JP2005002847A - Engine starting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine starting system, in which a quick starting can be made, while the starting is assisted as required by a starter motor, and the quietude is improved. <P>SOLUTION: At the time of engine stop before starting, combustion is produced in a cylinder 3C in a compression stroke to reverse once the engine. Then, at the time of engine stop, combustion is produced in a cylinder 3A in an expansion stroke. In the engine starting system, a starter motor 28 and a compression-level discrimination means are provided, which discriminates a compression level in the state of the cylinder 3A in which compression is attained by reversion of the engine. When the compression level is discriminated to be at most a specified level, starting in the forward direction is assisted by the starter motor 28 at a point in time or thereabout when the engine is shifted from reverse to forward rotation. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an engine starter, and more particularly to an engine starter that is suitable for a case where an engine is automatically stopped once at idling or the like and then automatically restarted thereafter.
[0002]
[Prior art]
In recent years, fuel consumption reduction and CO ₂ A so-called idle stop technology has been developed that automatically stops the engine when idling to suppress emissions, and then restarts the engine automatically when a restart condition such as start operation is established. ing.
[0003]
The restart at the idle stop requires quickness to start immediately according to the start operation, etc., so that the engine is started through cranking that drives the engine output shaft (crankshaft) by the starter motor. Conventional general start-up methods that require considerable time to complete are not preferred.
[0004]
Therefore, as a starting device suitable for restarting the idle stop, fuel is supplied to a specific cylinder (cylinder in the expansion stroke) of the stopped engine to cause ignition and combustion, and the engine is instantly started with the energy. What has been developed has been developed. Generally, even if fuel is simply supplied to a cylinder in an expansion stroke to ignite and burn, a sufficient torque for starting the engine is not always obtained. In order to perform the restart smoothly, the generated torque needs to be greater than a certain level, and the starting device is required to have a technique for satisfying this.
[0005]
As such technology, after IG OFF (ignition stop), control the exhaust valve closing timing and stop the engine with the piston in the proper position (generally near the top dead center and bottom dead center) What is made easy to do (for example, refer patent document 1) is known. When the piston is stopped at an appropriate position, an appropriate amount of air is obtained at the time of restart, and a torque exceeding a certain level is generated by combustion, so that restartability can be improved.
[0006]
While improving restartability in this way, technology has also been developed to ensure restarting even when the piston does not stop at the proper position or when the restartability is low due to other factors. ing. For example, there is known a starting device that assists starting (assuming driving force supplementarily) by a starter motor when starting of the engine is incomplete (see, for example, Patent Document 2).
[0007]
[Patent Document 1]
WO 01/44636 A2 publication
[Patent Document 2]
JP 2002-004985 A
[0008]
[Problems to be solved by the invention]
However, the starting device disclosed in Patent Document 2 detects the engine speed after a predetermined time has elapsed after starting, and assists the motor (starter motor) when the engine speed is below the predetermined speed. Therefore, a delay of at least the predetermined time is inevitable until the assist is started. For this reason, although a restart failure can be avoided, there remains a problem with respect to quick start-up.
[0009]
In addition, there is a high demand for quietness in the restart by idle stop. This is because the start does not depend on the driver's operation (ignition key ON), and therefore it is easy to give the driver a sense of discomfort even with relatively small noise. On the other hand, when assistance is provided by a general starting mechanism in which a pinion driven by a starter motor rotates a startering gear (directly connected to a crankshaft), the higher the engine speed, the greater the relationship between the pinion and the startering gear. There is a tendency that noise generated in the middle (so-called cranking noise) increases. Since the starting device shown in Patent Document 2 starts assist after the engine speed has increased to some extent, the assist is inevitably continued to a relatively high speed. For this reason, there was a problem that cranking noise tends to be large and quietness at the time of starting is low.
[0010]
SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides an engine starter capable of improving the quickness of start and further improving the quietness while assisting start by a starter motor as necessary. Is.
[0011]
[Means for Solving the Problems]
According to the first aspect of the present invention, when starting the engine, fuel is supplied to the cylinder substantially in the compression stroke and the cylinder substantially in the expansion stroke when the engine is stopped before the start. Ignition and combustion are performed in the cylinders in the compression stroke, and the engine is temporarily reversed until near the compression bottom dead center. Thereafter, ignition and combustion are performed in the cylinders substantially in the expansion stroke, and the engine is started in the forward rotation direction. In the engine starting device, a compression level determining means for determining a compression level when the cylinder substantially in the expansion stroke is in a compressed state due to the reverse rotation of the engine, and a driving force in the forward rotation direction is applied to the engine. When the engine rotation direction shifts from reverse rotation to normal rotation when the compression level determination means determines that the compression level is below a predetermined level. Optimum in the vicinity thereof, characterized in that to assist the starting of the forward direction by the starter motor.
[0012]
According to this configuration, fuel is supplied to the cylinder that is substantially in the compression stroke and the cylinder that is substantially in the expansion stroke when the engine is stopped before starting, and ignition and combustion are performed in the cylinder that is substantially in the compression stroke. To reverse the engine to near compression bottom dead center, and then the cylinder in the above expansion stroke (this cylinder is compressed by the piston moving in the reverse direction due to the reverse rotation, and the in-cylinder pressure increases. Therefore, it is possible to generate a torque sufficient to start the engine in the forward rotation direction, and to easily start the engine without applying an external driving force. That is, startability can be improved.
[0013]
The cylinder substantially in the compression stroke refers to a cylinder in a state where the volume in the sealed cylinder is reduced to compress the in-cylinder gas, and other than the cylinder in the original compression stroke, for example, The cylinder is in the exhaust stroke (the operation direction of the piston is the same as that of the compression stroke), but includes a cylinder in which the exhaust valve is closed using an electromagnetic valve or the like. Similarly, the cylinder substantially in the expansion stroke refers to a cylinder in a state where the gas volume in the sealed cylinder is expanded to increase the cylinder volume. In addition to the cylinder in the original expansion stroke, for example, Although the cylinder is originally in the intake stroke (the operation direction of the piston is the same as that of the expansion stroke), it includes one that burns with the intake valve closed using an electromagnetic valve or the like. Hereinafter, unless otherwise specified, a cylinder in a compression stroke (also referred to as a compression stroke cylinder) or a cylinder in an expansion stroke (also referred to as an expansion stroke cylinder) includes a cylinder that is substantially in the compression stroke (or expansion stroke). Shall be included.
[0014]
By the way, in order to perform a stable start by this starting method, it is necessary that the in-cylinder gas (air or air-fuel mixture) is sufficiently compressed to an extent that the expansion stroke cylinder is ignited reliably and good combustion is performed. Yes (in this specification, such a compression state is referred to as a high compression level). However, there are many variations in starting conditions such as the piston position when the engine is stopped and the length of the engine stopping period, and the compression level may be lowered depending on the conditions. Even in such a case, according to the configuration of the first aspect, the compression level determination means determines the compression level when the expansion stroke cylinder is in the compression state by the reverse rotation of the engine, and is below a predetermined level. When it is determined, the starter motor assists the start in the forward rotation direction, so that stable startability can be ensured.
