Patent Publication Number: US-2018037203-A1

Title: Hydraulic Control Apparatus and Brake System

Description:
TECHNICAL FIELD 
     The present invention relates to a hydraulic control apparatus and a brake system of a hydraulic brake that applies a braking force to a vehicle. 
     BACKGROUND ART 
     Conventionally, there has been known a technique discussed in PTL 1 as a hydraulic control apparatus. The technique discussed in this patent literature includes an input apparatus equipped with a master cylinder and a stroke simulator, a motor cylinder apparatus serving as a hydraulic source, and a control apparatus that controls a hydraulic pressure. 
     CITATION LIST 
     Patent Literature 
     PTL 1: Japanese Patent Application Public Disclosure No. 2012-106646 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, the technique discussed in PTL 1 includes a solenoid valve provided to the input apparatus for switching activation of the stroke simulator, thereby necessitating establishment of an electric connection with the control apparatus, thus involving a possibility of leading to a cost increase accompanying handling of a harness. An object of the present invention is to provide a hydraulic control apparatus and a brake system capable of preventing or cutting down the cost increase. 
     Solution to Problem 
     To achieve the above-described object, according to one aspect of the present invention, a hydraulic control apparatus includes a hydraulic source provided inside a housing and configured to generate a hydraulic pressure in a hydraulic generation unit mounted on a wheel via an oil passage, a switching electromagnetic valve provided integrally in the housing and configured to be used to permit an inflow of brake fluid into a stroke simulator provided separately from the housing and configured to generate a reaction force of a brake pedal operation performed by a driver, and a control unit provided integrally in the housing and configured to be used to drive the hydraulic source and the switching electromagnetic valve. 
     Advantageous Effects of Invention 
     In other words, the switching electromagnetic valve for permitting the inflow of the brake fluid into the stroke simulator is provided on the hydraulic control apparatus side, which allows omission of the harness and the like required to be provided between the hydraulic control apparatus and the stroke simulator, thereby succeeding in preventing or cutting down the cost increase. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a system diagram illustrating a brake system according to a first embodiment together with a hydraulic circuit. 
         FIG. 2  is a perspective view of the brake system according to the first embodiment. 
         FIG. 3  is a cross-sectional view of a first unit according to the first embodiment. 
         FIG. 4  is a perspective view illustrating a front right side of a second unit according to the first embodiment. 
         FIG. 5  is a perspective view illustrating a front left side of the second unit according to the first embodiment. 
         FIG. 6  is a left side view of the second unit according to the first embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
       FIG. 1  schematically illustrates a configuration of a brake system according to a first embodiment together with a hydraulic circuit.  FIG. 2  is a perspective view of the brake system according to the first embodiment.  FIG. 3  is a cross-sectional view of a first unit according to the first embodiment. The brake system according to the first embodiment is applied to a brake system of an electric vehicle, such as a hybrid vehicle including an electric motor (a generator) besides an engine and an electric vehicle including only the electric motor (the generator) as a prime mover that drives wheels. Such an electric vehicle can carry out regenerative braking, which brakes the vehicle by converting a kinetic energy of the vehicle into electric energy with use of a regenerative braking apparatus including the motor (the generator). The brake system supplies brake fluid working as hydraulic fluid to a brake activation unit mounted on each of wheels FL to RR of the vehicle via a wheel cylinder pipe  10  wc to generate a brake hydraulic pressure (a wheel cylinder hydraulic pressure), thereby applying a hydraulic braking force to each of the wheels FL to RR. 
     The brake activation unit including a wheel cylinder  8  is a so-called-disk type brake device. The brake activation unit includes a brake disk and a caliper (a hydraulic brake caliper). The brake disk is a brake rotor that rotates integrally with a tire. The caliper is disposed with a predetermined clearance (a space, or a gap due to loose mounting) generated between the caliper and the brake disk, and includes a brake pad that generates the braking force by being displaced by the wheel cylinder hydraulic pressure into contact with the brake disk. The brake system  1  includes two brake pipe systems (a primary P system and a secondary S system). For example, a so-called X-split pipe configuration is employed as the brake piping method. The brake system  1  may employ another piping method, such as a front/rear split pipe configuration. Hereinafter, when a component provided in correspondence with the P system and a component provided in correspondence with the S system should be distinguished from each other, indices P and S will be added at the ends of the respective reference numerals. 
     The brake system includes a first unit  1   a  and a second unit  1   b.  The first unit  1   a  is physically connected to a brake pedal  2  operated by a driver. The second unit  1   b  controls brake hydraulic pressures in the wheel cylinders  8 . The first unit  1   a  and the second unit  1   b  are connected via pipes or conduits (a connection pipe  10 R, a primary pipe  10 P, a secondary pipe  10 S, and a backpressure chamber pipe  10   x ) (refer to  FIG. 2 ). The first unit  1   a  includes the brake pedal  2 , a reservoir tank (hereinafter referred to as a reservoir)  4 , a master cylinder  5 , and a stroke simulator  27 . The brake pedal  2  serves as a brake operation member that receives an input of a brake operation performed by an operator (a driver). The reservoir  4  is a brake fluid source that stores the brake fluid therein, and is a low-pressure portion opened to an atmospheric pressure. The master cylinder  5  is connected to the brake pedal  2  and is also replenished with the brake fluid from the reservoir  4 , and generates a brake hydraulic pressure (a master cylinder pressure) by being activated by the operation that the driver performs on the brake pedal  2 . The stroke simulator  27  creates a pedal reaction force (a pedal reaction force and a pedal stroke amount) by an inflow of the brake fluid from the master cylinder  5  according to the brake operation performed by the driver. Details of the stroke simulator  27  will be described below. The second unit  1   b  includes a plurality of electromagnetic valves and the like, and an electronic control unit (hereinafter referred to as an ECU)  100 . The plurality of electromagnetic valves and the like receive supply of the brake fluid from the reservoir  4  or the master cylinder  5 , and generate the brake hydraulic pressure independently of the brake operation performed by the driver. The ECU  100  controls activation of this plurality of electromagnetic valves and the like, and a pump  70 . Hereinafter, the various kinds of electromagnetic valves will be referred to as electromagnetic valves  20 , when they are collectively referred to. 
