Control device

Abstract

To prevent achievement of a required braking torque during reduction processing of the required braking torque when an accelerator is turned off.SOLUTION: In a control device for controlling an engine, first and second motors and a transmission so as to achieve a required braking torque accompanied by fuel cut of the engine or motoring of the engine by driving and a first motor when an accelerator is turned off, during restriction of the fuel cut of the engine when the accelerator is turned off, in a case in which reduction processing of reducing the required braking torque is executed, the control device restricts the shift level of the transmission to a predetermined high speed level.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a control device. [Background technology]

[0002] Conventionally, this type of control device has been proposed as a control device installed in a vehicle having an engine with a filter attached to the exhaust system that captures particulate matter.When the temperature of the filter is above a threshold value, a temperature rise limiting control is used to limit fuel cut-off in the engine in order to prevent the filter from overheating (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-125720 Summary of the Invention [Problem to be solved by the invention]

[0004] In a vehicle in which a first motor, an engine, an intermediate shaft, and a second motor are connected to the sun gear, carrier, and ring gear of a planetary gear, a power storage device is connected to the power line together with the first and second motors, and a transmission is connected to the intermediate shaft and drive wheels, limiting engine fuel cutoff when the accelerator is released reduces engine friction and 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, the input power of the power storage device may significantly exceed the input limit. For this reason, a reduction process may be performed to reduce the required braking torque, thereby suppressing an increase in the regenerative torque of the second motor and suppressing an increase in the input power of the power storage device. If the transmission shifts to a higher gear (e.g., the highest gear) during this reduction process, the required braking torque may not be achieved.

[0005] The control device of the present disclosure has a primary object to prevent the required braking torque from becoming unrealizable during the process of reducing the required braking torque when the accelerator is released. [Means for solving the problem]

[0006] The present disclosure has adopted the following means to achieve the above-mentioned main object.

[0007] The control device disclosed herein is mounted on a vehicle having an engine, a first motor, a second motor, a planetary gear having three rotating elements respectively connected to the first motor, the engine, an intermediate shaft, and the second motor, an electric storage device capable of exchanging power with the first and second motors, and a transmission connected to the intermediate shaft and a drive shaft, and controls the engine, the first and second motors, and the transmission so that a required braking torque is realized by cutting or operating the engine and motoring the engine by the first motor when the accelerator is released.The gist of the control device disclosed herein is that when a reduction process is executed to reduce the required braking torque while limiting the engine fuel cut when the accelerator is released, the control device restricts the transmission from shifting to a predetermined high speed. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a hybrid vehicle 20. [Figure 2] 10 is a flowchart illustrating an example of a processing routine. [Figure 3] FIG. 10 is an explanatory diagram showing an example of a state when the accelerator is released in an HV driving mode. DETAILED DESCRIPTION OF THE INVENTION

[0009] 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 the 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 (electricity storage device) 50, a transmission 60, and a hybrid electronic control unit (hereinafter referred to as "HVECU") 70.

[0010] The engine 22 is configured as an internal combustion engine that outputs power using fuel such as gasoline or diesel. The exhaust system of the engine 22 is equipped with a purification device 25 that purifies unburned fuel and nitrogen oxides from the exhaust of the engine 22, and a PM filter 26 that captures particulate matter (PM) such as soot from the exhaust. The operation of 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 amount Qa of the engine 22 from an air flow meter, and the differential pressure ΔPf between before and after (upstream and downstream) the PM filter 26 from a differential pressure sensor 26a. The engine ECU 28 outputs control signals to a throttle valve, fuel injection valves, spark plugs, a display 29, and the like. The rotation speed Ne of the engine 22 is calculated based on the crank angle θcr, and the load factor KL of the engine 22 (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 rotation speed Ne. The PM accumulation amount Qpm (the accumulation 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 rotation speed Ne and the load factor KL.

[0011] The planetary gear 30 is configured as a single-pinion planetary gear mechanism, with a rotor of a motor MG1 connected to the sun gear, a crankshaft 23 of the engine 22 connected to the carrier, and an intermediate shaft 35 connected to the ring gear. A rotor of a motor MG2 is attached to the intermediate shaft 35. The motors MG1 and MG2 are configured as, for example, synchronous generator motors, and are rotationally driven by the HVECU 70 controlling the switching of multiple switching elements of 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 a drive shaft 36 which is connected to drive wheels 39a, 39b via a differential gear 38. The transmission 60 is controlled by the HVECU 70.

