Engine cooling device

Abstract

Engine cooling device, comprising: a flow rate control unit (12) that controls the flow rate of the coolant circulating between an engine and a radiator; a water temperature sensing unit (17) that detects the temperature of the cooling water distributed by the motor (1); a target water temperature calculation unit (21) which calculates a target water temperature of the cooling water based on an operating state of the engine (1); a deviation calculation unit (22) which calculates a water temperature deviation based on the water temperature recorded by the water temperature sensing unit (17) and the target water temperature calculated by the target water temperature calculation unit (21); a target opening calculation unit (24) which calculates a target opening of the flow rate setting unit (12) to achieve the target water temperature based on the water temperature deviation calculated by the deviation calculation unit (22); an opening / closing direction determination unit (25) that determines an opening / closing direction of the flow rate setting unit (12) on the basis of a change state of the target opening calculated by the target opening calculation unit (24); a control speed calculation unit (26) which calculates a control speed of the flow rate setting unit (12) on the basis of the water temperature deviation calculated by the deviation calculation unit (22) and calculates a higher control speed in a case where the opening / closing direction determined by the opening / closing direction determination unit (25) is on a closing side than in a case where the determined opening / closing direction is on an opening side; a valve control unit (27) that controls an opening of the flow rate control unit (12) based on the target opening calculated by the target opening calculation unit and the control speed calculated by the control speed calculation unit (26); a first storage unit that stores a relationship between a water temperature deviation and a predefined target opening, wherein the target opening calculation unit (24) calculates the target opening from the water temperature deviation on the basis of the relationship stored in the first storage unit, characterized by a water temperature deviation correction unit that uses the water temperature deviation as a base water temperature deviation to calculate a water temperature deviation after correction based on at least one proportional term and one integration term of the base water temperature deviation, wherein the first storage unit stores a relationship between the water temperature deviation after correction and the target opening, the target opening calculation unit (24) calculates the target opening based on the water temperature deviation after correction, the opening / closing direction determination unit (25) determines the opening / closing direction on the basis of the target opening, which is calculated on the basis of the water temperature deviation after correction, the control speed calculation unit (26) calculates the control speed on the basis of the base water temperature deviation, and the valve control unit (27) controls the orifice of the flow rate control unit (12) on the basis of the target orifice, which is calculated on the basis of the water temperature deviation after correction.

Description

field of technology

[0001] The present invention relates to an engine cooling device. Technical background

[0002] In related prior art, a cooling device of this type comprises a thermostat provided in a cooling water path connecting an engine to a radiator. The thermostat is set to gradually open and close between a fully open and a fully closed position within a temperature range of approximately 80°C to 90°C, for example, by utilizing the thermal expansion of a wax. A distribution of the cooling water between the engine and the radiator is maintained in accordance with the opening and closing of such a thermostat, and the engine is kept within a predetermined temperature range.

[0003] To address recent demands such as emissions control and improved fuel efficiency, an electronically controlled engine cooling device, as described, for example, in patent document 1, has been developed for practical use, as more precise water temperature control is required. According to the cooling device, the flow rate of coolant distributed between the engine and the radiator can be adjusted by a flow path diverter valve, and the engine coolant is maintained at a set temperature by controlling the opening of the flow path diverter valve based on a deviation between the set temperature (set, for example, based on the engine's operating condition) and the actual water temperature measured by a water temperature sensor.According to such a cooling device with electronic control, it is possible to arbitrarily set the opening / closing speed of the flow path diverting valve with respect to the water temperature deviation, and thus there is a case in which the property of the thermostat in the related prior art is simulated, for example, and the property of the relatively slow opening and closing of the flow path diverting valve with respect to the water temperature deviation is given. Prior art document (patent document)

[0004] Patent document 1: Japanese publication no. JP 2014 - 169 661 A

[0005] US 2019 / 0093546A1 discloses a coolant circuit for an engine cooling device comprising a first pass in which coolant flows through a radiator and a second pass in which coolant flows without passing through the radiator. A coolant control valve controls a flow rate in the first pass and a flow rate in the second pass. A coolant outlet temperature sensor detects a coolant outlet temperature, which is the coolant temperature upstream of a junction point between the first and second passes. An inlet coolant temperature sensor detects the inlet coolant temperature, which is the coolant temperature downstream of the junction point between the first and second passes.A coolant temperature estimator calculates the coolant temperature at the radiator, which is the coolant temperature at the coolant outlet of the radiator when the first-pass flow rate is greater than or equal to a certain flow rate. Summary of the invention; Problems to be solved by the invention

[0006] However, according to the cooling device in patent document 1, the temperature of the cooling water distributed by the engine deviates significantly from the target water temperature in a situation described below.

