Engine System

Abstract

To provide an engine system capable of improving fuel consumption by reducing pumping loss, while suppressing generation of an exhaust sound due to exhaust pulsation.SOLUTION: An engine system 100 of an engine 1 switchable between a full cylinder operation in which a fuel is supplied to all of a plurality of cylinders 2A-2D to be burnt, and a reduced-cylinder operation in which specific cylinders (2A, 2D) are stopped, includes: an exhaust passage 20; a throttle valve 26 for opening and closing the exhaust passage; and a controller 102 adjusting an opening of the throttle valve. The controller 102 is constituted to determine whether the engine 1 executes the cylinder-reduced operation or the full cylinder operation, determine whether an engine rotation speed is within a specific rotation speed range F in which the exhaust pulsation is lowered or not in a case when the cylinder-reduced operation is determined, and adjust the opening of the throttle valve to the opening between the full-open and full-close when the engine rotation speed within the specific rotation speed range, is determined.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an engine system, and more particularly to an engine system capable of switching between all-cylinder operation and reduced-cylinder operation in which specific cylinders are deactivated. [Background technology]

[0002] Patent Document 1 discloses a technique for suppressing the propagation of exhaust pulsation to the intake passage via the EGR cooler by narrowing the exhaust passage throttle valve during reduced-cylinder operation to reduce the passage cross-sectional area. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-65465 A Summary of the Invention [Problem to be solved by the invention]

[0004] As a result of extensive research and development into such technology, the inventors have discovered that throttling the throttle valve in the exhaust passage as in Patent Document 1 makes it difficult for exhaust gas to pass through, which increases pumping loss and can result in poor fuel economy.

[0005] Therefore, the present invention has been made to solve the above-mentioned problems, and aims to provide an engine system that can reduce pumping loss and improve fuel efficiency while suppressing the generation of exhaust noise due to exhaust pulsation. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the present invention provides an engine system for an engine that can switch between full-cylinder operation, in which fuel is supplied to all of a plurality of cylinders for combustion, and reduced-cylinder operation, in which fuel supply to specific cylinders among the plurality of cylinders is stopped to deactivate the specific cylinders, the engine system including an exhaust passage of the engine, a throttle valve provided in the exhaust passage for opening and closing the exhaust passage, and a controller connected to the throttle valve for adjusting the opening of the throttle valve, the controller determining whether the engine is in reduced-cylinder operation or full-cylinder operation, and when it is determined that the engine is in reduced-cylinder operation, the engine speed is increased, exhaust pulsation is reduced, and the engine speed is increased. This reduces the exhaust noise. It is judged whether the rotation speed is within a specific range, and if it is judged to be within the specific range, the opening of the throttle valve is Does not include full open and full closed It is configured to adjust the opening between fully open and fully closed.

[0007] According to the present invention thus configured, when the engine speed is within a specific range of rotational speeds where exhaust pulsation is low during reduced-cylinder operation, the throttle valve is opened between fully closed and fully open (an intermediate opening that does not include fully closed and fully open), so that it is possible to reduce pumping loss and improve fuel efficiency while suppressing the generation of exhaust noise due to exhaust pulsation. In other words, since exhaust pulsation (pressure wave in the exhaust passage) within the specific range of rotational speeds is relatively lower than exhaust pulsation at engine speeds outside the specific range of rotational speeds, exhaust noise does not increase excessively even if the throttle valve is not fully closed, and by opening the throttle valve between fully closed and fully open, it is possible to reduce pumping loss and improve fuel efficiency.

[0008] In the present invention, the opening degree of the throttle valve between the fully open and fully closed positions is preferably larger than the opening degree of the throttle valve when the engine speed is higher than the specific speed range. According to the present invention thus configured, first, when the engine speed is higher than the specific speed range, exhaust pulsation becomes relatively large, so exhaust noise can be suppressed by narrowing the throttle valve opening. Second, when the engine speed is within the specific speed range, which is lower than the high speed range, exhaust pulsation is relatively small, so by making the throttle valve opening between full open and full closed larger than the throttle valve opening at high speed, it is possible to reduce pumping loss and improve fuel efficiency while suppressing the generation of exhaust noise due to exhaust pulsation.

[0009] In the present invention, the throttle valve is preferably provided with a position sensor which detects its opening degree, and when the actual opening degree of the throttle valve detected by the position sensor deviates from the target opening degree, which is an opening degree between the fully open and fully closed positions of the throttle valve, the controller controls the throttle valve so that the opening degree of the throttle valve becomes the target opening degree. According to the present invention configured in this manner, the accuracy of the opening degree of the throttle valve is improved, so that an increase in exhaust noise can be more reliably suppressed and fuel economy can be more reliably improved.

