DE344081C - Device for braking four-stroke explosion engines - Google Patents

Description

Device for braking four-stroke explosion engines. It is known, - When driving downhill, the coupled engine of a motor vehicle acts as a powerful one To use the brake by one. the exhaust valve twice in every four stroke period opens. So far this has been achieved by having two cams on the control shaft attached and on each cam a special control lever: let, where. These control levers are gradually put into and out of action by turning the eccentric can be. But this makes a rather cumbersome and hardly reliable Type given. In addition, control shafts with auxiliary cams for brake control are known, which are shifted at the same time during the transition from the operating position to the braking position and. be twisted.

The device according to the present invention, on the other hand, uses also two cams on the control shaft, but aligns the control shaft so that it can be moved first and then rotated. This makes it possible to achieve precise control of the braking effect, with the simplest Means, whereby considerable operational reliability is achieved.

On the accompanying drawing is an example for execution the process serving device shown.

Fig. R shows a section through the camshaft, Fig. A the view a part of the camshaft, Fig, 3 and 4 the crankshaft and its position for Pistons and the, valves at the lowest and highest braking position, whereby through the Hatching the opening time of the exhaust valve is marked. Fig. 5 shows the Arrangement of the device for moving. and twisting the control shaft.

In Fig. I and z, E is the intake cam and A is the exhaust cam, the latter of width s - [- b, where s is the length of the axial cam displacement and b is the normal cam width. A 'is the exhaust cam with an inclined run-up surface a, which is opposed by 180 ° to the actual exhaust cam and only comes into play in the braking position. In Fig. 3 and q. means T 0 top dead center, T U bottom dead center. Since the camshaft rotates with half a revolution of the crankshaft, we have two lower and two upper dead center hinges on the camshaft, as can be seen in Fig. I. The exhaust cam starts, for example : 25 ' before bottom dead center and ends at top dead center.

If the camshaft is displaced by the amount s in the direction of the arrow k, the inlet cam is completely out of action, the inlet valve thus remains permanently closed. The exhaust valve is now raised twice during one revolution of the camshaft by the exhaust cams: A and A ', as shown in Fig. 2. When the crank T moves 0 to 50 ° (corresponding to 25 ° on the camshaft) in front of TU, the exhaust valve remains closed, the atmospheric tension air contained in the compression chamber is diluted, which has a slight braking effect on the crankshaft. Now the exhaust valve opens, actuated by cam A, pressure equalization with the outside air takes place and continues. Sucking in the air through the exhaust valve up to T U. During the subsequent upward movement of the piston according to the path of the crank from T U to T 0, the exhaust valve remains open and the previously sucked in air is expelled again without offering any significant resistance. At the. Next downward travel of the piston up to 50 ° before T U, the outlet valve remains closed again and is then opened by cam A and kept open during the subsequent pressure cycle of the piston up to T 0. With this camshaft position there is no compression work and, apart from the @ eer @ on: @i: Ierstand of the engine and the low resistance when the air is diluted, no braking work is done.

If, on the other hand, the camshaft is rotated in its direction of rotation with respect to its drive, for example by 77.5 ' or 155' on the crankshaft, the engine works as shown in Fig hacked. In Fig. Q., Crank position II, the exhaust valve closes 25 ° after bottom dead center, and during the upward movement of the piston that now follows, the previously sucked in air is compressed. With crank position III, in the example a5 °, before top dead center, the exhaust valve opens again and the compressed air is expelled as the piston continues upward to T 0, from T 0 to T U air is then sucked in again, etc. The engine is now working properly as a two-stroke compressor, performing maximum braking work. The same braking effect can of course also be achieved by rotating the camshaft in the opposite direction to its direction of rotation. However, in order to achieve the same effect as previously described, the camshaft must now be turned Io2.5 ° (corresponding to 2o5 ° on the crank) instead of 77.5 ° (corresponding to z55 ° on the crank handle). In all intermediate positions the camshaft rotation from o to 77.5 ° in one direction or o to ro2.5 ° in the other direction, the compression or braking work is correspondingly lower. It is thus up to you to change the braking work of the engine between a minimum and a maximum by turning the camshaft more or less.

The displacement of the camshaft as well as its rotation in relation to it the drive is effected in the following way. The one shown in Fig. 5 as a hollow shaft Camshaft F is mounted on solid shaft G so that it can be axially displaced by the dimension and is taken along by the spring wedge H. The solid shaft is through high helix threads stored in the hub of the drive gear Z, so that by axial displacement the solid shaft rotates the same and therefore also the camshaft in relation to it the drive gear Z takes place. The two axial displacements to be carried out one after the other can be used be set up by suitable rod connection such that they are of a Lever made in equal directional movement.

The device is only shown as an example, it can of course can be used in any four-stroke internal combustion engine with any number of cylinders.

Claims (1)

PATENT CLAIM: Device for braking four-stroke explosion engines with additional control cam on a movable and rotatable control shaft, characterized in that the control shaft is first moved and then thereafter is rotated.