EP0455763B1 - Hydraulic control device for the valves of a multi-cylinder internal-combustion engine - Google Patents

Abstract

The invention concerns an engine cylinder valve control device with a reservoir (26) associated with a pressure chamber (19) in the valve tappet, the reservoir having a piston (23) which also acts as a valve to separate the reservoir (26) from the pressure chamber (19). The piston (23) can be displaced, by a hydraulic control device (37, 38, 39) operating in conjunction with a magnetic valve (36), from its position of rest into a reservoir mode. This enables several valve-control units in an engine to be controlled by a single magnetic valve (36), provided their control times do not overlap.

Description

State of the art

The invention relates to a hydraulic valve control device for an internal combustion engine according to the preamble of the main claim.

In a known hydraulic valve control device of the generic type (DE-OS 3 511 820), the pressure line is controlled via a 2/2-way valve by, according to a special exemplary embodiment (FIGS. 8 and 9), the directional valve in one switching position, the pressure line with the Pressure chamber of a valve lifter and in the other switching position with the pressure chamber of another valve lifter connects and this using only a single liquid reservoir for both print rooms. One control position of the solenoid valve is used for two engine intake valves and only one accumulator is used for both intake valves. The precision of the control, i.e. how exactly the desired opening time cross-section of the engine valve can be reached, especially at high speeds, depends on how large the total oil volume that has to be pushed back and forth in the control and how many control channels with corresponding control cross-sections have to be flowed through . The solenoid valve is particularly noteworthy for the costs and the susceptibility to malfunction of such a hydraulic valve control device, the possible switching frequency of these solenoid valves being largely underutilized in the case of motors of the usual maximum speed.

It has also been proposed (DE-A-38 156 68) to design the accumulator piston as a movable valve member in a generic hydraulic valve control device, the end edge of the piston cooperating with a valve seat, as a result of which the connection between the pressure line and the accumulator chamber can be controlled. The storage piston also serves as the armature of a normally open solenoid valve, so that the pressure line is separated from the storage space when the magnet is energized. In this solution there is a combination of liquid storage and solenoid valve, in which the same part serves as a movable valve member of the solenoid valve and as a storage piston, but this requires that such a solenoid valve storage unit must be available for each valve control unit.

Advantages of the invention

The valve control device according to the invention with the characterizing features of claim 1 has the advantage that to switch on the liquid reservoir, ie to open the connection between the pressure line and the storage space, the storage piston only has to be shifted slightly from its rest position. All possible control devices are conceivable for such a slight displacement. In any case, however, the accumulator piston is only moved further if a corresponding hydraulic pressure is present in the pressure chamber of the valve tappet, which hydraulic pressure can only be present if the drive cam acts on this valve tappet. Accordingly, in all those valve control units in which the drive cam is not currently effective, the displacement of the storage piston from its rest position has no further effect. The bottom edge of the accumulator piston, which cooperates with a fixed seat, is preferably used for this control, so that, in the rest or initial position of the accumulator piston, the pressure channel is delimited radially by the circumferential surface of the accumulator piston, while the accumulator space is delimited by the end face. For this purpose, for example, an annular groove in the area of the seat be formed around the lateral surface, so that the pressure channel opens into this annular groove, as in the valve control device previously proposed above. However, this "accumulator solenoid valve" is open when de-energized, so that when the magnet is not energized, the pressure that expands from the pressure chamber via the pressure channel during the opening action of the drive cam shifts the accumulator piston from the accumulator chamber, as well as when the power supply fails. This is to ensure that if the plug on the solenoid valve fails, the motor cannot go through, but at the expense of a considerable reduction in function, apart from a rather complicated structure of this "storage solenoid valve". The valve control device according to the invention, on the other hand, enables the actual control device to be uncoupled from the high-pressure valve store.

Instead of a seat control, a slide control of the storage piston can of course also be provided, according to which the pressure channel is connected to the storage space only after a certain minimum path of the storage piston has been covered.

