JP2005086947A - Control unit of electric motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control unit of an electric motor that can easily be restarted from an idling state, even if a position detection circuit that is limited in detection range is used. <P>SOLUTION: It is determined from the state of an engine whether a position detection condition of a rotor is satisfied (step S5), and when it is determined that the condition is satisfied, the position prediction of the rotor, based on a counter electromotive force, is conducted (step S7, 8). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a motor control device, and more particularly to a synchronous motor that performs control to drive from the idling state in a synchronous motor in which a rotor of an electric motor is idled by an external force, for example, an electric motor that applies assist force by a synchronous motor. It relates to the control of a turbocharger motor.

  A synchronous motor that rotates in synchronization with the frequency of an alternating current to be applied is known. In such a synchronous motor, the rotation speed of the motor is controlled by changing the frequency of the alternating current by an inverter. The timing of switching the current phase in the inverter needs to be performed in synchronization with the position of the rotor. When a sensor for detecting the position of the rotor is provided, the motor can be started by controlling the phase switching timing of the inverter based on the sensor output. However, if a rotor position detection sensor is installed, the mechanism becomes complicated and the product cost increases, so sensorless motors without sensors are widely used, and this type of sensorless synchronous motor is started from the idling state. The technique described in Patent Document 1 is known as a method of causing this.

In this technology, when the rotor idles, one of the semiconductor switching elements of the inverter is turned on to short-circuit the motor winding, and the rotor position is estimated based on the winding current flowing at that time. Is to start.
Japanese Patent Laid-Open No. 11-75394 (paragraphs 0023 to 0043, FIG. 3)

  However, when the position of the rotor is estimated based on the winding current and voltage, the rotational speed range in which position detection is possible may be limited by the specifications of the position detection circuit. The lower limit of the rotation speed is caused by the fact that the generated winding current is small, and the upper limit is that it is difficult to determine the frequency due to disturbance of the waveform of the winding current. If an attempt is made to expand the rotation speed range where position detection is possible, the cost of the detection circuit will increase, and the advantage of using a sensorless motor will be reduced.

  Accordingly, an object of the present invention is to provide an electric motor control device capable of easily restarting from an idling state even when a position detection circuit having a limited detection range is used.

  In order to solve the above problems, an electric motor control device according to the present invention is an electric motor control device that can drive a rotor of a synchronous motor by an external force, and obtains a counter electromotive force of a coil of the electric motor. Rotation for driving the rotor by controlling the operation of the obtaining means, the rotor position estimating means for estimating the rotor position based on the counter electromotive force, and the inverter for applying electric power to the electric motor based on the rotor position When the driving state of the rotor is estimated from the state of the external driving force and the external driving force for driving the rotor, and the driving state is estimated to be within a predetermined range, the rotor position is estimated by the rotor position estimating means. Estimation start means.

  The motor control device according to the present invention uses a sensorless motor, and when the rotor of the motor is idled by an external force, the estimation start means estimates the idling state from the state of the external force, and the idling state Is estimated to be within a predetermined range, specifically, within a range in which position estimation with a predetermined accuracy can be performed by the rotor position estimation means, the rotor position estimation is executed.

  For example, the rotor of the electric motor is a rotating shaft of a turbocharger disposed in the internal combustion engine, and the external force is exhaust energy.

  The state of the external force used for estimating the driving state of the rotor may be estimated based on the rotational speed of the internal combustion engine and the fuel injection amount. Alternatively, the state of the external force used for estimating the rotor driving state may be estimated based on the supercharging pressure by the turbocharger and the intake air amount.