     The first unit  1   a  does not include an engine negative-pressure booster that boosts the brake operation force by utilizing an intake negative pressure generated by an engine of the vehicle. A push rod  30  is rotatably connected to the brake pedal  2 . The master cylinder  5  is a tandem-type master cylinder. The master cylinder  5  includes a primary piston  54 P connected to the push rod  30  and a secondary piston  54 S configured as a free piston as master cylinder pistons axially displaceable according to the brake operation performed by the driver. The primary piston  54 P is provided with a stroke sensor  90  that detects the pedal stroke. A magnet for detection is provided at the piston, and a sensor main body is attached to an outer surface of the housing. 
     The second unit  1   b  is provided between the first unit  1   a  and the wheel cylinders  8 . The second unit  1   b  includes the built-in pump  70 , and performs control so as to be able to individually supply the master cylinder pressure or a control hydraulic pressure to each of the wheel cylinders  8 . The second unit  1   b  includes a plurality of control valves as actuators for generating the control hydraulic pressure. The electromagnetic valves and the like perform opening/closing operations according to a control signal, thereby controlling a flow of the brake fluid. The second unit  1   b  can perform control of increasing the pressures in the wheel cylinders  8  with use of the hydraulic pressure generated by the pump  70  with the master cylinder  5  and the wheel cylinders  8  out of communication with each other. Further, the second unit  1   b  includes therein hydraulic sensors  91  to  93 , which detect a discharge pressure of the pump  70  and the master cylinder pressure. 
     The pump  70  draws the brake fluid from the reservoir  4  and discharges the brake fluid toward the wheel cylinders  8  by being rotationally driven by a motor M. In the present embodiment, the pump  70  is embodied by a plunger pump including five plungers, which is excellent in terms of a noise and vibration performance and the like. The pump  70  is used in common by both of the S and P systems. The pump  70  is driven by the single motor M. The motor M may be a brushless motor or may be a brushed motor. 
     Detection values transmitted from the stroke sensor  90  and the hydraulic sensors  91  to  93 , and information regarding a running state transmitted from the vehicle are input to the ECU  100 . The ECU  100  controls each of the actuators in the second unit  1   b  based on a program installed therein. More specifically, the ECU  100  controls the opening/closing operations of the electromagnetic valves that switch communication states of oil passages, and the number of revolution(s) of the motor M that drives the pump  70  (i.e., a discharge amount of the pump  70 ). By this operation, the brake system according to the first embodiment realizes boosting control for reducing a required brake operation force, anti-lock brake control (hereinafter referred to as ABS) for preventing or reducing a slip of a wheel that might be caused when the vehicle is braked, control of a motion of the vehicle (brake control for vehicle behavior stabilization control such as electronic stability control, which will be hereinafter referred to as motion control), automatic brake control such as adaptive cruise control, regenerative cooperative brake control that controls the wheel cylinder hydraulic pressure so as to achieve a target deceleration (a target braking force) by collaborating with the regenerative brake, and the like. In the boosting control, the ECU  100  drives the second unit  1   b  with use of the discharge pressure of the pump  70  as a hydraulic source, when the driver performs the brake operation. In the boosting control, the ECU  100  creates a higher wheel cylinder hydraulic pressure than the master cylinder pressure, thereby generating a hydraulic braking force for compensating for insufficiency of the brake operation force input by the driver. The boosting control allows the brake system to exert a boosting function that assists the brake operation. In other words, the brake system assists the brake operation force by activating the pump  70  of the second unit  1   b  instead of the engine negative-pressure booster. In the regenerative cooperative brake control, the ECU  100  generates a hydraulic braking force by which a regenerative braking force generated by the regenerative braking apparatus is insufficient to, for example, achieve a braking force requested by the driver. 
     The master cylinder  5  is a first hydraulic source connected to the wheel cylinders  8  via the primary pipe  10 P, the secondary pipe  10 S, and first oil passages  11 , which will be described below, and capable of increasing the wheel cylinder hydraulic pressures. The master cylinder  5  can increase the pressures in wheel cylinders  8   a  and  8   d  via an oil passage (a first oil passage  11 P) in the P system with use of a master cylinder pressure generated in a first fluid chamber  51 P. At the same time, the master cylinder  5  can increase the pressures in wheel cylinders  8   b  and  8   c  via a first oil passage  11 S in the S system with use of a master cylinder pressure generated in a second fluid chamber  51 S. The pistons  54 P and  54 S in the master cylinder  5  are inserted axially displaceably along an inner peripheral surface of a bottomed cylindrical cylinder. The cylinder includes a discharge port (a supply port)  501  and a replenishment port  502  for each of the P and S systems. The discharge port  501  is provided so as to be able to connect to the second unit  1   b  to communicate with the wheel cylinders  8 . The replenishment port  502  is connected to the reservoir  4  and is in communication with the reservoir  4 . A coil spring  56 P as a return spring is set in the first fluid chamber  51 P between the pistons  54 P and  54 S in a pressed and compressed state. A coil spring  56 S is set in the second fluid chamber  51 S between the piston  54 S and an axial end of the cylinder in a pressed and compressed state. The discharge ports  501  are normally or constantly opened to the first and second fluid chambers  51 P and  51 S. 
     A primary oil passage  510 P connected to the primary pipe  10 P and a secondary oil passage  510 S connected to the secondary pipe  10 S are connected to the discharge ports  501 , respectively. A first simulator oil passage  511  connected to a main chamber R 1  of the stroke simulator  27  is connected to the secondary oil passage  510 S. An auxiliary chamber (a backpressure chamber) R 2  of the stroke simulator  27  includes a backpressure chamber port  512  connected to the backpressure chamber pipe  10   x.    
