Electric vehicles

Abstract

To provide an electric vehicle capable of suppressing deterioration of electricity efficiency. [Solution] An electric vehicle includes an internal combustion engine (10), a first motor-generator (310), and a control device (100). A processing circuit (110) of the control device (100) performs scavenging operation by rotating the internal combustion engine (10) with the first motor-generator (310) after its autonomous operation has been stopped. When an execution condition for the scavenging operation is met, the processing circuit (110) acquires the engine rotation speed at that time as a first rotation speed and sets a second rotation speed as a target value for the engine rotation speed during the scavenging operation. After the autonomous operation of the internal combustion engine (10) is stopped based on the execution condition for the scavenging operation being met, the processing circuit (110) controls the first motor-generator (310) to reduce the engine rotation speed to the second rotation speed while maintaining the engine rotation speed at a value between the first rotation speed and the second rotation speed. The processing circuit (110) starts scavenging operation based on the engine rotation speed being reduced to the second rotation speed through control of the first motor-generator (310).

Description

[Technical Field]

[0001] The present disclosure relates to electric vehicles. [Background technology]

[0002] The electric vehicle of Patent Document 1 includes an internal combustion engine, a motor, and a control unit. The internal combustion engine is capable of stopping autonomous operation. The motor is capable of rotating the internal combustion engine when autonomous operation has stopped. The control unit controls the internal combustion engine and the motor. After the autonomous operation of the internal combustion engine has been stopped, the control unit performs scavenging operation to rotate the internal combustion engine using the motor.

[0003] If the engine rotation is stopped immediately after the internal combustion engine's self-sustaining operation is stopped during a cold start, moisture remaining in the combustion chamber of the internal combustion engine may adhere to the spark plug, which may deteriorate the startability the next time the engine is started. However, by performing the scavenging operation after the self-sustaining operation of the internal combustion engine is stopped as described above, the moisture remaining in the combustion chamber of the internal combustion engine is discharged, thereby suppressing deterioration in the startability the next time the engine is started. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-39347 Summary of the Invention [Problem to be solved by the invention]

[0005] After the autonomous operation of the internal combustion engine is stopped and before the scavenging operation is started, the engine speed is controlled by the motor so as to change from the value at the time of stopping the autonomous operation to the target value for the scavenging operation. Then, the scavenging operation is started when the engine speed after the autonomous operation of the internal combustion engine is stopped has decreased to the target value.

[0006] However, when the engine speed is controlled by the motor to the target value during scavenging operation after the internal combustion engine has stopped operating autonomously, the engine speed does not necessarily reach the target value by simply decreasing.

[0007] For example, depending on the driving conditions of the motor before the autonomous operation of the internal combustion engine is stopped, the motor may control the engine speed after the autonomous operation is stopped so that it is higher than the value at the time of the autonomous operation stop. In this case, the motor's power consumption increases until the engine speed after the autonomous operation is stopped is controlled to the target value for scavenging operation by the amount of control to increase the engine speed as described above. As a result, the electricity consumption of the electric vehicle deteriorates. [Means for solving the problem]

[0008] The means for solving the above problems and their effects will be described below. An electric vehicle that solves the above problem includes an internal combustion engine capable of stopping autonomous operation, a motor capable of rotating the internal combustion engine when autonomous operation has stopped, and a control unit that controls the internal combustion engine and the motor. After autonomous operation of the internal combustion engine is stopped, the control unit performs scavenging operation by rotating the internal combustion engine with the motor. When an execution condition for scavenging operation is met, the control unit acquires the engine rotation speed at that time as a first rotation speed and sets a second rotation speed as a target value for the engine rotation speed during scavenging operation. After autonomous operation of the internal combustion engine is stopped based on the execution condition for scavenging operation being met, the control unit controls the motor to reduce the engine rotation speed of the internal combustion engine rotated by the motor to a value between the first rotation speed and the second rotation speed and to the second rotation speed. The control unit starts the scavenging operation based on the engine rotation speed being reduced to the second rotation speed through control of the motor.

