JP7556282B2 - Engine System - Google Patents

Description

The present invention relates to an engine system equipped with an electromagnetic clutch that disconnectably connects a mechanical supercharger to a crankshaft.

In conventional engine systems installed in automobiles, etc., a technique is known in which a turbocharger is used to supercharge air into the engine's combustion chamber in order to increase engine torque when the engine is in a high-load range or high-speed range. In particular, mechanical turbochargers (so-called superchargers), which use the rotational driving force from the engine's crankshaft to perform supercharging, have better responsiveness than exhaust turbine turbochargers (so-called turbochargers), which use the engine's exhaust pressure.

The engine system described in Patent Document 1 is equipped with an electromagnetic clutch that connects the mechanical supercharger to the crankshaft when the engine reaches a specified high-load range. In this engine system, when the engine shifts from a low-load range to a high-load range by increasing the throttle opening, for example, and the engine speed enters the supercharging range, the electromagnetic clutch connects the crankshaft to the mechanical supercharger. This allows the mechanical supercharger to supercharge air into the engine's combustion chamber, increasing engine torque.

JP 2019-39393 A

The mechanical supercharger shown in Patent Document 1 has better responsiveness than an exhaust turbine supercharger, as described above, but there is concern that in driving modes that involve repeated acceleration and deceleration, such as sports mode, the delayed response of the supercharger may cause a delay in the vehicle's acceleration.

That is, in driving modes such as sports mode, the driver repeatedly accelerates and decelerates to drive as desired, so engine speed fluctuates drastically and the engine speed drops significantly more frequently than in normal driving modes (normal mode). When the engine speed drops below a certain speed, the electromagnetic clutch is disengaged and the mechanical supercharger is in a non-supercharged state, so even if the engine speed is increased when the vehicle accelerates again, there is a time lag until the electromagnetic clutch is re-engaged and supercharging begins. For this reason, in driving modes that repeatedly accelerate and decelerate, such as sports mode, there is a risk that a response delay in the supercharging by the mechanical supercharger will occur, causing a delay in the acceleration of the vehicle. The above problem can also occur in manual modes in which the driver manually changes gears and repeatedly accelerates and decelerates.

The present invention was made in consideration of the above circumstances, and aims to provide an engine system that can suppress the acceleration delay of a vehicle in a driving mode that involves repeated acceleration and deceleration, such as a sports mode.

When a driving mode that involves repeated acceleration and deceleration, such as a sports mode, is selected, the engine system of the present invention lowers the engine speed at which supercharging begins (the supercharging speed in the present invention), thereby maintaining supercharging by the mechanical supercharger and suppressing vehicle acceleration delays even when the vehicle is in a driving mode such as a sports mode and undergoes repeated acceleration and deceleration.

In order to solve the above problems, an engine system according to a first aspect of the present invention includes a supercharger driven by an engine crankshaft, an electromagnetic clutch that disconnectably connects the crankshaft and the supercharger, an engine speed detection unit that detects the rotation speed of the engine, an automatic transmission that is connected to the engine and automatically changes gears to transmit driving force to wheels, a driving mode selection device that is capable of selecting between a normal mode, which is a driving mode in which the automatic transmission performs normal gear changes, and a sports mode, which is a driving mode in which the automatic transmission changes gears at an engine speed that is relatively higher than the engine speed in the normal mode, and a controller that outputs a control signal to the electromagnetic clutch, the controller including a driving mode determination unit that determines whether the driving mode selected by the driving mode selection device is a sports mode, and a control signal output from the electromagnetic clutch based on the engine speed detection unit. and a supercharging control unit that controls the electromagnetic clutch to be engaged when the engine rotational speed detected by the engine rotational speed detection unit is equal to or higher than a predetermined supercharging rotational speed, wherein, when the driving mode determination unit determines that the driving mode is the sports mode, the supercharging control unit sets the supercharging rotational speed to be lower than the supercharging rotational speed in the case where the driving mode is determined to be the normal mode , and the supercharging control unit controls the electromagnetic clutch to be disengaged when the engine rotational speed detected by the engine rotational speed detection unit is equal to or lower than a predetermined non-supercharged rotational speed, and in the sports mode, the non-supercharged rotational speed is set to be lower than the supercharged rotational speed, and a difference between the supercharged rotational speed and the non-supercharged rotational speed in the sports mode is set to be larger than a difference between the supercharged rotational speed and the non-supercharged rotational speed in the normal mode .

In this configuration, when the driving mode determination unit determines that the driving mode selected by the driving mode selection device is the sports mode, the supercharging control unit sets the supercharging speed to be lower than the supercharging speed when the driving mode is determined to be the normal mode. Then, in the sports mode, the supercharging control unit controls the electromagnetic clutch to be connected when the engine speed is equal to or higher than the supercharging speed set low as described above. This makes it possible to maintain supercharging by the mechanical supercharger for a long time even when the sports mode is selected and driving involves repeated acceleration and deceleration. As a result, it is possible to eliminate the response delay of the supercharging and suppress the acceleration delay of the vehicle.

In the above engine system, the supercharging control unit controls the electromagnetic clutch to be disengaged when the engine speed detected by the engine speed detection unit is equal to or lower than a predetermined non-supercharged speed, and in the sports mode, the non-supercharged speed is set to be lower than the supercharged speed.

