ACTUATOR ASSEMBLY OF A DIGITAL INLET VALVE

Abstract

An actuator assembly of a digital inlet valve for a fuel pump adapted to cooperate with an inlet valve member includes an actuator body in which is fixed a coil, a cover closing the body and, a magnetic core arranged in a core guiding bore provided in the actuator body. The magnetic core is slidable along a main axis in order, in use, to close an air gap under the influences of a first compression spring, and of a magnetic field, the core cooperating with the valve member.

Claims

1-15. (canceled)

16. An actuator assembly of a digital inlet valve for a fuel pump, the actuator assembly being adapted to cooperate with an inlet valve member switching between an open state and a closed state, the actuator assembly comprising: an actuator body in which is fixed an electric coil adapted to generate a magnetic field when electrically energized; an actuator cover fixedly closing the actuator body; and a magnetic core arranged in a core guiding bore provided in the actuator body, the magnetic core being slidable along a main axis under the influence of said magnetic field against the force of a first compression spring in order, in use, to close an air gap, the magnetic core cooperating with the inlet valve member, characterized in that the air gap is calculated by the formula
G142=A144(B146+T196) where, A144 is an axial dimension intrinsic to the actuator body and, B146 is an axial dimension intrinsic to the actuator cover and, T196 is an axial dimension intrinsic to the magnetic core.

17. An actuator assembly as claimed in claim 16 wherein, the axial dimension intrinsic to the actuator body is measured between a lower face of the actuator body and a top face whereon lies a peripheral under face of the actuator cover and, the axial dimension intrinsic to the actuator cover is measured between the peripheral under face and a central under face and, the axial dimension intrinsic to the magnetic core is a thickness of a flange of the magnetic core.

18. An actuator assembly as claimed in claim 17 wherein an under face of the flange abuts against a disc face of the actuator body when in the open state and an upper face of the flange, opposed to the under face of the flange, abuts against an under face of the actuator cover when in the closed state.

19. An actuator assembly as claimed in claim 18 wherein the flange is maintained between said disc face and said under face of the actuator cover and wherein the first compression spring is compressed between the actuator cover and the magnetic core so that, the actuator body is closed by the actuator cover, the electric coil, the magnetic core and the first compression spring are held together forming an autonomous actuator assembly adapted to be fixedly arranged on the fuel pump.

20. An actuator assembly as claimed in claim 17 wherein the actuator body comprises an outer peripheral cylindrical wall and an inner cylindrical wall, both the outer peripheral cylindrical wall and the inner cylindrical wall extending along the main axis and the electric coil being arranged between the outer peripheral cylindrical wall and the inner cylindrical wall, an internal face of the inner cylindrical wall defining the core guiding bore.

21. An actuator assembly as claimed in claim 20 wherein the magnetic core integrally comprises a main cylindrical member and the flange, the flange radially outwardly extending from the main cylindrical member, the main cylindrical member being adjusted to be guided in the core guiding bore and to slide along the main axis.

22. An actuator assembly as claimed in claim 21 wherein the magnetic core further comprises an upper central blind bore axially extending through the flange and inside the main cylindrical member, said upper central blind bore enabling guidance of the first compression spring.

23. An actuator assembly as claimed in claim 17 wherein the flange is further provided with apertures enabling, in use, fuel to flow through said apertures.

24. An actuator assembly as claimed in claim 16 further comprising a first shim being an adjusting shim arranged in order to compensate for manufacturing tolerances, a thickness of the first shim reducing the air gap.

25. An actuator assembly as claimed in claim 24 further comprising a second shim being an amagnetic shim arranged in order avoid sticking of the magnetic core, the thickness of the second shim reducing the air gap.

26. An actuator assembly as claimed in claim 16 further comprising an electrical connector outwardly protruding from the actuator body and enabling, in use, complementary electrical connection with the electric coil.

