JP2022072799A - Control device of hybrid vehicle - Google Patents

Abstract

To suppress progression of deterioration of a catalyst for exhaust emission control in an internal combustion engine loaded on a hybrid vehicle.SOLUTION: In a control device of a hybrid vehicle, used for controlling the hybrid vehicle loaded with an internal combustion engine and a motor as a power source, when a prescribed condition capable of stopping the internal combustion engine which has been operated by firing is established, a period length from establishment of the condition until stop of the internal combustion engine is changed according to the height of a temperature of the catalyst for exhaust emission control at that time.SELECTED DRAWING: Figure 3

Description

The present invention relates to a control device for controlling a vehicle equipped with an internal combustion engine and an electric motor.

Recently, hybrid vehicles equipped with two types of power sources, an internal combustion engine and an electric motor, have seen a certain degree of widespread use. In a series hybrid vehicle (for example, refer to the patent document below), an internal combustion engine drives a motor generator for power generation to generate electric power, and the generated electric power is used as a power storage device, that is, a lithium ion secondary battery or a nickel hydrogen secondary battery. It is stored in a battery and / or a capacitor such as, and is supplied to a traveling motor generator. Then, the drive wheels of the vehicle are rotated by the traveling motor generator to travel.

Not only the motor generator for power generation but also the motor generator for traveling can generate power by regenerative braking and store the generated power in the power storage device. When the electric power is already stored up to the full capacity of the power storage device, the electric power obtained by regenerative braking is intentionally supplied to the motor generator for power generation, and this is operated as an electric motor to rotate and drive the internal combustion engine. This consumes surplus power.

In a hybrid vehicle, it is possible to drive the vehicle by the rotational driving force output by the traveling motor generator without performing the firing in which the internal combustion engine burns the fuel to generate the rotational driving force. Therefore, even during the operation of the vehicle, the state in which the rotation of the internal combustion engine is stopped may continue.

When the amount of charge stored in the power storage device decreases or when the required output for the traction motor generator is large, the internal combustion engine is started, fuel is supplied to the cylinders to burn it, and the rotary drive is output by the internal combustion engine. The power is used to drive the motor generator for power generation, and the power is generated to charge the power storage device or to increase the power supplied to the motor generator for driving.

In a series hybrid vehicle, the power generation motor generator also serves to motor, or crank, the internal combustion engine in preparation for starting the stopped internal combustion engine. At the time of cranking, the necessary power is supplied from the power storage device.

Japanese Unexamined Patent Publication No. 2020-156134

Generally, the exhaust passage of an internal combustion engine is equipped with a three-way catalyst that oxidizes / reduces harmful substances HC, CO, and NO _x contained in the exhaust gas discharged from the cylinder to make them harmless.

When the operation of the internal combustion engine is stopped when the temperature of the catalyst is remarkably high, the exhaust gas does not flow through the catalyst, and the atmosphere inside the catalyst is excessive oxygen (air-fuel ratio lean), the catalyst deteriorates. In a conventional vehicle that is not a hybrid vehicle (runs by inputting the engine torque output by the internal combustion engine to the drive wheels), the internal combustion engine is always fired during its operation except for a short fuel cut and idle stop. It operates in a ring, and even if the catalyst is hot, exhaust gas close to the stoichiometric air-fuel ratio continues to circulate.

On the other hand, in a hybrid vehicle, the internal combustion engine is intermittently operated during its operation. In other words, while the total operating time of the internal combustion engine is reduced, the internal combustion engine is repeatedly restarted and stopped, so that the period during which the exhaust gas does not circulate while the catalyst is in a high temperature state is long. Become. As a result, the deterioration of the catalyst is faster and more advanced than that of the conventional vehicle.

The present invention has been made by paying attention to the above problems for the first time, and an object of the present invention is to suppress the progress of deterioration of a catalyst for purifying exhaust gas of an internal combustion engine mounted on a hybrid vehicle.

In the present invention, a hybrid vehicle equipped with an internal combustion engine and an electric motor as a power source is controlled, and when a predetermined condition capable of stopping the internal combustion engine that has been fired and operated is satisfied. A control device for a hybrid vehicle is configured in which the length of the period from the establishment of the condition to the actual stop of the internal combustion engine is changed according to the temperature of the catalyst for exhaust gas purification at that time.

According to the present invention, it is possible to suppress the progress of deterioration of the catalyst for purifying the exhaust gas of the internal combustion engine mounted on the hybrid vehicle.

