Master cylinder unit

Provided is a master cylinder unit including a simulator pressure chamber which communicates with a pressure chamber of a master cylinder and moves a simulator piston by means of an introduced fluid pressure; a biasing chamber in which a biasing mechanism biasing the simulator piston against a fluid pressure introduced into the simulator pressure chamber is disposed; a first seal member which partitions a simulator supply chamber, the simulator supply chamber, and the simulator pressure chamber communicating with a master supply chamber; and a second seal member which partitions the simulator supply chamber and the biasing chamber and allows a brake fluid to flow from the simulator supply chamber to the biasing chamber when a pressure difference occurs between the simulator supply chamber and the biasing chamber.

TECHNICAL FIELD

The present invention relates to a master cylinder unit.

Priority is claimed on Japanese Patent Application No. 2015-152774, filed Jul. 31, 2015, the content of which is incorporated herein by reference.

BACKGROUND ART

There is a braking device which includes a stroke simulator applying a reaction force corresponding to a stepping force of a brake pedal to the brake pedal.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

Facilitation of air bleeding work in a braking device is desired.

An object of the present invention is to provide a master cylinder unit which enables facilitation of air bleeding work.

Solution to Problem

An aspect of the present invention includes a master cylinder that generates a fluid pressure in a pressure chamber inside a cylinder in accordance with an operation amount of a brake pedal; a reservoir that stores a brake fluid to be supplied to the pressure chamber; and a stroke simulator that communicates with the pressure chamber, generates a reaction force corresponding to an operation force of the brake pedal, and applies the reaction force to the brake pedal. The master cylinder includes a master piston which moves inside the cylinder in response to an operation of the brake pedal, and a master supply chamber which is connected to the reservoir at all times and communicates with the pressure chamber when the brake pedal is not in operation. The stroke simulator has a simulator piston which moves inside a simulator cylinder, a simulator pressure chamber which communicates with the pressure chamber of the master cylinder on one end side of the simulator piston inside the simulator cylinder and moves the simulator piston by means of an introduced fluid pressure, a biasing chamber in which a biasing mechanism biasing the simulator piston against the introduced fluid pressure is disposed on the other end side of the simulator piston inside the simulator cylinder, a simulator supply chamber which is disposed between the simulator pressure chamber and the biasing chamber on an outer circumferential side of the simulator piston and communicates with the master supply chamber, a first seal member which partitions the simulator supply chamber and the simulator pressure chamber, and a second seal member which partitions the simulator supply chamber and the biasing chamber and allows the brake fluid to flow from the simulator supply chamber to the biasing chamber when a pressure difference occurs between the simulator supply chamber and the biasing chamber.

Advantageous Effects of Invention

According to the master cylinder unit described above, air bleeding work can be facilitated.

DESCRIPTION OF EMBODIMENTS

First Embodiment

A first embodiment will be described below with reference toFIGS. 1 to 6. A braking device10illustrated inFIG. 1is a braking device for a four-wheeled vehicle. The braking device10has a brake pedal11, a master cylinder unit12, a power module13, a braking cylinder15FR, a braking cylinder15RL, a braking cylinder15RR, and a braking cylinder15FL. The braking cylinder15FR is a front right wheel braking cylinder provided in a wheel on the front right among four wheels. The braking cylinder15RL is a rear left wheel braking cylinder provided in a wheel on the rear left among the four wheels. The braking cylinder15RR is a rear right wheel braking cylinder provided in a wheel on the rear right among the four wheels. The braking cylinder15FL is a front left wheel braking cylinder provided in a wheel on the front left among the four wheels. The braking cylinders15FR,15RL,15RR, and15FL are fluid pressure actuation mechanisms such as disk brakes and drum brakes applying a brake on rotation of the wheels.

The master cylinder unit12has an input rod21and a stroke sensor22. A base end side of the input rod21is joined to the brake pedal11, and the input rod21moves in an axial direction in accordance with an operation amount of the brake pedal11. The stroke sensor22detects a movement amount of the input rod21. The power module13generates a brake fluid pressure. Furthermore, the power module13controls the brake fluid pressure of each of the braking cylinders15FR,15RL,15RR, and15FL based on a detection result of the stroke sensor22or the like. That is, the braking device10is a brake-by-wire-type braking device. Specifically, this braking device10is a braking device configuring a sideslip prevention device which prevents a sideslip of a vehicle.

The master cylinder unit12includes a reservoir25, a master cylinder26, and a stroke simulator27. The reservoir25contains a brake fluid for a brake. The master cylinder26can generate a brake fluid pressure corresponding to the operation amount of the brake pedal11. The master cylinder26exchanges the brake fluid with the reservoir25. The stroke simulator27generates a reaction force corresponding to a stepping force, which is an operation force of the brake pedal11, and applies the reaction force to the brake pedal11. The reservoir25is detachably attached to an upper side of the master cylinder26in a vertical direction. The stroke simulator27is provided on a lower side of the master cylinder26in the vertical direction. The stroke simulator27is provided integrally with the master cylinder26.

As illustrated inFIG. 2, the master cylinder unit12has a metal cylinder member31(cylinder main body) which is processed and formed of one raw material. This cylinder member31configures a main body part of the master cylinder unit12. This cylinder member31is shared by the master cylinder26and the stroke simulator27. In the cylinder member31, an MC cylinder32(cylinder) and an SS cylinder33(simulator cylinder) are integrally formed in parallel. The MC cylinder32configures the master cylinder26. The SS cylinder33configures the stroke simulator27. That is, the master cylinder26and the stroke simulator27are disposed in the cylinder member31which is integrally formed of one raw material.

A cylinder hole40is formed in the MC cylinder32of the master cylinder26. Thus, the MC cylinder32has a cylinder bottom portion41and a cylinder wall portion42. The cylinder bottom portion41is on a deep side of the cylinder hole40. The cylinder wall portion42has a tubular shape and extends from the cylinder bottom portion41to a cylinder opening43on a side opposite to the cylinder bottom portion41.

A primary piston46(master piston) is installed on the cylinder opening43side in the cylinder wall portion42to be movable in the axial direction. The primary piston46configures the master cylinder26and is made of a metal. In addition, a secondary piston47(master piston) is installed on the cylinder bottom portion41side of the primary piston46inside the cylinder wall portion42to be movable in the axial direction. The secondary piston47configures the master cylinder26and is made of a metal, similar to the primary piston46. As illustrated inFIG. 1, in the primary piston46and the secondary piston47, the primary piston46is disposed on a side closer to the brake pedal11than the secondary piston47. In the primary piston46and the secondary piston47, the secondary piston47is disposed on a side opposite to the brake pedal11of the primary piston46.

A tip end portion of the input rod21on a side opposite to the brake pedal11comes into contact with the primary piston46. The primary piston46receives a stepping force of the brake pedal11via the input rod21. The primary piston46moves inside the MC cylinder32in response to an operation of the brake pedal11. The stroke sensor22is attached to the primary piston46. The stroke sensor22detects the movement amount of the primary piston46. Accordingly, the stroke sensor22detects the movement amount of the input rod21which moves integrally with the primary piston46. That is, the stroke sensor22detects the operation amount of the brake pedal11.

As illustrated inFIG. 2, a tubular stopper member51is screwed into an end portion of the cylinder bottom portion41on a side opposite to the cylinder wall portion42. The input rod21is inserted through an inner side of this stopper member51. A flange member52is fixed to an intermediate portion of the input rod21. The stopper member51comes into contact with this flange member52from the side opposite to the cylinder bottom portion41. Accordingly, the stopper member51determines a movement limit position for the input rod21in a direction opposite to the cylinder bottom portion41. As illustrated inFIG. 1, an extendable boot53covering their gap is interposed between the stopper member51and the input rod21.

A space between the primary piston46and the secondary piston47inside the MC cylinder32of the master cylinder26serves as a primary pressure chamber56(pressure chamber). A spring unit57is provided between the primary piston46and the secondary piston47. The spring unit57determines the distance between the primary piston46and the secondary piston47in a non-braking state having no input from the brake pedal11. As illustrated inFIG. 2, the spring unit57has a retainer58and a primary piston spring59. The retainer58is extendable within a predetermined range. The primary piston spring59is a coil spring biasing the retainer58in an extending direction. The retainer58regulates extension of the primary piston spring59such that its maximum length does not exceed a predetermined length. The secondary piston47which is connected to the primary piston46via the spring unit57also moves inside the MC cylinder32in response to an operation of the brake pedal11. The master cylinder26has the primary piston46and the secondary piston47as the master pistons which move inside the MC cylinder32in response to an operation of the brake pedal11.

As illustrated inFIG. 1, a space between the secondary piston47and the cylinder bottom portion41inside the MC cylinder32of the master cylinder26serves as a secondary pressure chamber61(pressure chamber). A spring unit62is provided between the secondary piston47and the cylinder bottom portion41. The spring unit62determines the distance between the secondary piston47and the cylinder bottom portion41in a non-braking state having no input from the brake pedal11. As illustrated inFIG. 2, the spring unit62has a retainer63and a secondary piston spring64. The retainer63is extendable within a predetermined range. The secondary piston spring64is a coil spring biasing the retainer63in the extending direction. The retainer63regulates extension of the secondary piston spring64such that its maximum length does not exceed a predetermined length.

Both the primary piston46and the secondary piston47have a plunger shape. Thus, the master cylinder26is a so-called plunger-type master cylinder. In addition, the master cylinder26is a tandem-type master cylinder having two pistons, that is, the primary piston46and the secondary piston47. The present invention is not limited to application to the tandem-type master cylinder. The present invention need only be applied to a plunger-type master cylinder, and can be applied to any plunger-type master cylinder such as a single-type master cylinder in which one piston is disposed in an MC cylinder and a master cylinder having three or more pistons.

An attachment base portion65protruding upward in the vertical direction from the cylinder wall portion42of the master cylinder26is formed integrally with the MC cylinder32. An attachment hole66and an attachment hole67for attaching the reservoir25are formed in this attachment base portion65. The attachment hole66and the attachment hole67are formed such that their positions in a circumferential direction of the cylinder hole40coincide with each other. The attachment hole66and the attachment hole67are formed such that their positions in an axial line direction of the cylinder hole40are deviated from each other. The master cylinder unit12is disposed in a vehicle such that the axial line direction of the MC cylinder32including the cylinder hole40of the master cylinder26lies along a front/rear direction of the vehicle and the cylinder bottom portion41is in a posture toward the front of the vehicle.

In the cylinder wall portion42of the master cylinder26, a secondary discharge path68is formed in the vicinity of the cylinder bottom portion41. The secondary discharge path68extends upward from the cylinder hole40such that its central axial line is orthogonal to the central axial line of the cylinder hole40. In addition, a primary discharge path69is formed in the cylinder wall portion42of the master cylinder26on a side closer to the cylinder opening43than the secondary discharge path68. The central axial line of the primary discharge path69is parallel to a direction orthogonal to the central axial line of the cylinder hole40and extends horizontally in an in-vehicle state. The secondary discharge path68and the primary discharge path69communicate with the power module13as indicated with the two-dot chain line inFIG. 1. The secondary discharge path68and the primary discharge path69communicate with the braking cylinders15FR,15RL,15RR, and15FL via the power module13. The secondary discharge path68and the primary discharge path69are configured to be capable of discharging the brake fluids of the secondary pressure chamber61and the primary pressure chamber56toward the braking cylinders15FR,15RL,15RR, and15FL. The primary pressure chamber56and the secondary pressure chamber61communicate with the power module13.

