Patent Publication Number: US-8978599-B2

Title: Cooling apparatus of internal combustion engine for vehicle

Description:
CROSS-REFERENCE OF RELATED APPLICATION 
     The present application claims priority from Japanese Patent Application No. 2012-052734 filed Mar. 9, 2012, the disclosure of which is hereby incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a cooling apparatus of an internal combustion engine for a vehicle and more particularly relates to a cooling apparatus of an internal combustion engine for a vehicle which is capable of appropriately maintaining the temperature of the internal combustion engine by controlling a coolant passage of a coolant (cooling water) for the internal combustion engine. 
     BACKGROUND ART 
     Cooling apparatuses of an internal combustion engine mounted on a vehicle include a cooling device configured to control a coolant passage by using an electrically controlled control valve which is arranged instead of a thermostat in the coolant passage for a flow of a coolant (cooling water), so that fuel efficiency is improved by acceleration of coolant temperature rise. 
     Coolant temperature control using the control valve is performed in the following manner. Specifically, when the internal combustion engine is in a cold state, a coolant temperature is raised to a high temperature (110° C., for example) as quickly as possible. When the coolant temperature reaches the high temperature, the control valve is immediately controlled so that the temperature of the coolant is at a slightly lower temperature (90° C., for example) to avoid knocking. 
     Meanwhile, conventional cooling apparatuses include a cooling device having a minimum circulation path in addition to the coolant passage. When the internal combustion engine is started to be warmed up, all the control valves (selector valves) are closed to cause the coolant to flow through the minimum circulation path. Thereby, the internal combustion engine is warmed up quickly. 
     In a control device of a cooling system according to JP 2011-220156 A (“Patent Document 1”), a radiator configured to cool a coolant (cooling water) in an internal combustion engine, a heat exchanger for air conditioning, and an accessory of the internal combustion engine (a throttle body) are provided with coolant passages, respectively, and are connected to the internal combustion engine. These coolant passages are provided with control valves (selector valves), which are opened sequentially according to the coolant temperature. Specifically, when the coolant temperature reaches a predetermined set temperature, it is determined that the internal combustion engine is in the warmed-up state. The coolant passage for the radiator, the coolant passage for the heat exchanger for air conditioning, and the coolant passage for the accessory of the internal combustion engine are opened in this order. 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     In improving the fuel efficiency in the cooling apparatus of the internal combustion engine, it is important to reduce engine friction by accelerating temperature rise of hydraulic oil for the internal combustion engine, by use of the temperature rise of the coolant temperature. Before the hydraulic oil is in the warmed-up state, the coolant temperature is controlled to be maintained at a temperature, for example, 90° C. slightly lower than a target temperature to reliably avoid occurrence of knocking. However, the controlling of the control valve based only on the coolant temperature does not lead to thorough improvement of the fuel efficiency of the internal combustion engine in the cold state. Meanwhile, as described in Patent Document 1, it is preferable that the temperatures of the accessory of the internal combustion engine and the heat exchanger for air conditioning, which are vehicle accessories, be always maintained at appropriate temperatures. For example, when the accessory of the internal combustion engine is a throttle body, maintaining the temperature thereof constant makes it possible to stabilize an oxygen content of air passing through the throttle body and to maintain the heat exchanger for air conditioning in a heating-ready state. In other words, when in the cold state, the accessory of the internal combustion engine and the heat exchanger for air conditioning are preferably warmed up as soon as possible and maintained in a favorable condition. 
     Furthermore, although warming up the accessory of the internal combustion engine and the heat exchanger for air conditioning, a control device in Patent Document 1 has room for improvement in a point of early warming-up. 
     Hence, an object of the present invention is to provide a cooling apparatus of the internal combustion engine for a vehicle which is capable of quickly warming up an internal combustion engine and a vehicle accessory. 
     Means for Solving the Problems 
     The present invention is a cooling apparatus of an internal combustion engine for a vehicle, comprising: a coolant cooling device for cooling a coolant used for cooling the internal combustion engine; a control device for controlling a coolant passage according to a temperature state of the internal combustion engine; a first coolant passage which allows the coolant discharged from the internal combustion engine to flow in a circulated manner into the internal combustion engine via the coolant cooling device; a second coolant passage which allows the coolant discharged from the internal combustion engine to flow in a circulated manner into the internal combustion engine via a vehicle accessory; a third coolant passage which allows the coolant discharged from the internal combustion engine to flow in the circulated manner into the internal combustion engine, the third coolant passage having a cooling capacity lower than those of the first coolant passage and the second coolant passage; and at least one control valve by which coolant flow rates of the first coolant passage, the second coolant passage, and the third coolant passage are changed, wherein the control device includes: target temperature setting means for setting a target temperature of the coolant according to the temperature state of the internal combustion engine; feedback control means for controlling the control valve in such a manner that a temperature of the coolant is the target temperature; and shortcut control means for controlling the control valve in such a manner that, when the internal combustion engine is in a cold state, the target temperature setting means sets as the target temperature a warming-up temperature higher than a feedback control temperature which is set during feedback control, and the shortcut control means controls the control valve in such a manner as to keep the coolant flow rate of the third coolant passage higher than the coolant flow rates of the first coolant passage and the second coolant passage until the temperature of the coolant reaches the warming-up temperature. 
     Effects of the Invention 
