WO2013013325A1

WO2013013325A1 - Tire-tube pressure monitoring patch

Info

Publication number: WO2013013325A1
Application number: PCT/CH2011/000172
Authority: WO
Inventors: Christoph Martin Kleinlogel
Original assignee: Christoph Martin Kleinlogel
Priority date: 2011-07-25
Filing date: 2011-07-25
Publication date: 2013-01-31

Abstract

A tire-tube assembly (1) comprises a holder (20) to connect a sensor unit (30) to a tire-tube (10). A connector unit (40) is electrically connected to the sensor unit (30) and carries a sensor signal (S) indicative of a value of a physical parameter (p) such as a pressure of the tire-tube (10). A reversibly connectable transmission unit (50) can be mounted to the connector unit (40) and is adapted to receive the sensor signal (S) and transmit a transmission signal (T) which is indicative of the sensor signal (S), e.g., over a wireless link (L). Additionally, a kit for manufacturing such a tire-tube assembly (1) from a tire-tube (10) is disclosed. Further-more, a method for measuring a physical parameter of a tire-tube (10) by means of such a tire-tube assembly (1) is disclosed.

Description

Tlre-'tube pressure monitoring patch

Technical Field

The present invention relates to a device and method for measuring a physical parameter of a tire-tube as well as to a tire-tube assembly comprising such a de- vice .

Introduction and Background Art

It is known to use electronic monitoring systems to measure or monitor certain parameters of a car tire such as the inflation condition, the inflation pressure, or the temperature of the tire. These parameters are typically measured by a sensor element on the inside surface of the car tire which is positioned, e.g., below the crown of the tire or radially further inward. Other implementations comprise a valve-mounted sensor element. The data from this sensor element is processed by an electronic circuit and wirelessly transmitted to the car computer which can use the information, e.g., for warning the driver in the case of a decrease in tire pressure or for car control maneuvers such as in an Electronic Stability Program.

Different implementations of these electronic monitoring systems have been proposed or commercially available, e.g., a tire pressure control system by Continental AG, Hannover, Germany as introduced, e.g., on http : //www .motormobiles2. de/autoberichte/conti_rei_dru_ syst_0703.html and the URLs cited therein (accessed 22/06/2011) or on http://www.conti-online.com/generator /www/com/en/continental/pressportal/themes/press_releases /3_automotive_group/interior/press_releases/pr_20110418_d irect_tpms_en.html and the URLs cited therein (accessed 15/07/2011) .

The US Patent Application US 2007/0175554 Al describes a specific way to fix an electronic stress mon- itoring sensor on an inner surface of a car tire using a special "H-shaped patch" as a connecting element between the tire material and the electronic sensor.

However, the proposed monitoring systems have the disadvantage that they are not suitable for tube- based tires as frequently used, e.g., in bicycles, pede- lecs, or other (typically two-wheeled) vehicles.

Disclosure of the Invention

Hence, it is a general objective of the present invention to provide a device and method for measuring a physical parameter of a tube-based tire.

These objectives are achieved by the devices and method of the independent claims.

Accordingly, a tire-tube assembly for measuring at least one physical parameter of an airtight tire- tube comprises a tire-tube which consists of an elastic tubular wall material such as rubber. This wall material encloses an inside volume that is not in gas exchange with the outside world under normal operating conditions. At least one holder is arranged on this tire-tube, e.g., by vulcanization. One purpose of this holder is to mechanically connect at least one sensor unit comprising a sensor to the tire-tube. The sensor measures the desired physical parameter of the tire-tube and the sensor unit outputs an electrical sensor signal which is indicative of the magnitude of the physical parameter. In other words, the value of the physical parameter can be derived from the electrical sensor signal. A connector unit is electrically connected to the sensor unit and carries the sensor signal. Thus, the sensor signal can be conducted by the connector unit for optional further processing, thereby reducing the number of components which are permanently affixed to the tire-tube.

In a preferred embodiment, the physical parameter that is to be monitored is a pressure in the in- side volume of the tire-tube. The sensor unit comprises a pressure sensor, e.g., a direct pressure sensor or an indirect pressure sensor, e.g., relying on strain gauges measuring the strain of the wall material of the tire- tube. In the latter case, the pressure can be derived from the strain measurements. Measuring the pressure in a bicycle or pedelec tire-tube has the advantage that tire- lifetimes and general road safety are increased, power is saved while pedaling and/ or that maximum speeds can be increased.

