Patent Publication Number: US-2020290576-A1

Title: Vehicle brake device

Description:
TECHNICAL FIELD 
     The present disclosure relates to a vehicle brake device. 
     BACKGROUND ART 
     As disclosed in JP-A-2015-136957, there is a vehicle brake device configured to determine a brake situation to determine whether a sudden brake operation has been performed. Also, the vehicle brake device is configured to determine whether a brake operation member has been started, so as to appropriately start a brake control, separately from the determination of the brake situation. As an example, the vehicle brake device is configured to determine whether an operation of the brake operation member has been started, based on a detection value of a stroke sensor configured to detect a stroke of the brake operation member. Here, when it is determined as “brake start (operation start)”, pressurization control on a wheel cylinder is started. 
     CITATION LIST 
     Patent Literature 
     PTL  1 : JP-A-2015-136957 
     BRIEF SUMMARY 
     Technical Problem 
     In the vehicle brake device, the stroke (detection value) responds almost similarly to a usual gentle brake operation. However, for the sudden brake operation, an increase in stroke (detection value) tends to be delayed from the operation, due to performance of the stroke sensor. Therefore, when detecting the sudden brake operation, it is considered to use a detection value of a brake switch so as to improve responsiveness of the brake start determination. 
     However, the brake switch does not respond unless the brake pedal is depressed to some extent, due to its configuration. That is, the brake switch is effective in detection of sudden brake that is quickly depressed to the end for a sudden stop but is difficult to respond to a small amount of sudden operation that is a slight sudden operation (for example, an operation in which the brake pedal is quickly depressed halfway and then stopped or released). Therefore, upon the small amount of sudden operation, the brake start determination is performed only by the stroke of which response tends to be delayed. Thus, there is room for improvement in responsiveness of the brake start determination upon the small amount of sudden operation in which the brake pedal is quickly depressed slightly. 
     The present disclosure has been made in view of the above situations, and an object thereof is to provide a vehicle brake device capable or improving responsiveness of brake start determination upon a small amount of sudden operation while securing accuracy of the determination. 
     Solution to Problem 
     The present disclosure provides a vehicle brake device. The vehicle brake device includes a stroke simulator, a stroke sensor, a brake start determination unit. The stroke simulator includes a cylinder, a piston, an orifice, and a pressure sensor. The cylinder defines a liquid pressure chamber to which a brake liquid is supplied via a path in accordance with a stroke of a brake operation member. The piston is configured to slide in the cylinder by the brake liquid supplied to the liquid pressure chamber. The orifice is formed in the fluid path. The pressure sensor is configured to detect a reaction pressure that is a liquid pressure of the brake liquid supplied to the liquid pressure chamber in a part on a supply-direction upstream side of the orifice in the fluid path. A reaction force corresponds to the reaction pressure being applied to the brake operation member by the stroke simulator. The stroke sensor is configured to detect the stroke. The brake start determination unit determines an operation of the brake operation member has been started in a case where the reaction pressure detected by the pressure sensor becomes equal to or greater than a first threshold value and the stroke detected by the stroke sensor becomes equal to or greater than a second threshold value. 
     Advantageous Effects 
     According to the present disclosure, when a sudden brake operation (including a small amount of sudden operation.) has been performed, the reaction pressure is likely to increase due to the orifice. According to the present disclosure, the reaction pressure is used as an element of the brake start determination, so that even upon a small amount of sudden operation to which a brake switch does not respond, for example, it is possible to improve responsiveness of the brake start determination. Also, the stroke is used as an element of the brake start determination, together with the reaction pressure, so that it is possible to secure accuracy of the determination. Regarding the detection of the stroke, the determination is performed under an AND condition with the reaction pressure, so that the responsiveness can be prioritized over the accuracy. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a configuration view of a vehicle brake device of the present embodiment. 
         FIG. 2  is a time chart for illustrating brake start determination upon a small amount of sudden operation in the present embodiment. 