As illustrated inFIG. 2, in order from the cylinder bottom portion41side, a sliding inner diameter portion70, a large inner diameter portion71, and a female screw portion72are formed in an inner circumferential portion of the cylinder wall portion42. The sliding inner diameter portion70has a cylindrical surface-shaped inner diameter surface. The large inner diameter portion71has a cylindrical surface-shaped inner diameter surface having a diameter larger than that of the sliding inner diameter portion70. The female screw portion72has a diameter larger than that of the sliding inner diameter portion70. The central axial lines of the inner diameter surfaces of the sliding inner diameter portion70and the large inner diameter portion71coincide with each other. These central axial lines are the central axial lines of the cylinder hole40and the cylinder wall portion42.

The stroke sensor22fixed to the primary piston46is disposed inside the large inner diameter portion71. The stroke sensor22moves in the axial direction of the MC cylinder32inside this large inner diameter portion71. The primary piston46and the secondary piston47are slidably fitted to the inner diameter surface of the sliding inner diameter portion70. The primary piston46and the secondary piston47are guided along this inner diameter surface and move in the axial direction of the MC cylinder32.

A plurality of circumferential grooves, specifically four grooves, that is, a circumferential groove73, a circumferential groove74, a circumferential groove75, and a circumferential groove76are formed in the sliding inner diameter portion70, in that order from the cylinder bottom portion41side. All the circumferential grooves73to76are formed in annular shapes and all are formed in circular shapes. The circumferential grooves73to76have a shape recessed radially outward beyond the inner diameter surface of the sliding inner diameter portion70.

The circumferential groove73is on a side closest to the cylinder bottom portion41among the circumferential grooves73to76. The circumferential groove73is formed in the vicinity of the attachment hole66on the cylinder bottom portion41side, in the attachment hole66and the attachment hole67. A circular piston seal81is disposed inside the circumferential groove73to be held in the circumferential groove73.

An opening groove82is formed on the side closer to the cylinder opening43than the circumferential groove73in the sliding inner diameter portion70of the MC cylinder32. The opening groove82is recessed radially outward beyond the inner diameter surface of the sliding inner diameter portion70and is formed in an annular shape. This opening groove82causes a supply passage83to be open inside the cylinder hole40. The supply passage83has a linear shape in which one end is open inside the attachment hole66on the cylinder bottom portion41side, and the other end is open inside the cylinder hole40. Here, the positions of the opening groove82and the secondary piston47in the axial direction overlap each other, and a part surrounded by these serves as a secondary supply chamber84(master supply chamber). The secondary supply chamber84communicates with the reservoir25via the supply passage83at all times and is formed in an annular shape. A part of the secondary supply chamber84is formed by the secondary piston47.

An axial groove85is formed in an upper portion of the MC cylinder32on the side closer to the cylinder bottom portion41than the circumferential groove73of the sliding inner diameter portion70. The axial groove85is open to the circumferential groove73and extends linearly from the circumferential groove73toward the cylinder bottom portion41. The axial groove85is recessed radially outward beyond the inner diameter surface of the sliding inner diameter portion70. The secondary discharge path68is formed at a position between the cylinder bottom portion41and the circumferential groove73, that is, in the vicinity of the cylinder bottom portion41. The axial groove85causes the secondary discharge path68and the circumferential groove73to communicate with each other via the secondary pressure chamber61between the secondary piston47and the cylinder bottom portion41.

In the sliding inner diameter portion70of the MC cylinder32, the circumferential groove74is formed on a side opposite to the circumferential groove73of the opening groove82, that is, the cylinder opening43side. A circular partition seal86is disposed inside this circumferential groove74to be held in the circumferential groove74.

In the sliding inner diameter portion70of the MC cylinder32, the circumferential groove75is formed in the vicinity of the attachment hole67on the cylinder opening43side. A circular piston seal91is disposed inside this circumferential groove75to be held in the circumferential groove75.

An opening groove92is formed on the cylinder opening43side of the circumferential groove75in the sliding inner diameter portion70of the MC cylinder32. The opening groove92is recessed radially outward beyond the inner diameter surface of the sliding inner diameter portion70and is formed in an annular shape. This opening groove92causes a supply passage93to be open inside the cylinder hole40. The supply passage93has a linear shape in which one end is open inside the attachment hole67on the cylinder opening43side, and the other end is open inside the cylinder hole40. Here, the positions of the opening groove92and the primary piston46in the axial direction overlap each other, and a part surrounded by these serves as a primary supply chamber94(master supply chamber). The primary supply chamber94communicates with the reservoir25via the supply passage93at all times and is formed in an annular shape. A part of the primary supply chamber94is formed by the primary piston46. The master cylinder26has the secondary supply chamber84and the primary supply chamber94as master supply chambers which are connected to the reservoir25at all times.

An axial groove95is formed in an upper portion of the MC cylinder32on the side closer to the cylinder bottom portion41than the circumferential groove75of the sliding inner diameter portion70. The axial groove95is open to the circumferential groove75and extends linearly from the circumferential groove75toward the cylinder bottom portion41. The axial groove95is open to the circumferential groove74. The axial groove95is recessed radially outward beyond the inner diameter surface of the sliding inner diameter portion70. The primary discharge path69is formed at a position between the circumferential groove74and the circumferential groove75, that is, in the vicinity of the circumferential groove74. The axial groove95causes the primary discharge path69and the circumferential groove75to communicate with each other via the primary pressure chamber56between the primary piston46and the secondary piston47.

In the sliding inner diameter portion70of the MC cylinder32, the circumferential groove76is formed on a side opposite to the circumferential groove75of the opening groove92, that is, the cylinder opening43. A circular partition seal96is disposed inside this circumferential groove76to be held in the circumferential groove76.

The secondary piston47is disposed on the side closer to the cylinder bottom portion41than the primary piston46of the MC cylinder32. The secondary piston47has a cylindrical portion101and a bottom portion102formed at an intermediate position of the cylindrical portion101in the axial line direction, and has a plunger shape. The cylindrical portion101of the secondary piston47is fitted to each of the sliding inner diameter portion70of the MC cylinder32, the piston seal81provided in the sliding inner diameter portion70, and the partition seal86. The secondary piston47is guided by these and slides inside the MC cylinder32.

A plurality of ports103are formed at the end portion of the cylindrical portion101on the side closer to the cylinder bottom portion41. The plurality of ports103radially penetrate the cylindrical portion101. The plurality of ports103are formed in the cylindrical portion101in a radial manner at positions having equal intervals in the circumferential direction. The spring unit62is inserted into the secondary piston47of the cylinder bottom portion41side of the cylindrical portion101. In the spring unit62, one end of the retainer63in the axial direction comes into contact with the bottom portion102of the secondary piston47, and the other end of the retainer63in the axial direction comes into contact with the cylinder bottom portion41of the MC cylinder32. The secondary piston spring64determines the distance between the secondary piston47and the cylinder bottom portion41in a non-braking state having no input from the input rod21. The secondary piston spring64is reduced in length when there is an input from the input rod21, and biases the secondary piston47to the cylinder opening43using a force corresponding to the reduced length.

Here, a part surrounded by the cylinder bottom portion41, the cylinder bottom portion41side of the cylinder wall portion42, and the secondary piston47serves as the secondary pressure chamber61. The secondary pressure chamber61generates a brake fluid pressure in accordance with the operation amount of the brake pedal11and supplies the brake fluid pressure to the secondary discharge path68. In other words, the master cylinder26generates a fluid pressure in the secondary pressure chamber61inside the MC cylinder32in accordance with the operation amount of the brake pedal11. This secondary pressure chamber61communicates with the secondary supply chamber84, that is, the reservoir25, when the secondary piston47is at a position in which the ports103are open to the opening groove82. The secondary piston47causes the ports103to be open to the opening groove82when the brake pedal11is not in operation. In other words, the secondary supply chamber84included in the master cylinder26is connected to the reservoir25at all times and communicates with the secondary pressure chamber61when the brake pedal11is not in operation. The reservoir25stores a brake fluid to be supplied to the secondary pressure chamber61in this manner.

The partition seal86held by the circumferential groove74of the MC cylinder32is an integrally molded product made of synthetic rubber. The partition seal86is a cup seal of which the shape on one side of a radial cross-section including its central line is a C-shape. The partition seal86is disposed inside the circumferential groove74in which a lip part is in a state of being directed toward the cylinder opening43. In the partition seal86, the inner circumference is in slide contact with an outer circumferential surface of the secondary piston47, and the outer circumference comes into contact with the circumferential groove74of the MC cylinder32. Accordingly, the partition seal86seals the gap at the position of the partition seal86of the secondary piston47and the MC cylinder32at all times.

The piston seal81held by the circumferential groove73of the MC cylinder32is an integrally molded product made of synthetic rubber such as EPDM. The piston seal81is a cup seal of which the shape on one side of a radial cross-section including its central line is an E-shape. The piston seal81is disposed inside the circumferential groove73in which a lip part is in a state of being directed toward the cylinder bottom portion41. In the piston seal81, the inner circumference is in slide contact with the outer circumferential surface of the secondary piston47, and the outer circumference comes into contact with the circumferential groove73of the MC cylinder32. Accordingly, the piston seal81can seal the gap at the position of the piston seal81of the secondary piston47and the MC cylinder32.

The secondary piston47is at a non-braking position in which the ports103are open to the opening groove82, when there is no input from the input rod21. The piston seal81partially overlaps the ports103in the axial direction when the secondary piston47is at a non-braking position as illustrated inFIG. 2. In this state, the secondary pressure chamber61and the reservoir25communicate with each other via the secondary supply chamber84and the ports103.

In response to an input from the input rod21, the primary piston46moves to the cylinder bottom portion41side along its axial direction. Consequently, the secondary piston47is pressed by the primary piston46via the spring unit57and moves to the cylinder bottom portion41side along its axial direction. That is, the primary piston46linearly moves inside the MC cylinder32in response to a stepping force of the brake pedal11illustrated inFIG. 1. The secondary piston47also linearly moves inside the MC cylinder32in response to a stepping force of the brake pedal11.

In this case, as illustrated inFIG. 2, the secondary piston47slides on the inner circumference of the sliding inner diameter portion70of the MC cylinder32, and on the inner circumference of the piston seal81and the partition seal86held by the MC cylinder32. When the secondary piston47moves to the cylinder bottom portion41side, the ports103are in a state of being positioned closer to the cylinder bottom portion41than the piston seal81. In this state, the piston seal81is in a state of sealing a gap between the reservoir25and the secondary supply chamber84, and the secondary pressure chamber61. As a result, when the secondary piston47further moves toward the cylinder bottom portion41, the brake fluid inside the secondary pressure chamber61is pressurized. The brake fluid pressurized inside the secondary pressure chamber61is discharged from the secondary discharge path68.

