Patent ID: 12187261

DETAILED DESCRIPTION

First Embodiment

FIG.1is a block diagram illustrating a hybrid vehicle100. The hybrid vehicle100includes an Electric Control Unit (ECU)10, a battery12, a converter14, an inverter16, a motor generator (MG)18, a motor generator (MG)20, a power split mechanism22, a reduction gear24, drive wheels26, and an engine (internal combustion engine)30.

The engine30and the MG20function as a power source for driving the hybrid vehicle100. The MG20is also used, for example, when starting the engine30. The MG18functions as a power generator for charging the battery12.

The power split mechanism22transmits the driving force of the engine30and the MG20to the reduction gear24. The distribution between the power of the engine30and the power of the MG20is arbitrarily changed by the power split mechanism22. The power split mechanism22is constituted by a planetary gear including, for example, a sun gear, a planetary carrier, and a ring gear.

When the MG18or the MG20functions as a motor, the DC power discharged from the battery12is boosted by the converter14and converted into AC power by the inverter16. The AC power is supplied to the MG18or the MG20.

During charging of the battery12, the MG18or the MG20functions as a generator. AC power generated by the MG18or the MG20is converted into DC power by the invertor16, stepped down by the converter14, and then supplied to the battery12.

Schematic Configuration of Engine

FIG.2is a schematic view illustrating the engine30. As illustrated inFIG.2, a combustion chamber33is formed inside an engine body32of the engine30. A piston34, a connecting rod35, and a crankshaft36are disposed inside the engine body32. The piston34is connected to the crankshaft36by the connecting rod35. The engine body32is provided with a rotational speed sensor37, an ignition plug38, and a fuel injector39. The rotational speed sensor37detects the rotational speed of the engine30. The fuel injector39supplies fuel to the combustion chamber33(in-cylinder injection). The ignition plug38ignites the air-fuel mixture in the combustion chamber33. The fuel injector39may be provided in the intake path40to perform port injection.

An intake path40and an exhaust path41are connected to the engine body32. When a camshaft (not illustrated) rotates, an intake valve46and an exhaust valve47are opened and closed.

An air cleaner42, an air flow meter43, and a throttle valve44are provided in the intake path40from the upstream side to the downstream side. The air cleaner42removes dust and the like from air flowing in from the outside. The air flow meter43acquires an intake air amount. The throttle valve44is driven by, for example, an actuator (not illustrated) to adjust the intake air amount. When the opening degree of the throttle valve44increases, the intake air amount increases, and when the opening degree decreases, the intake air amount decreases.

When the intake valve46is opened, air is introduced from the intake path40into the combustion chamber33. The fuel injected from the fuel injector39and air form an air-fuel mixture, which is compressed by the piston34and ignited by the ignition plug38. The piston34reciprocates up and down in the combustion chamber33by the ignition, and the crankshaft36rotates. The exhaust gas after combustion is discharged from the exhaust path41.

The exhaust path41is provided with an air-fuel ratio sensor48, a pressure sensor53, a filter45, and a pressure sensor54in this order from the upstream side. The air-fuel ratio sensor48detects the air-fuel ratio of the gas flowing through the exhaust path41. The filter45is, for example, a gasoline particulate filter (GPF). The filter45has a structure in which front end portions and rear end portions of adjacent cells among a large number of cells are alternately sealed in a porous ceramic structure. The exhaust gas flows into a cell having an open upstream end of the filter45and passes through a porous wall between the cell and an adjacent cell. At this time, exhaust particulate matter (PM) in the exhaust gas is trapped. A noble metal such as platinum may be supported on the filter45. During the filter regeneration process, the noble metal promotes the oxidation reaction of the deposited PM.

The pressure sensor53detects a pressure on the upstream side of the filter45in the exhaust path41. The pressure sensor54detects a pressure on the downstream side of the filter45in the exhaust path41.

A temperature sensor49is provided near the filter45in the exhaust path41. The temperature sensor49detects the temperature of the filter45. The exhaust path41may be provided with a component for purifying exhaust gas, such as a three way catalyst.

One end of an EGR path50is connected to the exhaust path41, and the other end is connected to the intake path40. An EGR valve52is provided in the EGR path50. A part of the exhaust gas (EGR gas) flows into the intake path40through the EGR path50and is introduced into the combustion chamber33again. When the opening degree of the EGR valve52becomes larger, the flow rate of the EGR gas increases, and when the opening degree becomes smaller, the flow rate of the EGR gas decreases. The EGR path50may be provided with, for example, an EGR cooler that cools the EGR gas.

