Sealing device especially for an engine shaft

Abstract

The sealing device (1) comprises: a first annular shielding member (4) which can be engaged with a first stationary member (2) carrying an annular sealing lip (9) projecting radially and axially; and a second annular shielding member (7) which can be engaged with a second rotating member (3) and is idly fixed to the first shielding member on the opposite side of the sealing lip (9) in such a way as to define a labyrinth seal portion (19) of the static type; the second shielding member (7) is provided with a plurality of projections (20) which project axially, are located on the opposite side of the sealing lip (9), have a radial extension and are arranged so as to be separated from one another in the circumferential direction by respective circumferential recesses (22), so as to form a spiral portion (24) which defines a dynamic labyrinth seal portion (23), the spiral portion being designed to generate a fluid flow (25) which discharges external contaminants as a result of the relative rotation of the shielding members (4, 7).

Description

Technical Field

[0001] The present invention relates to a sealing device that can be inserted between two members that perform relative rotation. In particular, the present invention relates to a sealing device for an engine shaft that can be inserted between a rotating engine shaft and a fixed engine housing or body formed by a base or an oil pan, thereby performing a dual sealing function, that is, containing engine oil inside the oil pan and resisting external contaminants (water, mud, dust, etc.). Background Art

[0002] As is well known, in a sealing device located on an engine shaft, there is a problem of protecting a sealing lip, where the sealing lip makes sliding contact with the side surface of the engine shaft and is intended to prevent engine oil from seeping in and prevent external contaminants from entering. If the external contaminants come into direct contact with the sealing lip, it will cause premature wear of the sealing lip, resulting in oil leakage.

[0003] Currently, oil stop devices are available on the market that are provided with a plastic insert coated with rubber, which creates an additional labyrinth seal between the external environment containing many contaminants and the oil-side sealing lip. A sealing device for a high-pressure pump shaft is also known from US5368314, which includes a non-contact front seal between two elements of the sealing device that rotate relative to each other, due to axial facing recesses defined by grooves extending spirally in the radial direction, and a gas pressure is formed between the elements that rotate relative to each other.

[0004] The known sealing devices are not without defects. The device described in US5368314 is extremely complex, expensive, and bulky, and cannot be used for the engine shaft of a vehicle internal combustion engine.

[0005] Instead, the oil stop devices currently used in vehicle engines are reliable and compact, but in the long run, they are still unable to prevent certain contaminants (especially under critical operating conditions, such as when used in off-road vehicles) from penetrating the labyrinth seal and reaching the sliding contact lip, thereby aggravating its natural wear. In addition, the manufacture of the plastic insert coated with rubber is relatively expensive, thus requiring a double moulding operation. Summary of the Invention

[0006] Therefore, an object of the present invention is to overcome the disadvantages of the prior art, and in particular, to provide a reliable sealing device that, compared with the solutions of the prior art, has a compact size and low cost, while improving the sealing ability of the device with respect to external contaminants and oil, and generally improving the performance in terms of protecting the engine shaft assembly from contamination media.

[0007] Therefore, based on the present invention, there is provided a sealing device, in particular for an engine shaft, having the features recited in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The present invention will now be described with reference to the accompanying drawings, which illustrate two non - limiting examples of embodiments of the invention, wherein:

[0009] - Figure 1 A perspective three - quarter front view of the sealing device according to the present invention, as seen from the side opposite to the side exposed to engine oil during use, in other words, from the side facing the external environment during use, is shown in a schematic form.

[0010] - Figure 2 A side view of the sealing device taken along the Figure 1 plane II - II is shown, the sealing device being mounted between two members (shown in schematic form and only partially in dashed lines) that rotate relative to each other and are defined by a rotating engine shaft and a fixed engine base.

