JP2006112344A - Engine cooling system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve controllability of the cooling water temperature, by heightening the target cooling water temperature without reducing knocking resistant performance of an engine, in a cooling system for controlling the cooling water temperature of the engine at the target cooling water temperature. <P>SOLUTION: This cooling system has cooling water circulating passages 11 and 12 for circulating cooling water of the engine 1, a radiator 13 arranged in the cooling water circulating passages 11 and 12, and a flow control valve 16 for adjusting a cooling water flow rate passing through the radiator 13. An electronic control device ECU 30 controls the flow control valve 16 so that the cooling water temperature TO of the engine 1 becomes the target cooling water temperature Tt. Here, the ECU 30 sets the target cooling water temperature Tt in response to the intake temperature THIA, and actually, sets the target cooling water temperature Tt to the relatively high temperature when the intake temperature THIA is relatively low, and sets the target cooling water temperature Tt to the relatively low temperature when the intake temperature THIA is relatively high. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a cooling device that cools an engine by circulating cooling water through a cooling water circulation path including a radiator, and adjusts a cooling water flow rate that passes through the radiator by a flow rate adjusting means to target cooling water temperature. The present invention relates to a cooling device for an engine which is controlled to a water temperature.

  Conventionally, as a cooling device for an engine mounted on a vehicle or the like, for example, there is a water-cooling type cooling device described in Patent Document 1 below. The cooling device includes a cooling water circulation path including a water jacket of the engine body, a radiator, a water pump and a flow control valve provided in the cooling water circulation path, and an electronic control unit (ECU) that controls the opening degree of the flow control valve. Is provided. In this cooling device, when the water pump operates, the cooling water circulates through the cooling water circulation path, and heat is transferred between the engine body and the cooling water. The heat taken from the engine body to the cooling water is dissipated in the process of the cooling water passing through the radiator. Therefore, the ECU controls the flow rate control valve so that the actual cooling water temperature becomes the target cooling water temperature, thereby adjusting the cooling water flow rate passing through the radiator and controlling the cooling water temperature in the cooling water circulation path. The degree of engine cooling is controlled.

  Here, in the cooling device of Patent Document 1, the ECU determines the target cooling water temperature (target engine outlet water temperature Tt) according to the operating state of the engine. For example, when the engine is in an idling state, the ECU sets the target engine outlet water temperature Tt to a slightly lower temperature (for example, “90 ° C.”) as a countermeasure against knocking at the time of starting. When the engine is in a partial load (partial) operation state, the ECU sets the target engine outlet water temperature Tt to a higher temperature (for example, “100 ° C.”) in order to reduce friction loss. On the other hand, when the engine is in the full load (WOT) operation state, the ECU sets the target engine outlet water temperature Tt to a lower temperature (for example, “80 ° C.”) in order to increase the filling rate.

JP2003-239742A (5th page, FIGS. 1 and 2)

  However, in the cooling device of Patent Document 1 described above, when the cooling water temperature becomes high, there is a concern that the anti-knocking performance of the engine is lowered, and the target cooling water temperature cannot simply be raised so much. That is, the engine knocking phenomenon is said to be air column vibration caused by pressure waves generated by self-ignition of end gas in the engine cylinder. It is considered that this is likely to occur because the temperature of the air taken into the cylinder becomes higher and the compression pressure becomes higher as the cooling water temperature becomes higher. However, if the target cooling water temperature is simply set to a low value because there is a risk of knocking, the engine will have a friction loss and the fuel efficiency of the engine will deteriorate.

  The present invention has been made in view of the above circumstances, and an object of the present invention is an engine cooling apparatus that controls the engine cooling water temperature to the target cooling water temperature, and reduces the engine's anti-knocking performance. An object of the present invention is to provide a cooling device for an engine that can improve the controllability of the cooling water temperature by increasing the target cooling water temperature without causing it.

  In order to achieve the above object, an invention according to claim 1 is directed to a cooling water circulation path through which engine cooling water circulates, a radiator provided in the cooling water circulation path, and a flow rate of cooling water passing through the radiator. An engine cooling device comprising a flow rate adjusting means and controlling the flow rate adjusting means so that the engine coolant temperature becomes a target coolant temperature, wherein the target coolant temperature is set according to the outside air temperature. The objective cooling water temperature setting means is provided.

According to the above configuration, the engine coolant passes through the radiator while circulating through the coolant circulation path, and the flow rate of the coolant passing through the radiator is adjusted by the flow rate adjusting means. Then, the degree of cooling of the engine is controlled by controlling the flow rate adjusting means so that the engine coolant temperature becomes the target coolant temperature.
Here, if the target cooling water temperature is simply set high, the cooling water temperature becomes high, the temperature of the air taken into the engine becomes high, and there is a concern that the anti-knocking performance of the engine is lowered. In this invention, since the target cooling water temperature is set according to the outside air temperature, for example, when the outside cooling temperature is relatively low, the target cooling water temperature is set to a relatively high temperature, so that the air taken into the engine The engine is warmed up moderately while the temperature rise is suppressed.

