High-pressure fuel pump

Abstract

High-pressure fuel pump (10) for pressurising a fuel with high pressure, comprising an electromagnetic valve arrangement (16), wherein the electromagnetic valve arrangement (16) has an electromagnetic drive (26) for driving a valve element (18) which opens and closes the electromagnetic valve arrangement (16) during operation and which is designed as a diaphragm, wherein the electromagnetic drive (26) comprises: - a coil device (36) with a coil (34) for inducing a magnetic flux in the electromagnetic drive (26), and - a magnetically conductive housing (48) surrounding the coil device (36), wherein the housing (48) is designed as a cylindrical tube section (52) which is chamfered at at least one end (56) of its inner circumference (58) and which has a magnetically conductive disc (54) at the at least one end (56) for closing the tube section (52), wherein the magnetically conductive disc (54) is pressed into the inner circumference (58) of the pipe section (52) for sealing the pipe section (52).

Description

[0001] The invention relates to a high-pressure fuel pump with an electromagnetic valve arrangement in which a valve element can be opened and closed during operation of the valve arrangement via an electromagnetic drive.

[0002] High-pressure fuel pumps in fuel injection systems of internal combustion engines are used to pressurize a fuel to high pressure. For example, the pressure in gasoline engines ranges from 150 bar to 400 bar and in diesel engines from 1500 bar to 2500 bar. The higher the pressure that can be generated in the respective fuel, the lower the emissions generated during fuel combustion in a combustion chamber, which is particularly advantageous given the increasing desire to reduce emissions.

[0003] In the fuel injection system, valve arrangements can be provided at various positions along the path that the fuel takes from a tank to the respective combustion chamber, for example as an inlet valve on a high-pressure fuel pump that pressurizes the fuel, but also, for example, as a relief valve at various positions in the fuel injection system, for example on a common rail that stores the pressurized fuel before it is injected into the combustion chambers.

[0004] Electromagnetic valve assemblies, such as solenoid valves, are often used for this purpose. These valves can be opened and closed by a magnetic force. To induce this magnetic force, a coil is usually provided within a coil assembly, and the coil assembly is housed in a housing. This housing is advantageously designed to conduct the magnetic flux induced by the coil.

[0005] Until now, housings have been used for this purpose, in which all elements of the coil assembly must be precisely accommodated. Therefore, the housing must be manufactured with very tight tolerances and therefore as an expensive turned part. This makes the valve assembly relatively expensive overall.

[0006] DE 41 22 983 A1 describes a magnet for solenoid valves in which a coil body of a winding directly forms a holder for a contact part for contacting the winding from the outside.

[0007] DE 42 22 239 A1 discloses a housing for a magnetic coil, which is formed from a tube and a formation of the wall of the tube provided transversely to a longitudinal axis of the tube.

[0008] DE 195 04 185 A1 describes an electromagnet with a sleeve-shaped magnet housing with an integrated valve housing, wherein the pole core is formed as a separate part and is enclosed by the sleeve-shaped magnet housing, wherein the magnet housing has inward-directed beads evenly distributed over the circumference as axial support for the pole core in the direction of the electrical windings.

[0009] DE 10 2012 214 624 A relates to a pole tube for an actuator device with at least one magnet. To improve the pole tube for an actuator device with at least one magnet, the pole tube is combined with at least one coil carrier.

[0010] DE 199 63 718 B4 describes a magnetic coil with a winding housed in a magnet pot. To improve the thermal coupling of the winding to the environment, the winding is formed from a wire, in particular self-bonding wire, provided with a coating that holds the winding together. A method for producing a magnetic coil according to the invention is characterized in that the winding is inserted into the magnet pot and encapsulated with a low-viscosity potting material.

[0011] DE 10 2008 008 761 A1 relates to an actuating magnet for a solenoid valve for a non-magnetic pressure pipe, which is connected to at least one pole core in which an armature is formed and onto which at least two annular sleeves with a ring lying therebetween are placed, the region of which is arranged in a gap formed between the armature and the pole core.

[0012] The object of the invention is to propose a new, simpler and more cost-effective high-pressure pump with an electromagnetic valve arrangement.

[0013] This object is achieved with a high-pressure pump having the features of claim 1.

[0014] Advantageous embodiments of the invention are the subject of the dependent claims.

[0015] A high-pressure fuel pump for pressurizing a fuel with high pressure has an electromagnetic valve assembly. The electromagnetic valve assembly has an electromagnetic drive for driving a valve element that opens and closes the valve assembly during operation. The electromagnetic drive comprises a coil device with a coil for inducing a magnetic flux in the electromagnetic drive and a magnetically conductive housing surrounding the coil device. The valve element is designed as a diaphragm. The housing is designed as a cylindrical tube section that is chamfered at at least one end of its inner circumference and that has a magnetically conductive disc at at least one end for closing the tube section.

