WO2017029250A1

WO2017029250A1 - Longitudinally adjustable connecting rod

Info

Publication number: WO2017029250A1
Application number: PCT/EP2016/069312
Authority: WO
Inventors: Helmut Melde-Tuczai; Stefan LICHTENEGGER; Gerhard Heimel; Hubert Andreas Huemer
Original assignee: Avl List Gmbh
Priority date: 2015-08-14
Filing date: 2016-08-12
Publication date: 2017-02-23
Also published as: AT517624A1; DE112016003709A5; AT517492B1; AT517492A1; AT15561U1

Abstract

The invention relates to a longitudinally adjustable connecting rod (1) for a reciprocating piston engine, in particular for an internal combustion engine, comprising at least one first rod part (2) and a second rod part (4), which both rod parts (2, 4) can be moved in relation to each other in the direction of the longitudinal axis (1a) of the connecting rod (1) via a helical gearing (6). The helical gearing (6) has at least one first gearing part (7) and a second gearing part (8) engaging the first gearing part (7), the first gearing part (7) being designed as a spindle nut (9) or a lead screw (10) and the second gearing part (8) being designed as a lead screw (10) or a spindle nut (9). In order to allow the compression ratio to be changed in as simple a manner as possible, the helical gearing (6) is not of the self-locking type. A first gearing part (7), which is preferably rotatably mounted in the first rod part (2), is connected to at least one rotary locking mechanism (20) that can be switched by at least one switching element (30) and that prevents, in at least one first position, the first gearing part (7) from being rotated in at least one direction of rotation and that allows same in at least one second position.

Description

LENGTH-ADJUSTABLE CONNECTING ROD

The invention relates to a length-adjustable connecting rod for a reciprocating engine, in particular for an internal combustion engine, with at least a first rod part and a second rod part, which two rod parts via a helical gear in the direction of the longitudinal axis of the connecting rod are displaceable, wherein the helical gear at least a first gear part and with a Having the first gear part engaged second gear part, wherein the first gear part is designed as a threaded spindle or as a spindle nut and the second gear part as a spindle nut or threaded spindle.

Hydraulically actuated, length-adjustable connecting rods have the disadvantage that the hydraulic medium, in particular oil, is compressible to a certain extent, the compressibility depending on the gas content of the oil. This compressibility of the oil can lead to vibrations in engine frequency, which can lead to premature wear of the already loaded by very high pressure seals. These vibrations also lead to an increase in the oil temperature.

From the documents WO 06/1 15898 A1, US 5 406 91 1 A, GB 441 666 A it is known to adjust the length of connecting rods mechanically by a helical gear. In each case, the piston is rotated via its toothed piston skirt or via a thread in the region of the piston skirt.

Length adjustable connecting rods, which change the length of the connecting rod with a self-locking thread, must generate a rotational movement in order to rotate the two gear parts of the helical gear relative to each other. This relative rotation can be done with coarse thread and / or helical gears having further helical gear or hydraulic rotary valves. Since the adjustment can be made only in the very short periods in which the rod is free of load, the self-locking must be sufficient to allow adjustment only in the desired direction. The object of the invention is to allow the simplest possible way a change in the compression ratio. According to the invention this is achieved in that the helical gear is preferably not self-locking, with a - preferably rotatably mounted in the first rod part - first gear part is connected to at least one switchable by means of at least one switching device Drehsperreinrichtung which at least in a first position, a rotation of the gear part at least prevented in one direction of rotation and allows in at least a second position.

In this case, a helical gear is understood to mean a gear that is used to change movement quantities, in which a translatory movement of a displaceable component along a lifting axis results in a rotational movement of a rotatable component about an axis of rotation or a rotational movement of a rotatable component into a translational movement of a rotatable component is changed, with each other corresponding effective surfaces of the two coaxial components slide along each other. The active surfaces are removed from the common rotation or lifting axis, on the one hand in the region of the outer circumference of one - for example displaceable - component, and on the other hand in the region of the inner circumference of the other - for example rotatable - component arranged. The corresponding active surfaces have a defined pitch and can be formed by threads or by helical toothing of the components. Thus, it is provided in the context of the present invention that the threaded spindle has an external thread or an external helical toothing and the corresponding spindle nut has an internal thread or an internal helical toothing.

The terms thread, threaded spindle and spindle nut used here are thus by no means limitative to helical thread forms, but of course include embodiments in which the thread forms are formed by helical gears.

