KR20150143008A - Active hydraulic booster system in vehice and control method thereof - Google Patents

Abstract

Disclosed are an active hydraulic booster system for a vehicle and a control method thereof. According to an embodiment of the present invention, the active hydraulic booster system for a vehicle includes: a motor operating a pump which pumps brake oil from a reservoir of a master cylinder; an accumulator storing the pumped brake oil according to the operation of the operated pump; a hydraulic circuit including a discharge valve at an outlet and an inflow valve at an inlet of each wheel cylinder, to which the brake oil stored in the accumulator is supplied; a boost circuit making the brake oil flow in the hydraulic circuit or making the brake oil of each of wheel cylinder discharged to the reservoir; an apply valve making the brake oil in the accumulator flow in the hydraulic circuit; a release valve discharging the brake oil of each wheel cylinder to the reservoir; and an electronic control unit executing a pressurizing mode, pressurizing wheel pressure of the corresponding wheel cylinder by the PWM control of the release valve and the apply valve in the event of ESC control, a pressure reducing mode reducing the wheel pressure, and a maintaining mode maintaining the current wheel pressure.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active hydraulic booster system for a vehicle,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active hydraulic booster system for a vehicle and a control method thereof, and more particularly, to a vehicular active posture control system for controlling a pressure of each wheel individually to stabilize a vehicle posture when the behavior of the vehicle is out of steering intention (Hereinafter referred to as " ESC control ") and a control method thereof.

The existing braking system booster is connected to the engine to create a vacuum, which helps the driver to assist the driver with great braking force during braking. In the case of hybrid cars or electric vehicles, when the gasoline engine is not always operating or is not operating, the booster is difficult to operate at all times and does not produce sufficient vacuum. In order to solve this problem, an active hydraulic booster (hereinafter, referred to as "AHB") system is a system in which hydraulic pressure is directly generated by using a motor and a pump instead of a booster, and braking force is secured through the hydraulic pressure.

Such an AHB system performs ESC control to stabilize the vehicle posture by individually controlling the pressure of each wheel when the behavior of the vehicle deviates from the steering intention of the driver.

Generally, the ESC control increases the braking force of the outer wheel of the vehicle turning on the outer braking force of the vehicle on the outside of the vehicle when the oversteer condition is less than the yaw rate of the driver estimated from the vehicle model, And the braking force of the inner wheel of the turning wheel of the vehicle is higher than the braking force of the outer wheel of the turning wheel under the understeering condition in which the actual yaw rate of the vehicle is larger than the turning degree desired by the driver, Creating a compensating moment (inward moment). Thus, the driving stability of the vehicle is improved by controlling the wheel pressure so that the actual yaw rate of the vehicle maintains the yaw rate desired by the driver.

That is, the AHB system controls the operation of the motor and the pump, and the operation of the inlet valve and the outlet valve of the wheel cylinder during the ESC control to adjust the wheel pressure to stabilize the vehicle posture by adjusting the vehicle moment.

Conventionally, when controlling the pressure of each wheel, the inlet side valve and the outlet side valve of the wheel cylinder are turned on or off. As a result, operating noise of the inlet side valve and the outlet side valve largely occurs. Further, since the pressure of each wheel is controlled in a step-like manner by the ON or OFF operation of the inlet side valve and the outlet side valve, it is very difficult to accurately estimate the pressure of each wheel, so that relatively precise pressure control may not be performed.

According to an embodiment of the present invention, there is provided an active hydraulic booster system for a vehicle and a control method thereof, which can reduce operational noise of a valve during ESC control and improve precision of wheel pressure control.

According to an aspect of the present invention, there is provided an active hydraulic booster system for a vehicle, comprising: a motor for driving a pump for pumping brake oil from a reservoir of a master cylinder; An accumulator for storing the pumped brake oil according to an operation of the pump driven by the motor; A hydraulic circuit including an inlet valve provided at an inlet side of each wheel cylinder to which brake oil stored in the accumulator is supplied and an outlet valve provided at an outlet side; A boost circuit that allows the brake fluid stored in the accumulator to flow into the hydraulic circuit or the brake fluid of each wheel cylinder to be discharged to the reservoir; Wherein the boost circuit includes an apply valve for introducing the brake oil stored in the accumulator into the hydraulic circuit, and a release valve for discharging the brake oil of each wheel cylinder to the reservoir, And an electronic control unit that performs either a pressurizing mode for pressurizing the wheel pressure of the wheel cylinder by PWM control of the release valve, a pressure reducing mode for reducing the wheel pressure, or a holding mode for maintaining the current wheel pressure An active hydraulic booster system of the vehicle can be provided.

Further, the electronic control unit controls the target pressure to maintain the vehicle in a stable vehicle posture while performing the control mode of any one of the pressure mode, the depressurization mode, and the maintenance mode, The PWM duty ratio of the apply valve and the release valve may be adjusted for each control mode so that the final target pressure is determined by applying the corresponding target pressure change amount and the current wheel pressure follows the determined final target pressure .

