JPH0515146B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a disc-shaped eddy current brake device used in railway vehicles and the like.

(Prior art) A disc-type eddy current brake device for vehicles is
Generally, as shown in FIGS. 1 and 2, the axle 1
A brake disc 2 made of a magnetic material is fixed by press-fitting its boss portion 3 onto the axle 1, and a plurality of excitation coils 4 are installed on both sides of the outer circumference of the brake disc 2, respectively.
The excitation coil 4 is arranged in the circumferential direction of the brake disc so as to be close to and opposite to the two surfaces of the brake disc.
The magnetic pole core 5 is fixed to a fixed frame 6, and is supported by a bogie frame 7 via the fixed frame 6.

This eddy current brake device excites the excitation coil 4 to generate eddy current in the rotating brake disc 2, and the action of the eddy current generated in the brake disc 2 causes the brake disc 2 to move in its rotational direction ( This device applies braking force to the axle 1 by generating a brake torque in the opposite direction to the direction of rotation of the axle 1. In the conventional eddy current brake device, the excitation coil 4 facing the brake disc 2 is The polarity of the magnetic pole surface facing the disk 2 is different (one excitation coil 4
The magnetic pole surface facing the braking disk 2 of the other excitation coil 4 becomes the north pole, and the magnetic pole surface facing the braking disk 2 of the other excitation coil 4 becomes the south pole.

(Problem to be Solved by the Invention) However, in the eddy current braking device of the different polarity opposing type in which the polarities of the opposing magnetic pole surfaces of the excitation coils 4 facing each other with the braking disk 2 in between are set to different polarities, Local heating of the brake disc 2 occurs, which shortens the life of the brake disc 2, and there is also the problem that the braking force is reduced when the vehicle is running at low speeds. .

In other words, the brake disk 2 generates heat due to the generation of eddy current, but in the conventional eddy current brake device of the different polarity opposing method, the magnetic flux concentrates on the outer circumference of the brake disk 2, so the brake disk As shown in Fig. 3, the heat generation temperature distribution due to the eddy current in the plate 2 has a very high temperature peak near the outer periphery of the brake disc 2, and large thermal stress is generated in this locally heated area. Thermal deterioration of the brake disc 2 is severe, causing damage such as cracks on the surface and shortening its life. In addition, the excitation coil 4 of the eddy current brake device is normally excited with a constant excitation current, but in the conventional eddy current brake device, the vehicle speed (rotational speed of the brake disc 2) when the excitation current is constant is ), as shown in Figure 4, the braking force decreases extremely as the vehicle speed decreases, making it impossible to obtain sufficient braking force. It has become necessary to increase the size of the device or to use other brake devices such as an air brake device.

The present invention was made in view of the above-mentioned circumstances, and its purpose is to prolong the life of the brake disc by equalizing the heat generation temperature distribution of the brake disc. At the same time,
To provide an eddy current brake device capable of obtaining sufficient braking force even in a low speed range.

[Structure of the invention]

(Means for Solving the Problems) The eddy current brake device of the present invention has excitation coils placed on both sides of the outer periphery of a brake disc fixed to an axle in close opposition to the brake disc surface in the circumferential direction of the brake disc. In an eddy current braking device, a plurality of excitation coils are arranged in the eddy current brake system, and the excitation coil is excited to generate an eddy current in the brake disk to apply a braking force to the axle. The feature is that the polarity of the magnetic pole face facing the plate is the same.

(Function) That is, the present invention reduces the magnetic flux to the outer circumferential portion of the braking disc by making the polarity of the magnetic pole surface facing the braking disc of the excitation coil the same as that of the excitation coil that faces the braking disc with the braking disc in between. By avoiding concentration, the heat generation temperature distribution of the brake disc is made uniform, and the braking force is prevented from decreasing in the low speed range.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

As shown in FIG. 5, this eddy current brake device has an excitation coil 4 facing across a brake disk 2 so that the polarity of the magnetic pole surface facing the brake disk 2 is the same. . That is, for example, the one shown in FIG. 5 is excited so that the N poles are opposed to each other. The eddy current brake device of this embodiment has the same structure as the conventional eddy current brake device shown in FIGS. 1 and 2 except for the polarity of the excitation coil 4, so the explanation thereof will be omitted. are omitted with the same reference numerals in the drawings.

