Relay is a kind of automatic control device that when the input (electrical, magnetic, acoustic, optical and thermal) reaches a certain value, the output will change by leaps.The automobile relay is used in the automobile relay, this kind of relay switching load power, anti - impact, anti - vibration high.The power supply in the car is usually 12V, and the coil voltage is mostly designed to be 12V.Because of the battery power supply, voltage instability;Harsh environmental conditions, suction voltage V≤60%VH (fixed operating voltage);The coil overvoltage is allowed up to 1.5VH.Coil power consumption is large, generally 1.6 ~ 2W, high temperature rise.Environmental requirements are quite harsh: in the engine compartment, the environmental temperature range is required to be -40℃ ~ 125℃, and the environmental temperature range of other locations is -40℃ ~ 85℃.The relay used in the engine compartment should be able to withstand the damage of sand, water, salt and oil.Vibration, impact is quite harsh.

The working principle of

When a certain voltage or current is added to both ends of the coil of the electromagnetic relay, the magnetic flux generated by the coil passes through the magnetic circuit composed of core, yoke, armature and magnetic circuit working air gap. Under the action of the magnetic field, the armature is attracted to the pole surface of the core, thus pushing the contact normally closed contact to disconnect and normally open contact to close.When the voltage or current at both ends of the coil is less than a certain value and the mechanical reaction force is greater than the electromagnetic suction, the armature returns to the initial state and the normally open contact disconnects and the normally closed contact is connected.

Thus, the automobile relay can be regarded as an aggregation composed of two parts: the control circuit of coil operation and the main circuit of contact operation.In the control circuit of the relay, there is only a small working current. This is because the contact capacity of the control switch is small, which cannot be used to directly control the load with a large amount of electricity consumption. Only the contact of the relay can be used to control its on and off.

A relay is both a control switch and a control object.Take the relay of fuel oil pump as an example. It is the control switch of fuel oil pump. However, the coil of the relay of fuel oil pump can only form a loop through the receiving point of the electric control unit when the transistor is driven in the electric control unit.

Part of the

Automobile relay consists of magnetic circuit system, contact system and recovery mechanism.The magnetic circuit system is composed of core, yoke, armature and coil.The contact system is composed of static reed, moving reed, contact base and other parts.The restoring mechanism consists of a restoring reed or tension spring.

Installation method

1. Installation direction if the installation direction is consistent with the impact resistance direction of the relay, the performance of the relay can be given full play.It is suggested that if the impact direction is perpendicular to the movement direction of contact and armature, the vibration resistance and impact resistance of normally closed contact under non-excitation state can be effectively improved.During installation, the contact axis of the relay should be parallel to the ground, which can avoid splash and carbonization of the contact falling on the contact surface and improve the contact reliability.Multiple relays should avoid small load contacts below large load contacts.

2. Installation at close range when multiple relays are installed at close range, abnormal heating will occur, and 2mm spacing is generally recommended.Installation of polarity or magnetic latching relays at close range will affect the operating voltage.

3. Install the relay in the shell. Do not remove the shell and install it first.Tightening torque should be within the range of 0.5 ~ 70N·m.

4. The insertion strength of plug-in relay is recommended to be 40 ~ 70N.[1]

5, meet the same load requirements of the product has different dimensions, according to the allowed installation space, can choose a low height or small installation area of the product.

6. Installation methods of automobile relays include PCB board type, ISO socket type, ISO 280 socket type, shell fixing and clamping installation methods.For small size, not frequently replaced relays, generally choose PCB board type, for often replaced relays, choose socket installation.For relays whose main circuit current exceeds 20A, socket quick connection type is generally selected to prevent large current from passing through circuit board and causing circuit board heat damage (except short-term working relay).For large relays, shell mounting type can be selected to prevent damage of mounting foot under shock and vibration conditions.

maintenance

Welding process

1. Flux coating

PCB board type non-plastic sealed relays are highly susceptible to flux contamination. It is recommended to use anti-flux type or plastic sealed relays to prevent flux gas intrusion from the lead-off end and the gap between the base and the housing. Anti-flux type relays can be further protected against flux intrusion if they are preheated and dried (100℃ for 1 minute).

