JP4407832B2 - Engine control device - Google Patents

Description

  The present invention relates to an engine control device, and more particularly to a control device that starts an engine with combustion pressure generated by fuel injection and ignition in a cylinder.

  Conventionally, it has been common to use a starter motor when starting an engine. However, in recent years, in order to reduce the noise at the time of starting the engine and realize a quick start, the cranking by the starter motor is not performed. There has been proposed a starting device in which fuel is injected and ignited in a cylinder of an engine to start the engine. In particular, in recent years, from the viewpoint of environmental protection and energy saving, a vehicle that temporarily stops the engine when the vehicle stops, that is, a so-called idle stop has been proposed, and when the engine stopped at the idle stop is started again. Such a starting device is preferable because the engine can be started quickly without the need for cranking by the starter motor.

In this starting device, when an engine is stopped, a cylinder in an expansion stroke (hereinafter referred to as an expansion stroke cylinder) is determined, and when the engine is restarted in accordance with a vehicle start operation, a driver start operation, or the like, an expansion stroke is performed. After the fuel is injected into the cylinder, ignition is performed to burn the injected fuel, and the engine is started by the combustion pressure generated at this time.
However, when the engine is stopped, the compression pressure of residual air by the piston of the cylinder in the compression stroke, the frictional resistance of each part of the engine, or the urging force of the valve spring acts on the crankshaft via the camshaft. The piston stops when various forces acting on the crankshaft such as cam reaction force contribute. For this reason, when the engine is stopped, the stop position of the piston in each cylinder is not constant, and when the piston of the expansion stroke cylinder is stopped near the top dead center, for example, the combustion force capable of starting the engine is increased. There is a possibility that the engine cannot be started without ensuring a sufficient combustion chamber volume to obtain. On the other hand, if the piston of the expansion stroke cylinder has stopped near the bottom dead center, the piston stroke required for starting cannot be secured even if the engine is started by combustion of fuel in the expansion stroke cylinder. May not be able to start.

Therefore, if it is detected that the piston stop position is such that it is difficult to restart without securing the piston stroke necessary for starting, fuel is supplied to the cylinder that was in the compression stroke when the engine was stopped. Patent Document 1 proposes a starting device that changes the position of the piston to a position suitable for starting by igniting the fuel and rotating the engine in the reverse direction.
JP 2004-100616 A

However, in the starting device disclosed in Patent Document 1, when it is detected that the piston stop position is in a position where it is difficult to restart, the engine is reversely rotated by the combustion pressure generated by the ignition of the fuel supplied into the cylinder in the compression stroke. Therefore, there is a problem in that vibration and noise are generated along with combustion of the fuel during reverse rotation, and fuel consumption is consumed and fuel consumption is deteriorated.
In the case where the piston of the expansion stroke cylinder is in the vicinity of the top dead center and a sufficient combustion chamber volume cannot be ensured and the combustion force necessary for starting the engine cannot be obtained, the starter disclosed in Patent Document 1 uses the engine. Cannot start.

  The present invention has been made in view of such a problem, and an object of the present invention is to reliably start the engine by the combustion pressure in the cylinder of the engine without causing an increase in vibration or noise and a deterioration in fuel consumption. It is an object of the present invention to provide an engine control device that can be used.

  In order to achieve the above object, an engine control apparatus of the present invention is provided in each cylinder of an engine in which at least one of the plurality of cylinders is in a compression stroke and at least one of the remaining cylinders is in an expansion stroke. A fuel injection valve for injecting fuel into the cylinder, an ignition plug for igniting the fuel injected into the cylinder by the fuel injection valve, and supply of intake air by opening and closing of the intake valve of the engine. An air supply means for supplying air into the cylinder, a cylinder discrimination means for discriminating a cylinder in the expansion stroke and a cylinder in the compression stroke when the engine is stopped, and when the engine is stopped by the cylinder discrimination means A piston position detecting means for detecting a piston position of a cylinder determined to be in an expansion stroke; and the piston position detecting means when the engine is stopped. When the detected piston position is on the top dead center side from the first predetermined position, air is supplied from the air supply means to the cylinder determined to be in the expansion stroke by the cylinder determination means, while the engine is stopped. When the piston position detected by the piston position detection means is at the bottom dead center side from the second predetermined position set to the bottom dead center side from the first predetermined position, the cylinder discrimination means performs the compression stroke. Control means for supplying air from the air supply means to the cylinder determined to be present is provided (claim 1).

According to the engine control apparatus configured as described above, the first predetermined position is set in advance as the piston position at which the combustion pressure of the fuel in the cylinder in the expansion stroke becomes the combustion pressure necessary for starting the engine. A second predetermined position is set in advance on the bottom dead center side of the first predetermined position as a piston position capable of ensuring a piston stroke capable of starting the engine with the combustion pressure of the fuel. The piston position of the cylinder determined by the cylinder determining means as being in the expansion stroke when the engine is stopped is detected by the piston position detecting means, and the piston position detected by the piston position detecting means when the engine is stopped. piston but the when the first is at the top dead center side from a predetermined position, by supplying air from the air supply means to the determined cylinder and the expansion stroke when the engine is stopped, the cylinder which is judged to be in the expansion stroke Moves to the bottom dead center.

Further, when the engine is stopped and the piston position detected by the piston position detecting means is on the bottom dead center side from the second predetermined position , the cylinder determining means determines that the engine is in the compression stroke when the engine is stopped. By supplying air from the air supply means to the cylinder, the piston of the cylinder determined to be in the expansion stroke moves to the top dead center side.

