METHOD FOR OPERATING AN ELECTRIC MOTOR, CONTROLLER, PISTON PUMP

Abstract

A method for operating an electric motor, in particular of a piston pump. The electric motor has a rotor shaft and is actuated with a target rotational speed and a target rotational direction for the rotor shaft as a function of a power demand, wherein an actual rotational speed of the rotor shaft is monitored. In the method, the target rotational direction is changed for a specified period of time if the actual rotational speed is equal to zero and the target rotational speed is unequal to zero, and the electric motor is then actuated again at the target rotational speed and in the target rotational direction.

Claims

1-5. (canceled)

6. A method for operating an electric motor of a piston pump, wherein the electric motor includes a rotor shaft, the method comprising the following steps: actuating the electric motor with a target rotational speed and a target rotational direction for the rotor shaft as a function of a power demand; monitoring an actual rotational speed of the rotor shaft; and changing the target rotational direction is changed for a specified period of time when the actual rotational speed is equal to zero and a target rotational speed is unequal to zero and then actuating the electric motor again at the target rotational speed and in the target rotational direction.

7. The method according to claim 6, wherein, to actuate the electric motor, a motor winding is energized as a function of an angular position of the rotor shaft, and an actual angular position of the rotor shaft is detected and provided with an offset for the specified period of time to determine the angular position therefrom, wherein the offset is selected such that the rotational direction of the rotor shaft is changed.

8. The method according to claim 6, wherein the specified period of time is between 2 and 5 milliseconds.

9. A controller configured to operate an electric motor of a piston pump, wherein the electric motor includes a rotor shaft, the controller configured to: actuate the electric motor with a target rotational speed and a target rotational direction for the rotor shaft as a function of a power demand; monitor an actual rotational speed of the rotor shaft; and change the target rotational direction is changed for a specified period of time when the actual rotational speed is equal to zero and a target rotational speed is unequal to zero and then actuate the electric motor again at the target rotational speed and in the target rotational direction.

10. A piston pump, comprising: an electric motor including a rotor shaft, wherein the rotor shaft includes a cam or an eccentric disk; a piston of the piston pump abutting the cam or the eccentric disk such that a rotation of the rotor shaft causes a longitudinal displacement of the piston in an axial direction; and a controller configured to operate the electric motor of the piston pump, the controller configured to: actuate the electric motor with a target rotational speed and a target rotational direction for the rotor shaft as a function of a power demand; monitor an actual rotational speed of the rotor shaft; and change the target rotational direction is changed for a specified period of time when the actual rotational speed is equal to zero and a target rotational speed is unequal to zero and then actuate the electric motor again at the target rotational speed and in the target rotational direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 shows an electric motor with a controller and an inverter, according to an example embodiment of the present invention.

[0011] FIG. 2 shows a part of a piston pump according to an example embodiment of the present invention.

[0012] FIG. 3 shows a method for operating the electric motor, according to an example embodiment of the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0013] FIG. 1 shows an electric motor 1 comprising a motor winding 2 and a rotor shaft 3, on the front side of which a permanent magnet 4 is disposed. The electric motor 1 is an electrically commutated or brushless electric motor. The electric motor 1 is typically actuated as a function of a power demand with a target rotational speed n.sub.target and a target rotational direction for the rotor shaft 3. In the present case, to actuate the electric motor 1, the orientation of a magnetic field 5 of the permanent magnet 4 is detected by an appropriately configured sensor 6, from which an actual angular position φ.sub.actual of the rotor shaft 3 is ascertained. A controller 7 actuates an inverter 8, which energizes the motor winding 2 as a function of the power demand and an angular position φ. As a rule, the angular position φ corresponds to the actual angular position φ.sub.actual.

