FR2909745A1 - Hydromechanical actuator control valve for internal combustion engine, has closing unit movably assembled in body to close fluid passage between conduits relative to stable positions in event of reflux of fluid by outlet of one conduit - Google Patents

Abstract

The valve (10) has a body (2) arranged in two stable positions relative to a body (1). An outlet of a conduit (21) of the body (2) is placed relative to rectangular openings (12, 13) of the body (1) in the respective positions for alternatively establishing a fluid passage. The passage is formed by a non-crossing bore (56) between a rectangular opening (11) and one of the openings (12, 13). A closing unit with a rod (3) is movably assembled in the body (2) to close the passage formed between conduits (21, 22) relative to the positions, in case of reflux of the fluid by the outlet.

Description

TECHNICAL FIELD TO WHICH THE INVENTION RELATES The present invention

  relates generally to the control of hydromechanical actuators. It relates more particularly to a control valve of a hydromechanical actuator, comprising a first hollow body comprising a wall provided with an inlet and two pressurized fluid outlets, a second body movably mounted in said first body, having an inlet and a fluid outlet under pressure, the second body being adapted to take relative to the first body two stable positions, including a first stable position in which its output is placed opposite one of the outputs of the first body and a second position stable in which its output is placed opposite the other of the outputs of the first body, to establish alternately fluid passages between the inlet and one or other of the outputs of the first body. BACKGROUND ART Conventionally, an internal combustion engine comprises a valve actuating device provided with a camshaft which actuates the engine valves to cyclically close the intake and exhaust ducts of this engine. It is known that the opening moment of the valves influences the power and the consumption of the engine, as well as the volume of polluting emissions that it rejects. In order to advance or delay the opening of the valves of these engines, the valve actuator may comprise a hydromechanical actuator such as an angular displacement device of the camshaft. Such an offset device comprises one or more pairs of compression chambers separated by one or more vanes connected to the camshaft. The compression chambers are intended to be filled with a pressurized control fluid to exert effort in one direction or the other on each pallet to move and shift the camshaft.

In order to control this shifting device, a control valve as defined above is generally used, the two fluid outlets of the first body of which are each connected to one of the chambers of each pair of chambers of the shifting device.

The control valve thus drives the shifter by injecting the control fluid into either one of the two chambers of each pair to apply the desired pressure force to the pallet for moves in the desired direction to a desired position.

However, it is observed that the camshaft returns efforts on each pallet which oscillate periodically. In particular, some of these forces cause control fluid to flow back from the shifter to the control valve. As a result, the position of each pallet is unstable and the time of change of position of each pallet is large, which penalizes the engine control and therefore the performance of this engine. OBJECT OF THE INVENTION The object of the present invention is then to reduce the time of change of position of the pallet of the shifter and the instabilities of the pallet when its position must be kept constant. For this purpose, the invention proposes a control valve as defined in the introduction, which comprises closure means movably mounted in the second body so as to close, in one and the other of the two stable positions of the second body, a fluid passage provided between the inlet and the outlet of the second body, in case of reflux of the fluid through the outlet of the second body. During a fluid reflux through the outlet of the second body, the closing of the fluid passage makes it possible to stop the circulation of the control fluid, so that the position of the pallet remains stable. Thus, when the outputs of the first and second bodies are arranged to move the pallet of the shifter in one direction, the movement of the pallet in an opposite direction, which causes the reflux of the fluid, is limited by means of shutter means . The desired position of the hydro-mechanical actuator pallet is then reached more quickly. According to a first advantageous characteristic of the invention, the closure means comprise a substantially cylindrical body provided with a sealing ring. Thus, the translation of this cylindrical body into the second body allows the sealing ring to close or open the passage of the fluid between the inlet and the outlet of the second body.