         FIG. 3  is a configuration view of a modified embodiment of the vehicle brake device of the present embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinbelow, embodiments of the present disclosure will be described with reference to the drawings. The drawings used for descriptions are conceptual views, and shapes respective parts may not be strictly exact. As shown in  FIG. 1 , a vehicle brake device BF includes a master cylinder  1 , a reaction force generation device  2 , a first control valve  22 , a second control valve  23 , a servo pressure generation device  4 , an actuator  5 , wheel cylinders  541  to  544 , a brake ECU  6 , and a variety of sensors  71  to  76 . 
     The master cylinder  1  is a part configured to supply a brake liquid to the actuator  5 , in accordance with an operation amount on a brake pedal (corresponding to “brake operation member”)  10 , and has a main cylinder  11 , a cover cylinder  12 , an input piston  13 , a first master piston  14 , and a second master piston  15 . The brake pedal  10  may be any brake operating means with which a driver can perform a brake operation. 
     The main cylinder  11  is a substantially cylindrical bottomed housing of which front is closed and rear is opened. An inner wall part  111  protruding in an inwardly directed flange shape is provided in the vicinity of the rear on an inner periphery side of the main cylinder  11 . A center of the inner wall part  111  is formed as a through-hole  111   a  penetrating in a front and rear direction. Also, small-diameter parts  112  (rear) and  113  (front) of which inner diameters are slightly small are provided in front of the inner wall part  111  in the main cylinder  11 . That is, the small-diameter parts  112  and  113  protrude in an annular shape inwardly from an inner peripheral surface of the main cylinder  11 . In the main cylinder  11 , the first master piston  14  is disposed so as to be axially movable in sliding contact with the small-diameter part  112 . Likewise, the second master piston  15  is disposed so as to be axially movable in sliding contact with the small-diameter part  113 . 
     The cover cylinder  12  is configured by a substantially cylindrical cylinder part  121 , a bellows tube-shaped boot  122 , and a cup-shaped compression spring  123 . The cylinder part  121  is disposed on a rear end side of the main cylinder  11 , and is coaxially fitted in an opening on a rear side of the main cylinder  11 . An inner diameter of a front portion  121   a  of the cylinder part  121  is larger than an inner diameter of the through-hole  111   a  of the inner wall part  111 . Also, an inner diameter of a rear portion  121   b  of the cylinder part  121  is smaller than the inner diameter of the front portion  121   a.    
     The dust-proof boot  122  can be expanded and contracted in a bellows tube shape in the front and rear direction, and is attached on its front side so as to contact an opening on a rear end side of the cylinder part  121 . A through-hole  122   a  is formed at a rear center of the boot  122 . The compression spring  123  is a coil shaped urging spring disposed around the boot  122 , and a front side thereof is in contact with a rear end of the main cylinder  11  and a rear side is radially reduced so as to come close to the through-hole  122   a  of the boot  122 . A rear end of the boot  122  and a rear end of the compression spring  123  are coupled to an operation rod  10   a . The compression spring  123  urges rearward the operation rod  10   a.    
     The input piston  13  is a piston configured to slide in the cover cylinder  12  in accordance with an operation of the brake pedal  10 . The input piston  13  is a substantially cylindrical bottomed piston having a bottom surface at the front and an opening at the rear. A bottom wall  131  configuring the bottom surface of the input piston  13  has a larger diameter than other part of the input piston  13 . The input piston  13  is liquid-tightly disposed so as to be axially slidable in the rear portion  121   b  of the cylinder part  121 , and the bottom wall  131  is disposed on an inner periphery side of the front portion  121   a  of the cylinder part  121 . 
     In the input piston  13 , the operation rod  10   a  configured to operate in conjunction with the brake pedal  10  is disposed. A pivot  10   b  at a tip end of the operation rod  10   a  is adapted to push and move forward the input piston  13 . A rear end of the operation rod  10   a  protrudes outward through the opening on the rear side of the input piston  13  and the through-hole  122   a  of the boot  122 , and is connected to the brake pedal  10 . When the brake pedal  10  is depressed, the operation rod  10   a  is advanced while pushing and moving axially the boot  122  and the compression spring  123 . The input piston  13  is also advanced in conjunction with the advance of the operation rod  10   a.    
