EP0838587B1 - Lightened piston - Google Patents

Description

The invention relates to a piston for a Internal combustion engine according to the preamble of claim 1.

Such a piston is described in EP 0 385 390 A1 and typically has shaft surfaces that are not in all areas along the height of the piston skirt completely cylindrical and circular in cross-section are trained. Here, the piston skirt is in one upper area largely cylindrical to the space for the combustion taking place in an internal combustion engine complete. To reduce the weight of the piston Pin hubs for receiving the connecting rod pin in the direction of the diameter of the piston skirt set back inwards. This will remove the areas of the pin hubs that are used for the Recording the piston pin are indispensable from the Shaft surface, i.e. the outer surface of the piston inside, offset to the piston axis. Consequently, in the outside areas of material can be saved and it will achieved a weight reduction.

Such a piston with pin hubs offset inwards must also be at the level of the pin bosses and below the Bolt hubs have shaft wall sections, with which he after installation in the cylinder of an internal combustion engine on the Cylinder wall abuts. These shaft wall sections, too are referred to as load-bearing shaft wall sections because they ensure that the piston is guided in the cylinder thus radial in a lower region of the piston skirt opposite sides with respect to the pin axis, namely on the pressure side on the one hand and on the counter pressure side on the other hand, trained. At these points, they worry Shaft wall sections for supporting the piston in the Up and down movement in the cylinder where the piston can tilt around the piston pin axis. Especially done during this tilting movement in the top and bottom dead center Change in the side with which the piston bears against the cylinder wall, from the pressure to the Counter pressure side or vice versa. This tilting movement is through the load-bearing shaft wall sections as far as necessary limited. In the case of the generic pistons, the Piston skirt in its lower area connecting walls, which are set back inside and in which the Bolt hubs lie. These connecting walls extend to lower edge of the piston skirt. Thus missing at the bottom the piston a circumferential ring which is designed so that he the two opposite shaft wall sections connects with each other.

Such a piston guaranteed by the Material savings in the areas outside the recessed pin hubs the possibility of reducing the weight of the To reduce the piston considerably.

It is the object of the present invention in a such pistons to further reduce the weight and at the same time that on the pistons in terms of strength and to meet the requirements of low noise.

This task is carried out by a piston with the characteristics of Claim 1 solved.

As a result, the two shaft wall sections are one Dimension in the circumferential direction, so to speak a width formed, which is in the direction of the piston axis, that is the height of the piston. Furthermore, the

Connecting walls designed so that they follow the course of the In the direction of the piston axis of the edges of the Follow shaft wall sections. According to the invention is the width of the two shaft wall sections to the lower end of the Piston shaft is designed to become larger. The two Connecting walls thus inclined and inclined to each other in this way trained that their distance in a lower area larger is as in an upper range. In other words, get lost the connecting walls are somewhat conical to each other. By the invention according to the height of the piston changing width dimension of the shaft wall sections can be achieved that in particular in those zones in which the shaft wall sections are made narrower can, further material can be saved. The possible weight reduction for the Pistons according to the invention up to 15%.

According to the shaft wall sections are such designed that they as a whole Shaft wall sections are designed, and on the shaft walls no zones are formed to support the piston make no contribution to the inner wall of the cylinder. Such Areas are therefore not required for strength and are left out according to the invention. This is what it is about in particular those areas that are more than 0.2 mm are set back from the cylinder wall. Likewise can the course of the shaft wall sections to that of the Adjusted elasticity of the piston requirements become.

At the same time, the fact that the load-bearing Shaft wall sections, if necessary, are available good running properties for the piston are guaranteed. In particular, this can be done without shortening, for example of the piston skirt, which is a possible Weight loss measure represents, however, the There is a danger that the piston noises due to tilting in the cold Condition increase significantly. Furthermore, by the Resetting according to the invention in the area of Shaft wall sections a reduction in the wall thickness or a further resetting the pin hubs can be avoided what Although it saves weight, the strength of the Piston significantly reduced. Consequently, with the invention the piston has been improved in accordance with EP 0 385 390 A1, that with this piston over the entire height with a constant width formed shaft wall sections be narrowed in areas such that a noticeable Weight reduction without sacrificing strength and Supporting properties in the cylinder is achieved. How mentioned, the connecting walls are the course of the side Edges of the shaft wall sections are adapted.

