JP2012144219A - Hybrid vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure the detection accuracy of the air-fuel ratio variation abnormality between cylinders.SOLUTION: A hybrid vehicle includes: a multi-cylinders internal combustion engine; an electric motor; a detecting means that detects the air-fuel ratio variation abnormality between cylinders of the internal combustion engine; and a control means executable of a hybrid (HV) mode which drives the vehicle by both the internal combustion engine and the electric motor, and an engine mode to drive the vehicle only with the internal combustion engine. The control means controls the internal combustion engine, and the electric motor so that an actual operating point c11 of the internal combustion engine may move on a prescribed operation line b1 in the HV mode, changes the operation line to b2 when a prescribed change is requested in execution of the HV mode and shifts to the engine mode, and prohibits change of the operation line and transition to the engine mode when the variation abnormality detection is unexecuted or under execution during executing the HV mode running and maintains the hybrid mode.

Description

  The present invention relates to a hybrid vehicle, and more particularly, to a hybrid vehicle including two types of power sources, i.e., an internal combustion engine (engine) and an electric motor (motor), as driving power sources.

  In recent years, in vehicles equipped with a multi-cylinder internal combustion engine as a driving power source, it has been required to detect an abnormal variation in air-fuel ratio between cylinders in a vehicle-mounted state (so-called OBD; On-Board Diagnostics). There is also a movement to legislate. For example, when the fuel injection system of some cylinders fails, the air-fuel ratio between the cylinders varies greatly, and the exhaust emission of the vehicle deteriorates. There is a need to prevent such a vehicle from running.

JP 2009-013967 A

  There is a similar request for the hybrid vehicle. Generally, in a hybrid vehicle, in order to optimize the fuel consumption of the engine, the engine and the motor are controlled so that the actual operating point of the engine moves on a predetermined operating line, and the vehicle is driven by using both in combination.

  However, in such a hybrid vehicle, when there is a predetermined change request, the operation line may be changed and the vehicle may run only with the engine. At this time, if the operating line is changed while the engine and the motor are running and the variation abnormality is detected, and the engine is switched to running only with the engine, the engine operating conditions change before and after the switching. This makes it impossible to perform accurate detection.

  Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a hybrid vehicle that can sufficiently ensure the detection accuracy of the variation in air-fuel ratio between cylinders.

According to a first aspect of the invention,
A multi-cylinder internal combustion engine as a first power source for traveling;
An electric motor as a second power source for traveling;
Detecting means for detecting an air-fuel ratio variation abnormality between cylinders of the internal combustion engine;
Control means capable of executing a hybrid mode that is a control mode for driving a vehicle with both the internal combustion engine and the electric motor, and an engine mode that is a control mode for driving the vehicle with only the internal combustion engine; ,
With
The control means includes
In the hybrid mode, the internal combustion engine and the electric motor are controlled so that an actual operating point of the internal combustion engine moves on a predetermined operating line in a coordinate system defined by the rotational speed and torque of the internal combustion engine,
When there is a predetermined change request during execution of the hybrid mode, the operation line is changed to shift to the engine mode, and
The hybrid vehicle is characterized in that, when the variation abnormality detection is not executed or is being executed during the execution of the hybrid mode, the change of the operation line and the shift to the engine mode are prohibited and the hybrid mode is maintained. Provided.

  Preferably, the control means generates the change request when a charge amount of a battery that stores electric power supplied to the electric motor becomes a predetermined value or less.

Preferably, the control means includes
When a predetermined motor mode condition is established, a motor mode that is a control mode for driving the vehicle only by the electric motor can be executed, and
When the motor mode condition is satisfied when the variation abnormality detection is not being executed or is being executed, the motor mode and the stop idle stop control for stopping the idle operation of the internal combustion engine when the vehicle is stopped are prohibited, Preferably, the control means executes the hybrid mode or the engine mode.
When the motor mode condition is satisfied when the variation abnormality detection is not performed or is being performed, when the predetermined cancel condition is satisfied, or when the cancel condition is not satisfied and the motor mode switch is OFF In addition, the motor mode and the idling stop control at the time of stop are prohibited, and the hybrid mode or the engine mode is executed.

Preferably, the control means includes
When the motor mode condition is satisfied when the variation abnormality detection is not executed or is being executed, the motor mode is executed when the cancel condition is not satisfied and the motor mode switch is on.

According to a second aspect of the invention,
A multi-cylinder internal combustion engine as a first power source for traveling;
An electric motor as a second power source for traveling;
A generator driven by the internal combustion engine;
A battery that stores power supplied to the motor and is charged by the generator;
Detecting means for detecting an air-fuel ratio variation abnormality between cylinders of the internal combustion engine;
When the charge amount of the battery is less than or equal to a predetermined value, the variation abnormality detection is prohibited until the charge amount exceeds a predetermined value, and the generator is driven by the internal combustion engine to charge the battery. A control means that permits variation abnormality detection if exceeded,
A hybrid vehicle characterized by comprising:

According to a third aspect of the invention,
A multi-cylinder internal combustion engine as a power source for traveling;
Detecting means for detecting an air-fuel ratio variation abnormality between cylinders of the internal combustion engine;
A control means for performing idle stop control at stop when the vehicle is stopped, and prohibiting idle stop control at stop when variation abnormality detection is not performed or is being performed when the vehicle is stopped;
A vehicle characterized by comprising:

Preferably, the control means includes
When at least one of idle stop control during deceleration and free run control is executed during deceleration before the vehicle stops, and when variation abnormality detection is not executed or is being executed during deceleration, at least one of idle stop control during deceleration and free run control is executed. Prohibit one.

  According to the present invention, it is possible to provide an excellent effect that it is possible to provide a hybrid vehicle that can sufficiently ensure the accuracy of detecting an abnormality in the air-fuel ratio variation between cylinders.

