JP2008151024A - Engine starter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the occurrence of self-ignition of a fuel in a cylinder of an engine. <P>SOLUTION: This engine starter starts a multicylinder four cycle engine by driving the engine in the normal rotation by burning a fuel in an expansion-stroke cylinder in stop immediately after driving the engine in the reverse rotation by burning the fuel in a compression stroke in stop. The engine starter includes a fuel injection control means controlling fuel injection valves arranged on a cylinder basis, and a self-ignition prediction means predicting whether self-ignition of the fuel occurs in the cylinder in an exhaust stroke in stop in starting the engine. The fuel injection control means executes, to the fuel injection valve corresponding to the cylinder in the exhaust stroke in stop, control to inject the fuel in the intake stroke after the engine is driven in the normal rotation when the self-ignition prediction means predicts occurrence of self-ignition of the fuel and the fuel is injected in the initial compression stroke, and executes control to inject the fuel only in the intake stroke when the self-ignition prediction means predicts that the self-ignition of the fuel will not occur. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an engine starter that starts an engine without using a starter, and belongs to the technical field of engine control for controlling an engine by controlling combustion of fuel.

  2. Description of the Related Art Conventionally, there has been known an engine starter that starts an engine without using a starter, as described in Patent Document 1. This is a starter for a multi-cylinder four-cycle engine. First, fuel is supplied into a cylinder in a compression stroke when the engine is stopped (hereinafter referred to as a “compression cylinder at stop”), and the fuel is burned. To drive the engine in reverse. Next, before the piston of the cylinder in the expansion stroke when the engine is stopped (hereinafter referred to as “stop expansion cylinder”) reaches the top dead center, fuel is supplied into the expansion stroke cylinder during the stop. Burn the fuel. As a result, the engine starts to be driven at normal rotation. Subsequently, a cylinder in the intake stroke when the engine is stopped (hereinafter referred to as “intake stroke cylinder when stopped”) supplies fuel to the inside when the engine is driven in the normal rotation and is in the first compression stroke, A cylinder in the exhaust stroke when the engine is stopped (hereinafter referred to as “exhaust stroke cylinder at stop”) supplies fuel to the inside of the two cylinders when the engine is driven in the forward rotation and is in the first intake stroke. Each of the fuel supplied to the cylinder is burned during the expansion stroke of each cylinder. Thereafter, in each cylinder, fuel is supplied to the inside during the intake stroke, and the fuel is burned during the expansion stroke.

  The engine starting device for starting the engine in this way assumes a case where the engine is in a high temperature state at the time of starting. For example, it is assumed that the engine is controlled by a control system that automatically stops the engine when idling. Strictly speaking, it is assumed that a high-temperature engine that has been automatically stopped is started immediately after being stopped.

  In the engine starter described above, the reason why the fuel is supplied into the stop-time compression stroke cylinder and burned to drive the engine in reverse rotation is that the air in the stop-time expansion stroke cylinder is compressed and the combustion energy is reduced. This is to increase it. This is because, even if fuel is supplied to the stop expansion stroke cylinder to start the engine at normal rotation and the fuel is burned, if the cylinder piston is at the bottom dead center side, This is because sufficient torque may not be transmitted to the crankshaft and the crankshaft may not rotate sufficiently.

  Further, in the engine starter described above, the reason why the fuel is supplied to the stop intake stroke cylinder when the engine is driven to rotate forward and is in the first compression stroke is that fuel self-ignition occurs in the cylinder. It is for suppressing. This is because when fuel is supplied at the timing during the first intake stroke when the engine is driven forward, that is, at the timing during the intake stroke where the engine speed is small, the fuel is expanded by receiving heat from the high-temperature engine. This is because the fuel supplied at the timing during the compression stroke is less likely to diffuse into the combustion chamber as compared with the case where the fuel is supplied at the timing during the intake stroke. (Self-ignition is less likely to occur even when heat is received from the engine in the state, and the higher the engine speed, the more difficult the fuel will self-ignite.)

JP-A-2005-180208

  However, in the engine starter described above, when the exhaust stroke cylinder at the time of stop is driven in the forward rotation of the engine and is in the first intake stroke, fuel is supplied to the inside thereof and the fuel is burned in the subsequent expansion stroke. However, there is a possibility that the fuel supplied in the first intake stroke receives heat from the high-temperature engine and self-ignites before the expansion stroke. In addition, the fuel may self-ignite and burn in the compression stroke before the expansion stroke, which may cause the engine to start driving in reverse rotation.

