CN115732273A - Relay, adhesion detection circuit thereof and adhesion detection method - Google Patents

Abstract

The invention relates to the field of relays, in particular to a relay, an adhesion detection circuit and an adhesion detection method thereof. When the contacts of the relay are closed, the driving coil and the auxiliary coil are driven together to reduce the action time of the relay, only the driving coil is electrified in the maintaining stage, the power of the coil is reduced, and the heating power of the coil and the temperature of the relay are further reduced. The thermal management requirements of the relay are simplified and the service life is prolonged. When the relay is disconnected, the auxiliary coil loop generates induced current due to the movement of the movable iron core, and the controller can further identify the health state of the relay according to the induced current, so that the adhesion, micro-adhesion or aging of the relay can be identified. The circuit that the controller detected the relay health condition is kept apart from high-voltage circuit, can improve BMS detection circuitry's security and reduce cost.

Description

Relay, adhesion detection circuit thereof and adhesion detection method

Technical Field

The invention relates to the field of relays, in particular to a relay, an adhesion detection circuit and an adhesion detection method thereof.

Background

The relay is used for controlling the on-off of a high-voltage loop of the electric automobile, and the contact adhesion phenomenon caused by the on-load attraction or disconnection of the relay occurs sometimes; to ensure high voltage safety, it is usually necessary to detect the sticking condition of the relay.

The relay coil has the advantages that the heating power of the relay coil is large, so that the relay temperature rise is too high, the heat management problem is caused, and particularly, the cost increase problem and the technical challenge are caused by the cooling of the relay by the super quick charging application.

CN206225294U discloses a relay with an auxiliary contact, which detects the on-off condition of the contact through the auxiliary contact; the method increases the cost and the volume of the relay, and has poor reliability.

CN204758746U proposes a circuit for judging the adhesion of a relay; the detection method for judging the contact adhesion condition by measuring the current or voltage of the high-voltage DC circuit brings high-voltage isolation requirements to the BMS.

CN107015139B discloses a method for detecting a welding contactor by an AC signal.

Disclosure of Invention

The invention provides a relay; the relay is provided with a driving coil and an auxiliary coil, the driving coil and the auxiliary coil are simultaneously powered to quickly close the contact in the closing process of the relay, the auxiliary coil is kept to be disconnected in the holding stage after the contact is closed, and the magnetic field of the driving coil keeps the contact in a closed state; the auxiliary coil is powered off in the contact holding stage, so that the energy consumption and the heating power can be reduced. The drive coil cuts off the power supply to make the contact break off, because the magnetic flux change of the drive coil makes the induction current produce in the auxiliary coil, further the iron core movement of taking magnetism makes the induction current produce in the auxiliary coil in the contact break off process, produce above-mentioned two wave induction currents in the auxiliary coil and can judge the motion state of iron core, and then judge whether the contact breaks off normally.

The auxiliary coil is provided with a follow current loop, and after the driving coil is powered off, the health state of the relay contact is diagnosed by detecting the voltage waveform change at two ends of the follow current resistor of the auxiliary coil, whether the contact is adhered or not is identified, and the micro-adhesion or aging of the relay is further identified.

The specific technical scheme is as follows:

the relay is composed of a shell, a stationary contact, a movable contact, a ceramic cover, an upper push rod, a buffer spring, a lower push rod, a reset spring, a sealing seat, a stationary iron core, a movable iron core, a metal shell, a driving coil and an auxiliary coil. The shell is provided with a fixed interface and a driving interface, and the driving interface is electrically connected with the driving coil and the auxiliary coil; the static contact is provided with an electric contact surface and an electric connection end and is arranged on the ceramic cover; in order to meet the requirements of good conductivity and high-temperature ablation resistance, the fixed contact and the movable contact are preferably made of copper alloy materials; the static contact, the ceramic cover, the sealing seat and the metal shell enclose a sealing space capable of containing the movable contact, the upper push rod, the lower push rod, the buffer spring, the reset spring, the static iron core and the movable iron core; optionally, the sealed space is filled with a protective gas, such as hydrogen. The movable contact is fixed by a buffer spring and an upper push rod, the upper push rod is connected with a lower push rod, the lower push rod is connected with a movable iron core, namely the movable contact is driven by the movable iron core to realize the reciprocating motion. The static iron core can be fixedly connected with the sealing seat or the metal shell, the static iron core is provided with a through hole, and the lower push rod penetrates through the through hole and is in clearance fit with the through hole, namely the lower push rod can penetrate through the static iron core and can move relative to the static iron core in a low-friction mode. And a return spring is arranged between the static iron core and the movable iron core, and the movable iron core pushes the movable contact to be close to the static contact and needs to compress the return spring. The electromagnet is composed of the static iron core, the driving coil, the movable iron core and the auxiliary coil, the movable iron core moves towards the direction of the static iron core through the magnetic attraction of the static iron core in the contact attraction process, the static iron core magnetism is eliminated in the contact disconnection process, and the movable iron core is driven by the resilience force of the reset spring and further kept away from the static iron core.