Advantageously, the sensor is an analog sen^¬ sor and/ or the sensor signal is an analog signal.

Furthermore, the sensor unit can optionally comprise additional electronic devices such as an ampli^¬ fier (op-amp) for amplifying the sensor signal and/ or a memory (such as an (E)EPROM or another suitable memory device) for storing sensor specific data such as sensor calibration data, serial numbers, sensor-ID, front-/rear- tire identi ication etc. and/ or a preprocessor (e.g., a microcontroller) for data-preprocessing. In such a case, such an amplification, addition of information to the raw signal from the sensor, and/ or preprocessing of the raw signal from the sensor results in said sensor signal. This has the advantage that the tire-tube assembly can be produced cost efficiently because no or only few more ex^¬ pensive electronic components are required in the tire- tube assembly. Thus, the tire-tube assembly can be regarded as a disposable good after, e.g., a flat occurs. Then, the whole tire-tube assembly can be replaced cost- efficiently.

In a preferred embodiment, the holder, the sensor unit and the connector unit are arranged on an outside surface of the tire-tube, i.e., a surface of the wall material that faces away from the inside volume. Thus, the manufacturing process is simplified because no access to the inside volume of the sealed tire-tube is necessary to mount the components. Furthermore, tried- and-tested manufacturing techniques (e.g., as used in affixing a valve to a tire-tube) can be used to mount the components .

In another preferred embodiment, the holder is adapted to cover an opening (i.e., a small hole) in the wall material of the tire-tube. The sensor unit communicates (e.g., exchanges gas) with this opening (and thus with the inside volume of the tire-tube) , either because the sensor unit is arranged directly over the opening or it is connected to the opening via suitable tubing. Thus, a direct measurement of the physical parameter, e.g., the pressure in the inside volume of the tire- tube is possible. It is also possible to additionally cover the opening with a thin membrane, thus creating a sealed volume between the membrane and the holder that communicates with the sensor unit. Then, the sensor is not in direct gas exchange with the inside volume of the tire-tube any more but an, e.g., pressure-measurement from the inside volume is still possible due to a transmission of pressure-changes via the membrane. In other words, if the pressure in the inside volume of the tire- tube is reduced, the membrane bends inwards (i.e., towards the inside volume) due to forces from the sealed volume between the membrane and the holder, thus enlarging this sealed volume. The sealed volume can be designed in a way that it is filled with air or alternatively with a material having a low viscosity (like Dow Corning Syl- gard 527). Then, a change in the pressure of the sealed volume can be measured by the sensor and the pressure in the inside volume of the tire-tube can be derived from this measurement. The advantage is that possible contamination of the sensor unit from the inside volume of the tire-tube is avoided while a precise measurement of the physical parameter is still possible. In another advantageous embodiment, the tire- tube assembly additionally comprises a valve for inflat^¬ ing and/ or deflating the tire-tube, i.e., filling the inside volume of the tire-tube with pressurized gas such as air and/ or removing gas from the inside volume of the tire-tube thus lowering the pressure in the tire-tube. Furthermore, in this embodiment, the tire-tube is sub^¬ stantially of a toroid or doughnut shape (i.e., a shape that is created by revolving a plane circle around an axis of revolution (symmetry axis z) that lies in the plane of the circle but does not intersect the circle) . The term "substantially" includes deviations in the shape of the tire-tube from a perfect toroid of up to 10% of the largest diameter of the toroid and/ or single localized protrusions from the toroid (such as the valve) . In this embodiment, the valve is arranged at a first location at a first rotation (or polar) angle of φι=0^ο around the symmetry axis z. The holder is arranged at a second location "on the other side of the doughnut", i.e., at a second rotation angle 90°<φ2<270°. Particularly advantageous is a second rotation angle of (P2=180° because unbalanced masses are thus minimized. This leads to a more balanced rotation of the tire-tube.

More preferably, the holder is arranged such on a side of the tire-tube that it faces the symmetry axis z, i.e. on a rim-side of the tire-tube. Thus, the holder and the sensor unit are at least partially mechanically protected by a rim and/ or rim-shoulder when the tyre is run under nearly run-flat conditions and mechanical stress on the holder and the connected sensor unit is minimized during rotation.

