Drive control system

Abstract

To suppress electric power consumption required for starting an engine.SOLUTION: A drive control system includes: an engine having a cylinder and a piston provided slidably inside the cylinder, and rotating a crank shaft in accordance with sliding of the piston; an electric supercharger that supplies compressed air into the cylinder; and a control device that controls the engine and the electric supercharger. A processor of the control device executes processing that includes: transmitting a stop signal for stopping the engine to the engine; and stopping the piston at a position where a crank angle is within a predetermined range from 60° before a top dead center to 30° before the top dead center by supplying the compressed air into the cylinder by using the electric supercharger for a period until stop of the engine is completed after the stop signal is transmitted.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a drive control system.

Background Art

[0002] For example, Patent Document 1 discloses a technique for starting an engine. When starting the engine, if the position of the piston is not appropriate, a motor generator is used to drive the crankshaft, and the position of the piston is moved to an appropriate position before starting the engine.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the technique of Patent Document 1, since a stopped piston is moved to an appropriate position using a motor generator, a relatively large amount of power is consumed when moving the piston. Therefore, in the technique of Patent Document 1, including the power consumption for moving the piston, the power consumption for starting the engine increases.

[0005] Therefore, an object of the present invention is to provide a drive control system capable of suppressing the power consumption required for starting an engine.

Means for Solving the Problems

[0006] To solve the above problems, a drive control system according to an embodiment of the present invention includes an engine having a cylinder and a piston slidably provided inside the cylinder, and rotating a crankshaft in response to the sliding of the piston, An electric supercharger that supplies compressed air to the inside of the cylinder, A control device that controls the engine and the electric supercharger, Equipped with, The control device is One or more processors, One or more memory connected to the processor, It has, The aforementioned processor, To transmit a stop signal to the engine to stop the engine, After the transmission of the stop signal and during the period until the engine has finished stopping, the electric supercharger supplies compressed air into the cylinder so that the crank angle is within a predetermined range from 60° before top dead center to 30° before top dead center. and a position within a region where the starting torque required to start the engine is relatively reduced. To stop the piston, Execute the process that includes this. [Effects of the Invention]

[0007] According to the present invention, it is possible to suppress the power consumption required to start the engine. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing the configuration of a vehicle to which the drive control system according to this embodiment is applied. [Figure 2] Figure 2 is a diagram illustrating the details of the configuration of a vehicle to which the drive control system according to this embodiment is applied. [Figure 3] Figure 3 shows an example of the relationship between the piston's resting position and the torque required to start the engine. [Figure 4] Figure 4 is a timing chart illustrating the flow of engine stopping and starting operations. [Figure 5] Figure 5 shows an example of a turbocharging operation condition map. [Figure 6] Figure 6 is a flowchart illustrating the operation flow of the exhaust regeneration control unit. [Figure 7] Figure 7 is a flowchart illustrating the operation flow of the engine stop control unit. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described in detail below with reference to the attached drawings. The specific dimensions, materials, numerical values, etc., shown in these embodiments are merely examples to facilitate understanding of the invention and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals to avoid redundant explanations, and elements not directly related to the present invention are omitted from the illustrations.

[0010] Figure 1 is a schematic diagram showing the configuration of a vehicle 2 to which the drive control system 1 according to this embodiment is applied. The vehicle 2 includes an engine 10, a motor generator 12, a torque converter 14, a transmission 16, and wheels 18. The vehicle 2 is a hybrid electric vehicle equipped with an engine 10 and a motor generator 12 as drive sources. However, the vehicle 2 may also be a conventional engine vehicle in which the motor generator 12 is omitted and the engine 10 is equipped as the drive source.

[0011] The engine 10 is connected to a torque converter 14. The torque converter 14 is connected to a motor generator 12. The motor generator 12 is connected to a transmission 16. The transmission 16 is connected to wheels 18.

[0012] The driving force of the engine 10 is transmitted to the wheels 18 via the torque converter 14, the motor generator 12, and the transmission 16. Also, the driving force of the motor generator 12 is transmitted to the wheels 18 via the transmission 16. Further, when the load on the wheels 18 is greater than the output of the motor generator 12, the motor generator 12 can also function as a generator that generates electricity in response to the rotation of the wheels 18. Also, the motor generator 12 can function as a starter that starts the engine 10.

