JP2002195068A - Control device for on-vehicle internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for an on-vehicle internal combustion engine, capable of sufficiently obtaining effect on the improvement of fuel economy caused by the automatic stop of an internal combustion engine during driving. SOLUTION: A brake booster 8 for storing negative pressure being produced in an inlet passage 11 of an engine 2 as brake negative pressure and reducing the full pedal depression force of a brake pedal 7, based on the pressure difference between the brake negative pressure, and the atmospheric pressure is mounted on an automobile 1. The engine 2 is stopped automatically, as one of the conditions that the brake negative pressure reach a value necessary for the normal operation of the brake booster 8 (required value REQ2). The required value REQ2 of the brake negative pressure which is used as the condition of automatic stop of the engine 2 is varied, according to the braking state of the automobile 1, so as to become the optimum value for reconciling the normal operation of the brake booster 8 with the improvement of the fuel economy of the engine 2, independently of the braking state of the automobile 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a vehicle-mounted internal combustion engine.

[0002]

2. Description of the Related Art In recent years, in vehicles equipped with an internal combustion engine, the operation of the internal combustion engine is automatically started when predetermined conditions are satisfied, such as when the vehicle speed is "0 km / h" and there is no possibility of starting. It has been proposed to stop the engine and improve the fuel efficiency of the engine. Also in these cars,
A brake booster that reduces the depressing operation force of the brake pedal is installed as in a general automobile. As the brake booster, it is conceivable to adopt a type that accumulates a negative pressure generated in an intake system of an internal combustion engine as an operating pressure and operates based on the operating pressure.

[0003] However, when such a type of brake booster is employed in a vehicle in which the internal combustion engine automatically stops, one of the conditions for permitting the automatic stop of the internal combustion engine is as follows.
It is also added that the operating pressure has reached a level (required level) necessary for normal operation of the brake booster. This is because when the internal combustion engine is automatically stopped, a negative pressure is not generated in the intake system of the engine and the operating pressure is not accumulated, so that the operating pressure reaches the required level before the engine is automatically stopped. This is because it must be kept.

In order to further improve the fuel efficiency of an internal combustion engine for a vehicle, the automatic stop of the engine is not limited to the time when the vehicle is stopped (when the vehicle speed is "0 km / h"), and the time when the engine is decelerated is reduced. It is preferable to perform this even when the vehicle is not running. As an automobile for automatically stopping the internal combustion engine during running, for example, an automobile described in Japanese Patent Application Laid-Open No. 58-30438 is known. In the vehicle described in the publication, the fuel supply to the internal combustion engine is cut off and automatic stop is performed on condition that the operating pressure for operating the brake booster at the time of deceleration has reached a certain required level. .

As described above, by automatically stopping the internal combustion engine even while the vehicle is running, the fuel efficiency can be further improved. However, while the vehicle is running, for example, the operation of depressing the brake pedal (operation of the brake booster) is performed more frequently than when the vehicle is stopped, and the operating pressure stored in the brake booster tends to change to the atmospheric pressure side. Therefore, when automatically stopping the internal combustion engine during traveling such as deceleration, for example, even when frequent depression of the brake pedal is performed, the internal pressure of the internal combustion engine is ensured so that the operating pressure necessary for operating the brake booster is secured. The required level used as the automatic stop condition must be set to a more vacuum side.

When the internal combustion engine is automatically stopped during running, the operating pressure to be secured before the automatic stop to normally operate the brake booster after the automatic stop is determined by the running state and the operating condition of the brake pedal. For example, it changes within a predetermined range according to the braking situation of the automobile. Therefore,
Regardless of the braking condition of the vehicle during running, if it is intended to surely prevent the operating pressure from being insufficient to normally operate the brake booster after the automatic stop of the internal combustion engine, the automatic stop of the internal combustion engine The required level of the operating pressure used as a condition is set to the level on the most vacuum side within the predetermined range.

[0007]

However, if the required level is set as described above, there is a possibility that an appropriate automatic stop of the internal combustion engine for improving fuel efficiency may not be performed while the vehicle is running. That is, while the vehicle is running, in the braking situation at that time, although the operating pressure has reached a level sufficient to normally operate the brake booster after the automatic stop of the internal combustion engine, the operating pressure is equal to the above-described operating pressure. There is a possibility that the automatic stop of the internal combustion engine is not permitted because the required level set as described above has not been reached. in this case,
The automatic stop of the internal combustion engine is unnecessarily prohibited, and the effect of improving fuel efficiency by the automatic stop of the engine is hardly obtained.

