JP2007010200A - Air conditioner and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce frequency of thermo-on and thermo-off of an air conditioner comprising an invertor compressor. <P>SOLUTION: The magnitude of air conditioning load is determined on the basis of to which area of a plurality of predetermined temperature areas, the difference ΔT between an indoor suction air temperature and an indoor set temperature is correspond, and an upper limit frequency of driving frequency of the compressor is changed in several stages on the basis of a result of determination. That is, the upper limit frequency set when ΔT is correspond to a certain temperature area in the temperature areas, is set to the frequency higher than the upper limit frequency set when ΔT is correspond to the temperature area lower than the certain temperature area. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an air conditioner including an inverter compressor and a control method thereof, and more particularly to energy saving of the air conditioner and improvement of the reliability of the compressor.

  In the frequency control of an air conditioner equipped with a conventional inverter compressor, the difference between the set temperature and the room temperature of the air conditioning target space is calculated, and air conditioning is performed within the control value range of the maximum allowable frequency and minimum allowable frequency set for control. The operation is carried out with the drive frequency of the compressor determined according to the load. At this time, the inverter is controlling aiming at an ideal frequency line for outputting an output corresponding to the air conditioning load required by the compressor.

  Patent Document 1 includes an inverter-driven variable-capacity compressor and a commercial power-driven fixed-capacity compressor, and the number of operating and operating frequencies of these compressors are any of a plurality of patterns set in advance according to the air conditioning load. An example of an air conditioner that switches and controls the pattern depending on whether the frequency of the commercial power source is 50 Hz or 60 Hz is shown. Further, Patent Literature 2 includes an inverter-driven compressor, and in an air conditioner that determines an operating frequency of the compressor according to an air conditioning load and a predetermined operating frequency allocation condition, the operating frequency allocation condition includes: Applicable from the start of operation until it enters the stable range, applied when the air conditioning load after entering the stable range tends to be high, and after the air conditioning load after entering the stable range tends to be low There are three different assignment values from those applied in this case, and an example of selecting the operation frequency assignment condition according to the situation is shown.

Japanese Patent Laid-Open No. 05-157374 (page 3, FIG. 1, FIG. 4) JP 05-346259 A (3rd, 4th page, FIG. 4)

  In the conventional frequency control, an operation of output corresponding to the air conditioning load is attempted, but depending on the installation environment of the air conditioner, a short circuit in which the air discharged from the air conditioner is directly sucked into the air conditioner May occur, and an error may occur in the room temperature measured by the intake air temperature, or hunting may occur in the driving capacity, that is, the actual driving frequency due to inappropriate (excessive) capacity of the air conditioner with respect to the air conditioning load.

  As a result of the hunting of the actual drive frequency, the actual drive frequency increases or decreases with respect to the ideal frequency line, and compression occurs when this change becomes large (the absolute value of the actual drive frequency is small). The machine is stopped (hereinafter referred to as “thermo-off”). In other words, when the actual drive frequency falls below the minimum allowable frequency due to hunting of the actual drive frequency, a thermo-off occurs. When the room temperature rises with respect to the set temperature (in the case of cooling, it decreases in the case of heating), the compressor is started again (hereinafter referred to as thermo-on).

  Since the motor is burdened when the compressor is started, power consumption increases when the frequency of the thermo-off and the thermo-on, that is, the compressor is increased or decreased due to the above phenomenon. Further, an increase in the frequency of starting and stopping the compressor leads to a decrease in the reliability of the compressor.

  The thing of the said patent document 1 is not considered about the case where such an actual drive frequency hunts, and the thing of patent document 2 is also the same.

  An object of the present invention is to reduce the frequency of thermo-off and thermo-on caused by hunting of the actual drive frequency.

  In inverter control, the maximum permissible frequency is set in order to avoid damage due to over-rotation of the compressor and motor, and the compressor does not exceed a specific rotation speed. If so, the actual drive frequency is not suppressed.

  In addition to providing the maximum allowable frequency that defines the upper limit of the frequency of power supplied to the inverter compressor, the above-mentioned problem provides an upper limit frequency that defines the upper limit of the frequency of power supplied to the inverter compressor. By providing a plurality of stages for the upper limit frequency and changing the upper limit frequency according to the air conditioning load, it becomes possible to suppress frequency hunting caused by the air conditioning load condition.