According to an alternative embodiment of the invention, the closure means comprise a sealing ball. Other advantageous and non-limiting characteristics of the control valve according to the invention are as follows: there is provided a return spring of the closure means in a closed position of said fluid passage; the second body is adapted to take at least one intermediate position in which its outlet and the corresponding outlet of the first body overlap only partially and wherein said sealing means are adapted to close said fluid passage; said wall of the first body further comprises a third discharge outlet adapted to be placed in communication via discharge means provided on the second body with one or other of the outputs of the first body, when said outlet is cut off from the entrance of the first body by the second body; said wall of the first body comprises a plurality of discharge outlets adapted to be placed in communication with one or the other of the outlets of the first body, when said outlet is cut off from the entrance of the first body by the second body; ; Said evacuation means comprise at least one peripheral groove provided on the second body; the second body is movable in translation relative to the first body; - Means are provided for moving the second body relative to the first body in one of the stable positions and return means of the second cylindrical body relative to the first body in the other stable positions. DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT The following description with reference to the accompanying drawings, given as non-limiting examples, will make it clear what the invention consists of and how it can be achieved. In the accompanying drawings: FIG. 1 is an exploded view of a control valve according to the invention comprising a first and a second body; FIGS. 2 and 3 are diagrams of operation of the control valve of FIG. 1 in a first stable position of the second body with respect to the first body; Figures 4 and 5 are diagrams of operation of the control valve of Figure 1 in a second stable position of the second body with respect to the first body; Figures 6 and 7 are diagrams of operation of the control valve of Figure 1 in an intermediate position of the second body relative to the first body; and FIG. 8 is a view of a hydromechanical actuator connected to the control valve of FIG. 1. FIGS. 1 to 7 show a valve 10 for controlling a hydromechanical actuator 300 of an engine. internal combustion. As shown in FIG. 8, this hydromechanical actuator is in this case an offset device 300 of a camshaft 400 of the engine, which makes it possible to angularly offset this camshaft in order to advance or delay the opening of the valves of the engine. engine. The shifter 300 comprises in particular a body whose angular position is directly a function of the angular position of a crankshaft 20 of the engine. This body may for example be rotated by a chain link, or by a belt connected to the crankshaft. The body internally defines two chambers 301, 303 separated from each other by a pallet 302 which is mounted to rotate between two stops and which is angularly connected to the camshaft 400. Each of the two chambers 25 comprises control fluid inlet. The pressure difference between the two chambers 301, 303 makes it possible to exert a pressure force on the pallet to rotate it in one direction or the other. This pivoting thus makes it possible to shift the angular position of the camshaft 400. As shown in FIGS. 1 and 2, the control valve 30 comprises a first hollow body 1 and a second body 2 engaged inside the first body 1. The first body 1 comprises a tubular wall whose one end is partially closed by an end wall provided with a central opening 16.

The tubular wall of the first body 1 is, for its part, pierced by three rectangular openings 11, 12, 13 disposed above each other along the longitudinal axis of said first body 1, as well as two other openings 14. Diametrically opposite said first three apertures 11,12,13. One of the first three apertures forms an inlet 11 of control fluid (oil). It is intended to be connected to a pump bringing into the valve 10 the pressurized control fluid at a pressure marked P. The other two 12,13 of the first three openings form outlets 12, 13 of the control fluid. They are each connected to one of the chambers of the shifter 300. Finally, the two other openings 14, 15 of the first body 1 as well as the central opening of its end wall form discharge outlets 14, 15. , 16 of the control fluid. They are intended to be connected to a control fluid recovery well. The pressure of the control fluid at these exhaust outlets 14, 15, 16 therefore remains constantly low. The second body 2 has a cylinder shape slidably mounted in the first body 1. This second body 2 is pierced axially with a non-through bore 56. The second body 2 thus has a closed end and an open end. Once the second body 2 has been inserted into the first body 1, this open end is turned towards the end wall of the first body 1. The bore 56 has, over a major part of its length, a constant section of diameter called diameter nominal. However, it has, near its open end, a first portion 80 of larger section and, at its closed end, a second portion 81 of smaller section. The outlet of the bore 56 is sealed by a socket 5 screwed into a threaded portion of this bore. This socket 5 has a tubular side wall and a closed end wall. The inside diameter of its side wall is equal to the diameter of the second portion 81 of the bore 56. The open end of this sleeve is turned towards the inside of the bore 56. The second body 2 is also pierced radially. two ducts 21, 22 passing through a full diameter. These two ducts 21, 22 are arranged one above the other along the longitudinal axis of the second body 2, parallel to each other. A first duct 22 forms a control fluid inlet in the second body 2. The central portion of this first inlet duct 22 opens into the bore 56, close to the closed end thereof. A second conduit 21 forms a control fluid outlet out of the second body 2. The central portion of this second outlet conduit 21 opens into the bore 56 at the first enlarged portion 80 thereof.

It will be understood that the central portion of the bore 56 situated between the first and second portions 80, 81 of this bore forms a passage 56 of the control fluid from the first inlet conduit 22 to the second outlet conduit 21. The control valve 10 further comprises longitudinal displacement means 7 of the second body 2 relative to the first body 1 and return means 6 of the second body 2 in a stable position. The displacement means here comprise an electromagnet 7 with a plunger core connected by a rod 71 to the closed end of the second body 2. In particular, these displacement means make it possible to push the second body 2 towards the end wall of the second body. first body 1 when the coil of the electromagnet 7 is traversed by a current of high intensity. The return means comprise here a return spring 6 arranged in compression between the open end of the second body 2, around the sleeve 5, and the end wall of the first body 1, around its central opening 25. 16. These return means in particular allow to push the second body 2 away from the end wall of the first body 1 when the coil of the electromagnet 7 is traversed by a current of low intensity or zero. The second body 2 is thus adapted to take two stable positions relative to the first body 1.