[0012] 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, the HVECU 70 receives inputs such as 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 inputs such as a start signal from a start switch 80, a shift position (shift lever operating position) SP from a shift position sensor 82, an accelerator opening (accelerator pedal depression amount) Acc from an accelerator pedal position sensor 84, a brake pedal position (brake pedal depression amount) BP from a brake pedal position sensor 86, and a vehicle speed V from a vehicle speed sensor 87. It outputs control signals to the inverters 41 and 42, the transmission 60, and the like. The HVECU 70 calculates the rotational speeds Nm1 and Nm2 of the motors MG1 and MG2 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 storage rate SOC of the battery 50 is calculated based on the integrated value of the current Ib, and the input / output limits (allowable input / output power) Win, Wout of the battery 50 are calculated based on the storage rate SOC and the temperature Tb.

[0013] In the hybrid vehicle 20, the engine 22, motors MG1, MG2, and transmission 60 are controlled by cooperative control between the engine ECU 28 and the HVECU 70 so that the hybrid vehicle 20 travels in an electric drive mode (EV drive mode) in which the engine 22 is stopped, or in 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, MG2 are controlled so that a required torque Ti* of the intermediate shaft 35 is output to the intermediate shaft 35 with the engine 22 running or stopped. The required torque Ti is obtained by dividing a required torque Td* of the drive shaft 36 based on the accelerator pedal position Acc and the vehicle speed V by a rotation speed ratio Gt corresponding to the gear Gs of the transmission 60.

[0014] In particular, when the accelerator is released in HV driving mode, the engine 22 and motors MG1, 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 the motor MG1, and the regenerative torque of the 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* (torque on the braking side, hereinafter referred to as "basic braking torque Td2a") when the accelerator opening Acc is 0, or a torque smaller than that within the range of the braking side. In the following description of the accelerator release, for ease of explanation, absolute values will be omitted (assumed to be positive) for the braking torque of the drive shaft 36 and the intermediate shaft 35 (required braking torque Td2*, 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). 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. The engine 22 is subjected to a fuel cut when the filter temperature Tf is below a threshold Tfref that is slightly lower than the overheat temperature of the PM filter 26. As a result, air (oxygen) is supplied to the PM filter 26, burning 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 (for example, the lowest combustible amount) injected to prevent overheating of the PM filter 26. In this case, the friction of the engine 22 is reduced compared to when fuel cutoff is performed, and the engine brake torque is reduced, and the regenerative torque of the motor MG2 is increased to realize the required braking torque Td2* (required braking torque Ti2*), and the electric power Pb of the battery 50 is increased on the charging side.The target rotation speed Ne* is set to the basic rotation speed Nea when the power Pb of the battery 50 has a margin above the input limit Win, and when the power Pb reaches the input limit Win, it is increased relative to the basic rotation speed Nea within a range below the allowable upper limit rotation speed Nemax. For example, the basic rotation speed Nea is 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 of increase in target rotation speed Ne* is set so that the power Pb has a margin above the input limit Win.

[0015] 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. Fig. 2 is a flowchart showing an example of a processing routine executed by the HVECU 70. This routine is repeatedly executed when the accelerator is released in HV driving mode and the required braking torque Td2* reduction process, which will be described later, is not being executed in the current trip.

[0016] 2 is executed, the HVECU 70 first determines whether or not fuel cut of the engine 22 is to be restricted (step S100). The determination process in step S100 is performed, for example, by checking the value of a fuel cut restriction flag. The engine ECU 28 sets the fuel cut restriction flag to a value of 0 or a value of 1 when fuel cut of the engine 22 is to be performed or restricted, respectively, and transmits the flag to the HVECU 70. If it is determined in step S100 that fuel cut is not to be restricted, the routine ends. In this case, the basic braking torque Td2a described above is set to the required braking torque Td2*.

[0017] When 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 the embodiment, when a first condition is met, in which the electric power Pb of the battery 50 is equal to the input limit Win and the rotation speed Ne of the engine 22 is equal to or greater than a threshold value 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 value Neref is set to be higher as the vehicle speed V increases, taking into account that the allowable background noise increases as the vehicle speed V increases. Note that a constant value may be used for the threshold value Neref. The first condition means that the electric power Pb reaches the input limit Win because the input limit Win is small, and the target rotation speed Ne* (rotation speed Ne) is raised. Note that the input limit Win becomes small when the power storage percentage SOC of the battery 50 is sufficiently high or when the temperature Tb of the battery 50 is sufficiently low.

