JP2015100141A - Rotational phase detector of synchronous motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the rotational phase detector of a synchronous motor capable of detecting the rotational phase of a synchronous motor reliably at high speed, by means of one position sensor.SOLUTION: Assuming the amplitude of cogging torque is Ta, the degree of which is N, the frictional torque acting when a synchronous motor 1 is stopped is Tf, and the angle obtained by the following equation is X, a position sensor 2 is installed so that the rotational position of a rotor 11, when a position sensor signal from the position sensor 2 is switched, falls within a range capable of installing the position sensor separated by the angle X or more from a stable stop position determined by the cogging torque. X={sin(Tf/Ta)}/N.

Description

  The present invention relates to an apparatus for detecting the rotational phase of a synchronous motor, and more particularly to a rotational phase detection apparatus for a synchronous motor that can reliably and rapidly detect the rotational phase using a single position sensor.

  A control apparatus for a synchronous motor using a position sensor generates an estimated phase by interpolation calculation using a rotation speed calculated from time intervals of a plurality of position sensor signals, and controls an inverter based on the estimated phase. For example, in Patent Document 1, in a DC fan motor control device using a single position sensor, a start excitation pattern is started at a low speed from a stop state, and the speed and position sensor of the start excitation pattern are detected. There has been proposed a method of switching to control based on the position detected by the position sensor after the speeds coincide.

JP 2006-174647 A

  The technique disclosed in Patent Document 1 cannot start at high speed from a stopped state because it takes time until the control is switched to the control based on the position detected by the position sensor after starting with the starting excitation pattern. In addition, there is also a method in which starting by the technique of Patent Document 1 is performed in advance, the synchronous motor is further rotated at an extremely low speed, and the phase estimation based on the detected speed is immediately performed when a drive command for the synchronous motor is given. Although it is conceivable, there is a problem of excessive power consumption because it is necessary to constantly rotate the motor even in the standby state.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a rotational phase detector for a synchronous motor that can reliably and rapidly detect the rotational phase of the synchronous motor with a single position sensor.

The rotational phase detection device for a synchronous motor according to the present invention includes a sensor target attached to the rotor side of the synchronous motor and a relative position relationship in the circumferential direction with the sensor target attached to the stator side of the synchronous motor. Or a single position sensor that outputs a position sensor signal of L, detecting the rotational speed of the rotor based on the position sensor signal, and detecting the rotational phase based on the rotational speed and the position sensor signal.
The position sensor is installed so that the rotational position of the rotor when the position sensor signal is switched is a position separated from the stable stop point determined by the cogging torque generated in the synchronous motor by a predetermined angle or more.

  As described above, in the rotational phase detection device for a synchronous motor according to the present invention, the rotational position of the rotor when the position sensor signal is switched is a position separated by a predetermined angle or more from the stable stop point determined by the cogging torque. Since the position sensor is installed, when the synchronous motor is started, an increase in detection phase error caused by starting the rotor from the position where the position sensor signal is switched or the vicinity thereof is prevented, and one position sensor is used. However, the rotational phase of the synchronous motor can be detected reliably and at high speed.

It is a block diagram of the control apparatus of a synchronous motor including the structure which concerns on the rotation phase detection in Embodiment 1 of this invention. It is the figure which looked at the synchronous motor 1 of FIG. 1 from the axial direction. It is the fragmentary sectional view which looked at each part of Drawing 2 from the side. It is a figure explaining the relationship between the installation position of the position sensor of this invention, and cogging torque. It is a figure explaining the detail of a position sensor position. It is a flowchart explaining operation | movement of the control apparatus of the synchronous motor in Embodiment 1 of this invention. It is a control block diagram which shows the 2nd phase estimation means which bears step S4 of FIG. It is a timing chart explaining operation | movement of the 2nd phase estimation means of FIG. It is a control block diagram which shows the 1st phase estimation means which bears step S3 of FIG. 10 is a timing chart for explaining the operation of the first phase estimation means of FIG. 9. FIG. 11 is a timing chart for explaining the operation of the first phase estimation unit in FIG. 9 when the initial value of the position sensor signal is different from that in FIG. 10. It is a figure explaining the condition at the time of installing the position sensor 2 shifting from the original position. It is a timing chart explaining the operation | movement of a 1st phase estimation means in the case of FIG. It is the figure which looked at the synchronous motor for demonstrating the position sensor 2 and sensor target 12 in Embodiment 2 of this invention from the axial direction. It is a perspective view which shows 12 A of sensor targets in Embodiment 3 of this invention. It is the figure which looked at the synchronous motor for demonstrating the position sensor 2A and sensor target 12A in Embodiment 3 of this invention from the axial direction. It is the fragmentary sectional view which looked at each part of Drawing 16 from the side.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram for explaining a synchronous motor control device including a configuration related to rotational phase detection according to Embodiment 1 of the present invention. In the first embodiment, a case where a synchronous motor is used for driving an electric supercharger is taken as an example.
An electric supercharger is a device that drives a supercharger with an electric motor in order to increase the output of an internal combustion engine. Compared to conventional turbochargers (for example, superchargers and turbochargers), electric superchargers are characterized by having high start-up responsiveness by operating the supercharger by driving the motor at high speed. is there. Therefore, it is necessary to start the synchronous motor at a high speed from the stopped state.