[0015]
In addition, the compression level is determined based on the state during engine reverse rotation, and if necessary, the starter motor assists start in the normal rotation direction at or near the time when the engine shifts from reverse rotation to normal rotation. As a result, the speed of starting can be improved.
[0016]
Compared to the conventional technology that starts assisting after engine speed has increased to some extent, the engine speed at the time of assist can be lowered, so when a mechanism that assists using a pinion and a startering gear is adopted The cranking noise can be reduced, and the starting silence can be improved.
[0017]
In order to determine the compression level, there is provided a rotation speed level determination means for determining the rotation speed level at the time of reverse rotation of the engine. The compression level determination means increases the compression level as the rotation speed level by the rotation speed level determination means increases. (Claim 2).
[0018]
Here, the rotational speed level is an index that generally increases as the absolute value of the rotational speed increases. For example, the rotational speed level includes rotational speed detection means for detecting the rotational speed of the engine, and the rotational speed level is determined. The means can determine that the rotational speed level is higher as the absolute value of the maximum rotational speed during engine reverse rotation is higher. This maximum rotation speed may be replaced with an average rotation speed (claim 4).
[0019]
A high rotational speed level means that the piston moves fast during reverse rotation, indicating that the compression speed is high. If the compression speed is high, the increase in in-cylinder pressure due to compression becomes large, so that the torque generated during combustion can be increased. That is, if the other conditions are the same, the higher the rotational speed level, the higher the compression level.
[0020]
An in-cylinder pressure determining means for determining an in-cylinder pressure level of the cylinder substantially in the expansion stroke at the time of reverse rotation of the engine, the compression level determining means compresses as the in-cylinder pressure level is increased You may comprise so that it may discriminate | determine that a level is high (Claim 5).
[0021]
Here, the in-cylinder pressure level is an index that generally increases as the in-cylinder pressure increases. For example, if the in-cylinder pressure is directly measured by a finger pressure sensor or the like, the in-cylinder pressure level increases as the in-cylinder pressure increases. Can be high.
[0022]
A high in-cylinder pressure level indicates that the substantial compression ratio during reverse rotation is large. When the compression ratio is large, the torque generated during combustion can be increased. That is, if the other conditions are the same, the higher the in-cylinder pressure level, the higher the compression level.
[0023]
Here, the substantial compression rate refers to the volume change rate of the in-cylinder gas taking gas leakage into consideration. Normally, if there is a gas leak in the combustion chamber, it is extremely small, so the compression ratio (apparent compression ratio) obtained by the change in the cylinder volume can be made a substantial compression ratio. However, at the time of starting, although it depends on the length of the stop time, the gas leakage from the piston ring becomes relatively large. In such a case, the internal gas is not compressed as much as the apparent compression rate. That is, the substantial compression rate is low (the in-cylinder pressure level is also low). By reflecting the determination result of the in-cylinder pressure level in the determination of the compression level, it is possible to determine the compression level more accurately based on the substantial compression rate.
[0024]
In addition, piston movement amount detection means for detecting the movement amount of the piston at the time of engine reverse rotation is provided, and the compression level determination means has a compression level as the piston movement amount at the time of engine reverse rotation by the piston movement amount detection means increases. It may be configured so as to be determined as high (Claim 6).
[0025]
A large amount of piston movement indicates that the apparent compression rate is large if the original stop position is the same. As described above, the apparent compression rate may not match the actual compression rate due to gas leakage, but if the other conditions are the same, the movement amount of the piston is large (the apparent compression rate is large). It may be determined that the compression level is higher. Since the piston movement amount can generally be measured more inexpensively and easily than the in-cylinder pressure level, it is also effective to use the piston movement amount as a substitute for the in-cylinder pressure level for cost reduction.
[0026]
The engine further includes stop time measuring means for measuring the engine stop time before starting when the engine is stopped from the operating state and then starting the engine, and the compression level determining means is configured to stop the engine stop time by the stop time measuring means. It may be determined that the shorter the is, the higher the compression level is (claim 7).
[0027]
When the engine is stopped from the operating state, the gas in the compression stroke cylinder leaks from the piston ring, and the in-cylinder pressure decreases with the passage of time (after a certain period of time, it becomes equal to the atmospheric pressure). Accordingly, the torque for reversely rotating the engine at the initial stage of restart decreases as the stop time increases. When the reverse rotational torque decreases, the moving speed of the piston, that is, the rotational speed level also decreases, resulting in a decrease in the compression level.
[0028]
Further, as the stop time elapses, the oil film breakage of the piston ring also increases, and the amount of gas leakage at the time of restart increases. That is, since the substantial compression rate is lowered, the compression level is lowered.
[0029]
In either case, the compression level decreases as the stop time elapses, so that the shorter the stop time, the higher the compression level can be determined.
[0030]
According to an eighth aspect of the present invention, in the engine starter according to any one of the first to seventh aspects, the startering gear that rotates integrally with the crankshaft is switched between a meshing state and a non-meshing state with respect to the startering gear. And a pinion that transmits the driving force of the starter motor to the starter ring gear in the meshed state, and the starter motor has a rotation speed near zero at which the rotational direction of the engine shifts from reverse rotation to normal rotation. The pinion is switched to the meshing state while the motor is not driven, and the starter motor is driven only when the compression level is determined to be equal to or lower than a predetermined level by the compression level determination means.
[0031]
In this way, it is possible to reduce the operation delay due to the arithmetic processing for determining the compression level. The parameter for determining the compression level may include a parameter (for example, an average rotation speed) that is not fixed unless the engine reverse rotation period ends. In such a case, according to the present configuration, the pinion and the starter gear are engaged with each other without waiting for the determination result of the compression level in the vicinity of the rotation speed zero where the rotation direction of the engine shifts from the reverse rotation to the normal rotation. In this way, when the determination result obtained after the calculation processing time is necessary to assist, torque can be applied to the starter gear simply by rotating the pinion that is already meshed. A start assist with high silence can be performed.
[0032]
In this case, after the rotational direction of the engine has shifted from reverse rotation to forward rotation, the pinion is switched to the non-engaged state in the vicinity of the time point when the cylinder in the intake stroke (hereinafter referred to as the intake stroke cylinder) starts combustion when the engine is stopped (claim). Item 9) may be used.
[0033]
When combustion in the intake stroke cylinder starts after the expansion stroke cylinder and compression stroke cylinder, normal combustion is performed in the subsequent cylinders without any assistance from the starter motor, and a smooth start is performed. When the combustion in the intake stroke cylinder starts, the engine speed is generally still lower than the complete explosion speed (a slightly lower speed than the idle speed). If the pinion is switched to the non-meshing state at such a low rotation, the meshing is released earlier than the case where the pinion is switched to the non-meshing state after reaching the complete explosion speed. Is improved. It should be noted that the start of combustion in the intake stroke cylinder may be detected when the engine speed becomes equal to or higher than a predetermined speed slightly lower than the complete explosion speed.
[0034]
On the other hand, if the determination result of the compression level is that the assist is unnecessary, it is only necessary to quickly switch to the non-meshing state without rotating the pinion.
