State of the art
The invention relates to a device for injecting fuel
in a combustion chamber of an internal combustion engine according to the preamble of
Fuel injectors are electrically controlled. Includes
the fuel injector generally a control valve, which as
Solenoid valve is formed or operated with a piezoelectric actuator.
In the case of fuel injectors actuated by a piezo actuator,
is distinguished between inverse and non-inverse operated injectors.
With inversely operated injectors fuel is in the combustion chamber
injected as long as the piezoelectric actuator is not energized. To the
End injection process, the piezoelectric actuator is energized again
and expands with it. For non-inversely controlled fuel injectors
the injection process is started when the actuator is energized.
In non-inversely controlled fuel injectors, with a
Piezoelectric actuator operated, the control valve is in general
designed so that it opens,
when the piezoelectric actuator is energized and expands. This works
the piezoelectric actuator either directly or hydraulically translated to the valve member of the
Control valve. The hydraulic transmission is necessary to
to achieve an additional stroke for short-built actuators,
to open the control valve far enough
to be able to.
Such a directly controlled fuel injector with piezoelectric actuator
is known for example from DE-A 103 37 875.
Disclosure of the invention
a device according to the invention for
Injecting fuel into a combustion chamber of an internal combustion engine
becomes a control valve for driving an injection valve member
operated with an actuator that expands when power is supplied. at
energized actuator, the control valve is opened and not energized
Actuator closed. The actuator is from an upper housing part
enclosed, which opposite
the injector housing axially
is displaceable and that with a valve member of the control valve
connected is. During operation, the injection process starts
the piezoelectric actuator is energized and thereby expands. This will be the
upper housing part,
which in the injector axially
movable is shifted upwards. The with the upper housing part
connected valve member opens
the control valve lifted by a closing element from its seat
becomes. This makes it possible to have a
Fuel injector, usually
operated with a solenoid valve to operate with a piezoelectric actuator,
by the magnet assembly through the piezo actuator with the upper housing part
is replaced without further structural changes
are required at the injector. In a preferred embodiment
is the actuator that expands when power is a piezoelectric actuator.
In order to
during operation, no moving parts protrude from the actuator,
is the upper housing part
in a preferred embodiment
enclosed by a cover connected to the injector housing
is. As a cover is a plastic or metal cap, the
connected to the injector. The connection of the cover with
The injector can be done, for example, that on the cover
a beaded edge
is provided, which is screwed with a clamping nut on the injector
becomes. But it is also possible
the cover insoluble
with the injector housing
for example by welding
the actuator and the closing element connected to the valve member
is preferably accommodated a membrane through which the actuator against
Fuel is sealed. The membrane is designed in this way
that through this the opening and closing movement
the valve member is not hindered. To effectively counteract the actor
To seal fuel, the membrane is preferably both with
as well as liquid-tight with the valve member
connected. In one embodiment
the membrane is between an upper section and a lower section
Recorded portion of the valve member.
upper housing part
is preferably mounted with bolts on the valve member. Bolts
are guided by a plate,
the one with the injector housing
is firmly connected and on which the actuator is supported. By
the bolts that hold the upper housing part with the valve member
is connected, the valve member is moved in the direction of the actuator,
as soon as it expands. The connected to the valve member
is lifted from his seat and gives a connection of one
Control room to a fuel return
the opening movements
to support the control valve,
the membrane can be made of a resilient material.
and closing movement
the valve member is then supported by the spring force of the membrane. To the
Adjustment of the stroke is preferably between a closing element holder
provided on the valve member a shim. The stroke is set
through the thickness of the shim.
In one embodiment, the actuator with a top bracket is positively secured to the upper housing part. In this case, the movement of the actuator is transferred directly to the upper housing part In an alternative embodiment, the upper holder of the actuator is not connected to the upper housing part and between the upper holder and the upper housing part, a gap is formed. This gap forms a forward stroke, by which an optionally occurring lifting error can be compensated. In order to achieve a return movement of the closing element into its seat when the upper holder is not connected to the upper housing part, in this case between the upper housing part and the cover a spring element aufgenommnen, which is supported on the one hand on the upper housing part and on the other hand on the cover , Preferably, the spring element surrounds the upper housing part and is supported on a rib on the upper housing part. The spring element is for example designed as a helical spring compression spring. When the spring element is located between the upper housing part and the cover and acts on the upper end face of the upper housing part, for example, a plate spring or a leaf spring can be used. Advantage of the use of a plate spring or a leaf spring is that the space between the upper housing part and the cover can be kept small. This is also the case when the spring element encloses the upper housing part.