27. A fuel pump comprising: a pump head wherein is arranged a compression chamber within which, in use, fuel is able to enter via an inlet opening and exit via an outlet opening; an inlet valve which controls fuel entering the compression chamber via the inlet opening; and an outlet valve which controls fuel exiting the compression chamber via the outlet opening; wherein the inlet valve inlet valve has a valve member which is switched between an open state and a closed state by an actuator assembly the actuator assembly comprising: an actuator body in which is fixed an electric coil adapted to generate a magnetic field when electrically energized; an actuator cover fixedly closing the actuator body; and a magnetic core arranged in a core guiding bore provided in the actuator body, the magnetic core being slidable along a main axis under the influence of said magnetic field against the force of a first compression spring in order, in use, to close an air gap, the magnetic core cooperating with the inlet valve member, characterized in that the air gap is calculated by the formula
G142=A144(B146+T196) where, A144 is an axial dimension intrinsic to the actuator body and, B146 is an axial dimension intrinsic to the actuator cover and, T196 is an axial dimension intrinsic to the magnetic core.

28. A fuel pump as claimed in claim 27 wherein the valve member has a stem having an end portion outwardly protruding outside the pump head, the stem axially sliding in a bore of the pump head for the valve member to switch between the open state and the closed state.

29. A fuel pump as claimed in claim 28 further comprising a second spring arranged over the end portion of the stem, the second spring being compressed between a face of the pump head and a spring-seat fixed to an extremity of the stem.

30. A fuel pump as claimed in claim 29 wherein the inlet valve is a passive valve which, in absence of magnetic field generated by the electric coil, the magnetic core being pushed by the first spring abuts on the valve stem soliciting the valve member toward the open state and wherein, when the electric coil is energized, the magnetic core being pulled away from the valve stem, the second spring soliciting the valve member toward the closed state.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The present invention is now described by way of example with reference to the accompanying drawings in which:

[0047] FIG. 1 is a typical digital inlet valve of the prior art.

[0048] FIG. 2 is the valve of FIG. 1 with the functional dimensions.

[0049] FIG. 3 is a first embodiment of an actuator of a digital inlet valve as per the invention.

[0050] FIG. 4 is a second embodiment of an actuator as per the invention with the functional dimensions.

[0051] FIG. 5 is an isometric view of a first embodiment of a magnetic core of the actuator of FIG. 3 or 4.

[0052] FIG. 6 is a second embodiment of a magnetic core of the actuator of FIG. 3 or 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0053] In reference to FIGS. 3 and 4 is now described an embodiment of an actuator 42 as per the invention. To support the description the numeral references differ from those of the prior art simply by adding 100 when designating similar features. As an example, the digital inlet valve is referenced 110, the actuator assembly is 142.

[0054] The actuator body 144 comprises, in place to the small vertical foot 60, a lengthy cylindrical member 160 upwardly extending from the transverse floor 156 of the body to a distal upper disc face 162.

[0055] The actuator cover 146 comprises a disc member 164 which periphery fixedly lies on the top face 154 of the body 144. The inner face of the cover is centrally provided with a small shallow recess 174 enabling to position the top turns of the actuator spring 176.

[0056] The magnetic core 180 comprises a main cylindrical member 192 axially extending from a lower face 194 to an upper face 178. In the upper part, the core comprises a flange 196 radially protruding from the main cylindrical member 192, said flange 196 having a thickness T196. The flange 196 and the main cylindrical member 192 are, in the present example, shown integral to each other although in alternative embodiments, the flange 196 may be a separate component fixed on the top of the cylindrical member 178.

[0057] The core 180 is further provided with an upper central recess 198 for arranging the actuator spring 176 and, similarly to the prior art, the core is also provided on its bottom part with an upside-down cup-like shape arranged over the stem 32 of the valve member 24 and over the spring seat 40. The transverse bottom of the cup-like is indeed a transverse wall 184 on the top if which abuts the actuator spring 176.

[0058] As visible on FIG. 3, the core 180 is adjusted in the core guiding bore 158 and the flange 196 radially extends between the upper disc face 162 of the cylindrical member of the actuator body and the under face of the cover. Since the core is axially guided the flange is captured between said two faces and the core cannot disassemble from the actuator assembly 142.

[0059] Similarly to the prior art actuator 42, the actuator assembly 142 may comprise a first shim 188, for tolerance stack-up adjustment, and a second amagnetic shim 190 arranged on each side of the flange 196.

[0060] The actual operation of the actuator assembly 142 is indeed similar to the operation of the prior art.

