JP4811304B2 - Automatic stop device for vehicle engine - Google Patents

Description

  The present invention relates to a vehicular engine automatic stop device that automatically stops an engine when a predetermined stop condition is satisfied.

Conventionally, for the purpose of improving fuel consumption and emission, when a predetermined stop condition including that the vehicle speed becomes zero is satisfied, the engine is automatically stopped, and the predetermined start condition is set while the engine is stopped. A system that performs so-called idle stop that automatically starts the engine when it is established is known (see, for example, Patent Document 1).
JP 2004-86434 A

  By the way, in the conventional idle stop system, whether or not the vehicle speed is zero is determined based on the detection value of the vehicle speed sensor composed of an electromagnetic pickup, but the detection accuracy of the vehicle speed sensor is about 1 km / h or less. The vehicle speed can hardly be detected. For this reason, when performing the idling stop control, if the detected value of the vehicle speed sensor becomes about 1 km / h or less, it is considered that the vehicle speed has become zero, and the engine is automatically stopped.

  However, in this configuration, the engine may be automatically stopped even when the actual vehicle speed is not zero. In such a case, for example, in a vehicle equipped with an automatic transmission including a torque converter, the creep force is low. It will be gone. That is, there is a problem that the vehicle is suddenly stopped and a so-called pull-in shock is generated, which gives the passenger an uncomfortable feeling.

  The present invention has been made in view of this point, and an object of the present invention is to automatically stop the engine without causing a drawing shock.

According to one aspect of the present invention, an automatic stop device for a vehicle engine includes an engine mounted on a vehicle, vehicle speed detection means for detecting a vehicle speed, brake fluid pressure detection means for detecting brake fluid pressure, and the vehicle speed detection. The engine is automatically stopped when a predetermined stop condition is satisfied, including a vehicle speed condition in which the vehicle speed detected by the means is zero, and when a predetermined start condition is satisfied while the engine is stopped, The vehicle travels on the basis of automatic stop and start means for automatically starting the engine, and the deceleration and brake fluid pressure detected during deceleration of the vehicle before the detected vehicle speed becomes zero. Road surface inclination angle estimation means for estimating the inclination angle of the road surface being operated, and necessary brake pressure for calculating the brake fluid pressure necessary for stopping the vehicle based on the estimated road surface inclination angle. A liquid pressure calculating means, after the detected vehicle speed is increased once more than a predetermined vehicle speed, the pre-engine stop condition determining determines whether the pre-engine stop condition is satisfied, including a vehicle speed history conditions lower than the predetermined vehicle speed The road surface inclination angle estimating means includes an average value of the brake fluid pressure during a predetermined period after the pre-engine stop condition is satisfied and until the detected vehicle speed becomes zero, and the vehicle An inclination angle of the road surface is estimated based on the deceleration, and the actual brake fluid pressure detected by the brake fluid pressure detecting device is the required brake fluid pressure for the predetermined stop condition by the automatic stop / start device. The above brake fluid pressure conditions are included.

  According to this configuration, it is not determined that the vehicle has stopped based only on the vehicle speed detected by the vehicle speed detection means, but is determined that the vehicle has stopped based on the brake fluid pressure detected by the brake fluid pressure detection means. By doing so, the engine can be automatically stopped in a state where the vehicle is surely stopped. As a result, it is possible to prevent so-called retraction shock.

  Further, when determining that the vehicle is stopped based on the brake fluid pressure, the vehicle is traveling based on the vehicle deceleration and the brake fluid pressure detected before the detected vehicle speed becomes zero. In order to estimate the inclination angle of the road surface and to set the brake fluid pressure necessary to stop the vehicle according to the estimated inclination angle, it is necessary to confirm that the vehicle has stopped regardless of the inclination angle of the road surface. The engine can be accurately determined and the engine can be automatically stopped while reliably preventing the occurrence of a drawing shock.

