WO2003027506A2

WO2003027506A2 - Pressure amplifying device for hydraulic circuit

Info

Publication number: WO2003027506A2
Application number: PCT/FR2002/003287
Authority: WO
Inventors: Gilbert Beringer
Original assignee: Sa Beringer
Priority date: 2001-09-26
Filing date: 2002-09-26
Publication date: 2003-04-03
Also published as: WO2003027506B1; WO2003027506A3; FR2830058A1

Abstract

The invention concerns a pressure amplifying device for hydraulic circuit comprising means (1) (2) (3) for filling the circuit up to a predetermined pressure with a large flow rate, and beyond said pressure, for amplifying said pressure with a small flow rate. The invention is characterized in that: the means consists of a body or housing (1) for delimiting two coaxial inner recesses (1a) and (1b) of different cross-section (S1) (S2) communicating with the hydraulic circuit, to be subjected to an input pressure (P1) and an output pressure (P2); said recesses receiving with sealed sliding capacity a flanged piston delimiting two bearing surfaces (3a) and (3b) with same cross-section as that of the recesses. The piston (3) is designed to allow the free passage of the hydraulic fluid into one of the recesses communicating with the output, or for displacing it in accordance with the value of the input (P1) and output (P2) pressures in combination with an adjustable resistant force exerted on the piston, by sending compressed air into the other recess communicating with the input.

Description

PRESSURE AMPLIFIER DEVICE FOR HYDRAULIC CIRCUIT

The invention relates to the technical sector of braking or clutch control circuits in particular, for any type of vehicle, in particular automobile and motorcycle.

As indicated, the invention finds a particularly advantageous application for a hydraulic vehicle braking circuit, while observing that such an application should not be considered as limiting, given that the device finds an application in any type of hydraulic circuit, where it is necessary to exert, on an actuating member of the lever, pedal or other type, a certain effort to deliver a certain pressure capable of acting on members to be controlled (brake caliper, clutch, ...).

If we consider a brake circuit, we recall that the braking members, in particular the calipers, have pads controlled by pistons hydraulically connected to a master cylinder to be controlled by one or more actuating members which can be operated by hand or by hand. foot, depending on the type of vehicle considered.

The choice of a master cylinder for a given brake circuit always results from a compromise between the force-pressure ratio, which must be as low as possible because of the actuator member whose stroke must be as short as possible. For example, if a piston of small diameter is chosen for the master cylinder, a high pressure is obtained in the circuit for a low force applied to the actuator member. However, such an effort does not can compensate for the absorption of volume of the pressurized brake circuit generating an excessively long stroke of the actuator member subject to the master cylinder.

In an attempt to resolve this problem, vehicles are increasingly equipped with braking assistance systems, making it possible to reduce the force on the actuator member. Such a solution requires relatively large means of implementation, at a high cost, and is not always desired for certain types of vehicles, such as motorcycles and racing or competition cars.

It has also been observed that the disc brake calipers (or the receiving cylinders in the case of drum brakes) absorb a large part of the brake fluid at low pressure to simply bring into contact the various friction elements which have withdrawn when the actuator member is released. This results in two distinct phases in the operation of brake calipers or slave cylinders.

The first phase is the contacting of the friction elements which takes place at low pressure, of a value less than 5 to 10 bars approximately.

Such contacting absorbs the majority of the total volume required from 50 to 75%. In this respect, reference is made to the curves of FIGS. 1, 2, 3 and 4 which show the volume required as a function of the pressure applied for certain members of the hydraulic braking circuit considered. This first phase (A) corresponds to a dead race, not participating directly in the braking action as such. The second phase (B) corresponds to the pressurization of the friction elements on the disc or drum. The absorbed hydraulic fluid corresponds to the deformation of the parts (the retrier housing for example) under the effect of hydraulic pressure. We refer, as before, to Figures 1, 2, 3 and 4. As these different curves show, this results, depending on the component of the braking circuit considered, nearly 25 to 50% of the volume of hydraulic fluid total.

The object of the invention is to remedy these drawbacks in a simple, safe, effective and rational manner.

The problem which the invention proposes to solve is to reduce the force exerted on the actuating member (lever or pedal) while retaining an identical stroke, without being obliged to call upon a braking assistance system.

To solve such a problem, a pressure boosting device for a hydraulic circuit has been designed and developed. This device comprises means capable of filling the circuit up to a determined pressure with a large flow and, beyond said pressure, amplifying this pressure with a low flow.

According to the invention: Φ The means consist of a body or casing arranged to delimit two internal coaxial recesses and of different section in communication with the hydraulic circuit, to be subjected to an inlet pressure and an outlet pressure; Φ Said recesses receiving with sealed sliding capacity a shouldered piston delimiting two spans of the same section as that of the recesses;

Φ The piston has arrangements for the free passage of the hydraulic fluid in one of the recesses in communication with the outlet, or for its displacement as a function of the value of the inlet and outlet pressures in combination with an adjustable resistant force exerted on said piston by sending compressed air into the other recess in communication with the inlet.

