JP2021066309A - Control unit for series hybrid vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration of a catalyst by controlling a catalyst temperature to an appropriate temperature when driving an engine for power generation. A control device for a series hybrid vehicle 1 including an engine 2, a catalyst provided in an exhaust path of the engine, a power generation motor MG1, a battery 6, and a drive motor MG2 for traveling, wherein the battery is used. When the actual SOC of 6 is lower than the target value, the operating point determined by the engine torque and the engine speed can be reduced from the current operating point without changing the engine output. The control to change to is executed, and when the actual SOC is equal to or more than the target value, the control to reduce the engine output is executed. [Selection diagram] Fig. 1

Description

The present invention relates to a control device for a series hybrid vehicle.

Patent Document 1 describes a control device for a hybrid vehicle in which a traveling mode is switched between an EV mode and a series mode. When the traveling mode is switched from the EV mode to the series mode, the exhaust purifying catalyst provided in the exhaust path of the engine is warmed. It is disclosed to perform machine control.

JP-A-2018-052343

In the configuration described in Patent Document 1, the engine is stopped and the vehicle runs in the EV mode. Therefore, when the driving mode is switched from the EV mode to the series mode, the warm-up control is executed to exert the catalytic function. The catalyst temperature is raised to the predetermined temperature (active temperature) required for the above. On the other hand, in the case of the series mode, since the engine is driven to run, the exhaust gas of the engine continuously passes through the catalyst, and the catalyst temperature rises due to the heat of the exhaust gas. In the running state in which the engine is driven in this way, if the temperature of the catalyst becomes too high due to the heat of the exhaust gas, the catalyst may be rapidly deteriorated.

In particular, series hybrid vehicles are often configured by combining a small engine and a large capacity battery. In the case of a small engine (for example, a REEV engine), since it is often driven in a high load state for power generation, the frequency of discharging high-temperature exhaust gas increases and the frequency of high temperature of the catalyst increases. Therefore, in a series hybrid vehicle, it may be required to lower the catalyst temperature when driving the engine from the viewpoint of suppressing deterioration of the catalyst.

The present invention has been made in view of the above circumstances, and is a series hybrid vehicle capable of suppressing deterioration of the catalyst by controlling the catalyst temperature to an appropriate temperature when driving the engine for power generation. It is an object of the present invention to provide a control device for the above.

The present invention includes an engine, a catalyst provided in the exhaust path of the engine to purify the exhaust, a generator that generates power by the power output from the engine, a battery that stores the power generated by the generator, and the like. A control device for a series hybrid vehicle including a traveling electric motor driven by the power of a battery, and when the actual SOC, which is the actual SOC of the battery, is lower than the target value, the engine torque and the engine When the control is executed to change the engine operating point determined by the number of revolutions from the current operating point to an operating point where the exhaust temperature can be lowered without changing the engine output, and the actual SOC is equal to or higher than the target value. Is characterized by executing a control that reduces the engine output.

According to the present invention, when power is generated by a generator using an engine, the engine output is controlled according to the actual SOC of the battery, so that the exhaust temperature can be lowered and the increase in the catalyst temperature can be suppressed. .. As a result, the catalyst temperature can be controlled to an appropriate temperature, so that deterioration of the catalyst can be suppressed.

FIG. 1 is a skeleton diagram schematically showing a series hybrid vehicle of the embodiment. FIG. 2 is a flowchart showing a power generation control flow. FIG. 3 is an explanatory diagram for explaining the relationship between the temperature of the catalyst and the catalyst function. FIG. 4 is a map diagram for explaining changes in engine operating points. FIG. 5 is a diagram showing the relationship between the vehicle speed and the amount of power generation.

Hereinafter, the control device of the series hybrid vehicle according to the embodiment of the present invention will be specifically described with reference to the drawings. The present invention is not limited to the embodiments described below.

FIG. 1 is a skeleton diagram schematically showing a series hybrid vehicle of the embodiment. In the series hybrid vehicle 1, a power generation motor (hereinafter referred to as a power generation motor) MG1 is connected to the output shaft of the engine 2, and a driving motor (hereinafter referred to as a drive motor) MG2 is connected to a drive wheel via a drive shaft 3. 4a and 4b are connected. This series hybrid vehicle 1 includes an engine 2, a power generation motor MG1, a drive motor MG2, inverters 5a and 5b, a battery 6, and an electronic control device for hybrid traveling (hereinafter referred to as HVECU) 7.

