JP2020105917A - Control device for engine with supercharger - Google Patents

Abstract

To provide a control device for an engine 1 with a supercharger as a mechanical supercharger 44 for suppressing a temporary decline in the emission performance when the operating condition of an engine body 10 transits from a low load and low rotation operation region to a low load and high rotation operation region in association with increase in engine rotation speed.SOLUTION: Control means (an ECU 100) stops a mechanical supercharger 44 and makes an air-fuel ratio in a combustion chamber 17 or a weight ratio G/F of gas to fuel in the combustion chamber 17 lean to be equal to or greater than 25 when the operating condition of the engine body 10 is in the low load and low rotation operation region, drives the mechanical supercharger 44 when the operating condition of the engine body 10 is in the low load and high rotation operation region, and sets A/F or G/F in the combustion chamber 17 to be 14.5-15.0 when the operating condition of the engine body 10 transits from the low load and low rotation region to the low load and high rotation operation region as an engine speed is higher.SELECTED DRAWING: Figure 1

Description

The present invention belongs to a technical field related to a control device for a supercharged engine.

For example, Patent Document 1 describes an engine with a supercharger in which a mechanical supercharger is provided in an intake passage. This engine with a supercharger is provided in the intake passage, in addition to the mechanical supercharger, a clutch (electromagnetic clutch) that intermittently transmits the driving force from the output shaft of the engine body to the mechanical supercharger, An air bypass passage that bypasses the mechanical supercharger and a bypass control valve that opens and closes the air bypass passage are provided. Then, in Patent Document 1, when the operating state of the engine with the supercharger is in the high load region, the clutch is turned on to transmit the driving force to the mechanical supercharger and to close the bypass control valve. Then, the intake air is supercharged to the combustion chamber of the engine body. On the other hand, when the operating state of the engine with the supercharger is in the low load and low rotation operating region, the clutch is turned off and the bypass control valve is opened to prevent supercharging of intake air to the combustion chamber. To do so. Further, in Patent Document 1, when the operating state of the engine with the supercharger is in the low load and high rotation operating region, in order to prevent the supercharging of intake air to the combustion chamber while turning on the clutch, By opening the bypass control valve, part of the intake air compressed by the mechanical supercharger is circulated in the intake passage via the passage in which the mechanical supercharger is provided and the air bypass passage, The rest of the intake air compressed by the mechanical supercharger is sucked into the combustion chamber.

Japanese Patent No. 3564989

By the way, in the engine with a supercharger having the mechanical supercharger as in the above-mentioned Patent Document 1, the engine speed at which the clutch for interrupting the transmission of the driving force to the mechanical supercharger is changed from OFF to ON is It is difficult to make it too high in terms of clutch reliability. Therefore, as in Patent Document 1, even when supercharging is not required at a low load, when the low load low rotation operation region is shifted to the low load high rotation operation region (the engine rotation speed is equal to or higher than a predetermined rotation speed). The clutch is turned on. At this time, the intake air is circulated in the intake passage so that the intake air is not supercharged as in the above-mentioned Patent Document 1.

Here, the air-fuel ratio in the combustion chamber is usually a theoretical air-fuel ratio or a value close to it in the high-load operating region, while it is a lean air-fuel ratio larger than the theoretical air-fuel ratio in the low-load operating region. The lean air-fuel ratio is preferably 25 or more so that the NOx generation amount (RawNOx generation amount) is considerably reduced. That is, the amount of RawNOx generated decreases as the air-fuel ratio increases from around the time the air-fuel ratio exceeds the stoichiometric air-fuel ratio, and if the air-fuel ratio is 25 or more, no emission problem occurs. In the high load operation range, the amount of RawNOx generated is very large, but since the air-fuel ratio is at or near the stoichiometric air-fuel ratio, RawNOx can be purified by the three-way catalyst and emission performance is maintained well. be able to.

However, in the engine with a supercharger having the above mechanical supercharger, as the engine speed increases, from the low-load low-speed operation region where the lean air-fuel ratio is set, the low-load high-speed when the lean air-fuel ratio is also set. When the clutch is turned on when shifting to the rotational operation region, the temperature of the intake air compressed by the mechanical supercharger and sucked into the combustion chamber temporarily rises. This is because it is difficult for the intercooler provided on the downstream side of the mechanical supercharger to immediately cool the intake air in response to the above transition. When the intake air whose temperature has temporarily risen in this way is taken into the combustion chamber, the density of the taken intake air decreases, so that it is assumed that the sufficiently cooled intake air is taken in and the air-fuel ratio is, for example, 25. When the fuel is injected so as to become, the actual air-fuel ratio becomes smaller than 25. As a result, the RawNOx generation amount increases as the air-fuel ratio decreases. At such a lean air-fuel ratio, the purification rate of RawNOx by the three-way catalyst becomes low. Therefore, when the RawNOx generation amount increases due to the reduction of the air-fuel ratio as described above, the emission performance temporarily decreases. Become.

The present invention has been made in view of such a point, and an object thereof is to provide a control device for an engine with a supercharger having a mechanical supercharger in association with an increase in the rotation speed of an engine body. It is intended to suppress a temporary decrease in emission performance when the operating state of the engine main body shifts from a low load/low rotation operating region to a low load/high rotation operating region.

In order to achieve the above object, in the present invention, an engine main body having a cylinder in which a combustion chamber is formed, a mechanical supercharger arranged in an intake passage connected to the engine main body, and the mechanical type Targeting a control device for an engine with a supercharger having a clutch for intermittently transmitting driving force to the supercharger, the control device is provided with a control means for controlling the operation of the engine body including the operation of the clutch, Means, at least after warming up the engine body, when the operating state of the engine body is in a low load low rotation operating region of a low load side below a predetermined load and a low rotation side below a predetermined rotation speed, The clutch is disengaged to stop the mechanical supercharger, and the air-fuel ratio A/F in the combustion chamber or the weight ratio G/F of gas to fuel in the combustion chamber is set to lean of 25 or more. At the same time, when the operating state of the engine body is on the low load side of the predetermined load and in the low load high rotation operation region of the predetermined rotation speed or more, the clutch is connected to drive the mechanical supercharger. Then, when the operating state of the engine body shifts from the low load/low rotation operating region to the low load/high rotation operating region as the engine speed increases, the A/F or G/ F is set to be 14.5-15.0.

With the above configuration, when the operating state of the engine body shifts from the low load low rotation operating region to the low load high rotation operating region as the engine speed increases, it is considered that the intake air temperature temporarily rises. Also, by setting the air-fuel ratio A/F (or G/F) in the combustion chamber to 14.5 to 15.0, RawNOx can be satisfactorily purified by the three-way catalyst. Therefore, it is possible to suppress a temporary decrease in the emission performance when the operating state of the engine body shifts from the low load/low rotation operating region to the low load/high rotation operating region as the engine speed increases.

In one embodiment of the control device for a supercharged engine, the control means, when at least after the engine body is warmed up, the operating state of the engine body is in the low load high rotation operation region, the combustion is performed. The A/F or G/F in the room is configured to be 14.5-15.0.

As a result, when the operating state of the engine body shifts from the low-load low-rotation operating region to the low-load high-rotation operating region as the engine speed increases, the operating state of the engine body changes to the low-load high-rotation operating region. As long as the A/F or G/F in the combustion chamber is set to 14.5 to 15.0, even if the rotation speed of the engine body becomes higher in the low load high rotation operation region, the combustion chamber It becomes unnecessary to change the A/F or G/F.

In another embodiment of the control device for the engine with a supercharger, the control means is configured such that, at least after warming up the engine body, the operating state of the engine body is the predetermined value within the low load high rotation operation region. When the engine speed is in a specific engine speed range, which is a range from the engine speed to a higher engine speed by a predetermined amount, the A/F or G/F in the combustion chamber is set to 14.5 to 15.0 while the low load is increased. When it is in a region other than the specific rotation speed region in the rotational operation region, the A/F or G/F in the combustion chamber is made lean to 25 or more.

As a result, when the operating state of the engine body shifts from the low-load low-rotation operating region to the specific rotation speed region of the low-load high-rotation operating region as the engine speed increases, the A/F or Since the G/F is set to 14.5 to 15.0, it is possible to suppress a temporary decrease in emission performance. When the rotational speed of the engine body continues to rise and the operating state of the engine body shifts from the specific rotation speed region to a region excluding the specific rotation speed region in the low load/high rotation speed operation region, the A/F ( Alternatively, G/F) is set to 25 or more again. In this case, by appropriately setting the predetermined amount, the intake air is appropriately cooled by the intercooler at the stage of shifting from the specific rotation speed region to the region excluding the specific rotation speed region in the low load high rotation operation region. The emission will not be a problem. In addition, fuel efficiency can be improved in a region other than the specific rotation speed region within the low load, high rotation speed operation region.

