Master cylinder for a braking system

Abstract

A master cylinder for a brake system. The master cylinder comprises a chamber (120) delimited by a piston (110), the chamber (120) being fed by a brake fluid reservoir mounted on top of the master cylinder via a nipple engaged in a nozzle of the master cylinder body. The piston (110) has a nose (111) of reduced cross-section upstream of a skirt (112) of the piston (110), which is guided in a bore (102) of the master cylinder (100), and a nozzle (104) is connected to the chamber (120) via a hole (105) which at least partially opens into the chamber (120) upstream of the piston (110) in its rest position. A valve module (200) is mounted in the hole (105) for managing the communication between the reservoir and the chamber (120) as a function of the position of the piston (110) and the pressure in the chamber (120) relative to the pressure in the reservoir.

Description

Technical Field

[0001] The present invention relates to a master cylinder, in particular to a tandem master cylinder for a hydraulic brake system of a vehicle, in particular a motor vehicle. Background Art

[0002] The development of hydraulic brake systems primarily concerns active and passive safety devices intended to be integrated into many motor vehicle projects and requiring an effective re-feeding of the master cylinder that is significantly greater than that permitted by known master cylinders.

[0003] Currently, dual-circuit hydraulic systems are used for service braking and emergency braking, but are also used for autonomous braking.

[0004] Service brake systems use brake boosters, such as vacuum boosters or electromechanical boosters, that significantly amplify the force applied by the driver to the brake pedal. Both the service function and the emergency function must meet dimensional, functional, and regulatory requirements. Such brake systems can be coupled (i.e., the driver is directly connected to the brake system) or decoupled (the driver is indirectly connected to the brake system).

[0005] Autonomous braking systems are not controlled by the driver, but by an electromechanical amplifier of force activated via a program, which may or may not be directly connected to the system.

[0006] Conventional brake systems have at least one central hydraulic unit with an integrated electronic controller and pump (ESP system) for driver-independent pressure generation during active braking. The master cylinder (with its re-feed function) is typically the element responsible for ensuring pump pressure.

[0007] Tandem master cylinders are equipped with a special seal called a cup, which provides both sealing and re-feeding functions. However, the cup's design creates a conflict between sealing and re-feeding, limiting re-feeding capabilities. This is why, in its current state, tandem master cylinders are unable to provide the necessary flow for the new brake functions currently under development.

[0008] Figure 8 A tandem master cylinder according to the prior art is shown, comprising a primary piston and a secondary piston, each defining a chamber. These chambers are connected to nozzles 405, 406, respectively, which receive connections for a brake fluid reservoir.

[0009] The nozzles communicate with the chamber through corresponding feed holes that pass through an orifice ring formed in the skirt of the piston, close to its front end. The sealing of the piston in the master cylinder bore is achieved by means of seals and cups that function in the same way for both pistons:

[0010] The seal has a sealing function.

[0011] The cup has the following dual functions:

[0012] - Achieve sealing

[0013] - Allows refeeding of the chamber.

[0014] Figure 9 A detail of the contact between the piston and the cup is schematically shown, showing the communication of the feed hole with the orifice ring of the skirt of the piston when the piston is in the rest position.

[0015] according to Figure 10-13 :

[0016] Rest time ( Figure 10 ), the chamber is connected to the brake fluid storage chamber through the orifice ring of the piston and the hole in the master cylinder body that leads to the peripheral groove in order to feed all the holes in the piston.

[0017] Then( Figure 11 ), the piston advances and causes the orifice ring to pass under the cup, thus cutting off communication with the reservoir and allowing the chamber to be pressurized. This pressure is also exerted on the cup to perfect the seal.

[0018] Then( Figure 12 ), the piston continues to move forward to increase the pressure and deliver the brake fluid to the brake circuit.

[0019] Then( Figure 13 ), in the case of negative pressure in the chamber, the brake fluid is drawn by bypassing the cup (in its neck) and passing between the bore and the piston skirt. However, refilling the chamber is difficult and slow, which is not suitable for current brake circuits. Summary of the Invention

[0020] The object of the present invention is to develop a master cylinder whose refeed function is significantly improved while reducing the overall dimensions, without incurring cost or manufacturing difficulties.

