Powertrain control system

Abstract

This suppresses delays in engine starting during engine startup. [Solution] The powertrain control device comprises a powertrain 100 including an engine 4, an electrically operated variable valve timing device (intake S-VT44), and a controller. The valve opening and closing timing is set to a specific timing to improve engine starting when the engine is started from a standstill. Before the engine starts, the controller calculates the required pre-operation time for the variable valve timing device from the difference between the actual valve opening and closing timing and the specific timing, and the response speed. If the required pre-operation time is shorter than the allowable time, the controller starts changing the valve opening and closing timing when the start switch is turned on by the occupant. If the required pre-operation time is longer than the allowable time, the controller starts changing the valve opening and closing timing when a specific action by the occupant before the start switch is operated is detected.

Description

Technical Field

[0006] , ,

[0005] ,

[0001] The technology disclosed herein relates to a control device for a powertrain.

Background Art

[0002] Patent Document 1 describes a conventional control device for an internal combustion engine. The conventional control device for an internal combustion engine includes an electric variable valve timing device. After the internal combustion engine stops, the valve timing of the intake valve is set to the latest angle by the power of the electric motor. By setting the valve timing of the intake valve to the latest angle, the shock at the next start of the internal combustion engine is suppressed.

[0003] Patent Document 1 describes a problem that the set valve timing deviates due to rotational fluctuations before the complete stop of the internal combustion engine. To address this problem, the conventional control device for an internal combustion engine performs a first operation and a second operation related to the valve timing of the intake valve. The first operation is an operation of energizing the electric motor to set the valve timing of the intake valve to the latest angle in response to an engine stop request of the internal combustion engine. The second operation is an operation of energizing the electric motor after the rotation of the internal combustion engine has completely stopped to set the valve timing of the intake valve operated in the first operation to the latest angle.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the conventional control device, immediately after the engine stops, the valve timing is set to a specific timing. However, there is a concern that the valve timing may deviate from the specific timing before the engine starts.

[0006] Therefore, when the occupant turns on the start switch and the engine starts, an electrically operated variable valve timing device is thought to change the valve timing to a specific timing. However, if the amount of deviation in valve timing is large or if the response speed of the variable valve timing device is slow, it takes time to change the valve timing to the specific timing. If the valve timing is not changed to the specific timing, the engine cannot start. If it takes time to change the valve timing to the specific timing, another inconvenience arises: the start of the engine will be delayed after the start switch is turned on.

[0007] The technology disclosed herein suppresses delays in engine startup during engine ignition. [Means for solving the problem]

[0008] The technology disclosed herein relates to a powertrain control system. This powertrain control system is A powertrain installed in an automobile, which includes an engine, An electrically operated variable valve timing device for changing the opening and closing timing of the valves of the aforementioned engine, The system includes a controller that sets the opening and closing timing of the valve by outputting a control signal to the variable valve timing device, The opening and closing timing of the valve is set to a specific timing that enhances the starting performance of the engine when the engine starts up in conjunction with the startup of the powertrain. The controller sets the response speed of the variable valve timing device based on parameters relating to the response speed of the variable valve timing device before the engine is started, and calculates the necessary pre-operation time for the variable valve timing device to eliminate the difference between the actual opening and closing timing of the valves before the engine is started and the specific timing, and the response speed. The controller further, If the preparatory operation time is shorter than a preset allowable time, the variable valve timing device is instructed to start changing the valve opening and closing timing when the powertrain start switch is turned on by the occupant, thereby setting the valve opening and closing timing to the specified timing. If the preparatory operation time is greater than or equal to the allowable time, the variable valve timing device is instructed to start changing the opening and closing timing of the valve when a specific action by the occupant is detected before the occupant turns on the start switch, thereby setting the opening and closing timing of the valve to the specific timing.

[0009] Variable valve timing devices change the opening and closing timing of the valves in an engine installed in an automobile. Variable valve timing devices are electrically operated. As will be described later, variable valve timing devices change the opening and closing timing of the valves by receiving power from a battery.

[0010] The valve opening and closing timing is set to a specific timing that enhances engine starting performance when the engine starts up as the powertrain is activated.

[0011] The specific timing of the valve may be defined as the timing at which the intake valve closes, and which is the timing at the slowest angle set in the variable valve timing device, when the intake valve closing timing has passed the intake bottom dead center.

[0012] If the valve closing timing is set to the retarded timing, the amount of air compressed inside the cylinder during engine cranking is reduced, which improves engine starting performance.

[0013] When the engine starts, the controller controls the variable valve timing system so that the actual opening and closing timing of the valves is at a specific time. This is a preliminary operation of the variable valve timing system performed before the engine starts.

[0014] The controller first sets the response speed of the variable valve timing system based on parameters related to the response speed of the variable valve timing system before the engine starts. For example, if the engine temperature is low, the viscosity of the lubricating oil in the variable valve timing system is high. When the viscosity of the lubricating oil is high, the response speed of the variable valve timing system decreases. Engine temperature is one example of a parameter related to the response speed of the variable valve timing system.

[0015] The controller also determines the difference between the actual opening and closing timing of the valves before engine startup and a specific timing, and calculates the required pre-operation time for the variable valve timing device based on this difference and the response speed. A larger difference results in a longer pre-operation time, and a lower response speed also results in a longer pre-operation time.

[0016] The controller then, if the required preparatory time is shorter than the preset allowable time, initiates a change in the valve opening and closing timing of the variable valve timing device at the moment the powertrain start switch is turned on by the occupant. The valve opening and closing timing is quickly set to the specific timing. After that, the engine starts. The time from turning on the start switch to the start of engine starting is short. Also, because the valve opening and closing timing is set to the specific timing, the engine starts up quickly. Note that if the required preparatory time is shorter than the preset allowable time, this includes the case where the deviation is zero and the required preparatory time is zero. If the deviation is zero, the engine starts up without any change in the valve opening and closing timing after the start switch is turned on.

[0017] If the preparatory time required exceeds the allowable time, it will take time for the valve opening and closing timing to be set to the specific timing. If the valve opening and closing timing is set to the specific timing only after receiving the ON signal from the occupant pressing the engine start switch, the start of the engine will be delayed.

