JP5125735B2 - Control device for hybrid vehicle - Google Patents

Description

  The present invention relates to a hybrid vehicle that uses both an internal combustion engine and a motor generator as a vehicle drive source, and more particularly to control during automatic engine stop with fuel cut, such as during vehicle deceleration.

In vehicles equipped with an internal combustion engine, exhaust gas regulations are becoming stricter year by year in order to improve the air environment. Patent Document 1 relates to a hybrid vehicle capable of so-called idle stop, in which an internal combustion engine is automatically stopped at a temporary stop such as waiting for a signal and the internal combustion engine is automatically restarted at a subsequent departure. Immediately before stopping, the oxygen storage amount of the catalyst is intentionally changed from the neutral state to the air-fuel ratio rich side, and in the air-fuel ratio control at the restart after the automatic stop, the catalyst is supplied with insufficient oxygen. A technique for quickly returning the oxygen storage amount of the catalyst to the neutral state by performing fuel injection so that the air-fuel ratio becomes the lean side is disclosed.
JP 2003-148201 A

  In a hybrid vehicle in which a motor generator connected to drive wheels and an internal combustion engine connected to the motor generator are used in combination as a vehicle drive source and a clutch is interposed between the internal combustion engine and the motor generator, for example, When the vehicle is decelerated, by disengaging the clutch and stopping fuel injection, loss of engine friction can be eliminated and deceleration energy can be efficiently recovered by the motor generator. However, in this case, even if the fuel injection is stopped, the crankshaft rotates to some extent by inertia, and when the air passes through the catalyst due to the pumping action by this inertia rotation, oxygen is stored in the catalyst, and oxygen storage in the catalyst There is a problem that the amount changes from the neutral state to the lean side.

  In addition, in a so-called direct injection type internal combustion engine that directly injects fuel into the combustion chamber, a higher fuel pressure is required than that in which fuel is injected into the intake port. A high pressure fuel pump that supplies high pressure fuel to a high pressure fuel gallery connected to the fuel injection valve is used. Here, if there is no special pressure reducing mechanism for reducing the fuel pressure of the high-pressure fuel gallery, the fuel pressure cannot be reduced at the time of fuel cut when fuel injection is not performed. If the fuel pressure is high, the fuel pressure at the next engine restart becomes too high, and the fuel injection amount becomes excessive, which may cause deterioration of exhaust emission.

  The present invention has been made in view of such problems, and at the time of automatic engine stop accompanying fuel cut such as when the vehicle is decelerated, the fuel cut is performed while reducing the fuel pressure in the high-pressure fuel gallery to a fuel pressure suitable for starting. The main object of the present invention is to provide a novel hybrid vehicle control apparatus that can absorb and offset the lean oxygen storage amount of the catalyst and return the catalyst oxygen storage amount to a neutral state.

In a hybrid vehicle control device that uses a motor generator connected to drive wheels and an internal combustion engine connected to the motor generator as a vehicle drive source, a catalyst provided in an exhaust passage of the internal combustion engine, the internal combustion engine, A clutch interposed in a power transmission path with the motor generator, a plurality of fuel injection valves provided in the internal combustion engine, a high pressure fuel gallery connected to the plurality of fuel injection valves, and high pressure fuel to the high pressure fuel gallery And a high-pressure fuel pump to be supplied. Then, during the automatic stop request of the internal combustion engine, both when opening the clutch, until the fuel cut to stop the fuel injection from the clutch open, performing the rich operation for fuel injection at a target air-fuel ratio on the rich side. In the first aspect of the invention, the internal combustion engine is controlled so that the engine speed at the end of the rich operation becomes a predetermined speed. In the second aspect of the invention, the rich degree and the operation period in the rich operation are set so that the fuel pressure in the high-pressure fuel gallery is lowered to the start fuel pressure suitable for engine start.