  Specifically, the above problem is to determine the size of the air-conditioning load, and to change the upper limit frequency of the compressor driving frequency of the refrigerant whose rotational speed is controlled by the inverter in a stepwise manner based on the determination result. It is solved by the control method of the air conditioner.

  The rotational speed of the inverter compressor is determined by the size of the air conditioning load. When the air conditioning load is large, the rotational speed is large, and when the air conditioning load is small, the rotational speed is small, that is, the drive frequency of the compressor is also lowered.

  When the air conditioning load decreases, that is, when the compressor drive frequency decreases, the upper limit frequency is changed stepwise to reduce the increase in frequency due to frequency hunting to be less than the upper limit frequency. Along with this, the amount of frequency decrease due to frequency hunting is also reduced. By reducing the amount of frequency decrease due to frequency hunting, the frequency of causing the thermo-off by interrupting the minimum allowable frequency is also reduced.

  Conversely, when the air conditioning load increases, that is, when the drive frequency of the compressor increases, the upper limit frequency rises to a value corresponding to the load by increasing the upper limit frequency stepwise at the same time. It is avoided that it becomes an obstacle.

  The magnitude of the air conditioning load is determined based on which of a plurality of predetermined temperature ranges a difference ΔT between the air temperature of the space to be air-conditioned and the target air temperature, and the ΔT is The upper limit frequency that is set when the temperature falls within a certain temperature range is set to a frequency that is higher than the upper limit frequency that is set when ΔT falls within the temperature range lower than the certain temperature range. You can do it.

  When ΔT corresponds to the largest temperature range in the temperature range, a frequency obtained by adding a predetermined frequency to the upper limit frequency at that time is set as a new upper limit frequency, and ΔT is When the temperature falls within the lowest temperature range, the frequency obtained by subtracting a predetermined frequency from the upper limit frequency at that time may be set as a new upper limit frequency.

  Furthermore, it is desirable that the upper limit frequency is set to the maximum allowable frequency or the maximum settable upper limit frequency until a predetermined time elapses after the air conditioner is activated.

  In addition, there is provided a procedure for switching between control for setting an upper limit frequency different from the maximum allowable frequency and control for setting the maximum allowable frequency as the upper limit frequency without setting an upper limit frequency different from the maximum allowable frequency by an input signal from the outside. Alternatively, the upper limit frequency may be changed based on a command signal input from the outside.

  The above-mentioned problem also includes a compressor whose rotational speed is controlled by an inverter, a condenser that condenses and liquefies the refrigerant compressed by the compressor, and the liquid refrigerant generated by the condenser and the air in the air to be conditioned. A heat exchanger that exchanges heat; and a control unit that performs inverter control of the compressor, wherein the control unit is configured to determine a magnitude of an air conditioning load; and based on a result of the determination, The problem can also be solved by an air conditioner having upper limit frequency setting means for changing the upper limit frequency of the drive frequency stepwise.

  The determination means is configured to determine which of a plurality of predetermined temperature ranges a difference ΔT between an air temperature of a space to be air-conditioned and a target air temperature, and sets the upper limit frequency setting The means sets the upper limit frequency that is set when ΔT corresponds to a certain temperature region in the temperature region to a frequency that is higher than the upper limit frequency that is set when ΔT corresponds to a temperature region lower than the certain temperature region. It may be configured to be set.

  The upper limit frequency setting means sets a frequency obtained by adding a predetermined frequency to the upper limit frequency at that time as a new upper limit frequency when ΔT corresponds to the largest temperature range in the temperature range. , When ΔT corresponds to the smallest temperature range in the temperature range, a frequency obtained by subtracting a predetermined frequency from the upper limit frequency at that time is set as a new upper limit frequency It is good.

  The upper limit frequency setting means sets the upper limit frequency to the maximum allowable frequency or the maximum settable upper limit frequency regardless of the output of the determination means until a predetermined time elapses after the air conditioner is started. Desirably configured to be set.

