JP2006104859A - Door lock control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a door lock control system capable of deriving a distance to a smart key with high accuracy. <P>SOLUTION: In the door lock control system 10, when a request signal S1 is transmitted from an on-vehicle antenna 5 on the vehicle 11 side, a response signal S2 is returned in response from the smart key 3 carried with a user 12. When the response signal S2 is received by the on-vehicle antenna 5, door lock mechanisms 9L, 9R are unlocked. FM-CW which is continuous wave modulated in frequency is adopted to the response signal S2. Consequently, a response time can be obtained from frequency information obtained from FM-CW without directly clocking the response time. The distance to the smart key 3 can thereby be derived with high accuracy even if the distance is short. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a door lock control system that controls a door lock of a vehicle using wireless communication.

  Conventionally, a door lock control system such as a keyless entry system that controls the unlocking (unlocking) and locking (locking) of a door of a vehicle such as an automobile using wireless communication is known.

  As such a door lock control system, a system that detects the position of a portable device carried by a user and controls the opening and closing of the door lock based on the detected position is proposed. For example, in the technique of Patent Document 1, the distance to the mobile device is obtained based on the propagation time of the radio signal transmitted from the mobile device, and it is determined whether the mobile device exists inside or outside the vehicle from the obtained distance. Thus, opening and closing of the door lock is controlled.

Japanese Patent Laid-Open No. 3-148352

  However, the distance to be detected in the door lock control system, that is, the distance from the vehicle-side antenna to the portable device carried by the user is a relatively short distance of about 5 m or less. From this, since the propagation time of the radio signal between the antenna and the portable device becomes very short, to accurately derive the distance of the portable device based only on the propagation time as in the technique of Patent Document 1, Timekeeping performance with extremely high accuracy capable of recognizing nanoseconds is required. Realization of such timekeeping performance is difficult and expensive, and it has been difficult to practically adopt the technique of Patent Document 1 in a door lock control system.

  In addition, the radio wave signal received by the vehicle-side antenna includes a reflected wave reflected inside the vehicle in addition to the direct wave propagating directly from the portable device. Therefore, it has been difficult to correctly derive the distance of the portable device from the radio signal in which the direct wave and the reflected wave are superimposed.

  The present invention has been made in view of the above problems, and a first object thereof is to provide a door lock control system capable of deriving a distance to a portable device easily and with high accuracy.

  A second object of the present invention is to provide a door lock control system capable of accurately deriving the distance of a portable device even when a signal from the portable device includes a reflected wave.

  In order to solve the above-mentioned problem, the invention of claim 1 is a door lock control system for controlling a door lock of a vehicle using wireless communication, and is mounted on the vehicle and transmits a request signal, In response to reception of the request signal, a portable device that can be carried by a user who transmits a frequency-modulated response signal, a receiving unit that is mounted on the vehicle and receives the response signal, and frequency information obtained from the response signal And a control unit for controlling the door lock of the vehicle based on the distance of the portable device.

  According to a second aspect of the present invention, in the door lock control system according to the first aspect, the derivation means extracts information related to the direct wave of the response signal from the frequency information and relates to the direct wave. The distance of the portable device is derived based only on the information.

  The invention according to claim 3 is the door lock control system according to claim 1 or 2, wherein the transmission means has a transmission directivity in at least the first direction and the second direction, and the control means Is a first distance derived based on the response signal returned from the portable device in response to the request signal in the first direction, and in response to the request signal in the second direction The direction of the portable device is specified by comparing with the second distance derived based on the response signal returned from the portable device, and the door lock of the vehicle is controlled based on the specified direction of the portable device. .

  According to a fourth aspect of the present invention, in the door lock control system according to the first or second aspect, the receiving means has reception directivity from at least the first direction and the second direction, and the control means Comparing the first distance derived based on the response signal received from the first direction with the second distance derived based on the response signal received from the second direction, The direction of the mobile device is specified, and the door lock of the vehicle is controlled based on the specified direction of the mobile device.

