[0001] The invention relates to a method for adjusting an injection valve.
[0002] Injection valves are in wide spread use, in particular for internal combustion engines
where they may be arranged in order to dose the fluid into an intake manifold of the
internal combustion engine or directly into the combustion chamber of a cylinder of
the internal combustion engine.
[0003] Injection valves for an internal combustion engine comprise actuator units. In order
to inject fuel, the actuator unit is energized so that a fluid flow through the fluid
outlet portion of the injection valve is enabled.
[0004] In order to enhance the combustion process in view of the creation of unwanted emissions,
the respective injection valve may be suited to dose fluids under very high pressures.
The pressures may be in case of a gasoline engine, for example, in the range of up
to 200 bar and in the case of a diesel engine in the range of up to 2,000 bar. The
injection of fluids under such high pressures has to be carried out very precisely.
[0005] Injection valves are calibrated at the end of the manufacturing process to obtain
a defined and precise mass flow of the fluid through a fluid outlet portion of the
injection valve.
[0006] The object of the invention is to provide a method for adjusting an injection valve
which is to be carried out simply and which facilitates a reliable and precise function
of the injection valve.
[0007] This object is achieved by the features of the independent claim. Advantageous embodiments
of the invention are given in the sub-claims.
[0008] The invention is distinguished by a method for adjusting an injection valve, the
injection valve comprising a housing including a central longitudinal axis, the housing
comprising a cavity with a fluid outlet portion, a valve needle axially moveable in
the cavity, the valve needle preventing a fluid flow through the fluid outlet portion
in a closing position and releasing the fluid flow for the fluid outlet portion in
further positions, an actuator unit being coupled to the valve needle and enabling
the axial movement of the valve needle relative to the valve body upon actuation of
the actuator unit, and an adjusting arrangement. The adjusting arrangement comprises
a spring retaining element being coupable to the housing, a thermal compensation unit
being coupable to the spring retaining element and an adjusting spring arranged between
the thermal compensation unit and the spring retaining element and being enabled to
exert an axial preload force on the actuator unit. The method comprises the following
steps: providing the injection valve and coupling of the injection valve with a fluid
supply for the adjustment purpose, actuating of the actuator unit to release the fluid
flow through the fluid outlet portion, moving the spring retaining element relative
to the housing until a predetermined fluid flow through the fluid outlet portion is
obtained, carrying out a fixed coupling of the spring retaining element with the housing,
and carrying out a fixed coupling of the thermal compensation unit with the spring
retaining element.
[0009] The fixed coupling of the thermal compensation unit with the spring retaining element
and the fixed coupling of the spring retaining element with the housing is realized
at the end of the adjusting process.
[0010] This has the advantage that it is possible to obtain a precise fixing position of
the thermal compensation unit at the end of the adjusting process which allows a secure
operation of the thermal compensation unit due to changes of the temperature in the
ambience of the injection valve.
[0011] In an advantageous embodiment the coupling of the spring retaining element with the
housing is carried out by crimping. In a further advantageous embodiment of the invention
the coupling of the thermal compensation unit with the spring retaining element is
carried out by crimping. Crimping allows a fast, secure and precise fixed coupling
of the participating elements, in particular the spring retaining element and the
housing respectively the thermal compensation unit and the spring retaining element.
[0012] Exemplary embodiments of the invention are explained in the following with the aid
of schematic drawings. These are as follows:
- Figure 1,
- an injection valve in a longitudinal section view,
- Figure 2,
- an adjusting arrangement for the injection valve according to figure 1 in a longitudinal
section view, and
- Figure 3,
- an enlarged view of the adjusting arrangement for the injection valve according to
figure 2 in a longitudinal section view.
[0013] Elements of the same design and function that appear in different illustrations are
identified by the same reference characters.
[0014] An injection valve 10 (figure 1) that is used as fuel injection valve for an internal
combustion engine, comprises a housing 12, an adjusting arrangement 14 and an actuator
unit 16.
[0015] The housing 12 has a tubular shape. The actuator unit 16 is inserted into the housing
12 and comprises a piezo actuator, which changes its axial length depending on a control
signal applied to it. The actuator unit 16 may, however, also comprise another type
of actuator, which is known to a person skilled in the art for that purpose. Such
an actuator may be, for example, a solenoid.
[0016] The injection valve 10 comprises a valve body 20 with a central longitudinal axis
A and a cavity 24 which is axially led through the valve body 20. On one of the free
ends of the cavity 24, a fluid outlet portion 28 is formed, which is closed or open
depending on the axial position of a valve needle 22. The injection valve 10 further
has a fluid inlet portion 26 which is arranged in the housing 12 and which is hydraulically
coupled to the cavity 24 and a not shown fuel connector. The fuel connector is designed
to be connected to high pressure fuel chamber of an internal combustion engine, the
fuel is stored under high pressure, for example, under the pressure of about 200 bar.
[0017] The valve body 20 has a valve body spring rest 32 and the valve needle 22 comprises
a valve needle spring rest 34, both spring rests 32, 34 supporting a main spring 30
arranged between the valve body 20 and the valve needle 22.
[0018] The injection valve 10 is of an outward opening type. In an alternative embodiment
the injection valve 10 may be of an inward opening type. Between the valve needle
22 and the valve body 20 a bellow 36 is arranged which is sealingly coupling the valve
body 20 with the valve needle 22. By this a fluid flow between the cavity 24 and a
chamber 38 is prevented. Furthermore, the bellow 36 is formed and arranged in a way
that the valve needle 22 is actuable by the actuator unit 16.
