JPH06103978B2 - Eddy current type speed reducer - Google Patents

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【産業上の利用分野】本発明は主として大型車両の摩擦
ブレーキを補助する渦電流式減速装置、特に軸方向寸法
を短縮できる渦電流式減速装置に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eddy current type speed reducer mainly for assisting a friction brake of a large vehicle, and more particularly to an eddy current type speed reducer capable of shortening an axial dimension.

【０００２】[0002]

【従来の技術】特願平1-218498号に係る渦電流式減速装
置は、制動ドラムの内部へ突出する固定枠に、周方向等
間隔に多数の永久磁石を結合する磁石支持環を軸方向移
動可能に支持してなり、磁石支持環を制動ドラムの内部
へ移動して、永久磁石が制動ドラムの内周面へ磁界を及
ぼす制動位置と、磁石支持環を制動ドラムから引退させ
て、永久磁石が制動ドラムの内周面へ磁界を及ぼさない
非制動位置とに切り換えられる。2. Description of the Related Art An eddy current type speed reducer according to Japanese Patent Application No. 1-218498 has a fixed frame projecting inside a braking drum and a magnet support ring for coupling a large number of permanent magnets at equal intervals in the circumferential direction in the axial direction. It is movably supported and moves the magnet support ring into the inside of the braking drum so that the permanent magnet applies a magnetic field to the inner peripheral surface of the braking drum and the magnet support ring is retracted from the braking drum. The magnet is switched to a non-braking position where no magnetic field is exerted on the inner peripheral surface of the braking drum.

【０００３】上述の渦電流式減速装置は固定枠の軸方向
寸法が長く、例えば車体床下の変速機の出力回転軸と推
進軸の接続部の狭い取付空間に、減速装置を駐車ブレー
キと一緒に配設するには種々の困難がある。また、制動
能力が大きな減速装置では、永久磁石の幅（制動ドラム
の軸方向寸法）を拡げる必要があるが、この場合は固定
枠だけでなく、磁石支持環を駆動する空圧アクチユエー
タもストロークの長いものが必要になるなど、変更する
部品が多く、重量やコストの点からも好ましくない。In the eddy current type speed reducer described above, the axial dimension of the fixed frame is long, and for example, the speed reducer together with the parking brake is installed in a narrow mounting space of the connecting portion between the output rotary shaft of the transmission and the propulsion shaft under the floor of the vehicle body. There are various difficulties in arranging. Also, in a reduction gear with a large braking ability, it is necessary to widen the width of the permanent magnets (the axial dimension of the braking drum), but in this case not only the fixed frame but also the pneumatic actuator that drives the magnet support ring can be used for the stroke. There are many parts to change, such as the need for long ones, which is not preferable in terms of weight and cost.

【０００４】[0004]

【発明が解決しようとする問題点】本発明の目的は上述
の問題に鑑み、磁石支持環を軸方向に移動しないで制動
と非制動の切換えを行うことにより装置の軸方向寸法を
短縮できる、渦電流式減速装置を提供することにある。SUMMARY OF THE INVENTION In view of the above problems, the object of the present invention is to reduce the axial size of the device by switching between braking and non-braking without moving the magnet support ring in the axial direction. An object is to provide an eddy current type speed reducer.

【０００５】[0005]

【問題点を解決するための手段】上記目的を達成するた
めに、本発明の構成は回転軸に結合した制動ドラムの内
部に非磁性材からなる不動の磁石支持環を配設し、磁石
支持環の内部に周方向等間隔に回転軸と平行な多数の円
筒状の空部を設け、磁石支持環の外周壁に空部に対応し
て強磁性体からなる磁極板を備え、空部に制動ドラムの
内周面に対する極性が周方向に交互に異なるように並ぶ
不動の永久磁石と空部で半回転し得る可動の永久磁石と
を収容し、各空部で可動の永久磁石の極性が不動の永久
磁石と同方向に並ぶ制動位置と、各空部で可動の永久磁
石の極性が不動の永久磁石と逆方向に並ぶ非制動位置と
に切り換える磁石回動手段を備えたものである。In order to achieve the above object, in the structure of the present invention, a stationary magnet support ring made of a non-magnetic material is provided inside a braking drum connected to a rotary shaft, and a magnet support is provided. A large number of cylindrical voids parallel to the axis of rotation are provided inside the ring at equal intervals in the circumferential direction, and a magnetic pole plate made of a ferromagnetic material is provided on the outer peripheral wall of the magnet support ring so as to correspond to the voids. The permanent magnets that are immovable and the movable permanent magnets that can be half-rotated in the empty space are housed so that the polarities of the inner surface of the braking drum are alternately arranged in the circumferential direction. A magnet rotating means is provided for switching between a braking position aligned in the same direction as the stationary permanent magnet and a non-braking position in which the polarities of the movable permanent magnets in each void are aligned in the opposite direction to the stationary permanent magnet.

