U.S. patent application number 11/933529 was filed with the patent office on 2009-05-07 for tire sensor system and monitoring method.
This patent application is currently assigned to Infineon Technologies AG. Invention is credited to Bjoern Blixhavn, Terje Kvisteroey.
Application Number | 20090114005 11/933529 |
Document ID | / |
Family ID | 40568833 |
Filed Date | 2009-05-07 |
United States Patent
Application |
20090114005 |
Kind Code |
A1 |
Blixhavn; Bjoern ; et
al. |
May 7, 2009 |
TIRE SENSOR SYSTEM AND MONITORING METHOD
Abstract
A tire system includes a plurality of piezoelectric devices
mounted to the tire. The piezoelectric devices provide output
signals in response to deformation of the tire. A processor has
input terminals for receiving the signals from the piezoelectric
devices, and the processor is programmed to determine tire
parameters in response to the output signals from the piezoelectric
devices. A power converter has input terminals for receiving the
signals from the piezoelectric devices, and the power converter is
connected to the processor to power the processor.
Inventors: |
Blixhavn; Bjoern; (Tonsberg,
NO) ; Kvisteroey; Terje; (Horten, NO) |
Correspondence
Address: |
DICKE, BILLIG & CZAJA
FIFTH STREET TOWERS, 100 SOUTH FIFTH STREET, SUITE 2250
MINNEAPOLIS
MN
55402
US
|
Assignee: |
Infineon Technologies AG
Neubiberg
DE
|
Family ID: |
40568833 |
Appl. No.: |
11/933529 |
Filed: |
November 1, 2007 |
Current U.S.
Class: |
73/146.5 |
Current CPC
Class: |
B60C 23/0493 20130101;
B60T 8/1725 20130101; B60C 11/243 20130101; B60C 23/0411 20130101;
B60T 2240/04 20130101 |
Class at
Publication: |
73/146.5 |
International
Class: |
B60C 23/02 20060101
B60C023/02 |
Claims
1. A tire sensor system, comprising: a substrate; a plurality of
piezoelectric devices attached to the substrate, each of the
piezoelectric devices having an output terminal; a processing
device connected to the output terminals of the piezoelectric
devices, the processing device being programmed to receive output
signals from selected ones of the piezoelectric devices; and a
power converter connected to receive signals from the output
terminals of the piezoelectric devices to power the processing
device.
2. The tire sensor system of claim 1, wherein the substrate defines
a longitudinal axis, and wherein the piezoelectric devices are
symmetrically situated about the longitudinal axis.
3. The tire sensor system of claim 1, wherein the piezoelectric
devices are spaced apart from one another on the substrate.
4. The tire sensor system of claim 1, wherein the piezoelectric
devices include piezoelectric material situated between first and
second conductive layers.
5. The tire sensor system of claim 1, wherein the substrate
includes a PVDF material, and wherein the piezoelectric devices are
formed from the PVDF material sandwiched between conductive
layers.
6. The tire sensor system of claim 1, further comprising a
transmitter for transmitting data to a receiver.
7. The tire sensor system of claim 1, wherein the processing device
includes an input multiplexer connected to the output terminals of
the piezoelectric devices, and wherein the processing device is
programmed to operate the input multiplexer to receive signals from
selected ones of the piezoelectric devices in response to rotation
of a tire having the sensor system mounted therein.
8. A tire system, comprising: a tire; a plurality of piezoelectric
devices mounted to the tire, the piezoelectric devices adapted to
provide output signals in response to deformation of the tire; a
processor having input terminals for receiving the signals from the
piezoelectric devices, wherein the processor is programmed to
determine tire parameters in response to the output signals from
the piezoelectric devices; a power converter having input terminals
for receiving the signals from the piezoelectric devices, wherein
the power converter is connected to the processor to power the
processor.
9. The tire system of claim 8, wherein the piezoelectric devices
are mounted on a flexible substrate, and wherein the flexible
substrate is mounted to an inside surface of the tire.