The figure which shows the schematic structure of the series type hybrid vehicle and the control device in one Embodiment of this invention. The figure which shows the outline of the internal combustion engine mounted on the hybrid vehicle of the same embodiment. The timing diagram explaining the content of control by the control device of the same embodiment.

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of a main system of a hybrid vehicle according to the present embodiment. This hybrid vehicle includes an internal combustion engine 1, a power generation motor generator 2 driven by the internal combustion engine 1 to generate electricity, a power storage device 3 for storing the power generated by the power generation motor generator 2, a power generation motor generator 2 and /. Alternatively, it includes a traveling motor generator 4 that drives the drive wheels 62 of the vehicle by receiving electric power from the power storage device 3.

The hybrid vehicle of the present embodiment is a series hybrid type electric vehicle in which the internal combustion engine 1 is used only for power generation, and the driving force for traveling is supplied exclusively to the driving wheels 62 of the vehicle from the traveling motor generator 4. The internal combustion engine 1 and the drive wheel 62 are mechanically separated from each other, and the rotational driving force is not originally transmitted between the two. Therefore, the internal combustion engine 1 can rotate completely independently of the traveling motor generator 4 and the drive wheels 62, and can be stopped completely independently. Therefore, the power storage device 3 is sufficient even when the driver can drive the vehicle by depressing the accelerator pedal while the vehicle is operated with the ignition switch (power switch or ignition key) turned on. Under the condition that the charge is stored and the brake booster 15 stores a sufficient negative pressure, the operation of the internal combustion engine 1 accompanied by the combustion of fuel may not be carried out.

The crankshaft, which is the rotating shaft of the internal combustion engine 1, is mechanically connected to the rotating shaft of the power generation motor generator 2 via a gear mechanism. Then, by inputting the rotational driving force output by the internal combustion engine 1 to the power generation motor generator 2, the power generation motor generator 2 generates power. The generated electric power charges the power storage device 3 and / or supplies it to the traveling motor generator 4. Further, the power generation motor generator 2 also functions as a motoring motor that generates a rotational driving force by itself to rotationally drive the crankshaft of the internal combustion engine 1. For example, the power generation motor generator 2 executes cranking in preparation for starting the stopped internal combustion engine 1.

The traveling motor generator 4 generates a driving force for traveling the vehicle, and inputs the driving force to the drive wheels 62 via the speed reducer 61. Further, the traveling motor generator 4 is rotated by being rotated by the drive wheels 62 to generate electricity, and recovers the kinetic energy of the vehicle as electric energy. The electric power generated by this regenerative braking charges the power storage device 3.

However, if the charge is already stored up to the full capacity of the power storage device 3 and it is difficult to charge the battery any more, the traveling motor generator 4 dares to supply the regenerated electric power to the power generation motor generator 2 to generate electricity. The motor generator 2 is operated as an electric motor to rotate and drive the internal combustion engine 1. As a result, the surplus electric power is exhausted while maintaining the braking performance of the vehicle. Further, at this time, since the rotation of the internal combustion engine 1 is maintained, it is possible to execute a fuel cut that temporarily stops the fuel supply to the cylinder of the internal combustion engine 1.

The generator inverter 21 converts the AC power generated by the power generation motor generator 2 into DC power. Then, the DC power is input to the power storage device 3 or the drive unit inverter 41. Further, the generator inverter 21 converts the DC power supplied from the power storage device 3 and / or the drive inverter 41 into AC power when the power generation motor generator 2 is operated as an electric motor, and then the power generation motor generator 2. Enter in.

The drive inverter 41 converts the DC power supplied from the power storage device 3 and / or the generator inverter 21 into AC power, and then inputs the DC power to the traveling motor generator 4. Further, the drive inverter 41 converts the AC power generated by the traveling motor generator 4 into DC power when performing regenerative braking of the vehicle, and then inputs the AC power to the power storage device 3 or the generator inverter 21. The generator inverter 21 and the drive inverter 41 form a part of a PCU (Power Control Unit).

The power storage device 3 is a battery and / or a capacitor or the like. The battery is a high voltage secondary battery having a high energy density, such as a lithium ion secondary battery or a nickel hydrogen secondary battery. The power storage device 3 charges and stores the electric power generated by each of the power generation motor generator 2 and the traveling motor generator 4. Further, the power storage device 3 discharges electric power for operating each of the power generation motor generator 2 and the traveling motor generator 4 as an electric motor, and supplies the electric power required for the motor generators 2 and 4.

