Abstract:
An internal combustion engine control apparatus includes: a fuel injector; a cooling fan of a radiator that radiates the heat of coolant in a coolant passage in the internal combustion engine; a flow rate control mechanism that variably controls the flow rate of the coolant; an abnormality detector that detects an abnormality of the cooling fan; and a controller that controls the amount of fuel injected from the fuel injector to the internal combustion engine and the operation of the flow rate control mechanism in accordance with the result of the abnormality detector.

Description:
INCORPORATION BY REFERENCE 
       [0001]    The disclosure of Japanese Patent Application No. 2007-38455 filed on Feb. 19, 2007 including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to an internal combustion engine apparatus and an internal combustion engine control method. 
         [0004]    2. Description of the Related Art 
         [0005]    Japanese patent application publications No. 60-85215 (JP-A-60-85215) and No. 2002-276362 (JP-A-2002-276362) each describe an internal combustion engine cooling system in which coolant is delivered to coolant passages (water jacket) in the internal combustion engine using a water pump to absorb the heat from the internal combustion engine. The internal combustion engine cooling system sends the coolant that has been heated by absorbing the heat from the internal combustion engine to the radiator so that the heat of the coolant is radiated to the atmosphere. 
         [0006]    A fan is provided at the radiator to facilitate the heat radiation from the coolant. However, upon an operation failure of the fan, the heat radiation from the coolant becomes insufficient and thus the absorption of the heat from the internal combustion engine becomes insufficient. If the vehicle continues running in this state, the internal combustion engine may overheat. 
       SUMMARY OF THE INVENTION 
       [0007]    The invention provides an internal combustion engine control apparatus and an internal combustion engine control method that prevent the overheating of the internal combustion engine even when the cooling fan of the radiator is not normally operating. 
         [0008]    Aspects of the invention relates to an internal combustion engine control apparatus and method, including: a fuel injector; a flow rate control mechanism that variably controls the flow rate of the coolant in a coolant passage in the internal combustion engine; and controlling portion for detecting whether a cooling fan of a radiator that radiates the heat of the coolant have an abnormality and controlling, in accordance with the result of the detection, the amount of fuel injected from the fuel injector and the operation of the flow rate control mechanism. According to this apparatus and method, when the cooling fan has an abnormality, in order to prevent an excessive increase in the temperature of the coolant, the flow rate of the coolant is reduced so that the amount of heat absorbed by the coolant decreases. While then, the amount of fuel injected from the fuel injector is increased so that the vaporization heat of fuel suppresses an increase in the temperature of the internal combustion engine and thus the overheating of the internal combustion engine is prevented. As such, the internal combustion engine control apparatus and method of the invention prevents the overheating of the internal combustion engine even when the cooling fan of the radiator has an abnormality. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The foregoing and further objects, features and advantages of the invention will become apparent from the following description of preferred embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements and wherein: 
           [0010]      FIG. 1  is a view schematically showing the configuration of an internal combustion engine control apparatus according to an example embodiment of the invention; 
           [0011]      FIG. 2  is a view schematically illustrating the exhaust side coolant passage and the intake side coolant passage extend through the cylinder head of the internal combustion engine; and 
           [0012]      FIG. 3  is a flowchart showing an example of the control routine that the ECU executes to prevent the overheating of the internal combustion engine. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0013]    Hereinafter, an internal combustion engine control apparatus according to an example embodiment of the invention will be described with reference to the drawings.  FIG. 1  schematically shows the configuration of the internal combustion engine control apparatus of this example embodiment. 
         [0014]    Referring to  FIG. 1 , the internal combustion engine control apparatus is constituted of an engine  1 , a fuel injector  30 , a radiator  40 , a coolant circulation passage  50 , a water pump  60 , a vehicle speed sensor  80 , an ECU  90 , etc. 
         [0015]    The ECU  90  is constituted of a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc., and controls various components including the fuel injector  30 . The engine  1  is constituted of a cylinder head  10 , a cylinder block  20 , etc. 
         [0016]    The fuel injector  30  injects fuel into the respective engine cylinders (not shown in the drawings) of the engine  1 . The amount of fuel injected from the fuel injector  30  is controlled based on the command from the ECU  90 . Fuel is supplied to the fuel injector  30  from a fuel tank  31  via a fuel pump  32 . The coolant circulation passage  50  is a passage in which to circulate the coolant for cooling the engine  1 . Detail of the coolant circulation passage  50  will be described later. 
