JP2010180712A - Engine starting method and device therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quickly start an engine while reducing vibrations. <P>SOLUTION: When an engine 1 start condition is established, a motor-driven supercharger 18 arranged in an intake passage 50 is rotationally driven in a prescribed direction in which pressure in an intake port 34 is reduced (reduction of a compression ratio in a combustion chamber), for instance. With the motor-driven supercharger 18 driven in the prescribed direction, the rotation speed of an engine 1 during stop is abruptly increased, by an electric motor 2, to a prescribed level in which the variation in angular speed is small (the increase of temperature in the combustion chamber due to frictional heating produced by a slide of a piston 32). After the engine rotation speed reaches the prescribed level, fuel is injected into the combustion chamber 33 from a fuel injection valve 38 to start the engine so that self-excited rotation of the engine 1 is executed through combustion (completion of start). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an engine starting method and a starting method thereof.

  When starting the engine from a stopped state, the engine is cranked by an electric motor (starter motor), and the engine is started when the engine reaches a predetermined rotational speed that is sufficiently lower than the idle rotational speed. This is generally performed by injecting a large amount of fuel, and after the initial explosion is performed with the starting fuel, the engine speed is increased to the idle speed by combustion. In a hybrid vehicle, that is, a vehicle equipped with an engine that generates electric power while driving a traveling wheel by an electric motor, cranking at the time of engine start is also performed by an electric motor for engine start. .

  In Patent Document 1, particularly during the cold start of a diesel engine, by operating the electric supercharger provided in the intake passage to perform supercharging, the engine friction is increased and the in-cylinder temperature is increased. It is disclosed to improve ignitability.

JP 2005-188484 A

  By the way, in recent engines, there is a strong demand to make the engine start more quickly. For example, in a hybrid vehicle, when switching from a state where the engine is stopped to traveling by the engine, it is required to start the engine immediately. Further, in a vehicle that performs idle stop, it is required to start the engine promptly before the start of traveling.

  However, in the conventional engine starting method, fuel is injected for starting while cranking the engine and the engine rotational speed is considerably lower than the idle rotational speed. Therefore, it takes a considerable amount of time to reach a state where the engine can be rotated by combustion without the need for external force. In addition, when the engine speed is lower than the idling engine speed, the vibration becomes considerably large, but the engine speed is not particularly stable especially during the period from the start of cranking to the idling engine speed. However, a large amount of unpleasant vibration was generated for a long time.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an engine starting method and an engine starting device that can start the engine more quickly while reducing vibration. is there.

In order to achieve the above object, the following solution is adopted in the engine starting method according to the present invention. That is, as described in claim 1 in the claims,
An engine starting method in which an intake valve is interposed in an intake port,
When the engine start condition is satisfied, the electric supercharger is driven to rotate in a predetermined direction in which the pressure in the intake port decreases; and
A step of rapidly increasing the engine stopped by the electric motor to a predetermined rotational speed with a small variation in angular velocity in a state where the electric supercharger is driven in the predetermined direction;
After the engine speed reaches the predetermined speed, performing a fuel injection for starting in the cylinder, and causing the engine to self-rotate by combustion;
It is supposed to be equipped with.

  According to the above solution, by reducing the pressure in the intake port by the electric supercharger, the compression ratio of the engine is set to a low compression ratio, and the driving resistance for rotating the engine is extremely small. The In a state where the drive resistance is small, the engine speed can be rapidly increased to a predetermined speed with a small angular velocity fluctuation by the electric motor. The inside of the cylinder is sufficiently heated due to frictional heat generated by sliding of the piston. Therefore, by injecting the starting fuel while the engine speed is high and the in-cylinder temperature is raised, while ensuring ignitability and subsequent combustion stability (prevents unpleasant diesel knock noise associated with ignition delay) However, the engine can be started immediately. That is, the time required from the start of the pressure drop in the intake port by the electric supercharger to ignition is much shorter than that of the conventional starting method. In addition, since the engine speed is rapidly increased to a predetermined speed with small angular velocity fluctuation, it is possible to reduce the unpleasant vibration at the time of starting by passing through the engine speed region with a large vibration at a stretch.

