WO2018059624A1

WO2018059624A1 - Electrohydraulic valve train of an internal combustion engine

Info

Publication number: WO2018059624A1
Application number: PCT/DE2017/100820
Authority: WO
Inventors: Lothar Von Schimonsky; Oliver Hahn; Andreas Mayer
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2016-09-27
Filing date: 2017-09-26
Publication date: 2018-04-05
Also published as: DE102016218562B4; DE102016218562A1

Abstract

The invention proposes an electrohydraulic valve train for the variable opening actuation of two gas exchange valves (1, 2) of a cylinder in an internal combustion engine, comprising: - a master piston (5) and a pressure chamber (9) delimited by the master piston, - a first slave piston (6) and a second slave piston (7, 7') which delimit the pressure chamber and each actuate one of the gas exchange valves, - a pressure relief chamber (11) connected to the pressure chamber, - and a first hydraulic valve (10) which blocks the connection between the pressure relief chamber and the pressure chamber when in the closed state, wherein the second gas exchange valve (2) actuated by the second slave piston can be deactivated when the first gas exchange valve (1) opens. At least the first slave piston has a stepped diameter and, at the diameter step (17), delimits the pressure chamber and, at the end face (18) of smaller diameter, is hydraulically connected to the pressure chamber. A second hydraulic valve (19) blocks the connection between the end face of smaller diameter and the pressure chamber when in the closed state, wherein the opening actuation of the second gas exchange valve: - is deactivated when the second hydraulic valve is in the open state, and - is activated when the second hydraulic valve is in the closed state.

Description

Electrohydraulic valve train of an internal combustion engine

The invention relates to an electro-hydraulic valve drive for variable opening operation of two gas exchange valves of a cylinder of a combustion engine, comprising:

a master piston driven by the cam of a camshaft,

a pressure chamber bounded by the master piston,

a first slave piston and a second slave piston which delimit the pressure chamber at end faces and in each case actuate one of the gas exchange valves against the force of a valve spring acting in the closing direction of the gas exchange valve,

a pressure relief space hydraulically connected to the pressure chamber,

- And a first hydraulic valve, which interrupts the connection between the pressure relief chamber and the pressure chamber in the closed state.

The second gas exchange valve operated by the second slave piston can be deactivated when the first gas exchange valve is opened.

EP 2 597 276 A1 shows an electro-hydraulic valve drive for fully variable actuation of the gas exchange valves of an internal combustion engine. It is a four-valve engine with two intake and two exhaust valves, the valve train comprises a 3/3-way electrohydraulic switching valve interconnecting the pressure chamber, the pressure relief chamber and the slave pistons of the two intake valves so that in one of the switching valve positions the inlet valves is switched off and consequently only one inlet valve is actuated.

A likewise generic electrohydraulic valve train is disclosed in DE 10 2015 207 622 A1 and DE 10 2016 213 976, both of which are not prepublished. The present invention has for its object to provide an electro-hydraulic valve train of the type mentioned in an alternative structural design. This object is achieved in that at least the first slave piston is stepped in diameter and bounded at the diameter stage, the pressure chamber and is hydraulically connected at the end face of smaller diameter with the pressure chamber, wherein the valve drive a second hydraulic valve summarizes, in the closed state, the Interrupt connection between the face of smaller diameter and the pressure chamber, and wherein the opening operation of the second gas exchange valve:

- Is deactivated when the second hydraulic valve is in the open state, and

- Is activated when the second hydraulic valve is in the closed state.

The switching between the partial and complete pressurization of the first slave piston causes an unchanged change in the pressure, with which only one or both end faces of the first slave piston are acted upon, with the actuating force unchanged. Thus, with simplified, i. hydrostatic consideration of the basic pressure-area ratio:

F = p ^* A = pi (AR + Ακ) = P2 * AR

■ => pi / p ₂ = AR / (AR + AK) with:

F actuating force

pi pressure chamber pressure with deactivated second gas exchange valve (one-valve actuation)

P2 pressure chamber pressure with activated second gas exchange valve (two-valve actuation)

AR face of the diameter step

AK face of smaller diameter

For example, when switching from two to one valve actuation, the pressure halves when AK = AR. The pressure acting on the second slave piston pi is then too low to overcome the Vorspankraft the valve spring. As a result, the second gas exchange valve remains deactivated.

