Control device for internal combustion engine and control method for cooling device

The invention of the present application relates to a control device and a control method for a cooling device. A cooling device includes a first cooling water passage of a cylinder head, a second cooling water passage of a cylinder block, a control valve that changes a ratio between a flow rate of the first cooling water passage and a flow rate of the second cooling water passage, and a water pump. Then, the control device controls the control valve so that a ratio of the flow rate of the first cooling water passage increases when a cooling water circulation flow rate is insufficient due to failure of the water pump. Accordingly, it is possible to suppress damage of an engine body while suppressing deterioration in traveling performance of a vehicle when failure occurs in the water pump.

TECHNICAL FIELD

The present invention relates to a control device for an internal combustion engine and a control method for a cooling device, and particularly to a technique for controlling a cooling device of an internal combustion engine.

BACKGROUND ART

Patent Document 1 discloses an internal combustion engine which includes a cooling device for circulating cooling water by an electric water pump. Here, a vehicle operation mode is changed to a fail-safe mode when failure occurs in the electric water pump and the fail-safe mode includes a limit travel mode of limiting an opening degree of an electric throttle.

REFERENCE DOCUMENT LIST

Patent Document

Patent Document 1: Japanese Patent Application Laid-open Publication JP 2008-121656 A

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

In the cooling device of the internal combustion engine for a vehicle, when a refrigerant circulation flow rate in the internal combustion engine becomes insufficient due to failure of a pump for circulating a refrigerant and a decrease in discharge flow rate of the pump, a refrigerant flow rate in a cylinder head and a refrigerant flow rate in a cylinder block both decrease.

Then, when the cooling performance of the cylinder head is deteriorated due to a decrease in refrigerant circulation flow rate and hence a temperature of the cylinder head increases, thermal distortion occurs in the cylinder head and further there is a possibility of damaging an engine body due to knocking.

Here, when the radiation of heat from an engine is suppressed by limiting an increase in engine load in order to suppress the damage of the engine body caused by the deterioration in cooling performance of the cylinder head, a problem arises in that the traveling performance of the vehicle is largely deteriorated.

The invention has been made in view of the above-described problems and an object of the invention is to suppress damage of an engine body while suppressing deterioration in traveling performance of a vehicle when a refrigerant circulation flow rate is insufficient.

Means for Solving the Problems

Therefore, a control device according to the present invention is configured to control a cooling device including a first cooling medium passage provided in a cylinder head of an internal combustion engine, a second cooling medium passage provided in a cylinder block of the internal combustion engine, a control valve that changes a ratio between a refrigerant flow rate of the first cooling medium passage and a refrigerant flow rate of the second cooling medium passage, and a pump that circulates the refrigerant, the control device including a valve control unit that controls the control valve such that a ratio of the refrigerant flow rate of the first cooling medium passage becomes larger than that of a case where the pump is not in an abnormal state when the pump is in the abnormal state where an discharge flow rate of an operation state of causing the pump to eject a refrigerant is lower than an intended discharge flow rate by a predetermined value or more.

In addition, a control method according to the present invention is a control method for a cooling device including a first cooling medium passage provided in a cylinder head of an internal combustion engine, a second cooling medium passage provided in a cylinder block of the internal combustion engine, a control valve that changes a ratio between a refrigerant flow rate of the first cooling medium passage and a refrigerant flow rate of the second cooling medium passage, and a pump that circulates the refrigerant, the control method comprising:

a step of detecting whether the pump is in an abnormal state where an discharge flow rate of an operation state of causing the pump to eject a refrigerant is lower than an intended discharge flow rate by a predetermined value or more; anda step of controlling the control valve such that a ratio of the refrigerant flow rate of the first cooling medium passage becomes larger than that of a case where the pump is not in the abnormal state when the pump is in the abnormal state.

Effects of the Invention

According to the above-described invention, since it is possible to suppress deterioration in cooling performance of the cylinder head by increasing the ratio of the refrigerant flow rate of the first cooling medium passage when the pump is in the abnormal state where an discharge flow rate of an operation state of causing the pump to eject a refrigerant is lower than an intended discharge flow rate by a predetermined value or more, it is possible to suppress damage of the cylinder head by suppressing an increase in temperature thereof. Further, since the necessity of suppressing an increase in engine load decreases relatively, it is possible to improve the traveling performance in the abnormal pump state.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the invention will be described.

FIG. 1illustrates an example of a cooling device of an internal combustion engine for a vehicle that employs a control device according to the invention.

