WO2013084691A1

WO2013084691A1 - Automatic vehicle-engine control device

Info

Publication number: WO2013084691A1
Application number: PCT/JP2012/079774
Authority: WO
Inventors: 森　浩一; 元之服部
Original assignee: 日産自動車株式会社
Priority date: 2011-12-06
Filing date: 2012-11-16
Publication date: 2013-06-13
Also published as: JP2013119776A

Abstract

This automatic vehicle-engine control device is provided with the following: a braking-amount detecting means (master-cylinder pressure sensor (13)) that detects the amount by which the driver is braking (a master-cylinder pressure); an engine stopping/restarting means (engine control unit (10)) that, when coasting, stops the engine (1) if the detected braking amount falls below an upper threshold (BRKIN), and after stopping the engine (1), restarts the engine (1) when the detected braking amount falls below a lower threshold (BRKOUT); and an upper-threshold setting means (engine control unit (10)). The higher a deceleration (DVSP), the lower the upper-threshold setting means sets the upper threshold (BRKIN).

Description

Vehicle engine automatic control device

The present invention relates to an engine automatic control device that automatically stops and restarts an engine during traveling.

As a vehicle engine automatic control device, a technique described in Patent Document 1 is disclosed. This device stops the engine to improve fuel efficiency when the brake operation amount is equal to or greater than the engine stop determination threshold even when the vehicle is running, and the brake operation amount is equal to or less than the engine start determination threshold. When the engine restarts.

In a vehicle equipped with a brake master back that boosts the operating force of the brake pedal using negative pressure generated by engine rotation, if the brake operation amount increases while the engine is stopped, Negative pressure is not available. In the above-described conventional device, the engine is stopped when the brake operation amount is equal to or greater than the engine stop determination threshold regardless of the deceleration at a vehicle speed higher than the predetermined vehicle speed at which it is determined that the vehicle is running. There is a possibility that the braking force intended by the driver cannot be sufficiently obtained even when necessary.

The present invention has been made paying attention to the above problems, and an object of the present invention is to provide an automatic engine control device for a vehicle that can sufficiently secure a braking force.

Japanese Patent No. 4374805

In order to achieve the above object, in the vehicle automatic engine control apparatus of the present invention, the higher the deceleration, the smaller the engine start determination threshold value is set.

Therefore, even if the brake operation amount changes according to the deceleration, the engine can be restarted at a more appropriate timing, so that the fuel consumption can be further improved.

1 is a system diagram illustrating a configuration of a vehicle engine automatic control apparatus according to a first embodiment. 3 is a flowchart illustrating an engine automatic stop / restart control process according to the first embodiment. 6 is a time chart illustrating the operation of a coast stop permission threshold setting process during coast running according to the first embodiment. 6 is a time chart illustrating the operation of a coast stop permission threshold setting process during coast running according to the first embodiment. 7 is a flowchart illustrating an engine automatic stop / restart control process according to a second embodiment. 6 is a time chart illustrating the operation of a coast stop permission threshold setting process during coasting in Example 2; 12 is a flowchart illustrating an engine automatic stop / restart control process according to a third embodiment. 12 is a time chart illustrating the operation of the coast stop permission threshold value setting process during coasting according to the third embodiment.

[Example 1]
[System configuration]
FIG. 1 is a system diagram illustrating the configuration of the vehicle engine automatic control apparatus according to the first embodiment. A torque converter 2 is provided on the output side of the engine 1 which is an internal combustion engine. A belt type continuously variable transmission 3 is connected to the output side of the torque converter 2. The rotational driving force output from the engine 1 is input to the belt-type continuously variable transmission 3 via the torque converter 2 and is transmitted to the drive wheels 4 after being shifted by a desired gear ratio.

The engine 1 includes a starter 1a for starting the engine and an alternator 1b for generating power. The starter 1a is provided with a starter motor. The starter 1a drives the starter motor using the power supplied from the in-vehicle battery 1c based on the engine start command, and performs engine cranking. Further, when the fuel is injected and then the engine 1 can rotate independently, the starter motor is stopped. The alternator 1b generates electric power by being rotationally driven by the engine 1, and supplies the generated electric power to the in-vehicle battery 1c and the like.

The torque converter 2 amplifies the torque at a low vehicle speed and has a lock-up clutch. When the vehicle speed exceeds a predetermined vehicle speed CSVSP (for example, about 14 km / h), the lock-up clutch is engaged and the output shaft of the engine 1 and the belt The relative rotation with the input shaft of the continuously variable transmission 3 is restricted.

The belt-type continuously variable transmission 3 includes a starting clutch, a primary pulley and a secondary pulley, and a belt stretched around these pulleys, and achieves a desired gear ratio by changing the pulley groove width by hydraulic control. . The belt-type continuously variable transmission 3 is provided with an oil pump 30 driven by the engine 1, and when the engine is operated, the oil pump 30 is used as a hydraulic source to convert the converter pressure of the torque converter 2 and the lock-up clutch pressure. In addition, the pulley pressure and clutch engagement pressure of the belt-type continuously variable transmission 3 are supplied.

Furthermore, the belt-type continuously variable transmission (CVT) 3 is provided with an electric oil pump 31 in addition to the oil pump 30. If the oil pump 30 cannot supply hydraulic pressure due to automatic engine stop, the electric oil pump 31 is actuated so that necessary hydraulic pressure can be supplied to each actuator. Therefore, even when the engine is stopped, the hydraulic oil leakage can be compensated and the clutch engagement pressure can be maintained.

