WO2017109329A1

WO2017109329A1 - Cooling and lubrication system for a piston sealing device

Info

Publication number: WO2017109329A1
Application number: PCT/FR2016/053342
Authority: WO
Inventors: Vianney Rabhi
Original assignee: Vianney Rabhi
Priority date: 2015-12-24
Filing date: 2016-12-12
Publication date: 2017-06-29
Also published as: FR3046205B1; FR3046205A1

Abstract

The invention relates to a cooling and lubrication system (1) for a piston sealing device (2) for a piston (3) comprising a fixed skirt (7) and a sliding skirt (12) which are connected to one another by a mechanical inter-skirt connection (13) so as to axially compress a continuous extendable segment (15) by the action of a sliding skirt spring (20), said system (1) adding a sliding skirt stop ring (21) to the device (2) such as to insert a flow control valve (22) between the fixed skirt (7) and the continuous extendable segment (15), through which valve the mechanical inter-skirt connection (13) extends. At rest, the valve (22) is kept at a distance from the fixed skirt (7) by a valve return spring (30), said valve comprising a flow calibration port (27).

Description

COOLING SYSTEM AND LUBRICATION

FOR SEALING DEVICE FOR PISTON

The present invention relates to a cooling and lubrication system for a piston sealing device. Said invention is an improvement of the piston sealing device subject of the patent application FR 3009037 dated July 23, 2013 belonging to the applicant. Said device is particularly suitable for any piston operating under high pressure. The piston sealing device according to the patent application FR 3009037 is provided for a piston operating in a cylinder whose one end is closed by a fluid chamber, said piston comprising at least one piston head which comprises at least a fixed skirt, said head having on the one hand a plunger bearing face for exerting a force on any mechanical, hydraulic or pneumatic transmission means and, on the other hand, a compression face opening into the fluid chamber and able to receive the pressure of a fluid.

Still according to the patent application FR 3009037, the piston sealing device comprises a sliding skirt of cylindrical shape housed in a cylinder with a small clearance. Said skirt is further placed in the extension of the piston head on the side of the piston. compression side and in the axis of said head.

It is noted that said sliding skirt is connected to said head by an inter-skirt mechanical connection which allows it to move in longitudinal translation relative to said head while a pressure transmission channel arranged inside the sliding skirt crosses the latter from side to side in the axial direction.

The invention of the patent application FR 3009037 is also characterized by an extensible continuous ring-shaped continuous segment which is interposed between the fixed skirt and the sliding skirt. Said segment comprises an internal cylindrical segment face subjected to the pressure of the fluid via the pressure transmission channel, an outer cylindrical segment face that can come into contact with the cylinder, a fixed skirt-side segment axial face maintained directly or indirectly by sealing contact with the fixed skirt and an axial side segment sliding skirt side directly or indirectly in sealing contact with the sliding skirt. Finally, the invention relating to the patent application FR 3009037 is also characterized by a sliding skirt spring which tends to bring the sliding skirt closer to the fixed skirt and compress axially the continuous segment extensible or at least, which prohibits said slippery skirt to move away from the fixed skirt like a stop.

When reading patent FR 3009037, it is understood that the maximum leakage rate of fluid flowing between the piston and the cylinder is found when the pressure in the fluid chamber is sufficiently high to maximize the flow of fluid passing through. in the game left between the sliding skirt and the cylinder, but not yet high enough that the extensible continuous segment is plated in circumferential contact with the cylinder, which achieves almost complete sealing. Thus, according to the piston sealing device according to the patent application FR 3009037, a leak therefore remains transiently between the piston and the cylinder. This leak is in addition to that which occurs during the low-pressure phase found during the discharge stroke of a hydraulic motor or during the suction stroke of a hydraulic pump. Indeed, during said phase, the extensible continuous segment is parked and does not perform any other seal than that constituted by the restriction of fluid passage that forms the game left between said segment and the cylinder.