In order to
the piezoelectric actuator and the upper housing part by heating or
do not expand differently, is the upper housing part
preferably made of Invar. Advantage of Invar is that this
has a coefficient of thermal expansion, which is approximately the one
Brief description of the drawings
The invention is illustrated in the drawings and in the following
1 an inventively designed control valve of a fuel injector,
2 a section of an upper housing part and a cover in a second embodiment.
Embodiments of the invention
1 shows a control valve of an inventively designed fuel injector in a first embodiment.
An inventively designed device for injecting fuel into a combustion chamber of an internal combustion engine comprises a control valve 1 , which by an actor 2 is actuated, which expands when power is supplied. In the embodiment illustrated here, the actuator 2 a piezoelectric actuator. The actor 2 is between an upper bracket 3 and a lower bracket 4 clamped. The required preload of the actuator 2 is by a spring element 5 achieved. The spring element 5 is in the embodiment shown here designed as a tension spring Bourdon tube, which is the actuator 2 wraps around and with the top bracket 3 and the lower bracket 4 connected is. The upper bracket 3 is in the in 1 embodiment shown positively with an upper housing part 6 connected. The positive connection takes place in the embodiment shown here by welding. In addition to the positive connection by welding, it would also be conceivable that the upper holder by gluing or soldering or by a non-positive connection with the upper housing part 6 is connected. Suitable frictional connections are, for example, press-fitting or screwing.
The lower bracket 4 is with a plate 7 connected, the dimensionally stable with the injector housing 8th connected is. In the embodiment shown here, the lower bracket 4 with the plate 7 attached by a positive connection. In the plate 7 are breakthroughs 9 formed by the bolts 10 are guided, with the upper housing part 6 are connected. Bolts 10 are with an upper section 11 a valve member 12 connected.
To the actor 2 Instead of using a magnet assembly in a fuel injector of the same type, is the upper section 11 of the valve member 12 executed in the form of a valve pin an anchor group of a magnet assembly. The design of the upper section 11 in the form of an armature of a solenoid valve assembly also makes it possible to easily the bolt 10 connected to the upper housing part 6 connected to the upper section 11 of the valve member 12 connect to.
Instead of the bolts 10 can the upper section 11 of the valve member 12 also via threaded rods or pins with the upper housing part 6 get connected.
To the actor 2 To seal against the environment and to avoid that moving parts protrude from the fuel injector, the upper housing part 6 from a cover 13 enclosed. The cover 13 is in the embodiment shown here with a bead 14 Mistake. With a clamping nut 15 above the crimp rim 14 grasps is the cover 13 with the injector housing 8th connected.
A seal of the actuator 2 opposite to the fuel contained in the injector via a membrane 16 , In the embodiment shown here, the membrane 16 liquid-tight with the plate 7 connected. The connection is made for example via a weld. In the embodiment shown here, the membrane 16 under the upper portion of the valve member 12 carried out. The membrane 16 but can also be provided with an opening which the valve member 12 encloses. In the area of the opening becomes the membrane 16 with the valve member 12 connected liquid-tight. The connection is then preferably via a weld. To the membrane 16 closes a lower section 17 of the valve member 12 at. The lower section 17 includes a dial 18 , a closing element holder 19 and a closing element 20 , The closing element 20 is here spherical. Instead of spherical, the closing element 20 but also be formed, for example, conical or in the form of a flat seat. With closed control valve 1 is the closing element 20 in a seat 21 , Through the control valve 1 is a drainage channel 22 with a drain throttle received therein 23 lockable or releasable. The drainage channel 22 connects a control room 24 with a fuel return 25 , The control room 24 is on one side by an upper end face 26 a control piston 27 limited. Via an inlet throttle 28 is the control room 24 with a fuel feed 29 connected. The fuel feed 29 is connected, for example, to a high-pressure accumulator, not shown here, from which fuel under system pressure flows into the fuel injector. From fuel intake 29 branches a high-pressure channel 30 from which is connected to a nozzle chamber. From the nozzle chamber, when the injection valve member is open, the fuel flows into the combustion chamber of the internal combustion engine.
In order to mount the fuel injector are in the embodiment shown here, the drainage channel 22 with the outlet throttle 23 , the inlet throttle 28 , the control room 24 and a guide 31 for the control piston 27 in a valve piece 32 educated. Furthermore, the seat is 21 of the control valve 1 formed in the valve piece.
The activation of the actuator 2 via an electrical contact 33 , The electrical contact 33 is here through the plate 7 guided so that it is stationary and not with the upper housing part 6 is moved.
