Linearsolenoid

Abstract

Linear solenoid, featuring: a coil (1) which, when excited, generates a magnetic force; a cylindrical plunger piston (3) which is movably mounted in its axial direction inwards from the coil (1) and includes a vent line (14) which forms a connection in the axial direction; an output element (4) which is attached to one end of the plunger piston (3) on a first side in the axial direction; a magnetic attraction core (5) which magnetically attracts the plunger piston (3) in the axial direction due to the magnetic force generated by the coil (1); a cylindrical magnetic feed core (6) which delivers and receives the magnetic flux to and from an outer circumferential surface of the plunger piston (3); a rod-shaped central core (7) which transmits and receives the magnetic flux to and from an inner circumferential surface of the plunger piston (3); and a flange part (7a) which is arranged at one end of the central core (7) on a second side in the axial direction, wherein: the second side is a side opposite the first side in the axial direction; the flange part (7a) is formed in a shape whose diameter increases in the direction of an outer diameter side of the central core (7); the flange part (7a) closes off a space between one end of the magnetic feed core (6) on the second side in the axial direction and the end of the central core (7) on the second side in the axial direction; the output element (4) includes a contact part (X) which is brought into contact with one end of the central core (7) on the first side in the axial direction when the plunger piston (3) moves towards the second side in the axial direction; and when the contact part (X) is brought into contact with the end of the central core (7) on the first side in the axial direction, the plunger piston (3) defines an axial distance (S) between the plunger piston (3) and the flange part (7a).

Description

[0001] The present disclosure relates to a linear solenoid that generates a driving force in an axial direction.

[0002] The linear solenoid described, for example, in JP 2015-84395A is known as a linear solenoid that generates a driving force in the axial direction. The linear solenoid according to JP 2015-84395A includes a cylindrical plunger piston that is movably mounted in the axial direction. This plunger piston is located inside a cylindrical magnetic feed core and outside a rod-shaped central core.

[0003] The space between the other axial end of the magnetic feed core and the other axial end of the center core is closed by a flange attached to the center core. Accordingly, the volume of the space enclosed by the magnetic feed core, center core, plunger piston, and flange must be modified to allow the plunger piston to move axially. This is explained below, with this space being referred to as the first space. According to JP 2015-84395A, a vent line communicating axially is provided for the plunger piston to allow the volume change of the first space.

[0004] In particular, the plunger piston according to JP 2015-84395A includes, in the inward direction or within itself, a generally cylindrical bushing or bushing. This bushing is slidably supported by the outer circumferential surface of the plunger piston. A flange-shaped portion with an enlarged diameter, extending toward the outer diameter side, is integrally provided at the other axial end of the bushing disclosed in JP 2015-84395A. When the plunger piston is displaced toward the other axial end, this portion with the enlarged diameter is brought into contact with the flange portion, thus acting as a stop to limit the displacement of the plunger piston toward the other axial end.

[0005] Nevertheless, it is primarily the part with the larger diameter that blocks the inside of the vent pipe. This consequently impairs the responsiveness of the plunger piston.

[0006] Secondly, the contact area between the part with the increased diameter and the flange is large when the part with the increased diameter is in contact with the flange. This large contact area causes a sticking phenomenon at the contact point between the part with the increased diameter and the flange when the plunger piston is moved towards an axial end. Consequently, the plunger piston's response is reduced. The sticking phenomenon is characterized by a time lag in the fluid flowing into the contact point, even if the contact point can be quickly detached, thus hindering rapid removal of the contact point.

[0007] According to JP 2015-84395A, a technique is proposed to limit the adhesion phenomenon by radially forming many grooves on the flange part, thus reducing the contact area between the part with the increased diameter and the flange part. However, forming many grooves on the flange part results in an increase in cost. In other words, the responsiveness deteriorates if the flange part does not have many or enough grooves.

[0008] Further information on the state of the art can be found in the following documents.

