FR2537074A1 - PRESSURE CONTROL UNIT FOR A MOTOR VEHICLE BRAKING SYSTEM - Google Patents

Abstract

THE INVENTION RELATES TO A PRESSURE CONTROL UNIT INSERTED ON A BRAKE CIRCUIT OF A MOTOR VEHICLE AND INCLUDING A PRESSURE CONTROL VALVE INCLUDING A CONTROL PISTON 23 PUSHED BY PRESSURE AGAINST A SPRING 45 AND CLOSING A PASSAGE 35 FROM IT ON BY AN INTERVENTION PRESSURE BEYOND WHICH THE RISE OF THE OUTLET PRESSURE 19 IS REDUCED FROM THAT OF THE INLET 18. THE END OF THIS PISTON IS GUIDED IN A BLOCK HOLE 46 IN COMMUNICATION BY A LINE 47 WITH A PRESSURE-FREE FLUID TANK SUCH AS THE COMPENSATION TANK.

Description

The present invention relates to a pressure control unit for

  motor vehicle braking system, connected to a brake pressure generator and having at least one pressure control valve in which a valve passage for the pressure medium, located between an intake connected to the brake pressure generator and an output to a wheel brake, is controlled by a control piston displaceable according to the fluid pressure and a control force, which piston is movable in a sealed chamber with a seal against a pressure

  of fluid emitted by the brake pressure generator.

  Such a pressure control unit is known from US Patent No. 3,308,620. The known pressure control unit is located in a stepped bore in a housing and arranged at right angles to the axis of the bore. cylindrical brake pressure generator The control piston can be moved to the closed position, against the control force provided by a control spring taking a fixed support on the housing, until the shutter arranged on the control piston is in abutment-against the seat integral with the housing If the pressure supplied to the input of the brake pressure generator increases, the rise of the pressure of

  for example to a wheel brake is carried out first direc-

  As soon as the valve plug is applied to the seat, the different surfaces that the control piston applies to the pressure have the effect that, if the pressure still increases, the pressure growth rate is then lower at the outlet. At the inlet If the inlet pressure is decreased, a return flow valve opens

  communication from the exit room to the room of admission

  mission. By its end not turned towards the valve shutter,

  the control piston is guided with sealing in the small portion.

  the diameter of the stepped bore The chamber of this portion, limited by the end surface of the control piston, changes volume when

  the displacement of the control piston So that the movement of the piston

  control tone is only influenced by the control force pro-

  from the control spring and by the fluid pressure from the brake pressure generator and acting on the effective surfaces of the control piston, it is necessary that under the conditions

  of use, this room shall be free from overpressure or

  with respect to atmospheric pressure.

  Therefore, in the known pressure control unit, this chamber ends on the outer side of the housing and is separated from the atmosphere by an elastic membrane The closure of this chamber by the elastic membrane is however extremely subject

  If the membrane arranged externally on the body

  ter loses its sealing, by damage or by aging, there may be entry of dirt In addition, corrosion phenomena can occur in this chamber The displacement of the control piston to the closed position can be gene

  and, in some cases, be completely prevented, so that

  order is then compromised.

  The object of the present invention is to provide a pressure control unit of the kind mentioned at the beginning, having both a simple and compact structure, a high operational safety

  excellent control precision.

  According to the invention, this object is achieved by the fact that the chamber is in communication with another chamber which is at least partially filled with fluid and in which the pressure prevails.

  The chamber is thus filled with pressure fluid

  both at a volume displacement and having no pressure difference with respect to atmospheric pressure, a possible

  small pressure difference, hydrostatic in nature, being neglected

  gable A pressure or vacuum cushion, which affects the movement of the control piston, can not be established in the chamber. The movement of the control piston can no longer be compromised by corrosion or fouling. presence of fluid in this chamber improves the sliding of the control piston and therefore increases the control accuracy. The depth that the chamber must have in the axial direction of the control piston is determined by the displacement stroke. Advantageously, an extension of the chamber to the outer face of the housing thus becomes useless, so that we obtain a simple construction and

  The magnitude of a very small leak in the sealing area

  the control piston can then be adapted to

  slip decays, since the fluid of such a leak is sent

  to the fluid reserve of the other chamber.

