DE2855027A1 - DEVICE FOR ACTUATING AN ACTUATING ELEMENT IN A COMBUSTION ENGINE ON AN EXHAUST GAS RECIRCULATION CONTROL DEVICE - Google Patents

Description

285502? 5 ·

R. 5 1 9 3

1.12.1978 Bö / Ba

ROBERT BOSCH GMBH, 7000 Stuttgart 1

Device for actuating an exhaust gas recirculation control device Acting actuator in internal combustion engines

State of the art

The invention is based on a device according to the main claim. In such a known device, a load-analog signal is generated and z. B. by a load-dependent change in a cross section in a pressure medium supply line, a variable set pressure, which forms at an outflow throttle, is provided, the size of which corresponds to the load set on the fuel injection pump. However, this device has the disadvantage that for an accurate measurement of recirculated exhaust gas quantities in accordance with the characteristic map, a high expenditure for the measurement of flow cross-sections and their assignment to the respective load points has to be made.

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Advantages of the invention

The device according to the invention with the characteristic Features of the main claim has the advantage that the exhaust gas recirculation control device essentially occupies only two positions, either completely closed or completely open and that when a certain value is exceeded Load or a certain amount of fuel injected z. B. a certain high part load or the starting conditions characterized .. The dimensioning of the flow cross-sections can in this case with significantly less effort be performed. For internal combustion engines that require a small amount of exhaust gas recirculation to meet the legal requirements A device of this type is sufficient to meet regulations on the composition of the exhaust gas.

Through the measures listed in the subclaims advantageous developments and improvements of the device given in the main claim are possible. Particularly The embodiment according to the dependent claim in conjunction with claims 4 to 6 is advantageous Design is advantageously the otherwise present during the actuation of the exhaust gas recirculation control device Discharge of a fuel flush volume from the injection pump switched off. This flushing amount is advantageously determined by the amount of fuel required for the adjustment replaced so that the z. B. also for other control purposes regulated fuel pressure in the suction chamber of the injection pump is not influenced by the operation of the exhaust gas recirculation control device.

drawing

Five exemplary embodiments of the invention are shown in the drawing and are described in the following description explained in more detail. 1 shows a first embodiment

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example in a schematic representation, Pig. 2 a partial section by a fuel injection pump with an arrangement for generating a control variable when exceeded a certain load point, Fig. 3 shows a second embodiment with one of a hydraulic servomotor actuated poppet valve in the cross section of an exhaust gas return line, 4 shows a third exemplary embodiment with an arrangement for interrupting the flushing volume outflow from the suction chamber of a fuel injection pump according to Embodiment according to FIG. 2 when an exhaust gas recirculation control device is actuated, Fig. 5 shows a fourth embodiment with a control of the supply of an adjusting agent from a second pressure source, 'which is independent of the fuel injection pump and FIG. 6 shows a fifth exemplary embodiment with one compared to the exemplary embodiment according to FIG. 5 modified control of the actuating agent supply from one second pressure source.

Description of the exemplary embodiments

A return of controlled amounts of exhaust gas to the intake manifold of an internal combustion engine has proven to be an effective means proven to reduce the proportion of pollutants in the exhaust gases of the internal combustion engine ^^ u. In particular, can in self-igniting internal combustion engines, the high NOx content be reduced. Despite various known and complex control devices for the recirculation of exhaust gas The requirement remains to make such facilities as simple and reliable as possible. In particular, For smaller vehicles, the most inexpensive and simple possible control of the exhaust gas recirculation quantity is still sufficiently effective be achieved. Adjustment is particularly suitable for this; those with high fuel injection quantities z. B. at full load or at a start enrichment interrupts the recirculation of the exhaust gases in order to be critical in this

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Areas in which. Β. maximum performance is required of the internal combustion engine, no reduction in performance occurs due to exhaust gas recirculation. In the rest Areas can achieve an average good result with a correspondingly adjusted average exhaust gas recirculation amount can be achieved in the exhaust gas composition.