[0018] Therefore, in the technology disclosed herein, when the required time for preliminary operation is longer than the allowable time, the controller starts to change the opening and closing timing of the valve at the timing when a specific operation of the occupant before the occupant turns on the start switch is detected. The timing for changing the opening and closing timing of the valve is earlier than the operation of turning on the start switch. Even if it takes time for the opening and closing timing of the valve to be set to the specific timing, the opening and closing timing of the valve is set to the specific timing without a significant delay from the operation of turning on the start switch. After the occupant turns on the start switch of the engine, the engine can be started promptly.

[0019] The technology disclosed herein suppresses a delay in the start of the engine when the engine is started.

[0020] The controller may also pre-set the opening and closing timing of the valve to the specific timing such that the opening and closing timing of the valve when the engine starts becomes the specific timing when the controller receives a stop request signal for the engine and stops the engine.

[0021] If the opening and closing timing of the valve is pre-set to the specific timing when the engine is stopped, the starting performance of the engine can be improved when the engine is started.

[0022] Also, even if the opening and closing timing of the valve deviates from the specific timing after the opening and closing timing of the valve is set to the specific timing and before the start of the engine, as described above, after the operation of turning on the start switch, the opening and closing timing of the valve is promptly set to the specific timing, and then the engine starts. Also, when the required time for preliminary operation is longer than the allowable time, as described above, in response to the detection of a specific operation of the occupant before the occupant turns on the start switch, the opening and closing timing of the valve is set to the specific timing, and then the engine starts.

[0023] The controller may determine the deviation amount between the actual opening / closing timing of the valve and the specific timing between after the engine stops and before the engine starts.

[0024] As described above, when the opening / closing timing of the valve is preset to a specific timing when the engine is stopped, the controller determines the deviation amount between after the engine stops and before the engine starts. The controller can accurately determine the deviation amount of the opening / closing timing of the valve when the engine starts.

[0025] The controller may detect a parameter related to the response speed of the variable valve timing device at the timing when the specific operation of the occupant is detected, and set the response speed of the variable valve timing device.

[0026] When a parameter is detected at the timing when the specific operation of the occupant is detected, the controller can accurately acquire the parameter at the time of starting the engine. As described above, the parameter is, for example, the temperature of the engine.

[0027] The variable valve timing device receives power supply from the battery and changes the opening / closing timing of the valve. When the required time for preliminary operation calculated at the timing when the specific operation of the occupant is detected is equal to or longer than the allowable time, the controller causes the variable valve timing device to start changing the opening / closing timing of the valve. When the required time for preliminary operation is shorter than the allowable time, the controller does not cause the variable valve timing device to start changing the opening / closing timing of the valve at the timing when the specific operation of the occupant is detected.

[0028] When the required time for preliminary operation calculated at the timing when the specific operation of the occupant is detected is equal to or longer than the allowable time, it takes time to change the opening / closing timing of the valve. The controller causes the variable valve timing device to start changing the opening / closing timing of the valve at the timing when the specific operation of the occupant is detected.

[0029] If the preparatory time required at the moment a specific occupant action is detected is shorter than the allowable time, the controller will not initiate the variable valve timing device to change the valve opening and closing timing at the moment the occupant action is detected. This reduces battery power consumption.

[0030] The controller may, if the required preparatory time is shorter than the allowable time, instruct the variable valve timing device to start changing the opening and closing timing of the valve when the start switch is turned ON.

[0031] Because the preparatory time required is short, even if the valve opening and closing timing change is initiated at the same time the start switch is turned on, the valve opening and closing timing is quickly set to the specified timing. Engine starting is not delayed. Also, initiating the change in valve opening and closing timing too early is disadvantageous in terms of battery power consumption because it requires a longer time to maintain the valve opening and closing timing at the specified timing. Delaying the start of the change in valve opening and closing timing when the deviation is small reduces battery power consumption.

[0032] The controller may, upon detecting a specific action by the occupant, initiate a change in the opening and closing timing of the valve to the variable valve timing device, and then, if the opening and closing timing of the valve does not reach the specific timing after a predetermined time has elapsed, interrupt the change in the opening and closing timing of the valve.

[0033] If the change in the valve opening / closing timing is initiated prematurely, and the time required for the change becomes long, the change in valve opening / closing timing will be interrupted even if the valve opening / closing timing has not yet reached a specific timing. This reduces battery power consumption.

[0034] The powertrain control device further includes a DC-DC converter that starts up when the powertrain is started by receiving power from the battery. The allowable time may be defined as the time from when the start switch is turned ON until the DC-DC converter starts up.

[0035] If power is supplied to the variable valve timing device while the battery is supplying power to the DC-DC converter for startup, a drop in battery voltage may delay the startup of the DC-DC converter. By completing the change in valve opening and closing timing by the variable valve timing device before the DC-DC converter starts to start, both a quick startup of the DC-DC converter and a quick start of the engine can be achieved.

[0036] The specific action of the occupant may be defined as opening the driver's side door of the vehicle, sitting in the driver's seat, or pressing the brake pedal.

[0037] These specific actions are performed before the occupant turns on the start switch to start the engine. By initiating the modification of the valve opening and closing timing based on these specific actions, the valve opening and closing timing can be set to a specific timing at engine start without delaying the start of engine starting. [Effects of the Invention]

[0038] The aforementioned powertrain control device can suppress delays in engine startup. [Brief explanation of the drawing]

[0039] [Figure 1] Figure 1 shows a car equipped with a powertrain control device. [Figure 2] Figure 2 is a block diagram of the powertrain control system. [Figure 3]Figure 3 is a cross-sectional view showing the structure of the intake S-VT. [Figure 4] Figure 4 illustrates the phase shift of the intake S-VT when the engine is stopped. [Figure 5] Figure 5 is a time chart showing the control of the powertrain control unit when the phase shift of the intake S-VT is different. [Figure 6] Figure 6 is a time chart showing the control of the powertrain control unit at different engine temperatures. [Figure 7] Figure 7 shows the relationship between engine temperature and the response speed of the intake S-VT. [Figure 8] Figure 8 is a time chart showing the control of the powertrain control unit when the operation of the variable valve timing device is interrupted during the startup of the DC-DC converter. [Figure 9] Figure 9 is a flowchart showing the control procedure for the powertrain control device. [Figure 10] Figure 10 shows the relationship between the voltage of the low-voltage battery and the response speed of the intake S-VT. [Figure 11] Figure 11 is a time chart relating to the control of the powertrain control device, as shown in the modified example. [Modes for carrying out the invention]

[0040] The following describes an embodiment of the powertrain control device with reference to the drawings. The powertrain control device described here is an example.

