Brushless Motor

Abstract

The invention relates to a brushless electric machine (1), in particular a brushless DC motor, having a housing (2), at least one rotor (4) arranged on a shaft (3) rotatably supported in the housing (2), and a stator (7) fixed to the housing, wherein a non-contact rotor position recognition device is provided for the rotor (4), which rotor position recognition device has a multi-pole magnetic ring (9) arranged torsionally resistant on the shaft (3) and at least one magnetic field-sensitive sensor (10) arranged radially and fixed to the housing and assigned to the outer circumference of the magnetic ring (9). It is proposed here that the number of pole pairs (z4) of the rotor (4) and the number of pole pairs (z9) of the magnetic ring (9) are implemented as relatively prime to each other.

Description

Field of the Invention

[0001] The invention relates to a brushless motor, in particular a brushless DC motor, having a housing, at least one rotor arranged on a shaft rotatably supported in the housing, and a stator fixed to the housing, wherein a non-contact rotor position recognition device is provided for the rotor, which has a torsion-resistant and multi-pole magnetic ring arranged on the shaft and at least one magnetic field-sensitive sensor fixed to the housing and radially assigned to the outer circumference of the magnetic ring. Background Art

[0002] Brushless motors are known from the prior art. For their drive, it is important that the current rotational angle or the current rotational angle position of the rotor can be determined precisely in order to be able to control the stator. Only if the current rotational angle position is known can the correct commutation of the motor be achieved. Thus, for example, it is known that in a synchronous motor with an excited permanent magnet, a signal generator is torsion-resistant assigned to the rotor and a sensor element is axially arranged, which monitors the magnetic field of the signal generator, so that the complete 360° rotation angle of the signal generator can be known by the sensor. Thereby, the motor can be adjusted immediately after the system is started because the current rotational angle is immediately known. A structure is also known for which the signal generator has a multi-pole magnetic ring. Here, the advantage is that more possibilities are provided for the system because the magnetic ring can also be positioned, for example, between the rotor of the motor and the mechanical output (the drive pinion fixedly arranged on the shaft). However, this causes the sensor to be arranged radially relative to the magnetic ring in a fixed manner on the housing. Therefore, the mechanical rotational angle of the rotor cannot be unambiguously determined from the sensor signal without problems. Summary of the Invention

[0003] The motor according to the invention having the features of claim 1 has the advantage that the favorable construction of the motor allows an unambiguous correspondence between the sensor signal and the rotational angle or the rotational angle position of the rotor. For this purpose, it is provided according to the invention that the number of pole pairs of the rotor and the number of pole pairs of the magnetic ring are relatively prime (teilerfremd). By the relatively prime number of pole pairs, it is achieved that the rotational angle segments of the magnetic ring can be known in the shortest time by means of, in particular, the vernier principle or the slide rule principle and the current rotational angle can be known from the sensor signal based on the detected rotational angle segments. Thus, the invention provides a favorable solution for unambiguously determining the rotational angle with only a small additional effort. Therefore, although the motor cannot be adjusted immediately after being put into operation because it is not known in which direction the current and voltage have to be adjusted for the adjustment, the rotational angle position can be known with a sufficient small load torque in a sufficiently short time and thus the preset values of the current and voltage can also be known.

[0004] According to a preferred embodiment of the present invention, the rotor has a pole pair number of 4. Thus, the rotor corresponds to a commonly used rotor and an existing rotor can be adopted without additional cost.

[0005] Preferably, the magnetic ring has a pole pair number of 5, resulting in relatively prime pole pair numbers. Since the magnetic ring itself is constructed more simply than the rotor, the pole pair number can be adjusted to 5 or other relatively prime pole pair numbers at low cost. Thus, the motor particularly has a pole pair number of 4 for the rotor and a pole pair number of 5 for the magnetic ring.

