JP2008213725A - Hybrid car - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hybrid car which reduced a feeling of incompatibility in performing operation check. <P>SOLUTION: A hybrid car 100 is provided with an engine 1; an oxygen sensor 22 as a gas sensor arranged in an exhaust passageway 54 of the engine 1 for detecting an air-fuel ratio; a motor for generating a power for promoting a vehicle; and a control device for controlling the engine 1 and the motor. The control device performs correction by the learning of the output of the gas sensor in each of a plurality of regions whose intake air quantity is different. The control device performs the operation confirmation of the gas sensor in the region whose learning has ended among the plurality of regions, and inhibits the operation confirmation of the gas sensor in the region whose learning has not been performed among those plurality of regions. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hybrid vehicle, and more particularly to a technique for confirming sensor operation in a vehicle equipped with an internal combustion engine.

  In recent years, automobiles equipped with engines are often controlled to precisely control the fuel injection amount to achieve an ideal air-fuel ratio and reduce emissions. For this reason, an air-fuel ratio sensor or an oxygen sensor may be provided in the exhaust passage, and the fuel injection amount may be feedback controlled from the exhaust state.

  In the air-fuel ratio feedback control, a deviation occurs in the center value of the air-fuel ratio feedback correction coefficient due to changes with time of various sensors, manufacturing errors, and the like. Therefore, the air-fuel ratio learning value is learned in order to correct this deviation, and this air-fuel ratio learning value is reflected in the air-fuel ratio feedback control.

Japanese Patent No. 3341281 (Patent Document 1) discloses a hybrid vehicle equipped with an air-fuel ratio learning control device capable of executing accurate air-fuel ratio learning control earlier.
Japanese Patent No. 3341281 JP 2005-151645 A JP 2005-269705 A

  In recent years, OBD (On Board Diagnosis) that automatically executes operation checks of various sensors used for control for emission reduction may be required. By performing OBD, even if a vehicle has been running and becomes old, the necessity for repair can be immediately grasped, and emission reduction can be maintained for many years.

For example, such an operation check is performed for a gas sensor (air-fuel ratio sensor or oxygen sensor (O ₂ sensor)) for performing air-fuel ratio feedback control. The operation check is performed by temporarily stopping the air-fuel ratio feedback, forcibly increasing and decreasing the fuel injection amount, and observing that the output of the gas sensor changes. The condition for performing the operation check is that the intake air amount (GA) is large, and in this case, it is easy to detect a change in the sensor.

  The driving force required for running the hybrid vehicle is not particularly different from that of a normal gasoline vehicle. However, since the hybrid vehicle uses the engine and the motor together for driving the vehicle, it is possible to increase the driving force of the engine and reduce the driving force of the motor while keeping the driving force equal. Such an operation is referred to as raising the engine power (Pe). Increasing the engine power increases the intake air amount, which is preferable as a condition for performing OBD.

  However, in order to perform OBD, the learning of the air-fuel ratio learning value for correcting the deviation of the center value of the air-fuel ratio feedback correction coefficient must be completed at least once. This is because the lean / rich reference value (learned value P0 in FIG. 8) for changing the fuel injection amount between the rich side and the lean side during OBD execution is not known. Therefore, when the learning value is cleared by battery replacement or the like and the condition for executing OBD is satisfied before the learning is completed, the engine power is raised as shown by the broken line W6 in FIG. It can be considered that the OBD impossibility determination is repeated. Therefore, although the vehicle power does not change, there arises a problem that an uncomfortable feeling that the engine sound repeats changes is felt.

  An object of the present invention is to provide a hybrid vehicle that reduces a sense of incongruity during an operation check.

  In summary, the present invention is a hybrid vehicle, which is an internal combustion engine, a gas sensor that is disposed in an exhaust passage of the internal combustion engine, detects an air-fuel ratio, a motor that generates power for vehicle propulsion, and an internal combustion engine And a control device for controlling the engine and the motor. The control device performs correction by learning the output of the gas sensor in each of a plurality of regions having different intake air amounts. The control device confirms the operation of the gas sensor in the region where the learning is completed among the plurality of regions, and prohibits the operation confirmation of the gas sensor in the region where the learning is not performed among the plurality of regions.

