JP3536717B2 - Automatic engine stop / restart control system for vehicles - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent degradation of brake auxiliary performance due to reduction of an inner pressure in an intake manifold. SOLUTION: This controller has a means for deciding whether or not performance of a brake booster is sufficient and stops control for automatically stopping an engine, and when it is decided that the performance of the brake booster is not sufficient in the operation of the engine (steps 530, 560). With respect to the decision whether or not the performance of the brake booster is sufficient, when a pressure difference between a detection value of atmospheric pressure and a detection value of brake boost pressure becomes a prescribed value or less, it is decided that the performance of the brake booster is not sufficient.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake booster which assists a driver's braking operation by utilizing a negative pressure of an engine, and automatically stops the engine when a predetermined engine stop condition is satisfied. The present invention relates to an automatic engine stop / restart control device for a vehicle that restarts the automatically stopped engine when the engine restart condition is satisfied.

[0002]

2. Description of the Related Art Conventionally, a vehicle stops during running (vehicle speed becomes zero), and when a predetermined stop condition is satisfied, the engine is automatically stopped to save fuel, reduce exhaust emissions, reduce noise, and the like. A vehicle configured to achieve this is proposed and has already been put into practical use (for example,
-22035).

In such a vehicle, the engine is immediately restarted when a predetermined restart condition is satisfied by indicating the driver's (driver) intention to run such as depressing an accelerator pedal.

Further, in this technique, a brake booster for increasing a braking force and assisting a driver's braking operation is mounted. The negative pressure of the engine stored in the surge tank downstream of the throttle valve is used as a drive source of the brake booster. Specifically, the negative pressure is guided to the brake booster via a pressure guiding pipe branched from the surge tank.

[0005] Then, a negative pressure corresponding to the depression amount of the brake pedal acts on a diaphragm built in the brake booster, thereby assisting a brake operation force.

[0006]

However, in the above-mentioned technology (Japanese Patent Laid-Open No. 9-222035), since the engine is automatically stopped, the frequency of stopping the engine naturally increases. Therefore, during the automatic stop of the engine, the engine itself stops, so the negative pressure of the surge tank, which is the negative pressure source of the brake booster, drops (at or near atmospheric pressure), and the internal pressure (negative pressure) of the brake booster also drops. Would. For this reason, there is a problem that the brake assist performance during the automatic stop of the engine or immediately after the start is reduced.

That is, when the negative pressure of the surge tank cannot be secured, the pressure in the brake booster that secures the braking force by obtaining the negative pressure from the negative pressure (hereinafter referred to as the brake booster internal pressure) is also sufficient. It cannot be secured (the negative pressure will decrease).

The present invention has been made in view of such a problem, and a vehicle capable of always ensuring the original brake assist function of a brake booster regardless of whether the engine is operating or automatically stopped. It is an object of the present invention to provide an automatic engine stop / restart control device.

[0009]

According to a first aspect of the present invention, there is provided a brake booster which assists a driver's braking operation by utilizing a negative pressure of an engine , and wherein a throttle is fully provided .
An engine when the engine stop condition of Jo Tokoro in the closed is satisfied with automatically stopped, the predetermined automatic engine stop of the vehicle engine restart condition to restart the engine the automatically stopped when met-restart control device in the brake booster internal pressure detection means for detecting the internal pressure of the brake booster, rose throttle of the engine is opened
Detects intake pressure that drops when the throttle is closed
A pressure detecting means, a pressure comparison means for comparing the intake air pressure and the brake Kibusuta the pressure during engine operation, the intake
The difference between the air pressure and the internal pressure of the brake booster is smaller than a predetermined value.
Allow the automatic stop of the engine when it goes down
The above-mentioned problem has been solved by providing means .

[0010] The intake pressure and the shake in this way during the engine operating
By comparing the internal pressure (negative pressure) of the
Judge that Kibo booster internal pressure has been secured
It can be enough even if it enters the engine stop control
Brake assist performance can be realized.

Here, the "intake pressure" is, for example, in front of the engine.
Installed inside the surge tank to prevent air pulsation
It can be known by detecting the pressure.