[0016] The magnetic circuit of an electromagnetic valve assembly, such as a digital valve used in a high-pressure fuel pump, comprises several magnetically conductive components and a coil that induces the magnetic flux in the magnetic circuit. To close the magnetic circuit and conduct the magnetic field lines, the coil is surrounded by magnetically conductive components. Previously, the coil was surrounded by magnetically conductive components, then overmolded with plastic, and the entire assembly was then pressed into a magnetically conductive housing. To enable this press-fitting, the housing used had to be designed with very tight tolerances and therefore manufactured as an expensive turned part.

[0017] However, it is now proposed to design the housing as a simple cylindrical tube section and to provide a magnetically conductive disc that closes the tube section. Thus, the magnetically conductive volumes are divided into individual sections, allowing the entire electromagnetic valve assembly to be manufactured as an assembly with simple components, performing the same function as before, but at a lower cost to manufacture.

[0018] If the magnetically conductive disc is preferably designed as a stamped part and the pipe section is advantageously designed as, for example, a drawn, cut-to-length and chamfered component, the housing previously designed as a cost-intensive turned part can advantageously be replaced by an inexpensive pipe section and an inexpensive stamped part.

[0019] A pipe section is to be understood as a part of a pipe with a wall that is essentially cylindrical, wherein the pipe section is essentially hollow within this wall.

[0020] The magnetically conductive disc is pressed into the inner circumference of the pipe section to seal it. Advantageously, the coil device is pressed into the inner circumference of the pipe section from one end of the pipe section, opposite the magnetically conductive disc.

[0021] This advantageously allows the housing to be designed as a tube with a chamfered end, into which the magnetically conductive disc is pressed. The tube section and the disc are both magnetically conductive. The remaining components of the coil assembly can be pressed in from the other side as usual. This allows for a simple manufacturing process for the electromagnetic valve assembly.

[0022] Particularly preferably, the pipe section is chamfered at two opposite ends of its inner circumference.

[0023] It is particularly preferred if the pipe section has a magnetically conductive disc at each of two opposite ends for closing the pipe section.

[0024] Preferably, the magnetically conductive discs are pressed into the inner circumference of the pipe section to seal the pipe section and to ensure effective magnetic flux transfer between the parts.

[0025] In this possible variant, the magnetic circuit is constructed from the pipe section and two discs that are pressed into the pipe section. To facilitate pressing in, it is advantageous if the pipe section is chamfered at two ends.

[0026] In an advantageous embodiment, the coil device comprises a magnetically conductive yoke, a winding body and a winding wire for forming the coil, as well as at least one electrical connection, which are jointly enclosed by a plastic overmold. The yoke, together with the remaining components of the coil device, is integrated within the plastic overmold and is advantageously pressed into the inner circumference of the tube section together with the other components, for example, from a magnetically conductive disc opposite one another.

[0027] The advantage of the first variant—yoke within a plastic overmolding—is that a turned part, namely the commonly used housing, can be replaced with a low-cost piece of tubing and a low-cost stamped part with minimal effort. The plastic overmolding in which the yoke is integrated does not need to be modified compared to the conventional process.

[0028] Alternatively, however, it is also possible for the coil device to have a magnetically conductive yoke, a winding body and a winding wire for forming the coil, as well as at least one electrical connection, wherein the winding body, the winding wire and the at least one electrical connection are jointly surrounded by a plastic overmold, wherein the yoke is formed by one of the two opposing magnetically conductive discs for closing the tube section.

[0029] This second variant has the advantage that the yoke rests on the plastic overmolding and does not need to be overmolded by the plastic. Due to the different thermal expansion coefficients of the plastic of the plastic overmolding and the material from which the yoke is made, there is a risk of potential leakage paths between the plastic and the yoke, which, in the worst case, could lead to damage to the component. This can be prevented by placing the yoke outside the plastic overmolding.

[0030] It is advantageous if the pipe section has a lateral recess in order to be able to insert or press the coil device into the pipe section.

[0031] Since the electrical connections usually protrude laterally perpendicular to a longitudinal axis of the coil device, it is advantageous if a plug device formed by these electrical connections and the associated plastic overmolding can protrude laterally from the housing formed by the tubular section. Therefore, it is advantageous if the tubular section has a lateral recess for this purpose.

[0032] Preferably, the coil device with the magnetically conductive housing surrounding it is pushed onto an actuator arrangement of the electromagnetic drive, wherein the actuator arrangement has a movable armature and a fixed pole piece.