     The first master piston  14  is disposed to be axially slidable on the inner wall part  111  of the main cylinder  11 . The first master piston  14  has a pressurizing cylindrical part  141 , a flange part  142 , and a protrusion  143 , which are integrally formed sequentially from the front side. The pressurizing cylindrical part  141  is formed into a substantially cylindrical bottomed shape having an opening at the front, has a gap with the inner peripheral surface of the main cylinder  11 , and is in sliding contact with the small-diameter part  112 . In an inside space of the pressurizing cylindrical part  141 , a coil-shaped urging member  144  is disposed between the pressurizing cylindrical part and the second master piston  15 . The urging member  144  urges rearward the first master piston  14 . In other words, the first master piston  14  is urged toward a set initial position by the urging member  144 . 
     The flange part  142  has a larger diameter than the pressurizing cylindrical part  141 , and is in sliding contact with the inner peripheral surface of the main cylinder  11 . The protrusion  143  has a smaller diameter than the flange part  142 , and is liquid-tightly disposed to be slidable in the through-hole  111   a  of the inner wall part  111 . A rear end of the protrusion  143  protrudes into an inside space of the cylinder part  121  beyond the through-hole  111   a , and is spaced from an inner peripheral surface of the cylinder part  121 . A rear end face of the protrusion  143  is spaced from the bottom wall  131  of the input piston  13 , and a spacing distance thereof can be varied. 
     Herein, a“first master chamber  1 D” is defined by the inner peripheral surface of the main cylinder  11 , a front side of the pressurizing cylindrical part  141  of the first master piston  14 , and a rear side of the second master piston  15 . Also, a rear chamber is defined at the rear of the first master chamber  1 D by the inner peripheral surface (inner peripheral part) of the main cylinder  11 , the small-diameter part  112 , a front surface of the inner wall part  111 , and an outer peripheral surface of the first master piston  14 . A front end portion and a rear end portion of the flange part  142  of the first master piston  14  divide the rear chamber into front and rear, so that a “second liquid pressure chamber  1 C” is formed on the front side and a “servo chamber  1 A” is formed on the rear side. A volume of the second liquid pressure chamber  1 C decreases as the first master piston  14  is advanced, and increases as the first master piston  14  is retreated. Also, a “first liquid pressure chamber  1 B” is defined by the inner peripheral part of the main cylinder  11 , a rear surface of the inner wall part  111 , an inner peripheral surface (inner peripheral part) of the front portion  121   a  of the cylinder part  121 , the protrusion  143  (rear end portion) of the first master piston  14 , and a front end portion of the input piston  13 . 
     The second master piston  15  is disposed to be axially movable in sliding contact with the small-diameter part  113  on a front side of the first master piston  14  in the main cylinder  11 . The second master piston  15  is formed integrally with a tubular pressurizing cylindrical part  151  having an opening at the front, and a bottom wall  152  formed to close a rear side of the pressurizing cylindrical part  151 . The bottom wall  152  supports the urging member  144  between the bottom wall and the first master piston  14 . In an inside space of the pressurizing cylindrical part  151 , a coil-shaped urging member  153  is disposed between the pressurizing cylindrical part and a closed inner bottom surface hid of the main cylinder  11 . The urging member  153  urges rearward the second master piston  15 . In other words, the second master piston  15  is urged toward a set initial position by the urging member  153 . A “second master chamber  1 E” is defined by the inner peripheral surface and the inner bottom surface  111   d  of the main cylinder  11  and the second master piston  15 . 
     The master cylinder  1  is formed with ports  11   a  to  11   i  for communicating an inside and an outside of the master cylinder each other. The port  11   a  is formed at the rear of the inner wall part  111  of the main cylinder  11 . The port  11   b  is formed to face the port  11   a , in an axially similar position to the port  11   a . The port  11   a  and the port  11   b  communicate with each other via an annular space between the inner peripheral surface of the main cylinder  11  and an outer peripheral surface of the cylinder part  121 . The port  11   a  and the port  11   b  connect to a pipe  161  and also to a reservoir  171  (low-pressure source). 
