Relay and its sticking detection circuit and sticking detection method

Abstract

The present application relates to the field of relays, in particular to a relay and its sticking detection circuit and method. The contact of the relay is closed to drive the coil and the auxiliary coil together to reduce the action time of the relay. The holding stage only drives the coil to be energized, which reduces the power of the coil and further reduces the heating power of the coil and the temperature of the relay. 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 an induced current due to the movement of the moving iron core. The controller can further identify the health status of the relay according to the induced current, and can identify the sticking, micro-sticking or aging of the relay. The circuit for detecting the health status of the relay is isolated from the high-voltage loop, which can improve the safety of the BMS detection circuit and reduce the cost.

Description

Technical Field

[0001] This invention relates to the field of relays, and more specifically to relays and their adhesion detection circuits and methods. Background Technology

[0002] Relays are used to control the on / off state of the high-voltage circuit in electric vehicles. The phenomenon of relays sticking together due to contact during load engagement or disengagement often occurs. To ensure high-voltage safety, it is usually necessary to detect the sticking state of the relays.

[0003] Excessive heat generation from the relay coil leads to overheating and thermal management issues. In particular, super-fast charging applications increase the cost and present technical challenges to relay cooling.

[0004] CN206225294U discloses a relay with auxiliary contacts, which detects the on / off status of the contacts through the auxiliary contacts; this method increases the cost and size of the relay, and has poor reliability.

[0005] CN204758746U proposes a circuit for determining relay sticking; the detection method of determining contact sticking by measuring the current or voltage of a high-voltage DC circuit imposes high-voltage isolation requirements on the BMS.

[0006] CN107015139B discloses a method for detecting welding contactors using AC signals. Summary of the Invention

[0007] This invention provides a relay; the relay includes a drive coil and an auxiliary coil. During the relay closing process, the drive coil and the auxiliary coil are simultaneously powered, causing the contacts to close rapidly. After the contacts are closed, during the holding phase, the auxiliary coil is open, and the magnetic field of the drive coil keeps the contacts closed. During the holding phase, the auxiliary coil is de-energized, which reduces energy consumption and heat generation. During the process of the drive coil being de-energized and causing the contacts to open, the change in the magnetic flux of the drive coil induces a current in the auxiliary coil. Furthermore, during the contact opening process, the movement of the magnetic iron core induces a current in the auxiliary coil. The two waves of induced current generated in the auxiliary coil can determine the movement state of the iron core, and thus determine whether the contacts have opened normally.

[0008] A relay detection method is further proposed, wherein the auxiliary coil is provided with a freewheeling circuit. After the drive coil is de-energized, the health status of the relay contacts is diagnosed by detecting the voltage waveform change across the freewheeling resistor of the auxiliary coil, identifying whether the contacts are stuck together, and further identifying whether the relay has micro-sticking or aging.

[0009] The specific technical solution is as follows:

[0010] The relay consists of a housing, stationary contact, moving contact, ceramic cover, upper push rod, buffer spring, lower push rod, return spring, sealing seat, stationary iron core, moving iron core, metal shell, drive coil, and auxiliary coil. The housing has a fixed interface and a drive interface, the drive interface being electrically connected to the drive coil and auxiliary coil. The stationary contact has an electrical contact surface and an electrical connection end, and is mounted on the ceramic cover. To ensure good conductivity and resistance to high-temperature erosion, the stationary and moving contacts are preferably made of copper alloy. The stationary contact, ceramic cover, sealing seat, and metal shell together form a sealed space that accommodates the moving contact, upper push rod, lower push rod, buffer spring, return spring, stationary iron core, and moving iron core. Optionally, the sealed space is filled with a protective gas, such as hydrogen. The moving contact is fixed by the buffer spring and the upper push rod, the upper push rod being connected to the lower push rod, and the lower push rod being connected to the moving iron core; that is, the moving contact is driven by the moving iron core to achieve reciprocating motion. The stationary iron core can be connected and fixed to a sealing seat or a metal shell. The stationary iron core has a through hole through which the lower push rod passes, with a clearance fit, allowing the lower push rod to pass through the stationary iron core and move relative to it with low friction. A return spring is provided between the stationary and moving iron cores. The moving iron core pushes the moving contact closer to the stationary contact, requiring compression of the return spring. The stationary iron core and the drive coil, and the moving iron core and the auxiliary coil, form an electromagnet. During contact engagement, the moving iron core is attracted by the magnetic force of the stationary iron core and moves towards it. During contact disengagement, the magnetism of the stationary iron core dissipates, and the moving iron core is driven away from the stationary iron core by the restoring force of the return spring.

[0011] Furthermore, the aforementioned relay adhesion detection circuit connects the power supply and switch to the auxiliary coil, and the auxiliary coil is provided with a freewheeling circuit, which is composed of a diode and a freewheeling resistor connected in series; the voltage acquisition device is connected in parallel with the freewheeling resistor, and the controller is electrically connected to the voltage acquisition device and the switch.

