EXHAUST GAS RECIRCULATION (EGR) SYSTEM WITH A VACUUM REGULATOR IN AN AUTOMOTIVE VEHICLE

Abstract: An automotive vehicle having a diesel engine, a throttle system actuable to control the engine speed, a vacuum pump driven by the engine and forming, at least in part, a vacuum pressure source, and an exhaust gas recirculation [EGR] system. The EGR system comprises an EGR valve and a valve controller or vacuum regulator for governing the level of vacuum pressure communi­ cated to the EGR valve from the vacuum pressure source. The valve controller has a housing [1, 60] defining an output port for supplying operating pressure to the EGR valve, an input port communicating with the vacuum pres­ sure source, and an input port communicating with am­ bient atmospheric pressure. Regulator valving means in the housing [1, 60] includes a control members [5, 100] movable to control communication between the output port and the input ports to govern the valve operating vacuum pressure level. Throttle position responsive means exerts actuating force on the control member [5, 100] to alter the output pressure. The throttle position responsive means comprises a lever [11′, 130] connected to the throttle system, a cam [12′, 132] supported by the housing [1, 60] and driven by the lever [11′, 130] and a resiliently deflectable force transmitting element [10′, 134] between the cam [12′, 132] and the control member [5, 100] for applying force to the control member [5, 100] depending for the position of the lever [11′, 130]. An additional preferably adjustable pressure cam [15] is provided on the cam [12′] for providing a simply con­ structed vacuum regulator which permits a control of the vacuum in such a manner that this abruptly goes over to atmospheric pressure upon a certain position of the lever [11′, 130].

Description: Exhaust gas recirculation (EGR) system in an automotive vehicle and vacuum regulator for use therein. The present invention relates to exhaust gas recirculation (EGR) and more particularly relates to EGR control systems for use with automotive engines. The invention particularly relates to an exhaust gas recirculation (EGR) system in an automotive vehicle having a diesel engine, a throttle system actuable to control the engine speed, a vaccum pump driven by the engine and forming, at least in part a vacuum pressure source, the EGR system having an EGR valve assembly operable to recirculate exhaust gas to the engine air intake in relation to the degree of)valve operating vacuum pressure communicated thereto and, a vacuum regulator or valve controller for governing the level of vacuum pressure communicated to the EGR valve from the vacuum pressure source, and to a vacuum regulator, especially for use in such exhaust gas recirculating systems of motor vehicles with internal combustion engine and with a constant vacuum source, comprising a vacuum chamber and an atmospheric pressure chamber, between which a diaphragm is disposed having an auxiliary sealing disc movable in relation thereto said diaphragm selectively closing both the vacuum input port and a through port in said auxiliary sealing disc, and said auxiliary sealing disc being pressed resiliently towards said diaphragm and acted upon controllably in the other direction by a counter-force. Systems for controlling EGR in spark ignition engines have been in use for many years. EGR in spark ignition engines reduces the emission of oxides of nitrogen (NOx) from the engines, thus minimizing harm to the environment from these gases. Typical EGR control systems constructed for use with spark ignition engines utilize engine intake manifold vacuum, in one way or another, for providing actuating power for controlling positioning of the EGR valve itself. Because intake manifold vacuum levels are indicative of operating conditions of the engine, the intake manifold vacuum level was also sometimes used by prior art systems as a control parameter tending to indidicate the degree of opening of the carburetor throttle valve at a given load. Examples of such EGR control systems are disclosed by US-A- 3,884,200, US-A- 3;739,797 and US-A- 3,970,061 among others. The output of a vacuum regulator as mentioned above is a vacuum in the vacuum chamber controlled dependent on the counter-force, with the aid of which pressure driven exhaust gas recirculation valve (EGR valve) in the exhaust gas recirculation system of a motor vehicle with internal combustion engine is controlled, such as described for example in US-A3,970,061. Diesel engines have not been considered to emit significant amounts of Nox; however, in recent times the amounts of NOx entering the atmosphere from the exhaust of diesel engines has increase, at least in relative terms, and therefore the use of EGR control valves in diesel engines to reduce NOx emissions has become desirable. Diesel engines differ from spark ignition engines in a number of important ways, one being that the diesel engine does not include a valved, or throttled, intake manifold into which the combustion air is induced through a throttle and valve.. Diesel engines induce combustion air through manifold-like ducts; but the amount of gas induced is substantially