[0009] According to the above configuration, after the autonomous operation of the internal combustion engine is stopped based on the satisfaction of the execution condition for scavenging operation, the motor is controlled to reduce the engine speed to the second rotational speed while maintaining the engine speed at a value between the first rotational speed and the second rotational speed. Then, based on the engine speed being reduced to the second rotational speed, scavenging operation is started. As a result, after the autonomous operation is stopped, the motor is no longer controlled to increase the engine speed to a value higher than the value at the time of the autonomous operation stop, i.e., the first rotational speed, so that an increase in the power consumption of the motor at such a time can be suppressed. As a result, a deterioration in the electric fuel efficiency of the electric vehicle due to an increase in the power consumption of the motor can be suppressed. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram showing the overall configuration of a hybrid vehicle. [Figure 2] 2 is a diagram showing an HV driving range and an EV driving range in the hybrid vehicle of FIG. 1. FIG. [Figure 3] 3 is a flowchart showing a procedure for performing a scavenging operation of the internal combustion engine mounted on the hybrid vehicle of FIG. 1. [Figure 4] 5 is a time chart showing the transition of the engine rotation speed over time after the execution condition of the scavenging operation is satisfied. [Figure 5] 5 is a time chart showing the transition of the engine rotation speed over time after the execution condition of the scavenging operation is satisfied. [Figure 6] 5 is a time chart showing the transition of the engine rotation speed over time after the execution condition of the scavenging operation is satisfied. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of an electric vehicle will be described below with reference to FIGS. 1, a hybrid vehicle 500, which is an electrically powered vehicle, is equipped with an internal combustion engine 10 that uses hydrogen as fuel, and electric motors, a first motor generator 310 and a second motor generator 320. Furthermore, the hybrid vehicle 500 is equipped with a control device 100 that functions as a control unit that controls the internal combustion engine 10, the first motor generator 310, and the second motor generator 320.

[0012] The crankshaft 18 of the internal combustion engine 10 is mechanically connected to a carrier C of a planetary gear mechanism 350 that constitutes a power split device. A rotating shaft 310a of the first motor generator 310 is mechanically connected to a sun gear S of the planetary gear mechanism 350. A rotating shaft 320a of the second motor generator 320 and drive wheels 360 are mechanically connected to a ring gear R of the planetary gear mechanism 350.

[0013] The first motor generator 310 functions as a generator that generates electricity using engine output, and also functions as a starting starter that cranks the crankshaft 18 when starting the internal combustion engine 10. The first motor generator 310 is an electric motor that applies torque to the crankshaft 18 to motor the internal combustion engine 10.

[0014] Second motor generator 320 functions as an electric motor that generates driving force for drive wheels 360, and also functions as a generator that generates electricity by regeneration when hybrid vehicle 500 is decelerating.

[0015] The first motor generator 310 and the second motor generator 320 exchange electric power with the battery 250 via the PCU (Power Control Unit) 200. The battery 250 is charged using the output of the internal combustion engine 10 and supplies electric power to the first motor generator 310 and the second motor generator 320.

[0016] PCU 200 includes a converter that boosts and outputs a DC voltage input from battery 250, and an inverter that converts the DC voltage boosted by the converter into an AC voltage and outputs it to first motor generator 310 and second motor generator 320. PCU 200 is also connected to an external power supply terminal 300 that supplies power from battery 250 to equipment outside the vehicle. Examples of external power supply include power supply to power supply equipment installed in a home, a store, or the like.

[0017] <Details of the control device 100> The control device 100 controls the output and exhaust properties of the internal combustion engine 10 by controlling the intake air amount, fuel injection amount, and ignition timing. The control device 100 also operates an inverter via the PCU 200 to control the torque of the first motor generator 310. The control device 100 also operates an inverter via the PCU 200 to control the torque of the second motor generator 320. The control device 100 includes a processing circuit 110. The processing circuit 110 includes a CPU that executes various processes according to programs, and a ROM in which various programs are stored.

