JP2005224048A - Brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brushless motor whose drive system can smoothly be changed from a forced drive to a sensorless drive. <P>SOLUTION: In the forced drive (during a period of time t5 in Fig.), because a rotary magnetic field is not caused by the rotational position of a magnetic rotor 54 but forced to occur to a three-phase armature winding 52, conduction changing timing delays in comparison with the sensorless drive, in which the rotary magnetic filed is caused to occur while detecting the rotational position of the magnetic rotor 54. Thus, a sensorless drive transient period (during the period of time t6 in Fig.) is provided when the forced drive is shifted to the sensorless drive (during the period of time t7 in Fig.). During this sensorless drive transient period, the delay in the conduction changing timing by the forced drive can be eliminated by keeping the rotational speed of the magnetic rotor 54 at a changed rotational speed, and by fixing an electrical angle that delays a rotational position signal. As a result, a step-out is removed when the force drive is shifted to the sensorless drive so that the drive system can smoothly be changed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a brushless motor, and more particularly to drive system switching control.

  A brushless motor is known as a motor without a brush and a commutator. This brushless motor is suitable for long-term driving because the brushed motor is in contact with the commutator and the brush is free from frictional wear. For this reason, it is widely used in environments where the frequency of use is high and maintenance is not performed regularly, such as water pumps for cooling vehicles and drive motors for various home appliances.

  The brushless motor is composed of an armature winding and a magnet rotor. As shown in FIG. 7, the excitation (period t1 in FIG. 7) is performed from the start to the stable drive (drive at the target rotation speed). ), Forced driving (period t2 in FIG. 7), sensorless driving (period t3 in FIG. 7), and switching of the driving method are sequentially performed. That is, in starting the brushless motor, first, excitation (period t1 in FIG. 7) is performed to move the rotational position of the magnet rotor to the initial position, and then the armature winding is energized at a predetermined timing. Thus, a forcible drive (period t2 in FIG. 7) for generating a rotating magnetic field and forcibly rotating the magnet rotor is performed. When the magnet rotor is rotated by the forcible driving and the rotation speed is increased, an induced voltage is generated in the armature winding by the rotation of the magnet rotor. When the brushless motor reaches a rotational speed (switching rotational speed) at which an induced voltage is generated in the armature winding by forced driving, the driving method is switched to sensorless driving (period t3 in FIG. 7). In sensorless drive, the rotational position information of the magnet rotor is detected from the induced voltage generated in the armature winding due to the rotation of the magnet rotor, and energization is performed by delaying the phase (correcting the phase by a predetermined electrical angle). The switching timing (energization switching timing) is obtained. That is, in sensorless driving, the armature winding is energized at the energization switching timing with delayed rotational position information to generate a rotating magnetic field, and the magnet rotor rotates by receiving torque from the generated rotating magnetic field.

Here, in sensorless driving, the value of the current flowing through the brushless motor (motor current value) and the rotational speed of the magnet rotor are detected, and the delay time for delaying the rotational position information is obtained from the delay amount map. Then, the delay time obtained from the delay amount map becomes longer. Patent Document 1 discloses a technique for adjusting a delay time according to a motor current value.
JP 2002-300792 A

  However, in forced driving, the armature winding is energized at a predetermined timing regardless of the rotational position of the magnet rotor to generate a rotating magnetic field, so the energization switching timing is not always efficient for rotating the magnet rotor. As a result, the motor current value becomes large as compared with the sensorless driving without proper timing. For this reason, when switching from the forced drive to the sensorless drive, the motor current value becomes larger than that in the case of the sensorless drive, and the delay time obtained from the delay amount map becomes longer, so the energization switching timing is delayed. As a result, if the rotational speed is increased immediately after switching from forced driving to sensorless driving, the energization switching timing may be further delayed from an appropriate timing with respect to the rotational speed and step out.

  The present invention has been made in consideration of the above-described facts, and an object of the present invention is to provide a brushless motor that can smoothly switch the driving method from forced driving to sensorless driving.

