The present invention relates to a solenoid switch for use in a vehicle starter motor, and a vehicle starter motor comprising such a solenoid switch.

A starter motor for a motor vehicle normally consists of an electric motor, a transmission mechanism, a control mechanism and so on. Upon starting an engine of the vehicle, the electric motor generates rotating moment, and the rotating moment is transmitted to a gear ring on the flywheel of the engine through a drive gear of the transmission mechanism, thereby driving a crankshaft of the engine to rotate.

The control mechanism functions to control on-off of the starter motor circuit, and control engagement and disengagement between the drive gear and the gear ring. Currently, a widely-used control mechanism for the starter motor is a solenoid switch. Figure 1 is a structural schematic view showing a known solenoid switch for the starter motor. The solenoid switch mainly includes: a magnetic core 4 and an electromagnetic winding 6 fixedly mounted in a housing 2; two contact posts 10 carried by a cover 8 that is fixed on the housing 2; a plunger 16 axially movable inside the electromagnetic winding 6; a switch shaft 12 carried by and axially movable relative to the magnetic core 4 and the plunger 16; a pull rod 18 fixed on the plunger 16; a striking rod 20 fixed in the plunger 16; a contact bridge 14 mounted on a rear end of the switch shaft 12, and so on. A front end of the pull rod 18 is movably coupled to a shifting fork (not shown).

A rear end of the magnetic core 4 and a front end of the cover 8 are sandwiched, in such a manner of being opposite to each other, between a step 22 in a rear portion of the housing 2 and a rear flanging 24 of the housing 2, and sandwiched between the magnetic core 4 and the cover 8 is a disc spring 21 which is completely clamped axially, without the capacity of making further axial deformation.

After a vehicle igniting switch is switched on, the electromagnetic winding 6 generates an electromagnetic force in the plunger 16 such that the plunger 16 moves rearward toward the magnetic core 4. The striking rod 20 drives the switch shaft 12 to together move backwardly in an axial direction after the striking rod 20 is brought into contact with the switch shaft 12. The contact bridge 14 is driven by the switch shaft 12 to contact the two contact posts 10 so as to electrically connect them, thereby switching on a main circuit of the electric motor and thus driving the electric motor to rotate. After the contact bridge 14 is brought into contact with the two contact posts 10 and electrical connection is created between the two contact posts 10, the plunger 16 keeps on moving toward the magnetic core 4 by a certain travel until it strikes the magnetic core 4 and is held back by the same. During this process, the front end of the pull rod 18 pulls the transmission mechanism via the shifting fork so as to drive the gear to move forwardly to be in engagement with the gear ring on the engine flywheel, thereby starting the engine.

During the above igniting process, the generated axial striking force will be transferred from the magnetic core 4 to the flanging 24 through the disc spring 21 and the cover 8 when the plunger 16 strikes the magnetic core 4. The flanging 24 has a relatively small thickness, and thus will generate rearward and radially-outward elastic deformation. In this case, the cover 8 will rapidly move in a rearward direction by a very small distance. Then, the cover 8 gradually vibrates to go back its original position with disappearance of the striking force. At the moment when the cover 8 backwardly moves rapidly, the two contact posts 10 carried by it also backwardly move rapidly therewith, but the contact bridge 14 can not completely follow up the backward moving action of the contact posts 10. In this way, the contact bridge 14 may be disengaged from the contact posts 10, which may cause momentary break of the main circuit of the electric motor. The momentary break will cause momentary steep dropping of electric current in the main circuit of the electric motor, affecting operation of the electric motor. At the same time, electric arc can be generated between the contact bridge 14 and the contact posts 10. It is proved by experiments that the maximum power of the electric arc may reach 30 kilowatt and the produced energy may come to 8 Joule, and that energy will cause ablation and adhesion between the contact bridge 14 and the contact posts 10.

EP 0 290 734 A2 discloses a solenoid switch sealed against water and dust for use in a vehicle starter motor, comprising: a housing; a cover carrying a pair of contact posts, one end of the cover being fixed to the housing; and a magnetic core fitted in a groove in the inner wall of the housing opposite to the end of the cover.

