Monopole antenna for automotive vehicle wheel unit

Abstract

The invention relates to a monopole antenna (1) for a motor vehicle wheel unit, comprising a first end (10), a second floating end (20), and a body (30), the first end (10) extending in a first plane (P1) and comprising a feed lug (110) and a support foot (120), the body (30) comprising a connecting wall (310), extending from the first end (10) in a second plane (P2) perpendicular to the first plane (P1) and connecting the feed lug (110) and the support foot (120) by defining a recess (312), and a main portion (315) extending from the connecting wall (310) to the second end (20), the body (30) being configured so that the center of gravity of the antenna (1) is substantially at the right of the support foot (110). Figure for the abbreviation: Figure 1

Description

Title of the invention: Monopole antenna for a motor vehicle wheel unit. Technical field

[0001] The present invention relates to the automotive field and more particularly concerns a monopole antenna for a wheel unit of an automobile vehicle. Prior art

[0002] It is now known to equip motor vehicles with a sensor in each wheel in order to measure the air pressure inside the tire, or even its temperature or the acceleration of the wheel, and to communicate these measurements to an electronic control unit of the vehicle to inform the driver, for example in the event of a drop in air pressure in one of the wheels.

[0003] An antenna is used to transmit measurements from the sensor, called the wheel unit, to the electronic control unit. This antenna is mounted on an electrically powered printed circuit board.

[0004] The wheel unit communicates with the electronic control unit via the antenna at frequencies of 315 MHz and 433 MHz or according to a communication protocol allowing bidirectional data exchange over short distances using ultra-high frequency (UHF) radio waves, such as, for example, the Bluetooth® Low Energy (BLE) protocol at 2.4 GHz. A Bluetooth® Low Energy type interface advantageously allows bidirectional communication and also communication with a smartphone.

[0005] To communicate at 315 MHz or 433 MHz, wheel units typically use loop antennas. These loop antennas are made of folded metal and have two connection points to the printed circuit board. The loop antennas currently used at 315 MHz and 433 MHz have low efficiency at these frequencies, on the order of 1%, but wave propagation at these frequencies on a vehicle is more favorable than at 2.4 GHz because it results in fewer losses. Therefore, at 2.4 GHz, the antenna efficiency must be improved to compensate for these propagation losses, which requires a larger antenna to be sufficiently effective. This is not always suitable for applications in motor vehicles where space for this type of equipment is limited.

[0006] In order to remedy at least some of these drawbacks, it is known to use monopole antennas for a 2.4 GHz application, these antennas making it possible to obtain the best performance at this frequency. However, such an antenna is more Because it has only one connection point, the antenna is prone to deformation under centrifugal force during wheel rotation, making it less rigid. These deformations while driving lead to variability in the transmission of messages to the electronic control unit. Furthermore, these antennas can break after numerous cycles of deformation while the vehicle is in motion.

[0007] Furthermore, components are usually used to perform the matching function between the antenna and the printed circuit board. Communication technology enabling bidirectional data exchange over short distances using ultra-high frequency (UHF) radio waves, such as Bluetooth® Low Energy, requires the use of more components compared to an antenna operating at 315 MHz and 433 MHz. However, it is necessary to limit the size of the printed circuit board to meet the constraints of using the wheel unit, which consist of reducing the size and mass of the components to withstand centrifugal forces. These constraints make the design and integration of an efficient and stable Bluetooth® Low Energy antenna all the more difficult.

[0008] A simple, reliable and effective solution that would at least partially remedy these drawbacks would therefore be advantageous. Description of the invention

[0009] To this end, the invention first relates to a monopole antenna for a wheel unit of a motor vehicle, said wheel unit comprising a printed circuit board connected to a power supply and to at least one sensitive element for measuring at least the air pressure inside the wheel tire, said antenna comprising a first end, a second end and a body extending between said first end and said second end, the second end being intended to remain electrically free-floating, the antenna being notable in that:

[0010] - the first end extends in the foreground and includes a leg a power supply, configured to be fixed to said printed circuit board so as to form a first mechanical connection with the board and to be electrically powered by said power supply via said printed circuit board, and a support foot, configured to be fixed to the printed circuit board so as to form a second mechanical connection with the board,

[0011] - the body comprises a connecting wall, extending from the first end in a second plane perpendicular to the first plane and connecting the power supply leg and the support foot by defining a recess between said power supply leg and said support foot, and a main portion extending from the connecting wall to the second end, the body being configured so that the The center of gravity of the antenna is located approximately directly above the support foot, preferably directly above the middle of the support foot.