In another advantageous embodiment, the holder and the sensor unit are arranged at the valve. This has the advantage that, e.g., an "all-in-one valve" can be manufactured and connected to the tire-tube, thus sav- ing the step of affixing the holder during production of the tire-tube.

The sensor unit can advantageously additionally to the sensor comprise a support on which the actual sensor (sensor device) is arranged. This support can, e.g., comprise a printed circuit board or ceramic components and it consists of a material with an elastic modulus which is higher, in particular at least 10 times higher than the elastic modulus of the wall material of the tire-tube. Preferable, this support also forms at least a part of the connector unit. Thus, an advantageous protection and/ or mechanical decoupling between the wall material and the sensor is achieved.

Advantageously, the holder is made of a material which has an elastic modulus similar (i.e., 50% to 150%) of the elastic modulus of the wall material. Thus, a reliable mechanical connection between the wall material and the holder can be achieved and the mechanical properties and/ or elasticity of the wall material are not deteriorated to a large degree.

The connector unit advantageously comprises electrical contact plugs for establishing a detachable or reversible electrical connection with further devices. On the mechanics side, a snap-on fixture and/ or a bayonet fixture are preferred. Thus, further devices can be easily and reversibly (de-) connected.

As an example for such a further device, the tire-tube assembly can - in a preferred embodiment - additionally comprise a transmission unit which receives (by means of the connector unit) the sensor signal which is indicative of the measured physical parameter from the sensor unit. The transmission unit then processes this sensor signal and outputs a transmission signal which is indicative of the sensor signal and thus of the measured physical parameter. As described above, the electrical and mechanical connections between the sensor unit and the transmission unit are reversibly establishable by means of said connector unit. When the connections are established, the sensor signal is transferred from the sensor unit to the transmission unit by the connector unit. Thus, a single transmission unit can be used in combination with different sensor units and the tire-tube can be produced cheaper because the transmission unit can easily be re-used in the case of malfunction of the tire- tube.

Advantageously, the transmission signal from the transmission unit is a digital signal. In the case of an analog sensor signal, the transmission unit can comprise an analog-to-digital converter for converting the analog sensor signal to the digital transmission signal. Alternatively, the sensor signal can also already be digitized by the sensor unit (e.g., by a preprocessor) and conducted digitally to the transmission unit. By using a digital transmission signal, the transmission is less prone to errors, and, e.g., multiplexing of a plurality of sensor signals is facilitated.

In a preferred embodiment, the transmission unit additionally comprises a power supply for powering or feeding the transmission unit and the sensor unit (as long as the electrical connection between the two units is established) . Options for a power supply include autonomous power supplies drawing their energy, e.g., from the rotation of the tire-tube. Advantageously, the power supply can also consist of or comprise a battery. In particular, the battery should be user-replaceable, i.e., the customer should be able to easily change the battery as soon as its voltage drops under a certain threshold.

In an advantageous embodiment, the transmission unit comprises a transceiver or a transmitter which transmits the transmission signal over a wireless link. Particularly suitable transmission frequencies are in the radiofrequency (RF) range including 864 MHz and/ or 2.4 GHz. With wireless links, no fragile wired connections including, e.g., sliding contacts, are necessary between the transmission unit and optional display- or control- units when the tire-tube is in rotation. Preferred trans^¬ mission protocols include the ANT/ ANT+ protocols or the (low power) Bluetooth standard which are specifically suitable for low power wireless sensor networks.

In addition to the different embodiments of the tire-tube assemblies disclosed so far, a kit for manufacturing such a tire-tube assembly from a tire-tube comprises at least one holder that is connectable to the tire-tube. One purpose of this holder is to connect at least one sensor unit comprising a sensor to the tire- tube. The sensor measures the desired physical parameter of the tire-tube and outputs an electrical sensor signal which is indicative of the magnitude of the physical parameter. In other words, the value of the physical parameter can be derived from the electrical sensor signal. Δ connector unit is electrically connected to the sensor unit and carries the sensor signal. Thus, the sensor signal can be conducted by the connector unit.

