JP2010190142A - Cooling device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cooling device for an internal combustion engine achieving both responsiveness and suppression of overshoot. <P>SOLUTION: When it is determined that an absolute value of deviation of an actual water temperature from a target water temperature is a threshold value A or less and an absolute value of a change rate of the actual water temperature is a threshold value B or more, a correction flow rate is calculated based on the change rate. An operation flow rate is calculated from a PI control flow rate calculated based on the deviation, a reference flow rate set based on the target water temperature, and the correction flow rate, and a discharge amount of an electric water pump is controlled based on the operation flow rate. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a cooling device for an internal combustion engine comprising flow rate adjusting means for adjusting a supply flow rate of cooling water to the internal combustion engine.

  In Patent Document 1, a cylinder head side supply passage for supplying cooling water from a water pump to a cylinder head side jacket and a cylinder block side supply passage for supplying cooling water from the water pump to a cylinder block side jacket are provided at a branch portion. A cooling device is disclosed in which a distribution control valve for controlling the distribution of cooling water to both passages is arranged, and the water pump and the distribution control valve are controlled in accordance with the water temperatures of the cylinder head side jacket and the cylinder block side jacket. .

Japanese Patent Laying-Open No. 2005-083239

  By the way, when the cooling water supply flow rate is controlled based on the detection result of the water temperature as described above, there is a time delay until the change in the water temperature corresponding to the change in the supply flow rate is detected. There is a problem that it is difficult to suppress the occurrence of overshoot while changing with a high response toward.

  The present invention has been made in view of the above problems, and an object thereof is to provide a cooling device for an internal combustion engine that can achieve both responsiveness and suppression of overshoot.

  Therefore, in the cooling device for an internal combustion engine according to the present invention, the operation amount of the flow rate adjusting means for adjusting the flow rate of the cooling water supplied to the internal combustion engine includes the deviation between the cooling water temperature and the target value, and the change rate of the cooling water temperature. The operation amount is output to the flow rate adjusting means.

  According to the above invention, the operation amount required to bring the actual cooling water closer to the target is obtained from the deviation between the cooling water temperature and the target value, while the characteristics of the transient response can be determined from the change speed of the cooling water temperature. As a result, both responsiveness and suppression of overshoot can be achieved.

It is a whole block diagram of the cooling device in 1st Embodiment. It is a flowchart which shows the calculation process of the operation flow rate in the said 1st Embodiment. It is a block diagram which shows the calculation process of the operation flow rate in the said 1st Embodiment. It is a time chart which shows the change of the target water temperature, the actual water temperature, the water temperature change speed, and the correction amount when the correction process is performed according to the first embodiment. It is a whole block diagram of the cooling device in 2nd Embodiment. It is a flowchart which shows the calculation process of the operation flow rate in the said 2nd Embodiment. It is a figure which shows the characteristic of the target water temperature in the said 2nd Embodiment.

Embodiments of the present invention will be described below.
FIG. 1 shows the overall configuration of a cooling device for an internal combustion engine in the first embodiment.
In FIG. 1, an internal combustion engine 1 includes a cylinder block 2 and a cylinder head 3. A cylinder block side water jacket 4 is formed on the cylinder block 2, and a cylinder head side water jacket is formed on the cylinder head 3. 5 is formed.

  The radiator 6 is a radiator for radiating the heat of the cooling water heated in the internal combustion engine 1. One end of the suction pipe 7 is connected to the outlet 6 a of the radiator 6, and the suction pipe 7 Is connected to the suction port 8a of the electric water pump 8.

In the present application, “cooling water” includes a cooling liquid such as LLC (Long Life Coolant).
One end of a supply pipe 9 is connected to the discharge port 8 b of the water pump 8, and the other end of the supply pipe 9 is connected to an inlet 4 a of the cylinder block side water jacket 4.

  One end of the return pipe 10 is connected to the outlet 5 a of the cylinder head side water jacket 5, and the other end of the return pipe 10 is connected to the inlet 6 b of the radiator 6.

  The water pump 8 is rotationally driven by a motor 11 and sucks cooling water from the suction pipe 7 side and discharges the cooling water to the supply pipe 9 side. The internal combustion engine 1 (the cylinder block side water jacket 4 and the cylinder head side water jacket 5). ) Pump the cooling water toward

  The cooling water pumped from the water pump 8 passes through the cylinder block side water jacket 4, thereby depriving the heat of the cylinder block 2. Further, the cylinder block side water jacket 4 and the cylinder head side water jacket 5 communicate with each other. The fluid flows from the cylinder block side water jacket 4 into the cylinder head side water jacket 5 through the communicating passage 12 to take heat from the cylinder head 3.

  Then, the cooling water whose temperature has risen by cooling the cylinder block 2 and the cylinder head 3 is discharged from the outlet 5 a of the water jacket 5 on the cylinder head side, returns to the radiator 6 through the return pipe 10, and dissipates heat in the radiator 6. Then, after the temperature is lowered, it is sucked again by the water pump 8 and supplied to the internal combustion engine 1.

  That is, the cooling water circulates through the path (cooling circuit) of the radiator 6 → the cylinder block side water jacket 4 → the cylinder head side water jacket 5 → the radiator 6 to cool the internal combustion engine 1.