[0041] (Overall configuration of the automobile) Figure 1 shows a vehicle 1 equipped with a powertrain control device. The powertrain 100 of this vehicle 1 includes an engine 4 and a motor 5 for driving. Vehicle 1 is a hybrid vehicle.

[0042] Automobile 1 has a total of four wheels: two front wheels 1F and two rear wheels 1R. Engine 4 and motor 5 work together to drive the rear wheels 1R. By driving the rear wheels 1R, automobile 1 moves. Motor 5 is used not only as a power source but also as a generator during regenerative braking. Motor 5 is also used as a starting motor for engine 4.

[0043] Automobile 1 is equipped with a high-voltage battery 9. Power supplied from the high-voltage battery 9 enables the motor 5 to generate torque for driving automobile 1. An external power source 31 is connected to the high-voltage battery 9 via a power supply port 3. The high-voltage battery 9 is charged by the external power source 31. Automobile 1 is a so-called plug-in hybrid vehicle. Note that automobile 1 may also be a hybrid vehicle without the power supply port 3.

[0044] The powertrain 100 of the automobile 1 includes an engine 4 and a motor 5, as well as a K0 clutch 6, an inverter 7, and an automatic transmission 8.

[0045] (Powertrain details) Engine 4 is an internal combustion engine that burns, for example, fossil fuels. As shown in Figure 3, Engine 4 repeats the intake, compression, expansion, and exhaust cycles by the reciprocating motion of a piston 401 housed in a cylinder 40. In this way, Engine 4 generates rotational power for the crankshaft 48, which is connected to the piston 401 via a connecting rod 481. Engine 4 is a so-called four-stroke engine.

[0046] Engine 4 is a spark-ignition engine. Engine 4 may also be a compression-ignition engine. Engine 4 has multiple cylinders 40. The number of cylinders in engine 4 is not limited to a specific number.

[0047] Motor 5 is a permanent magnet type synchronous motor driven by a three-phase alternating current. Motor 5 is connected in series with engine 4 via a K0 clutch 6. Motor 5 is also connected in series with automatic transmission 8.

[0048] The K0 clutch 6 is interposed between the engine 4 and the motor 5. The K0 clutch 6 switches between a state in which the engine 4, motor 5, and automatic transmission 8 are connected, and a state in which the engine 4, motor 5, and automatic transmission 8 are separated. While the vehicle 1 is running, the K0 clutch 6 switches between the connected state and the separated state.

[0049] The motor 5 is connected to the high-voltage battery 9 via the inverter 7 and the high-voltage cable 32. A contactor 90 is interposed in the high-voltage cable 32.

[0050] The high-voltage battery 9 supplies a high-voltage direct current to the inverter 7. The inverter 7 converts this direct current into a three-phase alternating current and supplies it to the motor 5. The motor 5 is controlled by the inverter 7. The motor 5 and inverter 7 also supply regenerative energy to the high-voltage battery 9.

[0051] The high-voltage battery 9 is also connected to the DC-DC converter 10 via a high-voltage cable 32. The DC-DC converter 10 converts the high-voltage DC current to a low-voltage DC current of 12V and outputs it. The DC-DC converter 10 is connected to the low-voltage battery 11 (a so-called lead-acid battery) via a low-voltage cable 33. When the powertrain 100 is started, the DC-DC converter 10 starts up using power supplied from the low-voltage battery 11.

[0052] The DC-DC converter 10 is also connected to the CAN (Controller Area Network) 12 via a low-voltage cable 33. The DC-DC converter 10 supplies a low-voltage DC current to the CAN 12.

[0053] The low-voltage battery 11 is connected to various electrical components via the low-voltage cable 33. As will be described later, the low-voltage battery 11 supplies power to the intake S-VT44 and exhaust S-VT45 of the engine 4 (see the dashed arrows in Figure 2).

[0054] The automatic transmission 8 is a multi-speed automatic transmission (so-called AT). The automatic transmission 8 switches between, for example, forward gears from 1st to 8th gear, and reverse gears. The input shaft of the automatic transmission 8 is connected to the motor 5, as described above.

[0055] The output shaft of the automatic transmission 8 is connected to the differential gear 16 via the propeller shaft 15. The differential gear 16 is connected to a pair of drive shafts 17, 17 which are connected to the left and right rear wheels 1R, 1R. The power output through the propeller shaft 15 is distributed to the left and right by the differential gear 16 and then transmitted to each rear wheel 1R via the pair of drive shafts 17, 17.

[0056] (Engine configuration) As shown in Figure 2, the engine 4 includes a spark plug 41, an injector 42, a throttle valve 43, and an intake S-VT (Sequential-Valve Timing) 44 and an exhaust S-VT 45. The intake S-VT 44 and exhaust S-VT 45 are variable valve timing devices.

[0057] The spark plug 41 is installed in the engine 4. The spark plug 41 forcibly ignites the fuel-air mixture in the cylinder 40.

[0058] The injector 42 is mounted on the engine 4. The injector 42 injects fuel, for example, into the cylinder 40. The fuel and the air drawn into the cylinder 40 form a fuel-air mixture.

[0059] The throttle valve 43 is a butterfly valve installed in the intake passage of the engine 4. Changing the opening of the throttle valve 43 changes the amount of air drawn into the cylinder 40.

[0060] The intake S-VT44 continuously changes the opening and closing timing of the intake valve 470 (see Figure 4). The intake valve 470 is a poppet valve that opens and closes the intake port 472 connected to the cylinder 40. The intake camshaft 47 opens and closes the intake valve 470 via the rocker arm 471. The rocker arm 471 may be omitted. The intake S-VT44 changes the opening and closing timing of the intake valve 470 in relation to the rotation of the crankshaft 48 in the advance or retard direction. The intake S-VT44 is electrically operated. Details of the structure of the intake S-VT44 will be described later.

[0061] The exhaust S-VT45 continuously changes the opening and closing timing of the exhaust valve. The structure of the exhaust S-VT45 is substantially the same as that of the intake S-VT44. The exhaust S-VT45 changes the opening and closing timing of the exhaust valve in relation to the rotation of the crankshaft 48 in the advance or retard direction. The exhaust S-VT45 is electrically operated.

