JP7543897B2 - 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 or exceeds a predetermined engine speed. In this engine system, when the engine speed reaches or exceeds a predetermined speed while the vehicle is running, the electromagnetic clutch connects the crankshaft to the mechanical supercharger, allowing the mechanical supercharger to supercharge air into the engine's combustion chamber, thereby 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 are concerns that a delay in the response of the electromagnetic clutch may cause a delay in the vehicle's acceleration when driving with large steering turns, such as when driving on winding roads.

In other words, when driving with a large steering angle, such as when driving on winding roads, repeated acceleration and deceleration cause the engine speed to fluctuate wildly. For this reason, if the vehicle is driven near a specific engine speed at which the electromagnetic clutch that connects the mechanical supercharger to the crankshaft repeatedly engages and disengages, there is a risk that a delayed response of the mechanical supercharger's supercharging will occur if the vehicle suddenly accelerates from a disengaged state, causing a delay in the vehicle's acceleration.

The present invention was made in consideration of the above circumstances, and aims to provide an engine system that can suppress the delay in acceleration of the vehicle when the steering wheel is turned significantly, such as when driving on winding roads.

The engine system of the present invention is a system that maintains supercharging by the mechanical supercharger for a long period of time and suppresses vehicle acceleration delays when the steering angle reaches a predetermined first angle or greater while the supercharger is in a supercharged state during driving that requires large steering turns, such as when driving on winding roads.

In order to solve the above problems, an engine system of the present invention includes a supercharger driven by an engine crankshaft, an electromagnetic clutch that connects the crankshaft and the supercharger in a connectable and disconnectable manner, a steering angle detection unit that detects a steering angle, an engine speed detection unit that detects a speed of the engine, a steering angle determination unit that determines the steering angle detected by the steering angle detection unit, a supercharging region determination unit that determines whether the engine is operating in a supercharging region in which the electromagnetic clutch is connected or a non-supercharging region in which the electromagnetic clutch is disconnected based on the engine speed detected by the engine speed detection unit, and a supercharging control unit that controls the connection and disconnection of the electromagnetic clutch based on the determination results of the steering angle determination unit and the supercharging region determination unit, When a judgment unit judges that the engine is operating in the supercharging region and when the steering angle judgment unit judges that the steering angle is less than a predetermined first angle, and thereafter, the operating region of the engine transitions from the supercharging region to the non-supercharging region, the electromagnetic clutch is switched from a connected state to a disconnected state after a predetermined first period has elapsed; when a judgment unit judges that the engine is operating in the supercharging region and when the steering angle judgment unit judges that the steering angle is equal to or greater than the first angle, and thereafter, the operating region of the engine transitions from the supercharging region to the non-supercharging region and the steering angle becomes equal to or less than the first angle, the electromagnetic clutch is switched from a connected state to a disconnected state after a second period longer than the first period has elapsed.

In this configuration, the supercharging region determination unit determines whether the engine is operating in the supercharging region where the electromagnetic clutch is connected or in the non-supercharging region where the electromagnetic clutch is disconnected, based on the engine speed detected by the engine speed detection unit. As a basic control, the supercharging control unit performs control to switch the electromagnetic clutch from the connected state to the disconnected state after a predetermined first period has elapsed when the supercharging region determination unit determines that the engine is operating in the supercharging region and the steering angle determination unit determines that the steering angle is less than a predetermined first angle, and then the engine operating region transitions from the supercharging region to the non-supercharging region. In addition, when driving with a large steering angle, such as winding roads, the supercharging control unit maintains a long supercharging period by performing control to switch the electromagnetic clutch from the connected state to the disconnected state with a delay until after a second period longer than the first period has elapsed. Specifically, when the supercharging region determination unit determines that the engine is operating in the supercharging region and the steering angle determination unit determines that the steering angle is equal to or greater than a first angle, and then the engine operation region transitions from the supercharging region to the non-supercharging region and the steering angle becomes equal to or less than the first angle, the supercharging control unit performs control to switch the electromagnetic clutch from the connected state to the disconnected state after a second period longer than the first period has elapsed. This makes it possible to maintain supercharging by the mechanical supercharger for a long period of time and suppress acceleration delays of the vehicle when re-accelerating when the steering angle is equal to or greater than a predetermined first angle during driving that requires large steering, such as winding road driving.

