Vehicle starter and its electromagnetic switch

Abstract

Electromagnetic switch for a vehicle starter, including: a solid iron core (4); a forward and backward moving iron core (16); an electromagnetic coil (6) for generating a magnetic circuit that moves the movable iron core (16) backwards; a pair of terminal blocks (10) arranged behind the solid iron core (4); a push rod (30) made of a magnetic material, which is driven by the movable iron core (16) and extends axially through a guide through-hole (4e) in the solid iron core (4), so that a rear end of the push rod (30) protrudes from the rear part of the solid iron core (4); a contact bridge (14) attached to the rear end of the push rod (30) and facing the pair of terminal blocks (10); and a sleeve (20) pushed onto the push rod (30) and slidably engaging in the guide through-hole (4e) of the solid iron core (4), which has a thick-walled section (20a) and an adjoining thin-walled section (20b), wherein the thick-walled section (20a) is mounted on the push rod (30) and an annular space is defined between the thin-walled section (20b) and the push rod (30), wherein the contact bridge (14) is movably mounted forward relative to the push rod (30) at the rear end of the push rod (30), and wherein a return spring (22) for the contact bridge (14) is arranged between the sleeve (20) and the contact bridge (14), the return spring (22) for the contact bridge (14) being pushed onto the push rod (30), wherein the return spring (22) for the contact bridge (14) is immersed in the annular space with a front end and exerts a thrust force on the contact bridge (14) with a rear end, wherein the contact bridge (14) is mounted on the push rod (30) by means of a mounting base, wherein the return spring (22) for the contact bridge (14) is pressed with its front end against a stepped surface formed between the thick-walled section and the thin-walled section of the sleeve (20) and with its rear end against the mounting base.

Description

Technical area

[0001] The invention relates to an electromagnetic switch for a vehicle starter and a vehicle starter with the electromagnetic switch. State of the art

[0002] In a modern vehicle, an electric starter is typically used to start the vehicle's engine. The starter converts electrical energy supplied by a vehicle's battery into mechanical energy, driving the vehicle's engine to run and start the engine.

[0003] The starter motor essentially consists of a DC motor, a transmission, and a controller. When starting the vehicle's engine, the DC motor generates torque, which is transferred via a drive gear of the transmission to a starter ring gear, driving the engine's crankshaft to rotate.

[0004] The control is used to switch a starter circuit on or off and to control the engagement or disengagement of the drive gear with the ring gear. Currently, an electromagnetic switch is generally used as a starter control.

[0005] Fig. Figure 1 shows a schematic structure of a prior art electromagnetic switch for a starter. The electromagnetic switch includes a fixedly mounted fixed iron core 4 and an electromagnetic coil 6, two fixedly mounted connecting terminals 10, a push rod 12 axially movable within the fixed iron core 4, a contact bridge 14 clamped to a rear end of the push rod 12 by a mounting base 28, an axially movable movable iron core 16, a push rod 18 fixed to the movable iron core 16, a sleeve 20 fixed to a front portion of the push rod 12 and slidable within a guide through hole in the fixed iron core 4, and compression springs 22, 24, 26, each of which serves to return the contact bridge 14, the movable iron core 16, and the push rod 12.

[0006] When the vehicle is started by the ignition switch, the electromagnetic coil 6 is energized to generate an electromagnetic force in the movable iron core 16, causing the movable iron core 16 and the push rod 18 to move toward the fixed iron core 4 (backward). The push rod 18, with its front end, pulls the transmission mechanism via a shift fork (not shown) to move its drive gear toward the starter ring gear (forward). The push rod 18 then pushes the push rod 12 backward, causing the contact bridge 14 to contact the two connecting terminals 10 and electrically connect the two. Thus, a main circuit of the electric motor is energized via the two connecting terminals 10, causing the electric motor to rotate.The contact bridge 14 is prevented from moving further backward after contact with the two connecting terminals 10, while the push rod 12 continues to move backward until the movable iron core 16 rests against the fixed iron core 4. During the backward movement of the movable iron core 16, the drive gear engages with the starter ring gear, thereby transmitting the rotational movement of the electric motor to the engine flywheel to start the engine.

