JP2014181643A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine which can reduce disturbance of air fuel ratio.SOLUTION: An injector in cylinder and a port injector are disposed for each of a plurality of cylinders in an engine. A share rate of fuel injection amount from the injector in cylinder and fuel injection amount from the port injector is changed in accordance with a load. Imbalance judgment control which judges whether the air fuel ratio is unbalanced between the cylinders is performed in such a state that the share rate between fuel injection amount from injector in cylinder and fuel injection amount from a port injector is turned to a predetermined rate. A control device of the engine inhibits the completion of the imbalance judgment control when a load of the engine is fluctuated during execution of the imbalance judgment control, and inhibits the start of the imbalance judgment control when the load of the engine is fluctuated without execution of the imbalance judgment control.

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to an air-fuel ratio imbalance (imbalance) between cylinders in an internal combustion engine in which a cylinder injector and a port injector are provided for each of a plurality of cylinders. It relates to the technology to judge.

  There is known an internal combustion engine in which an in-cylinder injector for directly injecting fuel into a cylinder and a port injector for injecting fuel toward an intake port are provided in each of a plurality of cylinders. Japanese Patent Laying-Open No. 2010-169038 (Patent Document 1) discloses an example of a technique for detecting an air-fuel ratio imbalance among cylinders in such an internal combustion engine.

JP 2010-169038 A

  In an internal combustion engine provided with an in-cylinder injector and a port injector, it is preferable to change a share ratio between the fuel injection amount of the in-cylinder injector and the fuel injection amount of the port injector according to the load. However, during a transient when the load can change greatly, the intake air amount when the fuel injection amount from each injection valve is calculated may differ from the intake air amount when the fuel is actually injected. Easily different from air-fuel ratio. Furthermore, if the share ratio between the fuel injection quantity of the in-cylinder injector and the fuel injection quantity of the port injector changes during the transition, the fuel injection quantity from each injector also changes as the share ratio changes. The air-fuel ratio disturbance can be even more pronounced.

  The present invention has been made in view of the above-described problems, and an object thereof is to reduce air-fuel ratio disturbance.

  In the invention according to claim 1, the internal combustion engine is provided with an in-cylinder injector and a port injector for each of the plurality of cylinders. The sharing ratio between the fuel injection amount from the in-cylinder injector and the fuel injection amount from the port injector is changed according to the load. Imbalance determination control is performed to determine whether the air-fuel ratio is imbalanced between the cylinders with the ratio of the fuel injection from the in-cylinder injector and the fuel injection from the port injector set to a predetermined ratio. Is done. The control device for an internal combustion engine prohibits the end of the imbalance determination control when the load of the internal combustion engine fluctuates during the imbalance determination control, and the internal combustion engine when the imbalance determination control is not performed. When the engine load fluctuates, the start of imbalance determination control is prohibited.

  When the load on the internal combustion engine fluctuates, fluctuations in the sharing ratio that accompany the end or start of imbalance determination control are suppressed. Therefore, it is possible to suppress the air-fuel ratio disturbance associated with the change in the sharing ratio.

In the invention according to claim 2, when the imbalance determination control is not performed and the load of the internal combustion engine fluctuates, the control device determines that the sharing ratio at the time of the load variation is the same as when the imbalance determination control is performed. When the share ratio is close, the start of imbalance determination control is permitted.

  Thereby, it is possible to secure an opportunity to perform imbalance determination while suppressing the variation of the sharing ratio and suppressing the disturbance of the air-fuel ratio.

  In the invention according to claim 3, the control device determines whether the air-fuel ratio is imbalanced by the in-cylinder injector, and determines whether the air-fuel ratio is imbalanced by the port injector. The imbalance determination control is performed at a different sharing ratio. Further, when permitting the start of the imbalance determination control, the control device determines whether the air-fuel ratio is unbalanced by the in-cylinder injector, and the air-fuel ratio is unbalanced by the port injector. Of the imbalance control to determine whether or not, it is implemented from the imbalance determination control that is performed at a sharing ratio closer to the sharing ratio at the time of load change.