As mentioned, the two load-bearing shaft wall sections are with regard to their dimension in the circumferential direction upwards rejuvenated. This means that the Side wall sections largely as a side view reverse T are designed, and in a lower area are significantly wider than in an upper area, by being closed at the circumferentially border the trained area of the piston skirt. Further are the two in this preferred embodiment Connecting walls inclined towards each other upwards. Hence the distance between the two Connecting walls in a lower area larger than in an upper area, and by adjusting the orientation of the two connecting walls to the side edges of the Shaft wall sections is achieved that the strength of the shaft walls required for carrying is guaranteed.

According to the invention, it is conceivable to support the two Shaft wall sections with any curve-shaped Edges, and one for the connecting walls to provide any curved surface accordingly. As mentioned, it is provided according to the invention, if possible save a lot of material and thus weight, so that it is basically conceivable, of course largely flowing transitions the load-bearing shaft wall sections in to omit all those areas that are used for support on the inner wall of the cylinder are not required. So is it is advantageous according to this embodiment Shaft wall sections with any curvature Form edges.

It is known from US Pat. No. 5,076,225 for a piston, which both in the upper area and in the lower area in Has a circular cross-section in the circumferential direction and thus increased stability even in its lower area has, the shaft wall sections with a height to provide the piston skirt with a variable width. On However, such a piston can not with the generic Pistons are compared, because with this piston by the its lower end is formed around the ring Stability of the piston always in a lower area is guaranteed. Consequently, the Shaft wall sections with a variable Width are formed without the stability of the piston endanger. This measure is for the generic piston however, in terms of its strength and warranty the support in the inner wall of the cylinder more questionable and can only inventively be balanced that the connecting walls the course of the edges of the in the direction of the piston axis Shaft wall sections are formed as follows.

A similar piston is known from DE 41 22 921 A1. Here, the shaft wall sections are largely X-shaped designed, the lower area in turn by an am lower edge of the piston circumferential ring is formed. The shaft is thus cut out in places, and the connecting walls are in the area of the recesses also excluded. However, this will increase the strength of the Shaft wall sections impaired in that the Shaft surface not always completely on the cylinder wall is present. Rather, this is only due to the invention Training of the connecting walls achieved that none Are recessed, but for a support of the bearing shaft wall sections the course of their lateral Edges follow.

Furthermore, a piston is described in US Pat. No. 4,856,417 a piston rattling should be reduced. Here are the shaft wall sections overall tapering downwards trained, with no reference from this document it can be seen that the shaft wall sections on the load-bearing shaft wall sections can be reduced and thus can be tapered towards the top, resulting in significant weight savings according to the invention leads.

Furthermore, US 5,448,942 describes a piston, the bearing areas of the shaft walls the shape of an inverted T have. The other, non-supporting areas of the However, stem walls are also present on this piston, so that this piston is disadvantageous in terms of its weight is. This applies in the same way to the piston according to the US 5,058,489, in which the shaft walls through the actual contact area with the cylinder wall and others Areas are formed so that the resulting piston is unnecessarily difficult.

Although basically each for the piston according to the invention suitable material for a piston is conceivable preferred, the piston made of light metal, for example Aluminum or an aluminum alloy to train the Weight of the piston low due to this choice of material hold.

Advantageous embodiments of the invention are in the further claims described.

The shaft wall sections are accordingly preferably of such a type trained that they are in the area of their entire outer surface as load-bearing shaft wall sections for the support of the Ensure the piston on an inner wall of the cylinder. This allows how described, for the shaft wall sections each for each Place one along the height of the piston skirt Width dimension can be chosen, which for the guidance of the Piston is absolutely necessary. Any other Areas of the shaft wall sections which are designed in such a way that when installed in a cylinder by more than 0.2 mm can be set back against the cylinder wall to be dispensed with. When installing in the cylinder with the These zones provide the distance from the inner wall of the cylinder the shaft wall sections namely no contribution to wear and supporting the piston on the cylinder wall.