According to the embodiment of the invention, the accumulator piston can be displaced from its rest position by means of a control piston, the control piston for its adjustment, which results in the displacement of the accumulator piston, being acted upon by control fluid of low pressure in its working space, which can be supplied to the work area from a liquid source (engine oil circuit) via a control line and the control line can be controlled by the solenoid valve. This results in a clear separation between the high-pressure part with the pressure chamber and storage space on the one hand and the low-pressure part or control part with the working space and control fluid. As a result, the solenoid valve is basically only acted on by low hydraulic pressure, so that more precise control can be maintained due to the lack of oil compression. Of course, a corresponding coordination is required between the spring loading the storage piston and the pressure of the liquid source or the diameter of the control piston, so that, when the control liquid acts on the control piston, the storage piston can be moved out of its rest position, whereby it moves from its valve member function into its Storage function overrides. This decoupling of the two hydraulic circuits makes it possible to operate several but at least two control pistons with a simple 2/2 solenoid valve, with corresponding shifting of the associated accumulator pistons from the rest position. Those accumulator pistons whose assigned pressure chamber is not currently under high pressure from the drive cam immediately return to their starting position, driven by their accumulator spring, after the control pressure has been reduced. However, the accumulator piston, which is acted upon by the high pressure in the pressure chamber of the associated valve tappet, becomes counter to the force of the storage spring, displaced by liquid displaced from the pressure chamber.

According to an advantageous embodiment of the invention, the control piston is additionally loaded in the direction of the storage piston by a spring. Although this is a relatively weak spring, it nevertheless ensures that there is a positive connection between the accumulator piston and the control piston, in order to avoid any advance causing a control error.

According to a further advantageous embodiment of the invention, a radially sealingly guided pressure pin is used for the transmission of movement and force between the control piston and the storage piston. Such a pressure pin enables a largely free choice of cross-section of the control piston, so that, despite the low pressure of the control fluid, a sufficient actuating force is ensured for safely lifting the storage piston out of its rest position. In addition, the frictional forces of a radial seal on such a pressure pin are lower than in the case of a control piston of relatively large diameter.

According to a further advantageous embodiment of the invention, which is also claimed for itself and relates to a multi-cylinder internal combustion engine, in which a valve control unit is assigned to each engine cylinder, several of them become simultaneous Pressure lines controlled by only one solenoid valve, in which only such valve control units are controlled by the solenoid valve, in which the drive caused by the engine camshaft with drive cams does not overlap in time. Advantageously, several pressure lines connecting the pressure chamber of the valve tappet with the respective storage chamber can be controlled with only one solenoid valve, so that costs for unnecessary solenoid valves are saved and, in addition, the susceptibility to faults is reduced. In addition, the accumulators can be arranged very close to the valve lifters in order to keep the control volume and the construction volume as small as possible. The assignment of a valve tappet to a storage piston, which is important for good control precision, is advantageously retained.

According to a further advantageous embodiment of the invention, engine oil which is under delivery pressure serves as the liquid source and can be removed from the engine oil circuit which is usually present in every engine without an additional pump. Instead of the engine oil circuit, however, an extra control oil circuit for the engine valve control can be present in multi-cylinder internal combustion engines.

According to a further advantageous embodiment of the invention, the working space of the control piston is on the control line is connected upstream of the solenoid valve, a throttle being present in the control line upstream of this connection. This throttle decouples the area between the throttle and the solenoid valve, so that when the solenoid valve is open, the pressure in this intermediate section drops to such an extent that the control piston or accumulator piston remains loaded in the initial or rest position by the accumulator spring. It is a kind of passive control, in which an adjustment is only carried out when the solenoid valve is closed and this creates a dynamic pressure in the control line.

According to a further advantageous embodiment of the invention, the solenoid valve is designed as a 2/2-way valve. Depending on the application, such a valve can be designed to be extremely simple, since absolute tightness is not required and leaks do not have a disruptive effect as long as the amount of oil flowing in via the throttle maintains the dynamic pressure. The control fluid, which flows continuously when the solenoid valve is open, ensures that all rooms are filled evenly and that the fluid in the control line is renewed evenly.

