JP4075679B2 - Start control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In addition to starting by a starter, the present invention has an internal combustion engine having a function of performing “combustion start” in which fuel is injected into a cylinder in an expansion stroke or a compression stroke and burned, and the internal combustion engine is started at the combustion pressure. This relates to a start control device.
[0002]
[Prior art]
In recent years, some engines mounted on vehicles employ an engine automatic stop / start device (so-called idling stop device) for the purpose of reducing fuel consumption, reducing exhaust emissions, and reducing noise. This automatic engine stop / start device, for example, automatically stops the engine when the driver stops the vehicle, and then the driver tries to start the vehicle (for example, accelerator pedal depression operation). When starting, the starter is energized and the engine is automatically restarted. For this reason, when driving in an urban area where the frequency of stopping is high, the number of times the starter is driven increases, and the load applied to the starter and the battery increases.
[0003]
As a countermeasure, as shown in Patent Document 1 (Japanese Patent Laid-Open No. 2002-39038), when the engine is automatically started, fuel is injected into the cylinder in the expansion stroke and ignited to generate expansion stroke combustion. In addition, there is a type in which “combustion start” for starting the engine without using a starter is performed by rotationally driving (cranking) the crankshaft with the combustion pressure of the expansion stroke combustion.
[0004]
Recently, in order to improve the startability by the combustion start, it has been proposed to inject and ignite fuel in the cylinder in the compression stroke in addition to the cylinder in the expansion stroke. Generally, as shown in Patent Document 2 (Japanese Patent Laid-Open No. 2-191871), the ignition timing at the time of starting is set in the vicinity of the compression top dead center (TDC) in consideration of the startability.
[0005]
[Patent Document 1]
JP 2002-39038 A (pages 3 to 5 etc.)
[Patent Document 2]
Japanese Patent Laid-Open No. 2-191871 (page 4, etc.)
[0006]
[Problems to be solved by the invention]
However, at the start of combustion, initially, the expansion stroke combustion is generated in a state where the rotation of the engine is stopped and there is no rotational inertia, and the crankshaft is rotationally driven by the combustion pressure. If ignition occurs near the compression top dead center (TDC), the ignition timing is too early, and the combustion pressure in the compression stroke injection cylinder is not effectively converted into torque in the forward rotation direction, and the engine falls into a locked state and cannot be started. is there.
[0007]
The present invention has been made in view of such circumstances. Therefore, the object of the present invention is to optimize the ignition timing of the compression stroke injection cylinder at the start of combustion and improve the startability by the combustion start. An object of the present invention is to provide an engine start control device.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is an internal combustion engine start control device in which starter start and combustion start are switched according to a start condition, and is in an expansion stroke at a start position at the start of combustion. Ignition timing control means for performing first ignition for the expansion stroke injection cylinder and performing next ignition for the compression stroke injection cylinder in the compression stroke at the start position; When the next ignition is performed on the compression stroke injection cylinder in the compression stroke at the position, the ignition timing is retarded from the ignition timing at the start of the starter.
[0009]
Generally, since the ignition timing at the start of starter is set near the compression top dead center (TDC) , the compression stroke injection cylinder (hereinafter referred to as “first compression stroke injection cylinder”) in the compression stroke at the start position is referred to. When the next ignition is performed, if the ignition timing is delayed from the ignition timing at the starter start time, the ignition timing of the first compression stroke injection cylinder is retarded to some extent from the compression top dead center, and the compression stroke injection It is ignited after the piston of the cylinder descends. As a result, the combustion pressure of the first compression stroke injection cylinder can be converted into the torque in the positive rotation direction as effectively as the combustion pressure of the expansion stroke injection cylinder, and the crankshaft of the internal combustion engine can be reliably rotated forward. It is possible to start by driving in the direction, and startability by combustion start can be improved.