The electronic control unit may determine that the road surface on which the vehicle travels is one of a plurality of states of a dry state, a wet state, a snowy state (Snowy), and an ice state (Icy) The target pressure change amount can be set differently for each control mode according to the state.

Further, the pressurizing mode is divided into a maximum pressure mode for pressing the wheel pressure at the beginning of the ESC control and a pressurizing mode for pressing the wheel pressure if necessary after the maximum pressure mode afterward, and the electronic control unit Setting a first target pressure increase amount in accordance with the determined road surface condition so as to correspond to the mode and setting a second target pressure increase amount in accordance with the determined road surface condition to correspond to the pressurization mode, The target pressure reduction amount can be set according to the road surface condition.

In the ESC control, the electronic control unit determines the final target pressure in the maximum pressure mode section by applying the set first target pressure increase amount to the current target pressure during the maximum pressure mode period during the ESC control, Determines the final target pressure of the pressure mode section by applying the set second target pressure increase amount to the current target pressure in the pressure mode section, adjusts the PWM duty ratio of the apply valve and the release valve according to the target duty cycle, The PWM duty ratio of the apply valve and the release valve is adjusted in accordance with the determined final target pressure, and in the depressurization mode section, the set target pressure decrease amount is applied to the current target pressure, , And determines, based on the determined final target pressure, The PWM duty ratio of the Leize valve can be adjusted.

According to another aspect of the present invention, there is provided a method for controlling a brake fluid supply system including a motor for driving a pump for pumping brake oil from a reservoir of a master cylinder, an accumulator for storing the pumped brake oil according to an operation of the pump driven by the motor, A hydraulic circuit including an inlet valve provided at an inlet side of each wheel cylinder supplied with brake oil stored in the accumulator and an outlet valve provided at an outlet side of the wheel cylinder to allow the brake oil stored in the accumulator to flow into the hydraulic circuit, A boost circuit that is provided to discharge brake oil to the reservoir; an apply valve that introduces the brake oil stored in the accumulator into the hydraulic circuit; Valve included The present invention provides a control method of an active hydraulic booster system of a vehicle, comprising: a pressure mode for determining whether it is an ESC control and for pressing a wheel pressure of the wheel cylinder during the ESC control; a reduced pressure mode for reducing the wheel pressure; The present invention can provide a control method of an active hydraulic booster system of a vehicle that performs PWM control of the apply valve and the release valve so as to perform either one of the maintenance mode in which the hydraulic pressure booster is maintained.

The PWM control of the apply valve and the release valve may be performed by controlling the target pressure to maintain the vehicle in a stable vehicle posture during the execution of any one of the pressure mode, Determining a final target pressure by applying a set target pressure change amount corresponding to a road surface state on which the vehicle travels in each mode and determining whether the current wheel pressure is in accordance with the determined final target pressure, The PWM duty ratio of the valve can be adjusted.

According to one aspect of the present invention, a target pressure is determined for each control mode by using a target pressure increase amount and a reduction amount according to the road surface state during ESC control, and an apply valve and a release valve So that the operating noise of the valve can be reduced and the precision of the wheel pressure control can be improved.

1 is a hydraulic circuit diagram of an active hydraulic booster system of a vehicle according to an embodiment of the present invention.
2 is a schematic control block diagram of an active hydraulic booster system for a vehicle according to an embodiment of the present invention.
3 is a hydraulic circuit diagram for explaining the flow of hydraulic pressure when pressurizing wheel pressure during ESC control in an active hydraulic booster system of a vehicle according to an embodiment of the present invention.
4 is a timing diagram of each valve when the wheel pressure is applied during ESC control in the active hydraulic booster system of the vehicle according to the embodiment of the present invention.
5 is a hydraulic circuit diagram for explaining the flow of hydraulic pressure when the wheel pressure is reduced during the ESC control in the active hydraulic booster system of the vehicle according to the embodiment of the present invention.
6 is a timing diagram of each valve when reducing wheel pressure during ESC control in an active hydraulic booster system of a vehicle according to an embodiment of the present invention.
7 is a control flowchart of an active hydraulic booster system for a vehicle according to an embodiment of the present invention.
8 is a graph for explaining the wheel pressure control for each control mode in the ESC control in the active hydraulic booster system of the vehicle according to the embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments described below are provided by way of example so that those skilled in the art will be able to fully understand the spirit of the present invention. The present invention is not limited to the embodiments described below, but may be embodied in other forms. In order to clearly explain the present invention, parts not related to the description are omitted from the drawings, and the width, length, thickness, etc. of the components may be exaggerated for convenience. Like reference numerals designate like elements throughout the specification.

1 is a hydraulic circuit diagram of an active hydraulic booster system of a vehicle according to an embodiment of the present invention.

