Electro-hydraulic braking system

Abstract

Electro-hydraulic braking system with: several wheel brake arrangements designed to deliver braking forces to wheels; an electric brake booster with a motor to amplify a pedal force applied to a brake pedal; an electronic stability control (ESC) system comprising a pressure sensor for measuring hydraulic pressure and designed to open or close several valves arranged therein in order to distribute the hydraulic pressure to the multiple wheel brake assemblies; and an electronic control unit (ECU) designed to control a motor drive current within a range of current values ​​less than or equal to a first limiting current when the hydraulic pressure measured by the pressure sensor is less than or equal to a first reference value, and to control the motor drive current within a range of current values ​​greater than the first limiting current and less than or equal to a second limiting current when the hydraulic pressure is higher than the first reference value.

Description

Technical field

[0001] The present invention relates to an electro-hydraulic brake unit. background

[0002] The statements in this section merely provide background information regarding the present disclosure and do not necessarily represent prior art.

[0003] A braking system comprises a reservoir, one or more lines, and multiple wheel brake assemblies. Brake fluid dispensed from the reservoir flows through the one or more lines to the multiple wheel brakes. This electro-hydraulic braking system applies braking force to the vehicle's brakes using the pedal force of a driver.

[0004] However, with such a conventional electro-hydraulic brake, when the driver presses a pedal, the amplification limit of an electric brake booster motor is constantly set, regardless of the magnitude of the required force. This means that, since the motor's amplification limit is equal to its maximum value, the motor's rated point is set high based on this maximum amplification limit, even when the required braking force is low.

[0005] Therefore, a motor with a high torque specification should be used if the motor's rated point is set high. This, however, presents disadvantages regarding the motor's cost-effectiveness.

[0006] DE 11 2018 006 055 T5 discloses an electro-hydraulic braking device with several wheel brake assemblies configured to deliver braking forces to wheels; an electric brake booster with a motor for amplifying a pedal force applied to a brake pedal; an electronic stability control system comprising a pressure sensor for measuring hydraulic pressure and configured to open or close several valves arranged therein in order to distribute the hydraulic pressure to the several wheel brake assemblies; and an electronic control unit configured to limit a drive current of the motor when a condition for limiting the drive of the electric actuator is met. overview

[0007] According to at least one embodiment, the present disclosure provides an electro-hydraulic braking device comprising: several wheel brake assemblies configured to deliver braking forces to wheels; an electric brake booster with a motor for amplifying a pedal force applied to a brake pedal; an electronic stability control (ESC) system comprising a pressure sensor for measuring hydraulic pressure and configured to open or close several valves arranged therein in order to distribute the hydraulic pressure to the several wheel brake assemblies;and an electronic control unit (ECU) configured to control a drive current of the motor within a range of current values ​​less than or equal to a first limiting current when the hydraulic pressure measured by the pressure sensor is less than or equal to a first reference value, and to control the drive current of the motor within a range of current values ​​greater than the first limiting current and less than or equal to a second limiting current when the hydraulic pressure is higher than the first reference value. Brief description of the drawings Fig. Figure 1 is a block diagram of an electro-hydraulic braking device according to an embodiment of the present invention. Fig. Figure 2 is a block diagram of an electronic stability control system according to an embodiment of the present invention. Fig. Figure 3 is a graph of input / output characteristics according to an embodiment of the present invention. Fig. Figure 4 is a graph of a TNI curve of a motor according to an embodiment of the present invention. Reference symbol list 110 Main body 120 electric brake booster 130 electronic control unit 150 wheels 200 Hydraulic control system FL, RR, RL and FR wheel brakes Detailed description

[0008] According to one embodiment of the present invention, an intermediate amplification point is set for low-response braking, and a motor rating point is set based on this. This means that the motor rating point is set lower than that of a conventional motor. Because the motor rating point is set lower, the required motor power decreases. The present invention relates to the creation of an electric brake booster in which the size of the motor is reduced, and thus, due to the reduced motor power, the price of the motor is reduced, thereby lowering the manufacturing costs of the electric brake booster.

[0009] Some exemplary embodiments of the present disclosure are described below with reference to the accompanying drawings. In the following description, identical reference numerals preferably denote identical elements, even though the elements are shown in different drawings. Furthermore, for the sake of clarity and brevity, a detailed description of known functions and configurations included in some embodiments is omitted in the following description.