     Also, the port  11   b  communicates with the first liquid pressure chamber  1 B by a passage  18  formed in the cylinder part  121  and the input piston  13 . The passage  18  is formed so that it is blocked when the input piston  13  is advanced. Thereby, the first liquid pressure chamber  1 B and the reservoir  171  are cut off each other. The port  11   c  is formed at the rear of the inner wall part  111  and in front of the port  11   a , and communicates the first liquid pressure chamber  1 B and a pipe  162  each other. The port  11   d  is formed in front of the port  11   c , and communicates the servo chamber  1 A and a pipe  163  each other. The port  11   e  is formed in front of the port  11   d , and communicates the second liquid pressure chamber  1 C and a pipe  164  each other. 
     The port  11   f  is formed between both seal members G 1  and G 2  of the small-diameter part  112 , and communicates a reservoir  172  and the inside of the main cylinder  11  each other. The port  11   f  communicates with the first master chamber  1 D via a passage  145  formed in the first master piston  14 . The passage  145  is formed in a position in which the port  11   f  and the first master chamber  1 D are cut off when the first master piston  14  is advanced. The port  11   g  is formed in front of the port  11   f , and communicates the first master chamber  1 D and a pipe conduit  31  each other. 
     The port  11   h  is formed between both seal members G 3  and G 4  of the small-diameter part  113 , and communicates a reservoir  173  and the inside of the main cylinder  11  each other. The port  11   h  communicates with the second master chamber  1 E via a passage  154  formed in the pressurizing cylindrical part  151  of the second master piston  15 . The passage  154  is formed in a position in which the port  11   h  and the second master chamber  1 E are cut off when the second master piston  15  is advanced. The port  11   i  is formed in front of the port  11   h , and communicates the second master chamber  1 E and a pipe conduit  32  each other. 
     Also, a seal member such as an O-ring is appropriately disposed in the master cylinder  1 . The seal members G 1  and G 2  are disposed at the small-diameter part  112 , and are in liquid-tight contact with the outer peripheral surface of the first master piston  14 . Likewise, the seal members G 3  and G 4  are disposed at the small-diameter part  113 , and are in liquid-tight contact with the outer peripheral surface of the second master piston  15 . Also, seal members G 5  and G 6  are disposed between the input piston  13  and the cylinder part  121 . 
     A stroke sensor  71  is a sensor configured to detect a stroke (operation amount) of the brake pedal  10  made by a driver&#39;s operation, and is configured to transmit a detection signal to the brake ECU  6 . A brake switch  72  is a switch configured to detect whether or not a driver operates the brake pedal  10  by a binary signal, and is configured to transmit a detection signal to the brake ECU  6 . The brake switch  72  is also referred to as a brake stop switch. 
     The reaction force generation device  2  is a device configured to generate a reaction force that opposes an. operation force when the brake pedal  10  is operated, and mainly includes a stroke simulator  21 . The stroke simulator  21  is configured to generate a reaction pressure in the first liquid pressure chamber  1 B and the second liquid pressure chamber  1 C, in accordance with an operation of the brake pedal  10 . The stroke simulator  21  has a configuration where a piston  212  is slidably fitted in a cylinder  211 . The piston  212  is urged rearward by a compression spring  213 , and a reaction chamber (corresponding to “liquid pressure chamber”)  214  is formed on a rear surface-side of the piston  212  (the pipe  164 -side). The reaction chamber  214  is connected to the second liquid pressure chamber  1 C via the pipe  164  and the port  11   e , and the reaction chamber  214  is connected to the first control valve  22  and the second control valve  23  via the pipe  164 . 
