JP2007192033A - Cooling system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cooling system capable of reducing thermal distortion of a heat exchanger at very low temperatures while inhibiting driving of a cooling fan. <P>SOLUTION: The cooling system comprises a radiator 2 for heat exchange between air and cooling water, the cooling fan 3 for supplying air to the radiator 2, a drift detection means 5, 10-12 for detecting a factor related to generation of a drift of the cooling water in the radiator 2 and a cooling system ECU 14 for controlling driving of the cooling fan 3, wherein the cooling system ECU 14 is constructed to drive the cooling fan 3 when it is judged based on the factor related to the generation of a drift detected by the drift detection means 5, 10-12 that a drift generation condition is met. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cooling system, and is effective when applied to a cooling system of an internal combustion engine (engine) that forms a driving source for traveling of a vehicle.

  The vehicle is provided with a vehicle cooling system that performs heat exchange by circulating cooling water between the engine and the radiator.

  Since LLC (antifreeze) generally used as cooling water has a high viscosity at low temperatures, there is a drift that the cooling water does not flow uniformly throughout the radiator but flows only in some tubes at extremely low temperatures. . As a result, a portion where the cooling water easily flows (drift portion) and a portion where the cooling water does not easily flow (non-drift portion) become obvious, and a temperature difference occurs at the boundary to cause thermal distortion in the tube.

  Furthermore, if the flow rate of cooling water increases when drift occurs, a large amount of cooling water flows into the drift part, so that the temperature difference between the drift part and the non-bias part further expands, resulting in large thermal distortion. There's a problem.

  On the other hand, when the cooling water flow rate increases rapidly, it is conceivable that the cooling fan is forcibly driven regardless of the cooling water temperature to rapidly cool the radiator and eliminate the drift portion. Thereby, even if the cooling water flow rate increases, the cooling water can be prevented from concentrating and flowing into a part of the tubes, so that the occurrence of large thermal distortion can be suppressed.

  However, although the frequency of occurrence of drift is rare, when the cooling fan is driven, there is a problem that the life of the cooling fan motor is reduced and the fuel consumption is deteriorated due to an increase in power consumption.

  An object of this invention is to provide the cooling system which can reduce the heat distortion of the heat exchanger at the time of extremely low temperature, suppressing the drive of a cooling fan in view of the said point.

  In order to achieve the above object, in the present invention, a heat exchanger (2) that performs heat exchange between air and a heat medium, a cooling fan (3) that supplies air to the heat exchanger (2), and a heat exchanger (2) A drift detection means (5, 10-12) for detecting a factor related to the occurrence of the drift of the heat medium in (2) and a control means (14) for controlling the driving of the cooling fan (3) are provided. The means (14) drives the cooling fan (3) when it is determined that the condition for generating the drift is established based on the factors related to the occurrence of the drift detected by the drift detection means (5, 10-12). It is characterized by letting.

  “Diffusion of the heat medium” refers to a phenomenon in which the heat medium does not flow uniformly throughout the heat exchanger (2) but flows intensively in some parts.

  Thereby, only when a drift occurs in the heat exchanger (2), the cooling fan (3) is forcibly driven to rapidly cool the heat exchanger (2), and the heat medium is transferred to the heat exchanger (2). ) It is possible to suppress the drift by making the inside flow uniformly. For this reason, it becomes possible to reduce the thermal distortion of the heat exchanger (2) at the time of extremely low temperature while suppressing the driving of the cooling fan (3).

  In the present invention, the heat medium is used as a driving source for driving the vehicle, and is configured to circulate to the engine (1) whose output changes according to the amount of operation of the accelerator by the driver. The control means (14) is determined by the drift detection means (5, 10-12) that the drift generation condition is satisfied, and the accelerator manipulation amount detection means. The second feature is to drive the cooling fan (3) when the increase rate of the accelerator operation amount detected in (13) exceeds a predetermined value.