In the sports mode, the non-supercharged rotation speed is set to be lower than the supercharged rotation speed, so even if the deceleration is large and the engine rotation speed drops significantly while driving in the sports mode, the number of times and the time for which the electromagnetic clutch is disconnected are reduced by the engine rotation speed dropping to the non-supercharged rotation speed, which makes it possible to suppress the acceleration delay of the vehicle when re-accelerating after the engine rotation speed has dropped in the sports mode.
In the above engine system, the difference between the supercharged rotation speed and the non-supercharged rotation speed in the sports mode is set to be larger than the difference between the supercharged rotation speed and the non-supercharged rotation speed in the normal mode.
In this configuration, the difference between the supercharged rotation speed and the non-supercharged rotation speed in the sports mode is set to be larger than the difference in the normal mode. Therefore, even if the deceleration is large and the engine speed drops significantly while driving in the sports mode, the number of times and the time for which the engine speed drops to the non-supercharged rotation speed and the electromagnetic clutch is disconnected are reduced. As a result, it is possible to suppress the acceleration delay of the vehicle when re-accelerating after the engine speed drops in the sports mode.

In the above engine system, it is preferable that the non-supercharged speed in the sports mode is set to be lower than the non-supercharged speed in the normal mode.

In this configuration, by setting the non-supercharged speed in sports mode to be lower than the non-supercharged speed in normal mode, it is possible to suppress the acceleration delay of the vehicle when re-accelerating after the engine speed has dropped in sports mode.

According to a third aspect of the present invention, there is provided an engine system including: a turbocharger driven by an engine crankshaft; an electromagnetic clutch that disconnectably connects the crankshaft and the turbocharger; an engine speed detector that detects the engine speed; an automatic transmission that is connected to the engine and automatically changes gears to transmit driving force to wheels; a driving mode selection device that can select between a normal mode, which is a driving mode in which the automatic transmission performs normal gear changes, and a manual mode, which is a driving mode in which the gear stages are manually changed; and a controller that outputs a control signal to the electromagnetic clutch, the controller being a driving mode selection device that determines whether the driving mode selected by the driving mode selection device is the manual mode or not. and a supercharging control unit that controls the electromagnetic clutch to be engaged when the engine speed detected by the engine speed detection unit is equal to or higher than a predetermined supercharging speed, wherein, when the driving mode determination unit determines that the driving mode is the manual mode, the supercharging control unit sets the supercharging speed to be lower than the supercharging speed in the case where the driving mode is determined to be the normal mode , and the supercharging control unit controls the electromagnetic clutch to be disengaged when the engine speed detected by the engine speed detection unit is equal to or lower than a predetermined non-supercharged speed, and in the manual mode, the non-supercharged speed is set to be lower than the supercharged speed, and a difference between the supercharged speed and the non-supercharged speed in the manual mode is set to be larger than a difference between the supercharged speed and the non-supercharged speed in the normal mode .

In this configuration, when the driving mode determination unit determines that the driving mode selected by the driving mode selection device is manual mode, the supercharging control unit sets the supercharging speed to be lower than the supercharging speed when the driving mode is determined to be normal mode. Then, in manual mode, the supercharging control unit controls the electromagnetic clutch to be connected when the engine speed is equal to or higher than the supercharging speed set low as described above. This makes it possible to maintain supercharging by the mechanical supercharger for a long time even when manual mode is selected and driving involves repeated acceleration and deceleration. As a result, it is possible to eliminate the response delay of supercharging and suppress the acceleration delay of the vehicle.

The engine system of the present invention can suppress the acceleration delay of the vehicle in a driving mode in which acceleration and deceleration are repeated, such as in sports mode. Similarly, it can suppress the acceleration delay of the vehicle in a driving mode in which acceleration and deceleration are repeated, such as in manual mode.

1 is a system diagram showing an overall configuration of an engine system according to an embodiment of the present invention. FIG. 2 is a block diagram showing a control system of the engine system shown in FIG. 1 . 2 is an operation map showing an operation region of the engine and a supercharging region of the supercharger of FIG. 1; 1 is a graph showing a waveform of a heat release rate during SPCCI combustion (partial compression ignition combustion). 2 is a control flowchart of the electromagnetic clutch of FIG. 1 . 2 is a time chart relating to engine speed, switching of driving modes, and on-off of the electromagnetic clutch for controlling the electromagnetic clutch of FIG. 1 .

A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

(1) Overall configuration of the engine system The engine system shown in FIG. 1 is a four-stroke gasoline direct injection engine mounted on a vehicle as a power source for driving, and comprises an engine body 1, an intake passage 30 through which intake air introduced into the engine body 1 flows, an exhaust passage 40 through which exhaust gas discharged from the engine body 1 flows, and an external EGR device 50 that recirculates a portion of the exhaust gas flowing through the exhaust passage 40 back to the intake passage 30.

The engine body 1 has a cylinder block 3 in which the cylinders 2 are formed, a cylinder head 4 attached to the upper surface of the cylinder block 3 so as to close the cylinders 2 from above, and a piston 5 inserted in the cylinders 2 so as to be able to slide back and forth.

A combustion chamber 6 is defined above the piston 5, and fuel, mainly composed of gasoline, is supplied to this combustion chamber 6 by injection from an injector 15, which will be described later. The supplied fuel is then mixed with air in the combustion chamber 6 and combusted, and the piston 5 reciprocates up and down due to the expansion force caused by the combustion.

Below the piston 5 is the crankshaft 7 of the engine body 1. The crankshaft 7 is connected to the piston 5 via a connecting rod 8, and is driven to rotate around its central axis in response to the reciprocating motion (up and down movement) of the piston 5.

The cylinder block 3 is provided with a crank angle sensor SN1 that detects the rotation angle (crank angle) of the crankshaft 7 and the rotation speed (engine speed) of the crankshaft 7, and a water temperature sensor SN2 that detects the temperature of the cooling water (engine water temperature) flowing inside the cylinder block 3 and the cylinder head 4.