[0007] The opening of the flow path changeover valve is controlled based on the water temperature deviation. It is possible to allow the temperature to drop to the open side of the flow path changeover valve when the water temperature is greater than the setpoint temperature, while the flow path changeover valve remains closed when the water temperature is less than or equal to the setpoint temperature. At this point, the cooling water circulates through the engine's water jacket without being cooled by the radiator, and the water temperature T gradually increases due to heat absorption by the engine, as shown in [reference to diagram]. Fig. 4 is shown as A. Furthermore, the coolant remains at the radiator at this point and is cooled by the airflow, and the temperature gradually decreases.

[0008] If the water temperature T is above the target water temperature tgtT due to the temperature increase of the cooling water (see B in Fig.4) The flow path diverter valve is controlled to the open side. If the flow diverter valve is opened and closed slowly depending on the water temperature deviation, the control to the open side also occurs slowly at that time, as in Fig. 4 is represented as C. However, since the cooling water, cooled in the radiator, flows into the water jacket at a low temperature, the water temperature T changes from rising to falling and drops suddenly, as shown in Fig. 4 shown. Although the switching valve for the flow path closes again in response to the reduction in water temperature deviation associated with the temperature drop, the control to the closed side also occurs slowly at this time, as shown by the dashed line Ea in Fig.This illustrates that the drop in cooling water temperature cannot be sufficiently slowed, and the water temperature T deviates significantly from the target water temperature tgtT on the low-temperature side, as shown by the dashed line Fa in Fig. illustrated.

[0009] Such an inappropriate drop in coolant temperature occurs every time the flow path changeover valve switches, leading to the problem of deteriorating fuel efficiency and exhaust characteristics due to an increase in engine oil viscosity and a failure of fuel evaporation.

[0010] The present invention was made to solve such a problem, and one objective of the present invention is to provide an engine cooling device that is able to prevent a sudden drop in the cooling water temperature in advance when a flow path switching valve is controlled from a closed side to an open side, and to keep an engine within a satisfactory temperature range. Means to solve the problems

[0011] The invention is defined by the subject matter of claims 1 and 2. To achieve the above objective, an engine cooling device according to the present invention comprises: a flow rate control unit that regulates the flow rate of cooling water circulating between an engine and a radiator; a water temperature sensing unit that detects the temperature of the cooling water distributed by the engine; a target water temperature calculation unit that calculates a target water temperature of the cooling water based on an operating condition of the engine; and a deviation calculation unit that calculates a water temperature deviation based on the water temperature detected by the water temperature sensing unit and the target water temperature calculated by the target water temperature calculation unit.a target orifice calculation unit that calculates a target orifice of the flow rate control unit to achieve the target water temperature based on the water temperature deviation calculated by the deviation calculation unit; an opening / closing direction determination unit that determines an opening / closing direction of the flow rate control unit based on a change state of the target orifice calculated by the target orifice calculation unit;a control speed calculation unit that calculates a control speed of the flow rate control unit based on the water temperature deviation calculated by the deviation calculation unit, and which calculates a higher control speed in a case where the opening / closing direction determined by the opening / closing direction determination unit is on a closed side than in a case where the determined opening / closing direction is on an open side; and a valve control unit that controls the opening of the flow rate control unit based on the target opening calculated by the target opening calculation unit and the control speed calculated by the control speed calculation unit.

[0012] In another aspect, the engine cooling device may further include: a first storage unit that stores a relationship between a water temperature deviation and a predetermined target opening, and the target opening calculation unit that can calculate the target opening from the water temperature deviation based on the relationship stored in the first storage unit.