[0011] - Figure 3 A perspective three - quarter front view of the innovative components of the sealing device according to Figure 1 and Figure 2 is shown, that is, a view as seen from the side facing the external environment during use;

[0012] - Figure 4 is a cross - sectional view of the same components along the Figure 3 plane IV - IV;

[0013] - Figure 5 is a larger - scale cross - sectional view of the details of the cross - sectional view of Figure 4 ;

[0014] - Figure 6 , Figure 7 and Figure 8 show in schematic form and larger scale the corresponding details of the sealing device according to Figure 1 and Figure 2 ; and

[0015] - Figure 9 A perspective and radially - cut three - quarter front view of a possible variant of the sealing device according to Figure 1 is shown in schematic form. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] Referring to Figure 1 and Figure 2 , in Figure 1 and Figure 2In this, 1 as a whole represents a sealing device which can be inserted between a stationary first member 2 and a rotating second member 3, and the members are only shown Figure 2 in a schematic form and in dashed lines in the figure.

[0017] Specifically, in the example shown, the fixed member 2 is constituted by the base of an internal combustion engine of a vehicle which is shown and not shown for the sake of simplicity of illustration, and the rotating member 3 is formed by an engine shaft protruding axially from the base 2. The sealing device 1 is inserted radially between the members 2 and 3 so as to: on the one hand, retain the lubricating oil required for the operation of the engine within the base 2, and on the other hand, prevent any contaminants such as water, dust and dirt present in the environment where the vehicle travels from entering from the outside.

[0018] The sealing device 1 includes a first annular screen 4 which is provided with: a substantially cylindrical sleeve portion 5 which is configured to be rigidly engaged with the first member 2 in a known manner; and a flange portion 6 which extends radially from the sleeve portion 5 towards the axis of symmetry A of the sleeve portion 5.

[0019] The sealing device 1 further includes: a second annular screen 7 which is configured to be rigidly engaged with the second member 3 and is fixed to the first screen 4 in an idle manner as will be seen later; and an annular gasket 8 which is provided with at least a first annular sealing lip 9 which extends axially and projects radially from the flange portion 6 towards the axis of symmetry A and is located on the opposite side of the second screen 7.

[0020] The annular gasket 8 is made of an elastic material in a known manner according to a process called vulcanization gluing, and is formed in a known manner by injection molding or preferably compression molding on a metal frame 10 constituted by a metal sheet: the metal sheet is cut and folded to integrally form the sleeve portion 5 and the flange portion 6 of the screen 4.

[0021] The annular sealing lip 9 is made of the same elastic material as the gasket 8 and is integrally formed with the gasket 8 in onepiece. The sealing lip 9 is also configured to cooperate with the second member or the engine shaft 3 in a liquidtight manner by means of interference as schematically shown in the figure where the lip 9 is shown in an undeformed configuration. Figure 2 In order to obtain a contact pressure sufficient for ensuring a substantially constant sealing action between the lip 9 and the shaft 3, the lip 9 is provided with an annular spring 11 which pushes it against the shaft 3 during use.

[0022] Furthermore, the washer 8 is integrally provided with a second annular lip 12 which extends radially and projects axially from the sleeve portion 6 in a direction opposite and substantially symmetrical to the sealing lip 9, and the second annular lip 12 and the sealing lip 9 form a V-shape with the apex pointing to the sleeve portion 5 in the radial cross-section. The lip 12 is configured to cooperate with the shaft 3 but not to contact the shaft 3, thereby providing a labyrinth seal that protects the lip 9. The side 13 of the lip 9 pointing to the lip 12 is preferably provided with a known groove 14 for improving the sealing effect.

[0023] To allow the shielding members 4 and 7 to engage with each other in an idle manner, the annular shielding member 7 has a radially outer peripheral edge 15 which engages with an annular seat 16 of the sleeve portion 5 with axial and radial clearances Figure 2 ) inside.

[0024] The radial cross-section of the annular seat 16 is formed in a U-shape pointing to the axis of symmetry A, and in the illustrated non-limiting example, the annular seat 16 is delimited by an end 18 of the sleeve portion 5 of the first shielding member 4, and the end 18 is located on the opposite side of the first annular sealing lip 9 and is folded in the form of an asymmetrical U-shape.

