Non-excitation operation brake

Abstract

In a non-excitation actuated brake (1), the magnetic force of a permanent magnet (17) is used to hold a suction plate (13) at a brake force release position (13A) that is located away from a friction brake plate (12). The coil energization of an electromagnet (16) may be performed only when moving the suction plate (13) held at a brake force application position (13B) toward the brake force release position (13A) and when moving the suction plate (13) held at the brake force release position (13A) toward the brake force application position (13B). Heat generation and power consumption due to continuous coil energization can be suppressed. By setting the electromagnetic force by the electromagnet (16) to an appropriate value, it is possible to reliably and quickly switch between the brake force application state and the brake force release state.

Description

Non-excitation brake

[0001] The present invention relates to a non-excitation operating brake, and more particularly to a non-excitation operating brake with a built-in permanent magnet that maintains a brake force release state by the magnetic force of a permanent magnet.

[0002] A non-energized brake is installed in a servo motor or the like as a safety device when the motor is not in operation. As described in Patent Document 1, for example, a non-energized brake includes a friction brake plate, an attraction plate made of a magnetic material, and an electromagnet arranged axially around the outer periphery of the motor's rotating shaft. A braking force is applied to the rotating shaft by pressing the attraction plate, which is movable along the rotating shaft, against the friction brake plate attached to the rotating shaft so that it rotates integrally with the rotating shaft, using spring force. When the electromagnet facing the attraction plate is excited, the attraction plate moves away from the friction brake plate against the spring force due to magnetic attraction, thereby releasing the braking force. Generally, a non-energized brake has a fixed plate positioned at a fixed axial position of the rotating shaft to reliably generate braking force. A friction brake plate attached axially movably to the rotating shaft is sandwiched between the friction brake plate and the attraction plate, which is movable axially, is biased against the fixed plate by the spring force of a pressure spring. When the electromagnet is excited, the attraction plate is attracted, allowing the friction brake plate to rotate freely, and the braking force applied to the rotating shaft is released.

[0003] JP 2013-2617 A International Publication No. 2015 / 198399 International Publication No. 2006 / 103727

[0004] In conventional non-excitation operated brakes, power of, for example, 24V DC or 90V DC is typically supplied to the electromagnet to release the braking force when the actuator, motor, etc. are operating. The attraction operation that moves the attraction plate to the brake force release position is performed by applying voltage to the electromagnet's coil, which generates an electromagnetic force that attracts and attracts the attraction plate made of magnetic material. To maintain the released state of the braking force, current continues to flow through the electromagnet's coil. In other words, non-excitation operated brakes play a role in stopping the rotating shaft of the actuator or motor in an emergency stop such as during a power outage, but they require a constant voltage application except in emergency stops.

[0005] The temperature of the entire brake rises due to heat generated from the conductors caused by the current flowing through the electromagnet coil. This rise in brake temperature also raises the temperature of the actuator or motor in which the brake is incorporated, affecting the temperature of the windings and the internal temperature of the encoder.

[0006] In view of this, an object of the present invention is to provide a non-excitation brake that can maintain a released state of braking force without continuously passing current through the coil of an electromagnet, in order to suppress heat generation and power consumption caused by energizing the coil.

[0007] The non-excitation operating brake of the present invention is characterized by comprising: a friction brake plate attached to a rotating shaft to which a braking force is to be applied and rotated integrally with the rotating shaft; an attraction plate made of a magnetic material movable to a braking force application position pressed against the friction brake plate and a braking force release position spaced from the friction brake plate; a pressure spring that generates a retaining spring force to hold the attraction plate at the braking force application position; a permanent magnet that generates a retaining magnetic force to hold the attraction plate at the braking force release position; an electromagnet that can generate an electromagnetic force to move the attraction plate; and a brake control circuit that drives and controls the electromagnet so that the attraction plate held in the braking force release position moves toward the braking force application position when power is turned off, and so that the attraction plate held in the braking force application position moves toward the braking force release position when power is turned on.

[0008] Here, the brake control circuit can be configured to include: a power supply monitoring unit that monitors the power supply; a charging unit that stores power for exciting the electromagnet; a coil voltage control unit that, when the power supply monitoring unit detects that the power supply has been cut off, instantaneously energizes the coil of the electromagnet in a direction that cancels the retaining magnetic force of the permanent magnet, using power supplied from the charging unit, in order to move the attraction plate from the braking force release position toward the braking force application position; and an attraction / release detection unit that detects the attraction action and release action of the attraction plate.

