JP2014148979A - Control device of in-cylinder injection type engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of an in-cylinder injection type engine capable of restraining deterioration of a soot and smoke exhaust amount and an exhaust performance, when restarting is requested after an idle stop condition is satisfied and before the engine is stopped.SOLUTION: When restarting is requested after an idle stop condition is satisfied and before an engine is stopped, at least one of a fuel injection number and an air-fuel ratio of an air-fuel mixture to be combusted during a combustion cycle is changed for each cylinder according to a piston position at that time.

Description

  The present invention relates to an engine control device mounted on a vehicle or the like, and in particular, includes a fuel injection valve that directly injects fuel into a cylinder (combustion chamber), and the engine and the vehicle on which the engine is mounted satisfy a predetermined condition. The present invention relates to a control apparatus for an in-cylinder injection engine that performs an idle stop for temporarily stopping the engine.

  In recent years, from the viewpoint of environmental protection, vehicles (automobiles) have reduced combustion waste gas (exhaust gas), which is a greenhouse gas, and carbon monoxide (CO), hydrocarbon (HC), nitrogen oxide (NOx) contained therein. ), Etc. (referred to as “improvement of exhaust performance”) and reduction of fuel consumption (improvement of fuel efficiency) are demanded. The main purpose is to improve the exhaust performance and fuel efficiency, and further improve the engine output. As a result, an in-cylinder injection engine has been developed in which fuel injection by a fuel injection valve is directly performed in the combustion chamber of each cylinder.

  In order to further improve fuel efficiency and exhaust performance, when the engine and the vehicle on which the engine is mounted satisfy a predetermined condition (for example, a signal waiting state), an idle stop is performed to temporarily stop the engine, and then the engine is restarted. A vehicle with an idle stop function that drives a starter and restarts the engine when a start request is made has been put into practical use and is becoming popular recently.

  Various technologies related to idle stop (engine stop) -restart in vehicles equipped with in-cylinder injection engines have been proposed. For example, in Patent Document 1, it is determined whether or not the stop position of a piston in a cylinder is at a stop position where compression injection combustion can be performed, and the piston stop position in the cylinder performs the compression injection combustion. It has been proposed to start fuel injection when the vehicle is in a specific position.

  Further, for example, in Patent Document 2, if there is a restart request before engine (rotation) stop after the idle stop condition is satisfied, if the engine rotation speed at that time is higher than a predetermined value, fuel is supplied to the compression stroke cylinder. It has been proposed to perform ignition by injecting fuel and injecting fuel into the compression stroke cylinder and the expansion stroke cylinder when the engine speed falls below a predetermined value.

JP 2010-236546 A Japanese Unexamined Patent Publication No. 2007-23815

  As described above, in recent years, various restart technologies for the purpose of improving fuel efficiency and exhaust performance have been proposed for an in-cylinder injection engine mounted on a vehicle with an idle stop function. The number of times that the idle stop (engine stop) condition is established tends to increase, and restart technology in the event of a restart request due to the driver's intention before stopping the engine (rotation) is also important. It is increasing.

  The restart request before the engine (rotation) stop after the idle stop (engine stop) condition is satisfied is determined by the driver's will, but the piston position at the time of this restart request varies, and at extremely low rotation Therefore, if appropriate fuel injection (injection start time and injection time = injection amount) is not performed, the combustion instability, the increase in the amount of smoke (= Soot = soot) due to misfire, and the deterioration of exhaust performance are caused.

  The present invention has been made in view of such a problem. When a restart request is made after the idle stop condition is established and before the engine is stopped, fuel injection is appropriately performed according to the piston position of each cylinder. Therefore, an object of the present invention is to provide a control device for an in-cylinder injection engine that can suppress soot emission and deterioration of exhaust performance.

