U.S. patent application number 15/091425 was filed with the patent office on 2016-10-27 for tire condition monitoring device.
The applicant listed for this patent is ALPS ELECTRIC CO., LTD.. Invention is credited to Shinya TAKAHATA, Satoshi USHIDA.
Application Number | 20160311272 15/091425 |
Document ID | / |
Family ID | 57136483 |
Filed Date | 2016-10-27 |
United States Patent
Application |
20160311272 |
Kind Code |
A1 |
USHIDA; Satoshi ; et
al. |
October 27, 2016 |
TIRE CONDITION MONITORING DEVICE
Abstract
Each time a time corresponding to one period of an intermittent
reception process in a vehicle-side device elapses, a transmission
interval of a notification signal is controlled so that a
transmission time of a preamble of the notification signal is
shifted in a direction in which the transmission time is relatively
delayed from an execution time of the reception process. Further,
when the transmission time of the preamble passes through a range
of the execution time of the reception process during this relative
shift, the transmission interval of the notification signal is
controlled so that the entire transmission time of the preamble is
included in the range of the execution time of the reception
process.
Inventors: |
USHIDA; Satoshi;
(Miyagi-ken, JP) ; TAKAHATA; Shinya; (Miyagi-ken,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ALPS ELECTRIC CO., LTD. |
Tokyo |
|
JP |
|
|
Family ID: |
57136483 |
Appl. No.: |
15/091425 |
Filed: |
April 5, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60C 23/0435 20130101;
B60C 23/0462 20130101; B60C 23/0455 20130101 |
International
Class: |
B60C 23/04 20060101
B60C023/04 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 23, 2015 |
JP |
2015-088839 |
Claims
1. A tire condition monitoring device comprising: a transmitter
installed in a tire, configured to transmit a notification signal
for notifying of a condition of the tire; a receiver installed in a
vehicle body configured to receive the notification signal from the
transmitter; a tire-side control unit configured to cause the
transmitter to intermittently and periodically transmit the
notification signal, the notification signal including a
predetermined start signal indicating a start of a transmission of
the notification signal; and a vehicle-side control unit configured
to control the receiver to intermittently and periodically execute
a reception process for receiving the notification signal with a
predetermined cycle wherein the tire-side control unit controls a
transmission interval for the transmission of the notification
signal such that a first interval between a first reference time
which is a period of the predetermined cycle after a transmission
of the start signal started and an end time at which the
transmission of the start signal ends first time after the first
reference time is shorter than an execution time period for
executing the reception process, and that the first interval
between the first reference time and the end time is longer by a
first shift time than a transmission time period for transmitting
the start signal.
2. The tire condition monitoring device according to claim 1,
wherein the tire-side control unit performs the transmission of the
notification signal such that the transmission interval is set to
1/N (N is an integer greater than 1) of the predetermined cycle of
the reception process for (N-1) transmissions, and is increased for
an N-th transmission by the first shift time from the previous
transmission interval of 1/N of the predetermined cycle.
3. The tire condition monitoring device according to claim 2,
wherein the tire-side control unit sets the first shift time to 1/M
(M is an integer greater than 1) of the transmission interval which
is 1/N of the predetermined cycle of the reception process.
4. A tire condition monitoring device comprising: a transmitter
installed in a tire, configured to transmit a notification signal
for notifying of a condition of the tire; a receiver installed in a
vehicle body configured to receive the notification signal from the
transmitter; a tire-side control unit configured to cause the
transmitter to intermittently and periodically transmit the
notification signal, the notification signal including a
predetermined start signal indicating a start of a transmission of
the notification signal; and a vehicle-side control unit configured
to control the receiver to intermittently and periodically execute
a reception process for receiving the notification signal with a
predetermined cycle, wherein the tire-side control unit controls a
transmission interval for the transmission of the notification
signal such that a second interval between a second reference time
which is a period of the predetermined cycle after a transmission
of the start signal ends and a start time at which the transmission
of the start signal last started before the second reference time
is shorter than an execution time period for executing the
reception process, and the second interval between the second
reference time and the start time is longer by a second shift time
than a transmission time period for transmitting the start
signal.
5. The tire condition monitoring device according to claim 4,
wherein the tire-side control unit performs the transmission of the
notification signal such that the transmission interval is set to
1/N (N is an integer greater than 1) of the predetermined cycle of
the reception process for (N-1) transmissions, and is decreased for
an N-th transmission by the second shift time from the previous
transmission interval of 1/N of the predetermined cycle.
6. The tire condition monitoring device according to claim 5,
wherein the tire-side control unit sets the second shift time to
1/M (M is an integer greater than 1) of the transmission interval
which is 1/N of the predetermined cycle of the reception
process.
7. The tire condition monitoring device according to claim 1,
wherein the vehicle-side control unit continuously executes the
reception process if the vehicle-side control unit receives a
signal indicating that a driving system of the vehicle is in an
operation state, and intermittently executes the reception process
if the vehicle-side control unit receives a signal indicating that
the driving system is in a stop state.
8. The tire condition monitoring device according to claim 4,
wherein the vehicle-side control unit continuously executes the
reception process if the vehicle-side control unit receives a
signal indicating that a driving system of the vehicle is in an
operation state, and intermittently executes the reception process
if the vehicle-side control unit receives a signal indicating that
the driving system is in a stop state.
9. The tire condition monitoring device according to claim 1,
further comprising: a sensor configured to detect an air pressure
of the tire, wherein the tire-side control unit suppresses the
transmission of the notification signal from the transmitter if the
tire-side control unit determines that the air pressure is normal
based on a detection result of the sensor.
