JP2004301047A - Engine starter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine starter for further reducing fuel consumption, restraining a CO<SB>2</SB>discharge amount or the like by properly having the stop position of a piston and enhancing the restartability of an engine with a simple structure in an engine starter performing an idle stop. <P>SOLUTION: In the engine starter, when prescribed engine stopping conditions are met, fuel supply is automatically stopped to stop engine 1, and when restart conditions are met, a cylinder 3 in an expansion stroke is made to perform combustion to restart the engine. Part of driving force of the engine 1 is taken out as work periodically variable in accordance with a rotation angle of a crankshaft 6, and a high-pressure fuel pump 126 for increasing fuel pressure is provided. When the rotation angle of the crankshaft 6 is at an almost top dead center of each cylinder 3, the momentary work of the high-pressure fuel pump 126 comes into the maximum. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a starting device for an engine that automatically stops the engine temporarily at the time of idling or the like and then automatically restarts the engine after that.
[0002]
[Prior art]
In recent years, fuel economy and CO ₂ In order to reduce emissions, the engine is automatically stopped once when idling, and then automatically restarted when restart conditions, such as starting operation, are satisfied (hereinafter referred to as idle stop or I / S). Such an engine starter has been developed.
[0003]
Since the restart in the idle stop is required to be started immediately according to a start operation or the like, a start such as starting the engine through cranking that drives an engine output shaft by a starter (motor for starting) is performed. Conventional general start-up methods that require significant time to complete are not preferred.
[0004]
Therefore, it is desirable that fuel be supplied to a specific cylinder (cylinder in an expansion stroke) of the stopped engine to cause ignition and combustion, and that the engine be started immediately with the energy. However, even if fuel is supplied to a cylinder in an expansion stroke to ignite and burn, sufficient torque for starting the engine is not always obtained. In order to smoothly restart the engine, ignitability of a certain level or more and magnitude of generated torque are required.
[0005]
As a countermeasure against such a problem, for example, as shown in Patent Document 1, after IG OFF (ignition stop), the closing timing of the exhaust valve is controlled to make it easy to stop the engine with the piston at an appropriate position. Alternatively, as disclosed in Patent Document 2, a braking device is provided for a crankshaft of an engine, and the braking device is controlled so that a piston of a cylinder which is in an expansion stroke when the engine is stopped stops at an appropriate position during the stroke. And others have been proposed.
[0006]
The proper stop position of the piston for restarting is generally around 90 ° CA (crank angle) after the top dead center, that is, near the center between the top dead center and the bottom dead center, and the piston is stopped at this position. When this is done, good combustion is obtained with the moderately existing in-cylinder air and fuel supplied at the time of restart, and it is easy to generate torque sufficient for restart. That is, Patent Literature 1 and Patent Literature 2 attempt to regulate the stop position of the piston so that a sufficient restart torque is obtained by combustion.
[0007]
[Patent Document 1]
WO 01/44636 A2
[Patent Document 2]
Japanese Utility Model Publication No. 60-128975
[0008]
[Problems to be solved by the invention]
The starting device disclosed in Patent Document 1 described above is an indirect method that utilizes a change in in-cylinder gas pressure by controlling an exhaust valve, and thus tends to cause variations. Therefore, there has been a demand for a technique for stopping the piston at an appropriate position with a higher probability in order to smoothly restart. According to the starting device disclosed in Patent Document 2, a device that can brake the crankshaft is required separately from the braking device for the vehicle, and the braking device is accurately controlled so that the piston stops at an appropriate position. It was very difficult to do.
[0009]
In view of the above circumstances, the present invention reduces the variation in the stop position of the piston without providing a special braking device or the like separately, and enables the engine to be stopped at an appropriate position with a higher probability. The structure improves engine restartability, further reducing fuel consumption and reducing CO2 emissions. ₂ An object of the present invention is to provide an engine starting device capable of suppressing an emission amount and the like.
[0010]
[Means for Solving the Problems]
According to the first aspect of the present invention, when a predetermined engine stop condition is satisfied, the fuel supply is automatically stopped to stop the engine, and when the restart condition is satisfied after the engine is stopped, the cylinder in the expansion stroke is stopped. In an engine starting device that injects fuel to ignite and burn and restarts the engine, a part of the driving force of the engine is extracted as work that fluctuates periodically according to the rotation angle of the crankshaft, and the fuel is extracted. Mechanical high-pressure fuel pump that increases the fuel pressure for injecting the fuel, the instantaneous work of the high-pressure fuel pump is performed when the rotation angle of the crankshaft is substantially at the top dead center of some or all cylinders. When the rotation angle of the crankshaft is maximized and substantially halfway between the top dead center and the bottom dead center of some or all of the cylinders, the instantaneous There, characterized in that it is configured so as to minimize.
[0011]
When the engine is stopped by the idle stop, after the fuel supply is stopped, the engine stops several times by inertia. The piston position at the time of the stop tends to be relatively close to an appropriate position (substantially the middle position between the top dead center and the bottom dead center) even in the conventional structure. This is because the intake / exhaust valve opens and closes even without performing combustion, so that the air pressure in the cylinder increases when the piston is near the compression top dead center. That is, as the piston approaches the top dead center, the force acting in the direction away from the top dead center by the in-cylinder air pressure increases, so that the piston does not easily stop near the top dead center. In a multi-cylinder engine, when a piston of a certain cylinder moves away from the top dead center, a piston of another cylinder approaches the top dead center. Therefore, the pistons of all the cylinders are more likely to stop at a position as far as possible from the top dead center, that is, near the middle between the top dead center and the bottom dead center.
[0012]
According to the configuration of the present invention, the above tendency can be further strengthened. That is, it is possible to further increase the probability that the piston position at the time of stopping the engine will be an appropriate position. This is because the instantaneous work of the high-pressure fuel pump is configured to be minimized when the piston is approximately halfway between the top dead center and the bottom dead center. The high-pressure fuel pump is driven by the engine, ie acts as a load on the engine. Therefore, when the engine is stopped, a force acts in a direction that minimizes the load (instantaneous work of the high-pressure fuel pump), that is, a direction in which the piston is moved to approximately halfway between the top dead center and the bottom dead center. Makes the piston easier to stop.
[0013]
Further, the rotation angle of the crankshaft, at which the instantaneous work of the high-pressure fuel pump is minimized, is set to be slightly later than the middle between the top dead center and the bottom dead center in the stroke of some or all cylinders. According to claim 2, the probability that the piston stops at a more appropriate position (slightly closer to the bottom dead center than the middle position between the top dead center and the bottom dead center in the expansion stroke) can be increased.
[0014]
It has been conventionally known that the restartability can be enhanced when the stop position of the piston is approximately halfway between the top dead center and the bottom dead center. It has been confirmed that restartability can be enhanced most when the vehicle is stopped slightly behind the intermediate position between the top dead center and the bottom dead center in the stroke, that is, near the bottom dead center. This is because when restarting the combustion, combustion is performed in the cylinder in the expansion stroke, but a large amount of air is injected into the cylinder to burn a large amount of fuel and obtain a high restart torque. On the other hand, in this case, if the combustion is performed simply, the compression ratio of the air is low (the in-cylinder air pressure when the engine is stopped is almost equal to the atmospheric pressure), and the piston stroke to the bottom dead center becomes small. There is a concern that work cannot be taken out, but that is because the engine is momentarily reversed (combustion is performed in the cylinders in other compression strokes) before combustion is performed in the cylinders in the expansion stroke. The problem can be solved by moving the piston to the top dead center side and then burning.
