Position detection device for rotating electrical machine

Abstract

The present disclosure relates to a position detection device for detecting a rotor position of a rotating electrical machine, adapted to be mounted to the outside of the rotating electrical machine. The position detection device comprises a transmission gear set used for transmitting rotation information of a rotor of the rotating motor to the position detection device, the transmission gear set comprises a driving gear used for being coaxially fixed to an output shaft of the rotating motor, and the output shaft is fixedly connected with the rotor in the rotating motor; the driven gear is used for being meshed with the driving gear. The position detection device further comprises a magnet which is fixed to the driven gear and rotates together with the driven gear, and the magnetic pole direction of the magnet is arranged to be parallel to the plane where the driven gear is located. The position detection device further comprises a magneto-dependent sensor, the magnetic sensitive surface of the magneto-dependent sensor faces the magnet with a certain gap, and the magneto-dependent sensor is used for sensing the change of a magnetic field caused by rotation of the magnet and converting the sensed change of the magnetic field into an output electric signal.

Description

Technical Field

[0001] The present disclosure relates to the technical field of motors, and in particular to a position detection device for a rotating motor and a rotating motor including the position detection device. Background Art

[0002] The traction motor in pure electric vehicles and hybrid vehicles is a key safety component of the future powertrain. A major challenge in motor design is the "synchronization" of the stator current and the rotor position, that is, the rotating magnetic field generated by the stator current rotates at the same speed and in the same direction as the rotor. Whether it is synchronized will directly affect the motor's optimal efficiency, optimal torque control, and low torque variation. Currently, a resolver or eddy current sensor (ECS) is usually used to monitor the position and speed of the rotor.

[0003] A resolver is an electromagnetic sensor. It is a small AC motor used to measure angles. It is used to measure the angular displacement and speed of the rotating shaft of a rotating object. It consists of a stator and a rotor. The stator winding serves as the primary winding of the transformer, and the rotor winding serves as the secondary winding of the transformer. The working principle of a resolver is basically similar to that of an ordinary transformer, but the difference is that the relative positions of the primary and secondary windings of an ordinary transformer are fixed, so the ratio of its output voltage to the input voltage is a constant. The relative positions of the primary and secondary windings of a resolver will change with the angular displacement of the rotor, so the magnitude of its output voltage will also change with the angular displacement of the rotor. The voltage amplitude of the output winding is in a sine / cosine function relationship with the angular displacement of the rotor, or maintains a certain proportional relationship, or is linearly related to the angular displacement within a certain rotation range.

[0004] The working principle of eddy current sensors is based on the eddy current effect. They usually include a coil assembly and a metal target plate. The metal target plate needs to be mounted on the motor rotor. The target plate consists of several target lobes, and the number of target lobes matches the number of pole pairs of the motor. The coil assembly consists of a transmitting (Tx) coil and a receiving (Rx) coil, which are fixed to the motor stator and are usually arranged directly in the printed circuit board (PCB). The coils are in turn connected to the integrated circuit interface. The Tx coil is controlled by the sensor's control circuit and can generate an AC magnetic field after excitation. The target plate rotates with the motor's rotor and reflects the magnetic field to the coil according to its position. The Rx coil receives the field reflected by the target plate and generates a set of three AC signals (three-phase coil design). The position sensor interface chip converts the input signal from the Rx coil into differential sine / cosine (baseband) output signals. These signals are used to communicate with the electronic control unit. The electronic control unit (ECU) calculates the rotation angle from the sine / cosine signals through inverse tangent operation.

[0005] However, the above-mentioned rotary transformer and eddy current sensor have the following disadvantages: First, both the rotary transformer and the eddy current sensor require a large installation space, so, especially for the embedded permanent magnet motor (IPM), they cannot meet the need for miniaturization of their design. Second, the rotary transformer and the eddy current sensor are heavy, which is not conducive to fuel economy. Third, since the rotary transformer is a mechanical part, it does not have an active "functional safety" function (that is, a technology that avoids unacceptable functional risks through safety functions and safety measures), so it is difficult to detect the failure of the rotary transformer. Fourth, for eddy current sensors, in the case of a strong magnetic field, the output sine / cosine signal intensity is large, which can cause damage to the electronic circuit. Fifth, both the rotary transformer and the eddy current sensor are very sensitive to installation tolerances. Summary of the invention

[0006] The present invention provides a position detection device for the rotor of an electric motor installed outside a rotating electric motor, thereby replacing the above-mentioned detection mechanism for monitoring the position of the rotor through a rotating transformer or an eddy current sensor, and correspondingly alleviating and eliminating at least a part of the defects and deficiencies in the above-mentioned detection mechanism.