This leak is necessary for the lubrication and cooling of the extensible continuous segment on the one hand, and the piston on the other hand.

Depending on the type of pump or hydraulic motor to which the piston sealing device is addressed according to the patent application FR 3009037, the need for lubricating and cooling fluid may vary, in particular according to the importance of the effort radial force exerted by the piston on the cylinder.

Indeed, the greater the effort, the greater the energy dissipated by friction and shearing oil at the interface between the piston and the cylinder, is important. To evacuate said energy, sufficient circulating oil is required.

In addition, the need for lubricating oil tends to increase with said effort because it is necessary in all circumstances to ensure a sufficient thickness of the oil film which separates the piston and the cylinder, so as to prevent any metal-metal contact between said piston and said cylinder.

Furthermore, it will be noted that certain pumps or hydraulic motors comprise mechanical parts which are positioned opposite the fluid chamber receiving the fluid under pressure and which are lubricated and / or cooled by the leakage flow passing between the piston. and the cylinder.

The tight seal of the piston sealing device according to the patent application FR 3009037 may, as the case may be, cause a problem of insufficient lubrication flow and / or cooling for both the piston itself and for any parts mechanical means with which said piston cooperates.

One solution would be to place in various places of the pump housing or hydraulic motor one or more oil injectors to lubricate and / or cool the components that have just been listed. The problem is that such injectors inevitably complicate the hydraulic pump or the hydraulic motor that receives them. In addition, the lubrication of the piston in its cylinder may still be insufficient because the oil flow supplied by such injectors must reach parts of the cylinder made inaccessible by the piston.

The cooling and lubrication system for a piston sealing device according to the invention is therefore mainly intended for hydraulic pumps and motors equipped with the piston sealing device according to the patent application FR 3009037, the flow rate of cooling fluid and lubrication has become insufficient because of the tightness achieved by said device.

As such, depending on the type of application, the cooling and lubrication system for piston sealing device according to the invention allows, depending on its embodiment:

• Generate a significant amount of lubricating and cooling oil leakage at the cost of a minimum reduction in the volumetric and energy efficiency of the hydraulic pump or hydraulic motor that receives it;

• Avoid installing a lubricating or cooling injector (s) in the sump of any pump or hydraulic motor that receives the piston sealing device according to the patent application FR 3009037;

• Provide a flow of lubricating oil and cooling at the interface between the piston and the cylinder, in areas usually inaccessible to the jet of oil of an oil injector;

• To increase only marginally the manufacturing cost of the pump piston or hydraulic motor that receives the piston sealing device according to the patent application FR 3009037.

It is understood that besides its application to hydraulic pumps and hydraulic motors with axial or radial pistons, the cooling and lubrication system for a piston sealing device according to the invention can be applied to any other pump, motor, motor -pump or hydraulic or pneumatic cylinder whose configuration advantageously allows to operate said system.

The other features of the present invention have been described in the description and in the dependent claims directly or indirectly dependent on the main claim.

The cooling and lubricating system according to the present invention is provided for a piston sealing device, the latter being itself provided for a piston operating in a cylinder so as to constitute a fluid chamber, said piston comprising a piston head which comprises a fixed skirt and which has, on the one hand, a plunger bearing face for exerting a force on transmission means and, on the other hand, a compression face opening into the fluid chamber to receive the pressure of a fluid while a sliding skirt is housed in the cylinder with a small clearance, in the extension of the piston head on the side of the compression face and in the axis of said head, said sliding skirt being connected to said head by a mechanical inter-skirt connection, however, that a pressure transmission channel is arranged inside the sliding skirt and crosses the latter from one end to the other in the axial direction , the piston sealing device also comprising an extensible continuous segment interposed between the fixed skirt and the sliding skirt, said segment comprising an internal cylindrical segment face subjected to the pressure of the fluid via the pressure transmission, an outer cylindrical segment face that can contact the cylinder, a fixed skirt-side segment axial face held directly or indirectly in sealing contact with the fixed skirt, and an axial side segment of a sliding skirt segment maintained directly or indirectly in leaktight contact with the sliding skirt while a sliding skirt spring tends to bring the sliding skirt closer to the fixed skirt and compress axially the extensible continuous segment, said system comprising:

• At least one slide skirt ring stopper which prevents the sliding skirt from moving away from the piston beyond a certain distance;

• At least one flow valve axially traversed and more or less sealed by the inter-skirt mechanical connection and interposed between the extensible continuous segment and the piston head, said valve comprising firstly, an axial face of the valve head side plunger which has a circular flow closure range, the latter defining with a valve contact surface arranged on the compression face a circular contact line whose diameter is significantly smaller than that of the cylinder, said valve comprising second part, an axial slider-side valve-facing side held directly or indirectly in sealing contact with the expandable continuous segment, said valve comprising thirdly, a flow calibration orifice which passes axially through said valve; At least one intermediate fluid outlet chamber whose volume is formed inside the circular contact line by the axial face of the valve on the piston head side, by the compression face and by the external surface of the piston. inter-skirt mechanical connection; · At least one valve return spring that tends to move the flow valve away from the piston head.

The cooling and lubricating system according to the present invention comprises a valve return spring which acts as a sliding skirt spring. The cooling and lubricating system according to the present invention comprises a flow calibration orifice which consists of the clearance left between the flow valve and the inter-skirt mechanical connection. The cooling and lubricating system according to the present invention comprises a valve return spring which is housed inside the intermediate fluid outlet chamber.

The cooling and lubrication system according to the present invention comprises a slidable skirt spring which is housed inside a spring cup arranged or attached in the sliding skirt.

The cooling and lubricating system according to the present invention comprises a sliding skirt ring abutment which is traversed right through by at least one fluid passage opening.

The cooling and lubricating system according to the present invention comprises an outer cylindrical face of the piston head which has a circular decompression groove which limits the tightness of said head.

The following description with reference to the accompanying drawings and given by way of non-limiting example will better understand the invention, the features it has, and the benefits it is likely to provide:

Figure 1 is a schematic sectional view of a variable displacement axial piston hydraulic pump whose pistons receive the cooling system and lubrication according to the invention. Figure 2 is a schematic sectional view of the cooling system and lubrication according to the invention.

Figure 3 is a schematic sectional view of the cooling and lubrication system according to the invention, the valve return spring acts as sliding skirt spring. Figures 4 and 5 are schematic sectional views that illustrate the operation of the cooling system and lubrication according to the invention, the pressure in the fluid chamber being respectively low and high. Figure 6 is a three-dimensional view of an assembled piston which is equipped with the cooling and lubricating system according to the invention, and the piston sealing device which it perfects.

Figure 7 is an exploded three-dimensional view of a piston which is equipped with the cooling and lubrication system according to the invention, and the piston sealing device that it perfects.

DESCRIPTION OF THE INVENTION: Figures 1 to 7 show the cooling and lubricating system 1 for the piston sealing device 2, various details of its components, its variants, and its accessories.

The cooling and lubricating system 1 is provided for a piston sealing device 2, the latter being itself provided for a piston 3 operating in a cylinder 4 so as to constitute a fluid chamber 5, said piston 3 comprising a head piston 6 which has a fixed skirt 7 and which has, on the one hand, a piston bearing face 8 for exerting a force on transmission means 9 and on the other hand, a compression face 10 opening into the chamber fluid 5 for receiving the pressure of a fluid 1 1.

The piston sealing device 2 to which the cooling and lubricating system 1 according to the invention applies further comprises a sliding skirt 12 which is housed in the cylinder 4 with a small clearance, in the extension of the piston head. 6 on the side of the compression face 10 and in the axis of said head 6, said sliding skirt 12 being connected to said head 6 by an inter-skeletal mechanical connection 13 while a pressure transmission channel 14 is arranged at the inside of the sliding skirt 12 and crosses the latter from one side to the other in the axial direction.