     The present invention makes it possible to quickly warm up an internal combustion engine and an accessory for a vehicle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a system configuration diagram of a cooling apparatus of an internal combustion engine. (Embodiment) 
         FIG. 2A  is a diagram showing an operating state of a control valve during shortcut control.  FIG. 2B  is a diagram showing an operating state of the control valve during accessory warming-up control.  FIG. 2C  is a diagram showing an operating state of the control valve during cooling control. (Embodiment) 
         FIG. 3  is a main flowchart of control according to an embodiment. (Embodiment) 
         FIG. 4  is a flowchart of the shortcut control. (Embodiment) 
         FIG. 5  is a flowchart of the accessory warming-up control. (Embodiment) 
         FIG. 6  is a flowchart of a first method for calculating an intermediate temperature (β). (Embodiment) 
         FIG. 7  is a flowchart of a second method for calculating the intermediate temperature (β). (Embodiment) 
         FIG. 8  is a table for explaining outside-air temperatures and proportion values in the calculation of the intermediate temperature (β) shown in  FIG. 7 . (Embodiment) 
         FIG. 9  is a flowchart of a third method for calculating the intermediate temperature (β) (Embodiment) 
         FIG. 10  is a diagram for deciding an estimated cooling temperature relative to the outside-air temperature in the calculation of the intermediate temperature (β) shown in  FIG. 9 . (Embodiment) 
         FIG. 11  is a flowchart of the third method for calculating the intermediate temperature (β). (Embodiment) 
         FIG. 12  is a table for explaining outside-air temperatures and proportion values in the calculation of the intermediate temperature (β) shown in  FIG. 11 . (Embodiment) 
         FIG. 13  is a flowchart of the cooling control. (Embodiment) 
         FIG. 14  is a flowchart of feedback control. (Embodiment) 
         FIG. 15  is a graph showing changes of a coolant temperature. (Embodiment) 
         FIG. 16  is a system configuration diagram of a cooling apparatus for cooling an electrical motor. (Modification) 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     An object of the present invention is to quickly warm up an internal combustion engine and a vehicle accessory. The present invention achieves the object in such a manner that a flow rate of a coolant in a third coolant passage having a low cooling capacity is increased when the internal combustion engine is in a cold state and thereby the coolant is maintained in a high-temperature state. 
     Embodiment 
       FIGS. 1 to 15  show an embodiment of the present invention. 
     In  FIG. 1 , reference numeral  1  denotes a power unit mounted on a vehicle. 
     The power unit  1  integrally includes: an internal combustion engine  2  used for driving the vehicle and serving as a power source; and a transmission  3  coupled to the internal combustion engine  2 . 
     The internal combustion engine  2  is provided with a cooling apparatus  4 . The cooling apparatus  4  includes a coolant cooling device (a radiator)  5  configured to cool a coolant (cooling water) used for cooling the internal combustion engine  2 . 
     The cooling apparatus  4  is also provided with a first coolant passage  6  which allows the coolant discharged from the internal combustion engine  2  to flow in a circulated manner into the internal combustion engine  2  via the coolant cooling device  5 . The first coolant passage  6  has one end connected to one lateral portion of the internal combustion engine  2  and the other end connected to the other lateral portion of the internal combustion engine  2 . The first coolant passage  6  is divided into a first inlet-side coolant passage  6 A and a first outlet-side coolant passage  6 B while the coolant cooling device  5  is located therebetween in the course of the first coolant passage  6 . The first inlet-side coolant passage  6 A extends from the internal combustion engine  2  to the coolant cooling device  5 , and the first outlet-side coolant passage  6 B extends from the coolant cooling device  5  to the internal combustion engine  2 . 
     A second coolant passage  8  is provided between the first inlet-side coolant passage  6 A and the first outlet-side coolant passage  6 B in such a manner that the coolant discharged from the internal combustion engine  2  takes a shortcut without passing through the coolant cooling device  5  to flow in the circulated manner into the internal combustion engine  2  via a first vehicle accessory (a heat exchanger for air conditioning or a throttle body)  7 A included in a vehicle accessory  7 . The second coolant passage  8  includes a second main coolant passage  8 A and a second branch coolant passage  8 B which branches from the second main coolant passage  8 A and is connected to the first outlet-side coolant passage  6 B. On the second branch coolant passage  8 B, a second vehicle accessory  7 B included in the vehicle accessory  7  is arranged. 
     In addition, a third coolant passage  9  having a lower cooling capacity than those of the first coolant passage  6  and the second coolant passage  8  is provided between the first inlet-side coolant passage  6 A and the first outlet-side coolant passage  6 B and in parallel with the second coolant passage  8  in such a manner that the coolant discharged from the internal combustion engine  2  takes a shortcut without passing through the coolant cooling device  5  to flow into the internal combustion engine  2  in the circulated manner. 
     Furthermore, a control valve  10  is arranged in the course of the first inlet-side coolant passage  6 A. The control valve  10  is parallel-connected to one of the ends of the second coolant passage  8  and the third coolant passage  9 , respectively. The control valve  10  controls a portion of the first inlet-side coolant passage  6 A which is downstream of the control valve  10 , the second coolant passage  8 , and the third coolant passage  9 , so that flow rates of the coolant flowing through the first inlet-side coolant passage  6 A, the second coolant passage  8 , and the third coolant passage  9  are changed. The other ends of the second main coolant passage  8 A, the second branch coolant passage  8 B, and the third coolant passage  9 , respectively, are parallel-connected to the first outlet-side coolant passage  6 B. 
     The control valve  10  which is a three-way selector valve controlled electronically includes a case  11  and a valve element  13  having a crescent-shaped cross section which rotatably operates in an internal space  12  in the case  11 , as shown in  FIG. 2 . The control valve  10  causes the internal space  12  to communicate with the one ends of the first inlet-side coolant passage  6 A, the second coolant passage  8 , and the third coolant passage  9  in a switching manner by using a rotating operation of the valve element  13 . The control valve  10  is operated in any of the states in which shortcut control ( FIG. 2A ) is executed, accessory warming-up control ( FIG. 2B ) is executed, and cooling control ( FIG. 2C ) is executed. 
