Control device and control method

Abstract

To provide a control device and a control method capable of appropriately controlling a flow rate of a cooling medium.SOLUTION: A control device, which controls a flow rate of a cooling medium circulated in a cooling flow passage of an internal combustion engine, comprises: acquisition means which acquires a detection value of a temperature of the cooling medium at an outlet of the cooling flow passage; calculation means which calculates an inverse of the flow rate so as to compensate a delay in time until a difference between the temperature of the cooling medium at an inlet of the cooling flow passage and the detection value reaches a target value in accordance with flow rate control on the basis of a correlation between a difference in temperatures of the cooling medium between the inlet and the outlet of the cooling flow passage and the inverse of the flow rate and also calculates the flow rate on the basis of the inverse thereof; and correction means which calculates a target flow rate from the target value on the basis of the correlation, predicts at least either delay in response time with respect to the flow control or wasteful time from the target flow rate and corrects the difference on the basis of a prediction result.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a control device and a control method. [Background technology]

[0002] For example, a control device for an internal combustion engine such as an engine controls the flow rate of a cooling medium (e.g., cooling water) discharged from a pump to the internal combustion engine (see, for example, Patent Document 1). For example, the control device needs to quickly reduce the flow rate of the cooling medium to increase the temperature of the internal combustion engine in order to reduce cooling loss and mechanical loss of the internal combustion engine and improve combustion efficiency, and also needs to quickly increase the flow rate of the cooling medium to reduce the temperature of the internal combustion engine in order to suppress an increase in exhaust loss due to knocking of the internal combustion engine and abnormalities due to boiling of the cooling medium. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-3587 A Summary of the Invention [Problem to be solved by the invention]

[0004] The control device compensates for response delays to control based on the temperature of the cooling medium detected by a water temperature sensor at the outlet of the cooling passage of the internal combustion engine (hereinafter, outlet temperature) and controls the flow rate of the cooling medium so that the temperature reaches a target value. However, since an error occurs in the control value according to the change in the flow rate of the cooling medium, there is a risk that the temperature of the cooling medium will overshoot and not converge quickly.

[0005] The present invention has been made in consideration of the above problems, and has an object to provide a control device and a control method that can appropriately control the flow rate of a cooling medium. [Means for solving the problem]

[0006] The control device of the present invention is a control device for controlling the flow rate of a cooling medium circulating through a cooling flow path of an internal combustion engine, and includes an acquisition means for acquiring a detection value of the temperature of the cooling medium at the outlet of the cooling flow path, a calculation means for calculating a control value of the flow rate based on the difference between the temperature of the cooling medium at the inlet of the cooling flow path and the detection value so as to compensate for the delay until the temperature difference of the cooling medium at the inlet and outlet of the cooling flow path reaches a target value, a command means for commanding a pump that circulates the cooling medium through the cooling flow path to output in accordance with the control value, and a correction means for predicting at least one of the delay time and dead time of the response to the output command from a target flow rate corresponding to the target value, and correcting the difference based on the prediction result.

[0007] In the above control device, the correction means may, in response to the output command, record a history of the temperature difference of the cooling medium in chronological order, and obtain a value from the history of the temperature difference that is the waste time earlier and use the value to correct the difference.

[0008] In the above control device, the correction means may record a history of the temperature difference in chronological order based on a correlation between the temperature difference and the inverse of the flow rate from a current flow rate of the cooling medium.

[0009] In the above control device, the acquisition means may acquire a rotation speed of the pump, and the correction means may estimate the current flow rate of the cooling medium from the rotation speed.

[0010] In the above control device, the correction means may calculate a time constant according to the target flow rate, and predict the delay time from the time constant.

[0011] In the above control device, the calculation means may calculate a time constant according to the target flow rate, and compensate for the delay based on the time constant.

[0012] In the above control device, the calculation means may calculate the control value by using a temperature of the cooling medium at an inlet of the cooling flow passage as a fixed value.

[0013] The control method of the present invention is a method for controlling the flow rate of a cooling medium circulating through a cooling flow path of an internal combustion engine, in which a computer executes the following processes: obtaining a detection value of the temperature of the cooling medium at an outlet of the cooling flow path, calculating a control value for the flow rate based on the difference between the temperature of the cooling medium at the inlet of the cooling flow path and the detection value so as to compensate for the delay until the temperature difference of the cooling medium at the inlet and outlet of the cooling flow path reaches a target value, issuing an output command in accordance with the control value to a pump that circulates the cooling medium through the cooling flow path, predicting at least one of the delay time and dead time of the response to the output command from a target flow rate corresponding to the target value, and correcting the difference based on the prediction result.

[0014] The above control method may also be a method in which, in the process of correcting the difference based on the prediction result, a history of the temperature difference of the cooling medium is recorded in chronological order in response to the output command, and a value from the history of the temperature difference obtained the previous amount of dead time is obtained and used to correct the difference.

[0015] The above control method may also be a method in which, in the process of correcting the difference based on the prediction result, a history of the temperature difference is recorded in chronological order from the current flow rate of the cooling medium based on the correlation between the temperature difference and the inverse of the flow rate.

[0016] The above control method may further comprise a step of acquiring a rotation speed of the pump and estimating the current flow rate of the cooling medium from the rotation speed in the process of correcting the difference based on the prediction result.

[0017] The above control method may be a method in which, in the process of correcting the difference based on the prediction result, a time constant corresponding to the target flow rate is calculated, and the delay time is predicted from the time constant.

[0018] The above control method may be a method in which, in the process of calculating the control value of the flow rate, a time constant corresponding to the target flow rate is calculated, and a delay is compensated for based on the time constant.

[0019] The above control method may be a method in which, in the process of calculating a control value for the flow rate, the control value is calculated by using a temperature of the cooling medium at an inlet of the cooling flow passage as a fixed value. Effect of the Invention

[0020] According to the present invention, the flow rate of the cooling medium can be appropriately controlled. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a configuration diagram showing an example of an engine control system. [Diagram 2] FIG. 2 is a configuration diagram showing an example of an ECU (Electronic Control Unit). [Diagram 3] FIG. 13 is a diagram showing an example of a heat quantity map data table. [Figure 4] FIG. 4 is a diagram showing an example of the correlation between the flow rate of cooling water and the inlet / outlet water temperature difference in a thermal equilibrium state. [Diagram 5] FIG. 4 is a diagram showing an example of a correlation between the inverse of the flow rate of cooling water and the inlet / outlet water temperature difference. [Figure 6] FIG. 11 is a diagram illustrating an example of a time constant data table. [Figure 7] FIG. 13 is a diagram illustrating an example of a dead time data table. [Figure 8] FIG. 13 is a diagram showing an example of a convergence water temperature difference data table. [Figure 9] FIG. 2 is a block diagram illustrating an example of a feedback control system of a plant. [Figure 10] 4 is a flowchart showing an example of a flow rate control operation of an ECU. [Figure 11] 10 is a flowchart showing an example of an estimated inlet / outlet water temperature difference calculation process. [Figure 12] FIG. 11 is a diagram showing the change over time in outlet water temperature in a comparative example. [Figure 13] FIG. 4 is a graph showing the change over time in outlet water temperature in an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] (Control system configuration) 1 is a configuration diagram showing an example of a control system 9 for an engine 2. The control system 9 is mounted on a vehicle (including a hybrid vehicle) that uses the engine 2 as a drive source. The control system 9 has an ECU 1, the engine 2, a cooling system 3, and a sensor system 4.