10. The tire condition monitoring device according to claim 4,
further comprising: a sensor configured to detect an air pressure
of the tire, wherein the tire-side control unit suppresses the
transmission of the notification signal from the transmitter if the
tire-side control unit determines that the air pressure is normal
based on a detection result of the sensor.
Description
CLAIM OF PRIORITY
[0001] This application claims benefit of Japanese Patent
Application No. 2015-088839 filed on Apr. 23, 2015, which is hereby
incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a tire condition monitoring
device that transmits information for monitoring a condition of a
tire from a transmitter installed in the tire to a receiver
installed in a vehicle body.
[0004] 2. Description of the Related Art
[0005] A tire pressure monitoring system (TPMS) that detects a
pressure of a tire using a sensor, transmits the pressure to a
device on the vehicle side, and monitors whether the air pressure
is abnormal is known.
[0006] In general, in a device on the tire side, a transmitter is
controlled so that a transmission interval of a radio signal
becomes long at the time of stop of a vehicle in order to reduce
consumption of a battery. Further, in the device on the vehicle
side, a receiver is controlled to operate intermittently in order
to save power at the time of stop of an engine. Therefore, both the
transmitter and the receiver may operate intermittently, and it
becomes necessary to match timings of transmission and
reception.
[0007] In a tire pressure monitoring device described in Japanese
Unexamined Patent Application Publication No. 2005-153641 below, a
data transmission time of a transmitter is longer than an
intermittent startup time of a receiver. Accordingly, in a case in
which data transmission from the transmitter is performed, the
receiver can reliably receive data.
[0008] However, if an intensity of radio waves or the like is
regulated under regulations, the transmitter cannot take a long
time of one transmission. Further, if the transmission time is
long, the power of the transmitter increases. Accordingly, a
transmission output should be decreased so that the power does not
exceed a rated power. As a result, a sufficient reception
sensitivity may not be obtained in a receiver on the vehicle side.
In such a case, a method of increasing the transmission time as
described in Japanese Unexamined Patent Application Publication No.
2005-153641 cannot be adopted.
[0009] Instead of increasing the transmission time, decreasing an
interval of a reception operation in the receiver may be
considered. However, for example, in a case in which the receiver
is also used as another system (for example, a keyless entry
system), the method in Japanese Unexamined Patent Application
Publication No. 2005-153641 cannot be adopted since the interval of
the reception operation of the receiver cannot be freely
changed.
[0010] A method of providing a high-precision real-time clock in
both of the transmitter and the receiver may be considered in order
to match a transmission timing of the transmitter with a reception
timing of the receiver. However, this method has a problem that a
circuit configuration is complicated and costs increase.
SUMMARY OF THE INVENTION
[0011] The present invention provides a tire condition monitoring
device in which a receiver installed in a vehicle body can reliably
receive a signal from a transmitter installed in a tire with a
simple circuit configuration even when a transmission time of the
transmitter is shorter than a reception interval of the receiver in
a case in which the transmitter and the receiver operate
intermittently.
[0012] The present invention provides a tire condition monitoring
device that transmits a notification signal for notifying of a
condition of a tire from a transmitter installed in the tire to a
receiver installed in a vehicle body.
[0013] A tire condition monitoring device according to a first
aspect of the present invention includes a tire-side control unit
configured to intermittently transmit, from the transmitter, a
notification signal including a predetermined start signal
indicating start of transmission; and a vehicle-side control unit
configured to execute a reception process for receiving the
notification signal in the receiver, intermittently at a certain
period. The tire-side control unit controls a transmission interval
of the notification signal so that an interval between a reference
time at which the same time as one period of the reception process
has elapsed from a time at which the transmission of the start
signal starts and a time at which the transmission of the start
signal first ends after the reference time becomes shorter than
time taken for one execution of the reception process and becomes
longer by a first shift time than the transmission time of the
start signal.
[0014] According to the above configuration, the interval
(hereinafter referred to as an "interval Tx1" in this paragraph)
between the reference time at which the same time as one period of
the reception process has elapsed from the time at which the
transmission of the start signal starts and the time at which the
transmission of the start signal first ends after the reference
time is longer by the first shift time than the transmission time
of the start signal. Therefore, the time at which the transmission
of the start signal first starts after the reference time is
shifted in a direction in which the time is relatively delayed by
the first shift time from the reference time at which the same time
as one period of the reception process has elapsed from the time at
which the transmission of one start signal starts. That is, the
transmission period of the start signal is shifted in a direction
in which the transmission period is relatively delayed by the first
shift time from the execution period of the reception process each
time the time corresponding to one period of the reception process
elapses. Accordingly, the transmission period of the start signal
passes through the execution period of the reception process during
repetition of the reception process. At the time of the passage,
since the interval Tx1 is shorter than time taken for one execution
of the reception process, the entire transmission period of the
start signal is included in the execution period of the reception
process. Therefore, in this case, the entire start signal is
normally received in the receiver.
[0015] Preferably, the tire-side control unit may perform
intermittent transmission of the notification signal at a
transmission interval which is 1/N (N indicates an integer greater
than 1) of the period of the reception process. The tire-side
control unit may increase the transmission interval from the
previous transmission by the first shift time from the transmission
interval which is 1/N, for one transmission after repeating (N-1)
transmissions at the transmission interval which is 1/N.
[0016] According to the above configuration, each time the
transmission of the notification signal is repeated N times, the
transmission time of the notification signal is shifted in a
direction in which the transmission time is relatively delayed by
the first shift time from the execution time of the reception
process.