[0015]
According to a third aspect of the present invention, in the configuration of the first or second aspect, the work of the high-pressure fuel pump is taken out by rotation of a fuel pump cam having a rotation angle corresponding to a rotation angle of a crankshaft, The fuel pump is characterized in that the high-pressure fuel pump has a large instantaneous work in a cam nose having a large cam radius.
[0016]
In a so-called direct injection engine that injects fuel into a cylinder, a mechanical high-pressure fuel pump that increases the fuel pressure by extracting part of the engine's driving force as work that fluctuates periodically according to the rotation angle of the crankshaft It is an existing structure, and its work is generally taken out by rotating a cam for a fuel pump. In such a mechanism, the instantaneous work of the high-pressure fuel pump becomes large when the rotation angle of the crankshaft corresponds to the position of the cam nose, and becomes small at the position between the cam nose. Eventually, the work taken to increase fuel pressure will be a time average of it. In the conventional mechanism, the relationship between the position of the cam nose and the rotation angle of the crankshaft is arbitrary, and is not particularly defined.
[0017]
According to the third aspect of the present invention, the position of the cam nose is adjusted to the vicinity of the top dead center, and the position where the cam radius is small (between the cam nose and the cam nose) is inevitably between the top dead center and the bottom dead center. By adjusting the piston to an appropriate stop position, the configuration according to claim 1 or 2 can be realized.
[0018]
That is, by using the existing structure and devising the position of the cam nose, it is possible to easily increase the probability that the piston stops at an appropriate position without complicating, enlarging, or increasing the cost of the entire device. it can.
[0019]
The number of cam nose is preferably set to a multiple of one half of the number of cylinders of the engine (for example, any of 2, 4, 6,... For a four-cylinder engine) (Claim 3). It is desirable that the number be equal to the number of cylinders (claim 4).
[0020]
If the number of cam nose is equal to the number of cylinders of the engine, or 1.5 times, 2 times..., At least one cam nose can correspond to the compression top dead center of each cylinder. Even if the cylinder becomes an expansion stroke cylinder when the engine is stopped (hereinafter referred to as an expansion stroke cylinder), the probability that the piston stops at an appropriate position can be increased. Further, the inventor of the present invention has experimentally confirmed that even if the number of cam nose is set to one half of the number of cylinders of the engine, the probability can be increased.
[0021]
According to a sixth aspect of the present invention, in the configuration according to any one of the first or fifth aspects, a work of the high-pressure fuel pump is enabled by the rotation of the cam for the fuel pump, and a pump ON state for increasing the fuel pressure; Even if the fuel pump cam rotates, the high-pressure fuel pump does not make the work effective, and the fuel pump includes a pump switching means capable of switching to a pump OFF state in which the fuel pressure does not increase, at least after the predetermined engine stop condition is satisfied. The pump switching means is in a pump ON state from immediately before the engine is stopped until the engine is completely stopped.
[0022]
According to this configuration, the load is applied to the engine by turning on the pump immediately before the stop of the engine, and the piston is easily stopped at an appropriate position. By maintaining the pump ON state at least until the engine completely stops, it is easy to secure the fuel pressure at the time of restart. That is, appropriate fuel injection is performed at the time of restart, and restartability can be enhanced by favorable combustion.
[0023]
It is preferable that the pump switching means be in a pump OFF state for a predetermined period immediately after the predetermined engine stop condition is satisfied and immediately before the engine is stopped (claim 7).
[0024]
In this way, it is possible to prevent fuel leakage while the engine is stopped, and to prevent the fuel pressure during restart from becoming unnecessarily high. That is, after the engine stop condition is satisfied, the injection from the fuel injection valve is stopped (the fuel supply is stopped). If the pump ON state is continued in this state, the fuel pressure becomes unnecessarily high. As a result, there is a concern that fuel leakage is likely to occur, or the fuel pressure at the time of restart becomes too high, so that it becomes difficult to obtain good combustion at the time of restart.
[0025]
However, according to the above configuration, the pump is in the OFF state immediately before the engine is stopped so that the fuel pressure does not increase. Also in this configuration, by setting the pump to the ON state immediately before the engine is stopped, it is possible to obtain the above-described effects such as an improvement in the stop probability of the piston at an appropriate position and a fuel pressure at the time of restart.
[0026]
Further, the pump switching means may switch between the pump ON state and the pump OFF state so that the fuel pressure at the time of restarting the engine becomes a predetermined pressure (claim 8). It is further desirable that a fuel pressure detecting means for detecting the pressure is provided, and the switching between the pump ON state and the pump OFF state is performed by feedback control (claim 9).
[0027]
By doing so, the fuel pressure when the engine is stopped can be adjusted to a suitable value at the time of restart, so that restartability can be further improved. The fuel pressure suitable for the restart differs depending on the characteristics of the engine and the like. For example, it is preferable that the normal fuel pressure is set to 3 to 7 MPa and the restart fuel pressure is set to around 3 MPa. At that time, a pressure drop during stoppage of the engine may be taken into account as necessary.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2 show a schematic configuration of an engine according to an embodiment of the present invention. In these figures, the main body of the engine 1 is composed of a cylinder head 2a and a cylinder block 2. In this embodiment, the engine 1 is a four-cylinder four-cycle engine, and includes four cylinders 3 (specifically, the first cylinder 3A, the second cylinder 3B, the third cylinder 3C, and the fourth cylinder in order from the left in the state shown in FIG. 2). 3D). A piston 4 is fitted into each cylinder 3, and a combustion chamber 5 is formed above the piston 4. The piston 4 is connected to a crankshaft 6 via a connecting rod.
[0029]
A spark plug 7 is provided at the top of the combustion chamber 5 of each cylinder 3, and the tip of the plug faces the combustion chamber 5.
[0030]
Further, a fuel injection valve 8 for directly injecting fuel into the combustion chamber 5 is provided on a side portion of the combustion chamber 5. The fuel injection valve 8 has a built-in needle valve and a solenoid (not shown). When a pulse signal is input, the fuel injection valve 8 is driven and opened for a time corresponding to the pulse width at the pulse input time. Is configured to inject an amount of fuel according to the following. The injection direction of the fuel injection valve 8 is set so as to inject fuel toward the vicinity of the ignition plug 7. Fuel is supplied to the fuel injection valve 8 through a fuel passage or the like by a high-pressure fuel pump 126 provided near the camshaft 26 as described later, and is higher than the pressure in the combustion chamber in the compression stroke. A fuel supply system is configured to provide a fuel pressure.
[0031]
An intake port 9 and an exhaust port 10 are open to the combustion chamber 5 of each cylinder 3, and these ports 9 and 10 are provided with an intake valve 11 and an exhaust valve 12. The intake valve 11 and the exhaust valve 12 are driven by a valve mechanism including camshafts 26 and 27 and the like. The opening / closing timing of the intake / exhaust valve of each cylinder is set so that each cylinder 3 performs a combustion cycle with a predetermined phase difference, as described later in detail.
[0032]
The opening and closing timings of the intake valve 11 and the exhaust valve 12 are variable by the cam phase variable mechanisms 26a and 27a. The variable cam phase mechanisms 26a and 27a are conventionally known mechanisms that vary the rotational phase of the camshafts 26 and 27 with respect to the rotational phase of the crankshaft. As shown in FIG. 2, the camshaft 26 on the intake valve 11 side is provided with a variable cam phase mechanism 26a, and the camshaft 27 on the exhaust valve 12 side is provided with a variable cam phase mechanism 27a, which are independently controlled. ing. Therefore, the opening / closing timings of the intake valve 11 and the exhaust valve 12 can be independently varied forward and backward by the cam phase variable mechanisms 26a and 27a, respectively.
