GB2348116A - System which provides de-misting air to windscreen when wipers are used - Google Patents

Abstract

A vehicle windscreen system comprising a controller which when configured to operate the windscreen wiper arrangement also ensures that a responsive de-mist air flow is directed to the windscreen. The controller may be arranged such that an air flow is provided only when there is continuous wiper operation, preferably the air flow is dependent on the operational level of the wiper arrangement. The controller may ensure that there is an air flow by altering a distribution valve in an air conduit of a climate control system. A time out facility may be included wherein the air flow is interrupted for at least a period of time in order that other climate objectives within the vehicle are met.

Description

A Vehicle Windscreen Svstem The present invention relates to a vehicle windscreen system and more particularly to so-called demisting of a vehicle windscreen using air flows from a vehicle's ventilation arrangement.

Clearly, within a motor vehicle visibility is highly important to allow the driver to appropriately control the vehicle. Thus, any reduction in visibility through the vehicle windows and in particular the windscreen is to be avoided.

At present most vehicles include some form of window de-mist arrangement.

Generally, relatively warm air flows from a vehicle ventilation system are presented through vents directe towards the window. Thus, due to the localise increased dew point of the air immediately adjacent the window and the turbulent air flow, it will be understood that condense mist upon the window is disperse.

Regrettably, for onward control of window de-misting it is either necessary to have a number of sensors which provide a controller with information as to the current status of condensation on the window and humidity in order to stimulate demisting operation or, more normally the vehicle driver must specifically activate de-mist operation as required. The sensor based approach adds significantly to costs and to complexity whilst the second approach can be quite distracting to a driver.

It will be understood that windows and in particular windscreens are prone to mist in wet weather. The higher humidity or relatively rapid change in humidity over a short time period can be difficult for an automatic temperature control (ATC) system to accommodate. Furthermore, with less sophisticated manual systems, the control settings defined by a driver at the outset of a journey may not be appropriate when wet weather is encountered. In any event, whether the system is manual or automatic, there is no compensation for humidity changes without the additional cost and complexity of sensors to determine humidity.

It is an objective of the present invention to provide a vehicle windscreen system which can provide better de-mist function when wet weather is encountered, particularly when the vehicle has an automatic temperature control (ATC) system installe.

In accordance with the present invention there is provided a vehicle windscreen system comprising a controller to control a wiper arrangement for a windscreen and to control ventilation means directe towards that windscreen, the controller when configure to operate the wiper arrangement also reciprocally ensuring that a responsive de-mist air flow is directe to the windscreen.

Typically, the responsive de-mist air flow is dependent upon the manner of or configure operational level of the wiper arrangement.

The controller typically alters a paddle valve to take the responsive de-mist air flow from the vehicle ventilation system.

Generally, the controller will control the whole automatic temperature control system including the ventilation system so that the de-mist of the windscreen can be co-ordinated with other parts of the vehicle climate control regime.

An embodiment of the present invention will now be described by way of example only.

It is common to provide within a motor vehicle a climate control system which is controlled by a controller in accordance with pre-determined methodology. This methodology is defined by an algorithm or series of process steps stored in the controller. Generally, the controller will monitor a number of sensors. Thus, by comparison of the measurand values received from these sensors and the desired climat, the controller will operate the climate control system to best achieve that desired climate. Unfortunately, as with any control system, an inherent weakness is that the appropriateness of operation is limited by what conditions the sensors determine. Thus, in the present situation, as humidity may not be continuously monitored, the climate control system may not be able to react sufficiently quickly to avoid mist forming upon the windscreen. Furthermore, as the primary objective of the climate control system is not to de-mist the windscreen, there may be an unacceptably long time period before the windscreen is appropriately demisted without driver intervention. Such driver intervention as described previously may reduce the driver's concentration upon the road and so be dangerous in addition to adding to system burden by repeated short term alterations to the system's climate objective In the present invention, an effective over-ride feature is provided by the controller monitoring windscreen wiper operation. Thus, when the wiper arrangement is operated then the controller configures the climate control system to direct air flows towards vents directe to the windscreen. In particular, the controller will normally alter the set or tilt of a distribution flap in the air flow conduit of the climate control system. By such means, a proportion or higher proportion of air flow will be directe towards the windscreen in order to de-mist or inhibit formation of mist upon that windscreen.

As indicate previously, normally the air flow directe towards the windscreen will be warm. Thus, the distribution flap controlled by the controller in accordance with the present invention will be located in an air conduit from a heater for the climate control system.

Typically, hot air from a heater matrix will be mixed with ambient air in order to provide the warm air flow directe through vents towards the windscreen.

The relative mix of air flows may be varied to provide different temperature flows or to achieve a consistent temperature which is less dependent upon transient heater status or ambient air temperature. Alternatinvely, a steady air flow may pass through a heater matrix with a hot coolant or water flow valve controlling flow rate and so warm air temperature presented through the vents.

