[0001] The invention relates to an injection nozzle for use in a fuel injection system for
an internal combustion engine. In particular, but not exclusively, the invention relates
to an injection nozzle for use in a compression ignition internal combustion engine,
in which a valve needle is engageable with a seating surface to control the injection
of fuel to an associated combustion space through a nozzle outlet.
[0002] In one known injection nozzle, for example as shown in Figure 1, a valve needle 10
has a seating surface 12, or seating "line", which engages with a seat defined by
an internal surface of a nozzle body bore 14 within which the needle 10 moves. In
use, as the valve needle 10 is moved away from the seat, injection nozzle outlets
16 are opened to enable high pressure fuel to be injected to the associated engine
cylinder. When the valve needle 10 is moved to re-engage with the seat, the outlets
16 are closed and injection is terminated.
[0003] Immediately downstream of its seating line 12 the valve needle 10 includes a downstream
region 18 of frusto-conical form defining a first cone angle, ϑA, which typically
is around 60 degrees. The nozzle body bore 14 is also of conical form, and defines
a second cone angle, ϑB. The difference between the first and second cone angles is
typically about 1 degree.
[0004] Immediately upstream of its seating line 12, the valve needle 10 includes an upstream
region 20 of frusto-conical form. The upstream region 20 defines a third cone angle,
ϑC, that typically is around 45 degrees. The difference between the third cone angle,
ϑC, and the second cone angle, ϑB (i.e. that of the nozzle body bore) is typically
about 15 degrees.
[0005] A valve tip region 19, arranged immediately downstream of the region 18, defines
a cone angle, ϑD. The differential angle between the cone angle, ϑD, of the valve
tip region 19 and the cone angle, ϑB, of the nozzle body bore 14 is typically just
a few minutes. The valve tip region 19 terminates in a chamfered tip 22.
[0006] It is a recognised problem in injection nozzle design that the effective diameter
of the seating line varies with wear during nozzle service life. The effective seat
diameter influences fuel delivery pressure, or nozzle opening pressure (i.e. that
pressure at which the valve needle is caused to lift from the bore seat), and this
affects the quantity of fuel that is delivered during injection (i.e. when the valve
needle is lifted).
[0007] It has been found that a nozzle of the type shown in Figure 1 goes part way to addressing
this problem, and has the effect of reducing variations in the effective seat diameter
with nozzle wear. It has been found that the variation of the effective seat diameter
is reduced for significant periods of operation, and it is an advantage of this that
delivery quantity variations are also reduced. Our copending European patent application
EP 1 180 596 A1 describes an injection nozzle generally of the aforementioned type.
[0008] By way of further background to the present invention, US 5 890 660 describes an
injection nozzle in which a circumferential groove is provided downstream of the valve
needle seating line to prevent drift of the effective seat diameter in a downstream
direction. This also has the benefit that variations in nozzle opening pressure throughout
nozzle service life are reduced.
[0009] It is one object of the present invention to provide a further improved injection
nozzle in which the detrimental effects of nozzle wear, and in particular wear of
the seating line of the needle, are further reduced.
[0010] In accordance with a first aspect of the present invention, there is provided an
injection nozzle for an internal combustion engine, comprising a valve member including
at least first, second and third distinct regions and being engageable with a seating
surface, which defines a seat cone angle, so as to control fuel delivery through a
nozzle outlet. The second region provides a seat region, of part-conical form, defining
a first cone angle, and the third region, which is of part-conical form and is arranged
immediately downstream of the seat region, defines a second cone angle. The seat and
third regions define, at their intersection, a seating line for engagement with the
seating surface. A first differential angle between the first cone angle and the seat
cone angle is smaller than a second differential angle between the second cone angle
and the seat cone angle, the first and second differential angles being selected to
ensure the seating line tends to migrate in an upstream direction along the seat region
as the valve member is worn, in use. The valve member further includes an end region
of at least part-conical form (i.e. part-conical, or a full cone), which is arranged
immediately downstream of the third region and which defines an additional cone angle,
wherein a further differential angle between the additional cone angle and the seat
cone angle is smaller than the first differential angle.
