FR2889265A1 - PRESSURE AMPLIFICATION DEVICE FOR A HYDRAULIC ACTUATOR LOCATED IN A THERMAL MOTOR AND MOTOR INCORPORATING SUCH A DEVICE - Google Patents

Abstract

The pressure amplification device (10) for a hydraulic actuator situated in a heat engine according to the invention is remarkable in that it comprises: a differential piston cylinder (12) comprising a sliding differential piston (18) between first (22a) and second (22b) low pressure chambers, and a first high pressure chamber (28a), - a hydraulic control fluid distributor (34) having first and second control positions selectively controlling the filling or emptying the low-pressure chambers (22a, 22b); mechanical coupling means of the control spool (38) and the differential plunger (18) so as to control the switching of the position of the control spool (38) by means of the differential piston (18).

Description

Pressure amplification device for a hydraulic actuator

  located in a heat engine and engine incorporating such a device

  The present invention relates to a pressure amplification device for a hydraulic actuator located in a heat engine and a heat engine incorporating such a device.

  In a variable compression ratio engine or to actuate a shift device of a camshaft, it is known to implement a hydraulic actuator in a heat engine. This type of actuator must have a relatively high level of hydraulic fluid pressure while maintaining a limited size.

  Thus, it is known from EP 1 418 322, a variable compression ratio engine whose device for adjusting the compression ratio comprises a cam control shaft, pivotable to change the position of the top dead center of the piston and thus to vary the compression ratio of the engine. The rotation of the control shaft at the position corresponding to the operating conditions of the engine is controlled by a hydraulic actuator with two pressure chambers fed with hydraulic fluid under pressure from a source of hydraulic fluid under pressure. Finally, pressure control means are provided for variably controlling the pressure of the hydraulic fluid supplied to the hydraulic actuator according to the operating conditions of the engine. More specifically, the hydraulic actuator is actuated by means of the hydraulic fluid under pressure supplied by a pump, driven by the motor by means of a belt coupled to a pulley secured to the crankshaft. A solenoid valve controlled by the pressure control means makes it possible to supply one or the other of the two pressure chambers of the actuator in order to control the displacement of this actuator.

  Furthermore, US 6622672 discloses a variable compression ratio control device for an internal combustion engine comprising an engine-driven accessory hydraulic pump and a two-chamber hydraulic fluid accumulator system separated by a piston. mobile. A first chamber is supplied with high pressure hydraulic fluid by an accessory pump driven by the engine. A second chamber is fed with low pressure hydraulic fluid by a motor lubrication pump. The low pressure hydraulic fluid is compressed in the hydraulic fluid accumulator system by means of the high pressure hydraulic fluid contained in the first chamber and feeds a hydraulic actuator via an unloading valve, controlled by an actuator control module allowing to adjust the flow of hydraulic fluid through the unloading valve.

  Although the two described devices make it possible to supply high pressure hydraulic fluid to a hydraulic actuator situated in a heat engine, these have the disadvantage that the high pressure of the hydraulic fluid is, each time, provided by a hydraulic pump driven by the engine. However, the pump must be sized to provide sufficient hydraulic fluid flow, already at low engine speed. At high engine speed, the pump is then in excess of flow, this excess flow corresponding to a lost energy. Thus, the devices described, implementing high hydraulic fluid pressures, have energy yields that are not satisfactory.

  The object of the invention is therefore to provide a pressure amplification device for a hydraulic actuator located in a heat engine to correct the aforementioned drawbacks and in particular to minimize the level of pressure at the source to reduce the losses associated with the excess flow while ensuring a high level of pressure at the hydraulic actuator.

