JP2006132395A - Control method of hybrid vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology to perform a rich spike control without causing a torque shock. <P>SOLUTION: In a control method of a hybrid vehicle having a lean combustible internal combustion engine equipped with an NOx occlusion reduction catalyst to hold NOx and reduce the NOx in the exhaust gas corresponding to the exhaust gas air fuel ratio, and a motor, the torque output by the internal combustion engine and the torque output by the motor can be output from one output shaft at the same time. When performing the rich spike control to reduce the NOx held in the NOx occlusion reduction catalyst by temporarily making the exhaust gas air fuel ratio rich, a deviation in the driving torque of the hybrid vehicle from the target torque owing to that injected fuel is adhered to a wall surface is corrected by the torque the motor outputs. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a control method for a hybrid vehicle including an internal combustion engine having a NOx storage reduction catalyst.

  In recent years, hybrid vehicles have attracted attention from the viewpoint of low emissions and low fuel consumption. Among these types of hybrid vehicles, there are types that use both the output of the internal combustion engine and the motor as the driving force of the drive wheels. . In this type of hybrid vehicle, when traveling as the driving force of the drive wheels by combining the output of the internal combustion engine and the output of the motor, the total torque output by the two becomes the driver's required torque (target torque). It is necessary to control it.

In this connection, when the driver requests acceleration when the total torque output by both is controlled to the target torque, the internal combustion engine is compared with the response of the motor to the command value. In consideration of poor responsiveness, there is known a technique for controlling a motor so that a shortage of torque caused by a response delay of the internal combustion engine is supplemented by the torque of the motor (see, for example, Patent Documents 1 and 2).
Japanese Patent Laid-Open No. 10-23609 JP 2000-224711 A Japanese Patent No. 3286572 JP-A-11-107809 JP 2002-195064 A

  However, in Patent Documents 1 and 2, the reason why the response of the actual output torque of the internal combustion engine to the command value becomes worse is that the fuel injected from the fuel injection valve adheres to the wall surface of the intake port. Not considered. Therefore, even if the technique described in Patent Document 1 or 2 is used, the response of the output torque of the internal combustion engine further changes by the amount of fuel adhering to the wall surface of the intake port. It gives a sense of incongruity.

  Further, when the internal combustion engine used in the hybrid vehicle is an internal combustion engine capable of lean combustion, the following problems can be considered not only during acceleration but also during steady running.

That is, in the exhaust passage of a lean burnable internal combustion engine, NOx is maintained when the air-fuel ratio of the inflowing exhaust gas is lean in order to reduce nitrogen oxide (NOx) in the exhaust gas, When the air-fuel ratio becomes rich, there may be provided a NOx occlusion reduction type catalyst (hereinafter sometimes simply referred to as “NOx catalyst”) that releases the retained NOx and reduces it to N ₂ .

  In this NOx catalyst, before the NOx retention capacity is saturated, the air-fuel ratio of the exhaust gas (inflow exhaust gas) flowing into the NOx catalyst is made rich at a predetermined timing to release and reduce NOx retained in the NOx catalyst. It is necessary to restore the NOx retention ability of the NOx catalyst. Therefore, there is a case where rich spike control is executed in which the air-fuel ratio in the cylinder is temporarily changed to rich to temporarily change the air-fuel ratio of the inflowing exhaust gas to rich.

When this rich spike control is executed, there is a possibility that the fuel adheres to the wall surface of the intake port because a larger amount of fuel is injected than during lean combustion. In such a case, the response of the torque output from the internal combustion engine further changes, so that the total torque output from both the internal combustion engine and the motor deviates from the required torque (target torque), resulting in a torque shock. , Give the passengers a sense of incongruity.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a technique for executing rich spike control without causing torque shock.

  In order to achieve the above object, in the hybrid vehicle control method according to the present invention, the drive torque of the hybrid vehicle may shift from the target torque due to the injected fuel adhering to the wall surface. Is characterized by correcting with the torque output by the motor so that the deviation does not occur.

  More specifically, it has a lean combustion internal combustion engine that includes a NOx occlusion reduction type catalyst that holds NOx in exhaust gas or reduces the held NOx in accordance with the exhaust air-fuel ratio, and a motor. In the hybrid vehicle control method capable of simultaneously outputting the torque output from the internal combustion engine and the torque output from the motor from a single output shaft, the exhaust air-fuel ratio is temporarily made rich and the NOx occlusion reduction type catalyst is provided. When executing rich spike control to reduce the retained NOx, the difference between the driving torque of the hybrid vehicle and the target torque caused by the injected fuel adhering to the wall surface is corrected by the torque output by the motor. It is characterized by doing.

