JP6225457B2 - Compressor drive control device and air conditioner - Google Patents

Description

  The present invention relates to a compressor drive control device provided in an air conditioner and the like, and an air conditioner including the drive control device, and more particularly, a rectangular-wave energization type sensorless DC brushless motor (hereinafter referred to as a brushless DC motor). The present invention relates to a drive control device for a compressor to be driven and an air conditioner.

  Conventionally, in a refrigeration system used for an air conditioner or the like, a rotary compressor is widely used, and a compressor in which a refrigerant in a cylinder is compressed by changing a rotary motion of a brushless DC motor to a rotary motion of a roller is known. Hereinafter, a conventional compressor drive control apparatus will be described with reference to the drawings.

  FIG. 1 is a configuration diagram of a drive control device that drives a compressor with a rectangular wave energization method (120-degree energization method) three-phase four-pole brushless DC motor, and FIG. 2 is a detailed diagram of a position detection circuit.

  As shown in FIG. 1, the compressor drive control device includes an AC / DC conversion circuit 12 (rectifier circuit) that converts an AC power supply of a commercial power supply E into a DC power supply, an inverter 14, a position detection circuit 16, and a microcomputer. 18, and drives and controls the compressor 20 including the brushless DC motor M.

  In the inverter 14, semiconductor switching elements (transistors) 14 a to 14 f are three-phase (U-phase, V-phase, W-phase) bridge connection, and diodes 14 g to 14 l are connected in parallel to the respective transistors. The brushless DC motor M has a stator that is a stator and a rotor that is a rotor, and is driven by the output of the inverter 14, and the compressor 20 is driven by the brushless DC motor M.

  The position detection circuit 16 detects the rotational position of the rotor (not shown) from the induced voltage of the brushless DC motor M, and includes resistors 16b to 16g and a comparator 16a as shown in FIG. One ends of the resistors 16b to 16d are connected to the respective phases of the stator of the motor M, and the other ends of the resistors 16b to 16d are connected to each other. A resistor 16g is connected between a connection point of the resistors 16b to 16d and the ground, and a connection point of the resistors 16b to 16d and the resistor 16g is connected to a non-inverting input terminal of the comparator 16a. Hereinafter, the voltage at the connection point of the resistors 16b to 16d and the resistor 16g is referred to as a virtual neutral point voltage. Further, a resistor 16e and a resistor 16f are connected in series between the positive side Vdc of the AC / DC conversion circuit 12 and the ground, and the voltage at the connection point of the resistor 16e and the resistor 16f is used as a reference voltage, and an inverting input terminal of the comparator 16a. To be supplied. This reference voltage is set to be 1/2 of the applied voltage Vdc. The comparator 16a compares the virtual neutral point voltage with the reference voltage, thereby detecting the zero cross point of the virtual neutral point voltage (that is, the zero cross point of the induced voltage), and detecting the position of the rotor of the motor M (hereinafter referred to as “the rotor position of the motor M”). A position detection signal for simply “position detection” is output.

  As shown in FIG. 1, the microcomputer 18 generates an inverter drive signal based on the position detection signal from the position detection circuit 16 and outputs the inverter drive signal to the inverter 14. The U-phase upper arm, V-phase upper arm, W-phase upper arm, U-phase lower arm, V-phase lower arm, and W-phase lower arm of inverter 14 are driven based on this inverter drive signal.

  FIG. 3 is a timing chart of the compressor drive control by the microcomputer. From the top, the waveform of the induced voltage of the motor M at the virtual neutral point of the position detection circuit, the position detection timing, the energized phase switching processing timing, the upper and lower of the inverter The waveforms of the drive signals of the arm switching processing timing, U-phase upper arm, V-phase upper arm, W-phase upper arm, U-phase lower arm, V-phase lower arm, and W-phase lower arm are shown.