  This object of the invention is achieved by means of a pressure amplification device for a hydraulic actuator located in a remarkable thermal engine in that it comprises: a differential piston cylinder comprising a low pressure cylinder, at least a first high pressure cylinder in the extension of said low pressure cylinder, and a differential piston comprising a low pressure head, being able to slide in a sealed manner in said low pressure cylinder and dividing the internal volume of the low pressure cylinder into first and second low pressure chambers and a first high pressure head driven by said low pressure head and slidably mounted in said first high pressure cylinder so as to define with said first high pressure cylinder a first high pressure chamber, said first high pressure chamber having a first hydraulic fluid inlet. low pressure and a first output of flu hydraulic high-pressure device, - a control hydraulic fluid distributor comprising a bushing and a control spool slidable in said bushing between first and second control positions in which said first and second low pressure chambers respectively are in communication of fluid with a first, respectively a second, control input of the distributor, the second, respectively first, low pressure chamber being then isolated from said second, respectively first control input of the distributor and in fluid communication with a discharge outlet said distributor, mechanical coupling means of said control spool and said differential piston so as to control the switching of the position of said control spool by means of said differential piston.

  As will be seen in more detail in the following description, advantageously, the pressure amplification device according to the invention can be supplied with low pressure hydraulic fluid and provide high pressure hydraulic fluid compressed by means of the differential piston, regardless of the heat engine.

  Preferably, said distributor comprises bistable means for holding said control spool in position in said first and second control positions.

  With such bistable means for holding in position, it is advantageous to provide a bistable behavior of the control spool, which is stable in each of its control positions, despite the action of the hydraulic control fluid passing through the dispenser.

  Preferably, said bistable means for holding said control spool in position comprise first and second position-retaining recesses formed on said control spool, and a position-keeping blasting, secured to said sleeve and cooperating with said recess holding in position.

  The bistable behavior of the slide is thus advantageously carried out mechanically. Keeping the control spool in position is thus robust and economical.

  Preferably, said mechanical coupling means comprise a support comprising first and second control fingers penetrating into said differential piston cylinder so as to be pushed by said differential piston when approaching the first and second positions respectively. end of stroke of said piston, and first and second control projections adapted to push, under the effect of the displacement of the first and second control finger respectively, said control spool so as to bring said drawer from a position of control to the other control position.

  Thus, the differential piston controls, during its course, the movement of the slide from its first control position to its second control position and vice versa.

  Preferably, the pressure amplification device according to the invention further comprises means for rapidly switching the control position of said drawer.

  With such means of rapid switching of the control position of the slide, it is possible to escape any parasitic forces acting on the differential piston and the control spool which could result in a blockage of the device.

  Preferably, said fast switching means comprise a tooth formed on said support and resilient support means cooperating with said tooth, so that a translation of said support under the effect of the displacement of one of said fingers control causes, during a charging time, compression of said resilient support means, said support being then, during a discharge time, pushed by the sliding of said elastic means on said tooth, so as to push said control spool by means of said first, respectively second, control projection from the first, respectively second, control position of said drawer to the second, respectively the first, control position of said drawer.

  Thus, the fast switching means 25 are advantageously realized in purely mechanical form and in a simple manner.

  Preferably, said first, respectively second, control projection being in contact with said first, respectively second, end of said control spool, the second, respectively first, control projection is spaced from said second, respectively first, end of said spool. control by means of a clearance, so that during said charging time of said resilient support means, said differential piston can drive said support without moving said control spool and during said discharge time said resilient support means, the sliding of said support causes the sliding of said control slide.

  Thus, advantageously, it is possible to achieve, advantageously, rapid switching of the position of the control spool, escaping any parasitic forces acting on the differential piston and the control spool.

  Preferably, said differential piston cylinder further comprises a second high pressure cylinder made in the extension of said low pressure cylinder, opposite said first high pressure cylinder, and a second high pressure head in the extension of said low pressure head, driven by said low pressure head and slidably mounted in said second high pressure cylinder so as to delimit with said second high pressure cylinder a second high pressure chamber, said second high pressure chamber having a second low pressure hydraulic fluid inlet and a second high hydraulic fluid outlet pressure.

  Thus, advantageously, the differential piston compresses hydraulic fluid during each of its paths in the differential piston cylinder. This ensures a flow of hydraulic fluid output substantially larger than a single high pressure chamber.

