DE3421420A1 - Oil feed with return prevention device for bucket tappets with hydraulic valve clearance adjustment - Google Patents

Abstract

The patent application describes a bucket tappet with hydraulic valve clearance adjustment, which in addition to the reliable venting of the high pressure chamber by virtue of the sintered bushing (2) according to DE 2942926 A1, returns the oil displaced from the high pressure chamber as it drops by way of a bore (9) into the reservoir chamber (4). a) By means of a diaphragm (14) Fig. 6, it is proposed to prevent oil from running out of the tappet when the engine is at a standstill. b) If the cam is in an unfavourable position, the diaphragm (14) is intended to catch the oil expelled from the high pressure chamber (11). This is done according to the position of the diaphragm between the limits (14 and 14a). The chambers R1 and R2 are thereby formed. c) When starting up again, the oil in the chamber R2 is fed directly to the high pressure chamber (11) by way of the high pressure piston. If, in the process, air passes initially from the oil supply duct (13) into the oil reservoir chamber (4), only the chamber R1 is affected by this. The amount of oil from R2 is generally sufficient to fill the high pressure chamber. This is sufficient for starting. d) Finally an entirely closed system is possible by means of the innovation described. The description is aimed at silent starting of the valve gear with the minimum or no tappet oil requirement, so that the risk of contamination and polymerisation is reduced or excluded.

Description

Oil inlet with backstop for bucket tappets with hydraulic valve clearance compensation

Due to the favorable friction conditions, especially with regard to the reduction of the internal losses of a reciprocating engine with valve train, has the arrangement - "overhead camshaft Acting directly on the valve via bucket tappets "the best prerequisite for new designs To find application.

In contrast to other types of drive for valves, valve clearance adjustment is very complex. this is usually done by replacing thrust washers different thickness achieved. As a result, bucket tappets are used with hydraulic Valve clearance compensation desirable. A serious handicap is given here by the fact that the removal of the air in the oil is hardly or not at all guaranteed due to the position of the bucket tappets, because the air would have to be discharged against gravity through the play gap. With this problem deal with a number of registrations such as OS 2211 139, AS 1293 788, OS 19120 46, OS 294-9 926 A1, to name a few. The solutions are more or less satisfactory in this regard. The protection application DE 2949 926 A1 has proven to be sufficient in any positioning of the hydraulic cup tappet Claim 5 confirmed, in which the gas in the high-pressure chamber in every installation position of the plunger through the wall the can escape.

Whether to avoid starting chatter, which at

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The engine is started by the idle hydraulic valve arises, a certain oil supply in the plunger directly in the so-called storage room better or measures for Preventing the supply line from running empty at the cylinder head is not clearly applicable clear up. What is certain is that idling of the plunger cannot be accepted for reasons of noise.

This gives rise to the task of looking for a way that years ago would still be inevitable Taken start rattles prevented. Here, too, there are quite a number of registrations, but all of them so far are known, are position-dependent, i.e. have a residual oil container that, when turned off, in particular when it is hot The engine cannot be drained. To prevent the oil from draining out of the cylinder head supply bore, is not always easy to construct.

Experience has shown that apparently 200 to 600 mm Sufficient oil immediately in front of the inlet valve of the high-pressure cylinder to ensure noiseless starting. But this is where the problem begins, because the position of the tappet is not always such that the necessary oil is also available is.

Another problem is a) the size of the pantry

b) the venting of the same.

Experiments have clearly shown that the storage spaces of the bucket tappets are not in conventional designs always vent and thus act as a shaker, in which an air-oil mixture is created which is unusable. On the other hand, experience has shown that a small but sufficiently large storage room is cheaper if the requirement is oil and the air-oil mixture is not fulfilled.

This results in four design goals as a task:

1.) The ram works in every geometrical position 2.) Small but sufficient storage room 3.) Ventilation of the storage room

4 ·.) Ensure that the pantry in which geometrical position, when the engine is at a standstill, it cannot idle.

The solution to point 1.) was the subject of the registration DE 2829 4-23 A1 and DE 294-2 926 A1.

Figure 1 shows the insert (1) or the screw-in part made of steel. It was made with a sintered material Bushing (2), which results in a completely position-independent venting of the high-pressure chamber. this is screwed into the aluminum shaft part (3), which is in the area of the clamping sleeves (6) or the pins a closed wall (10) produced in an extrusion process (without breakthroughs) received. From this it emerged z \ tfischen support ($) of the screw-in part (1) and the Shaft part (3) a storage space (4-) of the desired size, i.e. as small as possible to accommodate the weight of the complete To keep the plunger as low as possible.

