Abstract:
Methods and apparatus are provided for vehicle windshield washing-wiping and wiper de-icing. Primary nozzles provide washing fluid to the windshield during normal operations and secondary nozzles bathe the wiper arms with washing fluid to de-ice the wipers during a de-icing mode. Washing fluid is drawn from a reservoir and delivered to the nozzles by a pump. When the outside air temperature T is greater than Tc, the critical temperature for ice formation, the wipers and washing-wiping proceed normally with washing fluid delivered to the primary nozzles for windshield washing. When T≦Tc and the wipers are not moving, a washer fluid supply line valve delivers washing fluid to the secondary nozzles to de-ice the wipers. The wiper motor, washing fluid pump and valve are operated by a controller based on inputs from wiper position and air temperature sensors, using predetermined information stored in on-board memory.

Description:
TECHNICAL FIELD  
       [0001]     The present invention generally relates to vehicle windshield wiper systems, and more particularly, to windshield wiper and washer systems providing wiper blade de-icing.  
       BACKGROUND  
       [0002]     It is well known in the art to provide vehicles with windshield wipers and windshield washers. In modern vehicles, the windshield washer nozzles are often mounted on the wiper blades so that they spray more of the washer fluid on the windshield where it is desired and inject less into the vehicle slipstream. Examples of various windshield wiping-washing arrangements are described in Patents GB  430366  to Rawlinson, U.S. Pat. No. 2,961,168 to Webb, U.S. Pat. No. 3,213,493 to Chichester, U.S. Pat. No. 3,230,564 to McDevitt, U.S. Pat. No. 6,234,410 B1 to Martin et al, and U.S. Pat. No. 6,082,636 to Yoshida et al. A wiper de-icing system is described in U.S. Pat. No. 6,438,789 B1.  
         [0003]      FIG. 1  is a simplified representation of prior art vehicle windshield wiping-washing system  20  comprising windshield  22  and wiper assemblies  24 ,  24 ′. Wiper assembly  24  has oscillating wiper arm spindle  25 , wiper arm  26 , wiper blade support bracket  27 , wiper blade  28  and spray nozzles  29  that emit spray  30  during the windshield washing mode. For convenience of explanation it is assumed that wiper assembly  24 ′ is functionally identical to wiper assembly  24 .  FIG. 1  illustrates windshield wiping-washing system  20  during a typical prior art windshield wiping-washing operation while wiper assemblies  24 ,  24 ′ are moving in directions  32 ,  32 ′ while emitting washing fluid spray  30 .  
         [0004]      FIG. 2  is a simplified flow chart showing operating process  60  of prior art vehicle windshield wiping-washing system  20  of  FIG. 1 . Process  60  begins with START  61 , which usually occurs on vehicle power-up. In WASH SWITCH ON? query step  62 , it is determined whether the operator has pressed the “wash windshield” switch or button (usually found on the wiper control stalk). If the outcome of query  62  is NO (FALSE) then as shown by path  62 A, process  60  loops back to start  61 . If the outcome of query  62  is YES (TRUE), this initiates the windshield washing cycle. START PUMP step  63  is executed causing the washer fluid pump to turn on and WW ON IN WINDSHIELD WASH MODE step  64  to be executed. (The abbreviation “WW” stands for “windshield wiper”.). In step  64  causes the wipers to begin moving across the windshield, usually in a low speed mode, suitable for a wash cycle. WASH SWITCH STILL ON? query  65  is then executed to determine whether the operator is still activating the “wash” switch. If the outcome of query  65  is YES (TRUE) then method  60  loops back as shown by path  65 A and the pump and windshield wipers remain on. If the outcome of query  65  is NO (FALSE), then STOP PUMP step  66  is executed and the washing fluid pump shuts off, thereby terminating spraying of the windshield with washing fluid. The combination of steps  62 - 65  cause nozzles  29  to emit washing fluid spray  30  onto the windshield as long as the operator is activating the “wash” switch. After STOP PUMP step  66  washing fluid no longer flows to nozzles  29  and WW ON IN WINDSHIELD DRY MODE FOR TIME t 1  step  67  is executed to dry the windshield for time duration t 1 . In step  67  the windshield wipers may be left in the same mode set in step  64  or changed to a different operating mode. The duration t 1  may be selected by the designer, depending upon particular vehicle&#39;s requirements. Following the expiration of time duration t 1 , method  60  executes RETURN WW TO PRIOR MODE step  68  whereby it returns operation of the wipers to whatever state or mode they were in prior to initial query  62 . Method  60  then returns to start  61  and initial query  62  as shown by path  69 .  
