EP0441100B1 - Device for controlling the exhaust valve of an internal combustion piston engine - Google Patents

Description

The invention relates to a device for controlling the exhaust valve of a reciprocating piston internal combustion engine according to the features of the preamble of claim 1. The current for the electromagnet is switched on and off by electrical signals dependent on the crank angle of the internal combustion engine, so that the machine does not have a camshaft drive for actuation of the exhaust valve.

A device of this type is known from EP-OS 139 566. In the known device, the servo piston is pressurized on both piston sides. The servo cylinder is therefore provided with a pressure medium connection on each piston side, via which the pressure medium is supplied and discharged. When the servo piston moves, pressure medium flows in on one piston side, while pressure medium flows out on the other piston side. The direction of flow of the pressure medium is reversed when the servo piston performs the opposite movement. With frequent and rapid movements of the servo piston, the reversal of the direction of flow of the pressure medium can lead to undesirable vibrations of the pressure medium columns in the servo cylinder spaces and the lines connected to them. The difference between the surfaces acted upon by the pressure medium on both sides of the piston is decisive for the speed of the servo piston movement. This gives there is a relatively large piston diameter and thus a relatively large moving piston mass. In addition, the servo cylinder design is relatively complex because of the pressure medium supply on both piston sides. The pilot valve of the known device is designed as a 3/2-way valve and has two valve seat surfaces, one on the pressure medium inflow side and one on the pressure medium outflow side. The closure part, which is movable between these two seat surfaces, must sit tightly on the associated seat surface in each end position, which places special demands on the manufacturing accuracy. The third connection of the pilot valve leads to the end face of the slide of the 4/2-way valve. The pilot valve is also structurally complex because of the two valve seat surfaces and because of the third connection. Finally, the known device is switched such that when the electromagnet is energized - the closure part of the pilot valve is in the closed position on the valve seat surface associated with the pressure medium supply, while the pressure medium discharge side is open. As a result, the end face of the slide is relieved of pressure medium and the slide has a position in which the servo piston is loaded by the pressure medium and the outlet valve opens. When the electromagnet is de-energized, however, the closing part of the pilot valve opens the pressure medium supply and blocks the pressure medium discharge, so that the end face of the slide is loaded by the pressure medium. This puts the slide in a position in which the servo piston is relieved and the exhaust valve is closed. This circuit is disadvantageous because even in the event of a power failure, for example as a result of a cable break or a fault in the control electronics, the outlet valve always remains closed. This will Wear behavior of the cylinder and piston of the internal combustion engine adversely affected.

The invention has for its object to improve a control device of the type mentioned in such a way that it is structurally simpler and that the disadvantages mentioned are avoided.

According to the invention, this object is achieved by the features of claim 1. This configuration of the control device ensures that the outlet valve also opens when the electromagnet is without current for the sake of a fault, so that no compression work is then carried out in the working cylinder and the wear between the working cylinder and piston is reduced. Because the servo cylinder of the new control device has a connection only for the pressure medium supply and a connection only for the pressure medium discharge, the servo cylinder has a clear flow direction of the pressure medium from the supply connection to the discharge connection, so that the pressure medium columns in the servo cylinder and in the lines connected to it are essential tend to vibrate less than in the known device. Because only one piston side of the servo piston is acted upon by the pressure medium, the diameter of the piston side acted on by the pressure medium can be dimensioned significantly smaller than in the known device, thereby reducing the moving piston mass. This has an advantageous effect in that the outlet valve can be actuated at a higher speed and with greater accuracy. The fact that the pilot valve is designed as a 2/2-way valve with only one valve seat surface results in a constructional simplification, because the closure part only has to close tightly in one end position and the valve housing has one connection less.

Fig.1

einen Vertikalschnitt durch den oberen Teil eines Arbeitszylinders mit einem Auslassventil sowie ein Schaltschema der Steuereinrichtung,

Fig. 2

einen Axialschnitt durch ein 4/2-Wegeventil der Steuereinrichtung,

Fig. 3

einen Axialschnitt durch ein Vorsteuerventil der Steuereinrichtung und

Fig. 4

einen gegenüber Fig. 3 um 90° gedrehten Axialschnitt durch den oberen Teil des Vorsteuerventils.