     In the following description, a brake hydraulic circuit of the second unit  1   b  will be described with reference to  FIG. 1 . Members corresponding to the individual wheels FL to RR will be distinguished from one another if necessary, by indices a to d added at the ends of reference numerals thereof, respectively. The second unit  1   b  includes the first oil passages  11 , normally opened shut-off valves  21 , normally opened pressure-increase valves (hereinafter referred to as SOL/V INs)  22 , an intake oil passage  12 , a discharge oil passage  13 , a normally-closed communication valve  23 P, a normally-closed communication valve  23 S, a first pressure-reduction oil passage  14 , a normally-opened pressure adjustment valve  24 , second pressure-reduction oil passages  15 , normally-closed pressure-reduction valves  25 , and a second simulator oil passage  17 . The first oil passages  11  connect the primary pipe  10 P and the secondary pipe  10 S, and the wheel cylinders  8  to each other. The shut-off valves  21  are provided in the first oil passages  11 . The SOL/V INs  22  are provided on the wheel cylinder  8  side in the first oil passages  11  with respect to the shut-off valves  21  in correspondence with the individual wheels FL to RR (in oil passages  11   a  to  11   d ), respectively. The intake oil passage  12  connects a fluid pool  12   r  provided at an intake portion of the pump  70  and the pressure-reduction oil passages  15 , which will be described below, to each other. The discharge oil passage  13  connects a portion in the first oil passages  11  between the shut-off valves  21  and the SOL/V INs  22 , and a discharge portion  71  of the pump  70  to each other. The communication valve  23 P is provided in a discharge oil passage  13 P connecting a downstream side of the discharge oil passage  13  and the first oil passage  11 P in the P system to each other. The communication valve  23 S is provided in a discharge oil passage  13 S connecting the downstream side of the discharge oil passage  13  and the first oil passage  11 S in the S system to each other. The first pressure-reduction oil passage  14  connects a portion between a discharge oil passage  13 P and the communication valves  23 P and  23 S, and the intake oil passage  12  to each other. The pressure adjustment valve  24  is provided in the first pressure-reduction oil passage  14 . The second pressure-reduction oil passages  15  connect a wheel cylinder  8  side in the first oil passages  11  with respect to the SOL/V INs  22 , and the intake oil passage  12  to each other. The pressure-reduction valves  25  serve as second pressure-reduction valves provided in the second pressure-reduction oil passages  15 . The second simulator oil passage  17  connects the backpressure chamber pipe  10   x  and a portion in the first oil passage  11 S between the shut-off valve  21 S and the SOL/V INs  22   b  and  22   c,  and the intake oil passage  12  to each other via a stroke simulator IN valve  31  and a stroke simulator OUT valve  32 . 
     In the pump  70 , the fluid pool  12   r  is provided at a portion where the connection pipe  10 R extending from the reservoir  4  is connected to the intake oil passage  12  of the pump  70 . The discharge oil passages  13 P and  13 S form communication passages connecting the first oil passage  11 P in the P system and the first oil passage  11 S in the S system to each other. The pump  70  is connected to the wheel cylinders  8   a  to  8   d  via the above-described communication passages (the discharge oil passages  13 P and  13 S) and the first oil passages  11 P and  11 S. The pump  70  serves as a second hydraulic source capable of increasing the wheel cylinder hydraulic pressures by discharging the brake fluid to the above-described communication passages (the discharge oil passages  13 P and  13 S). At least one of the shut-off valves  21 , the SOL/V INs  22 , the communication valve  23 P, the pressure adjustment valve  24 , and the pressure-reduction valves  25  of each of the systems (the SOL/V INs  22  and the pressure adjustment valve  24  in the present embodiment) is a proportional control valve, an opening degree of which is adjusted according to a current supplied to a solenoid. The other valves are ON/OFF valves, opening/closing of which is controlled to be switched between two values, i.e., switched to be either opened or closed. The proportional control valve can also be employed as the above-described other valves. 
     The shut-off valves  21  are provided in the first oil passages  11 P and  11 S. Bypass oil passages  120  are provided in parallel with the first oil passages  11  by bypassing the SOL/V INs  22 . Further, the bypass oil passages  120  include check valves  220 , which permit only a flow of the brake fluid from the wheel cylinder  8  side to the master cylinder  5  side. The hydraulic sensor  91  is provided on the master cylinder side of the first oil passages  11  with respect to the shut-off valves  11 S. The hydraulic sensor  91  detects a hydraulic pressure at this portion (a hydraulic pressure in the stroke simulator  27 , and the master cylinder pressure). The hydraulic sensors  92  are provided between the shut-off valves  21  and the SOL/V INs  22  in the first oil passages  11 . The hydraulic sensors  92  detect hydraulic pressures at these portions (the wheel cylinder hydraulic pressures). The hydraulic sensor  93  is provided between the discharge oil passage  13 P and the communication valve  23 . The hydraulic sensor  93  detects a hydraulic pressure at this portion (the discharge pressure of the pump). 
     Now, the details of the stroke simulator  27  of the first unit  1   a  will be described with reference to  FIGS. 1 to 3 . The stroke simulator  27  includes a piston  27   a,  a first spring  27   b   1 , a retainer member  27   b   2 , and a second spring  27   b   3 . The piston  27   a  is disposed axially displaceably in a chamber R while dividing an inside of the chamber R into two chambers (the main chamber R 1  and the auxiliary chamber R 2 ). The spring  27   b   1  is an elastic member set in the auxiliary chamber R 2  in a pressed and compressed state, and constantly biasing the piston  27   a  toward one side where the main chamber R 1  is located (in a direction for reducing a volume of the main chamber R 1  and increasing a volume of the auxiliary chamber R 2 ). The retainer member  27   b   2  holds the first spring  27   b   1 . The second spring  27   b   3  is an elastic member constantly biasing the retainer member  27   b   2  toward the main chamber R 1  side. A damper  27   d   1  is provided at a spring member  27   c  for the purpose of improving a pedal feeling (refer to  FIG. 3 ). Hereinafter, the first spring  27   b   1  and the second spring  27   b   3  will be collectively referred to as the springs  27   b.    
