EP1187971B1 - Electromagnetic actuator with hydraulic valve anti-backlash element - Google Patents

Description

The present invention relates to an electromagnetic actuator with a hydraulic valve clearance compensation element according to the preamble of claim 1 (see DE-A-197 38618).

Electromagnetic actuators for actuating a gas exchange valve a reciprocating internal combustion engine are sufficient known. These usually have two by far to each other arranged electromagnets, between whose pole faces an anchor against the force of return springs is guided back and forth. The one above Electromagnet serves as a closing magnet and the underlying electromagnet serves as an opening magnet, so that by alternately energizing the magnets, the gas exchange valve closed and can be opened. There due to temperature changes and / or wear the opening but especially the Closing conditions change and thus also the given Valve clearance changed, valve clearance compensation elements be provided. These work mostly on a hydraulic basis. In the known valve clearance compensation elements is i.d.R. a leakage is necessary, so that during the lifting movement sufficient fluid medium, in particular engine oil from the piston chamber of Play compensation element can drain, so that the Actuator on the change in length of the valve during the Working hours.

To ensure that even at low temperatures Play compensation of approx. 0.2 μm per working cycle ensured is, see the devices according to the state of Technique a leak gap, through the oil during the Opening the valve can escape. The leakage gap is here designed for all operating conditions, so that one Valve clearance compensation is always guaranteed. Right there At low temperatures, a valve clearance compensation required is, must the leakage gap for this operating condition be interpreted. Due to the temperature change the viscosity of the oil changes by a factor of 1000. Considering the speed difference between idling and maximum speed, this results in a factor of 10. Both factors go into the size of the leak flow on. The leakage gap is therefore for a warmed-up engine too big. The leakage is thus normal i.e. warm operating condition in which the engine is usually is operated, unnecessarily large. This creates on the Piston referenced a very different reset - one speaks here of way loss. In today's engines must Therefore, about 20 to 30% of the pump power of the oil pump for the valve clearance compensation be expended.

At low speeds, the opening time is considerable greater. This creates a very different Reset (loss of path), which has the consequence that the valve when closing at different speeds touches down. This is bearable in camshaft drive, since at low speeds anyway the valve speed is smaller. However, this is electromagnetic Valve drives are not the case and therefore a big problem.

There are valve lash adjusters known between the free end of the armature and the end of the valve stem are arranged. However, these have a relative high mass and require a relatively large installation space. Due to their size and the relatively high mass, the armature drive is disadvantageous to design large. Also these clearance compensation elements are conditional on theirs Construction with relatively large oil volume not very stiff.

Another problem arises when the engine is at a standstill in which, due to the leakage flow, the clearance compensation element drained and in electromagnetic valve trains results in a strong center offset of the anchor. From DE 198 18 993 is a valve clearance compensation element but not all of the above Disadvantages are resolved.

The object of the present invention is to provide an electromagnetic Provide actuator with clearance compensation element, by means of a high rigidity with low Fluctuations between the armature and the valve are therewith the impact velocity of valve and armature slightly are different. The hydraulic clearance compensation element must therefore a vanishingly small and have constant leakage flow and the trapped oil volume as small as possible and thus independent of the temperature and speed, i. in all operating states be stiff.

This object is achieved according to the invention with an electromagnetic Actuator solved with the features of claim 1. Further advantageous embodiments of the electromagnetic Actuators result from the features of Dependent claims.

The play compensation element according to the invention of the electromagnetic Actuator advantageously has a nearly speed independent Leakage or path loss. At a motor stop no leakage occurs, so that the Piston chamber of the lash adjuster element does not empty. From Another advantage is that the clearance compensation element a has only small harmful volume, resulting in a small elasticity of the device results. The leak flow is very small and is sized so that just the valve extension is compensated during a valve lift. This value is approx. 0.5 μm at low speeds. Due to the small elasticity and the small leakage flow is the difference between the valve and anchor placement speed advantageously low. The filling pressure varies with a conventional engine under consideration the opening pressure of the check valve between 0.3 and approx. 5.5 bar. This fluctuation affects very strong the stiffness, since the engine oil air fractions between Has 2 and 10%. Therefore, the pressure should be in one small area e.g. Fluctuate 4-6 bar. This can be up be solved in different ways.