2. Welding process

Care should be taken not to damage relay performance when using flux or automatic welding. Flux-resistant relays or plastic-sealed relays are suitable for immersion or wave soldering processes, but the maximum welding temperature and time should be controlled according to the selected relay.

1. Wave soldering: the recommended welding temperature is 240℃ ~ 260℃ for about 5 seconds, and the optimal welding temperature is 250℃.For other welding temperature and welding time (such as higher solder temperature will shorten the soldering time), please contact our technical service support or confirm the welding quality.

2. Manual welding: the recommended welding temperature is 300-350 ℃, and the welding time is controlled within 2 seconds.

3. Cooling: the heating of relay caused by soldering process can be relieved by cooling at the end of the process, so do not change the temperature suddenly, especially avoid cold impact on the thermal relay.

Cleaning process

Welding shall be carried out with clean free flux whenever possible and integral cleaning of the relay shall be avoided.Prevent cleaning agent from entering the relay and causing failure.Do not use ultrasonic cleaning, lest ultrasonic energy produce contact cold welding, enameled wire broken and other structural damage.After cleaning and drying, ventilation should be carried out immediately to bring the relay down to room temperature.

Application preservative:

Sometimes, in order to ensure the moisture resistance and high insulation of the circuit board, it is necessary to apply preservative treatment to the circuit board. The softer glue without silicon should be selected. The glue coating process should avoid the negative pressure generated by the relay and inhalation of preservative.

Maintenance and repair methods

(1) a simple method for judging the operating performance of relays

Switch on the ignition switch, and then listen to the control relay with the ear or stethoscope whether there is sound absorption, or feel the relay with the hand whether there is vibration feeling, if yes, that the relay works normally, electrical appliances do not work is caused by other reasons;Otherwise, the relay is not working properly.

It is also possible to unplug the relay for testing, for example, in case of failure of the air conditioner compressor, the engine can be started, and then the blower switch and the air conditioner switch can be switched on.Then unplug the plug connector of the air conditioning compressor relay for judgment.If the sound of the relay action can be heard, and the engine speed drops significantly when the relay is removed, and the engine speed increases when the relay is inserted, it indicates that the relay of the air conditioner compressor and its control circuit are normal.

As for the position of the relay, all relays and safety devices marked with dotted lines on the circuit schematic diagram are generally arranged in the central distribution box.

(2) common failures of relay baffling relays include coil burning, inter-turn short circuit (insulation aging), contact ablation, thermal decay and failure to adjust the initial operating current.

(1) relay coil burned out.In order to prevent this from happening, if the temperature may exceed 80℃ during maintenance and welding, the relay and electronic control unit that are sensitive to temperature should be removed.

(2) contact ablation.Such as jinbei sea lions (parameter | photo) cars (with 491 q - ME engine) of air conditioner condenser fan relay, it is just down to the bottom of the glass cleaning spray pipe, if the spray pipe burst, cleaning fluid will leak to the relay, the relay of the normally open contact corrosion and cannot be disconnected, can lead to air conditioning condenser fan often turn fault.Therefore, water inlet of relay should be strictly prevented.

(3) try to reduce the contact resistance of relay contacts

The contact resistance between the contact points of the vehicle relay mainly consists of contraction resistance and surface film resistance.Contact resistance is related to contact form, material properties and surface processing.Therefore, in order to reduce the contact resistance of relay contacts, the contact state and contact material can be improved under a certain contact pressure.

(4) the defective ECU may affect the normal operation of the relay. In a shenlong fukang 988 sedan, during normal driving, the engine will automatically turn off and start up again, unable to land.Switch on the ignition, no sound of the fuel pump running, no high-pressure fire.Test the ignition coil and find that there is no power supply on the plug, but the resistance on the primary side and the secondary side is normal.Measure the car's jet double seal relay, which is plugged in with a 12V power supply.Replace the spray double seal relay, there is still no high pressure fire, no relay suction sound.A wire is used to tie the no. 10 leg of the jet double-seal relay directly to the iron. The sound of relay suction can be heard, and the engine starts successfully.But the strange thing is, when you take the wire apart, the engine doesn't turn off, and you turn off the ignition, and you restart the engine, and it's working.The reason is that the engine ECU is badly connected, which leads to the low power supply voltage of relay coil (sometimes only about 2V), which makes it impossible for the relay to suck in.The relay has a voltage of 12V after the wire is directly connected with the iron, so the engine starts successfully.After removing the temporary connecting wire (the ignition switch is still on), the relay still has a low holding voltage (which is a common characteristic of relays). Even if the holding voltage is only 2V, the relay will not be disconnected, so the engine will not turn off.Turn off the ignition switch, the circuit generated a self-induction electromotive force is much higher than the supply voltage, under the action of this strong electromotive force, poor contact with the rail may return to normal, so the engine started normal.But the above faults will be repeated, so the way to eradicate the bad parts of the iron will be thoroughly handled.

