JP3003528B2 - Negative pressure control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative pressure control device for supplying a negative pressure to a brake booster, and more particularly to a negative pressure control for an internal combustion engine in which steady operation is performed in a state where an intake pipe pressure is close to an atmospheric pressure. Related to the device.

[0002]

2. Description of the Related Art In recent years, there are many vehicles equipped with a brake booster to reduce the depressing force of a brake pedal.
Generally, a negative pressure generated in an intake pipe downstream of a throttle valve is used as a power source of a brake booster.
That is, the negative pressure is guided to the brake booster via the pressure guiding pipe branched from the throttle valve downstream, and the negative pressure corresponding to the amount of depression of the brake pedal is applied to the diaphragm built in the brake booster, thereby increasing the brake operating force. .

However, in an internal combustion engine, such as a diesel engine, in which the amount of intake air is hardly controlled during operation, a negative pressure is hardly generated downstream of the throttle valve. Therefore, a vacuum pump for generating a negative pressure is installed and a negative pressure is applied to the brake booster. Some supply pressure. If the vacuum pump that generates a negative pressure becomes abnormal, a negative pressure supply device that closes a small amount of the throttle valve to generate a negative pressure downstream of the throttle valve and supplies the negative pressure to the brake booster is proposed. (See Japanese Patent Application Laid-Open No. 61-21831).

[0004]

However, the installation of the vacuum pump increases the load on the internal combustion engine, so that not only fuel efficiency is deteriorated but also an economical problem is caused. Furthermore, in order to improve the properties of exhaust gas in the low-speed, low-load range, which has been put into practical use in recent years, so-called stratification, in which a mixed gas having a stoichiometric air-fuel ratio is supplied only to the vicinity of the ignition plug in the cylinder and only air is supplied to other parts In the internal combustion engine, even in a steady operation state, since the throttle valve is almost fully opened, almost no negative pressure is generated in the intake pipe, so that a sufficient negative pressure cannot be supplied to the brake booster.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and provides a brake booster which does not increase the load on the internal combustion engine without increasing the load on the internal combustion engine even when the internal combustion engine is operated in a steady state with the intake pipe pressure close to the atmospheric pressure. An object of the present invention is to provide a negative pressure control device for an internal combustion engine capable of supplying a negative pressure.

[0006]

A negative pressure control device for an internal combustion engine according to a first aspect of the present invention is a brake booster for increasing a braking force by introducing a negative pressure from an intake pipe downstream of a throttle valve of an internal combustion engine performing stratified charge combustion. A pressure detecting means for detecting a pressure acting on the brake booster; and a throttle valve is closed by a predetermined amount when it is determined that the negative pressure is insufficient for the function of the brake booster based on the detection result of the pressure detecting means. When it is determined that the negative pressure is insufficient for the function of the brake booster based on the detection results of the throttle valve closing means and the pressure detecting means, the combustion method is switched from stratified combustion to homogeneous combustion. Means.

A negative pressure control device for an internal combustion engine according to a second aspect of the present invention acts on a brake booster for introducing a negative pressure from an intake pipe downstream of a throttle valve of a stratified combustion engine to increase a braking force, and a brake booster. Pressure detecting means for detecting the pressure to be applied, brake operation detecting means for detecting that the brake has been operated, and based on the detection result of the pressure detecting means when the brake operation detecting means detects that the brake has been operated. When it is determined that the negative pressure is insufficient for the function of the brake booster, it is detected that the brake has been operated by the throttle valve closing means for closing the throttle valve by a predetermined amount and the brake operation detecting means. When it is determined that the negative pressure is insufficient for the function of the brake booster based on the detection result of the pressure detecting means, the combustion system is activated. Comprising a combustion mode switching means for switching to the homogeneous combustion from the combustion, the.

[0008] The negative pressure control device for an internal combustion engine according to the third invention further includes a negative pressure storage tank installed between the brake booster and the intake pipe.