  The air-fuel ratio of the air-fuel mixture in the cylinder of the internal combustion engine performing the lean combustion operation is made rich in a short cycle, and the air-fuel ratio (exhaust air-fuel ratio) of the exhaust gas flowing into the NOx catalyst is temporarily made rich to make the NOx catalyst When rich spike control for reducing the retained NOx is executed, the air-fuel ratio of the air-fuel mixture in the cylinder becomes rich in a short cycle, and the torque of the internal combustion engine increases accordingly.

  When the rich torque control is executed when the total torque of the torque output from the internal combustion engine and the torque output from the motor is controlled to be the driver's required torque (target torque) as the driving torque of the hybrid vehicle, As the torque of the internal combustion engine increases, the driving torque of the hybrid vehicle increases from the target torque, and a torque shock occurs when the rich spike control is executed.

  In order to prevent such an adverse effect, the motor torque is decreased in synchronism with the increase in the torque of the internal combustion engine when the rich spike control is executed. However, after the start of rich spike control execution, the fuel is actually increased at the next fuel injection timing, and after the fuel is sucked into the cylinder, it is burned by ignition in the cylinder until the torque increases. There is a response delay. Therefore, it is necessary to reduce the torque of the motor so as to follow this response delay.

  Even if the motor torque is controlled to follow the response delay of the torque of the internal combustion engine in this way, if the injected fuel adheres to the wall surface of the intake port, the fuel adheres to the wall surface. Due to this, the following phenomenon may occur.

  In other words, the fuel that is originally sucked into the cylinder and burned adheres to the intake port and is not sucked into the cylinder, so the torque output from the internal combustion engine is reduced accordingly. Therefore, assuming that all the injected fuel is sucked into the cylinder and combusted, if the motor torque is reduced, the amount of fuel attached will increase the driving torque of the hybrid vehicle, which is the total torque of both. It will be less than the target torque.

  On the other hand, immediately after the rich spike control is performed, the fuel adhering to the wall surface of the intake port during the execution of the rich spike control may be vaporized and sucked into the cylinder during the lean combustion operation after the execution of the rich spike control. . In such a case, since the fuel that is not normally sucked into the cylinder is sucked into the cylinder, the torque output from the internal combustion engine increases accordingly. Therefore, if the motor torque is increased on the premise that the rich air-fuel ratio at the time of rich spike control completely returns to the lean air-fuel ratio at the time of lean combustion operation, the attached fuel will be delayed in the cylinder. As a result of the inhalation, the driving torque of the hybrid vehicle, which is the total torque of both, is increased from the target torque.

  In the hybrid vehicle control method according to the present invention, when the rich spike control is executed, the motor outputs the deviation between the drive torque of the hybrid vehicle and the target torque caused by the injected fuel adhering to the wall surface. Since the torque is corrected, the torque shock that occurs as described above can be prevented.

  Note that the difference between the driving torque of the hybrid vehicle and the target torque caused by the injected fuel adhering to the wall surface is caused by the fact that the injected fuel adheres to the wall surface and the torque of the internal combustion engine is output. Depends on the deviation to the required torque to do.

  This depends on the amount of fuel adhering to the wall surface, and the wall surface adhering amount correlates with the engine speed at the time of fuel injection, the torque of the internal combustion engine, or the coolant temperature. Therefore, the wall surface adhesion amount is estimated based on the engine speed, the internal combustion engine torque, or the coolant temperature, and the deviation between the internal combustion engine torque and the required torque is estimated based on the estimated wall surface adhesion amount. Then, by correcting the difference between the torque of the internal combustion engine and the required torque with the torque output by the motor, it is possible to prevent the drive torque of the hybrid vehicle from deviating from the target torque.

  Further, it is preferable to grasp the deviation between the driving torque of the hybrid vehicle and the target torque caused by the injected fuel adhering to the wall surface in consideration of the fuel properties. When the fuel used in the internal combustion engine is a heavy fuel, it has a property that it is less likely to volatilize than a normally used light fuel, so that the injected fuel is more likely to adhere to the intake port wall surface than the light fuel. Accordingly, the amount of wall surface adhesion is estimated in consideration of the fuel properties, and the difference between the torque of the internal combustion engine and the required torque is estimated based on the estimated wall surface adhesion amount, thereby driving the hybrid vehicle more accurately. It is possible to prevent the torque from deviating from the target torque.

  As described above, according to the present invention, rich spike control can be performed without causing a torque shock.

  The best mode for carrying out the present invention will be exemplarily described in detail below based on the following embodiments with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in the embodiments are not intended to limit the scope of the present invention only to those unless otherwise specified.