In Fig. 1, a fuel injection pump is schematically 1, which supplies an internal combustion engine with fuel via lines 2. From the exhaust manifold 5 the only schematically shown internal combustion engine leads an exhaust gas recirculation line 6 to the intake manifold 7 downstream of the Shaft 9 of a throttle valve 10 arranged in the intake manifold, with its part located downstream of the shaft 9, the outlet opening 11 of the exhaust gas recirculation line 9 is controllable and is closed at full load. The so educated The exhaust gas recirculation control device influences both the cross section through the position of the throttle valve the outlet opening 11 and the pressure gradient at this opening. The shaft 9 of the throttle valve is via a linkage 14 mechanically connected to an actuator 15 of a servomotor 16. The actuator is designed as an actuating piston and includes a working space 19 in a closed cylinder 18 and is on its opposite side from one Return spring 20 loaded. The working space 19 is an adjustable throttle 23 in the relief line 22 is arranged, connected to 'a fuel tank 24. Furthermore, there is between the working chamber 19 and the fuel-filled and under-fueled chamber, also referred to as the suction chamber Pressurized interior space 28 of the fuel injection pump connects via a control line 26, the cross section of which can be controlled by a valve 27.

The suction chamber 28 of the fuel injection pump is opened with the aid of a fuel feed pump 30 via a fuel supply line 31 is supplied with fuel from the reservoir 24. A pressure control valve is parallel to the fuel feed pump

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switched. The injection pump is in in this case a distributor injection pump of known design, in which the position of the control slide 34 the effective delivery stroke of the pump piston 35 is determined as a quantity adjustment element. According to the design principle of this distributor injection pump, the pump piston, as indicated by arrows, a reciprocating and simultaneously rotating movement. The adjustment of the control slide takes place in a known manner by means of a centrally mounted lever 38 which, on the one hand, connects to the control slide connected and on the other side of at least a regulating spring 39 applied with an adjustable bias will. Contrary to the force of this spring, the regulating sleeve 40 of a centrifugal governor 42 engages the lever in a known manner at. The regulating sleeve is adjustable by means of flyweights 4l, which are driven to rotate in proportion to the pump speed. Depending on the bias of the regulating spring 39, the regulating sleeve is shifted to a greater or lesser extent at a certain speed, so that the control slide 34 also has a higher or lower relative position to the pump piston 35 assumes. The position of the regulating sleeve as well as the lever 38 and the control slide 34 each represent a measure for the set fuel delivery rate or for the load.

As indicated in Fig. 1 by dashed lines, The cross-section of the valve 27 can be load-dependent according to the position of the control slide 34, the lever 38 or Regulating sleeve 40 can be adjusted. Such an adjustment can be made without any reaction, both mechanically and electrically Ways to be carried out. An advantageous embodiment for generating a mechanical, reaction-free control variable shows Fig. 2. There the carrier 43, on which the regulating sleeve 40 can be displaced by the flyweights, has a axial bore 45 which opens into an outer ring groove 46 on the carrier '. The annular surface of the outer ring groove 46 forms a first stationary throughflow opening 47 of the valve 27. The axial bore 45 is part of the control line 26. In the

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Wall of the regulating sleeve 40 is also provided with a second throughflow opening 48 which can be adjusted together with the regulating sleeve, which forms the other part of the valve 27. By shifting the regulating sleeve 40, the second throughflow opening is opened 48 can be brought into overlap with the first throughflow opening 47, as a result of which from a certain axial displacement the regulating sleeve a connection from the suction chamber 28 to the working chamber 19 via the control line 26 can be established.

The device described above can be regarded as a comparison device, the first stationary flow opening 47, the annular groove 46, a comparison or threshold value represents as a measure for a certain minimum load or minimum fuel injection quantity. Only when the second flow opening 48 is brought into overlap with the first throughflow opening, this comparison device emits a signal in the form of a fuel flowing through both flow openings Stromes, which is fed to the working space 19. A working pressure then accumulates at the throttle 23 Working space 19, which moves the actuator 15 and the throttle valve 10 in the closed position with respect to the Brings exhaust gas recirculation line.

The process described above can also be represented in a mechanical-electrical way, e.g. B. by a pair of contacts, one of which characterizes a fixed load and the other that of the time Actual load. When the set minimum load is reached, a circuit is closed via the contacts, which is a Actuator operated in such a way that the exhaust gas recirculation is prevented. Actuator can be an electric motor or a Be a magnet.

In the manner described above, the exhaust gas recirculation can be prevented from a certain adjustable load, so that a maximum possible charge can be supplied to the combustion chambers of the internal combustion engine during full load operation. Also will

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in the case of increased fuel supply when starting, there is no hindering the start-up of the cold internal combustion engine Exhaust gas recirculation carried out.

