JP3966238B2 - Engine starter - Google Patents

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 is more frequent than the initial start frequency at which the engine is first started. In the conventional general starting method in which the engine output shaft (crankshaft) is driven by the starter motor, the life of the starter motor is reduced. If the reliability of the starter motor is improved in terms of shortening and life, the cost increases accordingly. Therefore, such a starting method using a starter motor is not preferable.
[0004]
Therefore, as a starting device suitable for restarting the idle stop, fuel is supplied to a specific cylinder (cylinder in the expansion stroke; hereinafter referred to as an expansion stroke cylinder) of the stopped engine, and ignition and combustion are performed. Some have been developed to start the engine immediately. In general, a sufficient torque for starting the engine is not always obtained by simply supplying fuel to the expansion stroke cylinder to ignite and burn it. 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 can be obtained at the time of restart, and a restarting performance can be improved because a certain amount of torque is generated.
[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]
When combining the starting device shown in Patent Document 1 and the starting device shown in Patent Document 2 above, for example, increasing the probability of stopping the piston within the appropriate range, but not stopping within the appropriate range In addition, a device that performs a start assist by a starter motor as a backup can be considered.
[0009]
It is desirable to reduce the frequency of such start assist as much as possible in order to ensure the life of the starter motor. That is, it is desired to increase the frequency at which the engine can be restarted by combustion of the engine regardless of the start assist.
[0010]
On the other hand, as a technology for improving the restart certainty (startability) due to engine combustion, fuel is supplied to a specific cylinder (cylinder in the compression stroke; hereinafter referred to as compression stroke cylinder) of the stopped engine to ignite and burn The technology that reverses the engine once has been studied. In this method, the air in the expansion stroke cylinder is temporarily compressed by the reverse rotation of the engine, and combustion is performed there, thereby obtaining a higher starting torque in the forward rotation direction. In this way, the startability of the engine can be improved, but on the other hand, a time loss for temporarily reversing the engine is inevitably caused, which adversely affects the quickness of the start.
[0011]
In view of the above circumstances, the present invention further reduces the frequency of the starter motor by reducing the frequency while assisting the starter motor when necessary, and further increases the speed of the start as much as possible. An engine starter that can be enhanced is provided.
[0012]
[Means for Solving the Problems]
According to the first aspect of the present invention, when the engine in operation is stopped, and then the engine is restarted, fuel is supplied to the cylinder that is substantially in the expansion stroke when the engine is stopped, and ignition and combustion are performed. In the engine starting device for starting Provided with a stop time measuring means for measuring the stop time from when the engine automatically stops until restart is started, When the piston position when the engine is stopped is within a predetermined appropriate range suitable for starting, the engine is started by torque generated by combustion of the engine, and when it is outside the appropriate range, the starter motor is further driven from the initial start to start the engine. While assisting, By the stop time measuring means The engine stop time When the amount of oil remaining on the cylinder wall surface of the engine is large and the amount of decrease in the in-cylinder air density is small, within a few seconds or less Is characterized by expanding the appropriate range.
[0013]
According to this configuration, when the piston stop position when the engine is stopped is within a predetermined appropriate range suitable for starting, the engine is started by the torque generated by the combustion of the engine, so that the start can be performed without depending on the starter motor. When it is outside the proper range (the torque generated by the combustion of the engine is small), the starter motor is further driven from the beginning of the start to assist the start, so that a start failure can be effectively avoided. As a whole, since the starter motor can be operated only when the start assist is necessary, the use frequency of the starter motor can be reduced and the life can be extended.
[0014]
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, a cylinder that is substantially in the expansion stroke, which will be described later, refers to a cylinder that is in a state where the gas volume in the sealed cylinder is expanded to increase the cylinder volume, and other than the cylinder in the original expansion stroke. In addition, for example, the cylinder is originally in the intake stroke (the operation direction of the piston is the same as the expansion stroke), but includes a cylinder 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 substantially in the compression stroke (or expansion stroke). Shall be included.
[0015]
By the way, the appropriate range may be appropriately set as a range in which it is easy to restart by combustion when the piston of the expansion stroke cylinder stops within the range. It is preferable to set it near the middle between the top dead center and the bottom dead center so as to ensure a piston stroke above a certain level.
[0016]
In order to reduce the frequency of start assist by the starter motor, it is ideal to set the appropriate range to the maximum range where good startability can be obtained without performing the start assist. Hereinafter, such a virtual range is referred to as an ideal range for convenience. The ideal range is not constant but changes depending on conditions, and particularly depends greatly on the engine stop period. When the engine stop period is short, the in-cylinder pressure is less decreased and the in-cylinder air density is high, so that the torque generated by combustion increases. Further, the amount of oil film remaining on the cylinder wall surface is large, and the sliding resistance of the piston is reduced. In this way, when the engine stop time is short, many factors act in the direction of improving the startability, so that a good start can be performed even if the piston position is slightly shifted toward the top dead center or the bottom dead center. it can. That is, the ideal range is expanded.