[0006] Here, the pole pair number of the magnetic ring determines the number of rotational angle segments of the rotor position recognition device. At system startup, the rotational angle segment in which the rotor or the magnetic ring is located is first determined, and then the current rotational angle is determined based on the detected rotational angle segment. For this purpose, in particular, the following method is performed, which is preferably performed or executable by the controller of the motor. After the motor is initialized, the mechanical angle in the angular range of 0 to 360° is clearly determined and all possible corrections depending on the mechanical angle can now be applied, thus ensuring favorable commutation during subsequent operation of the motor.

[0007] According to a preferred improvement of the present invention, the brushless motor has a controller that is specifically configured to determine the rotational angle segment based on the signal of the sensor and determine the rotational angle based on the known rotational angle segment, as described above. This results in the advantages already mentioned. For this purpose, the controller is suitably electrically connected to the sensor, in particular to the sensor output of the sensor. The controller is especially configured to analyze the output signal of the sensor in order to analyze the magnetic field of the magnetic ring and its orientation and the influence on the sensor. Preferably, a TMR sensor (TMR = magnetic tunnel resistance or magnetoresistive effect) is present as the sensor.

[0008] In particular, it is provided that the controller first loads the stator with a first current in order to rotate the rotor into the selected first rotational angle segment in a first rotational direction, and there is a monitoring device by means of which the rotational movement of the rotor is monitored. If the machine or the rotor remains in the starting position, then the rotor is already in the selected first rotational angle segment. With the rotational angle segment known, the rotational angle position is now determined based on the sensor signal with the help of the rotational angle segment. However, if rotor movement or rotation is recognized, it follows that the rotor was not in the selected first rotational angle segment in its initial position. This already limits the search for the correct rotational angle segment. Preferably, the controller has at least one volatile or non-volatile memory in which the known results are stored for later use. In particular, it is stored whether the rotor rotates, and if so, in which direction (e.g., left or right) it rotates.

[0009] Thus, preferably, the monitoring device or the controller is configured to monitor the direction of rotation of the rotational movement. Depending on the direction of rotation detected during the first manipulation of the rotational movement, a second manipulation of the rotor is performed by the controller, and the second manipulation further restricts the selection of the rotational angle segments. By knowing the direction of rotation, it can be determined whether the rotor is moving in the first rotational direction as desired or in the opposite rotational direction. Depending on whether the rotor is moving in the desired rotational direction or in the opposite rotational direction, the rotor is then manipulated or loaded by the controller with a second current for a determined direction of rotation.

[0010] Particularly preferably, the controller is configured such that, when the rotor is moving in a rotational direction opposite to the first rotational direction or the expected rotational direction, in the next step, the stator is preferably loaded with a second current to cause the rotor to rotate two rotational angle segments in the rotational direction opposite to the first rotational direction, and the further rotational movement is monitored by the monitoring device. If the rotor does not move, i.e., the stopped state of the rotor is determined after the expiration of a pre-given duration, it is determined that the rotor is in the third or fourth segment with a pole pair ratio of 4:5 in the above-described embodiment (depending on the direction of rotation at the start of the method). Thus, the rotational angle segments are known and the rotational angle position can be clearly determined based on the sensor signal.

[0011] Preferably, the controller is configured to monitor the direction of rotation of the further rotational movement or to determine the direction of rotation of the rotational movement by means of the monitoring device. This is carried out as described above. In particular, the detected direction of rotation is compared with a second rotational direction, i.e., with the rotational direction opposite to the first rotational direction. For this purpose, the stored direction of rotation and the rotational movement are read from the memory and compared with each other by the controller. For this purpose, the controller particularly has an analysis logic, which is implemented by a microprocessor and / or an integrated circuit. If the rotor is moving in a direction opposite to the desired direction, the stator is loaded with a third current to cause the rotor to rotate only one rotational angle segment in the opposite direction. Now, the rotor must remain stationary and the current rotational angle segment can be determined. Depending on the corrected direction, the rotor or the magnetic ring is in the second or fourth rotational angle segment at the start of the system. Description of the Drawings

[0012] Other advantages and preferred features and combinations of features result from the foregoing description and from the claims. The present invention will be explained in detail below with the aid of the drawings. For this purpose, it is shown:

[0013] Figure 1 A brushless motor is shown in a simplified perspective view,

[0014] Figure 2A curve graph is shown for illustrating an advantageous operation method.