Therefore, it is required to prevent the cover from moving during a pickup process of the solenoid switch, so as to avoid failure of the solenoid switch due to adhesion and avoid affecting operation of the electric motor.

The present invention is intended to solve problems concerning the cover moving due to the above striking in the known solenoid switch for the vehicle starter motor and the caused ablation and adhesion between the contact bridge and the contact posts.

Therefor, the present invention in the first aspect provides a solenoid switch for use in a vehicle starter motor, comprising: a housing; a cover carrying a pair of contact posts, one end of the cover being fixed to the housing; and a magnetic core fitted in the housing opposite to the end of the cover; wherein an engaging structure between the magnetic core and the housing is independent of the cover such that a force acting on the magnetic core in a direction toward the end of the cover can be absorbed by the engaging structure.

According to preferred embodiments of the present invention, the housing has a segment being adjacent to the end of the cover and having a relatively small wall thickness, and the cover is retained in the housing by means of a flanging that is formed by inward bending the segment having a relatively small wall thickness; and/or the solenoid switch further comprises a plunger disposed in the housing and movable toward and away from the magnetic core, and the force is a striking force generated by the plunger striking the magnetic core during a working process of the solenoid switch.

According to preferred embodiments of the present invention, at least one portion of a periphery of the magnetic core is fixed to the housing in a positive-fit locking manner.

According to preferred embodiments of the present invention, an inner wall of the housing is provided with a locking groove, the periphery of the magnetic core is provided with a locking portion, and the locking portion is locked in the locking groove by rotating the magnetic core so as to fix the magnetic core to the housing.

According to preferred embodiments of the present invention, the locking portion abuts against a first side of the locking groove away from the end of the cover, and an elastic element is provided between the locking portion and an opposite second side of the locking groove; and/or the locking groove and/or the locking portion are configured to gradually lock up the magnetic core with rotation of the magnetic core; and/or the locking groove is defined by a step away from the end of the cover and a plurality of limiting protrusions adjacent to the end of the cover, any two adjacent limiting protrusions define a notch therebetween, the locking portion passes through the notch in a direction away from the end of the cover and the locking portion and the limiting protrusions are locked together by rotating the magnetic core.

According to preferred embodiments of the present invention, during an assembling process, a locking groove for locking at least one part of the periphery of the magnetic core is formed by inward pressing at least one part of the segment having a relatively small wall thickness, so as to fix the 'magnetic core to the housing.

According to preferred embodiments of the present invention, an inward-protruding limiting protrusion having a U-shaped cross section is formed by inward pressing the segment having a relatively small wall thickness.

According to preferred embodiments of the present invention, the magnetic core is fixed to the housing by welding; or a periphery of the magnetic core is provided with a recess, and one part of the housing comes into the recess by pressing the housing from the outside in a direction toward the recess during an assembling process, so as to fix the magnetic core to the housing; or a periphery of the magnetic core is provided with an external thread, an inner wall of the housing is provided with an internal thread, and the magnetic core is fixed to the housing by means of toothed engagement of the internal and external threads.

According to preferred embodiments of the present invention, the magnetic core is fixed to the housing by a bolt that is screwed into a corresponding hole on a periphery of the magnetic core through a wall of the housing; or the magnetic core is fixed to the housing by a pin that enters a corresponding hole on a periphery of the magnetic core through a through hole in a wall of the housing, and the pin is tightly fitted into the through hole and/or the corresponding hole on the periphery.

The present invention in the second aspect provides a vehicle starter motor, comprising: an electric motor; a transmission mechanism coupled to an output shaft of the electric motor; and a solenoid switch for controlling operation of the electric motor and the transmission mechanism, wherein the solenoid switch is a solenoid switch as claimed above.

According to the solenoid switch of the present invention, when the plunger strikes the magnetic core, the cover will not move axially since the magnetic core is directly fixed to the housing and no striking force is transmitted to the housing, thereby ensuring that no disengagement occurs between the contact bridge and the contact posts and avoiding the momentary break of the main circuit of the electric motor. Thus, it is possible to avoid momentary steep dropping of the electric current in the main circuit of the known electric motor and avoid ablation and adhesion between the contact bridge and the contact posts.

Hereinafter the present invention is described in more details with reference to the figures so as to better understand the principles, characteristics and advantages of the invention.

