U.S. patent application number 11/487127 was filed with the patent office on 2006-11-09 for detector and lock controller using same.
This patent application is currently assigned to OMRON Corporation. Invention is credited to Shoji Mafune, Kazuhiro Negoro, Tadao Nishiguchi, Yasuhiro Satoh.
Application Number | 20060250214 11/487127 |
Document ID | / |
Family ID | 32899914 |
Filed Date | 2006-11-09 |
United States Patent
Application |
20060250214 |
Kind Code |
A1 |
Mafune; Shoji ; et
al. |
November 9, 2006 |
Detector and lock controller using same
Abstract
A lock controller has main apparatus provided to a lockable door
and a detector for detecting an approaching or retreating target
object. The detector includes an oscillator device for generating a
transmission wave, a branching device for branching the
transmission wave, a transmission device for transmitting the
transmission wave into space as electromagnetic waves, a reception
device for receiving the transmission wave reflected by the target
object, a mixer for mixing a reception signal received by the
reception device and a branched signal branched by the branching
device to output a mixed signal, and a judging device for switching
on a detection output indicating the target object approaching and
retreating based on an increase and a decrease of the mixed signal
outputted from the mixer. A detection distance is set within 1/4
wavelength of frequency effective for the detection. The main
apparatus sends by wireless transmission a specified request signal
to a portable device carried by the user, and if an answer signal
is received from the portable device in response, causes the
lockable part to be unlocked after ascertaining that the received
answer signal is a correct signal.
Inventors: |
Mafune; Shoji; (Nagoya,
JP) ; Negoro; Kazuhiro; (Kasugai, JP) ; Satoh;
Yasuhiro; (Ootsu, JP) ; Nishiguchi; Tadao;
(Kyoto, JP) |
Correspondence
Address: |
BEYER WEAVER & THOMAS, LLP
P.O. BOX 70250
OAKLAND
CA
94612-0250
US
|
Assignee: |
OMRON Corporation
|
Family ID: |
32899914 |
Appl. No.: |
11/487127 |
Filed: |
July 13, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10759760 |
Jan 16, 2004 |
7102487 |
|
|
11487127 |
Jul 13, 2006 |
|
|
|
Current U.S.
Class: |
340/5.62 |
Current CPC
Class: |
G07C 2009/00793
20130101; G07C 2209/65 20130101; G07C 9/00309 20130101; B60R 25/246
20130101; G01S 13/56 20130101; G01S 13/88 20130101; Y10T 70/5973
20150401; G07C 2209/63 20130101 |
Class at
Publication: |
340/005.62 |
International
Class: |
G05B 19/00 20060101
G05B019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 20, 2003 |
JP |
2003-010821 |
Claims
1. A detector for detecting a target object approaching and
retreating, said detector comprising: an oscillator device for
generating a transmission wave; a branching device for branching
said transmission wave generated by said oscillator device; a
transmission device for transmitting said transmission wave into
space as electromagnetic waves; a reception device for receiving
the transmission wave transmitted by said transmission device and
reflected by said target object; a mixer for mixing a reception
signal received by said reception device and a branched signal
branched by said branching device to output a mixed signal; a
judging device for switching on a detection output indicating said
object approaching and retreating based on an increase and a
decrease of said mixed signal outputted from said mixer; wherein a
detection distance is set within 1/4 wavelength of frequency
effective for the detection.
2. The detector of claim 1 further comprising a speed correcting
device for changing said detection output based on the speed of
change of said mixed signal outputted from said mixer.
3. A lock controller comprising a detector according to claim 3 and
a main apparatus which is provided to a structure with a lockable
part having a handle and being adapted to open and close, wherein
said main apparatus is adapted to send by wireless transmission a
specified request signal to a portable device carried by said user,
to receive an answer signal from said portable device in response
to said request signal, and to cause said lockable part, if locked,
to be unlocked after ascertaining that said received answer signal
is a correct signal.
Description
[0001] This is a divisional of application Ser. No. 10/759,760
filed Jan. 16, 2004, currently pending.
BACKGROUND OF THE INVENTION
[0002] This invention relates to a detector for detecting the
user's hand as it approaches the door handle of an automobile and
generating a trigger signal for initiating the automatic unlocking
operation of a passive entry system for the automobile. The
invention also relates to lock controllers using such a
detector.