[0010]
Further, in claim 1, the ignition timing of the first compression stroke injection cylinder at the start of combustion is set within the range of ATDC 5 ° C. to ATDC 35 ° C. Here, “ATDC” means “after top dead center”. According to the results of experiments conducted by the inventor described later, when the ignition timing of the first compression stroke injection cylinder is earlier than ATDC 5 ° C. (when it is on the advance side), the combustion pressure is effectively converted into a torque in the forward rotation direction. May not start. If the ignition timing of the first compression stroke injection cylinder is later than ATDC 35 ° C. (on the retard side), the combustion pressure becomes low, and the torque in the positive rotation direction due to the combustion pressure becomes small. It may not be possible to start. Therefore, as in claim 2, if the ignition timing of the first compression stroke injection cylinder at the start of combustion is set within the range of ATDC 5 ° C. to ATDC 35 ° C., forward rotation by the combustion pressure of the first compression stroke injection cylinder The torque in the direction can be sufficiently generated, and the startability by the combustion start can be improved.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First, a schematic configuration of the entire engine control system will be described with reference to FIG. An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 that is an in-cylinder internal combustion engine, and an air flow meter 14 for detecting the intake air amount is provided downstream of the air cleaner 13. . A throttle valve 16 driven by a motor 15 such as a DC motor is provided on the downstream side of the air flow meter 14, and an opening degree (throttle opening degree) of the throttle valve 16 is detected by a throttle opening degree sensor 17.
[0012]
A surge tank 18 is provided on the downstream side of the throttle valve 16, and an intake pipe pressure sensor 19 for detecting the intake pipe pressure is provided in the surge tank 18. The surge tank 18 is provided with an intake manifold 20 that introduces air into each cylinder of the engine 11, and controls the in-cylinder airflow strength (swirl flow strength and tumble flow strength) in the intake manifold 20 of each cylinder. An airflow control valve 31 is provided.
[0013]
A fuel injection valve 21 that directly injects fuel into the cylinder is attached to an upper portion of each cylinder of the engine 11. A spark plug 22 is attached to the cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by the spark discharge of each spark plug 22.
[0014]
A knock sensor 32 that detects knocking, a cooling water temperature sensor 23 that detects the cooling water temperature, and a crank angle sensor 24 that detects the crank angle of the engine 11 are attached to the cylinder block of the engine 11. The crank angle sensor 24 is disposed so as to face the outer periphery of the signal rotor 37 fitted to the crankshaft of the engine 11, and teeth 37 a are formed on the outer periphery of the signal rotor 37 for each predetermined crank angle. At a specific crank angle position (crank angle reference position) on the outer periphery of the signal rotor 37, a missing tooth portion lacking 1 to 3 teeth 37a is formed. As a result, in the crank angle region other than the tooth missing portion with the rotation of the engine 11, crank angle pulse signals at equal intervals are output from the crank angle sensor 24 at every predetermined crank angle, and the tooth missing portion (crank angle reference position). Then, crank angle pulse signals with unequal intervals that increase the pulse interval are output.
[0015]
On the other hand, the exhaust pipe 25 of the engine 11 is provided with an upstream catalyst 26 and a downstream catalyst 27 for purifying the exhaust gas, and the air-fuel ratio or rich / lean of the exhaust gas is detected on the upstream side of the upstream catalyst 26. An exhaust gas sensor 28 (air-fuel ratio sensor, oxygen sensor, etc.) is provided. Further, a part of the exhaust gas is recirculated to the intake side between the downstream side of the upstream catalyst 26 in the exhaust pipe 25 and the surge tank 18 on the downstream side of the throttle valve 16 in the intake pipe 12. An EGR pipe 33 is connected, and an EGR valve 34 for controlling the exhaust gas recirculation amount (EGR amount) is provided in the middle of the EGR pipe 33.
[0016]
Outputs of the various sensors described above are input to an engine control circuit (hereinafter referred to as “ECU”) 30. The ECU 30 is mainly composed of a microcomputer, and executes various control programs stored in a built-in ROM (storage medium), so that the fuel injection amount of the fuel injection valve 21 and the fuel are controlled according to the engine operating state. The injection timing, the ignition timing of the spark plug 22 and the like are controlled.