[0010] In the present invention, the specific rotation speed is preferably determined by the configuration of a middle pipe of the exhaust passage. According to the present invention configured in this manner, it is possible to more effectively suppress the generation of exhaust noise due to exhaust pulsation while reducing pumping loss and improving fuel efficiency.

[0011] In the present invention, preferably, the range of the specific rotation speed is The exhaust pulsation reaches a valley between the two resonance points of the engine speed. This is the range of engine speeds including RPM. According to the present invention configured in this manner, it is possible to more effectively suppress the generation of exhaust noise due to exhaust pulsation while reducing pumping loss and improving fuel efficiency. Effect of the Invention

[0012] According to the engine system of the present invention, it is possible to reduce pumping loss and improve fuel efficiency while suppressing the generation of exhaust noise due to exhaust pulsation. [Brief description of the drawings]

[0013] [Figure 1] 1 is a diagram showing an overall configuration of an engine system according to an embodiment of the present invention. [Diagram 2] 1 is a control block diagram of a control device for an engine system according to an embodiment of the present invention. [Diagram 3] 4 is a map showing an operating region during full cylinder operation and reduced cylinder operation of the engine system according to the present embodiment, together with the presence or absence of EGR. [Figure 4] 4 is a diagram showing an example of increase and decrease in exhaust sound due to resonance / anti-resonance of exhaust pulsation in an exhaust passage versus engine speed. FIG. [Diagram 5] 3 is a flowchart showing a control flow of the engine system according to the present embodiment. [Figure 6] 5 is a flowchart showing a control flow of an exhaust shutter valve by the engine system according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an automobile suspension device according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First, the overall configuration of an engine system according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a diagram showing an overall configuration of an engine system according to an embodiment of the present invention. As shown in Fig. 1, the engine 1 to which the engine system 100 of this embodiment is applied is a four-stroke multi-cylinder gasoline engine mounted on a vehicle as a power source. Specifically, the engine 1 is an in-line four-cylinder engine arranged in a specific direction, and has four cylinders 2A to 2D. The engine 1 includes an intake passage 10 for introducing air for combustion into the engine 1, an exhaust passage 20 for discharging exhaust gas (combustion gas) generated in each of the cylinders 2A to 2D of the engine 1, and an EGR device 50 for recirculating a part of the exhaust gas flowing through the exhaust passage 20 to the intake passage 10 as EGR gas. The EGR device 50 includes an EGR passage 51 connecting the exhaust passage 20 and the intake passage 10, and an EGR cooler 52 and an EGR valve 53 provided in the EGR passage 51.

[0016] In addition, although not shown, engine 1 has a cylinder block in which cylinders 2A-2D are formed, and a cylinder head provided on the upper surface of the cylinder block, and the cylinder head is provided with intake ports for introducing air supplied from intake passage 10 into each of cylinders 2A-2D, exhaust ports for directing exhaust gas generated in each of cylinders 2A-2D to exhaust passage 20, intake valves for opening and closing the communication between each of cylinders 2A-2D and the intake ports, and exhaust valves for opening and closing the communication between each of cylinders 2A-2D and the exhaust ports.

[0017] The cylinder head is provided with an injector 8 (see FIG. 2) that injects fuel into each of the cylinders 2A to 2D, and a spark plug 9 (see FIG. 2) that discharges a spark into each of the cylinders 2A to 2D to combust the fuel injected from the injector 8. In the four-stroke, four-cylinder engine 1 of this embodiment, the ignition timing by the spark plug 9 is set so that combustion occurs every 180° CA in crank angle. Specifically, assuming that the cylinder 2A shown in FIG. 1 is the first cylinder, the cylinder 2B is the second cylinder, the cylinder 2C is the third cylinder, and the cylinder 2D is the fourth cylinder, the ignition timing is set so that combustion occurs every 180° CA at equal intervals in the order of the first cylinder 2A, the third cylinder 2C, the fourth cylinder 2D, and the second cylinder 2B.

