EP2670955B1 - Shaft such as camshaft comprising a hollow section - Google Patents

Description

The invention relates to a shaft, in particular camshaft with a hollow shaft portion, according to the preamble of claim 1.

In internal combustion engines and piston compressors leakage losses are observed in practice, which are due to an incomplete seal. These leakage losses are referred to as blowby gas and contain a significant amount of oil. With respect to internal combustion engines, it is therefore customary to direct the blow-by gas accumulating in the valve chamber back into the intake tract of the internal combustion engine. On the one hand to minimize the loss of oil by blow-by gas and on the other hand to ensure optimum combustion and minimum environmental impact, it is known to subject the blowby gas to oil separation and to pass the separated oil back into the oil circuit.

In a generic shaft, in particular camshaft, the blow-by gas is discharged through the hollow shaft section, whereby an oil separation device can also be integrated directly into the hollow shaft section. It should be noted that in the environment of a camshaft oil is often present in different droplet sizes. In addition to the finest oil droplets that are contained in the blow-by gas and are deposited, for example, by swirl generators, large oil droplets or oil splashes are often observed in the vicinity of a camshaft. Such large droplets or splashes can form, for example, if there is an oil bath or an oil foam in the area of the camshaft. In unfavorable cases, it can even happen that an oil jet reaches the shaft and in particular the hollow shaft section with the inlet opening for the discharge of the blow-by gas.

Since a subsequent separation of oil is associated with a high cost, it is advantageous if in a generic wave large oil droplets, oil spills and oil jets are kept away from the at least one inlet opening of the hollow shaft portion. Despite the ventilation and the possibility of discharging the blow-by gas, the loss of oil and contamination of the downstream equipment can then be kept low. If according to a preferred embodiment, a downstream Ölabscheidevorrichtung, for example, within the hollow shaft portion, is present, this Ölabscheidevorrichtung must only separate the fine oil droplets from the blowby gas, whereby a total of a very efficient and reliable de-oiling of the gas can be achieved.

A camshaft having a hollow shaft portion, which has at least one radial inlet opening for the discharge of a gas through the hollow shaft portion and with a splash guard, which is arranged in the region of the radial inlet opening on the hollow shaft portion, is known from EP 1 880 085 B1 known, wherein on the outer circumference of the shaft for the separation of oil, a pre-separator and an integrated in the hollow shaft portion swirl generator are provided as Endabscheider. The pre-separator is funnel-shaped and covers a plurality of radial inlet openings of the hollow shaft portion in the radial direction. However, the effect of splash protection is imperfect because obliquely injecting oil droplets or jets can not be prevented. The pre-separator is also constructed comparatively expensive and requires a considerable amount of space.

A shaft according to the preamble of claim 1 is known from US 4,714,139 known. An impeller, which has a certain splash protection allows is formed as an integral part of a shaft body, resulting in a relatively complex shape.

Against this background, the invention has for its object to provide a shaft with a hollow shaft portion and at least one radial inlet opening in the hollow shaft portion, wherein at least largely prevented by a structurally simple spray protection device, the injection of large oil droplets or oil jets in the at least one inlet opening ,

The object of the invention and solution of the problem is a shaft according to claim 1. Such a configuration can be achieved that essentially only blow-by gas passes into the passage openings and subsequently into the at least one inlet opening of the hollow shaft portion, while large oil droplets, oil spills and jets are held, the effectiveness of the splash guard usually increases with increasing speed of the shaft.

The projections generate upon rotation of the shaft a gas flow in the direction of rotation, which prevents at least to some extent the spewing of oil droplets or even the injection of an oil jet into the passage openings of the splash guard and in the at least one inlet opening of the hollow shaft portion. Furthermore, it should be noted that large oil droplets and splashes can not follow the rotation of the splash guard to the same extent as the blow-by gas. Thus, oil droplets and splashes are increasingly deposited at the rotation of the shaft due to their mass inertia at the projections, while the blowby gas follow the rotational movement and can flow into the passages. The passages are so as it were sealed off from the comparatively sluggish droplets of oil and splashes by the projections which are arranged between the passage openings. The efficiency of this foreclosure depends on the one hand on the shape of the Vorspünge, in particular their height and orientation and on the other hand on the volume flow of the blow-by gas. As the volume flow of the blow-by gas increases, under certain circumstances it can no longer be completely avoided that even larger oil droplets are entrained and get into the hollow shaft section. Nevertheless, the inventive design of the shaft with the described splash guard is characterized by a very efficient and extensive separation of larger oil particles. Even if the shaft or even the splash guard partially immersed in an oil bath, the penetration of oil can be effectively prevented. An oil bath in the region of a camshaft can occur in practice under extreme loads on an engine, for example an increased oil level in the cylinder head or during strong acceleration or braking maneuvers.