[0009] DE 100 39 083 A1 discloses a fuel injection valve for fuel injection systems of internal combustion engines. This valve comprises a solenoid coil, an armature actuated in a closing direction by a return spring, and a valve needle positively connected to the armature for actuating a valve closing element, which, together with a valve seat surface, forms a sealing seat. The armature abuts an inner pole with an inlet-side armature surface. A throttling point is formed on the inlet-side armature surface, which is created by an annular, stepped elevation on the inlet-side armature surface.

[0010] Furthermore, further state of the art is disclosed in JP S61 - 140 505 U.

[0011] The present disclosure addresses at least one of the aforementioned problems. Accordingly, one objective of the present disclosure is to create a linear solenoid that exhibits excellent responsiveness and is cost-effective.

[0012] To solve the problem underlying the present disclosure, a linear solenoid is provided, comprising a coil, a cylindrical plunger piston, a delivery element or output element, a magnetic attraction core, a cylindrical magnetic feed core, a rod-shaped central core, and a flange. Upon excitation, the coil generates a magnetic force. The plunger piston is movably mounted axially within the coil and includes a vent line that communicates or forms a connection in the axial direction. The output element is attached to one end of the plunger piston on a first side in the axial direction. The magnetic attraction force attracts the plunger piston in the axial direction due to the magnetic force generated by the coil. The magnetic feed core delivers or receives a magnetic flux to and from an outer circumferential surface of the plunger piston.The central core transmits and receives the magnetic flux to and from an inner circumferential surface of the plunger piston. The flange is located at one end of the central core on a second side in the axial direction. This second side is opposite the first side in the axial direction. The flange is shaped with a diameter that increases towards the outer diameter of the central core. The flange closes a gap between one end of the magnetic feed core on the second side in the axial direction and the end of the central core on the second side in the axial direction. The output element includes a contact element that comes into contact with one end of the central core on the first side in the axial direction when the plunger piston moves towards the second side in the axial direction.When the contact part is brought into contact with the end of the central core on the first side in the axial direction, the plunger piston defines an axial distance between the plunger piston and the flange part.

[0013] The foregoing and further aspects, features and advantages of the present disclosure are explained in more detail below with reference to the accompanying drawing. It shows: Fig. 1 a sectional view showing a linear solenoid along its axial direction according to a first embodiment; Fig. 2 a sectional view showing a main part of the linear solenoid according to the first embodiment; Fig. 3A a sectional view showing a plunger arrangement along its axial direction according to the first embodiment; Fig. 3B a diagram showing the plunger arrangement viewed from the other axial end side in the first embodiment; Fig. 4A a diagram showing a central core viewed from an axial end face according to the first embodiment; Fig. 4B a sectional view showing the central core along its axial direction in the first embodiment; Fig. 5A a sectional view showing a plunger arrangement along its axial direction in which a deformation part is a conically recessed part according to a second embodiment; Fig. 5B a sectional view showing the plunger arrangement along its axial direction, in which the deformation part is a recessed part with a linear or straight lower part, according to the second embodiment; Fig. 5C a sectional view showing the plunger arrangement along its axial direction, in which the deformation part is a protruding part that is bulged out in the form of a spherical surface, according to the second embodiment; Fig. 5D a sectional view showing the plunger arrangement along its axial direction, in which the deformation part is a protruding part with a linear or straight upper section, according to the second embodiment; Fig. 5E a sectional view showing the plunger arrangement along its axial direction, in which through holes are provided for an output element, according to the second embodiment; Fig. 6A a diagram showing the plunger arrangement viewed from the other axial end side, in which the deformation part is a protruding part or a recessed part whose shape is circular when viewed from the axial direction, according to the second embodiment; Fig. 6B a diagram showing the plunger arrangement viewed from the other axial end side, in which the deformation part includes grooves or strip-shaped projections whose shapes, viewed from the axial direction, spread radially from the center to an outer diameter side, according to the second embodiment; Fig. 6C a diagram showing the plunger arrangement viewed from the other axial end side, in which the deformation part, viewed from the axial direction, is formed into a groove or a strip-shaped projection according to the second embodiment; Fig. 6D a diagram showing the plunger arrangement viewed from the other axial end side, in which the shape-changing part is a groove or a plus-shaped protruding part whose shape, viewed from the axial direction, cross-intersects, according to the second embodiment; Fig. 6E a diagram showing the plunger arrangement viewed from the other axial end side in which the output element includes through holes, according to the second embodiment; Fig. 7A a sectional view showing a central core along its axial direction in a reference example when the shape-changing part is not located at a front end of the central core, in the second embodiment; Fig. 7B a sectional view showing a central core along its axial direction, in which a deformation part is a protruding part with a linear or straight upper section, according to a third embodiment; Fig. 7C a sectional view showing the central core along its axial direction, in which the shape-changing part is a recessed part with a linear or straight lower part, according to the third embodiment. Fig. 7D a sectional view showing the central core along its axial direction, in which the deformation part is a protruding part that is bulged out in the form of a spherical surface, according to the third embodiment; Fig. 8A a diagram showing a central core viewed from an axial end side in a reference example, when the deformation part is not located at the front end of the central core, in the second embodiment; Fig. 8B a diagram showing the central core viewed from an axial end side in which the deformation part, viewed from the axial direction, is formed into a groove or a strip-shaped projection according to the third embodiment; Fig. 8C a diagram showing the central core viewed from one axial end side in which the deformation part includes a protruding part whose shape is circular when viewed from the axial direction and on which a minus-shaped groove is formed, according to the third embodiment; Fig. 8D a diagram showing the central core viewed from one axial end side in which the deformation part is a recessed part or a protruding part whose shape is circular when viewed from the axial direction, according to the third embodiment; Fig. 8E a diagram showing the central core viewed from one axial end face in which the deformation part is a groove or a plus-shaped projecting part whose shape, viewed from the axial direction, cross-intersects, according to the third embodiment; and Fig. Figure 8F shows a diagram that views the central core from one axial end side in which the deformation part includes a protruding part whose shape is circular when viewed from the axial direction and on which a plus-shaped groove is formed, according to the third embodiment.

