U.S. patent application number 10/789116 was filed with the patent office on 2005-09-01 for tire parameter sensing system having a magnetically conductive rim and an associated method.
This patent application is currently assigned to TRW Automotive U.S. LLC. Invention is credited to Bortolin, Dino, Lin, Xing Ping.
Application Number | 20050188757 10/789116 |
Document ID | / |
Family ID | 34750550 |
Filed Date | 2005-09-01 |
United States Patent
Application |
20050188757 |
Kind Code |
A1 |
Lin, Xing Ping ; et
al. |
September 1, 2005 |
TIRE PARAMETER SENSING SYSTEM HAVING A MAGNETICALLY CONDUCTIVE RIM
AND AN ASSOCIATED METHOD
Abstract
A tire parameter sensing system (12) for sensing a parameter of
a tire (16) includes a power transmitting antenna (44) that is
actuatable for producing a magnetic field at a location of the tire
(16). A rim (140) upon which the tire (16) is mounted includes
first and second magnetically conductive surface portions (160 and
168) that form a drop well (156). A tire-based unit (34) is mounted
in the drop well (156) so that a coil antenna (96) of the
tire-based unit (34) is located adjacent to both the first and
second magnetically conductive surface portions (160 and 168). The
central axis of the coil antenna (96) extends in a direction
parallel to the first magnetically conductive surface portion (160)
and the first and second magnetically conductive surface portions
(160 and 168) guide magnetic flux of the magnetic field to the coil
antenna (96).
Inventors: |
Lin, Xing Ping; (Orchard
Lake, MI) ; Bortolin, Dino; (La Salle, CA) |
Correspondence
Address: |
TAROLLI, SUNDHEIM,COVELL & TUMMINO L.L.P.
SUITE 1111
526 SUPERIOR AVENUE
CLEVELAND
OH
44114-1400
US
|
Assignee: |
TRW Automotive U.S. LLC
Michelin Recherche et Technique S.A.
|
Family ID: |
34750550 |
Appl. No.: |
10/789116 |
Filed: |
February 27, 2004 |
Current U.S.
Class: |
73/146.5 |
Current CPC
Class: |
B60C 23/0408 20130101;
B60C 23/0413 20130101 |
Class at
Publication: |
073/146.5 |
International
Class: |
B60C 023/02 |
Claims
Having described the invention, I claim the following:
1. A tire parameter sensing system for sensing a parameter of a
tire of a vehicle, the tire parameter sensing system comprising: a
power transmitting antenna that is actuatable for producing a
magnetic field at a location of the tire; a rim upon which the tire
is mounted, the rim having a circumferential outer surface that is
contacted by the tire when the tire is mounted on the rim, at least
first and second magnetically conductive surface portions of the
rim forming a drop well located within the outer surface, the first
and second magnetically conductive surface portions being angled
relative to one another; and a tire-based unit for sensing a
parameter of the tire and for providing an indication of the sensed
parameter, a coil antenna of the tire-based unit being responsive
to the magnetic field for providing energy to the tire-based unit,
the coil antenna having a central axis, the tire-based unit being
mounted in the drop well of the rim so that the coil antenna is
located adjacent to both the first and second magnetically
conductive surface portions, the central axis of the coil antenna
extending in a direction parallel to the first magnetically
conductive surface portion and the first and second magnetically
conductive surface portions guiding magnetic flux of the magnetic
field to the coil antenna.
2. The tire parameter sensing system of claim 1 wherein the central
axis of the coil antenna also extends in a direction parallel to
the second magnetically conductive surface portion of the rim.
3. The tire parameter sensing system of claim 2 wherein the power
transmitting antenna is oriented relative to the rim so that the
magnetic flux of the magnetic field travels circumferentially
around the rim in a direction parallel to the central axis of the
coil antenna.
4. The tire parameter sensing system of claim 1 wherein the coil
antenna is located immediately adjacent a union that connects the
first and second magnetically conductive surface portions.
5. The tire parameter sensing system of claim 1 wherein the outer
surface of the rim is an annular, radially outer surface of the rim
and wherein the drop well extends radially inwardly, relative to an
axis of the rim, from the outer surface.
6. The tire parameter sensing system of claim 1 wherein the
tire-based unit in its entirety is located in the drop well and
below the outer surface of the rim.
