JP2015012779A - Driving device and driving method for sensorless brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sensorless brushless motor driving apparatus and a driving method thereof capable of reducing the driving rotational speed of a sensorless brushless motor. A sensorless brushless motor drive device (1) according to the present invention includes a zero cross point detection unit (71) for sequentially detecting a zero cross point of each of three phases, and a zero cross point detection unit (71) for detecting a zero cross point. First, the voltage command value of the voltage applied to the armature winding of the energized phase in the first predetermined period (period TQ1) immediately before detection is increased to a voltage at which the zero cross point detection unit (71) can detect the zero cross point. A control device (7) having a voltage setting unit (75) for setting the applied voltage, and applying a first applied voltage to the armature winding of the energized phase in a first predetermined period (period TQ1), A power converter (4) that increases the instantaneous rotational speed of the brushless motor (2) in a predetermined period (period TQ1). [Selection] Figure 5

Description

  The present invention relates to a sensorless brushless motor driving apparatus and a driving method thereof for estimating a rotor rotational position of a brushless motor and driving the brushless motor based on the estimated rotor rotational position.

  As an example of a sensorless brushless motor driving device, the invention described in Patent Document 1 can be cited. In the invention described in Patent Document 1, an induced voltage induced in the armature winding of the motor is detected, and the rotor rotational position is estimated based on the detected induced voltage. Then, on / off control (commutation operation) of the power transistor group is performed based on the estimated rotor rotational position.

Japanese Patent No. 3382740

  However, in the invention described in Patent Document 1, since the rotor rotational position is estimated by comparing the induced voltage with the reference voltage, the induced voltage decreases as the motor speed decreases, and the rotor rotational position is estimated. It becomes difficult. For this reason, when the rotational speed of the motor decreases, it becomes difficult to drive the motor.

  In electric oil pumps and water pumps used in electric vehicles and hybrid vehicles, there is a demand for driving the electric pump at a low rotation speed in order to improve fuel efficiency. Specifically, it is necessary to reduce the pump discharge amount by reducing the rotational speed of the electric pump, thereby reducing power consumption and preventing overcooling (overcooling).

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a sensorless brushless motor driving apparatus and a driving method thereof that can reduce the driving rotational speed of the sensorless brushless motor.

  The sensorless brushless motor driving apparatus according to claim 1 is a sensorless brushless motor driving apparatus that estimates a rotor rotational position of the brushless motor and drives the brushless motor based on the estimated rotor rotational position. When the rotor rotation position where the induced voltage generated in the armature winding of the non-energized phase is zero is defined as the zero cross point, the zero cross point detection unit that sequentially detects the zero cross point of each of the three phases, and the zero cross point The voltage command value of the voltage applied to the armature winding of the energized phase in the first predetermined period immediately before the detection unit detects the zero cross point is increased to a voltage at which the zero cross point detection unit can detect the zero cross point. A control device having a voltage setting unit for setting the first applied voltage; and the first predetermined Said applying said first voltage applied to the armature winding of the energized phase during, and a power converter for increasing the instantaneous rotational speed of the brushless motor in the first predetermined period.

  According to the sensorless brushless motor driving apparatus of claim 1, the applied voltage (first applied voltage) applied to the armature winding of the energized phase in the first predetermined period immediately before the zero cross point detecting unit detects the zero cross point. ) Is increased to a voltage at which the zero cross point detection unit can detect the zero cross point, and the zero cross point detection unit is compared with the case where the applied voltage applied to the armature winding of the energized phase is constant in one cycle of the electrical angle. Can detect a zero cross point up to a low rotational speed. Therefore, the sensorless brushless motor driving apparatus can reduce the rotational speed of the brushless motor.

  The sensorless brushless motor drive device according to claim 2 is the sensorless brushless motor drive device according to claim 1, wherein the voltage setting unit is a second after the zero cross point detection unit detects the zero cross point. A voltage command value of a voltage to be applied to the armature winding of the energized phase during a predetermined period is set to a second applied voltage that is smaller than the first applied voltage, and the power conversion device is configured to perform the second predetermined period. The second applied voltage is applied to the energized phase armature winding to reduce the average rotational speed of the brushless motor.

  According to the sensorless brushless motor driving device according to claim 2, the applied voltage (second applied voltage) applied to the armature winding of the energized phase in the second predetermined period after the zero cross point detecting unit detects the zero cross point. ) Is made smaller than the first applied voltage, so that after the zero cross point detection unit detects the zero cross point, the rotational speed of the brushless motor can be reduced, and the average rotational speed of the brushless motor can be reduced. Therefore, for example, when this drive device is used as a drive device for an electric pump such as an electric oil pump or a water pump, the number of revolutions of the electric pump can be reduced and the pump discharge amount can be reduced. Cool (overcooling) can be prevented.

  The sensorless brushless motor driving device according to claim 3 is the sensorless brushless motor driving device according to claim 2, wherein the control device counts the second predetermined period using the detection of the zero cross point as a trigger. A timing unit that completes timing of the second predetermined period before the zero cross point detection unit detects the zero cross point, and when the timing unit has completed timing of the second predetermined period The first predetermined period is started, and then the first predetermined period ends when the zero cross point detecting unit detects the zero cross point.

  According to the sensorless brushless motor driving device of the third aspect, the control device includes a time measuring unit for measuring the second predetermined period. Then, the first predetermined period starts in conjunction with the completion of timing of the second predetermined period, and the first predetermined period ends when the next zero cross point is detected. Therefore, it is possible to easily measure the first predetermined period and the second predetermined period, and it is possible to appropriately set the application time of the first application voltage and the second application voltage.

  The sensorless brushless motor drive device according to claim 4 is the sensorless brushless motor drive device according to any one of claims 1 to 3, wherein the control device is applied to the armature winding of the energized phase. A phase compensator for setting a lead angle for compensating for a phase delay of the voltage to be applied, and the power conversion device supplies a voltage advanced in phase by the lead angle set by the phase compensator. Applied to the armature winding.

  According to the sensorless brushless motor drive device of claim 4, the power converter applies a voltage compensated for the phase delay of the voltage applied to the energized phase armature winding to the energized phase armature winding. Therefore, compared with the case where the phase delay is not taken into account, the zero cross point detection accuracy by the zero cross point detector can be improved.