  By performing rich operation between clutch release and fuel cut at the time of engine stop request, the fuel pressure in the high-pressure fuel gallery can be reduced to a fuel pressure suitable for the next engine start, and exhaust caused by excessive fuel pressure It is possible to start the engine stably without deteriorating emissions. Also, by performing rich operation before fuel cut, the oxygen storage amount of the catalyst is enriched in advance, and the leaning of the catalyst oxygen storage amount due to inertia rotation accompanying the fuel cut is offset and absorbed, and the oxygen storage amount of the catalyst Can be quickly returned to a predetermined neutral state.

  FIG. 1 is a configuration diagram schematically showing a drive system of a hybrid vehicle according to an embodiment of the present invention. This vehicle is a so-called hybrid vehicle in which an internal combustion engine 11 and a motor generator 12 are used together as a vehicle drive source. The internal combustion engine 11 is a V-type spark ignition reciprocating internal combustion engine having left and right banks (cylinder groups), and an upstream side catalytic converter 14 such as a three-way catalyst and a downstream side in each exhaust passage 13 of each bank. A catalytic converter 15 is provided. Air-fuel ratio sensors (oxygen sensors) 16 and 17 for detecting the air-fuel ratio (or oxygen concentration) of the exhaust are provided upstream of the catalytic converters 14 and 15.

  The motor generator 12 exchanges power with the battery 19 via the inverter 18 and performs power running / regenerative operation according to the vehicle operating state. A stepped automatic transmission 21 and a final reduction gear 22 are provided in the power transmission path between the motor generator 12 and the drive wheels (rear wheels) 20.

  In this hybrid vehicle, a first clutch 23 provided in a power transmission path between the internal combustion engine 11 and the motor generator 12 and a second clutch 24 provided in a power transmission path between the motor generator 12 and the drive wheels 20 are provided. There are two clutches. As the second clutch 24, a clutch inside the automatic transmission 21 is used in this embodiment. During normal steady operation, the first clutch 23 is connected to connect the internal combustion engine 11 and the motor generator 12, and the internal combustion engine 11 and the motor generator 12 are used together to travel, and the battery 19 is charged as necessary. I do. Further, for example, when the vehicle starts, the first clutch 23 is opened to disconnect the internal combustion engine 11 and the motor generator 12 so that EV traveling with only the motor generator 12 is possible. Further, by disengaging the first clutch 23 when the vehicle is decelerated, loss of engine friction can be eliminated and highly efficient regeneration can be performed. Further, for example, when the shift range of the automatic transmission 21 is N (neutral) mode or P (parking) mode, the second clutch 24 is disengaged.

  The control unit 25 is a digital computer system having a function of storing and executing various control processes, and includes various sensors such as the air-fuel ratio sensors 16 and 17, a water temperature sensor 26 for detecting a cooling water temperature, and a fuel pressure sensor 51 described later. In addition to the above, to various actuators such as the inverter 18, the clutches 23 and 24, the fuel injection device of the internal combustion engine 11, the ignition device, the electric throttle, etc. A control signal is output to control the overall operation. For example, in the normal operation state after warm-up, the air-fuel ratio sensors 16 and 17 maintain the air-fuel ratio of the exhaust supplied to the catalytic converters 14 and 15 in the vicinity of a desired target air-fuel ratio such as the stoichiometric air-fuel ratio. Based on the detection signal, feedback control of the fuel injection amount is performed.

  FIG. 2 shows the fuel piping system of this embodiment. In the figure, a thin line is a low-pressure fuel line, a thick line is a high-pressure fuel line, and a broken line is a control line. The fuel in the fuel tank 31 is supplied to a feed pipe 35 that is a low-pressure fuel line by a feed pump 32 that is a low-pressure pump driven by a pump motor 33 and is regulated by a low-pressure pressure regulator 34. The feed pipe 35 is attached to the cylinder head side via a damper 36, and a fuel filter 37 is provided before and after the feed pump 32. The fuel in the feed pipe 35 is further pressurized by the high-pressure pump 40 and supplied to a high-pressure fuel gallery (also called a fuel rail) 41. The high-pressure fuel gallery 41 is connected with four fuel injection valves 42 corresponding to the respective cylinders.

