EP3436684A1

EP3436684A1 - Tappet, high pressure pump comprising at least one tappet, engine comprising at least one tappet, engine comprising a high pressure pump having at least one tappet and method of lubricating a surface of a cam

Info

Publication number: EP3436684A1
Application number: EP17713958.1A
Authority: EP
Inventors: David J LANE; Barrie Gilbert BARKER; Phil PAPAHARIDEMOU
Original assignee: Delphi Technologies IP Ltd
Current assignee: Delphi Technologies IP Ltd
Priority date: 2016-04-01
Filing date: 2017-03-28
Publication date: 2019-02-06
Anticipated expiration: 2037-03-28
Also published as: WO2017167761A1; GB2548900A; EP3436684B1

Abstract

The present invention relates to a roller tappet, the roller tappet comprising a body having a roller reception space that is formed at one end of the body and that is adapted to receive a roller, wherein the body further comprises a lubricant supply groove for the reception of lubricant and a tappet alignment groove, wherein a first fluid communicating connection is present between the lubricant supply groove and the roller reception space for the supply of lubricant to an outlet that opens into the roller reception space. The invention is characterized in that a second fluid communicating connection is present in the roller tappet that is provided to guide some of the lubricant supplied to the lubricant supply groove to a second point of application, with the second point of application being remote from the outlet. The invention further relates to a pump and to an engine respectively comprising at least one such tappet and to a method of lubricating a surface of a cam.

Description

Tappet, high pressure pump comprising at least one tappet, engine comprising at least one tappet, engine comprising a high pressure pump having at least one tappet and method of lubricating a surface of a cam

The present invention relates to a tappet, to a high pressure pump comprising at least one tappet, to an engine having at least one such tap- pet, to an engine comprising a high pressure pump comprising at least one such tappet and to a method of lubricating a surface of a cam.

Engines and their components are typically cooled and lubricated by means of oil that is circulated throughout the engine to lubricate and cool the various engine components, such as bearings and other moving parts. In this connection the oil drops from the top of the engine to the bottom of the engine via gravity. At the bottom of the engine the oil is collected in an oil sump. In some types of engines a relatively large so-called wet oil sump is provided at the bottom end of the engine. The oil is recirculated in such engines to the top of the engine directly from this oil sump for a continuous lubrication and cooling of the engine.

In contrast to this an engine comprising a dry sump is an engine in which the oil is caught in a relatively small so-called dry oil sump and the oil is transported from the dry sump to a secondary reservoir remote from the actual engine sump for cooling and storage purposes. Following the cooling of the oil in the remote secondary reservoir, the oil is subsequently pumped from the secondary reservoir back to the engine to lubricate the engine. To this end the oil is pumped back into the engine and to some of the components, like a fuel pump, associated with the engine at at least one specific point arranged at the top end of the engine or of the components from where it is then recirculated.

The top end of the engine typically comprises the cam shaft and the tappets operatively connected thereto, due to the point-like injection into the top of the engine, the components arranged at the top end may suffer from a lack of lubrication.

For this reason it is an object of the invention to provide an engine in which the lubrication of the top end of the engine is improved respectively an engine in which the lubrication of components associated therewith is improved, in particular an engine in which the lubrication of the cam and the roller operatively connected thereto is improved. This object is satisfied by a roller tappet having the features of claim 1 .

Such a roller tappet for an engine, preferably a diesel engine, and/or for a high pressure diesel fuel pump, comprises a body having a roller reception space that is formed at one end of the body and that is adapted to receive a roller, wherein the body further comprises a lubricant supply groove and a tappet alignment groove, wherein a first fluid communicating connection is present between the lubricant supply groove for the reception and/or at least intermediate storage of lubricant, such as oil, and the roller reception space for the supply of lubricant to an outlet that opens into the roller reception space. The invention is characterized in that a second fluid communicating connection is present in the roller tappet that is provided to guide some of the lubricant supplied to the lubricant supply groove to a second point of application, with the second point of application being remote from the outlet.