In such an engine control device, the control means is configured such that when the engine is in a stopped state, the piston position detected by the piston position detection means is between the first predetermined position and the second predetermined position. The air supply from the air supply means is performed until it falls within the range (Claim 2).
According to the engine control apparatus configured as described above, when the engine is stopped and the piston position detected by the piston position detecting means is on the top dead center side from the first predetermined position, the piston position is Air is supplied to the cylinder determined to be in the expansion stroke until it reaches a position between the first predetermined position and the second predetermined position, so that the cylinder determined to be in the expansion stroke The piston moves within a range between the first predetermined position and the second predetermined position.

  On the other hand, when the engine is stopped and the piston position detected by the piston position detecting means is on the bottom dead center side with respect to the second predetermined position, the piston position is from the first predetermined position to the second predetermined position. Until the position of the engine is stopped, the air is supplied to the cylinder determined to be in the compression stroke when the engine is stopped, so that the piston of the cylinder determined to be in the expansion stroke moves from the first predetermined position to the position It moves within the range up to the second predetermined position.

In such an engine control apparatus, when the engine is started, the control means supplies fuel from the fuel injection valve to the cylinder determined by the cylinder determining means as being in the expansion stroke when the engine is stopped. The fuel supply is ignited by the spark plug (claim 3).
According to the engine control apparatus configured as described above, when starting the engine, fuel is supplied from the fuel injection valve to the cylinder determined to be in the expansion stroke when the engine is stopped, and the above-described supply is performed by the spark plug. The piston is pushed down by the combustion pressure generated by igniting the fuel, and the engine is started. Preferably, the fuel pressure from the ignition of the supplied fuel can be increased by supplying fuel from the fuel injection valve and supplying air from the air supply means.

According to the engine control apparatus of the present invention, the piston of the cylinder that was in the expansion stroke when the engine was stopped cannot obtain the fuel combustion pressure necessary for starting the engine at the next engine start, so that the engine is started. Even if it stops at a position near the top dead center where it becomes difficult , the air is supplied from the air supply means to the cylinder, and the piston of the cylinder moves to the bottom dead center. can do.
Also, the piston of the cylinder that was in the expansion stroke when the engine was stopped could not secure a piston stroke that could start the engine with the fuel combustion pressure at the next engine start, and the engine would be difficult to start. Even if the engine stops at a position near the point, air is supplied from the air supply means to the cylinder that was in the compression stroke when the engine was stopped, so that the piston of the cylinder that was in the compression stroke moved to the bottom dead center side. By doing so, the piston of the cylinder in the expansion stroke moves to the top dead center side, so that the engine can be started reliably.

  Further, the fuel combustion pressure is not consumed for the movement of the piston, there is no noise or vibration associated with the combustion of the fuel, and the fuel consumption is not deteriorated. In addition, the air supply for moving the pistons in these cylinders is performed by air supply means for supplying air into the cylinders independently of the supply of intake air by opening and closing the intake valve of the engine. The amount of air required to move to the position can be supplied quickly and accurately into the cylinder.

Further, since the piston does not move beyond the top dead center or the bottom dead center, the piston can be moved relatively easily, and the amount of air supplied from the air supply means can be saved. it can.
According to the engine control apparatus of claim 2, the piston of the cylinder in the expansion stroke is moved to the first predetermined position by supplying air to the cylinder in the expansion stroke or the cylinder in the compression stroke when the engine is stopped. Therefore, it is possible to reliably ensure both the combustion chamber volume for obtaining the combustion pressure necessary for starting the engine and the piston stroke necessary for starting the engine. Therefore, the engine can be started more reliably by the combustion pressure of the fuel supplied to the cylinder that was in the expansion stroke at the time of stopping.

  According to the engine control apparatus of claim 3, when starting the engine, the engine is reliably started with the combustion pressure of the fuel supplied from the fuel injection valve to the cylinder that was in the expansion stroke when the engine was stopped. can do. Preferably, by supplying fuel from the fuel injection valve and supplying air from the air supply means, the combustion pressure for starting the engine can be increased, and the engine can be started more reliably.

Hereinafter, an embodiment in which the present invention is embodied in an engine control device mounted on a vehicle having an idle stop function will be described with reference to the drawings.
As shown in the overall configuration diagram of FIG. 1, the engine 1 of the present embodiment is configured as an in-cylinder injection type in-line four-cylinder engine, and a fuel injection valve 2 and a spark plug 4 are provided in each cylinder. The fuel injection valve 2 of each cylinder is configured to be able to directly inject fuel into the cylinder, that is, into the combustion chamber 6, and fuel is supplied to each fuel injection valve 2 from a fuel pump (not shown) at a predetermined pressure.

Intake is introduced into the combustion chamber 6 of each cylinder through the intake port 12 as the intake valve 10 driven by the intake cam 8 is opened, and a predetermined timing is given from the fuel injection valve 2 during the introduced intake. Then fuel is injected. The injected fuel is ignited by the ignition plug 4 in the vicinity of the compression top dead center, and the combustion pressure is applied to the piston 14 to rotationally drive the crankshaft 16.
On the other hand, the exhaust gas after combustion is discharged from the exhaust port 20 to the outside through an exhaust passage, a catalyst, a silencer and the like (not shown) when the exhaust valve 18 driven by an exhaust cam (not shown) is opened.

The intake port 12 is connected to an intake manifold 24 branched from the surge tank 22 for each cylinder, and an intake passage 28 provided with an electronic throttle valve 26 opened and closed by an electric actuator (not shown) on the upstream side of the surge tank 22. Is connected.
The surge tank 22 is provided with an intake pressure sensor 30 for detecting the pressure in the surge tank 22, that is, intake pressure, and an intake temperature sensor 32 for detecting the temperature in the surge tank 22, ie, intake temperature. .

