Vehicle control device and vehicle control method

Abstract

The present disclosure provides a vehicle control device and a vehicle control method. The vehicle control device is configured to intermittently stop the engine according to the vehicle's driving conditions, and if a request is received to restart the engine while the engine is rotating during the intermittent stop, the vehicle control device restarts the engine by self-recovery. The vehicle control device is configured to perform delayed injection control by setting the start time of the first fuel injection during the self-recovery engine restart to a later time than the start time of the second fuel injection.

Description

Technical Field

[0001] The present disclosure relates to a vehicle control device and a vehicle control method for performing intermittent engine stopping. Background Art

[0002] Japanese Patent Application Laid-Open No. 2016-136015 describes that when an engine speed is equal to or higher than a certain value and a request is made to restart the engine from an intermittent stop, the engine is started automatically without assistance from external power. Summary of the Invention

[0003] Problems to be solved by the invention

[0004] If the engine start is delayed when returning from the intermittent stop, the engine speed will decrease until the engine starts, resulting in the inability to start the engine automatically or delaying the re-acceleration of the vehicle after the engine starts.

[0005] Technical solutions to problems

[0006] A vehicle control device according to one embodiment of the present disclosure is configured to intermittently stop an engine based on vehicle driving conditions, and if a request is made to restart the engine while the engine is rotating during the intermittent stop, the device restarts the engine by self-recovery. The device performs delayed injection control by setting the start time of an initial fuel injection during a self-recovery engine restart to a later time than the start time of a second fuel injection.

[0007] A vehicle control method according to one embodiment of the present invention includes the following steps: performing intermittent engine stopping according to the driving condition of the vehicle; restarting the engine based on self-recovery when the engine is rotating during the intermittent stop; and setting the start time of the first fuel injection during the restart of the engine based on self-recovery to a period later than the start time of the second fuel injection. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a diagram schematically showing a configuration of a drive system of a hybrid vehicle equipped with an embodiment of a vehicle control device.

[0009] Figure 2 It schematically shows the Figure 1 A diagram of a structure of a vehicle control device of a hybrid vehicle.

[0010] Figure 3 yes Figure 2A flowchart of fuel injection control performed by a vehicle control device during COM recovery. DETAILED DESCRIPTION

[0011] Below, refer to Figures 1 to 3 An embodiment of a vehicle control device will be described in detail.

[0012] <Structure of a hybrid vehicle's drive system>

[0013] Reference Figure 1 The structure of the drive system of the hybrid vehicle controlled by the vehicle control device of this embodiment will be described. The hybrid vehicle includes a hybrid system 10 as a power source. The hybrid system 10 includes an engine 11, a generator motor 12, and a system clutch 15. Figure 2 As shown, each cylinder of the engine 11 is provided with two fuel injection valves: a port injection valve 40A that injects fuel into the intake port, and an in-cylinder injection valve 40B that injects fuel into the cylinder. The hybrid system 10 is configured to extract power from the rotating shaft of the generator motor 12. A system clutch 15 is provided between the crankshaft 13, which serves as the output shaft of the engine 11, and the system output shaft 14. The system clutch 15 disconnects and connects the crankshaft 13 and the system output shaft 14. The hybrid system 10 includes an inverter 16 and a battery 17. The inverter 16 controls the amount of power transferred between the generator motor 12 and the battery 17.

[0014] The hybrid vehicle is equipped with a transmission 20. The transmission 20 includes a torque converter 21 and a variator 22. The system output shaft 14 of the hybrid system 10 is connected to a transmission input shaft 23, which serves as the input shaft of the variator 22, via the torque converter 21. The variator 22 changes the speed of the rotation of the transmission input shaft 23 and transmits it to the wheels of the hybrid vehicle. The transmission 20 is equipped with a lockup clutch 24 that can directly connect the system output shaft 14 and the transmission input shaft 23 without intervening through the torque converter 21.

[0015] <Structure of vehicle control device>

[0016] Next, refer to Figure 2 The configuration of the vehicle control device of this embodiment will be described. The vehicle control device includes an electronic control unit 30. The electronic control unit 30 includes a processing unit 31 that executes various processes for vehicle control and a storage unit 32 that stores control programs and data.

