JPH1054286A - Negative pressure supply system for automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide stable negative pressure supply for a negative pressure operated apparatus which operates on negative pressure as a driving source. SOLUTION: Negative pressure is supplied alternatively from a negative pressure pump 9 fitted coaxially to an alternator 10 or an intake surge tank 4 which constitutes an intake passage by a switching valve 12 which is constituted of an electromagnetic solenoid valve to a brake booster 8 as an example of an negative pressure operated device. When the output signal of the alternator 10 is above a prescribed value, a negative pressure supply passage is switched to a negative pressure pump side as normal control when no abnormality occurs at the negative pressure pump 9, and when the output signal of the alternator 10 is below the prescribed value, the negative pressure supply passage is switched to the inlet surge tank 4 side as abnormality control when any abnormality occurs at the negative pressure pump 9. If any abnormality occurs at the negative pressure pump, throttle valve 3 opening control is conducted based on a fixed air/fuel ratio (for example, theoretical air-fuel ratio) so that negative pressure may occur in the intake passage, and a warning lamp 16 is let to tell a driver that any abnormality occurs.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative pressure supply system for an automobile, and more particularly to a technique for stably supplying a negative pressure.

[0002]

2. Description of the Related Art Conventionally, vehicles have been equipped with various devices that operate using a negative pressure as a drive source, and a typical device is a brake booster that reduces the depression force of a brake pedal. In a general gasoline engine vehicle, a negative pressure that is a driving source of such equipment is generated in the intake passage by closing a throttle valve interposed in the intake passage.
In a diesel engine vehicle having no throttle valve, since a negative pressure is not generated in the intake passage, a negative pressure pump using an engine output as a drive source is separately provided to generate a negative pressure.

[0003]

However, in the case of a configuration in which the engine output is transmitted to the negative pressure pump by a belt, for example, when the belt is broken, no negative pressure is generated, and this negative pressure is used as a drive source. Device does not work. In particular, in the case of the brake booster, the depression force of the brake pedal is not reduced, and the driver may feel that the brake is heavy.

[0004] Such a problem becomes a problem not only in a diesel engine vehicle but also in a vehicle equipped with a direct injection gasoline engine which has been developed in recent years. That is, in the direct injection gasoline engine, the air-fuel ratio during economic operation is lean (lean air-fuel ratio) and the air-fuel ratio during high load operation is stoichiometric (ideal air-fuel ratio). Since the required throttle opening for ()) differs depending on the air-fuel ratio, an electronically controlled throttle is required. In this case, as shown in FIG. 6, the negative pressure generated in the intake passage varies depending on the operating state (stoichiometric, lean, extra lean) with different air-fuel ratios. Negative pressure may be insufficiently generated even in a region where the opening is low. Therefore, even in a direct injection gasoline engine vehicle, a negative pressure pump using an engine output as a drive source may be mounted similarly to a diesel engine vehicle.

In view of the above-mentioned problems, the present invention provides a negative pressure supply system for an automobile capable of performing a stable negative pressure supply by duplicating a negative pressure supply source. The purpose is to:

[0006]

For this reason, as shown in FIG. 1, the invention according to claim 1 comprises a negative pressure operating device A which operates using a negative pressure as a drive source, and a negative pressure pump which generates a negative pressure. B
Abnormality determining means C for determining whether or not an abnormality has occurred in the negative pressure pump B; a throttle valve F provided in the intake passage E of the internal combustion engine D; The opening control of the valve F is performed based on the variable air-fuel ratio of the engine according to the engine operating state when the negative pressure pump is normal,
The opening degree control means G which performs based on the fixed air-fuel ratio of a predetermined engine when a negative pressure pump abnormality occurs, and a negative pressure supply path to the negative pressure operating device A. And a negative pressure supply path switching means H that switches to a path from the intake passage E downstream of the throttle valve F when a negative pressure pump abnormality occurs.

With this configuration, when the negative pressure pump is normal, the path is switched by the negative pressure supply path switching means so that the negative pressure is supplied from the negative pressure pump to the negative pressure operating device, and the opening degree control means is used. For example, the opening degree control of the throttle valve is performed based on the variable air-fuel ratio for the purpose of improving fuel efficiency and the like. However, when a negative pressure pump abnormality occurs, negative pressure is supplied from the intake passage to the negative pressure operating device by the negative pressure supply path switching means. The path is switched so that the pressure is supplied, and the opening control of the throttle valve based on the fixed air-fuel ratio is performed by the opening control means so that a negative pressure is generated in the intake passage.

