Solenoid valve

Abstract

Solenoid valve, comprising: a valve body (20) defining a first port (22) and a second port (24) isolated from the first port; a coil (30) mounted on the valve body (20) and comprising: a tube region (32); a connecting portion (34) formed at one end of the tube portion; a mounting portion (36) extending from the connecting portion in a direction away from the pipe portion and mounted on the valve body; and an opening (37) extending axially through the tube portion, the connection portion and the fastening portion; a winding (40) formed on the tubular portion (32) of the coil; a stator (50) installed in an end of the opening (37) in the coil remote from the mounting area; wherein a third port (52) is defined in the stator; a plunger (60) in which a cavity (62) is defined; a first and a second plug (63 64) mounted on the respective axial ends of the tappet; a magnetic flux return device (70) attached to the stator (50) and the coil (30) and configured to cooperate with the plunger (60) and the stator (50) to form a path for the magnetic flux generated by the winding (40); and a spring (69) attached to the plunger and arranged to urge the plunger toward the valve body, wherein the plunger (60) is slidably arranged in the opening (37) in the coil and is movable between a normal position in which the plunger (60) is adjacent to the valve body (20) and the first plug (63) closes the first port (22) and the second port (24) is connected to the third port (52) via a passage, and an actuated position in which the plunger (60) is adjacent to the stator (50) and the second plug (64) closes the third port (52) and the second port (24) is connected to the first port (22) via the opening (37) in the coil (30); and wherein the winding (40), when energized, moves the plunger (60) into the actuated position against the pressure of the spring (69), characterized in that the passage between the second port (24) and the third port (52) extends through the cavity (62) of the plunger (60); wherein the plunger (60) comprises a body portion (61) in which the cavity (62) is formed, the body portion (61) having a central section and two end portions extending from the respective end of the central section, an opening (68) being formed between an inner surface of the coil (30) and an outer surface of each of the end portions of the body portion (61) at a junction between the central region and each of the end portions for communicating the cavity (62) with a corresponding channel (67), the passage extending through the channels and the openings; wherein each end section has an outer diameter smaller than that of the central section.

Description

FIELD OF THE INVENTION

[0001] The invention relates to a solenoid valve and, more particularly, to a solenoid valve capable of generating a higher magnetic force. BACKGROUND OF THE INVENTION

[0002] Solenoid valves are commonly used in medical devices, such as patient massagers. US Patent No. 5,992,461 describes a typical solenoid valve comprising a valve body with two ports and an electromagnet. The electromagnet includes a magnetic flux return frame, a coil with an internal opening, a stator inserted into one end of the coil opening and forming another port, a winding formed on the coil, and a plunger disposed in the other end of the coil opening. The plunger defines an internal space in which a pair of plugs and an internal spring are installed. The internal spring is compressed between the plugs to hold the plugs in position. An external spring is disposed between the plunger and the stator. The frame has two ends, one end attached to the stator and the other end attached to the valve body.When energized, the plunger is attracted to the stator, one of the plugs in the plunger closes the stator port, and the two ports of the valve body communicate with each other. In the normal state, i.e. when the electromagnet is de-energized, the plunger is pushed away from the stator by the external spring, and the plug in the plunger closes the first port of the valve body. A channel is formed between an outer surface of the plunger and an inner surface of the valve body, which channel communicates the stator port with the second port of the valve body in the normal state. Therefore, a large gap is formed between the outer surface of the plunger and the edge of the end of the frame. The large gap has a high magnetic resistance and reduces the attractive force generated between the stator and the plunger when the electromagnet is energized.In order to provide the required attractive force, the winding requires high power and consumes a relatively large amount of current and generates heat that must be dissipated.

[0003] DE 10 2009 022 538 A1 discloses an electromagnet with a media-filled armature chamber. The electromagnet has an armature that is longitudinally movable within the media-filled armature chamber. A coil winding through which electric current flows generates a magnetic field. This field acts on the armature and moves it within the armature chamber. The armature has a penetration opening that can be filled with the medium.