[0017]
In this configuration, when the engine stop period is short, Specifically, when the amount of oil remaining on the cylinder wall of the engine is large and the amount of decrease in the in-cylinder air density is small, it is an extremely short time of about several seconds. Therefore, the appropriate range can be set so as to follow the ideal range that changes according to the length of the stop period. Thereby, the opportunity to perform the start assist by the starter motor can be reduced as much as possible, and the life reduction of the starter motor can be prevented.
[0018]
The engine starting device supplies fuel to the expansion stroke cylinder, and ignites and burns to start the engine. This includes a compression stroke cylinder prior to combustion in the expansion stroke cylinder. And the engine is once reversed (this allows the piston of the expansion stroke cylinder to be reversed once, thereby reducing the cylinder volume and increasing the cylinder pressure).
[0019]
The above ideal range becomes wider as the engine stop period is shorter. time But If it is within the above extremely short time, the stop time If the amount of expansion of the appropriate range is increased as the length is shorter, the start assist range by the starter motor can be made closer to the ideal range.
[0020]
Or stop the engine time But Within the above extremely short time In some cases, if the appropriate range is expanded by a predetermined amount for a longer case (Claim 3), the configuration of Claim 1 can be achieved by simple control that switches on / off the appropriate range. Can be realized.
[0021]
According to a fourth aspect of the present invention, when the engine under operation is stopped and then the engine is restarted, when the piston position during the engine stop is within a predetermined first appropriate range suitable for starting, the engine is substantially stopped. Then, fuel is supplied to the cylinder in the compression stroke, ignition and combustion are performed, and the piston of any cylinder is once rotated in the reverse direction within the range not exceeding the top dead center, and then substantially when the engine is stopped. In an engine starter that supplies fuel to a cylinder in an expansion stroke, performs ignition and combustion, and starts the engine by rotating it in the forward rotation direction. Provided with a stop time measuring means for measuring a stop time from when the engine is automatically stopped until restart is started, The engine stop time When the amount of oil remaining on the cylinder wall surface of the engine is large and the amount of decrease in the in-cylinder air density is small, within a few seconds or less Is provided with a second appropriate range suitable for starting, and when the piston position when the engine is stopped is within the second appropriate range, the rotation in the reverse direction is not performed and the above-mentioned normal range is It is characterized by starting by rotation in the rolling direction.
[0022]
According to this configuration, when the piston stop position is within the first appropriate range, combustion in the compression stroke cylinder is performed to reverse the engine once, and then combustion is performed in the expansion stroke cylinder to rotate the engine in the normal rotation direction. Therefore, the combustion torque in the expansion stroke cylinder in which the in-cylinder pressure is increased by the reverse rotation of the engine is high, and the startability can be improved.
[0023]
And when the engine stop period is short, Specifically, when the amount of oil remaining on the cylinder wall of the engine is large and the amount of decrease in the in-cylinder air density is small, it is an extremely short time of about several seconds. Is provided with a second appropriate range suitable for starting, and when the piston position when the engine is stopped is within the second appropriate range, the rotation in the reverse direction is not performed and the above-mentioned normal range is Since the engine is started by rotating in the rotation direction, the time loss caused by once reversing the engine can be eliminated, and the speed of starting can be improved.
[0024]
The reason for rotating the engine once and then rotating forward is that the torque generated in the expansion stroke cylinder is larger than when rotating forward from the beginning (because the in-cylinder pressure is increased in advance by the reverse rotation), and the startability is improved. Because. However, since the startability is high as described above when the engine stop period is short, sufficient startability can be ensured even if the engine is normally rotated depending on the stop position of the piston. The second appropriate range is set as a range of such a piston stop position.
[0025]
As with the first proper range, the second proper range is usually preferably set near the middle of the top dead center and the bottom dead center, but there is a mutual relationship between the first proper range and the second proper range. There is no direct relationship for restricting the other range, and a suitable range may be set independently. For example, depending on the characteristics of the engine, the ranges may be the same, the one may be included in the other, the portions partially overlapping each other, or the portions not overlapping each other.
[0026]
And the startability of the engine becomes higher as the stop period is shorter, so the engine stops accordingly time But If it is within the above extremely short time, the stop time If the second appropriate range is increased as the length is shorter, the frequency of starting the engine in the normal rotation direction from the initial stage increases, and the speed of starting can be further improved as a whole.
[0027]
Furthermore, in the engine starting device according to any one of claims 1 to 5, when the engine in operation is stopped, the throttle opening is increased for a predetermined period during the stopping operation (claim 6). As a result, the amount of air flowing into the cylinder increases when the engine is stopped, and the air acts so that it is difficult to stop the piston of each cylinder near the top dead center. As a result, a force acts in the direction in which the piston is pushed back by compression), so that the piston of each cylinder is likely to stop at a position as far away from the top dead center as possible, that is, near the middle position between the top dead center and the bottom dead center. . Accordingly, it is possible to increase the probability that the piston stops within the appropriate range, the first proper range, or the second proper range.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0029]
1 and 2 show a schematic configuration of an engine according to a first 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 the crankshaft 6 via a connecting rod.