  Accordingly, it is possible to secure an opportunity to perform imbalance determination that can identify the injector that causes the air-fuel ratio imbalance while suppressing the variation of the sharing ratio and suppressing the disturbance of the air-fuel ratio.

  In the invention according to claim 4, the control device changes the share ratio between the fuel injection amount from the in-cylinder injector and the fuel injection amount from the port injector when the load fluctuation amount of the internal combustion engine is larger than the threshold value. When the imbalance control is performed while the imbalance control is performed, if the amount of fluctuation in the load of the internal combustion engine is larger than the threshold value, the imbalance control is prohibited from being terminated, and the imbalance control is not performed. When the engine load fluctuation amount is larger than the threshold value, the start of imbalance control is prohibited.

  When there is a risk that the air-fuel ratio disturbance will increase beyond the allowable range due to large fluctuations in the load, the rate of change of the share ratio and the change of the share ratio are limited, and the air-fuel ratio disturbance is suppressed. Is done.

It is a schematic block diagram which shows the power train of a vehicle. It is an alignment chart of a power split mechanism. It is an alignment chart of a transmission. It is a schematic block diagram which shows an engine. It is a figure which shows the area | region and driving | running line of DI ratio r = 100%. It is a flowchart which shows the process which ECU performs.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  Referring to FIG. 1, in the present embodiment, the power train of the vehicle is engine 100, first motor generator 200, and power for synthesizing or distributing torque between engine 100 and first motor generator 200. The dividing mechanism 300, the second motor generator 400, and the transmission 500 are mainly configured.

  The engine 100 is a known power unit that burns fuel and outputs motive power, and is configured to be able to electrically control operating conditions such as throttle opening (intake amount), fuel supply amount, and ignition timing. Yes. The control is performed by, for example, an ECU (Electronic Control Unit) 1000 mainly composed of a microcomputer.

  The first motor generator 200 is a three-phase AC rotating electric machine as an example, and is configured to generate a function as an electric motor (motor) and a function as a generator (generator). First motor generator 200 is connected to power storage device 700 such as a battery via inverter 210. By controlling the inverter 210, the output torque or regenerative torque of the first motor generator 200 is appropriately set. The control is performed by the ECU 1000. The stator (not shown) of the first motor generator 200 is fixed and does not rotate.

  The power split mechanism 300 includes a sun gear (S) 310 that is an external gear, a ring gear (R) 320 that is an internal gear arranged concentrically with the sun gear (S) 310, and the sun gear (S). This is a known gear mechanism that generates a differential action by using a carrier (C) 330 that rotates and revolves a pinion gear meshing with 310 and a ring gear (R) 320 as three rotating elements. The output shaft of the engine 100 is connected to a carrier (C) 330 as a first rotating element via a damper. In other words, the carrier (C) 330 is an input element.

  On the other hand, the rotor (not shown) of the 1st motor generator 200 is connected with the sun gear (S) 310 which is a 2nd rotation element. Therefore, the sun gear (S) 310 is a so-called reaction force element, and the ring gear (R) 320 that is the third rotation element is an output element. The ring gear (R) 320 is connected to an output shaft 600 connected to drive wheels (not shown).

  FIG. 2 shows an alignment chart of the power split mechanism 300. As shown in FIG. 2, when the reaction torque generated by the first motor generator 200 is input to the sun gear (S) 310 with respect to the torque output from the engine 100 input to the carrier (C) 330, these torques are added or subtracted. The torque having the magnitude appears in the ring gear (R) 320 serving as an output element. In that case, the rotor of the first motor generator 200 is rotated by the torque, and the first motor generator 200 functions as a generator. In addition, when the rotation speed (output rotation speed) of ring gear (R) 320 is constant, the rotation speed of engine 100 is continuously (steplessly) changed by changing the rotation speed of first motor generator 200. ) Can be changed. That is, control for setting the rotation speed of engine 100 to, for example, the rotation speed with the best fuel efficiency can be performed by controlling first motor generator 200. The control is performed by the ECU 1000.