1 is a schematic view of a hybrid vehicle according to an embodiment of the present invention. It is the schematic of the internal combustion engine which concerns on this embodiment. It is a graph which shows the output characteristic of a pre-catalyst sensor and a post-catalyst sensor. It is a graph which shows the fluctuation | variation of the exhaust air fuel ratio according to the air-fuel ratio variation degree between cylinders. FIG. 5 is an enlarged view corresponding to a U portion in FIG. 4. It is a graph which shows the operating characteristic of an internal combustion engine. It is a flowchart which shows the routine of 1st Example of vehicle control. It is a flowchart which shows the routine of 2nd Example of vehicle control. It is a flowchart which shows the routine of 3rd Example of vehicle control. It is the schematic of a manual transmission vehicle. 1 is a schematic view of an automatic transmission vehicle. It is a time chart for demonstrating each engine stop control of 4th Example of vehicle control. It is a flowchart which shows the routine of 4th Example of vehicle control.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 schematically shows a hybrid vehicle 50 according to the present embodiment. The hybrid vehicle 50 includes an internal combustion engine, that is, an engine 1, a three-shaft power distribution mechanism 51 connected to a crankshaft 1 a as an output shaft of the engine 1, and a first electric motor capable of generating electricity connected to the power distribution mechanism 51. That is, the first motor generator (hereinafter abbreviated as the first motor) MG1, the reduction gear mechanism 52 connected to the ring gear shaft 51a that is the output shaft of the power distribution mechanism 51, and the first power generator capable of generating power connected to the reduction gear mechanism 52. Two electric motors, that is, a second motor generator (hereinafter abbreviated as “second motor”) MG2 and an electronic control unit (hereinafter referred to as “ECU”) 20 as control means for controlling the entire vehicle.

  The engine 1 serves as a first power source for traveling, and the first motor MG1 serves as a second power source for traveling. The second motor MG2 mainly functions as a generator for charging the battery 53 that stores the electric power supplied to the first motor MG1.

  The ECU 20 can include an engine ECU that controls the engine 1, a motor ECU that controls the motors MG <b> 1 and MG <b> 2, and a battery ECU that manages the battery 53.

  The engine 1 generates power by burning a fuel such as gasoline or light oil, and is composed of, for example, a multi-cylinder spark ignition internal combustion engine which will be described in detail later.

  The power distribution mechanism 51 includes a planetary gear mechanism, and includes a sun gear 54 disposed in the center, a ring gear 55 disposed in the outer peripheral portion, and a plurality of pinion gears 56 disposed between the sun gear 54 and the ring gear 55. And a carrier 57 for holding the pinion gear 56 so as to rotate and revolve freely.

  The crankshaft 1a of the engine 1 is connected to the carrier 57, the first motor MG1 is connected to the sun gear 54, and the reduction gear mechanism 52 is connected to the ring gear 55 via the ring gear shaft 51a.

  When the first motor MG1 functions as a generator, the power from the engine 1 input from the carrier 57 is distributed to the sun gear 54 side and the ring gear 55 side according to each gear ratio.

  When the first motor MG1 functions as an electric motor, the power from the engine 1 input from the carrier 57 and the power from the first motor MG1 input from the sun gear 54 are integrated and output to the ring gear 55 side. The power output to the ring gear 55 is finally transmitted from the ring gear shaft 51a to the vehicle drive wheels 60a and 60b via the gear mechanism 58 and the differential gear 59.

  Each of the first motor MG1 and the second motor MG2 is configured as a well-known synchronous generator motor having both functions of an electric motor and a generator. The first motor MG1 and the second motor MG2 are connected to the battery 53 via the first inverter 61 and the second inverter 62, respectively. Exchange power.

  The power line 63 connecting the inverters 61 and 62 and the battery 53 has a positive electrode bus and a negative electrode bus shared by the inverters 61 and 62, and the electric power generated by one of the motors MG1 and MG2 is generated by another motor. It can be consumed. Therefore, the battery 53 is charged / discharged by electric power generated from one of the motors MG1 and MG2 or insufficient electric power. Note that if the balance of electric power is balanced by the motors MG1 and MG2, the battery 53 is not charged / discharged.

  The ECU 20 receives signals necessary for controlling the motors MG1 and MG2, such as a signal from a rotational position detection sensor (not shown) for detecting the rotational position of the rotor of the motors MG1 and MG2, and the motors MG1 and MG2. A signal from a current sensor (not shown) for detecting the applied phase current is input. ECU 20 calculates the rotational speed of motors MG1, MG2 based on the signal from the rotational position detection sensor. The ECU 20 outputs a switching control signal to the inverters 61 and 62.

  The ECU 20 has a signal necessary for managing the battery 53, for example, a voltage signal from a voltage sensor (not shown) installed between the positive and negative terminals of the battery 53, and a current sensor (not shown) attached to the power line 63. ) And a battery temperature signal from a temperature sensor (not shown) attached to the battery 53 are input.

  Further, the ECU 20 may calculate the charge amount SOC of the battery 53 based on the integrated value of the charge / discharge current detected by the current sensor, or charge / discharge the battery 53 based on the charge amount SOC and the battery temperature. The input / output limit that is electric power is calculated.

  When calculating the charge amount SOC of the battery 53, the ECU 20 integrates the charge / discharge current of the battery 53 detected by the current sensor. At this time, the charging current is a positive value, the discharging current is a negative value, and the charge / discharge current integrated value is added to the charge amount SOC. The charge amount SOC may be calculated by other methods. Thus, ECU20 functions also as a charge amount detection means for detecting the battery charge amount.

