EP1205652B1 - Variable compression ratio mechanism with two hydraulically operated valves in the crank shaft - Google Patents

Description

The invention relates to a crankshaft for a reciprocating piston internal combustion engine, containing a crank pin and one on the crank pin with its cylindrical inner surface rotatably mounted eccentric sleeve, the sleeve at least has a locking recess into which a Locking element can intervene to the rotatability of the Sleeve to pick up the crank pin.

A crankshaft of the type mentioned is from the DE 197 03 948 C1 known. Such a crankshaft is used to the compression of a reciprocating internal combustion engine to change that as described below effective length of the connecting rod is shortened or lengthened becomes.

The connecting rod is in a known manner with its first end hinged to the piston, which is in the cylinder of the Motors moves up and down, and with its second end it is Connecting rod articulated on the crank pin of the crankshaft. The linear up and down movement is via the connecting rod of the piston in a continuous rotary motion of the Converted crankshaft. According to DE 197 03 948 C1 Connecting rod with its second end via an intermediate eccentric sleeve mounted on the crank pin. The eccentric sleeve has a cylindrical inner surface and an eccentric cylindrical outer surface. ever after rotating this eccentric sleeve relative to the crank pin the stroke is differently effective Stroke radius, which together with the connecting rod as a distance between the axis of rotation of the connecting rod on the piston and the Axis of rotation of the crankshaft can be defined. By a Rotation of the eccentric sleeve can thus in the displacement of the Compression of the engine piston and thus the engine behavior to be changed.

To make this change in compression specifically can instruct the sleeve disclosed in DE 197 03 948 C1 their two axial edges each have a recess, wherein the two recesses are in relation to the center of the Diametrically opposite sleeve. It is also at the end of the connecting rod a locking element arranged in parallel Slidable to the sleeve axis between two positions is. This locking element engages in the first position locking into the first recess of the sleeve, in the second position locking into the second recess. There the two recesses lie diametrically opposite one another on the sleeve, the sleeve must be used to switch between the two two engagement positions of the locking element by 180 ° rotate around the crank pin. The recesses of the sleeve are arranged with respect to the eccentricity of the sleeve that are in the locked positions of the locking element the maximum or minimum possible effective Adjusts the length of the connecting rod.

For actuating the locking element at the end of the connecting rod is from the connecting rod according to DE 197 03 948 C1 independent movable mechanism provided which with an arched stop surface at the edge of the movement space the connecting rod is arranged. It is a big Expansion of the stop surface is necessary, because that End of the connecting rod moves during engine operation and in a switching of the locking element in every possible position must be possible. Accordingly, it results in DE 197 03 948 C1 is a relatively complex, expensive and failure-prone mechanism for actuating the locking element or to change the effective length of the Connecting rod.

Furthermore, a device of the type mentioned also known from US 5 562 068. Here can by a first locking mechanism housed in the crank pin, which in a locking recess of the eccentric Sleeve engages, the sleeve fixed relative to the crank pin become. In addition, one is in the connecting rod second locking mechanism is provided with which the Sleeve can be locked relative to the connecting rod. By the alternative use of the two locking mechanisms the effective length of the connecting rod and thus the compression ratio of the internal combustion engine is variable to adjust.

From US 4 406 256 is a similar locking mechanism known an eccentric sleeve on a crank pin, a hydraulically movable housed in the sleeve Engage the pin in the recesses on the connecting rod can, so the eccentric sleeve relative to the connecting rod to lock.

Against this background, it was an object of the present invention a crankshaft of the type mentioned at the beginning improve that it can be produced at lower costs and enables reliable operation.

This task is accomplished by a crankshaft with the characteristics of claim 1 solved. Advantageous configurations are shown in contain the subclaims.

Contains the crankshaft for a reciprocating piston internal combustion engine therefore a crank pin, which is eccentric in the usual way is arranged to the axis of rotation of the crankshaft. Farther the crankshaft contains an eccentric sleeve that with its cylindrical inner surface rotatable on the crank pin is stored and the cylindrical outer surface is eccentric to the inner surface. This can be done on the outer surface of the sleeve one end of a connecting rod can be supported, with one Rotation of the sleeve around the crank pin due to the eccentricity the effective length of the connecting rod Stroke radius can be changed. The sleeve has at least a locking recess or pocket in which a Locking element can intervene to the rotatability of the Pick up the sleeve and thus close the sleeve on the crank pin lock. The sleeve is locked in place the current effective length of the connecting rod.