     The control valve  10  is connected with a control device  14  and electronically controlled by the control device  14 . 
     A water pump  15  is provided to the first outlet-side coolant passage  6 B in a portion closer to the internal combustion engine  2  than portions thereof connected to the other ends of the second main coolant passage  8 A, the second branch coolant passage  8 B, and the third coolant passage  9 . 
     The control device  14  is connected with: a power supply  16  configured to supply power; an ignition switch  17  configured to turn on/off the internal combustion engine  2 ; a knocking sensor configured to detect abnormal combustion in the internal combustion engine  2 ; a coolant temperature sensor  19  configured to detect a temperature (Tw) of the coolant (the cooling water) in the internal combustion engine  2 ; and an outside-air temperature sensor  20  configured to detect the outside-air temperature. 
     The knocking sensor  18  includes piezoelectric elements provided to the internal combustion engine  2 . The knocking sensor  18  detects vibration of the internal combustion engine  2  in predetermined cycles, and generates an electrical current therein upon reception of the vibration of the internal combustion engine  2 . 
     The control device  14  controls coolant flow rates in the respective coolant passages  6 ,  8 , and  9  according to the temperature state of the internal combustion engine  2 . 
     In this respect, the control device  14  includes target temperature setting means  21 , feedback control means  22 , shortcut control means  23 , accessory warming-up control means  24 , and cooling control means  25 . In other embodiments, the target temperature setting means  21 , feedback control means  22 , shortcut control means  23 , accessory warming-up control means  24 , and cooling control means  25  comprise individual or combined electronic control units (e.g. computer chip, PLC controller, microchip, etc.) containing the programs, memory, and structure to perform their respective functions. 
     The target temperature setting means  21  sets a target temperature (γ) of the coolant according to the temperature state of the internal combustion engine  2 . 
     The feedback control means  22  controls the control valve  10  in such a manner that the temperature of the coolant is the target temperature (γ) (see  FIG. 14 ). A failsafe valve  26  provided to the control valve  10  is connected with the feedback control means  22 . 
     The shortcut control means  23  controls the control valve  10  (see  FIG. 2A ,  FIG. 4 , and  FIG. 15 ) in such a manner that, when the internal combustion engine  2  is in a cold state, the target temperature setting means  21  sets as the target temperature (γ) a warming-up temperature (α) higher than a feedback control temperature (a first feedback control temperature A or a second feedback control temperature B) which is set during feedback control, and the shortcut control means controls the control valve in such a manner as to keep the coolant flow rate of the third coolant passage  9  higher than the coolant flow rates of the first coolant passage  6  and the second coolant passage  8  until the temperature of the coolant reaches the warming-up temperature (α). The first feedback control temperature A and the second feedback control temperature B have a relation of A&lt;B. 
     When the internal combustion engine  2  is in the warmed-up state, the accessory warming-up control means  24  increases the coolant flow rate of the second coolant passage  8  to warm up the vehicle accessory  7  (see  FIG. 5 ). 
     The accessory warming-up control means  24  controls the control valve  10  in such a manner that the third coolant passage  9  is maintained opened (see  FIG. 2B ). 
     Furthermore, the accessory warming-up control means  24  prohibits the cooling control until the coolant temperature (Tw) reaches an intermediate temperature (β) set at a temperature between the warming-up temperature (α) and the feedback control temperature (A or B) (see  FIG. 5 ). 
     Still further, the accessory warming-up control means  24  calculates the intermediate temperature (β) by subtracting an estimated cooling temperature estimated based on an outside-air temperature from the warming-up temperature (α) (see  FIGS. 9 and 10 ). 
     In addition, when the knocking sensor  18  detects abnormal combustion, the accessory warming-up control means  24  sets the intermediate temperature (β) at a temperature higher than in a case in which the knocking sensor  18  does not detect abnormal combustion (see  FIGS. 7 ,  8 ,  11 , and  12 ). 
     When the vehicle accessory  7  is warmed up, the cooling control means  25  increases the coolant flow rate of the first coolant passage  6  to cool the coolant (see  FIG. 13 ). 
     When the vehicle accessory  7  is in the warmed-up state, the cooling control means  25  controls the control valve  10  in such a manner that at least one of the coolant passages different from the first coolant passage  6  is maintained opened and that the coolant flow rate of the first coolant passage  6  is increased (see  FIG. 2C ). In this case, the different coolant passage is the second coolant passage  8 . 
     Furthermore, when the vehicle accessory  7  is in the warmed-up state, the cooling control means  25  controls the control valve  10  in such a manner that at least one of the coolant passages except the different coolant passage maintained opened is closed (see  FIG. 2C ). In this case, the coolant passage except the different coolant passage is the third coolant passage  9 . 
     A description is given of changes of the aforementioned coolant temperature (Tw). 
     The coolant temperature (Tw) is changed as shown in  FIG. 15 . Specifically, from the start up of the internal combustion engine  2  (time t 1 ) to the end of a first predetermined period T 1  (time t 2 ), only the third coolant passage  9  is opened, and the coolant temperature (Tw) is raised to the warming-up temperature (α). 
     After the coolant temperature (Tw) reaches the warming-up temperature (α), the third coolant passage  9  and the second coolant passage  8  are opened, so that the coolant loses the heat. The coolant temperature (Tw) lowers to the intermediate temperature (β) (time t 3 ) after a second predetermined period T 2  passes. 
     Since the coolant cooling device  5  and the vehicle accessory  7  are in the cold state before the coolant flows therein, the second predetermined period T 2  exhibits a sharp gradient in the first coolant circulation cycle. 
     Thereafter, when the coolant cooling device  5  and the vehicle accessory  7  are warmed up gradually, the gradient becomes gentle. That is, fans of the coolant cooling device  5  and the heat exchanger maintain certain cooling capacities, as long as the rotational speeds of the fans provided are not changed. In other words, the cooling capacities are changed in a quadratic curve to prevent linear cooling. 