The engine 2 is composed of a well-known internal combustion engine. Further, a catalyst for purifying the exhaust gas is provided in the exhaust path of the engine 2. That is, the series hybrid vehicle 1 includes a catalytic converter that purifies the exhaust gas with a three-way catalyst. The engine 2 is controlled by an electronic control device for an engine (hereinafter referred to as an engine ECU) 21.

The engine ECU 21 is composed of a microprocessor and includes a CPU, a ROM, a RAM, and the like. The engine ECU 21 is communicably connected to the HVECU 7, and controls the engine 2 based on a command signal input from the HVECU 7. For example, the engine ECU 21 controls fuel injection and ignition timing to the engine 2.

Both the power generation motor MG1 and the drive motor MG2 are composed of a motor generator. The power generation motor MG1 is a generator driven by the engine 2. The rotor of the power generation motor MG1 is connected to the output shaft of the engine 2, and the power generation motor MG1 generates power by the power output from the engine 2. The drive motor MG2 is a traveling electric motor that is driven by using the electric power of the battery 6. The rotor of the drive motor MG2 is connected to the drive shaft 3, and the drive motor MG2 is driven by using the electric power of the battery 6. The inverters 5a and 5b are electrically connected to the power generation motor MG1 and the drive motor MG2, and are also electrically connected to the battery 6. The power generation motor MG1 is electrically connected to the drive motor MG2 via the inverters 5a and 5b. Further, the power generation motor MG1 and the drive motor MG2 are controlled by an electronic control device for a motor (hereinafter referred to as a motor ECU) 31.

The motor ECU 31 is composed of the same microprocessor as the engine ECU 21. The motor ECU 31 is communicably connected to the HVECU 7. For example, the motor ECU 31 controls each of the motors MG1 and MG2 by switching and controlling a plurality of switching elements included in the inverters 5a and 5b based on a command signal input from the HVECU 7. More specifically, the motor ECU 31 executes control (power running control) in which the power generation motor MG1 functions as a generator and at the same time, the drive motor MG2 functions as an electric motor. Further, the motor ECU 31 executes control (regeneration control) in which the power generation motor MG1 functions as a generator and at the same time, the drive motor MG2 functions as a generator. Further, the motor ECU 31 executes control to minimize the amount of power generated by the power generation motor MG1 or to make the drive motor MG2 function as a generator without generating power by the power generation motor MG1.

The battery 6 is composed of a secondary battery such as a lithium ion battery or a nickel hydrogen battery. Further, the battery 6 is electrically connected to the inverters 5a and 5b. The battery 6 is controlled by an electronic control device for a battery (hereinafter referred to as a battery ECU) 61.

The battery ECU 61 is composed of a microprocessor and is communicably connected to the HVECU 7. The battery ECU 61 manages the state of charge (SOC) of the battery 6.

The HVECU 7 is composed of a microprocessor and controls the series hybrid vehicle 1. Signals from various sensors are input to the HVECU 7. The signals input to the HVECU 7 include an engine rotation speed signal from the engine rotation speed sensor 71 that detects the rotation speed of the engine 2, an accelerator opening signal from the accelerator opening sensor 72 that detects the amount of depression of the accelerator pedal, and a brake. A brake pedal position signal from the brake stroke sensor 73 that detects the amount of pedal depression, a vehicle speed signal from the vehicle speed sensor 74, an SOC signal from the SOC sensor 75 that detects the SOC of the battery 6, and a catalyst temperature sensor that detects the temperature of the catalyst. Examples include the catalyst temperature signal from 76. Then, the HVECU 7 can output a command signal to the engine ECU 21, the motor ECU 31, and the battery ECU 61 as a result of performing various calculations. The control device of the series hybrid vehicle 1 in the embodiment includes at least the HVECU 7 among the HVECU 7, the engine ECU 21, the motor ECU 31, and the battery ECU 61.

