Engine System

Abstract

To adjust a wall temperature of a combustion chamber with high responsiveness in accordance with a load of an engine.SOLUTION: An engine system 1 includes an engine 10, a circulation device 91 for circulating cooling water to a water jacket 20, and a controller (ECU 100). The circulation device includes a radiator flow passage 53 including a heat exchanger (radiator 27), a bypass flow passage 51, a flow control device (cooling water control valve 4), and a thermostat valve 28. The engine switches between first combustion in which an air-fuel mixture is burned without forcible ignition of an ignition device and second combustion in which the air-fuel mixture is burned by forcible ignition of the ignition device. The controller controls the flow control device so that a flow rate of the cooling water flowing in the water jacket is adjusted in accordance with a load by closing the radiator flow passage and adjusting a flow rate of the cooling water flowing through the bypass flow passage when the engine carries out the first combustion.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The technology disclosed herein relates to an engine system. [Background technology]

[0002] Patent Document 1 discloses an engine cooling device. This cooling device has a radiator path (23, the symbol shown in the specification; the same applies hereinafter) that circulates coolant between the engine and a radiator, and a radiator bypass path (24) that circulates coolant bypassing the radiator. A heater core (31) of an air conditioner and an ATF warmer (32) that warms lubricating oil for an automatic transmission are disposed in the radiator bypass path (24).

[0003] The cooling system includes a rotary flow control valve (50). The rotary flow control valve (50) opens and closes the radiator path (23) and the radiator bypass path (24) depending on the rotational position of a rotary valve element (51). The rotary flow control valve (50) also includes a radiator path connecting path (71) and a thermostat valve placement path (72). The radiator path connecting path (71) is connected to the radiator path (23). A thermostat valve (40) is provided in the thermostat valve placement path (72). When the thermostat valve 40 is open, the coolant flows from the thermostat valve placement path (72) to the radiator path (23).

[0004] When the engine is warm and the temperature of the cooling water is equal to or higher than a predetermined temperature, the rotary flow control valve (50) rotates the rotary valve element (51) to a rotational position that allows the cooling water to flow through both the radiator bypass path (24) and the thermostat valve path (72). When the engine is warm, the thermostat valve (40) opens, and the cooling water flows from the thermostat valve path (72) to the radiator path (23).

[0005] When the temperature of the cooling water further increases, the rotary flow control valve (50) adjusts the rotational position of the rotary valve element (51) to a rotational position that allows the cooling water to flow through all of the radiator bypass path (24), the thermostat valve installation path (72), and the radiator path connection path (71). Furthermore, the rotational position of the rotary valve element (51) is adjusted so that the flow rate of the cooling water into the radiator path (23) increases as the temperature of the cooling water, the engine load, and / or the engine speed increases. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-128652 Summary of the Invention [Problem to be solved by the invention]

[0007] After the engine has fully warmed up, the combustion chamber becomes very hot. To cool the combustion chamber, as in the cooling device of Patent Document 1, a flow path, known as a water jacket, through which coolant cooled by a radiator flows is provided around the combustion chamber in the cylinder bore, cylinder head, and other components that make up the main body of the engine.

[0008] Incidentally, the temperature inside the combustion chamber (in-cylinder temperature) is one of the important factors in engine combustion control. The more advanced the combustion control, the more precise control of in-cylinder temperature is required. For example, to stably control compression ignition combustion, it is necessary to control the in-cylinder temperature at a higher temperature than spark ignition combustion, and with high precision. In addition, the amount of heat generated in the combustion chamber changes depending on the engine load, so the in-cylinder temperature also changes.

[0009] The wall temperature of the combustion chamber is one of the important factors in controlling the temperature inside the cylinder. It is necessary to adjust the wall temperature of the combustion chamber with good responsiveness to changes in the engine load.

[0010] In this regard, the cooling device of Patent Document 1 lowers the temperature of the coolant by increasing the flow rate of the coolant flowing through the radiator path when the coolant temperature rises. When the coolant temperature changes, the amount of heat exchanged between the coolant and the combustion chamber changes. By changing the amount of heat exchange according to the amount of heat generated in the combustion chamber, the wall temperature of the combustion chamber can be adjusted.

[0011] However, because the heat capacity of the coolant is large, it takes a long time to change the coolant temperature, making it difficult to adjust the combustion chamber wall temperature in a responsive manner to changes in engine load by adjusting the coolant temperature.

[0012] The technology disclosed herein adjusts the wall temperature of the combustion chamber with high responsiveness in accordance with the engine load. [Means for solving the problem]

[0013] The inventors of the present application focused on the fact that the wall temperature of the combustion chamber can be adjusted by changing the heat transfer coefficient between the cooling water and the combustion chamber by changing the flow rate of the cooling water flowing through the water jacket, rather than by changing the temperature of the cooling water, and completed the technology disclosed herein.

[0014] The technology disclosed herein relates to an engine system, and the engine system includes: an engine having a water jacket disposed around a combustion chamber; a circulation device attached to the engine and circulating cooling water through the water jacket; a controller that controls the circulation device in accordance with an operating state of the engine, The circulation device is a radiator flow path including a heat exchanger; a bypass flow path that bypasses the heat exchanger; a flow rate adjusting device that adjusts the flow rate of the cooling water flowing through the water jacket by adjusting the flow rate of the cooling water flowing through the radiator flow path and the bypass flow path; a thermostat valve connected to the radiator flow path and opening to allow the coolant to pass through the heat exchanger; the engine has an ignition device that forcibly ignites the air-fuel mixture, and switches between a first combustion in which the air-fuel mixture is burned without forcible ignition by the ignition device and a second combustion in which the air-fuel mixture is burned by forcible ignition by the ignition device; The controller is electrically connected to the flow rate adjusting device, and When the engine is performing the first combustion, the flow control device is controlled to close the radiator flow path and adjust the flow rate of the cooling water flowing through the bypass flow path, thereby adjusting the flow rate of the cooling water flowing through the water jacket in accordance with the load of the engine.

[0015] According to this configuration, the cooling water passing through the water jacket of the engine exchanges heat with the combustion chamber. The cooling water is circulated through the water jacket by the circulation device.

[0016] The circulation device has a thermostatic valve that opens when the coolant is at a predetermined temperature. When the thermostatic valve opens, a portion of the coolant passes through a heat exchanger, lowering the coolant temperature. The thermostatic valve maintains the coolant at a specific temperature corresponding to the opening temperature of the thermostatic valve.

[0017] When the engine is performing the first combustion, the flow control device closes the radiator flow path. The coolant flows through the bypass flow path. The flow control device also adjusts the flow rate of the coolant, thereby changing the flow rate of the coolant flowing through the water jacket. Because the flow control device can change the flow rate of the coolant more quickly than the temperature of the coolant, the flow control device can adjust the flow rate of the coolant flowing through the water jacket with high responsiveness to changes in load.

[0018] When the flow rate of the cooling water flowing through the water jacket decreases, the heat transfer coefficient decreases, and when the flow rate of the cooling water flowing through the water jacket increases, the heat transfer coefficient increases. The amount of heat generated in the combustion chamber changes depending on the engine load. Therefore, in the engine system described above, the controller changes the flow rate of the cooling water flowing through the water jacket via the flow rate adjustment device depending on the engine load, so the wall temperature of the combustion chamber can be adjusted with high responsiveness.

[0019] When the engine is performing the second combustion, the controller Opening the radiator flow path and the bypass flow path, The flow rate adjusting device is controlled so that the cooling water flows through each of the radiator flow path and the bypass flow path. do.

[0020] When the engine is performing secondary combustion, that is, when the air-fuel mixture is burned by forced ignition of the ignition device, the thermal efficiency is lower than when the engine is performing primary combustion. The amount of heat radiated to the wall of the combustion chamber increases. When the engine is performing secondary combustion, the controller controls the flow rate adjustment device to allow the coolant to flow through both the radiator passage and the bypass passage. For example, by increasing the flow rate of the coolant flowing through the radiator passage, the coolant temperature decreases. When the engine is performing secondary combustion, the wall temperature of the combustion chamber reaches an appropriate temperature.

[0021] When the engine is performing the first combustion, the controller may increase the flow rate of the cooling water flowing through the water jacket when the load is high compared to when the load is low.

[0022] As the engine load increases, the amount of heat generated in the combustion chamber increases. When the load is high, the flow rate of the cooling water flowing through the water jacket increases compared to when the load is low, which increases the heat transfer coefficient. This helps maintain the combustion chamber wall temperature at an appropriate level.

[0023] The controller may adjust the temperature of the cooling water flowing through the water jacket in accordance with the load by adjusting the flow rate of the cooling water flowing through the bypass passage and the flow rate of the cooling water flowing through the radiator passage when the engine is performing the second combustion.

[0024] When the flow rate of the coolant flowing through the radiator passage increases, the temperature of the coolant drops. As the load increases, the amount of heat generated in the combustion chamber increases, but by adjusting the temperature of the coolant flowing through the water jacket according to the load, the wall temperature of the combustion chamber is kept at an appropriate temperature.

[0025] When the engine is performing the second combustion, the controller may reduce the flow rate of the cooling water flowing through the bypass passage and increase the flow rate of the cooling water flowing through the radiator passage when the load is high, compared to when the load is low.

