JP7757907B2 - control device - Google Patents

Description

This disclosure relates to a control device.

Conventionally, one such control device proposed is mounted on a vehicle with an engine that has a filter attached to the exhaust system that captures particulate matter. When the filter temperature exceeds a threshold, the control device limits fuel cut-off to prevent the filter from overheating (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2020-125720

In a vehicle in which a first motor, engine, drive wheels, and second motor are connected to the sun gear, carrier, and ring gear of a planetary gear, and an electric storage device is connected to the power line along with the first and second motors, limiting engine fuel cutoff when the accelerator is released reduces engine friction and the so-called engine braking torque generated by motoring the engine by the first motor. In this case, if the regenerative torque of the second motor is increased to achieve the vehicle's required braking torque, there is a possibility that the input power to the electric storage device will greatly exceed the input limit. For this reason, it is possible to reduce the required braking torque to suppress the increase in the regenerative torque of the second motor and thereby suppress the increase in input power to the electric storage device, but it is preferable to suppress this opportunity because it would reduce vehicle deceleration.

The primary purpose of the control device disclosed herein is to simultaneously prevent the input power of the power storage device from significantly exceeding the input limit and reduce opportunities to reduce the required braking torque.

This disclosure takes the following measures to achieve the above-mentioned primary objective:

The control device disclosed herein is mounted on a vehicle including an engine, a first motor, a second motor, a planetary gear in which three rotating elements are respectively connected to the first motor, the engine, the drive wheels, and the second motor, and an electrical storage device capable of exchanging electric power with the first and second motors. When the accelerator is released, the control device controls the engine and the first and second motors so that a required braking torque is achieved by cutting fuel to the engine or by operating the engine and motoring the engine using the first motor. When limiting fuel cut to the engine when the accelerator is released, if the input limit of the electrical storage device is smaller than a normal range, the control device executes a reduction process to reduce the required braking torque compared to when fuel to the engine is cut, and if the input limit is within the normal range, the control device does not execute the reduction process.

FIG. 2 is a schematic diagram of a hybrid vehicle 20. 10 is a flowchart illustrating an example of a processing routine. FIG. 10 is an explanatory diagram showing an example of a state when the accelerator is released in an HV driving mode.

Next, an embodiment of the present disclosure will be described with reference to the drawings. FIG. 1 is a schematic diagram of a hybrid vehicle 20 equipped with a control device according to an embodiment. As shown in the figure, the hybrid vehicle 20 includes an engine 22, an engine electronic control unit (hereinafter referred to as "engine ECU") 28, a planetary gear 30, motors MG1 and MG2, inverters 41 and 42, a battery (electrical storage device) 50, a transmission 60, and a hybrid electronic control unit (hereinafter referred to as "HVECU") 70.

The engine 22 is an internal combustion engine that uses fuels such as gasoline or diesel to generate power. The exhaust system of the engine 22 is equipped with a purification device 25 that purifies unburned fuel and nitrogen oxides from the engine's exhaust, and a PM filter 26 that captures particulate matter (PM) such as soot from the exhaust. The engine 22 is controlled by an engine ECU 28. The engine ECU 28 has a microcomputer that receives signals from various sensors, outputs various control signals, performs various calculations, and communicates with the HVECU 70. For example, the engine ECU 28 receives inputs such as the crank angle θcr of the crankshaft 23 of the engine 22 from a crank position sensor 23a, the intake air volume Qa of the engine 22 from an air flow meter, and the differential pressure ΔPf between the upstream and downstream sides of the PM filter 26 from a differential pressure sensor 26a. It outputs control signals to the throttle valve, fuel injection valves, spark plugs, display 29, and other devices. The engine 22 rotation speed Ne is calculated based on the crank angle θcr, and the engine 22 load factor KL (the ratio of the volume of air actually taken in per cycle to the stroke volume per cycle of the engine 22) is calculated based on the intake air amount Qa and the engine 22 rotation speed Ne. The PM accumulation amount Qpm (the amount of particulate matter accumulated on the PM filter 26) is calculated based on the differential pressure ΔPf, and the filter temperature Tf (the temperature of the PM filter 26) is calculated based on the engine 22 rotation speed Ne and the load factor KL.