[0003] In recent years, there have been proposals for vehicle entry
system apparatus for automatically operating an equipment on a
vehicle by carrying out two-way communications between a device
carried by the user and a vehicle-mounted main device and thereby
carrying out a required comparison, and some of such apparatus are
actually coming to be used. With such an apparatus adapted to carry
out two-way communications, an answer signal containing a necessary
code can be automatically transmitted from the device carried by
the user to the main device in response to a request signal (such
as a startup signal for starting up the device being carried)
transmitted from the main device and hence an equipment on a
vehicle can be caused to carry out a specified operation without
the user carrying out any operation at all. With a vehicle entry
system, for example, the user carrying a portable device may have
only to approach the door of a specified vehicle to which a
corresponding main device is mounted for establishing a two-way
communication between them such that a lock-opening command is
automatically outputted to the locked door and the locked door
becomes automatically unlocked. Such highly convenient entry
systems capable of locking and unlocking a vehicle door basically
without requiring any conscious effort on the part of the user are
sometimes referred to as a passive entry system (or a smart entry
system) as an improved version of general keyless entry systems,
and needs for such systems are becoming higher as they are capable
of increasing the market values of the vehicles.
[0004] If it is attempted with such a passive entry system to save
the power of the vehicle battery by transmitting request signals
from the main device only when they are necessary, a detector may
be required for detecting the user approaching or contacting the
vehicle (such as to its door handle).
[0005] Optical sensors, capacitance sensors and mechanical switches
(so-called micro-switches) have recently been used for such a
purpose. Optical sensors are adapted, for example, to detect the
user's hand approaching the door handle on the basis of a change in
the output from a light-receiving element as light outputted from a
light-emitting element is screened or reflected by the user's hand.
Capacitance sensors are so-called touch sensors and adapted, as
disclosed in Japanese Patent Publication Tokkai 2002-295064, to
detect the user's hand approaching the door handle based on a
change in the capacitance of a capacitor within the sensor by the
contact of the user's hand. Examples of a sensor of a non-contact
type include Doppler radars used for a startup switch device for an
automatic door, as disclosed in Japanese Patent 2785893.
[0006] Prior art technologies characterized as using a detector as
explained above have problems as explained below.
[0007] (A) Optical sensors may function incorrectly in the presence
of unwanted objects such as rain drops and dead leaves or due to
the incidence of light from a lamp or sunlight, while capacitance
sensors are weak against noise as a matter of principle and tend to
function incorrectly in the presence of dielectric matters such as
rain drops.
[0008] (B) Response characteristics of optical, capacitance and
mechanical sensors are not sufficient because their detection areas
are small (or their detection distance is short) and the system
depending on such a sensor may function incorrectly. If such a
sensor is set to the door handle of a vehicle for providing a
trigger for the transmission of a request signal in a passive entry
system of the vehicle, for example, the user's hand may not be
detected and hence the request signal may not be outputted until
the hand nearly touches the sensor. Thus, the user may be already
starting to pull the handle in order to open the door but the door
may not be unlocked yet. In other words, the user may try to open
the locked door quickly by using a passive entry system but its
automatic unlocking operation may be delayed and the door may
refuse to open immediately. In the case of a capacitance sensor or
a mechanical switch, in particular, detection is not made until the
user's hand makes a firm contact with the sensor. If the detector
is of a kind having such a sensor simply attached to the door, the
communication to the portable unit is completed and the door is
unlocked only after the user begins to pull the handle in order to
open it. Thus, this problem does not fail to appear.
[0009] (C) Since sensor elements which are relatively large and
hence are difficult to be contained must be provided to a vehicle
component such as a door handle intended to detect the approaching
target object of detection, the shape and the size of such a
component may have to be modified significantly to accommodate such
sensor elements and hence the freedom in its design is severely
restricted. In particular, when it is desired to detect the user's
hand approaching the door handle of a vehicle with a response
characteristic as high as possible by using an optical sensor or a
mechanical switch, a light-emitting element and a light-receiving
element must be placed near the door handle or a contact probe of a
mechanical switch must be placed at a position protruding from the
door handle. Thus, the design of the door handle or the body parts
of the vehicle in the vicinity is severely affected, In the case of
a capacitance sensor, a relatively bulky electrode must be buried
inside the handle and this also limits the freedom in the
design.
[0010] As explained above, Doppler radars used for automatic doors
are known examples of sensors of a non-contact type capable of
providing a large detection area and not affected by dirt or the
like. Thus, it may be considered to use such a Doppler radar as the
detector for a passive entry system, but prior art Doppler radars
are for detecting the speed and direction of the motion of a target
object of detection on the basis of changes in the frequency of
received waves and cannot be used directly for detecting a target
object approaching within a short distance by means of a simple
structure. The device according to aforementioned Japanese Patent
2785893, for example, is adapted to carry out complicated judging
processes with its signal processor comprising a microcomputer, its
power consumption rate is high and the signal processor becomes
big, requiring a large space for its setting. Thus, it is not
feasible to be used as the detector for a vehicle which uses
battery cells as its power source and is strongly required to be
energy-saving and compact.
