JP4066680B2 - Diesel engine start control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a start control device for a diesel engine, and particularly relates to an apparatus for reducing vibration by reducing a substantial compression ratio of a cylinder at a warm start.
[0002]
[Prior art]
  Conventionally, as this type of engine start control device, as disclosed in, for example, Japanese Patent Laid-Open No. 2000-34913, when the engine is automatically stopped or started under a predetermined condition, There is one that reduces the vibration. That is, when the engine is started, the engine rotation speed temporarily becomes extremely low, and vibrations caused by the pump work of each cylinder may be coupled to generate large vibrations in the engine and the power transmission system. When the engine is automatically started, the vibration is unexpected by the driver, which gives a sense of incongruity.
[0003]
  Therefore, in the conventional example, the opening / closing timing and lift amount of the intake valve are changed by the operation of the variable valve mechanism attached to the valve system of the engine, so that the cylinders can be substantially stopped when the engine is automatically stopped or automatically started. By reducing the typical compression ratio, the pump work for each cylinder is reduced to reduce vibration.
[0004]
[Problems to be solved by the invention]
  However, in general, a diesel engine injects fuel into a high-temperature and high-pressure combustion chamber in which air taken into the cylinder is compressed and burns it by self-ignition. When the compression ratio is substantially lowered, the ignition performance is lowered due to this, and there is a problem that the startability of the engine is impaired.
[0005]
  The present invention has been made in view of such a point, and the object of the present invention is to reduce vibration by substantially reducing the compression ratio of the cylinder when starting the diesel engine. The purpose is to ensure good startability by complementing the decrease in ignitability due to the decrease in the compression ratio.
[0006]
[Means for Solving the Problems]
  In order to achieve the above object, in the present invention,The intake throttle valve is kept closed until the warm restart after the engine stops automatically, and the on-off valve of the exhaust gas recirculation passage is also closed.When operating the variable valve mechanism so that the compression ratio of the cylinder is substantially low during the warm start of the engineOpens the on-off valve,At least a part of the exhaust gas is returned to the intake system to increase the temperature state of the intake air.
[0007]
  Specifically, the invention of claim 1 can change at least one of the motor M for starting the engine Eg and the opening / closing timing or lift amount of the intake valve of the engine Eg, as schematically shown in FIG. A variable valve mechanism VV, and a valve mechanism control means for operating the variable valve mechanism Vv so that the actual compression ratio of the cylinder C becomes relatively low when the engine Eg is warmly started by the motor M are provided. A diesel engine start control device is assumed. And engine EgIs mounted on the vehicle andAn exhaust gas recirculation passage Er for communicating the exhaust air passage Ex and the intake air passage In, an on-off valve Ev for opening and closing the exhaust gas recirculation passage Er,An intake throttle valve (not shown) that restricts the flow of intake air in the intake passage In upstream of the communication portion with the exhaust gas recirculation passage Er is provided.
[0008]
  Then, an intake throttle valve control means for closing the intake throttle valve when the vehicle is decelerated, an exhaust gas recirculation control means for opening the on-off valve Ev of the exhaust gas recirculation passage Er when the vehicle is decelerated, and operation of the engine Eg under predetermined conditions. An engine stop control means for stopping, and when the engine Eg is stopped by the engine stop control means after deceleration of the vehicle, the intake throttle valve control means until a subsequent warm restart of the engine Eg, Configured to keep the intake throttle valve closed,SaidWhen the engine Eg is stopped by the engine stop control means after deceleration of the vehicle, the exhaust gas recirculation control means closes the on-off valve Ev and opens the on-off valve Ev until a subsequent warm restart of the engine Eg. Keep it closed,During warm startIsThe on-off valve Ev is opened, and at least a part of the exhaust is recirculated to the intake passage In through the exhaust recirculation passage Er.It is comprised as follows.
[0009]
  The actual compression ratio is a substantial compression ratio when the gas sucked into the cylinder before the intake valve of the cylinder is closed is compressed at the compression top dead center. Unlike the geometrical compression ratio, the ratio is generally close to the ratio of the combustion chamber volume at the compression top dead center to the combustion chamber volume when the intake valve is closed.
[0010]
  With the above configuration,First,During warm start of the engine Eg, the variable valve mechanism Vv is controlled by the valve mechanism control means, and at least one of the opening / closing timing or lift amount of the intake valve of the engine Eg is changed, so that the cylinder C The compression ratio is substantially reduced. That is, for example, by changing the valve lift characteristic on the intake side so that the charging efficiency of the intake air into the cylinder C is reduced, the actual gas compression ratio (actual compression) even if the geometric compression ratio is the same. Ratio) is low. As a result, at least the compression work of the cylinder C is reduced, and accordingly, the angular speed fluctuation of the crankshaft of the engine Eg is reduced, and the vibration of the engine Eg is reduced.
[0011]
  On the other hand, when the vehicle is decelerated, the intake throttle valve is closed by the intake throttle valve control means, and the on-off valve Ev of the exhaust gas recirculation passage Er is opened by the exhaust gas recirculation control means, so that fuel is supplied to the engine Eg during deceleration. Even if the engine is stopped, the supply of new outside air is greatly suppressed thereafter, and the high-temperature exhaust gas discharged from the cylinder C to the exhaust passage Ex is recirculated to the cylinder C via the exhaust gas recirculation passage Er and the intake passage In. Inhaled and circulates through the intake and exhaust system of the engine Eg. In other words, even if the fuel supply to the engine Eg is stopped when the vehicle decelerates, the cylinder C and the intake / exhaust system of the engine Eg are suppressed from being cooled by outside air, and the high-temperature burned gas (exhaust gas) is circulated. Thus, it can be held inside the cylinder C and the intake / exhaust system.