7. The tire parameter sensing system of claim 1 wherein the second
magnetically conductive surface portion is located adjacent an end
of the coil antenna, the coil antenna extending in a direction
perpendicular to a circumference of the rim.
8. The tire parameter sensing system of claim 7 wherein the power
transmitting antenna is oriented relative to the rim so that the
magnetic flux of the magnetic field travels over the outer surface
of the rim in a direction parallel to an axis of the rim and
parallel to an axis of the coil antenna.
9. The tire parameter sensing system of claim 1 further including a
vehicle-based unit that is operatively connected to a display, the
indication of the sensed parameter that is provided by the
tire-based unit being a tire parameter signal that is received by
the vehicle-based unit, the vehicle-based unit, in response to
receiving the tire parameter signal, actuating the display so as to
provide an indication of the sense parameter.
10. A method for providing energy to a tire-based unit of a tire
parameter sensing system of a vehicle, the tire-based unit being
associated with a tire of the vehicle, the method comprising the
steps of: producing a magnetic field at a location of the tire;
mounting the tire upon a rim having a circumferential outer surface
that is contacted by the tire and at least first and second
magnetically conductive surface portions that form a drop well in
the outer surface of the rim, the first and second magnetically
conductive surface portions being angled relative to one another;
and mounting the tire-based unit in the drop well of the rim so
that a coil antenna of the tire-based unit is located adjacent to
both the first and second magnetically conductive surface portions
and so that a central axis of the coil antenna extends in a
direction parallel to the first magnetically conductive surface
portions and the first and second magnetically conductive coil
portions guide magnetic flux of the magnetic field to the coil
antenna.
11. The method of claim 10 wherein the step of mounting the
tire-based unit in the drop well of the rim further includes the
step of: mounting the tire-based unit so that the central axis of
the coil antenna also extends in a direction parallel to the second
magnetically conductive surface portion of the rim.
12. The method of claim 11 further including the step of: orienting
the power transmitting antenna relative to the rim so that the
magnetic flux of the magnetic field travels circumferentially
around the rim in-a direction parallel to the central axis of the
coil antenna.
13. The method of claim 10 wherein the step of mounting the
tire-based unit in the drop well of the rim further includes the
step of: mounting the tire-based unit so that the coil antenna is
immediately adjacent a union of the first and second magnetically
conductive surface portions.
14. The method of claim 10 wherein the step of mounting the
tire-based unit in the drop well of the rim further includes the
step of: mounting the tire-based unit so that the second
magnetically conductive surface portion is located adjacent an end
of the coil antenna, the coil antenna extending in a direction
perpendicular to a circumference of the rim.
15. The method of claim 14 further including the step of: orienting
the power transmitting antenna relative to the rim so that the
magnetic flux of the magnetic field travels over the outer surface
of the rim in a direction parallel to an axis of the rim and
parallel to an axis of the coil antenna.
Description
TECHNICAL FIELD
[0001] The present invention relates to a tire parameter sensing
system for a vehicle and to an associated method. More
particularly, the present invention relates to a tire parameter
sensing system in which a magnetically conductive rim is used for
guiding magnetic flux to an antenna that provides energy to a
tire-based unit. The present invention also relates to an
associated method for providing energy to a tire-based unit.
BACKGROUND OF THE INVENTION
[0002] Tire parameter sensing systems for vehicles typically
include a plurality of tire-based.-units and a single vehicle-based
unit. Each tire-based unit has an associated tire of the vehicle
and is operative to sense at least one parameter of the tire. The
sensed parameter(s) may include temperature, pressure, etc. Each
tire-based unit is also operative to transmit a parameter signal
indicative of the sensed parameter(s) to the vehicle-based unit.
The vehicle-based unit is connected to a display. In response to
receiving a parameter signal from a tire-based unit, the
vehicle-based unit outputs a signal to the display. The display is
responsive to the signal for displaying the sensed tire
parameter(s).
[0003] It is common for the tire-based units of a tire parameter
sensing system to be battery powered. Battery powered tire-based
units, however, have specific limitations, such as, for example, a
limited life, a limited current supply, and a limited operating
temperature range. The design of a tire parameter sensing system
using battery powered tire-based units must be mindful of these
limitations. As a result, it is common for a battery powered
tire-based unit to transmit parameter signals only in response to a
determination that a sensed parameter is outside of a desired
range. For example, if the desired pressure range is 32 to 36
pounds per square inch ("psi"), the battery powered tire-based unit
may transmit a parameter signal to the vehicle-based unit only when
the sensed tire pressure is determined to be below 32 psi or above
36 psi. By limiting the transmissions of the parameter signal, the
battery life of the battery powered tire-based unit may be
extended.
