KR102627371B1 - Valve train and method for actuating gas exchange valves - Google Patents

Abstract

A valve train for operating the intake and exhaust valves of an internal combustion engine, comprising an intake camshaft supporting each intake cam including an intake valve opening flank (11a) and an intake valve closing flank (11b), the exhaust valve opening A valve train is shown having an exhaust camshaft carrying each exhaust cam comprising a flank (10a) and an exhaust valve closing flank (10b). The exhaust valve closing flank 10b and the intake valve opening flank 11a are arranged so that, under full load and under partial load, the intake valve starts opening before the top dead center (OT) of the corresponding cylinder and the exhaust valve starts opening above top dead center (OT). It is configured in such a way that it is completely closed after OT). The exhaust valve closing flank 10b is formed in such a way that the exhaust valve is initially closed with a relatively large gradient and subsequently with a relatively small gradient, the change from the relatively large gradient to the relatively small gradient Taking place in the top dead center region, under maximum load, this relatively small gradient causes complete closure of the exhaust valve in the range of 60° KW to 30° KW prior to complete closure of the intake valve. The intake valve opening flank 11a is configured in such a way that the intake valve is initially opened with a relatively small gradient and subsequently with a relatively large gradient, which, under maximum load, is 90° before top dead center. Starting to open the intake valve in the range from ° KW to 60° KW, the change from the relatively small gradient to the relatively large gradient under maximum load takes place in the region of the top dead center.

Description

Valve train and method for operating gas exchange valves {VALVE TRAIN AND METHOD FOR ACTUATING GAS EXCHANGE VALVES}

The present invention relates to a valve train for operating a gas exchange valve in a cylinder of an internal combustion engine according to the preamble of claim 1. The invention also relates to a method for operating a gas exchange valve of a cylinder of an internal combustion engine according to the preamble of claim 6.

The basic structure of a valve train for operating a gas exchange valve in a cylinder of an internal combustion engine is known from practice. According to this, the valve train includes an intake camshaft that supports an intake cam, and the intake cam serves to operate the intake valve of the cylinder of the internal combustion engine. Additionally, the valve train includes an exhaust camshaft that supports an exhaust cam, and the exhaust cam serves to operate an exhaust valve of a cylinder of an internal combustion engine.

Each intake cam includes an intake valve opening flank for opening the corresponding intake valve and an intake valve closing flank for closing the corresponding intake valve. Each exhaust cam includes an exhaust valve opening flank along the corresponding exhaust valve and an exhaust valve closing flank for closing the corresponding exhaust valve.

DE 10 2016 112 447 From A1, a valve train is known, in the case of which a cam lever interacts with the cam of the camshaft, and the roller of the cam lever scans the cam contour of the corresponding cam. and transmits the cam contour to the gas exchange valve through a pushrod and rocker arm to operate the gas exchange valve.

From DE 10 2016 112 448 B4, an additional valve train for internal combustion engines is known, in the case of which the roller of the cam lever scans the cam contour of the cam, but without a rocker arm and through a pushrod. Delivers to the gas exchange valve.

From practice, it is known that valve overlap may exist between at least one intake valve and at least one exhaust valve of each cylinder of an internal combustion engine. Valve overlap is characterized in that each intake valve begins to open even before top dead center of that cylinder and each exhaust valve of that cylinder closes completely only after top dead center of that cylinder. The pressure difference between the supply air pressure at each exhaust port and the back pressure at each exhaust port can then be used to scavenge residual exhaust gases from the combustion chamber of the corresponding cylinder to the exhaust port with the help of fresh air.

Additionally, valve trains with variable valve actuation are known from practice for providing different valve actuation for the gas exchange valves of the cylinder at full load and part load. Thereby, cylinder supercharging can be improved, especially at partial load.

A valve train is needed that allows optimized operation of the internal combustion engine under full load and also under partial load, which in particular ensures good cooling of the exhaust valves in all load ranges and avoids fuel economy disadvantages.

Starting from this, the present invention is based on the object of providing a new type of valve train and corresponding method for operating a gas exchange valve.

This object is achieved through a valve train for actuating a gas exchange valve of a cylinder of an internal combustion engine according to claim 1.