         [0005]     These systems generally work well as far as cleaning the windshield is concerned. However, present day wiper-washer systems still suffer from a number of limitations or disadvantages. A significant problem with such systems is that they permit ice build-up on the wiper blades during cold weather driving conditions. When that happens, the wipers blades tend to lose contact with the windshield because the ice can prevent the blade from flexing to follow the contour of the windshield. When this happens the wiping and/or washing action of the blades becomes progressively less effective. A smeared windshield and reduced visibility can result. This is a significant disadvantage. A limitation of prior art blade de-icing arrangements is that they are more complicated and more expensive that is desired.  
         [0006]     Accordingly, it is desirable to provide an improved wiper-washer system that minimizes or eliminates blade icing in cold conditions. In addition, it is desirable that the blade de-icing apparatus and method be simple, rugged, reliable and require minimum modification of existing vehicle systems. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.  
       BRIEF SUMMARY  
       [0007]     An apparatus is provided for vehicle windshield washing-wiping and wiper de-icing. Primary wash-spray nozzles provide washing fluid to the windshield during normal washing operations. Secondary de-icing nozzles spray washing fluid on the wipers when the wipers are at rest. The best occurs when the outside air temperature drops below a critical temperature Tc for ice formation. Washing fluid is supplied to the nozzles by a pump coupled between a washing fluid reservoir and the nozzles. One or more valves in the washing fluid supply line(s) direct the washing fluid flow to the nozzles. There is desirably a sensor for determining outside air temperature, a wiper position sensor for determining when the wipers are at rest, a wiper actuation motor for running the wipers and a controller coupled to the pump, valve(s), sensors and wiper motor for managing the operation thereof.  
         [0008]     A method is provided for operating a vehicle windshield washing-wiping and wiper de-icing system. In response to a user activating a ‘wash’ switch or equivalent, the washing fluid pump is turned on to start the washing (and de-icing) cycle. It continues to run as long as the user activates that switch. When the outside air temperature T is greater than Tc, the critical temperature for ice formation, the wipers and washing-wiping proceed normally. The running pump delivers washing fluid from the reservoir to the primary wash-nozzles for windshield washing and no fluid is delivered to the secondary de-icing nozzles. When T≦Tc and the wipers are not moving, a valve in the washer fluid supply line operates and the running pump delivers washing fluid to the secondary nozzles to de-ice the wipers and/or reduce ice formation thereon. In the preferred embodiment, the secondary de-icing nozzles do not operate during normal washing operations and the primary wash-nozzles do not operate during de-icing, but this is not essential. When the user releases the ‘wash’ actuator, the pump shuts off, washing and de-icing stop and the wipers switch to a ‘drying’ mode for a time t 1 . Thereafter, the system preferably resets to whatever state or mode it was in prior to initiation of the wash cycle. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and  
         [0010]      FIG. 1  is a simplified representation of a prior art vehicle windshield wiping-washing system;  
         [0011]      FIG. 2  is a simplified flow chart showing an operating process of the prior art vehicle windshield wiping-washing system of  FIG. 1 ;  
         [0012]      FIGS. 3-4  are simplified illustrations of the windshield wiping-washing and wiper de-icing system of the present invention for different wiper arm positions;  
         [0013]      FIGS. 5-6  are simplified schematic piping diagrams of the windshield wiping-washing and wiper de-icing system of the present invention showing further details and illustrating washing fluid flow during different modes of operation;  
         [0014]      FIG. 7  is a simplified electrical schematic diagram of a control system for the wiping-washing and wiper de-icing system of the present invention; and.  
         [0015]      FIG. 8  is a simplified process flow chart of a method of operation of the wiping-washing and wiper de-icing system of the present invention, according to a preferred embodiment. 
     
    
     DETAILED DESCRIPTION  
       [0016]     The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description.  
         [0017]     The words “rest” or “pause” or “retracted” are used interchangeably herein to refer to the position or status of the wipers generally when motion is temporarily stopped during intermittent operation and the word “stowage” is used generally to refer to the wiper position or status when the wipers are OFF.  
