In a variety of engine-powered vehicles, monitoring devices are employed to detect the presence of various undesirable operating conditions, such as over heating of the engine, low oil pressure, low fuel and the like, and indicators are provided to warn the operator of such conditions.
The importance of the various monitored conditions usually varies as to criticality. For example, the air filter for the engine or the filter for the hydraulic fluid may gradually clog during operation of the vehicle. The vehicle operator should be warned of such clogging, but generally there is no need to remedy the situation until the end of the day when the vehicle returns for normal servicing and maintenance. A low fuel condition requires more immediate attention from the operator. A loss of engine oil pressure or a loss of hydraulic fluid represent conditions which require immediate operator attention to prevent damaging the vehicle.
Prior monitoring systems have detected the presence of undesirable conditions and then signaled the vehicle operator by means of dial indicators, indicator lamps, or audible means. The efficiency of these systems greatly depend upon the operator's careful attention to all of the various indicators and upon his judgement as to which may call for immediate correction. As the complexity of a vehicle increases, the number of monitored parameters generally increases. Therefore, the operator is required to direct more attention to the increasing number of indicators, and less attention to operating the vehicle.
U.S. Pat. No. 4,184,146, which issued to Fratzke et al. on Jan. 15, 1980 and is assigned to the assignee herein, recognizes and partially addresses the above problems. Fratzke et al. provides a system for warning a vehicle operator of an undesirable operating condition of one or more of a plurality of monitored operating parameters of an engine-powered vehicle. Three degrees of warning are given, depending upon the criticality of the monitored parameter. Individually energizable low-intensity warning indicators are provided for each of the monitored parameters, and a multiplexing circuit is provided for staggered pulsing of the indicators. The existence of any critical fault will cause an intermittent operation of a more intense warning device, while the existence of a highly critical fault results in an additional intermittent warning of a still greater degree of intensity.
Since the invention of the Fratzke et al. system, vehicles have become much more complex and the number of vehicle parameters requiring monitoring has increased dramatically. In Fratzke et al. and other prior systems, an increasing number of monitored parameters results in an increased number of warning indicators. However, increasing the number of indicators on a vehicle is undesirable from both an economic and operator standpoint.
Furthermore, in many instances it is desirable to provide an indication of the relative magnitude of the parameters which are in an undesirable condition. For example, in the instance of low oil pressure, it is desirable to provide an indication of the relative magnitude of the actual oil pressure. In order to provide an indication of this type, past systems have utilized separate indicators, such as dial indicators, for each monitored parameter which is to be displayed. Again this is undesirable because it adds to the cost of the vehicle and requires greater attention on the part of the vehicle operator. Hence, many prior systems only provide such an indication for a few selected parameters, such as fuel level, oil pressure, and engine temperature. However, it is desirable to provide such an indication for any monitored parameter which enters an undesirable condition without increasing the number of indicators on the vehicle. It is further desirable to provide a display which indicates the relative magnitude of selected parameters in the absence of any undesirable operating conditions.
The present invention is directed towards overcoming one or more of the problems as set forth above.