The present invention has been made in view of such circumstances, and has as its object to control a vehicle-mounted internal combustion engine capable of sufficiently obtaining the effect of improving fuel efficiency by automatically stopping the internal combustion engine during running. It is to provide a device.

[0009]

The means for achieving the above object and the effects thereof will be described below. To achieve the above object, according to the first aspect of the present invention, a negative pressure generated in an intake system of an internal combustion engine is accumulated as an operating pressure, and the negative pressure is mounted on a vehicle having a brake booster that is operated based on the operating pressure. In a control device for an on-vehicle internal combustion engine that permits automatic stop of the internal combustion engine while the vehicle is running on condition that the pressure has reached a required level, a variable means for varying the required level in accordance with a braking situation of the vehicle. Equipped.

When the brake pedal is depressed to brake the vehicle while the vehicle is running, the brake booster is activated and the operating pressure changes to the atmospheric pressure.
According to the above configuration, the required level used as the automatic stop condition of the internal combustion engine is changed to an appropriate level by a variable means in accordance with the braking situation of the vehicle that affects the change of the operating pressure to the atmosphere side. be able to. By making the required level of the operating pressure variable in this way, it is possible to prevent the operating pressure from becoming insufficient for normally operating the brake booster after the automatic stop of the internal combustion engine, and to prevent the internal combustion engine from running while the vehicle is running. Thus, the automatic stop of the vehicle can be appropriately executed to sufficiently improve the fuel efficiency.

According to a second aspect of the present invention, in the first aspect of the invention, the variable means increases the required level as the braking condition of the vehicle becomes such that the operating pressure tends to change to the atmospheric pressure side. It was set on the vacuum side.

[0012] According to the above configuration, in order to improve the fuel efficiency by appropriately executing the automatic stop of the internal combustion engine while the vehicle is running while suppressing the shortage of the operating pressure after the automatic stop of the internal combustion engine. The request level can be set appropriately.

According to a third aspect of the present invention, in the second aspect of the present invention, the variable means shifts the required level to the vacuum side as the braking condition of the vehicle becomes a situation where the operation frequency of the brake booster increases. It was set.

As the frequency of operation of the brake booster increases, the operating pressure tends to change to the atmospheric pressure side. However, according to the above-described configuration in which the required level of the operating pressure is set in accordance with the operation frequency of the brake booster, the shortage of the operating pressure after the automatic stop of the internal combustion engine is suppressed while the internal combustion engine is running while the vehicle is running. In order to improve fuel efficiency by properly executing automatic stop,
The required level can be appropriately set.

According to the invention described in claim 4, claim 1 or 2
In the invention described above, the variable means sets the required level to the vacuum side as the braking state of the vehicle becomes a state where the operation amount of the brake booster becomes large.

The larger the operation amount of the brake booster, the more easily the operation pressure changes to the atmospheric pressure side. However, according to the above configuration in which the required level of the operating pressure is set according to the operation amount of the brake booster, the shortage of the operating pressure after the automatic stop of the internal combustion engine is suppressed, and In order to improve the fuel efficiency by appropriately executing the automatic stop, the required level can be appropriately set.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the variable means varies the required level according to a parameter related to a braking condition of the vehicle. And

According to the above configuration, the required level of the operating pressure can be appropriately set according to the parameter related to the braking condition of the vehicle. According to a sixth aspect of the present invention, in the fifth aspect of the invention, the variable means includes:
The required level is made variable according to the vehicle speed.

According to the above configuration, the required level of the operating pressure can be appropriately set according to the vehicle speed which is one of the parameters related to the braking condition of the vehicle.
According to a seventh aspect of the present invention, in the fifth aspect of the invention, the variable means changes the required level in accordance with the acceleration / deceleration of the vehicle.

According to the above configuration, the required level of the operating pressure can be appropriately set according to the acceleration / deceleration of the vehicle, which is one of the parameters related to the braking condition of the vehicle.

According to an eighth aspect of the present invention, in the fifth aspect of the invention, the variable means varies the required level according to a brake operation state of the vehicle. According to the above configuration, the required level of the operating pressure is appropriately adjusted according to at least one of various brake operation states such as a brake operation amount, an operation speed, and an operation acceleration, which are parameters related to the braking state of the vehicle. Can be set to.

