JP6879159B2 - Eddy current speed reducer - Google Patents

Description

The present invention relates to a speed reducing device mounted as an auxiliary brake on a vehicle such as a truck or a bus. In particular, the present invention relates to an eddy current type speed reducer (hereinafter, also simply referred to as “speed reduction device”) using a permanent magnet (hereinafter, also simply referred to as “magnet”) to generate a braking force.

Generally, an eddy current speed reducer includes a cylindrical braking member. The braking member is a rotor attached to the rotating shaft of the vehicle. Usually, a plurality of magnets facing the inner peripheral surface of the rotor are arranged around a rotation axis. A plurality of pole pieces are arranged around the rotation axis in the gap between the inner peripheral surface of the rotor and the magnet. The switching mechanism switches the position of the magnet with respect to the pole piece, switching between braking and non-braking.

During braking, the magnetic flux from the magnet reaches the rotor through the pole piece. That is, a magnetic circuit is formed between the magnet and the rotor. As a result, an eddy current is generated on the inner peripheral surface of the rotor that rotates integrally with the rotating shaft. As a result, braking torque acts on the rotor, and the rotation speed of the rotating shaft decreases. On the other hand, when not braking, the magnetic flux from the magnet does not reach the rotor. That is, no magnetic circuit is formed between the magnet and the rotor. Therefore, no eddy current is generated on the inner peripheral surface of the rotor, and no braking torque is generated.

During braking, the rotor generates heat as the eddy current is generated. When the rotor generates heat, the magnet is heated by the radiant heat from the rotor. This is because the rotor surrounds the magnet. When the magnet is overheated, the magnetic force possessed by the magnet decreases, and the performance of the speed reducer deteriorates. Therefore, a plurality of fins are provided on the outer peripheral surface of the rotor. The fins efficiently release the heat generated in the rotor to the outside.

Here, when the vehicle is normally traveling, that is, when not braking, the fins rotate integrally with the rotor. Since the fins are exposed to the outside, it becomes a resistance that hinders the smooth rotation of the rotor (rotating shaft). Rotational resistance due to fins is also called wind loss. If the wind damage increases, it will lead to a decrease in fuel efficiency. Therefore, the speed reducer is required to suppress wind damage caused by the fins.

The technique for suppressing wind damage is disclosed in, for example, Jitsukaihei 7-3286 (Patent Document 1) and JP-A-5-308770 (Patent Document 2). In the conventional speed reducing device disclosed in Patent Document 1, a plurality of covers are arranged so as to cover the rotor provided with fins from the outer peripheral side. Each cover is movable so as to flip outward in the radial direction of the rotor. When not braking, each cover covers the fins. Therefore, wind damage due to fins can be reduced. On the other hand, during braking, each cover pops up and the fins are exposed to the outside. Therefore, the heat dissipation performance of the fins can be ensured.

In the conventional speed reducing device disclosed in Patent Document 2, a cylindrical cover is arranged so as to cover the rotor provided with fins from the outer peripheral side. The cover is slidable in the direction of rotation. When not braking, the cover covers the fins. Therefore, wind damage due to fins can be reduced. On the other hand, during braking, the cover slides and the fins are exposed to the outside. Therefore, the heat dissipation performance of the fins can be ensured.

Jikkenhei 7-3286 Japanese Unexamined Patent Publication No. 5-308770

In the conventional speed reducer disclosed in Patent Document 1, a plurality of covers cover the entire area in the rotation axis direction of the rotor from the outer peripheral side. Then, in order to secure the range of motion of each cover in the radial direction, the device itself expands in the radial direction. In the conventional speed reducer disclosed in Patent Document 2, the cover covers the entire area in the rotation axis direction of the rotor from the outer peripheral side. Then, in order to secure the range of motion of the cover in the rotation axis direction, the device itself expands in the rotation axis direction. That is, in the conventional speed reducing device, the expansion of the device itself becomes a problem. This is because the space in which the reduction gear is mounted is limited in the vehicle.

An object of the present invention is to provide an eddy current type speed reducer capable of suppressing wind damage and ensuring heat dissipation performance while suppressing expansion of the device itself.