Storage environment

Avoid direct sunlight and maintain room temperature · constant humidity · normal pressure;Temperature: 10℃ ~ 35℃ humidity: 5 ~ 85%RH air pressure: 86 ~ 106kPa

In high temperature and high humidity environment, when the ambient temperature changes rapidly, the interior of the relay may be exposed.It is especially easy to produce condensation when shipping by boat. Please pay attention to the transportation environment.Condensation is: high temperature, high humidity environment temperature change from high temperature speed into low temperature or speed from low temperature into high temperature high humidity environment, condensation of water vapor into water droplets.Condensation will lead to insulation drop, coil corrosion broken wire, corrosion and so on.

Freezing at low temperature: in dew-condensation and high humidity environment, when water is attached to the relay, the temperature falls below freezing point, the phenomenon of water freezing.Icing may cause adhesion of the moving part, delay in action, or ice to fall between contacts, causing contact failure.

In low temperature and low humidity, plastics may brittle.

Long-term storage in high temperature, high humidity and organic gas, vulcanized gas environment, the contact surface will form vulcanized film and oxide film, resulting in contact instability and contact failure.Please pay attention to the packaging form and minimize the influence of humidity, organic gas and vulcanized gas.

Relay shall be stored and installed in a clean environment. Please use dust cover or plastic sealing relay in the presence of dust pollution.

Attention should be paid to monitoring the storage temperature to avoid the relay storage time is too long.

During storage and transportation, if the relay is subjected to a large drop impact during transportation, it may cause functional dysfunction. Please pay attention to whether the appearance of the packaging material is complete.The relay is packaged with long tube. When the number of relays is small, if there is no limit, the relay will slip and affect the appearance and characteristics of the relay. Special attention should be paid.

Selection guide

Automobile relay selection can be analyzed and studied item by item according to the following key points: shape and installation mode;Input parameters;Output parameters;Environmental conditions;Electromagnetic compatibility;Installation and use requirements.

Parameter selection

Automobile relay input parameters include: 12VDC input parameters, 24VDC input parameters, 12VDC pulse input parameters, 24VDC pulse input parameters.The following parameters should be considered in the selection: the rated voltage of the coil, the action voltage of the coil power consumption and the maximum continuous energized current of the release voltage, the pulse width (magnetic latching relay) of the input parameter of the coil temperature rise pulse.

Input parameter selection concerns:

1. Ambient temperature: the influence of ambient temperature and coil temperature rise on the action voltage is generally divided into engine cabin (the highest temperature shall be 125℃) and cockpit (the highest temperature shall be 85℃);The coil resistance of relay varies with the temperature, which has obvious influence on the action and release voltage of relay.For every 1℃ rise in temperature, the coil resistance will rise by 4‰.When the relay coil is energized for a period of time, the coil heats up.At this time, the relay contact switching action is performed, and the action voltage is higher than the cold action voltage.

2, action voltage: when using transistors and integrated circuits to drive the relay, pay attention to the transistor and integrated circuit voltage drop and relay coil back potential damage to the transistor and integrated circuit.

3. Rated voltage of the coil: after the normally open contact of the relay is closed, it is generally required to apply a voltage above the minimum operating voltage on the coil. It is not recommended for the automobile relay to use a low holding voltage, because it will weaken the anti-vibration of the product and may cause misoperation during the severe turbulence of the automobile.