[0033]
An intake passage 15 and an exhaust passage 16 are connected to the intake port 9 and the exhaust port 10. The intake passage 15 has a branch intake passage 15a for each cylinder downstream of the surge tank 15b, and the downstream end of each branch intake passage 15a communicates with the intake port 9 of each cylinder, but the downstream end of each branch intake passage 15a. Near the end, a throttle valve 17 composed of a multiple rotary valve for simultaneously restricting and adjusting each branch intake passage 15a is provided. The throttle valve 17 is driven by a throttle valve actuator 18.
[0034]
An airflow sensor 20 for detecting the amount of intake air is provided in a common intake passage 15c in the intake passage 15 upstream of the surge tank 15b. The crankshaft 6 is provided with a crank angle sensor for detecting a rotation angle thereof. In the present embodiment, as described later in detail, the crankshaft 6 outputs crank angle signals that are out of phase by a certain amount. Two crank angle sensors 21 and 22 are provided. Further, a cam angle sensor 23 is provided for the camshafts 26 and 27, which can provide a cylinder identification signal by detecting a specific rotation position. Further, a starter 28 which is a motor for starting the engine 1 is provided, and the driving force of the starter 28 is directly transmitted to the crankshaft 6 via a starter gear (not shown), so that the engine 1 starts. It is configured as follows.
[0035]
In addition, as other detection elements necessary for controlling the engine 1, a water temperature sensor 24 for detecting the temperature of the engine cooling water and an accelerator opening sensor 25 for detecting the accelerator opening (accelerator operation amount) (see FIG. 6). Etc. are equipped.
[0036]
3 to 5 are explanatory diagrams of the fuel supply system 120. FIG. As shown in FIG. 3, a low-pressure pump 123, a low-pressure regulator 124, a fuel filter 125, a high-pressure fuel pump 126, and a low-pressure pump 123 are provided in a fuel passage 122 from the fuel tank 121 to the fuel injection valve 8. The distribution pipes 119 are arranged in order, and the fuel is supplied from the fuel distribution pipes 119 to the fuel injection valves 8 of the respective cylinders.
[0037]
Then, the fuel sucked from the fuel tank 121 by the low-pressure pump 123 is regulated by the low-pressure regulator 124, and then sent to the high-pressure fuel pump 126 while being filtered by the fuel filter 125.
[0038]
The high-pressure fuel pump 126 pressurizes the fuel supplied through the fuel filter 125 to a high pressure (for example, about 3 MPa to about 13 MPa, preferably about 3 MPa to 7 MPa), and sends the fuel to the fuel distribution pipe 119 under pressure. The fuel distribution pipe 119 is provided with a fuel pressure sensor 69 (see FIG. 4) as fuel pressure detecting means. The high-pressure fuel pump 126 includes a pump chamber 153 provided with a fuel suction portion 151 and a discharge portion 152 as shown in FIG. 4 and a pressurizing means 154 for pressurizing the fuel in the pump chamber 153. Have.
[0039]
The fuel suction portion 151 of the pump chamber 153 is provided with a suction valve 155 for opening and closing the fuel suction portion 151, a first biasing means 156 for biasing the suction valve 155 in a closing direction, and a push rod 157. Second urging means 158 composed of a compression coil spring for urging the suction valve 155 in the opening direction, and pulling the push rod 157 into the solenoid case 159 against the urging force of the second urging means 158. And a solenoid 160 for a high-pressure pump, which is driven in a direction away from the suction valve 155 by a pressure.
[0040]
The urging force of the first urging means 156 is set to a value smaller than the urging force of the second urging means 158, and in a normal state (the high-pressure pump solenoid 160 is OFF). The suction valve 155 is kept open according to the power. When the high pressure pump solenoid 160 is energized (ON) and the push rod 157 is pulled into the solenoid case 159, suction is performed according to the urging force of the first urging means 156 and the fuel pressure in the pump chamber 153. The valve 155 is closed.
[0041]
Therefore, when the high pressure pump solenoid 160 is turned ON, the suction valve 155 opens only when fuel flows from the fuel tank 121 toward the fuel injection valve 8 and closes when fuel flows backward, so that the fuel downstream of the suction valve 155 is closed. Hold pressure. That is, the high pressure fuel pump 126 is in a pump ON state in which the work is effective. On the other hand, when the high-pressure pump solenoid 160 is turned off, the suction valve 155 is always open. Therefore, even if the fuel pressure is increased in the pump chamber 153, the fuel flows backward to the fuel tank 121 and the fuel pressure in the fuel injection valve 8 increases. Does not rise. That is, the pump is turned off. As described above, the suction valve 155 and the high-pressure pump solenoid 160 function as a pump switching means for switching between the pump ON state and the pump OFF state.
[0042]
The fuel discharge section 152 of the pump chamber 153 is provided with a discharge valve 161 for opening and closing the fuel discharge section 152 and a discharge valve urging means 162 formed of a compression coil spring for urging the discharge valve 161 in a closing direction. In a normal state, the discharge valve 161 is held in a closed state according to the urging force of the discharge valve urging means 162. When the fuel in the pump chamber 153 is pressurized by the pressurizing means 154 and the fuel pressure rises above a certain value, the discharge valve 161 is opened in the opening direction against the urging force of the discharge valve urging means 162. , The fuel is fed to the fuel injection valve 8 by pressure.
[0043]
The pressurizing means 154 urges the plunger 163 for applying pressure to the fuel in the pump chamber 153, the fuel pump cam 164 for driving the plunger 163 up and down, and the lower end of the plunger 163. Plunger biasing means 166 that presses against the fuel pump cam 164 to move the plunger 163 up and down in response to the rotation of the fuel pump cam 164. Fuel is supplied and pressurized. That is, when the plunger 163 descends with the suction valve 155 opened, fuel is sucked into the pump chamber 153 from the fuel suction part 151, and then the plunger 163 rises with the suction valve 155 closed. The fuel in the pump chamber 153 is pressurized.
[0044]
The fuel pump cam 164 has four cam noses 165 protruding at an angle of 90 ° and is integrally attached to the camshaft 26 so that the plunger 163 can rotate while the camshaft 26 makes one rotation. Is driven up and down four times. Further, as shown in FIG. 5, the camshaft 26 is rotationally driven through a chain transmission mechanism 167 (which may be a belt transmission mechanism) driven by the crankshaft 6 of the engine body 1, whereby the crankshaft 6 is driven. The camshaft 26 makes one rotation and the plunger 163 goes up and down four times in response to two rotations (one cycle).
[0045]
As described above, the fuel pressure in the pump chamber 153 is increased by raising and lowering the plunger 163. When the pump work is instantaneously observed, the amount of work is large when the plunger 163 is raised and small when the plunger 163 is lowered. Then, while the state of work is periodically repeated between a large state and a small state, the fuel pressure is increased as the time averaged work.
[0046]
The four vertexes of the cam nose 165 are located at the top dead center of the compression stroke at the rotation angle (CA) of the crankshaft 6 or slightly behind (for example, about 10 ° CA) with respect to the cylinders 3A to 3D. Has been adjusted.
[0047]
As a result, in the pump ON state, the rise of the plunger 163 becomes maximum (plunger stroke maximum) in a 180 ° CA cycle in which one of the cylinders 3 is near the compression top dead center, and the instantaneous work of the high-pressure fuel pump 126 ( The load on the crankshaft 6 becomes maximum. (See FIG. 7).