  Further, each cylinder is provided with an air supply device 34 for supplying air directly into the combustion chamber 6 independently of supply of intake air from the intake port 12. The air supply device 34 has an electromagnetic air valve (air supply means) 36 having a discharge hole communicating with the combustion chamber 6 and a pressure accumulator 38 for storing compressed air supplied from a compressor (not shown). Compressed air is supplied to the air valve 36 from the pressure accumulator 38 through the air supply pipe 40, and the compressed air is directly supplied into the combustion chamber 6 by opening and closing the air valve 36.

The engine 1 includes a water temperature sensor 42 that detects the cooling water temperature of the engine 1, a crank angle sensor 46 that outputs a crank angle signal synchronized with the rotation of the crankshaft 16 using the rotation of the ring gear 44 that rotates together with the crankshaft 16, an intake air A cam angle sensor 50 that outputs a TOP signal in synchronization with the rotation of the cam shaft 48 is provided.
The ECU (control means) 52 is a control device for performing comprehensive control including operation control for operating the engine 1 such as fuel injection control and ignition timing control, and includes a CPU, a memory, a timer counter, and the like. In addition, various control amounts are calculated, and various devices are controlled based on the control amounts.

  On the input side of the ECU 52, in addition to the intake pressure sensor 30, the intake air temperature sensor 32, the water temperature sensor 42, the crank angle sensor 46, and the cam angle sensor 50 described above, in addition to collecting the information necessary for various controls, the vehicle travels. Various sensors such as a vehicle speed sensor 54 for detecting the speed, a shift position sensor 56 for detecting the operation position of the select lever provided in the driver's seat, and a brake switch 58 for detecting a brake operation by the driver, and an ignition switch 60 are connected. On the output side, various devices such as the fuel injection valve 2, the ignition plug 4, the electronic throttle valve 26, and the air valve 36 of each cylinder that are controlled based on the calculated control amount are connected.

The engine 1 thus configured is connected to an automatic transmission (not shown) and mounted on the vehicle, and the output of the engine 1 is transmitted to the drive wheels of the vehicle via the automatic transmission to drive the vehicle.
On the other hand, the ECU 52 executes idle stop control for temporarily automatically stopping the engine 1 while the vehicle is stopped due to a signal waiting or traffic jam. In this embodiment, as engine stop conditions, the vehicle speed detected by the vehicle speed sensor 54 is 0 km / h, the brake operation is detected by the brake switch 58, and the shift position detected by the shift position sensor 56 is The driving range such as the D (drive) range or the N (neutral) range is set, and when these conditions are satisfied, the ECU 52 stops the fuel injection control and the ignition timing control and stops the engine 1. .

  Further, as engine start conditions in the idle stop control, the release of the brake operation is detected by the brake switch 58, and the shift position detected by the shift position sensor 56 is a travel range such as the D range. If these conditions are satisfied, the ECU 52 restarts the fuel injection control and the ignition timing control and starts the engine 1.

The ECU 52 is started and stopped in order to respond to the stop command and start command of the engine 1 by the idle stop control as described above and to start and stop the engine 1 in response to the start and stop operation of the ignition switch 60 by the driver. The details of the start / stop control will be described below.
FIG. 2 shows a flowchart of the start / stop control, and the ECU 52 executes the start / stop control based on this flowchart at a predetermined control cycle during use of the vehicle. This start / stop control is always executed at a position other than the OFF position of the ignition switch 60, and is considered to continue even when the engine 1 is stopped after being switched to the accessory position by the driver's key operation and then restarted. Yes.

  When the start / stop control is started, it is first determined in step S2 whether or not the engine 1 is stopped. Specifically, it is determined whether or not the engine 1 is stopped by determining whether or not the engine rotational speed Ne obtained based on the detection signal of the crank angle sensor 46 is less than a stop determination value Ner (for example, 30 rpm). judge. If it is determined that the engine 1 is in operation and the engine 1 is not stopped in step S2, the process proceeds to step S4.

  In step S4, it is determined whether an engine stop command has been input. This engine stop command is input when the engine stop condition as described above is satisfied in the idle stop control or when the ignition switch 60 is turned OFF by the driver, and when the engine stop command is not input. Ends the start / stop control routine in the current control cycle, and repeats the process from step S2 in the next control cycle.

On the other hand, if an engine stop command is input, the process proceeds from step S4 to step S6, and after stopping the fuel injection control and the ignition timing control as a process for stopping the engine 1, the current control cycle is ended. . In this way, the engine 1 is stopped when fuel injection and fuel ignition of the engine 1 are not performed.
When the engine 1 is stopped in this way, in the next control cycle, it is determined in step S2 that the engine 1 is stopped, and the process proceeds to step S8.

  In step S8, it is determined whether an engine start command has been input. This engine stop command is input when the engine 1 is in a stopped state and the above-described engine start condition is satisfied in the idle stop control, or when the ignition switch 60 is started by the driver. If there is no input of a start command, the start / stop control in this control cycle is terminated, and in the next control cycle, the process proceeds again from step S2 to step S8 to determine the presence or absence of the engine start command.

Therefore, the processes of step S2 and step S8 are repeated every control cycle until an engine start command is input.
On the other hand, in parallel with such start / stop control, the ECU 52 performs start preparation control based on the flowchart of FIG. This start preparation control is a control for ensuring that the engine 1 can be started when the engine 1 is restarted after being stopped as described above, and is similar to the start / stop control of FIG. The control is executed at a predetermined control cycle, and is always executed at a position other than the OFF position of the ignition switch 60.