Referring to FIG. 1, an active hydraulic booster system of a vehicle is divided into a hydraulic control apparatus 100 and a power source unit 200.

The hydraulic control apparatus 100 includes a master cylinder 110 to which a force is transmitted from a brake pedal 30 operated by a driver during braking and a reservoir 115 Two hydraulic circuits HC1 and HC2 connected to the two wheels RR, RL, FR and FL respectively, an accumulator 120 for storing a certain level of pressure, A pedal simulator 180 provided to provide a reaction force of the brake pedal 30 and a simulation valve 186 provided in a flow path connecting the pedal simulator 180 and the reservoir 115. [

The hydraulic control apparatus 100 also includes two hydraulic circuits HC1 and HC2 and a hydraulic pressure control valve (not shown) for controlling the pressure delivered from the accumulator 120 to the wheel cylinders 20 provided on the wheels FL, FR, RL, And two boost circuits BC1 and BC2 connected thereto. The boost circuits BC1 and BC2 include the apply valves 141 and 142 and the release valves 143 and 144, respectively.

The power source unit 200 includes a pump 210 for sucking oil from the reservoir 115 to the accumulator 120 for discharging the oil to the accumulator 120 and a motor 220 for driving the pump 210 ).

The hydraulic control apparatus 100 and the power source unit 200 are connected to each other by an external piping 10. That is, the pump 210 of the power source unit 200 and the accumulator 120 of the hydraulic control apparatus 100 are connected by the external piping 10.

Hereinafter, the structure and function of each component constituting the active hydraulic booster system of the vehicle will be described in more detail.

First, the master cylinder 110 has a first piston 111 and a second piston 112 formed therein so as to have two hydraulic circuits, and is configured to generate hydraulic pressure by the pressing force of the brake pedal 30. The master cylinder 110 is connected to two hydraulic circuits HC1 and HC2, respectively. The master cylinder 110 has two hydraulic circuits in order to ensure safety in the event of failure. For example, the first one of the two hydraulic circuits of the master cylinder 110 is connected to the front wheel right wheel FR and the rear wheel right wheel RR of the vehicle and the remaining circuit is connected to the front wheel left wheel FL and the rear wheel left wheel FL .

The master cylinder 110 is provided with a reservoir 115 for storing oil on the upper side and oil discharged from the outlet through a wheel cylinder 20 provided on each of the wheels RR, RL, FR and FL Respectively.

Reference numeral 31 denotes an input rod provided on the brake pedal 30 for transmitting the pressure to the master cylinder 110.

At least one pump 210 is provided for pumping the oil introduced from the reservoir 115 to a high pressure to form a brake pressure. A pump 210 is provided at one side thereof with a motor 220 are provided.

The accumulator 120 is provided at the outlet side of the pump 210 and temporarily stores the high-pressure oil generated by the driving of the pump 210. [ That is, the accumulator 120 is connected to the pump 210 by the external piping 10. At this time, a check valve 135 is installed in the outer pipe 10 to prevent the high-pressure oil stored in the accumulator 120 from flowing backward.

The connection passage 130 is connected to the outer pipe 10 to transmit the brake oil stored in the accumulator 120 to the wheel cylinder 20. The connecting passage 130 includes a first boost circuit BC1 connected to the first hydraulic circuit HC1 and a second boost circuit BC2 connected to the second hydraulic circuit HC2. The first hydraulic circuit HC1 is connected to the front wheel right wheel FR of the vehicle and the rear wheel right wheel RR and the second hydraulic circuit HC2 is connected to the front wheel left wheel FL and the rear wheel left wheel RL do.

The first boost circuit BC1 includes a first apply valve 141 and a first release valve 143 provided on the first boost flow path 131. [ The first apply valve 141 regulates the amount of brake oil flowing into the first hydraulic circuit HCl from the accumulator 120. The first release valve 143 is provided to return some of the brake oil flowing into the first hydraulic circuit HC1 from the accumulator 120 to the reservoir 115 or to move the wheel cylinder 20 of the first hydraulic circuit HC1, So that the brake oil introduced into the reservoir 115 is discharged to the reservoir 115.

A first pressure sensor (103) is provided in the first boost passage (131). The first pressure sensor 103 detects the pressure of the brake oil transmitted to the first boost passage 131. The pressure detected by the first pressure sensor 103 corresponds to the pressure of the front wheel right wheel FR and the wheel cylinder 21 of the rear right wheel RR.

The second boost circuit BC2 includes a second apply valve 142 and a second release valve 144 provided on the second boost flow path 132. The second apply valve 142 regulates the amount of brake oil flowing from the accumulator 120 to the second hydraulic circuit HC2. The second release valve 144 may return some of the brake oil flowing into the second hydraulic circuit HC2 from the accumulator 120 to the reservoir 115 or the wheel cylinder 20 of the second hydraulic circuit HC2, So that the brake oil introduced into the reservoir 115 is discharged to the reservoir 115.