  In order to achieve such an object, the control device for a direct injection engine according to the present invention includes a fuel injection valve that directly injects fuel into the combustion chamber, and the engine and the vehicle on which the engine is mounted are in a state that satisfies a predetermined condition. When there is a restart request before the engine is stopped after the idle stop condition is established under the condition that the engine is temporarily stopped, and depending on the piston position at that time, for each cylinder It is characterized in that at least one of the number of fuel injections in one combustion cycle and the air-fuel ratio of the air-fuel mixture used for combustion is changed.

  In the in-cylinder injection engine control device according to the present invention, when there is a restart request before the engine is stopped after the idle stop (engine stop) condition is established, for each cylinder, according to the piston position at that time, Changing and / or changing at least one of the number of fuel injections in one combustion cycle and the air-fuel ratio of the air-fuel mixture used for combustion, in other words, calculating and selecting the optimum restart combustion mode according to the piston position at that time Therefore, it is possible to stabilize combustion, improve exhaust performance, and improve fuel efficiency.

  Problems, configurations, and effects other than those described above will be clarified by the following embodiments.

The schematic block diagram which shows one Embodiment of the control apparatus of the cylinder injection type engine which concerns on this invention. The schematic block diagram of the fuel system of the cylinder injection type engine shown by FIG. The figure which shows the internal structure and input-output relationship of the engine control unit shown by FIG. The flow block diagram which shows the processing content of the engine control unit shown by FIG. The flowchart which shows the detail of the processing content of the block 401 of FIG. The flowchart which shows the detail of the processing content of the block 405 of FIG. The figure which shows the relationship between a piston position when there is a restart request | requirement, area | region 1,2,3,4, and a restart combustion form. The figure which shows the relationship between the fuel pressure and the injection pulse width in the control apparatus shown by FIG. The figure which shows an example of the multistage injection performed in the control apparatus shown by FIG. The figure provided in order to demonstrate the effect of this invention Example compared with a prior art example.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing an embodiment of a control device according to the present invention together with an in-cylinder injection engine to which the control device is applied.

  The in-cylinder injection engine 1 of the illustrated example is an in-line four-cylinder gasoline engine having, for example, four cylinders (# 1, # 2, # 3, # 4), and is supplied to each cylinder 207b (combustion chamber 207c). The air taken in is taken from the inlet of the air cleaner 202, passes through the air flow sensor 203, enters the collector 206 through the throttle body 205 in which the electric throttle valve 205a is accommodated. The air sucked into the collector 206 is distributed to each intake manifold (manifold) 201 connected to each cylinder 207b, and then led to a combustion chamber 207c defined above the piston 207a via an intake valve 225. .

  From the air flow sensor 203, a signal representing the amount of intake air is output to the engine control unit 101 constituting the main part of the control device of the embodiment of the present invention. Further, a throttle sensor 204 for detecting the opening degree of the electric throttle valve 205a is attached to the throttle body 205, and a signal representing the opening degree is also output to the engine control unit 101.

  On the other hand, fuel such as gasoline is primarily pressurized from the fuel tank 250 by the low-pressure fuel pump 251 and regulated to a constant pressure (for example, 0.3 MPa) by the fuel pressure regulator 252, and further by a high-pressure fuel pump 209 described later. Secondary pressure is applied to a high pressure (for example, 5 MPa or 10 MPa), and the pressure is supplied to the fuel injection valve 254 provided in each cylinder 207b via a pressure accumulating chamber (hereinafter referred to as a common rail) 253, and is combusted from the fuel injection valve 254. It is directly injected into the chamber 207c. The mixture of the fuel injected into the combustion chamber 207c and the intake air is ignited by the spark of the spark plug 208 to which an ignition signal having a high voltage supplied by the ignition coil 222 is supplied, and is explosively combusted. (Exhaust gas) is discharged to the outside through an exhaust valve 226 from an exhaust passage 231 provided with an exhaust purification catalyst (three-way catalyst) 232. In the present embodiment, the fuel injection valve 254 is a side injection method in which injection is performed from the intake side of the engine 1, but may be a center injection method in which injection is performed directly above the combustion chamber 207c.