[0018] Here, the engine 1 of this embodiment is a variable cylinder engine that can perform not only all-cylinder operation in which all four cylinders 2A to 2D are operated by executing combustion, but also reduced-cylinder operation in which two of the four cylinders 2A to 2D are stopped (combustion is stopped) and the remaining two cylinders are operated (combustion is performed). In such a variable cylinder engine, in order to suppress vibrations occurring in the engine 1 during reduced-cylinder operation, it is desirable to select and stop specific cylinders whose ignition order (combustion order) is not consecutive. In this embodiment, during reduced-cylinder operation, the first cylinder 2A and the fourth cylinder 2D, whose ignition order is not consecutive, are stopped as specific cylinders, and only the remaining second cylinder 2B and third cylinder 2C are operated. Fuel injection by the injector 8 is stopped for the cylinders to be stopped.

[0019] During reduced cylinder operation, it is desirable to stop the opening and closing of the intake valves and exhaust valves of the deactivated cylinders from the viewpoint of reducing pumping loss, etc. Therefore, in this embodiment, a valve stop mechanism 14 (see FIG. 2) is built into the valve gear (not shown) to stop the opening and closing of the intake valves and exhaust valves of the first cylinder 2A and the fourth cylinder 2D (specific cylinders) that are deactivated during reduced cylinder operation and maintain them in a closed state.

[0020] The intake passage 10 has one intake pipe 11 extending from an air cleaner (not shown) on the upstream side toward the engine 1, a surge tank 12 of a predetermined capacity to which the downstream end of the intake pipe 11 is connected, and four independent intake pipes 13 branching off from the surge tank 12 and extending therefrom, the downstream ends of which are connected to the intake ports 4 of the cylinders 2A to 2D, respectively. An electric throttle valve 15 is provided in the intake pipe 11, and the passage cross-sectional area of ​​the intake pipe 11 is increased or decreased by opening and closing this throttle valve 15.

[0021] The exhaust passage 20 has an exhaust manifold 21 of a so-called 4-2-1 layout type, and one exhaust pipe 24 provided continuously with the downstream end of the exhaust manifold 21 . A first catalytic device 22 (so-called "direct catalyst") for purifying harmful components in the exhaust gas is provided in the exhaust manifold 21. Note that "upstream" and "downstream" of the exhaust passage 20 refer to the flow direction of the exhaust gas flowing inside the exhaust passage.

[0022] The 4-2-1 layout type exhaust manifold 21 is laid out so that the independent exhaust pipes for cylinders whose combustion order is not consecutive are joined together for reasons such as improving exhaust efficiency. That is, first, the independent exhaust pipes for the first cylinder 2A and the fourth cylinder 2D are joined together, and then the independent exhaust pipes for the second cylinder 2B and the third cylinder 2C are joined together, and these exhaust pipes are further joined together and connected to the exhaust pipe 24 described above.

[0023] An exhaust pipe 24 is connected to the downstream end of the exhaust manifold 21 via a second catalytic device 23 (so-called "main catalyst") that is separate from the first catalytic device 22. A pre-silencer 25 and an exhaust shutter valve (exhaust SV) 26 are provided midway through the exhaust pipe 24, and a main silencer 27 is connected to the downstream end of the exhaust pipe 24. The pre-silencer 25 reduces mainly high-frequency components in the exhaust sound. The main silencer 27 reduces mainly low-frequency components in the exhaust sound, and is formed with a larger capacity than the pre-silencer 25.

[0024] The exhaust shutter valve 26 is an electrically operated opening / closing valve provided to increase / decrease the passage cross-sectional area of ​​the exhaust pipe 24. An exhaust shutter valve position detection sensor (exhaust SV opening sensor) 28, SN7 (see FIG. 2) is attached to the exhaust shutter valve 26 to detect its opening.

[0025] Here, in the exhaust pipe 24, the section from the outlet of the second catalytic converter 23 to the inlet of the main silencer 27 is called the middle pipe 29. The configuration of this middle pipe 29 affects the loudness (volume) of the exhaust sound. That is, exhaust pulsation, which is a pressure wave generated when exhaust gas is discharged from the exhaust port, coincides with the natural frequency of cavity resonance determined by the configuration of the middle pipe 29, or the pressure waves cancel each other out, causing resonance (cavity resonance) and anti-resonance of the exhaust pulsation (see FIG. 4), which increases or decreases the volume of the exhaust sound. In this embodiment, in order to adjust the loudness of the exhaust sound, the opening degree of the exhaust shutter valve 26 is controlled according to the state of resonance and anti-resonance of such exhaust pulsation.