The pressure supply can be controlled by a pressure-controlled electric driven pump, that of the engine oil pump can be supported. It is also conceivable that the engine oil pump by a pressure-controlled electric driven pump is replaced.

Because the valve functions suffer from dirt, is advantageous in the supply lines to the clearance compensation element a filter provided. This one is in one Particularly preferred embodiment in a channel of the Anchor arranged.

The piston of the lash adjuster is preferably made of plastic and facing the cylinder, which forms the piston chamber, a seal consisting made of sliding gasket and elastomeric gasket, on. Alternatively, a sealing lip can also be provided.

To make a good connection between the piston and the valve lifter to achieve, the piston advantageously has a particular Round approximately hemispherical recess on, in the rests the end of the valve stem and rotatable is stored. The end of the valve stem is by means of a flexible holding element held on the piston, which The ram axially fixed and centered.

In an advantageous embodiment, a channel is provided, which leaked out of the pressure relief valve Leakage oil leads to the recess of the piston and thus a continuous lubrication of the connection piston-valve lifter guaranteed.

The overpressure-closing valve is advantageous by means of two Valve seats are formed, between which a valve actuator, in particular a ball, movable back and forth is stored. A spring presses the valve actuator against a valve seat and forms together with this the pressure relief valve, on reaching a certain Pressure in the piston chamber a defined amount of oil leakage can escape from the piston chamber.

In one possible embodiment of the overpressure closing valve, the ball has a diameter of 1.5 mm. The annular gap between the ball and the valve seat of the pressure relief valve forming valve seat portion is advantageously about 15 microns. The distance covered by the ball between the two valve seats should be chosen to be in the range 0.02-0.05 mm. In this dimensioning of the pressure-closing valve results in a leakage of about 0.04 mm ³ per stroke, which corresponds to a nearly constant path loss of about 2 pm. The loss of travel is thus advantageously small compared to the known solutions, where the loss of travel can be up to 200 times greater.

Subsequently, the inventive electromagnetic Actuator explained in more detail with reference to drawings.

Fig. 1:

eine Querschnittsdarstellung durch das freie Ende eines Ankers, in dem das Spielausgleichselement angeordnet ist;

Fig. 2:

eine Ringblattfeder zum Schließen des Rückschlagventils;

Fig.. 3:

einen bekannten Druckverlauf beim Öffnen und Schließen des Gaswechselventils und die Leckflußmenge, welche durch das Überdruck-Schließventil aus dem Kolbenraum abgeführt wird;

Fig. 4:

verschiedene Positionen des Überdruck-Schließventils.

Show it:

Fig. 1:

a cross-sectional view through the free end of an anchor, in which the clearance compensation element is arranged;

Fig. 2:

a ring leaf spring for closing the check valve;

Fig. 3:

a known pressure profile during opening and closing of the gas exchange valve and the Leckflußmenge, which is discharged through the pressure-closing valve from the piston chamber;

4:

different positions of the overpressure closing valve.