constant in all operating conditions of the engine. Accordingly the vacuum pressure existing in a diesel engine intake duct, is slight at most. The source of vacuum pressure provided by the intake manifold of a spark ignition engine is therefore not available in a diesel engine. Diesel engines utilized in automotive vehicles are often constructed and arranged to drive small vacuum pumps which form a source of operating vacuum pressure for various pneumatically operated components of the vehicle. The auxiliary vacuum pumps produce vacuum pressure levels adequately great to operate EGR valves for controlling recirculation of engine exhaust gas to the engine intake ducts. In a diesel engine the engine speed under a given load is controlled by the quantity of fuel injected into the engine combustion chambers and accordingly the "throttle" of the diesel engine is considered to be a manually operated foot pedal connected by a linkage to a fuel pump for supplying the engine fuel injectors. The foot operated pedal is actuated to govern the quantity of fuel delivered by the fuel pump to the combustion chambers of the engine and thus controls the engine speed under a given load. Since the gas induced into the combustion chamber remains constant while the quantity of fuel introduced into the combustion chamber varies, the production of NOx varies as a function of throttle setting. This being the case, EGR valves associated with diesel engines can be controlled in relation to operation of the engine throttle. The present invention is based on the object of providing a new and improved EGR control system for diesel engines wherein the EGR valve is provided with operating pressure varying as a predetermined function of the engine throttle position setting and thus enables close control over the recirculation of exhaust gas in the engine The invention is further based on the object of providing a vacuum regulator of the above-described type, which, while being of simple construction and not needing additional switching valves, dependent on different positions of a control lever permits a control of the vacuum in such a manner that the vacuum abruptly goes over to atmospheric pressure upon a certain position of the control lever Such a vacuum regulator ns especially used in exhaust gas recirculation systems of motor vehicles wherein the gas pedal in connection with the throttle flap adjustment lever or injection pump adjustment lever of a diesel injection pump is connected with the control lever for the counter-force. In a preferred embodiment of the invention an EGR system for an automotive vehicle diesel engine is provided wherein an EGR valve assembly is operable to recirculate exhaust gas to the engine air intake in relation to the degree of operating vacuum pressure communicated to the EGR valve by an EGR valve controller responsive to the engine throttle position. The EGR valve controller comprises a regulator and a throttle position responsive regulator actuator. The regulator includes a regulator control member movable to control communication between an output port: communicating with the EGR valve and input ports communicating with a vacuum pressure source and with atmospheric pressure. The control member is acted upon by differential pressure force between the output port pressure and atmospheric pressure and is also acted upon by actuating force exerted on it by the throttle position responsive actuator. Hence the control member can be stabilized to produce a given output pressure to the EGR valve in response to a given throttle position. The throttle position responsive actuator preferably comprises a lever driven cam and a resiliently deflectable force transmitting element between the cam and the regulator control member for applying force to the control member which depends upon the position of the lever-. The force transmitting element changes the force applied to the control member in response to a change in the cam position with the control member moving-in response thereto to-establish a changed output pressure to the EGR valve at which the forces acting on the control member are again balanced. The new EGR control system is constructed to be mounted conveniently on the engine or components thereof and is provided in a small yet rugged and inexpensive housing which is communicated to associated parts by small flexible hoses and the like. The further object is solved according to the invention in that for applying the controllable counterforce, a leaf spring which is fastened to the housing of the vacuum regulator and is in connection with the auxiliary sealing disc provided, a pressure cam disc being connected for fixed rotation with a control lever for acting upon said leaf spring, and that an additional pressure cam is provided on the pressure cam disc outside the cam curve. With such construction, it can be achieved that the vacuum delivered by the vacuum regulator abruptly goes over to atmospheric pressure for example in the position of the control lever according to the idle position of the gas pedal of an internal combustion engine, no additional switching valves being necessary for this control. Upon engagement