This second fluid communicating connection, e.g. present in the form of a bypass, provides the possibility of supplying oil or lubricant to a surface of a cam at a second point of application, to increase the lubrica- tion of the roller tappet and parts operatively connected thereto and hence to reduce the friction at the surface of a roller and to thereby increase a durability of the roller of the roller tappet. Moreover, this form of lubrication is made possible without the use of additional pumps and spray units. Thus, no extensive re-designs of parts of the cambox are necessary. Moreover, the roller tappet can simply replace prior art roller tappets as the lubricant supply is already present in any event, so that the roller tappets described herein can advantageously be retrofitted on engine or pump overhauls to increase the lifetime of the engine or the fuel pump associated therewith.

Advantageously at least a part of the second fluid communicating connection is provided in the form of a bore, a channel, groove and/or a passage. Such through holes or passages can be provided in simple manufacturing process either using a milling machine, a lathe or the like.

Preferably the second fluid communicating connection extends, at least in part, towards the end of the body that is adapted to receive the roller. In this way a lubricant can be directed via the roller tappet to the component adjacent to the roller of the roller tappet e.g. a cam and provide the oil directly in the vicinity of the cam without the use of an additional lubricant supply. Since the cam is in operative engagement with a roller of the roller tappet this second point of application of lubrication, in particular indirectly, also provides lubricant at the roller of the roller tappet. This is in stark contrast to designs in which the cambox is flooded with lubricant and which hence consume more lubricant. Advantageously the second fluid communicating connection is formed adjacent to the outlet of the first lubricant supply passage in a surface of the roller reception space. Thus, the flow of lubricant supplied to the outlet via the first lubricant supply passage can be utilized to provide the lubricant at the second point of application without the use of dedicat- ed further pumps or other similar mechanisms.

Preferably the outlet is provided as a recess in a surface of the roller reception space. In this way a lubricant reservoir is made available at the roller tappet by means of which the second fluid communicating connection can be supplied with lubricant to ensure the advanced lubrication by way of an inherently present motion of the roller tappet. Advantageously the second fluid communicating connection is provided as a, preferably open, channel in the surface of the roller reception space. A channel can be machined in a simple manner and due to the fact that the channel is open lubricant leaking from the channel can also be used to directly lubricate the roller of the roller tappet.

In this connection it should be noted that the channel preferably extends from the outlet to the one end of the body. In this way the channel opens adjacent to the surface of the cam cooperating with the roller of the roller tappet in order to improve the lubrication of the surface of the cam and thereby of the roller of the roller tappet.

Moreover, the channel can extend circumferentially within the surface of the roller reception space. In this way the channel follows the geometry of the roller reception space between the outlet and the end of the body, such that when a roller is present in the roller reception space a flow path is provided between the body and the roller in order to transfer the lubricant around the roller and onto the surface of the cam.

Preferably the second fluid communicating connection comprises the lubricant supply groove, the tappet alignment groove and a bore, passage, groove and/or channel that connects the lubricant supply groove to the tappet alignment groove. Thus, the roller tappet in accordance with the invention connects parts already present in a roller tappet to form the second fluid communicating connection, by machining various kinds of addi- tional pathways into such roller tappets.

It is preferred if the tappet alignment groove is open at the said one end of the body comprising the roller reception space and if it opens into the bore, passage or channel that connects the lubricant supply groove to the tappet alignment groove at the other end of the tappet alignment groove to thereby form at least part of the second fluid communicating connection.

This design is simple to manufacture and clearly defines the position of the second fluid communicating connection and provides an outlet for the lubricant at the open end. To this end the lubricant supply groove is preferably closed at each end of the roller tappet, to ensure that the lubricant is stored therein safely with respect to the surface of the cam, so that the lubricant can be provided at the most effective region of lubrication. Advantageously the second fluid communicating connection is provided in the form of a bore that passes through the body of the roller tappet.