4, maximum voltage coil: automobile relay to meet the requirements of low action voltage (60% rated voltage), the general design work consumption is higher, exert on the coil voltage for a long time, generally should be less than 120% of rated voltage, if need to reach more than 130% of rated voltage and the value, the need to contact the relay manufacturer, to obtain the technical support.Especially in high temperature, the coil temperature will be too high, aging accelerated -- the final coil insulation layer damage, turns short circuit and failure.

5. Release voltage: the release voltage of automobile relay is generally 10% of the rated voltage. If the residual voltage on the line is too large, the relay will not be released.

The output parameter

The following parameters should be considered when selecting the output parameters of the relay: contact group number contact form contact load contact material electrical life, mechanical lifeOne of the misunderstandings is that the practical load for users is not pure resistance load, but perceptual, lamp, motor or capacitive load, the load size is equal to or close to resistance load;The second misconception is that the load can be adapted from low level to rated load.It should be noted that relays capable of reliably converting 10A resistive loads are not capable of converting 10A inductive loads and may not be capable of reliably converting 10mA loads.Because the failure mechanism of electrical contact under different load conditions is completely different.The power supply of the automobile system is dc, and the dc voltage does not cross zero. When the contact is broken, an arc is generated. Moreover, due to the continuous maintenance of the applied voltage, only the arc is elongated and cannot be extinguished by itself.Arc thermal energy will make contact seriously burned, direct current always flows in one direction, will cause contact material transfer intensified.Most automotive relay load capacity, only nominal resistive load, but the actual use of automotive relay is often not resistive load, but inductive load, lamp load, motor load, because there is a high impact current, contact steady-state load size should be based on the impact current derated size use.It should be emphasized that contact fault is the main cause of relay failure.The electrical contact characteristics, failure phenomena and failure mechanism of contact are different under different load types and different load sizes.

Contact material contact material is the most critical material used by the relay, and its performance determines the quality level of the relay.

The time parameter

When selecting the time parameters of the relay, the following parameters should be considered:

When time test, the typical oscilloscope waveform (1) normally open contact (2) normally closed contact (3) first broken and then closed contact (O b s) note: action time jump back time bridge time

(4) release time of closed contact r, t and c after break is converted to stable closure time

1) the time parameter is generally not concerned when the automobile relay is used.

2) pay attention to the time of assembled automobile relays, such as flash frequency.

Environmental choice

The following environmental parameters should be considered when selecting relays:

1, the temperature

1) insulation materials soften and melt under high temperature;Under the condition of low temperature, the material cracks, insulation electrical resistance decreased, so that failure.But the engineering plastics with good performance can meet the requirements.

2) under the alternating action of high and low temperature, the structure becomes loose and the position of moving parts changes, resulting in uncontrollably sucking and releasing, poor contact or no contact.

3) at low temperature, the moisture inside the relay condenses and freezes, leading to a decline in insulation performance.

4) under the condition of high temperature, the coil resistance increases and the pickup voltage increases accordingly, resulting in no pickup or quasi-suction and non-suction, resulting in the failure of the relay.

5) under the condition of high temperature, when the contact switching power load, the arc breaking ability will be reduced, the contact corrosion and metal transfer will be intensified, the possibility of failure will be increased, and the life will be shortened.

2, hot and humid

Humidity and heat pose a threat to the performance of the relay, as follows:

1) long-term damp and heat will directly lead to the decline of insulation resistance level, so that the complete failure.Especially, the insulation of relay is polluted by sand and dust and then affected by damp and heat in the process of long-term exposed storage or use, which will lead to insulation failure.

2) under humid and hot conditions, the coil is broken due to electrochemical corrosion or mildew, and the contact is electrochemically corroded and oxidized.The corrosion rate of the metal parts increased significantly, the performance of the relay became worse, the reliability of the work became worse, so that the failure was complete.

3) under hot and humid conditions, when the contact is charged and the load is switched, the arcing phenomenon is intensified, resulting in the shortened electrical life.In the tropical, sub-tropical use of electronic products, product design, material selection must be fully considered heat and humidity.