[0010] Furthermore, alphanumeric codes such as first, second, i), ii), (a), (b), etc., are used in the numbering of components solely to distinguish one component from another, and not to imply or suggest the content, order, or sequence of the components. If a part is described as "containing" or "having" a component, this is to be understood throughout the description as meaning that the part may also have other components, but does not exclude this possibility, unless explicitly stated otherwise.

[0011] Fig. Figure 1 is a block diagram of an electro-hydraulic braking device according to an embodiment of the present invention.

[0012] Referring to Fig. 1 comprises an electro-hydraulic brake device 100 according to an embodiment of the present invention comprising a main body 110 and / or an electric brake booster 120 and / or an electronic control unit 130 and / or a hydraulic control system (hereinafter referred to as electronic stability control system (ESC)) 200 and / or several wheel brake arrangements FR, FL, RR and RL.

[0013] A main body 110 comprises a master brake cylinder 111 and / or a reservoir 112 and / or an actuating rod 113 and / or a reaction disc 114 and / or a push rod 115.

[0014] In this case, the master brake cylinder 111 is designed to compress a brake fluid in order to generate a hydraulic pressure used for braking.

[0015] The reservoir 112 is designed to hold the brake fluid. The actuating rod 113 is designed to transmit a driver's pedal force to the reaction disc 114. The reaction disc 114 is designed to pressurize the push rod 115. The push rod 115 is designed to pressurize the interior of the master brake cylinder 111.

[0016] An electric brake booster 120 has a motor 121 and / or a first gear 122 and / or a second gear 123 and / or a third gear 124 and / or a spindle nut 125 and / or a spindle 126 and / or a brake pedal 127.

[0017] The first gear 122, the second gear 123, and the third gear 124 are gears that transmit the rotary motion of the motor 121 to the spindle nut 125. The spindle nut 125 receives the rotary motion of the motor 121 and causes a linear movement of the spindle 126.

[0018] A right end of the master cylinder 111 is connected to a left end of the pushrod 115, which is designed to pressurize the master cylinder 16 of the master cylinder 111 to generate hydraulic pressure. A right end of the pushrod 115 is connected to a left end of the reaction disc 114. A left end of the actuating rod 113 is connected to the center of a right end of the reaction disc 114. The actuating rod 113 is connected to the driver's brake pedal 127. According to this connection, the actuating rod 113 pushes against the center of the right end of the reaction disc 114 with the pedal force of the driver's brake pedal 127.

[0019] The outer contour of the right end of the reaction disk 114 is connected to the spindle 126. The first gear 122 and the second gear 123 are rotated by receiving a torque from the motor 121 of the electric brake booster. This rotational movement is transmitted to the third gear 124. The third gear 124, to which the rotational movement of the first gear 122 and the second gear 123 is transmitted, transmits the torque generated by the rotational movement to the spindle nut 125. The spindle 126 moves linearly in accordance with the rotational movement of the spindle nut 125. The outer contour of the right end of the reaction disk 114 is thus subjected to pressure by the linear movement of the spindle 126. As a result, the pushrod 115 is subjected to pressure by the pedal force of the driver's brake pedal 127 and an amplifying force from the electric brake booster 120.

[0020] The master brake cylinder 111 is pressurized by the pushrod 115 to discharge brake fluid from the master brake cylinder 111 to an electronic stability control (ESC) system 200. The brake fluid discharged from the reservoir 112 is transferred to the master brake cylinder 111, and the brake fluid discharged from the master brake cylinder 111 is transferred to the ESC system 200.

[0021] In the present disclosure, a case in which the braking force is less than or equal to a first reference value (60 bar) is referred to as low-response braking, and a case in which the amount of pedal actuation by the driver is greater than the first reference value is referred to as high-response braking. In this case, the first reference value denotes an intermediate gain point (60 bar) of the graph in Fig. 3B.

[0022] A pressure sensor 201 is installed in the ESC system 200. When the driver presses the brake pedal 127, the pressure sensor 201 measures a hydraulic pressure value and transmits the hydraulic pressure value to an electronic control unit (ECU) 130.