The planetary gear 30 is configured as a single-pinion planetary gear mechanism, with the rotor of the motor MG1 connected to the sun gear, the crankshaft 23 of the engine 22 connected to the carrier, and the ring gear connected to the intermediate shaft 35. The rotor of the motor MG2 is attached to the intermediate shaft 35. The motors MG1 and MG2 are configured as, for example, synchronous generator-motors, and are rotated by the HVECU 70 controlling the switching of multiple switching elements of the inverters 41 and 42. The battery 50 is configured as, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery, and is connected to the power line 54 together with the inverters 41 and 42. The battery 50 is managed by the HVECU 52. The transmission 60 is configured as a stepped transmission, for example, with four, five, or six speeds. The input shaft of the transmission 60 is connected to the intermediate shaft 35, and the output shaft is connected to the drive shaft 36 which is connected to the drive wheels 39a, 39b via a differential gear 38. The transmission 60 is controlled by the HVECU 70.

The HVECU 70 has a microcomputer that receives signals from various sensors, outputs various control signals, performs various calculations, and communicates with the engine ECU 28. For example, it receives the rotational positions θm1 and θm2 of the rotors of the motors MG1 and MG2 from the rotational position sensors 43 and 44, and the voltage Vb, current Ib, and temperature Tb of the battery 50 from the voltage sensor 51a, current sensor 51b, and temperature sensor 51c. It also receives the start signal from the start switch 80, the shift position (shift lever operating position) SP from the shift position sensor 82, the accelerator opening (accelerator pedal depression amount) Acc from the accelerator pedal position sensor 84, the brake pedal position (brake pedal depression amount) BP from the brake pedal position sensor 86, and the vehicle speed V from the vehicle speed sensor 87. It outputs control signals to the inverters 41 and 42, the transmission 60, and the like. The rotation speeds Nm1 and Nm2 of the motors MG1 and MG2 are calculated based on the rotational positions θm1 and θm2. The power Pb of the battery 50 is calculated as the product of the voltage Vb and the current Ib, the battery 50 power storage rate SOC is calculated based on the integrated value of the current Ib, and the input/output limits (allowable input/output power) Win and Wout of the battery 50 are calculated based on the power storage rate SOC and the temperature Tb.

In the hybrid vehicle 20, the engine ECU 28 and the HV ECU 70 cooperatively control the engine 22, motors MG1 and MG2, and transmission 60 to travel in either an electric drive mode (EV drive mode) in which the engine 22 is stopped, or a hybrid drive mode (HV drive mode) in which the engine 22 is running. The transmission 60 is controlled so that the gear Gs becomes a target gear Gs* based on the accelerator pedal position Acc and the vehicle speed V. The engine 22 and motors MG1 and MG2 are controlled so that the required torque Ti* of the intermediate shaft 35 is output to the intermediate shaft 35 with the engine 22 either stopped or running. The required torque Ti is obtained by dividing the required torque Td* of the drive shaft 36, which is based on the accelerator pedal position Acc and the vehicle speed V, by the rotation speed ratio Gt corresponding to the gear Gs of the transmission 60.