[0035]
According to a tenth aspect of the present invention, in the engine starting device, when starting the engine, the fuel is supplied to the cylinder substantially in the expansion stroke when the engine is stopped before starting, and the engine is started by performing ignition and combustion. A starter motor that applies a driving force in the forward rotation direction, a starter ring gear that rotates integrally with the crankshaft, and a switchable state between the meshing state and the non-meshing state with respect to the startering gear. And a pinion that transmits the driving force of the starter motor to the startering gear. When the engine is in a predetermined state that is relatively difficult to start, the pinion is engaged and the starter motor is driven to assist in starting. After the engine starts in the forward direction, the cylinders in the intake stroke start burning when the engine stops Around time point, wherein the switching the pinion to the disengaged state.
[0036]
According to this configuration, even when the engine is relatively difficult to start, the engine can be started quickly and silently. In particular, as in the case of the ninth aspect, the quietness can be further improved as compared with the case where the pinion is switched to the non-engagement state after reaching the complete explosion speed. Note that this configuration is not limited to the case where the engine is once reversed at the time of starting, but also includes the case where the combustion is first performed in the expansion stroke cylinder and the engine is started from the normal rotation.
[0037]
Then, provided with a rotation speed detection means for detecting the rotation speed of the engine, the pinion is switched to the meshing state when the engine rotation speed is substantially zero, and only when the engine is in a predetermined state that is relatively difficult to start. Thereafter, if the starter motor is driven (claim 11), the start time of the pinion meshing can be advanced as early as possible, and the quickness and quietness can be further improved.
[0038]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0039]
1 and 2 show a schematic configuration of an engine according to an embodiment of the present invention. In these drawings, the main body of the engine 1 is composed of a cylinder head 2 a 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, the fourth cylinder in order from the left in the state shown in FIG. 2). 3D). A piston 4 is inserted 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.
[0040]
A spark plug 7 and a finger pressure sensor 26 for detecting the pressure in the combustion chamber 5 (in-cylinder pressure) are provided at the top of the combustion chamber 5 of each cylinder 3, and the tip thereof faces the combustion chamber 5.
[0041]
Further, a fuel injection valve 8 that directly injects fuel into the combustion chamber 5 is provided at a side portion of the combustion chamber 5. The fuel injection valve 8 includes a 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 timing. It is comprised so that the quantity of fuel according to may be injected. The injection direction of the fuel injection valve 8 is set so as to inject fuel toward the vicinity of the spark plug 7. The fuel injection valve 8 is supplied with fuel via a fuel supply passage or the like by a fuel pump (not shown), and a fuel supply system so that a fuel pressure higher than the pressure in the combustion chamber during the compression stroke can be applied. Is configured.
[0042]
An intake port 9 and an exhaust port 10 are opened to the combustion chamber 5 of each cylinder 3, and an intake valve 11 and an exhaust valve 12 are provided in these ports 9 and 10. The intake valve 11 and the exhaust valve 12 are driven by a valve mechanism comprising a camshaft 27 (one pair is provided on the cylinder head 2a, one of which is shown in the figure). As described later in detail, the intake / exhaust valve opening / closing timing of each cylinder 3 is set so that each cylinder 3 performs a combustion cycle with a predetermined phase difference.
[0043]
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 of each branch intake passage 15a. In the vicinity of the end, there is disposed a throttle valve 17 composed of a multiple rotary valve that simultaneously throttles the branch intake passages 15a. The throttle valve 17 is driven by a throttle valve actuator 18.
[0044]
An air flow sensor 20 for detecting the intake air amount is provided in the common intake passage 15c upstream of the surge tank 15b in the intake passage 15. The crankshaft 6 is provided with a crank angle sensor that detects its rotation angle. In this embodiment, as will be described in detail later, crank angle signals that are out of phase with each other by a certain amount are output. Two crank angle sensors 21 and 22 are provided. Further, a cam angle sensor 23 is provided that can give a cylinder identification signal to the camshaft 27 by detecting its specific rotational position.
[0045]
A startering gear 41 that rotates integrally with the crankshaft 6 is provided at one end of the crankshaft 6, and a large number of teeth are formed on the outer periphery thereof. On the other hand, a starter motor 28 and a pinion 29 for starting the engine 1 by rotating the starter gear 41 are provided. The pinion 29 is provided so as to be movable in the axial direction with respect to the starter motor 28, and a tooth profile that meshes with the starter ring gear 41 is formed on the outer peripheral portion thereof. The starter motor 28 rotates the pinion 29 by the drive, and moves the pinion 29 to a position where the pinion 29 meshes with the starter ring gear 41. When the drive of the starter motor 28 is stopped, the rotation of the pinion 29 is stopped and the pinion 29 is moved to a position where the pinion 29 is brought into the non-meshing state.
[0046]
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. 3). Etc. are equipped.
[0047]
FIG. 3 is a control block diagram of the engine 1, and shows a switch and a sensor for inputting a signal, a device and an actuator for outputting, etc., with an ECU (engine control unit) 30 as a center. Note that this block diagram is mainly described with respect to the configuration of the present invention, and other control-related portions are omitted.
[0048]
The air flow sensor 20, the crank angle sensors 21, 22, the cam angle sensor 23, the water temperature sensor 24, the accelerator opening sensor 25, and the finger pressure sensor 26 are connected to the input side of the ECU 30, and each detection signal is input.
[0049]
Further, the ignition plug 7, the fuel injection valve 8, the throttle valve actuator 18 and the starter motor 28 are connected to the output side of the ECU 30 to output drive signals to the various devices.
[0050]
The ECU 30 includes a throttle valve control means 31, a fuel injection valve control means 32, an ignition control means 33, an idle stop control means 34, and a compression level determination means 35 inside.
[0051]
The throttle valve control means 31 calculates the required opening of the throttle valve 17 from the engine opening speed based on the accelerator opening information from the accelerator opening sensor 25 and the crank angular speed information from the crank angle sensors 21 and 22. The throttle valve actuator 18 is controlled.
[0052]
The fuel injection valve control means 32 and the ignition control means 33 determine the required fuel injection amount based on 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 engine speed information. And the injection timing and appropriate ignition timing are calculated and a control signal is output to the fuel injection valve 8 and the spark plug 7.
[0053]
The throttle valve control means 31, the fuel injection valve control means 32, and the ignition control means 33, when performing idle stop (hereinafter also referred to as I / S), in addition to the above control, idle stop control means 34 described below. It is also controlled by.
[0054]
The idle stop control means 34 determines the I / S execution condition and the restart condition after the engine is stopped by the I / S, or provides information necessary for executing the I / S to each means in the ECU 30. To do.
[0055]
As the I / S execution conditions, for example, predetermined conditions are set such that the vehicle speed is zero, the foot brake is ON, the parking brake is ON, and the engine water temperature is equal to or higher than a predetermined value. Further, as a restart condition, a predetermined condition such as an accelerator depression amount equal to or greater than a predetermined value, a foot brake OFF, or a parking brake OFF is set.
[0056]
When a predetermined I / S execution condition is satisfied, the engine is automatically stopped. That is, the fuel injection from the fuel injection valve 8 is stopped and the ignition of the spark plug 7 is stopped.