First, an outline of the control device will be described.
The rotational phase of the rotor of the synchronous motor 1 is detected based on the position sensor signal output from the position sensor 2 such as one Hall IC, and this position sensor signal is sent to the control unit 3. In the control unit 3, the speed detection unit 4 detects the speed of the synchronous motor 1, and the phase estimation unit 5 estimates the rotational phase of the synchronous motor 1 and outputs it to the inverter control unit 6. The inverter control unit 6 generates a PWM signal based on the detected speed / phase and outputs it to the inverter 7 as a gate signal.
The inverter 7 converts the DC power supplied from the battery 8 into AC power based on the gate signal and supplies the AC power to the synchronous motor 1. The synchronous motor 1 drives the compressor 9 to compress air and perform supercharging. Do.

  2 and 3 are configuration diagrams for explaining the structure and arrangement of the position sensor 2 and the sensor target 12 that are responsible for rotational phase detection in the control apparatus for the synchronous motor 1 of FIG. FIG. 2 shows a view seen from the axial direction when the position sensor 2 and the sensor target 12 are installed in the synchronous motor 1, and FIG. 3 shows a partial cross-sectional view seen from the side.

The sensor target 12 is attached to the rotor side of the synchronous motor 1. The position sensor 2 is attached to the stator side, and outputs a position sensor signal in accordance with the circumferential relative positional relationship with the sensor target 12.
Specifically, the sensor target 12 is installed on the rotor 11 of the synchronous motor 1 via the shaft 14. The sensor target 12 is a gear tooth type magnetic body having irregularities in the radial direction.
For this reason, the sensor target 12 has few constituent members and can easily adjust the balance of the rotating shaft. In particular, when applied to an electric supercharger, the sensor target 12 has a robust and sufficient strength against the ultra-high speed rotating centrifugal force. Become.

  The position sensor 2 installed on the stator 13 has a magnet, detects a magnetic flux according to the vertical change in the facing distance to the sensor target 12, and compares the unevenness of the sensor target 12 with a predetermined threshold value. H or L digital position sensor signal corresponding to

  As shown in FIG. 2, the position sensor 2 is installed at the center of the U phase of the coil 10 of the stator 13, and the uneven edge of the sensor target 12 is positioned at the N pole center of the rotor 11. In this case, as will be described later with reference to FIG. 4, the H / L output of the position sensor signal is switched at the electrical angles of 0 deg and 180 deg.

  In the first embodiment, a case where a Hall IC is used as the position sensor 2 has been described as an example. The position sensor may be, for example, an MR sensor or an eddy current sensor as long as it can be substantially detected.

4 and 5 are diagrams for explaining a method for determining the arrangement position of the position sensor 2. FIG. 4 shows the relationship between the electrical angle and the cogging torque in the synchronous motor 1. The cogging torque is a component of the order of the value obtained by dividing the least common multiple of the number of poles and the number of stator slots by the number of pole pairs.
Assuming that the amplitude of the cogging torque is Ta, the order is N, and the electrical angle is θe, the cogging torque Tcog is expressed as shown in Equation (1). In the case of the first embodiment, since the number of poles is 4, the number of pole pairs is 2, and the number of slots is 6, the order N of the cogging torque is N = 6.

  Tcog = Ta × sin (N × θe) (1)

  In FIG. 4, a place indicated by a white circle is a so-called stable stop point. The stable stop point corresponds to a position where the cogging torque is zero and the inclination is negative, that is, the formula (2) is established.

  Tcog = 0 and dTcog / dθe <0 (2)

  At this position, the cogging torque is zero, and a torque that attempts to return to the original position even when passing through that position acts, so that it becomes a stable stop point at which the rotor is likely to stop. In the case of FIG. 4, the six electrical angles θe = 30, 90, 150, 210, 270, and 330 deg are stable stop points that are easily stopped by the magnetic attraction force of the cogging torque.