In particular, when the accelerator is released in HV driving mode, the engine 22 and motors MG1 and MG2 are controlled so that a required braking torque Ti2* of the intermediate shaft 35 is output to the intermediate shaft 35 by the so-called engine brake torque acting on the intermediate shaft 35 due to fuel cut or operation of the engine 22 and motoring of the engine 22 by motor MG1, and the regenerative torque of motor MG2. The required braking torque Ti2* is obtained by dividing the required braking torque Td2* of the drive shaft 36 by the rotation speed ratio Gt of the transmission 60. The required braking torque Td2* is set to the above-mentioned required torque Td* (brake-side torque, hereinafter referred to as "basic braking torque Td2a") when the accelerator opening Acc is zero, or a torque smaller than this within the brake-side range. In the following description of the accelerator release state, for ease of explanation, absolute values of the braking torques of the drive shaft 36 and the intermediate shaft 35 (required braking torques Td2* and Ti2*, engine braking torque, and regenerative torque of the motor MG2) and the input power of the battery 50 (power Pb and input limit Win) are omitted (assumed to be positive). The motor MG1 is controlled so that the engine 22 rotates at the target rotation speed Ne*, and the motor MG2 is controlled so that a torque equal to the difference between the required braking torque Ti2* and an engine braking torque estimated based on the torque of the motor MG1 is output. At this time, the battery 50 is charged and discharged based on the power of the motors MG1 and MG2. When the filter temperature Tf is below a threshold Tfref that is slightly lower than the overheat temperature of the PM filter 26, the engine 22 is subjected to a fuel cut. As a result, air (oxygen) is supplied to the PM filter 26, combusting particulate matter accumulated in the PM filter 26 and regenerating the PM filter 26. When the filter temperature Tf is equal to or higher than the threshold value Tfref, the engine 22 is operated with fuel cutoff limited and a relatively small amount of fuel (e.g., the lowest combustible amount) injected to prevent overheating of the PM filter 26. In this case, compared to when fuel cutoff is performed, the friction of the engine 22 is reduced, resulting in a smaller engine brake torque. Therefore, the regenerative torque of the motor MG2 is increased to achieve the required braking torque Td2* (required braking torque Ti2*), and the electric power Pb of the battery 50 is increased toward charging. When the electric power Pb of the battery 50 has a margin relative to the input limit Win, the basic rotation speed Nea is set as the target rotation speed Ne*. When the electric power Pb reaches the input limit Win, the target rotation speed Ne* is increased relative to the basic rotation speed Nea within a range not exceeding the allowable upper limit rotation speed Nemax. The base rotation speed Nea is, for example, the rotation speed Ne immediately before the accelerator is released. The target rotation speed Ne* is increased to accommodate the decrease in power Pb due to the increase in power consumption by motor MG1 and the decrease in regenerative power by motor MG2. The amount by which the target rotation speed Ne* is increased is set so that there is a margin for power Pb relative to the input limit Win.

Next, the operation of the hybrid vehicle 20, particularly the process for setting the required braking torque Td2* when the accelerator is released in HV driving mode, will be described. Figure 2 is a flowchart showing an example of a processing routine executed by the HV ECU 70. This routine is repeatedly executed when the accelerator is released in HV driving mode and the required braking torque Td2* reduction process described below is not being executed in the current trip.

When the routine of FIG. 2 is executed, the HVECU 70 first determines whether fuel cut of the engine 22 is to be restricted (step S100). The determination process of step S100 is performed, for example, by checking the value of a fuel cut restriction flag. The fuel cut restriction flag is set to a value of 0 or 1 by the engine ECU 28 when fuel cut of the engine 22 is to be performed or restricted, respectively, and is transmitted to the HVECU 70. If it is determined in step S100 that fuel cut is not to be restricted, this routine is terminated. In this case, the basic braking torque Td2a described above is set to the required braking torque Td2*.

If it is determined in step S100 that fuel cut of the engine 22 is restricted, it is determined whether the input limit Win of the battery 50 is smaller than the normal range (step S110). In this embodiment, when the first condition is met, in which the power Pb of the battery 50 is equal to the input limit Win and the engine 22 rotation speed Ne is equal to or greater than a threshold Neref that is lower than the allowable upper limit rotation speed Nemax, the input limit Win is determined to be smaller than the normal range. When the first condition is not met, the input limit Win is determined to be within the normal range. The threshold Neref is set to be higher as the vehicle speed V increases, taking into account that the higher the vehicle speed V, the greater the allowable background noise. Note that a fixed value may be used for the threshold Neref. The first condition means that the power Pb reaches the input limit Win due to the small input limit Win, thereby raising the target rotation speed Ne* (rotation speed Ne). The input limit Win may be small when the battery 50's power storage percentage SOC is sufficiently high or when the battery 50's temperature Tb is sufficiently low.

If step S110 determines that the input limit Win is smaller than the normal range, a reduction decision is made to reduce the required braking torque Td2* (step S120). At this time, the HVECU 70 sends a notification to the engine ECU 28, which then displays the notification on the display 29. The required braking torque Td2* is then reduced (step S130), and the routine ends. This reduction process waits a predetermined time (e.g., several seconds) after the reduction decision, then turns on the reduction request flag and gradually reduces the required braking torque Td2* from the basic braking torque Td2a. Once the reduction of the required braking torque Td2* is complete, the reduction completion flag is turned on. The amount of reduction in the required braking torque Td2* is set based on factors such as the vehicle speed V. By reducing the required braking torque Td2* (required braking torque Ti2*), the regenerative torque of the motor MG2 is prevented from increasing, and the battery 50 power Pb is prevented from significantly exceeding the input limit Win. Once the reduction completion flag is turned on, the required braking torque Td2* is set to a torque that is smaller than the basic braking torque Td2a but within the braking range while the accelerator is released, until the end of the current trip. This prevents frequent large changes in the required braking torque Td2* during the trip.