         [0018]      FIGS. 3-4  are simplified representations of the windshield wiping-washing and wiper de-icing system  50  of the present invention for different wiper arm positions  34 ,  35 . In  FIG. 3 , wiper assemblies  24 ,  24 ′ are shown in standard wiping-washing state  34 , similar to that shown in  FIG. 1 , that is, wiper assemblies  24 ,  24 ′ are up on the windshield moving according to arrows  32 ,  32 ′ and emitting washing fluid sprays  30 . This is analogous to the normal wiping-washing mode illustrated in  FIG. 1 . However, system  50  differs from prior art system  20  in that, among other things, auxiliary de-icing spray nozzles  36 ,  36 ′ are provided. Auxiliary de-icing spray nozzles  36 ,  36 ′ spray wiper assemblies  24 ,  24 ′ when they are in pause or stowage position  35  illustrated in  FIG. 4 . The washer fluid emitted as sprays  37 ,  37 ′ contains an antifreeze compound and therefore acts to melt ice that has accumulated on wiper assemblies  24 ,  24 ′. When wiper assemblies  24 ,  24 ′ are in retracted or stowage position  35 , windshield washing sprays  30  are desirably turned off, but this is not essential.  
         [0019]      FIGS. 5-6  are simplified schematic piping diagrams of windshield wiping-washing and wiper de-icing system  50  of the present invention showing further details and illustrating washing fluid flow during different modes of operation. For clarity, the details of wiper arm spindle  25 , wiper arm  26 , wiper blade support bracket  27  and wiper blade  28  are omitted in  FIGS. 5-6 . As shown in  FIGS. 5-6 , system  50  of the present invention includes washing fluid reservoir  52 , washing fluid pump  54 , valve  56 , and: (i) tubing or conduit  57  leading to wiper assemblies  24 ,  24 ′ with spray nozzles  29  emitting washing fluid sprays  30  (see  FIG. 5 ), and (ii) tubing or conduit  58  leading to nozzles  36  emitting washing fluid sprays  37  (see  FIG. 6 ). For convenience of explanation and not intended to be limiting, it is assumed that wiper assembly  24 ′ is like assembly  24  and operates in substantially the same way and likewise for nozzles  36 ′,  36  and sprays  37 ′,  37 . For convenience of description, unless otherwise expressly indicated, reference numbers  24 ,  36 ,  37  are intended to include their primed equivalents  24 ′,  36 ′,  37 ′.  
         [0020]     In  FIGS. 5-6  heavier dark lines are used to illustrate the paths followed by windshield washing fluid  53  from reservoir  52 , through pump  54  and valve  56  to wiper assembly spray nozzles  29  in  FIG. 5  or auxiliary de-icing spray nozzles  36  in  FIG. 6 .  FIG. 5  illustrates washing fluid flow during normal wiping-washing mode of operation. In  FIG. 5  washing fluid  53  flows from pump  54  through valve  56  through channel  57  to wiper assembly  24  and nozzles  29 , which produce sprays  30 .  FIG. 6  illustrates the arrangement of parts and washing fluid flow during the wiper de-icing operation of the present invention. In  FIG. 6  washing fluid  53  flows from reservoir  52  through pump  54 , through valve  56  and conduit  58  to nozzles  36 , which produce sprays  37 . Nozzles  36  are arranged with respect to wiper assembly  24  in retracted or rest position  35  so as to maximize coverage of wiper assemblies  24  by sprays  37 , especially coverage of support brackets  27  and blades  28  where ice formation can have the largest impact.  
         [0021]     In  FIGS. 5-6  valve  56  is assumed to be a two position exclusive OR valve, that is, washing fluid  53  flows either to nozzles  29  or nozzles  36  but not to both nozzles  29  and  36  at the same time. However, this is merely for convenience of description and not intended to be limiting. Persons of skill in the art will understand based on the description herein that valve  56  may, alternatively, be such that washing fluid  53  flows to nozzles  29  for sprays  30  whenever pump  54  is on and that valve  56  only switches on and off sprays  37 . Either arrangement is useful. Still further, persons of skill in the art will understand based on the description herein that valve  56  may embody two independent valves, one for nozzles  36  and sprays  37  and another for nozzles  29  and sprays  30 , but this is not essential. A dual valve arrangement has the advantage of flexibility of operation since sprays  30  and  37  may be independently controlled. In the preferred mode of operation sprays  37  come on when wiper assembly  24  is in retracted position  35  and sprays  30  come on when wiper assembly  24  is in wiping position  34  and the user has activated the “wash” mode switch.  
