JP2013231378A - Control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for a vehicle for determining a restart of an engine on the basis of a travel distance in an automatic stop.SOLUTION: A control device for a vehicle integrates a travel distance in an automatic stop (S404) when an engine is automatically stopped after a predetermined automatic stop condition is established (S400: Yes), and determines whether or not the travel distance is a predetermined distance or longer (S406). The predetermined distance used in a determination of the S406 is set based on a master cylinder pressure, a brake negative pressure for operating a brake booster, and a gradient of a road. When the travel distance in the automatic stop becomes the predetermined distance or longer (S406: Yes), the automatic stop is prohibited even when a vehicle speed is a predetermined speed or lower and a predetermined brake negative pressure required for operating the brake booster is secured, and the engine is restarted (S408).

Description

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

  Conventionally, when a predetermined automatic stop condition is satisfied, idle stop control is performed in which the engine is automatically stopped to improve fuel efficiency. It is said that the fuel consumption cannot be improved unless the engine is automatically stopped for a predetermined time or longer, for example, 5 seconds or longer. Therefore, even before the vehicle stops, the engine is automatically stopped and the automatic stop time is extended as much as possible when the automatic stop condition that the vehicle is supposed to stop based on the vehicle speed, the brake depressing operation, or the like is satisfied. It is considered.

  However, if the automatic stop is executed before the vehicle stops, the braking force may be insufficient when the vehicle needs to stop suddenly if the brake negative pressure necessary for operating the brake booster is not secured. .

  On the other hand, as disclosed in Patent Document 1, automatic stop of the engine is permitted when a predetermined brake negative pressure is ensured, and engine automatic is stopped when the predetermined brake negative pressure is not ensured. If the stop is prohibited, a shortage of braking force can be prevented by restarting the engine when a predetermined brake negative pressure is not ensured during the automatic stop.

JP 2010-248917 A

  However, as shown in FIG. 5, in the method of permitting automatic stop when a predetermined brake negative pressure is ensured, for example, because the brake disc is contaminated, the predetermined brake negative pressure is ensured. In spite of this, even when the braking force decreases, automatic stop is permitted, and the engine is automatically stopped if an automatic stop condition such as the vehicle speed is equal to or lower than a predetermined speed is satisfied.

  When the travel distance until the vehicle stops with the engine automatically stopped due to some cause such as a decrease in braking force, the possibility of various problems occurring increases. For example, in a hydraulic assist type power steering device that assists the steering force by driving the hydraulic pump by the rotation of the engine, the assist force of the steering force is insufficient during traveling in the automatic stop state. For example, the steering operation for changing the traveling direction of the vehicle becomes difficult.

  In addition, in the electrically assisted power steering device that assists the steering force with an electric motor, there is a problem that when the steering is operated during traveling in the automatic stop state, the battery voltage decreases due to power consumption.

  If the restart condition is satisfied by loosening the brake pedal or depressing the accelerator pedal during automatic stop, the engine is restarted. However, there is a problem that a time delay occurs until the assisting force of the steering force is recovered by restarting the engine and the vehicle is accelerated by depressing the accelerator.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a vehicle control device that determines restart of an engine based on a travel distance during automatic stop.

According to the vehicle control device of the present invention, the engine is restarted when the vehicle travel distance after the predetermined automatic stop condition is satisfied and the engine is automatically stopped exceeds the predetermined distance.
Thereby, it is possible to prevent the automatic stop of the engine from being continued in a state where the travel distance of the vehicle after the engine is automatically stopped for some reason becomes longer and the vehicle travels over a predetermined distance. As a result, when the travel distance after the automatic stop becomes a predetermined distance or more, the assist force of the steering force at the time of the steering operation can be ensured and the accelerator can be quickly accelerated when the accelerator pedal is depressed. Therefore, for example, when the driver performs a vehicle operation to avoid the obstacle, the vehicle can quickly execute the avoidance behavior for the obstacle.

  The travel distance from when the automatic engine stop is executed until the vehicle stops depends on the braking force. That is, the travel distance from when the automatic stop is executed until the vehicle stops is shorter as the brake pedal depression amount is larger, that is, the master cylinder pressure is larger, and the traveling distance is shorter as the brake negative pressure for operating the brake booster is lower.

  For this reason, it is desirable that the predetermined distance, which is a determination value for determining whether or not to restart the engine during traveling in the automatic stop state, is shorter as the master cylinder pressure is higher and shorter as the brake negative pressure is lower. Therefore, it is desirable to set the predetermined distance based on the master cylinder pressure and the brake negative pressure.

  The functions of the plurality of means provided in the present invention are realized by hardware resources whose functions are specified by the configuration itself, hardware resources whose functions are specified by a program, or a combination thereof. The functions of the plurality of means are not limited to those realized by hardware resources that are physically independent of each other.