When an input from the input rod21is reduced from a state in which the brake fluid inside the secondary pressure chamber61is pressurized, the secondary piston47tends to return to the cylinder opening43due to a biasing force of the secondary piston spring64of the spring unit62. The volumetric capacity of the secondary pressure chamber61increases due to this movement of the secondary piston47. In this case, a return of the brake fluid to the secondary pressure chamber61via the secondary discharge path68sometimes does not follow the increase of the volumetric capacity of the secondary pressure chamber61any longer. Consequently, after the fluid pressure of the secondary supply chamber84, which is the atmospheric pressure, and the fluid pressure of the secondary pressure chamber61become equal to each other, and the fluid pressure inside the secondary pressure chamber61becomes a negative pressure.

Consequently, due to this negative pressure inside the secondary pressure chamber61, the piston seal81is deformed and a gap is formed between the piston seal81and the circumferential groove73. Accordingly, the brake fluid of the secondary supply chamber84passes through this gap and is supplied to the secondary pressure chamber61. Accordingly, the returning speed of the fluid pressure of the secondary pressure chamber61from the negative pressure state to the atmospheric pressure increases. That is, the piston seal81is a check valve which allows the brake fluid of the secondary supply chamber84to flow to the secondary pressure chamber61and regulates the flow of the brake fluid in the opposite direction thereof.

The primary piston46is disposed on the side closer to the cylinder opening43than the secondary piston47of the MC cylinder32. The primary piston46has a cylindrical portion106and a bottom portion107formed at an intermediate position of the cylindrical portion106in the axial line direction, and has a plunger shape. The primary piston46is fitted to each of the sliding inner diameter portion70of the MC cylinder32, the piston seal91provided in the sliding inner diameter portion70, and the partition seal96. The primary piston46is guided by these and slides inside the MC cylinder32. The input rod21is inserted into the cylindrical portion106. The bottom portion107is pressed by this input rod21, and the primary piston46moves forward to the cylinder bottom portion41side.

A plurality of ports108are formed on the cylinder bottom portion41side of the cylindrical portion106. The plurality of ports108radially penetrates the cylindrical portion106. The plurality of ports108are formed in the cylindrical portion106in a radial manner at positions having equal intervals in the circumferential direction. The spring unit57is provided on the secondary piston47side of the primary piston46. The spring unit57determines the distance between the primary piston46and the secondary piston47in a non-braking state having no input from the input rod21. In the spring unit57, the retainer58comes into contact with the bottom portion102of the secondary piston47and the bottom portion107of the primary piston46. The primary piston spring59is reduced in length when there is an input from the input rod21and the distance between the primary piston46and the secondary piston47is reduced. The primary piston spring59biases the primary piston46toward the input rod21using a force corresponding to the reduced length.

Here, a part formed by being surrounded by the cylinder wall portion42, the primary piston46, and the secondary piston47of the MC cylinder32serves as the primary pressure chamber56. The primary pressure chamber56generates a brake fluid pressure in accordance with the operation amount of the brake pedal11and supplies the brake fluid to the primary discharge path69. In other words, the master cylinder26generates a fluid pressure in the primary pressure chamber56inside the MC cylinder32in accordance with the operation amount of the brake pedal11. Moreover, in other words, the primary piston46forms the primary pressure chamber56for supplying the fluid pressure to the primary discharge path69, between the secondary piston47and the MC cylinder32. This primary pressure chamber56communicates with the primary supply chamber94, that is, the reservoir25, when the primary piston46is at a position in which the ports108are open to the opening groove92as illustrated inFIG. 2. The primary piston46causes the ports108to be open to the opening groove92when the brake pedal11is not in operation. In other words, the primary supply chamber94included in the master cylinder26is connected to the reservoir25at all times and communicates with the primary pressure chamber56when the brake pedal11is not in operation. The reservoir25stores a brake fluid to be supplied to the primary pressure chamber56in this manner.

The partition seal96held by the circumferential groove76of the MC cylinder32is a component in common with the partition seal86, which is an integrally molded product made of synthetic rubber. The partition seal96is a cup seal of which the shape on one side of a radial cross-section including its central line is a C-shape. The partition seal96is disposed inside the circumferential groove76in which a lip part is in a state of being directed toward the cylinder bottom portion41. In the partition seal96, the inner circumference is in slide contact with the outer circumferential surface of the moving primary piston46, and the outer circumference comes into contact with the circumferential groove76of the MC cylinder32. Accordingly, the partition seal96seals the gap at the position of the partition seal96of the primary piston46and the MC cylinder32at all times.

The piston seal91held by the circumferential groove75of the MC cylinder32is a component in common with the piston seal81, which is an integrally molded product made of synthetic rubber such as EPDM. The piston seal91is a cup seal of which the shape on one side of a radial cross-section including its central line is an E-shape. The piston seal91is disposed inside the circumferential groove75in which a lip part is in a state of being directed toward the cylinder bottom portion41. In the piston seal91, the inner circumference is in slide contact with the outer circumferential surface of the primary piston46, and the outer circumference comes into contact with the circumferential groove75of the MC cylinder32. Accordingly, the piston seal91is capable of sealing the gap at the position of the piston seal91of the primary piston46and the MC cylinder32.

The primary piston46is at a non-braking position in which the ports108are open to the opening groove92, when there is no input from the input rod21. The piston seal91partially overlaps the ports108of the primary piston46in the axial direction when the primary piston46is at a non-braking position. In this state, the primary pressure chamber56and the reservoir25communicate with each other via the primary supply chamber94and the ports108.

In response to an input from the input rod21, the primary piston46moves toward the cylinder bottom portion41along its axial direction. In this case, the primary piston46slides on the inner circumference of the sliding inner diameter portion70of the MC cylinder32, and on the inner circumferences of the piston seal91and the partition seal96held by the MC cylinder32. When the primary piston46moves toward the cylinder bottom portion41, the ports108are in a state of being positioned closer to the cylinder bottom portion41than the piston seal91. In this state, the piston seal91is in a state of sealing a gap between the reservoir25and the primary supply chamber94, and the primary pressure chamber56. Accordingly, when the primary piston46further moves toward the cylinder bottom portion41, the brake fluid inside the primary pressure chamber56is pressurized. The brake fluid pressurized inside the primary pressure chamber56is discharged from the primary discharge path69.

When an input from the input rod21is reduced from a state in which the brake fluid inside the primary pressure chamber56is pressurized, the primary piston46tends to return to a side opposite to the cylinder bottom portion41due to a biasing force of the primary piston spring59of the spring unit57. The volumetric capacity of the primary pressure chamber56increases due to this movement of the primary piston46. In this case, a return of the brake fluid via the primary discharge path69sometimes does not follow the increase of the volumetric capacity of the primary pressure chamber56any longer. Consequently, after the fluid pressure of the primary supply chamber94, that is the atmospheric pressure, and the fluid pressure of the primary pressure chamber56become equal to each other, and the fluid pressure inside the primary pressure chamber56becomes a negative pressure.

Consequently, due to this negative pressure inside the primary pressure chamber56, the piston seal91is deformed and a gap is formed between the piston seal91and the circumferential groove75. Accordingly, the brake fluid of the primary supply chamber94passes through this gap and is supplied to the primary pressure chamber56. Accordingly, the returning speed of the fluid pressure of the primary pressure chamber56from the negative pressure state to the atmospheric pressure increases. That is, the piston seal91is a check valve which allows the brake fluid of the primary supply chamber94to flow to the primary pressure chamber56and regulates the flow of the brake fluid in the opposite direction thereof.

A cylinder hole120parallel to the cylinder hole40of the MC cylinder32is formed in the SS cylinder33of the stroke simulator27. Thus, the SS cylinder33has a cylinder bottom portion121and a cylinder wall portion122. The cylinder bottom portion121is on a deep side in the cylinder hole120. The cylinder wall portion122has a tubular shape and extends from the cylinder bottom portion121to a cylinder opening123on a side opposite to the cylinder bottom portion121. The cylinder hole40and the cylinder hole120are formed on the same side surface side of the cylinder member31, and the positions of their central axial lines in a horizontal direction coincide with each other. In other words, vertically below the central axial line of the cylinder hole40, the central axial line of the cylinder hole120is disposed in parallel thereto. The position of the cylinder bottom portion121of the SS cylinder33in the axial direction partially overlaps that of the cylinder bottom portion41of the MC cylinder32. The position of the cylinder opening123of the SS cylinder33in the axial direction coincides with that of the cylinder opening43of the MC cylinder32.

An SS piston126(simulator piston) is movably installed on the side closer to the cylinder bottom portion121in the cylinder wall portion122. The SS piston126configures the stroke simulator27and is made of a metal. The SS piston126moves inside the SS cylinder33. In addition, a reaction force generating mechanism127is provided on the side closer to the cylinder opening123than the SS piston126inside the cylinder wall portion122. The reaction force generating mechanism127biases the SS piston126toward the cylinder bottom portion121.

In order from the cylinder bottom portion121side, a sliding inner diameter portion130, an intermediate inner diameter portion131, a large inner diameter portion132, and a female screw portion133are formed in the inner circumferential portion of the cylinder wall portion122. The sliding inner diameter portion130has a cylindrical surface-shaped inner diameter surface. The intermediate inner diameter portion131has a cylindrical surface-shaped inner diameter surface having a diameter larger than that of the sliding inner diameter portion130. In the large inner diameter portion132, the inner diameter surface has a diameter larger than that of the intermediate inner diameter portion131. The central axial lines of the inner diameter surfaces of the sliding inner diameter portion130, the intermediate inner diameter portion131, and the large inner diameter portion132coincide with each other. These central axial lines are the central axial lines of the cylinder hole120and the cylinder wall portion122.

A plurality of circumferential grooves, specifically two grooves, that is, a circumferential groove136and a circumferential groove137are formed in the sliding inner diameter portion130, in that order from the cylinder bottom portion121. Both the circumferential grooves136and137are formed in annular shapes and both thereof are formed in circular shapes. The circumferential grooves136and137have a shape recessed radially outward beyond the inner diameter surface of the sliding inner diameter portion130.

A linear discharge passage141is formed at a position in the vicinity of the cylinder bottom portion121of the cylinder wall portion122. The discharge passage141extends upward from the cylinder hole120and is open inside the secondary pressure chamber61of the master cylinder26. In other words, the discharge passage141causes the cylinder hole40and the cylinder hole120to communicate with each other. Moreover, in other words, the stroke simulator27communicates with the secondary pressure chamber61of the master cylinder26via the discharge passage141. The central axial line of the discharge passage141is orthogonal to the central axial line of the cylinder hole40and is orthogonal to the central axial line of the cylinder hole120. The discharge passage141is coaxially formed on the same straight line as the secondary discharge path68of the master cylinder26while having the same diameter as the secondary discharge path68. Thus, the secondary discharge path68and the discharge passage141are formed through hole opening performed once using one drill. The circumferential groove136is formed on the side closer to the cylinder opening123than the discharge passage141.