  Preferably, first and second secondary outlet ducts opening respectively into said first and second high pressure chambers, and provided with a first and second non-return valve, respectively, towards the first and second high pressure chambers. , come together to form a main outlet pipe.

  This ensures the insulation of high pressure chambers where the pressure is lower than the pressure of the hydraulic fluid in the main outlet pipe.

  The invention also relates to a heat engine comprising a hydraulic actuator and a pressure amplification device as described above in all its variants, remarkable in that said hydraulic control fluid and / or said low pressure hydraulic fluid is the lubricating oil said engine.

  In this way, any problem of oil compatibility in the heat engine is advantageously avoided.

  Other advantages and characteristics of the invention will emerge from the description which follows, presented solely by way of illustrative and non-limiting example, with reference to the appended figures, in which FIGS. 1 and 2 diagrammatically show a device of FIG. pressure amplification for a hydraulic actuator located in a heat engine according to the invention, respectively in a first and a second operating phase corresponding, respectively, to a first and a second control position of the distributor spool.

  The pressure amplification device 10 as shown in FIG. 1 comprises a frame 11 inside which a differential piston cylinder 12 having a low-pressure cylinder 14 and first 16a and second 16b high-pressure cylinders formed has been formed. in the extension of the low pressure cylinder 14, the high pressure cylinders 16a, 16b being here, preferably, formed on opposite sides of said low pressure cylinder 14. The differential piston cylinder 12 also comprises a differential piston 18 comprising a piston head low pressure 20 being able to slide tightly in the low pressure cylinder 14 and dividing the internal volume of the low pressure cylinder 14 into first 22a and second 22b low pressure chambers. A first high-pressure piston head 24a is mounted in the extension of the low-pressure piston head 20, here, directly on the first front surface 26a (shown in dashed lines in the figures) of the low-pressure piston head 20, so as to slide, in a sealed manner, in the first high-pressure cylinder 16a so as to define with the first low-pressure cylinder 16a a first high-pressure chamber 28a. Equivalently, a second high-pressure piston head 24b is mounted in the extension of the low-pressure piston head 20, here directly on the second end surface 26b (shown in dashed lines in the figures) of the low piston head pressure 20, so as to slide, in a sealed manner, in the second high pressure cylinder 16b so as to define with the second low-pressure cylinder 16b a second high pressure chamber 28b.

  The first high pressure chamber 28a comprises, in this case, a single first port 29a of low pressure hydraulic fluid inlet and high pressure hydraulic fluid outlet.

  Similarly, the second high pressure chamber 28b comprises, in this case, a single second port 29b of low pressure hydraulic fluid inlet and high pressure hydraulic fluid outlet.

  Of course, other embodiments of the chambers are possible. In particular, low pressure hydraulic fluid inlet ports and separate high pressure hydraulic fluid outlet ports may be provided.

  Preferably, as shown in the figures, the low-pressure chambers and the high-pressure, cylindrical chambers are substantially coaxial, here with axis x-x '.

  It should be noted that the useful front surface 30 of the low-pressure piston head 20 is greater than the first useful front surface 32a of the first high-pressure piston head 24a, this first useful front surface 32a being here, preferably, substantially equal to the second useful front surface 32b of the second high-pressure piston head 24b.

  The pressure amplification device 10 also comprises a low-pressure hydraulic control fluid distributor 34, also provided inside the frame 11, comprising a bushing 36 and a control spool 38, able to slide in the bushing 36, substantially parallel to the x-x 'axis, between the first and second control positions. The distributor also comprises first 40a and second 40b control inputs, first 42a and second 42b control outputs and a discharge output 44. As shown in FIG. 1, in the first control position of the drawer 38, the first low-pressure chamber 22a is in fluid communication with the first control input 40a of the distributor 34 via the first control output 42a, while the second low-pressure chamber 22b is then isolated from the second control input 40b and in communication with fluid with the discharge outlet 44 of the distributor 34 via the second control output 42b. In the second control position of the drawer 38 shown in FIG. 2, the second low pressure chamber 22b is in fluid communication with the second control input 40b of the distributor 34 via the second control output 42b, while the first low chamber pressure 22a, is then isolated from the first control input 40a and in fluid communication with the discharge outlet 44 of the distributor 34 via the first control output 42a.