[0013] FIG. 2 is a diagram for explaining the details of the configuration of the vehicle 2 to which the drive control system 1 according to the present embodiment is applied. The vehicle 2 includes a high-voltage battery 20 that supplies power to the motor generator 12. The high-voltage battery 20 is, for example, a lithium-ion battery or the like, and is a secondary battery capable of charging and discharging.

[0014] The motor generator 12 is electrically connected to the high-voltage battery 20 through a high-voltage inverter 22. The motor generator 12 rotates according to the power supplied from the high-voltage battery 20. Also, when the motor generator 12 functions as a generator, it can charge the high-voltage battery 20 by supplying the generated power to the high-voltage battery 20.

[0015] The engine 10 has a piston 30, a cylinder 32, an intake port 34, an exhaust port 36, an intake valve 38, and an exhaust valve 40. The piston 30 is slidably accommodated inside the cylinder 32. The intake port 34 and the exhaust port 36 communicate with the inside of the cylinder 32. The intake valve 38 opens and closes the intake port 34. The exhaust valve 40 opens and closes the exhaust port 36.

[0016] When the intake valve 38 is in the open state, air is introduced into the cylinder 32 through the intake port 34. Further, fuel is injected into the cylinder 32. Inside the cylinder 32, the mixture of air and fuel burns, causing the piston 30 to slide inside the cylinder 32. The piston 30 is connected to the crankshaft 44 via the connecting rod 42. The crankshaft 44 is connected to the torque converter 14. When the piston 30 slides, the crankshaft 44 rotates. That is, the engine 10 rotates the crankshaft 44 in response to the sliding of the piston 30.

[0017] When the exhaust valve 40 is in the open state, the gas inside the cylinder 32 is discharged to the outside of the cylinder 32 through the exhaust port 36.

[0018] The vehicle 2 includes an intake passage 50 and an exhaust passage 52. The intake passage 50 is connected to the intake port 34. Air introduced into the cylinder 32 through the intake port 34 flows through the intake passage 50. The exhaust passage 52 is connected to the exhaust port 36. The gas discharged to the outside of the cylinder 32 through the exhaust port 36 flows through the exhaust passage 52.

[0019] In the intake passage 50, an air cleaner 60, an intercooler 62, and a throttle valve 64 are provided in order along the direction in which air flows. The air cleaner 60 removes foreign substances from the air taken into the intake passage 50. The intercooler 62 cools the air flowing through the intake passage 50. The throttle valve 64 adjusts the amount of air introduced into the cylinder 32 according to the driver's acceleration operation.

[0020] A catalyst 66 is provided in the exhaust passage 52. The catalyst 66 is, for example, a three-way catalyst or the like, and purifies the gas discharged from the cylinder 32.

[0021] Vehicle 2 is equipped with an electric supercharger 70. The electric supercharger 70 has an intake turbine 72, an exhaust turbine 74, and a supercharger motor 76. The intake turbine 72 is located in the intake passage 50, between the air cleaner 60 and the intercooler 62 in the intake passage 50. The exhaust turbine 74 is located in the exhaust passage 52, between the exhaust port 36 and the catalyst 66 in the exhaust passage 52. The exhaust turbine 74 rotates as gas flows through the exhaust passage 52. The supercharger motor 76 is connected to the intake turbine 72 and the exhaust turbine 74.

[0022] Vehicle 2 is equipped with a low-voltage battery 80. The low-voltage battery 80 is, for example, a lead-acid battery and is a rechargeable secondary battery. The voltage of the low-voltage battery 80 is, for example, 12V, which is lower than the voltage of the high-voltage battery 20.

[0023] The low-voltage battery 80 is electrically connected to the low-voltage inverter 82, electrical equipment 84, and DC-DC converter 86. The low-voltage battery 80 is electrically connected to the turbocharger motor 76 through the low-voltage inverter 82. The low-voltage battery 80 can supply power to the turbocharger motor 76 through the low-voltage inverter 82.

[0024] The electrical equipment 84 may be various electrical and electronic devices mounted on the vehicle 2 that operate at low voltage, such as an air conditioning system or a navigation system. The low-voltage battery 80 can supply power to the electrical equipment 84.

[0025] The input terminal of the DC-DC converter 86 is electrically connected to the high-voltage battery 20 and the high-voltage inverter 22. In other words, the input terminal of the DC-DC converter 86 is connected to the high-voltage electrical system, which is high-voltage electrical wiring. The output terminal of the DC-DC converter 86 is electrically connected to the low-voltage battery 80, the low-voltage inverter 82 and the electrical equipment 84. In other words, the output terminal of the DC-DC converter 86 is connected to the low-voltage electrical system, which is low-voltage electrical wiring.