[0004] In some tire parameter sensing systems, the tire-based units
do not include batteries. Tire-based units that do not include
batteries may receive energy through induction. When the tire-based
units receive power through induction, devices for producing a
magnetic field are located adjacent the tires having the tire-based
units. Each tire-based unit includes an antenna in which electrical
energy is induced when the antenna is placed in the magnetic field.
In order for a sufficient amount of electrical energy to be induced
in the antenna at all rotational positions of the tire-based
unit-relative to the magnetic field producing device, the antenna
typically is a loop antenna that extends completely around the
circumference of the tire.
[0005] U.S. Pat. No. 6,470,933 discloses a system in which a bead
of a tire forms the antenna of the tire-based unit. The bead of the
tire extends completely around the circumference of the tire so
that electrical energy will be induced at any rotational angle of
the tire relative to the vehicle.
SUMMARY OF THE INVENTION
[0006] The present invention relates to a tire parameter sensing
system for sensing a parameter of a tire of a vehicle. The tire
parameter sensing system comprises a power transmitting antenna
that is actuatable for producing a magnetic field at a location of
the tire. A rim upon which the tire is mounted has a
circumferential outer surface that is contacted by the tire when
the tire is mounted on the rim. At least first and second
magnetically conductive surface portions of the rim form a drop
well located within the outer surface. The first and second
magnetically conductive surface portions are angled relative to one
another. A tire-based unit senses a parameter of the tire and
provides an indication of the sensed parameter. A coil antenna of
the tire-based unit is responsive to the magnetic field for
providing energy to the tire-based unit. The coil antenna has a
central axis. The tire-based unit is mounted in the drop well of
the rim so that the coil antenna is located adjacent to both the
first and second magnetically conductive surface portions. The
central axis of the coil antenna extends in a direction parallel to
the first magnetically conductive surface portion and the first and
second magnetically conductive surface portions guide magnetic flux
of the magnetic field to the coil antenna.
[0007] According to another aspect, the present invention relates
to a method for providing energy to a tire-based unit of a tire
parameter sensing system of a vehicle. The tire-based unit is
associated with a tire of the vehicle. The method comprises the
steps of producing a magnetic field at a location of the tire;
mounting the tire upon a rim having a circumferential outer surface
that is contacted by the tire and at least first and second
magnetically conductive surface portions that form a drop well in
the outer surface of the rim, the first and second magnetically
conductive surface portions being angled relative to one another;
and mounting the tire-based unit in the drop well of the rim so
that a coil antenna of the tire-based unit is located adjacent to
both the first and second magnetically conductive surface portions
and so that a central axis of the coil antenna extends in a
direction parallel to the first magnetically conductive surface
portions and the first and second magnetically conductive coil
portions guide magnetic flux of the magnetic field to the coil
antenna.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The foregoing and other features and advantages of the
present invention will become apparent to those skilled in the art
to which the present invention relates upon reading the following
description with reference to the accompanying drawings, in
which:
[0009] FIG. 1 schematically illustrates a vehicle including a tire
parameter sensing system constructed in accordance with an
exemplary embodiment of the present invention;
[0010] FIG. 2 is a schematic block diagram of a tire-based unit of
the tire parameter sensing system of FIG. 1;
[0011] FIG. 3 is a schematic block diagram of a vehicle-based unit
of the tire parameter sensing system of FIG. 1;
[0012] FIG. 4 is a cross-sectional view of a wheel assembly having
a tire-based unit mounted to a rim of the wheel assembly in
accordance with an exemplary embodiment of the present
invention;
[0013] FIG. 5 schematically illustrates a portion of the tire
parameter sensing system constructed in accordance with an
exemplary embodiment of the present invention;
[0014] FIG. 6 is an enlarged sectional view of a portion of the
tire-based unit of FIG. 5;
[0015] FIG. 7 is an enlarged sectional view of a portion of the
tire-based unit of FIG. 5;
[0016] FIG. 8 schematically illustrates a portion of the tire
parameter sensing system constructed in accordance with a second
exemplary embodiment of the present invention; and
[0017] FIG. 9 is an enlarged sectional view of a portion of the
tire-based unit of FIG. 8.