[0018] The control device 100 refers to detection values ​​of various sensors. For example, the control device 100 refers to a detection value of an air flow meter 51 that detects the intake air amount GA of the internal combustion engine 10. The control device 100 refers to a detection signal Scr of a crank angle sensor 52 that detects the rotation angle of the crankshaft 18. The control device 100 refers to a detection value of a water temperature sensor 53 that detects a coolant temperature THW that is the temperature of the coolant of the internal combustion engine 10. The control device 100 refers to a detection value of an intake air temperature sensor 54 that detects an intake air temperature THA that is the temperature of the intake air of the internal combustion engine 10. The control device 100 refers to a detection signal of an accelerator position sensor 55 that detects an accelerator operation amount ACCP that is an operation amount of an accelerator pedal operated by the driver of the hybrid vehicle 500. The control device 100 refers to a detection signal of a speed sensor 56 that detects a vehicle speed SP of the hybrid vehicle 500. The control device 100 refers to a charging rate SOC of the battery 250 calculated by the PCU 200.

[0019] The control device 100 calculates the engine speed NE based on the detection signal Scr from the crank angle sensor 52. The control device 100 also calculates the engine load factor KL based on the engine speed NE and the intake air amount GA. The engine load factor KL represents the ratio of the current cylinder inflow air amount to the cylinder inflow air amount when the internal combustion engine 10 is steadily operated at the current engine speed NE under full load. The cylinder inflow air amount is the amount of air that flows into each cylinder during the intake stroke.

[0020] The control device 100 calculates the required driving torque Tr required for running the hybrid vehicle 500 based on the accelerator operation amount ACCP and the vehicle speed SP. Then, the control device 100 controls the torque of the internal combustion engine 10 and the torques of the first motor generator 310 and the second motor generator 320 so as to satisfy the required driving torque Tr.

[0021] As shown in Fig. 2, in an operating region where the operating point indicated by the required drive torque Tr and vehicle speed SP is equal to or greater than the boundary line indicated by solid line L1, HV running is performed, in which the vehicle runs using the torque of the internal combustion engine 10, the torque of the first motor generator 310, and the torque of the second motor generator 320. On the other hand, in an operating region where the operating point indicated by the required drive torque Tr and vehicle speed SP is less than the boundary line indicated by solid line L1, running is performed using only the motor. In other words, EV running is performed, in which the vehicle runs using only the torque of the second motor generator 320. During this EV running, combustion in the internal combustion engine 10 is stopped, thereby stopping the autonomous operation of the internal combustion engine 10.

[0022] <Scavenging operation> If the internal combustion engine 10 is stopped from self-sustaining operation immediately after it is stopped when cold, moisture remaining in the combustion chamber of the internal combustion engine 10 may adhere to the spark plug, which may deteriorate the startability the next time the engine is started. In particular, in an internal combustion engine 10 that uses hydrogen as fuel, moisture derived from the fuel is more likely to be generated in the combustion chamber than in an engine that uses gasoline or other fuel, and therefore the deterioration in startability described above becomes more pronounced.

[0023] To address this issue, the control device 100 performs a scavenging operation to remove moisture from the combustion chamber after stopping the self-sustaining operation of the internal combustion engine 10. This scavenging operation is an operation that performs so-called motoring, in which the internal combustion engine 10 is rotated with fuel injection stopped. The motoring of the internal combustion engine 10 is performed by driving the first motor generator 310 that receives power supply from the battery 250.

[0024] Fig. 3 is a flowchart showing the procedure for executing the scavenging operation. In step 101 (S101) of the series of processes shown in Fig. 3, the processing circuit 110 of the control device 100 determines whether or not the conditions for executing the scavenging operation are met. Whether or not the conditions for executing the scavenging operation are met is determined based on whether or not all of the following conditions (A1) to (A3) are met, for example.

[0025] (A1) The autonomous operation of the internal combustion engine 10 can be stopped, for example, the accelerator operation amount ACCP is "0" and the vehicle speed SP is equal to or less than a predetermined value. The predetermined value here may be, for example, "0." Alternatively, the predetermined value may be a value greater than "0."

