EP1815122B1 - Piston for an internal combustion engine and combination of a piston provided with an oil injection device - Google Patents

Description

Technical area

The invention relates to a piston for an internal combustion engine according to the preamble of claim 1 and a combination of such a piston with an oil injection arrangement.

Especially in the field of diesel engines, the development in recent years increasingly in the direction of increased power density. For this purpose, especially fast-running, supercharged diesel engines are provided. The increase in power leads to increased temperatures at the piston and higher mechanical loads due to the increasing ignition pressure. In view of these load increases, an increase in the hot strength of the piston alloys has hitherto been provided primarily. However, the use of aluminum alloys in particular is thermally limited, since the elements added to increase the heat resistance, in particular nickel and copper, lead to a lowering of the melting temperature. Other measures to increase the heat resistance of aluminum pistons consist in the introduction of reinforcements, for example, by remelting, alloying, introduction of metallic or ceramic fibers, or of dispersion materials. Furthermore, it is basically possible to produce pistons from composite materials. The previously known solutions have the disadvantage of high production costs.

State of the art

The invention is based on a prior art in the form of a piston with a cooling channel, which is known as Vorbenutzungsgegenstand. Known cooling channels may have different cross-sectional shapes and particular configurations, such as e.g. have a wave-shaped course.

From the US 5,081,959 a piston is known which has no combustion bowl. The piston is formed with two or more separate cooling channels, which are filled by an inclined nozzle, wherein holes for an oil supply in the cooling channels are arranged obliquely according to the jet direction.

From the JP 61-144242 Also, a piston is known, which has two separate cooling channels, wherein two inclined nozzles are provided for an oil supply and holes for an oil supply in the cooling channels are arranged obliquely in accordance with the beam direction.

Presentation of the invention

The invention has for its object to provide with simple means improved in terms of cooling effect piston and a populated arrangement with a cooling channel.

The solution to this problem is achieved by the piston described in claim 1.

Consequently, the piston according to the invention has two or more cooling channels, of which at least two are at different levels with respect to the height along the piston axis and / or in the radial direction.

Essentially, the basic idea of the invention is to provide a plurality of cooling channels, which run in different zones of the piston and thus bring about efficient cooling. In particular, this can be used to lower the temperatures in the entire piston without the hitherto chosen, complex measures being required. As to the arrangement "at different levels", it is meant to mean a superimposed and / or juxtaposed arrangement of self-contained cooling channels. In this regard, the teaching described herein differs from known cooling channels, which may have a wave-like course, and in which, accordingly, individual, comparatively short sections are at different levels. Furthermore, this difference exists with respect to cooling channels, which may have an annular section and one of which branches off, inclined section. Such sections are not at different levels insofar as they are directly connected. In particular, in such cooling channels no separate sections are provided in such a way that they can be seen as a separate openings in a sectional view containing the axis. Rather, one recognizes the connection between the different sections in the mentioned sectional view.

In contrast, the invention provides that, for example, cooling channels, which are located along the piston axis at different (axial) level, are delimited from each other in the region of the shortest connection between two such channels by piston material. However, they could be fluidly connected by a suitable, in the broadest sense helical connection. In addition, the connection between two such cooling duct sections can also be effected by connecting openings or bores extending substantially parallel to the piston axis. this applies In particular, when the two cooling duct sections are only in the direction of the piston axis, but not in the radial direction at different levels.

Two cooling channels extending in the radial direction, i. Starting from the piston axis to the piston skirt out, at different levels, so radially further outward or further inside, can also be connected by a largely helical connection or a largely straight connection opening or bore. Since the cooling duct sections are at radially different levels, such a connecting opening or bore would be inclined in a suitable manner with respect to the piston axis. If a cooling channel has at least two sections which, as described, are at different levels, the filling can be carried out such that the oil is brought into the upper channel, for example by means of a nozzle, and from there flows into the lower channel and finally exits ,

The measures according to the invention make it possible to produce an optimized cooling effect by means of a suitable, still comparatively simple design of one or more cooling channels. Namely, the cooling channels can be laid in the zones which are particularly exposed to temperature. There can be ensured by the cooling channels a favorable lowering of the temperature of the piston.