To solve the problem posed of allowing the free passage of the hydraulic fluid or the displacement of the piston according to the value of the pressure, the arrangements of the piston consist of two coaxial bores of different section while being in communication with each other and with the recesses , the bore of smaller section receiving a ball subject to a spring and cooperating with a finger that has a part of the body so as to allow, depending on the pressure, the free passage of the fluid through the recesses of the piston or the displacement of the piston.

According to another characteristic of the invention, at low pressure, of a value lower than that exerted by the elastic return member, the inlet and outlet pressures are equal, the hydraulic fluid passes freely through the bores of the piston, the ball pressing against the finger releasing a seat formed at the end of the corresponding bore, while at high pressure, when the value of the inlet pressure, multiplied by the difference in the piston cross-sections becomes greater than the force exerted by the compressed air the piston is moved causing, concomitantly, the blockage of the seat.

As indicated, the device finds a particularly advantageous application in the case of a vehicle brake circuit integrating a master cylinder acting on braking members. In this case, the device is positioned between the master cylinder and the braking members. More particularly, a body is positioned between the master cylinder and the front braking members, while another body is positioned between the master cylinder and the rear braking members, each of said bodies being adjusted, at a different trigger pressure by means compressed air.

The device can also advantageously be used in the case of a vehicle clutch circuit.

The invention is set out below in more detail with the aid of the figures of the appended drawings in which:

- Figure 1 shows the volume and pressure curves in the case of different braking circuit elements for a motorcycle;

- Figures 2 and 3 show the volume and pressure curves for each of the calipers of the motorcycle's braking circuit;

- Figure 4 shows the actual absorption curve of the volume as a function of the pressure, in the case of a hydraulic braking circuit of a production vehicle;

FIG. 5 is a view in longitudinal section of an embodiment of the device shown in the non-operating position, when the inlet and outlet pressures are equal, corresponding to the filling of the circuit;

- Figure 6 is a view corresponding to Figure 5 in the displacement position of the piston corresponding to the amplification of the pressure with a low flow;

- Figure 7 shows a theoretical curve of the operating principle of the device according to the invention;

- Figure 8 is a view similar to Figure 4, on which we have added spaced points representing the curve obtained with the pressure amplifier device according to the invention corresponding to the stroke of the master cylinder.

- Figure 9 is a longitudinal sectional view of a preferred embodiment of the device shown when the inlet and outlet pressures are equal. - Figure 10 is a view similar to Figure 9 showing the displacement of the piston corresponding to the amplification of the pressure with a low flow.

- Figure 11 is a purely schematic view showing an example of advantageous application of the device to a vehicle braking circuit.

The pressure booster device according to the invention consists of a compact and autonomous assembly, of reduced dimensions, capable of being integrated or added to a hydraulic circuit for the control, for example of a braking member, of a clutch. , ... In the embodiment of Figure 5, the device comprises a housing in the form of a cylindrical body (1) having two internal coaxial recesses (la) and (lb) of different section. The bore (la) has a section (SI) greater than the section (S2) of the recess (lb), the two recesses (la) and (lb) communicating with each other and with the outside to be connected to the hydraulic circuit.

For example, the bottom (the) of the body (1) has a through hole (ld) in communication with the recess (lb) to be connected by any type of known and appropriate connecting member, to the hydraulic circuit, being subjected at an outlet pressure (P2). In contrast, the open inlet of the cylindrical body (1) is closed, in a leaktight manner, by a plug (2) screwed for example into a threaded seat (le) of the body (1). The plug (2) has a through hole (2a) for communicating the recess (la) with the hydraulic circuit by means of any type of connecting member known and suitable for a person skilled in the art. At this level, the body (1) is subjected to an input pressure (PI).

In the preferred embodiment of FIGS. 8 and 9, the body (1) is open at one of its ends for mounting and fixing a cylindrical end piece (10) having a circular bearing (10a) engaged in the bore (la) of the body (1). The circular bearing surface (10a) has an internal recess opening opening inside the recess (la) of the body (1), and constituting the other recess (lb). The end piece (10) through an orifice (10b) is in communication with the hydraulic circuit and is subjected to the outlet pressure (P2). In contrast, the bottom (lg) of the body (1) is in communication with the hydraulic circuit while being subjected to the inlet pressure (PI). Inside the body (1) is mounted, with guided and sealed sliding capacity, a shouldered piston (3). This piston has a first cylindrical seat (3a), constituting the head, extended by another cylindrical seat (3b) constituting the body. The cross section of the bearing surface (3a) corresponds substantially to the section (SI) of the recess (la), while the cross section of the bearing surface (3b) corresponds substantially to the section (S2) of the recess (lb). Each of the bearing surfaces (3 a) and (3b) has a groove for mounting seals (4) and (5).