[0009]

In the negative pressure control device for an internal combustion engine according to the first invention, when the pressure for operating the brake booster approaches the atmospheric pressure, the negative pressure is applied to the surge tank by closing the throttle valve. Is generated, the function of the brake booster is ensured, and when the throttle valve is closed during execution of the combustion injection in the stratified injection mode during the medium-low load operation, the mode is switched to the uniform injection mode. In the negative pressure control device for an internal combustion engine according to the second invention, when the brake is operated and the pressure for operating the brake booster becomes close to the atmospheric pressure, the throttle valve is closed to open the surge tank. When the negative pressure is generated and the function of the brake booster is ensured, and when the throttle valve is closed during execution of the combustion injection in the stratified injection mode during the middle-low load operation, the mode is switched to the uniform injection mode.

[0010] In the negative pressure control device for an internal combustion engine according to the third aspect of the present invention, the negative pressure is stored in a negative pressure storage tank provided between the surge tank and the brake booster, and the opportunity to close the throttle valve is reduced. Decrease.

[0011]

FIG. 1 is a block diagram of an embodiment of a negative pressure control device for an internal combustion engine according to the present invention. An internal combustion engine 10 is a so-called stratified combustion internal combustion engine. That is, the internal combustion engine is
And a stratified fuel injection valve 13 that injects fuel directly into the cylinder for stratified combustion.

Surge tank 14 to which intake pipe 11 is connected
Is supplied with intake air through a throttle valve 15.
The depressing force of the brake pedal 16 is the brake booster 1
The pressure is amplified by the motor 7 and converted into a hydraulic pressure to drive a brake actuator (not shown) of each wheel. In order to use the negative pressure generated in the surge tank 14 as the driving force of the brake booster 17, the brake booster 17 and the surge tank 14 are connected by a connection pipe 18.

The control unit 19 is constituted by a microcomputer and has a pressure sensor 181 attached to the connection pipe 18.
In type brake booster operating pressure P _B detected,
A throttle valve opening command and a fuel injection command to the uniform combustion fuel injection valve 12 and the stratified combustion fuel injection valve 13 are output to the throttle valve actuator 151. The throttle valve actuator 151 and the throttle valve 15 are mechanically linked, and the throttle valve 15 is controlled to an opening according to a throttle valve opening command.

FIG. 2 is a flowchart of a first negative pressure generation routine executed by the control unit 19, which is executed as an interruption process at regular time intervals as a part of a main routine. In step 201, it calculates a reference throttle valve opening THR _B determined in accordance with the operating state of the internal combustion engine.

In step 202, the intake air amount Q and
Internal combustion engine speed N_eOpening time of the fuel injector as a function of
Calculate τ. In step 203, the valve opening time τ
Throttle valve closing correction execution determination time τ _MOr not
Is determined. Note that τ_MIs a fixed value. Step 2
If the determination is affirmative in step 03, the slot is
It is assumed that stable combustion is possible even when the
Proceeding to step 204, the brake booster operating pressure P_BTo
Read. In the following description, pressure is expressed as absolute pressure.
Have been.

In step 205, it is determined whether or not the throttle valve closing execution flag XFLAG is set, that is, whether or not the throttle valve closing correction has already been executed. If a negative determination is made in step 205, that is, if the throttle valve closing correction has not been executed, the routine proceeds to step 206, where the brake booster operating pressure P
_B is equal to or throttle valve closing correction execution determination pressure P _H or more.

If an affirmative determination is made in step 206, it is determined that sufficient negative pressure has not been accumulated for the function of the brake booster, and the flow proceeds to step 207. In step 207, the throttle valve closing execution flag X
After setting the FLAG, determining the corrected throttle valve opening DTHR as a function of the valve opening time τ of the engine speed N _e and the fuel injection valve the flow proceeds to step 208.

That is, the corrected throttle valve opening DT is calculated by the following equation.
Determine HR. _{DTHR = DTHR (N e, τ} ) Fig. 3 is a map for determining a correction throttle valve opening DTHR, the horizontal axis represents engine speed N _e, the vertical axis represents correction throttle valve opening DTHR, the parameters Represents the valve opening time τ of the fuel injection valve.

[0019] In step 209, calculates a throttle valve opening command THR is subtracted the reference throttle valve opening THR _B and corrected throttle valve opening DTHR. If the determination is positive at step 205, i.e., the process proceeds to step 210 if the throttle valve closing correction has already been performed, whether or not the brake booster operating pressure P _B is below the throttle valve closing correction cancel determining pressure P _L Is determined.