• Fig. 1 is a sectional view of a solenoid switch in a vehicle starter motor in the prior art;
• Fig. 2 is a schematic view of a fixing mode of a magnetic core in a rear end of a housing of the solenoid switch in the prior art;
• Figs. 3-7 are schematic views of several fixing modes of a magnetic core in a rear end of a housing of a solenoid switch according to the present invention; and
• Fig. 8 is a sectional view of one exemplary embodiment of the solenoid switch using the fixing mode as shown in Fig. 3.

Some embodiments of the present invention will be described hereinafter in more details with reference to the figures to better understand the basic concept of the invention.

At first, it shall be noted that when describing the solenoid switch of the invention, the word "front" indicating an orientation refers to a side close to a vehicle engine in an axial direction, and the word "rear" refers to a side away from the vehicle engine in the axial direction.

Fig. 2 shows a fixing mode of a magnetic core and a cover in a housing rear end of a housing 2 of a solenoid switch in the prior art shown in Fig. 1, wherein the cover 8, a disc spring 21 and the magnetic core 4 are fixedly clamped between a step 22 and a rear flanging 24 of the housing 2 with a certain axial preloading force, and the disc spring 21 is completely pressed axially between the cover 8 and the magnetic core 4, without the capacity of making further axial deformation, i.e., without any axial damping capacity. When the magnetic core 4 suffers from axial strike of a plunger 16, a striking force shown by an arrow in the figure is directly transferred to the rear flanging 24 through the disc spring 21 and the cover 8, which causes relatively great axial deformation of the rear flanging 24, making the cover to move axially. Such axial moving will cause the various problems as mentioned in the above Background Art portion.

The present invention aims to reduce or eliminate the axial moving of the cover by changing the fixing mode of the magnetic core. Figs. 3-7 schematically show the fixing modes of the magnetic core according to some exemplary embodiments of the invention.

In the embodiment shown in Fig. 3, an inner wall of the housing 2 is formed with a plurality of limiting protrusions 26 located on the same circumference and extending inward in the radial direction, and the plurality of limiting protrusions 26 are integrally formed on an inner side of the housing 2 and spaced apart from each other in the circumferential direction. That is, there is a notch between any two adjacent limiting protrusions 26. In order to show the notch more clearly, the left part of Fig. 3 schematically shows one limiting protrusion 26, which is spaced apart from the right limiting protrusion 26.

According to one embodiment, the plurality of limiting protrusions 26 are evenly distributed in the circumferential direction, so that the notches therebetween likewise are evenly distributed in the circumferential direction.

The peripheral edge of the magnetic core 4 is provided with locking protrusions 30 having the same amount as the limiting protrusions 26 and corresponding to the limiting protrusions 26 in position one by one, and the locking protrusions are sized and shaped to enable the locking protrusions to pass through the notches in the axial direction. When assembling, the locking protrusions 30 are axially aligned with the notches, and then the magnetic core 4 is axially moved to cause the locking protrusions 30 to come into circumferential grooves 32 defined by the step 22 and the limiting protrusions 26. Subsequently, the magnetic core 4 is rotated by a certain angle to axially align the locking protrusions 30 with the limiting protrusions 26, so that the magnetic core 4 is fixed within the housing 2. Preferably, the shape of the locking protrusions 30 of the magnetic core 4 is adapted to the shape of the grooves 32, so that the magnetic core 4 can hardly be locked within the grooves 32 in an axially movable manner. For example, at least one of contacting surfaces of the locking protrusions 30 and limiting protrusions 26 may be provided with a ramp that is gradually locked up with the rotation. Such a fixing mode facilitates the installation.

At this moment, the cover 8 is fixedly clamped between the limiting protrusions 26 and the rear flanging 24. In this case, when the plunger 16 strikes the magnetic core 4, the generated axial striking force is transferred from the magnetic core 4 directly to the housing 2 through the locking protrusions 30 and the limiting protrusions 26, not to the rear flanging 24. In this way, it is possible to overcome moving of the cover as in the prior art and the caused problems, i.e., momentary steep dropping of the electric current in the main circuit of the electric motor, and the ablation and adhesion problem between the contact bridge and the contact posts.