  The invention according to claim 1 is a brushless motor that rotates a magnet rotor by energizing an armature winding with a power source to generate a rotating magnetic field, and forcibly energizing the armature winding. Forced energization switching timing output means for outputting a predetermined switching timing, and rotational position information detection for detecting rotational position information of the magnet rotor based on an induced voltage generated in the armature winding due to rotation of the magnet rotor Means, energization switching timing calculation means for delaying the rotation position information detected by the rotation position information detection means and calculating a timing for switching the energization to the armature winding, and the rotational speed of the magnet rotor The rotational speed detected by the rotational speed detection means, the induced voltage is generated in the armature winding, and the rotational speed is detected by the rotational speed detection means. When the rotational position information is detected by the position information detection means, the energization to the armature winding is changed from the forced energization switching timing by the forced energization switching timing output means to the energization switching timing calculation means. Switching means for switching to the energization switching timing by, and for a predetermined period after switching by the switching means, the rotational speed of the magnet rotor is within a predetermined range based on the switching rotational speed It is characterized by maintaining.

  According to the first aspect of the present invention, the armature winding is energized at a predetermined timing (forced energization switching timing) for forcibly switching energization to the armature winding output by the forced energization switching timing output means. (Forced drive) is performed, and a rotating magnetic field is generated. The magnet rotor receives torque from the rotating magnetic field generated in the armature winding and rotates. When the magnet rotor rotates and reaches the switching rotational speed, the rotational position information detecting means detects rotational position information based on the induced voltage generated in the armature winding, so the switching means detects the rotational position detected from the induced voltage. Switching to energization (sensorless drive) at the energization switching timing with delayed information.

  At this time, the rotational speed of the magnet rotor is maintained within a predetermined range based on the switching rotational speed for a predetermined period after switching to the sensorless drive. In the brushless motor, by maintaining the rotation speed within the predetermined range for a predetermined period, it is possible to converge the delay of the energization switching timing generated by the forced drive. Therefore, it is possible to smoothly switch from forced driving to sensorless driving.

  The invention according to claim 2 is characterized in that, in the invention according to claim 1, the predetermined range is not less than the switching rotation speed and not more than 50% faster than the switching rotation speed.

  According to the second aspect of the present invention, in the brushless motor, when the rotation speed is maintained at the time of switching the drive, as the delay of the energization switching timing converges, the proper energization switching timing approaches and the efficiency of rotating the magnet rotor is high. Therefore, the rotation speed increases. Therefore, the predetermined range for maintaining the rotation speed is set to be not less than the switching rotation speed and not more than 50% faster than the switching rotation speed. It should be noted that the rotation speed may be maintained at the switching rotation speed by controlling a current to be energized.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, a delay amount by which the rotation position information is delayed by the energization switching timing calculation means during the predetermined period is set to a predetermined value. It is characterized by that.

  According to the third aspect of the present invention, the delay amount for delaying the rotational position information is set to a predetermined value (for example, an electrical angle of 30 °) for a predetermined period. In the brushless motor, by setting the delay amount to a predetermined value, it is possible to correct the delay of the energization switching timing generated by the forced drive.

  According to a fourth aspect of the present invention, there is provided a brushless motor that rotates a magnet rotor by energizing an armature winding with a power source to generate a rotating magnetic field, and forcibly energizing the armature winding. Forced energization switching timing output means for outputting a predetermined switching timing, and rotational position information detection for detecting rotational position information of the magnet rotor based on an induced voltage generated in the armature winding due to rotation of the magnet rotor Means, energization switching timing calculation means for delaying the rotation position information detected by the rotation position information detection means and calculating a timing for switching the energization to the armature winding, and the rotational speed of the magnet rotor The rotational speed detected by the rotational speed detection means, the induced voltage is generated in the armature winding, and the rotational speed is detected by the rotational speed detection means. When the rotational position information is detected by the position information detection means, the energization to the armature winding is changed from the forced energization switching timing by the forced energization switching timing output means to the energization switching timing calculation means. Switching means for switching to the energization switching timing according to the above, and a delay amount for delaying the rotational position information by the energization switching timing calculation means for a predetermined period after switching by the switching means is set to a predetermined value. It is characterized by doing.