  The ECU 20 includes a CPU, a ROM, a RAM, an input / output port, and the like (not shown). The ECU 20 includes an on / off signal from an ignition switch (not shown), a shift position signal from a shift position sensor (not shown) for detecting the operation position of the shift lever, and an accelerator opening sensor (see FIG. 2 (denoted by reference numeral 15 in FIG. 2), a brake pedal position signal from a brake position sensor (not shown) for detecting a brake pedal operation amount, a vehicle speed signal from a vehicle speed sensor 64, and driving the vehicle only by a motor. An on / off signal from an EV switch 65 serving as a motor mode switch for instructing to perform, an on / off signal from an eco switch (not shown) for instructing to give priority to vehicle fuel consumption, and the like are input via an input port.

  The ECU 20 calculates the required torque to be output to the ring gear shaft 51a as the drive shaft based on the accelerator opening corresponding to the accelerator pedal operation amount by the driver and the vehicle speed, and the required power corresponding to this required torque is the ring gear shaft. The engine 1 and the motors MG1, MG2 are controlled so as to be actually output to 51a.

  In particular, the ECU 20 is a hybrid mode that is a control mode for driving the vehicle 50 by both the engine 1 and the first motor MG1, an engine mode that is a control mode for driving the vehicle 50 only by the engine 1, and the vehicle 50. Can be executed in a motor mode, which is a control mode for driving the motor only with the first motor MG1.

  Next, the configuration of the engine 1 will be described with reference to FIG. The engine 1 burns a mixture of fuel and air in a combustion chamber 3 formed in the cylinder block 2 and generates power by reciprocating a piston in the combustion chamber 3. The engine 1 of this embodiment is a multi-cylinder internal combustion engine, more specifically, an in-line 4-cylinder spark ignition internal combustion engine. The internal combustion engine 1 includes # 1 to # 4 cylinders. However, the number of cylinders, the type, etc. are not particularly limited.

  Although not shown, the cylinder head of the engine 1 is provided with an intake valve for opening and closing the intake port and an exhaust valve for opening and closing the exhaust port for each cylinder. Each intake valve and each exhaust valve has a camshaft. It is driven to open and close by a valve mechanism that includes it. A spark plug 7 for igniting the air-fuel mixture in the combustion chamber 3 is attached to the top of the cylinder head for each cylinder.

  The intake port of each cylinder is connected to a surge tank 8 which is an intake air collecting chamber via a branch pipe 4 for each cylinder. An intake pipe 13 is connected to the upstream side of the surge tank 8, and an air cleaner 9 is provided at the upstream end of the intake pipe 13. An air flow meter 5 for detecting the intake air amount and an electronically controlled throttle valve 10 are incorporated in the intake pipe 13 in order from the upstream side. An intake passage is formed by the intake port, the branch pipe, the surge tank 8 and the intake pipe 13.

  An injector (fuel injection valve) 12 for injecting fuel into an intake passage, particularly an intake port, is provided for each cylinder. The fuel injected from the injector 12 is mixed with intake air to form an air-fuel mixture. The air-fuel mixture is sucked into the combustion chamber 3 when the intake valve is opened, compressed by the piston, and ignited and burned by the spark plug 7.

  On the other hand, the exhaust port of each cylinder is connected to the exhaust manifold 14. The exhaust manifold 14 includes a branch pipe 14a for each cylinder forming an upstream portion thereof and an exhaust collecting portion 14b forming a downstream portion thereof. An exhaust pipe 6 is connected to the downstream side of the exhaust collecting portion 14b. An exhaust passage is formed by the exhaust port, the exhaust manifold 14 and the exhaust pipe 6.

  A catalyst composed of a three-way catalyst, that is, an upstream catalyst 11 and a downstream catalyst 19 are attached in series to the upstream side and the downstream side of the exhaust pipe 6, respectively. First and second air-fuel ratio sensors for detecting the air-fuel ratio of the exhaust gas, that is, a pre-catalyst sensor 17 and a post-catalyst sensor 18 are installed on the upstream side and the downstream side of the upstream catalyst 11, respectively. The pre-catalyst sensor 17 and the post-catalyst sensor 18 are installed at positions immediately before and immediately after the upstream catalyst 11, and detect the air-fuel ratio based on the oxygen concentration in the exhaust gas. In this way, the single pre-catalyst sensor 17 is installed at the exhaust merging portion on the upstream side of the upstream catalyst 11.

  The spark plug 7, the throttle valve 10, the injector 12 and the like described above are electrically connected to the ECU 20. As shown in the figure, the ECU 20 includes, in addition to the air flow meter 5, the pre-catalyst sensor 17, and the post-catalyst sensor 18, a crank angle sensor 16 that detects the crank angle of the engine 1, and an accelerator opening that detects the accelerator opening. A sensor 15, a water temperature sensor 21 for detecting the cooling water temperature of the engine 1, and other various sensors are electrically connected. The ECU 20 controls the ignition plug 7, the throttle valve 10, the injector 12, etc. so as to obtain a desired engine output based on the detection values of various sensors, etc., and the ignition timing, fuel injection amount, fuel injection timing, throttle Control the opening and so on. The throttle opening is normally controlled to an opening corresponding to the accelerator opening.

  The ECU 20 calculates the engine speed Ne (rpm) based on the output of the crank angle sensor 16. Here, the engine speed is the engine speed per unit time and is synonymous with the rotational speed.

  The pre-catalyst sensor 17 is a so-called wide-range air-fuel ratio sensor, and can continuously detect an air-fuel ratio over a relatively wide range. FIG. 3 shows the output characteristics of the pre-catalyst sensor 17. As shown in the figure, the pre-catalyst sensor 17 outputs a voltage signal Vf having a magnitude proportional to the exhaust air-fuel ratio. The output voltage when the exhaust air-fuel ratio is stoichiometric (theoretical air-fuel ratio, for example, A / F = 14.6) is Vreff (for example, about 3.3 V).