  On the slide 38, first 46a and second 46b position holding recesses are made, in this case in the form of circular grooves, the first and second circular grooves 46a, 46b cooperating with a ball device 48 mounted on a solidarity spring of the frame 11 forming a holding shot in position 48 so as to maintain the slide 38 in its first, respectively second, control position. Thus, means for holding the control spool 38 in position are provided. Of course, other solutions are conceivable for producing these means for holding the control spool 38 in position, the latter enabling the dispenser to operate in a bistable manner and thus to escape the parasitic forces that may appear in particular at the control spool 38, such as jet forces or dynamic forces related to the environment of the device 10.

  The pressure amplification device 10 furthermore comprises means for mechanically coupling the spool 38 and the differential piston 18 so as to control the switching of the position of the spool 38 by means of the differential piston 18. Preferably, these means of mechanical coupling comprise a support 50, which in this case has a U-shape, and which comprises first 52a and second 52b lateral branches and a central branch 54, substantially parallel to the axis x-x ', of the first 56a and second 56b control fingers being mounted at the free end 58a, 58b of the first 52a, respectively second 52b, lateral branch so as to be substantially coaxial with each other and substantially parallel to the axis x-x '. These first 56a and second 56b control fingers respectively enter the first 22a and second 22b low pressure chamber of the differential piston cylinder 12, so that the differential piston 18 approaching its end positions results in , the first 56a, respectively the second 56b, control finger when the differential piston 18 moves in the direction of the arrow Fa, respectively in the direction of the arrow Fb, thus controlling the sliding substantially along the x-axis ', support 50 relative to the frame 11.

  Furthermore, on the first lateral branch 52a of the support 50, a first control projection 60a is produced, substantially parallel to the axis x-x ', so that the first control projection 60a can cooperate with a first end. 62a of the drawer 38 so as to push said drawer 38 from its first control position to its second control position.

  Similarly, on the second lateral branch 52b of the support 50, a second control projection 60b is produced, substantially parallel to the x-x 'axis, so that the second control projection 60b can cooperate with a second end. 62b of the drawer 38 so as to push said drawer 38 from its second control position to its first control position.

  Thus, the distributor 34 is disposed in the space delimited by the side branches 52a, 52b and central 54 of the support 50 and by the differential piston cylinder 12.

  The first 60a and second 60b control projections are made such that when the first control projection 60a, respectively the second control projection 60b, is in contact with the first end 62a of the drawer 38, respectively the second end 62b of the drawer 38, a set 64b, respectively a set 64a, separates the second end 62b of the drawer 38 and the second control projection 60b respectively the first end 62a of the drawer and the first control projection 60a.

  As shown in the figures, at the central branch 54 of the support 50, first 66a and second 66b switching recesses are arranged, separated by a triangular tooth 68, so that the first 66a, respectively second 66b , the switching recess receives a ball of a switching shot 70 in a first, respectively second, end position of the support 50 in which the first control projection 60a, respectively the second control projection 60b, bears on the first end. 62a of the drawer 38, respectively on the second end 62b of the drawer 38, the drawer 38 being in its first control position, respectively in its second control position. By blasting means a ball device mounted on a spring which, in this case, is integral with the frame 11.

  The switching recesses 66a, 66b may be replaced, for example, by abutment devices provided on each side of the frame 11 to cooperate with the lateral branches 52a, 52b of the support 50 or, in a less favorable embodiment, removed.

  Furthermore, the pressure amplification device 10 is coupled to a discharge circuit 71 comprising first 72a and second 72b secondary outlet lines, opening on the one hand, respectively in the first low pressure chamber 28a and in the second low pressure chamber 28b, and joining on the other hand so as to form a main outlet pipe 74.