[0057]
As control when the engine is stopped, a cylinder that is in the compression stroke when the engine is stopped (for convenience of explanation, this cylinder is assumed to be the third cylinder 3C, and hereinafter referred to as the compression stroke cylinder 3C) and a cylinder that is in the expansion stroke. (In the same way, assuming that the cylinder is the first cylinder 3A, hereinafter referred to as the expansion stroke cylinder 3A), in order to increase the resistance to the movement in the piston top dead center direction, at least the intake amount for these cylinders is increased, In order to supply more intake air to the cylinder 3A, the throttle valve 17 is opened for a predetermined period during the engine stop operation period.
[0058]
After the engine 1 is automatically stopped in this way, when a predetermined restart condition is satisfied, the engine is restarted. That is, the fuel injection from the fuel injection valve 8 and the ignition of the spark plug 7 are returned.
[0059]
As the control at the time of restart, first, the first combustion is performed on the compression stroke cylinder 3C and the engine is slightly reversed to increase the in-cylinder pressure by raising the piston of the expansion stroke cylinder 3A. Combustion is performed in the expansion stroke cylinder 3A.
[0060]
In the present embodiment, as described above, the initial combustion in the compression stroke cylinder 3C and the combustion in the expansion stroke cylinder 3A are performed, and the combustion air remains in the cylinder of the compression stroke cylinder 3C after the initial combustion to perform compression. The first restart control mode in which re-combustion is performed when the piston 4 of the stroke cylinder 3C starts to rise and the vicinity of the top dead center is reached, and the initial combustion in the compression stroke cylinder 3C and the combustion in the expansion stroke cylinder 3A The second restart control mode in which the combustion is performed but the recombustion in the compression stroke cylinder 3C is not performed, and the combustion in the expansion stroke cylinder 3A is performed while assisting with the starter motor 28 without performing the initial combustion in the compression stroke cylinder 3C. The third restart control mode in which the engine is started by combustion in the next compression stroke cylinder 3C is selectively executed according to the stop position of the piston 4.
[0061]
Further, in the first restart control mode and the second restart control mode, the compression level of the expansion stroke cylinder 3A (in this cylinder, the internal gas is compressed by the engine reverse rotation) during the engine reverse rotation at the initial restart stage (details) Is below a predetermined value, the starter motor 28 assists in starting.
[0062]
The compression level determination means 35 determines the compression level of the expansion stroke cylinder 3A during engine reverse rotation (hereinafter simply referred to as the compression level). In the present embodiment, the compression level is an index indicating the degree of advantage of the compression state in the cylinder with respect to ignitability and good combustion. That is, a compression state in which the ignition is surely performed and good combustion is performed is said to have a high compression level.
[0063]
The method for obtaining the compression level is based on an arithmetic expression obtained by theoretically or experimentally obtaining the relationship between parameters contributing to the compression level and the compression level, the degree of contribution of each parameter, and the like. In this embodiment, the rotational speed level, the in-cylinder pressure level, the piston movement amount, and the stop time (the time from when the engine automatically stops until the restart is started) are used as parameters.
[0064]
The rotation speed level is obtained by a rotation speed level determination unit 36 included in the compression level determination unit 35. In this embodiment, the absolute value (R1 shown in FIG. 14) of the maximum rotation speed during engine reverse rotation is used as the rotation speed level. Crank angle sensors 21 and 22 are used as the rotational speed detection means for obtaining the rotational speed level.
[0065]
A high rotational speed level means that the piston 4 moves fast during reverse rotation, and indicates that the compression speed is high. If the compression speed is high, the increase in in-cylinder pressure due to compression becomes large, so that the torque generated during combustion can be increased. That is, if the other conditions are the same, the higher the rotational speed level is, the higher the compression level is, as indicated by the characteristic M4 in FIG.
[0066]
The in-cylinder pressure level is obtained by an in-cylinder pressure level determination unit 37 included in the compression level determination unit 35. In this embodiment, the maximum in-cylinder pressure (detected by the finger pressure sensor 26, P1 shown in FIG. 14) of the expansion stroke cylinder 3A during engine reverse rotation is set as the in-cylinder pressure level.
[0067]
A high in-cylinder pressure level indicates that a substantial compression rate at the time of reverse rotation (a compression rate in consideration of gas leakage in the combustion chamber) is large. When the compression ratio is large, the torque generated during combustion can be increased. That is, if the other conditions are the same, the higher the in-cylinder pressure level is, the higher the compression level is, as shown by the characteristic M5 in FIG.
[0068]
The piston movement amount is obtained by a piston movement amount detection unit 38 included in the compression level determination unit 35. The piston movement amount detection means 38 calculates the movement amount of the piston 4 from the change amount of the crank angle detected by the crank angle sensors 21 and 22.
[0069]
The fact that the piston movement amount is large indicates that the apparent compression rate (compression rate determined by the change in the volume of the combustion chamber) is large if the original stop position is the same. That is, if other conditions are the same, the compression level increases as the piston movement amount increases, as indicated by the characteristic M6 in FIG.
[0070]
The stop time is obtained by a stop time measuring means 39 included in the compression level determining means 35. The stop time measuring means 39 measures the stop time from when the engine is automatically stopped until the restart is started by a timer in the ECU 30.
[0071]
If the stop time is long, the amount of in-cylinder gas leakage increases, and the in-cylinder pressure at the start of restart decreases (after a certain amount of time has elapsed, it becomes equal to atmospheric pressure). Moreover, the oil film breakage of the piston ring also increases, and the amount of gas leakage at the time of restart increases. Either action reduces the compression level over time. Therefore, if the other conditions are the same, the compression level becomes higher as the stop time is shorter as shown by the characteristic M7 in FIG.
[0072]
Next, the operation of the apparatus of the present embodiment as described above will be described.
[0073]
In the engine 1 which is a four-cylinder four-cycle engine, each cylinder 3 performs a cycle composed of intake, compression, expansion, and exhaust strokes with a predetermined phase difference. As shown in FIG. Are performed with a phase difference of 180 ° (180 ° CA) in terms of crank angle in the order of the first cylinder 3A, the third cylinder 3C, the fourth cylinder 3D, and the second cylinder 3B.
[0074]
When a predetermined idling state that does not require the output of the engine 1 is achieved while the engine 1 is in operation, an idle stop is executed based on whether or not the engine stop condition is met.
[0075]
When the engine stop condition is satisfied, a series of control for engine stop by idle stop is performed. In order to stop the engine, fuel supply is first stopped (fuel cut time t1). The engine speed at this time is an idle speed (about 650 rpm in this embodiment).
[0076]
Then, in order to stop the piston 4 within a preferable range for restarting (range A in FIG. 6), the fuel is cut at the fuel cut time t1, the throttle valve 17 is opened to a predetermined opening degree, and then the engine is rotated. Control is performed so that the throttle valve 17 is closed at a time point t2 when the number decreases to a predetermined rotation speed N1 (about 500 rpm in the present embodiment) set in advance.