         [0022]      FIG. 7  is a simplified electrical schematic diagram of control system  70  useful for wiping-washing and wiper de-icing system  50  of the present invention. System  70  comprises washer-on switch  72  (the “wash” mode switch) coupled to controller  74  by bus or leads  73 , memory  76  coupled to controller  74  by bus or leads  75 , temperature sensor  78  coupled to controller  74  by bus or leads  77 , washer fluid pump switch  80  coupled to controller  74  by bus or leads  81 , wiper actuator  82  coupled to controller  74  by bus or leads  83 , de-ice valve activator  84  coupled to processor  74  by bus or leads  85  and wiper position sensor  86  coupled to processor  74  by bus or leads  87 . Wiper actuator  82  and wiper position sensor  86  may be integrated in the same housing or interconnected as shown by bus or leads  89 . Washer-on switch  72  is what the operator uses to initiate a windshield washing operation, that is, to launch a wash cycle or wash mode. Memory  76  stores operating programs (e.g., see  FIG. 7 ), predetermined constants (e.g., t 1 , tp, Tc, etc.) and intermediate variable values used by controller  74  of control system  70  in operating system  50 . Pump switch  80  energizes pump  54  of  FIGS. 5-6 . Controller  74  manages overall operation of washer/wiper/de-icing system  50 . Wiper actuator  82 , e.g., a motor or motor assembly, causes wiper assembly  24  to move across windshield  22  in directions  32  and return to rest, pause and/or stowage position  35 , under the control of controller  74 . De-ice valve activator  84  opens and closes valve(s)  56  and wiper position sensor  86  monitors or determines the position of wiper assembly  24 , that is, whether it is in wiping position  34  or in retracted or stowage position  35 . Person of skill in the art will understand that the pause or rest position of wiper assembly  24  may be somewhat different than the stowage position. In general, in the rest or pause position, assembly  24  usually does not retracted as far toward or at the base of the windshield as in the stowage position. For the purposes of this invention, nozzles  36  may be located so that sprays  37  contact wiper assemblies  24  in either the pause or stowage positions or both according to the needs of the designer. Persons of skill in the art will also understand that different types valves may be used for valve(s)  56  and, as used herein, the words “de-ice valve actuator  84 ” are not intended to be limiting and are intended to include any type of mechanism as may be appropriate to operate the type of valve(s)  56  being used. The operation of system  70  will be more fully understood by reference to  FIG. 8 .  
         [0023]     Control system  70  may be a fully software programmable system wherein program instructions are stored in memory  76  and executed by controller  74  or it may be a hardwired logic system or a combination thereof. Control system  70  may be a dedicated controller substantially dealing only with washing/wiping/de-icing system  50  or may be part of an overall or shared vehicle electronic system dealing with system  50  on a part time basis, or a combination thereof. The various elements of system  70  may be dumb, that is, operating entirely under the direction of controller  74  or may be smart, that is, containing some logical functions and/or timers. The various elements in system  70  may operate under the general direction of controller  74  but provide certain sub-functions (e.g., timing, critical value comparisons, etc.) on their own. Either arrangement is useful. Various time intervals or time durations mentioned herein, e.g., t 1 , tp, etc. may be measured using software loops or other programmable means or may be measured by separate hardware timers or combinations thereof. For example, dry-mode time duration t 1  may be determined by controller  74  or may be determined by a timer built actuator  82  or elsewhere and the signals sent by controller  74  to operate actuator  82  adapted accordingly. Any and all of these variations are useful and persons of skill in the art will understand based on the description herein how to implement them depending upon the needs of their particular application.  
         [0024]      FIG. 8  is a simplified process flow chart of method  100  of operating wiping-washing and wiper de-icing system  50  of the present invention, according to a preferred embodiment. Method  100  is executed by control system  50  of  FIG. 7  in combination with reservoir  52 , pump  54  and valve(s)  56  of  FIGS. 5-6 . Method  100  begins with START  102  that desirably occurs at vehicle power-up, that is, when system  70  is energized when the vehicle is turned on. System  70  and method  100  are quiescent until the operator or other vehicle operator pushes or otherwise activates switch  72  to initiate a wash cycle, whereupon WASH SWITCH ON? query  104  results in a YES (TRUE) outcome. (Prior to that query  104  returns a NO (FALSE) outcome and loops back to start  102 .) Method  100  then progresses to START PUMP step  106  wherein, for example, controller  74  retrieves a “start wash” signal from switch  72  and sends an appropriate signal over bus or leads  81  to pump switch  80  thereby causing washing fluid pump  54  to start pumping fluid  53  from reservoir  52  through washing/de-icing system  50 . This initiates the windshield washing process. As will be subsequently explained, washing fluid pump stays on as long as the operator continues to activate switch  72 . Following START PUMP step  106 , method  100  executes OUTSIDE TEMP&gt;Tc? query  108  wherein it is determined whether or not the outside air temperature measured by temperature sensor  78  is greater than a predetermined critical Tc. Tc is the temperature at which there is a significant probability of ice formation on wiper assembly  24 , and is generally in the range of 0° C. to −39° C., usually about 0° C. to −20° C. and more likely about −7° C. However, some ice formation may occur even though the average ambient temperature is ≧0° C. because heat loss from evaporation may lower the temperature of residual water on wiper assembly  24  or wiper assembly  24  itself to below 0° C. Therefore, setting Tc in the range about +5° C. to −5° C. is convenient, with about 0° C. preferred. Tc may be retrieved from memory  76  by controller  74  or may be stored in sensor  78 . Either arrangement is useful.  
