Method and apparatus for the detection of the position of an operating switch for starting an electric motor

Patent metadata

Field	Value
Publication number	US-10063165-B2
Application number	US-201715488055-A
Country	US
Kind code	B2
Filing date	Apr 14, 2017
Priority date	Apr 14, 2016
Publication date	Aug 28, 2018
Grant date	Aug 28, 2018

Abstract

An electric motor is connected to a voltage source via a drive circuit and, between the drive circuit and the voltage source, the operating switch is arranged for the switching of the supply voltage (U) of the voltage source as the input voltage (U E ) on the drive circuit. Following the switch-out of the electric motor, the input voltage (U E ) on the drive circuit is monitored and a gradient of a rising voltage ramp (dU/dt) of the input voltage (U E ) is determined. The gradient of the rising voltage ramp (dU/dt) of the input voltage (U E ) thus determined is compared with a predefined limiting value and, in the event of an overshoot of the predefined limiting value, the operating switch is detected as closed, and the electric motor is restarted via the drive circuit.

First claim

What is claimed is:

1. A method for detecting a switch position of an operating switch for starting an electric motor, wherein the electric motor is connected to a voltage source via a drive circuit, and the operating switch is arranged between the drive circuit and the voltage source, the voltage source being configured to output a supply voltage (U), the operating switch being configured to switch the supply voltage (U) of the voltage source to the drive circuit as an input voltage (U E ), the method comprising the steps of:
a) monitoring the input voltage (U E ) of the drive circuit after a switching off of the electric motor;
b) determining a gradient (dU/dt) of a voltage increase of the input voltage (U E );
c) comparing the determined gradient (dU/dt) of the voltage increase to a predefined limit value; and,
d) recognizing the operating switch as closed when the predefined limit value is exceeded and restarting the electric motor via the drive circuit.

2. The method of claim 1 , wherein the restarting of the electric motor occurs after an opening of the operating switch.

3. The method of claim 1 , wherein the electric motor is started via the drive circuit only after a predefined voltage value (U 1 ) has been exceeded.

4. The method of claim 3 , wherein the exceeding of the predefined limit value by the determined gradient (dU/dt) of the voltage increase and the exceeding of the predefined voltage value (U 1 ) lie in a predefined time window (Δt).

5. The method of claim 4 , wherein the time window (Δt) extends over a time period of 80 to 200 milliseconds.

6. The method of claim 4 , wherein the time window (Δt) extends over a time period of 100 milliseconds.

7. The method of claim 5 further comprising the step of resetting the drive circuit after the time window (Δt) has closed.

8. The method of claim 1 , wherein the voltage increase of the input voltage (U E ) is determined only after a pause time (PZ) has elapsed after a switching off of the electric motor.

9. The method of claim 8 , wherein the voltage source is a battery and the pause time (PZ) is selected to be greater than a recovery time (EZ) of the battery.

10. The method of claim 1 , wherein, after the opening of the operating switch, the input voltage (U E ) of the drive circuit decreases to below a predefined limit value (U S ) over a time period of 1 to 4 seconds.

11. The method of claim 10 , wherein the input voltage (U E ) decreases to zero over the time period of 1 to 4 seconds.

12. An apparatus for detecting a switching position of an operating switch for starting an electric motor, the electric motor being connected to a voltage source configured to output a supply voltage (U) via a drive circuit, the operating switch being arranged between the drive circuit and the voltage source, the operating switch being configured to switch the supply voltage onto the drive circuit as an input voltage (U E ), the apparatus comprising:
a monitoring unit configured to have the input voltage (U E ) applied thereto;
said monitoring unit being configured to monitor a gradient (dU/dt) of a voltage increase of the input voltage (U E );
said monitoring unit being further configured to compare said gradient (dU/dt) of said voltage increase to a predefined limit value; and,
said monitoring unit being further configured to recognize the operating switch as being closed when said predefined limit value is exceeded and to transmit a start signal to the drive circuit via at least one control line so as to restart the electric motor via the drive circuit.

13. The apparatus of claim 12 , wherein said monitoring unit includes a timing element and said monitoring unit is configured to detect said gradient (dU/dt) of a voltage increase of the input voltage (U E ) only after said timing element has elapsed.

14. The apparatus of claim 12 , wherein said monitoring unit includes a comparator configured to compare said input voltage (U E ) to a predefined voltage value (U 1 , U S , U U ).

15. The apparatus of claim 12 , wherein the voltage source is a battery.

16. The apparatus of claim 15 , wherein:
the battery has a battery voltage (U);
the electric motor has an operating voltage (U B ); and,
the battery voltage (U) is greater than the operating voltage (U B ) of the electric motor.

Assignees

• Stihl Ag & Co Kg Andreas

Inventors

• Gurr Kay-Steffen
• Liebhard Gernot
• Kloeker Jens
• Siller Jochen
• Leufen Heinrich

Classifications

• H02P29/00

  Arrangements for regulating or controlling electric motors, appropriate for both AC and DC motors (arrangements for starting electric motors H02P1/00; arrangements for stopping or slowing electric motors H02P3/00; control of motors that can be connected to two or more different electric power supplies H02P4/00; regulating or controlling the speed or torque of two or more electric motors H02P5/00; vector control H02P21/00) · CPC title

• H02P1/02

  Details {of starting control} · CPC title

• H02H11/006 Primary

  in case of too high or too low voltage · CPC title

• H01H9/54 Primary

  Circuit arrangements not adapted to a particular application of the switching device and for which no provision exists elsewhere · CPC title

• H02P9/08

  Control of generator circuit during starting or stopping of driving means, e.g. for initiating excitation · CPC title