FR2582074A1 - BRAKE PRESSURE CONTROL VALVE DEVICE - Google Patents

Abstract

VALVE DEVICE INTENDED TO CONTROL AN OUTLET PRESSURE OF A FLUID AS A FUNCTION OF AN INLET PRESSURE OF THIS FLUID, WHILE KEEPING THE SAID OUTLET PRESSURE CONSTANT BETWEEN A LOWER VALUE AND A HIGHER VALUE OF THE SAID INLET PRESSURE, INCLUDING AN INLET CHAMBER AND AN OUTLET CHAMBER, A FIRST VALVE THAT CAN BE SWITCHED AS A FUNCTION OF THE PRESSURE AND BEING LOCATED BETWEEN THE SAID INLET CHAMBER AND THE SAID OUTLET CHAMBER, THE CLOSING ELEMENT OF THE SAID FIRST VALVE ADOPTING THE POSITION CLOSED UNDER THE ACTION OF A SPRING UNTIL THE SAID INPUT PRESSURE HAS REACHED THE SUPERIOR PRESSURE VALUE, AND INCLUDING A PISTON WHICH IS SUBJECT TO THE SAID INPUT PRESSURE AGAINST THE FORCE OF A SPRING, AND WHICH, UNTIL THE SAID INLET PRESSURE HAS REACHED THE LOWER PRESSURE VALUE, BLOCKS THE CLOSING MOVEMENT, PRODUCED BY A SPRING, OF A VALVE CLOSING ELEMENT, CHARACTERIZED IN THAT ITS PISTON 6 LADIT LIMIT E INPUT CHAMBER 8, BLOCKS THE CLOSING MOVEMENT OF SAID CLOSING ELEMENT 17 OF THE SAID FIRST VALVE 16, 17 UNTIL THE SAID LOWER PRESSURE VALUE P HAS BEEN REACHED, AND IS APPLIED AGAINST A STOP 12 AS SOON AS THIS ELEMENT CLOSING 17 HAS ADOPTED ITS CLOSED POSITION.

Description

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  The present invention relates to a valve device for

  tined to control an outlet pressure of a fluid as a function of an inlet pressure of this fluid, while keeping the outlet pressure constant between a lower value and an upper value of the inlet pressure, comprising a chamber inlet and outlet chamber, a first valve which can be switched as a function of pressure and being located between the inlet chamber and the outlet chamber, the closing element of this first valve adopting the closed position under the action of a spring until the inlet pressure has reached the higher pressure value, and

  comprising a piston which is subjected to the inlet pressure at the

  be of the force of a spring, and which, until the pressure

  has reached the lower pressure value, blocks the

  closing element, produced by a spring, of a closing element

re valves.

  In a known valve device of this type (request for

  German Patent No. 3,040,282, Figure 1), two valves are provided in-

  be the inlet chamber and the outlet chamber, the first being located in the closure element of the second. The piston is located in the outlet chamber and blocks the closing movement

  of the valve closing member until the inlet pressure

  has reached the lower of the two pressure values. It can therefore be seen that this embodiment requires two valves. In addition, the piston being located in the outlet chamber, its stroke is

  interrupted between the moment when the pressure value in-

  lower, at which the second valve closes, and the moment when the upper pressure value is reached, at which the first valve opens. After exceeding the higher pressure value, at which the first valve opens, the piston continues its course, if necessary to a stop. As the piston continues to travel, the volume of the outlet chamber increases. The rise in outlet pressure is therefore delayed. This is a drawback, especially when the valve device is located on a

  brake pressure line. Similarly, when the output of the dis-

  positive of valves is connected to the output of a pressure regulator,

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  so that these two devices cooperate, as is often the case.

  this is the case in brake pressure control systems

  installed in motor vehicles, an increase in pressure

  sion in the outlet chamber of the valve device, caused by the pressure regulator, can cause a considerable increase

  ble volume if the piston moves before reaching the stop.

  This can also delay the desired pressure rise and de-

  raise awareness of the regulation circuit of the regulation system of the

brake pressure.

  The object of the present invention is therefore to provide a device

  tif of valves of the type indicated above, intended in particular to be

  installed on brake pressure lines, making it possible to

  ter, by implementing reduced means, any delay in raising

  tion of the outlet pressure, in particular after exceeding the

higher pressure value.

  According to the invention, this object is achieved in that the piston defines the inlet chamber, blocks the closing movement

  of the closure element of the first valve until the value

  their lower pressure has been reached, and is applied against

  a stop as soon as the closing element has adopted its closed position.