According to another advantageous embodiment of the invention, the working space of the control piston is downstream of the solenoid valve on the control line connected. This ensures that the pump for the control liquid is less stressed, since only small amounts of liquid have to be replaced for the control process, namely what the control piston swallows during its stroke. In addition, due to the relatively large possible cross sections, a quick reaction when actuating the control piston can be achieved.

According to an advantageous embodiment of the invention, the solenoid valve is designed as a 3/2-way valve. As a result, a more precise switching behavior can be achieved, it being possible, for example, to work with a hydraulic accumulator due to the small amount of liquid to be moved for the control.

According to a further advantageous embodiment of the invention relating to both of the above-described variants, the storage space is connected via a compensating line to the low pressure fluid source (engine oil circuit), a non-return valve opening in the direction of the storage space being arranged in the compensating line. This ensures that, as long as the storage piston is in its rest position, there is a defined pre-pressure in the storage space in order to thereby keep the forces acting on the storage piston in its rest position defined. A corresponding filling device for the pressure channel or pressure chamber is known per se.

Further advantages and advantageous embodiments of the invention can be found in the following description, the drawing and the claims.

drawing

Fig. 1

einen Längsschnitt durch die Ventilsteuervorrichtung eines Ventils des ersten Ausführungsbeispiels

Fig. 2

einen entsprechenden Ausschnit aus einer Ventilsteuervorrichtung des zweiten Ausführungsbeispiels und

Fig. 3

ein Steuerdiagramm der Ventilsteuervorrichtung für eine 4-Zylinder-Brennkraftmaschine

Two embodiments of the object of the invention are shown in the drawing and described in more detail below. Show it

Fig. 1

a longitudinal section through the valve control device of a valve of the first embodiment

Fig. 2

a corresponding section from a valve control device of the second embodiment and

Fig. 3

a control diagram of the valve control device for a 4-cylinder internal combustion engine

Description of the embodiment

In Fig. 1, a first embodiment of a hydraulic valve control device according to the invention is shown in longitudinal section and as a hydraulic circuit diagram, which between a valve stem carrying a valve stem 2 and one with a Camshaft 3 rotating drive cam 4 is arranged. The valve stem 2 is guided in an axially displaceable manner in a valve housing 5 and is loaded in the closing direction of the valve by valve closing springs 6 and 7, as a result of which the valve plate 1 is pressed onto a valve seat 8 in the valve housing 5. The valve disk 1 controls a valve inlet opening 9 formed between it and the valve seat 8 when the valve is open.

The hydraulic valve control device has a control housing 11 inserted into the valve housing 5, in which a housing chamber and a spring chamber 12 are arranged coaxially therewith, the valve closing springs 6 and 7 being accommodated coaxially to one another in the spring chamber 12. In the control housing 11, a cup-shaped spring plate 13, which is anchored to the valve stem 2 and axially displaceable and loaded by the valve closing springs 6 and 7, is inserted from below. In a central axially continuous bore 14 of the control housing 11, a valve piston 15 cooperating with the valve stem 2 of the inlet valve and, above this, a working piston 16 of a cam piston 17 are arranged so as to be axially displaceable. The working piston 16 is loaded by a return spring 18 which is supported on the one hand on the control housing 11 and on the other hand engages a flange of the working piston 16 and thereby presses the cam piston 17 against the valve control cam 4.

An oil-filled pressure chamber 19 is enclosed in the housing bore 14 between the mutually facing end faces of the valve piston 15 and the working piston 16, the effective length of the entire valve tappet being determined by the amount of oil that is present in the pressure chamber 19. The effective opening stroke of the inlet valve is smaller when the amount of oil enclosed is reduced, and the stroke is maximal when the maximum filling is maintained.