From a static self-locking a helical gear is generally spoken when the pitch angle of the corresponding active surfaces, so the thread flanks of the thread or helical toothing, smaller than the arc tangent of Gleitreibzahl the material pairing of the first and second gear part. A static self-locking is thus prevented when the pitch angle of the active surfaces of the thread or helical gearing is at least equal to or greater than the arc tangent of Gleitreibzahl the material pairing of the first and second gear part. The fact that a self-locking of the helical gear is prevented, the acting over a relatively long time gas and inertial forces can be used to adjust the helical gear. In particular, it is possible with the gas force occurring in the internal combustion engine to shorten the length of the connecting rod and extend it with the existing mass force. These adjusting forces rotate the spindle nut over the non-self-locking thread and act during each cycle constantly, with the exception of a short phase, in which there is no load. An additional rotary drive according to the invention is preferably not required, whereby a reduced space requirement and lower manufacturing costs is realized.

The Drehsperreinrichtung has favorably at least one preferably designed as a pawl freewheel freewheel device, which locks in one direction and runs freely in the opposite direction. At least one freewheel device, which locks in only one direction of rotation, prevents the connecting rod constantly changes its length within a working cycle. The desired position is fixed via the switchable turnstile device. Thus it can be dispensed with a separate rotary drive for rotating the gear parts of the helical gear.

In a first embodiment of the invention, it is provided that the freewheel device is designed switchable and the switching device is integrated in the freewheel device, wherein the switching device has at least one preferably hydraulically switchable locking element which cooperates with at least one corresponding to the blocking element shaped locking receptacle, wherein blocking element and locking receptacle relative to each other about the axis of rotation of the first gear part are rotatable. Freewheel devices, in particular pawl freewheels are known from a variety of applications and in a variety of designs. Allen freewheel devices have in common that a torque transmission is possible only in one direction, but not in the other direction. With switchable pawl freewheels, the torque transmission can be prevented in both directions of rotation.

The locking receptacle is preferably arranged in an outer ring surrounding the cylindrical middle part, which is rotatably mounted in the first rod part.

A simple freewheel device can be achieved if at least one - preferably at least partially formed by a bore - locking receptacle in a first region has a stop and in a first region diametrically opposite to a normal to the axis of rotation of the first gear part standing central axis of the locking receiving opposite second region has a ramp. When the appropriately switched blocking element bears against the stop, blocking element and locking receptacle are connected to one another in a torque-proof manner and a torque transmission in the corresponding direction of rotation can be carried out. In the opposite direction of rotation, however, the blocking element slides over the flat-shaped ramp without a torque can be transmitted.

Conveniently, at least one locking element is formed by a locking piston displaceably mounted in a cylinder, wherein the cylinder is designed connecting rod-end, preferably in a central part of the rotary locking element fixedly connected to the first rod part and wherein the axis of the cylinder transversely, particularly preferably normal to the axis of rotation of the first transmission part is arranged. A cost-effective production is possible when locking receptacle is formed by a cylindrical sleeve cylindrical part which is rotatably mounted in the first rod part. The locking receptacle can be rotationally fixed, preferably form-fitting, connected to the first transmission part or integrally formed with the first transmission part.

In order to enable a simple control of the Drehsperreinrichtung, it is advantageous if the locking piston with a pressure application surface adjacent to a pressure chamber, in which a pressure oil line opens, wherein the locking piston by pressure increase in the pressure chamber against a restoring force of a spring acting on the locking piston is deflectable.

In a preferred embodiment of the invention, it is provided that the first transmission part is connected to a first freewheel device and a second freewheel device, which freewheel devices respectively lock or unlock different directions of rotation of the first transmission part. By the two freewheel devices, which lock in different directions of rotation, can be activated with the pressure of the actuating fluid once the one turnstile and once the other.

The two freewheel devices can be easily switched when the first freewheel device has a first locking piston and the second freewheel device has a second locking piston, wherein preferably the pressure engagement surfaces of the locking piston and / or the springs of the locking piston are dimensioned differently. In An advantageous embodiment of the invention is provided that the first spring of the first locking piston against the reverse direction and the second spring of the second locking piston are arranged to act in the reverse direction.

Thus, the first and second freewheel devices can be locked at different control pressures of the actuating fluid formed, for example, by lubricating oil of the internal combustion engine.

There are therefore only two different oil pressure levels in the lubrication system necessary to control the rod length via the electronic control unit of the engine load- and speed-dependent and thus to set the desired compression.