  Further, the upper limit frequency setting means includes means for receiving a command signal input from the outside, and when receiving a command signal not permitting the upper limit frequency control, the upper limit frequency is fixed to the maximum allowable frequency, and the upper limit frequency control is performed. When the command signal to be permitted is received, the upper limit frequency may be changed stepwise based on the output of the determination means, or the upper limit frequency may be changed based on the command signal input from the outside. It may be configured.

  According to the present invention, since the upper limit frequency of the compressor driving frequency is changed according to the air conditioning load condition, hunting of the actual driving frequency caused by the air conditioning load condition is suppressed, and the start / stop frequency of the compressor is reduced. As a result, useless start and stop of the air conditioner is reduced, the operation efficiency is improved, and energy saving and reliability are improved.

<Embodiment 1>
The first embodiment of the present invention will be described below based on the upper limit frequency control flowchart shown in FIG. The inverter drive control device for controlling the rotation speed of the inverter compressor has a microcomputer, and the upper limit frequency control according to the present invention is performed by software (control program) stored in the microcomputer as a control means. Executed.

  The inverter drive control device is provided with signal input means for inputting a signal from the outside, and through this signal input means, various control commands, control parameters, or outputs of various sensors are input to the software (control program). Alternatively, it can be added additionally. As the control command, for example, upper limit frequency control permission or upper limit frequency control permission is input.

  In addition, the software includes a part that constitutes a judgment unit that judges the magnitude of the air-conditioning load, and a part that constitutes an upper limit frequency setting unit that changes the upper limit frequency stepwise by receiving an output of the judgment unit and a control command In addition, a part for setting a driving frequency based on inputs from various sensors and control commands is included.

  Hereinafter, an example of the upper limit frequency control of the air conditioner including the inverter compressor will be described with reference to the flowchart shown in FIG. In the present embodiment, as a criterion for determining the magnitude of the air conditioning load, the difference ΔT between the indoor intake air temperature and the indoor set temperature is a temperature region higher than 4 ° C. and 2 at 4 ° C. or less. Three temperature ranges higher than 2 ° C. and 2 ° C. or less are set.

  When the air conditioner is turned on (step 101), it is first determined whether or not the upper limit frequency control is permitted. When the upper limit frequency control is not permitted, the process proceeds to normal control (control not applying the upper limit frequency) (step 103), and returns to step 102 every predetermined time.

When the upper limit frequency control is permitted, the upper limit frequency Hzj is set to the maximum allowable frequency (hereinafter referred to as the maximum frequency) Hzmax (step 104), and then the A timer is started (step 105). Since the condition of the air conditioning load cannot be predicted immediately after the start of operation, the operation is performed at a certain time T ₁ , 30 minutes in this embodiment, and the upper limit frequency Hzj is a value close to the maximum frequency Hzmax (in this embodiment, the maximum frequency Hzmax). To do. The A timer is set to 30 minutes, and when 30 minutes have elapsed since the timer was started (step 106), the process proceeds to step 107.

  In step 107, it is determined whether or not the cooling operation is being performed. In the case of the cooling operation, the routine proceeds to step 108, where ΔT is calculated by calculating ΔT = indoor intake air temperature−indoor set temperature. On the other hand, when not in the cooling operation, that is, in the heating operation, the routine proceeds to step 109, where ΔT is calculated by the calculation of ΔT = indoor set temperature−indoor intake air temperature. For the indoor intake air temperature and the indoor set temperature, the data input as the output of the temperature sensor and the control parameter are read.

  When ΔT is calculated, the process proceeds to step 110, where it is determined whether ΔT is larger than a preset constant A (4 ° C. in the present embodiment). When ΔT> A, the process proceeds to step 111, where the upper limit frequency Hzj is changed to a value obtained by adding 10 Hz to the upper limit frequency Hzj at that time, and then, in step 112, the changed upper limit frequency Hzj is greater than the maximum frequency Hzmax. Is also determined. When the changed upper limit frequency Hzj is equal to or higher than the maximum frequency Hzmax, the upper limit frequency Hzj is set to the maximum frequency Hzmax (step 113). When the changed upper limit frequency Hzj is smaller than the maximum frequency Hzmax, the upper limit frequency Hzj is changed. Is set to the upper limit frequency Hzj.

