Patent Application
20200075280
This application claims priority to European Patent Application No. EP 18191250.2, filed Aug. 28, 2018, the contents of which are hereby incorporated by reference in its entirety.
The present invention relates to an electromagnetic switch for a starting device, which electromagnetic switch has a coil carrier onto which a coil wire of a coil winding is wound. The invention furthermore relates to a starting device having a switch of said type.
For the starting of internal combustion engines, use is commonly made of starting devices. A starting device of said type commonly has a starting element, for example a pinion, which, for the starting of the internal combustion engine, is placed in engagement with a counterpart starting element of the internal combustion engine, for example a ring gear, and drives the latter in order to start the internal combustion engine.
A starting device of said type is known, for example, from DE 10 2009 052 938 A1. The starting device has an electromagnetic switch which has a coil carrier with a holding coil and an adjustment coil or attracting coil wound thereon, which coils are each wound from a coil wire around the coil carrier. During operation, the coils generate a magnetic field within the coil carrier, which magnetic field adjusts a ferromagnetic piston within the coil carrier in the direction of a core. The starting device furthermore has a drive motor which transmits a torque via a pinion to a ring gear of an internal combustion engine in order to start the internal combustion engine. The pinion is placed in engagement with the ring gear, and removed from such engagement, by means of the electromagnetic switch. The electromagnetic switch and the drive motor are in this case connected electrically in series, such that an electrical current flows through the coils in order to generate the magnetic field and subsequently to the drive motor in order to drive the latter.
In the case of such starting devices, it is desirable for sufficient torque for starting the internal combustion engine to be provided. This is normally realized by means of an increase of the electrical current supplied to the drive motor, which in turn leads to a stronger magnetic field in the coil carrier and thus to an increased adjustment force of the piston and ultimately of the pinion in the direction of the ring gear. This increased adjustment force however leads to more intense striking of the pinion against the ring gear, which can lead to damage to the pinion and/or to the ring gear.
It is furthermore desirable for the coil geometry of the electromagnetic switch to be left as far as possible unchanged.
To weaken the magnetic field generated within the coil carrier by means of the coils, DE 10 2009 052 938 A1 proposes that a ferromagnetic bypass body be provided on the coil carrier, which bypass body weakens the magnetic field generated within the coil body by the coils. This has the result that smaller structural spaces are available for the coil winding if it is sought to maintain an unchanged overall geometry. Said document also mentions winding a part of the coil winding in an opposite direction in relation to the rest of the coil winding.
US 2014/0240067 A1 proposes that the piston within the coil carrier be equipped with an encircling groove in order to reduce the influence of the magnetic field on the piston. The non-uniform profile of the shell surface of the piston however leads to non-uniform sliding of the piston within the coil carrier. Furthermore, the maximum possible dimensions of the groove are limited, such that a small reduction of the adjustment force is possible.
From US 2011/0260562 A1, it is known for a lug to be attached to the outside of a coil carrier of an electromagnetic switch, along which lug a coil wire of the coil winding is guided in order for the coil wire to be wound in opposite directions on mutually averted sides of the lug.
EP 3 131 101 A1 has disclosed a coil carrier which, on the outside, is equipped with an encircling separating body with a recess in order for the associated coil wire to be able to be guided through the recess and wound in opposite directions.
The present invention is concerned with the problem of specifying, for an electromagnetic switch of the above-stated type, and for a starting device having an electromagnetic switch of said type, improved or at least alternative embodiments which are distinguished in particular by an efficient reduction of the magnetic force acting on the piston and/or by a small structural space requirement.
Said object is achieved according to the invention by means of the subjects of the independent claim(s). The dependent claim(s) relate to advantageous embodiments.
The present invention is based on the general concept whereby, in an electromagnetic switch, a ferromagnetic bypass body which encloses a cavity of a coil carrier and which is arranged radially between the cavity and a coil winding is, in a passive position of a piston of the electromagnetic switch, arranged so as to axially overlap an axial gap between the piston and a core of the electromagnetic switch, and furthermore, at least one winding of a coil winding of the electromagnetic switch which is wound in an opposite direction in relation to the rest of the coil winding is arranged so as to axially overlap the bypass body. Here, the ferromagnetic bypass body serves for diverting the magnetic flux or the magnetic field that is generated by the coil winding during operation, that is to say when said coil winding is electrically energized. The at least one winding which is wound in the opposite direction serves for weakening the magnetic field in the cavity. The axially overlapping arrangement of the bypass body between the piston and the core in the passive position of the piston, and the axially overlapping arrangement of the at least one winding wound in the opposite direction with the bypass body, interact synergistically here in order to weaken the magnetic field between the piston and the core in an efficient manner and locally such that, during the operation of the coil winding, the piston is adjusted in the direction of the core with a lower adjustment force.