The eddy current speed reducer according to the embodiment of the present invention includes a cylindrical rotor, a plurality of fins, a plurality of permanent magnets, a switching mechanism, a disk-shaped cover, and a cover switching mechanism. The rotor is attached to a rotating shaft and can rotate in one direction. The plurality of fins are provided on the outer peripheral surface of the rotor and are inclined with respect to the rotation direction of the rotor. The plurality of permanent magnets are arranged around the rotation axis so as to face each other with a gap from the inner peripheral surface of the rotor. The switching mechanism switches between a braking state in which a magnetic circuit is formed between the permanent magnet and the rotor, and a non-braking state in which a magnetic circuit is not formed between the permanent magnet and the rotor. The cover includes an outer peripheral edge located between the top surfaces of the fins and the roots of the fins in the radial direction of the rotor. The cover faces the end face of one of the two end faces of the rotor in the direction of the rotation axis with a gap, and can slide in the direction of the rotation axis with respect to the rotor. The cover switching mechanism moves the cover away from the rotor in the braking state and brings the cover closer to the rotor in the non-braking state. The cover is arranged on the side of the two ends in the rotation axis direction of each of the plurality of fins, on the side where the leading end in the rotation direction of the rotor exists.

According to the eddy current type speed reducer according to the embodiment of the present invention, it is possible to suppress wind damage and secure heat dissipation performance while suppressing the expansion of the device itself.

FIG. 1 is a perspective view showing a part of a model of the speed reducer used in the simulation analysis. FIG. 2 is a cross-sectional view schematically showing the main configuration of the speed reducer. FIG. 3 is a plan view of the rotor as viewed from the outer peripheral side. FIG. 4 is a diagram showing the results when the thermo-fluid analysis of the airflow is performed using the model shown in FIG. FIG. 5 is a cross-sectional view schematically showing a main configuration of a speed reducer according to an embodiment of the present invention. FIG. 6A is a cross-sectional view schematically showing a state when the speed reducing device shown in FIG. 5 is not braking. FIG. 6B is a cross-sectional view schematically showing a state at the time of braking by the speed reducing device shown in FIG. FIG. 7 is a perspective view showing an example of the arrangement of magnets in the speed reducer shown in FIG. FIG. 8A is a cross-sectional view schematically showing a state when the speed reducing device shown in FIG. 5 is not braking. FIG. 8B is a cross-sectional view schematically showing a state at the time of braking by the speed reducing device shown in FIG. FIG. 9 is a diagram showing an evaluation result regarding wind damage during non-braking. FIG. 10 is a diagram showing an evaluation result regarding heat dissipation performance during braking. FIG. 11 is a perspective view showing an example of the arrangement of magnets. FIG. 12A is a cross-sectional view schematically showing a state when the speed reducing device shown in FIG. 11 is not braking. FIG. 12B is a cross-sectional view schematically showing a state at the time of braking by the speed reducing device shown in FIG. FIG. 13 is a perspective view showing an example of an arrangement of magnets different from that of FIG.

In order to solve the above problems, the present inventors carried out various experiments and simulation analyzes, and repeated diligent studies. As a result, the following findings were obtained.

FIG. 1 is a perspective view showing a part of a model of the speed reducer used in the simulation analysis. FIG. 2 is a cross-sectional view schematically showing the main configuration of the speed reducer. FIG. 3 is a plan view of the rotor as viewed from the outer peripheral side. The cross section shown in FIG. 2 is a cross section along the rotation axis.

With reference to FIGS. 1 to 3, the cylindrical (drum-shaped) rotor 1 as a braking member is attached to the rotating shaft 10 via the arm 5 and the wheel 6 and integrated with the rotating shaft 10. The rotor 1 rotates in one direction integrally with the rotating shaft 10. A plurality of fins 8 are provided on the outer peripheral surface 1a of the rotor 1 in order to dissipate the heat generated in the rotor 1. Each fin 8 is inclined with respect to the rotation direction of the rotor 1. Each fin 8 rotates with the rotation of the rotor 1, and each fin 8 receives pressure from the air flow. The pressure received by each fin 8 becomes the resistance to rotation. It is considered that wind damage occurs when each fin 8 receives pressure from the air flow in this way.

FIG. 4 is a diagram showing the results when the thermo-fluid analysis of the airflow is performed using the model shown in FIG. The result shown in FIG. 4 represents the distribution of the gas pressure acting on the region A shown in FIG. With reference to FIGS. 3 and 4, each fin 8 does not receive uniform pressure over the entire area.

Of the two end portions 8a and 8b of each of the fins 8, the end portion (hereinafter, also referred to as “leading end portion”) 8a that precedes in the rotation direction of the rotor 1 receives a high pressure locally. Therefore, the rotational resistance of each fin 8 is highest at the leading end 8a of each fin 8. Therefore, in order to effectively suppress wind damage during non-braking, the gas pressure received by the leading end portion 8a of each fin 8 may be reduced. That is, the limited area including the leading end portion 8a of each fin 8 may be covered with a cover.

