Brush direct current motor

Abstract

The utility model relates to a brush direct current motor, which comprises a commutator and an annular piezoresistor, the commutator is provided with a counter bore and a plurality of commutator segments uniformly distributed on the circumference, the annular piezoresistor is arranged in the counter bore and comprises a plurality of electrodes, and the commutator segments and the electrodes are welded in a one-to-one correspondence manner to form an integrated commutator structure. According to the brush direct current motor of the utility model, surge voltage is suppressed through the integrated commutator structure, conduction and radiation emission are reduced, sparks generated between the carbon brush and the commutator due to commutation are effectively suppressed, the electromagnetic compatibility of the motor is greatly improved, and the service life of the brush direct current motor is prolonged.

Description

Technical Field

[0001] This utility model relates to motors, and more specifically to a brushed DC motor. Background Technology

[0002] Traditional automotive electrical systems primarily rely on 12V or 24V voltage to power vehicle lighting, ignition, entertainment systems, electronic control units, and other functions. With the development of electric vehicle (EV) and hybrid electric vehicle (HEV) technologies, vehicles are beginning to adopt higher voltage power supply systems to reduce energy consumption, such as being directly powered by a 48V onboard battery.

[0003] During the operation of a brushed DC motor, as the rotor rotates at high speed, the carbon brushes slide on the commutator contacts, achieving timely switching of current direction. An electric arc, or commutation spark, is generated when the carbon brushes and commutator make contact and separate. In 12V or 24V automotive battery systems, the commutation spark is relatively small due to the lower voltage. However, in high-voltage environments, such as 48V, the increased voltage leads to a larger inrush current during commutation, which exacerbates the generation of commutation spark. This increased commutation spark not only increases mechanical wear and shortens the motor's lifespan, but also generates strong electromagnetic radiation and electromagnetic interference (EMI) due to the rapid changes in the local magnetic field caused by the spark, negatively impacting the motor's electromagnetic compatibility (EMC). Utility Model Content

[0004] To address the problem of enhanced commutation sparks in the prior art, this invention provides a brushed DC motor.

[0005] According to the present invention, a brushed DC motor includes a commutator and an annular varistor. The commutator has a countersunk hole and multiple commutator segments evenly distributed around the circumference. The annular varistor is disposed in the countersunk hole and includes multiple electrodes. The commutator segments and electrodes are welded one-to-one to form an integrated commutator structure.

[0006] In a preferred embodiment, the annular varistor further includes a substrate, and the electrodes are fan-shaped electrodes evenly distributed along the circumference and fixedly disposed on the substrate.

[0007] In a preferred embodiment, the commutator segment is fixed with bakelite powder, the height of which is lower than the height of the commutator segment to form a countersunk hole.

[0008] In a preferred embodiment, the electrode is disposed on the end face of the substrate facing away from the bakelite powder.

[0009] In a preferred embodiment, a ring-shaped varistor is connected in parallel between two adjacent commutator segments.

[0010] In a preferred embodiment, the number of commutator segments is consistent with the number of electrodes.

[0011] In a preferred embodiment, the commutator is an oxygen-free silver-copper sheet.

[0012] In a preferred embodiment, the electrode is a copper electrode or a silver electrode.

[0013] In a preferred embodiment, the brushed DC motor further includes carbon brushes mounted via a brush holder, which contact the commutator to change the direction of the current.

[0014] In a preferred embodiment, the carbon brush is a porous artificial graphite carbon brush.

[0015] The brushed DC motor according to this utility model suppresses surge voltage and reduces conducted and radiated emissions through an integrated commutator structure, effectively suppressing / weakening the sparks generated between the carbon brush and the commutator due to commutation, significantly improving the electromagnetic compatibility of the motor, and extending the service life of the brushed DC motor. Attached Figure Description

[0016] Figure 1 This is an exploded view of a brushed DC motor according to a preferred embodiment of the present invention.

[0017] Figure 2 yes Figure 1 A schematic diagram of the structure of a ring-shaped varistor.

[0018] Figure 3 yes Figure 1 A schematic diagram of the structure of a ring varistor and commutator.

[0019] Figure 4 Show Figure 3 An integrated commutator structure is formed by assembling a ring-shaped varistor and a commutator. Detailed Implementation

[0020] The preferred embodiments of this utility model are given below with reference to the accompanying drawings and described in detail.

[0021] like Figure 1 As shown, a brushed DC motor according to a preferred embodiment of the present invention includes a housing 1, a brush holder 2, and a rotor 3. The brush holder 2 is installed inside the housing 1 and is equipped with carbon brushes 201 and 202. The carbon brushes 201 and 202 cooperate with the rotor 3 so that the rotor 3 generates mechanical energy through the interaction of current and magnetic field.

[0022] The housing 1 is typically made of metal or plastic and has good mechanical strength and electrical insulation properties. It is used to fix and protect the internal components of the motor, provide mechanical support, and prevent the external environment from damaging the motor.

[0023] The brush holder 2 is typically made of insulating material to ensure electrical isolation. Traditional carbon brushes mainly use metallic graphite, with a copper content mostly ranging from 30% to 80%, which can meet the current density requirements of a 12V system. The carbon brushes 201 and 202 installed on the brush holder 2 of this invention use porous artificial graphite, increasing the overall porosity of the material. This improves the carbon brush's ability to absorb commutation energy and suppresses commutation sparks. Their copper content is preferably 10% to 25%, which satisfies commutation and current flow requirements without affecting the basic performance of the motor.