[0023] The pressure sensor 201 can be composed of several sensors. Since the ESC system 200 has multiple pressure sensors 201, even if one of the pressure sensors 201 malfunctions and there is a problem with braking performance, the hydraulic pressure can be measured by another pressure sensor 201. Therefore, normal braking of the wheel brakes FR, FL, RR, and RL by the ESC system 200 is possible. Because braking by the ESC system 200 is possible during emergency braking, redundancy of a hydraulic circuit is ensured.

[0024] On the other hand, a conventional braking device calculates a braking force requested by the driver by measuring the actuation speed of the pedal or the like, however, in the present disclosure an actual hydraulic pressure is measured directly in the ESC system 200 and a measured value is used for control, and thus more precise control is possible than with the conventional braking force measurement method.

[0025] The ECU 130 receives a hydraulic pressure value measured by the pressure sensor 201.

[0026] If the received hydraulic pressure value is less than or equal to the first reference value, the ECU 130 controls the electric brake booster 120 such that a current of a first limit (e.g., 60 A) or more does not flow through the motor 121. The ECU 130 removes the first limit, allowing a current of 60 A or more to flow through the motor 121 if the received hydraulic pressure value is greater than the first reference value. Conversely, the electric brake booster 120 is controlled such that a current of a second limit (e.g., 100 A) or more does not flow through the motor 121. If the current flowing through the motor 121 reaches a threshold value, the motor stops without continuing to rotate, with the threshold being a limit current.

[0027] The power output of motor 121 is determined by a torque specification of motor 121 and the rpm of motor 121, and in the present disclosure is, because the intermediate gain point (point d in Fig. 3) is set so that the motor's rated point is located at a point c in Fig. 4 to a point d in Fig. 4 reduced. Since the required torque specification and rpm required at the motor's rated point are lower than for the conventional motor, the 121 motor can therefore be used at a lower power output.

[0028] During weak braking, the motor's rated point is set based on the intermediate gain point. By setting the first limiting current (e.g., 60 A) to the motor's rated point, the conventionally required motor power is reduced from 400 W to 276 W. Since the motor 212 can be used at a lower power level, this results in a cost reduction for the motor 212 and the electric brake booster 120.

[0029] Fig. Figure 2 is a block diagram of an electronic stability control system according to an embodiment of the present invention.

[0030] Referring to Fig. 2 The ESC system 200 according to an embodiment of the present invention comprises a pressure sensor 201 and / or a first inlet line 210 and / or a second inlet line 211 and / or a third inlet line 220 and / or a fourth inlet line 221 and / or a first inlet valve 212 and / or a second inlet valve 213 and / or a third inlet valve 222 and / or a fourth inlet valve 223 and / or a first outlet valve 212a and / or a second outlet valve 213a and / or a third outlet valve 222a and / or a fourth outlet valve 223a and / or a first main line 230 and / or a second main line 240 and / or several pressure accumulators 252 and 254 and / or several traction control valves 256 and 257 and / or several high-pressure switching valves 258 and 259 and / or an actuator 260 and / or a hydraulic pump 262.

[0031] The multiple wheel brakes FR, FL, RR and RL include a first wheel brake FR for braking a right front wheel 141 of a vehicle and / or a second wheel brake FL for braking a left front wheel 152 of the vehicle and / or a third wheel brake RR for braking a right rear wheel 153 of a vehicle and / or a fourth wheel brake RL for braking a left rear wheel 154 of the vehicle.

[0032] The first main line 230 and the second main line 240 connect the master brake cylinder 111 and the ESC system 200. The first main line 230 and the second main line 240 are designed to supply brake fluid dispensed from the master brake cylinder 111 to the ESC system 200.

[0033] The multiple wheel brake arrangements FR, FL, RR and RL deliver braking forces to the multiple wheels 151, 152, 153 and 154 using a hydraulic pressure of the brake fluid output from the ESC system 200.

[0034] The ESC system 200 controls the opening and closing of the multiple traction control valves 256 and 257, the multiple high-pressure switching valves 258 and 259, the actuator 260, the multiple inlet valves 212, 213, 222 and 223, and the multiple outlet valves 212a, 213a, 222a and 223a such that the brake fluid is moved through the fluid line to the master brake cylinder 111, the reservoir 112 and the multiple wheel brake assemblies FR, FL, RR and RL.