Further, the HVECU 7 executes SOC control for managing the SOC of the battery 6 within the range of the battery charging capacity. For example, the HVECU 7 and the battery ECU 61 can detect (monitor) the actual SOC, which is the actual SOC of the battery 6, based on the SOC signal input from the SOC sensor 75 to the HVECU 7. Then, the HVECU 7 manages the power balance between the amount of power generated by the power generation motor MG1 and the amount of power consumed by the drive motor MG2 according to the running state of the series hybrid vehicle 1, and the battery 6 is overcharged and overdischarged. The SOC is controlled so as to be within the range of the battery charging capacity.

Further, when driving the engine 2, the HVECU 7 executes an operating point control for controlling an operating point (engine operating point) of the engine 2. The engine operating point is an operating point determined by the torque of the engine 2 (engine torque) and the rotation speed of the engine 2 (engine rotation speed). For example, when the series hybrid vehicle 1 is running and the power generated from the engine 2 is used to generate power with the power generation motor MG1, the HVECU 7 controls the engine 2 so that the engine operating point is located on the optimum fuel consumption line. To do. When the engine 2 is driven in this way, the exhaust gas is purified by a catalyst provided in the exhaust path of the engine 2. Therefore, the HVECU 7 executes power generation control that lowers the catalyst temperature based on the catalyst temperature during acceleration and steady running during deceleration. More specifically, at the time of deceleration, the HVECU 7 executes power generation control so as to adjust the power generation amount (engine power generation amount) in the power generation motor MG1 using the engine 2 based on the actual SOC of the battery 6 and the catalyst temperature. To do. An example of this power generation control is shown in FIG.

FIG. 2 is a flowchart showing a power generation control flow. The control shown in FIG. 2 is executed by the HVECU 7 while the series hybrid vehicle 1 is running.

The HVECU 7 constantly grasps the temperature of the catalyst while the series hybrid vehicle 1 is traveling (while the vehicle is traveling) (step S1). In step S1, the catalyst temperature is grasped based on the catalyst temperature signal input from the catalyst temperature sensor 76 to the HVECU 7. In step S1, the HVECU 7 may estimate the temperature of the catalyst and constantly grasp the temperature of the catalyst based on this estimated value. That is, the series hybrid vehicle 1 is not necessarily limited to the configuration including the catalyst temperature sensor 76.

Further, the HVECU 7 determines whether or not the accelerator is off while the vehicle is running (step S2). In step S2, it is determined whether or not the traveling state has changed from the traveling state in which the accelerator pedal is depressed, for example, during acceleration or steady traveling, to the traveling state in which the accelerator is off, that is, during deceleration. Specifically, it is determined whether or not the accelerator is turned off while the vehicle is running, based on the accelerator opening signal input from the accelerator opening sensor 72 to the HVECU 7.

If the accelerator is not turned off while the vehicle is running (step S2: No), this control routine returns to step S1.

When the accelerator is turned off while the vehicle is running (step S2: Yes), the HVECU 7 determines whether or not the actual SOC of the battery 6 is lower than the target SOC (step S3). The target SOC is the target value of the SOC. In the series hybrid vehicle 1, the engine 2 does not directly drive the drive wheels 4a and 4b, so the HVECU 7 currently determines the amount of power generation based on the SOC and the vehicle speed.

For example, regarding the magnitude relationship of the amount of power generation, when the SOC is the same at present, the determined amount of power generation changes to a large value as the vehicle speed changes to the high speed side. On the other hand, when the vehicle speed is the same, the determined power generation amount changes to a large value as the SOC changes to the lower side. That is, when comparing the first state where the SOC is currently low and the second state where the SOC is currently higher than the first state when the vehicle speed is the same, the first state where the SOC is low is higher than the second state where the SOC is high. Is also determined to be a large amount of power generation. Then, in the running state (during acceleration, steady running) in which the drive motor MG2 consumes electric power to drive the drive wheels 4a and 4b, the engine 2 is used to cover the amount of power generation currently determined by the SOC and the vehicle speed. It is driven and power is generated by the power generation motor MG1. At that time, if the determined power generation amount is smaller than the power consumption amount of the drive motor MG2, the power is taken out from the battery 6 and the SOC may decrease. That is, if the amount of power generation is insufficient with respect to the target SOC, the SOC will be lower than the target SOC. Therefore, in the above case, the power generation control is executed so as to increase the amount of power generated by the power generation motor MG1.

