JP2006177307A - Internal combustion engine control device for hybrid vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology capable of preventing lowering of driving force in a reverse direction caused by performing rich spike control when reversing. <P>SOLUTION: An internal combustion engine control device is provided for a hybrid vehicle having an internal combustion engine capable of lean combustion and comprising an NOx storage reduction catalyst which holds NOx in exhaust gas when an exhaust air-fuel ratio is lean, and reduces and eliminates the held NOx when the exhaust air-fuel ratio is a stoichiometric air-fuel ratio or rich. When the shift position of the hybrid vehicle is a reverse position, the execution of rich spike control of temporarily enriching the exhaust air-fuel ratio to reduce NOx held in the NOx storage reduction catalyst is forbidden. Alternatively, in the case of the reverse position, lean combustion operation is forbidden. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hybrid vehicle having an NOx storage reduction catalyst and having an internal combustion engine capable of lean combustion.

  One of the means for reducing nitrogen oxides (NOx) in exhaust gas discharged from a lean burnable internal combustion engine (engine) is a NOx occlusion reduction type catalyst (hereinafter simply referred to as “NOx catalyst”) in the exhaust passage. Is also known to have.

This NOx catalyst is a catalyst that holds NOx when the air-fuel ratio (exhaust air-fuel ratio) of the exhaust gas flowing into the catalyst is lean, releases the held NOx when the exhaust air-fuel ratio becomes rich, and reduces it to N ₂ It is. In this NOx catalyst, before the NOx retention capacity is saturated, the air-fuel ratio of the inflowing exhaust gas is made rich at a predetermined timing, and the NOx retained in the NOx catalyst is released and reduced to remove the NOx catalyst. It is necessary to restore the NOx retention ability of the.

  As a technique for making the exhaust air-fuel ratio rich, it has been proposed to execute rich spike control that temporarily changes the air-fuel ratio in the cylinder to rich to temporarily change the exhaust air-fuel ratio to rich.

However, by executing the rich spike control, the output torque of the engine increases and the torque fluctuation increases. On the other hand, in a hybrid vehicle, by generating a regenerative braking force in the motor in accordance with the timing of rich spike control, the increase in engine output torque is mitigated by the regenerative braking force of the motor to mitigate torque fluctuations. Has been proposed (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 11-62653 JP 2002-195064 A Japanese Patent Laid-Open No. 2000-104591 JP-A-11-223120

  On the other hand, a hybrid vehicle has an internal combustion engine (engine), a motor, and a generator (generator). The engine power is divided by a power split mechanism composed of planetary gears, on the one hand, directly driving the wheels, and the other generating power. Some have so-called parallel series hybrid systems that can be used. When such a hybrid vehicle moves backward (reverse running), it moves backward only with the driving force of the motor. Since the engine power acts in a direction that weakens the driving force in the reverse direction, the engine is brought into a stopped state or an idle operation state when the vehicle moves backward. However, when the SOC is low and the battery charge state is not good, power is generated by transmitting engine power to the generator via the power split mechanism, and the motor travels with the power.

  Therefore, if the rich spike control is executed during reverse drive and when the engine power is generated using the engine power when the engine is idling or when the SOC is lowered, the output torque of the engine increases and the reverse drive direction increases. The driving force is reduced. In particular, when driving backward and climbing a hill or when trying to climb, if the driving force in the backward direction decreases due to execution of rich spike control, the vehicle may slide down .

  The present invention has been made in view of the above-described problems, and an object of the present invention is to prevent the driving force in the reverse direction from being reduced due to the execution of the rich spike control during the reverse movement. It is to provide the technology that can.

  In order to achieve the above object, in the internal combustion engine control device for a hybrid vehicle according to the present invention, when the exhaust air-fuel ratio is lean, NOx in the exhaust gas is maintained, and the exhaust air-fuel ratio is the stoichiometric air-fuel ratio or rich. When the shift position of the hybrid vehicle is a reverse drive position in an internal combustion engine control device for a hybrid vehicle having an NOx occlusion reduction type catalyst that reduces and removes the retained NOx and has a lean burnable internal combustion engine The exhaust air-fuel ratio is temporarily made rich, and the execution of rich spike control for reducing NOx held in the NOx occlusion reduction type catalyst is prohibited.

  Execute rich spike control to reduce the NOx stored in the NOx storage reduction catalyst by temporarily changing the exhaust air / fuel ratio to rich by temporarily changing the air / fuel ratio in the cylinder to rich from the lean combustion state. Then, the output torque of the internal combustion engine increases.

