Abstract
Electromagnetic valve, particularly for controlling a fuel injector or for regulating the pressure of a high-pressure fuel accumulator, comprising a casing (2), an electromagnet (24, 25) formed of a yoke (24) and an electromagnetic coil (25) housed in the latter, and an armature (22) in one or more parts. An abutment disk (28) is provided between the transverse face of the armature (22) turned towards the yoke (24) and the transverse face facing the yoke (24), this abutment disk (28) being made of a magnetized or magnetizable material, particularly of a ferromagnetic material.
Claims
1. An electromagnetic valve, comprising: a casing (1, 2), an electromagnet (24, 25) formed of a yoke (24) and an electromagnetic coil (25) housed in an opening of the yoke, and an armature (22) in one or more parts, the yoke (24) opening towards the armature (22), characterized in that an abutment disk (28) is provided between on one hand a transverse face of the armature (22), said face of the armature (22) being turned towards the yoke (24), and on the other hand a transverse face of the yoke (24), the abutment disk (28) being made of a magnetized or magnetizable material, and in that a bearing surface of the abutment disk (28) is reduced by at least two orifices (34, 35, 36), wherein at least one of the at least two orifices (36) has a different size than the remaining orifices (34, 35), characterized in that the bearing surface of the abutment disk (28) is further reduced by a central drill hole (36).
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The present invention will be described below in greater detail with the aid of exemplary embodiments of an electromagnetic valve represented in the appended drawings in which:
(2) FIG. 1 shows in longitudinal section an electromagnetic valve according to the prior art applied to the example of a fuel injector,
(3) FIG. 2 is a detail on a larger scale of the electromagnetic valve of FIG. 1;
(4) FIGS. 3a-3c show on a larger scale a detail of the electromagnetic valve furnished with the magnetizable abutment disk according to the invention,
(5) FIGS. 4a-4b show other exemplary embodiments of the detail of an electromagnetic valve with a magnetizable abutment disk according to FIGS. 3a and 3b,
(6) FIGS. 5a-5c show other exemplary embodiments of the magnetizable disk according to the invention,
(7) FIG. 6 shows a pressure-regulation valve furnished with a magnetizable abutment disk according to the invention.
DETAILED DESCRIPTION
(8) FIG. 1 shows an exemplary embodiment of an electromagnetic valve as used many times in fuel injectors. The electromagnetic valve consists of a casing 1, 2, the lower portion 1 of which is in a single piece with the body of the fuel injector. As a variant, the electromagnetic valve may also form an independent module installed on a fuel injector or incorporated into a fuel injector. The transverse face of the lower portion 1 of the casing comprises a pot-shaped cavity delimited by spacers 11 parallel to the longitudinal axis of the electromagnetic valve. This pot-shaped cavity accommodates two other parallel spacers 12 made on the transverse face of the upper portion 2 of the casing, these spacers being engaged so as to thus form a chamber 10. The bottom side of the chamber 10 comprises a cavity accommodating a valve part 5. The side of the lower portion 1 of the casing comprises a high-pressure connection 6 connected to a channel 13 with an annular volume 14. The annular volume 14 is delimited by the lower portion 1 of the casing and by the valve part 5 and this volume is linked via a throttled inlet passage 15 to a control chamber 16. The control chamber 16 is delimited by the valve part 5 and by a valve piston 17. Opposite to the transverse face of the valve piston 17 delimiting the control chamber 16, the valve part comprises a throttled outlet passage 18. This throttled outlet passage 18 is closed by a ball forming a valve 19 when the electromagnetic valve is not actuated. The ball forming the valve 19 is locked in its position by means of a ball guide 20 and by the force developed by a valve spring 23, by means of a valve closure member 21 in order to be pushed against the valve part 5 so that no fuel can leave the control chamber 16 by passing through the throttled outlet passage 18. The ball guide 20 and the ball forming the valve 19 can also be produced on the valve closure member 21 as an alternative. Similarly, it is possible to envisage a guidance of one side of the valve closure member 21 with a half-ball in place of the valve ball 19, which removes any additional guidance 20 of the ball. As a variant, the electromagnetic valve can also be a pressure-balanced electromagnetic valve.
