JP5910743B2 - Cooling control device for internal combustion engine - Google Patents

Description

  The present invention relates to an apparatus for controlling a system for cooling an internal combustion engine, and more particularly to an apparatus for controlling circulation of cooling water.

  The internal combustion engine generates heat due to the combustion of fuel, and if the temperature becomes excessively high, the efficiency deteriorates due to abnormal combustion or the like, and therefore, a cooling device is provided. As a cooling method of the internal combustion engine by the cooling device, a water cooling type using water as a refrigerant, an oil cooling type using oil instead of water, an air cooling type using air as a refrigerant, and the like are known. In any type, if the internal combustion engine is not sufficiently cooled by the cooling device, the above-described abnormal combustion occurs, and conversely, if the cooling is excessive, combustion of the fuel is hindered.

  For example, Japanese Patent No. 4883225 discloses a first cooling water circuit that circulates cooling water so as to pass through the inside of the internal combustion engine, and a cooling water that passes through the exhaust heat recovery device without passing through the internal combustion engine. There is described a cooling device for a vehicle including a second cooling water circuit. In the apparatus described in this publication, a valve for reducing the flow rate of the cooling water in the first cooling water circuit by reducing the opening degree, and mixing the cooling waters of those cooling water circuits by increasing the opening degree. Is provided. The valve body of the valve is formed with a hole for circulating cooling water even at the closed position. And the temperature difference between the cooling water of the first cooling water circuit and the cooling water of the second cooling water circuit is a case where the temperature of the cooling water of the first cooling water circuit is equal to or higher than a predetermined determination value. When it is larger than another predetermined determination value, it is configured to determine that the valve body is fixed in a state where the opening degree of the valve is reduced.

  Japanese Patent Application Laid-Open No. 2007-46469 describes an exhaust heat recovery apparatus including a cooling water flow path that circulates cooling water so as to diverge from a radiator circuit that cools an internal combustion engine and pass through an exhaust heat recovery device. ing. A valve for opening and closing the cooling water flow path is provided in the middle of the cooling water flow path. The valve has a circulation part as a cooling water flow path and a minute hole orthogonal to the circulation part. Then, when the valve is rotated to connect the cooling water channel and the circulation part, the valve is opened, and the cooling water flows through the cooling water channel. Conversely, the valve is closed when the valve is rotated so that the flow passage is orthogonal to the cooling water flow path. In this valve-closed state, since the cooling water channel and the minute hole communicate with each other, a very small amount of cooling water flows through the cooling water channel.

  According to the vehicle cooling device described in the above-mentioned Japanese Patent No. 4883225, for example, even if the valve body is fixed in a state where the valve opening is reduced, the cooling water flows through the hole formed in the valve body. The cooling water can be circulated through the first cooling water circuit. However, when the hole is clogged with, for example, foreign matter, there is a possibility that the cooling water cannot be circulated through the first cooling water circuit.

  The present invention has been made paying attention to the above technical problem, and estimates the clogging amount of holes for ensuring the circulation of cooling water even when the opening of the valve is reduced, and its estimation accuracy. An object of the present invention is to provide a cooling control device for an internal combustion engine that can improve the efficiency.

  In order to achieve the above object, the present invention provides a cooling circuit in which cooling water for cooling the internal combustion engine circulates between a water pump and the internal combustion engine, and the cooling water circulates by bypassing the internal combustion engine. A bypass circuit, a first water temperature sensor that detects the temperature of the cooling water in the cooling circuit, a second water temperature sensor that detects the temperature of the cooling water in the bypass circuit, and the cooling circuit are provided to reduce the opening. A switching valve that increases the amount of cooling water circulating through the cooling circuit by decreasing the amount of cooling water circulating through the cooling circuit and increasing the opening degree, and the opening degree of the switching valve is reduced. An internal combustion engine cooling control device comprising: a circulation portion that circulates a small amount of the cooling water in the cooling circuit; and when the drive of the internal combustion engine is stopped, The temperature difference between the cooling water temperature of the cooling circuit detected by the first water temperature sensor and the cooling water temperature of the bypass circuit detected by the second water temperature sensor. It is provided with the estimation means which estimates the clogging amount of the said distribution part according to the temporal variation | change_quantity of this.

  Further, in this invention, the estimating means is configured to calculate the water pump from the amount of change in the temperature difference when the water pump is driven when the outside air temperature is lower than a predetermined temperature. Means for estimating the amount of clogging of the circulation portion that is reducing the opening degree by the amount of change in temperature obtained by subtracting the amount of change in the temperature difference due to the outside air temperature in a state where the driving of the air conditioner is stopped.

  Further, in the present invention, the estimating means may reduce the current driving amount of the water pump to the previous driving amount of the water pump when the estimated value of the clogging amount estimated last time is less than the first threshold value. Reducing the current clogging amount when the estimated value of the clogging amount is greater than the first threshold, and increasing the current driving amount of the water pump to be greater than the previous driving amount of the water pump. Means for estimating the amount of clogging can be included.

  In the present invention, the estimating means can include means for estimating the clogging amount of the flow section by increasing the driving amount of the water pump as the speed of the vehicle on which the internal combustion engine is mounted is higher.

