WO2012038190A1

WO2012038190A1 - Four-stroke internal combustion engine comprising an engine brake

Info

Publication number: WO2012038190A1
Application number: PCT/EP2011/064722
Authority: WO
Inventors: Gyula Toth; Michael Gröger
Original assignee: Avl List Gmbh
Priority date: 2010-09-23
Filing date: 2011-08-26
Publication date: 2012-03-29
Also published as: EP2619422A1; AT510528A1; EP2619422B1; AT510528B1

Abstract

The invention relates to a four-stroke internal combustion engine with an engine brake (4), with at least one exhaust valve (1) per cylinder, said valve being actuated by means of a cam (21) of a camshaft (2) and at least one first valve lever arrangement (5), the first valve lever arrangement (5) having a first lever arm (8) on the cam side and a second lever arm (9) on the exhaust valve side, and with an arrangement for advancing the exhaust control system (1). According to the invention, in order to produce an engine brake having dual braking phases as simply as possible and with minimal space requirements, the first valve lever arrangement (5) has a switching member (10) for moving the first lever arm (8) on the cam side between an operative position (A) and a braking position (B), and a cam-operated second valve lever arrangement (6) acts on the first lever arm (8) of the first valve lever arrangement (5).

Description

Four-stroke internal combustion engine with an engine brake

The invention relates to a four-stroke internal combustion engine with an engine brake, with at least one actuated via a cam of a camshaft and at least a first valve lever assembly exhaust valve per cylinder, wherein the first valve lever assembly comprises a cam-side first lever arm and an outlet valve-side second lever arm, with a device for Pre-adjustment of the outlet control.

It is known to arrange an internal engine brake valve in an internal combustion engine in addition to the exhaust valves, which is clocked during engine braking or constantly open. Such engine brake valves are usually actuated hydraulically or pneumatically and are known, for example, from DE 44 23 657 C2, DE 38 39 452 C2, DE 38 39 450 C2, AT 004.387 Ul or AT 003.600 Ul. From DE 41 25 831 AI further motor braking device is known, the engine brake valve is electrically actuated.

However, known actuators for engine brake valves require a relatively high construction cost and require a comparatively large amount of space in the cylinder head, which can be difficult to provide in many cases. In order to drain the cylinder pressure, an additional tank and a high-pressure oil system with a high-pressure pump and electro-hydraulic valves for each cylinder are usually required. In addition, known motor brake device on a high number of items, which increase the susceptibility to interference and adversely affect the manufacturing cost.

DE 39 36 808 A1 describes an exhaust cam-controlled engine brake for four-stroke internal combustion engines, in which the exhaust control is advanced by approximately one stroke, ie a crank angle of about 180 °, for the duration of the required braking action. This results in a doubling of the braking cycles and a decompression at the end of the compression stroke, whereby a higher retarding effect can be achieved.

US 6,000,374 A describes an engine brake for an internal combustion engine in which several braking phases can be realized per working cycle. In addition to intake and Auslaßkipphebel an additional brake rocker arm per cylinder is provided which - driven by a brake cam - actuates an exhaust valve. All rocker arms have a hydro element at their valve end. Solenoids can be used to influence which hydraulic elements are exposed to pressurized oil and which are not. This will achieve that in normal working operation, the brake rocker arm only runs empty and the exhaust valve is not operated via the brake rocker arm, because its hydro element without oil supply can not transmit the force. The intake and exhaust rocker arms operate during operation as long as their hydro elements are filled with oil. In braking mode, the hydroelements of the exhaust rocker arms are deactivated and the hydroelements of the brake rocker arms are activated. In this way it is also possible to hydraulically manipulate the valve movements to ensure brake power control and adaptation to any speed. The disadvantage is that a high control effort is required and that relatively much space is required by the additional brake lever.

The object of the invention is to avoid these disadvantages and to allow for a four-stroke internal combustion engine in the simplest possible and space-saving manner doubled braking phases.

According to the invention this is achieved in that the first valve lever assembly comprises a switching member for adjusting the cam-side first lever arm between a working position and a braking position and that acts on the first lever arm of the first valve lever assembly cam actuated second valve lever assembly, preferably the second valve lever assembly a working lever and a brake lever wherein the working lever and brake lever are preferably pivotally mounted about the same axis and wherein the working lever acts only in the working position and the brake lever only in the braking position on the first lever arm of the first valve lever assembly.

Doubled braking phases can be made possible by the fact that the brake lever is actuated by an angle of about 90 ° out of phase before the working lever through the camshaft.

In principle, working and brake levers can be actuated by different cams. To save space, but it is particularly advantageous if the working and the brake lever from the same cam of the camshaft can be actuated. To ensure that both the working lever, and the brake lever are in constant contact with the camshaft, it can be provided that the working lever and the brake lever are pressed by preferably a spring against the camshaft, preferably the spring on the one hand on the working lever and on the other hand is supported on the brake lever.