The ECU10includes a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), a storage device, and the like, and executes various types of control by executing a program stored in the ROM or the storage device. The ECU10is an example of a control device for the hybrid vehicle100.

The ECU10acquires a rotational speed detected by the rotational speed sensor37, an intake air amount detected by the air flow meter43, a temperature of the filter45detected by the temperature sensor49, and an air/fuel ratio detected by the air/fuel ratio sensor48.

The ECU10acquires pressures detected by the pressure sensors53and54. The ECU10calculates the difference (differential pressure) between the pressures detected by the pressure sensors53and54. The ECU10acquires an amount of PM deposited on the filter45based on the differential pressure. As the deposition amount of PM increases, the differential pressure increases.

The ECU10functions as a motor control unit that controls the MG18and the MG20. The ECU10controls the engine30, the MG18and the MG20to switch between electric driving (BEV driving) in which the engine30is not operated and hybrid driving (HEV driving) in which the engine30is operated. The ECU10controls charging and discharging of the battery12and the like. Instead of the ECU10, for example, both an engine ECU that controls the engine30and a motor ECU that controls the MG18, the MG20, the battery12, and the like may be provided. In this case, the engine ECU and the motor ECU are examples of the control device of the hybrid vehicle100.

The ECU10adjusts the ignition timing of the ignition plug38, the amount and the timing of fuel injection from the fuel injector39, and the opening degrees of the throttle valve44and the EGR valve52. The ECU10can stop the supply of fuel from the fuel injector39to the engine30(fuel cut). During the fuel cut, the ECU10causes the MG20to operate as a motor, for example, and causes the MG20to output power (motor assist).

The ECU10functions as a diagnostic unit that executes self-diagnosis (OBD process, that is, On Board Diagnosis) of components of the hybrid vehicle100during execution of the fuel cut. The components are, for example, the air-fuel ratio sensor48and the EGR valve52. For example, the air-fuel ratio sensor48is diagnosed in the following manner. When the fuel cut is started, the exhaust gas from the engine body32becomes the atmospheric air. For this reason, it is monitored whether or not a value of the sensor signal of the air-fuel ratio sensor48after the elapse of a predetermined time from the start of the fuel cut control is a value of the air-fuel ratio corresponding to the atmosphere. Thus, the presence or absence of a failure of the air-fuel ratio sensor48is determined. The diagnosis of the EGR valve52is executed as follows. During the fuel cut control, the load fluctuation of the engine30is small. For this reason, when the EGR valve52is normal, the intake pressure fluctuates relatively greatly along with the opening and closing of the EGR valve52. Therefore, during the fuel cut control, it is determined whether or not the difference between the intake pressure when the EGR valve52is forcibly fully opened and the intake pressure when the EGR valve52is forcibly fully closed exceeds a preset threshold value. In this way, it is determined whether or not there is a failure in the EGR valve52.

The ECU10functions as an estimation unit that estimates the time (OBD time) required from the start to the completion of the OBD based on, for example, a flow rate of the air, a type of the component, and the like.

When PM is deposited on the filter45, the ECU10executes a regeneration process of the filter45. For example, the ECU10executes fuel cut. Due to the fuel cut, air containing a large amount of oxygen flows into the exhaust path41. The PM deposited on the filter45is burned and removed.

During the filter regeneration process, the temperature of the filter45rises. The amount of heat generated by combustion of PM increases as the amount of oxygen supplied to the filter45increases, the deposition amount of PM increases, and the temperature of the filter45increases. The filter45might be damaged by heat. The ECU10functions as an upper limit setting unit that sets an upper limit of the time (F/C time) during which the fuel cut is executed. When the F/C time reaches the upper limit, the ECU10stops the fuel cut and restarts the fuel supply. By limiting the fuel cut time, damage to the filter45is suppressed.

When the F/C time reaches the upper limit, the fuel cut is forcibly terminated even if the self-diagnosis is not completed, and the self-diagnosis is also terminated without being completed. Although the motor assist is executed during the fuel cut, the fuel cut may be terminated while the self-diagnosis is not completed. The motor assist during the fuel cut is wasted. In order to secure an opportunity for self-diagnosis, fuel cut is executed again. When the motor assist is repeated in response to the fuel cut, power consumption increases. In the first embodiment, the number of times of motor assist is limited.