[0014] The following is an explanation of embodiments with reference to the accompanying drawing. The embodiments described below illustrate one example among many. (First embodiment)

[0015] With reference to Fig. A first embodiment is described in Figures 1 to 4B. A linear solenoid generates a driving force in the axial direction. In a specific example, the linear solenoid according to this embodiment is used for a valve timing control mechanism arranged in a machine used for vehicle operation.

[0016] The valve timing mechanism controls the amount of oil supplied, thus changing the advance angle of the camshaft according to the axial driving force exerted by the linear solenoid. Changing the advance angle of the camshaft to either an advance or a retardation side by the valve timing mechanism alters the valve timing of the engine.

[0017] The linear solenoid includes a coil 1 which generates a magnetic force after it has been excited, a plunger arrangement AS which is driven in the axial direction due to this magnetic force generated by the coil 1, and a stator through which the magnetic flux generated by the excitation of the coil 1 flows.

[0018] The plunger arrangement AS described above includes a plunger piston 3, on the inside of which a through-hole 2 is arranged, and an outlet element 4, which is attached to an axial end of this plunger piston 3.

[0019] The stator described above includes a magnetic attraction core 5, which magnetically attracts the plunger piston 3 in the axial direction due to the magnetic force generated by the coil 1; a cylindrical magnetic feeder core 6, which delivers or receives the magnetic flux to or from the outer circumferential surface of the plunger piston 3; a rod-shaped central core 7, which delivers or receives the magnetic flux to or from the inner circumferential surface of the plunger piston 3; and a yoke 8, which covers the outer circumference of the coil 1.

[0020] The components of the linear solenoid described above are explained in detail. One end face (first face) in the axial direction (i.e., left face in) Fig. 1) is referred to below as the “front side”, and the other end side (second side) in the axial direction (i.e. right side in Fig. 1) is referred to below as the "back". The front-to-back direction is for illustrative purposes only and does not restrict the installation direction of the linear solenoid.

[0021] Coil 1 is obtained by winding a conductive wire, coated with insulation, in many turns around a resin coil former. Once excited, coil 1 generates the magnetic force. The magnetic flux generated by coil 1 forms a magnetic flux loop that passes through the stator and the plunger piston 3.