  To achieve the above object, according to a second aspect of the present invention, in the first aspect of the present invention, the target cooling water temperature setting means sets the target cooling water temperature to be relatively high when the outside air temperature is relatively low. The purpose is to set the target cooling water temperature to a relatively low temperature when the outside air temperature is relatively high.

  According to the above configuration, the target cooling water temperature is set to a relatively high temperature when the outside air temperature is relatively low, and the target cooling water temperature is set to a relatively low temperature when the outside air temperature is relatively high. Thus, the same effect as that of the first aspect of the invention can be obtained. That is, the target cooling water temperature is set to a relatively high temperature when the outside air temperature is relatively low, so that the engine is warmed up moderately while suppressing an increase in the temperature of the air taken into the engine. Further, by setting the target cooling water temperature to a relatively low temperature when the outside air temperature is relatively high, the engine is appropriately cooled while suppressing an increase in the temperature of the air taken into the engine.

  According to the first aspect of the present invention, in the engine cooling device in which the engine coolant temperature is controlled to the target coolant temperature, the target coolant temperature is increased without degrading the engine anti-knocking performance. The controllability of the cooling water temperature can be improved. As a result, engine friction can be reduced and engine fuel efficiency can be improved.

  According to the invention described in claim 2, when the outside air temperature is relatively low, the target cooling water temperature is set to a relatively high temperature, and when the outside air temperature is relatively high, the target cooling water temperature is set to a relatively low temperature. By setting, the same effect as that of the invention described in claim 1 can be obtained.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an engine cooling device according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing an engine system in this embodiment. A multi-cylinder engine 1 mounted on a vehicle includes an engine body 2 including a cylinder block and a cylinder head. The engine body 2 is provided with a fuel injection valve and an ignition device (both not shown) corresponding to the combustion chamber of each cylinder (cylinder). The engine body 2 is provided with a piston (not shown) for each cylinder and a crankshaft 3 that is linked to each piston. The engine body 2 is provided with an intake passage 4 for taking air into each combustion chamber. The engine body 2 is provided with an exhaust passage 5 for exhausting exhaust gas from each combustion chamber. An air cleaner 6 and a throttle body 7 are provided in the intake passage 4. The air cleaner 6 cleans the air taken into each combustion chamber through the intake passage 4. The throttle body 7 is provided with a throttle valve 8 that is opened and closed to adjust the amount of air flowing through the intake passage 4 (intake amount), and a motor 9 that drives the valve 8 to open and close.

  The fuel injected from the fuel injection valve is supplied to each combustion chamber of the engine body 2. In each combustion chamber, the combustible mixture of fuel and air explodes and burns when the ignition device operates. When the piston operates by receiving this combustion energy, the crankshaft 3 rotates and power is generated in the engine 1. The exhaust gas after combustion generated in each combustion chamber is discharged to the outside through the exhaust passage 5. A part of the combustion energy generated in the engine 1 remains in the engine body 2 as heat. In order to prevent the engine main body 2 from being overheated by this residual heat, the engine 1 is provided with a water-cooled cooling device 10.

  The cooling device 10 includes a water jacket 11 provided in the engine body 2. The inlet 11 a and the outlet 11 b of the water jacket 11 are connected to the radiator 13 through the radiator passage 12. A water pump (W / P) 14 is provided in the vicinity of the inlet 11 a of the water jacket 11. The water pump 14 is drivingly connected to the crankshaft 3 via a pulley, a belt, and the like, and operates in conjunction with the operation of the engine 1. The water pump 14 sucks the cooling water flowing through the radiator passage 12 and discharges it to the water jacket 11. By this cooling water suction / discharge, the cooling water circulates in the clockwise direction indicated by the arrow in FIG. 1 starting from the water pump 14. During this circulation, the cooling water absorbs heat from the engine body 2 and rises in temperature in the process of passing through the water jacket 11. The raised cooling water releases heat in the process of passing through the radiator 13 to lower the temperature.

  A bypass passage 15 that bypasses the radiator 13 is connected to the radiator passage 12. One end of the bypass passage 15 (the right end in FIG. 1) is connected between the radiator 13 and the outlet 11 b of the water jacket 11 in the radiator passage 12. The other end (the left end in FIG. 1) of the bypass passage 15 is connected between the radiator 13 and the water pump 14 in the radiator passage 12. The water jacket 11 and the radiator passage 12 described above constitute a cooling water circulation path in the present invention.