When the start preparation control starts, it is first determined in step S102 whether or not the engine 1 is stopped by the same method as step S2 in the start / stop control of FIG.
When it is determined that the engine 1 is in operation and the engine 1 is not stopped in step S102, the process proceeds to step S104, the value of the engine stop flag F1 is set to 0, and the current control cycle is ended. The engine stop flag F1 indicates that the engine is stopped when the value is 1, and is set to 0 because the engine is not stopped at present.

Thus, the control cycle is ended, and it is determined whether or not the engine 1 is stopped again in step S102 of the next control cycle. Therefore, while the engine 1 is in operation, the processes in steps S102 and S104 are repeated. When the engine 1 is stopped by the start / stop control in FIG. 2, it is determined in step S102 that the engine 1 has stopped, and the process proceeds to step S106. .
In step S106, it is determined whether or not the value of the engine stop flag F1 is 1. This control cycle is the first control cycle after the engine is stopped, and the value of the engine stop flag F1 remains 0. The process proceeds to step S108, and the value of the engine stop flag F1 is set to 1.

  In the next step S110, based on the crank angle signal detected by the crank angle sensor 46 and the TOP signal detected by the cam angle sensor 50, a cylinder that has been in the compression stroke immediately before the engine is stopped (hereinafter referred to as a compression stroke cylinder). ) And a cylinder in the expansion stroke (hereinafter referred to as an expansion stroke cylinder) are determined (cylinder determination means), and the determination results are stored in the memory. Since the cylinder discrimination method itself has been conventionally performed, the description thereof will be omitted. However, since the engine 1 has already stopped at the time of proceeding to step S110, specifically, the crank angle and the TOP signal are determined. Based on the subroutine for performing cylinder discrimination based on this, cylinder discrimination is repeatedly performed during engine operation, and the determination result of the subroutine obtained last during engine operation is fetched and stored when the routine proceeds to step S110.

  Since the engine 1 is an in-line four cylinder, the operation stroke of each cylinder has a relationship as shown in FIG. 4, and when one cylinder (for example, the third cylinder) is in the compression stroke, One of the cylinders (for example, the first cylinder) is in the expansion stroke. Therefore, the piston 14 of the cylinder in the expansion stroke is at a position 180 degrees ahead of the piston position of the cylinder in the compression stroke.

  Next, in step S112, the piston position P of the expansion stroke cylinder determined in step S110 is detected using the crank angle after top dead center (ATDC) based on the crank angle signal detected by the crank angle sensor 46. (Piston position detection means), the detection result is stored in the memory, and the process proceeds to the next step S114. Also at this time, since the engine 1 has already stopped at the time of proceeding to step S112, specifically, the detection of the piston position is repeatedly performed during the engine operation by the subroutine for detecting the piston position in each cylinder based on the crank angle. The detection result of the subroutine finally obtained during engine operation is fetched and stored when the routine proceeds to step S112.

  In step S114, the piston position P of the expansion stroke cylinder detected in step S112 is smaller than the crank angle Pr1 (for example, ATDC 30 degrees) after top dead center corresponding to the first predetermined position relatively close to top dead center, that is, piston 14 It is determined whether or not the position is closer to the top dead center than the first predetermined position. If it is determined that the piston position P is equal to or greater than the crank angle Pr1, that is, the position of the piston 14 is not closer to the top dead center than the first predetermined position, the process proceeds to step S116, but is smaller than the crank angle Pr1, If it is determined that the position is closer to the top dead center than the predetermined position, the process proceeds to step S118.

  As will be described later, in order to supply fuel to the expansion stroke cylinder, ignite, and push down the piston 14 to start the engine 1, it is necessary to secure a volume of the combustion chamber 6 that can generate a certain amount of combustion pressure. There is. In this first predetermined position, the corresponding crank angle Pr1 is preset and stored in the ECU 52 as a limit of the piston position on the top dead center side where the volume of the combustion chamber 6 can be secured. 1 When the piston 14 is closer to the top dead center than the predetermined position, there is a possibility that the combustion pressure is insufficient and the engine 1 cannot be started.

  If it is determined in step S114 that the piston 14 is not closer to the top dead center than the first predetermined position and the process proceeds to step S116, the piston position P of the expansion stroke cylinder detected in step S112 is greater than the first predetermined position. It is determined whether the crank angle Pr2 after top dead center corresponding to the second predetermined position near the bottom dead center is larger than the crank angle Pr2 (for example, ATDC 120 degrees), that is, whether the piston 14 is closer to the bottom dead center than the second predetermined position. . When it is determined that the piston position P is equal to or less than the crank angle Pr2, that is, the piston 14 is not closer to the bottom dead center than the second predetermined position, the current control cycle is terminated, while the crank angle Pr2 is greater than the second predetermined position. If it is determined that the position is closer to the bottom dead center than the predetermined position, the process proceeds to step S122.

  When starting the engine 1 with the fuel combustion pressure in the expansion stroke cylinder, the piston stroke up to the bottom dead center of the expansion stroke cylinder is an important factor in addition to ensuring sufficient combustion pressure as described above. Therefore, the engine 1 cannot be started unless a certain piston stroke is secured. In this second predetermined position, the corresponding crank angle Pr2 is preset and stored in the ECU 52 as the limit of the piston position on the bottom dead center side where such a piston stroke can be secured. If the piston 14 is closer to the bottom dead center than the bottom dead center, there is a possibility that the piston stroke to the bottom dead center is insufficient and the engine 1 cannot be started.

