EP1799987B1 - Piston for a combustion engine, and combustion engine - Google Patents

Abstract

Disclosed is a piston for a combustion engine, comprising a cooling duct with a single inlet port and at least two outlet ports, at least two of which are separated from each other regarding the discharged coolant. Also disclosed is a combustion engine comprising at least one such piston.

Description

Technical area

The invention relates to a piston for an internal combustion engine and an internal combustion engine with a novel piston.

The pistons of internal combustion engines are exposed to high thermal loads during operation. In order to avoid too high temperatures, the pistons can be cooled by suitable measures. This is done essentially by the fact that the respective piston from the side of the crankcase forth with a cooling medium, usually oil, is applied. Such a cooling medium is at least over a certain period in contact with the piston material, so that it can absorb heat from this. By ensuring that the cooling medium which has been warmed up in this way drains off, and also ensures that relatively cool cooling medium flows after, the temperature of the piston can be kept in a safe range.

State of the art

The US 5,595,145 relates to a piston for an internal combustion engine, which has a largely circulating cooling chamber with an inlet opening and two drainage openings, which are interconnected by the cooling space.

From the DE 102 18 653 A1 a piston is known in which a ring carrier is provided with a cooling channel plate, which may have a plurality of flats. The flats can be drilled to form inflows and outflows. Since the formed cooling channel is circumferential, in the case that two drainage holes are provided, they are connected to each other.

This applies equally to the piston according to the EP 1 063 409 A2 , in which two symmetrical inflow openings are provided, of which only one, depending on the orientation during installation of the piston, is used. The remaining inflow opening can be used as a drain opening, but is also connected to the already provided drain opening.

Finally, leave the EP 1 231 374 A2 a piston which has different overhanging areas in areas adjacent to the piston pin bosses. These are acted upon from the side of the piston housing forth with cooling oil, which can flow in sections through so-called passage channels.

Presentation of the invention

The invention has for its object to provide a piston for an internal combustion engine and an internal combustion engine, which is improved in terms of the ability to provide reliable cooling.

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

As a result, the piston has a cooling channel with a single inflow opening and at least two outflow openings. At least two of the discharge openings are separated with respect to the outflowing coolant. This is to be understood that there is no flow connection between them in the region of the discharge openings. On the contrary, the cooling medium, which flows from the inflow opening via a corresponding channel section to a discharge opening which is fluidly separated from other outflow openings, can exit from this outflow opening unhindered. It does not occur that cooling medium flows out of different channel sections through one and the same outlet opening. Rather, each channel section or "sub-channel" at least one "own", so only this channel section associated drain opening. In particular, in the region of the outflow openings, a connection in the form of a preferably small passage can be provided. However, it is not intended that flows through this passage coolant from the one cooling passage portion in the other cooling passage portion or to its drain port. Rather, by appropriate design of the walls in the region of the respective outflow opening, the coolant is directed out of the respective cooling channel section to the respective outflow opening associated with this cooling channel section. As a result, influencing and disturbing the coolant outflow in the respective other cooling channel section is avoided in an advantageous manner. The inflow opening can also be referred to as an inflow, an inflow, an inlet, inlet, inlet or inlet opening. As well could the drain hole also be called just a drain or an outlet.

The measure according to the invention provides the following advantages. The cooling effect depends inter alia on the residence time of the cooling medium in the cooling channel. In particular, the desired cooling effect can be matched to the cooling medium leaving the cooling channel after a certain residence time. According to the invention, this can be ensured particularly well by allowing the coolant jet to escape unhindered at the outflow opening. In contrast to a situation in which two coolant flows combine at a discharge opening and influence one another, an undisturbed discharge of the coolant flow can take place in the piston according to the invention. This improves the cooling effect.

In particular, the cooling of a piston can be improved by the piston according to the invention, in which the cooling channel consists of two sections of unequal length. By the up and down movement of the piston namely creates a pulsed flow in the cooling channel. Thus, the pressure wave of the shorter cooling passage portion can reach the discharge port before the pressure wave of the longer portion, and hinder the leakage of the coolant flow from the longer portion. In this longer section thus creates a longer residence time of the coolant and a deterioration of the cooling. The inventive measure provides an effective remedy in such a situation and in particular allows efficient cooling even in a case in which a cooling channel has two sections of unequal length. In summary, a backflow or turbulence at the outlet of the coolant streams are prevented.