[0004] DE 23 22 669 A discloses an electromagnetically actuated control device, particularly for a high-pressure fluid, with one uncontrolled connection and two connections controlled in opposite directions by valves. A spring is supported at both ends on a respective valve closure element, whereby, by means of a magnetic armature via a driver, this spring can be biased at least approximately simultaneously in its closing direction and another spring can be biased against its closing direction.

[0005] DE 10 2013 205 273 A1 discloses a valve device, for example, a hydraulic valve device. The valve device has an electromagnet that serves to control the valve device and is attached to a housing. The electromagnet is secured to the housing in a form-fitting and force-fitting manner by means of a fastening device. The fastening device comprises a spring element and two radially elastic spring pins. Two spring tongues can be bent non-destructively between an assembly position and an engagement position.

[0006] Therefore, an improved solenoid valve is desired that can generate sufficient attraction force with less energy. BRIEF DESCRIPTION OF THE INVENTION

[0007] According to one aspect of the present invention, there is provided a solenoid valve comprising: a valve body defining a first port and a second port insulated from the first port; a coil mounted on the valve body, the coil comprising: a tube portion; a connecting portion formed at one end of the tube portion; a fixing portion extending from the connecting portion in a direction away from the tube portion and mounted on the valve body; and an opening extending axially through the tube portion, the connecting portion, and the fixing portion; a winding formed on the tube portion of the coil; a stator installed in an end of the opening in the coil remote from the fixing portion, a third port being defined in the stator; a plunger defining a cavity therein;a first and a second plug mounted at respective axial ends of the plunger; a magnetic flux return device attached to the stator and the coil and configured to cooperate with the plunger and the stator to form a path for the magnetic flux generated by the winding;and a spring attached to the plunger and arranged to urge the plunger towards the valve body, the plunger being slidably arranged in the opening in the coil and being capable of moving between a normal position, in which the plunger is adjacent to the valve body and the first plug closes the first port and the second port communicates with the third port via a passage, and an actuated position, in which the plunger is adjacent to the stator and the second plug closes the third port and the second port communicates with the first port via the opening in the coil; the winding, when energized, moving the plunger against the pressure of the spring into the actuated position;and wherein the passage between the second port and the third port extends through the cavity of the plunger. The plunger comprises a body portion in which the cavity is formed, the body portion comprising a central portion and a pair of end portions extending from respective ends of the central portion, an opening being formed between an inner surface of the coil and an outer surface of the respective end portion of the body portion at a junction between the central portion and the respective end portion to communicate the cavity with a corresponding channel, the passage extending through the channels and the openings. Each of the end portions has an outer diameter smaller than that of the central portion.;

[0008] Preferably, the plunger has a cap fixedly mounted around one of the end portions and defining a through opening allowing access to one of the plugs.

[0009] Preferably, the magnetic flux feedback device comprises: a U-shaped frame having a closed end and an open end, wherein the stator is fixed to the closed end of the frame; and a magnetic flux plate having an outer side and an inner side, wherein the outer side of the magnetic flux plate is fixed to the open end of the frame and wherein the inner side of the magnetic flux plate is fixed to the connecting portion of the coil by overmolding.

[0010] Preferably, the magnetic flux plate defines a through-hole through which the opening in the coil and material of the coil surrounding the opening extend, wherein the through-hole in the magnetic flux plate has an inner surface, the plunger has an outer surface opposite the inner surface of the through-hole, and a distance between the outer surface of the plunger and the inner surface of the through-hole of the magnetic flux plate is less than 1 mm.

[0011] Preferably, the magnetic flux plate defines a plurality of through holes through which material of the coil extends and forms connecting pins that interconnect two parts of the connecting region of the coil on opposite sides of the magnetic flux plate.

[0012] Preferably, the coil is pivotally connected to the valve body.

[0013] Preferably, either the mounting portion of the coil or the valve body defines an annular groove, while the respective remaining mounting portion of the coil or the remaining valve body defines a locking opening through which the locking pin extends and is received in the annular groove.

[0014] Preferably, a seal is provided between the mounting area of ​​the coil and the valve body, and another seal is provided between the coil and the stator.

[0015] Preferably, at least one of the plugs is spring loaded by a second spring disposed in the cavity in the plunger to limit the contact force between the plug and the corresponding port.