[0011] It is a feature of this aspect of the invention that whilst the tendency for the
seating line to wear causes fuel delivery variations, the effective diameter of the
seating line varies in an upstream direction, increasing in value, so that the fuel
delivery tends to decrease over the nozzle service life. This is a particular benefit
as wear in other parts of the fuel injection system can lead to fuel delivery increases,
so that the combination of effects tends to limit the net fuel delivery variations
to an acceptable level, or substantially avoids net variations altogether.
[0012] It may be advantageous to select the first differential angle so as to be less than
5 degrees, and preferably less than 3 degrees.
[0013] An additional region of the valve member upstream of the seat region may be of substantially
cylindrical form, or may also be of part-conical form.
[0014] It has been recognised that in some circumstances wear of the injection nozzle tending
to decrease fuel delivery quantity can be disadvantageous, particularly if small deliveries
are required (such as pilot injections of fuel). In accordance with a second aspect
of the invention, the injection nozzle for the internal combustion engine is therefore
provided with a valve member which is engageable with a seating surface, defining
a seat cone angle, so as to control fuel delivery through a nozzle outlet, the valve
member including an upper region of cylindrical form, a seat region arranged immediately
downstream of the upper region and defining a first cone angle, wherein the upper
region and the seat region define, at their intersection, a seating line for engagement
with the seating surface. The valve member further includes a second region, arranged
immediately downstream of the seat region, defining a second cone angle, and an end
conical region, arranged immediately downstream of the second region. A first differential
angle between the first cone angle and the seat cone angle is smaller than a second
differential angle between the second cone angle and the seat cone angle, the first
differential angle being selected to ensure the seating line migrates in a downstream
direction along the seat region as the valve member becomes worn, in use, and the
second differential angle being selected to prevent said migration of the seating
line beyond a pre-determined amount.
[0015] In a preferred embodiment, the seat region and the second region define a first intersection
therebetween, the seat and second regions being shaped such that a radial clearance
between the first intersection and the seating surface is sufficiently small for the
seat region to provide a load bearing surface for the needle during closure, thereby
to limit migration of the seating line, which results from wear, in the downstream
direction.
[0016] In a further preferred embodiment, the second region and the end region define a
second intersection therebetween, said second and end regions being shaped such that
a radial clearance between the second intersection and the seating surface is sufficiently
large to confine wear of the valve member to the seat and second regions.
[0017] Preferably, the end region defines a lower cone angle, and wherein a third differential
angle between the lower cone angle and the seat cone angle is approximately the same
as the first differential angle.
[0018] It is preferable if the second differential angle is up to 20 degrees greater than
the first differential angle, and more preferably if the second differential angle
is between 5 and 15 degrees greater than the first differential angle.
[0019] The invention also provides, in a third aspect, an injection nozzle for an internal
combustion engine includes a valve member having a major needle axis and being engageable
with a seating surface, defining a seat cone angle, so as to control fuel delivery
through a nozzle outlet, the valve member including a downstream seat region of part-conical
form, which defines a first cone angle, and, at its uppermost edge, a seating line
for engagement with the seating surface, a first circumferential groove, arranged
immediately downstream of the downstream seat region, an upper region arranged so
that a lower edge thereof defines, at its intersection with the downstream seat region,
the seating line, and a lower region arranged immediately downstream of the first
circumerferential groove. A lower edge of the first circumferential groove and the
lower region together define a line of intersection which itself defines, together
with the seating surface, a radial clearance that is sufficiently small so that the
downstream seat region defines a load bearing surface for the valve needle, and wherein
the first circumferential groove serves to prevent the seating line migrating beyond
a pre-determined amount, with wear of the needle.
[0020] This combination of features is particularly beneficial as wear of the seating line,
which occurs in a downstream direction, is not only confined to the seat region, but
is also limited due to the provision of the groove.
[0021] The lower region may be an end region, arranged immediately downstream of the first
circumferential groove, which defines a lower cone angle, and wherein the lower cone
angle is less than the first cone angle.
[0022] In one preferred embodiment, the upper region of the nozzle forms an upstream seat
region of part-conical form, said upstream seat region defining an upper cone angle,
wherein a first differential angle between the first cone angle and the seat cone
angle is substantially the same as a second differential angle between the upper cone
angle and the seat cone angle, thereby to ensure wear of the seating line, in use,
maintains the seating line at approximately the same axial position along the valve
member.