  Preferably, when checking the operation of the gas sensor, the control device reduces the power generated by the motor while maintaining the same driving force of the driving wheels, and instead increases the power generated by the internal combustion engine.

  More preferably, the control device determines whether or not the intake air amount after increasing the power generated by the internal combustion engine corresponds to a region that has not yet been learned among the plurality of regions.

  Preferably, the hybrid vehicle further includes a power generator and a power split mechanism that is mechanically coupled to the internal combustion engine, the motor, and the power generator and performs mechanical power split.

  According to the present invention, an inappropriate operation check request is eliminated, and the uncomfortable feeling at the time of operation check is reduced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

FIG. 1 is a diagram illustrating a main configuration of a hybrid vehicle.
Referring to FIG. 1, hybrid vehicle 100 has an engine 1 that is an internal combustion engine and a motor 2 that is auxiliary power as drive sources. The hybrid vehicle also includes a generator 3 that receives the output of the engine 1 to generate power. These engine 1, motor 2 and generator 3 are connected by a power split mechanism 4.

  The power split mechanism 4 has a role of distributing the output of the engine 1 to the generator 3 and the drive wheels 7. The power split mechanism 4 also has a role as a transmission for driving force transmitted to the drive wheels 7 via the differential gear 5 and the drive shaft 6.

  The motor 2 is an AC synchronous motor and is driven by AC power. The inverter 9 converts the electric power stored in the battery 8 from direct current to alternating current and supplies it to the motor 2, and converts the electric power generated by the generator 3 from alternating current to direct current to store it in the battery 8. Is. The generator 3 has basically the same configuration as the motor 2 described above, and has a configuration as an AC synchronous motor. While the motor 2 mainly outputs driving force, the generator 3 generates electric power mainly by receiving the output of the engine 1.

  The motor 2 mainly generates a driving force, but can also generate electric power (regenerative power generation) using the rotation of the driving wheels 7. At this time, since the drive wheel 7 is braked (regenerative brake), the hybrid vehicle can be braked by using this in combination with a foot brake (oil brake) or an engine brake. On the other hand, the generator 3 generates power by mainly receiving the output of the engine 1, but can also function as a starter motor that receives power from the battery 8 via the inverter 9 and starts the engine 1.

  Several states of the engine 1, the motor 2, and the generator 3 during traveling in the hybrid vehicle 100 having the above-described configuration will be exemplified below.

  When starting or at a light load, the hybrid vehicle 100 is driven by the driving force of the motor 2 by driving only the motor 2 with the electric power from the battery 8 using the characteristics of the motor 2 that can generate high torque in a low rotation state. .

  When a certain speed comes out or when the load becomes high, the engine 1 is driven, and the motor 2 driven by the driving force of the engine 1 and the electric power generated by the generator 3 by the output of the engine 1. The hybrid vehicle 100 is caused to travel by the driving force.

  When further output is required, such as during full-open acceleration, the motor 2 is driven by both the electric power from the generator 3 and the electric power from the battery 8, and the driving force of the engine 1 is also increased. The hybrid vehicle 100 is caused to travel with a driving force of 2.

  During deceleration or braking, the hybrid vehicle 100 is regeneratively braked by performing regenerative power generation by the motor 2 using the rotational force of the drive wheels 7. Further, when the charge amount of the battery 8 is reduced, the engine 1 is driven even when the load is light, the generator 3 is used to generate power using the output of the engine 1, and the battery is 8 is charged.

  These controls are performed by the control device 10. The control device 10 includes several electronic control units (ECUs). Specifically, the control device 10 includes a main ECU 15, an engine ECU 11, a motor ECU 12, a battery ECU 13, and a brake ECU 14.