In a first stable position shown in Figures 2 and 3, the mouth of the second outlet conduit 21 of the second body 2 is disposed opposite one of the outlets 12 of the first body 1. In this position , the mouth of the first inlet conduit 22 of the second body 2 is disposed vis-à-vis the inlet 11 of the first body 1.

This stable position is achieved thanks to the electromagnet 7 which generates an axial force on the second body 2 which maximizes the compression of the return spring 6. In this position, the control fluid arriving in the valve 10 by its inlet 11 can flow to its outlet 12 to open into one of the chambers 301 of the shifter 300. In addition, in this position, the other outlet 13 of the first body 1, the one connected to the other chamber 303 the shifter 300, is disposed opposite a peripheral groove 28 provided on the second body 2. This groove 28 10 forms a means of evacuation of the fluid from the other chamber 303 to the recovery well, via the exit d 14 discharge of the first body 1. Indeed, the fluid arriving in the outlet 13 of the first body 1 can flow in the groove 28, being channeled between the first body 1 and the second body 2, to the exit of evacuation 14 (see Figure 3).

The pallet of the shifter 300 can thus abut in a first shift position of the camshaft. In a second stable position shown in FIGS. 4 and 5, the mouth of the second outlet duct 21 of the second body 2 is disposed facing the other of the outlets 13 of the first body 1. In this position, The mouth of the first inlet duct 22 of the second body 2 is offset relative to the inlet 11 of the first body 1. However, the second body 2 has on its external surface another peripheral groove 82 which allows the fluid to flow. control to flow from the inlet 11 of the first body 1 to the mouth of the first conduit 22 input of the second body 2 (see Figure 5).

This second stable position is reached thanks to the return spring which generates an axial force on the second body 2. In this position, the control fluid arriving in the valve 10 through its inlet 11 can flow to its outlet 13 in order to to open in the other of the chambers 303 of the shifter 300.

Furthermore, in this position, the first outlet 12 of the first body 1, that connected to the first chamber 301 of the shifter 300, is arranged facing a peripheral groove 210 provided on the second body 2, on the its open end. This groove 210 forms a fluid discharge means 2909745 8 disposed in this first chamber 301 to the recovery well, via the discharge outlets 15, 16 of the first body. The pallet of the shifter 300 can thus abut in a second offset position of the camshaft.

According to a variant shown in Figures 6 and 7, the longitudinal displacement means 7 can position the second body 2 in an intermediate position between the first and second stable positions. This position is reached by circulating a very precise current of current in the coil of the electromagnet 7.

In this intermediate position, the mouth of the second outlet duct 21 of the second body 2 covers only partially the outlet 12 of the first body 1. Furthermore, the inlet 11 of the first body 1 is connected to the mouth of the first body conduit 22 input of the second body 2 by the groove 82 device.

Of course, according to this variant, the second body 2 can take another intermediate position (not shown) in which the mouth of the second outlet duct 21 of the second body 2 covers only partially the outlet 13 of the first body 1. in these two intermediate positions, the partial overlap of one or the other of the outlets 12, 13 of the first body 1 by the mouth of the second duct 21 of the second body 2 allows the control fluid to continue to feed the corresponding chamber 301, 303 of the shifter 300, limiting its flow to a flow rate just needed to compensate for leakage of the fluid in the chamber 301, 303, thereby keeping the pallet 302 of the shifter 300 in constant position between its two stops. According to a particularly advantageous characteristic of the invention, the control valve 10 comprises closure means 3 movably mounted in the bore 56 of the second body 2 so as to seal, in one or other of the stable positions or intermediate of the second body 2, the passage of the control fluid between the first inlet duct 22 and the second outlet duct 21 of the second body, in the event of fluid reflux through the second outlet duct 21 (see FIG. 4.7).

These sealing means comprise here, on the one hand, a rod 3 having a substantially cylindrical body provided with a sealing ring 31 of diameter equal to the nominal diameter of the bore 56, and, on the other hand , a return spring 4 of the rod 3 which is engaged thereon and which is arranged in compression between the sealing ring 31 and the sleeve 5. This rod 3 is disposed in the bore 56 of the second body 2 More specifically, one of its ends is engaged in the second portion 81 of reduced section of the bore 56 while the other of its ends is engaged in the sleeve 5. Its length is such that its two ends can not not simultaneously be in contact with the bottom of the second portion 81 of the bore 56 and the bottom of the sleeve 5. The rod 3 is thus maintained transversely and is adapted to translate longitudinally between two extreme positions. In a first extreme position shown in FIGS. 2, 4 and 7, the return spring 4 holds one of the ends of the rod 3 in abutment against the bottom of the second portion 81 of the bore 56. In this position , the sealing ring 31 is disposed below the first enlarged portion 80 of the bore 56, so that it obstructs the control fluid passage in this bore 56.