[0023] The engine 2 is an example of an internal combustion engine, and has a cylinder head 2a and a cylinder block 2b. Inside the cylinder head 2a and the cylinder block 2b, water jackets 20 and 23 are provided, respectively, through which cooling water flows to cool the engine 2. The cooling water is an example of a cooling medium, and the water jackets 20 and 23 are an example of a cooling flow path.

[0024] An inlet 24 of a water jacket 23 is provided in the cylinder block 2b, and outlets 21, 22 of a water jacket 20 are provided in the cylinder head 2a. Cooling water circulates between the cooling system 3 and the water jackets 20, 23. The cooling water flows from the cooling system 3 through the inlet 24 into the water jacket 23, and from the water jacket 23 into the water jacket 20 of the cylinder head 2a. The cooling water flows from the water jacket 20 into the cooling system 3 through the outlets 21, 22.

[0025] The cooling system 3 has an electric water pump (EWP) 30, a thermostat (T / S) 31, a radiator 32, a heater 33, a transmission thermal fluid exchanger (ATF / W) 34, an EGR (Exhaust Gas Recirculation) cooler (EGR / C) 35, and an outlet water temperature sensor 36. The cooling system 3 also has an EGR passage 37, a distribution passage 38, return passages 390 and 391, an ATF passage 380, a heater passage 381, and a radiator passage 382 as circulation passages through which the coolant circulates.

[0026] The EWP 30 is an example of a pump. The EWP 30 delivers cooling water to the water jackets 20 and 23. The cooling water flows from the EWP 30 through the inlet 24 into the water jacket 23. In this manner, the EWP 30 circulates the cooling water through the water jackets 20 and 23.

[0027] Cooling water flows into the EGR cooler 35 from the outlet 22 of the water jacket 20. The EGR cooler 35 cools the exhaust gas of the engine 2 with the cooling water. The EGR cooler 35 is provided in an EGR flow path 37, and the cooling water is discharged from the EGR cooler 35 to the EGR flow path 37.

[0028] The cooling water flows into the outlet water temperature sensor from the outlet 22 of the water jacket 20. The outlet water temperature sensor detects the temperature of the cooling water at the outlet 22 (hereinafter referred to as the “outlet water temperature”). The outlet water temperature sensor is provided in the distribution flow path .

[0029] The distribution passage 38 branches into an ATF passage 380, a heater passage 381, and a radiator passage 382. The ATF / W 34, the heater 33, and the radiator 32 are respectively provided in the ATF passage 380, the heater passage 381, and the radiator passage 382. The coolant flows from the outlet water temperature sensor 36 through the distribution passage 38 and is divided into the ATF passage 380, the heater passage 381, and the radiator passage 382.

[0030] The ATF / W 34 exchanges heat between the transmission cooling oil or the like and the cooling water in the ATF flow path 380. The heater 33 exchanges heat between the air in the passenger compartment of the vehicle equipped with the control system 9 and the cooling water in the heater flow path 381. The radiator 32 exchanges heat between the outside air of the vehicle and the cooling water in the radiator flow path 382.

[0031] The EGR passage 37, the ATF passage 380, and the heater passage 381 merge into one return passage 390. The coolant cooled by the radiator 32 is discharged into the other return passage 391. That is, the EGR passage 37, the ATF passage 380, and the heater passage 381 function as bypass passages that bypass the radiator 32. The coolant that has flowed through the EGR passage 37, the ATF passage 380, and the heater passage 381 flows back from the return passage 390 to the EWP 30. The coolant that has flowed through the radiator passage 382 flows back from the return passage 391 to the EWP 30 when an opening / closing valve 311 of the thermostat 31 is opened as described below.

[0032] The return passages 390 and 391 are provided with a thermostat 31. The thermostat 31 is provided with a temperature detection unit 310 and an on-off valve 311. The temperature detection unit 310 detects the temperature of the cooling water flowing in from the EGR passage 37, the ATF passage 380, and the heater passage 381. The on-off valve 311 blocks the flow of the cooling water flowing in from the radiator 32 or allows it to pass.

[0033] The temperature detection unit 310 includes, for example, wax that expands in response to the temperature of the cooling water. When the cooling water reaches a predetermined temperature (hereinafter referred to as the "valve opening determination water temperature"), the opening / closing valve 311 is opened by an opening / closing mechanism (not shown) in response to the expansion of the wax.

[0034] Therefore, when the temperature of the coolant flowing from the EGR passage 37, the ATF passage 380, and the heater passage 381 is lower than the valve opening judgment water temperature, the on-off valve 311 is closed, so that the coolant cooled by the radiator 32 is not returned to the EWP 30, and only the coolant in the EGR passage 37, the ATF passage 380, and the heater passage 381 is returned to the EWP 30. When the temperature of the coolant flowing from the EGR passage 37, the ATF passage 380, and the heater passage 381 is equal to or higher than the valve opening judgment water temperature, the on-off valve 311 is open, so that the coolant cooled by the radiator 32 is returned to the EWP 30 together with the coolant in the EGR passage 37, the ATF passage 380, and the heater passage 381. In this case, the on-off valve 311 opens so that the coolant passes through the radiator 32.

[0035] The ECU 1 is an example of a control device. The ECU 1 controls the torque of the engine 2. The ECU 1 sets a target value for the outlet water temperature of the coolant depending on the state of the engine 2. The ECU 1 obtains a detection value of the outlet water temperature sensor 36, and controls the discharge amount of the EWP 30 based on the detection value so that the outlet water temperature approaches the target value. In other words, the ECU 1 controls the flow rate of the coolant circulating through the distribution passage 38 and the EGR passage 37.

[0036] The sensor system 4 outputs various detection values ​​to the ECU 1. The sensor system 4 includes, for example, an air flow meter (AFM) 40, a throttle opening sensor (TA) 41, an intake pressure sensor (INP) 42, an exhaust pressure sensor (EXP) 43, and a revolution speed sensor (RS) 44. The AFM 40 detects the flow rate (intake amount) of air taken into the engine 2. The TA 41 detects the opening of a throttle (not shown) provided in the engine 2. The intake pressure sensor 42 and the exhaust pressure sensor 43 detect the intake pressure and exhaust pressure, respectively, of the engine 2. The revolution speed sensor 44 detects the revolution speed of the EWP 30. The ECU 1 controls the torque and the flow rate of coolant of the engine 2 based on the detection values ​​of the sensor system 4.