A bleeder passage142is formed in the cylinder wall portion122. The bleeder passage142is open to an upper portion of the intermediate inner diameter portion131on the side closer to the sliding inner diameter portion130. The bleeder passage142extends to a position on an outer surface of the cylinder member31. As illustrated inFIG. 1, a bleeder plug142afor opening and closing the bleeder passage142is disposed in this part of the bleeder passage142. The bleeder plug142athrows the bleeder passage142open to outside air in an opened state and blocks the bleeder passage142from outside air in a closed state. As indicated with the two-dot chain line inFIG. 1, the bleeder passage142also communicates with the power module13.

As illustrated inFIG. 2, a circular partition seal151(first seal member) is disposed inside the circumferential groove136(annular groove) to be held in the circumferential groove136. The partition seal151also configures the stroke simulator27. The partition seal151is provided on the SS cylinder33side, in the SS cylinder33and the SS piston126.

An axial groove152is formed in an upper portion of the SS cylinder33on the side closer to the cylinder bottom portion121than the circumferential groove136of the sliding inner diameter portion130. The axial groove152is open to the circumferential groove136and extends linearly from the circumferential groove136toward the cylinder bottom portion121side. The axial groove152is recessed radially outward beyond the inner diameter surface of the sliding inner diameter portion130. The axial groove152communicates with the discharge passage141.

A linear communication path155is formed on the side closer to the cylinder opening123than the circumferential groove136in the sliding inner diameter portion130of the SS cylinder33. The communication path155extends upward from the cylinder hole120and communicates with the opening groove82of the MC cylinder32, that is, the secondary supply chamber84. The communication path155is formed on the same straight line as the supply passage83of the master cylinder26to have a diameter smaller than that of the supply passage83. The supply passage83and the communication path155are formed through hole opening performed once using one stepped-drill. The communication path155is orthogonal to the central axial line of the cylinder hole40of the MC cylinder32and is also orthogonal to the central axial line of the cylinder hole120of the SS cylinder33. That is, the communication path155is formed in parallel to the discharge passage141.

In the sliding inner diameter portion130of the SS cylinder33, the circumferential groove137is formed in the vicinity of the end portion on its cylinder opening123side. A circular piston seal161(second seal member) is disposed inside this circumferential groove137, which is an annular groove, to be held by the circumferential groove137. The piston seal161also configures the stroke simulator27. The piston seal161is provided on the SS cylinder33side, in the SS cylinder33and the SS piston126.

In the partition seal151and the piston seal161, the partition seal151is disposed on the front side of the piston seal161(forward movement direction side) in a traveling direction of the input rod21, the primary piston46, and the secondary piston47at the time of stepping on the brake pedal11. The piston seal161is disposed on the rear side of the partition seal151(rearward movement direction side) in the traveling direction of the input rod21, the primary piston46, and the secondary piston47at the time of stepping on the brake pedal11.

A chamber forming groove162is formed on the cylinder bottom portion121side of this circumferential groove137in the sliding inner diameter portion130of the SS cylinder33. The chamber forming groove162is recessed radially outward beyond the inner diameter surface of the sliding inner diameter portion130and is formed in an annular shape. An axial groove163is formed in an upper portion of the SS cylinder33on the side closer to the cylinder bottom portion41than the circumferential groove137of the sliding inner diameter portion130. The axial groove163has one end open to the circumferential groove137and extends linearly from the circumferential groove137toward the cylinder bottom portion41. The axial groove163is recessed radially outward beyond the inner diameter surface of the sliding inner diameter portion130. The axial groove163has the other end open to the communication path155. An axial groove165is formed in an upper portion of the SS cylinder33on the side closer to the cylinder opening123than the circumferential groove137of the sliding inner diameter portion130. The axial groove165has one end open to the circumferential groove137and extends linearly from the circumferential groove137toward the cylinder opening123. The axial groove165is recessed radially outward beyond the inner diameter surface of the sliding inner diameter portion130.

As illustrated inFIG. 3, in the axial groove163, the shape of a cross section on a surface orthogonal to the central axial line of the sliding inner diameter portion130is an arc shape having a diameter smaller than that of the inner diameter surface of the sliding inner diameter portion130. Similarly, in the axial grooves152and165, the shape of a cross section on a surface orthogonal to the central axial line of the sliding inner diameter portion130is an arc shape having a diameter smaller than that of the inner diameter surface of the sliding inner diameter portion130(not illustrated). In the axial grooves85and95of the master cylinder26, the shape of a cross section on a surface orthogonal to the central axial line of the sliding inner diameter portion70is also an arc shape having a diameter smaller than that of the inner diameter surface of the sliding inner diameter portion70.

The SS piston126has a cylindrical portion171, a bottom portion172formed at an intermediate position of the cylindrical portion171in the axial direction, and a protrusion portion173protruding from the bottom portion172in the axial direction. Thus, the SS piston126has a plunger shape. The cylindrical portion171of the SS piston126is fitted to each of the sliding inner diameter portion130of the SS cylinder33, and the partition seal151and the piston seal161provided in the sliding inner diameter portion130. The SS piston126is guided by these and slides inside the SS cylinder33. In this case, both the partition seal151and the piston seal161annularly seal a gap between the inner circumference of the SS cylinder33and the outer circumference of the SS piston126. In the SS piston126, the bottom portion172is formed on the side closer to the cylinder opening123than the middle of the cylindrical portion171in the axial direction. The protrusion portion173protrudes from the bottom portion172to the cylinder opening123.

A small outer diameter portion176having an outer diameter smaller than that of a primary outer diameter portion175is formed at the end portion of the cylindrical portion171on the cylinder bottom portion121side. In the cylindrical portion171, a plurality of ports174are formed at positions in this small outer diameter portion176. The plurality of ports174radially penetrate the cylindrical portion171. The plurality of ports174are formed in the cylindrical portion171in a radial manner at positions having equal intervals in the circumferential direction. When the SS piston126is in a state of being in contact with the cylinder bottom portion121, the position of the small outer diameter portion176in the axial direction overlaps that of the discharge passage141. In this state, the SS piston126causes the ports174to communicate with the discharge passage141.

A part which is surrounded by the chamber forming groove162, the axial groove163, and the SS piston126of the SS cylinder33and is defined by the partition seal151and the piston seal161serves as an SS supply chamber178(simulator supply chamber). The SS supply chamber178also configures the stroke simulator27. In this SS supply chamber178, the region surrounded by the chamber forming groove162and the SS piston126has an annular shape. That is, the SS supply chamber178has an annular shape. The communication path155causes the secondary supply chamber84(one of the primary supply chamber94and the secondary supply chamber84) and the SS supply chamber178to communicate with each other. Thus, the communication path155causes the SS supply chamber178to communicate with the reservoir25via the secondary supply chamber84. The SS supply chamber178is disposed on an outer circumferential side of the SS piston126and communicates with the secondary supply chamber84. The communication path155causes the reservoir25, the secondary supply chamber84, and the SS supply chamber178to communicate with each other.

Here, a part surrounded by the cylinder bottom portion121, the cylinder bottom portion121side of the cylinder wall portion122, and the SS piston126serves as an SS pressure chamber181(simulator pressure chamber). The SS pressure chamber181also configures the stroke simulator27. The partition seal151partitions the SS supply chamber178and the SS pressure chamber181. The SS pressure chamber181communicates with the secondary pressure chamber61of the master cylinder26via the discharge passage141at all times. The SS pressure chamber181communicates with the secondary pressure chamber61of the master cylinder26on one end side of the SS piston126inside the SS cylinder33. The SS pressure chamber181moves the SS piston126by means of an introduced fluid pressure. In contrast, the reaction force generating mechanism127biases the SS piston126against a fluid pressure introduced into the SS pressure chamber181on the other end side of the SS piston126inside the SS cylinder33.

The partition seal151held by the circumferential groove136of the SS cylinder33is an integrally molded product made of synthetic rubber. The partition seal151is a cup seal of which the shape on one side of a radial cross-section including its central line is a C-shape. The partition seal151is disposed inside the circumferential groove136in which a lip part is in a state of being directed toward the cylinder bottom portion121. In the partition seal151, the inner circumference is in slide contact with the outer circumferential surface of the SS piston126, and the outer circumference comes into contact with the circumferential groove136of the SS cylinder33. Accordingly, the partition seal151seals the gap at the position of the partition seal151of the SS piston126and the SS cylinder33at all times.

The piston seal161held by the circumferential groove137of the SS cylinder33is an integrally molded product made of synthetic rubber such as EPDM. The piston seal161is a cup seal of which the shape on one side of a radial cross-section including its central line is an E-shape. The piston seal161is disposed inside the circumferential groove137in which a lip part is in a state of being directed toward the cylinder opening123. In the piston seal161, the inner circumference is in slide contact with the outer circumferential surface of the SS piston126, and the outer circumference comes into contact with the circumferential groove137of the SS cylinder33. Accordingly, the piston seal161can seal the gap at the position of the piston seal161of the SS piston126and the SS cylinder33.

The reaction force generating mechanism127has a metal lid member191, a rubber seal member192, and a cushioning member193(elastic member). The lid member191is fitted to the large inner diameter portion132of the SS cylinder33and is screwed into the female screw portion133. The seal member192is held by the lid member191and seals a gap between the lid member191and the large inner diameter portion132of the SS cylinder33. The cushioning member193is mounted in the lid member191.

The lid member191has a fitting portion195and a protrusion portion196. The fitting portion195is fitted to the SS cylinder33. The protrusion portion196has an outer diameter smaller than that of the fitting portion195and protrudes from the fitting portion195to the cylinder bottom portion121. A male screw portion197, a fitting outer diameter portion198, and a circumferential groove199are formed on the outer circumferential side of the fitting portion195. The male screw portion197is screwed into the female screw portion133. The fitting outer diameter portion198is fitted to the large inner diameter portion132. The circumferential groove199is recessed radially inward from the outer diameter surface of the fitting outer diameter portion198and has an annular shape. The seal member192, that is an O-ring, is disposed in the circumferential groove199. An engagement recess portion200is formed in the radial middle of the fitting portion195. The engagement recess portion200is recessed in the axial direction from the end surface on a side opposite to the cylinder bottom portion121of the fitting portion195. A screwing tool such as a hexagonal wrench engages with the engagement recess portion200when the male screw portion197of the fitting portion195is screwed into the female screw portion133of the SS cylinder33.

A recess portion201is formed on the cylinder bottom portion121side in the radial middle of the protrusion portion196. The recess portion201is recessed on a side opposite to the cylinder bottom portion121from a tip end surface on the cylinder bottom portion121side of the protrusion portion196. A columnar cushioning member193, which is an elastic member, is fitted and fixed in this recess portion201. When the cushioning member193is in a state of being in contact with the bottom surface of the recess portion201, the cushioning member193protrudes to the cylinder bottom portion121from the tip end surface of the protrusion portion196.