10. The tire system of claim 8, wherein the piezoelectric devices
are formed from a PVDF material sandwiched between conductive
layers.
11. The tire system of claim 8, wherein the piezoelectric devices
are spaced apart from one another and are situated symmetrically
about an inside surface of the tire.
12. The tire system of claim 8, wherein at least some of the
piezoelectric devices are situated on an inside surface of the tire
opposite a tread defined on an outside portion of the tire.
13. The tire system of claim 8, wherein at least some of the
piezoelectric devices are situated on an inside surface of the tire
opposite a sidewall of the tire.
14. The tire system of claim 8, wherein the processing device is
connected to receive the output signals from the piezoelectric
devices via an input multiplexer, and wherein the processing device
is adapted to operate the input multiplexer to receive the output
signals from selected ones of the piezoelectric devices in response
to a rotation frequency of the tire.
15. The tire system of claim 8, further comprising: a transmitter
receiving an output of the processing device; and a receiver
situated outside the tire for receiving data from the
transmitter.
16. A method for monitoring a tire, comprising: mounting a
plurality of piezoelectric devices to a tire; selectively
connecting predetermined ones of the plurality of piezoelectric
devices to a processing device to receive signals generated in
response to deformation of a portion of the tire; calculating
predetermined parameters of the tire in response to the received
signals; selectively connecting predetermined ones of the plurality
of piezoelectric devices to a power converter; and providing an
output from the power converter to the processing device to power
the processing device.
17. The method of claim 16, wherein mounting the plurality of
piezoelectric devices to the tire includes: mounting the
piezoelectric devices on a substrate; and mounting the substrate to
an inside surface of the tire.
18. The method of claim 16, wherein mounting the plurality of
piezoelectric devices to the tire includes mounting at least some
of the piezoelectric devices to an inside surface of the tire
opposite a tread defined on an outside surface of the tire.
19. The method of claim 16, wherein mounting the plurality of
piezoelectric devices to the tire includes mounting at least some
of the piezoelectric devices to an inside surface of the tire in a
sidewall area of the tire.
20. The method of claim 16, wherein mounting the plurality of
piezoelectric devices to the tire includes mounting the
piezoelectric devices symmetrically about a longitudinal axis of an
inside surface of the tire.
21. The method of claim 16, further comprising transmitting the
calculated parameters to a receiver situated outside the tire.
22. The method of claim 16, wherein selectively connecting
predetermined ones of the plurality of piezoelectric devices to the
processing device includes connecting the predetermined ones of the
plurality of piezoelectric devices to the processing device in
response to a rotation frequency of the tire.
23. A tire system, comprising: a tire; first means for generating
signals in response to deformation of portions of the tire; second
means connected to the first means for determining tire parameters
in response to the signals from the first means; third means
connected to the first means for powering the second means.
Description
BACKGROUND
[0001] Many different types of sensor devices exist for providing
information about the tires of a wheeled vehicle. Features such as
automatic stability and traction control in cars have made it
necessary to obtain information about the interaction between the
tires and the road surface. Such information is available from
several sources, including ABS sensors, tire pressure measurement
systems, and accelerometers and gyros located in the vehicle.
[0002] It is also desirable to obtain direct information about the
tire-road interface. Known sensors for providing such direct
information typically are mounted to the tire in various locations,
such as in the tread, sidewall, inflation stem, etc. Existing
sensor systems, however, tend to be complicated to operate and
difficult to mount to the tire. Further, known tire sensor systems
typically use only a single sensor attached to the tire lining or
embedded in the tread. This limits the amount of data available for
analysis. In particular, it is desirable to observe the tire
deformation at both the sidewalls and in the tread, and to be able
to observe short-term fluctuations (less than one wheel revolution)
in the forces between tire and road.