It can be appreciated that an elastic element 34 may be provided between the magnetic core 4 and the limiting protrusions 26 in order to damp the striking effect of the magnetic core 4 on the limiting protrusions 26, as shown in Fig. 4.

Actually, the fixing mode shown in Fig. 3 is involved with the positive-fit locking. One skilled in the art completely can conceive any other appropriate positive-fit locking modes. For example, Fig. 5 schematically shows another positive-fit locking mode, wherein a limiting protrusion 36 for fixing the magnetic core 4 is formed by pressing like the flanging 24. Specifically, during assembling process, after the magnetic core 4 is fitted into the housing 2 and abuts with its side against the step 22, a thinning portion 38 of the housing 2 is inwardly pressed in the radial direction to form the limiting protrusion 36, so as to clamp and fix the magnetic core 4 between the step 22 and the limiting protrusion 36. At this moment, the limiting protrusion 36 is generally U-shaped and axially comprises two layers of thinning portion 38 so as to be capable of bearing the striking force generated when the plunger 16 strikes the magnetic core 4, without transmitting the striking force to the cover 8.

Fig. 6 schematically shows a fixing mode of the magnetic core according to another exemplary embodiment of the present invention. As shown in Fig. 6, the magnetic core 4 is in contact with the step 22 at a first position 40 (the front end side) and with the inner wall of the housing 2 at a second position 42 (the peripheral edge). The magnetic core 4 is fixed to the housing 2 at the first position 40 and/or second position 42 by means of welding (such as electric resistance welding, friction welding, and any other proper welding manner). The cover 8 still is fixedly clamped on to the housing 2 by the flanging 24. At this moment, the magnetic core 4 and the corresponding portions of the housing 2 are welded together, and therefore the striking force generated when the plunger 16 strikes the magnetic core 4 will be directly transmitted to the housing 2 by the welding portion, not to the cover 8 even if the magnetic core 4 and the cover 8 are in contact with one another.

Fig. 7 schematically shows a fixing mode of the magnetic core according to another exemplary embodiment of the present invention. As shown in Fig. 7, the peripheral edge of the magnetic core 4 is machined to form a recess 44. During the assembling process, after the magnetic core 4 is fitted into the housing 2 and abuts with its side against the step 22, a thinning portion 38 of the housing 2 is inwardly and radially pressed toward the recess 44, and the thinning portion 38 is deformed, with one portion coming into the recess 44, thereby fixing the magnetic core 4. The cover 8 still is fixedly clamped on to the housing 2 by the rear flanging 24. At this moment, the striking force generated when the plunger 16 strikes the magnetic core 4 also is directly transmitted to the housing 2, not to the cover 8 even if the magnetic core 4 and the cover 8 are in contact with one another.

For one skilled in the art, in addition to the above fixing modes, the magnetic core 4 also may be fixed to the housing 2 by screwing a bolt into the peripheral edge of the magnetic core 4 from the outside. In this connection, a through hole through the wall of the housing 2 and a corresponding hole on the peripheral edge of the magnetic core 4 are provided, and both or one of the through hole through the wall of the housing 2 and the hole on the peripheral edge of the magnetic core 4 are a threaded hole. It can be appreciated that the bolt can be replaced by a tightly-fitted pin. Here, the striking force generated when the plunger 16 strikes the magnetic core 4 will be directly transmitted to the housing 2 through the bolt or pin, not to the cover 8.

Furthermore, it can be considered that the inner circumference of the housing 2 is provided with an internal thread, and the peripheral edge of the magnetic core 4 is provided with a corresponding external thread, such that the magnetic core 4 can be fixed to the housing 2 by screwing. Here, the striking force generated when the plunger 16 strikes the magnetic core 4 likewise will not be transferred to the cover 8.

A solenoid switch of a vehicle starter motor using the fixing mode as illustrated in Fig. 3 is schematically described hereinafter.

As shown in Fig. 8, the solenoid switch comprises a housing 2 with a generally cylindrical body 2a and a front end wall 2b disposed at a front end of the body (the left end in Fig. 8, i.e., the end facing the side of the vehicle engine), and an axial through hole is formed within the front end wall.