         [0017]    The radiator  40  is connected to the coolant circulation passage  50  and cools the coolant by radiating its heat to the air passing during traveling. A cooling fan  41  is used to send air to the radiator  40  to assist heat radiation of the radiator  40 . 
         [0018]    A water pump  60  circulates the coolant in the coolant circulation passage  50 . A flow-rate control valve  70  is provided at a given position in the coolant circulation passage  50  and operates in accordance with the command from the ECU  90 . A vehicle speed sensor  80  outputs signal indicating a vehicle speed V representing the present speed of the vehicle. 
         [0019]    Inside the cylinder head  10  and the cylinder block  20  are formed, an exhaust side coolant passage  51   a , an intake side coolant passage  51   b , and a cylinder-block side coolant passage  52 . The exhaust side coolant passage  51   a , the intake side coolant passage  51   b , and the cylinder-block side coolant passage  52  are collectively referred to as “water jacket”. 
         [0020]    The exhaust side coolant passage  51   a , the intake side coolant passage  51   b , and the cylinder-block side coolant passage  52  are branched from a common passage in the engine  1  and extend along the direction in which the engine cylinders are lined up. Thus, in the engine  1 , the coolant passage is branched into multiple passages. The exhaust side coolant passage  51   a  and the intake side coolant passage  51   b  are formed in the cylinder head  10  while the cylinder-block side coolant passage  52  is formed in the cylinder block  20 . 
         [0021]    The exhaust side coolant passage  51   a  and the intake side coolant passage  51   b  will be described with reference to  FIG. 1  and  FIG. 2 .  FIG. 2  is a view schematically illustrating the exhaust side coolant passage  51   a  and the intake side coolant passage  51   b  extend through the cylinder head  10 . Note that  FIG. 2  is a simplified view, so that the fuel injector  30  is not shown. 
         [0022]    Referring to  FIG. 2 , the exhaust side coolant passage  51   a  extends through the periphery of an exhaust port  5 . That is, the exhaust side coolant passage  51   a  is arranged to cool the periphery of the exhaust port  5 . 
         [0023]    On the other hand, the intake side coolant passage  51   b  extends through the periphery of each intake port  4 . That is, the intake side coolant passage  51   b  is arranged to cool the periphery of each intake port  4 . An intake pipe  2  is connected to a surge tank  3 , and the intake air is distributed to the respective engine cylinders via the intake ports  4 . Exhaust gas is discharged from each engine cylinder to the exhaust port  5 . 
         [0024]    The cross section of the exhaust side coolant passage  51   a  is larger than those of the intake side coolant passage  51   b  and the cylinder-block side coolant passage  52 , therefore the heat-adsorbing capacity of the coolant at the exhaust side coolant passage  51   a  is larger than those of the coolant at the intake side coolant passage  51   b  and the coolant at the cylinder-block side coolant passage  52 . 
         [0025]    Next, a description will be made of the reason why the exhaust side coolant passage  51   a  is formed such that the heat-absorbing capacity of the coolant at the exhaust side coolant passage  51   a  is larger than those of the coolant at the intake side coolant passage  51   b  and the coolant at the cylinder-block side coolant passage  52 . When the engine  1  is running at a high speed, generally the temperature of the engine  1  is high. At this time, in particular, the temperature of exhaust gas increases, and such an increase in the exhaust gas temperature causes an increase in the temperature in the periphery of the exhaust port  5 . For the purpose of preventing the overheating of the engine  1  due to such a temperature increase, related technology has been proposed which makes the air-fuel ratio fuel-rich by increasing the fuel injection amount so that the increase in the engine temperature is suppressed by the vaporization heat of fuel. In this method, however, the fuel economy deteriorates even though the engine overheating can be avoided. 
         [0026]    Namely, it is possible to suppress the increase in the engine temperature at a high engine speed by separating the engine coolant passage in the cylinder head  10  into the exhaust side coolant passage  51   a  and the intake side coolant passage  51   b  and making the cross section of the exhaust side coolant passage  51   a  relatively large so that the heat-absorbing capacity of the coolant at the exhaust side coolant passage  51   a  is larger than that of the coolant at the intake side coolant passage  51   b  as in the internal combustion engine control apparatus of the example embodiment. According to this structure, even when the engine  1  is running at a high speed, an excessive increase in the engine temperature can be avoided and thus deterioration of the fuel economy can be avoided even without making the air-fuel ratio fuel-rich. 