     When the coolant temperature (Tw) falls below the intermediate temperature (β), the accessory warming-up control is executed, so that the first coolant passage  6  and the second coolant passage  8  are opened. When a third predetermined period T 3  passes (time t 4 ) and the coolant temperature (Tw) reaches the feedback control temperature (A or B) at the end of the predetermined period T 3 , feedback control is started. 
     The feedback control temperature includes the first feedback control temperature A and the second feedback control temperature B as described above. A broken line M is used for showing changes of the coolant temperature (Tw) in a case in which the target temperature (γ) is set at the feedback control temperature (A) upon detection of knocking. 
     For a case in which knocking is present, the intermediate temperature (β) is set at a lower temperature than in a case in which knocking is absent, so that the cooling control is started earlier. 
     Next, description is given of control according to this embodiment. 
     As shown in a main flowchart in  FIG. 3 , upon start of a program of the control device  14  (Step A 01 ), it is first determined whether or not the power supply  16  is on, that is, whether or not a so-called accessory power supply is on (Step A 02 ). If Step A 02  results in NO, the determination is repeated. 
     If Step A 02  results in YES, the shortcut control is performed (Step A 03 ). The shortcut control in Step A 03  will be described specifically with reference to a flowchart in  FIG. 4  later. 
     The accessory warming-up control is performed after the shortcut control (Step A 04 ). The accessory warming-up control in Step A 04  will be descried specifically with reference to a flowchart in  FIG. 5  later. 
     The cooling control is performed after the accessory warming-up control (Step A 05 ). The cooling control in Step A 05  will be described specifically with reference to a flowchart in  FIG. 13  later. 
     The feedback control is performed after the cooling control (Step A 06 ). The feedback control in Step A 06  will be described specifically with reference to a flowchart in  FIG. 14  later. 
     After the feedback control, the program is terminated (Step A 07 ). 
     The aforementioned shortcut control in Step A 03  in  FIG. 3  is performed in accordance with the flowchart in  FIG. 4 . 
     The shortcut control is performed when the temperature of the internal combustion engine  2  has not reached the preset warming-up temperature (α) and thus the internal combustion engine  2  is determined as being in the cold state. Accordingly, the control valve  10  is controlled (see  FIG. 2A ) to warm up the internal combustion engine  2  quickly in the following manner. Specifically, the coolant flow rate of the third coolant passage  9  is made higher than those of the first coolant passage  6  and the second coolant passage  8  by closing the first coolant passage  6  and the second coolant passage  8  or making smaller the areas of openings thereof. As shown in  FIG. 4 , upon start of a program of the shortcut control means  23  (Step B 01 ), the coolant temperature (Tw) is firstly acquired from the coolant temperature sensor  19  (Step B 02 ), and it is determined whether or not the coolant temperature (Tw) is equal to or higher than the preset warming-up temperature (α) (TV≧α) (Step B 03 ). Note that in Step B 03 , the target temperature setting means  21  sets the target temperature (γ) of the coolant according to a factor such as the coolant temperature (Tw). 
     If Step B 03  results in NO, the control valve  10  is controlled (see  FIG. 2A ), so that the coolant flow rate of the third coolant passage  9  is made higher than those of the first coolant passage  6  and the second coolant passage  8  (Step B 04 ). This makes it possible to warm up the internal combustion engine  2  quickly. 
     After Step B 04 , the processing returns to Step B 02 . 
     If Step B 03  results in YES, the knocking sensor  18  performs knocking determination processing (Step B 05 ). 
     Then, it is determined whether or not knocking is present (Step B 06 ). In Step B 06 , the knocking sensor  18  detects a generated current. If a vibration value of the internal combustion engine  2  is equal to or higher than a predetermined value, it is determined that knocking is present. The knocking determination is repeated in cycles. Once knocking is detected in the predetermined cycles, it is determined that knocking is present. If no knocking is detected in the predetermined cycles, it is determined that knocking is absent. 
     If Step B 06  results in YES, the target temperature (γ) is set at the first feedback control temperature (A) (see  FIG. 15 ) (Step B 07 ). 
     On the other hand, if Step B 06  results in NO, the target temperature (γ) is set at the second feedback control temperature (B) (Step B 08 ). 
     After the processing in Step B 07  or Step B 08 , the program is terminated (Step B 09 ). 
     The aforementioned accessory warming-up control in Step A 04  in  FIG. 3  is performed in accordance with the flowchart in  FIG. 5 . 
     The accessory warming-up control is executed after the internal combustion engine  2  is warmed up according to the shortcut control, and thereby the vehicle accessory  7  is warmed up efficiently quickly. Specifically, the vehicle accessory  7  is warmed up while the control valve  10  (see  FIG. 2B ) is controlled in such a manner that the intermediate temperature (β) is calculated based on the warming-up temperature (α) and the target temperature (γ) and that the coolant flow rate of the second coolant passage  8  is increased until the coolant temperature (Tw) reaches the intermediate temperature (β). 
     As shown in  FIG. 5 , upon start of a program of the accessory warming-up control means  24  (Step C 01 ), the intermediate temperature (β) is first calculated (Step C 02 ). The intermediate temperature (β) is calculated in  FIGS. 6 to 12 , described later. 
     Then, the control valve  10  is controlled (see  FIG. 2B ) to increase the coolant flow rate of the second coolant passage  8  (Step C 03 ). This makes it possible to warm up the vehicle accessory  7  quickly. 
     Thereafter, it is determined whether or not the coolant temperature Tw≦the intermediate temperature β (Step C 04 ). If Step C 04  results in NO, the processing is moved back to Step C 02  to prohibit the cooling control. 
     On the other hand, if Step C 04  results in YES, the program is terminated (Step C 05 ). 
     To calculate the intermediate temperature (β) in aforementioned Step C 02 , there are the following first to fourth calculation methods. 
     (1) In the first calculation method, upon start of the program (Step D 01 ) as shown in  FIG. 6 , the intermediate temperature β is calculated in accordance with the following equation (Step D 02 ).
 