[0012] Furthermore, a detection method for the aforementioned adhesion detection circuit is provided. The controller can determine or diagnose the health status of the relay by identifying changes in the first and second voltages. When the drive coil is de-energized, the controller detects the voltage across the freewheeling resistor. (I) If the controller detects waveforms of both the first and second voltages within the set time window, it indicates that the relay contacts have successfully opened. (II) If the controller only detects the waveform of the first voltage within the set time window and does not detect the waveform of the second voltage, it indicates that the relay contacts are stuck, and the controller reports a relay sticking fault. (III) If the controller does not detect waveforms of either the first or second voltage within the set time window, it indicates that the voltage acquisition device has failed to properly measure the voltage across the freewheeling resistor, and the controller reports an abnormal relay sticking detection function fault. When the relay contacts successfully disconnect, the controller further diagnoses the relay's health status based on the peak value V2 of the second voltage waveform after each relay disconnection and the time interval t between the de-energization of the drive coil and the peak value V2. It can also diagnose the relay's health status based on the trends of V2 and t. (i) If V2 shows a step decrease or t shows a step increase with an amplitude greater than the limit, it indicates that the relay has experienced micro-adhesion, and the controller can report a micro-adhesion fault to prompt the user for repair. (ii) If V2 shows a gradual decrease or t shows a gradual increase, it indicates that the relay's mechanical components are aging due to the increased number of opening and closing cycles. Furthermore, if the values ​​of V2 and t do not exceed the limits, the relay is considered normal. If the values ​​of V2 or t exceed the limits, the relay is considered to have reached an aging state, and the controller can report the relay aging information to prompt the user to replace the relay. If V2 gradually decreases to 70% of its initial value compared to a new relay, or if t gradually increases to 120% of its initial value compared to a new relay, the relay is considered to have reached an aging state.

[0013] In this invention, the relay's contacts are closed, and both the drive coil and auxiliary coil are energized, reducing the relay's operating time. During the holding phase, only the drive coil is energized, maintaining the relay's closed state and reducing coil power, further lowering coil heat generation and relay temperature. This simplifies the relay's thermal management requirements and extends its service life.

[0014] When the relay of this invention is disconnected, the auxiliary coil circuit generates an induced current due to the movement of the moving iron core. The controller can further identify the health status of the relay based on the induced current, and can further diagnose whether the relay is stuck, slightly stuck, or aging. That is, it is not necessary to control the relay to operate according to a set timing sequence and detect the voltage of the relay stationary contact to determine whether the relay contacts are stuck. The high-voltage circuits connected to the auxiliary coil, moving contact, and stationary contact are isolated from each other, and the circuit of the controller that detects the health status of the relay is isolated from the high-voltage circuit, which can improve the safety of the BMS detection circuit and reduce costs. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a relay embodiment;

[0016] Figure 2 This is a cross-sectional schematic diagram of a relay embodiment;

[0017] Figure 3 This is a schematic diagram of the contact closure state in an embodiment.

[0018] Figure 4 This is a schematic diagram illustrating the movement of the electro-energized iron core driven by the de-energized coil in an embodiment.

[0019] Figure 5 This is a timing diagram of the closing, holding, and opening processes in the embodiment;

[0020] Figure 6 for Figure 5 Enlarged view of a specific area;

[0021] Figure 7 This is a schematic diagram of a relay control circuit;

[0022] Figure 8 A schematic diagram of the voltage waveform across the freewheeling resistor detected by the controller;

[0023] Figure 9 This is a flowchart for relay status detection.

[0024] Figure label:

[0025] 1-Housing, 2-Static contact, 3-Moving contact, 5-Drive coil, 6-Auxiliary coil, 7-Controller, 31-Upper push rod, 32-Buffer spring, 33-Reset spring, 34-Lower push rod, 35-Static iron core, 36-Moving iron core, 41-Ceramic cover, 42-Sealing seat, 43-Metal shell, 351-Through hole, 71-Diode, 72-Freewheeling resistor, 73-Voltage acquisition device, 74-Power supply, 75-Switch. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] like Figure 1 , Figure 2 , Figure 3 , Figure 4As shown, the relay consists of a housing 1, a stationary contact 2, a moving 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 stationary iron core 35, a moving iron core 36, a metal shell 43, a drive coil 5, and an auxiliary coil 6. The housing 1 is provided with a fixed interface 11 and a drive interface 12. The drive interface 12 is electrically connected to the drive coil 5 and the auxiliary coil 6. An external power supply can energize the drive coil 5 and / or the auxiliary coil 6 through the drive interface 12 to further control the relay to close, hold, or open. The stationary contact 2 is provided with an electrical contact surface 21 and an electrical connection end 22. The stationary contact 2 is mounted on the ceramic cover 41. To meet the requirements of good conductivity and high temperature erosion resistance, the stationary contact 2 and the moving contact 3 are preferably made of copper alloy. The stationary contact 2, the ceramic cover 41, the sealing seat 42, and the metal shell 43 together form a sealed space that can accommodate the moving contact 3, the upper push rod 31, the lower push rod 34, the buffer spring 32, the return spring 33, the stationary iron core 35, and the moving iron core 36. Optionally, the sealed space is filled with a protective gas, such as hydrogen. The moving contact 3 is fixed by a buffer spring 32 and an upper push rod 31. The upper push rod 31 is connected to a lower push rod 34. The buffer spring 32 is compressed between the moving contact 3 and the lower push rod 34. The lower push rod 34 is connected to the moving iron core 36, meaning the moving contact 3 is driven by the moving iron core 36 to achieve reciprocating motion. The stationary iron core 35 can be connected and fixed to the sealing seat 42 or the metal shell 43. The stationary iron core 35 has a through hole 351. The lower push rod 34 passes through the through hole 351 and is clearance-fitted with the through hole 351, meaning the lower push rod 34 can pass through the stationary iron core 35 and move relative to the stationary iron core 35 with low friction. A return spring 33 is provided between the stationary iron core 35 and the moving iron core 36. The process of the moving iron core 36 pushing the moving contact 3 closer to the stationary contact 2 requires the compression of the return spring 33. Figure 2 As shown, preferably, the drive coil 5 is located above the auxiliary coil 6, that is, the drive coil 5 is closer to the stationary iron core 35 than the auxiliary coil 6, and the stationary iron core 35 is located at the axis of the upper end of the drive coil 5; the moving iron core 36 is located at the axis of the upper end of the auxiliary coil 6. The stationary iron core 35 and the drive coil 5, and the moving iron core 36 and the auxiliary coil 6 form an electromagnet. During the process of the moving contact 3 and the stationary contact 2 being attracted, the drive coil 5 and the auxiliary coil 6 are energized, causing the stationary iron core 35 to generate magnetism. The moving iron core 36 is attracted by the magnetic force of the stationary iron core 35 and moves towards the stationary iron core 35. During the movement, the return spring 33 is compressed. Furthermore, the push rod 34 and the buffer spring 32 drive the moving contact 3 to adhere to the stationary contact 2. During the process of the moving contact 3 and the stationary contact 2 being disconnected, the magnetism of the stationary iron core 35 is deactivated due to the de-energization of the drive coil 5. The moving iron core 36 is driven away from the stationary iron core 35 by the rebound force of the return spring 33. Furthermore, the push rod 31 drives the moving contact 3 to separate from the stationary contact 2.

[0028] like Figure 2 , Figure 3 , Figure 5As shown, the relay's activation process is as follows: Energizing the drive coil 5 and auxiliary coil 6 causes the stationary iron core 35 to generate a magnetic force, attracting the moving iron core 36 towards the stationary iron core 35. The direction of movement of the moving iron core 36 is... Figure 2 In the direction of P1, the lower push rod 34 drives the buffer spring 32 and the moving contact 3 to move towards the stationary contact 2, until the moving contact 3 is in contact with the electrical contact surface 21 of the stationary contact 2. The moving contact 3 is pressed by the buffer spring 32 and remains stationary. After the moving iron core 36 contacts the stationary iron core 35, it remains stationary and the relay is in the connected state. At this time, both the buffer spring 32 and the reset spring 33 are in the compressed state. Figure 5 Table D1 shows the energizing state K1 of the drive coil 5 and the energizing state K2 of the auxiliary coil 6. Table D2 shows the gap L1 between the moving contact 3 and the stationary contact 2 and the magnetic flux M1 of the drive coil 5. Table D3 shows the current state of the auxiliary coil 6. At time T0, the drive coil 5 and the auxiliary coil 6 are energized at the same time. The magnetic flux M1 of the drive coil 5 increases and the gap L1 between the moving contact 3 and the stationary contact 2 decreases. By time T1, the gap L1 between the moving contact 3 and the stationary contact 2 is 0. The moving contact 3 has been in contact with the electrical contact surface 21 of the stationary contact 2, and the relay is in the ON state.

[0029] Relay holding phase: Drive coil 5 remains energized, auxiliary coil 6 is de-energized, and the magnetic attraction F of stationary iron core 35 to moving iron core 36 is sufficient to overcome the rebound force F1 of buffer spring 32 and return spring 33, as well as resist external interference force F2, keeping the relay in the connected state; the aforementioned external interference force F2 can be the resultant force of gravity and impact force; in one embodiment, when only drive coil 5 is energized, F is 40N, F1 is 18N, and under a 25g acceleration impact, F2 is 13N. F-F1-F2=9N>0 indicates that under a 25g impact, moving iron core 36 will not separate from stationary iron core 35, that is, stationary iron core 35 still has a sufficiently large attraction to keep moving iron core 36 in a stationary state, further keeping moving contact 3 in a stationary state, and further keeping the relay in the connected state. Figure 5 Table D1 shows the energizing state K1 of the drive coil 5 and the energizing state K2 of the auxiliary coil 6. Table D2 shows the gap L1 between the moving contact 3 and the stationary contact 2 and the magnetic flux M1 of the drive coil 5. Table D3 shows the current state of the auxiliary coil 6. During T1 to T2, the drive coil 5 and the auxiliary coil 6 are simultaneously energized. At time T2, the auxiliary coil 6 is de-energized, and the magnetic flux M1 of the drive coil 5 gradually decreases as the auxiliary coil 6 is de-energized. During T2 to T3, only the drive coil 5 remains energized, the gap L1 between the moving contact 3 and the stationary contact 2 remains 0, and the relay remains in the ON state.