On the other hand, the post-catalyst sensor 18 is a so-called O ₂ sensor, and has a characteristic that the output value changes suddenly with the stoichiometric boundary. FIG. 3 shows the output characteristics of the post-catalyst sensor 18. As shown in the figure, the output voltage when the exhaust air-fuel ratio is stoichiometric, that is, the stoichiometric equivalent value is Vrefr (for example, 0.45 V). The output voltage of the post-catalyst sensor 18 changes within a predetermined range (for example, 0 to 1 V). When the exhaust air-fuel ratio is leaner than stoichiometric, the output voltage of the post-catalyst sensor becomes lower than the stoichiometric equivalent value Vrefr, and when the exhaust air-fuel ratio is richer than stoichiometric, the output voltage of the post-catalyst sensor becomes higher than the stoichiometric equivalent value Vrefr.

  The upstream catalyst 11 and the downstream catalyst 19 simultaneously purify NOx, HC and CO, which are harmful components in the exhaust gas, when the air-fuel ratio A / F of the exhaust gas flowing into each of them is close to the stoichiometric range. The air-fuel ratio width (window) that can simultaneously purify these three with high efficiency is relatively narrow.

  Therefore, air-fuel ratio control (stoichiometric control) is executed by the ECU 20 so that the air-fuel ratio of the exhaust gas flowing into the upstream catalyst 11 is controlled in the vicinity of stoichiometric. This air-fuel ratio control is detected by a main air-fuel ratio control (main air-fuel ratio feedback control) that makes the exhaust air-fuel ratio detected by the pre-catalyst sensor 17 coincide with a stoichiometry that is a predetermined target air-fuel ratio, and detected by the post-catalyst sensor 18. The auxiliary air-fuel ratio control (auxiliary air-fuel ratio feedback control) is performed so that the exhaust air-fuel ratio thus made coincides with the stoichiometry.

  Now, for example, it is assumed that the injectors 12 of some cylinders out of all the cylinders have failed and air-fuel ratio variations (imbalance) occur between the cylinders. For example, the # 1 cylinder has a larger fuel injection amount than the other # 2, # 3, and # 4 cylinders, and its air-fuel ratio is greatly shifted to the rich side. Even at this time, if a relatively large correction amount is given by the above-described main air-fuel ratio feedback control, the air-fuel ratio of the total gas supplied to the pre-catalyst sensor 17 may sometimes be stoichiometrically controlled. However, looking at each cylinder, # 1 cylinder is larger and richer than stoichiometric, and # 2, # 3 and # 4 cylinders are leaner than stoichiometric. Is clear. Therefore, in the present embodiment, a means for detecting such an abnormality in the air-fuel ratio variation between cylinders is provided. If this variation abnormality can be detected, the fuel injection amount correction for each cylinder can be performed so as to eliminate the variation abnormality, and the emission for each cylinder can be improved.

  As shown in FIG. 4, when the variation in the air-fuel ratio between cylinders occurs, the fluctuation of the exhaust air-fuel ratio periodically with one engine cycle (= 720 ° CA) as one cycle increases. The air-fuel ratio diagrams a, b, and c in (B) are not varied, and the pre-catalyst in the case of a rich shift at an imbalance ratio of 20% for only one cylinder and a rich shift at an imbalance ratio of 50% for only one cylinder. An air-fuel ratio A / F detected by the sensor 17 is shown. As can be seen, the greater the degree of variation, the greater the amplitude of the air-fuel ratio fluctuation.

  Here, the imbalance ratio (%) is a parameter representing the magnitude of air-fuel ratio variation. In other words, the imbalance ratio is the amount of fuel injection in a cylinder (imbalance cylinder) causing the fuel injection amount deviation when only one of the cylinders has caused the fuel injection amount deviation. The ratio is a value indicating whether the fuel injection amount is not deviated from the fuel injection amount of the cylinder (balance cylinder) that has not caused the fuel injection amount deviation, that is, the reference injection amount. When the imbalance ratio is IB, the fuel injection amount of the imbalance cylinder is Qib, and the fuel injection amount of the balance cylinder, that is, the reference injection amount is Qs, IB = (Qib−Qs) / Qs. The greater the imbalance ratio IB, the greater the fuel injection amount deviation between the imbalance cylinder and the balance cylinder, and the greater the air-fuel ratio variation.

  When the air-fuel ratio variation abnormality occurs, the output variation of the pre-catalyst sensor 17 becomes large. Therefore, it is possible to detect the variation abnormality based on the output variation using this characteristic.

  In the present embodiment, an output fluctuation parameter that is a parameter correlated with the degree of fluctuation of the air-fuel ratio sensor output is calculated, and an abnormality is detected based on the output fluctuation parameter and a predetermined determination value.

  A method for calculating the output fluctuation parameter will be described below. FIG. 5 is an enlarged view corresponding to the U portion of FIG. 4, and particularly shows a fluctuation of the sensor output before the catalyst within one engine cycle. As the pre-catalyst sensor output, a value obtained by converting the output voltage Vf of the pre-catalyst sensor 17 into an air-fuel ratio A / F is used. However, the output voltage Vf of the pre-catalyst sensor 17 can be directly used.

As shown in FIG. 4B, the ECU 20 acquires the value of the pre-catalyst sensor output A / F every predetermined sample period τ (unit time, for example, 4 ms) within one engine cycle. The value A / F _n obtained in this timing (second timing), the absolute value of the difference .DELTA.A / F _n between the value A / F _n-1 obtained at the previous timing (first timing) It calculates | requires by following Formula (1). This difference ΔA / F _n can be restated as a differential value or a slope at the current timing.