  A crank angle sensor 216 attached to the crankshaft 207d of the engine 1 outputs a signal representing the rotational position of the crankshaft 207d to the engine control unit 101.

  The engine 1 also includes an intake side variable valve mechanism that varies the opening / closing timing of the intake valve 225 and an exhaust side variable valve mechanism that varies the opening / closing timing of the exhaust valve 226. A cam angle sensor 211 attached to a camshaft (not shown) outputs an angle signal representing the rotational position of the exhaust camshaft to the engine control unit 101, and rotates with the rotation of the exhaust camshaft. An angle signal representing the rotational position of the pump drive cam 200 at 209 is also output to the engine control unit 101. Based on the signals from the crank angle sensor 216 and the cam angle sensor 211, it is determined whether each cylinder is in one combustion cycle (intake stroke, compression stroke, expansion stroke, exhaust stroke) or the piston position (for example, crank stroke). The number of times before the top dead center of the compression stroke is calculated.

  The starter 260 is configured to rotationally drive the crankshaft 207d by a drive signal from the engine control unit 101.

FIG. 2 shows a schematic configuration diagram of a fuel supply system including the high-pressure fuel pump 209.
The high-pressure fuel pump 209 pressurizes fuel from the fuel tank 250 and pumps high-pressure fuel to the common rail 253.

  The fuel is led from the tank 250 to the fuel inlet of the pump body 209 by the low-pressure pump 251 after being regulated to a constant pressure by the pressure regulator 252. A high pressure pump control valve 209a, which is a normally closed solenoid valve (solenoid valve), is provided on the fuel inlet side to control the fuel intake amount. The high-pressure pump control valve 209a is closed when not energized and opened when energized.

  The fuel supplied by the low-pressure pump 251 controls the fuel pressure in the common rail (hereinafter referred to as fuel pressure) by adjusting the discharge amount by controlling the high-pressure pump control valve 209a by the engine control unit 101. The fuel is pressurized by the pump drive cam 200 and the pressurizing chamber 209b, and is pumped from the fuel discharge port to the common rail 253. A discharge valve 209c is provided at the fuel discharge port in order to prevent the downstream high-pressure fuel from flowing back into the pressurizing chamber. The common rail 253 is equipped with a fuel injection valve 254 and a pressure sensor 256 for measuring the fuel pressure in the common rail (hereinafter referred to as fuel pressure).

  FIG. 3 shows the internal configuration and input / output relationship of the engine control unit 101. The engine control unit 101 includes an I / O LSI 101a including an A / D converter, a CPU 101b, an EP-ROM 101c, a RAM 101d, and the like. The signal of the key switch 301 indicating an accessory, ignition ON, starter ON, accelerator sensor 302, brake switch 303, signals from various sensors including a vehicle speed sensor 304, an air flow sensor 203, a throttle sensor 204, a cam angle sensor 211, a crank angle sensor 216, a water temperature sensor 217, an air-fuel ratio sensor 218, a fuel pressure sensor 256, and an oil temperature sensor 219. As an input, execute predetermined arithmetic processing, output various control signals calculated as arithmetic results, an electric throttle 205a, a high-pressure pump control valve 209a, which is an actuator, each ignition coil 222 (for four cylinders), Low A predetermined control signal is supplied to the pressure fuel pump 251, each fuel injection valve 254 (for four cylinders), and the starter 260, common rail internal combustion pressure control, fuel injection control (injection start timing, injection time (injection amount), one combustion cycle The control circuit controls the number of injections, ignition timing control, starter control, etc. The I / OLSI 101a is provided with a drive circuit for driving each fuel injection valve 254, and the voltage supplied from the battery is supplied. The pressure is increased and supplied to the fuel injection valve 254 of each cylinder.

  Next, specific contents of the fuel injection control of the present embodiment will be described.