Preferred embodiments based on the above solution are as set forth in claims 2 to 8 in the claims. That is,
The predetermined rotation speed is set to a rotation speed at which the engine can stably rotate by self-excitation by fuel injection (corresponding to claim 2). In this case, the engine can be stably rotated immediately after the start when the engine can be self-excited. Also, since the predetermined rotational speed is sufficiently higher than the rotational speed at the time of conventional cranking, the frictional heat accompanying the piston sliding is ensured as much as possible to ensure ignitability and subsequent combustion stability. This is preferable. In particular, a hybrid vehicle is preferable for smoothly shifting to engine running.

  The predetermined rotation speed is set to be equal to or higher than the idle rotation speed (corresponding to claim 3). In this case, an effect similar to the effect corresponding to claim 2 can be obtained.

  The driving of the electric supercharger in the predetermined direction is terminated after fuel injection, and then the electric supercharger is driven in a direction opposite to the predetermined direction (corresponding to claim 4). . In this case, the rotational direction of the electric supercharger is driven in the direction opposite to that at the start of the engine after the engine is started, thereby shifting to the normal operating state of the engine without unnecessarily reducing the compression ratio. Can be made.

The electric supercharger is disposed in the intake passage of the engine and is used for supercharging intake air,
The predetermined direction is a direction opposite to the rotation direction when supercharging the intake air,
(Corresponding to claim 5). In this case, as the electric supercharger, an intake supercharger can be used effectively.

The electric supercharger is disposed in an EGR passage that supplies exhaust gas for EGR to the intake passage,
The predetermined direction is a direction opposite to a rotation direction when exhaust gas is supplied to the intake passage.
(Corresponding to claim 6). In this case, an electric supercharger for circulating EGR gas in the intake passage can be effectively used.

  When the engine is started, the intake valve is closed in a state where the intake valve is closed during the compression stroke (corresponding to claim 7). In this case, when the engine is started, the reduction of the compression ratio is further promoted, and the engine speed is rapidly increased to a predetermined speed, so that it can be reached in a shorter time or with a smaller force.

The electric supercharger is disposed in the intake passage of the engine and is used for supercharging intake air,
The predetermined direction is a direction opposite to the rotation direction when supercharging the intake air,
The electric motor is constituted by a traveling motor that drives a traveling wheel,
This is done (corresponding to claim 8). In this case, the engine can be started by effectively using the electric motor for traveling. In addition, since the traveling electric motor can output a very large force, it is extremely preferable for rapidly increasing the engine speed to a predetermined speed. Further, as an electric supercharger, an intake supercharger can be used effectively.

In order to achieve the above object, the engine starter according to the present invention employs the following solution. That is, as described in claim 9 in the claims,
An engine starting device in which an intake valve is interposed in an intake port,
An electric supercharger;
An electric motor for starting the engine;
A fuel injection valve for injecting fuel into the cylinder;
A controller for controlling the electric supercharger, the electric motor, and the fuel injection valve;
Have
The controller is configured to rotate the electric supercharger in a predetermined direction in which the pressure in the intake port decreases while a predetermined engine start condition is satisfied, and stop the engine by the electric motor. Is controlled to suddenly increase to a predetermined rotational speed with less angular speed fluctuation,
The controller further performs control for causing the engine to self-rotate by combustion by causing the fuel injection valve to perform start-up fuel injection after the engine speed reaches the predetermined speed.
It is like that. According to the above solution, an engine starting device for realizing the starting method according to claim 1 is provided.

A preferred mode based on the solution related to the starting device is as described in claim 10 and subsequent claims. That is,
The electric supercharger is disposed in the intake passage of the engine and is used for supercharging intake air,
The predetermined direction is a direction opposite to the rotation direction when supercharging the intake air,
The electric motor is constituted by a traveling motor that drives a traveling wheel,
(Corresponding to claim 10). In this case, an engine starter capable of obtaining the effect corresponding to claim 8 is provided.