     When the stroke simulator IN valve  31  and the stroke simulator OUT valve  32  are respectively controlled in closing directions with the shut-off valves  21  in the second unit  1   b  controlled in opening directions, the brake system (the first oil passages  11 ) connecting the first and second fluid chambers  51 P and  51 S of the master cylinder  5  and the wheel cylinders  8  to each other creates the wheel cylinder hydraulic pressures by the master cylinder pressure generated with use of the force of pressing the pedal, thereby realizing pressing force brake (non-boosting control). On the other hand, the brake system connecting the second fluid pressure  51 S of the master cylinder  5  and the wheel cylinders  8  to each other with the shut-off valves  21  controlled in closing directions, the stroke simulator IN valve  31  controlled in an opening direction, and the stroke simulator OUT valve  32  controlled in the closing direction creates the wheel cylinder hydraulic pressure with use of the brake hydraulic pressure flowing out of the auxiliary chamber R 2  reduced in volume according to the displacement of the piston  27   a  of the stroke simulator  27 , thereby realizing a second pressure force brake. Further, when the stroke simulator valve IN valve  31  and the stroke simulator OUT valve  32  are controlled in the closing direction and the opening direction, respectively, with the shut-off valves  21  controlled in the closing directions, the brake system connecting the reservoir  4  and the wheel cylinders  8  to each other (the intake oil passage  12 , the discharge oil passage  13 , and the like) creates the wheel cylinder hydraulic pressures by the hydraulic pressure generated with use of the pump  70 , and forms a so-called brake-by-wire system that realizes the boosting control, the regenerative cooperative control, and the like. The brake system may be configured to switch the brake control to the boosting control or the regenerative cooperative control after the second pressing force brake. 
     As illustrated in the cross-section of  FIG. 3 , the secondary oil passage  510 S is connected to the first fluid chamber  51 S of the master cylinder  5 , and the first simulator oil passage  511  connected to the main chamber R 1  of the stroke simulator  27  is also connected to the first fluid chamber  51 S of the master cylinder  5 . In this manner, the first simulator oil passage  511  is formed inside the first unit  1   a,  which eliminates a necessity of connecting the second unit  1   b  side and the main chamber R 1  to each other, thereby preventing or cutting down a cost increase accompanying an increase in the pipes. With the shut-off valves  21  controlled in the closing directions to block the communication between the master cylinder  5  and the wheel cylinders  8 , the stroke simulator  27  causes at least the brake fluid flowing out of the first fluid chamber  51 S of the master cylinder  5  to be introduced into the main chamber R 1  via the first simulator oil passage  511 , thereby creating the pedal reaction force. With the shut-off valve  21 S closed to block the communication between the master cylinder  5  and the wheel cylinders  8 , and the stroke simulator OUT valve  32  opened to establish the communication between the master cylinder  5  and the stroke simulator  27 , the stroke simulator  27  introduces and discharges the brake fluid from the master cylinder  5 , thereby creating the pedal reaction force, when the driver performs the brake operation (presses the brake pedal  2  or releases the pressed brake pedal  2 ). 
     More specifically, when a hydraulic pressure (the master cylinder pressure) equal to or higher than a predetermined pressure is applied to a pressure-receiving surface of the piston  27   a  in the main chamber R 1 , the piston  27   a  is axially displaced toward the auxiliary chamber R 2  side while pressing and compressing the spring  27   b,  thereby increasing the volume of the main chamber R 1 . As a result, the brake fluid is delivered from the secondary oil passage  510 S of the master cylinder  5  into the main chamber R 1  via the first simulator oil passage  511 . At the same time, the brake fluid is discharged from the auxiliary chamber R 2  into the intake oil passage  12  via the backpressure chamber pipe  10   x  and the second simulator oil passage  17  in the second unit  1   b.  When the pressure in the main chamber R reduces to lower than the predetermined pressure, the piston  27   a  is returned to an initial position due to the biasing force (an elastic force) of the spring  27   b.  The stroke simulator  27  introduces therein the brake fluid from the master cylinder  5  in this manner, thereby simulating hydraulic stiffness of the wheel cylinders  8  to imitate a feeling that the driver would have when pressing the pedal. 
     In this manner, the electromagnetic valve and the like are not provided in the first unit  1   a,  and the stroke simulator IN valve  31  and the stroke simulator OUT valve  32  for switching the activation of the stroke simulator  27  are provided in the second unit  1   b.  Therefore, the present embodiment does not require a controller for driving the electromagnetic valve in the first unit  1   a  and a wiring for controlling the electromagnetic valve between the first unit la and the second unit  1   b.  Therefore, the present embodiment can reduce the cost. Further, when the stroke simulator  27  in the first unit  1   a  and the second unit  1   b  are connected as the pipe, the main chamber R 1  of the stroke simulator  27  and the second unit  1   b  are not connected to each other, and only the backpressure chamber as the auxiliary chamber R 2  and the second unit  1   b  are connected to each other via the backpressure chamber pipe  10   x.  Therefore, the present embodiment allows the activation of the stroke simulator  27  to be switched without requiring a plurality of pipes, thereby succeeding in reducing the cost. 
     The ECU  100  forms a hydraulic control unit that activates the pump  70 , the electromagnetic valves, and the like based on various kinds of information to control the hydraulic pressures in the wheel cylinders  8 . The ECU  100  includes a brake operation amount detection unit  101 , a target wheel cylinder hydraulic pressure calculation unit  102 , a pressing force brake creation unit  103 , a boosting control unit  104 , and a boosting control switching unit  105 . The brake operation amount detection unit  101  detects a displacement amount (the pedal stroke) of the brake pedal  2  as the brake operation amount upon receiving the input of the value detected by the stroke sensor  90 . The target wheel cylinder hydraulic pressure calculation unit  102  calculates a target wheel cylinder hydraulic pressure. More specifically, the target wheel cylinder hydraulic pressure calculation unit  102  calculates the target wheel cylinder hydraulic pressure that realizes a predetermined boosting rate, i.e., an ideal characteristic about a relationship between the pedal stroke and a brake hydraulic pressure requested by the driver (a vehicle deceleration G requested by the driver) based on the detected pedal stroke. Further, in the regenerative cooperative brake control, the target wheel cylinder hydraulic pressure calculation unit  102  calculates the target wheel cylinder hydraulic pressure in relation to the regenerative braking force. More specifically, the target wheel cylinder hydraulic pressure calculation unit  102  calculates such a target wheel cylinder hydraulic pressure that a sum of the regenerative braking force input from a control unit of the regenerative braking apparatus and a hydraulic braking force corresponding to the target wheel cylinder hydraulic pressure can satisfy the vehicle deceleration requested by the driver. In the motion control, the target wheel cylinder hydraulic pressure calculation unit  102  calculates the target wheel cylinder hydraulic pressure for each of the wheels FL to RR so as to, for example, realize a desired state of the vehicle motion based on a detected amount of a state of the vehicle motion (a lateral acceleration or the like). 