[0017] Preferably, the tire-side control unit may set the first
shift time to 1/M (M indicates an integer greater than 1) of the
transmission interval which is 1/N.
[0018] A tire condition monitoring device according to a second
aspect of the present invention includes a tire-side control unit
configured to intermittently transmit, from the transmitter, a
notification signal including a predetermined start signal
indicating start of transmission; and a vehicle-side control unit
configured to execute a reception process for receiving the
notification signal in the receiver, intermittently at a certain
period. The tire-side control unit controls a transmission interval
of the notification signal so that an interval between a reference
time at which the same time as one period of the reception process
has elapsed from a time at which the transmission of the start
signal ends and a time at which the transmission of the start
signal last starts before the reference time becomes shorter than
time taken for one execution of the reception process and becomes
longer than the transmission time of the start signal by a second
shift time.
[0019] According to the above configuration, the interval
(hereinafter referred to as an "interval Tx2" in this paragraph)
between the reference time at which the same time as one period of
the reception process has elapsed from the time at which the
transmission of the start signal ends and the time at which the
transmission of the start signal last starts before the reference
time is longer by the second shift time than the transmission time
of the start signal. Therefore, the time at which the transmission
of the start signal last ends before the reference time is shifted
in a direction in which the time is relatively earlier by the
second shift time than the reference time at which the same time as
one period of the reception process has elapsed from the time at
which the transmission of one start signal ends. That is, the
transmission period of the start signal is shifted in a direction
in which the transmission period is relatively earlier by the
second shift time than the execution period of the reception
process each time the time corresponding to one period of the
reception process elapses. Accordingly, the transmission period of
the start signal passes through the execution period of the
reception process during repetition of the reception process. At
the time of the passage, since the interval Tx2 is shorter than
time taken for one execution of the reception process, the entire
transmission period of the start signal is included in the
execution period of the reception process. Therefore, in this case,
the entire start signal is normally received in the receiver.
[0020] Preferably, the tire-side control unit may perform
intermittent transmission of the notification signal at a
transmission interval which is 1/N (N indicates an integer greater
than 1) of the period of the reception process. The tire-side
control unit may decrease the transmission interval from the
previous transmission by the second shift time from the
transmission interval which is 1/N, for one transmission after
repeating (N-1) transmissions at the transmission interval which is
1/N.
[0021] According to the above configuration, each time the
transmission of the notification signal is repeated N times, the
transmission time of the notification signal is shifted in a
direction in which the transmission time becomes relatively earlier
by the second shift time than the execution time of the reception
process.
[0022] Preferably, the tire-side control unit may set the second
shift time to 1/M (M indicates an integer greater than 1) of the
transmission interval which is 1/N.
[0023] In the first aspect and the second aspect, the vehicle-side
control unit may continuously execute the reception process in a
case in which the vehicle-side control unit receives a signal
indicating that a driving system of a vehicle is in an operation
state, and may intermittently execute the reception process in a
case in which the vehicle-side control unit receives a signal
indicating that the driving system is in a stop state.
[0024] Accordingly, in a case in which the driving system of the
vehicle is in an operation state, if the notification signal is
transmitted in the transmitter, the notification signal is received
immediately in the receiver. Further, in a case in which the
driving system is in a stop state, power consumption due to the
reception process is reduced since the reception process is
executed intermittently in the receiver.
[0025] Further, the tire condition monitoring device according to
the aspect of the present invention may include a sensor configured
to detect an air pressure of the tire. The tire-side control unit
may suppress the transmission of the notification signal from the
transmitter in a case in which the tire-side control unit
determines that the air pressure is normal based on a detection
result of the sensor.
[0026] Accordingly, in a case in which the air pressure of the tire
is normal, consumption of power due to the transmission of the
transmitter is suppressed.
[0027] According to the present invention, the receiver installed
in a vehicle body can reliably receive the signal from a
transmitter installed in a tire with a simple circuit configuration
in which a real time clock or the like is not used even when a
transmission time of the transmitter is shorter than a reception
interval of the receiver in a case in which the transmitter and the
receiver operate intermittently.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 is a diagram illustrating an example of a
configuration of a tire condition monitoring device according to an
embodiment of the present invention.
[0029] FIG. 2 is a diagram illustrating an example of a
configuration of a tire-side device.
[0030] FIG. 3 is a diagram illustrating an example of a
configuration of a notification signal transmitted from a tire-side
device to a vehicle-side device.
[0031] FIG. 4 is a diagram illustrating an example of a
configuration of the vehicle-side device.
[0032] FIG. 5 is a diagram for explaining an example of an
operation of a tire condition monitoring device according to a
first embodiment.
[0033] FIG. 6 is a timing chart for explaining an example of an
operation of a tire condition monitoring device according to a
second embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
First embodiment
[0034] FIG. 1 is a diagram illustrating an example of a
configuration of a tire condition monitoring device according to an
embodiment of the present invention. The tire condition monitoring
device illustrated in FIG. 1 is a device that monitors a condition
of air pressure or the like in tires 5A to 5D of a vehicle 1, and
includes tire-side devices 2A to 2D provided in the tires 5A to 5D,
and a vehicle-side device 3 provided in a body of the vehicle 1. In
the following description, any one of the tires 5A to 5D is
referred to as "tire 5" as a representative, and any one of the
tire-side devices 2A to 2D is referred to as "tire-side device 2"
as a representative.