  FIG. 1 is a schematic configuration diagram of a hybrid vehicle 100 equipped with a hybrid system 1 according to the present embodiment. As shown in FIG. 1, the hybrid system 1 includes an internal combustion engine 2, a motor 3, a generator 4, a power split mechanism 5, a speed reducer 6, an inverter 7, a battery 8, an electronic control unit (ECU) 9, and the like as main components. Include as.

  The crankshaft 21 of the internal combustion engine 2, the rotating shaft 3 a of the motor 3, and the rotating shaft 4 a of the generator 4 are connected to each other via the power split mechanism 5. The power split mechanism 5 uses a known planetary gear (not shown) to transmit power (rotational force of the crankshaft 21) output from the internal combustion engine 2 to the rotary shaft 3a of the motor 3 and the rotary shaft 4a of the generator 4. Divide and transmit. Moreover, the rotating shaft 3a of the motor 3 and the crankshaft 21 can be appropriately connected or disconnected.

  The rotation shaft 3 a of the motor 3 is connected to the rotation shafts 10 a and 11 a of the drive wheels 10 and 11 via the speed reducer 6. Therefore, in a state where the rotating shaft 3a of the motor 3 and the crankshaft 21 are connected, the power output from the internal combustion engine 2 is transmitted as the rotational force of the drive wheels 10 and 11, and the generator 4 is driven to generate power. Is generated.

  The motor 3 receives power supplied from the battery 8 or the generator 4 and functions to apply rotational force to the drive wheels 10 and 11, and conversely applies rotational force from the drive wheels 10 and 11 and the internal combustion engine 2. As a result, the battery 8 may function to generate power and supply power for charging to the battery 8.

  Here, the internal combustion engine 2 is a four-stroke cycle reciprocating gasoline engine having a plurality of cylinders, and is a so-called lean burn engine that can be operated at a lean air-fuel ratio according to operating conditions.

  A schematic configuration of the internal combustion engine 2 will be described with reference to FIG. Each cylinder of the internal combustion engine 2 is loaded with a piston 22 slidable in the axial direction. The piston 22 is connected to the crankshaft 21 via a connecting rod 23. A combustion chamber 24 is formed above the piston 22, and open ends of an intake port 25 and an exhaust port 26 are formed in the combustion chamber 24. These open ends are attached to the internal combustion engine 2. They are opened and closed by an intake valve 27 and an exhaust valve 28, respectively.

  The intake port 25 communicates with the intake pipe 29, and the intake pipe 29 is connected to the air cleaner 30. The fuel injection valve 31 is attached to the cylinder head so that the injection hole faces the intake port 25. The intake pipe 29 is provided with a throttle valve 32 that opens and closes an intake passage in the intake pipe 29. An air-fuel mixture comprising fuel injected from the fuel injection valve 31 and air flowing through the intake passage is introduced into the combustion chamber 24 and ignited by a spark plug 33 attached to the cylinder head. On the other hand, the exhaust port 26 communicates with the exhaust pipe 34, and the exhaust pipe 34 is provided with an NOx storage reduction catalyst (hereinafter referred to as “NOx catalyst”) 35.

  The internal combustion engine 2 is provided with a known crank position sensor (not shown) and a water temperature sensor 36 that outputs an electric signal corresponding to the temperature of the cooling water.

  The ECU 9 provided in the hybrid vehicle 100 configured as described above includes a hybrid control computer (hereinafter referred to as “HVCC”) and an engine control computer (hereinafter referred to as “ECC”). These HVCC and ECC are arithmetic and logic circuits composed of a CPU, ROM, RAM, backup RAM, and the like.

Various sensors such as an accelerator position sensor (not shown) and a shift position sensor (not shown) attached to the hybrid vehicle 100 are connected to the HVCC via electric wiring, and output signals of the various sensors described above are input to the HVCC. It has come to be. The HVCC obtains a necessary internal combustion engine output based on detection values of various sensors and outputs a requested value to the ECC, and obtains a necessary torque to control the motor 3 and the generator 4. The ECU 9 obtaining the torque required for the motor 3 and controlling the torque of the motor 3 in this way is referred to as executing the prescribed motor torque control.

  In the hybrid system 1, the power (torque) generated by the internal combustion engine 2 and the motor 3 is appropriately used based on the control executed by the ECU 9 and transmitted to the drive wheels 10 and 11 of the vehicle. The battery 8 is charged by converting the driving force and the energy generated with the deceleration of the vehicle into electric power.

Hereinafter, the operation of the hybrid system 1 will be described with specific examples.
FIG. 3 shows how the power generated by the internal combustion engine 2 and the motor 3 and the power stored in the battery 8 are utilized according to the operating conditions of the hybrid system 1, focusing on the power and power transmission path. It is a schematic diagram demonstrated to. In each of FIGS. 3 (a), 3 (b), and 3 (c), a solid arrow indicates a power transmission path, and a broken arrow indicates a power transmission path.