[0011] It is therefore an object of this invention to make use of
the technology of Doppler radars to provide an improved detector
superior in operational reliability, response characteristics, and
capability of being mounted to a vehicle (from the points of view
of size, freedom in design and power consumption).
[0012] It is another object of this invention to provide a lock
controller using such a detector.
SUMMARY OF THE INVENTION
[0013] A detector according to a first embodiment of this invention
is for detecting a target object of detection approaching or
retreating from the detector and may be characterized as comprising
an oscillator device for generating a transmission wave, a
branching device for branching the transmission wave generated by
the oscillator device, a transmission device for transmitting the
transmission wave into space as electromagnetic waves, a reception
device for receiving the transmission wave transmitted by the
transmission device and reflected by the target object, a mixer for
mixing a reception signal received by the reception device and a
branched signal branched by the branching device to output a mixed
signal, a judging device for switching on a detection output
indicating the target object approaching and retreating based on an
increase and a decrease of the mixed signal outputted from the
mixer, wherein a detection distance is set within 1/4 wavelength of
frequency effective for the detection.
[0014] In the above, the target object may be a person's hand. The
oscillator device, the transmission device, the reception device
and the mixer are components of a Doppler radar and may be made
compact by using prior art components. The judging device may be
formed with a compact prior art circuit of a simple structure
including a high pass filter and a comparator. The oscillator
device is for generating an effective frequency. The wave generated
by the oscillator device may be the transmission wave itself or a
basic wave to serve as the source of the transmission wave and may
be a continuous wave or an impulse wave generated at the positions
of the rise or the fall of a rectangular wave. In other words, the
transmission wave of the Doppler radar may be a continuous wave, a
pulse wave or an impulse wave. The signal to be mixed with the
signal received by the mixer may be the wave obtained by modulating
the transmission wave.
[0015] The detection distance is the length of the detection area
in the direction in which the target object approaches and retreats
from the antennas. That the detection distance is set within 1/4
wavelength of frequency effective for the detection means that the
detector (such as its effective frequency) is set such that the
detection distance will be within 1/4 wavelength of the effective
frequency. It is not to be understood as meaning that the detection
distance is limited to any particular length.
[0016] By setting the effective frequency, transmission output
power and the reception sensitivity appropriately, a sufficiently
large detection area may be established. If the effective frequency
is 1 GHz, its 1/4 wavelength is 7.5 cm and this means that a
detection distance up to 7.5 cm may be set. This is sufficient for
detecting the user's hand approaching the door handle of a vehicle
and generating a trigger for the automatic unlocking of the
door.
[0017] According to this invention, the detection distance is set
within 1/4 wavelength of frequency effective for the detection. As
a result, the phase or the timing of the transmission and reception
waves may be appropriately set such that the output from the mixer
(herein referred to as the output V) will uniformly change
according to the distance L to the target object. For example, it
may be set such that V increases as L increases. Thus, a judging
device may be able to switch on a detection output indicative of a
target object approaching or retreating based on whether or not the
output V is increasing or decreasing. With such a judging device,
the motion of the target object can be detected in a non-contacting
manner. The judging device may be adapted to detect only an
approaching object, only a retreating object or both.
[0018] The aforementioned oscillator device is preferably one that
generates a non-sinusoidal wave with frequency less than 1/5 (more
preferably less than 1/10) of frequency effective for the
detection. The non-sinusoidal wave may be any wave other than a
sine wave such as a rectangular wave for generating a signal
including a wave with an effective frequency. Such an oscillator
device can be formed with an inexpensive circuit and the antennas
comprising the aforementioned transmission and reception devices
need not be adjusted to any particular frequency. This is
advantageous from the point of view of the freedom in the design of
the antennas.
[0019] A speed correcting device for changing the detection output
based on the speed of change of the output V from the mixer or a
speed signal outputting device for outputting a speed signal
indicative of the speed of motion of the target object based on the
speed of change of the output V from the mixer may be provided
additionally. The speed correcting device may be used such that the
detection output will be prevented from being switched on if the
detected speed of change is too fast and greater than a specified
threshold value (or too slow) although the judging device alone
would have switched on the detection output. The speed correcting
device may be used, instead, to prevent the detection output from
being switched on if the detected speed of change is within a
specified range. Such a speed correcting device may be formed with
a filter for passing only components of the output from the mixer
within a specified range placed on the output (downstream) side of
the mixer and the input (upstream) side of the judging device.