Such a bore is simple to manufacture does not decrease the sta- bility of the roller tappet and hence does not negatively influence the running properties of the roller tappet relative to a cambox into which it can be installed.

Preferably the bore is arranged perpendicular to both the tappet alignment groove and the lubricant supply groove and the bore connects the tappet alignment groove and the lubricant supply groove.

The oil is supplied to the roller tappet in a plane perpendicular to this bore and preferably in a pulsed manner, thus forming the bore per- pendicular to both the tappet alignment groove and the lubricant supply groove means that the pressure wave present during the injection of lubricant can be used for the supply of the lubricant from the lubricant supply groove to the tappet alignment groove. Advantageously the bore has a varying diameter over its length. Preferably the bore has at least two regions with different diameters, in particular with the smallest diameter being arranged adjacent to the lubri- cant supply groove. In this way the flow of lubricant from the lubricant supply groove to the tappet alignment groove can be controlled and/or regulated.

It is preferred if an annular groove is provided at an outer surface of the body in the end region of the body remote from the end of the body comprising the roller reception space. This groove can aid the lubrication of the cambox. In this way it is advantageous if the second fluid communicating connection comprises the annular groove. Advantageously the annular groove directly opens into the lubricant supply groove at a side of the roller tappet and wherein a lubricant supply channel connects the annular groove and the tappet alignment groove to form part of the second fluid communicating connection that is, in particular present between the tappet alignment groove and the lubri- cant supply groove.

Utilizing the annular groove as part of the second fluid communicating connection reduces the amount of machining that has to be carried out on a roller tappet.

A design option is made available by means of the provision of the lubricant supply channel as either a through bore or as a recess at the outer surface of the roller tappet at the side of the tappet remote from the lubricant supply groove.

In a further aspect the present invention relates to a high pressure pump having at least one roller tappet as described herein. Preferably the roller tappet 10 is in operative engagement with a surface of a cam. In a further aspect the present invention relates to an engine having at least one roller tappet as described herein that is optionally in operative engagement with a surface of a cam. The advantages described in connection with the roller tappet are likewise true in connection with the engine described herein.

In yet a further aspect the present invention relates to an engine having a high pressure pump having at least one roller tappet as described herein that is optionally in operative engagement with a surface of a cam. The advantages described in connection with the roller tappet are likewise true in connection with the high pressure pump.

In a further aspect the invention relates to a method of lubricating a surface of a cam by means of a roller tappet, in particular using a roller tappet as described herein. The method comprising the steps of:

- supplying oil to the roller tappet;

- guiding some of the oil through a first lubricant supply passage directly to a surface of a roller received in the roller tappet; and

- guiding some of the oil through a second bore or channel separate from the first lubricant supply passage to the surface of the cam.

The advantages described in connection with the roller tappet are likewise true in connection with the method described herein.

In this connection it should be noted that the roller tappet is configured for reciprocal motion, with the reciprocal motion corresponding to a pumping phase in a first direction of motion of the roller tappet and to a filling phase in a second direction of motion of the roller tappet. This means that the roller tappet is configured to collect lubricant in the tappet alignment groove during the pumping phase. During the filling phase the roller tappet is then configured to eject the lubricant collected in the tappet alignment groove for a lubrication of a cam surface that can be operatively connected to the roller tappet. Utilizing the filling phase to lubricate the cam surface means that the lubricant can be supplied to the surface of the cam in a pulsed manner by way of the inherently present reciprocal motion of the roller tappet. Preferably the tappet alignment groove is in operative engagement with a tappet alignment pin in an installed state of the roller tappet for controlling the reciprocal motion and wherein the roller tappet is further con- figured to eject the lubricant from the tappet alignment groove via the tappet alignment pin during the filling phase.

