JP2006112269A - Start control device for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve startability of an engine when fogging of an ignition plug occurs. <P>SOLUTION: This device is provided with a start demand detection means S1 detecting engine start demand of an operator, an engine condition estimation means S7 estimating indicating over supply quantity of fuel in a combustion chamber of the engine based on time required for engine start operation and start condition, and fuel injection quantity limiting means S2-S6 limiting fuel injection quantity at a time of start according to the scavenging rate at a time of detection of the start demand. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to fuel injection amount control when starting an engine, and more particularly to fuel injection amount control that improves startability when moisture or fuel adheres to a spark plug.

  Ignition of water that is formed by condensation of moisture in the combustion chamber at low temperatures, or fuel that remains unburned in the combustion chamber when the start-up operation is interrupted or the engine fails to start before the engine starts completely. When the so-called fogging state adhering to the stopper is reached, engine startability deteriorates.

  In addition, if the startup operation is attempted in the fogged state and the startup fails, or if the startup operation is interrupted for any reason before the complete explosion, the fuel injected during the startup operation adheres to the spark plug. In addition, the startability is further deteriorated.

As a technique for preventing such deterioration of startability, Patent Document 1 estimates the amount of water adhering to the spark plug before starting the engine, and determines that it is adhering in large quantities. In addition, there is disclosed a technique of removing moisture from the spark plug by limiting or stopping the fuel injection amount for a predetermined time during the start operation, or by energizing the spark plug for a predetermined time before starting the starter.
JP-A-5-33698

  However, in Patent Document 1, since the amount of water adhering to the spark plug is estimated based on the engine temperature (engine cooling water temperature), it is difficult to estimate the amount of adhering water with high accuracy. . In addition, since the control for removing the fog is set to a certain time regardless of the degree of the fog, it is necessary to set a long time in order to reliably eliminate the fog state, and the driver must The time from when the engine start operation is performed until the start operation is actually started becomes longer than necessary, which may give the driver a sense of incongruity. In addition, there is a problem that the power consumption of the battery increases when the ignition plug is energized.

  Furthermore, if the fog cannot be eliminated by stopping fuel injection for a certain period of time or energizing the spark plug, the next time the engine will start with more moisture than before the previous engine start, There is a problem that startability deteriorates more and more.

  Therefore, an object of the present invention is to perform appropriate start control according to the state of the spark plug, and improve engine startability from the fogged state.

  The engine start control device according to the present invention includes a start request detecting means for detecting an engine start request of a driver, a scavenging rate representing an amount of excessive supply fuel in the combustion chamber of the engine, a time required for the engine start operation, and a start. Engine state estimating means for estimating based on conditions, and correcting means for limiting the fuel injection amount at the start according to the scavenging rate when the start request is detected.

  According to the present invention, since the fuel injection amount at the start is limited according to the scavenging rate, the combustion chamber is scavenged by limiting the fuel injection amount when the spark plug is in a cover state. As a result, fogging of the spark plug is eliminated and engine startability is improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic view of an engine system to which this embodiment is applied.

  1 is an engine, 2 is an intake pipe for supplying intake air to the engine 1, 3 is a fuel injection valve for injecting fuel into the intake pipe 2, and 4 is intake air for adjusting the amount of intake air supplied to the engine 1 A throttle valve 10 provided upstream of the fuel injection valve 3 in the pipe 2 is an exhaust pipe for exhausting the gas burned in the engine 1. The opening degree of the throttle valve 4 is adjusted by electronic control.

  An ignition plug 6 is provided on the ceiling surface of the combustion chamber 8 and sparks the intake air supplied into the combustion chamber 8.

  The intake pipe 2 and the exhaust pipe 10 have an opening in the combustion chamber 8, and an intake valve 11 and an exhaust valve 12 are arranged in the openings, respectively. The intake valve 11 and the exhaust valve 12 open and close the communication between the combustion chamber 8 and the intake pipe 2 and the exhaust pipe 10 in response to a piston 13 slid into the cylinder 14 of the engine 1.

  Reference numeral 7 denotes a rotational speed detection sensor comprising an electromagnetic pickup or the like, which is provided in the vicinity of the outer periphery of the crankshaft pulley 9 locked to the end of the crankshaft (not shown), and detects the rotation of the crankshaft pulley 9, that is, the engine speed. To detect. The rotation speed detection sensor 7 is not limited to an electromagnetic pickup, and may be an optical sensor or the like.