[0012]
  Then, after the vehicle is decelerated, when the engine Eg is once stopped by the engine stop control means under a predetermined condition and then restarted,The on-off valve Ev of the exhaust gas recirculation passage Er is opened by the exhaust gas recirculation control means,High temperature held as aboveAt least a part of the exhaust gas is returned to the intake passage In.TheSince the exhaust gas recirculation increases the temperature state of the intake air, the temperature state of the combustion chamber in the latter half of the compression stroke of the cylinder C increases, which promotes vaporization of the fuel spray and improves ignitability. To do. Therefore, a good startability can be ensured by complementing a decrease in ignitability caused by a decrease in the compression ratio of the cylinder C.
[0013]
  Moreover, in the above configuration, when the engine Eg is stopped by the engine stop control means, the intake throttle valve and the on-off valve Ev of the exhaust gas recirculation passage Er are both closed until the subsequent warm restart. As a result, supply of new outside air is suppressed, and high-temperature exhaust is held inside the cylinder and the intake / exhaust system, and the operational effects of the above-described invention are further enhanced.
[0014]
  Therefore, for example, when the vehicle is stopped, the engine is automatically stopped (idle stop), or an electric motor for traveling is provided in addition to the engine, and the engine is automatically stopped when the vehicle is stopped or when traveling at a very low speed. In the hybrid vehicle, the effects of the present invention are particularly effective.
[0015]
  In the invention of claim 2, the turbine of the turbocharger is disposed in the exhaust passage downstream of the communication portion with the exhaust gas recirculation passage, and the exhaust gas to the turbine is discharged when the engine is warmly started by the motor. It is assumed that exhaust throttling means for throttling the flow is provided. Thus, when the engine is warmly started, the exhaust flow is throttled by the exhaust throttling means in the exhaust passage downstream of the communication portion with the exhaust recirculation passage, and the exhaust pressure rises, so that the exhaust through the exhaust recirculation passage increases. Is effectively carried out.
[0016]
  In the invention of claim 3, the variable valve mechanism is capable of adjusting at least the opening / closing timing of the intake valve within a predetermined range, and the valve mechanism control means reduces pump loss when starting the engine as compared with after starting. Thus, the variable valve mechanism is operated to adjust the closing timing of the intake valve.
[0017]
  As a result, the variable valve mechanism is actuated by the valve mechanism control means during the warm start of the engine, and the closing timing of the intake valve is adjusted, so that the pump loss is reduced compared to after the engine is started. . That is, for example, if the closing timing of the intake valve is relatively retarded, a part of the intake air sucked into the cylinder is blown back into the intake passage, thereby reducing the actual compression ratio of the cylinder. , Pump loss is reduced. Thereby, the vibration at the time of engine starting is reduced..
[0018]
  Claim4In the invention of claim1The turbocharger turbine is disposed in the exhaust passage downstream of the communication portion with the exhaust gas recirculation passage, and includes an exhaust throttle means for restricting the flow of exhaust to the turbine when the vehicle is decelerated. And Thus, when the vehicle is decelerated, the exhaust flow is throttled by the exhaust throttling means in the exhaust passage downstream of the communication portion with the exhaust recirculation passage, so that the exhaust from the cylinder is effectively recirculated by the exhaust recirculation passage. be able to.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0020]
  (overall structure)
  FIG. 2 shows an example of a combustion control apparatus A for a diesel engine according to an embodiment of the present invention, where 1 is a diesel engine mounted on a vehicle. This engine 1 has a plurality of cylinders 2, 2,... (Only one is shown), and a piston 3 is fitted into each cylinder 2 so as to be reciprocally movable. The combustion chamber 4 is partitioned. As shown in an enlarged view in FIG. 3, an injector 5 is disposed at the ceiling of the combustion chamber 4, and an injection nozzle 50 provided integrally at the tip of the injector 5 is an abbreviation of the ceiling surface 40 of the combustion chamber 4. Projects by a predetermined amount from the center. On the other hand, a cavity 3 a is formed on the top surface of the piston 3 which is the bottom of the combustion chamber 4, and the cavity is positioned so as to surround the periphery of the injection nozzle 50 of the injector 5 in the vicinity of the compression top dead center of the cylinder 2. Fuel is injected radially toward the inner peripheral wall of 3a.
[0021]
  Further, four intake / exhaust ports 41, 41, 42, 42 are formed so as to surround the four sides of the injector 5, and open to the combustion chamber 4. Two of the intake ports 41 and 41 (only one of them is shown) are curvedly extending from the combustion chamber 4 obliquely upward and open to one side of the engine 1 (the right side in FIG. 2). On the other hand, the two exhaust ports 42, 42 join together in the middle and extend to the other side surface (the left side surface in FIG. 2) of the engine 1. In addition, an intake valve 43 and an exhaust valve 44 for opening and closing the ports 41, 42,... Facing the combustion chamber 4 are disposed.
[0022]
  Although the intake valve 43 and the exhaust valve 44 are shown only in FIG. 3, two camshafts 45 and 46 respectively disposed in the cylinder head 4 are rotated by the crankshaft 8 via a timing belt (not shown). By being driven, each cylinder 2 is opened and closed at a predetermined timing as schematically shown in FIG. That is, as indicated by the solid line in the figure, basically, the closing timing EXC of the exhaust valve 44 is retarded from the intake top dead center (TDC) of the cylinder 2, while the intake valve 43 is opened. The timing IO is on the more advanced side than the TDC, and the valve opening period of the intake valve 43 and the valve opening period of the exhaust valve 44 overlap. Further, the closing timing IC of the intake valve 43 is on the retard side with respect to the intake bottom dead center (BDC).
[0023]
  The intake side camshaft 45 is provided with a known variable valve timing mechanism 47 (hereinafter abbreviated as VVT) that continuously changes the rotational phase with respect to the crankshaft 8 within a predetermined angle range. The opening / closing timing of the intake valve 43 is changed by the operation of the VVT 47. This VVT 47 has a schematic structure as shown in FIG. 5, and includes a rotor 47a fixed to the end of the camshaft 45, and a casing 47c arranged so as to cover the rotor 47a and fixed to the sprocket 47b. I have. Four vanes projecting radially outward are provided on the outer periphery of the rotor 47a, while four partition walls extending inward are provided on the inner periphery of the casing 47c. A plurality of hydraulic working chambers 47d, 47e,... Are formed between the vane and the partition wall so that the oil pressure of the engine oil as the working oil is adjusted by an oil control valve 47f (hereinafter referred to as OCV). It has become.