A second pressure sensor (104) is provided in the second boost passage (132). The second pressure sensor 104 detects the pressure of the brake oil transmitted to the second boost passage 132. The pressure detected by the second pressure sensor 104 corresponds to the pressure of the front wheel left wheel FL and the wheel cylinder 22 of the rear left wheel RL.

The first and second apply valves 141 and 142 and the first and second release valves 143 and 144 may be constituted by a normally closed type solenoid valve that maintains a normally closed state.

The first hydraulic circuit HC1 includes a first inlet valve 151 provided at the inlet side of the front wheel right wheel FR connected to the first boost circuit BC1 and the wheel cylinder 21 of the rear right wheel RR, And a first outlet valve 161 provided at the outlet side.

The second hydraulic circuit HC2 includes a front wheel left wheel FL connected to the second boost circuit BC2 and a second inlet valve 152 provided at the inlet side of the wheel cylinder 22 of the rear wheel left wheel RL, And a second outlet valve 162 provided on the outlet side.

The first inlet valve 151 may be a normally open type solenoid valve that maintains the normally open state. The first inlet valve 151 regulates the amount of brake oil supplied from the accumulator 210 to the wheel cylinder 20 as the first apply valve 141 is opened. The second inlet valve 152 may be configured to perform the same operation as the first inlet valve 151.

The first outlet valve 151 and the second outlet valve 152 may be composed of a normally closed type solenoid valve that maintains a normally closed state. The first outlet valve 161 and the second outlet valve 162 are connected to the wheel cylinders 21 and 22 and the master cylinder 110 so that the brake oil discharged from the wheel cylinders 21 and 22 is returned to the reservoir 115, Which is connected to the return flow path 160.

The first backup channel 171 and the second backup channel 172 are connected to each other by a brake pedal 30 so that emergency brake can be applied to the wheel cylinders 20 when the AHB system fails, And a flow path is formed between the wheel cylinder (110) and the wheel cylinder (20).

A first cut valve 173 for opening and closing the first backup channel 171 is provided in the middle of the first backup channel 171. A second cut valve 174 for opening and closing the second backup passage 172 is provided in the middle of the second backup passage 172.

The first backup passage 171 is connected to the first inflow passage BC1 131 via the first cut valve 173 and the second backup passage 172 is connected to the second backup passage 172 via the second cut valve 174. [ And is connected to the inflow passage (BC2) 132. The first backup channel 171 and the second backup channel 172 are blocked by the first cut valve 173 and the second cut valve 174 during AHB operation.

The first cut valve 173 and the second cut valve 174 may be normally open type solenoid valves that maintain the normally open state.

A pedal simulator 180 is provided on one side of the master cylinder 110 to form a pedal force of the brake pedal 30.

The pedal simulator 180 includes a simulation chamber 182 arranged to store the oil flowing out from the outlet side of the master cylinder 110 and a simulation valve 186 provided at the inlet side of the simulation chamber 182. The simulation chamber 182 is formed to have a range of displacements by the oil introduced into the simulation chamber 182, including the piston 183 and the resilient member 184. The simulator valve 186 is composed of a normally closed type solenoid valve that is kept in a normally closed state and is opened when the driver depresses the brake pedal 30 to transfer the brake fluid to the simulation chamber 182. [

A simulation check valve 185 is provided between the pedal simulator 180 and the master cylinder 110, that is, between the pedal simulator 180 and the simulation valve 186, (Not shown). The simulation check valve 185 is made such that the pressure in accordance with the pedaling force of the brake pedal 30 is transmitted to the pedal simulator 180 only through the simulation valve 186.

On the other hand, on the side of the brake pedal 30, a pedal stroke sensor 105 for detecting the pedal stroke of the brake pedal 30 is provided. The pedal stroke sensor 105 detects the pedal stroke of the brake pedal 30, which changes when the driver depresses the brake pedal 30.

2 is a schematic control block diagram of an active hydraulic booster system for a vehicle according to an embodiment of the present invention.

Referring to Fig. 2, the vehicle's active hydraulic booster system includes an electronic control unit 106 that performs overall control.

A second pressure sensor 104, a pedal stroke sensor 105, a wheel speed sensor 106, a steering angle sensor 107, a yaw rate sensor 108 ) And the lateral acceleration sensor 109 are electrically connected.

The first pressure sensor 103 detects the pressure of the brake oil transmitted to the first boost passage 131. The electronic control unit 102 controls the front right wheel FR and the rear right wheel RR of the first hydraulic circuit HC1 according to the pressure of the first boost passage 131 detected through the first pressure sensor 103, The pressure of the wheel cylinder 21 is recognized.

