JP7648901B2 - Electromagnetic brake - Google Patents

Description

The present invention relates to an electromagnetic brake that receives power through an overexcitation circuit.

An electromagnetic brake is known that has a yoke, a coil that excites the yoke by receiving power from an external source via a power supply path, and a braking means, and is also provided with an over-excitation circuit in the power supply path that temporarily over-excites the yoke, and is configured to switch the ON/OFF state of the brake using the braking force from the braking means and the excitation force through the power supply path (for example, Patent Document 1).

Figure 8 shows an electromagnetic brake MB whose basic operation is substantially the same as that of Patent Document 1.

This electromagnetic brake MB comprises a yoke 1, a coil 2 attached to the yoke 1, and a coil spring 3 as a braking means. The excitation force of the coil 2 and the spring force of the coil spring 3 enable the armature 4 to move forward and backward. When not excited, the coil spring 3 moves the armature 4 and sandwiches the disk 6 between it and the side plate 5, transmitting the braking force of the disk 6 to the motor shaft 10. When excited, the electromagnetic force moves the armature 4 away from the side plate 5 and attracts it to the attraction surface 1a of the yoke 1, thereby releasing the brake applied to the motor shaft 10 by the disk 6.

In this case, an over-excitation circuit 7 as shown in FIG. 8 is attached externally to the current path L, and the excitation to the yoke 1 is temporarily over-excited, thereby increasing the excitation force at the initial movement when the brake is released, and driving the armature 4 more effectively. After the armature 4 is attracted to the yoke attraction surface 1a, the excitation is switched to normal excitation to appropriately maintain the attraction state.

Patent document 1 uses a permanent magnet instead of a coil spring as a braking means, but the basic operation is the same as in Figure 8, and other devices such as leaf springs can also be used as appropriate braking means.

Japanese Patent Application Publication No. 9-273577

However, conventionally, this type of over-excitation circuit 7 has been attached externally to the yoke 1 as an over-excitation circuit component 70, as shown in Figures 9 and 10. For this reason, when attempting to use this yoke 1 to configure an electromagnetic brake as shown in Figure 8, the over-excitation circuit component 70 also has to be attached externally to the electromagnetic brake MB. As a result, additional space is required for the over-excitation circuit component 70, making it difficult to make the electromagnetic brake MB compact and imposing many restrictions on assembly to a motor, etc.

As such, it is considered an effective measure to incorporate the over-excitation circuit 7 into the electromagnetic brake MB. In that case, however, it is necessary to take appropriate measures to deal with the fact that this type of over-excitation circuit 7 is made up of electronic components and is therefore susceptible to thermal and electromagnetic influences.

The aim of this invention is to realize a new electromagnetic brake based on this idea.

In order to achieve the above objectives, the present invention takes the following measures:

That is, the electromagnetic brake of the present invention has a yoke, a coil that excites the yoke by receiving power from the outside through a power supply path, and a braking means, and is equipped with an over-excitation circuit in the power supply path that temporarily puts the excitation to the yoke into an over-excitation state, and is configured to switch the ON/OFF state of the brake by the braking force of the braking means and the excitation force through the power supply path, and is characterized in that a board on which the over-excitation circuit is mounted is integrated with the yoke together with the coil by resin molding.

In this way, the over-excitation circuit can be integrated into the yoke, making it possible to make the electromagnetic brake more compact. Furthermore, since the over-excitation circuit contains electronic components and is therefore susceptible to thermal effects, by resin-molding it into the yoke together with the coil, the heat can be dissipated through the resin-molded layer, reducing the thermal load on the over-excitation circuit.

It is preferable that the substrate is attached to the yoke via a heat dissipation sheet.

When continuous current is applied to release the brake, it is thought that the heat dissipation effect from the resin molded layer alone may be insufficient. However, by attaching the base to the yoke via a heat dissipation sheet, heat can be dissipated to the yoke. This ensures another heat dissipation path with a higher heat dissipation effect in addition to the heat dissipation from the resin molded layer, so the impact of thermal load can be more effectively reduced even if the base is integral with the yoke.

