Motor control device and motor control method

Abstract

In one embodiment of a motor control device and a motor control method according to the present invention, a detection signal of a current sensor for detecting a current flowing through an energizing phase of a three-phase brushless motor is acquired, the three-phase brushless motor is driven by 120 rectangular waves on the basis of a control current value based on the detection signal, and the three-phase brushless motor is driven by 120 rectangular waves on the basis of a control current value based on the detection signal. The control current value is obtained on the basis of a current value detected by the current sensor before the switching of the energization phase in the 120-degree rectangular wave drive and a current value detected by the current sensor after the switching. According to the structure, vibration of motor current can be suppressed.

Description

Technical Field

[0001] The present invention relates to a motor control device and a motor control method. Background Art

[0002] The control device of the compressor of Patent Document 1 comprises: a position detection unit for detecting the rotational position of the rotor of the brushless motor; an inverter control unit for energizing and sequentially switching specific two phases of the three-phase stator winding of the brushless motor according to the signal of the position detection unit, thereby driving the inverter; and a current control unit for controlling the current so that the current in the two-phase energization interval of the inverter becomes a waveform similar to the waveform of the no-load induced voltage of the brushless motor.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2001-263256 Summary of the invention

[0006] Problems to be solved by the invention

[0007] When a three-phase brushless motor is driven by a 120-degree rectangular wave, the motor current temporarily decreases when the energized phase is switched.

[0008] Therefore, if the detection value of the current sensor for detecting the current flowing through the energized phase of the three-phase brushless motor is directly used for energization control, the motor current will vibrate, which may cause overcurrent and torque control failure.

[0009] The present invention has been made in view of the conventional actual situation, and an object of the present invention is to provide a motor control device and a motor control method capable of suppressing vibration of motor current in 120-degree rectangular wave driving of a three-phase brushless motor.

[0010] Means for solving problems

[0011] In one embodiment of the motor control device involved in the present invention, the control unit of the motor control device is configured to obtain a detection signal of a current sensor for detecting the current flowing through the energized phase of the three-phase brushless motor, drive the three-phase brushless motor with a 120-degree rectangular wave according to a control current value based on the detection signal, and calculate the control current value based on the current value detected by the current sensor before switching of the energized phase and the current value detected by the current sensor after the switching.

[0012] In addition, in one embodiment of the motor control method involved in the present invention, it is a motor control method executed by a control unit to perform 120-degree rectangular wave driving on a three-phase brushless motor, and the motor control method includes: a step of obtaining a detection signal of a current sensor for detecting the current flowing through the energized phase of the three-phase brushless motor; a step of calculating a control current value based on the detection signal; and a step of outputting a control signal to a drive circuit of the three-phase brushless motor based on the control current value, and in the step of calculating the control current value, the control current value is calculated based on the current value detected by the current sensor before switching of the energized phase and the current value detected by the current sensor after the switching.

[0013] Effects of the Invention

[0014] According to the above invention, in the 120-degree rectangular wave driving of the three-phase brushless motor, the vibration of the motor current can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a system diagram of an internal combustion engine for a vehicle.

[0016] Figure 2 is a block diagram showing a control system of a three-phase brushless motor.

[0017] Figure 3 1 is a timing chart showing a PWM (Pulse Width Modulation) control mode of an inverter.

[0018] Figure 4 This is a timing chart illustrating the phase voltage and the inter-phase voltage when complementary PWM is not performed.

[0019] Figure 5 This is a timing chart illustrating the phase voltage and the inter-phase voltage when complementary PWM is implemented.

[0020] Figure 6 It is a timing chart showing the phase voltage and the shunt current when the pulse shift control is not performed.

[0021] Figure 7 It is a timing chart showing the phase voltage and the shunt current when the pulse shift control is implemented.

[0022] Figure 8 This is a timing chart showing how the phase current decreases when the energized phase is switched.

[0023] Fig. 9 is a timing chart showing the details of the response delay process.

[0024] Fig.10This is a timing chart showing a state where the response delay process is performed in a low rotation speed range of the electric motor.

[0025] Fig.11 This is a timing chart showing a state where the response delay process is performed in a high rotation speed region of the electric motor.

[0026] Fig.12 It is a timing chart showing the effect of the response delay processing.

[0027] Fig.13 is a diagram illustrating the decrease in phase current in the power running mode.

[0028] Fig.14 This is a diagram illustrating that the phase current does not drop in the regeneration mode. DETAILED DESCRIPTION

[0029] Embodiments of the present invention are described below.

[0030] Figure 1 The diagram shows a vehicle internal combustion engine including a three-phase brushless motor to which the motor control device and the motor control method according to the present invention are applied.

[0031] The internal combustion engine 101 includes an intake air amount sensor 103 in an intake duct 102 for detecting an intake air flow rate QA of the internal combustion engine 101 .

[0032] The intake valve 105 opens and closes the intake port of the combustion chamber 104 of each cylinder.