Utilizing an already present tappet alignment pin for carrying out not only a guidance of the roller tappet, but also spraying lubricant onto the surface of a cam means that no re-design of the cambox is required to spray the surface of the cam using the second fluid communicating connection.

Although the present invention is intended to be comprehensive in terms of its description using embodiments, it will be apparent to those skilled in the art that many alternatives, equivalents and variations of varying degree will fall within the scope of the present invention.

The invention will be described in detail by means of embodiments and with reference to the drawings. These show preferred embodiments of the roller tappet. The features described in the dependent claims, in the description and in the drawings may be configured in various combinations, which are encompassed by this document. The drawings show: Figs. 1 a & 1 b a schematic section through a first tappet in accordance with the invention installed in a cambox and a schematic view of the first tappet;

Fig. 2 a sectional illustration of a second tappet in accordance with the invention when installed in a cam box; Figs. 3a & 3b a sectional view of the tappet of Fig. 2 along the sectional line A : A (Fig. 3a) and a part sectioned part schematic view of the tappet of Fig 2 (Fig. 3b); and Figs. 4a & 4b a sectional view of a third kind of tappet similar to that of Fig. 2 (Fig. 4a) and a part sectioned part schematic view of the tappet of Fig 4a (Fig. 4b).

Fig. 1 a shows a schematic section through a roller tappet 10 ar- ranged in a cambox 12 and in operative engagement with a surface 14 of a cam 16. In order to lubricate a roller 18 of the tappet 10, oil is supplied from a lubricant store (not shown) to a lubricant supply groove 20 present in the body 22 of the tappet 10 via a first lubricant supply passage 24 and from there to the roller 18 via a second lubricant supply passage 26.

Some of the oil supplied via the second lubricant supply passage 26 is not directly impinged onto the roller 18, but rather is guided within a channel 25 provided at an inner surface 27 (also see Fig. 1 b in this regard) of the roller tappet 10 to an end of the roller tappet 10, where the lubricant is then supplied to the surface 14 of the cam 16 as indicated by the arrows A.

Due to the fact that the lubricant supplied via the channel 25 impinges the surface 14 of the cam 16 before the roller 18 comes into con- tact with that part of the cam 16 and that lubricant is directly supplied to the roller 18, the lubrication of both the surface 14 of the cam and that of the roller 18 is increased. This is because the surface 14 and the roller 18 rotate relative to one another and as both components are lubricated separately, the lubrication between these components is improved when they come into contact.

On the side of the tappet 10 remote from the lubricant supply groove 20 there is a tappet alignment groove 28 that is in operative en- gagement with a tappet alignment pin 30 that is provided in the cambox 12. The cooperation between the tappet alignment groove 28 and the tappet alignment pin 30 ensures a correct guidance of the reciprocal motion of the roller tappet 10 during an operation thereof and prevents the roller tappet 10 from rotating relative to the first lubricant supply passage within the cambox 12 and thereby from coming out of contact with the first lubricant supply passage 24.

Fig. 1 b shows a schematic view of the roller tappet 10. A roller re- ception space 32 can be seen that has the inner surface 27 adapted to the outer shape of the roller so that the roller 18 is journaled in the roller reception space 32. An outlet 31 of the second lubricant supply passage 26 opens into the roller reception space 32 for a lubrication of the roller 18 in the installed state of the roller 18. Moreover, the outlet 31 also provides a supply of lubricant to the channel 25 arranged within the inner surface 27.

The outlet 31 is provided in a recess 33 provided in the inner surface 27 of the roller reception space 32. The recess 33 not only functions as a reservoir for a direct supply of some of the lubricant onto the surface of the roller 18, but also as a supply of lubricant to the channel 25 provided in the inner surface 27. The recess 33 has a substantially rectangular shape with rounded edge regions in the present example.