[0012] As a comparison method, the intake pressure and the brake
The difference from the Kibo booster internal pressure may be determined, and the ratio may be determined.
And it may be possible to use a map, etc.
You.

[0013]

[0014]

[0015]

[0016]

According to a second aspect of the present invention, there is provided the configuration of the first aspect.
In addition, during the automatic stop of the engine, the intake pressure and the
The difference from the brake booster internal pressure is smaller than the other specified value.
Stop the automatic stop of the engine,
The above-mentioned problem is similarly solved by further providing a means for restarting the engine .

Therefore, according to the second aspect of the present invention,
With the engine stopped automatically,
Engine stopped when star pressure approached intake pressure
Since the intake pressure is close to the atmospheric pressure, the brake booth
This means that the negative pressure of the internal pressure has decreased (the pressure has increased).
You. In that case, the automatic stop of the engine is stopped and
The engine is restarted. As a result, as the intake pressure decreases
The brake booster internal pressure drops and sufficient brake assistance is provided.
Performance can be achieved.

[0019]

[0020]

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings.

[0022]

In the description of the present embodiment, as an example, a device of a vehicle equipped with an automatic transmission having a shift speed as a device for performing a shift will be described. However, the present invention is not particularly limited to this. Transmission, manual transmission (MT), continuously variable transmission (CV
T) also Ru applicable der the device for a vehicle equipped with.

[0024] First, drive the dynamic system of the present embodiment is applied
Will be explained.

[0025] In Fig. 3, 1 is an engine mounted on a vehicle, it is 2 an automatic transmission. The engine 1 includes a motor for restarting the engine 1 and a motor generator (MG ) functioning as a generator.
The crank shaft, clutch, is connected to via <br/> the chain及 beauty reducer configuration. Incidentally, separately provided an engine starter motor <br/> Generator, when the engine starts, or a combination of starter and motor generational data, may be used starter dedicated during cryogenic temperatures.

The reduction gear structure is a planetary gear type, Sangi A, key <br/> catcher Li A, comprises Ringugi A, brake, motor generational data及 beauty cladding through a one-way class <br/> pitch incorporated between the switch.

[0027] Oirupon flop for automatic transmission 2 is directly connected via a clutch to a crankshaft of the engine 1.
Known forward <br/> clutch that is engaged during forward travel is provided in the automatic in transmission 2.

[0028] The inverter is electrical connected to the motor Tajenere data. The inverter is made variable to <br/> rotational speed of the motor generational data by the supply of electrical energy to the battery or et motor generational data is a power source to the variable by switching. Further, it switches to charge the electric energy to the motor generational data or al <br/> battery.

[0029]KLuckChi'sIntermittent control and invarOf
Switching control, aircoEtc.ComplementMachineControl, etc.
ControlLA is provided.controlTo la
Is the switch for the automatic stop mode (eco-run mode).H
ofSignal and shift lever-(Shift position center
Sa no shinIssue is enteredYou. MaThis controlLe, D
ECU that controls the engine and automatic transmission
(A child control device) 80.

[0030] Figure 3 shows the flow and pressure conditions of the air in the intake and exhaust systems and brake systems to Matae engine 1
I have.

Reference numeral 1 denotes the aforementioned engine, and reference numeral 2 denotes an automatic transmission. The air is taken in from an air inlet 123 and is made fresh air through an air cleaner 121 that removes dust and dirt from impurities other than the air, and is sent to a surge tank 102 that prevents air pulsation. In addition,
As for the air, the amount of air taken into the engine is adjusted by the throttle valve 109.

The air sent to the surge tank 102 is supplied to the engine 1 via the intake manifold 117. The pressures of the surge tank 102 and the intake manifold 117 are substantially equal, and the pressures are substantially equal to the surge tank pressure (intake pressure) installed in the surge tank 102.
It is detected by the sensor 115. The engine 1 is provided with an engine rotation speed sensor 113, and the air intake port 123 is provided with an air flow meter 129 for detecting an intake air amount.

The surge tank 102 is connected to a brake booster 105 via a brake booster valve 125 in addition to the intake manifold 117. The brake booster 105 has a brake boost pressure sensor 107 for detecting a pressure PB in the brake booster 105.
Is installed.