This eliminates the need for a separate rotary drive of the spindle nut. A compression takes place only in the context of the games and the elastic deformation of the steel components and can not lead to heating of the actuating fluid. Wear-prone sealing systems for hydraulic pistons can be omitted.

In a second embodiment of the invention, it is provided that the switching device has at least one coupling element for the rotationally fixed connection of the first rod part or a fixedly connected to the first or second rod part - preferably formed by a bolt - part, and at least one freewheel device, preferably an inner ring of the freewheel device , having. Here, in a space-saving design, the coupling element is formed by a coaxially or parallel to the axis of rotation of the first gear part form-fitting part which produces a rotationally fixed connection between an inner ring at least one freewheel device and the bolt in at least one position, wherein preferably the pin coaxial with the axis of rotation of the first Coupling part is arranged.

For positive connection with at least one freewheel device, it is advantageous if the coupling element in an outer first jacket portion has an external toothing, which corresponds to at least one internal toothing in an inner shell region of an inner ring at least one freewheel device, wherein in the locking position, the external toothing of the coupling element in the internal toothing of Inner ring is pushed. For easy positive connection with the first or second rod part, it is advantageous if the coupling element in an inner second Mantle region has an internal toothing, which corresponds to at least one external toothing in an outer jacket region of the bolt, wherein in the locking position, the internal toothing of the coupling element is pushed into the outer toothing of the bolt. A very space-saving embodiment of the invention provides that the first and second cladding regions are arranged in a sleeve-like shaped section of the coupling element.

In order to be able to easily switch between long and short connecting rods, it is again particularly advantageous if the first transmission part is connected to a first freewheel device and a second freewheel device, which freewheel devices respectively lock or unlock different directions of rotation of the first transmission part. By the two freewheel devices, which lock in different directions of rotation, can be activated with the pressure of the actuating fluid once the one turnstile and once the other.

By the displacement of the coupling element in the direction of the longitudinal axis of the connecting rod optionally the first or the second freewheel device can be activated. This is done in a simple manner in that the coupling element in a first position produces a rotationally fixed connection between the inner ring of the first freewheel device and the bolt, and a second position establishes a rotationally fixed connection between the inner ring of the second freewheel device and the bolt. At the same time interrupts the coupling element in the first position, the rotationally fixed connection between the inner ring of the second freewheel device and the bolt, and in the second position, the rotationally fixed connection between the inner ring of the first freewheel device and the bolt.

The displacement of the coupling element can in principle be electromagnetically or mechanically. A particularly simple hydraulic or pneumatic actuation is possible according to the present invention, when the coupling element has a piston surface adjacent to a pressure chamber, wherein the coupling element by pressure increase in the pressure chamber, preferably against the force of a spring is deflectable. In the pressure chamber preferably opens a pressure line of the engine's own lubricating oil system. The invention will be explained in more detail below with reference to the non-limiting figures. Show in it

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

2 shows the detail II of Fig. 1,

3 shows a freewheel device in a plan view in detail,

4 shows a connecting rod according to the invention in a longitudinal section in a second embodiment,

5 shows the detail V of FIG. 1,

6 is a partial view of a connecting rod according to the invention in a longitudinal section in a third embodiment,

7 shows the connecting rod in a section along the line VII - VII in FIG. 6 in a position corresponding to a short connecting rod of the rotary locking element, FIG.

8 shows the connecting rod in a section along the line VII-VII in FIG. 6 in a position of the rotary locking element corresponding to a long connecting rod, FIG.

Fig. 9, the connecting rod in a section along the line VIII - VIII in Fig. 6 in a position corresponding to a short connecting rod of the rotary locking element and

Fig. 10, the connecting rod in a section along the line VIII - VIII in Fig. 6 in a position corresponding to a long connecting rod of the rotary locking element.

Functionally identical parts are provided in the embodiment variants with the same reference numerals.

Fig. 1 shows a length-adjustable connecting rod 1 for a reciprocating engine, such as an internal combustion engine. The connecting rod 1 has a first rod portion 2 in the region of a large connecting rod 3a and a second rod portion 4 in the region of a small connecting rod 3b, wherein the large connecting rod 3a a crank pin bearing for connection to a crankshaft not shown and the small connecting rod 3b a piston pin bearing for Form connection with a piston, not shown.

