Current measuring apparatus, image forming apparatus, conveyance apparatus and method for measuring current

Patent metadata

Field	Value
Publication number	US-2016274152-A1
Application number	US-201615063093-A
Country	US
Kind code	A1
Filing date	Mar 7, 2016
Priority date	Mar 20, 2015
Publication date	Sep 22, 2016
Grant date	—

Abstract

There is provided a current measuring apparatus for measuring a first current used for estimating a load torque of the motor, comprising: a detection unit configured to detect a first voltage; an amplification unit including a first input terminal at which the second signal is input, a second input terminal coupled to a first resistor and a second resistor by which an amplification factor is defined, an output terminal for outputting a third signal, a first power supply terminal that is grounded, and a second power supply terminal coupled to a first power supply; an input unit configured to input a second voltage at the first input terminal; a storage unit configured to store a third voltage; an acquisition unit configured to acquire a fourth voltage; and a calculation unit configured to calculate the first current based on a difference between the third voltage and the fourth voltage.

First claim

What is claimed is:

1 . A current measuring apparatus for measuring a first current flowing in a motor, the first current being used for estimating a load torque of the motor, the current measuring apparatus comprising:
a detection unit configured to detect a first voltage indicating a second current as a first signal, the second current being composed based on currents of respective phases of the motor; a smoothing unit configured to perform a smoothing operation on the first signal to generate a second signal; an amplification unit including a first input terminal at which the second signal is input, a second input terminal coupled to a first resistor and a second resistor by which an amplification factor is defined, an output terminal for outputting a third signal generated by amplifying the second signal in accordance with the amplification factor, a first power supply terminal that is grounded, and a second power supply terminal coupled to a first power supply; an input unit configured to input a second voltage at the first input terminal; a storage unit configured to store a third voltage indicated by the third signal in response to the motor being stopped; an acquisition unit configured to acquire a fourth voltage indicated by the third signal in response to the motor being rotated; and a calculation unit configured to calculate the first current based on a difference between the third voltage and the fourth voltage.

2 . The current measuring apparatus according to claim 1 , wherein the amplification unit is a single-power operational amplifier.

3 . The current measuring apparatus according to claim 1 , wherein the detection unit includes a shunt resistor for indicating the first voltage.

4 . The current measuring apparatus according to claim 3 , wherein a terminal of the shunt resistor is coupled to a motor power supply for supplying power to the motor.

5 . The current measuring apparatus according to claim 3 , wherein a terminal of the shunt resistor is grounded.

6 . The current measuring apparatus according to claim 1 , wherein
the smoothing unit includes a third resistor, the input unit includes a fourth resistor and a fifth resistor, and the calculation unit calculates the difference between the third voltage and the fourth voltage based on respective resistance values of the first resistor, the second resistor, the third resistor, the fourth resistor and the fifth resistor.

7 . The current measuring apparatus according to claim 6 , wherein
the fourth resistor includes a first terminal coupled to a second power supply and a second terminal coupled to the first input terminal, and the fifth resistor includes a third terminal that is grounded and a fourth terminal coupled to the first input terminal.

8 . The current measuring apparatus according to claim 7 , wherein the second power supply is the same power supply as the first power supply.

9 . The current measuring apparatus according to claim 7 , further comprising a diode, a cathode of the diode being coupled to the second terminal.

10 . The current measuring apparatus according to claim 7 , wherein the third resistor includes a fifth terminal at which the first signal is input and a sixth terminal coupled to the first input terminal.

11 . The current measuring apparatus according to claim 10 , further comprising a diode, a cathode of the diode being coupled to the fifth terminal.

12 . The current measuring apparatus according to claim 6 , wherein
the smoothing unit further includes a capacitor, and the smoothing unit attenuates a signal whose frequency is greater than or equal to a frequency defined in accordance with the third resistor and the capacitor, the signal to be attenuated being included in the first signal.

13 . The current measuring apparatus according to claim 1 , wherein the acquisition unit acquires a plurality of values of the fourth voltage to calculate an average of the plurality of values of the fourth voltage.

14 . An image forming apparatus comprising the current measuring apparatus according to claim 1 .

15 . A conveyance apparatus comprising the current measuring apparatus according to claim 1 .

16 . A method for measuring current performed by a current measuring apparatus for measuring a first current flowing in a motor, the first current being used for estimating a load torque of the motor, the current measuring apparatus including a detection unit configured to detect a first voltage indicating a second current as a first signal, the second current being composed based on currents of respective phases of the motor, a smoothing unit configured to perform a smoothing operation on the first signal to generate a second signal, an amplification unit including a first input terminal at which the second signal is input, a second input terminal coupled to a first resistor and a second resistor by which an amplification factor is defined, an output terminal for outputting a third signal generated by amplifying the second signal in accordance with the amplification factor, a first power supply terminal that is grounded, a second power supply terminal coupled to a first power supply, and an input unit configured to input a second voltage at the first input terminal, the method comprising:
storing a third voltage indicated by the third signal in response to the motor being stopped; acquiring a fourth voltage indicated by the third signal in response to the motor being rotated; and calculating the first current based on a difference between the third voltage and the fourth voltage.

Assignees

• Seki Takeo
• Ricoh Co Ltd

Inventors

• Seki Takeo

Classifications

• G01R19/25 Primary

  using digital measurement techniques · CPC title

• H02P6/00

  Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor (vector control H02P21/00) · CPC title

• G01R31/343

  in operation · CPC title

• G01L3/00

  Measuring torque, work, mechanical power, or mechanical efficiency, in general · CPC title

• G01R15/14

  Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks · CPC title