[0020] With such a speed correcting and/or speed signal outputting
device, it becomes possible to change the detection output
according to the speed of motion of the target object and/or to
output information on the speed of motion of the target object such
that the reliability in the detection of the target object can be
improved and it is convenient because such additional information
can be further communicated to another system. When the target
object of detection is a person's hand, for example, a recognition
error in the case of a different object moving much faster than the
normal motion of the hand or stationary objects can be reliably
prevented. An alarm can be provided such that a warning may be
outputted if the hand motion was too speedy such that the door
could not be unlocked before the hand reached the door handle to
try to open it.
[0021] A lock controller according to this invention is a control
unit for a passive entry system with which a vehicle or a building
may be equipped, using a detector according to this invention for
detecting the user's hand as it approaches the handle of a lockable
structure such as a door and using the detection output from this
detector as a trigger for an operation including that of unlocking
the door.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIGS. 1A and 1B are block diagrams respectively of a lock
controller and a detector embodying this invention, and FIG. 1C is
a graph showing a relationship between the distance to the target
object of detection and the detection output.
[0023] FIG. 2A is a block diagram of the judging device and FIGS.
2B and 2C are signal diagrams of the judging device when a positive
and negative standard voltage is applied, respectively.
[0024] FIG. 3 is a flowchart for the control of the lock
controller.
[0025] FIGS. 4A, 4B and 4C are block diagrams of other detectors
embodying this invention.
[0026] FIGS. 5A, 5B and 5C are diagrams for explaining the
transmission and reception waves.
DETAILED DESCRIPTION OF THE INVENTION
[0027] The invention is described next by way of examples with
reference to the drawings.
[0028] FIG. 1A shows a first embodiment of this invention as
applied, for example, to a control device of a passive entry system
of a vehicle, comprising a portable unit 10, a main device 20
mounted to the vehicle and a detector 30.
[0029] Although not illustrated in FIG. 1A in detail, the portable
unit 10 is provided with an antenna and a reception circuit for
receiving a low frequency (LF) startup signal of about 100-150kHz,
a transmission circuit and an antenna for the wireless transmission
of answer and operation (lock and unlock) signals to be described
below on a high-frequency wave (say, within the UHF band), a memory
(such as an EEPROM) for storing at least an identification check
code (or the "ID code"), a control circuit including a
microcomputer for controlling the entire operation of the portable
unit 10 and battery cells.
[0030] In the above, the startup signal is a signal for starting up
the microcomputer of the portable unit 10 in the power-saving WAIT
mode (or the SLEEP mode). The microcomputer of the portable unit 10
is programmed so as to transmit an answer signal including the
aforementioned ID code on a high-frequency electromagnetic wave. In
this sense, the aforementioned startup signal may be said to serve
as a request signal according to this invention.
[0031] Power which is required for the portable unit 10 (at least
at the time of the startup) may be arranged to be supplied from the
main device 20. Since the transmission from the main device 20 to
the portable unit 10 is by way of a low-frequency wave, power
transmission on this wave can be carried out relatively
efficiently. In fact, it is possible in principle to supply all of
the power required by the portable unit 10 from the main device 20
such that the portable unit 10 may not be required to contain any
battery cells.
[0032] The portable unit 10 may be provided with lock and unlock
switches (not shown) of a push-button type on its surface so as to
function as a remote controller (for one-way transmission) of an
ordinary keyless entry system. In other words, the portable unit 10
may be adapted to function not only so as to transmit the answer
signal for a specified number of times upon being started up by
receiving the startup signal but also so as to start up as the lock
switch or the unlock switch is operated and to carry out the
wireless transmission of a lock signal or an unlock signal
inclusive of the ID code. As the lock signal or the unlock signal
is received by the main device 20, the ID code is checked and the
vehicle door is immediately locked or unlocked.
[0033] The portable unit 10 according to this example is adapted to
automatically return to the WAIT mode as soon as a requested
operation (such as the transmission of the answer signal) is
completed and to remain in the WAIT mode until the startup signal
is received next such that wasteful consumption of power is
avoided. This feature, however, is not intended to limit the scope
of this invention. The portable unit 10 may be adapted to normally
remain in a standby mode and become intermittently activated into
an active mode at specified intervals to activate the reception
circuit. If a specified request signal (which may not be the
startup signal but may be only for requesting an answer signal and
need not be a low-frequency signal but may be a high-frequency
signal) is received from the main device 20 while the reception is
intermittently activated, the portable unit 10 may respond to it by
carrying out for a specified number of times the wireless
transmission of an answer signal inclusive of the ID code
registered in the memory on the side of the portable unit 10. The
portable unit 10 may be in the form of a card separate from the
ignition key of the vehicle or may be in the form of a key,
integrated with the ignition key.