The operating state of the engine 1 is controlled by the engine control unit 10. The engine control unit 10 includes a brake signal from a brake switch 11 that outputs an ON signal by a driver's brake pedal operation, an accelerator signal from an accelerator pedal opening sensor 12 that detects a driver's accelerator pedal operation amount, The brake operation amount signal (master cylinder pressure) from the master cylinder pressure sensor 13 that detects the master cylinder pressure generated based on the brake operation amount (brake pedal operation amount), and the wheels from the wheel speed sensor 14 provided for each wheel A speed (synonymous with a vehicle speed signal when detecting the vehicle speed from the wheel speed), a CVT state signal from a CVT control unit 20 described later, and signals such as engine water temperature, crank angle, and engine speed are input. The engine control unit 10 starts or automatically stops the engine 1 based on the various signals.

In place of the master cylinder pressure sensor 13, a brake pedal stroke amount or a brake pedal depression force sensor, or a wheel cylinder pressure sensor is used to detect the brake operation amount. The intention may be detected and is not particularly limited.

The CVT control unit 20 transmits and receives engine operation state and CVT state signals to and from the engine control unit 10, and controls the gear ratio of the belt type continuously variable transmission 3 based on these signals. Specifically, when the travel range is selected, the start clutch is engaged, the gear ratio is determined from the gear ratio map based on the accelerator pedal opening and the vehicle speed, and each pulley pressure is controlled. When the vehicle speed is lower than the predetermined vehicle speed CSVSP, the lock-up clutch is released, but when the vehicle speed is higher than the predetermined vehicle speed CSVSP, the lock-up clutch is engaged and the engine 1 and the belt type continuously variable transmission 3 are directly connected. Yes. Furthermore, when the engine is automatically stopped while the travel range is selected, the electric oil pump 31 is operated to ensure the necessary hydraulic pressure.

[Engine automatic stop / restart control]
Next, the engine automatic stop control process will be described. The vehicle automatic engine control apparatus (engine control unit 10) of the first embodiment stops engine idling when predetermined conditions (various conditions such as the brake pedal being fully depressed) are satisfied when the vehicle is stopped. The so-called idling stop control is performed. In addition, about idling stop control, since a well-known structure should just be implemented suitably, detailed description is abbreviate | omitted. In addition, even when the vehicle is running, the vehicle is decelerating, and after the deceleration fuel cut control, it is determined that there is a high possibility that the vehicle will stop and shift to the idling stop control. Take control. That is, fuel injection is stopped when the driver is in a coasting state (including a state where the brake pedal is operated) where the driver is coasting without operating the accelerator pedal.

During the deceleration fuel cut control, the fuel injection is stopped, and the engine speed is maintained via the lock-up clutch by the coast torque transmitted from the drive wheels 4. However, when the vehicle is decelerated to the predetermined vehicle speed CSVSP, the lock-up clutch is released, so that the engine 1 stops unless fuel is injected. Therefore, conventionally, deceleration fuel cut control is stopped at the timing when the lockup clutch is released, fuel injection is resumed to maintain engine self-sustained rotation, and then the engine is stopped after the vehicle is completely stopped. It was like that. However, fuel consumption can be improved if the fuel at the time of restarting the fuel injection can be further suppressed in the above-described process of restarting the fuel injection once and restarting the engine from the running state where the fuel injection is stopped in this way. It becomes possible. Therefore, in the coast stop control according to the first embodiment, when a predetermined condition is satisfied, the engine 1 is stopped without restarting the fuel injection (no fuel injection or the like is performed), and normal idling is performed after the vehicle stops. Transition to stop control is possible.

One condition for performing coast stop control is that the amount of brake operation by the driver is within a predetermined range. The reason for setting the brake operation amount as one of the conditions is that the start or end (stop) of the coast stop control should be performed based on the driver's braking intention.

In other words, if the amount of brake operation exceeds the lower limit threshold, the driver's intention to brake can be inferred, and there is a high possibility that the vehicle will stop and shift to idling stop control. To start. After the coast stop control starts, if the amount of brake operation decreases and falls below the lower threshold, the driver's non-braking intention (intention to continue running) can be inferred, so the stopped engine 1 is restarted and coast stop control is performed. End (cancel).

Further, in the first embodiment, not only the lower limit threshold value is provided as the threshold value of the brake operation amount for stopping / restarting the engine (starting / ending coast stop control) during traveling, but an upper limit value that is larger than the lower limit threshold value. A threshold was set. That is, even if the vehicle speed is less than the predetermined vehicle speed CSVSP, the coast stop control is stopped when the brake operation amount is equal to or greater than the upper limit threshold. Further, after the engine 1 is stopped, when the brake operation amount increases and exceeds the upper limit threshold value, the stopped engine 1 is restarted and the coast stop control is ended (stopped).

As described above, a threshold value of the brake operation amount as a condition for stopping and restarting the engine 1 is separately provided on the large brake operation amount side and the small brake operation amount side, and the brake operation amount is sandwiched between the above two threshold values. The engine 1 is stopped when it is within (between the upper and lower thresholds).

The upper threshold is set for the following reasons.
1. In a vehicle with a brake master back that boosts the operating force of the brake pedal using the negative pressure generated by the rotation of the engine 1, if the brake operation amount increases while the engine is stopped, Since the negative pressure due to engine rotation cannot be used, there is a possibility that the braking force intended by the driver cannot be obtained sufficiently.