[0035] The tire condition monitoring device illustrated in FIG. 1
generally operates as follows. First, each tire-side device 2
detects a condition of the air pressure or the like of the tire 5
using a sensor, and intermittently transmits a notification signal
for notifying of the detected state to the vehicle-side device 3.
The vehicle-side device 3 receives the notification signal from
each tire-side device 2 and monitors the condition of each tire 5.
In a case in which the vehicle-side device 3 receives a
notification signal indicating abnormality of the tire 5 from the
tire-side device 2, the vehicle-side device 3 notifies a
higher-level device (an electronic control unit; not illustrated)
mounted on the vehicle 1 of the detection of the abnormality.
Further, in a case in which a driving system of the vehicle 1 stops
(for example, in a case in which an ignition switch is off), the
vehicle-side device 3 intermittently executes a process of
receiving the notification signal at a certain period.
[0036] FIG. 2 is a diagram illustrating an example of a
configuration of the tire-side device 2. The tire-side device 2
illustrated in FIG. 2 is, for example, a device fixed to a wheel
portion of the tire 5 together with a tire valve or the like, and
includes a transmitter 21, an air pressure sensor 22 that detects
air pressure in the inside of the tire 5, an acceleration sensor 23
that detects an acceleration generated in the tire 5, a tire-side
control unit 24, and a storage unit 25. The tire-side device 2 is
operated by power supplied by a battery (not illustrated).
[0037] The transmitter 21 is a circuit that transmits a radio
signal to the vehicle-side device 3. In the example of FIG. 2, the
transmitter 21 includes a transmission circuit 210 and an antenna
211. The transmission circuit 210 performs predetermined signal
processing such as encoding, modulation, or amplification on data
for transmission generated in the tire-side control unit 24 to
generate a transmission signal, and transmits the transmission
signal as the radio signal from the antenna 211.
[0038] The tire-side control unit 24 is a circuit that is
responsible for an entire process of the tire-side device 2 and
includes, for example, a computer (for example, microprocessor) or
a dedicated logic circuit (for example, ASIC) that executes
commands based on a program stored in the storage unit 25.
[0039] The tire-side control unit 24 determines whether the air
pressure is included in a normal range based on a detection signal
indicating the air pressure in the inside of the tire detected by
the air pressure sensor 22. In a case in which the tire-side
control unit 24 determines that the air pressure is out of the
normal range, the tire-side control unit 24 intermittently
transmits a notification signal for notifying the vehicle-side
device 3 of the abnormality of the air pressure of the tire 5 from
the transmitter 21. In a case in which the air pressure is included
in the normal range, the tire-side control unit 24 suppresses the
transmission of the notification signal from the transmitter
21.
[0040] FIG. 3 is a diagram illustrating an example of a
configuration of the notification signal transmitted from the
tire-side device 2 to the vehicle-side device 3. In the example of
FIG. 3, the notification signal includes a "preamble", a "command",
and a "checksum".
[0041] The "preamble" is a signal indicating that the transmission
of the notification signal from the tire-side device 2 starts, and
corresponds to a start signal in the embodiment of the present
invention. In a case in which the preamble (start signal) is
included in a head part of a received signal, the vehicle-side
device 3 determines that the received signal is the notification
signal from the tire-side device 2, and performs a process of
further receiving the rest of the notification signal including the
preamble (start signal).
[0042] The "command" is a body of the notification signal, and
includes information on the condition of the tire 5 (condition of
air pressure in the example of FIG. 3).
[0043] The "checksum" is information for checking a reception error
of the notification signal in the vehicle-side device 3, and is
obtained by regarding data included in the notification signal as a
numerical value group and performing calculation such as
addition.
[0044] The tire-side control unit 24 controls a transmission
interval Tt1 of the notification signal which is intermittently
transmitted from the transmitter 21, as follows. That is, the
tire-side control unit 24 controls the transmission interval Tt1 of
the notification signal so that a transmission time Tp1 of the
preamble of the notification signal is relatively shifted with
respect to an execution time Tw1 of the reception process each time
the time corresponding to one period Tr1 of an intermittent
reception process in the vehicle-side device 3 elapse. Further, the
tire-side control unit 24 controls the transmission interval Tt1 of
the notification signal so that the entire transmission time Tp1 of
the preamble is included in a range of the execution time Tw1 of
the reception process when the transmission time Tp1 of the
preamble during this relative shift passes through a range of the
execution time Tw1 of the reception process.
[0045] For example, the tire-side control unit 24 controls the
transmission interval Tt1 of the notification signal so that an
interval Tx1 between a reference time at which the same time as one
period Tr1 of the reception process of the vehicle-side device 3
elapses from the time at which the transmission of the preamble of
the notification signal starts and a time at which the transmission
of the preamble of the notification signal first ends after this
reference time becomes shorter than one execution time Tw1 of the
reception process in the vehicle-side device 3 and becomes longer
than the transmission time Tp1 of the preamble by a first shift
time .DELTA.T1.
[0046] More specifically, the tire-side control unit 24 performs
intermittent transmission of the notification signal at the
transmission interval Tt1 (=Tr1/N) which is 1/N (N indicates an
integer greater than 1) of the period Tr1 of the reception process
of the vehicle-side device 3, and increases the transmission
interval from the previous transmission by the first shift time
.DELTA.T1 from the transmission interval Tt1 (=Tr1/N), for one
transmission after repeating (N-1) transmissions at the
transmission interval Tt1.