  As described above, when the piston position P of the expansion stroke cylinder is not less than the crank angle Pr1 and not more than the crank angle Pr2 by steps S114 and S116, that is, the piston 14 is within the range from the first predetermined position to the second predetermined position. If it is determined, since both the combustion pressure and the piston stroke necessary for starting the engine 1 can be secured, it is not necessary to do anything in preparation for the next start of the engine 1, The control cycle is terminated without doing so.

  On the other hand, if it is determined in step S114 that the piston position P of the expansion stroke cylinder is smaller than the crank angle Pr1, that is, the piston 14 is closer to the top dead center than the first predetermined position, the process proceeds to step S118. From the map indicating the relationship between the stored piston position P and the supplied air amount Qa, the supplied air amount Qa corresponding to the piston position P of the current expansion stroke cylinder detected in step S112 is read.

The relationship between the piston position P and the supply air amount Qa in this map is as shown in FIG. 5, and when the piston position P is smaller than the crank angle Pr1 after top dead center corresponding to the first predetermined position, 2 The supply air amount Qa is set when the crank angle Pr2 after the top dead center corresponding to the predetermined position is larger.
When the routine proceeds to step S118, that is, when the piston position P is smaller than the crank angle Pr1, the supplied air amount Qa moves the position of the piston 14 of the expansion stroke cylinder to the bottom dead center side from the first predetermined position. Therefore, the amount of air to be supplied to the expansion stroke cylinder is obtained in advance by experiments or the like, and the supply air amount Qa increases as the position of the piston 14 of the expansion stroke cylinder is closer to the top dead center side. It has become.

  In the next step S120, the compressed air stored in the pressure accumulator 38 is supplied into the expansion stroke cylinder by the opening / closing control of the air valve 36, and the amount of air supplied at that time is the supply air read in step S118. The quantity is Qa. By supplying compressed air to the combustion chamber 6 of the expansion stroke cylinder in this way, the piston 14 of the expansion stroke cylinder is pushed down, and the current control cycle ends.

If the engine 1 is still stopped in the next control cycle, the process proceeds from step S102 to step S106.
In step S106, it is determined whether or not the value of the engine stop flag F1 is 1. The engine stop flag F1 is set to 1 in the first control cycle after the engine is stopped. The process directly proceeds to step S112 without proceeding to step S108.

  In step S112, the piston position P of the expansion stroke cylinder determined and stored in step S110 as described above is used as the crank angle after top dead center (ATDC) based on the crank angle signal detected by the crank angle sensor 46. To detect. At this time, since the piston 14 of the expansion stroke cylinder is moved to the bottom dead center side by the processing of steps S118 and S120 in the previous control cycle, the piston position P increased from the previous time is detected, and the detected piston position P is stored in the memory by updating the previously stored piston position.

In this case as well, the detection of the piston position is repeatedly performed by the subroutine for detecting the position of the piston 14 of the expansion stroke cylinder based on the crank angle signal detected by the crank angle sensor 46 as described above, and the process proceeds to step S112. The detection result of the subroutine at the advanced stage is captured and stored.
Next, in step S114, as described above, it is determined whether or not the piston position P of the expansion stroke cylinder detected in step S112 is smaller than the crank angle Pr1 after top dead center corresponding to the first predetermined position. .

  The piston 14 of the expansion stroke cylinder is supplied with an amount of air necessary to move to the bottom dead center side from the first predetermined position in step S120 of the previous control cycle, so that the bottom dead center is obtained. Normally, it should have moved to the bottom dead center side from the first predetermined position, but changes in the engine temperature and frictional resistance, the state of the auxiliary machine coupled to the engine 1, etc. As a result, it is possible that the robot could not move to the bottom dead center side from the first predetermined position.

  In such a case, it is determined again in step S114 that the piston position P is smaller than the crank angle Pr1 after the top dead center corresponding to the first predetermined position, and the process proceeds to step S118. In step S118, the supply air amount Qa corresponding to the current piston position P detected in step S112 of this control cycle is read from the map, and in the next step S120, the air valve 36 of the expansion stroke cylinder enters the combustion chamber 6. By supplying the compressed air of the supply air amount Qa read in step S118, the piston 14 of the expansion stroke cylinder further moves to the bottom dead center side.

In this way, the supply of compressed air into the combustion chamber 6 of the expansion stroke cylinder by the air valve 36 is continued until the piston 14 of the expansion stroke cylinder moves from the first predetermined position to the bottom dead center side region. The piston 14 of the stroke cylinder can be reliably moved to the first predetermined position or the region on the bottom dead center side from the first predetermined position.
On the other hand, in the first control cycle after engine stop, it is determined in step S116 that the piston position P of the expansion stroke cylinder is larger than the crank angle Pr2, that is, the piston 14 is closer to the bottom dead center than the second predetermined position. When the routine proceeds to S122, the same map as that used in step S118 is used to read the supply air amount Qa corresponding to the piston position P of the current expansion stroke cylinder detected in step S112.

  The relationship between the piston position P and the supply air amount Qa in this map is as shown in FIG. 5 as described above, and is set when the process proceeds to step S122, that is, when the piston position P is larger than the crank angle Pr2. The supply air amount Qa increases as the position of the piston 14 of the expansion stroke cylinder approaches the bottom dead center from the second predetermined position. The supply air amount Qa set here is the amount of air supplied to the compression stroke cylinder for the following reason.

  That is, as described above, when the piston 14 of the expansion stroke cylinder is on the bottom dead center side with respect to the second predetermined position, the piston stroke to the bottom dead center is insufficient at the next engine start and the engine 1 Therefore, it is necessary to move the piston 14 of the expansion stroke cylinder to the top dead center side. However, in the supply of compressed air to the expansion stroke cylinder as in step S120, the piston 14 Cannot be moved to the top dead center.