  Supplementally, such a self-ignition of the stop-time exhaust stroke cylinder is likely to occur particularly when the combustion state of the stop-time intake stroke cylinder is defective. In other words, if combustion in the stop intake stroke cylinder is normally performed and the engine speed increases, self-ignition in the stop exhaust stroke cylinder even if the stop exhaust stroke cylinder in which combustion is performed next is in a high temperature state. Is unlikely to occur. However, if the combustion in the intake stroke cylinder at the time of stop is insufficient, the engine speed does not increase, and self-ignition tends to occur in the exhaust stroke cylinder at the time of stop where combustion is performed next.

  Accordingly, it is an object of the present invention to provide an engine starter that can suppress the occurrence of self-ignition of fuel in a stop-time exhaust stroke cylinder immediately after starting a high-temperature engine.

  In order to solve the above-mentioned problem, the invention according to claim 1 of the present application is that the engine is stopped immediately after the fuel is burned in the compression stroke cylinder when the engine is stopped and the engine is driven in reverse rotation. An engine starter for starting a multi-cylinder four-cycle engine by burning fuel in a cylinder at a time when an expansion stroke is stopped and driving the engine in a forward rotation, and a fuel injection provided for each cylinder A fuel injection control means for controlling the valve; and a self-ignition prediction means for predicting whether or not fuel self-ignition occurs in the exhaust stroke cylinder when the engine is stopped when the engine is stopped. When the self-ignition predicting means predicts the occurrence of fuel self-ignition with respect to the fuel injection valve corresponding to the exhaust stroke cylinder at the time of stop, the engine rotates forward. Control is performed so that fuel is injected during the first compression stroke after being driven and then fuel is injected during the intake stroke, and when the self-ignition prediction means predicts that self-ignition of the fuel will not occur, the intake stroke is in progress It is characterized in that the control for injecting the fuel only in the engine is executed.

  The invention according to claim 2 is the engine starting device according to claim 1, wherein the fuel injection control means is configured such that when the self-ignition prediction means predicts the occurrence of self-ignition of fuel, the engine is normal. Controlling the injection amount of the fuel injection valve corresponding to the stop exhaust stroke cylinder so that the air fuel ratio of the stop exhaust stroke cylinder driven by rotation during the first compression stroke becomes richer than the stoichiometric air fuel ratio. It is characterized by.

Furthermore, the invention according to claim 3 is the engine starter according to claim 1 or 2,
The self-ignition prediction means is configured to predict whether or not fuel self-ignition will occur in the intake stroke cylinder when the engine is stopped when the engine is stopped, and the fuel injection control means When the self-ignition predicting means predicts the self-ignition of fuel in the stop-intake stroke cylinder for the fuel injection valve corresponding to the stop-intake stroke cylinder, the engine is driven in the forward rotation for the first time. Control is performed so that fuel is injected during the compression stroke and then fuel is injected during the intake stroke, and when the self-ignition prediction means predicts that self-ignition of fuel will not occur in the intake stroke cylinder during stoppage, Control is performed to inject fuel only during the stroke.

  Furthermore, the invention according to claim 4 is the engine start device according to any one of claims 1 to 3, wherein the self-ignition prediction means is a value indicating the possibility of occurrence of self-ignition of fuel. Is configured to predict that fuel self-ignition will occur when the engine is higher than the threshold, and the threshold for predicting that fuel self-ignition will occur in the intake stroke cylinder during stop is It is characterized in that it is set to a value larger than a threshold value for predicting that fuel self-ignition occurs in the stroke cylinder.

  In addition, according to a fifth aspect of the present invention, in the engine starting device according to the fourth aspect, the value indicating the possibility of the occurrence of self-ignition of the fuel is an engine stop time, an engine coolant temperature, And at least one of the intake air temperatures.

  According to the first aspect of the present invention, it is predicted whether or not the fuel self-ignites within the stop-time exhaust stroke cylinder, and the engine for the stop-time exhaust stroke cylinder is driven in the forward rotation to supply the first fuel. If it is predicted that self-ignition will occur, the engine that is difficult to self-ignite will start to run in the forward rotation and run in the first compression stroke, and if it is predicted that no self-ignition will occur, the engine will be driven in the forward rotation And executed in the first expansion stroke. This suppresses the occurrence of self-ignition of fuel in the stop-time exhaust stroke cylinder immediately after starting the engine in a high temperature state.

  According to the second aspect of the present invention, when it is predicted that self-ignition of the fuel will occur, the air-fuel ratio of the exhaust stroke cylinder at the stop time during the first compression stroke when the engine is driven in the normal rotation is calculated as Fuel is supplied to the cylinder so as to be richer than the air-fuel ratio. When an amount of fuel larger than the amount corresponding to the stoichiometric air-fuel ratio is supplied, the exhaust stroke cylinder at the time of stop is further cooled (by removing heat from the inside of the cylinder or the wall surface of the cylinder when the fuel is vaporized). ). By cooling the cylinder, the fuel vaporized in the cylinder is less likely to self-ignite.

