WO2008043184A1

WO2008043184A1 - Methods and apparatus for mounting a sensor inside a wheel cavity

Info

Publication number: WO2008043184A1
Application number: PCT/CA2007/001828
Authority: WO
Inventors: Kian Sheikh-Bahaie; Shawn Lammers; Robert Gordon Patterson
Original assignee: Smartire Systems Inc.
Priority date: 2006-10-13
Filing date: 2007-10-12
Publication date: 2008-04-17
Also published as: WO2008043184B1; US20080110267A1; US7421902B2; WO2008043177A1

Abstract

An apparatus and method for mounting a sensor having an antenna inside a wheel cavity is disclosed. The apparatus includes a body having a holder for holding the sensor. The apparatus also includes a passive antenna circuit electrically isolated from the antenna of the sensor. The passive antenna circuit includes a receiving antenna adjacent a first end of the holder, for receiving radio frequency energy radiated by the antenna of the sensor. The passive antenna circuit also includes a conductor electrically connected to the receiving antenna and extending inside the holder. The passive antenna circuit further includes a mount on a second end of the holder, opposite the first end, the mount being electrically connected to the conductor and operably configured to mechanically connect the conductor to an interior extending portion of an electrically conductive valve stem of the wheel and to electrically connect the conductor to the interior extending portion such that an exterior extending portion of the valve stem radiates at least some radio frequency energy coupled into the receiving antenna from the antenna of the sensor.

Description

METHODS AND APPARATUS FOR MOUNTING A SENSOR INSIDE A

WHEEL CAVITY

BACKGROUND OF THE INVENTION 1. Field of Invention

This invention relates to sensing and more particularly to methods and apparatus for mounting and using a sensor inside a wheel cavity.

2. Description of Related Art Various systems for vehicle tire operating condition sensing are available.

Most systems involve measuring tire air pressure and or tire air temperature on individual tires and transmitting a radio frequency signal representing the sensed condition to a remote receiver. Each wheel on a vehicle is normally fitted with a tire condition sensing apparatus that includes a measurement device and a transmitter. Mounting tire condition sensing apparatus to a wheel can be challenging.

Some systems employ an externally mounted sensing unit that mounts directly to an exterior portion of a valve stem of a wheel. An example of an exterior mounted sensor for measuring tire pressure is provided in US Patent

Application No. 11/580,693 filed October 13, 2006.

Other systems employ mounting methods that enable the sensor apparatus to be mounted inside a wheel cavity formed between an interior wall of a tire and a wall of a wheel rim on which the tire is mounted.

An example of an interior mounted sensor is provided in US Patent No. 6,805,000 issued October 19, 2004 which describes an apparatus for mounting a sensor capsule to a wheel rim. The apparatus includes a housing having a receptacle having a shape complementary to the capsule to receive the capsule snugly therein. Additionally the apparatus may include a lock on the housing, cooperating with a surface on the capsule to lock the housing to the capsule, and a connector for connecting the housing to the wheel rim such that the capsule is between a portion of the wheel rim and the receptacle. The connector may include a strap, brackets secured to the wheel by screws or rivets, or a valve stem connector for mechanically securing the housing to a valve stem. In each of these cases the sensor is mounted inside the wheel cavity and the radio frequency transmitter of the sensor apparatus must be able to transmit a tire condition signal with enough signal strength that the signal passes through the tire and can be received by a receiver located in a desired location on the vehicle. This can require a significant amount of energy and relatively high power transmitter circuits, which increases the cost of the device and which requires batteries with sufficient capacity to supply the transmitter with power for a sufficiently long time. Alternatively, or in addition, multiple antennas may be used, but this also adds to the cost of the overall system

US Patent No. 5,838,229 describes a remote tire pressure sensor system that employs an output amplifier that is matched to a valve stem of the tire to enable the valve stem itself to be used as a transmitting antenna to transmit the sensed condition to a remote receiver. This type of system requires careful attention to electrically matching the output of the amplifier with the valve stem, which can limit the use of the sensor to wheels that are able to accommodate the specific valve stem to which the output amplifier is matched and requires replacement of the entire valve stem and sensor unit when a problem is encountered.

SUMMARY OF THE INVENTION

In accordance with one aspect of the invention, there is provided a method for operating a sensor having an antenna for radio frequency transmitting a representation of a measured value associated with a tire mounted on a wheel to a remote receiver. The sensor is mounted inside a wheel cavity formed by the tire and the wheel on which the tire is mounted. The method involves coupling radio frequency energy radiated by the antenna of the sensor into a passive antenna circuit electrically isolated from the antenna of the sensor and comprising an interior extending portion of an electrically conductive valve stem extending inside the wheel cavity such that an exterior portion of the valve stem extending outside the wheel cavity radiates, outside the wheel cavity, at least some of the radio frequency energy coupled into the passive antenna circuit.