[0048]
FIG. 6 is a control block diagram of the engine 1, showing a switch and a sensor for inputting a signal, and a device and an actuator for outputting a signal, mainly on an ECU (engine control unit) 30. Since this block diagram relates to idle stop control, other control-related portions are omitted.
[0049]
On the input side of the ECU 30, in addition to the air flow sensor 20, the crank angle sensors 21 and 22, the cam angle sensor 23, the water temperature sensor 24, the accelerator opening sensor 25, and the fuel pressure sensor 69, an I / S (idle stop) is performed. The sensors include a brake sensor 62 for detecting the depth of depression of a brake, a vehicle speed sensor 63 for detecting a vehicle speed, an inhibitor switch 64 for detecting a shift lever position of an AT (automatic transmission), and detecting ON / OFF of a parking brake. A parking brake switch 65 for turning on, a turn signal switch 66 for detecting ON / OFF of the turn signal, an air conditioner switch 67 for detecting ON / OFF of the air conditioner, and a brake negative pressure sensor 68 for detecting the brake negative pressure are connected to each other. Is entered.
[0050]
On the output side of the ECU 30, in addition to the ignition plug 7, the fuel injection valve 8, the high pressure pump solenoid 160, the throttle valve actuator 18, the cam phase variable mechanisms 26a and 27a and the starter 28, an idle stop display lamp 71, an electric oil The pump 72, the ATF switching valve 73, and the hill holder solenoid valve 74 are connected, and output a drive signal to each device.
[0051]
The idle stop display lamp 71 is a lamp for indicating to the driver the implementation status of the I / S. The details will be described later, but the engine is stopped by the I / S or the I / S is prohibited. This is a general term for lamps that indicate that the engine is restarting.
[0052]
The electric oil pump 72 is an electric oil pump that supplies oil pressure to the AT while the engine is stopped by the I / S. During normal operation, the clutch inside the AT operates using a mechanical oil pump (not shown) driven directly by being connected to the crankshaft 6 as a hydraulic supply source. Therefore, when the engine is stopped by the I / S, the hydraulic pressure drops and the clutch is released. In this case, after restarting the engine, a time loss for re-engaging the clutch occurs, and the startability deteriorates. To prevent this, the oil pressure is separately supplied to the AT by the electric oil pump 72 while the engine is stopped.
[0053]
The ATF switching valve 73 is a switching valve that switches an ATF (automatic transmission oil) passage from the hydraulic pressure supply source to the AT. The ATF is switched from the mechanical oil pump to the AT during normal operation, and from the electric oil pump 72 when the engine is stopped by the I / S.
[0054]
The hill holder solenoid valve 74 is a solenoid valve for driving a hill holder (not shown) that shuts off a brake oil supply passage. During normal operation, the booster linked to the engine operates and the brake oil pressure is increased. However, since the booster does not operate when the engine is stopped, the brake hydraulic pressure decreases, and the braking force decreases. Therefore, for example, when an idle stop is performed on a slope or the like, the vehicle may move due to insufficient braking force. In order to prevent this, the hill holder is configured to hold the brake oil pressure at a high level by shutting off the brake oil supply passage with the hill holder solenoid valve 74.
[0055]
The ECU 30 includes a throttle valve control unit 31, a fuel injection valve control unit 32, an ignition control unit 33, a cylinder identification unit 40, a high pressure pump control unit 41, an idle stop control unit 34, a cam phase control unit 35, and a display control unit 36. , AT control means 37 and hill holder control means 38.
[0056]
The throttle valve control means 31 calculates the required opening of the throttle valve 17 from the accelerator opening information from the accelerator opening sensor 25, the engine speed based on the crank angular speed information from the crank angle sensors 21 and 22, and the like. , The throttle valve actuator 18 is controlled.
[0057]
The fuel injection valve control means 32 and the ignition control means 33 determine the required fuel injection amount from the intake air amount information from the air flow sensor 20 and the cooling water temperature information from the water temperature sensor 24 in addition to the accelerator opening information and the engine speed information. And an injection timing and an appropriate ignition timing are calculated, and a control signal is output to the fuel injection valve 8 and the ignition plug 7.
[0058]
Feedback control is performed by the throttle valve control means 31 and the fuel injection valve control means 32 such that the engine speed at the time of idling becomes a predetermined target speed (for example, 650 ± 50 rpm at the time of warm) (bypasses the throttle valve 17). An ISC (idle speed control) valve that forms an intake path may be provided to control the idle speed.
[0059]
The cylinder identification unit 40 identifies a cylinder based on a crank angle signal input from the crank angle sensors 21 and 22 and a cam angle signal input from the cam angle sensor 23 when the engine 1 starts.
[0060]
The high-pressure pump control means 41 controls the energization timing of the high-pressure pump solenoid 160 to switch between a pump ON state and a pump OFF state. During normal operation, the fuel pressure is adjusted to a predetermined pressure by intermittently repeating the pump ON state and the pump OFF state. At this time, feedback control may be performed based on the measured value of the fuel pressure by the fuel pressure sensor 69. Then, when the engine 1 is automatically stopped by the idle stop, the fuel pressure is set to the pump ON state immediately before the engine is stopped and the fuel pressure at the time of restart is reduced while the fuel supply is stopped to prevent the fuel pressure from becoming too high as the pump OFF state. Secure. At this time, by performing feedback control, the fuel pressure (about 3MP) suitable for restart may be obtained.
[0061]
Further, if the pump is turned on immediately before the engine is stopped, the work of the pump becomes a load on the crankshaft 6, so that the engine 1 is in a position where the load is minimum, that is, the rise of the plunger 163 is minimum (the minimum plunger stroke). It becomes easier to stop at the position. In the present embodiment, since it is set at the intermediate position of each stroke or about 10 ° CA later than the cylinder, the cylinder which becomes the expansion stroke when the engine is stopped (for convenience of explanation, this is the first cylinder 3A). In the same manner, it is assumed that the cylinder in the compression stroke when the engine is stopped is the third cylinder 3C, and the piston 4 is stopped in the compression stroke cylinder 3C. There is a high probability that the position is between the top dead center and the bottom dead center, or near the bottom dead center by about 10 ° CA.
[0062]
The idle stop control unit 34 determines an I / S execution condition, and provides information necessary for executing the I / S to each unit in the ECU 30.
[0063]
The I / S execution conditions are classified into basic stop conditions, basic restart conditions, and I / S prohibition conditions. Each condition may be set as appropriate. For example, the brake depression depth obtained from the brake sensor 62 is equal to or more than a predetermined value, the vehicle speed obtained from the vehicle speed sensor 63 is zero, and the shift lever position of the AT obtained from the inhibitor switch 64 Is in the non-traveling range, the signal of the parking brake switch 65 is ON, the signal of the turn signal switch 66 is OFF, and the air conditioner switch 67 is OFF, the basic stop condition is satisfied.
[0064]
Also, for example, the brake depression depth is equal to or less than a predetermined value, or the vehicle speed is equal to or more than a predetermined value, or the shift lever position of the AT is in the travel range, the signal of the turn signal switch 66 is ON, or the air conditioner switch 67 is ON, or the brake negative pressure is set. The basic restart condition is satisfied when the brake negative pressure (negative pressure in the booster constituting the booster that supplements the braking force) obtained from the sensor 68 is equal to or less than a predetermined value.
[0065]
For example, when the engine coolant temperature Tc is equal to or lower than a predetermined value (for example, Tc <60 ° C.), when the monitor voltage of the battery is equal to or lower than a predetermined value, or when the elapsed time from the previous restart is equal to or lower than the predetermined value, the I / S is prohibited. The condition is satisfied.
