WO2016203043A1

WO2016203043A1 - Length-adjustable connecting rod

Info

Publication number: WO2016203043A1
Application number: PCT/EP2016/064179
Authority: WO
Inventors: Helmut Melde-Tuczai; Wolfgang Reik; Rolf Dreisbach
Original assignee: Avl List Gmbh
Priority date: 2015-06-18
Filing date: 2016-06-20
Publication date: 2016-12-22
Also published as: AT517109A4; AT517109B1

Abstract

The invention relates to a length-adjustable connecting rod (1) for a reciprocating piston engine, comprising at least one first rod part (4) and a second rod part (5), the two rod parts (4, 5) being telescopically displaceable to and/or into one another by an actuating medium, wherein the displacement of the rod parts (4, 5) can be controlled by a hydraulic control device (16) which is connected to at least one high-pressure chamber (9, 10) between the two rod parts (4, 5) via at least one oil duct (11, 12), which comprises at least one mounted part that can be displaced in the direction of a displacement axis (16a). The displacement axis (16a) is arranged in an oscillating plane (ε) of the connecting rod (1), preferably normal in relation to the longitudinal axis (1a) of the connecting rod (1). In order to expand the field of application, it is provided that at least one reciprocating part of the control device (16) comprises at least one buoyancy body (60, 61) or is at least partially designed as a buoyancy body (60, 61).

Description

Length adjustable connecting rod

The invention relates to a length-adjustable connecting rod for a reciprocating engine, with at least a first rod part and a second rod part, which two rod parts by an actuating medium telescopically zoom in and / or into each other, wherein the displacement of the rod parts by a hydraulic control device is controllable, which at least a displaceably mounted in the direction of a displacement axis part, wherein the displacement axis in a rocking plane of the connecting rod - preferably normal to the longitudinal axis of the connecting rod - is arranged.

The AT 51 1,803 B1 describes a length-displaceable connecting rod for an internal combustion engine with two telescopically movable rod parts, between the first and second rod part a high-pressure chamber is spanned, in which an oil passage opens, the flow is controlled by a control valve designed as a control device , Furthermore, from AT 514 071 B1 a telescopically adjustable connecting rod is known, wherein a rod part form a guide cylinder and another rod part of the connecting rod a longitudinally displaceable in the guide cylinder piston member, wherein between the piston member and the guide cylinder on one side of the piston, a first high-pressure chamber and on the On the other side of the piston, a second high-pressure chamber are clamped, open into which oil passages whose flow is controlled by means of a displaceable against the force of a return spring spool. Both in the AT 51 1.803 B and in the AT 514.071 B, the spool is located near the crankpin bearing in the rod end portion of the connecting rod forming the large connecting rod eye.

During rotation of the crankshaft, acceleration forces act on the spool against the force of the return spring. From a certain speed acting on the spool mass inertia forces are so large that the spool is moved solely by the acceleration forces against the restoring force, resulting in a lifting of the return spring and the control piston. This leads to a malfunction of the control device. Therefore, these known control devices can only be used up to a defined maximum speed.

The object of the invention is to expand the field of application and to provide a length-adjustable connecting rod, which is also suitable for higher speeds. According to the invention, this is achieved in that at least one displaceably mounted part, in particular reciprocating part, of the control device has at least one buoyant body or is at least partially designed as a buoyant body.

The float floating in the oil has a lower density than the actuating oil, such as engine oil. It can be designed as a hollow body or as a closed-cell foam body, for example made of polystyrene.

By firmly connected to the reciprocating part or formed integrally with this buoyancy body, the accelerated mass is reduced, the Archimedian principle that the static buoyancy of a body in a medium is the same as the weight of the body displaced medium to Application comes.

Preferably, at least one reciprocating part of the control device is formed by a control piston or spool displaceably mounted in a cylinder, whose first end face adjoin a control chamber which can be acted upon with oil and whose second end side adjoin a spring space having a return spring. In a preferred embodiment of the invention, it is provided that at least one buoyant body is arranged in the region of the first end face and / or in the region of the second end face of the control piston.

