GB2295884A

GB2295884A - Exhaust gas recirculation valve

Info

Publication number: GB2295884A
Application number: GB9521835A
Authority: GB
Inventors: Erwin Krimmer; Tilman Miehle; Andreas-Bernd Rosenbusch
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1994-10-26
Filing date: 1995-10-25
Publication date: 1996-06-12
Anticipated expiration: 2015-10-25
Also published as: DE4438250A1; GB9521835D0; GB2295884B; FR2726328B1; IT1276935B1; ITMI952107A0; ITMI952107A1; FR2726328A1

Description

1

DESCRIPTION

EXHAUST GAS RECIRCULATION VALVE 2295884 The invention is based on an exhaust gas recirculation valve of the generic type of Patent Claim 1. In such an exhaust gas recirculation valve known from DE-C-43 25 169, an actuating diaphragm subjected to an actuating pressure acting against the force of a spring is provided as the actuating drive. Such exhaust gas recirculation valve drives can only be effected, however, if an appropriate pneumatic source is available at the point of use. The provision of such a pressure medium is per se very complicated. Electromagnetically actuated exhaust gas recirculation valves have already been proposed which, as a rule, are designed in such a way that the actuator acts axially on the valve stem of the valve element. Such drives require magnets with a high actuating force in order to permit satisfactory operation of the exhaust gas recirculation valves. In particular, the closing function of the exhaust gas recirculation valve must also be ensured by means of this magnet. This makes the actuating magnet very large in construction and a corresponding energy source is necessary to operate such magnets.

Advantages of the invention The exhaust gas recirculation valve according to the invention with the characterizing features of Patent Claim 1 has, in contrast, the advantage that the actuating force necessary for actuating the exhaust gas recirculation valve is reduced in size in a simple manner by the use of a toggle lever. Substantially smaller magnets and smaller actuating forces can, correspondingly, be used.

2 - In an advantageous further development of the solution in accordance with the invention and according to Patent Claim 3, an adjustment block is provided into which the valve element is screwed and by means of which it is connected to the toggle lever. The valve element location, which has to be exact relative to the valve seat, can be set by screwing the valve stem in and out in such a way that, in the closed position, the toggle lever can be brought into an optimum end position which corresponds to a position in which it is almost fully extended. Once the adjustment has taken place, it is secured by the known self-locking means in accordance with Patent Claim 4. In such a solution, an actuating magnet, which can be made economically small given the small actuating force to be employed, can be used in a particularly advantageous manner. A solenoid plunger magnet in accordance with Patent Claim 6 is advantageously suitable for this purpose. In accordance with Patent Claim 7, the actuating magnet is then located with its axis transverse to the axis of the valve stem in such a way that the toggle lever principle is effectively used. In order to compensate for the f act that the position of the toggle point of the toggle lever, relative to its fixed support location, changes as a function of the location of the armature of the actuating drive, the suspension for the actuating magnet is designed to be movable, in accordance with Patent Claim 8.

A further advantageous configuration consists of the embodiment in accordance with Patent Claim 9 where, in an advantageous design manner, the actuating magnet can be rigidly installed in a casing. Compensation for the change in the relative position of the toggle point of the toggle lever relative to the support location is provided, in this solution, by the driving fork in accordance with Patent Claim 9 having a recess within which the pin which is inserted into the toggle point of the toggle lever can be adjusted. In an additionally advantageous configuration, a pair of toggle levers with two levers each are provided. These

1

Claims

are actuated, in accordance with Patent Claim 13, by means of two driving

f orks in which a common pin f or the two levers of each toggle lever engages. This results in a symmetrical construction which prevents the adjusting block from twisting or jamming.

Drawing Two embodiment examples of the invention are represented in the drawing and are explained in more detail in the following description. Figure 1 shows a first embodiment example of the exhaust gas recirculation valve with a movable magnet in a first functional position, Figure 2 shows the embodiment example of Figure 1 in a second functional position, Figure 3 shows a second embodiment example in longitudinal section with an actuating magnet supported at a fixed location in a casing, Figure 4 shows a section through the embodiment example of Figure 3 along the line IV-IV with the valve stem omitted and Figure 5 shows a perspective representation of the section in accordance with Figure 3.

Description of the embodiment examples Figure 1 shows a pipe 1 which can be part of an air induction conduit of an internal combustion engine or can also be part of an exhaust gas recirculation conduit. In the embodiment example, the pipe is designed as an intermediate piece of an induction conduit supplying air or fuel/air mixture to the internal combustion engine. It has a connecting flange 3 at one end and a hose connection mouthpiece 4 at the other end. The pipe has a connecting mouthpiece 6 which is closed by a flange 7. The flange serves as the retention feature for a mouthpiece 8 which is connected, in a manner not shown, to an exhaust gas recirculation conduit. This mouthpiece protrudes freely into the pipe. An end surface 10 is designed as a valve seat with which the sealing surface of a valve head 11 of a valve element 12 comes into contact. The valve head 11 is guided by a valve stem 14 which is in turn guided in a sealing bush 15 through which its end 16 protrudes out of the pipe. The bush 15 is seated in a guide mouthpiece 17 which stands out from the inner wall of the pipe.

