Fuel injector, solenoid assembly and method for manufacturing a fuel injector

Abstract

The invention relates to a fuel injector (1) extending along an injector axis (A) from a proximal side (1.1) and a distal side (1.2). In order to provide an improved design for plastic components of the fuel injector, the invention provides that the fuel injector (1) comprises: - a solenoid unit (11) comprising an excitation coil (15) in a solenoid housing (12), the solenoid unit (11) circumferentially surrounding a distal bore (32) around the injector axis (A); - a cable element (16) connected to the excitation coil (15); - a contiguous plastic main body (20) comprising: a solenoid portion (21) molded onto the solenoid unit (11); a cable portion (22) extending proximally from the solenoid portion (21) and molded onto the cable element (16); and a retainer portion (26) disposed proximally from the solenoid unit (11) and circumferentially surrounding a proximal bore (33) around the injector axis (A); and - an axially extending injector body (40) adapted to guide fuel from the proximal side (1.1) to a nozzle (47) at the distal side (1.2), the injector body (40) being received in the distal bore (32) and the proximal bore (33), wherein the retainer portion (26) comprises two half annular arch portions (27, 28) which are axially offset and disposed on opposite sides of an axial main body plane (B) relative to each other and connected at least adjacent to the main body plane (B) by two axially extending connection portions (29, 30) on opposite sides of the proximal bore (33).

Description

Technical Field

[0001] The present invention relates to a fuel injector, a solenoid assembly for a fuel injector, and a method for manufacturing a fuel injector. Background Technology

[0002] Fuel injectors are used in internal combustion engines to inject fuel into the flow path of an intake manifold, for example, before the cylinder intake valve, or directly into the combustion chamber of the engine cylinder. According to a known design, the injector includes an injector body having an internal channel for guiding fuel from a proximal side to a nozzle at a distal side, and the injector body contains movable parts of the injector, such as a pin for closing the nozzle and an armature for actuating the pin. Furthermore, the injector body typically includes at least one spring for biasing the pin and / or armature toward a position that typically corresponds to the nozzle being closed. The armature is actuated by a magnetic field generated by an excitation coil or solenoid surrounding the injector body and enclosed in a solenoid housing. The coil and solenoid housing are part of a solenoid assembly and are molded and overmolded with a plastic material. The solenoid assembly includes a plastic body that provides electrical insulation and mechanical protection for the coil-like electrical components and the cables connected thereto. In addition, the plastic body includes a cylindrical retainer portion with a central hole in which the ejector body (or at least a portion thereof) is housed. Remote from the plastic body, the central hole is defined by a coil spool and a flux washer, the flux washer being positioned proximal to the spool and used to guide the magnetic flux when the coil is energized. Finally, the plastic body typically includes a collar surrounding a cavity in which the contact portion of the cable is disposed, thereby providing a receptacle in which the contact portion is protected.

[0003] It is known that solenoid assemblies are manufactured from a plastic body before the injector body is inserted into the center bore. While most of the shape of the plastic body can be defined by two halves of a molding tool that closes around the solenoid housing, the cavities of the center bore and socket (which represent undercut areas relative to the molding process) need to be defined by additional movable sliders or cores that move forward before molding the plastic material and then retract to allow removal of the solenoid assembly from the molding tool. Typically, three cores are required: one core is introduced from the distal side into the center bore and flux washer within the spool, a second core moves from the proximal side to contact the flux washer to define the proximal portion of the center cavity, and a third core is used to define the cavity of the socket. Using these three cores makes the manufacturing process complex and expensive.

[0004] Another problem is that the inner radius of the flux washer corresponds to the outer radius of the injector body, and the second core will move to make sealing contact with the proximal edge of the flux washer, so its outer radius must be larger than the outer radius of the injector body. Therefore, the central cavity of the solenoid assembly also has a larger radius than the injector body and cannot provide a shape fit with the injector body. Consequently, additional elements such as support rings and sealing rings must be introduced into the gap between them, further complicating the manufacturing process and incurring additional costs. Summary of the Invention

[0005] Therefore, the object of this invention is to provide an improved design for the plastic components of fuel injectors.

[0006] This problem is solved by the fuel injector according to the invention, the solenoid assembly according to the invention, and the method for manufacturing the fuel injector according to the invention.

[0007] This invention provides a fuel injector. More specifically, it is a fuel injector for an internal combustion engine. The fuel injector extends from a proximal side to a distal side along the injector axis. The terms "distal" and "proximal" refer to the overall flow direction of fuel within the injector toward the distal side. Typically, the distal side is the side of the injector facing the engine. At least some portions of the injector may be symmetrical with respect to the injector axis, but typically, the injector axis only defines a reference frame, thereby implicitly defining the axial, radial, and tangential directions.

[0008] A fuel injector includes a solenoid unit, which in turn includes an excitation coil within a solenoid housing. The solenoid unit circumferentially surrounds a distal bore around the injector axis. The excitation coil, or solenoid, is configured to generate a magnetic field that actuates the movable parts of the injector, as will be discussed below. It is typically arranged circumferentially around the injector axis. A magnetic field is generated when current flows through the excitation coil. Although the windings of the excitation coil are typically individually insulated to avoid any short circuits, the excitation coil as a whole is usually encased in a plastic material. The coil is typically mounted on a spool, which is, of course, positioned radially inside the coil. The solenoid housing, made of metal, typically has a generally cylindrical portion that surrounds and is spaced apart from the excitation coil. The solenoid unit circumferentially surrounds a distal bore, which may also be referred to as a distal through-hole, and passes through a continuous axial bore of the solenoid unit.

