WO2004085805A1

WO2004085805A1 - Device for the actuation of charge exchange valves in reciprocating piston engines

Info

Publication number: WO2004085805A1
Application number: PCT/EP2004/002742
Authority: WO
Inventors: Helmut Schön
Original assignee: Thyssenkrupp Automotive Ag
Priority date: 2003-03-24
Filing date: 2004-03-17
Publication date: 2004-10-07
Also published as: DE10312962A1

Abstract

The invention relates to a device for the actuation of charge exchange valves in reciprocating piston engines, comprising a housing, a cam which is rotatably mounted in a rotating joint located inside the housing and the rotary movement of which is derived from a crankshaft, an intermediate member that is actuated by said cam via a first cam joint, and an output member which transfers said movement to the valve and is effectively connected in a direct manner or via additional transfer members to the intermediate member. Another cam joint is provided within the effective connection between the first cam joint and the output member and is used to specifically displace one of the transfer members, thereby at least temporarily keeping open the gas exchange valve and decompressing the reciprocating piston engine.

Description

Device for actuating charge exchange valves in

reciprocating engines

description

The invention relates to a device for actuating one or more charge exchange valves according to the preamble of claim 1.

Devices of this type are used to design the control of charge exchange valves in such a way that it is possible to operate reciprocating piston engines without the throttle valve which is otherwise customary.

DE-A 101 00 1 73 describes a fully variable mechanical valve train for a piston internal combustion engine, with a drive means for generating a lifting movement acting against the force of the closing spring on the charge exchange valve and with an intermediate element arranged between the drive means, for example a cam, and the charge exchange valve , which acts on the charge exchange valve in the direction of its axis of movement and whose stroke path can be changed in the direction of the axis of movement via an adjustable guide element.

DE-A 100 06 01 8 describes a variable valve train for load control of a spark ignition internal combustion engine. The valve train is formed from a cam, a camshaft and at least one inlet valve, with a direct valve actuating member, the output member, a transmission member and an adjusting means for influencing the lifting function of the transmission member. The transmission link is driving between the Cam and the output member installed and has a first, acted upon by the cam and a second surface acting on the output member.

In the prior art there are a large number of mechanically variable valve gears for the control or load control of reciprocating engines. The printing points cited above are therefore only to be regarded as examples. A common feature of the systems mentioned is that the rotational movement of the cam of a camshaft transmits a stroke movement to the charge exchange valve via the further transmission members of the valve transmission. The resulting elevation curve of these charge exchange valves can be changed during operation by relocating at least one of the transmission members located in the power flow. Both the valve lift and the valve opening angle are changed. So that the shift can be realized, at least one gear element is inserted between the driving cam and the output element that actuates the charge exchange valve in the valve gears mentioned. This creates at least one additional degree of freedom in the movement, so that the desired shift is possible.

The power and torque transmission between the links of the valve train takes place via cam, thrust and rotary joints. The moving gear links are supported directly or indirectly in the housing. The stroke movement of the charge exchange valve is adjusted, for example, by displacing joints or slide tracks in the housing, on which gear elements located in the power flow are supported.

Important criteria of such valve gearboxes are that when the valve stroke is changed, the opening angle, ie the duration of the valve rest, is also changed and that the contact between the cam and the intermediate element is constantly maintained. A known problem, also for non-variable valve gearboxes, is that when the engine is started, there is compression in the cylinders even though the cranking speed has not yet been reached. As a result, a considerable additional energy requirement is required to start the engine. Means are known in the prior art with the aid of which decompression in the cylinders is achieved by keeping the charge exchange valves open until the starting speed of the engine is reached. After the starting speed is reached, the charge exchange valves are opened and closed normally and the ignition is triggered so that the engine starts immediately.

EP 0 1 76 001 presents a method to solve the problem in which an additional auxiliary rocker arm holds the rocker arm during the starting phase in such a way that the charge exchange valve is not closed, the contact between the cam and the rocker arm being lost.

The invention has for its object to develop the device described in the generic part of the first claim in such a way that a decompression of the cylinders of the engine is possible when starting without using additional complex and expensive components.

This object is achieved with the features of claim 1. Advantageous training and further developments are described in claims 2 to 8. Claim 9 describes a method for operating a reciprocating piston engine using a device according to one of Claims 1 to 8.