The reaction force generating mechanism127has a metal spring206(biasing mechanism), a metal retainer207, a metal spring unit208, and a cushioning member209(elastic member). One end of the spring206comes into contact with the fitting portion195in a state in which the protrusion portion196is inserted into the inner side. The retainer207comes into contact with the other end of the spring206. The spring unit208is interposed between the retainer207and the SS piston126. The cushioning member209is disposed inside the spring unit208.

As illustrated inFIG. 4, the spring206is a biasing mechanism (coil spring) generating a biasing force. The retainer207has a lid portion221, a body portion222, and a flange portion223. The lid portion221has a disk shape. The body portion222extends in the axial direction from an outer circumferential edge portion of the lid portion221and has a cylindrical shape. The flange portion223extends radially outward beyond the body portion222from an end edge portion on a side opposite to the lid portion221of the body portion222and is formed in a circular shape. In the retainer207, the flange portion223comes into contact with the end portion of the spring206and interlocks therewith.

The spring unit208has a retainer226and a spring227(biasing mechanism). The retainer226is extendable within a predetermined range. The spring227is a biasing mechanism (coil spring) biasing the retainer226in the extending direction. The retainer226regulates extension of the spring227such that its maximum length does not exceed a predetermined length.

The retainer226has an interlock member231, a guide shaft232, and an interlock member233. The interlock member231has a disk shape, comes into contact with one end of the spring227, and interlocks therewith. The guide shaft232is fixed to the radial middle of the interlock member231and extends into the spring227from the interlock member231. The guide shaft232has a shaft portion236and a flange portion237. The shaft portion236extends from the interlock member231. The flange portion237extends radially outward beyond the shaft portion236from the end portion on a side opposite to the interlock member231of the shaft portion236and is formed in an annular shape.

The interlock member233has a slide portion241, a body portion242, and a flange portion243. The slide portion241is fitted to the shaft portion236of the guide shaft232and slides on the shaft portion236. The body portion242extends from the slide portion241to a side opposite to the interlock member231and has a tubular shape. The flange portion243extends radially outward beyond the body portion242from the end edge portion on a side opposite to the slide portion241of the body portion242and is formed in an annular shape. In the interlock member233, the flange portion243comes into contact with the other end of the spring227and interlocks therewith. In the retainer226, the slide portion241of the interlock member233comes into contact with the flange portion237of the guide shaft232, thereby regulating extension of the spring227.

In the spring unit208, the interlock member231is inserted into the retainer207and comes into contact with the lid portion221of the retainer207. In the spring unit208, in a state in which the interlock member233causes the protrusion portion173to be fitted inside the body portion242, the flange portion243is brought into contact with the bottom portion172of the SS piston126. The cushioning member209is an elastic member having a cylindrical shape. The cushioning member209is accommodated inside the body portion242of the interlock member233in a state of being disposed between the protrusion portion173of the SS piston126and the flange portion237of the guide shaft232.

A part surrounded by the SS piston126, the cylinder wall portion122of the SS cylinder33, and the lid member191configures a spring chamber245(biasing chamber). The spring chamber245also configures the stroke simulator27. The spring chamber245is defined against the SS supply chamber178by the piston seal161. The piston seal161partitions the SS supply chamber178and the spring chamber245. In addition, the piston seal161is a valve allowing a brake fluid to flow from the SS supply chamber178to the spring chamber245when a pressure difference occurs between the SS supply chamber178and the spring chamber245. That is, the piston seal161is a check valve which causes a brake fluid to flow from the SS supply chamber178to the spring chamber245and regulates the flow of the brake fluid in the opposite direction thereof when the fluid pressure inside the spring chamber245becomes lower than the fluid pressure inside the SS supply chamber178. One side of the SS supply chamber178is defined against the SS pressure chamber181by the partition seal151. The other side of the SS supply chamber178is defined against the spring chamber245by the piston seal161. Thus, the SS supply chamber178is disposed between the SS pressure chamber181and the spring chamber245.

The cushioning member193, the spring206, the retainer207, the spring unit208, and the cushioning member209of the reaction force generating mechanism127are disposed inside the spring chamber245. Thus, the springs206and227are disposed in the spring chamber245. The bleeder passage142of the SS cylinder33communicates with this spring chamber245. As illustrated inFIG. 1, the spring chamber245communicates with the bleeder plug142afor opening and closing this spring chamber245with respect to outside air. In addition, the spring chamber245communicates with the power module13. In the axial groove165of the SS cylinder33, one end is open inside the circumferential groove137and the other end is open to the spring chamber245.

When the SS piston126is in a state of being in contact with the cylinder bottom portion121of the SS cylinder33as illustrated inFIG. 2, in the spring unit208as illustrated inFIG. 4, one end comes into contact with the bottom portion172of the SS piston126while being reduced in length, and the other end comes into contact with the lid portion221of the retainer207. In addition, in this state, in the spring206, one end comes into contact with the flange portion223of the retainer207, and the other end comes into contact with the fitting portion195of the lid member191fixed to the SS cylinder33. In addition, in this state, the cushioning member193is separated from the lid portion221of the retainer207, and the cushioning member209is separated from the flange portion237of the guide shaft232of the spring unit208. The springs206and227biases the SS piston126in a direction toward the cylinder bottom portion121as illustrated inFIG. 2.

The partition seal151is provided on the SS cylinder33side, in the SS cylinder33and the SS piston126. Furthermore, the partition seal151is disposed on a side opposite to the springs206and227of the piston seal161of the SS piston126. The piston seal161is provided on the SS cylinder33side, in the SS cylinder33and the SS piston126. Furthermore, the piston seal161is disposed on the springs206and227side of the partition seal151of the SS piston126.

When the primary piston46moves to the cylinder bottom portion41side in response to an input from the brake pedal11illustrated inFIG. 1, the primary piston46pressurizes the brake fluid inside the primary pressure chamber56as described above. The brake fluid pressurized inside the primary pressure chamber56is sent out from the primary discharge path69to the power module13. However, in a normal state, the power module13blocks the fluid pressure from the primary discharge path69.

In addition, when the primary piston46of the master cylinder26moves to the cylinder bottom portion41side in response to an input from the brake pedal11, the secondary piston47is pressed by this primary piston46via the spring unit57and moves to the cylinder bottom portion41side. Consequently, the secondary piston47pressurizes the brake fluid inside the secondary pressure chamber61as described above. The brake fluid pressurized inside the secondary pressure chamber61is sent out from the secondary discharge path68to the power module13. However, in a normal state, the power module13blocks the fluid pressure from the secondary discharge path68. Therefore, the pressurized brake fluid inside the secondary pressure chamber61is introduced into the SS pressure chamber181of the stroke simulator27via the discharge passage141and pressurizes the brake fluid inside the SS pressure chamber181.

Consequently, the SS piston126moves in a direction of being separated from the cylinder bottom portion121, that is, a direction of approaching the lid member191. Consequently, first, the SS piston126causes the spring227of the spring unit208illustrated inFIG. 4to be reduced in length against the biasing force thereof. In this case, a reaction force corresponding to the reduced length of the spring227illustrated inFIG. 4is applied to the brake pedal11illustrated inFIG. 1. Next, in a state in which the spring227remains being reduced in length, the SS piston126causes the cushioning member209to come into contact with the flange portion237of the guide shaft232and causes the cushioning member209to be reduced in length against the biasing force thereof. In this case, a reaction force corresponding to the reduced length of the spring227and the cushioning member209illustrated inFIG. 4is applied to the brake pedal11illustrated inFIG. 1. Next, in a state in which the spring227and the cushioning member209remain being reduced in length, the SS piston126causes the spring206to be reduced in length against the biasing force thereof. In this case, a reaction force corresponding to the reduced length of the spring227, the cushioning member209, and the spring206illustrated inFIG. 4is applied to the brake pedal11illustrated inFIG. 1. Next, in a state in which the spring227, the cushioning member209, and the spring206remain being reduced in length, the SS piston126causes the retainer207to come into contact with the cushioning member193and causes the cushioning member193to be reduced in length against the biasing force thereof. In this case, a reaction force corresponding to the reduced length of the spring227, the cushioning member209, the spring206, and the cushioning member193illustrated inFIG. 4is applied to the brake pedal11illustrated inFIG. 1. In this manner, the stroke simulator27applies a reaction force corresponding to a stepping force of the brake pedal11illustrated inFIG. 1to the brake pedal11, thereby generating pseudo-operational feeling.

As illustrated inFIG. 2, in the partition seal151and the piston seal161provided with respect to the SS piston126, the piston seal161is disposed on the front side (forward movement direction side) of the partition seal151in the traveling direction of the SS piston126at the time of stepping on the brake pedal11. The partition seal151is disposed on the rear side (rearward movement direction side) of the piston seal161in the traveling direction of the SS piston126at the time of stepping on the brake pedal11.

As illustrated inFIG. 5, the power module13has a passage301, a passage302, a passage303, a passage304, and a passage305. The passage301communicates with the primary discharge path69of the master cylinder26illustrated inFIG. 1, through a communication port301aat an outer end. The passage302is branched from a terminal position301bin the passage301and communicates with the braking cylinder15FR. The passage303is branched from a position302ain the passage302and communicates with the braking cylinder15RL. The passage304is branched from the position301bin the passage301and communicates with the braking cylinder15RR. The passage305is branched from the position301bin the passage301and communicates with the braking cylinder15FL.

In addition, the power module13has a passage308, a passage309, a passage310, a passage311, and a passage312. The passage308communicates with the secondary discharge path68of the master cylinder26illustrated inFIG. 1, through a communication port308aat an outer end. As illustrated inFIG. 5, an inner end communicates with the position302ain the passage302. The passage309is branched from a position302bin the passage302and communicates with the reservoir25illustrated inFIG. 1through a communication port309aat the outer end. The passage310is branched from a position303ain the passage303and communicates with a position309bin the passage309. The passage311is branched from a position304ain the passage304and communicates with a position310ain the passage310. The passage312is branched from a position305ain the passage305and communicates with a position311ain the passage311.

In addition, the power module13has a passage315, a passage316, and a passage317. The passage315is branched from a position309cbetween the communication port309aand the position309bin the passage309and communicates with a position302cbetween the position302aand the position301bin the passage302. The passage315further communicates with a position311bbetween the position311aand the position310ain the passage311. The passage316is branched from a position302dbetween the position302aand the position302bin the passage302and communicates with a position309dbetween the position309band the position309cin the passage309. The passage317is branched from a position316ain the passage316and communicates with the bleeder passage142through a communication port317aat the outer end as illustrated inFIG. 1.

In addition, as illustrated inFIG. 5, the power module13has an opening/closing valve321, an opening/closing valve322, an opening/closing valve323, and an opening/closing valve324. The opening/closing valve321is provided at an intermediate position in the passage301and opens and closes the passage301. The opening/closing valve322is provided between the position301band the position302cin the passage302and opens and closes the passage302. The opening/closing valve323is provided between the position302aand the position302cin the passage302and opens and closes the passage302. The opening/closing valve324is provided between the position302band the position302din the passage302and opens and closes the passage302.