  According to a development, the invention provides that the connection between the brake pressure generator and the pressure control unit is performed by integrating said control unit into a housing that includes the brake pressure generator, which

  I leads to a compact construction.

  In addition, it is expected that the pressure control unit

  and the brake pressure generator have a common housing.

  There is no need for any separate line between the pre control unit

  and the brake pressure generator, so that it is possible

  not only a compact achievement but also an improvement

reliability.

  In another embodiment, it is intended that the link

  sound between the brake pressure generator and the pressure control unit is achieved by braking the pressure control unit

  on an outer face of the brake pressure generator

  mutual contact faces on the outer faces of the pres-

  These two components are assembled to each other by removable assembly elements and can therefore be replaced individually. It is therefore possible to replace both the braking element and the pressure control unit in a simple and precise manner. then possible to arrange, in an extremely simple way, on the brake pressure generator,

  pre-assembled pressure control units, having

different control

  In another embodiment, it is intended that the pis-

  control tone can slide in the chamber by a

  In another advantageous embodiment, the control piston pre-

  feels two stepped portions as to its diameter and is mobile, with

these portions, in the room.

  In a particularly advantageous development, it is provided that the other chamber is a compensation tank arranged on the brake pressure generator. The compensation tank thus assumes a dual function with respect to the brake pressure generator and the brake pressure generator. pressure control unit The arrangement of another separate chamber is thus avoided As the pressure control unit and the compensation tank are both arranged

  on the brake pressure generator, it follows that the

  nication of the chamber with the compensation tank has only short ducts It is then advantageous to provide, as communication between the chamber and the compensation tank, a channel

  l opening into a hole communicating with the compensation tank.

  This channel can then open into a fluid passage hole, this hole leaving the compensation tank, or lead into a compensation hole through which the compensation tank can be placed in communication with a pressure chamber of the pressure generator.

braking.

  The other chamber may advantageously be an annular chamber which is in communication with the compensation reservoir via a fluid passage hole and sealed on both sides, this annular chamber being formed on an actuating piston.

  mobile in a cylindrical bore of the casing.

  a communication to the annular chamber, since the latter, arranged on the actuating piston, is itself in communication

  with the compensation tank.

  munication particularly short and easy to achieve.

  In another embodiment, there is provided a connecting duct between the chamber and the compensation tank. It is furthermore provided that the pressure control unit has two pressure control valves each assigned to a braking circuit. Another embodiment, the two control pistons are advantageously movable in a sealed common chamber In a particularly advantageous embodiment, it is intended to arrange, on the control piston, a shutter of

  valve that can be applied against an annular valve seat to the ex-

  tremity of a portion of the pressure chamber assigned to the admission,

  this portion surrounding the control piston, said chamber of pres-

  being delimited by a tubular body which carries the valve seat and has a bearing surface for the control piston, and it is provided that the control piston is guided, by its end on the intake side, into a blind hole constituting the sealed chamber. This tubular body can be made simply and economically, without resorting to machining by metal removal, in the form of a

  The number and size of milling operations

  The blind hole can be made in a simple and precise way It serves to guide the control piston The range on the tubular body, for the control piston, and its

  guidance, are ultimately simply and reliably

  of the pressure control unit is simplified.

  Also advantageous is an embodiment in the

  the tubular body is kept in tight contact against the

  side of the casing on the inlet side, by an element delimiting the chamber

  of pressure connected to the outlet Thus, the admission chamber and

  the exit chamber are defined with simple means.

  In a preferred embodiment, the valve seat is provided on an elastic annular body which, elastically prestressed, is applied against an inner end surface.

  located at the end that the tubular body has output side.

  A return flow arrangement having a particularly simple structure can be obtained by arranging the return flow channel between the outer surface of the annular body and the

  tubularinternal surface, and if so provided, as a

  return, a sealing lip belonging to the annular body

  and closing only in the direction of the exit chamber.

