FR2756322A1 - DEVICE FOR CONTROLLING A SAFETY VALVE FOR MOTORS WITH TURBOCHARGER PRESSURE MECHANISM - Google Patents

Abstract

This device comprises a pressure box with a membrane acting by a rod on a safety valve ("waste-gate") to send at least part of the exhaust gases bypass relative to the exhaust turbine as a function of pressure. The pressure box (15) includes two membranes (26, 27) which face each other. The smaller one (27) acts by the rod (28) on the safety valve (arrow 40) if an overpressure exists in the pressure chamber (16) inside the housing (15). If there is a vacuum, the larger membrane (26) is pressed against the smaller one, with the pusher (38) interposed. The safety valve can be opened in both cases, in particular also during a cold start to accelerate the temperature setting of a catalytic converter. Applicable to motor vehicles.

Description

The invention relates to a device for controlling a gas valve

  exhaust system, called a safety valve, for turbocharged engines, a valve which, in the open position, releases a short-circuiting duct which bypasses an exhaust turbine and leads to a catalytic converter mounted downstream, the device comprising a pressure box provided with a pressure chamber, having a pressure connection, at least one diaphragm acting on an actuating rod of the safety valve, and a spring

  conferring prestressing to the membrane.

  It is generally known, in the case of turbochargers boosted by the exhaust gas, to circumvent the exhaust turbine by a short-circuiting duct, also called "waste-gate" channel, in order to pass the flow exhaust gas, or at least a part thereof, in front of or next to the turbine. The flow of gas

  in this duct is regulated by a safety valve ("waste" valve).

  The main purpose of the short-circuiting duct is to create, if the pressure is high, a bypass on the exhaust turbine in order to avoid damage. German patent DE 39 35 093 C2 discloses a device for controlling the amount of recycled exhaust gas from an internal combustion engine, wherein a recycle conduit is connected bypass to an exhaust pipe and leads to The exhaust gas recirculation valve has a pneumatic control for this purpose and the adjustment is carried out according to the pressure at which the valve is subjected With this known device, interfering influences in the suction and exhaust ducts must be avoided Proper regulation, using different or opposite directions of adjustment or actuation, is carried out

for this reason.

  The safety valve mentioned at the beginning has no function of controlling a quantity of exhaust gas to be recycled, but must

  allow the escape of the exhaust turbine.

  In addition to bypassing the exhaust turbine in the case of a too high pressure, it would however be advantageous to also allow the turbine to bypass the cold starting regime, in order to carry the catalytic converter as quickly as possible at the service temperature. By bypassing the turbine, the exhaust gas can reach the catalytic converter at a higher temperature. However, at this time, there is no overpressure in the suction system, but, as a rule, a vacuum, so that this known safety valve is not suitable for opening the shorting conduit in a such a situation. To solve this problem, one could provide an additional short-circuit conduit, which would be opened by a particular valve in the cold start regime. That would mean

however, a high expense.

  The present invention aims to create a device of the type mentioned at the beginning, by means of which a single short-circuiting duct to bypass an exhaust turbine can be opened both in

  presence of an overpressure only in the presence of a depression.

  According to the invention, this result is achieved by the fact that - a second membrane is provided in the pressure housing; the pressure chamber is delimited on opposite sides by a respective membrane and, on the periphery, by the body of the pressure housing; the two membranes have different diameters, the largest being connected directly or via intermediate parts to a pusher and the smaller membrane being connected directly or through intermediate parts to the actuating rod, and the largest membrane being pressed against the smaller one, with interposition of the pusher, if there is a depression in the pressure chamber, while the smaller membrane is pressed against the actuating rod if an overpressure

reigns in the pressure chamber.

  According to the invention, the pressure housing, provided with a second membrane, makes it possible to perform a common actuating function, using the same direction of actuation both in the presence of an overpressure as if there is a depression. Only one pressure feed line and only one pressure chamber has been provided. For the opening of the safety valve, the actuating movement is always effected in the same direction, regardless of the fact that

  depression or overpressure prevails in the pressure chamber.

  Other features and advantages of the invention will emerge

  more clearly from the following description of an exemplary embodiment

  non-limiting, and the accompanying drawings showing the principle of this example and in which: - Figure 1 shows the assembly of a device according to the invention and the air and exhaust gas circuits of the combustion engine internal; and - Figure 2 is an axial section of the pressure housing according to the invention. The device whose construction is explained below is incorporated in a system, shown in FIG. 1, for controlling the supply of air outside a motor 1, exhaust gas evacuation and recirculation of 'exhaust. The whole system is basically of a known type, which is why only the essential parts

  the invention will be described in more detail.