Furthermore, it has been found in investigations that a virtually laminar flow of the coolant, in particular of the cooling oil can be achieved by the measure according to the invention, which is extremely favorable for the heat transfer.

In this context, there is also the advantage that due to the ability to provide unequal length channel sections and yet to provide for efficient cooling, the inlet opening can be arranged off-center. In this case, however, a central arrangement of the outlet openings to the effect that they are located above the piston pin, in particular between the pin bosses and the small connecting rod eye, can be maintained. Such an arrangement is advantageous for the best possible lubrication of the articulated connection between the piston pin and the pin bosses or the connecting rod eye. The two outlet openings can be arranged in particular and advantageously to the left and right of the connecting rod, to provide here for an advantageous lubrication. This advantage can be realized in particular in the case of a coolant jet which runs largely parallel to the piston axis. In contrast, it is known in the art to use an inclined coolant jet, which, depending on the position of the piston in the up-down direction, enters one of two inflow or inlet openings. Even in such a case, the coolant jet is divided into individual channel sections. However, it comes to a much greater extent, up to 20%, to an unused "squirting" of the oil at the dividing rib between the two inlet openings. In contrast, the present invention possible, largely provided parallel to the piston axis coolant jet can be fully used because he, regardless of the up-down movement of the piston, always on the same place can impinge on a flow geometrically optimized dividing rib. Thus, the coolant jet, largely without losses, can be divided into two or more channel sections, which can be of different lengths.

In addition, it should be mentioned that a feature combination which is novel over the prior art and achieves the advantages according to the invention can be seen in that a substantially circumferential cooling channel has at least one inflow opening and at least two outflow openings which are separated from one another with regard to the outflowing coolant. By providing a piston provided with these features, improvements over the prior art can also be achieved. This also applies to a piston whose cooling channel has at least one inflow opening, to which connect at least two channel sections, each with a single, only the respective channel section associated discharge opening. These last described embodiments are to be regarded as the subject matter of the application and can in particular be combined with all the features mentioned above and below.

In addition, the cooling channel of the piston according to the invention is largely encircling. Although it is conceivable that only individual regions of the piston are cooled by the cooling channel designed according to the invention, it is preferable to provide two largely semicircular cooling channel sections. This means that the two outflow openings are arranged adjacent to one another but are separated from one another. As at this In some embodiments, no continuation of the orbiting design results, a cooling channel designed in this way will be described as substantially circumferential.

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

For flow conditions that are particularly efficient in terms of heat transfer, it has proved to be advantageous to provide at least one flow dividing element in the region of the inflow opening. This may be, for example, a rib or a bead, onto which flows the coolant stream supplied, for example, via a nozzle. The flow dividing element divides the coolant flow into the respective channel sections. Since, as mentioned, at least two channel sections each have their "own" discharge opening, an unhindered flow of the coolant can be ensured, and the subsequent flow of coolant is not hindered. The flow dividing element is preferably optimized by flow geometry such that the coolant flow can be divided into the at least two directions largely without turbulence losses. Preferably, the flow dividing element is formed at the inflow such that at best causes gentle changes in direction, and abrupt changes in direction are avoided. As a result, flow losses and turbulence can be largely excluded.

In experiments it has been found that already by the measures described above, a particularly low-loss and efficient in terms of heat transfer coolant flow can be ensured. Another However, improvement can be achieved by the preferred measure, according to which an at least substantially constant cross section is provided in the region of at least one cooling channel section between the inflow opening and the respective outflow opening. As a result, the flow conditions can be further improved.

As mentioned above, the measure according to the invention makes it possible for the cooling channel to have sections of unequal length. It has also been stated that this is advantageous with regard to the use of the supplied coolant jet. This can be achieved in particular by the preferred measure that the inflow opening is provided asymmetrically with respect to drainage openings. This is therefore preferred to allow a coolant jet which is substantially parallel to the piston axis and can be supplied at the entrance with particularly low losses.

By special measures, the piston according to the invention can be improved in addition to the improvement of the cooling with respect to the lubrication of the connection between the piston pin and the piston pin eyes or connecting rod eye. This can be achieved in that at least one outflow opening is directed in the direction of a piston pin eye. In other words, at the outflow opening, a preferably gentle deflection takes place in one direction away from the piston crown, or in the case of an ordinary orientation of the piston "downwards". Therefore, in this preferred embodiment, the exiting coolant jet is directed towards the piston pin and can provide beneficial lubrication. Also at this point can advantageously the desired deflection at the Drain opening so gently and without abrupt changes in direction done that the outlet of the coolant flow is largely unhindered and turbulence.