The channel 25 extends circumferentially within the inner surface 27 of the roller reception space 32 in a direction perpendicular to the z- axis. The channel 27 in this way extends from the outlet 31 to the end of the body 22 that is adjacent to at least a part of the surface 14 of the cam 16. The roller tappet 10 of Fig. 1 b has an at least substantially cylindrical outer shape. Furthermore, an annular groove 34 is provided in an end region 36 of the roller tappet 10 that is remote from the end of the roller tappet 10 having the roller reception space 32. A tappet spring reception space 38 (see Fig. 3a) is formed within the end region 36. A recess 40 is present in the outer surface of the roller tappet 10 and connects the tappet spring reception space 38 to the roller reception space 32.

The second lubricant supply passage 26 shown in Fig. 1 a extends in the y-direction, whereas the lubricant supply groove 20 and the tappet alignnnent groove 28 extend in the x-direction of the coordinate system shown in Fig. 1 b. The roller reception space 32 receives the roller 18 such that an axis of rotation of the roller 18 coincides with the z-direction.

Fig. 2 shows a second kind of roller tappet 10 in an illustration similar to that of Fig. 1 a. The difference being that a lubricant supply bore 42 is present within the body 22 of Fig. 2 rather than the channel 25. The lubricant supply bore 42 connects the lubricant supply groove 20 to the tappet alignment groove 28. This second lubricant supplying connection provides a further possibility of lubricating the surface 14 of the cam 16 as will now be explained.

The roller tappet 10 is stored in the cambox 12 for linear reciprocal motion along the x-axis. The motion of the roller tappet 10 is guided via the tappet alignment pin 30 that projects into the tappet alignment groove 28.

In order to ensure that the roller tappet 10 is always in operative engagement with the surface 14 of the cam 16, a tappet spring 44 is provided that biases the roller tappet 10 towards the cam 16. The left hand figure of Fig. 2 shows an upward movement of the roller tappet 10. In this illustration the roller tappet 10 moves upward during a pumping phase, during this the tappet alignment groove 28 fills with oil. The right hand figure of Fig. 2b shows the roller tappet 10 during a filling phase, during this the roller tappet 10 moves downward and the oil collected in the tappet alignment groove 28 is ejected from the tappet alignment groove 28 via the tappet alignment pin 30 as indicated by the arrow B.

The tappet alignment pin 30 shown in the Figures can be a tappet alignment pin 30 of prior art design; alternatively it can have a surface structure that permits an improved spraying of the oil onto the surface 14 of the cam 16.

It should nevertheless be noted that the roller tappet 10 described herein does not necessitate a re-design of the cambox 12 let alone of the engine (not shown), but merely requires the addition of a bore, channel, groove and/or recess at the roller tappet 10.

Thus, using the roller tappet 10 described in Fig. 2 oil is additionally pumped onto the surface 14 of the cam 16 in addition to the oil that is injected onto the roller 18, thereby increasing the amount of oil provided at the surface 14 of the cam 16. As can be seen in the right hand figure of Fig. 2, the oil is provided at the surface 14 of the cam 16 just before that part of the surface 14 comes into contact with the roller 18 to thereby improve not only the lubrication of the surface 14, but also that of the surface of the roller 18. This leads to an increase in durability of the roller 18 and of the surface 14.

In this connection it should be noted that the roller 18 is typically composed of a steel alloy, such as those commonly used in the automo- tive sector. The material of the roller tappet 10 can likewise be selected from a different metal alloy or a ceramic as is commonly used in the automotive industry. Fig. 3a shows a sectional view of the roller tappet 10 of Fig. 2. The lubricant supply bore 42 is arranged at approximately the middle of the height of the body 22, where it opens into a top end of the tappet alignment groove 28 that extends along approximately half of the outer surface at one side of the roller tappet 10.

At the other side of the roller tappet 10 the lubricant supply bore 42 opens into the lubricant supply groove 20. The lubricant supply groove 20 supplies oil both to the tappet alignment groove 28 and to the roller re- ception space 32. In this example the lubricant supply groove 20 has a length that corresponds at least approximately to a third of the height of the roller tappet 10.

