Note: Descriptions are shown in the official language in which they were submitted.
CA 02603067 2007-09-28
-1-
Lifting Piston Fuel Pump And Method For Starting And Operating A Motor Vehicle
Heating System
The present invention relates to a reciprocating piston fuel pump, in
particular for an automotive
heater that is electromagnetically driven and is provided for pumping liquid
fuel, having a
damping element comprising an elastomer for damping pulsations generated by
the reciprocating
piston fuel pump.
The present invention also relates to a method for starting and operating an
automotive heater
operated with liquid fuel, having a burner and a reciprocating piston fuel
pump having a damping
element comprising an elastomer for damping pulsations generated by the
reciprocating piston
fuel pump.
A generic reciprocating piston fuel pump is disclosed, for example, in the
publication Fahrzeug-
und Verkehrstechnik, Technische Mitteilungen [Automotive and Traffic
Engineering, Technical
Reports] 97 (2004), No. 1, pp. 9-11 and shown as a schematic sectional view in
Figure 1.
The reciprocating piston fuel pump 16' shown in Figure 1 is provided for
pumping liquid fuel in
the direction represented by the arrows, namely from the fuel inlet 18 to a
fuel outlet 20. As soon
as a suitable voltage is applied to an electric termina142, electricity flows
through a winding 22,
thus electromagnetically inducing a movement of a reciprocating piston 24.
First, fuel in a pump
chamber 30 is ejected through a nonreturn valve 28 against the hydraulic
resistance of the output
line. Then the electric current passing through the winding 22 is terminated.
A restoring spring
26 presses the reciprocating piston 24 toward the left into its resting
position. Liquid fuel is
drawn in through an intake valve 32, filling the pump chamber 30. With this
pump principle, it is
also possible to achieve conveyance of fuels that is very precise
volumetrically, even those fuels
having a very low viscosity. The delivery quantity can be controlled exactly
through the
frequency of the triggering voltage pulses.
However, unwanted pulsations occur in the fuel system due to the back-and-
forth movement of
the reciprocating piston 24. It is already known that to at least partially
suppress these pulsations,
a damping element 34 may be provided, comprising a bellows-like elastomer 36.
When liquid
fuel passes through a borehole 40 and comes in contact with the elastomer 36,
the elastomer 36
expands into a neighboring 38, which is provided in a damper housing formed by
a molded
plastic part 44. The prerequisite for this is a certain backpressure in the
fuel system which
ensures that the elastomer 36 will be "secured" in place.
One problem with the reciprocating piston fuel pump 16' shown in Figure 1 is
that the damping
element 34 has little or no function in extreme ambient cold, e.g., at a
temperature below -23 C,
because the elastomer 36 hardens or undergoes a glass transition (a typical
elastomer point [sic;
glass transition point] of the elastomer 36 is -23 C, for example). Another
problem is that so-
CA 02603067 2007-09-28
2
called Arctic' diesel, which is the only fuel approved for use at temperatures
below -20 C for
diesel burners, produces a much lower backpressure at temperatures below -20 C
than does
winter diesel at room temperature, for example, due to the lower viscosity.
The functionality of
the damping element 34 is therefore reduced even before reaching the elastomer
point [sic] of the
elastomer 36. At "moderately" cold temperatures above -20 C, for example, this
may under some
circumstances result in an increase in CO emissions by the vehicle heater
caused by pulsations in
the fuel system. At extremely low temperatures of less than -30 C, for
example, the problem may
even occur that stabilization of combustion operation is prevented due to
pulsations in the fuel
system. Although it is possible to start the burner in such cases, the burner
may become
destabilized over a period of time or may even be extinguished after the glow
plug goes out, i.e.,
when there is no supporting energy for the base of the flame. Such unwanted
extinction of the
flame may occur, for example, within 0 to 5 minutes after turning off the glow
plug.
The object of the present invention is to improve upon the generic
reciprocating piston fuel
pumps and the generic methods so that the problems described above are avoided
and pulsation-
free pumping of fuel is possible even at temperatures below -20 C, for
example.
This object is achieved through the features of the independent claims.
Advantageous embodiments and refinements of the invention are derived from the
dependent
claims.