  An engine control unit (ECM) 5 controls the opening degree of the throttle valve 4, the fuel injection amount of the fuel injection valve 3, the ignition timing of the spark plug 6, and the like based on detection signals from the rotation speed detection sensor 7 and the like. As will be described later, the ECM 5 determines a fuel injection amount limiting means, an engine state estimating means, a starting failure judging means, for appropriately controlling the starting fuel by judging the fogging state of the spark plug 6 at the time of starting, It functions as a limit amount correction means.

  Other detection signals input to the ECM 5 include a signal from a starter switch as a start request detecting means for detecting a start request of the engine 1 of the driver, an accelerator opening sensor for detecting the accelerator depression amount of the driver, and a vehicle speed. There is a vehicle speed sensor or the like that detects this.

  The fuel injection amount from the fuel injection valve 3 is a drive pulse in which the ECM 5 calculates the fuel injection amount according to the operating state based on the detection values of the respective sensors, and the valve opening time according to this fuel injection amount. It is controlled by inputting a signal to the fuel injection valve 3.

  Control of the engine system configured as described above when the engine is started will be described with reference to FIG.

  FIG. 2 is a flowchart for controlling the fuel injection amount when starting the engine.

  OFF even if the spark plug 6 sparks when starting the engine, but the engine fails to start without reaching a complete explosion for some reason, or before the complete explosion occurs even if the start switch is turned ON For example, when the start operation is stopped, an unburned air-fuel mixture containing fuel injected during the start operation remains in the cylinder 14. At low temperatures, the fuel introduced into the cylinder 14 remains without being sufficiently atomized, and when this fuel adheres to the spark plug 6, a so-called "fogging" state occurs and the startability is deteriorated thereafter. Cause.

  Therefore, in this embodiment, the startability of the engine 1 is improved by estimating the fogging state of the spark plug 6 when starting the engine and scavenging the unburned gas remaining in the cylinder 14 accordingly.

  In order to estimate the fogging state of the spark plug 6, an integrated scavenging rate expressed by the following equation (1) is used in the present embodiment.

Integrated scavenging rate = (Integrated displacement x Scavenging coefficient) / (Integrated fuel injection amount) (1)
In equation (1), the accumulated exhaust amount is the amount of air introduced into the cylinder 14 of the engine 1 per cycle, that is, the exhaust amount is integrated with the number of cycles, and the accumulated fuel injection amount is the fuel per cycle. The number of cycles is integrated with the injection amount. Since not all of the air introduced into the cylinder 14 is used for scavenging, the exhaust amount is corrected using the scavenging coefficient.

  That is, the integrated scavenging rate is the ratio of the amount of air used for scavenging and the fuel injection amount, and represents the degree of scavenging. When the integrated scavenging rate is small, there is a large amount of fuel remaining in the cylinder 14, and the ignition plug 6 is likely to be covered when the fuel is injected and the starting operation is performed. When the integrated scavenging rate is large, the engine is easily started contrary to the above.

  In the following, description will be given according to the steps of FIG.

  In step S1, it is determined whether there is an engine start request. Specifically, for example, the determination is made based on whether or not the starter switch is turned on. If there is a start request, the process proceeds to step S2, and if not, the process ends.

  In step S2, it is determined whether or not the integrated scavenging rate calculated in step S7, which will be described later, is larger than the startable lower limit scavenging rate as the first set value set as the lower limit scavenging rate at which the engine can be started. Proceeds to step S3, and if smaller, proceeds to step S12. The startable lower limit scavenging rate is a scavenging rate at which the ignition plug 6 is reliably covered and engine startup becomes difficult when the scavenging rate is further reduced. The scavenging rate is determined in advance by experiments and stored in the ECM 5. Keep it. In addition, when starting for the first time, the startable lower limit scavenging rate is assumed to be larger.

  In step S12, the decrease flag Fd and the increase flag Fi are set to Fd = 1 and Fi = 0, respectively, and the process proceeds to step S4. In the initial state, both the decrease flag Fd and the increase flag Fi are set to zero.