The block diagram which shows the vehicle control system by this embodiment. The flowchart which shows an idle stop control process. The flowchart which shows a predetermined distance setting process. The time chart which shows the relationship between the travel distance during an automatic stop, and an engine driving | running state. The time chart which shows the relationship between the conventional brake negative pressure and an engine driving | running state.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Vehicle control system)
A vehicle control system 2 shown in FIG. 1 includes an idle stop ECU (Electronic Control Unit) 10, an engine ECU 12, a brake negative pressure sensor 20, a master cylinder pressure sensor 22, an acceleration sensor (G sensor) 24, a vehicle speed sensor 26, a fuel injection valve. 30 and a starter 32. The idle stop ECU 10 and the engine ECU 12 are mainly configured by a microcomputer including a CPU, a ROM, a RAM, an input / output interface, and the like.

  The idle stop ECU 10 executes a control program stored in a ROM or flash memory (not shown) to output signals from various sensors such as the brake negative pressure sensor 20, the master cylinder pressure sensor 22, the G sensor 24, and the vehicle speed sensor 26. Based on the above, it is determined whether or not to automatically stop the engine and whether or not to restart the engine from the automatic stop. The idle stop ECU 10 may acquire output signals from various sensors directly or through communication via the sensor ECU.

  Then, the idle stop ECU 10 drives the starter 32 when the restart condition is satisfied during the automatic stop. The idle stop ECU 10 instructs the engine ECU 12 to stop the engine when a predetermined automatic stop condition is satisfied, and instructs the engine to restart when the restart condition is satisfied during the automatic stop.

  The engine ECU 12 controls the operating state of the engine based on output signals from various sensors. The engine ECU 12 may control the operating state of the engine according to a command from an ECU other than the engine ECU 12.

  As described above, when the engine stop command is issued from the idle stop ECU 10, the engine ECU 12 stops the fuel injection from the fuel injection valve 30 and stops the engine. Further, when the engine ECU 12 is instructed to restart the engine from the idle stop ECU 10 during the automatic stop of the engine, the engine ECU 12 starts fuel injection from the fuel injection valve 30 and restarts the engine.

(Automatic stop condition)
When all the following conditions are satisfied, the idle stop ECU 10 determines that the automatic stop condition is satisfied, and instructs the engine ECU 12 to automatically stop the engine. On the other hand, the idle stop ECU 10 determines that a restart condition for restarting the engine is satisfied when one of the following conditions is not satisfied during automatic stop, and instructs the engine ECU 12 to restart the engine.
・ Battery voltage is more than a specified voltage ・ Brake negative pressure is more than a specified pressure ・ Brake pedal depression ・ Accelerator pedal off ・ Vehicle speed is less than a specified speed ・ Driving distance during automatic stop is less than a specified distance For example, a gear neutral condition is added.

  One of the automatic stop conditions is when the vehicle speed is not 0 but less than or equal to a predetermined speed. If the above automatic stop condition is satisfied during vehicle deceleration, the engine is stopped and the automatic stop is executed before the vehicle stops. .

  Next, the idle stop control process and the predetermined distance setting process executed by the idle stop ECU 10 according to the control program stored in the ROM will be described based on FIGS. 2 and 3, respectively. The flowcharts of FIGS. 2 and 3 are executed at predetermined time intervals by a timer interrupt or the like. 2 and 3, “S” represents a step.

(Idle stop control process)
In FIG. 2, the idle stop ECU 10 determines whether or not the engine is automatically stopped by instructing the engine ECU 12 when the aforementioned automatic stop condition such as the vehicle speed is equal to or lower than the predetermined speed is satisfied (S400). ). If the vehicle is not automatically stopped (S400: No), the vehicle travel distance accumulated during the automatic stop is cleared (S402), and the present process is terminated.

  As shown in FIG. 4, when the engine is automatically stopped (S400: Yes), the travel distance during the automatic stop is integrated (S404), and it is determined whether the travel distance is equal to or greater than a predetermined distance (S406). The predetermined distance used in the determination of S406 is set in the distance setting process of FIG. If the traveling distance during the automatic stop is less than the predetermined distance (S406: No), this process is terminated.

  When the traveling distance during the automatic stop becomes equal to or longer than the predetermined distance (S406: Yes), the idle stop ECU 10 has a predetermined brake necessary for operating the brake booster as shown in FIG. Even when negative pressure is secured, automatic stop is prohibited. Then, the starter 32 is driven and the engine ECU 12 is instructed to restart the engine to restart the engine (S408).