  A flow rate control valve 16 is provided at a connection portion between the other end of the bypass passage 15 and the radiator passage 12. The flow rate control valve 16 is configured with a step motor as a drive source, and adjusts the flow rate of the cooling water flowing through the radiator passage 12 and the bypass passage 15 by controlling the valve opening degree ODV. This flow control valve 16 corresponds to the flow rate adjusting means in the present invention. Here, the flow rate control valve 16 is configured such that the flow rate of cooling water passing through the radiator passage 12 increases as the valve opening degree ODV increases.

  The flow rate control valve 16 controls the coolant temperature for cooling the engine body 2 by adjusting the coolant flow rate in the radiator passage 12. That is, by controlling the valve opening degree ODV of the flow control valve 16 to increase the coolant flow rate in the radiator passage 12, the ratio of the coolant water cooled by the radiator 13 out of the coolant water flowing through the engine body 2 is large. Thus, the temperature of the cooling water for cooling the engine body 2 is lowered. Further, by controlling the flow rate control valve 16 to reduce the cooling water flow rate in the radiator passage 12, the ratio of the cooling water cooled by the radiator 13 out of the cooling water flowing through the engine main body 2 is reduced. The temperature of the cooling water for cooling is increased.

  The radiator 13 is provided with a radiator outlet water temperature sensor 21 for detecting a cooling water temperature (radiator outlet water temperature T2) after passing through the radiator 13. The engine body 2 is provided with an engine outlet water temperature sensor 22 for detecting the coolant temperature (engine outlet water temperature TO) after passing through the outlet 11 b of the water jacket 11 as the coolant temperature of the engine body 2. Here, the engine outlet water temperature TO corresponds to the coolant temperature after passing through the engine.

  In addition to the bypass passage 15, the cooling device 10 further includes a plurality of heat receiving and radiating circuits provided in the radiator passage 12 so as to bypass the radiator 13. As these heat receiving and radiating circuits, a throttle body hot water circuit 31, an EGR cooler circuit 32, a hot water heating type hot air intake circuit 33, a heater circuit 34, and an oil cooler circuit 35 are provided.

  The throttle body warm water circuit 31 is connected to the throttle body 7, and the throttle body 7 is warmed in the process of cooling water (warm water) flowing through the circuit body 31. As a result, the operation of the throttle valve 8 at the time of extreme cold or the like is stabilized.

  The EGR cooler circuit 32 is connected in series downstream of the throttle body warm water circuit 31. A part of the EGR cooler circuit 32 is provided along the EGR device 36. As is well known, the EGR device 36 reduces the maximum combustion temperature of the combustible mixture by recirculating a part of the exhaust gas to the intake passage 4 in order to reduce nitrogen oxide (NOx) in the exhaust gas. It is. The EGR device 36 includes an EGR passage 37, an EGR valve 38, and an EGR chamber 39. The EGR passage 37 is provided between the exhaust passage 5 and the intake passage 4. The EGR valve 38 is provided in the middle of the EGR passage 37 and is configured to adjust the flow rate of EGR gas flowing through the EGR passage 37. The EGR chamber 39 is provided on the downstream side of the EGR passage 37, and is configured to guide EGR gas evenly to each cylinder. The EGR chamber 39, the EGR valve 38, and the intake passage 4 are cooled by the cooling water flowing through the EGR cooler circuit 32.

  The hot air intake circuit 33 is connected to the air cleaner 6. The circuit 33 includes a heater core (not shown) provided in the vicinity of the air cleaner 6, and air sucked into the intake passage 4 is warmed in the process in which cooling water passes through the heater core.

  The heater circuit 34 is connected to the heater core 40 of the vehicle interior heating device. The cooling water flowing through the heater circuit 34 is guided to the heater core 40 as a heat source, so that the vehicle compartment heating device functions.

  The oil cooler circuit 35 is connected to an oil cooler 41 for cooling the lubricating oil in the lubricating device of the engine 1 and the hydraulic oil (automatic transmission fluid: ATF) in the automatic transmission. When the cooling water flows through the oil cooler 41, the lubricating oil and ATF are quickly cooled at high temperatures. The oil cooler 41 also functions as an oil warmer when the temperature of the lubricating oil or ATF is low.

  The upstream portion of each of the above described heat receiving and radiating circuits is connected to the radiator passage 12 between the outlet 11 b of the water jacket 11 and the radiator 13. The downstream portions of these heat receiving and radiating circuits merge with each other and are connected to the water pump 14. A junction water temperature sensor 23 for detecting the cooling water temperature in the junction 42 as a junction water temperature T3 is provided in the vicinity of the junction 42 of each receiving and radiating circuit.