[0007] According to one aspect of the present disclosure, a position detection device for detecting the position of the rotor of a rotating electric machine is provided, which is suitable for being installed on the outside of the rotating electric machine. The position detection device includes: a transmission gear set, which is used to transmit the rotation information of the rotor of the rotating electric machine to the position detection device, and the transmission gear set includes: a driving gear, which is used to be fixed to the output shaft of the rotating electric machine in a coaxial manner, and the output shaft is fixedly connected to the rotor inside the rotating electric machine; a driven gear, which is used to mesh with the driving gear. The position detection device also includes: a magnet, which is fixed on the driven gear and rotates with the driven gear, and the magnetic pole direction of the magnet is set to be parallel to the plane where the driven gear is located. The position detection device also includes: a magnetic sensor, the magnetic sensitive surface of the magnetic sensor is arranged to face the magnet with a certain gap, and the magnetic sensor is used to sense the change of the magnetic field caused by the rotation of the magnet, and convert the sensed change of the magnetic field into an output electrical signal and output it.

[0008] According to an embodiment of the present disclosure, the position detection device further includes: an analysis unit, configured to determine the position of the rotor according to the output electrical signal.

[0009] According to an embodiment of the present disclosure, the transmission gear set is configured to have a gear ratio, which is set in association with the number of pole pairs of the rotating motor, wherein the gear ratio is the ratio of the number of teeth of the driving gear to the number of teeth of the driven gear, and the number of teeth of the driving gear is greater than or equal to the number of teeth of the driven gear.

[0010] According to an embodiment of the present disclosure, the gear ratio is set to 1 / n times the number of pole pairs of the rotating electric machine, where n is an integer greater than or equal to 1.

[0011] According to an embodiment of the present disclosure, the magnetic sensor is an anisotropic magnetoresistance (AMR) sensor or a tunnel magnetoresistance (TMR) sensor.

[0012] According to an embodiment of the present disclosure, the electrical signal output by the magnetic sensor is a two-path differential electrical signal.

[0013] According to an embodiment of the present disclosure, the position detection device further includes: an outer cover at least partially disposed around the driven gear, the magnet, and the magnetic sensor.

[0014] According to an embodiment of the present disclosure, a partition is provided inside the outer cover, and a through hole is provided on the partition; a gear shaft is provided on the driven gear, and the gear shaft passes through the through hole, one end of the gear shaft is fixed to the driven gear, and the other end is fixed to the magnet, so that the driven gear and the magnet are respectively rotatably supported on both sides of the partition, and when the magnet rotates driven by the driven gear, the gap between the magnet and the magnetic sensitive sensor can be maintained unchanged.

[0015] According to an embodiment of the present disclosure, the outer cover further includes: a fixing member for fixing the outer cover to the housing of the rotating electrical machine.

[0016] According to another aspect of the present disclosure, a rotating electric machine is provided, which includes the above-mentioned position detection device, and the position detection device is located outside the housing of the rotating electric machine.

[0017] Compared with the above-mentioned rotary transformer or eddy current sensor, the position detection device disclosed in the present invention has the following advantages:

[0018] First, the required installation space is small, which can especially meet the needs of motor miniaturization. Second, the weight of related components is light, which is conducive to the realization of fuel economy. Third, since the position detection device of the present invention is installed on the outside of the motor, and the magnetic field is generated by a separate external magnet, the interference of the larger magnetic field inside the rotating motor on the electronic circuit can be avoided. Fourth, the position detection device of the present invention can participate in the calculation of "functional safety". Fifth, the position detection device of the present invention is not sensitive to its installation position. Sixth, the decoding circuit and related algorithms are compatible with existing ECS ​​or rotary transformers. Seventh, by changing the gear ratio in the position detection device of the present invention, it can be matched with rotating motors with different numbers of motor pole pairs.