According to a second aspect of the present invention, the opening degree control means includes an air-fuel ratio storing means storing a variable air-fuel ratio of the engine according to the engine operating state, an operating state detecting means detecting the engine operating state, Air-fuel ratio setting means for setting an air-fuel ratio from the air-fuel ratio storage means based on the detected engine operating state. By doing so, an appropriate air-fuel ratio is set based on the detected engine operating state.

According to the third aspect of the present invention, the predetermined fixed air-fuel ratio is an ideal air-fuel ratio. With this configuration, when the opening of the throttle valve is in the low opening range, a negative pressure sufficient to operate the negative pressure operating device is generated in the intake passage. According to a fourth aspect of the present invention, when the negative pressure pump is mounted coaxially with an alternator, the abnormality determining means determines that the negative pressure pump is turned off when an output voltage from the alternator becomes lower than a predetermined value. It is determined that an abnormality has occurred in the pressure pump.

With this configuration, it is determined based on the output voltage of the alternator whether an abnormality has occurred in the negative pressure pump.
The invention according to claim 5 includes a negative pressure detection unit that directly detects a negative pressure generated from the negative pressure pump, wherein the abnormality determination unit determines that the detected negative pressure is less than a predetermined value. When this happens, it is determined that an abnormality has occurred in the negative pressure pump.

With this configuration, it is determined whether or not an abnormality has occurred in the negative pressure pump based on the negative pressure generated from the negative pressure pump. According to a sixth aspect of the present invention, the negative pressure supply path switching means includes a first pressure path for connecting the negative pressure pump to a negative pressure operating device.
A communication path, a second communication path communicating the intake passage downstream of the throttle valve with the negative pressure operating device, and a first communication path and a second communication path.
And a switching valve for selectively switching between the communication path and the communication path.

With this configuration, the path for supplying the negative pressure to the negative pressure operating device is switched by the switching valve. In the invention according to claim 7, the switching valve is an electromagnetic solenoid valve. In this way, by controlling the electromagnetic solenoid valve, the negative pressure supply path to the negative pressure operating device is switched.

In the invention according to claim 8, the switching valve is a diaphragm valve for selectively switching a negative pressure supply source having a large negative pressure among the two negative pressure supply sources. If you do this,
The negative pressure supply path to the negative pressure operating device is automatically switched based on the two negative pressures supplied to the diaphragm valve.
According to a ninth aspect of the present invention, the negative pressure actuating device is a brake booster that reduces the depression force of a brake pedal that operates a brake device of a vehicle.

Thus, even if an abnormality occurs in the negative pressure pump, the negative pressure is stably supplied to the brake booster. The invention according to claim 10 is provided with a notifying means for notifying a driver of the occurrence of an abnormality of the negative pressure pump, and when the abnormality determining means determines that an abnormality has occurred in the negative pressure pump, the notifying means is provided. Activated.

With this configuration, it is quickly notified that an abnormality has occurred in the negative pressure pump. According to an eleventh aspect of the present invention, a negative pressure supply path to a negative pressure operating device that operates by using a negative pressure as a drive source includes a first path from a negative pressure pump that generates a negative pressure and an intake path downstream of a throttle valve. When the negative pressure pump is normal, the negative pressure supply path is switched to the first path, and the opening of the throttle valve is controlled based on the variable air-fuel ratio according to the operating state. When a pump abnormality occurs, the negative pressure supply path is switched to the second path, and the opening control of the throttle valve is performed based on a fixed air-fuel ratio at which a negative pressure is generated in the intake passage.

With this configuration, when the negative pressure pump is normal, a negative pressure is supplied from the negative pressure pump to the negative pressure operating device, and the throttle valve is controlled based on the variable air-fuel ratio for the purpose of improving fuel efficiency. The opening control is performed, but when a negative pressure pump abnormality occurs, the negative pressure is supplied from the intake passage to the negative pressure operating device, and the throttle valve based on the fixed air-fuel ratio is generated so that the negative pressure is generated in the intake passage. Is controlled.