  The vehicle is provided with various sensors for detecting the operating state of the engine 1. In other words, the accelerator sensor 24 is provided in the accelerator pedal 43 provided in the driver's seat. The accelerator sensor 24 detects the depression amount (accelerator opening) ACCP of the accelerator pedal 43. A throttle sensor 25 provided in the throttle body 7 detects the opening degree (throttle opening degree) TA of the throttle valve 8. An intake pressure sensor 26 provided in the intake passage 4 downstream of the throttle body 7 detects the intake pressure PM in the intake passage 4. A rotational speed sensor 27 provided corresponding to the crankshaft 3 detects a rotational angle (crank angle) and a rotational speed (engine rotational speed) NE of the crankshaft 3. These sensors 24 to 27 correspond to an operation state detection means for detecting the operation state of the engine 1. In addition, the air cleaner 6 is provided with an intake air temperature sensor 51 for detecting the temperature (intake air temperature) THIA of the air taken into the intake passage 4. The intake air temperature sensor 51 detects the intake air temperature THIA instead of the outside air temperature, and corresponds to an outside air temperature detecting means. Here, the intake air temperature THIA is a factor that affects the volumetric efficiency and charging efficiency of the air taken into each cylinder of the engine 1 and, in turn, the compression pressure.

  In order to control the degree of cooling of the engine 1 in accordance with the operating state of the engine 1, the cooling device 10 controls the flow rate control valve 16 based on the operating state of the engine 1 to circulate the cooling water circulation flow rate in the cooling water circulation path. Adjust. In order to control this control, the cooling device 10 includes an electronic control unit (ECU) 30. The ECU 30 is connected to a radiator outlet temperature sensor 21, an engine outlet water temperature sensor 22, a junction water temperature sensor 23, and a flow rate control valve 16. In addition, an accelerator sensor 24, a throttle sensor 25, an intake pressure sensor 26, and a rotational speed sensor 27 are connected to the ECU 30 in order to capture the operating state of the engine 1. Further, an ignition switch (IGSW) 28 is connected to the ECU 30. The ignition switch 28 is operated to start and stop the engine 1. In addition, a vehicle speed sensor 51 and an outside air temperature sensor 52 are connected to the ECU 30.

  In this embodiment, the ECU 30 executes cooling water temperature control, and corresponds to the target cooling water temperature setting means in the present invention. As is well known, the ECU 30 includes a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), a backup RAM, an external input circuit, an external output circuit, and the like. The ECU 30 configures a logical operation circuit formed by connecting a CPU, a ROM, a RAM, a backup RAM, an external input circuit, an external output circuit, and the like through a bus. The ROM stores in advance a predetermined control program related to cooling water temperature control and the like. The RAM temporarily stores the calculation result of the CPU. The backup RAM stores data stored in advance. The CPU executes cooling water temperature control and the like according to a predetermined control program based on detection signals from various sensors 21 to 28 and 51 and the like input via the input circuit.

  Next, the content of the coolant temperature control executed by the ECU 30 will be described with reference to the flowcharts shown in FIGS. The ECU 30 periodically executes the routine shown in FIG. 2 at predetermined intervals.

  When the process proceeds to this routine, in step 100, the ECU 30 calculates the target engine outlet water temperature Tt based on the intake air temperature THIA obtained from the detected value of the intake air temperature sensor 51. The details of this calculation will be described in detail according to the flowchart shown in FIG.

  First, in step 101, the ECU 30 reads the intake air temperature THIA. Next, in step 102, the ECU 30 determines whether or not the read intake air temperature THIA is low. Here, for example, “15 ° C. or less” is assumed as “low temperature”. If the determination result is affirmative, in step 103, the ECU 30 sets the target engine outlet water temperature Tt to a higher “100 ° C.”. On the other hand, when the determination result of step 102 is negative, the ECU 30 shifts the process to step 104.

  In step 104, the ECU 30 determines whether or not the read intake air temperature THIA is an intermediate temperature. Here, for example, “15 to 35 ° C.” is assumed as “medium temperature”. If the determination result is affirmative, in step 105, the ECU 30 sets the target engine outlet water temperature Tt to “90 ° C.” that is slightly lower. On the other hand, if the determination result in step 104 is negative, the ECU 30 sets the target engine outlet water temperature Tt to a lower “80 ° C.” in step 106. In this way, the target engine outlet water temperature Tt in step 100 is calculated. Each value (100 degreeC, 90 degreeC, 80 degreeC) regarding the above-mentioned target engine outlet water temperature Tt is only an example. Here, the target engine outlet water temperature Tt corresponds to the target cooling water temperature in the present invention.