  In addition, a bypass pipe 12 for connecting the suction pipe 7 between the suction port 8a of the water pump 8 and the outlet 6a of the radiator 6 and the return pipe 10 is provided, and the suction pipe 7 of the bypass pipe 12 is provided. The connecting portion to is provided with a thermostat 13 that opens the bypass pipe 12 and circulates the cooling water by bypassing the radiator 6 when the cooling water temperature is lower than the set low temperature.

The thermostat 13 is an open / close valve that opens and closes the valve using thermal expansion of wax.
However, an electromagnetic on-off valve can be provided in place of the thermostat 13, and the electromagnetic on-off valve can be opened and closed by a signal from an electronic control unit (ECU) 20 described later.

  The electronic control unit 20 includes a microcomputer including a CPU, RAM, ROM, I / O, and the like, and the electronic control unit 20 includes a temperature sensor that detects the temperature of the cooling water in the internal combustion engine 1. 21 (detection means), a rotation sensor 22 that detects the rotational speed NE of the internal combustion engine 1, a load sensor 23 that detects the load of the internal combustion engine 1, and the like are input.

  The load sensor 23 includes, for example, a sensor that detects a publicly known state quantity indicating the engine load, such as the intake pipe negative pressure, the throttle opening, the intake air quantity, and the fuel injection quantity of the internal combustion engine 1. .

  The electronic control unit 20 (control means) calculates the operation amount of the motor 11 on the basis of signals from the various sensors, and drives and controls the motor 17 based on the operation amount, whereby the water pump 8 (flow rate) The discharge flow rate of the cooling water from the adjusting means) is controlled.

Next, the control of the motor 17 (water pump 8) by the electronic control unit 20 will be described in detail according to the flowchart of FIG.
In the routine shown in the flowchart of FIG. 2, first, in step S101, a basic value (basic flow rate) of the cooling water discharge flow rate from the water pump 8 is calculated.

The basic flow rate is set according to the target water temperature. Specifically, the basic flow rate is set larger as the target water temperature is lower, and the circulation amount of the cooling water is increased when the target water temperature is lower.
The target water temperature is a target of the cooling water temperature detected by the temperature sensor 21, and the electronic control unit 20 (target setting means) stores the target water temperature as a fixed value in advance, or the target water temperature Is variably set according to the operating conditions of the internal combustion engine 1.

  As an example in which the target value is variably set according to the operating conditions of the internal combustion engine 1, when the cooling water temperature reaches the fully warmed temperature, the target water temperature is set higher than the appropriate temperature when cooling down. While the cooling water discharge flow rate (cooling water circulation amount) from 8 is reduced and the temperature rise of the cooling water temperature (engine temperature) is accelerated, the target water temperature is set higher than during warming up after warming up. By setting the target temperature to a low value, the target temperature is set to be lower than the proper temperature at the time of high load / high rotation operation after warm-up. The discharge flow rate (cooling water circulation amount) of the cooling water from 8 is increased so that an excessive increase in the cooling water temperature (engine temperature) can be prevented in advance.

  The basic flow rate can be set based on the target water temperature and the engine rotational speed NE. The lower the target water temperature, the larger the basic flow rate, and the higher the engine rotational speed NE, the larger the basic flow rate. can do.

In step S102, the deviation between the cooling water temperature detected by the temperature sensor 21 and the target water temperature is calculated according to the following equation.
(Expression 1)... Water temperature deviation = Water temperature detection value−Target water temperature In step S103, the change rate of the cooling water temperature detected by the temperature sensor 21 is calculated according to the following expression.

(Expression 2) ... Water temperature change rate = (Current water temperature detection value-Previous water temperature detection value) / Change time The change time in Expression 2 is the elapsed time from the previous water temperature detection to the current water temperature detection. The amount of change in water temperature per unit time is calculated according to Equation 2.

  In step S104, it is determined whether or not the absolute value of the water temperature deviation calculated according to Equation 1 is equal to or less than the threshold A and the absolute value of the water temperature change rate calculated according to Equation 2 is equal to or greater than the threshold B.

  The determination in step S104 is over in feedback control for controlling the cooling water discharge flow rate (cooling water supply flow rate) from the water pump 8 so that the cooling water temperature detected by the temperature sensor 21 approaches the target water temperature. This is to predict the occurrence of shoots.

  That is, the state where the absolute value of the water temperature deviation is not more than the threshold value A is a state where the actual water temperature is a value within a predetermined range including the target water temperature, and the actual cooling water temperature is sufficiently close to the target water temperature. In this state, if the absolute value of the water temperature change rate is greater than or equal to the threshold value B and the actual water temperature is changing at a fast speed, the actual water temperature passes the target water temperature and causes a large deviation. It is predicted that overshoot will occur.

  In particular, if the actual water temperature overshoots higher than the target water temperature, the engine temperature becomes excessively high (overheating), and problems such as knocking, poor lubrication, and seizure may occur.

  Therefore, the thresholds A and B in step S104 are previously adapted based on actual equipment or simulation so that the occurrence of overshoot can be predicted from the water temperature deviation and the water temperature change rate.

  If it is determined in step S104 that the absolute value of the water temperature deviation is equal to or lower than the threshold A and the absolute value of the water temperature change rate is equal to or higher than the threshold B, it is determined that there is a high possibility that an overshoot will occur. Then, the process proceeds to step S105 in order to suppress the occurrence of the overshoot.