[0062] (Structure of S-VT) Figure 3 is a cross-sectional view showing the structure of the intake S-VT44. Note that the structure of the exhaust S-VT45 is substantially the same as that of the intake S-VT44.

[0063] The intake S-VT44 has a case 441 and a rotor 442. The case 441 and rotor 442 are coaxial with the axis X1 of the intake camshaft 47.

[0064] The case 441 has a sprocket 4411. The sprocket 4411 is formed on the outer circumference of the case 441. The sprocket 4411 is connected to the crankshaft 48 of the engine 4 via a timing chain 46. When the crankshaft 48 rotates, the case 441 and rotor 442 rotate.

[0065] The rotor 442 is housed within the case 441 so as to be rotatable relative to the case 441. The rotor 442 is fixed to the end of the intake camshaft 47. A ring gear 4421 is formed on the inner circumference of the rotor 442.

[0066] The intake S-VT44 has an inner gear 443. The inner gear 443 is located on an eccentric axis X2 parallel to the axis X1 of the intake camshaft 47. The inner gear 443 has external teeth, and some of the external teeth of the inner gear 443 mesh with the ring gear 4421. The number of teeth on the external teeth of the inner gear 443 is less than the number of teeth on the ring gear 4421, and the ring gear 4421 and the inner gear 443 constitute an internal planetary gear reducer.

[0067] The intake S-VT 44 has a control motor 444. The control motor 444 is supported by the engine 4. The control motor 444 is, for example, a brushless motor. The shaft 4441 of the control motor 444 is connected to the inner gear 443 via a cylindrical eccentric shaft 445.

[0068] As described later, the intake S-VT 44 and exhaust S-VT 45 are controlled by the S-VT drive unit 23. When the S-VT drive unit 23 maintains the phase of the intake camshaft 47 relative to the crankshaft 48, it sets the rotational speed of the control motor 444 to be equal to the rotational speed of the case 441. When advancing the opening and closing timing of the intake valve 470, it sets the rotational speed of the control motor 444 to be higher than the rotational speed of the case 441. When retarding the opening and closing timing of the intake valve 470, it sets the rotational speed of the control motor 444 to be lower than the rotational speed of the case 441.

[0069] (Powertrain control configuration) Figure 2 is a block diagram showing the powertrain control configuration, including the powertrain control unit. The powertrain control unit includes a PCM (Powertrain Control Module) 21, an ECM (Engine Control Module) 22, and an S-VT drive unit 23 as controllers. The PCM 21 is connected to the CAN 12, as shown in Figure 1. The PCM 21 controls the powertrain 100. The powertrain control unit has various sensors. Specifically, the powertrain control unit has an accelerator position sensor 51, a gear position sensor 52, a crank angle sensor 53, a water temperature sensor 54, and a cam angle sensor 59.

[0070] The accelerator pedal position sensor 51 outputs a signal to the PCM 21 corresponding to the operation of the accelerator pedal 18 (see Figure 1) operated by the occupant. The gear position sensor 52 outputs a signal to the PCM 21 corresponding to the gear position of the automatic transmission 8. The crank angle sensor 53 outputs a signal to the PCM 21 related to the rotation of the crankshaft 48. The water temperature sensor 54 outputs a signal to the PCM 21 related to the temperature of the coolant in the engine 4. The camshaft angle sensor 59 outputs a signal to the S-VT drive unit 23 related to the rotation of the camshaft.

[0071] Furthermore, the powertrain control unit has various switches. Specifically, the powertrain control unit has a start switch 55, a brake switch 56, a door open / close switch 57, and a seat occupancy switch 58.

[0072] The start switch 55 is a switch operated by the occupant to start the powertrain 100 and also to stop the powertrain 100. The start switch 55 is, for example, a push switch, and if operated while the powertrain 100 is stopped, it becomes an ON operation, and if operated while the powertrain 100 is running, it becomes an OFF operation. The start switch 55 outputs an ON operation signal and an OFF operation signal to the PCM 21. The OFF operation signal is a signal requesting the powertrain 100 to stop. The brake switch 56 outputs a signal to the PCM 21 corresponding to the operation of the brake pedal 19 (see Figure 1) operated by the occupant. When starting the powertrain 100, the occupant operates the start switch 55 ON at the same time as pressing the brake pedal 19. The door open / close switch 57 outputs a signal to the PCM 21 corresponding to the opening and closing of the driver's side door of the automobile 1. The seat occupancy switch 58 outputs a signal to the PCM21 corresponding to the fact that an occupant is seated in the driver's seat.

[0073] Based on the signals output by these sensors and switches, the PCM21 sets, for example, a target driving force for the powertrain 100. Based on the set target driving force, the PCM21 outputs control signals to the ECM22, K0 clutch 6, inverter 7, and automatic transmission 8 in order to control the powertrain 100.

[0074] The ECM22 primarily controls the engine 4. Specifically, based on information from the PCM21, the ECM22 sets the fuel injection amount, air amount, and ignition timing so that the engine 4 outputs the target torque. The ECM22 outputs control signals to the injector 42, throttle valve 43, S-VT drive unit 23, and spark plug 41 so that the set fuel injection amount, air amount, and ignition timing are executed.

[0075] The S-VT drive unit 23 controls the control motor 444 of the intake S-VT 44 and the control motor of the exhaust S-VT 45 based on the control signal from the ECM 22. Through the control of the control motor 444, the opening and closing timing of the intake valve 470 and the opening and closing timing of the exhaust valve are set to the target timing. As mentioned above, the intake S-VT 44 and exhaust S-VT 45 operate using the power of the low-voltage battery 11.

[0076] (Control of variable valve timing device) To improve the starting performance of engine 4, the closing timing of the intake valve 470 when starting engine 4 is set to a timing beyond intake bottom dead center. This is because the amount of air compression in cylinder 40 decreases when engine 4 is cranked. Therefore, when stopping engine 4, the intake S-VT44 sets the opening and closing timing of the intake valve 470 to the retarded timing in advance. As a result, when engine 4 starts, the opening and closing timing of the intake valve 470 is at the retarded timing, allowing engine 4 to start quickly.

[0077] However, if the gear resistance of the intake S-VT44 is low, the cam torque generated on the intake camshaft 47 by an external force after the engine 4 stops can change the phase of the intake S-VT44. As a result, the opening and closing timing of the intake valve 470 may deviate from the slowest timing set when the engine 4 stopped.