[0026] The DC-DC converter 86 converts the power from the high-voltage electrical system at the input terminal to the power from the low-voltage electrical system at the output terminal and outputs it from the output terminal. This allows, for example, the power from the high-voltage battery 20 to be supplied to the low-voltage battery 80, electrical equipment 84, and supercharger motor 76 through the DC-DC converter 86.

[0027] The supercharger motor 76 consumes power supplied through the low-voltage inverter 82 to drive the intake turbine 72. In the electric supercharger 70, the intake turbine 72 can also be driven in accordance with the rotation of the exhaust turbine 74.

[0028] The supercharger motor 76 drives the intake turbine 72 to compress the air taken into the intake passage 50 through the air cleaner 60, thereby generating compressed air. This compressed air is then supplied to the inside of the cylinder 32 through the intercooler 62, throttle valve 64, and intake port 34. In other words, the electric supercharger 70 is configured to generate compressed air and supply the generated compressed air to the inside of the cylinder 32. Hereafter, the operation of driving the intake turbine 72 to generate compressed air may be referred to as the supercharging operation.

[0029] Furthermore, the supercharger motor 76 can also function as a generator that generates electricity in accordance with the rotation of the exhaust turbine 74. By functioning as a generator, the supercharger motor 76 can convert the rotational energy of the exhaust turbine 74 into electrical energy. The electricity generated by the supercharger motor 76 is supplied to the low-voltage battery 80 through the low-voltage inverter 82. Hereafter, the operation of converting and recovering the rotational energy of the exhaust turbine 74 into electrical energy is sometimes referred to as exhaust regeneration.

[0030] Thus, the supercharger motor 76 is capable of performing both supercharging and exhaust regeneration. Supercharging and exhaust regeneration can be switched depending on the situation.

[0031] Vehicle 2 is equipped with an accelerator pedal sensor 90, an engine speed sensor 92, a crank angle sensor 94, and an oil temperature sensor 96. The accelerator pedal sensor 90 detects the amount of acceleration performed by the driver. The engine speed sensor 92 detects the engine speed, which is the rotational speed of the engine 10. The crank angle sensor 94 detects the crank angle, which is the rotational angle of the crankshaft 44. The oil temperature sensor 96 detects the oil temperature, which is the temperature of the lubricating oil in the engine 10.

[0032] Vehicle 2 is equipped with a storage device 100. The storage device 100 is composed of non-volatile memory elements. The non-volatile memory elements may include, for example, electrically readable and writable non-volatile elements such as flash memory. The storage device 100 has a supercharging operation condition map 102 pre-stored in it. The supercharging operation condition map 102 will be described in detail later.

[0033] Vehicle 2 is equipped with a control device 110. The control device 110 comprises one or more processors 112 and one or more memories 114 connected to the processors 112. The memories 114 include ROM, which stores programs, etc., and RAM as a work area. The processors 112 control the entire vehicle 2 by executing programs. For example, the control device 110 controls the engine 10 and the electric supercharger 70.

[0034] The processor 112 also functions as an exhaust regeneration control unit 120 and an engine stop control unit 122 by executing a program. The exhaust regeneration control unit 120 causes the supercharger motor 76 to perform exhaust regeneration while the engine 10 is idling.

[0035] The engine stop control unit 122 transmits a stop signal to the engine 10 when predetermined stop conditions for stopping the engine 10 are met. For example, the engine stop control unit 122 may consider the predetermined stop conditions to be met when it receives an input operation from the driver to turn off the ignition. The predetermined stop conditions may also be the same as the conditions under which idle stop is performed.

[0036] Upon receiving a stop signal, engine 10 stops fuel injection and ignition. As a result, the explosion of the fuel-air mixture that moves piston 30 is stopped, and the sliding of piston 30 gradually slows down. Finally, when piston 30 comes to a complete stop, engine 10 is shut down.

[0037] In this case, when the engine 10 is started from a completely stopped state, the piston 30 will begin to slide from its stopped position. Consequently, the torque required to start the engine 10 will differ depending on the stopped position of the piston 30.

[0038] Figure 3 shows an example of the relationship between the stopping position of the piston 30 and the torque required to start the engine 10. The horizontal axis of Figure 3 shows the crank angle before top dead center (BTDC), relative to top dead center, and indicates the stopping position of the piston 30. In Figure 3, examples of the torque required to start the engine 10 are plotted for each crank angle position from 180° before top dead center (corresponding to bottom dead center) to 0° before top dead center (corresponding to top dead center).

