US2377286A - Motor control system - Google Patents

Description

May 29, 1945.

J. WHITE MOTOR CONTROL SYSTEM Filed Sept. 7, 1942 Patented May 29, 1945 UNITED STATES PATENT OFFICE MOTOR CQNTROL SYSTEMy Joe White, Anderson, Ind., assignor to General* Motors Corporation, Detroit, Mich., a corpora'- tion of Delaware 7 Claims.

This invention relates to systems for a reversible servo-motor for operating a device such as an arm for steering a vehicle.

It is an object of the present invention to pro vide a controlling system including a quick acting relay for controlling the reversal of current through the motor armature. The advantage of using al quick acting relay'will be more apparent from the following descriptionof'an embodiment of the invention.

Fig. 1 is a wiring diagram showing the various elements of the system and their electrical'con'- nections.

Fig. 2 is a diagram similar to Fig. 1, with certain elements of the device, however', indifferent positions and effect from that shown in Fig. 1.

Fig. 3 is a similar view to Fig. Z-'showing other elements of the system in another position.

An electric motor M having a i'leld- F and any armatureA is connected for rotation in one di rection with the positive line I'and thenegative line Il of a current source 5f through the following circuit; switch I2, wire I3,I contact I4, contact I5, wire I6, armature AT, wire' I1, contact I8',l contact I9, wire 20, field F, and nega-A tive lineY I I. This causes fiow of current through the field inthe direction indicated by arrow 45v and through the armature as indicated by arrow af. Thev motor drives shaft 25 through' a speed reducing gear unit 26. Shaft 25' operates" an ann 21 connectible with a device to be op# erated,lsuch as the steering mechanism of a" vehicle. Arm ZImay stand in a normal, or'c'enter positionZlc or in extreme left position.v Z'IL or in extreme right position 21R or in intermediate positions.

The contacts I4, I5, I8' and ISare part of a relay unity 30 comprising a core 3|, surrounded by a winding 32 of relatively line wireV such-as" portedby an armature' 4I normally heldbyv aA spring 42 away from the relay core 3l,

The shaft 25 carriesan arm 51| of aflimit switch unit 50. Arm 5I carries a non-conducting stud 52 for engaging either of two resilient blade arms 53 or 54 carrying, respectively, contacts 55 and 56. Contact 55 normally engages a contact 51 carried byr blade 59, electrically connected` with b1ade54 and electrically connectedbyr wire 6I Winding 32 v with the junction 337of` relay coils 32y and 34. Contact 56v is normally separated from contact 58' on blade` 50r which is connected by wire 62 with wire I3. Wire IG Ais connected by switch 63 with blade 53.

To eiect rotation of arm 21 from the position 21e yclockwise toward the position 211., only switch I2f is closed and themotor operates with the circuit shown inv heavy lines in Fig. l. Current ows through-armature A as indicated by the arrow af and through the field F as indicatedby the arrow 45. The flow in relay coils 32 and 34 is-indicated by the arrow heads thereon and their effects are bucking as indicated by oppositely pointing arrows 32a and 34a in 1.

To effect rotationoinarmy 21 counterclockwise toward position 21R,-the switch 63 as Well as switch I2 is closed to cause first a reversal of current in relay coil 34 as indicated by arrow heads on thisl coil in- Fig. 2. The effect is to place coil-34 inassisting relation to coil 32 as indicated by arrows 32a and 34h pointing inthe same direction.l Relay armature 4I'i's attracted toward the core 3I and the motor reversing circuit is completed as shown in Fig. 3. Direction of iield current yiiow remains unchanged as indicatedfby arrow 45YinFig. 3, but armature cur-J rent ow is reversedas indicated by arrow ai'. The movement of armature 4I into'the position shown in Fig.- 3fcauses coil 34 to be short circuited and coil-32 alonev remains effective as indicated by arrow 32a, to holdfthe armature 4I in-attracted position since the air gap between the armature and core has beenreduced. When' the controlsystem is in the status shown-in Fig. 2, coil 34 is Lconnected with wire I0 through switch B3, limit switchcontacts 55, 51 and? wire 6I, and is connected withwire` Ilthrough wire 35, wire I1, contacts I8, I94 and field F. When the control system is in the status shown in Fig. 3, coil 34 is short-circuited by the closing of contacts 31, 36 thus placing both ends cfcoil 34 at the same voltage.

Rotation of arm 2l counterclockwise willv continue so long asswitch 63 as well as switch I2 re mainsclosed, but no `further than required for arm 5I to engage blade 53 to separate contact 55 from Contact 51. This separation has the same effect as opening switch 63, namely, to effect deenerg'ization of the' relay in the following manner: The'status ofcoil 34 changes from a condition of being short-circuited and inactive to a condition of being in bucking relation to coil 32 thus'quickly'deenergizing the relay and causing the'relay' armature 4I to return tov the position shown in Fig. 1the'rebycausing 'the motor to r0- tate the arm 21 clockwise and contacts 55 and 51 toengfage whereupon thearm 21. again rotates counter'clockwise and this cycle'isl repeated so long as switch 63 remains closed while switch I2 remains closed. Therefore the arm 21 oscillates through a very small angle while in the position 21R. This angle of oscillation is small because the operation of relay 30 is rapid. This rapidity is due to the fact that the status of coil 34 is changed from bucking to assisting to effect movement f the armature 4I toward the core; and the status of coil 34 is changed from nonoperating to bucking to cause rapid counteraction of the armature holding iiux of coil 32 to permit quick return of the armature 4I by the spring 42.