  Further, according to the third aspect of the present invention, it is predicted whether or not self-ignition will occur even in the intake stroke cylinder at the time of stop. When the engine for the intake stroke at the time of stop is driven in the forward rotation, the first fuel supply is executed in the first compression stroke when the engine that is difficult to self-ignite is driven in the forward rotation when the self-ignition is expected to occur. If it is predicted that no self-ignition will occur, the engine is driven in the forward rotation and executed in the first expansion stroke. As a result, the occurrence of self-ignition of fuel in the intake stroke cylinder during stop is suppressed.

  Furthermore, according to the fourth aspect of the present invention, it is predicted that self-ignition will occur when the value indicating the possibility of occurrence of self-ignition is higher than the threshold value, and self-ignition occurs in the intake stroke cylinder at the time of stop. The threshold value for predicting occurrence is set to be larger than the threshold value for predicting that self-ignition will occur in the stop-time exhaust stroke cylinder. This is because there is a possibility that hot exhaust gas remains in the exhaust stroke cylinder at the time of stop, and therefore the internal temperature of the exhaust stroke cylinder at the stop time may be higher than that of the intake stroke cylinder at the stop time. That is, it is because the self-ignition of the fuel is more likely to occur in the exhaust stroke cylinder at the time of stop. As a result, it is not excessively predicted that self-ignition will occur in the intake stroke cylinder at the time of stop, and it can be reliably predicted that self-ignition will occur in the exhaust stroke cylinder at the time of stop. Prediction of the occurrence of self-ignition for each exhaust stroke cylinder is appropriately performed.

  In addition, according to the invention described in claim 5, the value indicating the possibility of occurrence of self-ignition is calculated based on at least one of the engine stop time, the engine coolant temperature, and the intake air temperature. The Therefore, it is possible to predict the occurrence of fuel self-ignition without monitoring the fuel state in the cylinder.

  1 and 2 schematically show an engine control system including an engine starter according to an embodiment of the present invention.

  The engine control system denoted by reference numeral 10 in the figure is composed of an engine 16 having a cylinder head 12 and a cylinder block 14, and an ECU (engine controller unit) 18 for controlling the engine 16.

  The engine 16 is a four-cylinder four-cycle engine (an engine in which a combustion cycle including compression, expansion, exhaust, and intake stroke is executed in each cylinder), and includes four cylinders 20A to 20D. A piston 24 operatively connected to the crankshaft 22 is fitted and a combustion chamber 26 is formed at the upper part of the piston in each cylinder.

  A spark plug 28 for igniting the air-fuel mixture in the combustion chamber and combusting the air-fuel mixture is provided at the top of the combustion chamber 26 of each cylinder 20A to 20D, and the electrode at the tip of the spark plug faces the combustion chamber. Are arranged as follows. Further, a fuel injection valve 30 for injecting fuel into the combustion chamber is provided on the side of the combustion chamber 26 of each cylinder 20A to 20D so that the fuel injection valve can inject fuel toward the vicinity of the electrode of the spark plug 28. Is arranged. The fuel injection valve 30 is configured such that the injection amount is adjusted by the ECU 18 as will be described later, and fuel can be injected at a pressure higher than the pressure in the cylinder in the compression stroke.

  Further, an intake port 32 and an exhaust port 34 that open toward the combustion chamber are provided above the combustion chamber 26 of each cylinder 20A to 20D, an intake valve 36 is provided in the intake port, and an exhaust is provided in the exhaust port. A valve 38 is provided. The intake valve 36 and the exhaust valve 38 of each cylinder 20 </ b> A to 20 </ b> D are opened / closed by a valve operating mechanism including a camshaft (not shown), and the opening / closing timing corresponds to the rotation angle of the crankshaft 22.

  An intake passage 40 is connected to the intake port 32 of each of the cylinders 20A to 20D, and an exhaust passage 42 is connected to the exhaust port 34. As shown in FIG. 2, the downstream portion of the intake passage 40 close to the intake port 32 of each cylinder 20A to 20D is configured as a branch intake passage 40a connected to each cylinder, and the upstream end of each of the branch intake passages is surged. It is connected to the tank 40b. A portion 40c of the intake passage 40 upstream of the surge tank 40b is configured as a common intake passage common to the cylinders 20A to 20D, and a throttle valve 44 for adjusting the amount of intake air passing through the common intake passage, A throttle valve actuator 46 for driving the throttle valve is provided. An airflow sensor 48 for detecting the intake air amount is provided upstream of the throttle valve 44 in the common intake passage 40c, and an intake air temperature sensor 50 for detecting the intake air temperature and the intake air are provided downstream of the throttle valve 44. An intake pressure sensor 52 for detecting pressure is provided.

