KR101887965B1 - A Negative Pressure Forming Apparatus Using the Differential Pressure Valve - Google Patents

Abstract

The present invention relates to an automotive brake negative pressure apparatus, and more particularly, to a brake negative pressure apparatus for vehicle, which does not use a separate device such as a vacuum pump or a supercharger, To a negative pressure generating device for a vehicle.
According to an embodiment of the present invention, an intake manifold for supplying outside air to a combustion chamber of an engine is provided. A turbo charger composed of a turbine and a compressor, compresses the outside air using the exhaust gas discharged from the combustion chamber, and supplies the compressed air to the combustion chamber; An outside air inflow path for supplying outside air to the compressor; An LP-EGR flow path for recirculating the exhaust gas passed through the turbine to the outside air inflow passage at the front end of the compressor; A differential pressure valve for generating a negative pressure for unidirectional flow of the exhaust gas passing through the LP-EGR passage; A supercharging oil passage connecting the compressor and the intake manifold; A vacuum chamber for forming a back force of the brake; A first negative pressure forming flow path connected between the vacuum chamber and the intake manifold; A first negative pressure forming valve located on the first negative pressure forming flow path to open and close the first negative pressure forming flow path; A second negative pressure forming flow path connected between the vacuum chamber and the outside air inflow path; And a second negative pressure forming valve located on the second negative pressure forming flow passage for opening and closing the second negative pressure forming flow passage.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a negative pressure applying device using a differential pressure valve,

The present invention relates to an automotive brake negative pressure apparatus, and more particularly, to a brake negative pressure apparatus for vehicle, which does not use a separate device such as a vacuum pump or a supercharger, To a negative pressure generating device for a vehicle.

Generally, the term "exhaust gas recirculation (EGR)" refers to a technique in which a part of the exhaust gas of the engine is circulated back to the intake system of the engine to utilize the exhaust gas together with the outside air for combustion. And there is an advantage that NOx discharged into the atmosphere can be reduced by recirculating the exhaust gas.

An example of a diesel turbocharged engine in which EGR technology is actively applied to a classification system of exhaust gas recirculation technology will be described by taking as an example the position at which the gas flow is returned from the internal combustion engine exhaust system to the intake side, Therefore, EGR can be classified into HP-EGR (High Pressure EGR) and LP-EGR (Low Pressure EGR). More specifically, the HP-EGR utilizes a high-temperature and high-pressure exhaust gas having a low pressure drop as an EGR gas by using a recirculation flow path connected from the turbine front end of the turbocharger to the intake manifold side. In contrast, LP-EGR has a difference in that exhaust gas having a relatively lower pressure drop is used as EGR gas in comparison with HP-EGR using a recirculation flow path connected from the rear end of the turbine to the outside air intake flow path side of the compressor front end.

EGR technology is a combination of technologies such as DOC (Diesel Oxidation Catalyst), DPF (Diesel Particulate Filter) and SCR (Selective Catalytic Reduction) technologies in gasoline or diesel engines. ) Have been used to reduce.

In the past, this type of EGR technology has been used mainly for HP-EGR, which is advantageous in that the reaction speed is fast and the exhaust gas is recirculated without contamination of the turbocharger. However, in recent years, the HP-EGR and the LP- Many mixed EGR systems are used together. Unlike HP-EGR, LP-EGR also has advantages in that it is relatively more advantageous than HP-EGR in terms of intake-on-cooling and EGR distribution.

In addition, LP-EGR technology has been attracting attention in recent years in terms of fuel efficiency improvement in gasoline turbocharged engines. In the gasoline turbocharged engine, LP-EGR is more advantageous than HP-EGR because of the limited use of HP-EGR due to lack of pressure difference between intake and exhaust at low speed and high load (actual operation range) This is because the shortage of negative pressure in the intake manifold causes supercharging at the front end of the compressor (ie, using LP-EGR), which is advantageous in terms of securing the EGR flow rate. Due to these advantages, research and development of LP-EGR technology and related technologies are becoming more important.

In view of such a situation, the following description of the present invention discloses a brake negative pressure device for a vehicle using LP-EGR as a linkage technique of LP-EGR technology.

