Security is increasingly a design requirement for vehicles, and in particular concentrates on protection of the entry points and entry mechanisms of a vehicle.

Door locks may often be electrically operated and controlled by an on vehicle electronic control unit. This disconnects the locking mechanism from the handle of the vehicle making mechanical forcing of the handle ineffective. The unlocking of the door occurs in response to signals received by the locking mechanism generated by the driver actuating an electrical switch.

Commonly, in modern vehicles switches are fitted to the boot lids or tailgates of vehicle to enable access requests to be made. Typically, the switch is a mechanical push switch protected from the environment by being mounted behind a flexible waterproof membrane. Contact between the switch and the membrane in addition to the effects of the weather and outdoor environment limit the lifespan of the membrane and the moving parts within. Often such switches are mounted on the underside of an existing feature such as a styling feature or the rear number plate illumination so as to provide further protection for the switch and its membrane from moisture and the effects of weather and the environment and thus extend the working lifespan.

Protected mounting spaces such as these are less simple to arrange on the passenger doors and thus the adoption of such switches in these positions is limited.

It is therefore the object of the invention to provide an improved weather resistant switch which may be fitted to a vehicle body in order to control access to the vehicle.

According to the present invention there is provided a switching unit comprising a waterproof housing; an integrated circuit sensing element mounted within the housing, said sensing element operative to sense pressure applied to the housing; and means for communicating the output of the sensing element to external circuitry.

Such a switching unit has no moving parts and can be manufactured by moulding techniques to produce a switching unit that is virtually impervious to external environmental conditions and thus is more reliable and has a longer working lifespan than conventional mechanical push switches mounted behind flexible membranes.

Preferably, the housing is at least partly flexible. Preferably, the electronic sensing element is a strain gauge or a pressure sensor.

If the sensing element is a strain gauge it is mounted within the housing such that when pressure is applied to the housing, said pressure causes all or part of the housing to flex and thus apply a strain to the strain gauge, which generates an electrical signal in response to the applied pressure.

In the alternative embodiment wherein the sensing element is a pressure sensor it is mounted within the housing such that it is in communication with a cavity,

the cavity being compressed when pressure is applied to the housing and thus transmitting the applied pressure to the sensing element.

Preferably means are provided for converting the signal output by the sensing element to a signal more suitable for input into desired external circuitry. Typically the means for converting may act to convert the signals received from the sensing element to a binary output.

Preferably the means for converting comprises one or more threshold comparators operative to compare the signal generated by the sensing element with one or more threshold parameters so as to generate an output signal when the pressure applied to the housing exceeds a predetermined limit or when the rate of change of pressure applied to the housing exceeds a defined rate. In one preferred embodiment, there are two threshold parameters, an output signal exceeding a first threshold parameter indicating that the switch has been activated, and an output signal less than a second threshold parameter casing the sensor to output a signal indicating that the switch has not been activated.

The threshold parameters are preferably stored in memory means provided within the means for converting. The threshold parameters may be fixed or variable.

Threshold parameters may be varied to accommodate changes in sensitivity of the sensing element dependant upon operating voltage, temperature, ambient pressure or other environmental factors. The variations may be calculated by algorithm or may be determined from pre-stored look up tables. Additional sensing elements may be provided incorporated into the integrated circuit or on connected integrated circuits

mounted within the same housing to detect said variations in operating voltage, temperature, ambient pressure or other environmental factors.

In some preferred embodiments, further components may be incorporated into the switch unit in order to provide any suitable sensor control features including but not limited to a low current sleep mode, wake up signals being received from an external electronic control unit or generated internally at predetermined time intervals; low resolution monitoring of the sensing element; or multiplexing and or signalling systems conforming to standards such as the LIN bus standard adopted by many Automotive manufacturers.

The means for converting and other additional components to the sensing element may be formed as part of the same integrated circuit as the sensing element or may be formed on a connected integrated circuit also mounted within the housing.

In a preferred embodiment, the means for communicating the output of the sensing element to external circuitry are physical links of an electrically conductive material. Preferably, such physical links are connected to the integrated circuit incorporating the sensing element before the integrated circuit is packaged in the housing.

In a further preferred embodiment a radio frequency (RF) antenna and suitable control circuitry are additionally provided within the housing to provide the means for communicating. Suitable forms of antenna and control circuitry are known in the context of RF identification tags. In this embodiment therefore there is no permanent

physical connection between the switch unit and any external circuitry, communication taking place via the RF antenna.

In such embodiments wherein an RF link is provided, a power source is additionally provided. The power source may be a battery or may alternatively be a power extraction circuit of the type known from use in conjunction with RF identification tags or any other suitable power source.

