CONTACTLESS SENSOR FOR VEHICLE DIGITAL COMMUNICATIONS NETWORK

Abstract

A sensor 1 is arranged to read data transmitted on a digital vehicle network. The sensor comprises a wire holding unit 3, and a sensing unit 5. The wire holding unit and sensing unit are connectable to one another, the sensor further comprising a locking mechanism to lock the wire holding unit and the sensing unit together, when the wire holding unit and sensing unit are connected to one another.

Claims

1-21. (canceled)

22. A sensor for reading messages transferred over a digital communications network of a vehicle, the sensor comprising: a wire holding unit arranged to hold one or more wires of the network; and a sensing unit comprising: sensing means for detecting messages carried by the one or more wires using capacitive and/or inductive coupling; and processing means for generating digital output signals indicative of messages detected by the sensing means, wherein the wire holding unit and sensing unit are connectable to one another, the sensor further comprising locking means for, when the wire holding unit and the sensing unit are connected to one another, locking the wire holding unit and the sensing unit together.

23. The sensor of claim 22, wherein the wire holding unit comprises, for each of the one or more wires to be held, means for locating the wire relative to the wire holding unit, and means for retaining the wire such that it is securely attached to the wire holding unit.

24. The sensor of claim 22, wherein the wire holding unit further comprises means for biasing the wire into engagement with a respective sensing element of the sensing unit when the wire holding unit is connected to the sensing unit in use.

25. The sensor of claim 22, wherein the wire holding unit is configured to hold first and second wires of a digital vehicle network.

26. The sensor of claim 22, wherein the sensor is a capacitive sensor comprising one or more sensing element, the or each sensing element being a capacitive coupling element arranged to form a capacitive coupling with a respective wire held by the wire holding unit in use.

27. The sensor of claim 22, wherein one of the wire holding unit and the sensing unit comprises a plurality of hooks, and the other one of the wire holding unit and the sensing unit comprises a plurality of notches, wherein each hook is received by a respective notch to lock the wire holding unit and sensing unit together in use.

28. The sensor of claim 27, wherein the plurality of hooks are provided on the sensing unit and the notches are provided on the wire holding unit.

29. The sensor of claim 22, where the locking means comprise a releasable locking mechanism to permit the wire holding unit and the sensing unit to be disconnected from one another.

30. The sensor of claim 22, wherein the digital communications network has at least two states, wherein information in a message transferred over the network is represented by the state of the network, and wherein the processing means comprises a set of one or more digital logic gates to generate the digital output signals, which are indicative of the changing state of the network detected by the sensing means.

31. A sensor for reading messages transferred over a digital communications network of a vehicle, wherein the network has at least two states, and wherein information in a message transferred over the network is represented by the state of the network, the sensor comprising: wire holding means for holding one or more wires of the network; sensing means for detecting messages carried by the one or more wires using capacitive and/or inductive coupling; and processing means comprising a set of one or more digital logic gates for generating digital output signals indicative of the changing state of the network detected by the sensing means.

32. The sensor of claim 31, wherein the logic gates comprise one or more inverters.

33. The sensor of claim 31, wherein the sensor is arranged to sense signals transmitted on first and second wires of the digital vehicle network, and the processing means is arranged to obtain the one or more digital output signals based on a determined differential between signals transmitted on the first and second wires.

34. The sensor of claim 33, wherein the sensor comprises a comparator for detecting a differential between signals transmitted on the first and second wires.

35. The sensor of claim 34, wherein: a positive feedback is applied to the comparator; and a bias voltage is applied to the inputs of the comparator, such that the output of the comparator indicates the latest state of the network.

36. The sensor of claim 34, wherein the one or more digital logic gates operate on the output of the comparator.

37. A system for reading messages transferred over a digital communications network of a vehicle, the system comprising: a first housing comprising one or more clips configured to independently hold in place one or more wires of the network; a second housing comprising a sensing element configured to detect messages carried by the one or more wires using capacitive and/or inductive coupling, wherein each of the first housing and the second housing further comprise reciprocally cooperating elements configured to selectively lock the first housing and the second housing together; and one or more processors configured to generate digital output signals indicative of the detected messages.

38. The system of claim 37, further comprising a telemetric device electrically and communicatively linked to the one or more processors.

39. The system of claim 37, wherein the first housing comprises, for each of the one or more wires, a channel for receiving the respective wire.

40. The system of claim 37, wherein the first housing comprises, for each of the one or more wires, one or more clips configured to retain the respective wire such that it is securely retained within the first housing.