The second pressure sensor 104 detects the pressure of the brake oil transmitted to the second boost passage 132. The electronic control unit 102 controls the front wheel left wheel FL and the rear wheel left wheel RL of the second hydraulic circuit HC2 according to the pressure of the second boost passage 132 detected through the second pressure sensor 104. [ The pressure of the wheel cylinder 22 is recognized.

The pedal stroke sensor 105 detects the pedal stroke of the brake pedal 30.

The wheel speed sensor 106 detects each wheel speed of the vehicle.

The steering angle sensor 107 detects the steering angle of the vehicle.

The yaw rate sensor 108 detects the yaw rate of the vehicle.

The lateral acceleration sensor 109 detects the lateral acceleration of the vehicle. At this time, the vehicle's active hydraulic booster system does not include the wheel speed sensor 106, the steering angle sensor 107, the yaw rate sensor 108 and the lateral acceleration sensor 109, have.

The first and second release valves 141 and 142, the first and second release valves 143 and 144, the first and second cut valves 173 and 174, the simulation valve 186, (220) are electrically connected.

The electronic control unit 102 uses the motor 220 to drive the pump (not shown) so as to provide the braking force to the wheel based on the pedal stroke information of the brake pedal 30 detected through the pedal stroke sensor 105 in the AHB control 220 to directly generate hydraulic pressure, operate various valves to control the hydraulic pressure, and control the braking force of each wheel through the regulated hydraulic pressure.

On the other hand, the electronic control unit 102 generates a hydraulic pressure by operating the pump 22 using a motor so as to provide the target wheel pressure to each wheel in the ESC control, and controls the first and second applied valves 141 and 142, And the first and second release valves 143 and 144 to control the oil pressure thereof and control the pressure of the wheel cylinder of the wheel to reach the target wheel pressure through the regulated oil pressure.

At this time, when the first and second apply valves 141 and 142 and the first and second release valves 143 and 144 are operated, the electronic control unit 102 controls the application valves 141 and 142 and the release valves 143 and 144 to perform pulse width modulation (Pulse Width Modulation: PWM). Thus, valve operating noise can be minimized.

More specifically, the electronic control unit 102 PWM-controls the first and second apply valves 141 and 142 and the first and second release valves 143 and 144, which are solenoid valves that are normally kept closed, Adjusting the opening of the valve by adjusting the PWM duty ratio supplied to the valve. That is, instead of ON / OFF control, the valve is PWM controlled to open the valve at a time in the pressurizing mode, but at the beginning, only a part of the valve is opened and then opened little by little to control the wheel pressure to gradually increase linearly. In this case, the opening and closing degree of the valve adjusts the magnetic force of the solenoid coil in the valve through PWM control, and the magnetic force is proportional to the PWM duty ratio. That is, the PWM duty ratio of 0% means that the normally open type solenoid valve is fully opened, the PWM duty ratio is 100% when the valve is completely closed, and the middle value when the valve is partially opened.

Hereinafter, the operation of the electronic control unit 102 will be described in more detail.

3 is a hydraulic circuit diagram for explaining the flow of hydraulic pressure when the wheel pressure is pressed during ESC control in the active hydraulic booster system of the vehicle according to the embodiment of the present invention, Fig. 3 is a timing chart of each valve when the wheel pressure is applied during ESC control in the active hydraulic booster system of Fig.

3 and 4, when the wheel pressure is applied during the ESC control, the electronic control unit 102 controls the pump 210 via the motor 220 to generate the target pressure corresponding to the required compensation moment, . Accordingly, the accumulator 120 is filled with high-pressure brake oil by the operation of the pump 210. [

The electronic control unit 102 performs PWM control of the first and second applied valves 141 and 142 so that high-pressure brake fluid filled in the accumulator 120 can be supplied to each wheel cylinder 20. [

The electronic control unit 102 closes the first and second cut valves 173 and 174 provided in the first and second backup flow paths 171 and 172 while opening the apply valves 141 and 142. Accordingly, the first bypass path 131 and the first backup path 171 are blocked, and the second bypass path 132 and the second backup path 172 are blocked. The brake oil supplied to each wheel cylinder 20 through the first and second apply valves 141 and 142 is supplied to the first and second backup oil passages 171 and 172 by interrupting the first and second backup oil passages 171 and 172, .

A series of operations of the above components cause a hydraulic flow in the direction of the arrow. At this time, the first inflow valve 151 and the first outflow valve 161 of the first hydraulic circuit HC1 are kept off. In addition, the second inlet valve 152 and the second outlet valve 162 of the second hydraulic circuit HC2 are kept off. In addition, the first release valve 143 and the second release valve 144 may be kept off, or may be PWM-controllable as the case may be. As a result, brake oil flows into the front wheel right wheel FR and the wheel cylinder 21 of the right rear wheel RR, and the wheel pressure is increased. For reference, when the four wheels are individually controlled, the brake oil path to the wheel cylinder is controlled so that only the wheel pressure control of the wheel cylinder of the corresponding wheel can be performed by the apply valves 141 and 142 and the release valves 143 and 144 The first inlet valve 151 and the first outlet valve 161 of the first hydraulic circuit HC1 and the second inlet valve 152 of the second hydraulic circuit HC2 and the second inlet valve 152 of the second hydraulic circuit HC2, 2 outlet valve 162 operates.