[0039] In the example in Figure 3, the top dead center (TDC) indicates the TDC at the end of the compression stroke. Also, in the example in Figure 3, 90° before TDC corresponds to the crank angle at which the intake valve 38 closes.

[0040] As shown in Figure 3, the torque in the range from 90° before top dead center to 0° before top dead center is generally lower than the torque in the range from 180° before top dead center to 90° before top dead center. More specifically, the torque in the range from 60° before top dead center to 30° before top dead center is even lower than the torque in other ranges. In particular, the torque in the range from 55° before top dead center to 50° before top dead center is the lowest compared to the torque in other ranges. Specifically, the torque in the range from 60° before top dead center to 30° before top dead center is less than 50% of the torque around 90° before top dead center, and in particular, the torque in the range from 55° before top dead center to 50° before top dead center is less than 30% of the torque around 90° before top dead center, indicating that torque is significantly suppressed in these ranges.

[0041] Therefore, the engine stop control unit 122 stops the piston 30 at a position where the crank angle is within a predetermined range from 60° before top dead center to 30° before top dead center.

[0042] This makes it possible to suppress the torque required when starting the engine 10 from a state where the piston 30 is stopped. As a result, the power consumption of the motor generator 12 that drives the engine 10 can be suppressed, and the decrease in the State of Charge (SOC) of the high-voltage battery 20 when starting the engine 10 can be suppressed. Note that SOC (State of Charge) is the charge rate expressed as a percentage of the battery's full charge capacity.

[0043] In particular, it is preferable that the engine stop control unit 122 stops the piston 30 so that the crank angle is within the range of 55° before top dead center to 50° before top dead center.

[0044] This makes it possible to further reduce the torque required to start the engine 10 from a state where the piston 30 is stopped. As a result, the power consumption of the motor generator 12 that drives the engine 10 can be further reduced, and the decrease in the state of charge (SOC) of the high-voltage battery 20 can be further reduced.

[0045] Hereafter, for the sake of explanation, the crank angle range from 60° before top dead center to 30° before top dead center may be referred to as the target stopping range of piston 30. Also, the crank angle range from 55° before top dead center to 50° before top dead center may be referred to as the optimal stopping range of piston 30.

[0046] In this way, by stopping the piston 30 at a specific position within the target stopping range, particularly at a specific position within the optimal stopping range, the decrease in the State of Charge (SOC) of the high-voltage battery 20 can be suppressed, and as a result, the decrease in the driving range of the vehicle 2 can be suppressed.

[0047] In this case, the stopping position of the piston 30 was set by the crank angle before top dead center (TDC) at the end of the compression stroke. However, the stopping position of the piston 30 may also be set by the crank angle before top dead center (TDC) at the end of the exhaust stroke. However, it is more preferable that the stopping position of the piston 30 be set by the crank angle before top dead center (TDC) at the end of the compression stroke, rather than by the crank angle before top dead center (TDC) at the end of the exhaust stroke.

[0048] In this embodiment, the drive control system 1 utilizes an electric supercharger 70 to stop the piston 30 at a specific position within the target stopping range or the optimal stopping range.

[0049] In other words, the engine stop control unit 122 supplies compressed air into the cylinder 32 using the electric supercharger 70 during the period from the transmission of the stop signal until the engine 10 has finished stopping. As a result, the engine stop control unit 122 stops the piston 30 at a position where the crank angle is within a predetermined range from 60° before top dead center to 30° before top dead center.

[0050] Figure 4 is a timing chart illustrating the operation flow of stopping and starting the engine 10. The horizontal axis time is common to all time charts for vehicle speed, engine speed, electric supercharger status, power at the output terminal of the DCDC converter 86, and the state of charge (SOC) of the high-voltage battery 20. In the time chart for the SOC of the high-voltage battery 20, the solid line shows this embodiment where the electric supercharger 70 performs exhaust regeneration during idling, while the dashed line shows a comparative example where the electric supercharger 70 does not perform exhaust regeneration during idling.

[0051] As shown in Figure 4, before time T1, vehicle 2 is traveling at a constant speed, and engine 10 is being driven at a constant rotational speed. At this time, the electric supercharger 70 is performing supercharging operations, for example. Also at this time, the power at the output terminal of the DC-DC converter 86 is relatively high, and power from the high-voltage battery 20 is being supplied to the electric supercharger 70 through the DC-DC converter 86.