DESCRIPTION OF PREFERRED EMBODIMENT
[0018] FIG. 1 schematically illustrates a vehicle 10 including a
tire parameter sensing system 12 constructed in accordance with an
exemplary embodiment of the present invention. For illustrative
purposes, the vehicle 10 of FIG. 1 is an automobile having four
tires 16,18, 20, and 22. The present invention can be used with
vehicles having a number of tires other than four.
[0019] The vehicle 10 has a front 24, a rear 26, and opposite left
and right sides 28 and 30, respectively. FIG. 1 illustrates tire 16
at a front left corner location of the vehicle 10. Tire 18 is
located at a front right corner location of the vehicle 10. Tire 20
is located at a rear left corner location of the vehicle 10 and
tire 22 is located at a rear right corner location of the vehicle
10.
[0020] The tire parameter sensing system 12 includes four
tire-based units 34, 36, 38, and 40, a vehicle-based unit 42, and
four power transmitting antennas 44, 46, 48, and 50. Each tire 16,
18, 20, and 22 of the vehicle 10 includes an associated tire-based
unit 34, 36, 38, and 40, respectively, for sensing at least one
parameter, e.g., pressure, temperature, etc., of the tire and for
providing a tire parameter signal 54, 56, 58, and 60, respectively,
to the vehicle-based unit 42. The tire parameter signals 54, 56,
58, and 60 are indicative of the sensed parameter(s) of the tires
16, 18, 20, and 22, respectively. Preferably, the tire parameter
signals 54, 56, 58, and 60 are radio frequency ("RF") signals.
[0021] Each of the tire-based unit 34, 36, 38, and 40 has an
associated one of the power transmitting antennas 44, 46, 48, and
50. In the embodiment illustrated in FIG. 1, power transmitting
antenna 44 is associated with tire-based unit 34, power
transmitting antenna 46 is associated with tire-based unit 36,
power transmitting antenna 48 is associated with tire-based unit
38, and power transmitting antenna 50 is associated with tire-based
unit 40. Preferably, each of the power transmitting antennas 44,
46, 48, and 50 is located in a wheel well of the vehicle 10
adjacent the tire 16, 18, 20, or 22 having the tire-based unit 34,
36, 38, or 40 with which the power transmitting antenna is
associated.
[0022] The power transmitting antennas 44, 46, 48, and 50 are
operatively coupled to the vehicle-based unit 42 and are actuatable
for producing magnetic fields. The power transmitting antennas 44,
46, 48, and 50 may have any known structure for producing the
magnetic fields.
[0023] FIG. 5 illustrates an exemplary embodiment of the power
transmitting antenna 44. The power transmitting antennas 46, 48,
and 50 may have the same structure and operate in the same manner
at power transmitting antenna 44. The power transmitting antenna 44
of FIG. 5 includes a winding 66 and an air core. The power
transmitting antenna 44 is mounted in a wheel well 68 located at
the front left corner location of the vehicle 10. The power
transmitting antenna 44 of FIG. 5 is located in the wheel well 68
in a location that is radially outward of the tire 16. When
supplied with an alternating current, the power transmitting
antenna 44 provides the magnetic field, indicated generally by
reference character M.sub.F in FIG. 5. Preferably, the magnetic
field M.sub.F has a frequency of approximately 13 MHz.
[0024] FIG. 2 is a schematic block diagram of an exemplary
embodiment of a tire-based unit of the parameter sensing system 12
of FIG. 1. For purposes of example, FIG. 2 only illustrates
tire-based unit 34. Tire-based units 36, 38, and 40 may have
structures similar to tire-based unit 34 and may operate in a
manner similar to tire-based unit 34.
[0025] The tire-based unit 34 includes a housing 70, a parameter
sensing portion 72, and an energy supplying portion 74. In
accordance with an exemplary embodiment of the present invention,
both of the parameter sensing portion 72 and the energy supplying
portion 74 are mounted to the housing 70 and the housing is open to
the atmosphere of the associated tire, e.g., tire 16.
[0026] The parameter sensing portion 72 of the tire-based unit 34
includes a temperature sensor 78, a pressure sensor 80, and other
sensors 82. The temperature sensor 78 is operable for sensing
temperature within the associated tire 16 and providing temperature
signals. The pressure sensor 80 is operable for sensing pressure
within the associated tire 16 and for providing pressure signals.