Furthermore, a method of measuring at least one physical parameter of a tire-tube (such as the pressure in the inside volume of the tire-tube) by means of a tire-tube assembly as discussed above is disclosed. The method comprises the steps of measuring the physical parameter and outputting a sensor signal by means of the sensor unit and carrying said sensor signal by means of said connector unit.

Brief Description of the Drawings

The invention will be better understood and objectives other than those set forth above will become apparent when consideration is given to the following detailed description of the invention. This description makes reference to the annexed drawings, wherein: Figure 1 shows a schematic representation of a tire-tube assembly 1 and a transmission unit 50 according to a first embodiment of the invention,

figure 2 shows a tire-tube assembly 1 and a positioning of a holder 20, a sensor unit 30, a connection unit 40, and an optional transmission unit 50 on a tire- tube 10 according to a second embodiment of the invention,

figure 3 shows a magnified view of the tire-tube assembly 1 from figure 2,

figure 4 shows a perspective representation of a tire-tube assembly 1 according to a third embodiment of the invention,

figure 5 shows a perspective representation of a holder 20, a sensor unit 30, and a connection unit 40 for manufacturing a tire-tube assembly 1 from a tire-tube (10) .

Modes for Carrying Out the Invention

Description of the Figures:

Figure 1 shows a schematic representation of a tire-tube assembly 1 according to a first embodiment of the invention. It should be noted that Figure 1 is only a schematic representation to visualize the different parts and flows of information of the tire-tube assembly 1 and that it is not drawn to scale, in particular with regard to a tire-tube 10.

A tire-tube 10, in particular a bicycle or pedelec tire-tube 10, has a substantially toroid shape around a symmetry axis z (pointing out of the xy plane) . A physical parameter p, in particular a pressure p in an inside volume 12 of the airtight (i.e., hermetically sealed) tire-tube 10 is measured by a sensor 31 (such as a S7912 sensor from MEAS Inc., Hampton, VA, USA) which is part of a sensor unit 30. The sensor unit 30 is mechanically connected to a holder 20 which is arranged on the tire-tube 10, specifically on an elastic tubular wall material 11 of the tire-tube 10. It should be noted that the positioning shown in figure 1 is only schematic. One of the holder's purposes is to affix the (rigid) sensor unit 30 to the (elastic) tire-tube 10; another purpose is mechanical protection of the sensor unit 30. A different localization option would be to arrange the holder 20 and the sensor unit 30 at a valve 13 which is used to inflate and/ or deflate the inside volume of the tire-tube 10. The sensor unit 30 comprises an optional op-amp 33 (dotted) and/ or an optional EEPROM 34 (dotted) and/ or an optional preprocessor 35 (dotted) such as, e.g., an analog-to-digital converter and/ or a microcontroller. The op-amp 33 is used to amplify an electrical sensor signal S from the sensor 31, the EEPROM 34 stores sensor- specific data that can be added to the sensor signal S (e.g., calibration curves for the sensor 31 and/ or a serial number) and the preprocessor 35 is used for sensor- signal-preprocessing. The sensor signal S is indicative of the magnitude of the measured physical parameter p, e.g., it comprises an analog voltage value which is directly proportional to the measured pressure in the inside volume 12 of the tire-tube 10. The sensor signal S is transferred to a connector unit 40, e.g., in this embodiment via a support 32 comprising a printed circuit board 32 onto which the sensor 31 and the op-amp 33 are soldered and/ or bonded. Thus, the connector unit 40 is electrically connected to the sensor unit 30 and carries the sensor signal S. The connector unit 40 comprises electrical contact plugs 41a (which could also comprise contact springs or similar) on which the sensor signal S can be tapped. Furthermore, the connector unit 40 comprises a snap-on or bayonet fixture 42a with which, e.g., a transmission unit 50 can be reversibly connected to the connector unit 40. Reversible connection in this respect means that the user can reversibly connect (i.e., elec- trically connect via the contact plugs 41a and 41b and mechanically connect via the fixtures 42a and 42b) the transmission unit 50 to the connector unit 40. The advan^¬ tage of utilizing a snap-on fixture 42a or a bayonet fixture 42a is that the connection and removal of the trans^¬ mission unit 50 from the connector unit 40 can be accomplished without tools.