Most simply, this difference ΔA / F _n represents the fluctuation of the sensor output before the catalyst. This is because the gradient of the air-fuel ratio diagram increases as the degree of fluctuation increases, and the difference ΔA / F _n increases. Therefore it is possible to the value of the difference .DELTA.A / F _n at predetermined first timing and the output fluctuation parameter.

However, in the present embodiment for the accuracy, the average value of a plurality of difference .DELTA.A / F _n and the output fluctuation parameter. In the present embodiment, the difference ΔA / F _n is integrated at each timing within one engine cycle, the final integrated value is divided by the number of samples N, and the average value of the differences ΔA / F _n within one engine cycle is obtained. . And further, by integrating the M engine cycles (eg M = 100) Mean value of only the difference .DELTA.A / F _n, the final integrated value is divided by the number of cycles M, the average value of the difference .DELTA.A / F _n in the M engine cycles Ask for. The final average value thus obtained is used as an output fluctuation parameter, and is displayed as “X” hereinafter. The output fluctuation parameter X increases as the fluctuation degree of the pre-catalyst sensor output increases.

Since there is a case of decrease in the case where the pre-catalyst sensor output A / F is increased, only one seeking the difference .DELTA.A / F _n or the average value thereof for the cases of these respective, may be the same as the output fluctuation parameter .

  Also, any value that correlates with the degree of fluctuation in the pre-catalyst sensor output can be used as the output fluctuation parameter. For example, output fluctuation based on the difference between the maximum peak and minimum peak of the sensor output before the catalyst within one engine cycle (so-called peak to peak), or the absolute value of the maximum peak or minimum peak of the second derivative. Parameters can also be calculated. This is because the difference between the maximum peak and the minimum peak of the pre-catalyst sensor output increases as the degree of fluctuation of the pre-catalyst sensor output increases, and the absolute value of the maximum peak or minimum peak of the second-order differential value also increases.

  If the calculated output variation parameter X is equal to or greater than a predetermined determination value, it is determined that there is a variation abnormality, and if the calculated output variation parameter X is smaller than the determination value, it is determined that there is no variation abnormality, that is, normal.

  The precondition for executing the variation abnormality detection includes that the intake air amount Ga (specifically, the detected value), which is a substitute value of the exhaust gas flow rate, is greater than or equal to a predetermined value. This is because sufficient gas contact with the pre-catalyst sensor 17 is ensured, and the difference in sensor output fluctuation according to the degree of variation is clearly shown. The precondition includes that the engine 1 is in steady operation. This is because the rotational speed and intake air amount change during non-steady operation (particularly during transient operation) that is not in steady operation, which affects sensor output fluctuations and makes accurate detection difficult. This steady operation includes idle operation. Further, the precondition includes that the engine is under stoichiometric control. When such a precondition is satisfied, variation abnormality detection is executed or started.

  As a method for detecting the variation abnormality, any method other than the above-described method using the pre-catalyst sensor output fluctuation can be adopted. In other words, the variation abnormality detection method is not limited to the above method.

  In the hybrid vehicle 50 of the present embodiment, in the hybrid mode, the engine 1 and the first motor MG1 are arranged so that the actual operating point of the engine 1 moves on a predetermined operating line in order to optimize the fuel consumption of the engine 1. It is controlled and the vehicle is driven by using both.

  On the other hand, in the hybrid vehicle 50 of the present embodiment, when a predetermined change request is made during execution of the hybrid mode, the operation line may be changed to shift to the engine mode, and the engine 1 may run alone. At this time, if there is a change request during execution of hybrid mode and variation abnormality detection, and switching to the engine mode, the operation line is changed, and the engine operating conditions change before and after switching, so that detection with high accuracy is possible. Cannot be executed.

  This point will be described with reference to FIG. FIG. 6 shows operating characteristics of the engine 1 in the hybrid vehicle 50 of the present embodiment. As shown in the figure, the engine operating range is defined by a coordinate system having the horizontal axis and the vertical axis as the engine speed (rpm) and the engine torque (Nm), respectively. A plurality of oblique lines indicated by a represent iso-output lines relating to engine output, and the output increases toward the upper right in the figure. The torque corresponds to the force, whereas the output corresponds to the work amount per unit time. Therefore, the output increases as the rotational speed increases even if the torque is constant.

  In the vehicle control of this embodiment, a plurality of operation lines in the coordinate system are stored in advance in the ECU 20. In the hybrid mode and the engine mode, one operating line is selected based on the accelerator opening detected by the accelerator opening sensor 15, that is, the output request, and the actual operating point of the engine is selected. Engine 1 and motor MG1 are controlled to move. Here, the actual operating point is a point on the coordinate system represented by a set of the actual engine speed and torque.

  A typical example of this operation line is a fuel efficiency optimum line that is best indicated by b1 in FIG. This fuel efficiency optimum line b1 exists in the high torque range of the engine. During traveling in the normal hybrid mode, the engine 1 and the motor MG1 are controlled so that the fuel efficiency optimal line b1 is selected and the actual operating point (c11 or c12) moves on the fuel efficiency optimal line b1. The

  By the way, if there is a predetermined change request during the hybrid mode in which the fuel efficiency optimal line b is selected, the operation line is changed to the operation line b2 on the higher torque side, and the mode is shifted to the engine mode. The change request is a change request signal generated inside the ECU 20, and typically, the change request is generated when the charge amount SOC of the battery 53 becomes a predetermined value SOC1 (for example, 45%) or less.

