FR3096417A1 - Crankshaft retaining arrangement in a cylinder block of a heat engine - Google Patents

Abstract

The invention proposes an arrangement of a crankshaft in a cylinder block of a heat engine held by bearings with a crankshaft bearing shell surrounding a journal (12) and comprising an upper semi-cylindrical half-ring (30) whose concave wall (34) has a first section (42-1) of circular groove which extends from a first end (38-1) of the semi-cylindrical ring, only along a portion of the concave wall (34 ), and a second section (42-2) of circular groove which extends from a second end (38-2) of the semi-cylindrical ring, only along an angular portion of the concave wall (34), which are separated from each other by an arc of a circle with a chord length greater than or equal to the diameter of the distribution duct hollowed out in the crankshaft to connect the journal to a crankpin. Figure for the abstract: Fig. 2

Description

Description Title of the invention: Crankshaft retaining arrangement in a heat engine cylinder block Technical field

The invention relates to a crankshaft arrangement rotatably mounted about its axis in a heat engine cylinder block and held by a crankshaft bearing, and also a lubrication system for a crankshaft of said engine.

Prior technique

[0002] Combustion engines, in particular internal combustion engines, generally comprise an upper cylinder head and a cylinder block, also called a cylinder block, comprising at least one cylinder in which a piston slides back and forth.

[0003] The piston is connected by a connecting rod to a crankshaft at the level of a crank pin.

[0004] The crankshaft comprises at least one journal and at least one crankpin whose axes are parallel to the longitudinal axis of the crankshaft.

[0005] The crankshaft is rotatably mounted in a connecting rod chamber into which the cylinder opens.

The axis of the crankshaft is held in position in the connecting rod chamber by fixed bearings and bearing caps, each bearing and its associated bearing cap surrounding and guiding in rotation an associated journal of the crankshaft.

[0006] The crankshaft rotating at high speeds (from 800 rpm to 7500 rpm), the contact areas between a journal of the crankshaft and a bearing-bearing cap assembly must be lubricated accordingly in order to reduce friction which can cause overheating of the various components and overconsumption of fuel and avoid seizure of said engine.

[0007] Lubricating liquid, here oil, is therefore brought to these contact zones, from a main ramp arranged in the cylinder block, via a duct which is drilled into the body of the crankshaft and the bearing and which opens into the convex cylindrical wall of the bearing facing the crankshaft journal.

[0008] An intermediate duct is also drilled in the body of the crankshaft to connect the wall of the journal in contact with the bearing, and the wall of an adjacent crank pin on which a connecting rod head is rotatably mounted.

[0009] Thus, the oil is brought to the wall of the bearing in contact with the pin to allow the contact zones between the pin and the bearing to be lubricated.

[0010] Part of the oil is then directed from the wall of the pin to the wall of the crank pin in order to lubricate the contact zone of the crank pin with the big end of the connecting rod.

[0011] In known manner, a bearing is interposed radially between the journal on the one hand and the associated bearing cap assembly on the other.

Said bearing 2 surrounds the journal and also the crank pin.

[0012] Each bearing consists of two complementary semi-cylindrical hollow half-rings, an upper half-ring and a lower half-ring, to surround the convex cylindrical wall of the journal.

[0013] Each upper half-ring is installed immobile in the bearing and each lower half-ring is installed immobile in the bearing cap.

[0014] The upper half-ring is subsequently called the upper bearing and the lower half-ring the lower bearing.

[0015] The upper bearing comprises an outer cylindrical wall in contact with the wall of the bearing and an inner cylindrical wall in contact with the wall of the pin, and at least one bore or radial hole which is connected to the oil supply conduit .

In known manner, in its inner cylindrical wall, the upper bearing has a circular groove into which the radial bore opens, this groove being intended to direct the flow of oil over a surface portion of the journal.

According to this known design which is for example illustrated in document FR 2,979,666, the groove extends angularly over the entire length separating the two end edges of the upper bearing.

