JP5245579B2 - Engine torque shock suppression control device - Google Patents

Description

  The present invention relates to an engine torque shock suppression control device.

Conventionally, when shifting from a fuel cut operation in which fuel injection to each cylinder is stopped to a fuel cut recovery operation in which fuel injection is resumed, a rich spike that injects extra fuel is performed (see Patent Document 1). ). As a result, the air-fuel ratio can be made rich and oxygen absorbed by the three-way catalyst during the fuel cut operation can be released. Therefore, exhaust emission can be improved.
JP 2005-105963 A

  However, the above-described conventional apparatus has a problem in that since excessive fuel is injected during a rich spike, a torque shock is generated during a fuel cut recovery operation and the operation performance deteriorates.

  The present invention has been made paying attention to such conventional problems, and an object thereof is to suppress a torque shock during fuel cut recovery operation without deteriorating exhaust emission.

The present invention includes a fuel injection device that directly injects fuel into each cylinder, an ignition device that ignites a mixture of fuel and air injected from the fuel injection device, and fuel injected from the fuel injection device. A control device for suppressing a torque shock of an engine, comprising: a piston having a jump cavity guided around the ignition device on a crown surface; and an exhaust purification catalyst provided in an exhaust passage and having an oxygen storage function. There is a rich spike request for releasing oxygen absorbed by the exhaust purification catalyst by making the air-fuel ratio rich when shifting from a fuel cut operation that stops fuel injection of an injection device to a fuel cut recovery operation that restarts fuel injection Rich spike request determination means for determining whether or not, and when there is the rich spike request, fuel injection that divides the fuel injection into two A first fuel injection of the fuel injection divided by the splitting means and the fuel injection splitting means at least at a timing when an air-fuel mixture that contributes to combustion is formed around the ignition device, and a second fuel injection , fuel is injected at a timing earlier than the latter half of the compression stroke does not enter into the jump cavity, a fuel injection unit that forms form a stratified air-fuel mixture does not contribute to combustion at a position deviated from around the ignition device, in that it comprises Features.

  According to the present invention, when the fuel cut recovery operation is performed, if there is a rich spike request, the fuel injection is performed in two steps. The first fuel injection is performed at a timing at which an air-fuel mixture is formed at least around the ignition device, and the second fuel injection is injected at a timing at which the air-fuel mixture is formed at a position away from the periphery of the ignition device.

  Therefore, since the fuel injected by the second fuel injection does not contribute to combustion, torque shock can be suppressed even if the rich spike amount is increased. Further, since the rich spike amount can be increased, the exhaust emission is not deteriorated.

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

  FIG. 1 is an overall system diagram of a control device of a direct injection type spark ignition engine (hereinafter referred to as “engine”) 1 according to an embodiment of the present invention.

  The engine 1 is an in-line four-cylinder engine and includes an ignition device 10, a fuel injection device 20, an intake passage 30, and an exhaust passage 40.

  The ignition device 10 ignites the air-fuel mixture compressed in each cylinder.

  The fuel injection device 20 directly injects high-pressure fuel into each cylinder.

  The intake passage 30 is a passage for supplying air to each cylinder. The intake passage 30 includes an air flow sensor 31, an electronic control throttle 32, and an intake manifold 34.

  The air flow sensor 31 detects the intake air intake amount of the engine 1.

  The electronically controlled throttle 32 drives the throttle valve 33 with a control signal from the controller 50 described later, and controls the throttle opening according to the operating state.

  The intake manifold 34 is connected to the intake port of the engine 1 and distributes air evenly to each cylinder.

  The exhaust passage 40 is a passage for discharging exhaust (combustion gas, air, etc.) generated in each cylinder to the outside. The exhaust passage 40 includes an exhaust manifold 41 and a three-way catalyst 42.

  The exhaust manifold 41 is connected to the exhaust port of the engine 1 and collects the exhaust discharged from each cylinder.

  The three-way catalyst 42 efficiently purifies hydrocarbons (HC), carbon monoxide (CO), and nitrogen compounds (NOx) in the exhaust gas simultaneously during operation at the stoichiometric air-fuel ratio (stoichiometric). The three-way catalyst 42 has an oxygen storage function, and absorbs oxygen in the exhaust when the air-fuel ratio of the exhaust flowing into the three-way catalyst 42 is lean. On the other hand, when the air-fuel ratio of the exhaust gas flowing into the three-way catalyst 42 becomes rich, the absorbed oxygen is released. Thereby, even if the air-fuel ratio of the exhaust gas flowing into the three-way catalyst 42 is shifted to the lean side or the rich side, the internal atmosphere of the three-way catalyst 42 is substantially maintained at the stoichiometric air-fuel ratio.