[0026] The main factors in the configuration of the middle pipe 29 that affects the cavity resonance are the length and diameter of the exhaust system of the exhaust pipe 24, including the pre-silencer 25 and the exhaust shutter valve 26. These main factors of the exhaust system determine the natural frequency of the cavity resonance in the middle pipe 29. A specific rotation speed range F shown in Fig. 4, which will be described later, is determined by experiments or the like, based on the configuration of the middle pipe 29.

[0027] Next, a control block of the control device for an engine system according to an embodiment will be described with reference to Fig. 2. Fig. 2 is a control block diagram of the control device for an engine system according to an embodiment of the present invention. 2, the engine system 100 according to this embodiment has a controller (ECU) 102 that controls the valve stop mechanism 14, the exhaust shutter valve (exhaust SV) 26, etc. The controller 102 is configured with circuits and is a controller based on a well-known microcomputer. The controller 102 includes a microprocessor 104 as a central processing unit (CPU) that executes programs, a memory 106 configured with, for example, RAM or ROM and that stores programs and data, an interface circuit that inputs and outputs electrical signals, etc.

[0028] Using these hardware and software, the controller 102 functionally has, as will be described later, a calculation unit that calculates a target engine load, a cylinder stop determination unit that determines whether the engine 1 is operating in reduced cylinder operation or full cylinder operation, an exhaust SV control unit that controls the opening degree of the exhaust shutter valve 26 depending on whether it is operating in reduced cylinder operation or full cylinder operation, and further depending on reduced cylinder operation within a specific rotation speed range that will be described later, and a correction control unit that controls the actual opening degree of the exhaust shutter valve 26 to be the target opening degree.

[0029] The controller 102 also has a function of a cylinder number control unit, which determines whether the engine should operate with reduced cylinders or with all cylinders based on the engine operating conditions (load, rotation speed, etc.) identified from the detection values ​​of an airflow sensor, engine speed sensor SN5, and accelerator opening sensor SN6 (not shown), and controls the injector 8, spark plug 9, valve stop mechanism 14, etc. based on the result of the determination.

[0030] Connected to the input side of the controller 102 are mainly a water temperature sensor SN1 which detects the temperature of the engine coolant for the engine 1, an oil temperature sensor SN2 which detects the temperature of the engine oil for the engine 1, a vehicle speed sensor SN3 which detects the speed of the vehicle equipped with the engine system 100, a gear position sensor SN4 which detects the gear position of a transmission (not shown) equipped on the vehicle, an engine speed sensor SN5 which detects the engine speed, which is the rotation speed of the engine output shaft (crankshaft), an accelerator opening sensor SN6 which detects the opening of an accelerator pedal (not shown) operated by the driver who drives the vehicle, and an exhaust SV position sensor SN7 (indicated by reference symbol 28 in FIG. 1) which detects the opening of the exhaust shutter valve 26, and signals corresponding to the detection values ​​of each of the sensors SN1 to SN7 are input to the controller 102.

[0031] Furthermore, the output side of the controller 102 is mainly connected to the injector 8, the spark plug 9, the valve stop mechanism 14, the throttle valve 15, and the exhaust shutter valve 26, and the controller 102 controls them based on the output signals from the sensors SN1 to SN7. That is, the controller 102 controls the injector 8 to control the fuel injection timing, controls the spark plug 9 to control the ignition timing, controls the valve stop mechanism 14 to stop the opening and closing operation of the intake valve and exhaust valve to maintain the valve closed state, and controls the throttle valve 15 to change the passage cross-sectional area of ​​the intake pipe 11, thereby adjusting the amount of intake air into the combustion chamber of each cylinder 2A to 2D. In addition, the air-fuel ratio is controlled by controlling the throttle valve 15 and the injector 8, and the load (torque) generated by the engine 1 is controlled to become a target engine load by controlling the injector 8, the spark plug 9 and the throttle valve 15. In addition, in the cylinder stop region described below, the valve stop mechanism 14 is controlled to stop the opening and closing operation of the intake valve and exhaust valve, and the exhaust shutter valve 26 is controlled to increase or decrease the passage cross-sectional area of ​​the exhaust pipe 24, thereby controlling the flow rate of exhaust gas flowing through the exhaust pipe 24.

