Single-spring normally-closed direct current contactor

Abstract

The invention discloses a single-spring normally-closed direct-current contactor which comprises a static contact, an upper insulating bush, a movable contact, a lower insulating bush, a transmission rod, a return spring, a supporting sleeve, an armature, a static iron core and a coil. The static contact is located on the upper portion of the contactor, the movable contact is installed at the upper end of the transmission rod, and the upper end face of the movable contact is matched with the lower end face of the static contact. A spring sleeve is arranged in the middle of the transmission rod, the lower end of the transmission rod penetrates through the bottom of the supporting sleeve and then is fixedly connected with the armature, and the outer diameter of the spring sleeve is matched with the inner diameter of the supporting sleeve. A return spring is arranged between the opposite faces of the spring sleeve and the supporting sleeve, a static iron core is arranged below the armature, and the coil surrounds the periphery of the armature and the periphery of the static iron core. The contact pressure is directly and independently provided by the return spring, so that the number of parts is reduced, and the material cost and the assembly complexity are reduced. Moving parts are simplified, the dynamic characteristics of the system are changed, the probability of resonance in vibration and impact environments is effectively reduced, the risk of contact shake-off is reduced, and the working reliability is improved.

Description

Technical Field

[0001] This invention relates to a single-spring normally closed DC contactor. Background Technology

[0002] A DC contactor is an electrical component widely used in DC circuits to control the on / off state of the circuit. A normally closed DC contactor is in a conducting state when the coil is not energized and switches to an open state when energized.

[0003] Existing normally closed DC contactors with a single contact typically employ a dual-spring system: a return spring to reset the armature and close the contacts after coil de-energization; and a separate contact spring to provide sufficient contact pressure when the contacts are closed. This structure suffers from problems such as a large number of parts, high cost, and system complexity. Under mechanical environments such as vibration and impact, the dual-spring system is prone to resonance, leading to unstable contact, chattering, breakage, or even arcing, affecting reliability and lifespan. Furthermore, the moving contacts in the transmission mechanism, without the contact spring, are rigidly mounted and cannot automatically compensate for uneven wear caused by contact erosion, easily resulting in high contact resistance and excessive temperature rise. Therefore, a normally closed DC contactor with a simpler structure and better vibration resistance is needed. Summary of the Invention

[0004] The purpose of this invention is to address the problem that dual-spring systems are prone to resonance under mechanical environments such as vibration and impact, leading to unstable contact, contact breakage, or even arcing. This invention provides a single-spring normally closed DC contactor. By eliminating the independent contact spring and introducing a micro-moving contact mounting structure, the structure is simplified and reliability is improved.

[0005] The technical solution of this invention: A single-spring normally closed DC contactor includes a stationary contact, an upper insulating bushing, a moving contact, a lower insulating bushing, a transmission rod, a return spring, a support sleeve, an armature, a stationary iron core, and a coil. The stationary contact is located at the upper part of the contactor, and the moving contact is mounted on the upper end of the transmission rod, with the upper end face of the moving contact mating with the lower end face of the stationary contact. A spring sleeve is provided in the middle of the transmission rod, and the lower end of the transmission rod passes through the bottom of the support sleeve and is fixed to the armature. The outer diameter of the spring sleeve matches the inner diameter of the support sleeve. A return spring is provided between the opposing surfaces of the spring sleeve and the support sleeve. A stationary iron core is provided below the armature, and the coil surrounds the armature and the stationary iron core.

[0006] One end of the moving contact is machined into a semi-circular joint, which is installed in the mounting groove formed by the upper and lower insulating bushings. The upper and lower insulating bushings are fixed to the upper end of the transmission rod.

[0007] The bottom of the lower insulating bushing is supported by a limiting platform on the transmission rod, and a protruding ring is provided at the bottom of its outer wall; the upper insulating sleeve is fitted on the upper end of the lower insulating bushing and fixed by a retaining ring, and an axial gap is left between the upper insulating bushing and the semi-circular joint, and a radial gap is provided between the semi-circular joint and the lower insulating bushing.

[0008] An overtravel clearance is reserved between the lower end face of the support sleeve and the upper end face of the armature.

[0009] The lower end face of the armature is machined with a frustum-shaped groove, and the top of the stationary iron core is machined with a protrusion of the same size as the frustum-shaped groove.

[0010] When the coil is not energized, the spring force of the return spring acts upward on the spring sleeve of the transmission rod, pushing the transmission rod and armature to move upward, so that the moving contact and the stationary contact are in close contact.