2. When the brake pedal is strongly depressed, it is when the vehicle is decelerating rapidly, and it is considered that the time until the vehicle stops is short. At this time, the speed ratio of the transmission (belt-type continuously variable transmission 3) is set to the low speed stage at the time of start (the drive wheel is rotating and the transmission can be changed) until the vehicle stops. It is necessary to shift to the lowest level. In a vehicle equipped with a transmission that changes speed using the discharge pressure of the oil pump 30 driven by the engine 1, the speed of the oil pump 30 can be changed quickly until the vehicle stops as described above. It is necessary to secure the discharge amount. In particular, a relatively high pulley pressure needs to be supplied for shifting the belt type continuously variable transmission 3.
Therefore, it is not preferable to stop the engine 1 that is the drive source of the oil pump 30. Although it is conceivable to perform a shift with the hydraulic pressure supplied by the electric oil pump 31, it is not preferable because the electric oil pump 31 needs to be enlarged in order to perform the shift quickly.

3. During sudden deceleration, various controls to stabilize the vehicle behavior may be involved. For example, in ABS control for avoiding wheel lock, various gains are set in the control logic in consideration of torque input from the engine 1 side when increasing or decreasing the brake fluid pressure acting on the wheel. In addition, when the slip amount is large, there is a possibility that a traction control system or the like that suppresses engine torque may be activated. Therefore, if the engine is stopped carelessly, there is a concern about the influence on these controls.
Therefore, the engine stop determination threshold value (the upper limit threshold value BRKIN of the brake operation amount permitting the coast stop control) is set in consideration of the above circumstances (not limited to all), and the brake operation amount falls below the upper limit threshold value BRKIN. And the engine 1 is stopped, and the engine 1 is restarted when the brake operation amount exceeds the upper limit threshold value BRKIN.

Referring to the lower threshold, it can be considered that the vehicle stops as it is when the brake pedal is slowly depressed and that the brake pedal is released again and the vehicle restarts again. For example, when driving in a traffic jam, it is conceivable to operate the brake pedal gently to continue the driving state. In this case, if the engine 1 is stopped carelessly, the creep torque generated by the engine 1 cannot be used, and the engine stop and restart are repeated, which may cause the driver to feel uncomfortable.

Also, after the engine is stopped, if the engine is restarted with the brake pedal depressed gently, engine torque may be output to the drive wheels, giving a feeling of popping out. On the other hand, if the threshold value of the brake operation amount for restarting the engine is too low, the vehicle restarts slightly because the braking force by the brake pedal becomes small and the engine restarts.

Furthermore, the driver's brake operation amount fluctuates during deceleration traveling toward the stop, and the brake operation amount tends to decrease as the vehicle speed decreases. For example, when the vehicle wants to stop slowly, such as when it is about to stop at a red light, the brake fluid pressure required for deceleration decreases as the vehicle speed decreases, so the driver loosens the brake pedal. Here, if the engine 1 is inadvertently restarted in response to a decrease in the brake operation amount, the engine 1 will be restarted against the driver's intention to stop, and the fuel consumption may not be sufficiently improved. .

Therefore, the engine start determination threshold (the lower limit threshold BRKOUT of the brake operation amount that permits coast stop control) is set in consideration of the above circumstances, and the engine 1 is stopped when the brake operation amount exceeds the lower limit threshold BRKOUT, and the brake operation amount When the value falls below the lower threshold BRKOUT, the engine 1 is restarted.
In order to suppress frequent switching between engine stop and restart, hysteresis may be provided for the upper limit threshold value BRKIN and the lower limit threshold value BRKOUT, respectively.

[Engine automatic stop / restart control process]
FIG. 2 is a flowchart showing an engine automatic stop / restart control process executed by the engine control unit 10 of the first embodiment. This process is repeatedly executed at predetermined intervals during traveling. Whether or not the vehicle is traveling is determined, for example, based on whether or not the vehicle speed VSP is equal to or less than a predetermined value VSP0 representing the vehicle stop state. The predetermined value VSP0 may be zero, may be an extremely low vehicle speed range of about 1 to 2 km / h, and may be any value as long as it can be determined that the vehicle is almost stopped. Note that other conditions that do not appear in this flowchart may be additionally set as appropriate.

In step S101, it is determined whether or not the permission condition for engine automatic stop / restart control is satisfied, specifically, whether or not the vehicle is in a coasting state (the accelerator pedal operation amount is zero) and the brake pedal is operated. To do. When the accelerator pedal operation amount is zero and the brake pedal is operated, the process proceeds to step S102, and otherwise, the process proceeds to step S113 and the engine operation state is continued.

In step S102, the vehicle speed VSP, the deceleration DVSP, the brake operation amount (master cylinder pressure) BRKP, the upper limit threshold value (idling stop permission upper limit threshold value) and the lower limit threshold value (idling stop permission lower limit threshold value) of the brake operation amount BRKP that permits idling stop control. ), And an upper limit threshold value (coast stop permission upper limit threshold value BRKIN) and a lower limit threshold value (coast stop permission lower limit threshold value BRKOUT) of the brake operation amount BRKP permitting the coast stop control are read, and the process proceeds to step S103.

The vehicle speed VSP may be an average value of each wheel speed detected by the wheel speed sensor 14, or may be an average value of the driven wheel speed, and is not particularly limited.
The idling stop permission upper limit threshold is a value preset in the system, and is a fixed value in the first embodiment.

The coast stop permission upper limit threshold value BRKIN is set smaller as the deceleration DVSP is higher. In the first embodiment, the coast stop permission upper limit threshold value BRKIN is used when the deceleration DVSP is high (DVSP> CSDSP) and the high deceleration zone coast stop permission upper limit threshold BRKINL and the deceleration DVSP is low (DVSP ≦ CSDSP). The low deceleration zone coast stop permission upper limit threshold value BRKINH is set, and the high deceleration zone coast stop permission upper limit threshold value BRKINL is set to a value smaller than the reduced speed zone coast stop permission upper limit threshold value BRKINH.