An embodiment of the invention is explained in more detail in the following description with reference to the drawing. Show it:

Fig. 1

a vertical section through the upper part of a working cylinder with a Exhaust valve and a circuit diagram of the control device,

Fig. 2

an axial section through a 4/2-way valve of the control device,

Fig. 3

an axial section through a pilot valve of the control device and

Fig. 4

an axial section through FIG. 3 rotated through 90 ° through the upper part of the pilot valve.

1, a working cylinder 1 is formed in the machine housing of a 2-stroke diesel internal combustion engine, and then an exhaust duct 4 is formed in a separate housing 10 at its upper end. An outlet valve 2 is arranged in the housing 10 at the entrance of the exhaust duct 4 and, in the closed position shown, separates the combustion chamber 3 in the working cylinder 1 from the exhaust duct 4. In the working cylinder 1, a working piston 5 is guided up and down. The air to be compressed in the working cylinder is admitted into the cylinder chamber via slots (not shown) arranged in the lower region of the working cylinder 1 and is compressed in the combustion chamber 3 during the subsequent upward stroke of the working piston 5. The fuel is supplied with the aid of at least one injection nozzle (not shown) projecting into the combustion chamber 3.

At the end of the exhaust valve 2 facing away from the combustion chamber 3, a piston 6 is arranged, which is guided in a cylinder 7 of the housing 10. On the cylinder space 7 'located in FIG. 1 below the piston 6 A compressed air line 9 is connected via a check valve 8. The air enclosed in the cylinder space 7 'in this way forms an air spring which acts on the exhaust valve 2 in a closing sense.

On the upper side of the piston 6 in FIG. 1, a servo piston 11 actuated by a hydraulic pressure medium acts on a rod 11 ′ and is guided in a servo cylinder 13 to which a hydraulic control device 12 is connected. The control device 12 has a pilot valve 15 designed as a 2/2-way valve and actuated by an electromagnet 14 and a 4/2-way valve 16. The hydraulic pressure medium, for example oil, is supplied to the control device 12 via a line 17 from a pressure medium source 18 designed as an accumulator. The accumulator 18 receives the pressure medium from a reservoir 20 by means of a pump 19 which is driven by the crankshaft (not shown) of the internal combustion engine or electrically. The pressure medium in the accumulator 18 is under a pressure of, for example, 200 bar. The line 17 leading from the accumulator 18 to the control device 12 forks upstream of the 4/2-way valve 16 into two line branches 17 'and 17''. The line branch 17 'leads to the 4/2-way valve 16 and continues as line 27 to a connection point 21 on the servo cylinder 13. The line branch 17 ″ contains a throttle point 22 and leads on the one hand to the pilot valve 15 and on the other hand to an end face of the 4/2-way valve 16. On the servo cylinder 13 there is a further connection point 23 for a relief line 24 which leads to the 4/2-way valve 16 leads and continues as a drain line 24 ', which opens into the reservoir 20 via a check valve 25. There is also a vent line to the drain line 24 ' 26 connected, which branches off from the servo cylinder 13 above the piston 11 and has a throttle point 57. A relief line 28, which emanates from the pilot valve 15, opens into the outlet line 24 ′ upstream of the check valve 25.

The servo piston 11 has a blind bore 40 at its end facing away from the rod 11 ', which is connected to an annular space 58 at its lower end in FIG. 1 in the region of the connection point 21 via transverse bores 56. In the area of the connection point 23 there is an annular space 59 between the servo piston 11 and the servo cylinder 13.