If it is determined in step S110 that the input limit Win is within the normal range, the routine ends without executing steps S120 to S140. In this case, the basic braking torque Td2a is set to the required braking torque Td2*. This reduces opportunities to reduce the required braking torque Td2* (braking torque).

Figure 3 is an explanatory diagram showing an example of what happens when the accelerator is released in HV driving mode. As shown, even if fuel cutoff of the engine 22 is restricted (time t1), if the battery 50's power Pb has a margin relative to the input limit Win, it is determined that the input limit Win is within the normal range, and no judgment or reduction process is performed to reduce the required braking torque Td2*. Then, after the fuel cutoff restriction is lifted (time t2) and the fuel cutoff is subsequently restricted (time t3), when the battery 50's power Pb reaches the input limit Win (time t4), the engine 22 rotation speed Ne is gradually increased. When the rotation speed Ne reaches or exceeds the threshold value Neref (time t5), it is determined that the input limit Win is smaller than the normal range, a judgment is made to reduce the required braking torque Td2*, a message to that effect is displayed on the display 29, and the process to reduce the required braking torque Td2* is initiated. In this reduction process, after waiting a predetermined time from the reduction decision (time t6), the reduction request flag is turned on and the required braking torque Td2* is gradually reduced, and when the reduction in the required braking torque Td2* is complete (time t7), the reduction completion flag is turned on.

In the control device installed in the hybrid vehicle 20 of the embodiment described above, when limiting fuel cut-off of the engine 22 during accelerator release in HV driving mode, if the input limit Win of the battery 50 is smaller than the normal range, a reduction process is executed to reduce the required braking torque Td2* compared to when fuel cut-off of the engine 22 is performed. However, if the input limit Win is within the normal range, the reduction process is not executed. This makes it possible to prevent the electric power Pb of the battery 50 from significantly exceeding the input limit Win while also reducing opportunities to reduce the required braking torque Td2* (braking torque).

In the processing of step S110 of the processing routine of FIG. 2 in the above-described embodiment, instead of the first condition described above, a second condition may be used in which the battery 50 power Pb is equal to the input limit Win and the engine 22 rotation speed Ne is increasing at or above the threshold value Neref. A third condition may be used in which the required braking power Pd2* based on the required braking torque Td2* and the rotation speed of the drive shaft 36 is greater than the sum of the input limit Win and vehicle loss. A fourth condition may be used in which the required braking power Pd2* is greater than the sum of the input limit Win, vehicle loss, and the engine braking power of the intermediate shaft 35 when the engine 22 is rotating at the allowable upper limit rotation speed Nemax.

The hybrid vehicle 20 of the above embodiment does not necessarily need to be equipped with a transmission 60. Furthermore, the engine ECU 28 and the HV ECU 70 may be integrated into one unit.

This disclosure is not limited to the above-described embodiments, and may of course be implemented in various forms without departing from the spirit of this disclosure.

20 Hybrid vehicle, 22 Engine, 28 Engine ECU, 30 Planetary gear, 50 Battery, 70 HV ECU, MG1, MG2 Motor.

Claims (1)

a control device mounted on a vehicle including an engine, a first motor, a second motor, a planetary gear having three rotational elements respectively connected to the first motor, the engine, drive wheels, and the second motor, and an electric storage device capable of exchanging electric power with the first and second motors, the control device setting, when an accelerator is released, a required braking torque to be a required torque on the braking side when the accelerator opening is zero or a torque smaller than that within a range on the braking side, and controlling the engine and the first and second motors so that the required braking torque is realized by an engine brake torque resulting from fuel cut or operation of the engine and motoring of the engine by the first motor, and a regenerative torque of the second motor,
When limiting fuel cut of the engine during the accelerator release, if the conditions that the electric power of the power storage device is equal to the input limit of the power storage device and the engine speed is equal to or higher than a speed threshold are met , a reduction process is executed to make the required braking torque smaller than when fuel cut of the engine is executed, and if the conditions are not met , the reduction process is not executed.
Control device.