         [0025]     If the outcome of query  108  is YES (TRUE) meaning that the outside air temperature is high enough that ice formation on wiper assembly  24  is unlikely, then method  100  proceeds to steps  110 - 118 . Steps  110 - 118  are analogous to conventional wash cycle steps  64 - 68 , respectively. WW ON IN WINDSHIELD WASH MODE step  110  is executed. (The abbreviation “WW” stands for “windshield wiper”.). Step  110  causes the wipers to begin moving across the windshield, usually in a low speed mode, suitable for a wash cycle. WASH SWITCH STILL ON? query  112  is then executed to determine whether the operator is still activating the “wash” switch. If the outcome of query  112  is YES (TRUE) then method  60  loops back as shown by path  112 A and the pump and windshield wipers remain on. If the outcome of query  112  is NO (FALSE), then STOP PUMP step  114  is executed and the washing fluid pump shuts off, thereby terminating spraying of the windshield with washing fluid. The combination of steps  106 - 114  cause nozzles  29  to emit washing fluid spray  30  onto the windshield as long as the operator is activating the “wash” switch and the ambient temperature T&gt;Tc. After STOP PUMP step  114  washing fluid no longer flows to nozzles  29  and WW ON IN WINDSHIELD DRY MODE FOR TIME t 1  step  116  is executed to dry the windshield for time duration t 1 . In step  116  the windshield wipers may be left in the same mode set in step  110  or changed to a different operating mode. The duration t 1  may be selected by the designer, depending upon the particular vehicle&#39;s requirements. Approximately 10 seconds is a non-limiting example of a useful time duration for t 1 , but larger or smaller values can also be used. Following the expiration of time duration t 1 , method  100  executes RETURN WW TO PRIOR MODE step  118  whereby it returns operation of the wipers to whatever state or mode they were in prior to initial query  104 . Method  100  then returns to start  102  and initial query  104  as shown by path  119 .  
         [0026]     Most modern wiper systems can operate continuously at various speeds or in a pause or delay mode. In the delay mode, wiper assembly  24  operates in wiping position  34  for a predetermined wiping time and pauses in rest position  35  for a predetermined ‘pause’ time tp, and then repeats the sequence wipe-pause-wipe, etc. Returning now to query  108 , if the outcome of query  108  is NO (FALSE), then method  100  proceeds to WW ON IN DE-ICE MODE step  120 . The de-ice mode is preferably a minimum pause time operating mode, that is tp has its smallest value. Pause time tp may, for example, be retrieved by controller  74  from memory  76  or maybe built into actuator  82  or a combination thereof. Either arrangement is useful. Minimum pause times tp are conveniently in the range of 0 to 2 seconds, typically in the range of 0.1 to 1 seconds and preferably in the range of 0.25 to 0.50 seconds. Following step  120 , system  50  prepares to de-ice wiper assemblies  24  by executing WW MOVING? query  122 . In step  122 , system  70  determines whether wiper assembly  24  is moving or not, e.g., stuck in the ice or temporarily paused. If the outcome of query  122  is YES (TRUE) indicating that wiper assemblies  24  are moving, then method  100  proceeds to step  124 . In step  124  if de-ice valve  56  is already open to permit washer fluid  53  to flow to nozzles  36 , then valve  56  is closed. If valve  54  is already closed, then in step  124 , it remains closed. This is accomplished by controller  74  sending an appropriate signal to de-icing valve activator  84  controlling valve(s)  56 .  