Further features of the invention will become apparent from the following description and the figures, in which two embodiments of the invention are shown. Unless otherwise stated, the same or functionally identical features or components are provided with the same reference numerals. In each case in a highly simplified or schematic representation:

Figure 1 a, the first embodiment with identical slave piston at

Two valve actuation;

Figure 1 b, the first embodiment at Einventilbetätigung;

Figure 2 is the pressure-valve lift map of the first embodiment;

Figure 3 shows the second embodiment with different slave piston.

FIGS. 1 a and 1 b show the essential components of an electrohydraulic valve train of an internal combustion engine and the hydraulic connection of the components. It is a multi-valve engine with two identical gas exchange valves 1 and 2 per cylinder and present with two variably actuated intake valves 1 and 2. The variable opening operation also includes the complete and sole deactivation of the second intake valve 2. The valve train comprises one of the cam 3 of a camshaft by means of a Rollenschlepphebels 4 driven master piston 5 and two slave pistons 6 and 7, the actuate the inlet valves 1, 2 against the force acting in the closing direction of the valve springs 8. The master piston 5 and the slave piston 6, 7 define a pressure chamber 9, which is hydraulically connected via a first hydraulic valve 10 with a pressure relief chamber 1 1. The first hydraulic valve 10 is an electrically operated 2/2-way valve in normally open configuration, which accordingly interrupts the connection between the pressure chamber 9 and the pressure relief chamber 1 1 in the illustrated energized state. The printing Lastungsraum 1 1 is connected on the one hand via a check valve 12 to the pressure medium supply of the internal combustion engine and the other to a medium-pressure accumulator 13 with a spring-loaded accumulator piston 14. The first slave piston 6 actuating the first inlet valve 1 and the second slave piston 7 actuating the second inlet valve 2 have the same design with a stepped diameter and are each guided in a slave cylinder 15 and 16 which is correspondingly stepped thereto. Both slave piston 6, 7 limit the pressure chamber 9 at the diameter step 17. The first slave piston 6 is hydraulically connected to the end face 18 of smaller diameter with the pressure chamber 9. In the connection, a second hydraulic valve 19 is arranged, which interrupts this connection according to Figure 1 a and produces according to Figure 1 b.

An overflow line 20 hydraulically connects the two slave pistons 6, 7 to their front surfaces 18 of smaller diameter and is arranged between the slave cylinders 15, 16 such that the mouths of the overflow line 20 reach the slave pistons 6, 7 from their mouths until a predetermined opening stroke Outer jacket are closed. The second hydraulic valve 19 is connected to the three terminals slave cylinder 15 of the first slave piston 6, pressure chamber 9 and overflow 20, a 3/2-way valve, the closed state of Figure 1 a, the connection between the first slave piston 6 and the pressure chamber 9 and a connection 21 between the overflow 20 and the pressure chamber 9 interrupts. The connection 21 is connected to the overflow line 20 between throttle bodies 22, which serve as hydraulic valve brakes in the final closing phase of the inlet valves 1, 2 and the slave piston 6, 7. At the bottom of the slave cylinder 15, 16 each have a pressure relief valve 23 is arranged, which is connected on the one hand to the pressure relief chamber 1 1 and on the other hand to a slave cylinder 15 to closing check valve 24 to the pressure chamber 9. The pressure relief valves 23 are opened in the final closing phase of the inlet valves 1, 2 by the end faces 18 of smaller diameter of the slave pistons 6, 7 in order to allow complete closing of the inlet valves 1, 2 in the then already closed orifices of the overflow line 20. The overflow line 20 is further hydraulically connected to a recuperating high pressure accumulator 25 and to compensate for loss of hydraulic fluid in the slave cylinders 15, 16 with the pressure relief chamber 1 1. In the connection between the overflow line 20 and the pressure relief chamber 1 1 is a check valve 26 which opens to the high-pressure accumulator 25 and prevents the relatively high pressure in the high-pressure accumulator 25 in the pressure relief chamber 1 1 relaxed. The high-pressure accumulator 25, like the medium-pressure accumulator 13, has a spring-loaded accumulator piston 27.