[0014] FIG. 2 shows a part of a piston pump 9 with a piston 10 and a spring element 11. Said piston pump 9 can in particular be operated to generate hydraulic pressure in a brake circuit of the brake system. The piston 10 of the piston pump 9 abuts a cam 12. The cam 12 is connected to the rotor shaft 3 of the electric motor 1 in a rotationally fixed manner. In the present case, the cam 12 is attached directly to the rotor shaft 3 of the electric motor 1. The cam 12 is configured as an eccentric disk, i.e. it is circular and is eccentrically mounted on the rotor shaft 3. However, it is also possible for the cam 12 to not be attached directly to the rotor shaft 3, but rather to be connected to the rotor shaft 3 in a rotationally fixed manner via a gearing. The rotor shaft 3 rotates about an axis of rotation. The cam 12 converts the rotational movement of the rotor shaft 3 into a translational movement or longitudinal movement of a piston 10 of the piston pump 9. The cam 12 abuts the piston 10 such that the cam 12 exerts a compressive force on the piston 10, as a result of which the displaceably mounted piston 10 is moved in longitudinal direction. This displacement takes place against the spring element 11 and/or the pressure in the brake circuit. When the rotor shaft 3 is rotated further after the piston 10 has been displaced to the maximum extent, the piston 10 moves back in the original direction again because the piston 10 is pressed against the cam 12 by the spring element 11 due to pretension.

[0015] One advantageous method for operating the electric motor 1 of the piston pump 9 is described in the following with reference to FIG. 3. For this purpose, FIG. 3 shows the method using a flow chart. The method in particular ensures that a stalled electric motor 1 is identified and that actuation of the piston 10 is enabled again by suitable actuation of the electric motor 1.

[0016] In a step S1, the controller 7 ascertains a target rotational speed n.sub.target and a target rotational direction for the rotor shaft 3 as a function of a power demand, in particular to achieve a specific pressure or delivery volume of the piston pump 9 in the brake circuit. At the same time, the sensor 6 ascertains the actual angular position φ.sub.actual of the rotor shaft 3. In a step S2, the controller 7 ascertains an actual rotational speed n.sub.actual and compares it with the target rotational speed n.sub.target. Steps S1 and S2 are carried out continuously.

[0017] If the actual rotational speed n.sub.actual and the target rotational speed n.sub.target are the same, the method is continued with a step S5. However, if the actual rotational speed n.sub.actual is equal to zero and the target rotational speed n.sub.target is unequal to zero, the electric motor 1 stalls. Then an offset φ.sub.offset is ascertained in a step S3. This offset φ.sub.offset is selected such that the rotational direction of the rotor shaft 3 is changed because the motor winding 2 is energized differently than would be the case without the offset φ.sub.offset. The offset φ.sub.offset therefore causes the motor windings 2 to be energized such that, in the actual angular position φ.sub.actual, this results in the rotor shaft 3 rotating in the opposite direction. The motor windings 2 are thus energized such that the permanent magnet 4 attached to the rotor shaft 3 generates a torque in the changed rotational direction. For the actual angular position φ.sub.actual, which is in particular ascertained from the orientation of the magnetic field 5, the offset φ.sub.offset is thus determined such that the angular position φ as the sum of the actual angular position φ.sub.actual and the offset φ.sub.offset results in the advantageous energization of the motor windings 2.

[0018] In a step S4, the controller 7 actuates the inverter 8 as a function of the angular position φ. The angular position φ is the sum of the actual angular position φ.sub.actual and the offset φ.sub.offset for a specified period of time t. The motor winding 2 is energized in accordance with the power demand, so that the rotor shaft 3 of the electric motor 1 rotates in the opposite direction to the target rotational direction. The specified period of time t is between 2 and 5 milliseconds. By setting the specified period of time t to an interval between 2 and 5 milliseconds, the electric motor 1 is actuated for a sufficiently long period of time so that the rotor shaft 3 actually rotates in the opposite direction to the original target rotational direction. The specified period of time t is also sufficiently short, depending on the rotational speed of the rotor shaft 3, so that the rotor shaft 3 rotates in the changed target rotational direction in particular for only a specific part of a revolution. In step S5, the controller 7 actuates the inverter 8 as a function of the angular position φ. The angular position φ corresponds to the actual angular position φ.sub.actual. The motor winding 2 is energized in accordance with the power demand, so that the rotor shaft 3 of the electric motor 1 rotates in the target rotational direction with the target rotational speed n.sub.target.