The other sensors 82 are operable for sensing other parameters of
either the associated tire 16 or the tire-based unit 34 and for
providing other parameter signals indicative of the other sensed
parameters. For example, the other sensors 82 may include a voltage
sensor for determining a supply voltage within the tire-based unit
34.
[0027] The parameter sensing portion 72 of the tire-based unit 34
also includes a controller 84. The controller 84 is preferably a
microcomputer. Alternatively, the controller 84 may be formed from
discrete circuitry, an application-specific-integrated-circuit
("ASIC"), or any other type of control circuitry. The controller 84
is operatively coupled to the temperature sensor 78, the pressure
sensor 80, and the other sensors 82 and receives the temperature
signals, the pressure signals, and the other parameter signals. The
controller 84 performs a tire parameter sensing algorithm and
outputs a message packet that includes information indicative of
one or more of the sensed temperature, pressure, and other
parameters. Any known tire parameter sensing algorithm may be used
with the present invention.
[0028] A memory 86 is operatively coupled to the controller 84.
Alternatively, the memory 86 may form a portion of the controller
84. The memory 86 is a non-volatile memory. The tire parameter
sensing algorithm is stored in the memory 86. The memory 86 also
stores an identification code for identifying the tire-based unit
34. Each tire-based unit 34, 36, 38, and 40 has a unique associated
identification code. The controller 84 includes the identification
code in the output message packet.
[0029] The parameter sensing portion 72 of the tire-based unit 34
also includes signal transmitting circuitry 90. The signal
transmitting circuitry 90 is operatively coupled to the controller
84 and includes circuitry, such as a radio frequency ("RF")
amplifier (not shown) and other known circuitry, for transmitting
the parameter signal 54 via a transmitting antenna 92. The signal
transmitting circuitry 90 receives message packets from the
controller 84 and transmits the message packets in the tire
parameter signals 54. The message packets are modulated onto a
constant frequency carrier signal using known modulation
techniques, such as, for example, amplitude shift keying ("ASK").
Other signal modulation techniques, such as frequency shift keying,
phase shift keying, etc., are also contemplated by the present
invention.
[0030] The energy supplying portion 74 of the tire-based unit 34
includes an energy receiving antenna 96 and rectifying and
regulating circuitry 98. The energy receiving antenna 96 is a coil,
as is shown in FIG. 6. Electrical energy, i.e., a voltage and a
current, is induced in the energy receiving antenna 96 when the
antenna is placed within a magnetic field M.sub.F. The magnetic
field M.sub.F is produced by alternating current. The polarity of
the magnetic field M.sub.F alternates with the polarity of the
alternating current. As a result, the electrical energy induced in
the energy receiving antenna 96 also has an alternating
current.
[0031] The rectifying and regulating circuitry 98 receives the
electric energy from the energy receiving antenna 96, converts the
alternating current of the received electrical energy into direct
current, and outputs electrical energy having a regulated direct
current. The rectifying and regulating circuitry 98 provides the
rectified and regulated electrical energy to an energy storage
device (not shown), such as a capacitor, which provides the
electrical energy to the controller 84 of the parameter sensing
portion 72 of the tire-based unit 34.
[0032] FIG. 3 is a schematic block diagram of an exemplary
embodiment of the vehicle-based unit 42 of the tire parameter
sensing system 12 of FIG. 1. The vehicle-based unit 42 includes a
receiving antenna 102 that is coupled to signal receiving circuitry
104. The signal receiving circuitry 104 receives tire parameter
signals, e.g., parameter signal 54 (FIG. 1), from the receiving
antenna 102. The signal receiving circuitry 104 includes signal
conditioning circuitry (not shown), such as filters, amplifiers,
etc. The signal receiving circuitry 104 also includes signal
demodulating circuitry (not shown) for demodulating the received
tire parameter signals and for outputting message packets received
in the tire parameter signals to a controller 106 of the
vehicle-based unit 42.
[0033] The controller 106 of the vehicle-based unit 42 is
preferably a microcomputer. Alternatively, the controller 106 may
be formed from discrete circuitry, an
application-specific-integrated-circuit ("ASIC"), or any other type
of control circuitry. The controller 106 also performs a tire
parameter sensing algorithm.