  The controller 50 is configured by a microcomputer including a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). The controller 50 controls the amount of fuel injected from the fuel injection device 20 and the injection timing based on input signals from various sensors.

  Here, in the present embodiment, when the operating state of the engine 1 becomes a predetermined operating state such as at the time of deceleration, for example, a fuel cut operation that stops fuel injection to each cylinder is performed to improve fuel consumption. .

  However, since the air continues to flow into the three-way catalyst 42 during the fuel cut operation, the three-way catalyst 42 continues to absorb oxygen. If too much oxygen is absorbed by the three-way catalyst 42, the three-way catalyst 42 cannot maintain the internal atmosphere at the stoichiometric air-fuel ratio, so that the purification performance deteriorates.

  Therefore, there is a problem that the emission immediately after the fuel cut operation is finished and the fuel injection is restarted is deteriorated.

  Therefore, in the past, during fuel cut recovery operation in which fuel injection to each cylinder is resumed, a rich spike that temporarily increases the air-fuel ratio of the exhaust by correcting the fuel injection amount to increase is performed. As a result, the oxygen that has been absorbed excessively by the three-way catalyst 42 is forcibly released to suppress the deterioration of the emission.

  However, if the rich spike is temporarily performed during the fuel cut recovery operation, the amount of fuel is increased, and the engine output torque also temporarily increases. Therefore, there has been a problem that a torque shock occurs during the fuel cut recovery operation and the operation performance deteriorates.

  Therefore, in the present embodiment, when the rich spike is performed during the fuel cut recovery operation, the fuel is injected twice and the increased amount for the rich spike is injected at a timing that does not contribute to the combustion. That is, the first fuel injection is performed at a timing when a homogeneous air-fuel mixture is formed in the entire combustion chamber, and the air-fuel mixture formed by the first fuel injection is contributed to combustion. Then, the second fuel injection is performed at a timing when the air-fuel mixture is formed at a position deviated from the periphery of the ignition device, so that the air-fuel mixture formed by the second fuel injection does not contribute to combustion.

  As a result, since the air-fuel mixture formed by the second fuel injection does not contribute to combustion, even if the second injection amount, that is, the rich spike amount (the fuel injection amount increase correction amount) is increased, the fuel cut recovery operation is performed. Occasional torque shock can be suppressed.

  In addition, since the rich spike amount can be increased, oxygen that has been absorbed excessively by the three-way catalyst 42 can be quickly released, and deterioration of emissions can be suppressed.

  FIG. 2 is a diagram showing the state of the air-fuel mixture formed in the combustion chamber 11 when the rich spike is performed during the fuel cut recovery operation.

  As shown in FIG. 2, the first air-fuel mixture 101 formed in the entire combustion chamber 11 is formed by the first fuel injection. Then, the second fuel mixture 102 is formed at a position deviated from the periphery of the ignition device 10 by the second fuel injection.

  As shown in FIG. 2, a jump cavity 12 a is formed on the crown surface of the piston 12. The jump cavity 12 a guides the fuel injected toward the jump cavity 12 a around the ignition device 10.

  FIG. 3 is a diagram illustrating the timing of the first fuel injection IT1 and the timing of the second fuel injection IT2 when the rich spike is performed during the fuel cut recovery operation.

  As described above, in the present embodiment, it is necessary to form a homogeneous air-fuel mixture that contributes to combustion in the entire combustion chamber by the first fuel injection IT1. Therefore, the first fuel injection IT1 is injected when the intake valve is open. In this embodiment, as shown in FIG. 3, the fuel is injected at an appropriate time from the intake stroke to the first half of the compression stroke.

  On the other hand, it is necessary to form a rich spike mixture that does not contribute to combustion at a position away from the periphery of the ignition device 10 by the second fuel injection IT2. Therefore, the second fuel injection IT2 is injected at a time when the fuel injected from the fuel injection device 20 does not enter the jump cavity 12a formed on the piston crown surface. In this embodiment, as shown in FIG. 3, the fuel injected from the fuel injection device 20 is injected at a time before the latter half of the compression stroke entering the jump cavity 12a formed on the piston crown surface.

  By the way, in the first several cycles after the fuel cut recovery operation is started, the in-cylinder residual gas amount remaining in the cylinder is different for each cycle. This point will be described with reference to FIG.

