Device and method for lubricating a connecting rod bearing

Abstract

A device lubricates a connecting rod bearing on a crankshaft of an internal combustion engine. The device has a piston having an internal piston cooling fluid channel, and an outlet channel in fluid communication with the fluid channel. The device has a connecting rod, which is connected to the piston in an articulated, in particular pivotable, manner, and has a large connecting rod eye and a connecting channel. The large connecting rod eye is formed for receiving the connecting rod bearing. The connecting channel forms a fluid connection between the outlet channel and the large connecting rod eye so that a fluid, in particular a cooling lubricating fluid (e.g. oil), can be fed, or is fed, from the fluid channel to the large connecting rod eye via the outlet channel and the connecting channel. The connecting rod bearing can be lubricated by cooling oil from the fluid channel of the piston.

Claims

1. A device for lubricating a connecting rod bearing on a crankshaft of an internal combustion engine, comprising: a piston having a fluid channel comprising an internal piston cooling fluid channel, and an outlet channel in fluid communication with the fluid channel; a connecting rod connected to the piston in a pivotable manner, the connecting rod having a large connecting rod eye and a connecting channel, wherein: the large connecting rod eye is configured to receive the connecting rod bearing; and the connecting channel forms a direct fluid connection between the outlet channel and the large connecting rod eye such that a fluid in the form of a cooling lubricating fluid is fed from the fluid channel to the large connecting rod eye and the connecting rod bearing via the outlet channel and the connecting channel.

2. The device according to claim 1, wherein: the outlet channel has an outlet opening in a rounded piston head of the piston; and/or the connecting channel has an inlet opening in a rounded, outer circumferential surface of a small end of the connecting rod.

3. The device according to claim 1, wherein: the connecting channel has an inlet region formed by a step-shaped recess in an outer circumferential surface of a small end of the connecting rod.

4. The device according to claim 3, wherein the connecting channel further comprises: a slant bore extending from the recess and, at a spacing from a small connecting rod eye of the connecting rod, through the small end to a connecting rod shaft of the connecting rod; and a longitudinal bore extending from the large connecting rod eye through the connecting rod shaft to the slant bore.

5. The device according to claim 1, wherein: a small end of the connecting rod and a piston head of the piston are configured such that a spacing between a region of the piston head which adjoins an outlet opening of the outlet channel and a region of the small end which adjoins an inlet opening of the connecting channel is smaller than 0.1 cm.

6. The device according to claim 5, wherein: the region of the piston head and the region of the small end sweep over one another during a pivotal movement between the piston and the connecting rod.

7. The device according to claim 1, wherein: a small end of the connecting rod and a piston head of the piston are configured such that a spacing between a region of the piston head which adjoins an outlet opening of the outlet channel and a region of the small end which adjoins an inlet opening of the connecting channel is smaller than 0.01 cm.

8. The device according to claim 7, wherein: the region of the piston head and the region of the small end sweep over one another during a pivotal movement between the piston and the connecting rod.

9. The device according to claim 1, wherein: a piston head of the piston covers an inlet opening of the connecting channel during a movement of the piston from an upper dead center to a lower dead center, in particular for reducing the cavitation tendency in the connecting channel; and/or an outlet opening of the outlet channel overlaps an inlet opening of the connecting channel during a movement of the piston from a lower dead centre to an upper dead centre.

10. The device according to claim 1, wherein: a piston head of the piston covers an inlet opening of the connecting channel within an angular range which is smaller than a predetermined angular range within which the connecting rod is pivotably connected to the piston; and/or an outlet opening of the outlet channel overlaps an inlet opening of the connecting channel within an angular range which is smaller than a predetermined angular range within which the connecting rod is pivotably connected to the piston.

11. The device according to claim 1, wherein: a fluid connection between the outlet channel and the connecting channel is an intermittent fluid connection and/or exists substantially only during a movement of the piston from a lower dead center to an upper dead center.

12. The device according to claim 1, wherein: the connecting channel bypasses a small connecting rod eye of the connecting rod and/or a piston pin which connects the connecting rod pivotably to the piston.