[0022] The coil 1 is energized via a connector 11. The connector 11 is a connecting device used for electrical connection via a connecting wire to a control device that variably controls the advance angle of the camshaft. This connector 11 is formed by a portion of a secondary molded resin 12 from which the coil 1 is formed. A terminal 11a, which is electrically connected to both ends of the coil 1, is located in the resin connector 11.

[0023] The plunger piston 3 is made of a magnetic material, such as iron. The plunger piston 3 is generally cylindrical and is positioned inside the magnetic feed core 6 and outside the central core 7. The outer diameter of the plunger piston 3 is slightly smaller than the inner diameter of the magnetic feed core 6. A tiny gap is therefore formed between the plunger piston 3 and the magnetic feed core 6 along its entire circumference. Thus, the plunger piston 3 and the magnetic feed core 6 are positioned so that they do not make direct contact with each other.

[0024] The bushing 2 functions as part of the plunger piston 3 and is attached to the inner circumference of the plunger piston 3 by press fits. The inner diameter of the bushing 2 is slightly larger than the outer diameter of the central core 7, and a sliding gap is formed between the bushing 2 and the central core 7. The bushing 2 is thus slidably mounted on the outer circumferential surface of the central core 7. Consequently, the plunger piston 3 is slidably mounted in the axial direction.

[0025] The feedthrough 2 is made of a magnetic material, such as iron. A non-magnetic material layer 13, also made of a non-magnetic material, is arranged on the inner circumferential surface of the feedthrough 2. The non-magnetic material layer 13 is formed on the inner circumferential surface of the feedthrough 2 by a coating technique or the like and can be made of a resin material or a non-magnetic metal.

[0026] The plunger piston 3 includes a vent line 14 that communicates or forms a connection in the axial direction. According to this embodiment, the vent line 14 is provided by grooves designed to extend axially along the inner circumferential surface of the plunger piston 3. The grooves are arranged at regular intervals in the radial direction of the plunger piston 3 to prevent deflection of the magnetic flux. The passage 2 described above is located on the inner diameter side of the groove. Thus, the magnetic flux between the plunger piston 3 and the central core 7 is transmitted and received via the passage 2.

[0027] The output element 4 transmits the displacement of the plunger piston 3 to the valve timing mechanism described above and is made of a non-magnetic material, such as stainless steel. The output element 4 is a shaft in the form of a rod extending axially through the center of a cover 15 made of a magnetic material, which blocks the inner surface of the magnetic attraction core 5. A press-fit cylinder 4a, which is press-fitted into the plunger piston 3, is integrally arranged with the rear end of the output element 4.

[0028] The magnetic attraction core 5 is formed from a magnetic material, such as iron. According to this embodiment, the magnetic attraction core 5 is integrally arranged with the yoke 8, although this is not to be considered a limitation. The rear end of the magnetic attraction core 5 is arranged at an axial distance relative to the front end of the magnetic feed core 6. When the plunger piston 3 is moved forward, the magnetic attraction core 5 overlaps the outer circumferential surface of the front end of the plunger piston 3 in the axial direction. The outer circumferential surface of the magnetic attraction core 5 in the region that overlaps the plunger piston 3 in the axial direction includes a tapered surface whose diameter decreases towards the rear.This tapered surface is designed to ensure that the magnetic attraction force exerted on the plunger piston 3 remains unchanged, even if the stroke of the plunger piston 3 changes.

[0029] The magnetic feed core 6 is made of a magnetic material, such as iron. The magnetic feed core 6 has a cylindrical shape and is inserted into the coil 1. An annular rear plate 6a, extending from the rear end of the feed core 6 towards the outer diameter side, is integrally provided with the magnetic feed core 6, as shown in this embodiment. The outer circumference of this rear plate 6a is magnetically coupled to the rear end of the yoke 8.

[0030] The central core 7 is made of a magnetic material, such as iron. The central core 7 is rod-shaped and extends from front to back along the central part of the coil 1. A flange section 7a is integrally formed with the rear end of the central core 7. The flange section 7a has the shape of a circular plate whose diameter increases towards the outer diameter side at the rear end of the central core 7. This flange section 7a is magnetically coupled to the magnetic feed core 6 and fills the gap between the rear end of the magnetic feed core 6 and the rear end of the central core 7.