【０００６】[0006]

【作用】本発明では、磁石支持環に多数の永久磁石を周
方向等間隔にかつ制動ドラムの内周面に対する磁極が交
互に異なるように固定し、半回転し得る可動の永久磁石
を不動の永久磁石と軸方向に並べて支持する。可動の永
久磁石の磁極が不動の永久磁石と同方向に並ぶ制動位置
では、周方向に隣接する不動の永久磁石と可動の永久磁
石がそれぞれ制動ドラムとの間に磁気回路を形成する。
回転する制動ドラムが磁界を横切る時制動ドラムに渦電
流が流れ、制動ドラムが制動力を受ける。According to the present invention, a large number of permanent magnets are fixed to the magnet support ring at equal intervals in the circumferential direction so that the magnetic poles with respect to the inner peripheral surface of the braking drum are different from each other, and the movable permanent magnet that can rotate half a turn is immovable. It is supported side by side with the permanent magnet in the axial direction. At the braking position where the magnetic poles of the movable permanent magnet are aligned in the same direction as the stationary permanent magnet, the stationary permanent magnet and the movable permanent magnet adjacent in the circumferential direction form a magnetic circuit between the braking permanent drum and the stationary permanent magnet.
When the rotating braking drum crosses the magnetic field, an eddy current flows in the braking drum, and the braking drum receives a braking force.

【０００７】一方、可動の永久磁石を半回転して磁極が
不動の永久磁石と逆方向に並ぶ非制動位置では、可動の
永久磁石と不動の永久磁石が磁石支持環の内部で短絡的
磁気回路を形成し、制動ドラムに磁界を及ぼさないの
で、制動ドラムは制動力を受けない。On the other hand, in the non-braking position where the movable permanent magnet is half-turned and the magnetic poles are arranged in the opposite direction to the stationary permanent magnet, the movable permanent magnet and the stationary permanent magnet are short-circuited in the magnet support ring. And does not exert a magnetic field on the braking drum, the braking drum receives no braking force.

【０００８】[0008]

【発明の実施例】図１は本発明による渦電流式減速装置
が車両用変速機の後端部に配設される実施例を示す側面
断面図である。歯車箱３の後端壁に軸受２により支持し
た出力回転軸４に、取付フランジ６がスプライン嵌合さ
れ、かつナツト５により締結される。取付フランジ６に
公知の駐車ブレーキの制動ドラム１０の端壁と減速装置
の制動ドラム１３の端壁１２（スポークでもよい）とが
重ね合され、ボルト８とナツト９により締結される。回
転軸４と公知の推進軸とを連結するための自在継手のヨ
ーク７が、取付フランジ６に嵌合され、かつ図示してな
いボルトにより結合される。制動ドラム１３は外周壁に
周方向等間隔に多数の冷却フイン１５を備えている。1 is a side sectional view showing an embodiment in which an eddy current type speed reducer according to the present invention is arranged at a rear end portion of a vehicle transmission. A mounting flange 6 is spline-fitted to an output rotary shaft 4 supported by a bearing 2 on the rear end wall of the gear box 3 and fastened by a nut 5. An end wall of a braking drum 10 of a known parking brake and an end wall 12 (may be a spoke) of a braking drum 13 of a speed reducer are superposed on the mounting flange 6 and fastened with a bolt 8 and a nut 9. A yoke 7 of a universal joint for connecting the rotary shaft 4 and a known propulsion shaft is fitted to the mounting flange 6 and is joined by a bolt (not shown). The braking drum 13 has a large number of cooling fins 15 on the outer peripheral wall at equal intervals in the circumferential direction.