Further, an adhesion detection circuit of the relay is provided, a power supply and a switch are connected with an auxiliary coil, the auxiliary coil is provided with a follow current loop, and the follow current loop is provided with a diode and a follow current resistor which are connected in series; the voltage acquisition device is connected with the follow current resistor in parallel, and the controller is electrically connected with the voltage acquisition device and the switch.

Further, the controller can judge or diagnose the health state of the relay by identifying the change of the first voltage and the second voltage. The drive coil is powered off, and the controller detects the voltage at the two ends of the follow current resistor. And (I) if the controller detects the waveforms of the first voltage and the second voltage within a set time window, indicating that the relay contact is successfully opened. And (II) if the controller only detects the waveform of the first voltage and does not detect the waveform of the second voltage within the set time window, indicating that the contact points of the relay are adhered, and reporting the adhesion fault of the relay by the controller. (III) if the controller does not detect the waveforms of the first voltage and the second voltage in the set time window, the voltage acquisition device cannot normally measure the voltages at the two ends of the follow current resistor, and the controller reports the abnormal fault of the adhesion detection function of the relay. Under the condition that the relay contact is successfully opened, the controller further diagnoses the health state of the relay according to the peak value V2 of the second voltage waveform after the relay is opened every time and the time interval t from the power failure of the driving coil to the second voltage peak value V2, and according to the variation trends of V2 and t; if V2 shows that the step is reduced or t shows that the step is increased and the change amplitude is larger than the limit value, the micro-adhesion of the relay can be judged, and the controller can report the micro-adhesion fault of the relay to prompt a user to overhaul. (ii) if the variation trend of V2 is gradually reduced or the variation trend of t is gradually increased, the variation caused by aging of mechanical parts along with the increase of the opening and closing times of the relay is judged, further, the state of the relay is judged to be normal when the numerical values of V2 and t do not exceed the limit value, the relay is judged to reach the aging state when the numerical values of V2 or t exceed the limit value, and the controller can report the aging information of the relay to prompt a user to replace the relay. And V2 is gradually reduced to 70% of the initial value compared with the new relay, or t is gradually reduced to 120% of the initial value compared with the new relay, and then the relay is judged to reach the aging state.

The driving coil and the auxiliary coil are driven together when the contact of the relay is closed, so that the action time of the relay can be shortened, the closed state of the relay can be maintained and the power of the coil can be reduced only by electrifying the driving coil in the maintaining stage, and the heating power of the coil and the temperature of the relay are further reduced. The thermal management requirements of the relay are simplified and the service life is prolonged.

When the relay is disconnected, the auxiliary coil loop generates induction current due to the movement of the movable iron core, and the controller can further identify the health state of the relay according to the induction current, so that the adhesion, micro-adhesion or aging of the relay can be further diagnosed; the relay does not need to be controlled to act according to a set time sequence and the voltage of the static contact of the relay does not need to be detected to judge whether the contact of the relay is adhered or not. The high-voltage loop that auxiliary coil and movable contact and stationary contact are connected keeps apart each other, and the circuit that the controller detected relay health state keeps apart with high-voltage loop, can improve BMS detection circuitry's security and reduce cost.

Drawings

FIG. 1 is a schematic structural diagram of an embodiment of a relay;

FIG. 2 is a schematic cross-sectional view of an embodiment of a relay;

FIG. 3 is a schematic diagram of a contact closed state according to an embodiment;

FIG. 4 is a schematic view of the moving core of an embodiment with the drive coil de-energized;

FIG. 5 is a timing state diagram of an embodiment close, hold, and open process;

FIG. 6 is an enlarged partial view of FIG. 5;

FIG. 7 is a schematic diagram of a relay control circuit;

FIG. 8 is a schematic diagram of the controller detecting a voltage waveform across the freewheeling resistor;

fig. 9 is a relay state detection flowchart.

Reference numerals:

1-shell, 2-stationary contact, 3-movable contact, 5-driving coil, 6-auxiliary coil, 7-controller, 31-upper push rod, 32-buffer spring, 33-reset spring, 34-lower push rod, 35-stationary iron core, 36-movable iron core, 41-ceramic cover, 42-sealing seat, 43-metal shell, 351-through hole, 71-diode, 72-follow current resistor, 73-voltage acquisition device, 74-power supply and 75-switch.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.