  In this arrangement, only the first valve, in connection with the piston and the springs which act on the valve closing element and the piston, defines the lower pressure values and

  between which the first valve remains closed. For as-

  For this function, it is not necessary to provide an additional valve, associated with a valve closing element subjected to friction. Likewise, the significant additional piston stroke is eliminated as soon as the inlet pressure has exceeded the lower pressure value. In an arrangement comprising an auxiliary pressure generator which is connected in parallel to the outlet side and the outlet pressure of which is amplified, the rise in the outlet pressure is therefore not significantly delayed, due to a

  increase in the volume pressurized by the pressure generator.

  Conversely, in the event of a gradual reduction in the inlet pressure of the valve device, the outlet pressure is also

2582074-

  lowered without hysteresis, as in the case of an increase in inlet pressure. However, if the inlet pressure is suddenly reduced, the mass-spring assembly of the valve device, in connection with the friction of the piston, cannot always follow this pressure drop fast enough. In addition, this system can be caused to produce vibrations. This is even more true for a device

  of valves of the same type, in which an additional valve is provided

  shut up associated with a valve closing element subjected to the action

of a spring.

  To be able to reduce pressure practically without delay and

  with little vibration, it can be provided, in accordance with the invention

  tion, a second valve which is located in parallel to the first

  re, between the entry chamber and the exit chamber, which is open

  te when the outlet pressure is higher than the inlet pressure

  which is designed in the form of a grooved sealing cup. A cup of this type is of simple design and has a low mass, so that it reacts practically without delay and

  without producing vibrations. Since it is not subject to

  tically no friction, its wear is reduced.

  In addition, when in the open position, the element of

  closure of the first valve can be applied, via

  re of an extension provided on the inlet side, against the front surface of the piston, which is subjected to the inlet pressure. So the piston

  must keep this valve closing element in posi-

  open until the inlet pressure has exceeded the

  their bottom and takes off the piston from the valve closing element. In this arrangement, the extension can be guided, with

  a clearance, inside an axial bore of the valve casing, of the

  the valve closing element is not subjected to excessive

heavy friction wear.

  To vent a system, subject to action

  hydraulic fluid through a valve device, in application

  as for a vacuum (venting known as "vacuum"), provision may also be made to connect the side of the piston to the atmosphere

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  subjected to the action of a spring and opposite to the inlet chamber. In this case, the piston necessarily holds the closure element of

  the first valve in the open position when the vacuum is applied

  folded into the inlet chamber or the outlet chamber, so that any air contained in the system can escape.

  The various objects and characteristics of the invention are-

  will now be detailed in the description which follows, made to

  by way of nonlimiting example, with reference to the appended figures which represent: FIG. 1, a transverse section, in the axial direction,

  of an embodiment of a valve device in accordance with the

  vention, - Figure 2, a graph illustrating the relationship between the outlet pressure and the inlet pressure of the valve device

according to figure 1.

  In accordance with FIG. 1, a piece of bootmaker 3 is screwed

  sée in a bore 1 of a boot part 2, and its sealing relative to the bore 1 is ensured by a sealing ring 4. The boot part 3 has a stepped bore 5 which is coaxial with

  the bore 1, and in which a piston 6 slides axially. The water

  cheity of piston 6 with respect to bore 5 is ensured by a year-

  sealing ring 7, and the front surface of the piston 6 delimits an inlet chamber 8 in the stepped bore 5 formed in the workpiece

  housing 3. The inlet chamber 8 is connected to an inlet 11, practically

  quée in the bootmaker piece 2, through holes 9,

  which pass through the wall of the boot piece 3, and through

  diary of an annular chamber 10 provided between the boot parts 2 and 3. The piston 6 is subjected to the action of a spring 13 which takes

  support on the piston 6 and on a cover 12 mounted in the bore 5.

  In addition, in the axial bore 5 of the boot part 3, an insert 14 is housed in a pressure-tight manner and has a stepped bore 15 which passes entirely through it in the axial direction. One of the shoulder edges of the bore 15 constitutes the seat

  valve 16 of a valve closure element 17 of plastic material

  than. The valve closing element 17 is made up of a part

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  partially spherical 18 provided with axial cylindrical extensions 19 and 20. The valve closing element 17 is pushed against the valve seat 16 and the front surface of the piston 6 under the action of a spring 21. In this case, the spring 21 bears, on the one hand, on the partially spherical part 18 of the valve closing element and, on the other hand, on an annular shoulder 22 of the bore 5

  of the boot piece 3. The extension 19 of the closure element

  re valve 17 is guided with play to facilitate movement inside the portion of the bore 15 of the insert 14 which

  is on the side of the piston 6, and it also delimits, with the

  sage 15, an annular chamber. This annular chamber is connected to

  the inlet chamber 8 by means of radial bores 23.

  The end of the bore 5 of the boot piece 3, which is

  opposite the cover 12, is connected to an outlet chamber 24

bordered by an exit 25.