  If the engine 100 is stopped during traveling, the first motor generator 200 is rotating in the reverse direction. From this state, when the first motor generator 200 is caused to function as an electric motor and torque is output in the forward rotation direction, the carrier ( C) Torque in the direction of rotating the engine 100 connected to 330 acts in the forward direction, and the first motor generator 200 can start the engine 100 (motoring or cranking). In that case, torque in a direction to stop the rotation acts on the output shaft 600. Therefore, the driving torque for traveling can be maintained by controlling the torque output from the second motor generator 400, and at the same time, the engine 100 can be started smoothly.

  Returning to FIG. 1, second motor generator 400 is a three-phase AC rotating electric machine as an example, and is configured to generate a function as an electric motor and a function as a generator. Second motor generator 400 is connected to power storage device 700 such as a battery via inverter 310. By controlling the inverter 310, the power running and regeneration and the torque in each case are controlled. The stator (not shown) of second motor generator 400 is fixed and does not rotate.

  The transmission 500 is configured by a set of Ravigneaux planetary gear mechanisms. A first sun gear (S1) 510 and a second sun gear (S2) 520, which are external gears, are provided, and the first pinion 531 meshes with the first sun gear (S1) 510, and the first The pinion 531 meshes with the second pinion 532, and the second pinion 532 meshes with the ring gear (R) 540 arranged concentrically with the sun gears 510 and 520.

  Each pinion 531 and 532 is held by a carrier (C) 550 so as to rotate and revolve freely. Further, the second sun gear (S 2) 520 is meshed with the second pinion 532. Therefore, the first sun gear (S1) 510 and the ring gear (R) 540 form a mechanism corresponding to the double pinion type planetary gear mechanism together with the pinions 531 and 532, and the second sun gear (S2) 520 and the ring gear (R). 540 and the second pinion 532 constitute a mechanism corresponding to a single pinion planetary gear mechanism.

  Further, the transmission 500 is provided with a B1 brake 561 that selectively fixes the first sun gear (S1) 510 and a B2 brake 562 that selectively fixes the ring gear (R) 540. These brakes 561 and 562 are so-called friction engagement elements that generate an engagement force by a friction force, and a multi-plate type engagement device or a band type engagement device can be adopted. And these brakes 561 and 562 are comprised so that the torque capacity may change continuously according to the engaging force by oil_pressure | hydraulic. Further, the second motor generator 400 described above is connected to the second sun gear (S2) 520. Carrier (C) 550 is connected to output shaft 600.

  Therefore, in the above-described transmission 500, the second sun gear (S2) 520 is a so-called input element, and the carrier (C) 550 is an output element. By engaging the B1 brake 561, the transmission ratio is “ A high speed stage greater than 1 ″ is set. By engaging the B2 brake 562 instead of the B1 brake 561, a low speed stage having a higher gear ratio than the high speed stage is set.

  The speed change between the respective speeds is executed based on a traveling state such as a vehicle speed and a required driving force (or accelerator opening). More specifically, the shift speed region is determined in advance as a map (shift diagram), and control is performed so as to set one of the shift speeds according to the detected driving state.

  FIG. 3 shows an alignment chart of the transmission 500. As shown in FIG. 3, if the ring gear (R) 540 is fixed by the B2 brake 562, the low speed stage L is set, and the torque output from the second motor generator 400 is amplified in accordance with the gear ratio and applied to the output shaft 600. Added. On the other hand, if the first sun gear (S1) 510 is fixed by the B1 brake 561, the high speed stage H having a smaller gear ratio than the low speed stage L is set. Since the gear ratio at the high speed stage H is also larger than “1”, the torque output from the second motor generator 400 is increased according to the gear ratio and added to the output shaft 600.

  It should be noted that, in a state where the respective gear stages L and H are constantly set, the torque applied to the output shaft 600 is a torque obtained by increasing the output torque of the second motor generator 400 according to the gear ratio. In the shift transition state, the torque is affected by the torque capacity at each brake 561 and 562, the inertia torque accompanying the change in the rotational speed, and the like. The torque applied to the output shaft 600 is positive torque when the second motor generator 400 is driven, and is negative torque when the second motor generator 400 is driven.