Further, the cover may be kept away from the rotor during braking, and the cover may be brought close to the rotor during non-braking. If the cover is away from the rotor during braking, gas (air) is introduced into each fin 8 from the outside through the inner and outer circumferences of the cover, and the heat dissipation performance of the fins 8 can be ensured.

The present invention has been completed based on the above findings.

The eddy current speed reducer according to the embodiment of the present invention includes a cylindrical rotor, a plurality of fins, a plurality of permanent magnets, a switching mechanism, a disk-shaped cover, and a cover switching mechanism. The rotor is attached to a rotating shaft and can rotate in one direction. The plurality of fins are provided on the outer peripheral surface of the rotor and are inclined with respect to the rotation direction of the rotor. The plurality of permanent magnets are arranged around the rotation axis so as to face each other with a gap from the inner peripheral surface of the rotor. The switching mechanism switches between a braking state in which a magnetic circuit is formed between the permanent magnet and the rotor, and a non-braking state in which a magnetic circuit is not formed between the permanent magnet and the rotor. The cover includes an outer peripheral edge located between the top surfaces of the fins and the roots of the fins in the radial direction of the rotor. The cover faces the end face of one of the two end faces of the rotor in the direction of the rotation axis with a gap, and can slide in the direction of the rotation axis with respect to the rotor. The cover switching mechanism moves the cover away from the rotor in the braking state and brings the cover closer to the rotor in the non-braking state. The cover is arranged on the side of the two ends in the rotation axis direction of each of the plurality of fins, on the side where the leading end in the rotation direction of the rotor exists.

According to the speed reducer of the present embodiment, the cover is in the state closest to the rotor when not braking. That is, it becomes difficult for gas (air) to be introduced into the leading end of each fin from the outside. Therefore, the gas pressure received by the leading end of each fin can be reduced. As a result, wind damage due to fins can be suppressed. On the other hand, when braking, the cover is in the state of being farthest from the rotor. That is, the leading end of each fin is opened to the outside. This facilitates the introduction of gas from the outside into the leading end of each fin. As a result, the heat dissipation performance of the fins can be ensured.

Further, according to the speed reducer of the present embodiment, the outer peripheral end of the disk-shaped cover does not protrude outward from the top surfaces of the plurality of fins in the radial direction of the rotor. Therefore, the expansion of the device itself can be suppressed.

In the speed reducer of the present embodiment, the distance from the central axis of the rotating shaft to the outer peripheral end of the cover is preferably the same as the distance from the central axis of the rotating shaft to the top surfaces of the plurality of fins. In other words, the cover faces the entire area of the plurality of fins in the direction of rotation of the rotor. In this case, as shown in Examples described later, wind damage can be suppressed most efficiently.

In the reduction gear of the present embodiment, the length in the rotation axis direction of the rotor is W, the distance between the cover in the non-braking state and the end face of the rotor facing the cover is C1, and the cover in the braking state. When the distance between the cover and the end face of the rotor facing the cover is C2, C1 / W is preferably 2.0% or less, and C2 / W is preferably 2.5% or more and 6.0% or less. As shown in Examples described later, when C1 / W is 2.0% or less, the resistance torque of the rotor in the non-braking state is 85% or less of the speed reducer (comparative example) without a cover, which depends on the fins. Wind damage can be significantly suppressed. Further, when C2 / W is 2.5% or more, sufficient heat dissipation performance in the braking state can be ensured. Further, when C2 / W is 6.0% or less, the slide range of the cover does not become too large, and it is possible to suppress the reduction gear from expanding in the rotation axis direction.

In a typical example, the cover switching mechanism includes at least three rods that slidably support the cover along the axis of rotation and a fluid pressure cylinder connected to the cover. The actuation of the fluid pressure cylinder causes the cover to slide relative to the rotor. This slide switches between a state in which the cover is away from the rotor and a state in which the cover is close to the rotor. In this case, the number of rods supporting the cover is not particularly limited as long as it is at least three. The main role of the rod is to guide the slide of the cover in a stable manner. The cross-sectional shape of the rod is not particularly limited. The cross-sectional shape of a practical rod is circular. The fluid pressure cylinder is an air cylinder, a hydraulic cylinder, or the like.