In step S105, it is determined whether or not the actual water temperature has converged near the target water temperature.
In the convergence determination, for example, when the state where the absolute value of the water temperature deviation is equal to or less than the threshold value C (<threshold value A) continues for a predetermined time or more, the actual water temperature has converged near the target water temperature. to decide.

In other words, a state where the actual water temperature is stable at a value close to the target water temperature is defined as the actual water temperature convergence state.
If it is determined in step S105 that the actual water temperature has not converged near the target water temperature, the process proceeds to step S106, and a corrected flow rate for suppressing the occurrence of overshoot is calculated according to the following equation.

(Equation 3) ... corrected flow rate = gain × water temperature change rate × basic flow rate That is, the corrected flow rate is calculated as a flow rate of a predetermined ratio of the basic flow rate, and the larger the absolute value of the water temperature change rate, the greater the absolute value is calculated. Even if the water temperature change rate is the same, the larger the basic flow rate at that time, the larger the absolute value is calculated, and the water temperature change rate is converted into the predetermined ratio by the gain.

  In addition, since the water temperature change rate is calculated as a positive value when the water temperature increases, and is calculated as a negative value when the water temperature decreases, the correction flow rate is the cooling water when the water temperature increases. It becomes a positive correction term that suppresses the increase in water temperature by increasing the flow rate, and becomes a negative correction term that suppresses the decrease in water temperature by correcting the flow rate of cooling water when the water temperature decreases.

  The gain is preliminarily adapted as a value that can suppress the occurrence of an overshoot due to a rapid temperature change and does not excessively suppress the temperature change by the correction setting of the flow rate by the correction flow rate.

  The correction flow rate proceeds from step S104 to step S105 for the first time, and when the process proceeds from step S105 to step S106, that is, in the temperature region where the absolute value of the water temperature deviation is equal to or less than the threshold value A, the temperature change rate is equal to or greater than the threshold value B. It is calculated when it is determined for the first time, and the value is held until it is reset to zero in later-described step S109 or step S115.

  This is because, as a result of correcting the flow rate with the correction flow rate (≠ 0) based on the change rate of the cooling water temperature being equal to or higher than the threshold B, the change rate becomes slow. This is because if the value is changed to be smaller, the change speed is increased again, the absolute value of the correction flow rate (≠ 0) is increased again, and control is hunted.

  In step S107, the PI control flow rate, which is a feedback correction term for bringing the actual water temperature close to the target water temperature, is sequentially determined by proportional / integral operation (PI operation) based on the water temperature deviation (control error) as shown in the following equation. Update calculation.

(Expression 4) ... PI control flow rate = proportional gain x water temperature deviation + integral gain x ∫ (water temperature deviation) dt
Since the water temperature deviation is calculated as “water temperature deviation = water temperature detection value−target water temperature” as shown in Equation 1, the PI control flow rate increases when the water temperature detection value is higher than the target water temperature. The flow rate is feedback-controlled so as to bring the actual water temperature closer to the target water temperature by correcting and correcting the flow rate to decrease when the detected water temperature value is lower than the target water temperature.

  In step S108, an operation flow rate, which is a target flow rate of cooling water circulated between the cylinder block side water jacket 4 and the cylinder head side water jacket 5, is calculated according to the following formula based on the PI control flow rate, the correction flow rate, and the basic flow rate. After the calculation, the process returns to step S105 again to determine whether or not the actual cooling water temperature has converged to the target water temperature.

(Equation 5) ... operation flow rate = PI control flow rate + correction flow rate + basic flow rate The electronic control unit 20 controls the rotation speed of the motor 11 (water pump 8) so as to obtain a discharge flow rate corresponding to the operation flow rate. To do.

  Here, by controlling the water pump 8 so as to obtain a flow rate of “PI control flow rate + basic flow rate”, the actual water temperature can be changed following the target water temperature, but the change in the water temperature corresponding to the flow rate change. Since there is a response delay until the temperature is detected by the temperature sensor 21, an overshoot may occur.

  On the other hand, if the correction by the correction flow rate is added, the change in the actual water temperature in the state where the actual water temperature approaches the target water temperature (the absolute value of the water temperature deviation ≦ the state of the threshold A) is suppressed. Until the actual water temperature approaches the target water temperature, the water temperature is changed with a high response, and then the change speed is delayed to converge to the target water temperature, thereby suppressing the occurrence of overshoot.

  In particular, when the water temperature is raised toward the target water temperature, the actual water temperature is suppressed from becoming excessively high beyond the target water temperature, thereby avoiding the occurrence of knocking, poor lubrication, seizure, etc. due to overheating. It becomes possible to do.

  As described above, when the correction flow rate based on the water temperature change rate is added to the operation flow rate and the rotation of the motor 11 (the discharge amount of the water pump 8) is controlled, the actual water temperature converges to the target water temperature in step S105. Continue until it is judged.

  If it is determined in step S105 that the actual water temperature has converged to the target water temperature, the process proceeds to step S109, where the correction flow rate is reset to zero, and the flow rate correction control based on the water temperature change rate is stopped.