  The voltage value of the waveform of the induced voltage of the motor M at the virtual neutral point of the position detection circuit shown in FIG. 3 is a value obtained by dividing the sum of the voltages of each phase by 3. Accordingly, one of the three phases is Vdc, one phase is zero volts, and the remaining one phase generates an induced voltage. The voltage range is from zero to Vdc, so the maximum voltage is 2 Vdc / 3 and the minimum voltage is Vdc / 3 Further, the reflux section refers to a section in which a reflux current flows through the diode (14g to 14l in FIG. 1) due to the back electromotive force generated when the energized phase is switched. In the compressor drive control apparatus configured as described above, the energized phase of the brushless DC motor M is switched at the zero cross timing of the induced voltage (the timing of crossing the voltage Vdc / 2). Here, when detecting the zero cross timing of the rising induced voltage, the lower arm is used. When detecting the zero cross timing of the falling induced voltage, the upper arm is used to detect the zero cross timing of the falling induced voltage. In addition, since the output signal of the position detection circuit 16 is inverted by chopping, the correct zero cross timing cannot be detected. Therefore, the upper arm of the phase to be chopped (phases 14a, 14c, and 14e in FIG. 1 are switched) and the lower arm (of FIG. By switching the 14b, 14d, and 14f phases), it is possible to detect the zero-cross timing of the rising and falling induced voltages. Here, the time Tam from the zero cross timing of the induced voltage to the arm switching can be determined in advance by actual machine verification or the like.

  By the way, the operation of one rotation of the compressor is divided into a refrigerant gas suction process and a compression process. FIG. 4 shows an example of load characteristics per one rotation of the compressor. The horizontal axis is the rotation angle (mechanical angle). The section shown in FIG. 4 is one section from the position detection timing to the next position detection. In the case of a three-phase motor having four poles for driving the compressor, there are 12 sections per rotation. The energized phase is switched 12 times. As shown in FIG. 4, the compressor suction process includes a period in which the load torque is zero and a period in which the load torque is hardly generated in the section (in the example of FIG. 4, a section having a rotation angle of 0 to 30 °. , Also referred to as a zero load torque section). In this section, the motor can maintain its rotation due to inertia, but when the drive voltage is applied, the rotation speed of the motor is accelerated. Further, also from the viewpoint of improving the operation efficiency and suppressing the power consumption, the PWM (pulse width modulation) duty of the inverter is set to 0 (zero) so that the drive power is not supplied to the inverter 14 in a section where the motor drive power is not required. It is desirable to make it.

  However, as in the position detection circuit 16 of FIG. 2, the zero-cross timing of the induced voltage is output as a position detection signal by comparing the virtual neutral point voltage with a reference voltage obtained by dividing the applied voltage Vdc by half. In the case of the system, as shown in FIG. 5 (extracted from the section including the zero load torque section of the compressor), if the PWM duty is set to 0 in the section where the load torque hardly occurs, the subsequent position detection cannot be performed. There is a problem of end.

  More specifically, since chopping is not performed when the PWM duty is set to 0, the virtual neutral point voltage is fixed to 2 Vdc / 3, which is higher than the reference voltage when the upper arm is ON, When the arm is ON, it is fixed at Vdc / 3, which is a voltage lower than the reference voltage. Therefore, since it becomes impossible to detect the zero cross of the induced voltage from the virtual neutral point voltage, the position detection is not performed from the next time. As a result, the energized phase switching process and the upper / lower arm switching process performed in synchronization with the position detection are not performed, and the compressor drive control cannot be performed normally.

  For example, Patent Documents 1 to 3 are known as conventional techniques that deal with such problems. Patent Documents 1 and 2 estimate position detection timing from a section where the PWM duty is not zero. In Patent Document 3, the position detection circuit includes three comparators, and the position can be detected even when the PWM duty is zero.

JP-A-8-31538 JP 2012-65412 A International Publication No. 2004/042912

  However, in the techniques of Patent Documents 1 and 2 described above, if the actual timing deviates significantly because the position detection timing is not estimated, in the worst case, there is a possibility of stepping out. Further, the technique disclosed in Patent Document 3 has a problem that the cost and the mounting area increase because it is necessary to provide three comparators in the position detection circuit.