  The high-pressure pump 40 reciprocates the plunger 45 by a dedicated cam 44 provided on the camshaft 43 to boost the fuel. When the solenoid 46 is energized and the solenoid valve 48 is closed while the plunger 45 is raised, The pressure of the fuel is increased to push open the check valve 49, and high pressure fuel is supplied to the high pressure fuel gallery 41 through the orifice 50. The control unit 25 adjusts a pulse signal output to the solenoid 46 based on the fuel pressure in the high-pressure fuel gallery 41 detected by the fuel pressure sensor 51 to control the fuel pressure in the high-pressure fuel gallery 41.

  In this embodiment, a so-called return type is adopted in which a return pipe 53 is provided for returning excess fuel in the high-pressure fuel gallery 41 to the fuel tank 31 via the safety valve 52, but there is no return pipe. A returnless type may be used. Here, the return pipe 53 and the safety valve 52 in the return method are those in which the safety valve 52 is opened and depressurized only when the fuel pressure in the high-pressure fuel gallery 41 exceeds a predetermined limit fuel pressure, and the fuel pressure is actively reduced. It is not a possible decompression mechanism. That is, even in the return method, the fuel pressure in the high-pressure fuel gallery 41 is basically reduced only by fuel injection, as in the returnless method.

  Next, with reference to FIG. 3 to FIG. 5, a description will be given of the control at the time of vehicle deceleration, which is one of the engine automatic stop requests forming the main part of the present embodiment. FIG. 3 is a flowchart showing the flow of control during vehicle deceleration. In step S11, it is determined whether or not there is a vehicle deceleration request. For example, if it is determined that there is a deceleration request due to the accelerator pedal being OFF (accelerator opening is 0), the process proceeds to step S12 and the first clutch 23 is released. Thereby, the internal combustion engine 11 and the motor generator 12 are disconnected, and the deceleration energy can be efficiently recovered by the regenerative operation of the motor generator 12.

  In this embodiment, the fuel injection is not stopped, that is, the fuel cut (F / C) is not performed simultaneously with the opening of the first clutch 23, but from the release of the first clutch 23 in step S12 to the start of the fuel cut in step S17. In step S16, so-called rich operation is performed in which fuel is injected in accordance with the rich target air-fuel ratio (A / F). As the control at this time, for example, the fuel injection amount is increased or decreased so as to be the target air-fuel ratio on the rich side by feedback control based on detection signals of the air-fuel ratio sensors 16 and 17. The rich degree α1 and the rich operation period α2 of the target air-fuel ratio in the rich operation are set so as to satisfy the following two requirements [1] and [2] simultaneously.

[1] The fuel pressure is reduced to a starting fuel pressure suitable for engine starting (“7” in the examples of FIGS. 4A and 5A);
[2] The oxygen storage amount (hereinafter also abbreviated as OSC) of the catalyst after the fuel cut is in a neutral state (that is, not greatly biased to the lean side or the rich side);
First, the former [1] will be described. 4A and 5A, the numbers in the figures correspond to the fuel pressure. As shown in the figure, the fuel pressure in the high-pressure fuel gallery 41 is set according to the engine speed and the required load (torque), and is basically set so that the fuel pressure increases on the high-rotation high-load side. . However, as described above, the fuel pressure in the high-pressure fuel gallery 41 cannot be reduced except for fuel injection unless the special pressure-reducing mechanism is provided. Therefore, the fuel pressure is reduced during the fuel cut. I can't. Therefore, in this embodiment, the fuel pressure decrease amount is calculated based on the detection signal from the fuel pressure sensor 51 in step S13, and the rich degree α1 and the operation period α2 in the rich operation are set according to the fuel pressure decrease amount. That is, as shown in FIGS. 4 and 5, the rich degree α1 and the operation period α2 in the rich operation are set larger as the fuel pressure decrease amount becomes larger.