The cooling device illustrated inFIG. 1includes a radiator50, a first cooling water passage (first cooling medium passage)51, a second cooling water passage (second cooling medium passage)52, a cooling water supply path53, an electric water pump55, a flow rate control valve56, a cooling water returning path54a, a bypass path57, and a cooling water returning path54b. First cooling water passage51is provided in a cylinder head1aof an internal combustion engine1. Second cooling water passage52is provided in a cylinder block1bof internal combustion engine1. Cooling water supply path53has one end connected to an outlet50aof radiator50and is halfway branched into two parts to be respectively connected to inlet sides51aand52aof cooling water passages51and52. Electric water pump55is provided in cooling water supply path53between a branch part53aof cooling water supply path53and radiator50and discharges cooling water toward cooling water passages51and52. Flow rate control valve56is provided in cooling water supply path53between electric water pump55and radiator50. Cooling water returning path54ahas one end connected to an outlet side51bof first cooling water passage51and the other end connected to an inlet50bof radiator50. Bypass path57has one end connected to a middle position of cooling water returning path54aand the other end connected to flow rate control valve56. Cooling water returning path54bhas one end connected to an outlet side52bof second cooling water passage52and the other end connected to flow rate control valve56. The cooling device is a system which circulates cooling water or cooling liquid as a cooling medium in internal combustion engine1by electric water pump55.

Three channels including bypass path57, cooling water returning path54b, and cooling water supply path53extending from outlet50aof radiator50are connected to flow rate control valve56as a cooling water inflow side. Cooling water supply path53reaching a suction port of electric water pump55is connected to flow rate control valve56as a cooling water outflow side.

Then, flow rate control valve56is configured to adjust the amount of cooling water circulated through the three channels by changing the opening areas of the three channels at the inflow side in response to, for example, an operation angle of a rotor.

That is, a ratio between the amount of the cooling water passing through radiator50after passing through first cooling water passage51and the amount of the cooling water bypassing radiator50after passing through first cooling water passage51is changed so that a ratio between the amount of the cooling water flowing to first cooling water passage51and the amount of the cooling water flowing to second cooling water passage52can be changed.

For example, when the opening area of bypass path57is increased by flow rate control valve56and the opening area of a radiator passing path58extending from outlet50aof radiator50to flow rate control valve56is decreased, it is possible to increase the amount of the cooling water bypassing radiator50to be re-circulated among the cooling water passing through first cooling water passage51. Then, when the amount of the cooling water bypassing radiator50to be re-circulated is increased in a warming state, a warming operation can be promoted because the amount of heat radiated from the cooling water is decreased.

Furthermore, for example, if flow rate control valve56decreases the opening area of cooling water returning path54band increases the opening area of the channel returned from first cooling water passage51, the amount of the cooling water circulated in first cooling water passage51can be increased and the amount of the cooling water circulated in second cooling water passage52can be relatively decreased.

Here, flow rate control valve56can have, for example, the following configuration. When the rotor angle of flow rate control valve56is set to a minimal value, the flow rate in the channel bypassing radiator50becomes maximal. When the rotor angle is increased, the flow rate in the bypass channel is decreased and the flow rate in radiator50is relatively increased. When the rotor angle is further increased, the amount of the cooling water circulated in second cooling water passage52is decreased and the amount of the cooling water circulated in first cooling water passage51is increased.

FIG. 2is a diagram illustrating an example of internal combustion engine1illustrated inFIG. 1.

Internal combustion engine1illustrated inFIG. 2is a four-cycle multi-cylinder engine mounted on a vehicle as a driving source.

A fuel injection valve3is provided in an intake port2of each cylinder of internal combustion engine1. Fuel injection valve3injects fuel toward an umbrella portion of an intake valve4from the upstream side of intake valve4.

The fuel injected to fuel injection valve3is suctioned into a combustion chamber5through intake valve4in an intake cycle and is burned by a spark ignition of an ignition plug6.

In addition, a cylinder injection type internal combustion engine in which fuel injection valve3directly injects fuel into combustion chamber5can be used.

A combustion gas inside combustion chamber5is discharged to an exhaust passage8through an exhaust valve7in an exhaust cycle.

Internal combustion engine1includes an electronic control throttle10which is operated by a throttle motor9and the intake air amount of internal combustion engine1is adjusted by the opening degree of electronic control throttle10.

Furthermore, internal combustion engine1includes a fuel supply device13which pumps fuel inside a fuel tank11toward fuel injection valve3.

Fuel supply device13includes fuel tank11, a fuel pump12, a fuel gallery pipe14, and a fuel supply pipe15.

Fuel pump12is an electric pump disposed inside fuel tank11and suctions fuel inside fuel tank11to discharge the fuel.

One end of fuel supply pipe15is connected to an discharge port of fuel pump12, the other end of fuel supply pipe15is connected to fuel gallery pipe14, and a fuel supply port of fuel injection valve3of each cylinder is connected to fuel gallery pipe14.