  As described above, when the idling state of the rotor is estimated from the state of the external force and it is determined that the position estimation by the rotor position estimating means can be executed with a predetermined accuracy, the position estimation is executed, thereby the rotor It is possible to accurately perform the position estimation. As a result, the electric motor can be reliably restarted from the subsequent idling state.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same reference numerals are given to the same components in the drawings as much as possible, and duplicate descriptions are omitted.
FIG. 1 is a schematic configuration diagram of an internal combustion engine including an electric motor control device according to the present invention. Here, a case where an assist motor of a turbocharger is used as the motor will be described as an example. Further, here, a cylinder injection type gasoline engine will be described as an example, but the present invention can be similarly applied to a gasoline engine in which fuel is injected into an intake pipe and a diesel engine.

  The engine 1 is a multi-cylinder engine, but here, a cross section of only one cylinder is shown. The engine 1 is a type of engine in which fuel is injected onto the upper surface of a piston 4 in a cylinder 3 by an injector 2. The engine 1 is a so-called lean burn engine that enables stratified combustion. That is, the engine 1 compresses the air that has passed through the intake passage 5 and is sucked into the cylinder 3 with the piston 4, and injects the fuel from the injector 2 into the inside of the recess formed in the upper surface of the piston 4. The rich air-fuel mixture is collected in the vicinity of the spark plug 7 and ignited by the spark plug 7 to be burned. This enables combustion with a small amount of fuel relative to the air in the entire combustion chamber. Further, by performing lean combustion while supercharging more intake air with a turbocharger described later, fuel consumption is suppressed, and not only high output but also low fuel consumption is realized.

  An intake passage 5 and an exhaust passage 6 are connected to the cylinder 3, and opening and closing thereof are controlled by an intake valve 8 and an exhaust valve 9 provided therebetween. An air cleaner 10, a compressor side impeller 11 c of the turbo unit 11, an intercooler 12, a throttle valve 13, and an intake pressure sensor 19 are arranged on the intake passage 5 from the upstream side. On the other hand, on the exhaust passage 6, the turbine side impeller 11 d of the turbo unit 11 and the exhaust purification catalyst 23 are arranged from the upstream side. That is, the turbo unit 11 is arranged so as to straddle the intake passage 5 and the exhaust passage 6.

  The air cleaner 10 is a filter that removes dust and dirt in the intake air. The turbo unit 11 is a compressor-side impeller 11c (which functions as a compressor for compressing intake air; hereinafter simply referred to as a compressor) that is a rotor blade disposed on the intake passage 5 side, and a rotation disposed on the exhaust passage 6 side. A turbine-side impeller 11d (which functions as a turbine that is driven to rotate by exhaust energy. Hereinafter, simply referred to as a turbine) is connected by a common rotating shaft 11a. Further, a rotor (permanent magnet) is fixed to the rotating shaft 11a, and a stator (a coil wound around an iron core) is disposed around the rotating shaft 11a, thereby constituting an electric motor 11b having the rotating shaft as an output shaft. The electric motor 11b is a synchronous AC motor that is electrically connected to the inverter 21, and also functions as a generator having the rotating shaft 11a as an input shaft. The stator has three coils of U phase, V phase, and W phase corresponding to three-phase alternating current. The inverter 21 is electrically connected to the battery 22.

FIG. 2 is a block diagram for explaining details around the inverter 21. The inverter 21 includes switching element pairs SW ₁₁ and SW ₁₂ corresponding to the U-phase coil of the electric motor 11b, and freewheeling diode pairs BD ₁₁ and BD ₁₂ . Furthermore, the switching element pair SW ₂₁ and SW ₂₂ corresponding to the V-phase coil, the free wheel diode pair BD ₂₁ and BD ₂₂ , and the switching element pair SW ₃₁ and SW ₃₂ corresponding to the W-phase coil and the free wheel diode pair BD _31. , BD ₃₂ is provided.

  The power supply voltage of the battery 22 is applied to both ends of each switching element pair SW and the free wheel diode pair BD. The magnetic field generated by the U-phase coil, V-phase coil, and W-phase coil of the electric motor 11b is controlled by switching on / off each switching element pair SW, and the rotating shaft 11a of the electric motor 11b is rotated at a desired speed. (This is the rotor driving means according to the present invention).