Intermediate temperature β=(warming-up temperature α+target temperature γ)×0.5 (a proportion value: an average value)
 
     Here, the intermediate temperature is multiplied by 0.5 which is the proportion value, but may be multiplied by 0.8, for example, to set the intermediate temperature (β) at a higher value, so that control is performed to open the first coolant passage  6  earlier. This is because when it is determined that knocking is present, quick cooling is required. 
     Then, the program is terminated (Step D 03 ). 
     (2) In the second calculation method, the presence or absence of knocking is taken into consideration. As shown in  FIGS. 7 and 8 , if knocking is present, a first set value (C) is set, and the proportion value is set at 0.8. On the other hand, if knocking is absent, a second set value (D) is set, and the proportion value is set at 0.5. Here, the first set value (C) and the second set value (D) have a relation of C&lt;D. 
     As shown in  FIG. 7 , upon start of the program (Step E 01 ), it is determined whether or not the target temperature (γ) is the first set value (C: a lower set value) (Step E 02 ). 
     If Step E 02  results in YES, the intermediate temperature (β) is calculated in accordance with the following equation (Step E 03 ).
 
Intermediate temperature β=(warming-up temperature α+target temperature γ)×0.8
 
     On the other hand, if Step E 02  results in NO, the intermediate temperature (β) is calculated in the following equation (Step E 04 ).
 
Intermediate temperature β=(warming-up temperature α+target temperature γ)×0.5
 
     After the processing in Step E 03  or Step E 04 , the program is terminated (Step E 05 ). 
     (3) In the third calculation method, as shown in  FIGS. 9 and 10 , the estimated cooling temperature is obtained based on the outside-air temperature detected from the outside-air temperature sensor  20 . 
     For this reason, a table for deciding the estimated cooling temperature according to the outside-air temperature is set for  FIG. 10 . 
     As shown in  FIG. 9 , upon start of the program (Step F 01 ), the outside-air temperature outputted from the outside-air temperature sensor  20  is detected. Then, the estimated cooling temperature is estimated based on the detected outside-air temperature (Step F 02 ), as shown in  FIG. 10 . 
     Subsequently, the intermediate temperature (β) is calculated in accordance with the following equation (Step F 03 ).
 
Intermediate temperature β=warming-up temperature α−the estimated cooling temperature
 
     Thereafter, the program is terminated (Step F 04 ). 
     (4) In the fourth calculation method, the presence or absence of knocking is taken into consideration. As shown in  FIGS. 11 and 12 , if knocking is present, the first set value (C) is set, and the proportion value is set at 0.8. On the other hand, if knocking is absent, the second set value (D) is set, and the proportion value is set at 0.5. Here, there is a relation of the first set value C&lt;the second set value D. 
     The estimated cooling temperature is obtained based on the outside-air temperature detected from the outside-air temperature sensor  20 , as shown in  FIG. 10  described above. 
     As shown in  FIG. 11 , upon start of the program (Step G 01 ), the outside-air temperature outputted from the outside-air temperature sensor  20  is detected. Then, the estimated cooling temperature is estimated based on the detected outside air, as shown in  FIG. 10  (Step G 02 ). 
     Subsequently, the intermediate temperature (β) is calculated in accordance with the following equation (Step G 03 ).
 