It thus prevents any reflux of control fluid from the second outlet duct 21 to the first inlet duct 22 of the second body 2. This sealing ring 31 does not prevent the passage of the control fluid from first conduit 22 input to the second 25 conduit 21 output of the second body 2. Indeed, as shown in Figures 3, 5 and 6, when the pressure P of the fluid at the inlet 11 of the first body 1 is greater than the pressure of the fluid at the outlet 12, 13 of the first body 1 which is connected to the second outlet conduit 21 of the second body 2, this pressure difference 30 causes the translation of the rod 3 towards the socket 5, by compressing the return spring 4, which allows the control fluid to flow freely to open into the associated chamber 301, 303 of the shifter 300. Therefore, the valve 10 can control the position of the pallet 302. tell 300 offset positive; furthermore, by blocking any control fluid reflux, it prevents the position of this paddle 302 from being unstable even if the forces applied thereon by the camshaft vary greatly. According to an alternative embodiment of the invention, the closure means may comprise, in the place of the rod, a closure ball disposed in the first enlarged portion 80 of the bore 56. The operation of the valve of FIG. command remains in this variant identical to that exposed above. According to another variant, a structure of the valve could be provided in which the communication of the corresponding outlets of the first and second bodies would be achieved by another type of mobility of the second body 10 relative to the first body, such as a mobility of rotation.

Claims (10)

  , 1. Valve (10) for controlling a hydromechanical actuator (300), comprising: - a first hollow body (1) comprising a wall provided with an inlet (11) and two fluid outlets (12, 13) under pressure, a second body (2), movably mounted in said first body (1), having an inlet (22) and an outlet (21) of fluid under pressure, the second body (2) being adapted to take relative to the first body (1) two stable positions, including a first stable position in which its outlet (21) is placed facing one of the outputs (12, 13) of the first body (1) and a second stable position in which its outlet (21) is placed facing the other of the outlets (12, 13) of the first body (1), to alternately establish fluid passages between the inlet (11) and one or other of the outlets (12, 13) of the first body (1), characterized in that it comprises closure means (3) movably mounted in the second body (2) so as to close, in one and the other of the two stable positions of the second body (2), a passage (56) of fluid provided between the inlet (22) and the outlet (21) of the second body (2), in case of fluid reflux through the outlet (21) of the second body (2).   2. Control valve (10) according to the preceding claim, characterized in that the closure means (3) comprise a substantially cylindrical body provided with a sealing ring (31).   3. Control valve (10) according to claim 1, characterized in that the closure means comprise a sealing ball.   4. Control valve (10) according to one of the two preceding claims, characterized in that a return spring (4) is provided for the closure means (3) in a closed position of said passage (56). ) of fluid.   5. Control valve (10) according to one of the preceding claims, characterized in that the second body (2) is adapted to take at least one intermediate position in which its outlet (21) and the outlet (12,13) corresponding first body (1) overlap only partially and in which 2997 said shutter means (3) are adapted to close said fluid passage (56).   6. Control valve (10) according to one of the preceding claims, characterized in that said wall of the first body (1) further comprises a third outlet (14,15,16) discharge adapted to be implemented. communication via evacuation means (28, 210) provided on the second body (2) with one or other of the outputs (12, 13) of the first body (1), when said output (12) , 13) is cut off from the inlet (11) of the first body (1) by the second body (2). 10   7. Control valve (10) according to the preceding claim, characterized in that said wall of the first body (1) comprises a plurality of outlets (14,15,16) evacuation adapted to be placed in communication with one or the other of the outlets (12, 13) of the first body (1), when said outlet (12, 13) is cut off from the inlet (11) of the first body (1) by the second body (2). 15   8. Control valve (10) according to one of the two preceding claims, characterized in that said evacuation means comprise at least one groove (28, 210) peripheral provided on the second body (2).   9. Control valve (10) according to one of the preceding claims, characterized in that the second body (2) is movable in translation relative to the first body (1).   10. Control valve (10) according to one of the preceding claims, characterized in that it comprises displacement means (7) of the second body (2) relative to the first body (1) in one of the positions stable and return means (6) of the second cylindrical body (2) relative to the first body (1) in the other stable positions.