(9) The chamber 10 houses an electromagnet 24, 25 consisting of a magnetic core or of the yoke 24 and of an electromagnetic coil 25. The electromagnetic coil 25 comprises a contact pin 27 coming out of the upper portion 2 of the casing in a sealed manner with respect to the outside at the chamber 10 by means of a sealing element 26. The contact pin 27 is connected to a contact element 8 which, with the contact pin 27, forms an electric contact 8, 27 of the solenoid valve. To isolate the electric contact 8, 27, the upper portion 2 of the casing is closed by a cap 3 preferably made in the form of an injected cap. The upper portion 2 of the casing comprises at its center a drill hole 28 receiving a sleeve 9 serving as an abutment to the valve spring 23 and making it possible to adjust the prestress of the valve spring. As a variant, the spring can be adjusted for example by using appropriate adjustment shims. The sleeve 9 makes it possible to divert the leakages from the solenoid valve by passing through another hood 4 in the return 7.
(10) When the electromagnet 24, 25 is controlled by the electric contact 8, 27, a magnetic force is developed between the yoke 24 and the armature 22. This magnetic force attracts the armature 22 which interacts directly with the valve closure member 21 and thus releases the throttled outlet passage 18 of the valve part; this allows the injector to inject fuel in a known manner. As a variant, the injector closure member 21 can be formed on the armature 22.
(11) To prevent the armature 22 sticking to the yoke 24, as shown in FIG. 2, on the outside the armature 22 has a collar 32 against which the armature butts the spacer 12 of the upper portion 2 of the casing when the electromagnetic valve is controlled. It thus forms a residual air gap 33 between the yoke 24 and the armature 22. This residual air gap prevents the armature 22 sticking magnetically to the yoke 24.
(12) As a variant, also known are spacing elements, made of a non-magnetic or non-magnetizable material, installed between the armature 22 and the yoke 24 in order to prevent magnetic sticking.
(13) FIG. 3a shows a first exemplary embodiment of the electromagnetic valve according to the invention furnished with a magnetic or magnetizable abutment disk 28, in particular a ferromagnetic shim. The abutment disk is placed between the armature 22 and the inner pole 29 of the yoke 24.
(14) In operation of the electromagnetic valve, when closed, there is a gap between the electromagnetic armature 22 and the bearing shim 28 or between the abutment disk 28 and the yoke 24. Usually, this distance defines the maximum travel of the electromagnetic valve. In the operating position of the electromagnetic valve when completely open, the armature 22 and the abutment disk 28 and the abutment disk 28 and the yoke 24 are at least in contact via surface portions. Therefore, when the electromagnetic valve is open, there is an uninterrupted magnetic flux between the inner pole 29 of the yoke 24 and the armature 22 through the abutment disk 28. This uninterrupted magnetic flux gives to the electromagnetic valve according to the invention a higher magnetic force even for an identical space requirement. The contact surfaces that remain between the yoke 24 and the abutment disk 28 or between the abutment disk 28 and the armature 22 are then small enough so that, when the electromagnet (24, 25) has finished being powered, the residual magnetic force is significantly less than the force of the valve spring 23; this allows a rapid and clean break between the armature 22 and the bearing shim 28 or between the bearing shim 28 and the yoke 24.
(15) FIG. 3b shows another exemplary embodiment of the electromagnetic valve according to the invention comprising a magnetic or magnetizable, particularly ferromagnetic, abutment disk 28. The abutment disk 28 is placed between the armature 22 and the outer pole 30 of the yoke 24. As a variant, the abutment disk 28 can also be moved outwards in the direction of a portion of casing 1, 2 as shown in FIG. 3c; therefore, the portion of the transverse surface of the outer pole 30 turned towards the inner pole no longer covers it so that the bearing shim 28 is applied via its transverse face away from the yoke against the armature 22 and via its transverse face turned towards the armature 24, it overlaps the casing 1, 2 and in the operating position, with the solenoid valve open, and it rests against the spacer 12 of the upper portion 2 of the casing and against the yoke 24. As a variant, the abutment disk 28 may also be shaped to completely cover the outer pole 30 and protrude beyond it in the direction of the casing 1, 2. This arrangement also offers the possibility of diverting the abutment forces to a very large degree in order to pass beside the yoke 24 through the spacer 12, which reduces the mechanical stress of the yoke 24.
(16) FIG. 4a shows an advantageous development of the exemplary embodiment shown in FIG. 3a according to which the abutment disk 28 is placed, in the open operating state of the electromagnetic valve, between the inner pole 29 of the yoke 24 and the armature 22; the abutment disk 28 however covers only a fraction of the surface of the inner pole 29 of the yoke 24 along the direction of movement of the armature 22. In this context, the notion of overlap corresponds to the projection of the point of greatest extension of the abutment disk 28 on the surface of the yoke 24. This arrangement results in a denser combination of the magnetic-field lines in the portions of the yoke 24, which prevents an early magnetic saturation in the partial zones of the yoke 24 and generally results in a higher maximum magnetic force. In addition, the zone of the contact surfaces between the armature 22, the abutment disk 28 and the yoke 24 is thus reduced, which similarly reduces the risk of inconvenient magnetic sticking.