As a result of the determination in step S3, when the actual SOC is smaller than the target SOC (step S3: Yes), the HVECU 7 determines whether or not the catalyst temperature is equal to or higher than the predetermined temperature (step S4). This predetermined temperature is set to an arbitrary value within the range of 700 to 750 ° C.

Here, as shown in FIG. 3, it is necessary to raise the catalyst temperature to an active temperature or higher, for example, 300 to 400 ° C. or higher in order to exert the catalyst function. On the other hand, if the catalyst temperature is too high, the deterioration of the catalyst progresses rapidly, and in the worst case, there is a risk of melting damage. As shown in FIG. 3, when the upper limit temperature for normal use is set to 950 ° C., in a region higher than the upper limit temperature for normal use, for example, a rapid deterioration region is reached at 1000 ° C., and there is a risk of melting at 1200 ° C. Therefore, in the embodiment, the region to be used regularly at the catalyst temperature is set to the temperature range of 400 to 750 ° C. Therefore, the predetermined temperature used in step S4 is set to a value included in the normal temperature range (deterioration guarantee range) and is set to a value of 700 to 750 ° C., which is the upper limit value of the above-mentioned range to be used regularly.

As a result of the determination in step S4, when the catalyst temperature is equal to or higher than the predetermined temperature (step S4: Yes), the HVECU 7 regenerates by the traveling drive motor MG2 (step S5). In step S5, the regenerative control for causing the drive motor MG2 to function as a generator is executed by the HVECU 7 during deceleration. At that time, the HVECU 7 controls the engine 2 to an idle state or the engine 2 to a state in which the power generation by the power generation motor MG1 is the minimum power generation. In short, when it is positively determined in step S4, it is necessary to reduce the heat of the exhaust gas in order not to raise the catalyst temperature from the viewpoint of suppressing the deterioration of the catalyst. Therefore, the process of step S5 limits the amount of power generated during deceleration and lowers the catalyst temperature.

As a result of the determination in step S4, when the catalyst temperature is lower than the predetermined temperature (step S4: No), the HVECU 7 regenerates with the driving motor MG2 for traveling within the range of the battery charging capacity, and generates electricity using the engine 2. Power is generated by the motor MG1 (step S6). When the process of step S6 is executed, this control routine ends.

On the other hand, as a result of the determination in step S3, when the actual SOC is equal to or higher than the target SOC (step S3: No), the HVECU 7 determines whether or not the catalyst temperature is equal to or higher than the predetermined temperature (step S7). The predetermined temperature used in step S7 is the same as the predetermined temperature used in step S4 described above.

As a result of the determination in step S7, when the catalyst temperature is equal to or higher than the predetermined temperature (step S7: Yes), the HVECU 7 sets the engine operating point from the current operating point to the exhaust temperature without changing the amount of power generated by the engine 2. The control for changing to the operating point that can be lowered is executed (step S8). When the control in step S8 is executed, this control routine ends. The details of the control executed in step S8 will be described later with reference to FIG.

As a result of the determination in step S7, when the catalyst temperature is lower than the predetermined temperature (step S7: No), the HVECU 7 uses the regeneration by the drive motor MG2 for traveling and the engine 2 within the range of the battery charging capacity. Power is generated by the power generation motor MG1 (step S9). When the control in step S9 is executed, this control routine ends.

FIG. 4 is a map diagram for explaining changes in engine operating points. In FIG. 4, the optimum fuel consumption line L1 is shown by a thick broken line, the iso-output lines L2 to L4 are shown by a thin broken line, and the iso-temperature lines L5 to L8 are shown by a thin solid line. The equal output line has lower output in the order of L2> L3> L4. The isothermal line is on the lower temperature side in the order of L5> L6> L7> L8. Further, for convenience of explanation, it may be described as an engine operating point P.

As shown in FIG. 4, the HVECU 7 controls the engine operating point when driving the engine 2. For example, during steady driving, the engine operating point is controlled to move on the optimum fuel consumption line L1. Then, when the accelerator is released from the steady running state and the deceleration state is entered, the engine 2 generates power with the power generation motor MG1 during deceleration. At that time, the HVECU 7 changes the engine operating point according to the magnitude relationship between the actual SOC of the battery 6 and the target SOC.