In this case, it is preferable that the base is fixed to the yoke via a highly heat-conductive fastener.

Resin molding is prone to losing adhesion to the yoke due to shrinkage of the resin when it cools. In contrast, by using a highly heat-conductive fastener as described above, it is possible to ensure proper adhesion after resin molding and also create a new heat dissipation route through the fastener.

It is also preferable that a recess is provided in the yoke at the outer periphery of the coil, and the base is disposed within the recess.

When an over-excitation circuit is exposed to electromagnetic waves, the circuit acts as an antenna and receives the electromagnetic waves, which can easily have a negative effect on the function of the over-excitation circuit. In response to this, by providing a recess around the outer periphery of the coil and placing the board in this position, it is possible to ensure that electromagnetic waves are less likely to reach the board.

It is also preferable to place an electromagnetic wave blocking wall between the coil and the base.

By placing such an electromagnetic wave blocking wall, it is possible to block the electromagnetic waves emitted from the coil winding section (core section) around the yoke, and more effectively reduce the effect of the electromagnetic waves on the over-excitation circuit.

The present invention is particularly effective when the over-excitation circuit is configured to create a normal excitation state through PWM control.

When digital components are used in such over-excitation circuits, they are particularly susceptible to the effects of electromagnetic waves, making electromagnetic wave countermeasures particularly effective.

According to the present invention described above, it is possible to provide a new electromagnetic brake that can be made compact by assembling the over-excitation circuit integrally with the yoke and also deals well with thermal loads.

FIG. 2 is a perspective view showing a yoke portion of the electromagnetic brake according to the embodiment of the present invention. FIG. 2 is a partial longitudinal sectional view of FIG. FIG. 2 is an explanatory diagram of an over-excitation circuit constituting the embodiment. FIG. 3 is a partial cross-sectional view corresponding to FIG. 2 and showing a modified example of the present invention. FIG. 3 is a partial cross-sectional view corresponding to FIG. 2 and showing a modified example of the present invention. 3 is an explanatory diagram including a partial sectional view and a plan view corresponding to FIG. 2, showing a modified example of the present invention; FIG. FIG. 3 is an explanatory diagram including a partial sectional view corresponding to FIG. 2 and a perspective view of a coil bobbin, showing a modified example of the present invention. FIG. 1 is a diagram showing the configuration of a conventional electromagnetic brake. FIG. 1 is a diagram showing a conventional electromagnetic brake with an external over-excitation circuit. FIG. 1 is a diagram showing a conventional electromagnetic brake with an external over-excitation circuit.

One embodiment of the present invention will be described below with reference to the drawings.

Figures 1 and 2 show the yoke 1 portion of the electromagnetic brake configuration shown in Figure 8. In explaining this embodiment, Figure 8 will be used as appropriate, as it is the prerequisite configuration of the electromagnetic brake.

The yoke 1 is cylindrical with a bottom, has an annular gap 13 between the inner wall 11 and the outer wall 12, and has a through hole 14 inside the inner wall 11 for inserting a shaft. A coil bobbin 20 wound with a copper wire coil 2 is housed in the annular gap 13, and a rotating shaft is inserted into the through hole 14. The coil bobbin 20 is annular with a U-shaped opening on the outer periphery, and is made of a resin material.

The inner peripheral wall 11 and the outer peripheral wall 12 of the yoke 1, including the bottom wall 15, are made of iron core material and form a magnetic path through which magnetic flux passes. The end face (top face) on the opposite side of the bottom wall 15 is the attraction surface 1a of the armature 4 shown in Figure 8, and the armature 4 is attracted to the attraction surface 1a by connecting the magnetic path through the armature 4.