  On the other hand, a catalyst (not shown) for purifying exhaust gas is provided on the downstream side of the collection portion of the exhaust passage 42 where exhaust from each of the cylinders 20A to 20D collects.

  In addition to the air flow sensor 48, the intake air temperature sensor 50, and the intake pressure sensor 52, the engine 16 includes crank angle sensors 54 and 56 that detect a rotation angle in order to calculate the rotation direction and the rotation speed of the crankshaft 22, A cam angle sensor 58 that detects the rotation angle of a camshaft (not shown) corresponding to the opening / closing timing of the intake valve 36 and the exhaust valve 38, a water temperature sensor 60 that detects the temperature of engine coolant, and an accelerator opening (accelerator operation amount) And an accelerator opening sensor 62 for detecting the above.

  The ECU 18 is configured to read signals from the airflow sensor 48, the intake air temperature sensor 50, the intake air pressure sensor 52, the crank angle sensors 54 and 56, the cam angle sensor 58, the water temperature sensor 60, and the accelerator opening sensor 62. .

  The ECU 18 is configured to output a control signal to the fuel injection valve 30, an ignition device 64 that performs ignition by the spark plug 28, and the throttle valve actuator 46 (fuel injection control according to claims). Functions as a means).

  While the engine 16 is being driven, the ECU 18 outputs a control signal based on the signal from the accelerator opening sensor 18 to the throttle valve actuator 46 to control the intake air amount. The ECU 18 controls the intake air amount based on the signal from the air flow sensor 48. A fuel injection valve in which an amount of fuel is provided in the cylinder so that the air-fuel ratio of the air-fuel mixture in the cylinder in the intake stroke of the cylinders 20A to 20D becomes the stoichiometric air-fuel ratio based on the detected intake amount 30 is output to the fuel injection valve, and when the cylinder supplied with fuel is in the expansion stroke, a signal is output to the ignition device 64 of the spark plug 28 provided in the cylinder. Control is performed to burn the fuel. Hereinafter, this control is referred to as “normal combustion control”.

  For this purpose, the ECU 18 is configured to detect the current stroke of each cylinder 20A to 20D based on signals from the crank angle sensors 54 and 56 and the cam angle sensor 58, and the detected stroke of each cylinder. The timing of fuel injection by the fuel injection valve 30 and the timing of fuel ignition by the spark plug 28 are controlled based on the above.

  On the other hand, the ECU 18 executes the following control operation when starting the engine 16. The following control content assumes that the engine 16 before starting is in a high temperature state, for example, when the ECU 18 is configured to automatically stop the engine when idling, or immediately after the ignition key is turned off. It is assumed that the device is turned on again. Specifically, the engine 16 before the start is in a high temperature state, and the engine 16 is started so that fuel self-ignition does not occur in the stop intake stroke cylinder and the stop exhaust stroke cylinder among the plurality of 20A to 20D. The control operation to be executed is executed.

  The ECU 18 starts the engine 16 as shown in any of FIGS. 3 and 4 to be described later based on the temperature state of the engine 16, strictly speaking, the internal temperature of the exhaust stroke cylinder at the stop time among the plurality of cylinders 20A to 20D. The control operation related to is executed. For that purpose, the ECU 18 is based on a signal created from the intake air temperature sensor 50 and the water temperature sensor 60 and a map created in advance showing the corresponding relationship between the intake air temperature, the cooling water temperature, and the internal temperature of the stop-time exhaust stroke cylinder. The internal temperature of the exhaust stroke cylinder at the time of stop is calculated.

  Further, the ECU 18 causes the fuel injection valve 30 corresponding to the cylinder to inject an amount of fuel based on the calculated internal temperature of the stop-time exhaust stroke cylinder so that the air-fuel ratio in the cylinder becomes a predetermined target air-fuel ratio. It is configured as follows. The predetermined target air-fuel ratio varies depending on the internal temperature of the stop-time exhaust stroke cylinder, and the corresponding relationship is calculated in advance experimentally or theoretically, and is set to be richer than the theoretical air-fuel ratio. This effect will be described later.

  A control operation of the ECU 18 relating to starting of the engine 16 will be described with reference to FIGS.