  According to the fourth aspect of the present invention, the armature winding is energized at a predetermined timing (forced energization switching timing) for forcibly switching energization to the armature winding output by the forced energization switching timing output means. (Forced drive) is performed, and a rotating magnetic field is generated. The magnet rotor receives torque from the rotating magnetic field generated in the armature winding and rotates. When the magnet rotor rotates and reaches the switching rotational speed, the rotational position information detecting means detects rotational position information based on the induced voltage generated in the armature winding, so the switching means detects the rotational position detected from the induced voltage. Switching to energization (sensorless drive) at the energization switching timing with information delayed.

  At this time, the delay amount for delaying the rotational position information is set to a predetermined value (for example, an electrical angle of 30 °) for a predetermined period after switching. In the brushless motor, by setting the delay amount to a predetermined value, it is possible to correct the delay in the energization switching timing that has occurred due to the forced drive. Therefore, it is possible to smoothly switch from forced driving to sensorless driving.

  The invention according to claim 5 is the invention according to claim 3 or claim 4, wherein the armature winding is a three-phase armature winding, and the predetermined value is an electrical angle of 30 °. Features.

  According to the invention described in claim 5, when the armature winding is a three-phase armature winding, an appropriate value of the delay amount for delaying the rotational position information is an electrical angle of 30 °.

  FIG. 1 is a schematic configuration diagram of a brushless motor 50 and a brushless motor driving apparatus 10 according to the present embodiment.

  The brushless motor 50 includes a magnet rotor 54 and a three-phase armature winding 52 in which U, V, and W armature windings are star-connected.

  The brushless motor driving apparatus 10 is connected to a power source (not shown), detects the rotational position of the inverter unit 14 that switches the energization of the three-phase armature winding 52 in response to a driving signal to be described later, and the magnet rotor 54. A rotational position detection unit 16 that outputs a rotational position signal of a phase, a delay unit 20 that delays a rotational phase signal of three phases and outputs a three-phase energization switching timing signal, a delay unit 20 and a forced signal output unit described later 38, a switching unit 22 that switches the energization switching timing signal output from 38, a logic control unit 24 that outputs a drive signal based on the 3-phase energization switching timing signal, and a current (motor current) that flows through the inverter unit 14. Rotation speed for detecting the rotation speed of the magnet rotor 54 from the current detection unit 26 that detects and outputs a motor current signal and the U phase of the three-phase rotation position signal and outputs the rotation speed signal Based on the detection unit 28, a delay amount map 30 for storing a delay amount for delaying the rotational position signal in accordance with the motor current value, and the motor current signal and the rotational speed signal, the delay amount is obtained from the delay amount map 30 and rotated. A delay time calculation unit 34 that calculates a delay time for delaying the position signal, a microcomputer 36 that performs switching control between forced driving and sensorless driving, and a forced signal output unit 38 that outputs a three-phase energization switching timing signal in the forced driving. And.

  Each phase of the three-phase armature winding 52 is connected to the output terminal of the inverter unit 14 and the rotational position detection unit 16. The three-phase armature winding 52 is switched in energization by a drive signal to generate a rotating magnetic field of 120 ° square wave energization.

  The magnet rotor 54 rotates by receiving torque from the rotating magnetic field generated in the three-phase armature winding 52. In addition, when the magnet rotor 54 rotates, an induced voltage is generated in each phase of the three-phase armature winding 52.

  The inverter unit 14 is composed of a circuit in which three pairs (a total of six) switching elements U +, U−, V +, V−, W +, and W− are connected in a three-phase bridge. The current detector 26 and the three-phase armature winding 52 are connected to each phase. The inverter unit 14 receives a drive signal from the logic control unit 24 and performs energization switching of 120 ° square wave energization to the three-phase armature winding 52. Further, one end side of the switching elements U−, V−, and W− is GND.