[0019] These and other aspects of the disclosure will be apparent from and elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Further details, features and advantages of the present disclosure are disclosed in the following description of exemplary embodiments in conjunction with the accompanying drawings, in which:

[0021] Figure 1 is an external view of a position detection device mounted at an output shaft of a rotating electrical machine according to an exemplary embodiment;

[0022] Figure 2 is an internal cross-sectional view of a position detection device mounted to an output shaft of a rotating electrical machine according to an exemplary embodiment.

[0023] Figure 3 FIG. 2 is a schematic diagram showing the sensing principle of a magnetically sensitive sensor.

[0024] Figure 4 FIG. 4 is a schematic diagram showing two differential signals output by a magnetic sensitive sensor. DETAILED DESCRIPTION

[0025] Figure 1 An external view of a position detection device according to an exemplary embodiment is shown. Figure 2 An internal cross-sectional view of the position detection device according to this exemplary embodiment is shown.

[0026] like Figure 1 and Figure 2 As shown, the position detection device 100 is suitable for being installed outside the rotating electrical machine, and is particularly suitable for being installed at the output shaft 200 outside the rotating electrical machine housing 6 .

[0027] The position detection device 100 includes: a transmission gear set 1, a magnet 2 and a magnetic sensor 3. The transmission gear set 1 is used to collect the rotation information of the rotor of the rotating motor and transmit it to the position detection device 100. Driven by the transmission gear set 1, the magnet 2 rotates synchronously with the output shaft 200 to generate a magnetic field with a changing direction above the magnetic sensor 3. After the magnetic sensor 3 senses the magnetic field with a changing direction generated by the magnet 2, it converts the sensed magnetic field signal into an electrical signal and outputs it to determine the position of the rotor.

[0028] refer to Figure 1 and Figure 2The transmission gear set 1 further includes a driving gear 11 and a driven gear 12 meshing with the driving gear 11. The driving gear 11 is coaxially fixed to the output shaft 200 of the rotating motor, so that the driving gear 11 can rotate with the output shaft 200 under the drive of the output shaft 200 of the motor, and the driving gear 11 then drives the driven gear 12 meshing with it to rotate. Since the output shaft 200 is fixedly connected to the rotor inside the rotating motor, the rotation of the motor rotor can be directly reflected in the rotation of the output shaft 200, and then transmitted to the driving gear 11 and the driven gear 12. In this way, the rotation information of the rotor of the rotating motor is collected and input into the detection device 100.

[0029] In the example, the driving gear 11 can be in the form of a gear ring, which is coaxially sleeved and fixed on the output shaft. The driving gear 11 in the form of a gear ring is convenient for fixing with the output shaft 200 (for example, in an interference fit manner), and it is also convenient for aligning the axis of the driving gear 11 with the axis of the motor output shaft 200.

[0030] In the example, the rotation axes of the driving gear 11 and the driven gear 12 are parallel to each other, thereby forming a parallel axis gear set. The meshing of the parallel axis gear set is basically rolling, and the relative sliding is very small, so the efficiency is relatively high.

[0031] refer to Figure 2 , the magnet 2 is fixed on the driven gear 12 as a magnetic field generating component and thus rotates with the driven gear 12. The magnetic pole direction of the magnet 2 is set to be parallel to the plane where the driven gear 12 is located. In some examples, the magnet 2 is a permanent magnet. The magnetic sensor 3 is arranged facing the magnet 2 with an appropriate gap, and the appropriate gap enables the magnetic sensitive surface of the magnetic sensor 3 facing the magnet 2 to sense the magnetic field generated by the magnet 2 and the change of the magnetic field caused by the rotation of the magnet 2. The magnetic sensor 3 can also convert the sensed change of the magnetic field into an electrical signal and output it.

[0032] According to some embodiments of the present disclosure, the position detection device further includes a housing 5 disposed at least partially around the driven gear 12 , the magnet 2 , and the magnetic sensor 3 .

[0033] refer to Figure 2In a specific embodiment, the outer cover 5 has a partition 51 inside, and the partition 51 has a through hole 511 for the gear shaft 121 of the driven gear 12 to pass through. One end of the gear shaft 121 is fixed to the driven gear 12, and the other end is fixed to the magnet 2, so that the driven gear 12 and the magnet 2 are rotatably supported on both sides of the partition 51, respectively, and when the magnet 2 rotates driven by the driven gear 12, the gap between the magnet 2 and the magnetic sensor 3 can be kept unchanged. In this way, stable rotation support of the transmission gear can be achieved, and then stable magnetic field generation and stable and reliable output of electrical signals can be achieved.