[0030]
A spark plug 7 is provided at the top of the combustion chamber 5 of each cylinder 3, and its tip faces the combustion chamber 5. 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.
[0031]
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.
[0032]
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 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.
[0033]
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.
[0034]
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 it 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.
[0035]
As other detection elements necessary for controlling the engine 1, a water temperature sensor 24 for detecting the temperature of the engine cooling water, an accelerator opening sensor 25 for detecting the accelerator opening (accelerator operation amount), and an intake air temperature are detected. An intake air temperature sensor 26 that detects atmospheric pressure and an atmospheric pressure sensor 45 that detects atmospheric pressure (see FIG. 3 respectively) are provided.
[0036]
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.
[0037]
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, the intake air temperature sensor 26, and the atmospheric pressure sensor 45 are connected to the input side of the ECU 30 to detect each detection signal. Is entered.
[0038]
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.
[0039]
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 an appropriate piston stop position range calculation means 35.
[0040]
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.
[0041]
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.
[0042]
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.
[0043]
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.
[0044]
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.
[0045]
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.
[0046]
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, and in particular the expansion stroke 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.
[0047]
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.
[0048]
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.
[0049]
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.
[0050]
The piston proper stop position range calculating means 35 calculates the proper stop position range of the piston 4 of the expansion stroke cylinder 3A. The proper stop position of the piston 4 means a position where a good restart can be performed without assistance from the starter motor 28 when the piston 4 stops at that position.
[0051]
FIG. 4 is an explanatory diagram illustrating setting of a range for selecting a restart control mode according to the piston stop position. The circle shown in FIG. 4 indicates the stroke of the expansion stroke cylinder 3A, the upper end TDC of the circle indicates the upper dead center of the expansion stroke, and the lower end BDC of the circle indicates the lower dead center of the expansion stroke. As shown in FIG. 4, the range of the appropriate stop position (appropriate range C) is set near the middle between the top dead center and the bottom dead center. The proper range C includes a top dead center side proper range A and a bottom dead center side proper range B. Further, the top dead center-side appropriate range A includes a predetermined basic range A1 set in advance and a correction range A2 incremented by correction. Similarly, the bottom dead center side appropriate range B includes a predetermined basic range B1 set in advance and a correction range B2 incremented by correction. The correction ranges A2 and B2 are appropriate ranges that are enlarged particularly when the startability is high, such as when the engine is restarted after a short period of time (within about 10 seconds) since the engine stopped.
[0052]
Referring to FIG. 3 again, the piston proper stop position range calculating means 35 is a means for calculating the appropriate range C as described above and its breakdown, and includes a stop time measuring means 36, an engine operation history storage means 37, Piston sliding resistance estimation means 38 and in-cylinder air density estimation means 39 are included.
[0053]
The stop time measuring means 36 measures the stop time from when the engine is automatically stopped until restart is started by a timer in the ECU 30. The engine operation history storage means 37 stores the engine operation history from the IG-ON.
[0054]
The piston sliding resistance estimation means 38 estimates the sliding resistance of the piston 4 at the start of restart. FIG. 5 shows a block diagram of the estimation method of the piston sliding resistance estimation means 38. First, the oil temperature 38a of the engine oil is estimated from the water temperature 24a obtained from the water temperature sensor 24 and the engine operation history 37a obtained from the engine operation history storage means 37. The piston sliding resistance 38b is estimated from the oil temperature 38a and the engine stop time 36a obtained from the stop time measuring means 36. Even if the oil temperature is the same, the longer the engine stop time 36a, the greater the amount of oil falling on the cylinder wall surface, and the greater the sliding resistance 38b. If the engine stop time 36a is short (about several seconds), the amount of oil remaining on the cylinder wall surface is large, and the piston sliding resistance 38b is sufficiently small.
[0055]
FIG. 6 is a graph showing the relationship between the piston sliding resistance 38b obtained by the piston sliding resistance estimating means 38 and the correction ranges A2 and B2 calculated by the piston proper stop position range calculating means 35 thereby. The horizontal axis represents the piston sliding resistance, and the vertical axis represents the correction amount. When the oil temperature 38a is sufficiently high and the engine stop time 36a is sufficiently short, the piston sliding resistance 38b becomes a small value of R2 or less. At this time, the correction ranges A2 and B2 are maximized. The correction amount also decreases as the piston sliding resistance 38b increases (if the oil temperature 38a is constant, the longer the engine stop time 36a increases), and when the piston sliding resistance 38b is equal to or greater than R1, A2 = B2 = 0. That is, A = A1 and B = B1.
[0056]
In FIG. 6, changes in the correction ranges A2 and B2 are linearly shown, but may be curves according to engine characteristics as appropriate.
[0057]
Further, instead of the continuously changing characteristic, the presence or absence of correction may be switched on and off (correction range A2 ′, B2 ′) with a predetermined resistance value R3 as indicated by a broken line. good. The former can perform fine control according to the piston sliding resistance 38b, and the latter can simply perform the calculation for obtaining the correction amount.