[0013] In another aspect, the engine cooling device may further include: a water temperature deviation correction unit that uses the water temperature deviation as a base water temperature deviation to calculate a water temperature deviation after correction based on at least one proportional term and one integration term of the base water temperature deviation; the first storage unit that can store a relationship between the water temperature deviation after correction and the target aperture; the target aperture calculation unit that can calculate the target aperture based on the water temperature deviation after correction; and the opening / closing direction determination unit that can determine the opening / closing direction based on the target aperture calculated based on the water temperature deviation after correction.The unit for calculating the control speed can calculate the control speed based on the basic water temperature deviation, and the valve control unit can control the orifice of the flow rate adjustment unit based on the target orifice calculated based on the water temperature deviation after correction.

[0014] In another aspect, the engine cooling device may further include: a second storage unit that stores a relationship between a water temperature deviation and a control speed of the flow rate control unit on the preset open side and an unlimited value that is a control speed equal to or greater than a response speed of the flow rate control unit; the control speed calculation unit can calculate the control speed from the water temperature deviation based on the relationship stored in the second storage unit in a case where the opening / closing direction determined by the opening / closing direction determination unit is on the open side; and sets the unlimited value stored in the second storage unit as the control speed independent of the water temperature deviation in a case where the opening / closing direction determined by the opening / closing direction determination unit is on the open side.in which the specific opening / closing direction is on the closed side. Advantageous effects of the invention

[0015] According to the engine cooling device of the present invention, it is possible to prevent a sudden drop in the cooling water temperature in advance when the flow path switching valve is controlled from the closed side to the open side, and to keep the engine in a satisfactory temperature range. Brief description of the drawings Fig. Figure 1 is an overall configuration diagram showing an engine cooling device according to one embodiment. Fig. Figure 2 is a control block diagram showing the configuration of a control unit. Fig. Figure 3 is a flowchart showing a water temperature control routine executed by the ECU. Fig.Figure 4 is a time diagram comparing the state of the cooling water temperature control between the embodiment and the technology in patent document 1. Method for carrying out the invention

[0016] The following describes an embodiment of an engine cooling device that is achieved by implementing the present invention.

[0017] An engine 1 according to the present embodiment is installed as a drive source in a passenger car and is cooled by a water-cooling device 2. As in Fig.As shown in Figure 1, the cooling water expelled by a water pump 4 is distributed onto a water jacket 3 formed inside the motor 1 and then flows from the water jacket 3 into the interior of an outlet path 5, which is connected to one side of the motor 1. One end each of a main water path 6, a secondary water path 7, and a bypass water path 8 is connected to the outlet path 5, and the other end of the bypass water path 8 is connected to a suction side of the water pump 4.

[0018] A cooler 9 is inserted into the main water path 6, and the other end of the main water path 6 is connected to the suction side of the water pump 4. The secondary water path 7 is branched into two parts, containing an EGR valve 10, which returns exhaust gas to the suction side, and a throttle device 11, which regulates the intake air volume. The other end of each secondary water path 7 is connected to sections of the main water path 6 that are closer to the side of the water pump 4 than the cooler 9.

[0019] Therefore, the cooling water routed from outlet 5 to main water path 6 is cooled by the airflow during distribution through radiator 9 and returned to water pump 4 at a lower temperature. The cooling water routed from outlet 5 to secondary water path 7 is distributed through the EGR valve 10 and the throttling device 11; the temperature rises due to the cooling of these devices 9 and 10, and the cooling water is then returned to water pump 4. The cooling water routed from outlet 5 to bypass water path 8 is also returned to water pump 4 at an unchanged temperature.

[0020] A flow path diverter valve 12 is arranged within the outlet path 5, and the flow path diverter valve 12 sequentially adjusts the flow path of the cooling water. Specifically, an inlet port of the flow path diverter valve 12 is connected to the interior of the outlet path 5, and an outlet port of the flow path diverter valve 12 is connected to both the main water path 6 and the secondary water path 7. The flow path diverter valve 12 is configured as a rotary type, rotating an integrated rotor by the drive of a motor 13. The opening ratios on the main water path 6 side and on the secondary water path 7 side are sequentially adjusted according to an angle θ of the rotor, thus changing the flow rate of the cooling water from the outlet path 5 into the main water path 6 and the secondary water path 7.