[0032] Next, the operating regions of the engine system according to this embodiment in full cylinder operation and reduced cylinder operation will be described with reference to Fig. 3. Fig. 3 is a map of engine speed and engine load showing the operating regions of the engine system according to this embodiment in full cylinder operation and reduced cylinder operation with and without EGR. In Fig. 3, the operating region A is a region where the engine operates with reduced cylinders, and the other regions are regions where the engine operates with all cylinders. In the example of Fig. 3, the reduced cylinder operating region A is set in an overlapping region of the load range X of the engine load excluding the low load region near no load and the high load region, and the speed range Y of the engine speed (engine rotation speed) excluding the low speed region and the high speed region. In addition, the target EGR rate is set so that the presence or absence of EGR is switched at a boundary line L set outside the reduced-cylinder operation region A.

[0033] The cylinder number control unit of the controller 102 described above executes control for reduced cylinder operation to deactivate the first cylinder 2A and the fourth cylinder 2D when the operating conditions specified by the sensors SN1 to SN7 match the reduced cylinder operating region A. That is, the cylinder number control unit stops the operation of the injector 8 and the spark plug 9 of the first cylinder 2A and the fourth cylinder 2D, and drives the valve stop mechanism 14 to stop the opening and closing of the intake valve and the exhaust valve of the cylinders 2A, 2D. As a result, combustion is stopped in the first cylinder 2A and the fourth cylinder 2D, and combustion is performed only in the remaining cylinders (the second cylinder 2B and the third cylinder 2C).

[0034] On the other hand, the cylinder number control unit executes control for all-cylinder operation in which combustion is performed in all cylinders 2A-2D when the operating conditions are not compatible with the reduced-cylinder operating region A. That is, the cylinder number control unit executes control to operate the injectors 8 and spark plugs 9 of all cylinders 2A-2D, cancel the valve stopping operation by the valve stopping mechanism 14, and open and close the intake valves and exhaust valves of all cylinders.

[0035] The exhaust SV control section that the controller 102 functionally has described above basically controls the exhaust shutter valve 26 to be kept fully open (for example, 56 degrees) in regions other than the reduced-cylinder operation region A.

[0036] On the other hand, in the reduced cylinder operation region A, the exhaust shutter valve 26 is driven in the closing direction so that the opening degree of the exhaust shutter valve 26 is smaller than in other regions. This reduces the passage cross-sectional area of ​​the exhaust pipe 24 and increases the flow resistance of the exhaust gas. More specifically, in the reduced-cylinder operating region A, the exhaust shutter valve 26 is basically controlled to be maintained fully closed (e.g., 4 degrees), but in this embodiment, as described below, when the engine speed is in a specific speed range F (see Figure 4), the exhaust shutter valve 26 is controlled to be maintained at an intermediate opening angle (e.g., 18 degrees) between fully closed (e.g., 4 degrees) and fully open (e.g., 56 degrees).

[0037] Next, technical matters related to exhaust pulsation generated in the exhaust passage 20, particularly in the middle pipe 29 of the exhaust pipe 24, during operation of the engine 1 will be described with reference to Fig. 4. Fig. 4 is a graph showing an example of increase and decrease in exhaust sound due to resonance / anti-resonance of exhaust pulsation in the exhaust passage relative to engine speed. First, when the engine 1 is operating, the exhaust valve opens and closes the exhaust port opening at a predetermined time interval according to the engine speed, generating pressure pulsations (exhaust pulsations) of a predetermined frequency in the exhaust gas flowing through the exhaust passage 20. Here, the volume of the exhaust sound caused by exhaust pulsation is mainly affected by the configuration of the middle pipe 29 from the outlet of the second catalytic device 23 of the exhaust pipe 24 to the inlet of the main silencer 27, and fluctuates periodically with respect to the engine speed, as shown in Fig. 4. More specifically, the configuration of the middle pipe 29 that affects the exhaust pulsation is a configuration in which the length and diameter of the exhaust system including the exhaust pipe 24 (for example, the system including the exhaust pipe 24, pre-silencer 25, exhaust shutter valve 26, etc. shown in Fig. 1) are major factors, and as a result, the middle pipe 29 has a predetermined natural frequency of cavity resonance (natural frequency within the middle pipe 29).

[0038] The volume of the exhaust sound varies as shown in Figure 4 due to resonance between this natural frequency and the exhaust pulsation. For example, when the frequency of the exhaust pulsation in the middle pipe 29 matches the natural frequency of the cavity resonance in the middle pipe 29, the exhaust pulsation in the middle pipe 29 increases due to resonance. In the example shown in Figure 4, two resonance points occur, and the volume of the exhaust sound increases in the range near these resonance points (peaks of the exhaust pulsation due to resonance).

