JP4626557B2 - Engine stop control device - Google Patents

Description

  In the present invention, the engine is temporarily stopped when the vehicle is temporarily stopped or idling, and when the restart condition is satisfied, the air-fuel mixture of the cylinder stopped during the compression stroke is burned to reversely rotate the crankshaft. Further, the present invention relates to an engine stop control device in which fuel is injected into another cylinder stopped in the expansion stroke, and the fuel is ignited to restart the engine.

  In general, when an automobile is temporarily stopped, the engine is rotating in an idling state. However, such idling reduces the fuel efficiency of the automobile and increases carbon dioxide emissions that contribute to global warming. Let Therefore, in recent years, an engine that automatically stops the engine when the vehicle is paused or idling, and automatically restarts the engine when the vehicle starts or when the accelerator pedal is depressed (idle stop) is performed. Is used.

  By the way, a normal engine is started by a starter that is supplied with power from a battery. However, if the starter is used to restart the engine during idle stop, there is a problem that a gear meshing sound is generated and the passenger feels uncomfortable. Arise. Further, since cranking must be performed, there is a problem that it takes time to restart the engine and the vehicle cannot be started quickly. There is also a problem that the life of the starter and the battery is shortened.

Therefore, instead of using a starter for engine restart, first, the air-fuel mixture in the cylinder stopped in the compression stroke is burned to reversely rotate the crankshaft, and then fuel is injected into other cylinders stopped in the expansion stroke. There has been proposed an engine in which the conventional problem is solved by igniting the fuel and restarting the engine (see, for example, Patent Document 1).
JP 2004-292474 A (paragraph [0013], FIG. 1)

  By the way, when the engine is restarted by burning the air-fuel mixture or fuel in the cylinder without using the starter in this way, if burnt gas or exhaust gas remains in the cylinder, the mixture or fuel There is a possibility that the ignitability will deteriorate and the engine restart may be hindered. Note that since the amount of intake air decreases immediately before idling stop, burned gas or exhaust gas tends to remain in the cylinder.

  Therefore, in the engine that performs idle stop described in Patent Document 1, scavenging in the cylinder is performed by increasing the opening of the throttle valve immediately before the engine is temporarily stopped, and burned gas or exhaust gas in the cylinder. To be removed. However, even if the opening of the throttle valve is increased just before the engine is temporarily stopped, the period is very short, so the inside of the cylinder cannot be sufficiently scavenged, and the burned gas or exhaust gas still remains in the cylinder. There is a problem that gas remains.

  The present invention has been made to solve the above-described conventional problems, and is an engine that is restarted by burning an air-fuel mixture or fuel in a cylinder without using a starter for restart at idle stop. On the other hand, it is an object to be solved to provide means capable of sufficiently scavenging the inside of the cylinder at the time of idling stop and sufficiently improving the startability at the time of restarting the engine.

  An engine stop control device according to the present invention made to solve the above-described problem is (i) stopping an engine under a predetermined engine stop condition, while a predetermined engine restart condition is satisfied after the engine stop. Occasionally, the air-fuel mixture of the cylinder stopped in the compression stroke is combusted to reversely rotate the crankshaft, and then fuel is injected into other cylinders stopped in the expansion stroke, and the fuel is ignited and the engine is restarted. And (ii) scavenging means for promoting scavenging in the cylinder by increasing the opening of the throttle valve before the engine stops under the engine stop condition.

  The engine stop control device further includes (iii) an engine speed correction means for correcting an increase in the engine speed when the vehicle speed becomes a predetermined value or less before the engine stop condition is satisfied; and iv) braking state detecting means for detecting the braking state of the vehicle by the brake. Here, the engine speed correction means suppresses the increase correction of the engine speed when the degree of braking in the braking state detected by the braking state detection means is small compared to when it is large.

  In the engine stop control device according to the present invention, the engine speed correction means has a correction amount upper limit (or correction width) and / or a correction amount upper limit correction for the engine speed, compared to when the braking degree of the vehicle is small. Alternatively, it is preferable that the correction amount increasing speed (or the correction degree) is reduced. Here, when the correction amount increase speed is reduced, the engine speed correction means increases the vehicle speed at which the correction correction for increasing the engine speed is started, compared to when the braking degree is low, when it is high. More preferred.

  In the engine stop control device according to the present invention, it is preferable that the engine speed correction means increases the correction amount of the increase correction of the engine speed in accordance with a decrease in the vehicle speed. In the engine stop control device according to the present invention, it is preferable that the braking state detecting means detects the brake fluid pressure and detects the braking state based on the brake fluid pressure.

  According to the engine stop control device of the present invention, when performing an idle stop, an increase in the engine speed is corrected before the engine stop condition is satisfied, thereby increasing the intake air amount. The inside of the cylinder can be sufficiently scavenged, and the startability when the engine is restarted can be improved. Further, when performing idling stop, if the increase in the engine speed is large or sudden when the braking degree of the vehicle is small, the occupant feels uncomfortable, but according to the engine stop control device according to the present invention, the vehicle When the braking degree of the engine is small, for example, the correction amount upper limit value of the upward correction and / or the correction amount increase speed is reduced, so that the increase correction of the engine speed is suppressed. Can increase the sex.

  In the engine stop control device according to the present invention, the correction amount increase speed of the increase correction of the engine speed is reduced and the vehicle speed at which the increase correction is started is increased as compared with when the vehicle braking degree is small. If the braking degree is low, the engine speed increase correction is started from a higher vehicle speed, so even if the engine speed increase correction is performed slowly to reduce occupant discomfort, The engine speed can be sufficiently increased, and the scavenging performance can be sufficiently enhanced.

  In the engine stop control device according to the present invention, when the engine speed correction means increases the correction amount of the increase correction of the engine speed in accordance with the decrease of the vehicle speed, the engine speed decreases as the vehicle speed decreases. Since the engine speed gradually increases, scavenging performance can be improved while effectively reducing the occupant's uncomfortable feeling. Further, when the braking state detection means detects the braking state based on the brake fluid pressure, the braking state of the vehicle can be easily grasped using the existing brake fluid pressure sensor.

Hereinafter, embodiments of the present invention (best mode for carrying out the present invention) will be described in detail with reference to the accompanying drawings.
As shown in FIGS. 1 and 2, the main body portion of the engine E that performs idle stop according to the embodiment of the present invention includes a cylinder head 1 and a cylinder block 2. The engine E is a four-cylinder four-cycle engine and includes four cylinders 3 (first to fourth cylinders 3A to 3D). In this engine E, each cylinder 3 performs a cycle comprising intake, compression, expansion, and exhaust strokes with a predetermined phase difference, and these cycles include the first cylinder 3A and the third cylinder 3C. The fourth cylinder 3D and the second cylinder 3B are performed in the order of 180 ° (180 ° CA) phase difference in crank angle.