(1) At system startup When the hybrid system 1 is started, the internal combustion engine 2 is started to warm up. At this time, a part of the energy generated by the internal combustion engine 2 is converted into electric power through the generator 4 and stored in the battery 8 (FIG. 3A). When the temperature of the cooling water of the internal combustion engine 2 exceeds a predetermined value (when the warm-up is completed), the operation of the internal combustion engine 2 is stopped. The internal combustion engine 2 is started when the generator 4 cranks the internal combustion engine 2 using the power of the battery 8.

(2) Start / light load driving When the hybrid vehicle 100 starts or runs at a low speed, the power generated by the motor 3 is preferentially used under conditions where the thermal efficiency of the internal combustion engine 2 is low. Then, the vehicle (drive wheels 10 and 11) is driven (FIG. 3B).

(3) During steady running In an operating region where the internal combustion engine 2 has good engine efficiency, the vehicle travels mainly using power generated by the internal combustion engine 2. In such a case, the power generated by the internal combustion engine 2 is divided into an appropriate ratio by the power split mechanism 5 so that the power generated by the internal combustion engine 2 and the power generated by the motor 3 cooperate at an optimum ratio. Then, control is performed so as to drive the vehicle (drive wheels 10 and 11) (FIG. 3C).

  On the other hand, various sensors such as a crank position sensor and a water temperature sensor 36 are connected to the ECC via electric wiring, and output signals of the various sensors are input to the ECC. Further, the fuel injection valve 31 and the spark plug 33 are connected to the ECC via electric wiring, and the operation state of the internal combustion engine 2 is determined from output signals from various sensors, and then the required value output from the HVCC is obtained. In order to respond, the fuel injection valve 31, the spark plug 33, and the like are controlled according to the determined operating state.

  For example, the ECC performs input of output signals of various sensors such as a crank position sensor and a water temperature sensor 36, calculation of the engine speed, etc. in a basic routine to be executed at regular intervals, and requests for output of an internal combustion engine from the HVCC. Calculation of the fuel injection amount and calculation of the fuel injection timing are executed according to the values. On the other hand, the HVCC calculates a torque Te output from the internal combustion engine based on a torque command value to the generator 4 in a basic routine to be executed at regular intervals. Various signals input by ECC or HVCC in the basic routine and various control values obtained by calculating ECC or HVCC are temporarily stored in the ECC or HVCC RAM.

  The ECC reads various control values from the RAM in the interrupt processing triggered by the input of signals from various sensors and switches, the passage of a fixed time, or the input of a pulse signal from the crank position sensor. According to the values, control command values are output to the fuel injection valve 31, the spark plug 33, etc., and these are controlled.

  Here, when the air-fuel ratio of the exhaust gas flowing into the catalyst is a lean air-fuel ratio, the NOx catalyst 35 according to the present embodiment holds NOx in the exhaust gas so as not to be released into the atmosphere. When the air-fuel ratio of the exhaust gas flowing into the gas reaches the stoichiometric air-fuel ratio or the rich air-fuel ratio, the retained NOx is released and reduced.

  Therefore, when the internal combustion engine 2 is operated at a lean air-fuel ratio, that is, a lean combustion operation, the air-fuel ratio of the exhaust gas discharged from the internal combustion engine 2 becomes a lean air-fuel ratio, and NOx contained in the exhaust gas is reduced. The NOx catalyst 35 is held. When the lean combustion operation of the internal combustion engine 2 is continued for a long period of time, the NOx retention ability of the NOx catalyst 35 is saturated, and NOx in the exhaust gas is released into the atmosphere without being purified by the NOx catalyst 35. .

  Therefore, when the internal combustion engine 2 is in lean burn operation, the air-fuel ratio of the exhaust gas flowing into the NOx catalyst 35 is made rich and held in the NOx catalyst 35 before the NOx retention capacity of the NOx catalyst 35 is saturated. The released NOx needs to be released and reduced. Therefore, in the present embodiment, the ECC controls the amount of fuel injected from the fuel injection valve 31 to operate in a rich air-fuel ratio in a spiked (short time) manner in a relatively short cycle and flows into the NOx catalyst 35. Rich spike control is performed in which the air-fuel ratio of the exhaust gas to be made is changed to a rich air-fuel ratio in a spike manner.

  Further, when the rich spike control is executed in this way, the air-fuel ratio of the air-fuel mixture in the cylinder becomes rich in a short cycle, so that the torque of the internal combustion engine increases accordingly. When the rich spike control is executed during steady running where the total torque of the torque output from the internal combustion engine and the torque output from the motor is controlled so as to be the driver's required torque (target torque), As the torque increases, the driving torque of the hybrid vehicle increases from the target torque, and a torque shock occurs due to the execution of the rich spike control, giving the passenger an uncomfortable feeling.