[0012] The second end is configured to be electrically floating, thus making the antenna a monopole, thereby exhibiting better radio frequency efficiency compared to loop antennas, particularly at 2.4 GHz. The radio frequency efficiency is thus greater than or equal to 60%. The antenna according to the invention is therefore a monopole antenna having at least two mounting points on the printed circuit board, which allows it to be securely fixed to the board and thus withstand the accelerations of several hundred g that the rotating wheels of a vehicle can experience. Furthermore, by being located at the center of gravity of the antenna, the support foot provides significant stability to the antenna, particularly before it is fixed, for example by soldering, and during wheel rotations.The antenna essentially has an open loop shape, allowing the second end to be brought back to the plane of the first end, thus saving space when mounting the antenna in a small wheel unit.

[0013] Preferably, the antenna is in the form of a single piece of electrically conductive metal so as to be easy to manufacture and inexpensive in the case where the metal is of the type steel or iron or other inexpensive metal or alloy of metals.

[0014] In one embodiment, the antenna further comprises a plating made on the metal piece, preferably a metallic plating, for example in tin.

[0015] According to one aspect of the invention, the portion of material delimiting the recess between the power supply leg and the support foot is configured to adapt the impedance of the antenna to the impedance of the printed circuit board, in particular at the output of the integrated component (BLE), for example of 50 Q, in order to avoid adding an impedance matching stage on the printed circuit board.

[0016] Preferably, the edge of the connecting wall delimiting the recess has a concave shape, preferably a U-shape, making the recess convex, which makes the antenna easy to manufacture.

[0017] In one embodiment, the support foot comprises a longitudinal portion extending in the foreground and at least one transverse portion, extending from said longitudinal portion, preferably perpendicular to said longitudinal portion, also in the foreground.

[0018] For example, the support foot may advantageously have a T, h or H shape in order to provide sufficient stability.

[0019] In one embodiment, the second end is intended to and configured to remain free, i.e. not to be fixed on the printed circuit board.

[0020] In one embodiment, the second end comprises an arm extending towards the first end in a direction parallel to the second plane.

[0021] Advantageously, the arm is in the form of a plate extending in the same plane as the connecting wall. This makes it possible, in particular, to maintain a constant distance between the mass and the arm and to reduce the tolerance by eliminating the thickness of the solder paste, the tolerance arising solely from the dimensions of the antenna.

[0022] In one embodiment, the second end extends in the same plane as the first end (i.e. in the first plane) and is configured to be fixed to the printed circuit board, for example in the form of a fixing tab.

[0023] In one embodiment, the main portion includes a central portion extending perpendicularly from the connecting wall and parallel to the foreground.

[0024] In one embodiment, the main portion includes an oblique portion extending obliquely from the central portion towards the foreground.

[0025] In one embodiment, the main portion includes a reinforcing wall extending from at least a part of an edge of the central portion and / or the oblique wall.

[0026] In one embodiment, the main portion includes an intermediate portion connecting the oblique portion to the second end.

[0027] Advantageously, the central portion and / or the oblique portion and / or the intermediate portion include at least one stiffening, for example of the rib type.

[0028] The invention also relates to a wheel unit for a motor vehicle, said wheel unit comprising a power supply, a printed circuit board connected to said power supply, at least one sensitive element configured to measure at least the air pressure inside the wheel tire and a monopole antenna as previously described.

[0029] According to one embodiment, the printed circuit board includes in particular an electronic component to enable communication of the antenna according to a communication protocol allowing bidirectional exchange of data over short distances using ultra-high frequency or UHF radio waves.

[0030] In one embodiment, the printed circuit board includes in particular a Bluetooth® Low Energy electronic component to enable antenna communication according to the Bluetooth® Low Energy protocol.

[0031] The invention also relates to a motor vehicle comprising at least one wheel unit as presented above, mounted in at least one of the wheels of the vehicle. Brief description of the drawings

[0032] Other features and advantages of the invention will become apparent from the following description. This description is purely illustrative and should be read in conjunction with the accompanying drawings, in which:

[0033] [Fig-1] Fig. 1 schematically illustrates a first embodiment of the antenna according to the invention.

[0034] [Fig.2] The [Fig.2] is another perspective view of the antenna of the [Fig.1].

[0035] [Fig.3] The [Fig.3] is another perspective view of the antenna of the [Fig.1].

[0036] [Fig.4] Fig.4 schematically illustrates a second embodiment of the antenna according to the invention.

[0037] [Fig.5] Fig.5 schematically illustrates a third embodiment of the antenna according to the invention.

[0038] [Fig.6] The [Fig.6] is another perspective view of the antenna of the [Fig.5].

[0039] [Fig.7] Fig.7 schematically illustrates a fourth embodiment of the antenna according to the invention.