In the above engine system, it is preferable that the supercharging control unit switches the electromagnetic clutch from the connected state to the disconnected state after the second period longer than the first period has elapsed when the steering angle becomes equal to or smaller than a second angle smaller than the first angle.

With this configuration, counting of the second period starts when the steering angle becomes equal to or less than a second angle that is smaller than the first angle, so it is possible to start counting later than when the steering angle becomes equal to or less than the first angle. Therefore, when the steering angle is equal to or greater than a predetermined first angle during driving that requires large steering, such as winding roads, it is possible to maintain supercharging by the mechanical supercharger for a longer period of time and suppress acceleration delays of the vehicle when re-accelerating.

In the above engine system, it is preferable that the first angle is set to be smaller as the vehicle speed increases.

According to this configuration, when the vehicle is traveling at a high speed, the first angle is set to a small angle, so that even if the steering angle is small, the frequency with which the steering angle is equal to or greater than the first angle increases. This increases the frequency with which the supercharging control unit performs control to disconnect the electromagnetic clutch after the second period has elapsed, making it possible to effectively suppress the acceleration delay of the vehicle when re-accelerating according to the vehicle speed.

In the above engine system, it is preferable that the first angle is constant regardless of the gear stage.

With this configuration, the first angle is maintained constant even if the gear stage of the transmission gear changes. Therefore, even if the gear stage is frequently changed while driving on winding roads, it is possible to suppress the acceleration delay of the vehicle when reaccelerating regardless of the gear stage, and it is possible to accelerate according to the requested acceleration.

The engine system of the present invention can reduce the delay in vehicle acceleration when the steering wheel is turned significantly, such as when driving on winding roads.

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 the steering angle, engine speed, on-off of the electromagnetic clutch, and timer operation for controlling the electromagnetic clutch in FIG. 1 . 10 is a graph showing a relationship between vehicle speed and a first angle.

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 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 opening of the accelerator pedal (hereinafter referred to as accelerator opening) operated by the driver who drives the vehicle, a vehicle speed sensor SN8 that detects the vehicle's traveling speed (hereinafter referred to as vehicle speed), and a steering angle sensor SN9 (steering angle detection unit) that detects the steering angle of the steering wheel. The detection signals from these sensors SN7 to SN9 are also input sequentially to the PCM 100.

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 functionally includes a combustion control unit 101, a supercharging region determination unit 102, a steering angle determination unit 103, a supercharging control unit 104, and a timer 105 for delaying the disconnection of the electromagnetic clutch 34 for a predetermined time.

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 supercharging region determination unit 102 determines whether the engine is operating in the supercharging region (SCon region in Figures 3 and 6) where the electromagnetic clutch 34 is connected, or in the non-supercharging region (outside the SCon region in Figure 3 and the SOff region in Figure 6) where the electromagnetic clutch 34 is disconnected, based on the engine speed detected by the crank angle sensor SN1 (engine speed detection unit).

The steering angle determination unit 103 determines the steering angle θ detected by the steering angle sensor SN9 (steering angle detection unit). Specifically, the steering angle determination unit 103 determines whether the steering angle θ is equal to or greater than a predetermined first angle θ1 in order to determine whether the vehicle is traveling on a winding road. The steering angle determination unit 103 also determines whether the steering angle θ is equal to or less than the first angle θ1 (preferably, equal to or less than a second angle θ2 smaller than the first angle θ1) in order to control the disconnection of the electromagnetic clutch 34 during winding travel.

The supercharging control unit 104 controls the connection and disconnection of the electromagnetic clutch 34 based on the results of the judgments made by the steering angle judgment unit 103 and the supercharging region judgment unit 102. The specific method of connection control will be described in detail later.

The timer 105 counts the first period Δt0 and the second period Δt1 described below as a predetermined time for delaying the disengagement of the electromagnetic clutch 34.

(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 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.

In the engine system of this embodiment, the supercharging control unit 104 performs basic control to switch the electromagnetic clutch 34 from the connected state to the disconnected state after a predetermined first period Δt0 (see step S13 in FIG. 5 and FIG. 6) has elapsed when the supercharging region determination unit 102 determines that the engine operating region has transitioned from the supercharging region (specifically, the state in which the engine is in the SCon region in FIG. 3) to the non-supercharging region (the state in which the engine is not in the SCon region).

