Master cylinder for a braking system

Abstract

To provide a master cylinder which clearly improves its resupply without causing cost or difficulty in manufacturing while reducing overall size.SOLUTION: A master cylinder 100, in particular a tandem master cylinder, includes at least one chamber 120 defined by a piston 110 and supplied from a brake fluid reservoir installed above the master cylinder by a lower tip of a tank engaged in a nozzle on a body above the master cylinder. The piston has: a nose of a reduced cross section upstream of a skirt of the piston guided in a reaming hole 102 of the master cylinder; and nozzle connected to the chamber by a hole 105 opening at least partially into the chamber in a rest position. A valve module 200 is installed in the hole to manage communication between the tank and the chamber according to the position of the piston and pressure in the chamber with respect to pressure in the tank.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a master cylinder for a hydraulic brake system for a vehicle, particularly for an automotive vehicle, and more particularly to a tandem master cylinder.

Background Art

[0002] The development of hydraulic brake systems is related to active and passive safety means that require significantly higher and efficient replenishment of the master cylinder compared to well-known master cylinders, especially when integrated into a large number of projects for automotive vehicles.

[0003] Dual hydraulic systems are used not only for normal and emergency braking but also for automatic braking.

[0004] The normal braking system uses a braking booster such as a vacuum booster or an electric booster that significantly multiplies the force applied to the brake pedal by the driver. The two functions of normal and emergency are influenced by dimensions, operating characteristics, and regulatory requirements. Such a braking system can be connected, i.e., directly connect the driver to the braking system, or disconnected, i.e., indirectly connect the driver to the brake system.

[0005] The automatic braking system is controlled by an electric booster that can be operated by a program rather than the driver and can be either directly connected to the system or not.

[0006] Conventional braking systems include at least one central hydraulic unit having a built-in electronic controller and a pump (ESP system) that enables pressure to be generated independently of the driver during active braking operations. The master cylinder, by its replenishment function, is usually a component that ensures supply to the pump.

[0007] The tandem master cylinder is provided with a special joint called a cup that ensures a sealing function and a replenishment function. However, such a configuration of the cup involves a contradiction between the sealing function and the replenishment function, thereby restricting the possibility of replenishment. Therefore, at present, the tandem master cylinder does not enable the securing of the flow rate required for the new braking function during development.

[0008] FIG. 8 shows a tandem master cylinder according to the prior art having a main piston and an auxiliary piston that respectively define chambers. The chambers are respectively connected to nozzles 405, 406 that house the tip of the brake fluid tank.

[0009] The nozzles communicate with the chambers through supply holes passing through the top of holes made in the piston skirt near the front end thereof. The sealing of the piston in the reaming hole of the master cylinder is realized by joints and cups that operate similarly on the two pistons. The joint has a sealing function. The cup has two functions. It realizes sealing. It has a function that enables replenishment to the chamber.

[0010] FIG. 9 schematically shows the details of the contact portion between the piston and the cup, showing where the top of the hole in the piston skirt communicates with the supply hole when the piston is in the rest position.

[0011] According to FIGS. 10 to 13, At rest (FIG. 10), the chamber communicates with the brake fluid tank through the holes in the main body of the master cylinder that open to the top of the hole and the surrounding grooves to supply all the holes of the piston.

[0012] Next (FIG. 11), the piston advances, blocking the communication with the tank by passing the top of the hole under the cup, and enabling pressure to be applied to the chamber. This pressure is also applied to the cup to complete the sealing.

[0013] Thereafter (Figure 12), the piston continues to advance, increasing the pressure and delivering the brake fluid to the brake circuit.

[0014] Next (Figure 13), when the pressure in the chamber drops, the brake fluid is sucked from the tank while bypassing the cup in the groove and passing between the reaming hole and the piston skirt. However, since the replenishment to the chamber is difficult and progresses slowly, it is not suitable for the current brake circuit.

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0015] An object of the present invention is to develop a master cylinder that improves its replenishment clearly without generating costs or difficulties during manufacturing while reducing the overall dimensions.

[0016] The present invention also needs to realize a tandem master cylinder whose operation does not change as seen by the driver compared to the current master cylinder.