[0016] According to another aspect of the present invention, there is provided a solenoid valve comprising: a valve body defining a first port and a second port insulated from the first port; a coil mounted on the valve body, the coil comprising: a tube portion; a connecting portion formed at one end of the tube portion; a fixing portion extending from the connecting portion in a direction away from the tube portion and mounted on the valve body; and an opening extending axially through the tube portion, the connecting portion, and the fixing portion; a winding formed on the tube portion of the coil; a stator installed in an end of the opening of the coil remote from the fixing portion, the stator defining a third port; a plunger; first and second plugs mounted at respective axial ends of the plunger;a magnetic flux return device attached to the stator and the coil and configured to cooperate with the plunger and the stator to form a path for the magnetic flux generated by the winding; and a spring attached to the plunger and arranged to urge the plunger toward the valve body, wherein the plunger is slidably arranged in the opening in the coil and can move between a normal position in which the plunger is adjacent to the valve body and the first plug closes the first port and the second port communicates with the third port via a passage, and an actuated position in which the plunger is adjacent to the stator and the second plug closes the third port and the second port communicates with the first port via the opening in the coil;wherein the winding, when energized, moves the plunger against the pressure of the spring into the actuated position; and wherein the magnetic flux return device comprises a frame and a magnetic flux plate attached to the frame, wherein the stator is fixed to the frame and the magnetic flux plate is overmolded to the connection region of the coil, and wherein the magnetic flux plate defines a through-hole through which the opening of the coil extends continuously, the plunger has an outer surface opposite the through-hole, and a distance between the outer surface of the plunger and the inner surface of the through-hole of the magnetic flux plate is less than 1 mm.

[0017] Preferably, the plunger comprises a body portion having a cavity formed therein, the body portion having a central portion and a pair of end portions extending from respective ends of the central portion, a channel formed between an inner surface of the coil and an outer surface of each of the end portions, and an opening formed at the junction between the central portion and each of the end portions for communicating the cavity with a corresponding channel, the passage extending through the channels.

[0018] Preferably, each of the end portions has an outer diameter smaller than that of the central portion.

[0019] Preferably, the plunger further comprises a cap fixedly mounted around one of the end portions of the body portion adjacent the valve body and defining a through opening allowing access to one of the plugs.

[0020] According to another aspect of the present invention, there is provided a solenoid valve comprising: a valve body defining a first port and a second port isolated from the first port; a coil pivotally mounted on the valve body, the coil comprising: a tube portion; a connecting portion formed at one end of the tube portion; a fixing portion extending from the connecting portion in a direction away from the tube portion and mounted on the valve body; and an opening extending axially through the tube portion, the connecting portion, and the fixing portion; a winding formed on the tube portion of the coil; a stator installed in an end of the opening of the coil remote from the fixing portion, the stator defining a third port; a plunger;a first and a second plug mounted at the respective axial ends of the plunger; a magnetic flux return device attached to the stator and the coil and configured to cooperate with the plunger and the stator to form a path for the magnetic flux generated by the winding;and a spring attached to the plunger and arranged to urge the plunger towards the valve body, the plunger being slidably arranged in the opening in the spool and being able to move between a normal position in which the plunger is adjacent to the valve body and the first plug closes the first port and the second port communicates with the third port via a passage, and an actuated position in which the plunger is adjacent to the stator and the second plug closes the third port and the second port communicates with the first port via the opening in the spool;wherein the coil, when energized, moves the plunger against the pressure of the spring into the actuated position. The plunger comprises a body portion in which the cavity is formed, the body portion having a central portion and a pair of opposite end portions each extending from opposite ends of the central portion, an opening being formed between an inner surface of the coil and an outer surface of each of the opposite end portions of the body portion at a junction between the body portion and each of the opposite ends to communicate the cavity with a corresponding channel, the passage extending through the channels. Each of the end portions has an outer diameter smaller than that of the central portion.;

[0021] Preferably, one of the spool and the valve body defines an annular groove, and the remaining spool or the remaining valve body defines a mounting opening, with at least one locking bolt extending through the mounting opening to be received in the groove.