In order to supply power to the coil 2 from the outside, a pull-in portion 12a of the power supply path L is provided on the outer wall 12 of the yoke 1, and the power supply wiring 2a is pulled in from here. The illustrated pull-in portion 12a uses a groove provided to avoid interference with other parts, but if such grooves are provided in multiple locations, an appropriate groove can be used, or there may be no such groove at all, and only a hole can be provided in the outer wall 12 as the wiring pull-in portion.

An over-excitation circuit 7, shown in FIG. 3, is provided in the middle of the power supply path L. This over-excitation circuit 7 temporarily puts the excitation of the yoke 1 into an over-excitation state, allowing the initial movement of the armature 4 to be performed appropriately when the brake is released, and includes a voltage conversion unit 7a and a voltage switching timing control unit 7b.

The voltage conversion unit 7a converts the input voltage into a lower output voltage and passes it through the coil. It is configured to include a PWM control circuit using an operational amplifier, etc., and creates an output voltage that is artificially lower than the input voltage through pulse width conversion of the stepped input voltage. In the illustrated example, 24V is converted to 5V, but the input voltage may be other than 24V, and the output voltage may be, for example, 5 to 12V. The voltage switching timing control unit 7b performs a switching operation to output the input voltage (e.g., 24V) for a predetermined overexcitation period after the voltage is applied, and then switch to the voltage (e.g., 5V) converted by the voltage conversion unit 7a after the overexcitation period has elapsed, and outputs the voltage. It is configured using the time constant of an RC circuit, etc.

In the past, this over-excitation circuit 7 was attached externally to the electromagnetic brake MB as shown in Figures 8 to 10, which caused problems with the space required for placement. In light of this, in this embodiment, as shown in Figures 1 and 2, the board 7x on which this over-excitation circuit 7 is mounted is integrated into the yoke 1. In doing so, the over-excitation circuit 7 is easily affected by thermal and electromagnetic influences, and so the circuit has been carefully designed to be incorporated into the yoke 1.

Specifically, a part of the outer peripheral wall 12 of the yoke 1 is removed from the suction surface 1a toward the bottom wall 15 to form a notched recess 16, and a substrate 7x carrying an over-excitation circuit 7 is attached to the bottom surface 16a of the recess 16 by stacking it flat so that it is in close contact with the yoke 1 via a heat dissipation sheet 17 made of a common heat dissipation material.

In this state, a pair of input terminals of the over-excitation circuit 7 shown in FIG. 3 are connected to 24V wires 2a drawn from an external power source, for example, part of the drive power source of a motor (e.g., the drive power source of a robot) which is the device to which this electromagnetic brake is applied, and a pair of output terminals are connected to the coil 2 housed in the coil bobbin 20.

Then, in this state, resin made of a general material used for molding is poured into the annular gap 13 and the recess 16, forming a resin molded layer 8 (see FIG. 1(b)), which integrates the base 7x and the coil 2 into the yoke 1.

When the electromagnetic brake MB is assembled with the yoke 1 configured in this way, it operates as a non-excitation type electromagnetic brake, in that when it is not excited, it urges the armature 4 shown in FIG. 8 in a direction away from the yoke 1 using a braking means 3 such as a coil spring to activate the brake, and when a voltage is applied to the coil 2 to release the brake, it increases the initial excitation force at the time of brake release to effectively initiate the armature 4, and after the armature 4 is attracted to the attraction surface 1a, it switches to normal excitation to appropriately maintain the attraction state of the armature 4. This switching of operating states is repeated each time the 24V brake release command is turned ON/OFF.

As described above, the electromagnetic brake of this embodiment employs a configuration in which current is passed through the coil 2 through the over-excitation circuit 7 to excite the yoke 1, and the board 7x carrying the over-excitation circuit 7 is resin-molded to the yoke 1 together with the coil 2. In this way, by integrating the over-excitation circuit 7 with the yoke 1, the electromagnetic brake MB can be made more compact. Furthermore, since the over-excitation circuit 7 includes electronic components and is therefore susceptible to thermal effects, by resin-molding the board 7x carrying this circuit together with the coil 2 to the yoke 1, the heat dissipation through the resin mold layer 8 can reduce the thermal load on the over-excitation circuit 7.