  The essential parts for the operation of the engine 1, with regard to the supply of outside air and the exhaust gas discharge, comprise an external air duct 2 in which there is a compressor 3 and a cooler 4. charging air. The outside air is fed to a suction pipe 5 through the compressor 3 in that a bypass controlled by a control line 7 and a two-way and two-position valve 25 in combination has not been provided. with a thrust air recirculation valve 6. From the suction pipe 5, the outside air reaches the engine 1 through a conduit 8 to the motor. From the engine 1 or, more exactly, from the piston zones of this engine, an exhaust duct 9 leads to an exhaust turbine 10 which is followed by a catalytic converter

  12 installed in an exhaust pipe.

  circuit 13 bypasses the turbine 10, which is installed in the exhaust system between the exhaust duct 9 and the exhaust pipe 11. A safety valve 14 opens or closes the short-circuiting circuit 13. The valve is controlled by a device 15 in the form of a pressure housing. The latter comprises a pressure chamber 16 connected to a supercharging pressure regulating duct 17, which duct is connected through a three-way valve and three positions and a bypass duct 19 to the external air duct 2. Pressure regulating conduit 17 starts from a vacuum control conduit 17a. The latter conduit contains a two-way and two-position valve 20 and a check valve 21. The vacuum control conduit 17a opens again into the suction pipe 5. The valve 20 is controlled by a motor electronics 23 through a control line 22. Through a control line 24, this electronics also controls the valve 18 to

  three ways and three positions in the conduit 17 for regulating the pressure.

  The control duct 7 also contains the already mentioned two-way and two-position valve 25, which is also controlled by the motor electronics 23. The pressure chamber 16 is delimited peripherally by the body of the pressure casing And at both ends by a vacuum diaphragm 26 and an overpressure membrane 27 respectively. A rod

  actuator 28 establishes the connection with the safety valve 14.

  The exact construction of the pressure housing 15 is more clearly visible in FIG. 2. The peripheral wall of this housing has a frustoconical shape; the vacuum membrane 26 is placed as a delimitation of the pressure chamber 16 in the largest diameter area, while the overpressure membrane 27 is placed as a delimitation of this chamber in the area of the smaller diameter. The membranes, thus having different sizes, provide a pressure-tight closure of the chamber 16. On the larger diameter side, the housing 15 has a cover 29 with a stop 30 to limit the stroke of the vacuum membrane. 26, and an orifice 31. The latter can lead to the outside, so receive the ambient pressure, or be connected to a control pressure conduit 32. Between the cover 29 and the vacuum membrane 26 is created in this way a

  pressure equalization space 33.

  On the side remote from the pressure chamber 16 of the overpressure diaphragm 27 is, for the support of this smaller membrane, a disk 34 on the rear side of which at the same time a spring is used to produce the prestressing elastic pressure. On the remote side of the disk 34, this spring, designated 35, is supported on a part of the casing body which is constituted in this embodiment by an adjusting nut 36. This is connected by a threaded connection to the body 15. With this connection, the prestressing produced by the spring 35

can be adjusted or adjusted.

  The disk 34 between the spring and the vacuum diaphragm 27, as well as this diaphragm, rest on a stop 37 formed by the wall of the housing body in the zone of its outer periphery. The vacuum membrane 27 is at the same time tight by its edge

device at this location.

  At the vacuum diaphragm 26 is fixedly connected a pusher 38 which passes through the pressure chamber 16 and extends to the diaphragm with overpressure 27 where it is guided and can slide axially in a bushing 39 of pusher guide. This sleeve is in turn fixedly connected to the overpressure membrane 27. The device according to the invention operates in the following manner. When the pressure chamber 16 is subjected to a minimum overpressure from the pressure regulating conduit 17, the diaphragm with overpressure 27 is deflected - together with the thrust guide sleeve 39 and against the restoring force of the spring 35 - in the direction of actuation, that is to say in the direction of the arrow 40, with the result that

  the safety valve 14 opens and releases the short-circuit conduit

  circuit 13 for the bypass of the exhaust turbine 10. The bushing 39 of pusher guide is spaced, as a result of this movement, its position in abutment against the pusher 38. The vacuum diaphragm 26, together with the pusher 38 fixed to it, is applied by a stiffening 42 against the stop 30 and is not deviated. It means that this

  membrane does not act when an overpressure reigns in the chamber 16.