FIG. 4 is a flow block diagram showing the processing contents of the control device of the present embodiment.
In block 401, based on information obtained from the key switch 301, the accelerator sensor 302, the brake switch 303, the vehicle speed sensor 304, etc., it is determined whether or not the restart is permitted after the idle stop (engine stop) condition is satisfied. In addition, it is also determined whether or not the restart request is before the engine (rotation) stop after the idle stop condition is satisfied. If the restart request is before the engine stop, that is, during the engine rotation, the engine rotation indicating that The restart flag F is set to 1 (ON).

Details of the processing contents of the block 401 are shown in a flowchart in FIG.
The process shown in the flowchart in FIG. 5 is an interrupt process, and is repeatedly executed, for example, at a cycle of 10 ms. First, in step 502, it is determined whether or not the fuel for idling stop is being cut. In the subsequent step 503, it is determined whether or not there has been a restart request based on information obtained from the accelerator sensor 302 or the like. If there is a restart request, the process proceeds to step 504 to determine whether or not the engine is rotating. If the engine is rotating, it can be determined that a restart request has been made before the engine is stopped after the idle stop condition is established. Therefore, in step 505, an engine rotation restart flag F indicating that the engine is restarting is set. Set to 1.

  In block 402 of FIG. 4, when the engine rotation restart flag F becomes 1, driving of the starter 260 is started.

  In block 403, the target fuel pressure (pressure increase value) to be obtained is calculated, and in step 404, the high pressure pump 209 is driven so that the target fuel pressure is obtained. The purpose of increasing fuel pressure is to promote atomization of fuel to improve combustion, and to shorten the injection period and secure atomization time in response to restart requests that may be required in the second half of the compression stroke This is to shorten the injection time and increase the upper limit of the number of multistage injections. As means for increasing the fuel pressure, the target fuel pressure of the high-pressure fuel pump control is changed in the increasing direction.

  Here, under the same injection pulse width, the fuel injection valve has a characteristic that the injection amount increases as the fuel pressure increases, and the injection amount characteristic with respect to the injection pulse width is such that the injection pulse width is greater than a certain value. The linearity is maintained in the region, and the injection amount is not stable when the injection pulse width is less than a certain value. Therefore, the lower limit value that can be used as the ejection pulse width is limited to the minimum value that maintains linearity. FIG. 8 shows the relationship between the fuel pressure and the injection pulse width (corresponding to the injection time) when the fuel injection amount of the fuel injection valve is constant. When the fuel pressure increases, the injection pulse width decreases. At this time, the target fuel pressure is set so that the injection amount of the fuel injection valve is stable (linearity is maintained) and does not fall below the minimum value.

  In order to increase the fuel pressure in a short period of time until the engine is stopped, when the engine rotation restart flag F becomes 1, the high pressure pump is brought into a full discharge state.

  In block 405, based on the signals obtained from the crank angle sensor 216 and the cam angle sensor 211, the piston position in each cylinder when the engine rotation restart flag F becomes 1 is obtained, and the optimum piston position is obtained. The restart combustion mode is calculated and selected for each cylinder.

Details of the processing contents of the block 405 are shown in a flowchart in FIG.
The process shown in the flowchart in FIG. 6 is an interrupt process, and is repeatedly executed, for example, at a cycle of 10 ms. First, in step 602, it is determined whether or not the engine rotation restart flag F is 1, that is, whether or not the restart request is before the engine is stopped (during engine rotation). (Flag F is 1), the process proceeds to step 603, and otherwise, the process returns to the beginning. In step 603, the piston position of each cylinder is calculated based on signals from the crank angle sensor 216 and the cam angle sensor 211. If the piston position is in the latter half of the compression stroke, it is determined in step 604 that the region is region 1, and the restart combustion mode ISREST is set to 1 (step 605). If the piston position is in the middle of the compression stroke, it is determined in step 606 that the region is region 2, and the restart combustion mode ISREST is set to 2 (step 607). If the piston position is from the middle of the intake stroke to the first half of the compression stroke, it is determined in step 608 that the region is region 3, and the restart combustion mode ISREST is set to 3 (step 609). When the piston position is in the first half of the intake stroke, the restart combustion mode ISREST is set to 4 in step 610. The range of each region 1, 2, 3, and 4 varies depending on the combustion performance of the engine. Further, since the piston position of each cylinder at the time of restart request is different (in the case of four cylinders, the crank angle is shifted by 180 degrees), the restart combustion mode ISREST is calculated for each cylinder.