Korean Patent Registration No. 10-1448777 discloses a brake negative pressure generating apparatus for a vehicle. According to Korean Patent No. 10-1448777, a separate electric supercharger is provided in an internal combustion engine provided with a turbocharger for forming a negative pressure for energizing a brake operating force. The supercharger boosts the suction by operating the supercharger through the rotation of the crankshaft of the engine. In the prior art, when the negative pressure of the brake is insufficient, the supercharger operates to supplement the negative pressure. However, super-charger has a large volume due to the characteristics of a device using the rotation of the crankshaft, and can not expect a very high output increase effect compared with its size. Therefore, in order to generate a negative pressure necessary for the brake booster, Efficiency is very low.

In an internal combustion engine not provided with a supercharger, a separate additional component such as a vacuum pump may be provided for generating a negative pressure of the brake. However, the volume of the vacuum pump and the cost of providing a vacuum pump It will be difficult to consider it as the best way to form negative pressure.

Korean Patent No. 10-1448777

SUMMARY OF THE INVENTION In the present invention, there is a need to provide a vehicle brake negative pressure apparatus which forms a brake negative pressure through operation of a differential pressure generating valve that generates a differential pressure of LP-EGR without using a separate device such as a vacuum pump or a supercharger.

According to an aspect of the present invention, there is provided a brake negative pressure apparatus comprising: an intake manifold for supplying a mixer to a combustion chamber of an engine; A turbo charger composed of a turbine and a compressor, compressing outside air using exhaust gas discharged from the combustion chamber, and supplying a mixer to the combustion chamber; An outside air inflow path for supplying outside air to the compressor; An LP-EGR flow path for recirculating the exhaust gas passed through the turbine to the outside air inflow passage at the front end of the compressor; A differential pressure valve for generating a negative pressure for smooth flow of the exhaust gas passing through the LP-EGR passage; A supercharging oil passage connecting the compressor and the intake manifold; A vacuum chamber for forming a back force of the brake; A first negative pressure forming flow path connected between the vacuum chamber and the intake manifold; A first negative pressure forming valve located on the first negative pressure forming flow path to open and close the first negative pressure forming flow path; A second negative pressure forming flow path connected between the vacuum chamber and the outside air inflow path; And a second negative pressure forming valve located on the second negative pressure forming flow path to open and close the second negative pressure forming flow passage, wherein the differential pressure valve is controlled to be closed in a specific boost region in which the pressure of the intake manifold is greater than atmospheric pressure, And the second negative pressure forming valve is controlled to be opened so that a negative pressure can be formed in the vacuum chamber.

According to one embodiment, the differential pressure valve may be installed on the outside air inlet flow path at a front end of a portion to which the LP-EGR flow path is connected.

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Here, the throttle controlling the amount of intake air flowing into the intake manifold may be closed control.

According to an embodiment, the differential pressure valve is not closed-controlled in the remaining region excluding the specific supercharging region including the full load region, and the second negative pressure-forming valve may be closed-controlled.

According to an embodiment of the present invention, it is possible to further include a second recirculation flow path for recirculating the outside air supercharged from the supercharging flow path to the outside air inflow flow path, and a second recirculation valve for opening and closing the second recirculation flow path.

A method of forming a brake negative pressure using the differential pressure valve of the present invention comprises the steps of: (a) requesting a negative pressure for forming a brake force; (b) comparing the pressure of the intake manifold with the atmospheric pressure to determine whether the pressure of the intake manifold is formed to a pressure greater than the atmospheric pressure; (c) when the pressure of the intake manifold is formed to be higher than atmospheric pressure in the step (b), closing control is performed on the first negative pressure forming flow path connected between the vacuum chamber forming the power of the brake and the intake manifold A negative pressure forming flow path opening / closing control step of opening and closing a second negative pressure forming flow path connected between the vacuum chamber and the outside air inflow path; And (d) a differential pressure valve control step of controlling the differential pressure valve to close when the pressure of the intake manifold is formed to a pressure greater than the atmospheric pressure in the step (b).

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The present invention has the advantage of enabling the brake pressure to be formed without additional components such as a vacuum pump or a supercharger by making the differential pressure valve, which is configured for the negative pressure of the LP-EGR, be utilized as a negative pressure forming purpose of the brake booster have.

In general, the differential pressure valve of LP-EGR is not used to exert the differential pressure function of the EGR system in the entire load region (WOT) of the engine. It is advantageous to increase the efficiency of the EGR system .