  The present invention has been made in view of the above, and provides a low-cost compressor drive control device and an air conditioner capable of performing subsequent position detection even when the PWM duty is zero in a zero load torque section of the compressor. The purpose is to do.

In order to solve the above-described problems and achieve the object, a drive control device for a compressor according to the present invention includes a rectifier circuit that converts an AC power source into a DC power source, and the compressor using the DC power source via a switching element. An inverter that controls a brushless DC motor that is a driving source by inverter, a position detection circuit that detects a position of a rotor of the brushless DC motor and generates a position detection signal, and the inverter based on an output from the position detection circuit Control means for generating a drive signal for the switching element, and a drive control device for controlling the drive of the compressor by controlling the rotation of the brushless DC motor by PWM control of the inverter. a predetermined time period from the position detection for a given energization interval during operation process of the compressor before the next position detection Without chopping the WM duty to 0, the period from after a lapse the predetermined time period up to the next position detection is characterized by performing chopping with a PWM duty minimized.

In the compressor control device according to another aspect of the present invention, the control unit may specify a zero load torque section during the operation process of the compressor as the predetermined energization section. To do.

  Moreover, the air conditioner which concerns on this invention is an air conditioner provided with the drive control apparatus of the compressor mentioned above.

  According to the present invention, it is possible to provide a low-cost compressor drive control device and an air conditioner capable of performing subsequent position detection even when the PWM duty is set to 0 in a section where the load torque of the compressor is zero. There is an effect.

FIG. 1 is a block diagram of a compressor drive control apparatus according to the present invention. FIG. 2 is a detailed diagram of the position detection circuit of FIG. FIG. 3 is a diagram showing an example of a timing chart of compressor drive control by the conventional control means. FIG. 4 is a diagram illustrating an example of load characteristics per rotation of the compressor. FIG. 5 is a timing chart of compressor drive control by the conventional control means, and is a diagram illustrating an example of a case where position detection becomes impossible. FIG. 6 is a timing chart of compressor drive control by the control means of the compressor drive control apparatus according to the present invention. FIG. 7 is a configuration diagram of an air conditioner including a compressor drive control device according to the present invention. FIG. 8 is a block diagram of the microcomputer of the present invention.

  Embodiments of a compressor drive control device and an air conditioner according to the present invention will be described below in detail with reference to the drawings. The basic configuration of the present invention is substantially the same as the above-described conventional configuration, and the same configuration as the conventional configuration is denoted by the same reference numeral. Further, the present invention is not limited to the embodiments.

  As shown in FIG. 7, the compressor drive control device 10 according to the present invention is provided in the outdoor unit 30 of the air conditioner and controls the drive of the compressor 20. The compressor 20 constitutes a refrigerant circuit together with the four-way valve 34, the outdoor heat exchanger 32, the expansion valve 36, the indoor unit 40, the indoor heat exchanger 42, and the refrigerant pipe 38 connecting them. FIG. 1 and FIG. 2 are block diagrams of a compressor drive control apparatus 10 according to the present invention, in which an AC / DC conversion circuit 12 (rectifier circuit) for converting an AC power source of a commercial power source E into a DC power source, and an inverter 14, a position detection circuit 16, and a microcomputer 18 (control means), and drives and controls a compressor 20 including a brushless DC motor M.

  In the inverter 14, semiconductor switching elements (transistors) 14 a to 14 f are three-phase (U-phase, V-phase, W-phase) bridge connection, and diodes 14 g to 14 l are connected in parallel to the respective transistors. The brushless DC motor M is driven by PWM control of the inverter 14, and the compressor 20 is driven by the brushless DC motor M.

