EP3250812A1 - Servo injector - Google Patents

Servo injector

Info

Publication number
EP3250812A1
EP3250812A1 EP16700295.5A EP16700295A EP3250812A1 EP 3250812 A1 EP3250812 A1 EP 3250812A1 EP 16700295 A EP16700295 A EP 16700295A EP 3250812 A1 EP3250812 A1 EP 3250812A1
Authority
EP
European Patent Office
Prior art keywords
piezoelectric
valve
injector
control valve
extremity
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP16700295.5A
Other languages
German (de)
French (fr)
Inventor
Gael Guignon
Romain Vit
Christophe Tapin
Alexandre TORRESANI
Michael Cooke
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Delphi International Operations Luxembourg SARL
Original Assignee
Delphi International Operations Luxembourg SARL
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Delphi International Operations Luxembourg SARL filed Critical Delphi International Operations Luxembourg SARL
Publication of EP3250812A1 publication Critical patent/EP3250812A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M63/00—Other fuel-injection apparatus having pertinent characteristics not provided for in groups F02M39/00 - F02M57/00 or F02M67/00; Details, component parts, or accessories of fuel-injection apparatus, not provided for in, or of interest apart from, the apparatus of groups F02M39/00 - F02M61/00 or F02M67/00; Combination of fuel pump with other devices, e.g. lubricating oil pump
    • F02M63/0012—Valves
    • F02M63/0014—Valves characterised by the valve actuating means
    • F02M63/0015—Valves characterised by the valve actuating means electrical, e.g. using solenoid
    • F02M63/0026—Valves characterised by the valve actuating means electrical, e.g. using solenoid using piezoelectric or magnetostrictive actuators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M47/00—Fuel-injection apparatus operated cyclically with fuel-injection valves actuated by fluid pressure
    • F02M47/02—Fuel-injection apparatus operated cyclically with fuel-injection valves actuated by fluid pressure of accumulator-injector type, i.e. having fuel pressure of accumulator tending to open, and fuel pressure in other chamber tending to close, injection valves and having means for periodically releasing that closing pressure
    • F02M47/027—Electrically actuated valves draining the chamber to release the closing pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M61/00—Fuel-injectors not provided for in groups F02M39/00 - F02M57/00 or F02M67/00
    • F02M61/16—Details not provided for in, or of interest apart from, the apparatus of groups F02M61/02 - F02M61/14
    • F02M61/167—Means for compensating clearance or thermal expansion
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M2200/00—Details of fuel-injection apparatus, not otherwise provided for
    • F02M2200/50—Arrangements of springs for valves used in fuel injectors or fuel injection pumps
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/20—Piezoelectric or electrostrictive devices with electrical input and mechanical output, e.g. functioning as actuators or vibrators