[0025] A first labyrinth seal portion 19 of a static type is defined between the radially outer peripheral edge 15 of the second shielding member 7 and the U-shaped annular seat 16 of the first shielding member 4 (i.e., the U-shaped folded end 18 of the sleeve portion 5 that delimits it), because it can establish a winding path for any external contaminants attempting to pass through the shielding member 7 towards the first annular sealing lip 9. Therefore, the labyrinth seal portion 19 is a conventional type of labyrinth seal, i.e., a non-contact seal that prevents external contaminants from passing through in any case.

[0026] According to the present invention, the second shielding member 7 is provided with a plurality of protrusions 20 on the opposite side of the flange portion 6 of the first shielding member 4, and the protrusions 20 project axially and point in a direction opposite to the first annular sealing lip 9.

[0027] In the sense that the protrusions 20 have a radially extending portion: the protrusions 20 extend radially outward from the radially inner annular portion 21 of the shielding member 7 in a direction opposite to the axis A until a point close to the edge 15 but still maintaining a predetermined distance from the edge 15.

[0028] The protrusions 20 are circumferentially arranged in a ring shape on the second shielding member 7 and are spaced apart from each other circumferentially in such a way as to be separated by a plurality of circumferential recesses 22 defined between a pair of directly adjacent protrusions 20.

[0029] According to the present invention, the protrusions 20 and the corresponding circumferential recesses 22 separating them are configured to define, if necessary, together with the first shield 4, a second labyrinth seal 23 of the dynamic type, which is arranged in series with the first labyrinth seal 19 and is located on the opposite side of the first annular sealing lip 9.

[0030] Basically, the second labyrinth seal 23 is defined as a "labyrinth" type because it creates a contactless barrier against the entry of external contaminants in the manner of a conventional labyrinth seal such as the seal 19. However, unlike the seal 19, the dynamic labyrinth seal 23 does not create a meandering path, but is formed by the fact that the protrusions 20 and the corresponding circumferential recesses 22 separating them form a helix 24 ( Figure 3 and Figure 4 ), and the helix 24 is capable of generating a fluid flow 25 that repels external contaminants away from the shields 4 and 7 as the first shield 4 and the second shield 7 rotate relative to each other (schematically represented by the arrows in Figure 2 ).

[0031] To obtain the above-described dynamic "labyrinth" effect, each protrusion 20 is bounded radially outwardly by a first active surface and a second active surface 27, the first active surface 26 and the second active surface 27 forming an angle other than 180° with each other ( Figure 6 ), and being joined together to establish a vertex edge 28 that defines the radially outer end 29 of each protrusion 20 and is radially spaced from the edge 15.

[0032] The protrusions 20 have the same radial extension, so that their ends 29 all lie on or all pass through a circumference of radius R (not shown for the sake of simplicity of the drawing).

[0033] Referring to Figure 6 , for each protrusion 20, the first active surface 26 and the line p perpendicular to the radius R of the circumference on which all the ends 29 of the protrusion 20 lie and passing through the vertex edge 28 form a first angle α, while the second active surface 27 and the same line p perpendicular to the radius R and passing through the apex edge 28 form a second angle β.

[0034] According to one aspect of the present invention, the first angle α must be less than 75°, and the second angle β must be greater than 35°. Preferably, the first angle α is between 55° and 65°, and the second angle β is between 40° and 55°.

[0035] Furthermore, according to a preferred embodiment of the present invention, at least one or both of the first surface 26 and the second surface 27 are curved and have a concave surface pointing radially outward. In particular, at least the surface 27 has a profile that extends in a spiral manner to define a spiral portion.

[0036] More generally, the second shield 7 is formed in the manner of a flange, and the protrusion 20 is formed on the annular front face 30 that is the boundary of the second shield 7 on the opposite side of the first shield 4 (the annular front face that defines the second shield 7 on the opposite side of the first shield 4).