[0026] (A2) The air conditioning device of the hybrid vehicle 500 is not operating, in other words, there is no request to drive the internal combustion engine 10 in order to operate the air conditioning device. (A3) There is no request to prohibit scavenging operation. A request to prohibit scavenging operation is made, for example, when there is a possibility of starting the hybrid vehicle 500. Note that it is considered that the determination that there is a possibility of starting the hybrid vehicle 500 is made based on, for example, the current position of the hybrid vehicle 500 on a map and the display state of a traffic light ahead determined using a camera or the like.

[0027] If it is determined in S101 that the conditions for performing scavenging operation are not met, the processing circuit 110 ends this series of processes. On the other hand, if it is determined in S101 that the conditions for performing scavenging operation are met, the processing circuit 110 proceeds to S102. After acquiring the current engine rotation speed NE as the processing of S102, the processing circuit 110 sets the rotation speed NE as a first rotation speed NE1 to be used in subsequent processing. In the subsequent processing of S103, the processing circuit 110 stops fuel injection of the internal combustion engine 10, thereby stopping the self-sustaining operation of the internal combustion engine 10. Thereafter, the processing circuit 110 proceeds to S104.

[0028] In the process of S104, the processing circuit 110 determines whether or not there is a possibility of starting the internal combustion engine 10. Here, the determination that there is a possibility of starting the internal combustion engine 10 is made when, for example, at least one of the following conditions (B1) to (B3) is satisfied.

[0029] (B1) The air conditioning system of the hybrid vehicle 500 starts operating. (B2) The state of charge (SOC) of the battery 250 falls below a threshold. (B3) Hybrid vehicle 500 starts moving.

[0030] If it is determined in S104 that the internal combustion engine 10 is not startable, the process proceeds to S105. In S105, the processing circuit 110 sets a second rotation speed NE2, which is a target value of the engine rotation speed during scavenging operation. Specifically, based on the amount of moisture in the combustion chamber of the internal combustion engine 10, the engine rotation speed that can scavenge the moisture in the shortest time is determined by referring to a map or the like. The moisture amount can be calculated based on physical quantities and model equations that correlate with the moisture amount in the combustion chamber. Examples of physical quantities that correlate with the moisture amount in the combustion chamber include the engine rotation speed NE, the coolant temperature THW, the intake air temperature THA, the air-fuel ratio of the mixture, the combustion temperature of the mixture, the fuel injection amount, the fuel temperature, and the wall temperature of the intake manifold. The moisture amount may be detected using a sensor. The determined engine rotation speed is set as the second rotation speed NE2. Then, the process proceeds to S107. On the other hand, if it is determined in S104 that the internal combustion engine 10 is startable, the process proceeds to S106. In the process of S106, the processing circuit 110 sets the second rotation speed NE2 to an engine rotation speed suitable for starting the internal combustion engine 10. Then, the process proceeds to S107.

[0031] In the process of S107, the processing circuit 110 controls the first motor generator 310 so that the engine speed NE decreases from the first rotation speed NE1 toward the second rotation speed NE2. More specifically, the processing circuit 110 controls the first motor generator 310 so that the engine speed NE of the internal combustion engine 10 rotated by the first motor generator 310 is set to a value between the first rotation speed NE1 and the second rotation speed NE2, and decreases to the second rotation speed NE2. At this time, it is preferable to control the first motor generator 310 so that the engine speed NE does not increase, and it is more preferable to control the first motor generator 310 so that the engine speed NE decreases at a constant rate of change. Then, the process proceeds to S108.

[0032] In the process of S108, the processing circuit 110 determines whether there is a request to stop the scavenging operation. The request to stop the scavenging operation here is made, for example, when the internal combustion engine 10 needs to operate independently in order to satisfy the required drive torque Tr. If it is determined in S108 that there is no request to stop the scavenging operation, the process proceeds to S109. In the process of S109, the processing circuit 110 starts the scavenging operation when the engine rotation speed NE drops to the second rotation speed NE2. This scavenging operation is continued, for example, until an operation time determined according to the calculated amount of moisture in the combustion chamber has elapsed. Thereafter, the processing circuit 110 ends this series of processes.