Next, the operation of the eddy current brake device of the above embodiment will be explained. Figure 6 is a circumferential development diagram showing the magnetic flux distribution of a conventional eddy current brake device;
6 is a front view of FIG. 6, FIG. 8 is a developed view in the circumferential direction showing the magnetic flux distribution of the eddy current brake device of the above embodiment, and FIG. 9 is a front view of FIG. 8.

First, the reason for making the heat generation temperature distribution of the brake disc 2 uniform will be explained. In the conventional eddy current brake device, the opposing magnetic pole surfaces of the excitation coil 4 facing each other with the brake disc 2 in between are oppositely polarized with different polarities, as shown in FIGS. 6 and 7. The magnetic flux that penetrates the brake disc 2 without contributing almost to the braking force (magnetic flux indicated by the broken line in the figure)
exists regardless of speed.

This penetrating magnetic flux is generated only on the outer periphery of the brake disk due to the skin effect, and the reason for this will be explained below. When looking at the magnetic flux from one point on the brake disk, since different magnetic poles are lined up, an apparent alternating current magnetic flux is observed even when DC excitation is applied. In such cases, the magnetic flux is generally concentrated on the surface due to the skin effect derived from Maxwell's equation,
It is known that magnetic flux decreases exponentially as it progresses in the thickness direction. When the magnetic poles are opposite to each other, the outer periphery of the brake disk can also become a surface, and a part of the magnetic flux reaches the opposing magnetic poles through this portion. However, the magnetic flux cannot pass through the parts other than the outer periphery of the brake disc, and therefore flows to adjacent magnetic poles. Therefore, as described above, the vicinity of the outer circumference of the brake disc 2 is locally heated. On the other hand, in the eddy current brake device of the above embodiment, the excitation coils 4 facing each other with the brake disc 2 in between are
Since the polarities of the opposing magnetic pole faces are the same, the eighth
As shown in the figure and FIG. 9, there is no magnetic flux passing through the brake disc 2, and all the magnetic flux will enter the adjacent magnetic poles. Therefore, the vicinity of the outer periphery of the brake disc 2 is not locally heated.

In this way, in the eddy current brake device of the above embodiment, the polarity of the magnetic pole surface facing the braking disc 2 of the excitation coil 4 facing the braking disc 2 is the same, so that the above-mentioned reason can be solved. This prevents the concentration of magnetic flux on the outer circumferential portion of the brake disc 2, and the magnetic flux flows from the entire magnetic pole to the adjacent magnetic pole on average. Therefore, the heat generation temperature distribution of the brake disc 2 during braking is shown by the solid line in Figure 10. As shown in the figure, the temperature distribution is more uniform with no high-temperature peaks than the heat generation temperature distribution of the brake disk in the conventional eddy current brake device shown by the broken line in the figure. Therefore, according to this eddy current brake device, local heating of the brake disc 2 can be eliminated, thermal deterioration of the brake disc 2 can be suppressed, and the life of the brake disc 2 can be maintained for a long time.

Next, the reason why sufficient braking force can be obtained even in the low speed range will be explained.

In a conventional eddy current brake device, since the magnetic poles are opposite to each other, the magnetic flux exiting the magnetic poles passes through the circumferential direction of the brake disc 2 and enters the adjacent magnetic pole, as shown in FIGS. 6 and 7. (Magnetic flux shown as a solid line in the figure)
Then, the magnetic flux is divided into magnetic fluxes (magnetic flux shown by broken lines in the figure) that penetrate the outer circumference of the brake disk 2 and enter the opposing magnetic poles.
However, the eddy current brake device of the above embodiment,
Since the magnetic poles are opposite to each other, all the magnetic flux leaving the magnetic pole passes through the circumferential direction of the brake disc 2 and enters the adjacent magnetic pole, as shown in FIGS. 8 and 9.