The magnetic core 4 is fixedly mounted in the rear part of the body 2a of the housing 2. The magnetic core 4 is comprised of a generally disc-shaped rear great-diameter portion 4a, a generally cylindrical small-diameter portion 4b projecting forwardly from the great-diameter portion, and a generally truncated cone portion 4c projecting forwardly from the small-diameter portion. Formed on the periphery of the great-diameter portion 4a is a set of discrete, preferably circular arc-shaped, locking protrusions 30, which project radially and outwards, and which are evenly distributed on the same circumference and respectively extend by a radian in the circumferential direction. Furthermore, formed within the magnetic core 4 is a guide through hole being axially through in the front-back direction.

A generally cylindrical bushing 3 of a nonmagnetic material (such as brass) is mounted in the housing 2, wherein a front end of the bushing 3 is inserted into the front end wall 2b of the housing 2, and a rear end thereof is sleeved on the small-diameter portion 4b of the magnetic core 4, so that the bushing 3 is fixed in the housing 2. An electromagnetic winding 6 is mounted between the bushing 3 and the body of the housing 2 and supported by the bushing 3.

In an approximately front part of the bushing 3, the plunger 16 is arranged in an axially movable fashion. The plunger 16 is generally cylindrical.

A pull rod 18 is fastened to the front end of the plunger 16, wherein the rear end of the pull rod extends forwardly from the front end of the plunger 16, while the front end of the pull rod is used for operatively connecting an upper end of a shifting fork (not shown). The approximately middle part of the shifting fork is pivotally supported, and the lower end of the shifting fork is coupled to a transmission mechanism. In this way, the pull rod 18 when moving backwardly in the axial direction (toward the right in Fig. 8) can drive the transmission mechanism to move forwardly in the axial direction through the shifting fork, such that a drive gear of the transmission mechanism moves toward a gear ring on the engine flywheel and is engaged therewith. Conversely, the pull rod 18 when moving forwardly in the axial direction (toward the left in Fig. 8) can drive the transmission mechanism to move backwardly in the axial direction through the shifting fork, such that the drive gear of the transmission mechanism is disengaged from the gear ring on the engine flywheel.

A striking rod 20 is fixed in the approximately front part of the plunger 16. The front part of the striking rod 20 can be inserted into the rear part of the pull rod 18 to assist in positioning and fixing of the pull rod 18 relative to the plunger 16. The middle part of the striking rod 20 is fixed in a corresponding part of the striking rod 20. The rear part of the striking rod 20 extends into an axial receiving through hole in the plunger 16.

Arranged within the receiving through hole of the plunger 16 and the guide through hole of the magnetic core 4 is a switch shaft 12 that can axially move relative to the plunger 16 and the magnetic core 4. A guide sleeve 13 around the periphery of the switch shaft 12 can achieve guidance of the switch shaft 12 in the plunger 16 and in the magnetic core 4, and simultaneously assists in increasing a gap between an inner peripheral wall of the guide through hole of the magnetic core 4 and an outer peripheral surface of the switch shaft 12, so that a magnetic gap between the magnetic core 4 and the switch shaft 12 is increased, thereby reducing influence of the switch shaft 12 on a magnetic circuit generated by the electromagnetic winding 6.

A first reset spring 46, which is mounted between the front end of the switch shaft 12 and the front end of the magnetic core 4 (the generally truncated cone portion 4c), applies a forward force to the switch shaft 12 such that the switch shaft 12 is maintained at its most front original position under a non-operating condition of the solenoid switch.

A second reset spring 48, which is mounted in the receiving through hole and between the plunger 16 and the front end of the switch shaft 12, applies a forward force to the plunger 16 such that the plunger 16 is maintained at its most front original position under the non-operating condition of the solenoid switch.

The front part of the switch shaft 12 is located within the receiving through hole of the plunger 16, the middle part of the switch shaft 12 passes through the guide through hole of the magnetic core 4, and the rear end of the switch shaft 12 is exposed from the rear end surface of the magnetic core 4.

A contact bridge 14 is mounted on the rear end of the switch shaft 12. Specifically, a mounting base 15 is mounted on the rear part of the switch shaft 12 in an axially slideable manner, and the contact bridge 14 is carried by the mounting base 15.