  The sensorless brushless motor driving method according to claim 5 is a sensorless brushless motor driving method for estimating a rotor rotational position of the brushless motor and driving the brushless motor based on the estimated rotor rotational position. A zero cross point detecting step for sequentially detecting the zero cross point of each phase of three phases when the rotor rotational position at which the induced voltage generated in the armature winding of the non-energized phase becomes zero is the zero cross point, and the zero cross point The voltage command value of the voltage applied to the armature winding of the energized phase in the first predetermined period immediately before detecting the zero cross point in the detection step is increased to a voltage at which the zero cross point can be detected in the zero cross point detection step. A voltage setting step for setting the first applied voltage, and the communication in the first predetermined period. And applying the first voltage applied to the armature windings of phases, and a voltage output step of increasing the instantaneous rotational speed of the brushless motor in the first predetermined period.

  According to the driving method of the sensorless brushless motor according to claim 5, the applied voltage (first applied voltage) applied to the armature winding of the energized phase in the first predetermined period immediately before detecting the zero cross point in the zero cross point detecting step. ) Is increased to a voltage at which the zero cross point can be detected in the zero cross point detection step, so that the zero cross point detection step is performed as compared with the case where the applied voltage applied to the armature winding of the energized phase is constant in one cycle of the electrical angle. The zero cross point can be detected up to a low rotational speed. Therefore, the driving speed of the brushless motor can be reduced.

It is a block diagram which shows an example of the drive device 1 of a sensorless brushless motor. 2 is a cross-sectional view showing an example of an electric pump 5. FIG. It is explanatory drawing explaining the method to control the energized state and non-energized state of the armature winding of the brushless motor. It is a timing chart which shows an example of the time value of terminal voltage VU, VV, VW of each phase, zero crossing point detection signal Qs, and 1st timer Tm1-3rd timer Tm3. 3 is a block diagram illustrating an example of a control block of a control device 7. FIG. It is a figure which shows an example of the time-dependent change of the duty ratio of a PWM signal. It is a flowchart which shows an example of the procedure of the drive method of a sensorless brushless motor.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Each figure is a conceptual diagram and does not define the dimensions of the detailed structure.

<Driver 1 for sensorless brushless motor>
FIG. 1 is a configuration diagram illustrating an example of a sensorless brushless motor driving apparatus 1. As shown in the figure, the sensorless brushless motor drive device 1 of the present embodiment includes a power conversion device 4 provided between the brushless motor 2 and the DC power supply 3, and switching elements 41UU to 41WL of the power conversion device 4. And a control device 7 for controlling opening and closing.

  The brushless motor 2 is a known brushless motor, and includes a stator 21 in which armature windings 22, 23, and 24 are Y-connected, and a rotor 27. The armature windings 22, 23, and 24 constitute a U-phase winding, a V-phase winding, and a W-phase winding in this order. One end side of the U-phase armature winding 22 is connected to a U-phase terminal 25U, and the other end side of the U-phase armature winding 22 is connected to a neutral point 26N. The same applies to the V phase and the W phase.

  The armature windings 22, 23, and 24 can be wound by a known method such as concentrated winding or distributed winding. The brushless motor 2 can use, for example, a permanent magnet system in which the rotor 27 has a permanent magnet. There are no particular restrictions on the number of poles or the number of magnetic poles of the rotor 27. Further, the armature windings 22, 23, and 24 can be Δ-connected.

  The DC power supply 3 is a power supply device that supplies DC power. For example, a known lead storage battery (battery), a lithium ion battery, an electric double layer capacitor, or the like can be used. Note that a smoothing capacitor (not shown) is connected in parallel to the DC power source 3 to reduce the ripple voltage.

  The power converter 4 is provided between the brushless motor 2 and the DC power supply 3, converts DC power supplied from the DC power supply 3 into AC power, and supplies the brushless motor 2 with power. Specifically, the power conversion device 4 is a three-phase bridge circuit, and six switching elements 41UU, 41UL, 41VU, 41VL, 41WU, and 41WL are bridge-connected.

  As the switching elements 41UU to 41WL, for example, a known field effect transistor (FET) or an insulated gate bipolar transistor (IGBT) can be used. As shown in the figure, the switching elements 41UU to 41WL are provided with free-wheeling diodes. In the present embodiment, the freewheeling diode uses body diodes (parasitic diodes) of the switching elements 41UU to 41WL. Instead of the body diode, a free-wheeling diode can be separately provided and connected in parallel to the switching elements 41UU to 41WL.

  As shown in the figure, a U-phase positive switching element 41UU and a U-phase negative switching element 41UL are connected in series between the positive terminal 3U and the negative terminal 3L of the DC power supply 3. A U-phase output terminal 42U is provided between the switching elements 41UU and 41UL. Similarly, a V-phase output terminal 42V is provided between the V-phase positive switching element 41VU and the V-phase negative switching element 41VL, and between the W-phase positive switching element 41WU and the W-phase negative switching element 41WL. Is provided with a W-phase output terminal 42W. As described above, the first subscripts U, V, and W of the switching elements 41UU to 41WL indicate phases, the second subscript U indicates a positive side, and L indicates a negative side.

  The U-phase output terminal 42U is connected to the phase terminal 25U of the U-phase armature winding 22 by a power cable 43U. Similarly, the V-phase output terminal 42V is connected to the phase terminal 25V of the V-phase armature winding 23 by the power cable 43V. The W-phase output terminal 42W is connected to the phase terminal 25W of the W-phase armature winding 24 by a power cable 43W.

  The switching elements 41UU to 41WL are controlled to be switched to a conductive state or a cut-off state independently by energization control signals DUU to DWL transmitted from the control device 7. In the figure, the control signal for the switching element 41UU is indicated by DUU, and the control signal for the switching element 41UL is indicated by DUL. The same applies to the V phase and the W phase. Each phase terminal 25U, 25V, 25W of the stator 21 takes three states by the conduction | electrical_connection state or interruption | blocking state of the switching elements 41UU-41WL. Since the three states are the same in each phase, the U-phase terminal 25U will be described as an example.