In the next step S110, the change direction of the heat generation amount of the internal combustion engine 1 in a state where the flow rate of the cooling water is corrected by the corrected flow rate immediately before the convergence determination (a state where the corrected flow rate ≠ 0) is determined.
The heat generation amount of the internal combustion engine 1 can be estimated from the engine speed and the engine load, and more specifically, is calculated according to the following equation (heat generation amount estimation means).

(Equation 6) ... Engine heat generation amount = fuel injection amount × fuel heat generation amount × cooling loss In Equation 6, the fuel heat generation amount is stored in advance as a characteristic value of the fuel (gasoline) used in the internal combustion engine 1. Further, a map in which the cooling loss is set in accordance with the engine rotational speed NE and the engine load is stored in advance, and the cooling loss corresponding to the engine rotational speed NE and the engine load at that time is retrieved from the map.

  Further, the fuel injection amount is a state amount indicating the engine load that is supplied to the internal combustion engine 1, but in a gasoline engine that sets the fuel injection amount in accordance with the cylinder intake air amount, the fuel injection amount Instead of this, the cylinder intake air amount can be used.

  In a simple manner, it is possible to retrieve the heat generation amount corresponding to the engine rotation speed NE and the engine load at that time from a map in which the heat generation amount is set according to the engine rotation speed NE and the engine load.

  Further, in step S110, it is only necessary to be able to determine the change direction of the engine heat generation amount. Therefore, as a simple determination method, the engine load increase state is regarded as the engine heat generation increase change state, and the engine load decrease state is the engine heat generation. It can be regarded as a decrease in quantity.

  In step S111, the change direction of the engine heat generation amount and the change direction of the cooling water temperature in a state where the flow rate of the cooling water is corrected by the corrected flow rate (state where the corrected flow rate ≠ 0) are compared, and both are directed in the same direction. In other words, the cooling water temperature has risen in response to an increase in engine heat generation, or the cooling water temperature has changed in response to a decrease in engine heat generation. Determine if you were doing.

  Then, when the change direction of the engine heat generation amount and the change direction of the cooling water temperature are the same, for example, the flow rate of the cooling water is controlled to increase the actual cooling water temperature toward the target temperature. In this state, the engine heat generation amount has also changed in the direction of increasing the coolant temperature, and when the correction for the corrected flow rate is lost, the coolant temperature that has converged near the target coolant temperature is increased.

  In addition, when the flow rate of the cooling water is controlled so as to lower the actual cooling water temperature toward the target temperature, the engine heat generation amount shows a decreasing change in the direction of lowering the cooling water temperature. When the correction for the corrected flow rate is lost, the cooling water temperature converged near the target water temperature is decreased.

  On the other hand, when the change direction of the engine heat generation amount and the change direction of the cooling water temperature are opposite, the change of the engine heat generation amount was acting in a direction that hinders the change of the cooling water temperature, The correction flow rate according to the changing speed of the cooling water temperature does not suppress the change of the cooling water temperature due to the change of the engine heat generation amount.

  Therefore, if the change direction of the engine heat generation amount and the change direction of the cooling water temperature are the same, the process proceeds to step S112, and the integral term (integral operation amount) of the PI control flow rate is reset to zero. The previous correction flow rate is added, and the update calculation is performed with the integration term after the addition processing (integration operation) as the previous value.

By performing the process of reflecting the corrected flow rate in the integral term, it is possible to suppress fluctuations in the cooling water temperature after convergence near the target water temperature.
In step S113, the PI control flow rate is updated and calculated in the same manner as in step S107, but the integral term is updated with the value corrected by the corrected flow rate in step S112 as the previous value.

  In step S114, the operation flow rate is calculated according to the equation 5. However, since the correction flow rate is reset to zero in step S109, the operation flow rate is substantially calculated according to the following equation.

(Equation 7) ... operation flow rate = PI control flow rate + basic flow rate If it is determined in step S111 that the change direction of the engine heat generation amount and the change direction of the cooling water temperature are opposite, the cooling water temperature Since it is not necessary to reflect the correction flow rate corresponding to the change speed of the current value in the integral term, the process proceeds to step S116, and the PI control flow rate is updated by using the integral term immediately before the convergence determination in step S105 as the previous value.

Further, in step S117, the operation flow rate is calculated according to equation 5, but the operation flow rate is substantially calculated according to equation 7 based on the processing in step S109 where the correction flow rate is zero.
On the other hand, if it is determined in step S104 that the absolute value of the water temperature deviation is greater than the threshold value A and / or the absolute value of the water temperature change rate is less than the threshold value B, that is, actual cooling. When the water temperature is far from the target water temperature and / or when the water temperature change rate is slow, it is determined that the correction with the correction flow rate according to the change rate is unnecessary, and the process proceeds to step S115, where the correction flow rate is determined. Is set to zero.

  For example, even if the absolute value of the water temperature deviation is equal to or less than the threshold value A and the actual cooling water temperature is approaching the target water temperature, if the absolute value of the water temperature change rate at that time is less than the threshold value B, it is over Since a chute is not generated and is expected to converge to the target water temperature, it is not necessary to correct the flow rate with a correction flow rate corresponding to the change speed.