The coast stop permission lower limit threshold value BRKOUT is set larger as the deceleration DVSP is higher. In Example 1, the coast stop permission lower limit threshold value BRKOUT is used when the deceleration DVSP is high (DVSP> CSDSP) and the high deceleration zone coast stop permission lower limit threshold value BRKOUTH and the deceleration DVSP is low (DVSP ≤ CSDSP). The low deceleration zone coast stop permission lower limit threshold value BRKOUTL is set, and the reduced speed zone coast stop permission lower limit threshold value BRKOUTL is set to a value smaller than the high deceleration zone coast stop permission lower limit threshold value BRKOUTH.

The coast stop permission upper limit threshold value BRKIN is set larger than the coast stop permission lower limit threshold value BRKOUT, and the relationship between the threshold values is BRKINH> BRKINL> BRKOUTH> BRKOUTL.

The idling stop permission lower threshold is set to a value larger than the coast stop permission lower threshold BRKOUT. In this state, the idling stop is performed when the vehicle is stopped. When the engine is started in this state, the creep torque is output. However, when the braking force by the brake is low, the vehicle is inadvertently caused by the creep torque. This is because it may move. The coast stop state is during vehicle deceleration (that is, during travel). In this state, the aim is to improve fuel efficiency by stopping the engine as much as possible, and the engine 1 is restarted before the vehicle is stopped. Even if it is, it is because it is difficult for the driver to feel the pop-out feeling due to the creep torque while driving.

In step S103, it is determined whether or not the vehicle speed VSP is lower than a predetermined vehicle speed CSVSP that permits engine stop. When the vehicle speed falls below the predetermined vehicle speed CSVSP, the process proceeds to step S104. Otherwise, the process proceeds to step S113, and the engine operation state is continued.
In step S104, it is determined whether or not the deceleration exceeds a predetermined deceleration CSDVSP. When it exceeds the predetermined deceleration CSDVSP, the process proceeds to step S105, and otherwise, the process proceeds to step S109.

In step S105, it is determined whether or not the brake operation amount BRKP is below the high deceleration zone coast stop permission upper limit threshold BRKINL. When it falls below the upper limit threshold value BRKINL, the routine proceeds to step S106, and otherwise, the routine proceeds to step S108 and the engine start or operation state is continued.

In step S106, it is determined whether or not the brake operation amount BRKP exceeds the high deceleration zone coast stop permission lower limit threshold value BRKOUTH. When the lower limit threshold BRKOUTH is exceeded, the process proceeds to step S107 to stop the engine, and otherwise, the process proceeds to step S108 to continue the engine start or operation state.

In step S109, it is determined whether or not the brake operation amount BRKP is below a reduction speed zone coast stop permission upper limit threshold BRKINH. When it falls below the upper limit threshold value BRKINH, the process proceeds to step S110, and otherwise, the process proceeds to step S112 to continue the engine start or operation state.

In step S110, it is determined whether or not the brake operation amount BRKP exceeds the reduced speed zone coast stop permission lower limit threshold value BRKOUTL. When the lower limit threshold value BRKOUTL is exceeded, the process proceeds to step S111 to stop the engine, and otherwise, the process proceeds to step S112 to continue the engine start or operation state.

[Action]
Next, the effect | action based on the said control process is demonstrated using a comparative example.
(When the coast stop permission upper limit / lower limit threshold is changed according to the deceleration: Example 1)
First, the operation of the first embodiment will be described.
FIG. 3 is a time chart showing the operation of the setting process of the coast stop permission lower limit threshold value BRKOUT and the coast stop permission upper limit threshold value BRKIN at the time of coasting in the first embodiment. 3A shows the brake operation amount BRKP, FIG. 3B shows the deceleration DVSP, FIG. 3C shows the engine speed Ne, and FIG. 3D shows the change in the vehicle speed VSP. The driving state (precondition) at the first time in the time chart is a coasting driving state in which the driver releases his / her foot from the accelerator pedal during driving.

Before time t11, the vehicle speed VSP is equal to or higher than the predetermined vehicle speed CSVSP. Therefore, in the control process of FIG. 2, the flow proceeds from step S101 to step S102 to step S103 to step S113, and the engine 1 continues to operate. Also, the brake operation amount BRKP of the driver is gradually decreasing.

At time t11, the deceleration DVSP exceeds the predetermined deceleration CSDVSP, so the coast stop permission upper limit threshold BRKIN is selected as the high deceleration zone coast stop permission upper limit threshold BRKINL, and the coast stop permission lower limit threshold BRKOUT is the high deceleration zone coast stop. The lower permission threshold BRKOUTH is selected. At this time, the vehicle speed VSP is less than the predetermined vehicle speed CSVSP, but the brake operation amount BRKP is equal to or greater than the high deceleration zone coast stop permission upper limit threshold BRKINL. Therefore, in the control process of FIG. 2, the flow proceeds to steps S101 → S102 → S103 → S104 → S105 → S108, and the engine 1 continues to operate.

At time t12, the brake operation amount BRKP is below the high deceleration zone coast stop permission upper limit threshold BRKINL, but is greater than or equal to the high deceleration zone coast stop permission lower threshold BRKOUTH. Therefore, in the control process of FIG. 2, the flow proceeds from step S101 → S102 → S103 → S104 → S105 → S106 → S107, and the engine 1 is stopped. After time t12 when engine stop is started, the engine speed rapidly decreases toward zero.