  However, as shown in FIG. 4, in the engine 1, one of the cylinders remaining when one cylinder is in the expansion stroke is in the compression stroke, and the piston position of the compression stroke cylinder is determined by the crank angle from the piston position of the expansion stroke cylinder. Since the delay is 180 degrees, if compressed air is supplied into the combustion chamber 6 of the compression stroke cylinder and the piston 14 is pushed down, the piston 14 of the expansion stroke cylinder moves toward the top dead center side. become.

Therefore, the supply air amount Qa when the piston position P of the expansion stroke cylinder is larger than the crank angle Pr2 after the top dead center corresponding to the second predetermined position, the position of the piston 14 of the expansion stroke cylinder is changed from the second predetermined position. The amount of air to be supplied to the compression stroke cylinder for movement toward the top dead center is obtained in advance through experiments or the like and set in the map in the relationship shown in FIG.
In the next step S124, the compressed air stored in the pressure accumulator 38 is supplied into the compression stroke cylinder by opening / closing control of the air valve 36, and the amount of air supplied at that time is the supply air read in step S122. The quantity is Qa. By supplying compressed air to the combustion chamber 6 of the expansion stroke cylinder in this way, the piston 14 of the compression stroke cylinder is pushed down, and accordingly, the piston 14 of the expansion stroke cylinder preceding the crank angle by 180 degrees is at the top dead center side. The current control cycle ends.

If engine 1 is still stopped in the next control cycle, the process proceeds from step S102 to step S106.
In step S106, it is determined whether or not the value of the engine stop flag F1 is 1. The engine stop flag F1 is set to 1 in the first control cycle after engine stop, and the process does not proceed to step S108. The process proceeds directly to step S112.

  In step S112, the piston position P of the expansion stroke cylinder determined in step S110 as described above is detected using the crank angle after top dead center (ATDC) based on the crank angle signal detected by the crank angle sensor 46. . At this time, since the piston 14 of the expansion stroke cylinder is moved to the top dead center side by the processing of steps S122 and S124 in the previous control cycle, the piston position P decreased from the previous time is detected, and the detected piston position P is stored in the memory by updating the previously stored piston position.

In this case as well, the detection of the piston position is repeatedly performed by the subroutine for detecting the position of the piston 14 of the expansion stroke cylinder based on the crank angle signal detected by the crank angle sensor 46 as described above, and the process proceeds to step S112. The detection result of the subroutine at the advanced stage is captured and stored.
Next, in step S114, it is determined whether or not the piston position P of the expansion stroke cylinder detected in step S112 is smaller than the crank angle Pr1 after top dead center corresponding to the first predetermined position. The piston 14 of the expansion stroke cylinder is moved from the state at the bottom dead center side to the top dead center side from the second predetermined position by supplying compressed air to the compression stroke cylinder in the previous control cycle. As long as the amount of air supplied to the compression stroke cylinder is not excessive, the piston position P does not become smaller than the crank angle Pr1. Accordingly, here, it is determined that the piston position P is equal to or greater than the crank angle Pr1, and the process proceeds to step S116.

In step S116, as described above, it is determined whether or not the piston position P of the expansion stroke cylinder detected in step S112 is larger than the crank angle Pr2 after top dead center corresponding to the second predetermined position.
The piston 14 of the expansion stroke cylinder is supplied with an amount of air necessary to move to the top dead center side from the second predetermined position in step S124 of the previous control cycle, so that the top dead center is supplied. Normally, it should have moved to the top dead center side from the second predetermined position, but changes in the engine temperature and frictional resistance, the state of the auxiliary machine coupled to the engine 1, etc. As a result, it is possible that the robot could not move to the top dead center side from the second predetermined position.

  In such a case, it is determined again in step S116 that the piston position P is larger than the crank angle Pr2 after the top dead center corresponding to the second predetermined position, and the process proceeds to step S122. In step S122, the supply air amount Qa corresponding to the current piston position P detected in step S112 of this control cycle is read from the map, and in the next step S124, the air valve 36 of the compression stroke cylinder enters the combustion chamber 6. By supplying the compressed air of the supply air amount Qa read in step S122, the piston 14 of the compression stroke cylinder is pushed down, and the piston 14 of the expansion stroke cylinder further moves to the top dead center side.

In this way, the supply of compressed air into the combustion chamber 6 of the compression stroke cylinder by the air valve 36 is continued until the piston 14 of the expansion stroke cylinder moves from the second predetermined position to the region on the top dead center side. The piston 14 of the stroke cylinder can be reliably moved to the second predetermined position or the region on the top dead center side from the second predetermined position.
If the amount of air supplied into the expansion stroke cylinder by the processing of step S118 and step S120 is excessive, the piston 14 of the expansion stroke cylinder moves too far to the bottom dead center side and the second predetermined position. If a situation occurs that is closer to the bottom dead center side, the process proceeds to step S122 according to the determination in step S116 in the next control cycle, and the piston of the expansion stroke cylinder is supplied by supplying compressed air to the compression stroke cylinder. Since 14 is moved to the top dead center side, the piston 14 of the expansion stroke cylinder is reliably moved within the range from the first predetermined position to the second predetermined position.