The lubricant supply bore 42 has a region of smaller diameter where it connects to the lubricant supply groove 20 and a region of larger diameter where it connects to the tappet alignment groove 28. This is beneficial for lubricating pumping purposes.

Fig. 3b shows a part sectioned and part schematic view of the roll- er tappet 10 of Fig 2. A centering nose 46 can clearly be seen around which a tappet spring 44 (see Fig. 2) can be centered. The centering nose 46 has a part truncated cone shape that is simple to manufacture using machine tools (not shown). In order to ensure that oil can also come into contact with the tappet spring 44 the recess 40 is provided that connects the roller reception space 32 to the tappet spring reception space 38.

The left hand side of the roller tappet of Fig. 3b has a shoulder 48 that ex- tends perpendicular to a longitudinal extent of the roller tappet 10. This shoulder 48 is the upper boundary of the tappet alignment groove 28. Fig. 4a shows a sectional view of a second kind of roller tappet 10 similar to that of Fig. 2. The difference being that the second fluid communicating connection is formed between the lubricant supply groove 20 and the tappet alignment groove 28 via the annular grove 34 that directly opens into the lubricant supply groove 20 and that is connected to the tappet alignment groove 28 via a lubricant supply channel 50 that connects the annular groove 34 and the tappet alignment groove 28.

Moreover, so that the lubricant supply groove 20 can also supply lubricant to the annular groove 34 this has a length that corresponds at least approximately to two thirds of the height of the roller tappet 10.

Generally speaking the length of the lubricant supply groove 20 can be selected within the range of 25 to 75 %, preferably within 33 to 66%, of the height of the roller tappet 10.

In the present example the lubricant supply channel 50 is provided as a recess at the outer surface of the roller tappet 10. The lubricant supply channel 50 has a reduced depth relative to a depth of the tappet alignment groove 28. In the present example the depth of the lubricant supply channel 50 corresponds to approximately 50% of the depth of the tappet alignment groove 28. The lubricant supply channel 50 extends from the annular groove 34 to the shoulder 48, where it opens into the tappet alignment groove 28.

In the examples shown herein a bypass is provided that directs some of the lubricant that was previously directed to a surface of a roller of a roller tappet, to a surface 14 of the cam 16 that can be in operative engagement with the roller tappet 10.

In the first case of application the bypass is present in the form of the channel 25 (see Figs. 1 a and 1 b). In the second case of application the bypass forms a connection between the lubricant supply groove 20 and the tappet alignnnent groove 28 (see Figs. 2 to 4b).

List of reference numerals:

10 roller tappet

12 cam box

14 cam surface

16 cam

18 roller

20 lubricant supply groove

22 body

24 lubricant supply passage

25 channel

26 lubricant supply passage

27 inner surface

28 tappet alignment groove

30 tappet alignment pin

31 outlet

32 roller reception space

33 recess

34 annular groove

36 end region

38 tappet spring reception space

40 recess

42 lubricant supply bore

44 tappet spring

46 centering nose

48 shoulder

50 lubricant supply channel

A arrow

B arrow

Claims

1 . A roller tappet (10), the roller tappet (10) comprising a body (22) having a roller reception space (32) that is formed at one end of the body and that is adapted to receive a roller (18), wherein the body (22) further comprises a lubricant supply groove (20) for the reception and/or at least intermediate storage of lubricant and a tappet alignment groove (28), wherein a first fluid communicating connection (26) is present between the lubricant supply groove (20) and the roller reception space (32) for the supply of lubricant to an outlet (31 ) that opens into the roller reception space (32),

characterized in that

a second fluid communicating connection (25; 42; 34, 50) is present in the roller tappet (10) that is provided to guide some of the lubricant supplied to the lubricant supply groove (20) to a second point of application, with the second point of application being remote from the outlet (31 ).

