JPH0125310B2 - - Google Patents

Abstract

PURPOSE:To obtain a constant torque without electrically complicately controlling by using an iron steel material which contains carbon and silicon contents to the prescribed value or lower as a material of an outer rotor. CONSTITUTION:An eddy current brake has an outer rotor 1, an inner rotor 2, a plurality of exciting coils 4 provided in an inner stator 3, and a current source 5 for energizing the coils 4. The outer rotor is composed of an iron steel material which contains 0.12% of carbon content and 0.35% or less of silicon content. The outer rotor is formed in a concentrical structure of two types of iron steel materials, the inner peripheral rotor material is selected to that which contains the above contents from structural carbon steel tube, and is inserted to the outer peripheral rotor formed of a cast iron material.

Description

[Detailed description of the invention]

The present invention relates to an eddy current brake, and more particularly to an eddy current brake used in a load means such as an ergometer. One of the ergometers available on the market is the Monarch ergometer. This device consists of a flywheel that is rotationally driven by the bending and stretching movements of the legs, and a belt that applies a load to the flywheel using frictional force.
The amount of load is adjusted by a weight attached to the tip of the belt. If the flywheel rotates at a constant speed, this device can directly measure the amount of load using the applied weight, so accurate data can be obtained when measuring physical strength, but it is time consuming, the device is large, and adjustment is complicated. be. Also, ergometers equipped with electrical load means have recently been offered on the market. One of these is equipped with a flywheel manufactured from gray cast iron, a rotation sensor for detecting the number of revolutions of the flywheel, and a strain gauge for detecting torque.The output of the strain gauge and the rotation of the flywheel are There is a device that obtains a constant torque by controlling the current supplied to an electromagnetic brake device based on the correlation with several outputs. In addition, as another configuration, the above-mentioned relationship among the flywheel rotational speed, torque, and control current value is calculated and determined in advance by a computer, etc., and stored in a storage device, and the flywheel is There is a device that obtains a constant torque by determining the current to be passed through the braking coil based on the rotational speed of the brake and the target braking force. Of these two devices, since the former is equipped with a mechanical torque detection means, it is complicated to make adjustments before starting use or as the device changes over time. Furthermore, the latter requires complicated calculations to be performed in advance, and requires a separate storage device to store the results of these calculations as data. These devices attempt to obtain a constant torque by electrically controlling the load means in a complex manner. Also, since both have an inner rotor and outer stator structure,
There is a drawback that the outer stator, in which the excitation coil is arranged, is large and the inner rotor becomes hot. Therefore, the present invention has been made in view of the above-mentioned drawbacks, and focuses on the mechanical structure rather than the electrical structure of the load means, and provides an eddy current brake that can obtain a substantially constant torque with that structure itself. With the goal. An eddy current brake consisting of an outer rotor, an inner stator, a plurality of excitation coils provided in the inner stator, and a current source for energizing the excitation coils, wherein the outer rotor has an outer rotor and an inner stator. It has a concentric structure consisting of rotors, and the inner rotor has a carbon content of 0.12.
This can be achieved by using structural carbon steel pipes (STK or STKM) with a silicon content of 0.35% or less and a silicon content of 0.35% or less. Then, the rotor material for the inner peripheral part of the outer rotor is selected from steel pipes known as structural carbon steel pipes (STK or STKM) with a carbon content of 0.12% or less and a silicon content of 0.35% or less, and this is made of gray cast iron or the like. It is suitable to insert it into an outer peripheral rotor made of cast iron material. With the above configuration, it is possible to obtain an eddy current brake that provides constant torque without any complicated electrical control. In addition, the configuration of the present invention can significantly reduce the current value at the same load value compared to the conventional eddy current brake made of gray cast iron, so the brake device (flywheel member) generates less heat and particularly improves heat dissipation. There is no need to consider it. Furthermore, a non-ferrous material such as concrete may be used as the outer peripheral member of the outer rotor for the purpose of simply imparting a flywheel effect to the inner peripheral rotor. The present invention will be explained in detail below using the accompanying drawings. The present inventors analyzed the parameters that determine the characteristics of conventional eddy current brakes in order to determine the braking force when constructing an eddy current brake, and analyzed the parameters related to the material of the flywheel itself. It was found that resistivity and magnetic permeability are closely related. The present inventors focused on the above-described specific resistance (Ωcm) and magnetic permeability (H/m), created flywheels from various materials, and measured the relationship between the braking force and the excitation current of the excitation coil. The results are shown in FIG. The figure shows the braking force-excitation current characteristics of flywheels made of pure iron, cast steel, and conventional laminated gray cast iron. The pedal rotation speed of the load device at this time was 50 rpm. In this case, the gear ratio is set to 15, so the flywheel is at 750 rpm. As can be easily understood from the figure, pure iron flywheels provide the highest load with low current values, followed by cast steel flywheels, and flywheels with incomparably worse performance than these two. is the conventionally used flywheel made of gray cast iron. Therefore, it can be concluded that pure iron or cast steel is preferable for the flywheel material. Furthermore, the inventors investigated the relationship between the components of the iron materials used and braking characteristics, and found that Si
(Silicon) content is related to specific resistance,
It was found that the smaller the amount, the smaller the specific resistance, and that the content of carbon is related to magnetic permeability, and that the smaller the amount, the higher the magnetic permeability.
Table 1 shows the results of analyzing the components of each flywheel.