[0023] As the injection nozzle components wear, in use, contact pressure between the valve
member and its seating is distributed, in generally equal amounts, over both the upstream
and downstream seat regions, with the primary contact point on the valve needle which
engages with the seat remaining at approximately the same axial position. As a result,
the effective seating diameter changes very little with wear, so that variations in
fuel delivery quantity due to wear are limited.
[0024] The upper region that is immediately upstream of the upstream seat region may alternatively
be of cylindrical form.
[0025] In another embodiment, the injection nozzle may include a second circumferential
groove located downstream of the first circumferential groove and positioned axially
along the valve member so that, when the seating line is engaged with the seating
surface the second groove approximately aligns with the outlet.
[0026] The first and second grooves may be spaced apart by an intermediate region of part-conical
form which defines a further cone angle selected so that the intermediate region provides
an additional load bearing surface for the valve member. The provision of the intermediate
region further limits the extent of wear of the needle seat region (i.e. the combined
upper and lower portions).
[0027] The invention will now be described, by way of example only, with reference to the
accompanying drawings in which:
Figure 1 is a section drawing of a known injection nozzle generally of the type shown
in EP 1 180 596 A1,
Figure 2 is a schematic drawing of a first embodiment of the present invention providing
improved wear characteristics, and
Figures 3 to 6 are schematic drawings of alternative embodiments of the nozzle to
that shown in Figure 2.
[0028] As described previously, a generally known type of injection nozzle is shown in Figure
1, in which a valve member in the form of a needle 10 is engageable with a seating
to control fuel injection through a plurality of outlet openings 16 (two of which
are shown) into an associated engine cylinder or other combustion space.
[0029] Figure 2 shows an injection nozzle of a first embodiment of the invention, which
provides improved seat wear characteristics over the nozzle shown in Figure 1. Again,
the nozzle includes a valve needle 30 that is slideable within a bore provided in
a nozzle body 34 and engageable with a seating surface 32 defined by the bore. The
valve needle 30 is typically movable by means of an injection control valve arrangement
(not shown), typically of the type actuated by means of a piezoelectric actuator,
as would be familiar to a person skilled in the art.
[0030] Alternatively the valve needle 30 may be movable by electromagnetic means, or simply
by means of hydraulic forces causing the valve needle 30 to lift from its seating
32.
[0031] The nozzle body 34 is provided with a set of at least first and second outlets 36
which provide a flow path for fuel into the combustion chamber from an injection nozzle
delivery chamber 38. The delivery chamber 38 is together defined by the seating surface
32 and an outer surface of the valve needle 30 in a region downstream of a valve needle
seating surface, or seating line, 40 of annular form. The seating line 40 is engageable
with the seating surface 32 to control fuel flow into the delivery chamber 38 from
an upstream supply chamber 42. In use, the upstream supply chamber 42 is supplied
with high pressure fuel for injection. When it is required to inject fuel into the
engine cylinder the valve needle 30 is actuated or otherwise caused to lift so as
to move the seating line 40 away from its seating surface 32.
[0032] The valve needle 30 includes at least three distinct regions, and in this example
four distinct regions. A first region 44, at the uppermost end in the view shown in
Figure 2, is of substantially cylindrical form. A second region 46, of frusto-conical
or part conical form is arranged immediately downstream of the first region 44 and
defines, or includes, at its uppermost edge, the seating line 40. A third region 48
of substantially frusto-conical form is arranged immediately downstream of the second
region 46 and a fourth, or end region, 50 of substantially conical form is arranged
immediately downstream of the third region 48. The fourth region 50 includes, and
terminates in, a chamfered tip 52 which extends into a sac volume or chamber 53 defined
at the blind end of the nozzle body bore 32. The valve needle 30 is shaped such that
when the valve needle 30 is seated, the fourth region 50 is positioned in the vicinity
of, and so substantially occludes, the outlets 36. The second, third and fourth regions
46, 48, 50 of the valve needle 30 define first, second and third cone angles ϑ1, ϑ2,
ϑ3 respectively and each is of uniform cone angle along its respective lengths.
[0033] It is not readily apparent from the scale of the drawing in Figure 2, but the cone
angle, ϑ1, subtended by the second region 46 of the valve needle 30 is different from
the cone angle, ϑ2, subtended by the third region 48. The seating surface 32 defines
a seat cone angle, ϑs, (also referred to as the nozzle body cone angle), which is
different again from the first and second cone angles, ϑ1, ϑ2. The difference in cone
angle between ϑ1 and ϑs is typically between 0.1 and 3 degrees and the second region
46 of the valve needle has a length, d, (along its outer surface) of between about
0.05 to 0.4 millimetres.