For operation of the valve gear according to the invention:

Depending on its energizing state, the first hydraulic valve 10 ensures that the connection between the pressure chamber 9 and the pressure relief chamber 11 is either established or interrupted. Consequently, a hydraulic fluid flow from the pressure chamber 9 in the pressure relief chamber 1 1 is enabled or prevented, wherein a partial volume of the displaced by the driven master piston 5 hydraulic fluid is continuously displaced adjustable in the pressure relief chamber 1 1 depending on the valve opening time and duration. The variability of the intake valve actuation based on the correspondingly variable hydraulic fluid volume of the pressure chamber 9 extends on the one hand within the limits of maximum opening stroke of the intake valves 1 and 2 when the first hydraulic valve 10 is in the closed position during the entire stroke phase of the master piston 5 and the hydraulic displaced by the master piston 5 - Tel the slave piston 6, 7 applied according to the survey of the cam 3, and on the other hand complete deactivation of both intake valves 1 and 2, when the first hydraulic valve 10 is at least to the maximum elevation of the master piston 5 in the open position and the displaced by the master piston 5 hydraulic fluid completely in the pressure relief chamber 1 1 is pushed out.

This basic mode of operation applies both to the two-valve actuation, in which the two inlet valves 1, 2 are opened synchronously, and also to the one-valve actuation, in which the second inlet valve 2 is completely deactivated. In the case of the two-valve actuation, the second hydraulic valve 19 according to FIG. 1 a is in the closed state. Accordingly, the pressurization of the two slave pistons 6, 7 relevant for the synchronous opening actuation of the intake valves 1, 2 takes place mainly at the respective end face 28 of the diameter stage 17. The high-pressure accumulator 25, for the purpose of recuperation during each closing operation of the intake valves 1, 2 is biased by the displaced from the slave cylinders 15, 16 in the overflow 20 hydraulic fluid, supports the opening operation by the two end faces 18 of smaller diameter pressurized.

In the Einventilbetätigung is the second hydraulic valve 19 according to Figure 1 b in the open state. In this case, the first slave piston 6 is acted upon both on the end face 28 of the diameter step 17 and on the end face 18 of smaller diameter with the pressure in the pressure chamber 9. The enlargement of the pressurized end faces causes in the same area ratio, a reduction of the required pressure, which is transmitted to the first slave piston 6 upon actuation of the master piston 5. In the same ratio also reduces the radial load on the cam 3 and the camshaft bearings in favor of the friction in the bearings. The connection between the overflow line 20 and the pressure chamber 9 is also made via the second hydraulic valve 19, so that when closing the inlet valve 1, the displaced from the slave cylinder 15 in the overflow 20 hydraulic fluid only in the pressure chamber 9 and in the pressure relief space 1 first relaxed. Consequently, the high-pressure accumulator 25 remains inactive during Einventilbetätigung.