[0052] For example, suppose at time T1, the driver begins to reduce the amount of acceleration input, and at time T2, the amount of acceleration input becomes virtually zero. As a result, the vehicle speed decreases during the period from time T1 to time T3. The engine speed decreases during the period from time T1 to time T2 in accordance with the decrease in the amount of acceleration input, and from time T2 onward, since the amount of acceleration input is virtually zero, the engine speed becomes equivalent to idling speed.

[0053] In the comparative example where the electric supercharger 70 does not perform exhaust regeneration when the engine 10 is idling, the high-voltage battery 20 is charged by regeneration from the motor generator 12 as the vehicle speed decreases, and the state of charge (SOC) of the high-voltage battery 20 increases as shown by the dashed line.

[0054] In contrast, in this embodiment, the electric supercharger 70 stops its supercharging operation at time T2 when the engine 10 starts idling, and begins exhaust regeneration, continuously performing exhaust regeneration during the period from time T2 to time T4. When the electric supercharger 70 performs exhaust regeneration, the power generated by the supercharger motor 76 is supplied to the electrical equipment 84. As a result, the amount of power that needs to be supplied from the high-voltage battery 20 to the electrical equipment 84 decreases, and the power at the output terminal of the DC-DC converter 86 decreases.

[0055] As a result, the power supplied to the low-voltage electrical system via the DC-DC converter 86 is suppressed, thus preventing a decrease in the State of Charge (SOC) of the high-voltage battery 20. In addition to the high-voltage battery 20 being charged by regeneration from the motor generator 12, the power supplied to the low-voltage electrical system is reduced, so the SOC of the high-voltage battery 20 increases relatively further compared to the dashed line of the comparative example, as shown by the solid line.

[0056] Now, let's assume that at time T3, the engine stop control unit 122 sends a stop signal to the engine 10. As a result, the sliding of the piston 30 gradually slows down, and the engine speed decreases.

[0057] The engine stop control unit 122, at a predetermined time T4 within the period from time T3, when the stop signal is transmitted, until time T5, when the engine 10 has finished stopping, operates the electric supercharger 70 to control the stopping position of the piston 30. As a result, compressed air is sent into the cylinder 32, and at time T5, the piston 30 stops at a specific position within the target stopping range or the optimal stopping range.

[0058] Furthermore, when the electric supercharger 70 performs supercharging operation at time T4, the power at the output terminal of the DC-DC converter 86 increases in order to supply power from the high-voltage battery 20 to the electric supercharger 70.

[0059] However, by having the electric supercharger 70 perform exhaust regeneration when the engine 10 is idling, the state of charge (SOC) of the high-voltage battery 20 appears to increase when the electric supercharger 70 is activated to control the stopping position of the piston 30. As a result, even when the electric supercharger 70 is activated to control the stopping position of the piston 30, it appears that the power that has been previously secured by exhaust regeneration is being used. Therefore, by having the electric supercharger 70 perform exhaust regeneration when the engine 10 is idling, even when the electric supercharger 70 is activated to control the stopping position of the piston 30, the overall decrease in the SOC of the high-voltage battery 20 can be suppressed.

[0060] From time T5 onward, with the engine 10 stopped, the electric supercharger 70 is also stopped. At this time, the power at the output terminal of the DCDC converter 86 is the power according to the power consumption of the electrical equipment 84. In addition, the state of charge (SOC) of the high-voltage battery 20 decreases by the amount of power supplied from the high-voltage battery 20 to the electrical equipment 84 through the DCDC converter 86.

[0061] Suppose that the engine 10 restarts at time T6, after time T5. When the engine 10 restarts, the piston 30 starts sliding from a state where it is stopped at a specific position within the target stopping range or the optimal stopping range. At this specific position, the torque required to start the engine 10 is smaller than the torque at other positions. Therefore, the power consumption of the motor generator 12 during the restart of the engine 10 can be suppressed.

[0062] Furthermore, when engine 10 restarts, the engine speed increases from zero. Then, from time T7 onward, the acceleration input increases from zero, and the vehicle speed increases. As the acceleration input increases from zero, the electric supercharger 70 begins supercharging. In addition, the power at the output terminal of the DCDC converter 86 increases by the amount of power supplied from the high-voltage battery 20 to the electric supercharger 70.

[0063] Next, the specific control of the electric supercharger 70 for controlling the stopping position of the piston 30 will be described. The engine stop control unit 122 controls the stopping position of the piston 30 by controlling the electric supercharger 70 using the supercharging operation condition map 102 which is pre-stored in the storage device 100.