  Further, in this invention, the estimation means increases the drive amount of the water pump when the estimated value of the estimated clogging amount is larger than the first threshold value and smaller than a predetermined second threshold value, A means for increasing the opening of the switching valve when the estimated value of the clogging amount is larger than a predetermined second threshold value can be included.

  According to the cooling control apparatus for an internal combustion engine according to the present invention, for example, when the opening degree of the switching valve is reduced, if the circulation part is clogged, the cooling water does not circulate through the cooling circuit, so that the cooling water is circulated. There is no heat transfer. Therefore, after a predetermined time has elapsed, the temperature difference between the cooling water temperature detected by the first water temperature sensor and the cooling water temperature detected by the second water temperature sensor becomes large. On the other hand, when the circulation part is not clogged, heat moves through the cooling water, so that the amount of change in the temperature difference with time is small. That is, if the clogging amount of the circulation part is large, the temporal change amount of the temperature difference described above increases, and if the clogging amount is small, the temporal change amount of the temperature difference decreases. In the present invention, since the clogging amount of the circulation portion is estimated in accordance with the temporal change amount of the temperature difference, it is possible to obtain a cooling control device for an internal combustion engine that is excellent in the estimation accuracy of the clogging amount of the circulation portion. .

  According to the present invention, when the estimated value of the clogging amount estimated last time is less than the first threshold value, the current water pump driving amount is made smaller than the previous water pump driving amount. In comparison, it is possible to improve the estimation accuracy of the clogging amount this time.

  Furthermore, according to the present invention, for example, when a hybrid vehicle including an internal combustion engine and an electric motor as driving force sources is traveling at high speed, the internal combustion engine is driven frequently and the internal combustion engine is Long time driving the engine. Therefore, when the hybrid vehicle is traveling at a high speed, the amount of clogging can be quickly estimated by setting the driving amount of the water pump large. On the other hand, when the hybrid vehicle is traveling at a low speed, the operation of the internal combustion engine is stopped for a long time due to the high frequency of traveling by driving the electric motor. for that reason. When the hybrid vehicle has a low vehicle speed, the estimation accuracy of the clogging amount can be improved by setting the driving amount of the water pump small.

  According to the present invention, for example, when the internal combustion engine is not sufficiently warmed up and the amount of clogging in the flow part is small, the internal combustion engine cannot be sufficiently warmed up if the opening of the switching valve is increased. there is a possibility. Therefore, when the estimated value of the clogging amount is larger than the first threshold value and smaller than the second threshold value, the amount of cooling water circulating in the cooling circuit is secured by increasing the driving amount of the water pump. When the estimated value of the clogging amount is larger than the second threshold value, the amount of cooling water circulating through the cooling circuit is secured by increasing the opening degree of the switching valve.

It is a flowchart which shows an example of the control by the cooling control apparatus of the internal combustion engine which concerns on this invention. It is a figure which shows an example of the map of the securing time according to the drive duty of a water pump. It is a figure which shows typically the correlation of the initial temperature difference (DELTA) Tini and the temperature difference (DELTA) Tnow at the present time. It is a figure which shows an example of the map of the clogging amount according to temperature difference (DELTA) Td1. It is a flowchart which shows the other example of control by the cooling control apparatus of the internal combustion engine which concerns on this invention. It is a figure which shows an example of the map of the clogging amount according to temperature difference (DELTA) Td2. It is a flowchart which shows the other example of control by the cooling control apparatus of the internal combustion engine which concerns on this invention. 6 is a flowchart showing still another example of control by the cooling control apparatus for an internal combustion engine according to the present invention. It is a figure which shows an example of the map of the drive duty of the water pump according to a vehicle speed. It is a flowchart which shows the further another example of control by the cooling control apparatus of the internal combustion engine which concerns on this invention. It is a figure which shows an example of the map of the correction coefficient for correct | amending the drive duty of the water pump according to the amount of clogging. It is a figure which shows typically an example of the cooling control apparatus of the internal combustion engine which concerns on this invention.

  Next, the present invention will be specifically described. An apparatus to which the present invention can be applied includes at least a circuit that circulates cooling water so as to pass through an internal combustion engine mounted on a vehicle, and a circuit that circulates cooling water without passing through the internal combustion engine. ing. Further, the above-described device is provided with an electromagnetic switching valve that switches between the circuits by being electrically controlled according to, for example, the temperature of the internal combustion engine and the running state including start and stop of the vehicle and vehicle speed. ing. In addition, even if the electromagnetic switching valve circulates the cooling water without passing through the internal combustion engine, the flow of the cooling water in the circuit that circulates the cooling water so as to pass through the inside of the internal combustion engine. Is configured not to stop completely.

  The above vehicle is, for example, a hybrid vehicle including an internal combustion engine and a plurality of electric motors as a driving force source. The hybrid vehicle is configured to be able to set a plurality of travel modes, such as a travel mode in which the vehicle travels with the power generated by the internal combustion engine and the electric motor, and a travel mode in which the internal combustion engine travels with the power generated by the motor. Yes. These travel modes are switched according to the vehicle speed, for example. In addition, the vehicle may be a vehicle configured to drive the internal combustion engine when starting and stop the internal combustion engine when the vehicle stops. Therefore, the internal combustion engine in the present invention is configured to be driven and stopped according to the selected travel mode and the travel state of the vehicle. As the internal combustion engine, a gasoline engine, a diesel engine, or a natural gas engine can be employed. Note that the internal combustion engine is preferably configured to be able to electrically control the rotational speed and output torque. In the following description, this internal combustion engine is referred to as an engine 1. As the electric motor, a known AC motor having a function as a motor and a function as a generator can be adopted.