  The engine automatic stop device further includes an acceleration sensor that detects an inclination angle of a road surface in a state where the vehicle is stopped, and the automatic stop start unit includes the acceleration sensor after the brake hydraulic pressure condition is satisfied. The engine stop may be prohibited when the inclination angle of the road surface detected by the above is larger than a predetermined value.

  If the engine is automatically stopped when the slope of the road surface is relatively large, the vehicle may jump out or rearward when the engine is restarted. For this reason, it is desirable to prohibit the automatic stop of the engine when the inclination angle of the road surface is relatively large.

  As described above, while the vehicle is running before the detected vehicle speed becomes zero, the inertial force is applied, so the inclination angle of the road surface cannot be detected by the acceleration sensor. Although the road surface inclination angle is estimated based on the brake fluid pressure, the road surface inclination angle can be accurately detected by the acceleration sensor when the vehicle is stopped.

  Therefore, it is desirable to prohibit the engine from being stopped when the road inclination detected by the acceleration sensor is larger than a predetermined value after the brake fluid pressure condition is satisfied and the vehicle is stopped.

  The automatic stop start means starts the engine by injecting fuel into a predetermined cylinder of the engine and igniting and burning the engine, and the automatic stop start means further includes the vehicle speed condition and the brake hydraulic pressure condition. After both are established, before the engine is automatically stopped, scavenging of the engine may be performed by increasing the rotational speed of the engine.

  In a configuration in which restart is performed by injecting and igniting fuel into a predetermined cylinder (for example, a cylinder in an expansion stroke) of an engine without using a starting motor, air for combustion is injected into the cylinder in the expansion stroke. It is necessary to scavenge before stopping the engine in order to sufficiently secure the engine and improve the startability. In this case, if scavenging is performed by increasing the engine speed while the vehicle is not reliably stopped, the vehicle may jump out.

  In the above configuration, when both the vehicle speed condition and the brake fluid pressure condition are satisfied, the vehicle is prevented from popping out by increasing the engine speed and performing scavenging while the vehicle is reliably stopped by the brake device. Is done.

  As described above, according to the present invention, the stop state of the vehicle is determined based only on the detected vehicle speed, and the automatic stop of the engine is not executed, but the vehicle is detected based on both the detected vehicle speed and the brake fluid pressure. By determining the stop state and executing the automatic stop of the engine, it is possible to reliably prevent the so-called pulling shock.

  Further, by estimating the road surface inclination angle and setting the required brake fluid pressure according to the estimated inclination angle, it is possible to always reliably determine the stop state of the vehicle.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the following description of the preferred embodiment is merely illustrative in nature, and is not intended to limit the present invention, its application, or its use.

-Schematic configuration of idle stop system-
1 and 2 show an embodiment of an idle stop system including an engine automatic stop device according to the present embodiment. This system E includes an engine 1 having a cylinder head 10 and a cylinder block 11, and the engine 1. ECU2 (engine controller) for controlling the engine. As shown in FIG. 2, the engine 1 is provided with four cylinders 12A to 12D. Inside each of the cylinders 12A to 12D, pistons connected to the crankshaft 3 as shown in FIG. Thus, a combustion chamber 14 is formed above the piston 13 in each of the cylinders 12A to 12D.

  Here, in general, in a multi-cylinder four-cycle engine, each cylinder performs a combustion cycle composed of intake, compression, expansion, and exhaust strokes with a predetermined phase difference. In the case of a cylinder engine, when referred to as the first cylinder 12A, the second cylinder 12B, the third cylinder 12C, and the fourth cylinder 12D from one end in the cylinder row direction, the first cylinder (# 1), the third cylinder (# 3), Combustion is performed with a phase difference of 180 degrees in crank angle in the order of the fourth cylinder (# 4) and the second cylinder (# 2). Thus, the output torque accompanying the driving of the engine 1 is transmitted to the drive wheels 53 via the torque converter 51 and the automatic transmission (AT) 52 connected to the crankshaft 3.