[0017]
The ECU 30 determines whether the pulse interval of the crank angle pulse signal output from the crank angle sensor 24 is equal or unequal, and determines the position (missing tooth portion) where the unequal interval crank angle pulse signal is generated. Detected as a crank angle reference position, counts crank angle pulse signals at regular intervals from the crank angle reference position, detects the crank angle based on the counted number, discriminates the cylinder, and further generates crank angle pulse signals at regular intervals The engine speed is detected from the frequency.
[0018]
The ECU 30 also has an automatic engine stop / auto start function. When the driver stops the vehicle and a predetermined automatic stop condition is satisfied, fuel cut and ignition cut are executed to automatically start the engine 11. While stopping, the engine stop position at that time is detected and stored in the memory of the ECU 30. This engine stop position detection method is, for example, a stop position detection technique described in Japanese Patent No. 3186524, Japanese Patent Application Laid-Open No. 2002-39038, Japanese Patent Application Laid-Open No. 60-240875, Japanese Patent Application Laid-Open No. 11-107823, and the like. Can be used.
[0019]
The ECU 30 is stored in the memory of the ECU 30 when a predetermined automatic start condition (combustion start condition) is satisfied while the engine 11 is automatically stopped (when the driver performs an operation to start the vehicle). The cylinder is discriminated based on the engine stop position, the fuel is injected into the cylinders in the expansion stroke and the compression stroke and ignited to generate combustion, and the crankshaft is driven to rotate by this combustion pressure (cranking) ), The “combustion start” for starting the engine 11 without using the starter 38 is executed (see FIG. 2).
[0020]
Further, when the driver operates the ignition switch 39 to the start position while the engine is stopped, the ECU 30 executes “starter start” in which the starter 38 is energized to rotate the crankshaft to start the engine 11. The ignition timing at the start of the starter is set near the compression top dead center (TDC) in consideration of the startability. If the start by the combustion start fails, the starter 38 is automatically energized to start the starter.
[0021]
Here, the ignition / injection control at the start of combustion will be described with reference to FIG. FIG. 2 shows an example of ignition / injection control when starting combustion of the four-cylinder engine 11. In the example of FIG. 2, at the engine stop position, the first cylinder is in the expansion stroke, the third cylinder is in the compression stroke, the fourth cylinder is in the intake stroke, and the third cylinder is in the exhaust stroke. When an automatic start condition (combustion start condition) is established at this engine stop position, first, a cylinder (first cylinder) in the expansion stroke at the start position at the time of combustion start based on the engine stop position stored in the memory of the ECU 30 And the cylinder in the compression stroke (third cylinder) are discriminated, and fuel is injected into the cylinder in the expansion stroke (first cylinder) and the cylinder in the compression stroke (third cylinder), respectively. First, only the expansion stroke injection cylinder (first cylinder) is ignited to generate expansion stroke combustion, and the crankshaft is rotationally driven by the combustion pressure of the expansion stroke combustion. Thus, when the piston 40 of the compression stroke injection cylinder (third cylinder) gets over the compression top dead center (TDC) and reaches the target ignition timing set within the range of ATDC 5 ° C. to ATDC 35 ° C. A, the compression stroke The injection cylinder (third cylinder) is ignited to generate combustion, and the crankshaft is rotationally driven by this combustion pressure to start the engine 11.
[0022]
In the engine stop position, the cylinders in the intake stroke (fourth cylinder) and the cylinders in the exhaust stroke (second cylinder) are inducted in the respective cylinders as the crankshaft is rotationally driven by combustion start. Normal injection / ignition control is performed in which fuel is injected in the stroke and ignited near the compression top dead center (TDC). In addition, at the engine stop position, for the cylinders in the expansion stroke (first cylinder) and the cylinders in the compression stroke (third cylinder), the second and subsequent injections / ignitions are performed by compressing the fuel by injecting fuel in the intake stroke. Normal injection / ignition control is performed to ignite near the dead center (TDC).