  The U-phase terminal 25U is constrained to the power supply voltage VBAT when the U-phase positive switching element 41UU is conductive and the U-phase negative switching element 41UL is disconnected, and the U-phase negative switching element 41UU is disconnected when the U-phase positive switching element 41UU is disconnected. When side switching element 41UL is conductive, it is constrained to 0 voltage, and when both U-phase positive side switching element 41UU and U-phase negative side switching element 41UL are in the cut-off state, a high impedance state is established.

  An induced voltage VUi is induced at the U-phase terminal 25U in the high impedance state. The U-phase induced voltage VUi is generated when the magnetic flux from the rotor magnetic poles is linked to the U-phase armature winding 22 connected to the U-phase terminal 25U. Therefore, the U-phase induced voltage VUi changes based on the relative positional relationship between the U-phase armature winding 22 and the rotor 27 and serves as an index for detecting the rotor rotational position. It should be noted that control in which both the U-phase positive switching element 41UU and the U-phase negative switching element 41UL are in a conductive state is prohibited by providing a dead time, and a short circuit failure of the DC power supply 3 is prevented.

  In the present embodiment, the brushless motor 2 is mounted on the electric pump 5. The electric pump 5 can be, for example, a water pump that sends out coolant for the engine 6 of the vehicle. FIG. 2 is a cross-sectional view showing an example of the electric pump 5. As shown in the figure, the electric pump 5 includes a pump unit 50 that is a centrifugal pump, a brushless motor 2 that drives the pump unit 50, a power conversion device 4 that drives and controls the brushless motor 2, and a power conversion device 4. A DC power source 3 that supplies DC power and a control device 7 that controls the switching operation of the power converter 4 are provided.

  The brushless motor 2 is accommodated in a housing 51 of the electric pump 5, and the rotor 27 is rotatably supported by a pump shaft 52 fixedly provided in the housing 51. The pump unit 50 includes an impeller 53 and a pump cover 54 that covers the impeller 53. The impeller 53 is supported by the pump shaft 52 so as to be rotatable integrally with the rotor 27.

  The impeller 53 has a boss portion 55 having a central hole through which the pump shaft 52 passes, and a blade portion 57 erected forward from a disk-shaped rear shroud 56 fixed to the boss portion 55. The rear shroud 56 can also be formed integrally with the boss portion 55. Further, the pump cover 54 constitutes a suction pipe 58 provided at a position facing the center portion of the impeller 53.

  Radiating fins 59 are provided on the outer wall of the housing 51, and a substrate 70 is provided near the radiating fins 59 in the housing 51. The power conversion device 4 and the control device 7 are mounted on the substrate 70, and the DC power supply 3 is connected to the power conversion device 4 so as to be able to supply DC power. In the figure, an arithmetic device 7M which is a part of the control device 7 is shown.

  The electric pump 5 pumps cooling water stored in a reservoir tank (not shown) toward the engine 6 via a cooling rod (not shown). The cooling water absorbs the exhaust heat from the engine 6 in the engine 6 and the exhaust heat exchanger (not shown), and the absorbed cooling water is radiated through the radiator (not shown). Further, the output of the electric pump 5 necessary for cooling is calculated by the control device (not shown) of the control device 7 in accordance with the increase / decrease in the rotational speed of the engine 6, and the output (electric power) required for the brushless motor 2 , The reference duty ratio of the PWM signal input to the control device 7 is increased or decreased in accordance with the motor rotation speed or the like.

  Specifically, as the rotational speed of the engine 6 increases, the reference duty ratio of the PWM signal input to the control device 7 increases, and when the rotational speed of the engine 6 decreases, the PWM input to the control device 7. The reference duty ratio of the signal decreases. The relationship between the output of the brushless motor 2 and the reference duty ratio of the PWM signal can be derived in advance based on, for example, the rotational speed of the brushless motor 2, the motor current, the power supply voltage VBAT, and the like. The relationship between the output of the brushless motor 2 and the reference duty ratio of the PWM signal is stored in a memory in the host control device by a map, a table, a relational expression, or the like.

  The control device 7 includes an arithmetic device 7M having a CPU and a memory, and can drive the brushless motor 2 by executing a drive program stored in the memory. Specifically, the control device 7 applies a control voltage to the control electrodes of the switching elements 41UU to 41WL to control the conduction state and the cutoff state of the switching elements 41UU to 41WL.

  FIG. 3 is an explanatory diagram for explaining a method of controlling the energized state and the non-energized state of the armature winding of the brushless motor 2. As shown in the figure, the control device 7 performs state control of the phase terminals 25U, 25V, and 25W in six periods T1 to T6. The figure shows the state of each phase terminal 25U, 25V, 25W in the corresponding period, “Hi-Z” shows a high impedance state, “L” shows a state restricted to 0 voltage, “ “PWM” indicates a PWM control state.

  For example, in the period T1, the column of the U-phase terminal 25U is “Hi-Z”, and both the U-phase positive switching element 41UU and the U-phase negative switching element 41UL of the power conversion device 4 are in the cut-off state. , U-phase terminal 25U is in a high impedance state. The column of the V-phase terminal 25V is “L”, the V-phase positive switching element 41VU of the power conversion device 4 is cut off, the V-phase negative switching element 41VL is turned on, and the V-phase terminal 25V is turned on. Is constrained to 0 voltage.

  In the period T1, the column of the W-phase terminal is “PWM”, the W-phase negative switching element 41WL of the power conversion device 4 is turned off, and the W-phase positive switching element 41WU is commanded by the PWM frequency and duty ratio Indicates that the control is switched to a conductive state or a cut-off state. As a result, a rectangular voltage in which the power supply voltage VBAT and the zero voltage repeat periodically is generated at the W-phase terminal 25W. Therefore, the V-phase armature winding 23 and the W-phase armature winding 24 connected between the W-phase terminal 25W and the V-phase terminal 25V are energized by PWM control. The period T1 is a U-phase non-energization time zone, and the U-phase induced voltage VUi can be detected.

  Next, in the period T2, the column of the U-phase terminal 25U is “PWM”, and the U-phase terminal 25U has a rectangular shape in which the power supply voltage VBAT and the 0 voltage are periodically repeated at the commanded PWM frequency and duty ratio. Is generated. The column of the V-phase terminal 25V is “L”, which indicates that the constraint on the V-phase terminal 25V to 0 voltage continues. The column of the W-phase terminal is “Hi-Z”, which indicates that the W-phase terminal 25W is in a high impedance state. Thus, the U-phase armature winding 22 and the V-phase armature winding 23 connected between the U-phase terminal 25U and the V-phase terminal 25V are energized by PWM control. The period T2 is a W phase non-energization time zone, and the W phase induced voltage VWi can be detected.

