Self-commutated Actuator

Abstract

An integrated motor-transmission unit in which an output gear and a coaxial stationary gear coact with a driven eccentric ring gear that meshes therewith to provide for a direct drive of the output gear by driving the ring gear. A force vector is applied to the ring gear so as to move the ring gear such that the axis thereof travels in an orbital path about the output gear axis, and this movement of the ring gear is utilized to provide for rotation of the force vector. In the illustrated embodiment of the invention an electromagnet and switching circuit assembly provide for this movement of the force vector.

Parent Case Text

CROSS REFERENCE TO RELATED APPLICATIONS

Actuators of the general type to which this invention relates are disclosed in copending applications Ser. No. 678,951 filed October 30, 1967, now U.S. Pat. No. 3,516,765 a continuation-in-part of application Ser. No. 523,111 filed January 26, 1965, now abandoned and Ser. No. 667,459 filed September 13, 1967, assigned to the assignee of this application.

Description

BACKGROUND OF THE INVENTION

The actuator of this invention is an integrated motor-transmission unit which is driven by a rotating radial force vector in which a desired transmission ratio is an integral part of the structure.

SUMMARY OF THE INVENTION

The basic components of the actuator of this invention are described in detail in the aforementioned copending application Ser. No. 667,459 as consisting essentially of an output gear, a stationary gear mounted in a fixed position with respect to the output gear and in a coaxial relation therewith, and a ring gear which is eccentric with respect to the output gear axis and has two sets of teeth, one set meshing with the stationary gear and the other set meshing with the output gear.

The ring gear is mounted for "floating" movement, namely, movement in which the axis of the gear moves so that the gear does not move about a fixed center. The portions of the ring gear which mesh with the stationary and output gears enables the stationary gear to apply a reaction force to the ring gear which in turn enables the ring gear to apply an output force to the output gear causing it to rotate.

The motor input is a force, hereinafter referred to as a force, vector since it can be the resultant of several forces, applied to the ring gear at a position angularly spaced from the reaction and output forces so as to cause the ring gear to move in an orbital path about the axis of the output gear, with the ring gear experiencing epicyclic movement relative to both the output and stationary gears. The ring gear axis orbits in a small circle having a radius equal to the eccentricity of the ring gear relative to the output gear. Since the center of mass of the ring gear must therefore be moved only in a small circle, the polar moment of inertia of the ring gear is small compared to most conventional motors. This reduces the force necessary to accelerate or decelerate the moving portions of the motor. As a result, the motor of this invention can be operated with relatively small input forces, and is particularly adapted for controlled drives where changes in motor output velocity must be frequent and rapid.

The motor input force vector extends perpendicular to the axis of the stationary and output gears and must be moved in a circular path extending about that axis in order to keep the ring gear moving in its orbital path. The aforementioned copending application discloses apparatus which is external to the motor for moving the force vector in this circular path. The present invention includes structure responsive to movement of the ring gear for moving the force vector in its circular path. Hence, the actuator of this invention is referred to herein as being "self-committed" since it incorporates structure for keeping the force vector moving. This structure consists of a plurality of electromagnets which are extended about the gear axis and a switch assembly which provides for sequential energization of the electromagnets so as to effect the desired movement of the radially inwardly directed force vector. This switch assembly consists of a switch ring mounted on the ring gear in a concentric relation therewith and fixed arcuate switch segments arranged in a circular formation concentric with the output gear axis. The switch ring engages the segments and moves relative thereto so as to effect the desired commutation

Further objects, features and advantages of this invention will become apparent from a consideration of the following description, the appended claims, and the accompanying drawing in which:

FIG. 1 is a transverse sectional view of the actuator of this invention;

FIGS. 2 and 3 are sectional views of the actuator of this invention as seen from the lines 2-2 and 3-3, respectively, in FIG. 1;

FIGS. 4, 5, 6 and 7 are diagrammatic illustrations of the switch assembly of this invention with the ring gear in progressively moved positions; and

FIG. 8 is a diagrammatic view of a portion of the circuitry in the actuator of this invention.

