FR2786269A1 - DEVICE FOR THE INJECTION OF A FLUID COMPRISING A VARIATION IN THE PRESSURE OF THE FLUID INJECTED - Google Patents

Abstract

In this metered injection device having a body (1), a fluid chamber (3) and a valve needle (5), the needle (5) and the body (1) are such that a variation fluid pressure causes the same variation in length of needle (5) and body (1). Use in the automotive industry.

Description

i 2786269 Device for metered injection of a fluid

  The invention relates to a device for metered injection of fluid comprising a valve needle opening outwards and the stroke of the valve being independent of the pressure of the fluid. , and a

corresponding process.

  In a metering injection device opening outwards, it is applied when introducing fluid under high pressure (for example from 100 bar to 300 bar), intense forces on surfaces subjected to pressure. of the injection device metered. These forces cause dilation of the injection device body in a metered manner and expansion of the valve needle. Usually, these expansions do not compensate each other, which changes the stroke of the valve. If the dosing device is operated with a constant fluid pressure, this pressure expansion can be compensated for and is not a problem in the case of use. But if the metered injection device operates at different pressure levels, the stroke of the valve needle changes as a function of pressure. For a very high pressure (especially greater than 200 bar), it can occur inadvertent fluid leakage and automatic opening of the injection device metered. Until now, the automatic opening of the injection device metered was prohibited by a sufficiently strong return spring. The use of increasingly high fluid pressure levels makes this way expensive and can not be used if the route

  setting of the primary drive device is only small.

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  At the time of the patent application in the Federal Republic of Germany P 19839125.0, which was not accessible to the public on the priority date of which the present application is granted, there is described a fluid injection device, in which a device metering injection valve opening outwards operates by means of a piezoelectric drive member and a piston hydraulic transmission. A valve pusher is held tightly by a return spring located in

a fluid chamber.

  The aim of the invention is to reduce the influence of fluid pressure on

  the behavior at the opening of the injection device metered.

  According to the invention, this is achieved by a metering injection device comprising a body in which is mounted a motor member, a fluid chamber that can be loaded with fluid, at least one injection orifice which communicates with the fluid chamber and through which the fluid can pass from the fluid chamber to the outside, characterized by a valve needle which can be driven by the drive member, which passes into the fluid chamber and by means of the stroke of which an opening and closing of the injection port can be controlled, the valve needle opening outward, the axial surfaces effective from the point of view of the pressure of the valve needle and of the body being such that, in case of variation of the pressure of the fluid, the same variation of

  axial length on the valve needle and on the body.

  The invention is preferably directed to a metering device, characterized in that the fluid chamber consists of a cylindrically shaped fluid reservoir and a cylindrically shaped injection bore connected axially thereto. and centrally, the valve needle consists of a cylindrical base piece and a cylindrical end piece connected axially and centrally. The base piece and in part the end piece can pass into the fluid reservoir. The end piece can pass into the injection bore and is provided at its opposite end to the base piece of a valve head through which

  the injection port can be closed.

Preferably: - we have the relationship

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  dl2 - d32 (d42 - d2) 14.d32 12. (d52 - d42) 12 being the length of the tank, 14 being the length of the end piece, d3 being the diameter of the end piece, d4 being the the diameter of the reservoir and d5 the outside diameter of the body in the region of the fluid reservoir, the drive member can be driven by means of an electrostrictive or magnetostrictive piezoelectric actuator, - the actuator can be powered up by means of of a spring tube, - the valve needle can be applied to the injection port by means of a

spring.

  The subject of the invention is also a method for metered injection of fluid, in which the travel of a valve needle passing through a fluid chamber is controlled by means of a motor member mounted in a body. the fluid chamber, which can be pressurized with fluid, characterized in that axially effective surfaces with respect to pressure, valve needle and body are provided which are As the pressure of the fluid varies, the same variation in length occurs on the valve needle and on the body. In the initial state, at least one injection port communicating with the fluid chamber is closed by means of the valve needle, while during an opening operation the valve needle is raised from the valve port. injection to the outside by actuation of the drive member and fluid from the fluid chamber to the outside in a metered manner, and during the return operation, the valve needle being moved to the means of the motor member so as to apply sealingly to the injection port. The invention also preferably relates to a process characterized in that a fluid reservoir of cylindrical shape is used as fluid chamber together with a cylindrical injection bore connected to it axially and centrally, the valve needle consists of a cylindrical base piece and a cylindrical end piece connected to it axially and centrally, the base piece and in part the end piece pass into the fluid reservoir, the end piece passes into the injection bore and is provided at its end

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  opposite to the base part of a valve head through which the injection port can be closed, the relation d1 = d2 being satisfied, d1 being the diameter of the seat

  sealing and d2 the diameter of the base piece.