An atmospheric pressure sensor 127 for detecting the atmospheric pressure PA is provided outside the air suction port 123.

The exhaust from the engine is performed from the exhaust manifold 128.

FIG . 4 shows a specific example of the input / output elements of the ECU 80.

The ECU 80 has an engine speed sensor 113 for detecting the engine speed NE, a vehicle speed sensor 133 for detecting the vehicle speed Ve, and a brake booster pressure PB.
Pressure sensor 107 for detecting the pressure of the surge tank, an atmospheric pressure sensor 127 for detecting the atmospheric pressure, a throttle opening V
Throttle opening sensor 130 for detecting TA, shift position sensor 13 for detecting the position of the shift position
1. Signals such as a brake-on signal 140 are input and output.

Next, the operation of the present embodiment will be described.

In this embodiment, as described above, a system for automatically stopping the engine when a predetermined engine stop condition is satisfied and restarting the automatically stopped engine when a predetermined engine restart condition is satisfied is described. Has adopted. First of all, to explain the action.

[0040] At the time starting the engine click latch described above is the contact <br/> connection state, by driving the motor generational data for starting the engine 1 (in some cases the starter combination or alone, where the description do not do). In this door-out speed reduction mechanism
By turning on the blanking array key, motor generational other bets
Torque is transmitted in amplified from Sang Ya side of the speed reducer configured to career side. Accordingly, even when reduced capacity of the motor generational data and inverter <br/> over data, can be secured driving force required to crank the engine 1. After the start of the engine 1, motor generational data functions as a generator, storing electrical energy in the battery for example during braking of the vehicle.

[0041] The <br/> rotational speed of the motor generational data detected by the controller at the time of engine start, against the inverter,
Rotation of the motor generational data and outputs a switching signal so that the torque and rotational speed required to start the engine 1. For example if it air conditioning ON at engine start, because it is necessary a greater torque than that in the air conditioning off, the controller is a motor generational motor with a large torque and rotational speed to output a switching signal so as to be rotatable.

When a predetermined engine stop condition is satisfied with the eco-run mode signal turned on, the control is executed.
LA outputs a signal to cut off the fuel supply to the engine 1 and automatically stops the engine. Eco-run mode signal is input to the controller by pressing the driver Ekoransui' switch provided in the vehicle interior.

In this embodiment, the engine is automatically stopped when all of the following conditions are satisfied or confirmed.

(1) During engine start. (2) Cancel switch (S
W) is off (Ekoransui' switch is turned on). (3) The charge amount SOC of the battery is equal to or more than the predetermined value SOC1. (4) The brake negative pressure is sufficiently secured. (5) Good air conditioning performance. (6) Checking the running history. (7) The vehicle speed is zero. (8) The engine speed NE is the idle speed. (9) The shift position is neutral ("N"). And so on.

Each condition will be described.

Of the above conditions, conditions (1), (7),
(8), the engine rotational speed is an idle speed, the vehicle is situations that der the stopped state (the vehicle speed is zero). The condition (3) “good air conditioning performance” means that the temperature of the air conditioning in the vehicle
This is to determine whether the humidity is appropriate. That is, if the engine is automatically stopped when air conditioning is inappropriate, the driver may be uncomfortable.

The condition (9) is not particularly limited to "N" when the system automatically stops the engine at the drive position. In the case of manual transmission (MT), it is sufficient to replace the condition that the shift position is “N” and the driver's foot is separated from the clutch pedal.

In the above condition (3), “the battery charge amount SO
The reason that "C is secured equal to or more than the predetermined value SOC1" is that when the automatic stop control of the engine is started in a state where the charge amount SOC of the battery is insufficient, there is a possibility that a so-called low battery occurs. Also, the battery charge amount S
In the case of a system in which the engine is restarted when the OC decreases, the engine is restarted immediately after the charge amount SOC of the battery decreases after the automatic stop of the engine. This may cause a feeling of pleasure, and also imposes a burden on the starting system. Therefore, when the engine is automatically stopped, a time when a sufficient battery capacity is secured equal to or more than the predetermined value SOC1 is added to the engine automatic stop condition.