The two rod parts 2, 4 can be moved via a helical gear 6 relative to each other in the direction of the longitudinal axis 1a of the connecting rod 1. The helical gear 6 has a first gear part 7 and a stationary with the first gear part 7 in engagement second gear part 8, wherein one of the two gear parts 7, 8 as a spindle nut 9 and the other gear part 8, 7 is formed as a threaded spindle 10. In the illustrated embodiments, the first gear part 7 is formed as a sleeve-like spindle nut 9 and the second gear part 8 as a threaded spindle 10.

The spindle nut 9 has on its inner side active surfaces with a pitch, which are spaced from the longitudinal axis 1 a of the connecting rod 1 and which are formed as internal screw thread with a thread or more threads, or as internal helical teeth. Corresponding thereto, the threaded spindle 10 on its outer side corresponding active surfaces with a pitch, which are spaced from the longitudinal axis 1 a of the connecting rod 3 and which are formed as external screw thread with one thread or multiple threads, or as external helical teeth. The thread, in particular the pitch of the thread, is preferably designed so that a self-locking is reliably avoided. Self-locking can usually be avoided if the pitch angle is greater than 7 °. On the other hand, to limit the torque occurring, the pitch angle should not be made too large. In one embodiment, an optimum pitch angle was chosen at about 8 °.

The term "thread" (for example, in threaded spindle) is generally used here for both screw thread, and helical teeth and thus covers both training.

The first gear part 7 formed by the spindle nut 9 is rotatably mounted in a guide cylinder 5 formed by the first rod part 2, designed as a blind hole bore, but mounted axially immovably. The axial position of the first gear part 7 is in Direction of the small connecting rod 3b by a the upper end of the guide cylinder 5 final clamping sleeve 13 and an example, two-piece spacer ring 14 limited.

The first gear part 7 of the screw 6 is rotatably mounted, but axially immovable in the first rod part 2. The second gear part 8 of the helical gear 6 is displaceable in the direction of the longitudinal axis 1a, but rotatably mounted in the first rod part 2. The second gear part 8 is fixedly connected to the second rod part 4 or executed integrally therewith. The safeguard against rotation of the second gear part 8 via the anti-rotation 11, which also forms a stroke limit for the second rod part 4. The rotation 11 may be formed by a simple screw, which is screwed transversely to the longitudinal axis 1 a in the first rod part 2. It cooperates with a corresponding longitudinal groove 12 in the second rod part 2.

The first gear part 7 is connected to at least one switchable by means of at least one switching device 21 Drehsperreinrichtung 20, which prevents rotation of the first gear part 7 in at least one rotational direction in at least one first position and allows at least a second position.

The turnstile device 20 has at least a first freewheel device 22 and a second freewheel device 23, which are designed, for example, as pawl freewheels. Each of the freewheel devices 22, 23 forms a clutch for transmitting a torque which transmits torque in one direction of rotation, ie "locks" and transmits no torque in the opposite direction of rotation, ie "free running". The first freewheel device 22 and the second freewheel device 23 may be formed substantially the same, but be arranged inversely oriented one above the other, so that the locking and releasing directions of rotation are opposite.

By means of at least one switching device 30, each freewheel device 22, 23 are blocked at least in one direction of rotation by a temporary rotationally fixed connection with the first or second rod member 2, 4 is produced.

1 to 5 show embodiments in which the Drehsperreinrichtung 20 designed as a pawl Freewheel simple freewheel devices 22, 23 has. In this case, each freewheel device 22, 23 an inner ring 24, 25, which of an outer ring 26th is surrounded, between the two rings, at least one locking element 28 - for example, a ball - is arranged, which is arranged in a bounded by ramp surfaces 30a, 30b cavity 30 between each an inner ring 24, 25 and the outer ring 26 (Fig. 3). Each of the first and second inner rings 24, 25 has first and second internal teeth 32, 33, respectively. In this case, each freewheel device 22, 23 each have an outer ring, wherein the outer rings are rotatably connected to each other. In the exemplary embodiments shown in FIGS. 1 and 4, the two freewheel devices 22, 23 have a common outer ring 26. The outer ring 26 is rotatably connected to the first transmission element 7 via drivers and corresponding recesses 26 a.

The inner circumferential surface 24a, 25a of each inner ring 24, 25 is provided with an internal toothing 32, 33.