  In order to prevent such an adverse effect, in the above-described specified motor torque control, the torque of the motor is decreased in synchronization with the increase of the torque of the internal combustion engine when the rich spike control is executed.

  However, when the rich spike control is executed, the fuel is actually increased at the next fuel injection timing after the start of the rich spike control execution, and the fuel is sucked into the cylinder and then burned by ignition in the cylinder. Until the torque increases, there is a response delay as shown in FIG. Therefore, in the specified motor torque control, the motor torque is reduced so as to follow this response delay.

  That is, the value of the motor torque is changed so as to decrease the torque corresponding to the torque of the internal combustion engine that increases in accordance with the amount of fuel increased in executing the rich spike control. At that time, the time when the torque of the internal combustion engine actually increases is matched with the time when the motor torque is decreased. The magnitude of the torque of the internal combustion engine that increases as the rich spike control is executed can be calculated based on the fuel injection amount. Further, the time when the torque of the internal combustion engine increases has a correlation with the elapsed time from the fuel injection start time, and the elapsed time changes according to the engine speed (the higher the engine speed, the faster). A map that changes according to the engine speed can be created in advance, and the map can be derived by substituting the engine speed at the time of rich spike control into the map.

  However, even if the specified motor torque control is performed in consideration of the torque fluctuation during the rich spike control, the following phenomenon may occur.

  That is, in order to change the air-fuel ratio in the cylinder from the lean air-fuel ratio during the lean combustion operation to the rich air-fuel ratio, the amount of fuel injected from the fuel injection valve 31 increases, so that the injected fuel is difficult to vaporize. And / or it becomes difficult to be sucked into the cylinder, and there is a possibility of adhering to the wall surface of the intake port. In such a case, the fuel that is originally sucked into the cylinder and combusted adheres to the intake port and is not sucked into the cylinder. Therefore, the torque output from the internal combustion engine is reduced accordingly. Therefore, if the motor torque is reduced on the premise that all the injected fuel is sucked into the cylinder and burned, the total torque of both will decrease from the target torque as much as the fuel has adhered. As a result, a torque shock occurs, and the passenger feels uncomfortable (see FIG. 4A).

  On the other hand, immediately after the rich spike control is performed, the fuel adhering to the wall surface of the intake port during the execution of the rich spike control may be vaporized and sucked into the cylinder during the lean combustion operation after the execution of the rich spike control. . In such a case, since the fuel that is not normally sucked into the cylinder is sucked into the cylinder, the torque output from the internal combustion engine increases accordingly. Therefore, if the motor torque is increased on the premise that the rich air-fuel ratio at the time of rich spike control completely returns to the lean air-fuel ratio at the time of lean combustion operation, the attached fuel will be delayed in the cylinder. As a result of the inhalation, the total torque of the two increases beyond the target torque, causing a torque shock and giving the passenger a sense of incongruity (see FIG. 4A).

  In this embodiment, therefore, the amount of fuel adhering to the wall surface of the intake port (hereinafter also referred to as “wall surface adhering amount”) during execution of rich spike control is estimated, and the motor controlled by the prescribed motor torque control. Motor torque correction control is performed to correct the torque according to the amount of adhesion on the wall surface.

  When this motor torque correction control is outlined, the wall surface adhesion amount changes in accordance with the operating state of the internal combustion engine. Therefore, first, the wall surface adhesion amount is estimated from the operating state of the internal combustion engine when the rich spike control is executed. Thereafter, a change (increase / decrease) amount with respect to the fuel amount that should be sucked into the cylinder of the internal combustion engine is estimated based on the estimated wall surface adhesion amount, and a motor based on the prescribed motor torque control is estimated based on the estimated intake fuel change amount. A coefficient for correcting the torque (motor torque correction coefficient) is calculated, and based on the motor torque correction coefficient, the torque of the motor during the specified motor torque control is corrected.

  Hereinafter, the motor torque correction control according to the present embodiment will be specifically described with reference to the flowchart shown in FIG. This control routine is a routine that is stored in advance in the ROM of the ECU 9 (HVCC), and is a routine that is executed by the ECU 9 as an interrupt process triggered by elapse of a fixed time or input of a pulse signal from the crank position sensor. is there.

  In this routine, first, in step (hereinafter, simply referred to as “S”) 101, the engine speed Ne, the torque Te of the internal combustion engine, the coolant temperature THW, etc. stored in the RAM in the basic routine as described above. Read.

  Thereafter, the process proceeds to S102, and in this step, it is determined whether or not rich spike control is being executed. If a positive determination is made, the process proceeds to S103, and if a negative determination is made, the process proceeds to S107.