[0009] In this case, when the power supply monitoring unit detects that the power supply has been turned on, the coil voltage control unit is configured to charge the charging unit and to momentarily energize the coil of the electromagnet to generate an electromagnetic force to attract the attraction plate in order to move the attraction plate from the braking force application position toward the braking force release position.

[0010] Furthermore, the attraction plate can be attracted and held in the braking force release position by the magnetic attraction force of the permanent magnet, and the holding force can be increased by continuously energizing the coil of the electromagnet at a low voltage.

[0011] In this invention, the magnetic attraction force of a permanent magnet is used to hold the attraction plate in the brake force release position away from the friction brake plate. The electromagnet coil only needs to be energized when moving the attraction plate, which is held in the brake force application position, toward the brake force release position, or when moving the attraction plate, which is held in the brake force release position, toward the brake force application position. This reduces heat generation and power consumption due to continuous coil energization. Furthermore, by setting the holding spring force, holding magnetic force, and electromagnetic force of the electromagnet to appropriate values, switching between brake force application and brake force release can be performed reliably and quickly.

[0012] (A) is a schematic block diagram showing a non-excitation operation brake of the present invention incorporated into a motor system, and (B) is a schematic half-sectional view showing its brake mechanism part. (A) is a schematic flowchart showing the operation (attraction operation of the attraction plate) of the non-excitation operation brake when power is turned on, and (B) is an explanatory diagram showing the state of the brake mechanism part of the non-excitation operation brake transitioning from an initial state to a brake force release state (completion of attraction of the attraction plate). (A) is a schematic flowchart showing the operation (release operation of the attraction plate) of the non-excitation operation brake when power is turned off, and (B) is an explanatory diagram showing the state of the brake mechanism part of the non-excitation operation brake transitioning from a brake force release state (attraction state of the attraction plate) to a brake force application state (release state of the attraction plate).

[0013] An embodiment of a non-excitation actuated brake to which the present invention is applied will be described below with reference to the drawings. In the example described below, the non-excitation actuated brake of the present invention is applied to a motor system. However, the present invention is not limited to the configuration of the embodiment described below, and the non-excitation actuated brake can be applied to various rotary drive systems other than motor systems.

[0014] Fig. 1(A) is a schematic block diagram showing a case where a non-excitation operation type brake according to this embodiment is applied to a motor system, and Fig. 1(B) is a schematic half-sectional view showing a brake mechanism of the non-excitation operation brake. Referring to Fig. 1(A), the motor system 100 includes a motor 110, an encoder 130 that detects the rotation of a rotating shaft 120 of the motor 110, and a non-excitation operation brake 1 that applies a braking force to the rotating shaft 120. The non-excitation operation brake 1 includes a brake mechanism 10 and a brake control circuit 20 attached to the rotating shaft 120, and is supplied with power from a power source 30 such as a DC 24V power source.

[0015] 1(B), the brake mechanism 10 has the same basic configuration as a general non-excitation brake, and is arranged on the outer periphery of the rotating shaft 120. The brake mechanism 10 includes a fixed plate 11, a friction brake plate 12, an attraction plate 13 (armature), a pressure spring 15 incorporated into a yoke 14, and an electromagnet 16 consisting of a coil 16a also incorporated into the yoke 14. In addition to these, the brake mechanism 10 includes a permanent magnet 17 attached to the yoke 14.

[0016] The fixed plate 11 is fixedly disposed at a fixed distance in the axial direction from the yoke front end surface 14a of the yoke 14. The friction brake plate 12 is coaxially attached to a rotating shaft 120 to which a braking force is to be applied via an annular hub 18, rotates integrally with the rotating shaft 120, and is axially slidable by a spline connection between the friction brake plate 12 and the hub 18. Annular friction plates are affixed to both end surfaces of the friction brake plate 12. The attraction plate 13 is made of a magnetic material and faces the fixed plate 11 in the axial direction, sandwiching the friction brake plate 12 between them. The attraction plate 13 is supported axially slidably by a guide shaft 19 extending axially from the yoke front end surface 14a, and is slidable between a braking force release position 13A in contact with the yoke front end surface 14a and a braking force application position 13B in which the attraction plate 13 is pressed against the friction brake plate 12.

[0017] The pressure springs 15 are coil springs attached to the yoke 14 so as to protrude axially from the yoke front end surface 14a. For example, multiple pressure springs 15 are arranged at equal angular intervals in the circumferential direction, and the spring force of the pressure springs 15 can hold the attraction plate 13 at the brake force application position 13B where it is pressed against the friction brake plate 12. In this state, a predetermined brake force is applied to the rotating shaft 120. In contrast, the permanent magnet 17 is, for example, an annular magnet attached to the yoke 14 so that its annular end surface is exposed from the yoke front end surface 14a. The permanent magnet 17 can hold the attraction plate 13 at the brake force release position 13A by its magnetic attraction force against the spring force of the pressure springs 15. Note that the permanent magnet 17 may also be attached to the attraction plate 13 side.