In accordance with the concept of the invention, the electromagnetic switch has the coil carrier which has a carrier wall extending in an axial direction, which carrier wall encloses the cavity in the coil carrier. The carrier wall is thus in particular of cylindrical form. The piston is arranged in axially adjustable fashion in the cavity of the coil carrier. The coil winding is a coil wire wound on that side of the carrier wall which is averted from the cavity, or said coil winding has a wound coil wire of said type. During operation, the coil winding is flowed through by an electrical current and thereby generates a magnetic field within the cavity, which magnetic field adjusts the piston axially in the cavity. The piston is designed correspondingly for this purpose, for example is at least partially ferromagnetic. Here, the magnetic field generated by the coil winding adjusts the piston in the direction of a core, which is preferably axially fixed and in particular accommodated in the cavity. When the coil winding is not in operation, the piston is situated in the passive position. In said passive position, the axial gap is formed, in the cavity, between the piston and the core in an axial direction. The coil wire is wound in at least two winding sections in opposite winding directions. That is to say, the coil wire is, in a first axial winding section, wound in a first winding direction around the carrier wall. The first winding direction is that which serves for generating a magnetic field for the purposes of adjusting the piston in the direction of the core. In a second axial winding section, the coil wire is furthermore wound in a second winding direction around the carrier wall, wherein the second winding direction is opposite to the first winding direction. According to the invention, the bypass body is, in the passive position, arranged so as to axially overlap the axial gap, and at least one winding of the second winding section is arranged so as to axially overlap the bypass body. The bypass body diverts the magnetic field or the magnetic flux. Here, the bypass body has a saturation limit. The at least one winding of the second winding section which axially overlaps the bypass body reduces the magnetic flux through the bypass body, such that ultimately an increased magnetic flux can flow through the bypass body, until the latter has reached the saturation limit. This leads directly to a reduction of the magnetic field or of the magnetic flux between the piston and the core, such that the adjusting force is correspondingly reduced. Furthermore, the electrical energization of the electromagnetic switch, in particular of the coil winding, can be maintained, such that subsequent applications, in particular a supply of electricity to a downstream motor of an associated starting device for an internal combustion engine, remains unchanged, or, in the case of a reduced adjustment force on the piston, can be increased, such that it remains possible for an equal or increased torque to be transmitted by means of the motor. Said torque is commonly transmitted by means of a starting element of the associated starting device for starting the internal combustion engine to a counterpart starting element of the internal combustion engine, such that the torque required for the starting process remains constant, while the adjustment of the starting element in the direction of the counterpart starting element is reduced, and thus damage to starting element and counterpart starting element is prevented or at least reduced. Secondly, the torque can be increased, without the adjustment force being correspondingly increased.
In the present case, the stated directions relate to the axial direction. Here, axial means in the axial direction or parallel to the axial direction. Radial direction, and radial, mean perpendicular to the axial direction or perpendicular to the axial. The circumferential direction is also to be understood in relation to the axial direction or axial.
The first winding section is to be understood here to mean that section of the coil winding which is wound in the first winding direction and which thus extends axially. The first winding section may in this case furthermore extend radially, for example over two or more radially successive rows of the coil winding. Here, the first winding section may have different axial extents in the different rows. In particular, the first winding section is axially shorter in the row in which the second winding section is also arranged than in other rows.
The second winding section is that section of the coil winding in which the coil wire is wound in the second winding direction. Accordingly, the second winding section extends axially. It is also possible for the second winding section to extend across multiple radially successive rows of the coil winding.
The coil winding expediently has fewer windings in the second winding direction than in the first winding direction.
The switch may in principle have multiple coil windings or coils. In particular, the switch may have an attracting coil for adjusting the piston in the direction of the core and a holding coil for holding the core in one position. The coil winding described here is preferably the attracting coil.