The inventive reciprocating piston fuel pump is based on the generic state of
the art in that means
are provided for heating the elastomer. Heating of the elastomer by Ox C until
reaching the full-
load point corresponds to a direct expansion/reduction of the effective
operating range of the
damping element and thus in particular the characteristics map of the burner
of the automotive
heater by the same number Ox C into the negative temperature range. Due to
this inventive
approach, operation of an automotive heater with Arctic diesel at -30 C, for
example, is possible.
Due to the heated elastomer, which is therefore softer, the pulsation
intensity in the fuel system is
lower, so that the burner of an automotive heater can be operated under more
stable conditions
and thus with a more uniform and quieter combustion noise at moderately low
temperatures of
more than -20 C, for example (pulsations generate a "rough" combustion noise).
In conjunction
with automotive heaters, for example, the tendency to flame separation when
the temperature
falls below a certain limit temperature of -25 C, for example, is shifted
toward lower
temperatures due to the lower pulsations. At "higher" temperatures of 0 C of -
20 C, for example,
a reduction in CO emissions can be achieved with automotive heaters using both
Arctic diesel
and winter diesel due to the lower pulsations.
1 TN: The source consistently uses "Artikdiesel" when the tenn is properly
"Arctic diesel" - as done here without comment
below.
CA 02603067 2007-09-28
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The inventive reciprocating piston fuel pump has been improved upon
advantageously due to the
fact that the means for heating the elastomer comprise an electric heater. The
electric heater may
be operated both directly and indirectly. For example, a heating wire
introduced into the
elastomer material may be provided, such as that known for heating windshields
of vehicles as
well as for ski equipment and other equipment. Before the start of the actual
pumping of fuel, the
heating wire preferably receives an electric current so that the limit
temperature for the required
minimum elasticity is exceeded at the start of fuel pumping. The actual
heating, however, may
also include heating elements, e.g., PTC heating elements, which are provided
for heating liquid
fuel inside the reciprocating piston fuel pump. One or more such heating
elements may be
connected in parallel with the winding of the electromagnet, for example.
Separate triggering is
of course also possible. For example, PTC heating elements have a very high
resistance-
temperature coefficient. Therefore, in a cold start, the small amount of fuel
in the pump is rapidly
heated to a maximum temperature of 50 C, for example. At such a temperature
level, the
resistance of the heating conductor is so great that no mentionable heating
output is delivered.
The heated fuel then heats up the elastomer and consequently increases its
elasticity.
Additionally or alternatively, it is also possible for corresponding heating
elements to be
provided in proximity to the elastomer in order to heat it.
In addition, with the inventive reciprocating piston fuel pump, it is possible
for the means for
heating the elastomer to include a winding of the electromagnetic drive of the
reciprocating
piston fuel pump. The windings and/or magnetic coils of known reciprocating
piston fuel pumps
consume up to eight watts of power, for example, at low temperatures. This
power is converted
primarily to heat, and the heat can advantageously be utilized to heat the
elastomer.
In this context, an advantageous embodiment of the inventive reciprocating
piston fuel pump
provides for a material having a low thermal conductivity to be provided in an
area between the
elastomer and the environment. In principle, any thermal insulation material
with which those
skilled in the art are familiar may be used as the material having a low
thermal conductivity, e.g.,
foamed plastic and/or expanded metals. Due to such thermal insulation with
respect to the
environment, exhaust heat from the reciprocating piston fuel pump can
advantageously be
utilized to heat the elastomer. It is preferable here that not the entire
reciprocating piston fuel
pump but instead only the area of the damping element is insulated to avoid
overheating other
components of the reciprocating piston fuel pump.
Additionally or alternatively, with the inventive reciprocating piston fuel
pump, it is possible for
a material having a high thermal conductivity to be provided in an area
between the winding and
the elastomer. Metals in particular, e.g., aluminum, may be considered as the
material having a
high thermal conductivity. It is possible here for metal ribs or metal housing
components in
contact with the damping element to form one or more heat bridges.
CA 02603067 2007-09-28
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The inventive method is based on the generic state of the art in that the
elastomer is heated even
before the burner is ignited. The time horizon of the starting phase of the
automotive heater with
glow plug support may amount to 2 minutes, for example. This period of time is
minimally
usable to achieve heating of the elastomer and in many cases is sufficient to
achieve heating of
the metering pump and then the elastomer due to the uptake of power by the
heating elements
which are provided. If the waste heat of the reciprocating piston fuel pump is
used to heat the
elastomer, overheating of the reciprocating piston fuel pump at higher
temperatures is avoided
because the power uptake is lower at higher temperatures.