As shown in fig. 1, 2, 3, and 4, the relay is composed of a housing 1, a stationary contact 2, a movable contact 3, a ceramic cover 41, an upper push rod 31, a buffer spring 32, a lower push rod 34, a return spring 33, a seal seat 42, a stationary core 35, a movable core 36, a metal shell 43, a driving coil 5, and an auxiliary coil 6. A fixed interface 11 and a driving interface 12 are arranged on the shell 1, the driving interface 12 is electrically connected with the driving coil 5 and the auxiliary coil 6, an external power supply can electrify the driving coil 5 and/or the auxiliary coil 6 through the driving interface 12, and further control the relay to be closed, kept or opened; the static contact 2 is provided with an electric contact surface 21 and an electric connection end 22, and the static contact 2 is arranged on the ceramic cover 41; in order to meet the requirements of good conductivity and high-temperature ablation resistance, the fixed contact 2 and the movable contact 3 are preferably made of copper alloy materials; the static contact 2, the ceramic cover 41, the sealing seat 42 and the metal shell 43 enclose a sealing space which can contain the movable contact 3, the upper push rod 31, the lower push rod 34, the buffer spring 32, the reset spring 33, the static iron core 35 and the movable iron core 36; optionally, the sealed space is filled with a protective gas, such as hydrogen. The movable contact 3 is fixed by a buffer spring 32 and an upper push rod 31, the upper push rod 31 is connected with a lower push rod 34, the buffer spring 32 is arranged between the movable contact 3 and the lower push rod 34 in a compression mode, the lower push rod 34 is connected with a movable iron core 36, and the movable contact 3 is driven by the movable iron core 36 to move back and forth. The static iron core 35 can be fixedly connected with the sealing seat 42 or the metal shell 43, the static iron core 35 is provided with a through hole 351, and the lower push rod 34 penetrates through the through hole 351 and is in clearance fit with the through hole 351, namely, the lower push rod 34 can penetrate through the static iron core 35 and can move relatively with the static iron core 35 in a low-friction mode. A return spring 33 is arranged between the static iron core 35 and the movable iron core 36, and the return spring 33 needs to be compressed when the movable iron core 36 pushes the movable contact 3 to approach the static contact 2 in the moving process. As shown in fig. 2, preferably, the driving coil 5 is located above the auxiliary coil 6, that is, the driving coil 5 is closer to the static iron core 35 than the auxiliary coil 6, and the static iron core 35 is located at the axis of the upper end of the driving coil 5; the movable iron core 36 is positioned at the axis of the upper end of the auxiliary coil 6. The static iron core 35, the driving coil 5, the movable iron core 36 and the auxiliary coil 6 form an electromagnet, the movable contact 3 and the static contact 2 are attracted in the attraction process, the driving coil 5 and the auxiliary coil 6 are electrified to enable the static iron core 35 to generate magnetism, the movable iron core 36 is attracted to the static iron core 35 by the magnetic force of the static iron core 35 to move, the reset spring 33 is compressed in the movement process, and the underground push rod 34 and the buffer spring 32 further drive the movable contact 3 to be attached to the static contact 2; in the process of disconnecting the movable contact 3 from the fixed contact 2, the driving coil 5 is powered off, so that the fixed iron core 35 is magnetically faded away, the movable iron core 36 is driven by the resilience force of the return spring 33 to be further far away from the fixed iron core 35, and the push-up rod 31 further drives the movable contact 3 to be separated from the fixed contact 2.

As shown in fig. 2, 3 and 5, the pull-in process of the relay is as follows: the driving coil 5 and the auxiliary coil 6 are electrified to enable the static iron core 35 to generate magnetic force to attract the movable iron core 36 to move towards the direction close to the static iron core 35, the moving direction of the movable iron core 36 is the direction P1 in the drawing 2, the buffer spring 32 and the movable contact 3 are driven by the lower push rod 34 to move towards the static contact 2 until the movable contact 3 is attached to the electric contact surface 21 of the static contact 2, and the movable contact 3 is pressed by the buffer spring 32 and keeps static; the movable iron core 36 is kept in a static state after contacting the static iron core 35, the relay is in a connection state, and the buffer spring 32 and the return spring 33 are in a compression state. In fig. 5, table D1 shows an energization state K1 of the driving coil 5 and an energization state K2 of the auxiliary coil 6, table D2 shows a gap L1 between the movable contact 3 and the fixed contact 2 and a magnetic flux M1 of the driving coil 5, and table D3 shows a current state of the auxiliary coil 6; and at the time of T0, the driving coil 5 and the auxiliary coil 6 are electrified simultaneously, the magnetic flux M1 of the driving coil 5 is increased, the gap L1 between the movable contact 3 and the fixed contact 2 is reduced, the movable contact 3 is attached to the electric contact surface 21 of the fixed contact 2 when the gap L1 between the movable contact 3 and the fixed contact 2 is 0 and the relay is in a connection state.

A relay holding stage: the driving coil 5 is kept electrified, the auxiliary coil 6 is powered off, the magnetic attraction force F of the static iron core 35 to the movable iron core 36 overcomes the resilience force F1 of the buffer spring 32 and the return spring 33 and is enough to resist the external interference force F2, and the relay keeps the on state; the external disturbance force F2 may be a resultant force of gravity and impact force; in one embodiment, F is 40n, F1 is 18N, F2 is 13n, F-F1-F2=9N > 0, when only the driving coil 5 is kept in the energized state, and F2 is 13n, F-F1-F2=9N > 0, which indicates that the movable core 36 is not separated from the stationary core 35 in the case of 25g of acceleration impact, that is, the stationary core 35 still has a sufficiently large attraction force to maintain the movable core 36 in the stationary state, further maintain the movable contact 3 in the stationary state, and further maintain the relay in the on state. In fig. 5, table D1 shows an energization state K1 of the driving coil 5 and an energization state K2 of the auxiliary coil 6, table D2 shows a gap L1 between the movable contact 3 and the fixed contact 2 and a magnetic flux M1 of the driving coil 5, and table D3 shows a current state of the auxiliary coil 6; the drive coil 5 and the auxiliary coil 6 are simultaneously kept energized during the period from T1 to T2, the auxiliary coil 6 is de-energized until the time T2, the magnetic flux M1 of the drive coil 5 is gradually reduced along with the de-energization of the auxiliary coil 6, only the drive coil 5 is kept energized during the period from T2 to T3, the gap L1 between the movable contact 3 and the fixed contact 2 is kept at 0, and the relay is kept in the on state.