The piston sealing device 2 to which the cooling and lubricating system 1 according to the invention applies also comprises a segment continuously extending strut 15 interposed between the fixed skirt 7 and the sliding skirt 12, said segment 15 comprising an internal cylindrical segment face 16 subjected to the pressure of the fluid 1 1 via the pressure transmission channel 14, an outer cylindrical segment face 17 can contacting the cylinder 4, an axial face of the fixed skirt segment segment 18 held directly or indirectly in sealing contact with the fixed skirt 7 and an axial side segment sliding skirt side 19 maintained directly or indirectly in sealing contact with the sliding skirt 12 even though a sliding skirt spring 20 tends to bring the sliding skirt 12 closer to the fixed skirt 7 and to axially compress the extensible continuous segment 15.

As shown in FIGS. 1 to 5 and FIG. 7, the cooling and lubricating system 1 for a piston sealing device 2 according to the invention comprises at least one sliding skirt ring stop 21 which prevents the sliding skirt 12 to move away from the piston 3 beyond a certain distance;

FIGS. 1 to 7 illustrate that the cooling and lubricating system 1 for a piston sealing device 2 according to the invention comprises at least one flow valve 22 traversed axially and more or less tightly sealed by the inter-skid mechanical connection 13 and interposed between the continuous expandable segment 15 and the piston head 6.

Said valve 22 comprises, firstly, an axial piston-head-type valve face 23 which has a circular flow closure surface 24, the latter defining with a valve contact surface 26 arranged on the compression face 10 a nip circular 25 whose diameter is significantly smaller than that of the cylinder 4.

Said valve 22 comprises, on the other hand, an axial sliding-side valve face 28 held directly or indirectly in sealing contact with the extensible continuous segment 15.

Said valve 22 comprises thirdly, a flow calibration orifice 27 which passes through said valve 22 from one side to the other in the axial direction.

Note that according to a particular embodiment of the cooling and lubricating system 1 according to the invention, the flow valve 22 can be maintained radially centered in the cylinder 4 by the interjupes mechanical connection 13 around which it is mounted at low clearance, while the outer cylindrical surface of said valve 22 remains at a distance from the inner wall of the cylinder 4 without ever coming into contact with said wall.

As is evident from FIGS. 1 to 5, the cooling and lubricating system 1 for a piston sealing device 2 according to the invention comprises at least one intermediate fluid outlet chamber 29 whose volume is formed the inside of the circular contact line 25 - by the axial face of the valve on the piston head side 23, by the compression face 10 and by the external surface of the inter-skirt mechanical connection 13.

Finally, FIGS. 1 to 5 and FIG. 7 show that the cooling and lubricating system 1 for a piston sealing device 2 according to the invention comprises at least one valve return spring 30 which tends to move the flow valve away from the valve 22 of the piston head 6.

FIG. 3 illustrates that the cooling and lubricating system 1 for a piston sealing device 2 according to the invention provides that the valve return spring 30 can act as a sliding skirt spring 20.

In fact, the valve return spring 30 tends to bring the flow valve 22 closer to the sliding skirt 12 and to axially compress the extensible continuous segment 15 between said valve 22 and said skirt 12 as is provided by the device sealing ring for the piston according to the patent application FR 3009037.

This substitution can be acceptable especially when the cooling and lubricating system 1 for piston sealing device 2 according to the invention applies to certain hydraulic pumps.

As a variant, the flow calibration orifice 27 may consist of the clearance left between the flow valve 22 and the inter-skirt mechanical connection 13, said clearance being calculated to allow the fluid flow rate 1 1 desired to be passed since the fluid chamber 5 to the fluid outlet intermediate chamber 29.