[0009] The fuel injector also includes a cable element connected to the excitation coil. The cable element is, of course, conductive and electrically connected to the coil. Therefore, it is adapted to supply a voltage to the coil, thereby generating a current in the coil, which in turn generates the aforementioned magnetic field. To provide a closed circuit, the cable element typically comprises two separate electrical conductors. The term "cable element" is not interpreted in any limiting way herein. A cable element can be a cable comprising one or more wires, but it can also comprise different kinds of electrical conductors. Each conductor of the cable element may include a dedicated insulator, such as a plastic sheath or an insulating varnish applied to its surface. As will be explained below, such a dedicated insulator is not necessary because the cable element is covered by a plastic material.

[0010] The fuel injector also includes a coherent plastic body comprising: a solenoid portion molded onto a solenoid unit; a cable portion extending proximally from the solenoid portion and molded onto a cable element; and a retainer portion disposed proximally from the solenoid unit and circumferentially surrounding a proximal orifice around the injector axis. The plastic body is coherent, meaning it has a continuous form and is made as a single piece. It is made of a plastic material, which can typically be any polymer material, particularly thermoplastics suitable for injection molding. Therefore, the plastic body is typically formed by injection molding. It includes a solenoid portion molded onto the solenoid unit. Typically, the solenoid portion is at least partially disposed within either the solenoid unit or the solenoid housing. In other words, during the molding process, plastic material flows into or is pressed into the solenoid unit. Besides fixing the relative positions of the elements of the solenoid unit (such as the excitation coil and the solenoid housing), the solenoid portion provides electrical insulation for the excitation coil.

[0011] In addition, the plastic body includes a cable portion extending proximally relative to the solenoid portion (i.e., in a proximal direction relative to the injector axis, but not necessarily parallel to the injector axis). Typically, it is directly connected to the solenoid portion. It is molded onto the cable element such that the cable element is enclosed in the plastic material. If the cable element comprises several conductors without dedicated insulation, it should be understood that the plastic material is molded such that each conductor is individually covered to provide insulation between the conductors. Besides insulating the cable element (or its individual conductors), the cable portion also mechanically stabilizes the cable element and protects it from mechanical damage.

[0012] Furthermore, the plastic body includes a retainer portion, which may also be referred to as a cage portion. This retainer portion is positioned proximally from the solenoid unit, and typically also proximally from the solenoid portion, i.e., closer to the proximal side relative to the axial direction defined by the injector axis. The retainer portion circumferentially surrounds a proximal bore around the injector axis. The proximal bore (also referred to as a proximal through-hole) passes through the retainer portion in the axial direction. Accordingly, the retainer portion circumferentially surrounds the proximal bore and forms the boundary of the bore in the radial direction. Overall, the retainer portion has a closed structure along the tangential direction. Due to the coherent structure of the plastic body, the solenoid portion, the cable portion, and the retainer portion are at least indirectly connected to each other.

[0013] The components of the fuel injector mentioned so far—the solenoid unit, the cable element, and the plastic body—are parts of the solenoid assembly of the fuel injector. The solenoid assembly is bonded together by the molded plastic body, therefore it cannot be disassembled without damaging the plastic body.

[0014] Furthermore, the fuel injector includes an axially extending injector body adapted to guide fuel from a proximal side to a nozzle at a distal side, the injector body being received in both a distal and a proximal port. The injector body may include several axially oriented components connected in a fluid-tight manner to prevent any fuel leakage. Typically, the injector body (which may in particular be symmetrical with respect to the injector axis) is adapted to receive fuel through a corresponding port at the proximal side to guide the fuel (through at least one internal channel) to the distal side where the nozzle is located. Furthermore, fuel can be discharged through the nozzle in a controlled manner. Fuel discharge is typically controlled by a pin having an axially extending pin shaft and being axially movable between an open and closed position. In some embodiments, a ball is fixed to the distal side of the pin, and the ball engages a nozzle seat at the distal side of the housing, thereby closing the nozzle. When the movement of the pin is initiated by a change in a magnetic field generated by an excitation coil, the magnetic field typically does not directly drive the pin. Instead, the injector body typically includes an armature that is axially movable between a proximal and a distal position. For example, the armature is moved to a proximal position by a magnetic field, while the armature is moved to a distal position by spring force, wherein at least one movement may be assisted by fuel pressure and / or gravity. Typically, both the pin and the armature are biased toward a position by a dedicated spring, such as a position corresponding to the closed position.

[0015] Typically, the injector body also includes pole pieces disposed near the armature. These pole pieces are made of a ferromagnetic material. The function of the pole pieces is to be magnetized when the excitation coil generates a magnetic field (and, for example, to attract the armature disposed distally). The magnetic field is shaped and / or enhanced compared to the absence of pole pieces. It should be understood that there may be more than one pole piece, or a pole piece may consist of several parts. The pole pieces may be arranged circumferentially around the injector axis and may have a ring shape. The axial position of the pole pieces may at least partially correspond to the axial position of the excitation coil.

[0016] The injector body is received in both a distal and a proximal bore. In other words, it passes through or through these bores, thus being surrounded by the retaining portion of the plastic body and the solenoid unit, respectively. While the manner in which the injector body is attached to the solenoid assembly is not limited, the injector body can be retained at least partially in at least one bore, particularly the proximal bore, by friction. It can even be press-fitted into at least one bore.