  Further, even if the absolute value of the water temperature change rate is equal to or greater than the threshold value B, if the absolute value of the water temperature deviation is larger than the threshold value A and the actual cooling water temperature is sufficiently far from the target water temperature, the target water temperature is reached. It is not necessary to suppress the change toward the target, but rather, by maintaining the state, the target water temperature can be approached with a high response, and therefore the flow rate is not corrected by the corrected flow rate.

  Furthermore, if the absolute value of the water temperature deviation is larger than the threshold A, the actual cooling water temperature is sufficiently far from the target water temperature, and the absolute value of the water temperature change rate is less than the threshold B, the water temperature change is suppressed. There is no necessity, and in this case, the flow rate is not corrected by the corrected flow rate.

  In step S116, the PI control flow rate is updated, and in step S117, the operation flow rate is calculated according to Equation 5. However, since the correction flow rate is set to zero in step S115, the operation flow rate is substantially calculated according to Equation 7. .

  In the above embodiment, the discharge amount of the water pump 8 as the flow rate adjusting means is controlled in accordance with the operation flow rate. However, the flow rate control provided in the supply pipe 9 while keeping the rotation speed of the motor 11 constant. The flow rate of the cooling water supplied to the internal combustion engine 1 (the cylinder block side water jacket 4 and the cylinder head side water jacket 5) can be changed by the opening degree of the valve (flow rate adjusting means). The internal combustion engine 1 can be supplied with cooling water having a flow rate corresponding to the operation flow rate by combining the control of the rotational speed (pump discharge amount) and the opening degree control of the flow rate control valve.

FIG. 3 is a block diagram showing the function of calculating the correction flow rate based on the water temperature change rate and correcting the operation flow rate based on the correction flow rate, as shown in the flowchart of FIG.
In FIG. 3, a deviation between the actual water temperature detected by the temperature sensor (cooling water temperature detection device) 21 and the target water temperature is calculated in the first calculator 31, and the deviation is output to the PI control flow rate calculation unit 32. Is done.

The PI control flow rate calculation unit 32 calculates and outputs the PI control flow rate so that the actual cooling water temperature approaches the target water temperature by the proportional / integral operation based on the deviation.
Further, the water temperature change rate calculation unit 33 calculates the actual change rate of the water temperature detected by the temperature sensor 21, and outputs the calculated change rate to the correction flow rate calculation unit 34.

The corrected flow rate calculation unit 34 calculates and outputs a corrected flow rate for suppressing a change in water temperature based on the change speed and the water temperature deviation.
The correction by the correction flow rate is started when the absolute value of the water temperature deviation is equal to or lower than the threshold A and the absolute value of the water temperature change rate is equal to or higher than the threshold B as described above. Continue until it converges to the target water temperature.

The second calculator 35 adds the PI control flow rate calculated by the PI control flow rate calculation unit 32 and the correction flow rate calculated by the correction flow rate calculation unit 34.
The addition result in the second computing unit 35 is output to the zero limit unit 36, and the zero limit unit 36 performs a process of resetting to zero when the addition result is negative, so that “PI control flow rate + correction flow rate” is Avoid output as a negative flow rate.

  The basic flow rate calculation unit 37 calculates a basic flow rate based on the target water temperature, and the third calculation unit 38 adds the basic flow rate and the “PI control flow rate + correction flow rate” that has passed through the zero limit unit 36. The addition result is output to the flow control device (flow rate adjusting means) 39 as the operation flow rate.

  As described above, the flow rate control device 39 is constituted by the water pump 8 (motor 11) and / or the flow rate control valve, and the cooling circuit 40 (the cylinder block side water jacket 4 and the cylinder) of the internal combustion engine 1 according to the operation flow rate. The flow rate of the cooling water supplied to the head side water jacket 5) is controlled.

The time chart of FIG. 4 shows changes in water temperature, water temperature deviation, water temperature change rate, correction flow rate, and integral term when the flow rate of cooling water is controlled according to the routine shown in the flowchart of FIG.
In FIG. 4, at the time t1, the actual water temperature is lower than the target water temperature, but the absolute value of the deviation between the target water temperature and the actual water temperature is larger than the threshold A, so the correction flow rate is set to zero.

  On the other hand, the feedback control based on the PI control flow rate from the time t1 to the time t2 causes the absolute value of the deviation between the target water temperature and the actual water temperature to coincide with the threshold A at the time t2, and the time Since the absolute value of the water temperature change rate (water temperature increase rate) calculated at time t2 is equal to or greater than the threshold value B, the corrected flow rate is calculated based on the water temperature change rate at that time, and the operation flow rate is calculated based on the corrected flow rate. Correct.

  At time t2, since the water temperature is increasing, the correction flow rate is calculated to be a positive value that will increase the cooling water flow rate so as to suppress the increase in the water temperature by increasing the cooling water flow rate. .

  And by the increase correction | amendment of the operation flow rate by the said correction | amendment flow rate, an actual cooling water temperature converges to the target water temperature vicinity, without greatly exceeding a target water temperature (it becomes much higher than a target water temperature).

  If it is determined that the actual cooling water temperature has converged to the target water temperature at the time t3, the correction flow rate is reset to zero, but the correction flow rate of the internal combustion engine 1 is corrected by the correction flow rate from the time t2 to the time t3. The correction flow rate is added to the integral term when it is determined that the change direction of the heat generation amount is the same as the water temperature change direction (the engine heat generation amount increased and the water temperature increased during the correction period). (The integral term is increased and corrected by the correction flow rate) and updated.