At time t13, the deceleration DVSP is equal to or less than the predetermined deceleration CSDVSP, so the coast stop permission upper limit threshold BRKIN is selected as the reduction speed zone coast stop permission upper limit threshold BRKINH, and the coast stop permission lower limit threshold BRKOUT is the reduction speed zone coast stop permission. A lower threshold BRKOUTL is selected. After this time t13, the brake operation amount BRKP falls below the reduced speed zone coast stop permission upper limit threshold value BRKINH and is greater than or equal to the reduced speed zone coast stop permission lower limit threshold value BRKOUTL. Therefore, in the control process of FIG. 2, the flow proceeds from step S101 → S102 → S103 → S104 → S109 → S110 → S111, and the engine 1 is stopped.

(When the coast stop permission lower limit threshold is a fixed value regardless of deceleration: Comparative Example 1)
Next, the operation of the first comparative example in which the coast stop permission lower limit threshold value BRKOUT is set to a fixed value (for example, BRKOUTH) without changing according to the deceleration DVSP will be described.
Also in Comparative Example 1, the operation up to time t13 is the same as that of Example 1.

At time t13, the deceleration DVSP falls below the predetermined deceleration CSDVSP. However, the coast stop permission lower limit threshold value BRKOUT is set to the high deceleration zone coast stop permission lower limit threshold value BRKOUTH after time t13 as well as until time t13 (the chain line in FIG. 3A).
At time t14, the brake operation amount BRKP falls below the high deceleration zone coast stop permission lower limit threshold value BRKOUTH, so the engine 1 is restarted (the chain line in FIG. 3 (d)). Therefore, in the comparative example, the driver intends to stop and the engine 1 is restarted even though the engine can be stopped. Therefore, the fuel consumption can be sufficiently improved. Can not.

In contrast, in the first embodiment, the coast stop permission lower limit threshold value BRKOUT is set smaller as the deceleration DVSP is lower as described above. Therefore, even if the amount of brake operation changes according to the deceleration DVSP, the engine 1 can be restarted at a more appropriate timing according to the driver's intention, so that the fuel consumption can be further improved.

(When the coast stop permission upper limit threshold is a fixed value regardless of deceleration: Comparative Example 2)
Next, the operation of Comparative Example 2 in which the coast stop permission upper limit threshold value BRKIN is set to a fixed value (for example, BRKINH) without changing according to the vehicle speed DVSP will be described.

FIG. 4 is a time chart showing the operation of the setting process of the coast stop permission lower limit threshold value BRKOUT and the coast stop permission upper limit threshold value BRKIN during the coast running of the first embodiment. 4A shows the brake operation amount BRKP, FIG. 4B shows the deceleration DVSP, FIG. 4C shows the engine speed Ne, and FIG. 4D shows the change in the vehicle speed VSP. The operation of the first embodiment shown in FIG. 4 is the same as that of FIG.

In comparative low 2, even if the deceleration DVSP up to time t13 is within the predetermined deceleration CSDVSP or more, it is set to the reduction speed zone coast stop permission lower limit threshold value BRKOUTH (the dashed line in FIG. 4A).

At time t15, the brake operation amount BRKP falls below the reduced speed zone coast stop permission upper limit threshold BRKINH, so the engine 1 is stopped. After time t15 when engine stop is started, the engine speed rapidly decreases toward zero (the chain line in FIG. 4C). Since the engine 1 is stopped and the negative pressure due to engine rotation cannot be used, the brake pedal reaction force increases and the brake operation amount decreases (the chain line in FIG. 4A). For this reason, the deceleration DVSP is lowered (the dashed line in FIG. 4C), and the braking force intended by the driver cannot be sufficiently obtained (the dashed line in FIG. 4D).

On the other hand, in Example 1, the coast stop permission upper limit threshold value BRKIN is set smaller as the deceleration DVSP is higher as described above. Therefore, when the deceleration DVSP is high, the brake operation amount is difficult to enter the engine stop permission range, and the braking force can be ensured to continue the operation of the engine 1.

[effect]
As described above, the following effects can be obtained in the first embodiment.
(1) The master cylinder pressure sensor 13 (brake operation amount detection means) that detects the driver's brake operation amount (master cylinder pressure) and the engine when the detected brake operation amount falls below the upper threshold BRKIN during coasting. After the engine is stopped, the engine is restarted when the detected brake operation amount falls below the lower limit threshold value BRKOUT, and the upper limit threshold value BRKIN is set smaller as the deceleration DVSP is higher. Upper limit threshold setting means).
Therefore, when the deceleration DVSP is high, the brake operation amount is difficult to enter the engine stop permission range, and the braking force can be ensured to continue the operation of the engine 1.

(2) An engine control unit 10 (lower limit threshold setting means) is provided that sets the lower limit threshold value BRKOUT smaller as the deceleration DVSP is lower.
Therefore, even if the amount of brake operation changes according to the deceleration DVSP, the engine 1 can be restarted at a more appropriate timing according to the driver's intention, so that the fuel consumption can be further improved.

[Example 2]
Next, Example 2 will be described. Since the basic configuration is the same as that of the first embodiment, only different points will be described. FIG. 5 is a flowchart showing an engine automatic stop / restart control process executed by the engine control unit 10 of the second embodiment.
In the second embodiment, the coast stop permission upper limit threshold value BRKIN is set smaller as the deceleration DVSP is higher, and the coast stop permission lower limit threshold value BRKOUT is set smaller as the deceleration DVSP is lower. The engine control unit 10 has a map 1 indicating the relationship between the coast stop permission upper limit threshold value BRKIN and the deceleration DVSP and a map 2 indicating the relationship between the coast stop permission lower limit threshold value BRKOUT and the deceleration DVSP.

