenna.

  As shown in FIG. 2, the D seat antenna 11 a is disposed inside the center pillar between the D seat and the rear seat of the vehicle 40, and the P seat antenna 11 b is disposed between the P seat and the rear seat of the vehicle 40. It is placed inside a certain center pillar. The in-trunk antenna 11 c is disposed in the trunk room of the vehicle 40. The indoor antenna 11d is attached to the lower part of the center console of the vehicle 40, for example.

  Returning to FIG. 1, the RF receiving unit 12 performs processing such as amplification and demodulation on a response signal in the RF (high frequency) band received by the receiving antenna 12 a, for example. Also, the received signal strength (RSSI) of the response signal is detected during demodulation. For example, the receiving antenna 12a is disposed in the dash panel of the vehicle 40 together with the in-vehicle device 10 (see FIG. 2).

  The control unit 13 is configured as a computer including a CPU 13a, a memory 13b using a nonvolatile storage medium such as a flash memory, and peripheral circuits (not shown). Various functions of the vehicular wireless communication system 1 are realized by the CPU 13a executing the in-vehicle device control program stored in the memory 13b. The memory 13b stores a master code for collating the ID code of the portable device 20.

  A door switch 31, a door open / close detection unit 32, a door lock detection unit 33, a start switch 34, an outside air temperature sensor 35, and a door lock / unlock control unit 36 are connected to the in-vehicle device 10 via the I / O 14.

  The door switch 31 is a touch switch provided near a door knob for opening and closing the doors of the vehicle 40 (generically referred to as 47 and 48 (see FIG. 2), the same applies hereinafter), and a trunk door 49 (see FIG. 2) of the vehicle. The touch switch is provided near the door knob. A signal corresponding to a user operation on the door switch 31 is output to the control unit 13.

  The door open / close detection unit 32 includes a switch for detecting the open / closed state of the door and the trunk door 49. A signal indicating the open / closed state of the door and the trunk door is output from the door open / close detection unit 32 to the control unit 13.

  The door locking detection unit 33 includes a switch that detects the locking state of the door and the trunk door 49. A signal indicating the locked state of the door and the trunk door 49 is output from the door locking detection unit 33 to the control unit 13.

  The start switch 34 is a switch operated by a user in order to start a motor (engine or motor) of the vehicle 40 or permit the start (also referred to as an ignition switch or a push switch). The start switch 34 outputs a signal indicating the state of the start switch 34 to the control unit 13.

  The outside air temperature sensor 35 detects the outside air temperature (outside air temperature) of the vehicle 40. When the vehicle 40 includes a known air conditioner that performs indoor air conditioning, the outside air temperature may be acquired from an outside air temperature sensor included in the air conditioner. The outside air temperature sensor 35 outputs a signal indicating the outside air temperature to the control unit 13.

  The door locking / unlocking control unit 36 includes an actuator for locking and unlocking the door and the trunk door 49, and by driving each actuator based on a control command from the control unit 13, the door and trunk door 49 Lock / unlock control is performed.

  The portable device 20 includes a control unit 21 including a known CPU, a memory (none of which is shown), a receiving unit 22 connected to the control unit 21 for receiving a request signal from the in-vehicle device 10, and an in-vehicle device. 10 includes a transmission unit 23 that transmits a response signal to 10, and an operation unit 24 that is operated by a user.

  The control unit 21 determines whether or not the request signal is received based on the reception signal of the reception unit 22 and generates a response signal including an ID code for identifying the portable device for responding to the request signal. Then, the transmission unit 23 transmits the data.

  For example, the operation unit 24 is configured as a push switch group serving as a trigger for using the remote keyless entry function. When the user operates the operation unit 24, the door corresponding to the push switch and the trunk door 49 are unlocked or opened / closed.

  With the above-described configuration, the in-vehicle device 10 transmits a request signal for collation to the portable device 20, collates the ID code for identifying the portable device 20 and the master code included in the received response signal, Based on the collation result, for example, the control of predetermined functions in the vehicle such as locking / unlocking control of the door of the vehicle, permission to start the motor (engine or motor) is performed.

  The vehicle wireless communication system 1 is based on mutual communication between the in-vehicle device 10 and the portable device 20, in addition to the smart key system, a remote keyless entry system that does not perform verification of the portable device 20 and has only a remote keyless entry function. Thus, the present invention may be applied to a system (for example, a remote engine starter) that controls the operation of a predetermined function in the vehicle.

  In FIG. 2, the transmission range (namely, detection area of the portable device 20) of the request signal of each antenna (11a-11c) is shown. The detection area is formed in a substantially circular shape with a radius of 0.7 to 1.0 m centered on the antenna.