[0018] The electromagnet 16 can generate an electromagnetic attraction force that attracts the attraction plate 13, which is biased toward the braking force application position 13B, toward the braking force release position 13A against the spring force of the pressure spring 15, and can also release the attraction plate 13, which is attracted and held at the braking force release position 13A by the holding magnetic force of the permanent magnet 17, by being excited in the opposite direction (in a direction that cancels out the magnetic attraction force of the permanent magnet 17).

[0019] Next, the brake control circuit 20 excites the electromagnet 16 to perform an attraction plate release operation, which moves the attraction plate 13, which is attracted and held at the braking force release position 13A, to the braking force application position 13B, and an attraction plate attraction operation, which attracts the attraction plate 13, which is biased to the braking force application position 13B, and moves it to the braking force release position 13A. Referring to FIG. 1A , the brake control circuit 20 includes a power supply voltage monitor 21 (power supply monitor), a discharge / charge unit 22, a coil voltage control unit 24 for driving the electromagnet, and an attraction / release detector 23. The power supply voltage monitor 21 monitors the power supply 30 and detects power-on and power interruption, such as during a power outage. The discharge / charge unit 22 stores power for exciting the electromagnet 16. The attraction / release detector 23 detects the magnetic poles formed in the electromagnet 16 based on the current and voltage flowing through the coil 16a of the electromagnet 16, thereby confirming the attraction and release of the attraction plate 13. A magnetic pole sensor such as a Hall element may be disposed to detect the magnetic pole.

[0020] When the coil voltage control unit 24 detects that the driving power supply has been turned on, it charges the discharge / discharge charging unit 22 and, after the discharge / discharge charging unit 22 has been charged, excites the electromagnet 16 to generate an electromagnetic force (magnetic attraction force) for moving the attraction plate 13 from the braking force application position 13B toward the braking force release position 13A. When the coil voltage control unit 24 detects that the driving power supply has been turned off, it excites the electromagnet 16 using power supplied from the discharge / discharge charging unit 22 to release the attraction plate 13 from the permanent magnet 17 and move it from the braking force release position 13A toward the braking force application position 13B. The electromagnetic attraction force of the electromagnet 16 may be used in combination with the magnetic attraction force of the permanent magnet 17 to attract and hold the attraction plate 13 at the braking force release position 13A. In this case, the electromagnet 16 is excited with lower power than when the power supply is turned on or off, thereby suppressing heat generation and power consumption due to continuous current flow through the coil.

[0021] (When power is turned on: attraction operation of attraction plate) The operation of the non-excitation operation brake 1 when power is turned on will be described with reference to Figure 2. Figure 2(A) is a schematic flowchart showing the operation of the non-excitation operation brake 1 when power is turned on, and Figure 2(B) is an explanatory diagram showing the state of the brake mechanism unit 10 of the non-excitation operation brake 1 transitioning to a braking force release state (completion of attraction of the attraction plate). When power is turned on, the power supply voltage monitoring unit 21 detects power-on (step ST1 in Figure 2(A)), and the charging operation of the discharge / recharge force charging unit 22 is performed (step ST2 in Figure 2(A)). The brake mechanism unit 10 of the non-excitation operation brake 1 is in state B1 (initial state) as shown in Figure 2(B).

[0022] Next, an initial attraction operation of the attraction plate 13 is performed to move the attraction plate 13 to the braking force release position 13A (step ST3 in FIG. 2A). The coil voltage control unit 24 momentarily energizes the coil 16a of the electromagnet 16 (24 V), temporarily generating a magnetic attraction force that attracts the attraction plate 13. The magnetic attraction forces of the permanent magnet 17 and the electromagnet 16 cause the attraction plate 13 to slide against the spring force of the pressure spring 15, resulting in a state in which the attraction plate 13 is held at the braking force release position 13A and pressed against the yoke front end surface 14a (state B2 in FIG. 2B).

[0023] Next, the excitation of the electromagnet 16 is stopped (step ST4). The attraction / release detection unit 23 confirms the excited state of the electromagnet 16, and the initial attraction operation ends (step ST5 in FIG. 2A, state B3 in FIG. 2B). After this, the braking force release state is maintained by the magnetic attraction force of the permanent magnet 17. In this state, the motor system 100 is driven, and the rotating shaft 120 rotates.