The pressure chamber 19 is connected via a pressure channel 21 to a storage valve 22, which has a radially sealing cup-shaped storage piston 23 which is loaded by a storage spring 24 and rests on a valve seat in its rest position shown in broken lines. The lower end face of the storage piston 23 delimits a storage space 26, while part of the outer surface of the storage piston 23 delimits an annular channel 27 surrounding the latter, into which the pressure channel 21 opens.

The valve control device works with a hydraulic circuit, with a feed pump 28, which draws in the control oil from an oil tank 29 and supplies it to the control device via a feed line 31. To achieve a certain delivery pressure, a pressure control valve 33 is arranged in a line 32 branching off from the delivery line 31 and returning to the oil container 29. The delivery line 31 leads on the one hand to the ring channel 27 or pressure channel 21 and pressure chamber 19 and on the other hand to the storage space 26. Check valves 34 and 35 opening towards the ring channel 27 and the storage space 26 are arranged in both line sections.

The core of the control system is a 2/2-way solenoid valve 36, with which a control line 37 is controlled, which branches off from the delivery line 31 and leads to a working space 38, in which a control piston 39 is radially sealed and axially displaceable by the one in the control line 37 hydraulic pressure is applied. The control piston 39 is relieved of pressure on the side facing away from the working space 38 via a relief channel 41 to a return line 42 of the hydraulic circuit leading to the oil tank 29 without pressure. The control piston 39 is arranged coaxially with the storage piston 23, a pressure pin 43 being provided between the two mutually facing end faces of the pistons and being guided in the housing in a radially sealing and axially displaceable manner.

So that there is a positive connection via this pressure pin 43 between the pistons 23 and 39, the control piston 39 is loaded by a spring 44 in the direction of the storage piston 23. This spring has only a small force and is not in itself able to overcome the force of the storage spring 24. A control line 45 branches off from the control line 37 and leads to a further valve control unit.

However, a throttle 46 is arranged in the control line 37 upstream of the working space 38 downstream of the branch point of the delivery line 31. The control line 37 opens into the unpressurized return line 42 downstream of the solenoid valve 36.

According to the embodiment of the invention and the supply of two valve control devices according to the invention by a solenoid valve, further delivery lines 47 branch off from the delivery line 31, which on the one hand lead to the valve control devices controlled by the same solenoid valve 36 and on the other hand supply the remaining valve control devices of the internal combustion engine with hydraulic oil .

2 shows the second exemplary embodiment in which the entire valve control device corresponds to that in the first exemplary embodiment and in which only the actual control area or the core of the invention is designed differently. In this second exemplary embodiment, the control line 48 branches off from the delivery line 31 upstream of the solenoid valve 49. The solenoid valve is designed as a 3/2 solenoid valve (3 connections / 2 positions). The control line 48 designed here as a sack line ends in the working space 38 of the control piston 39, the control piston 39 being arranged between the pressure pin 43 and the spring 44, as in the first exemplary embodiment. The second control line 51 branches off from the control line 48 and leads to the pressure chamber of another one Valve control device leads and which is also designed as a bag line.

The function of the hydraulic valve control according to the invention is explained below using the diagram shown in FIG. 3. In this diagram, the opening stroke h of four intake valves I, II, III and IV of a four-cylinder internal combustion engine is shown via the crankshaft rotation angle ° KW. The ignition sequence of this internal combustion engine is one, three, four, two of the side-by-side engine cylinders with the intake valves I to IV.

As can be seen from the four curves of the engine valves I to IV in FIG. 3, there is no direct firing order between the cylinders of the engine valves I and IV and the engine valves III and II. As can be seen from the ordinates in this FIG. 3, there is therefore no one Overlap between the opening strokes of the associated engine valves I and IV or II and III. The maximum design of these valve control curves corresponds to the highest curve V, the cam profile of the respective drive cam 4, a corresponding cam being assigned to each inlet valve.