As a further advantage should be mentioned that the piston must be changed by the formation of multiple cooling channels in such a small extent that advantageously existing casting facilities can be used. For example, those special casting devices that are required for the introduction of reinforcing fibers can also be used. This also results in a particularly good economy of the piston according to the invention.

At least one inflow and / or outflow runs essentially parallel to the piston axis. Preferably, all inflows and / or outflows are formed parallel to the piston axis. Such inflows and / or outflows can be produced by casting cores or similar methods by means of conventional casting technology. This allows a cost-effective production. However, it is also conceivable to produce inflows and / or outflows subsequently by drilling or similar production measures.

The piston is preferably made of aluminum or an aluminum alloy, and is preferably installed in a diesel engine, preferably a direct-injection engine. Reinforcements, for example by remelting, alloying, introduction of metallic or ceramic fibers, or of dispersion materials can also be incorporated in the pistons.

Advantageous developments of the piston according to the invention are described in the further claims.

It is advantageous if the individual cooling channels have fluidically separate inflows and / or outflows. In the area of the inflow, this offers the advantage that, as explained in more detail below, either the oil pressure for the respective cooling channel can be adjusted separately, or by a slanted nozzle, the filling can be done by a single nozzle, and at the same time each cooling channel can be separated and reliably supplied with coolant. In the area of the outflow, the fluidic separation offers the advantage that the coolant can flow away unhindered and does not hinder the subsequent flow of colder coolant.

For the arrangement of the tributaries, insofar as these are provided separately, it is presently preferred that all tributaries, in particular two tributaries in the provision of two separate cooling channels, are located on the counter-pressure side of the piston. An envisaged second cooling nozzle namely requires an additional recess on the piston skirt, or a widening of an existing recess becomes necessary. Under these circumstances, the arrangement of both flows on the counter-pressure side has proven to be advantageous. However, it is also conceivable and may be preferred in certain applications that both inflows are arranged on the pressure side, or in each case an inflow to the pressure and an inflow is arranged on the counter-pressure side, which means a "cross-arrangement". A "crosswise" arrangement may be advantageous, for example due to fastening considerations.

For separate inflows and / or outflows, it has proved to be advantageous to arrange them in different axial and / or radial and / or circumferential directions. Such an axial displacement means that an inlet opening for a "higher" cooling channel or cooling channel section is accordingly at a higher level. As a result, a not always desirable tubular inlet can be avoided in a higher range. By a radially separate arrangement of inflows and / or outflows, the available piston material can be used in a favorable manner for the formation of inflows and / or outflows. This applies in the same way in the event that the inflows and / or outflows are arranged offset in the circumferential direction alternatively or in addition to the above measures.

In experiments, it has been found that a particularly good cooling effect can be achieved in an embodiment in which, in the case of a piston with a combustion chamber recess, at least one cooling channel is provided in the area radially adjacent to the combustion chamber recess. In other words, this is a cooling channel in a "upper" with respect to the piston axis, located in the vicinity of the piston crown area.

Optionally, in addition to this, it has proved to be advantageous to provide at least one cooling channel in a region axially below the combustion chamber trough. This cooling channel can be arranged, for example, in the region below an outer edge of the combustion bowl.

The piston of the invention unfolds in terms of the improved cooling effect already as such its advantages. However, there are particularly favorable embodiments in combination with advantageous oil injection arrangements. Consequently, such a combination is to be regarded as an object of the present invention.

In this case, it is preferred that the oil injection arrangement has at least two nozzles. In this way, the respective nozzle for the injection of coolant, in particular oil can be adjusted in the respective cooling channel.

Manufacturing advantages are obtained when the nozzles are provided on opposite sides.

In this context, it is currently preferred that the nozzle which is provided for the injection of coolant into a cooling channel in the region of the piston head, a higher oil pressure than other nozzles. As a result, the amount of coolant, in particular of the oil can be reduced in an advantageous manner.

As an alternative to the embodiment described above, however, it is conceivable for the piston to be combined with an oil injection arrangement which has a single nozzle. This results in a particularly simple structure.

In order nevertheless to achieve a separate filling of two or more cooling channels, a preferred embodiment is that the one nozzle provided has two or more outlet channels.