Intermediate temperature β=warming-up temperature α−estimated cooling temperature
 
     Thereafter, it is determined whether or not the target temperature (γ) is the first set value (C: the lower set value) (Step G 04 ). 
     If Step G 04  results in YES, the intermediate temperature (β) is calculated in accordance with the following equation (Step G 05 ).
 
Intermediate temperature β=(warming-up temperature α+target temperature γ)×0.8
 
     On the other hand, if Step G 04  results in NO, the intermediate temperature (β) is calculated in accordance with the following equation (Step G 06 ).
 
Intermediate temperature β=(warming-up temperature α+target temperature γ)×0.5
 
     After the processing in Step G 05  or Step G 06 , the program is terminated (Step G 07 ). 
     The aforementioned cooling control in Step A 05  in  FIG. 3  is performed in accordance with the flowchart in  FIG. 13 . 
     The cooling control is executed after the vehicle accessory  7  is warmed up according to the aforementioned accessory warming-up control. After the vehicle accessory  7  is warmed up, the coolant temperature (Tw) is controlled to reach the target temperature (γ) quickly. Specifically, upon completion of the warming-up of the vehicle accessory  7 , the control valve  10  is controlled (see  FIG. 2C ) in the following manner. The flow rate of the coolant flowing through the first coolant passage  6  is increased and the coolant cooling device (radiator)  5  is started to cool the coolant. At the same time, the third coolant passage  9  is closed to increase the hydraulic pressure in the first inlet-side coolant passage  6 A, so that the flow rate per unit hour of the coolant flowing through the coolant cooling device  5  is increased. Furthermore, since the second coolant passage  8  is maintained opened, the temperature of the vehicle accessory  7  can be maintained constant even during the cooling control. 
     The cooling control is characterized in that the cooling control is performed after the accessory warming-up control. When the accessory warming-up control is completed, the temperature of the vehicle accessory  7  is a predetermined or higher temperature. Thus, the second coolant passage  8  is used as the shortcut passage like the third coolant passage  9 . 
     Thereby, even though cooling by the coolant cooling device  5  is started, the coolant is less likely to be cooled rapidly. In addition, since the second coolant passage  8  is used, the temperature of the vehicle accessory  7  can be maintained stably. 
     As shown in  FIG. 13 , upon start of the program (Step H 01 ), the control valve  10  is controlled (see  FIG. 2C ) in such a manner that the coolant flow rate of the first coolant passage  6  is increased and the third coolant passage  9  is closed (Step H 02 ). 
     Then, it is determined whether or not the coolant temperature Tw≦the target temperature γ (Step H 03 ). If Step H 03  results in NO, the processing is moved back to Step H 02 . On the other hand, if Step H 03  results in YES, the program is terminated (Step H 04 ). 
     The aforementioned feedback control in Step A 06  in  FIG. 3  is performed in accordance with the flowchart in  FIG. 14 . 
     In the feedback control, the control valve  10  is controlled to maintain the coolant temperature (Tw) at the target temperature (γ). When the coolant temperature (Tw) is an abnormal overheat temperature (Ts) or higher, it is determined that the coolant is not cooled due to an anomaly occurring in the control valve  10 , and thus the failsafe valve  26  is opened. 
     As shown in  FIG. 14 , upon start of the program (Step I 01 ), it is determined whether or not the coolant temperature Tw&gt;the target temperature γ (Step I 02 ). 
     If Step I 02  results in YES, the control valve  10  is controlled in such a manner that the first coolant passage  6  is closed at predetermined degrees (Step I 03 ). In other words, the first coolant passage  6  is set to have a smaller area of the opening of the first coolant passage  6 . 
     On the other hand, if Step I 03  results in NO, the control valve  10  is controlled in such a manner that the first coolant passage  6  is opened at predetermined degrees (Step I 04 ). In other words, the first coolant passage  6  is set to have a larger area of the opening of the first coolant passage  6 . 
     After the processing in Step I 03  or Step I 04 , it is determined whether or not the coolant temperature Tw≧the abnormal overheat temperature Ts (Step I 05 ). 
     If Step I 05  results in YES, the failsafe valve  26  is opened (Step I 06 ), so that the processing is moved back to Step I 02 . 
     If Step I 05  results in NO, it is determined whether or not the ignition switch  17  is off (Step I 07 ). 
     If Step I 07  results in NO, the processing is moved back to Step I 02 . 
     If Step I 07  results in YES, the target temperature (γ) is reset (Step I 08 ), and the program is terminated (Step I 09 ). 
     Although the description has heretofore been given of the embodiment of the present invention, another description will be given while the configurations of the aforementioned embodiment are applied to claims. 
     First, in the invention according to claim  1 , the first coolant passage  6 , the second coolant passage  8 , the third coolant passage  9 , and the at least one control valve  10  are provided. The first coolant passage  6  allows the coolant discharged by the internal combustion engine  2  to flow in the circulated manner into the internal combustion engine  2  via the coolant cooling device  5 . The second coolant passage  8  allows the coolant discharged by the internal combustion engine  2  to flow in the circulated manner into the internal combustion engine  2  via the vehicle accessory  7 . The third coolant passage  9  has the lower cooling capacity than those of the first coolant passage  6  and the second coolant passage  8  and allows the coolant discharged by the internal combustion engine  2  to flow in the circulated manner into the internal combustion engine  2 . The control valve  10  changes the flow rates of the coolant flowing through the first coolant passage  6 , the second coolant passage  8 , and the third coolant passage  9 , respectively. In addition, the control device  14  includes the target temperature setting means  21 , the feedback control means  22 , and the shortcut control means  23 . The target temperature setting means  21  sets the target temperature (γ) of the coolant according to the temperature state of the internal combustion engine  2 . The feedback control means  22  controls the control valve  10  in such a manner that the temperature of the coolant is the target temperature (γ). The shortcut control means  23  controls the control valve  10  in such a manner that, when the internal combustion engine  2  is in a cold state, the target temperature setting means  21  sets as the target temperature (γ) a warming-up temperature (α) higher than a feedback control temperature (A or B) which is set during feedback control, and the shortcut control means controls the control valve in such a manner as to keep the coolant flow rate of the third coolant passage  9  higher than the coolant flow rates of the first coolant passage  6  and the second coolant passage  8  until the temperature of the coolant reaches the warming-up temperature (α). 
     Thereby, when the internal combustion engine  2  is in the cold state, the coolant flow rate of the third coolant passage  9  having the lower cooling capacity is increased to make it easier to maintain the coolant in a high-temperature state. With such a configuration, the target temperature setting means  21  can set the target temperature (γ) at the warming-up temperature (α) higher than the feedback control temperature (A or B) set during the feedback control, and thus can warm up the internal combustion engine  2  at earlier timing. 
     In the invention according to claim  2 , the control device  14  includes the accessory warming-up control means  24  and the cooling control means  25 . The accessory warming-up control means  24  warms up the vehicle accessory  7  by increasing the coolant flow rate of the second coolant passage  8  when the internal combustion engine  2  is in the warmed-up state. The cooling control means  25  cools the coolant by increasing the coolant flow rate of the first coolant passage  6  when the vehicle accessory  7  is warmed up. 
     With such a configuration, after the internal combustion engine  2  is in the warmed-up state, the coolant heated by the shortcut control means  23  is caused to flow into the vehicle accessory  7  before the flow rate of the coolant flowing through the coolant cooling device  5  is increased. Thus, the vehicle accessory  7  can be started to be warmed up at earlier timing than in the conventional technique. Moreover, since the coolant temperature (Tw) has reached the warming-up temperature ( ) at this time, the vehicle accessory  7  can be warmed up quickly using the high coolant temperature (Tw). Furthermore, when the vehicle accessory  7  is warmed up, the coolant has lost the heat due to the vehicle accessory  7 , and thus the coolant temperature (Tw) is close to the feedback control temperature (A or B). Accordingly, if the control by the cooling control means  25  is started after the vehicle accessory  7  is warmed up, the feedback control can be started in a short time. 
     In the invention according to claim  3 , the accessory warming-up control means  24  controls the control valve  10  in such a manner that the third coolant passage  9  is maintained opened. 
     With such a configuration, when the accessory warming-up control means  24  of the internal combustion engine  2  according to claim  2  warms up the vehicle accessory  7  by increasing the coolant flow rate of the second coolant passage  8 , the third coolant passage  9  is maintained opened. Thus, some of the coolant to flow into the internal combustion engine  2  flows in the circulated manner into the internal combustion engine  2  via the third coolant passage  9 . Therefore, even though the coolant consumes the heat for warming up the vehicle accessory  7 , the temperature of the third coolant passage  9  is raised simultaneously, so that the high-temperature coolant is always supplied to the vehicle accessory  7 . Thus, the vehicle accessory  7  can be warmed up quickly. Here, when the outside-air temperature is low, flow of the coolant through the vehicle accessory  7  might cause the coolant temperature (Tw) to be lower than the feedback control temperature (A or B). In this respect, the configuration is also effective to prevent rapid cooling. 
     In the invention according to claim  4 , the accessory warming-up control means  24  prohibits the cooling control until the coolant temperature (Tw) reaches the intermediate temperature (β) set at the value between the warming-up temperature (α) and the feedback control temperature (A or B). 
     Generally, the cooling control is executed immediately after the accessory warming-up control, and then cooling by the coolant cooling device  5  is started before the vehicle accessory  7  is warmed up. This might cause the rapid cooling, because the coolant loses heat at this time due to both the vehicle accessory  7  and the coolant cooling device  5 . Hence, the configuration described above makes it possible to maintain, until the coolant temperature (Tw) reaches the intermediate temperature (β), the warming-up of the vehicle accessory  7 , that is, a state where the coolant is cooled by the vehicle accessory  7  and thus to prevent the rapid cooling. 
     In the invention according to claim  5 , the accessory warming-up control means  24  calculates the intermediate temperature (β) by subtracting the estimated cooling temperature estimated based on the outside-air temperature from the warming-up temperature (α). 
     Such a configuration makes it possible to keep the control over the vehicle accessory  7  until the vehicle accessory  7  is in the warmed-up state and thus to warm up the vehicle accessory  7  quickly. In addition, when the cooling control is executed after the control of the vehicle accessory  7 , the temperature of the vehicle accessory  7  is prevented from being lowered. 