[0021] In the following description, a state for adjusting the opening ratio, achieved by the flow path switching valve 12, is primarily represented by an opening area on the side of the main water path 6, in other words, an opening A of the cooler 9. For example, a state in which the side of the main water path 6 is completely closed is expressed as cooler opening A = 0%, and at this point, the distribution of cooling water to the cooler 9 is stopped. A state in which the side of the main water path 6 is completely open is expressed as cooler opening A = 100%, and at this point, the flow rate of cooling water distributed through the cooler 9 is at its maximum.

[0022] If the flow path of the cooling water is successively adjusted in this way, the flow rate of the cooling water distributed between the engine 1 and the radiator 9 is adjusted, and the flow path switching valve 12 thus functions in the present embodiment as a flow rate adjustment unit according to the present invention.

[0023] The operating state of the cooling device 2 is controlled by an ECU 15 (electronic control unit), and the ECU 15 is configured with an input / output interface 15a, a storage device 15b (a ROM, a RAM, etc.) containing several control programs, a central processing unit 15c (CPU), a timer 15d, and the like. Various sensors, such as a position sensor 16 that detects the rotor angle of the flow path switching valve 12, a first water temperature sensor 17 that detects the temperature of the cooling water flowing from the engine 1 into the interior of the outlet path 5 as engine temperature T, and a second water temperature sensor 18 that detects the temperature of the cooling water after passing through the radiator 9, are connected to the input side of the ECU 15.

[0024] Furthermore, various devices, such as a motor 13 that drives the flow path switching valve 12 described above, are connected to the output side of the ECU 15. In the present embodiment, the engine temperature T corresponds to the temperature of the cooling water distributed by the engine 1 according to the present invention, and the first water temperature sensor 17, which detects the engine temperature T, functions as the water temperature sensing unit according to the present invention.

[0025] Next, a configuration of control unit 15 will be created based on the control block diagram in Fig. 2 described.

[0026] The target water temperature calculation unit 21 in the ECU 15 calculates a target water temperature tgtT of the cooling water based on the operating state of the engine 1, and the target water temperature tgtT is entered into the deviation calculation unit 22 together with the engine temperature T detected by the first water temperature sensor 17.

[0027] The deviation calculation unit 22 calculates a base water temperature deviation ΔTbase as the difference between the target water temperature tgtT and the engine temperature T and inputs the base water temperature deviation ΔTbase into a PI control unit 23. A P-term setting unit 23a of the PI control unit 23 sets a proportional term and an I-term setting unit 23b an integration term based on the base water temperature deviation ΔTbase, and these feedback terms are added by an addition unit 23c to calculate a water temperature deviation after correction ΔT based on the PI control.

[0028] In the present embodiment, the PI control unit 23 functions as the water temperature deviation correction unit according to the present invention. Note that PD control or PID control can be performed instead of PI control, and the PI control unit 23 can be omitted to treat the basic water temperature deviation ΔTbase as the water temperature deviation after correction ΔT.

[0029] The water temperature deviation after correction ΔT is input into the target opening calculation unit 24, and a target cooler opening tgtA is calculated based on the water temperature deviation after correction ΔT. For calculation processing, the storage device 15b of the ECU 15 stores a control characteristic that predefines a relationship between the water temperature deviation after correction ΔT and the target cooler opening tgtA. Table 1 below shows an example of the control characteristic map, which is set such that the target cooler opening tgtA increases along with an increase in the water temperature deviation after correction ΔT. For example, the target cooler tgtA is calculated as 0% when the water temperature deviation after correction ΔT = 0 °C, and the target cooler opening tgtA is calculated as 100% when the water temperature deviation after correction ΔT = 10 °C.