【０００９】制動ドラム１３の内周面１４と制動ドラム
１０の外周面との間の空部に、多数の永久磁石３２，３
２ａを収容する磁石支持環２０が配設される。このた
め、歯車箱３の後端壁に取付板１６ａを介して、補強リ
ブを有する円形の枠板１６が固定され、枠板１６の板面
に断面Ｌ字形をなす環状の支板１９が固定される。支板
１９の板面に磁石支持環２０が固定され、支板１９の円
筒部に駆動環１７が回転可能に支持される。A large number of permanent magnets 32, 3 are provided in an empty space between the inner peripheral surface 14 of the braking drum 13 and the outer peripheral surface of the braking drum 10.
A magnet support ring 20 that houses 2a is arranged. Therefore, the circular frame plate 16 having reinforcing ribs is fixed to the rear end wall of the gear box 3 via the mounting plate 16a, and the annular support plate 19 having an L-shaped cross section is fixed to the plate surface of the frame plate 16. To be done. The magnet support ring 20 is fixed to the plate surface of the support plate 19, and the drive ring 17 is rotatably supported by the cylindrical portion of the support plate 19.

【００１０】磁石支持環２０は磁性体の内筒２５と非磁
性体の外筒２３との両端に、非磁性体の環状の端壁２
８，２９を結合してなり、かつ回転軸４と平行な回転軸
３１に結合した円柱形の永久磁石３２と不動の永久磁石
３２ａとを収容する多数の円筒状の空部２７を周方向等
間隔に備えている。可動の永久磁石３２と不動の永久磁
石３２ａは軸方向に並び、不動の永久磁石３２ａは空部
２７の周壁すなわち外筒２３と内筒２５に固定される。
回転軸３１は不動の永久磁石３２ａを貫通し、端壁２
８，２９に軸受により支持される。回転軸３１の左端に
歯車１８が結合され、かつ駆動環１７に形成した歯車１
７ａと噛み合される。The magnet support ring 20 is provided at both ends of an inner cylinder 25 made of a magnetic material and an outer cylinder 23 made of a non-magnetic material, and has an annular end wall 2 made of a non-magnetic material.
8 and 29 are coupled to each other, and a large number of cylindrical cavities 27 for accommodating a cylindrical permanent magnet 32 coupled to a rotary shaft 31 parallel to the rotary shaft 4 and a stationary permanent magnet 32a are formed in a circumferential direction or the like. Be prepared for the interval. The movable permanent magnet 32 and the stationary permanent magnet 32a are arranged in the axial direction, and the stationary permanent magnet 32a is fixed to the peripheral wall of the empty portion 27, that is, the outer cylinder 23 and the inner cylinder 25.
The rotary shaft 31 penetrates the stationary permanent magnet 32a, and the end wall 2
It is supported by bearings 8 and 29. The gear 18 is formed by connecting the gear 18 to the left end of the rotary shaft 31 and forming the drive ring 17.
7a is meshed.

【００１１】図２に示すように、磁石支持環２０の外筒
２３の永久磁石３２，３２ａと対向する部分に、強磁性
体の磁極板２１がそれぞれ結合される。磁極板２１は外
筒２３をアルミニウム合金などから鋳造する際に鋳込ま
れる。回転軸３１の１つは枠板１６に支持した電動機
（図示せず）の軸と連結される。電動機により回転軸３
１を半回転すると、駆動環１７が回転し、各空部２７で
各永久磁石３２の磁極の向きが永久磁石３２ａと反対に
なる。As shown in FIG. 2, a magnetic pole plate 21 made of a ferromagnetic material is coupled to each portion of the outer cylinder 23 of the magnet support ring 20 that faces the permanent magnets 32, 32a. The magnetic pole plate 21 is cast when the outer cylinder 23 is cast from an aluminum alloy or the like. One of the rotating shafts 31 is connected to the shaft of an electric motor (not shown) supported by the frame plate 16. Rotating shaft 3 by electric motor
When 1 is rotated a half turn, the drive ring 17 is rotated, and the magnetic poles of the permanent magnets 32 in the respective empty portions 27 are in the opposite direction to the permanent magnets 32a.