In conjunction with the inventive method it is also possible in an
advantageous manner for the
elastomer to be heated by an electric heating device. The electric heating
device may comprise in
particular the components which have already been explained in conjunction
with the electric
heating device for the inventive reciprocating piston fuel pump. Reference is
made to the
respective discussion in order to avoid repetition here.
The same thing is also logically applicable to the case when in the inventive
method the
elastomer is heated by a winding of an electromagnetic drive of the
reciprocating piston fuel
pump.
Preferred embodiments of the invention are described in greater detail below
as an example on
the basis of drawings.
Figure 1 shows a schematic sectional view of a known reciprocating piston fuel
pump,
which was already explained in the introduction;
Figure 2 shows a schematic block diagram illustrating a vehicle heater
comprising the
inventive reciprocating piston fuel pump;
Figure 3 shows a schematic sectional view of a first embodiment of an
inventive
reciprocating piston fuel pump;
Figure 4 shows a schematic sectional view of a second embodiment of an
inventive
reciprocating piston fuel pump;
Figure 5 shows a schematic sectional view of a third embodiment of an
inventive
reciprocating piston fuel pump;
Figure 6 shows a schematic sectional view of a first embodiment of a fuel
valve which may
be part of the automotive heater from Figure 2;
Figure 7 shows a schematic sectional view of a second embodiment of a fuel
valve which
may be part of the automotive heater from Figure 2;
CA 02603067 2007-09-28
Figure 8 shows a schematic sectional view of a third embodiment of a fuel
valve which
may be part of the automotive heater from Figure 2 and
Figure 9 shows a schematic sectional view of a fourth embodiment of a fuel
valve which
may be part of the automotive heater from Figure 2.
In the drawings the same or similar reference numerals are used to refer to
the same or similar
components which are explained only once in some cases to avoid repetition.
Figure 2 shows a schematic block diagram illustrating a vehicle heater
comprising the inventive
reciprocating piston fuel pump. The automotive heater illustrated here may be
an additional
heater or an auxiliary heater, for example. The automotive heater 10
illustrated here includes the
inventive reciprocating piston fuel pump 16 with the help of which liquid fuel
can be pumped
from a fuel tank 12 to a burner/heat exchanger unit 14. Depending on whether
it is air heating or
water heating, the burner/heat exchanger unit 14 is connected to other air
and/or water lines (not
shown), as those skilled in the art will be well aware. The burner/heat
exchanger unit 14 also
includes a fuel valve 52 and/or 84 with which the fuel supply may be shut down
entirely or
partially. This fuel valve 52 and/or 84 need not necessarily be integrated
into the burner/heat
exchanger unit 14 but instead may also be arranged between the reciprocating
piston fuel pump
16 and the burner/heat exchanger 14.
The reciprocating piston fuel pump 16 illustrated in Figure 3 is intended for
pumping liquid fuel
in the direction represented by the arrows, namely from a fuel inlet 18 to a
fuel outlet 20. As
soon as a suitable voltage is applied to an electric terminal 42, electricity
flows through a
winding 22 so that movement of a reciprocating piston 24 is
electromagnetically induced. First
liquid fuel in a pump chamber 30 is ejected through a nonreturn valve 28
against the hydraulic
resistance of the output line. Thereafter, the electric current through the
winding 22 is
terminated. A restoring spring 26 forces the reciprocating piston 24 toward
the left into its resting
position. In doing so, liquid fuel is drawn in through an intake valve 32 and
the pump chamber
30, thereby filling the pump chamber. With this pump delivery principle, it is
also possible to
convey even fuels having a very low viscosity but to do so with precision
volumetrically, as
mentioned in the introduction, so that the delivery rate can be controlled
accurately via the
frequency of the triggering voltage pulses.
To at least partially suppress the pulsations that occur during operation of
the reciprocating
piston fuel pump, the damping element 34 mentioned in the introduction is
provided, comprising
a bellows-like elastomer 36. When liquid fuel passes through a borehole 40 and
comes in contact
with the elastomer 36, the elastomer 36 expands into a neighboring chamber 38
which is
provided in a damper housing formed by a molded plastic part 44. The
prerequisite for this is a
certain backpressure in the fuel system which ensures that the elastomer 36
will be "secured" in
CA 02603067 2007-09-28
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place. To this extent the reciprocating piston fuel pump shown in Figure 3
corresponds to the
known reciprocating piston fuel pump illustrated on the basis of Figure 1.
