JP5729264B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine.

As an internal combustion engine mounted on a vehicle such as an automobile, an engine that automatically stops and restarts during idling is known in order to improve fuel efficiency.
Such an automatic stop in the internal combustion engine is such that when the engine is idling and the throttle valve is in a fully closed state, as shown in Patent Document 1, fuel injection from the fuel injection valve in the engine is performed. It is realized by stopping. When the fuel injection from the fuel injection valve is stopped, the self-sustaining operation of the internal combustion engine is not performed, so that the engine rotation speed gradually decreases and finally the engine rotation stops. Thus, the fuel consumption of the internal combustion engine is improved by stopping the engine rotation.

  Further, when the engine rotation is stopped by the automatic stop of the internal combustion engine and the restart condition of the internal combustion engine is satisfied, the internal combustion engine is restarted. Specifically, by starting fuel injection from the fuel injection valve while cranking the internal combustion engine, the fuel injected from the fuel injection valve is mixed with air in the cylinder (combustion chamber) Is ignited. The fuel thus ignited is combusted, whereby the self-sustaining operation of the internal combustion engine is started and the restart of the engine is completed.

JP 2002-70699 A

  By the way, it is preferable that the restart of the internal combustion engine in a state where the engine rotation is stopped by the automatic stop is completed promptly after the restart condition is satisfied. In order to realize this, among the cylinders in the internal combustion engine, in the cylinder in which the piston is stopped in the intake stroke, the fuel is accurately ignited in the first compression stroke after the start of restart, and It is important to improve fuel combustion.

  However, the position of the piston when the engine rotation is stopped by the automatic stop of the internal combustion engine varies depending on the condition at that time, and is not necessarily a preferable position for restart. That is, depending on the position of the piston that is stopped in the intake stroke at the start of the restart, there is a possibility that the fuel cannot be burned well in the first compression stroke in the cylinder corresponding to the piston after the restart is started. There is.

  For example, if the piston is stopped at a position near the intake bottom dead center (BDC) as indicated by position P in FIG. 9 at the start of restart, the fuel injection valve of the internal combustion engine is directed toward the intake port of the engine. In the case of fuel injection, the fuel injected from the fuel injection valve cannot be sucked into the cylinder only by moving the piston toward the intake bottom dead center. For this reason, it becomes impossible to accurately ignite the fuel in the cylinder in the first compression stroke in the cylinder corresponding to the piston after the restart is started. As a result, misfire occurs in the cylinder, and fuel cannot be burned well in the first compression stroke in the cylinder.

  When a loss occurs in the first compression stroke after the start of restart in the cylinder corresponding to the piston, the cylinder corresponding to the next compression stroke, that is, the cylinder in the second compression stroke after the start of restart, Ignition is performed and the fuel is burned. Although this fuel combustion starts the self-sustaining operation of the internal combustion engine and the restart of the engine is completed, in this case, it takes time from the start of the restart to the completion of the restart, and the restart of the internal combustion engine is completed quickly. I can't let you.

  The present invention has been made in view of such circumstances, and an object of the present invention is to control an internal combustion engine capable of realizing a quick restart by adjusting the piston position to an appropriate position at the time of automatic stop. Is to provide.

According to the first or second aspect of the present invention, during the idling operation of the internal combustion engine, after the fuel injection from the fuel injection valve that injects the fuel toward the intake port of the engine with the establishment of the automatic stop condition is stopped, The opening degree of the throttle valve of the internal combustion engine is adjusted to a target opening degree that is a value on the opening side of the valve when fully closed. During the stop process of the internal combustion engine accompanying the stop of the fuel injection, the engine speed gradually decreases, and the internal combustion engine reverses due to the repulsive force of the compressed air in the cylinder that has reached the compression stroke immediately before the stop of the engine rotation. Rotate. Then, the piston moves from the intake bottom dead center toward the intake top dead center with the reverse rotation of the internal combustion engine, and then stops in the middle of the intake stroke. The position at which the piston stops at this time becomes a position closer to the intake top dead center as the target opening of the throttle valve is set to an open side value. This is because as the target opening of the throttle valve is set to the open side value, the amount of compressed air existing in the cylinder immediately before the reverse rotation of the engine during the stop process of the internal combustion engine increases, and the repulsion due to the compressed air occurs. This is because the force increases and the piston moves vigorously from the intake bottom dead center toward the intake top dead center, and then the piston stops.