  The detection area 41a of the D seat antenna 11a and the detection area 41b of the P seat antenna 11b overlap with the detection area 41c of the in-trunk antenna 11c. Also, the detection area (not shown) of the indoor antenna 11d may overlap with the detection areas 41a and 41b. However, as described above, since request signals are not transmitted simultaneously from the respective antennas, it is possible to determine in which detection area the portable device 20 exists.

  The in-vehicle device control process included in the in-vehicle device control program and executed by the CPU 13a will be described with reference to FIG. First, the vehicle state (the state of the door opening / closing detection unit 32, the door locking detection unit 33, and the start switch 34) is acquired (S11). Next, based on the vehicle state, it is determined whether or not the state has shifted to the estimable state, that is, whether or not the user has exited.

  The above-described configuration includes: “the in-vehicle device includes a state acquisition unit that acquires the state of the vehicle, and a state determination unit that determines whether or not the vehicle state has transitioned to a presumable state that is determined in advance. The unit estimates the ambient environment of the portable device when the state determination unit determines that the state of the vehicle has transitioned to an estimable state. With this configuration, it is possible to prevent the user's convenience from being lowered by adjusting the transmission power when it is not necessary.

  More specifically, “the state determination unit determines that the state of the vehicle has transitioned to an estimable state when it reflects that the vehicle occupant has got off the vehicle”. When the user gets off the vehicle, it is highly likely that the surrounding environment changes as the portable device 20 moves from the passenger compartment to the outside of the vehicle. With this configuration, transmission power can be adjusted at a more appropriate timing. When the user gets off, the portable device 20 is located in the vicinity of the vehicle and can communicate with the in-vehicle device 10 in many cases. Therefore, the transmission power is determined based on the communication between the in-vehicle device 10 and the portable device 20. It can also be adjusted.

The user's getting-off determination uses at least one of the following.
When the state of the D seat door 47 (see FIG. 2) output from the door open / close detection unit 32 changes from the open state to the closed state, it is determined that the user has got off the vehicle.
-When the state of all the doors which the door locking detection part 33 outputs changes into the locked state, it determines with the state which the user got off.
-When the state of the start switch 34 which the start switch 34 outputs changes into the stop state of a motor | power_engine, it determines with the state which the user got off.

  When transitioning to the estimable state (S12: Yes), a timer (for example, 1 minute timer) is started (S13). Next, a request signal is transmitted via the LF transmitter 11 (S14). Thereafter, a response signal from the portable device 20 is waited for.

  When the response signal is received (S15: Yes), the ID code included in the received response signal is collated with the master code stored in the memory 13b (S16). When both are matched and collation is correctly performed (normal collation, S17: Yes), the surrounding environment of the portable device 20 is estimated (S18).

  The above-described configuration is “the transmission unit transmits a request signal to the portable device, and the in-vehicle device transmits a response signal including an ID code for identifying the portable device, which is transmitted in response to the request signal from the portable device. A receiving unit for receiving, a collating unit for collating an ID code with a master code stored in advance, and the estimating unit estimates the surrounding environment when the collation result in the collating unit is correct. . With this configuration, even if a portable device of the same type used in another vehicle is in the vicinity of the vehicle, the transmission power is not adjusted and unnecessary operations can be prevented.

The ambient environment estimation method uses at least one of the following.
-The outside temperature is acquired from the outside temperature sensor 35, and the surrounding environment of the portable device is estimated based on the outside temperature.
The above-described configuration is “the in-vehicle device includes an outside air temperature acquisition unit that acquires the state of the temperature outside the vehicle, and the estimation unit estimates the surrounding environment based on the temperature outside the vehicle”. Regardless of the in-vehicle device 10 and the portable device 20, the wireless communication unit is easily affected by ambient temperature such as outside air temperature. In particular, the portable device 20 has a large variation in ambient temperature. With this configuration, transmission power can be adjusted more appropriately according to the surrounding environment.

In response to the received signal strength of the response signal received in step S15 or the newly transmitted calibration signal (may have the same content as the request signal), the received signal strength of the signal transmitted from the portable device 20 Based on the surrounding environment of the portable device 20 is estimated.
The above-described configuration is “the in-vehicle device includes an acquisition unit that acquires the received signal strength of the radio signal received from the portable device, and the estimation unit estimates the surrounding environment based on the received signal strength”. If the received signal strength differs in the estimable state, it is considered that the wireless communication unit of the portable device is affected by the surrounding environment. With this configuration, transmission power can be adjusted more appropriately according to the surrounding environment.

  Next, based on the estimation result of the surrounding environment, the transmission power of the LF transmission unit 11 is adjusted (S19). The adjustment method uses at least one of the following.