  A piston 4 is fitted in each cylinder 3, and a combustion chamber 5 is formed above the piston 4. The piston 4 is connected to the crankshaft 6 via a connecting rod or the like. A spark plug 7 is provided at the top of the combustion chamber 5 of each cylinder 3, and the plug tip faces the combustion chamber 5. A fuel injection valve 8 that directly injects fuel into the combustion chamber 5 is provided on the side of the combustion chamber 5. Although not shown in detail, the fuel injection valve 8 incorporates a needle valve and a solenoid, receives a pulse signal, is driven for a time corresponding to the pulse width at the pulse input timing, and opens the valve. The amount of fuel is injected according to the time. The fuel injection valve 8 is disposed so as to inject fuel toward the vicinity of the spark plug 7. Although not shown, the fuel injection valve 8 is supplied with fuel through a fuel supply passage or the like by a fuel pump and injects fuel at a fuel pressure higher than the pressure in the combustion chamber during the compression stroke. It has become.

  An intake port 9 and an exhaust port 10 are opened to the combustion chamber 5 of each cylinder 3, and an intake valve 11 and an exhaust valve 12 are provided in both the ports 9 and 10, respectively. The intake valve 11 and the exhaust valve 12 are driven by a valve operating mechanism including camshafts 26, 27 and the like. The opening / closing timings of the intake and exhaust valves of each cylinder 3 are set so that each cylinder 3 performs a combustion cycle with a predetermined phase difference.

  The opening / closing timings of the intake valve 11 and the exhaust valve 12 are variable by cam phase variable mechanisms 26a and 27a. The cam phase variable mechanisms 26 a and 27 a are well-known mechanisms that change the rotational phase of the cam shafts 26 and 27 with respect to the rotational phase of the crankshaft 6. As shown in FIG. 2, the camshaft 26 on the intake valve 11 side is provided with a cam phase variable mechanism 26a, and the camshaft 27 on the exhaust valve 12 side is provided with a cam phase variable mechanism 27a, which are independent of each other. Are controlled. Therefore, the opening / closing timings of the intake valve 11 and the exhaust valve 12 can be changed back and forth generally independently by the cam phase variable mechanisms 26a and 27a.

  An intake passage 15 and an exhaust passage 16 are connected to the intake port 9 and the exhaust port 10, respectively. The intake passage 15 has a branch intake passage 15a for each cylinder downstream of the surge tank 15b, and the downstream end of each branch intake passage 15a communicates with the intake port 9 of each cylinder 3. A throttle valve 17 for adjusting the amount of air introduced into the cylinder 3 (intake amount) is provided in the common intake passage 15c upstream of the surge tank 15b. The opening degree of the throttle valve 17 is adjusted by a throttle valve actuator 18. An airflow sensor 20 that detects the intake air amount is provided further upstream of the intake passage 15.

  An EGR passage 50 is provided between the portion of the common intake passage 15c downstream of the throttle valve 17 and the exhaust passage 16 to communicate these. An EGR valve 51 is provided in the EGR passage 50, and the opening degree of the EGR valve 51 is adjusted by an EGR valve actuator 52. When the EGR valve 51 is opened by the EGR valve actuator 52, a part of the exhaust gas flowing through the exhaust passage 16 is recirculated to the common intake passage 15c via the EGR passage 50, and is supplied to the cylinder 3 as a part of the intake air. Then, EGR (exhaust gas recirculation) is performed.

  Two crank angle sensors 21 and 22 for detecting the rotation angle (crank angle) of the crankshaft 6 are provided, and both crank angle sensors 21 and 22 generate crank angle signals whose phases are shifted from each other by a certain amount. Output. Further, a cam angle sensor 23 capable of outputting a cylinder identification signal by detecting the specific rotational position of the cam shafts 26 and 27 is provided. Further, a starter 28 that is a motor for starting the engine E is provided, and the driving force of the starter 28 is directly transmitted to the crankshaft 6 via a starter gear (not shown), so that the engine E is started.

  In addition to this, as a means for detecting signals necessary for controlling the engine E, a water temperature sensor 24 for detecting the temperature of the engine cooling water, and an accelerator opening sensor 25 for detecting the accelerator opening (accelerator operation amount) (FIG. 3). For example).

  FIG. 3 is a control block diagram of the engine E, showing the ECU (engine control unit) 30, various sensors and switches that send various detection signals to the ECU 30, and various devices and actuators that receive control signals from the ECU 30. Yes. Since FIG. 3 relates to idle stop control, the other control-related parts are omitted.

  As shown in FIG. 3, an airflow sensor 20, both crank angle sensors 21 and 22, a cam angle sensor 23, a water temperature sensor 24, and an accelerator opening sensor 25 are connected to the input side of the ECU 30. . Furthermore, on the input side of the ECU 30, as sensors for performing idle stop, a brake sensor 62 for detecting the depression depth of the brake pedal, a vehicle speed sensor 63 for detecting the vehicle speed, and an AT (automatic transmission) shift An inhibitor switch 64 for detecting the lever position, a parking brake switch 65 for detecting ON / OFF of the parking brake, a winker switch 66 for detecting ON / OFF of the winker, and an air conditioner switch 67 for detecting ON / OFF of the air conditioner. A brake negative pressure sensor 68 that detects the brake negative pressure and a brake hydraulic pressure sensor 69 that detects the brake hydraulic pressure are connected.

  Further, on the output side of the ECU 30, the spark plug 7, the fuel injection valve 8, the throttle valve actuator 18, the EGR valve actuator 52, the cam phase variable mechanisms 26a and 27a, the starter 28, and the idle stop display lamp 71 are provided. The electric oil pump 72, the ATF switching valve 73, and the hill holder solenoid valve 74 are connected.

  Here, the idle stop display lamp 71 is a lamp for indicating to the driver the implementation status of the idle stop. The engine E is stopped by the idle stop, the idle stop is prohibited, or the engine is stopped. A general term for lamps that indicate that E is restarted. The electric oil pump 72 is an electric oil pump that supplies hydraulic pressure to the AT while the engine is stopped due to idle stop. During normal operation, the clutch inside the AT operates using a mechanical oil pump (not shown) directly connected to the crankshaft 6 as a hydraulic pressure supply source. Therefore, when the engine E stops due to idle stop, the hydraulic pressure decreases and the clutch is released. In this case, after restarting the engine, a time loss for re-engaging the clutch occurs, and the startability deteriorates. In order to prevent this, hydraulic pressure is separately supplied to the AT by the electric oil pump 72 while the engine E is stopped.