  Preferably, a force is applied by means of a valve needle return spring which opposes a movement directed towards

  the outside of the valve needle.

  The idea of the invention is essentially based on the fact that the axially effective pressure surfaces of the valve needle and the body of the injection device in a metered manner are such that in the event of a variation of the fluid pressure , the same variation in length occurs on

  the valve needle and on the body.

  For this purpose, the dosing device comprises a body in which a motor unit is mounted and which delimits a fluid chamber which can be filled with a fluid under pressure. At least one injection port through which the fluid can pass from the fluid chamber to the outside communicates with the fluid chamber. In addition, there is provided a valve needle which can be driven by the motor member which passes into the fluid chamber and by means of the stroke of which can be controlled an opening and closing of the injection port, the valve needle opening outwards. The valve needle and the body have axially effective areas of pressure, i.e., subjected to pressure in the axial direction which are such that in the event of a change in fluid pressure , the same variation in length occurs

  axial on the valve needle and on the body.

  A metered injection device thus constituted has the advantage of being insensitive in its operation to a fluctuation of the

fluid pressure.

  In addition, a larger needle stroke and a very simple structure compared to the use of a fort are advantageously obtained.

spring.

  It is advantageous to drive the motor unit by

  piezoelectric, for example by means of a piezoelectric actuator.

  A piezoelectric drive member has a very fast switching time and a very short drive dead time. The present invention is

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  particularly advantageous in connection with a piezo motor

  electrical, because the piezoelectric drive member has a relatively small stroke (e.g., 30 μm to 40 μm), so that inadvertent opening of the injection device in a metered manner occurs relatively early. In addition to a piezoelectric drive member, it is also possible to use an electrostrictive or magnetostrictive drive member, both of which also give a good switching characteristic. The magnetostrictive driving device, however, has the disadvantage of having to use a relatively large coil to operate. The electrostrictive driving device has the disadvantage that the materials currently available have a relatively low Curie point, so that the operation of an electrostrictive driving device at a high

  temperature, for example in the area of an engine is not possible.

  The invention can also be applied to a valve

  electromagnetically or electrodynamically driven injection nozzle.

  It is also good to simplify the structure of the injection device in a metered manner, that the motor member can be sealed

vis-à-vis the fluid.

  Regardless of the type of drive, the invention can be advantageously applied to all kinds of injection devices so

  in which the flow rate depends on the stroke of the valve needle.

  It is further advantageous to be able to apply the valve needle to the injection port by means of a return spring. This relatively low return spring serves to bring the valve needle back and to prevent

  and inadvertent opening of the injection device metered.

  It is advantageous that the piezo training device

  electric is a multilayer ceramic piezoelectric actuator. It is advantageous that the ceramic actuator is put under a pre-pressure because thus preventing undesirable tensile stresses on the actuator. To simplify the structure, it is advantageous for the actuator to be pre-tensioned by a spring tube. For example, the ceramic actuator can be mounted in a cylindrical spring tube. But it is also possible to maintain, by means of a spring or several springs which are connected in parallel or in series, the actuator

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  piezoelectric power under a prior pressure, for example by means of a

disc spring.

  The metered injection device is particularly suitable for fuel injection, for example in a combustion engine. The dosing device can be used in a pressure range of 100 bar to 400 bar, especially as an injector

direct gasoline.

  Differently constituting the effective surfaces vis-à-vis the pressure of the valve needle and the body in the region of their surface subjected to pressure is particularly useful in the case where the valve needle has different diameters and / or the bore, in which the needle of

  valve passes, has different cross sections.

  To minimize the pressure dependence of an injection device in a metered manner, the radial dimensions, i.e. the cross sections and the axial dimensions i.e. the lengths of the valve needle and the body of the injector are built in the region subjected to the pressure so that the pressure of the fluid causes the same variation of

  body length and valve needle.

  Of course, the invention is not limited to a device

  of injection in an axially symmetrical dosing manner.

  The injection device in a metered manner according to the invention is represented in a more precise manner but schematically in the

following examples of embodiment.