[0066]
When the basic stop condition is satisfied and the I / S prohibition condition is not satisfied, it is determined that the engine stop condition is finally satisfied (this is referred to as the engine stop condition being satisfied in the present specification). Automatic stop of the engine is performed. That is, the fuel injection from the fuel injection valve 8 is stopped, and the ignition of the ignition plug 7 is stopped.
[0067]
As the control at the time of stopping the engine, in addition to the control by the high-pressure pump control means 41, at least the intake air to the cylinders 3A and 3C in the expansion stroke cylinder 3A and the compression stroke cylinder 3C is increased in order to increase the resistance to the movement toward the piston top dead center. The throttle valve 17 is opened for a predetermined period during the engine stop operation period so as to increase the amount, particularly to supply more intake air to the expansion stroke cylinder 3A.
[0068]
When the basic restart condition or the I / S prohibition condition is satisfied after the engine 1 is automatically stopped in this way, it is determined that the restart condition is finally satisfied (in this specification, this is referred to as the satisfaction of the restart condition). Restart is performed. That is, the fuel injection from the fuel injection valve 8 and the ignition of the ignition plug 7 are restored.
[0069]
At the time of restarting, first, the first combustion is performed on the compression stroke cylinder 3C to slightly reverse the engine, so that the in-cylinder pressure is increased by raising the piston of the expansion stroke cylinder 3A. The combustion is performed in the expansion stroke cylinder 3A.
[0070]
In the present embodiment, the first combustion in the compression stroke cylinder 3C and the combustion in the expansion stroke cylinder 3A are performed as described above, and the air for combustion is left in the compression stroke cylinder 3C after the first combustion to compress. A first restart control mode in which recombustion is performed when the piston 4 of the stroke cylinder 3C starts rising and reaches near the top dead center, and a first combustion in the compression stroke cylinder 3C and a combustion in the expansion stroke cylinder 3A. Restart control mode in which recombustion in the compression stroke cylinder 3C is not performed, and combustion and expansion in the expansion stroke cylinder 3A while assisting with the starter 28 without performing initial combustion in the compression stroke cylinder 3C. The third restart control mode for starting by combustion in the next compression stroke cylinder 3C is selectively executed in accordance with the stop position of the piston 4.
[0071]
The cam phase control means 35 outputs a phase change signal of the camshafts 26 and 27 with respect to the crankshaft 6 to the cam phase variable mechanisms 26a and 27a to control the opening / closing timing of the intake valve 11 and the exhaust valve 12. As a result, the optimal opening and closing timing of the intake and exhaust valves according to the engine speed is set, and control for obtaining high output over a wide rotation range is performed.
[0072]
The display control means 36 performs ON / OFF control of the idle stop display lamp 71 according to the execution status of the I / S. The idle stop display lamp 71 includes an automatic stop lamp, an idle stop prohibition lamp, and a restart lamp (not shown). During the automatic stop of the engine by the I / S, the automatic stop lamp is turned on, while the I / S prohibition condition is satisfied, the idle stop prohibition lamp is turned on, and when the engine is restarted, the restart lamp is turned on. In this way, the driver can recognize the control state of the idle stop.
[0073]
The AT control means 37 outputs a switching command signal to the ATF switching valve 73 when the pressure of the hydraulic oil supplied to the automatic transmission decreases due to the execution of the idle stop, and supplies the hydraulic oil supply path. Is switched from a mechanical oil pump (not shown) driven by the engine 1 to the electric oil pump 72, and an operation command signal for operating the electric oil pump 72 is output. It is configured to supply hydraulic oil at a predetermined pressure.
[0074]
The hill holder control means 38 controls the hill holder by the hill holder solenoid valve 74 while the engine is stopped by the I / S.
[0075]
The operation of the above-described device of the present embodiment will be described below.
[0076]
In the engine 1 that is a four-cylinder four-cycle engine, each cylinder 3 performs a cycle including intake, compression, expansion, and exhaust strokes with a predetermined phase difference. As shown in FIG. Are performed in the order of the first cylinder 3A, the third cylinder 3C, the fourth cylinder 3D, and the second cylinder 3B with a phase difference of 180 ° (180 ° CA) in crank angle.
[0077]
Similarly, the cam nose 165 of the fuel pump cam 164 raises and lowers the plunger 163 at a cycle of 180 ° CA, and the position corresponding to the top of the cam nose 165 is near the compression top dead center. It becomes maximum near the boundary of the stroke and becomes minimum near the middle of each stroke. When the high-pressure pump solenoid 160 is turned on, the load of the crankshaft 6 by the high-pressure fuel pump 126 corresponds to the increase or decrease of the plunger stroke.
[0078]
In a case where the engine 1 is operating and a predetermined idling state that does not require the output of the engine 1 is performed, the idle stop is executed based on the determination whether the engine stop condition is satisfied or not.
[0079]
When the engine stop condition is satisfied at time t1, a series of controls for stopping the engine by idling stop are performed. In order to stop the engine, first, the fuel supply is stopped (fuel cut). In performing the fuel cut, a fuel cut permissible rotation speed (fuel supply stop permissible rotation speed) region is provided, and the fuel cut is performed while aiming at a time when the engine rotation speed is within the fuel cut permissible rotation speed region. ing. For example, the target rotation speed range of the idle rotation speed is set to 650 ± 50 rpm, whereas the fuel cut allowable rotation speed range is set to 650 ± 10 rpm. That is, when the engine speed fluctuates in the range of 650 ± 50 rpm during idling, the fuel cut is performed aiming at the moment when the engine speed enters the range of 650 ± 10 rpm.
[0080]
This is performed to stop the piston 4 within a preferable range for restarting (the range A in FIG. 8). When the fuel cut is performed in the fuel cut allowable rotation speed range, the piston 4 falls within the preferable range. It has been confirmed that the probability of stopping at the vehicle increases. If the engine speed when the engine stop condition is satisfied is within the fuel cut allowable speed range, the fuel is cut immediately.
[0081]
When the engine speed falls within the fuel cut permissible speed range, fuel cut is performed (fuel cut time t2). At the same time, the drive signal of the high-pressure pump solenoid 160, which has been intermittently repeated ON-OFF, is temporarily fixed to OFF as shown in the figure. By doing so, even if the plunger 163 moves up and down, the work becomes ineffective, that is, the fuel is not fed to the fuel injection valve 8, so that the fuel pressure does not increase more than necessary and the injection amount immediately after restart is excessive. And the occurrence of fuel leakage is effectively prevented.
[0082]
Then, at the fuel cut time t2, the fuel is cut, the throttle valve 17 is opened to a predetermined opening, and thereafter, the time t3 when the engine speed drops to a predetermined speed N3 (N3 = 500 rpm in this embodiment). To control the throttle valve 17 to close. As a result, the probability that the engine stop position falls within a preferable range is increased by utilizing the pressure of the air in the cylinder 3.
[0083]
That is, from the time point t2 to the time point t3, the throttle valve 17 is opened to a predetermined opening degree, so that the intake negative pressure temporarily decreases (increases the intake air amount) with some time delay, and thereafter, the intake pressure negative pressure decreases. Although the pressure increases (the intake air amount decreases), the above-described predetermined rotation speed and the like are set in advance so that the period during which the intake negative pressure temporarily decreases substantially corresponds to the period during the intake stroke of the expansion stroke cylinder 3A. . As a result, compared to the case where the throttle valve 17 is not opened, the amount of air taken into each cylinder 3 before the engine stops is increased, and especially the amount of intake air flowing into the expansion stroke cylinder 3A is increased.