The “confirmation of traveling history” of the above condition (6)
It is a judgment of the current situation of the vehicle.

That is, when "N" and "R" are repeated from the shift position in a short time, it is determined that the garage (so-called garage shift) is being executed,
Control so as not to immediately enter the automatic stop control of the engine. In addition, appropriate automatic stop control is implemented when the oil temperature of various oils is low immediately after the engine is started, or when the oil temperature is extremely high due to high speed running or high speed running of the engine. The running history is checked because it may not be possible.

In addition, a condition that “these conditions continue for a predetermined time Tstop” may be added to these conditions. The predetermined time Tstop is counted by a timer, and is input to the ECU 80 and processed. The predetermined time Tstop corresponds to the time until the automatic stop of the engine is started, and may be changed or changed according to the situation.
Can be set. The predetermined time Tstop may be set to zero, and the engine may be automatically stopped as soon as the predetermined stop condition is satisfied. Alternatively, the automatic stop of the engine may be substantially prohibited by setting the engine to infinity. it can.

Next, the condition (4) which is a feature of the present invention will be described.

"Sufficient brake negative pressure is ensured" means that a sufficient negative pressure enough to perform brake assist in the brake booster 105 is secured.

In order to make that determination, in this embodiment,
The brake booster pressure sensor 107 detects the brake booster internal pressure PB, and the atmospheric pressure sensor 127 detects the atmospheric pressure PA, and compares the atmospheric pressure PA with the brake booster internal pressure PB.

This will be described more specifically with reference to FIG.

FIG. 2 shows the relationship between the intake pressure PIM and the brake boost pressure PB when the vehicle is at low altitude and high altitude.

Immediately after the ignition IG is turned on,
At low altitude, the intake pressure PIM (surge tank internal pressure) becomes higher atmospheric pressure PA (1), and at high altitude, the atmospheric pressure PA (1)
Atmospheric pressure PA (2) is slightly lower. At this time, the value K6 of the brake booster pressure PB, which is closer to vacuum (large negative pressure) by ΔPB than the atmospheric pressure PA (1), for example, is maintained. After the engine is started (STAON), the intake pressure PIM becomes a value K7 which is both low and high. The brake boost pressure PB decreases with a slight time delay from the intake pressure PIM (negative pressure increases), and a predetermined value K8 of a value slightly lower (smaller) than the predetermined value K7 of the intake pressure PIM after the engine is started. become.

As shown in the figure, when the throttle opening VTA is opened, the intake pressure PIM approaches the atmospheric pressure in both low and high altitudes, but the brake boost pressure PB becomes a predetermined value by closing the brake booster valve 125. It is almost maintained at K8.

Next, when the throttle is closed,
The intake pressure PIM approaches the vacuum side (predetermined value K7) again in both lowland and highland.

This embodiment compares the intake pressure PIM with the brake internal pressure (brake boost pressure) PB as a condition for entering the automatic engine stop control, and determines the intake pressure PIM.
The automatic stop of the engine is permitted only when the difference between the pressure and the brake booster internal pressure PB becomes smaller than a predetermined value K3.

Intake pressure PIM and brake booster internal pressure PB
The purpose of this comparison is to judge whether a sufficient negative pressure has been secured at the brake booster internal pressure PB to reliably stop the vehicle.

This is because attention is paid to the following circumstances (a) to (e).

(A) As is clear from the characteristics of FIG.
Immediately after the operation of the engine, a predetermined large difference ΔPB between the intake pressure PIM and the brake booster internal pressure PB.
Although (1) or ΔPB (2) exists, during the operation of the engine, the intake pressure PIM approaches a predetermined value K7 (when the throttle is closed), and accordingly, the brake booster internal pressure PB also increases. It decreases to K8 which is close to K7.

(B) When the throttle is opened, the intake pressure rises, but the brake booster internal pressure does not increase suddenly. (The fact that the throttle is open generally means that the brake pedal is not depressed and the brake booster internal pressure is increased.) Negative pressure is not consumed). Therefore, at this time, the difference between the intake pressure PIM and the brake booster internal pressure PB becomes large, although a sufficient negative pressure is secured for the brake booster internal pressure PB.