  In S103, the wall surface adhesion amount at the next fuel injection is estimated based on the value read in S101. In addition, the following methods can be illustrated as a method of estimating a wall surface adhesion amount.

  The lower the engine speed, the smaller the negative pressure in the cylinder and the more difficult it is for the injected fuel to be sucked into the cylinder and the greater the amount of wall surface adhesion. The relationship can be estimated by deriving these relationships beforehand through experiments and creating a map and substituting the engine speed read in S101 for the map.

  In addition, the lower the internal combustion engine torque, the smaller the intake air amount and the less the injected fuel is carried into the cylinder and the greater the wall surface adhesion amount. Therefore, it is possible to estimate these relationships by deriving them in advance through experiments or the like, creating a map, and substituting the engine speed read in S101 into the map.

  In addition, the lower the cooling water temperature is, the more difficult it is to vaporize the injected fuel and the greater the amount of wall surface adhesion.For example, there is a correlation between the cooling water temperature and the wall surface adhesion amount. It can be estimated by creating a map and substituting the engine speed read in S101 for the map.

  Alternatively, a correlation between the engine speed, at least two of the internal combustion engine torque and the coolant temperature, and the amount of wall surface adhesion is derived in advance by experiments or the like to create a map, and the engine speed read in S101 into the map By substituting a number or the like, it can be estimated more accurately.

  In S104, the amount of fuel that changes with respect to the amount of fuel originally taken into the cylinder (hereinafter sometimes referred to as “intake fuel change amount”) is estimated. That is, the difference between the amount of fuel injected for the next combustion (injection command value) and the amount of fuel actually sucked into the cylinder is estimated.

  Specifically, when the process proceeds to S104 after the execution of the process of S103 immediately after the start of the rich spike control execution, even if more fuel is injected than in the lean combustion operation in order to obtain a rich air-fuel ratio, the estimation is made in S103. Since the amount of fuel sucked into the cylinder is reduced by the amount of wall adhesion, the amount of intake fuel change is estimated to decrease by the amount of wall adhesion estimated in S103 in S104. That is, in such a case, the intake fuel change amount becomes a negative value.

  On the other hand, during the subsequent rich spike control, the injected fuel may adhere to the intake port wall surface, while the fuel adhering to the intake port wall surface during the previous injection vaporizes and enters the cylinder. May be inhaled. Therefore, in S104, the amount of change in intake fuel is reduced by the amount of wall surface adhesion estimated in S103, and the fuel adhering to the wall surface during the previous injection is vaporized at the next combustion and sucked into the cylinder. It is estimated that it will increase by the amount of fuel used. In other words, the amount of change in the intake fuel in this case is the amount of fuel adhering to the wall surface at the time of the next combustion with the fuel adhering to the wall surface during the previous injection rather than the amount of wall surface adhesion estimated in S103. If the amount is small, it is a negative value, if it is large, it is a positive value, and if it is the same, it is zero.

It should be noted that the amount of fuel vaporized during the next combustion and sucked into the cylinder by the fuel adhering to the wall surface at the time of the previous injection is the integrated value of the amount of wall surface adhesion so far, the engine speed, the internal combustion engine The map can be calculated by deriving the correlation with the torque or the coolant temperature or the like in advance through experiments or the like and substituting the values obtained in S101 and S103 into the map. In a simplified manner, all the fuel adhering to the intake port wall surface during the previous injection is vaporized and can be taken into the cylinder during the next combustion. In such a case, the amount of fuel vaporized at the next combustion and sucked into the cylinder by the fuel adhering to the wall surface at the time of the previous injection described above is estimated by the processing of S103 of the previous flow. It becomes the amount of adhesion.

  In S105, a motor torque correction coefficient Km is calculated based on the intake fuel change amount estimated in S104. Thereafter, the process proceeds to S106, and the motor torque calculated in S105 is added to the motor torque Tm when the specified motor torque control is executed. A motor torque Tm obtained by multiplying the correction coefficient Km is set as a new motor torque Tm at the time of executing the specified motor torque control.

  Note that the torque of the internal combustion engine changes with respect to the torque assumed in advance according to the intake fuel change amount. Further, the motor torque is changed with respect to the specified motor torque control as the torque of the internal combustion engine changes with respect to the torque assumed in advance. Thus, since there is a correlation between the intake fuel change amount and the change (correction) amount with respect to the motor torque (value before correction) at the time of the specified motor torque control, these relationships are derived in advance through experiments or the like. Based on this relationship, the relationship between the intake fuel change amount and the motor torque correction coefficient Km is derived in advance through experiments or the like to create a map. In S105, the motor torque correction coefficient Km is calculated by substituting the intake fuel change amount estimated in S104 into the map.