【００１２】図１に示すように、各空部２７において永
久磁石３２の磁極の向きが永久磁石３２ａの磁極と逆方
向に並んだ非制動状態では、永久磁石３２と磁極板２１
と永久磁石３２ａと内筒２５に鎖線で示す磁気回路が形
成される。つまり、磁石支持環２０の内部で短絡的磁気
回路が生じ、制動ドラム１３の内周面に磁界を及ぼさな
いので、制動ドラム１３は制動力を受けない。As shown in FIG. 1, in the non-braking state in which the magnetic poles of the permanent magnets 32 are aligned in the direction opposite to the magnetic poles of the permanent magnets 32a in each void 27, the permanent magnets 32 and the magnetic pole plate 21 are arranged.
A magnetic circuit indicated by a chain line is formed on the permanent magnet 32a and the inner cylinder 25. That is, since a short-circuit magnetic circuit is generated inside the magnet support ring 20 and no magnetic field is exerted on the inner peripheral surface of the braking drum 13, the braking drum 13 is not subjected to braking force.

【００１３】図２，３に示すように、電動機により各永
久磁石３２を半回転し、各空部２７において永久磁石３
２の磁極の向きが永久磁石３２ａの磁極と同方向に並ぶ
と、周方向に隣接する永久磁石３２と磁極板２１と制動
ドラム１３との間に図２に鎖線で示す磁気回路が形成さ
れ、同様に周方向に隣接する永久磁石３２ａと磁極板２
１と制動ドラム１３との間に磁気回路が形成される。回
転する制動ドラム１３が磁界を横切ると制動ドラム１３
に渦電流が流れ、制動ドラム１３が制動力を受ける。As shown in FIGS. 2 and 3, each permanent magnet 32 is half-turned by the electric motor, and each permanent magnet 3 is moved in each empty space 27.
When the two magnetic poles are aligned in the same direction as the magnetic poles of the permanent magnet 32a, a magnetic circuit shown by a chain line in FIG. 2 is formed between the permanent magnet 32, the magnetic pole plate 21, and the braking drum 13 which are circumferentially adjacent to each other. Similarly, the permanent magnet 32a and the magnetic pole plate 2 that are circumferentially adjacent to each other are
A magnetic circuit is formed between 1 and the braking drum 13. When the rotating braking drum 13 crosses the magnetic field, the braking drum 13
An eddy current flows through the brake drum 13, and the braking drum 13 receives the braking force.

【００１４】上述の実施例では、磁石回動手段は各回転
軸３１の歯車１８を、電動機により回転される駆動環１
７の歯車１７ａにそれぞれ噛み合せてなり、回転軸３１
を半回転することにより、減速装置の制動と非制動の切
換えを行うものであるが、図７に示すように、各回転軸
３１の歯車１８の相互間に、磁石支持環２０に支持した
小歯車１８ａを噛み合せ、回転軸３１の１つを枠板１６
に支板３５を介し支持した電動機３６により駆動しても
よい。また、歯車１８を互いに連動させるために、駆動
環１７の代りにコグベルトと称する無端歯付きベルトを
掛け回すか、歯車１８の代りに各回転軸３１に結合した
鎖車に無端チエーンを掛け回すか、各回転軸３１に結合
した腕をリンクにより環状に連結し、腕の１つを空圧ア
クチユエータにより揺動することにしてもよい。In the above-described embodiment, the magnet rotating means rotates the gear 18 of each rotating shaft 31 by the drive ring 1 rotated by the electric motor.
The gears 17a of the rotary shaft 31 are engaged with each other.
The rotation of the speed reducer is switched between braking and non-braking by rotating it halfway. However, as shown in FIG. The gear 18a is meshed and one of the rotary shafts 31 is connected to the frame plate 16
It may be driven by an electric motor 36 supported via a support plate 35. Further, in order to interlock the gears 18 with each other, an endless toothed belt called a cog belt is put around instead of the drive ring 17, or an endless chain is put around a chain wheel connected to each rotary shaft 31 instead of the gears 18. Alternatively, the arms connected to the respective rotary shafts 31 may be annularly connected by a link, and one of the arms may be swung by a pneumatic actuator.