  Although it is characteristic control as a hybrid vehicle, the drive by the engine 1 and the electrical drive by the motor 2 (and the generator 3) are comprehensively controlled by the main ECU 15. In a normal operating state, the main ECU 15 determines the output distribution to the engine 1 and the motor 2 so that the energy efficiency is optimal, and controls the engine 1, the motor 2 and the generator 3 based on this required output distribution. Therefore, each control command is output to the engine ECU 11 and the motor ECU 12.

  Further, the engine ECU 11 and the motor ECU 12 also transmit information on the engine 1, the motor 2, and the generator 3 to the main ECU 15. A battery ECU 13 that controls the battery 8 and a brake ECU 14 that controls the brake are also connected to the main ECU 15. The battery ECU 13 monitors the state of charge of the battery 8 and outputs a charge request command to the main ECU 15 when the amount of charge is insufficient. The main ECU 15 that has received the charge request performs control to generate power by the generator 3 in order to charge the battery 8. The brake ECU 14 controls the hybrid vehicle 100 and controls the regenerative braking by the motor 2 together with the main ECU 15.

  In hybrid vehicle 100 having the above-described configuration, engine 1 and motor 2 are used in combination as drive sources. Therefore, when a certain driving force is required as a vehicle, the distribution of the output of the engine 1 and the output of the motor 2 is changed, and the output of the engine 1 is changed without changing the total output required by the vehicle. You can also. That is, when a certain driving force is required as a vehicle, if the output of the motor 2 is increased, the output of the engine 1 can be suppressed correspondingly, and conversely, if the output of the motor 2 is suppressed, the output of the engine 1 is increased accordingly. Can be increased. The air-fuel ratio learning control apparatus of this embodiment uses such a change in output distribution for OBD.

FIG. 2 is a diagram showing details of the configuration related to the engine 1 of FIG.
With reference to FIG. 2, an intake passage 52 and an exhaust passage 54 communicate with engine 1. The intake passage 52 includes the air filter 16 at the upstream end. The air filter 16 is assembled with an intake air temperature sensor 18 for detecting the intake air temperature THA (that is, the outside air temperature).

  An air flow meter 24 is disposed downstream of the air filter 16. The air flow meter 24 is a sensor that detects an intake air amount GA flowing through the intake passage 52. A throttle valve 27 is provided downstream of the air flow meter 24. In the vicinity of the throttle valve 27, a throttle opening sensor 26 that detects the throttle opening TA and an idle switch 56 that is turned on when the throttle valve 27 is fully closed are disposed.

  A surge tank 28 is provided downstream of the throttle valve 27. Further, a fuel injection valve 30 for injecting fuel into the intake port of the engine 1 is disposed further downstream of the surge tank. Instead of or in addition to the fuel injection valve 30, a fuel injection valve that injects fuel directly into the cylinder may be provided.

  In the exhaust passage 54, the upstream catalyst 32 and the downstream catalyst 34 are arranged in series. These catalysts 32 and 34 can occlude a certain amount of oxygen. When the exhaust gas contains unburned components such as HC and CO, the catalysts 32 and 34 oxidize them using stored oxygen. Further, when the exhaust gas contains oxidizing components such as NOx, the catalysts 32 and 34 can reduce them and occlude the released oxygen. Exhaust gas discharged from the engine 1 is purified by being processed inside the catalysts 32 and 34.

  The exhaust passage 54 is further provided with an air-fuel ratio sensor 23 disposed upstream of the upstream catalyst 32 and an oxygen sensor 22 disposed between the upstream catalyst 32 and the downstream catalyst 34.

FIG. 3 is a diagram showing characteristics of the air-fuel ratio sensor and the oxygen sensor.
As shown in FIG. 3, the air-fuel ratio sensor (A / F sensor) 23 is a sensor that detects the oxygen concentration in the exhaust gas. On the other hand, the oxygen sensor (O ₂ sensor) 22 is a sensor that greatly changes the output before and after the oxygen concentration in the exhaust gas exceeds a predetermined value.

  By observing the output of the oxygen sensor 22, is the exhaust gas after being processed by the upstream catalyst 32 rich in fuel (including HC and CO) or fuel lean (including NOx)? Can be judged.