[0037] (ECU configuration) 2 is a configuration diagram showing an example of the ECU 1. The ECU 1 has a CPU (Central Processing Unit) 10, a ROM (Read Only Memory) 11, a RAM (Random Access Memory) 12, a storage memory 13, and an input / output port 14. The CPU 10 is electrically connected to the ROM 11, the RAM 12, the storage memory 13, and the input / output port 14 via a bus 19 so as to be able to input and output signals to and from each other. The ECU 1 is an example of a computer.

[0038] The ROM 11 stores a program that drives the CPU 10. The RAM 12 functions as a working memory for the CPU 10. The input / output port 14 inputs and outputs various signals between, for example, the sensor system 4, the outlet water temperature sensor 36, and the EWP 30. In this way, the CPU 10 communicates with the sensor system 4, the outlet water temperature sensor 36, and the EWP 30.

[0039] When the CPU 10 reads a program from the ROM 11, it functions as an operation control unit 100, a detection value acquisition unit 101, a torque control unit 102, a flow rate calculation unit 103, a water temperature difference correction unit 104, and a rotation speed command unit 105. The storage memory 13 also stores a heat quantity map data table 130, a time constant data table 131, a dead time data table 132, and a convergence water temperature difference data table 133. The storage memory 13 is realized by a flash memory, for example.

[0040] The operation control unit 100 controls the overall operation of the ECU 1. The operation control unit 100 instructs the detection value acquisition unit 101, torque control unit 102, flow rate calculation unit 103, water temperature difference correction unit 104, and rotation speed command unit 105 to operate in accordance with a predetermined sequence. At this time, the operation control unit 100 relays variables related to various processes between the detection value acquisition unit 101, torque control unit 102, flow rate calculation unit 103, and water temperature difference correction unit 104.

[0041] The detection value acquisition unit 101 is an example of an acquisition means. The detection value acquisition unit 101 acquires various detection values ​​from the sensor system 4 in accordance with instructions from the operation control unit 100. For example, the detection value acquisition unit 101 acquires a detection value of the outlet water temperature from the outlet water temperature sensor 36. The detection value acquisition unit 101 acquires the detection values ​​at different periods for each detection value, for example.

[0042] The torque control unit 102 controls the torque of the engine 2 in accordance with instructions from the operation control unit 100. At this time, the torque control unit 102 uses various detection values ​​of the sensor system 4 for the control.

[0043] The flow rate calculation unit 103 is an example of a calculation means. The flow rate calculation unit 103 calculates the flow rate of the cooling water based on the detection value of the outlet water temperature sensor 36. Based on the difference between the temperature of the cooling water at the inlet 24 (hereinafter referred to as the "inlet water temperature") and the detection value of the outlet water temperature (hereinafter referred to as the "water temperature difference detection value"), the flow rate calculation unit 103 calculates a control value of the flow rate so as to compensate for a delay until the temperature difference of the cooling water at the inlet 24 and the outlet 21 (hereinafter referred to as the "inlet / outlet water temperature difference") reaches a target value. Here, the flow rate calculation unit 103 sets a target value of the outlet water temperature of the cooling water according to the state of the engine 2 determined from various detection values ​​of the sensor system 4, and calculates a target value of the inlet / outlet water temperature difference from the difference between the target value and the inlet water temperature.

[0044] As described below, the flow rate calculation unit 103 calculates the reciprocal of the flow rate from the detected water temperature difference based on the correlation between the inlet / outlet water temperature difference and the reciprocal of the flow rate. The flow rate calculation unit 103 calculates a flow rate control value from the reciprocal of the flow rate. The flow rate calculation unit 103 notifies the rotation speed command unit 105 of the control value.

[0045] The rotation speed command unit 105 is an example of a command means. The rotation speed command unit 105 commands the EWP 30 to a rotation speed according to a control value of the flow rate.

[0046] A proportional relationship is established between the rotation speed of the EWP 30 and the flow rate of the cooling water, for example, with a proportionality constant corresponding to the inlet water temperature. The rotation speed command unit 105 calculates the rotation speed of the EWP 30 based on the proportional relationship from the control value of the flow rate. As the inlet water temperature of the cooling water, for example, the valve opening determination temperature of the thermostat 31 is used as a fixed value, but an estimated value calculated from the flow rate may also be used. The rotation speed of the EWP 30 is an example of the output of the pump. The command for the EWP 30 is not limited to the rotation speed, and may be, for example, a drive current value.

[0047] The water temperature difference correction unit 104 is an example of a correction means. The water temperature difference correction unit 104 predicts at least one of the delay time and dead time of the response to a rotation speed command from a target flow rate corresponding to the target value, and corrects the inlet / outlet water temperature difference detection value based on the prediction result. Here, the water temperature difference correction unit 104 calculates the target flow rate from the target value of the inlet / outlet water temperature difference based on the correlation between the inlet / outlet water temperature difference and the reciprocal of the flow rate.

[0048] The flow rate calculation unit 103 calculates a flow rate control value from the water temperature difference detection value corrected by the water temperature difference correction unit 104. For this reason, the flow rate calculation unit 103 estimates at least one of the delay time and dead time of the response to the command according to the change in the target flow rate, and can reduce the error in the control value based on the estimation.

[0049] In the heat quantity map data table 130, heat quantity parameters Kp are registered in advance in association with various detection values ​​of the sensor system 4, for example.

[0050] Kp = Qw / ρc (1)

[0051] The heat quantity parameter Kp is expressed, for example, by the above formula (1). In formula (1), the variable Qw indicates the amount of heat (J / s) per unit time received by the cooling water from the engine 2, and the constant ρ indicates the density of the cooling water (g / cm 3 ), and constant c indicates the heat capacity (J / K) of the coolant. The heat quantity parameter Kp is an example of a parameter related to the amount of heat that the coolant receives from the engine 2.

[0052] The flow rate calculation unit 103 calculates the reciprocal of the flow rate from the inlet and outlet water temperature difference, using the rate of change of the temperature difference with respect to the reciprocal of the flow rate in the correlation between the inlet and outlet water temperature difference of the coolant and the reciprocal of the flow rate as a heat parameter Kp. Therefore, the flow rate calculation unit 103 can appropriately calculate the reciprocal of the flow rate according to the heat generation state of the engine 2. Similarly, the water temperature difference correction unit 104 calculates the flow rate from the inlet and outlet water temperature difference of the coolant using the heat parameter Kp.

[0053] Fig. 3 is a diagram showing an example of the heat quantity map data table 130. Fig. 3 shows the change in the heat quantity parameter Kp relative to the intake air amount (L / min.) of the engine 2.

[0054] For example, the intake air amount and the heat quantity parameter Kp are associated with each other and registered in advance in the heat quantity map data table 130. The flow rate calculation unit 103 and the water temperature difference correction unit 104 refer to the heat quantity map data table 130 using, for example, the detection value of the intake air pressure sensor 42 as the intake air amount, and acquire the heat quantity parameter Kp corresponding to the intake air amount.