However, the embodiment of the inventive reciprocating piston fuel pump 16
shown in Figure 3
has an electric heater 16 to heat the elastomer 36. In the case presented
here, the electric heater
46 includes a plurality of PTC heating elements 46a arranged near the
elastomer 36, at least one
heating wire 46b which is integrated into the elastomer 36, and two PTC
heating elements 46c
arranged in the vicinity of pump chamber 30. It is clear that not all the
heating elements 46a, 46b
and 46c presented here need necessarily be present but instead it may
optionally be sufficient to
provide only one type of heating element 46a, 46b or 46c to heat the elastomer
36 suitably. To
optimize the effect of the PTC heating element 46a and 46c, it is advantageous
if a material
having a high thermal conductivity, e.g., a metal is provided between the area
to be heated, i.e.,
the elastomer 36 and/or the pump chamber 30 and the respective PTC heating
element. The most
direct heating of the elastomer 36 is achieved by the heating wire(s) 46b.
Heating of the fuel by
the PTC heating element 46c is advantageous not only for heating of the
elastomer 36 but also
preheating of the fuel allows better combustion. The PTC heating elements 46a
represent a
compromise inasmuch as they heat the material that comes in contact with the
elastomer 36 as
well as the material that comes in contact with the liquid fuel. Some or all
of the heating
elements 46a, 46b, 46c presented here may be connected to the winding 22 in
parallel or
triggered separately. Separate triggering is more complex but it allows
preheating to be
performed independently of pump operation.
The embodiment of the inventive reciprocating piston fuel pump 16 shown in
Figure 4 differs
from the embodiment according to Figure 3 in that no heating elements are
provided there but
instead the elastomer 36 is heated by the waste heat of the reciprocating
piston fuel pump 16. To
permit this heating and/or to optimize it, the area of the damping element
36is surrounded by a
materia150 having a low thermal conductivity, i.e., is surrounded by thermal
insulation.
Although this is not shown here, the material 50 having a low thermal
conductivity may
optionally have a layered structure. In any case it is preferable for the
reciprocating piston fuel
pump 16 not to be surrounded entirely with insulation material because this
could result in
overheating of the reciprocating piston fuel pump in particular at higher
outside temperatures.
The embodiment of the reciprocating piston fuel pump 16 shown in Figure 5
differs from the
embodiment according to Figure 3 in that no heating elements are provided
there but instead the
heating of the elastomer 36 is accomplished by the heat generated in the
winding 22. To this end,
a materia148 having a high thermal conductivity is provided between the
winding 22 and the
elastomer 36. The materia148 having a high thermal conductivity may be a metal
such as
aluminum in particular, in which case the metal may be shaped in the form of
ribs, for example,
to create a suitable heat bridge. Although this is not shown here, it may also
be advantageous to
place the heat bridge in areas that come in contact with the liquid fuel so as
to heat the fuel.
CA 02603067 2007-09-28
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However, in the case illustrated here, the materia148 having a high thermal
conductivity is
integrated in the form of metal ribs into the molded plastic part 44 and heats
only the elastomer
36.
It will be clear to those skilled in the art that the embodiments of the
inventive reciprocating
piston fuel pump explained with reference to Figures 3 through 5 may be
combined with one
another in any desired manner and all of these possible combinations are
herewith disclosed.
It will be also be clear that the inventive method for starting and operating
an automotive heater
that is operated with liquid fuel, e.g., the automotive heater 10 shown in
Figure 2, may be
performed with all the embodiments of the inventive reciprocating piston fuel
pump described
above by heating the elastomer 36 already before the ignition of the burner 14
(Figure 2). If heat
generated via the winding 22 is used for heating the elastomer 36, it may be
appropriate to apply
only a comparatively weak electric current to the winding 22 prior to ignition
of the burner,
namely so that a quantity of heat sufficient to heat the elastomer 36 is
generated without starting
the movement of reciprocating piston 24.