The engine 100 will be further described with reference to FIG.
Air is drawn into the engine 100 from the air cleaner 102. The intake air amount is adjusted by the throttle valve 104. The throttle valve 104 is an electronic throttle valve that is driven by a motor.

  The engine 100 is provided with a plurality of cylinders 106. In the cylinder 106, air is mixed with fuel. Fuel is directly injected into the cylinder 106 from the in-cylinder injector 108. That is, the injection hole of the in-cylinder injector 108 is provided in the cylinder 106.

  In addition to in-cylinder injector 108, engine 100 is provided with port injector 109 that injects fuel into the intake port. An in-cylinder injector 108 and a port injector 109 are provided for each cylinder 106.

  The ratio of the fuel injection amount from the in-cylinder injector 108 to the total injection amount that is the sum of the fuel injection amount from the in-cylinder injector 108 and the fuel injection amount from the port injector 109 (hereinafter also referred to as DI ratio r) is It is determined according to the load of 100 and the rotational speed. For example, in the region indicated by hatching in FIG. 5, the DI ratio r is set to 100%. That is, in the region indicated by the oblique lines in FIG. 5, fuel is injected only from the in-cylinder injector 108, and fuel injection from the port injector 109 is stopped.

  In other areas, the DI ratio r is determined in the range of 0% ≦ DI ratio r ≦ 100%. For example, at the operating point A in FIG. 5, the DI ratio r is determined in the range of 0% <DI ratio r <100%. As a result, at the operating point A, fuel is injected from both the in-cylinder injector 108 and the port injector 109.

  The DI ratio r uniquely corresponds to the share ratio between the fuel injection amount from the in-cylinder injector 108 and the fuel injection amount from the port injector 109.

  A broken line in FIG. 5 indicates an operation line of the engine 100. During normal times, engine 100 is controlled such that the operating point (load and rotational speed) of engine 100 moves on the operation line.

  Returning to FIG. 4, the air-fuel mixture in the cylinder 106 is ignited by the spark plug 110 and burns. The air-fuel mixture after combustion, that is, the exhaust gas is purified by the three-way catalyst 112 and then discharged outside the vehicle. The piston 114 is pushed down by the combustion of the air-fuel mixture, and the crankshaft 116 rotates.

  An intake valve 118 and an exhaust valve 120 are provided at the top of the cylinder 106. The amount and timing of air introduced into the cylinder 106 is controlled by the intake valve 118. The amount and timing of the exhaust gas discharged from the cylinder 106 is controlled by the exhaust valve 120. The intake valve 118 is driven by a cam 122. The exhaust valve 120 is driven by a cam 124.

  The intake valve 118 is changed in opening / closing timing (phase) by the VVT mechanism 126. The opening / closing timing of the exhaust valve 120 may be changed.

In the present embodiment, the camshaft (not shown) provided with the cam 122 is rotated by the VVT mechanism 126, whereby the opening / closing timing of the intake valve 118 is controlled. The method for controlling the opening / closing timing is not limited to this. In the present embodiment, V
The VT mechanism 126 is operated by hydraulic pressure.

  Engine 100 is controlled by ECU 1000. ECU 1000 controls the throttle opening, the ignition timing, the fuel injection timing, the fuel injection amount, and the opening / closing timing of intake valve 118 so that engine 100 is in a desired operating state. ECU 1000 receives signals from cam angle sensor 800, crank angle sensor 802, water temperature sensor 804, air flow meter 806, and air-fuel ratio sensor 808.

The cam angle sensor 800 outputs a signal representing the cam position. The crank angle sensor 802 outputs a signal representing the rotational speed (engine rotational speed) NE of the crankshaft 116 and the rotational angle of the crankshaft 116. Water temperature sensor 804 outputs a signal representing the temperature of cooling water of engine 100 (hereinafter also referred to as water temperature). Air flow meter 806 outputs a signal representing the amount of air taken into engine 100. The air-fuel ratio sensor 808 detects the air-fuel ratio based on the oxygen concentration in the exhaust gas. Note that an O ₂ sensor may be used as the air-fuel ratio sensor 808.