An electronic control device31includes a microcomputer including a CPU, a ROM, a RAM, an input/output circuit, and the like. Electronic control device31controls a main body of internal combustion engine1so that the fuel injection operation of fuel injection valve3, the ignition operation of ignition plug6, the opening degree of electronic control throttle10, and the like are controlled, controls electric water pump55and flow rate control valve56constituting the cooling device, and controls fuel pump12constituting fuel supply device13.

In addition, a plurality of electronic control devices having different control targets can be provided instead of electronic control device31.

Electronic control device31inputs signals output from various sensors for detecting an operation state of internal combustion engine1.

Examples of various sensors described above include a fuel pressure sensor33which detects a fuel pressure FUPR inside a fuel gallery pipe16, an accelerator opening degree sensor34which detects a stepping amount of an accelerator pedal (not illustrated), in other words, an accelerator opening degree ACC, an air flow sensor35which detects an intake air flow amount QA of internal combustion engine1, a rotation sensor36which detects a rotation speed NE of internal combustion engine1, a water temperature sensor37which detects a cooling water temperature TW of internal combustion engine1, an air fuel ratio sensor38which detects an air fuel ratio AF of a fuel-air mixture of internal combustion engine1based on an oxygen concentration in exhaust, and a knock sensor39which detects a vibration VIB caused by the knocking of internal combustion engine1.

Then, electronic control device31controls the opening degree of electronic control throttle10based on accelerator opening degree ACC and the like, controls the fuel injection amount of fuel injection valve3based on intake air flow amount QA, engine rotation speed NE, cooling water temperature TW, air fuel ratio AF, and the like, controls the ignition timing of ignition plug6based on an engine load, an engine rotation speed, occurrence of knocking, and the like, and controls a fuel discharge amount of fuel pump12based on an engine load, an engine rotation speed, and the like.

Furthermore, electronic control device31controls the discharge flow rate of electric water pump55based on cooling water temperature TW and the like. Specifically, electronic control device31calculates a target rotation speed NWPtg [rpm] of electric water pump55based on cooling water temperature TW and the like and outputs calculated target rotation speed NWPtg, as a pump control instruction value, to electric water pump55.

A controller (microcomputer) integrated with electric water pump55receives a signal (rotation speed instruction signal) of target rotation speed NWPtg transmitted from electronic control device31and controls a voltage applied to a motor constituting electric water pump55by PWM control or the like so that an actual rotation speed NWP [rpm] approaches target rotation speed NWPtg.

That is, electronic control device31and the controller provided in electric water pump55have a calculation function (pump control unit) of controlling electric water pump55.

Furthermore, electronic control device31has a function (diagnosis unit) of diagnosing whether an discharge flow rate becomes smaller than an instruction value due to the failure of electric water pump55so that a cooling water circulation flow rate is insufficient, a function (flow rate ratio setting unit and distribution ratio setting unit) of changing a ratio between the cooling water flow rate of first cooling water passage51and the cooling water flow rate of second cooling water passage52in response to the diagnosis result, a function (valve control unit) of controlling flow rate control valve56in response to the determined ratio, a function (ignition control unit) of controlling the ignition timing in response to the diagnosis result, a function (engine load control unit) of limiting an increase in engine load in response to the diagnosis result, and the like.

The flowcharts ofFIGS. 3 and 4illustrate a process of controlling flow rate control valve56by electronic control device31, that is, the functions as the diagnosis unit, the flow rate ratio setting unit, the valve control unit, the ignition control unit, and the engine load control unit.

A routine illustrated in the flowcharts ofFIGS. 3 and 4is performed as an interruption process by electronic control device31every predetermined time.

In step S101, electronic control device31diagnoses whether failure has occurred in electric water pump55, specifically, whether the cooling water circulation flow rate is insufficient due to a decrease in discharge flow rate caused by the failure of electric water pump55.

Here, the detail of the diagnosis process (the function of the diagnosis unit) in step S101will be described in accordance with the flowchart ofFIG. 5.

Electronic control device31reads target rotation speed NWPtg [rpm] of electric water pump55determined in accordance with cooling water temperature TW and the like in step S201and reads actual rotation speed NWP [rpm] of electric water pump55in next step S202.

When the motor driving electric water pump55includes an encoder or a magnetic pole position sensor, electronic control device31can scrape actual rotation speed NWP of electric water pump55from the output of the sensor. When the motor is controlled in a sensorless state without the sensor, electronic control device31can scrape actual rotation speed NWP from the estimation result of the rotation position of the motor. Furthermore, electronic control device31can scrape information on actual rotation speed NWP from the controller provided in electric water pump55.

In step S203, electronic control device31determines whether a deviation ΔNWP (ΔNWP=NWPtg−NWP) between target rotation speed NWPtg and actual rotation speed NWP is equal to or larger than a predetermined value SL.