In the control device for the engine with a supercharger, the control means, at least after warming up the engine body, when the operating state of the engine body is in a high load operation region of the predetermined load or more, the clutch is engaged. It is preferable that it is connected to drive the mechanical supercharger and that the A/F or G/F in the combustion chamber is set to 14.5 to 15.0.

With this, as the engine load increases, the operating state of the engine main body shifts from the low load low rotation speed operation area or the area other than the specific rotation speed area in the low load high rotation operation area to the high load operation area. Even when this occurs, it is possible to suppress a temporary decrease in emission performance. In addition, the engine load can be increased.

As described above, according to the control device for a supercharged engine of the present invention, the operating state of the engine body changes from the low load low rotation operating region to the low load high rotation operating region as the engine speed increases. When the transition is made, by setting the A/F or G/F in the combustion chamber to 14.5 to 15.0, it is possible to suppress a temporary decrease in the emission performance in the above transition.

It is a schematic diagram of an engine with a supercharger controlled by a control device concerning an embodiment of the present invention. It is a figure which shows typically some cooling systems of the said engine. It is a graph which shows an example of the characteristic to the temperature of the engine cooling fluid of a flow control valve. It is a block diagram which shows the structure of the said control apparatus. It is a figure which illustrates the operating area map of the engine main body of the said engine. FIG. 6 is a diagram showing the flow of intake air and the flows of engine cooling liquid and intercooler cooling liquid when the operating state of the engine body of the engine is in the low load/low rotation operating region A of FIG. FIG. 6 is a diagram showing the flow of intake air and the flows of engine cooling liquid and intercooler cooling liquid when the operating state of the engine body of the engine is in the low load/high rotation operating region B of FIG. FIG. 6 is a diagram showing the flow of intake air and the flows of engine cooling liquid and intercooler cooling liquid when the operating state of the engine body of the engine is in the high load operating region C of FIG. 5. 6 is a time chart showing an example of driving states of various devices related to the flow of intake air and the flows of engine cooling liquid and intercooler cooling liquid. It is a 5 equivalent figure which shows the example of another driving|running area map of the said engine main body.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a configuration of a supercharged engine 1 (hereinafter, simply referred to as an engine 1) controlled by a control device according to an embodiment of the present invention. The engine 1 is a four-stroke engine that operates by the combustion chamber 17 repeating an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. The engine 1 is mounted on a four-wheel vehicle (here, an automobile). The vehicle runs by driving the engine 1 (specifically, an engine body 10 described later). In the present embodiment, the fuel of the engine 1 is a liquid fuel containing gasoline as a main component. That is, the engine 1 is a gasoline engine.

(Engine configuration)
The engine 1 includes an engine body 10 having a cylinder block 12 and a cylinder head 13 mounted thereon and arranged in the engine room of the vehicle. A plurality of cylinders 11 (only one cylinder 11 is shown in FIG. 1) are formed inside a cylinder block 12 of the engine body 10. The plurality of cylinders 11 are arranged in a line in a direction perpendicular to the paper surface of FIG. That is, the engine 1 is an in-line multi-cylinder engine.

A piston 3 is slidably inserted in each cylinder 11. The piston 3 is connected to the crankshaft 15 via a connecting rod 14. The piston 3 defines a combustion chamber 17 together with the cylinder 11 and the cylinder head 13. The "combustion chamber" is not limited to the meaning of the space when the piston 3 reaches the compression top dead center. The term "combustion chamber" is sometimes used in a broad sense. That is, the “combustion chamber” may mean a space formed by the piston 3, the cylinder 11, and the cylinder head 13 regardless of the position of the piston 3.

A water jacket 12 a is provided around each cylinder 11 in the cylinder block 12. An engine cooling liquid that cools the engine body 10 flows through the water jacket 12a. Although not shown in detail, the engine coolant flows out of the engine body 10 after passing through the water jacket 12a and then through the water jacket provided in the cylinder head 13.

An intake port 18 is formed in the cylinder head 13 for each cylinder 11. The intake port 18 communicates with the combustion chamber 17. An intake valve 21 is arranged in the intake port 18. The intake valve 21 opens and closes between the combustion chamber 17 and the intake port 18. The intake valve 21 opens and closes at a predetermined timing by the valve mechanism. The valve operating mechanism may be a variable valve operating mechanism that makes valve timing and/or valve lift variable. In the present embodiment, the variable valve mechanism has an intake electric S-VT (Sequential-Valve Timing) 23 (see FIG. 4). The intake electric S-VT 23 is configured to continuously change the rotation phase of the intake camshaft within a predetermined angle range. Thereby, the opening timing and the closing timing of the intake valve 21 continuously change. The intake valve operating mechanism may have a hydraulic S-VT instead of the electric S-VT.

An exhaust port 19 is formed in the cylinder head 13 for each cylinder 11. The exhaust port 19 communicates with the combustion chamber 17. An exhaust valve 22 is arranged in the exhaust port 19. The exhaust valve 22 opens and closes between the combustion chamber 17 and the exhaust port 19. The exhaust valve 22 is opened and closed at a predetermined timing by a valve mechanism. The valve operating mechanism may be a variable valve operating mechanism that makes valve timing and/or valve lift variable. In this embodiment, the variable valve mechanism has an exhaust electric S-VT 24 (see FIG. 4). The exhaust electric S-VT 24 is configured to continuously change the rotation phase of the exhaust camshaft within a predetermined angle range. Thereby, the opening timing and the closing timing of the exhaust valve 22 continuously change. The exhaust valve mechanism may have a hydraulic S-VT instead of the electric S-VT.

An injector 6 for directly injecting fuel into the cylinder 11 is attached to the cylinder head 13 for each cylinder 11. The injector 6 is arranged so that its injection port faces the inside of the combustion chamber 17 from a central portion of the ceiling surface of the combustion chamber 17 (strictly, a portion slightly on the exhaust side from the center). The injector 6 directly injects an amount of fuel according to the operating state of the engine body 10 into the combustion chamber 17 at an injection timing set according to the operating state of the engine body 10.

An ignition plug 25 is attached to the cylinder head 13 for each cylinder 11. The spark plug 25 compulsorily ignites the air-fuel mixture in the combustion chamber 17. In this embodiment, the spark plug 25 is arranged on the intake side. The electrode of the spark plug 25 faces the combustion chamber 17 and is located near the ceiling surface of the combustion chamber 17. The spark plug 25 may be arranged on the exhaust side. Further, the spark plug 25 may be arranged on the central axis of the cylinder 11, while the injector 6 may be arranged on the intake side or the exhaust side of the central axis of the cylinder 11.

In the present embodiment, the geometric compression ratio of the engine body 10 is set to 13 or more and 30 or less. As will be described later, in the entire operating region after the engine body 10 has been warmed up, the combustion mode of the engine body 10 is such that the unburned air-fuel mixture in the combustion chamber 17 automatically burns the unburned air-fuel mixture during the flame propagation combustion of the air-fuel mixture by spark ignition. A compression ignition combustion mode is used for ignition. That is, the engine body 10 causes the mixture of fuel and intake air to be spark ignited by the spark plug 25 to perform SI (Spark Ignition) combustion, and the heat in the SI combustion causes the temperature in the combustion chamber 17 to rise. SPCCI (Spark Controlled Compression Ignition) combustion is performed in which unburned air-fuel mixture is self-ignited to perform CI (Compression Ignition) combustion. In SPCCI combustion, heat generation and pressure increase due to SI combustion are used to control the start timing of CI combustion. The geometrical compression ratio of the engine body 10 may be 14 to 17 in the regular specification (fuel octane number is about 91) and may be 15 to 18 in the high octane specification (fuel octane number is about 96). ..

An intake passage 40 is connected to one side surface of the engine body 10. The intake passage 40 communicates with the intake port 18 of each cylinder 11. The intake passage 40 is a passage through which intake air introduced into the combustion chamber 17 flows. As shown in FIGS. 1 and 2, the intake passage 40 according to the present embodiment includes a first air intake portion 141 that takes in fresh air having the same temperature as the outside air temperature, and a first air intake portion that takes in fresh air at a temperature higher than the outside air temperature. 2 air intake part 142. The configuration of each air intake part 141, 142 will be described later.

An air cleaner 41 for filtering fresh air is disposed in a portion of the intake passage 40 immediately downstream of the air intake portions 141, 142. A surge tank 42 is arranged near the downstream end of the intake passage 40. The intake passage 40 downstream of the surge tank 42 constitutes an independent passage branched for each cylinder 11. The downstream end of each independent passage is connected to the intake port 18 of each cylinder 11.

A throttle valve 43 is arranged between the air cleaner 41 and the surge tank 42 in the intake passage 40. The throttle valve 43 is configured to adjust the amount of fresh air introduced into the combustion chamber 17 by adjusting the opening of the valve.