  FIG. 3 shows the control operation when the internal temperature of the exhaust stroke cylinder at the stop time when the engine 16 is started is lower than a predetermined internal temperature when the engine 16 before the start is not in a high temperature state. (The internal temperature corresponds to a value indicating the possibility of the occurrence of self-ignition in the claims). On the other hand, FIG. 4 shows the control operation when the internal temperature of the exhaust stroke cylinder at the stop time when the engine 16 is started is higher than a predetermined internal temperature when the engine 16 before starting is in a high temperature state.

  3 (a) and 4 (a) are stroke diagrams of the engine 16, showing the relationship between the opening / closing timings of the intake valve 36 and the exhaust valve 38 and the stroke. Further, the timing of fuel injection (supply) by the fuel injection valve 30 for the stroke is indicated by F1 to F8, and the timing of fuel combustion by the spark plug 28 for the stroke is indicated by E1 to E6. The fuel injected at the timing FX (X is an integer) is burned at the timing EX. Further, in the figure, BDC indicates bottom dead center, and TDC indicates top dead center.

  On the other hand, FIGS. 3B and 4B are timing diagrams showing the fuel injection timings F1 to F8 and the fuel combustion timings E1 to E6 on the time axis.

  FIG. 5 shows an example of a flow of a control operation performed by the ECU 18 until the engine 16 in a stopped state is started and the above-described normal combustion control is started.

  First, as shown in FIG. 5, the ECU 18 determines whether or not the start of the engine 16 is requested in S <b> 10, for example, a signal indicating that the accelerator pedal is stepped on is output from the accelerator opening sensor 62 to the ECU 18. It is determined whether or not it has been done. When the start request of the engine 16 is confirmed, the process proceeds to the next step.

  Next, in S12, the ECU 18 reads the signal from the intake air temperature sensor 50 and the signal from the water temperature sensor 60, and detects the intake air temperature and the cooling water temperature.

  Subsequently, in S14, the ECU 18 calculates the internal temperature of the stop-time exhaust stroke cylinder among the plurality of cylinders 20A to 20D based on the detected intake air temperature, the coolant temperature, and the map described above.

  In S16, the ECU 18 calculates a predetermined target air-fuel ratio as described above based on the calculated internal temperature.

  From here, the ECU 18 starts to execute a control operation related to combustion, that is, control of the spark plug 28 and the fuel injection plug 30.

  First, in S18, the ECU 18 supplies fuel to the fuel injection valves 30 corresponding to the cylinders 20A to 20D at the time of the stop compression stroke (F1). For example, as shown in FIG. 6A showing the state of the plurality of cylinders 20A to 20D and the crankshaft 22 when the engine 16 is in the stopped state, when the compression stroke cylinder at the time of stop is the cylinder 20A, the cylinder 20A Fuel is supplied to the fuel injection valve 30 corresponding to.

  Next, in S20, the ECU 18 controls the spark plug 28 corresponding to the cylinder to ignite the fuel in order to burn the fuel supplied to the stop compression stroke cylinder. The fuel burns by ignition (E1).

  When the fuel is combusted in the stop-time compression stroke cylinder, the crankshaft 22 starts to reversely rotate (the engine 16 starts to reversely rotate) as shown in FIG. 6B.

  Subsequently, in S22, the ECU 18 causes the fuel injection valve 30 corresponding to the cylinder to be supplied to the stop expansion stroke cylinder among the plurality of cylinders 20A to 20D (F2). The fuel supply timing F2 is the timing during which the stop-time expansion stroke cylinder is in the expansion stroke, as shown in FIGS. 3 (a) and 4 (a) (the engine 16 shifts to the exhaust stroke by the reverse rotation drive of the engine 16). It is the previous timing.)

  In S24, the ECU 18 ignites the fuel by controlling the spark plug 28 corresponding to the cylinder in order to burn the fuel supplied to the stop expansion stroke cylinder. The fuel burns by ignition (E2). This fuel ignition timing E2 is, as shown in FIGS. 3A and 4A, when the stop-time expansion stroke cylinder is in the expansion stroke (strictly, when the corresponding piston comes close to top dead center). (This is the timing before the engine 16 shifts to the exhaust stroke by the reverse rotation driving of the engine 16).

  When the fuel is combusted in the expansion stroke cylinder at the time of stop, as shown in FIG. 6C, the crankshaft 22 starts to rotate forward (the engine 16 starts to rotate forward).

  When the engine 16 starts to rotate forward, the ECU 18 starts the above-described normal combustion control for the stop-time compression stroke cylinder and the stop-time expansion stroke cylinder in S26. That is, thereafter, in the stop-time compression stroke cylinder and the stop-time expansion stroke cylinder, fuel is supplied during the intake stroke (F5, F6), and the fuel is combusted in the subsequent expansion stroke (E5, E6).