Here, the target opening of the throttle valve is set to a value that stops the piston of the internal combustion engine within the range from the vicinity of the middle of the intake stroke to the intake top dead center when the engine rotation is stopped. For this reason, when restarting the internal combustion engine from the state where the engine rotation is stopped by the automatic stop, if the engine is cranked, the engine stops within the range from the vicinity of the middle of the intake stroke to the intake top dead center. The piston moves toward the intake bottom dead center. Furthermore, when the internal combustion engine is restarted, when fuel is injected from the fuel injection valve toward the intake port, the injected fuel is effectively sucked into the cylinder by the movement of the piston. Accordingly, in the first compression stroke in the cylinder corresponding to the piston after the restart of the internal combustion engine is started, the fuel in the cylinder can be accurately ignited, and in the first compression stroke in the cylinder. It is possible to improve the combustion of the fuel. Thereby, quick restart of an internal combustion engine is realizable.
The target opening of the throttle valve is preferably variably set based on the temperature of the cooling water of the internal combustion engine. Here, when the temperature of the cooling water of the internal combustion engine is low, the temperature of the lubricating oil of the engine becomes low and the viscosity of the lubricating oil increases, thereby increasing the resistance of engine rotation. On the other hand, when the temperature of the cooling water in the internal combustion engine is high, the engine temperature also rises. Therefore, when the engine rotation is stopped due to automatic stop, the air remaining in the cylinder receives the heat of the internal combustion engine and rises in temperature. It becomes easy to do. For this reason, if the position of the piston of the internal combustion engine in the stopped state is a position near the intake bottom dead center, the amount of air in the cylinder corresponding to the piston increases. The amount of heat held by receiving heat increases. In this case, when the air in the cylinder is compressed in the compression stroke when the internal combustion engine is restarted, the fuel in the cylinder may self-ignite, and good combustion of the fuel may not be obtained.
In consideration of these points, in the first aspect of the present invention, when the temperature of the cooling water is in a low temperature region lower than a prescribed intermediate temperature region, the target opening when the temperature of the cooling water is in the intermediate temperature region is considered. In comparison with the degree, the lower the temperature of the cooling water, the more the target opening is set to a value on the opening side. According to the above configuration, when the temperature of the cooling water of the engine becomes lower as the viscosity of the lubricating oil of the internal combustion engine becomes excessively high, the target opening of the throttle valve can be set to a further open side value. .
Further, in the invention according to claim 2, when the temperature of the cooling water is in a high temperature region higher than a specified intermediate temperature region, the temperature is compared with the target opening when the temperature of the cooling water is in the intermediate temperature region. As the temperature of the cooling water is higher, the target opening is set to a value on the opening side. According to the above configuration, the target opening of the throttle valve is set to a more open side value even when the temperature of the cooling water of the engine is higher as the heat received from the internal combustion engine of the air remaining in the cylinder is excessively increased. It becomes possible to do.
Thus, by variably setting the target opening based on the temperature of the cooling water of the internal combustion engine, the following can be realized. That is, when the temperature of the cooling water of the engine is low as the viscosity of the lubricating oil of the internal combustion engine becomes excessively high, even if the resistance of engine rotation increases due to the viscosity of the lubricating oil, the piston is placed in the middle of the intake stroke. It can be moved within the range from the vicinity to the intake top dead center and stopped in that state. In addition, when the temperature of the cooling water of the engine is so high that the heat received from the internal combustion engine of the air remaining in the cylinder becomes excessive, the intake top dead center in the range from the middle of the intake stroke to the intake top dead center. It can be moved to a position near the point and stopped in that state. In this case, since the amount of air remaining in the cylinder corresponding to the piston is reduced, it is possible to suppress an increase in the amount of heat that the air retains due to heat received from the internal combustion engine. Therefore, it can be avoided that fuel is self-ignited in the cylinder when the internal combustion engine is restarted due to an increase in the amount of heat of the air, thereby preventing good combustion of the fuel from being obtained.
The intermediate temperature region indicates a specified temperature range, and is a region that is controlled so that the target opening degree is constant with respect to a change in the temperature of the cooling water.

The target opening of the throttle valve by the setting means is set such that the piston is moved from the first half of the intake stroke, that is, from 90 ° CA before the intake top dead center when the engine rotation is stopped by automatic stop, as in the third aspect of the invention. It can be considered that the value is stopped within the range up to the intake top dead center. The target opening may be set to a value that stops the piston within a range from, for example, 80 ° CA before intake top dead center to intake top dead center when the engine rotation is stopped by automatic stop. It is. Further, the target opening is set by stopping the piston within a range from 100 ° CA before the intake top dead center to the intake top dead center or within a range from 110 ° CA before the intake top dead center to the intake top dead center. It is also possible to carry out so as to obtain a value to be obtained.

According to a fourth aspect of the present invention, the adjustment of the throttle valve to the target opening is performed after a predetermined delay time has elapsed after the fuel injection from the fuel injection valve is stopped based on the establishment of the automatic stop condition. Starts from. Here, if the adjustment to the target opening of the throttle valve is performed immediately after the stop of fuel injection, a large amount of air is sucked into the cylinder while the last injected fuel remains around the intake port. In addition, the fuel sucked into the cylinder together with the air may burn, and the engine speed may increase rapidly. In this regard, in the second aspect of the invention, even if the last injected fuel exists around the intake port, the fuel flows downstream to such an extent that the fuel cannot be combusted. The adjustment to the opening can be started. Thus, by starting the adjustment to the target opening of the throttle valve, it is possible to avoid the problem such as the sudden increase in the engine speed described above.

  According to the fifth aspect of the present invention, the target stop position of the piston when the engine rotation is stopped by the automatic stop is determined, and the target opening of the throttle valve is set to a value corresponding to the target stop position of the piston. Is done. When the actual stop position of the piston when the engine rotation is stopped by the automatic stop is deviated from the target stop position, that is, when a difference between the actual stop position and the target stop position occurs, the automatic stop is performed next time. The correction based on the difference is added to the target opening of the throttle valve when it is performed. By correcting the target opening in this way, the actual stop position of the piston when the engine rotation is stopped by the automatic stop is adjusted to the target stop position, and the deviation (difference) between the actual stop position and the target stop position. ) Can be eliminated.

1 is a schematic diagram showing an entire internal combustion engine to which a control device of the present invention is applied. Explanatory drawing which shows the change aspect of the intake stroke in each cylinder of an internal combustion engine with respect to the change of a crank angle, a compression stroke, an expansion stroke, and an exhaust stroke. The graph which shows the change aspect of an engine speed when automatic stop and restart of an internal combustion engine are performed. (A)-(d) is explanatory drawing which shows the range of the stop position of the piston in the cylinder which becomes an intake stroke when an engine rotation stops by an automatic stop. The flowchart which shows the detailed execution procedure of the automatic stop in an internal combustion engine. The graph which shows the change aspect of the target opening degree of the throttle valve with respect to the change of the cooling water of an internal combustion engine. (A) And (b) is the schematic which shows the position of the piston in the cylinder which becomes an intake stroke when engine rotation stops by an automatic stop. Explanatory drawing which shows the relationship between the temperature of the cooling water of an internal combustion engine, the position of the piston stopped by the intake stroke by automatic stop, and the presence or absence of self-ignition at the time of the first compression stroke ignition. Explanatory drawing which shows an example of the stop position of the piston in the cylinder which becomes an intake stroke when engine rotation stops by an automatic stop.