  ECU 1000 controls engine 100 based on signals input from these sensors, a map stored in ROM 1002, and a program.

  ECU 1000 executes air-fuel ratio feedback control that increases or decreases the fuel injection amount so that the air-fuel ratio approaches the target air-fuel ratio. For example, when the air-fuel ratio is greater than the target air-fuel ratio (lean), the fuel injection amount is increased. Conversely, if the air-fuel ratio is smaller than the target air-fuel ratio (if it is rich), the fuel injection amount is reduced.

  Further, ECU 1000 performs imbalance determination control in a state where DI ratio r is set to a predetermined ratio, and detects an imbalance abnormality in which the air-fuel ratio becomes imbalanced between cylinders 106. For example, when the fluctuation range of the air-fuel ratio becomes larger than the threshold value, it is determined that the air-fuel ratio is unbalanced between the cylinders 106. In addition, an imbalance abnormality may be detected from the fluctuation range of the rotational speed of the engine 100. Since a known general technique may be used as a method for detecting an imbalance abnormality, detailed description thereof will not be repeated here.

  The imbalance determination control for determining whether or not the air-fuel ratio is imbalanced by the in-cylinder injector 108 is different from the imbalance determination control for determining whether or not the air-fuel ratio is imbalanced by the port injector 109. Implemented at a ratio r.

  As an example, imbalance determination control for determining whether or not the air-fuel ratio is unbalanced is performed by the in-cylinder injector 108 with the DI ratio r being 100%. In addition, imbalance determination control for determining whether or not the air-fuel ratio is unbalanced by the port injector 109 in a state where the DI ratio r is a predetermined ratio in which 100% is smaller than 100% and larger than 0%. To be implemented. Imbalance determination control for determining whether or not the air-fuel ratio is unbalanced may be performed by the port injector 109 with the DI ratio r set to 0%.

  As described above, the DI ratio r is changed according to the load of the engine 100. However, in the present embodiment, the rate of change of the DI ratio r is limited when the load fluctuates. More specifically, if the load fluctuation amount (difference between the load before change and the load after change) is larger than the threshold value α, the DI ratio r corresponding to the load before change is changed to the load after change. The rate of change up to the corresponding DI ratio r is made smaller than the upper limit value β. Accordingly, the DI ratio r changes at a change rate smaller than the upper limit value β. The threshold value α and the upper limit value β are determined in advance by the developer based on results of experiments and the like.

  Furthermore, in the present embodiment, when the load of engine 100 fluctuates during the execution of imbalance determination control, the end of imbalance determination control is prohibited. Conversely, when the imbalance determination control is not being performed and the load on the engine 100 fluctuates, the start of the imbalance determination control is prohibited.

  More specifically, if the amount of change in the load of engine 100 is larger than the above-described threshold value α during imbalance determination control, termination of imbalance determination control is prohibited. When imbalance determination control is not being performed, if the amount of change in the load on engine 100 is greater than threshold value α, start of imbalance determination control is prohibited.

  In the present embodiment, since the imbalance determination control is performed in a state where the DI ratio r is set to a specific ratio, the end and start of the imbalance determination control are prohibited by prohibiting the end and start of the imbalance determination control. The fluctuation of the DI ratio r accompanying the can be suppressed.

  With reference to FIG. 6, the process which ECU1000 performs in this Embodiment is demonstrated.

  In step (hereinafter, step is abbreviated as S) 100, it is determined whether or not the fluctuation amount of the load of engine 100 is larger than threshold value α. If the load fluctuation amount is larger than threshold value α (YES in S100), the change rate of DI ratio r is limited in S102. Further, if imbalance determination control is being performed (YES in S104), termination of imbalance determination control is prohibited in S106. Conversely, if imbalance determination control is not being performed (NO in S104), the start of determination of an imbalance abnormality is prohibited in S108.