[0047] The tire-side control unit 24 sets the first shift time
.DELTA.T1 to a time shorter than a difference between the execution
time Tw1 of the reception process and the transmission time Tp1 of
the preamble. For example, the tire-side control unit 24 sets the
first shift time .DELTA.T1 to 1/M (M indicates an integer greater
than 1) of the transmission interval Tt1 (=Tr1/N).
[0048] Control of the transmission interval Tt1 described above in
the tire-side control unit 24 will be described below in detail
with reference to FIG. 5.
[0049] The tire-side control unit 24 performs control of the
transmission interval Tt1 according to the detection result of the
acceleration sensor 23, in addition to the control of the
transmission interval Tt1 described above. That is, the tire-side
control unit 24 performs a determination as to whether the vehicle
1 is in a stop state based on the detection result of the
acceleration sensor 23. In a case in which the vehicle 1 is
determined to be in the stop state, the tire-side control unit 24
increases the transmission interval Tt1 of the notification signal.
In a case in which the vehicle 1 is in a non-stop state (operation
state), the tire-side control unit 24 decreases the transmission
interval Tt1 of the notification signal. For example, in a case in
which an amount of change in the acceleration detected by the
acceleration sensor 23 is smaller than a predetermined threshold
value, the tire-side control unit 24 determines that the vehicle 1
is in a stop state and increases the transmission interval Tt1 of
the notification signal.
[0050] The storage unit 25 is, for example, a device that stores a
program of a computer in the tire-side control unit 24, prepared
data for processing, or data temporarily stored during processing,
and includes a ROM, a RAM, a nonvolatile memory, or the like.
[0051] FIG. 4 is a diagram illustrating an example of a
configuration of the vehicle-side device 3. The vehicle-side device
3 illustrated in FIG. 4 is a device installed in a body of the
vehicle 1, and includes a receiver 31, an interface unit 32, a
vehicle-side control unit 33, and a storage unit 34.
[0052] The receiver 31 is a circuit that receives the radio signal
which is transmitted from the tire-side device 2 of each tire 5. In
the example of FIG. 4, the receiver 31 includes a reception circuit
310, and an antenna 311. The reception circuit 310 performs
predetermined signal processing such as amplification,
demodulation, and decoding on the radio signal from the tire-side
device 2 received by the antenna 311 to generate reception data,
and outputs the reception data to the vehicle-side control unit
33.
[0053] The interface unit 32 is connected to a higher-level device
(for example, electronic control unit) installed in the vehicle 1
via a bus 4, and performs processing regarding communication with
the higher-level device according to a communication protocol, such
as a controller area network (CAN).
[0054] The vehicle-side control unit 33 is a circuit that is
responsible for entire processing of the vehicle-side device 3 and
includes, for example, a computer (for example, a microprocessor)
or a dedicated logic circuit (for example, ASIC) that executes
commands based on a program stored in the storage unit 34.
[0055] The vehicle-side control unit 33 receives a signal
indicating whether the driving system of the vehicle 1 stops, for
example, from the higher-level device through the interface unit
32. In a case in which the vehicle-side control unit 33 receives a
signal indicating that the driving system of the vehicle 1 is in an
operation state, the vehicle-side control unit 33 continuously
executes the process of receiving the notification signal in the
receiver 31. In a case in which the vehicle-side control unit 33
receives a signal indicating that the driving system of the vehicle
1 stops, the vehicle-side control unit 33 intermittently executes
the process of receiving the notification signal at a certain
period Tr1.
[0056] In a case in which a head part of the signal received by the
receiver 31 matches a predetermined pattern, the vehicle-side
control unit 33 determines that the received signal is the preamble
of the notification signal, and receives the rest of the
notification signal following the preamble. In a case in which the
vehicle-side control unit 33 receives the preamble of the
notification signal when intermittently executing the process of
receiving the notification signal, the vehicle-side control unit 33
continues to perform the reception process until the vehicle-side
control unit 33 receives all of the rest of the notification
signal.
[0057] In a case in which the receiver 31 receives the notification
signal from the tire-side device 2, the vehicle-side control unit
33 outputs a signal for urging an operation (for example, a warning
display in a dashboard of the vehicle 1) according to the
notification signal from the interface unit 32 to the higher-level
device.
[0058] The storage unit 34 is, for example, a device that stores a
program of a computer in the vehicle-side control unit 33, prepared
data for processing, or data temporarily stored during processing,
and includes a ROM, a RAM, a nonvolatile memory, a hard disk, or
the like. The program or the data stored in the storage unit 34 may
be downloaded from a server device (not illustrated) via the
interface unit 32 or another communication interface, or may be
read from a non-transitory storage medium, such as an optical disc
or a USB memory.
[0059] An operation of the tire condition monitoring device
according to the first embodiment having the above-described
configuration will be described herein with reference to a timing
chart of FIG. 5.
[0060] "CY(i)", "CY(i+1)", and "CY(i+2)" (i=1, 2, 3, . . . ) in the
timing chart of FIG. 5 indicate three consecutive cycles of the
reception process executed at a certain period Tr1 by the receiver
31 of the vehicle-side device 3. A value (i, i+1, i+2) in
parentheses denotes an order of the cycle of the reception process.
In this timing chart, a relationship between an execution timing of
the reception process of the three consecutive cycles and a timing
at which notification signals (S1, S2, S3, . . . ) are transmitted
from the transmitter 21 of the tire-side device 2 is represented
using a horizontal direction as a direction of a time axis.
Further, in FIG. 5, due to a limited width of paper, a timing chart
of three cycles in which time has progressed by one cycle is
illustrated just below the timing chart of the three consecutive
cycles. Thus, the timing chart from a cycle CY(1) to a cycle CY(12)
of the reception process is illustrated in FIG. 5.