[0034] The third region 48 of the valve needle 30 is shaped such that the differential angle
between its cone angle, ϑ2, and the seat cone angle, ϑs, is typically between 1 and
20 degrees greater than the further upstream differential angle, defined by the cone
angle, ϑ1, of the second region 46 and the seat cone angle ϑs.
[0035] The fourth region 50 is shaped to define a differential angle with the seat cone
angle ϑs of, typically, between 0 degrees (i.e. the cone angles are the same) and
2 degrees. The cone angle, ϑ3, of the fourth region 50 is typically less than the
second cone angle, ϑ2.
[0036] The third and fourth regions 48, 50 of the valve needle 30 are shaped so as to define,
at their line of intersection (identified at 55), a radial clearance or gap between
the seating surface 32, of between approximately 5 and 15 µm.
[0037] In operation, the effective diameter of the seating line 40 will tend to decrease
as the second region 46 of the valve needle 30 becomes worn. The relatively large
radial clearance between the line of intersection 55 and the seating surface 32 is
particularly beneficial as it ensures wear of the valve needle 30 is substantially
restricted to the second and third regions 46, 48. The finite length, d, of the second
region 46, as defined by the location of the third region 48, serves to limit the
extent of wear of the seating line 40, and thus limits the extent to which the effective
seating diameter is reduced. The limit of reduction in effective seating diameter
is defined by the diameter of a line of intersection 54 between the seat region 46
and the third region 48 of the needle 30.
[0038] By comparing the known valve needle in Figure 1 with the embodiment in Figure 2,
it will be appreciated that, effectively, an additional valve needle region, in the
form of the second region 46, is provided to define the seating line 40. This additional
region may be considered to provide a downstream seat region 46 for the needle, as
opposed to just a seating line 40. In use, the valve needle 'beds in' over this seat
region 46 as the needle wears and the seating line 40 is caused to migrate to lower
values (i.e. axially down the needle), with the effective diameter being limited by
the effective diameter of the intersection 54 between the second and third regions
46, 48. The cone angles and lengths of the second and third regions 46, 48 are shaped
so that a very small radial clearance, typically between 0.5 and 10 µm, is defined
between the valve needle surface at the intersection 54 and the seating surface 32,
so that the seat region 46 provides an effective load bearing surface for the needle
during closure.
[0039] Generally, as a consequence of wear of the valve needle and migration of the effective
seating diameter to lower values, the quantity of fuel injected during an injection
event will be increased (if all other control parameters remain the same). In the
Figure 2 embodiment, however, the extent of the reduction in the effective seating
diameter is limited, so that any such increase in fuel delivery quantity is also limited.
By selecting the length, d, of the seat region 46 carefully and by appropriate positioning
of the third region 48, a tolerable limit on fuel delivery increase can be achieved,
despite seat wear. Additionally, the length, d, of the seat region 46 is selected
to be between about 0.05 to 0.4 millimetres, and by incorporating this seat region
46 of relatively long length, loading of the needle is distributed over a large surface
area, with the effect that contact pressure, and hence wear, is reduced.
[0040] It will be appreciated that the aforementioned benefits are obtained regardless of
the shape of the first region 44 of the valve needle 30, upstream of the seating line
40, which may alternatively be of conical form, rather than cylindrical.
[0041] It has been found that the following combination of features provides a particularly
advantageous nozzle performance: (i) providing a downstream seat region 46, to define
the seating line 40, having a relatively long length and a relatively small differential
angle (with the seat cone angle) to reduce the effects of wear (ii) providing a further
(third) region 48, downstream of the seat region 46 and upstream of the fourth, end
region 50 of the needle, which has a larger differential angle (with the seat cone
angle) compared to that defined by the seat region 46 and which defines, at its intersection
with the seat region 46, a very small radial clearance with the seating surface 32,
such that the seat region 46 provides a load bearing surface for the needle, and (iii)
providing a relatively large radial clearance between an end region 50 of the valve
needle and the seating surface 32 so as to restrict valve needle 30 wear to the seat
region 46 and the region 48 immediately downstream of this.