In a low speed range (that is, when the rotational frequency of the brake disc is low), as is clear from Maxwell's equation, the penetration depth of the magnetic flux becomes deeper, so magnetic saturation does not occur and the magnetic resistance decreases. Therefore, most of the excitation ampere turns obtained by excitation of the magnetic poles will be consumed in the air gap where the magnetic resistance is highest. From this, "excitation ampere turn≒air gap ampere turn" is established.

When the excitation current of this eddy current brake device is kept constant, the braking force characteristics with respect to the vehicle speed (rotational speed of the brake disc 2) are as follows: When the thickness of the brake disc is set to a predetermined condition, the magnetic pole arrangement By arranging the same poles to face each other, the braking force increases in the low speed range, but as the speed increases, the depth of penetration of the magnetic flux into the brake disc becomes shallower, making it easier for magnetic saturation to occur. Experiments have confirmed that as the resistance increases, it decreases by that amount.

Figure 11 is for comparing the braking force characteristics of different-pole opposing and same-pole opposing.Special forged steel with a plate thickness of 36 mm is used as the braking disc, and the number of poles of the eddy current brake device is set to 4 on one side. This is a table created using actual measured data of speed braking force characteristics when the excitation current is 100A for the NSNS arrangement.The solid line shows the same-polarity opposing arrangement, and the broken line shows the different-polarity opposing arrangement. In the figure, the braking force characteristic indicated by the solid line indicating the same-pole opposing arrangement has a very small decrease in braking force in the low-speed range where a large braking force is required, compared to the brake force characteristic indicated by the broken line indicating the opposite-pole opposing arrangement. The vehicle was able to brake stably with sufficient braking force from high speed to low speed ranges.

Here, the thickness of the braking disk should be such that when the magnetic poles are opposite to each other, the magnetic flux does not penetrate at least in the medium and low speed region,
Specifically, for example, the minimum train speed that requires a predetermined (somewhat large) braking torque is set at approximately 20km/h (first
The required plate thickness will vary depending on the conditions of the train, but it will be approximately 20 mm if the rotation speed shown in Figure 1 is approximately 150 rpm, so any plate thickness greater than this is sufficient.

As explained above, according to the above-described embodiment of the present invention, the thickness of the braking disk is set to such a thickness that magnetic flux does not penetrate at least in the medium and low speed range when the magnetic poles are opposite to each other. By eliminating local heating of the brake disc and averaging the heat generation temperature distribution, the life of the brake disc can be maintained for a long time, and the reduction in braking force at low speeds can be suppressed to obtain sufficient braking force. This makes it possible to perform stable vehicle braking.

〔Effect of the invention〕

According to the present invention, the heat generation temperature distribution of the brake disc can be averaged to extend the life of the brake disc, and sufficient braking force can be obtained even in a low speed range.

[Brief explanation of the drawing]

Fig. 1 is a side view of a conventional eddy current brake device, Fig. 2 is a sectional view taken along the - line in Fig. 1, and Figs. 3 and 4 are heat generation temperatures of the brake disc in a conventional eddy current brake device. Distribution diagram and brake force characteristic diagram; FIG. 5 is a vertical cross-sectional view of an eddy current brake device showing an embodiment of the present invention; FIG. 6 is a circumferential developed view showing the magnetic flux distribution of a conventional eddy current brake device; 7 is a front view of FIG. 6, FIG. 8 is a circumferential developed view showing the magnetic flux distribution of the eddy current brake device of the present invention, FIG. 9 is a front view of FIG. 8, and FIGS. 10 and 11 are FIG. 3 is a heat generation temperature distribution diagram and a brake force characteristic diagram of a brake disc in the eddy current brake device of the present invention. 1... Axle, 2... Braking disk, 4... Excitation coil, 5... Magnetic pole iron core.

Claims (1)

[Claims] 1. The brake disc fixed to the axle has a thickness such that when the excitation coils are oppositely polarized, the magnetic flux is concentrated on the outer circumference at least in the medium and low speed range,
A plurality of excitation coils are arranged on both sides of the brake disc in the circumferential direction of the brake disc so as to closely face the brake disc surface,
In the eddy current brake device that excites the excitation coil to generate eddy current in the brake disk to apply a braking force to the axle, a magnetic pole surface facing the brake disk of the excitation coil that faces across the brake disk. An eddy current brake device characterized by having the same polarity.