The outer end of the valve stem is connected to a toggle lever 19. The latter has a first lever 20 which is supported, at one end 21, at a fixed location on a support point on a casing 23 which accommodates an actuating drive 22 of the exhaust gas recirculation valve. It is advantageous for the casing 23 to be connected integrally to the pipe 1. The other end 24 of the f irst lever is connected to one end 25 of a second lever 26 of the toggle lever 19, the other end 27 of which second lever having, finally, an articulated connection with the end 16 of the valve stem. At the connection between the ends 24 and 25 of the first and second levers with one another, there is a linkage point, the toggle point of the toggle lever, to which an armature 29 of an electrical actuating magnet 30 is now linked. This armature is designed as a solenoid plunger which, on excitation of the coil 31 of the electromagnet, is drawn into its guide against the f orce of a spring 32 and, in the process, extends the toggle lever 19. This causes the valve element to move into its closed position, as is shown in Figure 1.

In order to open the exhaust gas recirculation valve, the electrical actuating magnet is de-excited in such a way that the armature 29 is moved outwards by the spring 32 and, in the process, brings the toggle lever 19 from its extended position into its toggled position. This is shown in Figure 2. Because one end 21 of the first lever 20 of the toggle lever 19 is supported at a fixed location on the casing 23, the toggle point of the toggle lever 19 is moved upwards during this operation. So that it can follow this movement without difficulty, the electrical actuating magnet 22 is pivotably supported in the casing 23 by means of a pivot bearing 33.

Figure 3 shows an improved configuration which dispenses, in particular, with the pivoting capability of the electrical actuating magnet in order to achieve a compact embodiment with as few moving masses as possible. The configuration of Figure 3 permits, in particular, the coil of the electric actuating magnet in the casing to be sealed by injection so that the part carrying the electrical voltage is insulated in an optimum manner and is positionally secured. In this embodiment, as in the case of Figure 1, a valve element 12 is provided with a valve stem 114. The latter enters the casing 123 of the actuating drive by means of a sealing bush 35 and likewise leaves it via a bush 36 on the opposite side. Within the casing, the valve stem 114 has an external thread 37 with which it engages in a corresponding internal thread of an adjustment block 38 guided on the valve stem. For this purpose, the adjustment block has a through hole 39, part of which is threaded.

The external contour of the adjustment an essentially rectangular crosssection and 40 on the side where the valve stem enters 123. This foot 40 has a hole, which extends to the through hole 39, for accommodating Second levers 126 of the toggle lever 19, here as a pair, are supported on this pin sides of the adjustment block. These levers between the flat side surfaces 42 of the block and the housing walls 54 of the casing walls are respectively parallel to the block. The ends 43 of the pin 41 protruding block has has a foot the casing transverse a pin 4 1. configured 41 on both are guided adjustment 123, which adjustment beyond the levers are guided in casing slots 44 extending parallel to the axis of the valve stem and therefore prevent the adjustment block 38 from twisting on the valve stem.

The first levers 120 and the second levers 126 of the pair of toggle levers are connected together in an articulated manner by means of a common pin 45 and one end 121 of the first levers 120 is supported on a common, fixed location, pin 46 which is inserted into the casing in a transverse hole 47.

The connection between each of the toggle levers and their actuating drive takes place by means of a driving fork 48 which has a recess 49, which is represented more clearly in Figure 5. In the embodiment example, this is configured approximately in V-shape and is open towards the valve stem outlet end with a front boundary wall 50 located parallel to the axis of the valve stem and a rear oblique boundary wall 51 opposite to the front boundary wall. The respective end of the common pin 45 protrudes into this recess. The driving forks 48 are connected together by means of a web 52, the web being in turn connected to the end surface 53 of the armature 129. In the embodiment example, the web is conf igured in the form of an annular flange which is beaded into or engaged (snap connection) in an outer annular groove 55 on the armature 129 and which simultaneously represents a bottom stop for the armature because the annular part can be brought into contact with a flat casing part 56 which acts as the mating stop.

The driving forks respectively enclose the first levers 120 from the outside in such a way that the latter are guided between the driving forks and the second levers 126.

In the present embodiment example, the armature 129 is a solenoid plunger which is reset by a spring 132 in such a way that the toggle lever is moved into its extended position under the action of the spring. The spring makes the closing force for the exhaust gas recirculation valve available in such a way that compensation can be provided, in an elastic manner, for the tolerances in the closed position. In this embodiment example, it is also advantageous for the pair of toggle levers to be extended as far as possible (the position in which the maximum force transmission is achieved) when the exhaust gas recirculation valve is in the closed position.