13. The device according to claim 1, wherein: a small end of the connecting rod includes an increased wall thickness in a region through which the connecting channel extends; and/or the piston includes an increased wall thickness in a region through which the outlet channel extends.

14. The device according to claim 1, further comprising: a fluid injecting nozzle directed towards an inlet opening of an inlet channel of the piston, the fluid injecting nozzle in fluid communication with the fluid channel.

15. The device according to claim 14, wherein: the fluid injecting nozzle is provided separately from the piston and from the connecting rod; and/or the fluid injecting nozzle is received by or secured on a crankcase.

16. A motor vehicle, in particular a commercial vehicle, comprising a device for lubricating a connecting rod bearing on a crankshaft of an internal combustion engine, the device comprising: a piston having a fluid channel comprising an internal piston cooling fluid channel, and an outlet channel in fluid communication with the fluid channel; a connecting rod connected to the piston in an articulated, in particular pivotable, manner, the connecting rod having a large connecting rod eye and a connecting channel, wherein: the large connecting rod eye is configured to receive the connecting rod bearing; and the connecting channel forms a direct fluid connection between the outlet channel and the large connecting rod eye such that a fluid in the form of a cooling lubricating fluid is fed from the fluid channel to the large connecting rod eye and the connecting rod bearing via the outlet channel and the connecting channel.

17. A method for lubricating a connecting rod bearing on a crankshaft, comprising: feeding a cooling lubricating fluid from an internal cooling fluid channel of a piston to the connecting rod bearing via a connecting channel of a connecting rod, the connecting channel forming a direct fluid connection between an outlet channel of the piston, which is in fluid connection with the internal cooling fluid channel, and a large connecting rod eye of the connecting rod, in which the connecting rod bearing is received.

Description

(1) The above-described preferred exemplary embodiments and features of the invention can be combined with one another as desired. Further details and advantages of the invention are described below with reference to the accompanying drawings, which show:

(2) FIG. 1 a sectional view through a piston of an internal combustion engine according to an exemplary embodiment;

(3) FIG. 2 a sectional view through the exemplary piston, a connecting rod and a crankshaft of an internal combustion engine; and

(4) FIG. 3 a plurality of mutually adjacently arranged sectional views, which illustrate a movement of the piston and the connecting rod during a rotation of the crankshaft.

(5) The embodiments shown in the figures correspond at least in part, so similar or identical parts are provided with the same reference signs and are also explained via reference to the description of other embodiments or figures to avoid repetition.

(6) In FIG. 1, a piston 10 of an internal combustion engine is illustrated in a sectional plane which is eccentric to a centre axis of the piston 10. The internal combustion engine can be comprised for example in a motor vehicle, in particular a commercial vehicle. The commercial vehicle can be for example a heavy goods vehicle or a bus. The internal combustion engine can have a plurality of cylinders with a plurality of pistons 10.

(7) The piston 10 has a fluid channel 12 formed as an internal piston cooling channel. The fluid channel 12 can extend for example annularly in the interior of the piston 10. A fluid, in particular a cooling lubricating fluid, for example oil, can be injected into the fluid channel 12 by means of a fluid injecting nozzle 14. The fluid injecting nozzle 14 can be secured on a crankcase 16 (merely indicated schematically), for example. The fluid injecting nozzle 14 is directed towards an inlet opening 18 of an inlet channel 20 of the piston 10. The inlet channel 20 leads into the fluid channel 12. Fluid injected through the inlet opening 18 by the fluid injecting nozzle 14 makes its way into the fluid channel 12 via the inlet channel 20. The fluid cools the piston 10 here. The fluid channel 12 can be connected to an outlet channel (not visible in FIG. 1), which is arranged offset from the inlet channel 20 through 180° about the piston centre axis, for example.

(8) In FIG. 2, the piston 10 is illustrated in a further sectional view, wherein the section plane is centric to the centre axis of the piston 10. For the sake of clarity, the fluid injecting nozzle 14 and the crankcase 16 of FIG. 1 are not illustrated in FIG. 2.

