Abstract:
A method of diagnosing a cooling system of a vehicle engine, including the steps of: acquiring operating data relative to operation of the cooling system (cooling system radiator water temperature/fan rotation speed) during a trip time between turn-on of the engine and subsequent turn-off of the engine; processing the acquired data, and accumulating the data for each trip to create a database; and examining the location of the data within the database to determine malfunction and/or potential malfunction situations of the cooling system.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method of diagnosing a vehicle engine cooling system. 
     2. Description of the Related Art 
     Vehicle engine cooling systems are known in which a stream of fluid (normally water) is fed to the inlet of a radiator connected to one or more cooling fans, which direct a stream of air through the radiator to produce an outward heat exchange, so that the water at the outlet of the radiator is cooler than at the inlet. As is known, due to aging and wear of the radiator and/or members producing forced flow of the water, the efficiency of the engine cooling system decreases considerably, and therefore also the difference between the temperature of the water at the inlet and outlet. 
     A need therefore exists for a method of fully automatically determining such a situation, and of also determining gradual decline of the engine cooling system to predict pending malfunction of the system well in advance. 
     BRIEF SUMMARY OF THE INVENTION 
     According to the present invention, there is provided a method of diagnosing a cooling system of a vehicle engine, characterized by comprising the steps of: acquiring operating data relative to operation of the cooling system between turn-on of the engine and subsequent turn-off of the engine; processing the acquired operating data and accumulating the data to create at least one database; and examining the location of the data within said database to determine malfunction and/or potential malfunction situations of said cooling system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A preferred, non-limiting embodiment of the invention will be described by way of example with reference to the accompanying drawings, in which: 
     FIG. 1 shows the operations performed in the method according to the present invention; 
     FIG. 2 shows a first database employed in the method according to the present invention; 
     FIG. 3 shows a variation of the method according to the present invention; 
     FIG. 4 shows a second database employed in the method according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows the operations performed in a first embodiment of the method, according to the present invention, of diagnosing the cooling system of a vehicle engine, in particular of an industrial vehicle. 
     To begin with, a block  100  determines whether the engine relative to the cooling system is on; if it is not (engine off), block  100  remains on standby; otherwise (engine on), block  100  goes on to a block  110 . 
     Block  110  acquires and stores the temperature Tin of the water supplied to the cooling system radiator inlet, and the temperature Tout of the water at the cooling system radiator outlet. 
     Block  110  is followed by a block  120 , which calculates and stores the temperature difference ΔT between the water temperature Tin at the radiator inlet and the water temperature Tout at the radiator outlet, i.e.: 
      Δ T=T in− T out 
     Block  120  is followed by a block  125 , which forms a data structure defining and storing operating states S(ΔT, Tin) of the radiator as a function of the calculated ΔT value and the inlet water temperature Tin. 
     The data structure also stores the time lapse Ts the cooling system remains in each operating state S(ΔT, Tin). 
     For example, the database can be represented in a Cartesian X, Y plane by a spot graph—FIG.  2 —in which each spot corresponds to a state, and the diameter of the spot shows how long the operating state is detected, i.e., the time lapse the cooling system remains in that particular operating state. 
     Block  125  is followed by a block  130 , which determines whether the vehicle engine is off; if it is not (engine on and running), block  130  goes back to block  110 ; otherwise (engine off and not running), block  130  is followed by a diagnosis block  170 . 
     At the output of block  130 , the total trip time Ttrip (measured in seconds, minutes, or hours) between turning the engine on and off is also calculated, and equals the sum of the lapse times within the various detected operating states. 
     Blocks  100 - 130  thus determine the water temperature at the radiator inlet and outlet at successive instants, and calculate, for each finding, the temperature difference ΔT introduced by the radiator. Preferably, though not necessarily, blocks  100 - 130  are scanned so that temperatures Tin, Tout are determined and temperature difference ΔT calculated at predetermined time intervals, e.g., of one second. 
     It is known, in fact, that, when operating poorly or not at all, the radiator produces only a small reduction in the temperature of the fluid supplied to the inlet, i.e., temperature difference ΔT is close to zero or at least lower than normal operating values. 
     The operating states are thus stored and accumulated in different operating condition areas (shown by the grid in FIG.  2 ). 
     Alternatively, the operating states may be stored in the data structure as a function of the calculated ΔT value and the outlet water temperature Tout. 
     Alternatively or in addition, as opposed to the time lapse in each operating state, the time lapse in each state as a percentage of total trip time Ttrip may be stored. 