-The transmission power of the LF transmission part 11 is adjusted based on outside temperature. For example, the transmission power of the LF transmission unit 11 when the outside air temperature is 25 ° C. is set as a standard value, and the correction value is multiplied or added / subtracted from the standard value.

  As illustrated in FIG. 4, the correction value is set so that the transmission power of the LF transmission unit 11 is increased as the outside air temperature increases. When the outside air temperature rises, the internal noise of the receiving unit 22 increases and it becomes difficult to receive the request signal. Alternatively, even if it can be received, it may not be demodulated as a request signal. Therefore, the transmission power of the LF transmitter 11 is increased so that the portable device 20 can reliably receive the request signal.

Adjust the transmission power of the LF transmitter 11 based on the received signal strength. For example, the transmission power of the LF transmitter 11 when a response signal is received with a predetermined received signal strength is set as a standard value, and a correction value is multiplied or added / subtracted from the standard value.

  As shown in FIG. 5, the correction value is set so as to increase the transmission power of the LF transmission unit 11 as the received signal strength decreases. The low received signal strength is considered to be due to the low output power of the transmission unit 23 or the low S / N ratio of the response signal. That is, it seems that the communication performance of the portable device 20 is lower than usual. Therefore, the transmission power of the LF transmitter 11 is increased so that the portable device 20 can reliably receive the request signal.

  Returning to FIG. 3, when a response signal is not received (S15: No), or when collation is not performed correctly (S17: No), it is determined whether or not the timer has timed out (for example, 1 minute has passed). . When the time-out has not occurred (S21: No), the process returns to step S15 to return to the response signal reception waiting state. On the other hand, when a time-out occurs (S21: Yes), this process is terminated.

  The configuration described above is “the estimation unit does not estimate the surrounding environment when a predetermined time has elapsed since the transition to the estimable state”. With this configuration, it is possible to prevent the transmission power from being adjusted when it is not necessary, for example, when the user who has the portable device gets off the vehicle and leaves the vehicle.

  Although the embodiments of the present invention have been described above, these are merely examples, and the present invention is not limited to these embodiments, and the knowledge of those skilled in the art can be used without departing from the spirit of the claims. Various modifications based on this are possible.

DESCRIPTION OF SYMBOLS 1 Wireless communication system for vehicles 10 In-vehicle apparatus 11 LF transmission part (transmission part)
12 RF receiver (receiver)
13 Control part (estimation part, adjustment part, state determination part, collation part)
14 I / O (state acquisition unit, outside air temperature acquisition unit, acquisition unit)
20 portable device 40 vehicle

Claims (7)

Including an in-vehicle device mounted on a vehicle and a portable device possessed by a user, wherein the in-vehicle device and the portable device are capable of wireless communication with each other;
The in-vehicle device is
A transmitter for transmitting a radio signal to the portable device;
An estimation unit for estimating an ambient environment of the portable device;
An adjustment unit that adjusts transmission power of the transmission unit according to the estimated surrounding environment;
A vehicular wireless communication system. The in-vehicle device is
A state acquisition unit for acquiring the state of the vehicle;
A state determination unit that determines whether or not the state of the vehicle has transitioned to a predetermined estimable state;
With
The vehicular wireless communication system according to claim 1, wherein the estimation unit estimates an ambient environment of the portable device when the state determination unit determines that the state of the vehicle has transitioned to the estimable state.   The vehicular wireless communication system according to claim 2, wherein the estimation unit does not estimate the surrounding environment when a predetermined time has elapsed since transition to the estimable state.   The vehicle radio according to claim 2 or 3, wherein the state determination unit determines that the vehicle state has transitioned to the estimable state when the state of the vehicle reflects that an occupant of the vehicle has got off. Communications system. The transmitter transmits a request signal to the portable device,
The in-vehicle device is
A receiver for receiving a response signal including an ID code for identifying the portable device transmitted from the portable device in response to the request signal;
A collation unit for collating the ID code with a master code stored in advance;
With
The vehicular radio communication system according to any one of claims 1 to 4, wherein the estimation unit estimates the surrounding environment when a collation result in the collation unit is correct. The in-vehicle device is
An outside air temperature acquisition unit that acquires the state of the temperature outside the vehicle;
The vehicular wireless communication system according to any one of claims 1 to 5, wherein the estimation unit estimates the surrounding environment based on a temperature outside the vehicle. The in-vehicle device is
An acquisition unit for acquiring the received signal strength of the radio signal received from the portable device;
The vehicular wireless communication system according to any one of claims 1 to 6, wherein the estimation unit estimates the surrounding environment based on the received signal strength.

Images