[0026] When the flow rate of the coolant flowing through the radiator passage increases, the temperature of the coolant decreases. When the load is high and the amount of heat generated in the combustion chamber is large, the coolant temperature decreases, and the wall temperature of the combustion chamber becomes appropriate. Conversely, when the flow rate of the coolant flowing through the radiator passage decreases, the coolant temperature increases. When the load is low and the amount of heat generated in the combustion chamber is small, the coolant temperature increases, and the wall temperature of the combustion chamber becomes appropriate.

[0027] The controller may set the flow rate of the cooling water flowing through the water jacket to a maximum flow rate when the engine is performing the second combustion.

[0028] When the engine is performing secondary combustion, the amount of heat dissipated to the combustion chamber wall increases. By maximizing the flow rate of the coolant flowing through the water jacket, the wall temperature of the combustion chamber will be at an appropriate temperature when the engine is performing secondary combustion.

[0029] The controller may maintain a wall temperature of the combustion chamber at a constant temperature when the engine is performing the first combustion and when the engine is performing the second combustion.

[0030] The ideal combustion chamber wall temperature when an engine is performing primary combustion does not necessarily match the ideal combustion chamber wall temperature when the engine is performing secondary combustion. When primary combustion is being performed, the mixture burns by self-ignition, so a high combustion chamber wall temperature is preferable from the perspective of ignition stability. On the other hand, when secondary combustion is being performed, if the combustion chamber wall temperature is too high, it may lead to abnormal combustion, such as so-called knocking. Therefore, it is ideal to change the combustion chamber wall temperature in response to the change in combustion mode. However, because the combustion chamber wall also has a large heat capacity, it is difficult to raise or lower the temperature of the combustion chamber wall in a short period of time.

[0031] Therefore, the above configuration maintains the combustion chamber wall temperature at a specific temperature that is acceptable when the engine is performing the first combustion and when the engine is performing the second combustion. Specifically, when the engine is performing the first combustion, the wall temperature of the combustion chamber is maintained at the specific temperature by adjusting the flow rate of the coolant flowing through the water jacket according to the load while maintaining the coolant temperature using the thermostat valve. When the engine is performing the second combustion, the flow rate of the coolant flowing through the bypass passage and the radiator passage is adjusted to adjust the temperature of the coolant flowing through the water jacket according to the load, thereby maintaining the wall temperature of the combustion chamber at the same specific temperature. As a result, the wall temperature of the combustion chamber remains appropriate even when the engine's combustion mode changes.

[0032] The controller may lower the temperature of the cooling water flowing through the water jacket below a valve opening temperature of the thermostat valve when the engine is performing the second combustion.

[0033] When the engine is performing secondary combustion, the amount of heat radiated to the combustion chamber wall increases. By relatively lowering the temperature of the cooling water flowing through the water jacket when the engine is performing secondary combustion, the wall temperature of the combustion chamber can be kept at an appropriate temperature.

[0034] When the engine is performing primary combustion, the amount of heat radiated to the combustion chamber wall is reduced. When the engine is performing primary combustion, the temperature of the cooling water is determined by the opening temperature of the thermostat valve, as described above. By setting the opening temperature of the thermostat valve to a relatively high temperature, the temperature of the cooling water flowing through the water jacket increases relatively, allowing the wall temperature of the combustion chamber to be kept at an appropriate temperature.

[0035] The controller may be configured to increase the flow rate of the cooling water flowing through the radiator flow path when the engine is performing the second combustion and the load is lower than a predetermined load, so that the temperature of the cooling water flowing through the water jacket decreases as the load increases, and to increase the flow rate of the cooling water flowing through the radiator flow path when the load is equal to or greater than the predetermined load, so that the temperature of the cooling water flowing through the water jacket remains constant as the load increases.

[0036] When the load is lower than a specified load, the temperature of the cooling water flowing through the water jacket decreases as the load increases. The wall temperature of the combustion chamber can be maintained at a constant temperature regardless of the increase in load. When the load is higher than a specified load, the temperature of the cooling water flowing through the water jacket remains constant regardless of the increase in load. The wall temperature of the combustion chamber can be maintained at an appropriate temperature.

[0037] The controller may determine a combustion mode of the engine based on at least the detected accelerator opening, and control the circulation device in accordance with the determined combustion mode.

[0038] The combustion mode of the engine may be determined in accordance with at least the accelerator opening, in other words, the engine load.

[0039] the flow rate adjusting device is installed at a location where the bypass flow path and the radiator flow path branch off or at a location where the bypass flow path and the radiator flow path join together, the circulation device further includes a communication passage that connects the bypass passage and the radiator passage, The thermostat valve may open and close the communication passage.

[0040] With this configuration, when the radiator passage is closed and the temperature of the cooling water rises, the thermostat valve opens, allowing the cooling water to flow from the bypass passage to the radiator passage. The temperature of the cooling water drops, and the thermostat valve can maintain the cooling water at a predetermined temperature.

[0041] the flow rate adjusting device is installed at a location where the bypass flow path and the radiator flow path branch off or at a location where the bypass flow path and the radiator flow path join together, the circulation device further includes a communication passage that bypasses the flow rate adjustment device and connects the water jacket and the radiator passage, The thermostat valve may open and close the communication passage.

[0042] With this configuration, when the radiator passage is closed by the flow control device, if the coolant temperature rises and the thermostat valve opens, the coolant bypasses the flow control device and flows into the radiator passage. The coolant temperature drops. Even in this case, the thermostat valve can maintain the coolant at a predetermined temperature.

[0043] The flow rate adjusting device is a housing provided with a first port connected to the bypass flow path, a second port connected to the radiator flow path, and a third port connected to each of the first port and the second port; a rotary valve element that is rotatably accommodated in the housing, that is interposed between the first port, the second port, and the third port, and that has a first water passage opening that is connected to the first port and a second water passage opening that is connected to the second port; an actuator that adjusts the flow rate of cooling water flowing through each of the first port and the second port by rotating the rotary valve body to change the opening degree of each of the first water passage opening and the second water passage opening; It may also be said that the

[0044] The flow control device having a rotary valve body can selectively close the bypass passage and / or the radiator passage and can adjust the flow rate of the bypass passage and the flow rate of the radiator passage. An engine system equipped with the flow control device can achieve the above-mentioned flow rate adjustment of the water jacket with a simple configuration. [Effects of the Invention]

[0045] As described above, the engine system described above can adjust the wall temperature of the combustion chamber with high responsiveness in accordance with the engine load. [Brief explanation of the drawings]

[0046] [Figure 1] FIG. 1 illustrates an exemplary engine system. [Figure 2] FIG. 2 is a block diagram of an exemplary engine system. [Figure 3] FIG. 3 shows an example control map for an engine system. [Figure 4] FIG. 4 shows an exemplary circulation device. [Figure 5] FIG. 5 illustrates an exemplary flow regulator. [Figure 6] FIG. 6 shows an exemplary control of the circulation device. [Figure 7] FIG. 7 shows an exemplary control of the circulation device. [Figure 8] FIG. 8 shows an exemplary control procedure for the circulation device. [Figure 9] FIG. 9 shows an exemplary control procedure for the circulation device. [Figure 10] FIG. 10 shows an exemplary circulation device. DETAILED DESCRIPTION OF THE INVENTION

[0047] Hereinafter, an embodiment of an engine system will be described with reference to the drawings. The engine system described here is an example.

[0048] (Example of engine system configuration) 1 and 2 show an example of the configuration of an engine system 1. The engine system 1 is mounted on an automobile. The engine system 1 includes an engine 10, which is an internal combustion engine. When the engine 10 is operating, the automobile moves. The automobile may be a vehicle equipped with only the engine 10 as a power source for traveling, or may be a hybrid automobile equipped with both the engine 10 and an electric motor.

[0049] The engine 10 includes a cylinder block 11 and a cylinder head 12. A plurality of cylinders 13 are formed in the cylinder block 11. The engine 10 is a multi-cylinder engine.

[0050] The multiple cylinders 13 are aligned in a row along the crankshaft 14 (see also FIG. 4). A piston 15 is inserted into each cylinder 13. The piston 15 is connected to the crankshaft 14 via a connecting rod 151. The piston 15, the cylinder 13, and the cylinder head 12 form a combustion chamber 16.

[0051] The cylinder head 12 is formed with intake ports 121 that communicate with each cylinder 13. An intake valve 122 disposed in the intake port 121 opens and closes the intake port 121. An intake valve train 123 (see FIG. 2) opens and closes the intake valve 122 at a predetermined timing. The intake valve train 123 is a variable valve train that varies the valve timing and / or the valve lift.

[0052] Exhaust ports 124 communicating with each cylinder 13 are formed in the cylinder head 12. Exhaust valves 125 disposed in the exhaust ports 124 open and close the exhaust ports 124. An exhaust valve train 126 opens and closes the exhaust valves 125 at predetermined timing. The exhaust valve train 126 is a variable valve train that varies valve timing and / or valve lift.

[0053] An injector 131 is attached to the cylinder head 12 for each cylinder 13. The injector 131 directly injects fuel into the cylinder 13. A spark plug 132 is attached to the cylinder head 12 for each cylinder 13. The spark plug 132 forcibly ignites the air-fuel mixture in the cylinder 13.

[0054] An intake passage 17 is connected to one side of the engine 10. The intake passage 17 is in communication with an intake port 121. A throttle valve 171 is disposed in the intake passage 17. The throttle valve 171 adjusts the amount of air introduced into the cylinder 13. An exhaust passage 18 is connected to the other side of the engine 10. The exhaust passage 18 is in communication with an exhaust port 124.