[0017] Detection signals from various sensors installed in various parts of the hybrid vehicle are input to the electronic control unit 30. These sensors include an air flow meter 33, a water temperature sensor 34, an intake pressure sensor 35, a crank angle sensor 36, an accelerator pedal sensor 37, and a vehicle speed sensor 38. The air flow meter 33 detects the intake air flow rate GA of the engine 11. The water temperature sensor 34 detects the cooling water temperature THW of the engine 11. The intake pressure sensor 35 detects the intake pressure PM of the engine 11. The crank angle sensor 36 detects the crank angle CRNK, which is the rotational phase of the crankshaft 13 of the engine 11. The accelerator pedal sensor 37 detects the accelerator pedal operation amount ACC, which is the driver's operation amount of the hybrid vehicle's accelerator pedal. The vehicle speed sensor 38 detects the vehicle speed V of the hybrid vehicle. The electronic control unit 30 calculates the engine speed NE, which is the rotational speed of the crankshaft 13 of the engine 11, based on the detection results of the crank angle sensor 36.

[0018] The electronic control unit 30 controls the hybrid system 10 based on the detection results of these sensors. For example, the electronic control unit 30 controls the operating state of the engine 11 by operating actuators provided on the engine 11, such as the throttle valve 39, the port injection valve 40A, the in-cylinder injection valve 40B, and the ignition device 41. The electronic control unit 30 controls the torque of the generator motor 12 by controlling the inverter 16. The electronic control unit 30 also controls the system clutch 15. In the following description, the opening of the throttle valve 39 is referred to as the throttle valve opening TA.

[0019] The electronic control unit 30 intermittently stops the engine 11 based on the hybrid vehicle's driving conditions. For example, the electronic control unit 30 intermittently stops the engine 11 when the hybrid vehicle is decelerating or stopping. During this intermittent stop of the engine 11, the electronic control unit 30 disconnects the system clutch 15, disconnecting the engine 11 from the drive system. Furthermore, intermittent stopping refers to the cessation of combustion in the engine 11 due to the cessation of fuel injection and ignition, and does not mean that the engine 11 stops rotating. For a certain period of time after the intermittent stop, the engine 11 can rotate due to inertia.

[0020] If the accelerator pedal is depressed during intermittent stopping, the electronic control unit 30 restarts the engine 11. During this restart, if the engine 11 is stopped or the engine speed (NE) is low, the electronic control unit 30 engages the system clutch 15 to increase the engine speed (NE) using the torque of the generator motor 12, and then restarts the engine 11. On the other hand, if the engine speed (NE) is high, the electronic control unit 30 disengages the system clutch 15 and restarts the engine 11 under its own power, without the use of external power. In the following description, this restart of the engine 11 under its own power, independent of external power, is referred to as self-recovery.

[0021] After an intermittent stop, the engine 11 stops rotating after a certain period of time, making it impossible to recover automatically. Therefore, if the driver presses the accelerator pedal after the electronic control unit 30 initiates intermittent stopping in response to the hybrid vehicle's deceleration and requests a restart of the engine 11, the engine 11 is automatically restarted during the intermittent stop. In the following description, this automatic recovery of the engine 11 in response to the driver's accelerator operation is referred to as COM (Change of Mind) recovery.

[0022] exist Figure 1 In a hybrid vehicle, a fuel cut is sometimes implemented during deceleration to stop the fuel injection of the engine 11 while the system clutch 15 is connected. Such a fuel cut is performed, for example, to send fresh air to a PM (particulate matter) collection filter provided in the exhaust passage of the engine 11 to purify the PM accumulated on the filter. During the fuel cut process, the electronic control unit 30 interrupts the fuel cut and restarts the engine 11 when the engine speed NE becomes lower than a predetermined recovery speed or the vehicle speed V becomes lower than a predetermined recovery speed. The restart of the engine 11 at this time is performed in a state where the rotation is assisted by the torque transmitted from the wheels through the system clutch 15. Therefore, the restart of the engine 11 during fuel cut recovery does not fall under the self-recovery that does not rely on external power as defined in this article.