[0061] In the timing chart of FIG. 5, hatched portions in figures
indicating the notification signals S1, S2, S3, . . . indicate
preambles.
[0062] Focusing on a timing chart (i=1) of a first line in FIG. 5,
time t1 is a time at which transmission of the preamble of the
notification signal S1 starts, and time t2 is a reference time at
which the same time as a period Tr1 of the reception process
elapses from time t1 (t2-t1=Tr1). Further, time t3 is a time at
which transmission of the preamble of the notification signal first
starts after reference time t2, and time t4 is a time at which the
transmission of the preamble of this notification signal ends. The
tire-side control unit 24 of the tire-side device 2 controls the
transmission interval Tt1 of the notification signal so that an
interval Tx1 between time t4 and reference time t2 is shorter than
the execution time Tw1 of the reception process and is longer than
the transmission time Tp1 of the preamble by a first shift time
.DELTA.T1 (Tx1=Tp1+.DELTA.T1).
[0063] If the first shift time .DELTA.T1 is set to 0, the interval
Tx1 between time t4 and reference time t2 becomes equal to
transmission time Tp1 of the preamble, and reference time t2
matches transmission start time t3 of the preamble of the
notification signal S4. That is, at reference time t2 (=t3) at
which the same time as the period Tr1 elapses from time t1 at which
the transmission of the preamble of the notification signal S1
starts, the transmission of the preamble of the notification signal
S4 starts. This means that a relative timing between a period in
which the reception process of the vehicle-side device 3 is
executed and a period in which the preamble of the notification
signal is transmitted does not change. Since the transmitter 21 of
the tire-side device 2 and the receiver 31 of the vehicle-side
device 3 operate independently, a relative timing between both is
undefined, and is likely to be completely shifted in an initial
state. If the relative timing between both is shifted in the
initial state, this shift state is maintained and the vehicle-side
device 3 cannot receive the notification signal.
[0064] On the other hand, in the tire condition monitoring device
according to this embodiment, the first shift time .DELTA.T1 is set
to a predetermined period of time rather than 0. That is, time t3
at which the transmission of the preamble first starts after
reference time t2 is shifted in a direction in which time t3 is
relatively delayed by the first shift time .DELTA.T1 from reference
time t2 at which the same time as the period Tr1 of the reception
process elapses from time t1 at which the transmission of the
preamble starts. That is, the transmission period of the preamble
is shifted in a direction in which the transmission period is
relatively delayed by the first shift time .DELTA.T1 from the
execution period of the reception process each time the time
corresponding to the period Tr1 of the reception process elapses.
Accordingly, as is apparent from FIG. 5, the transmission period of
the preamble necessarily passes through the execution period of the
reception process during repetition of the reception process.
[0065] When the transmission period of the preamble passes through
the execution period of the reception process, the entire
transmission period of the preamble is included in the execution
period of the reception process since the interval Tx1
(=Tp1+.DELTA.T1) is shorter than the execution time Tw1 of the
reception process.
[0066] That is, since a time (Tp1+.DELTA.T1) obtained by summing a
length (Tp1) of the transmission period of the preamble and an
amount of shift (.DELTA.T1) of the transmission period of the
preamble in one period Tr1 is shorter than the execution time Tw1
of the reception process, if a portion of the transmission period
of the preamble in the cycle CY(i+1) is included in the execution
period of the reception process, the entire transmission period of
the preamble is included in the execution period of the reception
process in the cycle CY(i) or the cycle CY(i+2). Further, in a case
in which the transmission period of the preamble does not overlap
the execution period of the reception process at all, the
transmission period of the preamble does not passes through the
execution period of the reception process without overlapping the
execution period of the reception process with only the shift
(.DELTA.T1) of one cycle, and a state in which the entire
transmission period of the preamble is included in the execution
period of the reception process necessarily occurs.
[0067] If the entire transmission period of the preamble is
included in the execution period of the reception process, the
entire preamble is received by the receiver 31 of the vehicle-side
device 3, and the entire notification signal including this
preamble is received by the receiver 31. Therefore, the
notification signal is normally received by the receiver 31.
[0068] In the example of FIG. 5, the tire-side control unit 24
performs intermittent transmission of the notification signal at a
transmission interval Tt1 (=Tr1/3) which is 1/3 of the period Tr1
of the reception process of the vehicle-side device 3. Further, the
tire-side control unit 24 increases, for one transmission after
repeating two transmissions at the transmission interval Tt1, the
transmission interval from the previous transmission by a first
shift time .DELTA.T1 from the transmission interval Tt1
(Tt1+.DELTA.T1). For example, the transmission interval between the
notification signals S1 and S2 and the transmission interval
between the notification signals S2 and S3 are "Tt1", and the
transmission interval between the notification signals S3 and S4 is
"Tt1+.DELTA.T1".
[0069] Further, in the example of FIG. 5, the tire-side control
unit 24 sets the first shift time .DELTA.T1 to 1/3 of the
transmission interval Tt1 (=Tr1/3). A state in which the entire
transmission period of the preamble is included in the execution
period of the reception process occurs once for eight or eleven
transmissions of the notification signal (S1, S12, S20, and
S28).