(C) On the other hand, when the throttle is subsequently closed, the intake pressure PIM decreases again.
And the brake booster internal pressure PB becomes smaller.

(D) The fact that the difference from the intake pressure PIM is small in spite of the fact that the internal pressure of the brake booster is not ensured is due to the fact that the brake pedal is pumped in a state where the throttle is opened. I can't imagine.

(E) The engine can be automatically stopped only when the throttle is fully closed .

In consideration of the above-mentioned circumstances (a) to (e), when the difference between the intake pressure PIM and the brake booster internal pressure PB is small during operation of the engine, a sufficient negative pressure of the brake booster internal pressure PB is ensured. Therefore, it can be said that the engine may be automatically stopped.

The intake pressure (surge tank internal pressure) PIM
And the brake booster internal pressure PB may be compared, for example, by the following equation. PIM-PB ≦ K3 (1) Alternatively, PIM-PB = △ PB and ΔPB ≦ K3 (2). Here , K3 is a predetermined constant. When the intake pressure (surge tank pressure) sensor 115 is not installed, the calculated value PIMC of the intake pressure obtained from the output value from the air flow meter and the engine speed NE is used.
And the comparison result may be obtained from PIMC-PB ≦ K3 (3).

Although the difference has been described as an example, the difference may be obtained from the ratio, for example, PIM / PB ≦ K′3 (4). Here, K'3 is a predetermined constant close to 1. Furthermore, it can also be determined using a map or the like.

As described above, during the operation of the engine, the intake pressure PIM
By comparing the brake booster internal pressure (negative pressure) PB with the brake booster internal pressure (negative pressure), it can be determined that the brake booster internal pressure PB has been reliably ensured, and sufficient brake assist performance can be realized even when the engine stop control is started. become.

Next, the operation after the engine is automatically stopped will be described.

[0073] Returning to Figure 2, after stopping the engine 1 is automatically controller has outputs a control signal for cutting the electromagnetic clutch is in the non-power transmission state and the pulleys and the engine 1. On the other hand, to be air-conditioned and power steering engine 1 even stopped allowed to operate, the power steering pump, as the motor generational motor rotates at a torque load or the like of the air conditioner compressor is considered, the controller may inverter and it outputs a switching signal corresponding for the.

By the way, after the engine is stopped, the pressure in the intake manifold 117 and the pressure in the surge tank 102 become atmospheric pressure or close to atmospheric pressure. That is, in this embodiment, the brake booster valve 125 is closed after the engine automatic stop command to secure and maintain the negative pressure in the brake booster 105 so that the brake can be applied even when the engine 1 is stopped. This is because the negative pressure is reduced gradually over time, or suddenly due to pumping of the brake pedal.

Here, the deviation from the atmospheric pressure will be described again with reference to FIG.
Specifically describes an example of control based on the difference.

When the brake is depressed several times (so-called pumping operation) after the engine is stopped, or as a certain time elapses after the engine is stopped, the pressure (negative pressure) in the brake booster 105 is structurally reduced. Pressure) is no longer maintained, and the negative pressure drops.

If the pressure (negative pressure) in the brake booster 105 is no longer maintained, there arises a problem that the auxiliary performance of the brake naturally decreases.

The present invention detects the brake booster internal pressure PB by the brake boost pressure sensor 107 and the atmospheric pressure PA by the atmospheric pressure sensor 127 after stopping the engine so as not to lower the assist performance of the brake. , The atmospheric pressure PA and the brake booster internal pressure PB
When the difference is smaller than the predetermined value K5, the automatic stop of the engine is stopped.

Here, in this embodiment, the certainty is increased not by merely confirming the brake booster internal pressure PB but by confirming the brake assist function but by observing the difference from the atmospheric pressure PA.

As described above, when the engine stops, the brake booster internal pressure PB goes to the atmospheric pressure, but the atmospheric pressure PA (2) at high altitude is considerably lower than that at low altitude PA (1). Since the brake booster internal pressure PB does not become higher than the atmospheric pressure PA, when the vehicle is running at high altitude, the brake booster internal pressure PB is also detected to be considerably low. However, the brake booster can exhibit its original brake assist function when a "differential pressure" from the atmospheric pressure at that time is secured.