  Thereafter, returning to the flowchart of FIG. 2, in step 110, the ECU 30 determines the engine rotational speed NE and the engine load LE obtained from the detected values of the rotational speed sensor 27 and the intake pressure sensor 26, and the calculated target engine outlet water temperature. A cooling loss heat quantity QW is calculated based on Tt. In this calculation, the ECU 30 refers to function data (map) as shown in FIG. This map predetermines the relationship of the cooling loss heat quantity QW to the engine rotational speed NE, the engine load LE, and the target engine outlet water temperature Tt. FIG. 4 shows a change in the cooling loss heat quantity QW with respect to a certain value of the engine rotation speed NE. In this map, the cooling loss heat quantity QW is small when the engine load LE is small, and increases as the engine load LE increases. In this map, the cooling loss heat quantity QW increases as the target engine outlet water temperature Tt increases. This map is prepared for each value of the engine speed NE. Here, the cooling loss heat quantity QW increases as the engine speed NE increases. This is because the higher the engine speed NE is, the more fuel is supplied to the combustion chamber per unit time, and the more heat is generated in the engine body 2, and the more heat is taken away from the engine body 2 by the cooling water. Because it becomes.

  An engine load factor can be used instead of the engine load LE described above. The engine load factor is a parameter indicating a load ratio with respect to the maximum load. Also in this case, the smoothed engine load factor corresponding to the engine load factor is calculated, and a map according to FIG. 4 can be used.

  The above-described cooling loss heat quantity QW basically depends on the amount of heat generated from the engine body 2, and therefore, the engine load LE is a parameter related to the amount of heat generated from the engine body 2, for example, one combustion cycle. The fuel injection amount, the intake air amount, etc. can be used. The amount of intake air is a parameter indirectly related to the amount of heat generated from the engine body 2 because fuel according to the amount of intake air is injected in fuel injection control separately executed. In addition, as the engine load LE, it is possible to use the intake pressure PM detected by the intake pressure sensor 26, the throttle opening degree TA detected by the throttle sensor 25, etc., but in this case, the correction is made appropriately. It is desirable.

  Next, in step 120, the ECU 30 calculates a coolant flow rate (merging portion flow rate) V3 in the merging portion 42 based on the valve opening ODV of the flow control valve 16 and the engine speed NE. In this calculation, the ECU 30 refers to function data (map) as shown in FIG. This map predetermines the relationship of the junction flow rate V3 with respect to the valve opening degree ODV of the flow rate control valve 16 and the engine rotational speed NE. In this map, in the region where the valve opening degree ODV is small, as the valve opening degree ODV increases, the junction flow rate V3 gradually decreases. In the region where the valve opening degree ODV is medium to large, the junction flow rate V3 is substantially constant regardless of the valve opening degree ODV. Further, the merging portion flow rate V3 is small when the engine speed NE is low and increases as the engine speed NE increases. Here, the junction flow rate V3 corresponds to the coolant flow rate after passing through the circuit. As the above-described valve opening degree ODV, for example, the command opening degree ODC used by the ECU 30 for the flow control valve 16 in the previous control cycle can be applied.

Next, in step 130, the ECU 30 calculates the amount of received and radiated heat Qetc based on the various parameters obtained this time, that is, the merging portion flow rate V3, the merging portion water temperature T3, and the engine outlet water temperature TO. The ECU 30 calculates the amount of received and radiated heat Qetc (the total sum of the amounts of received and radiated heat in each of the circuits 31 to 35) in all the received and radiated circuits according to the following calculation formula (1). In the following calculation formula (1), “C” is a coefficient for converting the temperature into the flow rate, and is determined by, for example, the product of the specific heat of the cooling water and the density.
Qetc = C · V3 · (TOold−T3) (1)

Next, at step 140, the ECU 30 calculates the required radiator flow rate V2 based on the various parameters obtained this time, that is, the cooling loss heat quantity QW, the target engine outlet water temperature Tt, the radiator outlet water temperature T2, and the received and radiated heat quantity Qetc. The ECU 30 calculates the flow rate V2 according to the following calculation formula (2). In the following calculation formula (2), “C” means the same coefficient as described above.
V2 = (QW−Qetc) / {C · (Tt−T2)} (2)

  Next, in step 150, the ECU 30 calculates a command opening degree ODC for the flow rate control valve 16 based on the calculated required radiator flow rate V2 and the engine speed NE. In this calculation, the ECU 30 refers to function data (map) as shown in FIG. This map predetermines the relationship of the command opening degree ODC with respect to the required radiator flow rate V2 and the engine speed NE. In this map, the command opening degree ODC is small when the required radiator flow rate V2 is small, and increases as the required radiator flow rate V2 increases. Further, the command opening degree ODC changes greatly even when the required radiator flow rate V2 slightly changes when the engine speed NE is low. On the other hand, the command opening degree ODC does not change much when the engine speed NE is high unless the required radiator flow rate V2 changes much.

  Thereafter, in step 160, the ECU 30 drives and controls the flow rate control valve 16 based on the calculated command opening degree ODC, and then temporarily terminates the subsequent processing. By controlling the opening degree of the flow control valve 16 in this way, the flow rate of the cooling water passing through the radiator 13 is adjusted, and the engine outlet water temperature TO converges to the target engine outlet water temperature Tt.