[0023]
At the start of combustion, initially, since the rotation of the engine 11 is stopped and there is no rotational inertia, expansion stroke combustion is generated, and the crankshaft is rotationally driven by the combustion pressure. Therefore, compression is performed in the first compression stroke injection cylinder. If ignition is performed near the top dead center, the ignition timing is too early, and the combustion pressure in the compression stroke injection cylinder is not effectively converted into torque in the forward rotation direction, and the engine 11 may be locked and cannot be started.
[0024]
Therefore, in the combustion start of the present embodiment, the ignition timing of the first compression stroke injection cylinder is retarded from the ignition timing at the starter start (near the compression top dead center), and within the range of ATDC 5 ° C. to ATDC 35 ° C. I try to ignite. As a result, the combustion pressure of the first compression stroke injection cylinder can be effectively converted to the torque in the positive rotation direction in the same manner as the combustion pressure of the expansion stroke injection cylinder, and the crankshaft of the engine 11 is reliably positively rotated. It is possible to start by driving in the direction, and startability by combustion start can be improved.
[0025]
The present inventor conducted a test considering the appropriate range of the ignition timing of the first compression stroke injection cylinder at the start of combustion, and the test result is shown in FIG. In this combustion start test, the ignition timing of the first compression stroke injection cylinder is changed little by little in the range of BTDC 10 ° C. to ATDC 55 ° C., ignition is performed at each ignition timing, and crankshaft rotation that reaches at the combustion pressure is reached. The angle was measured. In this case, as the crankshaft rotation angle increases, the torque in the positive rotation direction generated by the combustion pressure of the first compression stroke injection cylinder increases, which means that startability is improved.
[0026]
3 is evaluated, when the ignition timing of the first compression stroke injection cylinder is within the range of ATDC 5 ° C. to ATDC 35 ° C., the crankshaft rotation angle reached by the combustion pressure of the first compression stroke injection cylinder becomes large. (In other words, the torque in the positive rotation direction generated by the combustion pressure of the first compression stroke injection cylinder increases), and it can be seen that the startability is good. On the other hand, when the ignition timing of the first compression stroke injection cylinder is earlier than ATDC 5 ° C. (when it is on the advance side), the combustion pressure is not effectively converted into the torque in the positive rotation direction. The torque in the rotational direction is reduced, the crankshaft rotation angle reached by the combustion pressure is reduced, and the startability is deteriorated. If the ignition timing of the first compression stroke injection cylinder is later than ATDC 35 ° C. (on the retard side), the combustion pressure becomes low, and the torque in the positive rotation direction due to the combustion pressure becomes small. The crankshaft rotation angle reached by the combustion pressure is reduced, and the startability is deteriorated.
[0027]
By the way, at the start of combustion, until the crank angle sensor 24 accurately detects the tooth missing portion (crank angle reference position) of the signal rotor 37, it is based on the count number of the crank angle pulse signal output from the crank angle sensor 24. The crank angle cannot be detected accurately. Therefore, detection of the crank angle and cylinder discrimination at the initial stage of combustion start are performed based on the engine stop position detected before start (when the engine was stopped last time). Therefore, it is difficult to accurately detect the engine stop position, so that even if the crank angle is detected from the count number of the crank angle pulse signal with the engine stop position as a reference, a crank angle detection error occurs.
[0028]
Therefore, in consideration of the control error of the ignition timing due to the detection error of the crank angle, the target ignition timing of the first compression stroke injection cylinder is in the range of ATDC 10 ° C. to ATDC 30 ° C., more preferably ATDC 15 ° C. A to ATDC 25 ° C. It is good to set to. If the detection error of the crank angle is large, the target ignition timing of the first compression stroke injection cylinder may be set to ATDC 20 ° C. which is the optimal ignition timing. In short, the target ignition timing is set in consideration of the crank angle detection error (ignition timing control error) so that the actual ignition timing falls within the proper range of ATDC 5 ° C. to ATDC 35 ° C. Just control.