In the embodiments shown in FIGS. 1 to 5, the switching device 30 has a coupling element 31 formed by a form-fitting part. In an outer first jacket portion 31a of the coupling element 31, an outer toothing 34 is arranged, which with the internal teeth 32, 33 of the inner circumferential surfaces 24a, 25a of the inner rings 24, 25 of the freewheel devices 22, 23 corresponds. The coupling element 31 is arranged axially displaceably about a central pin 35, which is fixedly connected to the first rod part 2 (FIG. 1, 2) or fixed to the second rod part 4 (FIG. 4, 5). The coupling element 31 and the bolt 35 are arranged coaxially with the longitudinal axis 1 a of the connecting rod 1 or coaxially with the axis of rotation 7 a of the first gear element 7. The coupling element 31 has, in an inner second jacket region 31b, an internal toothing 37 which corresponds to an external toothing 38 in an outer jacket region 35a of the bolt 35. The coupling element 31 is thus rotationally fixed, but axially displaceable, connected to the bolt 35.

In order to lock the first and second freewheel device 22, 23 in a rotational direction, the coupling element 31 is displaced in the axial direction, so that in the respective blocking position, the external teeth 34 of the coupling element 31 in the internal teeth 32, 33 of the corresponding inner ring 24, 25 is pushed is. As a result, a positive connection between the corresponding inner ring 24, 25 and the coupling element 31 is produced. Since the coupling element 31 is non-rotatably connected to the bolt 35 which is non-rotatably connected to the first rod part 2 (Fig. 1, 2) and second rod part 5 (Fig. 4, 5), the corresponding inner ring 24, 25th blocked. By axially displacing the coupling element 31, either the inner ring 24 of the first freewheel device 22 or the inner ring 25 of the second freewheel device 23 is blocked, and the other inner ring 25 or 24 is released, ie the positive connection with the bolt 35 is disconnected.

The coupling element 31 is actuated hydraulically in the illustrated embodiments by the oil pressure of the lubricating oil system of the internal combustion engine. To make this possible, the coupling element 31 has a piston surface 39 adjoining a pressure chamber 40, wherein the coupling element 31 can be deflected by increasing the pressure in the pressure chamber 40 counter to the force of a spring 41 acting on the coupling element 31. In the pressure chamber 40 opens a connected to the lubricating oil system via the crank pin bearing 15 pressing oil line 42 a.

Fig. 2 shows the coupling element 31 in its upper position, wherein the outer toothing 34 with the second inner toothing 33 of the second inner ring 25 is. The second freewheel device 23 is thus blocked, the first freewheel device 22 freely rotatable in both directions.

FIG. 5 shows the coupling element 31 in its lower upper position, the outer toothing 34 of the coupling element 31 being with the first inner toothing 32 of the first inner ring 24. The first freewheel device 22 is thus blocked, the second freewheel device 23 freely rotatable in both directions.

6 to 10 show a third embodiment of the invention, in which the switching device 30 is integrated into the freewheel devices 22, 23, which are thus designed as switchable freewheel devices 22, 23. In this case, each freewheel device 22, 23 has a switchable blocking element 50, 51. The blocking elements 50, 51 are each formed with a blocking piston 54, 55 displaceably mounted in a cylinder 52, 53, wherein the cylinder 52, 53 is arranged in a connecting part fixedly connected to the first or second rod part 2, 4 of the rotary blocking device 20 , The axes 52a, 53a of the cylinders 52, 53 are positioned approximately normal to the axis of rotation 7a of the first gear part 9. Furthermore, each blocking element 50, 51 has, for example, a cylindrical locking pin 56, 57 which cooperates with a locking receptacle 58, 59 shaped in accordance with the locking pin 56, 57. The locking receptacles 56, 57 are by corresponding to the cylindrical locking pin 56, 57th shaped recesses formed in the outer rings 26, 27 of the freewheel devices 22, 23 which surround the central part 60. In the embodiment shown in FIGS. 6 to 10, each freewheel device 22, 23 an outer ring 26, 27, wherein the outer rings 26, 27 rotatably connected via driver 26 b are interconnected. Furthermore, the outer ring 27 adjoining the spindle nut 9 and of the second freewheel device 23, which is upper in FIG. 6, is connected in a rotationally fixed manner to the spindle nut 9 via drivers 27b. It is of course also possible to carry out the two outer rings 26, 27 - analogous to the embodiments shown in FIGS. 1 to 5 - as the only common component. In addition, it is also conceivable to form the outer rings 26, 27 in one piece with the spindle nut 9.

Each locking piston 54, 55 adjoins with a pressure application surface 61, 62 to a pressure chamber 63, 64, in which a pressure oil line 67 opens, wherein the locking piston 54, 55 by increasing the pressure in the pressure chamber 63, 64 against a restoring force acting on the locking piston 54, 55 Spring 65, 66 is deflectable. The springs 65, 66 may be formed for example by leaf springs.