[0077]
By doing so, the intake valve negative pressure is temporarily decreased (intake amount increased) with a slight time delay by opening the throttle valve 17 to a predetermined opening between the time points t1 and t2, and thereafter The predetermined rotational speed is set in advance so that the intake pressure negative pressure increases (intake amount decreases), but the period during which the intake negative pressure temporarily decreases substantially corresponds to the intake stroke period of the expansion stroke cylinder 3A. Has been. Thereby, compared with the case where the throttle valve 17 is not opened, the amount of air sucked into each cylinder 3 before the engine is stopped increases, and among them, the amount of intake air that flows into the expansion stroke cylinder 3A in particular increases.
[0078]
When the engine is stopped, in the compression stroke cylinder 3C, as the piston 4 approaches top dead center, the air in the cylinder 3C is compressed and pressure is applied in a direction to push the piston 4 back, thereby causing the engine 1 to reverse. 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, and accordingly, the air in the cylinder 3A is compressed, The piston 4 of the expansion stroke cylinder 3A is pushed back toward the bottom dead center. In this way, the piston 4 is stopped after being vibrated to some extent. At this time, in the compression stroke and the expansion stroke, the force to push the piston 4 closer to the top dead center is larger, so the stop position of the piston 4 is the middle of the stroke. In many cases, the position is close to the portion (range A in FIG. 6).
[0079]
Since the intake air amount is increased before the engine is stopped as described above, the force to push back the piston 4 when approaching the top dead center is increased, so that the probability that the piston 4 stops within the range A is increased. Further, if the intake amount of the expansion stroke cylinder 3A is made larger than that of the compression stroke cylinder 3C by the control of the throttle valve 17 as described above, the piston 4 in the expansion stroke cylinder 3A is within the range close to the stroke intermediate portion. However, it often stops near the bottom dead center (range A2 in FIG. 6).
[0080]
In addition, since the engine 1 is rotated several times by inertia from the fuel cut until the engine 1 is completely stopped, the burned gas is discharged, and the inside of the cylinder becomes almost fresh even in the expansion stroke. Further, when the engine 1 is stopped, the pressure of the compression stroke cylinder 3C decreases with time.
[0081]
The throttle valve 17 may not be closed until the engine is stopped. However, since the intake amount continues to be large until the engine is stopped, the push-down force of the piston 4 due to the compression of the intake is difficult to attenuate. In some cases, the number of vibrations increases and the swing back increases when the engine stops. Therefore, it is desirable to close the throttle valve 17 at a suitable time t2 as shown in the present embodiment.
[0082]
The stop position of the piston 4 is detected by signals from the crank angle sensors 21 and 22 as follows. FIG. 7 is a pulse signal obtained by rotating the crankshaft 6, and shows a first crank angle signal CA 1 from the crank angle sensor 21 and a second crank angle signal CA 2 from the crank angle sensor 22. FIG. 7A shows the case of normal rotation (clockwise in the state of FIG. 1), and FIG. 7B shows the case of reverse rotation. At the time of forward rotation of the engine, as shown in FIG. 7A, the second crank angle signal CA2 is generated with 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 The second crank angle signal CA2 becomes Low when rising, and the second crank angle signal CA2 becomes High when the first crank angle signal CA1 falls. On the other hand, during reverse rotation of the engine, as shown in FIG. 7B, 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 On the contrary, the second crank angle signal CA2 becomes High when the first crank angle signal CA1 rises, and the second crank angle signal CA2 becomes Low when the first crank angle signal CA1 falls. The ECU 30 detects this difference and counts the pulse signal while determining whether the crankshaft 6 is rotating forward or rotating backward. 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 increase or decrease in the CA counter value is lost 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.
[0083]
FIG. 8 is an accumulation flowchart of CA counter values. 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. If it is YES, it indicates that the engine 1 is rotating forward, so that the process proceeds to step S52 and the measured pulse number is added to the CA counter value (CA counter up). If “NO” in the step S51, it indicates that the engine 1 is reversely rotated, so that the process proceeds to the step S53 and the number of pulses measured is subtracted from the CA counter value (CA counter down).
[0084]
FIG. 9 shows a schematic control flowchart of the ECU 30 until the engine stops in the idle stop. After the start, signals from various sensors (see FIG. 3) are read (step S1). Next, based on the signal, it is determined whether or not the engine stop condition is satisfied (step S2). If NO, the process returns. If YES, a series of control for automatic engine stop is subsequently performed. .
[0085]
First, the fuel supply from the fuel injection valve 8 is stopped (fuel cut) (step S7). In the subsequent step S11, the throttle valve 17 is opened to reduce the intake negative pressure. Thereafter, the throttle valve 17 is closed when the engine speed becomes lower than the predetermined speed N1 (about 500 rpm) (steps S13 and S15). Next, the CA counter value (see FIG. 8) during constant counting is read (step S16). In the next step S17, it is determined whether or not the engine 1 has completely stopped from the degree of change of the CA counter value. If YES, the stop position of the piston 4 determined from the CA counter value is stored (step S19). And return.
[0086]
Next, engine restart will be described. When the restart condition is satisfied after the engine is stopped, control for automatically restarting the engine 1 is performed. In restarting, in the present embodiment, any one of the first restart mode, the second restart mode, and the third restart mode is selected, and the normal combustion control is shifted to the start mode. Although details of each mode will be described later, in the first restart mode, combustion is performed in the compression stroke cylinder 3C and the engine is once reversed, and then combustion is performed in the expansion stroke cylinder 3A and the engine is normally rotated. Thereafter, the fuel is injected into the residual gas (including unburned air) and recombusted without exhausting the first combustion gas in the compression stroke cylinder 3C. The second restart mode is the same as the first restart mode in that the engine is once reversed, but recombustion in the compression stroke cylinder 3C is not performed. In the third restart mode, the engine is not reversely rotated and the starter motor 28 assists the start.
[0087]
FIG. 10 is a flowchart for selecting the restart mode. When a predetermined restart condition is satisfied during the automatic engine stop (YES in step S101), the piston stop position of the expansion stroke cylinder 3A (the position stored in step S19 in FIG. 9) is determined in steps S103 and S105. If the position is within the range A1 in FIG. 6, the process proceeds to step S107, and restart in the first restart mode is performed. If it is also in the range A2, the process proceeds to step S109, and restart in the second restart mode is performed. If it is also outside the range A, the process proceeds to step S111, and restart in the third restart mode is performed. Regardless of which mode is selected, the routine proceeds to normal combustion control in step S113 and returns.
[0088]
11 and 12 are schematic flowcharts of the first restart control mode. FIG. 13 shows the stroke of each cylinder of the corresponding engine and the combustion in each cylinder from the start of the start control (indicated by (1), (2), (3)... According to the order of combustion in the figure). It is a figure which shows a relationship and shows the operation direction of the engine by each combustion with an arrow. FIG. 14 shows temporal changes in the engine rotational speed, crank angle, in-cylinder pressure of the angular cylinder, the indicated torque, and the drive signal of the starter motor 28 when starting assist is performed in the first restart control mode. Yes.