of the additional pressure cam with the leaf spring, this is pressed down independent of the cam curve so that the auxiliary sealing disc goes into its lower most position and its through port connects the vacuum chamber and the atmospheric pressure chamber. The additional pressure cam is expediently adjustable in its point of action with the leaf spring, whereby different triggering points for the abrupt control of the vacuum to atmospheric pressure can be adjusted. The additional pressure cam is advantageously constructed as adjustment screw. The leaf spring is expediently constructed as double-armed spring with two fastening members provided along the one spring arm which are integrally formed with the leaf spring. This provides a positioning of the leaf spring which is especially insensitive to vibration. At the end of the leaf spring opposing the point of action of the pressure cam disc, means is advantageously provided, expediently an adjustment screw, for the adjustment of the spring bias. Advantageously, a helical pressure spring concentric to the vaccum input port and through port in the auxiliary sealing disc presses the auxiliary sealing disc towards the diaphragm. Other features and advantages of the invention will become apparent from a consideration of the following detailed description made with reference to the accompanying drawings which form a part of the specification. In the drawings Fig. 1 is a schematic illustration of an EGR control system for an automotive diesel engine embodying the present invention, Fig. 2 is a perspective view of an EGR valve controller or vacuum regulator embodying the invention, Fig. 3 is a partial cross sectional view seen approximately from the plane indicated by the line 3-3 of Fig. 2 with parts shown in alternate positions, Fig. 4 is a cross sectional view seen approximate ly from the plane indicated by the line 4-4 of Fig. 3 with portions broken away, Fig. 5 and 6 are views similar to Fig. 4 with parts shown in alternate positions, Fig. 7 is a cross section view seen approximate ly from the plane indicated by the line 7-7 of Fig. 3, Fig. 8 is a graphic illustration of operation of a device constructed according to the invention, Fig. 9 is a partial sectional view of a vacuum regulator according to the invention with non-adjustable additional pressure cam, Fig. 10 is a plan view of a leaf spring in a vacuum regulator according to the invention, Fig. 11 is a partial sectional view of a vacuum regulator according to the invention with adjustable additional pressure cam, and Fig. 12 is the vacuum output characteristic of a vacuum regulator according Fig. 9 to 11. An automotive vehicle is partially illustrated in Figure 1 of the drawings as comrising a diesel engine 12, a fuel pump 14 for supplying fuel to be injected into the engine combustion chambers, and a throttle system 16 for controlling the amount of fuel directed by the pump 14 to the engine The throttle system 16 is illustrated as comprising a foot-operated pedal 17 and a linkage 18 between the pedal 17 and the fuel pump 14. The vehicle 10 additionally includes a source of actuating vacuum pressure for operating various components associated with the vehicle. In the preferred embodiment an engine driven vacuum pump 20 is associated with-a vacuum reservoir tank, or accumulator, 22; the pump and reservoir tank forming the vacuum pressure source. The engine, fuel pump, throttle system, vacuum pump, and reservoir tank may all be of any conventional or suitable construction and therefore are schematically illustrated and not described in detail. An EGR system 30 constructed according to the invention recirculates controlled amounts of engine exhaust gas from the engine exhaust manifold 12a to the engine intake ducts 12b as a function of the engine throttle system setting. The EGR system 30 comprises an EGR valve assembly 32 for controlling the EGR flow and an EGR valve controller 34 for governing operation of the EGR valve assembly 32 by supplying controlled operating vacuum pressure to the valve assembly 32 depending upon the condition of the engine throttle system 16. The EGR valve assembly 32 provides modulated flows of exhaust gas to the engine intake. The assembly 32 is of generally conventional construction and as illustrated by FIGURE 1 includes a cross-over valve housing 40 containing a valve seat 42 and a poppet valving member 44 coacting with the seat 42 to control the flow through the valve housing 40. A valve housing inlet port 46 communicates with the exhaust manifold 12a and a housing outlet port 48 communicates. with the intake duct l2b. When the poppet valving member 44 moves from the seat 42 exhaust gas flows through the valve housing 40 to the intake ducts. The poppet valving member 44 is moved relative to the seat 42 by a vacuum operated valve actuator 50 which positions the poppet valving member 44 to maintain a controlled EGR flow. The valve actuator 50 comprises a poppet stem52 extending from the valving member 44 through a seal in the wall of the housing 40 to an actuating diaphragm assembly 54. The diaphragm assembly 54 is hermetically attached to the rim of a cup-like housing so that the diaphragm