The intake passage 40 is provided with a supercharging side passage 40a downstream of the throttle valve 43, in which a compressor of a mechanical supercharger 44 (hereinafter simply referred to as a supercharger 44) is arranged. The supercharger 44 is configured to supercharge the intake air introduced into the combustion chamber 17. In the present embodiment, the supercharger 44 is a supercharger driven by the engine body 10 (the crankshaft 15 that is the output shaft of the engine body 10). The supercharger 44 may be, for example, a Rishorum type. The structure of the supercharger 44 is not particularly limited. The supercharger 44 may be a roots type, a vane type, or a centrifugal type.

An electromagnetic clutch 45 is provided between the supercharger 44 and the engine body 10 (crankshaft 15). The electromagnetic clutch 45 transmits a drive force from the engine body 10 to the supercharger 44 between the supercharger 44 and the engine body 10 or interrupts the transmission of the drive force. As will be described later, the ECU 100 switches between disconnection and connection of the electromagnetic clutch 45 to switch the supercharger 44 between a driving state and a non-driving state. That is, the electromagnetic clutch 45 is a clutch that switches the driving state and the non-driving state of the supercharger 44.

An intercooler 46 is arranged immediately downstream of the supercharger 44 in the supercharging passage 40a. The intercooler 46 is configured to cool the intake air compressed in the supercharger 44. In this embodiment, the intercooler 46 is cooled by the intercooler cooling liquid. As will be described later in detail, the intercooler cooling liquid is a cooling liquid different from the above engine cooling liquid.

A bypass passage 47 is connected to the intake passage 40. The bypass passage 47 connects the upstream side portion of the intake air passage 40 (supercharging side passage 40a) and the downstream side portion of the intercooler 46 so as to bypass the supercharger 44 and the intercooler 46. The bypass passage 47 is provided with an air bypass valve 48 that opens and closes the bypass passage 47. In this embodiment, the air bypass valve 48 is an on/off type valve.

When the supercharger 44 is in the non-driving state (that is, when the electromagnetic clutch 45 is disengaged), the air bypass valve 48 is opened (on). As a result, the gas flowing through the intake passage 40 bypasses the supercharger 44 and is introduced into the combustion chamber 17 of the engine body 10. The engine 1 is operated in a non-supercharging state, that is, a state of natural intake.

When the air bypass valve 48 is open and the supercharger 44 is driven (that is, when the electromagnetic clutch 45 is engaged), the intake air passes through the throttle valve 43, It flows into the supply side passage 40a. A part of the intake air that has passed through the supercharger 44 flows back (is recirculated) upstream of the supercharger 44 through the bypass passage 47. At this time, in the combustion chamber 17 of the engine body 10, as in the case where the supercharger 44 is in the non-driving state, an amount of intake air (the remainder of the intake air that has passed through the supercharger 44) according to the engine specifications. be introduced. As a result, intake air can be introduced into the combustion chamber 17 in the non-supercharging state even when the supercharger 44 is in the driving state. It should be noted that supercharging is defined as a time when the pressure inside the surge tank 42 exceeds atmospheric pressure, and non-supercharging is a time when the pressure inside the surge tank 42 becomes equal to or lower than atmospheric pressure. Good.

On the other hand, when the air bypass valve 48 is in the closed state (OFF state) and the supercharger 44 is in the driven state, intake air is introduced into the combustion chamber 17 in the supercharged state. The intake amount at this time is larger than the intake amount introduced into the combustion chamber 17 in the non-supercharging state.

Thus, the air bypass valve 48 causes the supercharger 44 in the driven state to supercharge the intake air introduced into the combustion chamber 17, and the supercharger 44 in the driven state to introduce the intake air into the combustion chamber 17. It becomes possible to switch between not supercharging.

The air bypass valve 48 is not limited to an on/off type valve, and may be a valve whose opening can be continuously changed.

An exhaust passage 50 is connected to the other side surface of the engine body 10. The exhaust passage 50 communicates with the exhaust port 19 of each cylinder 11. The exhaust passage 50 is a passage through which the exhaust gas discharged from the combustion chamber 17 flows. Although not shown in detail, the upstream side portion of the exhaust passage 50 is configured by an exhaust manifold having an independent passage branched for each cylinder 11 and a gathering portion where the independent passages are gathered. The upstream end of each independent passage is connected to the exhaust port 19 of each cylinder 11.

An exhaust gas purification system having a plurality of catalytic converters (upstream and downstream catalytic converters) is disposed in the exhaust passage 50. Although not shown, the upstream catalytic converter is arranged in the engine room. The upstream catalytic converter has a three-way catalyst 511 and a GPF (Gasoline Particulate Filter) 512. The downstream catalytic converter is arranged outside the engine room. The downstream catalytic converter has a three-way catalyst 513. The exhaust gas purification system is not limited to the configuration shown in the figure. For example, the GPF may be omitted. Further, the arrangement order of the three-way catalysts 511, 513 and the GPF 512 may be changed as appropriate.

An EGR passage 52 forming an external EGR system is connected between the intake passage 40 and the exhaust passage 50. The EGR passage 52 is a passage for returning a part of exhaust gas to the intake passage 40. The upstream end of the EGR passage 52 is connected between the upstream catalytic converter and the downstream catalytic converter in the exhaust passage 50. The downstream end of the EGR passage 52 is connected to the upstream side of the supercharger 44 in the intake passage 40. Exhaust gas flowing through the EGR passage 52 (hereinafter referred to as “EGR gas”) does not pass through the air bypass valve 48 of the bypass passage 47 and flows into the supercharging side passage 40a of the intake passage 40 when being introduced into the intake passage 40. Has been done.

A liquid-cooled EGR cooler 53 is arranged in the EGR passage 52. The EGR cooler 53 cools the EGR gas passing through the EGR passage 52. An EGR valve 54 is arranged in the EGR passage 52. The EGR valve 54 is configured by a valve whose opening can be continuously changed, and is configured to adjust the flow rate of EGR gas flowing through the EGR passage 52. By adjusting the opening degree of the EGR valve 54, the recirculation amount of the cooled EGR gas can be adjusted. The EGR valve 54 may be an on/off type valve.

(Engine cooling system)
Next, the cooling system of the engine 1 will be described. As shown in FIG. 2, the cooling system of the engine 1 includes a first cooling path 60 that allows the engine cooling liquid to flow through the engine body 10 to cool the engine body 10, and an intercooler cooling liquid that flows through the intercooler 46. The second cooling path 70 is provided for cooling the intake air that has passed through the feeder 44.

In the first cooling path 60, a first pump 61, a first radiator 62 that cools the engine cooling liquid flowing through the first cooling path 60, and a temperature and a flow rate of the engine cooling liquid circulating through the first cooling path 60 are adjusted. And a flow control valve 63 for controlling the flow rate.

The first pump 61 is a mechanical pump that is driven in conjunction with the crankshaft 15 of the engine body 10. The discharge port of the first pump 61 is connected to the water jacket 12a of the cylinder block 12 of the engine body 10.

The first radiator 62 cools the engine coolant discharged from the cylinder head 13 through the water jacket 12 a of the cylinder block 12 and the water jacket of the cylinder head 13. The first radiator 62 cools the engine coolant by the traveling wind when the vehicle equipped with the engine 1 travels forward.

The flow rate control valve 63 is arranged in the middle of a path through which the engine coolant discharged from the first radiator 62 and flowing into the first pump 61 passes. That is, the flow rate control valve 63 is arranged on the inlet side to the engine body 10 in the first cooling path 60. In this embodiment, the flow rate control valve 63 is composed of an electric thermostat valve. Specifically, the flow rate control valve 63 is a thermostat valve having a heating wire built therein. The flow rate control valve 63 is basically configured to open according to the temperature of the engine cooling liquid when the temperature of the engine cooling liquid is equal to or higher than a preset liquid temperature, but a current is supplied to the heating wire. By flowing it, the engine coolant can be opened even when the temperature is lower than the set temperature.

FIG. 3 shows an example of the characteristic of the flow rate control valve 63 with respect to the temperature of the engine coolant. In FIG. 3, the temperature of the engine coolant shown on the horizontal axis is the temperature at the position of the flow rate control valve 63, and is different from the temperature of the engine coolant flowing into the first radiator 62. However, the temperature of the engine cooling liquid supplied from the engine body 10 to the first radiator 62 is substantially determined by the temperature at the position of the flow rate control valve 63.

As shown in FIG. 3, the flow control valve 63 starts to open when the temperature of the engine coolant is 95° C. to 96° C. when not energized, while the temperature of the engine coolant is below 95° C. when energized. Can be opened. As shown in FIG. 3, the temperature at which the flow rate control valve 63 starts to open decreases as the current flowing through the heating wire increases. Further, the opening degree of the flow rate control valve 63 when the temperature of the engine coolant is constant should be increased as the current flowing through the heating wire is increased in a range where the opening degree of the flow rate control valve 63 is smaller than full opening. You can According to the opening degree of the flow rate control valve 63, the flow rate of the engine cooling liquid circulating in the first cooling path 60 (that is, the flow rate of the engine cooling liquid supplied from the engine body 10 to the first radiator 62) is changed. Become. In the present embodiment, the set liquid temperature is set to 95°C to 96°C.