For example, when the actual SOC is equal to or higher than the target SOC and the difference between the actual SOC and the target SOC is large during deceleration when the accelerator is off during driving, the HVECU 7 determines the amount of power generated by the power generation motor MG1 (engine power generation amount). Perform control to lower the exhaust temperature without changing it. In this case, the control for changing the engine operating point P is executed at the operating point on the side where the exhaust temperature is low even if the output of the engine 2 is the same. As shown in FIG. 4, when the current engine operating point P is the operating point P1 on the optimum fuel consumption line L1, the HVECU 7 moves the operating point to the side where the exhaust temperature is lowered on the equal output line L2. Take control. As a result, the engine operating point P is changed from the operating point P1 on the equal output line L2 to the operating point P2 on the low exhaust temperature side. Further, when the current engine operating point P is the operating point P3 on the optimum fuel consumption line L1, the engine operating point P is moved on the equal output line L4 to the side where the exhaust temperature is lowered, so that the engine operating point P is on the equal output line L4. Is changed from the operating point P3 to the operating point P4.

On the other hand, when the actual SOC is lower than the target SOC or the actual SOC is equal to or higher than the target SOC but the difference between the actual SOC and the target SOC is small during deceleration when the accelerator is off during traveling, the HVECU 7 uses the power generation motor MG1. The amount of power generated in the system is limited and the catalyst temperature is controlled to be lowered. That is, by reducing the amount of power generated by the power generation motor MG1, the temperature of the engine exhaust is controlled to be lowered. In this case, control for reducing the output of the engine 2 is executed so that the amount of power generated by the power generation motor MG1 is reduced. This method of reducing the engine output can be realized by either a method of changing the engine operating point as shown in FIG. 4 or a method of gradually reducing the amount of power generation as shown in FIG.

As shown in FIG. 4, when the current operating point is the operating point P1 on the optimum fuel consumption line L1, the HVECU 7 moves the operating point toward the low output side on the optimum fuel consumption line L1 and is lower than the present. Change to the output area. As a result, the engine operating point P is changed from the operating point P1 on the optimum fuel consumption line L1 to the operating point P3 on the low output side of the engine output.

As shown by the broken line in FIG. 5, when the accelerator is off, the amount of power generated by the power generation motor MG1 is controlled to be gradually reduced. Moreover, when compared at the same vehicle speed, the amount of power generation is set to be larger when the accelerator is on than when the accelerator is off. In short, it is set to reduce the amount of engine power generation when the accelerator is switched from the accelerator on state to the accelerator off state while the vehicle is running. Then, when the accelerator is off, the amount of power generation is controlled to be gradually reduced based on the relationship between the catalyst temperature and the SOC described above.

As described above, according to the embodiment, it is possible to control the amount of engine power generation so that the catalyst temperature is lowered based on the SOC of the battery 6 and the catalyst temperature during deceleration. As a result, the catalyst temperature can be lowered while securing the required amount of power generation during deceleration, so that deterioration of the catalyst can be suppressed. As a result, both energy management during deceleration and durability of the catalyst can be achieved at the same time.

1 series hybrid vehicle 2 engine 3 drive shaft 4a, 4b drive wheel 5a, 5b inverter 6 battery 7 hybrid driving electronic control device (HVECU)
75 SOC sensor 76 Catalyst temperature sensor MG1 Power generation motor (power generation motor)
MG2 running motor (drive motor)

Claims (1)

With the engine
A catalyst provided in the exhaust path of the engine to purify the exhaust,
A generator that generates electricity from the power output from the engine,
A battery that stores the electric power generated by the generator and
A traveling electric motor driven by using the electric power of the battery,
It is a control device of a series hybrid vehicle equipped with
When the actual SOC, which is the actual SOC of the battery, is lower than the target value, the exhaust temperature is lowered without changing the engine output from the current operating point at the engine operating point determined by the engine torque and the engine speed. Execute control to change to the operating point that can be made
A control device for a series hybrid vehicle, characterized in that when the actual SOC is equal to or higher than a target value, control for reducing engine output is executed.

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