DE102009048172A1 - Piston for internal combustion engine of motor vehicle, has switchable valve device arranged at inner side at piston skirt and adjusting volume of pressurized medium in chamber, where valve device is designed as shut-off valve - Google Patents

Abstract

The piston (10) has piston parts movably coupled relative to each other by formation of a chamber, where the chamber is variable in volume and impinged with pressurized medium i.e. pressurized oil. A switchable valve device (20) is arranged at an inner side at a piston skirt (22) and adjusts volume of the pressurized medium in the chamber. The valve device is designed as a shut-off valve, where the pressurized medium is drained from the chamber over a cooling duct. The valve device is switchable between two operating conditions.

Description

The invention relates to a piston for a variable compression ratio internal combustion engine according to the preamble of claim 1.

Such pistons are well known. The DE 27 19 043 discloses a piston for a variable compression ratio internal combustion engine having an inner portion and an outer portion telescopically supported thereon that are relatively movable during working movement of the piston. In addition, a first and second control chamber is provided, whose volume is variable depending on the relative movement and of an incompressible amount of liquid present in them.

The US 2742027 shows a piston for an internal combustion engine having an upper part and parts which are able to perform a limited relative movement and form a first chamber and a second chamber, wherein the volumes of the first and the second chamber are variable.

From the DE 33 32 358 A1 a piston is known for internal combustion engines, wherein a piston head is provided, which is at least partially formed by a respect to the rest of the piston movable part, and wherein the part at each compression stroke, when the pressure in the associated cylinder reaches a predetermined value of a first position is movable to a second position in which the volume of the combustion chamber is increased. The second part maintains the second position until a predetermined pressure is reached on each expansion stroke and the part returns to its first position.

The DE 36 37 196 A1 describes an oil-cooled piston with a combustion recess for an internal combustion engine, wherein the bottom of the combustion chamber is formed by a heat-insulating adjusting body, which is axially adjustable relative to the piston body, and arranged between the adjusting body and the piston body two oil-filled chambers with variable volume, from the piston cooling system Be supplied with oil. The piston is assembled in three parts from oil-cooled ring carrier, adjusting body and lower piston part.

The DE 48 47 133 discloses a piston that allows a change in the compression ratio of an internal combustion engine, wherein the piston consists of two main parts that are movable relative to each other.

All of the pistons shown by the cited documents have the disadvantage that a volume of compression which can be changed by them only sets as a function of a combustion chamber pressure. An independent state for setting a compression ratio is not possible, whereby the advantages of a variable compression ratio can not be applied to all operating ranges of the internal combustion engine.

The DE 34 16 346 C2 discloses a piston with variable compression height for internal combustion engines, consisting of a hinged to the piston pin shaft, an inner part, a slidably held the piston head outer part and a first and a second interconnected chamber whose volumes are in a relative movement between the inner and outer part reciprocally changing by the first chamber with an incompressible, supplied from the outside via the first chamber and be discharged oil, wherein the first chamber, the oil is supplied via a control valve. In the flow direction of the oil, a pressure regulating valve and a check valve are successively arranged, wherein the pressure regulating valve keeps the pressure after the pressure regulating valve constant. In addition, it can be provided that the pressure regulating valve is integrated into the piston pin, wherein it comprises a slide displaceably mounted in the piston pin and spring-biased. The structure of this pressure control valve in the piston pin represents a switching facial expressions, which is very complex and very difficult to access, which means a complex structure and thus a complex production of the piston. This results in high costs for the piston.

From the DE 40 38 549 C1 a device for controlling the oil pressure in a control chamber of a reciprocating piston with variable compression height of internal combustion engines is known, wherein the control chamber between an inner piston connected to a connecting rod and an outer piston held displaceably formed on this and connected via a channel to an engine oil pump in the lubricating oil circuit of the internal combustion engine is, and wherein for adjusting the oil pressure in the control chamber, a pressure regulating valve is provided, which is controllable in dependence on operating parameters. The engine oil pump forms with the pressure control valve a controllable pump unit, from which the oil pressure in the control chamber is adjustable.

This device has the disadvantage that it requires a large amount of space. In addition, it is a massive intervention in the oil supply of main bearings and connecting rod bearings of the internal combustion engine.

It is therefore an object of the present invention to provide a piston of the type mentioned, which has low cost and low space requirement.