[0033] The fuel injection valve 106 injects fuel into the intake port 102a of each cylinder.

[0034] The fuel injected by the fuel injection valve 106 is sucked into the combustion chamber 104 together with the air through the intake valve 105 , and is ignited and combusted by spark ignition by the spark plug 107 .

[0035] Then, the combustion pressure pushes the piston 108 downward toward the crankshaft 109 , thereby driving the crankshaft 109 to rotate.

[0036] Furthermore, the exhaust valve 110 opens and closes the exhaust port of the combustion chamber 104 . When the exhaust valve 110 is opened, the exhaust gas in the combustion chamber 104 is discharged to the exhaust pipe 111 .

[0037] The exhaust pipe 111 includes a catalytic converter 112 which houses a catalyst such as a three-way catalyst.

[0038] The intake valve 105 opens and closes in accordance with the rotation of an intake camshaft 115 a which is rotationally driven by the crankshaft 109 .

[0039] The exhaust valve 110 is opened and closed in accordance with the rotation of an exhaust camshaft 115 b which is rotationally driven by the crankshaft 109 .

[0040] The electric variable valve timing mechanism 114 (hereinafter referred to as the VVT ​​mechanism 114) is a mechanism that changes the rotational phase of the intake camshaft 115a relative to the crankshaft 109 by the rotation speed of the three-phase brushless motor 12 as an actuator, thereby continuously changing the valve timing of the intake valve 105 as the valve of the internal combustion engine.

[0041] The VVT ​​mechanism 114 has a well-known structure disclosed in, for example, Japanese Patent No. 7085629.

[0042] The following is an overview of one aspect of the structure and operation of the VVT ​​mechanism 114 .

[0043] The VVT ​​mechanism 114 is disposed between a timing sprocket (not shown) and an intake camshaft 115 a , and includes a phase changing mechanism that changes the relative rotational phase between the timing sprocket and the intake camshaft 115 a .

[0044] The phase changing mechanism includes the three-phase brushless motor 12 and a speed reduction mechanism that reduces the rotation speed of the three-phase brushless motor 12 and transmits the speed to the intake camshaft 115 a .

[0045] When the three-phase brushless motor 12 is driven to rotate forward and reverse, the decelerated rotational force is transmitted to the intake camshaft 115a, whereby the intake camshaft 115a rotates forward and reverse relative to the timing sprocket, and the relative rotational phase between the intake camshaft 115a and the timing sprocket is switched.

[0046] Furthermore, the ignition module 116 is directly mounted on the spark plug 107 , and supplies ignition energy to the spark plug 107 .

[0047] The ignition module 116 includes an ignition coil and a power transistor for controlling energization of the ignition coil.

[0048] The control system for controlling the operation of the internal combustion engine 101 includes an engine control module 201 (hereinafter referred to as ECM 201 ) for controlling fuel injection by the fuel injection valve 106 , ignition by the spark plug 107 , and the like, and a VVT controller 202 for controlling valve timing by the VVT ​​mechanism 114 .

[0049] In addition, the VVT ​​controller 202 corresponds to a motor control device that controls the three-phase brushless motor 12 as an actuator of the VVT ​​mechanism 114 .

[0050] The ECM 201 is an electronic control device including a microcomputer 201 a , and the VVT ​​controller 202 is an electronic control device including a microcomputer 202 a .

[0051] The microcomputers 201 a and 202 a include a processor, a nonvolatile memory, a volatile memory, and the like.

[0052] The ECM 201 acquires signals output by various sensors, performs calculation processing according to a program pre-stored in a non-volatile memory, and thereby calculates and outputs operation amounts of the fuel injection valve 106, the ignition module 116, and the like.

[0053] The VVT ​​controller 202 obtains signals sent from the ECM 201 and signals output from various sensors, and performs calculation processing according to a program pre-stored in a nonvolatile memory, thereby calculating and outputting the operation amount of the three-phase brushless motor 12 of the VVT ​​mechanism 114 .

[0054] As the various sensors mentioned above, the internal combustion engine 101, in addition to the intake air amount sensor 103, also has: a crank angle sensor 203 that outputs a crank angle signal POS at each specified angular position of the crankshaft 109; an accelerator opening sensor 206 that detects the amount of depression of the accelerator pedal 207, in other words, detects the accelerator opening ACC; a cam angle sensor 204 that outputs a cam angle signal CAM at each specified angular position of the intake camshaft 115a; a water temperature sensor 208 that detects the temperature TW of the cooling water of the internal combustion engine 101; an air-fuel ratio sensor 209 that is arranged in the exhaust pipe 111 upstream of the catalytic converter 112 and detects the air-fuel ratio AF based on the oxygen concentration in the exhaust gas, etc.

[0055] The crank angle signal POS output by the crank angle sensor 203 is a pulse signal for each unit crank angle, and the signal output pattern is set so that one pulse is missing or a plurality of pulses are continuous for each crank angle corresponding to the stroke phase difference between cylinders.