  A spark plug 15 for igniting and burning the air-fuel mixture in the combustion chamber 14 is provided at the top of each combustion chamber 14 of each of the cylinders 12A to 12D. An electrode is disposed so as to face the combustion chamber 14. Further, a fuel injection valve 16 is disposed on the side of the combustion chamber 14 (right direction in FIG. 1) with the tip injection hole facing the combustion chamber 14. This fuel injection valve 16 incorporates a needle valve and a solenoid (not shown) and is driven to open for a time corresponding to the pulse width in response to the input of a pulse signal from the ECU 2 so that an amount of fuel corresponding to the driving time is supplied. The cylinders 12A to 12D are configured to inject directly. The fuel injection direction is adjusted so as to be directed to the vicinity of the electrode of the spark plug 15.

  Although not shown, fuel is supplied to the fuel injection valve 16 via a fuel supply passage or the like by a fuel pump, and the fuel supply pressure is in the middle of the compression stroke of each cylinder 12A to 12D. Thereafter, the pressure is set higher than the pressure in the combustion chamber 14 so that fuel can be injected into the high-pressure in-cylinder combustion chamber 14.

  An intake port 17 and an exhaust port 18 that open toward the combustion chamber 14 are provided in the upper part of the combustion chamber 14 of each of the cylinders 12A to 12D. An intake valve 19 and an exhaust valve are provided in these ports 17 and 18, respectively. 20 are arranged respectively. These intake valve 19 and exhaust valve 20 are driven by a valve operating mechanism including a camshaft (not shown), and as described above, each of the cylinders 12A to 12D performs a combustion cycle with a predetermined phase difference. The opening / closing timing of the intake / exhaust valves 19 and 20 for each cylinder is set.

  Further, an intake passage 21 and an exhaust passage 22 are provided so as to communicate with the intake port 17 and the exhaust port 18, respectively. As shown in FIG. An independent branch intake passage 21a is provided for each of the cylinders 12A to 12D, and the upstream end of each branch intake passage 21a communicates with the surge tank 21b. The intake passage 21 upstream of the surge tank 21b is a common intake passage 21c common to the cylinders 12A to 12D. The throttle valve 23 adjusts the cross-sectional area of the passage 21c by, for example, a butterfly valve to restrict the intake flow. And an actuator 24 for driving it, and as shown only in FIG. 2, an air flow sensor 25 for detecting the intake air amount is provided upstream of the throttle valve 23.

  On the other hand, a catalyst 29 for purifying the exhaust is disposed downstream of the collection portion of the exhaust passage 22 where exhaust from the cylinders 12A to 12D collects. The catalyst 29 may be a so-called three-way catalyst, but is not limited thereto, and may be a so-called lean NOx catalyst, for example.

  The engine 1 is provided with an alternator 28 that is drivingly connected to the crankshaft 3 by a belt or the like, and the electric power generated by the alternator 28 is stored in a battery (not shown). .

  Further, the engine system E is provided with two crank angle sensors 30 and 31 for detecting the rotation angle of the crankshaft 3, and the engine rotation speed is mainly based on a signal from one crank angle sensor 30. The rotation direction and the rotation angle of the crankshaft 3 are detected from the crank angle signals output from the two crank angle sensors 30 and 31 with the phases shifted from each other. In addition, the engine system E includes a cam angle sensor 32 that detects a specific rotational position of the camshaft and outputs it as a cylinder identification signal, and an ignition switch 33 that performs an on / off operation for manually switching between operation and stop of the engine 1. (IG switch), an accelerator opening sensor 34 that detects an accelerator operation amount, an acceleration sensor (G sensor) 35 that detects an inclination angle of a road surface particularly in a state where the vehicle is stopped, as will be described later, a brake hydraulic pressure A brake fluid pressure sensor 36 for detecting the vehicle speed, a vehicle speed sensor 37 including an electromagnetic pickup for detecting the vehicle speed, and the like are disposed.