Alternatively, a simple structure can be realized by a single nozzle is arranged obliquely so that the coolant jet is inclined, so that this, depending on the position of the piston, enters one or more different cooling channels. Due to the oblique formation of a coolant jet, the coolant can thus, for example, in different positions of the piston between the top and bottom dead center, i. in the direction of the piston axis, entering different inlet openings, which are located in the radial and / or circumferential direction at different locations. In other words, different cooling channels can be filled in different positions of the piston. Alternatively, it is conceivable that the coolant jet enters into a cooling channel only in one position, for example at bottom dead center, and in another position, for example at top dead center, the coolant jet strikes the piston crown and cools it. A second cooling channel can be filled by its own nozzle.

Brief description of the drawings

Fig. 1

eine Schnittdarstellung des erfindungsgemäßen Kolbens mit einer Öleinspritzanordnung;

Fig. 2

eine Darstellung der inneren Ausgestaltung des erfindungsgemäßen Kolbens;

Fig. 3

die in Fig. 1 gezeigte Kombination von einer Unterseite aus betrachtet;

Fig. 4

eine Schnittdarstellung einer zweiten Ausführungsform eines Kolbens mit einer Öleinspritzdüse; und

Fig. 5

eine weitere Schnittdarstellung des in Fig. 4 gezeigten Kolbens.

Hereinafter, an embodiment of the invention shown by way of example in the drawings will be explained in more detail. Show it:

Fig. 1

a sectional view of the piston according to the invention with an oil injection assembly;

Fig. 2

a representation of the internal configuration of the piston according to the invention;

Fig. 3

in the Fig. 1 shown combination viewed from a bottom;

Fig. 4

a sectional view of a second embodiment of a piston with an oil injection nozzle; and

Fig. 5

another sectional view of the in Fig. 4 shown piston.

Detailed description of a preferred embodiment of the invention

As in Fig. 1 it can be seen, the piston 10 according to the invention, which may be made of aluminum or an aluminum alloy, in particular cast, generally a combustion bowl 12, which may be ω-shaped, a plurality of annular grooves 14 and two (it is only one recognizable) piston pin bosses 16 on. The illustrated embodiment of the piston according to the invention along the (not shown) piston axis, which in accordance with Fig. 1 extends in the vertical direction, two cooling channels 18, 20. The cooling channels can, as in Fig. 1 to recognize, have a substantially circular cross-section. A first cooling channel 18 is located in a region "next to" the combustion chamber trough and in the axial direction to comparatively high level, in particular a short distance below the piston crown 22. In that regard, it is referred to below as the bottom cooling channel 18.

According to the invention, a second cooling channel 20 is provided at a level below the combustion chamber trough 12 and the bottom cooling channel 18. This cooling channel is referred to below as a hollow cooling channel 20. It is not only, as mentioned, with respect to the height in the direction of the piston axis at a lower level, but is also formed at a radially inner position. At this point, this well cooling channel 20 can provide particularly efficient for the cooling of the hot zones between the combustion bowl 12 and the piston pin 16.

The cooling channels 18, 20 are formed with inflows 32, 36 for a supply of coolant. The inflows 32, 36 are substantially parallel to the axis of the piston 10th

As in Fig. 1 can be seen, the supply of coolant, in particular cooling oil, in the embodiment shown by two separate nozzles 24, 26. In the embodiment shown, the two nozzles are arranged on opposite sides of the piston pin (not shown) which is mounted in the piston pin 16 is. They are thus arranged on the pressure and the counterpressure side, although for other applications it is presently preferred to arrange both nozzles on the counterpressure side. As can be seen, both nozzles produce an approximately vertically upwardly directed coolant jet 28 or 30, which enters the respective inflow 32, 36 of the cooling channel 18 and 20, respectively. At an approximately opposite point, as shown and explained in more detail below, in each case a drain opening is provided.

In Fig. 2 is complementary to the inner workings of the Fig. 1 Detected piston 10 can be seen. In the shown Embodiment, the two cooling channels 18 and 20 are annular and provided at a constant level. Here also the cross section does not change. However, it could also be changeable, in particular wave-shaped. In Fig. 2 It can be seen particularly well that the trough cooling channel 20 is provided not only at a lower level but radially within the bottom cooling channel 18. As a result, the space required for the inflow 32 of the floor cooling channel 18 is made available. As in Fig. 2 is clearly visible, both the inflows 32, 36 and the outflows 34, 38 are aligned substantially parallel to the piston axis.