     A branched pipe part  164   a  that is a part of the pipe  164  and is disposed in the vicinity of an inlet of the cylinder  211  is formed with an orifice  91 . The pressure sensor  73  is disposed at a part of the pipe  164  on an upstream side of the orifice  91  (an upstream side with respect to flow of a brake liquid upon depression). That is, the pressure sensor  73  is a sensor configured to detect a reaction pressure that is a liquid pressure in a part (upstream part) of the pipe  164  on a side closer to the brake pedal  10  than the orifice  91 . 
     Like this, it can be said that the stroke simulator  21  has the cylinder  211  configured to define the reaction chamber  214  to which a brake liquid is supplied via the pipe (corresponding to“fluid path”)  164  in accordance with a stroke of the brake pedal  10 , the piston  212  configured to slide in the cylinder  211  by the brake liquid supplied to the reaction chamber  214 , the orifice  91  provided in the branched pipe part  164   a  that is a part of the pipe  164 , and the pressure sensor  73  configured to detect a liquid pressure (reaction pressure) of the brake liquid supplied to the reaction chamber  214  in a part of the piper  164  on the supply-direction upstream side of the orifice  91 . The stroke simulator  21  is configured to apply a reaction force corresponding to the reaction pressure to the brake pedal  10 . 
     The first control valve  22  is an electromagnetic valve that closed in a non-energization state, and opening/closing thereof is controlled by the brake ECU  6 . The first control valve  22  is connected between the pipe  164  and the pipe  162 . Herein, the pipe  164  communicates with the second liquid pressure chamber  1 C via the port  11   e , and the pipe  162  communicates with the first liquid pressure chamber  1 B via the port  11   c . Also, when the first control valve  22  is opened, the first liquid pressure chamber  1 B is opened, and when the first control valve  22  is closed, the first liquid pressure chamber  1 B is closed. Therefore, the pipe  164  and the pipe  162  are provided to communicate the first liquid pressure chamber  1 B and the second liquid pressure chamber  1 C each other. 
     The first control valve  22  is closed in the non-energization state. At this time, the first liquid pressure chamber  1 B and the second liquid pressure chamber  1 C are cut off each other. Thereby, the first liquid pressure chamber  1 B is closed, so that there is no place for the brake liquid to flow, and the input piston  13  and the first master piston  14  operate in conjunction with each other while keeping a constant spacing distance. Also, the first control valve  22  is opened in an energization state. At this time, the first liquid pressure chamber  1 B and the second liquid pressure chamber  1 C communicate with each other. Thereby, a change in volumes of the first liquid pressure chamber  1 B and the second liquid pressure chamber  1 C as a result of the advance and retreat of the first master piston  14  is absorbed by movement of the brake liquid. 
     The pressure sensor  73  is a sensor configured to detect reaction pressures in the second liquid pressure chamber  1 C and the first liquid pressure chamber  1 B, and is connected to the pipe  164 . The pressure sensor  73  detects a pressure in the second liquid pressure chamber  1 C when the first control valve  22  is in the closed state, and also detects a pressure in the first liquid pressure chamber  1 B communicating with the second liquid pressure chamber when the first control valve in the opened state. The pressure sensor  73  is configured to transmit a detection signal to the brake ECU  6 . 
     The second control valve  23  is an electromagnetic valve that is opened in the non-energization state, and opening/closing thereof is controlled by the brake ECU  6 . The second control valve  23  is connected between the pipe  164  and the pipe  161 . Herein, the pipe  164  communicates with the second liquid pressure chamber  1 C via the port  11   e , and the  161  communicates with the reservoir 171  via the port  11   a . Therefore, the second control valve  23  does not generate the reaction pressure by communicating the second liquid pressure chamber  1 C and the reservoir  171  each other in the non-energization state, and generates the reaction pressure by cutting off the same each other in the energization state. 