[0056] Here, the ECM 201 detects a missing position of the pulse signal in the crank angle signal POS as a reference crank angle position.

[0057] The cam angle sensor 204 outputs a cam angle signal CAM at each crank angle corresponding to the stroke phase difference between the cylinders.

[0058] The ECM 201 acquires signals output by these various sensors, and further acquires an on / off signal of an ignition switch 205 which is a main switch for operating and stopping the internal combustion engine 101 .

[0059] The three-phase brushless motor 12 of the VVT ​​mechanism 114 includes Hall sensors 12u, 12v, and 12w as motor rotation position sensors for detecting the positional relationship between the three-phase coils of the U-phase coil, the V-phase coil, and the W-phase coil and the rotor.

[0060] Furthermore, the VVT ​​controller 202 obtains the signals output by the Hall sensors 12u, 12v, and 12w.

[0061] The ECM 201 calculates the target value of the rotational phase of the intake camshaft 115a relative to the crankshaft 109, i.e., the target rotational phase, based on the engine operating conditions such as the engine load and the engine speed obtained from the output signals of the above-mentioned various sensors, and also calculates the actual rotational phase based on the crank angle signal POS and the cam angle signal CAM.

[0062] Then, the ECM 201 calculates the target rotation speed Nt of the three-phase brushless motor 12 of the VVT ​​mechanism 114 so that the actual rotation phase approaches the target rotation phase, and sends a signal of the target rotation speed Nt to the VVT ​​controller 202 .

[0063] The VVT ​​controller 202, which has obtained the signal of the target speed Nt, obtains the target value of the motor current, i.e., the command current value CCV, so that the actual speed of the three-phase brushless motor 12 approaches the target speed Nt, and controls the operation amount of the three-phase brushless motor 12 so that the actual motor current approaches the command current value CCV.

[0064] That is, the VVT ​​controller 202 controls the current supplied to the three-phase brushless motor 12 of the VVT ​​mechanism 114 through speed feedback control.

[0065] Figure 2 1 is a block diagram showing a drive circuit 210 of the three-phase brushless motor 12 included in the VVT ​​controller 202 and a control function of the three-phase brushless motor 12 by the microcomputer 202 a of the VVT ​​controller 202 .

[0066] The microcomputer 202 a of the VVT ​​controller 202 drives the three-phase brushless motor 12 by sequentially switching 120-degree rectangular wave driving of two phases to which voltage is applied among the three phases of the three-phase brushless motor 12 .

[0067] That is, the microcomputer 202 a is a control unit that executes a motor control method for driving the three-phase brushless motor 12 with a 120-degree rectangular wave.

[0068] In a 120-degree rectangular wave drive, for example, every 60-degree rotation, the following are switched: a first mode in which current flows from the U phase to the V phase, a second mode in which current flows from the U phase to the W phase, a third mode in which current flows from the V phase to the W phase, a fourth mode in which current flows from the V phase to the U phase, a fifth mode in which current flows from the W phase to the U phase, and a sixth mode in which current flows from the W phase to the V phase.

[0069] By switching the energization mode, for example, in the case of the U phase, energization is performed between 120 degrees of the first mode and the second mode, non-energization is performed between 60 degrees of the third mode, and energization is performed between 120 degrees of the fourth mode and the fifth mode.

[0070] In addition, 120-degree rectangular wave driving is also called 120-degree energization or rectangular wave driving.

[0071] The three-phase brushless motor 12 includes three-phase coils of U-phase, V-phase, and W-phase connected in a star shape on a cylindrical stator, and a rotor composed of a permanent magnet is rotatably provided in a space formed in the center of the stator.

[0072] The Hall sensors 12u, 12v, and 12w are arranged at intervals of 120 degrees around the rotor, and the timing of switching the energization mode every 60 degrees is detected by combining the sensor signals of the Hall sensors 12u, 12v, and 12w.

[0073] The drive circuit 210 of the three-phase brushless motor 12 includes an inverter 211 , a DC power supply 212 for the inverter 211 , and an inverter drive circuit 213 .

[0074] The inverter 211 is configured by connecting semiconductor switching elements 211 a to 211 f such as FETs in a three-phase bridge configuration, and supplies AC power to the three-phase brushless motor 12 .

[0075] Each gate terminal of the semiconductor switching elements 211 a to 211 f of the inverter 211 is connected to an output port of the inverter drive circuit 213 .

[0076] Then, the semiconductor switch elements 211 a to 211 f are switched on and off according to the gate control signals outputted by the inverter drive circuit 213 to the gate terminals of the semiconductor switch elements 211 a to 211 f.

[0077] Furthermore, a shunt resistor 214 (in other words, a current sensor) for detecting a motor current is arranged on a DC bus between the inverter 211 and the ground GND.

[0078] Figure 3 One form of the PWM control mode of the semiconductor switching elements 211 a to 211 f in 120-degree rectangular wave driving is shown.