Normally, the windscreen wiper arrangement of a motor vehicle will have several levels of operation. Thus, the wiper arrangement may have respectively intermittent wipe, slow wipe and fast wipe settings. The present invention utilises the assumption that when the wiper arrangement is activated that there will be a higher humidity level due to increase moisture from rain fall or other precipitation. Higher humidity generally means there is a greater likelihood of mist condensation upon the windscreen. However, it will be understood that operation of the wiper arrangement at specific levels of operation also provides information as to the level of precipitation. Thus, intermittent wipe may indicate light rain or the windscreen wash/wipe feature has been activated so the likelihood of mist build up is low whilst continuous wipe arrangement operation at slow and high speed wipe levels will indicate heavier rain fall and so greater likelihood of mist forming upon the windscreen. In such circumstances, the controller in accordance with the present invention will provide a measured and reciprocal response by altering the proportion of air directe to the windscreen dependent upon the perceived threat of mist build up indicated by the windscreen wiper arrangement operational level selected.

Typically, the operational level of the wiper arrangement selected will be indicated by a switch mechanism on a stalk lever adjacent to the steering wheel which may also provide the traffic indicator operation arrangement. Thus, the level of wiper arrangement operation can be indicated to the controller by simple microswitch devices used to stimulate wiper operation also providing a control signal, either burst or stable, to the controller. In response the controller will then arrange for an appropriate proportion of air to be directe to the windscreen in order to de-mist that screen or inhibit mist build up by increasing air turbulence and temperature immediately adjacent the windscreen.

Clearly, over a long period of time the controller in accordance with the present invention may significantly alter the success of climate control in terms of temperature in the vehicle. Thus, the controller may have a time-out feature where after a specific time period air flow will return to that required for climate control for a period in order to approach or achieve the desired climate within the vehicle. In such circumstances, after a time period of normal air flow operation for climate control, the controller would return to that configuration of the system for de-mist of the windscreen. In any event, there would be no distracting direct control variations by the vehicle driver and specific sensors would not need to be provided for the climate control system whilst the dual objectives of de-mist and climate control will be substantially achieved.

It will be understood that the present invention will normally be implemented by altering the pre-determined response procedures of the controller set for combinations of sensed conditions and climate objective. In essence, the controller will be configure so that wiper arrangement operation over-rides the response procedure of the controller for sensed conditions. This over-ride provides mist condensation inhibition and demisting of the windscreen by warm air flows directe towards that screen to a greater degree than the controller would provide based upon its normal pre-determined response procedures.

Generally, in accordance with the present invention the controller will only interfere with air flow control when continuous wiper arrangement operation is indicated. Thus, as such continuous operation will only be selected by a vehicle driver when there is relatively heavy rain fall, it will be understood that the present invention provides for de-mist operation of the climat control system with indirect reference to humidity though wiper arrangement operation.

It will also be understood that even when rain fall has stopped and humidity may remain high due to evaporation, that the inherent spray created by other road vehicles will require operation of the wiper arrangement. Thus, as the wiper arrangement will still be operated, the controller will still direct air flows to the windscreen to inhibit mist condensation and provide demisting of that screen by evaporation.

Clearly, if high humidity is simply as a result of current atmospheric condition, wiper arrangement operation will not be required for rain or other precipitation falling upon the windscreen. However, there may be some condensation upon the exterior of the vehicle due to wind chill which may require operation of the wiper arrangement. This operation, in combination with other status conditions sensed by sensors of the climate control system, may stimulate the controller to direct some air flows internally to the vents directe towards the windscreen to inhibit or de-mist that screen.

Claims (7)

1. CLAIMS 1. A vehicle windscreen system comprising a controller to control a wiper arrangement for a windscreen and to control ventilation means directe towards that windscreen, the controller when configure to operate the wiper arrangement also reciprocally ensuring that a responsive de-mist air flow is directe to the windscreen.
2. 2. A system as claimed in claim 1 wherein the responsive demisting air flow is dependent upon a configure operational level of the wiper arrangement determined by the controller.
3. 3. A system as claimed in claim 1 or 2 wherein the controller ensures that there is only a responsive demisting air flow when that controller determines that there is continuous wiper arrangement operation.
4. 4. A system as claimed in claim 1, 2 or 3 wherein the controller ensures that there is a responsive de-mist air flow by altering a distribution valve in an air conduit of a climate control system.
5. 5. A system as claimed in any preceding claim wherein the controller inclues a time-out feature whereby after a pre-determined time period the controller arranges that the responsive de-mist air flow is interrupted for at least a period of time in order that other climate objectives within the vehicle are not compromised by provision of the responsive de-mist air flow to the windscreen.
6. 6. A system as claimed in claim 5 wherein the pre-determined time period is variable dependent upon the value of other factors sensed by sensors associated with the controller such as ambient air temperature or desired objective climate within a vehicle cahin.
7. 7. f vehicle windscreen system substantially as hereinbefore described.