  FIG. 12 is a diagram schematically showing an example of a cooling control apparatus for an internal combustion engine according to the present invention. A water jacket (not shown) is provided on the cylinder block and cylinder head of the engine 1. The water jacket cools the engine 1 by transferring heat generated in the engine 1 to cooling water. An electric water pump 2 for supplying cooling water to the water jacket is provided. Although not shown in detail, the water pump 2 includes an impeller that is rotated to send cooling water, and a motor that rotates the impeller. The discharge amount and discharge pressure of the water pump 2 can be changed by electrically controlling the rotational speed of the motor.

  The configuration of the water pump 2 will be briefly described. Although not shown in detail, the water pump 2 has a PWM (Pulse Width Modulation) circuit. The PWM circuit is a circuit for duty-controlling the rotational speed of the motor of the water pump 2 in accordance with a control signal output from an electronic control device to be described later. For example, when the driving duty output to the motor of the water pump 2 is increased, the rotational speed of the motor is increased, and when the driving duty is decreased, the rotational speed of the motor is decreased.

  The discharge port of the water pump 2 and the water jacket are connected by a supply pipe 3, and the suction port of the water pump 2 and the water jacket are connected by a return pipe 4. A first water temperature sensor 5 that detects the temperature of the cooling water that has flowed out of the water jacket is provided in the vicinity of the connection portion between the water jacket and the return pipe 4. The return pipe 4 is connected to a radiator 6. The radiator 6 is configured to cool the cooling water whose temperature has been increased by taking heat of the engine 1 by exchanging heat between the cooling water and the outside air. The structure of the radiator 6 is the same as that conventionally known. The cooling water cooled in the radiator 6 is supplied to the suction port of the water pump 2 via the thermostat 7.

  The thermostat 7 allows the cooling water to flow to the radiator 6 when the temperature of the cooling water is equal to or higher than a predetermined temperature. Conversely, when the temperature of the cooling water is lower than the predetermined temperature, the thermostat 7 The circulation of the cooling water to 6 is prohibited. The configuration of the thermostat 7 is the same as that conventionally known. The predetermined temperature is a temperature for determining whether or not the engine 1 has been warmed up as an example. This will be referred to as warm-up temperature in the following description. The thermostat 7 always allows the flow of cooling water from a bypass pipe 8 to be described later to the return pipe 4.

  A bypass pipe 8 that bypasses the engine 1 and connects the supply pipe 3 and the return pipe 4 is provided. A second water temperature sensor 9 is provided in the bypass pipe 8. A branch pipe 10 branched from the return pipe 4 between the engine 1 and the radiator 6 is connected to the bypass pipe 8. The branch pipe 10 is provided with an electromagnetic switching valve 11 that changes the flow rate of the cooling water supplied to the water jacket by opening and closing the branch pipe 10 under electrical control.

  The configuration of the electromagnetic switching valve 11 will be briefly described. For example, the electromagnetic switching valve 11 is configured to reduce the flow rate of cooling water supplied to the water jacket by reducing the opening degree in a state where a voltage is applied. On the contrary, when the voltage is cut off, the opening degree is increased and the flow rate of the cooling water supplied to the water jacket is increased. In addition, the electromagnetic switching valve 11 is provided with a circulation portion (not shown) to ensure the flow of cooling water in the branch pipe 10 even when a voltage is applied to reduce the opening of the electromagnetic switching valve 11. It has been. This circulation part may be, for example, a hole or notch that penetrates the valve body that opens and closes the input / output port of the electromagnetic switching valve 11. The flow part may be a pipe that communicates the upstream side and the downstream side of the electromagnetic switching valve 11. This distribution part is shown by a dotted line in FIG. In addition, compared with the flow path cross-sectional area of the branch pipe 10 orthogonal to the axial direction of the branch pipe 10, the flow path cross-sectional area of the flow part is formed smaller. The electromagnetic switching valve 11 is electrically connected to an auxiliary battery, although details are not shown. The auxiliary battery is a power source for operating auxiliary machines such as a headlight and an air conditioner mounted on the vehicle, and is connected to the main battery via a DC-DC converter.

  An electronic control device 12 for electrically controlling the electromagnetic switching valve 11 and the water pump 2 described above is provided. This is referred to as ECU 12 in the following description. The ECU 12 is configured mainly by a microcomputer as an example, performs an operation based on input data or data stored in advance, and sends a control signal as a result of the operation to the electromagnetic switching valve 11 or the water pump 2. It is configured to output. For example, the ECU 12 receives signals from various sensors and devices such as the water temperature sensors 5 and 9, the engine speed sensor, the vehicle speed sensor, and the igniter.