A substantial reduction in the accelerated mass can be achieved, in particular, when a buoyant body is arranged both in the region of the first end face and in the region of the second end face adjoining the spring chamber. For this purpose, it is necessary that the spring chamber is flooded with the oil. This can be achieved with very little effort if the control piston between the control chamber and the spring chamber has a defined leakage, wherein preferably the spring chamber is fluidly connected to a storage space, which may be arranged for example in the same rod part of the connecting rod as the control device.

If the storage space is connected to the crankcase via a throttle, an unobstructed oil return into the crankcase space can be achieved.

Thus, the spring chamber of the control piston or spool is thus always filled with the oil, as always enough oil from the storage space and / or can be sucked through the leaks by the reciprocating movements of the control piston or spool. The throttle allows damping of the movement of the control piston or the Spool, whereby this is less sensitive to any returning pressure waves.

In a particularly preferred embodiment of the invention it is provided that the control device comprises a first valve and a second valve, each having a valve body arranged in a valve body, which is pressed by a restoring force against a valve seat, and at least one reciprocating part by a the valve body is formed with one another connecting and displaceable between a first position and a second position connecting rod, wherein preferably the connecting rod has at least one buoyancy body or at least partially formed as a buoyant body. In this case, the connecting rod may for example be hollow and thus form a buoyant body itself. Alternatively or additionally, it can be provided that at least one valve body has at least one buoyancy body or is at least partially designed as a buoyancy body.

All of the measures mentioned contribute to the fact that the density of the entire system and the masses to which lateral accelerations as a result of the crankshaft revolution are substantially reduced. In this way, engine speeds can be realized well above 7000 U / min, without the function of the length adjustability of the connecting rod is limited.

The invention will be explained in more detail below with reference to the non-limiting figures. Show it

1 shows a connecting rod according to the invention in a longitudinal section in a first embodiment,

2 shows the control device of this connecting rod in a schematic representation,

3 shows the control device of the connecting rod of FIG. 1 in a detailed representation,

4 shows a control device of a connecting rod according to the invention in a second embodiment variant.

Functionally identical parts are provided in the embodiments with the same reference numerals. Fig. 1 shows a two-part connecting rod 1 with a small connecting rod 2 for a not further shown piston pin bearing and a large connecting rod 3 for a not further shown crank pin bearing an internal combustion engine. The rotational symmetry axes of the small or large connecting rod 2, 3 are denoted by 2a and 3a, respectively. The longitudinal axis of the connecting rod 1 is 1 a, one on the rotational symmetry axes 2 a and 3 a of the small and large connecting rod 2, 3 normal standing and the longitudinal axis 1 a of the connecting rod 1-containing longitudinal center plane - the swing plane - the connecting rod 1 is denoted by ε.

The connecting rod 1 has an upper first rod portion 4 with the small connecting rod 2 and a lower second rod portion 5 with the large connecting rod 3. The first rod part 4 is adjustable relative to the second rod part 5 between an extended position and an inserted position shown in Fig. 1 by an adjustment range AL in the direction of the longitudinal axis 1 a of the connecting rod 1. In the upper first rod part 4, a substantially cylindrical piston element 6 is fastened, for example, with a fastening screw 7 formed by a hexagon socket screw.

The piston element 6 is guided in an axially displaceable manner in a guide cylinder 8 of the lower second rod part 5 of the connecting rod 1, wherein between at least one position of the two rod parts 4, 5, a first end face 6a of the piston element 6 and the second rod part 5 facing the large connecting rod eye 3 first high-pressure chamber 9 is clamped. The piston element 6 designed as a stepped piston has a second end face 6b facing the small connecting rod eye 2, which adjoins a second high-pressure chamber 10 whose cylindrical lateral surface is formed by the guide cylinder 8 of the second rod part 5. Under a stepped piston is generally understood a piston - in the present case a "double-acting piston" - with different sized effective surfaces, one of the active surfaces (here: oriented against the second high pressure chamber 10 effective area) as an annular surface and the other effective surface formed as a circular area is. Due to the different effective surfaces, the pressure conditions described here can be realized.

The annular first and second end faces 6a, 6b form pressure application surfaces for an actuating medium, for example engine oil, which is led into the high-pressure chambers 9, 10 and is under pressure.