[0003] Moreover, such sensors require an energy source to power the
device--typically a battery. Eliminating the battery as the energy
source for tire-mounted sensors is desirable from cost, reliability
and environmental standpoints.
[0004] For these and other reasons, there is a need for the present
invention.
SUMMARY
[0005] In accordance with embodiments of the invention, a tire
system includes a plurality of piezoelectric devices mounted to the
tire. The piezoelectric devices provide output signals in response
to deformation of the tire. A processor has input terminals for
receiving the signals from the piezoelectric devices, and the
processor is programmed to determine tire parameters in response to
the output signals from the piezoelectric devices. A power
converter has input terminals for receiving the signals from the
piezoelectric devices, and the power converter is connected to the
processor to power the processor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] Embodiments of the invention are better understood with
reference to the following drawings. The elements of the drawings
are not necessarily to scale relative to each other. Like reference
numerals designate corresponding similar parts.
[0007] FIG. 1 is a block diagram conceptually illustrating aspects
of a typical tire.
[0008] FIG. 2 is a block diagram conceptually illustrating portions
of a tire system in accordance with exemplary embodiments of the
present invention.
[0009] FIG. 3 is a perspective view of a tire, illustrating further
aspects of a tire system accordance with exemplary embodiments of
the present invention.
[0010] FIG. 4 is a top view schematically illustrating an exemplary
embodiment of a sensor system in accordance with aspects of the
present invention.
[0011] FIG. 5 is a sectional end view illustrating a portion of a
tire having a sensor system mounted to an inside surface thereof in
accordance with embodiments of the present invention.
[0012] FIG. 6 is a sectional view of portions of an exemplary
embodiment of a sensor system in accordance with aspects of the
present invention.
[0013] FIG. 7 is a sectional view of portions of another exemplary
embodiment of a sensor system in accordance with aspects of the
present invention.
[0014] FIG. 8 illustrates a portion of an exemplary sensor system,
showing connections between piezoelectric devices an electronics
module in accordance with exemplary embodiments of the present
invention.
[0015] FIG. 9 is a block diagram conceptually illustrating portions
of an electronics module in accordance with exemplary embodiments
of the present invention.
[0016] FIG. 10 is a top view schematically illustrating an
exemplary embodiment of an alternative sensor system in accordance
with aspects of the present invention.
DETAILED DESCRIPTION
[0017] In the following Detailed Description, reference is made to
the accompanying drawings, which form a part hereof, and in which
is shown by way of illustration specific embodiments in which the
invention may be practiced. Regarding embodiments disclosed, the
term "exemplary" is merely meant as an example, rather than the
best or optimal. In this regard, directional terminology, such as
"top," "bottom," "front," "back," "leading," "trailing," etc., is
used with reference to the orientation of the Figure(s) being
described. Because components of embodiments of the present
invention can be positioned in a number of different orientations,
the directional terminology is used for purposes of illustration
and is in no way limiting. It is to be understood that other
embodiments may be utilized and structural or logical changes may
be made without departing from the scope of the present invention.
In addition, while a particular feature or aspect of an embodiment
may have been disclosed with respect to only one of several
implementations, such feature or aspect may be combined with one or
more other features or aspects of the other implementations as may
be desired and advantageous for any given or particular
application. The following detailed description, therefore, is not
to be taken in a limiting sense, and the scope of the present
invention is defined by the appended claims.
[0018] Many different types of wheeled vehicles use pneumatic tires
(in this specification, the term tire generally refers to a
pneumatic tire). Typically, a tire is mounted on the rim of a
vehicle wheel and is in contact with a surface upon which the
vehicle travels, such as a road surface. FIG. 1 conceptually
illustrates portions of a typical tire. The tire 10 includes an
outer periphery 12 that typically has a tread formed about its
circumference for contacting an underlying surface 14. The outer
peripheral portion 12 has a constant circumferential length which
is substantially round. However, under vehicle load, the outer
periphery 12 has a flattened area 16 at the tire-to-road surface
interface. The portion 16 of a tire that is in actual contact with
the road surface--the bearing surface of the tire 10--is referred
to as the contact area.