FIG. 2 shows an outline of the internal combustion engine 1 mounted on the hybrid vehicle of the present embodiment. The internal combustion engine 1 is a spark-ignition 4-stroke engine and includes a plurality of cylinders 11 (for example, three cylinders, one of which is shown in FIG. 1). An injector 111 that injects fuel toward the intake port is provided in the vicinity of the intake port of each cylinder 11. Further, a spark plug 112 is attached to the ceiling of the combustion chamber of each cylinder 11. The spark plug 112 induces a spark discharge between the center electrode and the ground electrode in response to the application of the induced voltage generated by the ignition coil.

The intake passage 13 for supplying intake air takes in air from the outside and guides it to the intake port of each cylinder 11. An air cleaner 131, an electronic throttle valve 132, a surge tank 133, and an intake manifold 134 are arranged in this order from the upstream on the intake passage 13. The air cleaner 131 is located at the most upstream position in the intake passage 13, that is, at the intake port for taking in air. The intake port is opened in front of the vehicle in order to take in cold air and improve the filling efficiency of the internal combustion engine.

The exhaust passage 14 for exhausting the exhaust guides the exhaust generated as a result of burning the fuel in the cylinder 11 to the outside from the exhaust port of each cylinder 11. An exhaust manifold 142 and a three-way catalyst 141 for exhaust purification are arranged on the exhaust passage 14.

The ECU (Electronic Control Unit) 0, which is a control device that controls the internal combustion engine 1, the power generation motor generator 2, the power storage device 3, the inverters 21, 41, and the traveling motor generator 4, is a processor, a memory, an input interface, an output interface, and the like. It is a microcomputer system having. The ECU 0 is a plurality of ECUs, that is, an EFI (Electronic Fuel Injection) ECU 01 that controls an internal combustion engine 1, a generator ECU 02 that controls a power generation motor generator 2 and a generator inverter 21, and a BMS (Battery Management) that controls a power storage device 3. System) ECU 03, drive motor ECU 04 that controls the drive motor generator 4 and drive inverter 41, and HV (Hybrid Battery) ECU 00, which is a higher-level controller that controls those controls, are CAN (Control Area Network) and the like. It is connected so that it can communicate with each other via the telecommunications line of.

For ECU 0, the vehicle speed signal a output from the vehicle speed sensor that detects the actual vehicle speed of the vehicle, the crank angle signal b output from the crank angle sensor that detects the rotation angle of the crank shaft of the internal combustion engine 1 and the engine rotation speed. , The accelerator opening signal output from the sensor that detects the amount of depression of the accelerator pedal by the driver as the accelerator opening (so to speak, the driving force required by the driver for the vehicle (driving motor generator 4)). c, a switch that detects that the driver is stepping on the brake pedal, a sensor that detects the amount of depression of the brake pedal by the driver, or a sensor that detects the master cylinder pressure, which is the pressure of the brake liquid discharged from the master cylinder 16. It is output from the brake depression signal d output from the temperature / pressure sensor that detects the intake air temperature and the intake air pressure in the intake passage 13 (particularly, the surge tank 133 or the intake manifold 134) connected to the cylinder 11 of the internal combustion engine 1. The intake air temperature / intake pressure signal e, the cooling water temperature signal f output from the water temperature sensor that detects the temperature of the cooling water of the internal combustion engine 1, and the sensor that detects the amount of charge stored in the power storage device 3 (particularly, the battery current and / Alternatively, the battery SOC (State Of Charge) signal g output from the battery voltage sensor), the negative pressure signal h output from the negative pressure sensor for detecting the negative pressure stored in the constant pressure chamber of the brake booster 15, and the like are input. ..

The ECU 0 is used for traveling according to the amount of depression of the accelerator pedal operated by the driver, the current vehicle speed, the amount of electric charge stored in the power storage device 3, and the like, which are sensed via various sensors. The magnitude of the rotational driving force output by the motor generator 4, the rotational driving force output by the internal combustion engine 1, and the electric charge generated by the power generation motor generator 2 is controlled to increase or decrease.

As a general rule, if the power storage device 3 currently stores sufficient electric charge and the output required for the traveling motor generator 4 is small, the supply of fuel to the internal combustion engine 1 is cut off and the internal combustion engine 1 is operated. do not. On the other hand, if the amount of charge stored in the power storage device 3 is below the threshold value or the output required for the traveling motor generator 4 is large, the internal combustion engine 1 is started to supply fuel to the cylinder 11. It executes firing to burn it, drives the generator motor generator 2 by the rotational driving force output from the internal combustion engine 1, generates electricity to charge the power storage device 3, or supplies it to the traveling motor generator 4. Increase power.