[0024]
  More specifically, the hydraulic working chambers 47d, 47e,... Are alternately divided into those on the advance side and those on the retard side in the circumferential direction, of which the hydraulic working chambers 47d, 47d on the advance side. When the hydraulic pressure increases, the rotor 47a is rotated in the direction in which the cam shaft 45 rotates (indicated by an arrow in the figure) with respect to the casing 47c, whereby the valve opening timing IO and the valve closing timing of the intake valve 43 are rotated. IC moves to the advance side. Conversely, when the hydraulic pressure in the retarded hydraulic working chambers 47e, 47e,... Increases, the rotor 47a rotates relative to the casing 47c in the direction opposite to the direction of rotation of the cam shaft 45. The valve opening timing IO and the valve closing timing IC of the intake valve 43 shift to the retard side. Due to this shift to the retard side, the opening / closing timings IO and IC of the intake valve 43 are changed by about 20 ° at the maximum, as indicated by the phantom line in FIG.
[0025]
  As shown in FIG. 2, the injector 5 for each cylinder 2 is connected to a common fuel supply pipe 6 (common rail) by branch pipes 6a, 6a,... (Only one is shown). The common rail 6 is connected to a high-pressure supply pump 9 by a fuel supply pipe 8, and is in a high-pressure state so that fuel supplied from the high-pressure supply pump 9 can be supplied to the injectors 5, 5,. The fuel pressure sensor 7 for detecting the internal fuel pressure (common rail pressure) is disposed. The high-pressure supply pump 9 is connected to a fuel supply system (not shown), and is drivingly connected to the crankshaft 10 by a toothed belt or the like, and pumps fuel to the common rail 6 and part of the fuel is an electromagnetic valve. The amount of fuel supplied to the common rail 6 is adjusted by returning to the fuel supply system via the. The opening of the electromagnetic valve is controlled by an ECU 38 (described later) in accordance with a value detected by the fuel pressure sensor 7 so that the fuel pressure is controlled to a predetermined value corresponding to the operating state of the engine 1.
[0026]
  A crank angle sensor 11 comprising an electromagnetic pickup for detecting the rotation angle (crank angle) is attached to the crankshaft 10, and a starter motor 12 is drivingly connected to the crankshaft 10. That is, a toothed pulley 10a is fixed to the end of the crankshaft 10, and a toothed belt (shown in phantom lines) is wound between the pulley 10a and the pulley of the starter motor 12, and the starter An electromagnetic clutch is disposed between the drive shaft of the motor 12 and the pulley, and the rotational force is transmitted or interrupted by the operation of this clutch. The starter motor 12 is connected to a large-capacity battery via a control circuit having an inverter (not shown), and a motor operation for driving the crankshaft 10 by receiving power supplied from the battery; The generator is switched to the generator operation that is rotated by the crankshaft 10 to generate electric power. Further, the engine 1 is provided with a cam angle sensor (not shown) for detecting the rotation angle of the intake side camshaft 45 and an engine water temperature sensor 13 for detecting the temperature of engine cooling water.
[0027]
  An intake passage 16 for supplying air (fresh air) filtered by an air cleaner 15 to the combustion chamber 4 of each cylinder 2 is connected to one side (right side in the figure) of the engine 1. A surge tank 17 is provided at the downstream end of the intake passage 16, and each passage branched on the downstream side thereof communicates with the combustion chamber 4 of each cylinder 2 through an intake port 41. The surge tank 17 is provided with an intake pressure sensor 18 for detecting the pressure state of the intake air.
[0028]
  The intake passage 16 is driven by a hot film type air flow sensor 19 for detecting the flow rate of air sucked into the engine 1 from the outside in order from the upstream side to the downstream side, and a turbine 27 to be described later. Are provided, an intercooler 21 for cooling the intake air compressed by the blower 20, and an intake throttle valve 22 including a butterfly valve. The intake throttle valve 22 is in an arbitrary state from the fully closed state to the fully opened state by rotating the valve shaft by the stepping motor 23. Even in the fully closed state, the intake throttle valve 22 and the intake passage 16 are connected to each other. A gap is formed between the peripheral wall and air to allow air to flow in.
[0029]
  On the other hand, an exhaust passage 26 is connected to the side surface on the opposite side (left side in the figure) of the engine 1 so as to discharge combustion gas (exhaust gas) from the combustion chamber 4 of each cylinder 2. An upstream end portion of the exhaust passage 26 is an exhaust manifold that branches into each cylinder 2 and communicates with the combustion chamber 4 through an exhaust port 42. The exhaust passage 26 downstream from the exhaust manifold is downstream from the upstream side. A turbine 27 that is rotated by receiving an exhaust flow and a catalytic converter 28 that can purify harmful components (unburned HC, CO, NOx, soot, etc.) in the exhaust are disposed in this order.
[0030]
  The turbocharger 30 comprising the turbine 27 and the blower 20 in the intake passage 16 changes the sectional area (nozzle sectional area) of the exhaust passage to the turbine 27 by means of movable flaps 31, 31,. The flaps 31, 31,... Are each connected to a diaphragm 32 through a link mechanism (not shown), and the negative pressure acting on the diaphragm 32 is negative. By adjusting the pressure control electromagnetic valve 33, the rotational positions of the flaps 31, 31,... Are adjusted to change the nozzle cross-sectional area.
[0031]
  The exhaust passage 26 is connected to an upstream end of an exhaust gas recirculation passage (hereinafter referred to as an EGR passage) 34 that recirculates a part of the exhaust gas to the intake side so as to branch from a portion upstream of the turbine 27 relative to the exhaust gas. ing. The downstream end of the EGR passage 34 is connected to the intake passage 16 between the intake throttle valve 22 and the surge tank 17, and a part of the exhaust gas taken out from the exhaust passage 26 is returned to the intake passage 16. ing. An exhaust gas recirculation amount adjustment valve (hereinafter referred to as an EGR valve) 35 whose opening degree can be adjusted is disposed near the downstream end in the middle of the EGR passage 34. The EGR valve 35 is of a negative pressure responsive type, and the magnitude of the negative pressure to the diaphragm is adjusted by the electromagnetic valve 36 in the same manner as the flaps 31, 31,. The flow rate of the exhaust gas recirculated to the intake passage 16 is adjusted by linearly adjusting the passage sectional area.