[0031] The yoke 8 is formed from a magnetic material, such as iron. The yoke 8 has a cylindrical shape that covers the outer circumference of the coil 1. An annular front plate 8a, whose diameter decreases from its front end towards its inner diameter, is integrally arranged with the yoke 8 according to this embodiment. The magnetic attraction core 5 described above is formed at the inner end of this front plate 8a.

[0032] The following is a description of the volume change in the linear solenoid. As explained above, the flange part 7a closes the gap between the rear end of the magnetic feed core 6 and the rear end of the central core 7. The space enclosed by the magnetic feed core 6, the central core 7, the plunger piston 3, and the flange part 7a is a chamber α. The volume of the first chamber α must be changed such that the plunger piston 3 is displaced in the axial direction. Thus, in this embodiment, the vent line 14, which is connected to the first chamber α, is arranged to allow the volume change of the first chamber α.

[0033] The space within the cover 15 is referred to as a second space β. The second space β is a space that is connected to the front end of the ventilation line 14 described above. The volume of the second space β, in addition to the first space α, must be modified such that the plunger piston 3 is displaced in the axial direction.

[0034] The second chamber β is connected to the space outside the magnetic attraction core 5 and inside the coil 1 by the distance between the magnetic attraction core 5 and the magnetic feed core 6. This chamber is referred to as a third chamber γ. The front plate 8a includes one or more through-holes 16 for connecting to the third chamber γ and the outside. The volume of the second chamber β can be changed through this through-hole 16.

[0035] The space formed within the press-fit cylinder 4a and between the front end of the central core 7 and the rear end of the output element 4 is referred to as a fourth space δ. The volume of the fourth space δ, in addition to the first space α and the second space β, must be modified so that the plunger piston 3 can be displaced in the axial direction.

[0036] The inner diameter of the press-fit cylinder 4a is longer than the outer diameter of the central core 7. This creates a radial ventilation gap between the press-fit cylinder 4a and the central core 7. A further gap exists between the rear end of the press-fit cylinder 4a and the front end of the bearing component. This configuration connects the fourth chamber δ to the ventilation line 14. Consequently, the volume of the fourth chamber δ can be adjusted.

[0037] The output element 4 includes a contact part X that comes into contact with the front end of the central core 7 when the plunger piston 3 is moved towards the rear. The contact part X is located inside the press-fit cylinder 4a and on the rear end surface of the output element 4. The contact part X is brought into contact with the front end of the central core 7, thus restricting the movement of the plunger piston 3 towards the rear.

[0038] The linear solenoid according to this embodiment brings the contact part X into contact with the front end of the central core 7 such that an axial distance S is formed between the rear end of the plunger piston 3 and the flange part 7a. This distance S is explained below, where it is referred to as a rear-end distance. For further understanding, a specific example is described in which the plunger piston 3 is configured so that it does not come into contact with the flange part 7a, either by making the dimension of the central core 7 slightly longer in the axial direction than in the prior art, or by making the dimension of the plunger piston 3 slightly shorter in the axial direction than in the prior art.

[0039] The dimension of the distance S at the rear end can be short in the axial direction within a range that can prevent the adhesion phenomenon described above, although this should not be understood as a limitation. For further understanding, a specific example is described in which the distance S at the rear end is approximately 0.2 mm to 2 mm long. Of course, this numerical value is given only as a reference example and should not be understood as a limitation.

[0040] The distance S at the rear end need not be uniform and can vary in the radial direction. A specific example that exhibits a radial variation in the gap distance is in Fig. 1 shown. Fig. 1. The gap spacing of the distance S at the rear end should be large in an area near the ventilation line 14, and conversely, the gap spacing of the distance S at the rear end should be small in an area away from the ventilation line 14 (i.e., near the outer circumferential edge of the distance S at the rear end).