  On the first outflow line 72a, a first check check valve 76a is mounted, performing the check function to the first high pressure chamber 28a.

  Similarly, on the second secondary outlet pipe 72b, a second exhaust check valve 76b is mounted, performing the anti-return function to the second high pressure chamber 28b.

  Furthermore, a first supply line 78a is stitched onto the first outlet line 72a, a first supply check valve 80a being mounted on this first supply line 78a so as to fulfill the function of anti -back to the power source 82.

  Similarly, a second supply line 78b is stitched on the second outlet line 72b, a second supply check valve 80b is mounted on this second supply line 78b so as to perform the function of return to power source 82.

  Preferably, the low-pressure hydraulic fluid supply source 82 for the high-pressure chambers 28a, 28b may be constituted by: the source of hydraulic fluid of the lubrication circuit of the heat engine; the source of hydraulic fluid supply for controlling the low-pressure chambers 22a, 22b.

  With this latter solution, it is possible to substantially increase the flow rate of the hydraulic fluid at the outlet of the high pressure chambers relative to the solution of supplying the high pressure chambers with the source of hydraulic fluid of the lubrication circuit of the engine. However, this solution also requires increasing the flow of hydraulic fluid taken from the engine lubrication circuit.

  Finally, the pressure amplification device 10 is coupled to a primary circuit 84 comprising an inlet main pipe 85 dividing upstream of the distributor 34 into first 86a and second 86b secondary inlet conduit opening at the level of the first 40a, respectively of the second 40b, control input of the distributor 34.

  The operation and advantages of the pressure amplification device 10 which has just been described result directly from the foregoing description.

  In the example presented hereinafter, the engine lubrication circuit fulfills the function of a source of hydraulic control fluid 88, the discharge outlet 44 then preferably opening into the hydraulic fluid tank 90 of the lubricating circuit of the engine. engine.

  The implementation of the engine lubrication circuit as a source of hydraulic control fluid, advantageously, to have a relatively large source flow.

  In Figure 1, the drawer 38 of the distributor 34 is in its first control position.

  In this first control position of the slide 38, the first low-pressure chamber 22a can be filled with hydraulic control fluid. Under these conditions, and as long as no flow is output from the pressure amplification device, the pressure of the hydraulic fluid in the first high pressure chamber 28a increases to ensure the equilibrium of the differential piston 18. In this equilibrium situation of the differential piston 18 and neglecting the counter-forces due to the presence of hydraulic fluid in the second high-pressure chamber 28b and in the second low-pressure chamber 22b, which is in fluid communication with the outlet discharge 44 of the distributor 34, the maximum pressure in the first high pressure chamber 28a is substantially: S PHP_max Pcom s (El) where: - PHP max represents the maximum pressure in the first high pressure chamber 28a, - Pcom the pressure of the fluid hydraulic control in the first low-pressure chamber 22a, S the useful front surface 30 of the low-pressure piston head 20, and s the useful front surface 32a of the first high pressure piston head 24a.

  Thus, the maximum pressure in the first high-pressure chamber 28a is directly related to the differential piston cylinder 12 and more particularly to the ratio between the useful front surface 30 of the low-pressure piston head 20 and the useful front surface 32a of the first head high pressure piston 24a.

  However, as long as no flow appears in the main outlet pipe 74, that is to say as long as the hydraulic actuator (not shown) does not consume high pressure hydraulic fluid and therefore it is not not actuated, the differential piston 18 is immobilized due to the increase of the pressure in the first high pressure chamber 28a and the pressure amplification device 10 therefore consumes no energy.

  When a flow occurs in the main outlet line 74, that is to say when the hydraulic actuator consumes hydraulic fluid, a slight pressure drop in the first high pressure chamber 28a appears, which, under the effect of the pressure in the first low-pressure chamber 22a, causes the displacement of the differential piston 18 to the right of Figure 1, as indicated by the arrow Fa in this Figure 1, this differential piston movement 18 tending to maintain the pressure PHP_max in the first high pressure chamber 28a, while the second low pressure chamber 22b empties.