The amount of electricity supplied to the flow rate control valve 63 is adjusted based on the operating state of the engine body 10 and the outside air temperature so that the temperature of the engine coolant becomes an appropriate temperature.

The flow rate control valve 63 may be an electromagnetic valve such as a solenoid valve instead of the thermostat valve. In the case of an electromagnetic valve, the temperature of the engine coolant cannot be adjusted, so the temperature of the engine coolant is adjusted by a grill shutter 81 and a radiator fan 82, which will be described later.

Although not shown, the first cooling path 60 also passes through the EGR cooler 53. That is, the EGR gas passing through the EGR passage 52 is cooled by exchanging heat with the engine coolant.

The second cooling path 70 is provided with a second pump 71 and a second radiator 72 that cools the intercooler cooling liquid flowing through the second cooling path 70.

The second pump 71 is an electric pump that is driven by being supplied with electric power. The second pump 71 is configured such that the larger the supplied power, the larger the discharge amount of the intercooler cooling liquid.

The second radiator 72 cools the intercooler cooling liquid discharged from the intercooler 46. In the present embodiment, the second radiator 72 is arranged adjacent to the lower side of the first radiator 62. The second radiator 72 cools the intercooler cooling liquid by the traveling wind when the vehicle equipped with the engine 1 travels forward. The intercooler cooling liquid cooled by the second radiator 72 flows into the second pump 71.

The cooling system of the engine 1 has a grill shutter 81 and a radiator fan 82 as a mechanism for allowing traveling air to pass through the first and second radiators 62 and 72.

The grill shutter 81 is provided on the vehicle front side of the first and second radiators 62 and 72. The grill shutter 81 is composed of a plurality of flappers 81a that rotate around an axis extending in the vehicle width direction. The grill shutter 81 is fully opened when each flapper 81a is vertical to the vertical direction, and is fully closed when each flapper 81a is substantially parallel to the vertical direction. The flow rate of the air taken into the engine room, that is, the air volume of the air (running wind) passing through the first and second radiators 62 and 72 is adjusted by the angle of each flapper 81a with respect to the vertical direction. The angle of each flapper 81a with respect to the vertical direction (that is, the opening degree of the grill shutter 81) is electrically adjustable. The "vertical direction" referred to here is the vertical direction with respect to the vehicle and corresponds to the direction perpendicular to the road surface.

The radiator fan 82 is provided on the vehicle rear side of the first and second radiators 62 and 72. The radiator fan 82 draws traveling wind by rotating, and assists the traveling wind to pass through the first and second radiators 62 and 72. The radiator fan 82 is configured such that the higher the number of revolutions, the greater the amount of running air drawn. The radiator fan 82 is configured to be electrically adjustable in rotation speed.

The traveling wind taken in from the grill shutter 81 exchanges heat with the cooling liquids flowing through the first and second radiators 62 and 72 to cool the cooling liquids. The traveling wind that has passed through the first and second radiators 62, 72 flows to the vehicle rear side of the radiator fan 82.

The grill shutter 81 and the radiator fan 82 together with the flow rate control valve 63 constitute liquid temperature adjusting means, and also constitute air volume adjusting means for adjusting the air volume of the air passing through the first radiator 62.

(Intake air fresh intake structure)
As described above, in the present embodiment, the intake passage 40 has the two air intake portions, the first and second air intake portions 141 and 142. As schematically shown in FIG. 2, the first air intake part 141 is provided on the vehicle front side of the grill shutter 81. The first air intake unit 141 takes in the outside air itself (air that has not been heated, etc.) into the intake passage 40. On the other hand, the second air intake portion 142 is provided on the vehicle rear side of the radiator fan 82. The second air intake part 142 takes in the air (traveling wind) flowing through the first and second radiators 62, 72 to the vehicle rear side of the radiator fan 82 into the intake passage 40. That is, the air warmed by heat exchange with the cooling liquid flowing through the first and second radiators 62 and 72 is taken in from the second air intake portion 142. Therefore, the second air intake part 142 takes in air having a temperature higher than the outside air temperature into the intake passage 40.

The first and second air intake portions 141, 142 are provided with an intake switching valve 143. The valve body of the intake switching valve 143 is arranged in each of the first and second air intake portions 141, 142, and each valve body operates in conjunction with each other. Specifically, the larger the opening degree of the valve body of the first air intake section 141, the smaller the opening degree of the valve body of the second air intake section 142. As a result, the total amount of air taken in from the first and second air intake units 141, 142 does not change, while the amount of air taken in from the first air intake unit 141 and the amount of air taken in from the second air intake unit 142. The ratio of changes. Therefore, the temperature of the air (fresh air) taken into the intake passage 40 can be adjusted by adjusting the opening degree of each valve body. Although illustration is omitted, the intake switching valve 143 according to the present embodiment changes the opening degree of each valve body in conjunction with each other by connecting each valve body with one shaft.

(Engine control system)
The engine 1 includes an ECU (Engine Control Unit) 100 that controls the operation of the engine body 10. The ECU 100 is a controller based on a well-known microcomputer, and as shown in FIG. 4, a central processing unit (CPU) 101 that executes a program, and a RAM (Random Access Memory) or a ROM, for example. A memory 102 configured by (Read Only Memory) for storing programs and data, and an input/output bus 103 for inputting/outputting electric signals are provided.

As shown in FIGS. 1 and 4, the ECU 100 includes an air flow sensor SW1, an intake air temperature sensor SW2, an exhaust gas temperature sensor SW3, a linear O2 sensor SW4, a lambda O2 sensor, a liquid temperature sensor SW6, a crank angle sensor SW7, and an accelerator. The opening sensor SW8 is connected. These sensors SW1 to SW8 output detection signals to the ECU 100, respectively.

The air flow sensor SW1 is arranged on the downstream side of the air cleaner 41 in the intake passage 40, and detects the flow rate of fresh air flowing through the intake passage 40. The intake air temperature sensor SW2 is attached to the surge tank 42 and detects the temperature of the intake air supplied to the combustion chamber 17. The exhaust temperature sensor SW3 is arranged near the downstream side of the exhaust manifold in the exhaust passage 50, and detects the temperature of the exhaust gas discharged from the combustion chamber 17. The linear O2 sensor SW4 is arranged upstream of the upstream catalytic converter in the exhaust passage 50, and detects the oxygen concentration in the exhaust gas. The lambda O2 sensor SW5 is arranged on the downstream side of the three-way catalyst 511 in the upstream catalytic converter and detects the oxygen concentration in the exhaust gas. The liquid temperature sensor SW6 is attached near the outlet of the engine cooling liquid in the cylinder head 13 of the engine body 10 and detects the temperature of the engine cooling liquid. The crank angle sensor SW7 is attached to the engine body 10 and detects the rotation angle of the crankshaft 15. The accelerator opening sensor SW8 is attached to the accelerator pedal mechanism and detects the accelerator opening corresponding to the operation amount of the accelerator pedal.

The ECU 100 determines the operating state of the engine body 10 based on the detection signals of the sensors SW1 to SW8, and calculates the control amount of each device. The ECU 100 sends a control signal related to the calculated control amount to the injector 6, the spark plug 25, the intake electric S-VT 23, the exhaust electric S-VT 24, the throttle valve 43, the electromagnetic clutch 45 of the supercharger 44, the air bypass valve 48, Output to the EGR valve 54, the flow rate control valve 63, the second pump 71, the grill shutter 81, the radiator fan 82, and the intake switching valve 143. The ECU 100 constitutes a control means for controlling the operation of the engine body 10 including the operation of the electromagnetic clutch 45.

For example, the ECU 100 calculates the engine speed of the engine body 10 based on the detection signal of the crank angle sensor SW7. The ECU 100 calculates the engine load of the engine body 10 based on the detection signal of the accelerator opening sensor SW8.

In addition, the ECU 100 determines the target EGR rate (that is, the total amount in the combustion chamber 17) based on the operating state of the engine body 10 (mainly the load of the engine body 10 and the rotation speed of the engine body 10) and a preset map. Ratio of EGR gas to gas) is set. Then, the ECU 100 determines the target EGR gas amount based on the target EGR rate and the intake air amount based on the detection signal of the accelerator opening sensor SW12, and adjusts the opening of the EGR valve 54 to adjust the opening of the combustion chamber 17. Feedback control is performed so that the amount of external EGR gas introduced therein becomes the target EGR gas amount.

Further, the ECU 100 executes air-fuel ratio feedback control when a predetermined control condition is satisfied. Specifically, the ECU 100 uses the air-fuel ratio A/F of the air-fuel mixture in the combustion chamber 17 (or the combustion chamber 17 based on the oxygen concentration in the exhaust gas detected by the linear O2 sensor SW4 and the lambda O2 sensor SW5). The fuel injection amount of the injector 6 is adjusted so that the weight ratio G/F of the gas to the fuel in the inside becomes a desired value.