The switch unit may be used to control operation of a vehicle door or similar.

Preferably, in such cases the external circuitry that the switch unit communicates with is an on vehicle electronic control unit. Preferably in such cases the housing of the switch unit is shaped and configured to fit into and blend or contrast with the local bodywork as part of the styling of the vehicle.

The switch unit described above may alternatively be used to control operation of systems or components in other circumstances wherein a users hands may be wet or wherein the switch is to be exposed to the elements including but not limited to washing machines or kitchen appliance such as microwave ovens, motorcycles or boats, ATMs, cellular telephones or other communication device, watches and clocks, burglar alarms or similar.

In order that the invention is more clearly understood one embodiment will be described in more detail below with reference to the accompanying drawings in which: Figure 1 is a block diagram showing the layout of the components of a switching unit according to the present invention;

Figure 2 is a cross-sectional view of the switching unit of figure 1 wherein the sensing element provided is a pressure sensing element; and Figure 3 is a cross-sectional view of the switching unit of figure 1 wherein the sensing element provided is a strain gauge.

The invention is embodied by an integrated circuit 100 mounted within a flexible waterproof housing (not shown). Techniques suitable for achieving this, such as encapsulation, are well known in the semiconductor industry.

Upon the integrated circuit 100 are formed a sensing element 102 a means for converting 104 and a data storage means 106. The sensing element 102 is operative to detect pressure applied to the housing and output a corresponding signal.

Typically, such pressure is applied by the finger of a user in order to activate the switch.

The means for converting 104 is operative to convert signals output by the sensing element 102 into an output indicative as to whether the switch has been activated. This is achieved by comparing the signals output by the sensing element 102 with threshold parameters stored in the data storage means 108. If the signal output by the sensing element 102 is greater than a first stored threshold parameter then the means for converting 104 outputs a signal indicative that the switch has been activated. If however, the signal output by the sensing element is less than a second stored threshold parameter the means for converting 104 outputs a signal indicative that the switch has not been activated. To prevent false indications that the switch has

been activated the means for converting may additionally monitor the rate of change of the output of the sensing element 102 and only output signals indicative that the switch has been activated when both the absolute signal and the rate of change of the signal exceed stored threshold parameters.

In alternative embodiments further circuitry may be provided to measure and hence to calculate appropriate adjustments to the threshold parameters in response to variations in ambient temperature, ambient pressure and supply voltage. In some embodiments this may be achieved by looking up alternative threshold parameters in look up tables stored in the data storage means 106. In some embodiments additional sensing elements (not shown) are provided sensitive to ambient temperature or ambient pressure. These additional sensing elements may be used to adjust the threshold parameters or assist in selecting the best fit parameters form a set of stored parameters.

Also provided are means for communicating with external circuitry (not shown) which act to pass the output of the means for converting to an external control unit, which may in the case of a vehicle be an on vehicle electronic control unit.

Furthermore the means for communicating is additionally adapted to pass signals to the means for converting 104 from external circuitry. The means for converting 104 can thus be controlled from a remote location, typically such signals might be used to cause the means for converting to vary the threshold parameters or to switch between a low power sleep mode and normal operation.

The means for communication can be physical links made from conducting material and connected to the means for converting 104 before it is encapsulated in

the housing or in certain embodiments can be an RF transceiver. If the means for converting is an RF transceiver then a power source is provided in order to enable the integrated circuit to operate. The power source can be a battery or can be a power extraction circuit of the type known from use in conjunction with RF identification tags.

The sensing element is either an integrated circuit pressure sensor or an integrated circuit strain gauge. Referring to figure 2, an embodiment of the invention having a pressure sensor 202 is shown. The pressure sensor 202 is mounted on a non flexible part of the housing 203 such that it is in communication with a cavity 201, the cavity being between the pressure sensor 201 and the flexible part of the housing 204.

When a user applies pressure 200 to the flexible part of the housing 204, the pressure sensor detects the resultant increase in pressure within the cavity. If a sufficiently large pressure or pressure increase is detected then the means for converting 104 outputs a signal indicating that the switch has been activated.

Referring to figure 3 an alternative embodiment of the invention having a strain gauge 302 is shown. The strain gauge 302 is mounted on a flexible part of the housing 304 such that when pressure 300 is applied to the housing by a user it causes the flexible part of the housing 304 to bend into a cavity 301 lying between the flexible part of the housing 304 and an inflexible part of the housing 303. The stretching force applied to the strain gauge 302 in this manner is detected. If a sufficiently large force is detected, the means for converting 104 outputs a signal indicating that the switch has been activated.

It is of course to be understood that the invention-is not to be restricted to the details of the above embodiment which has been described by way of example only.