Embodiments are preferable in which at least one winding of the second winding section furthermore axially overlaps the axial gap. Said winding may be the at least one winding which axially overlaps the bypass body. An improved weakening of the magnetic field in the axial gap, and thus between the piston and the core, is thus achieved.
Embodiments have proven to be advantageous in which the bypass body axially entirely overlaps the axial gap. That is, the entire axial length of the bypass body can be in axial overlap with the axial gap. This means in particular that the bypass body extends axially between face sides, which face toward one another and which delimit the axial gap, of the core and of the piston. The action of the bypass body is thus substantially concentrated on and limited to the axial gap, such that the magnetic field in the axial gap and thus between the piston and core is efficiently reduced and confined.
It is alternatively or additionally preferable for all of the windings of the winding section to axially overlap the axial gap. The action of the second winding section is thus locally limited to and concentrated on the axial gap, such that, in turn, effective weakening of the magnetic field between the piston and the core is achieved.
In principle, the bypass body and the second winding section may have any desired axial extents or lengths. In particular, the length of the bypass body may correspond to the length of the second winding section. Here, it is conceivable for the bypass body and the second winding section to be arranged so as to be aligned with one another axially on both sides. This leads to an advantageous interaction between bypass body and second winding section for the weakening of the magnetic field in the axial gap.
Embodiments are preferable in which the bypass body is spaced apart axially from the core. In this way, a magnetic flux from the bypass body to the core is prevented or at least reduced. Consequently, a more effective weakening of the magnetic field between the piston and the core is achieved. An axial distance or clearance between the bypass body and the core is preferably at least 2 mm.
The bypass body arranged radially between the cavity and the coil winding may be accommodated as desired in the switch.
The bypass body is advantageously accommodated in the carrier wall. This leads to simplified assembly of the electromagnetic switch and to an effective reduction of the magnetic field between the piston and the core. Here, the bypass body may be enclosed in a circumferential direction and/or radially by the carrier wall of the coil carrier.
The coil wire may also, in a third axial winding section, be wound in the first winding direction around the carrier wall, wherein the second winding section is arranged axially between the first winding section and the third winding section. This means that the third winding section corresponds to the first winding section, with the difference that, in the row in which the second winding section is arranged, the first winding section and the third winding section are arranged on axially mutually averted sides of the second winding section.
It is self-evident that the subject matter of this invention encompasses not only the electromagnetic switch but also a starting device having an electromagnetic switch of said type.
Further important features and advantages of the invention will emerge from the subclaims, from the drawings and from the associated Figure description based on the drawings.
It is self-evident that the features mentioned above and the features yet to be discussed below may be used not only in the respectively specified combination but also in other combinations or individually without departing from the scope of the present invention.
Preferred exemplary embodiments of the invention are illustrated in the drawings and will be discussed in more detail in the following description, wherein identical reference designations relate to identical or similar or functionally identical components.
In the drawings, in each case schematically:
An electromagnetic switch 1, hereinafter also referred to for short as switch 1, as shown for example in
The switch 1 has a coil carrier 16 which has a carrier wall 19, which carrier wall extends in cylindrical form in an axial direction 17 and encloses a cavity 18, and on which carrier wall the coil winding 13 is wound. In the example shown, the coil winding 13 extends from a radially projecting first end wall 39 to a radially projecting second end wall 40, which is situated axially opposite the first end wall 39, of the coil carrier 16. The end walls 39, 40 run in each case in closed form in a circumferential direction and are of disk-like form. Here, the coil winding 13 forms an attracting coil 20 of the switch 1. In the examples shown, the switch 1 furthermore has a holding coil 21, which is wound radially outside the coil winding 13. The coil winding 13 and the holding coil 21 are arranged in a housing 50 of the switch 1. When electrically energized, the coil winding 13 or the attracting coil 20 serves for the adjustment of the piston 12 in the direction of a core 22, which, like the piston 12, is accommodated in the cavity 18 but is fixed therein and is thus axially non-adjustable. For this purpose, during operation, that is to say when energized, the coil winding 13 and