[0034] The controller 106, upon receiving a message packet from the
signal receiving circuitry 104, determines whether the message
packet originated in one of the tire-based units 34, 36, 38, or 40
(FIG. 1) of the tire parameter sensing system 12. To determine
whether the message packet originated in one of the tire-based
units 34, 36, 38, or 40, the controller 106 compares the
identification code received in the message packet to
identification codes stored in a memory 108 associated with the
controller 106. The memory 108 is a non-volatile memory that
includes a lookup table having the identification codes of the
tire-based units 34, 36, 38, and 40 of the tire parameter sensing
system 12. The lookup table may also include associated location
information for each tire-based unit 34, 36, 38, and 40. For
example, the look-up table stored in memory 108 may associate the
identification code of tire-based unit 34 with the front left
corner location of the vehicle 10.
[0035] When the controller 106 determines that the received message
packet did not originate from one of the tire-based units 34, 36,
38, or 40, the controller 106 ignores the message packet. When the
controller 106 determines that the received message packet did
originate from one of the tire-based units 34, 36, 38, or 40, the
controller 106 analyzes the tire parameter information received in
the message packet, i.e., the information indicating the
temperature, the pressure, and/or the other sensed parameters.
[0036] The controller 106, after analyzing the tire parameter
information received in the message packet, outputs display signals
to a display 112. The display 112 is located in the occupant
compartment of the vehicle 10 and is operatively coupled to the
controller 106. The display 112 is responsive to receipt of display
signals for providing an indication of the tire parameter
information and, optionally, the associated corner location. For
example, the display 54 may provide an indication of sensed tire
temperatures and sensed tire pressures for each of the tires 16,
18, 20, and 22.
[0037] The vehicle-based unit 42 also includes a power source 114.
The power source 114 of the vehicle-based unit 42 provides
electrical power to the controller 106 for powering the
vehicle-based unit. The power source 114 preferably includes the
battery of the vehicle 10 and an appropriate voltage regulator (not
shown).
[0038] The power source 114 is also connected to a direct current
("DC") to alternating current ("AC") converter 116, such as an
oscillator. The DC to AC converter 116 outputs electrical energy
having an alternating current to relay circuitry 118. The relay
circuitry 118 includes four relay switches (not shown) and is also
operatively connected to the controller 106. The controller 106
controls the opening and closing of the four relay switches of the
relay circuitry 118.
[0039] Output wires 122, 124, 126, and 128 connect the relay
circuitry 118 to the power transmitting antennas 44, 46, 48, and
50, as is shown in FIG. 1. Figs.1 and 3 schematically illustrate
the output wires 122, 124, 126, and 128. Those skilled in the art
will appreciate that these are wire pairs. FIG. 5 illustrates
output wire 122 forming the winding 66 of the power transmitting
antenna 44.
[0040] Each output wire 122, 124, 126, and 128 has an associated
relay switch of the relay circuitry 118. When the controller 106
controls the relay circuitry 118 to close a relay switch,
electrical energy having an alternating current is supplied to the
power transmitting antenna 44, 46, 48, or 50 that is associated
with the closed relay switch. The power transmitting antennas 44,
46, 48, and 50 are responsive to the alternating current for
producing magnetic fields.
[0041] As an alternative to the embodiment illustrated in FIG. 3,
the relay circuitry 118 may receive electrical energy having a
direct current and multiple DC to AC converters may be located in
series with the output wires 122, 124, 126, and 128 for converting
the alternating current to direct current. The multiple DC to AC
converters may be located either at the vehicle-based unit 42 or
remote from the vehicle-base unit, such as near the power
transmitting antennas 44, 46, 48, and 50.
[0042] FIG. 4 is a cross-sectional view of tire 16 mounted to a rim
140. The tire-based unit 34 is mounted to a rim 140 and within a
cavity 142 of tire 16. For brevity, the mounting of only tire-based
unit 34 is discussed in detail below. Tire-based units 36, 38, and
40 may have similar mounting conditions on similar rims that are
associated with tires 18, 20, and 22, respectively.
[0043] The rim 140 is formed from a magnetically conductive
material, preferably, a metal. The rim 140 includes an annular base
wall 144 having an outer surface 148. Inner and outer bead flanges
150 and 152 are located on opposite sides of the base wall 144. A
drop well 156 extends into the base wall 144 from the outer surface
148. The drop well 156 extends circumferentially around the rim 140
and includes a lower surface 160 and opposite side surfaces 166 and
168. Each of the lower surface 160 and the side surfaces 166 and
168 is also magnetically conductive. A depth of the drop well 156,
which is defined as the radial distance between the outer surface
148 of the base wall 144 and the lower surface 160, is greater than
a height of the housing 70 of the tire-based unit 34, as is shown
in FIG. 6.