  Further, if the amount of air supplied into the compression stroke cylinder by the processing of step S122 and step S124 is excessive, the piston 14 of the expansion stroke cylinder moves too far to the top dead center side, and the first predetermined position is reached. In the case where a situation such as the top dead center side occurs, the process proceeds to step S118 by the determination in step S114 in the next control cycle, and the piston of the expansion stroke cylinder is supplied by the supply of compressed air to the expansion stroke cylinder. Since 14 is moved to the bottom dead center side, the piston 14 of the expansion stroke cylinder is reliably moved within the range from the first predetermined position to the second predetermined position.

  By performing the start preparation control as described above, when the engine 1 is stopped, supply of compressed air to the expansion stroke cylinder or the compression stroke cylinder causes the piston 14 of the expansion stroke cylinder to always move from the first predetermined position. It comes to be located within the range up to the second predetermined position. As a result, it is possible to reliably ensure both the combustion pressure and the piston stroke necessary for starting the engine 1 by the combustion of fuel in the expansion stroke cylinder described later.

  Further, the supply of compressed air to the expansion stroke cylinder or the compression stroke cylinder at this time is performed by an air valve 36 that supplies air directly into the combustion chamber 6 independently of the supply of intake air through the intake port 12. Therefore, an accurate amount of compressed air can be quickly supplied into the combustion chamber 6 of the expansion stroke cylinder or the compression stroke cylinder, and the piston of the expansion stroke cylinder can be accurately moved with high responsiveness.

Furthermore, the movement of the piston 14 by supplying compressed air to the expansion stroke cylinder or the compression stroke cylinder is not performed beyond the top dead center or the bottom dead center, so that the top dead center or the bottom dead center is exceeded. It is not necessary to use a large amount of air or high-pressure air, and the piston position in the expansion stroke can be adjusted efficiently.
Further, the movement of the piston 14 of the expansion stroke cylinder at this time is performed by supplying compressed air stored in the accumulator 38 from an air valve 36 provided in the expansion stroke cylinder or the compression stroke cylinder. In order to start the engine properly, the air valve 36 and the pressure accumulator 38 can be used to increase the combustion pressure of the expansion stroke cylinder as will be described later. In this case, the air supply means for adjusting the piston position and the air supply means for increasing the combustion pressure can be shared, and the cost does not increase.

Further, when the piston 14 of the expansion stroke cylinder is moved to a position suitable for starting the engine 1, the fuel combustion pressure or the like is not used, so that the fuel consumption is not deteriorated and the vibration and noise accompanying the fuel combustion are not deteriorated. It does not occur.
When the piston position in the expansion stroke cylinder after the engine is stopped is adjusted in this way, the start / stop control of FIG. 2 performs steps S2 and S8 for each control cycle as described above. Again, in step S8, it is determined whether an engine start command has been input.

This engine stop command is input when the engine 1 is in a stopped state and the above-described engine start condition is satisfied in the idle stop control, or when the ignition switch 60 is started by the driver.
When an engine start command is input and the process proceeds from step S8 to step S10, the air valve is applied to the expansion stroke cylinder determined and stored in step S110 in the start preparation control of FIG. By controlling opening and closing 36, the compressed air stored in the pressure accumulator 38 is supplied. The compressed air amount Qb at this time is read and set from a previously stored map based on the latest piston position P of the expansion stroke cylinder detected and stored in step S112 in the start preparation control.

The relationship between the piston position P and the supply air amount Qb is as shown in FIG. 6 and corresponds to the first predetermined position when the position of the piston 14 of the expansion stroke cylinder is adjusted by the start preparation control of FIG. The supply air amount Qb is set in a region between the crank angle Pr1 after the top dead center and the crank angle Pr2 after the top dead center corresponding to the second predetermined position.
Further, as shown in FIG. 6, the supply air amount Qb increases as the piston position P approaches the bottom dead center side, and this expands as the volume of the combustion chamber 6 of the expansion stroke cylinder increases. Because the amount of work is reduced, it is necessary to increase the combustion power by burning a large amount of fuel, and the amount of air to be supplied is increased accordingly.

  In the next step S12, fuel is injected from the fuel injection valve 2 into the expansion stroke cylinder. The fuel injection amount at this time is determined in step S10 of the start / stop control determined by the air amount in the expansion stroke cylinder calculated from the piston position of the latest expansion stroke cylinder stored in step S112 of the start preparation control. Is calculated based on the supply air amount Qb supplied from. Although the combustion pressure in the expansion stroke can be increased by supplying the air with the supply air amount Qb and the engine can be reliably started, the engine can be sufficiently started without supplying the air with the supply air amount Qb. In that case, step S10 may be omitted.

  In the next step S14, after a predetermined time has elapsed since the fuel injection in step S12, the fuel in the expansion stroke cylinder is ignited by the spark plug 4, and the current control cycle ends. At this time, the piston 14 of the expansion stroke cylinder is pushed down by the combustion pressure generated by the ignition of the fuel in step S14. The piston 14 of the expansion stroke cylinder has the combustion pressure and the combustion pressure necessary for starting the engine 1 by the start preparation control. Since it is within the range from the first predetermined position to the second predetermined position where the piston stroke can be obtained, the engine 1 starts reliably.

In the control cycle after the engine 1 is started in this way, since the engine rotation speed Ne is equal to or higher than the stop determination value Ner in step S2, it is determined that the engine 1 has not stopped, so step S4 again. Until it is determined that there is a command to stop the engine 1, the processes of step S2 and step S4 are repeated every control cycle.
Although not shown in the flowchart of FIG. 2, after the engine 1 is started by ignition of the expansion stroke cylinder in step S14, the engine 52 is sequentially operated for each subsequent cylinder by another engine operation control routine. Fuel injection and ignition necessary for the operation of 1 are executed.