[0030] like Figure 3 , Figure 4 , Figure 5 , Figure 6As shown, the relay disconnection process is as follows: the drive coil 5 is de-energized, the magnetism of the stationary iron core 35 is deactivated, and the moving iron core 36 separates from the stationary iron core 35; the rebound force of the compressed buffer spring 32 drives the lower push rod 34 to move away from the stationary contact 2, and the rebound force of the compressed reset spring 33 drives the moving iron core 36 to move away from the stationary contact 2. The direction of movement of the moving iron core 36 is... Figure 4 In the P2 direction; further push rod 31 pulls the moving contact 3 to separate from the stationary contact 2, and the relay is in the open state. Figure 5 Table D1 shows the energizing state K1 of the drive coil 5 and the energizing state K2 of the auxiliary coil 6; Table D2 shows the gap L1 between the moving contact 3 and the stationary contact 2 and the magnetic flux M1 of the drive coil 5; Table D3 shows the current state of the auxiliary coil 6. At time T3, the drive coil 5 is de-energized, and the magnetic flux M1 of the drive coil 5 decreases, that is, the process of the drive coil 5 being de-energized and the moving contact 3 and the stationary contact 2 being disconnected. According to the law of electromagnetic induction, the change in magnetic flux of the drive coil 5 causes the first induced current X1 to be generated in the auxiliary coil 6; during T3 to T4, as... As the magnetic flux M1 of the drive coil 5 decreases, the magnetic attraction between the stationary iron core 35 and the moving iron core 36 decreases. At time T4, the restoring force of the compressed buffer spring 32 drives the push rod 34 to move away from the stationary contact 2, and the restoring force of the compressed reset spring 33 drives the moving iron core 36 to move away from the stationary contact 2. As shown in Table D2, the gap L1 between the moving contact 3 and the stationary contact 2 gradually increases from time T4, that is, the moving contact 3 separates from the stationary contact 2. Further, during the process of the moving contact 3 disconnecting from the stationary contact 2, that is, the moving iron core 36 moves along... Figure 4 During the movement in the P2 direction, the moving iron core 36, which is magnetic and whose magnetism is gradually weakening, moves relative to the auxiliary coil 6, causing the auxiliary coil 6 to cut the magnetic field lines and generate a second induced current X2. At time T5, the current X2 reaches its peak value A2. By time T6, the moving contact 3 has completed its reset, and the moving iron core 36 stops moving. Typically, T3 to T6 lasts for about 20ms.

[0031] like Figure 5 , Figure 6 , Figure 7 , Figure 8As shown, the auxiliary coil 6 is provided with a freewheeling circuit. Preferably, the freewheeling circuit is composed of a diode 71 and a freewheeling resistor 72 connected in series. During the relay's activation process, the controller 7 closes the switch 75, and the power supply 74 and the auxiliary coil 6 form the first circuit S1. The moving 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 conductive. When the switch 75 is opened, the auxiliary coil 6 and the freewheeling circuit form the second circuit S2. The resistance of the second circuit S2 is mainly composed of the freewheeling resistor 72 and the resistance of the auxiliary coil 6. At the instant the controller 7 opens the switch 75, according to Lenz's law, the current direction in the auxiliary coil 6 will maintain the state before the switch 75 is opened. That is, the current in the auxiliary coil 6 passes through the diode 71 and the freewheeling resistor 72 and then further into the auxiliary coil 6. The energy in the auxiliary coil 6 is further dissipated by the resistance of the second circuit S2, thereby causing the current in the second circuit S2 to gradually decrease. When the drive coil 6 is de-energized, the change in magnetic flux of the drive coil 5 causes a first induced current X1 to be generated in the auxiliary coil 6. The first induced current X1 passes through the diode 71 and the freewheeling resistor 72 and then further to the auxiliary coil 6. The energy in the auxiliary coil 6 is further dissipated by the resistance of the second circuit S2, thus causing the current in the second circuit S2 to gradually decrease. Normally, the de-energization of the drive coil 5 causes the magnetism of the stationary iron core 35 to fade, and the magnetism of the moving iron core 36 gradually fades. The moving iron core 36 separates from the stationary iron core 35. The rebound force of the compressed buffer spring 32 drives the lower push rod 34 to move away from the stationary contact 2. The rebound force of the compressed reset spring 33 drives the moving iron core 36 to move away from the stationary contact 2. Furthermore, the upper push rod 31 pulls the moving contact 3 to separate from the stationary contact 2. During this process, the moving iron core 36, which is magnetic and whose magnetism is constantly fading, moves relative to the auxiliary coil 6, causing the auxiliary coil 6 to cut the magnetic field lines and generate a second induced current X2. The induced current in the auxiliary coil 6 flows through the diode 71 and the freewheeling resistor 72 and then back to the auxiliary coil 6. The energy in the auxiliary coil 6 is further dissipated by the resistance of the second circuit S2, which causes the current in the second circuit S2 to gradually decrease. The controller 7 measures the voltage V across the freewheeling resistor 72 through the voltage acquisition device 73. Figure 8 The waveform of the voltage V across the freewheeling resistor 72 measured by the voltage acquisition device 73 is shown. At time T3, the drive coil 5 is de-energized, and the magnetic flux M1 of the drive coil 5 decreases, i.e., the de-energization of the drive coil 5 causes the moving contact 3 to disconnect from the stationary contact 2. According to the law of electromagnetic induction, the change in magnetic flux of the drive coil 5 generates a first induced current X1 in the auxiliary coil 6. At the same time, a first voltage waveform Y1 can be measured across the freewheeling resistor 72. The peak value of the first induced current X1 is A1, and the peak value of the first voltage waveform Y1 is V1 = A1 * R1, where R1 is the resistance of the freewheeling resistor 72. At time T4, the moving contact 3 separates from the stationary contact 2, and the moving iron core 36 moves along... Figure 4During the movement in the P2 direction, the moving iron core 36, which is magnetic and whose magnetism is gradually weakening, moves relative to the auxiliary coil 6, causing the auxiliary coil 6 to cut the magnetic field lines and generate a second induced current X2. At the same time, a second voltage waveform Y2 can be measured across the freewheeling resistor 72. At time T5, the current X2 reaches its peak value A2, and the second voltage waveform Y2 reaches its peak value V2, where V2 = A2 * R1, and R1 is the resistance of the freewheeling resistor 72. The duration t from T3 to T5 is typically 10 to 15 ms. Preferably, the drive coil 5 is provided with a freewheeling circuit to accelerate the current decrease rate within the drive coil 5 and shorten the time consumed by the separation of the moving iron core 36 and the stationary iron core 35.