[0030] In the present embodiment, the storage device 15b, which stores the control card in Table 1, functions as the first storage unit according to the present invention. [Table 1] ΔT(°C) 0 1 2 3 4 5 6 7 8 9 10 tgtA(%) 0 0 1 3 6 13 22 34 51 73 100

[0031] The target cooler opening tgtA is input to the opening / closing direction determination unit 25, and the opening / closing direction determination unit 25 determines a change direction of the target cooler opening tgtA, in other words, an opening / closing direction of the flow path switching valve 12, based on the deviation of the target cooler opening tgtA calculated in a current or previous control cycle. In the present embodiment, a deviation between a current value and a previous value of the target cooler opening tgtA corresponds to the change state of the setpoint orifice according to the present invention.

[0032] On the other hand, the determination result of the opening / closing direction determination unit 25, together with the groundwater temperature deviation ΔTbase calculated by the deviation calculation unit 22, is entered into a switching unit 26a of the control speed calculation unit 26. The switching unit 26a is switched to a speed calculation unit 26b for the open side if the determination result of the opening / closing direction determination unit 25 is an open side, and is switched to a speed calculation unit 26c for the closed side if the determination result is a closed side. The base water temperature deviation ΔTbase is entered into the speed calculation unit 26b or 26c on the switched side, and a control speed θspd of the flow path switching valve 12 is calculated based on the base water temperature deviation ΔTbase.

[0033] For computational processing, the storage device 15b in the ECU 15 stores a control map that defines a relationship between the basic water temperature deviation ΔTbase and the control speed θspd in advance for each of the speed calculation units 26b and 26c. Table 2 shows an example of the control diagram applied to speed calculation unit 26b on the open side, and Table 3 shows an example of the control diagram applied to speed calculation unit 26c on the closed side.

[0034] In the present embodiment, the storage device 15b, in which the control maps of Tables 2 and 3 are stored, functions as a second storage unit according to the present invention. [Table 2] ΔT base (°C) 0~2.5 2.5~5 5~10 10~20 Open side θspd(% / sec) 0.008 0.08 0.8 8 [Table 3] ΔT base (°C) 0~20 Closed page θspd(% / sec) 200

[0035] As can be seen from Table 2, a higher control speed θspd is calculated with increasing base water temperature deviation ΔTbase when the flow path switching valve 12 is controlled to the open side. This characteristic is based on the understanding that a faster rotor angle control for the flow path switching valve 12 is required as the difference between the motor temperature T and the water setpoint temperature tgtT increases. However, the control speed θspd set to the open side in Table 2 is relatively low, and the flow path switching valve 12 is manufactured with a specification that provides a response speed sufficient to maintain a maximum control speed θspd = 8 (% / sec).

[0036] The target cooler opening tgtA, obtained from the water temperature deviation after correction ΔT, is applied to the processing of the determination of the opening / closing direction of the flow path switching valve 12 and the control of the radiator opening A, which will be described later. The base water temperature deviation ΔTbase is applied to the processing of the calculation of the control speed θspd based on the following findings. As will be described later, the actual cooler opening A, and thus the rotor angle θ of the flow path switching valve 12, is fed back as a function of the target cooler opening tgtA.Therefore, it is possible to appropriately control the cooler opening A and to appropriately determine the opening / closing direction of the flow path switching valve 12 controlled on the basis of the rotor angle by applying the target cooler opening tgtA on the basis of the water temperature deviation after the correction ΔT, which reflects the PI control.

[0037] On the other hand, the control speed θspd must be regulated in accordance with the state of the difference between the engine temperature T and the target water temperature tgtT at that time, as described above. Therefore, it is desirable to make the setting based on the basic water temperature deviation ΔTbase, which is a deviation between the actual target water temperature tgtT and the engine temperature T, and not the water temperature deviation after correction ΔT including a delay element caused by the I-control. Thus, it is possible to control the flow path switching valve 12 with a suitable control speed θspd.