Definitions

  • the present invention relates generally to servo injector and, more particularly to its piezoelectric control valve.
  • Servo injectors provided with a piezoelectric or magneto restrictive actuator are usually provided with hydraulic lash adjuster arranged between the actuator and the control valve of the injector, this in order to transmit force of displacement from the actuator to the valve. Therefore, the valve commutes between an open position, enabling fuel at high pressure to exit a control chamber and, a closed position forbidding said exit of fuel.
  • the adjusters comprise an actuator-side member, connected to the actuator, and a valve-side member connected to the valve.
  • the actuator-side member is solicited toward the actuator by a very stiff cage spring while the valve-side member is solicited by a lesser stiff coil spring toward a closed position of the control valve.
  • a chamber which in use is filled with fuel, so that the displacement of the actuator is transmitted to the valve-side member.
  • Recurring problems are the important overall length of the lash adjuster which consequently has a mass detrimental to fast valve movements and also, the complexity of the lash adjuster which adds technical difficulties and cost.
  • a piezoelectric control valve for a servo injector, the valve comprising a piezoelectric actuator controlling a valve member.
  • the piezoelectric actuator is adapted to be arranged in a bore provided in the injector body between axially opposed first and second transverse faces in order to control, in use, opening and closing of a return orifice enabling the hydraulic control of the displacements of a needle valve member enabling or forbidding fuel injection.
  • the piezoelectric actuator comprises an encapsulating tube extending along a main axis X from a first extremity to a second extremity closed by a closing member and, a piezoelectric stack axially compressed inside the encapsulating tube.
  • the upper extremity of the stack is in contact with the inner face of the closing member and, the lower extremity of the stack is in contact with a pusher member adapted to cooperate, in use, with the valve member in order to open or close said return orifice.
  • the piezoelectric control valve further comprises an adjusting member adapted, in use, to permanently maintain a compression force in the encapsulating tube independently of the energizing state of the piezoelectric stack and of the thermal expansion of the injector.
  • the adjusting member is a compression spring arranged in use between the outer face of the closing member and said second transverse face.
  • the spring is a leaf spring assembly which may comprise a single or a plurality of individual leaf spring.
  • Each leaf spring is a dome shaped washers.
  • the invention further extends to a servo injector having a body which peripheral walls internally define a bore extending along a main axis between a first transverse face and a distal second transverse face, the servo injector being provided with a piezoelectric control valve as previously, the piezoelectric actuator of said valve being arranged in the bore.
  • the piezoelectric actuator is arranged so that the compression force generated by the adjusting member is integrally transmitted via the encapsulating tube.
  • the servo injector is arranged to enable fuel injection when energizing the piezoelectric actuator and, to forbid fuel injection when not- energizing the piezoelectric actuator.
  • Figure 1 is an axial section of an injector provided with a
  • Figure 2 is a sketch of the piezoelectric control valve of figure 1, valve being energized.
  • Figure 3 is similar to Figure 2, the valve not being energized.
  • a fuel injector 10 which extends along a main axis X arbitrarily drawn vertically.
  • said non- limiting orientation may be utilized through words such as "top, bottom, upper, under".
  • the fuel injector 10 comprises an injector body 12 constituted of several elements fixedly coaxially maintained together by an injector nut.
  • a high pressure fuel circuit 14 extending from an inlet 16, usually on the top of the injector, to injection holes 18 arranged in the nozzle 20 of the injector 10, at the lower tip extremity of the injector 10.
  • a lateral branch of said high pressure circuit 14 is diverted toward a control chamber 22 wherefrom depart a return circuit 24 upwardly extending toward an outlet 26 wherefrom the fuel exits the injector 10 and flows at low pressure to return to a fuel tank.
  • a control valve 30 adapted to open or close a return orifice 42, therefore controlling the pressure in the control chamber 22.
  • a needle valve 28 axially extending between a top extremity protruding in the control chamber 22 and a tip cooperating with the injection holes 18 in order to enable or forbid fuel injection.