[0017]

As described above, according to the first or eleventh aspect of the present invention, the negative pressure is supplied from the negative pressure pump to the negative pressure operating device when the negative pressure pump is normal. In the event of an abnormality, a negative pressure is supplied from the intake passage, and the opening of the throttle valve is controlled so as to generate a negative pressure in the intake passage. Thus, the negative pressure can be stably supplied to the negative-pressure operating device regardless of whether or not an abnormality has occurred in the negative pressure pump.

According to the second aspect of the present invention, since an appropriate air-fuel ratio is set based on the detected engine operating state, it is possible to control the throttle valve based on a wide range of air-fuel ratio from super lean to stoichiometric. Become. According to the third aspect of the invention, since the throttle valve opening control is performed when the negative pressure pump is abnormal based on the ideal air-fuel ratio, when the throttle valve opening is in the low opening region, the throttle valve is placed in the intake passage. Negative pressure sufficient to operate the negative pressure operating device can be generated.

According to the fourth aspect of the present invention, since the negative pressure pump operates simultaneously with the alternator, it is possible to easily determine whether or not an abnormality has occurred in the negative pressure pump based on the output voltage of the alternator. According to the invention described in claim 5,
Since the operating state of the negative pressure pump is detected by the negative pressure detecting means, it is possible to easily determine whether or not an abnormality has occurred in the negative pressure pump based on the detected negative pressure.

According to the sixth aspect of the present invention, it is possible to switch the negative pressure supply path to the negative pressure operating device with a simple configuration including the first communication path, the second communication path, and the switching valve. According to the seventh aspect of the present invention, it is possible to switch the negative pressure supply path to the negative pressure operating device only by adding simple control of the electromagnetic solenoid valve. According to the invention described in claim 8, it is possible to automatically switch the negative pressure supply path to the negative pressure operating device based on the two negative pressures supplied to the diaphragm valve.

According to the ninth aspect of the present invention, even if an abnormality occurs in the negative pressure pump, the negative pressure is stably supplied to the brake booster, so that the depression force of the brake pedal is effectively reduced. The driver will not feel heavy on the brakes. According to the tenth aspect of the present invention, since the occurrence of an abnormality in the negative pressure pump is promptly notified, it is possible to take prompt measures such as repair.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the attached drawings. FIG. 2 shows an embodiment of a vehicle negative pressure supply system for supplying a negative pressure to a brake booster as an example of a negative pressure operating device in a vehicle equipped with a direct injection gasoline engine.

V in which two cylinder rows are arranged in a substantially V-shape
Air is drawn into the engine 1 through an air cleaner (not shown), an intake duct 2, a throttle valve 3, an intake surge tank 4 for smoothing the pulsation of intake air, and an intake manifold 5. The throttle valve 3 constitutes a so-called electronically controlled throttle (opening control means) whose opening is adjusted via a throttle actuator 7 which is driven and controlled by a control unit 6 containing a microcomputer. Note that an intake passage is configured to include the intake duct 2, the intake surge tank 4, and the intake manifold 5.

A negative pressure pump 9 for generating a negative pressure serving as a driving source of the brake booster 8 is mounted coaxially with the alternator 10, and has a pulley 1 a at the end of the crankshaft of the engine 1 and the alternator 10. The engine is driven by an engine output via a V-belt 11 wound around a pulley 10a at the end of the input shaft. Then, the negative pressure generated by the negative pressure pump 9 is supplied to the brake booster 8 via a pipe 13 in which a switching valve 12 described later is interposed.

The feature of the present invention is that the source of the negative pressure to the brake booster 8 is doubled. That is, the inside of the intake surge tank 4 located on the downstream side of the throttle valve 3 and the switching valve 12 are communicated via the pipe 14, and the negative pressure generated in the intake passage can also be supplied to the brake booster 8. It has a configuration. Here, piping 1
The switching valve 12 interposed in the control unit 3
The solenoid valve is a three-port, two-position solenoid valve driven and controlled by the vacuum pump 9 and the brake booster 8 when not operating (OFF).
N) connects the intake surge tank 4 and the brake booster 8. A check valve (not shown) is interposed in the pipe 14 that connects the intake surge tank 4 and the switching valve 12, and the pipe 14 also has a function as a negative pressure tank that keeps the negative pressure substantially constant. I have. Therefore, the throttle valve 3
When the negative pressure in the intake surge tank 4 becomes equal to or higher than a predetermined value due to the closing of the valve, the check valve is opened, and a negative pressure capable of operating the brake booster 8 a plurality of times is applied to the pipe 1.
4 is stored. The pipes 13 and 14 and the switching valve 12
And the control unit 6 constitutes a negative pressure supply path switching means. In particular, the pipe 13 is a first communication path, a pipe 1
4 corresponds to a second communication path.