     The servo pressure generation device  4  is a so-called hydraulic booster (boosting device), and includes a pressure decreasing valve  41 , a pressure increasing valve  42 , a pressure supply unit  43 , and a regulator  44 . The pressure decreasing valve  41  is a normally open electromagnetic valve (normally open valve) that is opened in the non-energization state, and a flow rate (or pressure) thereof is controlled by the brake ECU  6 . One side of the pressure decreasing valve  41  connected to the pipe  161  via a pipe  411 , and the other side of the pressure decreasing valve  41  is connected to a pipe  413 . That is, one side of the pressure decreasing valve  41  communicates with the reservoir  171  via the pipes  411  and  161  and the ports  11   a  and  11   b . When the pressure decreasing valve  41  is closed, the outflow of the brake liquid from a pilot chamber  4 D is prevented. In the meantime, the reservoir  171  and a reservoir  434  communicate with each other, although not shown. The reservoir  171  and the reservoir  434  may be the same reservoir. 
     The pressure increasing valve  42  is a normally closed electromagnetic valve (normally closed valve) that is closed in the non-energization state, and a flow rate (or pressure) thereof is controlled by the brake ECU  6 . One side of the pressure increasing valve  42  is connected to a pipe  421 , and the other side of the pressure increasing valve  42  is connected to a pipe  422 . The pressure supply unit  43  is a unit configured to mainly supply a high-pressure operating fluid to the regulator  44 . The pressure supply unit  43  includes an accumulator  431 , a liquid pressure pump  432 , a motor  433 , and the reservoir  434 . The pressure sensor  75  is configured to detect a liquid pressure in the accumulator  431 . Since the configuration of the pressure supply unit  43  is well known, the description thereof is omitted. 
     The regulator  44  is a mechanical regulator and has the pilot chamber  4 D formed therein. Also, the regulator  44  is formed with a plurality of ports  4   a  to  4   h . The pilot chamber  4 D is connected to the pressure decreasing valve  41  via the port  4   f  and the pipe  413 , and is connected to the pressure increasing valve  42  via the port  4   g  and the pipe  421 . When. the pressure increasing valve  42  is opened, a high-pressure brake liquid is supplied from the accumulator  431  to the pilot chamber  4 D via the ports  4   a ,  4   b  and  4   g , so that the piston is moved to expand the pilot chamber  4 D. In accordance with the expansion, the valve member is moved to communicate the port  4   a  and the port  4   c  each other, so that the high-pressure brake liquid is supplied to the servo chamber  1 A through the pipe  163 . On the other hand, when the pressure decreasing valve  41  is opened, the liquid pressure (pilot pressure) in the pilot chamber  4 D is lowered, so that a flow path between the port  4   a  and the port  4   c  is cut off by the valve member. In this way, the brake ECU  6  is configured to control the pressure decreasing valve  41  and the pressure increasing valve  42 , thereby controlling the pilot pressure corresponding to the servo pressure to control the servo pressure. An actual servo pressure is detected by the pressure sensor  74 . The present embodiment has a by-wire configuration in which the brake operating mechanism and the pressure adjusting mechanism are separated from each other. 
     The actuator  5  is a device configured to adjust a master pressure that is supplied through the pipe conduits  31  and  32  and to supply the same to the wheel cylinders  541  to  544 . The actuator  5  is an actuator configuring an ABS, and has a plurality of electromagnetic valves, a motor, a pump, a reservoir, and the like, which are not shown. The actuator  5  can execute a pressure increasing control, a keeping control and a pressure decreasing control for the wheel cylinders  541  to  544  under control of the brake ECU  6 . Also, the actuator  5  can execute an antiskid control (ABS control) and the like under control of the brake ECU  6 . Also, each wheel W is provided with the wheel speed sensor  76 . 
     (Brake Start Determination) 
     The brake ECU  6  is an electronic control unit having a CPU and a memory. The brake ECU  6  is communicatively connected to each of the sensors  71  to  76 , each of the control valves  22  and  23 , the servo pressure generation device  4 , and the actuator  5  (wires are not shown). The brake ECU  6  has, as functional units, a control unit  61 , and a brake start determination unit  62 . The control unit  61  is configured to calculate a target deceleration (target servo pressure) based on detection values of the stroke sensor  71  and the pressure sensor  73 , and to control each of the control valves  22  and  23 , the servo pressure generation device  4  and the actuator  5 , based on a result of the calculation. 