and cup form a chamber 57. A helical compression spring 58 in the chamber 57 reacts between the diaphragm assembly 54 and the cup 56 to bias the valving member 44 toward engagement with the seat 42. The cup 56 is provided with a vacuum port 56a through which EGR valve actuating vacuum is communicated from the controller 34. The diaphragm assembly 54 and cup 56 are supported on the valve housing 40 by a supporting bracket 59 having spoke-like legs which expose the side of the diaphragm assembly 54 opposite the chamber 57 to atmospheric pressure. When vacuum pressure is communicated to the chamber 57 the diaphragm assembly 54 is moved by the applied differential pressure force acting on it against the force of the spring 58 and disengages the poppet -vaiving member 44 from the seat - 42. The flow of exhaust gas through the valve housing 40 is controlled by the degree of EGR- valve opening which depends upon the level of vacuum pressure in the chamber The EGR valve controller 34 is effective to produce output vacuum, pressure for actuating the EGR valve assembly 32 from the vehicle vacuum pressure source in relation to operation of the engine throttle system 16. The EGR valve controller 34, illustrated by FIGURES 2-7, comprises a housing assembly 60, a regulator 62 and a regulator actuator 64. The regulator 62 is disposed in the housing 60 in communication with the vehicle vacuum source and the EGR valve assembly. The regulator actuator 64 is supported by the housing and coats with the throttle system 16 and the regulator 62. Referring to FIGURES 2 and 3 the housing assembly 60 comprises a bracket-iike support base 70 and a pair of die cast interfitting housing members 72, 74 attached to each other. The housing castings interfit and are preferably assembled together and then staked or crimped to maintain them assembled. The housing assembly thus constructed defines a regulator section 80 and an actuator section 82. The regulator section 80 defines an output pressure chamber 84 communicable with the EGR valve assembly 32 via an output port 86, an input port 90 communicating with the vacuum source, and an atmospheric pressure chamber 92 communicating with ambient atmospheric pressure via an input port 94. The regulator 62 is disposed in the regulator section 80 and controls communication of the output chamber 84 with the input vacuum and the atmospheric pressure chamber, respectively, to govern the EGR valve operating output pressure produced in the chamber 84 and thus control the position of the EGR valve. Referring to FIGURES 3-6 the preferred regulator 62 comprises a control member 100 movable to control communication between the output port and the input ports to govern the EGR valve operating pressure level. The illustrated regulator 62 comprises the control member 100, in the form of a movable valve body, a flexible diaphragm 102 supporting the valve body 100, a biasing spring 104 reacting against the valve body 10bur a fixed valve body 106, and a valving member 108 coaching with the movable valve body 100 and the fixed valye body 106. The control member valve body 100 is preferably an annular member defining a central valve body port extending axially through it and a valve seat 112 extending about the port for engagement with the valving member 108. The fixed valve body 106 is preferably a thin walled rigid tube disposed within the control member valve body port and projecting from the input vacuum port 90 through the output pressure chamber 84. The fixed valve body tube is supported by the housing member 72 and sealed to the housing member to prevent leakage between the input port and the output chamber. The fixed valve body 106 defines an annular valve seat 118 at its projecting end which is sealingly engageable with the valving member 108. The diameter of the fixed valve body tube is smaller than the control member valve body port to permit flow between them. The valving member 108 is preferably a button-lie structure molded integrally with the diaphragm 102 and urged resiliently toward sealing engagement with the seat 112 by narrow tongue-like strips of material (see FIGURE 3) continuous with the valving member 108 and the diaphragm 102. The diameter of the member 108 is greater than that of the seat 112 so the member 108 can sealingly engage the seat 112. The output pressure chamber 84 is alternatively communicable with the input vacuum pressure and the atmospheric pressure chamber 92 to alter the output pressure to the EGR valve assembly 32. When the valve body 100 moves in-a direction away from the output chamber 84, as shown by FIGURE 4, the valving member 108 is carried by the valve body 100 so that it is and remains sealingly engaged on the seat 112 while being disengaged from the annular seat 118 formed by the end of the fixed valve, body 106. This results in direct communication between the vacuum pressure source and the output pressure chamber 84 via the valve body 106 causing reduction of the pressure in the chamber 84 as it is evacuated. When the control member valve body 100 moves toward the output chamber 84 (see FIGURE 5) the valving member 108 sealingly engages the fixed valve body seat 118 so that