[0011] When the coil is energized, an electromagnetic attraction is generated between the armature and the stationary iron core. This attraction overcomes the elastic force of the return spring and drives the armature and transmission rod to move downward synchronously, causing the moving contact to separate from the stationary contact.

[0012] The outer diameter of the spring sleeve on the transmission rod matches the inner diameter of the support sleeve to achieve radial limiting of the transmission rod.

[0013] The beneficial effects of this invention are: 1. The contact pressure is provided directly by the return spring, which reduces the number of parts, lowers material costs and assembly complexity, and also reduces the overall weight of the force contact system.

[0014] 2. The moving parts have been simplified, the dynamic characteristics of the system have been changed, the probability of resonance in vibration and impact environments has been effectively reduced, the risk of contact breakage has been reduced, and the reliability of operation has been improved.

[0015] 3. The overtravel of the contact system is ensured by the gap between the support ring and the armature. The E-shaped structure of the transmission rod and the fit between the inner diameter of the support ring effectively limit the radial wobble of the transmission rod, ensuring the linearity and stability of the motion.

[0016] 4. The mounting holes for the contacts are designed with a semi-circular structure, and a small radial and axial clearance is maintained between the mounting holes and the lower and upper insulating bushings. This unique "semi-circular structure + double clearance" design allows the moving contact to generate a small-angle seesaw motion when under pressure. For the bridge-type double-break structure, when one side of the contact wears due to ablation, the moving contact can automatically adjust its angle through this micro-motion, ensuring that the contacts at the two breaks can still fit tightly, evenly distributing current and heat, thereby guaranteeing the electrical life of the contactor. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the present invention.

[0018] Figure 2 This is a magnified schematic diagram of a portion of the moving contact.

[0019] Figure 3 This is a partially enlarged schematic diagram of the E-type transmission rod structure.

[0020] Reference numerals: 1-stationary contact, 2-upper insulating bushing, 3-moving contact, 4-lower insulating bushing, 5-drive rod, 6-return spring, 7-support ring, 8-armature, 9-stationary iron core, 10-magnetic gap, 11-coil, 12-overtravel, 13-spring sleeve, 14-semi-circular connector, 15-radial distance between the moving contact mounting hole and the lower bushing, 16-axial distance between the moving contact and the upper bushing. Detailed Implementation

[0021] like Figure 1 As shown, a single-spring normally closed DC contactor of the present invention includes a stationary contact 1, an upper insulating bushing 2, a moving contact 3, a lower insulating bushing 4, a transmission rod 5, a return spring 6, a support ring 7, an armature 8, a stationary iron core 9, and a coil 10.

[0022] The stationary contact 1 is fixed to the upper part of the contactor structure (not shown in the figure). The moving contact 3 is installed on the upper end of the transmission rod 5 through the upper insulating bushing 2 and the lower insulating bushing 3. The transmission rod 5 has an E-type structure 13 in the middle, whose outer cylindrical surface mates with the inner cylindrical surface of the support ring 7, serving as a radial limit. The return spring 6 is sleeved on the transmission rod 5, its upper end abutting the lower surface of the groove in the E-type structure 13, and its lower end pressing against the upper end face of the support ring 7. Below the support ring 7 is the armature 8, with an overtravel allowance 12 between them. The armature 8 is fixed to the bottom end of the transmission rod 5. The stationary iron core 9 is fixed to the bottom of the structure, forming a magnetic gap 10 with the armature 8. The coil 11 surrounds the armature 8 and the stationary iron core 9.

[0023] Core innovation details such as Figure 2 : The mounting hole of the moving contact 3 is provided with a semi-circular structure 14. The lower insulating bushing 4 is installed in the hole, but the two are not an interference fit or a tight fit. In the radial direction, there is a radial distance 15 between the mounting hole of the moving contact and the lower insulating bushing 4; in the axial direction, there is an axial distance 16 between the moving contact mounting hole and the upper bushing. This "one arc, two surfaces" fit relationship together constitutes a hinge structure that allows the moving contact 3 to rotate at a small angle.

[0024] Working principle: Normally closed state Figure 1 When coil 11 is not energized, the preload of return spring 6 pushes the transmission rod E-type structure 13 upward, causing transmission rod 5 and armature 8 to move upward until moving contact 3 and stationary contact 1 are pressed together. At this time, the force of return spring 6 is directly converted into contact pressure between the contacts.