More specifically, in the preferred embodiment of Figures 9 and 10, the head (3) of the piston (3) is engaged with sealed sliding capacity in the stage bore (la) of the body (1). The body (3b) of the piston is engaged with a sealed guided sliding capacity, in the internal recess of the end piece (10) constituting the bore (1b).

The piston (3) has two coaxial bores (3c) and (3d) of different section, said bores being in communication with each other and with the recesses (la) and (lb) of the body (1).

The bore (3c), of small section, receives a ball (6) subjected to a spring (7) bearing for example on a ring (8) in abutment on the connecting shoulder between the two bores (3c) and (3d). The ball (6) cooperates with a coaxial finger (2b) formed in overflow from the internal face of the plug (2), (Figures 5 and 6) or in overflow from the bottom (lg) of the body (1) (Figures 9 and 10 ). The entry of the bore (3c) forms a seat (3cl) capable of being closed by the ball (6), as will be indicated in the following description. The inlet of this seat (3cl) is in communication with the fluid supply (2a) via, for example, channels (2c).

The bore (3d) receives a return spring (9), in support, in the bottom (the) of the body (1) and against the ring (8). The body (1) has an orifice (lf) for the evacuation of air, under the effect of displacement of the piston (3).

According to the preferred embodiment of FIGS. 9 and 10, in order to reduce the dead travel and to adjust the triggering threshold, the spring (9) is replaced by compressed air. For this purpose, the internal recess (la) of the body (1) has arrangements (11) for connection to a compressed air circuit to create a reaction force at the level of the head (3a) of the piston. It is therefore sufficient to adjust the air pressure, to increase or decrease the intensity of the reaction force, opposed to the displacement of the piston.

The operation of the device according to the invention is analyzed below, in an example of application to a hydraulic braking circuit.

The entire housing (1) as defined is positioned between the master cylinder (s) and the brake calipers. At the outlet of the master cylinder, the body (1) is at the inlet pressure (PI), while on the caliper side, the body (1) is at the outlet pressure (P2). If we consider the first phase corresponding to the contacting of the friction elements, the latter is carried out at low pressure, for example less between 5 and 10 bars depending on the setting of the spring (9) or the pressure exerted by the 'pressurized air. At this level, the pressure (PI) is equal to the pressure (P2). The hydraulic fluid flows freely through the piston (3).

In this phase, the ball (6) resting on the finger (2b), does not close the seat (3cl) allowing the free circulation of the hydraulic fluid. In this operating phase, the supply of the stirrups is done in a conventional manner, the amplifier device not being activated.

If we consider the second phase corresponding to the pressurization of the friction elements on the disc or the drum, the latter is carried out at high pressure greater than 5 to 10 bars, according to the example given. When the value of the pressure (PI) multiplied by the difference of the sections (SI) and (S2) reaches a value greater than the reaction force resulting from the injection of compressed air, the piston (3) moves according to the arrow (F), so that the ball (6) is no longer supported on the finger (3c), but comes to rest in the bottom of the seat (3cl) thus closing the communication hole between (PI) and (P2).

When the piston (3) starts to move, (PI) is equal to the trigger pressure (Pd). This results in an amplification of the pressure according to the relation:

^{S 1} (P2) = S2 Pl - Pd We refer to FIG. 7 which illustrates an example of a relationship that can be obtained between the pressures (PI) and (P2), namely that PI = P2 up to 10 bars and that P2 = 2 times PI after 10 bars .

We refer to FIG. 8 which shows an example of application of the device to a braking circuit of a conventional motorcycle by comparing the curves of the master cylinder as a function of the pressure obtained in the case of a hydraulic circuit according to the state prior art, that is to say without amplifier device (curve in solid lines) with the pressure amplifier device according to the invention (dotted curve).

The chosen ratio of the master cylinder is determined to provide a pressure of 3 bars under a force of 1 daN applied to the actuator member. It is advantageously possible to choose a master cylinder with a ratio of 1 daN for 2 bars and thus reduce the dead stroke thereof by 30%, since the piston which is larger, delivers more liquid for the same stroke. The dead race therefore goes from 48 to 31% of total travel.

If the device is set to 9 bars for example, it triggers this value and doubles the pressure (PI) which becomes twice the pressure (P2). We therefore have a final ratio of 1 daN for 4 bars.