In addition, when the vehicle is traveling with a large steering angle, such as when traveling on a winding road, the supercharging control unit 104 controls the electromagnetic clutch 34 to be switched from the connected state to the disconnected state after a second period Δt1 (see step S9 in FIG. 5 and FIG. 6) longer than the first period Δt0 has elapsed, thereby maintaining a long supercharging period. Specifically, when the supercharging region determination unit 102 determines that the engine is operating in the supercharging region, and the steering angle determination unit 103 determines that the steering angle θ is equal to or greater than the first angle θ1, and then the engine operation region transitions from the supercharging region to the non-supercharging region and the steering angle θ becomes equal to or less than the first angle θ1 (preferably, equal to or less than the second angle θ2 smaller than the first angle θ1), the supercharging control unit 104 controls the electromagnetic clutch 34 to be switched from the connected state to the disconnected state after the second period Δt1 has elapsed.

The first period Δt0 is set to, for example, about 1 second. The second period Δt1 is set to, for example, about 10 seconds, which is a time that is sufficiently longer than the first period Δt0.

Here, taking into consideration the fact that as the vehicle speed V increases, it is required to suppress the acceleration delay during re-acceleration even at a small steering angle θ, it is preferable to set the above-mentioned first angle θ1 so that it becomes smaller as the vehicle speed V increases. For example, as shown in the graph of FIG. 7, the first angle θ1 is set so that in a region where the vehicle speed V is low, the first angle θ1 gradually becomes smaller as the vehicle speed V increases, and in a region where the vehicle speed V is high, the first angle θ1 is constant.

In addition, taking into consideration the fact that it is necessary to accelerate according to the requested acceleration even if the gear stage is frequently changed while traveling on winding roads, it is preferable that the first angle θ1 be constant regardless of the gear stage.

(Control flow chart of the electromagnetic clutch 34)
In the engine system configured as described above, the operation control of the supercharger 33, specifically the control of the electromagnetic clutch 34, during winding road running is performed in the following procedure.

When driving on a winding road, the steering angle θ fluctuates greatly, as shown by the steering curve SR1 in the time chart of Figure 6. Note that the steering curve SR1 shows the absolute value of the steering angle θ.

As shown in the flowchart of FIG. 5, first, in step S1, the supercharging region determination unit 102 determines whether the engine operating region is transitioning to the supercharging region (the SCon region in FIG. 3). Specifically, the supercharging region determination unit 102 determines whether the engine speed RN (see FIG. 6) detected by the crank angle sensor SN1 (engine speed detection unit) is equal to or greater than a predetermined supercharging speed AN (corresponding to the fourth speed N4 in FIG. 3), and determines whether the engine is operating in the supercharging region (the SCon region).

If the engine operating range has transitioned to the SCon range in FIG. 3, the process proceeds to step S2, where the supercharging control unit 107 controls the electromagnetic clutch 34 to be connected (see the electromagnetic clutch on at time t2 in FIG. 6). As a result, the supercharger 33 connects to the crankshaft 7 and performs supercharging.

At the same time, in step S3, the timer 105 performs a first timer set to prepare for counting the first period Δt0. Specifically, at time t2 in FIG. 6, the timer 105 sets a flag for the first timer set TS1 at the same time that the electromagnetic clutch 34 is engaged.

Next, in step S4, the steering angle determination unit 103 determines whether the steering angle θ is equal to or greater than the first angle θ1. Specifically, at time t3 in FIG. 6, the steering angle determination unit 103 determines whether the steering angle θ is equal to or greater than the first angle θ1.

If the steering angle θ is equal to or greater than the first angle θ1 (i.e., if the steering angle θ becomes large due to winding driving), in step S5, the timer 105 sets the flag of the second timer set TS2 in preparation for counting the second period Δt1 (see time t3 in FIG. 6). At this time, the flag of the previous first timer set TS1 is cancelled.

Next, in step S6, the supercharging range determination unit 102 determines whether the engine operating range is in the SCon range in FIG. 3 in order to determine whether the engine operating range is transitioning from the supercharging range to the non-supercharging range. Specifically, the supercharging range determination unit 102 determines whether the engine operating range is transitioning from the supercharging range (SCon range) to the non-supercharging range (SOff range) based on the engine speed RN (see FIG. 6) (if still in the SCon range, step S6 is repeated).