  It is recommended that the tubular body is made in two parts and then has, at both ends, bearings for the control piston, and that this tubular body penetrates, with sealing in the blind bore, by its open end located intake side The pressure control unit can then be inserted as a component or cartridge-shaped module into the housing

  of the brake pressure generator, so that the number of

  separated, individually mounted, is reduced.

  that the spring biasing the resilient annular body bears against the tubular body via an intermediate washer If the tubular body, the intermediate washer and the element constitute a component, it is then easy to mount The facility also possible if one end of a control spring providing the control force is applied against a spring support member, arranged at the end that the control piston has the output side, and if the other end of this spring

  This embodiment is applied against the tubular body.

  also to a pressure control unit having a compact structure. In another preferred embodiment, the invention provides for arranging, between the elastic annular body and the inner end surface of the tubular body, which constitutes in the

  sense of opening a first stop stop for the obturating organ

  valve, a support ring with a second stop

  to stop, in the closing direction, the valve shutter.

  This stop imposes a defined value on the diving depth of the valve plug in the elastic annular body, so that the premature wear of the elastic annular body constituting

the valve seat.

  In a timely development, the invention provides, as

  connection between the brake pressure generator and the compression unit

  pressure gauge, screw connection, allowing replacement

  easy of the pressure control unit.

  It is advantageous to arrange a fluid channel, comprising an axial portion and a radial portion, passing between the support ring and the tubular body. This results in a better behavior of the fluid return since the return flow essentially passes through.

  on the outer peripheral surface of the support ring.

  The different objects and characteristics of the invention

  will now be detailed in the description that follows, made

  by way of non-limiting example, with reference to the appended figures which represent: FIG. 1, a brake pressure generator seen in partial section; Figure 2 is an end view through the left end 1 of the generator according to Figure 1; Figure 3 is a sectional view taken along the line III-III of Figure 2, showing a pressure control unit; Figure 4, another embodiment of a pressure control unit; Figure 5 is a sectional view of a brake pressure generator with a pressure control unit having two pressure control valves; and FIG. 6 is a sectional view of a pressure control unit. The corresponding elements are endowed with the same

references.

  The brake pressure generator 1, shown in FIGS. 1 and 2, is designed as a tandem master cylinder for a two-circuit braking system.

  its housing 3, it can be fixed to the wall of the structure of a vehicle.

  hicule Said housing 3 has an axial cylindrical bore 4 in which are arranged a first actuating piston (not shown)

  and a second actuating piston 5 in the form of an internal piston

  The two pistons delimit a first pressure chamber, for the first braking circuit, and a second pressure chamber 7 for the second braking circuit Each chamber is associated,

  in the rest position, a pressure fluid inlet

  in the form of a compensation hole to a compensation tank (not shown) for the pressure medium.

  compensation holes, only the hole 9 is shown in FIG.

  Two outlets of each pressure chamber, namely the outlets 10, 11 and 12, respectively, can be connected to the brake cylinders

  wheels Each compensation hole ends in a hole

  cord 16, 17 which is arranged in a connection means 14, 15 of the housing and in which a tip of the compensation tank can be fixed. The axes of the connection holes 16, 17 are located in

  a plane and are perpendicular to the axis of the cylindrical bore 4.

  The respective outputs 10, 11; 12, 13 of the rooms

  have threaded holes in crankcase fittings

  to screw wheel brake connection elements.

  The right part of the partial cross-sectional representation of FIG. 1 shows a section taken along the line I-I, while the other cut part shows, the section plane being rotated, the endpiece

  of the output 13 of the housing for the second braking circuit.

  A pressure control unit according to FIG. 3 or 4 can be inserted into this output 13 of the brake pressure generator. The output 19 of this control unit can be connected to a wheel brake cylinder. A wheel brake cylinder can it is directly connected to the second output 12 of this braking circuit, without itterposition of a pressure control unit This arrangement is also found in the case of the first braking circuit The tips that the casing includes for the outputs 10, 11; 12, 13, and the axes of the threaded holes they comprise, are arranged relative to each other, and relative to the axis of the cylindrical bore 4, at right angles to the axes of the pressure fluid outlets, 10, 11;

  12, 13, however, are inclined by about 45 relative to the plane of

  ended by the axes of the holes 16, 17 for the tank connection

compensation.

