JPS585514B2 - Brush brush - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a retaining device for a slip ring or a commutator and a brush attached to a high speed rotating shaft.

Conventionally, brush holding devices used in generators or electric motors are slip rings or commutators (hereinafter, slip rings and commutators are collectively referred to as slip rings), in which brushes are attached to a rotating shaft by a single spring. is being pressed.

Due to machining accuracy, assembly accuracy, rotational vibration of the shaft, etc., the rotation of the shaft causes periodic fluctuations, that is, vibrations, in the slip ring in the radial direction.

The vibration is a vibration with a frequency whose fundamental wave is the rotation speed of the shaft, and when the rotation speed of the generator or motor is low, the frequency of the vibration in the radial direction of the slip ring is low, but at high speeds. In a generator or electric motor, the rotational speed of the shaft is high, so the frequency of vibration of the slip ring in the radial direction is also high.

In order to minimize brush wear and maintain good electrical conductivity between the brush and slip ring, it is most important to minimize the generation of sparks caused by the brush attaching to or separating from the slip ring. In addition, in order to reduce wear due to friction between the brush and the slip ring, it is also necessary not to make the pressing force of the brush too large.

In order to prevent the brush from separating from the slip ring, the brush should completely follow the radial vibration of the slip ring. The pressing force of the brush must be greater than the force that the brush receives from the slip ring due to the radial vibration of the slip ring.

When the rotational speed of the generator or electric motor is low, the frequency of the radial vibration of the slip ring is low, so even if the brush is pressed against the slip ring with a single spring, a spring with a relatively small spring constant may be used. Use,
It is also possible to make the natural frequency of the system composed of the brush and the spring larger than the frequency of the radial vibration of the slip ring, so that the pressing force of the brush does not become too strong.

However, in high-speed rotating generators or electric motors, the frequency of radial vibration of the slip ring is high, so instead of using the conventional device that presses the brush against the slip ring with a single spring, the brush and spring are In order to increase the natural frequency of the constructed system, the spring constant of the spring is made very large.In order to assemble the brush to an appropriate strength so that the pressing force of the brush does not become too strong, it is necessary to increase the length of the spring a little. Since the pressing force changes greatly due to changes in the brush, it is necessary to manage an extremely small length, and assembly is extremely difficult.Also, even a small amount of wear on the brush drastically reduces the pressing force, and the pressing force is larger than the brush. becomes smaller than the force received from the slip ring, causing the brush to stick to and separate from the slip ring, generating sparks and rapidly increasing wear on the brush, and also significantly reducing conductive performance. Therefore, the pressing force of the brush must be readjusted or the brush must be replaced frequently.

As a result, the spring constant of the spring for brush suppression cannot be made too large, and the natural frequency of the brush holding system is set below the frequency of the shaft rotation, so that the brush follows the radial vibration of the slip ring. Sparks are generated from the contact area between the slip ring and the brush, which causes rapid wear on the brush, and not only increases the contact resistance between the slip ring and the brush, but also causes this contact resistance to become pulsating. This has the drawback of significantly reducing conductive performance.

An object of the present invention is to provide a brush holding device for high-speed rotation that can make the brush follow the vibration of a slip ring without particularly increasing the pressing force on the brush even when the shaft rotates at high speed. The purpose is to eliminate shortcomings.

Hereinafter, the configuration of an embodiment of the present invention will be explained with reference to the drawings.

A frame body 2 made of an insulating material such as synthetic resin is attached to the end face of a generator 1 that is directly connected to a high-speed rotating engine such as a gas turbine engine. A cylindrical holder 4 is mounted at equal radial intervals through a friction material 5 made of rubber or synthetic resin, and is pressed by screws 6, and inside the holder 4, a shaft 3 of the generator 1 is mounted. A brush 8 that contacts the slip lint tough and a weight 11 that contacts the inner surface of the holder 4 via an O ring 10 fitted in a groove 9 are attached to be movable in the radial direction with respect to the shaft 3. A spring 12 with a large spring constant that makes the natural frequency of the system made up of the brush 8 and the spring 12 larger than the frequency of the rotational speed of the shaft 3 is inserted between the weight 11 and the rear end of the holder 4. A spring 14 with a small spring constant and a large displacement is inserted between the lid body 13 and the lid body 13 which are screwed together. Holder 4 with the center of the
It is attached to the terminal 16 on the rear surface.