As signals for controlling the negative pressure supply system for a vehicle having such a configuration, the output voltage of an accelerator opening sensor 15 for detecting the opening of an accelerator pedal (not shown) and the alternator 10 are input to the control unit 6. The setting of the throttle opening and the selection of the negative pressure supply path are performed on the basis of the signals (1) and (2), and the control unit 6 outputs a drive signal to the throttle actuator 7 and the switching valve 12. Further, a warning light 16 (notification means) for notifying the driver of the occurrence of an abnormality due to a failure of the negative pressure pump 9 or the like is provided in the combination meter in the driver's seat, and the drive control of the warning light 16 is simultaneously performed. Is being done.

Next, an example of the control contents of such an automobile negative pressure supply system will be described with reference to the flowchart of FIG. The routine shown in this flowchart starts at the same time as the ignition switch is turned on, and is repeatedly executed at predetermined time intervals until the ignition switch is turned off. In step 1 (abbreviated as S1 in the figure, the same applies hereinafter), normal control is performed. In particular,
A characteristic variable mode in which the warning light 16 provided in the combination meter in the driver's seat is turned off (OFF), and the control mode of the throttle valve 3 is made variable in the air-fuel ratio according to the engine operating state (see FIG. 4A). And the switching valve 12
Is turned off so that the negative pressure of the negative pressure pump 9 is supplied to the brake booster 8 to form a negative pressure supply path. Here, the variable characteristic mode shown in FIG. 4A is based on the operating state from a memory (air-fuel ratio storage means) storing an air-fuel ratio ranging from stoichiometric to super lean according to the operating state (for example, engine load). An appropriate air-fuel ratio is set by software (air-fuel ratio setting means), a throttle opening corresponding to the accelerator opening from the accelerator opening sensor 15 is retrieved from a map, and a throttle actuator is determined based on the throttle opening. 7 is controlled. In this case, a sensor that detects an intake air flow rate corresponding to the engine load, an intake negative pressure, and the like,
Alternatively, processing such as software for setting the fuel supply amount to the engine corresponding to the engine load corresponds to the operating state detecting means.

In step 2, it is determined whether the negative pressure pump 9 is operating normally, that is, whether or not the negative pressure pump 9 is abnormal. Specifically, whether or not the output voltage Valt of the alternator 10 is equal to or higher than a predetermined value Valtmin (Valt ≧
Valtmin) is determined, and if Valt ≧ Valtmin (Yes), the process proceeds to step 1; if Valt <Valtmin (No), the process proceeds to step 3. That is, since the negative pressure pump 9 is mounted coaxially with the alternator 10, for example, when the V-belt 11 breaks, the alternator 10 does not operate at the same time that the negative pressure pump 9 does not operate. By monitoring the output voltage Valt of 10, it is possible to determine whether or not an abnormality has occurred in the negative pressure pump 9. Note that the processing in step 2 corresponds to an abnormality determination unit.

In step 3, an abnormal control is performed when the negative pressure pump 9 stops operating. Specifically, the warning light 16 provided in the combination meter in the driver's seat is turned on (ON), the throttle mode is switched to the characteristic fixing mode for fixing the stoichiometric characteristic (see FIG. 4B), and the switching valve is switched. When 12 is turned on, a negative pressure supply path for supplying the negative pressure in the intake surge tank 4 to the brake booster 8 is formed.