In addition, the power module13has an opening/closing valve325, an opening/closing valve326, and an opening/closing valve327. The opening/closing valve325is provided between the position302aand the position303ain the passage303and opens and closes the passage303. The opening/closing valve326is provided between the position301band the position304ain the passage304and opens and closes the passage304. The opening/closing valve327is provided between the position301band the position305ain the passage305and opens and closes the passage305.

In addition, the power module13has an opening/closing valve330, an opening/closing valve331, an opening/closing valve332, an opening/closing valve333, and an opening/closing valve334. The opening/closing valve330is provided in an intermediate position in the passage308and opens and closes the passage308. The opening/closing valve331is provided between the position302band the position309bin the passage309and opens and closes the passage309. The opening/closing valve332is provided between the position303aand the position310ain the passage310and opens and closes the passage310. The opening/closing valve333is provided between the position304aand the position311ain the passage311and opens and closes the passage311. The opening/closing valve334is provided between the position305aand the position311ain the passage312and opens and closes the passage312.

In addition, the power module13has a reservoir337and a pump339. The reservoir337is provided between the position309cand the position302cin the passage315, communicates with the reservoir25of the master cylinder unit12illustrated inFIG. 1, and contains the brake fluid. The pump339is driven by a motor338, suctions the brake fluid from the reservoir337, and discharges the brake fluid toward the position302c. The pump339is provided on the side closer to the position302cthan the reservoir337.

In addition, the power module13has an opening/closing valve340, an opening/closing valve341, and an opening/closing valve342. The opening/closing valve340is provided between the position302cand the position311bin the passage315and opens and closes the passage315. The opening/closing valve341is provided between the position302dand the position316ain the passage316and opens and closes the passage316. The opening/closing valve342is provided between the position316aand the position309din the passage316and opens and closes the passage316.

Here, the opening/closing valves321,324,325,326,327,330, and340are in an opened state as illustrated inFIG. 5in a non-driven state in which the valves are not electrically driven and are in a closed state in a driven state in which the valves are electrically driven. In addition, the opening/closing valves322,323,331,332,333,334,341, and342are in a closed state as illustrated inFIG. 5in a non-driven state in which the valves are not electrically driven and are in an opened state in a driven state in which the valves are electrically driven.

The power module13has a bypass passage345, a check valve346, a bypass passage347, a check valve348, a bypass passage349, and a check valve350. The bypass passage345bypasses the opening/closing valve324and connects the position302band the position302din the passage302to each other. The check valve346is provided in the bypass passage345and allows the brake fluid to flow only from the position302bto the position302dside. The bypass passage347bypasses the opening/closing valve325and connects the position303aand the position302ain the passage303to each other. The check valve348is provided in the bypass passage347and allows the brake fluid to flow only from the position303ato the position302aside. The bypass passage349bypasses the opening/closing valve326and connects the position304aand the position301bin the passage304to each other. The check valve350is provided in the bypass passage349and allows the brake fluid to flow only from the position304ato the position301bside.

In addition, the power module13has a bypass passage351, a check valve352, a bypass passage353, and a check valve354. The bypass passage351bypasses the opening/closing valve327and connects the position305aand the position301bin the passage305to each other. The check valve352is provided in the bypass passage351and allows the brake fluid to flow only from the position305ato the position301bside. The bypass passage353bypasses the opening/closing valve341and connects the position316aand the position302din the passage316to each other. The check valve354is provided in the bypass passage353and allows the brake fluid to flow only from the position316ato the position302dside.

In addition, the power module13has a pressure sensor357, a pressure sensor358, a pressure sensor359, and a pressure sensor360. The pressure sensor357is connected to the position302din the passage302and detects the pressure of this part. The pressure sensor358is connected to a location between the position301bin the passage305, and the opening/closing valve327and the non-return valve352and detects the pressure of this part. The pressure sensor359is connected to a location between the communication port308aand the opening/closing valve330in the passage308and detects the pressure of this part. The pressure sensor360is connected to a location between the pump339and the position302cin the passage315and detects the pressure of this part.

In the braking device10, when a driver steps on the brake pedal11in a normal power supply state, the input rod21moves to the cylinder bottom portion41side of the master cylinder26. Consequently, the stroke sensor22detects this movement of the input rod21. In accordance with this detection, the opening/closing valves321and330of the power module13are electrically driven and are in a closed state. The opening/closing valves322and323are electrically driven and are in an opened state. The opening/closing valve340is electrically driven and is in a closed state. Here, at the time of normally stepping on the brake pedal11, the opening/closing valve342is electrically driven and is in an opened state. At the time of suddenly stepping on the brake pedal11, the opening/closing valve342is not electrically driven and is in a closed state.

When the opening/closing valves321and330are in a closed state as described above, the passage301and the passage308are closed. Consequently, the opening/closing valves321and330blocks the brake fluid from being supplied from the secondary discharge path68and the primary discharge path69of the master cylinder26to the braking cylinders15FR,15RL,15RR, and15FL. Accordingly, when the primary piston46and the secondary piston47move to the cylinder bottom portion41side in accordance with the movement of the input rod21, the brake fluid of the secondary pressure chamber61is introduced into the SS pressure chamber181of the stroke simulator27via the discharge passage141. As a result, the fluid pressure of the SS pressure chamber181rises so that the SS piston126moves in a direction toward the lid member191. Accordingly, a reaction force corresponding to a stepping force of the brake pedal11is applied to the brake pedal11by means of the spring227of the spring unit208, the cushioning member209, the spring206, and the cushioning member193, thereby generating pseudo-operational feeling.

In addition, as described above, when the opening/closing valves322and323are electrically driven and are in an opened state, and when the opening/closing valve340are electrically driven and are in a closed state, the pump339communicates with the braking cylinders15FR,15RL,15RR, and15FL. In this case, the pump339communicates with the braking cylinders15FR,15RL,15RR, and15FL via a part from the pump339to the position302cin the passage315, and the passages302to305. Then, the motor338is driven based on the movement amount of the input rod21, and the like detected by the stroke sensor22. Consequently, the pump339suctions the brake fluid from the reservoir337and the reservoir25and discharges the brake fluid. The discharged brake fluid is supplied to the braking cylinder15FR through the passage315via the passage302between the position302cand the braking cylinder15FR. In addition, the discharged brake fluid is supplied to the braking cylinder15RL through the passage315via the passage302between the position302cand the position302a, and the passage303. In addition, the discharged brake fluid is supplied to the braking cylinder15RR through the passage315via the passage302between the position302cand the position301b, and the passage304. In addition, the discharge brake fluid is supplied to the braking cylinder15FL through the passage315via the passage302between the position302cand the position301b, and the passage305. In this manner, the braking cylinders15FR,15RL,15RR, and15FL are pressurized. Accordingly, a brake is applied to the wheels.

Here, at the time of failure of power supply, the opening/closing valves321and330of the power module13are not electrically driven and are in an opened state. Thus, the opening/closing valves321and330throw the passage301and the passage308open. In addition, the opening/closing valves322,323, and341are in a closed state, the opening/closing valves324to327are in an opened state, and the opening/closing valves331to334and342are in a closed state. Thus, the brake fluid discharged from the primary pressure chamber56of the master cylinder26to the passage301via the primary discharge path69is supplied to each of the braking cylinder15RR via the passage304, and the braking cylinder15FL via the passage305. In addition, the brake fluid discharged from the secondary pressure chamber61of the master cylinder26to the passage308via the secondary discharge path68is supplied to each of the braking cylinder15FR via the passage302between the position302aand the braking cylinder15FR, and the braking cylinder15RL via the passage303. At the time of returning the pedal, since a passage for connecting the reservoir25and the spring chamber245to each other is long, the SS piston126is unlikely to return due to pipeline resistance. As a result, there is a possibility that pedal feeling deteriorates. However, according to the present embodiment, even in circumstances in which the spring chamber245is under a negative pressure, the negative pressure is solved by the piston seal161. As a result, it is possible to acquire favorable pedal feeling even at the time of returning the pedal.

At the time of air bleeding of the braking device10, the primary pressure chamber56of the master cylinder26, the secondary pressure chamber61, and the SS pressure chamber181of the stroke simulator27are subjected to air bleeding. Since the SS pressure chamber181communicates with the secondary pressure chamber61via the discharge passage141, the SS pressure chamber181is subjected to air bleeding together with the secondary pressure chamber61. Next, the spring chamber245of the stroke simulator27is subjected to air bleeding.

At the time of normal power supply, when the spring chamber245is subjected to air bleeding, the primary piston46and the secondary piston47of the master cylinder26are plunged. Consequently, the stroke sensor22detects the movement of the input rod21as described above. As a result, the opening/closing valves321and330of the power module13are electrically driven and are in a closed state, the opening/closing valves322and323are electrically driven and are in an opened state, the opening/closing valve340is electrically driven and is in a closed state, and the opening/closing valve342is electrically driven and is in an opened state. In accordance with the opening/closing valves321and330which are electrically driven and are in a closed state, when the primary piston46and the secondary piston47are plunged, the fluid pressure of the secondary pressure chamber61rises and the brake fluid is introduced into the SS pressure chamber181of the stroke simulator27via the discharge passage141. Consequently, the SS piston126moves in a direction of being separated from the cylinder bottom portion121while the spring227of the reaction force generating mechanism127, the cushioning member209, the spring206, and the cushioning member193are reduced in length. At this time, the bleeder plug142ais opened, the bleeder passage142is thrown open to outside air, and air in the spring chamber245is discharged via the bleeder passage142.

Next, the bleeder plug142ais closed, the bleeder passage142is closed, and the plunged state of the primary piston46and the secondary piston47of the master cylinder26is canceled. Consequently, the SS piston126moves to the cylinder bottom portion121side due to a biasing force of the spring206and the spring227of the reaction force generating mechanism127, so that the spring chamber245is under a negative pressure. Consequently, since the opening/closing valve342is electrically driven and is in an opened state, the brake fluid flows from the reservoir25to the bleeder passage142via a part between the communication port309aand the position309din the passage309, a location between the position309dand the position316ain the passage316, and the passage317, thereby being introduced into the spring chamber245.

The spring chamber245is subjected to air bleeding and the spring chamber245is filled with a brake fluid by suitably and repetitively discharging air and introducing a brake fluid as described above.

When the spring chamber245is subjected to air bleeding at the time of power down, such as at the time of failure of power supply, the primary piston46and the secondary piston47of the master cylinder26are plunged, as illustrated inFIG. 6. Consequently, the fluid pressure of the secondary pressure chamber61rises and the brake fluid is introduced into the SS pressure chamber181of the stroke simulator27via the discharge passage141. At this time, if the bleeder plug142ais opened and the bleeder passage142is thrown open to outside air, the SS piston126moves in a direction of being separated from the cylinder bottom portion121while the spring227of the reaction force generating mechanism127, the cushioning member209, the spring206, and the cushioning member193are reduced in length. Due to this movement of the SS piston126, air in the spring chamber245is discharged via the bleeder passage142.