[0033] It is advantageous in manufacturing if the magnetic circuit of the electromagnetic valve assembly, which comprises an armature, a pole piece, and the coil assembly, is divided into the two elements that conduct the magnetic flux—the armature and the pole piece—and the coil assembly that induces the magnetic field. The armature and pole piece can then be fixed in their final position, and the coil assembly can be subsequently moved into position. For this purpose, it is advantageous if the coil assembly has a recess inside it, through which it can be easily pushed onto the area in which the armature and pole piece, along with a housing enclosing them, are already located.

[0034] The electromagnetic valve arrangement is advantageously designed as an inlet valve for admitting the fuel into a pressure chamber of the high-pressure fuel pump.

[0035] Advantageous embodiments of the invention are explained in more detail below with reference to the accompanying drawings, in which: Fig. 1 a longitudinal sectional view of a high-pressure fuel pump with an electromagnetic valve arrangement as an inlet valve for admitting fuel into a pressure chamber of the high-pressure fuel pump; Fig. 2 a longitudinal sectional view of a coil device of the electromagnetic valve arrangement of Fig. 1 in a first embodiment; and Fig. 3 a longitudinal sectional view of a coil device of the electromagnetic valve arrangement from Fig. 1 in a second embodiment.

[0036] Fig. Figure 1 shows a longitudinal section of a high-pressure fuel pump 10, which has a pressure chamber 12 (shown only rudimentarily) in which a fuel is pressurized to high pressure. To admit the fuel into the pressure chamber 12, an inlet valve 14 is provided. This valve is designed as a digital solenoid valve and thus forms an electromagnetic valve arrangement 16.

[0037] The electromagnetic valve assembly 16 comprises a valve element 18, which interacts with a valve seat 20 to open and close the electromagnetic valve assembly 16 as needed during operation. In the present embodiment, the valve element 18 is designed as a diaphragm and is connected to a valve pin 24, which pushes the valve element 18 toward a stop 22 to open the electromagnetic valve assembly 16.

[0038] The provision of the valve element 18 and the valve pin 24 shown is only an exemplary embodiment.

[0039] The valve pin 24 is moved by an electromagnetic drive 26 along a longitudinal axis 28 of the valve pin 24 to move the valve element 18 in order to lift the valve element 18 from the valve seat 20 or to relieve it so that it rests on the valve seat 20 again.

[0040] The electromagnetic drive 26 comprises a fixed pole piece 30 and a movable armature 32 which is connected to the valve pin 24.

[0041] Pole piece 30 and armature 32 are components of a magnetic circuit of the electromagnetic valve assembly 16, which additionally includes a coil 34 arranged symmetrically to the longitudinal axis 28 around pole piece 30 and armature 32. The coil 34 is arranged within a coil assembly 36, which includes further components, such as a sleeve 66, to close the magnetic circuit and conduct the magnetic field lines. These additional components are therefore designed as magnetically conductive components.

[0042] During operation of the electromagnetic valve arrangement 16, the coil 34 is energized, whereby the movable armature 32 moves towards the pole piece 30 and thus presses the valve pin 24 along the longitudinal axis 28 onto the valve element 18 so that it lifts off the valve seat 20.

[0043] Pole piece 30 and armature 32 therefore jointly form an actuator assembly 38, with which the valve pin 24 can be moved along the longitudinal axis 28. The actuator assembly 38 and the coil assembly 36 are separate components. This makes it possible to first install the actuator assembly 38 in the high-pressure fuel pump 10 and then subsequently slide the coil assembly 36 onto this actuator assembly 38 and align it. For this purpose, the coil assembly 36 has a central recess 40 through which it can be slid onto the actuator assembly 38.

[0044] The coil device 36 is shown in more detail in the Fig. 2 and Fig. 3 in two possible embodiments.

[0045] The coil device 36 includes elements conducting the magnetic circuit, such as the coil 34, which is formed by a winding wire 42 wound on a winding body 44, a magnetically conductive yoke 46, and a magnetically conductive housing 48, which is also magnetically conductive and surrounds the coil device 36. In addition, the coil device 36 includes at least one electrical connection 50, via which the coil 34 can be supplied with current from outside.

[0046] As in Fig. 2 and Fig. 3, the housing 48 is designed as a simple cylindrical tube section 52 into which the coil device 36 with all its associated components is inserted.

[0047] To close the pipe section 52, at least one disc 54 is provided, which is pressed into an inner circumference 58 of the pipe section 52 at one end 56 of the pipe section 52. To facilitate the pressing of this disc 54 into the inner circumference 58 of the pipe section 52, the pipe section 52 is chamfered at this end 56 on the inner circumference 58.