  The displacement of the differential piston 18 generates a depression in the second high pressure chamber 28b, which causes the opening of the second supply check valve 80b and the aspiration of the hydraulic fluid from the supply source 82 into hydraulic fluid. for the high-pressure chambers 28a, 28b, when the pressure in the second high-pressure chamber 28b becomes lower than the pressure of the supply source 82. The second high-pressure hydraulic chamber 28b thus fills substantially at the same time as the first chamber Low pressure hydraulic 28a is empty. It may be noted that the supply of the high pressure chamber 28b is facilitated if the supply source 82 is under pressure.

  On approaching the end-of-travel position of the differential piston 18 in the direction of arrow F0, the differential piston 18 comes into contact with the first control finger 56a and then drives it towards the right of FIG. control finger 56a being rigidly mounted on the support 50, its displacement causes the translation, along the x-x 'axis, to the right of Figure 1, the support 50. During a first time of this translation, said time of When the charging ball 70 is out of the first switching recess 66a, the blasting ball 70 is compressed by sliding the ball on a first face of the tooth 68. During this charging time of the switching blasting 70, the spool 38 of the dispenser 34 remains stationary thanks to the clearance 64b which prevents the second control projection 60b of the support 50 from driving the spool 34 to the right of FIG. 1. The switching blasting 70 is dimensioned so that from the moment this commu blasting Tation 70 passes into a discharge time, reached when the blasting ball 70 passes the tip of the tooth 68, at which point this switching blast 70 expands to retract the log ball 70 into the second switch recess 66b. , the energy restored by this switching shot 70 is sufficient to overcome the maintaining shot in position 48 of the control spool 38 of the distributor 34.

  Thanks to the switching jet 70, associated with the game 64, the control spool has a bistable operation, escaping any pressure equilibrium at the differential piston 18 which would have the effect of blocking the movement of the differential piston 18 and therefore also the control spool 38.

  Thus, the drawer 38 of the dispenser 34 reaches its second control position shown in FIG. 2, pushed by the second control projection 60b until the holding beam in position 48 enters the second holding recess in position 44b. .

  Upon this switching of the control slide control position 38, the first control input 40a of the valve 34 is closed, while the second control input 40b of the valve 34 is brought into fluid communication with the second control output. 42b of the distributor 34 and that the second control output 42a of the distributor 34 is in fluid communication with the discharge outlet 44 of the distributor. Thus, the supply of the first low-pressure chamber 22a is cut off, the second low-pressure chamber 22b is fed to the contrary and the control hydraulic fluid contained in the first low-pressure chamber 22a is evacuated.

  Under the effect of this new configuration corresponding to the second control position of the control spool 38, the movement of the differential piston 18 is reversed, the differential piston 18 then moving to the left of FIG. 2, as indicated by FIG. the arrow Fb in this figure 2.

  The displacement of the differential piston 18 in the direction of the arrow Fb generates a depression in the first high pressure chamber 28a, which causes the opening of the first supply check valve 80a and the suction of the low pressure hydraulic fluid from the supply source 82, when the pressure in the first high pressure chamber 28a becomes lower than the pressure of the supply source 82. The first high pressure hydraulic chamber 28a thus fills substantially at the same time as the second low hydraulic chamber pressure 28b is empty.

  On approaching the end position of the differential piston 18 in the direction of the arrow Fb, the differential piston 18 comes into contact with the second control finger 56b and then drives it to the left of FIG. second control finger 56b being rigidly mounted on the support 50, its displacement causes the translation, along the x-x 'axis, to the left of Figure 2, the support 50. During a load time during this translation the log ball 70 exits the second switch recess 66b and the log 70 is compressed by sliding the ball on the second face of the tooth 68. During this charging time of the switching shot 70, the slide 38 of the dispenser 34 remains stationary thanks to the clearance 64a which prevents the first control projection 60a of the support 50 from driving the slide 34 towards the left of FIG. 2. The switching projection 70, dimensioned so that the energy restored by this projection of switching 70 d the time of discharge is sufficient to overcome the maintaining shot in position 48 of the control spool 38 of the dispenser 34, brings the spool 38 of the dispenser 34 back to its first control position.