[0038] On the other hand, when the flow path switching valve 12 is closed, the control rate θspd = 200 (% / sec) is calculated constantly, regardless of the magnitude of the groundwater temperature deviation ΔTbase. This rate is significantly higher than the control rate θspd when open, as shown in Table 3. The control rate θspd is a value equal to or greater than the response rate of the flow path switching valve 12, which corresponds to the unlimited value according to the present invention, and the flow path switching valve 12 is necessarily operated at maximum speed. As described above, the flow path switching valve 12 is controlled at a relatively higher control rate θspd on the closed side than on the open side, in order to solve the problem of the technology described in patent document 1. This point will be described in detail later with reference to a timing diagram.

[0039] The control speed θspd calculated by the speed calculation unit 26b or 26c of the control speed calculation unit 26 is input into the valve control unit 27 together with the target cooler opening tgtA calculated by the target opening calculation unit 24. Although not shown, the storage device 15b of the control unit 15 stores the control map that defines the relationship between the cooler opening A and the rotor angle θ of the flow path switching valve 12, and the valve control unit 27 calculates the target rotor angle tgtθ from the target cooler opening tgtA with reference to the map. The feedback control is then executed, whereby the opening / closing speed of the flow path switching valve 12 is maintained at the control speed θspd based on a deviation between the target rotor angle tgtθ and the actual rotor angle θ detected by the position sensor 16.

[0040] The content of the aforementioned control process, carried out by the ECU 15, is described below using the flowchart in Fig. 3 described.

[0041] First, in step 1, acquisition information is read from each sensor. In the following step 2, the basic water temperature deviation ΔTbase is calculated, and in step 3, the water temperature deviation after correction ΔT is calculated. The processing in step 2 is performed by the deviation calculation unit 22, and the processing in step 3 is performed by the PI control unit 23. Then, in step 4, the target cooler opening tgtA is calculated based on the control chart in Table 1, and in step 5, a change direction for the target cooler opening tgtA is determined. The processing in step 4 is performed by the target opening calculation unit 24, and the processing in step 5 is performed by the opening / closing direction determination unit 25.

[0042] If the direction of change determined in step 5 is the open side, processing continues from step 6 to step 7, and the control speed θspd on the open side is calculated based on the control map in Table 2. If the direction of change is the closed side, processing continues from step 6 to step 8, and the control speed θspd on the closed side is calculated based on the control map in Table 3. The flow path switching valve 12 is then fed back in based on the target cooler opening tgtA and the control speed θspd in step 9.The processing in step 6 is performed by the switching unit 26a of the control speed calculation unit 26, the processing in step 7 is performed by the speed calculation unit 26b for the open side, the processing in step 8 is performed by the speed calculation unit 26c for the closed side, and the processing in step S10 is performed by the valve control unit 27.

[0043] Next, the status of the coolant temperature control is determined based on the processing performed by the ECU 15 mentioned above, using the time graph in Fig. 4 described.

[0044] The drawing shows a case where the target water temperature tgtT is kept constant for clarity. If the engine temperature T ≤ the target water temperature tgtT, the target radiator opening tgtA = 0% is calculated based on Table 1, and the flow path switching valve 12 completely closes the main water path 6. Therefore, the cooling water flows through the bypass water path 8 or the secondary water path 7 and is then circulated through the water jacket 3 of the engine 1 without being cooled by the radiator 9. The engine temperature T gradually increases due to the heat absorbed by the engine 1, as shown in Table 1. Fig. 4 shown. At this point, the coolant remains at the radiator 9 and is cooled by the airflow, and the temperature gradually decreases.

[0045] If, due to the temperature increase of the cooling water, the engine temperature T > the target water temperature tgtT is reached, as in Fig.As shown in Figure 4 (B), the flow path switching valve 12 is controlled to the open side based on the target cooler opening tgtA calculated from Table 1. The control speed θspd of the flow path switching valve 12 is set at this time based on Table 2, and the flow path switching valve 12 is controlled relatively slowly to the open side, as shown in Figure 4. Fig. 4 is represented as C. However, since the coolant cooled in the radiator 9 flows into the water jacket 3 at a low temperature, the engine temperature T changes from rising to falling and suddenly decreases, as shown in Fig. 4 is represented as D.