Then, in step S7, the steering angle determination unit 103 determines whether the steering angle θ is equal to or less than a second angle θ2 that is lower than the first angle θ1, as a specific example of determining whether the steering angle θ is equal to or less than the first angle θ1 (if the steering angle θ is not equal to or less than the second angle θ2, the process returns to step S6).

If both of the conditions in steps S6 and S7 above are met, that is, if the engine operating region is not in the SCon region in FIG. 3 (i.e., the engine operating region has transitioned from the supercharged region to a non-supercharged state) and the steering angle θ is equal to or less than the second angle θ2, in step S8, the timer 105 is activated and starts counting the second period Δt1 (see time t5 in FIG. 6).

Specifically, in the time chart of FIG. 6, after the engine speed RN transitions to the SCoff region below the supercharged speed AN at time t4, the timer 105 starts counting the second period Δt1 at the same time that the steering angle θ becomes equal to or less than the second angle θ2 at time t5 (see curve TM2 showing timer operation at time t5).

After the timer 105 counts a predetermined time Δt1 (e.g., 10 seconds) (step S9), the process proceeds to step S10, where the supercharging control unit 104 controls the electromagnetic clutch 34 to be disconnected (i.e., to transition from a connected state to a disconnected state). As a result, the supercharger 33 is disconnected from the crankshaft 7, and supercharging is stopped.

Therefore, when the vehicle is traveling with a large steering angle θ, such as when traveling on winding roads, the supercharging control unit 104 performs control to disconnect the electromagnetic clutch 34 after a delay of the second period Δt1, which is longer than the predetermined first period Δt0, as in steps S4 to S10 above. Moreover, the timing at which the timer 105 starts counting the second period Δt1 is delayed from time t4 when the engine speed RN transitions to the SCoff region below the supercharging speed AN, to time t5 when the steering angle θ becomes equal to or smaller than the second angle θ2 after time t4.

As a result, during winding road driving, it is possible to maintain supercharging by the supercharger 33 for a long supercharging period from time t2 to t6, as shown by the on/off curve C1 in Figure 6, which indicates the timing of connecting and disconnecting the electromagnetic clutch 34.

Note that if the engine is in the supercharging region (see the SCon region in Figures 3 and 6) when the electromagnetic clutch 34 is disengaged (time t6 in Figure 6), the electromagnetic clutch 34 may be allowed to continue to be engaged. On the other hand, if the engine is in the non-supercharging region (outside the SCon region in Figure 3 and the SOff region in Figure 6) when the electromagnetic clutch 34 is disengaged (simultaneous point t6), the electromagnetic clutch 34 may be disengaged after counting Δt1 (10 seconds) from time t5 to t6 and then counting Δt0 (1 second) (see timer operation curve TM2' from time t6 to t7).

On the other hand, in the above step S4, in the case of normal driving where the steering angle θ is smaller than the first angle θ1 (i.e., less than the first angle θ1) (i.e., in the case of the steering curve SR2 in FIG. 6), the process proceeds to step S11, and normal cut-off control of the supercharger 33 is performed (see the cut-off curve C2 in FIG. 6).

That is, in step S11, when the engine operating range is not in the SCon range, which is the supercharging range (i.e., the engine operating range has transitioned from the supercharging range to the non-supercharging range) (t4) (at this time t4, the engine has transitioned to the non-supercharging range, and the engine speed RN is in the SOff range, which is equal to or lower than the supercharging speed AN), the process proceeds to step S12, and after the timer 105 has counted a predetermined time Δt0 (e.g., 1 second) (see curve TM1 showing timer operation at time t4), the supercharging control unit 104 controls the electromagnetic clutch 34 to be disconnected (transitioning from the connected state to the disconnected state), and the supercharging of the supercharger 33 is stopped (see time t4+Δt0 of the connection/disconnection curve C2 in FIG. 6).

Comparing the on/off curves C1 and C2 of the electromagnetic clutch 34 in Figure 6 above, it can be seen that in normal driving where the steering angle θ is small, as shown by the on/off curve C2, the electromagnetic clutch 34 is disconnected after the period from time t2 to time t4 + Δ0 has elapsed, whereas in driving where the steering angle θ is large, such as winding driving, which is a feature of the present invention, the electromagnetic clutch 34 is disconnected after the long supercharging period from time t2 to time t6 has elapsed, so that the supercharging period can be maintained for a long period during winding driving.