2 illustrates the principle underlying the invention of the different pressures in the pressure chamber 9 designated therein as HPC, with which the slave piston or pistons 6, 7 in the single-valve or two-valve actuation depending on the opening stroke of the intake valves 1 , 2 be charged. The map is greatly simplified in that it is based on quasi-static consideration and thus does not take into account the dynamics of the valve train. The numerical values given refer to that in the figures 1 illustrated embodiment with the same size end faces AR and Ακ

As already explained at the outset, for the ratio of the pressure chamber pressures in single-valve and two-valve actuation: pi / P2 = AR / (AR + Ακ) = at AR = Ακ with:

pi pressure in the pressure chamber 9 with deactivated second inlet valve 2 (one-valve actuation)

P2 pressure in the pressure chamber 9 with activated second inlet valve 2 (two-valve actuation)

AR end face 28 of the diameter step 17

AKI face 18 smaller diameter of the first slave piston 6

AK2 end face 29 of the second slave piston. 7

The valve spring 8 is biased at 260 N with the intake valves 1, 2 closed, and its maximum force is 360 N at the maximum lift of the intake valve 1, 2 of 10 mm. This corresponds to a pressure chamber pressure between 45 bar and 62 bar in the two-valve operation and between 22.5 bar and 31 bar in the Einventilbetätigung.

On the one hand, the working pressure range of the high-pressure accumulator 25 is above the maximum pressure chamber pressure in the one-valve actuation so that the pressure chamber pressure present in the slave cylinder 15 can not relax into the high-pressure accumulator 25 with a corresponding stroke loss of the first inlet valve 1. The working pressure range, on the other hand, is below the minimum pressure chamber pressure in the two-valve actuation so as not to hydraulically block the complete closing of the inlet valves 1, 2 due to excessive pressure in the slave cylinders 15, 16 then separated from the pressure chamber 9.

In an alternative embodiment, not shown, the (optional) connection 21 between the overflow line 20 and the pressure chamber 9 can be omitted, in which case the second hydraulic valve 19 is designed as a 2/2 way valve.

The illustrated in Figure 3 second embodiment of an electro-hydraulic valve train differs from the previously described valve train for a fact that a recuperating high-pressure accumulator is missing. On the other hand, the two slave pistons 6 and 7 ^'are different in that only the first slave piston 6 is provided with the diameter step 17. The second slave piston 7 ^' is guided with a uniform diameter in a correspondingly ungestuften slave cylinder 16 ^' . The following relationship applies to the faces of the slave pistons:

AR = AKI = AK2 with:

AR end face 28 of the diameter step 17

AKI face 18 smaller diameter of the first slave piston 6

AK2 end face 29 of the second slave piston. 7

This also results in this second embodiment halving the - considered quasi-static pressure chamber pressure at the transition from the two-valve to the Einventilbetätigung.

The first slave piston 6 is hydraulically connected to the end face 28 of the diameter stage 17 via a branching line 30 to the pressure chamber 9. The second slave piston 7 ^' is hydraulically connected to the end surface 29 via the line 30 to the pressure chamber 9. The two line branches each contain a conventional hydraulic valve brake, which is symbolized by a non-return valve 31 and the throttling points 22 opening towards the slave cylinder 15 and 16 and which decelerates the closing inlet valve 1, 2 to an acoustically and mechanically acceptable valve seating speed. The first slave piston 6 is hydraulically connected to its end face 18 of smaller diameter with the pressure chamber 9. The connection comprises two lines 32 and 33, of which one line 32, the 2/2 way valve and the other line 33 includes a to the line 30 and thus to the pressure chamber 9 out opening check valve 34.

As an option, the first slave piston 6 is hydraulically connected to its end face 18 of smaller diameter via a pressure equalization line 35 with the pressure relief space 1 1. In the pressure equalization line 35, a check valve 36 is arranged, which opens to the first slave piston 6 out. Thus, in the two-valve operation, the formation of negative pressure or vacuum in the second slave cylinder 16 is prevented on the part of the end face 18 of smaller diameter, which is then not communicating with the pressure chamber 9.

In alternative embodiments, not shown, the components of the two previously described embodiments can be combined or interchangeable with respective hydraulic interconnection. For example, the recuperating high-pressure accumulator can be dispensed with in the first exemplary embodiment or supplemented in the second exemplary embodiment.