Next, the bleeder plug142ais closed to close the bleeder passage142, and the plunged state of the primary piston46and the secondary piston47of the master cylinder26is canceled. Consequently, the SS piston126moves to the cylinder bottom portion121side due to a biasing force of the spring206and the spring227of the reaction force generating mechanism127. Consequently, the inside of the spring chamber245is under a negative pressure, and the piston seal161is opened due to the pressure difference between the spring chamber245and the SS supply chamber178under the atmospheric pressure. Accordingly, the brake fluid is introduced into the spring chamber245via the reservoir25, the supply passage83, the secondary supply chamber84, the communication path155, and the SS supply chamber178. As a more specific flow from the communication path155, the brake fluid flows to the spring chamber245through the communication path155, the gap between the axial groove163and the SS piston126configuring the SS supply chamber178, the gap between the chamber forming groove162and the SS piston126configuring the SS supply chamber178, the gap between the piston seal161and the circumferential groove137, and the gap between the axial groove165and the SS piston126.

The spring chamber245is subjected to air bleeding and the spring chamber245is filled with a brake fluid by suitably and repetitively discharging air and introducing a brake fluid as described above.

The braking device disclosed in Patent Literature 1 includes a stroke simulator which applies a reaction force corresponding to a stepping force of a brake pedal to the brake pedal. In such a braking device, air bleeding of the stroke simulator is particularly troublesome, and facilitation of air bleeding work is desired.

In the first embodiment, the SS supply chamber178communicates with the secondary supply chamber84which is connected to the reservoir25at all times. In addition, the piston seal161partitioning the SS supply chamber178and the spring chamber245allows the brake fluid to flow from the SS supply chamber178to the spring chamber245when a pressure difference occurs between the SS supply chamber178and the spring chamber245. Thus, the brake fluid can be introduced into the spring chamber245from the reservoir25via the secondary supply chamber84and the SS supply chamber178of the master cylinder26. Therefore, air bleeding work can be facilitated.

In the first embodiment, the partition seal151and the piston seal161, both of which annularly seal a gap between the inner circumference of the SS cylinder33and the outer circumference of the SS piston126, are provided on the SS cylinder33of the stroke simulator27side. Furthermore, the piston seal161is provided to be on the springs206and227side of the partition seal151. The annular SS supply chamber178is defined by the partition seal151and the piston seal161. In addition, the piston seal161defines the spring chamber245and the SS supply chamber178in which the springs206and227are disposed. The secondary supply chamber84, the SS supply chamber178of the master cylinder26, and the reservoir25communicate with each other by the communication path155. The piston seal161allows the brake fluid to flow from the SS supply chamber178to the spring chamber245. Accordingly, the brake fluid can be introduced into the spring chamber245from the reservoir25via the secondary supply chamber84of the master cylinder26, the communication path155, and the SS supply chamber178. Therefore, air bleeding work can be facilitated.

Furthermore, since a component only for introducing a brake fluid into the spring chamber245is no longer necessary to be provided on the power module13side, the cost can be reduced. That is, in order to introduce a brake fluid into the spring chamber245when the communication path155, the SS supply chamber178, and the piston seal161are not provided, for example, it is possible to take the following measures into consideration. The reservoir25and the bleeder passage142are caused to communicate with each other using a part from the communication port309ato the position309din the passage309and the passage317of the power module13, and the brake fluid is introduced into the spring chamber245from the reservoir25. In this case, as indicated with the two-dot chain line inFIG. 5, it is possible to consider that a bypass passage380which bypasses the opening/closing valve342, and a check valve381which allows a brake fluid to flow from the communication port309ato the communication port317ain the bypass passage380are provided. That is, it is possible to consider that the bypass passage380and the check valve381which allows a brake fluid to flow from the reservoir25to the spring chamber245are provided. The bypass passage380and the check valve381required in a case of such a configuration can no longer be required in the first embodiment. Therefore, cost increase can be suppressed.

Here, a general check valve pressing a valve body by means of a spring is opened with a certain degree of a valve opening pressure. Accordingly, if a check valve of such type is used as the check valve381, when a brake fluid flows to the spring chamber245, the spring chamber245is closed in a state in which a negative pressure corresponding to the valve opening pressure remains in the spring chamber245. If a negative pressure remains in the spring chamber245in this way, air bleeding is hindered. In addition, if a brake fluid flows from the reservoir25to the spring chamber245via the power module13as described above, the length of its passage is also lengthened. As a result, air bleeding work becomes more troublesome. The first embodiment uses the piston seal161which is a cup seal having a small valve opening pressure compared thereto. Therefore, it is possible to prevent the negative pressure remaining in the spring chamber245. In addition, it is possible to remarkably shorten the length of the passage for a brake fluid from the reservoir25to the spring chamber245. Therefore, the volume of the passage can be suppressed. Thus, air bleeding work can be further facilitated. In addition, the SS piston126can favorably return to the cylinder bottom portion121side by the reaction force generating mechanism127. Therefore, it is possible to prevent the pedal stroke of the brake pedal11from varying.

In addition, in the primary supply chamber94and the secondary supply chamber84of the master cylinder26, the communication path155causes the secondary supply chamber84and the SS supply chamber178of the stroke simulator27to communicate with each other. Therefore, it is easy to dispose the MC cylinder32and the SS cylinder33while the positions thereof are aligned in the axial direction. Thus, it is possible to easily shorten the length of the master cylinder unit12in the axial direction.

Second Embodiment

Next, a second embodiment will be described mainly based onFIG. 7focusing on the differences from the first embodiment. Portions in common with those of the first embodiment are expressed using the same names and the same reference signs.

In the second embodiment, an SS piston126A (simulator piston) partially different from the SS piston126of the first embodiment is provided in the stroke simulator27.

A plurality of relief ports401are formed at an end portion of this SS piston126A on a side opposite to the ports174of the cylindrical portion171. The plurality of relief ports401radially penetrate the cylindrical portion171. The plurality of relief ports401are formed in the cylindrical portion171in a radial manner at positions having equal intervals in the circumferential direction. In other words, the SS piston126A includes the relief ports401in its part in the outer circumference. The relief ports401are formed on a side opposite to the ports174of the bottom portion172of the SS piston126A. Thus, the relief ports401communicate with the spring chamber245at all times.

As illustrated inFIG. 7, the SS piston126A comes into contact with the cylinder bottom portion121of the SS cylinder33. At this time, the relief ports401are disposed radially inward from the piston seal161provided in the SS cylinder33. At this time, the relief ports401are positioned closer to the cylinder bottom portion121than the piston seal161, thereby communicating with the SS supply chamber178. That is, the relief ports401cause the SS supply chamber178and the spring chamber245to communicate with each other. When the SS piston126A is slightly separated from the cylinder bottom portion121, the relief ports401are shut by the piston seal161. As a result, the relief ports401block communication of the SS supply chamber178and the spring chamber245.

The relief ports401cause the SS supply chamber178and the spring chamber245to communicate with each other in as state in which no fluid pressure is introduced into the SS pressure chamber181from the secondary pressure chamber61. In addition, the relief ports401block communication of the SS supply chamber178and the spring chamber245when a fluid pressure is introduced into the SS pressure chamber181from the secondary pressure chamber61.

In the second embodiment, the relief ports401causing the SS supply chamber178and the spring chamber245to communicate with each other are provided in the SS piston126A radially inward from the piston seal161. Therefore, air bleeding work can be further facilitated.

That is, in the first embodiment, when the spring chamber245is subjected to air bleeding at the time of power down such as at the time of failure of power supply, a brake fluid flows from the SS supply chamber178to the spring chamber245via the gap between the piston seal161and the circumferential groove137. At this time, although the piston seal161is made of rubber and is opened by a small valve opening pressure, as long as there is a valve opening pressure, a negative pressure corresponding to this valve opening pressure remains in the spring chamber245. This negative pressure hinders air bleeding. In contrast, in the second embodiment, the relief ports401cause the SS supply chamber178and the spring chamber245to communicate with each other at positions slightly before the SS piston126A comes into contact with the cylinder bottom portion121of the SS cylinder33. As a result, the spring chamber245can be favorably under the atmospheric pressure. Accordingly, air bleeding work can be further facilitated.

Third Embodiment

Next, a third embodiment will be described mainly based onFIG. 8focusing on the differences from the first embodiment. Portions in common with those of the first embodiment are expressed using the same names and the same reference signs.

In the third embodiment, a communication path155B partially different from the communication path155of the first embodiment is provided in the cylinder member31.

In the third embodiment, a linear passage hole411(hole) is drilled from a lower surface of the cylinder member31. The secondary supply chamber84and the SS supply chamber178are coupled to each other through the passage hole411. This passage hole411has a large-diameter hole portion412(opening portion) and a small-diameter hole portion413. The large-diameter hole portion412is on a lower side of the cylinder hole120. The small-diameter hole portion413extends to the cylinder hole40across the cylinder hole120. In the passage hole411, the large-diameter hole portion412forms an opening portion of the cylinder member31to the outside. The passage hole411has a central axial line obliquely intersecting the central axial line of each of the cylinder holes40and120instead of being orthogonal thereto. In other words, the passage hole411is inclined with respect to the central axial line of the cylinder hole120, that is, the central axial line of the SS cylinder33. The passage hole411is disposed to intersect the SS cylinder33.

The passage hole411is inclined to be positioned on the front side in the traveling direction of the primary piston46and the secondary piston47at the time of stepping on the brake pedal11while being further inclined on the upper side. In other words, the passage hole411is inclined to be positioned on the rear side in the traveling direction of the SS piston126at the time of stepping on the brake pedal11while being further inclined on the upper side. The small-diameter hole portion413passes through the position of the end portion of the axial groove163of the SS cylinder33on the circumferential groove136side and extends to the opening groove82of the MC cylinder32.

In regard to hole opening, the large-diameter hole portion412and the small-diameter hole portion413are formed through hole opening performed once using one stepped-drill. Then, in the passage hole411, a ball414is embedded in the large-diameter hole portion412at a lower position in the stroke simulator27, so that the position of the large-diameter hole portion412for the opening portion to the outside of the cylinder member31is closed. Accordingly, in the third embodiment, the upper side of the passage hole411than the ball414configures the communication path155B. The communication path155B causes the SS supply chamber178of the stroke simulator27, the secondary supply chamber84of the master cylinder26, and the reservoir25to communicate with each other.

The communication path155B of the third embodiment is inclined with respect to a linear motion direction of the SS piston126. An end portion of the communication path155B is shut by the ball414at the lower position in the stroke simulator27. In addition, the communication path155B of the third embodiment is formed through hole opening performed once using one drill. The communication path155B includes a part of the passage hole411through which a lower outer surface of the SS cylinder33, the SS supply chamber178, and the secondary supply chamber84of the stroke simulator27are linearly coupled to each other.