The advantage of the design of the variable valve train according to the invention is the reduction in the additional effort for the control and the reduction in the number of parts. In addition, the existing variability of the valve train can advantageously be used to achieve decompression. The basic mode of operation of variable valve train systems, in which the valve lift characteristic is adjusted by displacing one or more gear members in the power flow, can be characterized in the following way. The rotating cam actuates a first intermediate link. The intermediate link actuates the output link or one or more further intermediate links. The charge exchange valve is operatively connected directly to the output member. The movement is transmitted via at least two curved joints. At least one of the intermediate links can be displaced, so that an adjustment of the valve lift curve is made possible. During the cam circulation, the valve lift passes through a control area in which the charge exchange valve is opened with a correspondingly predetermined charge curve, and a rest area in which the charge change valve is closed. This means that in the flow of force between the cam joint, which is arranged between the cam and the intermediate member in contact with the cam, and the cam joint, which is arranged between the charge control valve and the output member, a further cam joint is arranged, which forms the locking area and one has the control section forming curve section. The areas are represented by corresponding areas in the contact surface of the cam joints of the gear links or the housing curves in which the gear links are supported. Combinations are also possible in which the locking area is represented by a surface area in the curved joint of the intermediate member and the control area by a surface area in the housing curve or vice versa. As a rule, at least one spring is arranged in the valve gear, which ensures the constant contact of all cam joints between the intermediate links and the intermediate link and the cam.

For the design of such valve gears, for example, the maximum valve lift curve is specified and, among other things, the geometries the rest and control area of the surfaces of the curve joint, which has the rest area and the control area forming curve section, and the

Adjustment curve for the displaceable gear element and its length, hereinafter referred to as the adjustment range, are determined. The adjustment range is determined as the range between the position for the largest predetermined valve lift and the position at which no or the minimum valve lift is generated.

The task according to the invention is essentially achieved in that the adjustment range of the displaceable transmission element is expanded to such an extent that a displacement is made possible in which the decisive cam joint is only or at least for predefined angular ranges of the rotating cam, in which during normal operation of the reciprocating piston engine that Charge control valve is closed, located in a region of the contact surface of the cam joint, in which the valve is open.

According to the invention, a further curve area, the decompression area, is formed on the intermediate member in addition to the control and locking area of the curve joint. The decompression area is arranged as a continuation at the end of the rest area, which is not adjoined by the control area, as an additional ramp. The displaceable intermediate member is then displaced beyond the point of the minimum valve lift in the adjustment range until the corresponding cam joint is in contact, at least temporarily in the decompression range. In this case, an elastic element, in the simplest case a spring, must ensure contact between the intermediate members involved so that the valve in the area is actually opened.

The ramp for forming the decompression area can be formed by any continuously differentiable curve. Circular tracks or straight sections are preferred because of the simple manufacture. It is completely clear that it is also possible to design the decompression area or the additional area on a surface in the housing on which a displaceable intermediate element of the valve gear is supported in a cam joint.

In the prior art, the area of the cam in which a valve lift is never generated is formed by a circular arc concentric with its center of rotation. In a further development of the invention, this area is advantageously designed in such a way that, in cooperation with the intermediate element actuated by the cam, the intermediate element constantly moves. A further advantageous design of this contour ensures that the intermediate member is continuously accelerated away from the cam in this area. The size of this acceleration is advantageously to be selected such that, on the one hand, taking into account manufacturing tolerances, the acceleration is actually always directed away from the cam and, on the other hand, the distance between the cam contour and its center of rotation always remains as large as possible, so that the camshaft is not unnecessarily weakened.

The control times and the course of the valve lift for decompression can be advantageously influenced by the described design of the cam.

Using the example of a four-membered mechanical variable valve train system, the invention will be explained with reference to FIGS. 1 to 5.

In Figures 1 and 2, a four-link valve transmission is shown. Figure 1 shows a position of the valve gear for valve detent and Figure 2 shows a position for valve lift.

FIGS. 3 and 4 show the same valve gear for a variant of the adjustment for decompression. FIG. 5 is an enlargement of the representation in FIG. 1. The adjustment range VB and the position of point 91 are shown here by way of example.

The cam 1 is rotatably supported in the housing G. As a link 2, a rocker arm is rotatably mounted in the pivot point 9. The rocker arm is operatively connected to the output member 6, a rocker arm, by a cam joint. The rocker arm transmits its movement directly to the charge exchange valve 5. As shown in FIGS. 1 and 2, the charge exchange valve 5 passes through a valve lift, shown in FIG. 2, and a valve catch, shown in FIG. 1, during the rotation of the rotating cam 1. The size of the valve lift is illustrated by the arrow marked 4. If the fulcrum 9 is shifted along the curve V, in the example a circular path, the size of the valve lift 4 and the angular ranges of the rotating cam 1 change during which the charge exchange valve 5 is in the rest or in the valve lift. The farther the pivot point 9 of the rocker arm is displaced in the direction of the arrow within the adjustment range VB, the smaller the maximum value of the valve lift 4. The angular range of the rotating cam 1 during which the charge exchange valve 5 is in the catch increases accordingly. On the rocker arm, on the contact surface forming the cam joint between the rocker arm and the rocker arm, the contact surface section for the latching region 7 and the contact surface section for the region of the valve lift, the control region 10, are formed.