[0089]
In the flowchart of FIG. 11, when the start in the first restart mode is started, the in-cylinder air amounts of the compression stroke cylinder 3C and the expansion stroke cylinder 3A are calculated based on the stop position of the piston 4 in step S151. Next, in step S153, the air amount calculated for the compression stroke cylinder 3C becomes a predetermined lean air-fuel ratio (read from a map of a predetermined characteristic M1 as a function of the stop position of the piston 4). Fuel is injected. Subsequently, with respect to the air amount calculated for the expansion stroke cylinder 3A in step S155, a predetermined air-fuel ratio (near the stoichiometric air-fuel ratio. Read from a map of a predetermined characteristic M2 as a function of the stop position of the piston 4). The fuel is injected so that Next, in step S157, after elapse of a set time considering a predetermined vaporization time, ignition (ignition F1 in FIG. 14) is performed in the compression stroke cylinder 3C, and initial combustion is performed ((1) in FIG. 13). However, since ignition may not be performed even if ignition is performed, that is, combustion may not be performed, it is determined whether or not the edges (the waveforms shown in FIG. 7) of the crank angle sensors 21 and 22 have been detected in the next step S159. Is done. If YES, it indicates that the crankshaft 6 has started to rotate, that is, combustion has been performed. If NO, it indicates that combustion has not been performed, so the routine proceeds to step S161 and reignition is performed.
[0090]
The piston 4 of the compression stroke cylinder 3C is pushed down to the bottom dead center side by the combustion pressure by this initial combustion (portion a in FIG. 14), and the engine 1 is driven in the reverse direction. Accordingly, the piston 4 of the expansion stroke cylinder 3A is driven. Approaches the top dead center, the air in the cylinder 3A is compressed and the in-cylinder pressure rises (part b in FIG. 14; the maximum compression pressure is P1).
[0091]
Next, in step S163 of the flowchart, a predetermined delay time (the time until the piston 4 of the expansion stroke cylinder 3A sufficiently approaches the top dead center. Read from a map of a predetermined characteristic M3 as a function of the stop position of the piston 4. .) After the lapse, ignition (ignition F2 in FIG. 14) is performed on the expansion stroke cylinder 3A, the fuel previously injected into the cylinder 3A is combusted ((2) in FIG. 13), and the combustion pressure ( The engine 1 is driven in the forward rotation direction at a portion c in FIG.
[0092]
When combustion {circle around (2)} is performed in the expansion stroke cylinder 3A, the engine 1 that has been reversely rotated (the engine speed is a negative value) is switched to the normal rotation direction. The switching point is when the engine speed is zero (time point t3 in FIG. 14). The minimum rotational speed R1 (maximum in absolute value) during engine reverse rotation and the maximum compression pressure P1 in the expansion stroke cylinder 3A shown in FIG. Stored by means 37.
[0093]
If YES (engine forward rotation) is determined in step S165 of the flowchart, the compression level of the expansion stroke cylinder 3A is calculated in the next step S167. The compression level is calculated by a predetermined arithmetic expression based on the maps of the characteristics M4, M5, M6, and M7 shown in FIGS. Then, in the next step S169 (hereinafter, FIG. 12), it is determined whether or not the compression level exceeds a predetermined value. If YES, the process proceeds to step S173. If NO, the process proceeds to step S171 before that. Then, the drive of the starter motor 28 is started. That is, when the compression level is equal to or lower than a predetermined value, it is determined that there is a high possibility of starting failure, and start assist is performed by the starter motor 28 in order to prevent it from occurring (as shown in FIG. The starter motor drive signal is turned on around time t3 when the number becomes zero).
[0094]
When the engine starts to rotate in the forward direction, the in-cylinder gas of the compression stroke cylinder 3C (since the exhaust valve 12 has not been opened since the restart was started, the burned gas from the first combustion (1) remains in the cylinder. Are compressed again. In the next step S173, fuel is injected and ignited (ignition F3 in FIG. 14), the second combustion ((3) in FIG. 13) is performed, and the combustion pressure (d portion in FIG. 14). The engine driving force can be increased. The air-fuel ratio (corresponding to the theoretical air-fuel ratio) and ignition timing at this time are read from a map of predetermined characteristics M8 and M9 as a function of the stop position of the piston 4.
[0095]
In step S175, the other cylinders are sequentially injected with fuel and ignited (ignitions F4 and F5 in FIG. 14), and combusted ((4) and (5) in FIG. 13). In the next step S177, it is determined whether or not the engine speed has become equal to or higher than a predetermined speed N2 (about 500 rpm). If YES, the process proceeds to steps S179 and S181, and the starter motor 28 is being driven. The drive is stopped (time t4 in FIG. 14). As shown in FIG. 14, the predetermined rotational speed N2 is the combustion in the fourth cylinder 3D (as shown in FIG. 13, this cylinder is in the intake stroke when the engine is stopped. Hereinafter also referred to as the intake stroke cylinder 3D). Is set to be the number of revolutions reached. That is, it is detected that the combustion in the intake stroke cylinder 3D has started when the engine speed reaches the predetermined speed N2. When combustion is performed in the intake stroke cylinder 3D, normal combustion is performed in the subsequent cylinders without any assistance from the starter motor, and a smooth start is performed. Further, the predetermined rotation speed N2 is a complete explosion speed (rotation speed indicating a state in which combustion in each cylinder is performed once or more in a normal start by cranking, and is slightly lower than the idle rotation speed. It is also set so as to be at a lower rotation than a certain number, for example, 550 to 600 rpm. Thus, since the drive of the starter motor 28 is stopped at a low rotation, cranking noise is suppressed and silence is increased.
[0096]
Next, starting in the second restart mode will be described. The second restart mode is also controlled according to the flowchart of the first restart mode. However, the fuel injection to the compression stroke cylinder 3C performed in step S153 is performed at a stoichiometric air fuel ratio or a slightly richer air fuel ratio, and the second combustion (3) in step S173 is not performed. The difference is not. In addition, when the engine 1 switches from reverse rotation to normal rotation, start assist by the starter motor 28 is performed when the compression level is equal to or lower than a predetermined value, as in the first start mode.
[0097]
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, whereby the engine 1 is effectively restarted. This point will be described with reference to FIG.
[0098]
FIG. 15 shows the relationship between the piston position when the engine is stopped and the required air-fuel ratio in the first combustion (for reverse rotation) of the compression stroke cylinder 3C, the air amount of the compression stroke cylinder 3C, the air amount of the expansion stroke cylinder 3A, and the generation frequency. As shown in this figure, when the engine is stopped, 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). As the air amount in the stroke cylinder 3C increases, the air amount in the expansion stroke cylinder 3A increases as the piston 4 in the expansion stroke cylinder 3A approaches the bottom dead center (the piston 4 in the compression stroke cylinder 3C approaches the top dead center). The amount of air in the compression stroke cylinder 3C is reduced.
[0099]
In the initial combustion in the compression stroke cylinder 3C, the engine is reversely rotated 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 performed. 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 close to the bottom dead center, the amount of air in the compression stroke cylinder 3C is large, and the predetermined position Since the torque required for reverse rotation up to is relatively small, the required air-fuel ratio becomes lean.