According to the diagram in FIG. 3, a crank angle 0 is assumed when the cam of motor valve III is just beginning to drive its valve, which then extends to over 200 ° until the valve closes KW can go. At 180 ° KW, however, the control cam of the engine valve IV already begins to act on the cam piston 17 assigned to it, so that here the inlet valve of the cylinder IV opens before the inlet valve of the cylinder III is closed. The same applies to the control cam 4 of the engine valve II, which becomes effective from 360 ° KW and from 540 ° KW the start of opening of the engine valve I. As described above, any interventions in the stroke of an intake valve can therefore only take place if a valve control cam for actuation of the valve acts on the cam piston 17 assigned to it.

The respective stroke control per inlet valve is indicated in the valve control curves in FIG. 3 by the various groups of curves indicated for each engine valve I to IV for 4 different desired control values. As can be seen in FIG. 1, when the camshaft 3 is rotated, the control surface of the valve control cam 4 runs on the cam piston 17, which presses the working piston 16 downward against the force of the return spring 18 and thereby the valve piston 15 via the oil volume enclosed in the pressure chamber 19 including valve stem 2 and inlet valve plate 1 presses against the force of the valve closing springs 6 and 7 downward, the valve plate 1 lifting off the valve seat 8.

As long as the accumulator piston 23 is still in its rest position on its seat 25, no oil can be displaced from the pressure chamber 19. The compressive forces acting on the outer surface of the accumulator piston 23 in the annular space 27 cancel each other out. No oil can flow out via the check valve 34. As long as this position is taken, the inlet valve is opened to the maximum, which is explained using the example of engine valve III, which corresponds to the outer curve V of the valve control diagram. As soon as a smaller stroke corresponding to a smaller time cross section of the valve opening 9 is to be set, the solenoid valve 36 is blocked, as is shown in FIG. 1, so that the hydraulic oil from the feed pump 28 and the feed line 31 no longer the control line 37 and the solenoid valve 36 can flow to the return line 42, but is blocked. In contrast, as long as there is a flow, that is, as long as the solenoid valve 36 is open, the throttle 46 achieves a certain decoupling of the pressure in the delivery line 31 or the delivery pump 28 to the control chamber 38, so that there is no need for an adjustment of the control piston 39 Pressure can arise. When the solenoid valve 36 is blocked, on the other hand, the effect of the throttle 46 is canceled due to the liquid jam, so that a control pressure is created in the control chamber 38, by means of which the control piston 39 is lifted from the seat 25 against the force of the spring 24 via the pressure bolt 43 and the storage piston 23, so that the storage space 26 is connected to the annular space 27 becomes. As a result, the oil pressure in the pressure chamber 19 is transferred via the pressure channel 21 into the storage chamber 26. Accordingly, only when the storage piston 23 is lifted from the valve seat 25 can the storage unit be effective as such, in which the storage piston 23 can be correspondingly displaced against the storage spring 24.

If the storage piston 23 is lifted off the valve seat 25 at a time at which the valve control cam 4 is currently in effect and a correspondingly higher pressure exists in the pressure chamber 19, the further opening function of the inlet valve is ended, in which the piston 16 continues to operate displaced oil is conveyed via the pressure channel 21 into the accumulator 26, the accumulator piston 23 being correspondingly displaced against the accumulator spring 24. 3 shows, using the example of the engine valve III, using curves VI, VII, VIII, how large the actually remaining opening cross section per ° KW can be. The later during the opening stroke of the engine valve, the solenoid valve 36 is blocked, the larger the total opening time cross section per intake valve, the area lying under the curve corresponding to the effective opening time cross section. While not only the valve stroke h is particularly low in curve VIII, the duration in ° KW until the valve closes, ie until the valve closing springs 6 and 7 have finally pressed the valve plate 1 onto the valve seat 8, is relatively short.

In the exemplary embodiment shown in FIG. 2, this control process, namely a reduction in the opening time cross section, is achieved by opening the solenoid valve 49. It is only because of the dynamic pressure in the control line 48 that the control piston 39 is displaced after the solenoid valve 49 is closed and causes the storage piston 23 to be lifted from the valve seat 25 accordingly.