This object is achieved by a piston for a variable compression ratio having internal combustion engine with the features of claim 1. Advantageous embodiments with expedient and non-trivial developments of the invention are specified in the dependent claims.

An inventive piston for a changeable compression ratio having internal combustion engine with a first piston part and a second piston part, which are coupled to form at least a first, with a pressure medium, in particular a pressurized fluid, acted upon and variable in volume chamber relative to each other movable, characterized characterized in that at least one switchable valve device is arranged on the inside on a piston skirt of the piston, by means of which a volume of the pressure medium in the first chamber is adjustable.

The piston according to the invention has the advantage that, due to the switchable valve device, at least two compression ratios of the internal combustion engine can be represented by at least two different positions of the piston parts, independently of a prevailing combustion chamber pressure. Thus, the advantages of the variable compression ratio of the internal combustion engine in all operating phases derselbigen be used because the setting of the compression ratio of the current operating point of the internal combustion engine is decoupled.

The use of at least one switchable valve device, the setting of the compression ratio is also extremely inexpensive to represent, which has a positive effect on the total cost of the internal combustion engine.

The arrangement of the valve device on the inside of the piston skirt also provides the advantage that the piston itself and devices for generating pressure and for supplying the piston with the pressure medium require an extremely small installation space. The given space conditions are thus used optimally, which avoids package problems in a particularly space-critical area such as the engine compartment.

Furthermore, the inventive arrangement of the switchable valve device allows a particularly good accessibility to this, which is particularly advantageous in a service case, ie when replacing or repairing the switchable valve device. This is accompanied by a faster repair or a faster replacement, which keeps the repair costs in a small frame.

The switchable valve device can be arranged, for example, in the flow direction of the pressure medium in front of the chamber. This means that the chamber, the pressure medium via the switchable valve device can be fed. However, it can also be provided that the switchable valve device is arranged after the first chamber. In any case, the volume of the pressure medium in the first chamber by means of the valve device is adjustable. Furthermore, it is possible to provide a plurality of switchable valve devices, which are arranged before and / or after the first chamber.

It should be noted at this point that the switchable valve device can therefore be switched between at least two states, which means that it is a non-intrinsically-medium-actuated valve device. The valve device is designed, for example, as a mechanically, electrically or electronically or magnetically switchable switching element and arranged in the manner according to the invention. The arrangement is carried out, for example, at the height of a piston pin of the piston according to the invention, which ensures the described good accessibility and protects the switchable valve device from any disturbing influences from the combustion chamber.

The adjustment of the compression ratio by an adjustment of the piston height thus takes place in the engine operation by the switchable valve device, whereby either with a reduction in the compression ratio, the pressure medium from the first chamber, which is also referred to as a working volume or as a control chamber, passed into a secondary volume or is pressed. With a corresponding increase in the compression ratio and / or when switching off the internal combustion engine, the pressure medium from the secondary volume is passed or pressed into the first chamber.

The piston or the control chamber is supplied, for example via a pressure medium supply, for example in the form of an oil supply to the internal combustion engine, via a supply channel in a connecting rod shank of a connecting rod assigned to the piston.

Compared to the prior art, this means that in particular is not massively intervened in an oil supply of main bearings and / or connecting rod bearings of the internal combustion engine and Thus, the lubrication of the main bearings and the connecting rod bearing is guaranteed safe in all operating phases of the internal combustion engine.

In an advantageous embodiment of the invention it is provided that the valve device is designed as a shut-off valve, by means of which a continuous flow of pressure medium in the first chamber and a volume of the pressure medium in this are adjustable.

This means that constantly pressure medium, such as oil, is promoted and superfluous pressure medium to maintain a certain pressure is controlled and advantageously discharged via a cooling passage of the piston in a crankcase of the internal combustion engine. Thus, a constant Druckmediumskreislauf or lubricating oil circuit and a constant cooling, in particular of the piston, realized, which ensures a safe lubrication of corresponding bearings and optimal heat dissipation from the piston, in all operating phases of the internal combustion engine.

In an advantageous embodiment of the invention, the piston has at least one second, which can be acted upon by the pressure medium and in its volume, in particular as a function of the volume or the volume change of the first chamber, variable chamber, which fluidly coupled to the first chamber via at least one adjustable throttle device is. The adjustable throttle device thus makes it possible to set a mass flow rate of pressure medium through its flow cross section, it being thus possible for the throttle device to be variable in its flow cross section.