  When the change request is generated, the operation of the motor MG1 is stopped, the engine output is increased by the motor output, the vehicle is driven by the engine alone, and the second motor MG2 is driven only by the engine. Power generation and battery charging. Then, the operating point c11 or c12 that was on the fuel efficiency optimal line b1 in the hybrid mode is moved to the operating point c21 or c22 on the operating line b2 on the same rotation and high output side. As a result, the accelerator opening and thus the throttle opening are increased while maintaining the same rotation, and the intake air amount Ga and thus the exhaust gas flow rate are increased.

  Then, the way the exhaust gas strikes the pre-catalyst sensor 17 also changes. Therefore, if the variation abnormality is detected before and after the change of the operation line or mode, the sensor output fluctuation state changes after the change, and it becomes impossible to perform accurate detection.

  Therefore, in this embodiment, in order to sufficiently secure the accuracy of abnormality detection, when the variation abnormality detection is not executed or is being executed during the execution of the hybrid mode, even if there is a change request, the change of the operation line is changed. The hybrid mode is maintained by forcibly prohibiting the transition to the engine mode. As a result, the intake air amount Ga and thus the exhaust gas flow rate can be prevented from changing, and the gas contact state and the sensor output fluctuation state to the pre-catalyst sensor 17 can be kept constant to sufficiently ensure the accuracy of abnormality detection. It becomes possible.

  Here, in this embodiment, variation abnormality detection is performed at least once during one trip. One trip refers to the time from when the ignition switch is turned on once to when it is turned off next time. And if the variation anomaly detection has not been performed once during the current trip and it has not been executed, even if there is a change request during the hybrid mode, the change of the operation line and the transition to the engine mode are forcibly prohibited. The hybrid mode is maintained. This is for preventing the change of the operation line and the control mode after the start of the variation abnormality detection since the possibility that the variation abnormality detection is started after that is not executed.

  A first preferred embodiment of the vehicle control including the operation line change prohibition will be described with reference to FIG. The control routine shown in FIG. 7 can be repeatedly executed by the ECU 20 every predetermined calculation cycle (for example, 4 ms).

  First, in step S101, it is determined whether variation abnormality detection during the current trip has not been executed or is being executed. If not executed or not being executed (if already executed), the routine is terminated. If not being executed or being executed, the process proceeds to step S102.

  In step S102, it is determined whether a hybrid mode condition, which is a predetermined condition for executing the hybrid (HV) mode, is satisfied. The hybrid mode condition is, for example, that the vehicle speed V exceeds a predetermined value V1 (for example, 40 km / h), or the vehicle speed V is not more than the predetermined value V1 and the water temperature Tw is not more than a predetermined value Tw1 (for example, 75 ° C.) (that is, It is established when the engine has not been warmed up.

  When the hybrid mode condition is not satisfied, the process proceeds to step S103, and it is determined whether or not a motor mode condition that is a predetermined condition for executing the motor mode is satisfied. The motor mode condition is satisfied, for example, when the vehicle speed V is equal to or lower than a predetermined value V1 and the water temperature Tw exceeds the predetermined value Tw1 (that is, the engine warm-up is finished).

  If it is determined in step S102 that the hybrid mode condition is satisfied, the process proceeds to step S105, where the hybrid mode is executed and the change of the operation line and the control mode is prohibited. Thus, the hybrid mode is maintained, and even if there is a change request before or during the execution of the variation abnormality detection, the change of the operation line and the transition to the engine mode can be prohibited. Then, accurate variation abnormality detection can be performed.

  After step S105, the process proceeds to step S104, and the above-described processing related to variation abnormality detection is executed.

  On the other hand, if it is determined in step S103 that the motor mode condition is satisfied, the process proceeds to step S106, where the motor mode and the idle stop control during stop are forcibly prohibited, and the hybrid mode or the engine mode is executed. The Here, the idling stop control at the time of stop is a control for stopping the idling operation of the engine when the vehicle is stopped, and is a control executed together with the hybrid mode or the engine mode.

  Under normal conditions, when the motor mode condition is satisfied, the engine is stopped (ie, fuel injection and ignition are stopped), and the motor mode is executed. However, this makes it impossible to detect variation abnormality. Therefore, in order to prohibit the stop of the engine and to detect variation abnormality, the motor mode and the deceleration idle stop control are forcibly prohibited and the engine is operated in the hybrid mode or the engine mode. As a result, it is possible to suitably perform variation abnormality detection even under operating conditions where the engine is originally stopped. In particular, since idling stop control at the time of stop is also prohibited, variation abnormality detection can be performed during idling operation, and more detection opportunities can be secured.

  After step S106, the process proceeds to step S104, and variation abnormality detection processing is executed.

  When it is determined in step S103 that the motor mode condition is not satisfied, the engine mode is executed, and in step S104, the variation abnormality detection process is executed.

  Next, a second preferred embodiment of vehicle control including prohibition of operation line change will be described with reference to FIG. The control routine shown in FIG. 8 can also be repeatedly executed by the ECU 20 every predetermined calculation cycle (for example, 4 ms).

  Steps S201 to S205 and S208 of the second embodiment are the same as steps S101 to S105 and S106 of the first embodiment, respectively. The second embodiment is different from the first embodiment in that steps S206, S207, and S209 are added.

When it is determined in step S203 that the motor mode condition is satisfied, the process proceeds to step S206, and it is determined whether or not a cancel condition that is a predetermined condition for canceling the motor mode is not satisfied.
The cancel condition is satisfied, for example, when the battery charge amount SOC becomes equal to or less than the predetermined value SOC1, or when a predetermined electric load (for example, defroster) is turned on, and is not satisfied otherwise. When the battery charge SOC is less than a predetermined value or when a predetermined electric load is turned on, the use of the first motor MG1 is prohibited to eliminate battery power consumption and charge the battery 53. This is because it is necessary to operate the engine 1 and the second motor MG2 in order to secure electric power necessary for operating the electric load.