[0064] Figure 5 shows an example of a turbocharging operation condition map 102. The turbocharging operation condition map 102 is a map that associates engine speed, oil temperature, and turbocharging operation conditions. The turbocharging operation conditions include, for example, the turbocharging start timing, the turbocharging duration, and the output of the electric turbocharger 70. More specifically, in the turbocharging operation condition map 102, the turbocharging start timing, the turbocharging duration, and the output of the electric turbocharger 70 are set for each combination of engine speed and oil temperature.

[0065] In the supercharging operation condition map 102, the supercharging start timing indicates the timing at which the supercharger motor 76 should begin supercharging operation during the period from the transmission of the stop signal until the engine 10 has finished stopping. In other words, the supercharging start timing indicates the timing at which the supply of compressed air to the cylinder 32 should begin. The supercharging start timing is defined by the time from the transmission of the stop signal to the engine 10 until the supercharger motor 76 begins supercharging operation.

[0066] In the supercharging operation condition map 102, the supercharging duration indicates the time during which the supercharger motor 76 continues supercharging after the transmission of the stop signal until the engine 10 has finished stopping. In other words, the supercharging duration indicates the time during which compressed air is continuously supplied.

[0067] The output of the electric supercharger 70 in the supercharging operation condition map 102 indicates the output of the electric supercharger 70 when the supercharger motor 76 performs supercharging operation during the period from the transmission of the stop signal until the engine 10 has finished stopping. The output of the electric supercharger 70 corresponds to the amount of compressed air supplied to the inside of the cylinder 32.

[0068] Here, the higher the engine speed, the longer the time it takes from the transmission of the stop signal to the engine 10 until the engine 10 has finished stopping. Therefore, in the supercharging operation condition map 102, the supercharging start timing may be set to be relatively later as the engine speed increases. Also, the higher the engine speed, the greater the force with which the piston 30 slides due to inertia. Therefore, in the supercharging operation condition map 102, the supercharging duration may be set to be relatively longer as the engine speed increases so that the compressed air can counteract the inertia of the piston 30. In the supercharging operation condition map 102, the output of the electric supercharger 70 may be set to be relatively higher as the engine speed increases so that the compressed air can counteract the inertia of the piston 30.

[0069] Furthermore, the lower the oil temperature, the higher the viscosity of the oil, and the greater the friction of the piston 30 sliding. When the friction of the piston 30 sliding is high, the time it takes from the transmission of the stop signal to the engine 10 until the engine 10 has finished stopping is shortened. Therefore, in the supercharging operation condition map 102, the supercharging start timing may be set to be relatively earlier as the oil temperature decreases. Also, when the friction of the piston 30 sliding is high, the force that causes the piston 30 to slide due to inertia is more easily suppressed by the friction. Therefore, in the supercharging operation condition map 102, the supercharging duration may be set to be relatively shorter as the oil temperature decreases, because the time for compressed air to resist the inertia of the piston 30 is shorter. In the supercharging operation condition map 102, the output of the electric supercharger 70 may be set to be relatively lower as the oil temperature decreases, because the force that compressed air exerts to resist the inertia of the piston 30 is less.

[0070] The engine stop control unit 122 determines the supercharging conditions for the electric supercharger 70 when controlling the stopping of the piston 30, based on the engine speed and oil temperature at the time of transmitting the stop signal and the supercharging operation condition map 102 stored in the storage device 100. For example, the engine stop control unit 122 applies the engine speed and oil temperature at the time of transmitting the stop signal to the supercharging operation condition map 102 to determine the supercharging start timing, supercharging duration, and output of the electric supercharger. The engine stop control unit 122 operates the electric supercharger 70 to supercharge according to the determined supercharging conditions, thereby stopping the piston 30 at a specific position before top dead center.

[0071] In this example, we have described how the supercharging operation conditions are determined based on engine speed and oil temperature. However, the engine stop control unit 122 may omit the oil temperature condition and determine the supercharging operation conditions based on engine speed. In that case, the oil temperature condition may be omitted in the supercharging operation condition map 102, and the engine speed and supercharging operation conditions may be associated with each other.

[0072] Figure 6 is a flowchart illustrating the operation flow of the exhaust regeneration control unit 120. The exhaust regeneration control unit 120 repeatedly executes the series of processes shown in Figure 6 each time a predetermined interrupt timing occurs at a predetermined interval.