  According to the engine cooling apparatus in this embodiment described above, the cooling loss heat quantity QW taken from the engine body 2 to the cooling water is calculated by the ECU 30 based on the operating state of the engine 1. In addition, the amount of received and radiated heat Qetc received and received between the receiving and radiating circuit (each circuit 31 to 35) and the cooling water is calculated by the ECU 30 based on the engine outlet water temperature TO, the merging portion water temperature T3, and the merging portion flow rate V3. The Further, in order to set the engine outlet water temperature TO to the target engine outlet water temperature Tt, the required radiator flow rate V2 of the cooling water required by the radiator 13 is calculated as the cooling loss heat quantity QW and the received and radiated heat quantity Qetc, respectively calculated as described above. In addition, the ECU 30 calculates the target engine outlet water temperature Tt and the radiator outlet water temperature T2. The command opening degree ODC is calculated by the ECU 30 based on the calculated required radiator flow rate V2, and the flow control valve 16 is driven and controlled based on the command opening degree ODC. The degree ODV is controlled. Thereby, the engine outlet water temperature TO is brought close to the target engine outlet water temperature Tt.

  Here, in this embodiment, as described above, the engine rotational speed NE and the engine load LE are reflected in the control of the valve opening degree ODV of the flow control valve 16 as the parameters relating to the operating state of the engine 1. For this reason, unlike the case where the valve opening degree ODV of the flow rate control valve 16 is controlled based solely on the temperature of the cooling water, the actual engine outlet water temperature TO is determined based on the engine rotational speed NE and the engine load LE. The target engine outlet water temperature Tt can be controlled. For example, when the engine 1 has a high output, the engine outlet water temperature TO can be lowered to increase the cooling efficiency of each cylinder. Further, when the engine 1 is operated with low fuel consumption, the engine outlet water temperature TO can be increased to improve the combustion efficiency in each cylinder. For this reason, the engine performance can be improved while satisfying the conflicting performances of high output and low fuel consumption.

  In this embodiment, the engine speed NE and the engine load LE are applied as parameters relating to the operating state of the engine 1 in order to calculate the cooling loss heat quantity QW. Thus, by applying the engine rotation speed NE and the engine load LE that influence the heat generation from the engine body 2 as parameters, the cooling loss heat quantity QW can be calculated with high accuracy. Further, since the cooling loss heat quantity QW is calculated based on both the engine rotation speed NE and the engine load LE, the calculation accuracy of the cooling loss heat quantity QW can be improved compared to the case where the engine rotation speed NE or the engine load LE is applied alone. Improvements can be made.

  In this embodiment, the cooling loss heat quantity QW is calculated based on the engine rotational speed NE indicating the operating state of the engine 1 and the engine load LE, and the calculated cooling loss heat quantity QW is reflected in the calculation of the required radiator flow rate V2. . Then, the valve opening degree ODV of the flow rate control valve 16 is controlled based on the calculated required radiator flow rate V2. For this reason, even if the operating state of the engine 1 changes and the cooling loss heat quantity QW changes, the valve opening degree ODV of the flow control valve 16 can be controlled according to the change in the cooling loss heat quantity QW, and the engine outlet The water temperature TO can be controlled to the target engine outlet water temperature Tt with good responsiveness.

  Here, in the conventional technique in which the valve opening degree of the flow rate control valve is feedback-controlled based only on the deviation (water temperature difference) between the cooling water temperature and the target cooling water temperature, it corresponds to the change in the cooling loss heat quantity QW in the engine body 2. Since this is not possible, it is difficult to obtain good responsiveness regarding control as in this embodiment. For this reason, in this embodiment, the engine outlet water temperature TO can be quickly decreased during the high-power operation of the engine 1 described above, and the engine outlet water temperature TO can be quickly increased during the low fuel consumption operation of the engine 1. It is possible to reduce the control loss that occurs when realizing both high output and low fuel consumption.

  Here, if the command opening degree ODC of the flow control valve 16 is directly calculated from the operating state of the engine 1 and the valve opening degree ODV of the flow control valve 16 is to be controlled based on the calculated command opening degree ODC. When flow control valves having different flow characteristics are used, it is necessary to calculate the command opening degree ODC again for each flow control valve, and the versatility is lacking. In contrast, in this embodiment, the required radiator flow rate V2 with respect to the radiator outlet water temperature T2 is once calculated, and the command opening degree ODC of the flow control valve 16 is calculated based on the calculated required radiator flow rate V2. . For this reason, even when flow control valves having different flow characteristics are used, it is not necessary to newly calculate the command opening degree ODC corresponding to the flow characteristics for each flow control valve.