  • the control valve assembly 30 of the present invention comprises a piezoelectric actuator 32 arranged in a bore 44 provided in the injector body 12 and, a control valve member 34 similar to the one described in application WO2015/024692.
  • said control valve member 34 comprises an upper two- way valve 36 normally biased in a closed state CS by a spring 38.
  • the bore 44 defines an internal cylindrical volume limited by a first transverse face 46, at the bottom of the figures, and by a second transverse face 48 drawn at the top of the figures.
  • the stem 40 of said upper two-way valve 36 upwardly protrudes in the center of the first transverse face 46 and, the second transverse face 48, top of the figures, may be provided with a top opening 52 to enable for instance extension of electric wire cables for energizing the piezoelectric actuator 32.
  • the piezoelectric actuator 32 comprises an encapsulating tube 54 vertically extending from a circular lower face 56 closed by a diaphragm 50 and which is in abutment against the first transverse face 46 to, an upper extremity that is closed by a closing member 58 that has an inner face 60 inside the tube 54 opposed to an outer face 62, outside the tube 54, arranged facing the second transverse face 48. Between said outer face 62 and the second transverse face 48 is compressed a leaf spring assembly 64.
  • the leaf spring assembly 64 comprises the stack- up of a first leaf spring being a dome shape washer 66 having its large circular edge abutting against the outer face 62 of the closing member 58, then an intermediate flat washer 68, above which a second leak spring dome shape washer 70, reversed relative to the first 66, is.
  • the large circular edge of said second washer 70 abuts against a final flat washer 72 arranged against the second transverse face 48 of the cylindrical bore 44.
  • This stack-up arrangement is compressed between the second transverse face 48 and the closing member 58 and, the deflection of the dome shape washers 66, 70, permanently generates a first vertical force Fl compressing the tube 54 against the first transverse face 46.
  • the compression force inside the tube varies during operation of the valve 30.
  • multiple other type of compression spring can be arranged and, in the case of leaf spring, a single dome washer or to the contrary, more than two dome washers can be utilized.
  • a spring tube 74 Inside the tube 54 are axially X encapsulated a spring tube 74, fixed at its upper extremity to the closing member 58, the spring tube 74, a piezoelectric stack 76 arranged inside the spring tube 74 and, a pusher member 78 fixed to the lower extremity of the spring tube 74.
  • the spring tube 74 is elongated so that, when it is relaxed after fixing both the closing member 58 and pusher member 78, the piezoelectric stack 74 is axially compressed between said two members 58, 78.
  • the pusher member 78 is externally adapted to cooperate with the stem 40 of the upper two-way valve in order to open or close said upper two-way valve 36 and to do so, the piezoelectric stack 76 can be electrically actuated via wire cables 80 arranged inside the injector body 12.
  • the piezoelectric stack 76 At rest when not energized, as represented on figure 3, the piezoelectric stack 76 is axially compressed by the spring tube 74 and its length is minimized so the pusher member 78 is lifted away from the stem 40. Indeed there is a gap G between the pusher member 78 and the stem 40 and, the force Fl generated by the leaf spring assembly 64 is integrally transmitted by the encapsulating tube 54 to the first transverse face 46.
  • the upper two-way valve 36 not being solicited by the actuator 32 remains in its normally closed state CS and, fuel injection is forbidden.
  • the piezoelectric stack 76 When energized, as represented on figure 2, the piezoelectric stack 76 axially expends and the pusher member 78 downwardly displaces. At first, it closes the gap G and it comes in contact with the stem 40 then, the pusher member 78 continues its displacement generating on the upper two-way valve 36 an downwardly oriented opening force F2 enabling the upper valve 36 to move to an open state OS for enabling fuel injection.
  • the opening force F2 acts in opposite directions, downwardly on the stem 40 and upwardly on the closing member 58. Therefore the compression force inside the encapsulating tube 54 reduces but, it remains always superior to said opening force F2 so, the encapsulating tube 54 is permanently compressed.
  • the injector 10 is subject to heat variations and its dimensions vary in operation.
  • the leaf spring 64 is chosen so it always generates a compression force in the tube 54. For instance, in the extreme condition when the axial X length of the bore 44 is maximized and the stack 76 is energized, the encapsulating tube 54 remains compressed.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Fuel-Injection Apparatus (AREA)