  In S28, the ECU 18 determines whether or not the stop-time intake stroke cylinder is in the compression stroke based on the signals from the crank angle sensors 54 and 56 and the cam angle sensor 58 as described above. When it is confirmed that the intake stroke cylinder during the stop is in the compression stroke, the routine proceeds to step 30.

  In step 30, the ECU 18 determines whether or not the internal temperature calculated in step 14 is higher than a predetermined temperature, that is, whether or not the engine 16 is in a high temperature state. If the internal temperature is lower than the predetermined temperature, the process proceeds to step 32. Otherwise (when the internal temperature is higher than the predetermined temperature), the process proceeds to step 40.

  In S32, as shown in FIG. 3A, the ECU 18 causes the fuel injection valve 30 corresponding to the cylinder to supply fuel to the stop-time intake stroke cylinder during the compression stroke (F3).

  Next, in S34, the ECU 18 causes the fuel injection valve 30 corresponding to the cylinder to be supplied with fuel to the stop-time exhaust stroke cylinder during the intake stroke (F4). The fuel injection timing F4 is substantially the same as the fuel injection timing F3, as shown in FIGS. 3 (a) and 3 (b). At this time, the ECU 18 causes the fuel injection valve 30 to supply an amount of fuel based on the theoretical air-fuel ratio.

  Subsequently, in S36, the ECU 18 determines whether or not the stop-time intake stroke cylinder is in an expansion stroke based on signals from the crank angle sensors 54 and 56 and the cam angle sensor 58 as described above. When it is confirmed that the intake stroke cylinder during the stop is in the expansion stroke, the routine proceeds to step 38.

  In S38, the ECU 18 controls the spark plug 28 corresponding to the cylinder to burn the fuel in the stop-time intake stroke cylinder during the expansion stroke (strictly speaking, immediately after shifting to the expansion stroke). Ignite. The fuel burns by ignition (E3). As the fuel burns, the rotational speed of the crankshaft 22 increases (the rotational speed of the engine 16 increases). Then, the process proceeds to S48.

  On the other hand, when it is confirmed in S30 that the internal temperature is higher than the predetermined temperature, in S40, as shown in FIG. 4 (a), the ECU 18 selects the cylinder corresponding to the stop intake stroke cylinder during the compression stroke. The fuel is supplied to the fuel injection valve 30 corresponding to (F3).

  Next, in S42, the ECU 18 determines whether or not the stop-time intake stroke cylinder is in an expansion stroke based on signals from the crank angle sensors 54 and 56 and the cam angle sensor 58 as described above. When it is confirmed that the intake stroke cylinder during the stop is in the expansion stroke, the routine proceeds to step 44.

  In S44, the ECU 18 controls the spark plug 28 corresponding to the cylinder to burn the fuel in the stop-time intake stroke cylinder during the expansion stroke (strictly speaking, immediately after shifting to the expansion stroke). Ignite. The fuel burns by ignition (E3). As the fuel burns, the rotational speed of the crankshaft 22 increases (the rotational speed of the engine 16 increases).

  Subsequently, in S46, the ECU 18 causes the fuel injection valve 30 corresponding to the cylinder to supply fuel to the stop exhaust stroke cylinder during the compression stroke (F4 '). At this time, the ECU 18 causes the fuel injection valve 30 to supply an amount of fuel based on the target air-fuel ratio calculated in S16. Then, the process proceeds to S48.

  In S48, the ECU 18 determines whether or not the stop-time exhaust stroke cylinder is in the expansion stroke based on signals from the crank angle sensors 54 and 56 and the cam angle sensor 58 as described above. When it is confirmed that the stop-time exhaust stroke cylinder is in the expansion stroke, the routine proceeds to step 50.

  In S50, the ECU 18 controls the ignition plug 28 corresponding to the cylinder to burn the fuel in the stop exhaust stroke cylinder during the expansion stroke (strictly speaking, immediately after shifting to the expansion stroke). Ignite. The fuel burns by ignition (E4). As the fuel burns, the rotational speed of the crankshaft 22 is further increased (the rotational speed of the engine 16 is further increased).

  When the rotational speed of the engine 16 further increases, in S52, the ECU 18 starts the above-described normal combustion control for the stop-time intake stroke cylinder and the stop-time exhaust stroke cylinder. That is, thereafter, in the stop-time intake stroke cylinder and the stop-time exhaust stroke cylinder, fuel is supplied during the intake stroke (F7, F8), and the fuel is combusted in the subsequent expansion stroke. Then, the control operation for starting the engine 16 of the ECU 18 ends.