[0070] As described above, according to the tire condition
monitoring device according to the first embodiment, each time the
time corresponding to one period Tr1 of the intermittent reception
process in the vehicle-side device 3 elapses, the transmission
interval Tt1 of the notification signal is controlled so that the
transmission time Tp1 of the preamble of the notification signal is
relatively shifted with respect to the execution time Tw1 of the
reception process. Further, when the transmission time Tp1 of the
preamble passes through a range of the execution time Tw1 of the
reception process during this relative shift, the transmission
interval Tt1 of the notification signal is controlled so that the
entire transmission time Tp1 of the preamble is included in the
range of the execution time Tw1 of the reception process.
[0071] Accordingly, in a case in which the transmitter 21 of the
tire-side device 2 and the receiver 31 of the vehicle-side device 3
operate intermittently, the receiver 31 can reliably receive the
notification signal from the transmitter 21 with a simple circuit
configuration in which a real time clock or the like is not used,
even when the transmission time of the transmitter 21 is shorter
than the execution interval of the reception process of the
receiver 31.
[0072] Further, since the transmission time of the transmitter 21
is shorter than the execution interval of the reception process of
the receiver 31, it is possible to reliably perform reception of
the notification signal while complying with regulations in a case
in which intensity of radio waves or the like is regulated under
regulations.
[0073] Further, according to the tire condition monitoring device
according to this embodiment, since the reception process is
continuously performed in the receiver 31 of the vehicle-side
device 3 in a case in which the driving system of the vehicle 1 is
in an operation state, if the notification signal is transmitted in
the transmitter 21 of the tire-side device 2, the receiver 31 can
immediately receive the notification signal and rapidly perform a
predetermined operation (for example, warning display in a
dashboard) according to the notification signal. Further, since the
reception process is performed intermittently in the receiver 31 in
a case in which the driving system of the vehicle 1 is in a stop
state, it is possible to reduce power consumption due to the
reception process in the receiver 31.
[0074] Further, according to the tire condition monitoring device
according to this embodiment, in a case in which the air pressure
is determined to be normal based on the detection result of the air
pressure sensor 22 in the tire-side device 2, the transmission of
the notification signal from the transmitter 21 is suppressed.
Accordingly, in a case in which the tire pressure is normal, it is
possible to suppress power consumption due to the transmission of
the transmitter 21.
Second Embodiment
[0075] Next, a second embodiment of the present invention will be
described.
[0076] In the tire condition monitoring device according to the
first embodiment described above, the transmission period of the
preamble is shifted in the direction in which the transmission
period is delayed by the first shift time .DELTA.T1 during periodic
repetition of the reception process of the vehicle-side device 3,
whereas in the tire condition monitoring device according to the
second embodiment, the transmission period of the preamble is
shifted in a direction in which the transmission period becomes
earlier.
[0077] The tire condition monitoring device according to the second
embodiment is different from the tire condition monitoring device
illustrated in FIG. 1 in a method of controlling the transmission
interval of the notification signal in the tire-side control unit
24 of the tire-side device 2, and other configurations are the same
as those in the tire condition monitoring device illustrated in
FIG. 1. Accordingly, a difference will be described.
[0078] In the tire condition monitoring device according to this
embodiment, the tire-side control unit 24 controls a transmission
interval Tt2 of the notification signal which is intermittently
transmitted from the transmitter 21, as follows. That is, the
tire-side control unit 24 controls the transmission interval Tt2 of
the notification signal so that a transmission time Tp2 of the
preamble of the notification signal is relatively shifted in a
direction in which the transmission time Tp2 is earlier than an
execution time Tw2 of the reception process each time the time
corresponding to one period Tr2 of an intermittent reception
process in the vehicle-side device 3 elapse. Further, the tire-side
control unit 24 controls the transmission interval Tt1 of the
notification signal so that the entire transmission time Tp2 of the
preamble is included in a range of the execution time Tw2 of the
reception process when the transmission time Tp2 of the preamble
during this relative shift passes through a range of the execution
time Tw2 of the reception process.
[0079] For example, the tire-side control unit 24 controls the
transmission interval Tt2 of the notification signal so that an
interval Tx2 between a time at which the same time as one period
Tr2 of the reception process of the vehicle-side device 3 elapses
from the time at which the transmission of the preamble of the
notification signal ends and a time at which the transmission of
the preamble of the notification signal last starts before such a
time becomes shorter than one execution time Tw2 of the reception
process in the vehicle-side device 3 and becomes longer than the
transmission time Tp2 of the preamble by a second shift time
.DELTA.T2.
[0080] More specifically, the tire-side control unit 24 performs
intermittent transmission of the notification signal at the
transmission interval Tt2 (=Tr2/N) which is 1/N (N indicates an
integer greater than 1) of the period Tr2 of the reception process
of the vehicle-side device 3, and decreases the transmission
interval from the previous transmission by the second shift time
.DELTA.T2 from the transmission interval Tt2 (=Tr2/N), for one
transmission after repeating (N-1) transmissions at the
transmission interval Tt2.
[0081] The tire-side control unit 24 sets the second shift time
.DELTA.T2 to a time shorter than a difference between the execution
time Tw2 of the reception process and the transmission time Tp2 of
the preamble. For example, the tire-side control unit 24 sets the
second shift time .DELTA.T2 to 1/M (M indicates an integer greater
than 1) of the transmission interval Tt2 (=Tr2/N).
[0082] FIG. 6 is a timing chart for explaining an operation of the
tire condition monitoring device according to the second
embodiment.