  In this way, only when the drift occurs in the heat exchanger (2) and the operation amount of the accelerator suddenly increases, that is, when an increase in the flow rate of the heat medium flowing through the heat exchanger (2) is predicted, the cooling fan (3 ) Is forcibly driven to rapidly cool the heat exchanger (2) so that the heat medium flows uniformly in the heat exchanger (2). For this reason, it becomes possible to reduce the thermal distortion of the heat exchanger (2) at the time of extremely low temperature while further suppressing the driving of the cooling fan (3).

  In the first and second features, the drift detection means is configured to have an outside air temperature detection means (10) for detecting the outside air temperature, and the factor related to the occurrence of the drift is defined as the outside air temperature detection means (10). The outside air temperature detected by the above can be included, and the drift generation condition can be configured to include that the outside air temperature is not more than a predetermined outside air temperature.

  Further, in the first and second features, the drift detection means is configured to have flow rate detection means (11) for detecting the flow rate of the heat medium flowing through the heat exchanger (2), and a factor relating to the occurrence of drift. Can be configured to include the heat medium flow rate detected by the flow rate detection means (11), and the drift generation condition can be configured to include that the heat medium flow rate is equal to or less than a predetermined flow rate.

  Further, in the first and second features, the drift detection means is configured to have a wind speed detection means (12) for detecting the wind speed of the air passing through the heat exchanger (2), and a factor relating to the occurrence of drift. Can be configured to include the air wind speed detected by the wind speed detecting means (12), and the drift generation condition can be configured to include that the air wind speed is equal to or lower than a predetermined wind speed.

  In the first and second features, the drift detection means is configured to have water flow detection means (5) for detecting whether or not the heat medium flows into the heat exchanger (2). The factors related to the generation of the heat flow are configured to include the presence or absence of the flow of the heat medium into the heat exchanger (2) detected by the water flow detection means (5), and the drift generation condition is set as the heat exchanger (2). It can be configured to include the inflow of the heat medium to the.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. In this embodiment, the cooling system according to the present invention is applied to cooling an engine (internal combustion engine) used as a driving source for driving a vehicle.

  FIG. 1 is a schematic diagram showing a cooling system according to the present embodiment. As shown in FIG. 1, the cooling system of this embodiment includes an engine 1 and a radiator 2. The engine 1 is a water-cooled type, and has a system in which the cooling water (heat medium) is cooled by the radiator 2. In this embodiment, LLC (antifreeze) is used as cooling water. LLC has the property of increasing viscosity at low temperatures.

  As is well known, the radiator 2 includes a heat exchange core portion that is a combination of a flat tube and a corrugated fin, and a tank portion that serves to distribute and collect cooling water to the tubes of the heat exchange core portion. Then, heat is exchanged between the air (cooling air) blown from the cooling fan 3 disposed in the vicinity of the radiator 2 (for example, the vehicle rear side) and the cooling water to cool the cooling water.

  The cooling fan 3 is rotationally driven by a fan motor 3a, and the rotation speed of the cooling fan 3 is controlled by a fan controller 3b. Since a control signal from a cooling system ECU 14 to be described later is input to the fan controller 3b, the amount of cooling air blown to the radiator 2 has a structure that changes under the control of the cooling system ECU 14.

  The engine 1 and the radiator 2 are connected by a first cooling water circuit A that forms a closed circuit between the engine 1 and the radiator 2. The first cooling water circuit A is provided with a water pump 4 that is mechanically driven by the power of the engine 1 and circulates the cooling water to the first cooling water circuit A and the like. In the first cooling water circuit A, the cooling water is circulated from the cooling water outlet 1 a of the engine 1 to the cooling water inlet 1 b of the engine 1 via the radiator 2.

  In the vicinity of the cooling water outlet 1a of the first cooling water circuit A, a cooling water temperature sensor 5 is disposed. The coolant temperature sensor 5 is configured to detect the coolant temperature immediately after being discharged from the coolant outlet 1a and to output a detection signal to a coolant system ECU 14 described later.