Then, when deviation ΔNWP is smaller than predetermined value SL, electronic control device31proceeds to step S206and determines that an intended discharge flow rate is obtained so that the cooling water circulation flow rate is sufficient, that is, electric water pump55is in a normal state.

Meanwhile, when deviation ΔNWP is equal to or larger than predetermined value SL, electronic control device31proceeds to step S204and determines whether a state where deviation ΔNWP is equal to or larger than predetermined value SL has been continued for a setting time or more.

The setting time is a time set based on a response delay or the like in the rotation speed control of electric water pump55and is set to a time longer than a time necessary for actual rotation speed NWP to follow a change in target rotation speed NWPtg.

Thus, when a state where deviation ΔNWP is equal to or larger than predetermined value SL has been continued for the setting time or more, it is considered that actual rotation speed NWP does not increase to target rotation speed NWPtg.

When a state where deviation ΔNWP is equal to or larger than predetermined value SL has not been continued for the setting time or more, there is a possibility that the current state is a transient state where actual rotation speed NWP follows a change in target rotation speed NWPtg. For this reason, electronic control device31proceeds to step S206and determines that electric water pump55is in the normal state where the intended discharge flow rate is obtained.

Meanwhile, when a state where deviation ΔNWP is equal to or larger than predetermined value SL has been continued for the setting time or more, electronic control device31proceeds to step S205and determines that electric water pump55is in a failure state where the intended discharge flow rate is not obtained, that is, the cooling water circulation flow rate is insufficient.

The embodiment illustrates a countermeasure in the event of failure in which the discharge flow rate of electric water pump55decreases compared with the normal state. For example, when the failure in which electric water pump55is not operated occurs due to short-circuiting or locking, electronic control device31performs a process different from the process illustrated in the flowcharts ofFIGS. 3 and 4.

The process performed by electronic control device31in the event of the failure in which electric water pump55is not operated is, for example, a process of causing a hybrid vehicle to travel by an electric motor while stopping internal combustion engine1or a process of performing a cylinder cutoff operation of internal combustion engine1so that a limp home mode is performed by internal combustion engine1and the electric motor.

When electronic control device31proceeds to step S205to determine the failure, it is determined that actual rotation speed NWP is lower than target rotation speed NWPtg and the actual discharge flow rate is lower than the discharge flow rate suitable for target rotation speed NWPtg, that is, the discharge flow rate is insufficient. In other words, electronic control device31determines in step S205that the actual circulation flow rate is insufficient compared with the cooling water circulation flow rate required to keep the temperature of the cooling water at an appropriate temperature.

When electronic control device31diagnoses the occurrence of the failure of electric water pump55in step S101, a routine proceeds to step S102to determine whether the failure of electric water pump55has been diagnosed.

Then, when electronic control device31determines that electric water pump55is normal and the cooling water circulation flow rate is sufficient in step S102, a routine proceeds to step S119.

In step S119, electronic control device31sets a target position (target rotor operation degree) of flow rate control valve56to a standard position (standard angle) so that a ratio between the cooling water flow rate of first cooling water passage51and the cooling water flow rate of second cooling water passage52becomes a standard value.

Electronic control device31can store the standard position as a fixed value in advance. Furthermore, electronic control device31can change the standard position in accordance with an operation condition such as cooling water temperature TW.

In addition, when the amount of the cooling water bypassing radiator50is adjusted by flow rate control valve56as in the cooling device illustrated inFIG. 1, electronic control device31can change the standard position in order to adjust the bypassing flow rate.

Meanwhile, when electronic control device31determines that the cooling water circulation flow rate is insufficient due to the failure of electric water pump55in step S102, a routine proceeds to step S103so that the actual discharge flow rate [L/min] of electric water pump55is calculated from actual rotation speed NWP of electric water pump55.

Next, electronic control device31sets a target position (target rotor operation angle AGtg) of flow rate control valve56in accordance with the actual discharge flow rate of electric water pump55, in other words, the insufficiency of the discharge flow rate in step S104. That is, electronic control device31changes the ratio between the cooling water flow rate of first cooling water passage51and the cooling water flow rate of second cooling water passage52from the standard value in order to handle the insufficiency of the discharge flow rate.

Specifically, electronic control device31changes target rotor operation angle AGtg of flow rate control valve56to relatively decrease the ratio of the cooling water flow rate of second cooling water passage52by increasing the ratio of the cooling water flow rate of first cooling water passage51. Accordingly, a decrease in cooling water flow rate of cylinder head1acaused by a decrease in discharge flow rate of electric water pump55is suppressed.

Furthermore, in step S104, electronic control device31performs a process of limiting a maximal intake air amount of internal combustion engine1to be lower than that of a case where electric water pump55is normal and the discharge flow rate is not insufficient, that is, a process of limiting an increase in load of internal combustion engine1to be lower than that of the normal state. As a process of limiting an increase in the intake air amount, electronic control device31performs, for example, a process of decreasing an upper limit of a target value in opening degree control of electronic control throttle10to be lower than that of a case where electric water pump55is normal.

