JP3080756B2 - Brake booster negative pressure control device - 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 a brake booster which boosts a brake operating force by utilizing a negative pressure of intake air of an engine.

[0002]

2. Description of the Related Art Conventionally, in order to reduce the operating force at the time of braking of a vehicle, a brake booster which boosts the brake operating force by using an engine intake negative pressure has been employed. A check valve is provided in the middle of the pipe connecting the intake pipe of the engine and the brake booster to maintain the maximum negative pressure. This negative pressure tends to increase as the engine speed increases and as the engine speed changes. In recent years, with the spread of electronically controlled fuel injection engines, the number of people who start the engine without stepping on the accelerator pedal has increased. This is because, in an electronically controlled fuel injection engine, the fuel injection amount is controlled in accordance with the intake air amount, so that the engine can be started without stepping on the accelerator pedal. Therefore, the negative pressure of the engine intake air immediately after the start of the engine is low, and the boosting of the brake booster may be insufficient.
In the case of a general automotive brake booster, a negative pressure of about -450 mmHg is required to obtain a predetermined boosting performance, but immediately after the engine is started, it is in a range of -150 to -200 mmHg.
And the function of the brake booster cannot be fully exhibited.

[0003]

Conventionally, a bypass passage is provided in an intake passage of an engine so as to bypass a throttle valve, and a bypass control valve for adjusting an amount of air passing through the bypass passage is provided. Therefore, there has been proposed a method of stabilizing the idle speed immediately after the engine is started by increasing the bypass air amount for a predetermined time from the normal time (Japanese Patent Application Laid-Open No. 2-140443). With the above control method, it is possible to increase the negative pressure of the brake booster, but in order to achieve this in a short time, the engine speed must be controlled considerably higher than the normal idle speed. And the driving car may be uncomfortable or uneasy. Therefore, an object of the present invention is to provide a brake booster negative pressure control device capable of resolving a lack of boost of the brake booster immediately after starting the engine in a short time without causing discomfort to the driving vehicle.

[0004]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an electronically controlled fuel injection engine for controlling the amount of fuel injection according to the amount of intake air, and a check valve for checking the negative pressure of the intake air of the engine. A bypass passage provided to bypass a throttle valve in an intake passage of an engine in a vehicle provided with a brake booster that boosts a brake operating force by utilizing the intake negative pressure. A bypass control valve for adjusting the amount of air passing through the passage, an engine speed sensor for detecting the engine speed, and a time counting means for counting time since the start of the engine;
Open the bypass control valve for a certain period of time immediately after starting the engine
Reciprocating control in the forward and backward directions to pass through the bypass passage
By changing the air volume, the engine speed can be
A negative pressure control means for moving is provided, variation in the engine rotation speed
Of the engine intake negative pressure via the check valve.
It is designed to accumulate in the key booster .

[0005]

When the start of the engine is detected, the negative pressure control means drives the bypass control valve to change the bypass air amount. As a result, the engine speed fluctuates within a predetermined range, and a negative pressure is accumulated in the brake booster via the check valve with the fluctuation of the engine speed. When a predetermined time has elapsed from the start of the engine, a predetermined negative pressure is accumulated in the brake booster, so that the negative pressure control of the bypass control valve is terminated. In the present invention, instead of uniformly increasing the engine speed, the negative pressure is accumulated in the brake booster while fluctuating the engine speed up and down by a predetermined width . It can be almost equal to the idle speed. Further, the fluctuation time of the engine speed for obtaining the predetermined brake booster negative pressure can be shortened as compared with the case where the engine speed is uniformly increased. Therefore, the lack of boost can be solved without giving the driving vehicle any discomfort or anxiety.

In the case of a vehicle provided with an idle speed control device, the bypass passage and the bypass control valve of the present invention may be used also as a bypass passage and a bypass control valve for controlling the idle speed. Further, it is possible to detect the negative pressure of the brake booster and control the bypass control valve without measuring the predetermined time from the start of the engine by the timing means as in the present invention. Will be needed. On the other hand, since the clocking means is built in a normal computer, another sensor or timer is not required, and the configuration can be simplified. The time for changing the engine speed is experimentally determined according to the type of engine, the capacity of the brake booster, and the like.

[0007]

1 shows a control system for an engine 1 and a brake booster 20 according to the present invention. The air sucked from the air cleaner 2 is sent to the intake passage 3 of the engine 1, passes through the throttle valve 4 and the fuel injection valve 5, and is sent to the combustion chamber 6 of the engine 1. A bypass passage 7 is provided in the intake passage 3 so as to bypass the throttle valve 4, and a bypass control valve 8 for adjusting a bypass air amount is provided in the middle of the bypass passage 7. The bypass control valve 8 is constituted by, for example, a duty control solenoid valve.