In the first high-pressure chamber 9, a first oil passage 1 1 and in the second high-pressure chamber 10, a second oil passage 12 opens. The oil supply of the first and second oil passage 1 1, 12 via the oil supply channel 13, which starts from the connecting rod bearing 3b of the large connecting rod 3 and thus fluidly connected to the crank pin bearing, not shown, as well as to the oil supply channel 13 connected connection channels 14, 15th

For controlling the pressures in the first and second high-pressure chambers 9, 10, a control device 16 in the connecting rod 1, in the lower second rod member 5, is provided which in the flow path between the first connecting channel 14 and the first oil passage 1 1, a first valve 17th with a first valve chamber 18, in which a biased by a first valve spring 19 first valve body 20 is pressed against a first valve seat 21. In the first valve chamber 18, the first oil channel 1 1 opens. Furthermore, the control device 16 has a second valve 22 with a second valve chamber 23, in which a biased by a second valve spring 24 second valve body 25 is pressed against a second valve seat 26, wherein the second oil passage 12 opens into the second valve chamber 23. Furthermore, the control device 16 has a connecting device 27 between the first valve 17 and the second valve 22 with at least one connecting element 28, which is formed in the embodiments by a normal to the longitudinal axis 1 a, in particular in the swing plane ε of the connecting rod 1 connecting rod 29 , The connecting element 28 is fixedly connected to a control piston 31 displaceable in a control cylinder 30. The spring-loaded by a return spring 32 control piston 31 is adjacent to a control chamber 33 into which a connected to the oil supply channel 13 and the connecting channel 15 control line 34 opens. The valve body 20 or 25 and the connecting device 27 are separate components. As a result, the connecting device 27 is at a distance from the first valve body 20 in the displacement position shown in FIG.

The first and second valve bodies 20, 25 of the first and second valves 17, 23 are preferably formed by balls.

By the valve body 20, 25 of the first and second valves 17, 23, the flow connections between the first supply channel 14 and the first oil channel 1 1 and between the second supply channel 15 and the second oil channel 12 are opened or closed. The existing example of plastic control piston 31 is actuated by the oil pressure of the internal combustion engine. If the oil pressure - for example, at light load - under a defined set pressure (of, for example, 0.8 bar) is maintained, the control piston 31 stops in its position shown in Fig. 2, because the spring force of the return spring 32 is greater than the force In this case, the connecting rod 29, which is fixed to the control piston 31 - for example, by a press fit - holds the valve body 25 for the connection to the second high-pressure chamber 10 via the second oil passage 12 is opened, while the first valve body 20 of the first valve 17 remains closed for connection to the first high-pressure chamber 9 through the first valve spring 19.

During the lifting movement acts in the region of the top dead center of the piston, not shown, a mass force on the connecting rod 1, which the first rod member together with piston 6 - in Fig. 1, 2 considered - and thus pulls the small eye up. In this case, oil is sucked in via the actually closed first valve 17, in that the first valve body 20 is raised counter to the restoring force of the first valve spring 19 by the suction effect produced in the first high pressure chamber 9; the lower first high-pressure chamber 9 fills with oil via the first oil channel 11, while oil from the upper second high-pressure chamber 10 is pressed into the second oil channel 12. The connecting rod 1 is thereby longer. The oil flow in the oil channels 1 1, 12 is shown by arrows in Fig. 2.

When the oil pressure at a higher engine load increases to a higher level, the return spring 32 of the control piston 31 is compressed, wherein the control piston 31 moves to a left stop of the control cylinder 30.

In this position, the connecting rod 29 presses the first valve body 20 of the first valve 17, which connects the lower first high-pressure chamber 9 with the oil supply channel 13. This allows the oil from the first high-pressure chamber 9 to flow back into the oil supply channel 13 and thus further into the oil supply system. Since the connecting rod 29 is lifted from the second valve body 25 and thus the second valve body 25 is pressed by the restoring force of the second valve spring 24 to the second valve seat 26, the second valve 22 is closed; at each ignition, the piston 6 is depressed and sucked oil into the second high-pressure chamber 10 by the suction in the second high-pressure chamber 10 via the actually closed second valve 22 by the opposite of the force of the second valve spring 24 contrasting second valve body 25 to the second high-pressure chamber 10 with oil is filled. When the oil pressure in the oil system is lowered again, the return spring 32 of the control piston 21 expands (FIG. 2) and the control piston 31 moves to the right as viewed in FIG. 2, the second valve 22 for the second high-pressure chamber 10 being opened and the first Valve 17 for the first high-pressure chamber 9 is closed again. The first high pressure chamber 9 pumps again in the manner described by acting on the second rod member and the piston member 6 at the top dead center of the piston mass forces and the connecting rod 1 is longer again.

