JP5656655B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner that controls the rotation speed of an outdoor fan motor.

  In a conventional air conditioner, a DC voltage is switched by an inverter and applied to a fan motor to control the motor to a target rotational speed. For example, Patent Document 1 below discloses a technique for changing the target rotational speed by a predetermined value in accordance with the peak hold value and effective value of the input current of the inverter. In the peak hold circuit or the average value circuit provided in the subsequent stage of the current detection circuit, fluctuations in the instantaneous value of the electric current of the motor are eliminated. Thereby, stable control of the electric motor is enabled.

JP 2001-286179 A (first page, FIG. 1)

  However, according to the above-described conventional technique, there is no effect on the pulsation component of the motor current generated at a frequency six times that of the motor or the pulsation of the current due to the load fluctuation caused by the disturbance on the propeller, and the fluctuation of the instantaneous value Cannot be excluded. For this reason, there is a problem in that there is a risk of generating noise due to the frequency fluctuation of the electric motor.

  The present invention has been made in view of the above, and the outdoor fan electric motor is optimally and stably driven against the influence of the frost formation and the outside wind of the outdoor heat exchanger during the heating operation. It aims at obtaining the air conditioner which improves.

  In order to solve the above-described problems and achieve the object, the present invention includes an electric motor that drives a blower fan that blows air to an outdoor heat exchanger, an inverter that applies a voltage to the electric motor using a DC power supply, and the DC A shunt resistor connected between a power source and the inverter, a charging unit for charging based on a voltage across the shunt resistor, a voltage connected to the charging unit in parallel, and a voltage charged in the charging unit being a predetermined time constant Discharge means for discharging at a voltage, and inverter control means for controlling a voltage output from the inverter, wherein the inverter control means detects a current value flowing through the shunt resistor based on the voltage discharged from the discharge means. When the detected current value exceeds a specified value, the frequency of the voltage output from the inverter to the motor is reduced, and the detected current value is When the lower value, increasing the frequency of the voltage output from the inverter to the motor is controlled such that a constant current flows, characterized in that.

  According to the present invention, by detecting the current of the electric motor that drives the outdoor fan and controlling the electric motor at an optimum rotational speed according to the current value, it is possible to reduce the load fluctuation due to the outdoor wind or frost formation of the outdoor heat exchanger. On the other hand, it is possible to secure strong controllability that allows the operation to be continued, and to suppress the beat sound of the motor due to the hunting of the rotational speed that can occur as a result of controlling the rotational speed of the motor.

FIG. 1 is a diagram illustrating a configuration example of an air conditioner. FIG. 2 is a diagram illustrating a configuration example of the voltage holding unit. FIG. 3 is a diagram illustrating the operation of the voltage holding unit. FIG. 4 is a diagram illustrating a configuration example of the inverter control unit. FIG. 5 is a diagram illustrating the operation of the position / speed estimation unit. FIG. 6 is a diagram illustrating a configuration example of the current detection unit. FIG. 7 is a diagram illustrating a configuration example of the rotation speed command calculation unit. FIG. 8 is a diagram illustrating a configuration example of the voltage control unit. FIG. 9 is a diagram illustrating the operation of the voltage control unit. FIG. 10 is a flowchart showing the control process of the inverter control unit. FIG. 11 is a diagram illustrating the operation of the air conditioner.

  Embodiments of an air conditioner according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment.
FIG. 1 is a diagram illustrating a configuration example of an air conditioner according to the present embodiment. Here, a separate type air conditioner will be described as an example. The air conditioner includes a compressor 1 that compresses refrigerant, a four-way valve 2 that switches the flow of refrigerant that has exited from the compressor 1, an outdoor heat exchanger 3 that performs heat exchange outdoors, and an expansion valve that reduces the pressure of the refrigerant. 4, the indoor heat exchanger 5 that performs heat exchange in the air-conditioned room, the compressor 1, the four-way valve 2, the outdoor heat exchanger 3, the expansion valve 4, and the indoor heat exchanger 5, and the refrigerant path A refrigerant pipe 6, a blower fan 7 that blows heat to the outdoor heat exchanger 3, an electric motor 8 that operates the blower fan 7, an inverter 9 that drives the electric motor 8 by applying a voltage, and a power source A DC power source 10 that is a supply source, an inverter control unit 11 that controls the inverter 9 by connecting to a control input terminal of the inverter 9, a DC voltage detection unit 12 that detects a DC voltage Vdc by the DC power source 10, Magnetic pole to detect magnetic pole position Includes a 置検 out portion 13, a shunt resistor 14 provided between the inverter 9 and the DC power source 10, a voltage holding section 15 for holding the terminal voltage Vsh of the shunt resistor 14, a.