When it is determined that the cancel condition is not satisfied, that is, when the use of the first motor MG1 is permitted, the process proceeds to step S207 to determine whether the EV switch 65 is on.
If it is determined that the EV switch 65 is on, the process proceeds to step S209, the motor mode is executed, and the routine is terminated. In other words, even when the variation abnormality detection is not performed or is being performed, when the motor mode condition is satisfied, the cancellation condition is not satisfied, and the EV switch 65 is turned on, the driver's intention is greater than the variation abnormality detection. Priority is given to the motor mode. At this time, if the variation abnormality detection is being executed, the variation abnormality detection is stopped halfway.

  On the other hand, if it is determined in step S206 that the cancel condition is not non-satisfied (satisfied), and if it is determined in step S207 that the EV switch 65 is not on (off), the process proceeds to step S208. The motor mode and the stop-time idle stop control are forcibly prohibited, and the hybrid mode or the engine mode is executed. Thereafter, the process proceeds to step S204, and the variation abnormality detection process is executed.

  As described above, according to the first and second embodiments, a constant engine operation can be performed even in a situation where a variation abnormality cannot be detected under a certain engine operating condition, or in a situation where abnormality detection itself cannot be performed. It is possible to detect variation abnormality under conditions, and it is possible to secure sufficient detection accuracy and increase detection opportunities.

  Next, a third embodiment of vehicle control will be described with reference to FIG. This vehicle control does not include prohibition of operation line change. The control routine shown in FIG. 9 can also be repeatedly executed by the ECU 20 every predetermined calculation cycle (for example, 4 ms).

Step S301 is the same as step S101. If it is determined in step S301 that the variation abnormality detection during the current trip is not being executed or is being executed, the process proceeds to step S302, where it is determined whether or not the battery charge amount SOC is equal to or less than a predetermined value SOC1.
When it is determined that the battery charge amount SOC is equal to or less than the predetermined value SOC1, the process proceeds to step S303 and the variation abnormality detection process is prohibited. In step S304, the hybrid mode or the engine mode is executed, and the second motor MG2 as a generator is driven mainly using the engine power to charge the battery 53. This routine is continued until a negative determination is made in step S302.

  On the other hand, if it is determined in step S302 that the battery charge amount SOC has exceeded the predetermined value SOC1, the variation abnormality detection process is permitted in step S305. Thereafter, in another routine (not shown), the variation abnormality detection process is executed simultaneously with the establishment of the precondition.

  According to the third embodiment, ensuring that the battery charge amount SOC is equal to or greater than the predetermined value SOC1 is prioritized over variation abnormality detection, so that it is possible to prevent the variation abnormality detection from hindering driving of the vehicle. Since the variation abnormality detection is performed after the battery charge amount SOC is ensured to be equal to or greater than the predetermined value SOC1, the detection is prevented from being stopped due to the lack of the battery charge amount SOC during the detection, and stable detection is performed. Is possible.

  Next, a fourth embodiment of vehicle control will be described. This vehicle control also does not include prohibition of changing the operation line, and is applied to vehicles other than the hybrid vehicle 50 as described above.

  A vehicle applied to the fourth embodiment is a manual transmission vehicle (hereinafter referred to as an MT vehicle) 60 as shown in FIG. 10, which is more general than the hybrid vehicle 50 described above, or an automatic transmission vehicle (hereinafter referred to as an MT) as shown in FIG. 70).

  An MT vehicle 60 shown in FIG. 10 includes the engine 1 and the ECU 20 described above, a friction clutch 61, and a manual transmission 62. A vehicle including a semi-automatic system that automatically operates the clutch 61 and the manual transmission 62 with an actuator is also included in the MT vehicle 60. A starter motor 63 is provided on the input side of the clutch 61, and the engine 1 can be automatically started by controlling the starter motor 63 with the ECU 20.

  An AT vehicle 60 shown in FIG. 11 includes the engine 1 and ECU 20 described above, a torque converter 71, and an automatic transmission 72. A starter motor 73 is provided on the input side of the torque converter 71, and the engine 1 can be automatically started by controlling the starter motor 73 with the ECU 20.

  In these vehicles 60 and 70, the ECU 20 can execute the above-described stop idle stop control. When the driver performs a predetermined operation during the idle stop control at the time of stop, the ECU 20 turns on the starter motors 63 and 73, and the engine 1 is automatically started. The predetermined operation performed by the driver is, for example, release of the brake pedal or depression of the clutch pedal in the MT vehicle 60 and release of the brake pedal in the AT vehicle 70.

  In these vehicles 60 and 70, the ECU 20 can execute idle stop control during deceleration. The idle stop control during deceleration is control for stopping the engine 1 during deceleration immediately before stopping the vehicle, that is, control for stopping fuel injection and ignition.

  In these vehicles 60 and 70, as shown in FIG. 12, deceleration fuel cut (F / C) control, that is, control for stopping fuel injection and ignition is executed when the vehicle or engine 1 is decelerated. In the deceleration fuel cut control, for example, when the accelerator opening degree Ac is substantially fully closed and the engine speed Ne is equal to or higher than a predetermined return speed (for example, 1200 rpm) slightly higher than a predetermined idle speed (for example, 800 rpm), Executed.

  In a normal vehicle, when the engine speed Ne falls below the return speed Ne1 during execution of the deceleration fuel cut control (time t1), the deceleration fuel cut control is canceled, the engine 1 is returned, and fuel injection and ignition are performed. Is resumed. However, in the vehicles 60 and 70 according to the present embodiment, the engine 1 is not operated for return even if the engine speed Ne falls below the return speed Ne1 due to execution of the idle stop control during deceleration. As a result, the engine is stopped until the vehicle stop time t2. Since the engine is stopped by the stop idle stop control even after the vehicle stop time t2, the engine stops after the engine is stopped by the idle stop control during deceleration until the stop idle stop control ends. The state remains.