This allows an exchange of pressure medium between the first and the second chamber, whereby a pumping of pressure medium between the chambers is realized. This is advantageous in that it allows lubrication and cooling of the piston as well as a damped transition from a set piston height (compression ratio) to another piston height (compression ratio). Thus, a cycle is closed, which avoids thermal overaging of the pressure medium, in particular of the oil.

In a particularly advantageous embodiment of the invention, at least one further chamber is provided in a cavity of the piston pin, which is fluidically coupled at least to the first chamber, and in which a with a spring force of at least one spring element acted upon, slidably held slide is arranged, by means of which Volume of the other chamber is changeable.

This additional chamber thus represents an additional pressure medium volume in the piston pin, which ensures a particularly high dynamics when switching between two piston heights (compression ratios). This switching can thus be done very quickly and within a few crankshaft revolutions, so that the piston height and thus the compression ratio of the internal combustion engine can be adjusted quickly and efficiently to operating point changes of the internal combustion engine. Such operating point changes can result, for example, from a change in a traffic situation in which a motor vehicle with the piston according to the invention or the internal combustion engine with the piston according to the invention is located.

If the piston parts are coupled via at least one spring element, this has the advantage that an automatic spring return from one to another piston height is thereby made possible. Thus, the force of the spring element spends the piston parts relative to each other in a position in which a balance of power with respect to the spring element or its spring force is achieved.

Finally, it can be stated that an internal combustion engine with a variable compression ratio can be produced in a very cost-effective manner by the piston according to the invention, in particular if the internal combustion engine is a V-type internal combustion engine. Especially in such a case, additional, complex engine kinematics are obsolete.

Due to the switchability of the valve device, which thus at least a two-point piston height adjustment is created, a great benefit at the same time low application cost is possible, which reduces the cost of the piston according to the invention and thus the internal combustion engine by a further measure.

At the same time, however, an adjustability of the compression volume is made possible in a wide range, with an adjustment of the compression ratio in the range of 5 inclusive to 6 units can be displayed.

Nevertheless, optimum lubrication and optimum cooling, in particular of the piston crown, are achieved, which reduces the load on the piston.

Further advantages, features and details of the invention will become apparent from the following description of several embodiments and with reference to the drawings. The features mentioned above in the description and Feature combinations as well as the features and feature combinations mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the respectively specified combination but also in other combinations or in isolation without departing from the scope of the invention.

The drawings show in:

1 a schematic cross-sectional view and a schematic longitudinal sectional view of a piston for a variable compression ratio internal combustion engine, wherein two possible positions for a switchable valve means are shown, which is arranged on the inside of a piston skirt of the piston, by means of which a volume of pressure oil in a first chamber of the piston is adjustable;

2 in each case a circuit diagram for setting two different piston heights of the piston according to 1 , whereby two different compression ratios of the internal combustion engine can be represented:

3 a longitudinal sectional view of an alternative embodiment of the piston according to 1 in a first switching position, and

4 a longitudinal sectional view of the piston according to 3 in a second switching position.

The 1 shows a piston 10 for a variable compression ratio internal combustion engine. The piston 10 is also in the 3 and 4 is shown and will be explained in conjunction with these figures. The piston 10 includes a first piston part 12 , as well as a second piston part 14 , the formation of a first, acted upon by a pressure medium in the form of a pressurized oil and variable in volume chamber 16 are coupled relative to each other, wherein between the piston part 12 and the piston part 14 a spring element 18 is provided, by which an automatic spring-return is possible.

To represent a large piston height s _max , the pressure oil is in the first chamber 16 promoted, via a switchable valve device 20 , which on the inside on a piston skirt 22 of the piston 10 is arranged, and by means of which a volume of the pressure oil in the chamber 16 is adjustable. In the 3 is for example by the illustrated position of the piston 10 a compression ratio of ε = 14 of the internal combustion engine can be displayed.

In the switchable valve device 20 this is a shut-off valve, and the chamber 16 it is a Absteuerkammer, so with the piston 10 constantly controlled pressure oil and a cooling channel 24 to dissipate a very good piston cooling in the crankcase of the internal combustion engine. To reduce the piston height and thus to reduce the compression ratio, the pressure oil from the chamber 16 what's promoted in the 4 is shown. The piston height is now only s _min , whereby, for example, a compression ratio of ε = 8 of the internal combustion engine can be displayed.