[0007] After the engine is started, the ignition switch is released. This dissipates the electromagnetic force generated by the electromagnetic coil 6 in the movable iron core 16. The movable iron core 16 moves forward under the action of a restoring force of the spring 24, so that the drive gear is pulled away from the starter ring gear by the shift fork. At the same time, the push rod 12 moves forward under the action of a restoring force of the spring 26. After a brief forward movement, the push rod 12 pulls the contact bridge 14 away from the two connecting terminals 10, thereby deactivating the main circuit of the electric motor and stopping the starter.

[0008] Fig. 2 shows a schematic structure of a previous electromagnetic switch for the starter, where the Fig. 1 shown push rod 18 and push rod 12 are replaced by a single push rod 30 which is attached to the movable iron core 16. Otherwise, the electromagnetic switch is in Fig. 2 similar to Fig. 1. When the ignition switch is released after starting the engine, the push rod 30 experiences thrust forces from both a rear return spring (not shown, corresponding to the spring 26 in Fig. 1) as well as from the front return spring 24, so that it pulls the contact bridge 14 more strongly away from the two connection terminals 10.

[0009] In the Fig. 1 and Fig. In the electromagnetic switches shown in Figure 2, the push rod 12 and the push rod 30 are typically made of a non-magnetic material such as copper, copper alloy, stainless steel, etc., to avoid influences on the magnetic circuit of the electromagnetic coil 6. However, all of the above materials used to make the push rod are not ideal. For example, stainless steel is harder than common steel, and it is more difficult to manufacture a complex shape with it, and the cost is higher. Copper and copper alloys are more expensive than common steel, but their mechanical properties are lower. This has led to a desire to solve the problem that exists in the prior art.

[0010] US 4 677 407 A shows an electromagnetic switch for a starter motor, with a housing made of a magnetic material, an annular stationary iron core arranged in the housing and fixed therein, an electromagnetic winding arranged in the housing, a movable iron core arranged in the electromagnetic winding, which is displaceable between a contact opening position and a contact closing position, a fixed contact arranged on the housing, a bushing arranged on a shaft part connected to the movable iron core and extending into the annular stationary iron core, and a moving contact arranged on the bushing to come into contact with the fixed contact when the movable iron core is in the contact closing position.The housing, together with the movable iron core, defines a magnetic circuit through which a magnetic flux generated by the electromagnetic winding can flow, electromagnetically driving the movable iron core between the contact opening and closing positions. A portion of the insulating sleeve, on which the moving contact is mounted, is formed from an electrically insulating material, and the remaining portion of the insulating sleeve is formed from a bearing material.

[0011] DE 10 2009 001 725 A1 relates to a starter relay for internal combustion engines, comprising a relay coil and a magnet armature, which interacts via a driver with a forked lever for pre-engaging a starter pinion, and a contact bridge, which is actuated by the magnet armature via a switching axis and interacts with switching contacts. A coupling connects the switching axis and the magnet armature with limited displacement relative to each other. To prevent welded contacts from being torn open and to ensure that the forked lever reaches its rest position when the relay is deactivated, a preloaded compression spring is inserted between the magnet armature and the end of the forked lever. Disclosure of the invention

[0012] The invention is based on the object of developing an electromagnetic switch for a vehicle starter in which a push rod made of a mass steel can be used without significantly changing the structure and assembly method of the previous electromagnetic switch.

[0013] To achieve the object, according to one aspect of the invention, an electromagnetic switch for a vehicle starter is proposed, comprising a fixed iron core, a forward-and-backward movable iron core, an electromagnetic coil for generating a magnetic circuit that moves the movable iron core backward, a pair of connecting terminals arranged behind the fixed iron core, a push rod made of a magnetic material, which is driven by the movable iron core and extends axially through a guide through-hole in the fixed iron core so that a rear end of the push rod protrudes from the rear part of the fixed core, a contact bridge attached to the rear end of the push rod and facing the pair of connecting terminals, and a sleeve slidably mounted on the push rod and slidably engaging in the guide through-hole of the fixed iron core.which has a thick-walled section and an adjoining thin-walled section, wherein the thick-walled section is mounted on the push rod and an annular space is defined between the thin-walled section and the push rod.