[0034] According to some embodiments of the present disclosure, the outer cover 5 further includes a fixing member 52 for fixing the outer cover 5 to the housing of the rotating motor. In some examples, the fixing member 52 may be, for example, a bolt. In this way, it is possible to ensure that the installation position of the position detection device 100 relative to the rotating motor is fixed, thereby ensuring stable and reliable engagement between the driving gear 11 and the driven gear 12.

[0035] According to some embodiments of the present disclosure, the position detection device 100 further includes an analysis unit for determining the position of the rotor according to the output electrical signal. The analysis unit can be fixed on the same circuit board 4 as the magnetic sensor 3. Alternatively, the analysis unit can also be arranged outside the outer cover 5 and away from the position of the magnetic sensor 3, for example, arranged in an electronic control unit (ECU) or as a part of the ECU. The signal electrically generated by the magnetic sensor 3 is transmitted to the ECU via the transmission line 7.

[0036] Compared with a rotary transformer or an eddy current sensor, the position detection device 100 disclosed in the present invention requires a smaller installation space and is lighter in weight, which can especially meet the needs of motor miniaturization and is conducive to the realization of fuel economy. In addition, since the position detection device disclosed in the present invention is installed outside the motor and the magnetic field is generated by a separate external magnet, the interference of the larger magnetic field inside the rotating motor on the electronic circuit can be avoided. In addition, the traditional rotary transformer is a mechanical part and currently has no quantified failure rate, so it does not have an active "functional safety" function. In contrast, the position detection device 100 disclosed in the present invention can participate in the calculation of "functional safety".

[0037] The magnetically sensitive sensor 3 of the present disclosure is described in detail below.

[0038] According to some embodiments of the present disclosure, the magnetic sensitive sensor 3 is a magnetoresistive element (MR) sensor. The MR sensor element is a magnetic sensor element that uses the magnetoresistive effect (MR effect). The MR effect is a phenomenon in which resistance changes with a magnetic field, which is an effect that occurs in magnetic materials.

[0039] According to some embodiments of the present disclosure, the magnetic sensor 3 may be an anisotropic magnetoresistance (AMR) sensor. The AMR sensor has a structure of a single magnetic layer (free layer), and current flows parallel to the film surface.

[0040] According to some embodiments of the present disclosure, the magnetic sensor 3 may also be a tunnel magnetoresistance effect (TMR) sensor. For a TMR sensor, it has a structure in which two layers of strong magnetic layers (free layer / fixed layer) sandwich a barrier layer of a thin insulator in the middle, and the current flows perpendicular to the film surface. The magnetization direction of the fixed layer is fixed, but the magnetization direction of the free layer changes according to the direction of the external magnetic field, and the resistance of the element also changes accordingly. When the magnetization directions of the fixed layer and the free layer are parallel, the resistance is minimum, and a large current flows through the barrier layer. In addition, when the magnetization directions are antiparallel, the resistance becomes extremely large, and almost no current flows through the barrier layer.

[0041] refer to Figure 3 Taking the TMR sensor as an example, when the magnet rotates on the TMR sensor, the magnetization direction of the free layer follows the direction of the magnetic field generated by the magnet, and the resistance of the element changes continuously. Since the resistance value is proportional to the relative angle between the magnetization directions of the fixed layer and the free layer, the rotation angle of the magnet relative to the TMR sensor can be sensed. It will be understood that the angle measurement principle of the AMR sensor is similar to that of the TMR sensor, and will not be repeated here.

[0042] The magnetic sensor operates in a saturated state, so within a certain installation tolerance range, the sensor parameters remain unchanged, and thus the magnetic sensor 3 is not sensitive to the installation position. In contrast, conventional rotary transformers and ECS are very sensitive to installation tolerances.

