EP2670955B2 - Shaft such as camshaft comprising a hollow section - Google Patents

Description

The invention relates to a camshaft with a hollow shaft section which has at least one radial inlet opening for discharging a gas through the hollow shaft section and with a splash protection device which is arranged in the area of the at least one radial inlet opening on the hollow shaft section.

In practice, leakage losses are observed in internal combustion engines and piston compressors, which can be attributed to incomplete sealing. These leakage losses are referred to as blowby gas and contain a significant proportion of oil. In relation to internal combustion engines, it is therefore common to direct the blow-by gas that occurs in the valve chamber back into the intake tract of the internal combustion engine. In order, on the one hand, to minimize the loss of oil due to blow-by gas and, on the other hand, to ensure optimal combustion and minimal environmental impact, it is known to subject the blow-by gas to oil separation and to lead the separated oil back into the oil circuit.

In the case of a camshaft, the blow-by gas is removed through the hollow shaft section, and an oil separator device can also be integrated directly into the hollow shaft section. It should be taken into account that oil is often present in a wide variety of droplet sizes in the area surrounding a camshaft. In addition to the finest oil droplets that are contained in the blowby gas and have to be separated, for example, by swirl generators, large oil droplets or oil splashes are also often observed in the vicinity of a camshaft. Such large droplets or splashes can form, for example, if there is an oil bath or oil foam in the area of the camshaft. In unfavorable cases, it can even happen that a jet of oil hits the shaft and in particular the hollow shaft section with the inlet opening for discharging the blow-by gas.

Since subsequent separation of oil involves a great deal of effort, it is advantageous if large oil droplets, oil splashes and oil jets are kept away from the at least one inlet opening of the hollow shaft section in a camshaft according to claim 1. Despite the ventilation and the possibility of discharging the blow-by gas, the loss of oil and contamination of the downstream facilities can be kept to a minimum. If, according to a preferred embodiment, a downstream oil separation device, For example, within the hollow shaft section, this oil separation device only has to separate the fine oil droplets from the blowby gas, which means that a very efficient and reliable deoiling of the gas can be achieved overall.

A camshaft with a hollow shaft section which has at least one radial inlet opening for discharging a gas through the hollow shaft section and with a splash protection device which is arranged in the area of the radial inlet opening on the hollow shaft section is from the EP 1 880 085 B1 known, with a pre-separator and a swirl generator integrated into the hollow shaft section being provided as a final separator on the outer circumference of the shaft for separating oil. The pre-separator is funnel-shaped and covers several radial inlet openings of the hollow shaft section in the radial direction. However, the splash protection effect is imperfect because oil droplets or jets that inject at an angle cannot be prevented. The pre-separator is also comparatively complex in design and requires a considerable amount of space.

A lubrication system for a shaft with an oil separator device is from the US 4,714,139 known. A pump wheel, which enables a certain amount of splash protection, is formed as an integral part of a shaft body, resulting in a relatively complex shape.

Against this background, the invention is based on the object of specifying a camshaft with a hollow shaft section and at least one radial inlet opening in the hollow shaft section, in which the injection of large oil droplets or oil jets into the at least one inlet opening is at least largely prevented by a structurally simple splash protection device .

The object of the invention and solution to the problem is a camshaft according to claim 1. With such a configuration it can be achieved that essentially only blow-by gas gets into the passage openings and subsequently into the at least one inlet opening of the hollow shaft section, while large oil droplets, oil splashes and -jets are prevented, with the effectiveness of the splash protection device usually increasing as the speed of the shaft increases.

When the shaft rotates, the projections generate a gas flow in the direction of rotation, which allows the injection of oil droplets or even the injection of an oil jet initially into the passage openings of the splash protection device and accordingly also prevented to at least a certain extent in the at least one inlet opening of the hollow shaft section. Furthermore, it must be taken into account that large oil droplets and splashes cannot follow the rotation of the splash guard to the same extent as the blow-by gas. As the shaft rotates, oil droplets and splashes are increasingly deposited on the projections due to their inertia, while the blow-by gas can follow the rotational movement and flow into the passage openings. The passage openings are, to a certain extent, sealed off from the comparatively sluggish oil droplets and splashes by the projections which are arranged between the passage openings. The efficiency of this isolation depends on the one hand on the shape of the projections, in particular their height and orientation, and on the other hand on the volume flow of the blowby gas. As the volume flow of the blow-by gas increases, it may no longer be possible to completely prevent larger oil droplets from being carried along and ending up in the hollow shaft section. Nevertheless, the design of the camshaft according to the invention with the splash protection device described is characterized by a very efficient and extensive separation of larger oil particles. Even if the camshaft or even the splash guard is partially immersed in an oil bath, the ingress of oil can be effectively prevented. In practice, an oil bath in the area of a camshaft can occur when an engine is under extreme load, for example an increased oil level in the cylinder head or during strong acceleration or braking maneuvers.