  If ΔT> A is not satisfied in step 110, the process proceeds to step 114, and it is determined whether ΔT is equal to or less than a preset constant B (A> B, 2 ° C. in the present embodiment). If ΔT ≦ B is not satisfied in step 114, that is, if B <ΔT ≦ A, the upper limit frequency Hzj is not changed, and the upper limit frequency Hzj at that time is applied as it is (step 115).

  If ΔT ≦ B in step 114, the process proceeds to step 116, where the upper limit frequency Hzj is changed to a value obtained by subtracting 10 Hz from the upper limit frequency Hzj at that time, and then, in step 117, the changed upper limit frequency Hzj is the minimum. It is determined whether the frequency is lower than the allowable frequency (hereinafter referred to as the minimum frequency) Hzmin. When the changed upper limit frequency Hzj is less than or equal to the minimum frequency Hzmin, the upper limit frequency Hzj is set to the minimum frequency Hzmin (step 118), and when the changed upper limit frequency Hzj is greater than the minimum frequency Hzmin, the upper limit frequency Hzj is changed. Is set to the upper limit frequency Hzj.

When the upper limit frequency Hzj is set in step 111, 113, 115, 116 or 118 and the operation is continued by applying the set upper limit frequency Hzj, the process proceeds to step 119, and the state where the upper limit frequency control is permitted continues. Is confirmed. If the state where the upper limit frequency control is permitted is not continued in step 119, the process returns to step 103, and the operation by the normal control is executed. In step 119, if the state where the upper limit frequency control is permitted is continued, the activated A timer is different from B timer in step 105 is activated (step 120), the predetermined time T ₂ after (step 121 ), Step 107 is started.

That is, as long as the state where the upper limit frequency control is permitted continues, steps 107 to 121 are repeated at a predetermined time interval T ₂ , for example, every 5 minutes. The time interval T ₂ are, at least, is set to more than the time required for the upper limit frequency Hzj is changed until ΔT varies.

As described above, since immediately after the start of operation is unpredictable states of the air conditioning load, until the elapse of time T ₁ which is the start of the operation, to operate the upper limit frequency Hzj to a value close to the maximum frequency Hzmax. Thereafter, a difference (ΔT) between the set temperature of the air conditioner and the room temperature is detected by a sensor, and the set value of the upper limit frequency is shifted stepwise according to the value of ΔT, such as the upper limit frequency Hzb and the upper limit frequency Hzc. When ΔT exceeds a preset constant A (for air conditioning load large judgment), the upper limit frequency value is stepped up. When ΔT falls below a preset constant B (for air conditioning load small judgment), the upper limit frequency value is Step down.

  According to the above procedure, when the magnitude of ΔT is reduced, that is, when it is determined that the air conditioning load is small, the upper limit frequency Hzj is changed to be small in increments of 10 Hz, and the fluctuation of the compressor driving frequency in a state where the air conditioning load is reduced. The width is suppressed. Further, when ΔT increases, that is, when it is determined that the air conditioning load is large, the upper limit frequency Hzj is greatly changed in increments of 10 Hz, and an increase in the actual drive frequency for increasing the compressor output is allowed.

  Therefore, according to the present embodiment, the protrusion width when the drive frequency protrudes upward by hunting is suppressed, and accordingly, the protrusion width when the drive frequency protrudes downward by hunting is reduced. This is effective for suppressing downward reduction by hunting of the drive frequency. Thereby, the frequency of the thermo-on and the thermo-off of the compressor is reduced, and there is an effect of saving energy and improving the reliability of the compressor by eliminating the operation at a high frequency and an inefficient frequency.

  In the present embodiment, signal input means for inputting an external input signal is provided in the inverter drive control device of the air conditioner, and the inverter drive control device is enabled with an external input signal that permits upper limit frequency control. The upper limit frequency control is executed only during the interval.

  The inverter drive control device can select a set value of a plurality of upper limit frequencies set in advance by an external input signal from the external device side, and arbitrarily set upper limits such as an upper limit frequency a, an upper limit frequency b, and an upper limit frequency c. The frequency can be shifted.