[0019] Determining the length of a tire's contact area 16, or
bearing surface, can be used to calculate desired tire parameters
and accordingly, can provide much useful information about the
tire. For example, the shape or length of the contact area can have
a great effect on the handling of the vehicle to which the tire is
mounted. The length of the contact area varies in relation to the
inflation pressure of the tire under a constant vehicle load. Thus,
if the vehicle load is constant, increasing the inflation pressure
shortens the contact area, and decreasing the inflation pressure
lengthens the contact area.
[0020] FIG. 2 is a block diagram conceptually illustrating a tire
system 100 in accordance with embodiments of the present invention.
The system 100 includes a tire 102 with a sensor system 110 that
transmits information about the tire 102 to a receiver 104. The
receiver 104 can be located in a vehicle to which the tire 102 is
mounted, or it can be separate from any such vehicle. Information
can be transmitted from the sensor system 110 to the receiver 104
in any suitable manner. The sensor system 110 outputs signals
representing desired parameters of the tire 102, such as
information about the contact area, sidewall deflection, tire
pressure, etc.
[0021] In exemplary embodiments of the invention, the sensor system
110 includes a plurality of piezoelectric devices mounted on the
inner surface 108 of the tire 102. FIG. 3 conceptually illustrates
further aspects of the tire system 100, showing piezoelectric
devices 112 mounted to the inside surface 108 of the tire 102,
opposite the tread 106. FIG. 4 illustrates an embodiment of the
sensor system 110, in which the piezoelectric devices 112 are
situated on a flexible substrate 114 that is mountable to the
inside surface 108 of the tire 102. The substrate 114 may be a
flexible film made from a suitable plastic material.
[0022] FIG. 5 is an end view illustrating a portion of the tire 102
with the substrate 114 mounted to the inside surface 108 with an
adhesive, for example. Portions of the inner surface 108 opposite
portions of the tire that are not under a load are generally
radiused as shown in the top portion of the tire 102 shown in FIG.
5. Portions of the tire 102 in the contact area 16, however, deform
when under load. A piezoelectric device generates an electric
potential in response to an applied mechanical stress. If the
material is not short-circuited, the applied charge induces a
voltage across the material. Thus, the piezoelectric devices 112
can detect deformation of portions of the tire 102 in contact with
the road as it rotates, generating a voltage in response to this
deformation. The piezoelectric devices 112 are connected to an
electronics module 130, which includes a processing device such as
a digital signal processor (DSP), microcontroller or
microprocessor, via conductors 132. In accordance with certain
aspects of the invention, the processing device calculates
information regarding selected parameters of the tire in response
to signals received from the piezoelectric devices.
[0023] The terms "coupled," "connected," along with derivatives and
other similar terms are meant to indicate that the relevant
elements co-operate or interact with each other regardless of
whether they are in direct physical or electrical contact.
Furthermore, it should be understood that embodiments of the
invention may be implemented in discrete circuits, partially
integrated circuits or fully integrated circuits and/or
software.
[0024] FIG. 6 is a sectional end view illustrating further aspects
of the exemplary sensor system 1 10. The piezoelectric devices 112
are sandwiched between conductive layers 134 acting as electrodes
on both sides of the piezoelectric devices 112. The electrodes 134
are connected to the conductors 132 on the substrate 114 with
conductive glue 136, such as silver-filled epoxy. Alternatives to
the conductive glue 136 include solder materials or metal sheet
laser weld connections. Further embodiments are envisioned wherein
several piezoelectric devices 112 are attached on top of each other
to create a multi-layer piezoelectric structure with increased
output voltage.