Note that the throttle valve closing correction release determination pressure P
_L is defined as the throttle valve closing correction execution determination pressure P _H is less than the pressure. If an affirmative determination is made in step 210, it is determined that a sufficient negative pressure has been accumulated for the function of the brake booster, and the routine proceeds to step 211, where the throttle valve closing execution flag XFLAG is reset, and the routine proceeds to step 212.

In step 212, the reference throttle valve opening THR _B is set as a throttle valve opening command THR. If a negative determination is made in step 206, that is, if there is a negative pressure necessary for the function of the brake booster, it is determined that there is no need to execute the throttle valve closing correction, and the process proceeds to step 212.

Further, if a negative determination is made in step 210, that is, if the negative pressure for the function of the brake booster is not sufficiently accumulated, the process proceeds to step 208 to execute the throttle valve closing correction. Step 20
Step 213 is executed following Step 9 or Step 212, the throttle valve opening command THR is output, and this routine ends.

That is, according to the negative pressure control device for an internal combustion engine of the present invention, when the negative pressure acting on the brake booster is not sufficient, the throttle valve is closed to generate a negative pressure regardless of the operating condition of the vehicle. . However, closing the throttle valve affects the combustion state because the amount of intake air decreases, so it is desirable to minimize the chance of closing the throttle valve.

A negative pressure control device for an internal combustion engine according to the present invention solves the above-mentioned problem, and a brake switch 161 indicating that the brake pedal 16 has been operated is added to the first embodiment. FIG. 4 is a flowchart of a second negative pressure generation routine, which is executed as an interruption process at regular time intervals.

In step 401, the reference throttle valve opening THR _B determined according to the operating state of the internal combustion engine
Is calculated. In step 402, it is determined whether or not a predetermined time α has elapsed after the start of the internal combustion engine, that is, after the internal combustion engine has become independent. When an affirmative determination is made in step 402, that is, when the predetermined time α has elapsed after the internal combustion engine has become independent, the routine proceeds to step 403, where the throttle valve closing execution flag XFL
Whether AG is reset, i.e. already determined whether non-execution state throttle valve closed correction.

When an affirmative determination is made in step 403, the process proceeds to step 404, in which it is determined whether the brake operation flag XBRK indicating the state of the brake switch 161 is in a set state indicating that the brake is operating.
If an affirmative determination is made in step 404, the process proceeds to step 405, where a brake counter CBK indicating the brake operation time is incremented.

Next, at step 406, the brake counter C
It is determined whether BK is equal to or greater than a predetermined determination value CBK ₀ . If an affirmative determination is made in step 406, that is, if the brake has been continuously operated for a predetermined time or more, in step 407, the throttle valve closing execution flag XF
The LAG is set and the process proceeds to step 408.

In step 408, the internal combustion engine speed N
_The corrected throttle valve opening DTHR is obtained as a function of _e . That is, the corrected throttle valve opening DTHR is determined by the following equation. DTHR = DTHR (N _e) FIG. 5 is a map for determining a correction throttle valve opening DTHR, the horizontal axis represents the engine speed N _e, the vertical axis represents the corrected throttle valve opening DTHR,.

[0029] by subtracting the a reference throttle valve opening THR _B and corrected throttle valve opening DTHR in step 409 calculates the throttle valve opening command THR. If a negative determination is made in step 404, that is, if the brake is not operated, the process proceeds to step 410, where the brake counter CBK is reset. Next, as there is no need to generate a negative pressure by closing the throttle valve when the brake is not operated, the reference throttle opening THR _B the throttle valve opening command THR at step 411.

If a negative determination is made in step 406, that is, if the brake has not been continuously operated for a predetermined time or more, it is determined that there is no need to close the throttle valve 15 to generate a negative pressure, and the process proceeds to step 411. move on. If a negative determination is made in step 402, that is, if the predetermined time α has not elapsed since the start of the internal combustion engine, step 41 is performed to secure an initial negative pressure regardless of the brake operation.
Proceed to 2.

Further, if a negative determination is made in step 403, that is, if the throttle valve closing correction is not performed, the process also proceeds to step 412. Brake booster operating pressure P _B in step 412 is equal to or less than the throttle valve closing correction execution determination pressure P _H. Step 4
If a negative determination is made in step 12, the process proceeds to step 407 to close the throttle valve 15 and generate a negative pressure because there is not enough negative pressure for the brake booster 17 to function.