Therefore, in this embodiment, the "differential pressure"
Is detected to confirm the assist function of the brake booster. As a result, qualitatively, the higher the altitude, the more difficult it is to secure the "differential pressure", so that the automatic stop of the engine tends to be stopped easily.

The comparison between the atmospheric pressure PA and the brake booster internal pressure PB may be performed, for example, by the following equation. PA-PB ≦ K5 (5) Alternatively, instead of PA (atmospheric pressure) −PB (brake boost internal pressure) = ΔPB (6), ΔPB ≦ K5 (7) may be used.

When the atmospheric pressure sensor 127 is not installed, the output value from the air flow meter and the calculated atmospheric pressure value PIMC obtained from the engine speed NE are used to obtain PIMC-PB (brake boost pressure). ≦ K5 (8) The comparison result may be obtained. Here, the difference is described as an example. However, similarly to the above, for example, PA / PB ≦ K′5.
It may be obtained from the ratio as in (9).

Since the engine is stopped, the comparison between the atmospheric pressure PA and the brake booster internal pressure PB is based on the comparison between the surge tank 102 internal pressure PIM and the brake booster 105 internal pressure PB.
The comparison with B is synonymous here.

That is, the atmospheric pressure PA in the above equation (5) may be replaced with the surge tank internal pressure PIM.

That is, PIM-PB ≦ K3 (5) ′ or PIM (surge tank internal pressure) −PB (brake boost pressure) = ΔPB ′ (6) ′, and ΔPB ′ ≦ K3 (7) As described above, when the surge tank pressure sensor 115 is not installed, the calculated value PIM
C ′ may be adopted, and the comparison result may be obtained from PIMC′−PB ≦ K3 (8) ′. Similarly, it may be obtained from the ratio of PIM / PB ≦ K′3 (9) ′.

As described above, by detecting the decrease in the internal pressure (negative pressure) of the brake booster during the automatic stop of the engine and stopping the automatic stop control of the engine, a sufficient internal pressure of the brake boost can be secured, and the brake assist performance can be secured. Can be prevented from lowering.

The predetermined value K5 may be set, for example, to a value slightly before the value just before the auxiliary performance of the brake booster for assisting the driver's braking operation decreases.

In addition, the restart of the engine may be, for example, when at least one of the above-mentioned conditions is not satisfied.

Regarding the shift position, in the present embodiment, the eco-run mode is entered when the vehicle is in the non-drive position, and the eco-run mode is terminated when it is detected that the vehicle is in the drive position. The present invention is not limited to this, and may be a system that performs eco-run only at the driving position, or a system that performs eco-run at both the driving position and the non-driving position. The present invention is also applicable to a manual transmission (MT).

Next, the control of this embodiment will be described with reference to the flowchart of FIG.

In FIG. 1, at step 510, the EC
U80, the atmospheric pressure PA from the atmospheric pressure sensor 127,
Brake boost pressure PB from brake boost pressure sensor 107, surge tank internal pressure PIM from surge tank pressure (intake pressure) sensor 115, throttle opening sensor 13
Throttle opening VTA from 0, engine speed NE from engine speed sensor 113, neutral signal from shift position sensor 131, vehicle speed sensor 1
The input of the signal of the vehicle speed Ve and the like from 33 is processed.

At step 520, it is determined whether or not a condition for permitting the automatic engine stop control is satisfied.

The conditions for permitting the automatic engine stop control are as follows:
As described above. If the automatic stop condition of the engine is not satisfied in step 520, the process returns to step 510. If the automatic stop condition is satisfied, the process returns to step 53.
Go to 0.

At step 530, the engine speed N
E is greater than or equal to a predetermined value K1 and the throttle opening degree VTA
Is less than or equal to the predetermined opening K2. Further, after satisfying this condition, the pressure between the surge tank internal pressure (intake pressure) PIM and the brake boost internal pressure PB is compared.