The piston is fed 10 or the chamber 16 via a feed channel 26 in a connecting rod of the piston 10 assigned connecting rod 28 ,

The piston 10 is there with the connecting rod 28 via a piston pin 30 connected. The piston pin 30 has a cavity 32 on, in the one on the one hand by a bulkhead wall 34 and on the other hand by a along the longitudinal direction of the piston 30 slidably held in the piston slide 36 educated, further chamber 38 is provided, which is variable in its volume, which compared to the 3 with the 4 becomes clear. The slider 36 is doing with the spring force of a spring element 38 acted upon, on the one hand to the slider 36 and on the other hand on a locking ring 40 is supported.

This additional pressure oil volume is a high dynamics of the piston 10 in an adjustment from one piston height to another piston height allows, as the chamber 38 with the chamber 16 is fluidically coupled. This means that with slight pressure fluctuations easily and quickly pressure oil from the chamber 38 in the chamber 16 or vice versa is eligible, which favors the rapid adjustment of two different piston heights.

As in particular on the basis of 1 becomes clear, is the said switchable valve device 20 inside on the piston skirt 22 arranged the piston and that approximately at the height of the piston pin 30 , The variable compression ratio internal combustion engine is, for example, a V-type internal combustion engine, with position 1 of the valve device 20 oriented towards an inside of this V-shape. The entprechend is the opposite position 2 of the valve device 20 oriented to an outer side of the V-shape or the crankcase of the internal combustion engine. This arrangement has an extremely compact design not only of the piston 10 , but also necessary periphery for the supply of the piston 10 with the pressure oil.

In addition, this arrangement allows optimal accessibility for the switchable valve device 20 , It should be noted that several switchable valve devices or hydraulic or fluidic switching element in conjunction with the piston 10 can be used, which in particular on the basis of 2 becomes clear.

In connection with the 3 and 4 be mentioned that in 1 the piston parts 12 and 14 of the piston are not explicitly shown, but are formed in their function analog.

The 2 shows in an upper circuit diagram switching positions corresponding hydraulic switching elements of the piston 10 , whereby a minimum piston height and thus a minimum compression ratio of the internal combustion engine is made possible. Furthermore, the shows 2 in a lower circuit diagram corresponding switching positions of the hydraulic components, whereby a maximum piston height and thus a maximum compression ratio of the internal combustion engine is made possible.

Next to the chamber 16 points the piston 10 a second, pressurizable oil and in volume reciprocal to the volume of the first chamber 16 changeable chamber 16 ' on which with the first chamber 16 via an adjustable throttle device 42 is fluidically coupled. The chamber 16 is supplied with pressurized oil, via a check valve 66 , which has the task to avoid an undesirable and undefined reflux of pressure oil. In addition, the chamber 16 via a valve device, not shown 43 and via a throttle device 48 supplied with pressure oil. The throttle 58 can also be designed as an adjustable throttle device.

Again 2 it can be seen, is through the valve device 44 a flow of pressurized oil into the chamber 16 avoided. There can only be a very low flow of pressurized oil into the chamber 16 via the throttle device 48 happen. On the other hand, the pressure oil from the chamber 16 also via a throttle device 48 ' and via a valve device, not shown 44 ' and a check valve 46 ' dischargeable. The check valve 46 ' prevents unwanted backflow of oil into the chamber 16 ,

The chambers 16 and 16 ' are the pressure oil via hydraulic connections 52 feedable or dischargeable. The chambers 16 and 16 ' are also called working volumes.

The valve device 44 ' allows drainage of a large amount of pressure oil from the chamber 16 , Likewise, the throttle device allows 48 this drain. In summary, this means that on the one hand an inflow of a large amount of pressure oil in the chamber 16 prevents and on the other hand, a drain of a large amount of pressure oil from the chamber 16 is possible. Thus, the chamber 16 acted upon only with a small amount of pressure oil and allows the representation of the low piston height and thus the low compression ratio.

The supply or the discharge of pressure oil via the throttle device 48 respectively. 48 ' ensure a minimum amount of circulation of the pressure oil to counteract thermal aging or even thermal destruction of the pressure oil and to ensure cooling of the piston.