Those running in the direction of the piston axis are preferred Edges of the load-bearing shaft wall sections in the course of their Taper according to those previously described Embodiments formed straight. If in trials can be determined that the supporting area of the Shaft areas are limited by largely straight lines can, so this training represents the load-bearing Shaft wall sections a comparatively simple design represents, which contributes to the simplicity of the molds used.

However, the side edges can also be beneficial the load-bearing shaft wall sections in the course of their Form taper curved, so that the connecting walls concave with respect to their course in the direction of the piston axis or are convexly curved. Consequently, the two would Connecting walls are then convexly curved, if the lateral edges of the shaft wall sections in the Side view would be curved outwards. It was the same proven to be favorable in special applications, the lateral edges of the load-bearing shaft wall sections form curved inside, so that the two Connecting walls not only upwards or downwards are inclined to each other, but also in each case concavely curved.

For the piston according to the invention it is further preferred that the piston skirt in its upper, over the set back

Stud hubs protruding area, on its underside is hollowed out. This measure is made possible by the fact that in the piston according to the invention the pin hubs as far as possible set back from the shaft walls. Consequently a certain protrusion of the upper, cylindrical piston area. These areas in the zone of Piston pin axes are not used to support the piston essential, since the piston is essentially only about the Piston pin axis can tilt, so that by hollowing out the Protruding beyond the piston pin axis further material and Weight can be saved without losing strength and strength Endangering the piston.

According to a further preferred embodiment provided that the pin bosses for use with a Stepped connecting rods stepped on their sides facing each other are trained. This measure is for the Piston according to the invention particularly suitable if the load-bearing shaft wall sections tapered towards the top are trained. This makes the two connecting walls inclined upwards towards each other, so that even those Zones in which the pin bosses are to be formed, especially in an upper area very far inwards are offset. In order to still have the necessary support surface for the Ensuring piston pins are preferred with this one Embodiment the pin bosses, as described, stepped formed so that the distance between the pin bosses in an upper area is less than a lower area Area. This means that despite the extensive transfer Bolt hubs provide the necessary support surface for the inside Piston pin guaranteed. When used with a Stepped connecting rod or a trapezoidal connecting rod, which is consequently in one upper area is narrower than in a lower Area of his pin hub, can by the invention Piston in this embodiment is particularly advantageous Weight saving while ensuring the strength and the Function can be achieved.

Fig. 1

eine schematische perspektivische Ansicht des erfindungsgemäßen Kolbens in einer ersten Ausführungsform;

Fig. 2

eine Seitenansicht des in Fig. 1 dargestellten Kolbens;

Fig. 3

eine Schnittansicht des erfindungsgemäßen Kolbens in einer zweiten Ausführungsform; und

Fig. 4

eine Seitenansicht des erfindungsgemäßen Kolbens in einer dritten bevorzugten Ausführungsform.

The invention is described in detail below with reference to exemplary embodiments illustrated in the drawings. Show it:

Fig. 1

a schematic perspective view of the piston according to the invention in a first embodiment;

Fig. 2

a side view of the piston shown in Fig. 1;

Fig. 3

a sectional view of the piston according to the invention in a second embodiment; and

Fig. 4

a side view of the piston according to the invention in a third preferred embodiment.

The piston 10 shown in FIG. 1 has a piston shaft 16 and an upper, largely cylindrical Area 14 on. In this upper area 14, i.e. the Ring field area, the piston 10 with one or more partially circumferential and parallel to the piston crown Slots. Below the cylindrical area 14 are the pin bosses 24 which are designed to accommodate the Piston pin (not shown) when assembling the piston serve with a connecting rod (not shown).

As can be clearly seen in Fig. 1, the Generic pistons, the two pin bosses 24 each in Reset direction of the diameter of the piston skirt 16, so that at the lower end of the upper region 14 of the piston 10th an overhang 26 arises. By resetting the

Bolt hubs 24 can be in the area below the overhang 26 the generic piston material can be saved so that the weight of the piston 10 can also be reduced.