[0040] [Fig.8] The [Fig.8] is another perspective view of the antenna of the [Fig.7]. Description of the implementation methods

[0041] Figures 1 to 8 illustrate four examples of a monopole antenna according to the invention.

[0042] The monopole antenna 1 is configured for use in a motor vehicle wheel unit.

[0043] Such a wheel unit makes it possible to measure the air pressure inside the wheel and to send these measurements to an electronic control unit of the vehicle, in a manner known per se. The wheel unit can also, for example, measure the air temperature inside the tire and / or the wheel acceleration.

[0044] The wheel unit comprises a printed circuit board connected to a power supply and a sensitive element for measuring the air pressure values ​​contained in the wheel. The power supply may, for example, be a button cell battery.

[0045] The printed circuit board includes in particular an electronic component to enable communication of the antenna according to a communication protocol allowing bidirectional exchange of data over short distances using ultra-high frequency or UHF radio waves and for example a Bluetooth® Low Energy electronic component to enable communication of the antenna 1 according to the Bluetooth® Low Energy protocol.

[0046] The antenna 1 is a single piece and is made from the same electrically conductive material, for example a metal such as steel, aluminum, iron or copper.

[0047] The antenna 1 comprises a first end 10, a second end 20 and a body 30 extending between said first end 10 and said second end 20 in a longitudinal direction DL.

[0048] The first end 10 extends in a first plane PI, in this example parallel to the longitudinal direction DL of the antenna 1. The first plane PI and the longitudinal direction DL have only been shown on some figures for clarity.

[0049] The first end 10 includes a power supply leg 110 and a support leg 120.

[0050] The power supply pin 110 is configured to be fixed to said printed circuit board, for example by soldering, so as to form a first mechanical connection with the board. The power supply pin 110 is configured to be electrically powered by the power supply of the wheel unit via the printed circuit board.

[0051] The support foot 120 is configured to be fixed to the printed circuit board, for example by soldering, so as to form a second mechanical link with the board.

[0052] In the various embodiments illustrated in the figures, the support foot 120 has an h-shaped form and comprises a longitudinal portion 121 extending in the plane of the first end 10 along the longitudinal direction DL of the antenna 1 and two transverse portions 122 extending perpendicularly from said longitudinal portion 121, each in an opposite direction.

[0053] The body 30 includes a connecting wall 310 extending perpendicularly from the first end 10 in a second plane P2 and connecting the power supply leg 110 and the support foot 120 by defining on one of its edges 311 connecting said power supply leg 110 and said support foot 120 a recess 312 between the power supply leg 110 and the support foot 120. The second plane P2 has only been shown in some figures for clarity.

[0054] The shape and dimensions of the recess 312 are configured to match the impedance of the antenna 1 to the impedance of the printed circuit board. In other words, the volume and shape of the gap between the feed pin 110 and the support foot 120 are calculated so that the impedance of the antenna 1 is matched to the output impedance of the component enabling antenna communication according to a communication protocol allowing bidirectional data exchange over short distances using ultra-high frequency (UHF) radio waves, such as a Bluetooth® Low Energy electronic component. The shape and dimensions of the recess 312 provide capacitive and inductive effects that allow the impedance of the antenna 1 to be matched to the output impedance of the Bluetooth® Low Energy electronic component.For example, if the impedance of antenna 1 is to be 50 ohms, then the shape and dimensions of the recess 312 are chosen to achieve 50 ohms, for example by empirical testing.

[0055] In the various embodiments illustrated in the figures, the edge 311 delimiting the recess 312 has a concave U-shaped form, giving a convex shape to the recess 312.

[0056] The body 30 comprises a main portion 315 extending from the connecting wall 310 to the second end 20.

[0057] In the non-limiting examples of the figures, the main portion 315 comprises a central portion 320 and an oblique portion 330.

[0058] The central portion 320 extends perpendicularly to the connecting wall 310 and parallel to the first plane PI of the first end 10.

[0059] The oblique portion 330 extends obliquely in the direction of the first plane PI from the first end 10 to the second end 20.

[0060] The first end 10, the body 30 and the second end 20 form an open loop.

[0061] The body 30 is configured so that the center of gravity of the antenna 1 is located substantially directly above the support foot 120, preferably substantially directly above the middle of the support foot 120, in order to ensure significant stability of the antenna 1 when said antenna 1 is mounted on the printed circuit board.

[0062] The second end 20 is electrically floating when the antenna 1 is mounted on the printed circuit board, i.e. it is not electrically connected to another element.

[0063] In the first embodiment illustrated in Figures 1 to 3 and in the second embodiment illustrated in [Fig.4], the second end 20 is intended to remain free when the antenna 1 is mounted on the printed circuit board.