The valve train includes an intake camshaft that carries intake cams for the intake valves of the cylinder, each intake cam including an intake valve opening flank and an intake valve closing flank. The valve train includes an exhaust camshaft carrying exhaust cams for the cylinder's exhaust valves, each exhaust cam including an exhaust valve opening flank and an exhaust valve closing flank. The valve train also includes a camshaft adjustment device for the intake camshaft, whereby the intake cam is adjustable relative to the exhaust cam, relative to the intake valves of the cylinder under the maximum load of the internal combustion engine: Provides a different valve operation than under partial load of the internal combustion engine.

The exhaust valve closing flank of the exhaust cam and the intake valve opening flank of the intake cam are configured such that under full load and under partial load for each cylinder, at least one intake valve initiates opening before top dead center of that cylinder and at least one It is configured in such a way that the exhaust valve of the cylinder is completely closed after top dead center of the corresponding cylinder.

The exhaust valve closing flank of the exhaust cam is formed in such a way that the at least one exhaust valve of each cylinder is initially closed with a relatively large gradient and subsequently with a relatively small gradient, from the relatively large gradient to the relatively small gradient. The change to a small gradient takes place in the region of top dead center of the corresponding cylinder, and under the maximum load of the internal combustion engine, said relatively small gradient corresponds to the range from 60° KW to 30° KW before complete closure of at least one intake valve. Completely close at least one exhaust valve of the cylinder. KW stands for crankshaft angle.

The intake valve opening flank of the intake cam is configured in such a way that at least one intake valve of each cylinder is initially opened with a relatively small gradient and subsequently with a relatively large gradient, under the maximum load of the internal combustion engine, said The relatively small gradient begins to open at least one intake valve of that cylinder in the range of 90° KW to 60° KW before the top dead center of each valve, and under full load the gradient changes from the relatively small gradient to the relatively large gradient. The change occurs in the area of top dead center of the relevant cylinder. KW stands for crankshaft angle.

In this valve train, a camshaft adjuster allows adjustment of the intake cam relative to the exhaust cam. The exhaust valve closing flank of the exhaust cam and the intake valve opening flank of the intake cam are formed in a defined manner to provide a defined valve overlap under full load and also under partial load, so that under full load and also under partial load, the charge air is discharged from the exhaust. It is used for scavenging of exhaust gases into the port and in the cooling process of the exhaust valve of the cylinder. On the other hand, fuel economy disadvantages are avoided through the defined contours of the exhaust valve closing flanks of the exhaust cam and the intake valve opening flanks of the intake cam. At full load and also at part load, an appropriate amount of valve overlap is available to ensure good cooling of the exhaust valves in all load ranges without fuel economy drawbacks.

Preferably, the camshaft adjustment device adjusts the intake cam by an angle β towards the retardation side during the above-mentioned change from full load to partial load. Under partial load, this relatively small gradient of the intake valve opening flank initiates the opening of at least one intake valve in the range from (90°-β) KW to (60°-β) KW before top dead center of that valve. Under partial load, this relatively small gradient causes the at least one exhaust valve to fully close in the range from (60°+β) KW to (30°+β) KW before fully closing the at least one intake valve. Preferably, β corresponds to 30° KW to 50° KW. KW stands for crankshaft angle.

This enables very advantageous operation of the internal combustion engine under partial load and also under maximum load. During full load and also during partial load, adequate cooling of the exhaust valves is ensured without fuel economy disadvantages.

A method for operating a gas exchange valve of a cylinder of an internal combustion engine is presented in claim 6.

Advantageous further developments of the invention can be obtained from the dependent claims and the following description. Exemplary embodiments of the present invention are hereby described in more detail using the drawings without limitation.

Figure 1 shows the open and closed flanks of the intake and exhaust cams of a valve train according to the invention at maximum load.
Figure 2 shows the open and closed flanks of the intake and exhaust cams of the valve train according to the invention at partial load.

The basic structure of the valve train of an internal combustion engine is known to those skilled in the art mentioned herein.