  Even if the synchronous motor 1 stops at the position of the stable stop point, the position of the synchronous motor 1 does not match the position where the position sensor signal switches from H to L or from L to H. It is possible to prevent the occurrence of a large detection phase error that causes a starting failure as described later, and to realize reliable and high-speed phase detection.

FIG. 5 explains the procedure for determining the position where the position sensor 2 should be installed from the above viewpoint.
FIG. 5 shows the relationship between the electrical angle and the load torque applied to the rotor 11. The load torque Tl is the sum of the cogging torque Tcog and the friction torque Tf, and is expressed as in Expression (3).

  Tl = Ta × sin (N × θe) + Tf (3)

FIG. 5 shows that the position where Tl = 0 and dTl / dθe <0 is shifted by an angle X from the previous stable stop point due to the load torque Tl including the friction torque Tf.
This angle X is expressed by equation (4) from FIG.

X = {sin ⁻¹ (Tf / Ta)} / N (0 ≦ X <2π / N) (4)

By the way, in consideration of the fact that the friction torque Tf actually changes below the maximum value of Tf, and the polarity can also change, the position where the friction is easy to stop is before and after the stable stop point determined by the cogging torque. It can vary within the range of X.
Therefore, as shown in FIG. 4, the range between the front and rear X of the stable stop point is set as a position sensor installation impossible range, and the position sensor 2 is installed in a position sensor installation range other than this impossible range.
In the configuration diagram of FIG. 2, the position sensor is arranged at an electrical angle of 0 deg (positioned at the left end in FIG. 4) 30 deg away from the stable stop point.

The lower part of FIG. 4 shows the waveform of the position sensor signal. As can be seen in correspondence with FIG. 2, the position sensor 2 is the center in the circumferential direction of the U-phase coil of the stator 13, and therefore the U-phase coil. The position sensor 2 outputs an L level signal when facing the convex portion of the sensor target 12, and outputs an H level signal when facing the concave portion.
Further, in the lowermost stage of FIG. 4, the magnetic pole N (S) of the rotor 11 is shown at the circumferential center position of the magnetic pole.

FIG. 6 is a flowchart for explaining the operation of the control unit 3 of the synchronous motor 1, mainly the operation of the phase estimation unit 5. First, in step S1, the speed detection unit 4 detects the rotation speed of the rotor 11 from the time interval at which the position sensor signal from the position sensor 2 is switched, and outputs a speed detection value.
However, as will be described later, in the first period after the synchronous motor 1 is started at a predetermined starting speed until the position sensor signal switching is detected twice, the time interval itself at which the position sensor signal switches is obtained. Therefore, in this first period, the speed detection unit 4 outputs speed detection value = 0.

In step S2, it is determined whether or not the speed detection value from the speed detection unit 4 is 0. If the speed detection value = 0 (YES in step S2), that is, in the first period, as shown in FIG. The first phase estimation means outputs the estimated phase θi (step S3).
In step S2, NO, that is, when the speed detection value is not equal to 0, and therefore the second period in which the speed detection value is obtained from the time interval when the position sensor signal is switched after the first period has elapsed, the second stage shown in FIG. The estimated phase θi is output by the two-phase estimation means (step S4).
The estimated phase θi from step S3 or S4 is output to the inverter control unit 6 to execute inverter control (step S5).

FIG. 7 is a control block diagram showing the second phase estimating means responsible for the operation of step S4 of FIG. From the time interval when the position sensor signal switches to H / L, the phase can be detected with an electrical angle resolution of 180 deg.
In FIG. 7, the reference phase detection unit 16 outputs a reference phase determined corresponding to H or L of the position sensor signal, that is, 180 deg when the position sensor signal is H, and 0 deg when the position sensor signal is L. Then, the speed detection unit 17 measures the edge interval at which the H / L of the position sensor signal is switched, and detects the speed from the measured time. The estimated phase θi can be output by adding the reference phase and the detected speed integral value (interpolation phase) to perform speed interpolation.

  FIG. 8 is a timing chart for explaining the operation of the second phase estimation means of FIG. The estimated phase θi at the detection speed ω and the control time ti is obtained by equations (5) and (6).

ω = (θ2-θ1) / (t2-t1) = 180 / (t2-t1) (5)
θi = ω × (ti−t2) + θ2 (6)

  In the above equation, the detection speed ω is a value obtained at the latest switching time (t2), that is, a value obtained by subtracting the reference phase previous value θ1 from the reference phase latest value θ2 (θ2−θ1), and the detection time latest value t2. A value obtained by subtracting the previous detection time value t1 from (t2-t1) is used.