[0041] The following describes a first effect of the first embodiment. As described above, the linear solenoid according to the first embodiment brings the output element 4 into contact with the front end of the central core 7, so that the distance S at the rear end is created between the plunger piston 3 and the flange part 7a when the plunger piston 3 moves from the front to the rear.

[0042] Consequently, defects do not arise, such as the fact that part of the ventilation line 14 is blocked by the part with the enlarged diameter described in the prior art, thereby improving the response of the plunger piston 3.

[0043] In a state where the contact part X is in contact with the front end of the central core 7, the gap S is formed at the rear end between the plunger piston 3 and the flange part 7a. This eliminates the need to machine the grooves on the flange part 7a, which is required in the prior art to prevent sticking. Thus, in the linear solenoid according to this first embodiment, the machining of the grooves on the flange part 7a to improve the response of the plunger piston 3 can be omitted. In other words, a solenoid with excellent response can be produced at low cost.

[0044] The following is a description of the second effect of the first embodiment. First, the description addresses some problems. In contrast to the first embodiment, if the magnetic material part of the bushing 2 or the plunger piston 3 comes into contact with the flange part 7a, a strong magnetic attraction is generated at the contact point. This impairs the responsiveness of the plunger piston 3 when it begins to move. Consequently, a non-magnetic layer must be formed on the contact point when the bushing 2 or the plunger piston 3 comes into contact with the flange part 7a, resulting in increased costs. In this first embodiment, the plunger piston 3, including the bushing 2, is not in contact with the flange part 7a due to the distance S at its rear end.Therefore, no non-magnetic layer needs to be formed on the contact part, thus reducing costs. This allows the linear solenoid, which exhibits excellent responsiveness, to be manufactured cost-effectively.

[0045] A third effect of the first embodiment is described below. The plunger piston 3 according to this first embodiment is slidably mounted on the outer circumferential surface of the central core 7 by the feedthrough 2, which is attached to the inside of the plunger piston 3. The feedthrough 2 has a simple cylindrical shape, and thus the accuracy of its inner circumferential surface can be improved relatively easily. Consequently, the inclination of the feedthrough 2 relative to the central core 7 can be prevented. This improves the sliding capability of the plunger piston 3, thereby reducing the hysteresis of the plunger piston 3.

[0046] A fourth effect of the first embodiment is described below. In this first embodiment, a shape-changing element A is arranged at the front end of the central core 7. The shape-changing element A is a part of the central core 7 whose shape is changed such that the contact area between the contact part X and the central core 7 is reduced. A specific example of the shape-changing element A includes at least one or more projecting parts that bulge in the axial direction, one or more recessed parts that are recessed in the axial direction, one or more strip-shaped projections, or one or more grooves that extend in the radial direction.

[0047] The following describes the shape-changing part A used in the first embodiment. A modification differing from the first embodiment will be explained later in a third embodiment. As in Fig. 4A and Fig. As shown in Figure 4B, the front end of the central core 7 includes the shape-changing part A, which is a combination of a projecting part that bulges towards the front and a recessed part that is recessed towards the rear. Regarding the shape of the projecting part and the recessed part, in one instance of this embodiment, the shape of the projecting part, viewed from the axial direction, is circular, and the recessed part has a conical shape, although this is obviously not to be understood as a limitation. In particular, the outer circumferential surface of the projecting part is designed to have a tapered surface, the diameter of which decreases towards the front.

[0048] By providing the deformation part A, by forming the recessed sections 20 at the front end of the central core 7, the contact area between the contact part X and the central core 7 can be reduced. The adhesion phenomenon between the contact part X and the central core 7 can therefore be prevented. Consequently, the response of the plunger piston 3 can be further improved. (Second embodiment)

[0049] The following is made with reference to Fig. Sections 5A to 6E describe a second embodiment. In the embodiments described below, the same reference numerals as in the first embodiment above denote their corresponding functional objects. Only modified parts of the first embodiment are explained below, and the embodiment described above applies to the parts not described in the second embodiment.