[0034] With reference still to FIG. 1A, the main device 20
comprises a control circuit 21, a transmission circuit 22 with a
transmission antenna 23, and a reception circuit 24 with a
reception antenna 25. The transmission circuit 22 and the
transmission antenna 23 are for the purpose of transmitting the
aforementioned low-frequency startup signal, and the reception
circuit 24 and the reception antenna 25 are for the purpose of
receiving the aforementioned high-frequency answer signal and
operation signals. The control circuit 21 includes a microcomputer
serving to carry out necessary operations for controlling the main
device 20 as a whole as well as a door lock actuator 1 of the
vehicle. It also includes a memory device such as an EEPROM for
storing the ID code.
[0035] The control circuit 21, the transmission circuit 22 and the
reception circuit 23 are inside a control unit which may be
disposed, for example, inside the door of the vehicle. The
transmission and reception antennas 23 and 25 may be provided to
the control unit 21 but may also be set at some other place such as
on the room mirror, the door mirror or the door handle either
together with or apart from the transmission and reception circuits
22 and 24.
[0036] The detector 30 is a door handle sensor adapted to detect a
body part (such as a hand or a finger) of the user approaching the
door handle of the vehicle and to generate a detection output which
will serve as a trigger for the automatic unlocking operation on
the door. As shown in FIG. 1A, it includes a sensor circuit 31, a
transmission antenna 32 ("transmission device") and a reception
antenna 33 ("reception device").f
[0037] As shown more in detail in FIG. 1B, the sensor circuit 31
includes an oscillator device 34, a branching device 35, a mixer
36, a judging device 37 and delay devices 38 and 39. The sensor
circuit 31 may be disposed inside the control unit together with
the control circuit 21 or inside the door handle. The transmission
and reception antennas 32 and 33, the oscillator device 34, the
branching device 35, the mixer 36 and the delay devices 38 and 39,
referred to above, are elements similar to those used in a Doppler
radar (or portions thereof downstream of the mixer except for the
signal processor) and hence will be explained below only
briefly.
[0038] The oscillator device 34 is for generating a continuous
transmission wave (such as a sinusoidal wave) with effective
frequency of, say, 500 MHz -1 GHz and may comprise an oscillator
circuit of a known kind formed with a quartz oscillator element, a
capacitor and a resistor or a high-level oscillator circuit such as
a PLL oscillator circuit. The branching device 35 is for branching
the transmission wave generated by the oscillator device 34. A
distributor of a known kind such as a Wilkinson distributor and a
distributor using a resistor may be used for the purpose. The
outputs of this branching device 35 are inputted to the two delay
devices 38 and 39.
[0039] The delay devices 38 and 39 may each be a circuit designed
for a delay but also may be a device of any kind that happens to
function as a delay device, making use of the delay due to a
circuit or a component. They may be of a simple structure with the
magnitude of the delay determined merely by the length of a
transmission line. The output from one of the delay devices (38) is
inputted to the transmission antenna 32 and that from the other
(39) is inputted to the mixer 36.
[0040] The transmission antenna 32 is for transmitting into space
as electromagnetic waves the transmission wave received from the
delay device 38, and the reception antenna 33 is for receiving the
electromagnetic waves transmitted from the transmission antenna 32
and reflected by an object of detection such as a person's hand.
Antennas of known kinds may be used for their purposes and may be
attached to the door handle or on the door somewhere near the door
handle.
[0041] The mixer 36 is for mixing together the signal received by
the reception antenna 33 and the signal branched by the branching
device 35 and passed through the delay device 39 and taking out the
signal component due to the presence of a target object by carrying
out a logical multiplication of these two signals (from the
transmission and reception waves). Such a mixer may be of a known
kind comprising a single diode.
[0042] The judging device 37 is adapted to switch on its output if
the output V from the mixer 36 increases or decreases, and this
output from the judging device 37 serves as the detection output
(or the signal indicative of the presence or absence of an
approaching target object) of the detector 30. This judging device
37 may be of a very simple circuit structure as shown in FIG. 2A,
basic in electronics adapted to apply a standard voltage C to one
of the input terminals of a comparator and an input signal A
(corresponding to the output V) to the other input terminal through
a high pass filter (HPF) (as filtered signal B). The output from
this comparator serves as the output signal D corresponding to the
aforementioned detection output.
[0043] In the above, if the standard voltage C is positive, the
output signal D is switched on when the input signal A is
increasing, as shown in FIG. 2B. If the standard voltage C is
negatively set, the output signal D is switched on when the input
signal A is decreasing.