[0025] Disconnected state: When coil 11 is energized, it generates an electromagnetic attraction force that drives armature 8 to move downward. Transmission rod 5 moves downward together against the force of return spring 6, ultimately causing moving contact 3 and stationary contact 1 to separate.

[0026] Wear compensation Figure 2 When the contacts are closed, if the contact plane of the stationary contact becomes non-parallel due to ablation, the reaction force acting on the moving contact 3 will be uneven. At this time, the moving contact 3 can use the semi-circular structure 14 as a fulcrum and the space provided by the radial spacing 15 and the axial spacing 16 to undergo a slight seesaw-like deflection, thereby making its own contact surface fit with the contact surface of the stationary contact, ensuring the reliability and stability of the contact.

[0027] Example 1: Normally Closed Conductive State When coil 11 is not connected to a 28V DC power supply, the return spring 6 is in a pre-compressed state. The 7N upward elastic force it generates acts on the E-type structure 13 of the transmission rod 5, pushing the transmission rod 5 to move upward along the axial direction, and simultaneously driving the armature 8 to move upward synchronously. Since the support ring 7 is fixed, when the transmission rod 5 moves upward, the moving contact 3 rises together with the transmission rod 5 until the upper end face of the moving contact 3 is completely in contact with the lower end face of the stationary contact 1. At this time, the preload of the return spring 6 is completely converted into the contact pressure 7N between the moving contact 3 and the stationary contact 1. The circuit is connected through "stationary contact 1 → moving contact 3". The measured contact resistance in the initial state of contact connection is 0.5mΩ. Under the rated current of 150A, the temperature rise is ≤75K and the ambient temperature is 85℃, which meets the requirements of GJB 1461-2017.

[0028] In this state, if the contactor is subjected to external vibrations such as the sinusoidal vibration of an aircraft with a frequency of 10Hz to 2000Hz and an acceleration of 15g, the radial displacement of the transmission rod 5 is approximately 0.059mm due to the radial limiting effect of the E-type structure 13 of the transmission rod 5 and the support ring 7. At the same time, the single-spring structure avoids the resonance problem of the double spring, and the contact break time meets the requirement of ≤10μs.

[0029] Example 2: Energizing the coil in the disconnected state When a 28VDC, 2A current is applied to coil 11, the magnetic field generated by coil 11 magnetizes the stationary iron core 9, creating an electromagnetic attraction of 15N between armature 8 and stationary iron core 9 (measured). Since this electromagnetic attraction of 15N is greater than the preload of the return spring 6 (7N), armature 8 is attracted downwards, causing transmission rod 5 to overcome the spring force and move axially downwards. During the downward movement of transmission rod 5, moving contact 3 also moves downwards. As transmission rod 5 moves downwards, moving contact 3 begins to separate from stationary contact 1; when it continues to move downwards to its maximum value, armature 8 and stationary iron core 9 are fully attracted, and the magnetic gap 10 becomes 0 mm. At this point, the single-sided distance between moving contact 3 and stationary contact 1 is 2 mm (4 mm on both sides), meeting the electrical clearance requirement of 2500VAC (50Hz RMS).

[0030] During the disconnection process, the oscilloscope monitoring showed that the time from the energization of coil 11 to the complete separation of the contacts was approximately 10ms, achieved through the built-in ceramic arc-extinguishing chamber with a volume of approximately 10cm³. 3 The permanent magnet blowout method achieves rapid arc extinguishing. After disconnection, the insulation resistance between contacts is ≥1000MΩ, 500VDC, and the dielectric withstand voltage is ≥2500VAC (50Hz RMS value). The insulation withstand voltage tester shows no leakage. When coil 11 is continuously energized, the temperature rise is ≤75K and the ambient temperature is 85℃, which complies with GJB 1461-2017.

[0031] Example 3: Automatic Compensation for Contact Wear Simulating a contactor contact erosion scenario after long-term use: A 150A, 0.6s on-time, 5.4s off-time, 10,000-cycle electrical life test was conducted to verify the uneven wear that may occur between stationary contact 1 and moving contact 3 after electrical life erosion. When the left and right heights of stationary contact 1 are inconsistent, the reaction forces on the left and right sides of moving contact 3 will be unbalanced. Under the action of the reaction force difference, moving contact 3 uses the lowest point of the semi-circular structure 14 as a fulcrum, and utilizes the 0.2mm gap in the radial spacing 15 and the 0.2mm movement space in the axial spacing 16 to slightly deflect by an angle of about 1°. After deflection, the upper end face of moving contact 3 is completely in contact with the lower end face of stationary contact 1 without gap.