MEANS FOR SOLVING THE PROBLEMS

[0017] For this purpose, the present invention aims at a master cylinder, particularly a tandem master cylinder, including at least one chamber defined by a piston, the chamber being connected to a brake circuit and supplied from a brake fluid tank installed above the master cylinder by a tip below a tank engaged with a nozzle above the body of the master cylinder. A) The piston has a nose with a reduced cross-section upstream of a piston skirt guided in the reaming hole of the master cylinder. B) The nozzle opens at least partially into the chamber upstream of the piston in the rest position and is connected to the chamber by a hole that at least partially overlaps the nose. C) A valve module is installed in the hole to manage the communication between the tank and the chamber according to the pressure in the chamber with respect to the position of the piston and the pressure in the tank.

[0018] The master cylinder of the present invention has the advantage of allowing direct communication between the brake fluid tank and the chamber to which the tank is connected by its tip, substantially without loss of the filling material therebetween. This communication is achieved by moving its nose from the rest position to the active position controlling the valve module. Initially, when the skirt first reaches under the cam of the valve module, the valve module is closed to cut off the communication. Then, when the pressure in the chamber drops, it is very efficiently and easily controlled by the movement of the piston that allows efficient replenishment by opening the valve module. Since this opening is instantaneous, there is no delay at all in replenishing the chamber, and this replenishment proceeds in a narrow and long pipeline or passage without being stopped by loss of the filling material, as is the case with well-known master cylinders.

[0019] The present invention makes it possible to remove the cup connected to the chamber of the master cylinder, which leads to a significant simplification of the mounting and assembly of the master cylinder. This avoids the risk of the reverse arrangement of the cup that would make its normal operation impossible.

[0020] Finally, the removal of the cup in the master cylinder makes it possible to shorten the master cylinder, the primary piston, and the secondary piston.

[0021] According to an advantageous feature, the valve module - will be installed in the hole of the master cylinder, - has a valve seat on the tank side, - and a stroke limiting stopper on the chamber side, and as a float valve, - is movable between the seal seat and the stopper, - and comprises a cylindrical body that houses what contacts the piston passing through the stopper, - the float valve - is connected to a cam supported by the nose or skirt of the piston, and the flap acts together with the valve seat, and the cam is a flap held in the box of the module, - It includes an elastic coupling piece between the flap and the cam to enable elastic compression of the flap by the pressure applied to the flap from the unfolded state.

[0022] Such an embodiment of the valve module is particularly easy and advantageous because the module is mounted in the hole of the master cylinder in the assembled state by being completely externally implemented on the master cylinder.

[0023] Adjustment of the operation of the valve module is extremely easy because such adjustment can displace the cam of the valve module into the reaming hole and operate with the nose and skirt of the piston. Such adjustment is almost immediate because the valve module is positioned in contact with the hole.

[0024] According to another advantageous feature, the outlet of the hole is positioned in the reaming hole and overlaps the nose of the piston in the rest position to open into this reaming hole, which shortens the length of the piston and the master cylinder as already described, and at the same time keeps the communication open and utilizes the maximum amplitude of the float valve between the rest position of the float valve when the cam is supported by the nose of the piston and the active position when the cam is supported by the skirt of the piston to enable automatic positioning.

[0025] According to another advantageous feature, the elastic coupling piece is implemented by slidably attaching the flap to the cam and is finished by a compression spring between the flap and the cam.

[0026] Such an elastic coupling piece is particularly feasible because it is not brittle and is less susceptible to material fatigue.

[0027] According to another advantageous feature, the cam includes a coupling rod into which the flap slides and the compression spring is fitted.

[0028] This enables easy assembly of the cam and the flap.

[0029] According to another advantageous feature, the flap is connected to the axial rod of the cam, the flap has a cavity behind its support surface, and the axial rod is held at its end provided with a hook and engages with the cavity of the head of the flap, where a relative sliding movement of the flap on the end of the rod is enabled between the maximum extension position and the maximum compression position defined by the end of the rod abutting against the bottom of the cavity.

[0030] According to another advantageous feature, the cam has a contact surface curved in particular in the shape of a spherical cup and is supported by the piston both at the nose of the piston and in its skirt.

[0031] The rounded contact surface enables efficient sliding contact between the cam and the moving piston.

[0032] According to another advantageous feature, the cam is covered at its edge and is supported by the stopper of the box by passing the support surface of the cam and contacting the piston.

[0033] In the following, the present invention will be described in more detail using the embodiment of the electromechanical brake booster device illustrated in the accompanying drawings, and in the drawings, the following are shown.