  The control related to the start of the engine 16 performed by the ECU 18 has been described above. To put it briefly, the ECU 18 checks whether or not the engine 16 is in a high temperature state when the engine 16 is started (exhaust stroke when stopped). Whether the internal temperature of the cylinder is high), and when the engine 16 is in a high temperature state (when the internal temperature of the exhaust stroke cylinder at the time of stop is high), the fuel supplied to the exhaust stroke cylinder at the time of stop is predicted to self-ignite Then, the engine 16 for the exhaust stroke cylinder at the time of stop is driven in the normal rotation, and the first fuel supply is performed in the compression stroke in which it is difficult to self-ignite. On the other hand, when the engine 16 is not in a high temperature state, it is predicted that the fuel supplied to the exhaust stroke cylinder at the time of stop does not self-ignite, and the engine 16 is driven in the normal rotation with respect to the exhaust stroke cylinder at the stop and the fuel burns the first fuel supply. The intake stroke is easy to diffuse into the room. As a result, in a high-temperature engine, the occurrence of fuel self-ignition in the exhaust cylinder when stopped is suppressed.

  Further, when the engine 16 is driven in the forward rotation and the initial fuel supply is performed in the compression stroke in which it is difficult to self-ignite, the air-fuel ratio in the cylinder is richer than the stoichiometric air-fuel ratio. An amount that provides a predetermined target air-fuel ratio is supplied to the cylinder via the fuel injection valve 30. When an amount of fuel larger than the amount corresponding to the stoichiometric air-fuel ratio is supplied, the exhaust stroke cylinder at the time of stop is further cooled (by removing heat from the inside of the cylinder or the wall surface of the cylinder when the fuel is vaporized). ). By cooling the cylinder, the fuel vaporized in the cylinder is less likely to self-ignite.

  Further, the ECU 18 predicts the occurrence of fuel self-ignition in the stop-time exhaust stroke cylinder based on the temperature in the cylinder, and calculates the temperature in the cylinder based on the temperature of the engine cooling water and the temperature of the intake air. is doing. Therefore, it is possible to predict the occurrence of fuel self-ignition without monitoring the state of the fuel in the cylinder.

  While the present invention has been described with reference to the above-described embodiment, the present invention is not limited to this.

  For example, in the above-described embodiment, when the engine for the stop exhaust stroke cylinder is driven in the normal rotation and the first fuel supply is performed in the compression stroke, the predetermined amount greater than the amount based on the stoichiometric air-fuel ratio supplied during the normal combustion control. The amount of fuel based on the target air-fuel ratio is supplied to cool the inside of the cylinder, and the self-ignition of the fuel in the exhaust stroke cylinder at the time of stop is surely suppressed. However, the amount may be an amount based on the stoichiometric air-fuel ratio as long as the fuel self-ignition in the stop-time exhaust stroke cylinder can be reliably suppressed only by supplying the fuel in the compression stroke. In this case, less fuel is used than in the above embodiment.

  In the above-described embodiment, the occurrence of self-ignition of fuel in the exhaust stroke cylinder at the stop is predicted based on the internal temperature of the exhaust stroke cylinder at the stop, and the internal temperature is based on the intake air temperature and the coolant temperature. Calculated. That is, the calculation accuracy is improved by calculating the internal temperature based on the two parameters of the intake air temperature and the coolant temperature. If the internal temperature can be calculated with high accuracy at least one of the intake air temperature and the cooling water temperature, the internal temperature does not have to be calculated based on the two parameters of the intake air temperature and the cooling water temperature.

  Relatedly, when the ECU is configured to automatically stop the engine when idling, the internal temperature of the exhaust stroke cylinder at the time of stop is calculated based on the engine stop time until the engine is stopped and restarted (The temperature of the entire engine that is automatically stopped when idling changes in accordance with the engine stop time). Further, the internal temperature of the stop-time exhaust stroke cylinder may be calculated based on the three parameters of the engine stop time, the intake air temperature, and the coolant temperature. In a broad sense, the present invention does not limit the parameters for calculation as long as the internal temperature in the exhaust stroke cylinder at the time of stop can be accurately calculated.

  Furthermore, in the above-described embodiment, the occurrence of fuel self-ignition only in the stop exhaust stroke cylinder is predicted, but the occurrence of fuel self-ignition in the stop intake stroke cylinder is also predicted. Good.

  For example, as in the exhaust stroke cylinder at the time of stop, the occurrence of self-ignition of fuel is predicted at the time of engine start for the intake stroke cylinder at the time of stop, and self-ignition occurs in the fuel injection valve corresponding to the intake stroke cylinder at the time of stop. If it is predicted that the engine is driven forward and fuel is injected during the first compression stroke, then fuel is injected during the intake stroke (the above-described embodiment), and it is predicted that self-ignition will not occur. In this case, the fuel may be injected only during the intake stroke.