     The pressing force brake creation unit  103  is configured to prohibit the stroke simulator  27  from functioning by controlling the shut-off valves  21  in the opening direction and the stroke simulator OUT valve  32  in the closing direction, thereby realizing the pressing force brake that creates the wheel cylinder hydraulic pressures from the master cylinder pressure. The boosting control unit  104  controls the shut-off valves  21  in the closing direction to thus make the second unit  1   b  ready to create the wheel cylinder hydraulic pressures by the pump  70 , thereby performing the boosting control. The boosting control unit  104  controls each of the actuators to realize the target wheel cylinder hydraulic pressure. Further, the ECU  100  closes the stroke simulator IN valve  31  and controls the stroke simulator OUT valve  32  in the opening direction, thereby causing the stroke simulator  27  to function. 
     The boosting control switching unit  105  controls the activation of the master cylinder  5  to switch the pressing force brake and the boosting control based on the calculated target wheel cylinder hydraulic pressure. More specifically, upon detection of a start of the brake operation by the brake operation amount detection unit  101 , the boosting control switching unit  105  causes the pressing force brake creation unit  103  to create the wheel cylinder hydraulic pressures if the calculated target wheel cylinder hydraulic pressure is equal to or lower than a predetermined value (for example, corresponding to a maximum value of the vehicle deceleration G that would be generated when the vehicle is normally braked without being suddenly braked). On the other hand, the boosting control switching unit  105  causes the boosting control unit  104  to create the wheel cylinder hydraulic pressures if the target wheel cylinder hydraulic pressure calculated at the time of the operation of pressing the brake exceeds the above-described predetermined value. Further, the boosting control switching unit  105  can also switch the brake control so as to apply the second pressing force brake to create the wheel cylinder hydraulic pressures, and then create the wheel cylinder hydraulic pressures by the boosting control unit  104  after that, when detecting the brake pressing operation state and detecting a sudden braked state. 
     Next, a configuration of the second unit  1   b  will be described.  FIG. 4  is a perspective view illustrating a front right side of the second unit according to the first embodiment.  FIG. 5  is a perspective view illustrating a front left side of the second unit according to the first embodiment.  FIG. 6  is a left side view of the second unit according to the first embodiment. The second unit  1   b  includes a housing  200 , a control unit housing  300 , and a mount  400 . The housing  200  is made of an aluminum alloy block and contains the electromagnetic valves  20  and the pump  70  therein. The control unit housing  300  is made of a resin material and contains the ECU  100  therein. The mount  400  supports these housing  200  and control unit housing  300  on the vehicle body side. 
     The housing  200  includes a first surface  201 , a second surface  202  (refer to  FIG. 6 ), a third surface  203 , a fourth surface  204 , a fifth surface  205 , and a sixth surface  206  (refer to  FIG. 6 ). The second surface  202  is located opposite from the first surface  201 . The third surface  203  is continuous from the first and second surfaces  201  and  202 . The fourth surface  204  is continuous from the first, second, and third surfaces  201 ,  202 , and  203 . The fifth surface  205  is located opposite from the fourth surface  204 . The sixth surface  206  is located opposite from the third surface  203 . A motor housing  250  containing the motor M for driving the pump  70  therein is attached to the first surface  201 . Further, master cylinder connection ports  201   a  and  201   b  connected to the primary pipe  10   p  and the secondary pipe  10 S, respectively, are formed on a portion of the first surface  201  that is located above the motor M when the second unit  1   b  is mounted on the vehicle. Further, the housing  200  includes front-side mount pins  202   a  and  202   b  fixed to the mount  400  on the first surface  201  and a lower position located on an opposite side from the master cylinder connection port  201   a  via a center of a rotation of the motor M. 
     The motor housing  250  is a bottomed cylindrical member, and includes a cylindrical portion  251 , a bottom portion  252 , and a flange portion  253 . The cylindrical portion  251  contains therein, for example, a rotor and a stator of the motor M on an inner periphery thereof. The bottom portion  252  closes one side of the cylindrical portion  251 . The flange portion  253  has an increased diameter to allow the motor housing  250  to be attached to the first surface  201  side. The flange portion  253  includes first, second, and third flange portions  253   a,    253   b,  and  253   c  for attaching the motor housing  250  to the first surface  201  with use of bolts  254 . The first flange portion  253   a  is provided at a position overlapping the center of the rotation of the motor M and on an upper side as viewed from a top surface when the second unit  1   b  is mounted on the vehicle. Further, the first flange portion  253   a  is provided between the master cylinder connection ports  201   a  and  201   b  as viewed from a horizontal direction, and is disposed in such a manner that a line passing through lower ends of the master cylinder connection ports  201   a  and  201   b  overlaps the first flange portion  253   a,  thereby achieving a reduction in the size. The second flange portion  253   b  and the third flange portion  253   c  are provided at positions sandwiching the first flange portion  253   a  and on a lower side as viewed from the top surface when the second unit  1   b  is mounted on the vehicle. The front-side mount pins  202   a  and  202   b  are disposed in such a manner that respective centers of the pins are located on lower sides and outer sides with respect to centers of the bolts of the second flange portion  253   b  and the third flange portion  253   c,  respectively. Therefore, The second unit  1   b  can be stably supported due to the support based on the two points, and can also be stably supported due to an increase in a distance between the supporting points. 