  On the other hand, it has an internal combustion engine (engine), a motor, and a generator, and the engine power is divided by a power split mechanism consisting of planetary gears, and on the other hand, a so-called parallel series hybrid system that can directly drive wheels and use the other for power generation In a hybrid vehicle, the vehicle moves backward only with the driving force of the motor when moving backward. In such a system, the engine power acts in a direction that weakens the driving force in the reverse direction, so that the internal combustion engine is in a stopped state or an idle operation state when moving backward. However, when the SOC is low and the battery charge state is not good, power is generated by transmitting engine power to the generator via the power split mechanism, and the motor travels with the power.

  Therefore, if the rich spike control is executed during reverse drive and when the engine power is being generated during engine idle operation or when the SOC is reduced, the output torque of the internal combustion engine increases, and the reverse drive direction. The driving force will decrease. In particular, when driving backward and climbing a slope, or when trying to climb, if the driving force in the backward direction decreases due to the execution of rich spike control, the vehicle may slide down. is there.

  On the other hand, in the internal combustion engine control device for a hybrid vehicle according to the present invention, when the shift position of the hybrid vehicle is the reverse position, execution of rich spike control is prohibited, so that the driving force in the reverse direction is reduced. Can be prevented. Therefore, it is possible to prevent the vehicle from sliding down even when the vehicle is going backward and climbing a hill or trying to climb.

  In the internal combustion engine control apparatus for a hybrid vehicle according to the present invention, the NOx in the exhaust gas is held when the exhaust air-fuel ratio is lean, and the NOx held when the exhaust air-fuel ratio is rich or stoichiometric. In an internal combustion engine control apparatus for a hybrid vehicle having an internal combustion engine capable of lean combustion that includes a NOx occlusion reduction type catalyst that reduces and removes the lean combustion operation when the shift position of the hybrid vehicle is a reverse position It is characterized by doing.

When the exhaust air-fuel ratio flowing into the catalyst is lean, the NOx occlusion reduction type catalyst keeps NOx in the exhaust gas so as not to be released into the atmosphere, and the exhaust air-fuel ratio flowing into the catalyst is the stoichiometric air-fuel ratio. Or when it becomes rich, the held NOx is released and reduced. Therefore, even when the NOx retention amount of the NOx storage reduction catalyst increases and it is necessary to execute rich spike control, if the shift position is the reverse position, the lean combustion operation is prohibited and the stoichiometric air-fuel ratio or rich By operating at an air-fuel ratio and setting the exhaust air-fuel ratio to a stoichiometric air-fuel ratio or rich, the amount of NOx retained in the NOx storage reduction catalyst can be reduced, so that it is not necessary to execute rich spike control. Can do.

  As a result, it is possible to prevent the drive force in the reverse direction from being reduced due to the execution of the rich spike control during reverse travel. Therefore, it is possible to prevent the vehicle from sliding down even when the vehicle is going backward and climbing a hill or trying to climb.

  As described above, according to the present invention, it is possible to prevent the driving force in the backward direction from being reduced due to the execution of the rich spike control during the backward movement.

  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, a hybrid system 1 includes an engine (internal combustion engine) 2, a motor 3, a generator (generator) 4, a power split mechanism 5, a speed reducer 6, an inverter 7, a battery 8, and an electronic control unit (ECU). 9 etc. are included as main components.

  The crankshaft 21 of the 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 divides the power from the engine 2 (rotational force of the crankshaft 21) into the rotary shaft 3a of the motor 3 and the rotary shaft 4a of the generator 4 using a known planetary gear (planetary gear). Then communicate. 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 engine 2 (engine power) is transmitted as the rotational force of the drive wheels 10 and 11, and the generator 4 is Drive to generate power.

  The motor 3 is supplied with electric power from the battery 8 or the generator 4 and functions to apply rotational force to the drive wheels 10 and 11, and conversely, the motor 3 is applied with rotational force from the drive wheels 10 and 11. In some cases, the battery 8 functions to generate power and supply charging power to the battery 8.

Here, the engine 2 is a four-stroke engine having a plurality of cylinders, and is an internal combustion engine capable of lean combustion that can be operated at a lean air-fuel ratio (lean combustion operation) in accordance with operating conditions. The intake passage 22 of the engine 2 is provided with an electronically controlled throttle (hereinafter referred to as “throttle”) 23 that is electrically controlled and adjusts the flow rate of intake air flowing through the intake passage 22. On the other hand, the exhaust passage 24 is provided with a NOx occlusion reduction type catalyst (hereinafter referred to as “NOx catalyst”) 25. An exhaust temperature sensor 26 that outputs an electrical signal corresponding to the temperature of the exhaust gas flowing through the exhaust passage 24 is attached to the exhaust passage 24 upstream of the NOx catalyst 25.