[0078] Figure 4 illustrates the phase shift of the intake S-VT44. In the graph of Figure 4, the horizontal axis represents the rotation angle of the crankshaft 48 when the engine 4 is stopped, and the vertical axis represents the torque of the intake camshaft 47 generated by external forces.

[0079] When the rotation angle of the crankshaft 48 is within a specific range when the engine 4 is stopped, the intake valve 470 is in an open state, as indicated by the symbol 4001. The reaction force of the valve spring is input to the intake camshaft 47 via the intake valve 470 and the rocker arm 471, generating negative cam torque. Negative cam torque is a torque in the opposite direction to the rotation of the crankshaft 48 and is a torque that changes the phase of the intake S-VT 44 toward the advance side. As shown by the dashed arrow in the graph of Figure 4, the phase of the intake S-VT 44 is changed by the negative cam torque from the phase of the retarded angle to the phase where the cam torque is zero. Note that, as indicated by the symbol 4002, when the base circle of the intake camshaft 47 hits the rocker arm 471 and the intake valve 470 is closed, the cam torque is zero. In this way, the opening and closing timing of the intake valve 470 is shifted from the retarded angle timing set when the engine 4 is stopped. Furthermore, if the rotation angle of the crankshaft 48 when the engine 4 is stopped is within a certain range, the cam torque becomes positive. When the cam torque is positive when the engine 4 is stopped, the phase of the intake S-VT 44 is changed to the retarded side, so the phase of the intake S-VT 44 set to the retarded phase is maintained at the retarded phase.

[0080] Since the phase of the intake S-VT44 shifts while engine 4 is stopped, it is conceivable to control the intake S-VT44 when starting engine 4 to change the closing valve timing of the intake valve 470 to the retardedest angle. Engine 4 is started when the occupant turns on the start switch 55, which activates the powertrain 100.

[0081] However, as shown in the graph in Figure 4, depending on the rotation angle of the crankshaft 48 when the engine 4 is stopped, the phase shift of the intake S-VT 44 can be large (indicated by 4003) or small (indicated by 4004). When the phase shift is large, it takes time to change the phase of the intake S-VT 44 to the slowest phase. If the opening and closing timing of the intake valve 470 is not changed to the slowest timing, the engine 4 cannot be started. When the phase shift of the intake S-VT 44 is large, another problem arises: the start of the engine 4 is delayed.

[0082] Furthermore, if the engine temperature is low and the viscosity of the lubricating oil in the intake S-VT44 is high, the response speed of the intake S-VT44 decreases. When the response speed of the intake S-VT44 is low, it takes time to change the phase of the intake S-VT44 to the slowest phase.

[0083] Therefore, the powertrain control device disclosed herein determines the time required for a preparatory operation to eliminate the phase difference of the intake S-VT44 when the engine 4 is started, based on the amount of phase difference of the intake S-VT44 and the response speed of the intake S-VT44. Then, the powertrain control device changes the start timing of the preparatory operation of the intake S-VT44 according to the required preparatory operation time. The start timing of the preparatory operation is the timing when the occupant turns on the start switch 55, or the timing when a specific action by the occupant is detected before the occupant turns on the start switch 55. In this case, the specific action by the occupant is the action of the occupant opening the door of the automobile 1. The fact that the door has been opened is determined based on the signal from the door open / close switch 57.

[0084] The phase shift of the intake S-VT44 is determined based on the signal from the cam angle sensor 59. The response speed of the intake S-VT44 is determined based on the engine temperature using the signal from the water temperature sensor 54.

[0085] Even if it takes time to change the phase of the intake S-VT44 to its slowest angle, if the phase change is started in advance, the phase of the intake S-VT44 will be quickly set to its slowest angle after the occupant turns on the start switch 55. The engine 4 can be started quickly after the occupant turns on the start switch 55.

[0086] Figure 5 shows a time chart related to the control of the powertrain control device. Figure 5 shows an example with different phase shift amounts for the intake S-VT44. The response speed of the intake S-VT44 is assumed to be constant. Because the response speed of the intake S-VT44 is constant, the larger the phase shift amount of the intake S-VT44, the longer the preparatory operation time required, and the smaller the phase shift amount of the intake S-VT44, the shorter the preparatory operation time required.

[0087] Time t0 indicates that the vehicle 1 is either moving or stationary. The powertrain 100 is operational, the start switch 55 is ON, and the DCDC converter 10 is also ON. Since the engine 4 is also running, the engine speed is not zero. The opening and closing timing of the intake valve 470 (closed valve timing: IVC in Figure 5) is set to a timing corresponding to the operating state of the engine 4.

[0088] At time t1, the occupant stops the powertrain 100 by operating the start switch 55. The DC-DC converter 10 is turned off after time t1.

[0089] After time t1 and before engine 4 stops, the intake S-VT44 sets the opening and closing timing of the intake valve 470 to the slowest angle. Then, at time t2, the rotational speed of engine 4 becomes zero and engine 4 stops. The occupants get out of vehicle 1.

[0090] As mentioned above, depending on the stopping position of engine 4, the phase of the intake S-VT44 may deviate from the phase of the slowest angle. In Figure 5, the solid line shows the case where the phase of the intake S-VT44 is maintained at the phase of the slowest angle. The dotted line shows the case where the phase of the intake S-VT44 deviates from the phase of the slowest angle, but the amount of deviation is relatively small. The dashed line shows the case where the phase of the intake S-VT44 deviates significantly from the phase of the slowest angle.

[0091] At time t3, the occupant opens the door. At this point, the amount of phase shift of the intake S-VT44 is determined. Alternatively, the determination of the amount of phase shift may be made when engine 4 stops, and the memory may hold the determination result.

[0092] First, let's explain the case where the phase difference is zero. Because the phase difference is zero, the intake S-VT44 does not need to perform any preparatory actions to eliminate the phase difference when starting the engine 4. After the occupant turns on the start switch 55 at time t4, the DCDC converter 10 starts up using power from the low-voltage battery 11 at time t5, a predetermined time after the turn-on operation. At time t6, when the DCDC converter 10 has finished starting up, the engine 4 begins cranking. The time from the turn-on operation of the start switch 55 (time t4) to the start of cranking (time t6) falls within the preset starting performance standard time.