     The control unit housing  300  is disposed on the second surface  202 . The control unit housing  300  contains the ECU  100  therein, and also includes a controller portion  302  covering various kinds of electromagnetic valves. Further, the control unit housing  300  includes a connector portion  301  provided on a fifth surface  205  side of the controller portion  302  and on an outer position with respect to the housing  200  as viewed from a direction along a rotational axis of the motor. The connector portion  301  is formed in such a manner that a connection is completed by insertion of a connector from the direction along the rotational axis of the motor. The connector portion  301  electrically connects the external apparatus or the stroke sensor  90  and the ECU  100  to each other. 
     The third surface  203  is a top surface when the second unit  1   b  is mounted on the vehicle. Wheel cylinder pipe ports  203   a,  to which the wheel cylinder pipes  10   wc  connecting the wheel cylinders  8  and the second unit  1   b  to each other are connected, are provided on the third surface  203 . The wheel cylinder pipes  10   wc  are disposed side by side at positions closer to the second surface  202  than to the first surface  201 . Further, an intake port  10 R 1  connected to the reservoir  4  via the connection pipe  10 R is formed on the third surface  203 . The intake port  10 R 1  is provided at a central portion in a direction in which the wheel cylinder pipes  10   wc  are disposed side by side and at a position closer to the first surface  201  than the wheel cylinder pipes  10   wc  are. Therefore, the present embodiment can realize a layout utilizing the space in the third surface  203 , thereby achieving the reduction in the size. 
     The fourth surface  204  is a side surface when the second unit  1   b  is mounted on the vehicle. A backpressure chamber port  204   a  connected to the backpressure chamber pipe  10   x  is formed at a lower portion of the fourth surface  204 . An obstacle such as the connector portion  301  provided on the fifth surface  205  side is not provided on the fourth surface  204  side, so that the backpressure chamber pipe  10   x  can be easily connected. In other words, a port or the like, such as the backpressure chamber port  204   a,  is not formed on the fifth surface  205 , which facilitates a connection when the connector is connected to the connector portion  301 . The sixth surface  206  is a bottom surface when the second unit  1   b  is mounted on the vehicle. The sixth surface  206  includes two lower-side mount pins  206   a  and  206   b  fixed to the mount  400 . 
     The mount  400  includes a first mount portion  401  facing the sixth surface  206 . The lower-side mount pin  206   b  is fixed to the first mount portion  401  via an insulator, and absorbs a vibration between the second unit  1   b  and the first mount portion  401 . The mount  400  includes leg portions  402  and flange portions  403  on sides of the first mount portion  402 . The leg portions  402  are formed by being bent downward from both the sides, respectively. The flange portions  403  are formed at lower ends of the leg portions  402 , and are fixed to the vehicle side. Three vehicle fixation bolt holes  403   a,  through which bolts for fixing the flange portion  403  to the vehicle side are inserted, are formed at each of the flange portions  403  side by side in the direction along the rotational axis of the motor. The mount  400  includes a leg portion  405  and a flange portion  406  on the second surface  202  side of the first mount portion  401 . The leg portion  405  is formed by being bent downward. The flange portion  406  is formed at a lower end of the leg portion  405 , and is fixed to the vehicle side. Vehicle fixation bolt holes  406   a,  through which bolts for fixing the flange portion  406  to the vehicle side, are provided at the flange portion  406 . 
     The mount  400  includes a front-side support surface  404  on the first surface  201  side of the first mount portion  401 . The front-side support surface  404  is formed by being bent toward one side where the cylindrical portion  251  of the motor housing  250  is located, and is curved along a shape of the cylindrical portion  251 . The mount  400  includes fixation portions  404   a  and  404   b  on both ends of the front-side support surface  404 . The fixation portions  404   a  and  404   b  fix the front-side mount pins  202   a  and  202   b  via insulators. Due to this configuration, the mount  400  absorbs a vibration between the second unit  1   b  and the front-side support surface  404 . In this manner, the second unit  1   b  is supported at the four lower and front portions, which allows the second unit  1   b  to be stably held. 
     [Advantageous Effects of First Embodiment] 
     In the following description, advantageous effects of the brake system according to the first embodiment will be listed. 
     (1) The hydraulic control apparatus includes the housing  200  including the oil passage formed therein, the pump  70  (a hydraulic source) provided inside the housing  200  and configured to generate the hydraulic pressure in the wheel cylinder  8  (a hydraulic generation unit) mounted on the wheel via the oil passage, the stroke simulator IN valve  31  and/or the stroke simulator OUT valve  32  (a switching electromagnetic valve) provided integrally in the housing  200  and configured to be used to permit the inflow of brake fluid into the stroke simulator  27  provided separately from the housing  200  and configured to generate the reaction force of the brake pedal operation performed by the driver, and the ECU  100  (a control unit) provided integrally in the housing  200  and configured to be used to control drive the pump  70 , and the stroke simulator IN valve  31  and/or the stroke simulator OUT valve  32 . 
     Therefore, the first embodiment can omit the harness between the stroke simulator  27  and the ECU  100  that is required in the case where the stroke simulator IN valve  31  and/or the stroke simulator OUT valve  32  is/are provided on the stroke simulator  27  side, thereby preventing or cutting down the cost increase. Further, the first embodiment can also prevent or reduce an influence of radiation noise due to the omission of the harness. 
     (2) The hydraulic control apparatus described in the above-described item (1) further includes the backpressure chamber pipe  10   x  (a first oil passage) at the housing  200 . The backpressure chamber pipe  10   x  is configured to supply the brake fluid flowing out of the auxiliary chamber R 2  (a backpressure chamber) of the stroke simulator  27  to the stroke simulator IN valve  31  and/or the stroke simulator OUT valve  32 . 