According to a ninth aspect of the present invention, in the fifth aspect of the invention, the variable means varies the required level in accordance with a hydraulic pressure state for operating a brake of the vehicle.

According to the above configuration, at least one of various hydraulic states such as a magnitude of a hydraulic pressure for brake operation, an increasing speed of the hydraulic pressure, and an increasing acceleration of the hydraulic pressure, which are parameters related to the braking condition of the vehicle. Thus, the required level of the operating pressure can be set appropriately.

According to the tenth aspect, the first to ninth aspects are provided.
In the invention according to any one of the first to third aspects, when the operating pressure becomes the atmospheric pressure side than the required level during the automatic stop of the internal combustion engine, the operating pressure securing means operating to change the operating pressure to the vacuum side is provided. Further provision.

According to the above configuration, the operating pressure can be easily maintained at the required level.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment in which the present invention is applied to an engine mounted on an automobile will be described below with reference to FIGS.

As shown in FIG. 1, an output shaft 3 of an engine 2 mounted on an automobile 1 is connected to wheels 5 via an automatic transmission 4 and the like, and the rotation of the engine 2 is stopped. Is also connected to a motor 6 for forcibly rotating the motor at the time of starting. Also, the vehicle 1 is provided with a brake pedal 7 provided in the vehicle interior and operated by a driver, a brake booster 8 for reducing a stepping force (stepping force) of the brake pedal 7, and a hydraulically operated device. A brake 9 for decelerating and stopping the automobile 1 is mounted.

The brake booster 8 operates using a negative pressure generated in an intake system of the engine 2. That is, engine 2
During operation of the negative pressure passage 10 from inside the brake booster 8.
Air is drawn into the intake passage 11 on the downstream side of the throttle valve 12 through the intake passage 11, and a negative pressure is accumulated in the brake booster 8 as an operating pressure (brake negative pressure) by the suction of the air. When the brake pedal 7 is depressed, the brake booster 8 is operated based on the pressure difference between the atmospheric pressure and the brake negative pressure, and the depressing operation force (depressing force) of the brake pedal 7 is reduced. The brake pedal 7
When the brake booster 8 is operated based on the stepping-on operation, the brake negative pressure stored in the brake booster 8 changes to the atmospheric pressure side.

The brake pedal 7 is connected to a master cylinder 13 for changing a hydraulic pressure for operating the brake 9 in accordance with the depression force of the pedal 7. When the hydraulic pressure changes by the master cylinder 13 in response to the depression operation of the brake pedal 7, the change in the hydraulic pressure is transmitted to the brake 9 through the hydraulic circuit 14. Based on the transmission of the hydraulic pressure, the brake 9 operates to decelerate and stop the vehicle 1.

The vehicle 1 has an electronic control unit (ECU) for controlling the driving of the engine 2 and the motor 6.
15 are mounted. The electronic control unit 15 includes a vacuum sensor 16 for detecting the pressure of the intake passage 11 on the downstream side of the throttle valve 12, and a brake pedal 7.
Sensor 17 for detecting the amount of depression of the brake pedal, negative pressure sensor 18 for detecting the negative pressure of the brake stored in the brake booster 8, hydraulic pressure sensor 19 for detecting the hydraulic pressure in the master cylinder 13, and used for calculating the vehicle speed Wheel speed sensor 2 that outputs a signal corresponding to the rotation of wheel 5 as a signal
0 etc. are connected.

The electronic control unit 15 controls the engine 2 according to the running state of the automobile 1 in order to improve the fuel efficiency of the engine 2.
To stop and restart automatically. That is, when an automatic stop condition of the engine 2 is satisfied, for example, when the vehicle speed is lower than a predetermined value and the brake pedal 7 is depressed and the possibility of self-propelling of the automobile 1 is lost, the fuel injection and ignition are stopped by the electronic control unit 15, The engine 2 is automatically stopped.

During the automatic stop of the engine 2,
When the automatic start condition of the engine 2 is satisfied, such as when the depression of the brake pedal 7 is released and the possibility of the vehicle 1 self-propelling occurs, the electronic control unit 15 starts fuel injection and ignition, and the engine 2 is restarted. . When the rotation of the engine 2 is stopped at the start of such restart, the drive of the motor 6 is controlled by the electronic control unit 15 in order to forcibly rotate the engine 2, and in this state, fuel injection and ignition are started. Will be performed.