1 is a conceptual diagram of a brake negative pressure apparatus using a differential pressure valve according to an embodiment of the present invention.
2 is a graph showing an operating state of a differential pressure valve for generating a negative pressure in a brake according to an embodiment of the present invention.
3 is a block diagram showing a negative pressure forming method of the brake negative pressure apparatus using the differential pressure valve according to an embodiment of the present invention.

The embodiments described below are provided so that those skilled in the art can easily understand the technical idea of the present invention, and thus the present invention is not limited thereto. In addition, the matters described in the attached drawings may be different from those actually implemented by the schematic drawings to easily describe the embodiments of the present invention.

The singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. Means that a feature, number, step, operation, element, component, or combination of features described in the specification is meant to imply the presence of one or more other features, A step, an operation, an element, a component, or a combination thereof.

Also, the expressions such as 'first, second', etc. are used only to distinguish a plurality of configurations, and do not limit the order or other features between configurations.

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

1 is a conceptual diagram of a brake negative pressure apparatus using a differential pressure valve according to an embodiment of the present invention. 2 is a graph showing an operating state of a differential pressure valve for generating a negative pressure in a brake according to an embodiment of the present invention. 3 is a block diagram showing a negative pressure forming method of the brake negative pressure apparatus using the differential pressure valve according to an embodiment of the present invention.

The brake negative pressure apparatus using a differential pressure valve according to an embodiment of the present invention includes an intake manifold 110 for supplying a mixer to a combustion chamber 100 of an engine; A turbocharger 130 composed of a turbine and a compressor (or an impeller), compresses outside air using exhaust gas discharged from the combustion chamber 100, and supplies a mixer to the combustion chamber; An outside air inflow passage 170 for supplying outside air to the compressor; An LP-EGR passage (150) for recirculating the exhaust gas passed through the turbine to the outside air inflow passage at the front end of the compressor; A differential pressure valve 173 for generating a negative pressure for unidirectional flow of the exhaust gas passing through the LP-EGR passage; A supercharging flow passage 190 connecting the compressor and the intake manifold 110; A vacuum chamber (230) for forming the force of the brake; A first negative pressure forming flow path 210 connected between the vacuum chamber 230 and the intake manifold 110; A first negative pressure forming valve 211 located on the first negative pressure forming passage 210 to open and close the first negative pressure forming passage 210; A second negative pressure forming flow path 220 connected between the vacuum chamber 230 and the outside air inflow path 170; And a second negative pressure forming valve 221 located on the second negative pressure forming passage 220 to open and close the second negative pressure forming passage 220.

For better understanding of the present invention, the components of the brake negative pressure device of the present invention will be described in detail with reference to FIG.

An intake manifold 110 for introducing air or a mixture of air and fuel is connected to one side of the combustion chamber 100 of the engine and an exhaust manifold for exhausting the exhaust gas generated in the combustion chamber 100 is connected to the other side Lt; / RTI >

According to an embodiment of the present invention, a turbocharger 130 (Turbo-Charger) is connected as a structure for compressing the air using the pressure of the exhaust gas discharged through the exhaust manifold and supplying the compressed air to the intake manifold . The turbine constituting the turbocharger 130 is connected to the exhaust manifold and the compressor (or impeller) constituting the turbocharger 130 may be connected to the intake manifold 110 side. An exhaust passage is formed in the exhaust manifold so as to guide the exhaust gas to the outside.

A catalytic converter is installed in the exhaust passage to reduce harmful components contained in the exhaust gas discharged through the exhaust passage. For example, the catalytic converter may correspond to a warm-up catalytic converter (WCC) 140 and an underfloor catalytic converter 160 (ufCC).

An exhaust gas recirculation (EGR) system may be installed in the exhaust passage between the two catalytic converters 140 and 160 to recirculate part of the exhaust gas to the intake system. The EGR system typically includes an exhaust gas recirculation cooler for reducing the temperature of the EGR flow path and a relatively high temperature exhaust gas, and an EGR valve 152 for controlling the exhaust gas flowing into the EGR flow path do.

Particularly, the LP-EGR system is applied to the EGR system here. The LP-EGR passes through the downstream end of the catalytic converter, so it has the advantage of using purified EGR gas and the advantage of using exhaust gas of low temperature.