According to a preferred embodiment of the invention, the splash protection device is designed so that the fine oil droplets of the blowby gas are not separated. Such a separation of the oil from the blowby gas preferably takes place in a separate, downstream oil separation device, which is provided, for example, in the form of a screw flight or several screw flights within the hollow shaft section. However, within the scope of the invention there is the advantage that such a downstream oil separation device is not additionally burdened by oil splashes or the like.

For the further design of the camshaft with the splash protection device, various particularly advantageous options arise within the scope of the invention. According to the invention, the jacket has a sleeve-shaped central section from which the projections protrude. The sleeve-shaped middle section is expediently essentially cylindrical or light conically shaped. The jacket therefore has a simple shape on which the projections and passage openings can be easily formed.

The splash protection device can be designed as a molded part, in particular a cast part, which enables simple production. The splash protection device can be shrunk on in a similar way to cams or fixed by expanding the hollow shaft section. However, since it is a component subject to comparatively little mechanical stress, simplified assembly is also possible. The splash protection device can also be formed from segments, in particular two longitudinally divided segments. The individual segments are then placed on the area of the hollow shaft section at the at least one radial inlet opening and clipped into place. The splash guard can be fixed to the hollow shaft section with adhesive or assembled from the segments. Additionally or alternatively, it is also possible to provide cooperating positive locking elements on the splash protection device and the hollow shaft section, which bring about a fixation.

Depending on the expected loads, in addition to metallic materials, plastic, ceramic or another resistant material can also be considered for the splash protection device.

With regard to the general shape of the splash protection device, it is advantageous if it is enlarged radially at one end and preferably at both ends when viewed in the longitudinal direction of the shaft, for which purpose, for example, flange-shaped formations can be provided. In the context of such a configuration, blow-by gas can easily flow against the radially exposed jacket, although oil injecting from immediately adjacent devices on the shaft, for example adjacent cams, can be effectively prevented by the widened ends of the splash protection device. When dimensioning the splash protection device, the installation space available in the longitudinal direction of the shaft and in the radial direction must be taken into account.

With regard to the specific design of the splash protection device, it is advantageous if the projections are designed as ribs that run straight or with a certain inclination in the longitudinal direction of the shaft.

A camshaft always has a predetermined direction of rotation. If there is a predetermined direction of rotation, the projections are expediently aligned so that separated oil is thrown outwards during rotation in the predetermined direction of rotation. If the projections are designed as ribs, they can be tilted in such a way that the free ends of the ribs point away from the specified or preferred direction of rotation. The tilting relative to an alignment that runs 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 due to the rotational movement by the projections arranged between the passage openings. Since the camshaft has a predetermined direction of rotation, it is advantageous if, viewed in the direction of rotation, a projection is provided immediately in front of each passage opening. The protection of the passage openings from injecting oil is further improved if the projections are inclined against the direction of rotation as described above and thus cover the passage openings to a certain extent when viewed precisely in the radial direction.

The passage openings can be, for example, longitudinal slots that run essentially parallel to the longitudinal axis of the shaft. The combination with ribs running in the longitudinal direction of the shaft then results in a particularly advantageous embodiment.

The splash protection device of the camshaft according to the invention is located upstream of the at least one radial inlet opening of the hollow shaft section in order to effectively prevent the oil from being injected. It is advantageous if a radial gap is provided between the jacket of the splash protection device with the passage openings provided therein and the hollow shaft section with the at least one passage opening. As part of such a configuration, there can be an offset in the longitudinal direction and/or circumferential direction of the shaft 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 making it possible to separate oil. At least it is avoided that fast oil droplets can get directly into the at least one inlet opening of the hollow shaft section without being deflected.

Typically, several inlet openings are provided on the hollow shaft section, which are evenly distributed around the circumference. In order to then achieve the described offset in the longitudinal and/or circumferential direction, the passage openings must be distributed accordingly on the circumference of the jacket of the splash protection device. In particular, the number of passage openings can be an integral multiple of the number of inlet openings.

In this context, it is also expedient if the projections and passage openings are distributed around the circumference of the jacket in a uniform arrangement in groups, in particular in pairs. When arranged in pairs, a first projection, a first passage opening, a second projection and a second passage opening are then arranged immediately one behind the other, viewed in the direction of rotation.

As already explained at the beginning, it is advantageous if a separate oil separation device is provided for the separation of the fine oil droplets from the blowby gas, which can be arranged within the hollow shaft section. For this purpose, for example, a screw-shaped swirl generator with one or more screw flights can be provided, the fine oil droplets of the blow-by gas being thrown outwards by the swirling movement and separated accordingly. By varying the pitch of the screw flights, the flow speed in the direction of flow can also be increased.