  The relation between the application of an overpressure to the chamber 16 and the stroke of the actuating rod 28, or the actuating force, can be changed by the appropriate choice of the size of the surface of the overpressure membrane. 27 and the magnitude of the force produced by the spring. It is also possible, for this purpose, to change the position of the nut of

  setting 36 appropriately.

  When a vacuum is applied to the chamber 16, for example in the cold start regime, in which the two-way, two-position valve 20 releases the passage through the vacuum control conduit 17a and the three-way valve 18 and three positions is closed in both directions, an ambient pressure of equal magnitude acts from the outside on the useful faces of different magnitudes of the vacuum diaphragm 26 and the overpressure diaphragm 27. Indeed, not only the Equalization space 33 is connected for this purpose to the environment, through the orifice 31, but a spring space 41 also communicates with it through a suitable slot provided in the adjusting nut 36. The two membranes are then bulging inwards. The pusher 38 and the socket 39 of

  Pusher guide are thus pressed in abutment against each other.

  However, since the useful face of the vacuum diaphragm 26 is larger, a resulting actuating force, acting along the arrow 40 against the force of the spring 35, is obtained. When this actuating force exceeds the spring force after a minimum pressure difference between the ambient pressure and the vacuum has been reached in the chamber 16, the spring 35 is compressed and the actuating rod 28 is moved into the chamber. actuation direction 40. The same direction of actuation is thus obtained in the presence of an overpressure. This means that the safety valve 14 is also open to the appearance of a vacuum and that it produces a bypass of the exhaust turbine 10 in the starting regime, with a view to

  faster temperature of the catalytic converter 12.

  Instead of a complete bypass of the exhaust turbine 10 by the flow of the exhaust gas through the short-circuiting duct 13, it is of course also possible to provide

partial flows.

  During a pressure regulation with application of an overpressure to the housing 15, the valve 18 is switched rhythmically between its passing position and its communication position with

  the environment, while the valve 20 is closed.

  The disk 34 has a dual function: to serve firstly as a support and contact surface for the overpressure membrane 27 and also to serve as a bearing and application surface for the spring 35. equalization space 33 does not communicate with the environment through the orifice 31, but with a control pressure conduit 32, the safety valve 14 can also be regulated in another way and it is also possible to establish other pressure relationships for the opening of

the safety valve 14.

Claims (8)

  1 - Control device of an exhaust gas valve, called a safety valve, for turbocharged engines, a valve which, in the open position, releases a short-circuit duct around an exhaust gas turbine and to a downstream catalytic converter, the device comprising a pressure housing provided with a pressure chamber, having a pressure connection, at least one diaphragm acting on an actuating rod of the safety valve, and than a spring conferring prestressing to the membrane, characterized in that: 1.1 a second membrane (26 or 27) is provided in the pressure housing (15); 1.2 the pressure chamber (16) is delimited on opposite sides by a respective diaphragm (26, 27) and, on the periphery, by the body of the pressure housing (15); 1.3 the two membranes (26, 27) have different diameters, the largest (26) being connected directly or by intermediate parts to a pusher (38) and the smaller membrane (27) being connected directly or by intermediate pieces to the actuating rod (28), and the larger diaphragm (26) being pressed against the smaller one (27), with the interposition of the pusher (38), if there is a depression in the pressure chamber (16) , while the smaller membrane (27) is pressed against the actuating rod (28) if an overpressure prevails in the pressure chamber (16).   2 - Device according to claim 1, characterized in that the smallest membrane (27) is provided, on the side facing the larger membrane (26), a bushing (39) of pusher guide, in which is guided the pusher (38).   3 - Device according to claim 1 or 2, characterized in that the actuating rod (28) is provided with a disk (34) of diaphragm and spring against which is applied the smallest membrane (27). ), the spring (35) being held under stress between the disk (34) and a portion (36) of the body of the pressure casing (15) which is away from this disc.   4 - Device according to claim 3, characterized in that said body portion is formed by an adjusting nut (36) to pre-set the pressure exerted by the spring.   - Device according to claim 3 or 4, characterized in that the   disc (34) is applied against a stop (37) formed by the casing body.   6 - Device according to one of claims 1 to 5, characterized in that   the pressure housing (15) has, on the side of the larger membrane (26) which is remote from the pressure chamber (16), a space (33)   pressure equalization device having an outlet (31).   7 - Device according to claim 6, characterized in that a stop (30) for the largest membrane (26) is arranged in space pressure equalization (33).   8 - Device according to claim 6 or 7, characterized in that   the outlet (31) is subjected to ambient pressure.   9 - Device according to claim 6 or 7, characterized in that   the outlet port (31) is connected to a control pressure line (32).