[0058]
Returning to FIG. 3, the description will be continued. The in-cylinder air density estimation means 39 estimates the in-cylinder air density at the start of restart. FIG. 7 shows a block diagram of the estimation method of the cylinder air density estimation means 39. First, the in-cylinder temperature 39a is estimated from the engine stop time 36a obtained from the stop time measuring means 36, the water temperature 24a obtained from the water temperature sensor 24, and the intake air temperature 26a obtained from the intake air temperature sensor 26. The in-cylinder air density 39b is estimated from the in-cylinder temperature 39a and the atmospheric pressure 45a obtained from the atmospheric pressure sensor 45. Even with the same water temperature and intake air temperature, the longer the engine stop time 36a, the lower the in-cylinder temperature 39a and the lower the in-cylinder air density 39b. When the engine stop time 36a is short (about several seconds), the decrease in the in-cylinder temperature 39a is small, and the in-cylinder air density 39b is sufficiently large (the decrease amount is small).
[0059]
FIG. 8 is a graph showing the relationship between the in-cylinder air density 39b obtained by the in-cylinder air density estimation unit 39 and the correction ranges A2 and B2 calculated by the piston proper stop position range calculation unit 35. The horizontal axis indicates the in-cylinder air density, and the vertical axis indicates the correction amount. When the in-cylinder temperature 39a is sufficiently low and the atmospheric pressure 45a is sufficiently high, the in-cylinder air density 39b has a large value of ρ2 or more. At this time, the correction ranges A2 and B2 are maximized. The correction amount also decreases as the in-cylinder air density 39b decreases (if the water temperature 24a, the intake air temperature 26a, and the atmospheric pressure 45a are constant, the longer the engine stop time 36a decreases), the in-cylinder air density 39b is less than ρ1. A2 = B2 = 0, that is, A = A1 and B = B1.
[0060]
The characteristic shown in FIG. 8 may be a curve corresponding to the characteristic of the engine as appropriate as in FIG. 6, and the presence or absence of correction is switched on / off at a predetermined in-cylinder air density ρ3 as indicated by the broken line (correction Range A2 ′, B2 ′) may be used.
[0061]
Incidentally, in FIG. 8, the correction range B2 is larger than the correction range A1, that is, the amount of expansion of the appropriate range is larger on the bottom dead center side than on the top dead center side. This is due to the following reason. When the piston 4 of the expansion stroke cylinder 3A is relatively large and stops near the bottom dead center, the factor inhibiting the restart is the amount of air in the compression stroke cylinder 3C (the piston 4 is stopped near the top dead center). There is a shortage. That is, as described above, at the time of restart, the combustion is first performed in the compression stroke cylinder 3C to reverse the engine once, but the amount of air for the combustion is insufficient. If the in-cylinder air density 39b is large, the shortage of air can be compensated effectively. In addition, since the amount of air in the expansion stroke cylinder 3A is large (both in-cylinder volume and in-cylinder air density 39b), the combustion torque in the expansion stroke cylinder 3A for rotating the engine in the forward rotation direction is also increased. be able to.
[0062]
On the other hand, when the piston 4 of the expansion stroke cylinder 3A is relatively large and stops near the top dead center, the factor that hinders the restart is the shortage of air in the expansion stroke cylinder 3A. If the in-cylinder air density 39b increases, this shortage of air is compensated, which is effective. However, at this time, although the piston 4 of the compression stroke cylinder 3C is close to the bottom dead center and the amount of air is increased, the combustion torque in the compression stroke cylinder 3C is sufficient to reverse the engine once and more than necessary. Even if the air volume is increased, there is no merit. Although details will be described later, when the piston 4 of the expansion stroke cylinder 3A stops near the top dead center, the combustion in the compression stroke cylinder 3C for reversing the engine burns at a lean air-fuel ratio. At that time, a lean air-fuel ratio exceeding the lean limit cannot be achieved for good combustion, so that it is necessary to inject more fuel than necessary, and as a result, it is possible that excessive reverse torque is generated.
[0063]
As described above, the merit when the in-cylinder air density 39b increases is greater when the piston 4 of the expansion stroke cylinder 3A stops near the bottom dead center than when it stops near the top dead center. Therefore, the correction range B2 is larger than the correction range A2.
[0064]
The piston proper stop position range calculating means 35 comprehensively determines the characteristics shown in FIGS. 6 and 8, and determines the final correction ranges A2 and B2. These are particularly dependent on the engine stop time 36a. If the engine stop time 36a is short (several seconds), the piston sliding resistance 38b is small and the in-cylinder air density 39b is large. The correction ranges A2 and B2 can be greatly enlarged.
[0065]
Next, the operation of the apparatus of the present embodiment as described above will be described.
[0066]
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.
[0067]
When the engine 1 is in a predetermined idling state that does not require the output of the engine 1 while the engine 1 is in operation, the idle stop is executed based on whether or not the engine stop condition is met.
[0068]
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).