  The ECU 2 receives signals from the sensors and the switches 25, 30 to 37, outputs a signal for controlling the fuel injection amount and the injection timing to the fuel injection valve 16, and an ignition device for the ignition plug 15. 27 outputs a signal for controlling the ignition timing, and further outputs a signal for controlling the throttle opening to the actuator 24 of the throttle valve 23. As will be described in detail below, the ECU 2 stops the fuel supply to each cylinder 12A to 12D (fuel cut) and automatically stops the engine when a predetermined engine stop condition is satisfied during idling. After that, when a predetermined engine restart condition is satisfied by the driver's accelerator operation or the like, the engine 1 is automatically restarted.

  Here, the engine 1 according to the present embodiment starts the engine 1 by itself without borrowing the power of the starter motor when restarting the engine 1. That is, first, the first combustion is performed in the cylinder 12 in which the piston 13 is stopped in the middle of the compression stroke, and the piston 13 is pushed down, so that the crankshaft 3 is slightly reversed, thereby being in the expansion stroke. The piston 13 of the cylinder 12 is raised and the air-fuel mixture in the cylinder 12 is compressed. Then, by igniting and burning the air-fuel mixture in the expansion stroke cylinder 12 that has been compressed in this manner and whose temperature and pressure have been increased, a torque in the forward rotation direction is applied to the crankshaft 3, and the engine 1 is I try to start it.

  In order to start the engine 1 by itself, the torque in the forward rotation direction is applied to the crankshaft 3 as much as possible by the combustion of the cylinder 12 in the expansion stroke at the time of stop. , Abbreviated as TDC), the cylinder 12 must overcome its compression reaction force (compression pressure) and exceed TDC. Therefore, in order to start the engine 1 reliably, it is necessary to ensure sufficient air for combustion in the stop-time expansion stroke cylinder 12.

  Therefore, as will be described in detail later, when the engine 1 is automatically stopped during idling, the throttle valve 23 is controlled in the opening direction so as to scavenge the cylinders 12A to 12D. The scavenging control is performed so that the rotation speed is reached. As a result, the amount of air drawn into the stop expansion stroke cylinder 12 and the stop compression stroke cylinder 12 is sufficiently increased.

  In the present embodiment, control for retarding the ignition timing by a predetermined amount is also executed in order to prevent engine blow-up associated with the scavenging control.

-Automatic engine stop control-
Next, control for automatically stopping the engine 1 by the ECU 2 will be described with reference to FIGS. FIG. 3 is a flowchart showing the procedure of stop control. FIG. 4 shows changes in detected vehicle speed and engine speed from the state in which the vehicle is running until the engine is stopped by automatic stop control. It is explanatory drawing shown.

  First, in step S1, it is determined whether or not a pre-engine stop condition is satisfied. Here, in the pre-engine stop condition, the vehicle speed history condition, which is a condition that the vehicle speed once rises above the predetermined vehicle speed and then becomes lower than the predetermined vehicle speed, the battery voltage is higher than the predetermined voltage, in other words, the battery is Battery conditions that do not require charging, air conditioning equipment that is not operating, that is, air conditioning that is that the air conditioning compressor is stopped, and engine water temperature that is above a predetermined temperature, that is, when it is cold The engine water temperature condition, which is not a condition, is included. When the pre-engine stop condition is not satisfied, the step S1 is repeated. When the pre-engine stop condition is satisfied, the process proceeds to the step S2.

  In step S2, based on the vehicle speed detected by the vehicle speed sensor 37, for example, the engine speed is set by referring to a map. As a result, as shown in FIG. 4, the engine speed is made higher than that during idling. This control is performed in order to increase the engine speed stepwise, for example, to prevent a sense of incongruity caused by a sudden increase in the engine speed when the vehicle is stopped by scavenging control, which will be described later.

