Hydraulic roller tappet for an OHV valve train of an internal combustion engine

Abstract

Hydraulic roller tappet (1) for an OHV valve train of an internal combustion engine, comprising a tubular housing (2) which has a circumferentially closed pocket (5) at one of its longitudinal ends (3) and bounded by a bottom (4), wherein the housing (2) is provided in the axial section of the pocket (5) with two diametrically opposed through-bores (6) in which a bolt (7) is rotatably inserted via its end sections (8), on which bolt (7) a cam roller (9) runs via a bearing (10), wherein a pressure piston (14) enclosing a reservoir (13) for hydraulic oil is guided in a bore (12) extending from another longitudinal end (11) of the housing (2), the upper end (15) of which has a pushrod assembly (16) and the lower end (17) of which has a check valve (18), between which lower end (17) and the bottom (4) of the pocket (5) a high-pressure chamber (19) for the hydraulic oil is formed,wherein an outer shell (20) of the housing (2) has a smooth-walled guide surface (21) extending from one longitudinal end (3) of the housing for receiving (22) a guide (23) on the internal combustion engine side, in which guide surface (21) a recess (24) spaced apart from one longitudinal end (3) with at least one radial bore (25) therein for supplying the hydraulic oil to the pressure piston (14) is arranged, characterized in that in an annular section (26) of the guide surface (21), between an annular edge (27) of the recess (24) facing one longitudinal end (3) and one longitudinal end (3), in the circumferential section of one or each through-bore (6), an axial channel (28) is applied, which begins spaced apart from the annular edge (27) and cuts off the through-bore (6) for supplying the hydraulic oil towards the bearing (10) for its lubrication downstream.

Description

[0001] The invention relates to a hydraulic roller tappet for an OHV valve train of an internal combustion engine, comprising a tubular housing having at one longitudinal end a circumferentially closed pocket defined by a base, wherein the housing is provided in the axial section of the pocket with two diametrically opposed through-bores in which a bolt is rotatably inserted via its end sections, on which bolt a cam roller runs via a bearing, wherein in a bore extending from another longitudinal end of the housing a pressure piston enclosing a reservoir for hydraulic oil is guided, the upper end of which has a push rod system and the lower end of which has a check valve, between which lower end and the base of the pocket a high-pressure chamber for the hydraulic oil is formed,wherein an outer shell of the housing has a smooth-walled guide surface extending from one longitudinal end thereof for receiving a guide on the internal combustion engine side, in which guide surface a recess spaced from the one longitudinal end is arranged with at least one radial bore therein for supplying the hydraulic oil to the pressure piston.

[0002] DE 11 2006 000 338 B4 shows a housing for a hydraulic roller tappet with a circumferentially closed roller pocket. A bolt passes through the roller pocket, which is accommodated in bores in the housing. A cam roller runs on the bolt via a rolling bearing. A bore extending from another longitudinal end of the housing accommodates a pressure piston (not shown). Specific lubrication of the bearing is not provided.

[0003] DE 10 2015 209 336 A1 discloses a fully assembled roller tappet with an open roller pocket.

[0004] The task is to propose a roller tappet with improved lubrication of its cam roller bearing.

[0005] According to the invention, this object is achieved in that in an annular section of the guide surface, between an annular edge of the recess facing one longitudinal end and the one longitudinal end, in the circumferential section of one or each through-bore, an axial channel is applied, which begins at a distance from the annular edge and intersects the through-bore for supplying the hydraulic oil in the direction of the bearing for its lubrication downstream.

[0006] It is standard, and this is where the invention comes in, that the roller tappet, when installed in the receptacle of the guide on the combustion engine side, has its recess at the level of a supply line for the hydraulic oil to the receptacle when the cam base circle is in contact. This means that the hydraulic oil can be directed to the reservoir of the pressure piston to compensate for play when the cam base circle is in contact. The radial bore in the recess can be positioned in the circumferential direction of the roller tappet so that it is directly intersected by the supply line or circumferentially offset from it. During the subsequent cam lift, the housing moves upwards in the receptacle with its recess in such a way that the recess is usually no longer in fluid connection with the supply line of the receptacle.