[0050] A first characteristic technique according to the second embodiment is described below. This second embodiment provides a shape-changing part A on a contact part X. The shape of the shape-changing part A, which is arranged on the contact part X, is not subject to any restrictions and can be modified in various ways, such as by... Fig. Figures 5A to 6E are shown. A specific example of the deformation part A, which is arranged on the contact part X, is explained. As shown in Fig. As shown in 5A, the deformation part A can be a conically recessed part. As in Fig. As shown in Figure 5B, the shape-changing part A can be a recessed part with a linear or straight lower section. As shown in Fig. As shown in 5C, the deformation part A can be a protruding part that is bulged out in the form of a spherical surface. As shown in Fig. As shown in 5D, the shape-changing part A can be a protruding part with a linear or straight upper section.

[0051] As in Fig. As shown in Figure 6A, the deformation part A can be a protruding part or a recessed part whose shape, viewed from the axial direction, is circular. As shown in Fig. As shown in Figure 6B, the deformation part A can consist of grooves whose shapes, viewed from the axial direction, spread radially from the center to the outer diameter side, or of strip-shaped projections that spread radially from the center to the outer diameter side. As shown in Fig. As shown in Figure 6C, the shape of the deformation part A, viewed from the axial direction, can be a groove or a strip-shaped projection. As shown in Fig. As shown in Figure 6D, the shape of the deformation part A, viewed from the axial direction, can be a groove that cross-cuts, or a plus-shaped protruding part that cross-cuts.

[0052] By providing the shape-changing part A to the contact part X, a similar effect to the fourth effect of the first embodiment can be achieved.

[0053] A second characteristic technique according to the second embodiment is described below. As in Fig. 5E and Fig. As shown in Figure 6E, an output element 4 according to this second embodiment includes one or more through-holes B that connect a fourth chamber δ and a second chamber β. This through-hole B is formed by axially penetrating the part that joins the rear end of the output element 4 and the front end of a press-fit cylinder 4a. By providing this through-hole B, the volume of the fourth chamber δ can be easily changed. Consequently, the responsiveness of a plunger piston 3 can be further improved.

[0054] By forming the through-hole B, burrs can form at its rear end. This combines the technique of providing the shape-changing part A with the technique of providing the through-hole B. This allows for the formation of non-contacting burrs. In particular, by providing the shape-changing part A with a protruding shape at the contact part X or at the front end of a central core 7, the rear end of the through-hole B can be designed to be non-contacting with the central core 7. In this way, the burrs are not in contact with the other elements, even if some burrs have formed at the through-hole B. Consequently, deburring or similar processes after forming the through-hole B can be omitted.This reduces the production costs for the through-hole B, thereby creating the linear solenoid with improved responsiveness through the through-hole B at low cost. (Third embodiment)

[0055] With reference to Fig. The third embodiment is described in sections 7A to 8F. This third embodiment shows modifications to the shape-changing part A, which is arranged at the front end of the central core 7. Fig. 7A and Fig. 8A are reference examples in which the shape-changing part A is not arranged at the front end of the central core 7, and are used when applying the above second embodiment.

[0056] A specific example of the shape-changing part A, which is located at the front end of the central core 7, is described. As in Fig. As shown in Figure 7B, the deformation part A can be a protruding part with a linear or straight upper section. As shown in Fig. As shown in Figure 7C, the deformation part A can be a recessed part with a linear or straight lower section. As shown in Fig. As shown in Figure 7D, the deformation part A can be a protruding part that is bulged out in the shape of a spherical surface.

[0057] As in Fig. As shown in Figure 8B, the shape of the deformation part A, viewed from the axial direction, can have a groove or a strip-shaped projection. As shown in Fig. As shown in Figure 8C, the deformation part A can be a protruding part whose shape, viewed from the axial direction, is circular, and a minus-shaped groove can be formed on this protruding part. As shown in Fig. As shown in Figure 8D, the shape of the deformation part A, viewed from the axial direction, can be a circularly recessed part or a circularly protruding part. As shown in Fig. As shown in Figure 8E, the shape of the deformation part A, viewed from the axial direction, can be a groove that cross-intersects, or a plus-shaped protruding part that cross-intersects. As shown in Fig. As shown in Figure 8F, the deformation part A can include a protruding part whose shape is circular when viewed from the axial direction, and a plus-shaped groove can be formed on this protruding part.