The crank angle sensor SN1 can also detect the engine speed (rpm) by detecting the rotation speed of the crankshaft 7, and functions as the engine speed detection unit of the present invention.

The engine is also connected to an automatic transmission 60 that automatically changes gears and transmits driving force to the wheels.

The cylinder head 4 is provided with an intake port 9 for introducing air supplied from the intake passage 30 into the combustion chamber 6, an exhaust port 10 for directing exhaust gas generated in the combustion chamber 6 to the exhaust passage 40, an intake valve 11 for opening and closing the opening of the intake port 9 on the combustion chamber 6 side, and an exhaust valve 12 for opening and closing the opening of the exhaust port 10 on the combustion chamber 6 side.

The intake valve 11 and exhaust valve 12 are opened and closed in conjunction with the rotation of the crankshaft 7 by a valve mechanism including a pair of camshafts arranged in the cylinder head 4.

The valve mechanism for the intake valve 11 incorporates an intake S-VT 13 that can change the opening and closing timing of the intake valve 11. Similarly, the valve mechanism for the exhaust valve 12 incorporates an exhaust S-VT 14 that can change the opening and closing timing of the exhaust valve 12. The intake S-VT 13 (exhaust S-VT 14) is a so-called phase-type variable mechanism that changes the opening and closing timing of the intake valve 11 (exhaust valve 12) simultaneously and by the same amount.

As shown in FIG. 1, the cylinder head 4 is provided with an injector 15 that injects fuel (gasoline) into the combustion chamber 6, and a spark plug 16 that ignites the mixture of the fuel injected from the injector 15 into the combustion chamber 6 and intake air. The injector 15 is located in the center of the ceiling surface of the combustion chamber 6 so that its tip faces the center of the crown surface of the piston 5. The spark plug 16 is located slightly offset toward the intake side from the injector 15.

As shown in FIG. 1, the intake passage 30 is connected to one side of the cylinder head 4 so as to communicate with the intake port 9. Air (fresh air) taken in from the upstream end of the intake passage 30 is introduced into the combustion chamber 6 through the intake passage 30 and the intake port 9.

In the intake passage 30, from the upstream side, there are provided an air cleaner 31 that removes foreign matter from the intake air, an openable and closable throttle valve 32 that adjusts the flow rate of the intake air, a supercharger 33 that compresses the intake air while sending it out, an intercooler 35 that cools the intake air compressed by the supercharger 33, and a surge tank 36.

Each portion of the intake passage 30 is provided with an airflow sensor SN3 that detects the intake air flow rate, an intake air temperature sensor SN4 that detects the intake air temperature, and an intake air pressure sensor SN5 that detects the intake air pressure. The airflow sensor SN3 and the intake air temperature sensor SN4 are provided in the intake passage 30 between the air cleaner 31 and the throttle valve 32, and detect the intake air flow rate and temperature passing through that portion. The intake air pressure sensor SN5 is provided in the surge tank 36, and detects the intake air pressure within the surge tank 36.

The turbocharger 33 is a mechanically-type supercharger that is mechanically linked to the engine body 1. There is no particular restriction on the specific type of the turbocharger 33, but any of the well-known turbochargers, such as the Lysholm type, Roots type, or centrifugal type, can be used as the turbocharger 33.

The mechanical supercharger 33 is driven by the crankshaft 7 of the engine body 1. The supercharger 33 is disposed in the intake passage 30 that leads to the combustion chamber 6 via the intake port 9 of the engine body 1.

An electromagnetic clutch 34 that can be electrically switched between connection and disconnection is provided between the turbocharger 33 and the engine body 1. The electromagnetic clutch 34 connects the crankshaft 7 and the turbocharger 33 in a disconnectable manner. That is, when the electromagnetic clutch 34 is connected, a driving force is transmitted from the engine body 1 to the turbocharger 33, and the turbocharger 33 performs supercharging. On the other hand, when the electromagnetic clutch 34 is disconnected, the transmission of the driving force is cut off, and supercharging by the turbocharger 33 is stopped.

The electromagnetic clutch 34 has a short connection time after receiving a control signal from the PCM 100 (described below), making it possible to connect the turbocharger 33 more quickly.

The intake passage 30 is provided with a bypass passage 38 for bypassing the turbocharger 33. The bypass passage 38 connects the surge tank 36 to an EGR passage 51, which will be described later. The bypass passage 38 is provided with a bypass valve 39 that can be opened and closed.

The exhaust passage 40 is connected to the other side of the cylinder head 4 (the side opposite the intake passage 30) so as to communicate with the exhaust port 10. The burnt gas generated in the combustion chamber 6 is exhausted to the outside through the exhaust port 10 and the exhaust passage 40.

A catalytic converter 41 is provided in the exhaust passage 40. The catalytic converter 41 contains a three-way catalyst 41a for purifying harmful components (HC, CO, NOx) contained in the exhaust gas flowing through the exhaust passage 40, and a GPF (gasoline particulate filter) 41b for collecting particulate matter (PM) contained in the exhaust gas.

An A/F sensor SN6 that detects the oxygen concentration in the exhaust gas is provided upstream of the catalytic converter 41 in the exhaust passage 40.

The external EGR device 50 has an EGR passage 51 that connects the exhaust passage 40 and the intake passage 30, and an EGR cooler 52 and an EGR valve 53 provided in the EGR passage 51. The EGR passage 51 connects a portion of the exhaust passage 40 downstream of the catalytic converter 41 to a portion of the intake passage 30 between the throttle valve 32 and the turbocharger 33. The EGR cooler 52 cools the exhaust gas (external EGR gas) that is recirculated from the exhaust passage 40 to the intake passage 30 through the EGR passage 51 by heat exchange. The EGR valve 53 is provided in the EGR passage 51 downstream of the EGR cooler 52 (the side closer to the intake passage 30) so as to be able to open and close, and adjusts the flow rate of the exhaust gas flowing through the EGR passage 51.