[0069]
Then, in order to stop the piston 4 within a preferable range for restarting (appropriate range C in FIG. 4), the fuel is cut at the fuel cut time t1, and the throttle valve 17 is opened to a predetermined opening, and then the engine Control is performed so that the throttle valve 17 is closed at a time point t2 when the rotational speed has decreased to a predetermined rotational speed N1 (N1 = about 500 rpm in the present embodiment) set in advance.
[0070]
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.
[0071]
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, it is close to the part. When divided by the range shown in FIG. 4, the majority (for example, about 90%) are in the basic ranges A1 and B1, most of the remaining are in the correction ranges A2 and B2, and very rarely at positions outside the appropriate range C. Stop.
[0072]
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 appropriate range C increases. 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 (appropriate range B in FIG. 4).
[0073]
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.
[0074]
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.
[0075]
The stop position of the piston 4 is detected by signals from the crank angle sensors 21 and 22 as follows. FIG. 10 is a pulse signal obtained when the crankshaft 6 rotates, 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. 10A shows the case of normal rotation (clockwise in the state of FIG. 1), and FIG. 10B shows the case of reverse rotation. During forward rotation of the engine, as shown in FIG. 10A, 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 is Low when rising, and the second crank angle signal CA2 is High when the first crank angle signal CA1 is falling. On the other hand, during reverse rotation of the engine, as shown in FIG. 10 (b), 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, thereby 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.
[0076]
FIG. 11 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).
[0077]
FIG. 12 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. .
[0078]
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 (500 rpm) (steps S13 and S15). Next, the CA counter value (see FIG. 11) during the constant count 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). To do. Subsequently, measurement of the engine stop time by the stop time measuring means 36 is started (step S21), and the process returns.
[0079]
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.
[0080]
FIG. 13 is a flowchart for selecting the restart mode. If a predetermined restart condition is satisfied during the automatic engine stop (YES in step S91), the measurement of the engine stop time by the stop time measuring means 36 is ended (step S93). Then, after the piston sliding resistance estimation means 38 estimates the piston sliding resistance 38b (step S95) and the cylinder air density estimation means 39 estimates the cylinder air density 39b (step S97), The proper stop position range calculation means 35 calculates the piston proper stop position range (step S99). Specifically, the correction ranges A2 and B2 calculated from the estimated values obtained in steps S95 and S97 are added to the preset basic ranges A1 and B1, and the top dead center side appropriate range A and the bottom dead center side. The appropriate range B is obtained.
[0081]
Subsequently, in step S103 and step S105, the piston stop position of the expansion stroke cylinder 3A (the position stored in step S19 in FIG. 12) is determined, and if the position is within the top dead center side appropriate range A in FIG. The process proceeds to step S107, and restart in the first restart mode is performed. Similarly, if it is in the bottom dead center side appropriate range B, the process proceeds to step S109, and restart in the second restart mode is performed. If it is outside the proper range C, 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.
[0082]
FIG. 14 is a schematic flowchart of the first restart control mode. 15 shows the stroke of each cylinder of the engine corresponding thereto and the combustion in each cylinder from the start of the start control (according to the order of combustion in the figure). Circles "1", "2", "3" ... It is a figure which shows the operation direction of the engine by each combustion with an arrow. FIG. 16 shows temporal changes in the engine speed, the crank angle, the in-cylinder pressure of the angular cylinder, and the indicated torque in the case of the first restart control mode.
[0083]
In the flowchart of FIG. 14, when starting 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 (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 is performed in the compression stroke cylinder 3C, and initial combustion is performed (in FIG. 15). "1" ). However, since ignition does not occur even when ignition is performed, that is, combustion may not be performed, it is determined whether or not the edges (the waveforms shown in FIG. 10) of the crank angle sensors 21 and 22 are 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.
[0084]
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. 16), and the engine 1 is driven in the reverse direction. Accordingly, the piston 4 of the expansion stroke cylinder 3A Approaches the top dead center, the air in the cylinder 3A is compressed and the in-cylinder pressure rises (portion b in FIG. 16).
[0085]
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 elapse, the expansion stroke cylinder 3A is ignited, and the fuel previously injected into the cylinder 3A is combusted (in FIG. 15). “2” ), The engine 1 is driven in the forward rotation direction by the combustion pressure (c portion in FIG. 16). In the next step S173, fuel is injected and ignited, and the second combustion (in FIG. 15). “3” ) And the engine driving force is increased by the combustion pressure (d portion in FIG. 16). The air-fuel ratio at this time is set to be richer than the stoichiometric air-fuel ratio by combining the characteristic M1 and the characteristic M8 determined in advance as a function of the stop position of the piston 4 in order to prevent premature ignition. Read from a map of predetermined characteristic M9 as a function of stop position. After that, the process returns to normal combustion control.
[0086]
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 point that the fuel injection to the compression stroke cylinder 3C performed in step S153 is the stoichiometric air fuel ratio or a slightly richer air fuel ratio, and the second combustion in step S173. “3” It is different from the point that is not made.
[0087]
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.
[0088]
FIG. 17 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.
[0089]
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.
[0090]
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.