[0058] Modifications to the foregoing embodiments are described below. The foregoing embodiments illustrate the example of a groove arranged on the inner circumferential surface of the plunger piston 3 as a means for forming the venting channel 14; however, the means for forming the venting channel 14 is not limited to this example. As a specific example, a groove extending in the axial direction may be provided on the outer circumferential surface of the plunger piston 3, or a hole may be provided that axially penetrates the plunger piston 3.

[0059] The foregoing embodiments illustrate the example of the feedthrough 2, which is arranged within the plunger piston 3; however, this example is not to be understood as a limitation. In particular, the non-magnetic material layer 13 can be formed directly on the inner circumferential surface of the plunger piston 3, and the inner circumferential surface of the plunger piston 3 slides directly on the outer circumferential surface of the central core 7.

[0060] The foregoing embodiments transfer the present disclosure to the linear solenoid, which transmits an axial force to the valve timing mechanism; however, this does not restrict the intended use of the linear solenoid.

[0061] Characteristic features of the linear solenoid according to the above embodiments can be explained as follows.

[0062] The output element 4 is brought into contact with one end of the central core 7, so that the plunger piston 3 and the flange part 7a are not in contact with each other. Thus, the output element 4 is brought into contact with one end of the central core 7, creating the axial distance S between the plunger piston 3 and the flange part 7a. This prevents defects such as the blockage of part of the vent line 14 by the part with the larger diameter, thereby improving the response of the plunger piston 3. The creation of the axial distance S between the plunger piston 3 and the flange part 7a eliminates the need to machine the groove on the flange part 7a to prevent sticking. Therefore, machining the groove on the flange part 7a to improve the response of the plunger piston 3 can be omitted.In other words, the cost-effective provision of the linear solenoid with excellent responsiveness is possible.

Claims

[1] Linear solenoid, having: a coil (1) which, when excited, generates a magnetic force; a cylindrical plunger piston (3) which is movably mounted in its axial direction inwards from the coil (1) and includes a vent line (14) which forms a connection in the axial direction; an output element (4) which is attached to one end of the plunger piston (3) on a first side in the axial direction; a magnetic attraction core (5) which magnetically attracts the plunger piston (3) in the axial direction due to the magnetic force generated by the coil (1); a cylindrical magnetic feed core (6) which delivers and receives the magnetic flux to and from an outer circumferential surface of the plunger piston (3); a rod-shaped central core (7) which transmits and receives the magnetic flux to and from an inner circumferential surface of the plunger piston (3); and a flange part (7a) which is arranged at one end of the central core (7) on a second side in the axial direction, wherein: the second side is a side opposite the first side in the axial direction; the flange part (7a) is formed in a shape whose diameter increases in the direction of an outer diameter side of the central core (7); the flange part (7a) closes off a space between one end of the magnetic feed core (6) on the second side in the axial direction and the end of the central core (7) on the second side in the axial direction; the output element (4) includes a contact part (X) which is brought into contact with one end of the central core (7) on the first side in the axial direction when the plunger piston (3) moves towards the second side in the axial direction; and when the contact part (X) is brought into contact with the end of the central core (7) on the first side in the axial direction, the plunger piston (3) defines an axial distance (S) between the plunger piston (3) and the flange part (7a). [2] Linear solenoid according to claim 1, further comprising a through-hole (2) which is arranged such that it is fixed inside the plunger piston (3) and which is slidably mounted on an outer circumferential surface of the central core (7), wherein the through-hole (2) has a cylindrical shape. [3] Linear solenoid according to claim 1 or 2, wherein the contact part (X) includes a deformation part (A) which reduces a contact area between the contact part (X) and the central core (7) when the contact part (X) and the central core (7) are in contact with each other. [4] Linear solenoid according to any one of claims 1 to 3, wherein the end of the central core (7) on the first side in the axial direction includes a deformation part (A) which reduces a contact area between the end of the central core (7) on the first side in the axial direction and the contact part (X) when the end of the central core (7) on the first side in the axial direction and the contact part (X) are in contact with each other.

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