[0093] Because the closing valve timing of the intake valve 470 is set to the retarded angle, the amount of compressed air in cylinder 40 is reduced, as mentioned above. After cranking begins, piston 401 can more easily overcome the first compression top dead center (see time t7), leading to the first combustion of engine 4 (time t8). Engine 4 starts up quickly.

[0094] Next, we will explain the case where the phase shift is relatively small (see the dotted line in Figure 5). This corresponds to the case where the time required for preparatory work is shorter than the allowable time. Since the phase shift is not zero, the intake S-VT44 performs preparatory work to eliminate the phase shift when starting the engine 4. As described above, at time t4 when the occupant turns on the start switch 55, the intake S-VT44 begins to change the opening and closing timing of the intake valve 470 to the slowest angle. Because the phase shift is small, the opening and closing timing of the intake valve 470 is set to the slowest angle by time t5 when the DCDC converter 10 starts up. From time t5 onward, the intake S-VT44 operates to maintain the opening and closing timing of the intake valve 470 at the slowest angle.

[0095] As described above, the DCDC converter 10 starts up at time t5, and the engine 4 starts cranking and starts up at time t6.

[0096] At the moment the occupant turns on the start switch 55, the phase of the intake S-VT 44 is shifted from the retarded angle. The intake S-VT 44 changes the opening and closing timing of the intake valve 470 to the retarded angle, so that the opening and closing timing of the intake valve 470 is set to the retarded angle before cranking begins. After turning on the start switch 55, cranking of the engine 4 can be started within the starting performance standard time. In addition, because the opening and closing timing of the intake valve 470 is set to the retarded angle, the starting performance of the engine 4 is improved.

[0097] Next, we will explain the case where the phase shift is relatively large (see the dashed line in Figure 5). This corresponds to the case where the time required for preparatory work exceeds the allowable time. The intake S-VT44 performs preparatory work to eliminate the phase shift when the engine 4 is started. As described above, if the intake S-VT44 starts changing the opening and closing timing of the intake valve 470 to the slowest angle at the moment the occupant turns on the start switch at time t4, it will not be possible to set the opening and closing timing of the intake valve 470 to the slowest angle by time t5. This is because the phase shift is large and it takes time to set the phase of the intake S-VT44 to the slowest angle. As mentioned above, the low-voltage battery 11 supplies both the starting power for the DCDC converter 10 and the driving power for the intake S-VT44. If the intake S-VT44 is driven while the DCDC converter 10 is starting up, the voltage drop may delay the starting of the DCDC converter 10.

[0098] Therefore, if the phase difference is relatively large, the intake S-VT44 starts a preparatory operation to eliminate the phase difference before the occupant turns on the start switch 55. Specifically, the intake S-VT44 starts its preparatory operation at time t3 when the door is opened. Even if the phase difference is large, the preparatory operation starts earlier than the start switch 55 is turned on, so the opening and closing timing of the intake valve 470 is set to the slowest angle by time t5 when the DCDC converter 10 starts up. After time t5, the intake S-VT44 operates to maintain the opening and closing timing of the intake valve 470 at the slowest angle.

[0099] Since the preparatory operation of the intake S-VT44 is completed, a delay in the startup of the DCDC converter 10 is avoided after the startup of the DCDC converter 10 begins at time t5. In addition, the engine 4 can be cranked within the starting standard time from the ON operation of the start switch 55.

[0100] By changing the start timing of the intake S-VT44's preparatory operation according to the required preparatory operation time, even when the phase shift is large, the engine 4 can be cranked within the standard starting time from the ON operation of the start switch 55. In addition, since the opening and closing timing of the intake valve 470 is set to the slowest angle, the starting performance of the engine 4 is improved.

[0101] There is a strong correlation between the occupant opening the door and the occupant subsequently turning on the start switch 55. There is a high probability that the engine 4 will start after the intake S-VT 44 has started its preparatory operation at the moment the occupant opens the door. Starting the intake S-VT 44's preparatory operation in advance does not waste power from the low-voltage battery 11.

[0102] On the other hand, if the required preparatory time is short, the intake S-VT44 will not start its preparatory operation when the occupant opens the door. If the intake S-VT44's preparatory operation were to start when the occupant opens the door, the time between the intake S-VT44's phase being set to its slowest angle and the start of engine 4 cranking would be longer. The intake S-VT44 would have to maintain the opening and closing timing of the intake valve 470 for a long time. This would result in wasted power from the low-voltage battery 11. If the required preparatory time is short, starting the intake S-VT44's preparatory operation when the start switch 55 is turned on would prevent delays in starting the engine 4 and suppress unnecessary power consumption.

[0103] Figure 6 shows an example with different engine temperatures for the intake S-VT44. We assume that the phase shift of the intake S-VT44 is the same. Because the phase shift of the intake S-VT44 is the same, the lower the temperature of the engine 4, the longer the preparatory time required, and the higher the temperature of the engine 4, the shorter the preparatory time required.

[0104] Here, Figure 7 shows the relationship between the temperature of the engine 4 (or the coolant temperature) and the response speed of the intake S-VT44. This relationship is pre-stored in the powertrain control device. The lower the temperature of the engine 4, the higher the viscosity of the lubricating oil in the intake S-VT44, and therefore the lower the response speed of the intake S-VT44. When the response speed of the intake S-VT44 decreases, it takes a longer time to eliminate the phase shift of the intake S-VT44. Note that if the temperature of the engine 4 is higher than a predetermined temperature, the viscosity of the lubricating oil becomes substantially constant, so the response speed of the intake S-VT44 may be kept constant.

[0105] The dotted line in Figure 6 is the same as the dotted line in Figure 5. The phase shift of the intake S-VT44 is relatively small, and the response speed of the intake S-VT44 is relatively high. Because the preparatory time required is short, the intake S-VT44 starts its preparatory operation at the moment the occupant turns on the start switch 55 (time t4). The phase of the intake S-VT44 is set to the slowest angle by time t5.

[0106] The dashed line in Figure 6 shows the case where the response speed of the intake S-VT44 is relatively low. Because the preparatory time required is long, the intake S-VT44 starts its preparatory operation at the moment the door opens (time t3). The phase of the intake S-VT44 is set to its slowest angle by time t5.