     Therefore, the first embodiment does not require the provision of the pipe connecting the main chamber R 1  of the stroke simulator  27  and the second unit  1   b  to each other, thereby succeeding in reducing the cost due to the reduction in the pipes. 
     (3) The hydraulic control apparatus described in the above-described item (2) further includes the backpressure chamber port  204   a  (a connection port) at the housing  200 . The backpressure chamber port  204   a  is connected to the backpressure pipe  10   x  and the oil passage connected to the stroke simulator  27 . 
     Therefore, the first embodiment can connect the stroke simulator  27  and the stroke simulator IN valve  31  and/or the stroke simulator OUT valve  32  in the second unit  1   b  to each other via simple piping. 
     In the hydraulic control apparatus described in the above-described item (1), the housing  200  includes the first surface  201  to which the motor M configured to drive the pump  70  is attached, the second surface  202  located opposite from the first surface  201  and having the ECU  100  disposed thereon, the third surface  203  formed continuously from the first surface  201  and the second surface  202 , and the fourth surface  204  formed continuously from the first surface  201 , the second surface  202 , and the third surface  203 . The wheel cylinder pipe port  203   a  (a pipe port) to which the wheel cylinder pipe  10   wc  (a pipe) leading to the wheel cylinder  8  is connected is formed on the third surface  203 . The backpressure chamber port  204   a  is formed on the fourth surface  204 . 
     The wheel cylinder pipe  10   wc  and the backpressure chamber port  204   a  are disposed so as to be distributed on different surfaces, and therefore the first embodiment can prevent or cut down the increase in the size of the housing. 
     (5) The hydraulic control apparatus described in the above-described item (4) further includes the connector portion  301  (a connector) configured to electrically connect the ECU  100  to an external apparatus, and the fifth surface  205  located opposite from the fourth surface  204 . The connector portion  301  is provided on the one side where the fifth surface  205  is located. 
     The connector portion  301 , the port, and the like are not provided on the fifth surface  205 , and therefore the first embodiment can improve workability when a wiring is connected to the connector portion  301 . 
     (6) The hydraulic control apparatus described in the above-described item (5) further includes the sixth surface  206  located opposite from the third surface  203 , and the mount  400  provided on the sixth surface  206 . The mount  400  is configured to be used to fix the housing  200  to the vehicle. 
     Therefore, the functions can be distributed to the individual surfaces, and therefore the first embodiment can prevent or cut down the increase in the size of the housing  200 . 
     (7) The hydraulic control apparatus described in the above-described item (4) further includes the connection pipe  10 R (an intake oil passage) connecting the reservoir  4  and the housing  200  to each other. The reservoir  4  stores the brake fluid. The pump  70  draws the brake fluid from the reservoir  4 . The third surface  203  is configured so as to become the top surface when the hydraulic control apparatus is mounted on the vehicle, and is provided with the intake port  10 R 1  connected to the connection pipe  10 R. 
     Therefore, the first embodiment allows the wheel cylinder pipe  10   wc  and the connection pipe  10 R to be provided on the third surface  203  that will become the top surface, thereby contributing to improvement of the workability of the pipe connection. 
     (8) The hydraulic control apparatus described in the above-described item (4) further includes the connection pipe  10 R connecting the reservoir  4  and the housing  200  to each other. The reservoir  4  stores the brake fluid that the pump  70  draws from the reservoir  4 . The wheel cylinder pipe port  203   a  includes the plurality of wheel cylinder pipe ports  203   a  formed along the longitudinal direction of the third surface  203 . The intake port  10 R 1  is formed closer to the first surface  201  than the wheel cylinder pipe ports  203   a  are. 
     The wheel cylinder pipe ports  203   a  and the intake port  10 R 1  are disposed offset from each other, and therefore the first embodiment can realize an efficient layout of the ports and the like, thereby preventing or cutting down the increase in the size of the housing  200 . 
     (9) In the hydraulic control apparatus described in the above-described item (8), the master cylinder connection port  201   a  or  201   b  to which the master cylinder pipe  10   p  or  10 S connected to the master cylinder  5  is connected is formed on the first surface  201 . 
     Therefore, the functions can be distributed to the individual surfaces, and therefore the first embodiment can prevent or cut down the increase in the size of the housing  200 . 
     (10) In the hydraulic control apparatus described in the above-described item (1), the front-side mount pin  202   a  or  202   b  (a second mount portion) for fixing the housing  200  to the vehicle is provided on the first surface  201 . 
     Therefore, the functions can be distributed to the individual surfaces, and therefore the first embodiment can prevent or cut down the increase in the size of the housing  200 . 
     (11) In the hydraulic control apparatus described in the above-described item (10), the front-side mount pin  202   a  or  202   b  includes the plurality of front-side mount pins. 
     Therefore, the first embodiment can stably hold the housing  200 . 
     In the following description, technical ideas recognizable from the above-described embodiment will be listed. 
     (12) A hydraulic control apparatus includes a housing including a plurality of oil passages formed therein, a connection port formed at the housing and connecting a stroke simulator separately provided from the housing and the oil passages to each other, a hydraulic source provided inside the housing and configured to discharge brake fluid to an oil passage connected to a hydraulic generation unit mounted on a wheel among the plurality of oil passages, a stroke simulator switching electromagnetic valve provided integrally in the housing, and a control unit provided integrally in the housing and configured to be used to drive the hydraulic source and the stroke simulator switching electromagnetic valve. 
     In other words, the stroke simulator switching electromagnetic valve is provided integrally in the housing, and therefore this configuration can omit the harness electrically connecting the stroke simulator and the hydraulic control apparatus to each other, thereby preventing or cutting down the cost increase. 
     (13) The hydraulic control apparatus described in the above-described item (12) further includes a first oil passage at the housing. The first oil passage is configured to supply the brake fluid flowing out of a backpressure chamber of the stroke simulator to the stroke simulator switching electromagnetic valve. 
     Therefore, this configuration does not require the provision of the pipe connecting the main chamber to which the brake fluid in the stroke simulator flows, and the housing to each other, and therefore can reduce the pipes and thus reduce the cost. 