[0017] According to the invention, the retainer portion comprises two semi-annular bow-shaped portions that are axially offset and disposed on opposite sides of an axial body plane relative to each other, and connected at least adjacent to the body plane by two axially extending connecting portions on opposite sides of a proximal bore. Each bow-shaped portion is semi-annular, and "semi-annular" should not be construed herein as referring to a precise 180° semicircle, but rather to the overall shape. Since the retainer portion surrounds the proximal bore as described above, each bow-shaped portion has an internal dimension (typically an inner radius) and an external dimension (typically an outer radius) relative to the injector axis. The bow-shaped portions may be concentrically disposed relative to the injector axis. They are axially offset relative to each other, i.e., their positions relative to the axial direction defined by the injector axis do not overlap. Within this scope, one of the bow-shaped portions may be referred to as the "proximal bow-shaped portion," and the other as the "distal bow-shaped portion." One of the bow-shaped portions is disposed on one side of the body plane, and the other bow-shaped portion is disposed on the other side of the body plane. The body plane is an axial plane, meaning that the injector axis passes through the body plane (i.e., the body plane includes the injector axis).

[0018] Due to their semi-annular shape and their non-overlapping position relative to the axial direction, each arcuate portion represents a shape without any undercut, meaning that in the molding process, it can be molded between two halves of a mold that can move perpendicular to the body plane. It should be understood that once the retainer portion has been formed, any undercut will prevent separation of the half mold or the plastic body. The absence of such an undercut greatly facilitates the molding operation. To provide a circumferentially closed structure around the proximal aperture, the arcuate portions are connected at least adjacent to the body plane by axially extending connecting portions. These connecting portions are located on opposite sides of the proximal aperture, i.e., in the areas where the arcuate portions are closest to each other. Typically, each connecting portion extends to both sides of the body plane. For ease of molding, it may be defined by a surface perpendicular to the body plane. Relative to the radial direction, the internal dimensions of the respective connecting portion are typically defined by the expected dimensions of the proximal aperture, while the external dimensions are typically similar to the dimensions of the arcuate portion. In some embodiments, the connecting portion may not be clearly distinguishable from the arcuate portion and may be at least partially part of the arcuate portion.

[0019] The innovative design of the retainer portion (i.e., with two axially offset arcuate sections) greatly facilitates the molding process of the plastic body. In contrast to designs with simple annular or cylindrical retainer portions, the retainer portion can be molded in a molding apparatus without requiring a dedicated core to define the proximal bore. For circular designs, this core must be moved into position parallel to the injector axis before the molding process begins, and then retracted parallel to the injector axis again once the plastic body has been molded. According to the invention, this core can be eliminated, which greatly simplifies the layout of the molding tools and reduces overall production costs. Furthermore, the design with two offset semi-annular arcuate sections and two connecting portions generally allows for a reliable connection between the retainer portion and the injector body, requiring less plastic material than a cylindrical retainer portion. This again reduces production costs and also reduces the weight of the fuel injector.

[0020] Within the scope of this invention, the bow-shaped portions are axially spaced apart from each other. In this configuration, there will be space along the axial direction where the connecting portions are bridged. According to another embodiment, the bow-shaped portions are arranged adjacent to each other along the axial direction. In other words, the distal edge of one bow-shaped portion is in the same position as the proximal edge of another bow-shaped portion. For a given axial dimension of a single bow-shaped portion, this design allows for a minimum axial dimension of the retainer portion and also allows for a minimum length of the connecting portion, thus reducing the amount of plastic material required.

[0021] According to the general design, the two arcuate portions are similar in size. In particular, the axial dimension of the first arcuate portion may differ from the axial dimension (or axial thickness) of the second arcuate portion by less than 10%, or may even be the same. On the other hand, in some embodiments, the axial dimensions of the arcuate portions may be significantly different.

[0022] In one embodiment, the retainer portion is connected to the cable portion via a connecting portion. This includes the possibility that the connecting portion is partially integrated into the cable portion, i.e., it cannot be clearly distinguished from the cable portion. It is also possible that the corresponding connecting portion branches off from the cable portion or belongs to a branch portion that branches off from the cable portion.

[0023] Unlike fuel injectors known in the prior art (where the injector body is received in an annular or cylindrical sleeve of a plastic body extending over a considerable portion of the injector body's length), the retainer portion of the fuel injector of this invention can be relatively short. According to one embodiment, the axial dimension of the retainer portion corresponds to less than 20% of the axial distance between the retainer portion and the solenoid unit. Of course, the axial dimension of the retainer portion is the sum of the axial dimensions of the two arcuate portions (optionally plus the axial distance between the arcuate portions). In this embodiment, the injector body is received in a proximal bore and a distal bore along the axial dimension of the retainer portion, while in between, a portion of the injector body having at least five times the axial dimension of the retainer portion is not received in either bore of the solenoid assembly. It should be understood that this embodiment significantly reduces the amount of plastic material required. In other cases where support over a longer axial distance is required, the axial dimension of the retainer portion can correspond to up to 50% or 80% of the axial distance between the retainer portion and the solenoid unit.

[0024] According to another embodiment that can be combined with the above embodiments, the axial dimension of at least one arcuate portion corresponds to less than 20% of the axial distance between the arcuate portion and the solenoid unit. If the two arcuate portions have the same axial dimension, the above embodiments are consistent with this embodiment. However, the axial dimensions of the arcuate portions can be different, even significantly different.

[0025] According to one such embodiment, an arcuate portion extends distally all the way to the solenoid unit. This is clearly the distal arcuate portion. On the other hand, the proximal arcuate portion along the injector axis can be quite short, for example, it can have the axial dimensions as in the aforementioned embodiments. In other words, while the proximal arcuate portion provides support for the injector body only over a relatively short distance, the distal arcuate portion extends all the way to the solenoid unit, where it can directly connect to the solenoid portion. Although the amount of plastic material required is greater than in other embodiments, the long arcuate portion helps to mechanically stabilize the plastic body and thus stabilize the fuel injector overall. Optionally, the distal arcuate portion can contact the cable portion along its entire length.

