WO2019072516A1

WO2019072516A1 - Electromagnetic switch and starter comprising electromagnetic switch

Info

Publication number: WO2019072516A1
Application number: PCT/EP2018/075480
Authority: WO
Inventors: Hongwang ZHAO; Renlin Xu
Original assignee: Robert Bosch Gmbh
Priority date: 2017-10-09
Filing date: 2018-09-20
Publication date: 2019-04-18
Also published as: CN109637855A

Abstract

An electromagnetic switch and a starter comprising the electromagnetic switch, wherein the electromagnetic switch comprises a housing (11); a fixed core (13), fixed to the housing; a movable core (14), mounted to the housing so as to be axially movable relative to the fixed core (13); a first electromagnetic coil (121, 122), which when energized generates a magnetic field having a force of attraction for the movable core (14) towards the fixed core (13); a push rod (15), connected to the movable core (14) and moving together with the movable core (14); and the electromagnetic switch further comprises a second electromagnetic coil (123) disposed in relation to the movable core (14); when the second electromagnetic coil (123) is energized, the second electromagnetic coil generates a magnetic field having a force of attraction away from the fixed core (13).

Description

Description Title

Electromagnetic switch and starter comprising electromagnetic switch Technical field

[0001] The present invention relates to an electromagnetic switch of a starter.

[0002] The present invention further relates to a starter comprising the electromagnetic switch.

Background art

[0003] Fig. 1 is a structural schematic diagram of an existing starter. The starter comprises a DC electric motor 40', a transmission mechanism 50' and a control mechanism. The DC electric motor 40' generates torque under the action of a DC voltage of a battery. When an engine of a vehicle is started, a shaft 41' of the DC electric motor rotates, and drives a crankshaft of the engine to rotate through the meshing or engagement of a drive gear 54' of the transmission mechanism 50' with a ring gear of a flywheel of the engine, thereby starting the engine. The transmission mechanism 50' of the starter is mounted on an extension shaft 41' of an armature of the DC electric motor. When the vehicle engine is started, the drive gear meshes with the engine flywheel gear, causing the engine to start. At the same time, once the vehicle engine has started, the drive gear 54' automatically disengages from the armature shaft 41' of the DC electric motor, to prevent electric motor overspeed.

[0004] The control mechanism of the starter is also called an electromagnetic switch 10'; the function thereof is to electromagnetically control the opening/closing of a starter circuit, and control the outward movement and return of the drive gear 54' which engages with the engine flywheel.

Fig. 2 is an enlarged drawing of the electromagnetic switch part of the starter in fig. 1. As shown in fig. 2, the electromagnetic switch 10' comprises a housing 11', an electromagnetic coil 12', a fixed core 13', a movable core 14' and a push rod 15'. The electromagnetic coil 12' and the fixed core 13' are inside the housing 11' and stationary with respect to the housing 11'; the movable core 14' is surrounded by the electromagnetic coil 12', and can move in an axial direction within the electromagnetic coil 12'; the push rod 15' runs through the fixed core 13' and the movable core 14', and is fixed to the movable core 13'. A contact bridge 17' is provided at one end of the push rod 15', said end projecting from the fixed core 13'; the contact bridge 17' is a moving contact, and two static contacts 18' are arranged opposite the contact bridge 17'. Referring to fig. 1, a shifting fork 51' of the transmission mechanism 50' is provided at one end of the push rod 15', said end projecting from the moveable core 14', and an extremity of the shifting fork 51' is connected to a rotation shaft 52'; one end of the rotation shaft 52' is connected to the armature shaft 41' of the DC electric motor 40', and another end of the rotation shaft 52' is connected to the drive gear 54'.