  The pressure control unit shown in FIG. 3,

  this unit can be inserted into the end-pieces that the housing

  for the outputs 11, 13 of the brake pressure generator,

  There is an inlet 18 and an outlet 19 for the pressure medium.

  The inlet 18 goes to a pressure chamber 20 which is essentially delimited by a tubular body 21, an elastic annular body 22 arranged near the open end of the tubular body 21, and a cylindrical control piston. 23, as well as by the crankcase regions

  which close the other end of the tubular body 21.

  On the outlet side, the tubular body 21 has an end surface 25 provided with openings 24 and has, at its other end, a collar 26 whose end remote from the axis is folded. This end is tightly pressed, with sealing, against the housing 3 by a member 27 in the form of a threaded sleeve This element 27 delimits

  at the same time the pressure chamber assigned to the exit 19.

  Through its peripherally-radially inner surface, the elastic annular body 22 surrounding the control piston 23 defines an annular fluid channel 28, which channel a valve plug 30 formed on the control piston 23 can close under the effect of a displacement of this piston 23 Between the elastic ring body

  22 and the end surface 25 located on the end that the body tu-

  21 has the output side, is provided a support ring 31 The bore 34 of the support ring 31 is stepped, the smaller diameter portion being turned towards the elastic annular body 22 Via an intermediate element 33, a spring 32 maintains this elastic annular body 22 in contact with the support ring 31 The spring 32 is supported, by means of an intermediate washer 39, against the region of the housing on the inlet side Instead, this intermediate washer 39 can also be related to the tubular body

21 not shown.

  In addition, it can be provided that the intermediate washer 39,

  the tubular body 21 and the element 27 are mutually secured.

  A pressure fluid channel, 35, passes between the inner periphery of the bore 34 in the bearing ring 31 and the cylindrical surface

external control piston 23.

  The staggering of the bore 34 of the support ring 31 creates a stop which is conjugated to a stop on the control piston

  23, formed by an annular portion These stops limiting the displacement

  The operation of the control piston 23 in the closing direction has the effect of defining the diving depth of the valve shutter 30.

  in the annular body 22, in other words the compression of the annular body

  22 through valve shutter member 30.

  The mutually conjugate faces of the support ring 31 and the tubular body 21 have an interval defining a pressure fluid channel 36 that can be placed in communication with the chamber

  This interval is fixed by a relief, formed at the pressure of

  on the end surface of the tubular body 21 This depression fluid channel 36, communicates via the openings 24 in the end surface lo of the tubular body 21 with the outlet 19 It is further connected to a return flow channel 38 formed by recesses 37 in the outer peripheral surface of the support ring 31, this return channel 38 leading to a return flow valve 40 at the outer periphery of the elastic body 22 This return flow valve 40 is formed by a sealing lip 41 of the annular body 22 applied against the inner periphery of the tubular body 21, and allows the return flow of the pressure medium only if there is a pressure difference directed from the outlet 19 to the room of

  pressure 20 and, therefore, to the inlet 18.

  The control piston 23 is stepped and has a larger diameter portion and a smaller diameter portion. On the smaller diameter portion is provided the valve shutter 30.

  having two annular portions 42, 43 different diameters.

  The annular portion 42 with smaller diameter cooperates, during closure, with the elastic annular body 22, while the annular portion 43 with larger diameter abuts, on closing, against the bearing ring 31 and limits the displacement and, in the other direction,

  in the rest position, is applied against the tubular body 21.

  At the end of the control piston 23 located c 8 tee output

  there is arranged a spring support member 44 against which

  plicated the control spring 45 taking a fixed support on the crankcase.

  By its region located between the spring support member 44, and the closure

  30, the control piston 23 is guided in the opening of the end face.