[0055] An EGR passage 19 is connected between the intake passage 17 and the exhaust passage 18. The EGR passage 19 recirculates a portion of the exhaust gas back into the intake passage 17. An EGR cooler 191 is disposed in the EGR passage 19. The EGR cooler 191 cools the exhaust gas. An EGR valve 192 is also disposed in the EGR passage 19. The EGR valve 192 adjusts the flow rate of the exhaust gas flowing through the EGR passage 19.

[0056] The engine system 1 includes an ECU (Engine Control Unit) 100 for operating the engine 10. The ECU 100 is a controller based on a well-known microcomputer, and includes a central processing unit (CPU) 101, a memory 102, and an I / F circuit 103. The CPU 101 executes programs. The memory 102 is configured, for example, by a RAM (Random Access Memory) or a ROM (Read Only Memory) and stores programs and data. The I / F circuit 103 inputs and outputs electrical signals. The ECU 100 is an example of a controller.

[0057] Various sensors SN1 to SN5 are connected to the ECU 100. The sensors SN1 to SN5 output signals to the ECU 100. The sensors include the following sensors. First water temperature sensor SN1: In a cooling water circulation device 91 described later, outputs a signal corresponding to the temperature of the cooling water flowing into the engine 10. Second water temperature sensor SN2: attached to the engine 10, outputs a signal corresponding to the temperature of the cooling water flowing inside the engine 10. Cylinder pressure sensor SN3: attached to the cylinder head 12 and outputs a signal corresponding to the pressure in each cylinder 13. Crank angle sensor SN4: attached to the engine 10 and outputs a signal corresponding to the rotation angle of the crankshaft 14. Accelerator opening sensor SN5: Attached to the accelerator pedal mechanism, it outputs a signal corresponding to the amount of accelerator pedal operation.

[0058] The ECU 100 determines the operating state of the engine 10 based on signals from these sensors SN1 to SN5, and calculates control variables for each device according to a predetermined control logic. The control logic is stored in the memory 102. The control logic includes calculating target variables and / or control variables using maps stored in the memory 102. The ECU 100 outputs electrical signals related to the calculated control variables to the injector 131, the spark plug 132, the intake valve train 123, the exhaust valve train 126, the throttle valve 171, the EGR valve 192, and the coolant control valve 4, which will be described later.

[0059] More specifically, the ECU 100 has a load calculation unit 104, a combustion type determination unit 105, a water temperature determination unit 106, and a CCV control unit 107 as functional blocks.

[0060] The load calculation unit 104 calculates a target load for the engine 10 based on the output signal of the accelerator opening sensor SN5. The combustion mode determination unit 105 determines the operating range of the engine 10 in a base map 301 (see FIG. 3), which will be described later, based on the load of the engine 10 and the output signal of the crank angle sensor SN4, and determines the combustion mode corresponding to the operating range. The water temperature determination unit 106 determines the temperature of the coolant flowing through a water jacket 20 (see FIG. 4) around the combustion chamber 16 based on the output signal of the second water temperature sensor SN2. The CCV control unit 107 cools the engine 10 by controlling the coolant control valve 4 according to the operating state of the engine 10.

[0061] (Engine operation control map) 3 illustrates a base map 301 related to the control of the engine 10. The base map 301 is stored in the memory 102 of the ECU 100. The illustrated base map 301 is the base map 301 when the engine 10 is fully warmed up.

[0062] The base map 301 is defined by the load and rotation speed of the engine 10. The base map 301 is roughly divided into four regions according to the high and low loads and the high and low rotation speeds. More specifically, the first region 311 includes a region from low load to high load at high rotation speeds and a region of high load at low and medium rotation speeds. The second region 312 is a region of low load at low and medium rotation speeds. The third region 313 is a region of low to medium load at low and medium rotation speeds. The fourth region 314 is a region of medium to high load at low and medium rotation speeds. Note that the low rotation speed region, medium rotation speed region, and high rotation speed region may respectively be defined as the low rotation speed region, medium rotation speed region, and high rotation speed region when the entire operating region of the engine 10 is divided into approximately three equal parts in the rotation speed direction into the low rotation speed region, medium rotation speed region, and high rotation speed region.

[0063] Next, a brief description will be given of the operation of the engine 10 in each range. The ECU 100 determines the operating range according to the target load on the engine 10 and the rotation speed of the engine 10, and according to the determined operating range, the ECU 100 changes the opening and closing operations of the intake valve 122 and the exhaust valve 125, the fuel injection timing, and whether or not forced ignition is performed. As a result, the combustion mode of the engine 10 changes to SI (Spark Ignition) combustion, HCCI (Homogeneous Charge Compression Ignition) combustion, MPCI (Multiple Premixed fuel injection Compression Ignition) combustion, and SPCCI (Spark Controlled Compression Ignition) combustion.

[0064] (SI combustion) When the operating state of the engine 10 is in the first region 311, the ECU 100 causes the mixture in the cylinder 13 to undergo flame propagation combustion. The intake valve train 123 opens the intake valve 122 at a predetermined timing and / or with a predetermined lift amount, and the exhaust valve train 126 opens the exhaust valve 125 at a predetermined timing and / or with a predetermined lift amount. The injector 131 injects fuel into the cylinder 13 during the intake stroke and / or compression stroke. The spark plug 132 ignites the mixture near the top dead center of the compression stroke.

[0065] (HCCI combustion) When the operating state of the engine 10 is in the second region 312, the ECU 100 causes the air-fuel mixture in the cylinder 13 to undergo compression ignition and combustion. The intake valve train 123 opens the intake valve 122 at a predetermined timing and / or with a predetermined lift amount, and the exhaust valve train 126 opens the exhaust valve 125 at a predetermined timing and / or with a predetermined lift amount. The injector 131 injects fuel into the cylinder 13 during the intake stroke. The spark plug 132 does not ignite the air-fuel mixture. The air-fuel mixture undergoes compression autoignition and combustion near the top dead center of compression.

[0066] (MPCI combustion) When the operating state of engine 10 is in third region 313, ECU 100 causes the air-fuel mixture in cylinder 13 to undergo compression ignition and combustion. Intake valve train 123 opens intake valve 122 at a predetermined timing and / or with a predetermined lift amount, and exhaust valve train 126 opens exhaust valve 125 at a predetermined timing and / or with a predetermined lift amount. Injector 131 injects fuel into cylinder 13 during both the intake stroke and the compression stroke. Injector 131 performs split injection. Spark plug 132 does not ignite the air-fuel mixture. The air-fuel mixture undergoes compression auto-ignition and combustion near top dead center of compression.

[0067] Split injection creates a non-homogeneous mixture in the cylinder 13. In this respect, MPCI combustion differs from HCCI combustion, which forms a homogeneous mixture. MPCI combustion makes it possible to control the timing of compression ignition when the engine 10 is operating under relatively high load.

[0068] (SPCCI combustion) When the operating state of the engine 10 is in the fourth region 314, the ECU 100 causes a portion of the mixture in the cylinder 13 to undergo flame propagation combustion and the remainder to undergo compression ignition combustion. The intake valve train 123 opens the intake valve 122 at a predetermined timing and / or with a predetermined lift amount, and the exhaust valve train 126 opens the exhaust valve 125 at a predetermined timing and / or with a predetermined lift amount. The injector 131 injects fuel into the cylinder 13 during the compression stroke. The spark plug 132 ignites the mixture near the top dead center of the compression stroke. The mixture begins flame propagation combustion. The heat generated by the combustion increases the temperature inside the cylinder 13, and the flame propagation increases the pressure inside the cylinder 13. As a result, the unburned mixture undergoes compression auto-ignition, for example, after the top dead center of the compression stroke, and begins combustion. After the compression ignition combustion begins, the flame propagation combustion and the compression ignition combustion proceed in parallel.

[0069] (Circulation system configuration) Next, the configuration of the circulation device 91 of the engine system 1 will be described with reference to Fig. 4. The circulation device 91 is attached to the engine 10 and circulates the cooling water through the water jacket 20.

[0070] The water jacket 20 is formed inside the engine 10. The water jacket 20 is connected to a circulation device 91 and, together with the circulation device 91, forms a circuit through which the coolant circulates. The water jacket 20 has an in-block jacket 21 and an in-head jacket 22. The in-block jacket 21 is formed in the cylinder block 11 so as to extend along the outer periphery of each cylinder 13.

[0071] The in-head jacket 22 is formed in the cylinder head 12. The in-head jacket 22 communicates with the in-block jacket 21 (see the dotted line in FIG. 4). The in-head jacket 22 has a first jacket 22a and a second jacket 22b. The first jacket 22a and the second jacket 22b are independent of each other.

[0072] The first jacket 22a is formed to extend along the upper portions of the plurality of combustion chambers 16 arranged in a row. The cooling water flowing through the first jacket 22a mainly exchanges heat with (mainly cools) the combustion chambers 16. In detail, the cooling water flowing through the first jacket 22a exchanges heat with the atmosphere in the combustion chambers 16 via the wall surfaces of the combustion chambers 16.

[0073] The second jacket 22b is formed to extend along the periphery of the exhaust ports 124 of the aligned cylinders 13. The cooling water flowing through the second jacket 22b mainly exchanges heat with (mainly cools) the exhaust ports 124 through which high-temperature exhaust gas flows.

[0074] A water pump 3 is installed in a cylinder block 11 at an end (inlet end 10a) of the engine 10. The water pump 3 constitutes a part of a circulation device 91.