Thus, the transmission unit 50 receives the sensor signal S from the sensor unit 30 via the connector unit 40. Then, the transmission unit 50 processes the sensor signal S, e.g., it first digitizes the sensor signal S with an analog-to-digital converter (ADC, not shown here) in the case that a digitization has not already been performed by the sensor unit 30. It then optionally performs one or more mathematical operations such as filtering, averaging, etc. This is achieved by a microcontroller ]iC with associated memory RAM. The transmission unit 50 then transmits a transmission signal T which is indicative of the sensor signal S and thus of the value of the measured physical parameter p. In this embodiment, the transmission signal T is a digital RF signal at 2.4 GHz which is transmitted over a wireless link L by a transceiver 52. The wireless link L and the transmission signal T are implemented according to the ANT+ standard (see http://www.thisisant.com and references cited therein for further information, accessed 29 June 2011) or according to the low power Bluetooth standard (http://www.bluetooth.com and the URLs cited therein, accessed July 12, 2011). For powering the different electronic components (i.e., the transmission unit 50 and the sensor unit 30) , the transmission unit 50 comprises a power supply 51. Here, the power supply 51 comprises a user-replaceable battery 51, i.e., a battery such as a CR2032 battery that can be replaced or recharged by the user, ideally without using tools. The power supply 51 can also comprise a motion detector (e.g., a vibrational switch) which powers down at least some of the electronic components as long as no movement or rotation is detected. As soon as the motion detector detects a motion, rotation, or vibration - or on reception of a wake-up signal (see below) - the components will be powered up again .

Besides the encoded tire-pressure value (or more generally speaking, the physical parameter (s) , the transmission signal T can also comprise additional information such as, e.g., state of the power supply 51 (or charge level of the battery) , a serial number of the devices, a sensor ID (e.g., for front-/rear-tire identification) , etc. Since the transmission unit 50 comprises a transceiver 52, it can also receive configuration parameters, wake-up and/ or sleep signals (for saving battery power), operating parameters/ modes, etc. from a display- or control-unit. Such a display-, recording- or control-unit can be implemented, e.g., as a smartphone app such as an iPhone app , it can be implemented in a bicycle computer or a wristwatch (just to name a few possibilities) . Generally, it displays the measured pressure values to the user and can, e.g, trigger an alarm in case that a certain pressure threshold is exceeded or under- run.

It should be noted that the connector unit 40 can also comprise two parts wherein the first part of the connector unit 40 is affixed on the sensor unit 30 and wherein the second part of the connector unit 40 is affixed to the transmission unit 50. The reversible electrical and mechanical connection between the sensor unit 30 and the transmission unit 50 is then again establish- able by means of the two-parted connector unit 40. Furthermore, at least a part of the connector unit 40 can be formed by the support 32.

The transmission unit 50 and the sensor unit 30 are separable devices that can be reversibly connected by means of the connector unit 40. Thus, it is economically attractive to produce the tire-tube assembly 1 comprising the tire-tube 10, the holder 20, the sensor unit

30, and the connector unit 40 as a package that is sold to the customer. For transmitting the transmission signal T, the customer then connects the transmission unit 50 to the tire-tube assembly (specifically to the sensor unit 30 via the connector unit 40) . In the case of a flat tire, the customer can remove the (more expensive) transmission unit 50 from the (cheaper) tire-tube assembly 1 (including the holder 20 and the sensor unit 30) . He can then replace the tire-tube assembly 20 with a new tire- tube assembly and reconnect and reuse the transmission unit 50.

Figure 2 shows a tire-tube assembly 1 and a positioning of the holder 20, the sensor unit 30, the connection unit 40, and an optional transmission unit 50 on a tire-tube 10 according to a second embodiment of the invention. In this embodiment, the tire-tube 10 is again of substantially toroid shape around an axis of revolution z and it comprises a valve 13 at a first location 101 (in figure 2 at a rotation angle of <pi=0° at the 12 o'clock position). To minimize unbalanced masses, the position of the holder 20, the sensor unit 30, and the connector unit 40 are preferably located "opposite" the valve 13, i.e., at a rotation angle q>2=180° (cf. second location 102 at 6 o'clock). Alternative positioning locations on the "other side of the valve 13" (cf. hatched area) between 9 o'clock (cp2=90°) and 3 o'clock (cp2=270°) are possible as well. In this embodiment, the holder 20 covers and hermetically seals an opening 14 (i.e., a hole) in the wall material 11 of the tire-tube 10. By communicating with the opening 14, the pressure sensor 31 of the sensor unit 30 can directly (optionally via a layer of soft material covering the actual die of the sensor

31, see below) measure the pressure p in the inside vol- ume 12 of the tire-tube 10. An alternative positioning of the holder 20, the sensor unit 30, and the connector unit 40 at the valve 13 is shown in figure 2 with dotted lines .