Coupling may involve positioning the antenna of the sensor in proximity to a receiving antenna of the passive antenna circuit.

Coupling may involve positioning the antenna of the sensor inside a receptacle of a sensor mounting apparatus.

Coupling may involve positioning the receiving antenna around the receptacle.

Coupling may involve electrically connecting the receiving antenna to the interior extending portion of the valve stem.

Electrically connecting may involve electrically connecting the receiving antenna to a conductor connected to a mount operably configured to be mounted to the interior extending portion of the valve stem.

The method may involve holding the conductor in a projection operably configured to cooperate with the sensor to hold the sensor inside the wheel cavity.

Holding the conductor may involve holding the conductor in an insulating projection surrounding the conductor.

Electrically connecting may involve mechanically securing the mounting apparatus to the interior extending portion of the valve stem. In accordance with another aspect of the invention, there is provided an apparatus for mounting a sensor having an antenna, inside a wheel cavity. The apparatus includes a body having a holder for holding the sensor. The apparatus also includes a passive antenna circuit electrically isolated from the antenna of the sensor. The passive antenna circuit includes a receiving antenna adjacent a first end of the holder, for receiving radio frequency energy radiated by the antenna of the sensor. The passive antenna circuit also includes a conductor electrically connected to the receiving antenna and extending inside the holder. The passive antenna circuit further includes a mount on a second end of the holder, opposite the first end, the mount being electrically connected to the conductor and operably configured to mechanically connect the conductor to an interior extending portion of an electrically conductive valve stem of the wheel and to electrically connect the conductor to the interior extending portion such that an exterior extending portion of the valve stem radiates at least some radio frequency energy coupled into the receiving antenna from the antenna of the sensor.

The body may include a positioner operably configured to position the antenna of the sensor in proximity to the receiving antenna.

The positioner may include a receptacle adjacent the holder, the receptacle being operably configured to receive the antenna of the sensor.

The receiving antenna may be positioned adjacent the receptacle.

The receiving antenna may surround the receptacle.

The receiving antenna may include first and second generally parallel spaced apart electrically connected conductor portions spaced apart sufficiently to permit the antenna of the sensor to be received therebetween. The holder may include a projection operably configured to be received in an opening of the sensor.

The projection may be formed of an electrically insulating material.

The conductor may include a recess for receiving at least some of the electrically insulating material to prevent separation of the electrically insulating material from the conductor.

The projection may include a stopper for stopping relative movement between the sensor and the projection.

The stopper may include a tab operably configured to interfere with movement of the sensor to confine the sensor between the receptacle and the tab.

The tab may include a resilient portion permitting the tab to be moved into a first position enabling relative movement between the sensor and the projection and the resilient portion urging the tab into a second position in which the tab interferes with movement of the sensor relative to the projection.

The mount may include a connector having a wall having a recess for receiving a complementary portion of the interior extending portion of the valve stem and wherein the wall has an elongated opening for receiving a fastener therethrough to mechanically secure the connector to the valve stem.

In accordance with another aspect of the invention, there is provided an apparatus for mounting a sensor having an antenna inside a wheel cavity. The apparatus includes holding provisions for holding the sensor inside the wheel cavity. The apparatus also includes electrically isolated radio frequency coupling provisions electrically isolated from the antenna of the sensor, for coupling radio frequency energy transmitted by the antenna of the sensor to an interior extending portion of an electrically conductive valve stem of the wheel such that an exterior extending portion of the valve stem radiates, outside the wheel cavity, at least some of the radio frequency energy radio frequency energy coupled from the antenna of the sensor.

The radio frequency coupling provisions may include a passive antenna circuit that may include a receiving antenna adjacent a first end of the holding provisions, for receiving radio frequency energy radiated by the antenna of the sensor. The passive antenna circuit may also include a conductor electrically connected to the receiving antenna and extending inside the holding provisions. The passive antenna circuit may further include a mount on a second end of the holding provisions, the mount being electrically connected to the conductor and operably configured to mechanically connect the holding provisions to the interior extending portion of the valve stem and electrically connect the conductor to the interior extending portion of the valve stem such that the valve stem radiates at least some of the radio frequency energy coupled into the receiving antenna from the antenna of the sensor.