The above-described automatic stop of the engine 2 is not limited to when the vehicle 1 is stopped (when the vehicle speed is "0 km / h"). This is also performed during running, thereby further improving the fuel efficiency of the engine 2. However, when the vehicle 1 is running, for example, the operation of depressing the brake pedal 7 is performed more frequently than when the vehicle 1 is stopped, and the brake negative pressure tends to change to the atmospheric pressure side.

Here, how the brake booster 8 and the brake 9 are affected by the change of the brake negative pressure to the atmospheric pressure side will be described with reference to FIG. FIG. 4 is a graph showing a transition of the hydraulic pressure of the master cylinder 13 (the hydraulic pressure for operating the brake 9) when the depression force of the brake pedal 7 changes.

The hydraulic pressure of the master cylinder 13 is set such that when the depression force of the brake pedal 7 is within the regions A and B in FIG.
As the pedaling force increases, the force gradually increases as shown by solid lines L1 and L2. The inclination of the solid lines L1 and L2, that is, the increase of the hydraulic pressure of the master cylinder 13 with respect to the increase of the depression force of the brake pedal 7 is more significant when the pedaling force is in the region B (solid line L1) than in the region A (solid line L1).
2) is smaller. This is because when the depression force of the brake pedal 7 is in the region B, the brake booster 8 does not assist the depression of the brake pedal 7 and the increase in the hydraulic pressure of the master cylinder 13 with respect to the increase in the depression force is reduced.

Therefore, in order to normally operate the brake 9 efficiently when the brake pedal 7 is depressed, the brake booster 8 and the like are set so that the practical range of the depression force of the brake pedal 7 exists in the area A. However, when the booster negative pressure changes to the atmosphere side, the solid line L2
Is gradually shifted to the low pressure side (lower side in the figure) as indicated by the two-dot chain lines L3 and L4. As a result, the upper limit of the region A and the lower limit of the region B shift to the side where the pedaling force decreases (the left side in the figure), the region A where the brake booster 8 operates normally becomes narrower, and the region where the brake booster 8 does not operate normally. B becomes wider.

When the brake negative pressure changes to the atmospheric pressure side, the area A becomes narrower, and when the practical range of the treading force extends from the area A to the treading force increasing side (right side in the figure), the brake negative pressure is reduced by the brake booster 8. Becomes less than the value (required value) necessary for the normal operation of. In this state, the transition from the area A to the area B occurs when the depression force of the brake pedal 7 increases, and the brake booster 8 does not operate during the transition. , The amount of change in the hydraulic pressure of the master cylinder 13 varies. Then, the brake 9
As a result, the braking force of the automobile 1 fluctuates, which adversely affects the operability of the brake 9 (the brake pedal 7).

As described above, the fact that the brake booster 8 does not operate normally due to the lack of the brake negative pressure means that after the engine 2 is automatically stopped while the automobile 1 is running, the brake negative pressure is applied to the brake pedal 7. May occur when changing to the atmospheric pressure side based on the Therefore, when the engine 2 is automatically stopped while the vehicle 1 is running, the required brake negative pressure is secured before the automatic stop of the engine 2, so that the brake load is reduced in accordance with the depressing operation of the brake pedal 7 after the automatic stop. It is ensured that the pressure is not insufficient for the brake booster 8 to operate normally.

In order to ensure the necessary brake negative pressure before the automatic stop, one of the conditions for automatically stopping the engine 2 is to set the brake negative pressure after the automatic stop of the engine 2 while the vehicle 1 is running. The condition that the value (required value) necessary for normally operating the brake booster 8 has been added is also added. By adding the above condition to one of the automatic stop conditions of the engine 2, the necessary brake negative pressure is accurately secured before the automatic stop, and the brake pedal 7 is depressed during traveling after the automatic stop. As a result, the brake negative pressure does not become insufficient.

By the way, while the automobile 1 is running, the engine 2
In order to operate the brake booster 8 normally, the brake negative pressure to be ensured before the automatic stop of the engine 2 depends on the braking condition of the automobile 1 such as the running condition and the operation condition of the brake pedal 7. It will be different depending on. Therefore, in the present embodiment, the required value of the brake negative pressure used as the condition for automatically stopping the engine 2 is made variable in accordance with the braking situation of the vehicle 1. Thus, after the automatic stop of the engine 2, the brake booster 8
In order to sufficiently obtain the effect of improving the fuel efficiency by automatically stopping the engine 2 during running while operating normally, the required value is set to an appropriate value irrespective of the braking condition of the automobile 1.