The control device 16 has a number of in the direction of the displacement axis 16 a of the control device 16 reciprocating parts, such as control piston 31, connecting rod 29 and valve body 20, 25. The displacement axis 16a of the control device is arranged in the rocker plane ε and approximately normal to the longitudinal axis 1 a of the connecting rod 1.

During the rotation of the crankshaft, acceleration forces act on reciprocating parts of the control device 16, in particular on the control piston 31 against the force of the return spring 32. From a certain speed on the control piston 31 acting mass inertia forces are so great that finally the force of the return spring 32 is exceeded and the control piston 31 would be moved by the acceleration forces against the restoring force alone, resulting in a malfunction of the controller 16 and thus the Speed range for the adjustment of the connecting rod 1 would restrict.

In order to avoid this, at least one reciprocating part of the control device 16 has at least one buoyancy body 60 or is at least partially designed as a buoyancy body. The buoyant body 60 may be formed as a hollow body or as a closed-cell foam body.

As shown in FIGS. 2 and 3, at least one buoyant body 60 may be arranged in the region of the first end face 31 a. Furthermore, a buoyancy body 61 can also be arranged in the region of the second end face 31b of the control piston 31. So that the buoyant body 61 floats in the oil, defined leaks are provided between the control chamber 33 and the spring chamber 32a.

Furthermore, the connecting rod 29 and / or the valve body 20, 25 may be designed as a buoyant body, for example as a hollow body. As is apparent from FIGS. 2 and 3, the spring chamber 32a is connected to a storage space 62, which is connected via a throttle 63 to the crank chamber of the crankcase, not shown. This allows an oil return in the crankcase space. Thus, the spring chamber 32a of the control piston 31 is always filled with oil, since by the reciprocating movements of the control piston 31 always enough oil from the storage space 32 and / or can be sucked through the leaks. The throttle 63 allows damping of the movement of the control piston 16, whereby an opening of the first valve 17 and thus of the first high-pressure chamber 9 can be avoided by a deflection of the control piston 16 and the displacement rod 29 to follow from the second high-pressure chamber 10 returning pressure waves.

Fig. 4 shows an embodiment in which the control device 16 instead of the two valves 17, 23 has a control spool formed as a control piston 31 which is slidably disposed in a control cylinder 30 along the displacement axis 16a. The control cylinder 30 is inserted into a stepped bore 65 of the second rod part 5 of the connecting rod 1 in the region of the large connecting rod 3 in the swing plane ε and normal to the longitudinal axis 1 a of the connecting rod 1 and sealed by sealing rings 66. The control piston 31 can be deflected against the force of the return spring 32 disposed in the spring chamber 32a of the control cylinder 30 by the oil pressure applied in the control chamber 33. The control chamber 33 is connected via a control line 34 to the oil supply channel 13. About the control piston 31 at least one leading to the first high-pressure chamber 9 hole 1 1 a of the first oil passage 1 1 is turned on. The control piston 31 is shown in Fig. 4 in two positions, wherein in the upper illustration of the control piston 31, the bore 1 1 a controlled and turned on in the lower illustration of the control piston 31.

The control piston 31 has in the control cylinder 30 a small clearance of, for example, 4 μηη, which can be dispensed with wear-intensive seals between moving parts.