  According to the first to fourth aspects of the present invention, since the distance of the portable device is derived based on the frequency information obtained from the frequency-modulated response signal, the distance of the portable device existing at a relatively short distance is derived with high accuracy. be able to.

  Further, according to the invention of claim 2 in particular, when the information relating to the direct wave is extracted and the distance of the portable device is derived based only on the information relating to the direct wave, the response signal is reflected in the vehicle or the like. Even so, the influence of the reflected wave can be eliminated and the distance of the portable device can be accurately derived.

  In particular, according to the third and fourth aspects of the invention, since the direction of the portable device can be specified, it is possible to control the door lock of only the door on which the user exists without providing an antenna for each door.

<1. Overall overview>
FIG. 1 is a diagram showing an overview of a door lock control system 10 according to an embodiment of the present invention. This door lock control system 10 controls the unlocking / locking of door lock mechanisms (left door lock mechanism 9L and right door lock mechanism 9R) provided on left and right doors of a vehicle (automobile in the figure) 11, respectively. It is.

  As shown in the figure, the door lock control system 10 is roughly divided into an in-vehicle device 2 mounted on the vehicle 11 side and a smart key (intelligent key) 3 which is a portable device carried on the user 12 side.

  The in-vehicle device 2 includes an in-vehicle antenna 5 that transmits / receives radio signals to / from the smart key 3 and a control unit 4 that performs overall control. The in-vehicle antenna 5 is disposed at a substantially central position on the left and right sides of the vehicle 11 and at a position where an object that shields a radio signal does not exist between the vehicle 11 and the vicinity of the door (for example, on a dashboard in the vehicle). . On the other hand, although the control unit 4 is arrange | positioned at the center console etc. in a vehicle, the arrangement position is not specifically limited.

  The door lock control system 10 unlocks the door lock mechanisms 9L and 9R without the key 12 being inserted into the keyhole of the user 12 when the user 12 carrying the smart key 3 approaches the vehicle 11. It has a function.

  In this unlocking operation, first, a request signal S1 is transmitted from the vehicle-mounted antenna 5 of the vehicle-mounted device 2. When this request signal S1 is received by the smart key 3, a response signal S2 is returned from the smart key 3 in response thereto. When this response signal S2 is received by the vehicle-mounted antenna 5, the presence of the smart key 3 is recognized by the control unit 4 based on this reception, and the door lock mechanisms 9L and 9R are unlocked. At the time of unlocking, the control unit 4 determines whether the smart key 3 exists on the left or right side of the vehicle 11, and the door lock mechanisms 9L and 9R only on the side where the smart key 3 exists (user side). Is unlocked.

  Below, the structure and process of the door lock control system 10 which implement | achieve such unlocking operation | movement are demonstrated in detail, referring drawings.

<2. Control unit>
First, the configuration of the control unit 4 will be described. FIG. 2 is a block diagram showing a functional configuration of the control unit 4. As shown in the figure, the control unit 4 includes a CPU 41 as a main body, a transmission processing circuit 42 that performs processing related to transmission of the request signal S1, and a reception processing circuit 44 that performs processing related to reception of the response signal S2. It has. The transmission processing circuit 42 and the reception processing circuit 44 are connected to the in-vehicle antenna 5 via the circulator 43, respectively.

  The transmission processing circuit 42 includes a request signal generator 61 that generates a request signal S1. As the request signal S1, for example, a short pulse signal of 2.45 GHz is used. The request signal S1 generated by the request signal generator 61 is transmitted to the in-vehicle antenna 5 via the circulator 43 and transmitted from the in-vehicle antenna 5 to the outside of the vehicle.

  The response signal S <b> 2 received by the vehicle-mounted antenna 5 is input to the reception processing circuit 44 via the circulator 43. The reception processing circuit 44 includes an amplifier circuit 62, a mixer 63, an A / D converter 64, and a DSP (Digital Signal Processor) 65 as a circuit for processing the response signal S2. Further, the reception processing circuit 44 includes a pattern signal generator 66 that generates a pattern signal S0 that is a signal having the same waveform pattern as the response signal S2. The distance between the in-vehicle antenna 5 and the smart key 3 is derived by the processing of each part of the reception processing circuit 44, and details thereof will be described later.