[0043] refer to Figure 4 According to the embodiment of the present disclosure, the electrical signal output by the magnetic sensor 3 is a two-way differential electrical signal. For example, two groups of magnetic sensitive elements may be integrated inside the magnetic sensor 3, which are used to sense the magnetic field components of the external magnetic field along the X-axis and Y-axis directions respectively. For example, two groups of AMR elements may be integrated inside the AMR sensor, and similarly, two groups of TMR elements may be integrated inside the TMR sensor. The direction signal of the magnetic field projected on the sensing surface of the magnetic sensor 3 is detected by the magnetic sensitive elements in the X-axis and Y-axis directions at the same time, so the output signal curve of the magnetic sensor 3 is two-way differential electrical signals. In this embodiment, the two-way differential electrical signals are mutually orthogonal sine and cosine voltage signals Va and Vb. According to the two-way differential electrical signals, the position information of the rotor is obtained by solving the inverse tangent function.

[0044] It will be understood that although Figure 4The phase difference between the two differential electrical signals shown in FIG. 1 is 90°, but the two differential electrical signals may also be set to have other phase differences. For example, the two differential electrical signals may be set to have a phase difference of 30°.

[0045] The transmission gear set 1 of the present disclosure is described in detail below.

[0046] According to some embodiments of the present disclosure, the transmission gear set 1 is configured to have a gear ratio, and the gear ratio is calculated as the ratio of the number of teeth of the driving gear to the number of teeth of the driven gear. Referring to equation (1),

[0047] i=Z1 / Z2(1), where i is the gear ratio, Z1 is the number of teeth of the driving gear, and Z2 is the number of teeth of the driven gear, wherein the number of teeth Z1 of the driving gear is greater than or equal to the number of teeth Z2 of the driven gear.

[0048] It will be understood that when Z1=Z2, the rotation speeds of the driving gear 11 and the driven gear 12 are consistent. When Z1>Z2, the rotation speed of the driven gear 12 is greater than that of the driving gear 11.

[0049] According to an embodiment of the present disclosure, the gear ratio i is set in association with the number of pole pairs P of the rotating electrical machine, that is, the value of the gear ratio i is correlated with the number of pole pairs P of the rotating electrical machine.

[0050] According to some embodiments of the present disclosure, the gear ratio i is set to 1 / n times the number of pole pairs P of the rotating motor, where n is an integer greater than or equal to 1, referring to equation (2):

[0051] i=P / n(2), where i is the gear ratio, P is the number of pole pairs of the rotating motor, and n=1, 2, 3, ... In other words, the number of pole pairs P can be equal to the gear ratio i (i.e., n=1), or it can be 2 times (i.e., n=2), 3 times (i.e., n=3), or a higher integer multiple of the gear ratio i. In this way, the gear ratio i can be adjusted to match the higher angle measurement accuracy brought by the number of pole pairs P of the rotating motor in the traditional way.

[0052] Specifically, the traditional rotary transformer improves its measurement accuracy by increasing the number of pole pairs. Generally, when in use, the number of pole pairs of the rotary transformer matches the number of pole pairs of the rotary motor. In a rotary motor, the circumferential mechanical angle is 360°, and the size of its electrical angle is related to the number of pole pairs P. The total circumferential electrical angle is P*360°. Therefore, a multi-pole rotary transformer can amplify the limited mechanical angle by P times. In this case, even if there is only a small relative angular displacement between the stator and the rotor, the amplitude of its output electrical signal will change significantly, thereby improving the resolution of the mechanical angular displacement.

[0053] Different from the above-mentioned method of improving the angle measurement accuracy by increasing the number of motor pole pairs P, the present disclosure adopts a mechanical method to improve the angle measurement accuracy. Specifically, the gear speed change principle is adopted to mesh the driving gear 11 (for example, having a large number of teeth Z1) and the driven gear 12 (for example, having a small number of teeth Z2). Under the premise of ignoring the influence of gear indexing and meshing errors, the driving gear 11 rotates one circle and the driven gear will drive the driven gear to rotate i (i=Z1 / Z2) circles. The resolution of the rotation angle can be increased by i times with the gear ratio i, so the accuracy can also be improved accordingly.