Furthermore, a third reset spring 50 is sleeved on the switch shaft 12 and located between the rear end of the guide sleeve 13 and the mounting base 15. The contact bridge 14 carried by the mounting base 15 can resist a pushing force of the third reset spring 50 to move (slide) axially and forwardly on the switch shaft 12, while the backward movement of the contact bridge 14 is blocked by a fastener 17 fixed on the rear end of the switch shaft 12.

The cover 8, which is normally made of a plastic material, is fixed at a rear part of the housing 2, and the two contact posts 10 extend through the cover 8 and fixed in the cover 8. A front enlarging portion of each of the contact posts 10 forms into a contact terminal 10a, and front end surfaces of the two contact terminals 10a face rear surface of the contact bridge 14. A front part of each of the contact posts 10 is fixed in the cover 8, and a rear part thereof is exposed from a rear surface of the cover 8 so as to form a connection terminal.

The cover 8 has a front end 8a that is fitted in the housing 2. As shown in Fig. 8, the rear end (the great-diameter portion 4a) of the magnetic core 4 and the front end 8a of the cover 8 are retained in the rear end portion of the housing 2 by using the fixing mode shown in Fig. 3. Therefore, as shown in Fig. 8, integrally formed on the rear end of the generally cylindrical body 2a of the housing 2 are a step 22 and a plurality of discrete limiting protrusions 26 that extend radially and inwards and are located on the same circumference, and circumferential grooves 32 are defined between the step 22 and the limiting protrusions 26. The limiting protrusions 26 are the same in the amount as the locking protrusions 30. A thinning portion 2c is formed behind the limiting protrusion 26, and the wall thickness of the thinning portion 2c is reduced in comparison to the body 2a.

The limiting protrusions 26 preferably are evenly spaced apart from each other in the circumferential direction. The locking protrusions 30 correspond, one by one, to the notches between the limiting protrusions 26 (also to the limiting protrusions 26), and are sized and shaped to axially pass through the notches and be mounted within the grooves 32.

During the assembling, the magnetic core 4 is placed into the housing 2 from the rear end of the housing 2 in such a way that its truncated cone portion 4c faces the front, and the locking protrusions 30 are aligned with the notches, and then the magnetic core 4 is axially displaced to cause the locking protrusions 30 into the grooves 32. Subsequently, the magnetic core 4 is rotated by a certain angle so as to cause the locking protrusions 30 aligned with and locked with the limiting protrusions 26, thereby fixing the magnetic core 4 within the housing.

The rear end of the thinning portion 2c is adapted to form a rear flanging 24 that extends radially and inwards after the magnetic core 4 and the cover 8 are placed into the housing 2. Thus, it can be understood that although Fig. 8 already draws the rear flanging 24, it actually is formed during the assembling process of the solenoid switch.

During the working process, when the plunger 16 strikes the magnetic core 4, the generated axial striking force will be transferred from the magnetic core 4 directly to the housing 2 through the limiting protrusions 26, not to the rear flanging 24.

It can be understood that in the solenoid switch shown in Fig. 8 the magnetic core also can employ the other above-mentioned fixing modes of the present invention, as an alternative solution.

It was proved by the simulation and experiments that according to the prior art solenoid switch, the cover obviously will move in the axial direction when the plunger strikes the magnetic core, which may result in disengagement between the contact bridge and the contact posts so as to cause the momentary break of the main circuit of the electric motor. Such momentary break will cause momentary steep dropping of the electric current in the main circuit of the electric motor, affecting the operation of the electric motor. At the same time, electric arc may be generated between the contact bridge and the contact posts, causing the ablation and adhesion between the contact bridge and the contact posts.

On the contrary, according to the present invention, when the plunger strikes the magnetic core, the striking force will not be transferred to the cover since the magnetic core is directly secured to the housing. The cover thus will not move axially so as to avoid the disengagement between the contact bridge and the contact posts, without causing the momentary break of the main circuit of the electric motor. Therefore, it is possible to overcome the problem concerning the momentary steep dropping of the electric current in the main circuit of the electric motor in the prior art, as well as the ablation and adhesion problem between the contact bridge and the contact posts.

Other aspects of the present invention relate to a vehicle starter motor comprising such a solenoid switch.