[0037] The protrusion 20 extends beyond or flush with the radially inner annular portion 21 of the shield 7, and the annular portion 21 also defines the radially inner annular portion of the face 30.

[0038] The annular portion 21 is preferably stepped and forms a cylindrical portion 31 on the annular face 30 with an outer diameter smaller than the outer diameter of the edge 15.

[0039] The vertex edge 28 of each protrusion 20 is angularly arranged with respect to the symmetry axis A ( Figure 7 ), and forms a third angle δ with a line c that is perpendicular to the annular front face 30 of the shield 7 and parallel to the symmetry axis A. The third angle δ is directed to the opposite side of the symmetry axis A and ranges between 5° and 11°. The purpose of this angle is to improve the fluid flow 25 for discharging external contaminants, especially for dispersing external contaminants away from the shields 4 and 7.

[0040] Finally, along the radial direction, the circumferential recess 22 has a circumferential width that gradually increases in a direction away from the symmetry axis A.

[0041] Now refer to Figure 9 , which shows a possible variant 100 of the above-described sealing device 1. For simplicity, the same reference numerals are used to denote details that are similar or identical to those already described.

[0042] The sealing device 100 includes: a shield 4, which is the same as the shield already described and is provided with an annular gasket 8; and a second annular shield 70, which is different from the above-described shield 7 due to the replacement of the protrusion 20 with a protrusion 200.

[0043] The protrusion 200 is defined by blades that have a generally spiral profile that expands radially outward with respect to the symmetry axis A and along the radial direction.

[0044] The vane 200 is formed to protrude axially from the radially outer annular portion 32 of the annular front face 30 of the shielding member 70 which is the boundary of the shielding member 70 on the opposite side of the first shielding member 40.

[0045] The vane 200 also extends radially protruding from the stepped annular portion 21 of the annular front face 30 and the shielding member 70 itself, and a circumferential recess 220 is defined between the vanes 200, and the circumferential recess 220 extends in such a manner as to be disposed radially between the radially outer free end 29 of the vane 200 (more generally, the radially outer end of the defined protrusion 200) and the stepped annular portion 21 of the second shielding member 70.

[0046] The vane 200 has adjacent effective surfaces 260 and 270, and the effective surfaces 260 and 270 define a vertex edge 28 and define the radially outer end 29 of the protrusion 200.

[0047] Only for the described embodiment, the critical values of the magnitudes of the angles α and β formed by the lines perpendicular to the radius R as described above can also be applied to the effective surfaces 260 and 270.

[0048] However, vanes 200 of different forms can be designed, such as vanes formed by thin flanges twisted along their respective radial extension directions, where the effective surface 260 has a small area.

[0049] Finally, in both of the described embodiments 1 and 100, in order to improve the fluid flow 25 for discharging external contaminants (only shown at the sealing device 1 for simpler illustration), the second shielding member 7 or 70 is preferably provided with a radial deflector 33 along its radially outer peripheral edge 15.

[0050] The radial deflector 33 is composed of an axial annular shoulder 34 ( Figure 5 and Figure 7 ), the axial annular shoulder 34 is formed along the radially outer peripheral edge 15, and is defined radially inwards and towards the protrusion 20 (200 in the case of the sealing device 100) by a plurality of adjacent teeth 35 ( Figure 8 ) having a serrated profile in the circumferential direction.

[0051] The teeth 35 are configured such that the radially outer end 29 of each protrusion 20 (200 in the case of the device 100) faces the bent portion 71 separating two adjacent teeth 35 of the annular shoulder 34, thereby facilitating the external disposal of the fluid flow 25.

[0052] Based on the above description, it is clear that although the lip 9 is a standard radial sealing lip for the oil seal that has been optimized for a specific application of the engine shaft 3 and ensures the sealing regardless of the rotational speed of the shaft 3, the shielding member 7 (or 70) integrally made of synthetic plastic resin by a single molding operation is still physically connected to the shaft 3 and rotates relative to the shielding member 4 (which is physically connected to the engine base 2 and is thus fixed) when the shaft 3 rotates.