[0026] As described above, at least some embodiments of the fuel injector of the present invention result in a significant reduction in the amount of plastic material. According to one such embodiment, there is a first region between the retainer portion and the solenoid unit, in which the plastic body extends tangentially about the injector axis by less than 90°. This, of course, contrasts with cylindrical arrangements known in the art, in which the plastic body extends 360° about the injector axis. Typically, this first region belongs to the cable portion. It may extend over at least 70% of the distance between the retainer portion and the solenoid unit, possibly over at least 90% or even 100% of that distance.

[0027] As described above, the retainer portion can be formed without using a dedicated core or slider, which, according to the prior art, results in the inner radius of the plastic body being larger than the outer radius of the ejector body. Therefore, the internal dimensions of the retainer portion can be precisely adapted to the external dimensions of the ejector body. Thus, it is preferable that the ejector body shape-fits the retainer portion. In other words, the ejector body and the retainer portion are in direct contact, such that the relative position of the ejector body with respect to the solenoid assembly is defined by this contact. It is conceivable to design the internal dimensions of the retainer portion to be slightly smaller than the external dimensions of the ejector body, so that the ejector body is press-fitted into the retainer portion, thereby increasing the effectiveness of the connection through enhanced friction.

[0028] Typically, any rotation of the injector body relative to the solenoid assembly should be prevented. This can be achieved by establishing a tangential fit (i.e., forced locking relative to the tangential direction) between the injector body and the solenoid assembly. A preferred embodiment specifies that the injector body includes a locking portion having a varying radial dimension along its circumference, which engages the retainer portion. Because the radial dimension varies along its circumference, forced locking with the corresponding surface of the retainer portion can be achieved, provided that the corresponding surface of the retainer portion also has a varying radial dimension. Additionally or alternatively, the varying radial dimension can result in increased pressure exerted by those radially projecting portions of the locking portion, leading to increased friction relative to the retainer portion.

[0029] Preferably, the locking portion engages the two arcuate portions. That is, the locking portion is positioned to overlap with the two arcuate portions and may cover the entire axial dimension of the retainer portion. This helps to increase the retaining effect of the locking portion and also helps to reduce stress on the individual arcuate portions.

[0030] According to one embodiment, the locking portion includes knurling. The knurling may include a plurality of physically formed grooves and ridges. As described above, the ridges cause an increase in pressure on the surface of the retainer portion, which may even lead to elastic or plastic deformation, as if the ridges were cutting into the surface of the retainer portion.

[0031] To provide a favorable distribution of the magnetic field within the fuel injector, the solenoid unit may include a flux washer disposed proximally to the solenoid housing and extending radially inward relative to the solenoid housing. The flux washer is made of a ferromagnetic material, such as an iron alloy. The inner portion of the flux washer may be relatively close to the aforementioned poles, such that the flux washer can be considered a "bridge" for the magnetic flux between the poles and the solenoid housing. Since the flux washer is part of the solenoid unit, which includes a distal bore, it also has a central bore around the injector axis. Furthermore, the flux washer is typically not perfectly circular but includes a groove through which the cable element passes.

[0032] In a preferred embodiment, the flux washer is welded to the proximal end of the solenoid housing. In this embodiment, the flux washer forms a radially inward flange at the proximal end of the solenoid housing. This embodiment is advantageous in terms of flux transmission between the flux washer and the solenoid housing. Furthermore, during the molding process, plastic material cannot unintentionally flow through the gap between the flux washer and the solenoid housing, as this gap is closed by the welded connection.

[0033] In one embodiment, the cable portion includes a collar formed around the contact portion of the cable element. This collar protects the contact portion of the cable element within an inner cavity, thereby protecting the contact portion from any unwanted electrical contact. Alternatively, the contact portion and the collar can be said to form a receptacle. Electrical contact with the contact portion can only be established by inserting a corresponding plug into the receptacle. During the molding process, the collar with the inner cavity can only be achieved by providing a movable core that prevents plastic material from flowing into the inner cavity. After the plastic body has been formed, the movable core must be retracted from the inner cavity to remove the solenoid assembly from the molding tool.

[0034] The present invention also provides a solenoid assembly for a fuel injector, the solenoid assembly extending from a proximal side to a distal side along the injector axis. The solenoid assembly includes a solenoid unit comprising an excitation coil within a solenoid housing, the solenoid unit circumferentially surrounding a distal aperture about the injector axis. The solenoid assembly also includes a cable element connected to the excitation coil and a coherent plastic body comprising: a solenoid portion molded onto the solenoid unit; a cable portion extending proximally from the solenoid portion and molded onto the cable element; and a retainer portion disposed proximally from the solenoid unit and circumferentially surrounding a proximal aperture about the injector axis, wherein the distal aperture and the proximal aperture are adapted to receive the injector body. The retainer portion includes two semi-annular arcuate portions that are axially offset and disposed on opposite sides of an axial body plane relative to each other, and connected at least adjacent to the body plane by two axially extending connecting portions on opposite sides of the proximal aperture.

[0035] All these terms have already been explained above with reference to the fuel injector of the present invention, and therefore will not be explained again. The preferred embodiment of the solenoid assembly corresponds to an embodiment of the fuel injector of the present invention.

[0036] The present invention also provides a method for manufacturing a fuel injector that extends along the injector axis from the proximal side to the distal side. The features of the method already described above with respect to the fuel injector of the present invention will not be repeated.