         [0027]    Referring to  FIG. 1 , the intake side coolant passage  51   b  and the cylinder-block side coolant passage  52  converge in the downstream side. Further, the flow rate control valve  70  is arranged downstream of the downstream end of the exhaust side coolant passage  51   a . A bypass passage  51   c  is formed so as to bypass the flow rate control valve  70 . The cross section of the bypass passage  51   c  is smaller than those of other coolant passages including the exhaust side coolant passage  51   a , the intake side coolant passage  51   b , and the cylinder-block side coolant passage  52 . 
         [0028]    Next, an example of the control routine that the ECU  90  executes to avoid the overheating of the engine  1  will be described with reference to  FIG. 3 . 
         [0029]    Referring to  FIG. 3 , in this control routine, the ECU  90  first determines whether the vehicle speed V detected by the vehicle speed sensor  80  is lower than a low-speed detection reference speed V LOW  (step  1 ). More specifically, in this step, the ECU  90  determines whether the value detected by the vehicle speed sensor  80  is smaller than a reference value. If it is determined that the vehicle speed V is lower than the low-speed detection reference speed V LOW , it indicates that the air flowing toward the radiator  40  during traveling is weak and thus the amount of heat that can be radiated from the coolant via the radiator  40  is small. That is, the overheating of the engine  1  tends to occur when the vehicle is running at a low speed. 
         [0030]    If it is determined in step  1  that the vehicle speed V is lower than the low-speed detection reference speed V LOW , the ECU  90  then determines whether the cooling fan  41  presently has an abnormality (step  2 ). More specifically, in this step, the ECU  90  determines whether the temperature detected by the coolant temperature sensor  61  is higher than a reference temperature. If it is higher than the reference temperature, the ECU  90  determines that the cooling fan  41  presently has an abnormality. When the cooling fan  41  presently has an abnormality, it makes it more difficult to radiate the heat of the coolant via the radiator  40  and thus the possibility of overheating of the engine  1  increases. 
         [0031]    If it is determined in step  2  that the cooling fan  41  presently has an abnormality, the ECU  90  then issues a command to close the flow rate control valve  70  (step  3 ). When the flow rate control valve  70  is closed, the coolant flow rate at the exhaust side coolant passage  51   a  decreases, and thus, the coolant from the exhaust side coolant passage  51   a  flows to the radiator  40  via the bypass passage  51   c . 
         [0032]    Because the coolant flow rate at the exhaust side coolant passage  51   a  is being reduced, the heat-absorbing capacity of the coolant at the exhaust side coolant passage  51   a  decreases, and this causes an increase in the temperature of the periphery of the exhaust port  5  of the cylinder head  10 . To overcome this, the ECU  90  executes the following process. 
         [0033]    That is, the ECU  90  issues a command to increase the fuel injection amount of the fuel injector  30  (step  4 ), so that the air-fuel ratio becomes fuel-rich and the heat in each engine cylinder is absorbed by the vaporization heat of fuel and the temperature of the periphery of the exhaust port  5  decreases. As such, by executing the process, an excessive increase in the temperature of the engine  1  is avoided, therefore the overheating of the engine  1  is avoided. 
         [0034]    Accordingly, if the vehicle speed V is determined to be a speed lower than the low-speed detection reference speed V LOW  and the cooling fan  41  is determined to have an abnormality, the ECU  90  takes it as a indication before the occurrence of overheating of the engine  1 . In this case, the ECU  90  executes step  3  and step  4  to avoid the overheating of the engine  1 . 
         [0035]    Further, because the flow rate control valve  70  reduces the coolant flow rate at the exhaust side coolant passage  51   a , the amount of heat that the coolant absorbs from the cylinder head  10  is effectively reduced, therefore an excessive increase in the coolant temperature is avoided. 
         [0036]    While the invention has been described with reference to the example embodiment thereof, it is to be understood that the invention is not limited to the example embodiment and construction. To the contrary, the invention is intended to cover various modifications and equivalent arrangements within the sprit and scope of the invention. 
         [0037]    While the determination as to the abnormality of the cooling fan  41  is performed based on the output of the coolant temperature sensor  61  in the foregoing example embodiment, an abnormality of the cooling fan  41  may be detected using physical detecting means. For example, a hall element that converts a change in magnetic field caused by the rotation of a motor of the cooling fan  41  into electric signal and outputs the electric signal may be provided. In this case, the ECU  90  may detect that the cooling fan  41  has an abnormality when the signal form the hall element is indicating that the motor is not running despite that the ECU  90  is sending an operation command to the cooling fan  41 . 
         [0038]    In the foregoing example embodiment, if the vehicle speed V is lower than the low-speed detection reference speed V LOW , the lower the vehicle speed V, the more the ECU  90  may increase the fuel injection amount.