  Next, the operation of the internal combustion engine cooling control apparatus having the configuration shown in FIG. 12 will be briefly described. For example, when the temperature of the engine 1 is low and the temperature of the cooling water is lower than the warm-up temperature, such as immediately after the engine 1 is started, the circulation of the cooling water to the radiator 6 is prohibited by the thermostat 7. On the other hand, the electromagnetic switching valve 11 is applied with a voltage to the electromagnetic coil portion 18 to reduce the opening thereof in order to promote warm-up of the engine 1. The cooling water discharged from the water pump 2 mainly flows in the order of the supply pipe 3, the bypass pipe 8, and the return pipe 4. At least a part of the cooling water flows through the flow part of the electromagnetic switching valve 11. Thus, since the amount of cooling water circulating through the water jacket is reduced, the temperature rise of the cooling water in the water jacket is promoted. In addition, since the cooling water circulates through the water jacket even in a small amount, the occurrence of high temperature portions and low temperature portions in the water jacket is prevented or suppressed.

  When the temperature of the cooling water is equal to or lower than the warming-up temperature and other temperature slightly lower than the warming-up temperature, the cooling water is still lower than the warming-up temperature, so that the cooling water is circulated to the radiator 6 through the thermostat 7. It is prohibited by The other temperature is referred to as a semi-warm-up temperature in the following description. On the other hand, the electromagnetic switching valve 11 has its opening degree increased by cutting off the voltage in order to moderate the temperature rise of the cooling water in the water jacket. In such a state, a part of the cooling water flows in the order of the supply pipe 3, the water jacket, the branch pipe 10, and the return pipe 4. The remaining cooling water flows in the order of the supply pipe 3, the bypass pipe 8, and the return pipe 4. As a result, the cooling water flowing through the water jacket and the cooling water flowing through the bypass pipe 8 are mixed in the bypass pipe 8 and the return pipe 4, so that the opening degree of the electromagnetic switching valve 11 is reduced. In comparison, the temperature rise of the cooling water in the water jacket can be moderated.

  When the temperature of the cooling water is equal to or higher than the warming-up temperature, the circulation of the cooling water to the radiator 6 is permitted by the thermostat 7. Moreover, the opening degree of the electromagnetic switching valve 11 is increased. A part of the cooling water is supplied to the radiator 6 and cooled. The cooling water cooled in the radiator 6 and the cooling water circulating through other circuits are mixed and discharged from the water pump 2 to circulate through each circuit. Therefore, it is possible to prevent or suppress the temperature of the cooling water in the water jacket from rising excessively. A circuit in which the cooling water is circulated so as to pass through the water jacket corresponds to the cooling circuit in the present invention, and a circuit in which the cooling water is circulated so as to pass through the bypass pipe 8 corresponds to the bypass circuit in the present invention. .

  In this invention, when the opening degree of the electromagnetic switching valve 11 is reduced, the clogging amount of the circulation part for circulating the cooling water through the water jacket is estimated. The clogging amount is, for example, the ratio (%) of the above-described channel cross-sectional area reduced by foreign matter such as dust or dust mixed in the cooling water in the channel cross-sectional area of the circulation part. Specifically, the case where the clogging amount is 15% is a case where 15% of the flow path cross-sectional area of the circulation portion is blocked by foreign matter. FIG. 1 is a flowchart for explaining an example of control by the cooling control apparatus for an internal combustion engine according to the present invention, and the routine shown here is repeatedly executed at predetermined time intervals.

  First, the temperature Thw of the cooling water flowing out from the water jacket is detected by the first water temperature sensor 5. This is referred to as the cooling water temperature Thw on the engine 1 side. The temperature Thb of the cooling water flowing through the bypass pipe 8 is detected by the second water temperature sensor 9. This is referred to as a cooling water temperature Thb on the bypass pipe 8 side. The temperature difference ΔTini is calculated by subtracting the cooling water temperature Thb on the bypass pipe 8 side from the cooling water temperature Thw on the engine 1 side. This will be referred to as an initial temperature difference ΔTini in the following description. It is determined whether or not the initial temperature difference ΔTini is greater than or equal to a predetermined temperature difference ΔTdet, and whether or not the engine 1 is stopped is determined (step S1).

  The above-described predetermined temperature difference ΔTdet is a temperature difference capable of determining the clogging amount of the circulation section within a predetermined time, and this can be determined in advance by experiments, simulations, or the like. In the example shown here, the temperature difference ΔTdet is 20 ° C., for example. The determination of whether or not the engine 1 is stopped can be made based on, for example, the current traveling state of the vehicle, the set traveling mode, or the vehicle speed. If the initial temperature difference ΔTini is equal to or smaller than the predetermined temperature difference ΔTdet, or if the engine 1 is driven and it is determined negative in step S1, this control is performed without executing the subsequent control. The routine is temporarily terminated.

  If the initial temperature difference ΔTini is higher than the predetermined temperature difference ΔTdet and the engine 1 is stopped, and the determination in step S1 is affirmative, the initial temperature difference ΔTini is temporarily stored. To do. The stored initial temperature difference ΔTini is used for control in step S4 described later. Further, the water pump 2 is driven and the opening degree of the electromagnetic switching valve 11 is reduced (step S2). Specifically, the opening of the electromagnetic switching valve 11 is reduced to reduce the flow passage cross-sectional area of the branch pipe 10. Then, the cooling water is circulated through the circulation part. In addition, the drive duty for driving the motor of the water pump 2 is set to an arbitrary value according to the traveling state of the vehicle, for example.