FIG. 7 shows the relationship between the piston position, the regions 1, 2, 3, and 4 and the restart combustion mode.
When the piston position is in region 1 (late compression stage), the restart combustion mode ISREST is set to 1. In this case, the restart combustion mode ISRES = 1 is determined (when the piston position is calculated, Immediately after the start request is made, fuel injection is started immediately. Accordingly, the restart initial injection timing (injection start timing) is the latter half of the compression stroke in region 1. This is to ensure the atomization time. Further, in order to suppress the emission of soot (soot), the fuel injection amount is set so that the fuel spray is stratified and the air-fuel ratio of the air-fuel mixture used for combustion becomes leaner than the stoichiometric.

  When the piston position is in region 2 (mid-compression stroke), the restart combustion mode ISREST is set to 2. In this case as well, the restart combustion mode ISRESET = 2 is determined (the time when the piston position is calculated or Immediately after the start request is made, fuel injection is started immediately. Therefore, the restart initial injection timing (injection start timing) is the middle of the compression stroke in region 2. This is to ensure the atomization time. Further, by performing fuel injection a plurality of times during one combustion cycle (execution of multistage injection), the mixture of fuel and air in the combustion chamber is improved and the air-fuel mixture concentration necessary for the ignition timing is ensured. FIG. 9 shows an example of multistage injection. Here, an example (four-stage injection) is performed in which injection is performed a total of four times, twice in the middle of the compression stroke in region 2 and twice in the latter half of the compression stroke.

  When the piston position is in region 3 (from the middle of the intake stroke to the first half of the compression stroke), the restart combustion mode ISREST is set to 3, and also in this case, when the restart combustion mode ISREST = 3 is determined (the piston position is calculated). The fuel injection is started immediately at almost the same time as when the engine was restarted or when a restart request was made. Therefore, the restart initial injection timing (injection start timing) is from the middle of the intake stroke in region 3 to the first half of the compression stroke. This is to ensure the atomization time. The starting end of the region 3 where ISTREST = 3 is set to the injection timing (best injection timing) with the best combustion performance during the intake stroke injection.

  When the piston position is in the region 4 (region other than the regions 1, 2 and 3), the restart combustion mode ISRES is set to 4, and in the region of the restart combustion mode ISREST = 4, the start end of the region 3 of ISREST = 3 The fuel injection is executed after waiting for the best injection timing.

  The first injection when restarting before engine stop (during engine rotation) is different from the case of restarting after the engine is completely stopped, so there is air flow and appropriate compression pressure in the combustion chamber. As described above, by performing appropriate stratification and multistage injection according to the piston position, combustion robustness is enhanced, and soot emission and exhaust performance deterioration can be suppressed.

  In blocks 405 to 409 in FIG. 4, the injection (start) timing, the injection pulse width (corresponding to the injection amount), the ignition timing, and the target throttle opening corresponding to the restart combustion mode ISRES are calculated. In 412, drive control of the fuel injection valve, the ignition coil, and the electric throttle is performed.

  Next, the effects of the embodiment of the present invention will be described in comparison with the conventional example with reference to FIG. FIGS. 10A and 10B show the case where the piston position of a certain cylinder is in region 2 (the middle of the compression stroke) when a restart request is made before the engine is stopped (during engine rotation) after the idle stop condition is satisfied. It is a time chart which shows the behavior change of each part.