[0022] Preferably, the magnetic flux feedback device comprises a frame having an open end and a plate attached to the open end of the frame, the stator being fixed to the frame and the plate being overmolded to the connecting portion of the coil; and the plate defining a through-opening through which the opening in the coil extends continuously, the plate having an inner surface surrounding the through-opening, the plunger having an outer surface opposite the coil, and a distance between the outer surface of the plunger and the inner surface of the plate being less than 0.85 mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] A preferred embodiment of the invention will now be described by way of example with reference to the accompanying drawings. Identical structures, elements, or parts that appear in more than one drawing figure are generally identified identically in all the figures in which they appear. The dimensions of components and features have been chosen for clarity of illustration and are not necessarily drawn to scale. The figures are listed below. Fig. 1 shows a solenoid valve with a solenoid assembly and a valve body according to a preferred embodiment of the present invention; Fig. 2 shows the solenoid valve of Fig. 1, wherein the electromagnet assembly is rotated relative to the valve body; Fig. 3 is an exploded view of the solenoid valve of Fig. 1; Fig. 4 is a sectional view of the solenoid valve of Fig. 1; Fig. 5 is a sectional view of a plunger of the solenoid valve of Fig. 1; Fig. 6 is an enlarged view of an area of Fig. 4; and Fig. 7 shows a magnetic flux feedback plate of the solenoid valve of Fig. 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Referring to the figures, an electromagnet 10 according to a preferred embodiment of the present invention includes a valve body 20, a coil 30, a winding 40, a stator 50, a plunger 60, and a magnetic flux return device 70.

[0025] The valve body 20 is preferably made of plastic and has a plurality of ports. In this embodiment, the valve body 20 has a first port 22 and a second port 24. In the valve body 20, the first port 22 is isolated from the second port 24. A cover 21 closes one end of an axial passage through the valve body that forms part of the first port. The use of a cover 21 facilitates molding of the valve body. Two bolt openings 28 extend through the valve body 20 to assist in securing the valve body to a device.

[0026] The coil 30 is attached to the valve body 20 and is made of electrically insulating material. The coil 30 has a tubular portion 32, a connecting portion 34 formed at an end of the tubular portion 32 remote from the stator 50, and a mounting portion 36 extending axially from the connecting portion 34. The mounting portion 36 is farther from the stator 50 than the connecting portion 34. The coil 30 has a central opening 37. In this embodiment, the opening 37 extends through the tubular portion 32, the connecting portion 34, and the mounting portion 36 and has a uniform dimension over its entire length.

[0027] The winding 40 is formed on the outer surface of the tubular portion 32 of the coil 30 within the area defined by flanges 33.

[0028] The stator 50, which is made of a magnetically conductive material, for example, ferromagnetic material or soft magnetic material, is inserted into one end of the opening 37 of the coil 30. A third port 52 is formed in the stator 50 and preferably extends therethrough in an axial direction of the stator 50.

[0029] The plunger 60, which is made of a magnetically conductive material, for example, ferromagnetic material or soft magnetic material, is installed in the other end of the opening 37 of the coil 30 and can move in the opening 37 relative to the stator 50. It is Fig. 5. The plunger 60 comprises a body portion 61 in which a cavity 62 in the form of an axial through-opening is defined. Plugs 63, 64, preferably made of rubber, are inserted into the respective ends of the cavity 62. A first elastic element, such as a coil spring 65, is inserted into the cavity 62 and is compressed between the plugs 63, 64 to urge the plug 64 projecting from the cavity 62 and beyond the corresponding end surface of the body portion 61 to close the third port 52 when the electromagnet 10 is in the energized state. The ends of the springs 65 are respectively attached to the plugs 63, 64. To secure the plug 63 in the valve body 20, a cap 66 enclosing this lower end of the tappet 60 is attached to the lower end of the tappet 60, which is adjacent to the valve body.The cap 66 has a through-opening 662 that allows access to the valve body 20 for contact with the plug 63. The end portions of the body portion 61 have a reduced diameter compared to the central portion of the body portion 61. This forms a channel 67 between the inner surface of the coil 30 and the outer surface of each of the end portions (see ). Fig. 4). The upper end portion of the plunger has vertical grooves 671 formed therein to increase the volume of the upper channel 27. The grooves compensate for the presence of a second spring 69 in the channel 27. A radial opening 68 formed at the junction between the middle portion and each of the end portions communicates the cavity 62 with a corresponding channel 67. A second elastically deformable element, such as spring 69, is compressed between the stator 50 and the other end of the plunger 60 to urge the plunger 60 away from the stator 50 when the electromagnet 10 is de-energized. The ends of the spring 69 are respectively attached to the stator 50 and the plunger 60.