  Similarly, in the period T3 to T6, the state of each phase terminal 25U, 25V, 25W, the armature winding to be energized, and the phase terminal capable of detecting the induced voltage are sequentially changed. Note that the control state in the periods T1 to T6 is repeated. Each of the periods T1 to T6 corresponds to an electrical angle of 60 °, and the period from the period T1 to the state T1 again after the period T6 corresponds to one cycle of the electrical angle.

  FIG. 4 is a timing chart showing an example of terminal voltages VU, VV, VW of each phase, zero cross point detection signal Qs, and time values of first timer Tm1 to third timer Tm3. A solid line L11 indicates the U-phase terminal voltage VU, and a broken line L12 indicates the U-phase torque constant. A solid line L13 indicates the V-phase terminal voltage VV, and a broken line L14 indicates the V-phase torque constant. A solid line L15 indicates the W-phase terminal voltage VW, and a broken line L16 indicates the W-phase torque constant. In addition, the horizontal axis of the figure shows the common electrical angle, and the periods T1 to T6 correspond to the periods T1 to T6 shown in FIG.

  When the energization time zone and the non-energization time zone of the brushless motor 2 are controlled as shown in FIG. 3, the voltage waveforms indicated by the solid lines L11, L13, and L15 in FIG. 4 are generated at the phase terminals 25U, 25V, and 25W. In the U-phase terminal voltage VU, a period T2 and a period T3 indicate energization time periods by PWM control, and a period T5 and a period T6 indicate energization time periods constrained to 0 voltage. In the U-phase terminal voltage VU, the increasing voltage waveform generated in the period T1 and the decreasing voltage waveform generated in the period T4 indicate the induced voltage VUi in the non-energization time zone.

  The same applies to the V-phase terminal voltage VV and the W-phase terminal voltage VW, except that the periods T1 to T6 are different. Further, in each phase terminal voltage VU, VV, VW, a surge voltage Z due to opening / closing of each switching element 41UU-41WL is generated, and is superimposed on the boundary of each period T1-T6. Although the surge voltage Z is shown with a predetermined time width in the figure, it is actually an instantaneous waveform.

  FIG. 5 is a block diagram illustrating an example of a control block of the control device 7. As shown in the figure, when viewed as a control block, the control device 7 includes a zero cross point detector 71, a timer 72, a rotor rotational position estimator 73, a phase compensator 74, and a voltage setting unit 75. Hereinafter, each control block will be described in detail.

(Zero cross point detector 71)
As shown in FIG. 1, the zero cross point detector 71 includes three-phase combined resistors 71U, 71V, 71W and a comparator 711, and sequentially detects the zero cross points of the three phases. The three-phase composite resistors 71U, 71V, 71W have the same resistance value, and are connected between the power cables 43U, 43V, 43W of the respective phases and the composite point 712. That is, the three-phase combined resistors 71U, 71V, 71W are Y-connected, and the combined point 712 is a neutral point of the Y-connection. A synthesized voltage obtained by synthesizing the induced voltages VUi, VVi, and VWi of each phase is generated at the synthesis point 712.

  The combined voltage has a waveform in which the surge voltage Z is superimposed on a waveform in which the induced voltages VUi, VVi, and VWi of each phase increase and decrease. In the waveform example shown in FIG. 4, the combined voltage is an increase in the U-phase induced voltage VUi in the period T1, a decrease in the W-phase induced voltage VWi in the period T2, an increase in the V-phase induced voltage VVi in the period T3, and a U-phase in the period T4. A decrease in the induced voltage VUi, an increase in the W-phase induced voltage VWi in the period T5, and a decrease in the V-phase induced voltage VVi in the period T6 result in a waveform in which the surge voltage Z is superimposed on the boundary between the periods T1 to T6.

  As shown in FIG. 1, the combining point 712 is connected to the positive input terminal (+) of the comparator 711, and the combined voltage is input to the positive input terminal (+) of the comparator 711. At the negative input terminal (−) of the comparator 711, an intermediate level value (= VBAT / 2) obtained by dividing the power supply voltage VBAT of the DC power supply 3 by two resistors 71R and 71R having the same resistance value is used as a reference voltage. Have been entered. The comparator 711 compares the combined voltage input to the positive input terminal (+) with the intermediate level value of the negative input terminal (−), and outputs a zero cross point detection signal Qs to the output terminal 713. That is, when the combined voltage is smaller than the intermediate level value, the zero cross point detection signal Qs is at the low level (Lo), and when the combined voltage is equal to or higher than the intermediate level value, the zero cross point detection signal Qs is at the high level. (Hi).

  The zero cross point detector 71 detects the zero cross point at the timing when the zero cross point detection signal Qs changes from the low level (Lo) to the high level (Hi), and the zero cross point detection signal Qs changes from the high level (Hi) to the low level (Hi). The next zero cross point can be detected at the timing of changing to Lo). Here, the zero cross point refers to a rotor rotational position where the induced voltage generated in the armature winding of the non-energized phase becomes zero.

  In the waveform example shown in FIG. 4, the zero cross point detector 71 detects the zero cross point at points P1 to P6 where the waveforms of the induced voltages VUi to VWi intersect with the intermediate level value. At this time, the phase terminal voltages VU, VV, and VW coincide with the intermediate level value (= VBAT / 2), and the induced voltage generated in the armature winding in the non-conduction phase is zero. Points P1 to P6 are electrical angles of 30 °, 90 °, 150 ° 210 °, 270 °, and 330 ° in this order, and a solid line L17 shown in the figure indicates the zero cross point detection signal Qs.

(Timekeeping unit 72)
The time measuring unit 72 includes a first timer Tm1, a second timer Tm2, and a third timer Tm3, and measures the detection interval of the zero cross point detection signal Qs and performs various times between the zero cross points. In FIG. 4, the solid line L18 indicates the time value of the first timer Tm1, the solid line L19 indicates the time value of the second timer Tm2, and the solid line L20 indicates the time value of the third timer Tm3.