[0025] FIG. 7 illustrates another embodiment that uses a substrate
114 made from PVDF (Polyvinylidene Fluoride), a material that can
be polarized to exhibit piezoelectric properties. This makes it
possible to create the piezoelectric devices 112 in the substrate
114 itself, rather than attaching separate devices to the substrate
114. The PVDF substrate 114' has conductive layers added on both
sides to form both the electrodes 134 and the conductors 132. It is
possible to polarize the PVDF film 114' only under the electrodes
134, so that the signal from the piezoelectric devices 112 is not
influenced by strain in the PVDF film 114' under the conductors
132.
[0026] FIG. 8 illustrates a portion of the sensor system 110,
showing some of the piezoelectric devices 112 and the electronics
module 130. One electrode 134 of each piezoelectric device 112 is
connected separately by a conductor 132 to the electronics module
130. The other electrode (not shown in FIG. 8) of each
piezoelectric device 112 is connected to a common terminal. In the
embodiments illustrated in FIGS. 6 and 7, the bottom electrode 134
is common to all the piezoelectric devices 112, and is connected to
the common input of the electronics module 130. The reverse
arrangement with the common electrode on top is equally
possible.
[0027] FIG. 9 is a block diagram conceptually illustrating portions
of the electronics module 130. As noted above, each of the
piezoelectric devices 112 has one electrode 134 connected to a
common terminal 140 of the electronics module 130. The other
electrode 134 of the piezoelectric devices 112 is connected to an
input terminal of the electronics module 130, where it splits, with
one branch leading to input switches of a power conversion unit
150, which is designed to convert the output of the piezoelectric
devices 112 to a low impedance power supply suitable to power other
portions of the electronics module 130. The other branch of
electrodes 134 is received by an input multiplexer 152, which
provides an output received by a digital-to-analog converter 154. A
signal processing unit 156 receives the output of the
digital-to-analog converter 154 and is programmed to calculate the
desired tire parameters in response to signals provided by the
piezoelectric devices 112. The electronic module 130 may contain
additional circuits and sensors, such as temperature sensors and/or
a pressure sensor, for example. Data output by the signal
processing unit 156 are received by a transmitter 158, which sends
the data via an antenna 160 to the receiver 104, which is typically
situated in the vehicle upon which the tire is mounted. In certain
embodiments, the antenna 160 is implemented in the form of
conductors placed on the substrate 114. Additional processing of
the tire data can be accomplished by further processing devices
associated with the receiver 104. The input to the input
multiplexer 152 has a high impedance so that it does not consume a
significant portion of the energy generated by the piezoelectric
film of the piezoelectric devices 112.
[0028] FIG. 10 illustrates an exemplary alternative layout of the
piezoelectric devices 112. The devices 112 can be made in various
shapes and located at various positions inside the tire or on the
substrate 114 so as to be most sensitive to tire deformation in a
particular area of the tire 102. Further, the substrate 114 may
have a varying width, as shown in FIG. 10, to adapt better to the
curved interior surface 108 of the tire 102. As shown in FIG. 10,
some of the piezoelectric devices 112 would be situated primarily
in the tread area 120, while others would be situated primarily in
the sidewall area 122.
[0029] In the exemplary systems 110 shown in FIGS. 4 and 10, the
piezoelectric devices 112 are laid out on the substrate 114 to
essentially cover the full inner circumference of the inside
surface 108 in the longitudinal direction (direction the tire
rotates, up-and-down the page in FIGS. 4 and 10). As shown in FIG.
5, in some embodiments, the piezoelectric devices 112 are further
situated to extend between the central tread area 120 and the
region between tread and sidewall 122 in the direction transverse
to the longitudinal axis. Accordingly, the substrate 114
illustrated in the embodiments shown in FIGS. 4 and 10 defines a
longitudinal length L (up and down the page) that is substantially
larger than the transverse width dimension W. The illustrated
piezoelectric devices 112 extend across the substrate 114 in the
width direction W (across the drawing page).