[0021] The present invention also enables a tandem master cylinder whose operation, from the driver's perspective, is unchanged compared to the operation of current master cylinders.

[0022] To this end, the invention relates to a master cylinder, in particular a tandem master cylinder, comprising at least one chamber delimited by a piston, connected to the brake circuit and fed by a brake fluid reservoir mounted on top of the master cylinder via a connector below the reservoir, which connector engages in a nozzle above the master cylinder body,

[0023] It is characterized in that

[0024] A) The piston has a nose of reduced cross-section upstream of the piston skirt, which is guided in the master cylinder bore,

[0025] B) the nozzle is connected to the chamber via a hole which opens at least partially into the chamber upstream of the piston in the rest position and at least partially overlaps the nose,

[0026] C) A valve module is mounted in the bore to manage communication between the reservoir and the chamber based on the position of the piston and the pressure within the chamber relative to the reservoir pressure.

[0027] The master cylinder according to the present invention has the advantage of allowing direct communication with virtually no pressure drop between the brake fluid reservoir and the chamber to which it is connected via its connector. This communication is controlled in a very efficient and simple manner by the movement of the piston, which causes its nose to move from a rest position to an activated position, thereby controlling the valve module. This first closes the valve module and cuts off communication with the reservoir when the skirt reaches below the valve module's cam, and then allows effective re-feeding by opening the valve module even when negative pressure develops in the chamber. This opening is almost instantaneous, so re-feeding of the chamber is not delayed, and this re-feeding is not slowed down by pressure drops in the pipes or by narrow, long passages (as is the case with known master cylinders).

[0028] The invention makes it possible to dispense with the cup associated with each chamber of the master cylinder, which greatly simplifies the manufacture of the master cylinder and its components. It also avoids the risk of the cup being positioned upside down, causing it to malfunction.

[0029] Finally, eliminating the cup in the master cylinder makes it possible to shorten the distance between the master cylinder and the primary and secondary pistons.

[0030] According to an advantageous feature, the valve module comprises

[0031] - a cylindrical body intended to be mounted in the bore of the master cylinder, and

[0032] - Valve seat on the reservoir side

[0033] - a stop on the chamber side for limiting the stroke, and

[0034] Accommodates a float valve which

[0035] - can move between the sealing seat and the stopper,

[0036] - exceeds the stop to come into contact with the piston,

[0037] -The float valve comprises:

[0038] - a valve connected to a cam supported on the nose or skirt of the piston, the valve cooperating with the valve seat and the cam, and being retained in the housing of the module,

[0039] - an elastic connection between the valve and the cam which, in its expanded state, allows the valve to be elastically compressed by a pressure applied to the valve.

[0040] This embodiment of the valve module is particularly simple and advantageous, since the module is produced completely outside the master cylinder in order to be mounted in the bore of the master cylinder in the assembled state.

[0041] Adjustment of the operation of the valve module is very simple, since it consists in moving the cam of the valve module in the bore so that it can cooperate with the nose of the piston and its skirt. Since the valve module is positioned against the bore, this adjustment is almost instantaneous.

[0042] According to a further advantageous feature, the outlet of the orifice is positioned in the bore so as to open into the bore while overlapping with the nose of the piston in its rest position, which makes it possible, as already indicated, to reduce the length of the piston and the master cylinder and at the same time automatically achieve positioning while benefiting from the maximum amplitude of the floating valve between its rest position in which the communication is open (and at this moment the cam bears on the nose of the piston) and said activated position in which the cam bears on the skirt of the piston.

[0043] According to another advantageous feature, the elastic connection is achieved by sliding mounting of the shutter on the cam and is completed by a compression spring between the shutter and the cam.

[0044] This elastic connection is particularly reliable since it is not very fragile and is less susceptible to material fatigue.

[0045] According to another advantageous feature, the cam comprises a connecting rod on which the shutter slides and on which the compression spring is mounted.