Abstract

A piezoelectric control valve (30) for a servo injector (10) has a piezoelectric actuator (32) which comprises an encapsulating tube (54) extending along a main axis (X) from a first extremity (56) to a second extremity closed by a closing member (58) and, a piezoelectric stack (76) axially compressed inside the encapsulating tube (54) between an upper extremity in contact with the inner face (60) of the closing member (58) and, a lower extremity in contact with a pusher member (78) adapted to cooperate with a valve member (36) in order to open or close a return orifice. The piezoelectric control valve (30) further comprises an adjusting member (64) adapted, in use, to permanently maintain a compression force (Fl) in the encapsulating tube (54) independently of the energizing state of the piezoelectric stack (76) and of the thermal expansion of the injector (10).

Description

Servo injector TECHNICAL FIELD
The present invention relates generally to servo injector and, more particularly to its piezoelectric control valve.
BACKGROUND OF THE INVENTION
Servo injectors provided with a piezoelectric or magneto restrictive actuator are usually provided with hydraulic lash adjuster arranged between the actuator and the control valve of the injector, this in order to transmit force of displacement from the actuator to the valve. Therefore, the valve commutes between an open position, enabling fuel at high pressure to exit a control chamber and, a closed position forbidding said exit of fuel.
DEI 02009000203 and DEI 02010029106 disclose hydraulic lash adjusters, also identified as hydraulic coupler, of similar embodiments. The adjusters comprise an actuator-side member, connected to the actuator, and a valve-side member connected to the valve. The actuator-side member is solicited toward the actuator by a very stiff cage spring while the valve-side member is solicited by a lesser stiff coil spring toward a closed position of the control valve. Between the actuator-side member and the valve-side member is provided a chamber which in use is filled with fuel, so that the displacement of the actuator is transmitted to the valve-side member.
Recurring problems are the important overall length of the lash adjuster which consequently has a mass detrimental to fast valve movements and also, the complexity of the lash adjuster which adds technical difficulties and cost.
SUMMARY OF THE INVENTION
It is an object of the invention to resolve or at least mitigate the above mentioned problem by providing a piezoelectric control valve for a servo injector, the valve comprising a piezoelectric actuator controlling a valve member. The piezoelectric actuator is adapted to be arranged in a bore provided in the injector body between axially opposed first and second transverse faces in order to control, in use, opening and closing of a return orifice enabling the hydraulic control of the displacements of a needle valve member enabling or forbidding fuel injection. The piezoelectric actuator comprises an encapsulating tube extending along a main axis X from a first extremity to a second extremity closed by a closing member and, a piezoelectric stack axially compressed inside the encapsulating tube. The upper extremity of the stack is in contact with the inner face of the closing member and, the lower extremity of the stack is in contact with a pusher member adapted to cooperate, in use, with the valve member in order to open or close said return orifice.
The piezoelectric control valve further comprises an adjusting member adapted, in use, to permanently maintain a compression force in the encapsulating tube independently of the energizing state of the piezoelectric stack and of the thermal expansion of the injector.
More particularly, the adjusting member is a compression spring arranged in use between the outer face of the closing member and said second transverse face.
In an embodiment, the spring is a leaf spring assembly which may comprise a single or a plurality of individual leaf spring. Each leaf spring is a dome shaped washers.
The invention further extends to a servo injector having a body which peripheral walls internally define a bore extending along a main axis between a first transverse face and a distal second transverse face, the servo injector being provided with a piezoelectric control valve as previously, the piezoelectric actuator of said valve being arranged in the bore.
Particularly, the piezoelectric actuator is arranged so that the compression force generated by the adjusting member is integrally transmitted via the encapsulating tube.
Specifically, the servo injector is arranged to enable fuel injection when energizing the piezoelectric actuator and, to forbid fuel injection when not- energizing the piezoelectric actuator.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention is now described by way of example with reference to the accompanying drawings in which: Figure 1 is an axial section of an injector provided with a
piezoelectric control valve as per the invention.
Figure 2 is a sketch of the piezoelectric control valve of figure 1, valve being energized.
Figure 3 is similar to Figure 2, the valve not being energized.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In reference to the figure 1 is presented a fuel injector 10 which extends along a main axis X arbitrarily drawn vertically. To ease and clarify the description said non- limiting orientation may be utilized through words such as "top, bottom, upper, under..."
The fuel injector 10 comprises an injector body 12 constituted of several elements fixedly coaxially maintained together by an injector nut. As it is well known, in the body 12 is arranged a high pressure fuel circuit 14 extending from an inlet 16, usually on the top of the injector, to injection holes 18 arranged in the nozzle 20 of the injector 10, at the lower tip extremity of the injector 10. A lateral branch of said high pressure circuit 14 is diverted toward a control chamber 22 wherefrom depart a return circuit 24 upwardly extending toward an outlet 26 wherefrom the fuel exits the injector 10 and flows at low pressure to return to a fuel tank. In the return circuit 26 is arranged a control valve 30 adapted to open or close a return orifice 42, therefore controlling the pressure in the control chamber 22. In the nozzle 20 is provided a needle valve 28 axially extending between a top extremity protruding in the control chamber 22 and a tip cooperating with the injection holes 18 in order to enable or forbid fuel injection.