  The ATF switching valve 73 is a switching valve that switches a passage of ATF (automatic transmission fluid) from the hydraulic supply source to the AT. During normal operation, the ATF is guided from the mechanical oil pump to the AT, and is switched from the electric oil pump 72 while the engine is stopped by I / S. The hill holder solenoid valve 74 is a solenoid valve for driving a hill holder (not shown) that blocks the brake oil supply passage. During normal operation, a booster linked to the engine E is activated to increase the brake fluid pressure. However, since the booster does not operate while the engine is stopped, the brake fluid pressure decreases and the braking force decreases. Therefore, for example, when idle stop is performed on a slope, the vehicle may move due to insufficient braking force. In order to prevent this, the hill holder holds the brake fluid pressure in a high state by blocking the brake oil supply passage by the hill holder solenoid valve 74.

  The ECU 30 is a comprehensive control device for the engine E, and although not shown in detail, a throttle valve control unit, a fuel injection valve control unit, an ignition control unit, an EGR valve control unit, a cam phase control unit, A stop control unit (automatic engine stop / restart control unit), a display control unit, an AT control unit, a hill holder control unit, a scavenging control unit (scavenging unit), and an engine speed correction unit (engine speed correction unit) are provided. .

  Here, the throttle valve control unit of the ECU 30 opens the necessary throttle valve 17 based on the accelerator opening information from the accelerator opening sensor 25 and the engine speed based on the crank angular speed information from the crank angle sensors 21 and 22. The degree is calculated and the throttle valve actuator 18 is controlled. Further, the fuel injection valve control unit and the ignition control unit determine the required fuel injection amount from the intake air amount information by the air flow sensor 20 and the cooling water temperature information by the water temperature sensor 24 in addition to the accelerator opening information and the engine speed information. And the injection timing and appropriate ignition timing are calculated and a control signal is output to the fuel injection valve 8 and the spark plug 7.

  The air-fuel ratio is determined by the intake air amount adjusted by the throttle valve control unit of the ECU 30 and the supplied fuel amount adjusted by the fuel injection valve control unit 32. That is, the throttle valve control unit and the fuel injection valve control unit function as air-fuel ratio control means. During normal idle operation, the air-fuel ratio is set to the stoichiometric air-fuel ratio or richer than this. As will be described later, in order to suppress fluctuations in the output torque during the engine stop operation period for idling stop, the air-fuel ratio is leaner than that during idle operation, more preferably leaner than the stoichiometric air-fuel ratio. Set to the side.

  The EGR valve control unit of the ECU 30 outputs the necessary opening degree of the EGR valve 51 to the EGR valve actuator 52 and controls the EGR amount (the amount of exhaust gas recirculated). During normal operation, by increasing the EGR amount, the amount of oxygen in the intake air is suppressed to lower the combustion temperature to reduce NOx emissions, or when the engine E is cold, the in-cylinder temperature is increased by the exhaust gas. Control. Then, during the engine stop operation period for idling stop, control is performed to close the EGR valve 51 in order to promote scavenging in each cylinder 3.

  The cam phase control unit of the ECU 30 outputs the phase fluctuation signals of the cam shafts 26 and 27 with respect to the crankshaft 6 to the cam phase variable mechanisms 26a and 27a, and controls the opening / closing timings of the intake valve 11 and the exhaust valve 12. During normal operation, an optimal intake / exhaust valve opening / closing timing is set according to the engine speed, and control for obtaining a high output over a wide rotation range is performed. Then, as will be described later, in the engine stop operation period for idling stop, control is performed to delay the closing timing of the intake valve 11 in order to suppress fluctuations in the output torque. The idle stop control unit determines an idle stop execution condition, and provides each control unit in the ECU 30 with necessary information for executing the idle stop.

  The scavenging control unit of the ECU 30 promotes scavenging in the cylinder 3 by increasing the opening of the throttle valve 17 before the engine E stops under the engine stop condition. The engine speed correction unit of the ECU 30 corrects the increase of the engine speed (idle speed) when the vehicle speed falls below a predetermined value before the engine stop condition is satisfied, while the brake fluid pressure sensor 69 When the brake fluid pressure (braking degree of the vehicle) detected by the (braking state detection means) is small, the increase correction of the engine speed is suppressed compared to when it is large.

  The idle stop execution conditions are classified into basic stop conditions, basic restart conditions, and idle stop prohibition conditions. Each condition can be set as appropriate. For example, the brake depression depth obtained from the brake sensor 62 is greater than or equal to a predetermined value, the vehicle speed obtained from the vehicle speed sensor 63 is zero, and the AT shift lever position obtained from the inhibitor switch 64 is the non-traveling range, The basic stop condition may be satisfied when the signal of the parking brake switch 65 is ON, the signal of the turn signal switch 66 is OFF, and the air conditioner switch 67 is OFF.

  Further, for example, whether the depth of depression of the brake pedal is a predetermined value or less, the vehicle speed is a predetermined value or more, whether the shift lever position of the AT is in the traveling range, the signal of the turn signal switch 66 is ON, the air conditioner The basic restart condition may be satisfied when the switch 67 is ON or the brake negative pressure obtained from the brake negative pressure sensor 68 is not more than a predetermined value. For example, the engine coolant temperature Tc is less than a predetermined value (for example, Tc <60 ° C.), the battery monitor voltage is less than a predetermined value, or the elapsed time since the previous restart is less than the predetermined value. In some cases, an idle stop prohibition condition may be satisfied.

  Hereinafter, the control mode when each condition is set as described above will be described. In this case, when the basic stop condition is satisfied and the idle stop prohibition condition is not satisfied, the engine E stop condition is finally satisfied, and the engine E is automatically stopped by the idle stop. That is, the fuel injection from the fuel injection valve 8 is stopped and the ignition of the spark plug 7 is stopped.

  As the control when the engine is stopped, first, if the EGR valve 51 is open when the engine stop condition is satisfied, this is closed so that scavenging in the cylinder 3 is promoted. Then, the ignition timing is retarded to suppress fluctuations in the output torque. Further, the throttle valve 17 is opened at a predetermined opening for a predetermined period to promote scavenging in the cylinder 3 after the fuel cut, and to make it easy for the piston 4 to stop at an appropriate position (range A in FIG. 4). .