[0015] Figure 3 A table is shown for further illustrating the method, and

[0016] Figure 4 A flowchart is shown for illustrating the method. Detailed Description

[0017] Figure 1 A brushless motor 1 is shown in a simplified illustration, which has a housing 2, and a shaft 3 is rotatably supported in the housing. A rotor 4 is arranged on the shaft 3, and a drive pinion 5 is arranged torsionally resistant on the free end. The shaft 3 is rotatably supported in the housing 2 by means of a plurality of bearings 6, in particular rolling element bearings. Furthermore, a stator 7 with at least one energizable stator winding is provided for the rotor 4, wherein the stator 7 is arranged coaxially with respect to the rotor 4.

[0018] Furthermore, on the shaft 3, a magnetic signal generator 8 in the form of a multipolar magnetic ring 9 is arranged torsionally resistant between the rotor 4 and the drive pinion 5. A sensor 10 is assigned to the magnetic ring 9 in a housing-fixed manner, and the sensor is configured to be magnetic field sensitive. The sensor 10 thus serves as a signal receiver for the signal generator 8.

[0019] The number of pole pairs of the rotor 4 and the magnetic ring 9 are configured to be relatively prime. According to this embodiment, the rotor 4 has a number of pole pairs z 4 = 4, and the magnetic ring 9 has a number of pole pairs z 9 = 5. With the sensor device composed of the sensor 10 and the magnetic ring 9, the rotational angle position of the rotor 4, especially during the start-up of the system of the motor 1, is determined by means of a controller 11, and the controller is set up to execute the method described below.

[0020] For this purpose, Figure 2 First, the characteristics of the motor 1 are shown in a plurality of curve graphs with respect to the mechanical rotational angle Here, the uppermost curve graph shows the characteristic curve of the mechanical rotational angle . The curve graph located below it shows the electrical rotational angle of the rotor 4 with a number of pole pairs of 4. The curve graph located below it shows the magnetic rotational angle of the magnetic ring 9 with respect to the mechanical rotational angle 4. Figure 2 The lowermost section of

[0021] The controller 11 is configured to first determine the rotational angle segment in which the current rotational angle of the rotor 4 lies by means of the vernier principle or the slide rule principle in order to determine the current rotational angle of the rotor 4, and to determine the current rotational angle based on the determined rotational angle segment by means of the signals detected by the sensor. In the case where the load torque is small enough, the rotational angle segment can be identified by means of the vernier principle or the slide rule principle in a short time.

[0022] Subsequently, the exact mechanical angle including all angle corrections is immediately determined. For this purpose, the sensor device is first initialized when the system is started. That is, it is known in which rotational angle segment the magnetic ring 9 is located. This is solved by means of the method described below with reference to Figure 3 and Figure 4 which determines the correct rotational angle segment by adjusting the electric field or the current.

[0023] Due to the number of pole pairs z 9 = 5, there are currently five different rotational angle positions in which the rotor 4 can be magnetically locked in the state without current, such that in the stopped state of the rotor, five different rotational angle segments I to V are obtained, in which the rotor can be located. By means of an advantageous method, the correct rotational angle segments I to V are known. For this purpose, it is preferably provided that the method is only carried out when the motor 1 can reach a state of low load torque or no load torque during startup, thereby reliably ensuring the locking of the rotor 4.