[0073] When a predetermined interrupt timing arrives, the exhaust regeneration control unit 120 determines whether the engine 10 is idling or not (S10). For example, the exhaust regeneration control unit 120 determines that the engine 10 is idling if the engine 10 is running and the amount of acceleration detected by the accelerator pedal sensor 90 is substantially zero.

[0074] If the system determines that the engine 10 is idling (YES in S10), the exhaust regeneration control unit 120 causes the supercharger motor 76 to perform exhaust regeneration (S11), and then terminates the current process.

[0075] If the system determines that the engine 10 is not idling (NO in S10), the exhaust regeneration control unit 120 stops exhaust regeneration by the supercharger motor 76 (S12) and terminates the current process.

[0076] Figure 7 is a flowchart illustrating the operation flow of the engine stop control unit 122. The engine stop control unit 122 waits until the stop condition is met (NO in S20), and if the stop condition is met (YES in S20), it executes the processes from step S21 onwards.

[0077] In step S21, the engine stop control unit 122 acquires the current engine speed detected by the engine speed sensor 92 (S21). Since a stop signal is transmitted in step S24, which will be described later, the engine speed acquired in step S21 corresponds to the engine speed at the time the stop signal is transmitted.

[0078] Next, the engine stop control unit 122 acquires the current oil temperature detected by the oil temperature sensor 96 (S22). Since a stop signal is transmitted in step S24, which will be described later, the oil temperature acquired in step S22 corresponds to the oil temperature at the time the stop signal is transmitted.

[0079] Next, the engine stop control unit 122 determines the supercharging conditions based on the acquired current engine speed, the acquired current oil temperature, and the supercharging operation condition map 102 (S23). This determines the supercharging start timing, supercharging duration, and the output of the electric supercharger 70, which are the supercharging conditions.

[0080] Next, the engine stop control unit 122 transmits a stop signal to the engine 10 (S24). Although not shown in Figure 7, the engine stop control unit 122 starts timing the elapsed time since transmitting the stop signal.

[0081] Next, the engine stop control unit 122 determines whether or not the supercharging start timing has arrived (S25). For example, the engine stop control unit 122 determines that the supercharging start timing has arrived if the elapsed time since the stop signal was transmitted reaches the time indicated by the supercharging start timing in the supercharging operation conditions. The engine stop control unit 122 waits until the supercharging start timing arrives (NO in S25).

[0082] If the engine stop control unit 122 determines that the timing for starting supercharging has arrived (YES in S25), it causes the supercharger motor 76 to perform supercharging (S26). At this time, the engine stop control unit 122 drives the supercharger motor 76 so that the output of the electric supercharger 70 becomes the output determined as the supercharging operation condition. Although not shown in Figure 7, the engine stop control unit 122 also starts measuring the elapsed time since the start of the supercharging operation.

[0083] Next, the engine stop control unit 122 determines whether or not the supercharging time has elapsed (S27). For example, the engine stop control unit 122 determines that the supercharging time has elapsed if the elapsed time since the start of the supercharging operation reaches the supercharging duration specified in the supercharging operation conditions. The engine stop control unit 122 waits until the supercharging time has elapsed (NO in S27).

[0084] If it is determined that the supercharging time has elapsed (YES in S27), the engine stop control unit 122 stops the supercharging operation of the supercharger motor 76 (S28) and terminates the series of processes.

[0085] As described above, in the drive control system 1 of this embodiment, after the transmission of the stop signal and during the period until the engine 10 has finished stopping, compressed air is supplied into the cylinder 32 by the electric supercharger 70, thereby stopping the piston 30 at a position where the crank angle is within a predetermined range from 60° before top dead center to 30° before top dead center.

[0086] As a result, the drive control system 1 of this embodiment can start the engine 10 with the piston 30 stopped at an appropriate position where the torque required to start the engine 10 is low. For example, if the piston 30 is stopped near bottom dead center, as shown in Figure 3, the torque required to start the engine 10 becomes high. However, in the drive control system 1 of this embodiment, the torque required to start the engine 10 can be reduced by stopping the piston 30 at a position where the crank angle is within a predetermined range from 60° before top dead center to 30° before top dead center. Therefore, the power consumption of the motor generator 12 that starts the engine 10 can be suppressed in the drive control system 1 of this embodiment.