The crankshaft also shows the feature that the at least one locking element arranged the crankshaft is and that the crankshaft control means for actuation contains the locking element. Different from certain Prior art embodiments are Locking element is therefore not arranged in the connecting rod, but on or in the crankshaft. this has the advantage that control means for actuating the Locking element also on or in the Crankshaft can be provided where they are manufacturing easier to accommodate and where to put them Interference are protected. Furthermore, are in the room below the connecting rod no complex and bulky additional elements required to operate the locking element. The crankshaft according to the invention thus also allows one more compact structure of the engine.

According to the present. Invention has the Crankshaft at least one to the outer surface of the crank pin (and thus to the inner surface of the sleeve) leading fluid supply channel on, and the sleeve is like this on its inner surface shaped that the supply of a fluid through the fluid supply channel a torque is generated on the sleeve around the crank pin. That is, effective for a change Length of the connecting rod necessary rotation of the sleeve around the Crank pin through the targeted supply of a fluid over the Fluid supply channel can be actively executed or supported can. The crankshaft according to the invention is therefore not on it instructed that the rotation of the sleeve after releasing the lock occurs on its own due to the acting forces, but this rotation can be active and in a predetermined Direction.

According to a preferred embodiment of the crankshaft the control means provided in the crankshaft are supply lines for a hydraulic fluid, and the locking elements can be operated hydraulically. In the crankshaft therefore only need channels for a hydraulic fluid be provided to the pressure-actuated locking elements to lead. For such channels is in the crankshaft enough space, and the arrangement of the Not least because of this, ducts are inexpensive to manufacture, because mostly oil channels in the crankshaft anyway Lubrication of the bearings must be provided.

The hydraulically operated locking elements can be in known way a displacement for receiving the hydraulic fluid and one by changing the volume of the displacement movable piston included. The locking elements are preferably mechanically biased into a rest position which they apply when using a hydraulic (excess) pressure can be moved. The rest position of the Locking element can both engage the locking element in the recess of the sleeve as well Retraction of the locking element from the sleeve correspond.

For a shaping of the sleeve on its inner surface, the too leads to the desired torque when a fluid is supplied, there are different options. In particular, the Have a circular sawtooth shape on their inner surface, the saw teeth running radially. When feeding one Fluids in the asymmetrical recesses between the Saw teeth are power components of different sizes in the positive and the negative direction of rotation generated, whereby in Overall result of the desired advance in one direction of rotation arises.

According to a development of the last-mentioned embodiment the crankshaft has a fluid drain channel which fluid can be removed, which the inner surface of the Sleeve was supplied via the above-mentioned fluid supply channel. The fluid is thus in a flow via the fluid supply channel and the inner surface of the sleeve into the fluid drainage channel passed, preferably in a circuit can be performed. On its way between the fluid supply channel and fluid drainage channel, the fluid interacts with the sleeve and calls the desired torque there out.

The crankshaft preferably contains two offset by 180 ° Crank pin arranged locking elements. The order "on the crank pin" means that the locking elements in the crank pin itself or on its edge, the means arranged in the so-called cheeks of the crankshaft are from where they are in the locking recess on the sleeve can intervene. Preferably there is only one Locking recess provided on the sleeve, so that too only one of the locking elements at any given time can engage in this recess. Since the Locking elements 180 ° opposite each other is with them a corresponding locking of two to each other by 180 ° rotated positions of the sleeve possible. The arrangement the recess on the sleeve and the locking elements preferably chosen so that in the locked Positions each the maximum possible or minimum possible effective length of the connecting rod is achieved.

For efficient storage of the supply lines to the locking elements and optionally the fluid supply channel the crankshaft preferably has one along its extension running inner bore in which separate channels are arranged for the above lines.

Fig. 1

einen schematischen Querschnitt durch die für die Erfindung wesentlichen Teile einer Kurbelwelle;

Fig. 2

eine perspektivische Darstellung der Hülse der Kurbelwelle von Figur 1;

Fig. 3

eine Aufsicht auf den Rand der Hülse aus der Richtung III von Figur 1.

The invention is explained below by way of example with the aid of the figures. Show it:

Fig. 1

a schematic cross section through the essential for the invention parts of a crankshaft;

Fig. 2

a perspective view of the sleeve of the crankshaft of Figure 1;

Fig. 3

a top view of the edge of the sleeve from the direction III of Figure 1.