The support (5) offers a corresponding one due to the determinable roughness and the screwing-in torques of both parts Leakage, which lets out gas bubbles that are formed analogous to the pressure in the storage space. This becomes a design goal 3.) achieved.

It is certain that a certain small amount of oil can escape at this point. This amount is going through Replaced inflow from the supply line. When wanted

If the high pressure bulb (8) falls, oil under high pressure over the wall of the sintering sleeve (2) becomes the largest of all Part 'returned through the bore (9) into the storage space (4). This oil is again available to supply the high-pressure cylinder to disposal. In this way, the oil requirement of the hydraulic valve valve should be kept very small. This comes very close to a closed system. With diesel engines in particular, this is often not the case clean engine oil, which could possibly impair the passage of gas through the sintered can.

Point 4 ·) contains the proposal according to the invention.

The pin (6) or the inlet tube, which one too Can take over the stiffness function, is with a lip consisting, for example, of highly heat-resistant, elastic mass (Fig. 2 and 3 (7) and (7a)) provided that the natural Has a tendency to be closed. This prevents oil from flowing into the storage space via the high-pressure cylinder (2) (4) not or only insignificantly braked. When the oil pressure of a few tenths of a bar is applied to the tappet, the External oil supply. When the engine is stopped and the pressure drops to zero, the lip (7) is independent from the closed position. No oil can drain off. Both the sintering can (2) and the leak on the support (5) do not allow any measurable amount of oil to escape.

The dimensions of the most suitable lip shape are determined through tests. Basically the lip is characterized by Extremely easy movement in the direction of flow and locks in the opposite direction. The lip consists of a temperature and oil-resistant material such as fluororubber.

Another possible variant is shown in Fig.Λ. A vulcanized, The rubber-like ring (2) forms the seat ring for the valve (21). The spring (22) supported on the Ring (23), presses over the plate (24) and the rod (26)

the valve (21) on its seat, which can also be made of a metallic material.

Securing the tube (6) with the oil return stop Element is given by pressing it slightly wide, as shown in Fig. 1 and Fig. 3 and 4- as a dash-dotted line.

The described embodiments Fig. 1 to Fig. 4 experience an extension of the function in that the backstop ± i the oil storage room is installed, whereby a larger working volume than is possible in the pipe valve.

As can be seen from Fig. 1 to 4, the lip (7) of the return valve (6) can be designed so that the desired

The amount of oil displaced sinks, approx. 7 to 10 mm, as a result of receding a bellows or piston is added.

From further considerations, the task arose, even when the high pressure piston (8) sank completely 150 mm of oil pressed through the sintered walls (2) or to ensure that no air can get into the storage space when the engine is restarted. The solution lies in the separation of the storage room (4) into two rooms, namely space R1 -direct inflow from the oil supply channel and space R2 -direct inflow to the high-pressure part.

The separation of the rooms can be done in different ways

a) through one or more flasks (12) with valves (16) or lips at the inlet points (6 and 15) of the oil supply channel (13) Fig. 5

b) through a membrane (14) with corresponding valves or lips (7 and 7a) Fig.6.

Here it becomes possible, not just when you want to sink of the HD piston (8) displaced oil, but also that of the Complete lowering of the high-pressure piston - when the engine is switched off, hot - to absorb the displaced oil and when it is renewed Start delivering a clean, air-separated oil. This is achieved by making a separation between the existing Oil and the air that initially emerges from the oil supply duct (13) when the engine is started.

It is obvious to get a completely closed system by moving the membrane (17) to the outside, as shown in Fig. 7, in that R1 is variable and R2 maintains a constant volume. A somewhat longer HP piston (8) is available as a A ring diaphragm is attached, so that a bellows-shaped space is created. This takes both the short-term sinking, as well as the oil that may be completely displaced from the HP area (11) during standstill, as described.

Function :

Figures 5, 6 and 7 show the rooms R1 and R2. They are formed by a separating element such as membrane Fig. 1 (H, 17) or piston Fig. 2 (12). The membrane (14) and the bulb (12) can assume any position during operation.

If gas is found in the HP space (11) at any point in time, this is printed by the sinter wall (2) Fig. 5 to 7 and passes through the bore (9) into the storage space (4 ·) Fig.1. This air is at some point on the dividing line (5) Fig. 1, 5 and 6 escape when there is a higher pressure inside, the oil flowing in from the oil supply channel (13) of the The motor enters the space R1 through the tube (6) or the bore (15). As soon as the membrane (14 ·) has a position like drawn Fig. 6, it is raised until it is stretched (14-a) and the valves or slots (7 / 7a u. 7b) so that the oil can flow over into space R2.