[0006] Once the starter has been started, the electromagnetic coil 12' is energized and generates an electromagnetic force. Under the action of the electromagnetic force, the moveable core 14' moves towards the fixed core 13', and the push rod 15' moves together with the moveable core 14'. As can be seen from fig. 1, under the action of the movement of the push rod 15' to the right, the shifting fork 51' on the push rod 15' pivots, causing the rotation shaft 52' to move to the left, and thereby causing the drive gear 54' to mesh with the engine flywheel. At the same time, the contact bridge 17' on the push rod 15' approaches the static contacts 18' until it comes into contact with the static contacts 18', so that a main circuit of the starter is closed.

[0007] A spring 16' is disposed between the fixed core 13' and the moveable core 14'. When the moveable core 14' moves to the right, the spring 16' is compressed. When the electromagnetic force generated by the electromagnetic coil 12' disappears, the moveable core 14' drives the push rod 15' to move to the left under the action of the restoring force of the spring, thereby pulling, via the shifting fork 51', the drive gear 54' away from the engine flywheel through the rightward movement of the rotation shaft 52'. The leftward movement of the push rod 15' also separates the contact bridge 17' from the static contacts 18', thereby breaking the main circuit of the starter, so that the starter stops running.

[0008] The rotation shaft 52' is rotatably supported in the starter by means of a bearing 53'. Due to the reciprocal motion of the rotation shaft 52', a surface of the bearing 53' in contact with the rotation shaft 52' experiences wear after a long period of time, causing an increase in the coefficient of friction between the rotation shaft 52' and the bearing 53', so that the frictional force increases. If the frictional force becomes greater than the spring restoring force, the rotation shaft 52' will be unable to pull the drive gear away from the engine flywheel, and the starter will fail.

Content of the invention

[0009] One aspect of the present invention is the provision of an electromagnetic switch, comprising:

a housing;

a fixed core, fixed to the housing;

a movable core, mounted to the housing so as to be axially movable relative to the fixed core;

a first electromagnetic coil, which when energized generates, for the movable core, a magnetic field having a force of attraction towards the fixed core;

a push rod, connected to the movable core and moving together with the movable core; the electromagnetic switch further comprises a second electromagnetic coil disposed in relation to the movable core; when the second electromagnetic coil is energized, the second electromagnetic coil generates a magnetic field having a force of attraction away from the fixed core.

[0010] In the electromagnetic switch, the second electromagnetic coil is arranged on one side of the first electromagnetic coil, said side being remote from the fixed core.

[0011] In the electromagnetic switch, at least a part of the movable core can move axially at an inner periphery of the second electromagnetic coil.

[0012] The electromagnetic switch further comprises a spring located between the fixed core and the movable core; under the action of the second electromagnetic coil and the spring, the push rod moves away from the fixed core together with the movable core.

[0013] In the electromagnetic switch, the first electromagnetic coil and the second electromagnetic coil are in the housing, and the second electromagnetic coil is equipped with a magnetically permeable bridge of the same material as the housing.

[0014] In the electromagnetic switch, the magnetically permeable bridge is an annular partition provided in the housing, the annular partition dividing the housing into a first space accommodating the first electromagnetic coil and a second space accommodating the second electromagnetic coil in an axial direction.

[0015] The electromagnetic switch further comprises a control apparatus for controlling the second electromagnetic coil; when the control apparatus detects that the electromagnetic switch is open, the second electromagnetic coil is controlled to be energized for a period of time.

[0016] In the electromagnetic switch, the control apparatus is an electronic control unit or a relay.

[0017] Another aspect of the present invention is the provision of a starter, comprising an electromagnetic switch of any one of the embodiments above; and

an electric motor, turned on by the electromagnetic switch, wherein

the electromagnetic switch further comprises a moving contact connected to the push rod and a relatively stationary static contact; when the moving contact moves with the push rod and comes into contact with the static contact, the static contact and the electric motor are energized.

[0018] The starter further comprises:

a transmission mechanism, comprising:

a shifting fork, provided on one end of the push rod of the electromagnetic switch, said end being remote from the fixed core;

a rotation shaft, having an input end connected to a shaft of the electric motor and an output end connected to a drive gear, wherein reciprocal motion of the push rod is transmitted to reciprocal motion of the rotation shaft via pivoting of the shifting fork.