The microcomputer 10 controls the fuel injection of the engine 1, the idling speed control, and the negative pressure control of the brake booster 20, and includes a throttle opening sensor 11 for detecting the opening of the throttle valve 4; An intake pressure sensor 12 for detecting the intake air pressure flowing through the intake passage 3 downstream of the valve 4, an intake temperature sensor 13 for detecting the intake air temperature, an engine water temperature sensor 14 for detecting the engine water temperature, and an engine for detecting the engine speed. A signal is input from each of the rotation speed sensors 15. Signals are also input from an external load sensor 16 for detecting an external load such as an air conditioner and a starter switch 17. The microcomputer 10 comprehensively determines these input signals and controls the fuel injection valve 5 and the bypass control valve 8. Specifically, the intake air amount is calculated from the intake pressure, the intake air temperature, and the engine speed, the basic injection amount per cycle is determined according to the intake air amount, and various corrections are performed on the final injection amount. The amount is determined, and control is performed so that the injection amount of the fuel injection valve 5 matches the final injection amount. During idling, the opening of the bypass control valve 8 is controlled according to the engine speed, and feedback control is performed so that the engine speed converges to a predetermined target idle speed. It is not included in a predetermined time t ₁ after starting the engine, which will be described later at the time of idling.

A pipe 21 leading to a brake booster 20 is connected to the intake passage 3 downstream of the throttle valve 4. A check valve 22 is provided in the middle of the pipe 21 so as to maintain the maximum negative pressure of the brake booster 20. In this embodiment, the brake booster 20 is a direct type located between the brake pedal 23 and the master cylinder 24. When the brake pedal 23 is depressed, the operating force is boosted by the brake booster 20 and transmitted to the master cylinder 24. You. The brake pressure is sent from the master cylinder 24 to brake devices (not shown) for the front and rear wheels.

Next, the operation of the control system having the above configuration, in particular, the negative pressure control of the brake booster 20 will be described with reference to FIG.
It will be described according to. First, in step S _1, determines whether or not the starter switch 17 turns ON. If I have turned ON, the starter switch 17 OF Step S ₂
It is determined whether or not F has been performed. If it is ON, the determination is continued until the starter switch 17 is turned OFF. In addition,
If the starter switch 17 has not been turned on from the beginning, the process ends.

After the starter switch 17 is turned on, the OF
When F determines whether the idling state in step S _3. This determination is for determining whether or not the engine continues to rotate at a certain speed or higher even after the starter switch 17 is turned off and the throttle valve 4 is closed (idle switch ON). If the engine is stopped immediately after turning off the throttle valve or the throttle valve 4 is opened, the process ends. If the idling state in step S _3, the elapsed time T after the engine start is set to 0 in step S _4, followed by the detected intake negative pressure P _M (absolute value by the intake pressure sensor 12 in step S ₅ ) Is compared with the set value A (absolute value) for negative pressure control of the brake booster 20. The set value A is set to a value at which the brake booster 20 can exhibit a predetermined boosting performance, and is about -450 mmHg in a normal case. P _M
If ≧ A, it means that a predetermined negative pressure has been accumulated in the brake booster 20, and the process ends immediately. If P _M <A, step S ₆ due to insufficient negative pressure
The following negative pressure control is executed.

[0012] First, compared with the set time t ₁ elapsed time T and the negative pressure control from the engine start at the step S _6. T
> In the case of t _1, since elapsed already time to perform control negative pressure, ended, in the case of T ≦ t _1, since has not elapsed yet time, the bypass control as Step S ₇ The valve 8 is controlled to open. Specifically, the duty ratio of the bypass control valve 8 is increased, the opening degree is increased, and the amount of air flowing through the bypass passage 7 is increased. This allows
Since the engine speed N is increased, comparing the engine speed N and the upper limit value n ₁ of the variation width in step S _8. N <n
When _one compares the elapsed time T and the set time t ₁ of the negative pressure control in step S _9. This set time t ₁ is experimentally obtained as a time required for the predetermined negative pressure A to be stored in the brake booster 20 when the engine speed N is varied between the upper limit value n ₁ and the lower limit value n _2. It is usually several seconds to several tens of seconds. If T> t ₁ , the process ends. If T ≦ t ₁ , the process from step S ₇ is performed again. If in step S ₈ in N ≧ n _1, then the bypass control valve 8 is controlled in the closing direction as step S _10. Specifically, the duty ratio of the bypass control valve 8 is reduced,
The amount of air flowing through the bypass passage 7 is reduced by reducing the opening degree. Thus, since the engine rotational speed N is decreased, comparing the engine speed N and the lower limit value n ₂ of the variation width in step S _11. Of the time N> n _2, is compared with the elapsed time T and the set time t ₁ of the negative pressure control in step S _12, T>
to end in the case of t _1. In the case of T ≦ t ₁ executes the following steps S ₁₀ again. In step S _11, N
Once the ≦ n _2, repeat the following control steps S _6.