A particularly simple operation is made possible when the first lever arm has a lever element which can be adjusted by the switching element, wherein preferably the switching element is formed by a hydraulically actuatable actuator. To switch between normal working and braking operation only relatively small forces are required if the cam has at least one flanked by the base circle relief section having a smaller distance from the axis of rotation of the camshaft than the base circle, preferably the relief section diametrically to a lifting section of Cam is arranged.

The switching of the switching member causes, in the working position of the working lever and in the braking position of the brake lever acts on the first lever arm of the first valve lever assembly, while the other lever of the second valve lever assembly is exempted from the first valve lever assembly.

The invention will be explained in more detail below with reference to FIGS. Show it :

1 shows an engine brake of an internal combustion engine according to the invention in an oblique view.

2 shows the engine brake in a front view.

3 shows the engine brake in the working position of a sectional view.

4 shows the engine brake in a braking position in a sectional view;

5 shows the engine brake in the working position with the exhaust valves closed;

6 shows the engine brake in working position with the exhaust valves open;

7 shows the engine brake in the braking position with the exhaust valves closed;

8 shows the engine brake in the braking position with the exhaust valves open;

9 is a valve lift diagram of the internal combustion engine in normal operation;

FIG. 10 is a valve lift diagram of the internal combustion engine in braking operation; FIG.

11 is another valve lift diagram of the internal combustion engine in

Braking operation; and

12 shows a cam of an internal combustion engine according to the invention in an end view. As shown in Fig. 1, exhaust valves 1 of the internal combustion engine are actuated by a valve actuator 3 having a camshaft 2. The valve actuating device 3 has an engine brake 4 with a first valve lever arrangement 5 and a second valve lever arrangement 6. The first valve lever arrangement 5 is designed essentially as a rocker arm pivotable about a first axis 7 with a cam-side first lever arm 8 and an exhaust valve-side second lever arm 9. The first lever arm 8 can be adjusted via a designed as a hydraulic actuator 11 switching member 10 with a between a normal working position A and a braking position B. To make this possible, the first valve lever assembly 5, a lever member 12 which is pivotally mounted about a fixedly connected to the first valve lever assembly 5 axis 13 between the working position A and the braking position B, wherein the lever member 12 by a spring 14 in the direction of Working position A is biased. The second lever arm 9 acts on a valve bridge 15 for actuating two exhaust valves 1 per cylinder.

The second valve lever assembly 6 consists of a working lever 16 and a brake lever 17 which are pivotally mounted about a common axis 22. By a spring 18 both levers 16, 17 are pressed by rollers 19, 20 to a common cam 21 of a camshaft 2. The working lever 16 and the brake lever 17 are arranged relative to the first valve lever assembly 5 so that in the working position A of the working lever 16, and in the braking position B of the brake lever 17 acts on the lever member 12 of the first valve lever assembly 5. The brake lever 17 is arranged with respect to the working lever 16 so that - viewed in the direction of rotation of the camshaft 2 - the contact point 17a of the brake lever 17 with the cam 21 by an angle α of about 90 ° in front of the contact point 16a of the working lever 16 with the cam 21 , This results in that the exhaust valves 1 in the braking position B by a crank angle of about 180 °, ie a work cycle, can be advanced.

Fig. 3 shows the engine brake 4 in a working position A, wherein the internal combustion engine is operated normally. In this working position A, the lever member 12 is held by the spring 14 in its upper position, the actuator 11 is deactivated, so switched without pressure. The camshaft 2 with the cam 21 is driven in accordance with the arrow 23, wherein the lifting portion 21a of the cam 21 first raises the brake lever 17 and then the working lever 16, as shown in FIGS. 5 and 6. In this working position A of the brake lever 17 is exempt from the first valve lever assembly 5, which is why the operation of the brake lever 17 has no effect on the lifting movement of the exhaust valves 1. In contrast, the deflection of the operating lever 16 by the lifting portion 21 a of the cam 21 causes the exhaust valves 1 are opened by the working lever 16 transmits the movement via the lever element 12 of the first lever arm 8 and the second lever arm 9 to the valve bridge 15 and the outlet valves 1 (FIG. 6).

Fig. 4 shows the engine brake 4 in its braking position B, wherein the cylinder chamber I Ia of the actuator 11 is acted upon by control pressure and the lever member 12 is moved to its braking position B shown in FIG. In this braking position B, the working lever 16 of the second valve lever assembly 6 is exempted from the first valve lever assembly 5, while the brake lever 17 acts directly on the lever member 12 a. This makes it possible to advance the exhaust valves 1 by about 180 ° crank angle KW, whereby they are already opened during the downward movement of the piston. The deflection of the brake lever 17 is transmitted via the lever element 12 of the first lever arm 8 of the first valve lever assembly 5 to the second lever arm 9, which opens the exhaust valves 1 via the valve bridge 15, as shown in FIGS. 7 and 8.