[0042] An alternative embodiment of the invention is shown in Figure 3. For some applications,
any increase in fuel delivery quantity over the service life of the nozzle can be
disadvantageous, even if the increase is limited (as for the embodiment described
previously). Moreover, in some fuel injection systems, and particularly common rail
fuel injection systems, other parts of the system also suffer from effects of wear
which tend to have a similar effect of increasing fuel delivery quantity. In systems
for which fuel delivery increase occurs due to wear in other parts of the system,
it is therefore advantageous if seat wear within the nozzle has the effect of decreasing
fuel delivery quantity as a means of compensation.
[0043] In Figure 3, similar parts to those shown in Figure 2 are denoted with like reference
numerals. In this example, the seat region 46 of the valve needle, is arranged immediately
upstream of the seating line 40, adjacent to the first region 44. The seat region
46 defines a cone angle ϑ1 and, together with the seat cone angle ϑs, defines a relatively
small differential angle of just a few degrees, typically between 0.5 and 5 degrees.
The third region 48 of the needle 30 downstream of the seating line 40 defines a cone
angle ϑ2 which, together with the seat cone angle ϑs, defines a differential angle
that is greater than that defined by ϑ1 and ϑs. Typically, for example, the third
region 48 in Figure 3 is shaped to define a differential angle with the seat cone
angle of between about 1 and 20 degrees.
[0044] The end region 50 of the valve needle 30 has a uniform cone angle along its entire
length (with the exception of the slight chamfering of its tip) and aligns in the
vicinity of the nozzle outlet when the valve needle is seated. Put another way, the
valve needle 30 is received in the nozzle bore so that the end region 50 locates within
that region of the bore in which the outlets 36 are provided.
[0045] The provision of a seat region 46, immediately upstream of the seating line 40, to
define a relatively small differential angle may be referred to as an "inverted" or
"negative" seat region; that is a seat region which wears in a direction upstream
of the seating line 40. This is in contrast with the embodiment of Figure 2, where
a "non-inverted" or "positive" seat region is included downstream of the seating line
40.
[0046] For the embodiment of Figure 3, as the seating line 40 is caused to wear the effective
seating diameter will tend to increase to higher values as the seating line 40 migrates
along the upstream seat region 46. This has the effect of decreasing fuel delivery
quantities and, thus, may compensate for the effects of wear in other parts of the
fuel injection system which give rise to an increase in fuel delivery quantity. The
valve needle 30 is therefore shaped to provide a means for compensating for the effects
of wear in the fuel injection system, this being provided by the seat region 46 upstream
of the seating line 40 having a relatively small differential angle (with the seat
cone angle) compared to the differential angle defined by the third region 48 (with
the seat cone angle) downstream of the seating line 40.
[0047] Figure 3 shows the first region 44 of the valve needle 30 upstream of the seat region
46, as being of cylindrical form, but it will be appreciated that the aforementioned
advantages are also achieved if the first region 44 is of conical form, either defining
the same differential angle with the seat cone angle, in which case it forms a continuous
region with the upstream seat region 46, or defining a greater differential angle
to that defined by the upstream seat region 46 (with the seat cone angle). The latter
configuration provides the benefit that migration of the seating line 40 is limited,
as determined by the finite length of the seat region 46.
[0048] In a particularly preferred embodiment it has been found that shaping the upstream
seat region 46 and the seating surface 32 to together define a differential angle
of less than 3 degrees provides a hydraulically self-centralising force to the end
region 50 the needle 30. If at least two outlets 36 are provided, this has the advantage
of achieving good "hole-to-hole" flow balance. For small values of needle lift, and
if fuel sprays are relatively wide, improved hole-to-hole flow balance is particularly
important and the selection of the upstream differential angle within this range provides
a particular benefit in such circumstances.
[0049] A possible disadvantage of the nozzle shown in Figure 3 compared to that in Figure
2 may occur in some applications for which very small fuel delivery quantities are
required, for example where it is required to deliver a low volume, pilot injection
of fuel prior to a main injection of fuel. If the effective seat diameter tends to
increase with wear, thus tending to decrease fuel delivery quantities, it is possible
that the pilot injection of fuel may disappear altogether.
