DE3611476A1 - Method for the actuation of valves for exhaust and refill in internal combustion engines with direct hydraulic transmission - Google Patents

Abstract

The application relates to a direct, hydraulic valve actuation, in which the engine oil replaces mechanical components such as levers and bucket tappets. A hydraulic piston acting as master piston (tappet) is moved by the cams of a camshaft, which piston in turn displaces oil, which by way of a closed chamber correspondingly actuates the required number of valves at suitable points by way of slave pistons. The master pistons can be controlled by rotatable sleeves with angular slits, so that the effective valve lift results, as required, in a shifting of the overlap, and/or causes an adjustment of the valve lift height and/or a valve angle adjustment. The arrangement of the camshaft is to a large extent freely selectable owing to the direct hydraulic actuation.

Description

 Prov. No: 53

In the following a method is described, which over Cam actuated tappet in a known manner, which in one Displacing enclosed oil, so that a second or further tappet piston the valve or several Valves open or close.

This results in a summary of various more desirable functions in the simplest way can be realized

• a) about the engine oil pressure is in a known manner Equalization created,
• b) the valve lift can be taken by suitable measures be adjusted as desired,
• c) the throttle valve control can be done through the intake valve change in tax times are replaced,
• d) with a camshaft z. B. a 16 valve Four-cylinder engines are created considerably greater freedom to arrange the camshaft,
• e) the masses for valve actuation are reduced puts. The result is a very low construction of the cylinder head.

State of the art:

The OHC engine is currently the state of the art in vehicle construction Technology for gasoline and diesel engines. Given the Saving of fuel through high performance yield and the endeavors to improve the exhaust gases are burning spatial forms become necessary due to the overhead Camshafts can best be realized.  

In the meantime, the development of the multi-valve engine usually with two camshafts around the Environmental requirements in Connection with converters from the latter to minimize the higher consumption caused or to eliminate.

A notable trend is in this regard the shift in the maximum torque one modern engine in the lower speed range, however if possible without noticeable loss of high performance levels. This is the adjustment of the overlap the valves in the OT during the gas exchange process are a criterion, which is why the development is the way to adjustable Camshaft goes. Especially with two-camshaft Motors can do this relatively easily, but is expensive via electric servomotors, hydraulically via crooked Levels, as well as by means of gear drives and levers, thereby associated with high costs. There's a lot here published patent applications.

Reducing vehicle drag what is ultimately a factor influencing consumption, raises the problem of the height of the motor. But through two overhead camshafts over the valves are arranged, in particular when using Cup tappet with hydraulic play compensation relatively high cylinder head arise, which is essential co-determined the entire engine height.

Nevertheless, this effort is justified for the reasons given and is also accepted by the buyer. In the case of cheaper, smaller vehicles - as could become interesting with the new legislation up to 1.4 l displacement - such additional expenditure is still questionable, although these measures are also desirable here.

For these reasons, the following task arises: A state-of-the-art cylinder head for an engine in Large series at an affordable price with 4 valves per cylinder, hydraulic valve clearance compensation as well as variable valve lift and changeable timing in the lowest design with only one camshaft and central spark plug is equipped.

Solution to the problem is shown in FIGS . 1 to 6 Darge. A camshaft ( 3 ) arranged centrally between the valves ( 1 ) and ( 18 ) in FIG. 3 actuates mushroom-shaped tappets ( 9 ) with one (or more) cams ( 4 ) which run in a cylinder body ( 5 ) with little play, which is connected to a space ( 7 ) in which a small piston ( 6 ) is located. The free space (7) is filled with oil, which is under a certain pressure so that, as in known hydraulic tappets of all kinds when encountering the cam on the pressure plate for immediate closing of a check valve (8) Fig. 1 of to increasing pressure by the cam ( 4 ) transmits outgoing force to the valve and so the valve opens and closes.

Through these arrangements, it is possible to place the camshaft ( 3 ) at a suitable point and to control the inlet and outlet cams with a single cam at the given spread a . Fig. 3, this is with rocker and rocker arms in this compact form not possible.

Another very important advantage is that the stroke Fig. 5 of the plunger ( 9 ), which is actuated directly by the cam ( 4 ), is constant, but this through control slots ( 10 ) buw. - The bores ( 11 ) can be infinitely adjusted with the least effort using the least amount of effort required via the build-up and release of the oil pressure, the stroke and the opening time of the valve.

This is a significant cost saving. In any case, the game is equalized.