Figure 3 shows a magnified view of the tire- tube assembly 1 from figure 2 denoted by the dotted rectangle. Here, it is obvious that the sensor 31 of the sensor unit 30 communicates with the opening 14 and can directly measure the pressure p of the inside volume 12 of the tire-tube 10. An optional thin (see below) membrane 15 (dotted) can be used to cover the opening 14, thus leading to an indirect measurement of the pressure via transferred pressure changes through the membrane 15 (see above) . The sealed volume 21 between the membrane 15 and the sensor 31 can be filled with a soft silicone gel like Dow Corning Sylgard 527 that mechanically protects the sensor 31 and its bonding wires with which the sensor is electrically connected to a support 32. The membrane 15 can be produced thin enough as not to deteriorate measurement precision to a large degree and it helps to avoid contamination of the sensor 31 from the inside volume 12 of the tire-tube 10, e.g., from thin slices of material from the wall material 11 or moisture. The remaining reference numbers denote the same parts as in figures

I and 2.

Figure 4 shows a perspective representation of a tire-tube assembly 1 according to a third embodiment of the invention. The holder 20 (shown in sectioned view for clarity) has an elastic modulus which is similar (see below) to an elastic modulus of the tubular wall material

II and it is vulcanized onto the wall material 11 of the tire-tube 10. The holder 20 is mechanically connected to the sensor unit 30 comprising a pressure sensor 31 and a support 32. Similar to the second embodiment, the holder 20 covers and seals an opening 14 in the wall material 11 of the tire-tube 10. The sensor 31 communicates with this opening 14 and directly measures the pressure p in the inside volume 12 of the tire-tube 10. It then outputs a sensor signal S which is conducted on tracks on a printed circuit board (serving as support 32) to the contact plugs 41a (hatched) of the connection unit 40. The snap- on fixture 42a provides mechanical connectibility to an optional transmission unit 50 (not shown) .

Figure 5 shows a holder 20 with sensor unit

30 and connector unit 40 of the same design as in the third embodiment discussed above in figure 4. These parts are connectable (e.g., via vulcanization) to a regular tire-tube 10 without sensors, thus providing an easy way to manufacture a tire-tube assembly 1 as disclosed above. Specifically, a pressure sensor 31 is sealed airtight in the holder 20 as shown in figure 4. The pressure sensor

31 outputs a sensor signal S which is tappable on the contact plugs 41a (hatched) of the connector unit 40 (which is in part formed by the support 32) . The snap-on fixture 42a provides mechanical connectibility to an optional transmission unit 50 (not shown) . The remaining reference numbers denote the same parts as in figures 4.

Definitions :

The term "membrane" 15 refers to a patch of material that is substantially thinner (i.e., at least by a factor of two) than the wall material 11 of the tire- tube 10. Typical wall-material-thicknesses are 0.45 to 1 mm, typical membrane thicknesses are below 0.225 mm or 0.5 mm, respectively. In theory, a measurement without opening 14 and membrane 15 is possible as well by attaching the sensor unit 30 to the wall material 11, but higher measurement errors might occur in such an embodiment .

The term "outside surface" of the tubular wall material 11 of the tire-tube 10 relates to the surface of the tire-tube wall that does not face the pres- surized enclosed inside volume 12 but the outside world. When the tire-tube is mounted in an, e.g., bicycle tire, the outside surface is in contact with the outer casing and the rim.

The term "symmetry axis z" with regard to a toroid or toroidal shape refers to an axis of revolution around which a plane geometrical figure is revolved when the toroid is created.