[0030] Moreover, the piezoelectric devices 112 in the embodiments
illustrated in FIGS. 4 and 10 are arranged generally symmetrical in
both the L and W directions. This facilitates gathering of data
relating to the entire tire. For example, the relatively small size
of the piezoelectric device 112 in the longitudinal direction makes
it possible to determine the shape and size of the contact area
with good accuracy, and the electronics module 130 can switch among
the piezoelectric devices 112 at a rate proportional to the wheel
rotation frequency, such that the area under observation remains at
one position irrespective of wheel rotation.
[0031] Thus, when the tire 102 rotates during driving of the
vehicle, the part of the tire 102 in contact with or close to the
road surface is subject to stress which acts to deform the tire
102. The piezoelectric devices 112 will also be deformed, the
deformation primarily taking the form of a flexing of the elements
112. This generates a voltage signal on the electrodes 134 of the
piezoelectric devices 112. The voltage is proportional to the
flexing of the piezoelectric device 112, thereby providing a signal
indicative of the mechanical deformation of the tire 102. By
selectively placing the piezoelectric devices 112 on different
parts of the substrate 114, signals can be obtained that contain
information about the deformation of different areas of the tire
102.
[0032] The input multiplexer 152 enables the signal processing unit
156 to select the signal from any of the piezoelectric devices 112
for analysis. Thus, by appropriately operating the input
multiplexer 152, the processing device can receive output signals
from selected ones of the piezoelectric devices. Such analyses can
include, for example, [0033] Detection of the time when an
electrode enters and leaves the contact area between the road and
the tire. This will, after one or more iterations, provide
information about the wheel rotation period and a first estimate of
the size of the contact area. [0034] Detection of signals from
electrodes which are placed in the transition zone between tire
tread and sidewall. This will provide information about the
deformation of the sidewall, which is related to the air pressure
of the tire and the dynamic forces due to linear and angular
acceleration of the vehicle. [0035] Detection of difference signals
between electrodes which are placed in the transition zones between
tire tread and the inner and outer sidewalls. This provides
additional information about forces acting on the wheel. [0036]
Detection of signals from electrodes placed on the tread. This will
provide information about the contact between the tire and the
road.
[0037] After the tire rotation period has been measured, it is
possible for the signal processing electronics to lock onto the
contact area of the tire 102 by switching the input multiplexer 152
to new piezoelectric devices 112 as they arrive at the contact area
16, selectively connecting the output of the appropriate
piezoelectric devices 112 to the signal processing unit 156. A
continuous monitoring of the tire contact area 16 is therefore
possible during driving.
[0038] The operation of the power converter 150 runs in parallel to
the signal processing unit 156 and associated devices, and is
synchronized such that information from the piezoelectric devices
112, in the form of voltage levels, is read by the signal
processing electronics before the charge associated with the signal
voltage is transferred to the power converter 150. Depending on the
placement of the piezoelectric devices 112, the maximum signal may
occur as the piezoelectric device 112 enters or leaves the contact
zone 16, or at some point between these two events. The timing of
the power converter 150 is therefore programmed in accordance with
the layout of the piezoelectric devices 112 and the desired signal
processing.
[0039] Alternative embodiments of the invention are envisioned
where the substrate 114 does not cover the whole length of the
inner surface 108 nor the whole width. Such implementations will
not be able to continuously monitor the contact area. However, if
the area covered by the piezoelectric devices 112 corresponds to
more than the maximum deformed area in the contact area, much
information is available even if only sampled once per wheel
rotation.
[0040] Although specific embodiments have been illustrated and
described herein, it will be appreciated by those of ordinary skill
in the art that a variety of alternate and/or equivalent
implementations may be substituted for the specific embodiments
shown and described without departing from the scope of the present
invention. This application is intended to cover any adaptations or
variations of the specific embodiments discussed herein. Therefore,
it is intended that this invention be limited only by the claims
and the equivalents thereof.
* * * * *