It is further preferred to provide at least one outflow opening in a region between the piston pin bosses, although usually offset to the edge. In this way, with regard to a particularly efficient lubrication of the piston pin, a favorable steering of the coolant jet to the areas to be lubricated can take place.

Preferably, the piston according to the invention is further combined with a piston pin and a connecting rod. With such a combination, particularly favorable lubrication conditions could be ascertained on the piston pin if at least one outflow opening is located in a region between a piston pin boss and the connecting rod eye, but typically at an edge of the piston. As a result, both the connection between the piston pin and the piston pin boss and the connection to the connecting rod eye can be efficiently lubricated by the exiting coolant flow.

In principle, the piston according to the invention presents itself as being capable of being used independently. However, it develops its advantages in particular in the state in which it is installed in an internal combustion engine. In this respect, an internal combustion engine with at least one such piston is considered as the subject of the application.

For the internal combustion engine designed in this way according to the invention, it is preferred for the efficient use of a coolant jet that it be a device for generating a coolant jet which is substantially parallel to the piston axis. By means of such a coolant jet, which can be used advantageously in a piston according to the invention with an asymmetrically provided inflow opening, significantly lower losses result at the inflow opening than is the case for the arrangements with tilted coolant jet known in the prior art. Although it is advantageous, as mentioned above, when the coolant jet is substantially parallel to the piston axis, this is not absolutely necessary. Rather, the coolant jet can also run in any manner obliquely or inclined to the piston axis.

Brief description of the drawings

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

Show it:

Fig. 1

schematically the cooling channel of the piston according to the invention and the flow generated therein;

Fig. 2

the underside of a piston according to the invention;

Fig. 3

a sectional view of the piston according to the invention in the region of the inflow opening; and

Fig. 4

a sectional view of a piston in the region of the discharge openings.

Detailed description of a preferred embodiment of the invention

Fig. 1 shows schematically the cooling channel 10 of the piston according to the invention. This has essentially two semicircular cooling duct sections 12.1 and 12.2. The coolant flows into the cooling channel 10 through a single inlet opening 14, at which the coolant flow is divided by a flow dividing element 16, preferably in the form of a rib or a bead, into the two partial flows in the cooling channel sections 12.1 and 12.2. The flow dividing element 16 is optimized in terms of flow such that no abrupt but gentle changes in direction take place, and the flow losses and turbulences remain low. The coolant flow leaves the respective cooling channel section 12.1 or 12.2 by their own separate, only the respective cooling channel section associated drain opening 18.1 and 18.2. In the region of the transition between the respective cooling channel section 12 and the drain opening 18, the walls required for the deflection are also designed to be so harmonious and optimized in terms of flow geometry that no abrupt changes in direction and turbulence occur. Rather, the coolant flow can escape from the respective outflow opening 18 largely unhindered. In particular, the two coolant streams do not interfere with each other due to the fluidic separation at the outlet. In terms of Fig. 1 It is understood that the representation is highly schematic, and usually neither the inflow nor the outflow "to the side" to or from the cooling channel 10 takes place. Rather, the cooling channel 10 is formed in a plane substantially perpendicular to the piston axis. The inflow and / or outflow is largely parallel to the Piston axis, ie from the bottom of the piston ago. This is in the schematic representation of Fig. 1 not recognizable, but goes out Fig. 2 out.

Fig. 2 shows a piston 20 according to the invention from the underside, so that the one inflow opening 14 and the two discharge openings 18 can be seen. Approximately in the region of the center of the inflow opening 14 is the flow dividing element 16, which is in the form of a rib or bead. By flowing against the flow divider element 16 with the coolant jet, this is partially in the one 12.1 and the other cooling duct section 12.2 (see. Fig. 1 ). According to Fig. 2 These sections 12 each extend approximately semicircular starting from the inflow opening 14 in the area above the in Fig. 2 to be recognized pin bosses 22. On the opposite side, the cooling channel sections 12 each have their own drain opening 18. In the region of the respective outflow opening 18, a deflection takes place "downwards", that is to say according to the illustration of FIG Fig. 2 in the direction of the viewer. In the installed state of the piston is located in the piston pin bosses 22 a piston pin, and between the piston pin eyes the connecting rod eye. The deflected in the direction of the piston pin coolant can be used advantageously for lubricating the connections between the piston pin and the piston pin bosses and the connecting rod. In this context results from Fig. 2 Furthermore, that the "area between the piston pin eyes" is understood to mean the approximately strip-shaped area between the inflow opening 14 and the outflow opening 18.2. In this area, in particular on an edge of the piston, in the embodiment shown, at least the drain opening 18. 2 is located, so that the coolant jet issuing therefrom at least partially reaches the piston pin (not shown) inserted in the piston pin bosses 22.