(Engine operation control)
FIG. 5 illustrates an operating region map of the engine body 10 when the engine body 10 is warm (that is, after the engine body 10 is warmed up). The operating region map of the engine body 10 is determined by the load of the engine body 10 (hereinafter, referred to as engine load) and the rotation speed of the engine body 10 (hereinafter, referred to as engine speed). It is divided into three driving areas according to the high and low. Specifically, the three operation regions include a low-load low-rotation operation region A (hereinafter, also referred to as region A) that includes idle operation, the engine speed is less than the predetermined rotation speed Ne, and the engine load is less than the predetermined load Tq. Low-load high-speed operation region B (hereinafter also referred to as region B) in which the engine speed is equal to or higher than the predetermined rotation speed Ne and engine load is less than the predetermined load Tq, and high-load operation region C in which the engine load is equal to or higher than the predetermined load Tq (hereinafter , Area C). Here, the predetermined rotation speed Ne may be, for example, about 3500 rpm. Even before the engine body 10 is warmed up, the same control as after warming up may be performed by using the same map as in FIG.

In the present embodiment, the main purpose of the engine 100 is to improve the combustion stability of the engine body 10 and to improve the fuel consumption thereof. The combustion mode of the main body 10 is set to the compression ignition combustion mode in which the unburned air-fuel mixture is self-ignited at once in the combustion chamber 17 during the flame propagation combustion of the air-fuel mixture by spark ignition. That is, the ECU 100 controls the timing of spark ignition by the spark plug 25 and the like so that SPCCI combustion is performed in the combustion chamber 17 in each of the regions A to C. In order to perform this SPCCI combustion stably, the ECU 100 controls the temperature of the intake air introduced into the engine body 10 by utilizing the cooling system of the engine 1. Hereinafter, the operation of the engine body 10 in each of the areas A to C will be described in detail with reference to FIGS. 6 to 9.

(Low load/low speed operation area A)
When the operating state of the engine body 10 is in the region A, SPCCI combustion is performed in the combustion chamber 17 of the engine body 10 in a lean state in which the air-fuel ratio A/F of the air-fuel mixture is larger than the stoichiometric air-fuel ratio. Specifically, the ECU 100 causes the injector 6 to inject fuel so that the air-fuel ratio A/F in the combustion chamber 17 becomes 25 or more, and operates the spark plug 25 at a desired timing. If the air-fuel ratio A/F is 25 or more, there will be no problem in emission. In order to perform SPCCI combustion (especially CI combustion) stably in a lean state, it is necessary to raise the compression end temperature. Therefore, the ECU 100 controls the operation of each device so that the intake air having the first intake air temperature Ta1 or higher is introduced into the engine body 10. The first intake air temperature Ta1 is, for example, about 80°C.

Specifically, when the operating state of the engine body 10 is in the region A, the ECU 100 causes the first air intake portion 141 to be fully closed and the second air intake portion 142 to be fully open, as shown in FIG. Then, the operation signal is output to the intake switching valve 143. Further, the ECU 100 outputs a control signal to the electromagnetic clutch 45 and the air bypass valve 48 so that the supercharger 44 is in the non-driving state and the bypass passage 47 is in the open state, so that the electromagnetic clutch 45 is in the disengaged state. At the same time, the air bypass valve 48 is fully opened. Further, the ECU 100 turns off the power supply to the flow rate control valve 63 so that the high temperature engine coolant flows into the first radiator 62. Further, the ECU 100 adjusts the opening degree of the grill shutter 81 and the rotation speed of the radiator fan 82 so that intake air having the first intake air temperature Ta1 or higher is taken in from the second air intake 142. The ECU 100 also fully closes the EGR valve 54. As described above, in the present embodiment, when the operating state of the engine body 10 is in the region A, the EGR gas is not introduced into the combustion chamber 17 because the EGR valve 54 is fully closed. It is also possible to introduce the EGR gas into the combustion chamber 17 when the operating state of the engine body 10 is in the region A. In this case, the fuel is injected from the injector 6 so that the weight ratio G/F of the gas in the combustion chamber 17 to the fuel becomes 25 or more.

When the flow control valve 63 is de-energized, the flow control valve 63 does not open until the engine coolant reaches or exceeds the set liquid temperature. Therefore, when the engine cooling liquid is below the set liquid temperature, the engine cooling liquid is warmed by the heat of the engine body 10 without circulating. When the engine cooling liquid reaches or exceeds the set liquid temperature, the flow rate control valve 63 starts to open and the engine cooling liquid starts to circulate in the first cooling path 60. As a result, the high temperature engine cooling liquid equal to or higher than the set liquid temperature flows into the first radiator 62. The engine cooling liquid that flows into the first radiator 62 is the engine cooling liquid that is supplied from the engine body 10 to the first radiator 62, and is the engine cooling liquid that has been warmed by the engine body 10 after passing through the flow rate control valve 63. It is a liquid. Therefore, the temperature of the engine cooling liquid supplied from the engine body 10 to the first radiator 62 (corresponding to the temperature detected by the liquid temperature sensor SW6) is higher than the set liquid temperature. When the operating state of the engine body 10 is in the region A, the opening degree of the flow rate control valve 63 is such that the temperature of the engine coolant at the position of the flow rate control valve 63 is the temperature range of the "region A" in the graph of FIG. Fluctuates with.

The ECU 100 controls the operation of the grill shutter 81 and the radiator fan 82 so that the detection result of the liquid temperature sensor SW6 becomes the first liquid temperature Tw1. When the detection result of the liquid temperature sensor SW6 is less than the first liquid temperature Tw1, the ECU 100 fully closes the opening of the grill shutter 81 and sets the rotation speed of the radiator fan 82 to 0 (that is, the radiator fan 82). To the non-driving state). Accordingly, when the engine cooling liquid is lower than the first liquid temperature Tw1, the engine cooling liquid is not cooled by the traveling wind and the liquid temperature rises. When the detection result of the liquid temperature sensor SW6 is equal to or higher than the first liquid temperature Tw1, the ECU 100 opens the grill shutter 81 and increases the rotation speed of the radiator fan 82. When the grill shutter 81 is opened and the radiator fan 82 is driven in a state where the high-temperature engine cooling liquid flows into the first radiator 62, the high-temperature running wind that has exchanged heat with the high-temperature engine cooling liquid flowing through the first radiator 62 is generated. , Flows to the vehicle rear side of the radiator fan 82. As a result, high-temperature running air, that is, intake air (fresh air) having the first intake air temperature Ta1 or higher is taken into the intake passage 40 from the second air intake portion 142. The first liquid temperature Tw1 is higher than the set liquid temperature and is, for example, about 105°C.

The high-temperature intake air taken in from the second air intake portion 142 flows into the surge tank 42 through the bypass passage 47, as shown in FIG. Then, the high-temperature intake air is introduced into the combustion chamber 17 of the engine body 10.

When the detection result of the liquid temperature sensor SW6 is lower than the first liquid temperature Tw1 or when the detection result of the intake air temperature sensor SW2 is lower than the first intake air temperature Ta1, the ECU 100 sets the opening degree of the grill shutter 81. At least one of the lowering control and the lowering of the rotation speed of the radiator fan 82 is executed. As a result, intake air having a temperature equal to or higher than the first intake air temperature Ta1 is stably introduced into the engine body 10. Further, the ECU 100 adjusts the opening of the grill shutter 81 in the low opening range in order to maintain the temperature of the engine cooling liquid as high as possible in the first liquid temperature Tw1 or higher. Specifically, the opening degree of the grill shutter 81 is adjusted within a range in which the acute angle side of the flapper 81a with respect to the vertical direction is less than 30°.

By controlling the operation of each device as described above, when the engine body 10 is operating in the area A (when the operating state of the engine body 10 is in the area A), the temperature is relatively high (the first intake air temperature). Intake of (Ta1 or more) is introduced into the engine body 10. As a result, when the engine body 10 is operating in the region A, SPCCI combustion can be stably performed.

Further, the ECU 100 outputs a control signal to the second pump 71 so that the intercooler cooling liquid is supplied to the intercooler 46 when the engine body 10 is operated in the region A. That is, when the intake air having the first intake air temperature Ta1 passes through the bypass passage 47, the supercharging side passage 40a is warmed by the heat transfer from the bypass passage 47. Therefore, at the moment when the operating state of the engine body 10 changes from the area A to the area for driving the supercharger 44 (for example, the area C), the high-temperature air warmed by the heat transfer is transmitted to the engine body 10. Will be introduced. In order to suppress this, even if the supercharger 44 is in the non-driving state (that is, the electromagnetic clutch 45 is in the disengaged state), the intercooler cooling liquid is supplied to the intercooler 46 so that the air in the supercharging side passage 40a is removed. I try not to overheat. At this time, the ECU 100 outputs a control signal to the second pump 71 so that the flow rate of the intercooler cooling liquid supplied to the intercooler 46 per unit time becomes the first flow rate.