The fact that in multi-cylinder internal combustion engines in the control of the individual intake valves, there are those whose control time seen from the valve control cam do not overlap with that of others (as described above), such valve control units can be controlled via only one solenoid valve. Correspondingly branching control lines 45 and 51 then go from the control lines 37 and 48 to these control units which are not simultaneously effective. As soon as the solenoid valve 36 closes at motor valve III at approximately 90 ° KW, this results in a valve control according to curve VI. The branching control line 45, which leads to the valve control unit of the engine valve II as described above, transmits this dynamic pressure from the control line 37 to the control piston 39 provided on the engine valve II, which likewise causes the storage piston 23 to be displaced from its rest position. However, since in motor valve II the assigned drive cam 4 is ineffective or just the base circle of this cam interacts with the cam piston 17 this control has no effect on the actual control of this valve that begins at 360 ° KW. However, the solenoid valve 36 has to open and close twice as often as if it had to control only a single valve control unit.

Of course, this combination of the control of several valve control units by means of only one solenoid valve is also possible in the case of internal combustion engines with a large number of engine cylinders. It is decisive that engine valve units are always controlled by only one solenoid valve, in which the respective control times do not overlap.

Claims (10)

1. Hydraulic valve-control device for internal-combustion engines

   - with an engine valve (1, 2) actuated axially by the actuating cam (4) of an engine camshaft (3) via a cam piston (16, 17), a pressure space (19) adjacent to the latter and filled with hydraulic fluid and a valve piston (15),

   - with an accumulator which is designed as accumulator valve (22), the valve member of which is an accumulator piston (23) which limits an accumulator space (26) and is loaded by an accumulator spring (27) and by means of which the pressure space (19) can be connected to the accumulator space (26) via a pressure line (21), the accumulator piston (23), loaded by the accumulator spring (24), coming to bear against a valve seat (25) separating the accumulator space (26) from the pressure space (19),
      - and with a solenoid valve (36, 49) for controlling the connection between the pressure space (19) and the accumulator space (26),

   characterized in that the accumulator piston (23) can be lifted off from its valve seat (25) by means of an adjustable control piston (29), in that this control piston (39), for its adjustment, can be loaded in its working space (58) by control fluid of lower pressure, which control fluid can be supplied to the working space (38) from a fluid source (28) via a control line (37, 45, 48, 51), and in that the control line (37, 48) can be controlled by the solenoid valve (36, 49) in order to control the pressure in the working space (38).
2. Valve-control device according to Claim 1, characterized in that the control piston (39) is additionally loaded in the direction of the accumulator piston (23) by a spring (44).
3. Valve-control device according to Claim 1 or 2, characterized in that a pressure pin (43) sealingly guided radially serves for transmitting movement and force between the control piston (39) and accumulator piston (23).
4. Valve-control device according to one of the preceding claims, characterized in that it is arranged in a multi-cylinder internal-combustion engine, in which a valve-control unit is assigned to each engine cylinder, the solenoid valve (36, 49) simultaneously controlling together several of those pressure channels (21), during the actuation of which, brought about by the engine camshaft (3) with actuating cams (4), no time overlap takes place.
5. Valve-control device according to one of the preceding claims, characterized in that engine oil which is under feed pressure serves as a fluid source (28).
6. Valve-control device according to one of Claims 2 to 5, characterized in that the working space (38) of the control piston (39) is connected to the control line (37) upstream of the solenoid valve (36), and in that a throttle (46) is present in the control line (37) upstream of this connection.
7. Valve-control device according to Claim 6, characterized in that the solenoid valve (36) is designed as a 2/2-way valve.
8. Valve-control device according to one of Claims 2 to 6, characterized in that the working space (38) of the control piston (39) is connected to the control line (48) downstream of the solenoid valve (49).
9. Valve-control device according to Claim 8, characterized in that the solenoid valve (49) is designed as a 3/2-way valve (49).
10. Valve-control device according to one of the preceding claims, characterized in that the accumulator space (26) is connected via a compensating line (31) to the fluid source (28) of low pressure, and in that a non-return valve (35) opening in the direction of the accumulator space (26) is arranged in the compensating line (31).

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