thus the attracting coil 20 and the holding coil 21 generate, within the cavity 18, a magnetic field which exerts an adjusting force on the piston 12 and thus adjusts said piston axially in the direction of the core 22. For this purpose, the piston 12 is at least partially, preferably entirely, ferromagnetic. With the holding coil 21, it is possible to hold the piston 12 in its respectively present position. The attracting coil 20 and the holding coil 21 in this case generate such a magnetic field, which subjects the piston 2 to an adjusting force opposed to the spring force of the at least one spring 14, such that, for the adjustment of the piston 12 in the direction of the core 22, the spring force is overcome, and for the holding of the piston 12 in its present position, a compensation of the spring force is realized. The piston 12 is mechanically connected, by means of a connecting element 23 which is of rod-like form in the example shown, to a switching element 24. During the adjustment of the piston 12 in the direction of the core 12, which is likewise at least partially ferromagnetic, the switching element 24 is adjusted in the direction of electrical contacts 25, wherein the switching element 24, when it makes contact with the electrical contacts 25, electrically connects said contacts 25 to one another. Thus, an electrical connection is produced between two lines 26 by means of which electricity is supplied to the electric motor 4. Here, for the starting of the internal combustion engine 3, the coils 20, 21 are electrically energized, and here, adjust the piston 12 in the direction of the core 22 until the switching element 24 produces an electrical connection between the electrical contacts 25. In this state, the electrical energization of the attracting coil 13 is stopped, and the holding coil 21 is electrically energized, in order to hold the piston 12 in position and thus maintain an electrical connection between the lines 26 that supply electricity to the electric motor 4. In this position, it is furthermore the case that the starting element 6 and the counterpart starting element 7 are in engagement, such that the electric motor 4 starts the internal combustion engine 3. When the internal combustion engine 3 has been started, the supply of electricity to the starting device 1 is stopped, such that no magnetic field is generated, and the spring force adjusts the piston 12 back into a passive position 27, which is illustrated in
In the examples shown, the coil wire 30 of the coil winding 13 is wound in multiple radially successive rows 31. Here, the row 31′ situated closest to the cavity 18 is referred to as first row 31′.
In the passive position 27, the piston 12 is separated from the core 22 by an axial gap 32 running in an axial direction 17, which axial gap extends axially between a face side 33, facing toward the core 22, of the piston 12, hereinafter also referred to as piston face side 33, and a face side 34, facing toward the piston 12, of the core 22, hereinafter also referred to as core face side 34.
To reduce the adjusting force, the electromagnetic switch 1 has a bypass body 41, which encloses the cavity 18 and which is arranged radially between the cavity 18 and the coil winding 13. Here, the bypass body 41 is, in the passive position 27 of the piston 12, arranged so as to axially overlap the axial gap 32. Furthermore, the coil winding 13, which forms the attracting coil 20, is wound at least partially oppositely to the winding direction 28 with which the coil winding 13, when electrically energized, adjusts the piston 12 in the direction of the core 22, hereinafter referred to as first winding direction 28, specifically is wound in a second winding direction 29. A coil wire 30 of the coil winding 13 is thus wound partially in the first winding direction 28 and partially in the second winding direction 29, wherein the different winding directions 28, 29 are illustrated or indicated in
Here, the first winding section 35 is to be understood to mean that section of the coil winding 13 which is wound in the first winding direction 28 and thus extends axially. The second winding section 36 is that section of the coil winding 13 in which the coil wire 30 is wound in the second winding direction 29. Accordingly, the second winding section 36 extends axially. It is also possible for the second winding section to extend across multiple radially successive rows 31 of the coil winding 13.
In the examples of
Here, at least one winding of the second winding section 36 is arranged so as to axially overlap the bypass body 41. In the example shown in
The exemplary embodiment shown in
A further exemplary embodiment of the switch 1 is illustrated in
The exemplary embodiment shown in
In the exemplary embodiment shown in
The exemplary embodiment shown in
The exemplary embodiment shown in
In the examples shown, the bypass body 41 is accommodated by means of the coil carrier 16. For this purpose, the coil body 16 has an axial shoulder 49 which extends in a circumferential direction. Here, the bypass body 41 is surrounded in form-fitting fashion by the carrier wall 19 or the shoulder 49.
In the example shown in
In all of the examples shown, the bypass body 41 is furthermore spaced apart axially from the core 22.
| Number | Date | Country | Kind |
|---|---|---|---|
| 18191250.2 | Aug 2018 | EP | regional |