  Further, by observing the output of the air-fuel ratio sensor 23, the air-fuel ratio of the air-fuel mixture subjected to combustion in the engine 1 can be detected based on the oxygen concentration in the exhaust gas flowing into the upstream side catalyst 32. . By using the air-fuel ratio sensor 23 that changes linearly, the engine ECU can perform more detailed feedback control of the air-fuel ratio.

  The exhaust purification system of this embodiment includes an engine ECU 11 as shown in FIG. In addition to the various sensors and the fuel injection valve 30 described above, the engine ECU 11 is connected to a water temperature sensor 44 that detects the cooling water temperature THW of the engine 1.

  In the system shown in FIG. 2, the exhaust gas discharged from the engine 1 is first purified by the upstream catalyst 32. Then, in the downstream side catalyst 34, the exhaust gas purification process that could not be completely purified by the upstream side catalyst 32 is performed. Since the upstream catalyst 32 is disposed at a position close to the engine 1, the temperature is raised to the activation temperature early after the engine 1 is started. For this reason, the upstream catalyst 32 exhibits a high exhaust gas purification capability immediately after the engine 1 is started.

  The upstream catalyst 32 purifies the exhaust gas by releasing oxygen into the fuel-rich exhaust gas and storing excess oxygen in the fuel-lean exhaust gas.

  Next, air-fuel ratio feedback control will be briefly described. As described above, the air-fuel ratio feedback control is to control the fuel injection amount so that the air-fuel ratio of the air-fuel mixture becomes the stoichiometric air-fuel ratio in order to reduce the exhaust emission. The air-fuel ratio feedback control is executed based on detection results from various sensors (see FIGS. 1 and 2) connected to the engine ECU 11 by a program built in the memory 58 in the engine ECU 11. Various sensors connected to the engine ECU 11 include an air-fuel ratio sensor 23, an air flow meter 24, an engine speed sensor 25, a throttle opening sensor 26, and the like.

  The air flow meter 24 is mounted on the intake passage 52 of the engine 1 and detects the amount of intake air taken into the engine 1. A hot wire type air flow meter 24 can be used.

  The engine speed sensor 25 detects the rotational speed of the engine 1 by detecting the rotational position of a crankshaft (not shown) of the engine 1. The throttle opening sensor 26 detects the opening degree of the throttle valve. Based on the outputs from the various sensors described above, the engine ECU 11 performs air-fuel ratio feedback control and other correction controls to finally determine the fuel injection amount, and the fuel injection amount determined from the fuel injection valve 30 is determined. Inject fuel.

  FIG. 4 is a flowchart for explaining control related to learning of the air-fuel ratio sensor. The process of this flowchart is called from a predetermined main routine and executed every time a predetermined time elapses or a predetermined condition is satisfied.

FIG. 5 is a diagram for explaining the learning area.
As shown in FIG. 5, the learning area is an area determined based on the intake air amount GA, and the learning areas A1 to A3 are defined in the range of the intake air amount. Note that the learning area may be defined as a two-dimensional or higher map based on the intake air amount GA and other parameters.

The control of the flowchart in FIG. 4 is executed for each learning region.
First, in step S1, it is determined whether or not a learning condition is satisfied. The learning condition indicates whether or not a stable state suitable for calibrating the air-fuel ratio sensor continues in the current learning region. When the learning condition is satisfied, the process proceeds from step S1 to step S2.

  In step S2, learning is performed and the learning value is stored in the memory 58 inside the engine ECU 11. Learning will be briefly described with reference to FIG. The engine ECU 11 detects that the output of the oxygen sensor 22 changes sharply from a high value to a low value by changing the fuel injection amount, and outputs V1 of the air-fuel ratio sensor 23 at this time as a detected value indicating the ideal air-fuel ratio. To learn. By performing this learning for each learning region, the characteristic variation of the air-fuel ratio sensor 23 is corrected.