  These transmission processing circuit 42 and reception processing circuit 44 are electrically connected to the CPU 41. As a result, the transmission processing circuit 42 and the reception processing circuit 44 operate under the control of the CPU 41, and the calculation result of the DSP 65 is input to the CPU 41. The CPU 41 is also electrically connected to the in-vehicle antenna 5 and the left and right door lock mechanisms 9L and 9R. Thereby, unlocking / locking of the door lock mechanisms 9L and 9R is controlled by the CPU 41, and the in-vehicle antenna 5 also operates under the control of the CPU 41.

<3. In-vehicle antenna>
Next, the configuration of the in-vehicle antenna 5 will be described. The in-vehicle antenna 5 is an antenna whose directivity can be changed. In the present embodiment, ESPAR antennas (Electronically Steerable Passive Array Radiator Antennas) capable of electronically controlling directivity are employed. .

  FIG. 3 is a diagram showing an external configuration of the in-vehicle antenna 5 configured as an ESPAR antenna. As shown in FIG. 3, the in-vehicle antenna 5 includes a columnar housing 51 and seven rod-like elements 52 and 53 that are arranged vertically from one surface thereof. Among these rod-shaped elements 52 and 53, one at the center is an excitation element 52, and six around it are parasite elements (non-excitation elements) 53. The parasite element 53 is arranged every 60 degrees on a circle separated from the excitation element 52 by a predetermined distance with reference to the position of the central excitation element 52. The excitation element 52 is responsible for transmitting the request signal S1 and receiving the response signal S2, while the parasite element 53 is responsible for changing the directivity of the in-vehicle antenna 5. Here, the directivity of the in-vehicle antenna 5 includes both the transmission directivity of the request signal S1 and the reception directivity of the response signal S2.

  FIG. 4 is a block diagram showing a functional configuration of the vehicle-mounted antenna 5. As shown in FIG. 4, a transmission / reception circuit 54 for transmitting / receiving a radio signal is connected to the excitation element 52. The transmission / reception circuit 54 is further connected to the circulator 43 of the control unit 4. With such a configuration, transmission of the request signal S1 and reception of the response signal S2 are performed by the excitation element 52.

  On the other hand, variable capacitance diodes 55 are connected to the six parasitic elements 53, respectively. The directivity of the in-vehicle antenna 5 is changed by changing the direct-current bias voltage applied to each of the variable capacitance diodes 55 and adjusting the reactance value. The direct current bias voltage to the variable capacitance diode 55 is changed by the directivity control circuit 56 disposed inside the housing 51. The directivity control circuit 56 is electrically connected to the CPU 41 of the control unit 4 and changes the DC bias voltage based on a signal from the CPU 41. With such a configuration, the directivity of the in-vehicle antenna 5 is controlled by the CPU 41 of the control unit 4.

  As shown in FIG. 5, the directivity of the vehicle-mounted antenna 5 according to the present embodiment is changed to two directions: a direction 8L toward the left door of the vehicle 11 and a direction 8R toward the right door. ing. When the directivity of the in-vehicle antenna 5 is directed in the left direction 8L, the vicinity range 80L of the left door is a main target range for transmission and reception of radio signals of the in-vehicle antenna 5. Conversely, when the directivity is directed in the right direction 8R, the vicinity range 80R of the right door is the main target range of transmission and reception of radio signals of the vehicle-mounted antenna 5.

<4. Smart Key>
Next, the configuration of the smart key 3 will be described. FIG. 6 is a block diagram showing a functional configuration of the smart key 3. As shown in the figure, the smart key 3 includes an antenna 31, a signal detection circuit 33 that detects a request signal S1, and a response signal generator 34 that generates a response signal S2. The signal detection circuit 33 and the response signal generator 34 are connected to the antenna 31 via the circulator 32.