[0014] According to the invention, the contact bridge is mounted on the rear end of the push rod so as to be movable forward relative to the push rod, wherein a return spring for the contact bridge is arranged between the sleeve and the contact bridge and is pushed onto the push rod, wherein the return spring for the contact bridge is immersed in the annular space with a front end and exerts a pushing force on the contact bridge with a rear end.

[0015] According to the invention, the contact bridge is mounted on the push rod by means of a mounting base, wherein the return spring for the contact bridge is pressed with the front end against a step surface formed between the thick-walled section and the thin-walled section of the sleeve and with the rear end against the mounting base.

[0016] According to a preferred embodiment of the present invention, the sleeve is made of an insulating plastic. Alternatively, the sleeve is made of a magnetic shielding material or an insulating plastic with a magnetic shielding material.

[0017] According to a preferred embodiment of the present invention, the push rod is mounted on the movable iron core and integrally comprises a front portion having a large diameter and a rear portion having a small diameter, wherein a transition step is formed between the front portion having the large diameter and the rear portion having the small diameter, and wherein the thick-walled portion of the sleeve is pressed against the transition step.

[0018] According to a preferred embodiment of the present invention, the thin-walled portion of the sleeve comprises a pair of thin-walled sections on the axially both sides of the thick-walled section, wherein the front thin-walled section encloses a rear end part of the front section with the large diameter and an annular space is formed between the rear thin-walled section and the rear section with the small diameter.

[0019] According to a preferred embodiment of the present invention, the push rod has a two-part construction and comprises a first rod section fastened to the movable iron core and a second rod section slidably mounted in the fixed iron core, wherein the second rod section can be moved at least backwards by the first rod section (it is therefore possible to move the second rod section forwards or backwards by the first rod section), wherein the sleeve is pushed onto the second rod section.

[0020] According to a preferred embodiment of the present invention, the first rod section and the second rod section are connected to each other by the sleeve. In this case, the sleeve is designed to allow a relative movement of a certain distance forward or backward between the first rod section and the second rod section.

[0021] According to a preferred embodiment of the present invention, the magnetic material from which the push rod is made is a mass steel.

[0022] According to another aspect, the present invention proposes a vehicle starter comprising an electric motor, a transmission connected to an output shaft of the electric motor, and an electromagnetic switch as described above, with which the actuation of the electric motor and the transmission can be controlled.

[0023] According to the invention, the electromagnetic switch for the vehicle starter is improved by using a new sleeve structure so that the push rod can be made of a magnetic material such as common steel, thus reducing the cost of the push rod. At the same time, the requirements for the mechanical properties of the push rod are still met without significantly changing the structure and assembly method of the electromagnetic switch itself. Brief description of the drawing

[0024] It shows Fig. 1 is a schematic representation of a structure of an electromagnetic switch of a vehicle starter according to the prior art, Fig. 2 is a schematic representation of a structure of another electromagnetic switch of a vehicle starter according to the prior art, Fig. 3 is a schematic representation of a structure of an electromagnetic switch of a vehicle starter according to a preferred embodiment of the invention, Fig. 4 a schematic representation of a single push rod and some relevant elements in the electromagnetic switch in Fig. 3, Fig. 5 and Fig. 6 perspective views from different aspects of the sleeve of the electromagnetic switch in Fig. 3 on average. Examples of implementation

[0025] In the following, preferred embodiments of the present invention are described with reference to the accompanying figures.

[0026] The Fig. The basic embodiment of the invention shown in Figure 3 represents a further development of the Fig. 2. However, it should be understood that the principles of the present invention, as discussed below, may also be applied to an electromagnetic switch of a vehicle starter having a different structure, as shown in Fig. 1 is shown.