     (14) In the hydraulic control apparatus described in the above-described item (13), the housing includes a first surface to which a motor configured to drive the pump is attached, a second surface located opposite from the first surface and having the control unit disposed thereon, a third surface formed continuously from the first surface and the second surface, and a fourth surface formed continuously from the first surface, the second surface, and the third surface. A pipe port to which a pipe leading to the hydraulic generation unit is connected is formed on the third surface. The connection port is formed on the fourth surface. 
     Therefore, the functions can be distributed to the individual surfaces, and therefore this configuration can prevent or cut down the increase in the size of the housing. 
     (15) The hydraulic control apparatus described in the above-described item (14) further includes a connector configured to electrically connect the control unit to an external apparatus, and a fifth surface located opposite from the fourth surface. The connector is provided on one side where the fifth surface is located. 
     The connector, the port, and the like are not provided on the fifth surface, and therefore this configuration can improve workability when a wiring is connected to the connector. 
     (16) The hydraulic control apparatus described in the above-described item (14) further includes an intake oil passage connecting a reservoir and the housing to each other. The reservoir stores the brake fluid that the hydraulic source draws from the reservoir. The third surface is configured so as to become a top surface when the hydraulic control apparatus is mounted on the vehicle, and is provided with an intake port connected to the intake oil passage. 
     Therefore, this configuration allows the pipe port and the intake port to be provided on the third surface that will become the top surface, thereby contributing to improvement of the workability of the pipe connection. 
     (17) The hydraulic control apparatus described in the above-described item (14) further includes an intake oil passage connecting a reservoir and the housing to each other. The reservoir stores the brake fluid that the hydraulic source draws from the reservoir. The pipe port includes a plurality of pipe ports formed along a longitudinal direction of the third surface. The intake port is formed closer to the first surface than the pipe ports are. 
     The pipe ports and the intake port are disposed offset from each other, and therefore this configuration can realize an efficient layout of the ports and the like, thereby preventing or cutting down the increase in the size of the housing. 
     (18) A brake system includes a first unit including a stroke simulator configured to generate a reaction force of a brake operation performed by a driver, and a second unit integrally including a hydraulic source configured to generate a hydraulic pressure in a hydraulic generation unit mounted on a wheel, a switching electromagnetic valve configured to be used to permit an inflow of the brake fluid into the stroke simulator, and a control unit configured to be used to drive the hydraulic source and the switching electromagnetic valve. 
     In other words, the stroke simulator is disposed in the first unit and the switching electromagnetic valve is provided in the second unit. Therefore, this configuration can omit the harness electrically connecting the stroke simulator and the hydraulic control apparats to each other, thereby preventing or reducing the cost increase. 
     (19) The hydraulic control apparatus described in the above-described item (18) further includes a first oil passage at the housing. The first oil passage is configured to supply the brake fluid flowing out of a backpressure chamber of the stroke simulator to the switching electromagnetic valve. 
     Therefore, this configuration does not require the provision of the pipe connecting the main chamber to which the brake fluid in the stroke simulator flows, and the housing to each other, and therefore can reduce the pipes and thus reduce the cost. 
     (20) The hydraulic control apparatus described in the above-described item (19) further includes an oil passage connecting the stoke simulator and the switching electromagnetic valve to each other. 
     Therefore, the stroke simulator and the switching electromagnetic valve in the second unit can be connected to each other via simple piping. 
     (21) In the hydraulic control apparatus described in the above-described item (20), the first unit includes the master cylinder including a piston configured to be activated according to a brake pedal operation performed by the driver, and a connection oil passage configured to supply the brake fluid flowing out of the master cylinder to the stroke simulator. 
     Therefore, the brake fluid in the master cylinder can be absorbed by the stroke simulator. 
     (22) In the hydraulic control apparatus described in the above-described item (18), the first unit includes a housing. The master cylinder, the stroke simulator, and the connection oil passage are built in the housing. 
     Therefore, the connection can be established within the first unit, and therefore this configuration does not require the provision of the pipe and the like between the first unit and the second unit, thereby succeeding in reducing the cost. 
     Having described merely several embodiments of the present invention, those skilled in the art will be able to easily appreciate that the embodiments described as the examples can be modified or improved in various manners without substantially departing from the novel teachings and advantages of the present invention. Therefore, such modified or improved embodiments are intended to be also contained in the technical scope of the present invention. The above-described embodiments may also be arbitrarily combined. 
     The present application claims priority under the Paris Convention to Japanese Patent Application No. 2015-21684 filed on Feb. 6, 2015. The entire disclosure of Japanese Patent Application No. 2015-21684 filed on Feb. 6, 2015 including the specification, the claims, the drawings, and the abstract is incorporated herein by reference in its entirety. 
     REFERENCE SIGN LIST 
       1  brake system 
       1   a  first unit 
       1   b  second unit 
       2  brake pedal 
       4  reservoir 
       5  master cylinder 
       8  wheel cylinder 
       10 P primary pipe 
       10 R connection pipe 
       10 R 1  intake port 
       10 S secondary pipe 
       10   wc  wheel cylinder pipe 
       10   x  backpressure chamber pipe 
       17  simulator oil passage 
       20  electromagnetic valve 
       27  stroke simulator 
       30  push rod 
       31  stroke simulator IN valve 
       32  stroke simulator OUT valve 
       70  pump 
       200  housing 
       201  first surface 
       201   a,    201   b  master cylinder connection port 
       202  second surface 
       202   a,    202   b  front-side mount pin 
       203  third surface 
       203   a  wheel cylinder pipe port 
       204  fourth surface 
       204   a  backpressure chamber port 
       205  fifth surface 
       206  sixth surface 
       206   a,    206   b  lower-side mount pin 
       250  motor housing 
       293   a  wheel cylinder pipe port 
       300  control unit housing 
       301  connector portion 
       302  controller portion 
       400  mount 
       510 P primary oil passage 
       510 S secondary oil passage 
       511  simulator oil passage 
       512  backpressure chamber port 
     M motor 
     R 1  main chamber 
     R 2  auxiliary chamber