The predetermined rotational speed is a rotational speed equal to or higher than the idle rotational speed,
The electric supercharger is disposed in the intake passage of the engine and is used for supercharging intake air,
The predetermined direction is a direction opposite to a rotation direction when supercharging intake air,
(Corresponding to claim 11). In this case, an engine starting device capable of obtaining the effects corresponding to claims 3 and 5 is provided.

The electric supercharger is disposed in the intake passage of the engine and is used for supercharging intake air,
The predetermined direction is a direction opposite to the rotation direction when supercharging the intake air,
The controller terminates driving of the electric supercharger in the predetermined direction after fuel injection, and then controls the electric supercharger to be driven in a direction opposite to the predetermined direction;
This is done (corresponding to claim 12). In this case, an engine starter capable of obtaining the effects corresponding to claims 4 and 5 is provided.

  According to the present invention, the engine can be started more quickly while reducing vibration.

The simplified top view which shows one Embodiment of this invention and shows a drive system. The system diagram which shows the engine shown in FIG. 1 with the intake / exhaust system. The principal part expanded sectional view of the engine shown in FIG. The figure which shows the example of a setting of the driving | operation area | region with an electric motor and an engine. The figure which shows the aspect of the engine starting by this invention typically. The figure which compares and shows the starting aspect of the conventional engine, and the engine starting aspect by this invention. The figure which shows the valve opening characteristic example of an intake / exhaust valve. The figure which shows the control system of this invention in a block diagram. The flowchart which shows the example of control of this invention. The 2nd Embodiment of this invention is shown, and the figure corresponding to FIG. The flowchart which shows the example of control in the 2nd Embodiment of this invention.

  FIG. 1 shows a drive system of a hybrid vehicle provided with an engine 1 and an electric motor 2. The engine 1 is a multi-cylinder (in-line four-cylinder in the embodiment) diesel engine, and is used for both power generation and driving. The electric motor 2 is used for running and for regeneration.

  The engine 1 (the crankshaft thereof) and the electric motor (the output shaft thereof) are positioned on the same axis, and a power transmission mechanism 3 is interposed between the engine 1 and the electric motor 2. The power transmission mechanism 3 includes a shaft member 5 in which a drive gear 4 is integrated. The shaft member 5 is positioned on the same axis line as the engine 1 and the electric motor 2, is connected to the engine 1 via the first clutch 6, and is connected to the electric motor 2 via the second clutch 7. ing.

  The power transmission mechanism 3 includes a shaft member 8 in parallel with the shaft member 5. A driven gear 9 integrated with the shaft member 8 is always meshed with the drive gear 4 (configures a speed reduction mechanism). A shaft member 12 in which a drive gear 11 is integrated is connected to the shaft member 8 via a third clutch 10.

  A driven gear 14 in a differential gear 13 is meshed with the drive gear 11 (configures a speed reduction mechanism). The differential gear 13 is connected to left and right drive wheels (front wheels in the embodiment) 16K and 16R via left and right drive shafts 15L and 15R.

  Driving force transmission from the engine 1 to the driving wheels 16L, 16 is performed via the first clutch 6, gears 4, 9, third clutch 10, gears 11, 14, differential gear 13, and drive shafts 15L, 15R. The driving force transmitted from the electric motor 2 to the driving wheels 16L, 16 is transmitted via the second clutch 7, the gears 4, 9, the third clutch 10, the gears 11, 14, the differential gear 13, and the drive shafts 15L, 15R. Done.

  FIG. 4 shows an example of setting the operation region according to the running state of the engine 1 and the electric motor 2. In FIG. 4, in the region A where the rotation speed is low and the vehicle speed is equal to or less than the middle vehicle speed, traveling is performed only by the electric motor 2. In the high vehicle speed region B, the vehicle is driven only by the engine 1. The other operation region C is an operation region using the driving forces of both the engine 1 and the electric motor 2. In the driving region C, the drive ratio between the engine 1 and the electric motor 2 is set such that the drive ratio of the engine 1 increases as the load increases or the vehicle speed increases (in the embodiment, the engine 1 and the electric motor 2). The drive ratio with the electric motor 2 is continuously variable in the range of “1:10” to “10: 1”).