[0027] In Fig. 3, the electromagnetic switch according to the present invention is in a non-actuated state. The electromagnetic switch comprises a housing 2 having a substantially cylindrical main body and a housing 3 provided at the front end of the main body (the left end in Fig. 3, the end facing the engine) arranged section 2a with a reduced diameter.

[0028] The fixed iron core 4 is fixedly arranged in the rear region of the main body of the housing 2. The fixed iron core 4 is preferably formed in one piece and consists of an approximately disc-shaped section 4a with a large diameter, which is fixed in the main body of the housing 2, an approximately cylindrical section 4b with a small diameter, which projects forward from the large-diameter section 4a, and an approximately frustoconical fitting section 4c, which projects forward from the small-diameter section 4b. Furthermore, a stop recess 4d is formed on the rear end surface of the fixed iron core 4. An axially continuous guide through-hole 4e is further formed in the fixed iron core 4.

[0029] A bushing 32 made of a non-magnetic material, such as brass, is mounted in the housing 2. Specifically, the bushing 32 has a roughly cylindrical shape. Its front end is inserted into the reduced-diameter section 2a of the housing 2, and its rear end is pushed onto the small-diameter section 4b of the iron core 4. This secures the bushing 32 in the housing 2.

[0030] An annular space is defined between the bushing 32 and the body of the housing 2. The electromagnetic coil 6 is installed in this annular space and supported by the bushing 32. The electromagnetic coil 6 comprises two parts, a holding coil and a suction coil. The two parts are preferably arranged coaxially, as shown in Fig. 3. Of course, other arrangements are also possible.

[0031] The movable iron core 16 is arranged axially displaceably approximately in the front region of the bushing 32. The movable iron core 16 has an approximately cylindrical shape, with a small-diameter mounting through-hole 16a, a spring receptacle 16b whose diameter is larger than that of the mounting through-hole 16a, and a fitting recess 16c whose radial dimension is larger than that of the spring receptacle 16b, arranged one behind the other in the interior of the iron core from front to back.

[0032] A single push rod 30 is fixedly supported by the movable iron core 16 so that it is axially displaceable together with the movable iron core 16. Specifically, the push rod 30, see Fig. 3, an approximately cylindrical front portion 30a with a large diameter and an approximately cylindrical rear portion 30b with a small diameter, which are arranged coaxially with each other and adjoin each other. The front portion 30a with the large diameter is fixed with its front part in the mounting through hole 16a of the movable iron core 16 and extends with its rear part in the spring receiver 16b of the movable iron core 16. A transition step between the front portion 30a with the large diameter and the rear portion 30b with the small diameter is located in the spring receiver 16b or the fitting recess 16c, axially near a transition region between the spring receiver 16b and the fitting recess 16c.

[0033] The small diameter rear portion 30b of the push rod 30 extends axially rearward from the large diameter front portion 30a and passes through the guide through hole 4e of the fixed iron core 4, whereby the rear end of the small diameter rear portion 30b projects from the rear end surface of the fixed iron core 4.

[0034] The front end of the large-diameter front section 30a protrudes from the front end face of the movable iron core 16. A flat head 30c is further attached to or integrally formed on the front end of the large-diameter front section 30a to connect to an upper end of the shift fork (not shown). The shift fork is pivotally supported in an approximately central region and connected to the transmission mechanism at a lower end. Thus, the push rod 30 can be pivoted during an axial backward movement (to the right in Fig. 3) move the transmission mechanism axially forward via the shift fork, so that the drive gear of the transmission mechanism is moved towards the starter ring gear and engaged with it. On the other hand, the push rod 30 can be moved axially forward (to the left in Fig. 3) move the transmission axially backwards via the shift fork so that the drive gear of the transmission is brought out of engagement with the starter ring gear.

[0035] As in Fig. 4 in combination with Fig. 3, Fig. 5, Fig. 6, a sleeve 20, a mounting base 28 behind the sleeve 20, and a compression spring 22 between the sleeve 20 and the mounting base 28 are pushed onto the rear portion 30b with the small diameter of the push rod 30.