(Features of this embodiment)
(1)
The engine system of this embodiment includes a turbocharger 33 driven by the crankshaft 7 of the engine, an electromagnetic clutch 34 that connects the crankshaft 7 and the turbocharger 33 in a disconnectable manner, a steering angle sensor SN9 (steering angle detection unit) that detects a steering angle θ, a crank angle sensor SN1 (engine rotation speed detection unit) that detects the engine speed RN, a steering angle determination unit 103 that determines the steering angle θ detected by the steering angle sensor SN9, a supercharging region determination unit 102 that determines whether the engine is operating in a supercharging region (see the SCon region in Figures 3 and 6) in which the electromagnetic clutch 34 is connected or a non-supercharging region (see outside the SCon region in Figure 3 and the SOff region in Figure 6) in which the electromagnetic clutch 34 is disconnected based on the engine speed RN detected by the crank angle sensor SN1, and a supercharging control unit 104 that controls the connection and disconnection of the electromagnetic clutch 343 based on the determination results of the steering angle determination unit 103 and the supercharging region determination unit 102.

When the supercharging region determination unit 102 determines that the engine is operating in the supercharging region (SCon region) and the steering angle determination unit 103 determines that the steering angle θ is less than a predetermined first angle θ1 (NO in step S4 of FIG. 6), and the engine operation region then transitions from the supercharging region to the non-supercharging region, the supercharging control unit 104 controls to switch the electromagnetic clutch 34 from the connected state to the disconnected state after a predetermined first period Δt0 has elapsed.

The supercharging control unit 104 also switches the electromagnetic clutch 34 from the connected state to the disconnected state after a second period Δt1 longer than the first period Δt0 has elapsed when the supercharging region determination unit 102 determines that the engine is operating in the supercharging region and the steering angle determination unit 103 determines that the steering angle θ is equal to or greater than the first angle θ1 (YES in step S4 of FIG. 6), and the engine operation region then transitions from the supercharging region to the non-supercharging region and the steering angle θ becomes equal to or less than the first angle θ1, or, in this embodiment, equal to or less than a second angle θ2 smaller than the first angle θ1.

In this configuration, the supercharging region determination unit 102 determines whether the engine is operating in the supercharging region where the electromagnetic clutch 34 is connected or in the non-supercharging region where the electromagnetic clutch 34 is disconnected, based on the engine speed RN detected by the crank angle sensor SN1. As a basic control, the supercharging control unit 104 performs control to switch the electromagnetic clutch 34 from the connected state to the disconnected state after a predetermined first period Δt0 has elapsed when the supercharging region determination unit 102 determines that the engine is operating in the supercharging region (SCon region) and the steering angle determination unit 103 determines that the steering angle θ is less than a predetermined first angle θ1 (if NO in step S4 of FIG. 6), and the engine operation region then transitions from the supercharging region to the non-supercharging region.

In addition, when the vehicle is traveling with a large steering angle θ, such as when traveling on a winding road, the supercharging control unit 104 controls the electromagnetic clutch 34 to switch from the connected state to the disconnected state with a delay until after the second period Δt1, which is longer than the first period Δt0, has elapsed, thereby maintaining a long supercharging period.

Specifically, when the supercharging region determination unit 102 determines that the engine is operating in the supercharging region, and the steering angle determination unit 103 determines that the steering angle θ is equal to or greater than the first angle θ1, and then the engine operation region transitions from the supercharging region to the non-supercharging region and the steering angle θ becomes equal to or less than the first angle θ1 (in this embodiment, when the steering angle θ becomes equal to or less than the second angle θ2 that is smaller than the first angle θ1 (see step S4 in FIG. 5 and time t3 in FIG. 6)), the electromagnetic clutch 34 is controlled to switch from the connected state to the disconnected state after a second period Δt1 longer than the first period Δt0 has elapsed (see steps S6 to S10 in FIG. 5 and time t4 to t6 in FIG. 6).

As a result, when the steering angle θ is equal to or greater than a predetermined first angle θ1 during driving that requires large steering turns, such as when driving on winding roads, it becomes possible to maintain supercharging by the mechanical supercharger 33 for a long supercharging period (see the period from time t2 to t6 of the on-off curve C1 in Figure 6) and suppress delays in the acceleration of the vehicle when re-accelerating.