[0044] The tire 16 includes a tread portion 172 and opposite side
walls 174 and 176. The side walls 174 and 176 of the tire 16
terminate at ends opposite the tread portion 172 with bead portions
178 and 180, respectively. When the tire 16 is mounted on the rim
140, bead portion 178 seats in bead flange 150 and bead portion 180
seats in bead flange 152. Also, when the tire 16 is mounted on the
rim 140, ends of the bead portions 178 and 180 contact the outer
surface 148 of base wall 144 of the rim 140. The tire 16 and the
rim 140 collectively form a wheel assembly 186.
[0045] FIG. 5 illustrates the wheel assembly 186, which includes
tire 16 and rim 140, mounted to the vehicle 10 in the wheel well
68. As FIG. 5 illustrates, the power transmitting antenna 44 is
also located in wheel well 68 in a location adjacent the wheel
assembly 186 and radially outward of the rim 140 and the tire 16.
When actuated by the controller 106 of the vehicle-based unit 42,
the power transmitting antenna 44 produces the magnetic field
M.sub.F. In an exemplary embodiment of the invention, a central
axis of the winding 66 of the power transmitting antenna 44 is
normal to the axis of the rim 140 and pointing generally toward the
center of the rim 140.
[0046] When the magnetically conductive rim 140 is placed in the
magnetic field M.sub.F, the rim 140 alters the path of the magnetic
flux of the magnetic field M.sub.F, as compared to when the wheel
well 68 is empty. When the rim 140 is placed in the magnetic field
M.sub.F, the magnetically conductive surfaces of the rim 140 act to
guide the magnetic flux of the magnetic field M.sub.F on the
surfaces of the rim. The magnetic flux of the magnetic field
M.sub.F becomes concentrated on the outer surface 148 of the base
wall 144 of the rim 140 and on the surfaces 160, 166, and 168 of
the drop well 156 of the rim. In the embodiment illustrated in FIG.
5, a path of the magnetic flux extends circumferentially around the
rim 140. The arrows of FIG. 5 illustrate the path of the magnetic
flux of the magnetic field M.sub.F around the circumference of the
rim 140. The path of the magnetic flux extends around the rim 140
in a direction tangential to the outer surface 148 of the base wall
144 and tangential to the lower surface 160 of the drop well
156.
[0047] In accordance with the present invention, the tire-based
unit 34 is mounted in the drop well 156 of the rim 140 in a
location adjacent at least one of the side surfaces 166 and 168 of
the drop well. When the tire-based unit 34 is mounted in the drop
well 156, the energy receiving antenna 96 is located adjacent the
lower surface 160 and at least one of the side surfaces 166 and 168
of the drop well 156. In the embodiment illustrated in FIGS. 6 and
7, the energy receiving antenna 96 is located adjacent the lower
surface 160 and side surface 168 of the drop well 156. Since the
magnetic flux is most concentrated on the metal surfaces of the rim
140, the energy receiving antenna 96 should be positioned as near
the surfaces as possible, while remaining electrically insulated
from the metal surfaces of the rim.
[0048] The energy receiving antenna 96 is a coil that is wound
about a central axis A, as shown in FIGS. 6 and 7. In an
exemplary-embodiment of the present invention, the axis A of the
energy receiving antenna 96 extends in a direction parallel to the
outer surface 148 of the base wall 144 of the rim 140, in a
direction parallel to the lower surface 160 of the drop well, and
in a direction parallel to the path of the magnetic flux relative
to the rim 140. In the embodiment illustrated in FIGS. 6 and 7, the
axis A of the energy receiving antenna 96 also extends in a
direction parallel to side surface 168 of the drop well 156 of the
rim 140.