The splash guard is designed according to a preferred embodiment of the invention so that the fine oil droplets of the blow-by gas are not deposited. Such separation of the oil from the blow-by gas preferably takes place in a separate, downstream oil separation device, which is provided, for example, in the form of a helical flight or several helical flights within the hollow shaft section. However, it is within the scope of the invention, the advantage that such a downstream Ölabscheidevorrichtung is not additionally burdened by oil splash or the like.

For the further embodiment of the shaft with the splash guard, various particularly advantageous possibilities arise within the scope of the invention. According to the invention, the jacket has a sleeve-shaped middle section, from which the projections protrude. The sleeve-shaped central portion is expediently substantially cylindrical or slightly conical. The jacket thus has a simple shape, on which the projections and openings can be easily formed.
The splash guard can be designed as a molded part, in particular cast part, whereby a simple production is possible. The splash guard can be shrunk similar to cams or fixed by the expansion of the hollow shaft portion. But since it is a mechanically comparatively low-loaded component, a simplified assembly is possible. Thus, the splash guard may also be formed of segments, in particular two longitudinally divided segments. The individual segments are then placed on the region of the hollow shaft portion at the at least one radial inlet opening and clipped. The splash guard can be fixed with adhesive on the hollow shaft portion or assembled from the segments. Additionally or alternatively, it is also possible to provide on the splash guard and the hollow shaft portion cooperating interlocking elements, which cause a fixation.

Depending on the expected loads can be considered for the splash guard in addition to metallic materials, a plastic, ceramic or other durable material into consideration.

With regard to the general shape of the splash guard, it is advantageous if viewed in the longitudinal direction of the shaft at one end and preferably at both ends is radially enlarged, for which purpose, for example, flange-shaped formations can be provided. In the context of such an embodiment, blow-by gas can easily dislodge the radially exposed jacket however, with the widened ends of the splash guard injecting oil from immediately adjacent means of the shaft, such as adjacent cams, can be effectively prevented. When dimensioning the splash guard, the space available in the longitudinal direction of the shaft and in the radial direction must be taken into account.

With regard to the specific embodiment of the splash guard, it is advantageous if the projections are formed as ribs which extend straight or with a certain inclination in the longitudinal direction of the shaft.

If the shaft is designed as a camshaft, this always has a predetermined direction of rotation. In other waves, a preferred direction of rotation is usually set. If a predetermined or at least a preferred direction of rotation is present, the projections are expediently oriented in such a way that separated oil is thrown outwards during the rotation in the predetermined or preferred direction of rotation. In an embodiment of the projections as ribs, these can thus be tilted such that the free ends of the ribs point away from the predetermined or preferred direction of rotation. The tilting with respect to an alignment extending exactly in the radial direction can be, for example, between 10 ° and 40 °, in particular between 15 ° and 30 °.

As explained above, the passage openings are protected by the rotational movement through the projections arranged between the passage openings. If the shaft has a predetermined or preferred direction of rotation, it is advantageous if, viewed in the direction of rotation, a projection is provided directly in front of each passage opening. The protection of the passage openings before injecting oil is further improved when the Projections as described above against the direction of rotation are tilted and as exactly in the radial direction, the passages cover to some extent.

The passage openings may be, for example, longitudinal slots which extend substantially parallel to the longitudinal axis of the shaft. In combination with extending in the longitudinal direction of the shaft ribs then results in a particularly advantageous embodiment.

The splash guard according to the invention is the at least one radial inlet opening of the hollow shaft portion upstream to effectively prevent injection of the oil. It is advantageous if a radial gap is provided between the jacket of the splash guard with the passage openings provided therein and the hollow shaft portion with the at least one passage opening. In the context of such an embodiment, namely, an offset in the longitudinal direction and / or circumferential direction of the shaft may be present between the passage openings and the at least one inlet opening. The gap then forms a flow channel for the gas to be discharged, with the further deflection of a separation of oil is possible. At least it is avoided that rapid oil droplets can pass without a deflection directly into the at least one inlet opening of the hollow shaft portion.

Usually, a plurality of inlet openings are provided on the hollow shaft section, which are distributed uniformly around the circumference. In order then to achieve the described offset in the longitudinal and / or circumferential direction, the passage openings are to be distributed according to the circumference of the shell of the splash guard. In particular, the number of passage openings be an integral multiple of the number of inlet openings.