[0033] On the other hand, if it is determined in S108 that there is a request to stop the scavenging operation, the process proceeds to S110. As the process of S110, the processing circuit 110 stops the scavenging operation of the internal combustion engine 10, and then ends this series of processes. At this time, the processing circuit 110 starts the internal combustion engine 10. As a result, the internal combustion engine 10 starts self-sustaining operation.

[0034] Next, the effects of the electric vehicle of this embodiment, that is, the hybrid vehicle 500, will be described. (1) When a condition for performing scavenging operation is satisfied during the autonomous operation of the internal combustion engine 10, the autonomous operation of the internal combustion engine 10 is stopped, for example, at timing T1 in FIG. 4 . Thereafter, the first motor-generator 310 is controlled so that the engine speed NE is maintained at a value between the first rotational speed NE1 and the second rotational speed NE2, as shown by the solid line in FIG. 4 , and is decreased to the second rotational speed NE2. Then, the scavenging operation is started based on the engine speed NE decreasing to the second rotational speed NE2 at timing T2 in FIG. 4 . As a result, after the autonomous operation of the internal combustion engine 10 is stopped, the first motor-generator 310 no longer controls the engine speed NE to increase above the value at the time of the autonomous operation stop, i.e., the first rotational speed NE1, as shown by the dashed line in FIG. 4 . Therefore, an increase in the power consumption of the first motor-generator 310 can be suppressed. As a result, a deterioration in the electricity consumption of the hybrid vehicle 500 due to an increase in the power consumption of the first motor-generator 310 can be suppressed.

[0035] (2) After the autonomous operation of the internal combustion engine 10 is stopped based on the satisfaction of the condition for performing the scavenging operation, it is possible to reduce the engine speed NE to the second speed NE2 through control of the first motor generator 310 while preventing an increase in the engine speed NE. In this case, when the engine speed NE is reduced from the first speed NE1 to the second speed NE2, the first motor generator 310 does not increase the engine speed NE as shown by the dashed line in FIG. 5 . As a result, an increase in the power consumption of the first motor generator 310 due to the driving of the first motor generator 310 can be suppressed. Therefore, a deterioration in the power consumption of the hybrid vehicle 500 caused by an increase in the power consumption of the first motor generator 310 can be effectively suppressed.

[0036] (3) As described above, when the engine speed NE is reduced from the first rotational speed NE1 to the second rotational speed NE2 through control of the first motor-generator 310, it is possible to control the first motor-generator 310 so that the engine speed NE is reduced at a constant rate of change. In this case, as shown by the solid line in Fig. 6, the engine speed NE is reduced from the first rotational speed NE1 to the second rotational speed NE2. This allows the engine speed NE to be reduced smoothly to the second rotational speed NE2.

[0037] (4) When the engine speed NE starts to decrease toward the second speed NE2 after the internal combustion engine 10 stops its independent operation based on the execution conditions for the scavenging operation, the second speed NE2 usually becomes a value that can shorten the scavenging operation. However, when there is a possibility of starting the internal combustion engine 10, the second speed NE2 becomes a value suitable for starting the internal combustion engine 10. Therefore, when a start request for the internal combustion engine 10 is made after the engine speed NE starts to decrease from the first speed NE1 toward the second speed NE2, the internal combustion engine 10 can be quickly restarted.

[0038] (5) After the autonomous operation of the internal combustion engine 10 is stopped based on the satisfaction of the conditions for performing the scavenging operation, when there is a request to stop the scavenging operation, the first motor generator 310 is controlled as follows: That is, the control of the first motor generator 310 for reducing the engine rotation speed NE to the second rotation speed NE2 is ended, and the first motor generator 310 is controlled to start the internal combustion engine 10. This makes it possible to prevent unnecessary scavenging operation from being performed.

[0039] The above embodiment can be modified as follows, for example: The above embodiment and the following modifications can be combined and implemented within the scope of technical compatibility. By omitting the processes of S108 and S110 in the series of processes shown in FIG. 3, the process may proceed to S109 after the process of S107 is executed.