FIGS. 1 to 5 and FIG. 7 illustrate that the valve return spring 30 can be housed inside the intermediate fluid outlet chamber 29, said spring 30 being of helical type, compression, traction or torsion, consisting of one or more "Belleville" washers stacked in series or in parallel, or of a type known to those skilled in the art. As shown in FIGS. 1, 2, 4, 5 and 7, the sliding skirt spring 20 can be housed inside a spring cup 31 fitted or attached in the sliding skirt 12, said spring 30 being able to be helical type, compression, traction or torsion, consisting of one or more "Belleville" washers stacked in series or in parallel, or of a type known to those skilled in the art.

It is particularly visible in FIGS. 4 and 5 that according to the cooling and lubricating system 1 for a piston sealing device 2 according to the invention, the sliding skirt ring abutment 21 can be traversed right through by at least one fluid passage opening 32 which allows the fluid 1 1 contained in the fluid chamber 5 to pass freely through said abutment 21 to, on the one hand, exert pressure on the inner cylindrical segment face 16 and on the other hand , cool and lubricate the piston 3 by opening from the intermediate fluid outlet chamber 29 after having entered the latter notably via the flow calibration orifice 27.

As can be seen in FIGS. 2 to 7, the outer cylindrical face of the piston head 6 may have a circular decompression groove 33 which limits the sealing of said head 6, which favors the operation of the continuous expandable segment 15, said circular groove 33 which - according to a particular embodiment of the articulated hitch 1 according to the invention - cooperate with at least one axial decompression groove 34 as shown in Figures 6 and 7 which connects said circular groove 33 with the face d piston support 8.

It is noted that advantageously, the axial decompression groove 34 may be helical to distribute the bearing pressure exerted by the outer cylindrical face of the piston head 6 on the cylinder 4.

OPERATION OF THE INVENTION: The operation of the cooling and lubrication system 1 for the piston sealing device 2 according to the invention is easily understood from FIGS. 1 to 7. Figure 1 shows the cooling and lubrication system 1 applied to a variable displacement axial piston hydraulic pump 35 known per se. It will be noted that the pistons 3 of said pump 35 are naturally equipped with the piston seal 2 which is the subject of the patent application FR 3009037 which is perfected by the cooling and lubricating system 1 according to the invention.

When a transmission shaft 36 that has said pump 35 is rotated by a drive source not shown, said shaft 36 in turn drives a barrel 37 in rotation, the latter being integral with said shaft 36.

When a tilt plate 38 provided by said pump 35 tilts, concomitantly, the pistons 3 of said pump 35 start to go back and forth in the cylinder 4 with which they cooperate. As a result, said pistons 3 suck up fluid 1 1 in an intake duct 39 which is supplied with said fluid 11 at a low pressure of, for example, 10 bar, and then expel said fluid 11 into a delivery pipe 40 in wherein said fluid 11 is brought to a pressure of, for example, four hundred bar. In accordance with the patent application FR 3009037 relating to the piston sealing device 2, the extensible continuous segment 15 of each piston 3 passes successively from the parked state when the pressure prevailing in the fluid chamber 5 with which it cooperates is ten bars in the sealed contact state with the cylinder 4 when the pressure in said chamber 5 is four hundred bars.

The tight seal that the extensible continuous segment 15 achieves with the cylinder 4 when the pressure in the fluid chamber 5 is four hundred bars allows only a very small amount of fluid to flow between said segment 15 and said cylinder 4. same, when the pressure prevailing in the fluid chamber 5 is only ten bars, although said segment 15 is parked, the small clearance left between the sliding skirt 12 and the cylinder 4 on the one hand, and between the segment continuous extensible 15 and the same said cylinder 4 on the other hand, leaves only very little fluid 1 1 to escape from the fluid chamber 5 via the clearance left between the piston 3 and the cylinder 4. However, the cooling and lubrication of the piston 3 may require more fluid 1 1 than let the continuous continuous segment 15 and the sliding skirt 12 with which it cooperates. This is why - as is clearly illustrated in FIG. 4 - according to the cooling and lubricating system 1 according to the invention, it is permissible for additional fluid 1 1 to pass directly from the fluid chamber 5 to the space that constitutes the clearance left between the piston 3 and the cylinder 4 without passing either by the clearance left between the sliding skirt 12 and the cylinder 4, nor by that left between the continuous continuous segment 15 and the same said cylinder 4.