  The antenna 31 is configured as an omnidirectional antenna and is responsible for receiving the request signal S1 and transmitting the response signal S2. The request signal S1 received by the antenna 31 is input to the signal detection circuit 33 via the circulator 32. When detecting the request signal S1, the signal detection circuit 33 inputs an instruction signal instructing generation of the response signal S2 to the response signal generator 34. In response to this, the response signal generator 34 generates a response signal S2. The generated response signal S2 is transmitted to the antenna 31 via the circulator 32 and transmitted from the antenna 31. With such a configuration, the smart key 3 returns a response signal S2 in response to receiving the request signal S1.

<5. Derivation of distance>
FM-CW (Frequency Modulated-Continuous Wave) is adopted as the response signal S2 generated by the response signal generator 34 of the smart key 3. In the door lock control system 10 of the present embodiment, the distance from the vehicle-mounted antenna 5 to the smart key 3 can be accurately derived by using this FM-CW as the response signal S2. Hereinafter, the principle of deriving the distance from the in-vehicle antenna 5 to the smart key 3 (hereinafter referred to as “key distance”) will be described.

  FM-CW is a frequency-modulated continuous wave. The upper part of FIG. 7 shows the time-series change of the frequency of FM-CW, and the lower part of FIG. 7 shows the time-series change of the waveform of FM-CW in the same time zone. As shown in the figure, FM-CW is a signal that is frequency-modulated so that the frequency becomes higher as time passes, and is also called a chirp signal.

  In the door lock control system 10, as shown in FIG. 8, the request signal S <b> 1 is transmitted from the vehicle-mounted antenna 5, and the FM-CW response signal S <b> 2 returned from the smart key 3 in response thereto is received by the vehicle-mounted antenna 5. Is done. Here, the time from when the request signal S1 is transmitted from the vehicle-mounted antenna 5 until it reaches the smart key 3 is defined as the request time T1, and from when the response signal S2 is transmitted from the smart key 3 until it reaches the vehicle-mounted antenna 5. When the time is the response time T2, the sum of the request time T1 and the response time T2 is the total time τ from when the in-vehicle antenna 5 transmits the request signal S1 until the response signal S2 is received. This total time τ is proportional to the key distance, and becomes longer as the key distance is longer.

  Meanwhile, in the control unit 4, an FM-CW pattern signal S0 having the same waveform pattern as the response signal S2 shown in FIG. 7 is generated by the pattern signal generator 66 simultaneously with the transmission of the request signal S1. Hereinafter, attention is paid to the pattern signal S0 and the response signal S2 received by the vehicle-mounted antenna 5.

  The upper part of FIG. 9 shows the frequencies of the pattern signal S0 and the response signal S2 on the same time axis. FIG. 9A shows a case where the key distance is relatively short, and FIG. 9B shows a case where the key distance is relatively long.

  The response signal S2 is delayed by a total time τ with respect to the pattern signal S0. Here, if the difference in frequency between the pattern signal S0 and the response signal S2 is taken and the difference in frequency is used as the beat frequency, the beat frequency is obtained by the pattern signal S0 and the response signal S2 as shown in the lower part of FIG. The value is constant in the overlapping time zone. That is, in FM-CW, the frequency is proportional to time, so the beat frequency is a constant value proportional to the total time τ. Therefore, the accurate total time τ can be obtained by obtaining the beat frequency, and the key distance can be derived from the total time τ.

  Such a calculation is performed by the DSP 65 and the CPU 41 of the control unit 4. More specifically, as shown in FIG. 2, the response signal S <b> 2 received by the vehicle-mounted antenna 5 is amplified by the amplifier circuit 62 and input to the mixer 63. On the other hand, the pattern signal S0 generated by the pattern signal generator 66 simultaneously with the transmission of the request signal S1 is also input to the mixer 63. The analog signal output from the mixer 63 is converted into a digital signal by the A / D converter 64 and input to the DSP 65. The DSP 65 performs discrete Fourier transform (DFT) on the input signal, which is information in the time domain, using a fast Fourier transform algorithm (FFT), and converts the input signal into information in the frequency domain. Thereby, as shown in FIG. 10, the frequency information which shows the receiving intensity for every frequency of a signal is obtained. In the frequency information shown in FIG. 10, the frequency at the position where the peak is 7 corresponds to the beat frequency.