[0100]
In the expansion stroke cylinder 3A, since the amount of air increases as the piston 4 is closer to the bottom dead center, more fuel can be burned.
[0101]
Accordingly, when the piston position of the expansion stroke cylinder 3A is within a predetermined range A2 near the bottom dead center from the middle portion (the piston position of the compression stroke cylinder 3C is near the top dead center) when the engine is stopped, the compression stroke cylinder 3C is in the initial combustion. The air-fuel ratio of the engine is made rich so as to meet the above requirements, and no combustion air remains after the first combustion, so the second combustion near the compression top dead center is not performed. A relatively large amount of fuel is injected, and after being compressed and then ignited and combusted, a relatively large torque is obtained, and further after the compression top dead center of the compression stroke cylinder 3C. The engine can be rotated until the compression top dead center of the next cylinder is exceeded, and restart can be achieved.
[0102]
On the other hand, when the engine is stopped, the piston position of the expansion stroke cylinder 3A is in the predetermined range A1 closer to the top dead center than the intermediate portion (the piston position of the compression stroke cylinder 3C is closer to the bottom dead center), compared to the case where the piston is in the range A2. Since the amount of air in the expansion stroke cylinder 3A is small, the torque obtained by the 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 corresponding to the above requirement, thereby Since the surplus air remaining after the first combustion is used and the second combustion near the compression top dead center is performed, the torque for driving in the engine forward direction is supplemented, and the combustion in the expansion stroke cylinder 3A Torque sufficient to achieve restart is obtained by both of the second combustion in the compression stroke cylinder 3C.
[0103]
By the way, in the present embodiment, when the engine is stopped as described above, the throttle valve 17 is kept in a predetermined open state for a predetermined period after the fuel supply is stopped, and the intake air amount is increased to increase the compression stroke cylinder 3C and the expansion stroke cylinder 3A. In FIG. 15, the resistance to the movement of the piston 4 in the direction of the top dead center is increased, and the intake air amount of the expansion stroke cylinder 3A is increased, so that the expansion stroke cylinder when the engine is stopped 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 within that range, it is often within the range A2 that is slightly closer to the bottom dead center. Effective restart is performed.
[0104]
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) with respect to the range A, a sufficient amount of movement in the engine reverse rotation direction is taken. Since the amount of air in the expansion stroke cylinder 3A is reduced, the torque obtained by the combustion in the expansion stroke cylinder 3A is reduced, and the bottom dead center side of the expansion stroke cylinder 3A (compression stroke cylinder) If it is too close to 3C (top dead center side), the amount of air in the compression stroke cylinder 3C decreases, so that sufficient torque for engine reverse rotation cannot be obtained. On the other hand, if the piston stop position is within the above 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. 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 can be secured in the expansion stroke cylinder 3A. Combustion energy can be increased and startability can be improved.
[0105]
Next, a description will be given of a third restart mode that is selected when the piston position when the engine is stopped is out of the above range A and in which start assist is performed from the initial stage of restart. FIG. 16 is a flowchart of the third restart mode (motor assist). When a predetermined restart condition is satisfied (YES in step S201), the starter motor 28 starts to be driven in step S202. In the next step S203, the air amounts of the compression stroke cylinder 3C and the expansion stroke cylinder 3A are calculated based on the stop position of the piston 4, and in step S204, the air-fuel ratios of the compression stroke cylinder 3C and the expansion stroke cylinder 3A are close to the theoretical air-fuel ratio. The fuel is injected so that In step S205, after the time set in consideration of the fuel vaporization time has elapsed after the fuel injection of the expansion stroke cylinder 3A, the cylinder is ignited. Therefore, the engine 1 starts to rotate in the forward direction from the beginning.
[0106]
Next, when the predetermined crank angle is reached in step S206, the compression stroke cylinder 3C is ignited and burned. Thereafter, in step S207, the other cylinders are sequentially burned by fuel injection and ignition. In the next step S208, it is determined whether or not the engine speed has become equal to or higher than a predetermined speed N2 (about 500 rpm). If YES, the process proceeds to step S209, and the drive of the starter motor 28 is stopped. Also in this case, like the start assist in the first and second start modes, the drive of the starter motor 28 is stopped at a low rotation speed equal to or less than the complete explosion speed, so that cranking noise is suppressed and silence is increased. .
[0107]
As mentioned above, although one Embodiment of this invention was described, the specific structure of the apparatus of this invention is not limited to the said embodiment, A various change is possible within a claim.
[0108]
For example, the means for applying the driving force from the starter motor 28 to the crankshaft 6 does not necessarily have to be based on the engagement of the pinion 29 and the startering gear 41, and any power transmission means such as a mechanism combining a driving belt and a clutch. Or a mechanism provided with switching means.
[0109]
The starter motor 28 of the above-described embodiment is configured to rotate the pinion 29 and to mesh with the starter ring gear 41 by driving, but the mechanism is made independent of these operations, that is, the pinion 29 is separately meshed. A mechanism that engages with the starter ring gear 41 and rotates the pinion 29 by driving the starter motor 28 may be used. As a result, when the engine speed is near zero, even if it is not yet determined whether or not the start assist is performed, the pinion 29 is engaged with the starter gear 41, and then it is determined that the assist is required. It is possible to provide a starting device that rotates the pinion 29 only to apply a driving force, and otherwise returns the pinion 29 to the non-meshing state without rotating.
[0110]
By doing in this way, since the meshing timing of the pinion 29 and the startering gear 41 can be brought closer to the time when the engine speed is zero, quickness and quietness can be further improved.
[0111]
The engine in this case is not necessarily limited to the engine that reverses once, but may be applied to an engine that rotates forward from the beginning. That is, the starter motor 28 may be driven as necessary by engaging the pinion 29 and the starter ring gear 41 simultaneously with the start of restart.
[0112]
In the above embodiment, the absolute value R1 of the maximum rotational speed during engine reverse rotation is used as the rotational speed level, but the absolute value of the average rotational speed may be used as the rotational speed level instead.
[0113]
The compression level determination means may use parameters other than those listed in the above embodiment, or conversely, may use some of the above parameters.
[0114]
In the above-described embodiment, the fuel injection to the expansion stroke cylinder 3A immediately after restart may be set substantially later or slower than the injection to the compression stroke cylinder 3C. For example, in the flowchart shown in FIG. 11, step S155 may be performed simultaneously with step S153, or conversely, may be performed immediately before step S163. The step close to step S153 is suitable for uniform combustion because the vaporization time in the expansion stroke cylinder 3A can be lengthened, and the step close to step S163 is suitable for stratified combustion because fuel tends to be unevenly distributed during ignition.
[0115]
【The invention's effect】
As described above, according to the engine starting device of the present invention, when starting the engine, fuel is supplied to the cylinders that are substantially in the compression stroke and the cylinders that are substantially in the expansion stroke when the engine is stopped before starting. The engine is ignited and burned in the cylinder substantially in the compression stroke, and the engine is temporarily reversed until near the compression bottom dead center, and then the ignition and combustion are performed in the cylinder substantially in the expansion stroke. In the engine starting device for starting in the forward rotation direction, a compression level determining means for determining a compression level when the cylinder substantially in the expansion stroke is in a compressed state due to reverse rotation of the engine, and forward rotation to the engine A rotation direction of the engine when the compression level is determined to be lower than a predetermined level by the compression level determination means. Since the starter motor assists the start in the forward direction at or near the time of transition from reverse to forward rotation, the starter motor assists the starter motor as necessary. The quickness of starting can be improved.