[0024] Here, in step ST4, the voltage applied to the electromagnet 16 can be switched to a low voltage to switch to a power-saving state in which the electromagnet 16 attracts the attraction plate 13. In this case, as shown in state B4 in FIG. 2B, a low voltage is continuously applied to the coil 16a of the electromagnet 16. In this case, the braking force release state is maintained by the magnetic attraction force of the permanent magnet 17 and the magnetic attraction force of the electromagnet 16.

[0025] (When power is cut off: Attraction plate release operation) Figure 3(A) is a schematic flowchart showing the operation of switching the non-excitation operation brake 1 from a brake force release state to a brake force application state when the driving power supply is cut off, and Figure 3(B) is an explanatory diagram showing the state of the brake mechanism unit 10 transitioning to the brake force application state (attraction plate release state). First, the state of the brake mechanism unit 10 of the non-excitation operation brake 1 is state B3 or state B4 in Figure 3(B). The power supply voltage monitoring unit 21 detects that the power supply has been cut off (step ST11 in Figure 3(A)). If the attraction plate 13 is attracted to the braking force release position 13A by the electromagnet 16 in addition to the permanent magnet 17 (state B4 in Figure 3(B)), the current to the coil of the electromagnet 16 is also stopped (step ST12 in Figure 3(A)).

[0026] When a power interruption is detected, the coil voltage control unit 24 instantaneously excites the electromagnet 16 using power supplied from the discharge / charge unit 22, thereby releasing the attraction plate 13, which is attracted and held at the braking force release position 13A by the holding magnetic force of the permanent magnet 17, from the attraction of the permanent magnet 17 (step ST13 in FIG. 3A ). In this case, the direction of current flow to the coil 16a of the electromagnet 16 is controlled to generate magnetic field lines in a direction that cancels the magnetic force of the permanent magnet 17. This triggers a reversal of the magnitude relationship of the forces acting on the attraction plate 13 (attraction plate biasing force by the pressure spring 15 < attraction plate attraction force by the permanent magnet 17). The spring force of the pressure spring 15 releases the attraction plate 13 from the attraction of the permanent magnet 17 and causes the attraction plate 13 to slide from the braking force release position 13A toward the friction brake plate 12, reaching the braking force application position 13B where it is pressed against the friction brake plate 12 (state B5 in FIG. 3B ).

[0027] The attraction / release detection unit 23 confirms the excited state of the electromagnet 16, and the release operation of the attraction plate 13 is completed (step ST14 in FIG. 3A, state B1 in FIG. 3B). After this, the braking force is maintained by the spring force of the pressure spring 15. In this state, the braking force acts on the friction brake plate 12, and the stopped state of the rotating shaft 120 is maintained.

Claims

1. A non-excitation operating brake comprising: a friction brake plate attached to a rotating shaft to which a braking force is to be applied and rotated integrally with the rotating shaft; an attraction plate made of a magnetic material movable to a braking force application position pressed against said friction brake plate and to a braking force release position spaced from said friction brake plate; a compression spring generating a retaining spring force to retain said attraction plate in said braking force application position; a permanent magnet generating a retaining magnetic force to retain said attraction plate in said braking force release position; an electromagnet capable of generating an electromagnetic force to move said attraction plate; and a brake control circuit which drives and controls said electromagnet so that when power is cut off, the attraction plate held in the braking force release position moves towards the braking force application position, and when power is turned on, the attraction plate held in the braking force application position moves towards the braking force release position.

2. A non-excitation operating brake as claimed in claim 1, wherein the brake control circuit comprises: a power supply monitoring unit which monitors the power supply; a charging unit which stores power for exciting the electromagnet; a coil voltage control unit which, when the power supply monitoring unit detects that the power supply has been cut off, instantaneously energizes the coil of the electromagnet in a direction which cancels the retaining magnetic force of the permanent magnet using power supplied from the charging unit, in order to move the attraction plate from the braking force release position towards the braking force application position; and an attraction / release detection unit which detects the attraction and release operations of the attraction plate.

3. A non-excitation operating brake as claimed in claim 2, wherein, when the power supply monitoring unit detects that the power supply has been turned on, the coil voltage control unit performs a charging operation on the charging unit and instantaneously energizes the coil of the electromagnet to generate an electromagnetic force for attracting the attraction plate in order to move the attraction plate from the braking force application position towards the braking force release position.

4. A non-excitation operating brake as claimed in claim 3, wherein the coil voltage control unit, when the attraction plate is held in the braking force release position, continuously energizes the coil of the electromagnet at a voltage lower than that during the momentary energization, thereby generating a holding electromagnetic force that holds the attraction plate in the braking force release position.

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