[0024] like Figure 1 As shown, the rotor 3 includes a shaft 301, an iron core 302, a winding 303, a commutator 304, and an annular varistor 305. The shaft 301 is connected to the output shaft, the iron core 302 is mounted on the shaft 301, the winding 303 is wound around the iron core 302 to generate a rotating magnetic field by passing current, the commutator 304 is mounted on the shaft 301 and contacts the carbon brushes 201 and 202 to change the direction of current, and the annular varistor 305 is fixed on the commutator 304.

[0025] like Figure 2 As shown, the annular varistor 305 includes a substrate 305a and multiple electrodes 305b, wherein the substrate 305a is an annular varistor ceramic substrate, and the electrodes 305b are fan-shaped electrodes evenly distributed along the circumference and fixedly disposed on the end face of the substrate 305a.

[0026] like Figure 3 As shown, the commutator 304 has a plurality of commutator segments 304a evenly distributed around its circumference, and the commutator segments 304a are fixed by bakelite powder 304b. Compared with the prior art where the height of the bakelite powder is at the same level as or slightly higher than the height of the commutator segments, the overall height of the bakelite powder 304b of the commutator 304 of this invention is lower than the height of the commutator segments 304a, thereby forming a countersunk hole 304c.

[0027] like Figure 4 As shown, a ring-shaped varistor 305 is disposed within a countersunk hole 304c, and the electrode 305b of the ring-shaped varistor 305 is disposed on the end face of the ring-shaped varistor 305 facing away from the bakelite powder 304b. The commutator segments 304a and electrodes 305b are welded one-to-one to form an integrated commutator structure. In a preferred embodiment, the commutator segment 304a is an oxygen-free silver-copper sheet, and the electrode 305b is a copper electrode or a silver electrode. The welding is performed by laser welding, using lead-free solder with a melting point up to 350°C. In a preferred embodiment, the number of commutator segments 304a is consistent with the number of electrodes 305b, for example, 3, 5, 7, or 8, etc.

[0028] Thus, the ring-shaped varistor 305 is connected in parallel between two adjacent commutator segments 304a of the commutator 304. When the carbon brushes 201 and 202 sweep from one commutator segment 304a to the other, a very high overvoltage is generated. At this time, the impedance of the base 305a of the ring-shaped varistor 305 drops sharply, forming a low-impedance circuit. The surge energy is then released through the ring-shaped varistor 305. This effectively suppresses / weakens the commutation sparks generated between the carbon brushes 201 and 202 and the commutator 304 due to rotation by suppressing surge voltage and reducing conducted and radiated emissions. This significantly improves the electromagnetic compatibility (EMC) of the motor and extends the service life of the brushed DC motor.

[0029] Compared to soldering the varistor ring to the commutator hook using soldering, this invention integrates the commutator 304 into the ring-shaped varistor 305 for assembly. This process is simpler, lower in cost, easier to operate, and more efficient. The resulting integrated commutator structure avoids the risks of cracks and debris caused by impacts during the assembly of traditional ring-shaped varistors, which can lead to motor failure and rotation stoppage. Furthermore, in this invention, the ring-shaped varistor 305 is located at the top of the commutator, closer to the interference source and the effective position of the carbon brushes 201 and 202 compared to the prior art where it is soldered to the hook. This improves the conductivity of the carbon brushes to the varistor, resulting in a better EMC suppression effect than soldering it to the commutator hook. Additionally, the ring-shaped varistor 305 is embedded inside the commutator 304, eliminating the need for additional volume along the rotor axis.

[0030] The integrated commutator structure of this invention is widely applicable to brushed DC motors, suitable for 12V, 24V, or 48V motors, and is particularly suitable for meeting the EMC requirements of 48V motors. Compared with traditional solutions, it has a simpler structure, is lighter, has lower manufacturing costs, and is more efficient.

[0031] The above description is merely a preferred embodiment of this utility model and is not intended to limit the scope of this utility model. Various variations can be made to the above embodiments of this utility model. That is, all simple and equivalent changes and modifications made based on the claims and description of this utility model application fall within the protection scope of the claims of this utility model patent. Any aspects of this utility model not described in detail are conventional technical content.

Claims

1. A brushed DC motor, characterized in that, The brushed DC motor includes a commutator and a ring-shaped varistor. The commutator has a countersunk hole and multiple commutator segments evenly distributed around the circumference. The ring-shaped varistor is disposed in the countersunk hole and includes multiple electrodes. The commutator segments and electrodes are welded one-to-one to form an integrated commutator structure.

2. The brushed DC motor according to claim 1, characterized in that, The ring-shaped varistor also includes a substrate, and the electrodes are fan-shaped electrodes that are fixedly disposed on the substrate and evenly distributed along the circumference.

3. The brushed DC motor according to claim 2, characterized in that, The commutator segments are fixed with bakelite powder, the height of which is lower than the height of the commutator segments to form countersunk holes.

4. The brushed DC motor according to claim 3, characterized in that, The electrode is disposed on the end face of the substrate that is away from the bakelite powder.

5. The brushed DC motor according to claim 1, characterized in that, A ring-shaped varistor is connected in parallel between two adjacent commutator segments.

6. The brushed DC motor according to claim 1, characterized in that, The number of commutator segments is consistent with the number of electrodes.

7. The brushed DC motor according to claim 1, characterized in that, The commutator is made of oxygen-free silver-copper sheet.

8. The brushed DC motor according to claim 1, characterized in that, The electrodes are copper or silver electrodes.

9. The brushed DC motor according to claim 1, characterized in that, The brushed DC motor also includes carbon brushes mounted via brush holders, which contact the commutator to change the direction of current.

10. The brushed DC motor according to claim 9, characterized in that, The carbon brush is a porous artificial graphite carbon brush.

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