An embodiment in which the present invention is applied to a four-cylinder internal combustion engine for an automobile will be described below with reference to FIGS.
In the internal combustion engine 1 shown in FIG. 1, a throttle valve 13 is provided in an intake passage 3 connected to the combustion chamber 2 of each of the first to fourth cylinders so that it can be opened and closed. Air is sucked and fuel injected from the fuel injection valve 4 toward the intake port 3a of the engine 1 is supplied to the combustion chamber 2. When the air / fuel mixture is ignited by the spark plug 5, the air / fuel mixture burns, the piston 6 reciprocates, and the crankshaft 7 that is the output shaft of the internal combustion engine 1 rotates. On the other hand, the air-fuel mixture after burning in the combustion chamber 2 is sent to the exhaust passage 8 as exhaust gas. The crankshaft 7 is connected to a starter 10 for forcibly rotating (cranking) the crankshaft 7 when starting the internal combustion engine 1.

  The combustion chamber 2 and the intake passage 3 in the internal combustion engine 1 are communicated and blocked through the opening / closing operation of the intake valve 11. The intake valve 11 opens and closes as the intake camshaft 12 that receives the rotation transmission from the crankshaft 7 rotates. Further, the combustion chamber 2 and the exhaust passage 8 in the internal combustion engine 1 are communicated / blocked through an opening / closing operation of the exhaust valve 14. The exhaust valve 14 opens and closes as the exhaust camshaft 15 that receives the rotation transmission from the crankshaft 7 rotates.

  An automobile equipped with such an internal combustion engine 1 is provided with an electronic control device 21 that executes various controls relating to the operation of the engine 1. This electronic control device 21 includes a CPU that executes various arithmetic processes related to the above control, a ROM that stores programs and data necessary for the control, a RAM that temporarily stores CPU calculation results, and the like. It has input / output ports for inputting / outputting signals.

Various sensors shown below are connected to the input port of the electronic control unit 21.
A water temperature sensor 25 that detects the temperature of the cooling water of the internal combustion engine 1.
A vehicle speed sensor 26 that detects the traveling speed (vehicle speed) of the automobile.

An accelerator position sensor 28 that detects the amount of depression (accelerator depression amount) of the accelerator pedal 27 that is depressed by the driver of the automobile.
A brake switch 29a that detects the on / off operation of the brake pedal 29 that is depressed by the driver.

A throttle position sensor 30 that detects the opening (throttle opening) of the throttle valve 13 provided in the intake passage 3.
An intake air temperature sensor 31 that detects the temperature of the air passing through the intake passage 3.

An air flow meter 32 that detects the amount of air passing through the intake passage 3 (intake air amount).
A cam position sensor 33 that outputs a signal corresponding to the rotation position of the shaft 12 based on the rotation of the intake camshaft 12.

A crank position sensor 34 that outputs a signal corresponding to the rotation of the crankshaft 7.
Connected to the output port of the electronic control device 21 are a drive circuit for various devices such as a drive circuit for the fuel injection valve 4, a drive circuit for the spark plug 5, a drive circuit for the starter 10, and a drive circuit for the throttle valve 13. Yes.

  The electronic control unit 21 then determines the engine operating state such as the engine speed and the engine load (the amount of air taken into the combustion chamber 2 per cycle of the internal combustion engine 1) based on the detection signals input from the various sensors. To grasp. The engine speed is obtained based on a detection signal from the crank position sensor 34. The engine load is calculated from the intake air amount of the internal combustion engine 1 obtained based on detection signals from the accelerator position sensor 28, the throttle position sensor 30, the air flow meter 32, and the like, and the engine rotational speed. The electronic control unit 21 outputs command signals to various drive circuits connected to the output port in accordance with the engine operating state such as the engine load and the engine speed. In this way, fuel injection control, ignition timing control, intake air amount control, starter 10 drive control, and the like in the internal combustion engine 1 are performed through the electronic control unit 21.

Next, control for automatically stopping or restarting the internal combustion engine 1 during idle operation will be described in order to improve the fuel efficiency of the internal combustion engine 1.
The internal combustion engine 1 is automatically stopped when a predetermined automatic stop condition is satisfied during idle operation. As the automatic stop condition, the accelerator operation amount is “0”, the output request of the internal combustion engine 1 is not requested, the vehicle speed is “0”, and the brake pedal 29 is depressed (the ON operation is performed). And the like. When all of these conditions are satisfied, it is determined that the automatic stop condition is satisfied. When it is determined that the automatic stop condition is satisfied, the fuel injection from the fuel injection valve 4 is stopped under the situation where the engine 1 is idling and the throttle valve 13 is fully closed. Is done. Since the self-sustained operation of the internal combustion engine 1 is not performed by stopping the fuel injection from the fuel injection valve 4, the engine speed gradually decreases. Then, immediately before the engine rotation finally stops, the internal combustion engine 1 rotates reversely by the repulsive force of the compressed air in the cylinder that has become the compression stroke. With the reverse rotation of the internal combustion engine 1, the piston 6 moves from the intake bottom dead center (BDC) toward the intake top dead center (TDC), and then stops in the middle of the intake stroke. As described above, the fuel consumption of the internal combustion engine 1 is improved by stopping the engine rotation.