  Therefore, as long as there is a flow of hydraulic fluid in the main outlet pipe 74, that is to say as long as the hydraulic actuator consumes hydraulic fluid or as the pressure in the main outlet pipe 74 is lower than the maximum PHP pressure, the differential piston 18 moves back and forth in the differential piston cylinder 12.

  It should be noted that the device according to the invention can be made solely mechanically and hydraulically, that is to say that it comprises for example no electronic element, which facilitates its integration into the engine.

  It is remarkable that the supply of the high pressure chambers takes only the useful energy for the implementation of the hydraulic actuator and compensate for any leaks.

  Moreover, the pressure amplification device according to the invention provides, at the efficiency, the energy it receives. The pressure being amplified, the returned flow is lower than the flow taken. In addition, the flow taken is generally not constant but instead depends on the engine speed. To overcome these constraints, the pressure amplification device according to the invention can supply a hydraulic actuator through a hydraulic accumulator. This accumulator must have the capacity to provide the necessary flow for a complete actuation of the hydraulic actuator thus ensuring an optimal response time of the actuator.

  The invention is not limited to the only exemplary embodiment described here by way of illustrative and nonlimiting example and many embodiments are possible without departing from the scope of the invention.

  For example, it is possible to envisage a device comprising only a high pressure chamber instead of two high pressure chambers as has been presented above, or a device in which the high pressure heads and the low pressure head would not be coaxial or else a device where the high pressure heads would not be made directly on the low pressure head but only coupled to this low pressure head (via a shaft for example).

  It is also conceivable that the switching shotage is integral with the support and that the switching recesses and the tooth cooperating with this projection are then integral with the frame. Moreover, this tooth may have a less regular shape than the shape of a triangle. Preferably, this tooth has a peak tip. More preferably, this tooth is substantially symmetrical. The switching jet device, that is to say the device comprising a ball mounted on a spring, can also be replaced by any resilient support means adapted to cooperate with the switching recesses and the tooth, such as As an illustrative and nonlimiting example, an elastic metal tongue.

  Similarly, one can design a pressure amplification device where the holding shot in the drawer position is integral with the control spool and where the holding recesses in position are formed inside the bushing of the dispenser. Again, the holding shot in position can be replaced by any bistable means for holding in position, such as, by way of illustrative and non-limiting example, an elastic metal blade.

  In addition, the dispenser may also include two discharge outlets, each of the discharge outlets being adapted to be placed in fluid communication with one of the low pressure chambers of the differential piston cylinder.

  Finally, it should be noted that the applications for such a pressure amplification device are numerous. Indeed, the pressure amplification device according to the invention can be implemented with any type of hydraulic actuator, in particular the hydraulic actuators arranged inside a heat engine, as, for illustrative example and not limiting, a hydraulic actuator for controlling the stroke of a piston in a variable compression ratio engine.

Claims (10)