[0007] A targeted and economical oil supply to the bearing of the cam roller is achieved via the at least one axial channel downstream in the guide surface, wherein preferably each through hole should be assigned an axial channel. When the cam base circle is in contact, it is therefore possible for the full amount of hydraulic oil to be available for valve clearance compensation. During cam lift, the recess in the housing is preferably no longer in fluid communication with the supply line for the hydraulic oil to the receptacle. When the cam lift begins, the supply line is initially closed off via an annular region of the annular section immediately axially below the recess. This annular region therefore acts largely as a sealing gap on the outer casing of the housing. Depending on the design of the area surrounding the roller tappet during its installation, other configurations are also conceivable. For example,It is also possible to supply oil to at least one axial channel at base circle contact in parallel with the supply of the reservoir of the pressure piston.

[0008] The variant with only one axial channel to one of the through holes is particularly cost-effective. If the axial channel offset for the recess is located circumferentially on the side of the supply line for the hydraulic fluid to the mount of the guide on the combustion engine side when installing the roller tappet, then a circulation channel in the guide surface of the housing can, but does not have to, be dispensed with.

[0009] Preferably, the bolt should be freely rotatable, allowing hydraulic oil to flow axially inward from an opening of the through-bore on the outer casing side. However, the bolt could also be caulked or otherwise fixed. In this case, at least one separate channel is provided in the through-bore and / or on the bolt, which is preferably applied outside of the bolt's load zone.

[0010] According to an expedient development of the invention, the at least one axial channel extends beyond the through-bore downstream to one longitudinal end. This enables additional lubrication of an outer surface of the cam roller and the approaching cam.

[0011] The solution proposed in a further development of the invention, with a circulation channel, which preferably intersects the at least one axial channel upstream at its upper edge and is spaced from the bottom-side annular edge of the recess, allows, for example, supply of the preferably provided additional (second) axial channel on a "rear side" of the roller tappet. The circulation channel can be used, for example, for the exclusive introduction of hydraulic oil into the axial channel, thus ensuring very short, sectional fluid contact with the supply line.

[0012] According to a further refinement of the invention, the inner surfaces of the housing pocket, which face the outer faces of the cam roller, are designed as inwardly thickened flat surfaces. The housing is thus thickened in the bearing area of ​​the bolt, which enables good force transmission and, at the same time, cam roller guidance.

[0013] It is also proposed to chamfer the openings of the housing's through-holes on the outside. These chamfers are designed significantly larger than the standard chamfers / edge breaks required by design. They allow for a simple and wear-free joining of the bolt to the housing. Furthermore, the chamfers can also serve as additional reservoirs for the hydraulic oil. These chamfers may only be present as segments.

[0014] About the drawing: • Fig. 1 shows the roller tappet in a spatial view obliquely from below; • Fig. 2 shows the roller tappet in longitudinal section across the cam roller and • Fig. 3 shows a side view of the roller tappet.

[0015] The figures show a hydraulic roller tappet 1 for an OHV valve train of an internal combustion engine.

[0016] The roller tappet 1 has a tubular housing 2, which has a circumferentially closed pocket 5 defined by a base 4 at one of its longitudinal ends 3, shown below. To support a pin 7, the housing 2 has two diametrically opposed through-holes 6 in the axial section of the pocket 5, which are provided with a chamfer 33 on the outside. The pin 7 is rotatably received in the through-holes 6. A cam roller 9 runs on the pin 7 via a bearing 10 designed as a full-complement needle bearing.

[0017] An axially movable pressure piston 14 is guided in a bore 12 extending from another longitudinal end 11 of the housing 2, which defines a reservoir 13 for hydraulic oil. An upper end 15 of the pressure piston 14 located within the bore 12 is provided with a push rod assembly 16. A lower end 17 of the pressure piston 14 has a check valve 18, which opens toward a high-pressure chamber 19 located below, which is defined by the bottom 4 of the pocket 5.

[0018] As can be seen from the Fig. 2, Fig. 3, an outer shell 20 of the housing 2 has a smooth-walled guide surface 21 extending from one of its longitudinal ends 3, which extends over approximately 2 / 3 of its height. The roller tappet 1 is guided over the guide surface 21 in a Fig. 2, of an internal combustion engine-side guide 23. A supply line 34 for hydraulic oil runs to the receptacle 22. The guide surface 21 is interrupted, as viewed from one longitudinal end 3, by a recess 24 with a radial bore 25 therein. The radial bore 25 serves to supply the hydraulic oil to the reservoir 13 of the pressure piston 14.