  If the basic restart condition or the idle stop prohibition condition is satisfied during the automatic stop of the engine E, the restart condition is finally satisfied, and the engine E is restarted. That is, the fuel injection from the fuel injection valve 8 and the ignition of the spark plug 7 are returned.

  As the control at the time of restart, first, the first combustion is performed on a cylinder that is in a compression stroke when the engine is stopped (for convenience, it is assumed that this is the third cylinder 3C, and hereinafter referred to as “compression stroke cylinder 3C”). Then, when the engine E is slightly reversed, the cylinder pressure is increased by the piston rise of the cylinder that is in the expansion stroke when the engine is stopped (for the sake of convenience, this is assumed to be the first cylinder 3A, hereinafter referred to as the “expansion stroke cylinder 3A”). Is increased, and combustion is performed in the expansion stroke cylinder 3A.

  In this embodiment, the first restart control mode, the second restart control mode, and the third restart control mode are selectively executed according to the stop position of the piston 4. Here, in the first restart control mode, initial combustion in the compression stroke cylinder 3C and combustion in the expansion stroke cylinder 3A are performed, and combustion air remains in the cylinder of the compression stroke cylinder 3C after the initial combustion. Thus, recombustion is performed when the piston 4 of the compression stroke cylinder 3C reaches the top dead center after the piston 4 starts to rise. In the second restart control mode, the initial combustion in the compression stroke cylinder 3C and the combustion in the expansion stroke cylinder 3A are performed, but the recombustion in the compression stroke cylinder 3C is not performed. In the third restart control mode, starting is performed by combustion in the expansion stroke cylinder 3A and combustion in the next compression stroke cylinder 3C while assisting with the starter 28 without performing initial combustion in the compression stroke cylinder 3C.

  The display control unit of the ECU 30 performs ON / OFF control of the idle stop display lamp 71 according to the execution state of idle stop. The idle stop display lamp 71 includes an automatic stop lamp, an idle stop prohibition lamp, and a restart lamp that are not shown. During the automatic stop of the engine E due to idle stop, the automatic stop lamp is turned on, while the idle stop prohibition condition is satisfied, the idle stop prohibited lamp is turned on, and when the engine E is restarted, the restart lamp is turned on. In this way, the driver can recognize the idle stop control status.

  The AT control unit of the ECU 30 supplies a switching command signal to the ATF switching valve 73 and supplies the hydraulic oil when the pressure of the hydraulic oil supplied to the automatic transmission decreases due to execution of the idle stop. The path is switched from a mechanical oil pump (not shown) driven by the engine E to the electric oil pump 72 side, and an operation command signal for operating the electric oil pump 72 is output. Supply hydraulic oil at a predetermined pressure to the transmission. Further, the hill holder control unit controls the hill holder by the hill holder solenoid valve 74 while the engine is stopped by the idle stop.

The stop position of the piston 4 when the engine is stopped due to idle stop is detected as follows by signals from the crank angle sensors 21 and 22.
5 (a) and 5 (b) respectively show pulse signals obtained by rotating the crankshaft 6 during forward rotation of the engine E (clockwise in the state of FIG. 1) and reverse rotation, that is, A first crank angle signal CA1 from the crank angle sensor 21 and a second crank angle signal CA2 from the crank angle sensor 22 are shown.

  As shown in FIG. 5 (a), during forward rotation of the engine E, the second crank angle signal CA2 has a phase delay of about a half pulse width with respect to the first crank angle signal CA1. As a result, the second crank angle signal CA2 becomes Low when the first crank angle signal CA1 rises, and the second crank angle signal CA2 becomes High when the first crank angle signal CA1 falls. On the other hand, as shown in FIG. 5B, when the engine E rotates in the reverse direction, the second crank angle signal CA2 has a phase advance of about a half pulse width with respect to the first crank angle signal CA1. Thereby, contrary to the forward rotation of the engine E, the second crank angle signal CA2 becomes High when the first crank angle signal CA1 rises, and the second crank angle signal CA2 becomes high when the first crank angle signal CA1 falls. It becomes Low.

  The ECU 30 detects this difference and counts the pulse signal while determining whether the crankshaft 6 is rotating forward or reverse. The counted value is stored as a crank angle counter value (CA counter value) and is constantly updated while the engine E is operating. The state in which the crank angle counter value no longer increases or decreases is the stop of the engine E, and the stop position of the piston 4 is detected based on the crank angle counter value at this time. Thus, after the start, the ECU 30 determines that the second crank angle signal CA2 is Low when the first crank angle signal CA1 rises, or the second crank angle signal CA2 is High when the first crank angle signal CA1 falls. It is determined whether or not. If either one of the conditions is satisfied, the engine E is rotating forward, and the measured number of pulses is added to the crank angle counter value. On the other hand, if both conditions are not satisfied, the engine E is rotating in reverse, and the measured number of pulses is subtracted from the crank angle counter value.

  Hereinafter, a control method of idle stop control by the ECU 30 will be described. First, the outline of the control method of idle stop control will be described. In this idle stop control, for example, when the driver visually recognizes a red signal or the like, when the vehicle is decelerated and stopped by releasing the foot from the accelerator pedal and depressing the brake pedal at an appropriate timing, for example. If the engine stop condition is satisfied, the engine E is automatically stopped. Then, when a preset engine restart condition is satisfied after the engine is stopped, the air-fuel mixture of the cylinder stopped in the compression stroke is combusted to reversely rotate the crankshaft 6, and then the engine is stopped in the expansion stroke. The fuel is injected into the cylinder and the fuel or mixture is ignited, and the crankshaft 6 is rotated forward to restart the engine E.

  Then, after the vehicle starts decelerating and before the engine stop condition is satisfied, when the vehicle speed becomes equal to or lower than a preset value (hereinafter referred to as “idle rotation increase start vehicle speed”), In order to promote scavenging, increase correction of the idle speed (engine speed) of the engine E is performed (hereinafter referred to as “rotational increase correction routine”). At that time, when the brake fluid pressure is low (that is, the degree of braking of the vehicle is small), the increase correction of the idle speed is suppressed compared to when the brake fluid pressure is high (that is, the degree of braking of the vehicle is large), Prevents passengers from feeling uncomfortable due to an unexpected increase in engine speed.