[0075] The water pump 3 is a mechanical pump in which a rotating shaft of the pump is connected to the crankshaft 14 of the engine 10 via a pulley, a belt, etc. The water pump 3 is operated by the driving force of the engine 10. However, the water pump 3 may also be an electric pump that can be operated independently of the engine 10.

[0076] The intra-block jacket 21 is connected to the discharge port 3a of the water pump 3 via a cooling water introduction passage 23. Therefore, the cooling water discharged from the water pump 3 flows into the intra-block jacket 21 through the cooling water introduction passage 23. The cooling water that has flowed into the intra-block jacket 21 flows into the intra-head jacket 22. More specifically, the cooling water is divided into the first jacket 22a and the second jacket 22b and flows therein.

[0077] A coolant control valve 4 (CCV, which corresponds to the "flow rate adjusting device" in the disclosed technology) is installed in the cylinder head 12 at the end (outlet end 10b) opposite to the inlet end 10a of the engine 10. The coolant control valve 4 constitutes a part of the circulation device 91.

[0078] A third port 65 (see FIG. 5) of the coolant control valve 4 is connected to the first jacket 22a via the first coolant outlet passage 24. Therefore, the coolant flowing through the first jacket 22a flows out of the engine 10 through the first coolant outlet passage 24 and flows into the coolant control valve 4 (the details of the coolant control valve 4 will be described later).

[0079] A second cooling water outlet passage 25 communicating with the second jacket 22b is formed in a portion of the outlet end portion 10b on the exhaust side of the cylinder head 12. Therefore, the cooling water flowing through the second jacket 22b passes through the second cooling water outlet passage 25, flows out of the engine 10, and enters a second circulation passage 31, which will be described later.

[0080] A third cooling water outlet passage 26 communicating with the block inner jacket 21 is formed in a portion of the intake side of the cylinder block 11 at the outlet end 10b. Therefore, a portion of the cooling water flowing through the block inner jacket 21 flows out of the engine 10 through the third cooling water outlet passage 26 and into a third circulation flow path 41, which will be described later.

[0081] The circulation device 91 includes a radiator 27 (corresponding to the "heat exchanger" in the disclosed technology) and a thermostat valve 28, in addition to the water pump 3 and the coolant control valve 4 described above. The engine system 1 including the circulation device 91 is broadly divided into a second circuit 30, a third circuit 40, and a first circuit 50 as flow paths through which the coolant circulates.

[0082] (2nd circuit) The second circuit 30 has a second circulation flow path 31 having two branched flow paths (a first branch flow path 31a and a second branch flow path 31b). An EGR cooler 191 and a heater 71 are disposed in the first branch flow path 31a. The heater 71 is incorporated in an air conditioner that regulates the air inside the vehicle cabin. A throttle valve (electric throttle body: ETB) 171 and an EGR valve 192 are disposed in the second branch flow path 31b. An upstream end of the second circulation flow path 31 is connected to the second coolant outlet path 25. A downstream end of the second circulation flow path 31 is connected to the suction port 3b of the water pump 3, with the second circulation flow path 31 merging with the first circuit 50 and the third circuit 40.

[0083] Inside the engine 10, the block inner jacket 21, the second jacket 22b, and the second coolant discharge passage 25 form a flow path of the second circuit 30. Therefore, in the second circuit 30, the coolant discharged from the water pump 3 flows through the block inner jacket 21 and the second jacket 22b, and then branches off into the first branch flow path 31a and the second branch flow path 31b. After merging, the coolant flows back to the water pump 3.

[0084] The coolant flowing through the second circuit 30 exchanges heat mainly with the exhaust port 124 of the engine 10. The coolant also exchanges heat with the EGR cooler 191, the heater 71, the throttle valve 171, and the EGR valve 192.

[0085] (3rd circuit) The third circuit 40 has a third circulation flow path 41 in which an oil cooler 72 and an ATF heat exchanger 73 are installed. The oil cooler 72 is installed in a system that circulates and supplies lubricating oil to the engine 10. The ATF heat exchanger 73 is installed in a system that circulates and supplies hydraulic oil for the automatic transmission. The upstream end of the third circulation flow path 41 is connected to the third coolant outlet path 26. The downstream end of the third circulation flow path 41 is connected to the suction port 3b of the water pump 3, where it merges with the first circuit 50 and the second circuit 30.

[0086] Inside the engine 10, the block inner jacket 21 and the third coolant outlet passage 26 form a flow path of a third circuit 40. Therefore, in the third circuit 40, of the coolant discharged from the water pump 3, a portion of the coolant flowing through the block inner jacket 21 flows through the third circulation passage 41 and returns to the water pump 3. The coolant flowing through the third circuit 40 exchanges heat with an oil cooler 72 and an ATF heat exchanger 73.

[0087] (1st circuit) The first circuit 50 has a bypass flow path 51, a communication flow path 52, and a radiator flow path 53. Inside the engine 10, the block inner jacket 21, the first jacket 22a, and the first coolant discharge path 24 form the flow path of the first circuit 50.

[0088] The flow path of the first circuit 50 branches into a bypass flow path 51 and a radiator flow path 53 at the coolant control valve 4. The downstream ends of the bypass flow path 51 and the radiator flow path 53 are joined with the second circuit 30 and the third circuit 40, respectively, and are connected to the suction port 3b of the water pump 3.

[0089] The radiator 27 is provided in the radiator flow path 53. The radiator 27 is installed behind the front grille of the automobile. The coolant flowing through the radiator 27 exchanges heat mainly with outside air caused by wind while the automobile is running. The coolant dissipates heat and is cooled as it flows through the radiator flow path 53.

[0090] As a result, the radiator flow path 53 cools the cooling water discharged from the water pump 3, which flows through the block inner jacket 21 and the first jacket 22a and is heated by heat exchange, in the radiator 27, and returns it to the block inner jacket 21 and the first jacket 22a.

[0091] The bypass flow path 51 is a flow path that bypasses the radiator flow path 53. The bypass flow path 51 is shorter than the radiator flow path 53. Only the thermostat valve 28 is provided in the bypass flow path 51. The thermostat valve 28 is connected to the radiator flow path 53 via the communication flow path 52, with the upstream side and downstream side of the bypass flow path 51 always communicating with each other.

[0092] As a result, the bypass flow path 51 returns the cooling water discharged from the water pump 3, which flows through the block inner jacket 21 and the first jacket 22a and exchanges heat, to the block inner jacket 21 and the first jacket 22a without being cooled by the radiator 27.

[0093] The thermostat valve 28 is a known device that opens and closes at a preset high temperature. The thermostat valve 28 has a valve element that is biased in the closing direction by the elastic force of a spring. The valve element is displaced by the action of wax, thereby opening and closing the thermostat valve 28. The opening temperature of the thermostat valve 28 of this engine system 1 is set higher than that of conventional thermostat valves.

[0094] When the thermostat valve 28 opens, the bypass flow path 51 communicates with the radiator flow path 53 via the communication flow path 52. Therefore, when the thermostat valve 28 opens, a portion of the coolant flowing through the bypass flow path 51 passes through the communication flow path 52 and flows into the radiator flow path 53.

[0095] (Cooling water control valve) 5 shows the cooling water control valve 4. The cooling water control valve 4 is a valve that can adjust the flow rate of the cooling water, and is composed of a housing 60, a rotary valve element 61, an actuator 62, and the like.

[0096] A cylindrical flow dividing chamber 60a is provided inside the housing 60. A cylindrical rotary valve element 61 is rotatably housed in the flow dividing chamber 60a. A first port 63 and a second port 64 are formed in the housing 60 so as to extend radially outward from predetermined positions on the outer periphery of the flow dividing chamber 60a. The first port 63 is connected to the bypass flow path 51. The second port 64 is connected to the radiator flow path 53.

[0097] One end of the flow dividing chamber 60a is open. This opening forms a third port 65 through which the coolant flows into the flow dividing chamber 60a. The housing 60 is attached to the cylinder head 12 so that the third port 65 is connected to the first coolant outlet passage 24 with its center aligned. As a result, the peripheral wall of the rotary valve element 61 is interposed between the third port 65 and each of the first port 63 and the second port 64.

[0098] A first water passage opening 61a and a second water passage opening 61b are formed at predetermined positions on the peripheral wall of the rotary valve element 61. The first water passage opening 61a is longer in the circumferential direction than the second water passage opening 61b and has a relatively larger opening area. Depending on the rotational position of the rotary valve element 61, the third port 65 is either in communication with the first port 63 or the second port 64 via the first water passage opening 61a or the second water passage opening 61b. Even when the third port 65 is in communication with the first port 63 or the second port 64, the degree of opening between the third port 65 and the first port 63 or the second port 64 varies depending on the rotational position of the rotary valve element 61.

[0099] The other end of the flow diversion chamber 60a is sealed by a sealing wall 66. An actuator 62 is housed inside the housing 60 on the opposite side of the sealing wall 66 from the flow diversion chamber 60a. A rotating shaft 62a of the actuator 62 passes through a shaft hole that opens in the center of the sealing wall 66 and protrudes into the flow diversion chamber 60a. A rotary valve element 61 is attached to the rotating shaft 62a that protrudes into the flow diversion chamber 60a via a support arm 62b. The ECU 100 outputs a control signal to the actuator 62. The ECU 100 controls the actuator 62, causing the rotary valve element 61 to rotate.