[0032] When a positive determination is made in step 412, the process proceeds to step 414, if not required to generate a negative pressure by closing the throttle valve 15, a throttle valve reference throttle valve opening THR _B opening command THR And When the processing of step 409, step 411 or step 414 is completed, a throttle valve opening command THR is output in step 415, and this processing ends.

That is, according to the above invention, if the brake is not operated for a predetermined time or more, it is not necessary to generate a negative pressure, and the combustion state of the internal combustion engine is disturbed because the throttle valve is not closed. The likelihood decreases. However, in the negative pressure generator according to the two inventions, the surge tank 14 and the brake booster 17 are connected to the connection pipe 1.
8, the brake booster 17
There isn't much time in which the can function.

A negative pressure control device for an internal combustion engine according to the present invention solves the above-mentioned problems. FIG. 6 is a configuration diagram of an embodiment of a negative pressure control device for an internal combustion engine. A negative pressure storage tank 182 is installed in the middle of a connection pipe, and a pressure sensor 181 is connected to the negative pressure storage tank 182.

That is, according to the negative pressure control device for an internal combustion engine according to the present invention, since the negative pressure is stored in the negative pressure storage tank 182, the time during which the brake booster 17 can function can be extended. In addition, it is possible to reduce the chance of closing the throttle valve 15. Also, in a stratified combustion internal combustion engine to which the present invention is mainly applied, the throttle valve 15
Is in the fully open state, so that the throttle valve 1
Closing 5 is effective.

However, closing the throttle valve 15 especially in a stratified combustion state may impair combustion stability. FIG. 7 is an explanatory diagram of the fuel injection mode of the stratified combustion internal combustion engine. ).

When the load of the internal combustion engine is equal to or greater than L _{0 and} equal to or less than L ₁ , fuel is injected only in the vicinity of the spark plug 101 in the compression stroke using the fuel injection valve 13 for stratified combustion, resulting in strong stratified combustion. If the internal combustion engine load is L ₁ or L ₂ or less, a two-split injection region, the fuel injection valve opening time τ
Among them, the fuel is injected in the compression stroke by using the stratified combustion fuel injection valve 13 by τ _c .

The remaining (τ-τ _c ) is supplied with fuel during the intake stroke using the uniform combustion fuel injection valve 12, and the air-fuel mixture in the cylinder becomes weakly stratified. Furthermore, when the internal combustion engine load is L ₂ or more, the fuel is supplied during the intake stroke by using the homogeneous combustion fuel injection valve 12 regardless of the fuel injection valve opening time. That is, the fuel injection valve 1 for stratified combustion
If the throttle valve 15 is closed in a state where fuel is supplied using the fuel injection valve 3, there is a possibility that an rich mixture is formed in the vicinity of the ignition plug 101 and ignition does not occur.

Further, the fuel to be injected by the injection valve 12 is used by using only the injection valve 13 without using the injection valve 12.
May be used during the intake stroke. The following invention has been made to solve the above problems. FIG. 8 is a flowchart of a third negative pressure control routine executed by the control unit 19, which is executed as an interruption process at regular time intervals.

In step 801, it is determined whether or not a predetermined time α has elapsed after the start of the internal combustion engine. If the determination is affirmative, the process proceeds to step 802, where it is determined whether the throttle valve closing execution flag XFLAG has been reset. I do. When an affirmative determination is made in step 802, that is, when the throttle valve closing correction has not been performed, the process proceeds to step 803, and it is determined whether the brake operation flag XBRK is in a set state.

If the result of the determination in step 803 is affirmative,
If so, proceed to step 804 to indicate the brake operation time.
Increment the brake counter CBK. Then
At step 805, the brake counter CBK reaches a predetermined judgment value.
CBK₀It is determined whether or not this is the case. Step 805
If the result is affirmative, that is, if the brake has been
If the operation is continued, the operation proceeds to step 806.
And brake booster operating pressure P _BIs a throttle valve closing supplement
Correct execution judgment pressure P_HIt is determined whether or not:

If an affirmative determination is made in step 806, it is determined that there is a negative pressure sufficient to cause the brake booster 17 to function, and the routine proceeds to step 807, where the throttle valve closing execution flag XFLAG is reset.
At 08, the reference throttle valve opening THR _B is set as a throttle valve opening command THR. If a negative determination is made in step 806, it is determined that there is no negative pressure for causing the brake booster 17 to function, and the routine proceeds to step 809, where the throttle valve closing execution flag XFLAG is set, and the routine proceeds to step 810.