By correcting the integral term based on the corrected flow rate, it is possible to suppress a change in water temperature after the actual water temperature has converged to the target water temperature.
At time t4, the target water temperature is changed to a higher value than before. However, the absolute value of the water temperature change speed does not exceed the threshold value B in a state where the actual water temperature is changed following the updated target water temperature. Therefore, the correction flow rate is kept at zero.

  On the other hand, at time t5, the target water temperature is changed to a value lower than the target water temperature at time t1, and as a result, the absolute value of the deviation between the target water temperature and the actual water temperature is switched to a state larger than the threshold value A.

  Then, feedback control based on the PI control flow rate is performed to eliminate the water temperature deviation, and at time t6, the absolute value of the deviation between the target water temperature and the actual water temperature becomes equal to the threshold value A, and the time Since the absolute value of the water temperature change rate (water temperature decrease rate) calculated at time t6 is equal to or greater than the threshold value B, the corrected flow rate is calculated based on the water temperature change rate at that time, and the operation flow rate is calculated based on the corrected flow rate. Correct.

  At time t6, since the water temperature is decreasing, the correction flow rate is calculated to be a negative value that will decrease and correct the cooling water flow rate in order to suppress the decrease in the water temperature by decreasing the cooling water flow rate. .

  And by the correction correction of the operation flow rate by the correction flow rate, the actual cooling water temperature converges to the vicinity of the target water temperature without greatly exceeding the target water temperature (becomes much lower than the target water temperature).

  If it is determined at time t7 that the actual cooling water temperature has converged to the target water temperature, the correction flow rate is reset to zero, but the correction flow rate of the internal combustion engine 1 is corrected by the correction flow rate from time t6 to time t7. The correction flow rate is added to the integral term when it is determined that the change direction of the heat generation amount is the same as the change direction of the water temperature (the engine heat generation amount decreased and the water temperature decreased during the correction period). (The integral term is corrected to decrease by the correction flow rate) and updated.

FIG. 5 shows an overall configuration of a cooling device for an internal combustion engine in the second embodiment.
In FIG. 5, the same components as those shown in FIG. 1 are denoted by the same reference numerals.

  In the second embodiment shown in FIG. 5, the cylinder block side water jacket 4 and the cylinder head side water jacket 5 are formed independently of each other, in other words, two cooling circuits independent of each other are provided. Composed.

  Then, the cooling water discharged from the water pump 8 is distributed and supplied to the cylinder block side water jacket 4 and the cylinder head side water jacket 5, respectively, and the cylinder block side water jacket 4 and the cylinder head side water jacket 5 are supplied. The cooling water discharged from the cylinder block side water jacket 4 and the cooling water discharged from the cylinder head side water jacket 5 are merged and returned to the radiator 6. Yes.

  Specifically, a supply pipe 9 having one end connected to the discharge port 8b of the water pump 8 branches from the middle into two, a first supply pipe 9a and a second supply pipe 9b, and the first supply pipe 9a is The second supply pipe 9b is connected to the inlet 4a of the cylinder block side water jacket 4 and is connected to the inlet 5b of the cylinder head side water jacket 5.

A distribution control valve 15 is provided at a portion where the supply pipe 9 branches into a first supply pipe 9a and a second supply pipe 9b.
Of the cooling water discharged from the water pump 8, the distribution control valve 15 supplies a flow rate to the cylinder head side water jacket 5 (first supply pipe 9a) and a cylinder block side water jacket 4 (second supply pipe). 9b) is a valve (flow rate adjusting means) that controls the ratio (distribution ratio) to the flow rate supplied to 9b).

  The distribution control valve 15 can be configured to change the distribution ratio by a rotary valve, and an opening / closing valve whose opening is controlled independently of each other is provided between the first supply pipe 9a and the second supply pipe 9b. It can be configured for each.

  Furthermore, one end of the first return pipe 10a is connected to the outlet 5a of the cylinder head side water jacket 5, and one end of the second return pipe 10b is connected to the outlet 4b of the cylinder block side water jacket 4. The other end of the first return pipe 10 a and the other end of the second return pipe 10 b merge and are connected to one end of the return pipe 10, and the other end of the return pipe 10 is connected to the inlet 6 b of the radiator 6. Connected.

  The second return pipe 10b is provided with a check valve (one-way valve) 16 that allows a flow of cooling water from the cylinder block side water jacket 4 toward the inlet 6b of the radiator 6 and blocks a reverse flow. It is disguised.

  In addition, although 1st Embodiment shown in FIG. 1 is provided with the communicating path 12 which connects the cylinder block side water jacket 4 and the cylinder head side water jacket 5, in the 2nd Embodiment shown in FIG. The cooling water does not flow from the cylinder block side water jacket 4 toward the cylinder head side water jacket 5 and from the cylinder head side water jacket 5 toward the cylinder block side water jacket 4.

  Similarly to the first embodiment, the electronic control unit 20 receives signals from a rotation sensor 22 that detects the rotational speed NE of the internal combustion engine 1 and a load sensor 23 that detects a load of the internal combustion engine 1. Signals are input from a block-side temperature sensor 21 a that detects the temperature of the cooling water in the cylinder block-side water jacket 4 and a head-side temperature sensor 21 b that detects the temperature of the cooling water in the cylinder-head-side water jacket 5.