Fig. 3 shows another embodiment of the exhaust gas recirculation control device, with an exhaust gas recirculation valve 49, which in the same way as in the embodiment according to Pig. I. and 2 is controlled. The confluence of the exhaust gas recirculation line 6 into the intake manifold 7 is shown there. the The inlet opening 15 is formed by a valve disk 51 controlled, des.en valve stem 52 in one of the Inlet opening 50 protruding into the suction pipe 7 on the opposite side inserted valve guide 54 is held. On one off the end protruding from the suction pipe 7, the valve stem 52 is connected to the clamping plate 55 for an adjusting diaphragm 56, which is the actuator of a hydraulic actuator 58. in the Housing 59 of this servomotor is of the operating diaphragm 56 of Working space. 19 included, in which the control line 26 ■ opens out and from which the relief line containing the throttle 23 22 leads to the fuel tank 24. The operating diaphragm 56 is controlled by a compression spring 60 via the clamping plate 55 loaded that it brings the valve stem 52 and valve disk 51 into a position closing the inlet opening 50. The who Compression spring 60 containing space 6l between the operating diaphragm 56 and suction pipe 7 is through a bore 62 to the suction pipe Pressure equalization connected.

This configuration, the exhaust gas recirculation control device has the advantage that the closing movement of the valve disk 51 is supported by the exhaust gas pressure. The design described of the hydraulic servomotor .has the advantage that no fuel can leak into the intake manifold of the engine. This essentially causes the use of the operating diaphragm 56, which the working chamber 19 regardless of the position of the Valve disk 51 closes tightly.

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As soon as fuel is passed into the working chamber 19 via the control line 26, it builds up there as a result of reaction the throttle 23 a pressure that moves the control diaphragm 56 against the force of the compression spring 60 and the Valve disk 51 lifts off its seat at inlet opening 50. If the flow openings 47 or 48 ' closed, the working chamber 19 is closed via the throttle

23 and the relief line 22 relieved, so that the valve plate 1 can return to its closed position. With the help of the throttle 23, the actuating speed of the Valve can be adjusted.

FIG. 4 shows a supplementary embodiment to the embodiment according to FIG. 3. Here it is an identical exhaust gas recirculation valve 49 is provided, as has already been described in connection with FIG. 3. However, it differs from the embodiment according to FIG. 3 a pressure switch 64 is provided, which consists of a membrane 66 firmly clamped in the pressure switch housing 65, which tightly encloses a pressure space 67 in the housing 65 and separates it from a second space 69, in the between the membrane and housing 'a compression spring 68 is arranged. A second relief line 70 protrudes into the room at right angles to Diaphragm 66, which when deflected against the force of the compression spring 68, the inlet opening 71 of the second relief line 70 can close. The space 69 is also with the non-closable second part, the to the fuel reservoir 24 leading relief line 70 connected. The pressure chamber 67, however, protrudes a branch line 73 with the control line 26 in connection.

The second relief line 70 leads, as in FIG. 1 can be removed from the suction chamber 28 to the fuel tank

24 and contains at the outlet from the suction chamber a throttle a flushing throttle 74 which, when the relief line is not closed, a fuel flushing quantity flowing out of the suction chamber 28 certainly. This rinse is done in the usual way

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for thermal relief and for degassing fuel injection pumps applied.

The device according to FIG. 4 operates as follows: When the flow openings 47 and 48 overlap are brought or if via the control line 26 to the When fuel flows into the working chamber 19 of the hydraulic servomotor, this fuel also reaches the pressure chamber 67 » in which the pressure building up at the throttle 23 is then set. Under the action of this pressure, the Diaphragm 66 deflected and closes the 'inlet opening 71 of the second relief line 70 and thus prevents that through the relief line fuel flushing reaches the fuel tank. In an advantageous manner in this version is the usual flush volume replaced by the amount of fuel passed through the throttle 23 flows into the fuel tank 24 and the same Puncture met. Advantageously, a constant internal pressure in the suction chamber 28 then flows continuously Fuel quantity through one of the throttles 23 oc "er 74, so that the regulated pressure in the suction chamber, the z. B. to spray "·, ι Adjustment is used, not when the exhaust gas recirculation device is actuated is disturbed. .