If a negative determination is made in step 801, that is, if the predetermined time α has not elapsed after the start of the internal combustion engine, the process proceeds to step 806 to secure an initial negative pressure regardless of the brake operation. Further, the process also proceeds to step 806 when a negative determination is made in step 802, that is, when the throttle valve closing correction is not performed.

[0044] In step 810, obtaining a corrected throttle valve opening DTHR as a function of engine speed N _e. That is, the corrected throttle valve opening DTHR is determined by the following equation. In DTHR = DTHR (N _e) and step 811 calculates the throttle valve opening command THR is subtracted the reference throttle valve opening THR _B and corrected throttle valve opening DTHR.

If a negative determination is made in step 803, that is, if the brake is not operated, step 8
After resetting the brake counter CBK in 12, the process proceeds to step 808 because the closing of the throttle valve is not necessary. Also, if a negative determination is made in step 805, the process proceeds to step 808 because it is not necessary to close the throttle valve.

When the processing of step 808 or step 811 is completed, the routine proceeds to step 813, where the throttle valve opening command THR is output, and this routine is terminated. FIG. 9 is a flowchart of a fuel injection mode control routine also executed by the control unit 19, and is executed as a part of the main routine. In step 901, the internal combustion engine speed _Ne and the accelerator opening θ are read, and in step 902, the fuel injection valve opening time τ is determined as a function of the internal combustion engine speed _Ne and the accelerator opening θ.

That is, the fuel injection valve opening time τ is determined by the following equation. τ = τ ( _Ne , θ) In step 903, the fuel injection valve opening time τ is set to the first
Determining whether a determination value tau ₁ or more. Step 9
If a negative determination is made in step 03, that is, if the vehicle is operating at a low load with a small fuel injection amount, the routine proceeds to step 904, where the fuel injection mode flag XINJ is set to "0" indicating that the fuel injection system is in the strong stratified injection mode.

If an affirmative determination is made in step 903, the process proceeds to step 905, where it is determined whether the fuel injection valve opening time τ is equal to or longer than a _second determination value τ2. The first
The determination value tau ₁ and the second determination value tau ₂ may be a fixed value, it may be determined as a function of engine speed N _e. If an affirmative determination is made in step 905, that is, during medium load operation, the routine proceeds to step 906, where the fuel injection mode flag XINJ is set to "1" indicating that the injection mode is the double injection mode.

If a negative determination is made in step 905, that is, if the vehicle is operating under a high load with a large fuel injection amount, step 9 is executed.
In step 07, the fuel injection mode flag XINJ is set to "2" indicating the uniform injection mode. Step 90
When the execution of 4, 906, or 907 is completed, the routine proceeds to step 908, where the throttle valve closing execution flag XFLA
It is determined whether or not G is in the set state, that is, whether or not the throttle valve 15 is closed due to generation of a negative pressure.

When the determination in step 908 is affirmative, the routine proceeds to step 909, where the fuel injection mode flag XI
NJ is forcibly replaced with “2” representing the uniform injection mode, and the process proceeds to step 910. That is, when the throttle valve is closed to generate a negative pressure at a medium load or a low load where the fuel injection amount is relatively small, the fuel is forcibly supplied in the uniform injection mode so that ignition is reliably performed.

If a negative determination is made in step 908, that is, if there is no closing of the throttle valve for generating a negative pressure, the flow directly proceeds to step 910. In step 910, it is determined whether or not the fuel injection mode flag XINJ is "0". If the determination is affirmative, the process proceeds to step 911, where the fuel injection parameters (fuel injection timing, ignition timing, exhaust The recirculation valve opening, the throttle valve opening, etc.) are calculated, and this routine ends.

If a negative determination is made in step 910, the process proceeds to step 912, where the fuel injection mode flag XINJ is set.
It is determined whether it is "1". When an affirmative determination is made in step 912, the process proceeds to step 913, where the fuel injection parameters in the double injection mode are calculated, and this routine ends. If a negative determination is made in step 912, the process proceeds to step 914, in which the fuel injection parameters in the uniform injection mode are calculated, and this routine ends.