The holding provisions may include positioning provisions for positioning the antenna of the sensor into proximity with the receiving antenna.

The positioning provisions may include a receptacle adjacent the holding provisions, the receptacle being operably configured to receive the antenna of the sensor.

The receiving antenna may be positioned adjacent the receptacle.

The receiving antenna may surround the receptacle.

The receiving antenna may include first and second generally parallel spaced apart electrically connected conductor portions spaced apart sufficiently to permit the antenna of the sensor to be received therebetween. The holding provisions may include a projection operably configured to be received in an opening of the sensor.

The positioning provisions may include a receptacle adjacent the holding provisions, the receptacle being operably configured to receive the antenna of the sensor and the receptacle and the mount may be disposed at opposite ends of the projection.

The projection may be formed of an electrically insulating material.

The conductor may include provisions for preventing separation of the electrically insulating material from the conductor.

The provisions for preventing separation may include a recess in the conductor, for receiving at least some of the electrically insulating material to prevent separation of the electrically insulating material from the conductor.

The projection may include stopping provisions for stopping relative movement between the sensor and the projection.

The positioning provisions may include a receptacle adjacent the holding provisions, the receptacle being operably configured to receive the antenna of the sensor and the stopping provisions may include a tab operably configured to interfere with movement of the sensor to confine the sensor on the projection between the receptacle and the tab.

The tab may include a resilient portion permitting the tab to be moved into a first position enabling relative movement between the sensor and the projection and the resilient portion urging the tab into a second position in which the tab interferes with relative movement between the sensor and the projection. The mount may include a connector having a wall having a recess for receiving a complementary portion of the valve stem and the wall may have an elongated opening for receiving a fastener therethrough to mechanically secure the connector to the valve stem.

In accordance with another aspect of the invention, there is provided a method of mounting a sensor inside a wheel cavity formed between a wheel and a tire. The method involves receiving a projection of a mounting apparatus for the sensor in an opening of the sensor until a mount at an end of the projection projects out of the opening, to position an antenna of the sensor adjacent a receiving antenna of a passive antenna circuit including the mount, while electrically isolating the antenna of the sensor from an electrically conductive valve stem of a wheel on which the tire is mounted. The method also involves mechanically and electrically connecting the mount to an interior extending portion of the valve stem such that when the antenna of the sensor transmits radio frequency energy, at least some of the radio frequency energy is coupled to the receiving antenna and radiated exteriorly of the tire by an exterior extending portion of the valve stem.

The apparatus may further include receiving the antenna of the sensor in a receptacle about which the receiving antenna extends.

The apparatus may further include stopping relative movement between the sensor and the projection.

The apparatus may further include moving a tab resiliently connected to the projection into a first position enabling relative movement between the sensor and the projection to install the sensor on the mounting apparatus and then permitting the tab to return to a second position in which the tab interferes with relative movement between the sensor and the projection to maintain the sensor on the mounting apparatus. Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

In drawings which illustrate embodiments of the invention,

Figure 1 is a fragmented view of a prior art sensor apparatus for measuring air pressure, shown mounted on a pressure coupler of a valve stem extension of a wheel.

Figure 2 is an exploded view of the sensor apparatus shown in Figure 1 mounted on a sensor mounting apparatus according to a first embodiment of the invention.

Figure 3 is a cross-sectional view of the sensor apparatus shown in Figure 2 shown fully mounted on the sensor mounting apparatus shown in Figure 2.

Figure 4 is an exploded partially cross-sectional view showing the sensor assembly of Figure 3 mounted on an interior portion of a valve stem of a wheel according to a method of mounting the sensor apparatus according to another embodiment of the invention.

Figure s is a perspective view of a receiving antenna of the sensor mounting apparatus shown in Figure 2.

Figure 6 is a side view of a passive antenna circuit of the sensor mounting apparatus shown in Figure 2 employing the antenna of Figure 5. Figure 7 is a perspective view of an integrated conductor and mount of the passive antenna circuit shown in Figure 6.

Figure 8 is a cross-sectional view of the sensor mounting apparatus shown in Figure 2.

Figure 9 is a perspective view of the sensor assembly shown in Figure 3 mounted on an interior portion of a valve stem of a wheel.

DETAILED DESCRIPTION

Referring to Figure 1 , a sensor apparatus shown generally at 10 is shown mounted on a pressure coupler 11 mounted on a valve stem extension 12 of a wheel (not shown), such as an automobile wheel. The sensor apparatus 10 is as described in U.S. Patent Application No. 11/580,693 and in this embodiment is for measuring air pressure (i.e. tire air pressure) inside a wheel cavity. Generally, however, the sensor may be adapted to sense any tire or wheel operating parameter, but will normally be of the type that measures air pressure or air temperature, for example.