As shown in fig. 3, 4, 5, and 6, the relay opening process is as follows: the driving coil 5 is powered off, the static iron core 35 is demagnetized, and the movable iron core 36 is separated from the static iron core 35; the resilience of the buffer spring 32 in the compressed state drives the lower push rod 34 to move in the direction away from the fixed contact 2, the resilience of the return spring 33 in the compressed state drives the movable iron core 36 to move in the direction away from the fixed contact 2, and the moving direction of the movable iron core 36 is the P2 direction in fig. 4; further, the upper push rod 31 pulls the movable contact 3 to be separated from the fixed contact 2, and the relay is in a disconnected state. In fig. 5, table D1 shows an energized state K1 of the driving coil 5 and an energized state K2 of the auxiliary coil 6, table D2 shows a gap L1 between the movable contact 3 and the stationary contact 2 and a magnetic flux M1 of the driving coil 5, and table D3 shows a current state of the auxiliary coil 6; at the time of T3, the driving coil 5 is powered off, the magnetic flux M1 of the driving coil 5 descends, namely, in the process that the driving coil 5 is powered off to disconnect the movable contact 3 from the fixed contact 2, according to the electromagnetic induction law, the magnetic flux of the driving coil 5 changes to enable the auxiliary coil 6 to generate a first induced current X1; during the period from T3 to T4, as the magnetic flux M1 of the driving coil 5 decreases, the magnetic attraction of the stationary iron core 35 to the movable iron core 36 decreases, and at the time point of T4, the resilience of the buffer spring 32 in the compressed state drives the lower push rod 34 to move in the direction away from the stationary contact 2, the resilience of the return spring 33 in the compressed state drives the movable iron core 36 to move in the direction away from the stationary contact 2, and the gap L1 between the movable contact 3 and the stationary contact 2 shown in table D2 gradually increases from the time point of T4, that is, the movable contact 3 is separated from the stationary contact 2; further, during the process of disconnecting the movable contact 3 from the stationary contact 2, that is, during the process of moving the movable iron core 36 along the direction P2 in fig. 4, the magnetic iron core 36 with magnetic property and magnetic property gradually decaying moves relative to the auxiliary coil 6, so that the auxiliary coil 6 cuts the magnetic induction line to generate a second induced current X2, and the current X2 reaches the peak value A2 at the time T5. At time T6, the movable contact 3 is reset and the movable iron core 36 stops moving. Typically, T3 to T6 last about 20ms.

As shown in fig. 5, 6, 7, and 8, the auxiliary coil 6 is provided with a freewheel circuit, preferably, a diode 71 and a freewheel resistor 72 connected in series; in the actuation process of the relay, the controller 7 closes the switch 75, the power supply 74 and the auxiliary coil 6 form a first loop S1, and the movable iron core 36 and the auxiliary coil 6 form an electromagnet; when the switch 75 is closed, no current flows through the freewheeling circuit because the diode 71 is unidirectionally conducting; when the switch 75 is turned off, the auxiliary coil 6 and the freewheeling circuit form a second circuit S2, and the resistance of the second circuit S2 mainly consists of the freewheeling resistor 72 and the auxiliary coil 6; at the moment when the controller 7 turns off the switch 75, according to lenz' S law, the current direction in the auxiliary winding 6 maintains the state before the switch 75 is turned off, that is, the current in the auxiliary winding 6 passes through the diode 71 and the freewheeling resistor 72 and then further reaches the auxiliary winding 6, and the energy in the auxiliary winding 6 is further dissipated by the resistor of the second loop S2, so that the current of the second loop S2 is gradually reduced. At the moment of power failure of the driving coil 6, a first induced current X1 is generated in the auxiliary coil 6 due to the change of the magnetic flux of the driving coil 5, the first induced current X1 further reaches the auxiliary coil 6 through the diode 71 and the freewheeling resistor 72, and the energy in the auxiliary coil 6 is further dissipated by the resistor of the second loop S2, so that the current of the second loop S2 is gradually reduced. Normally, the driving coil 5 is powered off to cause the magnetism of the fixed iron core 35 to fade away, further, the magnetism of the movable iron core 36 fades away gradually, the movable iron core 36 is separated from the fixed iron core 35, the resilience of the buffer spring 32 in the compressed state drives the lower push rod 34 to move in the direction away from the fixed contact 2, the resilience of the reset spring 33 in the compressed state drives the movable iron core 36 to move in the direction away from the fixed contact 2, and further, the upper push rod 31 pulls the movable contact 3 to separate from the fixed contact 2; this process moves the movable core 36, which is magnetic and has a decreasing magnetic property, relative to the auxiliary coil 6 so that the auxiliary coil 6 cuts the magnetic induction lines to generate a second induced current X2. The induced current in the auxiliary winding 6 flows through the diode 71 and the freewheeling resistor 72 and further to the auxiliary winding 6, and the energy in the auxiliary winding 6 is further dissipated by the resistor of the second loop S2, so that the current of the second loop S2 is gradually reduced; the controller 7 measures the voltage V across the freewheel resistor 72 via the voltage acquisition device 73. Fig. 8 shows that the voltage acquisition device 73 measures the waveform of the voltage V across the freewheel resistor 72, the drive coil 5 is powered off at time T3, the magnetic flux M1 of the drive coil 5 decreases, that is, the drive coil 5 is powered off to disconnect the movable contact 3 from the stationary contact 2, according to the electromagnetic induction law, a first induced current X1 is generated in the auxiliary coil 6 due to the change in the magnetic flux of the drive coil 5, and at the same time, a first voltage waveform Y1 can be measured across the freewheel resistor 72; the peak value of the first induced current X1 is A1, and the peak value V1= A1 × R1 of the first voltage waveform Y1, where R1 is the resistance value of the freewheeling resistor 72. At the time of T4, the moving contact 3 is separated from the stationary contact 2, the moving iron core 36 moves along the direction P2 in fig. 4, and the moving iron core 36 with magnetism and magnetism gradually declining moves relative to the auxiliary coil 6, so that the auxiliary coil 6 cuts the magnetic induction line to generate a second induction current X2, and meanwhile, a second voltage waveform Y2 can be measured at two ends of the follow current resistor 72; by time T5, the current X2 reaches the peak value A2, the second voltage waveform Y2 reaches the peak value V2, and V2= A2 × R1, where R1 is the resistance value of the freewheel resistor 72. T3 to T5 are of duration T, typically T is 10 to 15ms. Preferably, the driving coil 5 is provided with a follow current circuit to accelerate the current dropping speed in the driving coil 5, and the time consumed for separating the movable iron core 36 from the static iron core 35 is shortened.