[0091]
Accordingly, when the piston position of the expansion stroke cylinder 3A is in the bottom dead center side appropriate range B when the engine is stopped, the air-fuel ratio at the time of the first combustion is made rich so as to meet the above requirement in the compression stroke cylinder 3C, and after the first combustion Since the combustion air does not remain, the second combustion in the vicinity of the compression top dead center is not performed. However, the expansion stroke cylinder 3A has a relatively large amount of air, and is compressed after the corresponding fuel is injected. Since the ignition and combustion are performed after that, relatively large torque is obtained, and the engine can be rotated until it passes the compression top dead center of the compression stroke cylinder 3C and further exceeds the compression top dead center of the next cylinder. A restart can be achieved.
[0092]
On the other hand, when the engine is stopped, when the piston position of the expansion stroke cylinder 3A is in the top dead center side appropriate range A, the expansion amount is reduced because the amount of air in the expansion stroke cylinder 3A is smaller than that in the bottom dead center side appropriate range B. Although the torque obtained by the combustion in the stroke becomes small, 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 request, so that the surplus air remaining after the first combustion is used and compressed Since the second combustion near the top dead center is performed, the torque for driving in the forward direction of the engine is supplemented, and both the combustion in the expansion stroke cylinder 3A and the second combustion in the compression stroke cylinder 3C Sufficient torque is obtained to achieve restart.
[0093]
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. 17, since the resistance to movement in the direction of the top dead center of the piston 4 is increased and the intake amount of the expansion stroke cylinder 3A is increased, the expansion stroke cylinder when the engine is stopped is also shown in FIG. In most cases, the piston position at 3A is within the appropriate range C near the middle of the stroke, and is often within the appropriate range B at the bottom dead center side. Is restarted automatically.
[0094]
That is, if 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 appropriate range C, a sufficient amount of movement in the engine reverse rotation direction is taken. In addition, since the amount of air in the expansion stroke cylinder 3A is reduced, the torque obtained by combustion in the expansion stroke cylinder 3A is reduced, and the bottom dead center side of the expansion stroke cylinder 3A with respect to the appropriate range C ( If the compression stroke cylinder 3C is too close to the 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 appropriate range C, 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. If the piston can be sufficiently applied to the piston, and the piston stop position is in the bottom dead center side appropriate range B, a sufficiently large amount of air can be secured in the expansion stroke cylinder 3A, and the combustion energy in the expansion stroke cylinder 3A can be increased. , Startability can be improved.
[0095]
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 appropriate range C and in which start assist is performed from the initial stage of restart. FIG. 18 is a flowchart of the third restart mode (motor assist). After starting, the starter cancellation condition is read in step S200. In this case, when starting assistance is performed by the starter motor, the engine speed for canceling the start assist motor is read from a preset characteristic value. The characteristics are shown in FIG. As shown in this figure, the starter drive release rotational speed is set to be higher as the piston stop position of the expansion stroke cylinder 3A is closer to the bottom dead center (BDC) and lower as it approaches the top dead center (TDC). Yes.
[0096]
Returning to the flowchart, next, 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.
[0097]
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 exceeded the starter drive release rotational speed read in step S200. If YES, the process proceeds to step S209 to stop the starter motor 28 and return. To do.
[0098]
The first to third restart modes have been described above. However, if the correction ranges A2 and B2 are not provided and A = A1 and B = B1, the throttle valve 17 is controlled when the engine is stopped as described above. The piston 4 of the compression stroke cylinder 3C stops in the basic ranges A1 and B1 in many cases (for example, about 90%, depending on engine characteristics), and the first or second restart mode is selected. Moreover, although it is a small frequency, it may deviate slightly from the basic ranges A1 and B1, and the third restart mode may be selected. At this time, start assist by the starter motor 28 is provided, but since idling stop is performed many times during traveling, the use frequency of the starter motor 28 is greatly increased as a whole even if it is infrequent, and the life is unavoidable. .
[0099]
However, if the correction ranges A2 and B2 are provided in accordance with the high startability as in the present embodiment, the first range is obtained when the correction ranges A2 and B2 slightly deviate from the basic ranges A1 and A2. Alternatively, since the second restart mode is selected, the frequency with which the third restart mode is selected can be greatly reduced. That is, by reducing the number of times the starter motor 28 is operated as a whole, it is possible to prevent a decrease in the life. In the test by the inventor of the present application, the correction ranges A2 and B2 can be set to about 7 to 8 ° CA at maximum (however, depending on the characteristics of the engine), in which case the probability that the piston 4 stops within the appropriate range C Was almost 100%.
[0100]
Next, a second embodiment of the present invention will be described.
[0101]
Since the configuration of each part of the apparatus of the second embodiment is the same as that of the first embodiment, the description of the overlapping parts will be omitted. The second embodiment is completely the same as the first embodiment when the startability is relatively low (when A = A1, B = B1 in the first embodiment). However, the fourth restart mode is different from the fourth restart mode in that it has a fourth restart mode and the startability is high.