In the position shown in FIG. 1, the current at the electromagnet 14 of the pilot valve 15 is switched on, and the pressure medium supplied via the line branch 17 ″ acts on the end face of the 4/2-way valve 16; the pressure medium supply via the line branch 17 'and the line 27 to the servo cylinder 13 is shut off. In contrast, the 4/2-way valve 16 has made the passage from the relief line 24 to the drain line 24 ', so that the servo piston 11 in the servo cylinder 13 is relieved of the pressure of the pressure medium and the outlet valve 2 is influenced in a closing sense by the air spring under the piston 6 becomes. If the current at the electromagnet 14 is switched off, a connection is established in the pilot valve 15 between the line branch 17 ″ and the relief line 28, so that the end face of the 4/2-way valve 16 is relieved of pressure. The 4/2-way valve 16 thus interrupts the previous connection of the lines 24 and 24 'and now connects the line branch 17' to the line 27, so that pressurized pressure medium via the connection point 21 Space 58 and the transverse bores 56 enter the blind bore 40, as a result of which the servo piston 11 is moved downward and the outlet valve 2 opens.

2, the 4/2-way valve 16 essentially consists of a housing 30 with four connection points 31, 32, 33 and 34 and a slide 35 movable in the housing. The slide 35 has three piston-like thickenings 36, 37 and 38, which are closely guided in five bore sections with a corresponding diameter in the housing 30. Corresponding to the four connections 31 to 34, the housing 30 has four enlarged chambers 41, 42, 43 and 44 located between these bore sections, each of which via at least one channel 41 ', 42', 43 and 44 'with the associated connection 31 to 34 is connected. The relief line 24 coming from the servo piston 13 opens at the connection point 31, and the drain line 24 ′ leading to the reservoir 20 is connected to the connection point 32. The line 27 leading to the servo piston 13 is connected to the connection point 33 and the line branch 17 ′ coming from the accumulator 18 is connected to the connection point 34. At the upper end of the housing 30 in FIG. 2, a cover 45 is fastened to it, which is closed at its end not shown in FIG. 2 and has a stop bolt 46 in its center. The bolt 46 limits the upward movement of the slide 35 in FIG. 2. On the upper end of the slide 35 in FIG. 2, a compression spring 47 is supported, which is accommodated with its other end, not shown, in the cover 45 and which Slider 35 in Fig. 2 can move downward.

The fork point of the line 17 shown in FIG. 1 outside the 4/2-way valve is in the embodiment 2 integrated into the slide 35. For this purpose, the lowest piston-like thickening 38 in FIG. 2 is provided with a transverse bore 48 which continues downward into an axial blind bore 49. At the lower end of the blind bore 49 there follows a narrow transverse bore, which forms the throttle point 22. The throttle bore 22 continues outwards into a bore 50 which opens out into an incision 51 in the lateral surface of the thickened area 38. In the area of this incision 51, the thickening 38 leading bore section below the chamber 44 is slightly expanded, so that in the position shown, a pressure medium connection from the chamber 44 via the bores 48, 49, 22 and 50 to a space 52 below the lower end of the Slider 35 is made. The space 52 is delimited at the bottom in FIG. 2 by a connecting piece-like component 54 fastened to the housing 30 and is connected to the pilot valve 15 via a channel 53. The mouth of the channel 53 in the space 52 is opposite a flat surface 55 on the slide 35.

According to FIG. 3, the pilot valve 15 consists essentially of a housing 60 with two connection points 61 and 62, a closure part 63 movable in the housing and the electromagnet 14 actuating this closure part. The closure part 63 interacts with a seat part 65 inserted in the housing 60, which at its upper end in FIG. 3 has a valve seat surface, below which a plurality of channels 66 open, which are connected to the connection point 61 via an annular groove 67 and a channel 68. At the connection point 61, a line, not shown, is connected, which is connected to the channel 53 on the 4/2-way valve 16 (FIG. 2). In Fig. 3 above the seat part 65 is in the housing 60 Outflow chamber 69 is provided, which is connected to the connection point 62 via a narrowed throttle bore 70. The relief line 28 (FIG. 1) is connected to the connection point 62. In Fig. 3 below the closure part 63, a spring 71 is provided, which is supported on the closure part 63 and acts on it in the opening sense.