Next, a procedure for automatically stopping and restarting the engine 2 will be described with reference to the flowcharts of FIGS. 2 and 3 showing an engine automatic stop and restart routine. The engine automatic stop / restart routine is periodically executed by the electronic control unit 15 at, for example, a time interruption every predetermined time.

In the processing of steps S102 to S106 (FIG. 2) of the processing of the engine automatic stop / restart routine, the engine 2 is automatically stopped, and step S107 is performed.
In the processing of S111 (FIG. 3), the engine 2 is restarted.

In performing these various processes, it is first determined whether or not the engine 2 is operating (S in FIG. 2).
101). When an affirmative determination is made in step S101, whether or not the brake 9 is operated (brake-on) (S102) and whether or not the vehicle speed is less than a predetermined value a (S102)
Based on the determination of 103), it is determined whether or not the automobile 1 has a possibility of self-propelling. These steps S1
When the affirmative determination is made in both 02 and S103 and it is determined that there is no possibility of self-propelling of the automobile 1, the required value RE of the brake negative pressure used as one of the conditions for automatically stopping the engine 2 is given.
Q2 is calculated (S104).

The required value REQ2 is calculated based on the braking state of the vehicle 1 such as the running state of the vehicle 1 and the operation state of the brake pedal 7, and the atmospheric pressure. Thus, the required value R
The reason why the atmospheric pressure is used for the calculation of EQ2 is that the brake booster 8 is operated based on the differential pressure between the atmospheric pressure and the brake negative pressure. Because it changes. Note that, as the atmospheric pressure, an intake pressure determined based on a detection signal from the vacuum sensor 16 before the engine 2 is started can be used.

On the other hand, the running state of the vehicle 1 is represented by parameters related to the braking state of the vehicle 1, such as vehicle speed and acceleration / deceleration. The operation state of the brake pedal 7 is related to, for example, a braking state of the vehicle 1 such as a stepping amount, a stepping speed, and a stepping acceleration of the brake pedal 7, and a hydraulic pressure, a hydraulic pressure increasing speed, and a hydraulic pressure increasing acceleration of the master cylinder 13. Represented by parameters.

As a method of calculating the required value REQ2, for example, [1] the required value of the brake negative pressure required to normally operate the brake booster 8 after the automatic stop of the engine 2 is calculated as follows:
[2] Select the most required value from the plurality of required values obtained according to the above parameters [2] Select the required value selected as the most vacuum value from the atmospheric pressure And the corrected required value is calculated as the required value REQ2.
It is conceivable to adopt a method such as using.

Here, the required values obtained for each of the plurality of parameters in the above [1] will be described with reference to FIGS. FIG. 5 is a graph showing a transition of a request value (vehicle speed request value) obtained according to the vehicle speed. As shown by the solid line in the figure, the required vehicle speed gradually becomes a value on the vacuum side as the vehicle speed increases. This is because, as the vehicle speed increases, the amount and frequency of depression of the brake pedal 7 (operation frequency and amount of operation of the brake booster 8) are likely to increase, and the brake negative pressure increases based on the depression of the brake pedal 7. This is because it tends to change to the atmospheric pressure side.

FIG. 6 is a graph showing the transition of the required value (acceleration / deceleration request value) obtained according to the acceleration / deceleration. The acceleration / deceleration request value gradually becomes a value on the vacuum side as the deceleration or acceleration increases, as indicated by a solid line in the drawing. It is highly likely that the greater the deceleration, the greater the amount of depression of the brake pedal 7 (the amount of operation of the brake booster 8). This is because it is easy to change. Further, as a situation where the acceleration is large, there is a case where the vehicle is running on a steep downhill by inertia. At this time, when the brake pedal 7 is depressed, there is a high possibility that the depression amount is increased. For this reason, the acceleration / deceleration request value is set to the value on the vacuum side as the acceleration increases as described above so that the brake negative pressure does not excessively become the value on the atmospheric pressure side when stepping on.