(2) Control System Fig. 2 is a block diagram showing the control system of the engine system. The PCM 100 (controller) shown in the figure is a microprocessor for comprehensively controlling the engine and the like, and is composed of a well-known CPU, ROM, RAM, etc.

Detection signals from various sensors are input to PCM100. For example, PCM100 is electrically connected to the crank angle sensor SN1, water temperature sensor SN2, air flow sensor SN3, intake air temperature sensor SN4, intake pressure sensor SN5, and A/F sensor SN6 described above, and information detected by these sensors (i.e., crank angle, engine speed, engine water temperature, intake air flow rate, intake air temperature, intake pressure, and exhaust oxygen concentration) is input sequentially to PCM100.

The vehicle is also provided with an accelerator sensor SN7 that detects the degree of depression of the accelerator pedal (hereinafter referred to as accelerator depression) operated by the driver who drives the vehicle, and a vehicle speed sensor SN8 that detects the traveling speed of the vehicle (hereinafter referred to as vehicle speed). The detection signals from these sensors SN7 to SN8 are also input sequentially to the PCM 100.

Furthermore, a driving mode selection device SW1 is provided near the driver's seat of the vehicle. The driving mode selection device SW1 can select two driving modes, namely, a normal mode and a sports mode. The normal mode is a driving mode in which the automatic transmission 60 performs normal gear changes. The sports mode is a driving mode in which the engine speed at which the automatic transmission 60 changes gears is relatively higher than the engine speed in the normal mode. The driver manually operates the driving mode selection device SW1 to select one of these driving modes.

Furthermore, the driving mode selection device SW1 of this embodiment can select between a manual mode and a normal mode, which will be described later. The manual mode is a driving mode in which the driver manually changes the gear stage of the automatic transmission 60.

The PCM 100 controls each part of the engine while executing various judgments and calculations based on the input information from each of the above sensors. That is, the PCM 100 is electrically connected to the intake and exhaust S-VTs 13, 14, the injector 15, the spark plug 16, the throttle valve 32, the electromagnetic clutch 34, the bypass valve 39, and the EGR valve 53, and outputs control signals to each of these devices based on the results of the above calculations, etc.

Specifically, the PCM 100, which functions as the controller of the present invention, functionally includes a combustion control unit 101, a driving mode determination unit 102, and a supercharging control unit 103.

The combustion control unit 101 is a control module that controls the combustion of the air-fuel mixture in the combustion chamber 6, and controls each part of the engine so that the engine output torque, etc., are appropriate values according to the driver's requirements.

The driving mode determination unit 102 determines whether the driving mode selected by the driving mode selection device SW is a sports mode. In this embodiment, the driving mode determination unit 102 determines whether the driving mode is a sports mode or a normal mode. Furthermore, the driving mode determination unit 102 can also determine whether the driving mode is a manual mode or a normal mode, which will be described later.

The supercharging control unit 103 controls the connection of the electromagnetic clutch 34 based on the engine speed detected by the crank angle sensor SN1 and the determination result of the driving mode determination unit 102. The specific method of connection control will be described in detail later.

(3) Engine Combustion Control Next, engine combustion control will be described. An operation map showing the operating range of the engine and the supercharging range of the supercharger 33 is shown in FIG.

As shown in this figure, the engine operating range is roughly divided into four operating ranges A1 to A4 according to the difference in the combustion mode. If they are called the first operating range A1, the second operating range A2, the third operating range A3, and the fourth operating range A4, respectively, the third operating range A3 is a very low speed range where the engine speed is less than the first rotation speed N1, the fourth operating range A4 is a high speed range where the engine speed is equal to or greater than the third rotation speed N3, the first operating range A1 is a low speed/low load range where the load is relatively low among the speed ranges (low/medium speed ranges) other than the third and fourth operating ranges A3 and A4, and the second operating range A2 is the remaining range other than the first, third, and fourth operating ranges A1, A3, and A4.

In the example of FIG. 3, the first operating region A1 is a substantially rectangular region located inside the second operating region A2, and is surrounded by a first rotation speed N1, which is the lower limit rotation speed of the second operating region A2, a second rotation speed N2, which is lower than the upper limit rotation speed (third rotation speed N3) of the second operating region A2, a first load L1, which is higher than the minimum load of the engine, and a second load L2, which is higher than the first load L1.

In the first operating region A1 of low speed and low load, partial compression ignition combustion (hereinafter referred to as SPCCI combustion) is performed, which is a combination of SI combustion and CI combustion. SI combustion is a combustion form in which the mixture is ignited by a spark generated by the spark plug 16, and the mixture is forcibly burned by flame propagation that expands the combustion area from the ignition point to the surroundings. CI combustion is a combustion form in which the mixture is burned by self-ignition in an environment that is sufficiently high temperature and pressure due to compression of the piston 5, etc. And SPCCI combustion, which is a combination of these SI combustion and CI combustion, is a combustion form in which a part of the mixture in the combustion chamber 6 is SI burned by spark ignition performed in an environment just before the mixture self-ignites, and after the SI combustion (due to the further high temperature and pressure associated with SI combustion), the other mixture in the combustion chamber 6 is CI burned by self-ignition. Note that "SPCCI" is an abbreviation of "Spark Controlled Compression Ignition".