41. The system of claim 37, wherein the first housing comprises, for each of the one or more wires, a resilient strip for biasing the wire into engagement with a respective sensing element of the second housing when the first housing is connected to the second housing in use.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Some preferred embodiments of the present invention will now be described, by way of example only, and with reference to the accompanying drawings, in which:

[0062] FIG. 1 is a perspective view of a sensor in accordance with an embodiment of the invention, including a wire holding unit and a sensing unit, showing the wire holding unit attached to a pair of wires;

[0063] FIG. 2 is a perspective view of the wire holding unit for use in the sensor of FIG. 1;

[0064] FIG. 3 shows the wire holding unit of FIG. 2 from the underside to illustrate certain features in more detail;

[0065] FIG. 4 corresponds to FIG. 3 but with the wires omitted to illustrate certain feature of the wire holding unit in more detail;

[0066] FIG. 5 is a perspective view of the sensing unit of the sensor of FIG. 1;

[0067] FIG. 6 is a further perspective view of the sensing unit of FIG. 5, with the sensing elements omitted;

[0068] FIG. 7 is another view of the sensor of FIG. 1 taken from above, showing certain features of the locking mechanism in more detail;

[0069] FIG. 8 is a view corresponding to FIG. 7 but with the cover of the wire holding unit omitted to show the way in which the wires are biased into contact with the sensing means of the sensing unit more clearly;

[0070] FIG. 9 illustrates some exemplary circuitry which may be used in the sensor of the present invention;

[0071] FIG. 10A illustrates the transition between dominant and recessive states for a high speed CAN bus;

[0072] FIG. 10B illustrates the transition between dominant and recessive states for a low speed CAN bus;

[0073] FIG. 11 illustrates the correspondence of the output of the logic gates of the circuit shown in FIG. 9 to the states of the CAN bus; and

[0074] FIG. 12 is a schematic overview of the inputs and outputs of the sensor.

DETAILED DESCRIPTION

[0075] FIG. 1 illustrates a sensor for sensing data transmitted over a digital vehicle network in accordance with an embodiment of the invention. For the purposes of illustration, the sensor is described in relation to sensing data transmitted over a CAN bus of a vehicle. However, it will be appreciated that the sensor may be applied to other types of vehicle network e.g. a LIN network.

[0076] The sensor 1 is made up of two units; a wire holding unit 3, and a sensing unit 5. In the configuration shown in FIG. 1, the wire holding unit 3 and the sensing unit 5 are locked together, by operation of a locking mechanism which will be described below. The sensor 1 is shown in FIG. 1 being connected to the CAN high 7 and CAN low 9 wires respectively of the CAN bus.

[0077] The features of the wire holding unit 3 will now be described in more detail by reference to FIGS. 2-4. As shown in FIG. 2, along the longitudinal side of the wire holding unit 3, corresponding to the direction in which the wires extend, two notches 11, 13, in the form of slots extending through the wall of the unit 3, are provided. An identical pair of notches 15, 17 is provided on the opposite longitudinal side of the unit, as may be seen in FIG. 3, which is a view from the underside of the unit. These notches form one part of a locking mechanism for locking the wire holding unit 3 to the sensing unit 5, as described below.

[0078] The way in which the wires are retained by the wire holding unit 3 will now be described by reference to FIG. 4. FIG. 4 corresponds to FIG. 3, but with the wires omitted for ease of illustration. Here it may be seen that the wire holding unit 3 defines two longitudinally extending channels 8, 10, for locating the respective wires. At each longitudinal end of channel 8, a clip 19, 25 is provided. A corresponding pair of clips 21, 23 is provided, one at each of the longitudinal ends of the channel 10. These clips are used to retain the wires in their respective channels. Disposed in each of the channels is a respective strip of rubber material, 27, 29. The strip of rubber material is located between the base of the channel and the wire disposed therein in use, and acts to bias the wire into engagement with the capacitive coupling element associated with the wire when the wire holding unit 3 is connected to the sensing unit 5 in use. The wire engaging surface of each rubber strip 27, 29 has a dog tooth profile.

[0079] The sensing unit 5 will be described in more detail by reference to FIGS. 5 and 6. On one side the sensing unit 5 has a recess 31 for receiving the wire holding unit 3 when connected thereto in use. The base of the recess 31 includes a pair of PCB (printed circuit board) copper traces 33, 35, which provide capacitive coupling elements for capacitive coupling with the wires 7, 9 in use.

[0080] On one side of the recess, a pair of resilient hooks 37, 39 are provided, one at each longitudinal end. On the opposite side of the recess, a resilient wall 40 is provided, having a pair of resilient hooks 41, 43 at each of its longitudinal ends. This may be seen more clearly in FIG. 6. As described below, the hooks 37, 39, 41, 43 form part of the locking mechanism for locking the sensing unit 5 and wire holding unit 3 together in use.