  Next, the voltage holding unit 15 will be described. FIG. 2 is a diagram illustrating a configuration example of the voltage holding unit 15. The voltage holding unit 15 includes a backflow prevention unit 16 that prevents backflow of current, a charging unit 17 that is charged by the terminal voltage Vsh of the shunt resistor 14, and a discharging unit 18 that discharges the peak voltage Vc charged in the charging unit 17. . The voltage holding unit 15 receives the terminal voltage Vsh and outputs a peak value voltage Vc.

  The terminal voltage Vsh of the shunt resistor 14 is generated intermittently according to the switching timing of the inverter 9 and the current flowing through the motor 8. Therefore, in an actual air conditioner, when the detection is performed by a mounted microcomputer (including the inverter control unit 11 in the functional block of FIG. 1), it is necessary to detect in synchronization with the switching timing. It becomes complicated and requires an expensive microcomputer with high processing speed.

  The voltage holding unit 15 charges the charging unit 17 with the terminal voltage Vsh of the shunt resistor 14 via the backflow prevention unit 16, and also provides a discharging unit 18 in parallel with the charging unit 17, thereby changing the terminal intermittently. The peak value voltage Vc of the voltage Vsh is held until a peak voltage due to the next peak current is generated. The discharge unit 18 has a discharge resistance as an example, and the time constant when the discharge unit 18 discharges is set to be 1/6 times the period of the voltage output from the inverter 9 or more. As a method for charging the charging unit 17, for example, there is a method for charging a capacitor (not shown). Thereby, there is no problem even if the microcomputer detects at any timing, and an inexpensive microcomputer can be used. In addition, although the inverter control part 11 is contained in a microcomputer in the functional block shown in FIG. 1, you may include the other functional block shown in FIG. 1 in the same microcomputer.

  FIG. 3 is a diagram illustrating the operation of the voltage holding unit 15. The relationship between the current (total of Iu, Iv, and Iw), the voltage, and the voltage output from the voltage holding unit 15 in the shunt resistor 14 is shown. When the current shown in the upper part of FIG. 3 flows through the shunt resistor 14, the terminal voltage Vsh shown in the lower part of FIG. 3 is generated at both ends of the shunt resistor 14. The voltage holding unit 15 receives the terminal voltage Vsh and outputs the peak value voltage Vc by the operation of each of the above-described configurations.

  Next, the inverter control unit 11 will be described. The inverter control unit 11 generates PWM (Pulse Width Modulation) signals UP, VP, WP, UN, VN, and WN based on outputs of the DC voltage detection unit 12, the magnetic pole position detection unit 13, and the voltage holding unit 15. The switching elements 91 to 96 that are bridge-connected in the inverter 9 are driven to control the voltage applied to the electric motor 8.

  FIG. 4 is a diagram illustrating a configuration example of the inverter control unit 11. The inverter control unit 11 includes a position / speed estimation unit 19, a current detection unit 20, a rotation speed command calculation unit 21, and a voltage control unit 22.

  The position speed estimation unit 19 estimates the rotor position θ and the rotor speed ω of the rotor of the electric motor 8 based on the output signals (Hu, Hv, Hw) from the magnetic pole position detection unit 13, and the estimated rotor The position θ and the rotor speed ω are output to the voltage controller 22. FIG. 5 is a diagram illustrating the operation of the position / speed estimation unit 19. The relationship between the output signal from the magnetic pole position detector 13 and the rotor position θ is shown. For each electrical cycle, the rotor position θ moves from 0 to 360 °. As described above, the position / speed estimation unit 19 can obtain the rotor position θ by the combination of the output signals (Hu, Hv, Hw) at each control timing.

  FIG. 6 is a diagram illustrating a configuration example of the current detection unit 20. The current detection unit 20 includes a voltage / current conversion unit 23 that converts the input peak value voltage Vc into a current value, and a limiting unit 24 that outputs the bus current I based on the converted current value. The current detection unit 20 receives the peak value voltage Vc and obtains the bus current I based on the voltage (peak value voltage Vc) discharged from the discharge unit 18 of the voltage holding unit 15 and the resistance value of the shunt resistor 14. Output to the rotation speed command calculation unit 21.