Since the maximal intake air amount of internal combustion engine1is limited to be lower than that of the normal state, the generation of heat in internal combustion engine1is suppressed and hence the overheat of internal combustion engine1can be suppressed while the discharge flow rate of electric water pump55decreases.

In addition, electronic control device31can limit the maximal intake air amount of internal combustion engine1to a lower value as the discharge flow rate of electric water pump55further decreases. Furthermore, electronic control device31cancels the process of limiting the maximal intake air amount of internal combustion engine1to be lower than that of the normal state when the discharge flow rate of electric water pump55decreases by an amount smaller than a predetermined amount and hence can control an engine load as in a case where electric water pump55is normal.

When target rotor operation angle AGtg is set in step S104, electronic control device31proceeds to step S105and determines whether target rotor operation angle AGtg set in step S104exceeds a limit value AGlimit.

Here, when target rotor operation angle AGtg set in step S104exceeds limit value AGlimit, electronic control device31proceeds to step S106and sets limit value AGlimit to target rotor operation angle AGtg so that target rotor operation angle AGtg exceeding limit value AGlimit is not set.

Meanwhile, when target rotor operation angle AGtg set in step S104does not exceed limit value AGlimit, electronic control device31proceeds to step S107without changing target rotor operation angle AGtg set in step S104by skipping step S106.

As will be described in detail below, upper limit value AGlimit is an upper limit value of the ratio of the cooling water flow rate of first cooling water passage51, in other words, a value corresponding to a lower limit value of the ratio of the cooling water flow rate of second cooling water passage52.

In the description below, a process of setting target rotor operation angle AGtg in steps S104to S106will be described in detail with reference toFIG. 6.

In addition, in the embodiment, a direction in which the rotor angle of flow rate control valve56increases is set to a direction in which the ratio of the cooling water flow rate of first cooling water passage51increases. Here, the ratio of the cooling water flow rate of first cooling water passage51can be decreased in accordance with a decrease in rotor angle.

FIG. 6is a diagram illustrating the cooling water flow rate [L/min] of first cooling water passage51and the cooling water flow rate [L/min] of second cooling water passage52every rotor operation angle of flow rate control valve56.

The solid line ofFIG. 6indicates a characteristic of the normal state where actual rotation speed NWP of electric water pump55is converged to target rotation speed NWPtg and the discharge flow rate corresponding to target rotation speed NWPtg can be obtained. Meanwhile, the dotted line ofFIG. 6indicates a characteristic in the failure state where actual rotation speed NWP of electric water pump55does not reach target rotation speed NWPtg and the actual discharge flow rate becomes lower than the discharge flow rate suitable for target rotation speed NWPtg.

In the characteristic example illustrated inFIG. 6, when the rotor operation angle of flow rate control valve56is changed, a state where the cooling water flow rate of second cooling water passage52is minimal and the cooling water flow rate of first cooling water passage51is maximal is continuously changed to a state where the cooling water flow rate of second cooling water passage52is maximal and the cooling water flow rate of first cooling water passage51is minimal.

Then, when the actual discharge flow rate becomes lower than the discharge flow rate suitable for target rotation speed NWPtg due to the failure of electric water pump55, the cooling water flow rate decreases in both first cooling water passage51and second cooling water passage52.

Here, the cooling water flow rate of first cooling water passage51in the normal pump state is obtained from the discharge flow rate suitable for target rotation speed NWPtg and a standard value AGst of target rotor operation angle AGtg of flow rate control valve56.

Furthermore, the cooling water flow rate of first cooling water passage51when target rotor operation angle AGtg is kept at standard value AGst in the failure state of the pump is obtained from the actual discharge flow rate of electric water pump55and standard value AGst of target rotor operation angle AGtg of flow rate control valve56in the failure state calculated in step S103.

A difference between the obtained cooling water flow rate of first cooling water passage51in the failure state of the pump and the obtained cooling water flow rate of first cooling water passage51in the normal pump state becomes the insufficiency of the cooling water flow rate of first cooling water passage51.

When target rotor operation angle AGtg of flow rate control valve56is changed in a direction in which the ratio of the cooling water flow rate of first cooling water passage51increases in the failure state of the pump in which the cooling water flow rate of first cooling water passage51is insufficient, the insufficiency of the cooling water flow rate of first cooling water passage51can be decreased and hence the cooling water flow rate may be increased to the cooling water flow rate in the normal pump state.

Here, when the ratio of the cooling water flow rate of first cooling water passage51is increased, the cooling water flow rate of second cooling water passage52is decreased relatively, but the cooling water flow rate of second cooling water passage52needs to be kept at a predetermined amount or more.