  The rotational position detection unit 16 is connected to each phase of the three-phase armature winding 52 and the delay unit 20, and extracts a pseudo-induced voltage from the terminal voltage of the three-phase armature winding 52 through a low-pass filter. A zero-cross point is detected and a three-phase rotational position signal (U phase, V phase, W phase) is output to the delay unit 20.

  The delay unit 20 is connected to the rotational position detection unit 16, the switching unit 22, and the delay time calculation unit 34, and delays the delay time obtained by the delay time calculation unit 34 described later to the three-phase rotation position signal 3. Phase energization switching timing signals (U phase, V phase, W phase) are output.

  The switching unit 22 is connected to the delay unit 20, the logic control unit 24, and the forcible signal output unit 38, receives a switching instruction signal from the microcomputer 36 described later, and outputs a three-phase energization switching timing signal to the logic control unit 24. Is switched.

  The logic control unit 24 is connected to the switching unit 22, the inverter unit 14, and the microcomputer 36, and outputs a drive signal based on the timing at which the value of the energization switching timing signal changes. The drive signals U−, V−, and W− output from the logic control unit 24 are pulse width modulated (see the drive signal in FIG. 3), and are controlled by a duty ratio control signal output from the microcomputer 36 described later. The duty ratio of U−, V− and W− of the pulse width modulated drive signal is controlled.

  The current detection unit 26 is connected to the inverter unit 14 and the delay time calculation unit 34, detects the value of the current flowing through the GND side of the inverter unit 14 (motor current value), and outputs a motor current signal to the delay time calculation unit 34. To do.

  The rotational speed detection unit 28 is connected to the U phase of the rotational position signal, the delay time calculation unit 34, and the microcomputer 36, and detects the rotational speed of the magnet rotor 54 from the cycle in which the U phase signal of the rotational position signal is generated. The rotation speed signal is output to the delay time calculation unit 34 and the microcomputer 36.

  The delay amount map 30 is connected to the delay time calculation unit 34 and stores in advance an electrical angle for delaying the rotational position signal as a delay amount in accordance with the motor current value detected by the current detection unit 26. The electrical angle stored in the delay amount map 30 increases as the motor current value increases.

  The delay time calculation unit 34 is connected to the delay unit 20, the current detection unit 26, the rotation speed detection unit 28, the delay amount map 30, and the microcomputer 36, and the magnet rotor 54 of the motor current value detected by the current detection unit 26. The maximum value for each rotation period is obtained, and an electrical angle for delaying the rotational position signal is selected from the delay amount map 30 based on the maximum value. Further, based on the rotation speed detected by the rotation speed detection unit 28, a delay time for delaying the rotation position signal by the electrical angle selected from the delay amount map 30 is calculated and output to the delay unit 20 as a delay time signal.

  The microcomputer 36 is connected to the logic control unit 24, the rotation speed detection unit 28, the delay time calculation unit 34, the forcible signal output unit 38, and the switching unit 22, and a drive start instruction in which a target rotation speed is set (drive of FIG. 1). In response to the start instruction), the brushless motor 50 is driven and controlled. That is, the microcomputer 36 forcibly drives when it receives a drive start instruction. In the forced drive, a forced drive instruction signal is output to a forced signal output unit 38 described later, and a predetermined energization switching timing signal is output from the forced signal output unit 38. Also, a switching instruction signal for connecting the switching unit 22 to the forcible signal output unit 38 is output, and the energization switching timing signal output from the forcible signal output unit 38 is output to the logic control unit 24.

  Further, the microcomputer 36 compares the rotation speed of the magnet rotor 54 detected by the rotation speed detection unit 28 with the target rotation speed set in the drive start instruction, and adjusts the duty ratio of the drive signal of the logic control unit 24. The rotational speed of the magnet rotor 54 is controlled by outputting a duty ratio control signal.

  Further, the microcomputer 36 has a non-volatile memory (not shown) and stores in advance a switching rotational speed (see 36 in FIG. 1) for switching the driving method from forced driving to sensorless driving. The switching rotational speed is a rotational speed at which an induced voltage is generated in the three-phase armature winding 52 by the rotation of the magnet rotor 54 and the rotational position signal can be detected by the rotational position detector 16.