At this time, if the difference between the surge tank internal pressure (intake pressure) PIM and the brake booster internal pressure PB is equal to or smaller than the predetermined value K3 according to the comparison result, the routine proceeds to step 540.

Note that this comparison is made, as described above, by ΔPB
≦ K3, PIMC-PB ≦ K3.

If these conditions are not satisfied in step 530, the process returns to step 510, and if these conditions are satisfied, the process proceeds to step 540.

At step 540, a command for automatically stopping the engine is output to the ECU 80 to enter an automatic stop state of the engine.

At step 550, it is determined whether or not the automatic stop time of the engine has exceeded a predetermined time K4.
At this time, whether or not the engine is automatically stopped may be determined by detecting that the engine speed NE is zero.
The reason why the engine stop time is detected is that it is possible to determine that the pressure (negative pressure) in the brake booster is likely to be low after the predetermined time K4 has elapsed.

After the predetermined time K4 has elapsed, the routine proceeds to step 560, where the atmospheric pressure PA and the pressure PB in the brake booster 105 are compared.

Since the surge tank internal pressure PIM is (approximately) the atmospheric pressure PA when the engine is stopped, the surge tank internal pressure PIM may be compared with the brake booster 105 internal pressure PB.

Also, here, the comparison of PIM-P ≦ K5 can be substituted by ΔPB ≦ K5 and PIMC-P ≦ K5.

As described above, during the automatic stop of the engine, the atmospheric pressure P
A sufficient brake assist function can be reliably ensured by detecting a decrease in the differential pressure between A and the brake booster internal pressure (negative pressure) and stopping the automatic stop control of the engine.

When the engine is restarted, the engine may automatically return, or a start may be requested to the driver by a buzzer (step 570).

[0106]

According to the present invention, a sufficient brake assist function can always be ensured even in a vehicle that automatically stops.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an example of a control flow of control when the engine of a vehicle is stopped according to the present invention.

FIG. 2 shows the intake pressure PIM when the vehicle is in lowland and highland.
Showing the relationship between the pressure and the brake boost pressure PB

FIG. 3 is a diagram showing a state of air flow and pressure in an intake system, an exhaust system, and a brake system of an engine.

FIG. 4 shows an input to an ECU (electronic control device) according to the embodiment .
Diagram showing the relationship between output signals

[Explanation of symbols]

1 ... Engine 2 ... Automatic transmission 102 ... Surger
Link 105, brake booster 107 brake
Boost pressure sensor, 109 ... Throttle valve, 1
15 ... Surge tank pressure sensor, 113 ... Engine rotation
Speed sensor, 117 ... intake manifold, 12
1: Air cleaner, 125: Brake booster valve
127, atmospheric pressure sensor, 129, air flow meter
131, shift position sensor, 130 ...
Rottle opening degree sensor, 133 ... Vehicle speed sensor, 140
... brake sensor, NE ... engine speed.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02D 29/02 F02D 17/00

Claims (2)

(57) [Claims] 1. The method of claim 1, wherein the braking operation of the driver is performed under a negative pressure of the engine.
Equipped with a brake booster that assists using, Slot
When the turtle is fully closedWhen certain engine stop conditions are met
Automatically stop the engine at the same time and restart the specified engine
Restarts the automatically stopped engine when the operating conditions are met.
Automatic stop / restart control system for moving vehicles
hand, Brake booth for detecting the internal pressure of the brake booster
Internal pressure detection means,When the throttle of the engine opens, it rises and the throttle
Intake pressure detection means for detecting intake pressure that decreases when closed
When, With the intake pressure The bracesKibostarPressure to compare with pressure
Means of comparison, EngineDuring operation, the intake pressure and the inside of the brake booster
When the difference from the pressure becomes smaller than the specified value, the engine
Means for permitting the automatic stop.Features
Automatic stop / restart control system for vehicle. 2. The system according to claim 1 , wherein said intake pressure and said intake pressure are controlled during an automatic stop of said engine.
The difference from the brake booster internal pressure is smaller than another predetermined value.
If the engine runs out, stop the automatic stop of the engine
Characterized by further comprising means for restarting the engine
Vehicles of the engine automatic stop and restart control apparatus according to claim 1,.