[0032]
  Each of the injectors 5, the high pressure supply pump 9, the intake throttle valve 22, the VGT 30, the EGR valve 35, etc. operate in response to a control signal from a control unit (Electronic Control Unit: hereinafter referred to as ECU) 38. On the other hand, the ECU 38 receives at least output signals from the fuel pressure sensor 7, the crank angle sensor 11, the cam angle sensor, the engine water temperature sensor 13, the intake pressure sensor 18, the air flow sensor 19, and the like, and is not shown. Output signals from a vehicle speed sensor 37 that detects the traveling speed of the vehicle and an accelerator opening sensor 39 that detects the amount of depression of the accelerator pedal (accelerator opening) of the vehicle are input.
[0033]
  As basic control of the engine 1 by the ECU 38, the target fuel injection amount is determined mainly based on the accelerator opening, the fuel injection amount and the injection timing are controlled by the operation control of the injector 5, and the high pressure The operation of the supply pump 9 controls the fuel pressure, that is, the fuel injection pressure. Further, the recirculation ratio of the exhaust gas to the combustion chamber 4 is controlled by the operation control of the intake throttle valve 22 and the EGR valve 35, and the intake supercharging efficiency is further controlled by the operation control (VGT control) of the flaps 31, 31,. To improve.
[0034]
  In this embodiment, the operation of the engine 1 is automatically stopped under a predetermined condition (so-called idle stop) or automatically restarted. For this purpose, the ECU 38 controls the starter motor 12. A control signal is output to the circuit to control the operation state of the starter motor 12 in accordance with the running state of the vehicle, the operating state of the engine 1, the charge amount of the battery, and the like.
[0035]
  (Engine start control)
  Next, specific control procedures of the engine 1 and the starter motor 12 mainly at the time of starting will be described in detail with reference to FIGS.
[0036]
  First, in the flow of fuel injection control shown in FIG. 6, in step SA1 after the start, the fuel pressure sensor 7, the crank angle sensor 11, the cam angle sensor, the engine water temperature sensor 13, the intake pressure sensor 18, the air flow sensor 19, and the vehicle speed sensor 37. In addition, an output signal from the accelerator opening sensor 39 or the like is input, and a value of an ignition determination flag F (described later) is read from the memory of the ECU 38 (data input). Subsequently, in step SA2, the target torque Trq is read from the target torque map electronically stored in the memory of the ECU 38 based on the accelerator opening Acc and the vehicle speed V (setting of the target torque). For example, as shown in FIG. 7A, this target torque map is set so that the target torque Trq increases as the accelerator opening Acc increases and the vehicle speed V increases.
[0037]
  Subsequently, in step SA3, it is determined whether or not the engine 1 is being started. This is because, for example, when the target torque Trq is not a substantially zero set value Trq0≈0 (Trq> Trq0) and the engine 1 is not ignited, it is determined to be YES at the time of starting and the process proceeds to step SA4, but not so. Sometimes it is determined that the engine is not started, and the process proceeds to Step SA10 described later. That is, for example, if the accelerator pedal is depressed while the vehicle is stopped and the engine 1 is not ignited, it is determined that the engine 1 is being started. At this time, it is determined based on the value of an ignition determination flag F described later that the engine 1 has not been ignited. Then, in step SA4, which proceeds after determining YES when the engine is started, the control amount Mt of the starter motor 12 is set. This is based on reading a basic control amount Mtb from a table (not shown) set in advance based on the target torque Trq, outputting it to the control circuit of the starter motor 12, and based on a signal from the crank angle sensor 11. Feedback correction. That is, in step SA5, a control signal is output to the control circuit of the starter motor 12, and necessary electric power is supplied from this circuit to the starter motor 12 to rotationally drive the crankshaft 8 (motor operation).
[0038]
  Subsequently, in step SA6, it is determined whether or not the engine rotational speed ne exceeds the first set rotational speed ne1 (for example, 900 rpm). If the determination is NO and ne ≦ ne1, the process returns to the step SA1, while the determination is YES. If there is (ne> ne1), the process proceeds to step SA7 to set the fuel target injection amount Q and the target injection timing IT. The fuel injection amount Q and the target injection timing IT are set by reading the corresponding values at the time of start-up from maps (see FIGS. 7 (b) and 7 (c) described later) electronically stored in the memory of the ECU 38, respectively. Just do it.
[0039]
  In step SA8, it is determined for each cylinder 2, 2,... Of the engine 1 that the set injection timing IT has been reached, wait until this injection timing IT is reached (determination is NO), and the injection timing IT. If it becomes (determination is YES), it will progress to step SA9 and will output a control signal to the injector 5 (injection execution). In step SA10, the ignition of the engine 1 is determined, and then the process returns.
[0040]
  The ignition determination (step SA10) will be described. As described above, when the engine 1 is started, the crankshaft 8 is driven by the starter motor 12, and the rotational speed ne is detected based on the signal from the crank angle sensor 11. The power supplied to the starter motor 12 is feedback-controlled so that the detected value becomes a predetermined value. For this reason, when the engine 1 is ignited and rotates on its own, the power supplied to the starter motor 12 is greatly reduced at that moment, and ignition can be determined based on this fact. When it is determined that the ignition is performed, the ignition determination flag F is turned on (F ← 1).