When the relay normally breaks off, quiet iron core 35 magnetism subsides after drive coil 5 outage, and quiet iron core 35 diminishes to the magnetic attraction of moving iron core 36, and push rod 34 moves toward the direction of keeping away from stationary contact 2 under the resilience force drive of the buffer spring 32 of compression state, and the resilience force drive of the reset spring 33 of compression state moves iron core 36 and moves toward the direction of keeping away from stationary contact 2, further goes up push rod 31 pulling movable contact 3 and the separation of stationary contact 2. When the driving coil 5 is powered off, according to the law of electromagnetic induction, the magnetic flux of the driving coil 5 changes to generate induced electromotive force at two ends of the auxiliary coil 6, and the induced electromotive force E = n × Δ Φ/Δ t, where n is the number of turns of the auxiliary coil 6 and Δ Φ/Δ t is the rate of change of the magnetic flux. At this time, the auxiliary coil 6 and the freewheeling circuit form a second circuit S2, and the resistance of the second circuit S2 mainly comprises the freewheeling resistor 72 and the auxiliary coil 6; it is obvious that the second loop S2 has a first sensing current X1, and the magnitude I = E/R of the first sensing current X1, where R is the resistance value of the second loop S2. The first induced current X1 passes through the diode 71 and the freewheeling resistor 72 and further reaches the auxiliary winding 6, and the energy in the auxiliary winding 6 is further dissipated by the resistor of the second loop S2, so that the current of the second loop S2 is gradually reduced. Fig. 8 shows the waveform of the voltage V across the follow current resistor 72 measured by the voltage acquisition device 73, when the driving coil 5 is powered off at the time T3, the magnetic flux M1 of the driving coil 5 drops, that is, the driving coil 5 is powered off to disconnect the movable contact 3 from the stationary contact 2, according to the electromagnetic induction law, a first induced current X1 is generated in the auxiliary coil 6 due to the change of the magnetic flux of the driving coil 5, and simultaneously, a first voltage waveform Y1 can be measured across the follow current resistor 72; the peak value of the first induced current X1 is A1, and the peak value V1= A1 × R1 of the first voltage waveform Y1, where R1 is the resistance value of the freewheeling resistor 72. Further, the resilience force of the return spring 33 drives the movable iron core 36 to move in a direction away from the stationary contact 2, that is, the movable iron core 36 moves along the direction P2 in fig. 4, the movable iron core 36 with magnetism and with continuously reduced magnetism moves relative to the auxiliary coil 6 so that the auxiliary coil 6 cuts the magnetic induction lines to generate induced electromotive forces at two ends of the auxiliary coil 6, the induced electromotive forces E2= BLV sin θ, where B is magnetic induction intensity, L is the conductor length of the auxiliary coil participating in cutting the magnetic induction lines, V is the moving speed of the movable iron core, and θ is the included angle between V and B directions; the magnitude of the induced electromotive force E2 is in direct proportion to the moving speed V of the movable iron core. At this time, the switch 75 is turned off, the auxiliary coil 6 and the freewheeling circuit form a second circuit S2, and the resistance of the second circuit S2 mainly includes the freewheeling resistor 72 and the resistance of the auxiliary coil 6; it is obvious that the second loop S2 has a second sensing current X2, and the magnitude I2= E2/R of the second sensing current X2, where R is the resistance of the second loop S2. The second induced current X2 flows through the diode 71, the freewheeling resistor 72 and further to the auxiliary winding 6, and the energy in the auxiliary winding 6 is further dissipated by the resistor of the second loop S2, so that the current of the second loop S2 is gradually reduced. With reference to fig. 8, at time T4, the moving contact 3 is separated from the stationary contact 2, the moving iron core 36 moves along the direction P2 in fig. 4, and the magnetic moving iron core 36, which has magnetic property and gradually decays, moves relative to the auxiliary coil 6 so that the auxiliary coil 6 cuts the magnetic induction line to generate a second induction current X2, and meanwhile, a second voltage waveform Y2 can be measured at two ends of the follow current resistor 72; by time T5, the current X2 reaches the peak value A2, the second voltage waveform Y2 reaches the peak value V2, and V2= A2 × R1, where R1 is the resistance value of the freewheel resistor 72. The second voltage waveform Y2 gradually decreases after time T5 because the energy in the auxiliary winding 6 is further dissipated by the resistance of the second loop S2, and the current of the second loop S2 gradually decreases. T3 to T5 are of duration T, typically T is 10 to 15ms.