(9) The piston 10 is connected in an articulated manner, in particular pivotably, to a crankshaft 24 via a connecting rod 22. The crankshaft 24 is mounted on a crankcase so that it is rotatable about an axis of rotation relative to the crankcase. The piston 10 is capable of translatory movement relative to a cylinder wall of a cylinder (not illustrated). The translatory movements of the piston 10 in the cylinder are converted into a rotatory movement of the crankshaft 24 about its axis of rotation. The piston 10 can be supported on the cylinder wall during its translatory upward and downward movements.

(10) The piston 10 has an outlet channel 26. The outlet channel 26 extends between the fluid channel 12 and an outlet opening 28 in a piston head 30 of the piston 10. Starting from the piston head 30, the outlet channel 26 can be drilled into the piston 10. The outlet opening 28 is arranged in a rounded region of the piston head 30.

(11) The connecting rod 22 has a small end 32, a connecting rod shaft 34 and a big end 36. The connecting rod shaft 34 extends between the small end 32 and the big end 36.

(12) The small end 32 has a small connecting rod eye 38. In the small connecting rod eye 38, a piston pin 40 is mounted in a piston pin bearing 42, formed for example as a slide bearing. The piston pin 40 connects the connecting rod 22 pivotably to the piston 10. In detail, the connecting rod 22 is pivotable within a specified angular range, for example between 30° and 40°, relative to the piston 10 during the upward and downward movements of the piston 10. The piston pin 40 and the piston pin bearing 42 can be lubricated by fluid mist, for example oil mist, which results from the injection of fluid by the fluid injecting nozzle 14 (see FIG. 1). The piston pin 40 is retained axially in the piston 10, e.g. via retaining rings.

(13) The big end 36 has a large connecting rod eye 44. A connecting rod bearing 46 formed as a slide bearing, for example, is received in the large connecting rod eye 44. The connecting rod bearing 46 connects the connecting rod 22 pivotably to a crankpin of the crankshaft 24.

(14) To realise lubrication of the connecting rod bearing 46, the connecting rod 22 has a connecting channel 48. The connecting channel 48 can form a fluid connection between the outlet channel 26 and the large connecting rod eye 44. The fluid channel 12, the outlet channel 26 and the connecting channel 48 therefore form a device for lubricating the connecting rod bearing 46.

(15) The connecting channel 48 extends between an inlet opening 50 and an outlet opening 52. The inlet opening 50 is provided in a rounded circumferential surface 54 of the small end 32. The outlet opening 52 is provided in an inner circumferential surface 56 of the large connecting rod eye 44.

(16) The connecting channel 48 has, by way of example, an inlet region 58, a slant bore 60 and a longitudinal bore 62. The inlet region 58 is formed by a step-shaped recess in the outer circumferential surface 54 of the small end 32. The slant bore 60 extends from a base of the inlet region 58 to the connecting rod shaft 34. The slant bore 60 bypasses the small connecting rod eye 38 and the piston pin 40. The slant bore 60 can be drilled starting from the base of the recess. The slant bore 60 is a bore which is at a slant with respect to the longitudinal axis of the connecting rod 22. The longitudinal bore 62 extends from the inner circumferential surface 56 of the large connecting rod eye 44 through the connecting rod shaft 34 to an end of the slant bore 60. The longitudinal bore 62 can extend, for example, longitudinally or parallel to a centre longitudinal axis of the connecting rod 22. The longitudinal bore 62 can be drilled starting from the inner circumferential surface 56.

(17) In the region of the outlet opening 28 and the inlet opening 50, the piston head 30 and the small end 32 are specifically adapted to one another. The piston head 30 and the small end 32 are machined with respect to one another here so that there is only a small gap between the piston head 30 and the outer circumferential surface 54 of the small end 32. The gap can be smaller than 0.1 cm, in particular smaller than 0.01 cm, for example. The gap can preferably be in a range between 0.01 cm and 0.001 cm. To enable such a gap size to be produced mechanically, the small end 32 and the piston 10 have an increased material thickness in this region. The gap prevents the small end 32 from rubbing against the piston head 30. At the same time, the gap enables a fluid connection between the outlet channel 26 and the connecting channel 48 when the outlet opening 28 and the inlet opening 50 overlap.