3, sand dust

The failure of relay caused by dust pollution has not attracted enough attention from users.In the natural environment or general industrial workshop environment conditions, especially the electronic device used on the car, sand and dust often through the heat hole, crack position infiltration relay internal, after a long time, boot inspection, dust accumulation can be found, resulting in moving parts rotation (sliding) not working, stuck;Failure of electrical contact;Under the action of moisture, the corrosion of metal parts is intensified, the insulation performance of insulation parts is decreased, so as to cause failure.Some electric power protection relays, automotive relays before the factory inspection qualified, after one or two years of operation, the relay continues to break down.The hazards of sand and dust pollution must be fully considered in design and use.According to practical needs, users put forward specific requirements.

4. Chemical atmosphere pollution

Organic vapor, oxygen, sulfur dioxide, salt mist and so on in the ambient atmosphere have an erosive effect on relay contacts, metal parts, coils and insulating parts, resulting in poor electrical contact and failure;Lead wire corrosion and breakage, insulation level decreased.Chemical harmful gases are common in nature, but on different occasions, the kinds of harmful gases (steam) are different.The erosion can be mitigated and exempted by adopting technological measures, but the cost will be greatly increased.For example, for military sealed relays, the leakage rate can reach 10-8pa.cm3 /s through long-time high-temperature vacuum baking, filling the cavity of the relay with high purity N2 and using electron beam (or laser) for sealing welding.;Contact plating 1 ~ 3u gold.Civil relays are limited by the price, generally just add plastic sealing shell to alleviate the erosion of harmful gas (steam) in the atmosphere, when used, according to the relay load size, the pros and cons of the environment, can be appropriate to open the process hole, in order to improve the heat dissipation ability, reduce internal organic steam, sulfur dioxide pollution on the contact surface.

5. Mechanical vibration

The relay will encounter vibration in a certain frequency range and acceleration value around the strong power equipment and during transportation.Random vibration can represent the in-situ vibration stress of missile, high thrust jet and rocket engine.The influence of vibration on relay is shown as follows:

A. Vibration may lead to loosening, fatigue and fracture of mechanical structural parts;

B. The closed contact becomes invalid due to the instantaneous disconnection of vibration greater than the time specified in the standard;

C. The break contact fails due to the instantaneous closure generated by vibration which is longer than the time specified in the standard;

D. Cause relative motion between moving parts, resulting in noise, wear and other physical failures.

6, impact

Relay in transport, handling, use of the regular mechanical impact of the role.The impact on the relay is shown as follows:

1) due to impact, the structure becomes loose, damaged or fractured and loses its working ability.

2) as a result of impact, the closed contact is temporarily disconnected more than required and becomes invalid;The break contact produces an instant closure greater than the specified value and fails.Therefore, for (1), it is required that the relay should have the performance of impact strength, and the measurement results of specified items before and after the test should meet the requirements of product standards.For (2), the relay should have the performance of anti-impact stability, and the contact state of the contact should be dynamically monitored.

Safe choice

The following parameters should be considered when selecting the safety requirements of the relay:

1, insulation products used insulation materials should have good temperature resistance, long-term working temperature should reach 125℃.

2, insulation withstand voltage level relay withstand voltage between contacts, insulation resistance;Voltage resistance and insulation resistance between contact coils.Typical values of the automobile relay is voltage 500 VAC, 100 M Ω insulation resistance.

Electromagnetic compatibility (EMC) is the ability of automotive relays to work in an electromagnetic environment without interference or interference.EMC has become an important criterion of product quality.Electromagnetic compatibility (EMC) is divided into electromagnetic interference (EMI) and electromagnetic interference interference (EMS).Since the automobile relay USES a unified power source, high voltage will be formed when the relay coil is disconnected, which will interfere with other systems and modules. Therefore, plug-in automobile relays usually have parallel resistors or diodes for transient suppression, making the coil reverse potential less than 100V.When the relay contact is broken, it will produce arc and emit electromagnetic wave, which will affect IC work.In this case, the contact can be added to the arc circuit.It is also appropriate to increase the distance between the relay and IC.

Matters needing attention

I. matters needing attention for coil input

1. Rated voltage is the guarantee of the working reliability of the relay. Although the relay can work when the coil voltage exceeds the operating voltage, it will mismove the coil voltage to exceed the maximum working voltage under strong impact, which will cause coil insulation decline, inter-turn short circuit and burn out

2. Coil resistance of the relay will change by about 0.4%℃ due to the change of ambient temperature and the heating of the relay itself. Therefore, if the coil temperature increases, the action voltage and cut-off voltage will also increase.