[0037] The method involves surrounding a solenoid unit and a cable element between a first and a second mold half of a molding tool. The solenoid unit includes an excitation coil within a solenoid housing and circumferentially surrounds a distal aperture about an injector axis. The cable element is connected to the excitation coil. The first and second mold halves are movable perpendicular to a separation plane. The molding tool (or mold) is adapted for injection molding of plastic materials. It comprises two molded halves that are movable relative to each other perpendicular to a separation plane. To some extent, the separation plane corresponds to or is parallel to the contact surfaces of the molded halves. These molded halves partially define a mold cavity in which the solenoid housing and the cable element are positioned.

[0038] In another step (which can be performed before or after the half-mold is closed), the first core is moved proximally into the distal hole. The first core (also referred to as the first slider) typically has a radial dimension corresponding to the radial dimension of the distal hole, such that it seals against the solenoid unit from the inside. If the solenoid unit includes a flux washer, the first core is typically inserted proximally at least up to the position of the flux washer.

[0039] In another step (which may be performed before or after mold closure), the second core (or slider) is positioned near the contact portion of the cable element. As described above, the contact portion corresponds to the part of the cable element suitable for electrical contact with an external component such as a connector cable. The second core may be shaped to at least partially surround the contact portion of the cable element to keep the plastic material away from the contact portion. When the first core is positioned on the ejector axis, the second core is in an off-axis position. Moreover, as the first core moves axially, the second core typically moves at an angle relative to the ejector axis.

[0040] After performing the above steps, plastic material is injected into a mold cavity defined by a first half mold, a second half mold, a first core, and a second core to form a coherent plastic body, thereby forming a solenoid assembly. The plastic body includes: a solenoid portion molded onto a solenoid unit; a cable portion extending proximally from the solenoid portion and molded onto a cable element; and a retainer portion disposed proximally from the solenoid unit and circumferentially surrounding a proximal hole around the injector axis.

[0041] In another step (when the plastic material has cured), the first and second cores are removed and the mold half is opened to remove the solenoid assembly. The first and second cores are removed or retracted, with the direction of movement generally corresponding to the movement prior to the injection of the plastic material. It should be understood that each core can be removed before or after the mold half is opened. After both cores have been removed and the mold half has been opened (i.e., one mold half has been removed from the other), the solenoid assembly is removed from the mold, i.e., taken out of the mold.

[0042] In another step, the injector body is inserted so that it is received in the distal and proximal ports.

[0043] According to the invention, the retainer portion includes two semi-annular arcuate portions that are axially offset and disposed on opposite sides of the axial body plane, and are connected at least adjacent to the body plane by two axially extending connecting portions on opposite sides of the proximal hole. In the closed position of the molding tool, the separation plane typically corresponds to the body plane of the plastic body.

[0044] It should be understood that, without the step of inserting the injector body, the method of the present invention for manufacturing a fuel injector corresponds to the method for manufacturing a solenoid assembly. Attached Figure Description

[0045] Preferred embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which:

[0046] Figure 1 This is a first side view of a fuel injector based on existing technology;

[0047] Figure 2 yes Figure 1 A second side view of the fuel injector;

[0048] Figure 3 It is along Figure 2 Sectional view of line III-III in the middle;

[0049] Figure 3A yes Figure 3 Detailed images;

[0050] Figure 4 yes Figure 1 A top view of the solenoid assembly of the fuel injector;

[0051] Figure 5 yes Figure 4 A three-dimensional view of the solenoid assembly;

[0052] Figure 6 This is a first side view of a first embodiment of the fuel injector of the present invention;

[0053] Figure 7 yes Figure 6 A second side view of the fuel injector;

[0054] Figure 8 It is along Figure 7 A sectional view of line VIII-VIII in the middle;

[0055] Figure 8A yes Figure 8 Detailed images;

[0056] Figure 9 yes Figure 6 First side view of the solenoid assembly of the fuel injector;

[0057] Figure 10 yes Figure 9 Second side view of the solenoid assembly;

[0058] Figure 11 yes Figure 9 A three-dimensional view of the solenoid assembly;

[0059] Figure 12 It is along Figure 9 A sectional view of line XII-XII in the middle;

[0060] Figure 13 yes Figure 9 Top view of the solenoid assembly;

[0061] Figure 14 This is a first side view of a second embodiment of the fuel injector of the present invention;

[0062] Figure 15 yes Figure 14 A second side view of the fuel injector;

[0063] Figure 16 It is along Figure 15 A cross-sectional view of line XVI-XVI in the diagram;

[0064] Figure 17 yes Figure 14 A first perspective view of the solenoid assembly of the fuel injector; and

[0065] Figure 18 yes Figure 17 The second perspective view of the solenoid assembly. Detailed Implementation

[0066] Figures 1 to 5 A fuel injector 1 according to the prior art is shown, which can be used in an internal combustion engine. The fuel injector 1 extends along injector axis A from a proximal side 1.1 to a distal side 1.2. In the assembled state, the distal side 1.2 faces the internal combustion engine and is inserted therein. As main components, the fuel injector 1 includes a solenoid assembly 10 and an injector body 40. The injector body 40 includes an injector housing 41 made of metal. Strictly speaking, the injector housing includes two connecting portions, namely a proximal housing 42 and a distal housing 43. The injector housing 41 extends to the distal side 1.2 where a nozzle 47 is arranged. A fuel passage is formed within the housing 41, extending to the nozzle 47 and adapted to guide fuel through the injector body 40.