With reference to the drawing, the actuator of this invention indicated generally at 10, is illustrated in FIG. 1, as including a housing 12 on which a stationary gear 14, having external teeth 16, is fixedly mounted. The axis of the stationary gear 14 is shown at 18 and an output gear 20 having having external teeth 22 is mounted on bearings 24 for rotation about the axis 18. A floating ring gear 26, formed of a magnetically permeable material, such as iron or steel, so that it can function as an armature, is positioned so that its axis 28 is eccentric with respect to the axis 18 by a distance indicated at "e" in FIG. 2.

The ring gear 26 has a first set of internal teeth 30 which mesh with the stationary gear teeth 16 and a second set of internal teeth 32 which mesh with the output gear teeth 22. There are more teeth 30 than there are teeth 16 and there are more teeth 32 than there are teeth 22. As a result, and as explained in detail in the aforementioned copending application Ser. No. 667,459 when a force vector, indicated diagrammatically at F in FIGS. 4, 5, 6 and 7 is applied to the ring gear 26 at a point angularly spaced from the points on the ring gear 26 which mesh with the stationary gear 14 and the output gear 20, the ring gear 26 is moved in an orbital path having the radius " e" so as to produce rotation of the output gear 20 about the axis 18.

In the actuator 10, the force vector F is generated by electromagnets indicated generally at 34, 35, 36 and 37, each of which includes a core, indicated at 40, 41, 42 and 43, respectively, and a coil assembly 46, 47, 48 and 49, respectively. The electromagnets 34, 35, 36 and 37 are mounted on the housing 12 so that they extend in a circular path about the axis 18.

Referring now to FIGS. 4--7, the provision for generating force vectors causing counterclockwise rotation of the output gear 20 is illustrated. Such rotation is accomplished by sequentially energizing the coil assemblies 46--49 so as to provide a force vector F which rotates in a counterclockwise direction. A switch assembly, indicated generally at 52, is provided which includes a switch ring 54 mounted on the ring gear 26 in a concentric relation therewith, as shown in FIG. 1, the ring 54 being of continuous circular shape. The assembly 52 also includes a circular switch segment unit 58 which is concentric with the axis 18 and engages the switch ring 54 in a manner hereinafter described. The segment unit 58 includes four arcuate segments 62, 63, 64 and 65, shown in FIGS. 4, 5, 6 and 7.

As shown in FIGS. 1 and 4, the ring 54 is eccentric with respect to the segment unit 58 so that the ring 54 will engage the segment unit 58 at only one or two points on the periphery thereof in each moved position of the ring gear 26. As a result, during movement of the ring gear 26, the electromagnet coil assemblies 46--49 will be sequentially energized in a manner to produce the desired location and movement of the force vector F.

In FIGS. 1, 2 and 3, the ring gear 26 is in a downwardly moved position in which it engages the stationary gear 14 and the output gear 20 at what is referred to herein for ease of understanding as the "twelve o'clock " position. As will more clearly appear hereinafter, since there are four electromagnets 34--37 in the illustrated embodiment of the invention, the ring gear 26 will move in 45.degree. increments. Assume, therefore, that the ring gear 26 is in the twelve o'clock position shown in FIG. 4. In this position of the ring gear, the switch ring 54 will engage the segment unit 58 in the position illustrated in FIG. 4, namely, a position in which the ring 54 engages only the segments 63 and 64.

As shown in FIGS. 4, 5, 6 and 7, one end of each of the coil assemblies 46--49 is connected to a conductor 74. The opposite end of the coil 46 is connected to the segment 62, the opposite end of the coil 47 is connected to the segment 63, the opposite end of the coil 48 is similarly connected to the segment 64, and the opposite end of the coil 49 is connected to the segment 65. As a result, with the switch ring 54 positioned as shown in FIG. 4, and with the ring 54 connected by a lead 78 to one terminal of a suitable current source, such as a battery (not shown), and the conductor 74 connected to the other terminal, current will flow through the coils 47 and 48 so that magnetic forces, indicated at A and B, will be generated by the electromagnets 35 and 36. The resulting force vector will thus be in the direction illustrated by the arrow F shown in FIG. 4.