  The electronic control unit 20 is used to set the operation flow rate for setting the temperature of the cooling water in the cylinder block side water jacket 4 to the target water temperature and the temperature for the cooling water in the cylinder head side water jacket 5 to be the target water temperature. The operation flow rate is calculated individually, and the discharge amount of the water pump 8 and the distribution control valve 15 are controlled from the operation flow rate on the block side and the operation flow rate on the head side.

The flowchart of FIG. 6 shows the calculation process of the operation flow rate in the second embodiment.
In step S201, the target water temperature on the cylinder block side and the target water temperature on the cylinder head side are respectively set.

The target water temperature setting process in step S201 is performed as shown in FIG.
As shown in FIG. 7, the temperature conditions of the internal combustion engine 1 are classified into three types: cold (COLD), after warm-up (HOT), and heat resistance. The target water temperature is set to any one of three types of high water temperature, medium water temperature, and low water temperature (high water temperature> medium water temperature> low water temperature) by distinguishing between normal and WOT (fully open).

  Specifically, if the operation state is a cold machine (COLD) other than WOT (fully open), the coolant flow rate is set by setting both the target water temperature on the cylinder block side and the target water temperature on the cylinder head side to a high water temperature. The temperature of the internal combustion engine 1 (cooling water) rises quickly.

  Also, in the case of a cold machine (COLD) and WOT (fully open), and in the fully operating state after warming up (HOT), the compression ratio is improved by setting the target water temperature on the cylinder head side to the medium water temperature. In order to improve fuel efficiency by improving thermal efficiency, the target water temperature on the cylinder block side is set to a high water temperature.

  In other words, after the warm-up is completed, the temperature of the cylinder block 2 is kept higher than the temperature of the cylinder head 3 so that the thermal efficiency can be increased while suppressing the compression ratio from being lowered. To do.

  Furthermore, since it is required to quickly lower the temperature under heat-resistant conditions, the target water temperature is set to a low temperature, and the target water temperature is significantly lower than the actual water temperature, so that the flow rate of the cooling water is greatly increased. Thus, it is possible to quickly suppress the occurrence of problems due to overheating (overheating).

  When the target water temperature on the cylinder block side and the target water temperature on the cylinder head side are respectively set as described above, in the next step S202, the operation flow rate required in the cylinder head side water jacket 5 according to the flowchart of FIG. (Target flow rate) is calculated.

  In the calculation of the operation flow rate in step S202, the operation flow rate is calculated based on the target water temperature on the cylinder head side and the cooling water temperature in the cylinder head side water jacket 5 detected by the head side temperature sensor 21b.

In the next step S203, the operation flow rate (target flow rate) required in the cylinder block side water jacket 4 is calculated according to the flowchart of FIG.
In the calculation of the operation flow rate in step S203, the operation flow rate is calculated based on the target water temperature on the cylinder block side and the cooling water temperature in the cylinder block side water jacket 4 detected by the block side temperature sensor 21a.

  In step S204, the motor 11 is controlled based on the sum of the operation flow (target flow) on the cylinder head side and the operation flow (target flow) on the cylinder block side, and the operation flow on the cylinder head side and the operation on the cylinder block side are controlled. The distribution control valve 15 is controlled based on the comparison with the flow rate.

  That is, the sum of the flow rate of the cooling water required to be supplied to the cylinder head side water jacket 5 and the flow rate of the cooling water required to be supplied to the cylinder block side water jacket 4 is the water pump 8. The cooling water discharged from the water pump 8 is to be discharged from the cylinder block side water jacket 4 and the cylinder with a distribution ratio according to the ratio of the cylinder head side operation flow rate and the cylinder block side operation flow rate. Distribute to the head side water jacket 5.

  As a result, the target water temperature on the cylinder block side and the target water temperature on the cylinder head side can be individually realized, and the occurrence of overshoot with respect to each target water temperature can be suppressed and the target water temperature can be converged with good response. Can do.

  Therefore, in particular, the temperature on the cylinder block side after warm-up can be maintained at a high temperature while suppressing an excessive increase, and operation can be performed with high thermal efficiency while avoiding overheating (overheating).

  For example, when the sum of the operation flow on the cylinder head side and the operation flow on the cylinder block side is larger than the maximum discharge amount of the water pump 8, the side closer to the overheat (overheated) state (heat resistant temperature limit). The distribution ratio can be changed to increase the required flow rate preferentially.

  That is, when the sum of the operation flow on the cylinder head side and the operation flow on the cylinder block side is larger than the maximum discharge amount of the water pump 8, if the cooling water is distributed based on the operation flow rate ratio, The flow rate of the cooling water obtained will be insufficient compared to the operation flow rate (target flow rate).

  Here, when one of the cylinder head side and the cylinder block side is close to the overheat (overheated) state (heat-resistant temperature limit), the other has room before it becomes overheated (overheated) state (heat-resistant temperature limit). In order to give priority to temperature drop on one side, one operation flow rate is realized as it is, and the rest of the maximum discharge amount is supplied to the other, or the cooling water supplied to one side corresponds to the operation flow rate ratio. The amount is increased from the flow rate, and the supply amount to the other side is decreased by the increased amount.