In a typical example, the speed reducer comprises a plurality of pole pieces, a magnet holding ring, and a housing. The plurality of pole pieces are provided in the gap between the rotor and the permanent magnet, and are arranged around the rotation axis. The magnet holding ring holds the permanent magnet. The housing rotatably supports the magnet holding ring around the axis of rotation and holds the pole piece. The switching mechanism includes a fluid pressure cylinder connected to a magnet holding ring. By operating the fluid pressure cylinder, the magnet holding ring rotates with respect to the pole piece, and the position of the permanent magnet with respect to the pole piece is switched. The fluid pressure cylinder is an air cylinder, a hydraulic cylinder, or the like. The fluid pressure cylinder of the switching mechanism is different from the fluid pressure cylinder of the cover switching mechanism.

Hereinafter, embodiments of the eddy current type speed reducer of the present invention will be described in detail.

FIG. 5 is a cross-sectional view schematically showing a main configuration of a speed reducer according to an embodiment of the present invention. FIG. 6A is a cross-sectional view schematically showing a state when the speed reducing device is not braking. FIG. 6B is a cross-sectional view schematically showing a state at the time of braking by the speed reducing device. FIG. 7 is a perspective view showing an example of the arrangement of magnets in the speed reducer. FIG. 8A is a cross-sectional view schematically showing a state when the speed reducing device is not braking. FIG. 8B is a cross-sectional view schematically showing a state at the time of braking by the speed reducing device. The cross section shown in FIGS. 5 to 6B is a cross section along the rotation axis. The cross section shown in FIGS. 8A and 8B is a cross section perpendicular to the axis of rotation.

With reference to FIG. 5, the speed reducer includes a cylindrical rotor 1 and a stator 7 arranged inside the rotor 1. The rotor 1 corresponds to a braking member to which braking torque is applied. The rotor 1 is fixed to the rotating shaft 10 of the vehicle (eg, propeller shaft, drive shaft, etc.) via the arm 5 and the wheel 6. As a result, the rotor 1 rotates integrally with the rotating shaft 10. A plurality of fins 8 are provided on the outer peripheral surface 1a of the rotor 1. Each fin 8 is inclined at a predetermined angle (eg, in the range of 30 ° to 60 °) with respect to the rotation direction of the rotor 1 (see FIG. 3). The role of the fin 8 is to dissipate the heat generated in the rotor 1.

With reference to FIGS. 7 and 8A, the stator 7 includes a plurality of permanent magnets 3, a cylindrical magnet holding ring 2, a plurality of pole pieces 4, and a housing (not shown). The magnet holding ring 2 is arranged concentrically with the rotor. The magnet holding ring 2 is rotatably supported around a rotation axis by the housing. The housing is fixed to a non-rotating part of the vehicle (eg, a transmission cover) (not shown).

A plurality of permanent magnets 3 are fixed to the outer circumference of the magnet holding ring 2. The magnets 3 face the inner peripheral surface 1b of the rotor 1 with a gap, and are arranged around the rotation axis. The arrangement of the magnetic poles (N pole, S pole) of each magnet 3 is in the radial direction about the rotation axis. The arrangement of the magnetic poles of the magnets 3 adjacent to each other are alternately different.

With reference to FIG. 8A, a plurality of ferromagnetic pole pieces 4 are arranged in the gap between the inner peripheral surface 1b of the rotor 1 and the magnet 3. The pole pieces 4 are arranged around the axis of rotation. The arrangement angle of the pole piece 4 around the rotation axis coincides with the arrangement angle of the magnet 3 around the rotation axis. Each side of the pole piece 4 is held by a housing.

A lever (not shown) projects from the magnet holding ring 2 in parallel with the rotation axis. A piston rod of an air cylinder is connected to the lever via a link mechanism (not shown). An air cylinder corresponds to a fluid pressure cylinder. The air cylinder is fixed to the housing.

The air cylinder is powered by compressed air in response to a command from a control device (not shown). The operation of the air cylinder causes the piston rod to move forward and backward. As the piston rod moves forward and backward, the magnet holding ring 2 rotates, and the position of the magnet 3 with respect to the pole piece 4 is switched. As a result, braking and non-braking are switched.

With reference to FIGS. 5, 6A and 6B, the rotor 1 has two end faces 1c and 1d in the direction of rotation axis. In the following description, for convenience, one end surface 1c on the side where the leading end portion 8a of the fin 8 exists is also referred to as a first end surface. The other end face 1d is also referred to as a second end face. The disk-shaped cover 21 is arranged so as to face the first end surface 1c of the rotor 1 with a gap. The inner peripheral portion 21a of the cover 21 is recessed toward the housing of the stator 7. Three cylindrical holes 21b are provided in the inner peripheral portion 21a of the cover 21. The three cylindrical holes 21b are arranged on the same circumference at regular intervals.