     The brake start determination unit  62  is configured to determine whether an operation of the brake pedal  10  has been. started. In other words, the brake start determination unit  62  configured to determine whether or not to start a brake control. The brake start determination unit  62  can be said as a unit with which the control unit  61  detects a timing at which a pressure increasing control is to start. When the brake start determination unit  62  determines that the operation has been started, the control unit  61  starts a brake control (liquid pressure control). 
     Specifically, when the reaction pressure detected by the pressure sensor  73  becomes equal to or greater than a first threshold value and then the stroke detected by the stroke sensor  71  becomes equal to or greater than a second threshold value, the brake start determination unit  62  determines that the operation of the brake pedal  10  has been started (it can be said as an operation start or a brake control start). Also, the brake start determination unit  62  is configured to use, as the stroke (value), a detection value (raw value) of the stroke sensor  71  without passing through a filter  6   a . The filter  6   a  is a noise filter for removing noises to smoothly change a detection value. This determination is effective in a small amount of sudden operation in which the driver quickly depresses the brake pedal  10  slightly. 
     According to the present embodiment, as shown in  FIG. 2 , when a small amount of sudden operation is performed, the reaction pressure is rapidly increased by the orifice  91 . Therefore, the reaction pressure becomes equal to or greater than the first threshold value before the stroke becomes equal to or greater than the second threshold value. By the sudden brake operation, the brake liquid is rapidly supplied to the pipe  164 . However, before the brake liquid is rapidly supplied to the cylinder  211  of the stroke simulator  21 , the flow path is narrowed by the orifice  91  intentionally provided (or structurally formed) , so that a part on an upstream side of the orifice  91  is likely to temporarily become high pressure. In the present configuration, the action of the orifice  91  is used for the determination. 
     Also, since the raw value of the stroke sensor  71  changes in conjunction with the further actual brake operation, it is possible to improve responsiveness to the brake operation by using the raw value as a determination element. The filter  6   a  is not passed, so that accuracy of a numerical value itself is reduced due to noises and the like. However, since the operation start (brake control start) is determined by an AND condition of a condition relating to the raw value and a condition relating to the reaction pressure, the accuracy (robustness) of the determination is secured. As shown in brake determination and target deceleration of  FIG. 2 , according to the present embodiment, it is possible to implement the brake control having high responsiveness to the driver&#39;s operation even upon the small amount of rapid operation. 
     More specifically, for the brake start determination unit  62 , three types of determination methods including the above determination method are set. As the first determination method, the brake start determination unit  62  acquires two detection values transmitted through different wires from the stroke sensor  71 , as two filter values passing thorough the filter  6   a , and determines the operation start when both the two filter values become equal to or greater than a predetermined threshold value. The filter values have high accuracy because noises and the like are removed therefrom, and the determination is performed based on an AND condition. of the two filter values, so that robustness is also secured. The first determination method is a determination method that is effective upon a usual brake operation (relatively gentle operation) in which the filter value is likely to follow a brake operation. 
     As the second determination method, the brake start determination unit  62  determines the operation start when the brake switch  72  becomes on (an operation is detected) and the reaction pressure becomes equal to or greater than predetermined threshold value. The second determination method is a determination method that is effective upon a sudden brake in which the brake switch  72  becomes on in a highly responsive manner (an operation of suddenly depressing the brake pedal to the end to stop the vehicle). 
     As the third determination method, as described above, the reaction pressure and one raw value of the stroke are set as the determination element. This third determination method is a determination method that is effective upon the small amount of sudden operation, as described above. The three determination methods are all determination methods in which the determination is performed based on two determination elements (AND condition). The brake start determination unit  62  determines the operation start when the AND condition is satisfied in any one of the three determination methods. In. this way, the brake start determination unit  62  monitors two filter values of the stroke sensor  71 , one raw value of the stroke sensor  71 , the detection result of the brake switch  72 , and the detection value (reaction pressure) of the pressure sensor  73 , and determines the operation start, based on the elements. Thereby, it is possible to secure responsiveness and accuracy for all the brake operations. 