In order to avoid excessive overpressure in the area of the camshaft, a bypass valve with an adjoining bypass channel can also be provided within the hollow shaft section, which leads the blow-by gas past the oil separator 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 is explained below using a drawing that only shows an exemplary embodiment: It shows:

Fig. 1

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

Fig. 2

a cut along line AA of the Fig. 1 in a top view,

Fig. 3

the cut 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, according to its usual structure, has a large number of cams 2 and is held by bearing blocks 3. A splash protection device 4 is provided between two adjacent cams 2, the operation of which is explained in detail below.

The Fig. 1 It can already be seen that the splash protection device 4 is composed of two segments on a separating surface 5. Furthermore, it can be seen that the splash protection device 4 has flange-like widened ends 6a, 6b and has a sleeve-shaped, essentially cylindrical middle section 7 in between. On the middle section 7, passage openings 8 in the form of longitudinal slots and projections in the form of ribs 9 can be seen, which run in the longitudinal direction of the shaft.

The purpose of the splash protection device 4 and the exact design of the camshaft 1 can be seen from the illustration Fig. 2 to 4 . They show Fig. 2 and 3 similar cross sections, whereby in the Fig. 2 The exact alignment of the ribs 9 and the passage openings 8 can be seen in the top view of the cross section. In the perspective view of the Fig. 3 is, however, with additional consideration of the Fig. 1 the course of the ribs 9 and openings 8 in the longitudinal direction of the shaft can be seen better.

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 blow-by gas B through the hollow shaft section 10. The splash protection device 4 is intended to avoid the injection of large oil droplets or oil jets directly into the radial inlet openings 11a, 11b.

For this purpose, the ribs 9 and passage openings 8 are provided. When the camshaft 1 rotates in the predetermined direction of rotation D, a gas flow is generated in the circumferential direction, which prevents the injection of large oil droplets or even the injection of an oil jet. However, with a corresponding excess pressure, blowby gas B can follow the rotation of the camshaft 1 and flow into the inlet openings 11a, 11b. The path of the blowby gas B is shown in the sectional views Fig. 2 to 4 indicated by dashed lines.

In addition to the generation of a gas flow through the ribs 9, it must also be taken into account that due to the rotation of the splash protection device 4 and the inertia of larger particles or jets, these settle on the ribs 9. The Fig. 2 In this context it can be seen that, viewed in the direction of rotation D, there is a rib 9 in front of each passage opening 8. Large oil droplets, oil splashes and oil jets are first deposited on the ribs 9 before they can reach the passage openings 8.

The Fig. 2 It can also be seen that the ribs are tilted relative to the predetermined direction of rotation D in such a way that their free ends point away from the predetermined direction of rotation D. Compared to an alignment that runs exactly in the radial direction, the tilting can be between 10°, for example and 40°, in particular between 15° and 30°. In the exemplary embodiment, the tilt is approximately 25°. On the one hand, the described tilting of the ribs 9 ensures that the passage opening 8, which is set back immediately next to each rib 9, is even better protected. In addition, oil that has settled on the rib 9 is effectively pushed outwards due to the centrifugal forces and ultimately thrown away.

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

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

With regard to the further inlet openings 11b, through which the blow-by gas B can reach the bypass valve 13, according to the Fig. 2 at least an 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 inlet openings 11b leading to the bypass valve 13 are arranged exactly between two adjacent groups.

As already in connection with the Fig. 1 explained, the splash protection device 4 is formed from segments, in the exemplary embodiment from two longitudinally divided segments. The separating surface 5 between the segments is in the Fig. 2 and 3 recognizable, wherein the segments can be connected, for example, with an adhesive, in particular a two-component adhesive.

In order to attach the splash protection device 4 to the camshaft 1, an adhesive can also be provided. Additionally or alternatively, cooperating positive locking elements 15 can also be provided on the splash protection device 4 and the hollow shaft section 10, which are exemplary in the Fig. 4 are shown.

Claims (12)

1. A camshaft (1) with a hollow shaft section (10), which comprises at least one radial inlet opening (11a, 11b) 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, 11b) 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 camshaft according to claim 1, characterised in that the projections are constituted as ribs (9) which run in the longitudinal direction of the camshaft.
3. The camshaft 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 camshaft according to any one of claims 1 to 3, characterised in that the camshaft 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 camshaft according to any one of claims 1 to 4, characterised in that the through-openings (8) are constituted as elongated slots.
6. The camshaft 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 (11a, 11b), wherein an offset in the longitudinal direction and/or circumferential direction of the camshaft is provided between the through-opening (8) and the at least one inlet opening (11a, 11b).
7. The camshaft 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 camshaft.
8. The camshaft 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 camshaft 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 camshaft 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 camshaft 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 camshaft 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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