[0030] The magnetic flux return device 70 cooperates with the stator 50 and the plunger 60 to form a path for the magnetic flux generated by the winding 40. In this embodiment, the magnetic flux return device 70 comprises a U-shaped frame 72 having an open end and a closed end, and a magnetic flux plate 74 attached to the open end of the frame 72. The frame 72 and the plate 74 are made of a magnetically conductive material, preferably a metal such as mild steel. The magnetic flux plate 74 has a central through-opening 76 and a plurality of through-openings 78 (see Fig. 7) around the central opening 76. The magnetic flux plate 74 is preferably attached to the connecting portion 34 of the coil 30 by overmolding. During the molding of the coil 30, the plate 74 is recessed into the connecting portion 34 of the coil 30, and the material of the coil 30 extends through the opening 76 to form a connecting wall 77 (see Fig. 6), which connects two parts of the connecting region 34 of the coil 30 located on opposite sides of the plate 74. The through-holes 78 of the plate 74 are filled with material that forms connecting pins that interconnect the two parts of the connecting region 34. The connecting pins reinforce the mechanical strength of the coil 30, especially when the connecting wall 77 is thin.

[0031] The inner edge of the central opening 76 of the magnetic flux plate 74 is separated from the through-hole 37 of the coil 30 by the thickness of the connecting wall 77 and is therefore close to the outer surface of the plunger 60. The thickness of the connecting wall 77 of the coil 30 is preferably less than 1 mm. As a result, when the plunger makes sliding contact with the through-hole of the coil 30, a small distance W exists between the outer surface of the plunger 60 and the magnetic flux plate 74. That is, the gap in the flux path between the plunger 60 and the magnetic flux plate 74 is small. Preferably, the distance W is less than 1 mm. More preferably, the distance W is less than 0.85 mm. In this embodiment, the distance W is approximately 0.5 mm.Compared with the conventional solenoid valve described in US Pat. No. 5,992,461, the solenoid valve of the present invention has a greater magnetic force or attraction force because no fluid channel is formed between the inner edge of the magnetic flux plate 74 and the outer surface of the plunger 60, and the gap in the flow path between the magnetic flux plate 74 and the plunger 60 is thereby greatly reduced. The outer edges of the magnetic flux plate 74 can be attached to the open end of the frame 72 by welding, soldering, crimping, or a detachable connection via locking means or an interference fit. In this embodiment, the frame 72 is integrally formed as a single unit. Alternatively, the frame 72 can be composed of two L-shaped halves secured together.

[0032] Preferably, the closed end of frame 72 has an opening 73. Preferably, stator 50 has a cylindrical configuration. One end of stator 50 may be secured in opening 73 of frame 72 by conventional means such as welding, soldering, or a press fit, etc.

[0033] Sealing structures such as rubber O-rings 80 are disposed between the coil 30 and the valve body 20 and between the coil 30 and the stator 50. Two locking bolts 90 are used to attach the valve body 20 to the coil 30. Preferably, the mounting portion 36 of the coil 30 defines an annular groove 38. The valve body 20 defines a pair of locking openings 26. The locking bolts 90 extend through the respective locking openings 26 to be received in the groove 38 of the coil 30, thereby pivotally attaching the valve body to the coil 30. That is, the magnet assembly is pivotable relative to the valve body 20. This makes the solenoid valve of this embodiment suitable for a variety of applications requiring different port orientations. Fig. 2 shows the solenoid valve of Fig. 1 with the magnet arrangement of the coil 30, the winding 40, the stator 50 and the plunger 60 in a different orientation relative to the valve body 20. In Fig. 2, the magnet assembly is rotated 90° relative to the valve body. If desired, this mounting mechanism allows for interchangeability of the solenoid assembly or the valve assembly, allowing the use of a single solenoid assembly with a variety of valve body types to simplify assembly and reduce production costs.