Each locking receptacle 58, 59 is at least partially formed by a substantially radial bore in the outer ring 26, 27. In this case, the locking receptacles 58, 59 each have a stop 68, 69 in a first area 58a, 59a and a ramp 70, 71 in a second area 58b, 59b. The first region 58a, 59a and the second region 58b, 59b are each formed diametrically with respect to a radial center axis 58c, 59c of the blocking receptacle 58, 59 that is perpendicular to the rotational axis 7a of the first gear part 9.

As in the previously described embodiments, the first transmission part 9 is connected to the first freewheel device 22 and the second freewheel device 23, wherein the freewheel devices 22, 23 each lock or release different directions of rotation of the first gear part 9.

The gas and mass forces cause movement of the small connecting rod 3b along the longitudinal axis 1 a of the connecting rod 1. The axial movement is converted into a rotational movement of the spindle nut 9, which is transmitted to the non-rotatably connected to the spindle nut 9 outer rings 26, 27. Depending on the oil pressure level, one of the blocking elements 50, 51 is activated and shortening or lengthening the Connecting rod 1 allows, as the respective locking piston 54, 55 blocked in the direction of the stop 68, 69, but in the direction of the ramp 70, 71 permits.

7 and 9 show the positions of the first locking element 50 and the second locking element 51 with a short connecting rod 1, wherein the first freewheel device 22 is locked and the second freewheel device 23 is released. The locking pin 56 of the first locking element 50 is thereby pushed by deflection of the locking piston 54 radially into the locking receptacle 58, whereby a rotation of the first outer ring 26 is blocked in a rotational direction. The second locking piston 55 of the second locking element 51, however, is in its release position, in which the second outer ring 27 is released in both directions of rotation.

8 and 10 show the positions of the first locking element 50 and the second locking element 51 at long connecting rod 1, wherein the first freewheel device 23 is released and the first freewheel device 22 is released. The locking pin 57 of the second locking element 51 is thereby moved by deflection of the second locking piston 55 radially into the corresponding locking receptacle 59, whereby a rotation of the second outer ring 27 is blocked in one direction. The first locking piston 54 of the first locking element 50, however, is in its rest position defined by the spring 65, in which the first outer ring 26 is released in both directions of rotation.

In the embodiment, four locking receptacles 58, 59 are provided in each outer ring 26, 27. But there are also more, for example, eight or less, for example, two, locking recordings 58, 59 per outer ring 26, 27 possible.

The torque, which results from the gas power of the internal combustion engine via the power separation in helical gear 6 thread, must from the cylindrical second locking pin 57, the protruding from the fixed central portion 60 in the second outer ring 27 second locking element 51 on the bearing hole of the second locking receptacle 59 on one side be received against the direction of rotation of the torque. The torque from the mass force is about only one-third of the torque from the gas power. The first locking pin 56 for this torque can thus be performed daintier. At low oil pressure, ie, an oil pressure below a defined threshold, the spring force of the first spring 65 behind the first locking piston 54, whose diameter is greater than the diameter of the second locking piston 55. This prevents the spindle nut 9 is prevented from becoming shorter to turn the connecting rod 1. The mass force pulls the connecting rod 1 over the rotating spindle nut 9 apart until the stroke is limited by the rotation 11. The second locking pin 57 of the second blocking element 51, which is guided by the second spring 66 into the blocking position, prevents the connecting rod 1 from being shortened again under the gas force.

If the oil pressure in the pressure oil line 67 increased to a certain threshold, there is a compression of the second spring 66 behind the second locking piston 55 and the engagement of the second locking pin 57 in the second locking receptacle 59 of the second outer ring 27 is terminated. Thus, the lock is inactive and the outer ring 27 can rotate freely in the opposite direction.

Due to the higher oil pressure and the spring force behind the smaller first locking pin 56 of the first locking element 50 is overcome. The first locking pin 56 passes through the rotation of the spindle nut 9 via the ramps 70 in its first locking receptacle 58 in the first outer ring 26. There he lies on one side and can absorb the holding torque from the inertia force through his bed hole. The connecting rod 1 is thereby shortened until the second rod part 4 rests with its lower end of the shaft on the central part 60.