FIG. 9 is a control block diagram showing the first phase estimation means responsible for the operation of step S3 of FIG. Here, since the speed detection value = 0, speed interpolation based on the detection speed cannot be performed as in the second phase estimation means.
Therefore, the starting speed generating unit 19 gives a starting speed which is a predetermined constant value according to the starting method of the synchronous motor 1, and the phase at the time of starting is estimated by adding the integral value of the starting speed.

  FIG. 10 is a timing chart for explaining the operation of the first phase estimating means of FIG. The estimated phase θi at the control time ti is obtained by equation (7) using the starting speed ωstart.

  θi = ωstart × (ti−t1) + θ2 (7)

  Here, since the control unit 3 rotationally drives the synchronous motor 1 by so-called feedforward control using the starting speed ωstart as a speed command, the actual speed gradually increases from 0 after starting, but the phase estimation is Since the calculation is performed using the constant speed ωstart, the difference between the estimated phase and the actual phase value relatively increases.

  Since the speed detection value is obtained when the switching of the H / L of the position sensor signal is detected twice from the start at time t2, the detected value of step S4 described in FIG. This is a reliable phase estimation operation based on the speed detection value of the two-phase estimation means, and high-speed phase detection is possible particularly when compared with Patent Document 1.

  FIG. 11 is a timing chart for explaining the operation of the first phase estimating means when the level of the position sensor signal at the start is different from that in FIG. That is, in FIG. 10, the output of the position sensor signal at the start is L level and the reference phase at that time is θ1, whereas in FIG. 11, the output of the position sensor signal at the start is H level. Except for the fact that the reference phase at that time is θ2, it is the same as the case of FIG.

FIG. 12 shows a comparative example, which deviates from the requirements of the present invention regarding the installation position of the position sensor 2 and is positioned within the position sensor non-installable range so that the position sensor signal is switched near the stable stop point. The state which installed the sensor 2 is shown.
In the case of FIG. 4 in which the position sensor 2 is installed within the position sensor installable range inherent in the present invention, the stable stop points in the section where the position sensor signal is at the L level (0 to 180 deg) are 30, 90, and 150 deg. If the deviation from the stable stop point when the child 11 stops is ε, the estimated phase errors from the reference position 0 deg are 30 ± ε, 90 ± ε, and 150 ± ε.

On the other hand, in the case of FIG. 12 in which the position sensor 2 is installed at the stable stop point within the position sensor non-installable range, the stable stop points within the section where the position sensor signal is at the L level (30 to 210 deg) are 30, 90, At 150 and 210 deg, the estimated phase errors from the reference position 30 deg are ± ε, 60 ± ε, 120 ± ε, and 180 ± ε. Accordingly, there is a possibility that the estimated phase error is increased up to 180 degrees and the resolution of the position sensor signal.
This indicates that in FIG. 10 or FIG. 11, the estimated phase error during the period from the start to the time t1 can be large.

  FIG. 13 shows that, as a result of the position sensor 2 being installed in a state where the switching of the position sensor signal is located in the immediate vicinity of the stable stop point, the phase error at the start is large, exceeds 90 deg, and reverse torque is applied to the rotor. Shows a case where the engine reverses and a start failure occurs.

  As described above, in the synchronous motor rotational phase detection device according to the first embodiment of the present invention, the rotational position of the rotor 11 when the position sensor signal is switched is determined from the stable stop point to the amplitude Ta of the cogging torque, the friction torque. Since the position sensor 2 is installed so that the position is more than the angle X obtained by the equation (4) using Tf, even if only one position sensor 2 is used, there is no extreme increase in phase error. If the switching of the position sensor signal is detected twice, phase detection based on the detected rotation speed becomes possible, and reliable and high-speed phase detection is realized.

Embodiment 2. FIG.
FIG. 14 is a diagram of the synchronous motor 1 viewed from the axial direction for explaining the position sensor 2 and the sensor target 12 in the rotational phase detection apparatus for the synchronous motor according to the second embodiment of the present invention.
With respect to the arrangement of the position sensor 2 and the sensor target 12 in FIG. 2, the arrangement is shifted by 45 degrees while maintaining the mutual positional relationship.

  As described above, also in the rotational phase detection device of the synchronous motor according to the second embodiment, the mutual positional relationship between the position sensor 2 and the sensor target 12 is the same as that in the first embodiment. The condition that the position sensor 2 is installed so that the rotational position of the rotor 11 when the position sensor signal is switched is a position separated from the stable stop point by an angle X or more determined by the above equation (4). This is exactly the same as in the case of the first embodiment, and the same effects as described in the first embodiment are achieved.