  The first timer Tm1 measures the detection interval of the zero cross point detection signal Qs. Specifically, the first timer Tm1 starts timing at the timing when the zero cross point detection signal Qs changes from the low level (Lo) to the high level (Hi), and the zero cross point detection signal Qs becomes the high level (Hi). The timing is completed at the timing when the signal changes from low to low (Lo). The first timer Tm1 repeats the time measurement every time the zero cross point detection signal Qs is inverted. Since the zero cross point detection signal Qs is inverted every 60 ° in electrical angle, the time value of the first timer Tm1 indicates the time required for the rotor 27 to rotate 60 ° in electrical angle.

  The second timer Tm2 measures the time required for the rotor 27 to rotate 30 ° in electrical angle from the zero cross point. Specifically, the second timer Tm2 measures the time when the time value of the first timer Tm1 when the zero cross point detector 71 detects the zero cross point is halved. For example, it is assumed that the time value of the first timer Tm1 when the zero cross point detector 71 detects the zero cross point is 1000. At this time, the second timer Tm2 measures the time corresponding to the time value 500 obtained by halving the time value 1000 of the first timer Tm1.

  When the timing of the second timer Tm2 is completed, the control device 7 performs a commutation operation for switching between the energized state and the non-energized state of the armature winding of the brushless motor 2. As described above with reference to FIG. 3, for example, when the period T1 shifts to the period T2, the state of the U-phase terminal 25U is changed from “Hi-Z” to “PWM”, and the state of the W-phase terminal 25W. From “PWM” to “Hi-Z”. V-phase terminal 25V continues to be in the “L” state. The same applies to other periods. Thus, the time value of the second timer Tm2 indicates the commutation time from the zero cross point.

  The third timer Tm3 measures the time required for the rotor 27 to rotate 45 ° from the zero cross point by an electrical angle. Specifically, the third timer Tm3 measures the time obtained by multiplying the time value of the first timer Tm1 by 3/4 when the zero cross point detector 71 detects the zero cross point. For example, in the above-described example, the third timer Tm3 measures the time corresponding to the time value 750 obtained by multiplying the time value 1000 of the first timer Tm1 by 3/4.

  Here, a period from when the time measurement of the third timer Tm3 is completed to when the zero cross point detecting unit 71 detects the zero cross point is a period TQ1 (corresponding to a first predetermined period of the present invention). Further, a period from when the third timer Tm3 starts to measure time until the time measurement is completed is defined as a period TQ2 (corresponding to a second predetermined period of the present invention). Note that the timing of the third timer Tm3 is not limited to the above period (45 degrees in electrical angle). The third timer Tm3 (corresponding to the time measuring unit of the present invention) starts measuring the time period TQ2 triggered by the detection of the zero cross point, and then the time TQ2 before the zero cross point detecting unit 71 detects the zero cross point. Complete timing.

  Further, in the same figure, the points where the time values of the second timer Tm2 and the third timer Tm3 are set based on the time value of the first timer Tm1 are schematically shown by using arrows. Furthermore, the point which performs a commutation operation | movement by completion of the time measuring by 2nd timer Tm2 is typically shown using the arrow.

(Rotor rotational position estimation unit 73)
The rotor rotation position estimation unit 73 estimates the rotor rotation position θ1 of the brushless motor 2 based on the zero cross point detection signal Qs. Specifically, the rotor rotational position estimating unit 73 estimates the rotational speed (rotational speed) of the brushless motor 2 from the time value (zero cross point detection interval) of the first timer Tm1. Then, the rotor rotational position estimation unit 73 integrates the estimated rotational speed of the brushless motor 2 to estimate the rotational position θ1 of the rotor 27.

(Phase compensation unit 74)
The phase compensation unit 74 sets the advance angle θ2. The advance angle θ2 compensates for the phase lag of the voltage applied to the armature winding in the energized phase. The drive voltage of the brushless motor 2 is a motor drive voltage Vdrv, the current flowing through the armature winding in the energized phase is the motor current Im, and the output torque of the brushless motor 2 is the motor torque Tm. Hereinafter, the phase delay of the voltage applied to the armature winding of the energized phase will be described using the motor rotation speed n, the torque constant Kt, the counter electromotive force coefficient Kv, the motor inertia moment Ii, and the motor load coefficient Kp of the brushless motor 2. To do. Although the motor load coefficient Kp is described as being proportional to the motor rotation speed n, the motor load coefficient Kp can be appropriately set according to the load characteristics. For example, the motor load coefficient Kp can be expressed by a linear function or a quadratic function of the motor rotation speed n.

  The motor current Im is expressed by the following formula 1, and the relationship between the motor current Im and the motor torque Tm is expressed by the following formula 2. The equation of motion of the rotating body is expressed by the following equation (3).

  By substituting Equation 1 and Equation 2 into Equation 3, Equation 3 can be expressed by Equation 4 below. Further, when the following formula 4 is Laplace transformed, the formula 4 can be expressed by the following formula 5. However, the Laplace operator is denoted by s, the Laplace-converted motor drive voltage Vdrv is the motor drive voltage VDRV (s), and the Laplace-converted motor rotation speed n is the motor rotation speed N (s). In addition, the initial value of the motor rotation speed n is N (0).

  When the initial value N (0) of the motor rotation speed n is 0 in Equation 5, Equation 5 can be expressed by Equation 6 below. Further, the transfer function G (s) having the motor drive voltage VDRV (s) as an input and the motor rotation speed N (s) as an output can be expressed by the following formula 7 from the formula 6. Furthermore, the time constant Ts can be expressed by the following Expression 8 from Expression 7.

  As shown in Equation 7, the control system that receives the motor drive voltage Vdrv and outputs the motor rotation speed n is a first-order lag control system. Therefore, the phase of the voltage applied to the armature winding in the energized phase is delayed due to the phase delay of the motor drive voltage Vdrv. Therefore, in the present embodiment, the phase compensation unit 74 sets the advance angle θ2 that compensates for the phase delay of the voltage applied to the energized armature winding.