(Low load/high speed operation area B)
When the operating state of the engine body 10 is in the region B, in the combustion chamber 17 of the engine body 10, the SPCCI is in a state where the air-fuel ratio A/F (or G/F) of the air-fuel mixture becomes the stoichiometric air-fuel ratio or a value close thereto. Burning takes place. Specifically, the ECU 100 causes the injector 6 to inject fuel so that the air-fuel ratio A/F (or G/F) is 14.5 to 15.0, and operates the ignition plug 25 at a desired timing. .. When the air-fuel ratio A/F (or G/F) is 14.5 to 15.0, RawNOx generated in the combustion chamber 17 can be satisfactorily purified by the three-way catalysts 511 and 513. In the region B, since the engine speed is high, in order to perform SPCCI combustion (in particular, CI combustion) stably, it is necessary to raise the compression end temperature so that compression ignition is likely to occur. Therefore, the ECU 100 controls the operation of each device so that the intake air having the first intake air temperature Ta1 or higher is introduced into the engine body 10 when the operating state of the engine body 10 is in the region B.

Specifically, when the operating state of the engine body 10 is in the region B, the ECU 100 causes the first air intake section 141 to be fully closed and the second air intake section 142 to be fully open, as shown in FIG. 7. Then, the operation signal is output to the intake switching valve 143. In addition, the ECU 100 outputs a control signal to the electromagnetic clutch 45 and the air bypass valve 48 so that the supercharger 44 is driven and the bypass passage 47 is opened, and the electromagnetic clutch 45 is brought into a connected state. , The air bypass valve 48 is fully opened. Further, the ECU 100 turns on the power supply to the flow rate control valve 63. Further, the ECU 100 adjusts the opening degree of the grill shutter 81 and the rotation speed of the radiator fan 82 so that intake air having the first intake air temperature Ta1 or higher is taken in from the second air intake 142. The ECU 100 also opens the EGR valve 54 to introduce the EGR gas into the intake passage 40 (and thus the combustion chamber 17). It is also possible not to introduce the EGR gas into the combustion chamber 17 when the operating state of the engine body 10 is in the region B.

When the flow control valve 63 is turned on, the flow control valve 63 is opened even if the engine coolant is below the set liquid temperature. Therefore, the engine coolant circulates in the first cooling path 60 even when the engine coolant is below the set liquid temperature. As a result, the engine coolant below the first liquid temperature Tw1 flows into the first radiator 62. When the operating state of the engine body 10 is in the region B, the opening degree of the flow rate control valve 63 is such that the temperature of the engine coolant at the position of the flow rate control valve 63 is in the range of the "region B" in the graph of FIG. It fluctuates in a temperature range lower than the “region A”).

When the operating state of the engine body 10 is in the region B, the ECU 100 opens the grill shutter 81 and drives the radiator fan 82 even if the detection result of the liquid temperature sensor SW6 is lower than the first liquid temperature Tw1. More specifically, the ECU 100 adjusts the opening degree of the grill shutter 81 and the rotation speed of the radiator fan 82 so that the detection result of the liquid temperature sensor SW6 is lower than the first liquid temperature Tw1 and higher than the second liquid temperature Tw2. To do. Specifically, the ECU 100 adjusts the opening degree of the grill shutter 81 within a range in which the acute angle side angle of the flapper 81a with respect to the vertical direction is 30° or more and less than 60°. Further, the ECU 100 sets the rotation speed of the radiator fan 82 higher than when the operating state of the engine body 10 is in the region A. The traveling wind that has exchanged heat with the engine cooling liquid flowing through the first radiator 62 flows into the intake passage 40 from the second air intake portion 142 after flowing to the vehicle rear side of the radiator fan 82. At this time, the temperature of the intake air (fresh air) taken into the intake passage 40 from the second air intake portion 142 is higher than the outside air temperature, but lower than when the operating state of the engine body 10 is in the region A. The second liquid temperature Tw2 is lower than the first liquid temperature Tw1 and is, for example, about 90°C.

As described above, when the bypass passage 47 is in the open state and the supercharger 44 is in the driving state, a part of the intake air that has passed through the supercharger 44 passes through the bypass passage 47 as shown in FIG. It flows backward to the upstream side of the supercharger 44. Therefore, the intake air taken into the intake passage 40 from the second air intake portion 142 is temporarily compressed by the supercharger 44 through the supercharging side passage 40a, and a part of the compressed intake air is bypassed. While flowing back to the upstream side of the supercharger 44 in the intake passage 40 through the passage 47, the remaining intake air in an amount according to the engine specifications is introduced into the combustion chamber 17. The intake air that has flowed back to the upstream side of the supercharger 44 through the bypass passage 47 again passes through the supercharging side passage 40a (supercharger 44). As a result, the intake air in the intake passage 40 is circulated (recirculated) in the intake passage 40 via the supercharging side passage 40 a and the bypass passage 47. As a result, intake air can be introduced into the combustion chamber 17 in the non-supercharged state even when the supercharger 44 is in the driven state.

Since the intake air during recirculation is compressed by the supercharger 44, the temperature rises. Further, when the operating state of the engine body 10 is in the region B, the EGR valve 54 is in the open state, so that the EGR gas is taken into the recirculated intake air. The EGR gas has a higher temperature than the intake air taken into the intake passage 40 from the second air intake portion 142. For this reason, the temperature of the intake air in which the EGR gas is taken in rises.

Therefore, the ECU 100 outputs a control signal to the second pump 71 so that the intercooler 46 is supplied with the intercooler cooling liquid in order to prevent the intake air (fresh air+EGR gas) during the recirculation from becoming excessively hot. To do. As a result, the intake air during the recirculation is cooled by the intercooler 46. At this time, the ECU 100 outputs a control signal to the second pump 71 so that the flow rate of the intercooler cooling liquid supplied to the intercooler 46 per unit time becomes the second flow rate. The second flow rate is higher than the first flow rate, and is a flow rate such that the temperature of the recirculated intake air does not fall below the first intake air temperature Ta1.

As described above, when the engine body 10 is operated in the region B, the intake air is warmed by the recirculation of the intake air and the introduction of the EGR gas. Therefore, even if the flow rate control valve 63 is opened in a state where the engine cooling liquid is below the set liquid temperature, intake air having the first intake air temperature Ta1 or higher can be introduced into the combustion chamber 17 of the engine body 10. As a result, when the engine body 10 is operating in the region B, SPCCI combustion can be stably performed.

(High load operation area C)
When the operating state of the engine body 10 is in the region C, in the combustion chamber 17 of the engine body, the SPCCI is in a state in which the air-fuel ratio A/F (or G/F) of the air-fuel mixture becomes the stoichiometric air-fuel ratio or a value close thereto. Burning takes place. Specifically, the ECU 100 causes the injector 6 to inject fuel so that the air-fuel ratio A/F (or G/F) is 14.5 to 15.0, and operates the ignition plug 25 at a desired timing. .. When the engine load is high, the amount of fuel injection is large, so that as much intake air (fresh air) as possible is required to obtain an appropriate combustion torque. Further, when the engine load is high, the amount of fuel injection is large, so if the temperature of the engine body 10 is too high, the air-fuel mixture self-ignites during compression, resulting in early ignition of fuel at unintended timings. Will occur. Therefore, when the operating state of the engine body 10 is in the region C, in order to perform SPCCI combustion stably, it is necessary to introduce intake air (in particular, fresh air) having a low temperature and high density into the engine body 10. It is necessary to properly cool the engine body 10. Therefore, the ECU 100 controls the operation of each device so that the intake air having the second intake air temperature Ta2 or lower is introduced into the engine body 10 and the engine body 10 is appropriately cooled. The second intake air temperature Ta2 is lower than the first intake air temperature Ta1 and is, for example, about 60°C.

Specifically, when the operating state of the engine body 10 is in the region C, the ECU 100 causes the first air intake portion 141 to be fully opened and the second air intake portion 142 to be fully closed, as shown in FIG. 8. Then, the operation signal is output to the intake switching valve 143. Further, the ECU 100 outputs a control signal to the electromagnetic clutch 45 and the air bypass valve 48 so that the supercharger 44 is in the driving state and the bypass passage 47 is in the closing state, and brings the electromagnetic clutch 45 into the connected state. , The air bypass valve 48 is fully closed. Further, the ECU 100 turns on the power supply to the flow rate control valve 63. Further, the ECU 100 adjusts the opening degree of the grill shutter 81 and the rotation speed of the radiator fan 82 so that the engine cooling liquid and the intercooler cooling liquid are cooled. The ECU 100 also opens the EGR valve 54 to introduce the EGR gas into the intake passage 40 (and thus the combustion chamber 17). It is also possible not to introduce the EGR gas into the combustion chamber 17 when the operating state of the engine body 10 is in the region C.