[0061] The method to arrange the actuator assembly 142 over the pump head 14 solely comprises a preparation step where the body 144, the core 180, coil 172 the actuator spring 176 and the cover 146 are pre-assembled together in a complete sub-assembly, before the final step where said actuator assembly 142 is arranged and fixed in place over the pump head 14.

[0062] In reference to FIGS. 3 and 4, the dimensioning of the air gap G142 of this actuator assembly 142 is simplified as it only depends upon dimensions intrinsic to the components of the actuator and, dimensions of the pump head 14 are not needed.

[0063] The air-gap G142 is calculated by the following equation:

G142=A144(B146+T196+T1+T2) where [0064] G142 is the air gap [0065] A144, intrinsic to the body, is the axial distance from the upper disc face of the cylindrical inner member 162 to the top face; [0066] B146, intrinsic to the cover, is the axial distance from the under face of the disc portion to the under face of the cover where abuts the core; [0067] T196, intrinsic to the core, is the axial thickness of the flange 196; [0068] T1 and T2 are the respective thicknesses of the first 188 and second 190 shims.

[0069] The actuator assembly 142 represented on FIG. 3, and the actuator assembly represented on FIG. 4, differ by at least two characteristics. At first, the cover 146 of FIG. 3 comprises a small inner circular protrusion 198 defining a large recess in which the flange 196 axially travels. This small protrusion 198 has substantially a height equivalent to the thickness T196 of the flange 196. To the contrary, the cover 146 of FIG. 3 is not provided with such small protrusion but the flange 196 radially extends over the complete thickness of the cylindrical inner member 160, up to the coil 172. The cover 146 of FIG. 3 comprises three concentric plane disc-faces and a central minor recess for locating the actuator spring.

[0070] In operation, the digital inlet valve is filled with fuel and, the coil is protected by O-ring. The fuel is able to flow upward through long holes 200 provided in the wall thickness of the cylindrical inner member 160 of the actuator body 144. Alternatively to long holes, fuel passages can be arranged by creating flats on the main cylindrical member of the core 192.

[0071] Furthermore, in reference to FIGS. 5 and 6 two alternatives of a core 180 are described, each having apertures 202 provided in the flange 196. In the first alternative, FIG. 5, the flange 196 is provided with six through holes. Any other number is of course possible. In the second alternative of FIG. 6, the flange is provided at its periphery with six inwardly curved apertures so that when the edge of the flange slides against the small wall 198 or against a cylindrical face of the coil, said curved apertures forms easy passage for the fuel.

TABLE-US-00001 LIST OF REFERENCES prior art invention 10 110 digital inlet valve 12 fuel pump 14 pump head 16 bore 18 piston 20 compression chamber 22 valve 24 valve member 26 valve seat 28 opening 30 outlet 32 stem 34 valve guiding bore 36 valve spring 38 abutment face of the pump head 40 spring seat 42 142 actuator assembly 44 144 actuator body 46 146 actuator cover 48 148 peripheral wall 50 150 lower face of the wall 52 abutting face of the pump head 54 154 top face of the peripheral wall 56 156 transverse floor 58 158 core guiding bore 60 160 60: vertical foot-160: cylindrical inner member 162 upper disc face of the cylindrical inner member 64 164 disc member of the cover 66 cylindrical member of the cover 68 lower face of the cylindrical member 70 170 outer annular compartment 72 172 coil 74 174 central blind bore 76 176 actuator spring 78 178 upper face of the core 80 180 magnetic core 82 182 cylindrical wall of the core 84 184 84: transverse bottom-184: transverse wall of the core 88 188 first shim 90 190 second shim 192 main cylindrical member of the core 194 lower face of the core 196 flange 198 small protrusion 200 long holes 202 apertures X main axis V internal volume H height of the core guiding bore Kv stiffness of the valve spring Ka stiffness of the actuator spring OS open state of the valve CS closed state of the valve G42 air gap of the prior art actuator G142 air gap of the actuator as per the invention A44 A144 distance from the lower face to the top face of the body B46 B146 distance from the under face of the disc portion to the lower face of the cylindrical member C40 thickness of the spring seat D14 distance from the face of the pump head where abuts the spring seat to the face where abuts the actuator housing E84 thickness of the transverse bottom of the core T1 T1 thicknesses of the first shim T2 T2 thicknesses of the second shim T196 thickness of the flange