The turbocharger 130 is connected to an outside air inflow passage 170 through which outside air (or fresh air) is sucked from the outside and an LP-EGR air passage 150 is connected to the outside air inflow passage 170 The turbocharger 130 compresses the outside air and a part of the exhaust gas and supplies the compressed air to the intake manifold 110 side.

Meanwhile, the outside air inflow passage 170 is provided with an air cleaner 171 for filtering foreign substances contained in the outside air to be sucked, and an HFM (for example, 172 may be installed. A differential pressure valve 173 (DCV) is installed in the outside air inflow passage 170. The operation of the differential pressure valve 173 will be described later in detail.

The turbocharger 130 supplies a mixture of outside air and exhaust gas to the intake manifold 110 via a supercharging flow path 190. An intercooler 191 may be installed in the middle of the supercharging flow passage 190 to cool the mixer that is compressed by the turbocharger 130 and supply the cooled mixture to the intake manifold 110 side. Here, the intercooler 191 functions to cool the intake air injected through either the air cooling type or the water cooling type, and the intake air mixture flows into the intake manifold 110 in a state of being lowered to a temperature suitable for combustion. However, it should be noted here that the mixer refers to a mixture of outside air and exhaust gas and does not mean a mixture of fuel and air. In the present invention, since the mixer is supercharged at a predetermined pressure or higher through the turbocharger, the mixer may be referred to as a supercharger in some cases.

A throttle 192 may be installed on the supercharging flow passage 190 to control a mixer (or an intake flow rate) flowing into the intake manifold 110 through the intercooler 191. [ Further, pressure sensors 111 for measuring the pressure on the intake manifold supercharge passage 190 for pressure sensing may additionally be provided.

In addition, the negative pressure device according to an embodiment of the present invention may be provided with a second recirculation passage 180 and a second recirculation valve (RCV) 181 for selectively discharging the intake air flow rate from the supercharging passage 190.

The vacuum chamber 230 of the present invention is a component provided for the formation of power of the brake booster 240, and replenishes a deficient boosting force due to the negative pressure on the intake manifold 110 side. One end of the first negative pressure forming flow path 210 is connected to one side of the intake manifold 110 and the other end of the first negative pressure forming flow path 210 is connected to the side of the vacuum chamber 230.

If a negative pressure is formed in the intake manifold 110 while the vehicle is running, a negative pressure may be formed in the vacuum chamber 230 through the first negative pressure forming flow path 210, The booster 240 forms a boosting force by using a negative pressure so that a smooth brake operation is performed.

The second recirculation valve 181 is controlled by a method of forming a negative pressure in the intake manifold 110. Specifically, when the intake air flow rate is discharged again toward the outside air inflow passage 170 through the second recirculation valve 181, a negative pressure can be formed on the intake manifold 110 side as a result.

However, in the full load region (WOT) of the driving range of the vehicle, the boost can be performed to achieve the basic goal of output increase. Accordingly, in the full load region WOT, a positive pressure (or a boost pressure), not a negative pressure, is formed in the intake manifold. The static pressure inside the intake manifold is recirculated through the intake recirculation valve 181 There is a time limit to make negative pressure using. If the driver depresses the brake in this situation, a situation may occur in which the vacuum chamber 230 is not provided with sufficient negative pressure.

Therefore, in the present invention, a second negative pressure forming flow path 220 separate from the first negative pressure forming flow path 210 is provided so as to provide a sufficient negative pressure to form the brake force.

That is, in the present invention, the second negative pressure forming flow path 220 and the second negative pressure forming valve 221 for opening and closing the second negative pressure forming flow path are formed, and these configurations are applied to the LP- And provides a negative pressure to the vacuum chamber 230 in cooperation with the differential pressure valve 173 provided to generate the negative pressure. Here, in order to smoothly flow the exhaust gas recirculated in the LP-EGR passage, the differential pressure valve controls the flow of the exhaust gas from the downstream end of the catalytic converter, which is the discharge position, to the outside air inflow passage 170, A negative pressure can be generated on the flow path 170 side.