[0055] (Correlation between cooling water flow rate and inlet / outlet water temperature difference) 4 is a diagram showing an example of the correlation between the coolant flow rate V (L / min.) and the inlet / outlet water temperature difference ΔTw (K) in a thermal equilibrium state. Characteristic Fr shows the correlation between the actual coolant flow rate V and the inlet / outlet water temperature difference ΔTw, while characteristic Fb shows the correlation between the coolant flow rate V and the inlet / outlet water temperature difference ΔTw when there is no deviation α in the inlet coolant temperature due to disturbance. Characteristic Fp shows the correlation between the coolant flow rate V and the inlet / outlet water temperature difference ΔTw that is assumed when ECU1 controls the flow rate V based on characteristic Fb.

[0056] In each of the characteristics Fr, Fb, and Fp, a nonlinear relationship (effectively an inverse proportional relationship) is established between the flow rate V of the cooling water and the inlet / outlet water temperature difference ΔTw. Here, the proportionality constant is assumed to be the product (Vb×ΔTwb) of a predetermined flow rate Vb and the inlet / outlet water temperature difference ΔTwb in the characteristic Fp (see point Pc).

[0057] ΔTwact is the detected water temperature difference obtained from the detection value of the outlet water temperature sensor 36, and Vact is the flow rate corresponding to the detected water temperature difference ΔTwact in the characteristic Fr. ΔTwtgt is the target value of the inlet / outlet water temperature difference, and Vtgt is the target flow rate corresponding to the inlet / outlet water temperature difference ΔTwtgt in the specific Fp. Vcrc is the corrected flow rate for achieving the target inlet / outlet water temperature difference ΔTwtgt.

[0058] Here, the difference between the control target inlet / outlet water temperature difference ΔTwtgt and the inlet / outlet water temperature difference corresponding to the target flow rate Vtgt in the characteristic Fb is defined as γ, and the difference between each inlet / outlet water temperature difference corresponding to the target flow rate Vtgt in the characteristics Fb and Fr is defined as α. Also, the difference between the water temperature difference detected value ΔTwact and the inlet / outlet water temperature difference corresponding to the target flow rate Vtgt in the characteristic Fr is defined as ε. Therefore, the difference err between the inlet / outlet water temperature difference ΔTwtgt and the water temperature difference detected value ΔTwact is (α+γ+ε).

[0059] The flow rate Vcrc for controlling the inlet / outlet water temperature difference to the target inlet / outlet water temperature difference ΔTwtgt is calculated as follows.

[0060] Vcrc(ΔTwtgt-α)=Vact(ΔTwtgt+γ+ε)···(2) Vcrc=Vact{(ΔTwtgt+γ+ε) / (ΔTwtgt-α)} =Vact{1-err / (ΔTwtgt-α)} ···(3)

[0061] In the characteristic Fb, the product of the inlet / outlet water temperature difference and the flow rate is equal for point Pa corresponding to the flow rate Vact and point Pb corresponding to the flow rate Vcrc, so the above formula (2) is established. The flow rate Vcrc is calculated from formula (2) and the above definition of the difference err using formula (3).

[0062] In this way, when the flow rate V and the inlet / outlet water temperature difference ΔTw have a nonlinear relationship, it is difficult to compensate for the delay in response to flow rate control. If a control means is used that outputs the flow rate V from the inlet / outlet water temperature difference ΔTw, integral control (I control) using a nonlinear gain is required, making it difficult to perform rapid control and vulnerable to disturbances.

[0063] Therefore, the flow rate calculation unit 103 controls the flow rate V based on the linear relationship between the inverse of the flow rate V and the inlet / outlet water temperature difference ΔTw, instead of the nonlinear relationship between the flow rate V and the inlet / outlet water temperature difference ΔTw.

[0064] (Correlation between the inverse of the cooling water flow rate and the difference in water temperature between the inlet and outlet) FIG. 5 is a diagram showing an example of the correlation between the inverse v (=1 / V) (min. / L) of the cooling water flow rate V and the inlet / outlet water temperature difference ΔTw (K). The characteristics fr, fb, and fp correspond to the characteristics Fr, Fb, and Fp in FIG. 4, respectively. Here, the slope of the straight line of each characteristic Fr, Fb, and Fp coincides with the proportionality constant (Vb×ΔTwb) mentioned above. Furthermore, for vcrc, vff, and vact, vcrc=1 / Vcrc, vff=1 / Vtgt, and vact=1 / Vact hold.

[0065] ΔTw = Vb × ΔTwb × v (4)

[0066] The linear relationship shown in the above formula (4) is established between the inverse v of the cooling water flow rate V and the inlet / outlet water temperature difference ΔTw. Therefore, it is possible to treat the engine 2 and the cooling system 3, which are the plants to be controlled, as a linear behavior model.

[0067] ΔTw = Kp × v (5)

[0068] If the proportionality constant in equation (4), that is, the rate of change of the inlet / outlet water temperature difference ΔTw with respect to the reciprocal v of the flow rate V, is defined as the heat quantity parameter Kp, then the above equation (5) is established.

[0069]

number

[0070] Therefore, if the reciprocal of the control value Vcmd of the flow rate V is vcmd, the detected water temperature difference ΔTwact is expressed as the plant response by the above formula (6), where 1 / (Ts-1) represents the transfer function of the first-order lag element of the plant, and T is the time constant of the plant.

[0071] By treating the plant as a model of linear behavior in this way, it becomes possible to express the control system by a transfer function, and therefore the ECU 1 can compensate for the delay in the response of the plant to the flow rate control.

[0072] For example, by utilizing the above correlation, the ECU 1 can calculate the control value Vcmd of the flow rate V based on the detected coolant temperature difference value ΔTwact so as to compensate for the delay until the inlet / outlet water temperature difference ΔTw reaches the target value. However, if the coolant flow rate changes in accordance with a change in the target inlet / outlet water temperature difference ΔTwtgt, an error will occur in the control value Vcmd, and there is a risk that the outlet water temperature will overshoot and not converge quickly.

[0073] For this reason, the water temperature difference correction unit 104 predicts at least one of the response delay time and the dead time L in response to a command for the rotation speed of the EWP 30 from the target flow rate Vtgt corresponding to the target inlet / outlet water temperature difference ΔTwtgt, and corrects the detected water temperature difference ΔTwact based on the prediction result. In this example, the water temperature difference correction unit 104 predicts both the response delay time and the dead time, but it may predict only one of them.

[0074] The response delay time is calculated from the above-mentioned time constant T. The time constant T varies depending on the flow rate of the cooling water. Therefore, the water temperature difference correction unit 104 and the flow rate calculation unit 103 read out the time constant T from the time constant data table 131 based on the target flow rate Vtgt.

[0075] 6 is a diagram showing an example of the time constant data table 131. In the time constant data table 131, flow rates (L / min.) and time constants T (ms) are registered in association with each other. As an example, the time constant T decreases linearly as the flow rate increases. The time constant data table 131 is stored in advance in the storage memory 13 based on the results of experiments and simulations.