Figure 4 is a graph showing the combustion waveform when SPCCI combustion as described above is performed, that is, the change in heat release rate (J/deg) with crank angle. As shown in this figure, in SPCCI combustion, heat release due to SI combustion and heat release due to CI combustion occur consecutively in that order. At this time, since CI combustion has a faster combustion speed, the rise in heat release is steeper during CI combustion than during SI combustion. For this reason, the waveform of the heat release rate in SPCCI combustion has an inflection point X that appears at the timing when SI combustion switches to CI combustion (θci, described below).

As a specific form of SPCCI combustion as described above, in the first operating region A1, a control is executed to form an A/F lean mixture having an air-fuel ratio larger than the theoretical air-fuel ratio in the combustion chamber 6 and to perform SPCCI combustion of the mixture, in other words, a control to perform SPCCI combustion of a mixture with λ>1 (λ is an excess air ratio). At this time, the opening degree of the throttle valve 32 is set to a relatively large value such that more air than the air amount corresponding to the theoretical air-fuel ratio is introduced into the combustion chamber 6 through the intake passage 30. That is, in the first operating region A1, the target value of the air-fuel ratio (A/F), which is the weight ratio between the air (fresh air) introduced into the combustion chamber 6 through the intake passage 30 and the fuel injected into the combustion chamber 6 from the injector 15, is set to a value sufficiently larger than the theoretical air-fuel ratio (14.7). The opening degree of the throttle valve 32 that realizes this target value of the air-fuel ratio (target air-fuel ratio) is then determined each time, and the throttle valve 32 is controlled according to that determination.

When the engine is cold (engine wall temperature (temperature of cylinder block 3) is below 30 degrees), SI combustion occurs in all operating regions A1 to A4 in Figure 3. Also, when the engine is semi-warm (engine wall temperature is between 30 and 80 degrees), operating region A1 disappears and is included in operating region A2, but when the engine is completely warm (engine wall temperature is above 80 degrees), operating region A1 exists.

3, in the SCon region (area surrounded by dashed two-dot lines) corresponding to either the engine load being equal to or greater than load L3 or the engine speed being equal to or greater than N4 among all the engine operating regions A1 to A4, the electromagnetic clutch 34 connects the crankshaft 7 and the turbocharger 33, thereby putting the turbocharger 33 into a supercharged state. The engine speed N4 is set to a range equal to or greater than the upper limit N2 of the engine speed in the operating region A1 and equal to or less than the lower limit N3 of the engine speed in the operating region A4.

On the other hand, in the remaining region of the map in FIG. 3 (i.e., the region below engine load L3 and below engine speed N4), the turbocharger 33 is in a non-supercharged state.

During normal driving (normal driving), if the engine load and engine speed fall within the SCon region of the map in Figure 3 above, control is performed to put the turbocharger 33 into a supercharged state. However, in the present invention, when the driving mode is the sports mode, the setting of the engine speed N4 (which becomes the supercharged speed described below) at which supercharging begins in the map in Figure 3 above is lowered, and when the engine speed reaches or exceeds the supercharged speed set low for the sports mode, control is performed to put the turbocharger 33 into a supercharged state, thereby suppressing the response delay of the supercharger and the acceleration delay of the vehicle when driving in the sports mode.

That is, when the driving mode determination unit 102 determines that the driving mode is the sports mode, the supercharging control unit 103 of this embodiment sets the predetermined supercharging speed to be lower than the supercharging speed when the driving mode is determined to be the normal mode. Specifically, as in step S2 of FIG. 5 described below, the supercharging speed AN1 in the normal mode (e.g., about 2750 rpm) is reduced to the supercharging speed AN2 in the sports mode (about 1900 to 2100 rpm).

Then, when the engine speed RN detected by the crank angle sensor SN1 (engine speed detection unit) is equal to or higher than the low-set supercharged speed AN2 as described above, the supercharger control unit 103 controls the electromagnetic clutch 34 to be connected (see steps S3 to S4 in FIG. 5 and time point t4 in FIG. 6, which will be described later). As a result, the electromagnetic clutch 34 connects the supercharger 33 to the crankshaft 7, and the supercharger 33 enters a supercharged state.

When the engine speed detected by the crank angle sensor SN1 is equal to or lower than a predetermined non-supercharged speed BN2 (see step S5 in FIG. 5 and time point t5 in FIG. 6 described below), the supercharging control unit 103 controls the electromagnetic clutch 34 to be disconnected. As a result, the electromagnetic clutch 34 disconnects the supercharger 33 from the crankshaft 7, and the supercharger 33 enters a non-supercharged state.

In the sports mode, the non-supercharged speed BN2 is set to be lower than the supercharged speed AN2. For example, the non-supercharged speed BN2 in the sports mode is set to be around 1650 to 1850 rpm, which is lower than the supercharged speed AN2 (around 1900 to 2100 rpm).

In addition, the non-supercharged speed BN2 in sports mode (e.g., about 1650 to 1850 rpm) is set to be lower than the non-supercharged speed BN1 in normal mode (e.g., about 2650 rpm).

Furthermore, the difference α2 between the supercharged speed AN2 and the non-supercharged speed BN2 in sports mode is set to be larger than the difference α1 between the supercharged speed AN1 and the non-supercharged speed BN1 in normal mode. For example, if the supercharged speed AN1 in normal mode is 2750 rpm and the non-supercharged speed BN1 is 2650 rpm, the difference α1 will be 100 rpm, whereas if the supercharged speed AN2 in sports mode is 1900-2100 rpm and the non-supercharged speed BN2 is 1650-1850 rpm, the difference α2 will be around 200-300 rpm.