[0100] Returning to FIG. 4 , the first water temperature sensor SN1 is disposed in the flow path where the first circuit 50, the second circuit 30, and the third circuit 40 converge and flow into the water pump 3. The second water temperature sensor SN2 is disposed in the first jacket 22a. The first water temperature sensor SN1 measures the temperature of the coolant flowing into the engine 10. The second water temperature sensor SN2 measures the temperature of the coolant flowing through the water jacket 20, more precisely, the first jacket 22a. These sensors SN1 and SN2 are used for coolant control and combustion control. For example, the second water temperature sensor SN2 is used to estimate the wall temperature of the combustion chamber 16 when performing advanced combustion control. The second water temperature sensor SN2 is also used to control the actuator 62.

[0101] In this circulation device 91, the ECU 100 controls the coolant control valve 4 based on the measurement value of the second water temperature sensor SN2, thereby adjusting the flow rate of the coolant flowing through the first circuit 50, i.e., the bypass flow path 51 and the radiator flow path 53 (the flow of the coolant through the communication flow path 52 is automatically adjusted by the thermostat valve 28).

[0102] The cooling water flowing through the circulation device 91 is cooled mainly by the radiator 27 installed in the radiator flow path 53. The temperature of the cooling water is adjusted.

[0103] That is, the main component of this circulation device 91 is the first circuit 50. The flow rate and temperature of the cooling water in each of the second circuit 30 and the third circuit 40 change depending on the adjustment of the flow rate and temperature of the cooling water in the first circuit 50. In this circulation device 91, the first circuit 50 is essential, but the second circuit 30 and the third circuit 40 are not essential.

[0104] (How to drain cooling water) As described above, the cooling water flowing through the first jacket 22a mainly exchanges heat with the wall of the combustion chamber 16 to cool the wall of the combustion chamber 16. In this engine system 1, in order to stably and efficiently control combustion in the engine 10, multiple cooling water flow patterns are set according to the temperature of the cooling water flowing through the first jacket 22a (measurement value of the second water temperature sensor SN2). Figure 6 shows the water flow state of each circuit in the engine system 1 according to the cooling water temperature.

[0105] In the cooling water control valve 4, the actuator 62 is controlled to adjust the flow rate of the cooling water flowing through both the first port 63 and the second port 64. That is, the opening degrees of the first water passage opening 61a and the second water passage opening 61b are changed so that the rotary valve element 61 is in a predetermined rotation position.

[0106] "Low temperature" refers to a so-called cold state, such as immediately after starting the engine 10. "Low temperature" refers to a state in which the temperature t of the cooling water flowing through the first jacket 22a is lower than a first switch temperature t11 (for example, 40°C). "Complete warm-up" refers to a state in which the engine 10 has warmed up to a temperature suitable for operation, which is a so-called warm state. "Complete warm-up" refers to a state in which the temperature t of the cooling water flowing through the first jacket 22a is equal to or higher than a second switch temperature t12 (for example, 80°C). "Semi-warm-up" refers to a state between "low temperature" and "complete warm-up", that is, a transitional state. "Semi-warm-up" refers to a state in which the temperature t of the cooling water flowing through the first jacket 22a is equal to or higher than the first switch temperature t11 and lower than the second switch temperature t12, and refers to a state in which the temperature t of the cooling water is, for example, between 40°C and 80°C.

[0107] At "low temperature," as shown in state 81 on the left side of Fig. 6, no coolant flows through either the bypass passage 51 or the radiator passage 53 (the flow rate of both is zero). In other words, no coolant circulates through the first circuit 50. At this time, the rotary valve element 61 of the coolant control valve 4 is set to a rotation position where neither the first port 63 nor the second port 64 communicates with the third port 65.

[0108] Since the coolant does not flow through the radiator flow path 53, the coolant is not cooled by the radiator 27. Therefore, the coolant temperature rises quickly. Furthermore, the combustion chamber 16 is not cooled by the circulation of the coolant. The combustion chamber 16 can be quickly warmed by the heat of combustion. Since the engine 10 quickly reaches a temperature state suitable for combustion, fuel efficiency can be improved. At this time, the coolant discharged by the water pump 3 circulates through the second circuit 30 and the third circuit 40.

[0109] During "semi-warm-up," as shown in state 82 in the center of FIG. 6, coolant flows through the bypass flow path 51 but not through the radiator flow path 53 (the flow rate of the radiator flow path 53 is zero). That is, in the first circuit 50, coolant circulates only through the bypass flow path 51. At this time, in the coolant control valve 4, the rotary valve element 61 is set to a rotational position where only the first port 63 communicates with the third port 65. The opening of the first water passage opening 61a is, for example, fully open.

[0110] Because the coolant does not flow through the radiator flow path 53, the temperature of the coolant rises quickly. In contrast, because the coolant flows through the bypass flow path 51, the coolant flows into the first jacket 22a. The bypass flow path 51 is short. Furthermore, because the coolant control valve 4 is set to be fully open, most of the coolant flows through the bypass flow path 51 and the first jacket 22a.

[0111] The combustion chamber 16 can be quickly warmed by the circulating coolant. Because the coolant circulates, the combustion chamber 16 and its surrounding area can be heated evenly. The engine 10 quickly reaches a temperature suitable for combustion, improving fuel efficiency.

[0112] At this time, the remainder of the coolant discharged by the water pump 3 circulates through the second circuit 30 and the third circuit 40 (the same applies during "full warm-up"). Also, the temperature of the coolant during "semi-warm-up" is lower than the opening temperature of the thermostat valve 28. Therefore, the thermostat valve 28 is fully closed. No part of the coolant flows into the radiator flow path 53 from the bypass flow path 51.

[0113] During a "fully warmed-up" state, the engine 10 has reached a temperature suitable for combustion. As described above, after a "fully warmed-up" state, the engine 10 switches between combustion modes depending on the load and the engine speed. The engine system 1 controls the circulation device 91 so that the wall temperature of the combustion chamber 16 reaches a temperature suitable for the combustion mode. During a "fully warmed-up" state, the engine system 1 switches between a state 82 shown in the center of FIG. 6 and a state 83 shown on the right side of FIG. 6 depending on the operating state of the engine 10. As described above, in the state 82, the bypass flow path 51 is opened and the radiator flow path 53 is closed. However, during a "fully warmed-up" state, the temperature of the coolant is elevated, and therefore, the thermostat valve 28 may open, causing the coolant to flow through the radiator flow path 53, as described below. In the state 83, both the bypass flow path 51 and the radiator flow path 53 are opened, thereby circulating the coolant through the entire first circuit 50.

[0114] More specifically, in the case of "complete warm-up", which is the state 82 shown in the center, the rotary valve element 61 of the coolant control valve 4 is set to a rotational position where the first port 63 communicates with the third port 65 and the second port 64 does not communicate with the third port 65. Then, the flow rate of the coolant is adjusted in the first port 63 (bypass flow path 51) according to the load of the engine 10.

[0115] In the "complete warm-up" state 83 shown on the right, coolant flows through both the bypass flow path 51 and the radiator flow path 53. In this case, the rotary valve element 61 of the coolant control valve 4 is set to a rotational position where both the first port 63 and the second port 64 communicate with the third port 65. The flow rate of coolant is adjusted in both the first port 63 (bypass flow path 51) and the second port 64 (radiator flow path 53) according to the load of the engine 10.

[0116] (How to flush the coolant when the engine is fully warmed up) Fig. 7 shows a specific example of how the coolant flows during a complete warm-up. In Fig. 7, changes in the main specifications according to the magnitude of the load on the engine 10 are shown in charts (A) to (D).

[0117] Graph (A) shows a change G1 in the flow rate of the coolant passing through the coolant control valve 4, and a change G2 in the flow rate of the coolant passing through the radiator flow path 53. Graph (B) shows a breakdown of the change in the flow rate of the coolant flowing through the first circuit 50, that is, a change G3 in the flow rate of the coolant flowing from the coolant control valve 4 to the bypass flow path 51, a change G4 in the flow rate of the coolant flowing through the communication flow path 52, and a change G5 in the flow rate of the coolant flowing from the coolant control valve 4 to the radiator flow path 53.

[0118] (C) shows a change G6 in the temperature of the cooling water flowing through the first jacket 22a and a change G7 in the temperature of the cooling water flowing into the water pump 3. In other words, the changes in the measured values ​​of the second water temperature sensor SN2 and the first water temperature sensor SN1 are shown. (D) shows a change G8 in the wall temperature of the combustion chamber 16.

[0119] The load range of the engine 10 is divided into three regions in relation to the control of the coolant: a region below a first load L1, a region equal to or greater than a second load L2, and a region equal to or greater than the first load L1 but less than the second load L2. Each chart in FIG. 7 corresponds to a case where the engine 10 is operating at a low or medium speed. The region below the first load L1 is a region where the engine 10 performs HCCI combustion or MPCI combustion. The region equal to or greater than the second load L2 is a region where the engine 10 performs SI combustion. The region equal to or greater than the first load L1 but less than the second load L2 is a region where the engine 10 performs SPCCI combustion.

[0120] In this engine system 1, the coolant flow rate is controlled in the region where the engine 10 performs HCCI combustion or MPCI combustion, and the coolant temperature is controlled in the region where the engine 10 performs SPCCI combustion. The region where the engine 10 performs HCCI combustion or MPCI combustion is, in other words, the region where the air-fuel mixture burns without forced ignition by the spark plug 132, and the region where the engine 10 performs SPCCI combustion is, in other words, the region where the air-fuel mixture burns with forced ignition by the spark plug 132.