In addition, in this embodiment, when continuous current is applied to release the brake, the heat dissipation effect from the resin molded layer 8 alone may be insufficient. Therefore, the base 7x is attached to the yoke 1 (specifically, the bottom surface 16a of the recess 16 provided in the yoke 1) via the heat dissipation sheet 17, thereby dissipating heat to the yoke 1. This ensures another heat dissipation path with a higher heat dissipation effect in addition to the heat dissipation from the resin molded layer 8, so that the effects of thermal load can be more effectively reduced even if the base 7x is provided integrally with the yoke 1.

In addition, in this embodiment, when the over-excitation circuit 7 is exposed to electromagnetic waves, the circuit acts as an antenna to receive the electromagnetic waves, which can adversely affect the function of the over-excitation circuit. In consideration of this, a recess 16 is provided in the outer wall 12 of the yoke 1 at the outer periphery of the coil 2, and a base 7x is placed within the recess 16, thereby ensuring that electromagnetic waves are less likely to reach the base 7x.

In particular, the over-excitation circuit 7 of this embodiment creates a normal excitation state by PWM control, and since it uses digital components and is susceptible to the effects of electromagnetic waves, the above-mentioned electromagnetic wave countermeasures are particularly effective.

Although one embodiment of the present invention has been described above, the specific configuration of each part is not limited to the above-described embodiment. Below, modified examples of the present invention are described.

In the above embodiment, a recess 16 is provided in the outer peripheral wall 12 of the yoke 1 located at the outer periphery of the coil 2, and the base 7x is placed flat. However, as shown in FIG. 4(a), a vertical hole-shaped recess 116 may be provided in the outer periphery 12 of the yoke 1 located at the outer periphery of the coil 2, and the base 7x may be inserted vertically together with the heat dissipation sheet 17 to be in close contact with the outer peripheral wall 12 of the yoke 1.

Alternatively, as shown in FIG. 4(b), a recess 216 may be provided in the bottom wall 15 of the yoke 1 below the coil 2 (coil bobbin 20), and the base 7x may be attached to the recess 216 together with the heat dissipation sheet 17 in a flat position in close contact with the bottom wall 15.

Alternatively, as shown in FIG. 4(c), a vertical hole-shaped recess 316 may be provided in the inner peripheral wall 11 of the yoke 1 located at the inner circumference of the coil 2, and the base 7x may be inserted vertically together with the heat dissipation sheet 17 to be in close contact with the inner peripheral wall 11 of the yoke 1.

In either case, in addition to the heat dissipation effect from the resin molding that is performed afterwards, a heat dissipation effect from the part that is in close contact with the yoke 1 to the yoke 1 can be expected.

Also, as shown in FIG. 5(a), the base 7x may be fixed to the yoke 1 via a fastener 71 made of metal or the like and having high thermal conductivity. Specifically, a recess 16 is provided on the top surface of the yoke 1 and the fastener 71 is press-fitted into the yoke 1, while a hole 72 is provided in the base 7x and the large diameter part of the hole 72 is passed over the head of the fastener 71 so that the base 7x is placed flat on the yoke 1 together with the heat dissipation sheet 17, and then the base 7x is slid to move the fastener 71 relatively toward the small diameter part, thereby preventing the base 7x from coming loose.

When resin molding is cooled, the resin shrinks and the adhesion of the base 7x to the yoke 1 via the heat dissipation sheet 17 is easily lost. However, by using the above-mentioned highly heat-conductive fastener 71, the adhesion of the base 7x to the yoke 1 can be ensured after resin molding, and a new heat dissipation route to the yoke 1 through the fastener 71 can also be formed.