Generally, in the embodiment shown, the sensor apparatus 10 is for measuring air pressure and includes a housing 14 including an outer wall 16 defining a cavity 18 configured to hold a substrate 20 carrying a pressure sensor chip 22 and an RF transmitter 23. The pressure sensor chip 22 has a pressure sensor opening 24 for receiving fluid (air) under pressure, the pressure of which is to be measured. The transmitter 23 includes an RF antenna 27 mounted inside a plastic cover 29. The housing 14 also includes an inner wall 26 inside the cavity 18 defining a pressure sensing chamber 30, an opening 32 in the inner wall and a seal interface 34 about the opening. Aligning provisions (not shown) for aligning the pressure sensor opening 24 with the opening 32 in the inner wall 26 are provided to enable fluid communication between the pressure sensing chamber 30 and the pressure sensor opening 24. The housing 14 also includes urging provisions (not shown) for urging the pressure sensor chip 22 against a seal in the seal interface 34 such that the pressure sensor opening 24 is in fluid communication with the opening 32 in the inner wall 26 and such that the seal prevents ambient pressure from interfering with communication of fluid between the pressure sensor opening and the opening in the inner wall.

The opening 32 in the inner wall 26 is aligned with a corresponding opening 36 in the pressure coupler 11 and thus air pressure in the valve stem extension 12 is communicated through the pressure coupler 11 to the opening 32 in the inner wall 26 to the pressure chamber 30 and to the pressure sensor opening 24 to allow the pressure sensor chip 22 to sense the air pressure in the valve stem extension 12 and hence air pressure in the tire. The housing 14 has an opening 25 through which it receives the pressure coupler 11 and a nut 38 holds the housing on the pressure coupler. Typically the valve stem extension 12 extends outside the wheel and thus the sensor apparatus 10 is mounted outside the wheel.

To facilitate mounting of the above mentioned sensor apparatus 10 or similarly configured sensors, an apparatus is provided for mounting a sensor having an antenna, such as the sensor apparatus described above inside a wheel cavity. One embodiment of such an apparatus is shown generally at 50 in Figure 2 and includes a body 52 having a holder 54 for holding the sensor apparatus 10. Referring to Figure 3, the apparatus further includes a passive antenna circuit shown generally at 56 which is electrically isolated from the antenna 27 of the sensor. The passive antenna circuit 56 includes a receiving antenna 58 adjacent a first end 60 of the holder 54 for receiving radio frequency energy radiated by the antenna 27 of the sensor apparatus 10. The passive antenna circuit 56 further includes a conductor 62 electrically connected to the receiving antenna 58 and extending inside the holder 54. The passive antenna circuit 56 further includes a mount 64 on a second end 66 of the holder 54, opposite the first end 60. The mount 64 is electrically connected to the conductor 62.

Referring to Figure 4, the mount 64 is configured to mechanically connect the conductor 62 to an interior extending portion 68 of an electrically conductive valve stem 70 of a wheel 72 on which a tire 74 is mounted. The mount 64 also electrically connects the conductor 62 to the interior extending portion 68 and the value stem is electrically isolated from the wheel rim by an insulating bushing 75 such that an exterior extending portion 76 of the valve stem 70 radiates at least some radio frequency energy coupled into the receiving antenna 58 from the antenna 27 of the sensor apparatus 10.

Thus, the above mounting apparatus 50 enables the sensor apparatus 10 to be mounted inside a wheel cavity 78 formed by the tire 74 and the wheel 72. This makes the sensor apparatus 10 more versatile in that it can be mounted outside the wheel cavity 78 as shown in Figure 1 or inside the wheel cavity as shown in Figure 4.

Referring to Figure 5 to make the above mounting apparatus 50, the receiving antenna 58 is formed from a length of 10 gauge copper wire for example, into a shape as shown in Figure 5. The receiving antenna 58 includes first and second generally spaced apart electrically connected conductor portions 80 and 82 lying in respective planes and spaced apart sufficiently by a distance

84 to permit the antenna (27) of the sensor apparatus 10 to be received therebetween. Each of the first and second conductor portions 80 and 82 has a generally serpentine shape comprised of a plurality of approximately 180 degree bends shown generally at 86 and straight portions shown generally at

88 connected together by a semi-circular portion 90 at a first end of the receiving antenna 58. Generally, the first and second conductor portions 80 and 82 are mirror images of each other. At a second end of the receiving antenna 58, opposite the semi-circular portion 90, the first conductor portion

80 is terminated in a short straight portion 92 which is connected to an upright approximately 90 degree bend 94 and a straight portion 96 that extends generally perpendicular to the plane of the first conductor portion 80. The straight portion 96 is connected to a further bend 98 which is connected to a further, final straight portion 100 which extends in a parallel spaced apart plane spaced apart from the plane of the first conductor portion 80. This final straight portion 100 is connected to the conductor 62 as shown in Figure 6.