  Thereafter, it is determined whether or not a predetermined time t1 has elapsed (step S3). The predetermined time will be briefly described. For example, when the amount of clogging in the circulation part is large, the amount of cooling water passing through the circulation part is smaller than the intended amount of water. That is, since the amount of heat transferred through the cooling water is small, the temperature difference of the cooling water detected by the water temperature sensors 5 and 9 becomes large. On the contrary, when the amount of clogging in the circulation part is small, the amount of cooling water passing through the circulation part is larger than when the amount of clogging is large. That is, since the amount of heat transferred through the cooling water is large, the temperature difference of the cooling water detected by the water temperature sensors 5 and 9 is small. Further, there is an unavoidable delay in such a change in the cooling water temperature with respect to the operation for reducing the opening degree of the electromagnetic switching valve 11 described above. Therefore, it is necessary to secure time for the temperature change of the cooling water. This securing time is the aforementioned predetermined time t1. FIG. 2 is an example of a map of securing time according to the driving duty of the water pump 2. A map as shown in FIG. 2 may be prepared in advance, and the above securing time may be obtained using the map. As shown in FIG. 2, when the driving duty of the water pump 2 is large, this securing time is set short because the amount of cooling water flowing through the circulation portion increases. On the other hand, when the drive duty of the water pump 2 is small, the amount of cooling water flowing through the circulation portion is reduced, so the length is set longer.

  If a negative determination is made in step S3 because the predetermined time t1 has not elapsed, the control in step S3 is repeated until a positive determination is made in step S3. On the other hand, if the predetermined time t1 has elapsed and a positive determination is made in step S3, the coolant temperature Thw (now) on the engine 1 side is detected by the first water temperature sensor 5 at the present time. In addition, the coolant temperature Thb (now) on the bypass pipe 8 side is detected by the second water temperature sensor 9. Then, the temperature difference ΔTnow is calculated by subtracting the coolant temperature Thb (now) on the bypass line 8 side from the coolant temperature Thw (now) on the engine 1 side (step S4).

  Next, an estimated value of the clogging amount of the distribution unit is calculated (step S5). A method for calculating the estimated value of the clogging amount will be described. FIG. 3 is a diagram schematically showing the correlation between the initial temperature difference ΔTini and the current temperature difference ΔTnow. When foreign matter is not clogged in the circulation part or when the clogging amount is small, the cooling water is circulated through the water jacket, so the temperature difference ΔTnow at the present time becomes small. On the other hand, when the circulation part is completely clogged with foreign substances or when the clogging amount is large, the cooling water stays in the water jacket, so that the amount of heat transferred through the cooling water is small. For this reason, the current temperature difference ΔTnow is larger than when the amount of clogging is small. As a result, when there is no clogging amount in the circulation part, as shown in FIG. 3, the difference ΔTd1 calculated by subtracting the current temperature difference ΔTnow from the initial temperature difference ΔTini increases. On the other hand, when the circulation part is clogged with foreign matter, the temperature difference ΔTd1 calculated by subtracting the current temperature difference ΔTnow from the initial temperature difference ΔTini becomes smaller. In this way, the smaller the temperature difference ΔTd1 when a predetermined time has elapsed, the larger the clogging amount. FIG. 4 is an example of a map of the estimated value of the clogging amount according to the temperature difference ΔTd1. Using the map as shown in FIG. 4, an estimated value of the clogging amount of the circulation section corresponding to the difference ΔTd1 is calculated.

  Next, it is determined whether or not the estimated value of the clogging amount of the distribution unit calculated in step S5 is equal to or greater than a predetermined threshold PV1 (step S6). This threshold PV1 is a predetermined value for determining an estimated value of the clogging amount in the distribution unit. The threshold PV1 is set to 15% as an example. If the estimated value of the clogging amount calculated in step S5 is smaller than the threshold PV1, and if a negative determination is made in this step S6, this routine is temporarily terminated without executing the subsequent control. On the other hand, when the estimated value of the clogging amount calculated in step S5 is larger than the threshold value PV1, if the determination in step S6 is affirmative, the opening degree of the electromagnetic switching valve 11 is increased and the state is increased. Is maintained (step S7). As a result, the cooling water flowing out from the water jacket is circulated so as to flow through the branch pipe 10. This threshold PV1 corresponds to the first threshold in the present invention.

  As described above, according to the cooling control apparatus for an internal combustion engine according to the present invention, the clogging amount of the circulation portion is estimated, and when the estimated value of the clogging amount is larger than the threshold PV1, the clogging portion is clogged. As a result, the opening degree of the electromagnetic switching valve 11 is increased. Therefore, even if the circulation part is clogged with foreign matter, it is possible to ensure the circulation of the cooling water that passes through the water jacket.

  FIG. 5 is a flowchart for explaining another control example by the cooling control apparatus for an internal combustion engine according to the present invention. The control example shown here is executed when the outside air temperature is equal to or lower than a predetermined temperature. . In the flowchart shown in FIG. 5, the same processes as those in the flowchart of FIG. 1 are denoted by the same step numbers as in FIG. In the flowchart of FIG. 5, when an affirmative determination is made in step S1, it is determined whether or not the outside air temperature is equal to or lower than a predetermined temperature (step S8). This can be performed by an outside air temperature sensor (not shown). The predetermined temperature is, for example, a temperature at which cooling of the cooling water by natural heat dissipation cannot be ignored, and a temperature that is sufficiently lower than the warm-up temperature can be used. If the outside air temperature is not lower than the predetermined temperature and thus a negative determination is made in step S8, the process proceeds to step S102 in the flowchart shown in FIG. 1, and the control shown in FIG. 1 is executed.