Fig. 1 shows the free end of an armature 1 a electromagnetic actuator. In the free end of the anchor 1, a clearance compensation element is arranged, which with the valve stem 2 via the piston 4 of the lash adjuster is in communication. The anchor 1 has a Channel 1a, via a supply line 21 with a electrically driven pump 20 is in communication. This can be used as a free-piston pump according to the DE 10000045.2 described pump, whose Operation automatically shuts off when the engine oil pump a pressure of e.g. delivers over 4 bar. The channel 1a widens at its end 1b to a larger one Diameter. In this area is a filter F for filtering of the pumped fluid medium, in particular engine oil, arranged. The free end of the armature 1 has a Hole on, in which the clearance compensation element arranged is. The clearance compensation element consists of a cylindrical Part 3. In Part 3 are both the check valve and the overpressure-closing valve arranged. In this case, the part 3 forms the valve seat 16 for the Check valve and the valve seat 17 for the closing valve. The part 3 has on its cylindrical outer surface a circumferential groove 13. This groove 13 is with a further recess 12 in connection, which up in the area of the end of the channel 1a, 1b is sufficient so that in mounted state, the fluid medium from the channel 1a, 1b in the annular groove 13 can pass. In assembled condition is the part 3 in particular by means of a welded joint connected to the free end 1c of the armature 1. About additional holes 15, 10 passes the fluid medium from the groove 13 to the check valve 14, 15, 7 as well to the overpressure closing valve 18, 18a, 17, 9, 8, 8a. The Valve actuator 14 is a ball, which by means of a Ring leaf spring 7 pressurized against the valve seat 16 is. The ring leaf spring 7 is by means of a particular Spot welded connection attached to part 3. The Overpressure-closing valve has a ball as a valve actuator 9, which by means of a spring 18, which is with her an end against the end of a blind bore 18a of the part 3 is supported, against the valve seat formed by means of the part 8 is pressurized. The part 8 has a Passage 8a on, over which the fluid medium from the piston chamber 19 can pass around the ball 9 to the channel 10 around. The part 8 is used together with ball 9 and spring 18 and before joining (weld) in the bore of Part 3, that a defined Way sets, which the ball 9 between the valve seats must cover the overpressure-closing valve. The Welded connection is in particular by means of a laser realized. This process can be done automatically by means of a Adjustment laser welding device done.

The piston 4 is made in this embodiment Made of plastic and lies with its outside the inner wall of the sleeve-shaped portion 3a of the part 3 on. For sealing between the piston 4 and the part. 3 serves either, as on the right side of the piston shown, a seal consisting of an O-ring. 5 and a sleeve 6. However, there may be a sealing lip 25th be provided as on the left side of the piston. 4 shown. What kind of plastic material provided depends on the requirements. conditioned due to the small deflections of the piston 4 moves the elastomeric sleeve 6 not with the piston 4. In this way There are no frictional forces between the sleeve 6 and the Kolbenrauminnenwandung. The sliding seal ring 5 is in particular made of elastomer and is used in the Up and down movement of the piston 4 driven.

The sleeve-shaped portion 3a has a passage 3b on, a channel 4c of the piston 4 with a channel 11th connects, wherein the channel 11 through the inner wall of the Bore of the free end 1c of the anchor 1 and a recess is formed on the part 3. The channel 4c ends in a round recess 4b of the piston 4, in the form-fitting the round end 2a of the valve lifter 2b movable rests. About the channel 11, the passage 3b and the channel 4b of the piston 4, the oil passes between the Piston wall and the area 2a of the valve stem 2, whereby Lubricating this connection takes place. The valve lifter 2 is by means of a flexible member 26, which positively in the piston 4 by means of a collar 26b rests, held.

Due to the fact that the piston 4 and the part 3 can be made very flat, the piston chamber is 19th kept very small, so that a small elasticity of the clearance compensation element results. This is special at start-up i. Oil filling important in the the piston rests on the bottom of part 3.

The holding element conducts this for the lubrication of pistons 4 and valve lifter 2 used oil by means of its holding arms 26a in the direction of the extension to the valve guide.

As shown on the left side of Fig. 1, can as pressure generating means an electrically driven pump 20 are used, in particular by the engine oil pump 24 can be supported. In this embodiment is the engine oil pump 24 via a check valve 22 hedged.

Fig. 2 shows a possible embodiment of a ring leaf spring 7, as they can be used to close the check valve use. The ring leaf spring 7 is made of a thin flexible material, in which a window-like recess 7b is incorporated, in particular punched, so that a flexible tongue 7a is formed, which can pressurize the valve actuator 14 of the check valve by means of its free end 7c. The ring leaf spring 7 is firmly welded to the part 3, for example, by means of three spot welds S _T.