  The motor calculated in S105 is increased as the intake fuel change amount is negative, so that the motor torque calculated in S106 is larger than that during the prescribed motor torque control as the intake fuel change amount is negative. The torque correction coefficient Km is greatly calculated. On the other hand, the larger the intake fuel change amount is on the plus side, the smaller the motor torque calculated in S106 is compared to the prescribed motor torque control time. The torque correction coefficient Km is calculated to be small. When the intake fuel change amount is zero, the motor torque correction coefficient Km is 1 because it is not necessary to change the motor torque with respect to the specified motor torque control.

  If a negative determination is made in S102, the process proceeds to S107. In this step, it is determined whether or not a reference time has elapsed after the execution of the rich spike control. As described above, immediately after the rich spike control is executed, the fuel adhering to the intake port wall surface during the rich spike control is vaporized and sucked into the cylinder during the lean combustion operation after the rich spike control is executed. There is a risk that torque of the internal combustion engine will increase and torque shock will occur. Therefore, if a negative determination is made in this step, the processing of S104 and subsequent steps is executed, and the internal combustion engine that increases due to the fact that the fuel adhering to the wall surface of the intake port is sucked into the cylinder with a delay. The torque of the motor is decreased so as to follow the torque.

  Note that the reference time is an example of the maximum time during which the fuel adhering to the wall surface of the intake port during the rich spike control may be vaporized with a delay and be sucked into the cylinder. Can do. In such a case, the reference time changes according to the engine speed, the torque of the internal combustion engine, the cooling water temperature, or the like. Therefore, it is preferable to change the reference time based on these values at the end of execution of the rich spike control. It is.

  On the other hand, if an affirmative determination is made in S107, it is not necessary to correct the motor torque during the specified motor torque control, and therefore the motor torque correction coefficient Km is calculated as 1.

By executing such motor torque correction control, for example, immediately after the start of rich spike control execution, the wall surface adhesion amount estimated in S103 increases to change from the lean air-fuel ratio at the time of lean combustion to the rich air-fuel ratio. If the amount of fuel is about half the amount of fuel that has been changed, the amount of fuel that is about half of the amount of fuel that has been increased to change from the lean air-fuel ratio to the rich air-fuel ratio is decreased as the intake fuel change amount in S104 It is estimated that Accordingly, in S105, the motor torque correction coefficient Km is calculated as 1.2, for example. Then, in S106, the motor torque is calculated as 1.2 times the motor torque Tm at the time of the prescribed motor torque control, and the motor 3 is controlled to be the torque (Tm × 1.2) ( (Refer FIG.4 (b)).

  Then, during execution of rich spike control thereafter, the same amount of fuel attached to the wall surface adheres to the wall surface, and all the fuel attached to the wall surface during the previous injection is vaporized and sucked into the cylinder at the next combustion. In this case, the intake fuel change amount estimated in S104 is zero. Then, in S105, the motor torque correction coefficient Km is calculated as 1, and in S106, the motor torque is calculated as the same value as the motor torque Tm at the time of the prescribed motor torque control so that the torque (Tm × 1) is obtained. The motor 3 is controlled (see FIG. 4B).

  In such a case, immediately after the end of the rich spike control, the wall surface adhesion amount is zero, but all the fuel adhering to the wall surface during the previous injection is vaporized and taken into the cylinder at the next combustion, so a negative determination is made in S107 In step S104, the amount of intake fuel change is increased by about half of the amount of fuel that has been increased with respect to the injected fuel amount of the lean air-fuel ratio at the time of lean combustion in order to maintain the rich air-fuel ratio. It is estimated that Accordingly, in S105, the motor torque correction coefficient Km is calculated as 0.8, for example. Then, in S106, the motor torque is calculated as 0.8 times the motor torque Tm at the time of the prescribed motor torque control, and the motor 3 is controlled to be the torque (Tm × 0.8) ( (Refer FIG.4 (b)).

  By executing such motor torque correction control, control is performed so that the total torque of the internal combustion engine torque and motor torque becomes the required (target) torque even if fuel adheres to the intake port wall surface during rich spike control. Therefore, it is possible to prevent a torque shock from being generated due to the execution of the rich spike control, and to prevent the occupant of the hybrid vehicle from feeling uncomfortable.

  In this motor torque correction control, the torque output from the internal combustion engine is estimated in a certain sense by estimating the wall surface adhesion amount and the intake fuel change amount. There is a risk of deviation from the actual value due to variations in engine differences and changes over time.

  Therefore, it is preferable to detect the actual torque of the internal combustion engine and learn the motor torque correction amount (motor torque correction coefficient Km) based on the detected torque of the internal combustion engine. Since the torque of the internal combustion engine can be detected via the generator 4 as described above, the difference between the estimated torque of the internal combustion engine and the detected torque of the internal combustion engine is derived to obtain the correction amount of the motor torque. learn. Then, the driving torque of the hybrid vehicle can be controlled more accurately by controlling the motor torque according to the learned correction amount.