Brief Description of the Drawings

[0034]

Figure 1

Figure 2

Figure 2A

Figure 3

Figure 3A

Figure 3B

Figure 3C

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

DETAILED DESCRIPTION OF THE INVENTION

[0035] [FIG. 1] shows a partial axial sectional view of a single master cylinder or tandem master cylinder 100 that penetrates a reaming hole 102 that houses a piston 110 that defines a chamber 120 for containing brake fluid to be supplied to a brake circuit (not shown) by the main body 101.

[0036] A hole 105 for connecting a nozzle 104 that houses the tip of a brake fluid tank (not shown) opens into the chamber 120.

[0037] The hole 105 includes a valve module 200 that manages the passage of brake fluid between the tank and the chamber according to the position of the piston 110 and the pressure prevailing in the chamber 120.

[0038] For reasons of presentation, the pressure / pressure drop that is dominant in chamber 120 is the relative pressure, i.e., the difference between the absolute pressure in chamber 120 and the pressure in the tank, which is atmospheric pressure.

[0039] According to the operation of the master cylinder / tandem master cylinder 100, pressure or pressure drop becomes dominant in chamber 120, and zero pressure is by definition atmospheric pressure.

[0040] It should also be noted that the description of the present invention applies to both a tandem master cylinder and a single master cylinder, one having two pistons defining two chambers each connected to a brake circuit, and the other having only one chamber 120.

[0041] The operation described for only one chamber applies to the two chambers of the tandem master cylinder under the same conditions.

[0042] More specifically, according to FIGS. 2 and 2A, the master cylinder 100 of the present invention is composed of a body 101 having a reaming hole 102 for storing a piston 110 (primary piston or secondary piston) shown in the rest position for the portion shown in cross-section. In the active stage, the piston 110 moves forward in the direction A. Sealing between the reaming hole 102 and the piston 110 is ensured by a joint 108 stored in a groove at the periphery of the reaming hole 102. The joint 108 is located behind the outlet 105a of the hole 105 of a duct 103 that supports the brake fluid tank.

[0043] The piston 110 has a nose 111 with a diameter smaller than the nominal diameter of the skirt 112 of the body of the piston 110. The nose 111 has a straight or curved frustoconical shape.

[0044] The hole 105 is positioned relative to the piston 110 such that in the rest position, the piston 110 partially overlaps the outlet 105a of the hole 105 by its nose 111.

[0045] The hole 105 of the duct 103 connected to the nozzle 104 forms a peripheral shoulder 106 at the connection with the reaming hole 102 (this shoulder is shown very schematically and is not accurate in dimensions). The hole 105 communicates with the chamber 120 through its outlet 105a which remains open by the peripheral shoulder 106.

[0046] Figure 2A shows a valve module 200 in which the active components described below of the valve module 200 project from the outlet 105 and are housed in the hole 105 facing the shoulder 106 which abuts against the nose 111 or the skirt 112 of the piston 110 according to the position or movement of the piston.

[0047] The valve module 200 is composed of a box 10 in the form of a cylindrical body that houses a sealed seat block 20 and stores a float valve 30.

[0048] The description of the components 10, 20, 30 of the valve module 200 is made with reference to FIGS. 3, 3A, 3B, 3C which are cross-sections of the valve module 200.

[0049] According to the cross-sectional view of FIG. 3, the box 10 is a cylindrical sleeve having an outer diameter adapted to be fixed to the hole 105 of the duct 103. The cylindrical sleeve 10 has a shoulder 11 for housing the sealed seat block 20 at the upper side and a lower stopper 12 in the form of a flange leaving an opening 13 at the lower side according to the illustrated orientation which is the orientation in use.

[0050] According to FIG. 3A, the sealed seat block 20 is a component in the form of a perforated cap having an inlet 20 communicating with the lower valve seat 22. The peripheral side 23 of the block 20 is provided with a peripheral rib (FIG. 2A) for fixing and sealing the block above the box 10.

[0051] According to FIG. 3B, the float valve 30 is composed of a flap 31 connected to a cam 32 with a compression spring 33a interposed according to the illustrated orientation which is also the orientation during operation.

[0052] The flap 31 has a head 311 whose surface 311a contacts the valve seat 22 of the box 10 in the closed position of the valve module 200.