3 shows the known pressure profile when opening the gas exchange valve. After exceeding the valve force, or the pressure P _R in the piston chamber 19 opens the pressure relief valve, that is, the valve actuator 9 is moved against the spring force of the spring 18 away from the valve seat, so that through the channel 8a and the valve actuator 9 fluid medium from the piston chamber 19 can escape. For a short time, the fluid medium flows from the piston chamber 19. After reaching the valve seat 17, the valve actuator 9 closes the channel 18 a, so that no more fluid medium can escape from the piston chamber 19 more. The total amount of fluid medium Q, which exits the piston chamber 19 during the opening and closing phase of the overpressure closing valve, is composed of the two volumes Q ₁ and Q ₂ . The volume Q ₁ is given by the product of the cross-sectional area A of the valve actuator 9 and the path which travels the valve actuator 9 between the two valve seats of the overpressure-closing valve.

While the overpressure valve and the closing valve are open, fluid flows past the valve actuator 9 in the direction of the channel 18a through the defined gap s (see FIG. 4). This flowing medium has a certain volume Q _{2 as} a function of the viscosity and the pressure in the space 19.

4 shows the four operating states a to d of the overpressure closing valve. Panel a shows the pressure relief valve in the closed position. From the channel 8a, which is in communication with the piston chamber 19, no fluid medium reaches the channel 18a in this position. As soon as the pressure in the piston chamber 19 reaches the value P _R (see FIG. 3), the ball 9 (valve actuator) is moved against the spring force of the spring 18 towards the valve seat 17 (partial image b). When adjusting the ball 9, the ball displaces itself a volume Q ₁ . In addition, due to the gap s, the fluid medium flows around the ball 9 in the direction of the channel 18a. This amount of fluid medium is represented by Q2. The sum of Q ₁ and Q ₂ gives the total leakage current, which exits from the piston chamber 19 when the pressure P _{R is} exceeded. This flow supports the Schatl and closing process of the ball.

If the ball 9 abuts on the valve seat 17, no further fluid medium passes more from the channel 8a into the channel 18a (partial image c). As soon as the critical pressure P _R in the piston chamber 19 is fallen below (partial image d), the ball 9 is moved away from the valve seat of the closing valve in the direction of the valve seat of the pressure relief valve due to the spring force of the spring 18. Until the ball 9 has reached the valve seat of the relief valve, again flows a certain amount of fluid medium around the ball 9 from the channel 8a to the channel 18a. At the same time, however, the ball 9 displaces a volume Q ₁ due to its cross-sectional area and the distance traveled between the two valve seats. So that in this operating state as possible no fluid medium is derived from the piston chamber 19, Q ₁ should be equal to Q ₂ . Here, as described, the displacement volume counteracts the flow around. The appropriate dimensioning is done on the ball diameter, the gap width s and on the way, which must cover the ball 9 between the two valve seats of the pressure-closing valve. The path of the ball 9 is very small to choose. In addition, only very small tolerances are allowed during production. To adjust this path is the sleeve 8, which is used and positioned accordingly by means of a setting device not further explained here during assembly, whereby the required distance can be adjusted. Subsequently, the sleeve 8 is welded to the part 3. Due to the small path of the ball 9, which is for example less than 0.04 mm, and the small masses to be moved, the ball movement takes place in a very short time (for example, 0.2 ms). The movement process is supported by the effective pressure difference on the ball. The position according to partial image c is already reached during the valve opening and is maintained in the open state.