[0044] If the relationship between the distance L to the target
object of detection and the output V is set such that V will
increase as L increases (as shown, for example, in FIG. 1C), the
output V decreases as the target object approaches. Thus, if it is
so set, a circuit which functions as shown in FIG. 2C (switching on
the output when the output V decreases) is used for the judging
device 37.
[0045] Next, methods of setting a detection distance and the
frequency of the transmission wave for the detector 30 are
explained.
[0046] The detection distance for the detector 30 is set so as to
be equal to or less than 1/4 of the wavelength of the effective
frequency. If it is desired to set the detection distance at 3
cm-10 cm, for example, a frequency value (such as 1 GHz) is set
such that one quarter of the corresponding wavelength will be 7 cm
or over. The space within 3 cm from the antennas 32 and 33 of the
detector 30 will be filled with a material transmitting
electromagnetic waves but preventing the hand from penetrating such
that the detection area is appropriately reduced. The transmission
output and the reception sensitivity may be adjusted (for example,
through the specifications of the oscillator device 34 and the
antennas 32 and 33) such that the intensity of the reception wave
is too weak in the area away from the antennas 32 and 33 by 10 cm
or more and the target object at such distances cannot be
detected.
[0047] The delay devices 38 and 39 are designed such that the phase
difference between the signal path PA (from the branching device 35
through the delay device 38, the transmission antenna 32, air
space, the hand as the target object, air space again and the
reception antenna 33 to the mixer 36) and the signal path PB (from
the branching device 35 through the delay device 39 to the mixer
36) is such that the entire detection area will be within the range
from -1/4 wavelength through 0 (same phase) to +1/4 wavelength or
from +1/4 wavelength through the opposite-phase relationship to 1/4
wavelength. If the phase difference is thus set, a characteristic
as shown in FIG. 1C (that is, the characteristic of the output V
changing in one direction with respect to the distance L within the
detection area) can be obtained. It should be remembered that the
detection cannot be judged properly if the detection spans both of
these ranges.
[0048] With the detector 30 thus structured, the output V does not
fail to increase or decrease to switch on the detection output of
the judging device 37 if a person's hand approaches the detection
area from outside or moves in the approaching direction inside the
detection area. Thus, the approach of the person's hand can be
detected by electromagnetic waves in a non-contact manner over a
sufficiently large detection area.
[0049] Under the same principle, the detector 30 can also detect
the motion of the person's hand in the opposite (retreating)
direction either within the detection area or outward from the
detection area. If both a judging device for detecting an
approaching object and another device for detection a retreating
object are provided, objects of both kinds can be detected.
[0050] Next, the functions of the control circuit 21 and the
operations of the system of this invention are explained in basic
terms. If the detection output from the detector 30 is switched on
while the door of the vehicle is in the locked condition (or while
the door lock actuator 1 is activated), the aforementioned startup
signal is outputted from the transmission circuit 22 and the
transmission antenna 23 for a specified number of times and the
reception circuit 24 is also activated to receive wave signals. If
an answer signal is received from the portable unit 10 after the
startup signals are transmitted, it is checked to determine whether
or not the ID code contained in the answer signal corresponds to
the ID code preliminarily registered in the memory. If the codes
match, the door lock actuator 1 is controlled such that the locked
door of the vehicle is unlocked.
[0051] FIG. 3 shows an example of flowchart for the control process
explained above. The control circuit 21 may be adapted to repeat
the operations of FIG. 3 in a periodic manner.
[0052] In Step S1, it is determined whether the door is in the
locked condition or not. If the door is not locked (NO in Step S1),
the sequence of the processes is terminated. If the door is locked
(YES in Step S1), it is determined whether or not a person's hand
has been detected, that is, whether or not the detection output of
the detector 30 is switched on (Step S2). If the detection is being
made (YES in Step S2), the startup signal is transmitted for a
specified number of times (Step S4). Next, it is determined whether
or not an answer signal has been received and the ID code contained
in the received answer signal has been found to correctly match
(Step S5). If the ID code is found to be correct (Yes in Step S5),
the door is locked by controlling the door lock actuator 1 (Step
S6). If it is determined that the hand is not being detected in
Step 2 or if the ID code is found not to be correct in Step S5, the
sequence of the processes is terminated.
[0053] Favorable characteristics of the detector 30 as described
above as well as a lock controller using such a detector are
described next.
[0054] (1) Since the user's hand approaching the door is detected
electromagnetically in a non-contact way by using the Doppler radar
technology, errors in detection due to dirt or the like do not
occur and even the possibility of a detection error due to unwanted
objects such as rain drops and dead leaves is lower than by a
conventional optical sensor.