As shown in step S204 of FIG. 5, the map 1 has a boundary such that the coast stop permission upper limit threshold value BRKIN decreases stepwise (stepwise) as the deceleration DVSP changes from the low side to the high side. A line is drawn. A region where the brake operation amount is smaller than the boundary line is classified as a coast stop permission (OK) region, and a region where the brake operation amount is larger than the boundary line is classified as a coast stop prohibition (NG) region. Whether the coast stop (engine stop) is permitted or not is determined depending on which region the operating state (deceleration DVSP and brake operation amount BRKP) belongs to.

As shown in step S205 of FIG. 5, the map 2 has a boundary such that the coast stop permission lower limit threshold value BRKOUT increases stepwise (stepwise) as the deceleration DVSP changes from the low side to the high side. A line is drawn. A region where the brake operation amount is larger than the boundary line is classified as a coast stop permission (OK) region, and a region where the brake operation amount is smaller than the boundary line is classified as a coast stop prohibition (NG) region. Whether the coast stop (engine stop) is permitted or not is determined depending on which region the operating state (deceleration DVSP and brake operation amount BRKP) belongs to.

[Engine automatic stop / restart control process]
The process shown in FIG. 5 is repeatedly executed at predetermined intervals during traveling. Whether or not the vehicle is traveling is determined, for example, based on whether or not the vehicle speed VSP is equal to or less than a predetermined value VSP0 representing the vehicle stop state.
The predetermined value VSP0 may be zero, may be an extremely low vehicle speed range of about 1 to 2 km / h, and may be any value as long as it can be determined that the vehicle is almost stopped. Note that other conditions that do not appear in this flowchart may be additionally set as appropriate.

In step S201, it is determined whether or not a permission condition for engine automatic stop / restart control is satisfied, specifically, whether or not a condition such as a coasting driving state and a brake pedal being operated is satisfied. When the permission condition is satisfied, the process proceeds to step S302. Otherwise, the process proceeds to step S208, and the engine operation state is continued.

In step S202, the vehicle speed VSP, the deceleration DVSP, the brake operation amount (master cylinder pressure) BRKP, the brake operation amount BRKP for which idling stop control is permitted, the upper and lower thresholds, and maps 1 and 2 are read. Proceed to

In step S203, it is determined whether or not the vehicle speed VSP is lower than a predetermined vehicle speed CSVSP that permits engine stop. When the vehicle speed falls below the predetermined vehicle speed CSVSP, the process proceeds to step S204. Otherwise, the process proceeds to step S208, and the engine operation state is continued.

In step S204, it is determined whether the driving state (deceleration DVSP and brake operation amount BRKP) at that time belongs to the coast stop permission area or the coast stop prohibition area of map 1. When it is determined that it belongs to the coast stop permission area, the process proceeds to step S205, and when it is determined that it belongs to the coast stop prohibition area, the process proceeds to step S207, and the engine start or operation state is continued.

In step S205, it is determined whether the driving state (deceleration DVSP and brake operation amount BRKP) at that time belongs to the coast stop permission area or the coast stop prohibition area of map 2. When it is determined that it belongs to the coast stop permission area, the routine proceeds to step S206 and the engine is stopped. When it is determined that it belongs to the coast stop prohibition area, the routine proceeds to step S207 and the engine start or operation state is continued.

[Action]
Next, the operation based on the control process will be described. FIG. 6 is a time chart showing the operation of the setting process of the coast stop permission upper limit threshold value BRKIN and the lower limit threshold value BRKOUT during the coast running of the second embodiment. 6A shows the brake operation amount BRKP, FIG. 6B shows the deceleration DVSP, FIG. 6C shows the engine speed Ne, and FIG. 6D shows the change in the vehicle speed VSP.

Before time t11, the vehicle speed VSP is equal to or higher than the predetermined vehicle speed CSVSP. Therefore, in the control process of FIG. 5, the flow proceeds from step S201 to S202 to S203 to S208, and the engine 1 continues to operate. Also, the brake operation amount BRKP of the driver is gradually decreasing.

At time t11, the vehicle speed VSP becomes less than the predetermined vehicle speed CSVSP, and the permission condition for the engine automatic stop / restart control is satisfied. At this time, the driving state (the deceleration DVSP and the brake operation amount BRKP) belongs to the coast stop prohibition region in the map 1. Therefore, in the control process of FIG. 5, the flow proceeds from step S201 → S202 → S203 → S204 → S207, and the engine 1 continues to operate.

Thereafter, as the deceleration DVSP decreases, the coast stop permission upper limit threshold value BRKIN in the map 1 increases stepwise (stepwise), and the lower limit threshold value BRKOUT in the map 2 decreases stepwise (stepwise).

At time t12, the driving state (deceleration DVSP and brake operation amount BRKP) belongs to the coast stop permission area in map 1 and belongs to the coast stop permission area in map 2. Therefore, the flow proceeds from step S201 → S202 → S203 → S204 → S205 → S207, and the engine 1 (fuel injection) is stopped. After time t12 when engine stop is started, the engine speed decreases rapidly toward zero.

In Example 2, a plurality of coast stop permission lower limit threshold values BRKOUT are set so as to decrease as the deceleration DVSP decreases. Specifically, the coast stop permission lower limit threshold value BRKOUT is set to 3 or more unlike the first embodiment (two of the high deceleration zone coast stop permission lower limit threshold value BRKOUTH and the reduced speed zone coast stop permission lower limit threshold value BRKOUTL). In this way, by setting the coast stop permission lower limit threshold value BRKOUT more finely according to the vehicle speed VSP, the coast stop permission lower limit threshold value BRKOUT is prevented from changing rapidly, and the engine 1 is restarted at a more appropriate timing. be able to. Therefore, fuel consumption can be further improved.