  When traveling only with the engine 1, the first clutch 6 and the third clutch 10 are connected, and the second clutch 7 is disconnected. Further, when traveling only by the electric motor 2, the second clutch 7 and the third clutch 10 are connected and the first clutch 6 is disconnected. When traveling with the driving force of both the engine 1 and the electric motor 2, all of the first to third clutches 6, 7, and 10 are connected.

  During regeneration, the second clutch 6 and the third clutch 10 are connected and the first clutch 6 is disconnected. The engine 1 is started while the first clutch 6 and the second clutch 7 are connected and the third clutch 10 is disconnected while the engine 1 is rotationally driven by the electric motor 2. Details will be described later. In FIG. 1, 17 is a capacitor having a large capacity and high efficiency, and 18 is an electric supercharger described later. The electric motor 2 and the electric supercharger 18 are driven by receiving electric power from the capacitor 17. In FIG. 1, reference numeral 19 denotes an air conditioner (compressor), which is connected to the shaft member 8 and driven by the rotation of the shaft member 8.

  2 shows an intake / exhaust system of the engine 1 shown in FIG. 1, and details of the vicinity of the cylinder head of the engine 1 are shown in FIG. In the engine 1, as shown in FIG. 3, a combustion chamber 33 is defined by a cylinder block 30, a cylinder head 31, and a piston 32. An intake port 34 and an exhaust port 35 are opened in the combustion chamber 33. The intake port 34 is opened and closed by an intake valve 36, and the exhaust port 35 is opened and closed by an exhaust valve 37. In addition, a fuel injection valve 38 is exposed to the combustion chamber 33, and a sensor S1 that is used for both temperature detection and pressure detection is also exposed.

  An opening / closing cam (cam shaft) of the intake valve 36 is indicated by reference numeral 40, and an opening / closing cam (cam shaft) of the exhaust valve 37 is indicated by reference numeral 41. Each of the cams 40 and 41 is rotationally driven by a crankshaft interlocked with the piston 32, and variable valve mechanisms 42 and 43 for phase change are incorporated in the middle of the rotational drive path. An example of the opening characteristics of the intake valve 36 and the exhaust valve 37 is shown in FIG. In FIG. 7, the solid line indicates normal use, and when the engine is started, the intake valve 36 closes in the middle of the compression stroke (sufficiently after the intake bottom dead center) as indicated by the broken line. (Valve-opening characteristics with low intake ratio due to late intake closing). Such an engine 1 is a multi-cylinder engine having a plurality of cylinders spaced in the direction perpendicular to the plane of FIG. 3 (in-line four cylinders in the embodiment).

  As shown in FIG. 2, the intake passage 50 of the engine 1 has a surge tank 51. An intake port 34 of each cylinder is independently connected to the surge tank 51 through an independent intake passage 52. In the common intake passageway 53 for supplying intake air to the surge tank 51, the air cleaner 54, the throttle valve 55 (for changing the EGR rate), the compressor wheel 56a of the exhaust turbocharger 56, in order from the upstream side to the downstream side thereof, The intercooler 57 and the above-described electric supercharger 18 are connected.

  The electric supercharger 18 is composed of a compressor wheel 18a disposed in the common intake passage 50 and an electric motor 58b that drives the compressor wheel 58a. By driving the electric motor 18b in a normal direction, The compressor wheel 18a is driven to rotate forward, and the intake air is supercharged. Further, by rotating the electric motor 18b in the reverse direction, the compressor wheel 18a is rotationally driven in the direction opposite to the supercharging direction, and the intake port 34 is sucked, and the effective compression ratio of the engine 1 is reduced. It will be.

  The exhaust passage 60 of the engine 1 includes a turbine wheel 56b of the exhaust turbocharger 56, an oxidation catalyst 61, and a CDPF (particulate supplement filter) 62 on the downstream side of the portion where the exhaust ports 37 of the cylinders are gathered. It is connected. When the turbine wheel 56b is rotationally driven in response to the energy of the exhaust gas, the compressor wheel 56a is driven through the connecting shaft 56c, and the intake air is supercharged.

