JPH05146108A - Brush device for motor - Google Patents

Abstract

PURPOSE: To reduce interface resistance between a brush and a commutator by providing an elastic conductive support device in a configuration, for carrying two or more separate brush bodies that are arranged in the direction of the axial line of the electric motor and are connected electrically in parallel. CONSTITUTION: In a device, an edge cap 16 that is formed by plastic form a plastic brush retainer for supporting two sets of brush arms, and each set of brush arms is made of an elastic brush support part, namely a terminal part 17 that is connected to brush support plates 18 and 19. Then, brushes 20 and 21 are arranged in the direction of an axial line for the axial line in the longitudinal direction of the electric motor and are supported by the free edge part of each brush support plate and are pressed, so that they contact a commutator during use. Thus effective interface resistance is reduced and a higher current for the same coil winding resistance is carried, hence obtaining higher stopping/moving toque and current.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to electric motors, and more particularly to electric motor brush devices.

[0002]

Brush devices in small electric motors, especially fractional horsepower permanent magnet direct current (PMDC) electric motors, typically have a conductive conductive arm, ie, a carbon carried on the end of a brush support plate. It has a brush. The brush support plate is adapted to be biased to press the brush onto the commutator of the motor shaft. The brush device is
Typically, it is mounted in an end cap which carries a bearing for the motor shaft and which forms one part of the motor assembly.

[0003]

In low voltage electric motors, the total resistance of the electric motor is increasingly determined by the interfacial resistance between the brush and the commutator. It is highly desirable to reduce the interfacial resistance between the brush and the commutator because the resistance of the motor determines the maximum power range in which the motor can operate.

[0004]

According to the invention, two or more separate formations arranged axially side by side with respect to the longitudinal axis of the electric motor and electrically connected in parallel. There is provided a brush assembly for an electric motor, which is provided with an elastic conductive support device configured to carry the brush body.

The support device usually consists of a separate arm for each brush body. These separate arms can be configured to have different natural resonant frequencies. These brush bodies can be configured in different sizes and / or have different physical densities.

[0006] It is configured to carry two or more separately formed brush bodies that are arranged axially side by side with respect to the longitudinal axis of the electric motor and are electrically connected in parallel. It is possible to provide a fractional horsepower DC electric motor having a brush assembly provided with an elastic conductive support device.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Now, an embodiment of a fractional horsepower DC electric motor of less than one horsepower according to the present invention will be described with reference to the accompanying drawings. Referring to the accompanying drawings, in FIG. 1, a motor is a shaft 1 carrying a wound armature 11 and a commutator 12.
It has 0. The commutator 12 is formed longer in the axial direction than the commutator of a conventional electric motor of similar size. In the casing 13, two field magnets 14 and an end bearing 15 that supports the shaft 10 are mounted.

In FIGS. 2 and 3, an end cap 16 formed of plastic constitutes a plastic brush holder that supports two sets of brush arms.
Each set of brush arms comprises a resilient brush support portion, ie, a terminal portion 17 connected to brush support plates 18 and 19. The brushes 20 and 21 are arranged axially side by side with respect to the longitudinal axis of the electric motor and are supported by the free ends of the respective brush support plates. The brushes 20 and 21 are in use when the commutator 1 is used.
It is pressed so as to come into contact with 2.

In FIGS. 3 and 4, the terminal 17 and the brush support plates 18, 19 are fixed together by respective sets of rivets 22 and 23. Other forms of fixation, for example by means of clips, can also be used. The tops of the brushes 20 and 21 are shaped (see FIG. 6) and are retained by an interference fit in elongated slots located adjacent the free ends of the brush support plates 18 and 19, respectively.

Embodiments of the present invention provide a brush assembly in which two brushes or, if desired, a greater number of brushes are mounted in side-by-side relationship, but electrically in parallel during use. is doing. This is modified except that at the assembly stage of the motor, one brush is installed for each brush assembly, or two brushes are installed in each brush assembly, effectively in parallel. Means that they can have a common design. This maximizes the number of common components for different capacity motors. Two (or more) brushes are used in the embodiment described if a motor is needed for higher power.

In a modified embodiment, the brush support plate 18
And 19 are constructed of different elastic materials or have slightly different dimensions so that the natural frequencies of the brush support plates are different. A slot may be formed in the middle of both ends of one of the brush supporting plates in order to reduce its effective elasticity. This means that whenever the speed of the motor shaft matches the resonant frequency of one of the brush support plates, the brush supported by the other brush support plate maintains good contact with the commutator. It means to give rise to a tendency. Also, the brushes 20 and 21 may alternatively or additionally be formed to the same overall size to fit within elongated slots of the same size formed in the brush support plate, but with different physical dimensions. Composed of a brush material having a uniform density. However, the brushes can be configured in different overall sizes for the same purpose, and their tops are configured to have the same dimensions for an interference fit into a common sized slot in the brush support plate. Is preferred.

[0012]

Embodiments of the present invention, as described above, can reduce the effective interfacial resistance and can carry higher currents for the same winding resistance, which results in higher interruptions. Dynamic torque and current are obtained. Since there are two or more brushes, there is no need to increase the current density for each brush to do this. Higher current densities increase brush wear and, consequently, reduce brush life. In addition, the dynamic behavior of each brush is different, and this behavior is different as described above so that good brush contact is maintained over a range of velocities without simply increasing brush contact resistance. be able to. Increasing the contact resistance of the brushes reduces the useful life of each brush. The inherent degradation of dynamic behavior associated with increasing brush size is also avoided. Dynamic performance is important because the commutator is always somewhat imperfect in its roundness and rotates at very high speeds during use.

[Brief description of drawings]

FIG. 1 is a partially cutaway isometric view of an electric motor with an end cap removed.

FIG. 2 is an end view of the inside of the end cap showing the brush assembly.

3 is a side view showing the cross section of FIG. 2. FIG.

FIG. 4 is a top view of the brush assembly.

FIG. 5 is a side view of the brush assembly.

FIG. 6 is a different view showing a portion of the brush support plate and the brush of FIG.

[Explanation of symbols]

 10 shaft 11 armature 12 commutator 13 casing 14 field magnet 15 end bearing 16 end cap 17 terminal part 18 brush support plate 19 brush support plate 20 brush 21 brush 22 rivet 23 rivet

Claims (7)

[Claims] 1. An electric motor arranged in parallel with each other in the axial direction with respect to the longitudinal axis of the electric motor and electrically connected in parallel.
A brush assembly for an electric motor comprising an elastic conductive support device configured to carry one or more separately formed brush bodies. 2. The brush assembly of claim 1, wherein the support device comprises a separate arm for each brush body. 3. A brush assembly according to claim 1, wherein the separate arms are configured to have different natural resonance frequencies. 4. A brush assembly according to claim 1, wherein the brush bodies are of different sizes. 5. A fractional horsepower DC electric motor comprising a commutator and brush assembly according to any one of claims 1 to 4. 6. A brush assembly substantially as described with respect to any one or more of Figures 1-6. 7. A DC motor substantially as described with respect to any one or more of the drawings in FIGS.