Referring to Figure 6, in this embodiment the conductor 62 and mount 64 are integrally formed into a single unitary piece 65. The single unitary piece 65 may be formed of light weight aluminum, for example, to reduce effects of the mass of the apparatus 50 on the balance of the wheel (72). In this embodiment the conductor 62 includes a cylindrical portion 110 having a distal end 112, having an opening (not shown) for receiving the final straight portion 100 of the receiving antenna 58 therein. Desirably, the opening is tapered and sized such that the final straight portion 100 is snugly and securely received therein to ensure good electrical contact between the final straight portion and the conductor 62. An opposite end 114 of the cylindrical portion is terminated in a flared collar portion 116 which includes a wall 118 of increasing diameter. A recess, shown generally at 120 is formed by forming a groove immediately adjacent the flared collar portion 116. The recess 120 extends circumferentially around the conductor 62. The recess 120 is terminated in a flat wall 122 that defines a boundary between the conductor 62 and the mount 64.

Referring to Figures 6 and 7, the mount 64 has a generally cylindrical outer wall 130 having first and second recesses shown generally at 132 and 134 disposed on opposite sides of the cylindrical outer wall. First and second elongated openings 136 and 138 respectively are formed in the outer wall 130 adjacent the first and second recesses 132 and 134 respectively. The first recess 132 is relatively large and serves to keep the mass of the mount 64 to a minimum and provides access to the opening 136. The second recess 134 is defined by a curved portion 140 of the outer wall 130 which, referring to Figure 4 is complementary to a hemispherically shaped adapter 142 or end portion of the valve stem 70. The opening 138 shown in Figure 7 is elongated and large enough to receive therethrough a bolt, such as shown at 144 in Figure 4, to secure the mount 64 to the hemispherically shaped adapter or end portion 142 of the valve stem 70. The elongated opening 138 shown in

Figure 7 allows the position of the apparatus 50 on the hemispherically shaped adapter or end portion 142 to be angularly adjusted as will be appreciated by reference to Figure 4.

Referring to Figure 8, the body 52 of the apparatus 50 is formed by overmolding insulating plastic material 149 onto the assembly shown in Figure 6 to form the holder 54 and a positioner 150 for positioning the antenna (27) of the sensor apparatus (10) in proximity to the receiving antenna 58. A stopper 152 is also formed in the plastic material, for stopping relative movement between the sensor apparatus 10 and the projection 54.

The plastic material 149 is formed to completely surround the conductor 62. Plastic material flows into the recess 120 and completely surrounds the receiving antenna 58. By causing the plastic material 149 to be received in the recess 120, the plastic material is securely affixed to the conductor 62 and is unable to separate from the conductor 62 especially in an axial direction. The plastic material 149 is formed into a cylindrically shaped projection 151 about the conductor 62, which acts as the holder 54. The projection 151 has a diameter enabling it to be snugly received in the opening 25 of the condition sensor apparatus 10 as shown in Figure 2.

Referring back to Figure 8, in this embodiment the positioner 150 includes a receptacle 160 adjacent the holder 54 positioned, oriented and dimensioned to receive the antenna (27) of the sensor apparatus (10) when the projection 151 is received in the opening (25) of the sensor apparatus. The receiving antenna 58 is positioned adjacent the receptacle 160 by causing the first and second conductor portions shown generally at 80 and 82 to extend on opposite sides of the receptacle 160 such that the receptacle is formed therebetween. Thus, the receiving antenna 58 surrounds the receptacle 160 and thus surrounds the antenna 27 of the sensor apparatus 10 when the sensor apparatus is mounted on the holder 54 as shown in Figure 3.