[0046] The flow path switching valve 12 is controlled to the closed side based on the target cooler opening tgtA calculated from Table 1 in response to a decrease in the water temperature deviation after the correction ΔT, which accompanies the temperature decrease. The control speed θspd of the flow path switching valve 12 is set at this time based on Table 3, and the flow path switching valve 12 is rapidly controlled to the closed side, as indicated by the solid line Eb in Figure 1. Fig. 4 shown. Therefore, the decrease in engine temperature T is quickly slowed, and the engine temperature T begins to rise without deviating from the target water temperature tgtT on the low-temperature side as far as indicated by the solid line Fb in Fig.Figure 4 illustrates this. Although a decrease in engine temperature T, which deviates significantly from the target water temperature tgtT, can cause an increase in oil viscosity or fuel vaporization failure, it is possible to avoid such situations in advance, to keep engine 1 within a satisfactory temperature range, and thereby improve fuel efficiency and exhaust emission characteristics.

[0047] The significance of the cooling control for motor 1 in the present embodiment can be determined as described below. At the start of practical use of an electronically controlled cooling device, the characteristics of a thermostat are simulated, and in many cases, a characteristic of the relatively slow opening and closing of a flow path switching valve is employed. It is important to prevent overheating of the motor at this point, and in this context, it was considered that an increase in the control speed when opening the flow path switching valve should take precedence over that when closing the valve, in order to prevent a sudden rise in the motor temperature T.

[0048] This disadvantage arises from the phenomenon that the cooling water, with a low temperature within the radiator 9, flows into the water jacket 3 through the aforementioned control of the flow path switching valve 12. Furthermore, an inherent characteristic of the engine 1—that the decrease in water temperature due to cooling in the radiator 9 occurs abruptly compared to the increase in water temperature due to heat absorption by the engine 1—also has an impact. On the other hand, to meet the requirements regarding fuel efficiency and exhaust emissions, preventing overcooling of the engine 1, which can lead to an increase in oil viscosity and a failure of fuel vaporization, has become more important than preventing overheating of the engine 1.

[0049] As described above, it can be stated that a cooling control system that prioritizes preventing overcooling of the engine 1 is necessary both from the perspective of the engine 1's inherent characteristics and from the perspective of fuel efficiency and exhaust emission requirements. These requirements can be met by a cooling control system in which the control speed θspd is set higher when the flow path switching valve 12 is closed than when the valve is open, as in the present embodiment, thus achieving the effects mentioned above.

[0050] On the other hand, the target opening calculation unit 24 calculates the target cooler opening tgtA from the water temperature deviation after correction ΔT based on the control map stored in the storage device 15b in Table 1. Therefore, feedback control of the rotor angle θ of the flow path switching valve 12 is performed, which reflects not only the PI control based on the water temperature deviation after correction ΔT, but also characteristics of the control map. For example, the control map in Table 1 has the property that the target cooler opening tgtA rises steeply with respect to an increase in the water temperature deviation after correction ΔT, and it is thus possible to reliably limit an increase in the engine temperature T.In this way, it is possible to change the content of the feedback control based on the setting of the characteristic map properties as desired, thereby keeping motor 1 within a satisfactory temperature range.

[0051] Although the description of the embodiment is now concluded, aspects of the present invention are not limited to this embodiment. For example, although the aforementioned embodiment is implemented as the cooling device 2 for the engine 1 mounted in a passenger car, the present invention is not limited thereto. For example, the present invention can be implemented as a cooling device for an engine mounted in a motorcycle or an all-terrain vehicle (ATV). The configuration of the water passages in the Fig. The cooling device 2 shown in 1 is not limited to this and can be modified as desired. Explanation of reference symbols 1 engine 9 coolers 12 Flow path switching valve (flow rate control unit) 15b Storage device (first storage unit, second storage unit) 17 First water temperature sensor (water temperature sensing unit) 21 Target water temperature calculation unit 22 Deviation calculation unit 23 PI control unit (device for correcting water temperature deviation) 24 Target Opening Calculation Unit 25 Opening / closing direction determination unit 26 Control speed calculation unit 27 Valve control unit