In FIG. 9, the valve lift H is plotted against the crank angle KW for the normal working operation of the internal combustion engine, where I is the valve lift curve of the intake valves and E is the valve lift curve of the exhaust valves 1. With ZOT is the top dead center of the ignition, with UT the bottom dead center and with OT the top dead center of the gas exchange designated. The four strokes of the internal combustion engine - expansion, exhaust, intake, compression - are indicated by the reference Tl, T2, T3 and T4.

10 shows a diagram in which the valve lift H for the braking operation is plotted against the crank angle KW. As can be clearly seen, the valve opening of the exhaust valves 1 is pre-adjusted by one operating stroke compared to the working operation, whereby now the exhaust valves 1 are opened in descending piston. In order to avoid a mechanical overload of the entire valve train, a throttling in the Ausschubphase is required. During engine braking operation, the following steps take place during one cycle:

In the phase designated Bl residual gas is emptied into the exhaust manifold. This is followed by a free intake from the exhaust manifold in B2. In B3, the gas is expelled from the cylinder space while throttling. In phase B4, residual gas is emptied into the inlet plenum. This is followed by a free intake from the inlet plenum in B5. Finally, in B6, the gas within the cylinder space is pushed out in B6. The actual braking effect occurs in phases B3 and B6. With BE is a mechanical discharge phase for a free adjustment called. This mechanical relief phase BE is defined by a relief section 21c of the cam 21, which has a low Geren distance from the axis of rotation 2a of the camshaft 2, as the base circle 21b of the cam 21. The relief portion 21c is located diametrically to the lifting portion 21a on the cam 21 and is flanked by two base circle portions 21b. By the relief section 21c ensures that the operation of the engine brake 4 can be done with minimal effort.

The regulation of the braking power can be done either via an adjustment of an exhaust flap in the exhaust pipe or via an adjustment of the exhaust valve E during the braking operation B. In the latter case, a central stroke adjustment for all cylinder units is possible in that the control oil quantity fed into the cylinder chamber 11a of the actuator 11 is metered. The cylinder chamber 11a is fed in each case by a central oil channel 24 in the axis 7 of the first valve lever arrangement 5. In this way, the lifting movement of the exhaust valve 1 can be adjusted during braking operation B in any intermediate positions El, E2, E3, E4, E5, as shown in FIG. 11.

Claims

PATENT APPLICATIONS

1. four-stroke internal combustion engine having an engine brake (4), with at least one via a cam (21) of a camshaft (2) and at least a first valve lever assembly (5) actuated exhaust valve (1) per cylinder, wherein the first valve lever assembly (5) a cam-side first lever arm (8) and an outlet valve-side second lever arm (9), with a device for advancing the exhaust control (1), characterized in that the first valve lever assembly (5) a switching member (10) for adjusting the cam-side first lever arm (8 ) between a working position (A) and a braking position (B) and in that the first lever arm (8) of the first valve lever arrangement (5) engages a cam-actuated second valve lever arrangement (6).

2. Internal combustion engine according to claim 1, characterized in that the second valve lever assembly (6) has a working lever (16) and a brake lever (17), wherein working lever (16) and brake lever (17) preferably pivotally mounted about the same axis (22) are and wherein the working lever (16) only in the working position (A) and the brake lever (17) only in the braking position (B) on the first lever arm (8) of the first valve lever assembly (5) acts.

3. Internal combustion engine according to claim 2, characterized in that the brake lever (17) by an angle (a) of about 90 ° out of phase in front of the working lever (16) by the camshaft (2) is actuated.

4. Internal combustion engine according to claim 2 or 3, characterized in that the working and the brake lever (16, 17) of the same cam (21) of the camshaft (2) are actuated.

5. Internal combustion engine according to one of claims 2 to 4, characterized in that the working lever (16) and the brake lever (17) are pressed by preferably a spring (18) against the camshaft (2), wherein preferably the spring (18) on the one hand on the working lever (16) and on the other hand on the brake lever (17) is supported.

6. Internal combustion engine according to one of claims 1 to 5, characterized in that the first lever arm (8) from the switching member (10) adjustable lever element (12).

7. Internal combustion engine according to one of claims 1 to 6, characterized in that the switching member (10) by a hydraulically actuated actuator (11) is formed.

8. Internal combustion engine according to one of claims 1 to 7, characterized in that the cam (21) at least one of the base circle (21b) flanked on both sides relief portion (21c) which a smaller distance from the axis of rotation (2a) of the camshaft (2) as the base circle (21b), wherein preferably the relief portion (21c) is disposed diametrically to a lift portion (21a) of the cam (21).