  Specifically, the phase compensation unit 74 calculates the phase delay based on the time constant Ts shown in Equation 8, and sets the phase delay as the advance angle θ2. Then, the phase compensation unit 74 advances the phase by the advance angle θ2 with respect to the rotor rotation position θ1 estimated by the rotor rotation position estimation unit 73. The control device 7 applies a control voltage to each control electrode of the switching elements 41UU to 41WL based on the rotor rotational position (θ1-θ2) whose phase has been advanced, so that the switching elements 41UU to 41WL are turned on and off. To control. Note that the phase compensator 74 can set the advance angle θ2 in the same manner in the case of a control system including a second-order delay or a control system including dead time.

(Voltage setting unit 75)
The voltage setting unit 75 sets a voltage command value of a voltage to be applied to the energized phase armature winding. The voltage setting unit 75 can set a voltage command value of a voltage to be applied to the armature winding of the energized phase by a rectangular wave-shaped pulse width modulation signal (PWM signal).

  FIG. 6 is a diagram illustrating an example of a change over time in the duty ratio of the PWM signal. The horizontal axis represents the electrical angle and corresponds to the horizontal axis (electrical angle) shown in FIG. A solid line L31 indicates the energization period of the U-phase armature winding 22. A hatched region R31 schematically shows an increase / decrease in the duty ratio of the U-phase PWM signal. The vertical axis (positive direction) represents the duty ratio of the PWM signal of the U-phase positive side switching element 41UU, and the vertical axis (negative direction) represents the duty ratio of the PWM signal of the U-phase negative side switching element 41UL.

  A solid line L32 indicates the energization period of the V-phase armature winding 23. The hatched region R32 schematically shows the increase / decrease in the duty ratio of the V-phase PWM signal. A solid line L33 indicates the energization period of the W-phase armature winding 24. A hatched region R33 schematically shows an increase / decrease in the duty ratio of the W-phase PWM signal. The positive and negative directions of the vertical axis in the V phase and the W phase indicate the duty ratios of the PWM signals of the switching elements 41VU to 41WL, as in the case of the U phase.

  The voltage setting unit 75 sets the voltage command value of the voltage to be applied to the armature winding of the energized phase in the period TQ1 (corresponding to the first predetermined period of the present invention) immediately before the zero cross point detection unit 71 detects the zero cross point. The zero cross point detection unit 71 sets the first applied voltage that is increased to a voltage at which the zero cross point can be detected. Specifically, assuming that the duty ratio of the PWM signal corresponding to the first applied voltage is the first duty ratio DF1, and the reference duty ratio of the PWM signal is the second duty ratio DF2, the voltage setting unit 75 sets the period TQ1 (for example, The duty ratio of the PWM signal having an electrical angle of 15 ° to 30 ° is set to the first duty ratio DF1.

  The power conversion device 4 applies the first applied voltage to the armature winding of the energized phase in the period TQ1, and increases the instantaneous rotational speed of the brushless motor 2 in the period TQ1. As the number of rotations of the brushless motor 2 increases, the induced voltage generated in the armature winding of the non-conduction phase also increases. Therefore, compared with the case where the applied voltage applied to the armature winding in the energized phase is constant in one cycle of the electrical angle (periods T1 to T6), the zero cross point detection unit 71 detects the zero cross point up to a low rotational speed. be able to. In the present specification, “instantaneous rotational speed” refers to a local rotational speed in a period shorter than one cycle of the electrical angle.

  Further, the voltage at which the zero cross point can be detected can be derived in advance based on, for example, the rotational speed of the brushless motor 2, the motor current, and the power supply voltage VBAT. The first duty ratio DF1 is preset based on the derived voltage, and is stored in the memory of the control device 7 by a map, a table, a relational expression, or the like.

  In the present embodiment, the applied voltage (first applied voltage) applied to the armature winding of the energized phase in the period TQ1 (corresponding to the first predetermined period of the present invention) immediately before the zero cross point detecting unit 71 detects the zero cross point. Is increased to a voltage at which the zero cross point detection unit 71 can detect the zero cross point, so that the zero cross point detection unit is compared with the case where the applied voltage applied to the armature winding of the energized phase is constant in one cycle of the electrical angle. 71 can detect a zero cross point up to a low rotational speed. Therefore, the sensorless brushless motor driving apparatus 1 can reduce the driving rotational speed of the brushless motor 2.

  The voltage setting unit 75 sets the voltage command value of the voltage to be applied to the armature winding of the energized phase during the period TQ2 (corresponding to the second predetermined period of the present invention) after the zero cross point detection unit 71 detects the zero cross point. The second applied voltage is set to be smaller than the first applied voltage. Specifically, the voltage setting unit 75 sets the duty ratio of the PWM signal in the period TQ2 (for example, 30 ° to 75 ° in electrical angle) to the second duty ratio DF2. Note that the duty ratio of the PWM signal corresponding to the second applied voltage can be set to a duty ratio different from the reference duty ratio of the PWM signal.

  The power conversion device 4 applies the second applied voltage to the armature winding of the energized phase during the period TQ2 to reduce the average rotational speed of the brushless motor 2. In this specification, the “average rotational speed” refers to a global rotational speed during a period of one or more electrical angles. In the present embodiment, the period TQ2 (electrical angle 45 °) is longer than the period TQ1 (electrical angle 15 °). Thus, by setting the period TQ2 to be longer than the period TQ1, the average rotational speed of the brushless motor 2 can be easily reduced.

  In the present embodiment, an applied voltage (second applied voltage) to be applied to the armature winding in the energized phase during a period TQ2 (corresponding to the second predetermined period of the present invention) after the zero cross point detector 71 detects the zero cross point. Since the zero cross point detector 71 detects the zero cross point, the rotational speed of the brushless motor 2 can be reduced and the average rotational speed of the brushless motor 2 can be reduced. . Therefore, for example, when this drive device is used as a drive device for the electric pump 5 such as an electric oil pump or a water pump, the number of revolutions of the electric pump 5 can be reduced and the pump discharge amount can be reduced, thereby reducing power consumption. And overcooling (overcooling) can be prevented.

  The voltage setting unit 75 alternately sets the duty ratio of the PWM signal to the first duty ratio DF1 or the second duty ratio DF2. The duty ratio of the PWM signal is generated by comparing the triangular wave carrier waveform with the sine wave waveform. The voltage setting unit 75 can increase / decrease the voltage amplitude of the sine wave waveform to increase / decrease the time during which the switching elements 41UU to 41WL are in the conductive state, and the duty ratio of the PWM signal can be changed to the first duty ratio DF1 or the second duty ratio. The ratio can be switched to DF2. The frequency of the carrier waveform (carrier frequency) can be variably controlled.