  FIG. 4 is a diagram showing the in-cylinder residual gas amount remaining in the cylinders of each cylinder until several cycles elapse after the fuel cut recovery operation is started. The four strokes of intake, compression, expansion, and exhaust are defined as one cycle. The ignition order is in the order of # 1, # 4, # 2, # 3.

  As shown in FIG. 4, in the first cycle immediately after the start of the fuel cut recovery operation, the residual gas amount in each cylinder is almost zero. This is because the remaining gas is scavenged by the air passing through the cylinder during the fuel cut operation.

  In the second cycle, in the # 1 cylinder, a part of the exhaust of the own cylinder (# 1 cylinder) generated in the first cycle remains in the cylinder as a residual gas. Become.

  On the other hand, in the # 4 cylinder, a part of the exhaust of the own cylinder (# 4 cylinder) generated in the first cycle remains as residual gas, and a part of the exhaust generated in the other cylinder (# 1 cylinder) exhausts. It flows in through the manifold. Therefore, the sum of the residual gas of the own cylinder (# 4 cylinder) and the exhaust of the other cylinder (# 1 cylinder) that has flowed in via the exhaust manifold is the in-cylinder residual gas amount.

  In the # 2 cylinder, in-cylinder residual gas is the sum of the residual gas of the own cylinder (# 2 cylinder) and the exhaust of the other cylinders (# 1 cylinder and # 4 cylinder) flowing in via the exhaust manifold on the same principle. Amount. Similarly, in the # 3 cylinder, the sum of the remaining gas of the own cylinder (# 2 cylinder) and the exhaust of the other cylinders (# 1, # 4 and # 2 cylinders) flowing in through the exhaust manifold is in-cylinder. Remaining gas amount.

  Therefore, in the second cycle, the in-cylinder residual gas amount of the cylinder whose ignition order is later becomes larger than the in-cylinder residual gas amount of the cylinder whose ignition order is earlier.

  After the third cycle, the in-cylinder residual gas amount of each cylinder becomes a substantially constant amount.

  As described above, in the first several cycles after the fuel cut recovery operation is started, the in-cylinder residual gas amount remaining in the cylinder is different for each cycle. Therefore, if the same amount of fuel is injected in each cycle, the output torque of the engine in the first few cycles fluctuates, a torque shock occurs, and the driving performance deteriorates.

  Therefore, in the present embodiment, the injection amount of the first fuel injection IT1 that contributes to combustion is reduced in the first several cycles. After the first few cycles, the timing of the second fuel injection IT2 is retarded in order to increase the air-fuel mixture that contributes to combustion.

  FIG. 5A is a diagram showing the injection amounts of the first fuel injection IT1 and the second fuel injection IT2 for each cycle when the rich spike is performed during the fuel cut recovery operation. FIG. 5B is a diagram showing the injection timing of the first fuel injection IT1 and the second fuel injection IT2 for each cycle when the rich spike is performed during the fuel cut recovery operation.

  As shown in FIG. 5 (A), the fuel injection IT1 in the first cycle with a small amount of in-cylinder residual gas is minimized, and as the in-cylinder residual gas amount increases until the predetermined number of cycles is reached, 1 The amount of fuel injection IT1 is increased. On the other hand, the second fuel injection IT2 injects the required rich spike amount regardless of the number of cycles.

  As shown in FIG. 5B, the injection timing of the first fuel injection IT1 is set according to the operating state. On the other hand, the injection timing of the second fuel injection IT2 is retarded as the in-cylinder residual gas amount increases, so that the second half of the fuel injection IT2 enters the jump cavity. Thereby, a part of the second fuel injection IT2 can be contributed to the combustion, so that the combustion speed can be increased.

  Hereinafter, the torque shock suppression control during the fuel cut recovery operation described above will be described.

  FIG. 6 is a flowchart illustrating torque shock suppression control during fuel cut recovery operation according to the present embodiment. The controller 50 repeatedly executes this routine at a predetermined calculation cycle (for example, 10 ms).

  In step S1, the controller 50 determines whether or not the fuel cut recovery flag is set to 1. The fuel cut recovery flag will be described later (step S4). If the fuel cut recovery flag is set to 1, the controller 50 proceeds to step S5, and if it is set to 0, the controller 50 proceeds to step S2.

  In step S2, the controller 50 determines whether or not the fuel cut operation is being performed. If the fuel cut operation is in progress, the controller 50 proceeds to step S3, and if not, ends the current process.