Also, coast stop permission lower threshold BRKOUT is set based on Map 2. Accordingly, the degree of freedom in setting the coast stop permission lower limit threshold BRKOUT can be improved, and the calculation load of the engine control unit 10 can be reduced as compared with the case where the coast stop permission lower limit threshold BRKOUT is set based on, for example, the calculation formula. it can.

Also, multiple coast stop permission upper limit threshold values BRKIN are set so as to increase as the deceleration DVSP decreases. Specifically, the coast stop permission upper limit threshold value BRKIN is set to 3 or more unlike the first embodiment (two of the high deceleration zone coast stop permission upper limit threshold value BRKINL and the reduced speed zone coast stop permission upper limit threshold value BRKINH). In this way, by setting the coast stop permission upper limit threshold value BRKIN more precisely according to the deceleration DVSP, the coast stop permission upper limit threshold value BRKIN is prevented from changing suddenly, and the engine 1 is restarted at a more appropriate timing. can do. Therefore, the braking performance of the vehicle and the shift controllability of the belt type continuously variable transmission 3 can be further improved. Further, by setting the coast stop permission upper limit threshold value BRKIN based on the map 1, it is possible to improve the degree of freedom of setting the coast stop permission upper limit threshold value BRKIN while reducing the calculation load of the engine control unit 10.

[effect]
As described above, the following effects can be obtained in the second embodiment.
(3) The engine control unit 10 (upper limit threshold setting means) sets a plurality of upper limit threshold values BRKIN so that the upper limit threshold value BRKIN decreases as the deceleration DVSP increases.
Therefore, the braking force can be secured because the operation of the engine 1 is continued until a more appropriate timing.

(4) The engine control unit 10 (upper threshold setting means) sets the upper threshold BRKIN based on a predetermined map.
Therefore, the degree of freedom for setting the coast stop permission upper limit threshold value BRKIN can be improved.

(5) The engine control unit 10 (lower limit threshold setting means) sets a plurality of lower limit thresholds so that the lower limit threshold BRKOUT decreases as the deceleration DVSP decreases.
Therefore, since the engine 1 can be restarted at a more appropriate timing, fuel efficiency can be further improved.

(6) The engine control unit 10 (lower threshold setting means) sets the lower threshold BRKOUT based on a predetermined map.
Therefore, the degree of freedom for setting the coast stop permission lower limit threshold value BRKOUT can be improved.

Example 3
Next, Example 3 will be described. Since the basic configuration is the same as in the first and second embodiments, only different points will be described. FIG. 7 is a flowchart showing an engine automatic stop / restart control process executed by the engine control unit 10 of the third embodiment.
The engine control unit 10 uses a calculation formula 1 for calculating the coast stop permission upper limit threshold value BRKIN larger as the deceleration DVSP becomes lower, and a calculation formula 2 for calculating the coast stop permission lower limit threshold value BRKOUT larger as the deceleration DVSP becomes higher. The coast stop permission upper limit threshold value BRKIN and the lower limit threshold value BRKOUT are calculated based on the deceleration DVSP. For example, the

calculation formulas

1 and 2 can have characteristics in which the upper limit threshold value BRKIN or the lower limit threshold value BRKOUT changes linearly according to the change in the deceleration DVSP.

[Engine automatic stop / restart control process]
The process shown in FIG. 7 is repeatedly executed at predetermined intervals during traveling. Whether or not the vehicle is traveling is determined, for example, based on whether or not the vehicle speed VSP is equal to or less than a predetermined value VSP0 representing the vehicle stop state.
The predetermined value VSP0 may be zero, may be an extremely low vehicle speed range of about 1 to 2 km / h, and may be any value as long as it can be determined that the vehicle is almost stopped. Note that other conditions that do not appear in this flowchart may be additionally set as appropriate.

In step S301, it is determined whether or not a permission condition for engine automatic stop / restart control is satisfied, specifically, whether or not a condition such as a coasting driving state and a brake pedal being operated is satisfied. When the permission condition is satisfied, the process proceeds to step S302. Otherwise, the process proceeds to step S310 and the engine operation state is continued.

In step S302, the vehicle speed VSP, the brake operation amount (master cylinder pressure) BRKP, and the brake operation amount BRKP for which the idling stop control is permitted are read as the upper limit threshold value and the lower limit threshold value, and the process proceeds to step S303.

In step S303, it is determined whether or not the vehicle speed VSP is lower than a predetermined vehicle speed CSVSP that permits engine stop. When the vehicle speed falls below the predetermined vehicle speed CSVSP, the process proceeds to step S304. Otherwise, the process proceeds to step S310, and the engine operation state is continued.

In step 304, a coast stop permission upper limit threshold value BRKIN is calculated based on the deceleration DVSP and calculation formula 1, and the process proceeds to step S305.
In step S305, it is determined whether or not the brake operation amount BRKP is less than the calculated coast stop permission upper limit threshold value BRKIN. When it is determined that the brake operation amount BRKP is less than the coast stop permission upper limit threshold BRKIN, the process proceeds to step S306, and when it is determined that the brake operation amount BRKP is equal to or greater than the coast stop permission upper limit threshold BRKIN, the process proceeds to step S309 and the engine is started or Continue operating.

In step 306, a coast stop permission lower limit threshold value BRKOUT is calculated based on the deceleration DVSP and calculation formula 2, and the process proceeds to step S307.
In step S307, it is determined whether or not the brake operation amount BRKP exceeds the calculated coast stop permission lower limit threshold value BRKOUT. When it is determined that the brake operation amount BRKP is less than the coast stop permission lower limit threshold BRKOUT, the process proceeds to step S308, and when it is determined that the brake operation amount BRKP is less than the coast stop permission lower limit threshold BRKOUT, the process proceeds to step S309 and the engine is started or Continue operating.