The term "module of elasticity" (sometimes also called "elastic modulus") of a material relates to its elastic (i.e., non-permanent) stretchability or elastic deformation under stress. A "similar" elastic modulus relates to two elastic moduli that do not differ by more than 50% of the larger value.

The term "RF-link (L) " relates to a wireless link by which information is sent from a transmitter (52) to a receiver. RF-links typically operate in the frequency-range ,between 3 kHz and 300 GHz.

Tube-based tires are frequently used in bicycles, pedelecs, or other (typically two-wheeled) vehicles and comprise an inner "tire-tube" (often also referred to as "inner tube") and an outer casing (often also referred to as "tyre") .

Notes :

Typical pressure ranges that are to be measured by means of the tire-tube assemblies disclosed above are 0 to 12 bars in bicycle, pedelec, or e-bike tube- based tires.

The holder/sensor unit/connector unit combination ("sensor patch") is not designed to be taken off the tire-tube. Instead, tire-tubes assemblies comprising such a sensor patch are sold as an integral unit. Alternatively, such a sensor patch can be sold separately to enable a customer to manufacture his own tire-tube assembly: Then, the customer would punch a small hole (open- ing) into an existing tire-tube (ideally opposite the valve) and reseal this opening with the sensor patch, e.g., by vulcanization. A small weight that is screwed onto the valve can be sold with the sensor patch to reduce unbalanced masses.

The transmission unit can be mounted in a polymeric or silicone housing for mechanical protection and protection against environmental influences.

In a typical implementation, a pressure sensor 31 comprises a semiconductor die with the actual sensing elements. This die is typically coated with a layer of soft material such ^' as Dow Corning Sylgard 527 (which is also regarded as a part of the sensor 31) for protection of the die and the bonding wires that electrically connect the sensor 31. Nevertheless, if the sensor 31 stands in direct gas exchange with the inside volume of the tire-tube (e.g., via an opening 14 in the wall material 11) as described above, the measurement of the pressure is still referred to as a "direct measurement" of the pressure. The coating of the die of the sensor 31 should therefore not be confused with an optional additional membrane 15 covering the opening 14 in the wall material 11. Such a membrane 15 is not part of the sensor 31. In such an embodiment, the sealed volume 21 between the membrane 15 and the sensor 31, can at least be partly filled with the soft material (e.g., Dow Corning Sylgard 527) from the sensor 31.

As described above, the sensor unit 30 can additionally to the sensor 31 comprise a preprocessor 35 comprising, e.g., a microcontroller and an analog-to- digital converter for the sensor signal S. Then, the microcontroller μC on the transmission unit 50 can be reduced in functionality or even completely replaced by the preprocessor 35 on the sensor unit 30. Furthermore, a sensor serial number and/ or calibration data can be stored in an optional EEPRO 34 on the sensor unit 30 and included in the sensor signal S. While the (disposable) sensor unit 30 becomes slightly more expensive with such steps, added functionality like sensor calibration procedures are available in such embodiments.

While there are shown and described presently preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited to these embodiments but may be otherwise variously embodied and practiced within the scope of the following claims.

Claims

1. A tire-tube assembly (1) comprising a hermetically sealed tire-tube (10) made of an elastic tubular wall material (11) which encloses an inside volume (12),

at least one holder (20) arranged on said tire-tube (10),

at least one sensor unit (30) comprising a sensor (31) and mechanically connected to said holder (20) and adapted to measure a physical parameter (p) of said tire-tube (10) and to output an electrical sensor signal (S) indicative of a magnitude of said physical parameter (p) ,

a connector unit (40) electrically connected to said sensor unit (30) and carrying said sensor signal (S)^".

2. The tire-tube assembly (1) of claim 1 wherein said physical parameter (p) is a pressure in said inside volume (12) of said tire-tube (10) and wherein said sensor unit (30) comprises a pressure sensor (31).

3. The tire-tube assembly (1) of any of the preceding claims wherein said sensor unit (30) comprises an analog sensor (31) and/ or wherein said sensor signal (S) is an analog signal.

4. The tire-tube assembly (1) of any of the preceding claims wherein said holder (20) , said sensor unit (30), and said connector unit (40) are arranged on an outside surface of said tubular wall material (11) , wherein said outside surface faces away from said inside volume (12) of said tire-tube (10) .