In the brush holding device for high-speed rotation configured as described above, the pressing force of the brush 8 by the spring 14 is adjusted by changing the screwing amount of the lid 13.

Next, when a high-speed rotating engine such as a gas turbine engine is driven in this state, the shaft 3 of the generator 1 rotates at high speed, and the slip lint is caused by machining accuracy, assembly accuracy, vibration of the shaft, etc.
It vibrates at a frequency with the fundamental wave being the frequency of the rotational speed,
The mass of the weight 11 is set to be sufficiently larger than the mass of the brush 8, and a vibration damping effect is provided between the weight 11 and the holder 4 via an O-ring 10, so that the vibration of the brush 8 and spring 12 is damped. In contrast, the weight 11 can be treated as fixed, and the natural frequency of the system composed of the brush 8 and the spring 12 is greater than the frequency of the rotational speed of the shaft 3. can follow the vibrations of

As a result, the brush 8 does not separate from the slip lint tuff, and sparks are not generated between the brush 8 and the slip lint tuff as in the conventional case.

The lead wire 15' of the plan 8' can be attached to the terminal 16' by penetrating the side surface of the tip of the holder 4' as shown in FIG. The O-ring 10 can be made of any material that has a vibration damping effect.

Next, in order to further clarify the features of the present invention, the O-ring 10
We will discuss the effects of

When the brush holding device of the present invention is considered as a vibration system, it becomes as shown in FIG. 4. In FIG. 4, the brush 8 of the present invention corresponds to a small mass m, the weight 11 corresponds to a large mass M, and the spring 12 is a spring. The spring 14 corresponds to the spring k.

Also, an O-ring 10 provided between the weight 11 and the holder 4
corresponds to a dashpot C having a vibration damping effect between the weight 11 and the holder 4.

That is, since the O-ring 10 is provided, a vibration damping effect occurs between the weight 10 and the holder 4, and the dashpot C is added to the vibration model of FIG. 4.

Next, the effects of this dashpot C will be described.

The rotation of the shaft 3 causes the slip ring 7 to vibrate in the radial direction, but since the natural frequency of the system composed of the brush 8 and the spring 12 is made larger than the frequency of the rotation speed of the shaft 3, the brush 8 follows the vibration of the slip ring 7 in the radial direction.

Therefore, a periodic force due to the vibration of the slip ring 7 acts on the weight 11 through the spring 12.

Now, if the angular velocity of rotation of the shaft 3 is ω (omega), the force acting on the weight 11 through the brush 8 and the spring 12 becomes a periodic force expressed by Fcosωt.

However, F is a constant and t represents time.

That is, as shown in FIG. 5, the external force F cos ωt acts on the vibration system consisting of a spring mass M1 and one doss pot C.

Now, the natural frequency of the system consisting of mass M1, spring k, and dashpot C is ω.

Then, the displacement χ of the mass M depends on the magnitude of the damping effect of the dashpot C, as shown in FIG.

Therefore, if there is no dashpot C, there will be resonance at ω = ωn, and the displacement χ of the mass M will become extremely large, and as ω/ωn increases beyond 1, χ will become smaller, but if there is a dashpot C, ω = χ at ωn becomes smaller, and ω
When /ωn becomes large, χ becomes slightly smaller than when C=0.

This tendency increases as the value of C increases.

The effects shown in FIG. 6 above are specifically illustrated as follows.

(1) Since the natural frequency (=ωn) of the system constituted by the weight 11 and the spring 14 is small, the specific envelope /ωn of the rotation of the shaft 3 and the angular velocity ω is sufficiently larger than 1 during steady operation.