[0046] This allows for simple assembly of the cam and the flap.

[0047] According to another advantageous feature, the valve is connected to an axial rod of the cam, which has a cavity behind its bearing surface and in which the axial rod is engaged and retained by its end provided with a hook in the cavity of the head of the valve, thereby allowing relative sliding movement of the valve on the end of the rod, between a maximum extended position and a maximum compressed position limited by the abutment of the end of the rod against the bottom of the cavity.

[0048] According to a further advantageous feature, the cam has a contact surface, in particular raised in the form of a spherical dome, to come into contact with the nose of the piston or with the skirt of the piston.

[0049] The rounded contact surface allows for effective sliding contact between the cam and the moving piston.

[0050] According to another feature, the cam is covered by an edge so as to bear on a stop of the housing, while the bearing surface of the cam projects so as to come into contact with the piston. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The invention is described in more detail below with reference to an embodiment of the master cylinder according to the invention shown in the accompanying drawings, wherein:

[0052] Figure 1 is an axial cross-sectional view of the portion of the master cylinder defined at the bore, at the end of the piston and the chamber defined thereby, and in the chimney piece accommodating the connection for the brake fluid reservoir, not shown,

[0053] Figure 2 is based on Figure 1 Axial cross-section of a single chimney piece,

[0054] Figure 2A is an axial cross-section of a floating valve housed in a chimney member,

[0055] Figure 3 is an axial cross-sectional view of the housing of the floating valve,

[0056] Figure 3A This is an axial cross-sectional view of the seat block of the floating valve.

[0057] Figure 3 B is an axial cross-section of the floating valve in its rest position.

[0058] Figure 3C is an axial cross-section of the floating valve in compression.

[0059] Figure 4 Shows the master cylinder in its rest position.

[0060] Figure 5 Shows the status of the master cylinder at the beginning of its activation.

[0061] Figure 6 Shows a master cylinder with pressurized brake fluid in its chamber,

[0062] Figure 7 shows the decompression of the chamber,

[0063] Figure 8 is an axial cross-sectional view of a tandem master cylinder according to the prior art,

[0064] Figure 9 yes Figure 8 Axial cross-section of a tandem master cylinder showing details of the cup,

[0065] Figure 10 、 11 , 12 and 13 are various schematic details showing the operation of the cup of the master cylinder. DETAILED DESCRIPTION

[0066] Figure 1 Shown is a cross-sectional view of a portion of a single or tandem master cylinder 100 , whose body 101 is traversed by a bore 102 receiving a piston 110 delimiting a chamber 120 receiving brake fluid to feed a brake circuit not shown.

[0067] A bore 105 connected to a nozzle 104 , which receives a connection of a brake fluid reservoir (not shown), opens into the chamber 120 .

[0068] The orifice 105 is equipped with a valve module 200 which manages the passage of brake fluid between the reservoir and the chamber 120 as a function of the position of the piston 110 and the pressure prevailing in the chamber 120 .

[0069] By convention, the pressure / negative pressure prevailing in the chamber 120 is a relative pressure, ie the difference between the absolute pressure in the chamber 120 and the pressure in the reservoir, the pressure in the reservoir being atmospheric pressure.

[0070] Depending on the operation of the master cylinder / tandem master cylinder 100 , there is pressure or negative pressure in the chamber 120 , with zero pressure being, by definition, atmospheric pressure.

[0071] It should also be noted that the description of the present invention applies both to tandem master cylinders having two pistons defining two chambers, each connected to a brake circuit, and to single master cylinders having only one chamber 120 .

[0072] The operation described for only one chamber applies under the same conditions to both chambers of the master cylinder connected in series.

[0073] In more detail, according to Figure 2 and Figure 2A The master cylinder 100 according to the present invention comprises a body 101 having a bore 102, which houses a piston 110 (primary or secondary), shown in its rest position. During activation, the piston 110 advances in direction A. The seal between the bore 102 and the piston 110 is ensured by a seal 108 housed in a peripheral groove 107 of the bore 102. The seal 108 is located behind an outlet 105a of a bore 105 in a chimney 103 supporting a brake fluid reservoir.