[0024] As Figure 2 shown, due to the relatively prime pole pairs, an angular offset that is a multiple of 18° is generated: 360° / (z 4 x z 9 ) = 18°. Due to the overflow of the circle, the following relationship applies here: a lag angle α 4 of 3 x 18° also corresponds to a lag angle α 4' = - 2 x 18°. Similarly, it applies that a lag angle α 5 of 4 x 18° corresponds to a lag angle α 5' = - 1 x 18°, and here it depends on the rotational direction of the rotor 4. For better understanding, the following lag angles are used below: 0°; 18°; 36°; - 36°; - 18°.

[0025] This is achieved by the method implemented by the controller 11 described below, which enables the current to be switched on quickly, thus ensuring a particularly short initialization time. Here, the electric machine 1, which is configured as a DC machine with permanent magnet excitation, remains almost motionless when switched on, and in certain cases, a short rising ramp of the current is already sufficient for initializing and determining the current rotational angle of the rotor 4.

[0026] The precondition is that a jammed electric machine 1 or a jammed rotor 4 can be excluded.

[0027] Here, taking advantage of the fact that based on the number of pole pairs z 5 = 5 of the magnetic ring 9 and there are five different angular offsets of this magnetic ring 9 here, the correct rotational angle segments I to V can be determined with at most two corrections in the approximation method.

[0028] For this purpose, after system initialization in step S1, first in step S2, the sub-load current is set in such a way that the rotor 4 is adjusted in the direction of segment I. Here, the rotational movement of the rotor 4 is monitored in step S3. In sub-step S3a, first it is checked whether the rotational movement is in the pre-determined rotational direction, and in sub-step S3b, whether the rotational movement is in the direction opposite to the pre-given rotational direction. If the query shows that there is no rotational movement because no rotational movement in the rotational direction or in the direction opposite to the rotational direction is detected (n), then in step S4 it is determined that the rotor 4 is already in the rotational angle segment I.

[0029] However, if when the query S3a is answered affirmatively (j), the rotor 4 should move in the desired rotational direction, then in step S5 the current angle is adjusted in two segments as the first correction angle β 1 in the opposite direction, so that the rotor rotates in the opposite direction by two rotational angle segments. If the rotor 4 remains stationary, then the rotor 4 is in the third segment III at system startup, depending on which rotational direction was selected at the beginning. This is checked in step S6. If the machine moves in the direction opposite to the controlled direction (j), then in step S7 the current angle is adjusted in one segment as the second correction angle β 2 again in the opposite direction. Now, the rotor 4 must remain stationary. Depending on the direction of correction, the magnetic ring 9 is in the second segment II at system startup. If the query in step S6 shows that the rotor 4 is not moving (n), then in step S8 it is determined that the rotor is in the third segment and no further control is required.

[0030] If the query in step S3b reveals that the rotor 4 has rotated (j) against the first rotational direction, then in step S9 the stator 7 is energized in such a way that the rotor rotates in the opposite direction by two angular segments of rotation (β 1 = +36°). In the subsequent query S10, it is checked again whether angular movement in the desired direction has occurred. If this is the case (j), then the stator 7 is again energized in step S11 in such a way that the rotor 4 rotates by the angular segment β 2 = -18° against the first rotational direction, so that it can be determined that the rotor 4 is then located in the fifth angular segment V.

[0031] If the query in step S10 reveals that the rotor 4 has not moved, then no further manipulation is required and in step S12 it is determined that the rotor 4 is already located in the angular segment IV.

[0032] For this purpose, Figure 3 the method for this embodiment is shown in a table. In the first column, the segments I to V are listed.

[0033] In the second column, the hysteresis angle α is plotted. In the third column, the speed Ω 1 is detected after the first energization of the current. This speed is calculated in particular with the aid of the signal of the sensor 10. In the fourth column, the first correction angle β 1 is plotted, in the fifth column, the speed Ω 2 reached during the second energization of the current is plotted, and in the last column, the second correction angle β 2 is plotted.