In Figure 1 is a part of a schematic in a cross section Crankshaft shown. The crankshaft is in known way from shaft journal 1, which is concentric to the axis of rotation A of the crankshaft, as well as from eccentric arranged with respect to the axis of rotation A cylindrical crank pin 11. The crank pin 11 and the shaft pin 1 are connected via crank webs 13, which by their shape and Material distribution for a symmetrical, balanced weight distribution with respect to the axis of rotation A. The one in figure 1 shown section of the crankshaft is for everyone Cylinder of the associated internal combustion engine is provided, wherein the corresponding crank pins, however, relative to each other have an angular offset about the axis of rotation A.

Around the crank pin 11 is the end of a connecting rod (not shown) rotatably arranged, the other End of the connecting rod articulated with the piston of the engine connected is. In the crankshaft according to the invention the bearing of the connecting rod on the crank pin 11 over an intermediate sleeve 10. This has the special feature on that their cylindrical inner surface with which they are on the crank pin 11 is mounted, opposite the likewise cylindrical Outside surface is offset eccentrically. In the illustration of Figure 1, this is expressed in that the sleeve 10 has a greater thickness in the upper section than in lower cut. By rotating the sleeve 10 around the crank pin 11 can thus the position of the effective axis of rotation attached connecting rod and thus the effective stroke of the Crankshaft and the position of the top dead center of the piston be changed in the engine. This in turn can do that Compression ratio in the engine displacement vary because depending on the position of the sleeve 10, the volume of the combustion chamber increased or decreased in the cylinder.

So that the rotatably arranged on the shaft journal 11 Sleeve 10 for setting a desired effective stroke the crankshaft can be locked in certain positions, the locking elements 7 and 14 are provided. This Locking elements are arranged in the crankshaft, and in the embodiment according to FIG. 1 in particular in one the cheeks 13, the shaft journal 1 with the crank pin 11 connects.

The sleeve 10 has the locking elements 7, 14 on it facing edge a recess 8 (see FIGS. 2 and 3), in which the locking elements can engage. The situation shown in FIG. 1 intervenes in this Recess 8 the locking element 7 located radially on the outside on. This engagement turns the sleeve 10 around blocked the crank pin 11. In the basic function at not running engine is the spring-loaded piston of the locking element 7 as shown in Figure 1 in engagement with the recess 8 in the sleeve 10. The opposite second locking element 14 is opposed by a spring Biased direction so that its piston of the sleeve 10 is pulled away. Since the sleeve 10 is only a single one Recess 8 has only one at a time of the two locking elements 7 or 14 engage in them.

To the locking elements 7 and 14 from their by springs Switching biased rest positions out is a second piston connected to the first piston via a rod (not shown). The second piston can with one Locking element supplied oil pressure are applied whereupon he pulled a pull on the other piston exercises and this with sufficient pressure from its Rufertigung moved out. In this way, starting from the situation of Figure 1, the piston of the outer locking element 7 out of engagement with the recess 8 on the Sleeve 10 are brought so that the sleeve 10 around the Crank pin 11 can rotate. After turning around The recess 8 comes 180 ° in front of the radially inner locking element 14 to lie, the piston then by a corresponding hydraulic pressure in engagement with the recess 8 can be brought. Then the sleeve is 10 in locked in their second position relative to the crank pin 11, whereby the other extremum (in Fig. 1 the minimum) of the effective stroke of the crankshaft is set.

For hydraulic actuation of the locking elements 7 and 14 supply lines 2, 4 are provided for a hydraulic oil, which extend through the crankshaft through it. From the two supply lines 2 and 4 branch at for each cylinder lines 5 and 15, respectively the corresponding locking element 7 or 14 supply with hydraulic oil from the main line. About the oil pressure in the supply lines 2 and 4 can thus Locking elements 7 and 14 are operated selectively. In order to can then by rotating the sleeve 10 Compression ratio of the engine according to the engine speed and Adjust engine load.

In Figure 1, another oil channel 3 can be seen, which parallel to channels 2 and 4 along the extension the crankshaft runs. This channel 3 is via a line 12 connected to the outer surface of the crank pin 11, so that the bearing surface of the sleeve 10 on the crank pin 11 lubricating oil can be supplied.

In particular, however, a fluid, preferably oil, such as the inner surface of the sleeve 10 is supplied that there is a torque around the axis of the trunnion 11 is generated around. This torque can be a desired rotation of the sleeve in its unlocked state support or generate. To this end the inner surface of the sleeve 10 is configured in a suitable manner, e.g. by creating a circular sawtooth contour with chambers 9 (see Figures 2 and 3). After going through of the chambers 9, the fluid supplied is via a channel 6 dissipated in the cheek 13 of the crankshaft. Since it is the fluid is preferably a lubricating oil, the Channel 6 ends freely in the outer space of the crankshaft.