[0076] The flow rate calculation unit 103 calculates a time constant T corresponding to the target flow rate Vtgt using a time constant data table 131, and compensates for a delay in the plant's response to the flow rate control based on the time constant T. Therefore, the flow rate calculation unit 103 can use an appropriate time constant T corresponding to a change in the flow rate when compensating for the delay.

[0077] Furthermore, the water temperature difference correction unit 104 calculates the time constant T corresponding to the target flow rate Vtgt using the time constant data table 131, and predicts the delay time of the plant's response to the flow rate control from the time constant T. For this reason, the water temperature difference correction unit 104 can use an appropriate time constant T corresponding to the change in flow rate when predicting the delay time.

[0078] Further, the dead time L is variable according to the flow rate of the cooling water, similar to the time constant T. For this reason, the water temperature difference correction unit 104 and the flow rate calculation unit 103 read out the dead time L from the dead time data table 132 based on the target flow rate.

[0079] 7 is a diagram showing an example of the dead time data table 132. In the dead time data table 132, flow rates (L / min.) and dead time L (ms) are registered in association with each other. As an example, an inversely proportional relationship is established between the dead time L and the flow rate. The dead time data table 132 is stored in advance in the storage memory 13 based on the results of experiments and simulations.

[0080] In this way, the time constant T and the dead time L vary according to the flow rate. Here, the flow rate refers to the volumetric flow rate of the coolant passing through the entire engine 2, and is a factor that determines the heat transport and heat transfer speed by the coolant. For this reason, the water temperature difference correction unit 104 and the flow rate calculation unit 103 estimate with high accuracy from the target flow rate Vtgt the delay time and dead time L for the rotation speed command according to the control value Vcmd, and calculate a correction value for the water temperature difference detected value ΔTwact from the estimation result as the correction amount for the response expected from the command.

[0081] The flow rate calculation unit 103 corrects the target inlet / outlet water temperature difference ΔTwtgt by the corrected water temperature difference detected value ΔTwact, thereby enabling the flow rate calculation unit 103 to reflect the response delay and dead time L of the plant in the control value Vcmd.

[0082] The water temperature difference correction unit 104 calculates the convergent water temperature difference from the dead time L based on the convergent water temperature difference data table 133. The convergent water temperature difference is the inlet / outlet water temperature difference ΔTw after convergence estimated from the current flow rate V, and is acquired as a history of past inlet / outlet water temperature differences ΔTw going back by the dead time L from the current time when the control process is executed. The water temperature difference correction unit 104 records the history of the inlet / outlet water temperature difference ΔTw in chronological order in the convergent water temperature difference data table 133 for each predetermined cycle of the control process.

[0083] 8 is a diagram showing an example of the convergence water temperature difference data table 133. The convergence water temperature difference data table 133 registers the most recent N past inlet / outlet water temperature differences ΔTw, that is, convergence water temperature differences D[0] to D[N](K) (N: an integer of 2 or more).

[0084] The convergence water temperature difference D[0] is the latest inlet / outlet water temperature difference ΔTw, and the convergence water temperature difference D[N] is the oldest inlet / outlet water temperature difference ΔTw. The convergence water temperature difference D[0] is the value at the current time Tp when the control process is performed, the convergence water temperature difference D[1] is the value at the time (Tp-1×f) that is the control process cycle f before the current time Tp, and the convergence water temperature difference D[N] is the value at the time (Tp-N×f) that is N times the control process cycle f before the current time Tp. The initial values ​​of the convergence water temperature differences D[0] to D[N] are not limited, and may be set based on the flow rate of the response to the feedforward control based on the target value of the outlet water temperature, for example.

[0085] The water temperature difference correction unit 104 updates the latest convergence water temperature difference D[0] to the inlet / outlet water temperature difference ΔTw based on the current coolant flow rate V for each control processing cycle f. The water temperature difference correction unit 104 also updates the remaining convergence water temperature differences D[1] to D[N] to the pre-update convergence water temperature differences D[0] to D[N-1]. In other words, the water temperature difference correction unit 104 shifts each of the convergence water temperature differences D[0] to D[N-1] by one for each control processing cycle f.

[0086] The water temperature difference correction unit 104 determines the dead time L from the dead time data table 132, and refers to the convergent water temperature difference data table 133 based on the dead time L. In this way, the water temperature difference correction unit 104 obtains the convergent water temperature difference corresponding to the time (Tp-i×f) (i=1, 2, . . . , N) that is the dead time L before the current time Tp.

[0087] At this time, the water temperature difference correction unit 104 can calculate the sequence number i of the convergent water temperature difference D[1] to D[N] by, for example, dividing the dead time L by the control process cycle f. Specifically, the water temperature difference correction unit 104 calculates the value of the integer part of L / f as the sequence number i. For example, when L / f=5.3, the sequence number i corresponding to the dead time L is "5", and the convergent water temperature difference D[5] is obtained (see the dotted line frame).

[0088] In this way, the water temperature difference correction unit 104 records the history of the inlet and outlet coolant water temperature difference ΔTw in chronological order in the converged water temperature difference data table 133 in response to a rotation speed command according to the flow rate control value Vcmd, and obtains a value from the converged water temperature difference data table 133 the waste time L before and uses this value to correct the detected water temperature difference value ΔTwact. Therefore, the water temperature difference correction unit 104 can correct the detected water temperature difference value ΔTwact with high accuracy using the history of the inlet and outlet water temperature difference ΔTw. Note that the water temperature difference correction unit 104 is not limited to this, and may calculate the convergent water temperature difference from the waste time L using an approximation formula or the like.

[0089] Furthermore, the water temperature difference correction unit 104 records the history of the inlet and outlet water temperature difference ΔTw in chronological order in the converged water temperature difference data table 133 based on the above correlation between the inlet and outlet water temperature difference ΔTw and the reciprocal v of the flow rate V from the current flow rate V of the cooling water. That is, the water temperature difference correction unit 104 calculates the inlet and outlet water temperature difference ΔTw from the current flow rate V of the cooling water by the above equation (5). Therefore, compared to the case where the water temperature difference correction unit 104 calculates the inlet and outlet water temperature difference ΔTw from the control value Vcmd, it is possible to reduce errors caused by saturation and delays of the control value Vcmd due to the characteristics of the actual plant.

[0090] Furthermore, from the above-mentioned proportional relationship between the rotation speed of the EWP 30 and the cooling water flow rate V, the water temperature difference correction unit 104 estimates the current flow rate V based on the rotation speed acquired by the detection value acquisition unit 101 from the rotation speed sensor 44. Therefore, the water temperature difference correction unit 104 can acquire the current flow rate V and record the history of the inlet / outlet water temperature difference ΔTw without requiring a detection means for detecting the flow rate V, such as a flow meter.