Steps 1 and 3 correspond to the opening control means provided in the control unit 6 by software, and the opening control means includes the above-described air-fuel ratio storage means, operating state detection means, and air-conditioning means. It is configured to include fuel ratio setting means. In this way, the presence or absence of an abnormality in the negative pressure pump 9 is determined based on the output voltage of the alternator 10, and if it is determined that an abnormality has occurred in the negative pressure pump 9, the negative pressure applied to the brake booster 8 is increased. The pressure supply path is switched to the intake surge tank 4 side, and the control mode of the throttle valve 3 is switched to the characteristic fixed mode in which the stoichiometric characteristic is fixed so that a negative pressure is generated in the intake surge tank 4.
Therefore, when the accelerator opening is in the low opening region,
As shown in FIG. 6, a negative pressure sufficient to operate the brake booster 8 is generated, and the negative pressure is stored in the pipe 14 which also functions as a negative pressure tank, and the brake pedal depressing force is reduced. Is completed. In short, a stable negative pressure supply is enabled by making the negative pressure supply source double.

Further, when an abnormality occurs in the negative pressure pump 9, the warning lamp 16 is lit to notify the driver of the occurrence of the abnormality, so that a quick repair or the like can be taken. Incidentally, it is possible to determine whether or not an abnormality has occurred in the negative pressure pump 9 by another method. For example, it is possible to determine that an abnormality has occurred when the output from a negative pressure sensor that directly detects a negative pressure is less than a predetermined value, or it is possible to determine the output from a negative pressure switch that is activated by a negative pressure. It can be determined that an abnormality has occurred when is turned off (non-operating). Some vehicles currently on the market are equipped with a negative pressure sensor for detecting a negative pressure in the brake booster 8. In this case, the output from the negative pressure sensor should be used. It can be said that this is a realistic configuration.

Further, the switching of the negative pressure supply path to the brake booster 8 can be performed by the switching valve 12 constituted by a mechanical diaphragm valve instead of the electromagnetic solenoid. In this case, there is no need to control the electromagnetic solenoid, and there is an advantage that control is simplified. One example of the structure of the diaphragm valve 20 is, as shown in FIG. 5, an inner case 23 having two negative pressure chambers 22a and 22b divided by a substantially disk-shaped diaphragm 21, and a substantially central axis of the diaphragm 21. Shaft 24 having seal members 24a and 24b coupled to both ends thereof, respectively.
And an outer case 25 arranged so as to include the inner case 23. Seal portions 23a and 23b are formed on both walls of the inner case 23, respectively.
Opening valves A and B are respectively formed between the valves a and 24b. Then, the inside of the outer case 25 and one of the negative pressure chambers 22a and 22b conduct through this on-off valve. Diaphragm 2
An elastic body 21a having an initial deflection (bent rightward in the figure) is attached to 1 for the purpose of stopping at an intermediate position and preventing hunting. Negative pressure chamber 22
a and 22b are separate negative pressure sources (in this embodiment,
The suction surge tank 4 and the negative pressure pump 9) communicate with each other, and the inside of the outer case 25 communicates with the negative pressure supply destination (in this embodiment, the brake booster 8).

Next, the operation of the diaphragm valve 20 having such a configuration will be described. For example, in the state of FIG.
Assuming that the negative pressure of 2a has increased, the diaphragm 21
Is sucked toward the negative pressure chamber 22a, and at the same time the right open / close valve A closes, the left open / close valve B opens, and the negative pressure chamber 22a and the inside of the outer case 25 are electrically connected. Therefore, the negative pressure is supplied to the negative pressure supply destination from the negative pressure chamber 22a. On the other hand, when the negative pressure in the right negative pressure chamber 22b increases,
The operation reverse to that described above is performed, and the negative pressure is supplied to the negative pressure supply destination from the negative pressure chamber 22b.

The diaphragm valve 20 shown in FIG.
Is a diagram showing an example of a diaphragm valve for selectively switching a negative pressure supply source having a large negative pressure among two negative pressure supply sources, and a diaphragm valve having any configuration as long as it has a similar effect. It may be. Further, in the present embodiment, the brake booster that reduces the depression force of the brake pedal is used as the negative pressure operating device, but another negative pressure operating device may be used. In this case, it is possible to more stably achieve an effect that matches the device to which the apparatus is applied.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims of the present invention.

FIG. 2 is a configuration diagram of an embodiment of a negative pressure supply system for a vehicle according to the present invention.

FIG. 3 is a flowchart showing control contents of the above.