  In step S3, it is determined whether or not the integrated scavenging rate is smaller than the fog restart margin scavenging rate as the second set value set as the scavenging rate at which the engine can be restarted at the normal fuel injection amount. If so, the process proceeds to step S4. If larger, the process proceeds to step S13.

  It should be noted that the fog restart margin scavenging rate is a scavenging rate that can be reliably started even if fuel control during normal engine start is performed if the scavenging rate is higher than that, and is obtained in advance by experiments or the like and stored in the ECM 5 Keep it. In addition, at the initial start, it is assumed that it is smaller than the cover restart margin scavenging rate.

  In step S13, the decrease flag Fd and the increase flag Fi are set to Fd = 0 and Fi = 1, respectively, and the process proceeds to step S4.

  In step S4, it is determined whether or not the reduction flag Fd is zero. If it is zero, the process proceeds to step S5. If the reduction flag Fd is not zero, that is, it is 1, the process proceeds to step S14, where the fuel injection amount reduction is corrected, and the process proceeds to step S6.

  The reduction correction performed in step S14 is to reduce the fuel injection amount from the injection amount at the time of normal engine start in order to quickly eliminate fogging of the spark plug 6 by increasing the integrated scavenging rate. The fuel injection amount during the reduction correction can be expressed by the following equation (2).

Fuel injection amount = normal fuel injection amount × correction coefficient A (2)
Note that the fuel injection may be stopped by setting the correction coefficient A to zero.

  In step S5, it is determined whether or not the increase flag Fi is zero. If it is zero, the process proceeds to step S6. If it is not zero, that is, if it is 1, the process proceeds to step S15, and the fuel injection amount increase correction is performed. Then, the process proceeds to step S6.

  The increase correction performed in step S15 is to increase the fuel injection amount for starting the engine after the cover of the spark plug 6 is eliminated by scavenging. The fuel injection amount during the increase correction can be expressed by the following equation (3).

Fuel injection amount = normal fuel injection amount × correction coefficient B (3)
However, it is assumed that the correction coefficient B increases with time t. Therefore, it can be expressed as correction coefficient B = Δb × t. The time t is the time since the increase correction is started, and is counted by a timer built in the ECM 5.

  Thus, by gradually increasing the fuel injection amount after scavenging is completed, it is possible to avoid reoccurrence of fogging of the spark plug 6 due to excessive supply of fuel.

  In step S6, fuel injection is started. When the process proceeds from step S5 to step S6, the normal injection amount is used. When the process starts from steps S14 and S15, the injection amount is corrected in each step.

  In step S7, calculation of the integrated scavenging rate is started. Note that, at the second and subsequent engine start after the engine start failure, the calculation is started with the integrated scavenging rate at the end of the previous engine start operation as the initial value.

  In step S8, it is determined whether or not a complete explosion has occurred. The determination method is the same as the conventional engine start determination, and when the engine speed has reached a predetermined speed, it is determined that a complete explosion has occurred.

  If it is in the complete explosion state, the process proceeds to step S9, the decrease flag Fd and the increase flag Fi are set to zero, the integrated scavenging rate is reset, and the process ends. If it is not a complete explosion, the process proceeds to step S10.

  In step S10, it is determined whether the specified cycle has ended after the engine start operation has started. The specified cycle is set to about 10 cycles, for example.

  If the specified cycle has been completed, the process proceeds to step S11. If it has not been completed, the process ends and the process returns to step S1.

  In step S11, the calculation of the integrated scavenging rate is terminated, and the calculation result is stored in the ECM 5. The stored calculation result is used for determination in steps S2 and S3 at the next start.

  Next, the case where the control of this embodiment is performed will be described with reference to the time chart of FIG.

  The first start is performed with the normal fuel injection amount because both the decrease flag Fd and the increase flag Fi are set to zero. If the engine fails to start within the specified cycle and fails to start, the accumulated scavenging rate is smaller at the second start than at the first start, but is greater than the startable lower limit scavenging rate and the cover restart margin scavenging rate Therefore, both the decrease flag Fd and the increase flag Fi are zero, and the engine starts again with the normal fuel injection amount.

  When the integrated scavenging rate reaches the startable lower limit scavenging rate at t1 during the second starting operation, the reduction flag Fd becomes 1, and the fuel injection amount is corrected to decrease. Thereby, the integrated scavenging rate starts to increase. In addition, after t1 of the second starting operation, it is performed for scavenging.