In order to set the position of the valve stem relative to the adjustment block 38, the valve stem 140 has form-fit surfaces on its emerging end 57. It can be rotated by means of these surfaces and its axial position with respect to the adjustment block 38 can therefore be adjusted. After adjustment has taken place, the access to the end 57 can be closed by a cap 59 which is sufficiently far removed from the end 57 for the valve stem to carry out its opening motion.

This embodiment of the exhaust gas recirculation valve also makes it possible to effect a positional feedback in a simple manner. For this purpose, a brush 62 is provided on the foot 40 and this slides on an opposite resistance track 64 which is fixed to a casing part of the casing 123. Other displacement sensors can also, of course, be applied in the present case because the casing 123 can, in particular, be closed in an essentially leak-tight manner so that the inside of the casing which is not sealed by injection is secured against dirt and the influence of liquids.

The casing is advantageously of cup-shaped configuration with a metallic cup 65, which has plastic sprayed around it, which has openings 67 at intervals for the penetration of the injection compound and which is substantially filled by injection. The injection takes place after the electromagnet has been inserted while keeping free the open spaces necessary for the toggle lever arrangement and the displacement sensor. A cap 68 is then provided at the valve stem 114 end. This cap 68 tightly closes the casing 123 but also permits the casing to be opened for carrying out any possible corrections or repairs.

The injection of the plastic into the casing makes it simple to realize, for example, the casing slot 44 for guiding the adjustment block 38.

CLAIMS 1. Exhaust gas recirculation valve for controlling the exhaust gas recirculation quantities which are supplied to the induction end of an internal combustion engine, having a mouthpiece, which protrudes into a pipe. which is connected to the exhaust gas collecting system, which forms part of an exhaust gas recirculation conduit and whose end opening has a valve seat with which a valve element interacts, which valve element drive and has a valve stem through the wall of the pipe the moving element is connected to the valve stem is actuated by an actuating which is fed characterized in that of the actuating drive by means which is supported on a f ixed of a toggle lever support location.
2. Exhaust gas recirculation valve according to Claim 1, characterized in that the toggle lever consists of at least one pair of levers with two levers in each part of the pair, one first lever of which two levers is supported at one of its ends at a fixed support location provided on the casing of the actuating drive 11 is connected by means of its other end to one end of the other, second lever and is simul taneously connected there to the actuating drive and the second lever of which two levers is conner-ted, at least indirectly, by means of its other end to the valve stem.
3. Exhaust gas recirculation valve according to Claim 1, characterized in that the other end of the second lever is supported on an adjustment block which has a through hole transverse to the axis of the bearing of the second lever r which through hole has, over at least a part of its length, a thread into which a corresponding external thread on the valve stem can be screwed in order to adjust the axial position of the valve element.
4. Exhaust gas recirculation valve according to Claim 3, characterized in that the threaded connection between the valve stem and the adjustment block is provided with a self-locking appliance.
5. Exhaust gas recirculation valve according to Claims 1 to 4, characterized in that the actuating drive is an electrical actuating magnet,
6. Exhaust gas recirculation valve according to Claim 5, characterized in that the actuating magnet is a solenoid plunger magnet.
7. Exhaust gas recirculation valve according to Claim 5 or 6, characterized in that the armature of the actuating magnet is moved, by the actuating magnet, transverse to the axis of the valve stem,
8. Exhaust gas recirculation valve according to Claim 7, characterized in that the actuating magnet is arranged so that it can be pivoted in the direction of the axis of the valve stem in a casing, accommodating the valve stem.
9. Exhaust gas recirculation valve according to Claim 7, characterized in that the actuating magnet is arranged at a fixed location in a casing accommodating the actuating magnet and the arma ture of the actuating magnet has at least one driving fork with a recess extending in the axial direction of the valve stem one boundary wall extending transverse to the actuating direction of the armature, in which recess it is possible to latch an end of a common pin connecting the first levers to the second levers, the depth of the recess being dimensioned in such a way that the pin remains in engagement with the recess whatever the actuating position of the armature.
10. Exhaust gas recirculation valve according to Claims 5 to 9, characterized in that a stop is , having at least - 10 provided for the actuating motions of the armature and of the toggle lever position of the toggle lever a certain extended being determined by this stop as the usual position defining the closed position of the exhaust gas recirculation valve.
11. Exhaust gas recirculation valve according to one of the preceding claims, characterized in thata displacement sensor is provided which records the displacement of the valve stem relative to the casing of the actuating drive.
12. Exhaust gas recirculation valve according to one of the preceding claims 3 to 10, characterized in that a displacement sensor is provided with a and a f ixed part and its moving part is connected to the adjustment block.
13. Exhaust gas recirculation valve accordingto one of the preceding claims 9 to 11, characterized in that the toggle lever consists of a pair of levers with two levers in each part of the pair and a driving f ork engages each end of the pin which is common to this pair and by means of which the levers are respectively connected to one another in an articulated manner and the driving forks are connected to one another by means of a web connected to the end face of the armature.

moving part
14. An exhaust gas recirculation valve constructed and adapted to operate substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.