3. Automobile relay is driven by accumulator. When large load is switched on, the power voltage will decrease, which will affect the life of the relay.

4. Maximum continuous applied voltage of the coil: in addition to the working stability of the relay, the maximum continuous applied voltage of the coil is mainly limited by the insulation performance of enamelled wire. It is necessary to know the insulation grade of enamelled wire of the product.In the actual use of F grade insulation in the environment temperature of 40℃, it can be considered that the temperature rise limit in the resistance method to determine the maximum 115℃.However, due to the uneven inner and outer rings, the recommended value is 105℃.

5. Coil electric corrosion: the automobile relay works in the environment of temperature and humidity circulation for a long time. When the coil is continuously connected to the positive pole of the power supply (disconnect the negative pole), the coil will be electrically corroded and broken.

2. Matters needing attention for contact use

Contact is the most important part of relay. The working reliability of contact is affected by contact material, contact voltage and current (especially on and off voltage and current waveform), load type, on/off ratio and environmental conditions.Contact voltage: inductive load will produce a very high reverse voltage, the higher the voltage, the greater the energy, accelerate contact electrical corrosion, metal transfer, should be noted.Contact current: the current when the contact is closed or disconnected has a great influence on the contact.When the load is electric motor or headlamp, the impact current when closed is large, the contact loss and metal transfer is larger, and the contact transfer will cause contact bonding failure, which should be confirmed by test.1, contact protection reverse voltage: disconnect the relay coil series circuit or motor, electromagnet and other inductive load must use diode and other surge absorption to protect the contact.

When the inductive load is disconnected, the reverse voltage of hundreds to thousands of V will be generated, so that the electric corrosion of the contact increases dramatically and the service life is reduced.In addition, when the inductive load current is less than 1A, the arc generated by the reverse voltage will decompose the inner coil of the relay and the volatile organic gas of plastics, and generate the black acidified matter and carbonized matter on the contact, resulting in poor contact.Contact metal transfer: contact metal transfer refers to the single-direction contact material transfer of contact material under the direct current action. With the increase of on-off times, the anode contact produces pits, while the cathode contact produces bumps, which are easy to generate mechanical self-locking and cause contact adhesion.Anti - transfer contact material or protection circuit should be selected.Contact protection absorption circuit: the use of contact protection elements or protection circuit, can reduce the reverse voltage, but if not used correctly will have a negative effect.

3. Precautions for use of relay

1. In order to prevent surface contamination of the extraction end, direct contact with the extraction end shall be avoided, otherwise, the weldability may be reduced.

2. The position of the leading end should be

Match with the hole position of the printed plate, any improper fit may cause dangerous stress to the relay and damage its performance and reliability, please refer to the hole drilling diagram in the sample.

3. After the relay is inserted into the circuit board, the lead foot shall not be bent to avoid affecting the sealing or other performance of the relay.

4. Excessive pressure should not be exerted on the shell of relay during the process of insertion, so as to avoid the rupture of the shell or the change of action characteristics.

5. The inserting and pulling pressure of quick connecting pin is 10kg.Too much plugging force will cause relay damage, too little pressure will affect the contact reliability and current carrying capacity.

6. It is especially emphasized that if the relay falls off carelessly during installation or is hit, although the electrical parameters are qualified, the mechanical parameters may change greatly and there are serious hidden dangers, so it should not be used as far as possible.

7, do not use silicone resin and preservatives, can cause contact failure, even plastic sealed relay.

8, pay attention to the polarity of the coil power supply and contact power supply, contact is generally dynamic spring connected positive pole (+).

9. Avoid coil applied voltage exceeding the maximum allowable voltage or coil temperature rise exceeding enamelled wire insulation grade.

10. The rated load and service life are under the specified standard conditions, and it is impossible to cover the use requirements of automobile relays.

Actual application of contact load and life depending on the type of load, environmental conditions, operating frequency or other conditions will be very significant differences, please test test or contact relay manufacturers, obtain technical support.