The control valve assembly 30 of the present invention, further detailed in reference to schematic figures 2 and 3, comprises a piezoelectric actuator 32 arranged in a bore 44 provided in the injector body 12 and, a control valve member 34 similar to the one described in application WO2015/024692. Although multiple alternatives exist, said control valve member 34 comprises an upper two- way valve 36 normally biased in a closed state CS by a spring 38. The bore 44 defines an internal cylindrical volume limited by a first transverse face 46, at the bottom of the figures, and by a second transverse face 48 drawn at the top of the figures. The stem 40 of said upper two-way valve 36 upwardly protrudes in the center of the first transverse face 46 and, the second transverse face 48, top of the figures, may be provided with a top opening 52 to enable for instance extension of electric wire cables for energizing the piezoelectric actuator 32.
The piezoelectric actuator 32 comprises an encapsulating tube 54 vertically extending from a circular lower face 56 closed by a diaphragm 50 and which is in abutment against the first transverse face 46 to, an upper extremity that is closed by a closing member 58 that has an inner face 60 inside the tube 54 opposed to an outer face 62, outside the tube 54, arranged facing the second transverse face 48. Between said outer face 62 and the second transverse face 48 is compressed a leaf spring assembly 64.
In the illustrated example, the leaf spring assembly 64 comprises the stack- up of a first leaf spring being a dome shape washer 66 having its large circular edge abutting against the outer face 62 of the closing member 58, then an intermediate flat washer 68, above which a second leak spring dome shape washer 70, reversed relative to the first 66, is. The large circular edge of said second washer 70 abuts against a final flat washer 72 arranged against the second transverse face 48 of the cylindrical bore 44. This stack-up arrangement is compressed between the second transverse face 48 and the closing member 58 and, the deflection of the dome shape washers 66, 70, permanently generates a first vertical force Fl compressing the tube 54 against the first transverse face 46. As will be described, the compression force inside the tube varies during operation of the valve 30.
Alternatively to the illustrated example, multiple other type of compression spring can be arranged and, in the case of leaf spring, a single dome washer or to the contrary, more than two dome washers can be utilized.
Inside the tube 54 are axially X encapsulated a spring tube 74, fixed at its upper extremity to the closing member 58, the spring tube 74, a piezoelectric stack 76 arranged inside the spring tube 74 and, a pusher member 78 fixed to the lower extremity of the spring tube 74. During the assembly process, the spring tube 74 is elongated so that, when it is relaxed after fixing both the closing member 58 and pusher member 78, the piezoelectric stack 74 is axially compressed between said two members 58, 78.
The pusher member 78 is externally adapted to cooperate with the stem 40 of the upper two-way valve in order to open or close said upper two-way valve 36 and to do so, the piezoelectric stack 76 can be electrically actuated via wire cables 80 arranged inside the injector body 12.
At rest when not energized, as represented on figure 3, the piezoelectric stack 76 is axially compressed by the spring tube 74 and its length is minimized so the pusher member 78 is lifted away from the stem 40. Indeed there is a gap G between the pusher member 78 and the stem 40 and, the force Fl generated by the leaf spring assembly 64 is integrally transmitted by the encapsulating tube 54 to the first transverse face 46.
The upper two-way valve 36 not being solicited by the actuator 32 remains in its normally closed state CS and, fuel injection is forbidden.
When energized, as represented on figure 2, the piezoelectric stack 76 axially expends and the pusher member 78 downwardly displaces. At first, it closes the gap G and it comes in contact with the stem 40 then, the pusher member 78 continues its displacement generating on the upper two-way valve 36 an downwardly oriented opening force F2 enabling the upper valve 36 to move to an open state OS for enabling fuel injection. The opening force F2 acts in opposite directions, downwardly on the stem 40 and upwardly on the closing member 58. Therefore the compression force inside the encapsulating tube 54 reduces but, it remains always superior to said opening force F2 so, the encapsulating tube 54 is permanently compressed.
As an example, tests have been successfully completed in using a leaf spring assembly 64 generating a force Fl of 600N and a piezoelectric stack 76 that, when energized generates on the stem 40 an opening force F2 of 250N. The tube 54 is then compressed with an axial force of 350N while, when the stack is not energized the compression force inside the tube 54 is 600N.
It is also known that the injector 10 is subject to heat variations and its dimensions vary in operation. The leaf spring 64 is chosen so it always generates a compression force in the tube 54. For instance, in the extreme condition when the axial X length of the bore 44 is maximized and the stack 76 is energized, the encapsulating tube 54 remains compressed.
LIST OF REFERENCES X main axis
Fl force generated by the leaf spring
F2 opening force
OS open state
CS closed state
G gap
10 fuel injector
12 injector body
14 high pressure circuit
16 inlet
18 injection holes
20 nozzle
22 control chamber
24 return circuit
26 outlet
28 needle valve
30 control valve assembly
32 piezoelectric actuator
34 control valve member
36 upper two-way valve
38 spring
40 stem of the upper two-way valve
42 return orifice
44 bore
46 first transverse face
48 second transverse face
50 diaphragm
52 top opening
54 encapsulating tube
56 lower face of the tube
58 closing member
60 inner face of the closing member
62 outer face of the closing member
64 leaf spring assembly
66 first dome shape washer
68 intermediate flat washer
70 second dome shape washer
72 final flat washer
74 spring tube
76 piezoelectric stack
78 pusher member
80 wire cables