FIG. 7 is a graph showing the transition of the required value (stepping request value) obtained according to the stepping amount, stepping speed, and stepping acceleration of the brake pedal. The stepping demand value is, as shown by the solid line in the figure, the stepping amount of the brake pedal 7,
The values on the vacuum side increase as the stepping speed and the stepping acceleration increase. This corresponds to the amount of depression of the brake pedal 7, the depression speed,
Also, as the stepping acceleration increases, the operation amount of the brake booster 8 increases, and the brake negative pressure easily changes to the atmospheric pressure side.

FIG. 8 is a graph showing the transition of the required value (hydraulic required value) obtained according to the hydraulic pressure of the master cylinder 13, the hydraulic pressure increasing speed, and the hydraulic pressure increasing acceleration. As shown by a solid line in the figure, the required oil pressure value becomes a value on the vacuum side as the oil pressure of the master cylinder 13, the oil pressure increasing speed, and the oil pressure increasing acceleration increase. This means that the greater the hydraulic pressure of the master cylinder 13, the hydraulic pressure increase speed, and the hydraulic pressure increase acceleration, the greater the depression amount, the depression speed, and the depression acceleration of the brake pedal 7, and the brake load is reduced based on the depression of the brake pedal 7. This is because the pressure tends to change to the atmospheric pressure side.

Of the vehicle speed request value, acceleration / deceleration request value, stepping request value, and oil pressure request value that change according to each parameter as described above, the one with the most vacuum side is selected in the above [2], and the request value REQ2 Is used to calculate Therefore, the required value REQ2 is determined by the running state of the automobile 1 and the brake pedal 7
As the braking state of the automobile 1 is such a state that the brake negative pressure tends to change to the atmospheric pressure side, such as the operation state of, the value on the vacuum side is set to the value on the vacuum side.

After the required value REQ2 is calculated, it is determined whether the brake negative pressure BP obtained based on the detection signal from the negative pressure sensor 18 is a value on the vacuum side of the required value REQ2 (S105). . And if it is an affirmative decision,
It is determined that the brake negative pressure BP has reached the required level, and the engine 2 is automatically stopped by stopping fuel injection and ignition (S106). On the other hand, when a negative determination is made in the process of step S105 and it is determined that the brake negative pressure BP has not reached the required level, the automatic stop of the engine 2 is not performed. Therefore, such automatic stop of the engine 2 is permitted on condition that the brake negative pressure BP has reached the required level.

On the other hand, if a negative determination is made in the process of step S101, it is determined whether or not the engine 2 is automatically stopped (S107 in FIG. 3). Then, when an affirmative determination is made, it is determined whether or not the vehicle 1 is in a state in which there is no possibility of self-propelling based on whether or not the brake pedal 7 is depressed (S108). When an affirmative determination is made in this determination, a required value REQ1 of the brake negative pressure used as an automatic start condition of the engine 2 is calculated (S109).

The required value REQ1 is also the same as the required value R
Similarly to the EQ2, it is calculated based on the braking state of the vehicle 1 such as the running state of the vehicle 1 and the operation state of the brake pedal 7, and the atmospheric pressure. As a method of calculating the required value REQ1, for example, it is conceivable to employ the methods shown in the above [1] to [3] as in the case of the required value REQ2. However, the required values of the brake negative pressure required for each parameter related to the braking situation of the vehicle 1, that is, the required vehicle speed, the required acceleration / deceleration, the required stepping value, and the required hydraulic pressure are:
Even if the above parameters are the same as those obtained in the processing of step S104 (FIG. 2), they take different values.

Here, the transition trends of the vehicle speed request value, the acceleration / deceleration request value, the stepping request value, and the hydraulic pressure request value obtained in the process of step S109 are shown by broken lines in FIGS. As is clear from these figures, each required value (broken line) for calculating the required value REQ1 has a similar transition tendency to each required value (solid line) for calculating the required value REQ2. However, it becomes a value on the atmospheric pressure side from each of the required values (solid line). Accordingly, the request value REQ1 calculated based on the above-mentioned request values (broken lines) and the like also becomes a value on the atmospheric pressure side by a predetermined amount compared to the request value REQ1.

After the required value REQ1 has been calculated, it is determined whether or not the brake negative pressure BP obtained based on the detection signal from the negative pressure sensor 18 is a value on the atmospheric pressure side from the required value REQ1 (see FIG. 4). S110). If the determination is affirmative, it is determined that the brake negative pressure BP has not reached the required level, and the engine 2 is restarted by starting fuel injection and ignition (S111). On the other hand, step S11
0, a negative determination is made, and if it is determined that the brake negative pressure BP has reached the required level, the engine 2
Is not restarted (automatic start). Therefore,
Such automatic start of the engine 2 is permitted on condition that the brake negative pressure BP does not satisfy the required level.

