JPS6236979Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a non-excited electromagnetic brake that applies braking to a braked object using the attractive force of a permanent magnet and releases the braking by excitation of an electromagnetic coil, and controls the generated brake torque. It is an object of the present invention to provide a brake of this kind that can facilitate the release of braking force as well as completely release the braking force.

This type of electromagnetic brake generates braking force by attracting the armature based on the magnetic flux generated by the permanent magnet.On the other hand, when the brake force is released, current is supplied to the excitation coil, and the magnetic flux generated by this is directed in the opposite direction to the magnetic flux direction of the permanent magnet. The brake force is generated by the permanent magnet, and the brake torque is reduced to zero.

However, if the excitation current from the excitation coil is further increased after the magnetic flux from the permanent magnet has been completely canceled out, a brake torque will be generated due to the excitation force.

In other words, in a general non-excitation type electromagnetic brake,
The excitation current vs. brake torque characteristics as shown in FIG. 1 are shown. Therefore, the width of the excitation current value that makes the generated brake torque completely zero is almost infinitesimal, so due to slight variations in the permanent magnet characteristics, etc.
will change, resulting in an unstable braking action.

Conventionally, as a countermeasure for this, a spring has been used to generate torque in the opposite direction, but this has disadvantages such as the need for adjustment for each product due to variations in the spring.

This proposal was developed in view of this point, and has a characteristic that the generated brake torque is kept at zero between certain excitation current values regardless of the amount of excitation current. The main proposal will be explained in detail. In FIG. 2, 1 and 2 are annular yokes with a substantially L-shaped cross section, and an excitation coil 3 is placed in a cavity created by arranging them in opposite directions.
is accommodated, and an annular permanent magnet 4 having opposite polarity surfaces on both sides is clamped between the radially extending disk-shaped portions of both of these yokes. 5 is yoke 1,
2 is a braking friction plate provided over the inner and outer periphery of the open end that is the magnetic pole portion; 6 is an armature that faces each of the magnetic poles of the yokes 1 and 2 and the braking surface of the friction plate 5, and is a sliding ring. It can be attached to 7. The sliding ring 7 is spline-fitted to a hub 8 connected to a braked shaft (not shown). Numeral 9 is a retaining ring fitted into a groove on the outer periphery of hub 8, and 10 is a mounting plate fixed to yoke 2, which is used to fix the magnet portion of the brake according to the present invention to a mating machine or the like.

The above configuration is not essentially different from that of conventional brakes of this type, but in this case, the disk-shaped portion of one yoke 1 is used as a bypass magnet that serves as the main magnetic path for the excitation magnetic flux from the coil 3. By providing an annular groove in the path 1a and filling the groove with magnetic powder such as iron powder mixed with a bonding agent such as resin, the magnetic flux of the yoke 1 is created through which only the magnetic flux generated by the exciting current passes. A section 11 with extremely lower magnetic permeability than other sections is provided in the groove, and its function will be described later, but even if the groove is left empty without being filled with magnetic powder, The basic action is the same as when filled with magnetic powder.

In the above configuration, when no current is supplied to the excitation coil 3, a magnetic flux Φ ₁ is generated that exits the permanent magnet 4, passes through the yoke 1, the armature 6, and the yoke 2, and returns to the permanent magnet 4. The armature 6 is attracted toward the magnetic pole surfaces of the yokes 1 and 2 by the electromagnetic attraction force, is brought into pressure contact with the friction plate 5, and a brake is applied to a braked shaft (not shown) via the hub 8.

Furthermore, when a current is supplied to the excitation coil 3 in a direction that generates a magnetic flux Φ ₂ that cancels the magnetic flux Φ _{1 generated by this current, this magnetic flux Φ 2 passes} through this part because the magnetic resistance is high inside the permanent magnet. As shown in the figure, as the magnitude of the current passing through the bypass magnetic path 1a and being supplied to the coil is gradually increased, the electromagnetic attraction force on the armature 6 gradually decreases, and the generated brake torque also changes as shown in the line in Figure 3. When the magnetic fluxes Φ ₁ and Φ ₂ become equal, the brake torque becomes zero and the brake is released, as shown by a. , the magnetic flux Φ ₂ due to the exciting current is,
Where part 11 of yoke 1 is provided, that part 1
Since the magnetic permeability of No. 1 is extremely low, it passes through the back of that part. Now, when this back magnetic path is saturated, the magnetic flux Φ ₁ due to the permanent magnet is completely canceled out,
If the cross-sectional area of the magnetic path is set so that the brake torque becomes zero, even if the excitation current is increased after reaching this point, the magnetomotive force will remain in the area with low magnetic permeability until a certain current value. is consumed and does not contribute to brake torque generation.

That is, after the magnetic path at the location where the portion 11 is provided reaches the saturation point, the magnetic flux Φ ₂ for the excitation current at that location
The rate of increase in the magnetic flux is extremely low, and the torque generated by this magnetic flux is only consumed as mechanical loss in rotating parts such as bearings.The generated braking torque, which acts as a brake, is as shown by line b in Figure 3. When the excitation current is further increased, the brake torque will change to line c in Figure 3.
increases as shown in .

The width or range of the excitation current value that makes the generated brake torque zero, as shown by the line b in Figure 3, and the rate of increase in the generated brake torque with respect to the excitation current, as shown by the line c in the same figure, are as follows: The magnetic permeability of the low permeability portion 11 formed by filling can be varied by appropriately selecting the material, particle shape, filling rate, etc. of the filler material.

As is clear from the above, according to the present invention, the bypass magnetic path 1a, through which the magnetic flux generated mainly by the excitation current of the excitation coil passes, is juxtaposed with a portion 11 whose magnetic permeability is significantly lower than that of other magnetic path portions. This is designed to create a range in which the generated brake torque is zero within a certain current value of the current supplied to the excitation coil, making it easier to control the generated brake torque by the excitation current and at the same time releasing the brake force. It is possible to provide a brake that is perfectly leveled and has stable braking action.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing excitation current vs. brake torque characteristics of a conventional brake, and FIG. 2 is a front view of the brake showing an embodiment of the present invention, with the upper half shown as a longitudinal sectional view. FIG. 3 is a diagram showing the excitation current versus brake torque characteristics of the brake according to the present invention. 1, 2... Yoke, 11... Portion with low magnetic permeability.

Claims (1)

[Scope of utility model registration request] A permanent magnet is interposed in the middle, and in addition to providing a series of magnetic paths that serve as a common path for the magnetic flux of both the permanent magnet and the coil, a bypass magnet for the magnetic path is provided between the permanent magnet and the coil. establish a road,
In a non-excited electromagnetic brake that applies braking to a braked object by the attractive force of a permanent magnet and releases the brake by excitation of a coil, the area of the magnetic path is limited and this area is placed in the bypass magnetic path. The magnetic flux density of the limited magnetic path part is saturated at the point when the magnetic flux by the permanent magnet is completely cancelled.A part with extremely low magnetic permeability is installed in parallel, and the generated brake torque has a zero value in a certain excitation current value range. A non-excitation operated electromagnetic brake characterized by a wide range of