JPH0432207B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a valve opening connected to an exhaust passage in a cylinder head and having a valve seat for a throttle valve, which is connected to a combustion chamber side surface at the bottom of the cylinder head. This invention relates to an engine brake with a throttle valve installed in the cylinder head of an internal combustion engine, which is offset and installed at the bottom of a recess.

[Conventional technology]

An engine brake with such a throttle valve is known from DE 34 28 626 A1. The throttle valve that hangs down from the cylinder head is a mushroom valve, and the gas compressed in the cylinder during engine braking is pushed out into the exhaust passage through the valve opening controlled by this valve at the bottom of the cylinder head. be done. A control piston, which controls the throttle valve under the action of pressure oil or compressed air, is guided in a control hole in the cylinder head and rests on the valve stem. In order to avoid contact between the valve opening into the combustion chamber and the piston, the valve opening with its valve seat is arranged in a recess in the bottom of the cylinder head offset relative to the bottom surface of the cylinder head.

For reasons of combustion consumption and exhaust gas pollution, the recess is kept small. A relatively narrow annular gap is therefore created between the valve head and the recess, through which the gas must be forced during opening of the valve. This results in strong flow diversions or flow constrictions in the region of the valve head, which can create gas forces on the valve that are so high that they overcome the opening force and impulsively move the valve into the closed position, especially in the region of top dead center. There is sex. This process reduces engine braking power and creates undesirably high mechanical stresses in the structural elements involved.

[Problem to be solved by the invention]

The problem underlying the invention is to develop an engine brake of the initially open type to improve the flow around the valve head of the throttle valve in the open position of the valve.

[Means to solve the problem]

In order to solve this problem, according to the invention, the recess has an enlargement pointing towards the combustion chamber side surface, which enlargement is formed by a counterbore in the wall surrounding the recess.

〔Effect of the invention〕

According to the present invention, since the enlarged portion is provided which faces toward the combustion chamber side surface, the gas flowing from the combustion chamber to the valve opening is hardly diverted from the combustion chamber side opening of the enlarged portion and is shaped into a conical shape. Therefore, the braking effect is not reduced by blocking the outflow. Moreover, since the enlarged portion is formed by countersinking the recess with a countersink drill, the enlarged portion can be easily formed.

〔Example〕

Two embodiments of the invention will be explained below with reference to the drawings.

In FIG. 1, the cylinder head of a diesel engine is indicated at 1. In addition to the usual gas exchange valves, the cylinder head 1 includes a throttle valve 2 which is designed as a mushroom valve. This throttle valve 2 is a component of the engine braking system and controls a valve opening 4 in the bottom 3 of the cylinder head. The throttle valve 2 is actuated by a control piston 5 which is guided in a bore 6 in the cylinder head 1 and rests on a valve stem 7. By actuating the engine brake switch, the control piston 5 is acted upon by a pressure medium, for example pressure oil or compressed air, which moves the throttle valve into the open position. Thereby, the gas previously compressed in the cylinder by the piston is throttled through the valve opening 4 and forced out into the exhaust passage 8 of the engine. In order to avoid the valve head 9 of the throttle valve opening towards the cylinder hitting the piston, the valve opening 4 with its valve seat 10 is placed in a recess 11 in the cylinder head bottom 3 on the combustion chamber side of the cylinder head bottom. It is provided offset with respect to the surface 12.

According to the invention, the recess 11 has an enlargement 13 pointing towards the surface 12. This enlarged portion 13 is
This is produced by, for example, chamfering the wall delimiting the recess 11 with a countersink drill.

According to FIGS. 1 and 2, the enlarged view 13 occupies only part of the depth of the recess 11. The depth of the countersunk is adapted to the stroke of the throttle valve and is dimensioned such that the valve head 9 is in the area of the widening 13 when the throttle valve opens.

The embodiment shown in FIG. 3 differs from the embodiment shown in FIGS. 1 and 2 only in that the recess 11 has an enlarged part 14 extending over the entire depth of this recess. There is. In all embodiments, the enlarged portion 13
and 14, in addition to a slight increase in the flow gap between the valve head 9 and the recess 11 when the throttle valve 2 is opened.
The flow guidance of the compressed gas from the cylinder into the recess 11 is improved.

[Brief explanation of drawings]

Fig. 1 is a sectional view of the cylinder head in which the throttle valve is installed, Fig. 2 is a sectional view of the recess at the bottom of the cylinder head with an enlarged portion limited to a part of the depth of the recess, and Fig. 3. The figure is a sectional view of a recess with an enlarged section reaching the bottom. 1... Cylinder head, 2... Throttle valve, 3...
Cylinder head bottom, 4... Valve opening, 8... Exhaust passage, 10... Valve seat, 11... Recess, 12... Surface, 13, 14... Enlarged portion.

Claims (1)

[Claims] 1 A valve opening 4 connected to the exhaust passage 8 in the cylinder head 1 and having a valve seat 10 for the throttle valve 2 is provided at the bottom of the recess 11 offset with respect to the combustion chamber side surface 12 of the cylinder head bottom 3. in which the recess 11 has enlarged parts 13, 14 facing towards the combustion chamber side surface 12, the enlarged parts 13, 14
Engine brake with a throttle valve installed in the cylinder head of an internal combustion engine, characterized in that it is formed by a countersink in a wall surrounding a recess 11.