[0019] The electromagnetic force generated by the second electromagnetic coil impels the movable core to move away from the fixed core. The electromagnetic force generated by the second electromagnetic coil is in the same direction as the restoring force of the spring, therefore the provision of the second electromagnetic coil increases the force driving the movable core to move in a reverse direction.

[0020] The first electromagnetic coil and the electric motor are both turned on and energized by main contacts (i.e. a starting switch of the starter). When it is detected that the main contacts are disconnected, the second electromagnetic coil is energized. Once the second electromagnetic coil is energized, this is maintained for a period of time, helping the movable core to return to an initial position.

[0021] The push rod is fixed to the movable core; one end of the push rod is connected to the rotation shaft via the shifting fork, and the rotation shaft is connected to the drive gear meshed with an engine flywheel. The movement of the push rod in the reverse direction pulls the rotation shaft away from the engine flywheel. Due to the action of the second electromagnetic coil, the reverse action force on the push rod is increased, overcoming the frictional force between the rotation shaft and the bearing, ensuring disengagement of the rotation shaft from the engine flywheel, and extending the service life of the starter.

[0022] Other aspects and features of the present invention will become clear through the following detailed explanation, which makes reference to the accompanying drawings. However, it should be known that the drawings are designed purely for explanatory purposes, and do not limit the scope of the present invention, because this should make reference to the attached claims. It should also be known that the drawings are merely intended to conceptually illustrate the structure and procedure described here; unless stated otherwise, the drawings need not be drawn to scale.

Description of the accompanying drawings

[0023] By reading the following detailed explanation of particular embodiments with reference to the drawings, a fuller understanding of the present invention will be gained; identical reference labels in the drawings always represent identical elements in the drawings. Here:

Fig. 1 is a structural schematic diagram of a starter in the prior art.

Fig. 2 is an enlarged schematic diagram of the electromagnetic switch of the starter in fig. 1.

Fig. 3 is a structural schematic diagram of an embodiment of an electromagnetic switch of a starter to which the present invention relates.

Fig. 4 is a control circuit diagram to which the electromagnetic switch in fig. 3 relates. Particular embodiments

[0024] To help those skilled in the art to gain a precise understanding of the subject matter for which protection is claimed in the present invention, particular embodiments of the present invention are described in detail below with reference to the drawings.

[0025] Fig. 3 is a structural schematic diagram of an embodiment of an electromagnetic switch 10 to which the present invention relates. As shown in the figure, the electromagnetic switch 10 comprises a housing 11, a first winding 121, a second winding 122, a fixed core 13, a movable core 14 and a push rod 15. The housing 11 is made of a material with good magnetic permeability. The first winding 121, second winding 122 and fixed core 13 are disposed in the housing 11. In the embodiment shown in the figure, the first winding 121 and the second winding 122 are arranged coaxially, with the first winding 121 being wrapped around the second winding 122. The first winding 121 and the second winding 122 are fixed in the housing 11 by means of a support. The fixed core 13 is disposed at one side of the first winding 121 and the second winding 122. The movable core 14 is disposed at an inner periphery of the second winding 122, and can move axially relative to the fixed core 13 under the action of the first winding 121 and the second winding 122. The first winding 121 is an attractive winding, and can pull the movable core 14 to draw close to the fixed core 13. The second winding 122 is a holding winding, and can hold the pulled movable core 14.

[0026] The push rod 15 runs through the fixed core 13 and the movable core 14 and is fixed to the movable core 14. The push rod 15 may be an assembly-type push rod as shown in the figure, or a one-piece push rod. The push rod 15 is fixed to the movable core 14, and moves with the movable core 14. A contact bridge 17 is provided at one end of the push rod 15, said end projecting from the fixed core 13; the contact bridge 17 is a moving contact, and two static contacts 18 in the form of wiring terminals, corresponding to the moving contact, are provided in the housing 11. When the movable core 14 moves towards the fixed core 13 such that the contact bridge 17 on the end of the push rod 15 comes into contact with the static contacts 18, a starter main circuit is closed. A shifting fork, not shown, is connected to another end of the push rod 15, said end projecting from the moveable core; the shifting fork is in turn connected to a rotation shaft connected to a drive gear. When the push rod 15 moves, the shifting fork pivots, thereby driving the rotation shaft to move.