Incidentally, the EFI ECU 01, which forms a part of the ECU 0, acquires various information a, b, c, d, e, f, g, h necessary for the operation control of the internal combustion engine 1 via the input interface, and obtains the engine speed. And estimate the amount of air sucked into the cylinder 11. Then, the required fuel injection amount (necessary to realize the target air-fuel ratio), fuel injection timing (including the number of fuel injections for one combustion), fuel injection pressure, and ignition timing (once) corresponding to the intake air amount. The operating parameters of the internal combustion engine 1 such as the number of ignitions for combustion), the required EGR ratio (or the amount of EGR gas), and the like are determined. The EFI ECU 01 outputs various control signals i, j, k, l corresponding to the operation parameters to the igniter, injector 111, throttle valve 132, EGR valve 123, etc. of the spark plug 112 via the output interface.

As described above, when the electric charge of the power storage device 3 or more is already stored and / or the required driving force or the required output for the traveling motor generator 4 is lower than the threshold value, the rotation of the internal combustion engine 1 Can be stopped and the vehicle can be driven only by the traveling motor generator 4, or the vehicle can be stopped. When such a condition is satisfied, in the present embodiment, the internal combustion engine 1 may not always be stopped immediately and the operation of the internal combustion engine 1 may be continued for a certain period of time.

FIG. 3 shows the content of control of the internal combustion engine 1 by the ECU 0 of the present embodiment. In FIG. 3, the time point t ₀ is the time point when the condition for stopping the internal combustion engine 1 is satisfied. The broken line represents the control pattern when the temperature of the catalyst 141 at time point t ₀ is not significantly high. If the temperature of the current catalyst 141 is not high, deterioration of the catalyst 141 is unlikely to occur even if the internal combustion engine 1 is stopped immediately. Therefore, it is allowed to stop the internal combustion engine 1 immediately after the time point t ₀ .

On the other hand, the solid line in FIG. 3 shows the control pattern when the temperature of the catalyst 141 at the time point t ₀ is remarkably high. If the internal combustion engine 1 is stopped at this time, the exhaust gas does not flow through the catalyst 141, the temperature of the catalyst 141 does not easily drop and is kept at a high temperature, and the atmosphere inside the catalyst 141 becomes excessive in oxygen. , Deterioration of the catalyst 141 occurs. Therefore, the ECU ₀ of the present embodiment actually has an internal combustion engine from the time point t ₀ when the temperature of the catalyst 141 at the time point t ₀ is high and compared with the case where the temperature of the catalyst 141 at the time point t 0 is lower. The period until the point t ₁ at which 1 is stopped is extended.

ECU 0 iteratively estimates the current temperature of the current catalyst 141. As a method for estimating the temperature of the catalyst 141, a known method can be adopted. To give a specific example, regarding the temperature of the catalyst 141 during operation of the internal combustion engine 1, first, based on the operating region of the internal combustion engine [engine rotation speed, engine load factor (or opening degree of throttle valve 132)], The basic value of the temperature of the exhaust gas flowing into the catalyst 141 is obtained. Map data that defines the relationship between the operating area of the internal combustion engine and the basic value of the exhaust temperature is stored in the memory of the ECU 0 in advance. The ECU 0 searches the map using the parameter of the current operating area as a key, and obtains the basic value of the exhaust temperature.

Then, the basic value of the exhaust temperature is corrected according to the spark ignition timing at that time, the air-fuel ratio of the air-fuel mixture, the vehicle speed, and the like. The exhaust temperature rises as the ignition timing retards, decreases as the air-fuel ratio deviates from the stoichiometric air-fuel ratio, and increases as the vehicle speed increases (the flow rate of the running air blown into the engine room increases and the exhaust passage 14 becomes more air-cooled. (Because it is done) It will decrease.

Further, the estimated temperature of the catalyst 141 is calculated by taking into account the time required for the heat of the exhaust gas flowing into the catalyst 141 to be transferred to the catalyst 141 to raise the temperature of the catalyst 141. In addition, the estimated temperature may be corrected in consideration of the aging deterioration of the catalyst 141. Basically, the greater the degree of aging deterioration of the catalyst 141, the more the estimated temperature of the catalyst 141 is discounted.

Of course, in a system in which a sensor for detecting the temperature of the catalyst 141 is installed in the exhaust passage 14, it is possible to actually measure the current temperature of the catalyst 141 through the sensor.