It is expedient in this context, when the projections and openings are distributed in groups around the circumference of the shell in a uniform arrangement, in particular in pairs. In a pairwise arrangement, a first projection, a first passage opening, a second projection and a second passage opening are then arranged directly one behind the other as viewed in the direction of rotation.

As already explained at the outset, it is advantageous if, for the separation of the fine oil droplets from the blowby gas, a separate oil separation device is provided which can be arranged inside the hollow shaft section. For this purpose, for example, a helical swirl generator can be provided with one or more screw flights, wherein the fine oil droplets of the blow-by gas are thrown outwards by the twisting movement and are deposited accordingly. By varying the pitch of the screw flights, the flow velocity in the flow direction can also be increased.

In order to avoid excessive overpressure in the region of the camshaft, a bypass valve with an adjoining bypass channel can be provided within the hollow shaft section, which bypasses the blowby gas at the oil separation device.

Fig. 1

ein einbaufertiges Nockenwellenmodul mit einer Nockenwelle, welcher mit eine Spritzschutzeinrichtung versehen ist,

Fig. 2

einen Schnitt entlang der Linie A-A der Fig. 1 in einer Draufsicht,

Fig. 3

der Schnitt gemäß der Fig. 2 in einer perspektivischen Ansicht,

Fig. 4

ein Längsschnitt durch die Nockenwelle im Bereich der Spritzschutzeinrichtung.

The invention will be explained below with reference to a drawing showing only one embodiment:

Fig. 1

a ready-to-install camshaft module with a camshaft which is provided with a splashguard device,

Fig. 2

a section along the line AA the Fig. 1 in a plan view,

Fig. 3

the section according to the Fig. 2 in a perspective view,

Fig. 4

a longitudinal section through the camshaft in the area of the splash guard.

The Fig. 1 shows a ready-to-install camshaft module with a camshaft 1, which has a plurality of cams 2 according to their usual structure and is supported by bearing blocks 3. Between two adjacent cams 2, a splash guard 4 is provided, whose operation will be explained in detail below.

Of the Fig. 1 It can already be seen that the splash guard 4 is composed of a separating surface 5 of two segments. Furthermore, it can be seen that the splash guard 4 has widened flange ends 6a, 6b and therebetween a sleeve-shaped, substantially cylindrical central portion 7. At the central portion 7 are passage openings 8 in the form of longitudinal slots and projections in the form of ribs 9 can be seen extending in the wavelength direction.

The purpose of the splash guard 4 and the exact design of the camshaft 1 is apparent from the representation of Fig. 2 to 4 , The show Fig. 2 and 3 similar cross sections, wherein in the Fig. 2 in the plan view of the cross section, the exact alignment of the ribs 9 and the passage openings 8 can be seen. In the perspective view of Fig. 3 is with additional consideration of the Fig. 1 the course of the ribs 9 and passage openings 8 in the longitudinal direction of the shaft to better recognize.

In the sectional views, it can first be seen that the camshaft 1 has a hollow shaft section 10 which has at least one, in the exemplary embodiment, a total of six radial inlet openings 11a, 11b for the discharge of a blowby gas B through the hollow shaft section 10. The splash guard 4 is intended to avoid the injection of large oil droplets or oil jets directly into the radial inlet openings 11 a, 11 b into it.

For this purpose, the ribs 9 and passage openings 8 are provided. Upon rotation of the camshaft 1 in the predetermined direction of rotation D, a gas flow is generated in the circumferential direction, which prevents the spewing of large oil droplets or even the injection of an oil jet. Blowby gas B, however, can follow the rotation of the camshaft 1 at a corresponding overpressure and flow into the inlet openings 11a, 11b. The path of the blow-by gas B is in the sectional views of Fig. 2 to 4 indicated by dashed lines.

In addition to the generation of a gas flow through the ribs 9 is also to be considered that due to the rotation of the splash guard 4 and the inertia of larger particles or jets they settle on the ribs 9. Of the Fig. 2 is to be seen in this context that seen in the direction of rotation D before each passage opening 8, a rib 9 is present. Large droplets of oil, oil splashes and oil jets first settle on the ribs 9 before they can reach the passage openings 8.

Of the Fig. 2 It can also be seen that the ribs are tilted relative to the predetermined direction of rotation D such that their free ends point away from the predetermined direction of rotation D. Compared to an exactly running in the radial direction alignment, the tilt can for example be between 10 ° and 40 °, in particular between 15 ° and 30 °. In the embodiment, the tilt is about 25 °. By the described tilting of the ribs 9 on the one hand ensures that the immediately next to each rib 9 recessed arranged passage opening 8 is even better protected. In addition, oil that has deposited on the rib 9 is effectively forced outward due to centrifugal forces and eventually thrown away.