[0023] <Fuel injection control during COM recovery>

[0024] Reference Figure 3 , the fuel injection control of the engine 11 when COM is restored will be described. Figure 3 This is a flowchart of the fuel injection control during COM recovery executed by the electronic control unit 30. The electronic control unit 30 controls the fuel injection control during the period from when COM recovery is requested until the combustion of the engine 11 transitions to a stable complete combustion state. Figure 3 The fuel injection amount of the engine 11 and the start timing of the fuel injection are determined by the processing.

[0025] When to start Figure 3 When processing the command, the electronic control unit 30 first determines in step S100 whether the engine speed NE is rapidly decreasing based on the engine speed NE and its change ΔNE. If it determines that the engine speed NE is rapidly decreasing (S110: YES), the electronic control unit 30 advances the process to step S120. Then, in step S120, the electronic control unit 30 calculates the command fuel injection quantity Q, the amount of fuel required to bring the air-fuel ratio of the mixture combusted in the cylinder to the output air-fuel ratio, based on the engine load factor KL and the cooling water temperature THW. The engine load factor KL represents the filling rate of the intake air in the cylinders of the engine 11.

[0026] On the other hand, if the electronic control unit 30 determines that the engine speed NE is not rapidly decreasing (S110: NO), the process proceeds to step S130. In step S130, the electronic control unit 30 calculates the amount of fuel required to bring the air-fuel ratio of the mixture combusted in the cylinder to the stoichiometric air-fuel ratio, as the command injection quantity Q, based on the engine load factor KL and the cooling water temperature THW. The output air-fuel ratio is richer than the stoichiometric air-fuel ratio. Therefore, when the engine speed NE is rapidly decreasing, that is, when the degree of decrease in the engine speed NE is large, the fuel injection quantity of the engine 11 increases compared to when the degree of decrease is small.

[0027] After calculating the command injection quantity Q in step S120 or step S130, the electronic control unit 30 proceeds to step S140. In step S140, the electronic control unit 30 determines whether the fuel injection at the command injection quantity Q calculated in step S120 or step S130 is the first fuel injection during this COM recovery. If the fuel injection at the command injection quantity Q is the first fuel injection during this COM recovery (S140: Yes), in step S150, the electronic control unit 30 instructs the in-cylinder injection valve 40B to perform delayed injection. In this case, the electronic control unit 30 sets the fuel injection start timing to the latest time at which combustion can be established if the in-cylinder injection valve 40B injects fuel at the command injection quantity Q. In this case, the fuel injection start timing is set to a certain time during the compression stroke. On the other hand, if the fuel injection at the calculated command injection quantity Q is the second or subsequent fuel injection during this COM recovery (S140: No), in step S160, the electronic control unit 30 instructs the port injection valve 40A to perform normal injection. At this time, the electronic control unit 30 sets the time when the fuel of the command injection amount Q can be injected through the port injection valve 40A as the start time of fuel injection. In this case, the start time of fuel injection is set to a certain time during the intake stroke. The electronic control unit 30 sets the start time of fuel injection set at this time as a time suitable for starting the engine 11. Then, after the fuel injection is instructed in step S150 or step S160, the electronic control unit 30 ends the process. Figure 3 processing.

[0028] In this embodiment, by Figure 3 The recovery torque control is performed by processing steps S100 to S130. Figure 3 The delayed injection control is performed by processing in steps S140 to S160.

[0029] <Effects of the Implementation Method>

[0030] The operation and effects of this embodiment will be described.

[0031] If there is time left before the engine 11 starts starting after the request for COM recovery, the engine speed NE decreases until the engine 11 starts starting, making it difficult for the engine 11 to recover automatically. In addition, due to such a decrease in engine speed NE, the acceleration of the hybrid vehicle after COM recovery may be delayed.

[0032] In contrast, the electronic control unit 30 of the vehicle control device according to this embodiment performs delayed injection control, setting the start timing of the first fuel injection during COM recovery to a later time than the start timing of the second and subsequent fuel injections. Specifically, the electronic control unit 30 performs the first fuel injection via delayed injection from the in-cylinder injection valve 40B, starting fuel injection at a certain time during the compression stroke. Meanwhile, the electronic control unit 30 performs the second and subsequent fuel injections via normal injection from the port injection valve 40A, starting fuel injection at a certain time during the intake stroke. When the first fuel injection during COM recovery is performed via normal injection from the port injection valve 40A, the cylinder that first enters the intake stroke after the engine 11 is requested to restart is the cylinder that is the first to enter the compression stroke after the engine 11 is requested to restart. On the other hand, when the first fuel injection during COM recovery is performed via delayed injection from the in-cylinder injection valve 40B, the cylinder that first enters the compression stroke after the engine 11 is requested to restart is the cylinder that is the first to enter the compression stroke after the engine 11 is requested to restart. Therefore, if the initial fuel injection during COM recovery is performed by delayed injection from in-cylinder injection valve 40B, combustion in engine 11 can be started earlier than when fuel injection is performed by normal injection from port injection valve 40A. As a result, the timing of engine torque generation is shortened, thereby suppressing a decrease in engine speed NE during COM recovery.