  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 are input to the HVCC. It is like that. Further, the battery charge state (SOC) is input to the HVCC from the battery computer. The HVCC obtains necessary engine power based on detection values or SOCs of various sensors and outputs a requested value to the ECC, and obtains necessary torque to control the motor 3 and the generator 4.

  On the other hand, various sensors such as a crank position sensor (not shown) are connected to the above-described ECC via electric wiring, and output signals of the various sensors are input to the ECC. In addition, a fuel injection valve, throttle, etc. are connected to the ECC via electrical wiring, and the engine operating state (engine speed, etc.) is determined from output signals from various sensors, and the determined operating state, output from HVCC The air-fuel ratio is determined on the basis of the required value and a map that is created in advance and stored in the ROM, and the fuel injection valve and the throttle are controlled so that the determined air-fuel ratio is obtained. The map is such that when the required power from HVCC is small, the air-fuel ratio becomes lean, and when the required power is large, the air-fuel ratio becomes rich, and the larger the required power from HVCC, the smaller the air-fuel ratio. .

  In the hybrid system 1, the power (torque) generated by the 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 as appropriate. The battery 8 is charged by converting the energy to be generated and the energy generated with the deceleration of the vehicle into electric energy.

  Hereinafter, the operation of the hybrid system 1 will be described with specific examples.

  FIG. 2 shows how the power generated by the 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 transmission path of power and power. It is a schematic diagram to explain. In each of FIGS. 2A, 2B, 2C, and 2D, a solid line arrow indicates a power transmission path, and a broken line arrow indicates a power transmission path.

(1) At system startup When the hybrid system 1 is started, the engine 2 is started to warm up. At this time, a part of the energy generated by the engine 2 is converted into electric energy via the generator 4 and stored in the battery 8 (FIG. 2A). However, when it is not necessary to charge the battery 8, it is not necessary to convert part of the energy generated by the engine 2 into electric energy, so the engine 2 is set to idle operation in order to give priority to warm-up. When the warm-up of the engine 2 is completed (when the temperature of the cooling water exceeds a predetermined value), the operation of the engine 2 is stopped.

  The collinear chart illustrating the shaft rotation speed of the planetary gear of the power split mechanism 5 is a relationship in which the motor rotation speed, the engine rotation speed, and the generator rotation speed are always connected in a straight line at the rotation speed indicated on the vertical axis. While the engine 2 is warming up, the state is as shown in FIG.

(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 engine 2 is low. The vehicle (driving wheels 10 and 11) is driven (FIG. 2B). In such a case, the engine 2 remains stopped. Further, the alignment chart in such a case is as shown in FIG.

(3) During steady running In an operating region where the engine 2 has good engine efficiency, the engine 2 runs mainly using the power generated by the engine 2. The engine power is divided into two paths by the power split mechanism 5, and one is transmitted as power to the wheels. The other is driven by the generator 4 to generate electric power, and the motor 3 is driven by the electric power to assist the engine power. Then, control is performed so that the power generated by the engine 2 and the power generated by the motor 3 cooperate with each other at an optimum ratio to drive the vehicle (drive wheels 10 and 11) (FIG. 2C). However, the amount of power generated at this time is kept to a minimum in order to increase engine efficiency. The alignment chart in such a case is as shown in FIG.

(4) When moving backward The vehicle moves backward only with the driving force of the motor 3. Since the engine power acts in a direction that weakens the driving force in the reverse direction, the engine is in a stop state or an idle operation state during reverse operation (FIG. 2 (d)). However, when the SOC is low and the battery charge state is not good, the engine power is transmitted to the generator 4 via the power split mechanism 5 to generate electric power, and the electric power travels with the motor. The alignment chart in such a case is as shown in FIG.

  Here, when the air-fuel ratio (exhaust air-fuel ratio) of the exhaust gas flowing into the catalyst is a lean air-fuel ratio, the NOx catalyst 25 according to this embodiment retains NOx in the exhaust gas and does not release it into the atmosphere. Thus, when the air-fuel ratio (exhaust air-fuel ratio) of the exhaust gas flowing into the catalyst becomes the stoichiometric air-fuel ratio or the rich air-fuel ratio, the retained NOx is released and reduced and removed.