According to the embodiment described in detail above, the following effects can be obtained. (1) The required value REQ2 of the brake negative pressure used as the condition for automatically stopping the engine 2 is to improve the fuel efficiency by automatically stopping the engine 2 during running while operating the brake booster 8 normally after the engine 2 is automatically stopped. The value is changed according to the braking condition of the vehicle 1 so that the optimal value is obtained in order to obtain a sufficient effect. That is, the more the braking condition of the automobile 1 becomes a situation where the negative pressure of the brake tends to change to the atmospheric pressure side, that is, the more the running state or the brake operation state becomes the situation where the operation frequency and the operation amount of the brake booster 8 become large, The request value REQ2 is set to a value on the vacuum side. By making the request value REQ2 variable, the engine 2
After the automatic stop, the brake negative pressure required before the automatic stop can be secured so that the brake negative pressure does not become insufficient for the brake booster 8 to operate normally based on the depression operation of the brake pedal 7. Also, the brake negative pressure B
When P becomes a value on the vacuum side of the required value REQ2, the automatic stop of the engine 2 is appropriately executed during the running of the automobile 1, and the effect of improving the fuel efficiency of the engine 2 by the automatic stop can be sufficiently obtained. become able to.

(2) The required value REQ2 represents the braking condition of the automobile 1, that is, the vehicle speed, acceleration / deceleration, amount of depression of the brake pedal 7, stepping speed, stepping acceleration, oil pressure of the master cylinder 13, oil pressure increasing speed, oil pressure increasing acceleration. Is calculated based on various parameters such as That is, among the required values of the brake negative pressure (vehicle speed required value, acceleration / deceleration required value, stepping required value, hydraulic pressure required value) obtained for each of the plurality of parameters according to each of these parameters, the required value on the vacuum side is the largest. The result of the atmospheric pressure correction is set as the required value REQ2. Therefore, it is possible to appropriately set the required value REQ2 according to each of the above parameters.

(3) If the brake negative pressure becomes a value on the atmospheric pressure side from the required value REQ1 during the automatic stop of the engine 2, the automatic start condition is satisfied and the engine 2 is restarted. As a result, the required brake negative pressure is secured by changing the brake negative pressure to the vacuum side, so that the brake negative pressure can be easily maintained at the required level.

(4) The required value REQ1 used as the automatic stop condition and the required value R used as the automatic start condition
EQ1 is calculated such that a predetermined amount of difference is generated between them even under the condition that the above parameters are the same. Therefore, immediately after the brake negative pressure reaches the required value REQ2 and the engine 2 automatically stops, the brake negative pressure
It can be suppressed that the engine 2 is automatically started by changing to the atmospheric pressure side from Q1. Then, it is possible to suppress the deterioration of the fuel efficiency of the engine 2 due to the automatic start immediately after the automatic stop, for example, due to the fuel injection amount being increased at the start.

The present embodiment can be modified, for example, as follows. In the present embodiment, when the negative pressure of the brake falls below the required level (required value REQ1) during the automatic stop of the engine 2, the negative pressure of the brake is secured by automatically restarting the engine 2. However, the present invention is not limited to this. For example, the engine 6 may be forcibly rotated by the motor 6 instead of being restarted to operate independently, thereby generating a negative pressure in the intake passage 11 to secure the brake negative pressure. Further, only when the brake negative pressure becomes insufficient during the automatic stop of the engine 2, air is sucked from the brake booster 8 by using a drive source other than the engine 2 such as a vacuum pump, thereby securing the brake negative pressure. Is also good. Further, a vacuum tank for accumulating and holding a negative pressure during operation of the engine 2 is provided, and when the brake negative pressure is insufficient during the automatic stop of the engine 2, the vacuum tank and the brake booster 8 are communicated with each other. Alternatively, air may be sucked from the vacuum tank to the vacuum tank to secure the brake negative pressure.

When calculating the required values REQ1 and REQ2, the vehicle speed, acceleration / deceleration, the amount of depression of the brake pedal 7, the depression speed, the depression acceleration, the hydraulic pressure of the master cylinder 13, and the hydraulic pressure It is not always necessary to use all of the increase amount and the hydraulic pressure increase acceleration.