[0121] The engine system 1 maintains the wall temperature of the combustion chamber 16 at a specific constant temperature in low load and medium load ranges of the engine 10 by switching between flow rate control and temperature control (see G8).

[0122] That is, to achieve compression ignition combustion without forced ignition, such as HCCI combustion or MPCI combustion, the temperature inside the combustion chamber 16 (in-cylinder temperature) must be higher than that in SI combustion and controlled with high precision. On the other hand, SPCCI combustion involves forced ignition, although a portion of the mixture is combusted by compression ignition. Therefore, the temperature inside the combustion chamber 16 can be lower than that in HCCI combustion or MPCI combustion. Conversely, if the temperature inside the combustion chamber 16 is too high, the mixture may autoignite before forced ignition occurs, or the proportion of autoignition combustion may become too high in SPCCI combustion, which combines flame propagation combustion and autoignition combustion. In other words, if the temperature inside the combustion chamber 16 is too high, stable SPCCI combustion cannot be achieved.

[0123] Therefore, it would be ideal to increase or decrease the wall temperature of the combustion chamber 16 depending on the combustion mode. However, because the heat capacity of the combustion chamber 16 walls is large, it is difficult to change the wall temperature of the combustion chamber 16 responsively to changes in the combustion mode or load. Therefore, in this engine system 1, the wall temperature of the combustion chamber 16 is maintained at a specific constant temperature in the low- to medium-load range. This specific temperature is intermediate between the optimal temperature for HCCI combustion or MPCI combustion and the optimal temperature for SPCCI combustion, and is a temperature that is acceptable for both HCCI combustion and MPCI combustion, as well as for SPCCI combustion. By maintaining the wall temperature of the combustion chamber 16 at a constant temperature, the wall temperature of the combustion chamber 16 remains appropriate even when the combustion mode is switched or the load changes.

[0124] However, when the load on the engine 10 is low, the heat of combustion generally decreases, while when the load on the engine 10 is high, the heat of combustion generally increases. In order to maintain a constant wall temperature of the combustion chamber 16 regardless of the load on the engine 10, it is necessary to adjust the amount of heat exchanged by the coolant with high responsiveness in response to the generated heat of combustion.

[0125] One way to adjust the amount of heat exchange is to adjust the temperature of the coolant in accordance with the load on the engine 10. However, because the heat capacity of the coolant is large, it takes a long time to raise or lower the temperature of the coolant. It is therefore difficult to adjust the temperature of the coolant in a timely manner in response to changes in the load on the engine 10.

[0126] Therefore, this engine system 1 maintains the coolant temperature constant at a predetermined temperature, and uses the coolant control valve 4 to adjust the flow rate of the coolant flowing through the first port 63 and the first jacket 22a depending on the load of the engine 10. Because the flow rate can be adjusted with high responsiveness, the heat transfer coefficient of the coolant can be adjusted with high responsiveness in response to the generated combustion heat, and as a result, the wall temperature of the combustion chamber 16 can be maintained constant.

[0127] (HCCI combustion or MPCI combustion region) As shown in FIG. 7, in the region where HCCI combustion or MPCI combustion is performed, the coolant control valve 4 does not allow coolant to flow through the radiator flow path 53, but adjusts the flow rate of the coolant flowing through the bypass flow path 51 (see G3 and G5).

[0128] Because the radiator flow path 53 is closed, the temperature of the coolant is determined by the valve opening temperature of the thermostatic valve 28. The valve opening temperature of the thermostatic valve 28 is set to a relatively high temperature. The temperature of the coolant flowing through the first jacket 22a is constant at the first target temperature t21 regardless of the load (see G6). The first target temperature t21 is a temperature close to the temperature related to the reliability limit of the engine 10. By setting the coolant temperature to a relatively high temperature, it is possible to maintain the wall temperature of the combustion chamber 16 at a relatively high temperature (i.e., the target temperature tw) in the HCCI combustion or MPCI combustion range. A high wall temperature of the combustion chamber 16 is advantageous for stabilizing compression ignition combustion without forced ignition, such as HCCI combustion or MPCI combustion. Note that in the illustrated example, in the range below the first load L1, the temperature of the coolant flowing into the engine 10 gradually increases as the load of the engine 10 increases (see G7).

[0129] In the region of HCCI combustion or MPCI combustion, the flow rate of the cooling water flowing through the bypass flow path 51 is adjusted by the cooling water control valve 4 so that when the load on the engine 10 is low, the flow rate of the cooling water flowing through the bypass flow path 51 is low, and when the load on the engine 10 is high, the flow rate of the cooling water flowing through the bypass flow path 51 is increased.

[0130] At this time, in the coolant control valve 4, the actuator 62 is controlled so that the rotary valve element 61 is positioned at a rotational position where the third port 65 is not in communication with the second port 64 and is in communication with the first port 63. Then, the degree of opening between the third port 65 and the first port 63 is adjusted to a large or small value depending on the load on the engine 10.

[0131] In the HCCI combustion or MPCI combustion region, the flow rate of the cooling water flowing through the communication passage 52 changes in response to the change in the flow rate of the cooling water flowing through the bypass passage 51 when the thermostat valve 28 opens (see G4).

[0132] In the illustrated example, the load of the engine 10 and the flow rate of the cooling water have a linear relationship, but the relationship is not limited to a linear relationship.

[0133] The flow rate of the cooling water flowing through the first jacket 22a corresponds to the flow rate of the cooling water flowing through the bypass passage 51. Therefore, when the load of the engine 10 is low, the flow rate of the cooling water flowing through the first jacket 22a is low, and when the load of the engine 10 is high, the flow rate of the cooling water flowing through the first jacket 22a is high. In the example of FIG. 7, when the load of the engine 10 is the first load L1, the flow rate of the cooling water flowing through the first jacket 22a is the maximum flow rate (see G1). However, when the load of the engine 10 is the first load L1, the flow rate of the cooling water flowing through the first jacket 22a may be set to a flow rate lower than the maximum flow rate.

[0134] When the flow rate of the cooling water flowing through the first jacket 22a is low, the heat transfer coefficient with the combustion chamber 16 decreases. Therefore, even if the heat of combustion decreases, the wall temperature of the combustion chamber 16 can be adjusted to be high. When the flow rate of the cooling water flowing through the first jacket 22a is high, the heat transfer coefficient with the combustion chamber 16 increases. Therefore, even if the heat of combustion increases, the wall temperature of the combustion chamber 16 can be adjusted to be low.

[0135] In this way, while maintaining the temperature of the cooling water constant using the thermostat valve 28 (see G6), the flow rate of the cooling water flowing through the first jacket 22a is increased or decreased using the cooling water control valve 4 in a highly responsive manner depending on the load on the engine 10 (see G1, G3), thereby making it possible to maintain the wall temperature of the combustion chamber 16 constant at the target temperature tw (see G8).

[0136] (SPCCI combustion area) The flow rate of the coolant flowing through the coolant control valve 4, i.e., the flow rate of the coolant flowing through the first circuit 50, reaches its upper limit at the first load L1 (see G1). In other words, flow rate control cannot be performed at loads equal to or greater than the first load L1. Therefore, in the range of the first load L1 or greater and less than the second load L2, the temperature of the coolant is controlled. As the load on the engine 10 increases, the coolant flowing through the bypass flow path 51 is gradually diverted to the radiator flow path 53 for cooling, thereby maintaining the wall temperature of the combustion chamber 16 at the target temperature tw.

[0137] Specifically, while the coolant control valve 4 maintains the flow rate of coolant flowing through the first circuit 50 at a maximum, as the load of the engine 10 increases, the coolant control valve 4 gradually reduces the flow rate of coolant flowing through the bypass flow path 51 and gradually increases the flow rate of coolant flowing through the radiator flow path 53 (see G1, G2, G3, and G5). In the SPCCI combustion region, the coolant control valve 4 adjusts the flow rate of coolant flowing through the radiator flow path 53 to adjust the temperature of the coolant flowing through the first jacket 22a. Note that when the load of the engine 10 is equal to or greater than the first load L1, the flow rate of coolant flowing through the radiator flow path 53 exceeds the flow rate of coolant flowing through the bypass flow path 51. The load of the engine 10 at which the flow rates are reversed varies depending on the operating environment of the engine 10 (e.g., outside temperature, wind volume during driving, etc.).

[0138] In the coolant control valve 4, the actuator 62 is controlled so that the rotary valve element 61 is positioned at a rotational position where the third port 65 is in communication with both the first port 63 and the second port 64. Then, the degree of opening between the third port 65 and each of the first port 63 and the second port 64 is adjusted depending on the load of the engine 10.

[0139] As a result, the temperatures of the cooling water flowing through the first jacket 22a and the cooling water flowing into the engine 10 decrease as the load of the engine 10 increases (see G6 and G7). When the load of the engine 10 increases and the heat of combustion increases, the amount of cooling provided by the cooling water flowing through the first jacket 22a can be maintained even if the flow rate of the cooling water is constant, because its temperature is low. In addition, the flow rate of the cooling water flowing through the first circuit 50 is at the maximum flow rate, which is advantageous for cooling the combustion chamber 16. As a result, the wall temperature of the combustion chamber 16 can be maintained at the target temperature tw even in the SPCCI combustion region (see G8).

[0140] In order to suppress an excessive temperature rise in the combustion chamber 16, in this cooling system 2, a second target temperature t22 (e.g., 88°C) lower than the first target temperature t21 is set as the target temperature of the cooling water flowing through the first jacket 22a. Temperature control is performed until the temperature of the cooling water flowing through the first jacket 22a reaches this second target temperature t22.