There are also two in a lower region of the piston opposing shaft wall sections 16 trained that form the piston skirt. In the drawing is only that according to the chosen orientation of the piston 10 recognizable shaft wall section 16 located at the front. The two shaft wall sections 16 are by two Connecting walls 18 connected to each other between the side edges 20, 22 of the Shaft wall sections 16 are formed. In the for the Fig. 1 selected representation is of the two connecting walls 18 in turn only recognize that connecting wall 18 that the left edge 20 of FIG. 1 of the front Shaft wall section 16 with the corresponding edge 20 of the connects the rear shaft wall section. As in Fig. 1 too can be seen, the two connecting walls 18 extend to bottom of the piston skirt and are inside set back. Are in the two connecting walls 18 furthermore the bolt ends 24.

According to the two shaft wall sections 16 are with a dimension in the circumferential direction, so to speak one Width formed in the direction of the piston axis changed. By this measure, it is according to the invention possible in those areas of the shaft wall sections 16 the one for supporting the piston on an inner wall of the cylinder no additional material and thus weight are required save. According to the invention, the two connecting walls 18 further formed such that they follow the course of the Edges 20, 22 of the direction of the piston axis Shaft wall sections 16 follow. According to the in Fig. 1st illustrated embodiment, in which the two Shaft wall sections 16 tapered towards the top are thus an arrangement of the connecting walls 18, in which these are arranged inclined towards each other upwards are. In other words, the connecting walls are located 18 to a certain extent in an oblique position.

In the embodiment shown in Fig. 1, the lateral edges 20, 22 of the supporting shaft wall sections 16 also designed convexly curved. Hence they are Connecting walls 18 in the area of their surface, that is in the Course from the lower edge of the piston to below the Overhang 26 convexly curved.

2 in a direction perpendicular to the piston pin axis 28 is the curved course of the lateral edges 20, 22 of the front shaft wall section 16 recognizable again. Furthermore, the side view 2 clearly as in the piston 10 according to the invention the pin bosses 24 opposite the peripheral edge of the upper one Section 14 are set back so that an overhang 26th arises. As mentioned, this reset offers the Bolt hubs 24 the possibility of the left and right in Area of the pin axis 28 lying zones material save.

According to the invention, the weight savings achieved thereby further increased by the on with respect to the pin axis 28th formed radially opposite sides Shaft wall sections 16 not over their entire height Have width that that for supporting the piston 10th corresponds to the widest point required. Rather, it is Shaft wall section 16 only along its height wide as it is for the support of the piston 10th on an inner cylinder wall is required. For example can according to that shown in Fig. 2 up tapering design of the supporting shaft wall sections 16 a further significant weight reduction can be achieved. From the view of FIG. 2 it is further clarified that that on the piston 10 according to the invention at its lower edge no area is formed which is circular in cross-section and which corresponds in its dimensions to the upper region 14. Furthermore, the piston 10 along its circumference formed two recessed walls 18 set back.

FIG. 3 shows an advantageous development of the one shown in FIG. 1 and 2 shown piston 10. For one thing is in that taken in the area of the piston axis 30 3 again shows the sectional view of the invention to recognize oblique course of the two connecting walls 18. Here is from the convexly curved course Connecting walls 18 to recognize that the course of the (not shown) edges 20, 22 of the shaft wall sections 16 approximately corresponds to the course shown in FIGS. 1 and 2. Further can be seen in the sectional view that the two Bolt hubs 24 each from the outer edge of the top Area 14 are set back, however, over their entire Height along the piston axis 30 have the same width.

The piston 10 shown in Fig. 3 is also in the range of the overhang 26 of the upper region 14 over the pin hubs 24 provided with hollows 32. These hollows can because the upper region 14, such as described, has an overhang 26 in this area. Furthermore, the inclined position of the connecting walls 18 enables which increases the width of the overhang 26, the formation of cavities 32. These cavities can either be through Milling the cast piston or by suitable Casting cores are already formed during casting. Through this Measure can be achieved by saving material in the area of Cavities 32 for the piston 10 according to the invention another Reduction in his weight can be achieved.