The repetition of the same cycle occurs when arm 21 has rotated clockwise to position 21L as result of closing only switch I2 to complete the circuit shown in heavy lines in Fig. 1. Upon the arrival of arm 21 at 21L, stud 52 of arm 5I has engaged blade 54 and has caused contact 56 to engage 58. There is first a counterclockwise rotation of arm 21 sufiicient to permit opening of contacts 56 and 58 and then a clockwise rotation of arm 21 suicient to close these contacts. This cycle is repeated so long as switch I2 remains closed or until switch B3 is closed while switch I2 remains closed. The angle of oscillation of arm 21 at position 21L is small because the relay 30 is quick acting for reasons already given.

One advantage of this system is that only one relay is required. The switch I2 is the main control switch and also the switch which, when closed alone, causes clockwise rotation of the arm 21 toward the 21L position. When arm 21 has moved as far as 21L it will move no further in a clockwise direction. If it is desired to stop the arms 21 between 21C and 21L, the operator opens switch I2. If it is desired that the arm 21 should move counterclockwise toward the 21R position the switch 63 is closed while switch I2 remains to cause the relay 30 to reverse the operation of the motor. So long as switch 63 remains closed while switch I2 is closed, the arm 21 will move to position 21R but no further. If it is desired to stop movement of arm 21 in a counterclockwise direction before arriving at 21R, both switches I2 and 63 are opened. If it is desired to cause arm 21 to move clockwise immediately after having moved counterclockwise, only the switch 53 is opened. If the arm is oscillating at position 21L and it is desired to move to 21R, the switch 53 is closed while switch I2 remains closed. If the arm is oscillating at position 21R. and it is desired to move the arm to position 21L, then only is switch; 63 opened while switch I2 remains closed. If it is desired to move the arm from 21R to 21C, switches I2 and 63 being closed. switch 63 is opened and switch I2 remains closed until the arm arrives at 21C, and then switch I2 is opened. If it is desired to move the arm from 21L to 21C, switch I2 being closed, switch B3 is also closed until the arm arrives at 21C and then switch I2 is opened. Both switches are opened when use of the control system is discontinued.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. A motor control system comprising a ourrent source, an electric motor having a field and an arma-ture, a rotatable member operated by the motor, a circuit for connecting the source and motor for rotation of the member in one direction and including a manually closed switch and pairs of normally closed contacts, a circuit for connecting the source and motor for rotation of the member in the opposite direction and including said manually closed switch and pairs of engageable normally open contacts, a relay electromagnet having an armature for opening the normally closed contacts and for closing the normally open contacts, and having an armature main attracting winding and an armature holding winding, said windings being normally in bucking relation, a normally open limit switch and a circuit completed by the closing thereof for causing the windings to be placed in assisting relation to effect the attraction of the relay armature, means operated by the motor, and responding to movement of the member in the iirst )mentioned direction to a certain position for closing the limit switch, and a short circuit oi the armature main attracting winding established in response to the attractive movement of the armature, the attraction movement of the armature causing the motor to operate in said opposite direction to allow the limit switch to open, whereupon the relation of the relay windings becomes bucking and the relay armature returns to normail position and the motor rotates in the direction rst mentioned, and the cycle is repeated so long a5 the manually operated switch remains closed, whereby the member oscillates through a small angle at said certain position.

2. A motor control system comprising a current source, an electric motor having a iield and an armature a rotatable member operated by the motor, a circuit for connecting the source and motor for rotation of the member in one direction and including a manually closed switch and r pairs of normally closed contacts, a circuit for connecting the source and motor for rotation of the member in the opposite direction and including said manually closed switch and pairs of engageable normally open contacts, a relay electromagnet having an armature for opening the normally closed contacts and for closing the normally open contacts, and having an armature main attracting winding and an armature holding winding, said winding being normally in bucking relation, a circuit for causing the relay windings to be placed in assisting relation and comprising a second manually closed switch and a normally closed limit switch, whereupon the relay armature is attracted to effect reversal of direction of current iiow through the armature, whereby the motor is caused to rotate the member in said opposite direction, a short circuit of the armature main attracting winding established in response to the attractive movement of the armature, and means operated by the motor and responding to movement of said member in said opposite direction to a certain position for opening the limit switch whereupon the relation of the relay windings becomes bucking and the relay returns to normal status and the motor rotates the member in the iirst mentioned direction and the limit switch recloses to effect operation of the relay to cause the motor to reverse and open the limit switch, this cycle being repeated so long as the second manually operated switch is closed, whereby the member is caused to oscillate through a small angle at the said certain position.