continued movement of the movable valve body 100 disengages the seat 112 from the valving member 108 causing atmospheric air to flow from the atmospheric pressure chamber 92 through the movable valve body seat 112 and into the output chamber: 84. The position of the movable valve body 100 is determined by forces acting en it applied by the regulator actuator 64, the biasing spring 104 and a feedback force created by differential pressure acting across the valve body 100 and the diaphragm 102 between the chambers 84, 92. The spring 104 biases the valve body 100 away from the chamber 84, tending to cause the valve body seat 112 to lift the valving member 108- away from the seat 118 and communicate the output chamber 84 with the vacuum source. The spring force is opposed by both the regulator actuator force and the feedback force. The feedback force is created by differential pressure acting on the effective area provided by the diaphragm 102 and the valve body 100. The diaphragm 102 is sealed about its outer perimeter to the housing member 72 and is sealed to the valve body 100 about its inner perimeter. Thus the diaphragm and valve body form a movable wall between the output and atmospheric air chambers so that a feedback force which varies according to output pressure is exerted on the valve body 100. The regulator actuator and feedback forces are altered relative to each other so that they tend to balance the biasing spring force and the valve body 100 tends to be positioned with the valving member 108 blocking communication between the output chamber 84 and both the vacuum source and the chamber 92. For example, when the actuator force applied to the valve body 100 increases, tending to move the valve body 100 from the position illustrated by FIGURE 6, the regulator output vacuum decreases thus reducing the differential pressure feedback force on the valve body 100 so that the valve body 100 returns to the position illustrated by Figure 6. If the regulator'actuator force is decreased, tending to shift the valve body.100 to its position illustrated by FIGURE 4, the regulator output vacuum is increased, increasing the differential pressure feedback force acting on the valve body 100 and resulting in the valve body 100 being again positioned as illustrated by Figure 6. The differential pressure feedback force acting on the valve body 100 and the diaphragm 102 thus provides degenerative feedback in the form of a stabilizing force which changes in magnitude to oppose any unbalanced regulator actuator force on the valve body 100 so that the valve body 100 always tends to remain essentially stationary and in the position illustrated by Figure 6. The regulator actuator 64 is best illustrated by FIGURES 2, 3 and 7 and provides a controlled actuating force applied to the control member valve body 100 in response to engine throttle system settings to thus control the EGR valving member position The regulator actuator 64 comprises an engine throttle system engaging lever 130 drivingly connected to a regulator controlling cam 132 which exerts a lever position responsive force on the regulator member.100 via a resilient force transmitting element 134. As is best illustrated in FIGURES 2 and 3, the housing member 74 is formed with an integral bearing block projection 140 supporting a drive shaft 142 for rotation relative to the housing member. The cam 132 is keyed to the drive shaft 142. One end of the shaft 142 projects from the bearing block 140 and is keyed to the lever 130. The bearing block 140 encloses the cam 132 so that the chamber 92 is not exposed to dirt, dust, etc. present in the entironment of the housing 60. The force transmitting element 134 is preferably a leaf spring having its midsection 150 engaging arms 152 projecting from the regulator member 100 into the atmospheric pressure chamber 92 The ends of the arms 152 are formed-with guide projections extending loosely through guide slots in the spring element. The leaf spring element 134 defines a cam follower section 154 projecting cantilever fashion to the cam 132 from the arms 152. The preferred cam follower construction employs a bearing ball 155 seated in a pierced hole formed in the spring material. The ball 155 is trapped between the cam and the spring by the resilient spring forces applied to it. The hardness and wear resistance of the ball 155 assures low friction, abrasion free engagement between the cam and element 134. The opposite end of the spring element 134 projects cantilever fashion from the arms 152 to a calibration screw 156 which is threaded into the housing member 74 and bears on the spring element 134. The calibration screw is adjusted during manufacture of the valve controller and then sealed in place in the housing member 74. The spring element 134 is supported in the housing by arms 157 extending parallel to the main body of the spring element and riveted to the housing member 72. The arms 157 are narrow and readily flexible so that they support the spring element in place but do not contribute in any material way to the spring function of the element. As the throttle system is operated to control the engine speed, the cam 132 is rotated by the