FIG. 4 is a diagram showing the details of throttle valve opening control according to the first embodiment;

FIG. 5 is a configuration diagram of a diaphragm valve as an example of the switching valve according to the first embodiment;

FIG. 6 is a diagram showing a problem of the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2 Intake duct 3 Throttle valve 4 Intake surge tank 5 Intake manifold 6 Control unit 7 Throttle actuator 8 Brake booster 9 Negative pressure pump 10 Alternator 12 Switching valve 13, 14 Piping 20 Diaphragm valve

Claims (11)

[Claims] A negative pressure operating device that operates by using a negative pressure as a driving source; a negative pressure pump that generates a negative pressure; an abnormality determining unit that determines whether an abnormality has occurred in the negative pressure pump; When the negative pressure pump is normal, the opening control of the throttle valve is performed based on the variable air-fuel ratio of the engine according to the engine operating state based on the determination result of the throttle valve interposed in the passage and the abnormality determination means. Opening degree control means for performing based on the fixed air-fuel ratio of a predetermined engine when an abnormality of the pressure pump occurs, and switching a negative pressure supply path to the negative pressure operating device to a path from the negative pressure pump when the negative pressure pump is normal; And a negative pressure supply path switching means for switching to a path from the intake passage downstream of the throttle valve when a negative pressure pump abnormality occurs. 2. The engine control apparatus according to claim 1, wherein the opening degree control means includes an air-fuel ratio storage means storing a variable air-fuel ratio of the engine according to the engine operation state, an operation state detection means detecting the engine operation state, and a detected engine operation state. 2. The negative pressure supply system for a vehicle according to claim 1, further comprising: an air-fuel ratio setting unit that sets an air-fuel ratio from the air-fuel ratio storage unit based on the air-fuel ratio. 3. The negative pressure supply system for an automobile according to claim 1, wherein the predetermined fixed air-fuel ratio is an ideal air-fuel ratio. 4. The apparatus according to claim 1, wherein said negative pressure pump is mounted coaxially with an alternator.
The negative pressure for a vehicle according to any one of claims 1 to 3, wherein it is determined that an abnormality of the negative pressure pump has occurred when an output voltage from the alternator becomes less than a predetermined value. Feeding system. 5. The apparatus according to claim 1, further comprising a negative pressure detecting means for directly detecting a negative pressure generated from said negative pressure pump, wherein said abnormality determining means determines whether said detected negative pressure is less than a predetermined value. The negative pressure supply system for an automobile according to any one of claims 1 to 3, wherein it is determined that an abnormality has occurred in the negative pressure pump. 6. The negative pressure supply path switching means includes a first communication path for communicating the negative pressure pump with a negative pressure operating device, and a first communication path for communicating an intake passage downstream of the throttle valve with the negative pressure operating device. The vehicle according to any one of claims 1 to 5, comprising a two-way passage, and a switching valve for selectively switching between the first and second communication passages. For negative pressure supply system. 7. The negative pressure supply system for an automobile according to claim 6, wherein said switching valve is an electromagnetic solenoid valve. 8. The negative pressure supply for an automobile according to claim 6, wherein said switching valve is a diaphragm valve for selectively switching a negative pressure supply source having a large negative pressure among two negative pressure supply sources. system. 9. The apparatus according to claim 1, wherein the negative pressure actuating device is a brake booster that reduces a depression force of a brake pedal that operates a brake device of the vehicle. Negative pressure supply system for automobiles. 10. A notifying means for notifying a driver of the occurrence of an abnormality in the negative pressure pump, and activating the notifying means when the abnormality determining means determines that an abnormality has occurred in the negative pressure pump. The vehicle negative pressure supply system according to any one of claims 1 to 9, wherein: 11. A negative pressure supply path to a negative pressure operating device that operates by using a negative pressure as a drive source, a first path from a negative pressure pump that generates a negative pressure and a second path from an intake path downstream of a throttle valve. When the negative pressure pump is normal, the negative pressure supply path is switched to the first path, and the opening control of the throttle valve is performed based on the variable air-fuel ratio according to the operating state. A negative pressure supply system for an automobile, wherein the negative pressure supply path is sometimes switched to a second path, and the opening control of the throttle valve is performed based on a fixed air-fuel ratio at which a negative pressure is generated in the intake passage.