  In addition, in this way, the occurrence prediction of fuel self-ignition in both the stop intake stroke cylinder and the stop exhaust stroke cylinder is executed, and a value indicating the possibility of the occurrence of self-ignition (in the above embodiment, When it is predicted that self-ignition occurs when the internal temperature is higher than a threshold value (predetermined internal temperature), the threshold values (in the above-described embodiment, for predicting the occurrence of each self-ignition) The predetermined internal temperature is preferably set so as to be larger in the intake stroke cylinder during the stop.

  This is because there is a possibility that hot exhaust gas remains in the exhaust stroke cylinder at the time of stop, and therefore the internal temperature of the exhaust stroke cylinder at the stop time may be higher than that of the intake stroke cylinder at the stop time. That is, it is because the self-ignition of the fuel is more likely to occur in the exhaust stroke cylinder at the time of stop. By setting the threshold value for predicting the occurrence of each self-ignition so that it is larger in the intake stroke cylinder at the time of stop, it is overestimated that self-ignition will occur in the intake stroke cylinder at the time of stop In addition, it is possible to reliably predict that self-ignition will occur in the stop exhaust stroke cylinder, that is, it is possible to properly predict the occurrence of self-ignition for the stop intake stroke cylinder and the stop exhaust stroke cylinder. Become.

1 is a schematic view of an engine control system including an engine starter according to an embodiment of the present invention. 1 is a schematic view of an engine according to the present invention. FIG. 2 shows a stroke diagram and a timing diagram when starting an engine that is not in a high temperature state. FIG. 2 shows a stroke diagram and a timing diagram at the start of a high-temperature engine. It is a figure which shows an example of the flow of control operation | movement from engine starting to an engine being normally combustion-controlled. It is a supplementary figure for demonstrating in detail the starting method of an engine.

Claims (5)

Immediately after the fuel is burned in the cylinder during the compression stroke when the engine is stopped and the engine is driven in reverse rotation, the fuel is burned in the cylinder during the expansion stroke when the engine is stopped and the engine is rotated forward. An engine starter that starts a multi-cylinder four-cycle engine by driving with
Fuel injection control means for controlling a fuel injection valve provided for each cylinder;
Self-ignition prediction means for predicting whether or not self-ignition of fuel occurs in the exhaust stroke cylinder when the engine is stopped when the engine is stopped when starting the engine,
The fuel injection control means, for the fuel injection valve corresponding to the stop-time exhaust stroke cylinder,
When the self-ignition predicting means predicts the occurrence of fuel self-ignition, the engine is driven in the forward rotation to perform fuel injection during the first compression stroke, and thereafter to perform fuel injection during the intake stroke. ,
An engine starter characterized in that when the self-ignition prediction means predicts that self-ignition of fuel will not occur, control is performed to inject fuel only during the intake stroke. The engine starter according to claim 1,
The fuel injection control means is configured such that when the self-ignition prediction means predicts the occurrence of fuel self-ignition, the air-fuel ratio of the exhaust stroke cylinder during stoppage during the first compression stroke when the engine is driven in the normal rotation An engine starter characterized by controlling an injection amount of a fuel injection valve corresponding to an exhaust stroke cylinder at a stop so as to be richer than a fuel ratio. The engine starting device according to claim 1 or 2,
The self-ignition prediction means is configured to predict whether or not fuel self-ignition will occur in the intake stroke cylinder when the engine is stopped when the engine is stopped,
The fuel injection control means, with respect to the fuel injection valve corresponding to the stop-time intake stroke cylinder,
When the self-ignition predicting means predicts the self-ignition of fuel in the intake stroke cylinder at the time of stop, the engine is driven in the forward rotation to inject fuel during the first compression stroke, and thereafter the fuel is injected during the intake stroke. Execute the control to spray,
An engine starter characterized by executing control for injecting fuel only during an intake stroke when said self-ignition predicting means predicts that self-ignition of fuel will not occur in an intake stroke cylinder during stoppage. The engine starting device according to any one of claims 1 to 3,
The self-ignition prediction means is configured to predict that fuel self-ignition will occur when a value indicating the possibility of occurrence of fuel self-ignition is higher than a threshold value,
The threshold for predicting the occurrence of fuel self-ignition in the intake stroke cylinder during the stop is compared to the threshold for predicting the occurrence of fuel self-ignition in the exhaust stroke cylinder during the stop. The engine starting device is characterized by being set to a large value. The engine starting device according to claim 4,
The engine starter characterized in that the value indicating the possibility of the occurrence of self-ignition of the fuel is calculated based on at least one of an engine stop time, an engine coolant temperature, and an intake air temperature.

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