  In the present embodiment, the control device 7 includes a third timer Tm3 (corresponding to the time measuring unit of the present invention) that measures the period TQ2 (corresponding to the second predetermined period of the present invention). Then, the period TQ1 (corresponding to the first predetermined period of the present invention) starts in conjunction with the completion of the timing of the period TQ2, and the period TQ1 ends when the next zero cross point is detected. Therefore, the period TQ1 and the period TQ2 can be easily measured, and the application time of the first application voltage and the second application voltage can be set appropriately.

  Further, in the present embodiment, the control device 7 includes a phase compensator 74 that sets an advance angle θ2 that compensates for the phase delay of the voltage applied to the armature winding of the energized phase. Then, the power conversion device 4 applies a voltage whose phase is advanced by the advance angle set by the phase compensation unit 74 to the armature winding of the energized phase. Therefore, the detection accuracy of the zero cross point by the zero cross point detector 71 can be improved as compared with the case where the phase delay is not taken into consideration.

<Driving method of sensorless brushless motor>
The present invention can also be understood as a method for driving a sensorless brushless motor, and the method for driving a sensorless brushless motor can also be understood as a drive program for a sensorless brushless motor executed by causing the arithmetic device 7M to function. In these cases, the “XX section” described in the sensorless brushless motor driving apparatus 1 may be read as “XX process”. That is, the zero cross point detection unit 71 is in the zero cross point detection step, the time measurement unit 72 is in the time measurement step, the rotor rotation position estimation unit 73 is in the rotor rotation position estimation step, the phase compensation unit 74 is in the phase compensation step, and the voltage setting unit 75. Can be read as a voltage setting process. Moreover, the function in the power converter device 4 can be read as a voltage output process. Since the description about each process is the same as the above-mentioned description, the overlapping description is abbreviate | omitted.

  FIG. 7 is a flowchart illustrating an example of a procedure of a sensorless brushless motor driving method. First, it is determined whether or not the zero cross point detection signal Qs is inverted (step S101). Zero cross point detection when the zero cross point detection signal Qs changes from low level (Lo) to high level (Hi) or when the zero cross point detection signal Qs changes from high level (Hi) to low level (Lo) It is determined that the signal Qs is inverted. If the zero cross point detection signal Qs is inverted (in the case of Yes), the process proceeds to step S102. If the zero cross point detection signal Qs is not inverted (in the case of No), the process proceeds to step S105.

  In step S102, it is determined whether or not the time measurement by the third timer Tm3 is completed. When the time measurement by the third timer Tm3 has been completed (in the case of Yes), the process proceeds to step S103, and when the time measurement by the third timer Tm3 has not been completed (in the case of No), the process proceeds to step S105. That is, if the time measurement by the third timer Tm3 is not completed even if the zero cross point detection signal Qs is inverted, the process proceeds to step S105. Thereby, for example, when the zero cross point detection signal Qs is inverted by the surge voltage Z shown in FIG. 4, it is possible to prevent the processing in steps S103 and S104 from being erroneously performed.

  In step S103, the time values of the second timer Tm2 and the third timer Tm3 are set, and the time measurement by the second timer Tm2 and the third timer Tm3 is started. The time measured values of the second timer Tm2 and the third timer Tm3 are set based on the time measured values of the first timer Tm1 when the zero cross point detection signal Qs is inverted in step S101. Then, the process proceeds to step S104.

  In step S104, the duty ratio of the PWM signal is set to the second duty ratio DF2, and the process proceeds to step S105. In step S105, the rotor rotational position θ1 of the rotor 27 is estimated, and the advance angle θ2 is set. Then, the process proceeds to step S106. Note that the estimation of the rotor rotational position θ1 and the setting of the advance angle θ2 can be performed only when the condition is satisfied in Step S102 (in the case of Yes). In this case, when the conditions are not satisfied in Steps S101 and S102 (in the case of No), the rotor rotational position (θ1-θ2) is advanced by an amount corresponding to the control cycle. The control cycle is a cycle in which this routine is repeated.

  In step S106, it is determined whether or not the time measurement by the second timer Tm2 is completed. When the time measurement by the second timer Tm2 is completed (in the case of Yes), the process proceeds to step S107, and when the time measurement by the second timer Tm2 is not completed (in the case of No), the process proceeds to step S108. In step S107, the energization pattern is switched and the process proceeds to step S108. The switching of the energization pattern refers to a commutation operation that switches between an energized state and a non-energized state of the armature winding of the brushless motor 2.

  In step S108, it is determined whether or not the motor rotational speed is equal to or lower than a predetermined rotational speed. If the motor rotational speed is equal to or lower than the predetermined rotational speed (in the case of Yes), the process proceeds to step S109. If the motor rotational speed is greater than the predetermined rotational speed (in the case of No), the process proceeds to step S111. Note that the determination in step S108 is made after the motor speed has once exceeded a predetermined speed after starting. The predetermined rotation speed can detect the zero cross point when the brushless motor 2 is driven with the duty ratio of the PWM signal set to the reference duty ratio (second duty ratio DF2) over one electrical angle cycle. It is good to use a different driving speed.

  In step S109, it is determined whether or not the time measurement by the third timer Tm3 is completed. When the time measurement by the third timer Tm3 is completed (in the case of Yes), the process proceeds to step S110, and when the time measurement by the third timer Tm3 is not completed (in the case of No), the process proceeds to step S111. In step S110, the duty ratio of the PWM signal is set to the first duty ratio DF1, and the process proceeds to step S111. In step S111, a voltage is applied to the armature winding of the energized phase based on the set duty ratio of the PWM signal. And this routine is once complete | finished. In addition, the process shown by this flowchart is repeatedly performed with a predetermined space | interval (control period).

  The zero cross point detection process is performed in step S101, and the timing process is performed in steps S102, S103, S106, and S109. The rotor rotational position estimation step and the phase compensation step are performed in step S105, and the voltage setting step is performed in steps S104, S107, S108, and S110. The voltage output process is performed in step S111. In addition, each process can also be provided with processes other than the process shown in FIG.