  In the conventional example of (A), the injection is executed once at a low fuel pressure in the compression stroke. For this reason, the atomization time is not secured and proper stratification is not performed, and combustion may become unstable, leading to deterioration of engine startability, soot (Soot) emission and increase in HC. .

  In the example of the present invention, by increasing the fuel pressure after the idling stop condition is established, the compression stroke combustion itself at the time of restart is improved and the number of possible multistage injections is increased. Moreover, the multistage injection which is the optimal combustion form is adopted. As a result, the restartability is improved, and soot (Soot = soot) emission and increase in HC are suppressed.

  In other words, in the embodiment of the present invention, when there is a restart request before the engine is stopped after the idle stop (engine stop) condition is satisfied, the optimum restart combustion mode is selected according to the piston position of each cylinder. Therefore, combustion stabilization, exhaust performance, and fuel consumption can be improved.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various changes in design can be made without departing from the spirit of the present invention described in the claims. It can be done.

DESCRIPTION OF SYMBOLS 1 ... In-cylinder injection engine 101 ... Engine control unit 200 ... Pump drive cam 201 ... Each intake pipe 202 ... Air cleaner 203 ... Air flow sensor 204 ... Throttle sensor 205 ... Throttle body 206 ... Collector 208 ... Spark plug 209 ... High-pressure fuel pump 211 ... cam angle sensor 216 ... crank angle sensor 217 ... water temperature sensor 218 ... air-fuel ratio sensor 219 ... oil temperature sensor 222 ... ignition coil 225 ... intake valve 226 ... exhaust valve 250 ... fuel tank 251 ... low-pressure fuel pump 252 ... fuel pressure regulator 253 ... Common rail 254 ... Fuel injection valve 256 ... Fuel pressure sensor 260 ... Starter 301 ... Key switch 302 ... Accelerator opening sensor 303 ... Brake switch 304 ... Vehicle speed sensor

Claims (9)

A control device that controls to stop fuel injection from the fuel injection valve when an engine including a fuel injection valve that directly injects fuel into the combustion chamber or a vehicle on which the engine is installed satisfies a predetermined condition,
After the predetermined condition is satisfied and before the engine is stopped, at least one of a cylinder that performs the first injection after the predetermined condition is satisfied and a cylinder that deviates from the cylinder by a predetermined crank angle according to the piston position before the engine is stopped. And controlling at least one of the number of fuel injections of the multistage injection in one combustion cycle and the air-fuel ratio of the air-fuel mixture used for combustion.   2. The control device according to claim 1, wherein the piston position of the cylinder before the engine is stopped is a piston position of a cylinder that performs the initial restart injection.   The fuel injection amount is set so that the air-fuel ratio of the air-fuel mixture used for combustion becomes leaner than stoichiometric when the piston position is in the first specific period of the compression stroke. 2. The control device according to 2.   The fuel injection is executed a plurality of times during one combustion cycle when the piston position is in a second specific period before the first specific period of the compression stroke. Control device.   5. The control device according to claim 4, wherein the piston position performs fuel injection a plurality of times over a first specific period of a compression stroke and a second specific period before the first specific period. .   6. The fuel injection is started after waiting for a predetermined piston position when the engine is requested to restart after the predetermined condition is satisfied and before the engine is stopped. The control device described in 1.   7. The control device according to claim 1, wherein a target fuel pressure of fuel to be supplied to the fuel injection valve is increased while the predetermined condition is satisfied.   A fuel pump for pumping fuel to the fuel injection valve; and a fuel pressure accumulating chamber for storing fuel to be supplied to the fuel injection valve; in order to set the pressure of the fuel supplied to the fuel injection valve as the target fuel pressure, The control device according to claim 7, wherein the fuel pressure in the fuel pressure accumulation chamber is increased by setting the fuel pump to a full discharge state.   The control device according to claim 7 or 8, wherein the target fuel pressure is changed in accordance with a minimum injection pulse width of the fuel injection valve.