  Thereafter, the engine E is stopped when the vehicle speed further decreases and falls below a vehicle speed at which the idle stop is to be executed (hereinafter referred to as “idle stop execution vehicle speed”) (hereinafter referred to as an “engine stop routine”). When the idle stop is executed, the opening degree of the throttle valve 17 is increased in order to further promote scavenging in the cylinder 3. If the engine restart condition is satisfied, the engine E is restarted.

Hereinafter, a specific control method of the idle stop control by the ECU 30 will be described with reference to the flowchart shown in FIG. 6 and the time chart shown in FIG.
As shown in FIGS. 6 and 7, in this idle stop control, first, in step S1, various detection signals (control signals) detected by various sensors or switches 20 to 25 and 62 to 69 (see FIG. 3) are read. It is. Subsequently, in step S2, according to the brake fluid pressure detected by the brake fluid pressure sensor 69, an idling rotation increase start vehicle speed V1 or a rotation-up permission vehicle speed (for example, around 10 km / h) is set. Specifically, for example, as shown in FIG. 8A, the idling rotation rise start vehicle speed V1 is set so as to decrease as the brake fluid pressure increases.

  Next, in step S3, it is determined whether or not the vehicle speed is equal to or less than the idling rotation rise start vehicle speed V1. Here, if it is determined that the vehicle speed exceeds the idle rotation rise start vehicle speed V1 (NO), it is not necessary to start the idle rotation increase correction yet, so the following steps S4 to S17 are skipped. The process returns to step S1 (return). On the other hand, if it is determined in step S3 that the vehicle speed is equal to or lower than the idle rotation start vehicle speed V1 (YES), the vehicle speed exceeds a predetermined engine stop permission vehicle speed (for example, 0.8 km / h) in step S4. It is determined whether or not there is.

  If it is determined in step S4 that the vehicle speed exceeds the engine stop permission vehicle speed (YES), that is, if the vehicle speed is equal to or lower than the idle rotation rise start vehicle speed V1 and exceeds the engine stop permission vehicle speed, step S5 is performed. A rotation increase correction routine of S9 is executed. On the other hand, when it is determined in step S4 that the vehicle speed is equal to or lower than the engine stop permission vehicle speed (NO), the engine stop routine of steps S10 to S17 is executed.

In the time chart shown in FIG. 7, at time t ₁ , the driver removes his / her foot from the accelerator pedal, the throttle valve 17 is closed, the engine E enters an idling state, and the vehicle speed starts to decrease. The reduced speed until the idle rotation starts rising speed V1 (rotation up permission vehicle speed) at time t _2, the rotary-up permission flag is turned on, rotation increase correction routine is started. Thereafter, the vehicle speed is reduced until the engine stop permission vehicle speed at time t _3, the engine stop routine is started. However, it is initiated engine stop routine at time t _3, the actual engine stop operation, after waiting for a predetermined time (delay time) by delay timer is started at time t _4. Then, at time t _5, the engine is stopped routine has been completed. In this time chart, the engine stop routine is not started when the brake fluid pressure is less than the engine stop permission pressure.

  In the rotation increase correction routine (steps S5 to S9), first, in step S5, based on the brake fluid pressure, a correction amount upper limit value for idle rotation speed increase correction (hereinafter referred to as “idle rotation speed increase amount NoUP”), that is, An increase correction width (ceiling) of the idle speed is set. For example, as shown in FIG. 8B, the idle speed increase amount NoUP is set so as to increase as the brake fluid pressure increases (however, there is an upper limit). Subsequently, in step S6, based on the brake fluid pressure, a correction amount increase speed for idle speed increase correction (hereinafter referred to as “idle speed increase speed ΔNoUP”) is set. For example, as shown in FIG. 8C, the idle speed increase speed ΔNoUP is set so as to increase as the brake fluid pressure increases (however, there is an upper limit).

  Next, in step S7, the target value of the idle rotation speed is gradually increased at the idle rotation increase speed ΔNoUP. The increase in the idle speed is stopped when the correction amount for the idle speed Ne reaches the idle speed increase NoUP. That is, the idle speed does not exceed the sum of the normal idle speed and the idle speed increase amount NoUP. As described above, the idle rotation speed is gradually increased as the vehicle speed decreases, and the relationship between the vehicle speed and the correction amount of the idle rotation speed is, for example, as shown in FIG.

  Subsequently, in step S8, the retard amount of the ignition timing of the spark plug 7 is set. When the ignition timing is retarded (retarded), the output torque of the engine E decreases, so the ECU 30 attempts to increase the intake air amount by general engine control. Therefore, in this rotation increase correction control, for example, the ignition timing is retarded in a manner as shown in FIG. 7, and the intake air amount is increased to further promote scavenging of the cylinder 3. When the ignition timing is retarded in this manner, torque fluctuation is suppressed, variation in the rotational speed reduction characteristic when the engine is stopped is reduced, and the probability that the piston 4 stops at an appropriate position (range A in FIG. 4) is high. The effect that becomes. Thereafter, in step S9, the opening of the throttle valve 17 is set so that the target idle speed set in step S7 is obtained, and the process returns to step S1.

  Hereinafter, specific contents of the engine stop routine (steps S10 to S17) will be described. In this engine stop routine, first, in step S10, it is determined whether or not a predetermined delay time has elapsed after it is determined that the vehicle speed is equal to or lower than the engine stop permission vehicle speed. As described above, the delay time is provided because the vehicle is still moving slightly when it is determined that the vehicle speed is equal to or lower than the engine stop permission vehicle speed, so that the engine E stops after the vehicle is completely stopped. It is to make it. If it is determined in step S10 that the delay time has not elapsed (NO), the following steps S11 to S17 are skipped and the process returns to step S1 (return).

On the other hand, if it is determined in step S10 that the delay time has elapsed (YES), the engine E is actually stopped.
Figure 9 is a diagram showing in detail the operating state of the engine E in the period from approximately time t ₄ of a time chart shown in FIG. 7 to t _5, the operation of stopping the engine E proceeds in the manner shown in FIG. 9 To do. Specifically, first, in step S11, the throttle valve 17 is opened to a predetermined relatively large opening (already opened to some extent). This opening of the throttle valve 17 is performed in order to further increase scavenging in the cylinder 3 by increasing the intake air amount. Subsequently, in step S12, the fuel injection of the fuel injection valve 8 is stopped (fuel cut, fuel stop). In the time chart shown in FIGS. 7 and 9, the fuel injection is stopped at time t _4. At this time, ignition of the spark plug 7 is stopped (however, ignition may be continued).