  25 of the tubular body 21 The valve shutter 30 is thus inside the tubular body 21 By its other end,

  the control piston 23 is slidably guided and sealed

  relative to the pressure chamber 20, in a chamber 46 of the

  This chamber 46 is made in the form of a terminal hole

  This blind hole is part of a channel 47 which is in communication with another chamber at least partially filled with pressure medium, located on the brake pressure generator 1 and in which the

  atmospheric pressure is established. This "other chamber" is con-

  The path of the channel 47 is shown in FIG. 1. This channel 47 terminates in the compensation hole 59 which, for its part, establishes a communication between the compensation tank and an annular chamber 48 on the piston. intermediate 5, which is sealed against the pressure of the fluid in the pressure chambers of the tandem master cylinder by seals arranged on both sides In the same way, the chamber receiving the end of the piston of control of the valve

  control of the first braking circuit is connected to the

  thought of the first braking circuit During the displacement of the control piston 23, causing a change in the volume of the chamber 46> there is therefore a displacement without pressure of volume of the fluid since

  the compensation tank or to it.

  The pressure control unit described operates as described in the rest position shown, the control spring maintains the control piston 23 at its extreme position defined by the fact that the annular portion 43 abuts against the tubular body The inlet 18 and the outlet 19 communicate with each other via the pressure medium channels 28, 35 and 36 and the openings 24. In the event of an increase in the inlet pressure, the pressure goes to a certain level, engages on the pressure-actuatable effective surface (this surface having the diameter of the largest portion of the control piston) a force large enough to bring the control piston 23 to the closed position, by moving it

  against the force of the control spring 45.

  The end face of the end of the control piston 23 penetrating with sealing in the chamber 46 made in blind hole will certainly be unsolicited pressure since this chamber 46

  is in communication with the compensation tank connected to the

  From this pressure, called the intervention pressure, the pressure rise rate at the outlet 19 is less than at the inlet. Any pressure that the pressure generator produces at the inlet 18 and which is greater than the pressure In the case of a decrease in pressure 3 at the inlet 18, the pressure at the outlet 19 causes a reduced pressure in the ratio of the surfaces of the control piston 23 that can be urged by pressure. and in the wheel cylinder

  associated is reduced via the return valve 40.

  The pressure control unit shown in FIG. 4 corresponds, in principle, to the control unit according to FIG.

  and has the same mode of action In this realization, the body

  The first part 52 of the tubular body 51, turned towards the control spring 45, corresponds to the tubular body 21 of FIG. 3. The second part 53 is made in the form of a pot and has, at one end, a collar 54 by which it is applied against the flange 26 of the first part 52 On the second part 53 is formed a bearing surface for the intermediate washer 39 against which the spring 32 bears In a portion succeeding the previous one, it is provided a sealing member for

  the control piston 23, which is slidably guided in the

  the second part of the second part

  The end surface of the end portion of this second portion 53 of the tubular body 51 is open, so that the end surface of the control piston 23 is inserted sealingly into the chamber 46 in the form of a blind hole. lies, via the

  channel 47, in connection with the pressure medium, with the reservoir

  The second part 53 of the tubular body 51 pos-

  In this embodiment, the pressure control valve can be inserted as a pre-assembled component having the shape of an opening 55 through which its internal volume acting as a pressure chamber 20 is in communication with the inlet 18. a cartridge in the housing 3 of the brake pressure generator and to be held by the element 27 made in the form of a threaded sleeve. This channel 47 connecting the chamber 46 to a chamber containing fluid at atmospheric pressure may also, in a manner not shown, open into the compensation hole which, when the brake pressure generator is in the rest position, connects the reservoir of compensation to a generator pressure chamber

braking pressure.

  The chamber 46 can also be connected to the reservoir

  thought by a liaison pipe.

  FIG. 5 shows a pressure control unit with two pressure control valves, which is integrated in the housing 103 of a brake pressure generator 101 constituted by

  in tandem master cylinder The design and mode of operation

  The two pressure control valves, which are of identical design, are known per se from the German patent application DE-OS.

29 30 436.