In addition, in the third embodiment, a discharge passage141B partially different from the discharge passage141of the first embodiment provided in the cylinder member31.

The third embodiment includes a passage hole421and a passage hole422. The passage hole421extends from the cylinder hole40toward the cylinder hole120while being orthogonal to the central axial line thereof. The passage hole422is drilled in the cylinder bottom portion121from the upper portion of the cylinder hole120to be in parallel to the cylinder hole120. The passage hole421and the passage hole422are orthogonal to each other. Accordingly, these passage holes421and422configure the discharge passage141B causing the secondary pressure chamber61and the SS pressure chamber181to communicate with each other. The central axial line of the passage hole421is orthogonal to the central axial line of the cylinder hole40. The central axial line of the passage hole421is orthogonal to the central axial line of the cylinder hole120. The passage hole421is formed on the same straight line as the secondary discharge path68of the master cylinder26. The passage hole421is formed coaxially with the secondary discharge path68while having the same diameter. Thus, the secondary discharge path68and the passage hole421which configures a part of the discharge passage141B are formed through hole opening performed once using one drill.

According to the third embodiment, the communication path155B causing the secondary supply chamber84and the SS supply chamber178to communicate with each other is inclined with respect to the linear motion direction of the SS piston126. In addition, the end portion of the communication path155B is closed by the ball414at the lower position of the stroke simulator27. Therefore, the degree of freedom in layout of the communication path155B increases.

In addition, the communication path155B includes a part of the passage hole411through which the outer surface of the SS cylinder33, the SS supply chamber178, and the secondary supply chamber84of the stroke simulator27are linearly coupled to each other. Therefore, in regard to hole opening, the communication path155B can be formed through hole opening performed once using one drill. Therefore, machining is easily performed, so that the machining time can be shortened. Moreover, the partition seal151can be disposed close to the cylinder opening123side of the SS cylinder33. Therefore, the SS piston126can be reduced in size, so that the cylinder hole120can have a shallow depth. Therefore, machining is easily performed, the machining time can be shortened, and the cylinder member31can be reduced in size.

Fourth Embodiment

Next, a fourth embodiment will be described mainly based onFIG. 9focusing on the differences from the third embodiment. Portions in common with those of the third embodiment are expressed using the same names and the same reference signs.

In the fourth embodiment, a communication path155C partially different from the communication path155B of the third embodiment is provided in the cylinder member31.

In the fourth embodiment, a linear passage hole411C (hole) is drilled from the lower surface of the cylinder member31. The primary supply chamber94and the SS supply chamber178are coupled to each other through the passage hole411C. This passage hole411C has a large-diameter hole portion412C (opening portion) and a small-diameter hole portion413C. The large-diameter hole portion412C is on a lower side of the cylinder hole120. The small-diameter hole portion413C extends to the cylinder hole40across the cylinder hole120. The passage hole411C has a central axial line obliquely intersecting the central axial line of each of the cylinder holes40and120instead of being orthogonal thereto.

The passage hole411C is inclined to be positioned on the rear side in the traveling direction of the primary piston46and the secondary piston47at the time of stepping on the brake pedal11while being further inclined on the upper side. In other words, the passage hole411C is inclined to be positioned on the front side in the traveling direction of the SS piston126at the time of stepping on the brake pedal11while being further inclined on the upper side. The small-diameter hole portion413C passes through the annular chamber forming groove162of the SS cylinder33and extends to the opening groove92of the MC cylinder32.

The large-diameter hole portion412C and the small-diameter hole portion413C are formed through hole opening performed once using one stepped-drill. Then, in the passage hole411C, the ball414is embedded in the large-diameter hole portion412C at a lower position of the stroke simulator27, so that the position of the large-diameter hole portion412C is closed. Accordingly, in the fourth embodiment, the upper side of the ball414in the passage hole411C configures the communication path155C. The communication path155C causes the SS supply chamber178of the stroke simulator27and the primary supply chamber94of the master cylinder26to communicate with each other.

The communication path155C of the fourth embodiment is inclined with respect to the linear motion direction of the SS piston126. In addition, an end portion of the communication path155C is closed by the ball414at the lower position in the stroke simulator27. In addition, the communication path155C of the fourth embodiment is formed through hole opening performed once using one drill. The communication path155C includes a part of the passage hole411C through which a lower outer surface of the SS cylinder33, the SS supply chamber178, and the primary supply chamber94of the stroke simulator27are linearly coupled to each other.

Here, relief ports401similar to those of the second embodiment may be provided in the SS piston126of the third and fourth embodiments.

The embodiments described above include a reservoir which contains a brake fluid for a brake, a master cylinder which exchanges the brake fluid with the reservoir, and a stroke simulator which applies a reaction force corresponding to a stepping force of a brake pedal to the brake pedal. The master cylinder includes a master cylinder piston which linearly moves inside a cylinder of the master cylinder in response to a stepping force of the brake pedal, and an annular first supply chamber which is connected to the reservoir at all times. The stroke simulator includes the stroke simulator piston; a spring which biases the stroke simulator piston; a first cup seal which is provided on the cylinder side of the stroke simulator, is disposed on a side opposite to the spring of the stroke simulator piston, and annularly seals a gap between an inner circumference of the cylinder of the stroke simulator and an outer circumference of the stroke simulator piston; a second cup seal which is provided on the cylinder side of the stroke simulator, is disposed on the side close to the spring of the stroke simulator piston, and annularly seals a gap between the inner circumference of the cylinder of the stroke simulator and the outer circumference of the stroke simulator piston; an annular second supply chamber which is defined by the first cup seal and the second cup seal; and a spring chamber which is defined by the second cup seal against the second supply chamber and in which the spring is disposed. The second cup seal is a valve which allows the brake fluid to flow from the second supply chamber to the spring chamber and includes a communication path causing the reservoir, the first supply chamber, and the second supply chamber to communicate with each other. In this manner, the reservoir, the first supply chamber of the master cylinder, and the second supply chamber of the stroke simulator communicate with each other through the communication path. The second cup seal allows the brake fluid to flow from the second supply chamber to the spring chamber. Accordingly, the brake fluid can be introduced into the spring chamber from the reservoir via the first supply chamber of the master cylinder, the communication path, and the second supply chamber of the stroke simulator. Therefore, air bleeding work can be facilitated.

In addition, the master cylinder piston includes a primary piston which is disposed on the brake pedal side, and a secondary piston which is disposed on a side opposite to the brake pedal of the primary piston. The first supply chamber is configured of a primary supply chamber which is partially formed by the primary piston, and a secondary supply chamber which is partially formed by the secondary piston. The communication path causes the secondary supply chamber and the second supply chamber to communicate with each other. In this manner, in the primary supply chamber and the secondary supply chamber, the communication path causes the secondary supply chamber and the second supply chamber to communicate with each other. Therefore, the positions of the cylinder of the master cylinder and the cylinder of the stroke simulator are easily aligned in an axial direction.

In addition, the stroke simulator piston includes a relief port that is a part of the outer circumference of the stroke simulator piston and is provided radially inward from the second cup seal. Therefore, air bleeding work can be further facilitated.

In addition, the communication path is inclined with respect to a linear motion direction of the stroke simulator piston. An end portion of the communication path is closed by a ball at a lower position in the stroke simulator. Therefore, the degree of freedom increases in layout of the communication path.

In addition, the communication path includes a part of a hole through which the outer surface of the cylinder of the stroke simulator, the first supply chamber, and the second supply chamber are linearly coupled to each other. Therefore, in regard to hole opening, the communication path can be formed through hole opening performed once using one drill. Therefore, machining is easily performed, so that the machining time can be shortened.

As a master cylinder unit based on the embodiments described above, for example, it is possible to take the following aspects into consideration.

As a first aspect, a master cylinder unit includes a master cylinder that generates a fluid pressure in a pressure chamber inside a cylinder in accordance with an operation amount of a brake pedal; a reservoir that stores a brake fluid to be supplied to the pressure chamber; and a stroke simulator that communicates with the pressure chamber, generates a reaction force corresponding to an operation force of the brake pedal, and applies the reaction force to the brake pedal. The master cylinder includes a master piston which moves inside the cylinder in response to an operation of the brake pedal, and a master supply chamber which is connected to the reservoir at all times and communicates with the pressure chamber when the brake pedal is not in operation. The stroke simulator has a simulator piston which moves inside a simulator cylinder, a simulator pressure chamber which communicates with the pressure chamber of the master cylinder on one end side of the simulator piston inside the simulator cylinder and moves the simulator piston by means of an introduced fluid pressure, a biasing chamber in which a biasing mechanism biasing the simulator piston against the introduced fluid pressure is disposed on the other end side of the simulator piston inside the simulator cylinder, a simulator supply chamber which is disposed between the simulator pressure chamber and the biasing chamber on an outer circumferential side of the simulator piston and communicates with the master supply chamber, a first seal member which partitions the simulator supply chamber and the simulator pressure chamber, and a second seal member which partitions the simulator supply chamber and the biasing chamber and allows the brake fluid to flow from the simulator supply chamber to the biasing chamber when a pressure difference occurs between the simulator supply chamber and the biasing chamber.

As a second aspect, in the first aspect, the second seal member is a cup seal which is in slide contact with an outer circumference of the simulator piston and is disposed in an annular groove of the simulator cylinder.

As a third aspect, in the first or second aspect, the pressure chamber communicates with a power module which controls a braking cylinder provided in a wheel. The biasing chamber communicates with a bleeder plug for opening and closing the biasing chamber with respect to outside air and communicates with the power module.

As a fourth aspect, in any one of the first to third aspects, a relief port causing the simulator supply chamber and the biasing chamber to communicate with each other in a state in which no fluid pressure from the pressure chamber of the master cylinder is introduced into the simulator pressure chamber and blocking communication between the simulator supply chamber and the biasing chamber when a fluid pressure from the pressure chamber of the master cylinder is introduced into the simulator pressure chamber is formed in the simulator piston.

As a fifth aspect, in any one of the first to fourth aspects, the master cylinder and the stroke simulator are configured to be disposed in a cylinder main body which is integrally formed of one raw material. A communication path through which the reservoir, the master supply chamber, and the simulator supply chamber communicate with each other is formed by a hole which is disposed while being inclined with respect to a central axial line of the simulator cylinder and intersecting the simulator cylinder; and an opening portion of the hole outside the cylinder main body is closed.

As a sixth aspect, in any one of the first to fifth aspect, the master piston includes a primary piston which is disposed on the brake pedal side, and a secondary piston which is disposed on a side opposite to the brake pedal of the primary piston. The master supply chamber is configured of a primary supply chamber which is partially formed by the primary piston, and a secondary supply chamber which is partially formed by the secondary piston. The communication path through which the reservoir, the master supply chamber, and the simulator supply chamber communicate with each other causes the secondary supply chamber and the simulator supply chamber to communicate with each other.

INDUSTRIAL APPLICABILITY

According to the master cylinder unit described above, air bleeding work can be facilitated.

REFERENCE SIGNS LIST