[0074] The piston 110 has a nose 111 of reduced diameter starting from the nominal diameter of a skirt 112 of the body of the piston 110. The nose 111 has a straight or curved frustoconical shape.

[0075] The bore 105 is positioned relative to the piston 110 such that, in the rest position, the piston 110 partially covers the outlet 105 a of the bore 105 with its nose 111 .

[0076] The hole 105 of the chimney 103 connected to the nozzle 104 forms a peripheral shoulder 106 (represented in a very simplified manner and not geometrically accurate) at its connection with the bore 102. The hole 105 communicates with the chamber 120 through its outlet 105a, which is kept free by the peripheral shoulder 106.

[0077] Figure 2A A valve module 200 is shown which is to be received in the bore 105 by abutting against the shoulder 106 so that an activated portion of the valve module 200 (described below) can protrude through the outlet 105 and contact the nose 111 or skirt 112 of the piston 110 depending on the position or movement of the piston.

[0078] The valve module 200 comprises a housing 10 in the form of a cylinder which receives a sealing seat 20 and houses a float valve 30 .

[0079] The components 10, 20, 30 of the valve module 200 will be illustrated with the aid of Figure 3 、 3 A, 3B, 3C are carried out, Figure 3 、 3 A, 3B, and 3C are axial cross-sections of the valve module 200 .

[0080] according to Figure 3 In the cross-sectional view of FIG, the housing 10 is a cylindrical sleeve, the outer diameter of which is suitable for being fixed in the hole 105 of the chimney piece 103. The cylindrical sleeve 10 has a shoulder 11 on the top side for receiving the sealing seat 20, and a lower stop 12 at the bottom (in the direction shown, that is, the direction of use), for example in the form of a rim with an opening 13.

[0081] according to Figure 3A The sealing seat block 20 is a bored plug-shaped component, whose inlet 21 communicates with the valve seat 22 below. The peripheral side 23 of the block 20 has peripheral ribs for fixing and sealing the block in the top of the housing 10 ( Figure 2A ).

[0082] according to Figure 3 B, the floating valve 30 includes a valve 31 in the direction shown (that is, the operating direction), the valve 31 is associated with a cam 32 and has a compression spring 33a inserted therein.

[0083] The flap 31 has a head 311 , a surface 311 a of which contacts the valve seat 22 of the housing 10 in the closed position of the valve module 200 .

[0084] The head 311 has a cavity 312 provided with an axial orifice 313 through which the rod 321 of the cam 32 passes. The end 322 of the rod 321 is provided with a retaining hook 323 which engages by elastic deformation when assembled in the orifice 313 so as to then unfold in the cavity 312 behind the orifice and retain the shutter 31 in the cavity. Figure 3 B is shown in the rest position or extended position on the rod 321.

[0085] The cam 32 is covered by an edge 324 which, due to its dimensions, can bear against the stop 12 of the housing 10 and retain the valve 10 in the housing 10 .

[0086] This support position does not have a sealing function; when the edge 324 of the cam rests on the stopper 12 , brake fluid can pass through.

[0087] The surface 32 a of the cam 32 has a dome shape, for example a spherical dome shape, which projects through the opening 13 of the housing 10 and also through the outlet 105 a of the hole 105 to be able to project into the bore 102 and cooperate with the piston 110 .

[0088] The domed shape of the cam 32 and the slope of the tapered shape of the nose 111 of the piston 110 allow the piston to easily push back on the cam 32 and vice versa, which allows the cam 32 to descend while remaining supported on the piston 110 .

[0089] A compression spring 33 a , interposed between the shutter 31 and the top of the cam 32 , around the rod 321 , keeps the valve 30 at maximum extension, limited by the hook 322 of the rod 321 of the cam 32 .