Specifically, according to an embodiment of the present invention, the differential pressure valve performs a closing control in a specific boost region including a full load region (WOT), and at the same time forms a negative pressure by opening and controlling the second negative pressure forming valve. By providing a negative pressure formed on the outside air inflow passage 170 side to the vacuum chamber 230, it is possible to form a sufficient force of the brake. It is possible to provide a negative pressure to the vacuum chamber 230 by using a differential pressure valve 173 provided for the purpose of forming a differential pressure in driving the LP-EGR system without a separate negative pressure forming device such as a vacuum pump or a supercharger. However, in this case, it is important to control the timing of the vehicle by using a specific boost region. Timing control will be described later in detail with reference to FIG.

Further, when the negative pressure is provided through the first negative pressure forming flow path 210 by controlling the closing of the throttle 192 for controlling the amount of intake air flowing into the intake manifold, the brake force required by the driver can be formed more quickly .

On the other hand, since the differential pressure valve does not need to form a negative pressure using the second negative pressure forming flow channel in the regions other than the specific boost region including the full load region, the control process may not be used. Specifically, in a situation in which the EGR system is actively operated or a sufficient brake force is provided only by the negative pressure formed on the intake manifold 110 side, the differential pressure valve is not closed and the second negative pressure forming valve is closed .

2, G1 denotes an intake manifold side pressure, G2 denotes a compressor front end pressure, G3 denotes an accelerator pedal operation state, G4 denotes an accelerator pedal operation state, G5 denotes the operating state of the first negative pressure forming valve 211, G6 denotes the operating state of the second negative pressure forming valve 221, and G7 denotes the operating state of the differential pressure valve 173. The operating state of each pedal and valve may refer to the time of arrival of the particular control signal type delivered to the control portion of the vehicle.

Referring to graph G1 in FIG. 2, the intake manifold side pressure is monotonously decreased by taking a peak at a constant pressure (ex 1 bar) or more in a constant pressure state (or supercharging state) , The compressor front end pressure monotonously decreases at a constant pressure.

Referring to the G3 graph and the G4 graph, the Excel pedal changes from the On state to the Off state, and then the brake pedal changes from the Off state to the On state. Referring to the G5 graph and the G6 graph, when the first negative pressure forming valve 211 is switched from the open state to the closed state, the second negative pressure forming valve 221 is opened at the same time. Referring to the graph G7, the differential pressure valve 173 is also closed in the open state simultaneously with the closing operation of the brake pedal.

A portion indicated by a broken line in FIG. 2 may mean a period in which the effect of forming a negative pressure in the present invention appears. The range can achieve the effect of conformance for a predetermined period of time from the time point when the brake valve is closed (the time point when the differential pressure valve is closed).

For reference, the first negative pressure forming valve 211 and the second negative pressure forming valve 221 are respectively closed from the open state to the closed state within a predetermined short time after the on / off switching of the Excel pedal under the positive pressure state, It can be switched to the open state. What is important here is that the state control of the first negative pressure forming valve 211 and the second negative pressure forming valve 221 can be performed in advance for a predetermined time prior to the On control of the brake pedal for quick control. This feature is shown in detail on the time axis of FIG. This makes it possible to quickly provide the brake booster with the power.

The negative pressure build-up of the brake using the differential pressure valve will be described from a method perspective as shown in Fig.

The brake actuation step S310 may specifically mean receiving a negative pressure request from the driver for forming the brake force.

In step S320, it is determined whether the pressure of the intake manifold is greater than the atmospheric pressure. If the pressure of the intake manifold is greater than the atmospheric pressure If it is not formed, the brake negative pressure formation using the differential pressure valve is terminated. If the pressure of the intake manifold is formed to be higher than the atmospheric pressure, the process proceeds to the next step.

The brake negative pressure forming method of this embodiment closes the first negative pressure forming flow path connected between the vacuum chamber forming the brake force of the brake and the intake manifold when the pressure of the intake manifold is formed at a pressure higher than the atmospheric pressure, And a negative pressure forming flow path opening / closing control step (S330) for controlling opening and closing of a second negative pressure forming flow path connected between the vacuum chamber and the outside air inflow path. When the pressure of the intake manifold is formed to be higher than atmospheric pressure, (S340) for controlling closing of the differential pressure valve (DCV). For reference, reference numerals denoted by S310, S320, S330, S340, and S350 do not necessarily denote the time series. For example, the order of steps S330 and S340 may be reversed or concurrently performed.

The brake negative pressure device using the differential pressure valve according to another embodiment of the present invention is as follows.