That is, the limit value is the upper limit value of the cooling water flow rate of first cooling water passage51determined from the lower limit value of the cooling water flow rate of second cooling water passage52.

Here, electronic control device31calculates target rotor operation angle AGtg required to increase the cooling water flow rate of first cooling water passage51to the cooling water flow rate in the normal pump state in step S104. Furthermore, when electronic control device31determines that target rotor operation angle AGtg for solving the insufficiency of the cooling water flow rate exceeds limit value AGlimit in step S105, a routine proceeds to step S106so that limit value AGlimit is set to target value AGtg in the failure state of the pump.

According to the configuration, when the discharge flow rate of the pump decreases due to the failure, the insufficiency of the cooling water in cylinder head1acan be suppressed. Thus, the damage of internal combustion engine1caused by an increase in temperature of cylinder head1acan be suppressed and hence a minimal amount or more of cooling water can flow to cylinder block1b. Furthermore, since the cooling water flow rate of cylinder head1ais increased, a limitation on the engine load used to suppress an increase in temperature of cylinder head1acan be loosened and hence deterioration in traveling performance in the failure state of the pump can be suppressed.

In the above-described configuration, when target rotor operation angle AGtg for solving the insufficiency of the flow rate does not exceed limit value AGlimit, rotor operation angle AGtg in which the cooling water flow rate of first cooling water passage51is increased to the cooling water flow rate in the normal pump state is set as final target rotor operation angle AGtg.

Here, the invention is not limited to a configuration in which the cooling water flow rate of first cooling water passage51is increased to the cooling water flow rate in the normal pump state. For example, electronic control device31can set the target flow rate in the failure state of the pump to be lower than the cooling water flow rate in the normal pump state and set target rotor operation angle AGtg in which the cooling water flow rate of first cooling water passage51is increased to the target flow rate in the failure state.

In step S107of the flowchart ofFIG. 3, electronic control device31sets target rotor operation angle AGtg set in step S104or target rotor operation angle AGtg subjected to the limit process in step S106as a basic value AGtgba of the target rotor operation angle in the failure state of the pump.

Next, electronic control device31proceeds to step S108illustrated in the flowchart ofFIG. 4and determines whether knocking has occurred in internal combustion engine1based on the output signal of knock sensor39.

Then, when the knocking has not occurred, electronic control device31proceeds to step S109and determines whether a flag F representing the setting state of the target rotor operation angle as the knocking countermeasures is enabled.

As will be described below, a case where flag F is enabled represents a case where the target rotor operation angle is set as the knocking countermeasures and a case where flag F is disabled represents a case where the target rotor operation angle is not set as the knocking countermeasures.

When flag F is disabled, electronic control device31proceeds to step S110and sets basic value AGtgba of the target rotor operation angle in the failure state of the pump set in step S107as final target rotor operation angle AGtgde in the failure state of the pump. Then, electronic control device31adjusts the ratio between the cooling water flow rate of first cooling water passage51and the cooling water flow rate of second cooling water passage52by controlling the rotor operation angle of flow rate control valve56in accordance with target rotor operation angle AGtgde.

Meanwhile, when electronic control device31determines that the knocking has occurred in step S108, a routine proceeds to step S111so that basic value AGtgba of target rotor operation angle AGtg in the failure state of the pump is gradually changed to a value at which the cooling water flow rate of first cooling water passage51can be increased to the same level as the normal pump state and the changed value is set as final target rotor operation angle AGtgde.

That is, in step S111, electronic control device31cancels the limitation on the rotor operation angle imposed by limit value AGlimit and selects target rotor operation angle AGtg in which the cooling water flow rate of cylinder head1ain the failure state of the pump can be increased to a value close to the cooling water flow rate of cylinder head1ain the normal pump state.

When basic value AGtgba of target rotor operation angle AGtg in the failure state of the pump is limit value AGlimit, electronic control device31increases the cooling water flow rate of cylinder head1amore than limit value AGlimit up to target rotor operation angle AGtg in which the cooling water flow rate of cylinder block1bbecomes smaller than the minimal flow rate.

Here, in step S113, electronic control device31can set target rotor operation angle AGtg in which the cooling water flow rate of first cooling water passage51is increased to the flow rate lower than the cooling water flow rate of cylinder head1ain the normal pump state.

Next, electronic control device31enables flag F in step S112and then proceeds to step S113.

In step S113, electronic control device31adjusts the ratio between the cooling water flow rate of first cooling water passage51and the cooling water flow rate of second cooling water passage52by controlling the rotor operation angle of flow rate control valve56in accordance with target rotor operation angle AGtgde set in step S111. Furthermore, electronic control device31performs control of retarding the ignition timing in step S113along with the control of the rotor operation angle of flow rate control valve56.