[0141] 7, when the temperature of the coolant reaches the second target temperature t22, the flow rate of the coolant flowing through the radiator flow path 53 is less than the maximum flow rate. If the flow rate of the coolant flowing through the radiator flow path 53 is further increased, the temperature of the coolant can be further reduced. In other words, even if the load on the engine 10 exceeds L2, it is possible to maintain the wall temperature of the combustion chamber 16 at the target wall temperature tw.

[0142] In this way, the engine system 1 combines flow rate control and temperature control to enable the engine system 1 to maintain a constant wall temperature of the combustion chamber 16 over a wide range of loads, from low to medium, of the engine 10. Even when the combustion mode switches between HCCI combustion, MPCI combustion, and SPCCI combustion in response to changes in the load of the engine 10, the wall temperature of the combustion chamber 16 is maintained at an appropriate temperature, so each combustion mode is carried out stably.

[0143] The coolant control valve 4 having the rotary valve body 61 can selectively close the bypass passage 51 and / or the radiator passage 53, and can adjust the flow rate of the bypass passage 51 and the flow rate of the radiator passage 53. The engine system 1 equipped with the coolant control valve 4 can adjust the flow rate of the water jacket 20 described above with a simple configuration.

[0144] In the SPCCI combustion region, the amount of coolant flowing into the radiator flow path 53 through the communication flow path 52 gradually decreases and stops flowing as the load on the engine 10 increases (see G4). Specifically, the temperature of the coolant flowing into the bypass flow path 51 from the coolant control valve 4 gradually decreases from the first target temperature t21. Accordingly, the temperature of the coolant flowing through the thermostat valve 28 also decreases. Therefore, in the SPCCI combustion region, the thermostat valve 28 gradually closes and becomes fully closed. As a result, the amount of coolant flowing into the radiator flow path 53 through the communication flow path 52 gradually decreases and stops flowing.

[0145] 7, there is a proportional relationship between the decrease in the flow rate of the cooling water flowing through the bypass passage 51 and the increase in the flow rate of the cooling water flowing through the radiator passage 53, but this does not have to be the case. In the SPCCI combustion region, the flow rate of the cooling water flowing through the cooling water control valve 4 may be equal to or lower than the upper limit.

[0146] (SI combustion region) In the SI combustion region, the coolant control valve 4 adjusts the temperature of the coolant flowing through the first jacket 22a so that it is maintained at the second target temperature t22. Specifically, the actuator 62 is controlled to adjust the opening between the third port 65 and the second port 64 to increase and the opening between the third port 65 and the first port 63 to decrease as the load on the engine 10 increases. As a result, the amount of coolant flowing through the radiator passage 53 gradually increases, and the amount of coolant flowing through the bypass passage 51 gradually decreases (see G3 and G5). This allows the temperature of the coolant flowing through the first jacket 22a to be maintained at the second target temperature t22 (see G6).

[0147] In the region where SI combustion is performed, abnormal combustion such as knocking can be suppressed by keeping the coolant temperature relatively low.

[0148] In the aforementioned region of SPCCI combustion, in other words, the region between the first load L1 and the second load L2, in order to maintain a constant wall temperature of the combustion chamber 16, the temperature of the coolant flowing through the first jacket 22a is actively lowered as the load of the engine 10 increases, and the degree of change in the flow rate of the coolant flowing from the coolant control valve 4 to the bypass flow path 51 and the flow rate of the coolant flowing from the coolant control valve 4 to the radiator flow path 53 is relatively increased in response to an increase in the load of the engine 10. In other words, the slopes of G3 and G5 are large.

[0149] On the other hand, in the SI combustion region, in other words, the region equal to or greater than the second load L2, the coolant temperature is maintained at the second target temperature t22, so the degree of change in the flow rate of the coolant flowing from the coolant control valve 4 to the bypass flow path 51 and the flow rate of the coolant flowing from the coolant control valve 4 to the radiator flow path 53 as the load on the engine 10 increases is relatively small. In other words, the slopes of G3 and G5 are small, and the slopes of G3 and G5 change at the boundary of the second load L2.

[0150] Incidentally, even in the region of SI combustion, the proportional relationship between the decrease in the flow rate of the cooling water flowing through the bypass passage 51 and the increase in the flow rate of the cooling water flowing through the radiator passage 53 is not essential. In the region of SI combustion, the flow rate of the cooling water flowing through the cooling water control valve 4 may be equal to or lower than the upper limit.

[0151] In the SI combustion region, the flow rate of the cooling water flowing through the first jacket 22a is at a maximum, and the temperature of the cooling water is maintained at the second target temperature t22. As the load on the engine 10 increases, the amount of heat generated in the combustion chamber 16 increases, and therefore the wall temperature of the combustion chamber 16 gradually rises as the load on the engine 10 increases (see G8).

[0152] In the SI combustion region, the temperature of the coolant is maintained at the second target temperature t22, so the thermostat valve 28 is fully closed. No coolant flows through the communication passage 52. The bypass passage 51 and the radiator passage 53 constitute passages independent of each other.

[0153] Next, with reference to FIGS. 8 and 9, the control executed by the ECU 100 regarding the cooling of the engine 10 will be described.

[0154] 8 is a flowchart related to switching of the engine 10 between a low temperature state, a semi-warmed-up state, and a fully warmed-up state. First, in step S81 after starting, the ECU 100 acquires signal values ​​output by the various sensors SN1 to SN5. In the following step S82, the ECU 100 determines whether the coolant temperature t is equal to or higher than the second switch temperature t12 based on the signal from the second water temperature sensor SN2. If the coolant temperature t is equal to or higher than the second switch temperature t12, the process proceeds from step S82 to step S83. In step S83, the ECU 100 executes full warm-up control. Details of the full warm-up control will be described with reference to FIG. 9.

[0155] If the coolant temperature is lower than the second switch temperature t12, the process proceeds from step S82 to step S84. In step S84, the ECU 100 determines whether the coolant temperature t is equal to or higher than the first switch temperature t11. If the coolant temperature t is equal to or higher than the first switch temperature t11, the process proceeds from step S84 to step S85. In step S85, the ECU 100 executes semi-warm-up control. As described above, the ECU 100 opens the bypass passage 51 and closes the radiator passage 53 via the coolant control valve 4.

[0156] If the coolant temperature t is lower than the first switch temperature t11, the process proceeds from step S84 to step S86. In step S86, the ECU 100 executes low-temperature control. As described above, the ECU 100 closes the bypass flow path 51 and closes the radiator flow path 53 via the coolant control valve 4.

[0157] 9 shows a flow of the complete warm-up control in step S83. In step S91 after the start, the ECU 100 calculates a target load for the engine 10 based on the signal values ​​output by the sensors SN1 to SN5. In the following step S92, it is determined whether the combustion mode is HCCI combustion or MPCI combustion based on the target load L. If the determination in step S92 is YES, the process proceeds from step S92 to step S93. In step S93, the ECU 100 performs flow rate control. That is, the ECU 100 closes the radiator flow path 53 via the coolant control valve 4 and adjusts the flow rate of the bypass flow path 51 according to the load of the engine 10.

[0158] If the combustion type is neither HCCI combustion nor MPCI combustion, the process proceeds from step S92 to step S94. In step S94, the ECU 100 determines whether the combustion type is SPCCI combustion based on the target load L. If the determination in step S94 is YES, the process proceeds from step S94 to step S95. In step S95, the ECU 100 performs temperature control. That is, the ECU 100 adjusts the flow rates of the radiator passage 53 and the bypass passage 51 according to the load of the engine 10 via the coolant control valve 4 so that the wall temperature of the combustion chamber 16 remains constant.

[0159] If the combustion type is SI combustion, the process proceeds from step S94 to step S96. In step S96, the ECU 100 adjusts the flow rates of the radiator flow path 53 and the bypass flow path 51 according to the load of the engine 10 via the coolant control valve 4 so that the coolant temperature is constant.

[0160] (Modification of the circulator) 10 shows a circulation device 92 according to a modified example. This circulation device 92 differs from the circulation device 91 of FIG. 4 in the position of the thermostat valve 28.

[0161] Specifically, the thermostat valve 28 is attached to the outflow end 10b of the engine 10, not to the bypass flow path 51. The downstream end of the first jacket 22a provided in the cylinder head 12 branches into two. The coolant control valve 4 and the thermostat valve 28 are each connected to the first jacket 22a.

[0162] The thermostat valve 28 is also connected to a radiator flow path 53 via a communication flow path 52. More specifically, the communication flow path 52 is connected to the radiator flow path 53 upstream of the radiator 27.

[0163] It should be noted that the circulation device 92 does not have a communication flow path that connects the bypass flow path 51 and the radiator flow path 53 in the circulation device 91 of FIG.

[0164] The way in which the coolant flows in the circulation device 92 is the same as in the circulation device 91 of FIG. 4. In other words, when the coolant temperature t is "low temperature" below the first switch temperature t11, the coolant does not flow through either the bypass flow path 51 or the radiator flow path 53 (the flow rate of both is zero). At this time, in the coolant control valve 4, the rotary valve element 61 is set to a rotation position where neither the first port 63 nor the second port 64 communicates with the third port 65. In addition, the thermostat valve 28 is closed. Therefore, the coolant does not circulate in the first circuit 50.