[0067] The nozzle 47 can be closed by a pin 48 disposed within the injector housing 41. The pin 48 can be in the open position (not shown) and... Figure 3 and Figure 3AThe nozzle 47 can be moved axially between the closed and open positions. In the closed position, the ball located distal to the pin 48 abuts against the nozzle seat, thereby closing the nozzle 47. If the pin 48 moves proximally toward the open position, the ball lifts off the nozzle seat, thereby opening the nozzle 47. A first spring 50 is positioned between the housing and the pin 48. It is a helical spring aligned along the injector axis A and applying a force to bias the pin 48 distally, i.e., bias the pin 48 in the distal direction. The injector housing also includes an armature 49 having a generally annular shape and surrounding the pin 48. The armature 49 is axially movable within the injector housing 41 between a proximal position and a distal position. It is biased toward the distal position by a second spring 51. The armature 49 can be moved in the proximal direction by a magnetic field generated by the solenoid unit 11. In the proximal position, the proximal side of the armature 49 abuts against the pole piece 52. Simultaneously, the armature 49 engages the pin 48 to move the pin 48 to the open position against the force of the first spring 50. The electrode 52 is arranged circumferentially around the injector axis A, thereby surrounding the first spring 50 and the proximal portion of the pin 48.

[0068] The solenoid assembly 10 includes a solenoid unit 11, which is axially positioned similarly to the pole piece 52 and armature 49 of the injector body. It includes a generally cylindrical solenoid housing 12 that circumferentially surrounds and is concentrically arranged relative to the excitation coil 15. The coil 15 itself is wound around a generally cylindrical spool 14. A magnetic field is generated when current flows through the excitation coil 15. The details of the propagation of the magnetic field in the fuel injector 1 are irrelevant to the present invention and will not be discussed further. However, it should be noted that a magnetizable flux washer 13 is disposed inside the solenoid housing 12. It has a disc-shaped, generally annular shape with grooves allowing the cable element 16 connected to the excitation coil 15 to pass through. The inner radius of the flux washer 13 is substantially equal to the inner radius of the spool 14.

[0069] The plastic body 20 of the solenoid assembly 10 is molded onto the solenoid unit 11. Specifically, a portion of the plastic body 20 is disposed within the solenoid housing and encapsulates the excitation coil 15 and the cable element 16. The plastic body 20 extends proximally from the solenoid unit 11 and forms a cylindrical retainer portion 26 in which the main portion of the injector body 40 is housed. Another portion of the injector body 40 is housed within the solenoid unit and abuts against the flux washer 13, the spool 14, and the distal portion of the solenoid housing 12, respectively. A central bore 31 passes through the retainer portion 26 and the solenoid unit 11 along the injector axis A. The plastic body 20 also includes a cable portion 22, which is partially integrated into the retainer portion 26 and extends at an angle relative to the injector axis A to a collar 23 formed around the contact portion 17 of the cavity 34 and the cable element 16. Contact portion 17 and collar 23 are part of socket 24, and the plug of connector cable (not shown) can be connected to socket 24.

[0070] During the manufacturing process of the fuel injector 1, before inserting the injector body 40 into the axial extension hole 31 of the solenoid assembly 10, Figure 4 and Figure 5 The solenoid assembly 10 shown is manufactured as a separate component. The plastic body 20 is formed by covering the pre-assembled solenoid unit 11 and cable element 16. During injection molding, the partition plane between the two halves of the molding tool corresponds to... Figure 2 The cross-section is shown. While some portions of the shape of the plastic body 20 can be defined by a half-mold, the central hole 31 and the cavity 34 within the collar 23 need to be defined by movable cores or sliders. One core is needed to define the cavity 34 within the collar, while two additional cores are needed to prevent plastic material from entering the space for the hole 31. The first core moves forward from the distal side 1.2 toward the proximal side into the solenoid housing 12 until its proximal end is flush with the proximal end of the flux washer 13. The second core moves forward from the proximal side 1.1 toward the distal side into the space corresponding to the hole 31 until its distal end abuts against the flux washer 13. Thus, the second core seals the engagement of the flux washer 13 and prevents any leakage of plastic material. However, to provide this sealing effect, the second core needs to have a radius larger than the inner radius of the flux washer 13. Accordingly, the inner radius of the hole 31 is larger than the outer radius of the ejector body 40. Figure 3 As shown, a gap 53 is left, and the injector body 40 is received without a form fit within the hole 31. Therefore, the support ring 54 and the sealing ring 55 need to be positioned between the retainer portion 26 and the injector body 40. The spring clip 56 is secured to the proximal housing 42 to prevent axial movement of the injector body 40 relative to the solenoid assembly 10.

[0071] Figures 6 to 13A first embodiment of the fuel injector 1 of the present invention is shown. The fuel injector 1 also includes a solenoid assembly 10 and an injector body 40. The injector body 40 and Figures 1 to 3A The injector body shown is largely the same and will not be discussed further. The solenoid assembly 10 includes a solenoid unit 11 that is largely the same as the solenoid unit described above. However, in this embodiment, the solenoid unit 11 circumferentially surrounds the distal bore 32 around the injector axis A, and a flux washer 13 is disposed at the proximal end of the solenoid housing 12 and connected to the solenoid housing 12 by welding. Effectively, the flux washer 13 forms a radially inward flange on the solenoid housing 12. The plastic body 20 of the solenoid assembly includes three interconnecting portions, namely a solenoid portion 21 molded onto the solenoid unit 11, similar to the prior art example described above. A cable portion 22 extends proximally from the solenoid portion 21 and encapsulates the cable element 16. At a distance from the solenoid unit 11 and the solenoid portion 21, a retainer portion 26 is connected to the cable portion 22. The retainer portion 26 circumferentially surrounds and defines a proximal bore 33, the radius of which corresponds to the radius of the injector body 40.