Furthermore, it is possible to set the shift time of the upper limit frequency control (time to maintain at a certain upper limit frequency) to an arbitrary length in conjunction with the timer device, and the external input signal is controlled by the air conditioner. Remote centralized control may be performed by transmitting from a distance via a device.
<Embodiment 2>
FIG. 2 shows a flowchart according to the second embodiment of the present invention. The present embodiment differs from the first embodiment in that, in the first embodiment, when the value of ΔT exceeds the constant A, the upper limit frequency Hzj increases with time even if the value of ΔT is constant. In contrast, in the present embodiment, the upper limit frequency Hzj is assigned in advance to the value of ΔT, and the upper limit frequency Hzj does not change unless the value of ΔT changes. Hereinafter, description will be given with reference to a flowchart.

Step 201 to step 209 correspond to step 101 to step 110 in the flowchart shown in FIG. In the flowchart of FIG. 1, after the upper limit frequency Hzj set at step 104, after the time T ₁ has elapsed by starting the A timer, whereas the process proceeds to step 107, in this embodiment, the elapsed time after the upper limit frequency Hzj set rather, the elapsed time after the air conditioner starts is configured to proceed to step 206 when it exceeds the time T _1, substantially no difference can be either.

  In steps 209 to 211, it is determined whether ΔT is greater than A, A or less and greater than B, B or less and greater than C, or C or less. When ΔT is greater than A, the routine proceeds to step 212, where the upper limit frequency Hzj is set to the maximum frequency Hzmax, and when ΔT is less than A and greater than B, the routine proceeds to step 213, where the upper limit frequency Hzj is set to Hzb (Hzb <Hzmax). Is done. When ΔT is less than B and greater than C, the routine proceeds to step 214, where the upper limit frequency Hzj is set to Hzc (Hzc <Hzb), and when ΔT is less than C, the routine proceeds to step 215, where the upper limit frequency Hzj is Hzd (Hzd <Hzd <Hzb <Hzb). Hzc).

  Steps 216 to 217 correspond to steps 119 to 121 in FIG.

  Also according to this embodiment, depending on ΔT, that is, the load on the compressor, the upper limit frequency Hzj is increased when the load is high, and the upper limit frequency Hzj is decreased when the load is low, thereby suppressing hunting of the actual drive frequency. As a result, the frequency of thermo-off of the compressor can be reduced. In addition, by eliminating the operation at a frequency with a high rotational speed and an inefficient efficiency, there is an effect of energy saving and improvement of the reliability of the compressor.

  FIG. 3 shows an example of operation data of an inverter compressor to which the upper limit frequency control according to the present invention is applied, and FIG. 4 shows an operation of the inverter compressor operated under the same conditions but without applying the upper limit frequency control. Examples of data are shown below. In each case, the vertical axis represents frequency (Hz), the horizontal axis represents time, the actual drive frequency fluctuation state, maximum allowable frequency, minimum allowable frequency, thermo-off time, operation switch on (start-up) time, ideal frequency , A time zone where the air conditioning load is large, a region where the upper limit frequency is high, and a state where the upper limit frequency is changed step by step. Note that the operation data shown in FIG. 3 is an example in which the upper limit frequency is controlled in six stages instead of the four stages shown in the flowchart of FIG.

  In the example of FIG. 3, the upper limit frequency is maintained at the upper limit frequency a that is equal to the maximum allowable frequency for about one and a half hours after the operation switch is turned on (started), and the upper limit frequency b is gradually increased as the load decreases. The upper limit frequency c changes in order (upper limit frequency a> upper limit frequency b> upper limit frequency c).

  When the operation data shown in FIG. 3 is compared with the operation data shown in FIG. 4, the operation data shown in FIG. 3 protrudes to the upper side of the actual drive frequency in the time zone in which the upper limit frequency b to the upper limit frequency g are set. Fluctuations are suppressed, and in accordance with this, a drop that protrudes downward from the actual drive frequency is suppressed. It can be seen that there are fewer places where the actual drive frequency is 0 Hz, that is, the thermo-off.

It is a flowchart which shows the control procedure which concerns on Embodiment 1 of this invention. It is a flowchart which shows the control procedure which concerns on Embodiment 2 of this invention. It is a graph which shows the example of the air conditioner driving | operation data to which this invention was applied. It is a graph which shows the example of the air conditioner operation data by a prior art.