A brake negative pressure apparatus using a differential pressure valve according to another embodiment of the present invention includes a differential pressure valve for generating a negative pressure for smooth flow of exhaust gas in an EGR passage; A vacuum chamber for forming a back force of the brake; A negative pressure forming flow path connecting the vacuum chamber formed with the negative pressure by the differential pressure valve and the vacuum chamber; And a negative pressure forming valve for opening and closing the negative pressure forming flow passage.

The negative pressure forming flow path in this embodiment corresponds to the above-described second negative pressure forming flow path and performs a function similar to the second negative pressure forming flow path in the above-described embodiment.

Further, according to one embodiment, the EGR flow path herein may correspond to the LP-EGR flow path, and the differential pressure valve may be connected to the upstream side of the portion where the LP- And can form a negative pressure for providing the power of the brake in cooperation with the negative pressure forming valve.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

Therefore, the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

That is, the scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents are included in the scope of the present invention .

100: combustion chamber 180: second recirculation flow path
110: intake manifold 181: second recirculation valve
130: Turbocharger 190: Supercharged Euro
140, 160: catalytic converter 191: intercooler
150: LP-EGR Euro 192: Throttle
151: LP-EGR cooler 210: first negative pressure forming flow path
152: LP-EGR valve 211: first negative pressure forming valve
170: outside air inflow channel 220: second negative pressure forming channel
171: Air cleaner 221: Second negative pressure forming valve
172: HFM 230: vacuum chamber
173: Differential pressure valve 240: Brake booster

Claims (10)

An intake manifold for supplying outside air to a combustion chamber of the engine;
A turbo charger composed of a turbine and a compressor, compresses the outside air using the exhaust gas discharged from the combustion chamber, and supplies the compressed air to the combustion chamber;
An outside air inflow path for supplying outside air to the compressor;
An LP-EGR flow path for recirculating the exhaust gas passed through the turbine to the outside air inflow passage at the front end of the compressor;
A differential pressure valve for generating a negative pressure for smooth flow of the exhaust gas passing through the LP-EGR passage;
A supercharging oil passage connecting the compressor and the intake manifold;
A vacuum chamber for forming a back force of the brake;
A first negative pressure forming flow path connected between the vacuum chamber and the intake manifold;
A first negative pressure forming valve located on the first negative pressure forming flow path to open and close the first negative pressure forming flow path;
A second negative pressure forming flow path connected between the vacuum chamber and the outside air inflow path; And
And a second negative pressure forming valve located on the second negative pressure forming flow passage for opening and closing the second negative pressure forming flow passage,
Wherein the differential pressure valve is controlled to be closed in a specific boost region where the pressure of the intake manifold is larger than the atmospheric pressure and the second negative pressure forming valve is controlled to be opened to thereby form a negative pressure in the vacuum chamber. Brake negative pressure device.
The method according to claim 1,
Wherein the differential pressure valve is installed on a front end of a portion to which the LP-EGR passage is connected on the outside air inflow passage.
delete The method according to claim 1,
Wherein the fixed throttle for controlling the amount of intake air flowing into the intake manifold is closed-controlled.
The method according to claim 1,
Wherein the differential pressure valve is not closed-closed in a region other than a specific supercharging region including a full load region, and the second negative pressure forming valve is closed-controlled.
The method according to claim 1,
A second recirculation flow path for recirculating ambient air supercharged in the supercharging flow path to the outside air inflow flow path, and a second recirculation valve for opening and closing the second recirculation flow path.
(a) a negative pressure request step for forming a brake force;
(b) comparing the pressure of the intake manifold with the atmospheric pressure to determine whether the pressure of the intake manifold is formed to a pressure greater than the atmospheric pressure;
(c) when the pressure of the intake manifold is formed to be higher than atmospheric pressure in the step (b), closing control is performed on the first negative pressure forming flow path connected between the vacuum chamber forming the power of the brake and the intake manifold A negative pressure forming flow path opening / closing control step of opening and closing a second negative pressure forming flow path connected between the vacuum chamber and the outside air inflow path; And
(d) a differential pressure valve control step of controlling the differential pressure valve to close when the pressure of the intake manifold is formed to a pressure greater than the atmospheric pressure in the step (b);
And a pressure difference between the brake fluid and the brake fluid.
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