  If the learning condition is not satisfied in step S1 or if the learning in step S2 is completed, the process proceeds to step S3 and the control is transferred to the main routine.

  FIG. 6 is a flowchart for explaining control related to the OBD processing of the sensor. The process of this flowchart is called from a predetermined main routine and executed every time a predetermined time elapses or a predetermined condition is satisfied.

  Referring to FIG. 6, when the process is started, it is determined whether or not there is a sensor OBD execution request in step S11. For example, the sensor OBD execution request is generated when the condition that the vehicle is traveling steady at a speed of about 60 km / h overlaps with other conditions defined by laws and regulations.

  If there is a sensor OBD execution request in step S11, the process proceeds to step S12. In step S12, when the engine power (Pe) is raised, it is determined whether or not the learning area to which the raised state belongs changes to the learning area to which the current state belongs.

  If it is determined in step S12 that the learning area is changed, the process proceeds to step S13. In step S13, it is determined whether or not the learning described with reference to FIG. 4 has been completed at least once in the learning area after the Pe raising. Since this learning may be cleared when the auxiliary battery is replaced, for example, it is determined that learning is not completed in such a case. Specifically, for example, it is determined whether or not the content indicating the learning value in the memory 58 is an initial value.

  If it is determined in step S13 that learning has been completed, and if the learning area does not change even if the Pe is raised in step S12, the process proceeds to step S14. In step S14, the main ECU 15, the engine ECU 11, and the motor ECU 12 cooperate to increase the Pe, increase the engine power while maintaining the same total output, decrease the motor power, and easily understand the result of the sensor OBD. Change the vehicle state to the state. Then, the process proceeds from step S14 to step S15, and the OBD of the sensor is executed.

  If the processing of step S15 is completed, if there is no request for performing sensor OBD in step S11, and if learning is not completed in the learning area after the Pe raising in step S13, the processing proceeds to step S16 and control is performed. Moved to main routine.

  FIG. 7 is an operation waveform diagram showing the increase in engine power when the OBD process of the sensor is executed. In FIG. 7, a solid line indicates a case where the invention according to the present embodiment is applied, and a broken line indicates a case where the invention is not applied.

  Referring to FIGS. 6 and 7, first, at time t1, a request to perform sensor OBD is generated (YES in step S11).

  At this time, when the specified Pe raising is performed, the intake air amount GA also increases. Assume that the current vehicle state changes from, for example, the learning area A1 to A2 in FIG. In such a case, if learning in the learning area A2 is completed (YES in step S13), Pe raising is executed as indicated by the waveform W2 at time t2, and the intake air amount GA is reduced as indicated by the waveform W1. To increase. However, since the motor power Pm is reduced as indicated by the waveform W3, the total power Ptot maintains the same value as indicated by the waveform W4. The sensor OBD is executed in a state where such Pe raising is executed.

FIG. 8 is a diagram for explaining the execution of the OBD of the oxygen sensor.
In FIG. 8, the air-fuel ratio P0 is a value learned by the air-fuel ratio sensor 23 as the ideal air-fuel ratio. Based on this learned value P0, the engine ECU 11 changes the air-fuel ratio to P1 on the rich side and confirms that the output of the oxygen sensor becomes higher than the threshold value Vth. Further, the engine ECU 11 changes the air-fuel ratio to lean P2 with reference to the learning value P0, and confirms that the output of the oxygen sensor is lower than the threshold value Vtl. Thus, OBD is completed if it can be confirmed that the output of the oxygen sensor changes.

  As described above, in the present embodiment, since learning of the reference value of the air-fuel ratio sensor is given priority over OBD, occurrence of a hunting operation as indicated by broken lines W5 to W7 in FIG. 7 is prevented. The driver almost never feels uncomfortable when performing OBD.