[0033] Furthermore, if the degree of decrease in engine speed NE during self-recovery is not significant, the electronic control unit 30 calculates the amount of fuel that will achieve the stoichiometric air-fuel ratio as the value of the command injection quantity Q. On the other hand, if the degree of decrease in engine speed NE during self-recovery is significant, the electronic control unit 30 calculates the amount of fuel that will achieve the output air-fuel ratio as the value of the command injection quantity Q. In this way, the electronic control unit 30 performs recovery torque control such that, when the degree of decrease in engine speed NE during restart of the engine 11 is significant, the fuel injection quantity of the engine 11 is increased compared to when the degree of decrease is smaller. This allows the engine torque to be increased during startup when the degree of decrease in engine speed NE is significant, thereby suppressing the decrease in engine speed NE.

[0034] According to the vehicle control device of the present embodiment described above, the following effects can be achieved.

[0035] (1) The electronic control unit 30 performs delayed injection control by setting the start time of the first fuel injection upon COM recovery to a later time than the start time of the second and subsequent fuel injections. This allows the start of combustion in the engine 11, i.e., the generation of engine torque, to be advanced upon COM recovery. This prevents the engine 11 from becoming difficult to start automatically due to a decrease in engine speed NE after a COM recovery request. Furthermore, the hybrid vehicle's acceleration after the engine 11 restarts is less likely to be delayed.

[0036] (2) The electronic control unit 30 performs the initial fuel injection when COM is restored through the in-cylinder injection valve 40B, and performs the second and subsequent fuel injections through the port injection valve 40A. After the intake stroke is completed, fuel injection can also be performed from the in-cylinder injection valve 40B. Therefore, when fuel injection is performed through the in-cylinder injection valve 40B, the start time of fuel injection can be delayed compared to the case of using the port injection valve 40A. On the other hand, under the conditions when COM is restored, it is easier to stabilize combustion when fuel injection is performed through the port injection valve 40A than when fuel injection is performed through the in-cylinder injection valve 40B. Therefore, it is preferable to perform the initial fuel injection through the in-cylinder injection valve 40B and perform the second and subsequent fuel injections through the port injection valve 40A.

[0037] (3) The electronic control unit 30 performs the following recovery torque control: when the engine speed NE decreases significantly during COM recovery, the fuel injection amount of the engine 11 is increased compared to when the decrease is small. This can suppress a sharp drop in the engine speed NE during COM recovery.

[0038] (4) When the degree of decrease in engine speed NE is small, the electronic control unit 30 sets the fuel injection amount for achieving an air-fuel ratio suitable for improving emissions, i.e., the stoichiometric air-fuel ratio, as the fuel injection amount for COM recovery. On the other hand, when the degree of decrease in engine speed NE is large, the electronic control unit 30 sets the fuel injection amount for achieving an air-fuel ratio that produces a large engine torque, i.e., the output air-fuel ratio, as the fuel injection amount for COM recovery. Therefore, when the engine speed NE is rapidly decreasing during COM recovery, the engine torque can be increased to suppress the decrease in engine speed NE. When the engine speed NE does not rapidly decrease, the emissions of the engine 11 can be improved.

[0039] This embodiment can be implemented with the following modifications: This embodiment and the following modifications can be implemented in combination with each other within the scope of no technical contradiction.

[0040] If the self-recovery of the engine 11 is performed in addition to the COM recovery by the driver's accelerator operation, the electronic control unit 30 may perform the delayed injection control and the recovery torque control during the self-recovery in addition to the COM recovery.