  If the outside air temperature is equal to or lower than the predetermined temperature and a positive determination is made in step S8, the process proceeds to step S3. Next, the operation of the water pump 2 is stopped (step S9). Thereafter, it is determined whether or not a predetermined time t2 has elapsed since the operation of the water pump 2 was stopped (step S10). If a negative determination is made in step S10 because the predetermined time t2 has not elapsed, the control in step S10 is repeated until a positive determination is made in step S10. The predetermined time t2 is a time ensured for the change of the cooling water temperature as in the control in step S3 of FIG.

  If a positive determination is made in step S10 because the predetermined time t2 has elapsed, a decrease ΔTcold of the cooling water temperature due to the outside air temperature is calculated (step S11). For example, the cooling water temperature Thw (c) on the engine 1 side and the cooling water temperature Thb (c) on the bypass pipe 8 side when a predetermined time t2 has elapsed are detected. Then, by subtracting the temperature Thw (c) and Thb (c) from the initial temperature difference ΔTini, the temperature decrease ΔTcold is calculated.

  Thereafter, the water pump 2 is driven (step S12). Next, the process proceeds to step S3, and it is determined whether or not the above-described predetermined time t1 has elapsed. If a positive determination is made in step S3 because the predetermined time t1 has elapsed, the process proceeds to step S4, and the cooling water temperature Thw on the engine 1 side at the present time, that is, when the water pump 2 is driven. (Now) and the cooling water temperature Thb (now) of the bypass pipe 8 are detected by the water temperature sensors 5 and 9. Then, the temperature difference ΔTnow is calculated by subtracting the cooling water temperature Thb (now) on the bypass line 8 side from the cooling water temperature Thw (now) on the engine 1 side.

Next, an estimated value of the clogging amount of the circulation part is calculated by removing the cooling water temperature decrease ΔTcold due to the outside air temperature from the initial temperature difference ΔTini (step S13). Specifically, first, the temperature difference ΔTnow is calculated by subtracting the current temperature difference ΔTnow from the initial temperature difference ΔTini. This temperature difference ΔTd1 includes the amount of cooling water cooled by outside air. Therefore, a temperature difference ΔTd2 obtained by subtracting a decrease ΔTcold of the cooling water temperature due to the outside air from the temperature difference ΔTd1 is calculated using the following equation.
ΔTd2 = (ΔTini−ΔTnow) − (t1 + t2) × ΔTcold

  Although not shown in detail, as the temperature difference ΔTd1, the smaller the temperature difference ΔTd2, the greater the amount of clogging. FIG. 6 is an example of a map of the estimated value of the clogging amount according to the temperature difference ΔTd2. A map as shown in FIG. 6 is prepared in advance, and the estimated value of the clogging amount of the circulation portion according to the temperature difference ΔTd2 is calculated using the map. Thereafter, the process proceeds to step S6 in the flowchart shown in FIG.

  As described above, according to the control example shown in FIG. 5, it is possible to eliminate the influence of the outside air temperature in the case of estimating the clogging amount of the circulation section, so that it is possible to improve the estimation accuracy of the clogging amount estimation value. That is, it can be avoided that the clogging amount is not present or the clogging amount is estimated to be small even though the circulation part is clogged with foreign matter.

  FIG. 7 is a flowchart for explaining still another example of control by the cooling control apparatus for an internal combustion engine according to the present invention. The control example shown here is an example configured to improve the estimation accuracy of the estimated value of the clogging amount of the current distribution unit when the estimated value of the clogging amount of the previous distribution unit is equal to or greater than a predetermined threshold PV1. is there. That is, it is an example configured to avoid the determination that the distribution unit is clogged even though the distribution unit is not clogged with foreign matter. In the flowchart shown in FIG. 7, the same steps as those in FIG. 1 are given the same processes as those in the flowchart in FIG.

  Subsequent to the control in step S1, it is determined whether or not the estimated value of the clogging amount of the circulation section calculated in the previous trip is equal to or less than a predetermined threshold PV1 (step S14). If the estimated value of the amount of clogging in the previous trip is affirmative in step S14 because it is less than or equal to the predetermined threshold PV1, the driving duty of the water pump 2 in the current trip is It is set smaller than the drive duty in trip (step S15). More specifically, when the estimated value of the clogging amount in the previous trip is equal to or less than the threshold PV1, it is estimated that the estimated value of the clogging amount is equal to or less than the threshold PV1 even in the current trip. Therefore, the following control is executed while reducing the driving duty of the water pump 2 to suppress power consumption in the water pump 2 and improve fuel efficiency. When the drive duty of the water pump 2 in the previous trip is 50%, for example, the drive duty is set to 40% in the current trip.

  On the other hand, if the estimated value of the clogging amount in the circulation section is larger than the threshold PV1 in the previous trip, and the determination is negative in step S14, the drive duty of the water pump 2 is set to the maximum value. (Step S16). The amount of cooling water circulated through the water jacket is increased by increasing the discharge amount of the water pump 2 without increasing the opening of the electromagnetic switching valve 11.

  Subsequent to or in parallel with these controls, the initial temperature difference ΔTini is temporarily stored and the opening degree of the electromagnetic switching valve 11 is reduced (step S17). Then, it progresses to step S3 and it is judged whether predetermined time t1 passed.