The fuel injection parameters are stored in the control unit in the form of a map for each mode. That is, according to the present invention, it is possible to secure a negative pressure for operating the brake booster without impairing the ignition performance regardless of the operation state of the internal combustion engine.

[0054]

According to the first aspect of the present invention, when the pressure for operating the brake booster approaches the atmospheric pressure, the throttle valve is closed to apply a negative pressure to the surge tank. In the internal combustion engine in which the fuel injection is performed in the stratified injection mode during the middle and low load operation, the negative pressure for the brake booster operation is performed during the execution of the fuel injection in the stratified injection mode. When the throttle valve is closed due to pressure generation, switching to the uniform injection mode makes it possible to ensure ignition performance. According to the negative pressure control device for an internal combustion engine according to the second invention, when the brake is operated and the pressure for operating the brake booster becomes close to the atmospheric pressure,
It is possible not only to secure the function of the brake booster by closing the throttle valve and generating a negative pressure in the surge tank, but also to suppress the occurrence of unnecessary disturbance to the internal combustion engine. At the same time, when the throttle valve is closed to generate a negative pressure for operating the brake booster during execution of fuel injection in the stratified injection mode, it is possible to secure ignition performance by switching to the uniform injection mode.

According to the negative pressure control device for an internal combustion engine according to the third aspect of the present invention, the negative pressure accumulation tank is provided between the surge tank and the brake booster, so that the throttle valve closing valve for generating the negative pressure is closed. Opportunities can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment.

FIG. 2 is a flowchart of a first negative pressure generation routine.

FIG. 3 is a map for determining a corrected throttle valve opening;

FIG. 4 is a flowchart of a second negative pressure generation routine.

FIG. 5 is a map for determining a corrected throttle valve opening;

FIG. 6 is a configuration diagram of another embodiment.

FIG. 7 is an explanatory diagram of a fuel injection mode.

FIG. 8 is a flowchart of a third negative pressure generation routine.

FIG. 9 is a flowchart of a fuel injection mode control routine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine 101 ... Spark plug 12 ... Fuel injection valve for uniform combustion 13 ... Fuel injection valve for stratified combustion 14 ... Surge tank 15 ... Throttle valve 16 ... Brake pedal 161 ... Brake switch 17 ... Brake booster 18 ... Connection piping 181 ... Pressure sensor 182: negative pressure storage tank 19: control unit

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-58-23244 (JP, A) JP-A-5-208663 (JP, A) JP-A-62-214245 (JP, A) JP-A-4- 34166 (JP, A) JP-A-63-138119 (JP, A) JP-A-51-120307 (JP, A) JP-A-4-34166 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60T 13/00-13/74

Claims (3)

(57) [Claims] A brake booster for increasing a braking force by introducing a negative pressure from an intake pipe downstream of a throttle valve of an internal combustion engine performing stratified charge combustion; a pressure detecting means for detecting a pressure acting on the brake booster; A throttle valve closing means for closing the throttle valve by a predetermined amount when it is determined based on the detection result of the pressure detecting means that the negative pressure is insufficient for the function of the brake booster; Based on the detection result, when it is determined that the negative pressure is insufficient for the function of the brake booster, combustion mode switching means for switching the combustion mode from stratified combustion to homogeneous combustion, Negative pressure control device. 2. A brake booster for increasing a braking force by introducing a negative pressure from an intake pipe downstream of a throttle valve of an internal combustion engine performing stratified charge combustion, pressure detecting means for detecting a pressure acting on the brake booster, and a brake. Brake operation detecting means for detecting that the brake has been operated, and when the brake operation detecting means detects that the brake has been operated, the brake booster functions based on the detection result of the pressure detecting means. When it is determined that the negative pressure is insufficient, throttle valve closing means for closing the throttle valve by a predetermined amount, and when the brake operation detecting means detects that the brake has been operated, If it is determined that the negative pressure is insufficient for the function of the brake booster based on the detection result of the pressure detecting means, the combustion method Negative pressure control apparatus for an internal combustion engine provided with combustion mode switching means for switching to the homogeneous combustion from the stratified combustion, the. 3. The negative pressure control device for an internal combustion engine according to claim 1, further comprising a negative pressure storage tank installed between the brake booster and an intake pipe.