JPH0246228Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a brush holding device for a small commutator machine in which the upper surface shape of the brush pressed by a coil spring is improved.

[Technical background of the invention and its problems]

In general, a brush holding device for a small commutator machine has a prismatic brush 3 inserted through a coil spring 2 into a prismatic cylindrical brush holder 1 with an open end, as shown in Fig. 3. , a commutator 4 that rotates the tip of the brush 3 by the elastic force of the coil spring 2.
It is designed to come into pressure contact with the

As the brush 3 gradually wears out during operation and its length becomes shorter, the coil spring 2
The brush is gradually pushed out toward the tip side and slides inside the brush holder 1. Therefore, there is a gap G between the brush 3 and the inner wall surface of the brush holder 1.
However, if this gap G is narrow, it will become clogged with dust and metal powder and will prevent the brush 3 from sliding, so a certain amount of space is required.

However, as mentioned above, since the gap G is large, there is a problem in that a stick slip phenomenon occurs in which the brush 3 rotates from side to side within the brush holder 1, causing abnormal noise. To improve this point,
Conventionally, a brush holding device has been developed as shown in FIG. This is achieved by attaching a spring plate 5 to one side wall of the brush holder 1, which abuts near the tip of the side surface of the brush 3, and pressing the other side of the brush 3 in the direction of rotation of the commutator 4. By placing the brush 3 in close contact with the wall surface, the stick slip phenomenon caused by rotation of the brush 3 is prevented from occurring.

However, if the spring pressure of the spring plate 5 is large,
Although the brush 3 is in close contact with the inner wall surface of the brush holder 1 and does not rotate, the frictional force μsQ due to the friction coefficient μs increases during this time, making it difficult for the brush 3 to slide downward. For this reason, there is a problem that the contact between the brush 3 and the commutator 4 becomes poor, resulting in poor commutation.

Conversely, if the spring pressure Q of the spring plate 5 is small, the brush 3 rotates within the brush holder 1 as shown in FIG. 5, and the friction coefficient μ between the brush 3 and the commutator 4 changes. As a result, a stick slip phenomenon occurs, producing abnormal noise, and the effect of installing the spring plate 5 cannot be obtained.

For this reason, in conventional devices, it is necessary to consider the balance between the two and set the upper and lower limits so that the spring pressure Q of the spring plate 5 falls within a predetermined range, for example, 20 to 30 g. It was hot.

However, it is extremely difficult in terms of processing and production technology to obtain a spring plate 5 in which the upper and lower limits of the spring pressure Q are set within a predetermined range, and a countermeasure has been desired.

[Purpose of invention]

This invention was made in view of these points,
The extremely simple structure lowers the upper limit of the spring pressure Q of the spring plate, virtually eliminates the lower limit, making processing and assembly easier, and securely holding the brush, which eliminates abnormal noise due to stick slip phenomenon. The present invention provides a brush holding device for a small commutator machine that prevents this.

[Summary of the idea]

The present invention is a small commutator in which a prismatic brush is inserted through a coil spring into a prismatic cylindrical brush holder with an open tip, and the tip of the brush is pressed into contact with a rotating commutator. In the brush holder of the machine, on one side wall of the brush holder,
A spring plate is attached to one side of the tip of the brush that protrudes from the open end of the brush holder toward the commutator side and presses in the direction of rotation of the commutator, and the upper surface of the brush is rotated from the spring plate side. The angle β between the side surface of the brush on the spring plate side and the slope is 90°<β≦180°−γ, where γ=cot ^-1 μ, μ is the angle between the brush and the commutator. This is characterized by the coefficient of friction.

[Example of idea]

An embodiment of the present invention will be described in detail below with reference to FIGS. 1 and 2.

A prismatic brush 3 is inserted through a coil spring 2 into a square cylindrical brush holder 1 whose tip end is open, and its tip is pressed by the coil spring 2 and comes into pressure contact with a rotating commutator 4. It's becoming like that.

A spring plate 5 having a curved tip is attached to one side wall of the brush holder 1, and the curved tip of the spring plate 5 abuts the tip side of the side surface of the brush 3.
The brush 3 is pressed in the direction of rotation of the commutator 4 to bring the other side of the brush 3 into close contact with the inner wall of the brush holder 1.

Further, the upper surface of the brush 3 is an inclined surface 6 that rises in the direction of rotation from the spring plate 5 side, and the lower end of the coil spring 2 comes into contact with this inclined surface 6.