[0053] The head 311 has a cavity 312 with an axial orifice 313 through which the rod 321 of the cam 32 passes. The end 322 of the rod 321 is engaged with the orifice 313 during installation by elastic deformation and then deployed into the cavity 312 behind it, and has a retaining hook 323 that holds the flap 31 in its extended or rest position on the rod 321 shown in FIG. 3B.

[0054] The cam 32 is supported by the stopper 12 of the box 10 from its dimensions and is covered by an edge 324 that holds the valve 10 of the box 10.

[0055] This support position has no sealing function, and the brake fluid can pass while the edge 324 of the cam is supported by the stopper 12.

[0056] The surface 32a of the cam 32 has a curved shape and projects and extends, for example, through the opening 13 of the box 10 and further through the outlet 105a of the hole 105, and projects toward the reaming hole 102 and acts with the piston 110.

[0057] The curved shape of the cam 32 and the conical inclination of the nose 111 of the piston 110 allow the piston to easily push the cam 32 back in the reverse direction, which allows the cam 32 to descend while being continuously supported by the piston 110.

[0058] A compression spring 33a interposed between the flap 31 and above the cam 32 around the rod 321 extends the valve 30 to the maximum extent limited by the hook 322 of the rod 321 of the cam 32.

[0059] The slidable attachment of the flap 31 to the cam 32 while interposing the spring 33a forms an elastic coupling piece. Such an elastic coupling piece 33 that enables elastic compression (i.e., with repulsion) between the flap 31 and the cam 32 can also be realized by elastic deformation of the base of the flap 31, and its sealing surface 311a remains rigid subsequently. Elastic deformation of the rod 321 of the cam 32 can also be considered. This elastic deformation only needs to be made in the direction in which the length elastically shrinks from the rest length (LM) of the float valve 30, and this length is determined so as to keep the communication between the tank and the chamber 120 open when the master cylinder 100 is in the rest position.

[0060] Figure 3B shows the maximum extension LM and the minimum extension Lm in comparison with Figure 3C. The difference between these two states is represented by ΔL.

[0061] In Figure 3C, the flap 31 is inserted into the end 322 of the rod 321, and this abuts against the bottom of the cavity 312 of the flap 31.

[0062] The state shown in Figure 3C is an example of a limit, while the state in Figure 3B corresponds to the rest of the float valve 30 that is not subject to any external constraints.

[0063] The functions of these two states or at least the rest state and the compressed state of the float valve will be clarified by explaining the operation of the master cylinder with reference to Figures 4 to 7 below.

[0064] Figure 4 shows the rest state of the master cylinder 100, and the piston 110 is in the rest position, which retreats to the right and overlaps with the opening 105a of the hole 105 by its nose 111.

[0065] The float valve 30 is in the rest position and is supported by its nose 111 by the cam 32. The length LM of the float valve 30 at rest is such that the engagement between the surface 311a of the head of the flap 31 and the sealing seat portion 22 is released. In these states, the brake fluid tank communicates freely with the chamber 120.

[0066] Figure 5 shows the operation of the master cylinder 100. The piston 110 advances (in direction A), and its nose 111, and then its skirt 112, raise the float valve 30 by contacting the cam 32, causing the surface 311a of the flap 31 to strike the sealing seat 22 and cut off the communication between the brake fluid tank and the chamber 120. This closing is due to the length of the float valve 30, which keeps the passage between the seat 22 and the flap 31 disengaged when the valve 30 is in the lower position at rest (Figure 5), while in the active position shown in Figure 6, the rise of the float valve 30 enables the closing. In this upper position, the flap 31 may be compressed by the spring 33a if the length LM is longer than the interval that is filled by the float valve 30 at this position at this time.

[0067] According to Figure 6, the piston 110 continues to advance within the chamber 120. The brake fluid present here, including the brake fluid that wraps around the float valve 30 within the box 10, is compressed, which pushes the flap 31 more forcefully towards the seat 22, ensuring a complete seal.

[0068] According to Figure 7, a slight backward movement of the brake circuit or the piston 110 causes a pressure drop within the chamber 120, which rebounds into the valve module 200, pushing the flap 31 back and sucking in the brake fluid to resupply the chamber 120.

[0069] Therefore, there is no obstacle in the passage between the tank and the chamber 120, enabling immediate resupply of the chamber.

[0070] The alternating occurrence of pressurization (Figure 6) and pressure drop (Figure 7) may be repeated during the brake cycle, and such alternating occurrences may be continuously carried out at high speed to instantaneously react the float valve and be useful for the resupply and operation of the brake system.