[Action]
Next, the operation based on the control process will be described. FIG. 8 is a time chart showing the operation of the setting process of the coast stop permission upper limit threshold value BRKIN and the lower limit threshold value BRKOUT during coasting in the third embodiment. 8A shows the brake operation amount BRKP, FIG. 8B shows the deceleration DVSP, FIG. 8C shows the engine speed Ne, and FIG. 8D shows the change in the vehicle speed VSP.

Before time t11, the vehicle speed VSP is equal to or higher than the predetermined vehicle speed CSVSP. Therefore, in the control process of FIG. 8, the process proceeds from step S301 to S302, S303, and S310, and the engine 1 continues to operate. Also, the brake operation amount BRKP of the driver is gradually decreasing.

At time t11, the vehicle speed VSP becomes lower than the predetermined vehicle speed CSVSP, and the permission condition for engine automatic stop / restart control is satisfied. At this time, the brake operation amount BRKP exceeds the coast stop permission upper limit threshold value BRKIN calculated by the vehicle speed VSP and Formula 1. Therefore, the flow proceeds to steps S301 → S302 → S303 → S304 → S305 → S309, and the engine 1 continues to operate.
Thereafter, as the deceleration DVSP decreases, the coast stop permission upper limit threshold value BRKIN in Formula 1 increases linearly, and the lower limit threshold value BRKOUT in Formula 2 decreases linearly.

At time t12, the brake operation amount BRKP is less than the coast stop permission upper limit threshold value BRKIN calculated by the deceleration DVSP and Formula 1, and the coast stop permission lower limit threshold value BRKOUT calculated by the deceleration DVSP and Formula 2 is set. Exceed. Therefore, the flow proceeds to steps S301 → S302 → S303 → S304 → S305 → S306 → S307 → S308, and the engine is stopped. After the time t12 when the engine is stopped, the engine speed rapidly decreases toward zero.

In Example 3, the coast stop permission upper limit threshold value BRKIN and the coast stop permission lower limit threshold value BRKOUT are set based on Formula 1 and Formula 2, respectively. Therefore, for example, the amount of data stored in the engine control unit 10 can be reduced as compared with the case where the upper limit threshold value BRKIN and the lower limit threshold value BRKOUT are set using a map. In other words, if the upper limit threshold value BRKIN and the lower limit threshold value BRKOUT are set more finely according to the deceleration DVSP, the amount of data increases when the map is used, but the increase in the amount of data is suppressed by using the calculation formula. be able to.

[effect]
As described above, the following effects can be obtained in the third embodiment.
(7) The engine control unit 10 (upper threshold setting means) sets the upper threshold BKRIN based on a predetermined calculation formula.
Therefore, the data storage amount can be reduced.

(8) The engine control unit 10 (lower threshold setting means) sets the lower threshold BRKOUT based on a predetermined calculation formula.
Therefore, the data storage amount can be reduced.

[Other Examples]
As mentioned above, although this invention has been demonstrated based on Example 1 thru | or Example 3, it is not restricted to the said Example, It is contained in this invention even if it is another structure.
For example, in the first to third embodiments, the example in which the belt-type continuously variable transmission is adopted is shown, but a configuration including other stepped automatic transmissions, manual transmissions, and the like may be used. Moreover, although the example provided with the torque converter was shown, even if it is a vehicle which is not provided with the torque converter, it is applicable. In these cases, as a parameter for permitting coast stop control (automatic engine stop), not the predetermined vehicle speed CSVSP, but other parameters indicating whether or not the engine independent rotation can be maintained (combination of vehicle speed and speed ratio and engine speed) Can be used.

Further, in the first and second embodiments, the deceleration DVSP that is a threshold value for changing the coast stop permission upper limit threshold value BRKIN is not necessarily the same as the deceleration DVSP that is a threshold value for changing the coast stop permission lower limit threshold value BRKOUT. Alternatively, both deceleration DVSPs may be different.

Claims

Brake operation amount detection means for detecting the brake operation amount of the driver;
During coast running, the engine is stopped when the detected brake operation amount falls below the upper limit threshold, and after the engine stops, the engine stop / restart means for restarting the engine when the detected brake operation amount falls below the lower limit threshold;
An engine automatic control device for a vehicle, comprising: an upper limit threshold setting unit configured to set the upper limit threshold value smaller as the deceleration is higher.
In the vehicle engine automatic control apparatus according to claim 1,
The vehicle upper limit threshold setting means sets a plurality of upper limit thresholds such that the upper limit threshold decreases as the deceleration increases.
In the vehicle engine automatic control device according to claim 1 or 2,
The upper limit threshold setting means is an automatic engine control device for a vehicle that sets the upper limit threshold based on a predetermined map.
In the vehicle engine automatic control device according to claim 1 or 2,
The upper limit threshold setting means is an automatic engine control device for a vehicle that sets the upper limit threshold based on a predetermined calculation formula.
In the vehicle engine automatic control apparatus according to any one of claims 1 to 4,
An automatic engine control device for a vehicle provided with a lower threshold setting means for setting the lower threshold to be smaller as the deceleration is lower.
The vehicle engine control device according to claim 5,
The lower limit threshold setting means sets the plurality of lower limit thresholds such that the lower limit threshold decreases as the deceleration decreases.
In the vehicle engine control device according to claim 5 or 6,
The lower limit threshold setting means is an automatic engine control device for a vehicle that sets the lower limit threshold based on a predetermined map.
The engine control apparatus for a vehicle according to claim 5 or 6,
The lower limit threshold setting means is an automatic engine control device for a vehicle that sets the lower limit threshold based on a predetermined calculation formula.