  In the middle of the first cooling water circuit A, a bypass circuit B that bypasses the radiator 2 and circulates the cooling water is connected in parallel to the first cooling water circuit A. A thermostat 6 provided on the suction side of the water pump 4 performs switching control between the case where the cooling water is circulated through the bypass circuit B and the case where the cooling water is circulated through the radiator 2.

  The thermostat 6 is a cooling water temperature responsive valve and opens and closes the cooling water passage by displacing the valve body by using a volume change due to the temperature of the thermo wax (temperature sensitive member) as is well known. Specifically, when the cooling water temperature rises to a set temperature set by the thermo wax (86 ° C. in the present embodiment), the thermostat 6 opens the outlet side cooling water circuit of the radiator 2, and the cooling water enters the radiator 2. Flowing. On the other hand, when the cooling water temperature is equal to or lower than the installation temperature, the cooling water flows to the bypass circuit B.

  In the first cooling water circuit A, a branching portion 7 is formed downstream from a portion where the cooling water temperature sensor 5 is disposed, and a merging portion 8 is formed between the water pump 4 and the thermostat 6. ing. A second cooling water circuit C is provided between the branch portion 7 and the junction portion 8. A heater core 9 is disposed in the second cooling water circuit C. The heater core 9 heats the air-conditioning air blown from an air-conditioning blower (not shown) of a vehicle air-conditioner (not shown) by exchanging heat with the cooling water flowing in the heater core 9.

  The cooling system of the present embodiment includes an outside air temperature sensor 10 that detects outside air temperature, an engine speed sensor 11 that detects the number of revolutions of the engine 1, a vehicle speed sensor 12 that detects the speed of the vehicle, and a driver's accelerator pedal. Is provided with an accelerator opening sensor 13 for detecting the amount of depression (accelerator opening). Each of these sensors 10 to 13 is configured to output a detection signal to a cooling system ECU 14 described later. The accelerator opening sensor 13 corresponds to the accelerator operation amount detection means of the present invention.

  The cooling system ECU (control means) 14 is composed of a well-known microcomputer comprising a CPU, ROM, RAM, etc. and its peripheral circuits. The cooling system ECU 14 receives sensor signals from the cooling water temperature sensor 5, the outside air temperature sensor 10, the engine speed sensor 11, the vehicle speed sensor 12, and the accelerator opening sensor 13. Further, the cooling system ECU 14 outputs a control signal to the fan controller 3b based on the calculation result. The cooling water temperature sensor 5, the outside air temperature sensor 10, the rotation speed sensor 11 and the vehicle speed sensor 12 correspond to the drift detection means of the present invention.

  Next, cooling fan control of the cooling system configured as described above will be described with reference to FIGS. FIG. 2 is a flowchart showing cooling fan control performed by the cooling system ECU 14 of the cooling system in the present embodiment according to a program stored in the ROM, and FIG. 3 is a control diagram showing normal fan control in the present embodiment.

  In FIG. 2, first, normal fan control is performed (S100). That is, as shown in FIG. 3, a pulse signal for PWM control of the fan motor 3a in response to a water temperature control signal for keeping the cooling water temperature at a predetermined temperature from an engine ECU (engine electronic control unit, not shown). Output to the fan controller 3b.

  Returning to FIG. 2, it is determined whether or not the coolant temperature measured by the coolant temperature sensor 5 exceeds a predetermined coolant temperature (S110). Here, the predetermined cooling water temperature is set to the same temperature as the set temperature (86 ° C. in the present embodiment) set by the thermo wax of the thermostat 6. For this reason, it can be diagnosed whether the cooling water is flowing into the radiator 2 by determining whether or not the cooling water temperature is higher than the predetermined cooling water temperature. The cooling water temperature sensor 5 corresponds to the water flow detecting means of the present invention.