  The frequency information derived by the DSP 65 in this way is input to the CPU 41. The CPU 41 acquires the beat frequency from the position of the peak 7 of the frequency information, obtains the total time τ based on the acquired beat frequency, and further derives the key distance from the total time τ.

  As described above, in the door lock control system 10 according to the present embodiment, the total time τ is obtained from the beat frequency without directly measuring the total time τ. For this reason, the distance to the smart key 3 existing at a relatively short distance can be accurately derived without the timekeeping performance with very high accuracy.

  In the frequency information shown in FIG. 10, two peaks 7 are shown. These correspond to the direct wave and the reflected wave of the response signal S2 from the smart key 3. As shown in FIG. 11, the response signal S2 returned in response to one request signal S1 includes a direct wave S21 propagating directly from the smart key 3 to the vehicle-mounted antenna 5 and after being reflected in the vehicle. There is a reflected wave S22 propagating to the in-vehicle antenna 5. That is, the superposition of the direct wave S21 and the reflected wave S22 is received by the in-vehicle antenna 5 as the response signal S2. For this reason, in frequency information, the peak 7 corresponding to each beat frequency of direct wave S21 and reflected wave S22 arises.

  Here, the response time T2 related to the direct wave is relatively short, while the response time T2 related to the reflected wave is relatively long. Further, as described above, the beat frequency is proportional to the total time τ obtained by adding the request time T1 and the response time T2. For this reason, when a plurality of peaks 7 occur in the frequency information, the one with the lowest frequency corresponds to the direct wave. For this reason, when there are a plurality of peaks 7 in the frequency information, the CPU 41 extracts the smallest frequency indicated by them as the beat frequency corresponding to the direct wave, and derives the key distance based on this beat frequency. It is like that. As a result, the key distance can be accurately derived even from the response signal S2 in which the direct wave S21 and the reflected wave S22 are superimposed.

<6. Unlocking action>
Next, the unlocking operation by the door lock control system 10 will be described. FIG. 12 is a diagram illustrating the flow of the unlocking operation of the door lock control system 10. It is assumed that both the left and right door lock mechanisms 9L and 9R are in a locked state at the start of this operation.

  In the locked state of the door lock mechanisms 9L and 9R, the request signal S1 is transmitted from the vehicle-mounted antenna 5 at a predetermined time period (step ST1). At this time, the directivity of the in-vehicle antenna 5 is changed every time the request signal S1 is transmitted (step ST3). Accordingly, the request signal S1 is alternately transmitted in the left direction 8L and the right direction 8R. Transmission of the request signal S1 is repeated until the response signal S2 is returned from the smart key 3 (No in step ST2).

  When the response signal S2 from the smart key 3 is received by the in-vehicle antenna 5 (Yes in step ST2), the key distance is derived based on the received response signal S2 by the above-described arithmetic processing of the DSP 65, the CPU 41, and the like. The The derived key distance is the first distance (step ST4).

  Subsequently, the directivity of the in-vehicle antenna 5 is changed. That is, if the directivity of the in-vehicle antenna 5 when receiving the response signal S2 is the left direction 8L, the direction is changed to the right direction 8R, and if the directivity is 8R, the direction is changed to the left direction 8L (step ST5). And request signal S1 is further transmitted in the state where the directivity of in-vehicle antenna 5 was changed (Step ST6).

  The response signal S2 from the smart key 3 in response to the request signal S1 is received by the in-vehicle antenna 5 (step ST7), and the key distance is derived again based on the response signal S2. The key distance derived here is the second distance (step ST8). That is, the directivity of the corresponding in-vehicle antenna 5 is different between the first distance and the second distance.

  Here, if the directivity direction before the change in step ST5 is the first direction and the directivity direction after the change is the second direction, the first distance is returned in response to the request signal S1 in the first direction. The second distance is a distance derived based on the response signal S2 returned in response to the request signal S1 in the second direction. The first distance is a distance derived based on the response signal S2 received from the first direction, and the second distance is a distance derived based on the response signal S2 received from the second direction. It can also be expressed. The smart key 3 can be considered to exist in the direction of directivity corresponding to a short distance between the first distance and the second distance.