[0041]
  When the start of the engine 1 is completed in this manner, it is determined that the engine 1 is not started based on the value of the ignition determination flag F in step SA3. At this time, the process proceeds to step SA11 and the vehicle Judge whether the vehicle is decelerating. That is, for example, when the vehicle speed V is decreasing and greater than the set vehicle speed V1 and the target torque Trq is substantially zero (Trq = Trq0), it is determined that the vehicle is decelerating and the process proceeds to step SA12. On the other hand, if the situation is other than that, it is determined as NO and the process proceeds to step SA14. Then, in step SA12, which is determined to be decelerating as described above, the control amount to the control circuit of the starter motor 12 according to the vehicle speed V and the battery charge amount in order to operate the starter motor 12 by the running inertia of the vehicle. Mt is set, and in step SA13, the starter motor 12 is activated to convert the kinetic energy of the vehicle into electric energy and store it in the battery (energy regeneration). Then, the fuel is not injected by the injector 5, and the process returns.
[0042]
  That is, when the vehicle decelerates, fuel injection by the injector 5 is stopped (fuel cut), and energy is regenerated while applying a braking force to the vehicle by the generator operation of the starter motor 12. The energy regeneration is limited when the vehicle speed V is higher than the set vehicle speed V1 in consideration of the traveling feeling.
[0043]
  On the other hand, in step SA14, which is determined to be NO when the vehicle is not decelerating in step SA11, it is next determined whether the engine 1 is in a normal operation state or in an idle stop. That is, when the target torque Trq is substantially zero (Trq = Trq0) and the vehicle speed V is equal to or lower than the set vehicle speed (V ≦ V1), it is determined that the engine stops idling, and fuel injection by the injector 5 is not performed. The ignition determination flag F is turned off (step SA15: F ← 0), and the process returns.
[0044]
  If it is determined in step SA14 that the target torque Trq is not substantially zero (Trq> Trq0) or the vehicle speed V is higher than the set vehicle speed V1 (V> V1), the process proceeds to step SA16 to perform normal operation control. A target fuel injection quantity Q and a target injection timing IT are set. This target fuel injection amount Q is set based on the fuel injection amount map electronically stored in the memory of the ECU 38 based on the operating state (target torque Trq and engine speed ne) of the engine 1. Qb is read and corrected according to the intake pressure, engine water temperature, and the like. In the fuel injection amount map illustrated in FIG. 7B, the injection amount Qb is set to be larger as the target torque Trq is larger and the engine speed ne is higher.
[0045]
  Further, the target injection timing IT may be set based on an injection timing map as exemplified in FIG. In this map, the injection timing IT is set to be a value on the advance side as the target torque Trq is larger and the engine speed ne is higher. In step SA17, it is determined for each cylinder 2, 2,... Of the engine 1 that the set injection timing IT has been reached, wait until this injection timing IT is reached (NO determination), and the injection timing IT. If it becomes (determination is YES), the process proceeds to step SA18, a control signal is output to the injector 5 (injection execution), and then the process returns.
[0046]
  That is, in this embodiment, the engine 1 is automatically stopped under predetermined conditions, that is, when the target torque Trq of the engine 1 is a substantially zero set value (Trq0) and the vehicle is stopped or about to stop. For example, when the accelerator pedal is depressed and the target torque Trq increases, the engine 1 is automatically started. The start control unit 38a for automatically starting the engine 1 is configured by the control procedure of steps SA3 to SA10 in the flow shown in FIG. 6, and the engine 1 is automatically started by the control procedure of steps SA14 and SA15. A stop control unit 38b (engine stop control means for stopping the operation of the engine 1 under a predetermined condition) is configured.
[0047]
  (VVT control)
  Next, the control procedure of the VVT 47 by the ECU 38 will be specifically described based on the flowchart of FIG. 8. First, in step SB 1 after the start, the crank angle sensor 11, the cam angle sensor, the engine water temperature sensor 13, and the vehicle speed sensor 37. Then, an output signal from the accelerator opening sensor 39 or the like is input, and the value of the ignition determination flag F is read from the memory of the ECU 38. In the subsequent step SB2, it is determined whether or not the engine 1 is being started in the same manner as in step SA3 of the fuel injection control flow shown in FIG. If this determination is YES, the process proceeds to step SB6 described later. If the determination is NO, the process proceeds to step SB3, where it is determined whether the vehicle is decelerating in the same manner as in step SA11 of the fuel injection control flow. If this determination is YES, the process proceeds to step SB6 described later, while if the determination is NO, the process proceeds to step SB4, where it is determined whether or not to stop idling in the same manner as in step SA14 of the fuel injection control flow. If the determination is YES, the process proceeds to step SB6, and if the determination is NO, the process proceeds to step SB5.
[0048]
  In step SB5, the target value VT of the closing timing of the intake valve 43 corresponding to the operating state (target torque Trq and engine speed ne) of the engine 1 is determined from the valve timing map electronically stored in the memory of the ECU 38. Read. In this valve timing map, as shown in an example in FIG. 9, the valve closing timing VT of the intake valve 43 is set to be retarded as the target torque Trq is increased and the engine speed ne is increased. Has been. On the other hand, in step SB6, the target value VT of the closing timing of the intake valve 43 is set to a relatively retarded set value VT1 (indicated by a virtual line on the map of FIG. 9). In step SB7, a control signal for operating the VVT 47 is output to the OCV 47f so that the closing timing of the intake valve 43 becomes the target value VT. To do.
[0049]
  Note that the set value VT1 on the retard side of the closing timing of the intake valve 43 is such that part of the intake air once sucked into the cylinder 2 is blown back to the intake port 41 passage while the intake valve 43 is opened. Thus, the charging efficiency of the intake air into the cylinder 2 is reduced, and the compression ratio of the cylinder 2 is thereby substantially reduced. As a result, the compression work of the cylinder 2 is reduced and the angular speed fluctuation of the crankshaft 10 is reduced, so that vibration is greatly reduced when the engine 1 is started.
[0050]
  The actual compression of the cylinder 2 is performed either when the engine 1 is started by the starter motor 12, when the engine 1 is decelerated, or when the engine 1 is idling stopped by the control procedure of steps SB2 to SB6 in the flow shown in FIG. In order to reduce the ratio, a VVT control unit 38c (valve mechanism control means) is configured to operate the VVT 47 so that the closing timing of the intake valve 43 is relatively retarded. The VVT control unit 38c may be configured to control the operation of the VVT 47 as described above only when the starter motor 12 is warmly started.