  The intake passage 50 and the exhaust passage 60 are connected via a first EGR passage 70 and a second EGR passage 80. One end of the first EGR passage 70 is opened to the exhaust passage 60 on the downstream side of the CDPF 63, and the other end is opened to the common intake passage 53 between the throttle valve 55 and the compressor wheel 56a. An intercooler 71 and an electromagnetic EGR valve 72 are connected to the first EGR passage 70.

  One end of the second EGR passage 80 is opened to the exhaust passage 60 on the upstream side of the turbine wheel 56b, and the other end is common between the surge tank 51 and the electric supercharger 18 (the compressor wheel 18a). An intake passage 53 is opened. An intercooler 81 and an electromagnetic EGR valve 82 are connected to the second EGR passage 80. The second EGR passage 80 is provided with a bypass passage 83 that bypasses the intercooler 81. An electromagnetic switching valve 84 is connected to the upstream branch portion between the second EGR 80 and the bypass passage 83. The switching valve 84 switches between a state in which the exhaust gas from the passage exhaust passage 60 flows toward the intercooler 81 and a state in which the exhaust gas flows toward the bypass passage 83. That is, the switching valve 84 is switched so that exhaust gas (EGR gas) flows through the bypass passage 83 when the engine 1 is cold (for example, when the engine coolant temperature is less than 60 degrees C). When the engine is warm, the exhaust gas (EGR gas) is switched to flow through the intercooler 81 in its entirety.

  Here, the control contents at the start of the engine 1 will be described with reference to FIG. First, when a predetermined engine start condition is satisfied with the engine 1 stopped (at time t1 in FIG. 5), the first clutch 6 and the second clutch 7 are connected and the third clutch 10 is disconnected. The EGR valve 82 is fully closed, and the closing timing of the intake valve 36 is set to the intake-slow closing state shown by the broken line in FIG. The throttle valve 55 is preferably fully opened. In this state, the electric supercharger 18 is reversed and the intake port 34 is sucked to reduce the pressure, thereby reducing the effective compression ratio of the engine 1. At this time, the engine 1 is rotationally driven for starting by the electric motor 2, and this rotational driving is performed so as to rapidly increase to a predetermined rotational speed. More specifically, the engine 1 has an idle speed of, for example, 600 rpm. The predetermined speed is equal to or higher than the idle speed (for example, 700 to 800 rpm, and the engine vibration is at the idle speed). The number of rotations is smaller than that). When the engine 1 is started, the intake air is closed slowly as shown by the broken line in FIG. 7, and a lower compression ratio is further promoted.

  Due to the driving with a large driving force by the electric motor 2 for traveling, and because the engine 1 has a low compression ratio and its driving resistance is reduced, the engine 1 is extremely short in time up to the predetermined rotational speed. Will be reached. When the engine speed reaches a predetermined speed (at the time t2 is reached), start-up fuel is injected from the fuel injection valve 38, the engine 1 is started (initial explosion), and then is self-excited. (The engine 1 itself is rotated by combustion). In the embodiment, after the time t2 when the engine speed reaches the predetermined speed, the starting fuel is injected at the time t3 when a slight delay time has elapsed (after waiting for the in-cylinder temperature to rise sufficiently). Start fuel injection).

  Until the engine speed reaches a predetermined speed, the in-cylinder temperature is sufficiently increased by frictional heat due to sliding of the piston 32. Therefore, when starting fuel injection is performed, the ignitability is improved, the starting is performed reliably, and the combustion stability after ignition is sufficiently ensured. In addition, the amount of fuel injected at start-up is almost the same as during steady operation because the engine speed is sufficiently high and the in-cylinder temperature is sufficiently high, improving fuel efficiency. Etc. are also preferable. By the way, when performing fuel injection for starting at a low cranking rotation speed (for example, about 250 rpm) that is conventionally performed, an extremely large amount of fuel must be injected to obtain a reliable initial explosion. It is.