In the embodiment of the present invention, the request values REQ1, R
Although the method shown in the above [1] to [3] is adopted as a method for calculating EQ2, the request values REQ1 and REQ2 may be calculated using other methods.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an entire vehicle on which an engine to which a control device according to an embodiment is applied is mounted.

FIG. 2 is a flowchart showing a procedure for automatically stopping and restarting the engine.

FIG. 3 is a flowchart showing a procedure for automatically stopping and restarting the engine.

FIG. 4 is a graph showing a transition tendency of a hydraulic pressure of a master cylinder with respect to a change in a depression force of a brake pedal.

FIG. 5 is a graph showing a transition trend of a required value of a brake negative pressure (a required vehicle speed) with respect to a change in a vehicle speed.

FIG. 6 is a graph showing a transition trend of a required value of a brake negative pressure (acceleration / deceleration request value) with respect to a change in the acceleration / deceleration of the vehicle.

FIG. 7 is a graph showing a transition tendency of a required value of a brake negative pressure (stepping request value) with respect to a change in a stepping amount, a stepping speed, and a stepping acceleration of a brake pedal.

FIG. 8 is a graph showing a transition trend of a required value of a brake negative pressure (a required hydraulic pressure value) with respect to a change in a hydraulic pressure of the master cylinder, a hydraulic pressure increasing speed, and a hydraulic pressure increasing acceleration.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Car, 2 ... Engine, 6 ... Motor, 7 ... Brake pedal, 8 ... Brake booster, 9 ... Brake, 10 ...
Negative pressure passage, 12: throttle valve, 13: master cylinder, 15: electronic control unit, 16: vacuum sensor, 17: brake sensor, 18: negative pressure sensor, 19 ...
Hydraulic pressure sensor, 20: Wheel speed sensor.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Morihiro Matsuda 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Takahiro Shiraki 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation ( 72) Inventor Kazunori Oda 1 Toyota Town, Toyota City, Aichi Prefecture F-term in Toyota Motor Corporation (Reference) 3D049 BB42 HH08 HH42 HH47 KK07 RR01 RR04 RR13 3G093 AA05 BA22 DA03 DA13 DB05 DB15 EA00 EB04 EC05 FA10 FA11

Claims (10)

[Claims] The present invention is characterized in that a negative pressure generated in an intake system of an internal combustion engine is accumulated as an operating pressure, and is mounted on a vehicle having a brake booster that is operated based on the operating pressure, and that the operating pressure has reached a required level. A control device for a vehicle-mounted internal combustion engine that permits automatic stop of the internal combustion engine while the vehicle is running in a condition, comprising: a variable unit that changes the required level according to a braking situation of the vehicle. Control device. 2. The on-vehicle internal combustion engine according to claim 1, wherein the variable means sets the required level to a vacuum side as the braking state of the vehicle becomes such that the operating pressure tends to change to the atmospheric pressure side. Control device. 3. The control device for a vehicle-mounted internal combustion engine according to claim 2, wherein said variable means sets said required level to a vacuum side as the braking condition of said vehicle becomes a condition in which the operation frequency of said brake booster increases. 4. The control of an on-vehicle internal combustion engine according to claim 1, wherein said variable means sets said required level to a vacuum side as the braking state of said vehicle becomes a state where the operation amount of said brake booster becomes large. apparatus. 5. The control device for a vehicle-mounted internal combustion engine according to claim 1, wherein said variable means varies said required level in accordance with a parameter relating to a braking condition of said vehicle. 6. The control device for an on-vehicle internal combustion engine according to claim 5, wherein said variable means changes said required level according to a vehicle speed. 7. The control device for an on-vehicle internal combustion engine according to claim 5, wherein said variable means changes said required level in accordance with acceleration / deceleration of said vehicle. 8. The control device for an on-vehicle internal combustion engine according to claim 5, wherein said variable means changes said required level in accordance with a brake operation state of said vehicle. 9. The control device for an on-vehicle internal combustion engine according to claim 5, wherein said variable means varies said required level in accordance with a hydraulic pressure state for operating a brake of said vehicle. 10. The control device for a vehicle-mounted internal combustion engine according to claim 1, wherein, when the internal combustion engine is automatically stopped, when the operating pressure is on the atmospheric pressure side from the required level. A control device for a vehicle-mounted internal combustion engine, further comprising an operating pressure securing means that operates to change the pressure to a vacuum side.