[0035] The multiple traction control valves 256 and 257 are designed to interrupt the hydraulic pressure in the ESC system 200. A first traction control valve 256 can be suitably arranged along a line corresponding to the first main line 230, that is, supplying hydraulic pressure to the second and third wheel brakes FL and RR. A second traction control valve 257 can be suitably arranged along a line corresponding to the second main line 240, that is, supplying hydraulic pressure to the first and fourth wheel brakes FR and RL.

[0036] Here, the expression "to interrupt the hydraulic pressure" refers to the process of opening or closing the multiple valves in the ESC system 200, so that the hydraulic pressure supplied by the actuator 260 does not propagate towards the main lines 230 and 240. Thus, the hydraulic pressure generated by the actuator 260 can only be supplied within the ESC system 200.

[0037] The multiple high-pressure switching valves 258 and 259 are designed to interrupt the hydraulic pressure of the brake fluid supplied to the inlet of the hydraulic pump 262. A first high-pressure switching valve 258 can be suitably arranged along a line corresponding to the first main line 230, that is, supplying hydraulic pressure to the second and third wheel brakes FL and RR. A second high-pressure switching valve 259 can be suitably arranged along a line corresponding to the second main line 240, that is, supplying hydraulic pressure to the first and fourth wheel brakes FR and RL.

[0038] The multiple outlet valves 212a, 213a, 222a and 223a are arranged in the multiple outlet lines. The multiple outlet valves 212a, 213a, 222a and 223a are designed to interrupt the hydraulic pressures output from the multiple wheel brakes FR, FL, RR and RL.

[0039] The ESC system 200 can further comprise low-pressure accumulators 252 and 254. The multiple pressure accumulators 252 and 254 are designed to temporarily store the brake fluid released by the multiple wheel brakes FR, FL, RR, and RL. The pressure accumulators 252 and 254 can be arranged within the ESC system 200.

[0040] The first inlet line 210 has the first inlet valve 212. The second inlet line 211 has the second inlet valve 213. The first inlet valve 212 is located near the third wheel brake RR, and the second inlet valve 213 is located near the second wheel brake FL. The third inlet line 220 has the third inlet valve 222. The fourth inlet line 221 has the fourth inlet valve 223. The third inlet valve 222 is located near the first wheel brake FR, and the fourth inlet valve 223 is located near the fourth wheel brake RL.

[0041] The ESC system 200 opens and closes the multiple inlet valves 212, 213, 222, and 223 to change the hydraulic pressure of the brake fluid in the multiple inlet lines 210, 211, 220, and 221. This means that the first inlet line 210 transmits the brake fluid to wheel brake FR only, according to a change in hydraulic pressure. The second inlet line 211 transmits the brake fluid to wheel brake FL only, according to a change in hydraulic pressure. The third inlet line 220 transmits brake fluid to wheel brake RR only, according to a change in hydraulic pressure. The fourth inlet line 221 transmits brake fluid to wheel brake RL only, according to a change in hydraulic pressure.

[0042] The following is a general description of the ESC System 200.

[0043] The following is a description of the multiple wheel brakes FR, FL, RR and RL.

[0044] An H-shaped split structure is a structure in which two main lines control the front wheels 151 and 152 and the rear wheels 153 and 154, respectively. This means that the brake fluid transmitted by the first main line 230 controls only the front wheels 151 and 152, and the brake fluid transmitted by the second main line 240 controls only the rear wheels 153 and 154.

[0045] On the other hand, an X-shaped split structure according to an embodiment of the present disclosure is a structure in which the two main lines 230 and 240 each control a front wheel 151 or 152 and a rear wheel 153 or 154. In the X-shaped split structure, the variation between the hydraulic pressure values ​​measured by the multiple pressure sensors 201 is less than when using the H-shaped split structure. In the H-shaped split structure, a hydraulic pressure value for controlling the front wheels and a hydraulic pressure value for controlling the rear wheels are each measured when the hydraulic pressure values ​​are measured by controlling the front wheels 151 and 152 and the rear wheels 153 and 154, respectively. On the other hand, in the X-shaped split structure, the hydraulic pressure values ​​are measured individually during the crossing of the front and rear wheels when measuring the hydraulic pressure values.Thus, the X-shaped split structure reduces hydraulic deviation between the front wheel and the rear wheel compared to the H-shaped split structure.