lever 130 and drive shaft 142 to vary the force exerted by the leaf spring element 134 on the regulator control member 100. This in turn alters the controller output vacuum communicated to the EGR valve assembly by an amount dependent upon the positioning of the throttle system. When the output vacuum reaches its adjus-ted level the regulator control member 100 is retur-ned to its position illustrated by FIGURE 6 with the leaf spring element 134 deflecting to accommodate the small amount of regulator control member movement required. The spring element 134 is preferably formed from stainless sheet stock so that it is quite stiff. In the illustrated EGR system the controller output vacuum pressure varies as a function of the throttle system setting in the manner illustrated graphically by FIGURE 8. When the throttle is "closed, i.e., when the throttle system is positioned to prevent injection of fuel to the engine, the lever 130 is in an initial (zero degree) position which conditions the regulator against producing any vacuum output to the EGR valve assembly 32. No recirculation of exhaust gas occurs. As the throttle system is actuated to increase the supply of fuel to the engine, the vacuum output from the EGR valve controller 3 increases essentially as a linear function of the angular lever movement from the initial lever position wn9¯cated at 00 on the graph of FIGURE 8. The output of the valve controller 9s set at "zero" vacuum during manuracture by moving the lever 130 to its initial position and advancing the calibration screw 15o against the leaf spring element 134 until the force exerted on the regulator control valving member' 100 by the leaf spring 134 overcomes the biasing force of the spring 104 to Just move the control valving member to the positon indicated by FIGURE 5 of the drawings. As the lever 130 is moved angularly from its initial position, the force exerted by the cam 132 on the spring element -134 is diminished at a rate determined, by the shape of the cam periphery which, in the illustrated embodiment, is shaped to provide for the aforementioned linear increase in output vacuum as a function of angular displacement of the leve-r 130 from its initial position. When the throttle approaches its "wide open" position in which the fuel supplied to the engine is nearly maximum, the production of NOX by the engine is minimum and EGR is neither necessary nor desirable. Accordingly, when the throttle system reaches a predetermined position, the output vacuum from the EGR valve controller is reduced precipitously to zero, resulting in the EGR valve closing and preventing further recirculation. The reduction of output vacuum level is accomplished by a lobe 132a on the cam 132 which, when the lever 130 has been rotated, say, 20 degrees from its initial position, is moved into engagement with the leaf spring element 134 causing an abrupt increase in the force exerted by the leaf spring member 134 on the regulator control member. This force increase overcomes the biasing force of spring 104 and results in the regulator control member 100 being positioned as illustrated in FIGURE 5, the same as it was when the throttle was closed. The cam lobe 132a is configured to exert sufficient force on the leaf element 134 to positively insure the regulator control member 100 remains fixed in its position illustrated by FIGURE 5 as the lever 130 continues to be rotated beyond 20 degrees from its initial position. It should be apparent from the foregoing description that the vacuum output provided by the valve controller 34 can be programmed to vary as any reasonable function of the lever rotation by the throttle system since the valve controller output vacuum can be governed wholly as a function of' the shape of the cam 132. Hence, the EGR control system can be used to control EGR in virtually any diesel engine by making relatively minor constructional adjustments primarily to the cam 132. The vacuum regulator shown in Fig. 9 includes a housing 1 with a vacuum chamber 2 and an atmospheric pressure chamber 3. Between the vacuum chamber 2 and the atmospheric presser chamber 3 a diaphragm 4 with an auxiliary sealing disc 5 movable in relation thereto is disposed. A through port 6 in the auxiliary sealing disc 5 connects the atmospheric pressure chamber 3 and the vacuum chamber 2. Depending on the position of the auxiliary sealing disc 5 with respect to the diaphragm 4, the through port 6 is operated or closed by the diaphragm 4. Depending on its position the diaphragm 4 also closes a vacuum input port 7 in the vacuum chamber 2, which leads to a source of vacuum aV not shown. A helical pressure spring 8 presses the auxiliary sealing disc 5 towards the diaphragm 4. The vacuum chamber 2 has a vacuum output port 9, at which the controlled vacuum appears. In the atmospheric pressure chamber 3, a leaf spring 10' fastened to the housing l is provided, which is in connection with the auxiliary sealing disc 5 and presses down same against the force of the helical pressure spring 8. A pressure cam disc 12' connected for fixed rotation with a control lever11' pivotally positioned in the housing 1, and with a cam curve 131- acts upon the leaf