From the housing, the three rods 23 project parallel to the rotating shaft 10 so as to correspond to the positions of the three cylindrical holes 21b. The rod 23 includes a shaft portion 23a having a circular cross section and a flange portion 23b. Each shaft portion 23a is inserted into each cylindrical hole 21b of the cover 21. As a result, the cover 21 is slidably supported in the direction of the rotation axis 10. When the cover 21 is closest to the rotor 1, that is, in the non-braking state, the inner peripheral portion 21a of the cover 21 contacts the housing of the stator 7 over the entire circumferential direction. As a result, the region closer to the rotation shaft 10 than the inner peripheral portion 21a of the cover 21 is closed to the outside. When the cover 21 is farthest from the rotor 1, that is, in the braking state, a gap is formed between the inner peripheral portion 21a of the cover 21 and the housing of the stator 7. As a result, a region closer to the rotation shaft 10 than the inner peripheral portion 21a of the cover 21 is opened to the outside.

The cover 21 includes an outer peripheral end 22. In the radial direction of the rotor 1, the outer peripheral end 22 is located between the top surfaces 8c of the plurality of fins 8 and the roots 8d of the plurality of fins 8. Since the plurality of fins 8 are provided on the outer peripheral surface 1a of the rotor 1, the roots 8d of the plurality of fins 8 correspond to the outer peripheral surface 1a of the rotor 1. According to such a configuration, at least a part of the cover 21 faces the plurality of fins 8 in the rotation axis direction. Therefore, in the non-braking state, at least a part of the cover 21 covers the leading end portion 8a of the plurality of fins 8. As a result, wind damage in the non-braking state can be suppressed.

The effect of suppressing wind damage depends on the size of the region where the cover 21 faces the plurality of fins 8 in the rotation axis direction. If the cover 21 faces the entire region of the plurality of fins 8 in the rotation axis direction, the effect of suppressing wind damage is maximized. If the outer peripheral end 22 of the cover 21 is located outside the top surfaces 8c of the plurality of fins 8 in the radial direction of the rotor 1, the cover 21 can face the entire region of the plurality of fins 8 in the rotation axis direction. However, if the outer peripheral end 22 of the cover 21 is also located on the outer side of the top surfaces 8c of the plurality of fins 8, the speed reducer expands in the radial direction of the rotor 1. From this, in order to maximize the effect of suppressing wind damage and suppress the expansion of the reduction gear, the outer peripheral end 22 of the cover 21 is the same as the top surface 8c of the plurality of fins 8 in the radial direction of the rotor 1. The position is preferable. In other words, the distance L from the central axis Y of the rotating shaft 10 to the outer peripheral end 22 of the cover 21 is the same as the distance R from the central axis Y of the rotating shaft 10 to the top surfaces 8c of the plurality of fins 8. preferable.

As described above, in the present embodiment, the limited area near the leading end portion 8a of each fin 8 is covered by the cover 21 when not braking.

A piston rod of an air cylinder (not shown) is connected to the cover 21. This air cylinder is different from the air cylinder for rotating the magnet holding ring 2 described above. An air cylinder corresponds to a fluid pressure cylinder. The air cylinder is fixed to the non-rotating part.

The operation of the air cylinder causes the piston rod to move forward and backward in the direction of the rotation axis. As the piston rod moves forward and backward, the cover 21 slides in the direction of the rotation axis with respect to the rotor 1, and the relative positions of the cover 21 and the rotor 1 are switched. As a result, the cover 21 is switched between a state in which the cover 21 is moved away from the rotor 1 and a state in which the cover 21 is moved closer to the rotor 1.

When not braking, as shown in FIG. 8A, the pole piece 4 evenly straddles the adjacent magnets 3. In this state, no braking torque is generated.

The magnetic flux from the magnet 3 during non-braking is in the following situation. With reference to FIG. 8A, the magnetic flux emitted from the north pole of one of the magnets 3 adjacent to each other reaches the south pole of the other magnet 3 after passing through the pole piece 4. The magnetic flux emitted from the north pole of the other magnet 3 reaches the south pole of one magnet 3 through the magnet holding ring 2. That is, no magnetic circuit is formed between the magnet 3 and the rotor 1. Therefore, no braking torque is generated in the rotor 1 that rotates integrally with the rotating shaft 10.

Further, when not braking, the cover 21 is in the state closest to the rotor 1 as shown in FIG. 6A. Then, the cover 21 prevents the introduction of air into the leading end portion 8a of each fin 8. As a result, less air is introduced into the leading end portion 8a of each fin 8. Therefore, the gas pressure received by the leading end portion 8a of each fin 8 can be reduced. As a result, wind damage due to the fins 8 can be suppressed.