As described above, by turning on the power supply to the flow rate control valve 63, the flow rate control valve 63 is opened even when the engine cooling liquid is below the set liquid temperature. Therefore, the engine coolant circulates in the first cooling path 60 even when the engine coolant is below the set liquid temperature. As a result, the engine coolant below the set liquid temperature flows into the first radiator 62. When the operating state of the engine body 10 is in the region C, the opening degree of the flow rate control valve 63 is such that the temperature of the engine cooling liquid at the position of the flow rate control valve 63 is the temperature range of "region C" in the graph of FIG. (Temperature range lower than "region B").

When the operating state of the engine body 10 is in the region C, the ECU 100 opens the grill shutter 81 and drives the radiator fan 82. At this time, the ECU 100 adjusts the opening degree of the grill shutter 81 and the rotation speed of the radiator fan 82 so that the detection result of the liquid temperature sensor SW6 becomes the second liquid temperature Tw2. Specifically, the ECU 100 sets the opening degree of the grill shutter 81 to a high opening side range, that is, a range in which an acute angle side (including a right angle) of the flapper 81a with respect to the vertical direction is 60° or more and 90° or less. Adjust with. Further, the ECU 100 sets the rotation speed of the radiator fan 82 higher than that when the operating state of the engine body 10 is in the region B. As a result, when the operating state of the engine body 10 is in the region C, the first and second radiators 62, 72 are compared to when the operating state of the engine body 10 is in the low load operating region (region A and region B). The air volume of the air (traveling wind) that passes through increases. As a result, the engine coolant flowing through the first radiator 62 can be positively cooled and the engine body 10 can be appropriately cooled.

On the other hand, in the intake system, intake air (fresh air) is taken into the intake passage 40 from the first air intake portion 141. When the operating state of the engine body 10 is in the region C, the EGR valve 54 is in the open state, so the EGR gas is taken into the intake air taken into the intake passage 40 from the first air intake portion 141. Further, since the air bypass valve 48 is fully closed, intake air (fresh air+EGR gas) flows toward the supercharging side passage 40a. Since the electromagnetic clutch 45 is in the connected state and the supercharger 44 is in the driven state, the intake air flowing toward the supercharging side passage 40a is supercharged by the supercharger 44. As a result, the temperature of the intake air rises.

Therefore, the ECU 100 outputs a control signal to the second pump 71 so that the intercooler cooling liquid is supplied to the intercooler 46 so that the temperature of the intake air supercharged by the supercharger 44 becomes equal to or lower than the second intake air temperature Ta2. .. At this time, the ECU 100 outputs a control signal to the second pump 71 so that the flow rate of the intercooler cooling liquid supplied to the intercooler 46 per unit time becomes the third flow rate. The third flow rate is a flow rate higher than the second flow rate. In this way, by increasing the flow rate of the intercooler cooling liquid supplied to the intercooler 46, the temperature of the intake air can be made equal to or lower than the second intake air temperature Ta2. Further, as described above, when the operating state of the engine body 10 is in the region C, the air volume of the traveling wind passing through the second radiator 72 is greater than when the operating state of the engine body 10 is in the regions A and B. Is increased. For this reason, the temperature of the intercooler cooling liquid is lower than when the operating state of the engine body 10 is in the regions A and B. As a result, the temperature of the intake air can be more efficiently reduced to the second intake air temperature Ta2 or lower.

The intake air supercharged by the supercharger 44 and cooled to the second intake air temperature Ta2 or lower by the intercooler 46 is supplied to the combustion chamber 17 of the engine body 10 via the surge tank 42.

By controlling the operation of each device as described above, when the engine body 10 is operating in the region C, intake air of a relatively low temperature (second intake air temperature Ta2 or lower) is introduced into the engine body 10, and The body 10 is cooled appropriately. As a result, when the engine body 10 is operated in the region C, SPCCI combustion can be stably performed.

(Activation of each device due to changes in the operating state of the engine body)
FIG. 9 is a time chart showing changes in the operating state of each device associated with changes in the operating state of the engine body 10. First, it is assumed that the operating state of the engine body 10 is in the region A at time t0. At this time, as described above, the ECU 100 controls the operation of each device such that the temperature of the engine cooling liquid to the first radiator 62 becomes the first liquid temperature Tw1 and the intake air temperature becomes the first intake air temperature Ta1. Further, the ECU 100 causes the injector 6 to inject fuel so that the air-fuel ratio A/F in the combustion chamber 17 becomes a lean air-fuel ratio of 25 or more, and operates the ignition plug 25 at a desired timing. Further, the ECU 100 sets the electromagnetic clutch 45 to the disengaged state and sets the air bypass valve 48 to the fully open state.

In FIG. 9, the operations of the electromagnetic clutch 45, the air bypass valve 48, and the EGR valve 54 are omitted. To explain these operations, the electromagnetic clutch 45 maintains the disengaged state until time t1, changes from the disengaged state to the connected state at time t1, and thereafter maintains the connected state. The air bypass valve 48 maintains the fully open state until the time t2, becomes the fully closed state at the time t2, and thereafter maintains the fully closed state. The EGR valve 54 maintains the fully closed state until the time t1, becomes the open state at the time t2, and thereafter maintains the open state. The opening degree of the EGR valve 54 changes according to the operating state of the engine body 10.

Next, it is assumed that the engine speed increases and the operating state of the engine body 10 shifts from the region A to the region B at time t1. At this time, the ECU 100 keeps the second air intake section 142 fully opened by the intake switching valve 143 (in the same manner as in the area A, fresh air is taken in from the second air intake section 142). Further, the ECU 100 sets the electromagnetic clutch 45 in the connected state, sets the supercharger 44 in the driven state, leaves the air bypass valve 48 in the fully open state, and recirculates part of the intake air in the intake passage 40. Let Further, the ECU 100 causes the temperature of the engine cooling liquid supplied from the engine body 10 to the first radiator 62 to be lower than the first liquid temperature Tw1 and higher than the second liquid temperature Tw2, and the intake temperature to become the first intake temperature Ta1. To control the operation of each device. Specifically, the ECU 100 starts energizing the flow rate control valve 63, increases the opening degree of the grill shutter 81, and increases the rotation speed of the radiator fan 82 to increase the temperature of the engine coolant to the first radiator 62. Is set to a temperature lower than the first liquid temperature Tw1 and higher than the second liquid temperature Tw2. Further, the ECU 100 opens the EGR valve 54. Further, the ECU 100 increases the flow rate of the second pump 71 (from the first flow rate to the second flow rate). In this way, the intake air temperature is set to the first intake air temperature Ta1. Furthermore, the ECU 100 causes the injector 6 to inject fuel so that the air-fuel ratio A/F (or G/F) becomes the stoichiometric air-fuel ratio or a value close thereto (14.5 to 15.0), and the desired timing is obtained. The spark plug 25 is operated with.

Thus, when the operating state of the engine body 10 shifts from the region A to the region B as the engine speed increases, the air-fuel ratio A/F (or G/F) in the combustion chamber 17 is 25 or more. From the value, it will be set to a value of 14.5-15.0.

If the air-fuel ratio A/F (or G/F) is set to a lean air-fuel ratio of 25 or more in the region B as well as in the region A, the operation of the engine body 10 increases as the engine speed increases. When the electromagnetic clutch 45 is turned on when the state shifts from the region A to the region B, the temperature of the intake air compressed by the supercharger 44 and sucked into the combustion chamber 17 temporarily rises. This is because it is difficult for the intercooler 46 provided on the downstream side of the supercharger 44 to immediately cool the intake air in response to the above transition. Here, in the present embodiment, when the operating state of the engine body 10 is in the region A, as described above, the intercooler cooling liquid is supplied to the intercooler 46 by the second pump 71 at the first flow rate, and is completely supplied. It is possible to cool the intake air earlier by the intercooler 46 at the time of the above transition, as compared with the case where it is not performed. However, even in such a case, the temperature of the intake air taken into the combustion chamber 17 temporarily rises.

When the intake air whose temperature has temporarily risen in this way is taken into the combustion chamber 17, the density of the taken intake air decreases, so that the air-fuel ratio is assumed to be the intake of sufficiently cooled intake air, for example. When the fuel is injected to reach 25, the actual air-fuel ratio becomes smaller than 25 (for example, about 23). As a result, the RawNOx generation amount increases as the air-fuel ratio decreases. With such a lean air-fuel ratio, the purification rate of RawNOx by the three-way catalysts 511, 513 becomes low, so that the air-fuel ratio A/F (or G/F) becomes small as described above, and the amount of RawNOx generation increases. Then, the emission performance is temporarily reduced.

On the other hand, in the present embodiment, when the operating state of the engine body 10 shifts from the region A to the region B as the engine speed increases, even if the intake air temperature temporarily rises, By setting the fuel ratio A/F (or G/F) to 14.5 to 15.0, RawNOx can be satisfactorily purified by the three-way catalysts 511 and 513. Therefore, it is possible to suppress a temporary decrease in emission performance when the operating state of the engine body 10 shifts from the region A to the region B as the engine speed increases.