  The vibration accompanying the rotation of the engine 1 becomes the smallest at a predetermined reference rotational speed that is in the vicinity of the idle rotational speed (more specifically, a rotational speed that is slightly higher than the idle rotational speed). The vibration gradually increases as the rotational speed increases from the reference rotational speed. Similarly, the vibration gradually increases as the rotational speed decreases from the reference rotational speed. However, the vibration in the low rotation region is much larger than the vibration in the high rotation region than the reference rotation number. In particular, the vibration in the rotation region near the cranking rotation speed (for example, 250 rpm) by the starter motor, which has been conventionally performed, becomes extremely large.

  In the present invention, the engine 1 is suddenly increased from a stopped state to a predetermined rotational speed that is equal to or higher than the idle rotational speed, that is, the rotational speed at which the angular speed fluctuation is small and the vibration is sufficiently small. Passing through the rotation region where the vibration is large at a stretch, it is practically prevented that an unpleasant large vibration is given to the occupant.

  The time between t1 and t3 in FIG. 5 is substantially the delay time T1 for starting. FIG. 6 shows a conventional delay time for performing fuel injection for starting at the time of cranking at a low speed by the conventional starter motor as T2. Note that the delay time T2 is the time from the start start time t11 of the starter motor to the time when the idle rotation speed is reached after the time t12 when the start fuel injection is performed. Compared with T2, T1 takes a very short time of a fraction. Note that in the present invention, the time point t1 in FIG. 5 corresponds to the time point t11 in FIG. 6 that is the control start point for starting the engine, and the engine 1 is self-rotated at a rotational speed that is at least equal to or higher than the idle speed. The time until is extremely short in the present invention.

  FIG. 8 is a block diagram showing a control system for performing the engine start control described above. In FIG. 8, U is a controller (control unit) configured using a microcomputer. The controller U receives signals from various sensors S1 to S3. As described above, the sensor S1 detects the temperature and pressure in the cylinder. The sensor S2 detects the vehicle speed. The sensor S3 detects the accelerator opening as the engine load. The controller U also has an electric motor 2, clutches 6, 7, 10. The fuel injection valve 38, the electric motor 18, the EGR valve 82, the variable valve mechanism 42 for the intake valve, the throttle valve 55, and the like are controlled.

  The contents of control by the controller U will be described with reference to the flowchart of FIG. 9. In the following description, Q indicates a step. First, in Q1, signals from various sensors S1 to S3 are read. Thereafter, in Q2, it is determined whether or not the current driving region is based only on the electric motor 2 (including whether or not the vehicle is stopped depending on whether or not it is the region A in FIG. 4). If the determination in Q2 is YES, it is determined in Q3 whether or not the conditions for starting the engine 1 are satisfied. For example, when the current operating state is close to the region B or the region C shown in FIG. 4 or when the accelerator opening (or the rate of increase) is equal to or greater than a predetermined value, the Q3 is determined. It is said that the condition is satisfied.

  If the determination in Q3 is YES, suction in the intake port 34 by the electric supercharger 18 (reduction in the compression ratio in the cylinder) and abrupt drive toward the predetermined speed of the engine 1 by the electric motor 2 Is executed. In addition, at this time, as described above, the EGR valve 82 is fully closed, the intake air intake valve is closed slowly, the throttle valve 55 is fully opened, the first clutch 6 and the second clutch 7 are connected, and the third The clutch 10 is disconnected.

  After Q4, at Q5, it is determined whether or not the actual engine speed has reached a predetermined speed. If the determination in Q5 is YES, start fuel injection is executed in Q6. Thereafter, at Q7, it is determined whether or not ignition has occurred. This determination of Q7 is performed by looking at the signal from the sensor S1. If the determination in Q7 is YES, it means that ignition has been performed (initial explosion) and self-excited rotation has been performed (starting completion). At this time, the routine proceeds to Q8 and normal operation is performed. The normal operation at Q8 is, for example, an operation in the supercharging direction of the intake air in the electric supercharger 18 (forward rotation), and the EGR valve 82 and the throttle valve 55 have a predetermined EGR rate. The opening degree is controlled, the intake valve 34 is controlled to have a valve opening characteristic corresponding to the operating state, and the first clutch 6 and the third clutch 10 are connected. The second clutch 7 is connected or disconnected in accordance with the travel region, regeneration, etc. shown in FIG.