[0064] In both of these embodiments, the second end 20 comprises an arm 21 extending in the direction of the first end 10 in a direction parallel to the first plane PI of the first end 10.

[0065] The arm 21 is formed by a return of flat material which is in the form of a plate extending in the same plane as the connecting wall 310, namely the second plane P2.

[0066] In the third embodiment illustrated in Figures 5 and 6 and in the fourth embodiment illustrated in Figures 7 and 8, the second end 20 is in the form of a mounting tab 22 extending in the same plane as the first end 10, namely the first plane PL. The mounting tab 22 is configured to be fixed to the printed circuit board, for example by soldering.

[0067] In the second embodiment illustrated in [Fig. 4], the body 30 further comprises a reinforcing wall 340 extending in the second plane P2 of the connecting wall 310 along the central portion 320. This reinforcing wall 340 could also be present in other embodiments. Similarly, other types Reinforcing elements could be used in all forms of embodiment, such as for example a stiffener formed along the longitudinal median part of the central portion 320 and / or the oblique portion 330.

[0068] In the four embodiments illustrated in the figures, the body 30 includes an intermediate portion 350 connecting the oblique portion 330 and the second end 20. The intermediate portion 350 extends parallel to the first plane PI of the first end 10 and allows the shape of the antenna 1 to be adapted geometrically, in particular the positioning of the second end 20 with respect to the rest of the antenna 1 and in particular with respect to the connecting wall 310.

[0069] The invention therefore makes it possible to produce an efficient monopole antenna for a wheel unit which can be securely fixed to the printed circuit board while simply allowing impedance matching to the output impedance of the BLE component.

Claims

Demands

1. Monopole antenna (1) for a motor vehicle wheel unit, said wheel unit comprising a printed circuit board connected to a power supply and to at least one sensing element for measuring at least the air pressure inside the wheel tire, said antenna (1) comprising a first end (10), a second end (20) and a body (30) extending between said first end (10) and said second end (20), the second end (20) being intended to remain electrically floating, the antenna (1) being characterized in that: - the first end (10) extends in a first plane (PI) and comprises a power supply tab (110), configured to be fixed to said printed circuit board so as to form a first mechanical connection with the board and to be electrically powered by said power supply via said printed circuit board, and a support foot (120),configured to be fixed to the printed circuit board so as to form a second mechanical link with the board, - the body (30) comprises a connecting wall (310), extending from the first end (10) in a second plane (P2) perpendicular to the first plane (P1) and connecting the feed pin (110) and the support foot (120) by defining a recess (312) between said feed pin (110) and said support foot (120), and a main portion (315) extending from the connecting wall (310) to the second end (20), the body (30) being configured so that the center of gravity of the antenna (1) is substantially directly above the support foot (110).

2. Antenna (1) according to claim 1, wherein the edge (311) of the connecting wall (310) delimiting the recess (312) has a concave shape, preferably a U-shape.

3. Antenna (1) according to any one of the preceding claims, wherein the support foot (120) comprises a longitudinal portion (121) extending in the first plane (PI) and at least one transverse portion (122), extending from said longitudinal portion (121) also in the first plane (PI).

4. Antenna (1) according to any one of the preceding claims, wherein the second end (20) comprises an arm (21) extending towards the first end (10) in a direction parallel to the second plane (PI).

5. Antenna (1) according to the preceding claim, wherein the arm (21) is in the form of a plate extending in the same plane (P2) as the connecting wall (310).

6. Antenna (1) according to any one of the preceding claims, wherein the second end (20) extends in the same plane (PI) as the first end (10) and is configured to be fixed to the printed circuit board.

7. Antenna (1) according to any one of the preceding claims, wherein the main portion (315) comprises a central portion (320) extending perpendicularly from the connecting wall (310) and parallel to the foreground (PI).

8. Antenna (1) according to the preceding claim, wherein the main portion (315) comprises an oblique portion (330) extending obliquely from the central portion (320) in the direction of the foreground (PI).

9. Antenna (1) according to any one of claims 7 or 8, wherein the main portion (315) comprises a reinforcing wall (340) extending from at least a part of an edge of the central portion (320) and / or the oblique wall (330).

10. Antenna (1) according to any one of the preceding claims, wherein the main portion (315) comprises an intermediate portion (350) connecting the oblique portion (330) to the second end (20).

11. Wheel unit for motor vehicle, said wheel unit comprising a power supply, a printed circuit board connected to said power supply, at least one sensing element configured to measure at least the air pressure inside the wheel tire, and a monopole antenna (1) according to any one of the preceding claims.

12. Motor vehicle comprising at least one wheel unit according to the preceding claim, mounted in at least one of the wheels of the vehicle.

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