  It is determined whether or not the estimated value of the clogging amount in the current trip calculated in step S5 in FIG. 7 is greater than or equal to the threshold PV2 (step S18). This threshold PV2 is set to a value larger than the above-described threshold PV1, and is, for example, 60%. If the estimated value of the clogging amount of the circulation part in this trip is affirmative because it is greater than or equal to the threshold PV2, it is judged that the circulation part is blocked by foreign matter, that is, an abnormality has occurred. Is done. In addition, the opening degree of the electromagnetic switching valve 11 is increased and the state is maintained (step S19).

  If the estimated value of the clogging amount in the distribution unit is negative in step S18 because it is smaller than the threshold PV2, it is determined whether or not the estimated value of the clogging amount is greater than or equal to the threshold PV1 (step S20). ). If the estimated value of the clogging amount of the circulation part is smaller than the threshold value PV1 and a negative determination is made in step S20, it is determined that the circulation part is not blocked by foreign matter, that is, normal (step). S21). On the other hand, if the estimated value of the clogging amount is greater than or equal to the threshold PV1 and a positive determination is made in step S20, the process proceeds to step S22. In step S22, the estimated value of the clogging amount of the distribution unit is the threshold value. It is determined that an abnormality has occurred provisionally by being PV1 or more and smaller than the threshold PV2. This is referred to as provisional abnormality determination. In step S22, in addition to performing the provisional abnormality determination, the drive duty of the water pump 2 that can improve the estimation accuracy of the estimated value of the clogging amount in the next trip from the current estimation accuracy is calculated. May be. In the next trip, the clogging amount may be estimated using the driving duty of the water pump 2 estimated in step S22.

  Thus, according to the control example shown in FIG. 7, when the estimated value of the clogging amount estimated in the previous trip is equal to or greater than the threshold PV1, the clogging amount in the state where the driving duty of the water pump 2 is increased in the current trip. Therefore, the retention of the cooling water in the water jacket is suppressed as compared with the case where the drive duty of the water pump 2 is small. Therefore, the estimation accuracy of the estimated value of the clogging amount in the current trip can be improved as compared with the previous trip.

  FIG. 8 is a flowchart for explaining still another control example by the cooling control apparatus for an internal combustion engine according to the present invention. The control example shown here is an example configured to change the drive duty of the water pump 2 in accordance with the vehicle speed when estimating the clogging amount of the flow section. The control example shown in FIG. 8 can be applied to, for example, a hybrid vehicle including an internal combustion engine and an electric motor as driving force sources. In the flowchart shown in FIG. 8, the same steps as those in FIG. Following the control in step S1, the initial temperature difference ΔTini is temporarily stored, and the drive duty of the water pump 2 corresponding to the vehicle speed is set (step S23). FIG. 9 is an example of a drive duty map of the water pump 2 according to the vehicle speed. A map as shown in FIG. 9 is prepared in advance, and the drive duty may be obtained using the map. In the above map, when the vehicle speed is equal to or higher than a predetermined speed, the driving duty of the water pump 2 is maximized because the heat generation amount of the engine 1 is large due to the high frequency of driving mainly by driving the engine 1. Is set. The vehicle speed can be detected by a vehicle speed sensor (not shown). Thereafter, the process proceeds to step S3 in the flowchart of FIG.

  As described above, according to the control example shown in FIG. 8, when the hybrid vehicle is traveling at a low speed, the operation of the internal combustion engine is stopped due to the high frequency of traveling by driving the electric motor. Long time. Therefore, since the time during which the engine 1 is driven is short, even if the clogging amount is estimated by reducing the driving duty of the water pump 2 compared to the case of high vehicle speed, the engine 1 is driven during the control. Is unlikely. Therefore, the estimation accuracy of the clogging amount can be improved as compared with the case of high vehicle speed. Moreover, since the amount of circulating cooling water can be suppressed, warm-up of the engine 1 can be promoted. On the other hand, when the hybrid vehicle is traveling at a high speed, it takes a long time to drive the internal combustion engine because the frequency of traveling by driving the internal combustion engine is high. Therefore, by increasing the drive duty of the water pump 2, it is possible to quickly estimate the clogging amount in a short period when the operation of the engine 1 is stopped.

  FIG. 10 is a flowchart for explaining still another example of control by the cooling control apparatus for an internal combustion engine according to the present invention. The control example shown here is an example in which the amount of cooling water to be circulated through the water jacket is changed according to the estimated value of the clogging amount in the circulation section when the opening degree of the electromagnetic switching valve 11 is reduced. is there. In the flowchart shown in FIG. 10, the same processes as those in the flowchart in FIG. 1 are denoted by the same step numbers as in FIG.

  In the flowchart of FIG. 10, following the control of step S5, it is determined whether or not the estimated value of the clogging amount is equal to or greater than a threshold PV3 (step S24). The threshold PV3 is set to a value larger than the above-described threshold PV1 and smaller than the threshold PV2, and is, for example, 50%. If the estimated value of the clogging amount is greater than or equal to the threshold PV3 and an affirmative determination is made in step S24, the opening degree of the electromagnetic switching valve 11 is increased and the state is maintained (step S25). That is, when the estimated value of the clogging amount is large, the cooling water flowing out from the water jacket is circulated through the branch pipe 10.