  By the way, in this embodiment, since the radiator passage 12 is provided with a plurality of heat receiving and radiating circuits (each circuit 31 to 35) so as to bypass the radiator 13, in the process of cooling water passing through each circuit 31 to 35, each part Heat is received and released (received and radiated) between the cooling water and the cooling water. The cooling water after receiving and radiating heat passes through the radiator passage 12 from the junction 42 through the water pump 14 and again passes through the water jacket 11 of the engine body 2. When the amount of heat received and radiated heat Qetc in each circuit 31 to 35 is large, it is difficult to converge the engine outlet water temperature TO to the target engine outlet water temperature Tt unless the received and radiated heat amount Qetc is taken into consideration, and the cooling water temperature is exceeded. There is concern that shooting and undershooting will occur. Here, “overshoot” is a phenomenon in which the target engine outlet water temperature Tt cannot be maintained after the engine outlet water temperature TO reaches the target engine outlet water temperature Tt, and rises. The “undershoot” is a phenomenon in which, after the engine outlet water temperature TO reaches the target engine outlet water temperature Tt, the target engine outlet water temperature Tt cannot be maintained and falls.

  In this way, when many overshoots and undershoots occur in the cooling water temperature, it is necessary to consider the heat resistance of each component such as the engine body 2 to ensure the normal operation of each component. It is necessary to lower Tt. On the other hand, when the target engine outlet water temperature Tt is lowered, the engine outlet water temperature TO is lowered, so that friction may increase in the engine 1 or the automatic transmission, resulting in deterioration of fuel consumption.

  On the other hand, in this embodiment, the amount of received and radiated heat Qetc in all the heat receiving and radiating circuits (all of the circuits 31 to 35) is calculated, and the calculated amount of received and radiated heat Qetc is reflected in the calculation of the required radiator flow rate V2. . Therefore, even if the amount of received and radiated heat Qetc in each circuit 31 to 35 changes, the convergence property of the engine outlet water temperature TO with respect to the target engine outlet water temperature Tt is improved. For this reason, overshoot and undershoot in the cooling water temperature control can be reduced, and it is not necessary to lower the target engine outlet water temperature Tt in consideration of the heat resistance related to the components such as the engine body 2. As a result, it is possible to suppress an increase in friction associated with a decrease in the target engine outlet water temperature Tt, and thus a deterioration in fuel consumption of the engine 1.

  In this embodiment, when the water temperature difference between the merging portion water temperature T3 and the engine outlet water temperature TO is small, the amount of received and radiated heat Qetc in each circuit 31 to 35 is small, and conversely, when the water temperature difference is large, each circuit 31 to The amount of heat received and radiated at Q35 is large. Further, when the junction flow rate V3 is small, the amount of received and radiated heat Qetc in each circuit 31 to 35 is small, and when the junction portion flow rate V3 is large, the amount of received and radiated heat Qetc in each circuit 31 to 35 is large. With respect to this point, in this embodiment, the amount of received and radiated heat Qetc in each of the circuits 31 to 35 is calculated based on the merging portion flow rate V3, the merging portion water temperature T3, and the engine outlet water temperature TO. Therefore, since the merging portion flow rate V3, the merging portion water temperature T3, and the engine outlet water temperature TO as parameters that influence the received and radiated heat quantity Qetc as described above are applied to the calculation, the received and radiated heat quantity Qetc can be accurately calculated. . Therefore, the required radiator flow rate V2 can be calculated with high accuracy, and the flow control valve 16 can be controlled with high accuracy.

  On the other hand, conventionally, when the cooling water temperature becomes high, there is a concern that the anti-knocking performance of the engine is lowered, and the target engine outlet water temperature Tt cannot be raised so much. However, if the target engine outlet water temperature Tt is simply set low because there is a risk of knocking, it is possible that friction loss occurs in the engine and the fuel efficiency of the engine deteriorates.

  Here, if the target engine outlet water temperature Tt is simply set high, the engine outlet water temperature TO becomes high, thereby increasing the temperature of the air taken into each cylinder, and there is a concern that the anti-knocking performance of the engine 1 is lowered. On the other hand, in the cooling device 10 of this embodiment, the target engine outlet water temperature Tt is set according to the intake air temperature THIA corresponding to the outside air temperature. In particular, in this embodiment, when the intake air temperature THIA is relatively low “15 ° C. or less”, the target engine outlet water temperature Tt is set to “100 ° C.”, which is a relatively high temperature (high), and the intake air temperature THIA is When the engine temperature is relatively medium “15 to 35 ° C.”, the target engine outlet water temperature Tt is set to “90 ° C.” which is a relatively medium temperature (slightly lower), and the intake air temperature THIA is relatively high “35 ° C. or higher”. ", The target engine outlet water temperature Tt is set to" 80 ° C ", which is a relatively low temperature (lower). Therefore, when the intake air temperature THIA is relatively low, the target engine outlet water temperature Tt is set to a relatively high “100 ° C.”, thereby suppressing the temperature rise of the air taken into each cylinder of the engine 1. The engine body 2 is warmed up appropriately. Further, when the intake air temperature THIA is relatively high, the target engine outlet water temperature Tt is set to a relatively low “80 ° C.”, thereby suppressing the temperature rise of the air taken into each cylinder of the engine 1. The engine body 2 is cooled appropriately. For this reason, in the engine cooling device in which the cooling water temperature of the engine 1, that is, the engine outlet water temperature TO is controlled to the target engine outlet water temperature Tt, the target engine outlet water temperature Tt is reduced without reducing the anti-knocking performance of the engine 1. Thus, the controllability of the cooling water temperature can be improved. As a result, engine friction can be reduced and engine fuel efficiency can be improved.