As a result, with equal lever stroke and equal circuit pressure, it is therefore possible, according to this example, to reduce by 25% the force necessary to be applied to the brake lever or other actuating member. As indicated, the device therefore makes it possible to reduce the force at the level of the actuating member, which is particularly advantageous for an unassisted braking circuit, as is the case for motorcycles or competition vehicles. Figure 11 shows the application of the device to a braking circuit mounted in combination with the front calipers (EAN) and the rear calipers (EAR). One of the bodies (1) is positioned between the front master cylinder (MCAN) and the corresponding brake calipers (EAN) while another body (1) is positioned between the rear master cylinder (MCAR) and the corresponding calipers (EAR) Depending on the quantity of compressed air sent into one or other of the bodies (1), an adjustable trigger pressure is obtained between the front and the rear. - For braking with maximum deceleration, we set for a distribution between the predetermined front and rear (for example 70% at 1 front and 30% at the rear). - For braking with the vehicle turning, it is necessary to have a predominance of pressure at the rear (for example 40% at the front and 60% at the rear), to make the car survive.

Thus in the first case corresponding to a maximum decelaration, and considering for example a pressure of 60 bars, the two devices are triggered. In the second case, to make the car survive and considering a pressure of 20 bars, the amplifier device mounted in combination with the front master cylinder, does not trigger (set at 25 bars for example) while the amplifier device mounted in combination with the rear master cylinder will trigger by being set at 5 bars for example. The following relationships between the front and the rear can thus be envisaged

1.3 - 1.5 - 1.7 - 2. Obviously, this trigger pressure can be controlled by any known and appropriate system.

Given the characteristics of the amplifier device according to the invention, the latter can perfectly be integrated into a hydraulic clutch circuit having characteristics close to the braking circuit. Indeed, the effort becomes dense only when it is necessary to compress the clutch springs, which represents only a small part of the stroke of the actuator member, namely the pedal. As indicated above, such an effort can be reduced by triggering the device.

The amplifier device according to the invention can also be added to an existing circuit to: - Take advantage of the reduction in travel created by replacing the rubber hoses with low-expansion hoses. Indeed, this additional available stroke can be converted into higher pressure by the device. - Adapt a caliper to a master cylinder (for example the caliper has pistons too small compared to the pistons of the master cylinder). - Change the distribution of front / rear braking on a competition car by mounting the device, either on the front circuit or on the rear circuit.

The advantages are apparent from the description.

Claims

-1- Pressure amplifier device for a hydraulic circuit comprising means (1) (2) (3) capable of filling the circuit up to a determined pressure with a large flow rate and, beyond said pressure, amplifying this pressure with a low flow rate, characterized:

Φ The means consist of a body or casing (1) arranged to delimit two coaxial internal chambers (la) and (lb) of different section (SI) (S2) in communication with the hydraulic circuit, to be subjected to a pressure d input (PI) and output pressure

(P2);

Φ Said chambers receiving with sealed sliding capacity a shouldered piston delimiting two spans (3a) and (3b) of the same section as that of the chambers; Φ The piston (3) has arrangements for the free passage of hydraulic fluid in one of the chambers in communication with the outlet, or for its movement depending on the value of the inlet (PI) and outlet (P2) pressures ) in combination with an adjustable resistant force exerted on said piston, by sending compressed air into the other chamber in communication with the inlet.

-2- Device according to claim 1, characterized in that the internal chambering of the body in communication with the inlet has connection arrangements with a compressed air circuit to create the resisting force at the level of the head (3a) of the piston. -3- Device according to claim 1, characterized in that the arrangements of the piston (3) are constituted by two coaxial bores (3c) and (3d) of different sections being in communication with each other and with the chambers (la) and (lb), the bore of smaller section (3c) receiving a ball (6) subject to a spring (7) and cooperating with a finger (2b) presented by a part (2) of the body (1), so as to to allow, depending on the pressure, the free passage of the fluid through the chambers of the piston or the movement of the piston (3).

-4- Device according to claim 1, characterized in that at low pressure, of a value lower than that exerted by the elastic return member (9), the inlet (PI) and outlet (P2) pressures ) are equal, the hydraulic fluid passes freely through the bores of the piston (3), the ball (6) resting against the finger (2b) releasing a seat (3c 1) formed at the end of the corresponding bore (3c) , while at high pressure, when the value of the inlet pressure, multiplied by the difference in the sections of the piston becomes greater than the force exerted by the compressed air, the piston (3) is moved causing, by a concomitantly, the sealing of the seat (3cl) by the ball (6).

-5- Application of the device according to any one of claims 1 to 4, to a vehicle brake circuit integrating a master cylinder acting on braking members, the body (1) being positioned between the master cylinder and said members.

-6- Application of the device according to claim 5, characterized in that a body (1) is positioned between the master cylinder and the organs of front braking, while another body (1) is positioned between the master cylinder and the rear braking members, each of said bodies being adjusted to a different trigger pressure by means of compressed air.

-7- Application of the device according to any one of claims 1 to 4, to a clutch circuit.