[0040] By omitting the processes of S104 and S106 in the series of processes shown in FIG. 3, the process may proceed to S105 after the process of S103 is executed. After the autonomous operation of the internal combustion engine 10 is stopped based on the satisfaction of the conditions for performing the scavenging operation, it is not essential to reduce the engine rotation speed NE at a constant rate of change through control of the first motor generator 310.

[0041] After the autonomous operation of the internal combustion engine 10 is stopped based on the satisfaction of the conditions for performing the scavenging operation, the engine speed NE is reduced to the second speed NE2 through control of the first motor-generator 310 while preventing an increase in the engine speed NE, but this is not essential. In other words, the engine speed NE may be temporarily increased as long as it is between the first speed NE1 and the second speed NE2.

[0042] The internal combustion engine 10 does not necessarily need to be one that uses hydrogen as fuel, but may be one that uses other fuels such as gasoline. Although the hybrid vehicle 500 has been exemplified as an electrically powered vehicle, the present invention may also be applied to an electrically powered vehicle that is equipped with an internal combustion engine exclusively for power generation and that runs solely on a motor. [Explanation of symbols]

[0043] 10...internal combustion engine, 18...crankshaft, 51...air flow meter, 52...crank angle sensor, 53...water temperature sensor, 54...intake air temperature sensor, 55...accelerator position sensor, 56...speed sensor, 100...control device, 110...processing circuit, 200...PCU, 250...battery, 300...terminal for external power supply, 310...first motor generator, 310a...rotating shaft, 320...second motor generator, 320a...rotating shaft, 350...planetary gear mechanism, 360...drive wheels, 500...hybrid vehicle.

Claims

1. An electric vehicle comprising: an internal combustion engine fueled by hydrogen, capable of stopping independent operation; a motor capable of rotating the internal combustion engine when independent operation has stopped; and a control unit that controls the internal combustion engine and the motor, wherein the control unit performs scavenging operation to rotate the internal combustion engine by the motor after independent operation of the internal combustion engine has been stopped, When the condition for performing the scavenging operation is satisfied, the control unit acquires the engine rotation speed at that time as a first rotation speed and sets a second rotation speed as a target value of the engine rotation speed during the scavenging operation, and after autonomous operation of the internal combustion engine is stopped based on the satisfaction of the condition for performing the scavenging operation, controls the motor to reduce the engine rotation speed of the internal combustion engine rotated by the motor to a value between the first rotation speed and the second rotation speed and to the second rotation speed, and starts the scavenging operation based on the engine rotation speed being reduced to the second rotation speed through the control of the motor.

2. 2. The electric vehicle according to claim 1, wherein, after autonomous operation of the internal combustion engine is stopped based on the satisfaction of the execution condition for scavenging operation, when controlling the motor to reduce the engine rotation speed of the internal combustion engine rotated by the motor to the second rotation speed while keeping the engine rotation speed at a value between the first rotation speed and the second rotation speed, the control unit controls the motor so as not to increase the engine rotation speed.

3. 3. The electric vehicle according to claim 2, wherein, after autonomous operation of the internal combustion engine is stopped based on the satisfaction of the execution condition for scavenging operation, when controlling the motor to reduce an engine rotation speed of the internal combustion engine rotated by the motor to the second rotation speed while maintaining the engine rotation speed at a value between the first rotation speed and the second rotation speed, the control unit controls the motor so that the engine rotation speed reduces at a constant rate of change.

4. 4. The electric vehicle according to claim 1, wherein the control unit sets the second rotation speed to a value that minimizes the scavenging operation, and when there is a possibility of starting the internal combustion engine after stopping self-sustaining operation of the internal combustion engine, sets the second rotation speed to a value that is suitable for starting the internal combustion engine.

5. 4. The electric vehicle according to claim 1, wherein when there is a request to stop the scavenging operation after the internal combustion engine stops self-sustaining operation, the control unit terminates control of the motor to reduce the engine rotation speed to the second rotation speed and controls the motor to start the internal combustion engine.

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