  At the third start after the second start failure, the integrated scavenging rate is smaller than the cover restart margin scavenging rate, so the decrease flag Fd = 1 and the increase flag Fi = 0. Therefore, the start is started with the weight reduction corrected. When the fog restart margin scavenging rate is reached at t2, the reduction flag Fd = 0 and the increase flag Fi = 1, and the fuel injection amount is increased and corrected. As a result, the integrated scavenging rate begins to decrease again. At this time, since the injection amount is corrected so as to gradually increase, it is possible to prevent the fogging from recurring due to the excessive supply of fuel.

  Thereafter, if engine startup continues to fail, the starting operation is repeated for the nth time and the n + 1th time while correcting the fuel injection amount in accordance with the integrated scavenging rate as in the second and third times.

  Since the integrated scavenging rate is larger than the startable lower limit scavenging rate from the start of the second start to t1, a complete explosion state may be reached.

  As described above, in the present embodiment, the following effects can be obtained.

  A scavenging rate that represents the amount of over-supplied fuel in the combustion chamber of the engine is estimated, and when the engine 1 is started, the fuel injection amount at the time of starting is limited according to the scavenging rate. Is limited, the fogging of the spark plug 6 can be eliminated.

  When the engine does not reach a complete explosion state within the specified number of cycles from the start of the start operation, it is determined that the engine has failed, and at the next start, the fuel injection amount limit is corrected according to the scavenging rate. At the time of restart after failure, it becomes possible to set the fuel injection amount according to the state in the cylinder 14.

  When the scavenging rate becomes smaller than the lower limit scavenging rate that can be set in advance as the lower limit value at which the engine can be started, the fuel injection amount is corrected to decrease, so that the fogging state of the spark plug 6 is prevented from further worsening at the time of restart. be able to.

  When the scavenging rate becomes larger than the fog restart margin scavenging rate set as the value when scavenging in the engine is completed, the fuel injection amount is corrected to increase, so that scavenging for eliminating the fog of the spark plug 6 is more than necessary. Can be prevented from running for a long time, and can be restarted quickly.

  Since the increase correction is performed so that the fuel injection amount gradually increases with the passage of time from the start of the increase correction correction, it is possible to prevent the fogging of the spark plug 6 from recurring.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

  The present invention can be applied to start control of a spark ignition engine.

It is the schematic of the system configuration | structure of this embodiment. It is a flowchart of control of this embodiment. It is a time chart when the control of this embodiment is performed.

Explanation of symbols

1 Engine 2 Intake pipe 3 Fuel injection valve 4 Throttle valve 5 Engine control unit (ECM)
6 Spark plug 7 Rotational speed detection sensor 8 Combustion chamber 9 Crankshaft 10 Exhaust pipe 11 Intake valve 12 Exhaust valve 13 Piston 14 Cylinder

Claims (6)

Start request detection means for detecting the engine start request of the driver;
Engine state estimating means for estimating a scavenging rate representing an amount of over-supplied fuel in the combustion chamber of the engine based on a time and a start condition required for the engine start operation;
An engine start control device comprising: a fuel injection amount limiting means for limiting a fuel injection amount at the start according to the scavenging rate when detecting the start request.   2. The engine start control device according to claim 1, wherein the scavenging rate is a ratio between an integrated fuel amount injected during the start operation and an integrated air amount provided for scavenging in the engine during the start operation. Start failure determination means for determining that start failure has occurred when the engine has not reached a complete explosion state within a specified number of cycles from the start of the start operation;
A limit amount correction means for correcting a limit amount of the fuel injection amount in accordance with the scavenging rate at the next start when it is determined that the start has failed;
An engine start control device according to claim 1 or 2.   The limit amount correction means corrects the fuel injection amount so as to decrease from the normal start when the scavenging rate becomes smaller than a first set value preset as a lower limit value at which the engine can be started. The engine start control device according to 1.   The limit amount correction means corrects the fuel injection amount to be increased from that at the normal start when the scavenging rate becomes larger than a second set value set as a value when scavenging in the engine ends. The engine start control device according to claim 3 or 4.   6. The engine start control device according to claim 5, wherein the limit amount correction means corrects the fuel injection amount to gradually increase as time elapses from the start of correction when correcting the fuel injection amount to increase.

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