(18) As described in detail below with reference to FIG. 3, the piston head 30 in the region of the outlet opening 28 and the small end 32 in the region of the inlet opening 50 sweep over one another during the operation of the internal combustion engine so that an intermittent fluid connection is formed between the fluid channel 12 and the connecting rod bearing 46.

(19) In FIG. 3, the piston 10 is illustrated during an upward and downward movement. In the case of the upward movement, the piston 10 moves from a so-called lower dead centre to a so-called upper dead centre. In the case of the downward movement, the piston moves from the upper dead centre to the lower dead centre.

(20) During the upward movement, the outlet opening 28 and the inlet opening 50 overlap. The overlap takes place within an angular range (for example smaller than 10°, 15° or 20°) which is smaller than the specified angular range within which the connecting rod 22 is pivotably connected to the piston 10. During the upward movement, fluid from the fluid channel 12 is pressed from the outlet opening 28 into the connecting channel 48 via the gap and the inlet opening 50. For example, in this case, fluid pressures up to 6 bar can be achieved as a result of the high acceleration of the connecting rod 22. The fluid can flow to the connecting rod bearing 46 and lubricate this. The fluid can finally flow off into an oil sump, for example via radial bores (not illustrated) in the big end 36.

(21) During the downward movement, the inlet opening 50 is covered by the piston head 30. The covering of the inlet opening takes place within an angular range (for example smaller than 15°, 20° or 25°) which is smaller than the specified angular range within which the connecting rod 22 is pivotably connected to the piston 10. As a result of covering the inlet opening 50, a cavitation tendency of the fluid in the connecting channel 48 during the downward movement can be reduced. The cavitation could otherwise considerably impair a throughflow through the connecting channel 48 during the subsequent upward movement.

(22) The device disclosed herein for lubricating the connecting rod bearing 46 is based on an innovative lubricating method. This method of lubrication comprises feeding, in particular injecting, a fluid, for example oil, into the fluid channel 12 of the piston 10 by means of the fluid injecting nozzle 14. The method further comprises feeding the fluid from the fluid channel 12 to the connecting rod bearing 46 via the outlet channel 26 of the piston 10 and the connecting channel 48 of the connecting rod 22. It is pointed out that, to carry out the method, other configurations, in particular of the outlet channel 26 and the connecting channel 48, are also possible.

(23) The invention is not restricted to the preferred exemplary embodiments described above. Instead, a plurality of variants and modifications is possible, which likewise make use of the inventive idea and therefore fall within the scope of protection. In particular, the invention also claims protection for the subject matter and the features of the subclaims independently of the claims to which they refer. In particular, the features of the independent claim 1 are disclosed independently of one another. In addition, the features of the subclaims are also disclosed independently of all the features of the independent claim 1 and for example independently of the features relating to the presence and/or the configuration of the piston and/or the connecting rod of the independent claim 1.

LIST OF REFERENCE SIGNS

(24) 10 Piston

(25) 12 Fluid channel

(26) 14 Fluid injecting nozzle

(27) 16 Crankcase

(28) 18 Inlet opening

(29) 20 Inlet channel

(30) 22 Connecting rod

(31) 24 Crankshaft

(32) 26 Outlet channel

(33) 28 Outlet opening

(34) 30 Piston head

(35) 32 Small end

(36) 34 Connecting rod shaft

(37) 36 Big end

(38) 38 Small connecting rod eye

(39) 40 Piston pin

(40) 42 Piston pin bearing

(41) 44 Large connecting rod eye

(42) 46 Connecting rod bearing

(43) 48 Connecting channel

(44) 50 Inlet opening

(45) 52 Outlet opening

(46) 54 Outer circumferential surface

(47) 56 Inner circumferential surface

(48) 58 Inlet region

(49) 60 Slant bore

(50) 62 Longitudinal bore