(Control flow chart of the electromagnetic clutch 34)
In the engine system configured as described above, the operation control of the supercharger 33 in the sports mode and normal mode, specifically, the control of the electromagnetic clutch 34, is performed in the following procedure.

As shown in the flowchart in FIG. 5, first, in step S1, the driving mode determination unit 102 of the PCM 100 determines whether the driving mode selected by the driving mode selection device SW1 is the sports mode.

If the driving mode is the sports mode, the process proceeds to step S2, where the supercharging control unit 103 sets the supercharging speed AN2 to be lower than the supercharging speed AN1 when the driving mode is determined to be the normal mode. That is, as at time t3 in the engine speed RN chart in FIG. 6, the supercharging speed setting is changed to be lowered from AN1 to AN2 when the driving mode selection device SW1 switches to the sports mode. At this time, the non-supercharging speed is also lowered from BN1 to BN2.

Next, in steps S3 and S4, when the vehicle is traveling in the sports mode, the supercharging control unit 103 controls the electromagnetic clutch 34 to be connected when the engine speed RN is equal to or higher than the supercharging speed AN2, which is set low as described above (see time t4 in FIG. 6). As a result, the supercharger 33 connects to the crankshaft 7 and performs supercharging (step S3 is repeated when the engine speed RN is lower than the supercharging speed AN2).

As shown in the time chart of FIG. 6, after the sports mode is selected (t3), when the engine speed RN becomes equal to or higher than the supercharged speed AN2 while driving in the sports mode (t4), the electromagnetic clutch 34 turns on and the supercharger 33 is connected. After that, even if the engine speed fluctuates near the supercharged speed AN1 and non-supercharged speed BN1 in normal mode while repeatedly accelerating and decelerating while driving in the sports mode, the supercharger 33 remains connected for a long period of time (see the section where the electromagnetic clutch is connected on from time t4 to t5).

After that, in steps S5-6, when the engine speed RN becomes equal to or lower than the non-supercharged speed BN2, which is lower than the supercharged speed AN2, the supercharger control unit 103 controls the electromagnetic clutch 34 to be disconnected. As a result, the supercharger 33 is disconnected from the crankshaft 7, and supercharging is stopped. Note that when the engine speed RN becomes equal to or lower than the non-supercharged speed BN2 (t5), a timer may be set to count a predetermined time (e.g., 1 second) before the electromagnetic clutch 34 is disconnected.

Therefore, as described above, when the sports mode is selected by the driving mode selection device SW1, the supercharged speed AN2 and non-supercharged speed BN2 in the sports mode are set lower than the supercharged speed AN1 and non-supercharged speed BN1 in the normal mode. This allows the supercharger 33 to remain connected for a long period of time until the engine speed RN falls below the non-supercharged speed BN2, even if the engine speed RN fluctuates near the supercharged speed AN1 and non-supercharged speed BN1 in the normal mode while driving in the sports mode (see the section from time t4 to t5 when the electromagnetic clutch is connected on). This makes it possible to keep the supercharger 33 connected for a long time in a driving mode that involves repeated acceleration and deceleration, such as the sports mode, and suppresses the response delay of the supercharger.

While driving in the above-mentioned sports mode, it is possible to return from the sports mode to the normal mode by manually operating the driving mode selection device SW1 (see time t6 in the time chart of FIG. 6). This changes the settings from the supercharged speed AN2 and non-supercharged speed BN2 in the sports mode to the supercharged speed AN1 and non-supercharged speed BN1 in the normal mode.

If the driving mode determination unit 102 does not determine in step S1 that the sport mode is selected, for example, during the period before the sport mode is selected such as from time t1 to t3 in the time chart of FIG. 6, the process proceeds to step S9, where control of the supercharger 33 in normal mode is performed, that is, connection control of the electromagnetic clutch 34 is performed based on the supercharged speed AN1 and the non-supercharged speed BN1 in normal mode.

That is, in step S7, when the engine enters the SCon region shown in the map of FIG. 3 (t1) (at this time t1, the engine has entered the SCon region, and the engine speed RN becomes the supercharged speed AN1 in normal mode), the process proceeds to step S8, where the supercharge control unit 103 controls the electromagnetic clutch 34 to be connected, and the supercharger 33 starts supercharging (note that if the engine is not in the SCon region in step S7, step S7 is repeated). The supercharged speed AN1 corresponds to the fourth speed N4 in the map of FIG. 3.

Next, when the engine is no longer in the SCon region in step S9 (t2) (at this time t2, the engine speed RN becomes the non-supercharged speed BN1 in normal mode), the supercharging control unit 103 controls the electromagnetic clutch 34 to be disconnected, as shown in step S6 above, and stops supercharging by the supercharger 33. Even in normal mode, when the engine speed RN becomes equal to or lower than the non-supercharged speed BN1 (t2), a timer may be set to count (for example, 1 second) before the electromagnetic clutch 34 is disconnected.

In normal mode as described above, the turbocharger 33 starts supercharging when the engine enters the SCon region (i.e., when the engine speed RN is equal to or higher than the supercharged speed AN1) (t1), and stops supercharging when the engine enters the SCon region (i.e., when the engine speed is equal to or lower than the non-supercharged speed BN1) (t2). Therefore, in normal mode, the supercharging period is only a short period from t1 to t2, and repeated acceleration and deceleration can easily cause a delayed response of the supercharging. In light of this, it can be seen that setting the supercharged speed AN2 and non-supercharged speed BN2 low in sport mode as described above is effective in suppressing a delayed response of the supercharging.

