Analysis of automotive starter solenoid switch most prone to failure

Automobile starter by a DC motor, electromagnetic switches , one-way clutch three major components, starter solenoid switch is the most prone to failure of components , the failure phenomenon is often uninterruptible power electromagnetic switch adhesions , resulting in damage to the starter , even battery damage. Electromagnetic switch adhesions is a serious fault , the following reasons for blocking electromagnetic switch will be analyzed and introduced emergency response measures .

1.1 is a stationary contact plane

In general, the electromagnetic switch terminals are copper bolt , the bolt head is a plane that is fixed contact , moving contact is usually a flat , so that when the solenoid switch suction timely , dynamic and static contact on the contact plane contact plane , but , in fact, when the two planes ablation, good contact is not possible , but only a point or several points of contact between two planes , a strong current flows from the contact point of date , the pull- momentary disconnection will produce a strong arc , this arc will make moving contact and static contact surface ablation, ablation of two surfaces in contact after worse , creating a vicious cycle , when severe dynamic and static contact sintering stick together , making off after the starter relay , solenoid switch dynamic and static contact can not be separated , forming a solenoid switch adhesions. This phenomenon will lead to the starter kept running until it burned. Electromagnetic switch user requirements become smaller , the current density increases, the starter each job requires more and more time , such plane stationary contact structure appears adhesion phenomena frequency will be higher. Therefore , the structure of the plane stationary contacts will be phased out .

1.2 stripe -shaped stationary contact

Stripe -shaped stationary contact on the contact surface is pressed flat stationary contacts a series of streaks. Such contact points are scattered stripe , stripe and fringe spacing , which is conducive to arcing dispersed conducive interrupter . Therefore, the use of such an electromagnetic switch stationary contact structure, which greatly reduced the adhesion phenomenon .

1.3 striped sphere stationary contact

 Stripe spherical contact surface of the spherical stationary contact and pressed thick stripes thereon. This configuration is beneficial to both the stationary contact stripe -shaped stationary arc contact dispersed , and in a period of time to increase the contact area, reducing the current density. This will greatly extend the life of the electromagnetic switch .

1.4 mosaic stationary contact

 Such static contact head thickness 2-2.5mm, material is copper , the use of cold forging technology embedded into its steel bolts. Due to low copper prices higher than steel , greatly reducing the cost and use of effects is not much difference , but also to accommodate larger tightening torque requirements.

1.5 welded stationary contact

  With the improvement of China's auto parts production capacity , there has been welded stationary contacts within the industry at present .

Is to is to copper stationary contacts with steel bolts welded together. This static contact is more economical than the mosaic stationary contact , the cost can be reduced. But now the process is not very mature , mainly welding surface pores no effective solution . This should be the future trend .

1.6 welded silver contacts

  Some high-power electromagnetic switch due to the current moment passed too large, more than 1400A, higher demands on the contacts , it is usually with silver alloy contacts . This will greatly extend the life of the contact , but the cost is too high. Usually there are no special requirements are not adopted .

In order to solve the problem of adhesion contacts , some domestic enterprises have also studied the use of copper -plated alloy plated silver oxide and other processes , the effect is different.

2.1 return spring tension

The so-called spring return , also called power spring . After the engine has been started , which requires fast starter off , one-way clutch ring gear quickly from the engine , otherwise the engine anti- rotation starter drag . Fast power, is the key at this time . In this case there are three forces interaction : Reset the reverse magnetic force and the spring force of the coil between the two push the movable core , the movable contact spring back open, which requires adequate return spring force . Spring force is too large, will directly affect the pull-in voltage , resulting in pull-in voltage increases ; spring force is too small , will not have enough power to separate static and dynamic contact, resulting in the release voltage is too low , not even released.

Since the return spring in which the space is small, which requires the number of coils is not much, but better verticality . Generally designed for 4-8 laps, about 1mm wire diameter , shape, design according to product requirements, inverted trapezoidal , drum -shaped , in-line type ......

Generally, the spring is compressed several times , the height is reduced, the fatigue strength will be reduced. Therefore, the requirements of spring fatigue strength is better .

2.2 Integral electromagnetic switch due to the dynamic contact with moving core is connected to an axis , and is firmly fixed . When moving core is pushed , the moving contact and also passive core forcibly opened. For increased reliability , the general design of the return spring is relatively large , and also with a relatively small return spring , the two springs together effect. Due to the overall electromagnetic switch these advantages, greatly reducing the adhesion failure. However, due to the integral solenoid switch moving core and the movable contact connected together , the manufacturing process is relatively cumbersome , require a higher precision of the parts , so the cost is higher relative to the split . In the increasingly demanding user , the overall electromagnetic switch may be the future direction of development, especially in high-power electromagnetic switch significantly better than the overall split switch.

3.1 Emergency response is very simple, if found not stop starter starter , first turn off, turn off the power . If it is convenient to take , such as a wrench or hammer percussion instruments electromagnetic switch , make contact separation movement under vibration effect. In fact, because the movement contacts in a molten state or in a critical state , it is easy to separate.

3.2 If the above , this mode is not working , seize the time to disconnect the battery 's power , stop the starter 's job,

Prevent long power lead to the starter , battery , etc. burned to prevent further enlargement of losses . Then sent for repair professionals .

3.3 In general, electromagnetic switches are all life limit . Countries have mandatory standards , gasoline 35,000 times , diesel 20,000 times. When you find yourself working frequency electromagnetic switch to the standard value, the proposed replacement , repair away from home in order to avoid difficulties .