[0046] Since the ECU 130 of the present disclosure controls the electric brake booster according to an average of the hydraulic pressure values ​​measured by the multiple pressure sensors 201, it is also possible to obtain a more accurate measurement, as the deviation is reduced compared with conventional measurement methods that use only one sensor.

[0047] Fig. Figure 3 is a graph of input / output characteristics according to an embodiment of the present invention.

[0048] The probability of a driver applying the brakes while driving within the braking force range of 0 to 30 bar is 98%. The probability of application within the braking force range of 0 to 60 bar is 99.7%. This means that the probability of applying the brakes at a braking force of 60 bar or more is only 0.3%. If the probability of application above 60 bar is 0.3%, this will occur 1,500 times in 500,000 instances.

[0049] When the driver presses the brake pedal, the electric brake booster amplifies the driver's pedal force to generate braking force for the vehicle. The braking force is the resultant force of the driver's pedal force and the booster force from the motor.

[0050] Referring to Fig. In section 1, the amplifying force of motor 121 increases with the increase in pedal force. Conversely, in section 2, the amplifying force generated by the motor does not increase further, and only the rider's pedal force increases. The point between section 1 and section 2 is referred to as the motor's amplification limit. The torque and rpm of the conventional motor at the amplification limit are values ​​at point c in Fig. 4A.

[0051] The motor operates at a constant speed before its amplification force reaches its rated power. In this case, constant operation means that the current flowing through the motor increases with the rider's pedal force without being limited. This means that after the motor's rated power, a limiting current is set within the motor, so the amplification force no longer increases and remains constant. Therefore, the braking force is only increased by an increase in the rider's pedal force.

[0052] The size and power of the electric brake booster's motor are determined by reference to the motor's rated point on the input / output curve. The smaller the motor's size and power, the lower the motor's cost. A lower rated point reduces motor costs because of the reduced power and size, resulting in cost savings for the electric brake booster.

[0053] Fig. Figure 3A is a graph of input / output characteristics of a conventional general-purpose electric brake booster.

[0054] The amplification force applied by the motor at its maximum amplification (100 bar) is 90 bar, and the rider's pedal force is 10 bar. A motor output (torque x rpm) corresponding to 90 bar is referred to as a conventional motor rating point.

[0055] Fig. Figure 3B is a graph of the input / output characteristics of an electric brake booster according to an embodiment of the present disclosure. A gain limit according to an embodiment of the present invention is 100 bar, which is the same as in the graph in Figure 3B. Fig. 3A. However, the electric brake booster according to an embodiment of the present invention sets an intermediate boost point at 60 bar. Here, the intermediate boost point is a region (point d) at which the solid line and the dashed line of the graphic in Fig. 3B meet each other. The amplifying force applied by the motor at the intermediate amplification point is 55 bar, and the pedal force of the rider is 5 bar. The motor output corresponding to 55 bar is referred to as the motor's rated point according to one embodiment of the invention.

[0056] When the braking force is greater than or equal to 60 bar, the pressure sensor 201 of the ESC system 200 detects the braking force and the ECU immediately lifts the first current limit of 60 A. This allows a current of up to a second current limit of 100 A to flow. If the intermediate gain point of the motor 121 is set such that the current limits differ between low and high braking force requirements, it is possible to use a motor with an output power of 276 W, i.e., less than 400 W, thus reducing costs.

[0057] Fig. Figure 4 is a graph of a TNI curve of a motor according to an embodiment of the present invention.

[0058] If the maximum torque is 4 Nm, the speed at the conventional motor's rated point is 1000 rpm and a current of up to 100 A can flow. After the amplification limit is reached, the amplification force generated by the motor is fixed without any further increase, and thus a current of up to 100 A can flow. Therefore, the motor's limiting current is 100 A. This is the rated point of the conventional motor, and in this case, the motor's output power is 400 W.

[0059] If the maximum torque is 2.4 N*m, then at the motor's rated point, according to one embodiment of the present disclosure, the rotational speed is 1100 rpm and a current of up to 60 A can flow. Therefore, the first limiting current of the motor is 60 A. This is the motor's rated point of the present disclosure, and in this case, the motor's output power is 276 W.

[0060] With a weak braking response (60 bar or less) according to the present embodiment, the ECU sets the first limiting current in the motor. In this case, the first limiting current is, for example, 60 A. A current of up to 60 A can flow in the motor. This means that the motor's output power is 276 W, since the motor's intermediate gain point is set to its rated power.