[0041] In the recovery torque control in the above embodiment, the electronic control unit 30 calculates the command injection amount Q based on the engine load factor KL and the cooling water temperature THW, but the command injection amount Q may be calculated in another manner.

[0042] In the above-described embodiment, during the recovery torque control, the electronic control unit 30 sets the fuel injection amount to the amount of fuel that achieves the output air-fuel ratio when the degree of decrease in engine speed NE is large, and sets the fuel injection amount to the amount of fuel that achieves the stoichiometric air-fuel ratio when the degree of decrease is small. However, the electronic control unit 30 may also implement the recovery torque control by setting the fuel injection amount to an amount of fuel other than the above-described amount, provided that a larger fuel injection amount is set when the degree of decrease in engine speed NE is large than when the degree of decrease is small.

[0043] The electronic control unit 30 may perform only the delayed injection control instead of the recovery torque control.

[0044] In the delayed injection control of the above-described embodiment, the electronic control unit 30 performs the initial fuel injection upon COM recovery through the in-cylinder injection valve 40B. Alternatively, the electronic control unit 30 may perform the initial fuel injection through the port injection valve 40A, as long as the start of fuel injection is set later than the second and subsequent fuel injections upon COM recovery. Alternatively, the electronic control unit 30 may perform the second and subsequent fuel injections through the in-cylinder injection valve 40B, as long as the start of fuel injection is set earlier than the initial fuel injection upon COM recovery. In these cases, the vehicle control device of the above-described embodiment is also applicable to vehicles equipped with an engine 11 equipped only with the port injection valve 40A or the in-cylinder injection valve 40B.

[0045] The vehicle control device of the above embodiment can also be applied to a vehicle having Figure 1 In other words, any vehicle may be configured to intermittently stop the engine according to the vehicle's driving conditions, and to restart the engine by self-recovery when a request is made to restart the engine while the engine is rotating during the intermittent stop.

[0046] The electronic control unit 30 is not limited to executing various processes according to a program. For example, the electronic control unit 30 may include a dedicated hardware circuit (e.g., an ASIC) that executes at least a portion of the processes executed in the above-described embodiments. In other words, the electronic control unit 30 only needs to include a processing circuit having any of the following configurations (a) to (c).

[0047] (a) A processing circuit including all processing devices that execute the above-mentioned processing according to a program and a program storage device such as a ROM that stores the program.

[0048] (b) A processing circuit including a processing device and a program storage device for executing part of the above-mentioned processing according to a program, and a dedicated hardware circuit for executing the remaining processing.

[0049] (c) A processing circuit including dedicated hardware circuits for executing all of the above-mentioned processes.

[0050] Here, there may be a plurality of software execution devices or dedicated hardware circuits including a processing device and a program storage device.

Claims

1. A vehicle control device configured to intermittently stop an engine according to a vehicle's driving condition, and to restart the engine by self-recovery when a request is made to restart the engine while the engine is rotating during the intermittent stop, wherein: Each cylinder of the engine is provided with two fuel injection valves, an in-cylinder injection valve and a port injection valve. The vehicle control device is configured to perform delayed injection control by setting a start timing of a first fuel injection when the engine is restarted based on the self-recovery to a time later than a start timing of a second fuel injection; The vehicle control device is configured such that, in the delayed injection control, the initial fuel injection is implemented through the in-cylinder injection valve, the second fuel injection is implemented through the port injection valve, and the start timing of the second fuel injection is set to a certain period in the intake stroke, and the start timing of the initial fuel injection is set to a certain period in the compression stroke.

2. A vehicle control method comprising the following steps: Perform intermittent engine stops according to vehicle driving conditions; When a restart of the engine is requested while the engine is rotating during the intermittent stop, restarting the engine by self-recovery; and Delayed injection control sets the start timing of the first fuel injection at the time of restarting the engine based on the self-recovery to a time later than the start timing of the second fuel injection, Each cylinder of the engine is provided with two fuel injection valves, an in-cylinder injection valve and a port injection valve. In the vehicle control method, in the delayed injection control, the initial fuel injection is implemented through the in-cylinder injection valve, and the second fuel injection is implemented through the port injection valve, and the start timing of the second fuel injection is set to a certain period in the intake stroke, and the start timing of the initial fuel injection is set to a certain period in the compression stroke that is later than the start timing of the second fuel injection.

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