  Further, as described above, when the rich spike control is executed, the motor torque is controlled so that the time when the torque of the internal combustion engine actually increases and the time when the motor torque is decreased are matched. There is a risk that the time will be shifted due to such reasons.

Therefore, it is preferable to learn the time when the torque of the internal combustion engine actually increases after the execution of the rich spike control, and to control the motor torque to decrease at the learned time. Since the increase in the torque of the internal combustion engine accompanying the rich spike control can be detected via the generator 4, as a method of learning the time when the torque of the internal combustion engine actually increases after the start of the rich spike control execution, It can be exemplified by calculating and learning the time from fuel injection (rising of the injection signal) until the generator 4 detects that the torque of the internal combustion engine has actually increased.

  As described above, after the start of rich spike control execution, the time when the torque of the internal combustion engine actually increases is learned, and the motor torque is controlled based on the learned time, thereby controlling the driving torque of the hybrid vehicle more accurately. can do.

  In the present embodiment, the torque of the motor is controlled in consideration of the fuel property as compared with the first embodiment.

  An internal combustion engine does not necessarily use a fuel having a certain property, but may use a heavy fuel having a property that is less likely to volatilize than a normally used light fuel. Since the heavy fuel is less likely to volatilize, the injected fuel is more likely to adhere to the intake port wall surface than the light fuel. Therefore, in this embodiment, the fuel properties are determined in a basic routine that is periodically executed, and the motor torque is controlled in consideration of the determined fuel properties.

  As a method for determining the properties of the fuel to be used, a well-known method for determining based on fluctuations in engine speed in a transient state, or a method for determining based on the difference in engine speed before and after the change of the fuel injection timing Etc. can be illustrated.

  The motor torque correction control according to the present embodiment can be executed by basically using the same control routine as the control routine according to the first embodiment shown in FIG. 5 as the control routine. In addition to the matters described in the item 1 above, the amount of wall surface adhesion is estimated in consideration of the fuel properties.

  Specifically, when the fuel property determined in the basic routine is heavy fuel, the fuel property and the wall surface adhesion amount increase so that the fuel is less likely to vaporize than the light fuel and the wall surface adhesion amount increases. Therefore, it is possible to estimate the adhesion amount on the wall surface by deriving these relationships through experiments and the like in advance and creating a map and substituting the fuel properties determined by the basic routine into the map. it can.

  In addition, a correlation between fuel properties, at least one of the engine speed, the torque of the internal combustion engine and the coolant temperature, and the amount of wall surface deposition is derived in advance through experiments or the like, and a map is created. By substituting the determined fuel properties and the like, it can be estimated more accurately.

  In this way, by controlling the motor torque in consideration of the fuel properties, even if fuel adheres to the intake port wall surface during rich spike control, the total torque of the internal combustion engine torque and the motor torque is required (target). Since the torque is controlled to become torque, it is possible to prevent a torque shock from occurring during the rich spike control.

1 is a diagram illustrating a schematic configuration of a hybrid vehicle according to a first embodiment. 1 is a diagram illustrating a schematic configuration of an internal combustion engine according to a first embodiment. 1 is a schematic diagram illustrating a transmission path of power and electric power of a hybrid system in a hybrid vehicle according to a first embodiment. It is a time chart which shows the fluctuation | variation of the torque at the time of rich spike control execution. It is a flowchart of the control routine of motor torque correction control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hybrid system 2 Internal combustion engine 3 Motor 4 Generator 5 Power split mechanism 6 Reducer 7 Inverter 8 Battery 9 ECU
31 Fuel Injection Valve 33 Spark Plug 36 Water Temperature Sensor

Claims (2)

An internal combustion engine having a NOx occlusion reduction catalyst capable of holding NOx in exhaust gas or reducing the held NOx in accordance with the exhaust air-fuel ratio, and a motor capable of lean combustion, and the output of the internal combustion engine In a hybrid vehicle control method capable of simultaneously outputting torque to be output and torque output from the motor from one output shaft,
Driving the hybrid vehicle caused by the injected fuel adhering to the wall surface during execution of rich spike control in which the exhaust air-fuel ratio is temporarily rich to reduce NOx held in the NOx occlusion reduction type catalyst. A hybrid vehicle control method, wherein a deviation between a torque and a target torque is corrected by a torque output from the motor.   2. The hybrid vehicle control according to claim 1, wherein a shift between a driving torque of the hybrid vehicle and a target torque caused by the injected fuel adhering to the wall surface is grasped in consideration of fuel properties. Method.

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