[0079] exist Figure 3 In the operation example, the following lower arm chopper control is adopted: the semiconductor switch elements 211a, 211c, and 211e of the upper arm are fixed to be turned on, while the on and off of the semiconductor switch elements 211b, 211d, and 211f of the lower arm are PWM controlled.

[0080] For example, when current flows from the V phase to the W phase, the semiconductor switch element 211 c as the upper arm of the V phase is fixed to be on, while the on and off of the semiconductor switch element 211 f as the lower arm of the W phase is PWM controlled.

[0081] At this time, the terminal voltage of the V phase becomes the power supply potential by turning on the semiconductor switch element 211c, and the terminal voltage of the W phase becomes the ground potential by turning on the semiconductor switch element 211f, thereby generating a potential difference between the energized phases and causing current to flow from the V phase to the W phase.

[0082] That is, during the on-period of the semiconductor switching element of the lower arm that is subjected to PWM control, the current of the energized phase flows through the shunt resistor 214 .

[0083] Therefore, the microcomputer 202a samples the current flowing through the shunt resistor 214 at the timing when the current of the energized phase flows through the shunt resistor 214, that is, during the on-period of the semiconductor switching element of the lower arm, and detects the current value of the energized phase.

[0084] In addition, it is possible to adopt upper arm chopper control in which the semiconductor switching element of the lower arm is fixed to be on, while on and off of the semiconductor switching element of the upper arm is PWM controlled.

[0085] Furthermore, the microcomputer 202 a can implement complementary PWM (in other words, upper and lower complementary switching) in 120-degree rectangular wave driving.

[0086] Complementary PWM refers to switching control in which a semiconductor switching element of a lower arm and a semiconductor switching element of an upper arm are turned on and off in phases opposite to each other.

[0087] Figure 4 An example of switching operation when a current is caused to flow from the U phase to the V phase without implementing complementary PWM is shown.

[0088] exist Figure 4 In the case of , the semiconductor switch element 211a as the upper arm of the U phase is kept on, and the semiconductor switch element 211b as the lower arm of the U phase is kept off.

[0089] The semiconductor switch element 211d as the lower arm of the V phase is PWM-controlled to be turned on and off with "command voltage / power supply voltage VB" as a duty ratio, and the semiconductor switch element 211c as the upper arm of the V phase is kept off.

[0090] exist Figure 4 In the case where complementary PWM is not performed as shown, the interphase voltage during non-energization corresponds to the induced voltage, so the average voltage is different from the command voltage, and the controllability of the current and the rotation speed of the three-phase brushless motor 12 is reduced.

[0091] on the other hand, Figure 5 An example of switching operation when a current is caused to flow from the U phase to the V phase in the case of implementing complementary PWM is shown.

[0092] exist Figure 5 In this case, the on and off of the semiconductor switch element 211a as the upper arm of the U phase is PWM controlled with a duty cycle of "50% + command voltage / power supply voltage VB / 2", and the semiconductor switch element 211b as the lower arm of the U phase is turned on and off with a phase opposite to that of the semiconductor switch element 211a as the upper arm.

[0093] In addition, the on and off of the semiconductor switching element 211c as the upper arm of the V phase is PWM controlled with a duty cycle of "50% - command voltage / power supply voltage VB / 2", and the semiconductor switching element 211d as the lower arm of the V phase is turned on and off with a phase opposite to that of the semiconductor switching element 211c as the upper arm.

[0094] exist Figure 5 When complementary PWM is implemented as shown, there is no non-energized period except for dead time, and the phase voltage is fixed to 0 V or power supply voltage VB. Therefore, the average voltage becomes the command voltage, and the controllability of the current and rotation speed of the three-phase brushless motor 12 is good.

[0095] Furthermore, when the duty ratio of the PWM control is small, the microcomputer 202 a can perform pulse shift control, which is a process of ensuring a current detection period by the shunt resistor 214 , by shifting the phase of the PWM pulse.

[0096] Figure 6 This is a switching operation when a current flows from the U phase to the V phase, and shows the phase voltage and shunt current when pulse shift control is not performed.

[0097] In this case, if the duty ratio is small, the time during which the shunt current flows becomes shorter than a predetermined minimum time (lower limit time) during which current detection is possible, and current detection cannot be performed.

[0098] In contrast, Figure 7This is a switching action when the current flows from the U phase to the V phase, and shows the phase voltage and shunt current when the pulse shift control is implemented.

[0099] The microcomputer 202a advances the phase of the PWM pulse that controls the U-phase voltage through pulse shift control, and on the other hand, delays the phase of the PWM pulse that controls the V-phase voltage, thereby making the period during which the U-phase-V phase voltage becomes +power supply voltage VB longer than the case where pulse shift control is not implemented. On the other hand, the period during which the U-phase-V phase voltage becomes -power supply voltage VB is generated by the amount that is longer than the period during which the U-phase-V phase voltage becomes +power supply voltage VB, and the average voltage remains unchanged.