  The sensorless brushless motor driving method according to the present embodiment is a sensorless brushless motor driving method that estimates the rotor rotational position of the brushless motor 2 and drives the brushless motor 2 based on the estimated rotor rotational position. A point detection process, a voltage setting process, and a voltage output process are provided. In the zero cross point detection step, the zero cross points of the three phases are sequentially detected. In the voltage setting step, the voltage command value of the voltage applied to the armature winding of the energized phase in the period TQ1 (corresponding to the first predetermined period of the present invention) immediately before the zero cross point is detected in the zero cross point detection step is set to the zero cross point. In the detection process, the first applied voltage is set to a value that can increase the zero cross point to a detectable voltage. In the voltage output step, the first applied voltage is applied to the armature winding of the energized phase in the period TQ1, and the instantaneous rotational speed of the brushless motor 2 in the period TQ1 is increased.

  In the present embodiment, the applied voltage (first applied voltage) applied to the armature winding of the energized phase in the period TQ1 (corresponding to the first predetermined period of the present invention) immediately before the zero cross point is detected in the zero cross point detecting step. Since the zero cross point is increased to a voltage at which the zero cross point can be detected in the zero cross point detection step, the voltage applied to the armature winding in the energized phase is constant in the zero cross point detection step in one cycle of the electrical angle. The zero cross point can be detected up to the rotational speed. Therefore, the drive rotation speed of the brushless motor 2 can be reduced.

<Additional notes>
The following technical idea can also be grasped from the above description.
(Additional item 1)
The voltage setting step compares a voltage command value of a voltage applied to the armature winding of the energized phase in the second predetermined period after the zero cross point is detected in the zero cross point detection step with the first applied voltage. Set to a small second applied voltage,
The sensorless brushless motor according to claim 5, wherein in the voltage output step, the second applied voltage is applied to the armature winding of the energized phase in the second predetermined period to reduce the average rotational speed of the brushless motor. Driving method.
(Appendix 2)
A timing step of starting timing of the second predetermined period using the detection of the zero cross point as a trigger and then completing timing of the second predetermined period before detecting the zero cross point in the zero cross point detecting step; Prepared,
The first predetermined period is started when the timing of the second predetermined period is completed in the time measuring step, and the first predetermined period is ended when the zero cross point is detected in the zero cross point detecting step next. The driving method of the sensorless brushless motor according to additional item 1.
(Additional Item 3)
A phase compensation step for setting a lead angle for compensating for a phase delay of a voltage applied to the armature winding of the energized phase;
The voltage output step applies the voltage advanced in phase by the advance angle set in the phase compensation step to the armature winding of the energized phase. Driving method for sensorless brushless motor.

<Others>
The present invention is not limited to the embodiment described above and shown in the drawings, and can be implemented with appropriate modifications within a range not departing from the gist. For example, the duty ratio of the PWM signal is not limited to changing to a rectangular wave shape. For example, the duty ratio of the PWM signal can be changed to a triangular wave shape, a sawtooth wave shape, or a sine wave shape. Further, the rotational speed (rotational speed) of the brushless motor 2 estimated by the rotor rotational position estimating unit 73 can be fed back to perform speed control, and torque control can also be performed.

1: Sensorless brushless motor drive device,
2: Brushless motor,
4: Power converter,
7: Control device,
71: Zero cross point detection unit, 72: Time measuring unit, 74: Phase compensation unit, 75: Voltage setting unit,
TQ1: first predetermined period, TQ2: second predetermined period

Claims (5)

A sensorless brushless motor drive device that estimates a rotor rotational position of a brushless motor and drives the brushless motor based on the estimated rotor rotational position,
When the rotor rotation position at which the induced voltage generated in the armature winding of the non-energized phase becomes 0 is the zero cross point,
A zero cross point detector that sequentially detects the zero cross point of each of the three phases;
A voltage command value of a voltage applied to the armature winding of the energized phase in a first predetermined period immediately before the zero cross point detection unit detects the zero cross point, and a voltage at which the zero cross point detection unit can detect the zero cross point A voltage setting unit for setting the first applied voltage increased to
A control device comprising:
A power converter that applies the first applied voltage to the armature winding of the energized phase in the first predetermined period to increase the instantaneous rotational speed of the brushless motor in the first predetermined period;
A sensorless brushless motor drive device comprising: The voltage setting unit compares a voltage command value of a voltage to be applied to the armature winding of the energized phase in a second predetermined period after the zero cross point detection unit detects the zero cross point with the first applied voltage. Set to a small second applied voltage,
2. The sensorless brushless motor according to claim 1, wherein the power converter applies the second applied voltage to the armature winding of the energized phase during the second predetermined period to reduce the average rotational speed of the brushless motor. Drive device. The control device starts timing of the second predetermined period using the detection of the zero cross point as a trigger, and then measures the time of the second predetermined period before the zero cross point detecting unit detects the zero cross point. With a timekeeping part to complete,
The first predetermined period starts when the time measuring unit completes the time measurement of the second predetermined period, and then ends the first predetermined period when the zero cross point detection unit detects the zero cross point. The sensorless brushless motor driving device according to claim 2. The control device includes a phase compensation unit that sets a lead angle that compensates for a phase delay of a voltage applied to the armature winding of the energized phase,
The said power converter device applies the voltage which advanced the phase by the said advance angle set by the said phase compensation part to the armature winding of the said energized phase. Sensorless brushless motor drive device. A sensorless brushless motor driving method for estimating a rotor rotational position of a brushless motor and driving the brushless motor based on the estimated rotor rotational position,
When the rotor rotation position at which the induced voltage generated in the armature winding of the non-energized phase becomes 0 is the zero cross point,
A zero cross point detecting step of sequentially detecting the zero cross point of each of the three phases;
The voltage command value of the voltage to be applied to the armature winding of the energized phase in the first predetermined period immediately before detecting the zero cross point in the zero cross point detecting step, and the voltage capable of detecting the zero cross point in the zero cross point detecting step A voltage setting step for setting the first applied voltage increased to
A voltage output step of applying the first applied voltage to the armature winding of the energized phase during the first predetermined period to increase the instantaneous rotational speed of the brushless motor during the first predetermined period;
A sensorless brushless motor driving method comprising:

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