     In the invention according to claim  6 , the internal combustion engine  2  is provided with the knocking sensor  18  configured to detect abnormal combustion in the internal combustion engine  2 . In addition, when the knocking sensor  18  detects abnormal combustion, the accessory warming-up control means  24  sets the intermediate temperature ( ) at a temperature higher than in a case in which the knocking sensor  18  does not detect abnormal combustion. 
     Generally, when having abnormal combustion, the internal combustion engine  2  needs to be cooled quickly to solve the abnormal combustion. Hence, with the configuration as described above in which the intermediate temperature ( ) is set at the higher temperature when the abnormal combustion is detected, the cooling control can be started at earlier timing to achieve the quick cooling. 
     In the invention according to claim  7 , the cooling control means  25  controls the control valve  10  in such a manner that when the vehicle accessory  7  is in the warmed-up state, at least one of the coolant passages different from the first coolant passage  6  is maintained opened, and the coolant flow rate of the first coolant passage  6  is increased. 
     Generally, the coolant cooling device  5  is used to cool the coolant flowing through the first coolant passage  6 . However, the coolant cooling device  5  itself is in the cold state, the coolant is cooled rapidly at the time of initial influx of the coolant, and thus might be supercooled. Hence, with the configuration as described above, the different coolant passage is maintained opened at the time of the initial influx into the coolant cooling device  5 . Thus, the configuration makes it possible to make the rapid cooling slower and thus to prevent the supercooling. Specifically, the cooling control means  25  prevents the supercooling of the coolant in the following manner. The control valve  10  is controlled in such a manner that the third coolant passage  9  having the low cooling capacity and the second coolant passage  8  used for the warming-up are used as the shortcut passages. Thereby, some of the coolant is caused not to be cooled to flow into the internal combustion engine  2 . 
     In the invention according to claim  8 , the different coolant passage according the claim  7  described above is the second coolant passage  8 . 
     Such a configuration makes it possible to maintain constant the temperature of the vehicle accessory  7  during the control, and thus is preferable in running a vehicle. 
     In the invention according to claim  9 , the cooling control means  25  controls the control valve  10  in such a manner that when the vehicle accessory  7  is in the warmed-up state, at least one of the coolant passages, except the different coolant passage maintained opened, is closed. 
     With such a configuration, at least one of the coolant passages, except the different coolant passage, is closed at the initial influx into the coolant cooling device  5 , and thereby the pressure in the first coolant passage  6  is increased to increase the flow rate of the coolant. Thus, the flow rate per hour of the coolant passing through the coolant cooling device  5  is increased. For this reason, heat of the coolant is increased and then provided for the coolant cooling device  5 , so that the cold state is overcome quickly. 
     In the invention according to claim  10 , the coolant passage except the different coolant passage according to claim  9  described above is the third coolant passage  9 . 
     With such a configuration, closing the third coolant passage  9  makes it possible to enhance the efficiency of the cooling control. 
     It should be noted that the cooling apparatus  4  may be configured as follows in the present invention. 
     For example, in a modification, an electric motor  27  is cooled as the power source instead of the internal combustion engine  2  in the cooling apparatus  4  according to the aforementioned embodiment so that the cooling apparatus  4  can be used for an electrically driven vehicle such as a hybrid vehicle or an electric vehicle, as shown in  FIG. 16 . Specifically, a hole portion is formed in a resin motor case covering a coil which is a heat-producing body in the electric motor  27 . A metal pipe is put through the hole portion to be used as a coolant passage. Alternatively, a coolant passage may be formed integrally with a metal motor case. Meanwhile, an electric vehicle does not include the internal combustion engine  2  and thus does not have a throttle body. For this reason, only the first vehicle accessory  7 A is arranged as the vehicle accessory  7  on the second main coolant passage  8 A. 
     As described above, the configuration in which the electric motor is mounted on the vehicle can also provide operations and advantageous effects similar to those in the aforementioned Embodiment. 
     Moreover, the following configuration may be employed. Specifically, to detect knocking occurrence timing with higher accuracy, it is determined that control in which anti-knocking means retards ignition timing is started upon detection of knocking by the knocking sensor. Then, the target temperature of the control valve is changed from 110° C. to 90° C., for example. 
     INDUSTRIAL APPLICABILITY 
     The cooling apparatus according to the present invention is applicable to various internal combustion engines. 
     REFERENCE SIGNS LIST 
     
         
           2  internal combustion engine 
           4  cooling apparatus 
           5  coolant cooling device 
           6  first coolant passage 
           7  vehicle accessory 
           8  second coolant passage 
           9  third coolant passage 
           10  control valve 
           14  control device 
           15  water pump 
           16  power supply 
           17  ignition switch 
           18  knocking sensor 
           19  coolant temperature sensor 
           20  outside-air temperature sensor 
           21  target temperature setting means 
           22  feedback control means 
           23  shortcut control means 
           24  accessory warming-up control means 
           25  cooling control means