Claims

1. A piezoelectric control valve (30) for a servo injector (10), the valve (30) comprising a piezoelectric actuator (32) controlling a valve member (36), the piezoelectric actuator (32) being adapted to be arranged in a bore (44) provided in the injector body (12) between axially (X) opposed first (46) and second (48) transverse faces in order to control, in use, opening and closing of a return orifice (42) enabling the hydraulic control of the displacements of a needle valve member (28) enabling or forbidding fuel injection, the piezoelectric actuator (32) comprising:
an encapsulating tube (54) extending along a main axis (X) from a first extremity (56) to a second extremity closed by a closing member (58) and,
a piezoelectric stack (76) axially compressed inside the encapsulating tube (54) between an upper extremity in contact with the inner face (60) of the closing member (58) and, a lower extremity in contact with a pusher member (78) adapted to cooperate, in use, with the valve member (36) in order to open or close said return orifice (42),
characterized in that
the piezoelectric control valve (30) further comprises an adjusting member (64) adapted, in use, to permanently maintain a compression force (Fl) in the encapsulating tube (54) independently of the energizing state of the piezoelectric stack (76) and of the thermal expansion of the injector (10).
2. A piezoelectric control valve (30) as claimed in the previous claim wherein the adjusting member (64) is a compression spring arranged in use between the outer face (62) of the closing member and said second transverse face (48).
3. A piezoelectric control valve (30) as claimed in claim 2 wherein the spring is a leaf spring assembly (64).
4. A piezoelectric control valve (30) as claimed in claim 3 wherein the leaf spring assembly (64) comprises a plurality of individual leaf spring (66, 70) being dome shaped washers.
5. A servo injector (10) having a body (12) which peripheral walls internally define a bore (44) extending along a main axis (X) between a first transverse face (46) and a distal second transverse face (48), the servo injector (10) being provided with a piezoelectric control valve (30) as claimed in any one of the preceding claims, the piezoelectric actuator (32) of said valve (30) being arranged in the bore (44).
6. A servo injector (10) as claimed in claim 5 wherein the piezoelectric actuator (32) is arranged so that the compression force (Fl) generated by the adjusting member (64) is integrally transmitted via the encapsulating tube (54).
7. A servo injector (10) as claimed in any one of the claims 5 or 6 wherein fuel injection is enabled when energizing the piezoelectric actuator (32) and, fuel injection is forbidden when not-energizing the piezoelectric actuator (32).
EP16700295.5A 2015-01-27 2016-01-07 Servo injector Withdrawn EP3250812A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB1501295.8A GB201501295D0 (en) 2015-01-27 2015-01-27 Servo injector
PCT/EP2016/050232 WO2016120040A1 (en) 2015-01-27 2016-01-07 Servo injector

Publications (1)

Publication Number Publication Date
EP3250812A1 true EP3250812A1 (en) 2017-12-06

Family

ID=52673958

Family Applications (1)

Application Number Title Priority Date Filing Date
EP16700295.5A Withdrawn EP3250812A1 (en) 2015-01-27 2016-01-07 Servo injector

Country Status (3)

Country Link
EP (1) EP3250812A1 (en)
GB (1) GB201501295D0 (en)
WO (1) WO2016120040A1 (en)

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19826339A1 (en) * 1998-06-12 1999-12-16 Bosch Gmbh Robert Valve for controlling liquids
DE19928179B4 (en) * 1999-06-19 2008-07-31 Robert Bosch Gmbh piezo actuator
DE102005045893A1 (en) * 2005-09-26 2007-04-05 Siemens Ag Hydraulic compensation unit for compensating for linear differences e.g. for piezo actuators of fuel injectors comprises an outer plate fixed within a housing to delimit hydraulic chambers with inner plates guided within the housing
DE102006026381A1 (en) * 2006-06-07 2007-12-13 Robert Bosch Gmbh Fuel injector with pressure booster and piezo actuator arranged on the low pressure side

Also Published As

Publication number Publication date
GB201501295D0 (en) 2015-03-11
WO2016120040A1 (en) 2016-08-04

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