[0032] After 10,000 cycles of operation under a rated current of 150A, the contact temperature rise between the moving contact 3 and the stationary contact 1 was monitored: the temperature rise on both sides did not exceed 75K, the temperature difference between the two sides was small, there was no local overheating, and the contact resistance was stable and met the specified ≤15 mΩ, proving that the wear compensation structure is effective.

[0033] Example 4: Reset State In the open state, when the power supply to coil 11 is disconnected, the electromagnetic attraction disappears, and the preload of return spring 6 pushes transmission rod 5 upward again, causing armature 8 and moving contact 3 to move upward synchronously. During the upward movement of armature 8, the magnetic gap 10 between armature 8 and stationary iron core 9 gradually returns to 2 mm. When moving contact 3 and stationary contact 1 are in contact again, transmission rod 5 stops moving, and the contactor returns to the normally closed conducting state.

[0034] The response time during the reset process, from coil de-energization to contact closure, is 14ms. After reset, the contact pressure remains at 7N, and the contact resistance stabilizes at around 0.5mΩ. After 10,000 reset cycles, no components are loose, functions are normal, electrical performance is normal, and overall performance is stable.

Claims

1. A single-spring normally closed DC contactor, characterized in that: The contactor includes a stationary contact (1), an upper insulating bushing (2), a moving contact (3), a lower insulating bushing (4), a transmission rod (5), a return spring (6), a support sleeve (7), an armature (8), a stationary iron core (9), and a coil (11). The stationary contact (1) is located on the upper part of the contactor. The moving contact (3) is installed on the upper end of the transmission rod (5), and the upper end face of the moving contact (3) is matched with the lower end face of the stationary contact (1). A spring sleeve (13) is provided in the middle of the transmission rod (5). The lower end of the transmission rod (5) passes through the bottom of the support sleeve (7) and is fixed to the armature (8). The outer diameter of the spring sleeve (13) matches the inner diameter of the support sleeve (7). A return spring (6) is provided between the opposite faces of the spring sleeve (13) and the support sleeve (7). A stationary iron core (9) is provided below the armature (8). The coil (11) surrounds the armature (8) and the stationary iron core (9).

2. The single-spring normally closed DC contactor according to claim 1, characterized in that: One end of the moving contact (3) is machined into a semi-circular connector (14), which is installed in the mounting groove formed by the upper insulating bushing (2) and the lower insulating bushing (4). The upper insulating bushing (2) and the lower insulating bushing (4) are fixed to the upper end of the transmission rod.

3. The single-spring normally closed DC contactor according to claim 2, characterized in that: The bottom of the lower insulating bushing (4) is supported by a limiting platform on the transmission rod (5), and a protruding ring is provided at the bottom of its outer wall; the upper insulating sleeve (2) is fitted on the upper end of the lower insulating bushing (4) and fixed by a retaining ring; there is an axial gap between the upper insulating bushing (2) and the semi-circular joint (14), and a radial gap between the semi-circular joint (14) and the lower insulating bushing (4).

4. The single-spring normally closed DC contactor according to claim 1, characterized in that: An overtravel clearance (12) is reserved between the lower end face of the support sleeve (7) and the upper end face of the armature (8).

5. The single-spring normally closed DC contactor according to claim 1, characterized in that: The lower end face of the armature (8) is machined with a frustum-shaped groove, and the top of the stationary iron core (9) is machined with a protrusion of the same size as the frustum-shaped groove.

6. The single-spring normally closed DC contactor according to claim 1, characterized in that: When the coil (11) is not energized, the elastic force of the return spring (6) acts upward on the spring sleeve (13) of the transmission rod (5), pushing the transmission rod (5) and armature (8) to move upward, so that the moving contact (3) and the stationary contact (1) are in close contact.

7. The single-spring normally closed DC contactor according to claim 1, characterized in that: When the coil (11) is energized, an electromagnetic attraction is generated between the armature (8) and the stationary iron core (9). This attraction overcomes the elastic force of the return spring (6) and drives the armature (8) and the transmission rod (5) to move downward synchronously, so that the moving contact (3) separates from the stationary contact (1).

8. The single-spring normally closed DC contactor according to claim 1, characterized in that: The outer diameter of the spring sleeve (13) on the transmission rod (5) matches the inner diameter of the support sleeve (7) to achieve radial limiting of the transmission rod (5).

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