LIST OF REFERENCE NUMBERS

1 gas exchange valve / first inlet valve

2 gas exchange valve / second inlet valve

3 cams

4 roller rocker arms

5 master piston

6 first slave piston

7 second slave piston

8 valve spring

9 pressure chamber

10 first hydraulic valve

1 1 pressure relief room

12 check valve

13 medium pressure accumulator

14 accumulator pistons 15 slave cylinders

16 slave cylinders

17 diameter step

18 face of smaller diameter

19 second hydraulic valve

20 overflow line

21 connection

22 throttle point

23 pressure relief valve

24 check valve

25 high-pressure accumulator

26 check valve

27 accumulator piston

28 face of the diameter step

29 end face of the second slave piston

30 line

31 check valve

32 line

33 line

34 check valve

35 Pressure compensation line

36 check valve

Claims

claims

Electrohydraulic valve train for variable opening operation of two gas exchange valves (1, 2) of a cylinder of an internal combustion engine, comprising:

a master piston (5) driven by the cam (3) of a camshaft,

a pressure chamber (9) delimited by the master piston (5),

- A first slave piston (6) and a second slave piston (7, 7 ^' ) at the end faces (18, 28, 29) delimiting the pressure chamber (9) and each one of the gas exchange valves (1, 2) against the force of a closing direction of the gas exchange valve (1,

2) actuate the valve spring (8),

- One with the pressure chamber (9) hydraulically connected pressure relief chamber (1 1),

- And a first hydraulic valve (10) which interrupts the connection between the pressure relief chamber (1 1) and the pressure chamber (9) in the closed state,

the second gas exchange valve (2) actuated by the second slave piston (7, 7 ^' ) can be deactivated when the first gas exchange valve (1) is opened, characterized in that at least the first slave piston (6) is stepped in diameter and at its diameter step (17) Pressure chamber (9) limited and at its end face (18) of smaller diameter to the pressure chamber (9) is hydraulically connected, wherein the valve drive comprises a second hydraulic valve (19) in the closed state, the connection between the end face (18) of smaller diameter and the pressure chamber (9) interrupts, and wherein the opening operation of the second gas exchange valve (2):

- Is deactivated when the second hydraulic valve (19) is in the open state, and

- Is activated when the second hydraulic valve (19) is in the closed state.

Valve gear according to claim 1, characterized in that the pressure cavities (9) limiting end face (29) of the second slave piston (7, 7 ^' ), the end face (18) of smaller diameter and the end face (28) of the diameter step (17) are equal.

3. Valve drive according to claim 1 or 2, characterized in that the slave piston (6, 7) are identical parts.

4. Valve drive according to claim 3, characterized in that the slave piston (6, 7) in slave cylinders (15, 16) are guided and at their end faces (18) of smaller diameter via an overflow line (20) with each other and with a high-pressure accumulator (25). are hydraulically connected, wherein the mouths of the overflow line (20) in the slave cylinders (15, 16) are arranged such that the orifices are closed until reaching a predetermined opening stroke of the slave piston (6, 7) of these.

5. Valve drive according to claim 4, characterized in that the second hydraulic valve (19) is a 3/2 way valve which connects the overflow line (20) hydraulically with the pressure chamber (9) in the open state.

6. Valve drive according to claim 4 or 5, characterized in that the overflow line (20) with the pressure relief space (1 1) is hydraulically connected and that in the connection between the overflow and the pressure relief chamber (10) a check valve (26) is arranged, which opens to the high-pressure accumulator (25).

7. Valve gear according to claim 1 or 2, characterized in that only the first slave piston (6) is stepped in diameter.

8. Valve drive according to claim 7, characterized in that the first Nehmmer piston (6) at its end face (18) of smaller diameter over a

Pressure equalization line (35) to the pressure relief chamber (1 1) is hydraulically connected and that in the pressure equalization line (35) a check valve (36) is arranged, which opens to the first slave piston (6) out.