In this case, one end of the base 7x may be fixed in contact with the side wall 16a of the recess 16, and the other end of the base 7x may be fastened at one point with a fastener. Also, as shown in FIG. 5(b), two or more points of the base 7x may be fixed to the yoke 1 with fasteners 71 in the form of screws. Alternatively, the fasteners 71 in FIG. 5(a) and the fasteners 71 in FIG. 6(a) may be combined.

As shown in Figure 6, it is also effective to place an electromagnetic wave shielding wall 9 made of a material that blocks electromagnetic waves between the coil 2 and the base 7x.

By arranging such an electromagnetic wave shielding wall 9, the electromagnetic waves emitted from the winding part (core part) of the yoke 1 and the coil 2 can be blocked by the electromagnetic wave shielding wall 9, and the influence of the electromagnetic waves on the over-excitation circuit 7 mounted on the board 7x can be effectively reduced. In this case, the board 7x can be stacked flat in a recess 16 provided in the outer peripheral wall 12 of the yoke 1 as shown in FIG. 6(a), or it can be attached to its outer peripheral surface using the electromagnetic wave shielding wall 9 as shown in FIG. 6(b). In either case, it is effective to set the upper end of the electromagnetic wave shielding wall 9 to be higher than the board 7x.

Alternatively, even when the base 7x is placed in close contact with the bottom wall 15 of the yoke 1 via a heat dissipation sheet 17 as shown in FIG. 6(c), the heat dissipation effect can be improved by fixing the base 7x to the bottom wall 15 of the yoke 1 via a fastener 71 with high thermal conductivity such as metal, and electromagnetic wave measures can be taken by providing an electromagnetic wave blocking wall 9 wider than the base 7x under the coil bobbin 20 to block electromagnetic waves.

Alternatively, in the above embodiment, the base 7x is attached to the yoke 1 via the heat dissipation sheet 17, but if, for example, the electromagnetic brake is not frequently switched on and off and high heat dissipation is not required, a flange 20a may be provided on the coil bobbin 20, this flange 20a may be placed in the recess 16 of the yoke 1, and the base 7x may be attached to this flange 20a via a foamed double-sided tape 117, as shown in Figures 7(a) and (b). Even in this case, heat dissipation from the resin mold layer 8 can be expected by subsequent resin molding.

However, doing so would result in an irregular shape of the coil bobbin 20, which would increase the amount of resin used during molding and the associated costs. Therefore, in terms of moldability and ease of quality control of the bobbin, it is preferable to attach the base 7x without changing the shape of the coil bobbin 20, as in the above embodiment. If there is a protrusion such as the flange 20a at the base attachment point, this could cause winding problems (scratches or breaks) in the coil 2.

Other configurations can also be modified in various ways without departing from the spirit of the present invention.

1... yoke 2... coil 3... damping means (coil spring)
7: over-excitation circuit 8: resin mold layer 9: electromagnetic shielding wall 16: recess 17: heat dissipation sheet 71: fastener L: power supply path

Claims (5)

A brake device comprising: a yoke; a coil for exciting the yoke by receiving power from an external source via a power supply path; and a braking means, and further comprising an over-excitation circuit disposed in the power supply path for temporarily over-exciting the yoke; and configured to switch between ON/OFF states of a brake by a braking force by the braking means and an excitation force via the power supply path,
an electromagnetic brake, characterized in that a board on which the over-excitation circuit is mounted is integrated with the yoke together with the coil by resin molding. The electromagnetic brake of claim 1, in which the base is in close contact with the yoke via a heat dissipation sheet. The electromagnetic brake according to claim 2, wherein the base is fixed to the yoke via a highly heat-conductive fastener. An electromagnetic brake according to any one of claims 1 to 3, in which a recess is provided in the yoke at the outer periphery of the coil, and the base is disposed within the recess. An electromagnetic brake according to any one of claims 1 to 4, in which an electromagnetic wave blocking wall is disposed between the coil and the base.

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