[0071] At the end of the braking phase, the piston 110 is returned to the rest position and returns to the state of Figure 4.

Explanation of Reference Numerals

[0072] 100 master cylinder / tandem master cylinder 101 main body of master cylinder 102 reaming hole of master cylinder 103 duct of master cylinder 104 nozzle 105 hole 105a outlet 106 shoulder 107 groove 108 joint 110 piston 111 nose of piston 112 skirt of piston 120 chamber 200 valve module 10 box / cylindrical body 11 arrangement of seat 12 lower stopper / stroke limiting flange 13 opening 20 block / sealing seat 21 inlet 22 valve seat 23 peripheral side 30 float valve 31 flap 311 head 311a surface of head 312 cavity 313 orifice 32 cam 32a surface of cam 321 cam rod 322 end of rod 323 hook 324 edge of cam 33 elastic coupling piece 33a elastic spring 400 known master cylinder 401 main piston 402 secondary piston 403, 404 chambers 405, 406 nozzles Supply holes 407, 408 Top of the skirt holes 412, 413 Joints 421, 422 Cups 423, 424 A Forward direction of the piston

Claims

【Claim 1】 In a master cylinder, comprising at least one chamber (120) delimited by a piston (110), said chamber (120) being connected to a brake circuit and being supplied as a brake fluid tank by a tip below said tank engaged with a nozzle above the body of said master cylinder and installed above said master cylinder, A) said piston (110) has a nose (111) of reduced cross-section upstream of a skirt (112) of said piston (110) guided in a reaming hole (102) of said master cylinder (100), B) the nozzle (104) opens into said chamber (120) which is at least partially upstream of said piston (110) in a rest position and is connected to said chamber (120) by a hole (105) which at least partially overlaps said nose (111), C) a valve module (200) is installed in said hole (105) to manage the communication between said tank and said chamber (120) according to the position of said piston (110) and the pressure in said chamber (120) with respect to the pressure in said tank, The valve module (200) is - to be installed in said hole (105) of said master cylinder, - provided with a valve seat (22) on the side of said tank, and - a stroke limiting stopper (12) on the side of said chamber, and as a float valve (30), - is movable between a sealing seat portion (22) and said stopper (12), - and comprises a cylindrical body (10) accommodating something which passes through said stopper (12) and contacts said piston (110), Said float valve (30) is - a flap (31) connected to a cam (32) supported by said nose (111) or said skirt (112) of said piston (110), which acts together with the valve seat (22), and said flap (31) held in said cylindrical body (10) of said valve module (200) by said cam (32), and - an elastic coupling piece (33) between said flap (31) and said cam (32) for enabling elastic compression of said flap (31) by a pressure applied to said flap (31) from an unfolded state (LM), A master cylinder characterized by the above. **Claim 2**: The outlet (105a) of the hole (105) is positioned in the reaming hole (102) and at least partially overlaps with the nose (111) of the piston (110) in the rest position. The master cylinder according to claim 1, characterized in that. **Claim 3**: The elastic coupling piece (33) is implemented by slidably attaching the flap (31) to the cam (32), and is finished by a compression spring (33a) between the flap (31) and the cam (32). The master cylinder according to claim 1, characterized in that. **Claim 4**: The cam (32) is provided with a rod (321) into which the flap (31) slides and the compression spring (33a) is fitted. The master cylinder according to claim 3, characterized in that. **Claim 5**: The flap (31) is connected to the rod (321), the flap (31) has a head (311) provided with a support surface (311a) and a cavity (312) behind the support surface, and the rod (321) is held at an end (322) of the rod provided with a hook (323) and engages with the cavity (312), between the maximum extension position (LM) and the maximum compression position (Lm) defined by the end (322) of the rod (321) abutting against the bottom of the cavity (312), enabling relative sliding movement of the flap (31) on the end (322) of the rod (321). The master cylinder according to claim 4, characterized in that. **Claim 6**: The cam (32) has a curved surface (32a) in the shape of a spherical cup and abuts against the piston. The master cylinder according to claim 1, characterized in that. **Claim 7**: The cam (32) is covered by an edge (324) and is supported by the stopper (12) of the cylindrical body (10) by contacting the piston through the support surface (32a) of the cam (32). The master cylinder according to claim 1, characterized in that. **Claim 8**: The master cylinder is a tandem master cylinder (100). The master cylinder according to claim 1.

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