Referring to Figures 3 and 8, the stopper 152 includes a tab 161 having a resilient portion 162 that permits the tab to be moved into a first position shown in broken outline at 164, enabling relative movement between the sensor apparatus 10 and the projection 151. The resilient portion 162 urges the tab 161 into a second position shown in solid outline in which the tab interferes with movement in particular axial movement of the sensor apparatus 10 relative to the projection 151. Referring to Figure 8, the tab 161 includes a sloped portion 166 which engages a front surface of the sensor apparatus 10 causing the tab to be moved up into the opening 136 in the first recess 132, to assume the first position shown in broken outline at 164. This allows the projection 151 to be fully received through the opening 25 in the sensor apparatus 10. When the sensor apparatus 10 is fully received on the projection 151 , the antenna 27 is fully received in the receptacle 160 as shown in Figure 3. Also when the sensor apparatus 10 is fully received on the projection 151 , the tab 161 assumes the second position shown in solid outline and an outer surface 168 of the sensor apparatus 10 is disposed between a flat surface 170 on the tab 161 and the receptacle 160. Referring to Figure 3, the flat surface 170 interferes with axial movement of the sensor apparatus 10 in the direction shown at 172 while a wall 173 surrounding an opening of the receptacle 160 interferes with axial movement of the sensor apparatus 10 in the opposite direction. Thus, the sensor apparatus 10 is secured to the sensor mounting apparatus 50 to form a sensing assembly 180 comprised of the sensor apparatus 10 and the mounting apparatus 50.

Referring to Figure 4, to mount the sensing assembly 180 inside a wheel cavity 78, the tire 74 is removed from the wheel 72 to expose the interior portion 68 of the valve stem 70. If the interior portion 68 of the valve stem 70 has a shape other than the shape of the hemispherically shaped adapter 142, then the hemispherically shaped adapter 142 is used with the apparatus shown in this embodiment. The mount 64 is placed over the hemispherically shaped adapter 142 and a hollow bolt 144 is inserted through the opening 138 to clamp the mount onto the hemispherical adapter as the bolt engages interior threads in an opening (not shown) of the interior portion 68 of the valve stem 70. The valve stem 70 itself is mechanically attached to the wheel 72 using the electrically insulating bushing or washer 75 so that the valve stem is electrically isolated from the wheel 72.

Referring to Figures 1 and 9, the assembly (180) is shown fully installed on the valve stem 70 in Figure 9. In operation, the tire pressure sensor chip 22 senses the pressure of air in the wheel cavity 78 and produces an electrical signal representing this pressure. The electrical signal is provided to the transmitter 33 of the sensor and the transmitter causes a radio frequency signal to be radiated as RF energy by the antenna 27 of the sensor apparatus 10. This radio frequency energy is coupled into the passive antenna circuit 56 comprising the receiving antenna 58 as shown in Figure 3 and such coupling is performed completely in electrical isolation from the circuits of the sensor apparatus 10. The coupling is solely by way of a wireless radio frequency signal that is coupled from the antenna 27 of the sensor into the passive antenna circuit 56 by the receiving antenna 58. Since the mount 64 is electrically conductive and since it is connected to the conductor 62 which is in turn connected to the receiving antenna 58, the radio frequency energy received by the receiving antenna is conveyed through the conductor and the mount to the interior extending portion 68 of the valve stem 70 of Figure 9, which excites the valve stem, causing it to act as an antenna such that the exterior extending portion 76 of the valve stem radiates at least some, and desirably most, of the radio frequency energy coupled into the receiving antenna from the antenna 27 of the sensor apparatus 10. By mounting the sensor apparatus 10 inside the wheel cavity 78 in the above manner, the sensor apparatus is protected from road debris and harsh environmental conditions thereby preserving its life. Furthermore, by mounting the sensing assembly 180 to the valve stem 70 in the manner indicated, no straps or belts are required to extend circumferentially around the wheel, nor are cavities required in the wheel, nor is glue required in order to glue the sensor to the wheel, nor are separate electrical connections required between the sensor apparatus and the valve stem. The above system permits the sensor apparatus 10 to be easily removed and replaced using only the tools required to remove the tire and remove the bolt 144. Furthermore, since the sensor apparatus 10 is compatible with both the above mentioned sensing mounting apparatus 50 described herein and the mounting arrangement shown in

Figure 1 , the sensor apparatus 10 may be used externally or internally of the wheel. In other words a single apparatus of the type described may be used either internally or externally of the wheel. This allows a single type of sensor apparatus 10 as described to be manufactured and used in two different applications thereby increasing the versatility of the sensor apparatus.

While specific embodiments of the invention have been described and illustrated, such embodiments should be considered illustrative of the invention only and not as limiting the invention as construed in accordance with the accompanying claims.