When the relay is abnormally disconnected, if the movable contact 3 is adhered to the fixed contact 2, the position of the movable contact 3 is fixed, and the movement of the movable iron core 36 is further restricted; even if the magnetism of the stationary core 35 is removed after the driving coil 5 is powered off, the magnetic attraction of the stationary core 35 to the movable core 36 becomes small, and the resilience of the return spring 33 is not enough to drive the movable contact 3 to separate from the stationary contact 2, so that the movable core 36 moves away from the stationary contact 2. That is, the moving speed V =0 of the movable iron core 36 relative to the auxiliary coil 6, no induced electromotive force is generated at both ends of the auxiliary coil 6, and further, the controller 7 measures the voltage at both ends of the freewheeling resistor 72 through the voltage acquisition device 73 to detect the second voltage waveform Y2 when the relay is normally opened. In fig. 5, table D1 shows an energization state K1 of the driving coil 5 and an energization state K2 of the auxiliary coil 6, table D2 shows a gap L1 between the movable contact 3 and the fixed contact 2 and a magnetic flux M1 of the driving coil 5, and table D3 shows a current state of the auxiliary coil 6; table D4 shows a gap L2 between the movable contact 3 and the stationary contact 2 in the relay adhesion state and a magnetic flux M2 of the driving coil 5, and table D5 shows a current state of the auxiliary coil 6 in the relay adhesion state. At the time of T3, the driving coil 5 is powered off, the magnetic flux M1 of the driving coil 5 descends, namely, in the process that the driving coil 5 is powered off to disconnect the movable contact 3 from the fixed contact 2, according to the electromagnetic induction law, the magnetic flux of the driving coil 5 changes to enable the auxiliary coil 6 to generate a first induced current X1; during the period from T3 to T4, as the magnetic flux M1 of the driving coil 5 decreases, the magnetic attraction force of the stationary core 35 to the movable core 36 decreases, and since the movable contact 3 and the stationary contact 2 are adhered to each other, the gap L2 between the movable contact 3 and the stationary contact 2 shown in table D4 is maintained at 0 from T3, that is, the moving speed V =0 of the movable core 36 with respect to the auxiliary coil 6, and table D5 shows the current curve of the auxiliary coil 6 in the relay adhesion state, the first induced current X1 gradually decreases, and the second induced current X2 is not generated during the period from T3 to T6. While the controller 7 may measure the first voltage waveform Y1 and the peak value V1 of the first voltage waveform Y1 across the freewheel resistor 72. The controller 7 fails to detect the second voltage waveform Y2 across the freewheel resistor 72 during T3-T6.