  If NO in Q2 or NO in Q3, the process returns to Q1. If NO in Q5 or NO in Q7, the process returns to Q4. Note that after Q5, after confirming from the signal from the sensor S1 that the in-cylinder temperature has become equal to or higher than the predetermined temperature, the start fuel injection in Q6 may be performed.

  10 and 11 show a second embodiment of the present invention. In the present embodiment, the electric supercharger 18 is provided in the EGR passage 80 instead of providing the electric supercharger 18 in the intake passage 50. The electric supercharger 90 includes a compressor wheel 90a disposed in the EGR passage 80, and an electric motor 90b that rotationally drives the compressor wheel 90a. The electric supercharger 90 is for sufficiently supplying the EGR gas to the intake passage 50 even when the exhaust pressure is small (the rotation direction is normal). Further, when the engine is started, the electric supercharger 90 sucks the intake port 34 in a state where the EGR passage 80 is opened (a state where the EGR valve 82 is fully opened) to reduce the compression ratio in the cylinder. Will be reversed.

  FIG. 11 is a flowchart showing control contents in the second embodiment, and Q21 to Q27 correspond to Q1 to Q7 in FIG. However, in the control example of FIG. 11, the inside of the intake port 34 is sucked by the electric supercharger 90 instead of the electric supercharger 18 (EGR valve 82 is fully opened).

  In the control example of FIG. 11, steps Q29 to Q31 are added to the control example of FIG. That is, if NO in Q27, that is, if ignition is not confirmed, the rotation direction of the electric supercharger 90 is switched from the reverse rotation direction to the normal rotation direction in Q29, and the EGR gas is sucked in. It is set as the aspect supplied to the channel | path 50. FIG. That is, since the ignition is not ignited, the starting fuel is discharged as unburned gas into the exhaust passage 60, and the unburned gas is circulated through the intake passage 50. In Q30, the amount of unburned gas circulated from the EGR passage 80 is determined (estimated) by model control, and the starting fuel injection amount to be injected next is determined (the fuel amount to be injected from the fuel injection valve 38). As the amount obtained by subtracting the amount of unburned gas circulated through the EGR passage 80 from the required fuel amount). Thereafter, in Q31, the fuel amount determined in Q30 is injected from the fuel injection valve 38. By controlling Q29 to Q31, the engine 1 can be started without wasting unburned gas.

  Although the embodiment has been described above, the present invention is not limited to the embodiment, and can be appropriately changed within the scope described in the scope of claims. For example, the invention includes the following cases. . The present invention can be applied not only to a diesel engine (compression ignition type engine) but also to a gasoline engine (spark ignition type engine). The exhaust turbo supercharger 56 may not be provided. The electric supercharger may be provided in both the intake passage 50 and the EGR passage 80 (both the electric supercharger or one of the electric superchargers, and the low Compression ratio can be performed). The predetermined rotational speed that is the target rotational speed that is rapidly increased at the time of starting may be a rotational speed in the vicinity of the idle rotational speed and lower than the idle rotational speed. The intake air slow closing may not be performed when the engine is started. The vehicle may be a vehicle that is not a hybrid vehicle (the electric motor 2 is not for traveling, but is dedicated to starting, for example). In FIG. 1, a transmission mechanism may be interposed between the first clutch 6 and the drive gear 4 (for changing the rotation ratio between the engine 1 and the drive gear 4). Of course, the object of the present invention is not limited to what is explicitly stated, but also implicitly includes providing what is substantially preferred or expressed as an advantage.

  The present invention can be used, for example, as a starting method and a starting device for an automatic engine.