[0018] The document DE19826460-A1 also proposes lubrication of the lower half-ring of the bearing thanks to two grooves substantially diametrically opposed to the edges of the half-ring and extending along a reduced arc of a circle.

[0019] Document EP2813717-Al discloses an upper half-ring comprising two grooves extending angularly on the inner wall of said half-ring facing the axis of the pin or crank pin of the crankshaft, said two grooves being separated by a solid angular strip along an arc, the length of the arc of which is less than the diameter of the lubricating fluid supply duct in order to allow constant lubrication of the inner wall of said bearing half-ring.

This ensures continuity of lubrication.

[0020] The designs in said bearings have the particular drawback of reducing the hydrodynamic lift, a phenomenon which is particularly important in the case of heavy loads oriented towards said bearing which has a reduction in useful width, which is in particular the case under the effect inertia forces linked in particular to the reciprocating masses of the pistons.

It is then necessary to increase the width of the half-rings of the bearing and therefore of the bearing itself, which leads to an increase in the length of the journals of the crankshaft and therefore of the engine.

The invention aims in particular to remedy this drawback and to optimize the hydrodynamic lift without increasing the width of the bearing.

Presentation of the invention 3 100221 The invention proposes a crankshaft arrangement in a cylinder block held by at least one bearing and bearing cap and comprising a crankshaft bearing bush formed by an upper half-ring and half-ring which are complementary hollow semi-cylindrical, said upper half-ring comprises, in its concave wall:

[0023] - two sections of circular groove in the angular extension, each of said sections extending from one end of the semi-cylindrical ring and only along an angular portion of the concave wall, comprises an associated radial bore which communicates with the circular groove and is intended to be connected with an oil distribution duct hollowed out in the crankshaft between a crankpin and a pin,

[0024] Characterized in that the two sections are separated from each other by a cord length at least equal to the diameter of the distribution duct.

[0025] According to other characteristics of the invention:

[0026] - the two sections are symmetrical with respect to an axial median plane.

-each angular groove section comprises a radial opening connected with a fluid supply conduit.

The invention also proposes a system for lubricating a motor vehicle engine crankshaft which comprises:

[0029] - a crankshaft comprising at least one rotational guide pin and a crank pin connected to each other by a distribution duct;

[0030] - a bearing which is interposed radially between the pin and a fixed bearing of the engine comprising an oil inlet duct, characterized in that the bearing is produced according to the invention.

[0031] The invention finally proposes a heat engine for a motor vehicle characterized in that it is equipped with a lubrication system according to the invention.

Brief description of the drawings

Other characteristics and advantages of the invention will appear during the reading of the detailed description which will follow for the understanding of which reference will be made to the appended drawings in which:

[0033] - [fig.

I] is a view which schematically represents in axial longitudinal section a crankshaft and its lubrication system; And

[0034] - [fig.2] is a large-scale perspective view of the upper semi-cylindrical ring of a bearing according to the invention suitable for equipping the main bearings of the crankshaft of figure 1.

DETAILED DESCRIPTION OF FIGURES

In the remainder of the description, elements having an identical structure or similar functions will be designated by the same references.

In the following description, we will adopt in a non-limiting manner longitudinal or axial orientations with reference to the axis of the bearing, and radial with reference to the axial orientation of the bearing.

There is shown schematically in Figure 1 a crankshaft 10 of an internal combustion engine of a four-cylinder motor vehicle.

The crankshaft 10 includes at least one cylindrical journal 12 which is surrounded by a bearing 14 and a bearing cap 16, and includes at least one crankpin 18 which is surrounded by a big end (not shown).

The crankshaft lubrication system comprises a main oil rail 20 which is arranged in a part of the engine, not shown, and which is fed by an oil pump 22.

The ramp 20 is connected to an oil supply conduit 24 which opens through the bearing 14 in a concave cylindrical wall facing the cylindrical journal 12.