spring 10.' and presses same to a greater or lesser degree towards the helical pressure spring ,8, depending on position of the control lever 11 On the pressure cam discl2r an additional pressure cam 14' is further provided outside the cam curve 139, said pressure cam 14' pressing down the leaf spring in addition to the depression effected by the cam curve 13' in such a manner that the auxiliary sealing disc 5 is pressed upon a slight control lever rotation into its lowermost position against the helical pressure spring 8. In the embodiment of the vacuum regulator shown in Fig.l 1, the additional pressure cam14, is constructed as adjustable pressure cam in the form of an adjustment screw 15'. Fig. 10 shows a leaf spring10' in plan view. The leaf spring 10'is constructed as two-armed spring with two fastening members 17' provided along the one spring arm16' integral therewith. By means of this construction, the leaf spring louis especially insensitive to vibration. At the end of the leaf spring 10' opposite to the point of action of the pressure cam disc 12-' means is provided over the spring arm 16? thereof for adjusting the spring bias in the form of an adjustment screw 18. The vacuum regulator is designed in such a manner that in the position of the control lever 11' shown in Fig. 9 and 11, the maximum vacuum or as compared to atmospheric pressure occurs. If the control lever 11' is moved towards the right into the position shown in Fig. 9 and 11 the auxiliary sealing disc 5 is pressed down so that the through port 6 is opened and the vacuum chamber 2 is brought into communication with the atmospheric pressure chamber 3. The vacuum in the vacuum chamber 2 as compared to the atmospheric pressure, also acting via the diaphragm on the auxiliary sealing disc 5, decreases until the auxiliary sealing disc 5 is again raised into the position opposite to the diaphragm 4 in which the through port 6 is closed via the diaphragm 4. Thus a balance has become established upon a lower vacuum or in the vacuum chamber 2. If the control lever 11'is pivotted from the position shown in Fig. 3 andli towards the left, the additional pressure cams41 or the adjustment screw', respectively, presses the leaf spring upon a lever rotation about a very small angle , for example l,5 , and thus presses the auxiliary sealing disc 5 into a downward position in which a complete pressure compensation of the vacuum qV in the vacuum chamber 2 as compared to atmospheric pressure takes place. Such a vacuum output characteristic is shown in Fig. 12, in which the vacuum csV in the pressure chamber 2 is shown as compared to atmospheric pressure via the angle of rotation of the control lever 11' . The curve of the vacuum and the maximum value thereof can be determined by the choice of the cam c'urval"-3',of the pressure cam disc 12'.The drop in vacuut-,- caused by-the additional pressure cam 14'or the a-djüstment screw 15', respectively, can be altered by shif tingt,-he-po$int of action of this pressure cam 14'or the adjustment screw 15'in the direction of the leaf spring. The construction of the vacuum regulator according to the invention with the leaf spring being fixed has a high vibrational stability, whereby at two unloaded ends there is no influence on the output vacuum oV. Merely by varying the point of contact of the adjustment screw 18'in the leaf spring plane is it possible to either adjust tolerances or to achieve different output characteristics. Normally there is a limit in the gradient of the change of vacuum versus the rotation of the control lever. This means that a complete "switch-off" of the vacuum or over ashort rotation, for instance 10, as e.g. is required in "switchoff" of an exhaust gas recirculating valve (EGR valve) actuating vacuum on idling in a diesel engine, is not possible by changing the cam curve 13'. In the vacuum regulator according to the invention, an additional pressure cam 14'combined with the pressure cam disc 12'is used, which is touching the leaf spring 10'on a certain point which allows a short lever movement by means of the leaf spring 10'more or less as lever, hereby overriding the regulator, and by an abrupt movement of the auxiliary sealing disc 5 opens the vacuum chamber 2 to atmospheric pressure. The vacuum input port 7 is closed under this condition so that a vacuum consumption on idling is avoided. The touch point of the additional pressure cam 14'or the adjustment screw 15',respectively, can be easily been chosen by means of the adjustment screw 18'in order to vary the amount of the maximum vacuum, or the actuation radius of the additional pressure cam 14' can be modified in order to achieve another gradient of the drop in vacuum versus the control lever rotation. While embodiments of the invention have been illustrated and described herein in considerable detail, the invention is not to be considered limited to the precise constructions shown. Various adaptations, modifications and uses of the invention may occur to those skilled in the art to which the invention relates and the invention is to cover hereby all such adaptions, modifications and uses which fall within the scope or spirit of the appended claims.