  Further, when the engine rotation is stopped by the automatic stop of the internal combustion engine 1 and the restart condition of the internal combustion engine 1 is satisfied, the internal combustion engine 1 is restarted. Examples of the restart condition include a condition that the accelerator operation amount becomes larger than “0”, that the depression of the brake pedal 29 is released (an off operation is performed), and the like. Then, it is determined that the restart condition is satisfied when at least one of these conditions is satisfied. When it is determined that the restart condition is satisfied in this way, the internal combustion engine 1 is cranked through driving of the starter 10 and fuel injection from the fuel injection valve 4 is started during the cranking. Thus, the fuel injected from the fuel injection valve 4 toward the intake port 3a is sucked into the cylinder (combustion chamber 2) through the movement of the piston 6 toward the intake bottom dead center in the intake stroke. Further, air is also taken into the combustion chamber 2 from the intake port 3a together with the fuel. Then, the fuel is ignited by the spark plug 5 in a state where the fuel is mixed with air in the combustion chamber 2, and the fuel is combusted through the ignition, whereby the self-sustaining operation of the internal combustion engine 1 is started and the engine 1 is restarted. Complete.

Next, the operation of the control device for the internal combustion engine 1 in the present embodiment will be described.
The restart of the internal combustion engine 1 in a state where the engine rotation is stopped by the automatic stop is preferably completed promptly after the restart condition is satisfied. In order to realize this, among the first to fourth cylinders in the internal combustion engine 1, in the cylinder in which the piston 6 is stopped in the intake stroke, the fuel is supplied to the fuel in the first compression stroke after the start of restart. It is important that the fuel is properly ignited and that the fuel combustion is good. Note that the ignition of the fuel in the first compression stroke after the start of the restart is hereinafter referred to as “initial compression stroke ignition”.

  FIG. 2 shows changes in the intake stroke, compression stroke, expansion stroke, and exhaust stroke in each cylinder with respect to changes in the crank angle in the internal combustion engine 1. Suppose that when the engine rotation is stopped by automatic stop, the piston 6 of the first cylinder # 1 stops in the middle of the intake stroke (T1 to T3). In this case, after the internal combustion engine 1 is restarted, the fuel in the cylinder # 1 is accurately ignited (initial compression stroke ignition) at the end of the first compression stroke (T4) in the first cylinder # 1. If the combustion of the fuel can be improved, the engine rotation speed can be started to rise early (T4) after the restart is started, as shown by the solid line in FIG. For this reason, the engine rotation speed can be increased to a value at which the internal combustion engine 1 can be operated autonomously at an early stage after the start of the restart, and the restart of the internal combustion engine 1 can be completed quickly.

  On the other hand, after the restart of the internal combustion engine 1, the first compression stroke ignition in the first cylinder # 1 shown in FIG. 2 cannot be performed accurately, and the fuel combustion in the same cylinder # 1 is made good. If not, the fuel in the cylinder is ignited in the same compression stroke (T5) in the cylinder (third cylinder # 3 in this example) that reaches the second compression stroke after the start of restart. Note that the ignition of the fuel in the second compression stroke after the start of the restart is hereinafter referred to as “second compression stroke ignition”. When this second compression stroke ignition is the ignition of the first fuel after the start of restart, even if the combustion of the fuel based on the ignition is performed well, the increase in the engine rotational speed is indicated by a two-dot chain line in FIG. As shown, it is inevitable to be late. For this reason, it is delayed that the engine speed is increased to a value at which the internal combustion engine 1 can be operated independently after the restart is started, and thus the restart completion of the internal combustion engine 1 is also delayed. As a result, it takes time from the start of restart to the completion of restart, and the restart of the internal combustion engine 1 cannot be completed promptly.

  The reason why the first compression stroke ignition cannot be accurately performed is that the stop position of the piston 6 in the cylinder that becomes the intake stroke when the engine rotation is stopped by the automatic stop is much larger than the vicinity of the middle of the intake stroke. It is mentioned that the position is close to the intake bottom dead center. For example, in the example of FIG. 2, the piston 6 of the first cylinder # 1 is at a position much closer to the intake bottom dead center than the middle (T2) of the intake stroke (T1 to T3), that is, a position close to T3 in the drawing. When stopped, the fuel injected from the fuel injection valve 4 cannot be sucked into the cylinder (first cylinder # 1) only by moving the piston 6 toward the intake bottom dead center. For this reason, in the first compression stroke in the cylinder corresponding to the piston 6 after the restart is started, it becomes impossible to accurately ignite the fuel in the cylinder. As a result, misfire occurs in the cylinder, and fuel cannot be burned well in the first compression stroke in the cylinder.

  In order to cope with such a situation, in this embodiment, after the fuel injection from the fuel injection valve 4 is stopped in order to automatically stop the internal combustion engine 1, the throttle valve 13 is set to a value that is more open than when it is fully closed. The target opening degree tTA is adjusted.

  As described above, in the stop process of the internal combustion engine 1 accompanying the stop of the fuel injection, the engine speed gradually decreases, and the repulsion due to the compressed air in the cylinder that has become the compression stroke immediately before the stop of the engine rotation. The internal combustion engine 1 rotates in reverse by the force. Then, with the reverse rotation of the internal combustion engine 1, the piston 6 moves from the intake bottom dead center toward the intake top dead center, and then stops in the middle of the intake stroke. The position at which the piston 6 stops at this time becomes a position closer to the intake top dead center as the target opening degree tTA of the throttle valve 13 is set to the opening side value. Hereinafter, the reason for this will be described in detail by taking the case of FIG. 2 as an example.

  In the example of FIG. 2, the engine rotation is stopped in a state where the cylinder # 1 is in the intake stroke. For this reason, immediately before the engine rotation is stopped, the first cylinder # 1 is in the compression stroke, and the internal combustion engine 1 is reversely rotated by the repulsive force of the compressed air in the first cylinder # 1. When the internal combustion engine 1 rotates in the reverse direction by the repulsive force of the compressed air in the first cylinder # 1, the air in the cylinder is compressed in the second cylinder # 2 in the expansion stroke. Trying to prevent reverse rotation of. For this reason, when the piston 6 of the first cylinder # 1 is moved close to the intake top dead center by the reverse rotation of the internal combustion engine 1, it exists in the first cylinder # 1 that is in the compression stroke at the start of the reverse rotation. It is necessary to increase the amount of air. As the air amount increases, the piston 6 of the first cylinder # 1 moves vigorously from the intake bottom dead center toward the intake top dead center after the reverse rotation, and the amount of movement at that time increases, and the piston 6 is inhaled. It becomes possible to move to near the top dead center.