  Finally, the present embodiment will be summarized with reference to FIG. 1 and FIG. The hybrid vehicle 100 is disposed in the engine 1, the exhaust passage 54 of the engine 1, an oxygen sensor 22 that is a gas sensor for detecting an air-fuel ratio, a motor 2 that generates power for vehicle propulsion, and an engine 1. And a control device 10 for controlling the motor 2. The control device 10 performs correction by learning the output of the gas sensor in each of a plurality of regions having different intake air amounts. The control device 10 performs OBD, which is operation confirmation of the gas sensor, in a region where learning has been completed among the plurality of regions, and operation confirmation of the gas sensor in regions where learning is not performed among the plurality of regions. OBD is prohibited.

  Preferably, when checking the operation of the gas sensor, the control device 10 reduces the power generated by the motor 2 while keeping the driving force of the drive wheels 7 the same, and instead uses the power generated by the engine 1. increase.

  More preferably, as shown in steps S12 and S13 of FIG. 6, the control device 10 has not yet learned the intake air amount after increasing the power generated by the engine 1 in a plurality of regions. It is determined whether or not the area is applicable.

  Preferably, hybrid vehicle 100 further includes a power generator 3, and a power split mechanism 4 that is mechanically coupled to engine 1, motor 2, and power generator 3 to split mechanical power.

  In the present embodiment, the learning area is an area determined based on the air amount (Ga), but may be an area represented on a two-dimensional or three-dimensional map with more parameters.

  In addition, the control methods disclosed in the above embodiments can be executed by software using a computer. A program for causing a computer to execute this control method is read from a recording medium (ROM, CD-ROM, memory card, etc.) recorded in a computer-readable manner into a computer in a vehicle control device, or provided through a communication line. You may do it.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a figure which shows the main structures of a hybrid vehicle. It is the figure which showed the detail of the structure relevant to the engine 1 of FIG. It is the figure which showed the characteristic of the air fuel ratio sensor and the oxygen sensor. It is a flowchart for demonstrating the control regarding learning of an air fuel ratio sensor. It is a figure for demonstrating a learning area | region. It is a flowchart for demonstrating the control regarding the OBD process of a sensor. It is the operation | movement waveform diagram which showed the raising of the engine power when the OBD process of a sensor is performed. It is a figure for demonstrating execution of OBD of an oxygen sensor.

Explanation of symbols

  1 Engine, 2 Motor, 3 Generator, 4 Power split mechanism, 5 Differential gear, 6 Drive shaft, 7 Drive wheel, 8 Battery, 9 Inverter, 10 Control device, 11 Engine ECU, 12 Motor ECU, 13 Battery ECU, 14 Brake ECU, 15 Main ECU, 16 Air filter, 18 Intake temperature sensor, 22 Oxygen sensor, 23 Air / fuel ratio sensor, 24 Air flow meter, 25 Engine speed sensor, 26 Throttle opening sensor, 27 Throttle valve, 28 Surge tank, 30 Fuel injection valve, 32, 34 catalyst, 44 water temperature sensor, 52 intake passage, 54 exhaust passage, 56 idle switch, 58 memory, 100 hybrid vehicle, A1 to A3 learning region.

Claims (4)

An internal combustion engine;
A gas sensor disposed in an exhaust passage of the internal combustion engine for detecting an air-fuel ratio;
A motor for generating power for vehicle propulsion,
A control device for controlling the internal combustion engine and the motor,
The control device performs correction by learning the output of the gas sensor in each of a plurality of regions having different intake air amounts, and checks the operation of the gas sensor in a region of the plurality of regions where learning has been completed. A hybrid vehicle that prohibits the operation check of the gas sensor in a region where learning is not performed among the plurality of regions.   When the operation of the gas sensor is checked, the control device reduces the power generated by the motor while maintaining the same driving force of the driving wheels, and increases the power generated by the internal combustion engine instead. The hybrid vehicle according to claim 1.   The control device determines whether or not an intake air amount after increasing the power generated by the internal combustion engine corresponds to a region that has not yet been learned among the plurality of regions. The hybrid vehicle described in 1. A generator,
The hybrid vehicle according to claim 1, further comprising a power split mechanism that is mechanically coupled to the internal combustion engine, the motor, and the generator and splits mechanical power.

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