[0090] The sliding assembly of the valve 31 relative to the cam 32 and the insertion of the spring 33a form an elastic connection. This elastic connection 33, which allows elastic compression (i.e., return) between the valve 31 and cam 32, can also be achieved by elastic deformation of the bottom of the valve 31, while its sealing surface 311a remains rigid. Elastic deformation of the stem 321 of the cam 32 is also conceivable. This elastic deformation should only occur in a direction that elastically reduces the length of the float valve 30 from its rest length (LM), which is defined as the length that opens the communication between the reservoir and the chamber 120 when the master cylinder 100 is in the rest position.

[0091] Figure 3 B shows the maximum extension LM, in contrast, Figure 3C The minimum extension Lm is shown. The length difference between these two states is denoted by ΔL.

[0092] exist Figure 3C In the embodiment shown in FIG. 3 , the shutter 31 is completely pressed onto the end 322 of the rod 321 , which abuts against the bottom of the cavity 312 of the shutter 31 .

[0093] Figure 3C The state shown is a critical case, and Figure 3 The state B corresponds to a rest state in which the float valve 30 is not subjected to any external force.

[0094] The function of these two states, or at least the rest state and the compressed state of the float valve will be achieved by Figure 4-7 The operation of the master cylinder will be described.

[0095] Figure 4 The rest state of the master cylinder 100 is shown: the piston 110 is in the rest position; it is retracted to the right and overlaps with its nose 111 with the opening 105 a of the bore 105 .

[0096] The float valve 30 is in its rest position, supported by its cam 32 on the nose 111. In the rest state, the length LM of the float valve 30 is such that the surface 311a of the head of the valve 31 is clear of the sealing seat 22. Under these conditions, the brake fluid reservoir is in free communication with the chamber 120.

[0097] Figure 5 The actuation of the master cylinder 100 is shown. The piston 110 advances (direction A) and its nose 111 and then its skirt 112 raise the float valve 30 by their contact with the cam 32, so that the surface 311a of the valve 31 abuts against the sealing seat 22 and cuts off the communication between the brake fluid reservoir and the chamber 120. This closure is caused by the length of the float valve 30, which, when the valve 30 is in the low position, is at rest, leaving the passage between the seat 22 and the valve 31 free, while when it is in the Figure 6 In the activated position shown, the lifting of the valve 30 allows the closing to occur. In this high position, if the length LM is greater than the distance occupied by the floating valve 30 in this position, the shutter 31 can also be compressed by the spring 33a.

[0098] according to Figure 6 , the piston 110 continues to move forward in the chamber 120. The brake fluid present therein, as well as the brake fluid surrounding the float valve 30 in the housing 10, is pressurized, which causes the valve 31 to be pressed even more strongly against the valve seat 22 and ensures a perfect seal.

[0099] according to Figure 7A slight backward movement of the brake circuit or piston 110 creates a vacuum in chamber 120 , which causes a reaction in valve module 200 and recalls valve 31 , thereby sucking in brake fluid to re-feed chamber 120 .

[0100] Thus, the passage between the reservoir and the chamber 120 is unobstructed and allows immediate refeeding of the chamber.

[0101] Pressurization can be repeated during the braking cycle ( Figure 6 ) and decompression ( Figure 7 ) alternating operation, there is even a series of rapid alternating operations and instantaneous response of the floating valve for refeeding and operation of the braking system.

[0102] At the end of the braking phase, the piston 110 returns to the rest position, i.e. Figure 4 status.