  The current detection unit 20 stores the detected bus current value in a storage unit (not shown) (specifically, a mounted microcomputer or the like), and then compares the detected bus current value with the detected bus current value. The operation of holding one value is repeated for a certain period, and the highest bus current value in that period is set as the current flowing through the motor 8. At this time, the holding period is set to a time required for changing by the rotation speed of the lowest control unit of the rotation speed control when the deceleration process of the electric motor 8 is performed.

  FIG. 7 is a diagram illustrating a configuration example of the rotation speed command calculation unit 21. The rotation speed command calculation unit 21 includes a constant current rotation number calculation unit 25 that calculates the rotation speed based on the bus current I and a current command value I * corresponding to the current control state, and a speed command value based on the rotation speed. a rotation speed command limiting unit 26 that outputs ω *. The rotational speed command calculation unit 21 receives the bus current I as an input, obtains a speed command value ω *, and outputs it to the voltage control unit 22.

  FIG. 8 is a diagram illustrating a configuration example of the voltage control unit 22. The voltage control unit 22 includes a voltage command amplitude calculation unit 27 for obtaining a voltage command value V * for driving the electric motor 8 from the speed command value ω * and the rotor speed ω, a voltage command value V *, and a direct current of the DC power source 10. A three-phase voltage command calculator 28 for obtaining voltage command values Vu *, Vv *, Vw * in a three-phase state for driving the electric transmitter 8 based on the information of the voltage Vdc and the rotor position θ; A PWM generator 29 for obtaining PWM signals UP, VP, WP, UN, VN, WN for controlling ON / OFF of the switching elements 91 to 96 of the inverter 9 from the command values Vu *, Vv *, Vw *; Is provided. The voltage controller 22 receives the DC voltage Vdc from the DC voltage detector 12, the rotor position θ and the rotor speed ω from the position / speed estimator 19, and the speed command value ω * from the rotational speed command calculator 21. PWM signals UP, VP, WP, UN, VN, WN are output.

  FIG. 9 is a diagram illustrating the operation of the voltage control unit 22. The method for obtaining the PWM signals UP, VP, WP, UN, VN, and WN shown in the lower stage from the relationship between the carrier shown in the middle stage and the voltage command values Vu *, Vv *, and Vw * can be performed by a conventional method. It is. The upper part of FIG. 9 shows the rotor position θ, and the upper part and the middle part of FIG. 9 show the relationship in the three-phase voltage command calculation unit 28. The voltage control unit 22 performs control to prohibit acceleration of the electric motor 8 for a certain period after the start of the next current detection after the period in which the current detection unit 20 holds the maximum value of the bus current value expires. For example, the length of the period during which acceleration is prohibited is set to 1/6 or more of the rotation cycle of the electric motor 8.

  Next, a process performed by the inverter control unit 11 with respect to the peak value voltage Vc detected by the voltage holding unit 15 will be described. FIG. 10 is a flowchart showing a control process in the inverter control unit 11.

  First, the inverter control unit 11 determines whether or not the motor 8 for driving the blower fan 7 is operating (step S1). Whether or not the vehicle is operating can be determined by inputting the peak value voltage Vc to the current detector 20. When the electric motor 8 is operating (step S1: Yes), the inverter control unit 11 determines whether the current peak value holding timer (time_hold) is being counted (step S2). The current peak value holding timer (time_hold) may be provided in the current detection unit 20, or may be provided in another configuration not shown in FIG.

  When the current peak value holding timer (time_hold) is counting (step S2: Yes), the inverter control unit 11 determines whether or not the count value of time_hold is equal to or greater than the current peak value holding time (time refresh) (step S3). . When the current peak value retention time is exceeded (step S3: Yes), the inverter control unit 11 resets time_hold, restarts counting from 0, and starts counting the acceleration prohibition timer of the electric motor 8 (step S4). The acceleration prohibition timer may be provided in the voltage control unit 22 or may be provided in another configuration not shown in FIG. In addition, when it is less than the current peak value holding time (step S3: No), step S4 is omitted.