In this way, when the wheel pressure is applied during the ESC control, the first apply valve 141, which can be PWM-controlled, is used instead of the first inflow valve 151 that is turned on or off of the first hydraulic circuit HC1, The wheel pressure of the wheel cylinder 21 of the right wheel FR and the wheel cylinder 21 of the rear wheel right wheel RR is pressurized and the PWM control is performed in place of the second inflow valve 152 operated on or off of the second hydraulic circuit HC2 The second apply valve 142 can be used to reduce the valve noise by pressurizing the wheel pressures of the front wheel left wheel FL and the wheel cylinders 22 of the rear wheel left wheel RL. In addition, since the wheel pressure is applied by using the apply valves 141 and 142, the first pressure sensor 103 and the second pressure sensor 104 can be used to pressurize the wheel pressure, Can be improved.

FIG. 5 is a hydraulic circuit diagram for explaining the flow of hydraulic pressure when the wheel pressure is reduced during ESC control in the active hydraulic booster system of the vehicle according to the embodiment of the present invention, and FIG. In which the wheel pressure is reduced when the ESC control is performed in the active hydraulic booster system of Fig.

Referring to FIGS. 5 and 6, when the wheel pressure is reduced during the ESC control, the electronic control unit 102 turns off the apply valves 141 and 142 in the valve operating state when the wheel pressure is depressed, (143, 144). Accordingly, the brake fluid of the wheel cylinders 20 and 21 is discharged to the reservoir 115 via the release valves 143 and 144, whereby the wheel pressure of the wheel cylinders 20 and 21 is reduced.

A series of operations of the above components cause a hydraulic flow in the direction of the arrow. At this time, the first inflow valve 151 and the first outflow valve 161 of the first hydraulic circuit HC1 are kept off. In addition, the second inlet valve 152 and the second outlet valve 162 of the second hydraulic circuit HC2 are kept off. Accordingly, the brake fluid of the front wheel right wheel FR and the wheel cylinder 21 of the rear right wheel RR is returned to the reservoir 115 via the release valves 143 and 144 to reduce the wheel pressure.

In this way, when the wheel pressure is reduced during the ESC control, the first release valve 143, which can be PWM-controlled, is used instead of the first outlet valve 161, which is turned on or off for the first hydraulic circuit HC1, The wheel pressure of the wheel FR of the wheel cylinder 21 of the rear right wheel RR is depressurized and the PWM controllable agent 16 is used instead of the second outlet valve 162 of the second hydraulic circuit HC2, 2 release valve 144 is used to reduce the wheel pressure of the wheel cylinders 22 of the front wheel left wheel FL and the rear wheel left wheel RL to reduce valve noise. Further, since the wheel pressure is reduced by using the release valves 143 and 144, the first pressure sensor 103 and the second pressure sensor 104 can be used to reduce the wheel pressure, thereby improving the control precision at the time of reducing the wheel pressure .

7 is a control flowchart of an active hydraulic booster system for a vehicle according to an embodiment of the present invention.

Referring to FIG. 7, the electronic control unit 102 determines the state of the road on which the vehicle travels during ESC control (302). For example, it is estimated whether the road surface on which the vehicle travels is in a dry state, a wet state (Wet), a snowy state (Snowy), or an ice state (Icy). Judgment of the road surface state follows the known technique. For example, as disclosed in Japanese Patent Application Laid-Open No. 10-2009-0047249, the vehicle speed, the rotational speed of the wheel, the actual rolling radius of the tire, the traction force Fx applied to each wheel, The slip ratio s and the friction coefficient μ are obtained by using a normal force Fz or the like and the dry state of the road surface is determined using the obtained slip ratio s and friction coefficient μ, (Wet) state, a snowy state (Snowy), and an ice state (Icy). Further, as disclosed in Japanese Patent Application Laid-Open No. 10-2011-0125130, the vehicle mass, the wheel speed, and the vehicle acceleration are measured; It is also possible to estimate the friction coefficient of the road surface using the measured vehicle mass, the wheel speed, and the vehicle acceleration, and determine the road surface condition using the estimated friction coefficient of the road surface. In addition, various methods of estimating the road surface friction coefficient, such as disclosed in Japanese Unexamined Patent Application Publication No. 1991-0014684 and Japanese Unexamined Patent Application Publication No. 2001-0088352, and determining the road surface state using the estimated road surface friction coefficient can be used.