  FIG. 1 is a diagram of a usual dosing device opening outwards, FIG. 2 is a diagrammatic sectional view of an exemplary embodiment of a metered injection device which is not shown in FIG. does not depend on the pressure and, Figure 3 is a schematic sectional view of another embodiment of a metered injection device having a

  Needle stroke that does not depend on pressure.

  FIG. 1 represents a direct injector with axial symmetry with the exception of the conduit 7 for supplying the fluid. In a drive chamber 11 inside a body 1 is mounted a motor member 2 in the form of a piezoelectric actuator. The piezoelectric actuator is located

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  in a spring tube 9 by which the piezoelectric actuator is maintained under a prior pressure. On the side of the spring tube 9 which is remote from the body 1, there is a valve needle 5. The valve needle 5 goes from the spring tube 9 through a passage 12 and through a fluid chamber 3 to the outer side of the body 1. The fluid chamber 3 is filled with a fluid F at a pressure P a conduit 7 for supplying fuel. It consists of a fluid reservoir 31 and an injection bore 32. The fluid chamber 3 is such that it

  opens out through an injection port 6 of the injection bore 32.

  The valve needle 5 has at its outward leading end which is remote from the spring tube 9, the shape of a valve head 51. The orifice 6

  injection can be closed by the valve head 51.

  In the injection bore 32, there is a return spring 8 which pushes the valve head 51 onto the body 1, so that the injection port 6 is closed. But the return spring 8 is however too weak to be able to ensure an application of the valve head 51 on the body 1 to the

  full pressure P of the fluid (for example from 100 bar to 300 bar).

  To ensure the sealing of the drive member 2 located in the drive chamber 11 and the spring tube 9 vis-à-vis the fluid F, it is

  provided in the passage 12 an O-ring 4 surrounding the valve needle 5.

  In the initial state, the piezoelectric actuator is discharged or short-circuited and takes its smallest (axial) length. Terminals

  electric motor 2 are not shown. The piezo actuator

  ceramic electric is always maintained under a certain pressure by the spring tube 9 so that it can not occur harmful traction that could cause cracks. In the initial state, the spring tube 9 also has a minimum axial length. The valve needle 5 is maximally withdrawn so that the valve head 51 is applied to the body 1 and closes the injection port 6. The closure of the injection orifice 6 is also ensured by the

return spring 8.

  During an opening operation, an electrical signal is applied to the motor member 2, so that it extends in the axial direction. The motor member 2 extends the spring tube 9 which in turn moves the valve needle in the same direction. The valve head 51

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  is thus raised from the body 1 so that the injection port 6 is open. Of

  fluid F thus passes from the fluid chamber to the outside.

  To terminate the opening operation, the motor member is again contracted in the axial direction for example by a short circuit, by a discharge of the piezoelectric actuator. The valve needle 5 is thus again removed, so that the valve head 51 closes again.

the injection port 6.

  FIG. 2 is a cross-sectional view of a metering device which is driven directly and opens outwards, the

  The stroke of the valve is independent of the pressure.

  In the drive chamber 11, an actuator is provided

  multi-layer piezoelectric ceramic inserted into a tube

  spring 9, the latter being fixed to the body 1. On the side of the spring tube 9 opposite the attachment to the body 1, is the valve needle 5 which is in contact with the spring tube 9 or is separated by a slit from 1 pm to 31 pm wide at rest. The valve needle 5 goes from the spring tube 9 to the outer side of the body 1 through the drive chamber 11, the passage 12 and the fluid chamber 3. The valve needle 5 is axially slidably mounted in the passage 12. In the drive chamber 11, there is the return spring 8 by which the valve needle 5 is pushed onto the spring tube. The return spring 8 is supported on the body and on an elastic ring attached to the valve needle 5. The bushing 12 is sealed against the fluid vis-à-vis the fluid chamber 3 for reasons of

  safety by means of two O-rings.

  2) 5 To further ensure that fluid F can not pass from the fluid chamber 3 to the drive chamber 11, it opens into the passage 12 a discharge 32 through which fluid possibly arriving in the passage 12 can be evacuated for example in a tank. On the opposite side to the drive chamber 11, the passage 12 opens into the fluid chamber 3. The fluid chamber 3 is filled by means of a conduit 31 for supplying fluid of a fluid F in this case of gasoline. The fluid chamber 3 is designed as a bore having two different diameters radially. The portion of the fluid chamber 3 having the largest diameter d4 corresponds to the fluid reservoir 31, lu, Tf

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  while the portion of the fluid chamber 3 having the smallest diameter d1

  corresponds to the injection bore 32.