According to this, the valve train that operates the gas exchange valve of the cylinder of the internal combustion engine includes an intake camshaft that supports the intake cam. The intake cam serves to operate the gas exchange valve of the cylinder of the internal combustion engine, which is formed as an intake valve, and each intake cam has an intake valve opening flank for opening the corresponding intake valve and an intake valve for closing the corresponding intake valve. Includes valve closure flank.

Additionally, the valve train includes an exhaust camshaft that supports the exhaust cam. The exhaust cam serves to actuate the gas exchange valve of the cylinder of the internal combustion engine, which is designed as an exhaust valve, to open and close the exhaust valve. According to this, each exhaust cam includes an exhaust valve opening flank for opening the corresponding exhaust valve and an exhaust valve closing flank for closing the corresponding exhaust valve.

Additionally, the valve train includes camshaft adjustments. Using a camshaft adjuster, the intake camshaft can be adjusted to adjust the intake cam relative to the exhaust cam on the exhaust camshaft. Accordingly, individual valve action for the intake valves of the cylinder can be provided for the full load of the internal combustion engine and also for partial loads of the internal combustion engine.

1 and 2 the action on the exhaust and intake valves of the cylinder is shown for full load operation (see Fig. 1) and for part load operation (see Fig. 2), the curved profile 10 showing the exhaust Corresponding to the actuation of the exhaust valve by the open and closed flanks of the cam, the curved profile 11 corresponds to the actuation of the intake valve by the open and closed flanks of the intake cam.

The opening of each exhaust valve is determined by the exhaust valve opening flank 10a of each exhaust cam, and the closing of each exhaust valve is determined by the exhaust valve closing flank 10b of each exhaust cam. The exhaust valve opening flank 10a is shown with a continuous drawn line, and the exhaust valve closing flank 10b is shown with a dashed line. The opening of each intake valve according to the curved profile 11 is determined by the intake valve opening flank 11a, while the closing of each intake valve according to the curved profile 11 is determined by the intake valve closing flank 11b. It is decided. The intake valve opening flank 11a is shown with a dashed line, and the intake valve closing flank 11b is shown with a continuously drawn line.

1 and 2 show that, according to the curved profile 10, the exhaust valve begins to open starting at angle αA1 and completely closes at angle αA2. The exhaust valve opening flank 10a starts to open each exhaust valve at angle αA1. The exhaust valve closing flank 10b completely closes each exhaust valve at angle αA2. At full load and at partial load, these angles (αA1 and αA2) are the same.

According to the curved profile 11, the intake valve starts opening at angle αE1 or α*E1 and completely closes at angles αE2 and α*E2, respectively. The intake valve opening flank 11a begins to open each intake valve at angles αE1 and α*E1, respectively, and the intake valve closing flank 11b completely closes each intake valve at angles αE2 and α*E2, respectively. I order it. From the comparison of Figures 1 and 2, it can be seen that at partial load in Figure 2 compared to full load in Figure 1, the intake cam, which determines the curved profile 11, is adjusted relative to the exhaust cam, which determines the curved profile 10, i.e. It can be seen that it is adjusted to the delay side. This adjustment is made by angle β. Accordingly, the following applies.

α*E1=αE1+β

α*E2=αE2+β

The exhaust valve closing flank 10b of the exhaust cam and the intake valve opening flank 11a of the intake cam are such that, both at full load (see Fig. 1) and at partial load (see Fig. 2), each intake valve is in the so-called corresponding cylinder. in such a way that it starts opening before top dead center (OT), i.e. at the angle αE1 at full load according to FIG. 1 and at angle α*E1 at partial load according to FIG. 2 and at least one exhaust valve of the corresponding cylinder respectively. It is formed in such a way that it is completely closed after top dead center (OT) of the cylinder in question, i.e. at angle αA2 in each case.

The exhaust valve closing flank 10b of the exhaust cam is also implemented in such a way that at least one exhaust valve of the corresponding cylinder is closed initially with a relatively large gradient and subsequently with a relatively small gradient. The change from the relatively large gradient of the exhaust valve closing flank to the relatively small gradient takes place in the region of the top dead center (OT) of the cylinder in question.