[0049] The electrical energy induced in the energy receiving
antenna 96 is proportional to the concentration of the magnetic
flux passing through the antenna. As set forth above, when the
magnetically conductive rim 140 is placed in the magnetic field
M.sub.F, the magnetic flux becomes concentrated on the surfaces
148, 160, 166, and 168 of the rim 140. By mounting the tire-based
unit 34 in the drop well 156 so that the energy receiving antenna
96 is adjacent to the lower surface 160 and at least one of the
side surfaces 166 and 168 of the drop well 156, magnetic flux is
guided to the energy receiving antenna 96. When the energy
receiving antenna 96 is positioned adjacent to and parallel with
two of the surfaces, e.g., surfaces 160 and 168 as shown in FIGS. 6
and 7, magnetic flux will be guided through the entire length of
the energy receiving antenna 96. As a result, a sufficiently large
amount of electrical energy for powering the tire-based unit 34 is
induced in the energy receiving antenna 96.
[0050] FIG. 8 schematically illustrates a portion of the tire
parameter sensing system constructed in accordance with a second
exemplary embodiment of the present invention. The structures of
FIG. 8 that are the same or similar to those shown and discussed
with reference to FIGS. 1-7 are labeled with the same reference
numbers.
[0051] FIG. 8 illustrates the power transmitting antenna 44 in the
wheel well 68 located at the front left corner location of the
vehicle 10. The power transmitting antenna 44 includes a winding 66
and an air core. The power transmitting antenna 44 is mounted in
the wheel well 68 at a location axially adjacent to the rim 140,
relative to an axis X of the rim 140. Preferably, the winding 66 of
the power transmitting antenna 44 is positioned relative to the rim
140 so that a central axis of the winding 66 extends across the rim
140 in a direction parallel to the axis X of the rim. When supplied
with an alternating current, the power transmitting antenna 44
provides the magnetic field, indicated generally by reference
character M.sub.F.
[0052] FIG. 8 also illustrates a cross-sectional view of tire 16
mounted to a rim 140. The tire-based unit 34 is mounted to in a
drop well 156 of the rim 140. The rim 140 is formed from a
magnetically conductive material, preferably, a metal.
[0053] When the magnetically conductive rim 140 is placed in the
magnetic field M.sub.F, the rim 140 alters the path of the magnetic
flux of the magnetic field M.sub.F, as compared to when the wheel
well 68 is empty. When the rim 140 is placed in the magnetic field
M.sub.F, the rim 140 acts as a field guide for the magnetic flux of
the magnetic field M.sub.F. The arrows of FIGS. 8 and 9 illustrate
the path of the magnetic flux of the magnetic field M.sub.F when
the power transmitting antenna 44 is located axially adjacent to
the rim 140, as is shown in FIG. 8. As illustrated in FIG. 8, the
path of the magnetic flux extends across the surfaces 148, 160,
166, and 168 of the rim 140 in a direction generally perpendicular
to the circumference of the rim 140.
[0054] In accordance with the present invention, the tire-based
unit 34 is mounted in the drop well 156 of the rim 140 so that the
central axis A of the energy receiving antenna 96 extends parallel
to the path of the magnetic flux across the surfaces 148, 160, 166,
and 168 of the rim 140. The tire-based unit 34 is also mounted in
the drop well 156 so that-the energy receiving antenna 96 is
located adjacent the lower surface 160 of the drop well 156 and at
least one of the side surfaces 166 and 168 of the drop well. FIG. 9
illustrates the tire-based unit 34 mounted in the drop well 156 so
that the energy receiving antenna 96 is adjacent to the lower
surface 160 of the drop well and side surface 166. In FIG. 9, an
end of the energy receiving antenna 96 is adjacent side surface 166
of the drop well 156. In the embodiment illustrated in FIG. 9, the
central axis A of the energy receiving antenna 96 extends across
the rim 140 in a direction parallel to axis X (FIG. 8). When the
energy receiving antenna 96 is positioned adjacent to the two
surfaces 160 and 166 of the drop well 156, and particularly, when
the energy receiving antenna 96 extends in a direction parallel to
the lower surface 160 of the drop well and in a direction parallel
to the path of the magnetic flux on the rim 140, the magnetic flux
of the magnetic field M.sub.F is guided to the energy receiving
antenna 96. The electrical energy induced in the energy receiving
antenna 96 is proportional to the concentration of the magnetic
flux passing through the antenna. Positioning the energy receiving
antenna 44 as illustrated in FIG. 9 enables a sufficiently large
amount of electrical energy for powering the tire-based unit 34 to
be induced in the energy receiving antenna 96.
[0055] From the above description of the invention, those skilled
in the art will perceive improvements, changes and modifications.
Such improvements, changes and modifications within the skill of
the art are intended to be covered by the appended claims.
* * * * *