[0029]
The ECU 30 executes a start target ignition timing setting routine shown in FIG. 4 every predetermined time or every predetermined crank angle when a start request of either combustion start or starter start occurs, and is referred to in the claims. It plays the role of ignition timing control means. When this routine is started, first, at step 101, it is determined whether or not it is ignition of the first compression stroke injection cylinder at the time of starting. If it is not ignition of the first compression stroke injection cylinder, the subsequent processing is performed. This routine is finished without executing. In this case, the target ignition timing is set by a target ignition timing setting routine (not shown) during normal operation.
[0030]
On the other hand, if it is determined in step 101 that the first compression stroke injection cylinder is ignited at the time of starting, the routine proceeds to step 102 where it is determined whether or not the starting mode is the combustion starting mode. If it is determined as “No” (in the case of starter start), the routine proceeds to step 104 where the target ignition timing is set to the compression top dead center (TDC). Even when the start by the combustion start fails, it is determined as “No” in the above step 102, the process proceeds to step 104, the target ignition timing is set to the compression top dead center (TDC), and the starter 38 is energized. Perform starter start.
[0031]
On the other hand, if it is determined in step 102 that the start mode is the combustion start mode, the routine proceeds to step 103, where the target ignition timing is set to the optimal ignition timing, ATDC 20 ° C. As a result, even if there is an ignition timing control error due to crank angle detection error at the beginning of combustion start, the actual ignition timing is controlled to fall within the proper range of ATDC 5 ° C. to ATDC 35 ° C. .
[0032]
According to the present embodiment described above, the ignition timing of the first compression stroke injection cylinder is retarded from the ignition timing (TDC) at the starter start at the time of combustion start, and within the range of ATDC 5 ° C. A to ATDC 35 ° C. A. Therefore, the torque in the positive rotation direction can be effectively generated by the combustion pressure of the first compression stroke injection cylinder, and the crankshaft can be reliably driven and started in the positive rotation direction. In addition, startability by combustion start can be improved.
[0033]
In the start target ignition timing setting routine of FIG. 4, the target ignition timing of the first compression stroke injection cylinder at the start of combustion is set to the optimal ignition timing ATDC 20 ° C., but this target ignition timing is set to the coolant temperature. In consideration of the starting conditions such as the above and the detection error of the crank angle, it may be changed within the appropriate range of ATDC 5 ° C. to ATDC 35 ° C.
[0034]
In addition, it goes without saying that the present invention is not limited to a four-cylinder engine and can be applied to an engine having three or less cylinders or five or more cylinders.
[Brief description of the drawings]
FIG. 1 is a diagram showing an entire engine control system according to an embodiment of the present invention. FIG. 2 is a diagram showing the relationship between the stroke of each cylinder, the injection timing at the start of combustion, and the ignition timing. FIG. 4 is a diagram showing test data for examining the relationship between the ignition timing of the compression stroke injection cylinder and the crankshaft rotation angle reached by the combustion pressure. FIG. 4 is a flowchart showing the processing flow of the start target ignition timing setting routine. Explanation of]
DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 16 ... Throttle valve, 21 ... Fuel injection valve, 22 ... Spark plug, 24 ... Crank angle sensor (crank angle pulse signal generation means), 30 ... ECU (ignition timing control) Means), 37 ... Signal rotor, 38 ... Starter, 39 ... Ignition switch, 40 ... Piston.

Claims (1)

“Starter start”, in which the crankshaft of the internal combustion engine is rotationally driven by the drive force of the starter to start the internal combustion engine, and fuel is injected into the cylinder in the expansion stroke or compression stroke, and the internal combustion engine is burned by the combustion pressure. In the internal combustion engine start control device, which switches between “combustion start” for starting the internal combustion engine by rotationally driving the crankshaft according to the start condition,
There is provided an ignition timing control means for performing the first ignition for the expansion stroke injection cylinder in the expansion stroke at the start position at the start of combustion and performing the next ignition for the compression stroke injection cylinder in the compression stroke at the start position. ,
The ignition timing control means sets the ignition timing of the first compression stroke injection cylinder at the start of combustion within a range of 5 ° C. A after top dead center to 35 ° C. after top dead center. Start control device.

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