In this engine stop routine, although the throttle valve 17 is so as to stop the fuel injection at time t ₄ when opened to a predetermined opening degree, the fuel cut permitted rotation speed range provided, engine speed fuel cut permitted rotation speed You may make it perform a fuel cut only when it exists in an area. In this case, if the engine speed at time t ₄ has not entered the fuel cut permitted rotation speed range, until the engine rotational speed enters the fuel cut permitted rotation speed region, thereby delaying the stopping of the fuel injection. For example, as shown in FIG. 9, the fuel cut permitted rotation speed range is equal to or N2 or less, stopping the fuel injection is delayed until time t _12.

  Next, in step S13, it is determined whether or not the engine speed is equal to or less than a preset engine determination speed (predetermined speed). The engine stall determination rotational speed is set to a rotational speed (for example, 300 to 500 rpm) at which the engine E will cause engine stall soon. In FIG. 9, the engine stall determination rotational speed is indicated by N3. If it is determined in this step S13 that the engine speed exceeds the engine stall determination speed (NO), the engine E is still in a state of continuing rotation, so all steps S14 to S17 below are skipped. Return to step S1 (return).

On the other hand, if it is determined in step S13 that the engine speed is equal to or less than the engine stall determination speed (NO), the throttle valve 17 is closed in step S14. Thereby, the probability that the engine stop position falls within a preferable range can be increased by using the pressure of air in the cylinder 3. That is, from the time t ₄ at time t _13, by opening the throttle valve 17 to a predetermined opening, temporarily intake negative pressure decreases with some time lag (intake air amount is increased) to. Thereafter, the intake pressure negative pressure increases (intake amount decreases), but the predetermined rotation speed is previously set so that the period during which the intake negative pressure temporarily decreases substantially corresponds to the period of the intake stroke of the expansion stroke cylinder 3A. Etc. are set. As a result, compared to the case where the throttle valve 17 is not opened, the amount of air sucked into each cylinder 3 before the engine is stopped increases, and among them, the amount of intake air flowing into the expansion stroke cylinder 3A in particular increases.

  When the engine E is stopped, in the compression stroke cylinder 3C, the air in the cylinder 3C is compressed as the piston 4 approaches top dead center, and pressure acts in a direction to push the piston 4 back. As a result, the engine E rotates in the reverse direction and the piston 4 of the compression stroke cylinder 3C is pushed back toward the bottom dead center. As a result, the piston 4 of the expansion stroke cylinder 3A moves to the top dead center side, and the air in the cylinder 3A is compressed accordingly. With this pressure, the piston 4 of the expansion stroke cylinder 3A is pushed back toward the bottom dead center. In this way, the piston 4 is stopped after being vibrated to some extent, and at this time, the force to push back the piston 4 increases as the piston 4 approaches the top dead center in the compression stroke and the expansion stroke. For this reason, the stop position of the piston 4 often becomes a position close to the middle part of the stroke (range A in FIG. 4). Furthermore, if the intake air amount of the expansion stroke cylinder 3A is larger than that of the compression stroke cylinder 3C by the control of the throttle valve 17, the piston 4 in the expansion stroke cylinder 3A slightly falls within the range close to the middle of the stroke. It often stops near the point (range A2 in FIG. 4).

Thus, scavenging is performed when the engine E is rotated several times by inertia between the time t ₄ (or t ₁₂ ) when the fuel injection is stopped and the time t ₅ when the engine E is completely stopped. For this reason, coupled with scavenging in the rotation increase correction routine, the inside of the cylinder is almost fresh even in the expansion stroke. Further, when the engine E is stopped, the pressure leaks even in the compression stroke cylinder 3C. Therefore, after the engine is stopped, in any cylinder 3, there is almost a fresh air at atmospheric pressure in the cylinder. The throttle valve 17 may not be closed until the engine is stopped. However, in this case, since the state where the intake air amount is large continues until the engine is stopped, the pushing-down force of the piston 4 due to the compression of the intake air is difficult to attenuate. For this reason, the number of vibrations of the piston 4 increases and the swing back may increase when the engine is stopped.

  Next, in step S15, the crank angle counter value being constantly counted is read in order to determine whether the engine is stopped. Subsequently, in step S16, it is determined whether the engine E has completely stopped based on the degree of change in the crank angle counter value. Here, when it is determined that the engine E is not completely stopped (NO), steps S15 to S16 are repeatedly executed until the engine E is completely stopped. On the other hand, when it is determined in step S16 that the engine E is completely stopped (YES), the stop position of the piston 4 determined from the crank angle counter value is stored in step S17, and the process returns to step S1 ( return).

  Hereinafter, the control method of the restart control of the engine E by the ECU 30 when the engine restart condition is satisfied after the engine E is stopped by the control method shown in FIG. 6 will be described. When the basic restart condition or the idle stop prohibition condition is satisfied after the engine is stopped, the restart condition is satisfied, and the restart control of the engine E is automatically started. At this time, if the stop position of the piston 4 is within a predetermined range near the middle of the stroke in the expansion stroke cylinder 3A and is within the range A1 (see FIG. 4) near the top dead center, the first restart control mode is set. Is executed.

  FIG. 10 shows the stroke of each cylinder of the engine in the case of the first restart control mode and the combustion in each cylinder 3 from the start of the restart control (according to the order of combustion in FIG. 10 (1), (2), (3)... And the direction of operation of the engine E by each combustion is indicated by arrows. FIG. 11 shows temporal changes in the engine speed, the crank angle, the cylinder pressure of each cylinder, and the indicated torque in the case of the first restart control mode.

  As shown in FIGS. 10 and 11, in the case of the first restart control mode, first, the combustion air-fuel ratio is made leaner than the stoichiometric air-fuel ratio in the compression stroke cylinder 3C, and the initial combustion ((1) in FIG. 10). ) Is performed. Then, the piston 4 of the compression stroke cylinder is pushed down to the bottom dead center side by the combustion pressure (part indicated by a in FIG. 11) by the initial combustion, and the engine E is driven in the reverse direction. Along with this, the piston 4 of the expansion stroke cylinder 3A approaches the top dead center, the air in the cylinder 3A is compressed, and the cylinder pressure rises (portion indicated by b in FIG. 11).

  When the piston 4 of the expansion stroke cylinder 3A is sufficiently close to the top dead center, the cylinder 3A is ignited. As a result, the fuel previously injected into the cylinder 3A burns ((2) in FIG. 10), and the engine E is driven in the forward rotation direction by the combustion pressure (portion indicated by c in FIG. 11). Further, fuel is injected into the compression stroke cylinder 3C at an appropriate timing, and the second combustion in the cylinder 3C is performed near the top dead center of the compression stroke cylinder 3C ((3) in FIG. 10). The driving force of the engine E is increased by the combustion pressure (portion indicated by d in FIG. 11).