The application of the force vector shown in FIG. 4 to the ring gear 26, which is now in a position in which it engages the stationary gear 14 and the output gear 20 at the twelve o'clock position, will be to move the ring gear 26 counterclockwise through an angle of 45.degree. to the position illustrated in FIG. 5. In this position of the switch ring 54, it engages only the segment 63, so that only the electromagnet 35 is energized. This results in the generation of the single magnetic force indicated by the arrow B, so that the resulting force vector will be located as shown by the arrow F in FIG. 5.

Application of the force vector F shown in FIG. 5 to the ring gear 26, will cause counterclockwise rotation of the ring gear 26 to the nine o'clock position in which the switch ring 54 will be positioned as shown in FIG. 6. As shown in FIG. 6, the ring 54 engages the segments 62 and 63. This results in the generation of magnetic forces by the electromagnets 34 and 35 indicated by the arrows B and C in FIG. 6. The resulting force vector F is, as shown in FIG. 6, moved 45.degree. degrees from the position shown in FIG. 5.

Application of the force vector F shown in FIG. 6 to the ring gear 26 causes counterclockwise rotation of the ring gear 26 to the position shown in FIG. 7 in which the switch ring 54 engages only the segment 62. As a result, only the electromagnet 34 is energized resulting in only the magnetic force indicated by the arrow C so as to locate the force vector F at the position shown. The force vector F shown in FIG. 7 will in turn cause an additional counterclockwise rotation of the ring gear 26 through an angle of 45.degree.. Subsequently, therefore, the switch ring 54 is moved to positions in which electromagnets 34 and 37 are energized, then to a position in which only electromagnet 37 is energized then to a position in which electromagnets 36 and 37 are energized, then to a position in which only electromagnet 36 is energized, finally to return to the position shown in FIG. 4. At such time the force vector F has made one complete revolution in a counterclockwise direction causing rotation of the output gear 20 through a small angle determined by the difference in the numbers of teeth on the ring, output and stationary gears.

The above cycle is continuously repeated to obtain continuous counterclockwise rotation of the output gear 20.

As shown in FIG. 1 the switch assembly 52 is located at one side of the housing 12. A similar switch assembly 53 consisting of a switch ring 56 and a circular switch segment unit 60 is mounted on the opposite side of the housing 12. It should be noted from FIGS. 4--7 that each segment 62--65 is disposed on the clockwise side of the coil assembly 46--49 to which it is connected. In the unit 60, segments identical to the segments 62--65 are employed but each of these segments is located on the counterclockwise side of the coil assembly to which it is connected. One of the four segments 80 in the unit 60 is shown in FIG. 8, and further illustration and description of these segments is believed to be unnecessary because of their similarity to segments 62--65.

Each of the coil assemblies 46--49 is connected to the conductor 74 and a pair of the segments in the units 58 and 60, as illustrated diagrammatically in FIG. 8 for the coil 48. A pair of segments 64 and 80 in the units 58 and 60, respectively, are engageable with the switch rings 54 and 56, respectively, which are in turn connected by leads 78 and 82, respectively, to the current source. Switches 84 and 86 are interposed in the leads 78 and 82 so that either the ring 54 or the ring 56 can be energized. As a result, when the conductor 74 and the ring 54 are connected to the current source, counterclockwise rotation of the output gear 20 is obtained and when the conductor 78 and the ring 56 are connected to the current source, clockwise rotation of the output gear 20 is obtained.