[0053] For this purpose, the radial inner part 21 is defined by a radial inner edge 72 that is configured to slightly interfere-engage with the shaft or the rotating member 3 (e.g., with an h6 / H7 fit according to the tolerance system of the base shaft).

[0054] During use, the shaft 3 also causes the plastic insert or the shielding member 7 (or 70) to rotate during rotation. The protrusions 20 or the vanes 200 forming the outer part of the plastic shielding member 7 or 70 generate a fluid-dynamic pumping effect that pumps the contamination particles away from the gasket 8 before any contamination particles (dust, metal particles, etc.) can reach and contaminate the conventional type of labyrinth seal 19.

[0055] In this way, when the external contaminants come into contact with the spiral part 24, the external contaminants will be discharged, thereby reducing the risk of contaminants entering the labyrinth seal 19.

[0056] The form of the spiral part 24, i.e., the form of the protrusions 20 / 20 and the recesses 22 / 220 forming it, is designed such that due to the intervals defined by the recesses 22 / 220 between the vanes 200 / protrusions 20 (which increases the respective circumferential width or extension from the inside to the outside), it helps to expel the contaminants towards the outer diameter of the shielding member 7 / 70, thus fully exploiting the maximum peripheral speed.

[0057] In fact, due to the described geometry and the selected values for the angles α and β, the resultant of the vector synthesis between the peripheral velocity vector and the centrifugal force vector of the effective surface 26 or 260 and the edge 15 of the shielding member 7 / 70 is oriented parallel, thus allowing for the maximum possible flow rate for the fluid flow 25.

[0058] Therefore, all the objects of the present invention are achieved.

Claims

1. A sealing device (1; 100) that can be inserted between a stationary first member (2) and a rotating second member (3), the sealing device comprising: - A first annular shielding member (4) provided with a sleeve portion (5) and a flange portion (6), the sleeve portion being configured to be rigidly engaged with the first member, and the flange portion extending radially from the sleeve portion protruding towards the axis of symmetry (A) of the sleeve portion; - A second annular shielding member (7; 70) configured to be rigidly engaged with the second member and idly fixed to the first annular shielding member (4); And - An annular gasket (8) provided with at least a first annular sealing lip (9), the first annular sealing lip extending axially and protruding radially from the flange portion (6) towards the axis of symmetry (A), located on the opposite side of the second annular shielding member (7; 70), and configured to cooperate with the second member (3) in a liquid-tight manner by means of interference; - A first labyrinth seal portion (19) of a static type is defined between the first annular shielding member (4) and the second annular shielding member (7; 70), and the first labyrinth seal portion can establish a meandering path for any external contaminants passing towards the first annular sealing lip; It is characterized in that: i - The second annular shielding member (7; 70) is provided with a plurality of protrusions (20; 200) on the opposite side of the flange portion (6) of the first annular shielding member, the protrusions protruding axially and pointing in the opposite direction of the first annular sealing lip, and the protrusions having a radially extending portion; ii - The protrusions (20; 200) are circumferentially arranged in a ring shape on the second annular shielding member and are spaced apart from each other circumferentially in such a way as to be separated by a plurality of circumferential recesses (22; 220) defined between a pair of directly adjacent protrusions; iii - The protrusions (20; 200) and the corresponding circumferential recesses (22; 220) separating them are configured to define a second labyrinth seal portion (23), and the second labyrinth seal portion is continuously arranged with the first labyrinth seal portion (19) and is located on the opposite side of the first annular sealing lip (9); iv - The second labyrinth seal portion (23) is of a dynamic type, and the protrusions and the corresponding circumferential recesses separating them form a spiral portion (24), and the spiral portion is designed to generate a fluid flow (25) that discharges external contaminants away from the first annular shielding member and the second annular shielding member as the first annular shielding member and the second annular shielding member rotate relative to each other; The second annular shielding member has a radially outer peripheral edge (15), and there is a predetermined distance between the protrusions (20; 200) and the radially outer peripheral edge (15) such that the protrusions (20; 200) do not extend into the first labyrinth seal portion (19).