[0051]
  (Control of intake throttle valve 22 and EGR valve 35)
  Next, a specific control procedure of the intake throttle valve 22 and the EGR valve 35 by the ECU 38 will be described with reference to the flowchart of FIG.
[0052]
  First, in step SC1 after the start, output signals from the crank angle sensor 11, the engine water temperature sensor 13, the vehicle speed sensor 37, the accelerator opening sensor 39, etc. are input, respectively, and the value of the ignition determination flag F from the memory of the ECU 38. Is read. Subsequently, in step SC2, it is determined whether or not the engine 1 is being started in the same manner as in step SA3 of the fuel injection control flow shown in FIG. If this determination is NO, the process proceeds to step SC9 described later. If the determination is YES, the process proceeds to step SC3, and it is determined whether the engine speed ne is lower than a second set speed ne2 (for example, 500 rpm). If this determination is YES (ne <ne2), the process proceeds to step SC4, where the target value EGR of the opening degree of the EGR valve 35 is set to the substantially fully closed first set opening degree EGRi≈0, while if the determination is NO ( ne ≧ ne2) Proceeding to step SC5, the target value EGR of the opening degree of the EGR valve 35 is set to the second set opening degree EGRs> EGRi. The second set opening degree EGRs sets the EGR valve 35 to an open state that is closer to full open than to full close (for example, about 4/5 to 2/3 of the fully open state).
[0053]
  Subsequently, in step SC6, the control target value Tv is set so that the intake throttle valve 22 is in an open state (for example, about 4/5 to 2/3 of the fully open state) that is closer to full open than fully closed (Tv = tv1), the control signal is output from the ECU 38 to the electromagnetic valve 36 of the diaphragm of the EGR valve 35 in the following step SC7 (EGR valve operation), and the control signal is output from the ECU 38 to the stepping motor 23 of the intake throttle valve 22 in the subsequent step SC8. (Intake throttle valve operation) and then return. That is, when the engine 1 is started, the EGR valve 35 is opened relatively large so that a large amount of exhaust gas is recirculated through the EGR passage 34. As a result, if the temperature of the engine 1 is warm, the temperature state of the exhaust gas is higher than that of the outside air. Therefore, the exhaust gas recirculation increases the temperature state of the intake air, which promotes vaporization of the fuel spray and ignitability. Will improve.
[0054]
  On the other hand, in step SC9, which is determined to be NO when the engine 1 is not started in step SC2, it is determined whether the vehicle is decelerating in the same manner as in step SA11 of the fuel injection control flow. If this determination is NO, the process proceeds to step SC12 described later. If the determination is YES, the process proceeds to step SC10, and the target value EGR of the opening degree of the EGR valve 35 is set to a third opening degree EGRr that is substantially fully open. Subsequently, the process proceeds to step SC11, the control target value Tv is set so that the intake throttle valve 22 is substantially fully closed, and the process proceeds to steps SC7, SC8 to drive the EGR valve 35 and the intake throttle valve 22, respectively. Then return after a while.
[0055]
  That is, when the vehicle decelerates, the exhaust from the cylinder 2 is returned to the intake passage 16 through the EGR passage 34 while the intake throttle valve 22 is closed to almost prevent new outside air from being supplied to the intake passage 16 of the engine 1. Thus, the intake / exhaust system of the engine 1 is circulated. As a result, the combustion chamber 4 and the intake / exhaust system in the cylinder 2 of the engine 1 are not cooled by the outside air, and high-temperature exhaust gas is held inside the cylinder 2 and the intake / exhaust system. .
[0056]
  In step SC12, which is determined to be NO when the vehicle is not decelerated in step SC9, this time, it is determined whether or not the engine is idling stopped in the same manner as in step SA14 of the fuel injection control flow. If the determination is NO, the process proceeds to step SC14. If the determination is YES, the process proceeds to step SC13, where the target value EGR of the opening degree of the EGR valve 35 is set to a first fully-closed opening EGRi. Proceeding to step SC11, the control target value Tv is set so that the intake throttle valve 22 is substantially fully closed, and further proceeding to steps SC7 and SC8 to operate the EGR valve 35 and the intake throttle valve 22, respectively. Then return.
[0057]
  That is, during idle stop of the engine 1, the intake throttle valve 22 is substantially fully closed to substantially prevent the supply of new outside air, and the EGR valve 35 is also substantially fully closed so that the cylinder 2 of the engine 1 is closed. In addition, high-temperature exhaust is held inside the intake / exhaust system. It should be noted that the EGR valve 35 may be slightly opened without being substantially fully closed.
[0058]
  Further, in step SC14, which is determined to be NO that is not idling stop in step SC12, the opening degree of the EGR valve 35 corresponding to the operating state of the engine 1 is determined from the EGR map electronically stored in the memory of the ECU 38. Read target value EGR. In this map, as shown in an example in FIG. 11A, the opening degree of the EGR valve 35 is set to be smaller as the target torque Trq is larger and the engine rotational speed ne is higher. Subsequently, in step SC15, a target value Tv of the opening degree of the intake throttle valve 22 corresponding to the operating state of the engine 1 is read from a table electronically stored in the memory of the ECU 38. In this table, as shown in an example in FIG. 11B, the opening degree of the intake throttle valve 22 is set to gradually increase as the engine rotational speed ne increases. Then, the process proceeds to steps SC7 and SC8 to drive the EGR valve 35 and the intake throttle valve 22, respectively, and then returns.
[0059]
  According to the control procedures of steps SC5, SC7, and SC10 of the flow shown in FIG. 10, the EGR valve 35 is opened relatively wide when the vehicle is decelerated and the engine 1 is started, and a large amount of exhaust gas is recirculated to the intake passage 16. EGR control unit 38d (exhaust gas recirculation control means) is configured.
