EP0870904A1 - Hydraulic tappet assembly - Google Patents
Hydraulic tappet assembly Download PDFInfo
- Publication number
- EP0870904A1 EP0870904A1 EP98106592A EP98106592A EP0870904A1 EP 0870904 A1 EP0870904 A1 EP 0870904A1 EP 98106592 A EP98106592 A EP 98106592A EP 98106592 A EP98106592 A EP 98106592A EP 0870904 A1 EP0870904 A1 EP 0870904A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- mounting member
- piston
- hydraulic tappet
- tappet assembly
- assembly
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
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Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
- F01L1/20—Adjusting or compensating clearance
- F01L1/22—Adjusting or compensating clearance automatically, e.g. mechanically
- F01L1/24—Adjusting or compensating clearance automatically, e.g. mechanically by fluid means, e.g. hydraulically
- F01L1/245—Hydraulic tappets
- F01L1/25—Hydraulic tappets between cam and valve stem
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Valve-Gear Or Valve Arrangements (AREA)
Abstract
A hydraulic tappet assembly (10) comprises a tappet body (11)
providing a being surface (13), a mounting member (15) within the tappet body
(11), and a piston (17) mounted in the body (11) by the mounting member (15), the
assembly further comprising an inside wall (26) of the body (11) which is provided
with an interference formation (40) and the mounting member (15) is retained in
the body (11) at least primarily as an interference fit with the interference
formation (40).
Description
This invention relates to a hydraulic tappet assembly of the kind
comprising a tappet body providing a bearing surface, a mounting member within
the tappet body, and a piston mounted in the body by the mounting member.
Conventionally the bodies of such hydraulic tappet assemblies are made
from steel and the bearing surface is hardened by a suitable hardening process to
withstand and give sufficient durability to bear on a cam lobe of a cam shaft of an
internal combustion engine.
The mounting members too are conventionally made of steel and are
fixed within a hollow of the body by welding or blazing or a similar technique.
Notwithstanding that the bearing surfaces of the tappet bodies are
hardened, the steel does not give optimum wear properties and an inherently
harder material for the tappet bodies would be preferred, such as for example, cast
iron. However, steel is an ideal material for the mounting members, but the steel
cannot be fixed to an iron body by conventional fixing techniques.
According to a first aspect of the invention we provide a hydraulic
tappet assembly comprising a tappet body providing a bearing surface, a mounting
member within the tappet body, and a piston mounted in the body by the mounting
member characterised in that an inside wall of the body is provided with an
interference formation and the mounting member is retained in the body at least
primarily as an interference fit with the interference formation.
Thus in a hydraulic tappet assembly in accordance with the invention,
there is no barrier to the tappet body being made of one material and the mounting
member being made of a different material, so that the optimum materials for these
two components may be used.
The bearing surface of even an iron tappet body may need some surface
treatment but the material is inherently harder and gives improved wear
characteristics.
Typically the body is generally cylindrical providing a generally
cylindrical hollow therein in which the mounting member is retained, and the
interference formation of the inside wall of the body may comprises a groove e.g.
extending around the cylindrical inside wall of the body in which a peripheral
portion of the mounting member is received.
The peripheral portion may comprise all or substantially all of the entire
circular periphery of the mounting member in which case the groove may extend
around the entire inside wall, or a part only of the circular periphery.
In each case the peripheral portion of the mounting member may be of
curved configuration in cross section and the corresponding surface part of the
groove may be shaped to correspond closely to the curved configuration of the
peripheral portion so that there is a minimal gap or space between the mounting
member and the inside wall of the body.
In the event there is any gap between the mounting member and the
inside wall of the tappet body, this may be closed with a filling material, such as an
anaerobic adhesive.
Further, where the entire circular periphery of the mounting member is
not received in the groove, e.g. the periphery of the mounting member may
comprises a plurality of separated segments, any gaps or spaces which could
otherwise permit oil to leak therethrough, may be sealed with such adhesive.
