Method for operating an electric motor, controller, piston pump
By monitoring the rotor shaft speed and briefly changing the motor's rotation direction, the motor lock-up problem was solved, ensuring the piston pump operated normally, preventing an increase in motor torque, and achieving stable operation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ROBERT BOSCH GMBH
- Filing Date
- 2021-08-11
- Publication Date
- 2026-06-16
Smart Images
Figure CN116194347B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for operating an electric motor, particularly a piston pump.
[0002] The present invention also relates to a controller for an electric motor and a piston pump. Background Technology
[0003] Braking control systems, particularly anti-lock braking systems (ABS) or electronic stability programs (ESP), as part of a motor vehicle's braking system, typically include at least one piston pump that can be driven by an electric motor. The piston pump operates to generate hydraulic pressure in the braking circuit of the braking system. For this purpose, a cam or eccentric disc is torsionally connected to the rotor shaft of the electric motor. The cam can be directly mounted on the rotor shaft or torsionally connected to the rotor shaft via the transmission. The rotor shaft rotates about its axis of rotation. The rotational motion of the rotor shaft is converted by the cam into translational or longitudinal motion of the piston of the piston pump. The cam rests against the piston, thereby loading the piston with a compressive force, which displaces the movable piston in the longitudinal direction. This displacement opposes the spring elements and / or the pressure in the braking circuit. The electric motor must apply a driving torque to overcome the load torque caused by the displacement of the piston against the spring forces and / or the pressure in the braking circuit, which depend on the displacement path. The maximum driving torque available from the electric motor is typically greater than the maximum load torque. When the piston reaches its maximum displacement, the load torque is at its maximum within one revolution of the cam, because both the spring force, depending on the displacement path, and the pressure in the braking circuit are at their maximum here. If the rotor shaft rotates further, the piston displacement returns to its original direction because the piston is pressed against the cam by the spring element due to prestress. The electric motor is typically driven according to power requirements to achieve a specific pressure or delivery volume of the piston pump in the braking circuit using a target rotational speed and target direction of rotation for the rotor shaft. However, if the electric motor's drive torque is insufficient to overcome the load torque, the motor may lock up. This can occur particularly due to low on-board grid voltage in the vehicle, which limits the motor's power consumption and thus the maximum drive torque, or due to high temperatures in the motor windings, resulting in higher resistance, or due to increased friction on the piston. With a locked-up motor, the power requirements cannot be met or the piston of the piston pump cannot be operated. To overcome this lock-up, it is known to construct an electric motor with a maximum drive torque greater than that required to overcome the assumed maximum load torque, so that motor lock-up is not possible. Summary of the Invention
[0004] In the method according to the invention, the electric motor has a rotor shaft and is driven according to power requirements using a target rotational speed and a target rotational direction for the rotor shaft, wherein the actual rotational speed of the rotor shaft is monitored. According to the invention, when the actual rotational speed is equal to zero and the target rotational speed is not equal to zero, the target rotational direction is changed within a predetermined time period, and then the motor is driven again with the target rotational speed and the target rotational direction. As known from the prior art, the electric motor is initially driven according to power requirements using a target rotational speed and a target rotational direction for the rotor shaft of the motor. The actual rotational speed of the rotor shaft is also monitored here. The motor being locked is identified by the actual rotational speed being equal to zero and the target rotational speed being not equal to zero. To release the motor from lockup, according to the invention, when the motor is identified as locked up, the target rotational direction is changed within a predetermined time period, causing the rotor shaft to briefly rotate in the opposite direction. After this predetermined time period, the motor is driven again with the target rotational speed and the target rotational direction, causing the rotor shaft to rotate again in the original predetermined direction. The change in rotational direction is based on the assumption that the motor must overcome a lower load torque when rotating in the opposite direction than when rotating in the original predetermined direction, and therefore the requirement for the motor's drive torque is reduced or at least lower. This assumption is based on the piston arrangement described at the beginning on the cam, where the load torque is at its maximum within one revolution of the cam when the piston reaches its maximum displacement, because the spring force, which depends on the displacement path, and the pressure in the braking circuit are both at their maximum here. The change in rotational direction causes the piston to displace rearward, and the load torque and therefore the required drive torque of the motor decrease. If the motor is driven again in the target rotational direction after a predetermined time period, the additional kinetic energy generated by acceleration can be used to overcome the load torque rotating in the direction of maximum load torque in the target rotational direction, thereby overcoming the load torque without having to increase the target torque. Therefore, the method according to the invention has the advantage that the locked motor can be identified and the piston can be actuated again by appropriate drive of the motor, by the rotor shaft of the motor briefly rotating in the opposite direction and then rotating again in the target rotational direction. This is achieved without increasing the target torque of the motor. In particular, it is not necessary to use a motor with a higher maximum torque.