  In this case, in the initial combustion of the compression stroke cylinder 3C, air remains in the cylinder 3C even after the initial combustion because the air-fuel ratio is lean, so that the second combustion is possible. Since the fuel is injected and compression is performed while the temperature in the compression stroke cylinder 3C is high due to the initial combustion, the second combustion in the cylinder 3C is performed by compression self-ignition. After the second combustion is performed in this way, after reaching the compression top dead center of the cylinder (fourth cylinder 3D) that reaches the compression stroke next to the cylinder 3C, the combustion is sequentially performed in each cylinder by the normal control. Restart is complete.

  When restarting when the stop position of the piston 4 is within a predetermined range near the middle of the stroke in the expansion stroke cylinder 3A and within the range A2 near the bottom dead center (see FIG. 4), the second restart control mode is used. Control is performed. In the control in the second restart control mode, first, the combustion air-fuel ratio is made substantially stoichiometric or richer in the compression stroke cylinder 3C, and initial combustion (combustion corresponding to (1) in FIG. 10) is performed. Is called. Then, the piston 4 of the compression stroke cylinder 3C is pushed down by the initial combustion, and the engine E is driven in the reverse direction. Along with this, the piston 4 of the expansion stroke cylinder 3A approaches the top dead center, thereby compressing the air in the cylinder 3A and increasing the cylinder internal pressure.

  The cylinder 3A is ignited when the piston of the expansion stroke cylinder 3A is sufficiently close to the top dead center, and the fuel previously injected into the cylinder 3A is combusted (corresponding to (2) in FIG. 10). .) As a result, the engine E is driven in the forward rotation direction as in the case of control in the first restart control mode. However, in the second restart control mode, combustion (combustion (3) in FIG. 10) is not performed when the compression stroke cylinder 3C passes the top dead center after the combustion of the expansion stroke cylinder 3A, and then the compression stroke is performed. The rotation of the engine E is maintained by inertia until the compression top dead center of the cylinder (fourth cylinder 3D) to be reached is reached. After this, normal control is entered and the restart is completed. As described above, the engine E can be restarted effectively by properly using the first restart control mode and the second restart control mode depending on the stop position of the piston 4, but FIG. This will be specifically described with reference to FIG.

  FIG. 12 shows the relationship among the required air-fuel ratio, the amount of air in the compression stroke cylinder 3C, the amount of air in the expansion stroke cylinder 3A, and the frequency of occurrence in the initial combustion (for reverse rotation) of the compression stroke cylinder 3C with respect to the piston position when the engine is stopped. Yes. As shown in FIG. 12, the air amount in the expansion stroke cylinder 3A decreases as the piston 4 of the expansion stroke cylinder 3A approaches the top dead center (the piston 4 of the compression stroke cylinder 3C approaches the bottom dead center) when the engine is stopped. The amount of air in the compression stroke cylinder 3C increases. Conversely, as the piston 4 of the expansion stroke cylinder 3A approaches the bottom dead center (the piston 4 of the compression stroke cylinder 3C approaches the top dead center), the amount of air in the expansion stroke cylinder 3A increases, and the amount of air in the compression stroke cylinder 3C increases. Will be less.

  In the initial combustion in the compression stroke cylinder 3C, the engine E is moved to a predetermined position where the piston 4 of the compression stroke cylinder 3C is slightly before the bottom dead center (the piston 4 of the expansion stroke cylinder 3A is slightly before the top dead center). It is required to generate enough torque to reverse. However, if the piston 4 of the compression stroke cylinder 3C is near the top dead center, the amount of air in the compression stroke cylinder 3C decreases, and the torque required for reverse rotation to the predetermined position becomes relatively large. For this reason, the required air-fuel ratio becomes rich. On the other hand, if the piston 4 of the compression stroke cylinder 3C is near the bottom dead center, the amount of air in the compression stroke cylinder 3C increases, and the torque required for reverse rotation to the predetermined position becomes relatively small. For this reason, the required air-fuel ratio becomes lean.

  In the expansion stroke cylinder 3A, the amount of air increases as the piston 4 is closer to the bottom dead center, so that more fuel can be burned. Therefore, when the piston of the expansion stroke cylinder 3A is in the predetermined range A2 near the bottom dead center from the middle portion (the piston position of the compression stroke cylinder 3C is near the top dead center) when the engine is stopped, the compression stroke cylinder 3C is in the initial combustion. The air-fuel ratio is made rich so as to meet the above requirements. Therefore, since combustion air does not remain after the first combustion, the second combustion near the compression top dead center is not performed. However, in the expansion stroke cylinder 3A, the amount of air is relatively large, and fuel corresponding to this is injected, and after being compressed, ignition and combustion are performed. For this reason, a relatively large torque can be obtained, the engine can be rotated until the compression top dead center of the next cylinder exceeds the compression top dead center of the compression stroke cylinder 3C, and restart can be achieved. it can.

  On the other hand, when the engine is stopped, the piston position of the expansion stroke cylinder 3A is in the predetermined range A1 closer to the top dead center than the middle portion (the piston position of the compression stroke cylinder 3C is closer to the bottom dead center), compared to the range A2. Since the amount of air in the expansion stroke cylinder 3A is small, the torque obtained by combustion in the expansion stroke is small. However, in the compression stroke cylinder 3C, the air-fuel ratio at the time of initial combustion is made lean in response to the above request. As a result, the surplus air remaining after the first combustion is used, the second combustion is performed near the compression top dead center, and the torque for driving in the normal engine rotation direction is compensated. For this reason, sufficient torque to achieve restart can be obtained by both the combustion in the expansion stroke cylinder 3A and the second combustion in the compression stroke cylinder 3C.

Incidentally, in this embodiment, as described above, during the engine stop, and from the time t ₄ when the engine stop condition is satisfied after the delay time has elapsed by increasing the degree of opening of the predetermined time period only the throttle valve 17 to increase the intake air amount Yes. Thereby, in the compression stroke cylinder 3C and the expansion stroke cylinder 3A, the resistance to the movement of the piston 4 in the top dead center direction is increased, and the intake amount of the expansion stroke cylinder 3A is increased. For this reason, as shown in FIG. 12, the piston position in the expansion stroke cylinder 3A when the engine is stopped is almost within a predetermined range A near the middle of the stroke. Even in such a case, it is often within the range A2 near the bottom dead center, and the restart can be effectively performed by adjusting the stop position in this way.