It can thus be seen from FIGS. 4--7 that the force vector F will be rotated counterclockwise in 45.degree. increments continuously so long as there is current flow through the switch ring 54 and the conductor 74. The application of the force vector F to the ring gear 26 results in the desired movement of the ring gear 26 so that the axis 28 thereof orbits in a counterclockwise direction about the output gear axis 18 with the ring gear movement being utilized to rotate the force vector F. Thus, in the motor 10 of this invention, the structure of the motor itself provides the desired movement of the radially directed force vector F so that it rotates about the axis 18. Hence, the description of the actuator 10 as being "self-commutated."

It is to be understood that the illustrated arrangements of the principal actuator components, namely, the stationery gear 14, the output gear 20, and the ring gear 26 is for illustrative purposes only, since these components are subject to a large number of arrangements within the scope of this invention, all as described in the aforementioned copending application Ser. No. 667,459. Also, the relative numbers of gear teeth employed on these components can be varied to effect the direction of rotation of the output gear 20 relative to the direction of rotation of the vector F. In all cases, these components are formed of metal or an equivalent rigid material and while these components have been illustrated as gears to accomplish a driving engagement therebetween, this driving engagement can be accomplished without the use of teeth on the components. For example, frictional engagements of the components can be employed.

It will be understood that the self-commutated actuator which is herein disclosed and described is presented for purposes of explanation and illustration and is not intended to indicate limits of the invention, the scope of which is defined by the following claims.

Claims

I claim:

1. An actuator comprising a stationary member, a rotatably mounted output member, said members being arranged in a coaxial relation, a floating ring member drivingly engaged with said stationary member and drivingly engaged with said output member, said ring member having an axis arranged eccentric with respect to the axis of said stationary and output members and being mounted for movement in an orbital path in which the axis of said ring member moves about said stationary and output member axis, first means for applying a resultant force to said ring member which is directed substantially perpendicularly relative to said stationary and output member axis, said force being applied to said ring member at one position thereon angularly spaced from the portions of said ring member which are drivingly engaged with said stationary and output members so as to move said ring member in one direction in said orbital path, and second means operable in response to said movement of said ring member to vary operation of said first means to provide for rotated movement of said force to a second position angularly spaced from said first position in a direction effective to provide for continued movement of said ring member in said one direction in said orbital path, said second means being operable continuously to provide for said rotated movement of said force to obtain said orbital movement of said ring member.

2. An actuator according to claim 1 wherein said stationary, output and ring members are gears having teeth arranged so that the teeth on said ring gear engage the teeth on said stationary and output gears and said force is continuously applied to said ring gear at a position thereon angularly spaced from the teeth on said ring gear which are engaged with said stationary and output gear teeth.

3. An actuator according to claim 1 wherein said means for applying a force to said ring member includes electromagnet means arranged in a circular formation concentric with said stationary and output members, said ring member being formed of a magnetically permeable material and being disposed adjacent said electromagnet means for movement thereby.

4. an actuator according to claim 1 wherein said means for applying a force to said ring member includes a plurality of electromagnets arranged in a circular formation about said stationary and output member axis, circuit means including said electromagnets, said circuit means including switch means operable in response to movement of said ring member to provide for sequential energization of said electromagnets so as to effect said movement of said force.

5. An actuator according to claim 4 wherein said switch means includes a plurality of arcuate segments arranged in a circular formation and a continuous circular ring eccentric with respect to said segments.

6. An actuator according to claim 5 wherein each of said segments is connected to one of said electromagnets and is angularly offset therefrom.

7. An actuator according to claim 4 wherein said switch means comprises a pair of continuous switch rings mounted for movement with said ring member and a pair of substantially circular axially spaced segment units corresponding to said switch rings, said segment units being concentric with each other and with said stationary and output member axis and eccentric with respect to said switch rings.

8. An actuator according to claim 7 wherein each segment unit includes a plurality of spaced arcuate segments arranged in a circular formation, each of said segments being connected to one of said electromagnets.

9. An actuator according to claim 8 wherein each of said switch rings is positioned so that it can be moved to a position extending between the adjacent ends of adjacent segments in the corresponding segment unit.