[0027] A third winding 123 relating to the movable core 14 is also provided in the housing 11, and has the function of a return winding for causing the movable core 14 to move back. When the third winding 123 acts on the movable core 14, the movable core 14 moves away from the fixed core 13.

[0028] The third winding 123 is fixed in a similar manner to the other electromagnetic coils, i.e. the first winding 121 and the second winding 122, also being fixed in the housing 11 by means of a support. The arrangement of the movable core 14 relative to the third winding 123 is based on Lenz's law, i.e. the magnetic field of an induced current must always oppose the change in magnetic flux which gives rise to the induced current; when the third winding 123 is excited and generates a magnetic field, the movable core 14 tends to move in such a way as to oppose the change in magnetic flux of the magnetic field generated by the third winding 123. As shown in the figure, the third winding 123 is arranged at that side of the first winding 121 and the second winding 122 which is remote from the fixed core 13; when the third winding 123 is excited, the movable core 14 tends to move in a reverse direction.

[0029] A spring 16 is also disposed between the fixed core 13 and the moveable core 14. When the first winding 121 and the second winding 122 generate an electromagnetic force, the movable core 14 moves towards the fixed core 13; at this time, the spring 16 is compressed. When the electromagnetic force generated by the first winding 121 and the second winding 122 disappears, the restoring force of the spring 16 causes the movable core 14 to move away from the fixed core 13. When the third winding 123 is energized, the electromagnetic force generated by the third winding 123 combined with the restoring force of the spring 16 can increase the force applied to the movable core 14 to make the latter move away from the fixed core 13, helping the movable core 14 and the push rod 15 to drive the shifting fork to move in the opposite direction to the fixed core 13, and thereby increasing the force pulling the drive gear away from the engine flywheel.

[0030] The axial distance between the third winding 123 and the movable core 14 must not be too great. When the movable core 14 moves away from the fixed core 13, at least a part of the movable core 14 moves at an inner periphery of the third winding 123.

[0031] The housing 11 is extended axially due to the addition of the third winding 123. The interior of the housing 11 comprises a first space accommodating the first winding 121 and the second winding 122, and a second space accommodating the third winding 123. In order to enhance the movable core return effect, the third winding 123 may be equipped with a magnetically permeable bridge 124. The magnetically permeable bridge

124 is made using the same magnetically permeable material as the housing 11. The magnetically permeable bridge 124 may be an annular partition disposed in the housing 11, located between the first space and the second space.

[0032] Fig. 4 shows a circuit diagram of connections among the various coils in the starter to which the present invention relates. As shown in the figure, a starting switch of the starter is shown as main contacts 31 in the circuitry; once the starting switch is closed, a DC electric motor M (40) is connected and operates. The contact bridge on the end of the push rod and the static contacts are shown as auxiliary contacts 32 in the circuitry; once the contact bridge and the static contacts are in contact, the static contacts and the electric motor are energized, and a main circuit 60 is closed. The first winding 121 and the second winding 122 are both connected to the main contacts 31; once the main contacts 31 are closed, the first winding 121 and the second winding 122 are energized, generating a magnetic field force which causes the movable core to move. The third winding 123 is connected to a control apparatus 125, in order to control the time at which the third winding 123 is energized. When the control apparatus 125 detects that the main contacts 31 are disconnected, the third winding 123 is controlled so as to be energized for a preset period of time, in order to provide an electromagnetic force causing the movable core to move in a reverse direction. The control apparatus

125 may be an electronic control unit (ECU) or a relay.