Fig. 5 shows a modified embodiment in which very little fuel effluent for actuation of the exhaust gas recirculation valve is necessary. The same as in the previous exemplary embodiments is used here a control pressure in the control pressure line 26 by throttling of the fuel flowing through the flow openings and 48 located in overlap at the throttle 23 is formed. Deviating from the embodiment according to Fig. 3 or 4, a pressure switch 76 is provided with a switching membrane 77a the pressure chamber in the housing 78 of the pressure switch 79 includes. The control line 26 opens into this. From the side opposite the pressure chamber 79 is the switching diaphragm is loaded by a compression spring 80. On this side there is also one more isolated from the housing

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Contact 8l arranged ₃ with which the switching membrane 77 is brought into contact when deflected against the force of the spring 80. The switching membrane is designed to conduct electricity and is connected to one pole of a voltage source 83, the other pole of which leads to contact 81. Furthermore, the solenoid winding of a solenoid valve 84 is connected in the connecting line between voltage source 83 and contact 81.

The solenoid valve is located in an actuating agent supply line 86 which leads from a pressure source 87 into the working space 19 ′ of a pressure-actuated servomotor 88. This servomotor is designed as a diaphragm servomotor with an actuating diaphragm 89 ^{which tightly encloses the working chamber 19 1} and which serves as an actuating member of the exhaust gas recirculation valve 49 '. In a modification of the above exemplary embodiments, the servomotor is designed in such a way that it can be actuated by negative pressure. For this purpose, a compression spring 90 is arranged in the working space 19 ', which acts on the control diaphragm 89 in an adjustment direction that closes the exhaust gas recirculation valve 49'. To relieve the work space "19", a relief line 91, which contains a throttle 92, is also provided here. The vacuum source can be implemented in the form of a vacuum reservoir or in the form of a suction pump 93.

The device works as follows: As soon as the throttle 23 is due to the inflowing fuel a pressure builds up, which also comes into effect in the pressure chamber 79, the switching membrane 77 is in contact brought to contact 81 and the circuit is closed. The solenoid valve 84 pulls in and establishes the connection between pressure source 87 and working space 19 '. Due to the negative pressure that builds up there, the operating diaphragm becomes 89 deflected against the force of the spring 90 and that Exhaust gas recirculation valve 49 'open. If the pressure falls in the

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Control line 26 from, the circuit is opened and the actuating agent supply line 86 through the solenoid valve 84 closed. The exhaust gas recirculation valve 49 ′ accordingly closes after pressure equalization via the drosel 92.

Due to this configuration, only a very small amount of fuel is available. Actuation of the pressure switch 76 necessary, so that the pressure in the suction chamber 28 of the fuel injection pump when the necessary actuation of the Exhaust gas recirculation device would not be significantly disturbed. Advantageously, one can already be in the with the Internal combustion engine operated vehicle existing pressure source for actuating the exhaust gas recirculation device be exploited. This can e.g. B. be the use of the intake manifold vacuum. But it can also be used an existing compressed air brake system, the brake reservoir pressure for the actuation of a correspondingly modified Use exhaust gas recirculation valve.

Fig. 6 shows a modified embodiment in which the amount of fuel flowing out of the suction chamber of the injection pump when the flow openings 47 and 48 overlap is used as a control variable for a switching valve through which an auxiliary energy source can be connected to a servomotor for the exhaust gas recirculation valve. An embodiment is shown which works in the same way as in the embodiment according to FIG. 5 with negative pressure as the setting medium. In this respect, these statements correspond to one another. In contrast, however, instead of a solenoid valve 84 in the actuating agent supply line 86, a pressure switch 95 is used which has an actuating diaphragm 97 which tightly encloses a pressure chamber 96 in the housing. On the other hand, the operating diaphragm 97 encloses a fuel-filled space 100 in which an operating diaphragm 97 is loaded

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Compression spring 98 is arranged and in the nozzle-shaped part of the adjusting agent supply line 86 opens ₃ so that the mouth part 99 of the adjusting diaphragm 97 is opposite and this serves as a valve closing member. The actuating agent supply line 86 leads non-closable from the space 100 to the pressure source 87.