[0055] (2) Since the detection area can be made sufficiently large
(or the detection distance sufficiently long), an appropriate
response characteristic can be easily obtained. Since the user's
hand can be detected at a position sufficiently before it contacts
the door handle, the door which was in the locked condition when
the user was merely beginning to pull the door in order to open it
can be automatically unlocked in a reliable manner, unless the user
moves the hand at an exceptionally fast speed, such that the
convenience of a passive entry system is sufficiently utilized.
[0056] (3) It is not necessary to set all of the components of the
detector 30 (such as the sensor circuit 31) at a specified position
(such as the position of the door handle) where the object to be
detected is approaching. It is only the antennas 32 and 33 that are
required to be located at or near the specified position. Since the
detection is judged on the basis of changes in the received output
and the microcomputer is not used for the judgment, the structure
of the sensor circuit 31 is particularly simplified and compact
such that the detector 30 inclusive of its sensor circuit 31 can be
installed inside the door handle relatively easily. Thus, the shape
and the size of the door handle need not be modified and the
freedom in its design is not significantly affected.
[0057] (4) As explained above, the microcomputer need not be used
for the judgment. Thus, the power consumption is significantly less
than by a prior art Doppler radar which carries out operations by
using a microcomputer for a complicated judgment analysis, and the
detector can be mounted easily to a vehicle for the generation of a
trigger for a passive entry system because there is no problem of
using up the battery cells.
[0058] FIGS. 4A, 4B and 4C shows detectors according to other
embodiments of the invention. In these figures, like components are
indicated by the same symbols as used in FIG. 1 and are not
described in a repetitious manner for the convenience of
disclosure.
[0059] FIG. 4A shows a sensor circuit according to a second
embodiment of the invention characterized as comprising an
oscillator device 34a adapted to generate a non-sinusoidal wave
with frequency less than 1/5 and preferably less than 1/10 of the
effective frequency as the base wave to serve as the base of the
transmission wave. Filtering devices (the "filters") 40 and 41 are
also provided respectively on the output side of the delay devices
38 and 39.
[0060] The aforementioned non-sinusoidal wave may be a rectangular
impulse wave, say, of frequency 1 MHz for generating a signal
including effective frequency such as 1 GHz (harmonics, to be
explained below) and the filtering devices 40 and 41 are for the
purpose of limiting the unnecessary frequency components other than
the effective frequency. In this case, harmonics due to the ringing
at the fall time of the rectangular wave (base wave) generated by
the oscillation device 34a, as shown in FIG. 5A, is transmitted
from the transmitted from the transmission antenna 32 through the
filtering device 40 as the transmission wave with the effective
frequency ("effective wave") and inputted through the filtering
device 41 into the mixer 36. Symbol .lamda. in FIG. 5A indicates
the wavelength of the aforementioned harmonics (effective wave).
Symbol t in FIG. 5A indicates the period of repetition of the
aforementioned rectangular wave.
[0061] In this example, the signal path difference between the
aforementioned signal paths PA and PB is arranged to be less than a
few wavelengths (for example, within .+-.2-3.lamda., and preferably
within .+-.1.lamda.) of the aforementioned harmonics (the effective
wave) in view of the desired size of the detection area. In other
words, the output from the filtering device 41 and the output from
the reception antenna 33 must match in timing within this extent.
Since the waveform of the output from the reception antenna 33
repeats with a period of t, however, the aforementioned signal path
difference may include a path difference of corresponding to an
integral multiple of this period t. If the signal path difference
satisfies this condition, the inputs to the mixer 36 through the
paths PA and PB overlap on the time axis as shown in FIG. 5B and
the mixer 36 makes an effective mixing. If the signal path
difference does not satisfy the condition described above, the
signals arriving at the mixer 36 through the signal paths PA and PB
are not sufficiently synchronized, as shown in FIG. 5C and the
mixer 36 fails to mix signals effectively for the purpose of the
detection.
[0062] This embodiment has all the advantages of the detector
according to the first embodiment. It is further advantageous in
that the oscillator device 34a can be formed with a less expensive
circuit and that the characteristics of the antennas 32 and 33 do
not have to be adjusted to any particular frequency such that there
is a greater freedom in their design.
[0063] FIG. 4B shows a sensor circuit according to a third
embodiment of the invention which may be considered a variation of
the second embodiment, characterized wherein the circuits of the
delay devices 38 and 39 and the frequency characteristics of the
antennas 32 and 33 are designed such that frequency components
other than the effective frequency are controlled. Normally,
circuits and antennas have their own frequency characteristics.
According to this embodiment, these frequency characteristics are
specified such that the filtering devices 40 and 41 of the second
embodiment shown in FIG. 4A are dispensed with. This embodiment is
advantageous, therefore, in that the circuit structure is
accordingly simpler.