  When the rotational speed of the magnet rotor 54 is increased by forced driving and becomes the switching rotational speed, the driving method is switched to sensorless driving. At this switching, the microcomputer 36 switches the switching unit 22 to connect with the delay unit 20. An instruction signal is output to cause the logic control unit 24 to output an energization switching timing signal output from the delay unit 20. Further, a fixed delay instruction signal is output to the delay time calculation unit 34 for a predetermined period (for example, 100 ms) after switching to the sensorless drive, and a delay amount for delaying the rotational position signal by the delay time calculation unit 34 is set to a predetermined value. (In this embodiment, the electrical angle is 30 °). Further, a duty ratio control signal for controlling the duty ratio so as to maintain the rotation speed at the switching rotation speed for the predetermined period is output.

  The forcible signal output unit 38 is connected to the microcomputer 36 and the switching unit 22. When the forcible drive instruction signal is received from the microcomputer 36, the forcible signal output unit 38 first outputs an energization signal for exciting the three-phase armature winding 52. In addition, a predetermined timing (forced energization switching timing) for forcibly switching energization of the three-phase armature winding 52 is output as an energization switching timing signal.

  Next, the operation of the present embodiment will be described.

  When the microcomputer 36 receives a drive start instruction in which the target rotational speed is set, the microcomputer 36 outputs a forced drive instruction signal to the forced signal output unit 38, and further, a switching instruction signal for connecting the forced signal output unit 38 to the switching unit 22. Is output to start driving the brushless motor 50.

  The forcible signal output unit 38 first outputs an energization signal for performing excitation (period t4 in FIG. 2) to the three-phase armature winding 52, and moves the rotational position of the magnet rotor 54 to the initial position. Next, the energization switching timing signal shown in FIG. 3 is output to perform forced driving (period t5 in FIG. 2).

  The logic control unit 24 receives the energization switching timing signal and outputs a 120 ° square wave energization drive signal shown in FIG. 3 based on the timing at which the energization switching timing signal changes from 0 to 1, 1 to 0. Here, for example, at the timing when the V phase of the energization switching timing signal changes from 0 to 1 (see arrow t8 in FIG. 3), the drive signal U + is turned off and the drive signal W + is turned on.

  The inverter unit 14 is energized by a power source (not shown) according to a drive signal for 120 ° square wave energization to generate a rotating magnetic field in the three-phase armature winding 52. The magnet rotor 54 receives torque from the generated rotating magnetic field and rotates.

  When the rotational speed of the magnet rotor 54 (see FIG. 1) increases due to forced driving, an induced voltage is generated in the three-phase armature winding 52 due to the rotation of the magnet rotor 54. When the induced voltage is generated, the rotational position detector 16 detects the terminal voltage of each phase of the three-phase armature winding 52 and outputs a three-phase rotational position signal (see the rotational position signal in FIG. 3). The rotational speed detector 28 detects the rotational speed of the magnet rotor 54 from the U phase period of the rotational position signal and outputs the rotational speed signal to the delay time calculator 34 and the microcomputer 36.

  Here, in the forcible drive, a rotating magnetic field is forcibly generated in the three-phase armature winding 52 regardless of the rotating position of the magnet rotor 54. Therefore, a rotating magnetic field is generated while detecting the rotating position of the magnet rotor 54. It is known that the energization switching timing is delayed as compared with the sensorless driving. For example, in the case of FIG. 3, in the U-phase energization switching timing signal and the rotational position signal, the energization switching timing signal is delayed from the rotational position signal by an electrical angle of 60 ° (period t12 in FIG. 3). The amount of delay (electrical angle) is larger than that in the case of sensorless driving (see period t13 in FIG. 5). For this reason, as shown in the motor current value in the period t9 in FIG. 4, the amplitude of the motor current value increases to rotate the magnet rotor 54, and a large amount of current flows through the inverter unit 14, resulting in poor efficiency.