The pressure chamber 96 is connected to the control pressure line 26, so that when the pressure rises in the control line 26, the operating diaphragm 97 is deflected against the force of the spring 98 and the passage opening 99 of the Adjusting agent supply line 86 is closed. Then follows as in the previous embodiment after the pressure in the working chamber 19 'has been relieved, the exhaust gas recirculation valve 49' is closed · In this exemplary embodiment no electrical switching means are necessary in an advantageous manner. Also needs for a quick Actuation of the exhaust gas recirculation device supplies only a small amount of fuel to the interior of the fuel injection pump Control purposes are taken so that the regulated pressure in the suction chamber of the fuel injection pump is not disturbed. This pressure is used e.g. B. the actuation of the injection adjustment. Advantageously, in this embodiment also in In contrast to the embodiment according to FIGS. 1 to 4, the fuel kept away from the exhaust gas recirculation valve, which heats up strongly during operation.

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Claims (1)

^R 5 19 3 December 4, 1978 Bö / Ba ROBERT BOSCH GMBH, 7000 Stuttgart 1 Expectations 1J device for actuating one on one Exhaust gas recirculation control device acting actuator in internal combustion engines with a fuel injection pump, which has an adjustable fuel quantity adjustment element according to the load, the a Weggeber'with a downstream amplification device the control variable generated by the position sensor to form a manipulated variable that actuates the final control element is assigned, characterized in that the displacement encoder with a threshold value comparison device (43/47, 40/48) is connected to compare the load-dependent Path signal with a minimum value representing a high fuel injection quantity and that. the output signal is fed to the comparison device of the amplification device. 2. Device according to claim. 1, characterized in that a pair of contacts in one as a comparison device 030028/0103 - .2 - Λ Γ ^: '2855 (M ⁹³ the drive of the actuator containing circuit is used, with a stationary contact and a corresponding the adjustment of the fuel quantity adjustment element adjustable contact, the position of the stationary Contact represents the minimum value. 3. Device according to claim 1, characterized in that the pairing of two by as a comparison device Displacement in overlap is used throughflow openings, of which one flow opening (47) is stationary and the second throughflow opening (48) corresponds to the adjustment of the fuel quantity adjusting element (40, 38, 43) is adjustable and that when both flow openings overlap a drain opening for pressurized fuel from a fuel storage chamber (suction chamber 28) of the injection pump (1) is formed and the fuel flow from the fuel reservoir as a control variable for the actuation of the actuator (15, 56, 89) is used. 4. Device according to claim 3 _S, characterized in that the downstream flow opening (47) is connected to a control pressure for triggering the actuation of the exhaust gas recirculation device (11, 49, 49 ') leading control line (26) via an adjustable. Throttle (23) with a first relief line (22) 030 0 2 8/0103 " connected is. 5. Device according to claim 4, characterized in that the control line also serves as an adjusting agent supply line is used and is connected to the working space (19) of a hydraulic servomotor (19, 58) whose Control element (15, 56) with the exhaust gas recirculation device (10, 49) is connected. 6. Device according to claim 5 using a fuel injection pump, one of the fuel storage space (Suction chamber) (28) discharging and ein.Spüldrossel (74) containing, an adjustable fuel purging amount second discharge line (70) characterized in that a pressure switch (64) is connected to the control line (26), which generates a control signal when an adjustable pressure is exceeded, by means of which the second relief line (70) can be closed (FIG. 4). 7. Device according to claim 6, characterized in that that the pressure switch is one loaded by a spring (68) and one connected to the control line (26) Pressure chamber (69) enclosing membrane (66), through which the cross section of the second relief line (70) can be closed when the pressure that can be set on the spring is exceeded. - 4 030028/0103. 5 285502? 8. Device according to claim 4, characterized in that with the control line (26) a pressure switch (76, 95) is connected, which when a pressure value that can be set is exceeded, a control signal ■ to actuate the actuator (Fig. 5). . 9. Device according to claim 8, characterized in that the pressure switch has a spring (98) loaded and a pressure chamber ($ 6) connected to the control line (26) enclosing the adjusting diaphragm (97) through which the cross-section of an adjusting agent supply line (86) can be produced from a "second pressure source (87) to the working space (19 ') of a pressure-actuated servomotor (88) connected to the exhaust gas recirculation device (49") (FIG. 6). 10. Device according to claim 8, characterized in that the pressure switch (76) with a solenoid valve (84) is connected, which in one, from a second pressure source (87) to the working space (19 ') of the servomotor (88) leading actuating agent supply line (86) is arranged (Fig. 5) 11. Device according to one of the preceding claims, characterized in that the exhaust gas recirculation control device there is a poppet valve (51) which opens against the exhaust gas flow and which is connected to the servomotor (58) is connected, which is acted upon by the control pressure against the force of a return spring. 030028/0103.