[0019] Figures 2 and 3 show the adjusting arrangement 14. The housing 12 has a recess 54
with an inner wall 56. In the recess 54 of the housing 12 a thermal compensation unit
40, a spring retaining element 42 and an adjusting spring 44 are arranged. The thermal
compensation unit 40 has a first section 45 which is coupled to a piston 46 of the
actuator unit 16. The spring retaining element 42 has a cylindrical spring retaining
element cavity 43 in which a cylindrical second section 48 of the thermal compensation
unit 40 is arranged.
[0020] The thermal compensation unit 40 has a thermal compensation unit spring rest 50 and
the spring retaining element 42 comprises a spring retaining element spring rest 52,
both spring rests 50, 52 supporting the adjusting spring 44 arranged between the thermal
compensation unit 40 and the spring retaining element 42.
[0021] In the following, the function of the injection valve 10 will be described:
[0022] The fuel is led from the fluid inlet portion 26 and the housing 12 towards the valve
body 20 and then towards the fluid outlet portion 28. The fluid flow from the fluid
outlet portion 28 to the chamber 38 with the actuator unit 16 is prevented by the
bellow 36.
[0023] The valve needle 22 prevents a fluid flow through the fluid outlet portion 28 in
the valve body 20 in a closing position of the valve needle 22. Outside of the closing
position of the valve needle 22 the valve needle 22 enables the fluid flow through
the fluid outlet portion 28.
[0024] In the case that the actuator unit 16 has a piezo electric actuator, the piezoelectric
actuator may change its axial length if it gets energized in an expansion duration
of some microseconds. By changing its length the actuator unit 16 may effect a force
on the valve needle 22. Due to the elasticity of the bellow 36 the valve needle 22
is able to move in axial direction out of the closing position. Outside of the closing
position of the valve needle 22 there is a gap between the valve body 20 and the valve
needle 22 at an axial end of the injection valve 10 facing away from the actuator
unit 16. The gap forms a valve nozzle 29.
[0025] The main spring 30 can force the valve needle 22 via the valve needle spring rest
34 towards the actuator unit 16. In the case that the actuator unit 16 is de-energized
the actuator unit 16 shortens its length. The main spring 30 can force the valve needle
22 to move in axial direction in its closing position. It is depending on the force
balance between the force on the valve needle 22 caused by the actuator unit 16 and
the force on the valve needle 22 caused by the main spring 30 whether the valve needle
22 is in its closing position or not.
[0026] In the following, the method for adjusting the injection valve 10 will be described
in detail:
[0027] The injection valve 10 is provided and coupled with the fluid supply in particular
a high pressure fuel chamber. The actuator unit 16 is actuated and the gap between
the valve body 20 and the valve needle 22 at the axial end of the injection valve
10 facing away from the actuator unit 16 allows to release the fluid flow through
the fluid outlet portion 28.
[0028] The spring retaining element 42 is moved in axial direction relative to the housing
until a predetermined fluid flow through the fluid outlet portion 28 is obtained.
The movement of the spring retaining element 42 relative to the housing 12 in direction
to the actuator unit 16 results in a compression of the adjusting spring 44 thereby
exerting an axial preload force on the actuator unit 16 via the first section 45 of
the thermal compensation unit 40. If the predetermined fluid flow through the fluid
outlet portion 28 is obtained the spring retaining element 42 and the housing 12 are
crimped together in first crimping directions C1 to obtain a fixed coupling between
the spring retaining element 42 and the housing 12. In a further step the thermal
compensation unit 40 and the spring retaining element 42 are crimped together in second
crimping directions C2 to obtain a fixed coupling between the thermal compensation
unit 40 and the spring retaining element 42.
[0029] By this, the housing 12, the spring retaining element 42 and the thermal compensation
unit 40 are fixedly coupled just in the end of the adjusting process. This has the
advantage that the position of the thermal compensation unit 40 is defined very precisely
as the crimping process allows a very exact definition of the positions of the parts
which are crimped together.
[0030] After carrying out the method for adjusting the injection valve 10 the fluid supply
can remain to be coupled with the injection valve 10. However, preferably the fluid
supply is disconnected from the injection valve after the method for adjusting the
injection valve 10 has been carried out.
1. Method for adjusting an injection valve (10), the injection valve (10) comprising
- a housing (12) including a central longitudinal axis (A), the housing (12) comprising
a cavity (24) with a fluid outlet portion (28),
- a valve needle (22) axially movable in the cavity (24), the valve needle (10) preventing
a fluid flow through the fluid outlet portion (44) in a closing position and releasing
the fluid flow through the fluid outlet portion (44) in further positions,
- an actuator unit (16) being coupled to the valve needle (22) and enabling the axial
movement of the valve needle (22) relative to the valve body (20) upon actuation of
the actuator unit (16), and
- an adjusting arrangement (14) comprising
- a spring retaining element (42) being coupable to the housing (12),
- a thermal compensation unit (40) being coupable to the spring retaining element
(42), and
- an adjusting spring (44) arranged between the thermal compensation unit (40) and
the spring retaining element (42) and being enabled to exert an axial preload force
on the actuator unit (16),
the method comprising the following steps:
- providing the injection valve (10) and coupling of the injection valve (10) with
a fluid supply for the adjustment purpose,
- actuating of the actuator unit (16) to release the fluid flow through the fluid
outlet portion (28),
- moving the spring retaining element (42) relative to the housing (12) until a predetermined
fluid flow through the fluid outlet portion (28) is obtained,
- carrying out a fixed coupling of the spring retaining element (42) with the housing
(12), and carrying out a fixed coupling of the thermal compensation unit (40) with
the spring retaining element (42).
2. Method in accordance with claim 1 with the coupling of the spring retaining element
(42) with the housing (12) is carried out by crimping.
3. Method in accordance with claim 1 with the coupling of the thermal compensation unit
(40) with the spring retaining element (42) is carried out by crimping.