2. The sealing device according to claim 1, characterized in that, The outer peripheral edge thereof is joined with axial and radial clearances to the inner side of the annular seat (16) of the sleeve portion (5), and the radial cross-section of the annular seat is formed in a U-shape pointing to the symmetry axis (A); a first labyrinth seal portion (19) of the static type is defined between the outer peripheral edge (15) of the second annular shield and the U-shaped annular seat of the first annular shield; the U-shaped annular seat (16) is defined by the first end (18) of the sleeve portion of the first annular shield, which is on the opposite side of the first annular seal lip (9).

3. The sealing device according to claim 1 or 2, characterized in that, Each of the protrusions (20; 200) is bounded radially outwardly by a first effective surface (26; 260) and a second effective surface (27; 270), an angle other than 180° is formed between the first effective surface and the second effective surface, and they are connected together to establish a vertex edge (28) defining the outer radial end (29) of each of the protrusions.

4. The sealing device according to claim 3, characterized in that, The first effective surface (26; 260) and the second effective surface (27; 270) respectively form a first angle (α) and a second angle (β) with the same line (p) perpendicular to the radius (R) of the second annular shield (7; 70) and passing through the vertex edge (28) connecting the first effective surface and the second effective surface; the first angle (α) is less than 75°; the second angle (β) is greater than 35°.

5. The sealing device according to claim 4, characterized in that, The first angle (α) is between 55° and 65°; the second angle (β) is between 40° and 55°.

6. The sealing device according to claim 3, characterized in that At least one or both of the first effective surface (26; 260) and the second effective surface (27; 270) are curved and have a concave surface pointing radially outward.

7. The sealing device according to claim 1 or 2, characterized in that, The second annular shield (7; 70) is flange-shaped, and the protrusions are formed on the annular front surface (30) of the second annular shield, which is the boundary of the second annular shield on the opposite side of the first annular shield; the vertex edge (28) of each of the protrusions is angularly arranged relative to the symmetry axis (A), and forms a third angle (δ) with a line (c) perpendicular to the annular front surface (30) of the second annular shield and parallel to the symmetry axis, and the third angle is on the opposite side of the symmetry axis and ranges from 5° to 11°, which improves the fluid flow for discharging external contaminants.

8. The sealing device (100) according to claim 1 or 2, characterized in that, The protrusion is defined by a vane (200) which has a generally helical profile that extends radially outwards relative to the axis of symmetry (A) and along the radial direction; the vane (200) is formed to project axially from a first radially outer annular portion (32) of an annular front face (30) of the second annular shield (70) which is a boundary of the second annular shield on the opposite side of the first annular shield (4); the vane (200) also extends to project radially from a second stepped annular portion (21) of the annular front face of the second annular shield, and a circumferential recess (220) is defined between the vanes, and the circumferential recess extends until it is disposed radially between the radially outer end (29) of the vane and the second stepped annular portion (21) of the annular front face of the second annular shield.

9. The sealing device according to claim 1 or 2, characterized in that, Along the radial direction, the circumferential recess (22; 220) has a circumferential width that gradually increases in a direction away from the axis of symmetry.

10. The sealing device according to claim 1 or 2, characterized in that, The second annular shield (7; 70) is provided with a radial deflector (33) at its radially outer peripheral edge (15) for improving the fluid flow for discharging external contaminants; the radial deflector (33) is formed by an axial annular shoulder (34) which is formed along the radially outer peripheral edge (15) and is defined radially inwards and towards the protrusion by a plurality of adjacent teeth (35) having a serrated profile in the circumferential direction; the radially outer end (29) of each protrusion faces a bent portion that separates two adjacent teeth (35) of the axial annular shoulder.

11. The sealing device according to claim 1, characterized in that, The sealing device can be inserted between the base of an internal combustion engine and the engine shaft.

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