[0034] In the operating state, when the winding 40 is energized, the plunger 60 is attracted to the stator 50 and moves toward the stator 50 until the end face of the plunger 60 comes into contact with the end face of the stator 50. In the actuated position, the plug 64 closes the third port of the stator 50. In the actuated position, the plug 64 of the plunger 60 closes the third port 52 of the stator 50. The plug 63 is spaced from the port 22. The ports 22 and 24 of the valve body 20 are connected to each other via a portion of the opening 37 of the coil 30 below the plunger 60. The fluid can pass between the port 22 and the port 24. When the coil is turned off, the magnetic attraction force between the stator 50 and the plunger 60 is extinguished, and the plunger 60 is returned to the original position (also called the normal position) by the second spring 69.In the normal position, the plunger 60 is spaced from the stator 50, and the third port 52 is open, while the first port 22 is closed by the plug 63. The second port 24 is connected to the third port 52 via a passage comprising the channels 67, the openings 68, and the cavity 62. This allows a fluid such as air to pass between the port 24 and the port 52.

[0035] The solenoid valves according to the present invention can be used in medical devices, for example, in devices for treating vascular thrombosis. Alternatively, the solenoid valves according to the present invention can also be used in other applications, for example, in pneumatic or hydraulic systems for controlling piston movement, in nebulization systems, in lumbar supports or lumbar supports for vehicle seats, etc.

[0036] The embodiments described above are merely examples. Those skilled in the art will recognize that various modifications are possible within the scope of the invention, as defined by the appended claims.

[0037] Certain features of the invention that have been described in connection with separate embodiments for clarity may also be combined in a single embodiment. Conversely, various features that have been described in one embodiment for brevity may also be present separately or in suitable subcombinations.

[0038] Verbs such as "comprise," "comprise," "contain," and "have," as well as their variations, in the description and claims of this application are to be understood in an inclusive sense. They indicate the presence of the stated element or feature, but do not exclude the presence of further elements or features.