[0107] Furthermore, if the phase shift of the intake S-VT44 is large and the response speed of the intake S-VT44 is low, the required preparatory operation time will be even longer. Even if the preparatory operation of the intake S-VT44 starts at the same time the door is opened, it may not be possible to set the phase of the intake S-VT44 to the slowest angle in time before the DCDC converter 10 starts up. In this case, as shown in Figure 8, the preparatory operation of the intake S-VT44 may be interrupted after the start of the DCDC converter 10 to prioritize the start of the DCDC converter 10 (see dashed line in Figure 8).

[0108] Specifically, the intake S-VT44 begins its preparatory operation at the moment the door opens (time t3). The phase of the intake S-VT44 is gradually changed to the slowest angle, but at time t5, the phase of the intake S-VT44 has not yet reached the slowest angle.

[0109] Time t5 is the time when the DCDC converter 10 starts up. Power is supplied from the low-voltage battery 11 to the DCDC converter 10, and the DCDC converter 10 starts up. From time t5 to t6, from the start of the DCDC converter 10's startup until it is complete, the intake S-VT44 maintains its phase without changing. This suppresses the power consumption of the intake S-VT44, and thus suppresses the voltage drop of the low-voltage battery 11. The DCDC converter 10 starts up without delay, and the startup of the DCDC converter 10 is completed at time t6.

[0110] After the DCDC converter 10 has finished starting, if the phase of the intake S-VT 44 is out of step with respect to the retarded angle, the intake S-VT 44 resumes changing its phase. As a result, at time t61, the phase of the intake S-VT 44 reaches the retarded angle. The engine 4 starts cranking at time t61. Although the starting time exceeds the reference time due to the intake S-VT 44 interrupting its preparatory operation, the engine 4 quickly completes the starting process.

[0111] Figure 9 is a flowchart of the control performed by the powertrain control unit. This flowchart starts when the occupant opens the door (time t3 in Figures 5, 6, or 8) and ends when engine 4 starts cranking (time t6 in Figures 5 or 6, or time t61 in Figure 8).

[0112] First, in step S11, the PCM21 is started. Then, in step S12, the ECM22 is started, and in step S13, the S-VT drive unit 23 is started. The process from the start of the PCM21 to the start of the S-VT drive unit 23 is controlled by sequence control.

[0113] In step S14, the phase shift amount of the intake S-VT44 is read, and in step S15, the response speed of the intake S-VT44 is set using the relationship between the engine 4 water temperature and Figure 7. In step S16, the time required to set the phase of the intake S-VT44 to the slowest angle, i.e., the preparatory time, is calculated from the phase shift amount and the response speed. The preparatory time is calculated as phase shift amount / response speed.

[0114] Once the required preparatory time is calculated, in step S17, the required preparatory time is compared with the allowable time to determine whether the phase of the intake S-VT44 can be set to the slowest angle within the allowable time. This allowable time is the time from when the occupant turns on the start switch 55 until the DCDC converter 10 starts up, that is, the time from time t4 to t5. If the determination in step S17 is Yes, the process in Figure 9 proceeds to step S22. If the determination in step S17 is No, the process in Figure 9 proceeds to step S18. In step S18, the intake S-VT44 operates to set its phase to the slowest angle. Step S18 corresponds to the intake S-VT44 starting its preparatory operation at the time the door is opened.

[0115] In the following step S19, it is determined whether a predetermined time has elapsed since the intake S-VT44 began its preparatory operation. If the predetermined time has not elapsed, in step S20, it is determined whether the phase of the intake S-VT44 has reached its slowest angle. If the phase of the intake S-VT44 has not reached its slowest angle, the process in Figure 9 returns to step S18, and the intake S-VT44 continues its preparatory operation. In step S20, if the phase of the intake S-VT44 has reached its slowest angle, in step S21, the intake S-VT44 maintains its phase at the slowest angle. In step S19, if the predetermined time has elapsed, the process in Figure 9 proceeds to step S22. Whether the phase of the intake S-VT44 has reached its slowest angle or not, once the predetermined time has elapsed, the preparatory operation of the intake S-VT44 is terminated. This is to suppress the power consumption of the low-voltage battery 11.

[0116] In step S22, the low-voltage battery 11 cuts off power to the intake S-VT44. Then, in step S23, with the occupant pressing the brake pedal 19, the start switch 55 is turned ON (see time t4 in Figures 5, 6, or 8).

[0117] In step S24, it is determined whether the phase of the intake S-VT44 is at its slowest angle. If it is not at its slowest angle, the process in Figure 9 proceeds to step S25, where the intake S-VT44 operates to achieve its slowest phase. Step S25 corresponds to the intake S-VT44 starting its preparatory operation when the start switch 55 is turned ON. If the phase of the intake S-VT44 is at its slowest angle in step S24, the intake S-VT44 maintains its phase in step S26.

[0118] In step S27, it is determined whether the DCDC converter 10 is starting up (see time t5 in Figures 5, 6, or 8). If it is starting up, in step S28, the intake S-VT44 maintains its phase in order to interrupt the preparatory operation of the intake S-VT44. Starting up the DCDC converter 10 takes priority. Note that even if the phase of the intake S-VT44 is at its slowest angle, the intake S-VT44 maintains its phase in step S28. If the DCDC converter 10 is not starting up, the process in Figure 7 proceeds to step S29.

[0119] In step S29, it is determined whether the startup of the DCDC converter 10 is complete (see time t6 in Figure 5, Figure 6, or Figure 8). If startup is not complete, the process in Figure 9 returns to step S24. If startup is complete, in step S30, it is determined whether the phase of the intake S-VT 44 is at its slowest angle. If it is not at its slowest angle, the process in Figure 9 moves to step S31, and the intake S-VT 44 operates to achieve its slowest phase. Once the phase of the intake S-VT 44 is at its slowest angle (see time t5 in Figure 5 or Figure 6, or t61 in Figure 8), the engine 4 starts cranking (see time t6 in Figure 5 or Figure 6, or t61 in Figure 8).

[0120] In step S28, instead of interrupting the preparatory operation of the intake S-VT44 and maintaining the phase of the intake S-VT44, the phase of the intake S-VT44 may be continued to be changed to the slowest angle while reducing the rate of phase change of the intake S-VT44. In other words, the preparatory operation of the intake S-VT44 may be continued. By reducing the rate of phase change, the power consumption of the intake S-VT44 is reduced. Even if the operation of the intake S-VT44 continues, the startup of the DCDC converter 10 will not be delayed.