  The position detection circuit 16 shown in FIG. 2 detects the rotational position of the rotor (not shown) from the induced voltage of the brushless DC motor M, and includes resistors 16b to 16g and a comparator 16a. One end of each of the resistors 16b to 16d is connected to each phase of the stator of the motor M, and the other end of each of the resistors 16b to 16d is connected to each other. A resistor 16g is connected between a connection point of each of the resistors 16b to 16d and the ground, and a connection point of the resistors 16b to 16d and the resistor 16g is connected to a non-inverting input terminal of the comparator 16a. Hereinafter, the voltage at the connection point between the resistors 16b to 16d and the resistor 16g is referred to as a virtual neutral point voltage. Further, a resistor 16e and a resistor 16f are connected in series between the positive side Vdc of the AC / DC conversion circuit 12 and the ground, and the voltage at the connection point of the resistor 16e and the resistor 16f is used as a reference voltage, and an inverting input terminal of the comparator 16a. To be supplied. This reference voltage is set to be 1/2 of the applied voltage Vdc. The comparator 16a detects the zero cross point of the virtual neutral point voltage (that is, the zero cross point of the induced voltage) by comparing the virtual neutral point voltage with the reference voltage, and detects the position of the rotor of the motor M. A position detection signal is output.

  As shown in FIG. 8, the microcomputer 18 as the control means includes a drive signal generation means 18a, a load torque zero section determination means 18b, and a duty 0 processing means 18c. The microcomputer 18 of the prior art has only 18a among these 18a to 18c, is provided with 18b and 18c, and it is a feature of the present invention to perform control by them. As shown in FIG. 1, the drive signal generation means 18 a generates an inverter drive signal based on the position detection signal from the position detection circuit 16 and outputs it to the inverter 14. The U-phase upper arm, V-phase upper arm, W-phase upper arm, U-phase lower arm, V-phase lower arm, and W-phase lower arm of inverter 14 are driven based on this inverter drive signal. The load torque zero section determination means 18b determines an energization section where the load torque of the compressor is zero. The duty 0 processing means 18c performs chopping by setting the PWM duty to 0 in a current-carrying section in which the load torque becomes zero and minimizing the PWM duty after a predetermined time.

  Here, the load torque zero section determination means 18b of the microcomputer 18 of the compressor drive control apparatus 10 according to the present invention configured as described above first determines the load torque zero section during the operation process of the compressor 20 as preprocessing. Perform the process. In this case, normal operation is performed in advance until the rotational speed becomes stable, and the zero load torque section is determined in a stable state, thereby specifying this section as a predetermined section. For this purpose, each section time is obtained from the position detection signal from the position detection circuit 16, and the section with the shortest section time is determined as the zero load torque section. Alternatively, the section where the change in the section time changes most greatly in the decreasing direction may be regarded as the section where the rotational speed is accelerated most, and the section may be determined as the zero load torque section. It should be noted that once the zero load torque section is determined, the same section does not change, so it is not necessary to determine again while continuing the operation.

  Then, with respect to the load torque zero section specified by the load torque zero section determination means 18b, the duty 0 processing means 18c sets the PWM duty to 0 for a predetermined period from the position detection at the start of the load torque zero section until the next position detection. Control is performed so that the position can be detected by performing chopping with a minimum PWM duty after a predetermined period has elapsed without performing chopping.

The details of this control will be described more specifically with reference to FIG.
FIG. 6 is a timing chart of compressor drive control according to the present invention excerpted from the above-described section including the zero load torque section of the compressor. In order from the top, the load torque characteristics of the compressor and the induction detected by the position detection circuit. Voltage waveform, position detection timing, energized phase switching processing timing, inverter upper / lower arm switching processing timing, U phase upper arm, V phase upper arm, W phase upper arm, U phase lower arm, V phase lower arm, W phase lower The waveform of each arm drive signal is shown.

  As shown in FIG. 6, first, when the induced voltage zero cross is detected in the energized phase immediately before the load torque zero section and the energized phase is switched to enter the load torque zero section, until the arm is switched from the zero cross timing of the induced voltage. The arm to be chopped is switched at the time Term from the zero cross timing of the induced voltage. By doing so, the next zero-cross timing of the induced voltage can be detected. Here, the time Tarm is set within a range in which position detection is not missed in actual machine verification or the like (for example, a time corresponding to an electrical angle of 45 °).