[0036] The sleeve 20 can be made of an insulating plastic. Using a plastic material can reduce the cost of the sleeve.

[0037] As a possible embodiment, the sleeve 20 can be made of a magnetic shielding material or an insulating plastic with a magnetic shielding material. By using a magnetic shielding material, the influence of the push rod on the magnetic circuit can be reduced.

[0038] The sleeve 20 has an approximately cylindrical shape and includes a central thick-walled portion 20a and thin-walled portions 20b at both ends of the sleeve 20. Between the central thick-walled portion 20a and the thin-walled portions 20b, a stepped surface 20c is formed perpendicular to the axis of the sleeve 20. The two thin-walled portions 20b preferably have the same shape and dimensions, so that the sleeve 20 has a symmetrical structure with respect to the longitudinal direction to facilitate attachment of the sleeve 20 to the small-diameter rear portion 30b (without considering the orientation of the sleeve 20).

[0039] As in Fig. 3, Fig. 4, the sleeve 20 is slidably mounted on the small-diameter rear portion 30b with an inner wall of the middle thick-walled portion 20a, and surrounds the rear end of the large-diameter front portion 30a with the front thin-walled portion 20b, and defines an annular receiving space for inserting the front end of the compression spring 22 between its rear thin-walled portion 20b and the small-diameter rear portion 30b. In addition, the front step surface of the sleeve 20 abuts the transition step between the large-diameter front portion 30a and the small-diameter rear portion 30b, and the rear step surface is pressed by the front end of the compression spring 22. The rear end of the compression spring 22 is pressed against the front end surface of the mounting base 28.

[0040] In Fig. In the non-actuated state of the electromagnetic switch shown in Figure 3, an axial clearance exists between the movable iron core 16 and the fixed iron core 4. The sleeve 20 is inserted with the front thin-walled section 20b and a part of the middle thick-walled section 20a into the spring receptacle 16b and the fitting recess 16c of the movable iron core 16. The front end face of the sleeve 20 does not reach the bottom of the spring receptacle 16b in the axial direction.

[0041] The mounting base 28 may be made of an insulating plastic. As an alternative embodiment, the mounting base 28 may be made of a magnetic shielding material or an insulating plastic with a magnetic shielding material.

[0042] The mounting base 28 has an approximately cylindrical shape and is slidably mounted with its inner wall on the small-diameter rear portion 30b. The mounting base 28 comprises a front cylindrical portion 28a, a central collar 28b, and a rear cylindrical portion 28c. The outer diameter of the central collar 28b is larger than that of the front cylindrical portion 28a and the rear cylindrical portion 28c. A contact bridge 14 is mounted on the rear cylindrical portion 28c and is clamped between the central collar 28b and a fastening means (such as a nut screwed onto the rear end of the push rod 30) 42.

[0043] In a situation where the contact bridge 14 is clamped to the rear end of the push rod 30 in the manner described above, the push rod 30 can move (slide) axially forward against a thrust force of the compression spring 22 on the rear portion 30b with the small diameter of the push rod 30. However, its backward movement is prevented by the fastening means 42.

[0044] It should be understood that the clamping of the contact bridge 14 by means of the fastening means 42, such as a nut, and the mounting base 28 at the rear end of the push rod 30 is merely exemplary. Any structures and elements that allow forward movement of the contact bridge 14 on the push rod 30 and prevent backward movement of the contact bridge 14 are applicable.

[0045] In addition, the middle collar 28b is dimensioned such that the collar 28b is suitable to be inserted into the stop recess 4d of the fixed iron core 4 and to be struck there.

[0046] A cover 8 is attached to the rear of the housing 2. Two connecting terminals 10 are guided through the cover 8 and secured there. The front end faces of the two connecting terminals 10 face the rear surface of the contact bridge 14. The compression spring 26 is arranged between the rear end of the push rod 30 and the cover 8. For example, the compression spring 26 is pressed with its front end against the fastening means 42 and is received with its middle part and the rear part in a spring receptacle 8a formed in the front end face of the cover 8.