[0039] On the other hand, in the rotation speed range between the two resonance points, the frequency of the exhaust pulsation in the middle pipe 29 does not match the natural frequency of the cavity resonance in the middle pipe 29, and the pressure waves cancel each other out, weakening the exhaust pulsation, resulting in a so-called anti-resonance point. As shown in Figure 4, at such an anti-resonance point and its vicinity (the valley of the exhaust pulsation due to anti-resonance), the volume of the exhaust sound decreases.

[0040] In this embodiment, as shown in Figure 4, the exhaust shutter valve 26 is controlled so that the opening degree of the exhaust shutter valve 26 is the above-mentioned intermediate opening degree (for example, 18 degrees) in the engine speed range that includes the anti-resonance point engine speed (in the example shown in Figure 4, the engine speed at which the exhaust sound volume is lowest between 1700 rpm and 2200 rpm) and where the exhaust pulsation of the above-mentioned "exhaust system" becomes a valley and the volume of the exhaust sound decreases.

[0041] In this embodiment, the engine speed range in which the exhaust shutter valve 26 is opened to an intermediate degree is set to a specific speed range F in which the volume of the exhaust sound is low (1700 rpm to 2200 rpm in the example of the engine 1 of this embodiment, which is equivalent to a frequency range of approximately 85 Hz to approximately 110 Hz), as shown in FIG. 4. By opening the exhaust shutter valve 26 to an intermediate degree, the generation of exhaust sound due to exhaust pulsation is suppressed, while pumping loss is reduced and fuel efficiency is improved.

[0042] The fluctuations in exhaust sound volume shown in Figure 4 correspond to the fluctuations in the pressure waves of the exhaust pulsation, and represent the fluctuations when the exhaust pressure (exhaust gas pressure) in the middle pipe 29 increases three times per rotation of the engine output shaft. The specific rotation speed range F varies depending on the type and model of the engine. In that case, the rotation speed range is appropriately determined so that the exhaust noise caused by exhaust pulsation is reduced, taking into account the relationship between the natural frequency of the system that constitutes the "exhaust system", such as the exhaust pipe and exhaust shutter valve, as described above, and the exhaust pulsation.

[0043] Next, the control of the engine system 100 executed by the controller 102 according to this embodiment will be described with reference to Fig. 5 and Fig. 6. Fig. 5 is a flowchart showing the control flow of the engine system according to this embodiment, and Fig. 6 is a flowchart showing the control flow of the exhaust shutter valve by the engine system according to this embodiment. In Fig. 5 and Fig. 6, S indicates each step. First, as shown in FIG. 5, in S1, the values ​​of the sensors SN1 to SN7 (see FIG. 2) are read, and in S2, a target engine load is calculated based on the value (accelerator position) of the accelerator opening sensor SN6 read in S1.

[0044] Next, the process proceeds to S3, where it is determined whether the engine speed and engine load are such that the cylinders can be stopped (reduced cylinder operation is possible) based on the value of the engine speed sensor SN5 read in S1 and the value of the target engine load calculated in S2. That is, in this S3, it is determined whether the engine is in the reduced cylinder operation region A as shown in FIG. In this embodiment, the engine load determination value is the above-mentioned load range X (see FIG. 3), which is set to a range in which fuel economy can be improved without significantly affecting the vehicle's power performance by stopping the cylinders. The engine speed determination value is set to a low to medium speed range Y of 1100 rpm to 3400 rpm. If it is determined in S3 that the engine speed is within the speed range Y and the engine load is within the load range X, it is determined that the cylinder can be stopped and the process proceeds to S4.

[0045] In S4, it is determined whether the engine water temperature and oil temperature are values ​​that allow cylinder stop based on the values ​​of the water temperature sensor SN1 and the oil temperature sensor SN2 read in S1. In this embodiment, the determination value of the engine water temperature is set to -40°C or higher, and the determination value of the engine oil temperature is set to 25°C or higher. If these determination values ​​are met in S4, the process proceeds to S5. In S5, it is determined that the cylinder can be stopped if the vehicle speed is 5km / h or more based on the value of the vehicle speed sensor SN3 read in S1. If it is determined that the cylinder can be stopped in S5, the process proceeds to S6, where it is determined that the cylinder can be stopped if the gear position is second gear or higher based on the value of the gear position sensor SN4 read in S1.