When the knocking occurs while the discharge flow rate of electric water pump55decreases in the failure state of the pump, electronic control device31promotes the cooling of cylinder head1aby changing target rotor operation angle AGtg so that the cooling water flow rate of cylinder head1aincreases, and further performs a process of retarding the ignition timing of internal combustion engine1in order to promptly solve the knocking.

That is, there is a case where, even when control of increasing the cooling water flow rate of cylinder head1ais performed, the knocking is not immediately solved by a decrease in temperature of cylinder head1aand the knocking suppressing effect due to an increase in cooling water flow rate of cylinder head1ais exhibited slowly. Here, electronic control device31can obtain the knocking suppressing effect by retarding the ignition timing to promptly solve the knocking while increasing the cooling water flow rate.

When the knocking continuously occurs in the failure state of the pump, electronic control device31proceeds from step S108to steps S111to S113in order to solve the knocking. Meanwhile, when the knocking does not occur, electronic control device31proceeds from step S108to step S109.

Here, flag F in enabled in step S112in the knocking occurrence state. When the knocking occurrence state is solved and a routine proceeds to step S109, electronic control device31determines that flag F is enabled and proceeds to step S114.

In step S114, electronic control device31determines whether target rotor operation angle AGtgde is set so that the cooling water flow rate of cylinder head1aincreases in relation to basic value AGtgba of target rotor operation angle AGtg, that is, whether the cooling water flow rate of cylinder head1ais temporarily increased to solve the knocking.

Here, when target rotor operation angle AGtgde is changed so that the cooling water flow rate of cylinder head1aincreases in relation to basic value AGtgba of target rotor operation angle AGtg, electronic control device31proceeds to step S115and sets, as current target rotor operation angle AGtgde, a value obtained by changing a precedent value of target rotor operation angle AGtgde by a predetermined value ΔAG in a direction in which the cooling water flow rate of cylinder head1ais decreased.

Then, electronic control device31proceeds to step S116and controls the rotor operation angle of flow rate control valve56in accordance with target rotor operation angle AGtgde changed in step S115whenever this routine is performed.

For example, when a direction in which the cooling water flow rate of cylinder head1ais decreased is a direction in which the rotor operation angle decreases, electronic control device31sets, as current target rotor operation angle AGtgde, an operation angle obtained by subtracting predetermined value ΔAG from precedent target rotor operation angle AGtgde in step S115.

That is, when the knocking is detected, electronic control device31changes target rotor operation angle AGtgde in a direction in which the cooling water flow rate of cylinder head1ais increased. Then, when the knocking is converged, electronic control device31gradually changes target rotor operation angle AGtgde in a direction in which the cooling water flow rate of cylinder head1adecreases so that the cooling water flow rate of cylinder block1bis relatively increased gradually.

When the cooling water flow rate of cylinder head1ais largely decreased based on the non-detection of the knocking, there is a possibility that the knocking occurs again because the cooling water flow rate of cylinder head1adecreases before the temperature of cylinder head1asufficiently decreases. Here, when the knocking is converged, electronic control device31gradually decreases the cooling water flow rate of cylinder head1ato suppress the repeated occurrence of the knocking.

When target rotor operation angle AGtgde returns to basic value AGtgba as a result of the process in step S115, electronic control device31proceeds to step S117after determining in step S114that target rotor operation angle AGtgde is not set so that the cooling water flow rate of cylinder head1aincreases in relation to basic value AGtgba of target rotor operation angle AGtg, that is, precedent target rotor operation angle AGtgde is substantially equal to basic value AGtgba.

In step S117, electronic control device31disables flag F. Then, in next step S118, electronic control device31controls the rotor operation angle of flow rate control valve56by setting basic value AGtgba to target rotor operation angle AGtgde and ends the changing of target rotor operation angle AGtgde as the knocking countermeasures.

FIG. 7illustrates a change in target rotor operation angle AGtg in the event of the knocking.

In the failure state of the pump in which the knocking does not occur, target rotor operation angle AGtgde is determined by the limitation using limit value AGlimit. However, when the knocking occurs, electronic control device31cancels the limitation of limit value AGlimit and gradually changes target rotor operation angle AGtgde so that the cooling water flow rate of cylinder head1aincreases in relation to the case of limit value AGlimit. For example, the target rotor operation angle is gradually changed to the vicinity of the operation angle in which the flow rate in the normal pump state can be obtained.

While the knocking continuously occurs, electronic control device31keeps target rotor operation angle AGtgde at the vicinity of the operation angle in which the flow rate in the normal pump state can be obtained. When the knocking does not occur, target rotor operation angle AGtgde is gradually changed toward limit value AGlimit from the vicinity of the operation angle in which the flow rate in the normal pump state can be obtained.