[0033] Referring to figs. 3 and 4, the starting switch starts the electric motor, the main contacts 31 close, the first winding 121 and the second winding 122 are energized and generate a magnetic field force, the movable core 14 moves towards the fixed core 13, and the spring 16 is compressed, until the contact bridge 17 comes into contact with the static contacts 18, thereby closing the auxiliary contacts 32. Once the auxiliary contacts 32 are closed, the main circuit 60 is closed. When the main contacts 31 are disconnected, this is detected by the control apparatus 125, which immediately commands the third winding 123 to be energized and maintains this for a preset time; the third winding 123 generates a magnetic field, and the electromagnetic force and the spring restoring force together cause the movable core 14 to move away from the fixed core 13.

[0034] Although particular embodiments of the present invention have been shown and described in detail in order to explain the principles of the present invention, it should be understood that the present invention may be implemented in other ways, without departing from such principles.

Claims

1. An electromagnetic switch (10), comprising:

a housing (11);

a fixed core (13), fixed to the housing (11);

a movable core (14), mounted to the housing (11) so as to be axially movable relative to the fixed core (13);

a first electromagnetic coil (121, 122), which when energized generates, for the movable core (14), a magnetic field having a force of attraction towards the fixed core; a push rod (15), connected to the movable core (14) and moving together with the movable core (14);

characterized in that the electromagnetic switch (10) further comprises a second electromagnetic coil (123) disposed in relation to the movable core (14); when the second electromagnetic coil (123) is energized, the second electromagnetic coil (123) generates a magnetic field having a force of attraction away from the fixed core.

2. The electromagnetic switch as claimed in claim 1, characterized in that the second electromagnetic coil (123) is arranged on one side of the first electromagnetic coil (121, 122), said side being remote from the fixed core (13).

3. The electromagnetic switch as claimed in claim 1, characterized in that at least a part of the movable core (14) can move axially at an inner periphery of the second electromagnetic coil (123).

4. The electromagnetic switch as claimed in claim 1, characterized in that the electromagnetic switch (10) further comprises a spring (16) located between the fixed core (13) and the movable core (14); under the action of the second electromagnetic coil (123) and the spring (16), the push rod (15) moves away from the fixed core (13) together with the movable core (14).

5. The electromagnetic switch as claimed in claim 1, characterized in that the first electromagnetic coil (121, 122) and the second electromagnetic coil (123) are in the housing (11), and the second electromagnetic coil (123) is equipped with a magnetically permeable bridge (124) of the same material as the housing (11).

6. The electromagnetic switch as claimed in claim 5, characterized in that the magnetically permeable bridge (124) is an annular partition provided in the housing (11), the annular partition dividing the housing (11) into a first space accommodating the first electromagnetic coil (121, 122) and a second space accommodating the second electromagnetic coil (123) in an axial direction.

7. The electromagnetic switch as claimed in claim 1, characterized in that the electromagnetic switch (10) further comprises a control apparatus (125) for controlling the second electromagnetic coil (123); when the control apparatus (125) detects that the electromagnetic switch is open, the second electromagnetic coil (123) is controlled to be energized for a period of time.

8. The electromagnetic switch as claimed in claim 7, characterized in that the control apparatus (125) is an electronic control unit or a relay.

9. A starter, characterized by comprising

the electromagnetic switch (10) as claimed in any one of claims 1 - 8; and an electric motor, turned on by the electromagnetic switch (10), wherein

the electromagnetic switch (10) further comprises a moving contact connected to the push rod and a relatively stationary static contact; when the moving contact moves with the push rod and comes into contact with the static contact, the static contact and the electric motor are energized.

10. The starter as claimed in claim 9, characterized in that the starter further comprises: a transmission mechanism, comprising:

a rotation shaft, having an input end connected to a shaft of the electric motor and an output end connected to a drive gear, wherein

reciprocal motion of the push rod is transmitted to reciprocal motion of the rotation shaft via pivoting of the shifting fork.