[0034] The method or the controller 11 described can be applied or used in all co-prime combinations of the number of pole pairs of the rotor 4 and the magnetic ring 9, whereupon the individual steps are then matched accordingly in order to obtain unambiguous conclusions.

Claims

1. A brushless motor (1) comprising a housing (2), at least one rotor (4) arranged on a shaft (3) rotatably supported in the housing (2), a stator (7) fixed to the housing, and a controller (11), wherein: A rotor position detection device operating in a contactless manner is provided for a rotor (4), the rotor position detection device having a multi-pole magnetic ring (9) arranged in a rotationally fixed manner on a shaft (3) and at least one magnetic field-sensitive sensor (10) which is radially assigned to the outer circumference of the magnetic ring (9) in a manner fixed to a housing, characterized in that the number of pole pairs (z4) of the rotor (4) and the number of pole pairs (z9) of the magnetic ring (9) are mutually prime, wherein: The controller (11) is configured to determine when the motor is turned on: In which of a plurality of predetermined angular segments the angular position of the rotor is located; Each of the plurality of predetermined angular segments includes a corresponding angular range, and a combination of the corresponding ranges totals 360°; The determination is performed by executing a program that predetermines the following sequence of algorithmic steps: (a) deriving a corresponding current output corresponding to a corresponding target movement of the rotor in a corresponding predetermined direction at a corresponding target movement angle; (b) subsequently correspondingly determining whether the rotor moves in the corresponding predetermined direction corresponding to the corresponding current output; and during the step sequence, determining different combinations of the rotor in response to the corresponding current output: (a) moving in the corresponding predetermined direction, (b) moving opposite to the corresponding predetermined direction, and (c) not moving, thereby indicating that the rotor is positioned within a corresponding one of a plurality of predetermined angular segments in response to the corresponding current output, the predetermined different combinations including, for each of the predetermined angular segments, when at least one corresponding combination is determined to occur by the controller (11), this results in the controller (11) of the rotor correspondingly determining that the rotor is located in the corresponding predetermined angular segment.

2. The brushless motor according to claim 1, characterized in that: The rotor (4) has a pole pair number (z4) of 4.

3. The brushless motor according to claim 1, characterized in that: The magnetic ring (9) has a pole pair number (z9) of 5.

4. The brushless motor according to any one of claims 1 to 3, characterized in that: The number of pole pairs (z9) of the magnetic ring (9) determines the number of rotation angle segments of the rotor position detection device.

5. The brushless motor according to any one of claims 1 to 3, characterized in that A controller (11) is specially configured to determine the rotation angle segment of the magnetic ring (9) based on the signal of the sensor and to determine the rotation angle based on the determined rotation angle segment (1V).

6. The brushless motor according to claim 5, characterized in that: The controller (11) applies a first current to the stator (7) in order to determine the rotation angle segment (1V) so as to rotate the rotor (4) along a first rotation direction into a first rotation angle segment (I), and a monitoring device is provided by means of which the rotational movement of the rotor (4) is monitored.

7. The brushless motor according to claim 6, characterized in that: The monitoring device is designed to monitor the rotational direction of the rotational movement.

8. The brushless motor according to claim 6 or 7, characterized in that: The controller (11) applies a second current to the stator (7) in order to rotate the rotor (4) by two rotation angle segments (β1) in a rotation direction opposite to the first rotation direction, and the monitoring device monitors the rotational movement of the rotor (4).

9. The brushless motor according to claim 8, characterized in that: The monitoring device is designed to monitor the rotational direction of the rotational movement.

10. The brushless motor according to claim 6 or 7, characterized in that: If the monitoring device has detected that the rotor (4) has rotated in the first rotational direction by the second current, the controller (11) applies a third current to the stator (7) in order to rotate the rotor (4) in the first rotational direction by a rotation angle segment (β1).

11. The brushless motor according to claim 1, characterized in that: The brushless motor (1) is a brushless DC motor.

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