[0060]
  Further, according to the control procedures of steps SC8, SC11, and SC15, the intake throttle valve 22 is substantially fully closed when the vehicle is decelerated. Thereafter, when the engine 1 is automatically stopped, the engine 1 is restarted. In the meantime, an intake throttle control unit 38e (intake throttle valve control means) is configured to maintain the intake throttle valve 22 in a fully closed state.
[0061]
  Therefore, according to the diesel engine start control device A according to this embodiment, first, when the accelerator pedal is closed and fuel injection by the injector 5 is stopped while the vehicle is running (fuel cut), an example is shown in FIG. When the vehicle speed V decreases and the vehicle is decelerated (t = t0), the EGR control unit 38d of the ECU 38 causes the EGR valve 35 to be fully opened and the intake throttle control unit 38e. As a result, the intake throttle valve 22 is substantially fully closed. As a result, the supply of new outside air to each cylinder 2 of the engine 1 is almost blocked, and the high-temperature burned gas (exhaust gas) discharged from each cylinder 2 before the fuel cut passes through the EGR passage 34. Through the intake / exhaust system of the engine 1.
[0062]
  At that time, the valve closing timing of the intake valve 43 is greatly retarded by the operation control of the VVT 47 by the VVT control unit 38c, and the intake charge efficiency of the cylinders 2, 2,. The actual compression ratio of the cylinder 2 becomes much lower than the geometric value, and the pump work becomes considerably small. As a result, the effectiveness of the engine brake is reduced, so that the kinetic energy of the vehicle is effectively transmitted to the starter motor 12 that operates the generator, and energy regeneration is effectively performed. When the vehicle speed V drops below the set vehicle speed V1 (t = t1), it is determined that the vehicle is idle stopped, and the EGR control unit 38d closes the EGR valve 35 substantially fully.
[0063]
  Thus, when the vehicle stops (t = t2) and the operation of the engine 1 is automatically stopped, the intake throttle valve 22 is maintained in the fully closed state until the engine 1 is restarted thereafter. The high-temperature exhaust gas is held inside the cylinder 2 and the intake / exhaust system of the engine 1.
[0064]
  Subsequently, when the accelerator pedal is depressed (t = t3), the crankshaft 10 of the engine 1 is driven by the starter motor 12, the vehicle starts, and the vehicle speed V increases. At this time, the intake throttle valve 22 is immediately opened, while the EGR valve 35 is kept closed, so that high-temperature exhaust remains inside the EGR passage 34. Also at this time, the closing timing of the intake valve 43 remains largely retarded, which reduces the pump work of the cylinders 2, 2,. The force is effectively transmitted to the wheels, and even when the engine speed ne is extremely low, the vibration of the engine 1 does not become so great, and the engine speed ne quickly increases.
[0065]
  When the engine rotational speed ne becomes equal to or higher than the second set rotational speed ne2 (t = t4), the EGR valve 35 is opened widely and a large amount of high-temperature exhaust gas flows into the intake passage 16, and the cylinders 2, 2 together with the outside air When the engine rotational speed ne exceeds the first set rotational speed ne1 (t = t5), the fuel injection by the injector 5 is started, and this fuel spray is ignited and burned. As a result, the engine 1 rotates by itself (starting of the engine 1). At this time, even if the closing timing of the intake valve 43 is retarded as described above and the actual compression ratio of the cylinders 2, 2,... The temperature state of the combustion chamber 4 in the latter half of the compression stroke of each cylinder 2 becomes sufficiently high, and vaporization and atomization of the fuel spray is promoted and good ignitability is obtained.
[0066]
  Further, if the engine rotational speed ne exceeds the first set rotational speed ne1, the angular speed fluctuation of the crankshaft 10 is smoothed to reduce the vibration, so that the intake valve 43 is closed by the VVT controller 38c. The operation control of the VVT 47 is performed so that the timing returns to the advance side, and the actual compression ratio of the cylinders 2, 2,. Thus, when the start of the engine 1 is completed, thereafter, the opening degree of the intake throttle valve 22 and the EGR valve 35 is controlled in accordance with the operating state of the engine 1, and the opening / closing timing of the intake valve 43 is also determined. It is controlled according to the operating state. Further, the starter motor 12 is stopped immediately after power transmission to the crankshaft 10 is interrupted.
[0067]
  In addition, the structure of this invention is not limited to the thing of the said embodiment, Various other structures are included. That is, the embodimentStateIn the engine 1, the VVT 47 that advances or retards the opening timing and closing timing of the intake valve 43 in synchronization with each other as the variable valve mechanism is used. Alternatively, the cam angle of the cam on the intake side cam shaft 45 may be changed so that the operating angle of the cam with respect to the intake valve 43 is switched. Alternatively, using an electromagnetic valve mechanism that directly opens and closes the intake valve 43 with an electromagnetic solenoid or the like without using the camshaft 45, the opening and closing timing of the intake valve 43 is changed by controlling the energization of the electromagnetic solenoid. You may make it do.
[0068]
  Further, in the above-described embodiment, the flaps 31, 31,... Of the VGT 30 may be closed when the vehicle is decelerated or when the engine 1 is started by the starter motor 12, and the flow of exhaust gas to the turbine 27 may be restricted. By doing so, the exhaust flow is throttled in the exhaust passage 26 downstream of the communication portion with the EGR passage 34, and the exhaust pressure rises. Therefore, the exhaust gas recirculation through the EGR passage 34 is more effectively performed. Can be done. The operation control of the flaps 31, 31,... Of the VGT 30 can be realized by executing a predetermined control program by the CPU of the ECU 38. In this case, the control program and the flaps 31, 31,. The exhaust throttle means is configured to throttle the flow of exhaust to the turbine 27 when the engine 1 is started or the vehicle is decelerated.