Two independent oil channels are thus integrated in the crankshaft, to separate oil from the bearings and control valves 7, 14 to forward. The oil can go through the main bearings the bearing sleeve as well as a cast tube in the Crankshaft are fed to the front of the crankshaft. The local connections for the sleeves and the control valves are drilled for every consumer. The oil supply at the front of the crankshaft when entering the crankshaft only needs a simple sealing ring be sealed. For easy installation and Manufacturing the control valves 7 and 14 are preferred arranged in two longitudinal bores in the crankshaft.

The control valve 7, 14 is a two-sided piston arrangement with return spring. The valve consists of a straight tube with an opening between the pistons. The tube improved the arrangement of the valve in the crankshaft. For fixation A small spigot can be inserted vertically into the tube Cheek, which is the twisting of the tube in the bore prevented. The two pistons of a valve are connected by a rod. They are welded, brazed or punched.

The control of the oil flow to the control valves 7, 14 is preferably carried out via electromagnetic valves. The oil pressure is increased by an oil pump or a dual oil pump.

In Figure 2, the sleeve 10 is shown in perspective. To A radially extending flange of the sleeve can be seen 10, which the semicircular recess 8 as well its inside has a sawtooth shape with asymmetrical Has chambers 9. The recess 8 can on a Side have a ramp 16, which over a certain length distributes a constant thinning of the flange to the recess 8 includes. Through the ramp 16 against one another the locking element pressing the flange upon rotation the sleeve 10 axially in over a longer area Move towards the recess so that it is not on one Must snap into place at the moment when the recess 8 faces exactly.

FIG. 3 shows a top view from viewing direction III of FIG 1. Here is a piece of the flange of the sleeve 10 as well to see a partial section through the shaft journal 11. To recognize is in particular that the fluid supply channel 12, which is formed in the shaft journal 11 to a chamber 9 on the Inside of the sleeve 10 leads. When introducing a fluid such as, in particular, an oil via the feed channel 12 is due the shape of the chamber 9 in the circumferential direction is asymmetrical Generates pressure which results in a net torque (in FIG 3 counterclockwise, cf. Arrow) leads. If the Sleeve is unlocked, this torque can be an active one Rotation of the sleeve 10 about the crank pin 11 are generated.

The position of the fluid drainage channel is also shown in broken lines in FIG 6 indicated. This can be done via this channel 6 the supply channel 12 to a chamber 9 supplied fluid a further rotation of the sleeve in the direction of the arrow.

Claims (7)

1. Crankshaft for a reciprocating-piston internal combustion engine, containing a crankpin (11) and an eccentric sleeve (10) rotatably mounted with its cylindrical inner face on the crankpin (11), the sleeve (10) having at least one locking recess (8), into which a locking element (7, 14) can engage, in order to cancel the rotatability of the sleeve (10) about the crankpin (11), and the locking element (7, 14) being arranged on the crankshaft, and the crankshaft containing activation means (2, 4, 5, 15) for actuating the locking element, and a crankshaft having at least one fluid supply duct (3, 12) leading to the outer face of the crankpin (11), characterized in that the sleeve (10) is shaped on its inner face in such a way that the supply of a fluid via the fluid supply duct generates on the sleeve a torque about the crankpin.
2. Crankshaft according to Claim 1, characterized in that the locking elements (7, 14) can be actuated hydraulically and the activation means are supply lines (2, 4, 5, 15) for a hydraulic medium.
3. Crankshaft according to Claim 2, characterized in that the locking elements (7, 14) are prestressed mechanically into a position of rest and can be moved out of the position of rest when a hydraulic pressure is applied.
4. Crankshaft according to one of Claims 1 to 3, characterized in that the sleeve (10) has a radial sawtooth shape peripherally on its inner face.
5. Crankshaft according to one of Claims 1 to 4, characterized in that it has a fluid outflow duct (6), via which fluid which has been supplied to the inner face of the sleeve via the fluid supply duct (3, 12) can be discharged.
6. Crankshaft according to at least one of Claims 1 to 5, characterized in that it contains two locking elements (7, 14) which are arranged on the crankpin (11) so as to be offset at 180° and which can engage alternately into a locking recess (8) on the sleeve (10).
7. Crankshaft according to at least one of Claims 1 to 6, characterized in that it has an inner bore which runs along the crankshaft and in which are arranged separate ducts (2, 3, 4) for supply lines to the locking elements (7, 14), for a fluid supply duct (12) or the like.

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