[0072] The structure of the retainer section 26 is defined by two semi-annular arcuate sections 27 and 28 and two connecting sections 29 and 30. Refer to the main body plane B containing the injector axis A (see...). Figure 7 The bow-shaped portions 27 and 28 are disposed on opposite sides of the main body plane B. Furthermore, they are axially offset from each other, or more specifically, they are axially adjacent to each other. Therefore, they can be referred to as the proximal bow-shaped portion 27 and the distal bow-shaped portion 28, respectively. In the region near the main body plane B, the bow-shaped portions 27 and 28 are connected by a first connecting portion 29 and a second connecting portion 30, the second connecting portion 30 being directly connected to or integrated into the cable portion 22. In this embodiment, the total axial dimension of the retainer portion 26 corresponds to approximately 18% of the axial distance between the retainer portion 26 and the solenoid unit 11. However, this ratio can be larger or possibly even smaller without compromising the overall stability of the plastic body 20 and the fuel injector 1. The axial dimensions of the two bow-shaped portions 27 and 28 are identical, but this can also be varied to some extent.

[0073] The retainer portion 26 is only a small part of the total length of the injector body 40 (or more specifically, the proximal housing 42), so the amount of plastic material required for the plastic body 20 is relatively small compared to... Figures 1 to 5 The prior art shown has been greatly reduced. More importantly, the retainer portion 26 does not have an undercut region relative to the direction perpendicular to the body plane B, as in... Figure 12The proximal hole 33 is best visible in the cross-sectional view. Therefore, in the molding process, no special core or slider is required to define the proximal hole 33 in the retainer portion 26. Instead, the retainer portion 26 can be completely defined by the two halves of the molding tool. On the one hand, this greatly simplifies the molding process. On the other hand, since the sealing contact with the proximal edge of the flux washer 13 can be established by the two halves of the mold without a slider, the inner diameter of the proximal hole 33 can be freely adapted to best fit the ejector body 40. Thus, the ejector body 40 forms-fits the two arcuate portions 27, 28 of the retainer portion 26. To prevent any rotation of the ejector body 40 relative to the solenoid assembly 10, the ejector housing 41 includes a locking portion 44 with knurling 45. The knurling 45 engages with the retainer portion 26 and includes multiple axial ridges and grooves, wherein the ridges can even elastically or plastically deform the inner surface of the retainer portion 26, thereby “cutting” into the inner surface. This greatly enhances the form fit between the retainer portion 26 and the ejector body 40. Even if the knurling 45 does not deform the retainer portion 26, the knurling 45 helps to significantly increase friction along the tangential direction.

[0074] Since the retainer portion 26 extends only over a relatively small area along the injector axis A, there exists a first region 25 that extends over the entire interval between the retainer portion 26 and the solenoid unit 11, wherein the plastic body 20 (or more specifically, the cable portion 22) extends tangentially at less than 90°. This also demonstrates a reduction in the amount of plastic material required compared to the prior art.

[0075] Figures 14 to 18 A second embodiment of the fuel injector 1 of the present invention is shown. The second embodiment is substantially the same as the first embodiment and therefore will not be described further. While the size and position of the proximal arcuate portion 27 are the same as in the first embodiment, the distal arcuate portion 28 extends all the way to the solenoid unit 11, where it connects directly to the solenoid portion 21. Furthermore, it connects to the cable portion 22 along its entire axial length. The two connecting portions 29 and 30 also extend all the way to the solenoid unit 11. Clearly, this design greatly increases the torsional stiffness of the plastic body 20, as the shape of the retainer portion 26 generally corresponds to a semi-cylinder. Although the amount of plastic material is increased relative to the first embodiment, it is still significantly less than... Figures 1 to 5 The prior art example shown is illustrated. Since the cross-sections of the arcuate portions 27 and 28 in this embodiment are the same as in the first embodiment, the plastic body 20 of the solenoid assembly 10 can also be molded without requiring a dedicated core defining the proximal hole 33. Therefore, the advantages described with respect to the first embodiment also apply to this embodiment.

[0076] Reference figures explanation:

[0077] 1. Fuel Injector

[0078] 1.1 Proximal

[0079] 1.2 Distal

[0080] 10 Solenoid Assembly

[0081] 11 Solenoid Unit

[0082] 12 Solenoid housing

[0083] 13. Flux Washer

[0084] 14 spools

[0085] 15 Excitation Coil

[0086] 16 Cable components

[0087] 17 Contact Part

[0088] 20 Plastic body

[0089] 21. Solenoid section

[0090] 22 Cable Section

[0091] 23 rings

[0092] 24 sockets

[0093] 25 First District

[0094] 26. Retainer section

[0095] 27, 28 Arch-shaped sections

[0096] 29, 30 Connection parts

[0097] Holes 31, 32, and 33

[0098] 34 Cavity

[0099] 40 Injector body

[0100] 41 Injector housing

[0101] 42 Proximal shell

[0102] 43 Distal shell

[0103] 44 Locked section

[0104] 45 Knurling

[0105] 46. ​​Cavity

[0106] 47 Nozzles

[0107] 48 shaft pins

[0108] 49 Armature

[0109] 50, 51 Springs

[0110] 52 electrode film

[0111] 53 gap

[0112] 54 Support ring

[0113] 55 Sealing ring

[0114] 56 Spring Clip

[0115] A. Injector axis

[0116] B Main Plane

Claims

1. A fuel injector (1) extending along an injector axis (A) from a proximal side (1.1) to a distal side (1.2), the fuel injector comprising: - A solenoid unit (11) including an excitation coil (15) in a solenoid housing (12), the solenoid unit (11) circumferentially surrounding a distal bore (32) about the injector axis (A); - Cable element (16), which is connected to the excitation coil (15); - A continuous plastic body (20) comprising: a solenoid portion (21) molded onto the solenoid unit (11); a cable portion (22) extending proximally from the solenoid portion (21) and molded onto the cable element (16); and a retainer portion (26) disposed proximally from the solenoid unit (11) and circumferentially surrounding a proximal aperture (33) about the injector axis (A); and - An axially extending injector body (40) adapted to guide fuel from the proximal side (1.1) to a nozzle (47) at the distal side (1.2), the injector body (40) being received in the proximal orifice (33) and the distal orifice (32). The retainer portion (26) includes two semi-annular bow-shaped portions (27, 28) which are axially offset and disposed on opposite sides of the axial body plane (B) and are connected at least adjacent to the body plane (B) by two axially extending connecting portions (29, 30) on opposite sides of the proximal hole (33).

2. The fuel injector according to claim 1, wherein, The bow-shaped portions (27, 28) are arranged adjacent to each other in the axial direction.

3. The fuel injector according to claim 1 or 2, wherein, The retainer portion (26) is connected to the cable portion (22) via a connecting portion (29, 30).

4. The fuel injector according to claim 1 or 2, wherein, The axial dimension of the retainer portion (26) corresponds to less than 20% of the axial distance between the retainer portion (26) and the solenoid unit (11).

5. The fuel injector according to claim 1 or 2, wherein, The axial dimension of at least one arcuate portion (27, 28) corresponds to less than 20% of the axial distance between the arcuate portion (27, 28) and the solenoid unit (11).

6. The fuel injector according to claim 1 or 2, wherein, An arc-shaped portion (27, 28) extends distally all the way to the solenoid unit (11).

7. The fuel injector according to claim 1 or 2, wherein, In the first region (25) between the retainer portion (26) and the solenoid unit (11), the plastic body (20) extends less than 90° tangentially around the injector axis (A).

8. The fuel injector according to claim 1 or 2, wherein, The injector body (40) is shaped to fit the retainer portion (26).

9. The fuel injector according to claim 8, wherein, The injector body (40) includes a locking portion (44) having a varying radial dimension along its circumference, which engages the retainer portion (26).

10. The fuel injector according to claim 9, wherein, The locking portion (44) engages the two bow-shaped portions (27, 28).

11. The fuel injector according to claim 1 or 2, wherein, The solenoid unit (11) includes a flux washer (13) disposed near the proximal side of the solenoid housing (12) and extending radially inward relative to the solenoid housing (12).

12. The fuel injector according to claim 11, wherein, The flux washer (13) is welded to the proximal side of the solenoid housing (12).

13. The fuel injector according to claim 1 or 2, wherein, The cable portion (22) includes a collar (23) formed around the contact portion (17) of the cable element (16).

14. A solenoid assembly (10) for a fuel injector (1) extending from a proximal side (1.1) to a distal side (1.2) along an injector axis (A), the solenoid assembly (10) comprising: - A solenoid unit (11) including an excitation coil (15) in a solenoid housing (12), the solenoid unit (11) circumferentially surrounding a distal bore (32) about the injector axis (A); - Cable element (16), which is connected to the excitation coil (15); as well as - A continuous plastic body (20) comprising: a solenoid portion (21) molded onto the solenoid unit (11); a cable portion (22) extending proximally from the solenoid portion (21) and molded onto the cable element (16); and a retainer portion (26) disposed proximally from the solenoid unit (11) and circumferentially surrounding a proximal aperture (33) about the injector axis (A). The distal hole (32) and the proximal hole (33) are adapted to receive the injector body (40), and the retainer portion (26) includes two semi-annular bow-shaped portions (27, 28) that are axially offset and disposed on opposite sides of the axial body plane (B) relative to each other, and are connected at least adjacent to the body plane (B) by two axially extending connecting portions (29, 30) on opposite sides of the proximal hole (33).

15. A method for manufacturing a fuel injector (1) extending along an injector axis (A) from a proximal side (1.1) to a distal side (1.2), the method comprising: - A solenoid unit (11) and a cable element (16) are surrounded between the first and second halves of the molding tool. The solenoid unit includes an excitation coil (15) in a solenoid housing (12) and circumferentially surrounds a distal hole (32) about the injector axis (A). The cable element is connected to the excitation coil (15). The first and second halves of the mold are movable perpendicular to the separation plane. - Move the first core proximally into the distal hole (32); - Position the second core near the contact portion (17) of the cable element (16); - Plastic material is injected into a mold cavity defined by the first half mold, the second half mold, the first core, and the second core to form a coherent plastic body (20), thereby forming a solenoid assembly (10), the plastic body comprising: a solenoid portion (21) molded onto the solenoid unit (11); a cable portion (22) extending proximally from the solenoid portion (21) and molded onto the cable element (16); and a retainer portion (26) disposed proximally from the solenoid unit (11) and circumferentially surrounding a proximal hole (33) about the injector axis (A); - Remove the first core and the second core and open the first half mold and the second half mold to remove the solenoid assembly (10); and - Insert the injector body (40) so that it is received in the distal port (32) and the proximal port (33), The retainer portion (26) includes two semi-annular bow-shaped portions (27, 28) which are axially offset and disposed on opposite sides of the axial body plane (B) and are connected at least adjacent to the body plane (B) by two axially extending connecting portions (29, 30) on opposite sides of the proximal hole (33).

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