  1. A pressure amplification device (10) for a hydraulic actuator located in a heat engine characterized in that it comprises: a differential piston cylinder (12) comprising a low pressure cylinder (14), at least a first high pressure cylinder (16a) in the extension of said low pressure cylinder (14), and a differential piston (18) comprising a low pressure head (20), being able to slide in a sealed manner in said low pressure cylinder (14) and dividing the volume interior of the low pressure cylinder (14) at first (22a) and second (22b) low pressure chambers, and a first high pressure head (24a) driven by said low pressure head (20) and slidably mounted in said first high pressure cylinder (24a) so as to define with said first high pressure cylinder (16a) a first high pressure chamber (28a), said first high pressure chamber having a first hydraulic fluid inlet low pressure (29a) and a first high pressure hydraulic fluid outlet (29a), - a control hydraulic fluid distributor (34) having a bushing (36) and a control spool (38) slidable in said bushing ( 36) between first and second control positions in which said first (22a), respectively second (22b), low pressure chamber is in fluid communication with a first (40a), respectively a second (40b), control input of the distributor (34), the second (22b), respectively first (22a), low pressure chamber then being isolated from said second (40b), respectively first (40a), control input of the distributor (34) and in fluid communication with a discharge outlet (44) of said distributor (34), - mechanical coupling means of said control spool (38) and said differential plunger (18) so as to control the switching of the position of said control spool (38) by means of in said differential piston (18).   2. A pressure amplification device (10) according to claim 1, characterized in that said distributor (34) comprises bistable means for holding in position said control spool (38) in said first and second control positions.   3. A pressure amplification device (10) according to claim 2, characterized in that said bistable means for holding said control spool (38) in position comprise first (46a) and second (46b) retaining recesses in position. provided on said control spool (38), and a holding mantle (48), integral with said bushing (36) and cooperating with said retaining recesses in position (46a, 46b).   4. A pressure amplification device (10) according to one of claims 1 to 3, characterized in that said mechanical coupling means comprise a support (54) having first (56a) and second (56b) control fingers penetrating into said differential piston cylinder (12) so as to be pushed by said differential piston (18) on approaching the first, respectively second, end position of said piston (18), and first ( 60a) and second (60b) control projections able to push, under the effect of the displacement of the first (56a), respectively the second (56b), control finger, said control spool (38) so as to bring said drawer (38) from one control position to the other control position.   5. A pressure amplification device (10) according to claim 4, characterized in that it further comprises means for rapidly switching the control position of said drawer (34).   6. Pressure amplification device according to claim 5, characterized in that said rapid switching means comprise a tooth (68) provided on said support (54) and resilient support means (70) cooperating with said tooth ( 68), so that a translation of said support (54) under the effect of the displacement of one of said control fingers (56a, 56b) causes, during a charging time, a compression of said resilient support means (70), said support (54) being then, during a discharge time, pushed by the sliding of said elastic means (70) on said tooth (68), so as to push said control spool (38) by means of said first (60a), respectively second (60b), control projection from the first, respectively second, control position of said drawer (38) to the second, respectively the first, control position of said drawer (38).   7. A pressure amplification device (10) according to claim 6, characterized in that said first (60a), respectively second (60b), control projection being in contact with said first (62a), respectively second (62b). ), end of said control spool (38), the second (60b), respectively first (60a), control projection is spaced from said second (62b), respectively first (62a), end of said spool (38) at by means of a clearance (64a, 64b), so that during said charging time of said resilient support means (70), said differential piston (18) can drive said support (50) without moving said control (38) and that, during said discharge time of said resilient support means (70), the sliding of said support (50) causes said control slide (38) to slide.   8. Pressure amplification device according to any one of the preceding claims, characterized in that said differential piston cylinder (12) further comprises a second high pressure cylinder (16b) formed in the extension of said low pressure cylinder (14). ), opposite said first high pressure cylinder (16a), and a second high pressure head (24b) in the extension of said low pressure head (20), driven by said low pressure head (20) and slidably mounted in said second high cylinder pressure (16b) to define with said second high pressure cylinder (16b) a second high pressure chamber (28b), said second high pressure chamber (28b) having a second low pressure hydraulic fluid inlet (29b) and a second outlet high pressure hydraulic fluid (29b).   9. Pressure amplification device according to any one of the preceding claims, characterized in that first (72a) and second (72b) secondary outlet pipes respectively opening into said first (28a) and second (28b) high chambers. pressure, and provided with a first (76a), respectively a second (76b), non-return valve to the first (28a) and second (28b) high pressure chambers, join to form a main pipe of output (74).   10. A thermal engine comprising a hydraulic actuator and a pressure amplification device (10) according to any one of the preceding claims, characterized in that said hydraulic control fluid and / or said low pressure hydraulic fluid is oil lubricating said engine.