1: Engine 2: Electric motor 16L, 16R: Wheel 18: Electric supercharger 32: Piston 33: Combustion chamber 34: Intake port 35: Exhaust port 36: Intake valve 37: Exhaust valve 38: Fuel injection valve 42: Variable Valve mechanism (for slow intake closing)
50: Intake passage 80: EGR passage 90: Electric supercharger (FIG. 10)
U: Controller S1: Sensor (for in-cylinder temperature and pressure detection)
S2: Sensor (for vehicle speed detection)
S3: Sensor (for engine load detection)

Claims (12)

An engine starting method in which an intake valve is interposed in an intake port,
When the engine start condition is satisfied, the electric supercharger is driven to rotate in a predetermined direction in which the pressure in the intake port decreases; and
A step of rapidly increasing the engine stopped by the electric motor to a predetermined rotational speed with a small variation in angular velocity in a state where the electric supercharger is driven in the predetermined direction;
After the engine speed reaches the predetermined speed, performing a fuel injection for starting in the cylinder, and causing the engine to self-rotate by combustion;
An engine starting method comprising: In claim 1,
The engine starting method according to claim 1, wherein the predetermined number of revolutions is a number of revolutions at which the engine can stably rotate by self-excitation by fuel injection. In claim 2,
The engine starting method, wherein the predetermined rotational speed is set to be equal to or higher than an idle rotational speed. In claim 1,
A method for starting an engine, comprising: driving the electric supercharger in the predetermined direction after fuel injection, and thereafter driving the electric supercharger in a direction opposite to the predetermined direction. In claim 1,
The electric supercharger is disposed in the intake passage of the engine and is used for supercharging intake air,
The predetermined direction is a direction opposite to the rotation direction when supercharging the intake air,
An engine starting method characterized by the above. In claim 1,
The electric supercharger is disposed in an EGR passage that supplies exhaust gas for EGR to the intake passage,
The predetermined direction is a direction opposite to a rotation direction when exhaust gas is supplied to the intake passage.
An engine starting method characterized by the above. In claim 1,
A method for starting an engine, characterized in that when the engine is started, the intake valve is closed in a closed state in which the closing timing of the intake valve is in the middle of the compression stroke. In claim 1,
The electric supercharger is disposed in the intake passage of the engine and is used for supercharging intake air,
The predetermined direction is a direction opposite to the rotation direction when supercharging the intake air,
The electric motor is constituted by a traveling motor that drives a traveling wheel,
An engine starting method characterized by the above. An engine starting device in which an intake valve is interposed in an intake port,
An electric supercharger;
An electric motor for starting the engine;
A fuel injection valve for injecting fuel into the cylinder;
A controller for controlling the electric supercharger, the electric motor, and the fuel injection valve;
Have
The controller is configured to rotate the electric supercharger in a predetermined direction in which the pressure in the intake port decreases while a predetermined engine start condition is satisfied, and stop the engine by the electric motor. Is controlled to suddenly increase to a predetermined rotational speed with less angular speed fluctuation,
The controller further performs control to cause the engine to perform self-excited rotation by combustion by causing the fuel injection valve to perform start-up fuel injection after the engine speed reaches the predetermined speed.
An engine starting device. In claim 9,
The electric supercharger is disposed in the intake passage of the engine and is used for supercharging intake air,
The predetermined direction is a direction opposite to the rotation direction when supercharging the intake air,
The electric motor is constituted by a traveling motor that drives a traveling wheel,
An engine starting device. In claim 9 or claim 10,
The predetermined rotational speed is a rotational speed equal to or higher than the idle rotational speed,
The electric supercharger is disposed in the intake passage of the engine and is used for supercharging intake air,
The predetermined direction is a direction opposite to a rotation direction when supercharging intake air,
An engine starting device. In claim 9 or claim 10,
The electric supercharger is disposed in the intake passage of the engine and is used for supercharging intake air,
The predetermined direction is a direction opposite to the rotation direction when supercharging the intake air,
The controller terminates driving of the electric supercharger in the predetermined direction after fuel injection, and then controls the electric supercharger to be driven in a direction opposite to the predetermined direction;
An engine starting device.

Images