An oil distribution duct 28 is drilled in the body of the crankshaft and it extends between the peripheral wall, cylindrical concave, of the bearing 14 and a wall, cylindrical convex, of the pin 18 to bring oil captured at the wall of pin 12 towards crankpin 18 and lubricate the contact zone between the crankpin and an associated connecting rod (not shown).

In known manner, a bearing 100 is interposed radially between the convex cylindrical peripheral wall of the journal 12 and the concave internal cylindrical wall half formed in the “lower” bearing 14 and the “upper” bearing cap 16.

[0043] Each bearing 100 is formed by two semi-cylindrical and complementary half-rings, an upper half-ring 30 housed between the bearing 14 and the pin, and a lower half-ring (not shown) housed against the cap. of landing 16.

[0044] The upper semi-cylindrical half-ring 30 and the lower half-ring are commonly referred to respectively as the upper bearing (line or crankshaft) and lower bearing (line or crankshaft).

[0045] The invention here relates at least to the design of the upper breast-cylindrical ring constituting the upper bearing, a preferred embodiment of which is illustrated in FIG. 2 arranged around a journal of the heat engine crankshaft.

The upper semi-cylindrical half-ring 30 illustrated in Figure 2 is delimited by a convex cylindrical outer wall 32 and by a concave cylindrical inner wall 34.

Said half-ring 30 is delimited axially by two opposite side edges 36 and angularly by a first end edge 38-1 and by a second end edge 38-2.

These two end edges 38-1 and 38-2 are the connecting edges forming the connection joint plane with the other lower half-ring lower scrni-cylindrical not shown.

[0049] This connection or junction zone is also called the “unclamping zone”.

According to the invention, the concave cylindrical inner wall 34 comprises two sections of circular groove, 42-1 and 42-2 in the extension, the first section 42-1 extends angularly from the first end edge 38-1 on an arc of a circle whose angle is less than 90° and the second section 42-2 which extends angularly in the extension of the first to the second end edge 38-2.

Said two sections 42-1, 42-2 are separated from each other by a chord length greater than or equal to a threshold.

In other words, there is a portion or angular section - here an intermediate central portion 44 - of the concave cylindrical inner wall 34 which has no groove.

In a known manner, the distribution duct hollowed out in the crankshaft between the journal and the crank pin emerges from the convex cylindrical peripheral wall of the journal 12 in a substantially median manner.

Said outlet comes vis-à-vis each circular groove section, 42-1 and 42 during rotation of the crankshaft and therefore the journal around the axis of the crankshaft.

The lubricating liquid can then flow from the circular groove sections into the distribution duct.

The two circular groove sections are of rectangular section and, without limitation, here rectilinear extending in a radial plane centered with respect to the two opposite side edges 36.

The first section 42-1 of circular groove extends angularly from the first end edge 38-1 of the semi-cylindrical ring 30, to its opposite angular end which is defined by a first associated radial bore crossing 46-1 which communicates with this first section 42-1 of circular groove.

Here symmetrically with respect to a median axial plane of symmetry of the semi-cylindrical ring 30, the groove comprises a second section 42-2 of circular groove which extends angularly from the second end edge 38- 2 of the semi-cylindrical ring 30, as far as its opposite angular end which is defined by a second associated radial bore through 46-2 which communicates with this second section 42-2 of circular groove.

Thus, each angular groove section 42-1, 42-2 extends angularly between one end 38-1, 38-2 of the semi-cylindrical ring 30 and the associated bore 46-1, 46-2.

Each bore 46-1, 46-2 thus puts the associated groove section 42-1, 42-2 in communication with the outer wall 32 of a convex cylindrical shape. 6

When the crankshaft rotates, a film of lubricating fluid separates the surface of the concave cylindrical inner wall 34 from the wall of the facing journal.