  In step S3, the controller 50 determines whether to start the fuel cut recovery operation according to the operating state of the engine. The controller 50 shifts the process to step S4 when starting the fuel cut recovery operation, and ends the current process when continuing the fuel cut operation.

  In step S4, the controller 50 sets a fuel cut recovery flag to 1. The fuel cut recovery flag is a flag that is set to 1 during the fuel cut recovery operation.

  In step S5, the controller 50 determines whether there is a request for a rich spike. Specifically, the determination is made based on the time during which the fuel has been cut (the time during which the fuel cut operation has been performed). This is because if the fuel cut time is short, the amount of oxygen absorbed by the three-way catalyst 42 is small, and it is not necessary to perform rich spike. The controller 50 proceeds to step S8 when there is a request for rich spikes, and proceeds to step S6 when there is no request.

  In step S6, the controller 50 performs normal combustion control. Specifically, stratified combustion is performed at low rotation and low load, and homogeneous combustion is performed at high rotation and high load.

  Note that stratified combustion here refers to lean combustion in which fuel is injected only once during the compression stroke and the air-fuel mixture is ignited before compression top dead center in a state where fuel is unevenly distributed in the vicinity of the ignition device 10. Say. Homogeneous combustion refers to combustion in which fuel is injected once during the intake stroke, and an air-fuel mixture having a uniform air-fuel ratio is formed in the entire combustion chamber and then ignited.

  In step S7, the controller 50 sets a fuel cut recovery flag to 0.

  In step S8, the controller 50 performs a torque shock suppression process. The specific contents of the torque shock suppression process will be described later with reference to FIG.

  FIG. 7 is a flowchart for explaining torque shock suppression processing.

  In step S81, the controller 50 calculates the number of cycles after the fuel cut recovery operation is started.

  In step S82, the controller 50 calculates the target equivalent ratio according to the number of cycles and the operating state after the fuel cut recovery operation is started, and calculates the fuel injection amount IT based on the target equivalent ratio.

  In step S83, the controller 50 divides the fuel injection amount IT into a fuel injection amount IT1 injected for the first time and a fuel injection amount IT2 injected for the second time.

  In step S84, the controller 50 sets the first fuel injection timing and the second fuel injection timing.

  In step S85, the controller 50 sets the ignition timing.

  FIG. 8 is a time chart for explaining the operation of the torque shock suppression control during the fuel cut recovery operation. In addition, in order to clarify the correspondence with the flowchart, description will be made with the step number of the flowchart.

  When the fuel cut operation is shifted to the fuel cut recovery operation at time t1 (No in S1, Yes in S2, Yes in S3), the fuel cut recovery flag is set to 1 (FIG. 8 (B); S4). Determines whether there is a request for a rich spike (Yes in S1, S5). Since there is a rich spike request here (FIG. 8C; Yes in S5), the controller 50 executes torque shock suppression processing (S8).

  When the torque shock suppression process is executed, the controller 50 calculates the cycle number of the combustion cycle of each cylinder after the fuel cut recovery operation is started (S81). Then, the fuel injection amount IT is calculated according to the calculated number of cycles and the operating state (FIG. 8D; S82). Thereafter, the calculated fuel injection amount IT is divided into a fuel injection amount IT1 to be injected for the first time and a fuel injection amount IT2 to be injected for the second time (FIGS. 8E and 8F; S83). Then, the timing of the first fuel injection and the timing of the second fuel injection are set according to the calculated number of cycles and the operating state (FIG. 8 (G); S84).

  When there is no rich spike request at time t2 (FIG. 8C; No in S5), the fuel cut recovery flag is set to 0 (FIG. 8B; S7).

  According to the present embodiment described above, when the fuel cut operation is shifted to the fuel recovery operation, if there is a rich spike request, the fuel is divided and injected twice, and the fuel is burned by the first fuel injection. A contributing homogeneous mixture is formed throughout the combustion chamber. Then, by the second fuel injection, an air-fuel mixture for rich spike that does not contribute to combustion is formed at a position away from the periphery of the ignition device.

  Thereby, since the air-fuel mixture formed by the second fuel injection does not contribute to combustion, it is possible to suppress the occurrence of torque shock during the fuel cut recovery operation even if the rich spike amount is increased.

  Further, since the rich spike amount can be increased, oxygen that has been absorbed excessively by the three-way catalyst 42 can be quickly released, and deterioration of emissions can be suppressed.