  Then, the PWM duty is set to zero until a predetermined period T1, which is a time corresponding to an electrical angle (60−α) ° (where α> 0), has elapsed from the zero cross timing at the start of the zero load torque section. When T1 elapses, the PWM duty for position detection is set to the minimum and output. More specifically, the position detection timing by the next zero cross is predicted based on the position detection timing by the induced voltage zero cross until the previous time, and the PWM duty is set to 0 slightly before the next position detection timing is reached. From the state, the minimum PWM duty that allows position detection is set, and after the position detection, the PWM duty is returned to normal PWM control. Although the relationship between T1 and Term is T1 ≧ Tarm, in reality, in order to make the PWM duty 0 state as long as possible, it is desirable that T1> Term.

  Here, the minimum duty at which position detection is possible can be determined from the time constant on the input side of the comparator 16 a in the position detection circuit 16 and the pulse width detectable at the input port of the microcomputer 18. T1 is a time corresponding to an electrical angle (60−α) ° (where α> 0), and can be obtained from a position detection section time before one rotation of the motor. Here, α is determined to be as small as possible within a range where position detection is not missed in actual machine verification or the like. Therefore, the PWM duty is set to the minimum after T1 from the position detection timing, and the chopping signal is generated until the position detection signal is received from the position detection circuit. As a result, even if the comparator uses one position detection circuit 16, the PWM duty can be set to 0 in a section in which the load torque of the compressor hardly occurs. Therefore, the position detection circuit of the brushless DC motor has 3 Since position detection is possible without providing a single comparator, cost and mounting area can be reduced. Furthermore, power consumption is reduced, and uneven rotation due to unnecessary acceleration is prevented.

  In particular, when considering the operation of an air conditioner, when the temperature stabilizes to some extent after the start of operation, the compressor rotation speed is lowered to enter the steady operation. long. Therefore, when a section in which the PWM duty is set to 0 and the power consumption is zero is provided during the compressor process as in the present invention, the power consumption of the air conditioner can be reduced in the long run, so that energy saving can be achieved. This is preferable.

  In the above embodiment, the case where the number of poles of the brushless DC motor is four has been described. However, the present invention is not limited to this, and the brushless of any number of poles such as a two-pole motor or a six-pole motor is used. It can be applied to a DC motor. Further, when a plurality of load torque zero sections exist during one rotation of the motor, the present invention can be applied to each load torque zero section.

  As described above, according to the present invention, there is provided a low-cost compressor drive control device and an air conditioner capable of performing subsequent position detection even when the PWM duty is set to 0 in a section where the load torque of the compressor hardly occurs. Can be provided.

10 Compressor Drive Control Device 12 AC / DC Conversion Circuit (Rectifier Circuit)
14 Inverter 14a-14f Switching element (transistor)
14g to 14l Diode 16 Position detection circuit 16a Comparator 16b to 16g Resistance 18 Microcomputer (control means)
18a Drive signal generation means 18b Load torque zero section determination means 18c Duty 0 processing means 20 Compressor 30 Outdoor unit 32 Outdoor heat exchanger 34 Four-way valve 36 Expansion valve 40 Indoor unit 42 Indoor heat exchanger M Brushless DC motor E Commercial power supply

Claims (3)

A rectifier circuit that converts an AC power source into a DC power source, an inverter that controls a brushless DC motor that is a driving source of a compressor by the DC power source via a switching element, and a position of a rotor of the brushless DC motor are detected. A position detection circuit for generating a position detection signal; and a control means for generating a drive signal for a switching element of the inverter based on an output from the position detection circuit. In the drive control device that controls the drive of the compressor by controlling the rotation of the compressor,
The control means for a predetermined period from the position detection for a given energization interval during operation process of the compressor before the next position detection without chopping with a PWM duty to 0, the predetermined time period A drive control apparatus for a compressor, characterized in that chopping is performed with the PWM duty being minimized during a period from the elapse of time until the next position detection . 2. The drive control apparatus for a compressor according to claim 1, wherein the control unit specifies a load torque zero section during an operation process of the compressor as the predetermined energization section .   An air conditioner comprising the compressor drive control device according to claim 1.

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