[0087] Therefore, according to the drive control system 1 of this embodiment, it is possible to suppress the power consumption required to start the engine 10. Furthermore, for example, in the drive control system 1 of this embodiment, it is not necessary to move the piston 30 to an appropriate position before starting the engine 10, thus suppressing the power consumption required to start the engine 10.

[0088] Furthermore, in the drive control system 1 of this embodiment, the predetermined range is the range from 55° before top dead center to 50° before top dead center when the crank angle is set. As a result, the power consumption required to start the engine 10 can be further reduced in the drive control system 1 of this embodiment.

[0089] Furthermore, in the drive control system 1 of this embodiment, exhaust regeneration is performed by the supercharger motor 76 while the engine 10 is idling. Also, in the drive control system 1 of this embodiment, at a predetermined timing after the transmission of a stop signal, the supercharger motor 76 is made to perform a supercharging operation, and compressed air is supplied to the inside of the cylinder 32, thereby stopping the piston 30 at a position where the crank angle is within a predetermined range. As a result, in the drive control system 1 of this embodiment, the power required to perform the supercharging operation of the supercharger motor 76 can be secured in advance by exhaust regeneration, and even if the supercharger motor 76 performs a supercharging operation, the increase in power consumption can be suppressed overall.

[0090] Furthermore, in the drive control system 1 of this embodiment, the timing for starting the supply of compressed air to the cylinder 32, the duration for which the compressed air supply is continued, and the amount of compressed air supplied are determined based on the rotational speed of the engine 10 at the time the stop signal is transmitted. As a result, the drive control system 1 of this embodiment can appropriately stop the piston 30 at the appropriate position through the supercharging operation of the electric supercharger 70.

[0091] Embodiments of the present invention have been described above with reference to the attached drawings, but it goes without saying that the present invention is not limited to these embodiments. It is clear to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally also fall within the technical scope of the present invention. [Explanation of symbols]

[0092] 1. Drive control system 10 Engines 30 pistons 32 liters 44 Crankshaft 70 Electric Supercharger 72 Intake Turbine 74 Exhaust Turbine 76 Supercharger motor 110 Control device 112 processors 114 memory

Claims

1. An engine having a cylinder and a piston slidably mounted inside the cylinder, which rotates a crankshaft in accordance with the sliding of the piston, An electric supercharger that supplies compressed air to the inside of the cylinder, A control device that controls the engine and the electric supercharger, Equipped with, The control device is One or more processors, One or more memories connected to the processor, It has, The aforementioned processor, To transmit a stop signal to the engine to stop the engine, After the transmission of the stop signal and during the period until the engine has finished stopping, the electric supercharger supplies compressed air into the cylinder to stop the piston at a position where the crank angle is within a predetermined range from 60° before top dead center to 30° before top dead center, and within a region where the starting torque required to start the engine is relatively reduced. A drive control system that performs processing including the following.

2. The drive control system according to claim 1, wherein the predetermined range is the range in which the crank angle is from 55° before top dead center to 50° before top dead center.

3. The aforementioned electric supercharger is, An intake turbine is provided in the intake passage of the aforementioned engine, An exhaust turbine provided in the exhaust passage of the aforementioned engine, A supercharger motor capable of performing a supercharging operation to drive the intake turbine and generate the compressed air, and capable of performing exhaust regeneration to convert the rotational energy of the exhaust turbine into electrical energy, It has, The aforementioned processor, While the engine is idling, the supercharger motor is made to perform exhaust regeneration, At a predetermined timing after the transmission of the stop signal, the supercharger motor is made to perform a supercharging operation and compressed air is supplied into the cylinder, thereby stopping the piston at a position where the crank angle is within the predetermined range. A drive control system according to claim 1 or 2, which performs a process including the following:

4. The aforementioned processor, Based on the engine speed at the time the stop signal is transmitted, the timing for starting the supply of compressed air to the cylinder, the duration for which the supply of compressed air is continued, and the amount of compressed air supplied are determined. A drive control system according to claim 1 or 2, which performs a process including the following:

5. The processor is When the engine is stopped, the power stored in the battery by the exhaust regeneration performed while the engine is idling is supplied to the electrical equipment of the vehicle having the electric supercharger. The drive control system according to claim 3, which performs a process including the following:

6. The processor is Based on the engine speed and the oil temperature (the temperature of the engine's lubricating oil) at the time the stop signal is transmitted, the timing for starting the supply of compressed air to the cylinder, the duration for which the supply of compressed air is continued, and the amount of compressed air supplied are determined. A drive control system according to claim 1 or 2, which performs a process including the following:

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