  The motor control circuit 16a has a function of detecting voltages generated at both ends of the U-phase coil, V-phase coil, and W-phase coil of the electric motor 11b (hereinafter referred to as U voltage, V voltage, and W voltage, respectively). (It is a back electromotive force acquisition means according to the present invention). Based on these voltages, the angular position of the rotor in the electric motor 11b (hereinafter simply referred to as the rotor position) is estimated (rotor position estimating means according to the present invention), and based on the estimated position. Thus, a gate signal for controlling on / off of each switching element SW of the inverter 21 is generated to control a three-phase AC signal applied to the electric motor 11b.

  A turbo controller 16b is connected to the motor control circuit 16a. A VOC signal synchronized with the rotation of the electric motor 11b is sent from the motor control circuit 16a to the turbo controller 16b. The turbo controller 16b sends the motor control circuit 16a to the motor control circuit 16a. The start signal is output. Furthermore, the collector side of the npn-type inverter disconnect transistor 16c is connected to the six signal lines that send the gate signal from the motor control circuit 16a to the inverter 21, and the base of the transistor 16c is connected to the turbo controller 16b, and the emitter Is grounded. By switching all the gate signals to the ground potential by the inverter disconnection transistor 16c, it is possible to turn off all the switches in the inverter 21 at the same time and fix the inverter 21 in an inoperative state.

  The motor control circuit 16a and the turbo controller 16b are built in, for example, the engine ECU 16. In this case, it may be separated from other control units by hardware, but may be divided by software by sharing a CPU. Of course, the engine ECU 16 may be provided independently.

  An air-cooled intercooler 12 is disposed on the intake passage 5 downstream of the compressor 11c. This intercooler 12 cools the intake air whose temperature has increased due to air compression (pressure increase) during supercharging by the compressor 11c of the turbo unit 11, thereby reducing its volume and improving the efficiency of filling the cylinder 3 It is something to be made.

  A throttle valve 13 that adjusts the intake air amount is disposed downstream of the intercooler 12. The throttle valve 13 is a so-called electronically controlled throttle valve and is driven by a throttle motor 17. A throttle positioning sensor 18 for detecting the opening degree is arranged.

  The crankshaft is provided with a crank angle sensor 26 and the accelerator pedal 14 is provided with an accelerator opening sensor 15, and the signal is input to an engine ECU 16 for engine control. In addition, the engine ECU 16 receives signals from the throttle positioning sensor 18, the intake pressure sensor 19, and the battery 22 (voltage), and controls the operation of the injector 2, spark plug 7, throttle motor 17, and inverter 21. The engine ECU 16 is a control device for an internal combustion engine according to the present invention.

  The turbo unit 11 according to the present embodiment can be operated as a normal turbocharger that performs supercharging only by exhaust energy. However, the compressor 11c and the turbine 11d are forcibly driven by the electric motor 11b to increase the supercharging efficiency. It is also possible to raise. In particular, when the driver depresses the accelerator pedal 14, by performing this forced driving, the time lag of the operation of the turbocharger can be reduced, the engine speed can be increased early, and the response is improved. . Further, the turbine 11d is driven by exhaust gas, and the rotating shaft 11a, which is the input shaft of the electric motor 11b, is rotated to generate regenerative power. The generated electric power is stored in the battery 22 and a part of the exhaust energy is recovered. You can also.

  By the way, in order to start the forced drive of the rotating shaft 11a by the electric motor 11b when the rotating shaft 11a is idling, the rotating shaft 11a (more precisely, the rotor of the electric motor 11b attached to the rotating shaft 11a). It is necessary to switch on and off the switching element SW in the inverter 21 in synchronization with the rotation of. For this purpose, it is necessary to accurately detect the rotor position. However, since the electric motor 11b of this embodiment is a sensorless motor that does not have a rotor position detecting means, the rotor position can be known directly. I can't. Therefore, it is necessary to determine the rotor position when starting up.