On the other hand, during braking, as shown in FIG. 8B, the magnet holding ring 2 rotates about half of the arrangement angle of the magnet 3 from the non-braking state. In this case, the pole piece 4 completely overlaps the magnet 3.

The magnetic flux from the magnet 3 during braking is in the following situation. With reference to FIG. 8B, the magnetic flux emitted from the north pole of one of the magnets 3 adjacent to each other penetrates the pole piece 4 and reaches the rotor 1. The magnetic flux that reaches the rotor 1 reaches the S pole of the other magnet 3 through the pole piece 4. The magnetic flux emitted from the north pole of the other magnet 3 reaches the south pole of one magnet 3 through the magnet holding ring 2. That is, a magnetic circuit by the magnet 3 is formed between the magnets 3 adjacent to each other in the circumferential direction, the magnet holding ring 2, the pole piece 4, and the rotor 1. Such a magnetic circuit is formed over the entire circumferential direction by alternately reversing the direction of the magnetic flux. In this case, an eddy current is generated on the inner peripheral surface of the rotor 1. As a result, a braking torque in the direction opposite to the rotation direction is generated in the rotor 1 that rotates integrally with the rotation shaft 10. Further, the rotor 1 generates heat.

Further, during braking, as shown in FIG. 6B, the cover 21 slides from the non-braking state. Then, the inner peripheral portion 21a (cylindrical hole 21b) of the cover 21 comes into contact with the flange portion 23b of the rod 23, and is in a state of being farthest from the rotor 1. As a result, air is introduced into each fin 8 from the outside through the open end of the inner circumference of the cover 21. As a result, the heat dissipation performance of the fin 8 can be ensured. The heat generated in the rotor 1 is released to the outside from each fin 8.

A thermo-fluid analysis was performed to confirm the effect of the speed reducer of this embodiment.

[Test condition]
An analysis model of the speed reducer provided with the cover shown in FIG. 5 was created. The distance L from the central axis of the rotating shaft to the outer peripheral edge of the cover is the same as the distance R from the central axis of the rotating shaft to the top surfaces of the plurality of fins. In the analysis, the distance C1 between the cover in the non-braking state and the end face of the rotor facing the cover, and the distance C2 between the cover in the braking state and the end face of the rotor facing the cover were variously changed. As a comparative example, a speed reducer without a cover was assumed.

The main characteristics used in the analysis are as follows.
・ Rotor rotation speed: 3000 rpm
-Length in the direction of the rotor rotation axis W: 1.000
-Rotor outer radius including fins R: 2.552
Here, the numerical values of the characteristics W and R for which the unit is not described represent the ratio with the length W in the rotor rotation axis direction as the reference 1.000.

[Evaluation method]
The wind damage caused by the fins during non-braking and the heat dissipation performance of the fins during braking were evaluated. For the evaluation of wind damage, the resistance torque generated in the rotor when all fins receive pressure from the airflow was calculated. The lower the resistance torque, the better the suppression of wind damage. Therefore, the wind loss can be evaluated by comparing the resistance torques. In the analysis for evaluating wind damage, assuming a non-braking state, the inner peripheral portion of the cover is brought into contact with the housing of the stator, and the region closer to the rotation axis than the inner peripheral portion of the cover is directed to the outside. And closed it.

In order to evaluate the heat dissipation performance, the average heat transfer coefficient of the surface (all fins and the outer peripheral surface of the rotor) exposed on the outer peripheral side of the rotor was calculated. Here, the integrated value of the average heat transfer coefficient of the exposed surface and the total area of the exposed surface indicates the amount of heat radiated from the exposed surface. The larger the amount of heat radiation, the better the heat dissipation performance. In this analysis, since the total area of the exposed surface is uniform, the larger the average heat transfer coefficient, the better the heat dissipation performance. Therefore, the heat dissipation performance can be evaluated by comparing the average heat transfer coefficient. In the analysis for evaluating the heat dissipation performance, the cover was slid to open the area closer to the rotation axis than the inner peripheral portion of the cover to the outside, assuming the state at the time of braking.

[result]
FIG. 9 is a diagram showing an evaluation result regarding wind damage during non-braking. FIG. 10 is a diagram showing an evaluation result regarding heat dissipation performance during braking. In FIG. 9, the horizontal axis shows the ratio C1 / W of the distance C1 between the cover and the end face of the rotor facing the cover in the non-braking state with respect to the length W in the rotation axis direction of the rotor. The vertical axis shows the resistance torque, which is an index of wind damage. The numerical value of the resistance torque on the vertical axis indicates the ratio (%) to the resistance torque of the comparative example (without cover). In FIG. 10, as in FIG. 9, the horizontal axis shows the ratio C2 / W of the distance C2 between the cover and the end face of the rotor facing the cover in the braking state with respect to the length W in the rotation axis direction of the rotor. .. The vertical axis shows the average heat transfer coefficient, which is an index of heat dissipation performance. The numerical value of the average heat transfer coefficient on the vertical axis of FIG. 10 indicates the ratio (%) to the average heat transfer coefficient of the comparative example (without cover).