[Table] Therefore, the present inventors believe that when constructing an eddy current brake, by specifying the composition of the flywheel material, it is possible to obtain excellent characteristics and a large load with a small current. I've come to a conclusion. According to this conclusion, if the flywheel is constructed using pure iron, which has the lowest carbon and silicon content among iron materials, the best characteristics and the maximum load value can be obtained with a small current. However, since pure iron is difficult to obtain on the market and is expensive, the inventors manufactured a flywheel using cast steel, which has properties similar to those of pure iron, and found that the properties were almost satisfactory. was able to obtain. In this case, considering the various characteristics of the flywheel and its ease of availability in the market, we will use structural carbon steel pipes that are easily available in the market (STK or STK in JIS).
STKM (specified as STKM) is the inner part facing the excitation coil, and in order to create a flywheel effect on the outer part, even if the outer part is made of gray cast iron, the whole part is made of cast steel. It was found that almost the same results were obtained. However, in this case, JIS only sets an upper limit for the composition of structural carbon steel pipes called STK or STKM, so when using structural carbon steel pipes, they must be manufactured as standard products. A steel pipe that satisfies or matches the desired carbon and silicon content conditions must be selected from among the steel pipes. As an example, a flywheel made of conventional gray cast iron is made into type A, and the inner peripheral side facing the excitation coil is coated with a carbon and silicon content (C = 0.12% or less, Si = 0.35) from STK-50.
% or less) are selected as B.
An eddy current brake was constructed as a model. The characteristics of this eddy current brake with a double structure and a flywheel made of gray cast iron are shown in Figures 3 to 8.
Shown in the figure. FIGS. 3 and 4 show the W-Is characteristics of the eddy current brakes according to the prior art and the present invention. As shown in FIGS. 1 and 2, with the same applied current value, using the flywheel according to the present invention can obtain a larger load force and the load value at each rotation speed There is little difference between them, and the curve can be approximated by a squared curve. In particular, in Figure 3, the curve at 40 rpm deviates considerably from the other curves. FIGS. 5 and 6 show the torque-rotational speed characteristics of the eddy current brakes according to the conventional brake system and the present invention. Table 2 shows a comparison of the current value and torque variation ranges, assuming that the practical rotation speed range of the pedal of a load device using an eddy current brake is 40 to 60 rpm.

[Table] As can be easily understood from the above comparison, the flywheel configuration according to the present invention is much faster than the conventional example in the practical rotational speed range of the flywheel pedal when the current value of the excitation coil is kept constant. There is little fluctuation and a high output load can be obtained. FIGS. 7 and 8 show torque-excitation current characteristics based on each rotation speed. The shaded area in the figure shows the fluctuation range of the rotational speed and torque within the practical rotational speed, and is a portion that must be compensated for by further controlling the current value to maintain an accurate constant load. be. Assuming that the torque is within the practical range of 38.8 kg-cm, which is the point of 300 W at 50 rpm, the shaded area shown in FIG. 8 is almost negligible compared to the shaded area shown in FIG. 7. This means that the eddy current brake using the flywheel of the present invention can obtain constant torque characteristics in a practical range with approximately square characteristics of the excitation current without correction by a special compensation circuit from the outside. FIG. 9 is a diagram showing an embodiment of the eddy current brake according to the present invention, in which an inner rotor 2 made of structural carbon steel pipe (STK-50) is fitted into an outer rotor 1 made of gray cast iron. ing. On the other hand, six excitation coils 4 are arranged on the inner stator 3 so as to face the rotor 2, and the excitation coils are connected in series with each other, and both ends thereof are connected to an external power source 5. has been done. As described above, the eddy current brake equipped with the flywheel according to the present invention is superior to conventional brakes by limiting the amount of carbon and silicon among the compositional components of the flywheel material to below a certain value. Not only can extremely excellent constant torque characteristics be obtained, but also a high load can be obtained with the same current value of the excitation coil, so the amount of heat generated by the brake device can be kept low. In addition, a structural carbon steel tube with a carbon and silicon content below a certain value is selected from among the structural carbon steel tubes that are easily available on the market, and this is used as the inner rotor and inserted into the conventional gray cast iron outer rotor. This makes it possible to obtain the same characteristics (close to pure iron) as when the entire rotor is made of cast steel, making it possible to manufacture it easily and at low cost. Furthermore, in the above configuration, even if the outer peripheral member of the outer rotor is made of a non-ferrous material such as concrete, the same performance as when the entire outer rotor is made of cast steel members can be obtained, and the same performance as that of the inner peripheral member can be obtained. A flywheel effect can be added. Further, unlike the conventional structure, the structure of the present invention has an inner stator and an outer rotor, so there is an advantage that the outer rotor, which generates heat, can naturally radiate heat through convection caused by its rotation.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the braking force-exciting current characteristics depending on the material of the flywheel, Fig. 2 is a diagram showing the braking force-exciting current characteristic of pure iron, and Fig. 3 is a diagram showing the braking force-exciting current characteristics of pure iron.
4 and 4 are diagrams showing the W-Is characteristics of the conventional and the present invention, FIGS. 5 and 6 are diagrams showing the torque-rotation speed characteristics of the conventional and the present invention, and FIG. 7 and FIG. FIG. 8 is a diagram showing the torque-excitation current characteristics of the conventional and the present invention, and FIG. 9 is a diagram showing an embodiment of the eddy current brake of the present invention. (Symbols in the figure) 1: Outer rotor, 2: Inner rotor, 3: Stator, 4: Excitation coil, 5: Power supply.

Claims (1)

[Scope of Claims] 1. An eddy current brake consisting of an outer rotor, an inner stator, a plurality of excitation coils provided in the inner stator, and a current source for energizing the excitation coils, wherein the outer rotor is It has a concentric structure consisting of an outer rotor and an inner rotor, and the inner rotor has a carbon content of 0.12.
% or less and a structural carbon steel tube (STK or STKM) with a silicon content of less than 0.35%. 2. The eddy current brake according to claim 1, wherein the outer circumference of the concentric outer rotor is made of any non-ferrous material, and a flywheel effect is imparted to the inner circumference. .