  Between inlet 11 and outlet 25, the boot piece 3 is provided with an outer circular groove 26 in which is housed a valve closing element 27 formed by a grooved sealing cup. A circumferential lip 28 of the grooved sealing cup seals the boot part 3 with respect to the bore 1 of the boot part 2 when the inlet pressure Pe is greater than the outlet pressure Pa 'With the bore 1 of the boot part 2, the grooved sealing cup 27 therefore forms a non-return valve which closes the passage of hydraulic fluid from

  inlet 11 to outlet 25 through the annular chamber 10 pre-

  view between shoemaker parts 2 and 3, but which opens it in the opposite direction. The cylindrical portion 29 of the valve closure member 27, which is adjacent to the circular groove 26, is overlapped by a

  C-shaped ring 30 which surrounds the boot piece 3 between the

  port 11 and valve closure member 27, and which is provided, at its

  periphery, of axial through channels designed in the form of grooves

  res. The C-shaped ring 30 prevents any radial bulging of the cylindrical portion 29 in the event of axial compression of the cup

  throat seal 27 due to a sudden passage of hydraulic fluid

  only from the inlet side to the outlet side of the valve device, and

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  therefore guarantees the opening of valve i, 27 by applying the

  lip 28, in the radial direction, against the cylindrical portion 29.

  The rear chamber provided in the bore 5 between the piston 6

  and the cover 12, where the spring 13 is housed, is brought to the atmosphere.

  re via a pressure compensation hole 31. This pressure compensation hole 31 is covered by an O-ring 32 which prevents the intrusion of impurities and which allows air

  to pass almost freely through the hole 31 for main-

  set an air pressure balance at the rear of the piston 6.

  The mode of operation of the valve device shown in Figure 1 will now be explained in detail, with reference to

  pressure graph of figure 2.

  It will be assumed that, in the position shown, the inlet pressure Pe and the outlet pressure outlet pressure Pa are initially equal to zero. When the inlet pressure Pe increases, the

  pressure propagates freely through inlet 11, the annu- lar chamber

  area 10, the holes 9, the inlet chamber 8, the holes 23, the

  annular chamber of the bore 15, the open valve 16, 17 and the part

  end tie, outlet side, from the axial bore 5 of the boot part 3, to the outlet chamber 24 and the outlet 25. During this time,

  the piston 6 is held in abutment against the insert 14 at the

  yen of spring 13 until the inlet pressure Pe reaches a lower value Pel corresponding to approximately 1.6 bar, this value

  being determined by the spring 13 and by the active area of the surface

  this front of the piston 6. When the piston 6 is in this position, the extension 19 of the valve closing element 17 is also in abutment against the front surface of the piston 6 under the action of the spring 21, the valve 16, 17 remaining open because the spring 21 is weaker than the spring 13. The outlet pressure Pa therefore increases in the

  same proportions as the inlet pressure Pe until the pressure

  input pressure Pe reaches the lower value Pel 'As soon as the value Pel is exceeded, the thrust force applied to the front surface of the piston 6 by the input pressure Pe exceeds the force of the spring 13,

  so that the piston 6 is detached from the insert 14 and

  placed upwards against the stop formed by the cover 12 as soon as the inlet pressure Pe is slightly higher. Practically when the piston 6 is detached from the insert 14, the valve closing element 17 also rests on the valve seat 16, while the piston 6 only has to travel a very short distance to reach the cover 12 designed in the form of a stop. The piston 6 being detached from the insert 14, the valve 16, 17 is therefore closed, as is also the valve 1, 27. The dimensions of the spring 21 and the active area of the valve closing element 17 are calculated so that the valve 16, 17 only opens

  when the inlet pressure Pe reaches a significantly higher Pe2 value

  higher, equal to around 9 bars in this example. Up to the value Pe2, the outlet pressure Pa therefore maintains the lower value

  Pal = Pel 'As soon as the inlet pressure Pe exceeds the higher value

  Pe2, the pushing force applied to the valve closing element 17 by the inlet pressure Pe exceeds the force of the spring 21, which has the effect of opening the valve 16, 17 and allowing the pressure output Pa increase again linearly with the

  inlet pressure Pe 'Then, when the inlet pressure Pe drops again

  gradually ash from a value greater than Pe2 'the pressure curve shown in Figure 2 is traversed in reverse: when

  the inlet pressure Pe2 is reached, the valve 16, 17 closes, and when

  that the inlet pressure Pel is reached, it is opened again

by piston 6.

  The valve 1, 27 itself could be omitted for this operating mode. However, if necessary

  lower the outlet pressure Pa by abruptly reducing the pressure

  inlet pressure Pe, the lowering of the pressure on the outlet side may be delayed because the valve closing element 17

  Puts the piston 6 can't follow the pressure reduction fast enough

  input c8té because because of their mass and the load imposed

  by the spring, they both tend to move with a certain

  delay and vibrate (twists) when suddenly subjected to a pressure difference. Another delay is notably

  caused, at the piston 6, by the friction of the sealing ring

  7 and by its own friction in the bore 5.