【００１５】図４に示す実施例では、可動の永久磁石３
２と不動の永久磁石３２ａが円錐状をなし、永久磁石３
２，３２ａが接近する部分へ至るに従い磁極板２１が厚
くなつている。この構成によれば、制動力を大きくする
ために永久磁石３２，３２ａを軸方向に長くしても、非
制動時は磁石支持環２０の内部に安定した短絡的磁気回
路が生じ、制動ドラム１３への磁気洩れによる引摺りト
ルクを抑えることができる。In the embodiment shown in FIG. 4, the movable permanent magnet 3
2 and the stationary permanent magnet 32a form a conical shape, and the permanent magnet 3
The magnetic pole plate 21 becomes thicker as the portions 2 and 32a come closer to each other. According to this structure, even if the permanent magnets 32, 32a are lengthened in the axial direction in order to increase the braking force, a stable short-circuit magnetic circuit is generated inside the magnet support ring 20 during non-braking, and the braking drum 13 It is possible to suppress drag torque due to magnetic leakage to the.

【００１６】図５に示す実施例では、各空部２７に２組
の可動の永久磁石３２と不動の永久磁石３２ａとを交互
に並べたものである。この構成によれば、制動時は大き
な制動力が得られる一方、非制動時は磁石支持環２０の
内部に鎖線で示す安定した短絡的磁気回路が得られる。In the embodiment shown in FIG. 5, two sets of movable permanent magnets 32 and stationary permanent magnets 32a are alternately arranged in each void 27. According to this configuration, a large braking force is obtained during braking, while a stable short-circuit magnetic circuit indicated by a chain line is obtained inside the magnet supporting ring 20 during non-braking.

【００１７】図６に示すように、両端側に不動の永久磁
石３２ａを、中間部分に軸方向に長い可動の永久磁石３
２を設ければ、構成は簡単になり、制動時は大きな制動
力が、非制動時は磁気洩れのない安定した短絡的磁気回
路が得られる。As shown in FIG. 6, stationary permanent magnets 32a are provided at both ends, and a movable permanent magnet 3 having a long axial direction is provided at an intermediate portion.
If 2 is provided, the structure is simplified and a stable short-circuit magnetic circuit with a large braking force during braking and no magnetic leakage during non-braking can be obtained.

【００１８】[0018]

【発明の効果】本発明は上述のように、回転軸に結合し
た制動ドラムの内部に非磁性材からなる不動の磁石支持
環を配設し、磁石支持環の内部に周方向等間隔に回転軸
と平行な多数の円筒状の空部を設け、磁石支持環の外周
壁に空部に対応して強磁性体からなる磁極板を備え、空
部に制動ドラムの内周面に対する極性が周方向に交互に
異なるように並ぶ不動の永久磁石と空部で半回転し得る
可動の永久磁石とを収容し、各空部で可動の永久磁石の
極性が不動の永久磁石と同方向に並ぶ制動位置と、各空
部で可動の永久磁石の極性が不動の永久磁石と逆方向に
並ぶ非制動位置とに切り換える磁石回動手段を備えたも
のであり、制動と非制動の切換えが永久磁石の軸方向移
動によらず、永久磁石の回転（自転）で得られるので、
磁石支持環が制動ドラムの内部にコンパクトに収まり、
装置の軸方向寸法が従来例に比べて大幅に短縮され、車
両への搭載が容易になる。As described above, according to the present invention, the stationary magnet support ring made of a non-magnetic material is provided inside the braking drum connected to the rotating shaft, and the magnet support ring is rotated at equal intervals in the circumferential direction. A large number of cylindrical cavities parallel to the axis are provided, and a magnetic pole plate made of a ferromagnetic material is provided on the outer peripheral wall of the magnet support ring so as to correspond to the cavities. A stationary permanent magnet arranged alternately in different directions and a movable permanent magnet capable of half-rotation in the empty space are housed, and the polarity of the movable permanent magnet in each empty space is aligned in the same direction as the stationary permanent magnet. It is provided with a magnet rotating means for switching between a position and a non-braking position in which the polarities of the movable permanent magnets movable in each space are arranged in the opposite direction to the permanent magnets immovable, and switching between braking and non-braking is performed by the permanent magnet. Since it can be obtained by rotation (rotation) of the permanent magnet regardless of axial movement,
The magnet support ring fits compactly inside the braking drum,
The axial dimension of the device is greatly reduced compared to the conventional example, and the mounting on the vehicle becomes easy.