FIG.3is a view illustrating the upper limit of the fuel cut time. A horizontal axis represents the amount of PM deposited on the filter45. A vertical axis represents the temperature of the filter45. The ECU10sets the upper limit TL of the fuel cut time (F/C time in the drawing) according to the deposition amount of PM and the temperature of the filter45. Four upper limits TL1, TL2, TL3and TL4are illustrated inFIG.3. The time is shorter as the deposition amount of PM is larger and the temperature is higher. Of the four upper limits, TL1is the longest. TL2is shorter than TL1. TL3is shorter than TL2. TL4is shorter than TL3.

FIG.4is a flowchart illustrating processing according to the first embodiment. The ECU10sets the upper limit TL of the F/C time (step S10) executes the fuel cut (step S11). The ECU10estimates the OBD time T (step S12). The ECU10determines whether or not the self-diagnosis is incomplete (step S13). In the case of a positive determination (Yes), the ECU10determines whether or not the estimated self-diagnosis time T is equal to or less than the upper limit TL (step S18). When the determination is affirmative, the ECU10permits the motor assist (step S22). The motor assist is executed during the fuel cut.

In the case of negative determination (No) in step S13or S18, the ECU10prohibits the motor assist (step S24). The motor assist is not executed during the fuel cut. After step S22or S24, the processes inFIG.4end.

According to the first embodiment, the ECU10diagnoses the components (the air fuel ratio sensor48and the like) during the fuel cut. The ECU10estimates the time T required for the self-diagnosis and sets an upper limit TL for the fuel cut time. When the estimated OBD time T is greater than the upper limit TL, the ECU10limits the motor assist. The limitation of the motor assist is to reduce the number of times of the motor assist, and the motor assist may be prohibited (step S24). This prohibits useless motor assist such that fuel cut is interrupted while OBD is not completed. When the estimated OBD time T is equal to or less than the upper limit TL, there is a high possibility that the OBD is completed during the fuel cut. The ECU10permits motor assist (step S22).

The useless motor assist is prohibited, and the motor assist is executed during the fuel cut in which it is estimated that the OBD is completed. By limiting the opportunity of the motor assist, it is possible to suppress an increase in power consumption. Since it is not needed to drive the MG for charging the battery12, fuel efficiency is improved.

As illustrated inFIG.3, the ECU10determines the upper limit TL based on, for example, the deposition amount of PM and the temperature of the filter45. By setting the F/C time T to be equal to or less than the upper limit TL, damage to the filter45is suppressed.

Second Embodiment

Description of the same configuration as that of the first embodiment will be omitted. The configurations illustrated inFIGS.1and2are common to the second embodiment.

The ECU10functions as a first measurement unit that measures the number of times the diagnosis is not completed (the number of times the OBD failed). The ECU10functions as a second measurement unit that measures the time elapsed during the fuel cut.

FIG.5is a flowchart illustrating processing according to the second embodiment. The ECU10executes steps S10, S11, S12and S13. The ECU10measures the number F of OBD failures and determines whether or not the number F is equal to or greater than a predetermined number Fth (step S14). When a negative determination is made, the ECU10determines whether or not there is a request for the motor assist (step S16). When an affirmative determination is made in step S16, the ECU10permits the motor assist (step S22). When a negative determination is made in step S16, the ECU10prohibits the motor assist (step S24).

When an affirmative determination is made in step S14, the ECU10determines whether or not the estimated time T of the OBD is equal to or less than the upper limit TL (step S18). When the determination is negative, the ECU10prohibits the motor assist (step S24).

When an affirmative determination is made in step S18, the ECU10measures the time Tr actually elapsed during the fuel cut, and determines whether or not the time Tr is equal to or greater than the predetermined time Tth (step S20). When the determination is affirmative, the ECU10permits the motor assist (step S22). When the determination is negative, the ECU10prohibits the motor assist (step S24). After step S22or S24, the processes inFIG.5end.

FIG.6is a view illustrating a time chart. A fuel cut flag, a self-diagnosis counter, a completion flag of self-diagnosis, a failure history flag of self-diagnosis, a temperature of the filter45, a deposition amount of PM, a prohibition flag of fuel cut, a fuel cut counter, and a motor assist flag are illustrated in order from the top. In the example ofFIG.6, fuel cut is executed five times. The plurality of fuel cuts are assumed to be F/C1, F/C2, F/C3, F/C4, and F/C5from the first in the order. The fuel cut counter corresponds to the time Tr elapsed during the fuel cut.