[0081] The other part of the sensing unit 5 has a cover 45, and houses the processing means of the unit, for obtaining digital signals indicative of data transmitted on the CAN bus. An output, which is illustrated as a 4-pin output, is provided, for connection to a power and data cable, to enable the sensor to be connected to a telematics unit in use.

[0082] The sensing unit 5 may be connected to the wire holding unit 3, and locked thereto by means of a locking mechanism. The locking mechanism is provided by engagement of the resilient hooks 37, 39, 41 and 43 on the sensing unit 5 with the notches 11, 13, 15, 17 on the wire holding unit 3, when the wire holding unit 3 is pressed into the recess 31 in the sensing unit 5, as shown in FIG. 1. FIG. 1 shows the engagement of the resilient hooks 41, 43 with the notches 11, 13. FIG. 7 shows more clearly the engagement of the hooks 37, 39 with the notches 15, 17 on the other side of the wire holding unit 3. When the wire holding unit 3 is connected to the sensing unit 5 in this way, the wires 7, 9 are pressed into contact with the capacitive coupling elements 33, 35 respectively.

[0083] FIG. 8 is a view similar to FIG. 7, but with the cover of the wire holding unit 3 removed to illustrate certain features more clearly. Here it may be seen how the rubber strips 27, 29 engage the wires 7, 9, and bias them into engagement with the underlying capacitive coupling elements 33, 35.

[0084] The resilient wall 40 is a release element, which may be deflected outwardly by a user to disengage the hooks 41, 43 from the notches 11, 13 respectively, enabling the wire holding unit 3 to be removed from the sensing unit 5, when desired.

[0085] One embodiment of suitable circuitry 100 of the processing means of the sensing unit 5 for obtaining digital output signals indicative of data transmitted on the CAN bus will now be described by reference to FIG. 9.

[0086] The inputs to the circuit are the capacitance sensed in respect of the CAN high 7 and CAN low wires 9, by virtue of the capacitive coupling between the wires and the capacitive coupling elements 33, 35. The sensed capacitance for each wire provides an analogue signal indicative of the data sent on the wire. The two inputs in respect of the CAN high and CAN low wires are labelled CAN_HIGH and CAN_LOW.

[0087] The circuitry 100 is arranged to provide digital output signals, one in respect of each of the CAN HIGH and CAN LOW wires, each in the form of a digital signal indicative of the state of the CAN bus. This is achieved using a comparator 102 and a set of logic gates 104.

[0088] As indicated in FIGS. 10A, and 10B, both high speed and low speed CAN buses transition between recessive and dominant states. A high speed CAN is defined in ISO 11898-2, while a low speed CAN is defined in ISO 11898-3. In the case of both high and low speed CANs, the bus can be determined to be in either a recessive or dominant state based on a differential between the CAN high and CAN low voltages. For example, as shown in FIG. 10A, for a high speed CAN, the CAN bus is deemed to be in a dominant state when the differential between the CAN high and CAN low voltages exceeds a certain threshold. FIG. 10B shows the corresponding recessive and dominant states for a low speed CAN.

[0089] In accordance with the invention, in the case of either a low speed or high speed CAN, the comparator 102 detects a differential between the input CAN low and CAN high voltages, and is therefore able to detect a transition between the recessive and dominant states of the CAN bus. This data is input to a set of logic gates 104, in the form of inverters (D2, D3). One inverter is provided in respect of each of the outputs of the circuit.

[0090] In the circuit, C1 and C2 indicate the coupling capacity between the CAN HIGH and CAN low wires respectively and the sensing elements of the sensing unit. R1 and R2 are bias voltage resistors, and R3 and R4 are feedback resistors. D1 is a further inverter used for obtaining a further feedback signal.

[0091] The comparator 102 is trigged by CAN signal transitions, because only voltages changes (transients) can be capacitive coupled. Due to biasing and the positive feedback, the comparator 102 stores the latest state of the CAN bus during the time between transients, i.e. when the CAN signals are static. The resistors R1, R2, R3 and R4 determine the trigger value of the sensor according to the bias voltage and the comparator output voltage. Without the positive feedback, which is provided by resistors R3 and R4, the comparator could be unstable between transients (on the CAN bus) because the compactor input voltage can be about zero (0V).