[0091] (Block diagram) FIG. 9 is a block diagram showing an example of a feedback control system for a plant P. The feedback control system includes transfer functions F, Pn -1 ,LIM,Pn, where F,Pn is the transfer function -1 , LIM are processed by a flow rate calculation unit 103, and the process of the transfer function Pn and the process of calculating the feedback water temperature difference ΔTwfb from the water temperature difference detection value ΔTwact are executed by a water temperature difference correction unit 104.

[0092] Pn -1 =(Ts+1) / Kp (7) Pn = Kp e -Ls / (Ts+1) (8)

[0093] Transfer function Pn -1 is expressed by the above formula (7) from the above formula (6) based on the linear relationship between the inverse v of the flow rate V and the inlet / outlet water temperature difference ΔTw. The transfer function Pn is expressed by the above formula (8). -1 The transfer element of the transfer function Pn is denoted as the "inverse plant model", and the transfer element of the transfer function Pn is denoted as the "plant response assumption model".

[0094] For the inverse plant model, the transfer function Pn -1 outputs a control value vcmd (=1 / Vcmd) of the reciprocal of the cooling water flow rate for compensating for the first-order lag element of the response of the plant P. The time constant T in equation (7) is determined from the time constant data table 131 as described above, and is used as a first-order lead element. As a result, the inverse plant model compensates for the delay until the inlet / outlet water temperature difference ΔTw reaches the target inlet / outlet water temperature difference ΔTwtgt.

[0095] However, due to the law of causality, the inverse plant model cannot compensate for the dead time L. For this reason, the dead time L is handled by the plant response assumed model. The transfer function Pn outputs the assumed inlet / outlet water temperature difference ΔTwcmd based on the first-order lag element and dead time element of the response of the plant P from the control value vcmd.

[0096] As described above, for the plant response assumed model, the water temperature difference correction unit 104 obtains the assumed inlet / outlet water temperature difference ΔTwcmd by estimating the response delay and dead time L from the target flow rate Vtgt. Examples of the dead time L of the plant P include, but are not limited to, the delay time in the calculation of the detection value Tout of the outlet water temperature sensor 36 and the delay time in the transportation of the cooling water. The time constant T in equation (8) is determined from the time constant data table 131 as described above, and is used as a first-order lag element. The dead time L is also determined from the time constant data table 131, and is used as a first-order lead element.

[0097] The detected water temperature difference ΔTwact, which is the response of the plant, is subtracted by the assumed inlet / outlet water temperature difference ΔTwcmd calculated by the plant response assumption model before being fed back. In this way, the water temperature difference correction unit 104 predicts the response delay and dead time L of the plant P from the target flow rate Vtgt, and corrects the detected water temperature difference ΔTwact based on the prediction result.

[0098] Therefore, the flow rate calculation unit 103 can calculate an appropriate control value Vcmd by reducing the response delay of the plant P and the deviation of the response delay assumed by the inverse plant model, and by reducing the influence of the dead time L. This absorbs disturbances and modeling errors, improving the stability and responsiveness of the flow rate control.

[0099] A flow rate calculation unit 103 determines a target inlet / outlet water temperature difference ΔTwtgt based on, for example, various detection values ​​of the sensor system 4. The control target inlet / outlet water temperature difference ΔTwtgt is subtracted by the corrected water temperature difference detection value ΔTwact' and input as a feedback water temperature difference ΔTwfb to a transfer element of the transfer function F. In addition, a water temperature difference correction unit 104 calculates a target flow rate Vtgt from the target inlet / outlet water temperature difference ΔTwtgt based on the above-mentioned correlation between the inverse v of the cooling water flow rate V and the inlet / outlet water temperature difference ΔTw.

[0100] F = 1 / (T F s+1) (9)

[0101] The transfer function F corresponds to a low-pass filter and is expressed, for example, by the above formula (9). F is the time constant of the low-pass filter. The feedback water temperature difference ΔTwfb is filtered by the transfer function F before being input to the inverse plant model. In other words, the flow rate calculation unit 103 performs filtering on the feedback water temperature difference ΔTwfb using a low-pass filter.

[0102] This suppresses the fluctuation of the feedback water temperature difference ΔTwfb caused by noise, etc. Therefore, the variation of the control value Vcmd is suppressed, and the stability of the flow control is improved. Note that this filtering process does not need to be provided if the fluctuation of the feedback water temperature difference ΔTwfb is sufficiently small.

[0103] Furthermore, the transfer function LIM limits the control value Vcmd depending on the state of the cooling system 3. The transfer function LIM sets, for example, a lower limit value of the flow rate when the on-off valve 311 of the thermostat 31 is determined to be open, or a lower limit value of the flow rate for preventing the cooling water in the drill path of the water jacket 23 from boiling.

[0104] (ECU flow control operation) 10 is a flowchart showing an example of the flow rate control operation of the ECU 1. The following operation is an example of a control method.

[0105] First, the detection value acquisition unit 101 acquires each detection value from the outlet water temperature sensor 36 and the sensor system 4 (step St1). Next, the flow rate calculation unit 103 acquires the heat quantity parameter Kp by referring to the heat quantity map data table 130 based on the detection value of the intake air volume among the detection values ​​of the sensor system 4 (step St2). Next, the flow rate calculation unit 103 determines the target value To of the outlet water temperature (target outlet water temperature) based on the detection values ​​of the sensor system 4 (step St3).

[0106] ΔTwtgt = To - Tin (10)

[0107] Next, the flow rate calculation unit 103 calculates the target inlet / outlet water temperature difference ΔTwtgt from the above formula (10) (step St4). Here, Tin is a predetermined inlet water temperature, but may be an estimated value of the inlet water temperature as described later.

[0108] ΔTwact = Tout - Tin (11)

[0109] Next, the flow rate calculation unit 103 calculates the detected water temperature difference value ΔTwact from the above formula (11) (step St5). Here, Tout is the detection value of the outlet water temperature sensor 36. Also, since the inlet water temperature Tin is a fixed value, the control process is easier than when the inlet water temperature Tin is estimated from the flow rate V, for example. When the inlet water temperature Tin is a fixed value, the deviation of the outlet water temperature due to the error between the inlet water temperature Tin and the actual inlet water temperature is absorbed as a deviation by the control value vcmd of the feedback control in the same way as a disturbance.

[0110] ΔTwcmd = Pn vcmd (12)

[0111] Next, the water temperature difference correction unit 104 calculates the assumed inlet / outlet water temperature difference ΔTwcmd from the control value vcmd calculated in step St9 described below and the transfer function Pn of the plant response assumed model according to the above formula (12) (step St6). As a result, the water temperature difference correction unit 104 predicts the response delay of the plant P and the dead time L until the water temperature difference detected value ΔTwact reaches the target inlet / outlet water temperature difference ΔTwtgt. Specifically, the water temperature difference correction unit 104 makes the prediction using the target flow rate Vtgt, and the details of this process will be described later.