With reference to FIG. 9, if C1 / W was about 2.4%, the resistance torque was about 85% of the comparative example. When C1 / W was about 1.2%, the resistance torque was about 80% of the comparative example. When C1 / W was about 0.6%, the resistance torque was about 78% of the comparative example. From this, it was found that the resistance torque is suppressed as the cover is brought closer to the rotor during non-braking, and the wind damage due to the fins can be suppressed.

If the wind loss is to be remarkably suppressed as compared with the comparative example, the resistance torque is preferably 85% or less of the comparative example. Therefore, C1 / W in the non-braking state is preferably 2.0% or less. More preferably, C1 / W in the non-braking state is 1.0% or less. The lower limit of C1 / W is not particularly limited. This is because the smaller the C1 / W in the non-braking state, the more the wind damage can be suppressed. However, if C1 / W is too small, the distance between the cover and the rotor is too close, and the cover may interfere with the rotor. Therefore, C1 / W is preferably 0.5% or more.

With reference to FIG. 10, when C2 / W was about 1.2%, the average heat transfer coefficient was about 85% of the comparative example. When C2 / W was about 2.4%, the average heat transfer coefficient was about 95% of the comparative example. When C2 / W was about 5.8%, the average heat transfer coefficient was almost the same as that of the comparative example. That is, when C2 / W is about 6.0% or more, the heat dissipation performance is equivalent to that of a speed reducer without a cover, that is, a speed reducer in which the rotor fins are completely open. From this, it was found that the average heat transfer coefficient increases as the cover is moved away from the rotor during braking, and the heat dissipation performance is high.

In order to ensure heat dissipation performance, the average heat transfer coefficient is preferably 85% or more of the comparative example. Therefore, the C2 / W in the braking state is preferably 1.0% or more. More preferably, the C2 / W in the braking state is 2.5% or more. The upper limit of C2 / W is not particularly limited. This is because the larger the C2 / W in the braking state, the higher the heat dissipation performance. However, if C2 / W is about 6.0% or more, the heat dissipation performance will not be further improved. Further, when C2 / W is about 6.0% or more, the slide range of the cover is large and the reduction gear expands in the rotation axis direction. Therefore, preferably, C2 / W is 6.0% or less.

The embodiment of the present invention has been described above. However, it goes without saying that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

In the above-described embodiment, the case where the magnetic poles of the magnets are arranged in the radial direction of the rotating shaft has been described. However, the arrangement of the magnetic poles of the speed reducer of the present embodiment is not limited to this.

FIG. 11 is a perspective view showing an example of the arrangement of magnets. The plurality of magnets 3 are arranged around the axis of rotation. The arrangement of the magnetic poles of the magnet 3 is in the circumferential direction of the rotation axis. The arrangement of the magnetic poles of the magnets 3 adjacent to each other are alternately different.

FIG. 12A is a cross-sectional view schematically showing a state when the speed reducing device shown in FIG. 11 is not braking. The magnetic flux from the magnet 3 during non-braking is in the following situation. When not braking, the pole piece 4 completely overlaps the magnet 3. The magnetic flux emitted from the north pole of one magnet 3 reaches the south pole of the same magnet 3 after passing through the pole piece 4 or the magnet holding ring 2. That is, no magnetic circuit is formed between the magnet 3 and the rotor 1. Therefore, no braking torque is generated in the rotor 1 that rotates integrally with the rotating shaft 10.

FIG. 12B is a cross-sectional view schematically showing a state at the time of braking by the speed reducing device shown in FIG. During braking, as shown in FIG. 12B, the magnet holding ring 2 rotates about half the arrangement angle of the magnet 3 from the non-braking state. The magnetic flux from the magnet 3 during braking is in the following situation. The magnetic flux emitted from the north pole of one magnet 3 penetrates the pole piece 4 and reaches the rotor 1. The magnetic flux that reaches the rotor 1 reaches the S pole of the same magnet 3 through the pole piece 4. That is, a magnetic circuit by one magnet 3 is formed between the pole piece 4 and the rotor 1. As a result, a braking torque in the direction opposite to the rotation direction is generated in the rotor 1 that rotates integrally with the rotation shaft 10. A part of the magnetic flux emitted from the north pole of one magnet 3 reaches the south pole of the same magnet 3 after passing through the magnet holding ring 2.