  The pressure control valves are arranged coaxially, in opposite directions, in a common bore 108 which is arranged parallel to the cylindrical bore 104 of the brake pressure generator 101. The ends of the two control pistons 123, 123 'of the valves pressure control device enter a common chamber 146 located between the pressure control valves and constituted by a portion of the bore 108 This chamber 146 is closed, by means of

  sealing means, vis-à-vis the fluid pressures that the general-

  braking pressure transmitter sends via admissionsl 18, 118 'The

  control force acting on the ends of the two compression pistons

  Mande 123, 123 'is provided by a common control spring 145 arranged in the chamber 146 between the ends of the control pistons 123, 123' A spacer sleeve 180 sets the axial distance of the

two control valves.

  According to the invention, the chamber 146 is connected, via a channel 147, to an annular chamber 148, sealed from both sides, arranged on an actuating piston 105 of the tandem master cylinder, this piston 21 being The channel 147 opens into an annular enlargement 181 of the chamber 146 and is in fluid communication with the chamber 146 via holes.

  182 in the spacer sleeve 180 For its part, the annular chamber

  148 is in communication via the compensation hole 159 with

  the compensation tank not shown.

  When the pressure control valves execute a

  control, the displacement of the ends of the two control pistons 123, 123 'in the chamber 146 causes a change in the volume of this chamber 146 It follows a displacement, substantially without pressure, fluid volume from or to the reservoir compensation connected to the atmosphere, this displacement taking place via the channel

  147, the annular chamber 148 and the compensation hole 159.

  FIG. 6 shows another embodiment of a pressure control unit intended to be connected to a brake pressure generator whose design and operation are known per se.

  by the German patent application DE-OS 2 26 499.

  The stepped control piston 223 is guided with sealing in bore portions by a smaller diameter region and a larger diameter region. Between the bore portions a radially limited chamber 246 is provided. on the other hand, by the portions of the control piston and, on the other hand, by the casing is sealed with respect to the fluid pressure prevailing in the inlet 18 and the outlet 219 of the control unit.

pressure control.

  When the pressure control valve executes a control process, the control piston 223 moves, with its parts of different diameters, in the chamber 246 so that the volume thereof varies. According to the invention, this chamber 246 is connected by an opening 270 and unrepresented connections to another chamber at least partially filled with fluid, constituted for example by a compensation tank of the pressure generator

  The atmospheric pressure prevails in this "other room".

  Thus, during a control process, a substantially fluid-free displacement is produced via the opening 270 and the

  connections, this displacement taking place to or from the fuel tank

  thought of the brake pressure generator.

  It is obvious that the foregoing descriptions have

  given as a non-limitative example and that many variants can be envisaged without departing from the scope

of the invention.

Claims (16)