【００１９】従来例に比べて車両の取付空間に余裕がで
き、それだけ永久磁石を長くすることにより、制動力を
増大でき、また磁石回動手段の変更を要せず、制動力の
異なる減速装置を製造するのにコスト、重量などの点で
有利である。Compared with the conventional example, there is more space in the vehicle mounting space, and the braking force can be increased by lengthening the permanent magnets accordingly, and there is no need to change the magnet rotating means, so a reduction gear with different braking force can be obtained. Is advantageous in terms of cost, weight and the like.

【００２０】永久磁石の回動量を加減すれば、制動ドラ
ムに及ぼす磁界の強さが変化し、走行条件に応じて制動
力を制御できる。By adjusting the amount of rotation of the permanent magnet, the strength of the magnetic field exerted on the braking drum changes, and the braking force can be controlled according to the running conditions.

【図面の簡単な説明】[Brief description of drawings]

【図１】本発明に係る渦電流式減速装置の非制動状態を
示す側面断面図である。FIG. 1 is a side sectional view showing an eddy current type speed reducer according to the present invention in a non-braking state.

【図２】図１の線２Ａ−２Ａによる渦電流式減速装置の
制動状態を示す正面断面図である。FIG. 2 is a front sectional view showing a braking state of the eddy current type speed reducer taken along line 2A-2A in FIG.

【図３】図３は図１の要部を拡大して示す側面断面図で
ある。FIG. 3 is a side sectional view showing an enlarged main part of FIG.

【図４】本発明の第２実施例に係る渦電流式減速装置の
正面断面図である。FIG. 4 is a front sectional view of an eddy current type speed reducer according to a second embodiment of the present invention.

【図５】本発明の第３実施例に係る渦電流式減速装置の
側面断面図である。FIG. 5 is a side sectional view of an eddy current type speed reducer according to a third embodiment of the present invention.

【図６】本発明の第４実施例に係る渦電流式減速装置の
側面断面図である。FIG. 6 is a side sectional view of an eddy current type speed reducer according to a fourth embodiment of the present invention.

【図７】渦電流式減速装置における永久磁石の回転駆動
手段を示す正面図である。FIG. 7 is a front view showing a rotation driving means for a permanent magnet in an eddy current type speed reducer.

【符号の説明】[Explanation of symbols]

４：回転軸 １３：制動ドラム １７ａ，１８，１８
ａ：歯車 ２０：磁石支持環 ２１：磁極板 ２７：空
部 ３１：回転軸 ３２，３２ａ：永久磁石 ３６：電
動機4: rotating shaft 13: braking drum 17a, 18, 18
a: gear 20: magnet support ring 21: magnetic pole plate 27: empty part 31: rotating shaft 32, 32a: permanent magnet 36: electric motor

Claims (1)

【特許請求の範囲】[Claims] 【請求項１】回転軸に結合した制動ドラムの内部に非磁
性材からなる不動の磁石支持環を配設し、磁石支持環の
内部に周方向等間隔に回転軸と平行な多数の円筒状の空
部を設け、磁石支持環の外周壁に空部に対応して強磁性
体からなる磁極板を備え、空部に制動ドラムの内周面に
対する極性が周方向に交互に異なるように並ぶ不動の永
久磁石と空部で半回転し得る可動の永久磁石とを収容
し、各空部で可動の永久磁石の極性が不動の永久磁石と
同方向に並ぶ制動位置と、各空部で可動の永久磁石の極
性が不動の永久磁石と逆方向に並ぶ非制動位置とに切り
換える磁石回動手段を備えたことを特徴とする、渦電流
式減速装置。1. A stationary drum supporting ring made of a non-magnetic material is provided inside a braking drum connected to a rotating shaft, and a large number of cylindrical members parallel to the rotating shaft are arranged at equal intervals in the circumferential direction inside the magnet supporting ring. Is provided, a magnetic pole plate made of a ferromagnetic material is provided on the outer peripheral wall of the magnet support ring so as to correspond to the empty portion, and the polarities with respect to the inner peripheral surface of the braking drum are arranged in the empty portion so as to be alternately different in the circumferential direction. A stationary permanent magnet and a movable permanent magnet that can rotate halfway in the empty space are housed, and the polarity of the movable permanent magnet in each empty space is aligned in the same direction as the stationary permanent magnet and the movable position is movable in each empty space. An eddy current type speed reducer characterized by comprising magnet rotating means for switching the permanent magnet of (1) to a non-braking position in which the polarity of the permanent magnet is immovable and the permanent magnet arranged in the opposite direction.