Although the invention has been developed particularly to enable a
hydraulic tappet assembly to be produced in which the tappet body is made of cast
iron and the mounting member is made of steel, the invention may be utilised
where one or both of these components are made of other materials or are both
made of one of these materials.
In each case, the mounting member may comprise a generally central
opening in which the piston is mounted, usually received in a cylinder which is
retained by the mounting member such that the piston may move relative to the
cylinder and the mounting member in use. Preferably a spring means is provided
between the piston and the cylinder to bias the piston outwardly of the cylinder.
According to a second aspect of the invention we provide a method of
retaining a mounting member for a piston in a body of a hydraulic tappet assembly
comprising the steps of providing in an inside wall of the body, a retaining
formation and inserting the mounting member into the tappet body so that the
mounting member is an interference fit with the retaining formation.
The invention will now be described with reference to the
accompanying drawings in which:-
Referring first to Figure 1 and Figure 1a, there is shown a hydraulic
tappet assembly 10 comprising a generally hollow tappet body 11 which in this
example is generally cylindrical shape, having at one end thereof, an end wall 12
providing a bearing surface 13 which in use typically would bear on a lobe of a
camshaft or the like of an internal combustion engine.
Within the hollow of the body 11 there is provided mounting member
15 for mounting a piston assembly 16 which comprises a hollow piston 17 received
in a cylinder 18. Between the piston 17 and the cylinder 18 there is provided a
spring 19, the piston 17 being able to move within the cylinder 18 against the
biasing force of spring 19 away from the end wall 12 of the body 11, as hydraulic
fluid, typically oil enters a working space 20 of the tappet body 11 through an
opening 21 in the cylindrical wall 22 of the body 11. The oil is transmitted via a
passageway 23 into the hollow of the piston 17 and acts against the piston to urge it
inwardly of the cylinder 18 against the force of the spring. Oil is supplied to the
opening 21 from an oil way of the internal combustion engine in which the tappet
assembly 10 is provided.
The working space 20 of the body 11 is defined by the mounting
member 15 which comprises a peripheral portion 25 of generally circular
configuration, which conventionally is welded or braised to all inside surface 26 of
the tappet body 11 both to fix the mounting member 15 in the hollow of the body
11, and the provide an oil seal around the mounting member 15 between the
mounting member 15 and the inside wall 26 of the body 11.
The mounting member 15 is made from steel, usually as a pressing, and
the piston assembly 16 is retained by the mounting member 15, by a circlip 30
received in a circumferential groove of the cylinder 18, which a circlip prevents the
cylinder 18 from being withdrawn from the mounting member 18 in a direction
away from the end wall 12. Nevertheless, it will be appreciated that the cylinder
18 can be moved towards the end wall 12 by deforming the spring 19, and that the
pressure of oil in the working space 20 of the body 11 and in the hollow of the
piston, will move the cylinder 18 away from the end wall 12 to the maximum
extent permitted by the circlip 30 and by a value stem or connecting rod bearing on
an end surface 27 of the piston 18.
In Figure 1a the detail of the connection between the mounting member
15 and the inside wall 26 of the body 11 is shown.
Referring now to Figure 2 and 2A similar parts of the hydraulic tappet
assembly 10 to the conventional prior art assembly shown in Figures 1 and 1A are
indicated by the same reference numerals.
In this arrangement, rather than fixing the mounting member 15 to the
inside wall 26 of the tappet body by welding oil braising as shown in Figure 1A, the
mounting member 15 is retained in the hollow of the body 11 and an interference
fit, the peripheral portion 25 of the mounting member 15 engaging in a retaining
formation 40 provided in the inside wall 26 of the body 11.
The retaining formation 40 comprises a very shallow groove to receive
the peripheral portion 25 of the mounting member 15 and prevent the mounting
member 15 from moving outwardly of the hollow of the body 11.