  The valve needle 5 is formed as a part having a base portion 52 of a diameter d2 and an end portion 53 which is centrally centered with a diameter d3 smaller. The base portion 52 of the valve needle 5, which is driven by the spring tube 9, passes through the passage 12. In the fluid reservoir 31, the valve needle 5 has a constriction of the cross-sectional area of the valve. a smaller diameter d3. At the end of the end portion 53 of the valve needle 5 leading outwardly, this needle is formed as a valve head 51. The length 11 (axial) of the injection bore 32 goes from the point o applies the valve head 51 to the fluid reservoir 31 which has a length 12. The length 14 of the end portion 53 is from the point where the valve needle 5 applies to the body 1 to the cross-sectional narrowing, i.e., to the transition from the small cross-section to the large cross section of the needle 5 in the initial state, while

  that the length 13 of the base portion reproduces that of the base portion 52.

  By the diameter dl sealing seat, denotes the diameter of the injection bore 32 and the base diameter d2, the diameter of the base portion 52. By d3 denotes the diameter of the end portion 53 and d4 the diameter of the reservoir 31 fluid. D5 is the outside diameter of

  body 1 in the region of the reservoir 31 to fluid.

  The lengths 11 to 14 and the diameters d1 to d5 are such that d1 = d2, so that the diameter d1 of the sealing seat corresponds to the diameter d2 of the base part. It thus obtains that it does not apply additional force under the effect of the pressure P of the fuel, on the return spring 8 and on the valve seat. The lengths 11 and 13 are substantially independent of the pressure P, while the lengths 12 and 14 have

slopes.

  On annular surfaces which are effective from the axial point of view vis-à-

  pressure screws, which delimit the end portion 53 of the valve needle 5, it applies as a function of the pressure P, a force luilf F P .. (d 1 -d32) by which the part 53 end is stretched that is to say that under the influence of pressure length 14 increases. The flexibility kl of the end portion 53 is calculated by Eor: od3 2

  k. E 4 d32 E being the modulus of elasticity.

  4.14 The elongation A14 caused by the pressure thus becomes equal to A14 F P (d12-d32) k. 4. For the elongation of the housing 1, there is approximately a similar calculation. On the annular surfaces which are axially effective from the point of view of the pressure and which delimit the fluid reservoir 31, the force F 2 = P 7 A (d 4 -d d 12) applies. The corresponding flexibility k 2 is calculated by k 2 = E The elongation caused by the pressure of the fluid reservoir 31 thus becomes A 12 _ F 2 P * (d-d 2) k 12 (d 2 - d)

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  In order that the pressure variations do not act on the curve of the valve needle, the injection device is dosed in such a way as to have aS = a> (di - d) - (d4 - d) 14 À d 12 À (d2 dc4) These estimates are only approximate, since the radial elongation of the fluid reservoir 31 which also results in a modification of the length 12 of the fluid reservoir 31. has not been taken into account. A more precise determination to no longer depend on the

  pressure is possible for example by the finite element method.

  An inwardly directed metered injection device of this type is particularly suitable for

  direct injection of gasoline into a combustion engine.

  FIG. 3 is a sectional view of another embodiment of a metered injection device whose valve stroke is

independent of the pressure.

  By keeping a notation similar to that of FIG. 2, only the valve needle 5 and the fluid chamber 3 were made differently. A stroke independent of the pressure of the valve needle is obtained by suitable adaptation of the length 11 and the cross-section d3, of the end portion 53 and / or by a conformation of the diameter d3 of the fluid reservoir 31 and the outer diameter d5 of the body 1 in the region of the fluid reservoir 31. Here again, the diameter d1 of the sealing seat corresponds to the diameter d2 of the base part, so that the pressure P of the fluid does not cause the application of a force on the return spring 8 or on the valve seat . The precise arrangement can in this case

  be determined using simulation calculations.