When the relay is abnormally disconnected, if the movable contact 3 and the fixed contact 2 are slightly adhered, after the driving coil 5 is powered off, the magnetism of the fixed iron core 35 is removed, the magnetic attraction of the fixed iron core 35 to the movable iron core 36 is reduced, the resultant force of the rebound force of the buffer spring 32 and the rebound force of the reset spring 33 is greater than the adhesion force of the movable contact 3 and the fixed contact 2, namely, the movable contact 3 is separated from the fixed contact 2 under the action of the resultant force, and the movable iron core 36 is further driven to move towards the direction far away from the fixed contact 2. In one embodiment, the movable contact 3 and the fixed contact 2 are slightly adhered, the force F3 required for the separation of the slight adhesion is 8N, the resultant force F1 of the resilience forces of the buffer spring 32 and the return spring 33 is 18N, and when the magnetic attraction force F of the fixed iron core 35 to the movable iron core 36 is attenuated to be less than 10N, the resultant force F1 of the resilience forces of the buffer spring 32 and the return spring 33 can drive the movable iron core 36 to move away from the fixed contact 2, so that the movable contact 3 is further separated from the fixed contact 2. In this case, the moving iron core 36 has a moving speed with respect to the auxiliary coil 6, but since the initial acceleration of the moving iron core 36 is relatively small, the moving speed V is relatively small, and further, an induced electromotive force smaller than that in the case of normal opening of the relay is generated at both ends of the auxiliary coil 6, and a time consumed from the power-off of the driving coil 5 to the reset of the moving contact 3 is also longer; further, the controller 7 may detect the second voltage when the relay is abnormally turned off by measuring the voltage across the freewheel resistor 72 through the voltage acquisition device 73. Fig. 8 shows the waveform of the voltage V across the follow current resistor 72 measured by the voltage acquisition device 73, when the driving coil 5 is powered off at the time T3, the magnetic flux M1 of the driving coil 5 drops, that is, the driving coil 5 is powered off to disconnect the movable contact 3 from the stationary contact 2, according to the electromagnetic induction law, a first induced current X1 is generated in the auxiliary coil 6 due to the change of the magnetic flux of the driving coil 5, and simultaneously, a first voltage waveform Y1 can be measured across the follow current resistor 72; the peak value of the first induced current X1 is A1, and the peak value V1= A1 × R1 of the first voltage waveform Y1, where R1 is the resistance value of the freewheeling resistor 72. At the time T4, the moving contact 3 is separated from the stationary contact 2, the moving iron core 36 moves along the direction P2 in fig. 4, and the magnetic property of the moving iron core 36 which gradually declines moves relative to the auxiliary coil 6, so that the voltage waveform Y3 can be measured at the two ends of the follow current resistor 72; the voltage waveform Y3 reaches the peak V3 by time T7. Since the moving speed V of the plunger 36 is relatively reduced, the peak value V3 of the voltage waveform Y3 is smaller than the peak value V2 of the voltage waveform Y2 in the normal off state of the relay, and the time T2 consumed from T3 to T7 is longer than the time T consumed from T3 to T5 when the relay is normally off.

In some embodiments, the relay gradually ages as the number of times of opening and closing increases, and it is expected that the friction resistance of the moving parts such as the lower push rod 34 and the movable iron core 36 increases, and the stiffness coefficient of the return spring 33 attenuates; the aging process of the relay can cause the acceleration of the movable iron core 36 separating the static iron core 35 to be gradually reduced, the movement speed V is also gradually reduced, further, the two ends of the auxiliary coil 6 can generate induced electromotive force smaller than that generated when the relay is normally disconnected, and meanwhile, the time consumed from the power-off of the driving coil 5 to the reset of the movable contact 3 is also gradually side length; furthermore, the controller 7 can detect a second voltage when the relay is switched off by measuring the voltage across the freewheeling resistor 72 through the voltage acquisition device 73, and the second voltage becomes smaller as the relay ages. Fig. 8 shows that the voltage acquisition device 73 measures the waveform of the voltage V across the freewheel resistor 72, and since the moving speed V of the plunger 36 also gradually decreases with the aging of the relay, the peak value V3 of the voltage waveform Y3 gradually decreases with respect to the peak value V2 of the voltage waveform Y2 in the off state of the new relay, while the time T2 consumed from T3 to T7 gradually increases with respect to the time T consumed from T3 to T5 when the new relay is normally off.

As shown in fig. 9, the controller 7 is used to judge or diagnose the health state of the relay by recognizing the changes of the first voltage and the second voltage. The drive coil 5 is de-energized and the controller 7 detects the voltage across the freewheel resistor 72 via the voltage acquisition device 73. If the controller 7 detects the waveforms of the first and second voltages within a set time window, which typically lasts about 20ms, the relay contacts are successfully opened. If the controller only detects the waveform of the first voltage and does not detect the waveform of the second voltage within the set time window, the movable contact 3 and the fixed contact 2 of the relay are adhered, and the controller 7 reports the adhesion fault of the relay; in some embodiments, the controller 7 sends the relay adhesion fault to the vehicle control unit through the CAN signal, and the vehicle control unit further controls the meter to display the relay adhesion fault information. If the controller 7 does not detect the waveforms of the first voltage and the second voltage within the set time window, it indicates that the voltage acquisition device 73 cannot normally measure the voltages at the two ends of the freewheeling resistor 72, and the controller 7 reports the relay adhesion detection function abnormal fault. In the case of successful opening of the relay contacts, the controller 7 further diagnoses the health state of the relay according to the peak value V2 of the second voltage waveform and the time interval t for the driving coil to be deenergized to the second voltage peak value V2 after each relay opening, and further according to the trend of variation of V2 and t; if V2 shows that the step is reduced or t shows that the step is increased and the change amplitude is larger than the limit value, the micro-adhesion of the relay can be judged, and the controller 7 can report the micro-adhesion fault of the relay to prompt a user to further overhaul the vehicle. In some embodiments, if V2 is reduced in a step manner by 20% compared with the last normal off state, or t is increased in a step manner by more than 10ms compared with the last normal off state, it is determined that the micro-sticking of the relay occurs. If the V2 variation trend is gradually reduced or the t variation trend is gradually increased, the change of the relay caused by the aging of mechanical parts along with the increase of the opening and closing times is judged, and when the numerical values of V2 and t do not exceed the limit value, the state of the relay is judged to be normal; when the value of V2 or t exceeds the limit value, the relay is judged to reach the aging state, and the controller 7 can report the aging information of the relay to prompt a user to replace the relay. In some embodiments, if V2 is gradually decreased from the new relay to 70% of the initial value, or t is gradually decreased from the new relay to 120% of the initial value, it is determined that the relay has reached the aging state.