The self-diagnosis is executed during the fuel cut. The self-diagnosis counter corresponds to the time of the self-diagnosis. When the self-diagnosis counter reaches Cth, the self-diagnosis is completed. When the self-diagnosis is completed, a self-diagnosis completion flag is turned on. When the self-diagnosis is suspended, the completion flag is kept off. When the number F of failures in the self-diagnosis becomes equal to or greater than the predetermined number Fth, the failure history flag is turned on (step S14inFIG.5). In the example ofFIG.6, Fth is two times.

The prohibition flag is a prohibition flag for fuel cut accompanied by the motor assist. When the prohibition flag is off, the fuel cut accompanied by the motor assist is permitted. When the prohibition flag is on, the fuel cut accompanied by the motor assist is prohibited, and the motor assist is not executed. When the motor assist flag is off, the motor assist is prohibited. When the motor assist flag is on, the motor assist is permitted.

During the period from the time t1to the time t2during the execution of fuel cut1and during the period from the time t3to the time t4of fuel cut2, the motor assist flag is on and the motor assist is executed. The self-diagnosis is executed during the fuel cut1and the fuel cut2. The self-diagnosis counter is shorter than Cth. The self-diagnosis is not completed. Since the self-diagnosis failed twice, the failure history flag is turned on (step S14inFIG.5).

During the execution of fuel cut3, the self-diagnosis is executed but is not completed (the completion flag is off). During the time period from t5to t6during the execution of the fuel cut3, when the motor assist flag is turned on as indicated by a broken line, the motor assist flag is set. However, since the self-diagnosis is not completed, the motor assist is wasted.

According to the second embodiment, when the fuel cut3is executed, the temperature of the filter45is higher than the temperature indicated by the broken line. The PM deposition amount is larger than the amount indicated by the broken line. The ECU10sets the upper limit TL of the F/C time according to the temperature and the deposition amount (step S10). When the estimated time T is greater than the upper limit TL, the ECU10turns on the prohibition flag to prohibit the fuel cut with the motor assist (steps S18and S24inFIG.5). As illustrated inFIG.6, the motor assist flag is turned off and motor assist is not executed.

During the execution of fuel cut4, the self-diagnosis is executed but is not completed (the completion flag is off). During the time period from t7to t8during the execution of the fuel cut4, when the motor assist flag is turned on as indicated by a broken line, the motor assist flag is set. However, since the self-diagnosis is not completed, the motor assist is wasted. According to the second embodiment, the motor assist is prohibited while the fuel cut counter (time Tr) is less than Tth (steps S20and S24inFIG.5). The fuel cut4is finished before the fuel cut counter reaches Tth. The motor assist is not executed during the fuel cut4.

During the execution of fuel cut5, the fuel cut counter reaches Tth. Thereafter, the motor assist flag is turned on from time t9to time t10. The motor assist is permitted (step S22inFIG.5). At time t10, the self-diagnostic counter becomes greater than or equal to Cth. The self-diagnosis is complete.

According to the second embodiment, the self-diagnosis and the motor assist are executed in the fuel cut1and the fuel cut2, but the self-diagnosis fails. It is presumed that the self-diagnosis of a component (for example, the air-fuel ratio sensor48) takes a long time. When the number of times of failure of the self-diagnosis becomes, for example, two, the ECU10turns on the failure history flag (affirmative determination in step S14ofFIG.5). When the estimated OBD time T is greater than the upper limit TL, the ECU10prohibits the motor assist (steps S18and S24inFIG.5, the fuel cut3inFIG.6). By reducing the number of times of motor assist, it is possible to suppress an increase in power consumption. Since it is not needed to drive the MG for charging the battery12, fuel efficiency is improved.

When the failure history flag is on and the fuel cut time Tr is less than Tth, the motor assist is prohibited (steps S20and S24inFIG.5, the fuel cut4inFIG.6). When the self-diagnosis fails, the motor assist is not executed. An increase in power consumption is suppressed.

Even if the failure history flag is on, when the fuel cut time Tr is equal to or greater than Tth, the motor assist is permitted (steps S20and S22inFIG.5, the fuel cut5inFIG.6). The self-diagnosis is complete and the motor assist is executed. The opportunity of the motor assist is limited when self-diagnosis is successful. It is possible to suppress useless motor assist and suppress an increase in power consumption.

The threshold value Fth for the number of times of failure of self-diagnosis may be, for example, one time, two times, or three times or more. The threshold value Tth for the fuel cut counter may be, for example, 2 seconds, 3 seconds, 4 seconds, 5 seconds, or the like.

Although some embodiments of the present disclosure have been described in detail, the present disclosure is not limited to the specific embodiments but may be varied or changed within the scope of the present disclosure as claimed.