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Claims (17)

  A metered injection device comprising: a body (1) in which a driving member (2) is mounted; a fluid chamber (3) that can be loaded with pressure by a fluid (F); an injection port (6) which communicates with the fluid chamber (3) and through which fluid (7) can pass from the fluid chamber (3) to the outside, characterized by - a needle (5) of valve which can be driven by the drive member (2), which passes into the fluid chamber (3) and by means of which the opening and closing of the injection port (6) can be controlled - The valve needle (5) opens outwards, - the effective axial pressure surfaces of the valve needle (5) and the body (1) are such that, in the case of variation of the pressure (P) of the fluid (F), the same variation in axial length   the valve needle (5) and the body (1).   Metering device according to claim 1, characterized in that the fluid chamber (3) consists of a cylindrically shaped fluid reservoir (31) and a bore (32). cylindrical injection axially and centrally connected thereto; - the valve needle (5) consists of a cylindrical base piece (52) and a cylindrical end piece (53); 'connecting axially and centrally, 1l11-1 - 13 2786269   the base piece (52) and the end piece (53) in particular can pass into the fluid reservoir (31); the end piece (53) can pass into the bore (32) of injection and is provided at its end opposite to the piece (52) of a base base (51) valve through which the orifice (6) of injection can be closed, and we have the relation dl = d2, dl being the diameter of the sealing seat and d2 the diameter of the base piece.   3. Injection device metered according to claim 2, characterized in that one has the relation dl2 -d32 (d42-d1l2) 14 d32 12 (d52 - d42) 12 being the length of the reservoir, 14 being the length of the end piece, d3 being the diameter of the end piece, d4 being the diameter of the reservoir and d5 the outer diameter of the body (1) in the region of the fluid reservoir (31). 4. Injection device dosed according to one of   preceding claims, characterized in that the driving member (2) can   be driven by means of an electrostrictive piezoelectric actuator or magnetostrictive.   Metering injection device according to Claim 4, characterized in that the actuator can be switched on beforehand by means of a spring tube (9).   6. Injection device metered according to one of   preceding claims, characterized in that the valve needle (5)   can be applied to the injection port (6) by means of a return spring.   7. Injection device metered according to one of   preceding claims, characterized in that the fluid (F) is   gasoline. 8. Injection device metered according to one of   claims 6 or 7, characterized in that it is in a motor with   combustion. 9. A method of metered injection of fluid, wherein 14 2786269   - Control by means of a motor member (2) mounted in a body (1), the stroke of a valve needle (5) passing through a fluid chamber (3), - the fluid chamber (3) can be pressurized to a fluid (F), characterized in that axially effective surfaces of the pressure, the valve needle (5) and the body (1) are provided which are that in case of variation of the pressure (P) of the fluid (F), the same variation in length occurs on the needle (5) of the valve and on the body (1), a- in the state initial at least one injection port (6) communicating with the fluid chamber (3) is closed by means of the valve needle (5), - during an opening operation, the valve needle (5) is raised from the injection port (6) to the outside by actuation of the drive member (2) and fluid (F) passes from the fluid chamber (3) to the outside in a manner during the return operation, the valve needle (5) is moved by means of the driving member (2) so as to be sealingly applied to the injection port (6).   10. A method according to claim 9, characterized in that a fluid reservoir (31) of cylindrical shape is used as a fluid chamber (3) together with a cylindrical injection bore (32). Axially and centrally connected thereto, the valve needle (5) consists of a cylindrical base part (52) and a cylindrical end piece (53) connected axially and centrally therein. the base piece (52) and the end part (53) in particular pass through the fluid reservoir (31); the end piece (53) passes into the injection bore (32); and is provided at its opposite end to the base piece (52) of a valve head (51) through which the injection port (6) can be closed, the relation d1 = d2 being satisfied, d1 being the seat diameter   sealing and d2 the diameter of the base piece.   11. Process according to claim 10, characterized in that the following relationship is satisfied 2786269   dl2 -d32 (d42-d 12) 14d d32 12 (d52-d42) 12 being the length of the tank, 14 being the length of the end piece, d3 being the diameter of the end piece, d4 being the reservoir diameter and d5 being the outer diameter of the body (1) in the fluid reservoir region (31).   12. Process according to one of Claims 9 to 11, characterized   in that a force is applied by means of a valve spring return spring (5) which opposes an outwardly directed movement of the valve needle (5).   13. Injection method dosed according to one of   Claims 9 or 10, characterized in that the driving member (2) is driven   by means of a piezoelectric, electrostrictive or magnetostrictive actuator.   14. Process according to claim 13, characterized in that   the actuator is pressurized.   15. Process according to one of Claims 9 to 14, characterized   in that the pressure (P) of the fluid is between 100 bar and 300 bar.   16. Process according to one of Claims 9 to 15, characterized   in that gasoline is used as fluid (F).   17. Process according to claim 16, characterized in that   is used in a combustion engine. 1EI1T