In Fig. 2 It can also be seen that the inflow opening 14 is provided asymmetrically with respect to the outflow openings 18, and consequently that the cooling channel section is in the same direction as in FIG Fig. 1 left drain opening 18.1 is shorter than the other cooling passage section. However, due to the fluidically separated outflow openings, an unfavorable obstruction of the outflow from the longer cooling passage section can be avoided by a pressure wave which would first reach a common outflow opening from the side of the shorter cooling passage section. However, the inflow opening 14 may also be arranged centrally between the piston pin bosses 22. Likewise, she may, unlike in Fig. 2 shown further provided offset in the direction of the piston pin bosses 22.

Fig. 3 shows in a radial section of the piston 10, the two cooling duct sections 12.1 and 12.2. In the region of the common inflow opening 14, the flow dividing element 16 can be seen. Out Fig. 3 also shows that the cross section of the cooling channel sections 12.1, 12.2 is at least substantially constant over the extent of the respective section, so that the favorable and largely unhindered flow of the coolant is supported. The cross section remains constant, in particular starting from the point at which the flow dividing element 16 is inclined relative to the respective cooling channel section 12.1 or 12.2. In the embodiment of Fig. 3 It can also be seen that the inflow opening 14 is off-center. This results from the fact that in the representation of Fig. 3 the piston is twisted slightly to the right, so that the inner surface of the left piston pin eye 22 can be seen.

In contrast, goes from the sectional view of Fig. 4 indicates that it is a view perpendicular to a (imaginary) piston pin axis. In Fig. 4 It can be seen that in this view, the two drain holes 18.1 and 18.2 are symmetrical to each other, while from the comparison with the Fig. 3 shows that the inflow opening is provided asymmetrically. In Fig. 4 It can also be seen that the two outlet openings 18.1 and 18.2 are indeed connected to each other by a small passage 24. The deflection of the respective coolant flow, however, takes place by inclined walls 26 such that the coolant flow is at least largely exclusively by only one, namely the respective cooling channel section 12.1 and 12.2 associated drain port 18.1 and 18.2, and no unfavorable, mutual interference occurs. Overall, due to the harmonious design of the inclined and slightly concave walls 26, a fluidically favorable deflection of the respective coolant flow down, in the area between the piston pin bosses 22, to provide in the installed state for a favorable lubrication of the piston pin. Furthermore, unlike in Fig. 4 shown, the walls 26 may be connected to the provided below the passage 24 provided "nose" 26. In this case, the drainage holes 18.1 and 18.2 are completely separated from each other. This can, as already in the embodiment of Fig. 4 the case is no coolant from one side to the other, and there is no impairment of the coolant outflow at the respective outflow opening 18.1 and 18.2.

Claims (9)

1. Piston (20) for an internal combustion engine, which piston (20) has a largely circular cooling duct (10) with a single inlet port (14) and at least two outlet ports (18), of which at least two (18.1, 18.2) are completely separated from one another with respect to the outflowing coolant.
2. Piston according to claim 1, characterised in that at least one flow-dividing element (16) is provided in the region of the inlet port (14).
3. Piston according to claim 1 or 2, characterised in that an at least largely constant cross-section is provided in the region of at least one cooling duct section (12.1, 12.2) between the inlet port (14) and the particular outlet port (18.1, 18.2).
4. Piston according to one of the preceding claims, characterised in that the inlet port (14) is provided asymmetrically with respect to the outlet ports (18).
5. Piston according to one of the preceding claims, characterised in that at least one outlet port (18) is directed in the direction of a gudgeon pin.
6. Piston according to one of the preceding claims, characterised in that at least one outlet port (18) is arranged in a region between gudgeon-pin bosses (22).
7. Piston according to one of the preceding claims, characterised in that the latter is combined with a gudgeon pin and a connecting rod, and at least one outlet port (18) is provided in a region between a gudgeon-pin boss (22) and a connecting-rod boss.
8. Internal combustion engine having at least one piston according to one of the preceding claims.
9. Internal combustion engine according to claim 8, characterised in that the latter has a device for producing a coolant jet which runs largely parallel to the piston axis.

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