[0019] A circulation channel 29 is applied at an axial distance from a lower ring edge 27 of the recess 24. Two axial channels 28 branch off from this channel, leading downstream to the through holes 6 (see Fig. 1, Fig. 3 us arrow indication in Fig. 3), which are ground in. The axial channels 28 extend beyond the through-bores 6 to the lower longitudinal end 3 of the housing 2. This design enables the circulation channel 29 to briefly intersect the supply line 34 at the receptacle 22 of the engine-side guide 23 during operation of the roller tappet 1, during cam lift and thus outside of a cam base circle phase. Hydraulic oil can thus be directed downstream of the two axial channels 28 to the through-bores 6 and from there axially inward to the bearing 10 for lubrication purposes. The chamfers 33 of the through-bores 6 to the guide surface 21 serve as additional oil reservoirs.

[0020] Out of Fig. 1 it can also be seen that the inner circumferential surfaces 30 of the pocket 5 of the housing 2 are inwardly thickened flat surfaces, directly in front of which the outer ends 31 of the cam roller 9 run. List of reference numbers 1 roller tappet 2 housings 3 Longitudinal end 4 Floor 5 bag 6 through hole 7 bolts 8 Final section 9 Cam roller 10 Storage 11 Longitudinal end 12 holes 13 Storage room 14 pressure pistons 15 Upper forehead 16 Pushrod system 17 Lower forehead 18 Check valve 19 High-pressure room 20 Outer jacket 21 Guide surface 22 recording 23 Guide 24 puncture 25 Radial bore 26 ring section 27 ring edge 28 axial channel 29 Circulation channel 30 inner surface 31 Outer forehead 32 Mouth 33 chamfer 34 supply line QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 11 2006 000 338 B4

[0002] DE 10 2015 209 336 A1

[0003]

Claims

[1] Hydraulic roller tappet (1) for an OHV valve train of an internal combustion engine, with a tubular housing (2) which has at one of its longitudinal ends (3) a circumferentially closed pocket (5) delimited by a base (4), wherein the housing (2) is provided in the axial section of the pocket (5) with two diametrically opposed through-bores (6) in which a bolt (7) is rotatably inserted via its end sections (8), on which bolt (7) a cam roller (9) runs via a bearing (10), wherein in a bore (12) extending from another longitudinal end (11) of the housing (2) a pressure piston (14) enclosing a reservoir (13) for hydraulic oil is guided, the upper end (15) of which has a push rod system (16) and the lower end (17) of which has a check valve (18), between which lower end (17) and the base (4) of the A high-pressure chamber (19) for the hydraulic oil is formed in the pocket (5),wherein an outer shell (20) of the housing (2) has a smooth-walled guide surface (21) extending from one longitudinal end (3) thereof for receiving (22) a guide (23) on the internal combustion engine side, in which guide surface (21) a recess (24) spaced from the one longitudinal end (3) is arranged with at least one radial bore (25) therein for supplying the hydraulic oil into the pressure piston (14), , characterized by in that in an annular section (26) of the guide surface (21), between an annular edge (27) of the recess (24) facing the one longitudinal end (3) and the one longitudinal end (3), in the circumferential section of one or each through-bore (6), an axial channel (28) is applied, which begins at a distance from the annular edge (27) and intersects the through-bore (6) for supplying the hydraulic oil in the direction of the bearing (10) for its lubrication downstream. [2] Roller tappet according to claim 1, characterized bythat the axial channel (28) extends beyond the through hole (6) to one longitudinal end (3). [3] Roller tappet according to claim 1 or 2, characterized by in that in the annular section (26) of the guide surface (21), axially spaced from the annular edge (27) of the recess (24) facing the one longitudinal end (3), a circulation channel (29) for the hydraulic oil is applied, which cuts through the axial channel (28) and, in the case of one axial channel (28) per through-bore (6), connects these axial channels (28) in a segment-like manner or all-round in the guide surface (21). [4] Roller tappet according to claim 1, characterized by that inner circumferential surfaces (30) of the pocket (5) of the housing (2), which outer ends (31) of the cam roller (9) are designed as inwardly thickened flat surfaces. [5] Roller tappet according to claim 1, characterized bythat an opening (32) of the respective through-bore (6) on the guide surface (21) is provided with a segment-like or fully circumferential chamfer (33).

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