  In the subsequent step S3, the vehicle deceleration is calculated based on the vehicle speed detected by the vehicle speed sensor 37, and the average brake fluid pressure is calculated based on the brake fluid pressure detected by the brake fluid pressure sensor. Then, in step S4, it is determined whether or not the vehicle speed detected by the vehicle speed sensor 37 has become 0 km / h. In other words, the vehicle speed detected by the vehicle speed sensor 37 is less than 1 km / h, and the vehicle speed can be regarded as 0 km / h because of the detection accuracy of the vehicle speed sensor 37 made of an electromagnetic pickup that is difficult to detect less than 1 km / h. It is determined whether or not. When this determination is NO, step S4 is repeated, while when the determination is YES, the process proceeds to step S5. Here, also when the determination is YES and the process proceeds to step S5, the actual vehicle speed indicated by the broken line in FIG. 4 is not 0 km / h.

  In step S5, the predicted inclination angle of the running road surface is calculated based on the average value of the vehicle deceleration and brake fluid pressure calculated in step S3. In other words, when the deceleration is relatively small with respect to the magnitude of the brake fluid pressure (see the two-dot chain line in FIG. 4), the road surface has a downward slope, and the deceleration against the magnitude of the brake fluid pressure When the road surface is relatively large (refer to the one-dot chain line in FIG. 4), the road surface is an uphill slope. The road surface inclination angle may be calculated according to the following.

  In the subsequent step S6, the brake fluid pressure necessary for stopping the vehicle is calculated according to the map preset and stored in the ECU 2, based on the inclination angle predicted in step S5. Here, the necessary brake fluid pressure is set higher when the road surface is a downward slope than when it is an upward slope.

  In step S7, it is determined whether or not the actual brake fluid pressure detected by the brake fluid pressure sensor 36 is equal to or higher than the necessary brake fluid pressure calculated in step S6 (brake fluid pressure condition). When the brake pressure is equal to or greater than the required brake fluid pressure, it is determined that the vehicle has stopped (see the intersection of the broken line and the solid line in FIG. 4), the process proceeds to step S8, and idle stop is permitted.

  On the other hand, when NO is not greater than the required brake fluid pressure, the routine proceeds to step S9, where idle stop is prohibited. That is, it determines with a vehicle not stopping. In this case, in step S10, the idling speed increased in step S2 is reduced to prevent the vehicle from jumping out, and then the flow ends.

  On the other hand, after idling stop is permitted in step S8, it is determined in step S11 whether an engine stop condition (fuel cut condition) is satisfied. The engine stop condition here includes that the brake switch is on and the accelerator is off. When the engine stop condition is not satisfied, step S11 is repeated, while when it is satisfied, the process proceeds to step S12.

  In step S12, since the vehicle is in a stopped state, the inclination angle of the road surface is calculated based on the detection value of the G sensor 35, and it is determined whether or not the road surface gradient is steep. Here, immediately after the vehicle stops, the detection value of the G sensor 35 does not become constant due to inertia. Therefore, as shown in FIG. 4, after a predetermined time elapses after the brake hydraulic pressure condition is satisfied, It is preferable to calculate the inclination angle of the road surface based on the detected value. In the determination of step S12, when the slope is YES, the flow of the vehicle ends as it is to prohibit the idling stop because the vehicle jumps out or rearwardly occurs when the engine 1 is restarted.

  On the other hand, if NO at step S12, which is not a steep slope, the routine proceeds to step S13 where scavenging control (see FIG. 4) is performed by controlling the throttle valve 23 in the opening direction to increase the engine speed, as described above. An ignition timing retard control is performed to prevent the engine from rising, and then an idle stop is executed in step S14 (the engine 1 is automatically stopped by fuel cut).

  Accordingly, the road surface inclination angle estimating means 41 is constituted by steps S3 and S5, and the necessary brake fluid pressure calculating means 42 is constituted by step S6.

  Thus, in the idle stop system described above, the vehicle speed sensor is not used to determine the stop state of the vehicle based on only the detection value of the vehicle speed sensor 37, but also to determine the stop state of the vehicle based on the brake fluid pressure. It is possible to accurately determine the stop state of the vehicle without depending on the detection accuracy of 37. Thereby, the timing of the automatic stop of the engine 1 can be optimized and the occurrence of a so-called pulling shock can be prevented.