Figure 6 shows a schematic sectional view of a first embodiment of a fuel
valve 52 which may
be part of the automotive heater 10 from Figure 2. The fuel valve 52 is an
electromagnetically
operated coaxial valve which has a fuel inlet 54 and a fuel outlet 56. As soon
as a suitable
voltage is applied to an electric termina174, electricity flows through a
winding 58 so that a
valve piston 60 is set in motion to the right based on the diagram in Figure 6
so that the fuel
valve 52 is opened and fuel can flow from the fuel inlet 54 to the fuel outlet
56. In the currentless
state of the winding 58, a restoring spring 62 presses the valve piston 60 to
the left based on a
diagram in Figure 6 so that the valve piston 60 cooperates with a valve seat
64 to close the fuel
valve 52.
Although in many cases it is sufficient to equip the reciprocating piston fuel
pump itself with a
damping element, the fuel valve 52 shown in Figure 6 has an additional damping
element 66
which also contributes toward suppressing pulsations in the fuel system. The
damping element
66 also includes a bellows-like elastomer 68 in this case. When liquid fuel
passes through a
borehole 72 and comes in contact with the elastomer 68, the elastomer 68
expands into a
neighboring chamber 70 which is provided in a damper housing formed by a
molded plastic part
76. The prerequisite for this is a certain backpressure in the fuel system
which ensures that the
elastomer 68 will be "secured" in place.
To prevent the elastomer 68 which is made of the material FKN2, for example,
from undergoing
a glass transition even at the very low temperatures of less than -23 C, for
example, the damping
element 66 is provided with an electric heater 78. In the case presented here,
the electric heater
2 TN: abbreviation of unknown expansion ("F" likely stands for "Faser" (fiber)
and "K" for "Kunststoff" (plastic)).
CA 02603067 2007-09-28
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78 includes a plurality of PTC heating elements 78a which are arranged near
the elastomer 68
and at least one heating wire 78b which is integrated into the elastomer 68.
It is clear that not all
the heating elements 78a and 78b illustrated here need be present but instead
optionally only one
type of heating element 78a or 78b may be sufficient to suitably heat the
elastomer 68. To
optimize the effect of the PTC heating elements 78a, it is advantageous if a
material having a
high thermal conductivity, e.g., a metal is provided between the area to be
heated, i.e., the
elastomer 36 and the respective PTC heating element. Direct heating of the
elastomer 68 is
achieved by the heating wires 78b. The PTC heating elements 78a heat up both
the material that
comes in contact with the elastomer 68 and the material that comes in contact
with the liquid
fuel. Preheating of fuel serves to provide indirect heating of the elastomer
68 and leads to better
combustion. Other heating elements (not shown) may optionally also be
provided, serving
exclusively to heat the liquid fuel. Some or all of the heating elements 78a
and 78b shown here
may be connected in parallel to the winding 58 or may be triggered separately.
Separate
triggering is more complex but it allows reheating independently of the valve
setting.
The fuel valve 52 shown in Figure 7 differs from the embodiment according to
Figure 6 in that
no heating elements are provided there but instead the elastomer 68 is heated
by the waste heat
from the fuel valve 52. To permit this heating and/or to optimize it, the area
of the damping
element 66 is surrounded by a material 82 having a low thermal conductivity,
i.e., thermal
insulation. Although this is not shown here, the material 82 having the low
thermal conductivity
may optionally have a layered design. It is clear that when the fuel valve 52
is open, sufficient
waste heat is generated due to the corresponding electric current applied to
the winding 58 to
heat the elastomer 68. However, the fuel valve 52d may also be designed in
such a way that a
low level of electric current through the winding 58 which is not sufficient
to open the fuel valve
52d is sufficient to heat the elastomer 68.
The embodiment of the fuel valve 52 shown in Figure 8 differs from the
embodiment according
to Figure 6 in that no heating elements are provided there but instead the
heating of the elastomer
is accomplished by the heat generated in the winding 58 and by the heat
carried over at least one
heat bridge to the elastomer 68. To this end a material 80 having a high
thermal conductivity is
provided between the winding 58 and the elastomer 68. The material 80 having a
high thermal
conductivity may be in particular a metal such as aluminum, in which case the
shaping may be in
the form of ribs, for example, to create a suitable heat bridge. Although this
is not shown here, it
may also be advantageous to place the heat bridge in areas that come in
contact with the liquid
fuel in order to heat the fuel. In the case depicted here, the material 80
having a high thermal
conductivity is integrated in the form of metal ribs into the molded plastic
part 76 and heats at
least primarily only the elastomer 68.