After determining the state of the road surface on which the vehicle travels during ESC control, the electronic control unit 102 sets the first target pressure increase amount corresponding to the full rise mode based on the determined road surface condition. At this time, the full rise mode is a pressurization mode that is performed at the first rise (initial rise) in ESC control. At this time, the first target pressure increase amount corresponding to the full rise mode is set in advance for each road surface state. The first target pressure increase amount may be higher for a relatively high friction road surface, and may be lower for a lower friction road surface.

Further, the electronic control unit 102 sets the second target pressure increase amount corresponding to the pressure mode (Rise mode) based on the determined road surface condition. The pressure mode (Rise mode) is a pressurizing mode except for the full rise mode which is performed at the time of the first pressurization (initial rise) in the ESC control. At this time, the second target pressure increase amount corresponding to the pressure mode (Rise mode) is set in advance for each road surface state. The second target pressure increase may be higher for a relatively high friction surface, and may be lower for a lower friction surface.

Further, the electronic control unit 102 sets a target pressure reduction amount corresponding to the reduced mode (Dump mode) based on the determined road surface condition. The target pressure reduction amount corresponding to the depressurization mode (Dump mode) is set in advance for each road surface state. The target pressure reduction amount can be higher for a relatively high friction road surface and lower for a low friction road surface.

The electronic control unit 102 determines whether the current control mode is the maximum pressure mode (310).

If it is determined in operation mode 310 that the current control mode is the maximum pressure mode, the electronic control unit 102 determines the target pressure by applying the first target pressure increase amount set in the operation mode 304 (312). For example, this target pressure determines the final target pressure as the pressure value obtained by adding the first target pressure increase amount at the target pressure corresponding to the current compensation moment for stably maintaining the current vehicle.

After determining the target pressure, the electronic control unit 102 performs wheel pressure control (314) to PWM control the applied valve corresponding to the controlled wheel so that the current pressure reaches the determined target pressure.

If it is determined that the current control mode is not the maximum pressure mode, the electronic control unit 102 determines whether the current control mode is the pressurizing mode (316).

If it is determined in operation mode 316 that the current control mode is the pressurization mode, the electronic control unit 102 applies the second target pressure increase amount set in the operation mode 306 to determine the target pressure (318). For example, the target pressure may be a pressure value obtained by adding the second target pressure increase amount to the target pressure corresponding to the current compensation moment for stably maintaining the current vehicle.

After determining the target pressure, the electronic control unit 102 performs wheel pressure control (314) to PWM control the applied valve corresponding to the controlled wheel so that the current pressure reaches the determined target pressure.

On the other hand, if it is determined in operation mode 316 that the current control mode is not the pressurizing mode, the electronic control unit 102 determines whether the current control mode is the reduced pressure mode (320).

If the current control mode is the reduced pressure mode as a result of the determination in the operation mode 320, the electronic control unit 102 determines the target pressure by applying the target pressure reduction amount set in the operation mode 308. [ For example, the target pressure may be a pressure value obtained by subtracting the target pressure reduction amount from the target pressure corresponding to the current compensation moment for stably maintaining the current vehicle.

After determining the target pressure, the electronic control unit 102 performs wheel pressure control (314) to PWM control the release valve corresponding to the controlled wheel so that the current pressure reaches the determined target pressure. At this time, it is possible to check the pressure value through the first pressure sensor 103 or the second pressure sensor 104 capable of performing the wheel pressure control according to the road surface condition and detecting the pressure value corresponding to the wheel cylinder of the wheel to be controlled More precise wheel pressure control is possible.

If it is determined that the current control mode is not the depressurization mode, the electronic control unit 102 determines that the current control mode is the maintenance mode and maintains the current pressure, And the pressure control for PWM control of the release valve is performed (324).

Then, after performing the wheel pressure control or the pressure maintaining control, the electronic control unit 102 judges whether or not the ESC control is finished. If the ESC control is ended, the routine returns to the predetermined routine, and if the ESC control is not finished, the operation mode of the operation mode 302 or less is performed.

8 is a graph for explaining the wheel pressure control for each control mode in the ESC control in the active hydraulic booster system of the vehicle according to the embodiment of the present invention.

As shown in FIG. 8A, in the conventional ESC control, the inlet valves 151 and 152 are operated in the respective control modes such as the full rise (intial rise), the pressurization mode (R), and the maintenance mode (D) It is very difficult to accurately estimate the pressure of each wheel since the pressure of each wheel is controlled in a step-like manner due to the ON or OFF operation of the valve, so that a relatively precise pressure control Is not achieved.

However, as shown in FIG. 8 (b), in an embodiment of the present invention, when ESC control is performed, each control such as full rise (intial rise), pressurization mode (R) The target pressure is determined according to the control mode by using the target pressure increase amount and the reduction amount according to the road surface condition, and the wheel pressure to the determined target pressure PWM control of the apply and release valves for control can reduce valve operating noise when wheel pressure is controlled and ensure a relatively high pressure increase rate at the beginning of ESC control and then allow for linear pressure control Therefore, the precision of the wheel pressure control can be improved.