[0100] Thus, even when the duty ratio is small, the time during which the shunt current flows can be maintained to be longer than the minimum time during which current detection can be performed by pulse shift control, thereby enabling current detection.

[0101] Next, we will explain in detail Figure 2 The microcomputer 202a shown has a control function of the three-phase brushless motor 12.

[0102] The microcomputer 202 a includes functional units such as a phase current detection unit 222 , a response control unit 223 , a current control unit 224 , a command voltage / duty ratio conversion unit 225 , an energized phase determination unit 226 , and a PWM signal generation unit 227 .

[0103] Phase current detection unit 222 converts the potential difference between both ends of shunt resistor 214 into a current value to obtain a detected current value DCV (in other words, a raw current value before processing) which is the current value flowing through the energized phase of three-phase brushless motor 12 .

[0104] That is, the shunt resistor 214 and the phase current detection unit 222 constitute a current sensor for detecting the current flowing through the energized phase of the three-phase brushless motor.

[0105] As described above, the phase current detection unit 222 samples the current value based on the potential difference between both ends of the shunt resistor 214 as the detection current value DCV during the on-control period of the PWM-controlled semiconductor switching elements among the semiconductor switching elements 211 a to 211 f constituting the inverter 211 .

[0106] The response control unit 223 is a functional unit that processes the detection current value DCV detected by the phase current detection unit 222 to obtain the actual phase current value used to control the inverter 211, namely, the control current value ACV (in other words, the identification current value of the microcomputer 202a), and implements a processing to delay the response of the control current value ACV to the detection current value DCV when the energized phase is switched.

[0107] The function of the response control unit 223 will be described in detail later.

[0108] The current control unit 224 obtains the control current value ACV (in other words, the actual phase current) output by the response control unit 223 and the command current value CCV (in other words, the target phase current) based on the control error of the rotation phase, and obtains the command voltage value CVV.

[0109] The command voltage / duty ratio conversion unit 225 converts the command voltage value CVV obtained from the current control unit 224 into a duty ratio in PWM control of the semiconductor switching elements 211 a to 211 f constituting the inverter 211 .

[0110] The energized phase determination unit 226 generates switching information of the energized phase (in other words, designation information of the energized phase) every 60 degrees of rotation by combining the sensor signals of the Hall sensors 12u, 12v, and 12w.

[0111] The PWM signal generating unit 227 obtains a duty cycle signal from the command voltage / duty cycle converting unit 225 , and obtains switching information of the energized phase from the energized phase determining unit 226 .

[0112] Then, the PWM signal generation unit 227 generates PWM signals for each of the semiconductor switching elements 211 a to 211 f constituting the inverter 211 based on the acquired duty ratio signal and the switching information of the energized phase.

[0113] The inverter drive circuit 213 obtains the PWM signal generated by the PWM signal generation unit 227 , and outputs a gate signal of each of the semiconductor switching elements 211 a to 211 f of the inverter 211 based on the obtained PWM signal.

[0114] The function of the response control unit 223 will be described in detail below.

[0115] Figure 8 This is a timing chart showing a state in which the detection current value DCV detected by the shunt resistor 214 temporarily drops along with the switching of the energized phase, and the motor current oscillates as a result of the control.

[0116] In the 120-degree rectangular wave drive, the energized phase of the three-phase brushless motor 12 is switched every 60 degrees of rotation. However, due to the switching of the energized phase, current begins to flow through the phase that has not been flowing before, so the phase current drops immediately after the energized phase is switched.

[0117] The microcomputer 202a increases the command voltage by sampling the phase current that decreases with the switching of the energized phase. Since the phase current increases by increasing the command voltage, the phase current vibrates immediately after the switching of the energized phase.

[0118] The vibration of the phase current may cause an overcurrent or a torque control failure, which may cause damage to the motor drive circuit or the mechanism of the VVT ​​mechanism 114 .

[0119] Therefore, when the energized phase is switched, the response control unit 223 implements a process of delaying the response of the control current value ACV with respect to the detected current value DCV (hereinafter referred to as response delay process). Thus, even if the detected current value DCV temporarily decreases accompanying the switching of the energized phase, the control current value ACV used for motor control is suppressed from decreasing in the same manner, thereby suppressing the vibration of the phase current.

[0120] Furthermore, by suppressing the vibration of the phase current through the response delay process, it is possible to suppress the occurrence of overcurrent and torque control failure, and to prevent damage to the motor drive circuit or the mechanism portion of the VVT ​​mechanism 114 before it occurs.

[0121] As the response delay processing, the response control unit 223 obtains the control current value ACV based on the detection current value DCV before the switching of the energized phase and the detection current value DCV after the switching.

[0122] Fig. 9 This is a timing chart for explaining the details of response delay processing.

[0123] The microcomputer 202 a (response control unit 223 ) updates and records the detection current value DCV in the built-in memory every time the detection current value DCV is sampled.

