Abstract:
In order to prolong the life of the engine the maximum temperature and engine speed thereof are limited in accordance with the temperature of the engine coolant by controlling the amount of fuel supplied to said engine. During &#34;running-in&#34; of the engine the maximum temperature and engine speed limits are gradually increased until a predetermined amount of distance has been traversed by the vehicle in which the engine is disposed.

Description:
This application is a continuation-in-part of U.S. patent application Ser. No. 569,494 filed on Jan. 9, 1984 now abandoned in the name of Seishi Yasuhara. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to an internal combustion engine and more specifically to a method and apparatus for automatically controlling the engine in a manner to prevent same from operating at excessively high temperatures and engine speeds. 
     2. Description of Related Art 
     In order to prevent engine damage due to operating same at excessively high temperature and/or engine speeds it is common to provide warning lamps and/or tachometers on the instrument panel of the vehicle in which the engine is mounted. This enables the driver of the vehicle to suitably control the vehicle in the event he or she becomes aware of the abnormal condition. 
     However, this type of control has not satifactorily prevented excessive wear occuring, especially during &#34;running-in&#34; of the engine, nor the rapid deterioration of the engine lubricant which occurs when the engine is operated at excessively high temperatures and speeds. This is especially so in the case of diesel engines which are particularly prone to the above mentioned problems due to the high compression ratios at which they operate. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to obviate excessive engine wear and/or damage via automatic engine control. 
     In brief, the present invention features an arrangement wherein in order to prolong the life of the engine and the lubricant used therein, the maximum temperature and engine speed thereof are limited by controlling the amount of fuel supplied to said engine in accordance with with the temperature of the engine coolant. During &#34;running-in&#34; of the engine the maximum temperature and engine speed limits are gradually increased until a predetermined amount of distance has been traversed by the vehicle in which the engine is disposed. During idling of the engine, the engine speed is raised in the event that excessive temperatures are encountered to improve coolant circulation and therefore cooling efficiency. 
     More specifically, a first aspect of the present invention takes the form of a method of operating an internal combustion engine including the steps of: sensing the temperature of the engine coolant, and protecting said engine from damage and/or excessive wear by controlling the amount of fuel supplied to said engine in accordance with the sensed engine coolant temperature and therefore limiting the maximum temperature and engine speed of said engine to predetermined limits. 
     A further aspect of the present invention comes in the form of an internal combustion engine including a coolant sensor and a control arrangement responsive to the output of the temperature sensor for controlling the amount of fuel supplied to the engine, the control circuit being arranged to limit the maximum temperature and engine speed of the engine in a manner to prevent damage and/or excessive wear. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages of the arrangement of the present invention will become more clearly appreciated from the following description taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a schematic diagram showing an internal combustion engine equipped with a microprocessor which controls the engine in accordance with the present invention; 
     FIGS. 2(a), 2(b) and 2(c) respectively show, in graphical form, a maximum fuel injection control schedule, a maximum engine speed control schedule and an engine idling control schedule (all as a function of engine coolant temperature) which characterize an embodiment of the present invention; 
     FIG. 3 shows in graphically form a &#34;running-in&#34; control schedule according to the present invention; and 
     FIG. 4 is a flow chart showing the steps which characterize an embodiment of the invention implemented via microprocessor or like device. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows an internal combustion engine 10 (which by way of example takes the form of a diesel engine) equipped with a fuel injector 12, an engine speed sensor 14, a coolant sensor 16, and a microprocessor 18 which receives inputs from the engine speed sensor 14 and coolant temperature sensor 16 and an accelerator pedal position sensor 20. A control output of the microprocessor 18 is fed to a fuel injection control unit 22 (including a fuel pump) which is operatively connected with the accelerator pedal 24. The microprocessor 18 further receives inputs from a circuit 26 such as an odometer, indicating (a) the total distance traversed by the vehicle (not shown) in which the engine 10 is mounted, and from the fuel injection control unit 22 indicating (b) the actual amount of fuel being injected. This latter mentioned input may, by way of example, take the form of the injection control signal pulse width in the case of a gasoline engine or a signal indicative of the position of a fuel injection pump drain port sleeve valve, in the case of a diesel engine. 
     As shown, the microprocessor 18 includes a RAM, a ROM and a CPU operatively interconnected with the sensors 14, 16, 20 and 26 and the fuel injection control unit 22 via input and output interfaces I/O. 