  Next, the inverter control unit 11 compares the current peak value of the electric motor 8 currently held with the current value based on the latest detected Vc (step S5). When the current value based on the latest Vc is larger (step S5: Yes), the inverter control unit 11 updates the current value to be held and holds the current value based on the latest Vc (step S6). Since the value held for the first time is zero, the current value based on the unconditionally detected Vc is held. If the current value based on the latest Vc is smaller (step S5: No), step S6 is omitted.

  Next, the inverter control unit 11 compares the latest current peak value of the electric motor 8 held with the threshold value for deceleration (step S7). If the current peak value being held is equal to or greater than the deceleration threshold value and deceleration has been completed (step S7: Yes), the frequency of the inverter voltage applied to the motor 8 to decelerate the rotational speed command Is performed (step S8). Specifically, the voltage control unit 22 performs processing.

  In step S1, when not operating (step S1: No), the inverter control unit 11 stops the related timer used for controlling the electric motor 8 and ends this process (step S9).

  Moreover, when not counting in step S2 (step S2: No), the inverter control part 11 starts the count of a corresponding timer (step S10). Then, it progresses to step S5.

  In step S7, when the current peak value held is less than the deceleration threshold (step S7: No), the inverter control unit 11 determines whether the current peak value held is less than the acceleration permission threshold ( Step S11). If the current peak value being held is equal to or greater than the acceleration permission threshold value (step S11: No), this process is terminated as it is. When the held current peak value is less than the acceleration permission threshold (step S11: Yes), the inverter control unit 11 determines whether or not the acceleration prohibition timer that has started counting in step S4 has passed the prohibition time. (Step S12). If the timer count value is equal to or shorter than the prohibited time (step S12: No), the process is terminated as it is. When the timer count value exceeds the prohibition time (step S12: Yes), the inverter control unit 11 performs a process of increasing the frequency of the inverter voltage applied to the motor 8 in order to accelerate the rotation speed command (step S12). S13). At this time, the acceleration prohibit timer is cleared.

  Specifically, the inverter control unit 11 fixes and presets the rotational frequency of the electric motor 8 when the electric current flowing through the electric motor 8 decreases due to the stall of the electric motor 8 and the current falls below a predetermined level. When the above-described current peak value is reduced to a certain current value level for frequency increase permission determination, control for increasing the frequency of the voltage applied to the electric motor 8 is performed. Thereby, it can avoid that the rotation speed of the electric motor 8 becomes unstable. In addition, when the frequency is once reduced, the increase in the number of rotations is prohibited for at least 1/6 of the rotation frequency of the electric motor 8. Thereby, control with higher stability can be performed.

  When the air conditioner is operated for heating, generally the ambient temperature of the outdoor unit is low and the air density is high. Therefore, the output torque of the electric motor 8 necessary for the operation of the blower fan 7 increases, and the flowing current increases. In addition, frost is generated in the outdoor heat exchanger 3, and the torque necessary to drive the blower fan 7 to block the heat exchanger increases with the passage of time of operation.

  FIG. 11 is a diagram illustrating the operation of the air conditioner. In the conventional control, the inverter control unit 11 operates so as to control the electric motor 8 at a constant rotation speed, and therefore, as shown in FIG. 11 (left side), the current value according to the frost formation amount that progresses with time. Increases from I0 to I1 (current increase possible range). Therefore, even if frosting occurs, it is necessary to set the rotational speed N0 of the electric motor 8 so as not to reach the overcurrent cutoff value, and the heating capacity cannot be improved by increasing the rotational speed.

  Therefore, in the control in the present embodiment, as shown in FIG. 11 (right side), the inverter control unit 11 performs control (current constant control) that uses current up to I1 at the time of a light load where frost formation does not progress. The number of revolutions is increased accordingly and the heating capacity is improved. As a result, by performing control so that the current value is constant (for example, constant I1) within a range where the overcurrent cutoff value is not reached, the number of revolutions at the time of light load where frosting is not progressing is increased from N0 to the maximum N1. Therefore, the outdoor heat exchanger 3 can efficiently exchange heat, and an air conditioner capable of improving the heating capacity can be obtained.

  Moreover, when the wind of the reverse direction to a ventilation direction blows on the ventilation fan 7, the load of the electric motor 8 increases and an electric current value may increase. In the conventional control, since it is difficult to control the current value, the electric motor 8 stops due to overcurrent interruption due to the increase in the current value, and heat exchange cannot be performed efficiently, so that the heating capacity is reduced. In the present embodiment, since the inverter control unit 11 controls the current value to be constant, it reduces the rotational speed even when wind is generated, and increases the rotational speed when the wind stops. It becomes possible to continue the heating operation, and it is possible to obtain an air conditioner that is highly reliable and capable of improving the heating capacity.