         [0027]     If the outcome of query  122  is NO (FALSE) indicating that wiper assemblies  24  are not moving, e.g., one or both of assemblies  24 ,  24 ′ are held fast by ice or in a temporary pause, then in step  126 , de-icing valve activator  84  is energized to open valve  56  causing washer fluid  53  to flow to nozzles  36  so that sprays  37  are directed toward wiper assemblies  24  while in retracted or paused position  35 . Following steps  124  or  126 , WASH SWITCH STILL ON? query  128  is executed wherein controller  74  determines the state of switch  72  (or  80 ). If the outcome of query  128  is NO (FALSE) indicating that the operator has released switch  72 , then method  100  proceeds to STOP PUMP step  114 , WW ON IN WINDSHIELD DRY MODE FOR TIME t 1  step  116 , RETURN WW TO PRIOR MODE step  118  and return to START  102  via path  119 , as already discussed. If the outcome of query  128  is YES (TRUE) indicating that the operator has ‘wash’ switch  72  (and therefore pump switch  80 ) still activated, then method  100  loops back to step  122  as shown by path  129 . As long as the operator continues to depress or otherwise activate switch  72 , method  100  will activate sprays  37  whenever wiper assemblies  24  are paused or stuck in position  35  and thereby provide de-icing fluid to assemblies  24 .  
         [0028]     There are two scenarios of interest: First, if wiper assembly  24  is frozen, unable to move and is stuck in the pause or rest or stowage position, method  100  continues to bathe wiper assembly  24  in washing fluid de-icing spray  73  as long as switch  72  is activated; and Second, if wiper assembly  24  can move and shuttle back and forth in the direction of arrows  32 , then in the de-ice mode provided by step  120 , each time wiper assembly  24  stops in pause or rest position  35 , valve  56  opens in response to step  126  and wiper assemblies  24  are bathed with washing fluid de-icing spray  73  during the pause interval. This serves to retard or prevent further ice buildup when the wipers are operating in cold weather conditions. Method  100  continues around this loop (steps  120 ,  122 ,  124 / 126 ,  128 ) until the operator releases switch  72  and pump  54  shuts off in step  114 . Then, as already discussed, method  100  proceeds to WW ON IN WINDSHIELD DRY MODE FOR TIME t 1  step  116 , RETURN WW TO PRIOR MODE step  118  and then returns to START  102  as shown by path  119 .  
         [0029]     In the preferred embodiment, the operator controls the amount of windshield washer fluid by maintaining the switch  72  in the active position, but this is not essential. Alternatively, controller  74  or the vehicle computer can control the amount of windshield washer fluid delivered during the wash cycle and/or the de-ice cycle. This has the advantage that the state of the vehicle can be used to determine the time required for the various steps executed in method  100 . For example and not intended to be limiting, the pump-on time and the wash and/or de-ice time can be made dependant on vehicle geometry, vehicle speed, wind speed, wiper speed, wiper motor feedback, windshield size, pump flow, ambient temperature, wash fluid composition, washer fluid temperature, other factors and/or combinations thereof. This allows the system to deliver an appropriate amount of fluid and wiper and/or de-ice cycle times as function of the current vehicle state. For example, when the vehicle is parked, the de-ice mode spray interval and the wipe intervals can be lengthened to help combat accumulating snow or other adverse conditions.  
         [0030]     While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. For example, while operation of system  50  has been described in terms of nozzles  29  being mounted on wiper assemblies  24 , this is not essential. Alternatively, nozzles  29  may be mounted on the vehicle itself, for example, at the periphery of windshield  22  and spray onto windshield  22  during the windshield washing cycle before or during wiper motion  32 . Either arrangement is useful. It will also be noted that, in contrast to prior art wiper de-icing arrangements such as are described for example in U.S. Pat. No. 6,438,789 B1, nozzles  36  are preferably fixed and that a pop-up blade de-icing arrangement is not necessary. This significantly simplifies blade de-icing and is a significant advantage over the prior art.  
         [0031]     It will be further noted that although in the preferred embodiment sensor  78  is used to measure ambient air temperature T and query  108  is executed in preferred method  100  to determine whether T&gt;Tc, this is not essential. The present invention will also operate if temperature sensor  78  is omitted and query  108  is replaced with a timing or randomizing step that toggles method  100  between branches  110 - 112  and branch  120 - 128  (the branches rejoin at step  114 ) at periodic or random intervals. Some washing fluid will be wasted when freezing is unlikely, but this alternative arrangement provides a useful backup in case sensor  78  fails. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the invention as set forth in the appended claims and the legal equivalents thereof.