  1 pressure control unit for a motor vehicle braking system, connected to a brake pressure generator and having at least one pressure control valve in which a valve passage for the pressure medium, located between an intake connected to the brake pressure generator and an output going to a wheel brake, is controlled by a control piston displaceable according to the pressure of the fluid and a control forci, this piston being movable in a closed chamber with sealing screw- a pressure of fluid emitted by the brake pressure generator, characterized in that the chamber (46, 146, 246) is in communication with another chamber which is at least partially filled with fluid and which prevails the atmospheric pressure <2 pressure control unit according to claim 1, characterized in that the connection between the brake pressure generator (101) and the unit pressure control is performed by integrating said pressure control unit into a housing   that includes the housing of the brake pressure generator (1, 101).   3 Pressure control unit according to any one of   preceding claims, characterized in that this unit of   pressure control and brake pressure generator (1, 101)   have a common housing (3, 103).   4 pressure control unit according to claim 1, characterized in that the connection between the brake pressure generator and the pressure control unit is performed by clamping the pressure control unit on an outer face of the generatrix. braking pressure.   Pressure control unit according to any one of   preceding claims, characterized in that the control piston   (23, 123, 123 ') can slide in the chamber (46, 146) by a terminal portic. 6 Pressure control unit according to any one of   previous versions, characterized in that the control piston   of (223) has two stepped portions as to its diameter, and   it is mobile, with these portions, in the room (246).   7 Pressure control unit according to any one of   preceding claims, characterized in that the other chamber   is a compensation tank arranged on the pressure generator braking (1, 101).   Pressure control unit according to claim 7,   characterized in that it is provided as communication between the room   (46, 146) and the compensation tank, a channel (47, 147)   opening into a hole in communication with the compensation tank   tion. 9 pressure control unit according to claim 8, characterized in that the channel (47) opens into a through hole   fluid (59), this hole from the compensation tank.   Pressure control unit according to claim 8,   characterized in that the channel (47) opens into a compensating hole   tion by which the compensation tank may be placed in   nication with a pressure chamber of the pressure-braking generator. 11 Pressure control unit according to any one of   preceding claims, characterized in that the other chamber   is an annular chamber (148) in communication with the compensating reservoir via a fluid passage hole (159) and sealing on both sides, this chamber being formed on an actuating piston ( 105) movable in a cylindrical bore (104) in the housing (103).   Pressure control unit according to claim 7,   characterized in that a connecting conduit is provided between the chamber   (246) and the compensation tank.   13 Pressure control unit according to any one of   preceding claims, characterized in that it has   two pressure control valves each assigned to a circuit braking.   Pressure control unit according to Claim 13, characterized in that the two control pistons (123, 123 ') are   movable in a sealed common chamber (146).   15 Pressure control unit according to any one of   preceding claims, characterized in that on the piston of   control (23) is arranged a valve shutter (30) which can be applied against an annular valve seat at the end of a portion of the pressure chamber (20) assigned to the inlet (18), this portion surrounding the control piston (23), said pressure chamber (20) being delimited by a tubular body (21, 51) which carries the valve seat and has a seat for the control piston (23), and in that the control piston (23) is guided, by its end on the intake side, in a blind hole constituting the sealed chamber (46).   Pressure control unit according to claim 1, characterized in that the tubular body (21, 51) is held in sealing contact against the region of the inlet-side housing by an element (27) delimiting the pressure chamber connected to the the release (19).   17 Pressure control unit according to any one   of the preceding claims, characterized in that the seat of   valve is arranged on an elastic annular body (22) which, elastically precontracted, is applied against an inner end surface located at the end that the tubular body (21, 51) has the output side. 18 Pressure control unit according to any one of   of the preceding claims, characterized in that one end   of a control spring (45) -providing the command force is   applied against a spring support member (44) arranged at the end   the control piston (23) has an outlet side, and that the other end of this spring is applied against the tubular body (21, 51).   19 Pressure control unit according to any one of   of the preceding claims, characterized in that a flow   back, in a return flow arrangement, passes between the outer surface of the annular body (22) and the inner surface of the   tubular body (21,51), and in that it is provided as a check valve   back (40), a sealing lip (41) belonging to the body   annular (22) and closing only in the direction of the outlet chamber.   Pressure control unit according to any one   of the preceding claims, characterized in that the body   bulaire (51) is made in two parts, in that it has, at its two ends, bearings for the control piston (23), and in that it penetrates, with sealing, in the blind bore , this by   its open end located on the intake side.   21 Pressure control unit according to any of the   preceding claims, characterized in that there is, between   elastic annular body (22) and the inner terminal surface TO of the tubular body (21, 51), which constitutes in the opening direction a first stop for the valve shutter member (30), an annulus support (31) which has a second stop, in the closing direction, for the valve shutter ( 30).   22 Pressure control unit according to any one of   of the preceding claims, characterized in that the spring   (32) biasing the resilient annular body (22) bears against   the tubular body (21, 51) by means of an internal washer mediator (39).   23 Pressure control unit according to any one of   of the preceding claims, characterized in that the tubular body   (21, 51), the intermediate washer (39) and the element (27). constitute a component.   24 Pressure control unit according to any one of   of the preceding claims, characterized in that it is provided   as a connection between the brake pressure generator and the unit   pressure control, screw connection.   Pressure control unit according to claim 21, characterized in that a fluid channel (36, 38) having an axial portion and a radial portion passes between the support ring   (31) and the tubular body (21, 51).