  For this reason, when the first distance and the second distance are acquired, these distances are then compared, and the directivity direction corresponding to the short distance is specified by the CPU 41 as the direction in which the smart key 3 exists. (Step ST9). When the direction in which the smart key 3 exists is specified, the door lock mechanisms 9L and 9R in the specified direction are unlocked by the CPU 41 (step ST10).

  Thus, in the door lock control system 10, the direction in which the smart key 3 exists is specified by changing the directivity of the vehicle-mounted antenna 5 in two directions and comparing the two distances obtained before and after the change. . For this reason, the door lock mechanism only on the side where the user exists (the side where the smart key 3 exists) can be unlocked without adopting a complicated configuration such as providing an antenna for each door.

<7. Modification>
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible.

  In the above embodiment, it has been described that the request signal S1 is transmitted at a predetermined time period in the locked state. However, for example, the request signal S1 may be transmitted when a user presses a door switch as a trigger.

  In the above embodiment, the ESPAR antenna is used as the vehicle-mounted antenna. However, the ESPAR antenna has directivity in at least two directions, for example, an antenna having rotational directivity in a specific direction. Any antenna may be used as long as it is present.

  In the above-described embodiment, the transmission of the request signal S1 and the reception of the response signal S2 are performed by the single vehicle-mounted antenna 5, but the transmission antenna responsible for the transmission of the request signal S1 and the response signal S2 A receiving antenna for receiving data may be provided separately. In this case, an antenna having directivity in at least two directions may be adopted for one of the transmitting antenna and the receiving antenna, and an omnidirectional antenna may be adopted for the other.

It is a figure which shows the outline | summary of a door lock control system. It is a block diagram which shows the functional structure of a control unit. It is a figure which shows the external appearance structure of a vehicle-mounted antenna. It is a block diagram which shows the functional structure of a vehicle-mounted antenna. It is a figure which shows the directivity of a vehicle-mounted antenna. It is a block diagram which shows the functional structure of a smart key. It is a figure which shows the change of the frequency with respect to the time of FM-CW. It is a figure which shows transmission / reception of the electromagnetic wave signal between a vehicle-mounted antenna and a smart key. It is a figure which shows the frequency of a pattern signal and a response signal. It is a figure which shows the frequency information obtained from a response signal. It is a figure which shows the direct wave and reflected wave of a response signal. It is a figure which shows the flow of the unlocking operation | movement of a door lock control system.

Explanation of symbols

2 On-vehicle device 3 Smart key 4 Control unit 5 On-vehicle antenna 10 Door lock control system 11 Vehicle 12 User

Claims (4)

A door lock control system for controlling a door lock of a vehicle using wireless communication,
A transmission means mounted on the vehicle for transmitting a request signal;
In response to receiving the request signal, a portable device that can be carried by a user who transmits a frequency-modulated response signal;
Receiving means mounted on the vehicle for receiving the response signal;
Derivation means for deriving the distance of the portable device based on frequency information obtained from the response signal;
Control means for controlling a door lock of the vehicle based on the distance of the portable device;
A door lock control system comprising: The door lock control system according to claim 1,
The derivation means extracts information related to the direct wave of the response signal from the frequency information, and derives the distance of the portable device based only on the information related to the direct wave. system. The door lock control system according to claim 1 or 2,
The transmission means has a transmission directivity in at least the first direction and the second direction,
The control means includes
A first distance derived based on the response signal returned from the portable device in response to the request signal in the first direction;
Comparing the second distance derived based on the response signal returned from the portable device in response to the request signal in the second direction to identify the direction of the portable device;
A door lock control system that controls a door lock of the vehicle based on the identified direction of the portable device. The door lock control system according to claim 1 or 2,
The receiving means has reception directivity from at least the first direction and the second direction,
The control means includes
A first distance derived based on the response signal received from the first direction;
Comparing the second distance derived based on the response signal received from the second direction to identify the direction of the portable device;
A door lock control system that controls a door lock of the vehicle based on the identified direction of the portable device.

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