  Furthermore, in these vehicles 60 and 70, the ECU 20 can also execute free-run control. Free-run control is control for stopping the operation of the engine 1 when the accelerator opening is substantially fully closed and the manual transmission 62 or the automatic transmission 72 is in the neutral position, that is, control for stopping fuel injection and ignition. is there. When the accelerator opening is substantially fully closed and the transmissions 62 and 72 are in the neutral position, the driver can be regarded as not requiring the engine output, so the engine is stopped. Generally, the engine is stopped when the driver fully closes the accelerator pedal at the time of deceleration before the vehicle stops and the transmissions 62 and 72 are operated to the neutral position, and the engine stop state continues until the vehicle stops thereafter. It becomes.

  Now, if any of these engine stop controls, that is, idle stop control during stop, idle stop control during deceleration, or free run control is executed, the engine is stopped during the execution. It cannot be performed and the detection opportunity is lost.

  Therefore, in the fourth embodiment, these engine stop controls are forcibly prohibited, and more detection opportunities for variation abnormality detection are secured.

  The control routine of the fourth embodiment will be described with reference to FIG. The control routine shown in FIG. 13 can also be repeatedly executed by the ECU 20 every predetermined calculation cycle (for example, 4 ms).

Step S401 is the same as step S101. If it is determined in step S401 that the variation abnormality detection during the current trip has not been performed or is being performed, the process proceeds to step S402, where it is determined whether or not the vehicle speed V is zero.
If it is determined that the vehicle speed V is zero, the routine proceeds to step S403, where the stop idle stop control is prohibited. As a result, the engine can be idled. Then, the process proceeds to step S404, and variation abnormality detection processing is executed during idle operation.

  On the other hand, when it is determined in step S402 that the vehicle speed V is not zero, the process proceeds to step S405, and it is determined whether or not the conditions for permitting the deceleration idle stop control or the free-run control are satisfied. The permission condition for the idle stop control during deceleration is, for example, that the engine speed Ne falls below the return speed Ne1 during execution of the fuel cut control. The conditions for permitting free-run control are, for example, that the vehicle speed is greater than zero, the accelerator opening is substantially fully closed, and the manual transmission 62 or the automatic transmission 72 is in the neutral position.

  When it is determined that the permission condition is not satisfied, the process proceeds to step S404, and the variation abnormality detection process is executed. Naturally, the variation abnormality detection process is not executed during the deceleration fuel cut.

  On the other hand, if it is determined that the permission condition is satisfied, the process proceeds to step S406, and the idle stop control during deceleration or free-run control corresponding to the satisfied permission condition is prohibited. As a result, the engine is in an operating state without being stopped. Next, the process proceeds to step S404, and variation abnormality detection processing is executed during engine operation (typically during idle operation).

  Note that at least one of the idle stop control and the free run control during deceleration may be performed. In this example, both are performed, but only one of them may be performed.

  The preferred embodiment of the present invention has been described in detail above, but various other embodiments of the present invention are conceivable.

  The embodiment of the present invention is not limited to the above-described embodiment, and includes all modifications, applications, and equivalents included in the concept of the present invention defined by the claims. Therefore, the present invention should not be construed as being limited, and can be applied to any other technique belonging to the scope of the idea of the present invention.

1 Internal combustion engine
12 Injector 11 Upstream catalyst 17 Pre-catalyst sensor 20 Electronic control unit (ECU)
50 Hybrid vehicle 53 Battery MG1 First motor MG2 Second motor

Claims (5)

A multi-cylinder internal combustion engine as a first power source for traveling;
An electric motor as a second power source for traveling;
Detecting means for detecting an air-fuel ratio variation abnormality between cylinders of the internal combustion engine;
Control means capable of executing a hybrid mode that is a control mode for driving a vehicle with both the internal combustion engine and the electric motor, and an engine mode that is a control mode for driving the vehicle with only the internal combustion engine; ,
With
The control means includes
In the hybrid mode, the internal combustion engine and the electric motor are controlled so that an actual operating point of the internal combustion engine moves on a predetermined operating line in a coordinate system defined by the rotational speed and torque of the internal combustion engine,
When there is a predetermined change request during execution of the hybrid mode, the operation line is changed to shift to the engine mode, and
When the variation abnormality detection is not executed or is being executed during execution of the hybrid mode, the change of the operation line and the shift to the engine mode are prohibited, and the hybrid mode is maintained. The hybrid vehicle according to claim 1, wherein the control unit generates the change request when a charge amount of a battery that stores electric power supplied to the electric motor becomes a predetermined value or less. The control means includes
When a predetermined motor mode condition is established, a motor mode that is a control mode for driving the vehicle only by the electric motor can be executed, and
When the motor mode condition is satisfied when the variation abnormality detection is not being executed or is being executed, the motor mode and the stop idle stop control for stopping the idle operation of the internal combustion engine when the vehicle is stopped are prohibited, The hybrid vehicle according to claim 1, wherein the hybrid mode or the engine mode is executed. The control means includes
When the motor mode condition is satisfied when the variation abnormality detection is not performed or is being performed, when the predetermined cancel condition is satisfied, or when the cancel condition is not satisfied and the motor mode switch is OFF The hybrid vehicle according to claim 3, wherein the motor mode and the idle stop control at the time of stop are prohibited and the hybrid mode or the engine mode is executed. The control means includes
The motor mode is executed when the motor mode condition is satisfied when the variation abnormality detection is not executed or is being executed, and the cancel condition is not satisfied and the motor mode switch is on. The hybrid vehicle according to claim 4.

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