[0047] Furthermore, the compression spring 24 is arranged between the movable iron core 16 and the fixed iron core 4, as shown in Fig. 3. The compression spring 24 is located with its front end in the spring receptacle 16b and is pressed against the bottom of the spring receptacle 16b. The compression spring 24 is pushed onto the front thin-walled section 20b and the middle thick-walled section 20a of the sleeve with its middle and rear sections. The rear end of the compression spring 24 is pressed against the front end surface of the fixed iron core 4 (namely, the end surface of the fitting section 4c).

[0048] As will be described below, the compression spring 22 serves as a return spring for the contact bridge 14 and the compression springs 24, 26 serve as a return spring for the push rod 30. In the event that the compression spring 24 itself can provide a sufficient return force for the push rod 30, the compression spring 26 can be omitted.

[0049] When assembling the Fig. 3, the fixed iron core 4 with the bushing 32 and the electromagnetic coil 6 can first be installed into the housing 2. Then, the movable iron core 16 with the push rod 30, the sleeve 20, and the compression spring 24 can be installed into the housing 2 from the front, with the rear end of the push rod 30 passing through the fixed iron core 4 and protruding from the rear end of the housing 2. The compression spring 22, the mounting base 28, the contact bridge 14, and the fastener 42 are then attached to the push rod 30 from the rear. The cover 8 with the two connection terminals 10 is then mounted on the rear of the housing 2, with the compression spring 26 being installed (inserted into the spring receptacle 8a) between the rear end of the push rod 30 and the cover 8.It can be seen that the electromagnetic switch according to the present invention can be easily assembled and its installation process is substantially the same as that of the prior art.

[0050] The operation of the vehicle starter and its electromagnetic switch of the present invention will be described below.

[0051] When the vehicle is started with the ignition switch, the electromagnetic coil 6 of the electromagnetic switch is energized. The magnetic fluxes of the holding coil and the suction coil of the electromagnetic coil 6 are directed in the same direction. Thus, the two magnetic fluxes overlap, generating a strong electromagnetic force in the movable iron core 16, which moves the movable iron core 16 with the push rod 30 toward the fixed iron core 4 (backward) against the thrust of the springs 24, 26.

[0052] The front end of the push rod 30 pulls the transmission through the shift fork (not shown) to move its drive gear toward the starter ring gear (forward). The rear end of the push rod 30, together with the contact bridge 14, moves toward the two connecting terminals 10. The contact bridge 14 then contacts the two connecting terminals 10, electrically connecting them. Thus, the main circuit of the electric motor is energized through the two connecting terminals 10, causing the electric motor to rotate.As soon as the contact bridge 14 contacts the two connecting terminals 10, it is prevented from moving further backward, while the push rod 30 continues to move backward against the thrust of the spring 22, 24, 26 until the movable iron core 16 strikes the fixed iron core 4, that is, the fitting portion 4c of the fixed iron core 4 is inserted into the fitting recess 16c of the movable iron core 16. At the same time, during the backward movement of the movable iron core 16, the drive gear engages with the starter ring gear on the engine flywheel, thereby transmitting the rotational movement of the electric motor to the engine flywheel, thus starting the engine.

[0053] After the engine is started, the ignition switch is released. At this point, the magnetic fluxes of the holding coil and the suction coil of the electromagnetic coil 6 cancel each other out, so that the electromagnetic force generated in the movable iron core 16 disappears. The movable iron core 16 moves forward under the action of a restoring force of the compression spring 24, 26 (even the compression spring 22), so that the drive gear is pulled away from the starter ring gear on the engine flywheel by the shift fork. After the push rod 12 has moved forward a short distance, the fastener 42 contacts the contact bridge 14 and pulls it away from the two connecting terminals 10, thus switching off the main circuit of the electric motor and thus stopping the starter.After the middle collar 28b of the mounting base 28 enters the stop recess 4d of the fixed iron core 4 and is struck there, the forward movement of the movable iron core 16 ends.