  The microcomputer 36 (see FIG. 1) outputs a switching instruction signal for connecting the delay unit 20 to the switching unit 22 when the rotational speed of the magnet rotor 54 becomes the switching rotational speed (see arrow t10 in FIG. 2) by forced driving. Then, the driving method is switched from forced driving to sensorless driving. Further, a sensorless drive excessive period (see period t6 in FIG. 2) is provided for 100 ms after switching. During this sensorless driving excessive period, the microcomputer 36 controls the duty ratio so as to maintain the rotation speed of the magnet rotor 54 at the switching rotation speed (see FIG. 2) switched from forced driving to sensorless driving, A delay fixing instruction signal is output to fix the electrical angle for delaying the rotational position signal to 30 °. Thereby, in the sensorless driving excessive period, the energization switching timing signal is corrected in the correct (efficient) direction, so that a large torque is generated immediately after switching the driving method, and the magnet rotor 54 is accelerated. From the viewpoint of electrical energy, in the sensorless driving excessive period (period t11 in FIG. 4), since the unnecessary energy stored by the forced driving is released, the motor current value is changed after switching the driving method. Is less than the value of normal sensorless driving (period t14 in FIG. 4) (in this embodiment, the motor current value in period t11 in FIG. 4 is substantially zero), the rotation of the magnet rotor 54 due to inertia The speed temporarily increases (the rotation period t16 in FIG. 4 is shorter than t15 and the rotation speed is increased). This sensorless driving excessive period is the period in which the energy stored by forced driving is released. When the stored energy is released, the motor current recovers (converges) to the normal value of sensorless driving, and the magnet The rotational speed of the rotor 54 is stabilized at the switching rotational speed (the rotational period t17 in FIG. 4 is the period of the switching rotational speed). For this reason, it is possible to smoothly shift from the sensorless drive excessive period (period t11 in FIG. 4) to the sensorless drive (period t14 in FIG. 4). In this embodiment, the sensorless driving excessive period is set to 100 ms. However, since it is a period in which the energy stored by forced driving is released, it is changed according to the configuration of the brushless motor 50 and the brushless motor driving device 10. Is preferred.

  In this way, in the sensorless driving excessive period, the unnecessary energy stored by the forced driving is released, so that the motor current value can be converged to the current value by the sensorless driving. Further, by fixing the electrical angle for delaying the rotational position signal to 30 °, it is possible to correct the delay of the electrical angle due to the forced drive and to obtain an appropriate value with high efficiency. In the configuration of the brushless motor 50 and the brushless motor driving apparatus 10 according to the present embodiment, if the electrical angle for delaying the rotational position signal by the delay fixing instruction signal is too small, the energization switching timing is too early, and therefore the electrical angle of 30 ° is set. It is known in advance from experiments that the value is appropriate. Further, the electrical angle for delaying the rotational position signal by the delay fixing instruction signal needs to be changed according to the configurations of the brushless motor 50 and the brushless motor driving device 10.

  When the sensorless driving excessive period has passed, the microcomputer 36 (see FIG. 1) stops outputting the fixed delay instruction signal and adjusts the rotation speed of the magnet rotor 54 to the target rotation speed (see FIG. 2). A duty ratio control signal is output to perform sensorless driving (period 7 in FIG. 2).

  In sensorless driving, the rotational position detector 16 (see FIG. 1) detects the terminal voltage of each phase of the three-phase armature winding 52 and outputs the three-phase rotational position signal shown in FIG. .

  The current detection unit 26 detects the motor current (see the period t14 in FIG. 4) and outputs a motor current signal to the delay time calculation unit 34.

  The rotational speed detector 28 detects the rotational speed of the magnet rotor 54 from the period of the U phase of the rotational position signal (see the rotational position signal in FIG. 5) and outputs the rotational speed signal to the delay time calculator 34 and the microcomputer 36. To do.