If the mounting member 15 is of the same configuration as the
mounting member 15 shown in Figures 1 and 1A, it will be appreciated that a small
gap G would be provided between the peripheral portion of the mounting member
15 and the inside wall 26 of the body 11, which gap may be exacerbated by the
provision of the retaining groove 40. Any gap may be sealed by using an adhesive
such as an anaerobic adhesive to prevent oil escaping from the working space 20
between the end wall 13 of the body and the mounting member 15. However the
mounting member is primarily retain as an interference fit.
As indicated in Figure 2a however, the peripheral portion 25 of the
mounting member 15 is modified slightly in configuration so that the peripheral
portion 25 corresponds closely to the configuration of the retaining formation 40
provided in the inside wall 26 of the body, such that no or minimal gap occurs
between the adjoining faces of the peripheral portion 25 of the mounting member
15 and the inside wall 26. Thus an aerobic or other adhesive to provide an oil seal
may not be required.
In this embodiment, the tappet body 11 is not made of steel as with the
prior art example as shown in figures 1 and 1A. Rather, the tappet body 11 is made
from chilled grey cast iron so that the bearing surface 13 of the tappet body 11 is
inherently much harder than steel, and more durable in use.
Referring Figures 3a, 3b and 3c, Figure 3a shows a mounting member
15 which has a generally circular peripherally 25 without there being any
interruptions. If the retaining groove in the inside wall 26 of the body 11 is
sufficiently shallow, it is envisaged that such a mounting member 15 with a circular
periphery 25 may be used as minimum deflection of the periphery 25 is required in
order for the mounting member 15 to be inserted in the position shown in Figure
2a.
Particularly but not exclusively in the event that a deeper retaining
groove 40 is required than indicated in Figure 2a the periphery 25 may be divided
into peripheral segments 25a, 25b, 25c and 25d for example shown in Figure 3b.
In Figure 3b, the segment portions 25a to 25d are separated by small notches 41
which permit greater deflection of the peripheral portion segments to 25a to 25d as
the mounting member 15 is inserted in position.
In figure 3c, similar notches 41 are shown, but of an alternative
configuration.
If a mounting member 15 such as shown in Figure 3b or 3c is inserted
into the body 11, the gaps provided by the notches 41 would need to be sealed by
for example, an anaerobic adhesive, to prevent the escape of hydraulic oil from the
working space 20 of the tappet body 11.
Various modifications may be made without departing from the scope
of the invention.
For example, whereas it is preferred for the tappet body 11 to be made
of a hard material such as iron, this may be made of alternative materials. In any
event, the bearing surface 13 of the tappet body 11 may need to be treated by some
hardening process to give desired wear characteristics. Thus essentially, other
tappet body 11 need not be made of a similar material to the mounting member 15.
Although in the example described the mounting member 15 is
conveniently made as a pressing in steel, it may be made in other materials, and by
alternative manufacturing techniques as desired. Although preferred it is not
essential for the body 11 of the tappet assembly 10 to be cylindrical in
configuration although this is most useful.
The piston 17 need not have an internal recess as described in this
example but other configurations are possible to both the piston assembly 16, and
body 11 and mounting member 15 without departing from the scope of the
invention.
Claims (10)
- A hydraulic tappet assembly (10) comprising a tappet body (11) providing a bearing surface (13), a mounting member (15) within the tappet body (11), and a piston (17) mounted in the body (11) by the mounting member (15) characterised in that an inside wall (26) of the body (11) is provided with an interference formation (40) and the mounting member (15) is retained in the body (11) at least primarily as an interference fit with the interference formation (40).
- A hydraulic tappet assembly (10) according to claim 1 characterised in that the body (11) is generally cylindrical providing a generally cylindrical hollow therein in which the mounting member (15) is retained.
- A hydraulic tappet assembly (10) according to claim 1 or claim 2 characterised in that the interference formation (40) of the inside wall (26) of the body (11) comprises a groove in which a peripheral portion (25) of the mounting member (15) is received.