When the oil pressure is lowered again, the spring force of the spring 65 behind the small first locking piston 54 overcomes the force from the oil pressure - the first locking pin 54 is deflected out of the first locking receptacle 58. The lower first freewheel device 22 is no longer locked, the first outer ring can now rotate in the opposite direction. The upper second locking piston 55 is now pushed by the second spring 66 of the second locking element 51 during rotation by the inertial force via the second ramp 71 in its second locking receptacle 59. Now the upper second freewheel device 23 is locked, a rotation of the spindle nut 9 only possible in a direction of rotation corresponding to the long connecting rod. A rotation of the spindle nut 9 in the opposite direction by the gas force is prevented. The connecting rod 1 is thus longer again until the lower edge of the groove 12 in the second rod part 4 rests against the rotation 1 1.

The turnstile device (20) according to the invention thus preferably has two switching states, a first at an oil pressure below a defined threshold and a second above the threshold at which the restoring forces of the springs 65, 66 are overcome.

Preferably, it can also be provided that in the first switching state, instead of a low oil pressure, at least substantially no oil pressure is applied to the blocking piston 54, 55. Preferably, it can be provided for this purpose that the connecting rod (1) has a switching valve, in particular an electromagnetically actuated switching valve which controls the inflow of oil through the pressure oil line (42).

Preferably, such a switching valve has two switching positions, namely a first switching position in which the Drehsperreinrichtung (20) is drained, and a second switching position in which the Drehsperreinrichtung (20) is acted upon by oil pressure and therefore oil is supplied. More preferably, such a switching valve in addition to a third, neutral switching position, in which the pressure oil line (42) is closed or blocked and the respective present switching state of the rotary locking device (20) is maintained without an actuation of the switching valve.

Claims

Length-adjustable connecting rod (1) for a reciprocating engine, in particular for an internal combustion engine, with at least a first rod part (2) and a second rod part (4), which two rod parts (2, 4) relative to each other via a helical gear (6), in particular in direction the longitudinal axis (1 a) of the connecting rod (1), are displaceable, wherein the helical gear (6) at least a first gear part (7) and with the first gear part (7) in engagement second gear part (8), wherein the first Gear part (7) as a spindle nut (9) or threaded spindle (10) and the second gear part (8) as a threaded spindle (10) or as a spindle nut (9), wherein one, preferably in the first rod part (2) rotatably mounted, first transmission part (7) with at least one by means of at least one switching device (30) switchable turnstile device (20) is connected, which in at least a first position, a rotation of the first Getriebet eils (7) prevented in at least one direction of rotation and allows in at least a second position.

Connecting rod (1) according to claim 1, dadu rch geken nzeich net that the Drehsperreinrichtung (20) at least one preferably designed as a pawl freewheel device (22, 23) which locks in one direction and runs freely in the opposite direction.

Connecting rod (1) according to claim 2, dadu rch geken nzeich net, that the freewheel device (22, 23) is designed switchable and the switching device (30) in the freewheel device (22, 23) is integrated, wherein the switching device (30) at least one preferably hydraulically switchable locking element (50, 51) which cooperates with at least one corresponding to the blocking element (50, 51) shaped locking receptacle (58, 59), wherein blocking element (50, 51) and locking receptacle (58, 59) relative to each other around the Rotary axis (7a) of the first gear part (7) are rotatable.

Connecting rod (1) according to Claims 3, characterized in that at least one blocking element (50, 51) is formed by a blocking piston (54, 55) displaceably mounted in a cylinder (52, 53), wherein the cylinder (52, 53) connecting rods, preferably in a fixedly connected to the first rod part (2) central part (60) of the Drehsperreinrichtung (20) is formed and wherein the axis (52a, 53a) of the cylinder (52, 53) transversely, particularly preferably normal to the axis of rotation (7a) of the first transmission part (7) is arranged.

Connecting rod (1) according to claim 3 or 4, dadu rch geken Nzeichnet that the locking receptacle (58, 57) in a cylindrical central part (60) surrounding outer ring (26, 27) is arranged, which rotatably mounted in the first rod part (2) is.

Connecting rod (1) according to one of claims 3 to 5, characterized in that at least one outer ring (26, 27) is connected to the first gear part (9) so as to be non-rotatable, preferably positive, or integral with the first gear part (9). is trained.

Connecting rod (1) according to one of claims 4 to 6, characterized in that the blocking piston (54, 55) with a pressure application surface (61, 62) adjoins a pressure chamber (63, 64) in which a hydraulic medium line, in particular a pressure oil line, (67) opens, wherein the locking piston (54, 55) by pressure increase in the pressure chamber (63, 64) against a restoring force of the locking piston (54, 55) acting spring (65, 66) is deflectable.