  FIG. 3 is a flowchart of a control routine of the electric motor 11b including this determination process. This control routine is repeatedly executed by the motor control circuit 16a while the power switch of the vehicle is turned on and the engine 1 is started.

  In step S1, it is determined whether or not it is necessary to detect the position of the rotor. The case where the rotor position needs to be detected is a case where the electric motor 11b is in an inoperative state and is idling due to exhaust energy, and a case where the forced driving condition of the turbo unit 11 by the electric motor 11b is satisfied.

  If the condition is not satisfied, it is determined that it is not necessary to detect the position of the rotor, the rotor position detection flag FlagSR is reset to 0 (step S2), and the process ends. If the condition is satisfied, the value of the rotor position detection flag FlagSR is checked to determine whether or not the rotor position has already been successfully detected (step S3). When the value of FlagSR is 1, it is detected that the subsequent processing is skipped and the processing is terminated.

  If the position detection of the rotor is required but the position detection has not been completed, the process proceeds to step S5 to determine whether or not the current state of the engine 1 satisfies the rotor position detection condition. In order to accurately measure the rotor position by the motor control circuit 16a, the number of rotations of the idling rotor (rotating shaft 11a) needs to be within a predetermined range. This is because, on the low rotation side, the voltage generated in the stator coil during idling is small and it is difficult to measure accurately, and on the high rotation side, the voltage waveform is disturbed and the frequency becomes high, which is also accurate. This is because it is difficult to measure well. Normally, the used rotation speed region of the turbo unit 11 is 6000 to 200,000 rotations / minute, and in order to always detect the rotor position, detection in the entire used rotation speed region is necessary. However, since the initial rotational speed when forcedly driven by the electric motor 11b is 6000 to 100,000 revolutions / minute, for example, the motor control circuit 16a can accurately position the rotor (for example, within ± 0.2 degrees). ) By detecting the rotor position and executing the electric drive in a range where the rotation speed of the rotating shaft 11a is 10,000 to 100,000 rotations / minute, the electric drive can be performed in the entire use rotation speed range.

  In the present embodiment, since the rotational speed of the rotating shaft 11a cannot be directly detected, the turbo unit 11 is idled in this rotational speed range from the state of exhaust energy that drives the turbo unit 11, that is, the driving state of the engine 1. It is determined whether or not. Specifically, it is determined that the condition is satisfied when the engine speed and the fuel injection amount, or the supercharging pressure and the air flow rate are within a predetermined range. Whether or not this determination condition is satisfied is transmitted from the engine ECU 16 to the motor control circuit 16a and determined in the motor control circuit 16a, and whether or not the condition is satisfied is determined in the engine ECU 16. Then, the determination result may be transmitted to the motor control circuit 16a. In the former case, the estimation start means according to the present invention is the motor control circuit 16a. In the latter case, the engine ECU 16 and the motor control circuit 16a cooperate to constitute the estimation start means according to the present invention. To do.

  If the position detection condition is not satisfied, the subsequent process is skipped and the process is terminated. When the position detection condition is satisfied, the process proceeds to actual position detection processing. First, in order to turn off each switching element SW while fixing the gate signal to the ground potential, the inverter disconnecting transistor 16c is turned on (step S7). Next, the motor control circuit 16a estimates the rotor position based on the back electromotive force generated in each phase coil (step S9). In estimating the rotor position, in order to suppress the influence of fluctuations in the rotational speed of the rotor, detection is performed a plurality of times within a predetermined time while fluctuations in the operating conditions of the engine 1 are within a predetermined range. It is preferable to confirm that it is within a predetermined range expected from fluctuations in the operating conditions of the engine 1. Next, it is determined whether or not the rotor position estimation is successful (step S11). If the rotor position is successfully estimated, the rotor position detection flag FlagSR is set to 1 (step S13), and the process is terminated. If it fails, the process ends.