  Next, the latter [2] will be described. When the fuel cut is performed in step S17, the main rotation system including the crankshaft is rotated to some extent by inertia. By the pumping action by this inertia rotation, air passes through the catalyst and oxygen is stored in the catalyst. As shown by the symbol β1 in FIG. 5, the oxygen storage amount inevitably shifts to the lean side. Therefore, in anticipation of the shift of the oxygen storage amount to the lean side due to such inertia rotation, the rich operation described above is performed, and the oxygen storage amount is shifted to the rich side in advance as shown by the symbol β2 in FIGS. In addition, the shift of the oxygen storage amount to the lean side due to inertial rotation is offset and ball type so that the oxygen storage amount after inertial rotation quickly becomes a predetermined neutral state.

  Here, the number of idling due to inertial rotation varies depending on the engine speed (rotational speed) at the time of stopping fuel injection, and increases as the engine speed increases. The degree β1 of the shift of the oxygen storage amount to the lean side also changes depending on the number of idling times. Therefore, in order to equalize the degree of transition β1 of the oxygen storage amount due to inertial rotation to the lean side, the engine speed at the end of the rich operation is set to a predetermined speed (for example, 1000 rpm) Controls an internal combustion engine. As the control at this time, the throttle opening is adjusted so as to maintain the engine speed at a predetermined speed, for example, as in the known idle speed control. Here, since the first clutch 23 is disengaged during the rich operation, the engine speed is kept constant without being affected by the vehicle speed or the gear ratio of the automatic transmission 21 as in the idling operation. It can be easily realized.

  In this embodiment, the leaning degree β1 of the oxygen storage amount due to idling is set according to the riching degree β2 due to the rich operation when the fuel pressure reduction amount is small (minimum) as shown in FIG. For this reason, as shown in FIG. 5, when the fuel pressure in the driving state immediately before the vehicle deceleration request is high, that is, the amount of fuel pressure decrease due to the rich driving is large, and the rich degree α1 and the driving period α2 increase, The amount enrichment degree β2 becomes larger than the lean degree β1. Therefore, in this embodiment, in step S14, it is determined whether or not to perform the preliminary fuel cut operation for stopping the fuel injection between the time when the first clutch 23 is released and the time when the rich operation is performed in accordance with the fuel pressure decrease amount. . Specifically, as shown in FIG. 5, when the fuel pressure decrease amount is large, the process proceeds to S15 and the preliminary fuel cut operation is performed. By performing such a preliminary fuel cut operation, the oxygen storage amount of the catalyst is shifted to the lean side as indicated by the symbol β3 so that the oxygen storage amount after inertial rotation becomes a neutral state. That is, the operation period of the preliminary fuel cut operation is set so that the sum of the lean degree β3 due to the preliminary fuel cut operation and the lean degree β1 due to the idling of the inertial rotation balances the rich degree β2 due to the rich operation. .

  As described above, in this embodiment, when the deceleration is requested (when the engine stop is requested), the rich operation is performed between the opening of the first clutch 23 and the fuel cut, so that the fuel pressure in the high pressure fuel gallery 41 is changed to the next engine. The starting fuel pressure suitable for starting can be reduced, and stable engine starting can be performed without deteriorating exhaust emission due to excessive fuel pressure. Also, by performing rich operation before fuel cut, the oxygen storage amount of the catalyst is pre-riched (β2), and the leaning of oxygen storage amount (β1) due to inertial rotation accompanying fuel cut is offset and absorbed, The oxygen storage amount of the catalyst can be quickly and satisfactorily returned to a predetermined neutral state.

  Further, since the internal combustion engine is controlled so that the engine speed at the end of the rich operation becomes a predetermined speed, the degree of leaning (β1) due to inertial rotation of the crankshaft is made uniform, and this lean By setting the rich degree α1 and the operation period α2 of the rich operation according to the degree of conversion, the oxygen storage amount of the catalyst can be accurately and reliably returned to the neutral state.