By performing the above-described negative pressure control, the engine speed N fluctuates between an upper limit value n ₁ and a lower limit value n ₂ as shown in FIG. Due to the fluctuation of the engine speed, the negative pressure of the intake passage 3 also fluctuates, and only the maximum negative pressure is accumulated in the brake booster 20 by the action of the check valve 22. Therefore, the lack of boost of the brake booster immediately after the start of the engine can be eliminated in a short time, and the braking performance is improved. In order to eliminate an uncomfortable feeling or uneasiness of the driver, the average value of the upper limit value n ₁ and the lower limit value n ₂ to the vicinity of the target idle speed, the fluctuation width (n ₁ -n ₂₎ the rotational speed of the target idle It is desirable to set to 20% or less. Since the target idle speed changes depending on an external load such as an air conditioner, the upper limit value n ₁ and the lower limit value n ₂ may be set accordingly. Elapsed time T from engine start
Is longer than the set time t ₁ , the negative pressure control is automatically terminated, and thereafter, the control may be shifted to the normal idle speed control.

In the electronically controlled fuel injection engine of the above embodiment, the intake air amount is calculated from the intake air temperature, intake pressure and engine speed to determine the fuel injection amount per cycle. Alternatively, the intake air amount may be directly measured to determine the fuel injection amount per cycle from the intake air amount. Further, in the above-described embodiment, the vehicle having the idle speed control device has been described, but the present invention can be applied to a vehicle having no such device. However, since the microcomputer that executes the fuel injection control and the idle speed control can be used for the negative pressure control of the present invention, it is not necessary to mount another microcomputer, and the bypass control valve, the intake pressure sensor, and the intake temperature are not required. Since devices such as a sensor and an engine speed sensor are mounted on a general automobile, there is no need to provide a device dedicated to the present invention, and the device can be realized only by changing the software of the microcomputer.

[0015]

As is apparent from the above description, according to the present invention, the amount of bypass air is changed only for a fixed time immediately after the start of the engine, thereby changing the engine speed within a predetermined range. In addition, a negative pressure is accumulated in the brake booster with the fluctuation of the engine speed, and the lack of boost is eliminated in a short time. Further, since only the engine speed is changed, there is no need to abnormally increase the idle speed, and the fluctuation time of the engine speed can be shortened as compared with the case where the engine speed is uniformly increased. Therefore, the lack of boost can be solved without giving the driving vehicle any discomfort or anxiety.

[Brief description of the drawings]

FIG. 1 is a control system diagram including a negative pressure control device according to the present invention.

FIG. 2 is a flowchart showing the operation of the negative pressure control device according to the present invention.

FIG. 3 is a time chart at the time of negative pressure control according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 3 Intake passage 4 Throttle valve 5 Fuel injection valve 7 Bypass passage 8 Bypass control valve 10 Microcomputer 12 Intake pressure sensor 13 Intake temperature sensor 15 Engine speed sensor 20 Brake booster 22 Check valve

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B60T 13/46-13/56

Claims (1)

(57) [Claims] 1. An electronically controlled fuel injection engine for controlling a fuel injection amount in accordance with an intake air amount, a negative intake pressure of the engine being introduced through a check valve, and a brake operation using the negative intake pressure. In a motor vehicle equipped with a brake booster for boosting power, a bypass passage provided to bypass a throttle valve in an intake passage of an engine, a bypass control valve for adjusting an amount of air passing through the bypass passage, and an engine rotation An engine speed sensor for detecting the engine speed, a timer for measuring the time after the engine is started, and a reciprocating control of the bypass control valve in the opening and closing directions for a certain period immediately after the engine is started.
Control to vary the amount of air passing through the bypass passage,
Jin rpm provided a negative pressure control means for varying up and down in a predetermined width, the intake of the engine with the engine speed fluctuation
Negative pressure is stored in the brake booster via a check valve
Negative pressure control apparatus for a brake booster, characterized in that the the like.