  For this reason, when the 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 engine 2 becomes a lean air-fuel ratio, and NOx contained in the exhaust gas becomes NOx catalyst. 25. When the lean combustion operation of the engine 2 is continued for a long period of time, the NOx retention ability of the NOx catalyst 25 is saturated, and NOx in the exhaust gas is released into the atmosphere without being purified by the NOx catalyst 25.

  Therefore, when the engine 2 is in lean burn operation, the air-fuel ratio of the exhaust gas flowing into the NOx catalyst 25 is made rich air-fuel ratio before the NOx retention capacity of the NOx catalyst 25 is saturated, and is held by the NOx catalyst 25. NOx must be released and reduced.

  Therefore, in this embodiment, when the rich spike control execution condition is satisfied, the ECC controls the amount of fuel injected from the fuel injection valve and the like in a spike (short time) with a relatively short period. Rich spike control is performed in which the operation is performed with a rich air-fuel ratio, and the air-fuel ratio of the exhaust gas flowing into the NOx catalyst 25 is spiked into the rich air-fuel ratio.

  As the rich spike control execution condition, for example, the NOx catalyst 25 is in an active state, and the estimated amount of NOx held in the NOx catalyst 25 is not less than a predetermined amount. As a technique for estimating the amount of NOx retained in the NOx catalyst 25, the following technique can be exemplified.

First, the accelerator opening calculated based on the detection value of the accelerator position sensor, the engine speed calculated based on the detection value of the crank position sensor, and the accelerator opening previously created and stored in the ROM of the ECU The NOx emission amount is calculated based on the NOx emission amount map using the engine speed as a parameter.

  Thereafter, the NOx retention amount is calculated based on the exhaust temperature calculated based on the NOx emission amount and the detection value of the exhaust temperature sensor 26. More specifically, the retention rate of the NOx catalyst 25 corresponding to the exhaust temperature is obtained from a map or the like, and the retention rate is multiplied by the NOx emission amount to calculate the NOx retention amount.

  Then, the NOx retention amount calculated this time is added to the accumulated NOx retention amount so far to obtain the accumulated NOx retention amount. The predetermined amount is set in advance in a range smaller than the saturation retention amount of the NOx catalyst 25.

  Here, when the rich spike control is executed, the air-fuel ratio of the air-fuel mixture in the cylinder becomes rich in a short cycle, so that the engine power increases accordingly.

  Therefore, if the rich spike control is executed when the engine is driven, such as when the engine is driven backward, and when the engine is driven using the engine power when the engine is idling or when the SOC is lowered, driving in the backward direction is performed. The engine power that works in the direction that weakens the force increases, and the driving force in the reverse direction decreases. In particular, when driving backward and climbing a hill or when trying to climb, if the driving force in the backward direction decreases due to execution of rich spike control, the vehicle may slide down .

  Therefore, in this embodiment, even when the rich spike control execution condition is satisfied, the rich spike control is not executed when the vehicle is traveling backward (when the shift position is “R” (reverse position)), and the vehicle is traveling backward. In other cases, rich spike control execution enable / disable control is performed so that rich spike control is executed.

  Hereinafter, the rich spike control execution feasibility 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, and is a routine that is executed by the ECU 9 as an interrupt process triggered by the passage of a fixed time or the input of a pulse signal from the crank position sensor.

  In this routine, first, in step (hereinafter simply referred to as “S”) 101, it is determined whether or not the above-described rich spike control execution condition is satisfied. If an affirmative determination is made, the process proceeds to S102. If a negative determination is made, execution of this routine is terminated.

  In S102, it is determined whether or not the shift position detected by the shift position sensor is “R” (reverse position). If the determination is affirmative, the process proceeds to S103, and execution of rich spike control is prohibited. On the other hand, if a negative determination is made, the process proceeds to S104 and rich spike control is executed.

  By performing the rich spike control execution enable / disable control, even if the rich spike control execution condition is satisfied, the rich spike control is reliably prohibited during reverse travel (when the shift position is “R” (reverse travel position)). Therefore, it is possible to prevent the drive force in the reverse direction from being reduced during reverse travel.

In the first embodiment, when the rich spike control execution condition is satisfied, the rich spike control execution enable / disable control is executed to determine whether or not to execute the rich spike control according to whether or not the vehicle is moving backward. However, in the present embodiment, when the rich spike control execution condition is satisfied, it is determined whether or not the lean combustion operation that is the operation at the lean air-fuel ratio is permitted depending on whether or not the vehicle is traveling backward. The combustion operation propriety control is executed. That is, the present embodiment is different from the first embodiment only in that the lean combustion operation feasibility control is executed instead of the rich spike control feasibility control, and the others are the same, and the detailed description thereof is omitted.