[0121] The control in the powertrain control device described above is not limited to the control of the intake S-VT44, but can also be applied to the control of the exhaust S-VT45. The opening and closing timing of the exhaust valve when starting the engine 4 is also set to a specific timing that improves the starting performance of the engine 4. Since the opening and closing timing of the exhaust valve when starting the engine 4 may deviate from the specific timing, the start timing of the preparatory operation of the exhaust S-VT45 may be changed depending on the amount of deviation and / or the temperature of the engine 4.

[0122] (modified version) Furthermore, it is not a mandatory requirement in the technology disclosed herein for the intake S-VT44 to set the opening and closing timing of the intake valve 470 to the slowest angle when the engine 4 is stopped.

[0123] Furthermore, in step S15 of the flow in Figure 9, the response speed of the intake S-VT44 may be set according to the engine water temperature, or it may be set according to the engine water temperature and also according to the voltage of the low-voltage battery 11. Figure 10 illustrates the relationship between the voltage of the low-voltage battery 11 and the response speed of the intake S-VT44. When the voltage of the low-voltage battery 11 is low, the response speed of the intake S-VT44 is low, and when the voltage of the low-voltage battery 11 is high, the response speed of the intake S-VT44 is high.

[0124] Furthermore, the intake S-VT44 is not limited to starting its preparatory action when the door is opened; for example, it may start its preparatory action when the occupant sits in the driver's seat. The timing of the occupant sitting in the driver's seat is determined based on the signal from the seat occupancy switch 58. Also, for example, the intake S-VT44 may start its preparatory action when the occupant presses the brake pedal 19. The timing of the occupant pressing the brake pedal 19 is determined based on the signal from the brake switch 56.

[0125] Furthermore, the technology disclosed herein is not limited to application to hybrid vehicles. The technology disclosed herein may also be applied to internal combustion engine vehicles that do not have a motor 5 and a high-voltage battery 9. Figure 11 illustrates a time chart when applied to an internal combustion engine vehicle. In this case, the DCDC converter 10 is not installed in the vehicle 1. The intake S-VT 44 does not need to set its phase to the slowest angle before the DCDC converter 10 starts to start up; it only needs to set its phase to the slowest angle by time t6 when the engine 4 starts cranking. In other words, the period from time t4 to time t6 corresponds to the allowable time. Compared to the time chart in Figure 5, even if the response speed of the intake S-VT 44 is low, the intake S-VT 44 can set the opening and closing timing of the intake valve 470 to the slowest angle within the starting reference time. [Explanation of Symbols]

[0126] 1. Automobile 11 Low-voltage batteries 19 Brake pedal 21 PCM (Controller) 22 ECM (Controller) 23 S-VT drive unit (controller) 4 engines 44. Intake S-VT (Variable Valve Timing System) 45. Exhaust S-VT (Variable Valve Timing System) 470 Intake valve 55 Start switch

Claims

1. A powertrain installed in an automobile, which includes an engine, An electrically operated variable valve timing device for changing the opening and closing timing of the valves of the aforementioned engine, The system includes a controller that sets the opening and closing timing of the valve by outputting a control signal to the variable valve timing device, The opening and closing timing of the valve is set to a specific timing that enhances the starting performance of the engine when the engine starts up in conjunction with the startup of the powertrain. The controller sets the response speed of the variable valve timing device based on parameters relating to the response speed of the variable valve timing device before the engine is started, and calculates the necessary pre-operation time for the variable valve timing device to eliminate the difference between the actual opening and closing timing of the valves before the engine is started and the specific timing, and the response speed. The controller further, If the preparatory operation time is shorter than a preset allowable time, the variable valve timing device is instructed to start changing the valve opening and closing timing when the powertrain start switch is turned on by the occupant, thereby setting the valve opening and closing timing to the specified timing. If the preparatory operation time is greater than or equal to the allowable time, at the timing when a specific action by the occupant is detected before the occupant turns on the start switch, the variable valve timing device is instructed to start changing the opening and closing timing of the valve, and the opening and closing timing of the valve is set to the specific timing. Powertrain control system.

2. In the powertrain control device according to claim 1, When the controller receives a stop request signal for the engine and stops the engine, it pre-sets the opening and closing timing of the valve to the specific timing so that the opening and closing timing of the valve when the engine starts is the specific timing. Powertrain control system.

3. In the powertrain control device according to claim 2, The controller determines the amount of discrepancy between the actual opening and closing timing of the valve and the specific timing between the engine stopping and the engine starting. Powertrain control system.

4. In the powertrain control device according to claim 1, The controller detects the response speed parameters of the variable valve timing device at the timing when a specific action of the occupant is detected, and sets the response speed of the variable valve timing device. Powertrain control system.

5. In the powertrain control device according to claim 4, The variable valve timing device receives power from the battery and changes the opening and closing timing of the valve. The controller, when the required preparatory time calculated at the time the specific action of the occupant is detected is greater than or equal to the allowable time, instructs the variable valve timing device to start changing the opening and closing timing of the valve; however, when the required preparatory time is shorter than the allowable time, the controller does not instruct the variable valve timing device to start changing the opening and closing timing of the valve at the time the specific action of the occupant is detected. Powertrain control system.

6. In the powertrain control device according to claim 5, If the preparatory operation time is shorter than the allowable time, the controller will instruct the variable valve timing device to start changing the opening and closing timing of the valve when the start switch is turned ON. Powertrain control system.

7. In the powertrain control device according to claim 5, The controller, upon detecting a specific action by the occupant, initiates a change in the opening and closing timing of the valve to the variable valve timing device. If the valve opening and closing timing does not reach the specific timing after a predetermined time has elapsed, the controller interrupts the change in the valve opening and closing timing. Powertrain control system.

8. In the powertrain control device according to claim 5, The powertrain is further equipped with a DC-DC converter that starts up by receiving power from the battery, The aforementioned allowable time is the time from when the start switch is turned ON until the DC-DC converter starts up. Powertrain control system.

9. In the powertrain control device according to claim 1, The specific actions of the occupant include opening the driver's side door of the vehicle, sitting in the driver's seat, or pressing the brake pedal. Powertrain control system.

10. In the powertrain control device according to claim 1, The aforementioned specific timing of the valve is the timing at which the intake valve's closing timing has passed the intake bottom dead center, and is the timing at the slowest angle set in the variable valve timing device. Powertrain control system.

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