According to the latest investigations MTZ Febr. 1986 it seems to be sufficient to make the inlet valve variable. Here it is therefore close to control the valve elevation so that a minimum of valve lift and at full load the maximum lift is driven at idle. The valve lift and the opening time are controlled in accordance with the map by actuating the accelerator pedal. The rate of descent and placement of the valve on the valve seat is accomplished by an adjustable throttle ( 19 ) Fig. 8.

Functional description

A mushroom-shaped tappet ( 9 ) is pressed into the cylinder space ( 7 ) filled with pressure oil via the camshaft ( 3 ) Fig. 1 and the cam ( 4 ). The resistance that occurs from the valve spring ( 2 ) and the mass of the valve via the piston ( 6 ) causes a corresponding pressure increase in the cylinder space ( 7 ), which causes the valve movement in the same way as with the hydraulic tappet element. The direction reverses above the maximum valve lift height; the valve spring pushes the system back. As with the hydraulic tappet, a certain loss in lift height compared to the cam lift height is included in order to ensure that the valve closes safely. The loss is compensated for by a non-return valve ( 8 ) in which oil can flow in from the engine circuit. By a vent screw attached to the highest point of the system ( 13 ) Fig. 4, which allows a certain gap and is set in this position festge or can be replaced by a sintered plate ( 13 a) Fig. 3, possibly mitge is carried out continuously Gas or air derived.

The arranged between the tappets ( 9 ) Fig. 8 shaft ( 14 ) is the adjusting shaft for the stroke of the valve. In the example of stroke was left constant and controlled the stroke end, respectively, pressure drop that valve stroke and end of stroke can be determined in FIG. 9. This is effected in that during the lifting of the plunger (9) in the example Fig. 8 and 9 show two existing holes (15 u . 16 ) remain closed during the full stroke of the valve and therefore no pressure loss occurs.

If the adjusting shaft ( 14 ) Fig. 8, which is provided on the circumference similarly to a diesel injection with a slope ( 17 ) Fig. 9, is rotated in a certain direction, the hole ( 16 ) is first released, but with a certain throttling effect as long as the slope ( 17 ) does not yet clear the entire area of the hole ( 16 ). That means shortly before the summit of the theoretical valve curve, the curve is flattened and the valve touches up earlier; it closes earlier. The more the hole ( 16 ) is released, the earlier the inlet valve ( 18 ) Fig. 3 closes in this case. After opening the hole ( 16 ) completely, the hole ( 15 ) is opened, which results in a further shortening of the stroke.

Since the influence of the throttling decreases at higher engine speeds, the throttling must also be variable. This is done with the help of a conical pin ( 19 ) Fig. 8, which is controlled depending on the speed and changes the cross section of the outflow bore ( 20 ) in a manner similar to a nozzle needle in the carburetor. As the example of Figures 3 and 4 show., The overall height of the cylinder head is extremely low. Only one camshaft is sufficient for multi-valve arrangements.

Claims (7)

1. A method for actuating gas exchange valves in internal combustion engines in a known manner controlled by cams, characterized in that the valves are actuated directly and directly via moving hydraulic pistons ( 9 and 6 ). 2. According to claim 1, characterized in that two or more hydraulic pistons ( 9 and 6 ) have a common space ( 7 ), of which a piston of the master piston or tappet ( 9 ) is controlled by the cam Fig. 2nd 3. According to claims 1 and 2, characterized in that the rotation of the master piston ( 9 ) Fig. 7 in a sleeve ( 21 ) Fig. 5 u. 6 runs, which by turning Fig. 7 about its central axis via oblique grooves ( 17 ) controls the lifting height of the valve piston ( 6 ) Fig. 6. 4. According to claim 3, characterized in that the sleeve ( 21 ) Fig. 5 u. 6 is fixed, and the master piston ( 9 ) is rotated. 5. According to claims 1 and 2, characterized in that the rotating unhindered master piston ( 9 ) Fig. 8 runs through bores ( 15 and 16 ) in the cylinder, which by opening and closing with the aid of a cam with slots ( 17 ) provided shaft ( 22 ) controls the lift height of the valve piston. 6. According to claim 1 to 5, characterized in that here is achieved by the smallest possible height of cylinder heads with overhead camshaft Fig. 3 u. 4th 7. According to claims 1 to 5, characterized in that the valves (z. B. 1 and 18 ) can have any position to the camshaft and vice versa.