     According to the present embodiment, the reaction pressure that is influenced by the orifice  91  is used as the determination element. Therefore, for example, even upon the small amount of sudden operation to which the brake switch  72  does not respond, it is possible to improve responsiveness of the brake start determination. Also, the stroke is used as the determination element, together with the reaction pressure, so that it is possible to secure accuracy of the determination. Regarding the detection of the stroke, the determination is performed under the AND condition with the reaction pressure, so that the responsiveness can be prioritized over the accuracy. In the present embodiment, the raw value of the stroke is used, so that the responsiveness is prioritized. The raw value of the stroke directly linked with the brake operation is used, so that the responsiveness is further improved. In the meantime, the responsiveness can be prioritized by setting the second threshold value small, for example. 
     &lt;Other Modified Embodiments&gt; 
     The present disclosure is not limited to the above embodiment. For example, as shown in  FIG. 3 , the vehicle brake device BF may have an electromagnetic valve  92  provided at a part of the pipe  164  between the cylinder  211  and the pressure sensor  73 . In this case, the brake ECU  6  further has an electromagnetic valve control unit  63 . The electromagnetic valve control unit  63  controls the electromagnetic valve  92  so that, when a probability that the operation of the brake pedal  10  is determined to be started is high, an amount of increase in reaction pressure with respect to an amount of increase in stroke is greater, as compared to a case in which the probability is low. 
     The case in which the probability that the operation of the brake pedal  10  is determined to be started is high includes a case in which an inter-vehicle distance is less than a predetermined value, and the like. That is, when an inter-vehicle distance detected by a radar or the like is less than a predetermined value, it is determined that the probability is high. When the probability is high, the electromagnetic valve control unit  63  narrows a flow path of the electromagnetic valve  92  (controls the valve to a closed. state), thereby increasing an orifice effect to improve a rate of increase in reaction pressure with respect to an increase in stroke. Thereby, when the probability is high, the reaction pressure is more likely to increase, so that it is possible to improve the responsiveness of the brake start determination. According to this configuration, it is possible to adjust responsiveness in accordance with traveling situations. In the meantime, the electromagnetic valve  92  may be provided to the pipe  164  (as an orifice), instead of the orifice  91 . 
     Also, the brake start determination unit  62  may be configured so that the greater a temperature correlation value is, which correlates with a temperature of the brake liquid to generate the reaction pressure, the smaller the first threshold value is. For example, when a temperature of the brake liquid in the pipe  164  becomes higher, viscosity of the brake liquid is lowered, so that an increase in reaction pressure is likely to be slow. Therefore, when a temperature correlation value of the brake liquid is acquired by a temperature sensor or an estimation calculation and the first threshold value is changed in accordance with the value, the responsiveness is ensured more securely. The brake start determination unit  62  may reduce the first threshold value when the temperature correlation value becomes equal to or greater than a predetermined value, for example. 
     Also, when a change gradient of the reaction pressure becomes equal to or greater than a third threshold value, the brake start determination unit  62  may determine that the operation of the brake pedal  10  has been started, irrespective of the reaction pressure and the stroke. When the change gradient of the reaction pressure is calculated by a first numerical operation (for example, 1 or 2operation) after the detection value of the pressure sensor  73  is acquired and the change gradient is used as the determination element, the operation start can be detected earlier than when the reaction pressure becomes equal to or greater than the first threshold value. That is, it is possible to further improve the responsiveness. For example, this determination method may be set as a fourth determination method. 
     Also, the actuator  5  may be a type of an actuator capable of performing pump pressurization to the wheel cylinders  541  to  544 , and executing a side antiskid control. Also, the boosting mechanism is not limited to the hydraulic booster such as the servo pressure generation device  4 , and may be an electric booster configured to drive a ball screw under control of an electric motor, thereby driving a master piston.