[0050] Figure 4 shows a further embodiment of the invention which ensures the effective
seating diameter tends to decrease with wear (i.e. as in the Figure 2 embodiment).
[0051] In this embodiment the first region 44 of the valve needle 30 is of cylindrical form,
and the seat region 46 is shaped to define a cone angle, ϑ1. The differential angle
defined by the cone angle ϑ1 of the seat region 46 and the seat cone angle ϑs is typically
between about 0 degrees 10 minutes and 3 degrees (i.e. relatively small). Thus, as
the seating line 40 wears it tends to migrate downstream along the seat region 46
and, thus, the effective diameter tends to decrease. Any variation in fuel delivery
quantity due to this wear is therefore in the form of an increased fuel delivery quantity.
[0052] In Figure 4, it can be seen that the valve needle 30 also includes a circumferential
groove 58 immediately downstream of the seat region 46. The provision of the groove
58 serves to limit the extent to which the seat region 46 can wear, in use, so that
there is a limit on the variation (increase) in fuel delivery quantity, and nozzle
opening pressure, with such seat wear. In this respect the groove 58 provides a similar
function to the third region 48 in the Figure 2 embodiment. Immediately downstream
of the groove 58, the lower end region 50 of the valve member 30 defines a cone angle,
ϑ3, which is greater than the first cone angle, ϑ1, of the seat region 46.
[0053] The embodiment shown in Figure 4 is similar to the injection nozzle described in
US 5 890 660. However, in US 5 890 660 the effective seating diameter tends to migrate
to higher values (i.e. as defined by the upstream region of the valve needle) due
to the inverted differential angle upstream of the seating line 40. In contrast, Figure
4 provides an injection nozzle for which the effective seating diameter tends to migrate
to lower values, due to the differential angle defined by the seat region 46 (with
the surface 32), so that any problems associated with reduced fuel delivery quantities
which may arise in the nozzle in US 5 890 660 are overcome.
[0054] A line of intersection 55 is defined between the circumferential groove 58 and the
lower end region 50. The radial clearance between the line of intersection 55 and
the seating surface 32 is very small, typically between 0.5 and 10 µm (and preferably
between 0.5 and 5 µm), to ensure that the seat region 46 provides an effective load
bearing surface for the needle 30 as it seats, in use.
[0055] An alternative embodiment to that shown in Figure 4 is shown in Figure 5, in which
the needle is provided with both an upstream seat region 46a (i.e. that region immediately
upstream of the seating line 40) and a downstream seat region 46b (i.e. that region
immediately downstream of the seating line 40). The cone angles of the upstream and
downstream seat regions 46a, 46b are both selected to define relatively small differential
angles with the seat cone angle, ϑs. Typically, for example, the upstream and downstream
seat regions 46a, 46b are shaped so that each defines a differential angle with the
nozzle body cone angle, ϑs, of between about 0 degrees 10 minutes and 5 degrees. Preferably,
the differential angles defined by the seat regions 46a, 46b are substantially the
same, but alternatively they may be slightly different, providing always that they
are relatively small.
[0056] The embodiment in Figure 5 also includes a circumferential groove 58, which serves
to limit the extent of wear of the downstream seat region 46 of the valve needle 30.
[0057] When the injection nozzle is used initially, the effective seating diameter is defined
by the surface or line of intersection 40 between the upstream seat region 46a and
the downstream seat region 46b. As the injection nozzle components wear, in use, contact
pressure between the valve needle 30 and the surface 32 tends to distribute approximately
equally over both seat regions 46a, 46b, although the primary line of contact remains
at approximately the same axial position (i.e. that of the original seating line 40).
As a result, the effective seating diameter changes very little with wear, and hence
the fuel delivery quantity and nozzle opening pressure also varies only a little.
[0058] A further alternative embodiment to that shown in Figures 4 and 5 is shown in Figure
6, in which the valve needle is provided with a first circumferential groove 58 located
immediately downstream of the downstream seat region 46b (as in Figure 5), with a
second circumferential groove 60 being provided further downstream so as to approximately
align with the outlets 36 when the valve needle 30 is seated. The first and second
circumferential grooves 58, 60 are separated by an intermediate region 62 of the valve
needle 30. The intermediate region 62 defines a differential cone angle with the seat
cone angle ϑs which, typically, is between about 10 minutes and 3 degrees. This region
62 provides a load bearing surface upon needle closure, which serves to reduce the
loading on, and hence wear of, the upper and lower seat regions 46a, 46b.