[0046] If all of the determination conditions in S3 to S6 described above are satisfied, the process proceeds to S7, where it is determined that the cylinders can be stopped, and the above-described control of the engine 1 during reduced cylinder operation is executed. On the other hand, if any of the determination conditions in S3 to S6 described above is not satisfied, the process proceeds to S8, where it is determined that cylinder stop is not possible and the above-mentioned control of the engine 1 during all-cylinder operation is executed.

[0047] Next, the process proceeds to S9, where it is determined whether the engine 1 is in reduced cylinder operation, i.e., whether the process of S7 is being executed. If it is determined in S9 that the engine 1 is in reduced cylinder operation, the process proceeds to S10, where the exhaust shutter valve control shown in FIG. 6 is executed. On the other hand, if the process of S8 is executed and it is determined in S9 that the engine is in all-cylinder operation, the process returns to S1 and the above-mentioned processes are executed again.

[0048] Next, as shown in FIG. 6, in the exhaust SV control (the process of S10 in FIG. 5), first, in S11, the value of the engine speed sensor SN5 (see FIG. 2) is read. Next, the process proceeds to S12, where it is determined whether the engine speed read in S11 is within a specific engine speed range. The "specific engine speed range" in S12 is the "specific engine speed range F" shown in Fig. 4 described above, which is a range of 1700 rpm to 2200 rpm in this embodiment. In S12, if the engine speed is within the specific speed range, the process proceeds to S13, where the opening of the exhaust shutter valve 26 (target SV opening) is set to an opening between fully open and fully closed. More specifically, as described above, the opening of the exhaust SV 26 is set to an intermediate opening between fully closed (e.g., 4 degrees) and fully open (e.g., 56 degrees). In this embodiment, 18 degrees is set as the target intermediate opening.

[0049] On the other hand, if it is determined in S12 that the engine speed is not within the specific range, the process proceeds to S14, in which it is determined whether the engine speed exceeds the specific range. In S14, if the engine speed exceeds a specific range (exceeds 2200 rpm), the process proceeds to S15, where the opening of the exhaust shutter valve 26 is set to fully closed (for example, 4 degrees) to suppress an increase in exhaust noise. In S14, if the engine speed does not exceed the specific range (if it is below 1700 rpm), the process proceeds to S16, where the opening of the exhaust shutter valve 26 is set to full open (for example, 56 degrees) to reduce exhaust resistance.

[0050] Next, after the SV opening setting process of S13, S15 or S16 is executed, the process proceeds to S17, where the exhaust shutter valve 26 is driven and controlled so as to achieve the opening set in each process.

[0051] Next, S18 is executed when the intermediate opening is set after the process of S13. In S18, the exhaust shutter valve 26 is corrected (feedback controlled) to the intermediate opening as the target value set in S13 while reading the value of the actual opening of the exhaust shutter valve 26 detected by the exhaust SV position sensors SN7 and 28. Factors that cause the actual opening of the exhaust SV 26 to deviate from the target opening (command value) include thermal expansion of the exhaust SV 26 due to thermal effects such as the ambient temperature around the exhaust SV 26 and the exhaust temperature. The correction control in S18 may also be executed when the fully closed opening degree is set through S15 and / or when the fully open opening degree is set through S16.

[0052] Next, the effects of the engine system 100 according to this embodiment will be described. The engine system 100 according to this embodiment is an engine system 100 for an engine 1 that can switch between full-cylinder operation, in which fuel is supplied to all of a plurality of cylinders 2A to 2D and burned, and reduced-cylinder operation, in which fuel supply to specific cylinders (e.g., 2A, 2D) among the multiple cylinders is stopped to deactivate the specific cylinders, and is equipped with exhaust passages 20, 24 of the engine 1, a throttle valve (exhaust shutter valve) 26 provided in the exhaust passages 20, 24 for opening and closing the exhaust passages 20, 24, and a controller 102 connected to the throttle valve 26 and adjusting the opening of the throttle valve 26, and is configured to determine whether the engine 1 is in reduced-cylinder operation or full-cylinder operation (S9), and if it is determined that the engine 1 is in reduced-cylinder operation, determine whether the engine speed is within a specific rotation speed range F in which exhaust pulsation is low (S12), and if it is determined that the engine speed is within the specific rotation speed range, adjust the opening of the throttle valve to an opening between fully open and fully closed (S13, S17). According to this embodiment configured as above, when the engine speed is within the specific speed range F where exhaust pulsation is low during reduced cylinder operation, the throttle valve 26 is opened between fully closed and fully open (an intermediate opening that does not include fully closed and fully open), so that it is possible to reduce pumping loss and improve fuel efficiency while suppressing the generation of exhaust noise due to exhaust pulsation. In other words, since the exhaust pulsation (pressure wave in the exhaust passage) within the specific speed range F is relatively lower than the exhaust pulsation at engine speeds other than the specific speed range F, the exhaust noise does not increase excessively even if the throttle valve 26 is not fully closed, and by opening the throttle valve between fully closed and fully open, it is possible to reduce pumping loss and improve fuel efficiency.