[0054] When the contact bridge 14 is pulled away from the two connecting terminals 10, the push rod 30 experiences a forward restoring force generated by the return springs 24, 26, which is sufficient to quickly separate the contact bridge 14 from the two connecting terminals 10 in order to avoid material sticking between the contact bridge 14 and the two connecting terminals 10 (such material sticking can lead to burnout of the connecting terminals).

[0055] During the forward and backward movement of the push rod 30, the sleeve 20 moves in the guide through hole 4e of the fixed iron core 4 and serves to support and guide the push rod 30. Furthermore, a large part of the sleeve 20 lies axially in a region defined by the electromagnetic coil 6 during the forward and backward movement of the push rod 30.

[0056] It can be seen that the sleeve 20 in the electromagnetic switch of the present invention according to Fig. 3 an enlarged diameter compared to that in Fig. 2, which requires a correspondingly enlarged diameter of the guide through-hole 4e of the fixed iron core 4. As a result, the gap between the inner wall of the guide through-hole 4e of the fixed iron core 4 and the outer periphery of the small-diameter rear portion 30b of the push rod 30 is increased, resulting in an increasing magnetic gap between the fixed iron core 4 and the push rod 30, so that the influences of the push rod 30 on the magnetic circuit generated by the electromagnetic coil 6 are reduced, thereby enabling the push rod 30 to be manufactured from a magnetic material.

[0057] Thus, according to an important aspect of the invention, the push rod 30 is made of a magnetic material. The magnetic material can be steel. Compared to the use of a non-magnetic material such as copper, copper alloy, stainless steel, etc. in the prior art, the use of steel allows for cost reduction. At the same time, requirements for the mechanical properties of the push rod are met and processability is improved.

[0058] One skilled in the art can understand that steels according to quality classification generally include: (1) common steel (P≤0.045%, S≤0.050%); (2) stainless steel (both P, S≤0.035%); (3) quality stainless steel (P<0.035%, S<0.030%).

[0059] By using standard steel (e.g., 10# steel), the cost of the push rod can be reduced. At the same time, the mechanical properties of the push rod are still met without significantly changing the structure and assembly method of the electromagnetic switch itself.

[0060] Furthermore, an annular receiving space for the insertion of the compression spring 22 is defined between the thin-walled portion 20b of the sleeve 20 and the small-diameter rear portion 30b. Thus, a part of the compression spring 22 is held in the receiving space, thereby significantly increasing the stability of the compression spring 22 to ensure that the compression spring 22 does not burn the fixed iron core 4 due to deformation, thereby preventing the magnetic circuit from being disturbed by the contact of the compression spring 22 with the fixed iron core 4.

[0061] In summary, the present invention proposes an improved sleeve structure in which the push rod can be made of a magnetic material such as common steel.

[0062] It is to be understood that the information provided with reference to Fig. 3 described sleeve and related structures can be used in combination with push rods of various shapes.

[0063] For example in Fig. 3, the large-diameter front portion 30a and the small-diameter rear portion 30b of the push rod 30 are integrally formed. Alternatively, the large-diameter front portion 30a and the small-diameter rear portion 30b may be formed separately and then joined together, meaning that the push rod 30 may have a two-piece structure (a first rod portion fixed to the movable iron core and a second rod portion movably mounted on the fixed iron core). For example, the sleeve 20 may enable the connection between the two rod portions, and the sleeve 20 may be formed to have a detachable connection structure such as a claw. Furthermore, the sleeve 20 may be formed such that a small clearance exists between the two rod portions for axial movement relative to each other.

[0064] In addition, the provisions made with reference to Fig. 3 described sleeve and the relevant structures also for the conversion of the electromagnetic switch according to the Fig. 1 shown state of the art can be used.

[0065] For example, the outer diameter of the sleeve can be 20 in Fig.1 can also be enlarged, while a guide through-hole with a correspondingly enlarged diameter is formed in the fixed iron core 4. At the same time, a similar thin-walled portion is formed, and a part of the compression spring 22 is inserted into the receiving space defined between the thin-walled portion and the push rod 12. In this case, the push rod 12 can be made of a magnetic material such as common steel. Furthermore, the push rod 12 and the push rod 18 can be connected to each other by the sleeve 20. In this case, the push rod 18 and the push rod 12 can be regarded as the first rod portion and the second rod portion of the split push rod, respectively.