In FIGS. 3 and 4, the pivot point 9 of the rocker arm is shifted in the arrow direction of curve V over the adjustment range VB to a special point 91, so that the contact surface on the rocker arm, which forms the cam joint between rocker arm and rocker arm, in the example always through contact surface section 8 is formed. This contact surface section 8 is designed so that the charge exchange valve 5 is open during the entire rotation of the cam 1 or at least during the angular range during which the intake of the combustion gases is compressed. A spring, not shown here, ensures that the transmission links: cam 1, rocker arm and rocker arm are constantly in contact. In the event of adjustment to the special point 91 of the valve spring, this spring counteracts so that the valve 5 can be opened at least temporarily.

The particular advantage of this arrangement is that the transition from the decompression, which is to take place during the starting of the engine, to the engine start, in which generally small valve lift curves are to be realized, is achieved by a very small displacement of the pivot point 9.

Analogously, a contour on which a rocker arm is supported can be formed and / or the corresponding housing contour can be shifted accordingly.

In the examples, curve V is shown as a circular path. However, the invention can also be applied to adjustment areas VB which are not on a circular path but, for example, on a straight line. Point 91 also does not necessarily have to lie on curve V.

LIST OF REFERENCE NUMBERS

1 cam

2 pontic

4 valve lift

5 charge exchange valve

6 output link

7 locking area of the contact surface

8 Decompression area of the contact surface

9 pivot point rocker arm

1 0 Control area of the contact area

91 point

G housing

V curve

VB adjustment range

Claims

claims

1.Device for actuating one or more charge exchange valves (5) in reciprocating piston engines with a housing in which a rotatably mounted camshaft with cams (1) is arranged, one of these cams (1) actuatable via a first cam joint (2) and one output member (6) moved directly or via further transmission members, at least one further cam joint being provided between the intermediate member (2) and the output member (6), which is formed by two contact surfaces, one of the contact surfaces having a control region (10) and has a latching area (7) which directly adjoins the control area (10) at one end, whereby a displacement of the intermediate link (2) or one of the further transmission links along a fixed curve (V) within an adjustment range (VB) Change in the opening time and / or the opening stroke of the gas exchange valve is reached and where di e movement of the output member (6) is transmitted to the charge exchange valve (5), characterized in that an additional area (8) is arranged at the other end of the latching area (7), which is shaped such that it is displaced by the displacement of the intermediate member (2 ) or one of the other transmission elements to a point (91) that lies outside the adjustment range (VB), causes a new valve opening.

2. Device according to claim 1, characterized in that an elastic element, in the simplest case a spring, is provided which keeps the transmission members in constant contact and the displacement in the direction of the minimum opening time and / or the minimum valve lift over the adjustment range (VB ) to a predetermined point (91).

3. Device according to claim 1 or 2, characterized in that the intermediate member (2), the displacement of which leads to a change in the valve opening duration and / or the valve lift, directly with the output member (6), for example a rocker arm, a rocker arm or a bucket tappet, is in contact.

4. Apparatus according to claim 1 or 2, characterized in that the further curve joint is in constant contact with a displaceable curve arranged in the housing, which is formed by a curve, the shape of which has an additional contact surface area (8) which during Keeping the charge exchange valve (5) open at least temporarily.

5. Device according to one of claims 1 to 4, characterized in that the charge exchange valve (5) remains open during the entire rotation of the cam (1).

6. Device according to one of claims 1 to 5, characterized in that the contour of the cam (1) in the contour section, in the positioning of the gear members within the adjustment range (VB), in which exactly no valve lift (4) is always generated , is in contact with the intermediate member (2) actuated directly by the cam (1), is designed in such a way that the intermediate member (2) actuated by the cam (1) is constantly in motion during this contact and / or is continuously accelerated away from the cam ,

7. Device according to one of claims 1 to 6, characterized in that several valves of the same reciprocating piston engine are controlled simultaneously. Method for operating a reciprocating piston engine using a device according to one of claims 1 to 7, characterized in that the compression of the gases in the cylinder during the starting process of the reciprocating piston engine is at least partially prevented by keeping the charge exchange valve open at least temporarily and is permitted again after the starting speed has been reached ,