The film of oil generates a “negative” hydrodynamic lift between the cylindrical walls of the bearing and of the facing pin, in particular between the concave cylindrical inner wall 34 devoid of groove of the upper half-ring and the convex wall of the pin.

To ensure this hydrodynamic lift, it is known to increase the length of the semi-cylindrical half-ring of the bearing along the axis of the bearing, which is likely to increase the size of the crankshaft and therefore of the engine. .

According to the invention, the separation between the two sections of circular groove allows the generation of hydrodynamic lift between said two sections.

Preferably, said dynamic lift must not be altered or even eliminated by the passage of the outlet of the distribution duct.

The minimum separation threshold between the two circular groove sections is equal to the diameter of the distribution duct.

Said diameter is of the order of 5 to 6 mm or greater.

More specifically, the chord length separating the two circular groove sections is at least equal to the diameter of the distribution duct.

[0063] Thus, the loss of negative hydrodynamic lift due to the presence of the groove is reduced, compared to the state of the art in which the groove extends angularly over the entire length separating the first end edge 38 -1 of the second end edge 38-2 and therefore the increase in the bearing surface by increasing the length of the bearing along its axis is no longer necessary, which contributes to the compactness of the heat engine.

[0064] This is particularly important in cases of operation in which the main direction of the load at the line bearing is directed "upward" in the direction of the upper bearing, which is particularly the case under the effect of the forces of inertia linked in particular to the reciprocating masses of the pistons.

[0065] This problem is advantageously solved while satisfying the requirements for supplying oil to the crankpins of the connecting rod(s) and for evacuating pollution such as particles present in the lubricating oil, this evacuation taking place in the zone referred to as "unpinching" mentioned above.

[0066] The intermediate central zone or portion 44 devoid of a groove is advantageously the zone most stressed at high rotational speeds of the crankshaft.

The preferred embodiment which has just been described having a general symmetry of design is advantageous in that it does not require keying for mounting the upper bearing in one or the other of its two possible positions. disassembly.

[0068] According to variants of the invention not shown: 7

- for each groove section, the radial bore is not necessarily arranged at one end of the section.

8 [Claim 1] [Claim 2] [Claim 3] [Claim 4] [Claim 5]

Claims (1)

CLAIMS Crankshaft arrangement (11) in a cylinder block held by at least one bearing (14) and bearing cap (16) and comprising a crankshaft bearing bush (100) formed by an upper half-ring (30) and lower half-ring which are complementary hollow semi-cylindrical, said upper half-ring (30) comprises in its concave wall facing the crankshaft two sections of circular groove (42-1 and 42-2) in the angular extension of one on the other, each of said sections extends from one end (38-1,38-2) of the upper semi-cylindrical ring (30) and only along an angular portion of the internal concave wall (34) , comprises an associated radial bore (46-1,46-2) which communicates with the circular groove and is intended to be connected with an oil distribution duct (28) hollowed out in the crankshaft between a crankpin (18) and a trunnion (12), characterized in that the two sections (42-1 and 42-2) are separated from each other by an arc of a circle with a chord length at least equal to the diameter of the conduit of delivery (28). Crankshaft arrangement according to Claim 1, characterized in that the two sections (42-1 and 42-2) are symmetrical with respect to an axial median plane. Crankshaft arrangement according to Claim 1 or 2, characterized in that each angular groove section (42-1 and 42-2) comprises a radial opening (46-1.46-2) connected with a fluid supply conduit. Lubrication system for a motor vehicle engine crankshaft which comprises: - a crankshaft (11) comprising at least one pin (12) for guiding in rotation and a crank pin (18) connected to each other by a distribution (28); - a bearing (100) which is interposed radially between the pin (12) and a fixed bearing (14) of the engine comprising an oil inlet duct, characterized in that the bearing (100) is. made according to claims 1 to 3. Motor vehicle engine characterized in that it is equipped with a lubrication system according to claim 4.