[0092] The outputs of the circuit at OUT_LOW and OUT_HIGH, are in the form of digital signals indicative of the state of the CAN bus. The signals comprise data indicative of the changes of the CAN bus between dominant and recessive states, which is, in turn, indicative of data e.g. messages transmitted on the CAN bus. The OUT_LOW and OUT_HIGH outputs provide digital signals which may be indicative of data transmitted on the CAN high and CAN low wires respectively.

[0093] FIG. 11 illustrates the way in which the outputs of the circuit are mapped to the states of the CAN bus. It will be seen that a recessive state of the CAN will result in the OUT_LOW output signal, being 1, and the OUT_HIGH signal being 0. Conversely, a dominant state will result in OUT_LOW=0 and OUT_HIGH =1.

[0094] The output of the logic gates 104 provides the outputs OUT_LOW and OUT_HIGH of the sensor. Each one of these outputs corresponds to the output of one of the inverters D2 and D3 respectively. These outputs are provided to the output 47 of the sensing unit. In the illustrated embodiment, the output 47 of the sensing unit is a 4 pin connector, with the OUT_LOW and OUT_HIGH signals being provided at two of the pins. This is indicated in FIG. 12. FIG. 12 schematically illustrates the operation of the sensor 1. The sensor has inputs CAN high and CAN low, corresponding to CAN_HIGH and CAN_LOW in FIG. 9. The outputs of the sensor include signals representative of the CAN Low and CAN high signals of the CAN bus. These correspond to OUT_LOW and OUT_HIGH in FIG. 9.

[0095] The OUT_LOW and OUT_HIGH sensor outputs (corresponding to CAN low and CAN high in FIG. 12), are provided to directly as inputs to a telematics unit, through connection of a power and data cable to the sensor outputs. It has been found that providing the output of logic gates directly to a telematics unit in this way leads to benefits in terms of power consumption and reduced current requirement.

[0096] The use of the comparator and logic gates as exemplified herein has been found to be particularly simple and effective.

[0097] The sensor 1 forms part of a system for obtaining data from a CAN bus, and providing it to a telematics device. The system also includes a (power and data) cable which is connected to the output 47 of the sensor 1 at one end, and a telematics control unit, such as a TomTom® LINK device, which may be installed or to be installed in a vehicle. The other end of the cable is connected to an input of the telematics device in use. This system has been found to be particularly power efficient, and may operate at relatively low current levels. The sensor derives its power from the telematics device via the power cable. Particular benefits in power consumption reduction are found if the cable has a length of less than 1 m.

[0098] Use of the sensor will now be described. The user takes the wire holding unit 3, and clips the CAN low and CAN high wires of a vehicle CAN bus into the respective channels 8, 10 thereof. This will involve untwisting a length e.g. around 3-4 cm of the wires. The user then connects the wire holding unit 3 to the sensing unit 5, pushing the wire holding unit 3 into the recess 31 of the sensing unit 5, so that the resilient hooks 37, 39, 41 , 43 enter their respective notches 11, 13, 15, 17 with an audible click.

[0099] The user then connects one end of a power and data cable to the output 47 of the sensing unit 5, and connects the other end of the cable to the input of a telematics device.

[0100] It will be appreciated that where a vehicle includes multiple CAN buses, the sensor may be connected to either CAN bus. If desired, a second (or further) sensor may be connected to a second (or further) CAN bus. Each further sensor may be connected by a respective further (power and data) cable to a further input of the telematics device.

[0101] Some suitable dimensions of a sensor device in accordance with one embodiment of the invention will now be described, by way of example only. The assembled sensor 1 has a length L of 40 mm, a width W of 30 mm and a depth D of 12.5 mm. The capacitive sensing elements 33, 35 each have an area of 34.5 mm×3.0 mm. The wire holding unit 3 has a length l of 40.5 mm, a width w of 12.0 mm and a depth d of 11.0 mm.

[0102] It has been found that the current consumption of the sensor may be less than 2 mA at 5V, which corresponds to less than 1 mA at 14V. This is considerably lower than prior art sensors, which may, for example, require around 6.5 mA at 14 V. The current consumption of an exemplary telematics control unit connected to two of the sensors (in respect of the CAN bus 1 and CAN bus 2 of the vehicle), in a sleep mode would be less than 3 mA at 14V. This is in comparison to around 14 mA at 14 V for prior art sensors. This leads to benefits in terms of cost reduction. It has also been found that the power wiring of the sensors may be achieved more easily than prior art sensors which may require separate connection to a board voltage.

[0103] The sensor has been found to be suitable for use with both high speed CAN buses and low speed CAN buses.

[0104] A reduced power consumption is beneficial in that the sensor may be able to always be on, but in a sleep mode, waking up a telematics device when data is detected.