2. A roller tappet (10) in accordance with claim 1 , wherein at least a part of the second fluid communicating connection (25; 42; 34, 50) is pro- vided in the form of a bore, a channel, a groove and/or a passage.

3. A roller tappet (10) in accordance with claim 1 or claim 2, wherein the second fluid communicating connection (25; 50) extends, at least in part, towards the end of the body (22) that is adapted to receive the roller.

4. A roller tappet (10) in accordance with at least one of the preceding claims, wherein the second fluid communicating connection (25) is formed adjacent to the outlet (31 ) of the first lubricant supply passage (26) in a surface (27) of the roller reception space (32); and/or wherein the out- let (31 ) is provided as a recess (33) in a surface (27) of the roller reception space (32).

5. A roller tappet in accordance with at least one of the preceding claims, wherein the second fluid communicating connection is provided as a channel (25) in the surface (27) of the roller reception space (32), with the channel (25) preferably extending from the outlet (31 ) to the one end of the body (22); and with the channel (25) in particular extending circum- ferentially within the surface (27) of the roller reception space (32).

6. A roller tappet (10) in accordance with at least one of the preceding claims, wherein the second fluid communicating connection comprises the lubricant supply groove (20), the tappet alignment groove (28) and a bore (42), passage, groove (34) and/or channel (50) that connects the lubricant supply groove (20) to the tappet alignment groove (28).

7. A roller tappet (10) in accordance with claim 6, wherein the tappet alignment groove (28) is open at the said one end of the body (22) comprising the roller reception space (32) and opens into the bore (42), passage or channel (50) that connects the lubricant supply groove (20) to the tappet alignment groove (28) at the other end of the tappet alignment groove (28); and/or wherein the lubricant supply groove (20) is closed at each end of the roller tappet (10).

8. A roller tappet (10) in accordance with at least one of the preceding claims, wherein the second fluid communicating connection comprises a bore (42) that passes through the body (22) of the roller tappet (10).

9. A roller tappet (10) in accordance with claim 8,

wherein the bore (42) is arranged perpendicular to both the tappet alignment groove (28) and the lubricant supply groove (20) and the bore (42) connects the tappet alignment groove (28) and the lubricant supply groove (20); and/or wherein the bore (42) has a varying diameter over its length.

10. A roller tappet (10) in accordance with at least one of the preceding claims,

further comprising an annular groove (34) at an outer surface of the body (22) in the end region of the body (22) remote from the end of the body comprising the roller reception space (32).

1 1 . A roller tappet (10) in accordance with claim 10, wherein the second fluid communicating connection comprises the annular groove (34).

12. A roller tappet (10) in accordance with claim 10 or claim 1 1 ,

wherein the annular groove (34) directly opens into the lubricant supply groove (20) at a side of the roller tappet (10); and wherein a lubricant supply channel (50) connects the annular groove (34) and the tappet alignment groove (28) to form part of the second fluid communicating con- nection, in particular wherein the lubricant supply channel (50) is provided as a through bore or as a recess at the outer surface of the roller tappet (10) at the side of the roller tappet (10) remote from the lubricant supply groove (20).

13. A high pressure pump having at least one roller tappet (10) in accordance with at least one of the preceding claims.

14. An engine having at least one roller tappet (10) in accordance with at least one of the preceding claims and/or having a high pressure pump in accordance with claim 13, with the roller tappet optionally being in operative engagement with a surface (14) of a cam (16).

15. A method of lubricating a surface (14) of a cam (16) by means of a roller tappet (10), in particular using a roller tappet in accordance with at least one of the preceding claims 1 to 12, the method comprising the steps of:

- supplying oil to the roller tappet (10); - guiding some of the oil through a first lubricant supply passage (26) directly to a surface of a roller (18) received in the roller tappet (10); and

- guiding some of the oil through a second bore, passage, groove and/or channel (25; 42; 34, 50) separate from the first lubricant supply passage (26) to the surface (14) of the cam (16).