During the delay period from the time t ₀ when the condition for stopping the internal combustion engine 1 is satisfied to the time t ₁ when the internal combustion engine 1 is actually stopped, the firing of the internal combustion engine 1 is continued, and the exhaust gas discharges the catalyst 141. It maintains the state of circulation and promotes the temperature drop of the catalyst 141. The air-fuel ratio of the air-fuel mixture and exhaust gas during the delay period is set to the stoichiometric air-fuel ratio or a target air-fuel ratio in the vicinity thereof (the fuel injection amount is adjusted accordingly). The engine speed during the delay period may be the same as the engine speed before the delay period, or may be lower than the engine speed before the delay period. The engine load factor (or the opening degree of the throttle valve 132) during the delay period may also be the same as the engine load factor before the delay period, or may be smaller than the engine load factor before the delay period. During the delay period, it is possible that the internal combustion engine 1 is operated in an idle operation or a region of low rotation and low load close to idle operation.

If it is considered that the temperature of the catalyst 141 has dropped below a certain value (for example, about 750 ° C.) throughout the delay period, the delay period is terminated, the firing of the internal combustion engine 1 is stopped, and the rotation of the internal combustion engine 1 is started. Stop it. After all, the time point t ₁ at which the internal combustion engine 1 is actually stopped changes depending on the temperature of the catalyst 141. If the temperature of the catalyst 141 is already equal to or lower than a certain value at the time point t ₀ , the internal combustion engine 1 may be stopped immediately, and in this case, the length of the delay period becomes substantially 0.

If the amount of electricity stored in the electricity storage device 3 decreases or the amount of depression of the accelerator pedal by the driver increases during the delay period, the power generation by the motor generator 2 for power generation is restarted. The operation is not stopped, and the firing is continued as it is to drive the motor generator 2 for power generation. In that case, the engine speed may be increased and / or the engine load factor may be increased as compared with the delay period.

In the present embodiment, when a predetermined condition that the internal combustion engine 1 that has been fired and operated can be stopped is satisfied, the condition is changed according to the temperature of the exhaust gas purification catalyst 141 at that time. The control device 0 of the hybrid vehicle that changes the length of the period from the establishment to the actual stop of the internal combustion engine 1 is configured.

According to the present embodiment, in the hybrid vehicle, the situation where the catalyst 141 has a remarkably high temperature, the exhaust gas does not flow through the catalyst 141, and the atmosphere in the catalyst 141 is excessive in oxygen continues. Can be avoided. As a result, the progress of deterioration of the catalyst 141 can be effectively suppressed, and the purification efficiency of harmful substances by the catalyst 141 can be maintained for a long period of time.

The present invention is not limited to the embodiment described in detail above. In the above embodiment, when the internal combustion engine 1 that has been fired and operated is stopped, the temperature value of the current catalyst 141 is specifically estimated or actually measured, and based on this, the internal combustion engine 1 is actually stopped. The length of the delay period was determined.

In addition to this, the temperature value of the catalyst 141 is not specifically estimated or actually measured, and the internal combustion engine 1 is actually stopped according to the operating region of the internal combustion engine 1 before the condition for stopping the internal combustion engine 1 is satisfied. The length of the delay period up to may be determined. For example, the demand for generated power from the power generation motor generator 2 or the demand for driving force from the traveling motor generator 4 is large, and the internal combustion engine 1 is operated with a high load at a certain engine speed or higher and / or at a certain engine load factor or higher. If so, it is conceivable to provide a longer delay period than otherwise. This is because it is presumed that the catalyst 141 inevitably has a significantly high temperature when the internal combustion engine 1 is operated under a high load before the stop condition is satisfied.

On the other hand, when the internal combustion engine 1 is not operated with such a high load, a shorter delay period is provided or the delay period is set to substantially 0, and the internal combustion engine 1 is stopped promptly. This is because it is presumed that the catalyst 141 is not so hot if the high load operation has not been performed before the condition for stopping the internal combustion engine 1 is satisfied.

Further, the object to which the present invention is applied is not limited to the series type hybrid vehicle.

In addition, the specific configuration of each part and the content of the processing can be variously modified without departing from the spirit of the present invention.

The present invention can be applied to the control of a hybrid vehicle.

0 ... Control unit (ECU)
1 ... Internal combustion engine 2 ... Generator, motoring motor (motor generator for power generation)
3 ... Power storage device 4 ... Driving motor (driving motor generator)
62 ... Drive wheels

Claims (1)

It controls a hybrid vehicle equipped with an internal combustion engine and an electric motor as a power source.
When a predetermined condition that can stop the internal combustion engine that has been fired and operated is satisfied, the internal combustion engine is actually operated from the condition that the condition is satisfied according to the temperature of the catalyst for exhaust gas purification at that time. A hybrid vehicle control device that changes the length of the period until it is stopped.

Images