(17) Such an abutment disk 28 with a small zone of overlap can also be placed between the outer pole 30 of the yoke 24 and the armature 22 and thus pass beyond the outer pole so that the abutment disk rests at least partly against the spacer 12 of the upper portion 2 of the casing.
(18) FIG. 5a shows another exemplary embodiment of the abutment disk 28. In this example, the contact surface between the abutment disk 28 and the yoke 24 or between the abutment disk 28 and the armature 22 is reduced by openings preferably in the form of circular orifices 34. As a variant, these orifices 34 obtained simply by cutting out on a press from the abutment disk 28 may also have any other geometric shape, in particular an oval, rectangular, hexagonal, diamond or star shape. These orifices 34 may also serve as a variant for the drill hole for access to the contact pins 27 for the connection of the coil 25 of the electromagnet 24, 25. Moreover, the abutment disk 28 comprises a central drill hole 36 in which the member 21 for closing off the electromagnetic valve moves.
(19) FIG. 5b shows as a variant an abutment disk having many orifices 34; the bearing surface of the abutment disk 28 against the armature 22 and against the yoke 24 is yet more reduced, which further reduces the residual magnetic sticking.
(20) FIG. 5c shows another preferred exemplary embodiment of the abutment disk 28; in addition to the circular orifices 34, this disk also comprises another opening in the form of an elongated slot 35. This slot is preferably centered in the abutment disk 28. This means that the slot preferably passes through the axis of the abutment disk 28 in order to divide the abutment disk 28 into two halves of the same dimensions and accordingly reduce the eddy currents in the abutment disk 28, which improves the performance of the establishment and reduction of the magnetic forces in the electromagnetic valve.
(21) FIG. 4b shows an advantageous development of the exemplary embodiment of FIG. 3b; this example comprises an abutment disk 28 installed between the outer pole 30 of the yoke 24 and the armature 22, completely covering the surface of the outer pole 30 and/or protruding beyond the transverse surface of the outer pole 30. Overlapping in this instance means the projection of the point of greatest extension of the abutment disk over the transverse face of the yoke. This arrangement of the abutment disk 28 makes it possible to spread the magnetic-field lines more widely in the portions of the yoke 24, which maximizes in particular the magnetic flux between the yoke 24, the abutment disk 28 and the armature 22. In addition, it makes it possible to reduce the mechanical stresses exerted on the yoke 24 at the time of the impact of the armature 22, because the mechanical forces are directed by the abutment disk 28 which protrudes into the casing 1, 2, particularly into the upper portion 2 of the casing. Such an abutment disk 28, which covers a larger surface than the surface of the adjacent pole 29, 30 of the yoke 24, can also be installed between the armature 22 and the inner pole 29 in order to optimize the magnetic flux in this zone or to carry away the mechanical forces at the time of the impact of the armature 22 to the casing 1, 2, particularly to the upper portion 2 of the casing.
(22) FIG. 6 is a longitudinal section of an electromagnetic valve for regulating pressure in a high-pressure fuel accumulator comprising an abutment disk 28 according to the invention. The use of a magnetized or magnetizable abutment disk 28 in the electromagnetic valve reduces the air gap between the armature 22 and the yoke 24 without in parallel also reducing the hydraulic air gap between the armature 22 and the yoke. This increases the magnetic force developed by the electromagnetic valve without reducing the weakness of the electromagnetic valve with respect to the particles. Increasing the magnetic force increases the force for holding the closure member 21 of the electromagnetic valve and thus produces a higher seal of the electromagnetic valve. In addition, the upper portion 2 of the casing can accommodate an insert 37 limiting the travel of the armature 22.
COMPONENT LIST
(23) 1 Lower portion of the casing 2 Upper portion of the casing 5 Valve part 6 High-pressure connection 10 Chamber 11 Spacers 12 Spacers 13 Channel 14 Annular volume 15 Throttled inlet passage 16 Control chamber 17 Valve piston 18 Throttled outlet passage 19 Ball forming valve 20 Ball guide 21 Closure member 22 Armature 23 Valve spring 24 Yoke 25 Electromagnetic coil 26 Sealing element 27 Contact pin 28 Abutment disk 29 Inner pole 30 Outer pole 34 Orifice 35 Elongated slot 36 Central drill hole 37 Insert