[0124] Furthermore, if the energized phase is switched, then as the first step in response delay processing, the microcomputer 202a reads out the detection current value DCV sampled immediately before the switch from the memory, and in the first interval from the switching of the energized phase to the elapse of the first time T1, the control current value ACV is maintained at the detection current value DCV immediately before the switch.

[0125] Furthermore, after the first time T1 has elapsed since the switching of the energized phase, as a second step of the response delay process, the microcomputer 202a gradually brings the control current value ACV close to the detection current value DCV over a second time T2.

[0126] Then, after making the control current value ACV coincide with the detection current value DCV, the microcomputer 202a continues to make the control current value ACV coincide with the detection current value DCV until the next switching of the energized phase is performed.

[0127] The microcomputer 202 a obtains the control current value ACV in the second time period T2 (second period) according to the following equation.

[0128]

[0129] Here, the microcomputer 202a gradually decreases the gain G in the above equation from 1 to 0 over the second time T2, thereby gradually approaching the control current value ACV from the detection current value DCV before switching over the second time T2 to the latest detection current value DCV.

[0130] The first time T1 is determined, for example, when the target value of the phase current is the maximum current, based on the time it takes for the phase current to recover to within the allowable current amplitude (for example, ±5 A) from the state where it has decreased due to the switching of the energized phase (hereinafter referred to as the recovery time), and is stored as a constant in a non-volatile memory.

[0131] That is, as one aspect of the first time T1 , even when the command value of the phase current is the maximum current, the first time T1 can be determined as the time when the detected current value DCV after the switching of the energized phase returns to [(detected current value DCV before switching)−5 A].

[0132] In addition, since the recovery time changes according to the magnitude of the phase current before switching, the microcomputer 202a can variably set the first time T1 based on the current value before switching instead of acquiring the first time T1 as a fixed value.

[0133] That is, the microcomputer 202a can determine the time until the detected current value DCV falls within the allowable current amplitude with respect to the control current value ACV based on the detected current value DCV before switching or the command current value CCV before switching, and variably set the first time T1 based on the determined time.

[0134] Here, the response of the motor current is a response of a primary delay system based on the motor phase resistance and inductance. The difference ΔDC between the detection current value DCV before switching and the detection current value DCV after switching is expressed by Equation 1.

[0135]

[0136] In Formula 1, τ is the time constant of the motor current, and t is the elapsed time from the switching of the power supply.

[0137] The microcomputer 202 a obtains the time t required until the difference ΔDC reaches the allowable current amplitude according to Expression 1, and sets the obtained time t as the first time T1 .

[0138] According to this configuration, it is possible to suppress the control current value ACV from being excessively maintained at the detection current value DCV immediately before switching, and to maintain the control responsiveness to the command current value CCV.

[0139] Furthermore, if the second time T2 is short, the current responsiveness is improved but the current ripple is increased, and conversely, if the second time T2 is long, the current ripple is reduced but the current responsiveness is deteriorated.

[0140] Therefore, the second time T2 is set so as to achieve both current responsiveness and current fluctuation suppression, and is stored in the nonvolatile memory as a constant.

[0141] In addition, the microcomputer 202a can change the gain G at a fixed speed during the second time period T2, and can also increase the speed of decrease of the gain G as time passes.

[0142] In the following, it will be described that the response delay process by the response control unit 223 can be applied to both the low-speed rotation and the high-speed rotation of the three-phase brushless motor 12 .

[0143] Fig.10 The state in which the response delay processing by the response control unit 223 is applied when the three-phase brushless motor 12 rotates at a low speed and the magnitude relationship among the energized phase switching period, the motor control period and the current drop period becomes energized phase switching period>>motor control period>current drop period is shown.

[0144] As for the motor control, it is required that the control current value ACV does not incorporate the phase current that decreases due to the switching of the energized phase.

[0145] Here, in the interval of the first time T1 from the switching of the energized phase, the control current value ACV is maintained at the detected current value DCV before the switching of the energized phase, and in the subsequent second time T2, the control current value ACV is close to the detected current value DCV, so that during low-speed rotation, the control current value ACV is suppressed from being incorporated into the phase current that decreases with the switching of the energized phase.

[0146] Furthermore, as a motor control, it is required to be able to control the motor current value to the command current value CCV except for the falling period of the phase current accompanying the switching of the energized phase.

[0147] Here, after the decrease of the phase current accompanying the switching of the energized phase converges, the control current value ACV is consistent with the detection current value DCV, and the motor control based on the detection current value DCV is essentially implemented. Therefore, during low-speed rotation, the motor current value can be controlled to the command current value CCV outside the period of decrease of the phase current.

[0148] That is, when the three-phase brushless motor 12 is rotating at a low speed, the response delay processing based on the response control unit 223 is applied, thereby suppressing the phase current decrease accompanying the switching of the energized phase from being reflected in the control and controlling the motor current value to the command current value CCV.