[0054] Therefore, by using a transmission gear set, on the one hand, for rotating motors with different pole pairs P, the corresponding measurement accuracy can be obtained by correspondingly changing the gear ratio i of the transmission gear set 1 (for example, by adjusting the number of teeth Z1 of the driving gear 11 and / or the number of teeth Z2 of the driving gear 12). In this way, the higher angle measurement accuracy brought by the pole pair number P of the rotating motor in the traditional way can be matched. On the other hand, for a rotating motor with a given motor pole pair number P, when the gear ratio i is set to be equal to the motor pole pair number P (that is, i=P), it can achieve the optimal angular displacement measurement accuracy.

[0055] Another aspect of the present disclosure relates to a rotating electrical machine, which includes the above-mentioned position detection device 100 , and the position detection device 100 is located outside a housing of the rotating electrical machine.

[0056] Reference numerals list

[0057] 1 Transmission gear set

[0058] 2 Magnets

[0059] 3 Magnetic sensor

[0060] 4 Circuit Board

[0061] 5 Outer cover

[0062] 6 Rotating motor housing

[0063] 7 Transmission Lines

[0064] 11 Driving gear

[0065] 12 Driven gear

[0066] 51 partition

[0067] 52Fixed parts

[0068] 100 Position detection device

[0069] 200 Rotating motor output shaft

[0070] 121 gear shaft

[0071] 511 through hole

Claims

1. A position detection device (100) for detecting a rotor position of a rotating electrical machine, adapted to be mounted outside the rotating electrical machine, the position detection device (100) comprising: A transmission gear set (1) is used to transmit the rotation information of the rotor of the rotating electrical machine to the position detection device, and the transmission gear set (1) comprises: a driving gear (11) for being coaxially fixed to an output shaft (200) of the rotating electric machine, wherein the output shaft is fixedly connected to the rotor inside the rotating electric machine, and A driven gear (12), used for meshing with the driving gear (11); a magnet (2) fixed on the driven gear (12) and rotating together with the driven gear (12), wherein the magnetic pole direction of the magnet (2) is arranged to be parallel to the plane where the driven gear (12) is located; and A magnetic sensor (3), wherein the magnetic sensitive surface of the magnetic sensor (3) is arranged facing the magnet (2) with a certain gap, and the magnetic sensor (3) is used to sense the change of the magnetic field caused by the rotation of the magnet (2), and convert the sensed change of the magnetic field into an output electrical signal.

2. The position detection device according to claim 1, wherein: The position detection device (100) further comprises: An analysis unit is used to determine the position of the rotor according to the output electrical signal.

3. The position detection device according to claim 1, wherein: The transmission gear set (1) is configured to have a gear ratio (i), which is set in association with the number of pole pairs (P) of the rotating electrical machine. The transmission (i) is the ratio of the number of teeth (Z1) of the driving gear to the number of teeth (Z2) of the driven gear, and the number of teeth (Z1) of the driving gear is greater than or equal to the number of teeth (Z2) of the driven gear.

4. The position detection device according to claim 3, wherein: The gear ratio (i) is set to 1 / n of the number of pole pairs (P) of the rotating electric machine, where n is an integer greater than or equal to 1. 5 . The position detection device according to claim 1 , wherein the magnetic sensor is an anisotropic magnetoresistance (AMR) sensor or a tunnel magnetoresistance (TMR) sensor. 6 . The position detection device according to claim 1 , wherein the electrical signal output by the magnetic sensor is a two-path differential electrical signal.

7. The position detection device according to claim 1, wherein: The position detection device also includes: The outer cover (5) is at least partially disposed around the driven gear (12), the magnet (2), and the magnetic sensor (3).

8. The position detection device according to claim 7, wherein: The outer cover (5) has a partition (51) inside, and the partition (51) has a through hole (511); The driven gear (12) has a gear shaft (121), the gear shaft (121) passes through the through hole (511), one end of the gear shaft (121) is fixed to the driven gear (12), and the other end is fixed to the magnet (2), so that the driven gear (12) and the magnet (2) are rotatably supported on both sides of the partition (51), respectively, and when the magnet (2) rotates driven by the driven gear (12), the gap between the magnet (2) and the magnetic sensor (3) can be kept unchanged.

9. The position detection device according to claim 7, wherein: The outer cover also includes: A fixing member (52) is used to fix the outer cover (5) to the housing (6) of the rotating electrical machine.

10. A rotating electrical machine, comprising a position detection device (100) according to any one of claims 1 to 9, wherein the position detection device is located outside a housing (6) of the rotating electrical machine.

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