[0005] According to a preferred embodiment of the invention, in order to drive the motor, the motor windings are energized according to the angular position of the rotor shaft, and the actual angular position of the rotor shaft is detected and offset within a predetermined time period to determine the angular position, wherein the offset is selected in such a way that the rotation direction of the rotor shaft changes. If the motor is an electrically commutated or brushless motor, in order to drive the motor, the motor windings are preferably energized according to the angular position of the rotor shaft. For this purpose, the actual angular position of the rotor shaft is first detected. In particular, a permanent magnet is placed on the rotor shaft such that a sensor aligning the permanent magnet, particularly a Hall effect-based sensor, detects the alignment of the magnetic field of the permanent magnet and obtains the actual angular position therefrom. The angular position used for driving the motor is determined by offsetting the actual angular position within a predetermined time period after the motor lockup is thus detected. Therefore, the angular position corresponds to the sum of the actual angular position and the offset. This offset is selected in such a way that the rotation direction of the rotor shaft changes because the energization of the motor windings is different from the case without offset. Therefore, the motor windings are energized in this way due to the offset, such that in the actual angular position, this causes the rotor shaft to rotate briefly in the opposite direction. Therefore, the rotor shaft is brought to a new actual angular position. From this new actual angular position, the motor must overcome a lower load torque than when rotating in the original predetermined direction when the rotation direction changes again. After a predetermined time period, the angular position no longer has an offset, making this angular position correspond to the actual angular position. Therefore, the advantage of having an offset in the angular position is that it is not necessary to pass the change in the target rotation direction as a parameter to the controller specifically constructed for driving the motor; instead, the change is directly generated by the manipulated angular position.
[0006] According to another preferred embodiment, the predetermined time period is between 2 and 5 milliseconds. Setting the predetermined time period within an interval of 2 to 5 milliseconds advantageously ensures that the motor is driven for a sufficiently long period, such that the rotor shaft actually rotates in the opposite direction to the original target rotation direction. Depending on the rotor shaft speed, the time period is also advantageously short enough that the rotor shaft rotates only a specific number of revolutions or in a specific portion of a revolution in the changed target rotation direction. Particularly advantageous is that the load torque to be overcome by the motor has at least its maximum value within one revolution of the rotor shaft, especially when the cam is directly arranged on the rotor shaft.
[0007] The controller for an electric motor according to the invention is characterized in that it is specifically configured to execute the method according to the invention. This results in the advantages already mentioned. Further preferred features and combinations thereof are derived from the description of the invention.
[0008] The piston pump according to the invention has an electric motor, wherein the electric motor has a rotor shaft, wherein the rotor shaft has a cam or eccentric disc, wherein the piston of the piston pump is abutted against the cam or eccentric disc such that rotation of the rotor shaft causes longitudinal displacement of the piston in the axial direction. The piston pump is characterized by a controller according to the invention. This also produces the advantages already mentioned. Further preferred features and combinations of features are derived from the description of the invention. Attached Figure Description
[0009] The invention will now be explained in more detail with the aid of the accompanying drawings.
[0010] Figure 1 A motor with a controller and an inverter is shown.
[0011] Figure 2 A portion of the piston pump is shown, and
[0012] Figure 3 A method for operating an electric motor is shown. Detailed Implementation
[0013] Figure 1 An electric motor 1 is shown, having motor windings 2 and a rotor shaft 3, with permanent magnets 4 arranged at the ends of the rotor shaft. The electric motor 1 is either electrically commutated or brushless. The electric motor 1 typically utilizes a target speed n for the rotor shaft 3, depending on power requirements. Soll The motor is driven and controlled according to the target rotation direction. To drive the motor 1, in the current case, the alignment of the magnetic field 5 of the permanent magnet 4 is detected by the sensor 6 aligning the permanent magnet, and the actual angular position of the rotor shaft 3 is determined from this sensor. Controller 7 drives inverter 8, which operates according to power requirements and angular position. Energize motor winding 2. Typically, angular position... This corresponds to the actual angular position. .
[0014] Figure 2A portion of a piston pump 9 with a piston 10 and a spring element 11 is shown. The piston pump 9 can be operated to generate hydraulic pressure in the brake circuit of a braking device. The piston 10 of the piston pump 9 rests against a cam 12. The cam 12 is torsionally connected to the rotor shaft 3 of the electric motor 1. In the present case, the cam 12 is directly mounted on the rotor shaft 3 of the electric motor 1. The cam 12 is constructed as an eccentric disc, i.e., it is circular and eccentrically mounted on the rotor shaft 3. However, it is equally possible that the cam 12 is not directly mounted on the rotor shaft 3, but is torsionally connected to the rotor shaft 3 via a transmission. The rotor shaft 3 rotates about a rotational axis. The rotational motion of the rotor shaft 3 is converted by the cam 12 into translational or longitudinal motion of the piston 10 of the piston pump 9. The cam 12 rests against the piston 10 such that the piston 10 is loaded with a compressive force by the cam 12, by which the movable piston 10 is displaced in the longitudinal direction. This displacement counteracts the pressure in the spring element 11 and / or the brake circuit. If the rotor shaft 3 rotates further after the piston 10 has been displaced to its maximum extent, the piston 10 will return to its original direction because the piston 10 is pressed against the cam 12 by the spring element 11 due to prestress.