According to the cooling and lubrication system 1 according to the invention, said additional fluid 1 1 can indeed pass successively via the fluid passage opening 32 arranged in the sliding skirt ring stop 21, the pressure transmission channel 14 , the flow calibration orifice 27, the intermediate fluid outlet chamber 29 and the clearance left between the circular flow closure surface 24 and the valve contact surface 26. Note that this last set exists only when the pressure in the fluid chamber 5 is low, in the vicinity of only ten bars according to the example retained here.

Indeed, as illustrated in Figure 4, when the pressure in the fluid chamber 5 is low, the force exerted by the pressure of the fluid 1 1 on the axial face of the sliding skirt valve side 28 is less than 1 the force exerted by the valve return spring 30 on the axial face of the valve on the piston head side 23.

As a result, the flow valve 22 remains remote from the piston 3 and the clearance left between the piston 3 and the cylinder 4 is supplied with fluid 1 1 for cooling and lubricating the piston 3. It is noted that the diameter and the length of the the flow calibration orifice 27 are provided to produce the pressure drop required to obtain the desired fluid flow rate at low pressure.

It will also be noted that the force exerted by the pressure of the fluid 11 on the axial face of the sliding skirt-side valve 28 corresponds approximately to the product of the pressure of said fluid 11 by the area of the section of the cylinder 4 minus the defined by the interior of the circular flow closing range 24. Thus, the pressure prevailing in the fluid chamber 5 above which the flow valve 22 is closed - i.e. above which the circular flow closure surface 24 is in contact with the contact surface valve 26 - depends on the relationship between the tare and the stiffness of the valve return spring 30 on the one hand, and the area defined by the inside of the circular flow closing range 24 on the other hand.

It is understood that at low pressure, the continuous extensible segment 15 is kept strongly compressed between the flow valve 22 and the sliding skirt 12 because the force produced by the valve return spring 30 is significantly greater than that produced by the spring. sliding skirt 20.

As soon as the pressure in the fluid chamber 5 exceeds the threshold of displacement of the flow valve 22 - as illustrated in FIG. 5, the sliding skirt 12 takes off from the sliding skirt ring stop 21 and the extensible continuous segment 15 is held compressed only by the sliding skirt spring 20. Said segment 15 can then operate in conditions identical to those provided by the piston sealing device 2 as described in the patent application FR 3009037.

If the cooling and lubricating system 1 according to the invention is provided so that the force exerted by the fluid pressure 1 1 on the axial face of the sliding skirt valve 28 becomes greater than the force exerted by the spring of valve reminder 30 on the axial face of the valve on the piston head side 23 from a pressure of fifteen bar prevailing in the fluid chamber 5 and that, taking into account the stiffness of the valve return spring 30, the valve of flow 22 is completely closed at twenty-five bars, then fluid 1 1 for cooling and lubricating the piston 3 will pass through the flow calibration orifice 27 when the pressure in the fluid chamber 5 is included between a few millibars and twenty-five bars.

Also, the ratio between the fluid flow 1 1 cooling and lubrication on the one hand, and the pressure in the fluid chamber 5 on the other hand, is well fixed by the pressure drop that constitutes the orifice of flow calibration 27 to which is added the sum of the pressure losses encountered on its path between the fluid chamber 5 and the outlet of the cylinder 4 opposite said chamber 5, by the fluid 1 1 debiting. It is noted that the total energy lost due to said flow fluid 1 1 remains in all cases low because the pressure at which said flow rate remains low.

Thus, the cooling and lubrication system 1 for a piston sealing device 2 according to the invention makes it possible to provide the piston 3 with significant additional cooling and lubrication at a lower energy cost, without jeopardizing the almost complete seal. -perfect and the low friction losses of the piston sealing device 2 as provided in the patent application FR 3009037.