5. The tire-tube assembly (1) of any of the preceding claims wherein said holder (20) covers an opening (14) in said wall material (11) of said tire-tube (10) , wherein said sensor unit (30) communicates with said opening (14).

6. The tire-tube assembly (1) of claim 5 wherein said opening (14) is covered by a membrane (15) , and wherein said membrane (15) is thinner than the wall material (11) of the tire-tube (10) by at least a factor of two.

7. The tire-tube assembly (1) of any of the preceding claims wherein said tire-tube (10) has a substantially toroid shape about a symmetry axis (z) and comprises a valve (13) at a first location (101) of said tire-tube (10) for inflating and/ or deflating said tire- tube (10),

wherein said holder (20) is arranged at a second location (102) of said tire-tube (10),

wherein said first location (101) is arranged at a first rotation angle cpi=0° around said symmetry axis, and

wherein said second location (102) is arranged at a second rotation angle 90°<cp2<270° around said symmetry axis (z), in particular at a rotation angle cp₂=180° .

8. The tire-tube assembly (1) of claim 7 wherein said holder (20) faces said symmetry axis (z) of said tire-tube (10) .

9. The tire-tube assembly (1) of any of the claims 1 to 6 wherein said tire-tube (10) has a substantially toroid shape and comprises a valve (13) for inflating and/ or deflating said tire-tube (10) and wherein said holder (20) and said sensor unit (30) are arranged at said valve (13) .

10. The tire-tube assembly (1) of any of the preceding claims wherein said sensor unit (30) comprises a support (32), wherein said sensor (31) is arranged on said support (32), and wherein said support (32) is made of a material with a module of elasticity which is higher, in particular at least 10 times higher, than the module of elasticity of said wall material (11) .

11. The tire-tube assembly (1) of claim 10 wherein said connector unit (40) is at least in part formed by said support (32).

12. The tire-tube assembly (1) of any of the preceding claims wherein said holder (20) is made of a material with a module of elasticity in the range of 50% to 150% of a module of elasticity of said wall material (11).

13. The tire-tube assembly (1) of any of the preceding claims wherein said connector unit (40) comprises electrical contact plugs (41a) and/ or a snap-on fixture (42a) and/ or a bayonet fixture (42a) .

14. The tire-tube assembly (1) of any of the preceding claims further comprising a transmission unit (50) adapted to receive said sensor signal (S) from said sensor unit (30), to process said sensor signal (S), and to output a transmission signal (T) indicative of said sensor signal (S) ,

wherein an electrical and mechanical connection between said sensor unit (30) and said transmission unit (50) is reversibly establishable by means of said connector unit (40), and

wherein when said connection is established, said connector unit (40) is adapted to transfer said sensor signal (S) from said sensor unit (30) to said transmission unit (50) .

15. The tire-tube assembly (1) of claim 14 wherein said transmission signal (T) is a digital signal.

16. The tire-tube assembly (1) of any of the claims 14 or 15 wherein said transmission unit (50) comprises a power supply (51) for powering said transmission unit (50) and said sensor unit (30).

17. The tire-tube assembly (1) of any of the claims 14 to 16 wherein said power supply (51) is a battery, in particular a user-replaceable battery.

18. The tire-tube assembly (1) of any of the claims 14 to 17 wherein said transmission unit (50) comprises a transceiver (52) or a transmitter (52) which is adapted to transmit said transmission signal (T) over a wireless link (L) , in particular an RF-link (L) .

19. The tire-tube assembly (1) of claim 18 wherein said wireless link (L) and/ or said transmission signal (T) is/ are implemented according to the Bluetooth-standard and/ or the ANT or ANT+ protocol.

20. The tire-tube assembly (1) of any of the preceding claims, wherein said sensor unit (30) additionally comprises one or more of the group of an amplifier (33), a memory (34), and a preprocessor (35).

21. A kit for manufacturing a tire-tube assembly (1) according to any of the preceding claims from a tire-tube (10), the kit comprising

at least one holder (20) connectable to a tire-tube (10) ,

a connector unit (40) electrically connected to said sensor unit (30) and carrying said sensor signal (S) .

22. A method for measuring at least one physical parameter (p) of a tire-tube (10) using a tire- tube assembly (1) of any of the claims 1-20.