  In the delay time calculation unit 34, the rotation period is obtained from the rotation speed of the magnet rotor 54, and the electrical angle for delaying the rotation position signal is selected from the delay amount map 30 based on the maximum value of the motor current for each rotation period. A delay time for delaying the rotational position signal by the electrical angle is calculated based on the rotational speed. Here, as indicated by the period t11 in FIG. 4, since the motor current has already converged in the sensorless driving excessive period, the electrical angle selected from the delay amount map 30 in the sensorless driving (period t14 in FIG. 4) is It is an appropriate value that is efficient for the brushless motor 50 to drive.

  The delay unit 20 delays the three-phase rotation position signal by the delay time obtained by the delay time calculation unit 34, and sends the three-phase energization switching timing signal (see the energization switching timing signal in FIG. 5) to the logic control unit 24. Output.

  The logic control unit 24 outputs a 120 ° square wave energization drive signal (see the drive signal in FIG. 5) to the inverter unit 14 based on the timing when the value of the 3-phase energization switching timing signal changes, and outputs the 3-phase armature winding. A rotating magnetic field is generated on the line 52 to rotate the magnet rotor 54.

  FIG. 6 shows a flow relating to switching of the driving method of the brushless motor 50.

  In step 100, the three-phase armature winding 52 is excited (see period t4 in FIG. 2), the rotational position of the magnet rotor 54 is moved to the initial position, and the process proceeds to step 102.

  In step 102, a predetermined energization switching timing signal is output from the forcible signal output unit 38 to perform the aforementioned forcible driving (see period t5 in FIG. 2). When the rotation speed of the magnet rotor 54 becomes the switching rotation speed (see arrow t10 in FIG. 2) due to the forcible driving, the routine proceeds to step 104.

  In step 104, the duty ratio control signal is used to maintain the rotational speed of the magnet rotor 54 at the switching rotational speed (see FIG. 2) from the microcomputer 36 for 100 ms as the sensorless driving excessive period (see the period t6 in FIG. 2). In addition, a delay fixing instruction signal is output to fix the electrical angle for delaying the rotational position signal to 30 °. When 100 ms has elapsed, the routine proceeds to step 106.

  In step 106, the motor current is detected, a delay time is calculated based on the motor current value and the rotational speed of the magnet rotor 54, and the sensorless driving (described above) is performed based on the energization switching timing signal obtained by delaying the rotational position signal by the delay time. The period t7 in FIG. 2 is started. Further, when the sensorless driving ends, the process shifts to the end.

  As described above, according to the brushless motor of the present embodiment, the sensorless driving excessive period is provided when shifting from the forced driving to the sensorless driving, and the rotational speed of the magnet rotor 54 is maintained at the switching rotational speed in the sensorless driving excessive period. By doing so, the motor current value can be converged to the current value by the sensorless drive, so that the delay time obtained from the motor current value becomes appropriate, and the delay of the energization switching timing by the forced drive can be eliminated. In addition, by setting the electrical angle for delaying the rotational position signal to 30 °, it is possible to correct the delay of the electrical angle due to the forced drive and to obtain an appropriate value with high efficiency. That is, since excessive energy is released by forced driving in the sensorless driving excessive period, it is possible to smoothly shift to sensorless driving.

  In this embodiment, in the sensorless driving excessive period, the rotation speed of the magnet rotor 54 is maintained at the switching rotation speed and the electrical angle for delaying the rotation position signal is 30 °. However, only one of them is used. May be.

  Further, the rotational speed of the magnet rotor 54 is maintained at the switching rotational speed (for example, 500 rpm) in the sensorless driving excessive period. However, in the sensorless driving excessive period, excessive energy is released due to forced driving and torque is generated. Since the rotational speed temporarily increases according to the rotational load, the rotational speed of the magnet rotor 54 may be maintained at a rotational speed faster than the switching rotational speed (for example, 750 rpm that is about 50% faster than the switching rotational speed). Further, the range in which the rotational speed is maintained may be within a predetermined range based on the switching rotational speed (for example, within a rotational speed range about 50% faster based on the switching rotational speed).

  Furthermore, in the present embodiment, the rotational speed of the magnet rotor 54 is detected from the rotational position signal. However, the rotational speed may be detected by providing a rotation sensor on the rotating shaft around which the magnet rotor 54 rotates.