Claims

[1] Solenoid valve, comprising: a valve body (20) defining a first port (22) and a second port (24) isolated from the first port; a coil (30) mounted on the valve body (20) and comprising: a tube region (32); a connecting portion (34) formed at one end of the tube portion; a mounting portion (36) extending from the connecting portion in a direction away from the pipe portion and mounted on the valve body; and an opening (37) extending axially through the tube portion, the connection portion and the fastening portion; a winding (40) formed on the tubular portion (32) of the coil; a stator (50) installed in an end of the opening (37) in the coil remote from the mounting area; wherein a third port (52) is defined in the stator; a plunger (60) in which a cavity (62) is defined; a first and a second plug (63 64) mounted on the respective axial ends of the tappet; a magnetic flux return device (70) attached to the stator (50) and the coil (30) and configured to cooperate with the plunger (60) and the stator (50) to form a path for the magnetic flux generated by the winding (40); and a spring (69) attached to the plunger and arranged to urge the plunger toward the valve body, wherein the plunger (60) is slidably arranged in the opening (37) in the coil and is movable between a normal position in which the plunger (60) is adjacent to the valve body (20) and the first plug (63) closes the first port (22) and the second port (24) is connected to the third port (52) via a passage, and an actuated position in which the plunger (60) is adjacent to the stator (50) and the second plug (64) closes the third port (52) and the second port (24) is connected to the first port (22) via the opening (37) in the coil (30); and wherein the winding (40), when energized, moves the plunger (60) into the actuated position against the pressure of the spring (69), characterized by that the passage between the second port (24) and the third port (52) runs through the cavity (62) of the plunger (60); wherein the plunger (60) comprises a body portion (61) in which the cavity (62) is formed, the body portion (61) having a central section and two end portions extending from the respective end of the central section, an opening (68) being formed between an inner surface of the coil (30) and an outer surface of each of the end portions of the body portion (61) at a junction between the central region and each of the end portions for communicating the cavity (62) with a corresponding channel (67), the passage extending through the channels and the openings; wherein each end section has an outer diameter smaller than that of the central section. [2] The solenoid valve of claim 1, wherein the plunger (60) further comprises a cap (66) fixedly mounted around one of the end portions and defining a through opening (662) allowing access to one of the plugs. [3] The solenoid valve according to claim 1 or 2, wherein the magnetic flux feedback device (70) comprises: a U-shaped frame (72) having a closed end and an open end, the stator (50) being fixed to the closed end of the frame; and a magnetic flux plate (74) having an outer side and an inner side, wherein the outer side of the magnetic flux plate is fixed to the open end of the frame (72) and the inner side of the magnetic flux plate is fixed to the connecting region (34) of the coil (30) by overmolding. [4] The solenoid valve of claim 3, wherein the magnetic flux plate (74) defines a through-hole (76) through which the opening (37) in the coil (30) and material of the coil surrounding the opening extend, the through-hole (76) in the magnetic flux plate having an inner surface, the plunger (60) having an outer surface opposite the inner surface of the through-hole (76), and a distance (W) between the outer surface of the plunger and the inner surface of the through-hole of the magnetic flux plate being less than 1 mm. [5] The solenoid valve of claim 3 or 4, wherein the magnetic flux plate (74) defines a plurality of through holes (78) through which the material of the coil extends and forms connecting pins that interconnect two parts of the connecting portion (34) of the coil (30) on opposite sides of the magnetic flux plate (74). [6] Solenoid valve according to one of claims 1 to 5, wherein the coil (30) is pivotally mounted on the valve body (20). [7] The solenoid valve of claim 6, wherein one of the mounting portions (36) of the coil (30) and the valve body (20) defines an annular groove (38) and the other mounting portion (36) of the coil and the valve body (20) defines a locking opening (26), wherein a locking bolt (90) extends through the locking opening (26) and is received in the annular groove (38). [8] Solenoid valve according to one of claims 1 to 7, wherein a seal (80) is provided between the fastening region (36) of the coil (30) and the valve body (20) and a further seal (80) is provided between the coil (30) and the stator (50). [9] Solenoid valve according to one of claims 1 to 8, wherein at least one of the plugs (63, 64) is spring-loaded by a second spring (65) arranged in the cavity (62) in the plunger (60) to limit the contact force between the plug (63, 64) and the corresponding port (22, 52). [10] Solenoid valve, comprising: a valve body (20) defining a first port (22) and a second port (24) isolated from the first port; a coil (30) mounted on the valve body (20) and comprising: a tube region (32); a connecting portion (34) formed at one end of the tube portion; a mounting portion (36) extending from the connecting portion in a direction away from the tube portion and mounted on the valve body; and an opening (37) extending axially through the tube portion, the connecting portion, and the mounting portion; a winding (40) formed on the tubular portion (32) of the coil; a stator (50) installed in an end of the opening (37) in the coil remote from the mounting area; wherein a third port (52) is defined in the stator; a plunger (60); a first and a second plug (63 64) mounted on the respective axial ends of the plunger (60); a magnetic flux return device (70) attached to the stator (50) and the coil (30) and configured to cooperate with the plunger (60) and the stator (50) to form a path for the magnetic flux generated by the winding (40); and a spring (69) attached to the plunger (60) and arranged to urge the plunger toward the valve body (20), wherein the plunger (60) is slidably arranged in the opening (37) in the coil and is movable between a normal position in which the plunger (60) is adjacent to the valve body (20) and the first plug (63) closes the first port (22) and the second port (24) is connected to the third port (52) via a passage, and an actuated position in which the plunger (60) is adjacent to the stator (50) and the second plug (64) closes the third port (52) and the second port (24) is connected to the first port (22) via the opening (37) in the coil; and wherein the winding (40), when energized, moves the plunger (60) into the actuated position against the pressure of the spring (69), characterized by that the coil (30) is pivotally mounted on the valve body (20); wherein the plunger (60) comprises a body portion (61) in which the cavity (62) is formed, the body portion (61) having a central section and two end portions extending from the respective end of the central section, an opening (68) being formed between an inner surface of the coil (30) and an outer surface of each of the end portions of the body portion (61) at a junction between the central region and each of the end portions for communicating the cavity (62) with a corresponding channel (67), the passage extending through the channels and the openings; wherein each end section has an outer diameter smaller than that of the central section.

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