  When the cooling water temperature measured by the cooling water temperature sensor 5 does not exceed the predetermined cooling water temperature (S110: NO), it is diagnosed that the cooling water does not flow to the radiator 2 through the bypass circuit B, and S100. Return to.

  On the other hand, when the cooling water temperature measured by the cooling water temperature sensor 5 is higher than the predetermined cooling water temperature (S110: YES), the cooling water is flowing to the radiator 2, that is, the radiator 2 may be drifted. It is determined that the outside air temperature measured by the outside air temperature sensor 10 is below a predetermined outside air temperature (S120).

  The drift of the cooling water occurs when the outside air temperature is extremely low (for example, −20 ° C. or lower). This is because the viscosity of the LLC used for the cooling water rapidly increases at a very low temperature, so that the cooling water easily flows only to some of the tubes and is difficult to flow uniformly over the radiator 2. Therefore, the predetermined outside air temperature is set to the temperature at which drift starts, that is, a temperature at which drift is likely to occur below this temperature (−20 ° C. in this embodiment), and the outside temperature measured by the outside temperature sensor 10. Is compared with a predetermined outside air temperature, it is possible to diagnose whether or not there is a possibility of drifting of the cooling water. The outside air temperature sensor 10 corresponds to the outside air temperature detecting means of the present invention.

  As a result, when the outside air temperature measured by the outside air temperature sensor 10 is not lower than the predetermined outside air temperature (S120: NO), the outside air temperature does not satisfy the drift generation condition (at the time of extremely low outside air temperature), that is, Diagnose that no drift has occurred in the radiator 2, and return to S100.

  On the other hand, when the outside air temperature measured by the outside air temperature sensor 10 is lower than the predetermined outside air temperature (S120: YES), the outside air temperature satisfies the drift generation condition, that is, the radiator 2 has drift. The engine speed measured by the engine speed sensor 11 is less than a predetermined speed (S130).

  The uneven flow of the cooling water is generated when the flow rate of the cooling water flowing through the radiator 2 is low. This is because the cooling water easily flows through the entire radiator 2 when the flow rate is high, but the cooling water easily flows only through some tubes when the flow rate is low. Further, when the water pump 4 is mechanically driven by the power of the engine 1 as in this embodiment, the flow rate of the cooling water flowing through the radiator 2 is proportional to the engine speed. For this reason, the predetermined rotation speed is set to the engine rotation speed (1500 rpm in the present embodiment) at which the occurrence of drift is likely to occur when the rotation speed is equal to or less than the rotation speed, and measured by the engine speed sensor 11. It is possible to diagnose whether or not there is a possibility that a drift has occurred by comparing the engine speed thus obtained with a predetermined engine speed. The engine speed sensor 11 corresponds to the flow rate detecting means of the present invention.

  As a result, when the engine speed measured by the engine speed sensor 11 does not fall below the predetermined speed (S130: NO), the engine speed, that is, the coolant flow rate is a condition for generating a drift (at a low flow rate). Is satisfied, that is, no drift has occurred in the radiator 2, and the process returns to S100.

  On the other hand, when the engine rotational speed measured by the engine rotational speed sensor 11 is below the predetermined rotational speed (S130: YES), the engine rotational speed, that is, the coolant flow rate satisfies the condition for generating the drift, that is, It is diagnosed that there is a possibility of drift in the radiator 2, and it is determined whether or not the vehicle speed measured by the vehicle speed sensor 12 is below a predetermined vehicle speed (S140).

  The drift of the cooling water occurs when the speed of the cooling air passing through the radiator 2 is low. This is because when the cooling air is at a high wind speed, the entire radiator 2 can be cooled to a uniform temperature, but when the flow rate is low, the entire radiator 2 cannot be reliably cooled, and the temperature of the entire radiator 2 is uniform. It is because it cannot be made. Further, since the cooling air speed passing through the radiator 2 can be determined from the vehicle speed when the cooling fan 3 is not driven, there is a possibility that the predetermined vehicle speed is generated at the drift start speed, that is, the drift is generated below this vehicle speed. By setting the speed (15 km / h in the present embodiment) and comparing the vehicle speed measured by the vehicle speed sensor 12 with a predetermined vehicle speed, it is possible to diagnose whether or not there is a possibility of drifting. . The vehicle speed sensor 12 corresponds to the wind speed detecting means of the present invention.