  Further, the air-fuel mixture formed by the second fuel injection is formed at a position away from the periphery of the ignition device. Therefore, the air-fuel mixture around the ignition device does not become excessively rich. Therefore, it can suppress that a fuel misfires without being vaporized.

  Further, in this embodiment, the first few cycles after the fuel cut recovery operation is started differ in the in-cylinder residual gas amount remaining in the cylinder for each cycle. The fuel injection amount for the first time was reduced as the number of cycles decreased.

  Thereby, it is possible to more reliably suppress the occurrence of torque shock during the fuel cut recovery operation.

  In the present embodiment, the fuel injection in the second half of the second fuel injection enters the jump cavity 12a during the fuel cut operation after the cylinder residual gas amount remaining in the cylinder becomes substantially constant. did.

  Thereby, a part of the second fuel injection can be contributed to the combustion, so that the combustion speed can be increased. Therefore, combustion can be stabilized.

  Note that the present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  For example, in this embodiment, an in-line four-cylinder engine has been described as an example. However, the number of cylinders is not limited to this, and can be applied to various engines such as an in-line, V-type, or horizontally opposed engine.

1 is an overall system diagram of a control device for an in-cylinder direct fuel injection spark ignition engine. It is a figure which shows the state of the air-fuel | gaseous mixture formed in a combustion chamber when implementing a rich spike at the time of fuel cut recovery driving | operation. It is the figure which showed the timing of the 1st fuel injection when performing rich spike at the time of fuel cut recovery, and the timing of the 2nd fuel injection. It is the figure which showed the cylinder residual gas amount which remains in the cylinder of each cylinder until several cycles pass after a fuel cut recovery driving | operation is started. It is the figure which showed the injection quantity and injection timing of the 1st fuel injection and the 2nd fuel injection at the time of implementing a rich spike at the time of a fuel cut recovery driving | operation. It is a flowchart explaining the torque shock suppression control at the time of fuel cut recovery driving | operation. It is a flowchart explaining a torque shock suppression process. It is a time chart explaining operation | movement of the torque shock suppression control at the time of fuel cut recovery driving | operation.

Explanation of symbols

1 In-cylinder direct fuel injection spark ignition engine (engine)
DESCRIPTION OF SYMBOLS 10 Ignition device 12 Piston 12a Jump cavity 20 Fuel injection device 40 Exhaust passage 42 Three-way catalyst (exhaust purification catalyst)
S5 Rich spike request determining means S81 Cycle number detecting means S83 Fuel injection dividing means S84 Fuel injection means

Claims (4)

A fuel injection device that directly injects fuel into each cylinder;
An ignition device for igniting a mixture of fuel and air injected from the fuel injection device;
A piston having a jump cavity on the crown surface for guiding the fuel injected from the fuel injection device around the ignition device;
An exhaust purification catalyst provided in the exhaust passage and having an oxygen storage function;
A control device for suppressing torque shock of an engine comprising:
A rich spike request for releasing the oxygen absorbed by the exhaust purification catalyst by making the air-fuel ratio rich when shifting from a fuel cut operation for stopping fuel injection of the fuel injection device to a fuel cut recovery operation for restarting fuel injection Rich spike request determination means for determining whether or not there is,
When there is a request for the rich spike, a fuel injection splitting means for splitting the fuel injection twice;
The first fuel injection divided by the fuel injection dividing means is injected at a timing at which a homogeneous mixture that contributes to combustion is formed at least around the ignition device, and the second fuel injection is and injected at the timing earlier than the latter half of the compression stroke does not enter into the jump cavity, a fuel injection unit that forms form a stratified air-fuel mixture does not contribute to combustion at a position deviated from around said ignition device,
An engine torque shock suppression control device comprising: Cycle number detecting means for detecting the number of cycles of each cylinder after the fuel cut recovery operation is started,
2. The engine torque according to claim 1, wherein the amount of fuel injected by the first fuel injection is smaller as the number of cycles is smaller until the number of cycles becomes larger than a predetermined number of cycles. Shock suppression control device. After pre-number system cycles is greater than the number of said predetermined cycle, according to claim 2, wherein the second time of the fuel injection, a portion of the second half of the injected fuel, characterized in that the injection timing of entering the Jean cavity An engine torque shock suppression control device according to claim 1. The engine according to any one of claims 1 to 3, wherein the rich spike request determination unit determines that a rich spike request is present if the fuel cut operation time is longer than a predetermined time. Torque shock suppression control device.