[0083] Focusing on a timing chart (i=1) of a first line in FIG. 6,
time t5 is a time at which transmission of the preamble of the
notification signal S1 ends, and time t8 is a reference time at
which the same time as a period Tr2 of the reception process
elapses from time t5 (t8-t5=Tr2). Further, time t6 is a time at
which the transmission of the preamble of the notification signal
last starts before reference time t8, and time t7 is a time at
which the transmission of the preamble of this notification signal
ends. The tire-side control unit 24 of the tire-side device 2
controls the transmission interval Tt2 of the notification signal
so that an interval Tx2 between time t6 and reference time t8 is
shorter than the execution time Tw2 of the reception process and is
longer than the transmission time Tp2 of the preamble by a second
shift time .DELTA.T2 (Tx2=Tp2+.DELTA.T2).
[0084] If the second shift time .DELTA.T2 is set to 0, the interval
Tx2 between time t6 and reference time t8 becomes equal to
transmission time Tp2 of the preamble, and reference time t8
matches transmission end time t7 of the preamble of the
notification signal S3. That is, at reference time t8 (=t7) at
which the same time as the period Tr2 elapses from time t5 at which
the transmission of the preamble of the notification signal S1 end,
the transmission of the preamble of the notification signal S3 end.
This means that a relative timing between a period in which the
reception process of the vehicle-side device 3 is executed and a
period in which the preamble of the notification signal is
transmitted does not change. If the relative timing between both is
shifted in an initial state, this shift state is maintained and the
vehicle-side device 3 cannot receive the notification signal.
[0085] On the other hand, in the tire condition monitoring device
according to this embodiment, the second shift time .DELTA.T2 is
set to a predetermined period of time rather than 0. That is, time
t7 at which the transmission of the preamble last ends before
reference time t8 is shifted in a direction in which time t7
becomes relatively earlier by the second shift time .DELTA.T2 than
reference time t8 at which the same time as the period Tr2 of the
reception process elapses from time t5 at which the transmission of
the preamble end. That is, the transmission period of the preamble
is shifted in a direction in which the transmission period becomes
relatively earlier by the second shift time .DELTA.T2 than the
execution period of the reception process each time the time
corresponding to the period Tr2 of the reception process elapses.
Accordingly, as is apparent from FIG. 6, the transmission period of
the preamble necessarily passes through the execution period of the
reception process during repetition of the reception process.
[0086] When the transmission period of the preamble passes through
the execution period of the reception process, the entire
transmission period of the preamble is included in the execution
period of the reception process since the interval Tx2
(=Tp2+.DELTA.T2) is shorter than the execution time Tw2 of the
reception process.
[0087] That is, since a time (Tp2+.DELTA.T2) obtained by summing a
length (Tp2) of the transmission period of the preamble and an
amount of shift (.DELTA.T2) of the transmission period of the
preamble in one period Tr2 is shorter than the execution time Tw2
of the reception process, if a portion of the transmission period
of the preamble in the cycle CY(i+1) is included in the execution
period of the reception process, the entire transmission period of
the preamble is included in the execution period of the reception
process in the cycle CY(i) or the cycle CY(i+2). Further, in a case
in which the transmission period of the preamble does not overlap
the execution period of the reception process at all, the
transmission period of the preamble does not passes through the
execution period of the reception process without overlapping the
execution period of the reception process with only the shift
(.DELTA.T2) of one cycle, and a state in which the entire
transmission period of the preamble is included in the execution
period of the reception process necessarily occurs.
[0088] If the entire transmission period of the preamble is
included in the execution period of the reception process, the
entire preamble is received by the receiver 31 of the vehicle-side
device 3, and the entire notification signal including this
preamble is received by the receiver 31. Therefore, the
notification signal is normally received by the receiver 31.
[0089] As described above, according to the tire condition
monitoring device according to this embodiment, the transmission
interval Tt2 of the notification signal is controlled so that the
transmission time Tp2 of the preamble of the notification signal is
shifted in a direction in which the transmission time Tp2 is
relatively earlier than the execution time Tw2 of the reception
process each time the time corresponding to one period Tr2 of the
intermittent reception process in the vehicle-side device 3 elapse.
Further, the transmission interval Tt2 of the notification signal
is controlled so that the entire transmission time Tp2 of the
preamble is included in a range of the execution time Tw2 of the
reception process when the transmission time Tp2 of the preamble
during this relative shift passes through the range of the
execution time Tw2 of the reception process.
[0090] Therefore, the receiver 31 can reliably receive the
notification signal from the transmitter 21 with a simple circuit
configuration in which a real time clock or the like is not used
with the transmission time of the transmitter 21 being shorter than
the execution interval of the reception process of the receiver 31,
as in the first embodiment.
[0091] While several embodiments of the present invention have been
described above, the present invention is not limited to the
above-described embodiments and includes various other
variations.
[0092] While the example in which the intermittent transmission of
the notification signal is performed at the transmission interval
which is 1/N of the period of the reception process, and the
transmission interval from the previous transmission is shifted
(increased or decreased) by a predetermined shift time from the
transmission interval which is 1/N, for one transmission after
repetition of (N-1) transmissions at the transmission interval
which is 1/N has been described in the above-described embodiment,
the present invention is not limited thereto. In another embodiment
of the present invention, generation of the shift time may be
equally distributed to N-transmission intervals.
[0093] Further, the vehicle-side device 3 in the above-described
embodiment may also be used as a keyless entry system that performs
vehicle control such as unlocking according to a signal from a
portable device, and may be provided independently of the keyless
entry system.
[0094] It should be understood by those skilled in the art that
various modifications, combinations, sub-combinations and
alterations may occur depending on design requirements and other
factors insofar as they are within the scope of the appended claims
of the equivalents thereof.
* * * * *