  As described above, when the exhaust air-fuel ratio flowing into the catalyst is lean, the NOx catalyst 25 according to the present embodiment holds NOx in the exhaust gas so as not to be released into the atmosphere and flows into the catalyst. When the exhaust air-fuel ratio to be performed is the stoichiometric air-fuel ratio or rich, the retained NOx is released and reduced and removed. Therefore, even if the rich spike control execution condition is once established by executing the lean combustion operation propriety control, if the exhaust air-fuel ratio is the stoichiometric air-fuel ratio or rich, the NOx held by the NOx catalyst 25 is changed. Since it is released and reduced and removed, the amount of NOx retained in the NOx catalyst 25 can be reduced, and the rich spike control need not be executed.

  As a result, it is possible to prevent the drive force in the reverse direction from being reduced due to the execution of the rich spike control during reverse travel. Therefore, it is possible to prevent the vehicle from sliding down even when the vehicle is going backward and climbing a hill or trying to climb.

  Hereinafter, the lean combustion operation propriety 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, and is a routine that is executed by the ECU 9 as an interrupt process triggered by the passage of a fixed time or the input of a pulse signal from the crank position sensor.

  The processing of S201 and S202 in this routine is the same as the processing of S101 and S102 in the rich spike control execution enable / disable control of the first embodiment. Therefore, the detailed description is abbreviate | omitted.

  If an affirmative determination is made in S202, that is, if it is determined that the shift position is “R” (reverse drive position), the process proceeds to S203 to prohibit the lean combustion operation that is the operation at the lean air-fuel ratio. The operation is performed at the stoichiometric or rich air-fuel ratio. On the other hand, when a negative determination is made in S202, that is, when it is determined that the shift position is not “R”, the process proceeds to S204, and the lean combustion operation is permitted.

  Even if the rich spike control execution condition is satisfied by performing the lean combustion operation enable / disable control, the lean combustion operation is surely prohibited when the vehicle is traveling backward, and the operation at the stoichiometric or rich air / fuel ratio is performed. Thus, the amount of NOx retained in the NOx catalyst 25 can be made smaller than the predetermined amount, so that it is not necessary to execute rich spike control.

  As a result, it is possible to prevent the drive force in the reverse direction from being reduced due to the execution of the rich spike control during reverse travel. Therefore, it is possible to prevent the vehicle from sliding down even when the vehicle is going backward and climbing a hill or trying to climb.

1 is a diagram illustrating a schematic configuration of a hybrid vehicle 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 figure which shows the alignment chart of the hybrid system which concerns on Example 1. FIG. 3 is a flowchart of a control routine of rich spike control execution enable / disable control according to the first embodiment. 7 is a flowchart of a control routine for lean combustion operation propriety control according to a second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hybrid system 2 Engine 3 Motor 4 Generator 5 Power split mechanism 6 Reducer 7 Inverter 8 Battery 9 ECU
DESCRIPTION OF SYMBOLS 21 Crankshaft 22 Intake passage 23 Throttle valve 24 Exhaust passage 25 NOx storage reduction type catalyst 26 Exhaust temperature sensor 100 Hybrid vehicle

Claims (2)

When the exhaust air-fuel ratio is lean, NOx in the exhaust gas is retained, and when the exhaust air-fuel ratio is rich or stoichiometric, it is equipped with a NOx occlusion reduction type catalyst that reduces and removes the retained NOx and is capable of lean combustion In an internal combustion engine control device for a hybrid vehicle having an internal combustion engine,
When the shift position of the hybrid vehicle is a reverse position, execution of rich spike control for reducing the NOx held in the NOx storage reduction catalyst by temporarily setting the exhaust air-fuel ratio to be rich is prohibited. An internal combustion engine control device for a hybrid vehicle. When the exhaust air-fuel ratio is lean, NOx in the exhaust gas is retained, and when the exhaust air-fuel ratio is rich or stoichiometric, it is equipped with a NOx occlusion reduction type catalyst that reduces and removes the retained NOx and is capable of lean combustion In an internal combustion engine control device for a hybrid vehicle having an internal combustion engine,
An internal combustion engine control apparatus for a hybrid vehicle, wherein lean combustion operation is prohibited when the shift position of the hybrid vehicle is a reverse position.

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