  The delay amount is selected from the delay amount map 30 based on the motor current value. However, the delay amount is determined based on the rotation speed of the magnet rotor 54, the voltage value detected from the terminals of the three-phase armature winding 52, the voltage waveform, and the like. The amount may be selected and may be obtained by calculation from the motor current value, the rotational speed of the magnet rotor 54, the terminal voltage value of the three-phase armature winding 52, the waveform of the terminal voltage, etc. without using the delay amount map 30. Good.

It is a schematic block diagram of the brushless motor of this Embodiment and a brushless motor drive device. It is a relationship diagram of the switching of the driving method and the rotation speed of the present embodiment. It is each waveform figure at the time of the forced drive of this Embodiment. It is a wave form diagram of a motor current in each drive system of this embodiment. It is each waveform figure at the time of the sensorless drive of this Embodiment. It is a flowchart which shows the switching of the drive system of this Embodiment. It is a related figure of the switching of the drive system of the conventional brushless motor, and rotational speed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Brushless motor drive device, 14 Inverter part, 16 Rotation position detection part (Rotation position information detection means), 20 Delay part (Energization switching timing calculation means), 22 Switching part (switching means), 24 Logic control part, 26 Current detection , 28 Rotational speed detection part (Rotational speed detection means), 30 Delay amount map, 34 Delay time calculation part, 36 Microcomputer, 38 Forced signal output part (Forced energization switching timing output means), 50 Brushless motor, 52 3-phase Armature winding, 54 magnet rotor

Claims (5)

A brushless motor that rotates a magnet rotor by energizing an armature winding with a power source to generate a rotating magnetic field,
Forced energization switching timing output means for outputting a predetermined timing for forcibly switching energization to the armature winding;
Rotational position information detecting means for detecting rotational position information of the magnet rotor based on an induced voltage generated in the armature winding by the rotation of the magnet rotor;
Energization switching timing calculating means for delaying the rotational position information detected by the rotational position information detecting means and calculating timing for switching energization to the armature winding;
Rotation speed detection means for detecting the rotation speed of the magnet rotor;
When the rotational speed detected by the rotational speed detection means is a switching rotational speed at which the induced voltage is generated in the armature winding and the rotational position information is detected by the rotational position information detection means, Switching means for switching energization to the armature winding from the forced energization switching timing by the forced energization switching timing output means to the energization switching timing by the energization switching timing calculation means,
A brushless motor, wherein the rotational speed of the magnet rotor is maintained within a predetermined range based on the switching rotational speed for a predetermined period after switching by the switching means.   2. The brushless motor according to claim 1, wherein the predetermined range is not less than the switching rotation speed and not more than 50% faster than the switching rotation speed.   3. The brushless motor according to claim 1, wherein a delay amount by which the rotation position information is delayed by the energization switching timing calculation unit during the predetermined period is set to a predetermined value. 4. A brushless motor that rotates a magnet rotor by energizing an armature winding with a power source to generate a rotating magnetic field,
Forced energization switching timing output means for outputting a predetermined timing for forcibly switching energization to the armature winding;
Rotational position information detecting means for detecting rotational position information of the magnet rotor based on an induced voltage generated in the armature winding by the rotation of the magnet rotor;
Energization switching timing calculating means for delaying the rotational position information detected by the rotational position information detecting means and calculating timing for switching energization to the armature winding;
Rotation speed detection means for detecting the rotation speed of the magnet rotor;
When the rotational speed detected by the rotational speed detection means is a switching rotational speed at which the induced voltage is generated in the armature winding and the rotational position information is detected by the rotational position information detection means, Switching means for switching energization to the armature winding from the forced energization switching timing by the forced energization switching timing output means to the energization switching timing by the energization switching timing calculation means,
A brushless motor characterized in that a delay amount by which the rotation position information is delayed by the energization switching timing calculation means is set to a predetermined value after switching by the switching means. The armature winding is a three-phase armature winding;
The brushless motor according to claim 3 or 4, wherein the predetermined value is an electrical angle of 30 °.

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