[0102]
In the fourth restart mode, the engine is not reversed due to the initial combustion in the compression stroke cylinder 3C, the start assist by the starter motor 28 is not performed (except for the backup when a start failure occurs), and the expansion stroke cylinder 3A is not operated. Is started by combustion in the next compression stroke cylinder 3C. Since the compression in the expansion stroke cylinder 3A is not performed by reversing the engine once, it is required to have a higher startability than in the first and second restart modes.
[0103]
FIG. 20 is an explanatory diagram illustrating setting of a range for selecting a restart control mode according to the piston stop position in this embodiment (when the engine is in a high startability state). The appropriate range C (hereinafter referred to as the first appropriate range C to be distinguished from the second appropriate range D described later) is set in the vicinity of the top dead center and the bottom dead center, and in particular, the second appropriate range close to the middle. It consists of a range D, and an upper dead center side appropriate range A and a lower dead center side appropriate range B outside thereof. The second appropriate range D is based on a predetermined upper dead center side appropriate range A and lower dead center side appropriate range B (which correspond to the basic ranges A1 and B1 of the first embodiment). It is set in a range corresponding to the high startability so as to be superimposed on top (prior to A and B). The range may be increased or decreased according to the piston sliding resistance 38b or the in-cylinder air density 39b in accordance with the characteristics shown in FIGS. 6 and 8, and may be switched on / off at a predetermined boundary point. May be.
[0104]
At the time of restart, when the stop position of the piston 4 of the expansion stroke cylinder 3A is in the top dead center side appropriate range A, the first restart mode is set. When the stop position is in the bottom dead center side appropriate range B, the second restart mode is set. However, when it is outside the first appropriate range C, the third restart mode is selected, and when it is within the second appropriate range D, the fourth restart mode is selected.
[0105]
FIG. 21 is a flowchart for selecting the restart mode. Steps S106 and S110 are added in accordance with the first embodiment shown in FIG. That is, the stop position of the piston 4 is classified by steps S103, S105, and S106. When the piston 4 is in the second appropriate range D, the routine proceeds to step S110 to perform forward rotation start in the fourth restart mode. Yes.
[0106]
For the control in the fourth restart mode, the flowchart is omitted, but the starter motor 28 may not be driven in the control in the third start mode shown in FIG. The start in the fourth restart mode can eliminate the time loss caused by once reversing the engine, so that the quick start can be improved.
[0107]
Although the embodiment of the present invention has been described above, the specific configuration of the apparatus of the present invention is not limited to the above embodiment, and various modifications can be made within the scope of the claims.
[0108]
For example, in the first and second restart modes in the first embodiment, the engine is normally rotated from the beginning without being reversed once according to the characteristics of the engine (particularly in the case of an engine having a high startability) (in the second embodiment). The control corresponding to the fourth start mode may be performed).
[0109]
In the second embodiment, it is not always necessary to provide the top dead center side appropriate range A and the bottom dead center side appropriate range B outside the second suitability range D, and when the second proper range D is the maximum. The upper dead center side appropriate range A and the lower dead center side appropriate range B may be included. The second appropriate range D does not necessarily need to be set inside the first appropriate range C, and a part or all of the second appropriate range D may be set outside the first appropriate range C according to engine characteristics. .
[0110]
The first embodiment and the second embodiment may be combined. That is, when the engine stop period is short and the startability is high, the second proper range D may be set while the top dead center side proper range A and the bottom dead center side proper range B are expanded. good. By doing so, it is possible to independently obtain the life of the starter motor 28 and quick start-up.
[0111]
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. 14, 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.
[0112]
【The invention's effect】
As described above, according to the engine starting device of the present invention, when the engine in operation is stopped and then the engine is restarted, fuel is supplied to the cylinder substantially in the expansion stroke when the engine is stopped, and ignition is performed. In the engine starting device for starting the engine by burning, Provided with a stop time measuring means for measuring the stop time from when the engine automatically stops until restart is started, When the piston position when the engine is stopped is within a predetermined appropriate range suitable for starting, the engine is started by torque generated by combustion of the engine, and when it is outside the appropriate range, the starter motor is further driven from the initial start to start the engine. While assisting, By the stop time measuring means The engine stop time When the amount of oil remaining on the cylinder wall surface of the engine is large and the amount of decrease in the in-cylinder air density is small, within a few seconds or less Since the appropriate range is expanded, the frequency of the starter motor can be reduced and the life of the starter motor can be prevented from being reduced while assisting the starter motor when necessary.
[0113]
Further, when stopping the engine during operation and then restarting the engine, if the piston position during engine stop is within a predetermined first appropriate range suitable for starting, the compression stroke is substantially reduced when the engine is stopped. Fuel is supplied to a cylinder, ignited and burned, and the piston of any cylinder is once rotated in the reverse direction within a range not exceeding the top dead center, and then the cylinder is substantially in the expansion stroke when the engine is stopped. In an engine starter that supplies fuel to, ignites and burns and starts the engine by rotating it in the forward direction, when the engine stop period is short, Specifically, when the amount of oil remaining on the cylinder wall surface is large and the amount of decrease in the cylinder air density is small, it is an extremely short time within about a few seconds. Is provided with a second appropriate range suitable for starting, and when the piston position when the engine is stopped is within the second appropriate range, the rotation in the reverse direction is not performed and the above-mentioned normal range is Since start-up is performed by rotation in the rolling direction, the speed of start-up can be increased as much as possible.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of an engine provided with a starting device according to a first 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 an explanatory diagram showing setting of a range for selecting a restart control mode according to a piston position when the engine is stopped in the first embodiment.
