JPH0699722B2 - Magnetic powder for electromagnetic clutch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention is a so-called electromagnetic clutch that transmits a rotational force by utilizing a magnetic coupling force acting between magnetic powder particles when the magnetic powder is magnetized. In particular, the present invention relates to a magnetic powder for use in an electromagnetic clutch having excellent wear resistance and a high saturation magnetic flux density.

[Prior Art] Magnetic powders for electromagnetic clutches are required to have various characteristics. Among them, magnetic characteristics such as magnetic permeability and saturation magnetic flux density,
Mechanical properties such as abrasion resistance and chemical properties such as oxidation resistance are emphasized. Fe-Co alloy powder (Japanese Patent Laid-Open No. 54-9345) is known as a magnetic powder for an electromagnetic clutch that emphasizes magnetic characteristics, and Fe-Co alloy powder is a magnetic powder for an electromagnetic clutch that emphasizes oxidation resistance. Cr-based stainless steel powder and the like are known.

[Problems to be Solved by the Invention] However, the demand for miniaturization of electromagnetic clutches tends to increase more and more in recent years, and the amount of magnetic powder used in one clutch tends to decrease. Therefore, a magnetic powder having a higher saturation magnetic flux density, that is, a magnetic powder capable of obtaining a higher torque under the same current is required.

Fe-Co alloy powder is a magnetic powder with high magnetic properties, especially high saturation magnetic flux density, and has the advantage of being able to transmit high torque even with a small amount of use, but it has poor wear resistance because it is not so high in hardness. There are drawbacks. Therefore, during use of the electromagnetic clutch, the magnetic powder is abraded and pulverized, and the binding force between the powder particles is reduced, resulting in a decrease in torque. Further, when the magnetic powder is pulverized, the torque cutoff time (the time from when the current is cut off until the torque becomes 0) becomes longer, and it is observed that the driven shaft continues to rotate for a while. It becomes a problem in the required application.

The present invention has been made in view of these circumstances,
An object of the present invention is to provide a magnetic powder for an electromagnetic clutch which has sufficient saturation magnetic flux density, that is, torque characteristics and is excellent in wear resistance.

[Means for Solving the Problems] However, the magnetic body for an electromagnetic clutch of the present invention which has achieved the above object contains Si: 0.2 to 7% and Co: 5 to 50%, and the balance is Fe and inevitable impurities. The point is that it is made of Fe-based alloy.

[Function] The constituent components of the magnetic powder for an electromagnetic clutch according to the present invention and the compounding ratio thereof will be described below with respect to their respective limiting reasons.

Si: 0.2 to 7% Si is a component that contributes to an increase in hardness and increases hardness to prevent wear of the magnetic powder, but for this purpose, addition of 0.2% or more is necessary. On the other hand, if it is added in excess of 7%, the powder becomes brittle and prone to cracking and the saturation magnetic flux density is lowered. Therefore, it is necessary to avoid adding more than necessary. For this reason, the amount of Si added is specified to be 0.2 to 7% in the present invention.

Co: 5-50% The torque characteristics of the electromagnetic clutch depend on the saturation magnetic flux density of the magnetic powder, and the saturation magnetic flux density of the magnetic powder is basically proportional to the Fe content. That is, the components other than Fe decrease the saturation magnetic flux density of the powder as the content thereof increases. However, Co is the only exceptional element.
The saturation magnetic flux density of the Fe-based alloy can be increased. In addition, the effect is not recognized with the addition of less than 5%. The torque characteristics are improved by adding more than 5%, and the torque characteristics are about 30-35.
%, It reaches the maximum value, but if it is added more than 50%, the torque characteristic gradually decreases from the maximum value, and if it exceeds 50%, it becomes equal to or less than the torque characteristic without Co addition. I will end up. Therefore, in order to improve the magnetic characteristics, especially the torque characteristics, 5 to 50%, more preferably 20 to 40% Co
Need to be added.

It should be noted that Si among the elements other than Fe and Co is indispensable for increasing the hardness as described above, but addition of other elements should be avoided. For example, elements such as Al and Cr have the effect of improving high temperature oxidation resistance, and their addition may be recommended as a general theory depending on the application of the magnetic powder, but in the present invention, addition of these elements Based on the principle of avoiding the adverse effect of deterioration of magnetic properties, their addition is positively excluded.

The magnetic powder for an electromagnetic clutch according to the present invention requires the addition of the above alloy elements, and the balance is Fe and unavoidable impurities, and substantially does not include expensive elements other than Si, Co and Fe. By satisfying such a constitution, it is possible to economically obtain the magnetic powder for the electromagnetic clutch, which is excellent in wear resistance and magnetic characteristics.

[Examples] Atomized powders having the component compositions shown in Table 1 were experimentally manufactured, the hardness thereof was measured, and a torque characteristic test was performed by actually loading the atomized powder in an electromagnetic clutch of an actual device. In addition, for some powders, measured torque and torque break time after 500 hours of use were measured and compared with the data at the start of use. The result is
The results are shown in Tables 1 and 2. In Table 1, A1 to A7 are examples, B1 to B3 are comparative examples, and C1 and C2 are conventional examples.

As shown in Tables 1 and 2, B3, which has low hardness and poor wear resistance,
A large amount of fine powder was generated in C1 and C2, and the rate of decrease in torque and the rate of increase in torque dead time were large. On the other hand, it was confirmed that the powder of the example has a small decrease rate of torque and a small increase rate of torque cut-off time, and has good wear resistance.

Next, FIG. 1 shows the relationship between the Co amount of the example powders A1 to A7 and the measured torque.

As shown in FIG. 1, although there is some variation depending on the amount of Si, a remarkable improvement in torque characteristics is recognized by the addition of 5 to 50% Co. The data of B1 and B2 are shown in FIG. 1 for reference.

Fig. 2 shows the relationship between the amount of Si and the hardness of A1 to A7 and B2, B3. It is confirmed that the hardness increases with the addition of Si, although there is some variation depending on the amount of Co. Was done.

[Advantages of the Invention] The present invention is configured as described above, has excellent magnetic properties,
Moreover, it was possible to economically provide magnetic powder for an electromagnetic clutch, which is excellent in wear resistance.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between Co amount and measured torque,
The figure is a graph showing the relationship between the amount of Si and hardness.

Claims (1)

[Claims] 1. An electromagnetic clutch comprising Si: 0.2 to 7% (meaning weight%; the same applies hereinafter) and Co: 5 to 50%, with the balance being Fe and an Fe-based alloy which is an unavoidable impurity. For magnetic powder.