[0053] Furthermore, according to this embodiment, the opening degree (intermediate opening degree) of the throttle valve 26 between fully open and fully closed within the specific rotation speed range F of the engine 1 is larger than the opening degree of the throttle valve 26 when the engine rotation speed is higher than the specific rotation speed range F, so exhaust noise can be suppressed by narrowing the opening degree of the throttle valve 26. On the other hand, when the rotation speed is within the specific rotation speed range F, which is lower than at such high rotation speeds, exhaust pulsation is relatively small, so by making the intermediate opening degree of the throttle valve 26 larger than the opening degree of the throttle valve 26 at high rotation speeds, it is possible to reduce pumping loss and improve fuel efficiency while suppressing the generation of exhaust noise due to exhaust pulsation.

[0054] Furthermore, according to this embodiment, when the actual opening of the throttle valve 26 detected by the exhaust SV position sensor 28 deviates from the target opening, which is an opening between the fully open and fully closed positions of the throttle valve 26, the controller 102 controls the throttle valve 26 so that the opening of the throttle valve 26 becomes the target opening, thereby improving the accuracy of the opening of the throttle valve 26. Therefore, it is possible to more reliably suppress an increase in exhaust noise and more reliably improve fuel efficiency.

[0055] According to this embodiment, the specific rotation speed at which exhaust pulsation becomes low (anti-resonance point of exhaust pulsation) is determined by the configuration of the middle pipe 29 of the exhaust passages 20, 24, and the specific rotation speed at which exhaust pulsation becomes low is a rotation speed range that includes the anti-resonance rotation speed. According to this embodiment, it is possible to more effectively suppress the generation of exhaust noise due to exhaust pulsation while reducing pumping loss and improving fuel efficiency.

[0056] The present invention is also applicable to multi-cylinder engines other than those described above, for example, four-stroke six-cylinder gasoline engines. [Explanation of symbols]

[0057] 1 Engine 2A~2D cylinders 10 Intake passage 20 Exhaust passage 21 Exhaust manifold 22 First catalyst device 24 Exhaust pipe 25 Pre-silencer 26 Exhaust shutter valve (exhaust throttle valve / exhaust SV) 27 Main silencer 28 Exhaust Shutter Valve Position Sensor 29 Exhaust middle pipe 100 Engine System 102 Controller

Claims

1. An engine system for an engine capable of switching between an all-cylinder operation in which fuel is supplied to all of a plurality of cylinders and combusted, and a reduced-cylinder operation in which fuel supply to a specific cylinder among the plurality of cylinders is stopped to deactivate the specific cylinder, an exhaust passage of the engine; a throttle valve provided in the exhaust passage for opening and closing the exhaust passage; a controller connected to the throttle valve and adjusting the opening degree of the throttle valve; The controller is configured to determine whether the engine is operating in reduced cylinder operation or full cylinder operation, and if it is determined that the engine is operating in reduced cylinder operation, determine whether the engine speed is within a specific speed range at which exhaust pulsation is reduced and thereby exhaust noise is reduced, and if it is determined that the engine speed is within the specific speed range, adjust the opening of the throttle valve to an opening between fully open and fully closed, but not including fully open and fully closed.

2. 2. The engine system according to claim 1, wherein an opening degree of said throttle valve between full open and full closed is larger than an opening degree of said throttle valve when the engine speed is higher than said specific speed range.

3. The throttle valve is provided with a position sensor that detects its opening.

3. The engine system according to claim 1 or 2, wherein, when an actual opening degree of the throttle valve detected by the position sensor deviates from a target opening degree which is an opening degree between fully open and fully closed positions of the throttle valve, the controller controls the throttle valve so that the actual opening degree of the throttle valve becomes the target opening degree.

4. 4. The engine system according to claim 1, wherein the specific rotation speed is determined based on a configuration of a middle pipe of the exhaust passage.

5. 5. The engine system according to claim 1, wherein the specific range of engine speeds is a range of engine speeds including a speed at which exhaust pulsation forms a valley between two resonance points of the engine speed.

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