[0032] When the relay is normally disconnected, the magnetism of the stationary iron core 35 diminishes after the drive coil 5 is de-energized, and the magnetic attraction of the stationary iron core 35 to the moving iron core 36 decreases. The restoring force of the compressed buffer spring 32 drives the lower push rod 34 to move away from the stationary contact 2, and the restoring force of the compressed return spring 33 drives the moving iron core 36 to move away from the stationary contact 2. Further, the upper push rod 31 pulls the moving contact 3 away from the stationary contact 2. At the instant the drive coil 5 is de-energized, according to the law of electromagnetic induction, the change in magnetic flux of the drive coil 5 induces an electromotive force (EMF) at both ends of the auxiliary coil 6. The induced EMF is E = n * ΔΦ / Δt, where n is the number of turns of the auxiliary coil 6, and ΔΦ / Δt is the rate of change of magnetic flux. At this point, the auxiliary coil 6 and the freewheeling circuit form the second circuit S2. The resistance of the second circuit S2 is mainly composed of the freewheeling resistor 72 and the resistance of the auxiliary coil 6. Obviously, the second circuit S2 will have a first induced current X1, the amplitude of which is I = E / R, where R is the resistance of the second circuit S2. The first induced current X1 passes through the diode 71 and the freewheeling resistor 72, and then further to the auxiliary coil 6. The energy in the auxiliary coil 6 is further dissipated by the resistance of the second circuit S2, thus causing the current in the second circuit S2 to gradually decrease. Figure 8 The diagram shows the waveform of the voltage V across the freewheeling resistor 72 measured by the voltage acquisition device 73. At time T3, the drive coil 5 is de-energized, and the magnetic flux M1 of the drive coil 5 decreases, i.e., the de-energization of the drive coil 5 disconnects the moving contact 3 from the stationary contact 2. According to the law of electromagnetic induction, the change in magnetic flux of the drive coil 5 generates a first induced current X1 in the auxiliary coil 6. Simultaneously, a first voltage waveform Y1 can be measured across the freewheeling resistor 72. The peak value of the first induced current X1 is A1, and the peak value of the first voltage waveform Y1 is V1 = A1 * R1, where R1 is the resistance of the freewheeling resistor 72. Further, the restoring force of the return spring 33 drives the moving iron core 36 to move away from the stationary contact 2, i.e., the moving iron core 36 moves along... Figure 4During the movement in the direction of P2, the moving iron core 36, which is magnetic and whose magnetism is constantly diminishing, moves relative to the auxiliary coil 6. This causes the auxiliary coil 6 to cut magnetic field lines, generating an induced electromotive force (EMF) at its ends. The induced EMF is E2 = BLV*sinθ, where B is the magnetic field strength, L is the length of the conductor in the auxiliary coil that cuts the magnetic field lines, V is the velocity of the moving iron core, and θ is the angle between V and B. The magnitude of the induced EMF E2 is proportional to the velocity V of the moving iron core. At this time, switch 75 is open, and the auxiliary coil 6 and the freewheeling circuit form a second circuit S2. The resistance of the second circuit S2 is mainly composed of the freewheeling resistor 72 and the resistance of the auxiliary coil 6. Obviously, the second circuit S2 will have a second induced current X2, the amplitude of which is I2 = E2 / R, where R is the resistance of the second circuit S2. The second induced current X2 flows through diode 71, freewheeling resistor 72, and then further to the auxiliary coil 6. The energy in the auxiliary coil 6 is further dissipated by the resistance of the second circuit S2, thus gradually reducing the current in the second circuit S2. Figure 8 At time T4, the moving contact 3 separates from the stationary contact 2, and the moving iron core 36 moves along... Figure 4 During the movement in the direction of P2, the moving iron core 36, which is magnetic and whose magnetism is gradually weakening, moves relative to the auxiliary coil 6. This causes the auxiliary coil 6 to cut the magnetic field lines, generating a second induced current X2. Simultaneously, a second voltage waveform Y2 can be measured across the freewheeling resistor 72. At time T5, the current X2 reaches its peak value A2, and the second voltage waveform Y2 reaches its peak value V2, where V2 = A2 * R1, and R1 is the resistance of the freewheeling resistor 72. Because the energy within the auxiliary coil 6 is further dissipated by the resistance of the second circuit S2, the current in the second circuit S2 gradually decreases, and the second voltage waveform Y2 gradually decreases after time T5. The duration t from T3 to T5 is typically 10–15 ms.