[0149] Fig.11 The following state is shown, that is, the relationship between the power-on phase switching period and the control period is that the power-on phase switching period is less than the motor control period, and when the three-phase brushless motor 12 rotates at a high speed with the power-on phase switching period being less than the first time T1, the response delay processing based on the response control unit 223 is applied.

[0150] In the control of a motor at high speed, it is required to realize current limiting that can suppress the actual phase current > the command current value CCV.

[0151] Here, the microcomputer 202a uses the phase current before switching the energized phase which becomes the peak current in the energization control, and does not use the phase current that decreases with the switching of the energized phase in the energization control, thereby achieving current limiting that suppresses the actual phase current>command current value CCV.

[0152] Furthermore, the motor control is required to be able to follow changes in the command current value CCV.

[0153] Here, the microcomputer 202a performs motor control using the phase current before switching of the energized phase, which is the latest value among the reliable current values, and thus can make the motor current value follow the command current value CCV.

[0154] Fig.12 2 is a timing chart showing the effect of the response delay process performed by the response control unit 223 .

[0155] Fig.12 Before time t1, the rotation direction of the three-phase brushless motor 12 and the direction of the applied voltage to the three-phase brushless motor 12 are the same as the power running mode, and the response control unit 223 performs the response delay process to obtain the control current value ACV.

[0156] In the power running mode, a current drop occurs due to switching of the energized phase, and the AD conversion value of the detection signal of the current sensor, that is, the detection current value DCV, fluctuates according to the current drop due to switching of the energized phase.

[0157] In contrast, the control current value ACV used for motor control is calculated based on the detected current value DCV, but is processed in a manner that does not pick up the current drop associated with the switching of the energized phase. Therefore, by controlling the motor based on the control current value ACV, the vibration of the motor current can be suppressed within an allowable range.

[0158] on the other hand, Fig.12After time t1, the three-phase brushless motor 12 is in a regeneration mode in which the rotation direction and the direction of the applied voltage to the three-phase brushless motor 12 are opposite to each other, and no current drop occurs due to switching of the energized phase.

[0159] Therefore, in the regeneration mode, the microcomputer 202a stops the response delay processing by the response control unit 223 and sets the control current value ACV to the detection current value DCV (ie, the current raw value detected by the current sensor) including immediately after switching the energized phase.

[0160] Fig.13 It shows the current of each phase when switching from a mode in which the current flows from the U phase to the W phase to a mode in which the current flows from the V phase to the W phase in a power operation mode in which the motor current is a positive current, the voltage of each phase just after the switching and the current flowing through the shunt resistor 214, and the current path just after the switching.

[0161] In the power running mode, if the mode in which the current flows from the U phase to the W phase is switched to the mode in which the current flows from the V phase to the W phase, while the return current flows through the body diode (in other words, the parasitic diode) of the semiconductor switch element 211b of the lower arm of the U phase, the terminal voltage of the U phase is maintained at the ground potential (Low) due to the back electromotive force.

[0162] Therefore, in the current sampling interval during which a potential difference occurs between the V-phase and the W-phase as energized phases, only the current Iv of the V-phase immediately after energization starts flows through the shunt resistor 214, causing a current drop.

[0163] on the other hand, Fig.14 The diagram shows the current of each phase when switching from a mode in which the current flows from the U phase to the W phase to a mode in which the current flows from the V phase to the W phase in a regeneration mode in which the motor current becomes a negative current, the voltage of each phase just after the switching, the current flowing through the shunt resistor 214, and the current path just after the switching.

[0164] In the regeneration mode, if the switching is implemented from the power-on mode in which the current flows from the U phase to the W phase to the power-on mode in which the current flows from the V phase to the W phase, while the return current flows through the body diode (parasitic diode) of the semiconductor switch element 211a of the upper arm of the U phase, the terminal voltage of the U phase is maintained at the power supply potential (High) due to the back electromotive force.

[0165] Therefore, during the period when a potential difference occurs between the V phase and the W phase as energized phases, that is, in the current sampling interval, the current Iw of the W phase that has been energized since before the switching of the energized phase flows through the shunt resistor 214, and no current drop occurs.

[0166] Thus, in the power running mode and regeneration mode, the open circuit phase ( Fig.13 , Fig.14 The path through which the return current of the U phase in the power operation mode flows changes, so a difference occurs in the current flowing through the shunt resistor 214. In the power operation mode, the current decreases as the energized phase is switched. In contrast, in the regeneration mode, the current does not decrease as the energized phase is switched.

[0167] Therefore, the microcomputer 202a implements the response delay processing by the response control unit 223 in the power running mode and stops the response delay processing by the response control unit 223 in the regeneration mode, thereby suppressing the reduction of current responsiveness in the regeneration mode and reducing the calculation load for the response delay processing.

[0168] The technical concepts described in the above embodiments can be used in combination as appropriate unless there is any contradiction.