[0103] Reference Signs List

[0104] 100 master cylinder / tandem master cylinder

[0105] 101 master cylinder body

[0106] 102 master cylinder boring

[0107] 103 master cylinder chimney parts

[0108] 104 nozzles

[0109] 105 holes

[0110] Exit 105a

[0111] 106 Shoulders

[0112] 107 grooves

[0113] 108 seals

[0114] 110 piston

[0115] 111 piston nose

[0116] 112 piston skirt

[0117] 120 chambers

[0118] 200 valve module

[0119] 10 Shell / Cylinder

[0120] Seat 11 location

[0121] 12 Lower stop / travel limiting edge

[0122] 13 Opening

[0123] 20 sealing blocks / sealing seats

[0124] 21 entrances

[0125] 22 valve seat

[0126] 23 outer side

[0127] 30 Float Valve

[0128] 31 valves

[0129] 311 Head

[0130] 311a Head surface

[0131] 312 cavity

[0132] 313 orifice

[0133] 32 cams

[0134] 32a Cam surface

[0135] 321 cam rod

[0136] 322 rod end

[0137] 323 hook

[0138] 324 Cam Edge

[0139] 33 elastic bonding

[0140] 33a compression spring

[0141] 400 known master cylinders

[0142] 401 main piston

[0143] 402 Pistons

[0144] Chambers 403 and 404

[0145] 405, 406 nozzles

[0146] 407, 408 feeding holes

[0147] 412, 413 skirt eyelets

[0148] 421, 422 seals

[0149] 423, 424 cup-shaped parts

[0150] A Piston's forward direction

Claims

1. A master cylinder (100) comprising at least one chamber (120) delimited by a piston (110), said chamber (120) being connected to a brake circuit and fed by a brake fluid reservoir mounted on top of said master cylinder through a connector below said reservoir, said connector engaging in a nozzle above the body of said master cylinder, A) the piston (110) has a nose (111) of reduced cross-section upstream of the skirt (112) of the piston (110), which is guided in a bore (102) of the master cylinder (100), B) the spout (104) is connected to the chamber (120) via a hole (105) which at least partially opens into the chamber (120) upstream of the piston (110) in its rest position and at least partially overlaps the nose (111), C) a valve module (200) mounted in the bore (105) for managing communication between the reservoir and the chamber (120) as a function of the position of the piston (110) and the pressure in the chamber (120) relative to the pressure in the reservoir, It is characterized by: The valve module (200) includes - a cylindrical body intended to be mounted in said hole (105) of said master cylinder, and - A valve seat (22) is provided on the reservoir side - a stop (12) is provided on the chamber side for limiting the travel, and Accommodates a float valve (30) which - able to move between the sealing seat (22) and the stopper (12), - exceeds the stop (12) to come into contact with the piston (110), - The floating valve (30) comprises: a valve (31) connected to a cam (32) supported on the nose (111) or skirt (112) of the piston (110), the valve (31) cooperating with the valve seat (22) and the cam to be retained in the housing (10) of the module (200), - an elastic connection (33) between the valve (31) and the cam (32) for allowing elastic compression of the valve (31) by pressure applied thereto, based on its deployed state (LM).

2. The master cylinder according to claim 1, It is characterized by: The outlet (105a) of the hole (105) is located in the bore for at least partially overlapping the nose (111) of the piston (110) in the rest position.

3. The master cylinder according to claim 1, It is characterized by: The elastic connection (33) is achieved by sliding the valve (31) on the cam (32) and is completed by a compression spring (33a) between the valve (31) and the cam (32).

4. The master cylinder according to claim 1, It is characterized by: The cam (32) includes a connecting rod on which the shutter (31) slides and to which a compression spring (33a) is fitted.

5. The master cylinder according to claim 4, It is characterized by: The valve (31) is connected to an axial rod (321) of the cam (32), the valve having a head (311) with a support surface (311a) and a cavity (312) behind the support surface (311a), the rod (321) being engaged and retained in the cavity (312) by its end (322) provided with a hook (323), thereby allowing the valve (31) to slide relative to the end (322) of the rod (321), the relative sliding movement being carried out between a maximum extension position (LM) and a maximum compression position (Lm), the maximum compression position (Lm) being limited by the end (322) of the rod (321) abutting the bottom of the cavity (312).

6. The master cylinder according to claim 1, It is characterized by: The cam (32) has a raised surface (32a) for abutting against the piston.

7. The master cylinder according to claim 1, It is characterized by: The cam (32) is covered by an edge (324) to be supported on the stopper (12) of the housing (10), and a supporting surface (32a) of the cam (32) protrudes to contact the piston (110).

8. The master cylinder according to claim 1, It is characterized by: The master cylinder is a tandem master cylinder.

9. The master cylinder according to claim 6, It is characterized by: The surface (32a) is in the form of a spherical dome.

Images