[0033] When the relay disconnects abnormally, if the moving contact 3 sticks to the stationary contact 2, the position of the moving contact 3 is fixed, further restricting the movement of the moving iron core 36. Even if the magnetism of the stationary iron core 35 dissipates after the drive coil 5 is de-energized, the magnetic attraction of the stationary iron core 35 to the moving iron core 36 decreases, and the restoring force of the return spring 33 is insufficient to drive the moving contact 3 to separate from the stationary contact 2, thus causing the moving iron core 36 to move away from the stationary contact 2. That is, the movement speed of the moving iron core 36 relative to the auxiliary coil 6 is V = 0, and no induced electromotive force is generated at the two ends of the auxiliary coil 6. Furthermore, the controller 7, through the voltage acquisition device 73, measures the voltage across the freewheeling resistor 72 but fails to detect the second voltage waveform Y2 when the relay is normally disconnected. Figure 5Table D1 shows the energized state K1 of the drive coil 5 and the energized state K2 of the auxiliary coil 6; Table D2 shows the gap L1 between the moving contact 3 and the stationary contact 2 and the magnetic flux M1 of the drive coil 5; Table D3 shows the current state of the auxiliary coil 6; Table D4 shows the gap L2 between the moving contact 3 and the stationary contact 2 and the magnetic flux M2 of the drive coil 5 in the relay sticking state; Table D5 shows the current state of the auxiliary coil 6 in the relay sticking state. At time T3, the drive coil 5 is de-energized, and the magnetic flux M1 of the drive coil 5 decreases. This is the process of the moving contact 3 disconnecting from the stationary contact 2 due to the de-energization of the drive coil 5. According to the law of electromagnetic induction, the change in magnetic flux of the drive coil 5 causes a first induced current X1 to be generated in the auxiliary coil 6. During T3 to T4, as the magnetic flux M1 of the drive coil 5 decreases, the magnetic attraction between the stationary iron core 35 and the moving iron core 36 decreases. Due to the adhesion between the moving contact 3 and the stationary contact 2, the gap L2 between the moving contact 3 and the stationary contact 2, as shown in Table D4, remains 0 from T3 onwards. That is, the speed of movement of the moving iron core 36 relative to the auxiliary coil 6 is V = 0. Table D5 shows the current curve of the auxiliary coil 6 in the relay adhesion state. The first induced current X1 gradually decreases, and no second induced current X2 is generated during T3 to T6. At the same time, the controller 7 can measure the first voltage waveform Y1 and the peak value V1 of the first voltage waveform Y1 across the freewheeling resistor 72. During the period from T3 to T6, controller 7 failed to detect the second voltage waveform Y2 across freewheeling resistor 72.