(Control of the turbocharger 33 in the manual mode)
Like the sports mode, the manual mode is also a driving mode in which acceleration and deceleration are repeated. Therefore, even when the driving mode selection device SW1 selects the manual mode instead of the above-mentioned sports mode, control similar to the control when the sports mode is selected in steps S1 to S6 of the flowchart in FIG. 5 can be performed.

Specifically, in this embodiment, when the driving mode determination unit 102 determines that the driving mode is manual mode (when the manual mode is selected in step S1 of the flowchart in FIG. 5), the supercharging control unit 103 sets the predetermined supercharging speed to be lower than the supercharging speed when the driving mode is determined to be normal mode.

Then, the supercharging control unit 103 controls the electromagnetic clutch 34 to be connected when the engine speed RN detected by the crank angle sensor SN1 (engine speed detection unit) is equal to or higher than the supercharging speed AN2 set low as described above (see steps S3 to S4 in Figure 5 and time t4 in Figure 6).

Then, when the engine speed detected by the crank angle sensor SN1 is equal to or lower than a predetermined non-supercharged speed BN2 (see step S5 in FIG. 5 and time t5 in FIG. 6), the supercharging control unit 103 controls the electromagnetic clutch 34 to be disconnected.

Even in manual mode, the non-supercharged speed BN2 is set to be lower than the supercharged speed AN2, and is also set to be lower than the non-supercharged speed BN1 in normal mode.

Furthermore, even in manual mode, the difference α2 between the supercharged speed AN2 and the non-supercharged speed BN2 is set to be greater than the difference α1 between the supercharged speed AN1 and the non-supercharged speed BN1 in normal mode.

(Features of this embodiment)
(1)
The engine system of this embodiment includes a turbocharger 33 driven by the engine crankshaft 7, an electromagnetic clutch 34 that disconnectably connects the crankshaft 7 and the turbocharger 33, a crank angle sensor SN1 (engine speed detection unit) that detects the engine speed, an automatic transmission 60 that is connected to the engine and automatically changes gears to transmit driving force to the wheels, a driving mode selection device SW1 that can select between a normal mode, which is a driving mode in which the automatic transmission 60 performs normal gear changes, and a sports mode, which is a driving mode in which the engine speed RN at which the automatic transmission 60 changes gears is relatively higher than the engine speed in the normal mode, and a PCM 100 (controller) that outputs a control signal to the electromagnetic clutch 34. The PCM 100 includes a driving mode determination unit 102 that determines whether the driving mode selected by the driving mode selection device SW1 is a sports mode or not, and a supercharging control unit 103 that controls the electromagnetic clutch 34 to be connected when the engine speed RN detected by the crank angle sensor SN1 is equal to or higher than a predetermined supercharging speed (AN1 or AN2).

When the driving mode determination unit 102 determines that the driving mode is the sports mode, the supercharging control unit 103 sets the supercharging speed AN2 to be lower than the supercharging speed AN1 when the driving mode is determined to be the normal mode (see supercharging speeds AN1 and AN2 in Figure 6).

In this configuration, when the driving mode determination unit 102 determines that the driving mode selected by the driving mode selection device SW1 is the sports mode, the supercharging control unit 103 sets the supercharging speed AN2 to be lower than the supercharging speed AN1 when the driving mode is determined to be the normal mode. Then, in the sports mode, the supercharging control unit 103 controls the electromagnetic clutch 34 to be connected when the engine speed RN is equal to or higher than the supercharging speed AN2 set low as described above. This makes it possible to maintain supercharging by the mechanical supercharger 33 for a long time even when the sports mode is selected and driving involves repeated acceleration and deceleration. As a result, it is possible to eliminate the response delay of the supercharging and suppress the acceleration delay of the vehicle.

(2)
In the engine system of this embodiment, the supercharging control unit 103 controls the electromagnetic clutch 34 to be disengaged when the engine speed RN detected by the crank angle sensor SN1 is equal to or lower than a predetermined non-supercharged speed BN2. In the sports mode, the non-supercharged speed BN2 is set to be lower than the supercharged speed AN2 (see the supercharged speed AN2 and the non-supercharged speed BN2 in FIG. 6).

In sports mode, the non-supercharged rotation speed BN2 is set to be lower than the supercharged rotation speed AN2, so even if the deceleration is large while driving in sports mode and the engine speed RN drops significantly, the number of times and the time that the engine speed RN drops to the non-supercharged rotation speed BN2 and the electromagnetic clutch 34 is disconnected are reduced. This makes it possible to suppress the acceleration delay of the vehicle when re-accelerating after the engine speed RN drops in sports mode.

(3)
In the engine system of the present embodiment, the non-supercharged rotation speed BN2 in the sports mode is set to be lower than the non-supercharged rotation speed BN1 in the normal mode (see the non-supercharged rotation speeds BN1, BN2 in FIG. 6).

In this configuration, by setting the non-supercharged speed BN2 in the sports mode to be lower than the non-supercharged speed BN1 in the normal mode, it is possible to suppress the acceleration delay of the vehicle when re-accelerating after the engine speed RN has decreased in the sports mode.

(4)
In the engine system of this embodiment, the difference α2 between the supercharged speed AN2 and the non-supercharged speed BN2 in the sports mode is set to be larger than the difference α1 between the supercharged speed AN and the non-supercharged speed BN1 in the normal mode (see differences α1, α2 in Figure 6).

In this configuration, the difference α2 between the supercharged rotation speed AN2 and the non-supercharged rotation speed BN2 in the sports mode is set to be larger than the difference α1 in the normal mode. Therefore, even if the deceleration is large while driving in the sports mode and the engine speed RN drops significantly, the number of times and the time that the engine speed RN drops to the non-supercharged rotation speed BN2 and the electromagnetic clutch 34 is disconnected are reduced. As a result, it is possible to suppress the acceleration delay of the vehicle when re-accelerating after the engine speed RN drops in the sports mode.