  That is, if the piston stop position is too close to the top dead center side of the expansion stroke cylinder 3A (the bottom dead center side of the compression stroke cylinder 3C) than the range A, the amount of movement in the engine reverse rotation direction can be sufficiently taken. And the amount of air in the expansion stroke cylinder 3A is reduced. For this reason, the torque obtained by the combustion in the expansion stroke cylinder 3A is reduced. Further, if the air pressure is too close to the bottom dead center side of the expansion stroke cylinder 3A (the top dead center side of the compression stroke cylinder 3C) from the above range, the air amount of the compression stroke cylinder 3C decreases. For this reason, sufficient torque for reversing the engine E cannot be obtained.

  On the other hand, if the piston stop position is within the above range A, the reverse rotation drive by the initial combustion in the compression stroke cylinder 3C is possible, and the combustion in the expansion stroke cylinder 3A is favorably performed and the combustion is performed. Enough energy can be applied to the piston. In particular, if the piston stop position is in the range A2 near the bottom dead center of the expansion stroke cylinder 3A, a sufficient amount of air can be secured in the expansion stroke cylinder 3A, and the combustion energy in the expansion stroke cylinder 3A can be increased. , Startability can be improved.

  When the piston position when the engine is stopped is out of the above range A, or when the in-cylinder temperature decreases while the engine is stopped and the cooling water temperature Tc is lower than the predetermined temperature (Tc <60 ° C.). The third restart control mode is executed and the starter 28 assists the start.

  As described above, according to the embodiment of the present invention, the engine E can be restarted by burning the air-fuel mixture or fuel in the cylinder 3 without using a starter in principle for restarting the engine E. Further, without giving the passenger a sense of incongruity due to the increase correction of the engine speed, the inside of the cylinder can be sufficiently scavenged at the time of idling stop, and the startability at the time of restarting the engine can be improved.

It is a typical front sectional view of an engine provided with a stop control device concerning the present invention. FIG. 2 is a schematic plan view of the engine shown in FIG. 1. It is a block diagram which shows the control system of the engine shown in FIG. It is a figure which shows the setting of the range for the restart control mode selection according to the piston position at the time of an engine stop. (A) And (b) is a figure which shows the crank angle signal from two crank angle sensors at the time of engine forward rotation and engine reverse rotation, respectively. It is a flowchart which shows the control method of idle stop control. It is a time chart which shows the change characteristic with respect to time of the state of an engine at the time of performing idle stop control. (A) is a graph which shows the change characteristic with respect to the brake fluid pressure of idle rotation rise correction start speed, (b) is a graph which shows the change characteristic with respect to the brake fluid pressure of idling speed increase amount NoUP, (c) is It is a graph which shows the change characteristic with respect to the brake fluid pressure of idling speed rising speed (DELTA) NoUP, (d) is a graph which shows the change characteristic with respect to the vehicle speed of the correction amount of engine speed. It is a figure which shows the engine speed at the time of an engine stop, the throttle opening degree, the change of an intake pipe negative pressure, and the cycle of each cylinder. It is a figure which shows the cycle and combustion operation | movement of each cylinder at the time of engine restart. It is a figure which shows the engine speed at the time of engine restart, a crank angle, the in-cylinder pressure of each cylinder, and the change of illustration torque. It is a figure which shows the relationship of the required air-fuel ratio of a compression stroke cylinder, the air quantity of a compression stroke cylinder, the air quantity of an expansion stroke cylinder, and generation frequency with respect to the piston position at the time of an engine stop.

Explanation of symbols

  E engine, 1 cylinder head, 2 cylinder block, 3 cylinder, 3A 1st cylinder, 3B 2nd cylinder, 3C 3rd cylinder, 3D 4th cylinder, 4 piston, 5 combustion chamber, 6 crankshaft, 7 spark plug, 8 Fuel injection valve, 9 intake port, 10 exhaust port, 11 intake valve, 12 exhaust valve, 15 intake passage, 15a branch intake passage, 15b surge tank, 15c common intake passage, 16 exhaust passage, 17 throttle valve, 18 throttle valve actuator , 20 Air flow sensor, 21 Crank angle sensor, 22 Crank angle sensor, 23 Cam angle sensor, 24 Water temperature sensor, 25 Accelerator opening sensor, 26a Cam phase variable mechanism, 27a Cam phase variable mechanism, 28 Starter, 30 ECU, 50 EGR Passage, 51 EGR valve, 52 EGR valve act Eta, 62 brake sensor, 63 vehicle speed sensor, 64 inhibitor switch, 65 parking brake switch, 66 turn signal switch, 67 air conditioner switch, 68 brake negative pressure sensor, 69 brake fluid pressure sensor, 71 idle stop indicator lamp, 72 electric oil pump, 73 ATF switching valve, 74 Hill holder solenoid valve.

Claims (6)

While stopping the engine under a predetermined engine stop condition, when a predetermined engine restart condition is satisfied after the engine stop, the air-fuel mixture of the cylinder stopped in the compression stroke is burned to reversely rotate the crankshaft, Thereafter, engine automatic stop / restart control means for injecting fuel into the other cylinders stopped in the expansion stroke and igniting the fuel to restart the engine,
An engine stop control device comprising scavenging means for increasing scavenging in a cylinder by increasing the opening of a throttle valve before the engine stops under the engine stop condition,
Before the engine stop condition is satisfied, an engine speed correction means for correcting an increase in the engine speed when the vehicle speed becomes a predetermined value or less;
Braking state detection means for detecting the braking state of the vehicle by the brake,
The engine stop is characterized in that the engine speed correction means suppresses the increase correction compared to when the degree of braking in the braking state detected by the braking state detection means is small. Control device.   2. The engine according to claim 1, wherein the engine speed correction means is configured to reduce a correction amount upper limit value of the increase correction when the degree of braking is small compared to when the degree of braking is large. Stop control device.   2. The engine according to claim 1, wherein the engine speed correction means is configured to reduce a correction amount increase speed of the increase correction when compared with a case where the degree of braking is small. Stop control device.   4. The engine stop according to claim 3, wherein the engine speed correction means is configured to increase a vehicle speed at which the increase correction is started when compared to when the degree of braking is small. Control device.   2. The engine stop control device according to claim 1, wherein the engine speed correction means increases the correction amount of the increase correction in accordance with a decrease in vehicle speed.   2. The engine stop control device according to claim 1, wherein the braking state detecting means detects a brake fluid pressure and detects a braking state based on the brake fluid pressure.

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