[0034] When the relay disconnects abnormally, if the moving contact 3 and the stationary contact 2 become slightly stuck together, the magnetism of the stationary iron core 35 will dissipate after the drive coil 5 is de-energized. The magnetic attraction of the stationary iron core 35 to the moving iron core 36 will decrease, and the combined force of the rebound force of the buffer spring 32 and the return spring 33 will be greater than the sticking force between the moving contact 3 and the stationary contact 2. That is, under the action of the above combined force, the moving contact 3 will separate from the stationary contact 2, further driving the moving iron core 36 to move away from the stationary contact 2. In one embodiment, the moving contact 3 and the stationary contact 2 become slightly stuck together. The force F3 required for the separation of the slight sticking is 8N, and the combined force F1 of the rebound force of the buffer spring 32 and the return spring 33 is 18N. When the magnetic attraction F of the stationary iron core 35 to the moving iron core 36 decreases to less than 10N, the combined force F1 of the rebound force of the buffer spring 32 and the return spring 33 can drive the moving iron core 36 to move away from the stationary contact 2, further separating the moving contact 3 from the stationary contact 2. In this case, the moving iron core 36 has a relative speed to the auxiliary coil 6. However, since the initial acceleration of the moving iron core 36 is relatively smaller, the speed V is also relatively smaller. Consequently, a smaller induced electromotive force is generated at both ends of the auxiliary coil 6 than when the relay is normally disconnected. At the same time, the time consumed from the de-energization of the drive coil 5 to the reset of the moving contact 3 is also longer. Furthermore, the controller 7 can detect the second voltage when the relay is abnormally disconnected by measuring the voltage across the freewheeling resistor 72 through the voltage acquisition device 73. Figure 8The waveform of the voltage V across the freewheeling resistor 72 measured by the voltage acquisition device 73 is shown. At time T3, the drive coil 5 is de-energized, and the magnetic flux M1 of the drive coil 5 decreases, i.e., the de-energization of the drive coil 5 causes the moving contact 3 to disconnect from the stationary contact 2. According to the law of electromagnetic induction, the change in magnetic flux of the drive coil 5 generates a first induced current X1 in the auxiliary coil 6. At the same time, a first voltage waveform Y1 can be measured across the freewheeling resistor 72. The peak value of the first induced current X1 is A1, and the peak value of the first voltage waveform Y1 is V1 = A1 * R1, where R1 is the resistance of the freewheeling resistor 72. At time T4, the moving contact 3 separates from the stationary contact 2, and the moving iron core 36 moves along... Figure 4 During the movement in the P2 direction, the moving iron core 36, which is magnetic and whose magnetism is gradually diminishing, moves relative to the auxiliary coil 6, causing a voltage waveform Y3 to be measured across the freewheeling resistor 72. At time T7, the voltage waveform Y3 reaches its peak value V3. Since the moving speed V of the moving iron core 36 also decreases relatively, the peak value V3 of the voltage waveform Y3 is less than the peak value V2 of the voltage waveform Y2 when the relay is normally open. At the same time, the time t2 consumed from T3 to T7 is greater than the time t consumed from T3 to T5 when the relay is normally open.

[0035] In some embodiments, the relay gradually ages as the number of opening and closing cycles increases. It is foreseeable that the frictional resistance of moving parts such as the push rod 34 and the moving iron core 36 will increase, and the stiffness coefficient of the return spring 33 will decrease. The aging process of the relay will cause the acceleration of the moving iron core 36 separating from the stationary iron core 35 to gradually decrease, and the movement speed V will also gradually decrease. Consequently, a smaller induced electromotive force will be generated at both ends of the auxiliary coil 6 than when the relay is normally disconnected. At the same time, the time consumed from the de-energization of the drive coil 5 to the reset of the moving contact 3 will gradually increase. Furthermore, the controller 7 can detect the second voltage when the relay is disconnected by measuring the voltage across the freewheeling resistor 72 through the voltage acquisition device 73. The second voltage gradually decreases as the relay ages. Figure 8 The waveform of the voltage V across the freewheeling resistor 72 measured by the voltage acquisition device 73 is shown. As the relay ages, the speed V of the moving iron core 36 gradually decreases. Consequently, the peak value V3 of the voltage waveform Y3 gradually decreases relative to the peak value V2 of the voltage waveform Y2 when the new relay is disconnected. At the same time, the time t2 consumed from T3 to T7 gradually increases relative to the time t consumed from T3 to T5 when the new relay is normally disconnected.

[0036] like Figure 9As shown, the controller 7 uses the changes in the first and second voltages to determine or diagnose the health status of the relay. When the drive coil 5 is de-energized, the controller 7 detects the voltage across the freewheeling 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, it indicates that the relay contacts have successfully opened. Typically, the time window T3 to T6 lasts approximately 20ms. If the controller only detects the waveform of the first voltage within the set time window and does not detect the waveform of the second voltage, it indicates that the moving contact 3 and the stationary contact 2 of the relay are stuck together, and the controller 7 reports a relay sticking fault. In some embodiments, the controller 7 sends the relay sticking fault to the vehicle controller via a CAN signal, and the vehicle controller further controls the display of the relay sticking fault information on the instrument panel. If the controller 7 does not detect the waveforms of the first and second voltages within the set time window, it indicates that the voltage acquisition device 73 has failed to properly measure the voltage across the freewheeling resistor 72, and the controller 7 reports a relay sticking detection function malfunction. When the relay contacts successfully disconnect, the controller 7 further diagnoses the health status of the relay based on the peak value V2 of the second voltage waveform after each relay disconnection and the time interval t between the de-energization of the drive coil and the peak value V2. It can also diagnose the relay's health status based on the changing trends of V2 and t. If V2 shows a step decrease or t shows a step increase with an amplitude greater than the limit, it can be determined that the relay has experienced micro-adhesion, and the controller 7 can report a relay micro-adhesion fault to prompt the user to further inspect the vehicle. In some embodiments, if V2 decreases by 20% compared to the previous normal disconnection state, or t increases by more than 10ms compared to the previous normal disconnection state, it is determined that the relay has experienced micro-adhesion. If the changing trend of V2 is gradually decreasing or the changing trend of t is gradually increasing, it is determined that the change is due to the aging of mechanical components caused by the increase in the number of opening and closing cycles. When the values ​​of V2 and t do not exceed the limits, the relay is considered to be in normal condition; when the values ​​of V2 or t exceed the limits, the relay is considered to have reached an aging state, and the controller 7 can report relay aging information to prompt the user to replace the relay. In some embodiments, if V2 gradually decreases to 70% of its initial value compared to the new relay, or if t gradually increases to 120% of its initial value compared to the new relay, the relay is determined to have reached an aging state.