[0116]
Furthermore, when the driving force transmission means uses a starter motor and a starter ring gear, it is possible to reduce cranking noise and improve quietness.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of an engine equipped 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 schematic control block diagram of the engine.
FIG. 4 is a characteristic diagram showing the relationship between each parameter and a compression level, where (a) is a rotational speed level, (b) is an in-cylinder pressure level, (c) is a piston movement amount, and (d) is a graph. Each stop time is a parameter.
FIG. 5 is an explanatory diagram showing changes in engine speed, throttle opening, intake pipe negative pressure, and cycle of each cylinder when the engine is stopped.
FIG. 6 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.
7A and 7B show crank angle signals from two crank angle sensors, where FIG. 7A is a signal when the engine is rotating forward and FIG. 7B is a signal when the engine is rotating backward.
FIG. 8 is a flowchart showing a process for detecting a piston position when the engine is stopped.
FIG. 9 is a flowchart showing a control flow when the engine is stopped.
FIG. 10 is a flowchart showing a control flow when the engine is restarted.
FIG. 11 is a flowchart (first half) showing a first restart mode subroutine in the flowchart shown in FIG. 10;
12 is a flowchart (second half) showing a subroutine of the first restart mode in the flowchart shown in FIG.
FIG. 13 is an explanatory diagram showing the cycle and combustion operation of each cylinder at the time of engine restart.
FIG. 14 is an explanatory diagram showing changes in engine speed, crank angle, in-cylinder pressure of each cylinder, indicated torque, and starter motor drive signal when starting assist is performed when the engine is restarted.
FIG. 15 is an explanatory diagram showing the relationship between the piston position when the engine is stopped and the required air-fuel ratio of the compression stroke cylinder, the air amount of the compression stroke cylinder, the air amount of the expansion stroke cylinder, and the generation frequency.
FIG. 16 is a flowchart showing a third restart mode subroutine in the flowchart shown in FIG. 10;
[Explanation of symbols]
1,1a engine
3 cylinders
3A No. 1 cylinder, expansion stroke cylinder (cylinder substantially in expansion stroke)
3C No. 3 cylinder, compression stroke cylinder (cylinder in the compression stroke)
4 Piston
6 Crankshaft
7 Spark plug
8 Fuel injection valve
21, 22 Crank angle sensor (rotational speed detection means)
26 Shiatsu pressure sensor
28 Starter motor
29 Pinion
30 ECU
35 Compression level discrimination means
36 Rotational speed discrimination means
37 In-cylinder pressure discrimination means
38 Piston movement detection means
39 Stop time measuring means
41 Startering gear

Claims (11)

When starting the engine, fuel is supplied to a cylinder that is substantially in the compression stroke and a cylinder that is substantially in the expansion stroke when the engine is stopped before starting, and ignition is performed in the cylinder that is substantially in the compression stroke. In an engine starter that performs combustion and reverses the engine to the vicinity of compression bottom dead center, and then ignites and burns in the cylinder substantially in the expansion stroke, and starts the engine in the forward rotation direction.
Compression level determining means for determining a compression level when the cylinder substantially in the expansion stroke is in a compressed state due to reverse rotation of the engine;
A starter motor that applies driving force in the forward direction to the engine,
When the compression level determination means determines that the compression level is below a predetermined level, the starter motor starts the forward rotation direction at or near the time when the engine rotation direction shifts from reverse rotation to normal rotation. An engine starter characterized by assisting. Rotational speed level discriminating means for discriminating the rotational speed level at the time of engine reverse rotation,
2. The engine starter according to claim 1, wherein the compression level determination means determines that the compression level is higher as the rotation speed level by the rotation speed level determination means is higher. A rotation speed detecting means for detecting the rotation speed of the engine;
3. The engine starter according to claim 2, wherein the rotational speed level determining means determines that the rotational speed level is higher as the absolute value of the maximum rotational speed during engine reverse rotation is higher. A rotation speed detecting means for detecting the rotation speed of the engine;
3. The engine starting device according to claim 2, wherein the rotational speed level determining means determines that the rotational speed level is higher as the absolute value of the average rotational speed during engine reverse rotation is higher. In-cylinder pressure determining means for determining an in-cylinder pressure level of the cylinder substantially in the expansion stroke at the time of reverse rotation of the engine,
5. The engine starter according to claim 1, wherein the compression level determining unit determines that the higher the in-cylinder pressure level by the in-cylinder pressure level determining unit is, the higher the compression level is. . A piston movement amount detecting means for detecting the movement amount of the piston at the time of engine reverse rotation is provided,
6. The compression level determination unit according to claim 1, wherein the compression level determination unit determines that the compression level is higher as the piston movement amount during engine reverse rotation by the piston movement amount detection unit is larger. Engine starter. When the engine is stopped from the operating state, and then the engine is started, a stop time measuring means for measuring the engine stop time before starting is provided,
7. The engine starter according to claim 1, wherein the compression level determination unit determines that the compression level is higher as the engine stop time by the stop time measurement unit is shorter. A startering gear that rotates integrally with the crankshaft;
It is configured to be switchable between a meshing state and a non-meshing state with respect to the startering gear, and includes a pinion that transmits the driving force of the starter motor to the startering gear in the meshed state,
The pinion is switched to the meshing state while the starter motor is in a non-driving state near the rotation speed zero where the rotation direction of the engine shifts from reverse rotation to normal rotation, and the compression level by the compression level determination means is below a predetermined level. The engine starter according to any one of claims 1 to 7, wherein the starter motor is driven only when it is determined that 9. The engine according to claim 8, wherein the pinion is switched to the non-meshing state in the vicinity of a time point when the cylinder in the intake stroke starts combustion when the engine is stopped after the rotational direction of the engine is changed from reverse to forward. Starting device. When starting the engine, in the engine starting device for supplying fuel to the cylinders that are substantially in the expansion stroke when the engine is stopped before starting, and starting by performing ignition and combustion,
A starter motor that applies driving force in the forward direction to the engine;
A startering gear that rotates integrally with the crankshaft;
It is configured to be switchable between a meshing state and a non-meshing state with respect to the startering gear, and includes a pinion that transmits the driving force of the starter motor to the startering gear in the meshed state,
When the engine is relatively difficult to start, the pinion is engaged and the starter motor is driven to assist the start.
An engine starter characterized in that, after the engine has started in the forward direction, the pinion is switched to the non-engaged state in the vicinity of the time when the cylinder in the intake stroke starts combustion when the engine is stopped. A rotation speed detecting means for detecting the rotation speed of the engine;
11. The starter motor is driven only when the pinion is switched to a meshing state when the engine rotation speed is substantially zero and only in a predetermined state where the engine is relatively difficult to start. Engine starter.

Images