     In this embodiment the ROM contains the control schedules shown in FIGS. 2(a), (b), (c) and 3, in the form of look-up tables. In the case of the tables shown in FIGS. 2(a)-(c) the X-axis is graduated in terms of engine coolant temperature while on the Y-axis thereof is plotted a factor by which the normal injection or engine speed should be modified for any given temperature within the plotted range. On the other hand in the table of FIG. 3, the abscissa is calibrated in terms of vehicle mileage while the ordinate is calibrated in terms of a factor which which the maximum engine speed and temperature should be modified during running-in. In this example, the factor varies from 0.5 to 1.0. 
     FIG. 4 shows in flow chart form the characterizing steps of a program which utilizes the data contained in the above mentioned four tables and via which the fuel injection controlled unit is controlled. 
     As shown, following the START of the program in step 101, the program proceeds in step 102, to read the instantaneous value of the engine coolant temperature and obtain, via table look-up, the corresponding values of factors k 1  -k 3 . In step 103 the program reads the vehicle mileage and determines the corresponding values of K 1  and K 2  via table look-up. Of course if the vehicle has run more than 1000 Km (for example) the values of both K 1  and K 2  will both be &#34;1&#34;. 
     In step 104 the program determines if K 1  is greater than k 1 . If the answer to this inquiry is NO, the program in step 105, sets the value of k 1  equal to K 1  so as to suitably reduce the amount of fuel injected during the &#34;running in&#34; period and proceeds to step 106. If the answer to the inquiry made at step 104 is YES, then the program proceeds directly to step 106 wherein K 2  is compared with k 2 . If the result of this comparison indicates that k 2  is larger than K 2  then the program goes to step 107 wherein the value of k 2  is set equal to the lower of the two values, i.e. to K 2  for &#34;running in&#34;. 
     In step 108 the instantaneous fuel injection quantity &#34;Q&#34; and engine speed &#34;n&#34; are read. In step 109 the maximum amount of fuel (Q max )which should be injected is derived using the equation Q MAX  =k 1  ×Q 0  (where Q 0  is the maximum possible injection quantity) and compared in step 110 with the actual value (Q). If the outcome of this comparison indicates that the amount of fuel being injected (Q) is greater than the derived value (Q max ) the program reduces the amount of fuel to be injected to a value corresponding to the derived one. However, if in the instance the quantity of fuel (Q) being injected is less than the derived value (Q max ) the program maintains the injection quantity as is and proceeds to step 112 wherein the maximum engine speed N max  is derived. It should be noted that N 0  in the equation N MAX  =K 2  ×N 0  is the maximum permissible engine speed. 
     In step 113 the actual engine speed &#34;n&#34; is compared with the drived value. In the event of this comparison indicates that the &#34;n&#34; is greater than the derived N max  value the program proceeds to step 114 wherein the injection quantity (step 111) is reduced incrementally as shown, and returns to step 113. This loop is maintained until such time as the instantaneous &#34;n&#34; value becomes equal to or slightly less than the derived N max  value. 
     At step 115 the minimum engine speed (viz,. that required during idling) is derived, it being noted that &#34;N i  &#34; indicates the lowest RPM at which the engine can operate stably. In the event that the engine is idling and the instanteous engine speed &#34;n&#34; is below the derived value, the injection quantity is increased incrementally as shown in step 117 until the appropriate engine idling is acheived. This increase in idling speed increases the rate at which water or like coolant is circulated about the engine proper and therefore increases the cooling efficiency thereof. However, in the case of an engine wherein the engine coolant is not circulated by a water pump and the cooling efficiency of the engine is not increased by the increased idling speed, then the steps 115, 116 and 117 should be omitted. 
     The program terminates in step 118 and returns to step 101. 
     Thus, it will be understood that with the invention, by controlling a given parameter such as the amount of fuel fed to the engine, the maximum temperature and speed of the engine can be controlled in a manner to obviate excessive wear and damage to either the engine or the lubricant. Of course with the deterioration of the engine lubricant engine wear will tend to increase irrespective of the temperature and engine speed. Accordingly, as the present invention constantly monitors the engine temperature and speed, the deterioration of the engine lubricant is slowed, synergistically adding to the expected life-prolonging effects of the control which characterizes the present invention. 
     It will be understood that other methods of reducing engine speed and temperature fall within the scope of the present invention which is not necessarily limited to fuel quantity control. For example, one or more cylinders of the engine may be rendered inoperative via fuel cut-off during deceleration and/or idling, ignition timing control, turbocharger waste gate control or the like, in addition to the disclosed fuel injection control method.