[0048] Both the tube section 52 and the disc 54 are made of magnetically conductive materials and are thus suitable for closing the magnetic circuit and conducting the magnetic field lines induced by the coil 34.

[0049] In the first embodiment of the coil device 36, shown in Fig. 2, all components of the coil device 36 are housed in a common plastic overmolding 60, meaning that the yoke 46 is also arranged within this plastic overmolding 60. The coil device 36 is pressed into the tube section 52 from one end 56, which is opposite the end 56 with the disc 54.

[0050] In a second embodiment, shown in Fig. 3, the yoke 46 is not arranged in the common plastic overmolding 60, but rather two magnetically conductive discs 54 are provided, which are pressed into the inner circumference 58 of the tube section 52 at opposite ends 56 of the tube section 52. The coil device 36 without a yoke within the plastic overmolding 60 is arranged between these two discs 54. The yoke 46 is therefore formed by one of the two opposing magnetically conductive discs 54.

[0051] In order to facilitate the pressing of components into the pipe section 52, it is advantageous if the inner circumference 58 of the pipe section 52 is chamfered not only at one end 56, but at both ends 56.

[0052] The tubular section 52 has a recess 62 through which a plug region 64 of the coil device 36 can extend into the surrounding area. The at least one electrical connection 50, via which the coil 34 is supplied with current to induce the magnetic circuit, is arranged in this plug device.

Claims

[1] High-pressure fuel pump (10) for pressurising a fuel with high pressure, comprising an electromagnetic valve arrangement (16), wherein the electromagnetic valve arrangement (16) has an electromagnetic drive (26) for driving a valve element (18) which opens and closes the electromagnetic valve arrangement (16) during operation and which is designed as a diaphragm, wherein the electromagnetic drive (26) comprises: - a coil device (36) with a coil (34) for inducing a magnetic flux in the electromagnetic drive (26), and - a magnetically conductive housing (48) surrounding the coil device (36), wherein the housing (48) is designed as a cylindrical tube section (52) which is chamfered at at least one end (56) of its inner circumference (58) and which has a magnetically conductive disc (54) at the at least one end (56) for closing the tube section (52), wherein the magnetically conductive disc (54) is pressed into the inner circumference (58) of the pipe section (52) for sealing the pipe section (52). [2] High-pressure fuel pump (10) according to claim 1, characterized by that the at least one magnetically conductive disc (54) is designed as a stamped part and / or that the pipe section (52) is designed as a turned part or as a drawn, cut-to-length and chamfered component. [3] High-pressure fuel pump (10) according to one of claims 1 or 2, characterized by that the coil device (36) is pressed into the inner circumference (58) of the pipe section (52) from one end (56) of the pipe section (52) opposite the magnetically conductive disc (54). [4] High-pressure fuel pump (10) according to one of claims 1 to 3, characterized by that the pipe section (52) is chamfered at two opposite ends (56) of its inner circumference (58). [5] High-pressure fuel pump (10) according to one of claims 1 to 4, characterized by that the pipe section (52) has a magnetically conductive disc (54) at each of two opposite ends (56) for closing the pipe section (52), wherein the magnetically conductive discs (54) are pressed in particular into the inner circumference (58) of the pipe section (52) for sealing the pipe section (52). [6] High-pressure fuel pump (10) according to claim 5, characterized byin that the coil device (36) has a magnetically conductive yoke (46), a winding body (44) and a winding wire (42) for forming the coil (34), as well as at least one electrical connection (50), which are jointly surrounded by a plastic injection molding (60), or in that the coil device (36) has a magnetically conductive yoke (46), a winding body (44) and a winding wire (42) for forming the coil (34), as well as at least one electrical connection (50), wherein the winding body (44), the winding wire (42) and the at least one electrical connection (50) are jointly surrounded by a plastic injection molding (60), wherein the yoke (46) is formed by one of the two opposing magnetically conductive disks (54) for closing the tube section (52). [7] High-pressure fuel pump (10) according to one of claims 1 to 6, characterized bythat the tube section (52) has a lateral recess (62) for inserting the coil device (36). [8] High-pressure fuel pump (10) according to one of claims 1 to 7, characterized by that the coil device (36) with the magnetically conductive housing (48) surrounding it is pushed onto an actuator arrangement (38) of the electromagnetic drive (26), which has a movable armature (32) and a fixed pole piece (30). [9] High-pressure fuel pump (10) according to one of claims 1 to 8, wherein the electromagnetic valve arrangement (16) is designed as an inlet valve (14) for admitting the fuel into a pressure chamber (12) of the high-pressure fuel pump (10).

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