Claims

[1] Engine cooling device comprising: a flow rate control unit (12) that controls the flow rate of the coolant circulating between an engine and a radiator; a water temperature sensing unit (17) that detects the temperature of the cooling water distributed by the motor (1); a target water temperature calculation unit (21) which calculates a target water temperature of the cooling water based on an operating state of the engine (1); a deviation calculation unit (22) which calculates a water temperature deviation based on the water temperature recorded by the water temperature sensing unit (17) and the target water temperature calculated by the target water temperature calculation unit (21); a target opening calculation unit (24) which calculates a target opening of the flow rate setting unit (12) to achieve the target water temperature based on the water temperature deviation calculated by the deviation calculation unit (22); an opening / closing direction determination unit (25) that determines an opening / closing direction of the flow rate setting unit (12) on the basis of a change state of the target opening calculated by the target opening calculation unit (24); a control speed calculation unit (26) which calculates a control speed of the flow rate setting unit (12) on the basis of the water temperature deviation calculated by the deviation calculation unit (22) and calculates a higher control speed in a case where the opening / closing direction determined by the opening / closing direction determination unit (25) is on a closing side than in a case where the determined opening / closing direction is on an opening side; a valve control unit (27) that controls an opening of the flow rate control unit (12) based on the target opening calculated by the target opening calculation unit and the control speed calculated by the control speed calculation unit (26); a first storage unit that stores a relationship between a water temperature deviation and a predefined target opening, wherein the target opening calculation unit (24) calculates the target opening from the water temperature deviation on the basis of the relationship stored in the first storage unit, characterized by a water temperature deviation correction unit that uses the water temperature deviation as a base water temperature deviation to calculate a water temperature deviation after correction based on at least one proportional term and one integration term of the base water temperature deviation, wherein the first storage unit stores a relationship between the water temperature deviation after correction and the target opening, the target opening calculation unit (24) calculates the target opening based on the water temperature deviation after correction, the opening / closing direction determination unit (25) determines the opening / closing direction on the basis of the target opening, which is calculated on the basis of the water temperature deviation after correction, the control speed calculation unit (26) calculates the control speed on the basis of the base water temperature deviation, and the valve control unit (27) controls the orifice of the flow rate control unit (12) on the basis of the target orifice, which is calculated on the basis of the water temperature deviation after correction. [2] Engine cooling device comprising: a flow rate control unit (12) that controls the flow rate of the coolant circulating between an engine and a radiator; a water temperature sensing unit (17) that detects the temperature of the cooling water distributed by the motor (1); a target water temperature calculation unit (21) which calculates a target water temperature of the cooling water based on an operating state of the engine (1); a deviation calculation unit (22) which calculates a water temperature deviation based on the water temperature recorded by the water temperature sensing unit (17) and the target water temperature calculated by the target water temperature calculation unit (21); a target opening calculation unit (24) which calculates a target opening of the flow rate setting unit (12) to achieve the target water temperature based on the water temperature deviation calculated by the deviation calculation unit (22); an opening / closing direction determination unit (25) that determines an opening / closing direction of the flow rate setting unit (12) on the basis of a change state of the target opening calculated by the target opening calculation unit (24); a control speed calculation unit (26) which calculates a control speed of the flow rate setting unit (12) on the basis of the water temperature deviation calculated by the deviation calculation unit (22) and calculates a higher control speed in a case where the opening / closing direction determined by the opening / closing direction determination unit (25) is on a closing side than in a case where the determined opening / closing direction is on an opening side; a valve control unit (27) that controls an opening of the flow rate control unit (12) based on the target opening calculated by the target opening calculation unit and the control speed calculated by the control speed calculation unit (26), characterized by a second storage unit that stores a relationship between a water temperature deviation and a control speed of the flow rate control unit (12) on the opening side, which has been preset, and an unlimited value which is a control speed equal to or greater than a response speed of the flow rate control unit (12), wherein the control speed calculation unit (26) calculates the control speed from the water temperature deviation on the basis of the relationship stored in the second storage unit in a case where the opening / closing direction determined by the opening / closing direction determination unit (25) is on the opening side, and sets the unlimited value stored in the second storage unit as the control speed independent of the water temperature deviation in a case where the determined opening / closing direction is on the closing side.

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