4 is another embodiment of the Piston 10 according to the invention shown. In this In one embodiment, the piston 10 is suitable for use with a stepped connecting rod (not shown). At a Step connecting rod is the eyelet in which the piston pin is recorded, narrower in an upper area trained as in a lower area. Accordingly are the pin bosses 24 shown in Fig. 4 Embodiment of the piston 10 according to the invention designed. This means that the inner edges 34 of the pin bosses 24 are designed so that they are in an upper area have a smaller distance than in a lower area. This measure can also in the event that the Bolt hubs are set back very far, for example at the embodiment shown in Fig. 4, up to the lateral edges 20, 22 of the shaft wall section 16, for a sufficiently large storage area for the piston pin is provided become. This is due to the widening of the pin bosses 24 reached in their upper ranges. The same applies for so-called trapezoidal connecting rods.

It should also be noted that the connecting walls 18 are not absolutely so straight between those to be connected Shaft wall sections 16 must be formed in that Side and cross-sectional views of FIGS. 2 to 5 only their outlines are recognizable. Rather you can the connecting walls 18 in the area of the pin bosses 24 be spherical on the outside, so that in a bottom view an outwardly curved "plan" of the connecting walls 18 would be recognizable. It is essential to the invention that the Connecting walls 18 with respect to their in the side and Sectional view of the outline of the height of the piston 10 changing width of the Shaft wall sections 16 follow. As a result, despite the Recess of the shaft wall sections 18 in the for Adequate zones not required Strength of the piston 10 according to the invention guaranteed become.

Claims (6)

1. Piston (10), especially made of light metal, with:

   a piston shaft (16),

   an upper, essentially cylindrical area (14),

   pin bosses (24), which are set back from the piston axis (28) in the direction of the pin axis (28),

   two shaft wall sections (16) constructed by these in a lower section of the essentially cylindrically constructed area (14) on radially opposite sides in relation to the pin axis (28), and

   two connecting walls (18) connecting the shaft wall sections (16), which are set back, in which the pin bosses (24) lie and which extend as far as the lower edge of the piston shaft,
   characterised in that

   the two shaft wall sections (16) are constructed as supporting shaft wall sections and that those areas that offer no assistance to the support of the piston (10) on the cylinder inner wall are left open,

   the two shaft wall sections (16) have lateral edges (20, 22), which are constructed in any curved shape, wherein the two shaft wall sections (16) are constructed so as to taper upwards in the direction of circumference in a largely corresponding manner with respect to their dimension, and

   the connecting walls (18) follow the thereby determined course of the edges (20, 22) of the shaft wall sections (16) running in the direction of the piston axis (30) in such a way that they incline upwards towards each other.
2. Piston according to claim 1, characterised in that the shaft wall sections (16) are constructed in such a way that in the area of their overall outer surface they ensure the support of the piston (10) on the cylinder wall as supporting shaft wall sections (16).
3. Piston according to at least one of the claims 1 or 2, characterised in that the lateral edges (20, 22) of the supporting shaft wall sections (16) are constructed so as to be largely rectilinear in the progression of their tapering.
4. Piston according to at least one of the claims 1 or 2, characterised in that the lateral edges (20, 22) of the supporting shaft wall sections (16) are constructed so as to be curved in the progression of their tapering, and that the connecting walls (18) in relation to their progression are constructed so as to be curved in either a concave. or convex manner in the direction of the piston axis (30).
5. Piston according to at least one of the previous claims, characterised in that the piston (10) is hollowed out on its underside (32) in the upper area (26) overhanging the set back pin bosses (24).
6. Piston according to at least one of the previous claims cheracterised in that the pin bosses (24) are constructed for use with a stepped connecting rod or trapezoidal connecting rod on its sides (34) turned towards each other, in such a way that the distance between the pin bosses (24) is smaller in an upper area than in a lower area.

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