[0069]
【The invention's effect】
  As described above, according to the start control device for a diesel engine according to the invention of claim 1,For an engine mounted on a vehicle, when the vehicle is decelerated, the intake throttle valve is closed upstream of the communication portion with the exhaust recirculation passage of the engine, and the open / close valve of the exhaust recirculation passage is opened. While suppressing the intake / exhaust system and the like from being cooled by outside air, high-temperature exhaust gas can be circulated and held therein. And when the engine is automatically stopped after deceleration of the vehicle and then restarted automatically,The variable valve mechanism is operated so that the compression ratio of the cylinder is substantially lowered, and the engine vibration is reduced by reducing the pump work of the cylinder.ButAt the time of startingHeld at a high temperature as mentioned aboveBy recirculating at least a portion of the exhaust gas to the engine intake system and increasing the temperature state of the intake air, the temperature state of the combustion chamber at a later stage of the compression stroke of the cylinder is sufficiently increased to promote vaporization of the fuel spray. In addition, it is possible to compensate for a decrease in ignitability caused by a decrease in the compression ratio and to ensure a good startability.
[0070]
  MoreoverWhen the engine is stopped after the vehicle decelerates, until the engine is warmly restarted,SaidInlet throttle valveAnd on-off valveBy maintaining the closed state, the supply of new outside air to the intake / exhaust system etc. can be suppressed even when the vehicle is stopped.MemorandumThe effect of light can be further enhanced.
[0071]
  According to the second aspect of the present invention, the exhaust gas can be effectively recirculated by restricting the flow of the exhaust gas in the exhaust passage downstream of the communication portion with the exhaust recirculation passage when the engine is started.
[0072]
  According to the invention of claim 3, the vibration can be reduced by adjusting the closing timing of the intake valve by the operation of the variable valve mechanism at the time of starting the engine so that the pump loss becomes lower than after the engine is started..
[0073]
  Claim4According to the invention, when the vehicle is decelerated, the exhaust gas can be recirculated effectively by restricting the flow of the exhaust gas in the exhaust gas passage downstream of the communication part with the exhaust gas recirculation gas passage.1The effects of the invention can be further enhanced.
[Brief description of the drawings]
FIG. 1 is an explanatory view schematically showing a configuration of an invention according to claim 1;
FIG. 2 is an overall configuration diagram of a start control device according to an embodiment of the present invention.
FIG. 3 is an enlarged cross-sectional view showing the structure of a combustion chamber.
FIG. 4 is an explanatory diagram showing valve usage characteristics of an intake valve and an exhaust valve.
FIG. 5 is a perspective view showing the schematic configuration of the variable valve mechanism partially cut away.
FIG. 6 is a flowchart showing a procedure of fuel injection control at the time of engine start and the like.
FIG. 7 is an explanatory diagram showing an example of an engine target torque map (a), an injection amount map (b), and an injection timing map (c).
FIG. 8 is a flowchart showing a procedure of VVT control at the time of engine start and the like.
FIG. 9 is an explanatory diagram showing an example of a valve timing map of an engine.
FIG. 10 is a flowchart showing a procedure for controlling the EGR valve and the intake throttle valve when the engine is started.
FIG. 11 is an explanatory diagram showing an example of an engine EGR control map (a) and an intake throttle control map (b).
FIG. 12 shows changes in accelerator opening, fuel supply state, vehicle speed, engine speed, EGR valve opening, intake throttle valve opening, and intake valve opening / closing timing when the vehicle is decelerated, automatically stopped, and restarted. FIG.
[Explanation of symbols]
A Diesel engine start control device
1 engine
2-cylinder
12 Starter motor
16 Air intake passage
22 Inlet throttle valve
26 Exhaust passage
27 Turbine
30 VGT (turbocharger)
31 Flap (exhaust throttle means)
34 EGR passage (exhaust gas recirculation passage)
35 EGR valve (open / close valve)
38 Control unit
38b Stop control unit (engine stop control means)
38c VVT controller (valve mechanism control means)
38d EGR control unit (exhaust gas recirculation control means)
38e Intake throttle control unit (intake throttle valve control means)
43 Intake valve
47 VVT (Variable Valve Mechanism)

Claims (4)

A motor for starting the engine;
A variable valve mechanism capable of changing at least one of the opening / closing timing or lift amount of the intake valve of the engine;
In a diesel engine start control device, comprising: a valve mechanism control means for operating the variable valve mechanism so that an actual compression ratio of a cylinder is relatively low at the time of warm start of the engine by the motor;
Engine is a one that is mounted on a vehicle, the exhaust gas recirculation passage communicating the exhaust passage and an intake passage of its opening and closing valve for opening and closing the exhaust gas recirculation passage, than communicating portion between the exhaust gas recirculation passage upstream An intake throttle valve for restricting the flow of intake air in the intake passage on the side,
An intake throttle valve control means for closing the intake throttle valve during deceleration of the vehicle;
Exhaust recirculation control means for opening the exhaust recirculation passage on-off valve when the vehicle decelerates;
Engine stop control means for stopping operation of the engine under a predetermined condition;
With
The intake throttle valve control means is configured to maintain the intake throttle valve in a closed state until a subsequent warm restart of the engine when the engine is stopped by the engine stop control means after deceleration of the vehicle. ,
The exhaust gas recirculation control means closes the on-off valve when the engine is stopped by the engine stop control means after deceleration of the vehicle, and closes the on-off valve until a subsequent warm restart of the engine. maintaining, open the warm the on-off valve during start, start control of the diesel engine, characterized in <br/> that is configured to recirculated to the intake passage by the exhaust recirculation passage at least a portion of the exhaust apparatus. In claim 1,
The turbocharger turbine is disposed in the exhaust passage downstream of the communication portion with the exhaust recirculation passage,
A diesel engine start control device comprising exhaust throttle means for restricting a flow of exhaust gas to the turbine when the engine is warmly started by a motor. In claim 1,
The variable valve mechanism can adjust at least the opening / closing timing of the intake valve within a predetermined range,
The valve mechanism control means adjusts the closing timing of the intake valve by operating the variable valve mechanism so that the pump loss is reduced when the engine is started compared to after the engine is started. Diesel engine start control device. In claim 1,
The turbocharger turbine is disposed in the exhaust passage downstream of the communication portion with the exhaust recirculation passage,
A diesel engine start control device comprising exhaust throttling means for throttling the flow of exhaust gas to the turbine when the vehicle decelerates .

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