[0165] During "semi-warm-up" when the coolant temperature t is equal to or higher than the first switch temperature t11 and lower than the second switch temperature t12, coolant flows through the bypass flow path 51 but not through the radiator flow path 53 (the flow rate through the radiator flow path 53 is zero). At this time, the rotary valve element 61 of the coolant control valve 4 is set to a rotational position where only the first port 63 communicates with the third port 65. The opening of the first water passage opening 61a is, for example, fully open. Also, because the coolant temperature is low, the thermostat valve 28 is closed. In the first circuit 50, coolant circulates only through the bypass flow path 51.

[0166] When the cooling water temperature t is equal to or higher than the second switching temperature t12, ie, "complete warm-up," the circulation device 92 is controlled in accordance with the switching of the combustion mode.

[0167] Specifically, flow control is performed when the operating state of the engine 10 is in the region of HCCI combustion or MPCI combustion. The temperature of the coolant is kept constant by the thermostat valve 28. The coolant control valve 4 opens the bypass passage 51 and closes the radiator passage 53. However, when the thermostat valve 28 is open, the coolant may pass through the radiator 27. The coolant control valve 4 adjusts the flow rate of the coolant flowing through the bypass passage 51 depending on the load on the engine 10. In this way, the wall temperature of the combustion chamber 16 is maintained at the target temperature tw.

[0168] When the operating state of the engine 10 is in the region of SPCCI combustion, temperature control is performed. The coolant control valve 4 opens both the bypass passage 51 and the radiator passage 53. More specifically, as the load of the engine 10 increases, the coolant control valve 4 reduces the flow rate of coolant flowing through the bypass passage 51 and increases the flow rate of coolant flowing through the radiator passage 53. This maintains the wall temperature of the combustion chamber 16 at the target temperature tw.

[0169] When the operating state of the engine 10 is in the SI combustion region, the coolant control valve 4 adjusts the flow rate of the coolant flowing through the bypass passage 51 and the radiator passage 53 so that the coolant temperature t is constant at the second target temperature t22. More specifically, as the load on the engine 10 increases, the coolant control valve 4 reduces the flow rate of the coolant flowing through the bypass passage 51 and increases the flow rate of the coolant flowing through the radiator passage 53. The thermostat valve 28 is closed.

[0170] The engine system 1 equipped with the circulation device 92 also performs flow control in the HCCI combustion or MPCI combustion region, so that the flow rate of the cooling water flowing through the first jacket 22a can be changed with high response in response to changes in the load of the engine 10, and the wall temperature of the combustion chamber 16 can be kept constant.

[0171] Furthermore, by performing temperature control in the SPCCI combustion region, the wall temperature of the combustion chamber 16 can be maintained at the target temperature tw, so the wall temperature of the combustion chamber 16 does not change even when the combustion mode of the engine 10 switches between HCCI combustion, MPCI combustion, and SPCCI combustion. HCCI combustion and MPCI combustion without forced ignition can be stably executed, and SPCCI combustion with forced ignition can also be stably executed.

[0172] The circulation device 92 does not have the thermostat valve 28 provided downstream of the coolant control valve 4. The communication flow path 52 is a flow path that bypasses the coolant control valve 4. Therefore, even if the coolant control valve 4 fails, such as being stuck, the thermostat valve 28 opens when the coolant temperature reaches the opening temperature of the thermostat valve 28, allowing the coolant to be cooled by the radiator 27. The circulation device 92 is advantageous in improving the reliability of the engine system 1 because it can prevent the coolant temperature from becoming excessively high.

[0173] (Other embodiments) 4, the position of the coolant control valve 4 may be changed. Specifically, the coolant control valve 4 may be provided at the point where the bypass flow path 51 and the radiator flow path 53 join (the point surrounded by the dashed line in FIG. 4). In this configuration, the upstream end of the bypass flow path 51 and the upstream end of the radiator flow path 53 are connected to the first jacket 22a independently of each other. Furthermore, the communication flow path 52 communicates the bypass flow path 51 with the radiator flow path 53 downstream of the radiator 27, and the thermostat valve 28 may be provided to open and close the communication flow path 52.

[0174] Similarly, the position of the coolant control valve 4 may be changed in the circulation device 92 of Fig. 10. Specifically, the coolant control valve 4 may be provided at the point where the bypass flow path 51 and the radiator flow path 53 join (the point surrounded by the dashed line in Fig. 10). In this configuration, the upstream end of the bypass flow path 51 and the upstream end of the radiator flow path 53 are connected to the first jacket 22a independently of each other. In addition, the communication flow path 52 may connect the downstream of the radiator 27 and the upstream of the water pump 3 in the radiator flow path 53 so as to bypass the coolant control valve 4, and the thermostat valve 28 may be provided to open and close the communication flow path 52.

[0175] Furthermore, the flow rate adjustment device is not limited to being configured by the cooling water control valve 4 having the rotary valve body 61. The flow rate adjustment device may be configured by a first flow rate adjustment valve that adjusts the flow rate of the cooling water flowing through the bypass flow path 51, and a second flow rate adjustment valve that adjusts the flow rate of the cooling water flowing through the radiator flow path 53, and is independent of the first flow rate adjustment valve.

[0176] 3 shows an example of control of the engine system 1. The switching of the combustion mode is not limited to the example shown in FIG. [Explanation of symbols]

[0177] 1 Engine System 10 Engine 16 Combustion chamber 100 ECU (Controller) 132 Spark plug (ignition device) 22a No. 1 Jacket (Water Jacket) 27 Radiator (heat exchanger) 28 Thermostatic valve 4 Cooling water control valve (flow regulator) 51 Bypass flow path 52 Connecting Channel 53 Radiator flow path 91 Circulation device 92 Circulation device

Claims

1. An engine having a water jacket disposed around a combustion chamber; a circulation device attached to the engine and configured to circulate cooling water through the water jacket; a controller that controls the circulation device in accordance with an operating state of the engine; The circulation device includes: a radiator flow path including a heat exchanger; a bypass flow path that bypasses the heat exchanger; a flow rate adjusting device that adjusts a flow rate of the cooling water flowing through the water jacket by adjusting a flow rate of the cooling water flowing through each of the radiator flow path and the bypass flow path; a thermostat valve connected to the radiator flow path and opening to allow the coolant to pass through the heat exchanger; the engine has an ignition device that forcibly ignites an air-fuel mixture, and switches between a first combustion in which the air-fuel mixture is burned without forced ignition by the ignition device and a second combustion in which the air-fuel mixture is burned by forced ignition by the ignition device; The controller is electrically connected to the flow control device and controlling the flow rate adjustment device to adjust the flow rate of the cooling water flowing through the water jacket in accordance with a load of the engine by closing the radiator flow path and adjusting a flow rate of the cooling water flowing through the bypass flow path when the engine is performing the first combustion; When the engine is performing the second combustion, the flow rate control device is controlled to open the radiator passage and the bypass passage so that the cooling water flows through each of the radiator passage and the bypass passage. Engine system.

2. 2. The engine system according to claim 1, An engine system, wherein the controller increases the flow rate of cooling water flowing through the water jacket when the load is high compared to when the load is low when the engine is performing the first combustion.

3. 3. The engine system according to claim 1, the controller adjusts a flow rate of the cooling water flowing through the bypass passage and a flow rate of the cooling water flowing through the radiator passage when the engine is performing the second combustion, thereby adjusting a temperature of the cooling water flowing through the water jacket in accordance with the load. Engine system.

4. 4. The engine system according to claim 3, When the engine is performing the second combustion, the controller reduces a flow rate of the cooling water flowing through the bypass passage and increases a flow rate of the cooling water flowing through the radiator passage when the load is high, compared to when the load is low. Engine system.

5. In the engine system according to any one of claims 1 to 4, The controller sets a flow rate of the cooling water flowing through the water jacket to a maximum flow rate when the engine is performing the second combustion. Engine system.

6. In the engine system according to any one of claims 1 to 5, The controller maintains a wall temperature of the combustion chamber at a constant temperature when the engine is performing the first combustion and when the engine is performing the second combustion. Engine system.

7. 7. The engine system according to claim 6, The controller reduces a temperature of the cooling water flowing through the water jacket below a valve opening temperature of the thermostat valve when the engine is performing the second combustion. Engine system.

8. 5. The engine system according to claim 4, the controller increases a flow rate of the cooling water flowing through the radiator passage so that a temperature of the cooling water flowing through the water jacket decreases in response to an increase in the load when the engine is performing the second combustion and the load is lower than a predetermined load, and increases a flow rate of the cooling water flowing through the radiator passage so that a temperature of the cooling water flowing through the water jacket remains constant in response to an increase in the load when the load is equal to or higher than the predetermined load. Engine system.

9. In the engine system according to any one of claims 1 to 8, The controller determines a combustion mode of the engine based on at least the detected accelerator opening degree, and controls the circulation device in accordance with the determined combustion mode. Engine system.

10. In the engine system according to any one of claims 1 to 9, The flow rate control device is installed at a location where the bypass flow path and the radiator flow path branch off or at a location where the bypass flow path and the radiator flow path join together, The circulation device further includes a communication passage that communicates the bypass passage and the radiator passage, The thermostat valve opens and closes the communication passage. Engine system.

11. In the engine system according to any one of claims 1 to 9, The flow rate control device is installed at a location where the bypass flow path and the radiator flow path branch off or at a location where the bypass flow path and the radiator flow path join together, The circulation device further includes a communication passage that bypasses the flow rate adjustment device and connects the water jacket and the radiator passage, The thermostat valve opens and closes the communication passage. Engine system.

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