[0169] Furthermore, although the contents of the present invention have been specifically described with reference to preferred embodiments, it is obvious that those skilled in the art can adopt various modified forms based on the basic technical concept and teaching of the present invention.

[0170] For example, the three-phase brushless motor 12 of the above-mentioned embodiment has Hall sensors 12u, 12v, and 12w as rotation position sensors for detecting the position of the motor, but the motor control device and motor control method involved in the present application can also be applied to a sensorless three-phase brushless motor that does not have a rotation position sensor such as a Hall sensor.

[0171] In sensorless 120-degree energization, for example, the motor rotation position is detected by detecting the zero-crossing point of the induced voltage appearing in the non-energized phase.

[0172] In addition, in the above-mentioned embodiment, the microcomputer 202a maintains the control current value ACV at the detection current value DCV before the switching of the energized phase until the first time T1 has passed since the switching of the energized phase, but is able to set the first time T1 at which the detection current value DCV before the switching of the energized phase is maintained to zero, and from the beginning of the switching of the energized phase, it takes a prescribed time for the control current value ACV to gradually approach the detection current value DCV from the detection current value DCV before the switching.

[0173] Furthermore, the microcomputer 202a can perform low-pass filtering on the detection current value DCV to obtain the control current value ACV.

[0174] That is, the response control unit 223 only needs to be able to suppress the control current value ACV from changing in response to the drop in the detection current value DCV when the energized phase is switched.

[0175] The three-phase brushless motor is not limited to the motor for VVT mechanism 114 , and is not limited to the motor that operates in the power running mode and the regeneration mode.

[0176] Description of Reference Numerals

[0177] 12…three-phase brushless motor, 114…VVT mechanism, 202…VVT controller (motor control device), 202a…microcomputer (control unit), 211…inverter, 213…inverter drive circuit, 214…shunt resistor (current sensor), 222…phase current detection unit, 223…response control unit, 224…current control unit, 225…command voltage / duty ratio conversion unit, 226…energized phase determination unit, 227…PWM signal generation unit.

Claims

1. A motor control device, characterized in that: The control unit of the motor control device is configured to obtain a detection signal from a current sensor for detecting a current flowing through an energized phase of the three-phase brushless motor, and drive the three-phase brushless motor with a 120-degree rectangular wave according to a control current value based on the detection signal. Furthermore, the control unit obtains the control current value based on a current value detected by the current sensor before switching of the energized phase in the 120-degree rectangular wave drive and a current value detected by the current sensor after the switching.

2. The motor control device according to claim 1, wherein: The control unit maintains the control current value at the current value detected by the current sensor before the switching of the energized phase until a first time has passed since the switching of the energized phase, and gradually brings the control current value closer to the current value detected by the current sensor over a second time after the first time has passed.

3. The motor control device according to claim 2, wherein: The control unit changes the first time according to a motor current value or a command current value.

4. The motor control device according to claim 1, wherein: When the rotation direction of the three-phase brushless motor is opposite to the direction of the applied voltage of the three-phase brushless motor, the control unit sets the control current value to the current value detected by the current sensor.

5. The motor control device according to claim 1, wherein: The current sensor is configured to include a shunt resistor disposed on a DC bus of an inverter that supplies AC power to the three-phase brushless motor.

6. The motor control device according to claim 5, wherein: The control unit is configured to perform PWM control on an inverter that supplies AC power to the three-phase brushless motor to drive the three-phase brushless motor with a 120-degree rectangular wave. By performing pulse shift control for shifting the phase of the PWM pulse, the time during which the current flows through the shunt resistor is set to be equal to or longer than the minimum time during which the current can be detected.

7. A motor control device, characterized in that: The control unit of the motor control device is configured to obtain a detection signal from a current sensor for detecting a current flowing through an energized phase of the three-phase brushless motor, and drive the three-phase brushless motor with a 120-degree rectangular wave according to a control current value based on the detection signal. Furthermore, when switching of the energized phase in the 120-degree rectangular wave driving is performed, the control unit delays a response of the control current value to the current value detected by the current sensor.

8. A motor control method, which is executed by a control unit and drives a three-phase brushless motor with a 120-degree rectangular wave, comprising: A step of obtaining a detection signal of a current sensor for detecting a current flowing through an energized phase of the three-phase brushless motor; A step of obtaining a control current value based on the detection signal; and The step of outputting a control signal to a drive circuit of the three-phase brushless motor based on the control current value, In the step of obtaining the control current value, The control current value is obtained based on a current value detected by the current sensor before switching of the energized phase in the 120-degree rectangular wave drive and a current value detected by the current sensor after the switching.

9. The motor control method according to claim 8, wherein: The step of obtaining the control current value includes: The step of maintaining the control current value at the current value detected by the current sensor before the switching of the energized phase until a first time has passed since the switching of the energized phase; and After the first time has elapsed, taking a second time, the control current value is gradually brought close to the current value detected by the current sensor.

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