[0018] When it is determined in step S110 that the input limit Win is smaller than the normal range, a reduction determination is made to reduce the required braking torque Td2* (step S120). At this time, the HVECU 70 transmits a notification to the engine ECU 28, which then displays the notification on the display 29. Next, a reduction process for the required braking torque Td2* is initiated (step S130), and the gear Gs of the transmission 60 is restricted from being set to a predetermined high speed (e.g., the highest speed) (step S140). Upon completion of the reduction process (step S150), the restriction on setting the gear Gs to the predetermined high speed is lifted (step S160), and the routine ends. In the reduction process, after waiting for a predetermined time (e.g., several seconds) from the reduction determination, a reduction request flag is turned on and the required braking torque Td2* is gradually reduced from the basic braking torque Td2a. When the reduction of the required braking torque Td2* is completed, a reduction completion flag is turned on. The reduction amount of the required braking torque Td2* is set based on the vehicle speed V, etc. By reducing the required braking torque Td2* (required braking torque Ti2*), the regenerative torque of the motor MG2 is prevented from increasing, and the electric power Pb of the battery 50 is prevented from significantly exceeding the input limit Win. Furthermore, by restricting the shift stage Gs of the transmission 60 from being set to a predetermined high speed stage during the reduction process, the braking torque that can be output to the drive shaft 36 (drive wheels 39a, 39b) is prevented from decreasing, and the required braking torque Td2* is prevented from being unable to be realized. 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 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.

[0019] If it is determined in step S110 that the input limit Win is within the normal range, this routine ends without executing the processes of steps S120 to S140. In this case, the basic braking torque Td2a is set to the required braking torque Td2*. This makes it possible to reduce opportunities to reduce the required braking torque Td2* (braking torque).

[0020] 3 is an explanatory diagram showing an example of a state when the accelerator is released in HV driving mode. As shown in the figure, even if fuel cutoff of the engine 22 is restricted (time t1), if the electric power Pb of the battery 50 has a margin relative to the input limit Win, it is determined that the input limit Win is within a normal range, and a determination to reduce the required braking torque Td2* or a reduction process is not performed. Then, the fuel cutoff restriction is lifted (time t2), and after the fuel cutoff is restricted (time t3), the electric power Pb of the battery 50 reaches the input limit Win (time t4). The rotation speed Ne of the engine 22 is gradually increased. When the rotation speed Ne reaches or exceeds a threshold value Neref (time t5), it is determined that the input limit Win is smaller than the normal range, a determination to reduce the required braking torque Td2* is performed, and a message to that effect is displayed on the display 29. Furthermore, the shift stage Gs of the transmission 60 is restricted from being shifted to a predetermined higher stage, and a process to reduce the required braking torque Td2* is initiated. In this reduction process, after waiting for a predetermined time from the reduction decision (time t6), the reduction request flag is turned on to gradually reduce the required braking torque Td2*, and when the reduction of the required braking torque Td2* is completed (time t7), the reduction completion flag is turned on and the restriction on changing the gear stage Gs of the transmission 60 to a predetermined high speed stage is lifted.

[0021] In the control device of the embodiment described above, when the accelerator is released and the process of reducing the required braking torque Td2* is being executed during the restriction of fuel cut of the engine 22, the gear position Gs of the transmission 60 is restricted from being set to a predetermined high speed position. This makes it possible to prevent the required braking torque Td2* from becoming unrealizable during the process of reducing the required braking torque Td2* when the accelerator is released.

[0022] 2 in the above-described embodiment, in place of the first condition described above, a second condition may be used in which the electric power Pb of the battery 50 is equal to the input limit Win and the rotation speed Ne of the engine 22 is increasing and is equal to or greater than 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 the 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, the vehicle loss, and the engine braking power of the intermediate shaft 35 when the engine 22 rotates at the allowable upper limit rotation speed Nemax.

[0023] The hybrid vehicle 20 of the above-described embodiment does not necessarily have to include the transmission 60. Furthermore, the engine ECU 28 and the HVECU 70 may be configured as an integrated unit.

[0024] The present disclosure is not limited to the above-described embodiments, and it goes without saying that the present disclosure can be implemented in various forms without departing from the spirit of the present disclosure. [Explanation of symbols]

[0025] 20 Hybrid vehicles, 22 Engines, 28 Engine ECUs, 30 Planetary gears, 50 Batteries, 60 Transmissions, 70 HVECUs, MG1 and MG2 motors.

Claims

[Claim 1] A control device mounted on a vehicle including an engine, a first motor, a second motor, a planetary gear having three rotating elements respectively connected to the first motor, the engine, an intermediate shaft, and the second motor, an electric storage device capable of exchanging electric power with the first and second motors, and a transmission connected to the intermediate shaft and a drive shaft, the control device controlling the engine, the first and second motors, and the transmission so that a required braking torque is realized by cutting fuel or operating the engine and motoring the engine by the first motor when an accelerator is released, When the accelerator is released and a reduction process for reducing the required braking torque is executed during a restriction on fuel cut of the engine, the gear stage of the transmission is restricted from being set to a predetermined high speed stage. Control device.

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