  If the estimated value of the clogging amount is smaller than the threshold PV3 and a negative determination is made in step S24, it is determined whether or not the estimated value of the clogging amount is greater than or equal to the threshold PV1 (step S26). If the estimated value of the clogging amount is smaller than the threshold value PV1 and a negative determination is made in step S26, this routine is temporarily terminated.

  On the other hand, if the estimated value of the clogging amount is equal to or greater than the threshold PV1 and an affirmative determination is made in step S26, in order to set the drive duty according to the estimated value of the clogging amount, A correction coefficient for correcting the drive duty output to the pump 2 is calculated (step S27). FIG. 11 is a map of correction coefficients corresponding to the estimated clogging amount. A map as shown in FIG. 11 may be prepared in advance, and the correction coefficient may be obtained using the map.

  Next, the drive duty corrected by the correction coefficient is set (step S28). Specifically, the drive duty calculated by multiplying the current drive duty of the water pump 2 by the correction coefficient is output to the water pump 2. When the estimated value of the clogging amount is 15% or more and less than 50%, the discharge amount of the water pump 2 is increased by the correction coefficient corresponding to the estimated value of the clogging amount. The maximum value of the drive duty calculated by multiplying the correction coefficient is a value that does not deteriorate the fuel consumption even if the drive duty is output to the water pump 2. This can be obtained in advance by experiments or simulations. That is, by increasing the drive duty of the water pump 2 without deteriorating the fuel consumption, the range of the estimated value of the clogging amount that can secure the amount of cooling water circulating through the water jacket is equal to or higher than the threshold PV1 described above. The range is less than the threshold PV3. On the other hand, when the estimated value of the clogging amount is equal to or greater than the threshold PV3, the fuel consumption may be deteriorated by increasing the driving duty of the water pump 2 to ensure the circulating cooling water amount. Therefore, the opening degree of the electromagnetic switching valve 11 is increased.

  As described above, according to the control example shown in FIG. 10, when the estimated value of the clogging amount is smaller than the threshold PV3, the opening degree of the electromagnetic switching valve 11 is not increased, so that the engine 1 is prevented from being overcooled. Or it can be suppressed. Further, when the estimated value of the clogging amount is equal to or larger than the threshold PV3, the opening degree of the electromagnetic switching valve 11 is increased, so that deterioration of fuel consumption caused by excessively increasing the driving duty of the water pump 2 is prevented or suppressed. be able to.

  Here, the relationship between the above-described specific example and the present invention will be briefly described. The function of executing the control of Step S2 to Step S6, Step S8 to Step S13, Step S14 to Step S16, and Step S23. The objective means corresponds to the “estimating means” in the present invention.

Claims (5)

A cooling circuit in which cooling water for cooling the internal combustion engine circulates between a water pump and the internal combustion engine; a bypass circuit in which the cooling water circulates by bypassing the internal combustion engine; and a temperature of the cooling water in the cooling circuit. A first water temperature sensor for detecting, a second water temperature sensor for detecting a temperature of the cooling water in the bypass circuit, and an amount of cooling water provided in the cooling circuit to reduce the amount of the cooling water circulating in the cooling circuit by reducing an opening degree. And a switching valve that increases the amount of the cooling water circulating through the cooling circuit by increasing the opening, and a small amount of the cooling water is circulated through the cooling circuit when the opening of the switching valve is reduced. In a cooling control device for an internal combustion engine comprising a circulation part,
When the driving of the internal combustion engine is stopped, the temperature of the cooling water in the cooling circuit detected by the first water temperature sensor while reducing the opening of the switching valve and driving the water pump and detecting the first water temperature sensor, 2. An internal combustion engine comprising: an estimation unit that estimates a clogging amount of the circulation portion according to a temporal change amount of a temperature difference from a temperature of the cooling water of the bypass circuit detected by the two water temperature sensors. Cooling control device. When the outside air temperature is lower than a predetermined temperature, the estimating means determines the outside air temperature when the water pump is stopped from the amount of change in the temperature difference when the water pump is driven. 2. The cooling control for an internal combustion engine according to claim 1, further comprising means for estimating a clogging amount of the circulation portion in which the opening degree is reduced by a change amount in temperature obtained by subtracting a change amount in the temperature difference due to the temperature difference. apparatus. When the estimated value of the clogging amount estimated last time is less than the first threshold value, the estimation means decreases the current driving amount of the water pump from the previous driving amount of the water pump, and When the estimated value of the clogging amount is larger than the first threshold value, the current driving amount of the water pump is increased from the previous driving amount of the water pump to estimate the clogging amount of the current circulation unit. The cooling control apparatus for an internal combustion engine according to claim 1 or 2, further comprising means. 4. The estimating means includes means for estimating a clogging amount of the circulation section by increasing a driving amount of the water pump as a speed of a vehicle on which the internal combustion engine is mounted is higher. The cooling control apparatus for an internal combustion engine according to any one of the above. The estimation means increases the driving amount of the water pump when the estimated value of the estimated clogging amount is larger than the first threshold and smaller than a predetermined second threshold, and the estimated value of the clogging amount 5. The cooling control apparatus for an internal combustion engine according to claim 1, further comprising means for increasing the opening degree of the switching valve when is greater than a predetermined second threshold value.

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