Rotation detecting apparatus

• US 4,710,683 A
• Filed: 02/24/1987
• Issued: 12/01/1987
• Est. Priority Date: 12/05/1985
• Status: Expired due to Fees

• Current Assignee: Secoh Giken Incorporated
• Original Assignee: Secoh Giken Incorporated
• Inventors: Okada, Hideo, Bahn, Itsuki
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US07/018,724
• Time in Patent Office: 280 Days
• Field of Search: 318/254, 318/254 A, 318/138, 318/439, 318/314-317
• US Class Current: 318/400.04
• CPC Class Codes: G01P 3/46 by measuring amplitude of generated current or voltage in general G01R19/00
• CPC Class Codes: H02K 29/08 using magnetic effect devices, e.g. Hall-plates, magneto-resistors H02K29/12 takes precedence
• CPC Class Codes: H02K 29/14 with speed sensing devices H02K29/03 takes precedence
• CPC Class Codes: H02P 6/06 Arrangements for speed regulation of a single motor wherein the motor speed is measured and compared with a given physical value so as to adjust the motor speed

Abstract

A rotation detecting apparatus for a rotary machine such as a DC motor, the apparatus including a magnet having a plurality of magnetic poles which rotates along with a rotary shaft of a rotary machine, electromagnetic conversion elements disposed in the magnetic field of the magnet, inductance elements disposed in the magnetic field, the inductance elements being spaced with a predetermined interval from the electromagnetic conversion elements, and an electric circuit for obtaining a voltage proportional to the number of rotations of the rotary machine, signals in proportion to the output voltages of the electromagnetic conversion elements and inductance elements being used as input signals to the electric circuit.

Claims

1. A rotational detecting apparatus for producing an output proportional to rotational speed of a rotary machine having a rotary shaft, comprising:

a magnetic means, having a plurality of magnetic poles, arranged to rotate along with said shaft of said rotary machine so as to provide a rotating magnetic field flux density of which varies at fixed points in time relation to said rotational speed;

a first means, fixedly disposed in said rotating magnetic field, comprising electromagnetic conversion means including at least one Hall element operating on the Hall principle to provide a first output voltage the amplitude of which is a function only of magnetic flux density of said rotating magnetic field;

a second means, fixedly disposed in said rotating magnetic field, comprising an inductance means operating by electromagnetic induction to provide a second output voltage the amplitude of which is a function of both flux density of said magnetic field and its rotational speed; and

electric circuit means for receiving said first and second output voltages and producing as an output a third output voltage corresponding to a quotient of the value of said second output voltage divided by the value of said first output voltage, said third output voltage being directly proportional to said rotational speed of said rotating magnetic field and independent of its flux density.

2. The apparatus as set forth in claim 1 wherein said rotary machine is a DC motor and said magnetic means is the sole driving rotor of said DC motor.

3. The apparatus as set forth in claim 1 wherein said rotary machine is a DC motor and said electromagnetic conversion means are position detecting Hall elements of the DC motor.

4. The apparatus as set forth in claim 1, wherein said first output voltage and said second output voltage are each formed of sine pulses, respectively.

5. The apparatus as set forth in claim 1 wherein said first output voltage and said second output voltage are each formed of expotential pulses, respectively.

6. The apparatus as set forth in claim 1 wherein said inductance means is a plurality of armature coils attached to a fixed armature of said rotary machine, said magnetic means is a field magnet adapted for rotation along with the rotary shaft of the rotary machine with said magnetic poles facing said armature so that said magnetic field may penetrate through said armature coil, and a plurality of said electromagnetic conversion means comprise Hall element detectors which are fixed to positions at the same phase angle as multi-phase armature coils of said rotary machine so that said electromagnetic conversion means can detect the magnetic field strength of said field magnetic;

said apparatus further comprising an electric circuit for obtaining a voltage in proportion to the number of rotations of said rotary shaft by using both an output voltage of said multi-phase armature coils and an output voltage of said electromagnetic conversion means as input signals to said electric circuit means.

7. The apparatus as set forth in claim 6 wherein said rotary machine is a DC motor and said fixed armature comprises a fixed armature for driving said motor which supplies electric power to corresponding armature coils through each output of said electromagnetic conversion means to generate a driving torque of said motor and a fixed armature for power generation which includes a plurality of armature coils for power generation, each being disposed in positions at the same phase angle as respective ones of said Hall element detectors of said electromagnetic conversion means.

8. The apparatus as set forth in claim 6 wherein said rotary machine is a DC motor and said fixed armature is a fixed armature for driving said motor which supplies electric power to corresponding armature coils through each output of said electromagnetic conversion means to generate a driving torque of said motor;

said apparatus further comprising a multi-phase counter electromotive force detecting circuit for detecting counter electromotive forces at each phase of said armature coils by using both an output of said detecting circuit and an output of said electromagnetic conversion means as input signals to said electric circuit means.

9. The apparatus as set forth in claim 6 wherein said electric circuit means comprises a plurality of amplifier circuits which amplify outputs of said plurality of electromagnetic conversion means, a negative feedback circuit which detects the difference between the power generation outputs of said multi-phase armature coils and an output from the amplifier circuit which amplifier circuit amplifies outputs of the electromagnetic conversion means corresponding to each of the armature coils and supplies an error signal thus obtained to control current lines of said electromagnetic conversion means, thereby controlling output levels of said control current lines so that power generation output is equal to the output of the amplifier circuit, and a rotation detecting circuit which receives an input signal proportional to the number of rotations of the field magnetic and corresponding to a current value of current to be fed to said control current lines of said electromagnetic conversion means.

10. A rotation detecting apparatus for detecting the rotational rate of a rotary machine, having a rotary shaft, comprising:

means for driving said shaft in forward and reverse rotating directions;

magnet means having a plurality of adjacent equal and alternately arranged radial magnetic poles, said magnetic means being rotatable with said rotary shaft, for generating a magnetic field radially outwardly of said rotary shaft, said magnetic field corresponding to said plurality of magnetic poles and reversing its polarity with respect to fixed points radially outward of said rotary shaft as said rotary shaft rotates,

electromagnetic conversion means, including at least one Hall element operating on the Hall principle, fixedly disposed in said magnetic field, for providing a first voltage signal having an amplitude proportional to only the flux density of said magnetic field;

inductance means, operating by electromagnetic induction, fixedly disposed in said magnetic field and spaced at a predetermined interval from said electromagnetic conversion means in a rotating direction of said rotary shaft, for providing a second voltage signal corresponding to a voltage induced therein by said rotating magnetic field as said magnetic means rotates with said rotary shaft; and

electric circuit means in operable connection with said electromagnetic conversion means and said inductance means, for providing a third voltage signal proportional to the rotational rate of said rotary shaft, said third voltage signal corresponding to the quotient of the value of said second voltage signal divided by the value of said first voltage signal.

11. The rotation detecting apparatus of claim 10, wherein said electric circuit means provides said third voltage signal as a direct current voltage having positive polarity corresponding to rotation of said rotary shaft in said forward direction and having negative polarity corresponding to rotation of said rotary shaft in said reverse direction.