- A hydraulic tappet assembly (10) according to claim 3 characterised in that the peripheral portion (25) of the mounting member (15) is of curved configuration in cross section and the corresponding surface part of the groove (40) is shaped to correspond closely to the curved configuration of the peripheral portion (25).
- A hydraulic tappet assembly (10) according to any one of the preceding claims characterised in that a filling material closes any residual gap between the mounting member (15) and the inside wall (26) of the tappet body (11).
- A hydraulic tappet assembly (10) according to any one of claims 3 to 5 where appendant to claim 3 characterised in that all or substantially all of the entire periphery (25) of the mounting member (15) is received in the groove (40).
- A hydraulic tappet assembly (10) according to any one of claims 3 to 6 where appendant to claim 3 characterised in that the periphery (25) of the mounting member comprises a plurality of separated segments (25a, 25b,25c and 25d).
- A hydraulic tappet assembly (10) according to any one of the preceding claims characterised in that the mounting member (15) comprises a generally central opening in which the piston (17) is mounted.
- A hydraulic tappet assembly (10) according to claim 8 characterised in that the piston (17) is received in a cylinder (18) which is retained by the mounting member (15) such that the piston (17) may move relative to the cylinder (18) and the mounting member (15) in use, and a spring means (19) is provided between the piston (17) and the cylinder (18) to bias the piston (17) outwardly of the cylinder (18).
- A method of retaining a mounting member (15) for a piston (17) in a body (11) of a hydraulic tappet assembly (10) comprising the steps of providing in an inside wall (26) of the body (11), a retaining formation (40) and inserting the mounting member (15) into the tappet body (11) so that the mounting member (15) is an interference fit with the retaining formation (40).
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB9707387 | 1997-04-11 | ||
GBGB9707387.8A GB9707387D0 (en) | 1997-04-11 | 1997-04-11 | Hydraulic tappet assembly |
Publications (1)
Publication Number | Publication Date |
---|---|
EP0870904A1 true EP0870904A1 (en) | 1998-10-14 |
Family
ID=10810662
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP98106592A Withdrawn EP0870904A1 (en) | 1997-04-11 | 1998-04-09 | Hydraulic tappet assembly |
Country Status (2)
Country | Link |
---|---|
EP (1) | EP0870904A1 (en) |
GB (1) | GB9707387D0 (en) |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE4124484C1 (en) * | 1991-07-24 | 1993-01-14 | Fa. Carl Freudenberg, 6940 Weinheim, De | |
DE4138995A1 (en) * | 1991-11-27 | 1993-06-03 | Schaeffler Waelzlager Kg | Tappet with hydraulic valve play compensation - has guide and tappet sleeves with design such that compensation element is lightly supported |
EP0770764A1 (en) * | 1995-10-27 | 1997-05-02 | EATON AUTOMOTIVE S.p.A. | Hydraulic weldless tappet provided with a siphon device |
-
1997
- 1997-04-11 GB GBGB9707387.8A patent/GB9707387D0/en active Pending
-
1998
- 1998-04-09 EP EP98106592A patent/EP0870904A1/en not_active Withdrawn
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE4124484C1 (en) * | 1991-07-24 | 1993-01-14 | Fa. Carl Freudenberg, 6940 Weinheim, De | |
DE4138995A1 (en) * | 1991-11-27 | 1993-06-03 | Schaeffler Waelzlager Kg | Tappet with hydraulic valve play compensation - has guide and tappet sleeves with design such that compensation element is lightly supported |
EP0770764A1 (en) * | 1995-10-27 | 1997-05-02 | EATON AUTOMOTIVE S.p.A. | Hydraulic weldless tappet provided with a siphon device |
Also Published As
Publication number | Publication date |
---|---|
GB9707387D0 (en) | 1997-05-28 |
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STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN |
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18D | Application deemed to be withdrawn |
Effective date: 19990415 |