Claims (28)

1. Electromagnetic actuator for a valve of an internal-combustion engine, comprising an armature (1), wherein the armature (1) can be moved back and forth between two end positions by means of at least one solenoid and adjusts the valve against the spring force of a valve spring, a hydraulic play compensating element being arranged on the armature (1) or between the armature (1) and valve or valve stem, wherein the play compensating element has a piston (4) displaceably mounted in a piston chamber (19), and a pressure-generating means (20, 24) delivers a fluid medium via at least one feed line (21) into the piston chamber (19) and generates a working pressure there which pressurises the piston (4) in the direction of the valve, characterised in that a parallel connection consisting of a check valve and a pressure relief closing valve connects the at least one feed line (21) to the piston chamber (19) of the play compensating element.
2. Electromagnetic actuator according to Claim 1, characterised in that the piston (4) in the piston chamber (19) is adjusted by a first distance on opening of the valve (8, 9) as soon as the reaction force exerted by the armature (1) on the charge changing valve exceeds a minimum value, wherein a defined volume of the fluid medium leaves the piston chamber (19) via the pressure relief closing valve.
3. Electromagnetic actuator according to Claim 1 or 2, characterised in that the piston (4) is adjusted by a second distance on or after closing of the valve, as soon as the reaction force exerted by the armature (1) on the valve falls below a predetermined minimum value, wherein fluid medium arrives in the piston chamber (19) via the check valve.
4. Electromagnetic actuator according to any one of Claims 1 to 3, characterised in that the pressure-generating means is an, in particular, electrically driven oil pump (20) and/or the engine oil pump (24), the pressure fluctuating, in particular, in a small range of 4 to 6 bar.
5. Electromagnetic actuator according to any one of the preceding claims, characterised in that the hydraulic medium flows through a channel (1a, 1b) in the armature (1).
6. Electromagnetic actuator according to any one of the preceding claims, characterised in that between the play compensating element and the pressure-generating means or between the armature and the pressure-generating means, the hydraulic medium flows through a flexible line, in particular a pliable tube.
7. Electromagnetic actuator according to any one of the preceding claims, characterised in that the check valve has an, in particular, spherical valve control element (14) which is pressurised by means of a spring (7), in particular an annular leaf spring, against a valve seat (16), and in that the check valve opens when a pressure differential between the piston chamber (19) and the feed line (21, 1a, 1b) determined by the spring (7) is exceeded.
8. Electromagnetic actuator according to any one of the preceding claims, characterised in that the fluid medium arrives from the piston chamber via the pressure relief closing valve back into the medium circuit, in particular into a pressure supply line or a storage container or chamber, whence it can be delivered from the pressure-generating means back into the piston chamber.
9. Electromagnetic actuator according to Claim 8, characterised in that the pressure relief closing valve is formed by means of two valve seats and a valve control element (9), in particular a sphere, movably arranged between the two valve seats, wherein a spring (18) pressurises the valve control element (9) in the direction of one valve seat.
10. Electromagnetic actuator according to Claim 9, characterised in that when a predetermined pressure is exceeded in the piston chamber (19), the pressure relief valve of the pressure relief closing valve opens and after a predetermined volume has passed and/or when a specific flow speed of the fluid medium has been exceeded when the pressure relief valve is open, the valve control element (9) rests on the valve seat (17) of the closing valve in a sealing manner.
11. Electromagnetic actuator according to Claim 10,
    characterised in that the valve control element (9), in particular the diameter of the sphere is formed or dimensioned such that when the pressure relief valve is open, the fluid medium can flow around the valve control element (9).
12. Electromagnetic actuator according to Claim 11, characterised in that the pressure relief closing valve is dimensioned such that at the operating temperature of the valve, on movement of the valve control element (9) from the valve seat (17) of the closing valve towards the valve seat of the pressure relief valve, the quantity of fluid medium displaced by the valve control element (9) is equal to the quantity of fluid medium flowing around the valve control element (9) in the direction of the valve seat (17) of the closing valve, so during this movement of the valve control element (9) no, or only very little, fluid medium escapes from the piston chamber (19).