  As a result, when the vehicle speed measured by the vehicle speed sensor 12 does not fall below the predetermined vehicle speed (S140: NO), the vehicle speed, that is, the cooling wind speed passing through the radiator 2 satisfies the drift generation condition (at the time of low wind speed). No, i.e., no drift has occurred in the radiator 2, and the process returns to S100.

  On the other hand, when the vehicle speed measured by the vehicle speed sensor 12 is lower than the predetermined vehicle speed (S140: YES), the vehicle speed, that is, the cooling air speed passing through the radiator 2 satisfies the drift generation condition (at the time of low wind speed). Further, together with the diagnosis results of S110 to S130, it is diagnosed that a drift has occurred in the radiator 2, and whether or not the increase rate of the accelerator opening measured by the accelerator opening sensor 13 exceeds a predetermined value. Determine (S150).

  As the vehicle accelerates and the engine speed increases, the flow rate of cooling water flowing into the radiator 2 increases. For this reason, it is determined in advance whether the rate of increase of the accelerator opening exceeds a predetermined value (accelerator opening suddenly increases), that is, whether or not the accelerator opening signal indicates a step response. It is possible to predict whether or not the cooling water flow rate will increase.

  As a result, when the increase rate of the accelerator opening measured by the accelerator opening sensor 13 does not exceed the predetermined value (S150: NO), it is diagnosed that the flow rate of the cooling water flowing into the radiator 2 does not increase, and S100 Return to.

  On the other hand, when the increase rate of the accelerator opening measured by the accelerator opening sensor 13 exceeds a predetermined value (S150: YES), it is diagnosed that the flow rate of the cooling water flowing into the radiator 2 increases, and the cooling fan 3 Is forcibly driven for several seconds (S160), and the process returns to S100.

  The outside air temperature, the cooling water flow rate, the cooling wind (air) wind speed, and the presence or absence of water flow to the radiator 2 correspond to the “factors related to the occurrence of drift” in the present invention. Further, the extremely low outside air temperature, the low cooling water flow rate, the low cooling wind speed and the water flow to the radiator 2 correspond to the “drift generation condition” of the present invention.

  As described above, when all the conditions of the extremely low outside air temperature, the low cooling water flow rate, and the low cooling air speed are satisfied and the thermostat 6 is opened and water is passed through the radiator 2, the drift is generated in the radiator 2. Only when a diagnosis is made and it is further diagnosed that the flow rate of cooling water increases in the state of occurrence of drift, the cooling fan 3 is forcibly driven to rapidly cool the radiator 2 so that the cooling water flows uniformly to all the tubes. By doing, generation | occurrence | production of a thermal distortion can be suppressed. Therefore, it is possible to reduce the thermal distortion of the radiator 2 at a very low temperature while suppressing the driving of the cooling fan 3. Thereby, while being able to improve the lifetime of the fan motor 3a, power consumption can be reduced and a fuel consumption can be improved.

  Furthermore, since it is possible to determine the occurrence of drift using existing sensors mounted on the vehicle, the heat distortion of the radiator 2 at extremely low temperatures can be reduced with a simple configuration while suppressing the driving of the cooling fan 3. It becomes possible to do.

(Other embodiments)
In the above embodiment, when the cooling system ECU 14 satisfies all the conditions for generating a drift (extremely low outside air temperature, low cooling water flow rate, low cooling wind speed, and water passing through the radiator 2), the radiator 2 Although it is configured to diagnose that a drift of cooling water has occurred in the inside, not limited to this, it may be configured to diagnose that a drift has occurred when at least one of the conditions for occurrence of drift is satisfied. Good.