     At the end of each vehicle trip, i.e., when the engine is turned off, the three-dimensional data structure therefore contains the time lapses in the various detected operating states. 
     Repeated vehicle trips result in the generation of a database containing all the states in which the radiator has operated. 
     According to the present invention, block  170  periodically checks the database containing all the accumulated data structures to determine any malfunction situations. 
     For which purpose, the X, Y plane map (FIG. 2) shows a number of calibratable areas, including: 
     a danger area Z 1 ; 
     a prealarm area Z 2 ; and 
     a normal or safe operating area Z 3 . 
     Areas Z 1 , Z 2  and Z 3  in the X,Y plane can be calibrated as a function of the type of trip and the characteristics of the vehicle. 
     The check by block  170  can be made in three ways: 
     by checking the data structure at the end of each trip of each vehicle to determine instantaneous malfunctions (e.g., at least one operating state in danger area Z 1 ); 
     by checking the data structures of a number of trips of each vehicle to determine decline situations (e.g., migration of accumulated operating states from normal operating area Z 3  to areas Z 1  and Z 2 ; and 
     comparing the data structures of different vehicles to determine anomalies of one vehicle with respect to the rest of the fleet (e.g., a mean concentration of fleet radiator operating conditions in a normal operating sub-area, and individual vehicle operating conditions concentrated in a different normal operating sub-area). 
     Malfunctioning of the radiator may be determined on the basis of a number of criteria, including: 
     an operating state within danger area Z 1  over and above a given maximum time lapse, i.e., malfunctioning is determined when the temperature difference produced by the radiator remains small for a long total period of time and for numerous vehicle trips; 
     migration of the time lapse values in various operating states towards danger area Z 1 , i.e., the temperature difference decreases with time as the radiator gradually declines: 
     an operating state distribution differing from that of the other vehicles in the fleet. 
     In the FIG. 3 method, a first block  200  determines whether the engine relative to the cooling system is on; if it is not (engine off), block  200  remains on standby; otherwise (engine on), block  200  goes on to a block  210 . 
     Block  210  acquires and stores the rotation speed ωv of the cooling system radiator fan. 
     Block  210  is followed by a block  230 , which determines whether the vehicle engine is off; if it is not (engine on and running), block  230  goes back to block  210 ; otherwise (engine off and not running), block  230  is followed by a block  240 . 
     At the output of block  230 , the total trip time Ttrip (measured in seconds, minutes, or hours) between turning the engine on and off is also calculated. 
     Blocks  200 - 230  thus determine fan rotation speed at successive instants, to obtain n speed samples. Preferably, though not necessarily, blocks  200 - 230  are scanned so that fan rotation speed is determined at predetermined time intervals, e.g., of one second, during trip time Ttrip. 
     Block  240  calculates the mean fan rotation speed value ωv_med, i.e.            ω                 v_med     =       ∑     i   =   1       i   =   n            ω                 vi         n                          
     where n is the number of speed samples acquired repetitively by blocks  200 - 230  within the trip time. 
     Block  240  is followed by a block  250 , which calculates the fan rotation speed variance σ:          σ   2     =       [     ∑       (       ω   vi     -     ω   v_med       )     2       ]     n                            
     where n is the number of speed samples acquired repetitively by blocks  200 - 230  within the trip time. 
     Block  250  is followed by a block  260 , which stores the calculated mean speed and variance values in respective databases. 
     At the end of each vehicle trip, i.e., when the engine is turned off, the database is therefore updated to accumulate the calculated mean speed and variance values of the concluded trip. 
     Repeated vehicle trips result in the generation of a database containing a mean speed value for each trip, and a database containing a variance value for each trip. 
     FIG. 4 shows an example of a database showing mean speed values accumulated over successive trips. 
     According to the present invention, a process, independent of the operations in blocks  200 - 260  and indicated by block  270  in FIG. 3, periodically checks one or both databases to determine any malfunction situations. 
     Malfunctioning of the radiator may be determined on the basis of a number of criteria, including: 
     mean speed and/or variance values exceeding prealarm and alarm (minimum or maximum) values; 
     a check of the development over time of the mean speed and/or variance values to determine migration towards prealarm and alarm values. 
     The prealarm and alarm values can be calibrated. 
     The method according to the present invention therefore provides for fully automatically determining a malfunction situation of the engine cooling system. 
     Moreover, the method also determines gradual deterioration of the engine cooling system to predict malfunctioning of the system.