[0084]
Then, when the engine is stopped, in the compression stroke cylinder 3C, as the piston 4 approaches the top dead center, the air in the cylinder 3C is compressed and a pressure acts in a direction to push the piston 4 back, so that the engine 1 reverses. When the piston 4 of the compression stroke cylinder 3C is pushed back to the bottom dead center side, the piston 4 of the expansion stroke cylinder 3A moves to the top dead center side, whereby the air in the cylinder 3A is compressed, and The piston 4 of the expansion stroke cylinder 3A is pushed back to the bottom dead center side. In this way, the piston 4 stops after it has vibrated to some extent. At this time, in the compression stroke and the expansion stroke, the closer the piston 4 is to the top dead center, the greater the force to push it back. In many cases, the position is close to the part (range A in FIG. 6).
[0085]
By increasing the intake air amount before stopping the engine as described above, the force for pushing back the piston 4 when approaching the top dead center increases, so that the probability that the piston 4 stops within the range A increases. Further, if the intake amount of the expansion stroke cylinder 3A is set to be larger than that of the compression stroke cylinder 3C by controlling the throttle valve 17 as described above, the piston 4 in the expansion stroke cylinder 3A may be in the range close to the middle of the stroke. However, it often stops slightly near the bottom dead center (range A2 in FIG. 6).
[0086]
As described above, the engine speed N2 at the fuel cut time t2 is set within the fuel cut allowable rotation speed range 83, and the torque generated after the fuel cut is suppressed. Is easily stopped in the range A2.
[0087]
Since the engine 1 rotates several times by inertia from the fuel cut to the complete stop of the engine 1, the burned gas is discharged and the inside of the cylinder becomes almost fresh even during the expansion stroke. Further, when the engine 1 stops, the pressure immediately leaks even in the compression stroke cylinder 3C. Therefore, after the engine is stopped, all cylinders are in a state in which fresh air of approximately atmospheric pressure exists in the cylinder.
[0088]
Further, the throttle valve 17 may not be closed until the engine stops. However, since the intake amount continues to be large until the engine stops, the pushing force of the piston 4 due to the compression of the intake is hardly attenuated. In some cases, the number of vibrations increases, and the swing back increases when the engine is stopped. Therefore, it is desirable to close the throttle valve 17 at a suitable time t3 as shown in the present embodiment.
[0089]
Then, when the engine speed decreases and immediately before the stop, the high-pressure pump solenoid 160 is turned on again as shown in the drawing to turn the pump ON. By doing so, the fuel pressure at the time of restart is ensured. The timing at which the pump is turned on is set so that the fuel pressure at the time of restarting becomes an appropriate value (about 3 MP) in consideration of the pressure drop during engine stop. At this time, the fuel pressure may be determined by feeding back the fuel pressure by the fuel pressure sensor 69.
[0090]
The stop position of the piston 4 when the engine is stopped is detected as follows based on signals from the crank angle sensors 21 and 22. FIG. 9 is a pulse signal obtained by rotation of the crankshaft 6, and shows a first crank angle signal CA1 from the crank angle sensor 21 and a second crank angle signal CA2 from the crank angle sensor 22. FIG. 9A shows the case of normal rotation (clockwise in the state of FIG. 1), and FIG. 9B shows the case of reverse rotation. During normal rotation of the engine, as shown in FIG. 9A, the second crank angle signal CA2 has a phase delay of about a half pulse width with respect to the first crank angle signal CA1, so that the first crank angle signal CA1 At the time of rising, the second crank angle signal CA2 becomes Low, and at the time of falling of the first crank angle signal CA1, the second crank angle signal CA2 becomes High. On the other hand, when the engine is running in reverse, as shown in FIG. 9B, the second crank angle signal CA2 is generated with a phase advance of about a half pulse width with respect to the first crank angle signal CA1, so that when the engine is running forward. Conversely, when the first crank angle signal CA1 rises, the second crank angle signal CA2 becomes High, and when the first crank angle signal CA1 falls, the second crank angle signal CA2 becomes Low. The ECU 30 detects this difference and counts the pulse signals while determining whether the crankshaft 6 is rotating forward or reverse. The counted value is stored as a CA counter value, and is constantly updated while the engine 1 is operating. The state in which the CA counter value does not increase or decrease is the stop of the engine 1, and the stop position of the piston 4 is detected based on the CA counter value at that time.
[0091]
FIG. 10 is a flowchart for integrating the CA counter value. After the start, in step S51, the second crank angle signal CA2 is low when the first crank angle signal CA1 rises, or the second crank angle signal CA2 becomes high when the first crank angle signal CA1 falls. It is determined whether the engine 1 is running, and if YES, it indicates that the engine 1 is rotating forward, so the flow shifts to step S52 to add the measured pulse number to the CA counter value (CA counter up). If “NO” in the step S51, it indicates that the engine 1 is running in the reverse direction, and the process shifts to a step S53 to subtract the measured pulse number from the CA counter value (CA counter down).
[0092]
Next, the restart of the engine will be described. When the basic restart condition or the I / S prohibition condition is satisfied after the engine is stopped, it is determined that the restart condition has been satisfied, and control for automatically restarting the engine 1 is performed. At this time, if the stop position of the piston 4 is within the predetermined range near the middle of the stroke in the expansion stroke cylinder 3A and is in the range A1 (FIG. 8) near the top dead center, the first restart control mode is executed. Is done.
[0093]
FIG. 11 shows the stroke of each cylinder of the engine in the first restart control mode and the combustion in each cylinder from the start of the start control ((1), (2), (3)... , And the operation direction of the engine by each combustion is indicated by an arrow, and FIG. 12 shows the engine rotation speed, the crank angle, and the angular cylinder in the first restart control mode. The time-dependent changes in the cylinder pressure and the indicated torque are shown.
[0094]
As shown in these figures, in the case of the first restart control mode, first, the first combustion is performed while the combustion air-fuel ratio in the compression stroke cylinder 3C is leaner than the stoichiometric air-fuel ratio ((1) in FIG. 11). The piston 4 of the compression stroke cylinder is pushed down to the bottom dead center side by the combustion pressure (a portion in FIG. 12) by this initial combustion, and the engine 1 is driven in the reverse rotation direction, and accordingly, the expansion stroke cylinder 3A When the piston 4 approaches the top dead center, the air in the cylinder 3A is compressed and the in-cylinder pressure rises (portion b in FIG. 12). Then, when the piston 4 of the expansion stroke cylinder 3A sufficiently approaches the top dead center, ignition is performed on the cylinder 3A, and the fuel previously injected into the cylinder 3A burns ((2) in FIG. 11). ▼), the engine 1 is driven in the normal rotation direction by the combustion pressure (portion c in FIG. 12). Further, by injecting fuel into the compression stroke cylinder 3C at an appropriate timing, the second combustion in the cylinder 3C is performed near the top dead center of the compression stroke cylinder 3C ((3) in FIG. 11). ▼). The combustion pressure (d portion in FIG. 12) increases the engine driving force.
[0095]
In this case, in the first combustion of the compression stroke cylinder 3C, since the air-fuel ratio is lean, air remains in the cylinder 3C even after the first combustion, so that the second combustion can be performed. Then, since the fuel is injected and the compression is performed in a state where the temperature in the compression stroke cylinder 3C is high by the first combustion, the second combustion in the cylinder 3C is performed by the compression self-ignition.
[0096]
After the second combustion has been performed in this way, after reaching the compression top dead center of the cylinder (the fourth cylinder 3D), which is in the next compression stroke after the cylinder 3C, the cylinders are sequentially controlled by the normal control. Combustion is performed and restart is completed.