  Here, the more the target opening degree tTA of the throttle valve 13 is set to a value on the open side, the more in the cylinder (in the example of FIG. 2, the compression stroke becomes the compression stroke immediately before the reverse rotation of the engine 1 in the stop process). The amount of air in cylinder # 1) increases. This is because the change in the engine speed before and after the reverse rotation in the internal combustion engine 1 becomes more gradual as the target opening tTA is set to the open side value and the throttle valve 13 is opened. Yes. Thus, when the change in engine rotation before and after the reverse rotation in the internal combustion engine 1 becomes gentle, the time during the intake stroke in the cylinder that becomes the compression stroke immediately before the start of the reverse rotation becomes longer. In the intake stroke, the amount of air sucked into the cylinder increases. Therefore, as the target opening degree tTA is set to a value on the open side, the amount of air in the cylinder that becomes the compression stroke immediately before the reverse rotation of the internal combustion engine 1 increases.

  Incidentally, the target opening degree tTA is a value at which the piston 6 stops within the range from the middle of the intake stroke to the intake top dead center in the cylinder that becomes the intake stroke when the engine rotation is stopped by the automatic stop. Is set. Therefore, when the internal combustion engine 1 is restarted from the state where the engine rotation is stopped by the automatic stop, if the cranking of the engine 1 is performed, the engine stops within the range from the middle of the intake stroke to the intake top dead center. The piston 6 that has been moved moves toward the intake bottom dead center. Further, when the internal combustion engine 1 is restarted, when fuel is injected from the fuel injection valve 4 toward the intake port 3a, the injected fuel is effectively sucked into the cylinder by the movement of the piston 6. Therefore, in the first compression stroke in the cylinder corresponding to the piston 6 after the restart of the internal combustion engine 1 is started, the fuel in the cylinder can be accurately ignited (initial compression stroke ignition). The combustion of the fuel in the first compression stroke in the cylinder can be improved. Thereby, the quick restart of the internal combustion engine 1 is realizable.

  Note that the target opening degree tTA is specifically the piston top 6 of the cylinder that is in the intake stroke when the engine rotation is stopped by the automatic stop in the first half of the intake stroke, in other words, the intake top deadline shown in FIG. It is conceivable to set the value to stop within the range h1 from 90 ° CA before the point to the intake top dead center. Further, the target opening degree tTA can be set to a value at which the piston 6 stops within a range h2 from 80 ° CA before the intake top dead center to the intake top dead center shown in FIG. Further, the value at which the piston 6 stops within the range h3 from 100 ° CA before the intake top dead center to the intake top dead center shown in FIG. 4C, or 110 before the intake top dead center shown in FIG. It is also possible to set the target opening tTA to a value that stops within the range h4 from CA to the intake top dead center. When the target opening degree tTA is set corresponding to any one of the ranges h1 to h4, the piston 6 is set to stop at a target stop position within the range. This target stop position is an ideal stop position of the piston 6 that changes according to the temperature of the cooling water of the internal combustion engine 1 and the intake air temperature. For example, the vibration of the internal combustion engine 1 at the time of restart is set to an allowable level. However, the position is as close to the intake top dead center as possible.

  Next, a detailed procedure of the automatic stop in the internal combustion engine 1 will be described with reference to a flowchart of FIG. 5 showing an automatic stop routine. This automatic stop routine is periodically executed through the electronic control device 21 by, for example, a time interruption every predetermined time.

  In this routine, first, it is determined whether or not an automatic stop condition for the internal combustion engine 1 is satisfied (S101). If the determination is affirmative, fuel injection from the fuel injection valve 4 is performed to automatically stop the internal combustion engine 1. Is stopped (S102). After the fuel injection from the fuel injection valve 4 is stopped, it is determined whether or not a predetermined delay time has elapsed (S103). When an affirmative determination is made in S103, processing for adjusting the throttle valve 13 to the target opening degree tTA is executed (S104, S105).

  If the adjustment to the target opening degree tTA of the throttle valve 13 is performed immediately after the fuel injection from the fuel injection valve 4 is stopped, regardless of whether or not the delay time has elapsed, The following problems arise. That is, the amount of fuel that has been injected last before the fuel injection from the fuel injection valve 4 remains around the intake port 3a while the throttle valve 13 is opened to the target opening degree tTA. Air is sucked into the cylinder, and the fuel sucked into the cylinder together with the air is combusted through ignition by the spark plug 5, so that the engine speed rapidly increases. In order to avoid such a problem, the adjustment of the throttle valve 13 to the target opening tTA is started after the delay time has elapsed after the fuel injection from the fuel injection valve 4 is stopped. Incidentally, the delay time is necessary for the fuel finally injected toward the intake port 3a to flow downstream to the extent that it cannot be combusted in the cylinder before the fuel injection from the fuel injection valve 4 is stopped. It is set beforehand by experiment etc. so that it may become a long time.

  As the process for adjusting the throttle valve 13 to the target opening degree tTA (S104, S105), the target opening degree tTA is first set (S104). Specifically, the target opening degree tTA based on the temperature of the cooling water of the internal combustion engine 1 is a value for stopping the piston 6 of the cylinder that is in the intake stroke when the engine rotation is stopped by automatic stop at the target stop position described above. Further, a correction corresponding to a correction value TAH is added to the target opening degree tTA so as to cope with variations due to individual differences of the internal combustion engine 1. Thereafter, the throttle valve 13 is adjusted to the corrected target opening degree tTA (S105). Specifically, the throttle valve 13 is driven based on the actual opening detected by the throttle position sensor 30 and the target opening tTA so that the opening of the throttle valve 13 becomes the corrected target opening tTA. The

  Here, the target opening degree tTA is made variable as shown in FIG. 6, for example, with respect to the change in the temperature of the cooling water of the internal combustion engine 1 through the processing of S104. As can be seen from the figure, when the temperature of the cooling water is in the intermediate temperature range (Tp2 to Tp3), the target opening degree tTA is substantially constant with respect to the change in the temperature of the cooling water.