Here, the heat resistant temperature limit on the cylinder head side and the heat resistant temperature limit on the cylinder block side can be different temperatures.
In addition, when the actual flow rate is reduced from the operation flow rate, the actual flow rate is limited so that it does not fall below the minimum limit value. Further, the minimum limit value is set to the heat-resistant limit temperature and the cooling at that time. It can be variably set according to the difference with the water temperature and the operating conditions of the internal combustion engine 1.

  Further, in the cooling device having the above configuration, as a countermeasure against the occurrence of abnormality, when the distribution control valve 15 is a rotary valve, the distribution ratio between the cylinder head side and the cylinder block side at the default position (energization stop state) is If the distribution control valve 15 is an on-off valve provided on each of the cylinder head side and the cylinder block side, the default position of these on-off valves is set to the fully open position. Set to.

When an abnormality occurs, the motor 11 is controlled so that the discharge amount of the water pump 8 becomes the maximum discharge amount, and the distribution control valve 15 is set to the default position.
Here, as a method of determining the abnormal state of the cooling device, the abnormality can be determined when the characteristic of the change in the detected water temperature value with respect to the change in the operation flow rate is greatly changed from the initial state. Therefore, the abnormality can be determined when the occurrence of knocking is detected, and the abnormality can be determined when the occurrence of pre-ignition is estimated from the detected value of the intake air temperature and the detected value of the water temperature.

Here, technical ideas other than the claims that can be grasped from the above embodiment will be described together with effects.
(A) In the cooling device for an internal combustion engine according to claim 3,
The control means is
While correcting the operation amount calculated based on the deviation between the detected value of the cooling water temperature and the target value, the correction operation amount based on the change rate of the cooling water temperature,
An internal combustion engine that corrects an operation amount after convergence of the cooling water temperature based on the correction operation amount for suppressing a change in the cooling water temperature in the same direction as the change direction of the heat generation amount. Cooling system.

According to the above invention, a rapid temperature change can be suppressed, and an excessive suppression of the temperature change can be reduced.
(B) In the cooling device for an internal combustion engine according to any one of claims 1 to 3 and (a),
The cooling apparatus for an internal combustion engine, wherein the flow rate adjusting means is a flow rate control valve or a water pump.

According to the above invention, the supply flow rate of the cooling water to the internal combustion engine can be adjusted by adjusting the opening of the flow control valve (adjusting the opening area) or adjusting the discharge amount of the water pump.
(C) In the cooling device for an internal combustion engine according to any one of claims 1 to 3 and (A),
The cooling apparatus for an internal combustion engine, wherein the flow rate adjusting means distributes cooling water to a plurality of cooling circuits.

According to the above invention, by distributing the cooling water to the plurality of cooling circuits, the flow rate of the cooling water supplied to the cooling circuit to be controlled is increased or decreased, and the cooling water temperature in the cooling circuit to be controlled is set. Can be controlled.
(D) In the internal combustion engine cooling device according to claim (c),
The control unit calculates a required flow rate in each of the plurality of cooling circuits, and outputs an operation amount to the flow rate adjusting unit so as to preferentially realize a required flow rate for avoiding overheating. A cooling device for an internal combustion engine.

  According to the above invention, when there is a cooling water circuit that requires an increase in the cooling water supply flow rate in order to avoid overheating among the plurality of cooling circuits, this overheating avoidance is given priority over other increase requests. By supplying cooling water preferentially to the required cooling water circuit, the occurrence of overheating can be reduced.

  DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 2 ... Cylinder head, 3 ... Cylinder block, 4 ... Cylinder block side water jacket, 5 ... Cylinder head side water jacket, 6 ... Radiator, 8 ... Water pump, 9 ... Supply piping, 10 ... Return piping, DESCRIPTION OF SYMBOLS 11 ... Motor, 12 ... Communication path, 20 ... Electronic control unit, 21 ... Temperature sensor, 22 ... Rotation sensor, 23 ... Load sensor

Claims (3)

Flow rate adjusting means for adjusting the supply flow rate of cooling water to the internal combustion engine;
Detecting means for detecting a temperature of the cooling water;
Target setting means for setting a target value of the cooling water temperature;
Based on the deviation between the coolant temperature detected by the detection means and the target value of the coolant temperature set by the target setting means, and the change rate of the coolant temperature detected by the detection means, the flow rate A control unit that calculates an operation amount of the adjustment unit and outputs the operation amount to the flow rate adjustment unit;
A cooling device for an internal combustion engine, comprising:   When the cooling water temperature is within a predetermined range including the target value, the control means greatly corrects the operation amount in such a direction that the change in the cooling water temperature is suppressed as the change speed increases. The cooling device for an internal combustion engine according to claim 1. A heat generation amount estimating means for estimating a heat generation amount of the internal combustion engine;
A deviation between the cooling water temperature detected by the detection means and the target value of the cooling water temperature set by the target setting means; a change rate of the cooling water temperature detected by the detection means; and 3. The operation amount of the flow rate adjustment unit is calculated based on the heat generation amount of the internal combustion engine estimated by the heat generation amount estimation unit, and the operation amount is output to the flow rate adjustment unit. A cooling apparatus for an internal combustion engine as described.

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