Next, it is assumed that the engine load increases and the operating state of the engine body 10 shifts from the region B to the region C at time t2. At this time, the ECU 100 fully closes the air bypass valve 48 while keeping the electromagnetic clutch 45 in the connected state (while keeping the supercharger 44 in the driven state), and the supercharged intake air is supplied to the engine body 10. To be done. Further, the ECU 100 controls the operation of each device such that the temperature of the engine cooling liquid supplied from the engine body 10 to the first radiator 62 becomes the second liquid temperature Tw2 and the intake air temperature becomes the second intake air temperature Ta2. .. Specifically, the ECU 100 keeps the energization of the flow rate control valve 63 turned on. Further, the ECU 100 further increases the opening degree of the grill shutter 81 and further increases the rotation speed of the radiator fan 82. With these, the temperature of the engine cooling liquid becomes the second liquid temperature Tw2. Further, the ECU 100 operates the intake switching valve 143 so that fresh air is taken in from the first air intake portion 141. Further, the ECU 100 further increases the flow rate of the second pump 71 (from the second flow rate to the third flow rate). With these, the intake air temperature becomes the second intake air temperature Ta2. Further, the ECU 100 causes the injector 6 to inject fuel so that the air-fuel ratio A/F (or G/F) becomes a theoretical air-fuel ratio or a value close thereto (14.5 to 15.0), and at a desired timing. The spark plug 25 is activated.

Therefore, in this embodiment, since the air-fuel ratio A/F (or G/F) in the combustion chamber 17 in the region B is set to 14.5 to 15.0, the engine speed increases as the engine speed increases. When the operating state of the main body 10 shifts from the area A to the area B, it is possible to suppress a temporary decrease in emission performance.

Further, in the present embodiment, even when the operating state of the engine body 10 shifts from the region A to the region C as the engine load increases, it is possible to suppress a temporary decrease in emission performance.

The present invention is not limited to the above-mentioned embodiment, and can be substituted within the scope not departing from the spirit of the claims.

For example, in the above embodiment, the ECU 100 is configured to set the air-fuel ratio A/F (or G/F) in the combustion chamber 17 to 14.5 to 15.0 in the entire region B. For example, as shown in FIG. 10, when the ECU 100 is in the specific rotation speed region B1 which is a region from the predetermined rotation speed Ne in the region B to a rotation speed (Ne+α) higher by the predetermined amount α, the ECU 100 The air-fuel ratio A/F (or G/F) of 1 is set to 14.5 to 15.0, while the air-fuel ratio A in the combustion chamber 17 is set in the region B2 other than the specific rotational speed region B1 in the region B. /F (or G/F) may be configured to have a lean air-fuel ratio of 25 or more. Even in this case, as in the above embodiment, when the operating state of the engine body 10 shifts from the region A to the region B1 as the engine speed increases, the air-fuel ratio A/F (or G/ F) is changed from a value of 25 or more to a value of 14.5 to 15.0, and a temporary decrease in emission performance can be suppressed. When the engine speed continues to increase and the operating state of the engine body 10 shifts from the region B1 to the region B2, the air-fuel ratio A/F (or G/F) in the combustion chamber 17 is set to 25 or more again. It In this case, by setting the value of the predetermined amount α to an appropriate value, the intake air is appropriately cooled by the intercooler 46 at the stage of shifting from the region B1 to the region B2. Further, the fuel economy can be improved by setting the air-fuel ratio A/F (or G/F) in the combustion chamber 17 in the region B2 to 25 or more. Further, even when the operating state of the engine body 10 shifts from the region A or B2 to the region C as the engine load increases, it is possible to suppress a temporary decrease in emission performance. Note that control other than the air-fuel ratio A/F (or G/F) in the region B (region B1 and region B2) may be the same as the control in the region B in the above embodiment.

Further, in the above-described embodiment, the intercooler cooling liquid is supplied to the intercooler 46 even when the operating state of the engine body 10 is in the region A. However, when the operating state of the engine body 10 is in the region A, it is not always necessary. It is not necessary to supply the intercooler cooling liquid to the intercooler 46. Even in this case, the air-fuel ratio A/F (or G/F) in the combustion chamber 17 in the region B (or region B1) is set to 14.5 to 15.0, so that the engine speed increases. Accordingly, it is possible to suppress the temporary deterioration of the emission performance when the operating state of the engine body 10 shifts from the region A to the region B.

Further, in the above-described embodiment, the SPCCI combustion is performed in the combustion chamber 17 in the entire operating region after the engine body 10 is warmed up, but the present invention is not limited to this. For example, SPCCI combustion may be performed only when the operating state of the engine body 10 is in the region C, and SI combustion may be performed in the regions A and B where supercharging is not performed. Alternatively, SI combustion may be performed in the entire operating region of the engine body 10. Further, not only after warming up the engine body 10 but also before warming up, SPCCI combustion may be performed, or SI combustion may be performed before warming up.

Further, in the above-described embodiment, the air intake portion of the intake passage 40 is the first intake intake portion 141 and the second air intake portion 142, but the present invention is not limited to this, and the air intake portion of the intake passage 40 is not limited to this. May be only the first intake intake section 141. However, it is preferable to provide the first intake air intake portion 141 and the second air intake portion 142 from the viewpoint that the intake air having the first intake air temperature Ta is supplied to the engine body 10 when the engine load is low. ..

Furthermore, in the above embodiment, when the operating state of the engine body 10 is in the region B, the ECU 100 controls the intake switching valve 143 so that the first air intake part 141 is fully closed and the second air intake part 142 is fully open. The operation was controlled so that it would be in the state. Not limited to this, the ECU 100 controls the operation of the intake switching valve 143 so that both the first air intake portion 141 and the second air intake portion 142 open when the operating state of the engine body 10 is in the region B. May be. In this case, the ECU 100 controls the first air intake portion 141 so that the ratio of the amount of fresh air taken in from the second air intake portion 142 becomes an appropriate ratio. The opening degree of the intake section 141 and the opening degree of the second air intake section 142 are adjusted.

The embodiments described above are merely examples, and the scope of the present invention should not be limitedly interpreted. The scope of the present invention is defined by the scope of the claims, and all modifications and changes belonging to the equivalent range of the scope of the claims are within the scope of the present invention.

The present invention relates to an engine main body having a cylinder in which a combustion chamber is formed, a mechanical supercharger arranged in an intake passage connected to the engine main body, and transmission of driving force to the mechanical supercharger. It is useful for a control device for an engine with a supercharger, which has a clutch for connecting and disconnecting.

1 Engine with Supercharger 10 Engine Main Body 40 Intake Passage 44 Mechanical Supercharger 45 Electromagnetic Clutch 100 ECU (Control Unit)

Claims (4)

An engine body having a cylinder in which a combustion chamber is formed, a mechanical supercharger disposed in an intake passage connected to the engine body, and a clutch for intermittently transmitting driving force to the mechanical supercharger A control device for a supercharged engine having:
A control means for controlling the operation of the engine body including the operation of the clutch,
The control means, at least after warming up the engine body,
When the operating state of the engine body is in the low load/low rotation operating region where the load is lower than the predetermined load and lower than the predetermined rotation speed, the clutch is disengaged to stop the mechanical supercharger. And the air-fuel ratio A/F in the combustion chamber or the weight ratio G/F of the gas in the combustion chamber to the fuel is set to lean of 25 or more,
When the operating state of the engine body is in the low load high rotation operating region of the load lower than the predetermined load and the predetermined number of revolutions or more, the clutch is connected to drive the mechanical supercharger,
When the operating state of the engine body shifts from the low-load low-rotation operating region to the low-load high-rotation operating region as the engine speed increases, the A/F or G/F in the combustion chamber is changed. A control device for a supercharged engine, wherein the control device is configured to be 14.5 to 15.0. The control device for the engine with the supercharger according to claim 1,
At least after warming up the engine body, the control means sets the A/F or G/F in the combustion chamber to 14.5 to 10 when the operating state of the engine body is in the low load and high rotation operation region. A control device for an engine with a supercharger, which is configured to be 15.0. The control device for the engine with the supercharger according to claim 1,
The control means, at least after warming up the engine body, has a specific rotation speed in which the operating state of the engine body is a region from the predetermined rotation speed to a rotation speed higher by a predetermined amount in the low load high rotation operation region. When it is in the several range, the A/F or G/F in the combustion chamber is set to 14.5 to 15.0, while when it is in the range other than the specific rotation speed range in the low load high rotation operation range. A control device for an engine with a supercharger, wherein the A/F or G/F in the combustion chamber is configured to be leaner than 25. The control device for the engine with a supercharger according to any one of claims 1 to 3,
The control means drives the mechanical supercharger by connecting the clutch when the operating state of the engine body is in a high-load operating region of the predetermined load or more, at least after the engine body is warmed up. In addition, the control device for the engine with a supercharger is characterized in that the A/F or G/F in the combustion chamber is set to 14.5 to 15.0.

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