Claims (12)

An air conditioner control method in which the magnitude of an air-conditioning load is determined, and the upper limit frequency of the refrigerant compressor drive frequency whose rotation speed is controlled by an inverter is changed stepwise based on the determination result. 2. The air conditioner control method according to claim 1, wherein the magnitude of the air conditioning load is set such that a difference ΔT between an air temperature of a space to be air-conditioned and a target air temperature is in a plurality of predetermined temperature regions. The upper limit frequency that is determined when the ΔT corresponds to a certain temperature region in the temperature region is set when the ΔT corresponds to a temperature region lower than the certain temperature region. A method for controlling an air conditioner, characterized in that the frequency is set to be higher than an upper limit frequency to be set. 2. The air conditioner control method according to claim 1, wherein the magnitude of the air conditioning load is set such that a difference ΔT between an air temperature of a space to be air-conditioned and a target air temperature is in a plurality of predetermined temperature regions. When the ΔT corresponds to the largest temperature range in the temperature range, the frequency obtained by adding a predetermined frequency to the upper limit frequency at that time is a new upper limit frequency. When ΔT corresponds to the smallest temperature range in the temperature range, a frequency obtained by subtracting a predetermined frequency from the upper limit frequency at that time is set as a new upper limit frequency. An air conditioner control method characterized by the above.   4. The method of controlling an air conditioner according to claim 1, wherein the upper limit frequency is a maximum allowable frequency or a maximum settable upper limit frequency until a predetermined time elapses after the air conditioner is started. A method for controlling an air conditioner, characterized in that   5. The control method for an air conditioner according to claim 1, wherein the upper limit frequency different from the maximum permissible frequency is set, and the maximum permissible frequency is set to the upper limit frequency without setting the upper limit frequency different from the maximum permissible frequency. The control method of the air conditioner characterized by including the procedure which switches the control to by the input signal from the outside.   5. The method of controlling an air conditioner according to claim 1, further comprising a procedure for changing an upper limit frequency based on a command signal input from the outside. .   A compressor whose rotational speed is controlled by an inverter, a condenser that condenses and liquefies the refrigerant compressed by the compressor, and heat exchange that exchanges heat between the liquid refrigerant generated by the condenser and the air in the air-conditioned space. And a control means for inverter-controlling the compressor, the control means determining means for determining the magnitude of the air conditioning load, and an upper limit frequency of the compressor drive frequency based on the result of the determination An air conditioner comprising upper limit frequency setting means for changing the phase in a stepwise manner.   8. The air conditioner according to claim 7, wherein the determining means determines which of a plurality of predetermined temperature ranges a difference ΔT between an air temperature of a space to be air-conditioned and a target air temperature falls. The upper limit frequency setting means is configured to determine when ΔT corresponds to a temperature range within the temperature range, and the upper limit frequency set when ΔT corresponds to a temperature range lower than the temperature range. An air conditioner that is configured to be set to a frequency that is greater than an upper limit frequency that is set to 1.   8. The air conditioner according to claim 7, wherein the determining means determines which of a plurality of predetermined temperature ranges a difference ΔT between an air temperature of a space to be air-conditioned and a target air temperature falls. The upper limit frequency setting means is configured to determine a new frequency obtained by adding a predetermined frequency to the upper limit frequency at that time when ΔT corresponds to the largest temperature range in the temperature range. When the ΔT corresponds to the lowest temperature region in the temperature range, a frequency obtained by subtracting a predetermined frequency from the upper limit frequency at that time is set as a new upper limit frequency. An air conditioner characterized by being configured to perform.   The air conditioner according to any one of claims 7 to 9, wherein the upper limit frequency setting means has an upper limit frequency regardless of the output of the determination means until a predetermined time elapses after the air conditioner is activated. Is set to the maximum allowable frequency or the maximum settable upper limit frequency.   The air conditioner according to any one of claims 7 to 10, wherein the upper limit frequency setting means includes means for receiving a command signal input from the outside, and when receiving a command signal not permitting upper limit frequency control, An air, wherein the upper limit frequency is fixed to a maximum allowable frequency, and the upper limit frequency is changed stepwise based on the output of the determination means when a command signal permitting upper limit frequency control is received. Harmony machine. 12. The air conditioner according to claim 11, wherein the upper limit frequency setting means is configured to change the upper limit frequency based on a command signal input from the outside.

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