  Therefore, if the above-described conditions of the present invention are satisfied, an appropriate attachment position according to the structural condition relating to the attachment of the position sensor 2 and the sensor target 12 to the stator 13 and the rotor 11, respectively. Should be selected.

Embodiment 3 FIG.
FIG. 15 is a perspective view showing a sensor target 12A according to Embodiment 3 of the present invention. In the first embodiment, the gear tooth-shaped sensor target 12 has a shape with unevenness in the radial direction. However, as shown in FIG. 15, the unevenness in which the facing distance to the position sensor 2A increases and decreases in the axial direction. It is good also as a shape with.
16 is a view of the synchronous motor 1 viewed from the axial direction for explaining the position sensor 2A and the sensor target 12A, and FIG. 17 is a partial cross-sectional view of each part viewed from the side.

  In FIG. 16, the edge of the sensor target 12 </ b> A is arranged at the center of the N and S poles as in the first embodiment. Further, as shown in FIG. 17, the position sensor 2A is arranged so as to detect irregularities from the axial direction of the sensor target 12A.

  As described above, in the rotational phase detection device for a synchronous motor according to Embodiment 3 of the present invention, the position sensor 2A is arranged in the axial direction of the shaft 14 of the rotor 11 so that the sensor target 12A is rotated at a high speed. Even when it vibrates in the radial direction by centrifugal force, the distance between the position sensor 2A and the sensor target 12A can be kept constant, and a stable position sensor signal can be obtained against axial vibration.

  It should be noted that the present invention can be freely combined with each other within the scope of the invention, and each embodiment can be appropriately modified or omitted.

  The rotational phase detection device for a synchronous motor according to the present invention is suitably applied to an electric supercharger in that a rotational phase can be detected easily and reliably using a single position sensor. Needless to say, the present invention can be widely applied to electric motors used for general purposes other than a supercharger, and has the same effect.

1 synchronous motor, 2, 2A position sensor, 3 control unit, 4 speed detection unit,
5 phase estimation unit, 11 rotor, 12, 12A sensor target, 13 stator,
16 Reference phase detector, 17 Speed detector, 18 Integrator, 19 Start speed generator.

Claims (7)

One sensor target attached to the rotor side of the synchronous motor and one position sensor signal attached to the stator side of the synchronous motor to output an H or L position sensor signal according to the relative positional relationship with the sensor target in the circumferential direction In this case, the rotational speed of the rotor is detected based on the position sensor signal, and the rotational phase is detected based on the rotational speed and the position sensor signal.
The position sensor is installed such that the rotational position of the rotor when the position sensor signal is switched is a position separated by a predetermined angle or more from a stable stop point determined by a cogging torque generated in the synchronous motor. A rotational phase detector for a synchronous motor. 2. The predetermined angle X is set by the following equation, where Ta is an amplitude of the cogging torque, N is an order of the cogging torque, and Tf is a friction torque acting when the synchronous motor is stopped. The rotational phase detector of the synchronous motor as described.
X = {sin ⁻¹ (Tf / Ta)} / N The position sensor is a magnetic sensor that detects magnetism and outputs the position sensor signal according to the magnitude thereof, and the sensor target has an unevenness in which the distance to the position sensor increases and decreases every 180 degrees in electrical angle. 3. The synchronous motor rotation phase detection device according to claim 1, wherein the rotation phase detection device is made of a formed magnetic material. 4. The rotational phase detection device for a synchronous motor according to claim 3, wherein the sensor target is formed with unevenness in which the distance from the position sensor increases and decreases in the radial direction of the rotor. 4. The rotational phase detection device for a synchronous motor according to claim 3, wherein the sensor target is formed with irregularities whose vertical distance to the position sensor increases and decreases in the axial direction of the rotor. A speed detection unit that detects a rotation speed of the rotor from a time interval at which the position sensor signal switches; and a phase estimation unit that estimates a rotation phase of the rotor based on the rotation speed and the position sensor signal. The rotational phase detection device for a synchronous motor according to any one of claims 3 to 5, wherein: The phase estimation unit corresponds to the position sensor signal H or L in a first period after the synchronous motor is started at a predetermined start speed until the position sensor signal switching is detected twice. Switched between the first phase estimating means for estimating the phase from the sum of the reference phase determined in this way and the interpolation phase obtained by integrating the starting speed from the starting time and the second period after the first period has elapsed. Second phase estimation means for estimating a phase from a sum of the reference phase based on the position sensor signal and an interpolation phase obtained by integrating the rotational speed detected before the switching from the switching time is provided. The rotational phase detector for a synchronous motor according to claim 6.

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