  On the other hand, when the temperature of the cooling water is in the low temperature range (Tp1 to Tp2), the target opening tTA gradually changes to a value on the open side as the temperature of the cooling water becomes lower than the value in the middle temperature range. go. Incidentally, when the temperature of the cooling water of the internal combustion engine 1 is low, the temperature of the lubricating oil of the engine 1 is also lowered and the viscosity of the lubricating oil is increased, thereby increasing the resistance of engine rotation.

  However, by adjusting the throttle valve 13 to the target opening tTA that is variable as described above in the low temperature region, it is possible to cope with an increase in resistance to engine rotation caused by the high viscosity of the lubricating oil. It becomes possible. That is, when the temperature of the cooling water of the engine 1 is lower as the viscosity of the lubricating oil of the internal combustion engine 1 becomes excessively high, the piston 6 is sucked into the piston 6 even if the resistance of the engine rotation increases due to the viscosity of the lubricating oil. It can be moved to the target stop position within the range from the middle of the stroke to the intake top dead center, and can be stopped in that state.

  Further, when the temperature of the cooling water is in the high water temperature region (Tp3 to Tp4), the target opening tTA gradually changes to a value on the open side as compared with the value in the intermediate temperature region as the temperature of the cooling water increases. Go. By the way, when the temperature of the cooling water of the internal combustion engine 1 is high, the engine temperature also becomes high. Therefore, the air remaining in the cylinder receives the heat of the internal combustion engine 1 when the engine rotation is stopped by the automatic stop. Temperature rises easily. For this reason, if the position of the piston 6 of the internal combustion engine 1 in a stopped state is a position near the intake bottom dead center as shown in FIG. 7A, the amount of air in the cylinder corresponding to the piston 6 Therefore, the amount of heat that the air retains due to heat received from the internal combustion engine 1 increases. In this case, when the air in the cylinder is compressed in the compression stroke when the internal combustion engine 1 is restarted, the fuel in the cylinder may be ignited and good combustion of the fuel may not be obtained. FIG. 8 shows the relationship between the cooling water temperature of the internal combustion engine 1, the position of the piston 6 stopped in the intake stroke by the automatic stop, and the presence or absence of the self-ignition at the time of initial compression stroke ignition.

  However, in the high temperature region, as the throttle valve 13 is adjusted to a target opening tTA that is variable as shown in FIG. 6, the heat received from the internal combustion engine 1 by the air remaining in the cylinder becomes excessive. When the temperature of the cooling water of the engine 1 is high, the position of the piston 6 when the engine rotation is stopped by the automatic stop can be set to the position of FIG. 7B, for example. That is, the position near the intake top dead center in the range from the middle of the intake stroke to the intake top dead center is the target stop position of the piston 6, and after moving the piston 6 to that position, the piston 6 is moved. The target opening degree tTA is set so that it can be stopped. In this case, since the piston 6 is stopped at the position shown in FIG. 7B, the amount of air remaining in the cylinder corresponding to the piston 6 is reduced. It is possible to suppress an increase in the amount of heat held by receiving heat. Therefore, when the internal combustion engine 1 is restarted, when the internal combustion engine 1 is restarted, the fuel self-ignites in the cylinder when the internal combustion engine 1 is restarted. It can be avoided that it cannot be obtained.

  Furthermore, when the temperature of the cooling water of the internal combustion engine 1 is in the excessively high temperature region (Tp4 or more) shown in FIG. 6, the target opening degree tTA is set to “0”, that is, a value corresponding to full closure. This is because in the excessively high temperature region, when the engine rotation is stopped due to automatic stop, the heat remaining from the internal combustion engine 1 of the air remaining in the cylinder becomes excessive, and the target opening degree tTA is set to the open side so that the piston This is because, even if 6 is stopped at a position close to the intake top dead center, it is inevitable that the self-ignition occurs during the first compression stroke ignition at the time of restart. Therefore, in order to prevent the throttle valve 13 from being unnecessarily adjusted to the open side value even when fully closed after the automatic stop is started, the target opening tTA is set to “0” as described above in the excessively high temperature region. Is done.

  In the automatic stop routine of FIG. 5, the processing of S106 to S107 is for calculating a correction value TAH used for correcting the target opening degree tTA in S104. In this series of processing, it is first determined whether or not the engine rotation has stopped due to the stop of fuel injection from the fuel injection valve 4 for automatically stopping the internal combustion engine 1 (S106). If it is a stroke determination here, it is determined whether or not a feedback condition, which is a condition for calculating the correction value TAH, is satisfied (S107). Here, as the feedback condition, the temperature of the cooling water of the internal combustion engine 1 is in the middle temperature range (Tp2 to Tp3) in FIG. 6, the intake air temperature of the internal combustion engine 1 is not excessively high, and so on. Is given. Then, it is determined that the feedback condition is satisfied when all of these conditions are satisfied. When it is determined that the feedback condition is satisfied, the correction value TAH is calculated based on the difference between the actual stop position and the target stop position of the piston 6 of the cylinder that is in the intake stroke when the engine rotation is stopped. In addition, the calculated correction value TAH is stored in the nonvolatile memory of the electronic control unit 21 (S108 in FIG. 5). When the correction value TAH is added to the target opening degree tTA in the process of S104, the stored correction value TAH is used.