FIG. 13 is a perspective view showing an example of an arrangement of magnets different from that of FIG. The plurality of magnets 3 are arranged in the axial direction of the rotation axis. The arrangement of the magnetic poles of the magnet 3 is in the axial direction of the rotation axis. The arrangement of the magnetic poles of the magnets 3 adjacent to each other in the axial direction of the rotation axis is alternately different. Further, the plurality of magnets 3 are also arranged in the circumferential direction of the rotation axis. The magnetic pole arrangements of the adjacent magnets 3 in the circumferential direction of the rotation axis are alternately different. In this case, not only can the braking torque be generated in the first row R1 in which the positions of the rotating shafts in the axial direction are the same, but also the braking torque can be generated in the second row R2. Therefore, the braking torque can be adjusted arbitrarily. The number of rows of magnets in the axial direction of the rotation axis is not limited to two, and may be three or more.

The present invention is useful for eddy current speed reducers using permanent magnets.

1 Rotor 1a Outer peripheral surface of rotor 1b Inner peripheral surface of rotor 1c End surface of rotor (first end surface)
1d rotor end face (second end face)
2 Magnet holding ring 3 Permanent magnet 4 Pole piece 5 Arm 6 Wheel 7 Stator 8 Fin 8a Fin end (leading end)
8b Fin end 8c Fin top surface 8d Fin root 10 Rotating shaft 21 Cover 21a Inner circumference 21b Cylindrical hole 22 Outer peripheral end 23 Rod 23a Shaft 23b Flange

Claims (5)

A cylindrical rotor that is attached to the rotating shaft and can rotate in one direction,
A plurality of fins provided on the outer peripheral surface of the rotor and inclined with respect to the rotation direction of the rotor, and
A plurality of permanent magnets arranged around the rotation axis so as to face each other with a gap from the inner peripheral surface of the rotor.
A switching mechanism that switches between a braking state in which a magnetic circuit is formed between the permanent magnet and the rotor and a non-braking state in which a magnetic circuit is not formed between the permanent magnet and the rotor.
Includes an outer peripheral end located between the top surfaces of the plurality of fins and the roots of the plurality of fins in the radial direction of the rotor, and provides a gap with one end surface of the two end surfaces of the rotor in the rotation axis direction. A disk-shaped cover that faces the rotor and slides in the direction of the rotation axis with respect to the rotor.
A cover switching mechanism for moving the cover away from the rotor in the braking state and bringing the cover closer to the rotor in the non-braking state is provided.
The cover is an eddy current type speed reducer that is arranged on the side of the two ends of each of the plurality of fins in the rotation axis direction where the end that precedes the rotor in the rotation direction exists. The eddy current type speed reducer according to claim 1.
An eddy current speed reducer having the same distance from the central axis of the rotating shaft to the outer peripheral end of the cover as the distance from the central axis of the rotating shaft to the top surfaces of the plurality of fins. The eddy current type speed reducer according to claim 1 or 2.
The length of the rotor in the direction of the rotation axis is W, the distance between the cover in the non-braking state and the end face of the rotor facing the cover is C1, and the cover and the cover in the braking state. When the distance between the cover and the end face of the rotor facing the cover is C2,
An eddy current type speed reducer having C1 / W of 2.0% or less and C2 / W of 2.5% or more and 6.0% or less. The eddy current type speed reducer according to any one of claims 1 to 3.
The cover switching mechanism is
At least three rods that slidably support the cover in the direction of rotation, and
Including a fluid pressure cylinder connected to the cover.
An eddy current speed reducer in which the cover slides with respect to the rotor by the operation of the fluid pressure cylinder, and the cover is switched between a state in which the cover is moved away from the rotor and a state in which the cover is brought closer to the rotor. The eddy current type speed reducer according to any one of claims 1 to 4.
The speed reducer
A plurality of pole pieces provided in the gap between the rotor and the permanent magnet and arranged around the rotation axis, and
A magnet holding ring that holds the permanent magnet and
A housing that rotatably supports the magnet holding ring around the rotation axis and holds the pole piece is provided.
The switching mechanism includes a fluid pressure cylinder connected to the magnet holding ring.
An eddy current type speed reducer in which the magnet holding ring rotates with respect to the pole piece by the operation of the fluid pressure cylinder, and the position of the permanent magnet with respect to the pole piece is switched.

Images