To start the injection process, the actuator becomes 2 energized. As a result, the actuator expands 2 out. Because the lower bracket 4 with the plate 7 stationary in the injector housing 8th is recorded, the actor acts 2 on the upper bracket 3 and thus on the upper housing part 6 , This is raised. This also raises the upper section 11 of the valve member 12 , with the upper housing part 6 is connected to. This also raises the closing element 20 out of his seat and gives the connection from the drainage channel 22 in the fuel return 25 free. Fuel flows out of the control room 24 in the fuel return 25 , This reduces the pressure in the control room 24 from. The compressive force acting on the upper face 26 of the control piston 27 acts, thereby becomes smaller. The control piston is no longer balanced and moves into the control room 24 hineein. As a result, the volume of a control chamber, not shown here, increases from the end of the control piston 24 is limited, that of the upper end face 26 opposite. The second control chamber is further limited by an injection valve member. Due to the decreasing pressure, a lower pressure force acts on the injection valve member, so that this is lifted from its seat. The injection process begins.
To stop the injection process, the current supply of the actuator 2 canceled. The actor 2 contracts. As a result, the upper housing part 6 , which with the upper bracket 3 connected, moved back down. This also moves the upper section 11 of the valve member 12 in the direction of the seat 21 , The one with the upper section 11 connected lower section 17 of the valve member 12 also moves in the direction of the seat 21 , The closing element 20 will be in his seat 21 posed. The connection of the drainage channel 22 with the fuel return 25 is closed. About the inlet throttle 28 Under system pressure, fuel flows into the control room 24 , In the control room 24 Thus system pressure builds up again. As a result, the pressure force on the upper end surface decreases 26 of the control piston 27 works, too. The control piston 27 is moved in the direction of the second control room. As a result, the volume decreases in the second control chamber, whereby the pressure in this increases. Due to the increasing pressure, the pressure force on the injection valve member increases. This is put in his seat. As a result, the connection is closed from the nozzle chamber to the injection opening. It can no longer flow fuel from the nozzle chamber via the injection port into the combustion chamber.
2 shows a section of a inventively designed fuel injector in a second embodiment.
At the in 2 illustrated embodiment, the upper bracket 3 of the actor 2 not with the upper housing part 6 connected. So that the upper housing part 6 through the actor 2 and the upper bracket 3 Can be lifted is on the upper bracket 3 one shoulder 40 educated. The shoulder 40 acts with a second shoulder 41 at the upper housing part 6 together. Once the actor 2 energized and expands, raises the upper housing part 3 in the direction of the upper housing part 6 , As soon as the shoulder 40 the upper bracket 3 with the second shoulder 41 of the upper housing part 6 is in contact, the upper housing part 6 raised. With not energized actuator 2 is between the shoulder 40 the upper bracket 3 and the second shoulder 41 of the upper housing part 6 A gap 42 educated. The gap 42 serves as a forward stroke, with which any occurring Hubfehler can be compensated. This is the case, for example, when the piezoelectric actuator, if it is not energized, contracts further if the upper housing part moves in the direction of the control valve 1 lets move.
Also in the in 2 illustrated embodiment, the upper housing part 6 from a cover 13 enclosed. The cover 13 is stationary with the injector housing 8th connected. To after completion of the injection process, when the energization is canceled and the actuator 2 The upper housing part contracts 6 move back down to allow the control valve 1 is closed, encloses a spring element in the embodiment shown here 43 the upper housing part 6 , The spring element 43 is in the embodiment shown here designed as a spiral spring compression spring. So that the upper housing part 6 with not energized actuator 2 in the direction of the control valve 1 is moved, the spring element is supported 43 with one side against the cover 13 and with the other side against an extension 44 from the upper housing part. As soon as the injection begins, the actuator 2 is energized and expands and thereby the upper housing part 6 raises, the spring element 43 curious; excited. When the energization of the actuator 2 is canceled to end the injection process, the spring force of the spring element acts 43 on the extension 44 of the movable upper housing part 6 and push this down. This will be the control valve 1 closed by the closing element 20 in his seat 21 is provided. In order to achieve a faultless function of the fuel injector, it is absolutely necessary that the cover 13 in the in 2 illustrated embodiment is fixedly connected to the injector, so that they can not move. To provide a sufficiently large spring force on the extension 44 on the upper housing part 6 acts, is the spring element 43 even when not energized and thus not extended actuator 2 already preloaded. The selected preload depends on the force applied to the extension 44 on the upper housing part 6 should work.