[0064] FIG. 4C shows a sensor circuit according to a fourth
embodiment of the invention characterized as having the output from
the mixer divided into two ways and having another filtering device
42 provided to one of the output sides of the mixer 36 for
outputting data of another kind to be explained below, the other
output of the mixer 36 being inputted to the judging device 37.
[0065] This filtering device 42 may be a high pass filter for
allowing only high-frequency components to pass, a low pass filter
for allowing only low-frequency components to pass, or a band pass
filter for allowing only components within a specified frequency
range to pass. The speed (frequency) at which the output V from the
mixer 36 goes up or down changes, depending on the speed of the
target object of detection. Thus, the output V from the mixer 36
can be outputted through this filter 42 if the speed of the target
object is within a certain range determined by the frequency
characteristics of the filtering device 42 but the output V fails
to be outputted from the filtering device 42 if the speed of the
target object is not within this specific range.
[0066] In summary, this filtering device 42 functions as an output
device for a speed signal corresponding to the speed of the target
object, and some unique advantages can be enjoyed by using the
outputs from such a filtering device. Firstly, such a filtering
device is useful because it becomes possible to transmit to the
control unit 21 not only information related to the approach of the
target object (such as the output signal from the judging device
37) but also information on its speed. If a speed exceeding the
range of normal hand motion is detected, for example, the result of
detection can be forcibly changed into non-detection even if the
judging device 37 would be concluding that the detection output
should be switched on. In other words, the control unit 21 may
function such that the automatic unlocking of the door will not be
effected. In this manner, erroneous detection of objects other than
a person's hand such as fast-moving objects and stationary objects
can be avoided. An alarm may be incorporated such that the user can
be warned if an attempt is made to open the door with a hand motion
too quick such that the automatic unlocking of the door could not
be effected in time and the door fails to open.
[0067] Although FIG. 5C shows an arrangement wherein the filtering
device 42 and the judging device 37 are connected in parallel, a
similar filtering device may be connected in series with the
judging device 37 (that is, on the output side of the mixer 36 and
on the input side of the judging device 37). Such a filtering
device functions as a speed correcting means for changing the
detection output from the judging device 37 on the basis of the
speed change outputted from the mixer 36. If this change of speed
is too fast or too slow and hence if the speed of motion of the
target object is too fast or too slow, the detection output may be
forcibly made not to be switched on. Thus, erroneous detection of
objects other than a person's hand such as fast-moving objects and
stationary objects can be avoided even more reliably with such a
filtering device.
[0068] Although the invention has been described by way of only a
limited number of examples, these examples are not intended to
limit the scope of the invention. Many modifications and variations
are possible within the scope of the invention. Indeed, the
invention is not limited to the unlocking of a door but may be
applied to many other kinds of objects of control and contents of
control. For example, a detector according to this invention may be
used to generate a trigger for an automatic locking operation of a
passive entry system. It may also be used for the automatic locking
and unlocking of the trunk of an automobile, a door of other kinds
of vehicles such as a boat and a small plane or a door of a
building such as a residential house or an office building. The
detector of this invention need not be used for the detection of a
person's hand. It may be used for the detection of other kinds of
objects as long as the object can reflect electromagnetic waves
effectively.
[0069] The aforementioned request signal within the context of this
invention may include not only a startup signal for starting up the
portable unit in a SLEEP mode (the microcomputer being in the WAIT
mode) but also a signal for asking the portable unit already
started up (whether or not the microcomputer is still in the WAIT
mode) to transmit a specified answer signal. Such a request signal
is not required to be sent on the LF band but may be sent on other
bands such as the UHF band, although the use of the LF band is
advantageous because power transmission can be effected relatively
efficiently.
[0070] The request signal may contain its own characterization code
(preferably different from the aforementioned ID code for security
reasons) because there may be many vehicles having entry systems of
the same kinds parked in the neighborhood. In such a situation, the
portable unit will be receiving request signals transmitted from
all these vehicles and it is therefore necessary to arrange it such
that the portable unit will not be required to transmit an answer
signal each time such a request signal is received and will
transmit the answer signal only after checking the characterization
code of each received request signal.
[0071] The antennas on the main device and those on the detector
may be integrated into one common antenna if there is no problem,
say, with the different frequency bands to be used.
[0072] In summary, the present invention provides a detector which
is superior in reliability, response characteristics, operability
by the user and suitability to a vehicle (say, in terms of size,
design limitations and power consumption rate), as well as a lock
controller (or a controller for a passive entry system) of a
superior quality.
* * * * *