Claims

What is claimed is:

1. A method for operating a sensor having an antenna for radio frequency transmitting a representation of a measured value, associated with a tire mounted on a wheel to a remote receiver, wherein the sensor is mounted inside a wheel cavity formed by the tire and the wheel on which the tire is mounted, the method comprising:

coupling radio frequency energy radiated by the antenna of the sensor into a passive antenna circuit electrically isolated from the antenna of the sensor and comprising an interior extending portion of an electrically conductive valve stem extending inside the wheel cavity such that an exterior portion of the valve stem extending outside the wheel cavity radiates, outside the wheel cavity, at least some of said radio frequency energy coupled into said passive antenna circuit.

2. The method of claim 1 wherein said coupling comprises positioning the antenna of the sensor in proximity to a receiving antenna of said passive antenna circuit.

3. The method of claim 2 wherein said coupling comprises positioning the antenna of the sensor inside a receptacle of a mounting apparatus.

4. The method of claim 3 wherein said coupling comprises positioning said receiving antenna around said receptacle.

5. The method of claim 2 wherein said coupling comprises electrically connecting said receiving antenna to said interior extending portion of the valve stem.

6. The method of claim 5 wherein electrically connecting comprises electrically connecting said receiving antenna to a conductor connected to a mount operably configured to be mounted to said interior extending portion of the valve stem.

7. The method of claim 6 further comprising holding said conductor in a projection operably configured to cooperate with the sensor to hold the sensor inside the wheel cavity.

8. The method of claim 7 wherein holding said conductor comprises holding said conductor in an insulating projection surrounding said conductor.

9. The method of claim 5 wherein electrically connecting comprises mechanically securing said mounting apparatus to said interior extending portion of the valve stem.

10. An apparatus for mounting a sensor having an antenna inside a wheel cavity, the apparatus comprising:

a body having a holder for holding the sensor; and

a passive antenna circuit electrically isolated from the antenna of the sensor, said passive antenna circuit comprising:

a receiving antenna adjacent a first end of the holder, for receiving radio frequency energy radiated by the antenna of the sensor;

a conductor electrically connected to the receiving antenna and extending inside the holder; and a mount on a second end of the holder, opposite said first end, said mount being electrically connected to the conductor and operably configured to mechanically connect the conductor to an interior extending portion of an electrically conductive valve stem of the wheel and to electrically connect the conductor to the interior extending portion such that an exterior extending portion of the valve stem radiates at least some radio frequency energy coupled into the receiving antenna from the antenna of the sensor.

11. The apparatus of claim 10 wherein said body comprises a positioner operably configured to position the antenna of the sensor in proximity to the receiving antenna.

12. The apparatus of claim 11 wherein said positioner comprises a receptacle adjacent the holder, said receptacle being operably configured to receive the antenna of the sensor.

13. The apparatus of claim 12 wherein said receiving antenna is positioned adjacent said receptacle.

14. The apparatus of claim 12 wherein said receiving antenna surrounds said receptacle.

15. The apparatus of claim 10 wherein said receiving antenna includes first and second generally parallel spaced apart electrically connected conductor portions spaced apart sufficiently to permit the antenna of the sensor to be received therebetween.

16. The apparatus of claim 10 wherein said holder comprises a projection operably configured to be received in an opening of the sensor.

17. The apparatus of claim 16 wherein said projection is formed of an electrically insulating material.

18. The apparatus of claim 17 wherein said conductor includes a recess for receiving at least some of said electrically insulating material to prevent separation of said electrically insulating material from said conductor.

19. The apparatus of claim 16 wherein said projection includes a stopper for stopping relative movement between the sensor and the projection.

20. The apparatus of claim 19 wherein said stopper comprises a tab operably configured to interfere with movement of the sensor to confine the sensor between said receptacle and said tab.

21. The apparatus of claim 19 wherein said tab includes a resilient portion permitting the tab to be moved into a first position enabling relative movement between the sensor and said projection and said resilient portion urging the tab into a second position in which said tab interferes with movement of the sensor relative to the projection.

22. The apparatus of claim 10 wherein said mount comprises a connector having a wall having a recess for receiving a complementary portion of said interior extending portion of the valve stem and wherein said wall has an elongated opening for receiving a fastener therethrough to mechanically secure said connector to the valve stem.

23. Use of the apparatus of claim 10 for mounting inside a wheel cavity of a wheel on which a tire is mounted a sensor having an antenna for radio frequency transmitting a representation of an operating condition of the tire to a remote receiver.