[0015] The following is for reference. Figure 3 An advantageous method is described for using an electric motor 1 to operate a piston pump 9. For this purpose, Figure 3 The method is illustrated with a flowchart. In particular, this method ensures that the locked motor 1 is identified and that the manipulation of the piston 10 is made possible again through the proper drive of the motor 1.
[0016] In step S1, controller 7 determines the target rotational speed n for rotor shaft 3 based on the power requirements. Soll And the target rotation direction, especially to achieve a specific pressure or delivery volume of the piston pump 9 in the braking circuit. At the same time, sensor 6 determines the actual angular position of the rotor shaft 3. In step S2, controller 7 calculates the actual rotational speed n. Ist and compare it with the target rotational speed n Soll Comparison. Steps S1 and S2 are executed consecutively.
[0017] If the actual rotational speed n Ist and target rotational speed n Soll If the actual rotational speed n is the same, the method continues to step S5. Ist Equal to zero and the target rotational speed n Soll If the value is not zero, then motor 1 is locked. Then, the offset is calculated in step S3. The offset This choice changes the rotation direction of rotor shaft 3 because the energizing method of motor winding 2 is different from that without offset. The situation is different. Motor winding 2 therefore has an offset. This energization ensures that the actual angular position is... This causes the rotor shaft 3 to rotate in the opposite direction. Therefore, the motor winding 2 is energized in this way, causing torque to be generated in the changed direction of rotation through the permanent magnet 4 mounted on the rotor shaft 3. The actual angular position here is specifically determined by the aligned magnetic field 5. At that time, offset Therefore, this determination makes the actual angular position... and offset angular position of the sum This causes favorable energization of motor winding 2.
[0018] In step S4, controller 7 determines the angular position. Drive-controlled inverter 8. Corner position Here, the actual angular position corresponds to the predetermined time period t. and offset The sum of the values. Motor winding 2 is energized according to power requirements, causing the rotor shaft 3 of motor 1 to rotate against the target rotation direction. The predetermined time period t is between 2 and 5 milliseconds. By setting the predetermined time period t within an interval between 2 and 5 milliseconds, motor 1 is driven for a sufficiently long period, causing the rotor shaft 3 to actually rotate in the opposite direction to the original target rotation direction. Depending on the rotational speed of rotor shaft 3, the predetermined time period t is also sufficiently short, causing rotor shaft 3 to rotate only in a specific portion of one revolution along the changed target rotation direction. In step S5, controller 7 determines the angular position... Drive-controlled inverter 8. Corner position This corresponds to the actual angular position. The motor winding 2 is energized according to the power requirement, causing the rotor shaft 3 of the motor 1 to rotate at the target speed n in the target direction. Soll Rotate.
Claims
1. A method for operating an electric motor (1), wherein, The electric motor (1) has a rotor shaft (3) and utilizes a target speed (n) for the rotor shaft (3) according to power requirements. Soll The rotor shaft (3) is driven and controlled by the actual rotational speed (n) of the rotor shaft (3) and the target rotational direction. Ist ) is monitored, characterized in that, at the actual rotational speed (n Ist ) equals zero and the target rotational speed (n) Soll The target rotation direction is not equal to zero when the predetermined time period (t) is changed, and then the target rotation direction is changed again at the target rotation speed (n). Soll (1) and target rotation direction drive motor. In order to drive the motor (1), the motor winding (2) is adjusted according to the angular position of the rotor shaft (3). ) is energized, and the actual angular position of the rotor shaft (3) is ( ) is detected and has an offset within a predetermined time period (t). ), so as to determine the angular position ( ), where the offset ( This choice changes the rotation direction of the rotor shaft (3).
2. The method according to claim 1, characterized in that, The predetermined time period (t) is between 2 and 5 milliseconds.
3. The method according to claim 1 or 2, characterized in that, The electric motor (1) is the electric motor (1) of the piston pump (9).
4. A controller (7) for an electric motor, characterized in that, The controller (7) is specifically configured to perform the method according to any one of claims 1 to 3.
5. A piston pump (9) having an electric motor (1), wherein, The electric motor (1) has a rotor shaft (3), wherein the rotor shaft (3) has a cam (12) or an eccentric disk, wherein the piston (10) of the piston pump (9) is abutted against the cam (12) or the eccentric disk such that rotation of the rotor shaft (3) causes longitudinal displacement of the piston (10) in the axial direction, characterized by the controller (7) according to claim 4.