Therefore, when the slip ring 7 vibrates in the radial direction due to the rotation of the shaft 3, the movement of the weight 11 due to the vibration of the slip ring 7 is damped by providing an O-ring 10 between the weight 11 and the holder 4. It is smaller if

In other words, strictly speaking, the weight 11 cannot be treated as fixed for the system composed of the brush 8 and the spring 12, but by providing a damping effect between the weight 11 and the holder 4, the damping effect can be improved. Since the movement of the weight 11 can be made smaller than in the case where there is no such thing, the ability of the system made up of the brush 8 and the spring 12 to follow vibrations of the slip ring 7 is improved.

(2) Consider the case where the gas turbine engine directly connected to the generator 1 is decelerated from steady operation.

In this case, due to the influence of the moment of inertia of the rotating body, the rotation does not decrease rapidly but gradually.

However, when the brush 8 is energized, a braking action is applied to the rotating body, and the rotation can be rapidly reduced.

In this case, the ratio of the angular velocity ω of the rotation of the shaft 3 to the natural frequency ωn of the system composed of the weight 11 and the spring 14 is ω/
ωn becomes smaller as the rotational speed of the shaft 3 decreases.

At this time, if there is no damping effect between the weight 11 and the holder 4, the displacement of the weight 11 will increase rapidly as the rotation of the shaft 3 decreases, as shown in FIG. Since the vibration is not in the same phase as the vibration of the slip ring 7, no matter how much you increase the natural frequency of the system composed of the brush 8 and the spring 12, the weight 11 will move greatly, so the brush 8 will follow the vibration of the slip ring 7. Can not.

However, the O-ring 10 is inserted between the weight 11 and the holder 4.
By providing a damping effect, the displacement of the weight 11 can be reduced as shown in FIG. Also, the brush 8 can be made to follow the vibration of the slip ring 7.

As described above, the present invention allows the brush 8 to follow the vibration of the slip ring 7 using a system composed of the spring 12 having a large spring constant and the brush 8, and prevents the generation of sparks between the brush 8 and the slip ring 1. This has the effect of significantly reducing the wear of the brush 8 and significantly improving the conductive performance.Furthermore, since the weight 11 is pressed by the spring 14 with a small spring constant and a large amount of deflection, the wear of the brush 8 is significantly reduced. This has the effect of almost eliminating changes in the pressing force due to
By interposing, for example, an O-ring 10 having a vibration damping effect between the slip ring 7 and the slip ring 7, the ability of the brush 8 to follow the vibrations of the slip ring 7 can be further improved.

[Brief explanation of the drawing]

Fig. 1 is a cutaway side view of one embodiment of the present invention, Fig. 2 is a cutaway front view thereof, Fig. 3 is a cutaway front view of another aspect of the present embodiment corresponding to Fig. 2, and Figs. The figure is an explanatory diagram showing the vibration system of this embodiment, and FIG. 6 is a characteristic diagram showing the vibration characteristics of this embodiment. 3...Shaft, 4,4'...Holder, 7.
...Slip ring, 8,8'...Brush, 10...C ring, 11.11'...
・・Weight, 12, 12′・・・・Spring,
14... Spring.

Claims (1)

[Claims] 1. In a brush that is attached to a holder so as to maintain contact with a slip ring or a commutator attached to a rotating shaft and to be movable in the suppression direction, a spring with a large spring constant is attached to the rear surface of the brush. A weight is provided to be movable in a direction in which the brush is suppressed, and a spring with a small spring constant for pressing the brush is provided between the weight and the holder, and a spring with a small spring constant is provided between the weight and the holder. The feature is that an O-ring is interposed as an elastic body to damp vibrations at the time of resonance when the natural frequency of the vibration system composed of a spring with a small spring constant and the rotation speed of the rotating shaft match or approach. Brush holding device for high-speed rotation.