Under the maximum load of the internal combustion engine, the relatively small gradient of the exhaust valve closing flank 10b is such that at angle αA2 before the complete closure of at least one intake valve at angle αE2 (before 60 KW to 30 KW at maximum load) Close at least one exhaust valve of the relevant cylinder. KW stands for crankshaft angle.

Under partial load, the relatively small gradient of the exhaust valve closing flank 10b is such that before the complete closure of at least one intake valve of the corresponding cylinder at angle α*E2 ((60+β) KW to (30+β ) KW ahead) close at least one exhaust valve of the corresponding cylinder at angle αA2. KW stands for crankshaft angle.

Moreover, the intake valve opening flank 11a of the intake cam is configured in such a way that at least one intake valve of the corresponding cylinder opens initially with a relatively small gradient and subsequently with a relatively large gradient.

Under the maximum load of the internal combustion engine (see Figure 1), this relatively small gradient begins to open at least one intake valve of the cylinder in question at an angle αE1, which angle αE1 is between 90° KW and 60°C before top dead center of the cylinder in question. ° Belongs to the range of KW.

Under partial load, the relatively small gradient of the intake valve opening flank begins to open at least one intake valve of that cylinder at an angle α*E1, where the angle α*E1 is before top dead center (OT) of that valve. It ranges from (90°-β) KW to (60°-β) KW. KW stands for crankshaft angle.

Under maximum load, the change from the relatively small gradient of the intake valve opening flank 11a to the relatively large gradient of the intake valve opening flank 11a takes place in the region of the top dead center (OT) of the cylinder in question. Under partial load, the change from the relatively small gradient of the intake valve opening flank 11a to the relatively large gradient of the intake valve opening flank 11a is adjusted to lag the maximum load by β.

By means of the above-described configuration of the intake and exhaust cams and the exhaust valve closing flank 10b of the exhaust cam and the intake valve opening flank 11a of the intake cam, under full load according to FIG. 1 and under partial load according to FIG. 2, proper A large valve overlap 12 is provided, which is characterized by the angular range between the onset of opening of the corresponding intake valve and the complete closing of the corresponding exhaust valve. Accordingly, at full load according to FIG. 1 the valve overlap 12 is defined as αA2-αE1, and in part load operation as αA2-α*E1. Accordingly, this angular range of valve overlap 12 is suitably large under full load and also suitably large under part load to ensure cooling of the exhaust valves via charge air in all load ranges without loss of fuel economy.

10a: Exhaust valve opening flank
10b: Exhaust valve closing flank
11a: intake valve opening flank
11b: intake valve closing flank
12: Valve overlap

Claims (10)