The exact structure of the hollow shaft portion 10 is in the Fig. 4 to recognize. Accordingly, the hollow shaft section 10 has different inlet openings 11a, 11b. Between the central portion 7 of the splash guard 4 and the hollow shaft portion 10, a radial gap 12 is formed, through which the blowby gas B flows. Three inlet openings 11a lead to an annular region within the hollow shaft section 10, which supplies the blow-by gas B for oil separation to a swirl generator, not shown. In order to enable rapid discharge of the blow-by gas even without cleaning at a high overpressure, a bypass valve 13 with an adjoining bypass channel 14 is arranged centrally in the hollow shaft section 10. From the gap 12, the blowby gas B can pass through further inlet openings 11 b to the bypass valve 13.

According to the Fig. 4 is provided between the passage openings 8 of the splash guard 4 and the first inlet openings 11 a offset in the longitudinal direction. The blowby gas B is thus diverted, so too in this deflection even larger oil droplets can be deposited. In particular, there is no continuous line of sight along which oil droplets can pass into said inlet openings 11a.

With regard to the further inlet openings 11 b, through which the blowby gas B can reach the bypass valve 13, lies in accordance with Fig. 2 at least one offset in the circumferential direction. This is achieved in that the passage openings 8 and ribs 9 are arranged in groups, each with two passage openings 8 and ribs 9. These six groups are then arranged so that the leading to the bypass valve 13 inlet openings 11 b are arranged exactly between two adjacent groups.

As already related to the Fig. 1 explained, the splash guard 4 is made of segments, in the embodiment of two longitudinally divided segments. The interface 5 between the segments is in the Fig. 2 and 3 recognizable, wherein the segments may be connected, for example, with an adhesive, in particular a two-component adhesive.

To attach the splash guard 4 to the camshaft 1, an adhesive may also be provided. Additionally or alternatively, co-operating interlocking elements 15 may be provided on the splash guard 4 and the hollow shaft portion 10, which are exemplified in the Fig. 4 are shown.

Claims (12)

1. A shaft, in particular a camshaft (1) with a hollow shaft section (10), which comprises at least one radial inlet opening (11 a, 11 b) for the removal of a gas through the hollow shaft section (10) and with a splash protection device (4), which is disposed in the region of the at least one radial inlet opening (11a, 11 b) on the hollow shaft section (10), wherein the splash protection device (4) comprises a radially exposed casing with radial through-openings (8) and projections between the through-openings (8), and wherein the projections protrude radially opposite the through-openings, and that the casing comprises a sleeve-shaped middle section (7), from which the projections protrude.
2. The shaft according to claim 1, characterised in that the projections are constituted as ribs (9) which run in the longitudinal direction of the shaft.
3. The shaft according to claim 2, characterised in that the shaft has a preselected or preferred rotational direction (D), wherein the ribs (9) are tilted in such a way that their free ends point away from the preselected or preferred rotational direction (D).
4. The shaft according to any one of claims 1 to 3, characterised in that the shaft has a preselected or preferred rotational direction (D) and that, viewed in the rotational direction (D), a projection is provided in front of each through-opening (8).
5. The shaft according to any one of claims 1 to 4, characterised in that the through-openings (8) are constituted as elongated slots.
6. The shaft according to any one of claims 1 to 5, characterised in that a radial gap (12) is provided between the casing of the splash protection device (4) and the hollow shaft section (10) with the at least one inlet opening (11 a, 11 b), wherein an offset in the longitudinal direction and/or circumferential direction of the shaft is provided between the through-opening (8) and the at least one inlet opening (11 a, 11 b).
7. The shaft according to any one of claims 1 to 6, characterised in that the splash protection device (4) comprises ends (6a, 6b) which are radially enlarged as viewed in the longitudinal direction of the shaft.
8. The shaft according to any one of claims 1 to 7, characterised in that the projections and through-openings (8) are distributed in groups, in particular in pairs, around the circumference of the casing in a uniform arrangement.
9. The shaft according to any one of claims 1 to 8, characterised in that a bypass valve (13) and/or an oil separation device are provided inside the hollow shaft section (10).
10. The shaft according to any one of claims 1 to 9, characterised in that the splash protection device (4) is constituted by segments, in particular by two longitudinally split segments.
11. The shaft according to any one of claims 1 to 10, characterised in that the splash protection device (4) is fixed with adhesive on the hollow shaft section (10).
12. The shaft according to any one of claims 1 to 11, characterised in that the splash protection device (4) and the hollow shaft section (10) comprise interacting form-fit elements (15).

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