13. Electromagnetic actuator according to Claim 12, characterised in that to achieve small leakage quantities via the pressure relief closing valve on closing the pressure relief valve, the spherical diameter of the valve control element (9), the path of the valve control element to be covered between the two valve seats, as well as the gap between the sphere and the valve housing are dimensioned in accordance with the viscosity of the fluid medium at operating temperature.
14. Electromagnetic actuator according to any one of the preceding claims, characterised in that the free end (1c) of the armature (1) has a recess, in particular a hole, which forms the cylinder of the play compensating element or is arranged in one part (3) which forms the cylinder, the check valve and/or the pressure relief closing valve being arranged in the part (3) or the free end (1c) of the armature (1).
15. Electromagnetic actuator according to Claim 14, characterised in that the part (3) with its outside and the recess of the armature (1) with its inner wall form a channel (12, 13) in which the channel (1a, 1b) of the armature (1) ends.
16. Electromagnetic actuator according to Claim 14 or 15, characterised in that in the part (3) are feed channels (10, 15) which are formed, in particular, by blind holes which connect the channel (13), in each case, to the check valve and the pressure relief closing valve.
17. Electromagnetic actuator according to any one of Claims 9 to 16, characterised in that the two valve seats of the pressure relief closing valve are formed by means of a first and a second valve seat part, the first valve seat part encloses the second valve seat part, at least in sections, and in that the first valve seat part is formed by means of the part.
18. Electromagnetic actuator according to any one of the preceding claims, characterised in that the piston (4), in particular made of plastics material, has a seal, the seal being formed by means of a sealing lip (25).
19. Electromagnetic actuator according to any one of the preceding claims, characterised in that the piston (4), in particular made of plastics material, has a seal, the seal being formed by means of a peripheral groove-shaped recess in the outer piston wall in which an annular sealing element (5) rests which is surrounded by a ring or cylinder (6) consisting of a low-friction material, in particular Teflon, the ring or cylinder resting in a sealing manner on the inner wall of the piston chamber (19) of the cylinder.
20. Electromagnetic actuator according to any one of the preceding claims, characterised in that the piston (4) and the end (2a) of the stem (2) of the valve or the valve tappet are connected by means of a joint.
21. Electromagnetic actuator according to Claim 20, characterised in that the end (2a) of the stem (2) of the valve or the valve tappet rests in a movable manner in an at least partially round recess (4b) of the piston (4) and is held by means of an, in particular, flexible holding element (26) in the recess (4b), the end (2a) of the stem (2) being formed in particular corresponding to the recess (4b).
22. Electromagnetic actuator according to Claim 21, characterised in that a connecting channel (4c) connects the channel (11, 12, 13) formed by the part (3) and the recess in the armature to the round recess (4b).
23. Electromagnetic actuator according to any one of Claims 20 to 22, characterised in that fluid medium leaving the piston chamber (19) via the pressure relief closing valve lubricates the connection of the piston (4) and end (2a) of the stem (2) of the valve or the valve tappet.
24. Electromagnetic actuator according to any one of the preceding claims, characterised in that a filter (F), is arranged, in particular, in the channel (1a, 1b) of the armature (1) between the pressure-generating means (20, 24) and the play compensating element.
25. Electromagnetic actuator according to any one of the preceding claims, characterised in that the pressure-generating means is an electrically driven pump, by means of which a specific pressure can be adjusted in the feed line to the play compensating element.
26. Electromagnetic actuator according to any one of the preceding claims, characterised in that the pressure-generating means consists of a parallel connection of the engine oil pump and an electrically controlled backing pump, the pressure side of the backing pump being connected to the engine oil pump via a check valve.
27. Electromagnetic actuator according to any one of the preceding claims, characterised in that the play compensating element is dimensioned such that when the closing valve (9, 17) is closed, the space between the valve control element (9) and the piston (4) is as small as possible.
28. Method for producing an electromagnetic actuator according to any one of the preceding Claims 17 to 27, characterised in that the second valve seat part is a sleeve which is introduced into the first valve seat part or into the part by means of an assembly device, the assembly device adjusting the distance for the valve control element between the two valve seats while the parts are positioned with respect to one another and subsequently, the first and second valve seat part or the part and the second valve seat part are permanently connected to one another, in particular by laser welding.

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