(5)
The engine system of this embodiment is configured to perform control similar to that performed when the sports mode is selected, even when the manual mode is selected instead of the sports mode.

That is, the engine system of this embodiment includes a supercharger 33 driven by the crankshaft 7 of the engine, an electromagnetic clutch 34 that disconnectably connects the crankshaft 7 and the supercharger 33, a crank angle sensor SN1 (engine speed detection unit) that detects the engine speed, an automatic transmission 60 that is connected to the engine and automatically changes gears to transmit driving force to the wheels, a driving mode selection device SW1 that can select between a normal mode, which is a driving mode in which the automatic transmission 60 performs normal gear changes, and a manual mode, which is a driving mode in which the gear stage is manually changed, and a PCM 100 (controller) that outputs a control signal to the electromagnetic clutch 34. The PCM 100 includes a driving mode determination unit 102 that determines whether the driving mode selected by the driving mode selection device SW1 is the manual mode, and a supercharging control unit 103 that controls the electromagnetic clutch 34 to be connected when the engine speed RN detected by the crank angle sensor SN1 is equal to or higher than a predetermined supercharging speed (AN1 or AN2).

When the driving mode determination unit 102 determines that the driving mode is manual mode, the supercharging control unit 103 sets the supercharging speed AN2 to be lower than the supercharging speed AN1 when the driving mode is determined to be normal mode.

In this configuration, when the driving mode determination unit 102 determines that the driving mode selected by the driving mode selection device SW1 is the manual mode, the supercharging control unit 103 sets the supercharging speed AN2 to be lower than the supercharging speed AN1 when the driving mode is determined to be the normal mode. Then, in the manual mode, the supercharging control unit 103 controls the electromagnetic clutch 34 to be connected when the engine speed RN is equal to or higher than the supercharging speed AN2 set low as described above. This makes it possible to maintain supercharging by the mechanical supercharger 33 for a long time even when the manual mode is selected and driving involves repeated acceleration and deceleration. As a result, it is possible to eliminate the response delay of the supercharging and suppress the acceleration delay of the vehicle.

1 Engine body 7 Crankshaft 33 Supercharger 34 Electromagnetic clutch 60 Automatic transmission 100 PCM (controller)
102: Driving mode determination unit 103: Supercharging control unit SW1: Driving mode selection device

Claims (3)

a supercharger driven by the engine crankshaft;
an electromagnetic clutch that disconnectably connects the crankshaft and the turbocharger;
an engine speed detection unit that detects the engine speed;
an automatic transmission connected to the engine and automatically changing gears to transmit driving force to wheels;
a driving mode selection device capable of selecting a normal mode, which is a driving mode in which the automatic transmission performs normal gear shifting, and a sports mode, which is a driving mode in which the automatic transmission performs gear shifting at an engine speed that is relatively higher than the engine speed in the normal mode;
a controller that outputs a control signal to the electromagnetic clutch;
The controller includes:
a driving mode determination unit that determines whether the driving mode selected by the driving mode selection device is a sports mode;
a supercharging control unit that controls the electromagnetic clutch so as to be engaged when the engine speed detected by the engine speed detection unit is equal to or higher than a predetermined supercharging speed,
the supercharging control unit, when the driving mode determination unit determines that the driving mode is the sports mode, sets the supercharging rotation speed to be lower than the supercharging rotation speed when the driving mode is determined to be the normal mode ,
the supercharging control unit controls the electromagnetic clutch to be disengaged when the engine speed detected by the engine speed detection unit is equal to or lower than a predetermined non-supercharging speed,
In the sports mode, the non-supercharged rotation speed is set to be lower than the supercharged rotation speed,
a difference between the supercharged rotation speed and the non-supercharged rotation speed in the sports mode is set to be larger than a difference between the supercharged rotation speed and the non-supercharged rotation speed in the normal mode.
An engine system comprising: 2. The engine system according to claim 1 ,
1. An engine system comprising: an engine control unit configured to control a rotational speed of the engine in a sports mode so as to be lower than the rotational speed of the engine in a normal mode. a supercharger driven by the engine crankshaft;
an electromagnetic clutch that disconnectably connects the crankshaft and the turbocharger;
an engine speed detection unit that detects the engine speed;
an automatic transmission connected to the engine and automatically changing gears to transmit driving force to wheels;
a driving mode selection device that can select a normal mode, which is a driving mode in which the automatic transmission performs normal gear shifting, and a manual mode, which is a driving mode in which the gear stage is manually shifted;
a controller that outputs a control signal to the electromagnetic clutch;
The controller includes:
a driving mode determination unit that determines whether the driving mode selected by the driving mode selection device is a manual mode;
a supercharging control unit that controls the electromagnetic clutch so as to be engaged when the engine speed detected by the engine speed detection unit is equal to or higher than a predetermined supercharging speed,
the supercharging control unit, when the traveling mode determination unit determines that the traveling mode is the manual mode, sets the supercharging rotation speed to be lower than the supercharging rotation speed when the traveling mode is determined to be the normal mode ,
the supercharging control unit controls the electromagnetic clutch to be disengaged when the engine speed detected by the engine speed detection unit is equal to or lower than a predetermined non-supercharging speed,
In the manual mode, the non-supercharged rotation speed is set to be lower than the supercharged rotation speed,
a difference between the supercharged rotation speed and the non-supercharged rotation speed in the manual mode is set to be larger than a difference between the supercharged rotation speed and the non-supercharged rotation speed in the normal mode.
An engine system comprising:

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