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  The valve 1, 27 makes it possible to avoid the appearance of a delay in response of this type, because the valve closing element 27 reacts practically without delay due to its reduced mass and elasticity as well as its absence friction, which, in the event of a sudden drop in the inlet pressure Pe, makes it possible to reduce the outlet pressure Pa at a corresponding speed through the

  valve 1, 27 and the through axial channels made at the periphery

of the C-shaped ring 30.

  As shown in Figure 2, when the inlet pressure Pe

  increases, an outlet pressure greater than Pal = 1.6 bar does not appear

  when the inlet pressure Pe has exceeded the comparative value

  tively high of Pe2 = 9 bars, while the outlet pressure Pa

  is equal to the inlet pressure Pe until the inlet pressure

  very Pel is reached. This dependence between the outlet pressure Pa and the inlet pressure Pe is particularly desirable in a braking system of a motor vehicle whose front wheel brakes are supplied by a braking master cylinder, and whose wheel brakes rear are powered by an amplifier which is provided upstream of the brake master cylinder, and which, in its

  principle, includes a pressure advance. In practice, the dis-

  positive of the described valves would be installed between the amplifier and the rear wheel brake, and the higher value Pe2 of the inlet pressure Pe would be expected equal to the response pressure of the front wheel brake. These two brakes would therefore react to the same brake pressure. Similarly, if a brake pressure regulator is provided for identical front and rear brakes, the valve device described can be installed between the amplifier and the rear wheel brake. The lower Pel value is chosen to correspond to the pressure drop that occurs in the planned piping system

  downstream of the valve device described.

  When the valve device described is used to ele-

  ver the response threshold of a brake whose brake pressure is

  regulated by a pressure regulator parallel to the valve device

  ves, the pressure appearing on the outlet side of the valve device may exceed the inlet pressure Pe because the regulator of

  pressure provides additional pressure on the outlet side.

  Since, during use, before the pressure regulator is triggered, the inlet pressure Pe is greater than Pel, the piston 6 is already applied against the cover 12 when the pressure regulator is triggered, so that the piston 6 does not continue its course, even if the outlet pressure Pa and, therefore, the

  inlet pressure Pe increases, and the volume of the system, which is

  put to the effect of the additional hydraulic fluid under the action of the pressure regulator, remains constant. The pressure of the pressure regulator can therefore act without delay in the braking system. Of

  even an additional delay in the pressure regulation circuit

  does not affect the regulating action of the pressure regulator

  and therefore does not cause desensitization.

  In the event of assisted venting (venting by vacuum), care must be taken that the valve device remains in the open position to guarantee free flow of the liquid between the wheel cylinders and the reservoir. In this case, the surface of the piston 6 subjected to the effect of the vacuum acts in the

  same direction as the spring 23 and assists the latter in its function.

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Claims (6)

  1. Valve device intended to control an outlet pressure of a fluid as a function of an inlet pressure of this fluid,   while keeping said outlet pressure constant between a   their lower and upper value of said inlet pressure, comprising an inlet chamber and an outlet chamber, a first valve which can be switched as a function of the pressure and being located between said inlet chamber and said chamber outlet, the closing element of said first valve adopting the closed position under the action of a spring until said inlet pressure has reached the higher pressure value, and comprising a piston which is subjected to said inlet pressure against   the force of a spring, and which, until said pressure of in-   has reached the lower pressure value, blocks movement   closing element, produced by a spring, of a valve closing element, characterized in that said piston (6) delimits said inlet chamber (8), blocks the closing movement of said closing element (17) said first valve (16, 17) until said lower pressure value (Pel) has been reached, and is applied against a stop (12) as soon as said closure member (17) adopted its closed position.   2. Valve device according to claim 1, comprising   taking a second valve which is located in parallel to said first valve, between said inlet chamber and said   outlet, and which is open when said outlet pressure is   less than said inlet pressure, characterized in that said se-   conde valve (1, 27) is a grooved sealing cup.   3. Valve device according to claim 1 or 2,   characterized in that said closure element (17) of said pre-   the first valve (16, 17) is made of plastic.   4. Valve device according to any one of the   vendications 1 to 3, characterized in that in the open position, said   closing element (17) of said first valve (16, 17) is ap- -1: 2582074   bent, via an extension (19) provided on the inlet side, against the front surface of said piston (6) which is subjected to said inlet pressure (Pe)   5. Valve device according to claim 4, ca-   characterized in that said extension (19) is guided with clearance   the interior of an axial bore (15) of the valve housing (12, 3).   6. Valve device according to any one of the   vendications 1 to 5, characterized in that the side of said piston (6) subjected to the action of a spring and opposite to said inlet chamber (8) is connected to the atmosphere.