Although the preferred embodiments of the present patent have been described in detail, the present patent is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present patent within the knowledge of those skilled in the art.

Claims (10)

1. A relay, characterized by: the relay consists of a shell (1), a fixed contact (2), a movable contact (3), a ceramic cover (41), an upper push rod (31), a buffer spring (32), a lower push rod (34), a reset spring (33), a sealing seat (42), a fixed iron core (35), a movable iron core (36), a metal shell (43), a driving coil (5) and an auxiliary coil (6);

the shell (1) is provided with a fixed interface (11) and a driving interface (12), the driving interface (12) is electrically connected with the driving coil (5) and the auxiliary coil (6), and an external power supply energizes the driving coil (5) and/or the auxiliary coil (6) through the driving interface (12); the static contact (2) is provided with an electric contact surface (21) and an electric connection end (22), and the static contact (2) is arranged on the ceramic cover (41); the static contact (2), the ceramic cover (41), the sealing seat (42) and the metal shell (43) enclose a sealing space which can contain the movable contact (3), the upper push rod (31), the lower push rod (34), the buffer spring (32), the reset spring (33), the static iron core (35) and the movable iron core (36); the movable contact (3) is fixed by a buffer spring (32) and an upper push rod (31), the upper push rod (31) is connected with a lower push rod (34), the buffer spring (32) is arranged between the movable contact (3) and the lower push rod (34) in a compression mode, and the lower push rod (34) is connected with a movable iron core (36); the static iron core (35) is fixedly connected with the sealing seat (42) or the metal shell (43), the static iron core (35) is provided with a through hole (351), and the lower push rod (34) penetrates through the through hole (351) and is in clearance fit with the through hole (351); a return spring (33) is arranged between the static iron core (35) and the movable iron core (36).

2. The relay according to claim 1, characterized in that: the driving coil (5) is positioned above the auxiliary coil (6), and the static iron core (35) is positioned at the axis of the upper end of the driving coil (5); the movable iron core (36) is positioned at the axle center of the upper end of the auxiliary coil (6).

3. The relay according to claim 1, characterized in that: the fixed contact (2) and the movable contact (3) are made of copper alloy materials.

4. The relay according to claim 1, characterized in that: the sealed space is filled with a protective gas, such as hydrogen.

5. The control circuit of the relay according to any one of claims 1 to 4, characterized in that: a power supply (74) and a switch (75) are connected with an auxiliary coil (6), the auxiliary coil (6) is provided with a follow current loop, and the follow current loop is provided with a diode (71) and a follow current resistor (72) which are connected in series; the voltage acquisition device (73) is connected with the freewheeling resistor (72) in parallel, and the controller (7) is electrically connected with the voltage acquisition device (73) and the switch (75).

6. The adhesion detection method of the control circuit using the relay of claim 5, characterized in that: the driving coil (5) is powered off, and the controller (7) detects the voltages at two ends of the follow current resistor (72) through the voltage acquisition device (73);

if the controller (7) detects two voltage waveforms, namely a first voltage waveform Y1 and a second voltage waveform Y2, in a set time window, the relay contact is successfully opened, and normally;

(II) if the controller only detects the first voltage waveform in the set time window, the movable contact (3) and the fixed contact (2) of the relay are adhered, and the controller (7) reports the adhesion fault of the relay;

(III) if the controller (7) does not detect any voltage waveform in the set time window, the voltage acquisition device (73) cannot normally measure the voltages at the two ends of the follow current resistor (72), and the controller (7) reports the relay adhesion detection function abnormal fault.

7. The detection method of the detection circuit according to claim 6, wherein: for the situation (I), under the condition that the relay contact is successfully opened, the controller (7) diagnoses the health state of the relay according to the peak value V2 of the second voltage waveform after the relay is opened and the time interval t of the power-off of the driving coil to the second voltage peak value V2, and further according to the variation trends of V2 and t;

if V2 shows a step-type decrease or t shows a step-type increase and the change amplitude is larger than a limit value, judging that the relay is slightly adhered, and reporting the micro-adhesion fault of the relay by a controller (7) to prompt a user to further overhaul the vehicle;

(ii) if the V2 variation trend is gradually reduced or the t variation trend is gradually increased, judging that the relay is changed along with the increase of the opening and closing times and the aging of the mechanical component; when the values of V2 and t do not exceed the limit value, the state of the relay is judged to be normal; when the value of V2 or t exceeds the limit value, the relay is judged to reach the aging state, and the controller (7) reports the aging information of the relay to prompt a user to replace the relay.

8. The detection method of the detection circuit according to claim 6, wherein: the time window lasts 20ms.

9. The detection method of the detection circuit according to claim 7, wherein: and (i), if V2 is reduced by 20% in a step mode compared with the last normal open state or t is increased by more than 10ms in a step mode compared with the last normal open state, judging that the micro-adhesion of the relay occurs.

10. The detection method of the detection circuit according to claim 7, wherein: and (ii) if V2 is gradually reduced to 70% of the initial value compared with the new relay or t is gradually reduced to 120% of the initial value compared with the new relay, the relay is judged to reach the aging state.

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