Modified Example When the imbalance determination control is not performed and the load of the engine 100 varies when the imbalance determination control is not performed in order to secure an opportunity to perform the imbalance determination control, the DI ratio r at the time of the load variation is the imbalance determination control. If it is close to the DI ratio r at the time of implementation, the start of imbalance determination control may be permitted. That is, even if the imbalance determination control is performed, if the change amount of the DI ratio r is smaller than a predetermined threshold value, the start of the imbalance determination control may be permitted.

  More specifically, an imbalance determination control for determining whether the air-fuel ratio is imbalanced by the in-cylinder injector 108 and an imbalance determination for determining whether the air-fuel ratio is imbalanced by the port injector 109 You may implement from the imbalance determination control implemented by DI ratio r close | similar to DI ratio r at the time of the fluctuation | variation of load among control. That is, the fluctuation amount of the DI ratio r when the imbalance determination control for determining whether or not the air-fuel ratio is imbalanced by the in-cylinder injector 108 is the same as whether the air-fuel ratio is imbalanced by the port injector 109 or not. If the amount of fluctuation of the DI ratio r is smaller than when the imbalance determination control is performed, the in-cylinder injector 108 performs the imbalance determination control for determining whether the air-fuel ratio is unbalanced. . Conversely, the fluctuation amount of the DI ratio r when the imbalance determination control for determining whether or not the air-fuel ratio is imbalanced by the in-cylinder injector 108 is the amount of fluctuation of the air-fuel ratio by the port injector 109. The imbalance determination control for determining whether or not the air-fuel ratio is unbalanced is performed by the port injector 109 when the amount of fluctuation of the DI ratio r is larger than when the imbalance determination control for determining whether or not is performed. .

  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.

  100 engine, 102 air cleaner, 104 throttle valve, 106 cylinder, 108 in-cylinder injector, 109 port injector, 808 air-fuel ratio sensor, 1000 ECU.

Claims (4)

An in-cylinder injector and a port injector are provided for each of the plurality of cylinders, and a sharing ratio between the fuel injection amount from the in-cylinder injector and the fuel injection amount from the port injector is changed according to a load, Imbalance determination control for determining whether or not the air-fuel ratio is imbalanced between the cylinders in a state where the share ratio between the fuel injection amount from the in-cylinder injector and the fuel injection amount from the port injector is a predetermined ratio. A control device for an internal combustion engine to implement,
During the imbalance determination control, when the load of the internal combustion engine fluctuates, the imbalance determination control is prohibited from ending.
A control device for an internal combustion engine, which prohibits the start of the imbalance determination control when the load of the internal combustion engine fluctuates when the imbalance determination control is not performed.   When the imbalance determination control is not performed and when the load of the internal combustion engine fluctuates, if the share ratio at the time of load change is close to the share ratio at the time of execution of the imbalance determination control, The control device for an internal combustion engine according to claim 1, wherein the start of the imbalance determination control is permitted. The imbalance determination control for determining whether or not the air-fuel ratio is unbalanced by the in-cylinder injector and the imbalance determination control for determining whether or not the air-fuel ratio is unbalanced by the port injector differ. Carried out in proportion,
When permitting the start of the imbalance determination control, the imbalance determination control for determining whether or not the air-fuel ratio is unbalanced by the in-cylinder injector, and whether or not the air-fuel ratio is unbalanced by the port injector The control device for an internal combustion engine according to claim 2, wherein the control device is implemented from an imbalance determination control that is performed at a sharing ratio that is closer to a sharing ratio at the time of load fluctuation. When the fluctuation amount of the load of the internal combustion engine is larger than a threshold value, the rate of change of the share ratio between the fuel injection amount from the in-cylinder injector and the fuel injection amount from the port injector is limited,
During the execution of the imbalance control, if the fluctuation amount of the load of the internal combustion engine is larger than the threshold value, prohibiting the end of the imbalance control,
2. The control of the internal combustion engine according to claim 1, wherein when the imbalance control is not performed and the load fluctuation amount of the internal combustion engine is larger than the threshold value, the start of the imbalance control is prohibited. apparatus.

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