In Fig. 3 In addition to the details shown above, both drainage openings are shown. The opening for the drain 34 for the radially inner trough cooling channel is in the embodiment shown opposite the inflow 36. This also applies to the drain 38 for the bottom cooling channel 18, which is located opposite to its inflow 32.

Fig. 4 shows a sectional view of a second embodiment of a piston 10, in which two cooling channel sections 40, 42 are provided, which are in terms of height along the piston axis at different levels. In contrast, they are in the embodiment shown in the radial direction at the same level. These are cooling duct sections 40, 42, in contrast to separate cooling ducts, as provided in the first embodiment, because in the second embodiment, a connection 44 is present. This connection consists essentially of a connecting channel extending approximately parallel to the piston axis, which could also be referred to as a bore. As in Fig. 4 can be seen on the right side, a nozzle 24 is provided, which brings a coolant jet 30 in the region of the upper cooling channel section 42. So that the coolant jet 30th In a sense, "through" the lower cooling passage section 40 can reach into the upper cooling passage section 42, a bore or an approximately parallel to the piston axis extending connection 52 is provided between them. The connection 52 and the inflow 54 are substantially parallel to the piston axis. The injected oil flows through the upper cooling channel 42 and can pass through the connection 44, which is provided in the embodiment shown approximately opposite to the inflow opening, into the lower cooling channel. The connection of the lower cooling passage 40 to the lower side is closed by a shutter 46 so that the coolant flows through the lower cooling passage portion 40 and cools the surrounding portions of the piston. The exit of the coolant takes place near the entrance.

This is supplementary in Fig. 5 to recognize. Fig. 5 shows a section of the piston 10 of Fig. 4 in the area of the coolant inlet. As can be seen, the coolant jet 30 reaches into the area of the upper cooling passage section 42. In the embodiment shown, where the coolant jet 30 impinges on the upper boundary of the cooling passage section 42, a kind of elevation or rib 48 is provided which separates the coolant jet 30 in accordance with Fig. 5 left and right half of the cooling channel section 42 divides. On the opposite side of the coolant, as shown Fig. 4 can be seen through the opening 44 in the lower cooling passage portion 40 and can in the vicinity of the coolant inlet, as in Fig. 5 can be seen through a widened compared to the compound 52, provided on the underside of the coolant section 40 opening 50 emerge.

Claims (10)

1. Piston (10) for an internal combustion engine, having at least two cooling channels (18, 20), of which at least two (18, 20) are located at different levels with respect to the height along the piston axis and/or in radial direction, characterised in that at least one feed (32, 36) and/or discharge (38, 34) runs parallel to the piston axis, and in that the individual cooling channels (18, 20) have feeds (32, 36) and/or discharges (38, 34) which are separated in terms of flow technology and which are located at different points in peripheral direction.
2. Piston according to claim 1, characterised in that two feeds are provided on the counter-pressure side of the piston (10).
3. Piston according to claim 1 or 2, characterised in that the feeds (32, 36) and/or discharges (38, 34) are located at different points in axial and/or radial direction.
4. Piston according to one of the preceding claims, characterised in that the piston (10) has a combustion chamber pan (12), and at least one cooling channel (18) or cooling channel section is provided radially next to the combustion chamber pan (12).
5. Piston according to one of the preceding claims, characterised in that the piston (10) has a combustion chamber pan (12), and at least one cooling channel (20) or cooling channel section is located axially below the combustion chamber pan (12).
6. Piston according to one of the preceding claims in combination with a coolant injection arrangement.
7. Piston according to claim 6, characterised in that the coolant injection arrangement has at least two nozzles (24, 26).
8. Piston according to claim 7, characterised in that the nozzles (24, 26) are provided on opposite sides.
9. Piston according to claim 7 or 8, characterised in that the nozzle (26), which is provided for injection of coolant into a cooling channel (18) provided radially next to the combustion chamber pan (12), produces a higher oil pressure than other nozzles.
10. Piston according to claim 6, characterised in that the coolant injection arrangement has a single nozzle.

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