The cooling and lubrication system possibilities 1 for piston sealing device 2 according to the invention according to the invention are not limited to the applications which have just been described and it must also be understood that the description which precedes has been given as an example and it does not limit the scope of said invention which would not be out by replacing the execution details described by any other equivalent.

Claims

CLAIMS Cooling and lubrication system (1) for a piston sealing device (2), the latter being provided for a piston (3) operating in a cylinder (4) so as to constitute a fluid chamber (5), said piston (3) comprising a piston head (6) which comprises a fixed skirt (7) and which has, on the one hand, a piston bearing face (8) for exerting a force on transmission means (9) and on the other hand, a compression face (10) opening into the fluid chamber (5) to receive the pressure of a fluid (1 1) while a sliding skirt (12) is housed in the cylinder (4) with a slight clearance, in the extension of the piston head (6) on the side of the compression face (10) and in the axis of said head (6), said sliding skirt (12) being connected to said head ( 6) by an inter-skirt mechanical connection (13) while a pressure transmission channel (14) is arranged inside the sliding skirt (12) and passes therethrough axially in the axial direction, the piston sealing device (2) also comprising an extensible continuous segment (15) interposed between the fixed skirt (7) and the sliding skirt (12), said segment (15) ) comprising a cylindrical inner segment face (16) subjected to fluid pressure (1 1) via the pressure transmission channel (14), an outer cylindrical segment face (17) engageable with the cylinder (4). ), a fixed skirt-side segment axial face (18) held directly or indirectly in sealing contact with the fixed skirt (7) and a sliding skirt-side segment axial face (19) maintained directly or indirectly in sealing contact with the sliding skirt (12) even though a sliding skirt spring (20) tends to bring the sliding skirt (12) closer to the fixed skirt (7) and axially compress the continuous expandable segment (15), said system (1) being characterized in that it includes: · At least u a sliding skirt ring stop (21) which prevents the sliding skirt (12) from moving away from the piston (3) beyond a certain distance;

• At least one flow valve (22) traversed axially and more or less tightly by the inter-skirt mechanical connection (13) and interposed between the extensible continuous segment (15) and the piston head (6), said valve (22) comprising, firstly, an axial piston-head-side valve face (23) which has a circular flow closing range (24), last defining with a valve contact surface (26) arranged on the compression face (10) a circular contact line (25) whose diameter is significantly smaller than that of the cylinder (4), said valve (22) comprising second part, a sliding-skirt-side axial valve face (28) held directly or indirectly in sealing contact with the expandable continuous segment (15), said valve (22) comprising thirdly, a flow calibration orifice (27) which crosses said valve (22) from one side in the axial direction;

• At least one intermediate fluid outlet chamber (29) whose volume is formed - within the circular contact line (25) - by the axial face of the piston head-side valve (23), by the face compression member (10) and the outer surface of the inter-skirt mechanical link (13);

• At least one valve return spring (30) which tends to move the flow valve (22) away from the piston head (6).

Cooling and lubrication system according to Claim 1, characterized in that the valve return spring (30) functions as a sliding skirt spring (20).

Cooling and lubrication system according to Claim 1, characterized in that the flow calibration orifice (27) consists of the clearance left between the flow valve (22) and the inter-skirt mechanical connection (13).

Cooling and lubrication system according to Claim 1, characterized in that the valve return spring (30) is housed inside the intermediate fluid outlet chamber (29).

Cooling and lubrication system according to claim 1, characterized in that the sliding skirt spring (20) is housed inside a spring cup (31) arranged or attached in the sliding skirt (12).

Cooling and lubrication system according to Claim 1, characterized in that the sliding skirt ring stop (21) is traversed right through by at least one fluid passage opening (32). Cooling and lubrication system according to claim 1, characterized in that the outer cylindrical face of the piston head (6) has a circular decompression groove (33) which limits the sealing of said head (6).