[0037] The preferred embodiments of this patent have been described in detail above. However, this patent is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this patent.

Claims

1. A relay control circuit, characterized in that: The relay consists of a housing (1), a stationary contact (2), a moving 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 stationary iron core (35), a moving iron core (36), a metal shell (43), a drive coil (5), and an auxiliary coil (6). The housing (1) is provided with a fixed interface (11) and a drive interface (12). The drive interface (12) is electrically connected to the drive coil (5) and the auxiliary coil (6). An external power supply energizes the drive coil (5) and / or the auxiliary coil (6) through the drive interface (12). The stationary contact (2) is provided with an electrical contact surface (21) and an electrical connection end (22). The stationary contact (2) is mounted on the ceramic cover (41). The stationary contact (2), the ceramic cover (41), the sealing seat (42), and the metal shell (43) together form a structure that can accommodate the moving contact (3), the upper push rod (31), the lower push rod (34), the buffer spring (32), the reset spring (33), and the stationary iron core. (35) Sealed space of moving iron core (36); the moving contact (3) is fixed by buffer spring (32) and upper push rod (31), the upper push rod (31) is connected to lower push rod (34), the buffer spring (32) is compressed between the moving contact (3) and lower push rod (34), and the lower push rod (34) is connected to moving iron core (36); the stationary iron core (35) is connected and fixed to sealing seat (42) or metal shell (43), the stationary iron core (35) is provided with through hole (351), the lower push rod (34) passes through the above through hole (351) and is clearance-fitted with through hole (351); a return spring (33) is provided between stationary iron core (35) and moving iron core (36); The drive coil (5) is located above the auxiliary coil (6), and the stationary iron core (35) is located at the axis of the upper end of the drive coil (5); the moving iron core (36) is located at the axis of the upper end of the auxiliary coil (6); the power supply (74) and the switch (75) are connected to the auxiliary coil (6), and the auxiliary coil (6) is provided with a freewheeling circuit, which is composed of a diode (71) and a freewheeling resistor (72) connected in series; the voltage acquisition device (73) is connected in parallel with the freewheeling resistor (72), and the controller (7) is electrically connected to the voltage acquisition device (73) and the switch (75).

2. The relay control circuit according to claim 1, characterized in that: The stationary contact (2) and the moving contact (3) are made of copper alloy.

3. The relay control circuit according to claim 1, characterized in that: The sealed space is filled with a protective gas of hydrogen.

4. The adhesion detection method for the relay control circuit according to any one of claims 1-3, characterized in that: When the drive coil (5) is de-energized, the controller (7) detects the voltage across the freewheeling resistor (72) through the voltage acquisition device (73); (I) If the controller (7) detects two voltage waveforms—the first voltage waveform Y1 and the second voltage waveform Y2—within the set time window, it indicates that the relay contacts have been successfully disconnected. (II) If the controller only detects the first voltage waveform within the set time window, it indicates that the moving contact (3) and the stationary contact (2) of the relay are stuck together, and the controller (7) reports a relay sticking fault. (III) If the controller (7) does not detect any voltage waveform within the set time window, it indicates that the voltage acquisition device (73) has failed to measure the voltage across the freewheeling resistor (72) normally, and the controller (7) reports a relay sticking detection function abnormality fault.

5. The adhesion detection method according to claim 4, characterized in that: In case (Ⅰ), if the relay contacts are successfully disconnected, the controller (7) further diagnoses the health status of the relay based on the peak value V2 of the second voltage waveform after the relay is disconnected and the time interval t from the de-energization of the drive coil to the peak value V2 of the second voltage. (i) If V2 decreases in a step or t increases in a step and the change amplitude is greater than the limit, it is determined that the relay has micro-adhesion, and the controller (7) reports the relay micro-adhesion fault to prompt the user to further inspect the vehicle. (ii) If the trend of V2 is gradually decreasing or the trend of t is gradually increasing, it is determined that the change is caused by the aging of mechanical parts due to the increase of the number of opening and closing of the relay; if the values ​​of V2 and t do not exceed the limit, the relay is judged to be in normal condition; if the values ​​of V2 or t exceed the limit, the relay is judged to have reached the aging state, and the controller (7) reports the relay aging information to prompt the user to replace the relay.

6. The adhesion detection method according to claim 5, characterized in that: The time window lasts for 20ms.

7. The adhesion detection method according to claim 5, characterized in that: In (i), if V2 decreases by 20% compared to the previous normal disconnection state, or if t increases by more than 10ms compared to the previous normal disconnection state, then the relay is judged to have micro-sticking.

8. The adhesion detection method according to claim 5, characterized in that: In (ii), if V2 gradually decreases to 70% of the initial value compared to the new relay, or if t gradually increases to 120% of the initial value compared to the new relay, then the relay is judged to have reached the aging state.

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