[0112] ΔTwact'=ΔTwact-ΔTwcmd ···(13)

[0113] Next, the water temperature difference correction unit 104 calculates a corrected water temperature difference detected value ΔTwact' from the difference between the water temperature difference detected value ΔTwact and the assumed inlet / outlet water temperature difference ΔTwcmd according to the above formula (13) (step St7). In this way, the water temperature difference correction unit 104 corrects the water temperature difference detected value ΔTwact based on the prediction results of the response delay and dead time L of the plant P.

[0114] ΔTwfb=ΔTwtgt-ΔTwact' (14)

[0115] Next, the flow rate calculation unit 103 calculates the feedback water temperature difference ΔTwfb from the difference between the target inlet / outlet water temperature difference ΔTwtgt and the corrected water temperature difference detected value ΔTwact′ in accordance with the above equation (14) (step St8).

[0116] vcmd=F·Pn -1 ΔTwfb (15)

[0117] Next, the flow rate calculation unit 103 calculates the inverse plant model and each transfer function Pn -1 , F and the feedback water temperature difference ΔTwfb, a control value vcmd of the reciprocal of the flow rate V is calculated (step St9).

[0118] Next, the flow rate calculation unit 103 calculates a control value Vcmd (=1 / vcmd) of the flow rate V from the control value vcmd (step St10). Next, the rotation speed command unit 105 calculates a command value Rcmd for the rotation speed of the EWP 30 from the control value Vcmd (step St11). For example, the command value Rcmd is calculated by Kc·Vcmd, where Kc is a proportional constant. Next, the rotation speed command unit 105 issues the command value Rcmd to the EWP 30 (step St12). In this way, the rotation speed command unit 105 issues a command value Rcmd for the rotation speed to the pump in accordance with the control value Vcmd.

[0119] Next, the flow rate calculation unit 103 judges whether or not it has received an instruction to end the flow rate control from the operation control unit 100 (step St13). If the flow rate calculation unit 103 has not received the instruction to end (No in step St13), the operation from step St1 onwards is executed again. On the other hand, if the flow rate calculation unit 103 has received the instruction to end (Yes in step St13), this operation ends.

[0120] In this way, the ECU 1 controls the flow rate V of the cooling water circulating through the water jackets 20, 23 of the engine 2. The detection value acquisition unit 101 acquires the detection value Tout of the outlet water temperature of the water jacket 20. The flow rate calculation unit 103 calculates a control value Vcmd based on the water temperature difference detection value ΔTwact so as to compensate for the delay until the inlet / outlet water temperature difference ΔTw of the cooling water reaches the target inlet / outlet water temperature difference ΔTwtgt.

[0121] 11 is a flowchart showing an example of a process for calculating the assumed inlet / outlet water temperature difference ΔTwcmd. This process is executed in step St6 described above.

[0122] Vtgt=Pn -1 ΔTwtgt (16)

[0123] The water temperature difference correction unit 104 calculates the target flow rate Vtgt from the target inlet / outlet water temperature difference ΔTwtgt according to the above equation (16) based on the above correlation between the reciprocal v of the flow rate V and the inlet / outlet water temperature difference ΔTw (step St21).

[0124] Next, the water temperature difference correction unit 104 determines the dead time L corresponding to the target flow rate Vtgt by referring to the dead time data table 132 based on the target flow rate Vtgt (step St22). In this way, the water temperature difference correction unit 104 can obtain an appropriate dead time L corresponding to the target flow rate Vtgt achieved by the control value Vcmd.

[0125] Next, the water temperature difference correction unit 104 calculates the sequence number i (=L / f) of the convergence water temperature difference data table 133 from the cycle f of this process and the dead time L (step St23). Next, the water temperature difference correction unit 104 acquires the convergence water temperature difference D[i] corresponding to the sequence number i from the convergence water temperature difference data table 133 (step St24). The convergence water temperature difference D[i] is calculated by Kp·e in the above formula (8). -Ls This corresponds to the value obtained by multiplying this by the reciprocal vcmd of the control value Vcmd.

[0126] In this way, the water temperature difference correction unit 104 obtains from the history of the inlet / outlet water temperature difference ΔTw the value from the previous time period L. Therefore, the water temperature difference correction unit 104 can estimate the inlet / outlet water temperature difference ΔTw with high accuracy from the past history, taking into account the influence of the dead time L.

[0127] Next, the water temperature difference correction unit 104 acquires the rotation speed of the EWP 30 by the detection value acquisition unit 101 (step St25). Next, the water temperature difference correction unit 104 estimates the current flow rate V from the rotation speed of the EWP 30 based on the correlation between the rotation speed and the flow rate V (step St26). Therefore, the water temperature difference correction unit 104 can acquire the current flow rate V without requiring a detection means for detecting the flow rate V, such as a flow meter.

[0128] Next, the water temperature difference correction unit 104 estimates the inlet / outlet water temperature difference ΔTw from the reciprocal v of the current flow rate V according to the above equation (5) (step St27).

[0129] Next, the water temperature difference correction unit 104 updates the convergence water temperature differences D[0] to D[N] in the convergence water temperature difference data table 133 (step St28). At this time, the water temperature difference correction unit 104 updates the convergence water temperature differences D[1] to D[N] to the convergence water temperature differences D[0] to D[N-1], and updates the convergence water temperature difference D[0] to the estimated inlet / outlet water temperature difference ΔTw. Therefore, the convergence water temperature difference data table 133 always records the history of the latest N inlet / outlet water temperature differences ΔTw as the convergence water temperature differences D[0] to D[N].

[0130] In this way, the water temperature difference correction unit 104 records the history of the inlet and outlet water temperature difference ΔTw in chronological order in the converged water temperature difference data table 133 based on the above-mentioned correlation between the inverse v of the flow rate V of the cooling water based on the current flow rate V of the cooling water and the inlet and outlet water temperature difference ΔTw.

[0131] Next, the water temperature difference correction unit 104 determines the time constant T corresponding to the target flow rate Vtgt by referring to the time constant data table 131 based on the target flow rate Vtgt (step St29). In this way, the water temperature difference correction unit 104 can obtain an appropriate time constant T corresponding to the target flow rate Vtgt achieved by the control value Vcmd.

[0132] ΔTwcmd=D[i] / (Ts+1) ···(17)

[0133] Next, the water temperature difference correction unit 104 calculates the assumed inlet / outlet water temperature difference ΔTwcmd from the convergent water temperature difference D[i] and the time constant T according to the above equation (17) (step St30). Equation (17) is based on the above equations (12) and (8). The water temperature difference correction unit 104 corrects the detected water temperature difference ΔTwact by the assumed inlet / outlet water temperature difference ΔTwcmd as described above. As a result, the target inlet / outlet water temperature difference ΔTwtgt is corrected to the feedback water temperature difference ΔTwfb by the detected water temperature difference value ΔTwact, allowing the flow rate calculation unit 103 to calculate an appropriate control value Vcmd.