  In addition, depending on the amount of decrease in the fuel pressure of the high-pressure fuel gallery 41, the preliminary fuel cut operation is performed between the time when the first clutch 23 is released and the time when the rich operation is performed, so that the fuel pressure immediately before the deceleration request is satisfied. Thus, it is possible to achieve both the above-described reduction in the starting fuel pressure [1] and return to the neutral state of the oxygen storage amount of the catalyst [2].

  As described above, the present invention has been described based on the specific embodiments. However, the present invention is not limited to the above-described embodiments, and includes various modifications and changes. For example, in the above embodiment, the control at the time of deceleration of the vehicle has been described. However, the control of the present embodiment can be applied also at the time of automatic stop of the internal combustion engine at an idle stop, for example.

The block diagram which shows simply the drive system of the hybrid vehicle which concerns on one Example of this invention. The block diagram which shows the fuel piping system of a present Example simply. The flowchart which shows the flow of control at the time of vehicle deceleration. A fuel pressure setting map (A) and a timing chart (B) when the fuel pressure immediately before deceleration is low. A fuel pressure setting map (A) and a timing chart (B) when the fuel pressure immediately before deceleration is high.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Internal combustion engine 12 ... Motor generator 13 ... Exhaust passage 14, 15 ... Catalytic converter (catalyst)
20 ... Drive wheel 23 ... First clutch (clutch)
40 ... High pressure fuel pump 41 ... High pressure fuel gallery 42 ... Fuel injection valve 51 ... Fuel pressure sensor

Claims (5)

In a hybrid vehicle control device that uses a motor generator connected to drive wheels and an internal combustion engine connected to the motor generator as a vehicle drive source,
A catalyst provided in an exhaust passage of the internal combustion engine;
A clutch interposed in a power transmission path between the internal combustion engine and the motor generator;
A plurality of fuel injection valves provided in the internal combustion engine;
A high pressure fuel gallery connected to the plurality of fuel injectors;
A high pressure fuel pump for supplying high pressure fuel to the high pressure fuel gallery,
During the automatic stop request of the internal combustion engine, both when opening the clutch, until the fuel cut to stop the fuel injection from the clutch open, have rows rich operation of the fuel injected at the target air-fuel ratio richer,
A control apparatus for a hybrid vehicle , wherein the internal combustion engine is controlled so that the engine speed at the end of the rich operation becomes a predetermined speed . In a hybrid vehicle control device that uses a motor generator connected to drive wheels and an internal combustion engine connected to the motor generator as a vehicle drive source,
A catalyst provided in an exhaust passage of the internal combustion engine;
A clutch interposed in a power transmission path between the internal combustion engine and the motor generator;
A plurality of fuel injection valves provided in the internal combustion engine;
A high pressure fuel gallery connected to the plurality of fuel injectors;
A high pressure fuel pump for supplying high pressure fuel to the high pressure fuel gallery,
During the automatic stop request of the internal combustion engine, both when opening the clutch, until the fuel cut to stop the fuel injection from the clutch open, have rows rich operation of the fuel injected at the target air-fuel ratio richer,
The hybrid vehicle control apparatus is characterized in that the rich degree and the operation period in the rich operation are set so that the fuel pressure in the high-pressure fuel gallery is reduced to a start fuel pressure suitable for engine start . 3. The hybrid vehicle according to claim 2 , wherein when the amount of decrease in the fuel pressure is large, a preliminary fuel cut operation for stopping fuel injection is performed between the time when the clutch is released and the time when the rich operation is performed. Control device. The control apparatus for a hybrid vehicle according to any one of claims 1 to 3 , wherein the internal combustion engine is of a direct injection type that injects fuel directly into a combustion chamber. Control apparatus for a hybrid vehicle according to any one of claims 1 to 4, the automatic stop request of the internal combustion engine is characterized in that the vehicle is decelerating.

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