  Furthermore, even when the outdoor unit heat exchanger 3 becomes blocked due to aging or the volume of dust and the like, and the torque required to drive the blower fan 7 increases, the outdoor unit heat exchanger 3 operates at an optimum rotational speed at which the current value is constant. Therefore, it is possible to obtain an air conditioner that is highly reliable and capable of improving the heating capacity.

  In addition, it is possible to suppress the roaring sound of the motor caused by the hunting of the rotational speed that can occur as a result of controlling the rotational speed of the motor.

  As described above, in the present embodiment, in the air conditioner, the inverter control unit 11 that controls the inverter 9 that drives the motor 8 of the blower fan 7 detects the current of the motor 8, and the current value is constant. Thus, the inverter 9 that drives the electric motor 8 is controlled. Thereby, when load arises by the frosting etc. of the ventilation fan 7, a heating capability can be improved compared with the past. Further, even when wind blown in the direction opposite to the blowing direction blows to the blower fan 7, the heating operation can be continued by increasing the number of rotations when the wind stops. The heating capacity can be improved.

DESCRIPTION OF SYMBOLS 1 Compressor 2 Four-way valve 3 Outdoor heat exchanger 4 Expansion valve 5 Indoor heat exchanger 6 Refrigerant piping 7 Blower fan 8 Electric motor 9 Inverter 10 DC power supply 11 Inverter control part 12 DC voltage detection part 13 Magnetic pole position detection part 14 Shunt resistance 15 Voltage holding unit 16 Backflow prevention unit 17 Charging unit 18 Discharging unit 19 Position speed estimation unit 20 Current detection unit 21 Rotation speed command calculation unit 22 Voltage control unit 23 Voltage current conversion unit 24 Limiting unit 25 Constant current rotation number calculation unit 26 Rotation number Command restriction unit 27 Voltage command amplitude calculation unit 28 Three-phase voltage command calculation unit 29 PWM generation unit 91, 92, 93, 94, 95, 96 Switching element

Claims (8)

An electric motor that drives a blower fan that blows air to the outdoor heat exchanger;
An inverter that applies a voltage to the motor using a DC power source as a power source;
A shunt resistor connected between the DC power source and the inverter;
Charging means for charging based on the voltage across the shunt resistor;
Discharging means connected in parallel with the charging means, and discharging the voltage charged in the charging means with a predetermined time constant;
Inverter control means for controlling the voltage output from the inverter;
With
The inverter control means detects the current value flowing through the shunt resistor based on the voltage discharged from the discharge means, and when the detected current value exceeds a specified value, the voltage of the voltage output from the inverter to the motor lowering the frequency, whereas, if the detected current value falls below the value of the defined, increases the frequency of the voltage output from the inverter to the motor, and controls such that a constant current flows,
The value of the constant current is a value smaller than an overcurrent cutoff value, and a value larger than a current value during normal operation when the rotational speed of the blower fan is controlled at a constant rotational speed,
An air conditioner characterized by that. The charging means includes a capacitor and charges the capacitor through a diode.
The air conditioner according to claim 1. The predetermined time constant is set to 1/6 times or more of the period of the voltage output from the inverter,
The air conditioner according to claim 1 or 2, characterized in that. The inverter control means detects a current value based on a voltage discharged from the discharge means and a resistance value of the shunt resistor;
The air conditioner according to claim 1, 2, or 3. The inverter control means stores the detected current value, repeats the operation of holding the current value having the larger value by comparing with the detected current value for a certain period, and the highest current in the period. Let the value be the current flowing through the motor,
The air conditioner as described in any one of Claims 1-4 characterized by the above-mentioned. How long to keep the maximum value of the current value, the time required for deceleration processing of the electric motor,
The air conditioner according to claim 5. The inverter control means prohibits acceleration of the electric motor for a certain period from the start of the next current detection after the period for holding the maximum value of the current value has expired.
The air conditioner according to claim 5 or 6, characterized by the above. The length of the period during which acceleration of the motor is prohibited is set to 1/6 or more of the rotation period of the motor.
The air conditioner according to claim 7.

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