[0061] On the other hand, during hard braking (over 60 bar), the ECU temporarily suspends the motor's first current limit of 60A and sets the second current limit. In this case, the second current limit is, for example, 100A. Accordingly, a current of up to 100A can flow through the motor.

[0062] According to one embodiment of the present disclosure, the motor power can be reduced because the limiting current, which is conventionally 100 A, is reduced to 60 A during weak braking. That is, conventionally a motor with a power rating of 400 W is required, but a motor with a power rating of 276 W can be used as the motor according to the present disclosure. Thus, the size of the motor can be reduced because the motor power is lowered. Consequently, it is possible to reduce the cost of the motor and the manufacturing costs of the electric brake booster.

[0063] As previously described, in the present embodiment, a section for weak braking and a section for strong braking are separated from each other, a motor rating is set for the weak braking section, and a limiting current of a motor rating is temporarily suspended in the strong braking section to meet a required braking force. This method results in a reduction of the motor rating of an electric brake booster, thereby reducing the price of the motor and the manufacturing costs of the electric brake booster.

[0064] Although exemplary embodiments of the present disclosure have been described for illustrative purposes, it is apparent to the person skilled in the art that numerous different modifications, additions, and substitutions are possible without departing from the scope and spirit of the claimed invention. Therefore, exemplary embodiments of the present disclosure have been described for the sake of brevity and clarity. The scope of the technical concept of the present embodiments is not limited by the illustrations. Accordingly, it is understandable to a person skilled in the art that the scope of the claimed invention is not limited by the preceding descriptions but by the claims and their equivalents.

Claims

Electro-hydraulic braking device comprising: several wheel brake assemblies designed to deliver braking forces to wheels; an electric brake booster with a motor for amplifying a pedal force applied to a brake pedal; an electronic stability control (ESC) system comprising a pressure sensor for measuring hydraulic pressure and designed to open or close several valves arranged therein in order to distribute the hydraulic pressure to the several wheel brake assemblies;and an electronic control unit (ECU) designed to control a drive current of the motor within a range of a current value less than or equal to a first limiting current when the hydraulic pressure measured by the pressure sensor is less than or equal to a first reference value, and to control the drive current of the motor within a range of a current value greater than the first limiting current and less than or equal to a second limiting current when the hydraulic pressure is greater than the first reference value. Electro-hydraulic braking device according to claim 1, in which the sensor contained in the ESC system is designed as multiple sensors. Electro-hydraulic braking device according to claim 2, wherein the ECU controls the drive current of the motor according to an average value of values ​​measured by the multiple pressure sensors. Electro-hydraulic braking device according to claim 1, wherein the ESC system has an X-shaped divided structure. Electro-hydraulic braking device according to claim 1, wherein the ESC system further comprises: a traction control valve configured to interrupt hydraulic pressure supplied by a master brake cylinder when the brake pedal is actuated; an inlet valve configured to interrupt hydraulic pressure supplied to multiple wheel brakes; an actuator configured to supply hydraulic pressure to the multiple wheel brakes; and a high-pressure switching valve configured to interrupt hydraulic pressure supplied by the master brake cylinder. Electro-hydraulic braking device according to claim 1, wherein the ESC system further comprises an outlet valve configured to adjust the hydraulic pressure supplied to the multiple wheel brake arrangements. A method for controlling an electro-hydraulic brake, comprising the following steps: measuring a hydraulic pressure value by a pressure sensor provided in an electronic stability control (ESC) system; transmitting the hydraulic pressure value to an electronic control unit (ECU); and controlling a drive motor within a range of current values ​​less than or equal to a first limiting current when the hydraulic pressure measured by the pressure sensor is less than or equal to a first reference value, and controlling the drive current of the motor within a range of current values ​​greater than the first limiting current and less than or equal to a second limiting current when the hydraulic pressure is higher than the first reference value. Method according to claim 7, wherein measuring a hydraulic pressure value comprises measuring the hydraulic pressure in the ESC system with an X-shaped divided structure. Method according to claim 7, wherein the measurement of a hydraulic pressure value comprises obtaining an average of hydraulic pressure values ​​measured by several pressure sensors.

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