Claims: CLAIMS: 1. Exhaust gas recirculation (EGR) system in an automotive vehicle having a diesel engine (12), a throttle system (16) actuable to control the engine speed, a vaccum pump (20) driven by the engine and forming, at least in part, a vacuum pressure source (20, 22), the EGR system (30) having an EGR valve assembly (32) operable to re circulate exhaust gas to the engine air intake in relation to the degree of valve operating vacuum pressure communicated thereto and, a vacuum regulator or valve controller (34) for governing the level of vacuum pressure source, characterized by said valve controller (34) comprising: : a) a housing (1, 60) difining an output port communicating with the EGR valve (32) for supplying operating pressure thereto, an input port communicating with the vaccum pressure source (20, 22), and an input port communicat ing with ambient atmospheric pressure; b) a regulator valving means in said housing (1, 60) including a control member (5, 100) movable to control communication between said output port and said input ports to govern the valve operating vacuum pressure level, said control member (5, 100) acted upon by differential pressure force between the output pressure and the pressure at one of said input ports; and c) throttle position responsive means for exerting actuating force on said control member (5, 100) which varies as a predetermined function of throttle system operation to alter the output pressure, said throttle position responsive means comprising: i) a lever (11', 130) connected to said throttle system (16); ii) a cam (12', 132) supported by said housing (1, 60) and driven by said lever (11', 130); and iii) a resiliently deflectable force transmitting element (10, 134) between said cam (12', 132) and said control member (5, 100) for applying force to said control member (5, 100) depending on the position of said lever (11', 130), said force transmitting element effective to change the force applied to said control member in response to change in the cam position with said control member moving in response thereto to establish a changed output pressure to said EGR valve (32) at which the forces acting on said control member are balanced. 2. EGR system as claimed in claim 1, characterized in that said controller (34) comprises a housing (60) defining a lever supporting bearing porting (140) ,said cam supported by said bearing portion within said housing. 3. EGR system as claimed in claims 1 or 2, characterized in that said force transmitting element (10, 134) comprises a resilient spring element extending between said cam (12', 132) and said regulator member (5, 100) and further including an adjustably movable calibration element (18, 156) engageable with said spring element. 4. EGR system as claimed in claim 3, characterized in that said spring element (10, 134) is a leaf spring having a midsection (16', 150) engaging said regulator member (5, 100) and oppositely extending end portions resiliently engaging said cam (12', 132) and said calibration element (18', 156), respectively. 5. EGR system as claimed in claim 4, characterized by a spring member (8, 104) biasing said regulator member (5, 100) against said spring element (10', 134). 6. EGR system as claimed in claim 5, characterized in that said cam (12', 132) includes a lobe portion (132a) effective to engage said spring element (12', 132) and produce a force on said regulator member (5, 100) which exceeds the force of said spring member (8, 104) for preventing said valve controller (34) from opening said EGR valve (32) when said lever (11', 130) is in a position for maximizing the fuel supplied to the engine. 7. Vacuum regulator, especially for use in exhaust gas recirculating (EGR) systems as claimed in any one of claims 1 to 6 of motor vehicles with internal combustion engine and with a constant source of vacuum, comprising a vacuum chamber (2) and an atmospheric pressure chamber (3), between which a diaphragm (4) is disposed having an auxiliary sealing disc (5) movable in relation thereto, said diaphragm (4) selectively closing both the vacuum input port (7) and a through port (6) in said auxiliary sealing disc (5), and said auxiliary sealing disc (5) being pressed resiliently towards said diaphragm (4) and acted upon controllably in the other direction by a counter-force, characterized in that for applying said controllable counter-force, a leaf spring (10') which is fastened to the housing (1) of said vacuum regulator and is in connection with said auxiliary sealing disc (5) is provided, a pressure cam disc (12') being connected for fixed rotation with a control lever (11') for acting upon said leaf spring, and that an additional pressure cam (14', 15') is provided on said pressure cam disc (12') outside the cam curve (13'). 8. Vacuum regulator according to claim 7, characterized in that said additional pressure cam (15') is adjustable in its point of action with said leaf spring (10'). 9. Vacuum regulator according to claims 7 or 8, characterized in that said additional pressure cam is constructed as adjustment screw (15'). 10. Vacuum regulator according to claims 7, 8 or 9, characterized in that the leaf spring (10') is constructed as two-armed spring with two fastening members (17') provided along the one spring arm (16'), which are integral with the leaf spring. 11. Vacuum regulator according to any one of the claims 7 to 10, characterized in that at the end of the leaf sprin (10') opposing the point of action of the pressure cam disc (12'), means (18') is provided for adjusting the spring bias. 12. Vacuum regulator according to claim 11, characterized in that the means for adjusting the spring basis an adjustment screw (18'). 13. Vacuum regulator according to any one of claims 7 to 12, characterized in that a helical pressure spring (8) concentric to the vacuum input port (7) and through port (6) in the auxiliary sealing disc (5) presses said auxiliary sealing disc (5) towards said diaphragm (4).

Inventors: PIESCHE, GUNTER, DIPL.-ING., Piesche, Günter, Dipl.-Ing.
Applicants: RANCO INCORPORATED
Application year: 1982
Main classification: F02D21
IPC codes: F02D21, G05D16, F02B3