3. A motor control system comprising a current source, an electric motor having a iield and an armature, a rotatable member operated by the motor, a circuit for connecting the source and motor for rotation of the member in one direction and including a manually closed switch and pairs of normally closed contacts, a circuit 'for connecting the source and motor for rotation of the member in the opposite direction and including said manually closed switch and pairs of engageable normally open contacts, ak relay electromagnet having an armature for opening the normally closed contacts and for closing the normally open contacts and having an armature main attracting winding and an armature hold ing winding, said Winding ybeing normally in bucking relation, a first circuitl for causing the relay windings to be placed in assisting relation and including a normally open limit switch, a second circuit for causing the relay windings to be placed in assisting relation and including a normally closed limit switch and a second manually closed switch, the placing of said relay wind ings in assisting relation causing the attraction of the relay armature to a position for causing the motor to rotate the member in said opposite direction, a short circuit of the armature main attracting winding established by the attractive movement of the relay armature, means operated by the motor and responding to movement of said member in said rst mentioned direction to a certain first position for closing the normally open limit switch and means operated by the motor and responding to movement of said member in said opposite direction to a certain second position for opening the normally closed limit switch, whereby when the first mentioned manual switch is closed and the other manual switch is open the motor will cause the member to move to said certainrst position and there to oscillate through a small angle, or when both manually operated switches are closed, the motor will cause the member to move to said certain second position and then to oscillate through a small angle.

4. A motor control system comprising a current source, an electric motor, a relay having an armature and an electromagnet for attracting the armature and having an armature main attracting coil and an armature holding coil normally in bucking relation, first manually closed switch, a circuit completed by the first manual switch and the relay armature when in normal position for causing the motor to rotate in one direction, a circuit completed by the first manual switch and the relay armature when in attracted position for causing the motor to rotate in the opposite direction, a normally open first circuit for causing the relay windings to be in assisting relation'and having a normally open limit switch closed upon certain rotation of the motor the said iirst mentioned direction, a second circuit for causing the relay windings to be placed in assisting relation and having a manually closed switch and a normally closed limit switch opened upon a certain rotation of the motor in said opposite direction, the placing of the relay windn ings in assisting relation causing the electromagnet to attract the armature to cause the motor to rotate in said opposite direction, and a short circuit of the armature main attracting winding established by the attractive movement of the armature, the interruption of the circuits whichv placed the relay windings in assisting relation causing the relation of the relay windings to return to the normal bucking relation from a condition in which only the holding winding was effective.

5. A control device for an electric motor having armature and field circuits; means for connecting said circuits to a source of electric power to effect motor operation in either direction, said means comprising an electromagnetic relay provided with an armature which` when in normal, biased position, completes motor circuits for motor operation in one direction, and when in its attracted position completes motor circuits for motor operation in the opposite direction, said relay having a magnet winding for moving the armature out of its biased into its operated position; a power switch for connecting the relay armature with the power source to render the motor operative; a second winding on the relay for neutralizing the elect of the first mentioned relay winding when only said power switch is closed; and a second switch for connecting said second winding with the power source to render said second winding ineffective as a neutralizing winding and effective to cooperate with the first mentioned winding while the iirst switch is closed, for attracting the relay armature from its biased position and change motor connections to reverse its operation.

6. A control device for an electric motor having eld and armature circuits means for connecting said motor circuits to a source of electric power to effect rotation of the motor in either direction, said means comprising, a two position electromagnetic switch adapted when in normal biased position to complete motor connections for one directional rotation and when moved from its biased into the attracted position to change connections for motor rotation in the oppositev direction; a power switch for connecting the relay with the power source; two windings on the electromagnet connected to the power source to oppose each other and render the relay inactive when said power switch is closed; a second switch adapted to connect one of said windings with the power source in such a manner as to render it effective to assist the other winding in rendering the electromagnet active for changing motor connections and reversing its rotation; limit switches electrically connected with said other switches;

and motor driven means for actuating the limit' switches to control the operation of the motor in either direction within predetermined limits.

7. A control device for a reversible electric motor having field and armature circuits; a source of electric power, an electromagnet switch having two magnet windings and a contactor shiftable to reverse the armature circuit connection with one end of the field circuit; a control switch, when closed, connects the source of power with the motor field and armature circuit through the electromagnet switch contactor and with the magnet windings to energize them to have a bucking eiect and thus be ineffective to actuate the contactor whereby the motor operates in one direction; and a second control switch, which, when closed while the first mentioned control switch is closed, completes a reverse current flow through one of the said magnet windings, render ing it effective to cooperate with the other magnet winding to actuate the electromagnet switch contactor from its normal to its operated position in which it reverses the connection of the armature circuit with the field circuit of the motor to effect reverse rotation of the motor.

JOE WHITE.

Images