  Note that the actual stop position of the piston 6 used when calculating the correction value TAH when the engine rotation is stopped is obtained by monitoring detection signals from the crank position sensor 34 and the cam position sensor 33 during the engine rotation stop process. Is possible. The target stop position of the piston 6 here is a position within the range from the middle of the intake stroke to the intake top dead center, and the condition that the cooling water of the internal combustion engine 1 is in the intermediate temperature range. In other words, the position is as close to the intake top dead center as possible while setting the vibration of the internal combustion engine 1 at the restart to an allowable level. The target stop position is obtained based on the temperature of the cooling water of the internal combustion engine 1 and the intake air temperature. In the process of S108, if the actual stop position of the piston 6 matches the target stop position, the correction value TAH is set to “0”. On the other hand, when the actual stop position of the piston 6 is shifted closer to the intake bottom dead center with respect to the target stop position, the correction value TAH is larger than “0” as the shift is larger, that is, the target opening tTA. Is calculated as a value for correcting to the open side. When the actual stop position of the piston 6 is deviated closer to the intake bottom dead center with respect to the target stop position, the correction value TAH is smaller than “0” as the deviation is larger, that is, the target opening degree. It is calculated as a value for correcting tTA to the closing side.

According to the embodiment described in detail above, the following effects can be obtained.
(1) After the fuel injection from the fuel injection valve 4 is stopped in order to automatically stop the internal combustion engine 1, the throttle valve 13 is adjusted to a target opening degree tTA that is a value on the opening side of the fully closed state. . As the target opening degree tTA is set to a value on the opening side, the piston 6 stops at a position closer to the intake top dead center in the cylinder that becomes the intake stroke when the engine rotation is stopped by the automatic stop. Considering this, the target opening tTA is within the range from the vicinity of the middle of the intake stroke to the intake top dead center in the cylinder that takes the intake stroke when the engine rotation is stopped by the automatic stop. Is set to a value that stops at the target stop position. For this reason, when the internal combustion engine 1 is restarted from the state where the engine rotation is stopped by the automatic stop, when the cranking of the engine 1 is performed, a target within the range from the vicinity of the middle of the intake stroke to the intake top dead center is obtained. The piston 6 stopped at the stop position moves toward the intake bottom dead center. Further, when the internal combustion engine 1 is restarted, when fuel is injected from the fuel injection valve 4 toward the intake port 3a, the injected fuel is effectively sucked into the cylinder by the movement of the piston 6. Therefore, the first compression stroke ignition after the restart of the internal combustion engine 1 can be accurately performed, and the fuel combustion in the first compression stroke in the same cylinder can be improved. Thereby, the quick restart of the internal combustion engine 1 is realizable.

  (2) The throttle valve 13 is adjusted to the target opening degree tTA after a predetermined delay time has elapsed after the fuel injection from the fuel injection valve 4 is stopped for the automatic stop of the internal combustion engine 1. Be started. Assuming that the delay time is set to “0”, the throttle valve 13 is used while the fuel injected last before the fuel injection from the fuel injection valve 4 stops around the intake port 3a. With the opening to the target opening tTA, a lot of air is sucked into the cylinder, and the fuel sucked into the cylinder together with the air burns through ignition by the spark plug 5. There is a problem that the engine speed rapidly increases through the combustion of the fuel. Considering this, the delay time is set downstream so that the fuel finally injected toward the intake port 3a before the fuel injection from the fuel injection valve 4 is stopped cannot be combusted in the cylinder. And the time required to flow. Therefore, even if the last fuel injected before stopping the fuel injection from the fuel injection valve 4 exists around the intake port 3a, the fuel flows downstream to such an extent that the fuel cannot be combusted. Adjustment to the target opening degree tTA of the valve 13 is started. Thus, by starting the adjustment of the throttle valve 13 to the target opening degree tTA, it is possible to avoid the occurrence of the problem such as the sudden increase in the engine speed described above.

  (3) When the temperature of the cooling water is in the low temperature region (Tp1 to Tp2 in FIG. 6) through the variable setting of the target opening tTA based on the temperature of the cooling water of the internal combustion engine 1, the target opening tTA is the cooling water. As the temperature decreases, the value gradually changes to a value on the open side as compared with the value in the middle temperature region. By adjusting the throttle valve 13 to the target opening tTA that can be varied in this manner, when the temperature of the cooling water of the engine 1 becomes lower as the viscosity of the lubricating oil of the internal combustion engine 1 becomes excessively higher, Even if the resistance to engine rotation increases due to the viscosity, the piston 6 can be moved to a target stop position within the range from the middle of the intake stroke to the intake top dead center. And it can stop in the state which moved the said piston 6 to the target position.

  (4) Through the variable setting of the target opening degree tTA based on the cooling water temperature of the internal combustion engine 1, when the cooling water temperature is in the high temperature region (Tp3 to Tp4 in FIG. 6), the target opening degree tTA is As the temperature rises, it gradually changes to a value on the open side as compared with the value in the middle temperature region. When the throttle valve 13 is adjusted to the target opening tTA that is variable in this way, the temperature of the cooling water of the engine 1 is higher as the heat received from the internal combustion engine 1 of the air remaining in the cylinder is excessively increased. The stop position of the piston 6 in the cylinder that becomes the intake stroke when the engine rotation is stopped by the automatic stop can be determined as follows corresponding to the target stop position. That is, the piston 6 can be moved to a target stop position near the intake top dead center in the range from the vicinity of the middle of the intake stroke to the intake top dead center, and can be stopped in that state. In this case, the amount of air remaining in the cylinder corresponding to the piston 6 is reduced, so that the amount of heat held by the heat received from the internal combustion engine 1 can be suppressed. Therefore, when the internal combustion engine 1 is restarted, when the internal combustion engine 1 is restarted, the fuel self-ignites in the cylinder when the internal combustion engine 1 is restarted. It can be avoided that it cannot be obtained.