102: electronic control unit 103: first pressure sensor
104: second pressure sensor 105: pedal stroke sensor
131: first boost passage 132: second boost passage
141: first apply valve 142: second apply valve
143: first release valve 144: second release valve
200: power source unit 210: pump
220: motor

Claims (7)

In an active hydraulic booster system for a vehicle,
A motor for driving a pump for pumping brake oil from the reservoir of the master cylinder;
An accumulator for storing the pumped brake oil according to an operation of the pump driven by the motor;
A hydraulic circuit including an inlet valve provided at an inlet side of each wheel cylinder to which brake oil stored in the accumulator is supplied and an outlet valve provided at an outlet side;
A boost circuit that allows the brake fluid stored in the accumulator to flow into the hydraulic circuit or the brake fluid of each wheel cylinder to be discharged to the reservoir; Wherein the boost circuit includes an apply valve for introducing brake oil stored in the accumulator into the hydraulic circuit, and a release valve for discharging the brake oil of each wheel cylinder to the reservoir,
A pressure mode for pressurizing the wheel pressure of the wheel cylinder by PWM control of the apply valve and the release valve during ESC control, a pressure reduction mode for reducing the wheel pressure, and a maintenance mode for maintaining the current wheel pressure And an electronic control unit for performing the hydraulic control of the vehicle. The method according to claim 1,
The electronic control unit controls the target pressure to maintain the stable vehicle posture while the vehicle is performing any one of the pressure mode, the depressurization mode, and the maintenance mode, and corresponds to the road surface state in which the vehicle travels for each control mode Determining a final target pressure by applying a set target pressure change amount and adjusting the PWM duty ratio of the apply valve and the release valve for each control mode so that the current wheel pressure follows the determined final target pressure, Hydraulic booster system. 3. The method of claim 2,
Wherein the electronic control unit determines that the road surface state on which the vehicle travels is one of a plurality of states of a dry state, a wet state, a snowy state, and an ice state, The target pressure change amount is set differently for each control mode. The method of claim 3,
Wherein the pressurizing mode is divided into a maximum pressure mode in which the wheel pressure is initially applied at the beginning of the ESC control and a pressurization mode in which the wheel pressure is pressurized when necessary after the maximum pressure mode,
The electronic control unit sets a first target pressure increase amount in accordance with the determined road surface state to correspond to the maximum pressurization mode and sets a second target pressure increase amount according to the determined road surface state to correspond to the pressurization mode, And sets the target pressure reduction amount in accordance with the determined road surface condition so as to correspond to the reduced pressure mode. 5. The method of claim 4,
Wherein the electronic control unit determines the final target pressure in the maximum pressure mode section by applying the set first target pressure increase amount to the current target pressure during the maximum pressure mode period during the ESC control, The PWM duty ratio of the apply valve and the release valve is adjusted,
Determining a final target pressure of the pressure mode section by applying the set second target pressure increase amount to the current target pressure in the pressure mode section and setting the PWM duty of the apply valve and the release valve according to the determined final target pressure, Adjusting the ratio,
Determining a final target pressure in the reduced pressure mode section by applying the set target pressure decrease amount to the current target pressure in the reduced pressure mode section and setting the PWM duty ratio of the applied valve and the released valve to Active hydraulic booster system of the vehicle to regulate. An accumulator for storing the pumped brake oil according to an operation of the pump driven by the motor; and an accumulator for storing brake oil supplied to the accumulator, A hydraulic circuit including an inlet valve provided at the inlet side of the wheel cylinder and an outlet valve provided at the outlet side of the wheel cylinder, and a hydraulic circuit for allowing the brake oil stored in the accumulator to be introduced into the hydraulic circuit or the brake oil of each wheel cylinder being discharged to the reservoir A boost circuit provided; Wherein the boost circuit includes an apply valve for introducing brake oil stored in the accumulator into the hydraulic circuit and a release valve for discharging the brake oil of each wheel cylinder to the reservoir As a result,
ESC control,
Wherein the controller is configured to control the application valve and the release valve to be in a PWM mode so as to perform one of a pressurizing mode for pressurizing the wheel pressure of the wheel cylinder during the ESC control, a depressurizing mode for depressurizing the wheel pressure, Control method of an active hydraulic booster system of a controlled vehicle. The method according to claim 6,
The PWM control of the apply valve and the release valve may be performed by controlling the target pressure to maintain the vehicle in a stable vehicle posture while performing the control mode of any one of the pressure mode, A target pressure change amount set in correspondence with a road surface state on which the vehicle is traveling is determined to determine a final target pressure and a current wheel pressure is determined to be in accordance with the determined final target pressure, Control method of an active hydraulic booster system for a vehicle that adjusts the PWM duty ratio.

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