[0134] (Example of outlet water temperature control) Fig. 12 is a diagram showing the change over time of the outlet water temperature in a comparative example. In this example, a case is shown in which the plant response assumption model does not assume a response delay and dead time L of the plant P. Fig. 12 shows the target value of the outlet water temperature corresponding to the target inlet / outlet water temperature difference ΔTwtgt, the command value of the outlet water temperature corresponding to the control value Vcmd, the assumed value of the outlet water temperature corresponding to the assumed inlet / outlet water temperature difference ΔTwcmd, and the actual outlet water temperature as a response to the flow rate control.

[0135] If the dead time L is not taken into account, the expected value rises at substantially the same time as the target value. The actual water temperature starts to rise in accordance with the command value, delayed by the dead time τ from that time, but due to the deviation A1 from the expected value, control is performed to excessively raise the actual water temperature. This causes the actual water temperature to overshoot the target value. Note that T1 is the peak value T1 of the command value.

[0136] Fig. 13 is a diagram showing a change over time in the outlet water temperature in the embodiment. In this example, a case is shown in which the plant response assumption model assumes a dead time L of the plant P. Note that in Fig. 13, the description of parameters common to Fig. 12 is omitted.

[0137] The assumed value rises with a delay from the target value rise timing by assuming a dead time L according to the transfer function Pn (see symbol X). Also, the command value is held lower than in the comparative example according to the delay of the assumed delay value. Specifically, the peak value T2 of the command value is lower by ΔT than the peak value T1 of the command value in the comparative example due to the convergent water temperature difference D[i] obtained from the dead time L.

[0138] Also, the actual water temperature starts to rise with a delay from the timing when the command value starts to rise, but since the delay is close to the dead time L, it acts to lower the actual water temperature that has exceeded the target value, as shown by arrow A2. This results in an appropriate relationship between the control timing and the response timing. As a result, the overshoot of the actual water temperature is suppressed to a significantly lower level than in the comparative example.

[0139] In this way, the water temperature difference correcting unit 104 predicts the delay including the dead time L of the response to the flow rate control, thereby appropriately adjusting the control value Vcmd (vcmd) and the relationship between the control timing and the response timing.

[0140] Pn = Kp e -Ls (8a) Pn = Kp / (Ts + 1) (8b)

[0141] In addition, as in this example, the transfer function Pn when only the dead time L is considered is expressed by the above formula (8a). On the other hand, the transfer function Pn when only the response delay of the plant to the control is considered is expressed by the above formula (8b). Even when the transfer function Pn of formula (8b) is used, the same action and effect as above can be obtained.

[0142] The above-described embodiment is a preferred example of the present invention, but the present invention is not limited to this embodiment and can be modified in various ways without departing from the scope of the present invention. [Explanation of symbols]

[0143] 1 ECU (computer) 2. Engine (internal combustion engine) 9. Control System 10 CPU 20,23 Water jacket (cooling passage) 21,22 Exit 24 Entrance 30 EWP (Pump) 31 Thermostat 32 Radiator 36 Outlet water temperature sensor 37 EGR passage 38 Distribution Channel 101 Detection value acquisition unit (acquisition means) 103,103a Flow rate calculation unit (calculation means) 104 Water temperature difference correction section (correction means) 105 Rotational speed command unit (command means) 380 ATF flow passage 381 Heater Channel 382 Radiator Flow 390,391 Return channel 130 Heat Map Data Table 131 Time constant data table 132 Dead Time Data Table 133 Convergence Water Temperature Difference Data Table

Claims

1. A control device for controlling a flow rate of a cooling medium circulating through a cooling passage of an internal combustion engine, an acquisition means for acquiring a detection value of the temperature of the cooling medium at an outlet of the cooling flow path; a calculation means for calculating a control value of the flow rate based on a difference between the temperature of the cooling medium at the inlet of the cooling flow path and the detected value so as to compensate for a delay until the temperature difference of the cooling medium at the inlet and the outlet of the cooling flow path reaches a target value; a command means for commanding a pump that circulates the cooling medium through the cooling flow passage to output an output in accordance with the control value; a correction means for predicting at least one of a delay time and a dead time of a response to a command for the output from a target flow rate corresponding to the target value, and correcting the difference based on the prediction result; Control device.

2. the correction means, in response to the command for output, records a history of the temperature difference of the cooling medium in chronological order, obtains a value of the temperature difference from the history of the temperature difference by the dead time and uses the value for correcting the difference; The control device according to claim 1 .

3. the correction means records a history of the temperature difference in time series based on a correlation between the temperature difference and the inverse of the flow rate from a current flow rate of the cooling medium; The control device according to claim 2.

4. The acquisition means acquires a rotation speed of the pump, The correction means estimates the current flow rate of the cooling medium from the rotation speed. The control device according to claim 3.

5. The correction means calculates a time constant according to the target flow rate, and predicts the delay time from the time constant. A control device according to any one of claims 1 to 4.

6. The calculation means calculates a time constant according to the target flow rate and compensates for the delay based on the time constant. A control device according to any one of claims 1 to 4.

7. the calculation means calculates the control value by using a temperature of the cooling medium at an inlet of the cooling flow path as a fixed value. A control device according to any one of claims 1 to 4.

8. A method for controlling a flow rate of a cooling medium circulating through a cooling passage of an internal combustion engine, comprising: obtaining a detection value of the temperature of the cooling medium at an outlet of the cooling flow path; calculating a control value of the flow rate based on a difference between the temperature of the cooling medium at the inlet of the cooling flow path and the detected value so as to compensate for a delay until the temperature difference of the cooling medium at the inlet and the outlet of the cooling flow path reaches a target value; commanding a pump that circulates the cooling medium through the cooling flow passage to output in accordance with the control value; A process is executed by a computer to predict at least one of a delay time and a dead time of a response to a command for the output from a target flow rate corresponding to the target value, and correct the difference based on the prediction result. Control methods.

9. In the process of correcting the difference based on the prediction result, a history of the temperature difference of the cooling medium is recorded in chronological order in response to the command for output, and a value from the history of the temperature difference obtained by the time period preceding the dead time is used for correcting the difference. The control method according to claim 8.

10. In the process of correcting the difference based on the prediction result, a history of the temperature difference is recorded in chronological order based on a correlation between the temperature difference and the inverse of the flow rate from a current flow rate of the cooling medium. The control method according to claim 9.

11. In the process of correcting the difference based on the prediction result, a rotation speed of the pump is acquired, and the current flow rate of the cooling medium is estimated from the rotation speed. The control method according to claim 10.

12. In the process of correcting the difference based on the prediction result, a time constant corresponding to the target flow rate is calculated, and the delay time is predicted from the time constant. A control method according to any one of claims 8 to 11.

13. In the process of calculating the flow rate control value, a time constant corresponding to the target flow rate is calculated, and a delay is compensated for based on the time constant. A control method according to any one of claims 8 to 11.

14. In the process of calculating the control value of the flow rate, the control value is calculated by setting the temperature of the cooling medium at the inlet of the cooling flow path as a fixed value. A control method according to any one of claims 8 to 11.

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