  Further, the required brake fluid pressure is set according to the road surface inclination angle estimated based on the vehicle deceleration and the brake fluid pressure, so that the vehicle is stopped regardless of the road surface gradient. Can be determined accurately.

  While the vehicle is moving (before the vehicle is stopped), the inclination angle is determined based on the deceleration of the vehicle and the brake fluid pressure. On the other hand, when the vehicle is stopped, the detection value of the G sensor 35 is detected. Since the road surface inclination angle is determined based on the above, the road surface gradient can be accurately determined.

  In addition, since the engine 1 according to the idle stop system restarts without using the starter motor, as described above, it is necessary to perform scavenging before the engine 1 is stopped. Since this is performed after the necessary brake fluid pressure is secured, it is possible to reliably prevent popping out and the like associated with increasing the engine speed.

  In the above-described embodiment, the engine 1 is restarted without using the starter motor. However, the present invention can be applied to a configuration in which the engine 1 is restarted using the starter motor. It is. In that case, scavenging control before the automatic stop of the engine 1 becomes unnecessary.

  As described above, the present invention is useful as an automatic stop device for a vehicle engine because it can automatically stop the engine while preventing the so-called retraction shock.

1 is a schematic configuration diagram of an idle stop system according to an embodiment of the present invention. It is a schematic diagram which shows the structure of the intake system and exhaust system of an engine. It is a flowchart which shows the control which concerns on an engine automatic stop. It is a time chart which shows an example of the change of the detection vehicle speed and engine speed in the state from the driving | running | working state of a vehicle to an engine automatic stop.

Explanation of symbols

1 Engine 12 Cylinder 2 ECU (automatic stop / start means)
35 Acceleration sensor 41 Road surface inclination angle estimation means 42 Required brake hydraulic pressure calculation means

Claims (3)

An engine mounted on the vehicle,
Vehicle speed detection means for detecting the vehicle speed;
Brake fluid pressure detecting means for detecting the brake fluid pressure;
When a predetermined stop condition is satisfied, including a vehicle speed condition in which the vehicle speed detected by the vehicle speed detecting means is zero, and when the predetermined start condition is satisfied while the engine is stopped And automatic stop starting means for automatically starting the engine,
A road surface inclination angle that estimates the inclination angle of the road surface on which the vehicle is traveling based on the vehicle deceleration and brake fluid pressure detected during deceleration of the vehicle before the detected vehicle speed becomes zero. An estimation means;
Necessary brake fluid pressure calculating means for calculating a brake fluid pressure necessary for stopping the vehicle based on the estimated road surface inclination angle;
Pre-engine stop condition determining means for determining whether or not a pre-engine stop condition including a vehicle speed history condition that becomes lower than the predetermined vehicle speed after the detected vehicle speed has once increased above a predetermined vehicle speed ;
The road surface inclination angle estimation means is configured to calculate an average value of the brake fluid pressure for a predetermined period and a deceleration of the vehicle provided until the detected vehicle speed becomes zero after the pre-engine stop condition is satisfied. Based on the inclination angle of the road surface,
The automatic stop device for an engine includes a brake fluid pressure condition in which the actual brake fluid pressure detected by the brake fluid pressure detection unit is equal to or higher than the necessary brake fluid pressure in the predetermined stop condition by the automatic stop start unit .
The automatic engine stop device according to claim 1,
An acceleration sensor for detecting an inclination angle of a road surface in a state where the vehicle is stopped;
The automatic stop / starting means prohibits the engine from being stopped when a road surface inclination angle detected by the acceleration sensor is larger than a predetermined value after the brake fluid pressure condition is established. The automatic engine stop device according to claim 1,
The automatic stop start means injects fuel into a predetermined cylinder of the engine and ignites and burns it to start the engine,
The automatic stop / starting unit further increases the engine speed and performs scavenging of the engine after the vehicle speed condition and the brake hydraulic pressure condition are both satisfied and before the engine is automatically stopped. Automatic engine stop device.

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