(2)
In the engine system of this embodiment, when the steering angle θ becomes equal to or less than a second angle θ2 which is smaller than the first angle θ1 (see step S7 in FIG. 5 and time t5 in FIG. 6), the supercharging control unit 104 controls the electromagnetic clutch 34 to switch from a connected state to a disconnected state after a second period Δt1 which is longer than the first period Δt0 has elapsed (see steps S7 to S10 in FIG. 5 and times t5 to t6 in FIG. 6).

In this configuration, counting of the second period Δt1 starts when the steering angle θ becomes equal to or less than the second angle θ2, which is smaller than the first angle θ1 (time t5 in FIG. 6), so it is possible to start counting later than when the steering angle becomes equal to or less than the first angle θ1. Therefore, when the steering angle is equal to or greater than the predetermined first angle θ1 during driving that requires large steering, such as winding roads, it is possible to maintain supercharging by the mechanical supercharger for a longer period of time and suppress acceleration delays of the vehicle when re-accelerating.

(3)
In the engine system of this embodiment, the first angle θ1 is set to be smaller as the vehicle speed V is higher (see the graph in FIG. 7). In this configuration, when the vehicle speed V is high, the first angle θ1 is set to a small angle, so that even if the steering angle θ is small, the frequency with which the steering angle θ is equal to or larger than the first angle θ1 increases. This increases the frequency with which the supercharging control unit 104 performs control to disconnect the electromagnetic clutch 34 after the second period Δt1 has elapsed, making it possible to effectively suppress an acceleration delay of the vehicle when re-accelerating according to the vehicle speed.

The setting of the first angle θ1 associated with the vehicle speed V is not limited to the example shown in the graph of FIG. 7, and various settings may be used. For example, the first angle θ1 may be decreased at the same rate of change over the entire range of the vehicle speed V, or the first angle θ1 may be decreased in stages.

(4)
In the engine system of this embodiment, the first angle θ1 is constant regardless of the gear stage. In this configuration, even if the gear stage of the transmission gear changes, the first angle θ1 is maintained constant. Therefore, even if the gear stage is frequently changed while traveling on a winding road, it is possible to suppress the acceleration delay of the vehicle when re-accelerating regardless of the gear stage, and it is possible to accelerate according to the requested acceleration.

REFERENCE SIGNS LIST 1 engine body 7 crankshaft 33 turbocharger 34 electromagnetic clutch 102 turbocharger region determination unit 103 steering angle determination unit 104 turbocharger control unit 105 timer SN9 steering angle sensor

Claims (4)

a supercharger driven by the engine crankshaft;
an electromagnetic clutch that disconnectably connects the crankshaft and the turbocharger;
a steering angle detection unit that detects a steering angle of a steering wheel;
an engine speed detection unit that detects the engine speed;
a steering angle determination unit that determines the steering angle detected by the steering angle detection unit;
a supercharging region determination unit that determines whether the engine is operating in a supercharging region in which the electromagnetic clutch is engaged or in a non-supercharging region in which the electromagnetic clutch is disengaged, based on the engine speed detected by the engine speed detection unit;
a supercharging control unit that controls connection/disconnection of the electromagnetic clutch based on the determination results of the steering angle determination unit and the supercharging region determination unit,
The supercharging control unit is
when the supercharging region determination unit determines that the engine is operating in the supercharging region and the steering angle determination unit determines that the steering angle is less than a predetermined first angle, and thereafter, when the operating region of the engine transitions from the supercharging region to the non-supercharging region, switching the electromagnetic clutch from a connected state to a disconnected state after a predetermined first period has elapsed;
an engine system comprising: when the supercharging region determination unit determines that the engine is operating in the supercharging region and the steering angle determination unit determines that the steering angle is equal to or greater than the first angle, and thereafter, when the operating region of the engine transitions from the supercharging region to the non-supercharging region and the steering angle becomes equal to or less than the first angle, the electromagnetic clutch is switched from a connected state to a disconnected state after a second period longer than the first period has elapsed. 2. The engine system according to claim 1,
the supercharging control unit switches the electromagnetic clutch from a connected state to a disconnected state after the second period that is longer than the first period has elapsed when the steering angle becomes equal to or smaller than a second angle that is smaller than the first angle. 3. The engine system according to claim 1,
An engine system, characterized in that the first angle is set to be smaller as a vehicle speed increases. In the engine system according to any one of claims 1 to 3,
An engine system, wherein the first angle is constant regardless of gear stage.

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