[0097]
In order to properly perform the fuel injection at the initial stage of the restart as described above, it is desirable that the fuel pressure be a predetermined value (for example, about 3MP). In this embodiment, the fuel pressure is increased just before the engine is stopped by setting the pump to the ON state. Further, since the pump is kept ON even when the engine is stopped, the fuel pressure is rapidly increased at the time of restart, and good combustion is easily obtained. This is the same in the second restart control mode and the third restart control mode described below.
[0098]
When the stop position of the piston 4 is within the predetermined range near the middle of the stroke in the expansion stroke cylinder 3A and in the range A2 near the bottom dead center (see FIG. 8), the restart is performed according to the second restart control mode. Control is performed.
[0099]
As control in the second restart control mode, first-time combustion (combustion corresponding to (1) in FIG. 11) is performed in the compression stroke cylinder 3C while the combustion air-fuel ratio is set to substantially the stoichiometric air-fuel ratio or richer. Is Then, the piston 4 of the compression stroke cylinder 3C is depressed by the first combustion, and the engine 1 is driven in the reverse direction. As the piston 4 of the expansion stroke cylinder 3A approaches the top dead center, the air in the cylinder 3A is compressed. When the in-cylinder pressure rises and the piston of the expansion stroke cylinder 3A sufficiently approaches the top dead center, the cylinder 3A is ignited, and the fuel previously injected into the cylinder 3A burns ( The fact that the engine 1 is driven in the normal rotation direction by (corresponding to (2) in FIG. 11) is the same as the control in the first restart control mode. However, in the second restart control mode, when the compression stroke cylinder 3C passes the top dead center after the combustion of the expansion stroke cylinder 3A, the combustion (the combustion of (3) in FIG. 11) is not performed. The rotation of the engine is maintained by inertia until the compression cylinder reaches the compression top dead center of the arriving cylinder (the fourth cylinder 3D).
[0100]
As described above, the first restart control mode and the second restart control mode are selectively used depending on the stop position of the piston 4, so that the engine 1 is effectively restarted. This will be described with reference to FIG.
[0101]
FIG. 13 shows the relationship between the piston position when the engine is stopped and the required air-fuel ratio, the amount of air in the compression stroke cylinder 3C, the amount of air in the expansion stroke cylinder 3A, and the frequency of occurrence in the first combustion (for reverse rotation) of the compression stroke cylinder 3C. As shown in this figure, as the piston 4 of the expansion stroke cylinder 3A approaches the top dead center (the piston 4 of the compression stroke cylinder 3C approaches the bottom dead center) when the engine is stopped, the amount of air in the expansion stroke cylinder 3A decreases and the compression increases. The air amount of the stroke cylinder 3C increases, and conversely, the air amount of the expansion stroke cylinder 3A increases as the piston 4 of the expansion stroke cylinder 3A approaches the bottom dead center (the piston 4 of the compression stroke cylinder 3C approaches the top dead center). The amount of air in the compression stroke cylinder 3C decreases.
[0102]
Further, in the first combustion in the compression stroke cylinder 3C, the engine is reversed to a predetermined position where the piston 4 of the compression stroke cylinder 3C is slightly before the bottom dead center (the piston 4 of the expansion stroke cylinder 3A is slightly before the top dead center). However, if the piston 4 of the compression stroke cylinder 3C is close to the top dead center, the amount of air in the compression stroke cylinder 3C is small, and the reverse rotation to the predetermined position is required. Since the required torque is relatively large, the required air-fuel ratio becomes rich. On the other hand, if the piston 4 of the compression stroke cylinder 3C is near the bottom dead center, the amount of air in the compression stroke cylinder 3C is large and the predetermined position The required air-fuel ratio is lean because the torque required for the reverse rotation up to is relatively small.
[0103]
In the expansion stroke cylinder 3A, since the amount of air is larger as the piston 4 is closer to the bottom dead center, more fuel can be burned.
[0104]
Therefore, when the piston position of the expansion stroke cylinder 3A is within a predetermined range A2 closer to the bottom dead center than the middle portion (the piston position of the compression stroke cylinder 3C is closer to the top dead center) when the engine is stopped, the compression stroke cylinder 3C is in the initial combustion state. The air-fuel ratio is made rich so as to meet the above requirement, and the second combustion near the compression top dead center is not performed because the combustion air does not remain after the first combustion. However, the air amount is small in the expansion stroke cylinder 3A. A relatively large amount of fuel is injected, and then, after being compressed, ignition and combustion are performed, a relatively large torque is obtained, and the compression stroke of the compression stroke cylinder 3C exceeds the compression top dead center. The engine can be rotated until it exceeds the compression top dead center of the next cylinder, and restart can be achieved.
[0105]
On the other hand, when the engine is stopped, the piston position of the expansion stroke cylinder 3A is in a predetermined range A1 closer to the top dead center than the middle portion (the piston position of the compression stroke cylinder 3C is closer to the bottom dead center), compared to the case where the piston position is in the range A2. Since the amount of air in the expansion stroke cylinder 3A is small, the torque obtained by combustion in the expansion stroke is small. However, in the compression stroke cylinder 3C, the air-fuel ratio at the time of the first combustion is made lean in response to the above-mentioned demand. Since the excess air remaining after the first combustion is used to perform the second combustion near the compression top dead center, the torque for driving the engine in the normal rotation direction is supplemented, and the combustion in the expansion stroke cylinder 3A is reduced. Both the second combustion in the compression stroke cylinder 3C provides enough torque to achieve a restart.
[0106]
By the way, in the present embodiment, when the engine is stopped, the throttle valve 17 is opened for a predetermined period after the fuel supply is stopped and the intake air amount is increased for a predetermined period, thereby increasing the compression stroke cylinder 3C and the expansion stroke cylinder 3A. Since the resistance of the piston 4 to the movement toward the top dead center is increased and the intake amount of the expansion stroke cylinder 3A is increased, as shown in FIG. In most cases, the piston position at 3A is within a predetermined range A near the middle of the stroke, and among them, it is often within a range A2 closer to the bottom dead center, and thus the stop position is adjusted. The restart is performed effectively.
[0107]
That is, when the piston stop position is too close to the top dead center side of the expansion stroke cylinder 3A (the bottom dead center side of the compression stroke cylinder 3C) from the range A, a sufficient amount of movement in the engine reverse direction is required. And the amount of air in the expansion stroke cylinder 3A decreases, so that the torque obtained by combustion in the expansion stroke cylinder 3A decreases, and the bottom dead center side of the expansion stroke cylinder 3A (compression stroke cylinder) exceeds the above range. If it is too close to 3C (top dead center side), the amount of air in the compression stroke cylinder 3C becomes small, so that sufficient torque for engine reverse rotation cannot be obtained. On the other hand, if the piston stop position is within the range A, the reverse rotation drive by the initial combustion in the compression stroke cylinder 3C is possible, and the combustion in the expansion stroke cylinder 3A is favorably performed, and the combustion energy is reduced. The piston can sufficiently act on the piston. In particular, if the piston stop position is in the range A2 near the bottom dead center of the expansion stroke cylinder 3A, a sufficiently large amount of air in the expansion stroke cylinder 3A can be ensured, and the expansion stroke cylinder 3A Combustion energy can be increased and startability can be improved.
[0108]
In the rare case where the piston position when the engine stops is out of the range A, or when the in-cylinder temperature decreases while the engine stops and the coolant temperature Tc becomes Tc <60 ° C., the third resetting is performed. The start control mode is executed, and the starter 28 assists the start.