CA 02603067 2007-09-28
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It will be cleared to those skilled in the art that the embodiment of the fuel
valve 52 explained
with reference to Figures 6 through 8 may also be combined with one another in
any manner and
all of these possible combinations are also disclosed here.
Figure 9 shows a schematic sectional view of another embodiment of a fuel
valve 84 which may
be part of the automotive heater 10 from Figure 2 instead of the fuel valve 52
explained above.
In the case of the fuel valve 84, it is an electromagnetically operated
coaxial valve that has a fuel
inlet 86 and a fuel outlet 88. As soon as a suitable voltage is applied to an
electric termina198,
electricity flows through a winding 90, so that a valve piston 92 is set in
motion toward the right
based on the diagram in Figure 9 so that the fuel valve 84 opens and fuel can
flow from the fuel
inlet 86 to the fuel outlet 88. In the currentless state of the winding 90 a
restoring spring 94
presses the valve piston 92 to the left based on the diagram in Figure 9 so
that the valve piston 92
cooperates with a valve seat 96 to close the fuel valve 84.
The fuel valve 84 shown in Figure 9 is designed to preheat fuel. For
preheating the fuel, heat
generated by the winding 90 is used, with a material 88 having a high thermal
conductivity being
provided between the winding 90 and the area with which the fuel comes in
contact. The
material 88 having a high thermal conductivity may be in particular a metal
such as aluminum.
Heating of the fuel is optimized by providing a material 100 which has a low
thermal
conductivity, i.e., a thermal insulator, in the outside area of the fuel valve
84. The material 100
having a low thermal conductivity may in principle be formed by any insulation
material with
which those skilled in the art are familiar, e.g., expanded metal and/or
plastic foam. Although
this is not shown here, the material 100 having a low thermal conductivity may
also have a
layered structure. It is clear that when the fuel valve 84 is open, sufficient
waste heat is generated
due to the corresponding electricity flowing through the winding 90 to preheat
the fuel.
However, the fuel valve 84 may also be designed so that, even if a lower
current flow through
the winding 90 is not sufficient to open the fuel valve 84, it is still
sufficient to preheat the fuel.
Due to the use of the fuel valve 84 shown in Figure 9, it may optionally be
possible to omit a
heating cartridge which is generally used. Such heating cartridges often have
a high power
consumption of 40 watts, for example, and therefore do not receive electric
power during the
entire burning operation of the automotive heater but instead only during the
startup phase. In
contrast with that, the fuel may be preheated during the entire burner
operation with fuel valve
84, and fuel valve 84 may have an increased electric power consumption, if
necessary. The fuel
heating results in an increase in the enthalpy of the fuel and a reduction in
viscosity, which has a
positive effect on combustion operation.
The features of the present invention disclosed in the preceding description
and in the drawings
and claims may be essential to the embodiment of the invention either
individually or in any
combination.
CA 02603067 2007-09-28
List of reference numerals:
10 Automotive heater
12 Fuel tank
14 Burner/heat exchanger unit
16 Reciprocating piston fuel pump
18 Fuel inlet
Fuel outlet
22 Winding
24 Reciprocating piston
26 Restoring spring
28 Nonreturn valve
Pump chamber
32 Intake valve
34 Damping element
36 Elastomer
38 Chamber
Bore
42 Electric terminal
44 Molded plastic part
46 Heating element
48 Material having a high thermal conductivity/metal rib
Material having a low thermal conductivity/insulator
52 Fuel valve
54 Fuel inlet
56 Fuel outlet
58 Winding
Valve piston
62 Restoring spring
64 Valve seat
66 Damping element
68 Elastomer
Chamber
72 Bore
74 Electric terminal
76 Molded plastic part
78 Heating element
Material having a high thermal conductivity/metal rib
82 Material having a low thermal conductivity/insulator
CA 02603067 2007-09-28
ll
84 Fuel valve
86 Fuel inlet
88 Fuel outlet
90 Winding
92 Valve piston
94 Restoring spring
96 Valve seat
98 Electric terminal
100 Molded plastic part/insulator