(Predetermined distance setting process)
In S410 of FIG. 3, the idle stop ECU 10 sets the predetermined distance used in the determination of S406 of FIG. 2 from a map or an expression based on the master cylinder pressure, the brake negative pressure, and the road gradient.

  As described in the section [Means for Solving the Problems], the predetermined distance is set to be shorter as the master cylinder pressure is higher and shorter as the brake negative pressure is lower. Therefore, the predetermined distance is appropriately set according to the braking force. Is set.

  In addition, if the braking force is the same, the travel distance from when the automatic stop is executed before the vehicle stops until the vehicle stops is shorter as the slope of the uphill is larger and longer as the slope of the downhill is larger.

  The driver recognizes that the traveling distance until the vehicle stops on the downhill is longer than that on the uphill. Therefore, if the predetermined distance that is the judgment value when restarting the engine on the downhill is made the same length as that of the uphill, the engine is restarted at a shorter travel distance than recognized, so the driver feels uncomfortable. Feel.

  Therefore, the predetermined distance is set shorter as the slope of the uphill is larger and longer as the slope of the downhill is larger. Thereby, it is possible to prevent the engine from being restarted unnecessarily at a short traveling distance on the downhill. Whether the road is uphill or downhill, and the magnitude of the road gradient are detected based on the output signal of the G sensor 24.

  In the present embodiment described above, even if the driver does not indicate the intention to restart the engine by stopping the brake pedal operation or depressing the accelerator pedal, the predetermined automatic stop condition is satisfied and the engine is automatically stopped. The engine is restarted when the travel distance of the vehicle exceeds a predetermined distance.

  Thereby, while assisting the steering steering force while the vehicle is traveling in the automatic stop state, it is possible to accelerate quickly when the accelerator pedal is depressed. Therefore, when the driver performs a vehicle operation to avoid the obstacle while the engine is restarted from the automatic stop state, the vehicle can quickly execute the avoidance behavior for the obstacle.

[Other Embodiments]
In the above-described embodiment, the master cylinder pressure, the brake negative pressure, and the road gradient are used as parameters for determining a predetermined distance for determining whether or not to restart the vehicle while the engine is automatically stopped. On the other hand, the predetermined distance may be set based on one of the brake negative pressure, the master cylinder pressure, or the road gradient.

  Further, the predetermined distance may be determined based on vehicle weight, temperature, weather, road surface condition, and the like as parameters other than those described above for setting the predetermined distance. The vehicle weight can be acquired from vehicle information stored in advance in a ROM or the like, and the air temperature can be acquired from an intake air temperature sensor. The temperature, weather, and road surface condition can be acquired from weather information at the vehicle position received from the center, for example.

Further, the predetermined distance may be set to a fixed value regardless of the brake negative pressure, the master cylinder pressure, the road gradient, the traveling state of the vehicle, the engine operating state, and the like.
In the above embodiment, the idle stop ECU 10 and the engine ECU 12 are configured as separate ECUs, but may be configured as a single ECU.

  In the above embodiment, the idle stop ECU 10 drives the starter at the time of restart. However, the engine ECU 12 may drive the starter according to a command from the idle stop ECU 10.

  In the above embodiment, the functions of the automatic stop means, the distance acquisition means, the restart means, and the distance setting means are realized by the idle stop ECU 10 whose functions are specified by the control program. On the other hand, at least some of the functions of the plurality of means may be realized by hardware whose functions are specified by the circuit configuration itself.

  As described above, the present invention is not limited to the above-described embodiment, and can be applied to various embodiments without departing from the gist thereof.

2: Vehicle control system, 12: Idle stop ECU (vehicle control device, automatic stop means, distance acquisition means, restart means, distance setting means)

Claims (4)

Automatic stop means (10, S400) for automatically stopping the engine when a predetermined automatic stop condition is satisfied before the vehicle stops;
Distance acquisition means (10, S404) for acquiring the travel distance of the vehicle after the engine has been automatically stopped;
Restarting means (10, S408) for restarting the engine when the travel distance acquired by the distance acquiring means during the automatic stop exceeds a predetermined distance;
A vehicle control device comprising: Distance setting means (10, S410) for setting the predetermined distance based on the master cylinder pressure and the brake negative pressure of the brake;
The restarting means restarts the engine when the travel distance during automatic stop becomes equal to or greater than the predetermined distance set by the distance setting means.
The vehicle control device according to claim 1.   The vehicle control apparatus according to claim 2, wherein the distance setting unit sets the predetermined distance based on the master cylinder pressure, the brake negative pressure, and a road gradient. A distance setting means (10, S410) for setting the predetermined distance based on a road gradient;
The restarting means restarts the engine when the travel distance during automatic stop becomes equal to or greater than the predetermined distance set by the distance setting means.
The vehicle control device according to claim 1.

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