[0109]
The specific configuration of the device of the present invention is not limited to the above embodiment, but can be variously modified within the scope of the claims. For example, although the number of the cam nose 165 is four, the number of the cam nose 165 may be two (the plunger stroke is 360 ° CA cycle) in a similar four-cylinder engine. Alternatively, the number may be 6, 8,..., But if it is too large, the amplitude of the load by the high-pressure fuel pump 126 will be small, and the effect of stopping the piston 4 at the appropriate position will be small.
[0110]
For engines other than four cylinders, for example, engines such as six cylinders and eight cylinders, the number of cam nose 165 may be set according to the number of cylinders and the type of cylinder arrangement (serial or V-type). For example, in the case of an inline 6 cylinder, the number of cam nose 165 is set to 6 or 3, and in the case of a V-type 6 cylinder, a high-pressure fuel pump 126 is provided for each bank (three cylinders arranged in a straight line). The number is three, and so on.
[0111]
Further, the type of the high-pressure fuel pump 126 does not need to be the plunger 163 and the fuel pump cam 164 as in the present embodiment, but is taken out as work that fluctuates periodically according to the rotation angle of the crankshaft 6. If it is, another type, for example, a gear pump or a vane pump, may be used.
[0112]
In the above embodiment, when the engine is started when the piston position when the engine is stopped is within a predetermined range, the first combustion is performed in the compression stroke cylinder 3C, the engine is slightly reversed, and then the combustion in the expansion stroke cylinder 3A is performed. Although the engine is not reversed by the initial combustion in the compression stroke cylinder 3C, the fuel is supplied to the expansion stroke cylinder 3A immediately when the engine is stopped and ignited after a predetermined time, thereby igniting the expansion stroke cylinder 3A. May be performed first.
[0113]
【The invention's effect】
As described above, according to the engine starter of the present invention, when a predetermined engine stop condition is satisfied, the fuel supply is automatically stopped to stop the engine. In an engine starting device that injects fuel into a cylinder in a stroke to cause ignition and combustion and restarts the engine, a part of the driving force of the engine is periodically changed according to the rotation angle of the crankshaft. A mechanical high-pressure fuel pump for increasing the fuel pressure for injecting fuel, taking out as a fluctuating work, comprising, when the rotation angle of the crankshaft is substantially at the top dead center of some or all cylinders, When the instantaneous work of the pump is maximized, and the rotation angle of the crankshaft is approximately halfway between the top dead center and the bottom dead center of some or all cylinders, Since the instantaneous work of the high-pressure fuel pump is configured to be minimized, variation in the stop position of the piston is reduced without providing a special braking device or the like, and the piston is stopped at an appropriate position with a higher probability. be able to. That is, by improving the restartability of the engine with a simple structure, further reduction in fuel consumption and CO ₂ Emissions can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of an engine provided with a starting device according to an embodiment of the present invention.
FIG. 2 is a schematic plan view of the engine.
FIG. 3 is a block diagram showing a specific configuration of a fuel supply system.
FIG. 4 is an explanatory diagram showing a specific structure of a high-pressure fuel pump.
FIG. 5 is an explanatory diagram showing an installation state of a high-pressure fuel pump.
FIG. 6 is a schematic control block diagram of an engine.
FIG. 7 is an explanatory diagram showing an engine speed, a throttle opening, a change in intake pipe negative pressure, a plunger stroke, a drive signal for a high-pressure pump solenoid, and a cycle of each cylinder when the engine is stopped.
FIG. 8 is an explanatory diagram showing setting of a range for selecting a restart control mode according to a piston position when the engine is stopped.
FIGS. 9A and 9B show crank angle signals from two crank angle sensors, wherein FIG. 9A shows a signal at the time of forward rotation of the engine, and FIG. 9B shows a signal at the time of reverse rotation of the engine.
FIG. 10 is a flowchart showing a process for detecting a piston position when the engine is stopped.
FIG. 11 is an explanatory diagram showing a cycle and a combustion operation of each cylinder when the engine is restarted.
FIG. 12 is an explanatory diagram showing changes in engine speed, crank angle, in-cylinder pressure of each cylinder, and indicated torque when the engine is restarted.
FIG. 13 is an explanatory diagram showing a relationship between a piston position when the engine is stopped, a required air-fuel ratio of a compression stroke cylinder, an air amount of a compression stroke cylinder, an air amount of an expansion stroke cylinder, and an occurrence frequency.
[Explanation of symbols]
1,1a engine
3 (3A, 3B, 3C, 3D) cylinder (first cylinder,..., Fourth cylinder)
4 piston
6 Crankshaft
7 Spark plug
8 Fuel injection valve
11 Intake valve
12 Exhaust valve
17 Throttle valve
30 ECU
69 Fuel pressure sensor (fuel pressure detecting means)
120 Fuel supply system
126 High pressure fuel pump
155 Suction valve (pump switching means)
160 High pressure pump solenoid (pump switching means)
163 plunger
164 Fuel pump cam
165 Cam Nose

Claims (9)

When the predetermined engine stop condition is satisfied, the fuel supply is automatically stopped to stop the engine, and when the restart condition is satisfied after the engine is stopped, fuel is injected into a cylinder in an expansion stroke to ignite, In an engine starting device that causes combustion and restarts the engine,
Equipped with a mechanical high-pressure fuel pump that extracts a part of the driving force of the engine as work that fluctuates periodically according to the rotation angle of the crankshaft, and increases the fuel pressure for injecting fuel.
When the rotation angle of the crankshaft is substantially at the top dead center of some or all cylinders, the instantaneous work of the high-pressure fuel pump is maximized, and the rotation angle of the crankshaft is part or all. An engine starting device characterized in that the instantaneous work of the high-pressure fuel pump is minimized when the cylinder is approximately halfway between the top dead center and the bottom dead center of the cylinder. The rotation angle of the crankshaft at which the instantaneous work of the high-pressure fuel pump is minimized is set to be slightly later than the middle between the top dead center and the bottom dead center in the stroke of some or all cylinders. The engine starting device according to claim 1, wherein The work of the high-pressure fuel pump is taken out by rotation of a fuel pump cam having a rotation angle corresponding to the rotation angle of a crankshaft, and the high-pressure fuel pump has a cam nose having a large cam radius. 3. The engine starting device according to claim 1, wherein the instantaneous work of the pump is configured to be large. The engine starting device according to claim 3, wherein the number of the cam nose is a multiple of one half of the number of cylinders of the engine. The engine starting device according to claim 4, wherein the number of the cam nose is equal to the number of cylinders of the engine. The rotation of the fuel pump cam makes the work of the high-pressure fuel pump effective, and the pump is in an ON state in which the fuel pressure is increased. Even if the fuel pump cam rotates, the work of the high-pressure fuel pump is not effective, and Pump switching means capable of switching to a pump OFF state where the pressure does not increase,
6. The pump switching unit according to claim 1, wherein the pump switching unit is in a pump ON state at least from immediately before the engine is stopped after the predetermined engine stop condition is satisfied until the engine is completely stopped. Engine starter. 7. The engine starting device according to claim 6, wherein the pump switching means keeps the pump OFF for a predetermined period immediately before the engine is stopped after the predetermined engine stop condition is satisfied. 8. The engine starting device according to claim 6, wherein the pump switching means switches between the pump ON state and the pump OFF state so that the fuel pressure at the time of restarting the engine becomes a predetermined pressure. . 9. The engine starting device according to claim 8, further comprising fuel pressure detecting means for detecting a fuel pressure, wherein the switching between the pump ON state and the pump OFF state is performed by feedback control.

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