24. An apparatus for mounting a sensor having an antenna inside a wheel cavity, the apparatus comprising:

holding means for holding the sensor inside the wheel cavity; and

electrically isolated radio frequency coupling means electrically isolated from the antenna of the sensor, for coupling radio frequency energy transmitted by the antenna of the sensor to an interior extending portion of an electrically conductive valve stem of the wheel such that an exterior extending portion of the valve stem radiates, outside the wheel cavity, at least some of said radio frequency energy radio frequency energy coupled from the antenna of the sensor.

25. The apparatus of claim 24 wherein said radio frequency coupling means comprises a passive antenna circuit comprising:

a receiving antenna adjacent a first end of the holding means, for receiving radio frequency energy radiated by the antenna of the sensor;

a conductor electrically connected to the receiving antenna and extending inside the holding means;

a mount on a second end of the holding means, said mount being electrically connected to the conductor and operably configured to mechanically connect the holding means to the interior extending portion of the valve stem and electrically connect the conductor to the interior extending portion of the valve stem such that the valve stem radiates at least some of the radio frequency energy coupled into the receiving antenna from the antenna of the sensor.

26. The apparatus of claim 24 wherein said holding means comprises positioning means for positioning the antenna of the sensor into proximity with the receiving antenna.

27. The apparatus of claim 26 wherein said positioning means comprises a receptacle adjacent the holding means, said receptacle being operably configured to receive the antenna of the sensor.

28. The apparatus of claim 27 wherein said receiving antenna is positioned adjacent said receptacle.

29. The apparatus of claim 27 wherein said receiving antenna surrounds said receptacle.

30. The apparatus of claim 25 wherein said receiving antenna includes first and second generally parallel spaced apart electrically connected conductor portions spaced apart sufficiently to permit the antenna of the sensor to be received therebetween.

31. The apparatus of claim 25 wherein said holding means comprises a projection operably configured to be received in an opening of the sensor.

32. The apparatus of claim 31 wherein said positioning means comprises a receptacle adjacent the holding means, said receptacle being operably configured to receive the antenna of the sensor and wherein said receptacle and said mount are disposed at opposite ends of said projection.

33. The apparatus of claim 31 wherein said projection is formed of an electrically insulating material.

34. The apparatus of claim 33 wherein said conductor includes means for preventing separation of said electrically insulating material from said conductor.

35. The apparatus of claim 34 wherein said means for preventing separation comprises a recess in said conductor, for receiving at least some of said electrically insulating material to prevent separation of said electrically insulating material from said conductor.

36. The apparatus of claim 31 wherein said projection includes stopping means for stopping relative movement between the sensor and the projection.

37. The apparatus of claim 36 wherein said positioning means comprises a receptacle adjacent the holding means, said recepeacle being operably configured to receive the antenna of the sensor and wherein said stopping means comprises a tab operably configured to interfere with movement of the sensor to confine the sensor on the projection between said receptacle and said tab.

38. The apparatus of claim 37 wherein said tab includes a resilient portion permitting the tab to be moved into a first position enabling relative movement between the sensor and said projection and said resilient portion urging the tab into a second position in which said tab interferes with relative movement between the sensor and said projection.

39. The apparatus of claim 25 wherein said mount comprises a connector having a wall having a recess for receiving a complementary portion of the valve stem and wherein said wall has an elongated opening for receiving a fastener therethrough to mechanically secure said connector to the valve stem.

40. A method of mounting a sensor inside a wheel cavity formed between a wheel and a tire, the method comprising:

receiving a projection of a mounting apparatus for the sensor in an opening of the sensor until a mount at an end of said projection projects out of said opening, to position an antenna of the sensor adjacent a receiving antenna of a passive antenna circuit including the mount, while electrically isolating the antenna of the sensor from an electrically conductive valve stem of a wheel on which the tire is mounted;

mechanically and electrically connecting said mount to an interior extending portion of the valve stem such that when the antenna of the sensor transmits radio frequency energy, at least some of said radio frequency energy is coupled to said receiving antenna and radiated exteriorly of the tire by an exterior extending portion of the valve stem.

41. The method of claim 40 further comprising receiving the antenna of the sensor in a receptacle about which said receiving antenna extends.

42. The method of claim 40 further comprising stopping relative movement between the sensor and said projection.

43. The method of claim 42 further comprising moving a tab resiliently connected to said projection into a first position enabling relative movement between the sensor and said projection to install the sensor on the mounting apparatus and then permitting said tab to return to a second position in which said tab interferes with relative movement between the sensor and said projection to maintain the sensor on the mounting apparatus.