A valve train for operating gas exchange valves of cylinders of an internal combustion engine, each cylinder including at least one intake valve and at least one exhaust valve as a gas exchange valve,
The valve train includes an intake camshaft supporting intake cams for intake valves of a cylinder, each intake cam comprising an intake valve opening flank (11a) and an intake valve closing flank (11b). Contains,
The valve train includes an exhaust camshaft supporting exhaust cams for the exhaust valves of the cylinder, each exhaust cam comprising an exhaust valve opening flank (10a) and an exhaust valve closing flank (10b). Contains,
The valve train includes a camshaft adjustment device for the intake camshaft, whereby the intake cam is adjustable relative to the exhaust cam, relative to the intake valves of the cylinder under the maximum load of the internal combustion engine. , providing a different valve operation than under partial load of the internal combustion engine,
The exhaust valve closing flank 10b of the exhaust cam and the intake valve opening flank 11a of the intake cam are such that, under full load and under partial load for that cylinder, at least one intake valve is positioned before top dead center (OT) of that cylinder. and configured in such a way that the at least one exhaust valve is fully closed after top dead center (OT) of the corresponding cylinder,
The exhaust valve closing flank 10b of the exhaust cam is formed in such a way that at least one exhaust valve of the corresponding cylinder is initially closed with a relatively large gradient and subsequently with a relatively small gradient, from said relatively large gradient. The largest of the relatively small gradient changes are in the region of top dead center (OT) of the cylinder in question, and under maximum load of the internal combustion engine, the relatively small gradient changes when the at least one intake valve is completely closed. Completely closing at least one exhaust valve of the cylinder in question in the range from 60° KW to 30° KW,
The intake valve opening flank 11a of the intake cam is formed in such a way that at least one intake valve of the corresponding cylinder opens initially with a relatively small gradient and subsequently with a relatively large gradient, under the maximum load of the internal combustion engine. , the relatively small gradient begins to open at least one intake valve of the corresponding cylinder in the range of 90° KW to 60° KW before top dead center (OT) of the corresponding valve, and from the relatively small gradient under maximum load, the A valve train in which the largest change in relatively large gradient occurs in the area of the top dead center (OT) of the cylinder. The valve train according to claim 1, wherein the camshaft adjustment device adjusts the intake cam by an angle β toward the retardation side during a change from full load to partial load. 3. The method of claim 2, wherein under partial load, the relatively small gradient is in the range of (90°-β) KW to (60°-β) KW before top dead center (OT) of the valve in question. The valve train is what starts the intake valves open. 4. The method of claim 2 or 3, wherein under partial load, the relatively small gradient is in the range of (60°+β) KW to (30°+β) KW before complete closure of at least one intake valve. A valve train that completely closes at least one exhaust valve of the valve train. The valve train according to claim 2 or 3, wherein β corresponds to 30° KW to 50° KW. A method for operating a gas exchange valve of a cylinder of an internal combustion engine, comprising:
Each cylinder includes at least one intake valve and at least one exhaust valve as a gas exchange valve,
Each intake valve of that cylinder is actuated for opening and closing, starting from an intake cam comprising an intake valve opening flank (11a) and an intake valve closing flank (11b),
Each exhaust valve of that cylinder is actuated for opening and closing, starting from an exhaust cam comprising an exhaust valve opening flank (10a) and an exhaust valve closing flank (10b),
During fluctuations between full and partial load of the internal combustion engine, the intake cam is adjusted relative to the exhaust cam, so as to provide a different valve actuation for the intake valves under full load than under partial load,
Under maximum load and under partial load for each cylinder, the intake valve opening flank 11a of the corresponding intake cam begins to open at least one intake valve before the top dead center (OT) of the corresponding cylinder, and the intake valve opening flank 11a of the corresponding exhaust cam begins to open at least one intake valve before the top dead center (OT) of the corresponding cylinder. The exhaust valve closing flank 10b completely closes at least one exhaust valve of the cylinder after top dead center (OT) of the cylinder,
The exhaust valve closing flank 10b of the exhaust cam closes at least one exhaust valve of the corresponding cylinder, initially with a relatively large gradient and subsequently with a relatively small gradient, from said relatively large gradient to said relatively small gradient. The largest fluctuations in flow occur in the region of the top dead center (OT) of the cylinder in question, and under the maximum load of the internal combustion engine, the relatively small gradient occurs between 60° KW and before complete closure of at least one intake valve. Completely closing at least one exhaust valve of the relevant cylinder in the range of 30° KW,
The intake valve opening flank 11a of the intake cam opens at least one intake valve of the corresponding cylinder initially with a relatively small gradient and subsequently with a relatively large gradient, wherein, under the maximum load of the internal combustion engine, the relatively small gradient opens. The gradient begins to open at least one intake valve of the cylinder in the range of 90° KW to 60° KW before top dead center (OT) of that valve, from the relatively small gradient to the relatively large gradient under maximum load. A method in which the largest change among the changes occurs in the area of the top dead center (OT) of the relevant cylinder. 7. Method according to claim 6, wherein during a change from full load to partial load of the internal combustion engine, the intake cam is adjusted by the intake camshaft by an angle β towards the retardation side. 8. The method of claim 7, wherein under partial load, the relatively small gradient is in the range of (90°-β) KW to (60°-β) KW before top dead center (OT) of the valve in question. The method is to start opening the intake valve. 9. The method of claim 7 or 8, wherein under partial load, the relatively small gradient is in the range of (60°+β) KW to (30°+β) KW before complete closure of at least one intake valve. A method wherein at least one exhaust valve is completely closed. The method of claim 7 or 8, wherein β corresponds to 30° KW to 50° KW.

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