At its upper end in FIG. 3, the closure part 63 is detachably connected to an armature 73 of the electromagnet 14 via a rod 72. The armature 73 also has a bar 72 ′ corresponding to the bar 72 at its other end. The upper end of the rod 72 'in FIG. 3 interacts with a stop bolt 74 which is adjustably fastened in a cover 75 of the magnet housing 76. The armature 73 is axially movable and is held by two spring spiders 77 and 77 ', which are releasably attached to the center of the rod 72 and 72', respectively. On their outer circumference, the spring spiders are clamped between a nozzle-like component 64 in the magnet housing 76 and the housing 60 or between the magnet housing 76 and the cover 75. The armature 73 is surrounded by a brass sleeve 78 which is sealed off from the magnet housing 76 and the component 64. The brass sleeve 78 is in turn surrounded by a magnet coil 79, which is provided with a power supply (not shown) via a lateral opening 80 in the magnet housing 76. The armature 73 has a continuous channel 81 which extends in the axial direction and which continues at its lower end into a channel 81 'in the component 64. The two end faces of the armature 63 are connected to the drain chamber 69 in the valve housing 60 via the channels 81 and 81 '.

As shown in FIG. 4, a channel 82 is provided in the magnet housing 76 outside the magnet coil 79, which extends between the upper end face of the armature 73 and the spring spider 77 ', continues downward in the valve housing 60 and via a transverse bore 83 to the connection point 62 ( Fig. 3) leads. In this way, when the closure part 63 is open, different hydraulic pressure prevails on both end faces of the armature 73, so that the armature 73 is flowed through by pressure medium upwards. At the same time, the space above the armature 73 is vented, specifically via the channel 82 and the bore 83. This significantly increases the repetition accuracy of the actuating movement of the pilot valve.

In the position shown in FIGS. 3 and 4, the electromagnet 14 is energized and holds the closure part 63 in the closed position. This prevents the discharge of pressure medium from the space 52 via the channel 53 of the 4/2-way valve, and the slide 35 moves upwards in FIG. 2. This movement is initially relatively rapid and is damped as soon as the lower boundary edge of the incision 51 enters the bore section in the housing 30 that guides the piston-like thickening 38. This damping means that the slider 35 slows down against the stop bolt 46. In this slide position, the connection points 31 and 32 are connected to one another via the chambers 41 and 42, so that the servo piston 11 is relieved and the outlet valve 2 closes. At the same time, the connection point 34 and thus the chamber 44 are separated from the chamber 43 via the piston-like thickening 38, so that no pressure medium can reach the connection point 33. However, the chamber 44 is through the bores 48, 49, 22 and 50 and the incision 51 during the first phase of movement of the slide 35 in connection with the space 52, so that a pressure builds up in the space 52 due to the closed pilot valve, which moves the slide. Towards the end of this movement, ie during the slowed-down movement due to the damping described above, only a little pressure medium flows into the space 52.

When the current of the electromagnet 14 is switched off, the spring 71 presses the closure part 63 into the open position, so that the previously blocked pressure medium from the bores 66 via the outflow space 69, the channels 81 ', 81 and 82 and the bore 83 and Connection point 62 flows into the relief line 28. At the same time, a smaller amount of pressure medium flows through the throttle bore 70 and the connection point 62 into the relief line 28. This escape of the pressure medium acts via the channel 53 on the 4/2-way valve 16 on the pressure of the pressure medium in the space 52 under the slide 35. The slide 35 consequently moves downward and thereby establishes the connection between the chambers 44 and 43 as soon as the thickening 38 emerges from the bore section between these chambers. Pressure medium can thus pass from the chamber 44 via the connection point 33 into the line 27 and - as described in relation to FIG. 1 - load the servo piston 11. When the connection between the chambers 44 and 43 is established, the connection between the chambers 41 and 42 is interrupted because the thickening 36 enters the bore section between these two chambers. The relief line 24 is thus separated from the drain line 24 '. When the slide 35 comes with its flat surface 55 near the mouth of the channel 53, there is also a damping of the movement of the slide 35.