As in the case of the first exemplary embodiment described with reference to FIGS. 2 and 3, the control piston 31 also has buoyancy bodies 60, 61, which are firmly connected to the control piston 31, in the second exemplary embodiment shown in FIG. In this case, a first buoyancy body 60 adjoining the control chamber 33 is arranged in the region of the first end face 31a and a second buoyancy body 61 adjoining the spring space 32a is arranged in the region of the second end face 31b of the control piston 31. The spring chamber 32a is fluidly connected to a storage space 62, which in turn via a throttle 63 with the not shown crank chamber of the reciprocating engine is connected. Due to the small clearance between control piston 31 and control cylinder 30 occur small - intended - leaks between the control chamber 33 and the spring chamber 32 a, whereby the buoyancy bodies 60, 61 are always largely surrounded by oil and swim. As a result, the well-known Archimedean principle that the static buoyancy of a body in a medium is just as great as the weight of the body displaced by the medium, is used. The lateral acceleration force, which would cause a lifting of the control piston 31 and the return spring 32 is thus substantially reduced, so that malfunction of the control device 16 can be avoided. All described embodiments allow by the use of the buoyancy bodies 60, 61, the density of the entire system and the masses on which lateral accelerations act as a result of the crankshaft revolution to reduce substantially. Thus, engine speeds can be realized well above 7000 U / min, without the function of the length-adjustable connecting rod 1 must be limited.

Claims

PATE CLAIMS

Length-adjustable connecting rod (1) for a reciprocating engine, with at least a first rod part (4) and a second rod part (5), which two rod parts (4, 5) by an actuating medium, in particular telescopically, and / or slidable into each other, wherein the displacement of the rod parts (4, 5) can be controlled by a hydraulic control device (16) which has at least one part displaceably mounted in the direction of a displacement axis (16a), wherein the displacement axis (16a) in a rocker plane (ε) of the connecting rod (1 ) - Preferably, normal to the longitudinal axis (1a) of the connecting rod (1) - is arranged, characterized in that at least the displaceably mounted part, in particular a reciprocating part of the control device (16) at least one buoyancy body (60, 61) or at least partially designed as a buoyancy body (60, 61).

Length-adjustable connecting rod (1) according to claim 1, wherein the hydraulic control device (16) with at least one high-pressure chamber (9, 10) between the two rod parts (4, 5) via at least one hydraulic channel, in particular oil passage (11, 12) is connected.

Connecting rod (1) according to claim 1 or 2, characterized in that the buoyant body (60, 61) has a lower density than the actuating medium, preferably engine oil.

Connecting rod (1) according to one of claims 1 to 3, characterized in that at least one buoyant body (60, 61) is designed as a hollow body.

Connecting rod (1) according to one of claims 1 to 4, characterized in that at least one buoyant body (60, 61) as a closed-cell foam body, preferably made of polystyrene, is formed.

Connecting rod (1) according to one of claims 1 to 5, characterized in that the buoyant body (60, 61) is fixedly connected to the reciprocating part or formed integrally therewith.

7. connecting rod (1) according to one of claims 1 to 6, wherein the displaceably mounted part, in particular a reciprocating part, the control device by a in a control cylinder (30) slidably mounted control piston (31) is formed, whose first end face (31a) to a controllable with the actuating medium control chamber (33) and the second end face (31b) to a return spring (32) having spring space (32a) boundaries, characterized in that at least one buoyancy body (60, 61) in the region of the first End face (31a) and / or in the region of the second end face (31b) of the control piston (31) is arranged, wherein the control piston (31) preferably between the control chamber (33) and the spring chamber (32a) has defined leaks.

8. connecting rod (1) according to claim 7, characterized in that the spring chamber (32 a) with a storage space (62) is fluidly connected, wherein the storage space (62) preferably in the same rod part (4) of the connecting rod (1) as the control device ( 16) is arranged.

9. connecting rod (1) according to claim 8, characterized in that the storage space (62) via a throttle (63) is connected to a crank chamber.

10. connecting rod (1) according to one of claims 1 to 9, characterized in that the control device (16) a first valve (17) and a second valve (22) each having a in a valve chamber (18; 23) arranged valve body ( 20; 25) which is pressed by a restoring force against a valve seat (21; 26), and at least one reciprocating member by a valve body (20; 25) operatively interconnecting and displaceable between a first position and a second position Connecting rod (29) is formed, wherein preferably the connecting rod (29) has at least one buoyant body or at least partially formed as a buoyant body.

Connecting rod (1) according to claim 10, characterized in that at least one valve body (20, 25) has at least one buoyant body or at least partially formed as a buoyant body.