As described above, when the engine 1 is started by fuel injection and ignition to the expansion stroke cylinder, compressed air is supplied from the air valve 36 to the expansion stroke cylinder, and the expansion stroke cylinder including the compressed air is supplied. Since the fuel corresponding to the amount of air is injected into the cylinder, the combustion pressure required to start the engine 1 can be obtained.
Although the description of the engine starting device according to one embodiment of the present invention has been completed above, the present invention is not limited to the above embodiment.

  For example, in the above embodiment, as the supply air amount Qa to the expansion stroke cylinder or the compression stroke cylinder, what is read according to the piston position P based on the relationship of FIG. 5 is used as it is. Accordingly, the amount of air necessary to move the piston 14 fluctuates. For example, the supplied intake air amount Qa may be corrected based on the cooling water temperature of the engine 1 detected by the water temperature sensor 42. In this case, as the coolant temperature of the engine 1 is lower, that is, the temperature of the engine 1 is lower, the supply air amount Qa is corrected in a decreasing direction. By correcting in this way, it is possible to move the piston 14 of the expansion stroke cylinder within the range from the first predetermined position to the second predetermined position with higher accuracy.

  Further, correction may also be applied to the supply air amount Qb of air supplied to the expansion stroke cylinder when the engine 1 is started. That is, in order to accurately obtain the necessary combustion pressure, it is necessary to accurately control the mass of air supplied to the expansion stroke cylinder. However, since the density of the supplied air varies depending on the temperature, for example, by the water temperature sensor 42. The supply air amount Qb may be corrected in accordance with the detected in-cylinder temperature estimated from the detected coolant temperature of the engine 1 or the intake air temperature detected by the intake air temperature sensor 32.

In this case, since the density of the supply air decreases as the temperature in the cylinder increases, the supply air amount Qb is corrected in the increasing direction. In this way, the amount of air required for starting the engine 1 can be obtained more accurately.
Further, in the above embodiment, the start preparation control is always executed except at the OFF position of the ignition switch 60. However, the processing is continued even after the ignition switch 60 is turned OFF, and the piston of the expansion stroke cylinder is continued. The control may be terminated when the position 14 falls within the range from the first predetermined position to the second predetermined position. In this case, when the piston 14 in the expansion stroke is not within the range from the first predetermined position to the second predetermined position, the process from steps S118 and S120 or the processes from steps S122 and S124 to the second predetermined position from the first predetermined position. The start preparation control is finished after the piston 14 moves within the range up to.

Further, the above embodiment is applied to the in-line four-cylinder engine 1, but the engine type and the number of cylinders are not limited to this, and when the at least one cylinder is in the compression stroke, it remains. It is sufficient if at least one of the cylinders is in an expansion stroke.
Further, in the above-described embodiment, the present invention is applied to the engine 1 that performs the idle stop control. However, the engine 1 is started and stopped only by operating the ignition switch 60 without performing the idle stop control. The present invention can also be applied to an engine.

1 is an overall configuration diagram of an engine control apparatus according to an embodiment of the present invention. It is a flowchart which shows the content of the start stop control performed with the control apparatus of FIG. It is a flowchart which shows the content of the start preparation control performed with the control apparatus of FIG. It is a figure which shows the operating state of each cylinder in the engine of FIG. It is a figure which shows the relationship between the piston position P and the supply air quantity Qa which are used by the start preparation control of FIG. It is a figure which shows the relationship between the piston position P used by the start stop control of FIG. 2, and the supply air quantity Qb.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Fuel injection valve 4 Spark plug 36 Air valve (air supply means)
52 ECU (control means, cylinder discrimination means, piston position detection means)

Claims (3)

A fuel injection valve that is provided in each cylinder of an engine in which at least one of the plurality of cylinders is in the compression stroke and at least one of the remaining cylinders is in the expansion stroke, and injects fuel into the cylinder;
A spark plug for igniting the fuel injected into the cylinder by the fuel injection valve;
Air supply means for supplying air into the cylinder independently of supply of intake air by opening and closing an intake valve of the engine;
Cylinder discriminating means for discriminating each of a cylinder in an expansion stroke and a cylinder in a compression stroke when stopping the engine;
Piston position detecting means for detecting a piston position of a cylinder determined to be in an expansion stroke when the engine is stopped by the cylinder determining means;
The piston position detected by the piston position detecting means when the engine is stopped is set in advance as a piston position at which the combustion pressure of fuel in the cylinder in the expansion stroke becomes the combustion pressure necessary for starting the engine . 1. When the cylinder is determined to be in the expansion stroke by the cylinder determining means when the position is on the top dead center side from the predetermined position, air is supplied from the air supplying means to the cylinder determined to be in the expansion stroke, while the piston is in the stopped state and the piston position detecting means The piston position detected by the above is a second piston position set in advance to the bottom dead center side from the first predetermined position as a piston position capable of ensuring a piston stroke capable of starting the engine with the combustion pressure of fuel in the expansion cylinder. When the cylinder is determined to be in the compression stroke by the cylinder determining means when it is on the bottom dead center side from the predetermined position, The engine control apparatus being characterized in that a control means for supplying air from the air supply means.   The control means supplies the air until the piston position detected by the piston position detection means falls within a range between the first predetermined position and the second predetermined position when the engine is stopped. 2. The engine control apparatus according to claim 1, wherein the air supply from the means is performed.   When the engine is started, the control means supplies the fuel from the fuel injection valve to the cylinder determined to be in the expansion stroke when the engine is stopped by the cylinder determining means, and supplies the supplied fuel with the spark plug. The engine control device according to claim 1, wherein ignition is performed.

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