In addition, when the time during which the flow rate of the cylinder block is lower than the minimal flow rate reaches the setting time, electronic control device31can change target rotor operation angle AGtgde toward limit value AGlimit or rapidly change target rotor operation angle AGtgde toward limit value AGlimit even in the event of the knocking.

While the content of the invention has been described in detail with reference to the preferred embodiment, it is obvious that various modifications can be made by the person skilled in the art based on the basic technical idea and teaching of the invention.

It is obvious that the cooling device including first cooling water passage51provided in cylinder head1aand second cooling water passage52provided in cylinder block1bof internal combustion engine1is not limited to the configuration exemplified inFIG. 1. For example, the control device and the control method according to the invention can be also applied to the cooling device having the configuration illustrated inFIG. 8.

The cooling device illustrated inFIG. 8includes radiator50, first cooling water passage (first cooling medium passage)51, second cooling water passage (second cooling medium passage)52, cooling water supply path53, a cooling water returning path54, electric water pump55, and flow rate control valve (three-way electromagnetic valve)56. First cooling water passage51is provided in cylinder head1aof internal combustion engine1. Second cooling water passage52is provided in cylinder block1bof internal combustion engine1in parallel to first cooling water passage51. Cooling water supply path53has one end connected to outlet50aof radiator50and is halfway branched into two parts to be respectively connected to inlet sides51aand52aof cooling water passages51and52. Cooling water returning path54is connected to each of outlet sides51band52bof cooling water passages51and52, merged at the downstream side, and connected to inlet50bof radiator50. Electric water pump55is provided in outlet50aof radiator50. Flow rate control valve56is provided in the branch part of cooling water supply path53and changes a ratio between the cooling water flow rate of first cooling water passage51and the cooling water flow rate of second cooling water passage52. The cooling device is a system which circulates cooling water (or cooling liquid) as a cooling medium in internal combustion engine1by electric water pump55.

In addition, flow rate control valve56is a mechanism which continuously changes the ratio between the cooling water flow rate of first cooling water passage51and the cooling water flow rate of second cooling water passage52in accordance with, for example, the operation angle of the rotor.

In the cooling device illustrated inFIG. 8, the cooling water discharged from electric water pump55is distributed to each of first cooling water passage51and second cooling water passage52in accordance with the ratio adjusted by flow rate control valve56. Then, the cooling water flowing in first cooling water passage51increases in temperature by taking the heat of cylinder head1aand the cooling water flowing in second cooling water passage52increases in temperature by taking the heat of cylinder block1b. The cooling water increasing in temperature after passing through first cooling water passage51and second cooling water passage52enters radiator50together. The cooling water decreasing in temperature after losing the heat by radiator50is suctioned into electric water pump55so that the cooling water is supplied to each of first cooling water passage51and second cooling water passage52.

That is, the cooling water is circulated in a closed path in order of internal combustion engine1(first cooling water passage51and second cooling water passage52), radiator50, electric water pump55, internal combustion engine1, and so on.

Furthermore, for example, the control of target rotor operation angle AGtg based on the detection of the knocking can be omitted, and the process of limiting an increase in engine load in the event of detecting the knocking can be performed.

Furthermore, when the process of limiting an increase in engine load is performed, electronic control device31can notify a driver of a vehicle equipped with internal combustion engine1of a state where the process of limiting an increase in engine load (engine output torque) is performed, by the use of an alarm lamp or the like.

Furthermore, flow rate control valve56is not limited to the rotor type. For example, an electromagnetic valve may be used as flow rate control valve56, or a combination of a plurality of electromagnetic valves may be used as flow rate control valve56.

Furthermore, electronic control device31can detect the failure in which the discharge flow rate of the pump decreases based on a decrease in pressure of the cooling water or the like.

Furthermore, when the failure in which the discharge flow rate of the pump decreases occurs, electronic control device31operates an electric fan provided in radiator50so that the heat radiation efficiency for the cooling water in radiator50is improved and the cooling water temperature at the outlet of radiator50decreases. Accordingly, an increase in temperature of cylinder head1acan be suppressed.

Furthermore, the control device and the control method according to the invention can also be applied to the cooling device including an engine drive type water pump driven by internal combustion engine1instead of electric water pump55. In the case of the cooling device including the engine drive type water pump, electronic control device31detects the occurrence of the failure in which the discharge amount of the engine drive type water pump decreases based on, for example, an increase in cooling water temperature or a decrease in cooling water pressure.

Then, when the refrigerant circulation flow rate becomes insufficient due to a decrease in discharge amount of the engine drive type water pump, electronic control device31can control flow rate control valve56so that the ratio of the refrigerant flow rate of first cooling water passage51becomes larger than that of a case where the refrigerant circulation flow rate is not insufficient, and further perform control of increasing the ratio of the refrigerant flow rate of first cooling water passage51based on the occurrence of the knocking and/or retarding the ignition timing based on the occurrence of the knocking.

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