The amount of oil in the storage space (4 ·) is the sum of R1 and R2. Entrained gas is discharged via the dividing line (5). The when the high-pressure flask (8), Fig.1.5 »6.7 Displaced oil flows through the hole (9) into the room Ri and is again available to the HP cylinder (11) when the lowering in the base circle area is corrected. The membrane will therefore make a slight fibrillation movement during operation.

If the engine is switched off and the cam is in an unfavorable position, the HD piston (8) is pressed against the stop then the displaced oil will slowly flow through the wall (2) and the hole (9) into the reservoir R2, the membrane (14-) and (17) will recede, because valves or slots are and remain closed. The position is arbitrary, up to the contact of the membrane (14-) on the wall of the shaft part (3) Fig. 6 or the valve spring retainer Fig. 7. Should be on this one If the HP area (11) has not yet been emptied, a pressure corresponding to the valve spring is created and the oil gradually escapes over the dividing line (5) in the embodiment of FIGS. 1 to 6.

When you start again, the movement of the high-pressure piston (8) will create a suction effect and draw clean oil from the reservoir R2, because the membrane has prevented it from flowing out. Should air flow from the supply duct via the hole (15) into the

Flow into space R1, the membrane (14-) causes a separation - Air in room R1 but not in room R2. The space ratios R1 / R2 are designed so that even in the worst case the The necessary amount of oil from R2 is available in the HP part, so that the tappet for some time without an external oil supply Fig. 5 and 6 can function reliably. The air from the oil supply duct (13) will - when it arrives in space R2 - on discharged in the manner described.

Fig.7 shows a closed system where the external The membrane is not influenced by the oil pressure but by the atmospheric pressure. The wanted, on the line (5) Fig. 5 u. The leakage shown for the discharge of air is of course not present in the form of FIG. Nevertheless it is possible In order to take account of all leaks, leakage losses through a controlled connection with the oil supply channel to be replaced over a longer period of time.

Claims (11)

Claims [1.ycup tappet has hydraulic valve clearance compensation consisting of insert (1), shaft part (3) and sintered bush (2) as well as the widely used oil reservoir (4-) characterized in that no oil when the engine is at a standstill, regardless of the position and installation position Block return (Fig. 2 to Fig. 4-) from the The plunger can drain and the storage space (4 ·) in two Rooms R1 and R2 can be divided as soon as this is done to prevent air from entering the oil supply duct (13 in the storage room, e.g. when starting, is necessary or useful for a completely closed system appears. 2. bucket tappet according to claim 1, characterized in that by sealing the high pressure bulb (8) in connection With the sintering bush (2) the oil displaced by the intended sinking back into the storage room (Λ) flows in via the bore. 3. bucket tappet according to claim 2, characterized in that that this function take over one or more, made of a suitable elastic material lips that are arranged so that only one flow into the storage space (4-) and / or the HP cylinder (8) is guaranteed and not the other way around. 4 .. bucket tappet according to claim 1, characterized in that that the space R1 directly with the inflow (6) and (15) from the oil supply channel (13) and the space R2 directly is connected to the HD flask (8). 5 · Cup tappet according to claim 1 and 4 · characterized in that that the space R1 can disappear completely compared to the space R2, and the ratio R1 / R2 between boundary positions can be changed is. 6. bucket tappet according to claim 1, 4- and 5, characterized in that that the separating element between the spaces R1 and R2 can be a membrane (1-4). 7. bucket tappet according to claim 1,4.-6, characterized in that the separating element has one or more small flanges (12) could be. 8. Cup tappet according to claim 1, 4 to 7, characterized in that that the separating elements are designed so that an overflow mainly in the direction R1 in R2 can take place. 9. bucket tappet according to claim 1, 4- to 8, characterized in that the separating elements are designed so that the amount of oil displaced by lowering the high-pressure piston (8) can be absorbed, so that as little as possible or no contaminated oil from the engine circuit is used at all. 10. bucket tappet according to claim 1, 4 to 6, 8 and 9 thereby characterized in that the separating element (17) Fig.7 is placed outside, with a completely closed System arises. 11. bucket tappet according to claim 10, characterized in that this closed system by suitable connection with the oil supply channel can replace leakage losses that can occur over longer periods of operation.