Connecting rod (1) according to one of claims 4 to 7, characterized in that at least one - preferably at least partially formed by a bore - locking receptacle (58, 59) in a first area a stop (68, 69) and in a ramp (70, 71) diametrically opposite the central region (58a, 59a) of the locking receptacle (58, 59), which is diametrically opposed to the axis of rotation (7a) of the first gear part (7).

Connecting rod (1) according to one of claims 1 to 8, characterized in that the first gear part (7) is connected to a first freewheel device (22) and a second freewheel device (23), which freewheel devices (22, 23). respectively lock or unlock different directions of rotation of the first gear part (7).

10. Connecting rod (1) according to claim 8, dad u rch geken net nets that the first freewheel device (22) has a first locking piston (54) and the second freewheel device (23) has a second locking piston (55).

1 1. connecting rod (1) according to claim 10, dadu rch geken net nets that the first spring (65) of the first locking piston (54) against the reverse direction and the second

Spring (66) of the second locking piston (55) are arranged to act in the reverse direction.

12. connecting rod (1) according to claim 10 or 1 1, dad u rch geken nzeichnet that the pressure application surfaces (61, 62) of the locking piston (54, 55) and / or the springs (65, 66) of the locking piston (54, 55 ) are dimensioned differently.

13. connecting rod (1) according to claim 2 or 10, dadu rch geken nzeich net that the switching device (30) at least one coupling element (31) for the rotationally fixed connection of the first (2) or second rod part (4) or one with the first ( 2) or second rod part (4) firmly connected - preferably by a bolt (35) formed - part, and at least one freewheel device (22, 23), preferably an inner ring (24, 25) of the freewheel device (22, 23).

14. connecting rod (1) according to claim 13, dadu rch geken net nets that the coupling element (31) by a coaxial or parallel to the axis of rotation (7 a) of the first gear part (7) displaceable form-fitting part is formed, which in at least one position a non-rotatable Connection between an inner ring (24, 25) at least one freewheel device (22, 23) and the bolt (35) produces, wherein preferably the bolt (35) coaxial with the axis of rotation (7a) of the first gear part (7) is arranged.

15. connecting rod (1) according to claim 13 or 14, dadu rch geken net nets that the coupling element (31) in an outer first jacket portion (31 a) has an outer toothing (34) which at least one internal toothing (32,

33) in an inner jacket portion (24a, 25a) of an inner ring (24, 25) at least one freewheel device (22, 23) corresponds, wherein in at least one locking position, the outer toothing (34) of the coupling element (31) in the internal toothing (32, 33 ) At least one inner ring (24, 25) is slidable.

16. connecting rod (1) according to claim 15, dadu rch geken nzeich net, that the coupling element (31) in an inner second cladding region (31 b) has an internal toothing (37), which with at least one external toothing (38) in an outer cladding region (35a) of the bolt (35) corresponds, wherein in at least one locking position, the internal toothing (37) of the coupling element (31) in the outer toothing (38) of the bolt (35) is pushed.

17. connecting rod (1) according to claims 15 or 16, dad u rch geken characterized in that the first and second jacket portions (31 a, 31 b) are arranged in a sleeve-like shaped portion of the coupling element (31).

18 connecting rod (1) according to one of claims 13 to 17, dadu rch geken nzeichnet that the coupling element (31) has a to a pressure chamber (40) adjacent piston surface (39), wherein the coupling element (31) by pressure increase in the pressure chamber ( 40), preferably against the force of a spring (41) is deflectable.

19 connecting rod (1) according to one of claims 14 to 18, dadu rch in that the coupling element (31) in a first position, a rotationally fixed connection between the inner ring (24) of the first freewheel device (22) and the bolt (35) produces , And in a second position, a rotationally fixed connection between the inner ring (25) of the second freewheel device (23) and the bolt (35) produces.

20. Connecting rod (1) according to claim 19, dadu rch geken net nets that the coupling element (31) in the first position, the rotationally fixed connection between the inner ring (25) of the second freewheel device (23) and the bolt (35) interrupts, and in the second position, the rotationally fixed connection between the inner ring (24) of the first freewheel device (22) and the bolt (35) interrupts.

21 connecting rod (1) according to one of claims 1 to 20, dad u rch geken nzeich net, that the threaded spindle (10) has an external thread or an external helical gearing and the corresponding spindle nut (9) has an internal thread or an internal helical gearing.

22 connecting rod (1) according to one of claims 1 to 21, dad u rch geken nzeich net that the helical gear (6) is not self-locking.