[0066] Here, the present invention will be described with reference to specific embodiments. However, the scope of the present invention is not limited to the details shown. Various changes to these details are possible without departing from the basic principles of the present invention.

Claims

[1] Electromagnetic switch for a vehicle starter, comprising: a solid iron core (4); a forward and backward movable iron core (16); an electromagnetic coil (6) for generating a magnetic circuit moving the movable iron core (16) backward; a pair of connecting terminals (10) arranged behind the fixed iron core (4); a push rod (30) made of a magnetic material, driven by the movable iron core (16) and extending axially through a guide through hole (4e) in the fixed iron core (4) so ​​that a rear end of the push rod (30) protrudes from the rear part of the fixed iron core (4); a contact bridge (14) mounted at the rear end of the push rod (30) and facing the pair of connecting terminals (10); and a sleeve (20) pushed onto the push rod (30) and slidably engaging in the guide through hole (4e) of the fixed iron core (4), said sleeve having a thick-walled portion (20a) and an adjoining thin-walled portion (20b), wherein the thick-walled portion (20a) is mounted on the push rod (30) and an annular space is defined between the thin-walled portion (20b) and the push rod (30), wherein the contact bridge (14) is mounted on the rear end of the push rod (30) so as to be movable forwards relative to the push rod (30), and that a return spring (22) for the contact bridge (14) is arranged between the sleeve (20) and the contact bridge (14) and is pushed onto the push rod (30), wherein the return spring (22) for the contact bridge (14) is immersed in the annular space with a front end and exerts a thrust force on the contact bridge (14) with a rear end, wherein the contact bridge (14) is mounted on the push rod (30) by means of a mounting base, wherein the return spring (22) for the contact bridge (14) is pressed with the front end against a step surface formed between the thick-walled section and the thin-walled section of the sleeve (20) and with the rear end against the mounting base. [2] Electromagnetic switch according to claim 1, characterized by that the sleeve (20) is made of an insulating plastic. [3] Electromagnetic switch according to one of claims 1 to 2, characterized by that the sleeve (20) is made of a magnetic shielding material or an insulating plastic with a magnetic shielding material. [4] Electromagnetic switch according to one of claims 1 to 3, characterized bythat the push rod (30) is fastened to the movable iron core (16) and integrally comprises a front section with a large diameter and a rear section with a small diameter, wherein a transition step is formed between the front section with the large diameter and the rear section with the small diameter, and that the thick-walled section of the sleeve (20) is pressed against the transition step. [5] Electromagnetic switch according to claim 4, characterized by in that the thin-walled portion of the sleeve (20) comprises a pair of thin-walled sections on the axially two sides of the thick-walled section, wherein the front thin-walled section encloses a rear end part of the front section with the large diameter and an annular space is formed between the rear thin-walled section and the rear section with the small diameter. [6] Electromagnetic switch according to one of claims 1 to 3, characterized by in that the push rod (30) has a two-part construction and comprises a first rod section fastened to the movable iron core and a second rod section slidably mounted in the fixed iron core (4), wherein the second rod section can be moved at least backwards by the first rod section, wherein the sleeve (20) is pushed onto the second rod section. [7] Electromagnetic switch according to claim 6, characterized by that the first rod section and the second rod section are connected to each other by the sleeve (20). [8] Electromagnetic switch according to claim 7, characterized by that the sleeve (20) is designed to allow a relative movement by a distance forwards or backwards between the first rod section and the second rod section. [9] Electromagnetic switch according to one of claims 1 to 8, characterized by that the magnetic material from which the push rod (30) is made is a mass steel. [10] Vehicle starter, comprising: an electric motor; a transmission connected to an output shaft of the electric motor; and an electromagnetic switch according to one of claims 1 to 9, with which the actuation of the electric motor and the transmission mechanism can be controlled.

Images