The angle β between the inclined surface 6 of the brush 3 and the side surface of the brush on the spring plate 5 side is 90°<β≦180°−γ (where γ=cot ⁻¹ μ, μ is the angle between the brush 3 and the commutator 4). ).

Next, the operation of the brush holding device will be explained. Spring pressure of spring plate 5 is Q, coil spring 2
The pressing force of P is P, and the horizontal component of the pressing force P is P ₁ ,
Assuming that the vertical component force is P ₂ and γ=180°−β, the relationship between the forces is shown in FIG.

Therefore, the ratio between the vertical component force P2 and the horizontal component force _P1 of the pressing force P of the coil spring ₂ acting on point A is expressed by the following equation.

P ₁ /P ₂ = cotγ (1) Further, the frictional force at point C is expressed as μP ₂ as the product of the vertical component force P ₂ of the pressurized portion P and the friction coefficient μ.

Further, the spring pressure Q of the spring plate 5 at point B is applied in the horizontal direction.

Therefore, in order to prevent the brush 3 from rotating, A
Horizontal component force P ₁ at point and spring pressure Q at point B
The sum of the horizontal components of and must be equal to or larger than the frictional force μP ₂ , which is expressed by the following relationship.

P ₁ +Q≧μP ₂ …(2) Here, if the spring pressure Q is extremely small, the condition for balance is shown by the relationship P ₁ = μP ₂ …(3), and the above equations (1) and (3) It is shown by the relationship cotγ=μ γ=cot ^-1 μ (4). Also, since the friction coefficient μ is μ>0, γ<90°, and as a result, the angle β is in the range of 90°<β≦180°−γ (5), and the friction coefficient μ is about 0.35 at most. Therefore, β generally falls within the range of 90° or more to approximately 110°.

In other words, the previous equation shows the relational expression when the spring plate 5 is not in contact and the spring pressure Q is 0, but in reality it is the resultant force of the horizontal component P ₁ +Q with the spring pressure Q>0 added. Become. Therefore, even if the spring pressure Q has a small value, it is possible to satisfy the above equation and prevent the brush 3 from rotating, and by reducing this component force _P1 , the angle β
is also small, and the inclination of the inclined surface 6 can be made gentle.

Further, the rotation of the brush 3 is actually determined by the balance of rotational moments about the point D rather than the relationship between vectors of horizontal components. Pressure points A and B are far apart above and below the brush 3, and the distance AD is the distance BD.
Since it is larger, the moment due to the pressing force P of the coil spring 2 applied to the point A occupies a large weight, and the spring pressure Q can actually be made even smaller than the balance relationship based on the horizontal component.

As a result, in the conventional model shown in Fig. 4, the spring pressure Q was set in the range of 20 to 30 g, but in the present invention, the spring pressure is sufficient to be greater than 0 g and less than 20 g, and the upper limit is set. In addition to being able to lower the spring pressure, it is also possible to set the spring pressure to a value that has virtually no lower limit.

[Effect of idea]

As explained above, according to the present invention, the upper limit of the spring pressure Q of the spring plate is lowered, and the lower limit is effectively It is possible to obtain a brush holding device for a small commutator machine that eliminates the value, facilitates processing and assembly, securely holds the brushes tightly in the brush holder, and prevents the generation of abnormal noise due to the stick slip phenomenon. It is.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional view of a brush holding device according to an embodiment of the present invention, Fig. 2 is an explanatory diagram showing the relationship of forces applied to the brush in Fig. 1, and Fig. 3 is a longitudinal cross-sectional view of a conventional brush holding device. The plan view, FIGS. 4 and 5 are longitudinal cross-sectional views showing a conventional brush holding device equipped with a leaf spring. DESCRIPTION OF SYMBOLS 1... Brush holder, 2... Coil spring, 3... Brush, 4... Commutator, 5... Spring plate, 6... Inclined surface.

Claims (1)

[Scope of claim for utility model registration] Inside the rectangular cylindrical brush holder with an open tip,
In a brush holding device for a small commutator machine in which a prismatic brush is inserted through a coil spring and the tip of the brush is pressed against a rotating commutator, the brush is attached to one side wall of the brush holder. A spring plate is attached that contacts one side of the brush tip side that protrudes from the open end of the retainer toward the commutator side and presses the commutator in the rotating direction, and the upper surface of the brush is oriented in the rotating direction from the spring plate side. The angle β between the brush side surface on the spring plate side and the slope surface is 90°<β≦180°−γ, where γ=cot ^-1 μ, μ is the coefficient of friction between the brush and commutator. A brush holding device for a small commutator machine.