[0059] One benefit of providing the second groove 60, approximately at the same axial position
along the major axis of the valve needle 30 as the outlets 36, is that it permits
fuel pressure to homogenise within that region of the delivery chamber adjacent to
the inlet ends (i.e. inner ends) of the outlets 36. This has the effect of equalising
fuel delivery quantity through each of the outlets 36, and helps to ensure equal spray
formations are achieved through each outlet also.
[0060] If the nozzle is provided with a second set of outlets, occupying a different axial
position along the valve member to the first set of outlets 36, an additional circumferential
groove may be provided to align with this second set, as described above for the first
set. For each set of outlets provided, a further circumferential groove may be provided
in the same manner.
[0061] All of the injection nozzles described hereinbefore are of VCO (valve covered orifice)
type, in which the valve needle 30 covers or occludes the inlet end of the or each
nozzle outlet 36 when it is seated (i.e. when no injection takes place). The present
invention is equally applicable, however, to sac-type injection nozzles in which the
or each nozzle outlet is not covered by the valve needle when it is seated, but the
inlet end of each outlet is in constant communication with the sac chamber at the
blind end of the nozzle body bore. In sac-type nozzles it is unseating and seating
of the valve needle that again controls whether or not injection occurs through the
outlets, as in VCO-type nozzles.
[0062] It will be appreciated that the differential angles (i.e. the difference in cone
angle between two different surfaces), the cone angles and other dimensions stated
in the previous description are given by way of illustrative example only, and that
values falling outside of the specified ranges and having different values to those
quoted may also be implemented to provide substantially the same technical function
of the invention, as set out in the accompanying claims.
1. An injection nozzle for an internal combustion engine, the nozzle comprising:
a valve member (30) including at least first (44), second (46) and third (48) distinct
regions and being engageable with a seating surface (32), which defines a seat cone
angle (ϑs), so as to control fuel delivery through a nozzle outlet (36),
wherein the second region provides a seat region (46) of part-conical form, defining
a first cone angle (ϑ1), and the third region (48), which is of part-conical form
and arranged immediately downstream of the seat region (46), defines a second cone
angle (ϑ2), the seat region (46) and the third region (48) defining, at their intersection,
a seating line (40) for engagement with the seating surface (32),
wherein a first differential angle between the first cone angle (ϑ1) and the seat
cone angle (ϑs) is smaller than a second differential angle between the second cone
angle (ϑ2) and the seat cone angle (ϑs), said first and second differential angles
being selected to ensure the seating line (40) tends to migrate in an upstream direction
along the seat region (46) as the valve member (30) is worn, in use,
the valve member (30) further including an end region (50) of at least part-conical
form, which is arranged immediately downstream of the third region (48) and which
defines an additional cone angle (ϑ3), wherein a further differential angle between
the additional cone angle (ϑ3) and the seat cone angle (ϑs) is smaller than the first
differential angle.
2. The injection nozzle as claimed in Claim 1, wherein when the valve needle (30) is
seated, the end region (50) is located in the vicinity of the nozzle outlet (36).
3. The injection nozzle as claimed in Claim 1 or Claim 2, wherein the first differential
angle is selected to be less than 3 degrees.
4. The injection nozzle as claimed in any one of Claims 1 to 3, wherein an additional
region (44) of the valve member (30) upstream of the seat region (46) is of substantially
cylindrical form.
5. An injection nozzle for an internal combustion engine, the nozzle comprising:
a valve member (30) having a major needle axis and being engageable with a seating
surface (32), defining a seat cone angle (ϑs), so as to control fuel delivery through
a nozzle outlet (36), the valve member including a downstream seat region (46; 46b)
of part-conical form, which defines a first cone angle (ϑ1), and, at its uppermost
edge, a seating line (40) for engagement with the seating surface (32);
a first circumferential groove (58) arranged immediately downstream of the downstream
seat region (46; 46b);
an upper region (44; 46b) arranged so that a lower edge thereof defines, at its intersection
with the downstream seat region (46; 46b), the seating line (40), and
a lower region (50) arranged immediately downstream of the first circumerferential
groove (58), a lower edge of the first circumferential groove (58) and the lower region
(50) together defining a line of intersection (55) which defines, together with the
seating surface (32), a radial clearance that is sufficiently small so that the downstream
seat region (46) defines a load bearing surface for the valve needle (30), wherein
the first circumferential groove (58) serves to prevent the seating line (40) migrating
beyond a pre-determined amount with wear of the needle.