  Here, the relationship between the intake air temperature THIA and knocking is shown in a graph in FIG. This graph represents the relationship of the shaft torque (crankshaft 3 torque) with respect to the ignition timing of the engine by the difference in intake air temperature THIA. As is apparent from this graph, as the intake air temperature THIA increases, the shaft torque decreases and the trace knock point advances. From this, it can be seen that the higher the intake air temperature THIA, the lower the anti-knocking performance. In contrast, in this embodiment, as the intake air temperature THIA increases as described above, the target engine outlet water temperature Tt is set to a relatively low temperature. Therefore, the engine outlet water temperature TO becomes relatively higher as the intake air temperature THIA increases. As a result, the temperature of the air taken into each cylinder is lowered, and it can be seen that a decrease in the anti-knocking performance of the engine 1 can be suppressed.

  In this embodiment, the merging portion flow rate V3 is calculated based on the valve opening degree ODV and the engine rotational speed NE, which are control amounts of the flow rate control valve 16, and accordingly, according to the cooling water flow rate in the cooling water circulation path such as the radiator passage 12. Thus, the amount of received and radiated heat Qetc is calculated more accurately. As a result, the required radiator flow rate V2 can be calculated more accurately, the command opening degree ODC of the flow control valve 16 can be calculated more accurately, and the flow control valve 16 can be controlled more accurately. Can do. Thereby, the engine outlet water temperature TO can be more suitably converged to the target engine outlet water temperature Tt, and the controllability of the cooling water temperature of the engine 1 can be further improved.

  In addition, this invention is not limited to the said embodiment, In the range which does not deviate from the meaning of invention, it can also implement as follows.

  (1) In the above embodiment, the intake air temperature THIA detected by the intake air temperature sensor 51 is used as the outside air temperature to calculate the target engine outlet water temperature Tt. However, the outside air temperature detected by the outside air temperature sensor is used as the target engine outlet water temperature Tt. It may be used for calculation.

  (2) In the above embodiment, a plurality of circuits, that is, the throttle body hot water circuit 31, the EGR cooler circuit 32, the hot air intake circuit 33, the heater circuit 34, and the oil cooler circuit 35 are provided as the heat receiving and radiating circuits. On the other hand, all these circuits 31 to 35 may be omitted from the heat receiving and radiating circuit, and at least one of the circuits 31 to 35 may be provided as the heat receiving and radiating circuit. Also in this case, basically, the same effect as that of the first embodiment can be obtained.

The schematic block diagram which shows an engine system. The flowchart which shows the content of cooling water temperature control. The flowchart which shows a part in detail the content of cooling water temperature control. The map which shows the relationship of a cooling loss calorie | heat amount with respect to engine speed, engine load, and target engine exit water temperature. The map which shows the relationship of the valve opening degree and the flow volume of a junction part with respect to an engine speed. A map showing the relationship between the required radiator flow rate and the command opening relative to the engine speed. The graph which shows the relationship of the shaft torque with respect to ignition timing and intake air temperature.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Engine 10 ... Cooling device 11 ... Water jacket (cooling water circulation path)
12. Radiator passage (cooling water circulation path)
13 ... Radiator 16 ... Flow rate control valve (flow rate adjusting means)
30 ... ECU (target cooling water temperature setting means)
TO ... Engine outlet water temperature Tt ... Target engine outlet water temperature QW ... Cooling heat loss V2 ... Required radiator flow rate

Claims (2)

A cooling water circulation path through which engine cooling water circulates; a radiator provided in the cooling water circulation path; and a flow rate adjusting means for adjusting a cooling water flow rate passing through the radiator; An engine cooling apparatus configured to control the flow rate adjusting means so as to have a cooling water temperature,
An engine cooling apparatus comprising a target cooling water temperature setting means for setting the target cooling water temperature according to an outside air temperature. The target cooling water temperature setting means sets the target cooling water temperature to a relatively high temperature when the outside air temperature is relatively low, and sets the target cooling water temperature to a relatively low temperature when the outside air temperature is relatively high. The engine cooling device according to claim 1, wherein the engine cooling device is set to a temperature.

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