Such a circulation is also due to a further switchable throttle device 42 allows over which the chamber 16 with the other chamber 16 ' is coupled. The throttle device 42 allows pumping between the chambers 16 and 16 ' and thus also avoiding the thermal aging of the pressure oil and ensuring the cooling of the piston 10 , This in the 2 arrangement shown allows a maintenance of the set compression ratio at different pressure conditions in a combustion chamber 50 a cylinder associated with the piston of the internal combustion engine and thus a representation of the desired compression ratio derselbigen in all operating points.

Similarly, the corresponding hydraulic components in the lower circuit diagram are connected to represent a maximum piston height and thus a maximum compression ratio. The valve device 44 now allows an inflow of a large amount of pressure oil into the chamber 16 of the piston 10 while the valve device 44 ' a drain of a large amount of pressure oil from the chamber 16 avoids. This means a high inflow of pressure oil into the chamber 16 and a low outflow of the pressure oil from this. Thus, the maximum compression ratio is also independent of the pressure conditions in the combustion chamber 50 in any operating point of the internal combustion engine 10 adjustable.

The different arrangements of the spring element 18 in the 2 indicate that by the spring element 18 an automatic spring return to a desired initial position of the piston parts 12 and 14 relative to each other, this being dependent on the design of the spring element 18 to realize. this means so that the spring element 18 in terms of itself, the piston parts 12 and 14 either press in the desired starting position or just pull. Such a starting position can be, for example, the minimum or also the maximum piston height or compression volume.

LIST OF REFERENCE NUMBERS

10

piston

12

piston part

14

piston part

16, 16 '

chamber

18

spring element

20

valve means

22

skirt

24

cooling channel

26

feed

28

pleuel

30

piston pin

32

hollow

34

bulkhead

36

pusher

38

chamber

40

circlip

41

spring element

42

throttling device

44, 44 '

valve means

46, 46 '

check valve

48, 48 '

throttling device

50

combustion chamber

52

hydraulic connections

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 2719043 [0002]
• US 2742027 [0003]
• DE 3332358 A1 [0004]
• DE 3637196 A1 [0005]
• DE 4847133 [0006]
• DE 3416346 C2 [0008]
• DE 4038549 C1 [0009]

Claims (9)

Piston ( 10 ) for a variable compression ratio internal combustion engine with a first piston part ( 12 ) and with a second piston part ( 14 ), which at least a first, with a pressure medium, in particular a pressurized fluid, actable and variable in volume chamber ( 16 ) are coupled relative to each other movable, characterized in that at least one switchable valve device ( 20 . 44 . 44 ' ) on the inside on a piston skirt ( 22 ) of the piston ( 10 ) is arranged, by means of which a volume of the pressure medium in the first chamber ( 16 ) is adjustable. Piston ( 10 ) according to claim 1, characterized in that the valve device ( 20 . 44 . 44 ' ) is designed as a shut-off valve, by means of which a continuous pressure medium flow into the first chamber ( 16 ) And a volume of the pressure medium in this are adjustable. Piston ( 10 ) according to one of claims 1 or 2, characterized in that the pressure medium via a cooling channel ( 24 ) from the first chamber ( 16 ) is dissipatable. Piston ( 10 ) according to one of the preceding claims, characterized in that the valve device ( 20 . 44 . 44 ' ) is switchable at least between two operating states. Piston ( 10 ) according to one of the preceding claims, characterized in that the piston ( 10 ) at least one second, acted upon by the pressure medium and variable in volume chamber ( 16 ' ), which communicates with the first chamber ( 16 ) via at least one adjustable throttle device ( 42 ) is fluidically coupled. Piston ( 10 ) according to claim 5, characterized in that the throttle device ( 42 ) on the inside of the piston skirt ( 22 ) of the piston ( 10 ) is arranged. Piston ( 10 ) according to one of the preceding claims, characterized in that at least one further chamber ( 38 ) in a cavity ( 32 ) of a piston pin ( 30 ) of the piston ( 10 ) is provided, which at least with the first chamber ( 16 ) is fluidically coupled. Piston ( 10 ) according to claim 7, characterized in that in the further chamber ( 38 ) with a spring force of at least one spring element ( 41 ), displaceable in the further chamber ( 38 ) held slide ( 36 ) is arranged, by means of which the volume of the further chamber ( 38 ) is changeable. Piston ( 10 ) according to one of the preceding claims, characterized in that the piston parts ( 12 . 14 ) via at least one spring element ( 18 ) are coupled.

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