In a departure from the exemplary embodiment described, it is also possible - instead of arranging the channel 82 in the magnet housing 76 - to lead the channel 82 outward through the cover 75 and then to connect it to the relief line 28 via a special line. In addition, for reasons of symmetry, it is advantageous to arrange several such channels in the armature 73 instead of one channel 81. Correspondingly, several channels are also provided in component 64.

Claims (9)

1. Device for controlling the exhaust valve (2) of a reciprocating-piston internal combustion engine, which valve is operatively connected at its end which is distant from the closure part to a servo piston (11), which is guided in a servo cylinder (13) and one side of which is acted upon by a hydraulic pressure medium in the valve opening direction during the power stroke of the engine, which medium is supplied to the servo cylinder (13) from a pressure medium source (18) via a pressure medium line (17, 17', 27), a pilot valve (15), which is operated by a solenoid (14), and a 4/2 way valve (16), which comprises a mobile slide (35), being arranged in the pressure medium line (17, 17', 27) between the pressure medium source (18) and the servo cylinder (13) such that one front face (55) of the slide (35) - depending on the position of the mobile closure part (63) of the pilot valve (15) - is acted upon by hydraulic pressure medium and the pilot valve (15) is closed when the current in the solenoid (14) is switched on and open when the current in the solenoid (14) is switched off, characterised in that, in addition to the connection (21) for the pressure medium supply line (17, 27), the servo cylinder (13) comprises a connection (23) for a pressure medium removal line (24), which is connected to the 4/2 way valve, that the other side of the servo piston (11) is not acted upon by the pressure medium, that the pilot valve (15) is formed as a 2/2 way valve with just one valve seat face, that the other front face of the slide (35) is supported at a spring (47), and that the pilot valve (15) and the 4/2 way valve (16) are arranged with respect to one another such that when the pilot valve (15) is closed the front face (55) of the slide (35) is acted upon by pressure medium and the slide (35) occupies a position in which it opens the pressure medium removal line (24), so that the servo piston (11) is relieved of pressure medium and the exhaust valve (2) is closed, and that when the pilot valve (15) is open the front face (55) of the slide (35) is relieved of pressure medium and the slide (35) is in a position in which which it opens the pressure medium supply line (17, 17', 27), so that the servo piston (11) is acted upon by pressure medium and opens the exhaust valve (2).
2. Device according to claim 1, characterised in that an accumulator (18), which stores the pressure medium under pressure, is provided as the pressure medium source.
3. Device according to claim 1 or 2, characterised in that the armature (73) of the solenoid (14) comprises at least one passage (81), which connects its two front ends and communicates at its end which faces the pilot valve (15) with the discharge chamber (69) of the pilot valve, and that the passage (81) communicates at its end which is distant from the pilot valve (15) with the discharge side of the pilot valve via a channel (82).
4. Device according to claim 3, characterised in that the channel (82) extends in the housing (76) of the solenoid (14).
5. Device according to claim 3, characterised in that there is a throttle connection (70) between the discharge chamber (69) and the discharge side of the pilot valve.
6. Device according to one of claims 1 to 5, characterised in that the pressure medium supply (17'') to the pilot valve (15) passes via the slide (35) of the 4/2 way valve (16).
7. Device according to claim 6, characterised in that the slide (35) of the 4/2 way valve (16) is provided with a damping device which becomes operative after the slide (35) has established the connection between the pressure medium source (18) and the servo cylinder (13) and broken the connection between the servo cylinder (13) and the removal line (24').
8. Device according to claim 6, characterised in that the slide (35) of the 4/2 way valve (16) is provided with a damping device which becomes operative after the slide (35) has established the connection between the servo cylinder (13) and the removal line (24) and broken the connection between the pressure medium source (18) and the servo cylinder (13).
9. Device according to one of claims 1 to 8, characterised in that the exhaust valve (2) is connected to an air spring which acts on the exhaust valve in the closing direction.

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