  (5) Through the variable setting of the target opening degree tTA based on the temperature of the cooling water of the internal combustion engine 1, when the temperature of the cooling water is in the excessively high temperature region (Tp4 or more in FIG. 6), the target opening degree tTA is “0”. That is, it is a value corresponding to full closure. Here, in the excessively high temperature region, when the engine rotation is stopped by the automatic stop, the heat remaining from the internal combustion engine 1 of the air remaining in the cylinder becomes excessive, and the target opening degree tTA is set to the open side to set the piston 6 Even if the stop position is close to the intake top dead center, it is inevitable that the self-ignition occurs at the time of the first compression stroke ignition at the time of restart. As described above, when the target opening degree tTA is set to “0” in the excessively high temperature region, it is possible to avoid the throttle valve 13 from being unnecessarily adjusted to the open side value even when fully closed after the start of the automatic stop.

  (6) When the actual stop position of the piston 6 in the cylinder that is in the intake stroke when the engine rotation is stopped by automatic stop is deviated from the target stop position of the piston 6, the actual stop position and the target stop position Based on the difference, the correction value TAH is calculated, and when the next automatic stop is performed, the correction for the correction value TAH is added to the target opening degree tTA. In this way, by correcting the target opening tTA, the actual stop position of the piston when the engine rotation is stopped by the automatic stop is adjusted to the target stop position, and the deviation between the actual stop position and the target stop position ( (Difference) can be eliminated.

In addition, the said embodiment can also be changed as follows, for example.
It is not always necessary to add the correction value TAH to the target opening degree tTA of the throttle valve 13 and calculate the correction value TAH.

  The target opening degree tTA is not necessarily variably set based on the temperature of the cooling water of the internal combustion engine 1, and the stop position of the piston 6 is a position within any one of the ranges h1 to h4 described above. You may fix with the value which becomes. In this case, it is preferable to fix to an optimum value determined by the target opening degree tTA experiment or the like.

  -It is not always necessary to provide a delay time when starting adjustment of the throttle valve 13 to the target opening degree tTA.

  DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 2 ... Combustion chamber, 3 ... Intake passage, 3a ... Intake port, 4 ... Fuel injection valve, 5 ... Spark plug, 6 ... Piston, 7 ... Crankshaft, 8 ... Exhaust passage, 10 ... Starter, 11 DESCRIPTION OF SYMBOLS ... Intake valve, 12 ... Intake camshaft, 13 ... Throttle valve, 14 ... Exhaust valve, 15 ... Exhaust camshaft, 21 ... Electronic control device (control means, setting means), 25 ... Water temperature sensor, 26 ... Vehicle speed sensor, 27 Accelerator pedal 28 Accelerator position sensor 29 Brake pedal 29a Brake switch 30 Throttle position sensor 31 Intake air temperature sensor 32 Air flow meter 33 Cam position sensor 34 Crank position sensor

Claims (5)

An internal combustion engine that stops engine rotation by stopping fuel injection from the fuel injection valve in the engine when an automatic stop condition is satisfied during an idle operation of the internal combustion engine having a fuel injection valve that injects fuel toward the intake port In the engine control device,
Control that adjusts the opening degree of the throttle valve of the internal combustion engine to a target opening degree that is a value on the opening side of the valve when it is fully closed after the fuel injection from the fuel injection valve is stopped based on the establishment of the automatic stop condition. Means,
And a setting means for setting a value for stopping in the range of the intake top dead center of the piston of the internal combustion engine to the target opening degree at the time of stopping the engine rotation from the intermediate vicinity of the intake stroke,
The setting means variably sets the target opening based on the temperature of the cooling water of the internal combustion engine, and when the temperature of the cooling water is in a low temperature region lower than a specified middle temperature region, the cooling water compared to the target opening when the temperature is in the intermediate temperature range, the control apparatus for an internal combustion engine, wherein a more open side of the value and to Rukoto the target opening the higher the temperature of the cooling water is low. An internal combustion engine that stops engine rotation by stopping fuel injection from the fuel injection valve in the engine when an automatic stop condition is satisfied during an idle operation of the internal combustion engine having a fuel injection valve that injects fuel toward the intake port In the engine control device,
Control that adjusts the opening degree of the throttle valve of the internal combustion engine to a target opening degree that is a value on the opening side of the valve when it is fully closed after the fuel injection from the fuel injection valve is stopped based on the establishment of the automatic stop condition. Means,
And a setting means for setting a value for stopping in the range of the intake top dead center of the piston of the internal combustion engine to the target opening degree at the time of stopping the engine rotation from the intermediate vicinity of the intake stroke,
The setting means variably sets the target opening based on the temperature of the cooling water of the internal combustion engine, and when the temperature of the cooling water is in a high temperature region higher than a prescribed intermediate temperature region, the cooling water compared to the target opening when the temperature is in the intermediate temperature range, the control apparatus for an internal combustion engine, wherein a more open side of the value and to Rukoto the target opening the higher the temperature of the cooling water is high. The control device for an internal combustion engine according to claim 1 or 2 , wherein the setting means sets the target opening to a value that stops the piston of the internal combustion engine in the first half of the intake stroke when the engine rotation is stopped. The control means starts adjustment to the target opening of the throttle valve after a predetermined delay time has elapsed after stopping fuel injection from the fuel injection valve based on the establishment of the automatic stop condition. Item 4. The control device for an internal combustion engine according to any one of Items 1 to 3 .   The setting means sets the target opening to a value corresponding to a target stop position of a piston in the internal combustion engine when the engine rotation is stopped by the automatic stop, and when the engine rotation is stopped by the automatic stop. 5. The correction based on the difference is added to the target opening when the automatic stop is performed next time when a difference occurs between the actual stop position of the piston and the target stop position in the internal combustion engine. The control apparatus for an internal combustion engine according to claim 1.