FIG. 5 is an estimation method block diagram in piston sliding resistance estimation means in the control block diagram.
FIG. 6 is a graph showing the relationship between the piston sliding resistance of the engine and the correction range.
FIG. 7 is an estimation method block diagram in the cylinder air density estimation means of the control block diagram.
FIG. 8 is a graph showing the relationship between the in-cylinder air density of the engine and the correction range.
FIG. 9 is an explanatory diagram showing changes in engine speed, throttle opening, intake pipe negative pressure, and cycles of each cylinder when the engine is stopped.
FIGS. 10A and 10B show crank angle signals from two crank angle sensors, where FIG. 10A is a signal at the time of normal engine rotation, and FIG. 10B is a signal at the time of engine reverse rotation.
FIG. 11 is a flowchart showing a process for detecting a piston position when the engine is stopped.
FIG. 12 is a flowchart showing a control flow when the engine is stopped.
FIG. 13 is a flowchart showing a control flow when the engine is restarted according to the first embodiment.
FIG. 14 is a flowchart showing a first restart mode subroutine in the flowchart shown in FIG. 13;
FIG. 15 is an explanatory diagram showing the cycle and combustion operation of each cylinder when the engine is restarted.
FIG. 16 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. 17 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. 18 is a flowchart showing a third restart mode subroutine in the flowchart shown in FIG. 13;
FIG. 19 is a graph showing the relationship between the piston stop position of the expansion stroke cylinder and starter drive release rotation speed when starting assist is performed in the engine.
FIG. 20 is an explanatory diagram showing setting of a range for restart control mode selection according to the piston position when the engine is stopped in the second embodiment.
FIG. 21 is a flowchart showing a control flow when the engine is restarted according to the second embodiment.
[Explanation of symbols]
1 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 substantially)
4 Piston
7 Spark plug
8 Fuel injection valve
17 Throttle valve
18 Throttle valve actuator
28 Starter motor
30 ECU
31 Throttle valve control means
39 Stop time measuring means
A Top dead center side appropriate range
B Bottom dead center side appropriate range
C proper range, first proper range
D Second appropriate range

Claims (6)

In an engine starting device for stopping an engine in operation and then restarting the engine, fuel is supplied to a cylinder substantially in an expansion stroke when the engine is stopped, and ignition and combustion are performed to start the engine. ,
Provided with a stop time measuring means for measuring the stop time from when the engine automatically stops until restart is started,
When the piston position when the engine is stopped is within a predetermined appropriate range suitable for starting, the engine is started by torque generated by combustion of the engine, and when it is outside the appropriate range, the starter motor is further driven from the initial start to start the engine. While assisting,
When the engine stop time by the stop time measuring means is an extremely short time within a few seconds where the amount of oil remaining on the cylinder wall surface of the engine is large and the amount of decrease in the cylinder air density is small, the appropriate range is expanded. An engine starter characterized by: 2. The engine starter according to claim 1 , wherein when the stop time of the engine by the stop time measuring means is within the extremely short time, the amount of expansion of the appropriate range is increased as the stop time is shorter. . 2. The engine starting device according to claim 1, wherein when the engine stop time by the stop time measuring means is within the extremely short time , the appropriate range is expanded by a predetermined amount with respect to a longer time. . When stopping the engine and then restarting the engine, if the piston position when the engine is stopped is within a predetermined first appropriate range suitable for starting, the cylinder is substantially in the compression stroke when the engine is stopped Fuel is supplied to the cylinder, ignited and burned, and the piston of any cylinder is once rotated in the reverse direction within the range not exceeding the top dead center, and then the cylinder substantially in the expansion stroke when the engine is stopped. In an engine starter that supplies fuel, ignites and burns and starts the engine by rotating it in the forward direction,
Provided with a stop time measuring means for measuring the stop time from when the engine automatically stops until restart is started,
It is suitable for starting when the engine stop time by the stop time measuring means is an extremely short time of about several seconds within which the oil remaining amount on the cylinder wall surface of the engine is large and the amount of decrease in the cylinder air density is small . When the second proper range is provided and the piston position when the engine is stopped is within the second proper range, the rotation in the reverse direction is not performed and the start by the rotation in the normal direction from the start is started. An engine starter characterized in that: 5. The engine starter according to claim 4 , wherein when the engine stop time by the stop time measuring means is within the extremely short time, the second appropriate range is increased as the stop time is shorter.   The engine starter according to any one of claims 1 to 5, wherein when the engine being operated is stopped, the throttle opening is increased for a predetermined period during the stop operation.

Images