6. The injection nozzle as claimed in Claim 5, wherein the radial clearance is between
0.5 and 5 µm.
7. The injection nozzle as claimed in Claim 5 or Claim 6, wherein the lower region (50)
defines a lower cone angle (ϑ3) that is less than the first cone angle (ϑ1).
8. The injection nozzle as claimed in any one of Claims 5 to 7, wherein the lower region
(50) forms an end region of the valve member (30).
9. The injection nozzle as claimed in any one of Claims 5 to 8, wherein the upper region
(44; 46b) forms an upstream seat region (46a) of part-conical form, said upstream
seat region (46a) defining an upper cone angle which defines, together with the seat
cone angle (ϑs), a first differential angle that is substantially the same as a second
differential angle between the first cone angle (ϑ1) and the seat cone angle (ϑs),
thereby to ensure wear of the seating line (40), in use, maintains the seating line
(40) at approximately the same axial position along the valve member (30).
10. The injection nozzle as claimed in any one of Claims 5 to 9, further comprising a
second circumferential groove (60) located downstream of the first circumferential
groove (58) and positioned axially along the valve member (30) so that when the seating
line (40) is engaged with the seating surface (32) the second groove (60) approximately
aligns with the outlet (36).
11. The injection nozzle as claimed in Claim 10, wherein the first and second grooves
(58, 60) are spaced apart by an intermediate region (62) of part-conical form which
defines a further cone angle selected so that the intermediate region (62) provides
an additional load bearing surface for the valve needle (30).
12. An injection nozzle for an internal combustion engine, the nozzle comprising:
a valve member (30) which is engageable with a seating surface (32), defining a seat
cone angle (ϑs), so as to control fuel delivery through a nozzle outlet (36),
the valve member (30) including a cylindrical upper region (44), a seat region (46),
arranged immediately downstream of the upper region (44), defining a first cone angle
(ϑ1), wherein the upper region (44) and the seat region (46) define, at their intersection,
a seating line (40) for engagement with the seating surface (32), a second region
(48), arranged immediately downstream of the seat region (46), defining a second cone
angle (ϑ2), and an end conical region (50), arranged immediately downstream of the
second region (48),
wherein a first differential angle between the first cone angle (ϑ1) and the seat
cone angle (ϑs) is smaller than a second differential angle between the second cone
angle (ϑ2) and the seat cone angle (ϑs), said first differential angle being selected
to ensure the seating line (40) migrates in a downstream direction along the seat
region (46) as the valve member (30) becomes worn, in use, and the second differential
angle being selected to prevent said migration of the seating line (40) beyond a pre-determined
amount.
13. The injection nozzle as claimed in Claim 12, wherein the seat region (46) and the
second region (48) define a first intersection (54) therebetween, said regions (46,
48) being shaped such that a radial clearance between the first intersection (54)
and the seating surface (32) is sufficiently small for the seat region (46) to provide
a load bearing surface for the needle (30), thereby to limit migration of the seating
line (40) in the downstream direction due to wear.
14. The injection nozzle as claimed in Claim 12 or Claim 13, wherein the second region
(48) and the end region (50) define a second intersection (55) therebetween, said
regions (48, 50) being shaped such that a radial clearance between the second intersection
and the seating surface (32) is sufficiently large to confine wear of the valve needle
to the seat and second regions (46, 48).
15. The injection nozzle as claimed in any one of Claims 12 to 14, wherein the end region
(50) defines a lower cone angle (ϑ3), and wherein a third differential angle between
the lower cone angle (ϑ3) and the seat cone angle (ϑs) is approximately the same as
the first differential angle.
16. The injection nozzle as claimed in any one of Claims 12 to 15, wherein the second
differential angle is up to 20 degrees greater than the first differential angle.
17. The injection nozzle as claimed in Claim 16, wherein the second differential angle
is between 5 and 15 degrees greater than the first differential angle.
18. The injection nozzle as claimed in any one of Claims 1 to 17 , being one of (i) VCO-type
or (ii) sac-type.