  Further, in the above embodiment, the accelerator opening signal is directly input from the accelerator opening sensor 13 to the cooling system ECU 14, but the accelerator opening signal is input from the accelerator opening sensor 13 to the engine ECU. An accelerator opening signal may be input from the ECU to the cooling system ECU 14. Similarly, a vehicle speed signal may be input from the vehicle speed sensor to the meter ECU, and a vehicle speed signal may be input from the meter ECU to the cooling system ECU.

  Moreover, in the said embodiment, although the mechanical pump was used as the water pump 4, an electric pump may be used.

It is a mimetic diagram showing a cooling system concerning an embodiment of the present invention. It is a flowchart which shows the cooling fan control in embodiment of this invention. It is a control diagram showing normal fan control in an embodiment of the present invention.

Explanation of symbols

  2 ... Radiator (heat exchanger), 3 ... Cooling fan, 5 ... Cooling water temperature sensor (water flow detecting means), 10 ... Outside air temperature sensor (outside air temperature detecting means), 11 ... Engine speed sensor (flow rate detecting means), DESCRIPTION OF SYMBOLS 12 ... Vehicle speed sensor (wind speed detection means), 13 ... Accelerator opening degree sensor (accelerator operation amount detection means), 14 ... Cooling system ECU (control means).

Claims (6)

A heat exchanger (2) for exchanging heat between air and a heat medium;
A cooling fan (3) for supplying air to the heat exchanger (2);
Drift detection means (5, 10-12) for detecting factors related to the occurrence of drift of the heat medium in the heat exchanger (2);
Control means (14) for controlling the driving of the cooling fan (3),
When the control means (14) determines that the drift generation condition is satisfied based on a factor related to the occurrence of the drift detected by the drift detection means (5, 10-12), the cooling fan A cooling system characterized by driving (3). The heat medium is used as a driving source for driving the vehicle, and is configured to circulate to the engine (1) whose output changes according to the amount of accelerator operation by the driver.
An accelerator operation amount detection means (13) for detecting the operation amount of the accelerator;
The control means (14) determines that the drift generation condition is satisfied by the drift detection means (5, 10-12) and detects the acceleration detected by the accelerator operation amount detection means (13). The cooling system according to claim 1, wherein the cooling fan (3) is driven when an increase rate of an operation amount exceeds a predetermined value. The drift detection means includes outside air temperature detecting means (10) for detecting outside air temperature,
The factors relating to the occurrence of drift include the outside air temperature detected by the outside air temperature detecting means (10), and the drift current generation conditions include that the outside temperature is not more than a predetermined outside temperature. The cooling system according to claim 1, wherein the cooling system is provided. The drift detection means has flow rate detection means (11) for detecting the flow rate of the heat medium flowing through the heat exchanger (2),
The factors relating to the occurrence of drift include the heat medium flow rate detected by the flow rate detection means (11), and the drift generation conditions include that the heat medium flow rate is not more than a predetermined flow rate. The cooling system according to any one of claims 1 to 3, wherein the cooling system is provided. The drift detection means has a wind speed detection means (12) for detecting the wind speed of the air passing through the heat exchanger (2),
The factors relating to the occurrence of the drift include the air wind speed detected by the wind speed detecting means (12), and the drift generation conditions include that the air wind speed is equal to or lower than a predetermined wind speed. The cooling system according to any one of claims 1 to 4, characterized in that: The drift detection means has water flow detection means (5) for detecting whether or not a heat medium flows into the heat exchanger (2),
The factors relating to the occurrence of the drift include the presence or absence of inflow of a heat medium into the heat exchanger (2) detected by the water flow detection means (5). 6. Cooling system according to any one of the preceding claims, characterized in that there is an inflow of a heat medium into the heat exchanger (2).

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