  The forced drive of the turbo unit 11 is based on the start signal from the turbo controller 16b, and the gate signal is controlled based on the rotor position estimated by the motor control circuit 16a to switch the switching elements SW on and off. Is performed by synchronously rotating at a predetermined rotational speed. Thereby, the starting of the electric motor 11b from the idling state can be performed smoothly.

  Thus, in the detection circuit that estimates the position of the rotor, even if the rotational speed range in which position estimation is possible is limited, the condition of the external force that drives the rotor, here, the state of exhaust energy Yes, this is also the operating condition of the engine 1, so that it is possible to estimate the position of the rotor with high accuracy by estimating that the position is within the speed range where position estimation is possible and detecting the actual speed. The start-up control from the idling time of the turbocharger with an electric motor using a sensorless motor becomes simple and reliable.

  In addition, this invention is not limited to embodiment mentioned above. For example, in the above-described embodiment, the output shaft of the electric motor 11b coincides with the rotation shaft of the compressor 11c / turbine 11d. However, the present invention can also be applied to a turbocharger with an electric motor in which the output shaft of the electric motor does not coincide with the rotation axis of the compressor / turbine (for example, when a reduction mechanism using a gear or the like is used).

  Furthermore, in addition to a turbocharger with an electric motor, the present invention can also be applied to an electric motor that is idling with an external force, such as a hybrid vehicle having an electric motor directly connected to a drive shaft.

1 is a schematic configuration diagram of an internal combustion engine including a motor control device according to the present invention. It is a block diagram explaining the detail around the inverter of the apparatus of FIG. It is a flowchart of the control routine of the electric motor of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Injector, 3 ... Cylinder, 4 ... Piston, 5 ... Intake passage, 6 ... Exhaust passage, 7 ... Spark plug, 8 ... Intake valve, 9 ... Exhaust valve, 10 ... Air cleaner, 11 ... Turbo unit, DESCRIPTION OF SYMBOLS 11a ... Rotary shaft, 11b ... Electric motor, 11c ... Compressor side impeller, 11c ... Compressor, 11d ... Turbine side impeller, 11d ... Turbine, 12 ... Intercooler, 13 ... Throttle valve, 14 ... Accelerator pedal, 15 ... Accelerator opening sensor, DESCRIPTION OF SYMBOLS 16 ... Engine ECU, 16a ... Motor control circuit, 16b ... Turbo controller, 16c ... Inverter cutting transistor, 17 ... Throttle motor, 18 ... Throttle positioning sensor, 19 ... Intake pressure sensor, 26 ... Crank angle sensor, 21 ... Inverter, 22 …Battery 23 ... exhaust gas purifying catalyst, BD ... reflux diode pair, SW ... switching element.

Claims (4)

A control device for an electric motor capable of driving a rotor of a synchronous electric motor with an external force,
Back electromotive force acquisition means for acquiring back electromotive force of the coil of the motor;
Rotor position estimating means for estimating the rotor position based on the back electromotive force;
Rotor driving means for controlling the operation of an inverter for applying electric power to the electric motor based on the rotor position to drive the rotor;
Estimation start means for estimating the rotor position from the state of external force driving the rotor and estimating the rotor position by the rotor position estimating means when the driving state is estimated to be within a predetermined range; ,
An electric motor control device comprising:   The motor control device according to claim 1, wherein the rotor of the electric motor is a rotating shaft of a turbocharger disposed in an internal combustion engine, and the external force is exhaust energy.   3. The motor control device according to claim 2, wherein the state of the external force used for estimating the driving state of the rotor is estimated based on the rotational speed of the internal combustion engine and a fuel injection amount.   3. The motor control device according to claim 2, wherein the state of the external force used for estimating the driving state of the rotor is estimated based on a supercharging pressure by the turbocharger and an intake air amount.

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